ORCID Profile
0000-0002-0163-2507
Current Organisation
University of Western Australia
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Publisher: American Astronomical Society
Date: 13-06-2008
Publisher: American Astronomical Society
Date: 12-2007
DOI: 10.1086/523853
Publisher: Oxford University Press (OUP)
Date: 12-11-2023
Abstract: The WALLABY pilot survey has been conducted using the Australian SKA Pathfinder (ASKAP). The integrated 21-cm H i line spectra are formed in a very different manner compared to usual single-dish spectra Tully–Fisher measurements. It is thus extremely important to ensure that slight differences (e.g. biases due to missing flux) are quantified and understood in order to maximise the use of the large amount of data becoming available soon. This article is based on four fields for which the data are scientifically interesting by themselves. The pilot data discussed here consist of 614 galaxy spectra at a rest wavelength of 21 cm. Of these spectra, 472 are of high enough quality to be used to potentially derive distances using the Tully–Fisher relation. We further restrict the s le to the 251 galaxies whose inclination is sufficiently close to edge-on. For these, we derive Tully–Fisher distances using the deprojected WALLABY velocity widths combined with infrared (WISE W1) magnitudes. The resulting Tully–Fisher distances for the Eridanus, Hydra, Norma, and NGC4636 clusters are 21.5, 53.5, 69.4, and 23.0 Mpc, respectively, with uncertainties of 5–10 per cent, which are better or equivalent to the ones obtained in studies using data obtained with giant single dish telescopes. The pilot survey data show the benefits of WALLABY over previous giant single-dish telescope surveys. WALLABY is expected to detect around half a million galaxies with a mean redshift of $z = 0.05 (200\\, \\mathrm{Mpc})$. This study suggests that about 200 000 Tully–Fisher distances might result from the survey.
Publisher: Wiley
Date: 08-02-2019
DOI: 10.1111/AZO.12291
Publisher: American Astronomical Society
Date: 04-1990
DOI: 10.1086/115401
Publisher: American Astronomical Society
Date: 04-2009
Publisher: American Astronomical Society
Date: 03-2009
Publisher: American Astronomical Society
Date: 16-10-2009
Publisher: American Astronomical Society
Date: 05-05-2009
Publisher: Springer Science and Business Media LLC
Date: 05-06-2023
Abstract: A measurement of the top-quark mass ( m t ) in the $$ t\\overline{t} $$ t t ¯ → lepton + jets channel is presented, with an experimental technique which exploits semileptonic decays of b -hadrons produced in the top-quark decay chain. The distribution of the invariant mass m ℓμ of the lepton, ℓ (with ℓ = e, μ ), from the W -boson decay and the muon, μ , originating from the b -hadron decay is reconstructed, and a binned-template profile likelihood fit is performed to extract m t . The measurement is based on data corresponding to an integrated luminosity of 36.1 fb − 1 of $$ \\sqrt{s} $$ s = 13 TeV pp collisions provided by the Large Hadron Collider and recorded by the ATLAS detector. The measured value of the top-quark mass is m t = 174 . 41 ± 0 . 39 (stat.) ± 0 . 66 (syst.) ± 0 . 25 (recoil) GeV, where the third uncertainty arises from changing the P ythia 8 parton shower gluon-recoil scheme, used in top-quark decays, to a recently developed setup.
Publisher: American Astronomical Society
Date: 2004
DOI: 10.1086/379805
Publisher: Oxford University Press (OUP)
Date: 22-11-2019
Abstract: Using Hubble Space Telescope ACS/WFC data we present the photometry and spatial distribution of resolved stellar populations of four fields within the extended ultraviolet disc (XUV disc) of M83. These observations show a clumpy distribution of main-sequence stars and a mostly smooth distribution of red giant branch stars. We constrain the upper end of the initial mass function (IMF) in the outer disc using the detected population of main-sequence stars and an assumed constant star formation rate (SFR) over the last 300 Myr. By comparing the observed main-sequence luminosity function to simulations, we determine the best-fitting IMF to have a power-law slope α = −2.35 ± 0.3 and an upper mass limit $M_{\\rm u}=25_{-3}^{+17} \\, \\mathrm{M}_\\odot$. This IMF is consistent with the observed H $\\rm \\alpha$ emission, which we use to provide additional constraints on the IMF. We explore the influence of deviations from the constant SFR assumption, finding that our IMF conclusions are robust against all but strong recent variations in SFR, but these are excluded by causality arguments. These results, along with our similar studies of other nearby galaxies, indicate that some XUV discs are deficient in high-mass stars compared to a Kroupa IMF. There are over one hundred galaxies within 5 Mpc, many already observed with HST, thus allowing a more comprehensive investigation of the IMF, and how it varies, using the techniques developed here.
Publisher: Elsevier BV
Date: 11-2020
Publisher: SPIE
Date: 11-10-2004
DOI: 10.1117/12.552799
Publisher: SPIE
Date: 26-02-2003
DOI: 10.1117/12.474053
Publisher: Springer Science and Business Media LLC
Date: 06-1995
DOI: 10.1038/375742A0
Publisher: CSIRO Publishing
Date: 27-10-2022
DOI: 10.1071/AM22011
Abstract: Tasmanian populations of the eastern quoll (Dasyurus viverrinus) represent the last wild stronghold of this species after its extirpation from the Australian mainland, but they have experienced declines of more than 50% over the past three decades. We investigated the feasibility of supplementing wild populations with captive-bred in iduals in attempts to halt and reverse observed declines in Tasmanian populations. We released 20 captive-bred eastern quolls into an extant wild population in the Tasmanian central plateau, and monitored their short-term survival, dispersal and body condition. We recorded high initial survival and low initial dispersal of captive-bred in iduals relative to previous release attempts in unfenced areas of mainland Australia. Further work to determine long-term survival of released in iduals, and the genetic and population-level impacts on local populations is ongoing. Our preliminary results support the use of population supplementation as an effective conservation action, which allows for early intervention to address species declines while testing hypotheses about their underlying causes.
Publisher: Oxford University Press (OUP)
Date: 26-11-2020
Abstract: Given the limited availability of direct evidence (pre-explosion observations) for supernova (SN) progenitors, the location of supernovae (SNe) within their host galaxies can be used to set limits on one of their most fundamental characteristics, their initial progenitor mass. We present our constraints on SN progenitors derived by comparing the radial distributions of 80 SNe in the Survey for Ionised Neutral Gas Galaxies (SINGG) and Survey of Ultraviolet emission in Neutral Gas Galaxies (SUNGG) to the R-band, H α, and UV light distributions of the 55 host galaxies. The strong correlation of Type Ia SNe with R-band light is consistent with models containing only low-mass progenitors, reflecting earlier findings. When we limit the analysis of Type II SNe to apertures containing 90 per cent of the total flux, the radial distribution of these SNe best traces far-ultraviolet emission, consistent with recent direct detections indicating Type II SNe have moderately massive red supergiant progenitors. Stripped-envelope (SE) SNe have the strongest correlation with H α fluxes, indicative of very massive progenitors (M* ≳ 20 M⊙). This result contradicts a small, but growing, number of direct detections of SE SN progenitors, indicating they are moderately massive binary systems. Our result is consistent, however, with a recent population analysis, suggesting binary SE SN progenitor masses are regularly underestimated. SE SNe are centralized with respect to Type II SNe and there are no SE SNe recorded beyond half the maximum disc radius in the optical and one third the disc radius in the ultraviolet. The absence of SE SNe beyond these distances is consistent with reduced massive star formation efficiencies in the outskirts of the host galaxies.
