89 research outputs found
Non-linear screening of external charge by doped graphene
We solve a nonlinear integral equation for the electrostatic potential in
doped graphene due to an external charge, arising from a Thomas-Fermi (TF)
model for screening by graphene's electron bands. In particular, we study
the effects of a finite equilibrium charge carrier density in graphene,
non-zero temperature, non-zero gap between graphene and a dielectric substrate,
as well as the nonlinearity in the band density of states. Effects of the
exchange and correlation interactions are also briefly discussed for undoped
graphene at zero temperature. Nonlinear results are compared with both the
linearized TF model and the dielectric screening model within random phase
approximation (RPA). In addition, image potential of the external charge is
evaluated from the solution of the nonlinear integral equation and compared to
the results of linear models. We have found generally good agreement between
the results of the nonlinear TF model and the RPA model in doped graphene,
apart from Friedel oscillations in the latter model. However, relatively strong
nonlinear effects are found in the TF model to persist even at high doping
densities and large distances of the external charge.Comment: 12 pages including 6 figure
Two-Stage Convolutional Neural Network for Breast Cancer Histology Image Classification
This paper explores the problem of breast tissue classification of microscopy
images. Based on the predominant cancer type the goal is to classify images
into four categories of normal, benign, in situ carcinoma, and invasive
carcinoma. Given a suitable training dataset, we utilize deep learning
techniques to address the classification problem. Due to the large size of each
image in the training dataset, we propose a patch-based technique which
consists of two consecutive convolutional neural networks. The first
"patch-wise" network acts as an auto-encoder that extracts the most salient
features of image patches while the second "image-wise" network performs
classification of the whole image. The first network is pre-trained and aimed
at extracting local information while the second network obtains global
information of an input image. We trained the networks using the ICIAR 2018
grand challenge on BreAst Cancer Histology (BACH) dataset. The proposed method
yields 95 % accuracy on the validation set compared to previously reported 77 %
accuracy rates in the literature. Our code is publicly available at
https://github.com/ImagingLab/ICIAR2018Comment: 10 pages, 5 figures, ICIAR 2018 conferenc
Optimized Microstrip Antennas with Metamaterial Superstrates Using Particle Swarm Optimization
Two new designs of compact microstrip antennas, where metamaterials are placed on structure as superstrate, are proposed. The newly designed metamaterial unit cell and antenna feed position optimized by particle swarm optimization. It was found that the characteristics of novel microstrip antennas with designed metamaterials placed on the superstrate are comparable to the conventional patch antennas, while their gain, directivity and radiating efficiency are noticeably improved. Gain of microstrip antenna is increased 3dB to 4dB and level of back lobe is decresed
A Field Guide to Pandemic, Epidemic and Sporadic Clones of Methicillin-Resistant Staphylococcus aureus
In recent years, methicillin-resistant Staphylococcus aureus
(MRSA) have become a truly global challenge. In addition to the long-known
healthcare-associated clones, novel strains have also emerged outside of the
hospital settings, in the community as well as in livestock. The emergence and
spread of virulent clones expressing Panton-Valentine leukocidin (PVL) is an
additional cause for concern. In order to provide an overview of pandemic,
epidemic and sporadic strains, more than 3,000 clinical and veterinary isolates
of MRSA mainly from Germany, the United Kingdom, Ireland, France, Malta, Abu
Dhabi, Hong Kong, Australia, Trinidad & Tobago as well as some reference
strains from the United States have been genotyped by DNA microarray analysis.
