895 research outputs found
Distribution of Spectral Lags in Gamma Ray Bursts
Using the data acquired in the Time To Spill (TTS) mode for long gamma-ray
bursts (GRBs) collected by the Burst and Transient Source Experiment on board
the Compton Gamma Ray Observatory (BATSE/CGRO), we have carefully measured
spectral lags in time between the low (25-55 keV) and high (110-320 keV) energy
bands of individual pulses contained in 64 multi-peak GRBs. We find that the
temporal lead by higher-energy gamma-ray photons (i.e., positive lags) is the
norm in this selected sample set of long GRBs. While relatively few in number,
some pulses of several long GRBs do show negative lags. This distribution of
spectral lags in long GRBs is in contrast to that in short GRBs. This apparent
difference poses challenges and constraints on the physical mechanism(s) of
producing long and short GRBs. The relation between the pulse peak count rates
and the spectral lags is also examined. Observationally, there seems to be no
clear evidence for systematic spectral lag-luminosity connection for pulses
within a given long GRB.Comment: 20 pages, 4 figure
A Molecular-Rotor Device for Nonvolatile High-Density Memory Applications
A novel memory device based on an electrically driven molecular rotor was fabricated and demonstrated to have
bistable switching effects. The device showed an on/off ratio of approximately 10^4, a read window of about 2.5 V, and retention performance of greater than 10^4 s. The analysis of the device I–V characteristics suggests the source of the observed switching effects to be the redox-induced ligand rotation around the copper metal center, which is consistent with the observed temperature dependence of the switching behavior. This organic monolayer
device holds a potential for nonvolatile high-density memory applications due to its scalability and reduced cost
Room temperature negative differential resistance of a monolayer molecular rotor device
An electrically driven molecular rotor device comprised of a monolayer of redox-active ligated copper compounds sandwiched between a gold electrode and a highly doped P+Si substrate was fabricated. Current-voltage spectroscopy revealed a temperature-dependent negative differential resistance (NDR) associated with the device. Time-dependent density functional theory suggests the source of the observed NDR to be redox-induced ligand rotation around the copper metal center, an explanation consistent with the proposed energy diagram of the device. An observed temperature dependence of the NDR behavior further supports this hypothesis
Contributions of prognostic factors to socioeconomic disparities in cancer survival : protocol for analysis of a cohort with linked data
Introduction Socioeconomic disparities in cancer survival have been reported in many developed countries, including Australia. Although some international studies have investigated the determinants of these socioeconomic disparities, most previous Australian studies have been descriptive, as only limited relevant data are generally available. Here, we describe a protocol for a study to use data from a large-scale Australian cohort linked with several other health-related databases to investigate several groups of factors associated with socioeconomic disparities in cancer survival in New South Wales (NSW), Australia, and quantify their contributions to the survival disparities. Methods and analysis The Sax Institute's 45 and Up Study participants completed a baseline questionnaire during 2006-2009. Those who were subsequently diagnosed with cancer of the colon, rectum, lung or female breast will be included. This study sample will be identified by linkage with NSW Cancer Registry data for 2006-2013, and their vital status will be determined by linking with cause of death records up to 31 December 2015. The study cohort will be divided into four groups based on each of the individual education level and an area-based socioeconomic measure. The treatment received will be obtained through linking with hospital records and Medicare and pharmaceutical claims data. Cox proportional hazards models will be fitted sequentially to estimate the percentage contributions to overall socioeconomic survival disparities of patient factors, tumour and diagnosis factors, and treatment variables. Ethics and dissemination This research is covered by ethical approval from the NSW Population and Health Services Research Ethics Committee. Results of the study will be disseminated to different interest groups and organisations through scientific conferences, social media and peer-reviewed articles
Eriodictyol protects skin cells from UVA irradiation-induced photodamage by inhibition of the MAPK signaling pathway
Solar UVA irradiation-generated reactive oxygen species (ROS) induces the expression of matrix metalloproteinase 1 (MMP-1), leading to photoaging, however the molecular mechanism remains unclear. In the present study, we found that eriodictyol remarkably reduces UVA-mediated ROS generation and protects the skin cells from oxidative damage and the ensuing cell death. Moreover eriodictyol pretreatment significantly down-regulates the UVA-induced MMP-1 expression, and lowers the inflammatory responses within the skin cells. Pretreatment with eriodictyol upregulates the expression of tissue inhibitory metalloproteinase 1 (TIMP-1) and collagen-I (COL-1) at the transcriptional level in a dose-dependent manner. UVA-induced phosphorylation levels of c-Jun N-terminal kinase (JNK), extracellular signal-regulated kinase (ERK) and p38 leading to increased MMP-1 expression are significantly reduced in eriodictyol-treated skin cells. In addition, eriodictyol pretreatment significantly suppresses inflammatory cytokines and inhibits the activation of MAPK signaling cascades in skin cells. Taken together, our results demonstrate that eriodictyol has both potent anti-inflammatory and anti-photoaging effects.</p
A Modified Scalar-Tensor-Vector Gravity Theory and the Constraint on its Parameters
A gravity theory called scalar-tensor-vector gravity (STVG) has been recently
developed and succeeded in solar system, astrophysical and cosmological scales
without dark matter [J. W. Moffat, J. Cosmol. Astropart. Phys. 03, 004 (2006)].