Publisher: IEEE
Date: 04-07-2021
Publisher: Elsevier BV
Date: 09-2018
Publisher: Oxford University Press (OUP)
Date: 28-11-2023
Abstract: We examine the H i gas kinematics of galaxy pairs in two clusters and a group using Australian Square Kilometre Array Pathfinder (ASKAP) WALLABY pilot survey observations. We compare the H i properties of galaxy pair candidates in the Hydra I and Norma clusters, and the NGC 4636 group, with those of non-paired control galaxies selected in the same fields. We perform H i profile decomposition of the s le galaxies using a tool, baygaud, which allows us to deblend a line-of-sight velocity profile with an optimal number of Gaussian components. We construct H i superprofiles of the s le galaxies via stacking of their line profiles after aligning the central velocities. We fit a double Gaussian model to the superprofiles and classify them as kinematically narrow and broad components with respect to their velocity dispersions. Additionally, we investigate the gravitational instability of H i gas discs of the s le galaxies using Toomre Q parameters and H i morphological disturbances. We investigate the effect of the cluster environment on the H i properties of galaxy pairs by iding the cluster environment into three subcluster regions (i.e. outskirts, infalling, and central regions). We find that the denser cluster environment (i.e. infalling and central regions) is likely to impact the H i gas properties of galaxies in a way of decreasing the litude of the kinematically narrow H i gas ($M_{\\rm {narrow}}^{\\rm {H\\, \\small {\\rm I}}}$/$M_{\\rm {total}}^{\\rm {H\\, \\small {\\rm I}}}$), and increasing the Toomre Q values of the infalling and central galaxies. This tendency is likely to be more enhanced for galaxy pairs in the cluster environment.
Publisher: Oxford University Press (OUP)
Date: 29-12-2018
Publisher: American Astronomical Society
Date: 12-08-2011
Publisher: Oxford University Press (OUP)
Date: 28-04-2016
DOI: 10.1093/MNRAS/STW993
Publisher: American Astronomical Society
Date: 04-1996
DOI: 10.1086/117895
Publisher: Cambridge University Press (CUP)
Date: 08-2009
DOI: 10.1017/S1743921310003443
Abstract: We studied the star cluster population properties in the nearby collisional ring galaxy NGC 922 using HST/WFPC2 photometry and population synthesis modeling. We found that 69% of the detected clusters are younger than 7 Myr, and that most of them are located in the ring or along the bar, consistent with the strong Hα emission. The images also show a tidal plume pointing toward the companion. Its stellar age is consistent with pre-existing stars that were probably stripped off during the passage of the companion. We compared the star-forming complexes observed in NGC 922 with those of a distant ring galaxy from the GOODS eld. It indicates very similar masses and sizes, suggesting similar origins. Finally, we found clusters that are excellent progenitor candidates for faint fuzzy clusters.
Publisher: American Astronomical Society
Date: 25-08-2009
Publisher: Elsevier BV
Date: 11-2018
Publisher: Oxford University Press (OUP)
Date: 06-08-2013
Publisher: Elsevier BV
Date: 09-2016
Publisher: MDPI AG
Date: 03-09-2019
DOI: 10.3390/SU11174804
Abstract: Purpose: This paper studies organisational and personal factors affecting the behaviour of academic staff in Saudi universities. It seeks to investigate the beliefs of academic staff regarding the use of ICT and other factors to enhance the productivity of their scientific research. Also, this study aims to improve the sustainability of publication in Saudi universities. ICT includes using the library system for accessing research repository databases such as Science Direct, Web of Science, Scopus, etc. and other factors. The authors also developed the Importance Performance Map Analysis (IPMA) for these factors in order to provide guidelines for Saudi universities to build university systems to manage and measure the research productivity of academic staff. In summary, this research identifies factors critical to enhancing research productivity in Saudi universities. This will help to improve the sustainability of publication in Saudi universities. By enhancing the sustainability of publication, the reputation of Saudi universities will be improved and the reputation of academic staff in Saudi universities. As well the sustainability of publication will assist the promote of Saudi academic staff. Approach: This paper analysed 200 papers related to the enhancement of research productivity from various research databases such as Science Direct, IEEE and Scopus. We included the usage of ICT in research analysis, university policy, university research funding and the number of publications published by academic staff. The authors used different databases and systematic literature reviews (SLR) to find the most important factors which could improve research productivity in universities. An online questionnaire answered by 375 academic staff from four developing Saudi universities that are Taif University, Taibah University, Jeddah University, Hail University—was used to determine the relationship between information technology factors and research performance together with other factors such as university policy, international collaboration, research funding and job satisfaction. In this study, we used SmartPLS v3 to analyse the results from the questionnaires. Findings: The results show that personal factors such as personal use of ICT and organisational factors such as job satisfaction, university policy, IT funding, international collaboration and the level of ICT use in the university have positive effects on scientific research productivity among academic staff at Saudi universities. Those results are based on the beliefs of academic staff regarding the use of information technology for research purposes and other factors. This paper finds that university policy recorded an importance of 0.523, job satisfaction was 0.224, international collaboration was 0.103, personal use of ICT was 0.102, the level of using ICT in the university was 0.074 and the importance of ICT funding was –0.156. Also, the results from SmartPLS show that university policy has a 0.215 effect size on research performance, job satisfaction has a 0.045 effect size on research performance, international collaboration has a 0.009 effect size on research performance, personal use of ICT has a 0.011 effect size on research performance, a university’s use of ICT has a 0.006 effect size on research performance and ICT funding has a 0.014 effect size on the research performance of academic staff in Saudi universities. These results will help to improve the sustainability of publication in Saudi universities in order to enhance the universities’ rankings and the reputation of academic staff. Sustainability is a target for any organization, both for profit-making entities or non-profit organizations such as universities. This means that Saudi universities should enhance the sustainability of their publication. In order to achieves the goals of higher education institutions. Originality: No study has investigated the factors affecting the performance of academic staff in Arab countries, especially in Saudi universities. Therefore, the originality of this study resides in being the first study to investigate the impact of researchers’ attitudes to enhancing the research productivity performance of researchers in Saudi universities. Also, it is one of the few studies which discusses sustainability in Saudi universities.
Publisher: American Astronomical Society
Date: 30-08-2013
Publisher: Oxford University Press (OUP)
Date: 07-09-2019
Abstract: We report on observations of ESO156−G029, member of a galaxy group which is positioned at the virial radius of cluster Abell 3193. ESO156−G029 is located ∼1.4 Mpc in projected distance from the brightest cluster galaxy NGC1500. We show that ESO156−G029 has disturbed gas kinematics and a highly asymmetric neutral hydrogen (H i) distribution, which are consequences of group pre-processing, and possibly of ram pressure. Based on the current data we propose a scenario in which ESO156−G029 had a minor gas-rich merger in the past and now starts to experience ram pressure. We infer that the galaxy will undergo rapid evolution once it gets closer to the cluster centre (less than 0.5 Mpc) where ram pressure is strong enough to begin stripping the H i from the galaxy.
Publisher: American Astronomical Society
Date: 20-06-2001
DOI: 10.1086/321422
Publisher: American Astronomical Society
Date: 09-2001
DOI: 10.1086/322475
Publisher: Elsevier BV
Date: 11-2021
Publisher: American Astronomical Society
Date: 30-04-2010
Publisher: Society for Neuroscience
Date: 28-05-2008
DOI: 10.1523/JNEUROSCI.1039-08.2008
Abstract: Psychostimulants and other drugs of abuse activate extracellular signal-regulated kinase (ERK) in the striatum, through combined stimulation of dopamine D 1 receptors (D1Rs) and glutamate NMDA receptors. Antipsychotic drugs activate similar signaling proteins in the striatum by blocking dopamine D 2 receptors (D2Rs). However, the neurons in which these pathways are activated by psychotropic drugs are not precisely identified. We used transgenic mice, in which enhanced green fluorescent protein (EGFP) expression was driven by D1R promoter ( drd1a -EGFP) or D2R promoter ( drd2 -EGFP). We confirmed the expression of drd1a -EGFP in striatonigral and drd2 -EGFP in striatopallidal neurons. Drd2 -EGFP was also expressed in cholinergic interneurons, whereas no expression of either promoter was detected in GABAergic interneurons. Acute cocaine treatment increased phosphorylation of ERK and its direct or indirect nuclear targets, mitogen- and stress-activated kinase-1 (MSK1) and histone H3, exclusively in D1R-expressing output neurons in the dorsal striatum and nucleus accumbens. Cocaine-induced expression of c-Fos and Zif268 predominated in D1R-expressing neurons but was also observed in D2R-expressing neurons. One week after repeated cocaine administration, cocaine-induced signaling responses were decreased, with the exception of enhanced ERK phosphorylation in dorsal striatum. The responses remained confined to D1R neurons. In contrast, acute haloperidol injection activated phosphorylation of ERK, MSK1, and H3 only in D2R neurons and induced c-fos and zif268 predominantly in these neurons. Our results demonstrate that cocaine and haloperidol specifically activate signaling pathways in two completely segregated populations of striatal output neurons, providing direct evidence for the selective mechanisms by which these drugs exert their long-term effects.
