1,692 research outputs found
Permutation Polynomials modulo n
Based on preliminary numerical computations, we give complete results for linear and quadratic polynomials. Rivest’s result holds in the linear case while there are plenty of counterexamples in the quadratic case
Fabrication and characterization of thermally oxidized TiO2 thin films on Si(100) substrates
Mixed phase TiO2 is known to have better photocatalytic property as the resulting grain boundaries and interfaces between substrate, anatase and rutile phases play a crucial role in transferring/trapping photogenerated electrons. Here we have grown three different thicknesses (10 nm, 30 nm and 50 nm) of Ti thin films on Si(100) substrate in a sputter coater. Thermal oxidation in air at 600 °C for 1 h leads to the formation of mixed phase TiO2 thin films. Surface morphology and crystalline quality of thin film are discussed using XRD, SEM and TEM results. Moiré fringes resulting from interfacial strain have been discussed using lattice resolved HRTEM images
Oxidation mechanism in metal nanoclusters: Zn nanoclusters to ZnO hollow nanoclusters
Zn nanoclusters (NCs) are deposited by Low-energy cluster beam deposition
technique. The mechanism of oxidation is studied by analysing their
compositional and morphological evolution over a long span of time (three
years) due to exposure to ambient atmosphere. It is concluded that the
mechanism proceeds in two steps. In the first step, the shell of ZnO forms over
Zn NCs rapidly up to certain limiting thickness: with in few days -- depending
upon the size -- Zn NCs are converted to Zn-ZnO (core-shell), Zn-void-ZnO, or
hollow ZnO type NCs. Bigger than ~15 nm become Zn-ZnO (core-shell) type: among
them, NCs above ~25 nm could able to retain their initial geometrical shapes
(namely triangular, hexagonal, rectangular and rhombohedral), but ~25 to 15 nm
size NCs become irregular or distorted geometrical shapes. NCs between ~15 to 5
nm become Zn-void-ZnO type, and smaller than ~5 nm become ZnO hollow sphere
type i.e. ZnO hollow NCs. In the second step, all Zn-void-ZnO and Zn-ZnO
(core-shell) structures are converted to hollow ZnO NCs in a slow and gradual
process, and the mechanism of conversion proceeds through expansion in size by
incorporating ZnO monomers inside the shell. The observed oxidation behaviour
of NCs is compared with theory of Cabrera - Mott on low-temperature oxidation
of metal.Comment: 9 pages, 8 figure
A Stochastic Approach To Reconstruct Gamma Ray Burst Lightcurves
Gamma-Ray Bursts (GRBs), being observed at high redshift (z = 9.4), vital to
cosmological studies and investigating Population III stars. To tackle these
studies, we need correlations among relevant GRB variables with the requirement
of small uncertainties on their variables. Thus, we must have good coverage of
GRB light curves (LCs). However, gaps in the LC hinder the precise
determination of GRB properties and are often unavoidable. Therefore, extensive
categorization of GRB LCs remains a hurdle. We address LC gaps using a
'stochastic reconstruction,' wherein we fit two pre-existing models (Willingale
2007; W07 and Broken Power Law; BPL) to the observed LC, then use the
distribution of flux residuals from the original data to generate data to fill
in the temporal gaps. We also demonstrate a model-independent LC reconstruction
via Gaussian Processes. At 10% noise, the uncertainty of the end time of the
plateau, its correspondent flux, and the temporal decay index after the plateau
decreases, on average, by 33.3% 35.03%, and 43.32%, respectively for the W07,
and by 33.3%, 30.78%, 43.9% for the BPL. The slope of the plateau decreases by
14.76% in the BPL. After using the Gaussian Process technique, we see similar
trends of a decrease in uncertainty for all model parameters for both the W07
and BPL models. These improvements are essential for the application of GRBs as
standard candles in cosmology, for the investigation of theoretical models and
for inferring the redshift of GRBs with future machine learning analysis.Comment: 20 pages, 6 tables, 11 figure
Signatures of the disk-jet coupling in the Broad-line Radio Quasar 4C+74.26
Here we explore the disk-jet connection in the broad-line radio quasar
4C+74.26, utilizing the results of the multiwavelength monitoring of the
source. The target is unique in that its radiative output at radio wavelengths
is dominated by a moderately-beamed nuclear jet, at optical frequencies by the
accretion disk, and in the hard X-ray range by the disk corona. Our analysis
reveals a correlation (local and global significance of 96\% and 98\%,
respectively) between the optical and radio bands, with the disk lagging behind
the jet by days. We discuss the possible explanation for this,
speculating that the observed disk and the jet flux changes are generated by
magnetic fluctuations originating within the innermost parts of a truncated
disk, and that the lag is related to a delayed radiative response of the disk
when compared with the propagation timescale of magnetic perturbations along
relativistic outflow. This scenario is supported by the re-analysis of the
NuSTAR data, modelled in terms of a relativistic reflection from the disk
illuminated by the coronal emission, which returns the inner disk radius
. We discuss the global energetics in
the system, arguing that while the accretion proceeds at the Eddington rate,
with the accretion-related bolometric luminosity erg s , the jet total kinetic energy
erg s, inferred from the dynamical
modelling of the giant radio lobes in the source, constitutes only a small
fraction of the available accretion power.Comment: 9 pages and 6 figures, ApJ accepte
A recent survey of permutation trinomials over finite fields
Constructing permutation polynomials is a hot topic in the area of finite fields, and permutation polynomials have many applications in different areas. Recently, several classes of permutation trinomials were constructed. In 2015, Hou surveyed the achievements of permutation polynomials and novel methods. But, very few were known at that time. Recently, many permutation binomials and trinomials have been constructed. Here we survey the significant contribution made to the construction of permutation trinomials over finite fields in recent years. Emphasis is placed on significant results and novel methods. The covered material is split into three aspects: the existence of permutation trinomials of the respective forms , and , with Niho-type exponents