However, two assumptions have been used: (i) , where and
are and in the Schwarzschild coordinates (static and
spherically symmetric); (ii) scalar field in the solar system. These
two assumptions actually imply that the standard parametrized post-Newtonian
parameter . In this paper, we relax these two assumptions and study
STVG further by using the post-Newtonian (PN) approximation approach. With
abandoning the assumptions, we find in general cases of STVG.
Then, a version of modified STVG (MSTVG) is proposed through introducing a
coupling function of scalar field G: . We have derived the metric
and equations of motion (EOM) in 1PN for general matter without specific
equation of state and point masses firstly. Subsequently, the secular
periastron precession of binary pulsars in harmonic coordinates
is given. After discussing two PPN parameters ( and ) and two
Yukawa parameters ( and ), we use of four
binary pulsars data (PSR B1913+16, PSR B1534+12, PSR J0737-3039 and PSR
B2127+11C) to constrain the Yukawa parameters for MSTVG:
m and if
we fix .Comment: 39 pages, 4 figures, accepted by PR
Pair production of charged Higgs bosons in the Left-Right Twin Higgs model at the ILC and LHC
Left-Right twin Higgs(LRTH) model predicts the existence of a pair of charged
Higgs . In this paper, we study the production of the charged Higgs
bosons pair via the process at
the International Linear Collider(ILC). The numerical results show that the
production rates are at the level of several tens fb, this process can produce
the adequate distinct multi-jet final states and the SM background can be
efficiently reduced. We also discuss the charged Higgs boson pair production
via the process at the Large Hadron
Collider(LHC) and estimate there production rates. We find that, as long as the
charged Higgs bosons are not too heavy, they can be abundantly produced at the
LHC. The possible signatures of these new particles might be detected at the
ILC and LHC experiments.Comment: 15 pages, 5 figures, discussion extended, reference added, typos
fixed, revised version to be published in Eur.Phys.J.
Facilitating Memory for Novel Characters by Reducing Neural Repetition Suppression in the Left Fusiform Cortex
Gui Xue is with Beijing Normal University and University of Southern California, Leilei Mei is with Beijing Normal University and University of California Irvine, Chuansheng Chen is with University of California Irvine, Zhong-Lin Lu is with University of Southern California, Russell A. Poldrack is with UT Austin, Qi Dong is with Beijing Normal University.Background -- The left midfusiform and adjacent regions have been implicated in processing and memorizing familiar words, yet its role in memorizing novel characters has not been well understood. Methodology/Principal Findings -- Using functional MRI, the present study examined the hypothesis that the left midfusiform is also involved in memorizing novel characters and spaced learning could enhance the memory by enhancing the left midfusiform activity during learning. Nineteen native Chinese readers were scanned while memorizing the visual form of 120 Korean characters that were novel to the subjects. Each character was repeated four times during learning. Repetition suppression was manipulated by using two different repetition schedules: massed learning and spaced learning, pseudo-randomly mixed within the same scanning session. Under the massed learning condition, the four repetitions were consecutive (with a jittered inter-repetition interval to improve the design efficiency). Under the spaced learning condition, the four repetitions were interleaved with a minimal inter-repetition lag of 6 stimuli. Spaced learning significantly improved participants' performance during the recognition memory test administered one hour after the scan. Stronger left midfusiform and inferior temporal gyrus activities during learning (summed across four repetitions) were associated with better memory of the characters, based on both within- and cross-subjects analyses. Compared to massed learning, spaced learning significantly reduced neural repetition suppression and increased the overall activities in these regions, which were associated with better memory for novel characters. Conclusions/Significance -- These results demonstrated a strong link between cortical activity in the left midfusiform and memory for novel characters, and thus challenge the visual word form area (VWFA) hypothesis. Our results also shed light on the neural mechanisms of the spacing effect in memorizing novel characters.This study was supported by the Program for New Century Excellent Talents in University, the National Science Foundation (grant numbers BCS 0823624 and BCS 0823495), the National Institute of Health (grant number HD057884-01A2), and the 111 Project of China (B07008). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.Psycholog
Bi-Large Neutrino Mixing See-Saw Mass Matrix with Texture Zeros and Leptogenesis
We study constraints on neutrino properties from texture zeros in bi-large
mixing See-Saw mass matrix and also from leptogenesis. Texture zeros may occur
in the light (class a)) or in the heavy (class b)) neutrino mass matrices. Each
of these two classes has 5 different forms which can produce non-trivial three
generation mixing with at least one texture zero. We find that two types of
texture zero mass matrices in both class a) and class b) can be consistent with
present data on neutrino masses, mixing and produce the observed baryon
asymmetry of the universe. None of the neutrinos can have zero masses with the
lightest of the light neutrinos having a mass larger than about 0.039 eV for
class a) and 0.002 eV for class b). In these models although CKM CP violating
phase vanishes, non-zero Majorana phases, however, can exist and play an
important role in producing the observed baryon asymmetry in our universe
through leptogenesis mechanism. The requirement of producing the observed
baryon asymmetry can further distinguish different models and also restrict the
See-Saw scale to be in the range GeV.Comment: 21 pages, 7 figures revised version, some references added, to be
submitted to PR
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