Publisher: Institute of Advanced Engineering and Science
Date: 08-2021
DOI: 10.11591/IJEECS.V23.I2.PP1120-1127
Abstract: This study assesses the user experience of a COVID-19 tracking application, as employed as a case study of AMAN mobile application based on user experience. This paper proposed an assessment of user experience (UX) for AMAN application (COVID-19 tracking mobile application in Jordan) by implementing a user experience questionnaire tool. The study aims to get feedback and identify UX based on user interaction and usage with the tracking application. The data are taken from 1208 participants who have experience using the application an online questionnaire was implemented and distributed through social media groups. The research method that was adopted used the instrument from user experience questionnaire (UEQ) of Arabic and English versions. The results from the UX assessment using UEQ showed that there are four scales which are categorized as excellent they are Attractiveness (Mean=1.9), Efficiency (Mean=2.4), Dependability (Mean=2.1), Stimulation (Mean=1.8), while the two scales on the benchmark of good are Perspicuity (Mean=2.0) and Novelty (Mean=1.6). From the scores, above & 0.8 show a positive evaluation. All scores are above & ,08 indicating that the evaluation of UX has a positive impression. It can be concluded that the AMAN application is very good–satisfying users to track infected cases of COVID 19.
Publisher: IOP Publishing
Date: 08-2001
DOI: 10.1086/322915
Publisher: Society for Neuroscience
Date: 09-10-2013
DOI: 10.1523/JNEUROSCI.1927-13.2013
Abstract: The ability of animals to extract predictive information from the environment to inform their future actions is a critical component of decision-making. This phenomenon is studied in the laboratory using the pavlovian–instrumental transfer protocol in which a stimulus predicting a specific pavlovian outcome biases choice toward those actions earning the predicted outcome. It is well established that this transfer effect is mediated by corticolimbic afferents on the nucleus accumbens shell (NAc-S), and recent evidence suggests that δ-opioid receptors (DORs) play an essential role in this effect. In DOR-eGFP knock-in mice, we show a persistent, learning-related plasticity in the translocation of DORs to the somatic plasma membrane of cholinergic interneurons (CINs) in the NAc-S during the encoding of the specific stimulus–outcome associations essential for pavlovian–instrumental transfer. We found that increased membrane DOR expression reflected both stimulus-based predictions of reward and the degree to which these stimuli biased choice during the pavlovian–instrumental transfer test. Furthermore, this plasticity altered the firing pattern of CINs increasing the variance of action potential activity, an effect that was exaggerated by DOR stimulation. The relationship between the induction of membrane DOR expression in CINs and both pavlovian conditioning and pavlovian–instrumental transfer provides a highly specific function for DOR-related modulation in the NAc-S, and it is consistent with an emerging role for striatal CIN activity in the processing of predictive information. Therefore, our results reveal evidence of a long-term, experience-dependent plasticity in opioid receptor expression on striatal modulatory interneurons critical for the cognitive control of action.
Publisher: American Astronomical Society
Date: 12-1995
DOI: 10.1086/117721
Publisher: PeerJ
Date: 18-08-2022
Abstract: The computerization of both fetal heart rate (FHR) and intelligent classification modeling of the cardiotocograph (CTG) is one of the approaches that are utilized in assisting obstetricians in conducting initial interpretation based on (CTG) analysis. CTG tracing interpretation is crucial for the monitoring of the fetal status during weeks into the pregnancy and childbirth. Most contemporary studies rely on computer-assisted fetal heart rate (FHR) feature extraction and CTG categorization to determine the best precise diagnosis for tracking fetal health during pregnancy. Furthermore, through the utilization of a computer-assisted fetal monitoring system, the FHR patterns can be precisely detected and categorized. The goal of this project is to create a reliable feature extraction algorithm for the FHR as well as a systematic and viable classifier for the CTG through the utilization of the MATLAB platform, all the while adhering to the recognized Royal College of Obstetricians and Gynecologists (RCOG) recommendations. The compiled CTG data from spiky artifacts were cleaned by a specifically created application and compensated for missing data using the guidelines provided by RCOG and the MATLAB toolbox after the implemented data has been processed and the FHR fundamental features have been extracted, for ex le, the baseline, acceleration, deceleration, and baseline variability. This is followed by the classification phase based on the MATLAB environment. Next, using the guideline provided by the RCOG, the signals patterns of CTG were classified into three categories specifically as normal, abnormal (suspicious), or pathological. Furthermore, to ensure the effectiveness of the created computerized procedure and confirm the robustness of the method, the visual interpretation performed by five obstetricians is compared with the results utilizing the computerized version for the 150 CTG signals. The attained CTG signal categorization results revealed that there is variability, particularly a trivial dissimilarity of approximately (+/−4 and 6) beats per minute (b.p.m.). It was demonstrated that obstetricians’ observations coincide with algorithms based on deceleration type and number, except for acceleration values that differ by up to (+/−4). The results obtained based on CTG interpretation showed that the utilization of the computerized approach employed in infirmaries and home care services for pregnant women is indeed suitable. The classification based on CTG that was used for the interpretation of the FHR attribute as discussed in this study is based on the RCOG guidelines. The system is evaluated and validated by experts based on their expert opinions and was compared with the CTG feature extraction and classification algorithms developed using MATLAB.
Publisher: Engineering, Technology & Applied Science Research
Date: 12-06-2021
DOI: 10.48084/ETASR.4132
Abstract: Portals are gateways that provide users with the information they need from different sources and display it on a single page. It is important to see that universities utilize the resources and services provided by their student portals. With the rapid development of Information and Communication Technology (ICT), the Ministry of Education in Saudi Arabia aims to develop and improve student portals by providing high-quality teaching services through the university portal systems. This paper discusses the importance of student portal usage in Saudi Arabian universities and investigates the factors that influence the utilization of student portals as perceived by the students of the Saudi universities. Based on these factors, a model is proposed which identifies students’ expectations about the Saudi university portals. A quantitative methodology was employed to develop the model. The results revealed that 8 out of 10 factors of the model are significant and positively affect student portal usage. The enhancement of student portals based on the identified significant factors will assist the universities to increase their utilization and their provided services.
Publisher: Springer Science and Business Media LLC
Date: 11-2021
Publisher: American Astronomical Society
Date: 29-06-2012
Publisher: Springer New York
Date: 2008
Publisher: American Astronomical Society
Date: 05-2006
DOI: 10.1086/501529
Publisher: American Astronomical Society
Date: 07-2002
DOI: 10.1086/341043
Publisher: Oxford University Press (OUP)
Date: 21-05-2013
DOI: 10.1093/MNRAS/STT747
Publisher: American Astronomical Society
Date: 23-01-2014
Publisher: American Astronomical Society
Date: 16-04-2014
Publisher: Cambridge University Press (CUP)
Date: 1997
DOI: 10.1071/AS97077
Abstract: Recent results on NGC 2915, the first blue compact dwarf galaxy to have its mass distribution modelled, are summarised. NGC 2915 is shown to have H I well beyond its detected optical extent. Its rotation curve is well determined and fit with maximum disk mass models. The dark matter halo dominates the mass distribution at nearly all radii, and has a very dense core compared to those of normal galaxies. High-mass star formation energises the H I in the centre of the galaxy, but appears to be maintained in viriai equilibrium with the dark matter halo. The implications of these results are briefly discussed.