Agricultural innovation and adaptation to climate change: empirical evidence from diverse agro-ecologies in South Asia
While impacts of climate change on agricultural systems have been widely researched, there is still limited understanding of what agricultural practices evolves over time in response to both climatic and non-climatic drivers and how actors mobilize their resources, institutions and practices in South Asia. Through eight case studies and a survey of300 households in 15 locations in India, Nepal and Bangladesh, this paper generates empirical evidence on emerging agricultural interventions in contrasting socio-economic, geographical and agro-ecological contexts. The study shows that several farm practices emerge out in response to multiple drivers over time; some of them can be further adjusted to the challenge of climate change by planned adaptation programs. Most actors, however, have considered private risks in the short run. Although there has been some progress in streamlining climate change into strategic planning in different countries of South Asia, policy, research and extension systems lack adequate attention to wider resilience of the system. Based on this analysis, we recommend that adaptation policies should complement farmers’ responses to climate change through informed research and extension systems and pro-poor government policies that improve adaptation and coordinate activities of different actors
Association of Panton Valentine Leukocidin (PVL) genes with methicillin resistant Staphylococcus aureus (MRSA) in Western Nepal: a matter of concern for community infections (a hospital based prospective study)
BACKGROUND: Methicillin resistant Staphylococcus aureus (MRSA) is a major human pathogen associated with nosocomial and community infections. Panton Valentine leukocidin (PVL) is considered one of the important virulence factors of S. aureus responsible for destruction of white blood cells, necrosis and apoptosis and as a marker of community acquired MRSA. This study was aimed to determine the prevalence of PVL genes among MRSA isolates and to check the reliability of PVL as marker of community acquired MRSA isolates from Western Nepal. METHODS: A total of 400 strains of S. aureus were collected from clinical specimens and various units (Operation Theater, Intensive Care Units) of the hospital and 139 of these had been confirmed as MRSA by previous study. Multiplex PCR was used to detect mecA and PVL genes. Clinical data as well as antimicrobial susceptibility data was analyzed and compared among PVL positive and negative MRSA isolates. RESULTS: Out of 139 MRSA isolates, 79 (56.8 %) were PVL positive. The majority of the community acquired MRSA (90.4 %) were PVL positive (Positive predictive value: 94.9 % and negative predictive value: 86.6 %), while PVL was detected only in 4 (7.1 %) hospital associated MRSA strains. None of the MRSA isolates from hospital environment was found positive for the PVL genes. The majority of the PVL positive strains (75.5 %) were isolated from pus samples. Antibiotic resistance among PVL negative MRSA isolates was found higher as compared to PVL positive MRSA. CONCLUSION: Our study showed high prevalence of PVL among community acquired MRSA isolates. Absence of PVL among MRSA isolates from hospital environment indicates its poor association with hospital acquired MRSA and therefore, PVL may be used a marker for community acquired MRSA. This is first study from Nepal, to test PVL among MRSA isolates from hospital environment. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1186/s12879-016-1531-1) contains supplementary material, which is available to authorized users
Health and lifestyle of Nepalese migrants in the UK
Background: The health status and lifestyle of migrants is often poorer than that of the general
population of their host countries. The Nepalese represent a relatively small, but growing,
immigrant community in the UK, about whom very little is known in term of public health.
Therefore, our study examined the health and lifestyle of Nepalese migrants in the UK.
Methods: A cross-sectional survey of Nepalese migrants in UK was conducted in early 2007 using
a postal, self-administered questionnaire in England and Scotland (n = 312), and telephone
interviews in Wales (n = 15). The total response rate was 68% (327 out of 480). Data were analyzed
to establish whether there are associations between socio-economic and lifestyle factors. A
multivariate binary logistic regression was applied to find out independent effect of personal factors
on health status.
Results: The majority of respondents was male (75%), aged between 30 and 45 (66%), married or
had a civil partner (83%), had university education (47%) and an annual family income (69%) ranging
from £5,035 to £33,300. More than one third (39%) of the respondents have lived in the UK for 1
to 5 years and approximately half (46%) were longer-term residents. Most (95%) were registered
with a family doctor, but only 38% with a dentist. A low proportion (14%) of respondents smoked
but more than half (61%) consumed alcohol. More than half (57%) did not do regular exercises and
nearly one fourth (23%) of respondents rated their health as poor. Self reported 'good' health
status of the respondents was independently associated with immigration status and doing regular exercise
Conclusion: The self reported health status and lifestyle, health seeking behaviour of Nepalese
people who are residing in UK appears to be good. However, the overall regular exercise and dentist registration was rather poor. Health promotion, especially aimed at Nepalese migrants could help encourage them to exercise regularly and assist them to register with a dentist
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