Publisher: American Astronomical Society
Date: 20-07-2005
DOI: 10.1086/430592
Publisher: Elsevier BV
Date: 09-2021
Publisher: American Astronomical Society
Date: 20-11-2018
Publisher: Oxford University Press (OUP)
Date: 16-06-2023
Abstract: We present a multiwavelength (from far-ultraviolet to ${\\rm H}\\, \\rm {\\small I}$ emission) study of star formation feedback on the kinematics of the interstellar medium in the Sculptor galaxy, NGC 253. Its three well-known features (a disrupted stellar disc, a previously reported declining rotation curve, and anomalous ${\\rm H}\\, \\rm {\\small I}$ gas) are studied in a common context of disc asymmetries. About 170 h of on-source ATCA observations are collected and reduced into two versions of ${\\rm H}\\, \\rm {\\small I}$ data cubes of different angular resolution (30 arcsec/2 arcmin) and H i column density sensitivity (7.4 × 1019 cm−2/4 × 1018 cm−2). We separate the anomalous gas from the disc using a custom-made line profile fitting toolkit called FMG. Two star formation tracers (H α, FUV emission) are carefully processed and studied. We find that at R & 7.5 kpc, the star formation activity is strongly lopsided (SFRNE & SFRSW), and investigate several other properties (H α/FUV, dust temperature, stellar age, and disc stability parameters). We also find that the declining nature of the rotation curve perceived by previous studies is not intrinsic but a combined effect of kinematical asymmetries at R = 7.5–16 kpc. This is likely the consequence of star formation triggered outflow. The mass distribution and the time-scale of the anomalous gas also imply that it originates from gas outflow, which is perhaps caused by galaxy–galaxy interaction considering the crowded environment of NGC 253.
Publisher: Wiley
Date: 04-05-2021
DOI: 10.1002/DAC.4857
Abstract: Unmanned aerial vehicles (UAVs) are key components of future Internet of Things as they facilitate efficient data sensing and transmission. However, UAVs will be sparsely placed and data dissemination among UAVs is a challenge. In this regard, cellular users can help to propagate the data between UAVs by using multi‐hop device‐to‐device (D2D) communication. A key challenge for multi‐hop D2D communication to support inter‐UAV communication is to select optimal forwarding D2D nodes that reduce the communication delay. In this paper, we propose a multi‐hop data dissemination protocol for inter‐UAV communication using D2D‐enabled user equipment (UEs). We consider factors such as channel quality and queuing delay to find suitable forwarding D2D nodes. To improve reliability of transmission, the proposed protocol selects forwarding nodes within a forwarding area where packets can be successfully received. Simulation results verify that the proposed protocol can reduce end‐to‐end delay and improve reliability of multi‐hop UAV data dissemination.
Publisher: American Astronomical Society
Date: 20-12-2007
DOI: 10.1086/523640
Publisher: American Astronomical Society
Date: 09-1999
DOI: 10.1086/307603
Publisher: Elsevier BV
Date: 10-2021
Publisher: American Astronomical Society
Date: 10-06-2006
DOI: 10.1086/503539
Publisher: Oxford University Press (OUP)
Date: 11-1998
Publisher: American Astronomical Society
Date: 18-03-2011
Publisher: American Astronomical Society
Date: 11-1999
DOI: 10.1086/301064
Publisher: Springer Science and Business Media LLC
Date: 27-04-2021
Publisher: American Astronomical Society
Date: 20-05-2006
DOI: 10.1086/501512
Publisher: American Astronomical Society
Date: 08-04-2004
DOI: 10.1086/421016
Publisher: PeerJ
Date: 23-03-2021
DOI: 10.7717/PEERJ-CS.414
Abstract: The Internet of Medical Things (IoMTs) is gradually replacing the traditional healthcare system. However, little attention has been paid to their security requirements in the development of the IoMT devices and systems. One of the main reasons can be the difficulty of tuning conventional security solutions to the IoMT system. Machine Learning (ML) has been successfully employed in the attack detection and mitigation process. Advanced ML technique can also be a promising approach to address the existing and anticipated IoMT security and privacy issues. However, because of the existing challenges of IoMT system, it is imperative to know how these techniques can be effectively utilized to meet the security and privacy requirements without affecting the IoMT systems quality, services, and device’s lifespan. This article is devoted to perform a Systematic Literature Review (SLR) on the security and privacy issues of IoMT and their solutions by ML techniques. The recent research papers disseminated between 2010 and 2020 are selected from multiple databases and a standardized SLR method is conducted. A total of 153 papers were reviewed and a critical analysis was conducted on the selected papers. Furthermore, this review study attempts to highlight the limitation of the current methods and aims to find possible solutions to them. Thus, a detailed analysis was carried out on the selected papers through focusing on their methods, advantages, limitations, the utilized tools, and data. It was observed that ML techniques have been significantly deployed for device and network layer security. Most of the current studies improved traditional metrics while ignored performance complexity metrics in their evaluations. Their studies environments and utilized data barely represent IoMT system. Therefore, conventional ML techniques may fail if metrics such as resource complexity and power usage are not considered.
Publisher: American Astronomical Society
Date: 09-2006
DOI: 10.1086/505680
Publisher: EDP Sciences
Date: 11-2020
DOI: 10.1051/0004-6361/202038894
Abstract: Aims. We present the results of three commissioning H I observations obtained with the MeerKAT radio telescope. These observations make up part of the preparation for the forthcoming MHONGOOSE nearby galaxy survey, which is a MeerKAT large survey project that will study the accretion of gas in galaxies and the link between gas and star formation. Methods. We used the available H I data sets, along with ancillary data at other wavelengths, to study the morphology of the MHONGOOSE s le galaxy, ESO 302-G014, which is a nearby gas-rich dwarf galaxy. Results. We find that ESO 302-G014 has a lopsided, asymmetric outer disc with a low column density. In addition, we find a tail or filament of H I clouds extending away from the galaxy, as well as an isolated H I cloud some 20 kpc to the south of the galaxy. We suggest that these features indicate a minor interaction with a low-mass galaxy. Optical imaging shows a possible dwarf galaxy near the tail, but based on the current data, we cannot confirm any association with ESO 302-G014. Nonetheless, an interaction scenario with some kind of low-mass companion is still supported by the presence of a significant amount of molecular gas, which is almost equal to the stellar mass, and a number of prominent stellar clusters, which suggest recently triggered star formation. Conclusions. These data show that MeerKAT produces exquisite imaging data. The forthcoming full-depth survey observations of ESO 302-G014 and other s le galaxies will, therefore, offer insights into the fate of neutral gas as it moves from the intergalactic medium onto galaxies.
Publisher: Oxford University Press (OUP)
Date: 14-01-2016
Publisher: Springer Science and Business Media LLC
Date: 03-08-2011
DOI: 10.1038/NPP.2011.144
Publisher: AIP
Date: 1997
DOI: 10.1063/1.53774
Publisher: American Association for the Advancement of Science (AAAS)
Date: 31-01-2020
Abstract: An intriguing characteristic of the striatum is the random spatial distribution and high degree of intermingling between expression of dopamine receptor types 1 (D1) and 2 (D2) within striatal projection neurons (SPNs). The resulting highly entropic mosaic extends through a homogeneous space and is mostly devoid of histological boundaries. The rules established locally by D1- and D2-expressing SPNs (D1-SPNs and D2-SPNs) are thus likely critical in defining how functional territories develop throughout the striatum. Matamales et al. found that activated D2-SPNs access and modify developing behavioral programs encoded by regionally defined ensembles of transcriptionally active D1-SPNs. This process is slow because it depends on the molecular integration of additive neuro-modulatory signals. However, with time, it creates the regional functional boundaries that are necessary to identify and shape specific learning in the striatum. Science , this issue p. 549
Publisher: American Astronomical Society
Date: 10-1995
DOI: 10.1086/176328
Publisher: Cold Spring Harbor Laboratory
Date: 26-09-2019
DOI: 10.1101/780346
Abstract: Extinction learning allows animals to withhold voluntary actions that are no longer related to reward and so provides a major source of behavioral control. Although such learning is thought to depend on dopamine signals in the striatum, the way the circuits mediating goal-directed control are reorganized during new learning remains unknown. Here, by mapping a dopamine-dependent transcriptional activation marker in large ensembles of striatal projection neurons (SPNs) expressing dopamine receptor type 1 (D1-SPNs) or 2 (D2-SPNs) in mice, we demonstrate an extensive and dynamic D2- to D1-SPN trans-modulation across the dorsal striatum that is necessary for updating previous goal-directed learning. Our findings suggest that D2-SPNs suppress the influence of outdated D1-SPN plasticity within functionally relevant striatal territories to reshape volitional action.
Publisher: Springer International Publishing
Date: 2023
Publisher: Cambridge University Press (CUP)
Date: 1985
DOI: 10.1017/S1323358000018075
Abstract: We present here the best of a series of models of the Magellanic stream. The dominant force in these models is gas drag. Gaseous cloudlets are torn from the bridge between the Large and Small Magellanic Clouds as the Magellanic system passes through a hot gaseous halo about our galaxy. The cloudlets are then stretched apart from each other by tidal and drag forces to form the Magellanic stream. Our best model closely reproduces the position of the stream on the sky and the run of radial velocities along the Magellanic stream. The agreement is almost as good as the best purely tidal model. In our best model the Magellanic system is only loosely bound to our galaxy and is on the first encounter with it. This overcomes some of the problems with purely tidal models. Our series of models indicate that there is a wide range of parameters that will produce a reasonable stream under the forces of gas drag and gravity.
Publisher: International Association of Online Engineering (IAOE)
Date: 28-02-2022
DOI: 10.3991/IJIM.V16I04.26471
Abstract: User Experience (UX) evaluation has a significant importance for any interactive application. Mobile device applications have additional limitations to convey good user experiences (UX) due to the usage and features of mobile devices in ubiquitous computing contexts. There are a lot of automated tools available for evaluating, such applications particularly developed for Android and iOS. Automated UX evaluation provides a number of strengths which are able to overcome the limitations of non-automated (moderated) counterparts. Automated UX evaluation is regarded as unexplored field, especially when it is adopted for the UX evaluation of complex mobile application. Despite these, automated UX evaluation tools are unexplored and should only be used in coupling with traditional UX evaluation techniques. Hence, this study aims to discuss the literature in automated UX evaluation and to highlight the UX measurements that merit further investigation. This paper presents the most frequently used automated UX evaluation tools for mobile applications. Therefore, the study analyzes existing automated UX tools and frameworks and identifies which UX attributes and measurements of automated UX evaluation are likely to be of use in future research. Moreover, we discuss the strengths and limitations of automated UX evaluation methods for mobile applications. Finally, the paper provides an overview of automated UX evaluation techniques and tools. It also presents the strengths and limitations for comparing various evaluation methods.
Publisher: American Astronomical Society
Date: 17-06-2011
Publisher: Oxford University Press (OUP)
Date: 10-11-2020
Abstract: We present and explore the resolved atomic hydrogen (H i) content of 13 H i-rich and late-type dominated groups denoted ‘Choirs’. We quantify the H i content of the Choir galaxies with respect to the median of the H i-mass fraction ($f_{\\rm{{H {\\small I}}}}$) of their grandparent H i Parkes All Sky Survey (HIPASS) s le. We find that the H i-mass fraction of the Choir galaxies is dispersed around the HIPASS median in the range $-1.4\\le \\Delta f_{\\rm{{H {\\small I}}}}\\textrm{[dex]}\\le$ 0.7, from H i-excess to H i-deficient galaxy regime. The H i-excess/H i-deficient galaxies contain more/less than 2.5 times their expected H i content with respect to the HIPASS median. We show and discuss that the environmental processing in Choirs occurs via tidal stripping and galaxy mergers. Our analysis suggests that tidal stripping contributes to the loss of the H i, while galaxy mergers contribute to the enhancement of the H i. Exploring the mid-infrared properties of Choir galaxies, we find possible environmental processing in only nine Choir galaxies, which indicates that environmental processing is more perceptible in the H i content than the mid-infrared properties. Moreover, we find that environmental processing occurs in Choir groups regardless of their global environment, whether they are in isolation or in proximity to the denser structures, such as cosmic web filaments. We explore possible scenarios of the Choirs evolution, taking into account their H i content, velocity dispersion, crossing time, and their global environment. We conclude that the most likely evolution for the majority of Choir groups is that they will become more compact as their members undergo multiple H i-rich mergers.
Publisher: Public Library of Science (PLoS)
Date: 17-06-2016
Publisher: Oxford University Press (OUP)
Date: 21-07-2017
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 2021
Publisher: MDPI AG
Date: 23-06-2021
DOI: 10.3390/ELECTRONICS10131519
Abstract: The emergence of unmanned aerial vehicles (also referred to as drones) has transformed the digital landscape of surveillance and supply chain logistics, especially in terrains where such was previously deemed unattainable. Moreover, the adoption of drones has further led to the proliferation of erse drone types and drone-related criminality, which has introduced a myriad of security and forensics-related concerns. As a step towards understanding the state-of-the-art research into these challenges and potential approaches to mitigation, this study provides a detailed review of existing digital forensic models using the Design Science Research method. The outcome of this study generated in-depth knowledge of the research challenges and opportunities through which an effective investigation can be carried out on drone-related incidents. Furthermore, a potential generic investigation model has been proposed. The findings presented in this study are essentially relevant to forensic researchers and practitioners towards a guided methodology for drone-related event investigation. Ultimately, it is important to mention that this study presents a background for the development of international standardization for drone forensics.
Publisher: Springer Science and Business Media LLC
Date: 12-04-2022
Publisher: American Astronomical Society
Date: 10-09-2004
DOI: 10.1086/422830
Publisher: Public Library of Science (PLoS)
Date: 28-12-2012
Publisher: Oxford University Press (OUP)
Date: 07-1993
Publisher: Computers, Materials and Continua (Tech Science Press)
Date: 2022
Publisher: AIP
Date: 2008
DOI: 10.1063/1.2973562
Publisher: Elsevier BV
Date: 04-2016
DOI: 10.1016/J.NEURON.2016.03.006
Abstract: For goal-directed action to remain adaptive, new strategies are required to accommodate environmental changes, a process for which parafascicular thalamic modulation of cholinergic interneurons in the striatum (PF-to-CIN) appears critical. In the elderly, however, previously acquired experience frequently interferes with new learning, yet the source of this effect has remained unexplored. Here, combining sophisticated behavioral designs, cell-specific manipulation, and extensive neuronal imaging, we investigated the involvement of the PF-to-CIN pathway in this process. We found functional alterations of this circuit in aged mice that were consistent with their incapacity to update initial goal-directed learning, resulting in faulty activation of projection neurons in the striatum. Toxicogenetic ablation of CINs in young mice reproduced these behavioral and neuronal defects, suggesting that age-related deficits in PF-to-CIN function reduce the ability of older in iduals to resolve conflict between actions, likely contributing to impairments in adaptive goal-directed action and executive control in aging. VIDEO ABSTRACT.
Publisher: IEEE
Date: 15-06-2021
Publisher: Elsevier BV
Date: 05-2021
Publisher: IAEME Publication Chennai
Date: 15-01-2021
Publisher: SPIE
Date: 26-02-2003
DOI: 10.1117/12.460259
Publisher: American Astronomical Society
Date: 10-1997
DOI: 10.1086/313045
Publisher: American Astronomical Society
Date: 25-02-2010
Publisher: Oxford University Press (OUP)
Date: 24-04-2018
Publisher: IEEE
Date: 15-06-2021
Publisher: Springer Science and Business Media LLC
Date: 09-02-2023
Publisher: Oxford University Press (OUP)
Date: 21-09-2008
Publisher: American Astronomical Society
Date: 05-07-2013
Publisher: American Astronomical Society
Date: 04-10-2018
Publisher: eLife Sciences Publications, Ltd
Date: 23-10-2017
DOI: 10.7554/ELIFE.29908
Abstract: The acquisition of motor skills involves implementing action sequences that increase task efficiency while reducing cognitive loads. This learning capacity depends on specific cortico-basal ganglia circuits that are affected by normal ageing. Here, combining a series of novel behavioural tasks with extensive neuronal mapping and targeted cell manipulations in mice, we explored how ageing of cortico-basal ganglia networks alters the microstructure of action throughout sequence learning. We found that, after extended training, aged mice produced shorter actions and displayed squeezed automatic behaviours characterised by ultrafast oligomeric action chunks that correlated with deficient reorganisation of corticostriatal activity. Chemogenetic disruption of a striatal subcircuit in young mice reproduced age-related within-sequence features, and the introduction of an action-related feedback cue temporarily restored normal sequence structure in aged mice. Our results reveal static properties of aged cortico-basal ganglia networks that introduce temporal limits to action automaticity, something that can compromise procedural learning in ageing.
Publisher: American Astronomical Society
Date: 13-01-2011
Publisher: Elsevier BV
Date: 06-2020
Publisher: Cambridge University Press (CUP)
Date: 2011
DOI: 10.1071/AS11008
Abstract: We present VLA 21-cm observations of the spiral galaxy ESO 481-G017 to determine the nature of remote star formation traced by an H ii region found 43 kpc and ∼800 km s −1 from the galaxy center (in projection). ESO 481-G017 is found to have a 120 kpc H i disk with a mass of 1.2 × 10 10 M ⊙ and UV GALEX images reveal spiral arms extending into the gaseous disk. Two dwarf galaxies with H i masses close to 10 8 M ⊙ are detected at distances of ∼200 kpc from ESO 481-G017 and a H i cloud with a mass of 6 × 10 7 M ⊙ is found near the position and velocity of the remote H ii region. The H ii region is somewhat offset from the H i cloud spatially and there is no link to ESO 481-G017 or the dwarf galaxies. We consider several scenarios for the origin of the cloud and H ii region and find the most likely is a dwarf galaxy that is undergoing ram pressure stripping. The H i mass of the cloud and H i luminosity of the H ii region (10 38.1 erg s −1 ) are consistent with dwarf galaxy properties, and the stripping can trigger the star formation as well as push the gas away from the stars.
Publisher: Oxford University Press (OUP)
Date: 11-1998
Publisher: American Astronomical Society
Date: 19-02-2013
Publisher: American Astronomical Society
Date: 20-08-2009
Publisher: American Astronomical Society
Date: 20-09-2002
DOI: 10.1086/342151
Publisher: American Physical Society (APS)
Date: 19-08-2021
Publisher: MDPI AG
Date: 13-04-2022
DOI: 10.3390/S22082976
Abstract: Emotions are an essential part of daily human communication. The emotional states and dynamics of the brain can be linked by electroencephalography (EEG) signals that can be used by the Brain–Computer Interface (BCI), to provide better human–machine interactions. Several studies have been conducted in the field of emotion recognition. However, one of the most important issues facing the emotion recognition process, using EEG signals, is the accuracy of recognition. This paper proposes a deep learning-based approach for emotion recognition through EEG signals, which includes data selection, feature extraction, feature selection and classification phases. This research serves the medical field, as the emotion recognition model helps diagnose psychological and behavioral disorders. The research contributes to improving the performance of the emotion recognition model to obtain more accurate results, which, in turn, aids in making the correct medical decisions. A standard pre-processed Database of Emotion Analysis using Physiological signaling (DEAP) was used in this work. The statistical features, wavelet features, and Hurst exponent were extracted from the dataset. The feature selection task was implemented through the Binary Gray Wolf Optimizer. At the classification stage, the stacked bi-directional Long Short-Term Memory (Bi-LSTM) Model was used to recognize human emotions. In this paper, emotions are classified into three main classes: arousal, valence and liking. The proposed approach achieved high accuracy compared to the methods used in past studies, with an average accuracy of 99.45%, 96.87% and 99.68% of valence, arousal, and liking, respectively, which is considered a high performance for the emotion recognition model.
Publisher: Oxford University Press (OUP)
Date: 23-11-2015
Publisher: Cold Spring Harbor Laboratory
Date: 29-03-2022
DOI: 10.1101/2022.03.28.486040
Abstract: Performing several actions in swift succession is often necessary to exploit known contingencies in the environment. However, in order to remain successful when contingency rules change, streamlined action sequences must be adaptable. Here, by combining analyses of behavioural microstructure with circuit-specific manipulation in mice, we report on a relationship between action timing variability and successful adaptation that relies on post-synaptic targets of primary motor cortical (M1) projections to dorsolateral striatum (DLS). Using a two-lever instrumental task, we found that mice build successful action sequences by first establishing action scaffolds, from which they dynamically elongate as task requirements extend. Specific interruption of the M1→DLS circuit altered these dynamics, prompting actions that were less variable in their timing, overall reducing opportunities for success. Our results reveal a role for M1→DLS circuitry in setting the exploration/exploitation balance that is required for adaptively guiding the timing and success of instrumental action. Based on evidence from transsynaptic tracing experiments, we propose that such function may involve additional downstream subcortical processing relating to collateralisation of descending motor pathways to multiple basal ganglia centres.
Publisher: Oxford University Press (OUP)
Date: 15-04-1993
Publisher: Elsevier BV
Date: 09-2017
Publisher: Oxford University Press (OUP)
Date: 12-06-2018
Publisher: Oxford University Press (OUP)
Date: 07-01-2013
DOI: 10.1093/MNRAS/STS524
Publisher: MDPI AG
Date: 31-03-2021
DOI: 10.3390/SU13073870
Abstract: This study aims to develop a new approach based on machine learning techniques to assess sustainability performance. Two main dimensions of sustainability, ecological sustainability, and human sustainability, were considered in this study. A set of sustainability indicators was used, and the research method in this study was developed using cluster analysis and prediction learning techniques. A Self-Organizing Map (SOM) was applied for data clustering, while Classification and Regression Trees (CART) were applied to assess sustainability performance. The proposed method was evaluated through Sustainability Assessment by Fuzzy Evaluation (SAFE) dataset, which comprises various indicators of sustainability performance in 128 countries. Eight clusters from the data were found through the SOM clustering technique. A prediction model was found in each cluster through the CART technique. In addition, an ensemble of CART was constructed in each cluster of SOM to increase the prediction accuracy of CART. All prediction models were assessed through the adjusted coefficient of determination approach. The results demonstrated that the prediction accuracy values were high in all CART models. The results indicated that the method developed by ensembles of CART and clustering provide higher prediction accuracy than in idual CART models. The main advantage of integrating the proposed method is its ability to automate decision rules from big data for prediction models. The method proposed in this study could be implemented as an effective tool for sustainability performance assessment.
Publisher: The World Academy of Research in Science and Engineering
Date: 15-02-2021
DOI: 10.30534/IJETER/2021/16922021
Abstract: Severalstudies stated that Computer Science (CS) students at Saudi Arabia universities face difficulties in programming languages learning (PLL) and need more assistance. Fortunately, Massive Open Online Courses (MOOCs) have been recognized as modern meansthat could be acceptable amongst CS learners. This piece of research aims to clarify the importance of enhancing PLL via MOOCs in Saudi Arabia. This research applied a quantitative research approach that utilized questionnaire as a research instrument. The survey was distributed among CS students to illustrate the current situation of the students’ need and acceptance of MOOCs on PLL. The investigation included 132 participants from different departments in the faulty of Computer Science (CS) at Umm Alqura University and Taif University in Saudi Arabia. The questionnaire results show that 98% believe that they need additional courses in PLL and 94% are accepting the idea of utilizing MOOCs on PLL, on the other hand, the results also show that 77% of the participants have not attended a single PLL course via MOOC. Other results and future research are discussed as wel
Publisher: Elsevier BV
Date: 06-2012
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 2021
Publisher: Springer Science and Business Media LLC
Date: 02-09-2009
Publisher: Oxford University Press (OUP)
Date: 27-03-2018
DOI: 10.1093/MNRAS/STY792
Publisher: Oxford University Press (OUP)
Date: 09-03-2018
DOI: 10.1093/MNRAS/STY275
Publisher: American Astronomical Society
Date: 22-07-2013
Publisher: IEEE
Date: 15-06-2021
Publisher: Oxford University Press (OUP)
Date: 20-11-2013
Publisher: Springer Science and Business Media LLC
Date: 08-2021
DOI: 10.1140/EPJC/S10052-021-09402-3
Abstract: Jet energy scale and resolution measurements with their associated uncertainties are reported for jets using 36–81 fb $$^{-1}$$ - 1 of proton–proton collision data with a centre-of-mass energy of $$\sqrt{s}=13$$ s = 13 $${\text {Te}}{\text {V}}$$ TeV collected by the ATLAS detector at the LHC. Jets are reconstructed using two different input types: topo-clusters formed from energy deposits in calorimeter cells, as well as an algorithmic combination of charged-particle tracks with those topo-clusters, referred to as the ATLAS particle-flow reconstruction method. The anti- $$k_t$$ k t jet algorithm with radius parameter $$R=0.4$$ R = 0.4 is the primary jet definition used for both jet types. This result presents new jet energy scale and resolution measurements in the high pile-up conditions of late LHC Run 2 as well as a full calibration of particle-flow jets in ATLAS. Jets are initially calibrated using a sequence of simulation-based corrections. Next, several in situ techniques are employed to correct for differences between data and simulation and to measure the resolution of jets. The systematic uncertainties in the jet energy scale for central jets ( $$|\eta | .2$$ | η | 1.2 ) vary from 1% for a wide range of high- $$p_{{\text {T}}}$$ p T jets ( $$250 _{{\text {T}}} ~{\text {Ge}}{\text {V}}$$ 250 p T 2000 GeV ), to 5% at very low $$p_{{\text {T}}}$$ p T ( $$20~{\text {Ge}}{\text {V}}$$ 20 GeV ) and 3.5% at very high $$p_{{\text {T}}}$$ p T ( $$ .5~{\text {Te}}{\text {V}}$$ 2.5 TeV ). The relative jet energy resolution is measured and ranges from ( $$24 \pm 1.5$$ 24 ± 1.5 )% at 20 $${\text {Ge}}{\text {V}}$$ GeV to ( $$6 \pm 0.5$$ 6 ± 0.5 )% at 300 $${\text {Ge}}{\text {V}}$$ GeV .
Publisher: American Astronomical Society
Date: 18-02-2015
Publisher: Elsevier BV
Date: 09-2021
Publisher: Cambridge University Press (CUP)
Date: 12-2007
DOI: 10.1017/S1743921308020735
Abstract: We examine the fate of ionizing radiation from massive stars on global scales. First, we compare the observed Hα luminosities of LMC H ii regions with those predicted by the latest generation of stellar atmosphere models. Our results imply that classical H ii regions are on average radiation-bounded, rather than density-bounded, as we found a decade ago. This is likely to necessitate an additional ionizing source for the diffuse, warm ionized medium (WIM) in galaxies. Secondly, we present new results from the SINGG Hα galaxy survey, showing that starburst galaxies have a lower fraction of WIM emission than normal star-forming galaxies. The most intriguing and consequential possible cause for this effect is the escape of ionizing radiation from starbursts. We show that the observations are also consistent with our predictions for the escape of ionizing radiation. Nevertheless, other observations do not necessarily support this scenario and other possible explanations must be considered.
Publisher: American Astronomical Society
Date: 06-2007
DOI: 10.1086/517867
Publisher: American Astronomical Society
Date: 17-01-2005
DOI: 10.1086/425251
Publisher: Cambridge University Press (CUP)
Date: 08-2006
DOI: 10.1017/S1743921307002815
Abstract: Intergalactic HII regions, far from the confines of a galactic disk, represent a mode of star formation in low-density gas outside of galaxies. The figure below (left) shows an R-band continuum image of NGC 1533 from the SINGG Hα survey (Meurer et al . 2006) overlaid with HI contours and the location of three intergalactic HII regions discovered by Ryan-Weber et al . (2004). The HI contours are 1.6, 2.0, 2.4, 2.8, 3.2 and 4.0 ×10 20 cm −2 and have a resolution of ~1′. ACS/HRC images of the intergalactic HII regions (right) are composites of UV, V, and I bands. The half-light radii of the clusters associated with regions 1, 2, and 5 are 24.7, 21.7, and 17.0 pc, respectively, at the distance to NGC 1533 (21 Mpc Tonry et al . 2001). Assuming a Salpeter IMF with M up = 100, Hα/UV ratios indicate a small number of ionizing O stars relative to the total number of UV-emitting O and B stars. These young (4-6 Myr), intergalactic stellar populations lend valuable insight to our understanding of the methods by which star formation is triggered and may even represent the first episodes of star formation in emerging galaxies.
Publisher: American Astronomical Society
Date: 03-2004
DOI: 10.1086/381905
Publisher: Society for Neuroscience
Date: 22-01-2014
DOI: 10.1523/JNEUROSCI.4592-13.2014
Abstract: Decision-making depends on the ability to extract predictive information from the environment to guide future actions. Outcome-specific Pavlovian-instrumental transfer (PIT) provides an animal model of this process in which a stimulus predicting a particular outcome biases choice toward actions earning that outcome. Recent evidence suggests that cellular adaptations of δ-opioid receptors (DORs) on cholinergic interneurons (CINs) in the nucleus accumbens shell (NAc-S) are necessary for PIT. Here we found that modulation of DORs in CINs critically influences D 1 -receptor (D1R)-expressing projection neurons in the NAc-S to promote PIT. First, we assessed PIT-induced changes in signaling processes in dopamine D 1 - and D 2 -receptor-expressing neurons using drd2 -eGFP mice, and found that PIT-related signaling was restricted to non-D2R-eGFP-expressing neurons, suggesting major involvement of D1R-neurons. Next we confirmed the role of D1Rs pharmacologically: the D1R antagonist SCH-23390, but not the D2R antagonist raclopride, infused into the NAc-S abolished PIT in rats, an effect that depended on DOR activity. Moreover, asymmetrical infusion of SCH-23390 and the DOR antagonist naltrindole into the NAc-S also abolished PIT. DOR agonists were found to sensitize the firing responses of CINs in brain slices prepared immediately after the PIT test. We confirmed the opioid-acetylcholinergic influence over D1R-neurons by selectively blocking muscarinic M4 receptors in the NAc-S, which tightly regulate the activity of D1Rs, a treatment that rescued the deficit in PIT induced by naltrindole. We describe a model of NAc-S function in which DORs modulate CINs to influence both D1R-neurons and stimulus-guided choice between goal-directed actions.
Publisher: American Astronomical Society
Date: 13-03-2008
Publisher: American Physical Society (APS)
Date: 18-08-2023
Publisher: American Astronomical Society
Date: 1992
DOI: 10.1086/116041
Publisher: American Astronomical Society
Date: 07-2006
DOI: 10.1086/504685
Publisher: American Astronomical Society
Date: 06-1994
DOI: 10.1086/117013
Publisher: Springer Science and Business Media LLC
Date: 11-07-2022
DOI: 10.1140/EPJC/S10052-022-10472-0
Abstract: This paper presents studies of Bose–Einstein correlations (BEC) in proton–proton collisions at a centre-of-mass energy of 13 TeV, using data from the ATLAS detector at the CERN Large Hadron Collider. Data were collected in a special low-luminosity configuration with a minimum-bias trigger and a high-multiplicity track trigger, accumulating integrated luminosities of 151 $$\upmu $$ μ b $$^{-1}$$ - 1 and 8.4 nb $$^{-1}$$ - 1 , respectively. The BEC are measured for pairs of like-sign charged particles, each with $$|\eta | 2.5$$ | η | 2.5 , for two kinematic ranges: the first with particle $$p_{\mathrm {T}} 100$$ p T 100 MeV and the second with particle $$p_{\mathrm {T}} 500$$ p T 500 MeV. The BEC parameters, characterizing the source radius and particle correlation strength, are investigated as functions of charged-particle multiplicity (up to 300) and average transverse momentum of the pair (up to 1.5 GeV). The double-differential dependence on charged-particle multiplicity and average transverse momentum of the pair is also studied. The BEC radius is found to be independent of the charged-particle multiplicity for high charged-particle multiplicity (above 100), confirming a previous observation at lower energy. This saturation occurs independent of the transverse momentum of the pair.
Publisher: American Astronomical Society
Date: 10-06-1997
DOI: 10.1086/304139
Publisher: American Astronomical Society
Date: 20-09-2006
DOI: 10.1086/504681
Publisher: Springer International Publishing
Date: 2016
Publisher: American Astronomical Society
Date: 10-08-1999
DOI: 10.1086/307523
Publisher: Physical Education and Sport Faculty
Date: 31-08-2021
Publisher: Cold Spring Harbor Laboratory
Date: 22-03-2021
DOI: 10.1101/2021.03.22.436417
Abstract: Psychostimulants such as hetamine target dopamine neuron synapses to engender drug-induced plasticity. While dopamine neurons modulate the activity of striatal cholinergic interneurons (ChIs) with regional heterogeneity, how hetamine affects ChI activity has not been elucidated. Here, we applied quantitative fluorescence imaging approaches to map the dose-dependent effects of a single dose of hetamine on ChI activity at 2.5 and 24 hours after injection across the mouse striatum using the activity-dependent marker phosphorylated ribosomal protein S6 (p-rpS6). We found that hetamine did not induce neurotoxic effects on ChIs, as their distribution and morphology were not affected. While low- or high-dose hetamine did not affect ChI activity after 2.5 hours, ChI activity was significantly reduced in all striatal subregions after 24 hours, with a dose-dependent effect in the nucleus accumbens. Thus, our findings suggest that a single dose of hetamine has delayed regionally heterogeneous effects on ChI activity. Using the activity dependent marker phosphorylated ribosomal protein S6 (p-rpS6), we mapped hetamine effects on the activity of cholinergic interneurons (ChIs) across the striatum. Amphetamine caused a delayed attenuation of ChI activity in all striatal subregions, and a dose-dependent effect in the ventral striatum/nucleus accumbens, a critical site of psychostimulant action.
Publisher: American Astronomical Society
Date: 20-09-1998
DOI: 10.1086/306154
Publisher: American Astronomical Society
Date: 11-1997
DOI: 10.1086/118609
Publisher: Elsevier BV
Date: 07-2013
Publisher: American Astronomical Society
Date: 05-2022
Abstract: In the local universe, OH megamasers (OHMs) are detected almost exclusively in infrared-luminous galaxies, with a prevalence that increases with IR luminosity, suggesting that they trace gas-rich galaxy mergers. Given the proximity of the rest frequencies of OH and the hyperfine transition of neutral atomic hydrogen (H i ), radio surveys to probe the cosmic evolution of H i in galaxies also offer exciting prospects for exploiting OHMs to probe the cosmic history of gas-rich mergers. Using observations for the Looking At the Distant Universe with the MeerKAT Array (LADUMA) deep H i survey, we report the first untargeted detection of an OHM at z 0.5, LADUMA J033046.20−275518.1 (nicknamed “Nkalakatha”). The host system, WISEA J033046.26−275518.3, is an infrared-luminous radio galaxy whose optical redshift z ≈ 0.52 confirms the MeerKAT emission-line detection as OH at a redshift z OH = 0.5225 ± 0.0001 rather than H i at lower redshift. The detected spectral line has 18.4 σ peak significance, a width of 459 ± 59 km s −1 , and an integrated luminosity of (6.31 ± 0.18 [statistical] ± 0.31 [systematic]) × 10 3 L ⊙ , placing it among the most luminous OHMs known. The galaxy’s far-infrared luminosity L FIR = (1.576 ±0.013) × 10 12 L ⊙ marks it as an ultraluminous infrared galaxy its ratio of OH and infrared luminosities is similar to those for lower-redshift OHMs. A comparison between optical and OH redshifts offers a slight indication of an OH outflow. This detection represents the first step toward a systematic exploitation of OHMs as a tracer of galaxy growth at high redshifts.
Publisher: Cold Spring Harbor Laboratory
Date: 15-09-2022
DOI: 10.1101/2022.09.14.508004
Abstract: Multidisciplinary evidence suggests that instrumental performance is governed by two major forms of behavioural control: goal-directed and autonomous processes. Brain-state abnormalities affecting the striatum, such as ageing, often shift control towards autonomous—habit-like—behaviour, although the neural mechanisms responsible for this shift remain unknown. Here, combining instrumental conditioning with cell-specific functional mapping and manipulation in striatal neurons, we explored strategies that invigorate goal-directed action capacity in aged mice. In animals performing instrumental actions, D2- and D1-neurons of the aged striatum were engaged in a characteristically counterbalanced manner, something that related to the propensity to express autonomous behaviour. Long-lasting, cell-specific desensitisation of D2-neurons in aged transgenic mice recapitulated the uneven D2-to D1-neuron functional correspondence observed in young mice, an effect that enabled successful goal-directed action. Our findings contribute to the understanding of the neural bases of behavioural control and propose neural system interventions that enhance cognitive functioning in habit-prone brains.
Publisher: American Astronomical Society
Date: 29-03-2019
Publisher: Springer Science and Business Media LLC
Date: 1989
DOI: 10.1007/BF00646358
Publisher: American Astronomical Society
Date: 04-2002
DOI: 10.1086/339165
Publisher: American Astronomical Society
Date: 10-05-2008
DOI: 10.1086/533523
Publisher: Elsevier BV
Date: 02-2021
Publisher: Public Library of Science (PLoS)
Date: 10-03-2009
Publisher: Elsevier BV
Date: 08-2021
Publisher: Cambridge University Press (CUP)
Date: 03-2016
DOI: 10.1017/S174392131601139X
Abstract: The HI in galaxies often extends past their conventionally defined optical extent. I report results from our team which has been probing low intensity star formation in outer disks using imaging in Hα and ultraviolet. Using a s le of hundreds of HI selected galaxies, we confirm that outer disk HII regions and extended UV disks are common. Hence outer disks are not dormant but are dimly forming stars. Although the ultraviolet light in galaxies is more centrally concentrated than the HI, the UV/HI ratio (the Star Formation Efficiency) is nearly constant, with a slight dependency on surface brightness. This result is well accounted for in a model where disks maintain a constant stability parameter Q. This model also accounts for how the ISM and star formation are distributed in the bright parts of galaxies, and how HI appears to trace the distribution of dark matter in galaxy outskirts.
Publisher: Oxford University Press (OUP)
Date: 07-07-2006
Publisher: Oxford University Press (OUP)
Date: 18-12-2014
Publisher: American Astronomical Society
Date: 10-12-2010
Publisher: ASCE
Date: 1999
DOI: 10.1063/1.58622
Publisher: American Astronomical Society
Date: 07-1997
DOI: 10.1086/118452
Location: United States of America
No related grants have been discovered for Gerhardt Meurer.