This technique allowed the assignment of the MRSA isolates to 34 distinct
lineages which can be clearly defined based on non-mobile genes. The results
were in accordance with data from multilocus sequence typing. More than 100
different strains were distinguished based on affiliation to these lineages,
SCCmec type and the presence or absence of PVL. These
strains are described here mainly with regard to clinically relevant
antimicrobial resistance- and virulence-associated markers, but also in relation
to epidemiology and geographic distribution. The findings of the study show a
high level of biodiversity among MRSA, especially among strains harbouring
SCCmec IV and V elements. The data also indicate a high
rate of genetic recombination in MRSA involving SCC elements, bacteriophages or
other mobile genetic elements and large-scale chromosomal replacements
A Field Guide to Pandemic, Epidemic and Sporadic Clones of Methicillin-Resistant Staphylococcus aureus
In recent years, methicillin-resistant Staphylococcus aureus
(MRSA) have become a truly global challenge. In addition to the long-known
healthcare-associated clones, novel strains have also emerged outside of the
hospital settings, in the community as well as in livestock. The emergence and
spread of virulent clones expressing Panton-Valentine leukocidin (PVL) is an
additional cause for concern. In order to provide an overview of pandemic,
epidemic and sporadic strains, more than 3,000 clinical and veterinary isolates
of MRSA mainly from Germany, the United Kingdom, Ireland, France, Malta, Abu
Dhabi, Hong Kong, Australia, Trinidad & Tobago as well as some reference
strains from the United States have been genotyped by DNA microarray analysis.
This technique allowed the assignment of the MRSA isolates to 34 distinct
lineages which can be clearly defined based on non-mobile genes. The results
were in accordance with data from multilocus sequence typing. More than 100
different strains were distinguished based on affiliation to these lineages,
SCCmec type and the presence or absence of PVL. These
strains are described here mainly with regard to clinically relevant
antimicrobial resistance- and virulence-associated markers, but also in relation
to epidemiology and geographic distribution. The findings of the study show a
high level of biodiversity among MRSA, especially among strains harbouring
SCCmec IV and V elements. The data also indicate a high
rate of genetic recombination in MRSA involving SCC elements, bacteriophages or
other mobile genetic elements and large-scale chromosomal replacements
Diversity of methicillin-resistant staphylococcus aureus strains isolated from residents of 26 nursing homes in orange county, california
Nursing homes represent a unique and important methicillin-resistant Staphylococcus aureus (MRSA) reservoir. Not only are strains imported from hospitals and the community, strains can be transported back into these settings from nursing homes. Since MRSA bacteria are prevalent in nursing homes and yet relatively poorly studied in this setting, a multicenter, regional assessment of the frequency and diversity of MRSA in the nursing home reservoir was carried out and compared to that of the MRSA from hospitals in the same region. The prospective study collected MRSA from nasal swabbing of residents of 26 nursing homes in Orange County, California, and characterized each isolate by spa typing. A total of 837 MRSA isolates were collected from the nursing homes. Estimates of admission prevalence and point prevalence of MRSA were 16% and 26%, respectively. The spa type genetic diversity was heterogeneous between nursing homes and significantly higher overall (77%) than the diversity in Orange County hospitals (72%). MRSA burden in nursing homes appears largely due to importation from hospitals. As seen in Orange County hospitals, USA300 (sequence type 8 [ST8]/t008), USA100 (ST5/t002), and a USA100 variant (ST5/t242) were the dominant MRSA clones in Orange County nursing homes, representing 83% of all isolates, although the USA100 variant was predominant in nursing homes, whereas USA300 was predominant in hospitals. Control strategies tailored to the complex problem of MRSA transmission and infection in nursing homes are needed in order to minimize the impact of this unique reservoir on the overall regional MRSA burden. Copyright © 2013, American Society for Microbiology. All Rights Reserved
Blood antioxidant levels and alterations of serum calcium and pH in hemodialysis patients
Background: The risk of atherosclerosis and cancer is high in hemodialysis (HD) patients. There is evidence that HD causes oxidative stress. However, the causative factors of oxidative stress are unknown. It has been suggested that HD imposes an additional oxidative stress on patients with chronic renal failure by activation of granulocytes on dialyzer membranes resulting in an imbalance between oxidants and antioxidants. In this regard, a number of reports, either measuring specific analytes or enzymes, or estimating the total antioxidant activity of the plasma have given contradictory and inconclusive results. To investigate the oxidative stress status in Iranian HD patients, in this study, we evaluated GSH and FRAP levels along with Ca and pH in the blood of these patients.Methods: Along with 20 healthy age and gender matched control subjects, 24 patients underwent dialysis, three times per week, for four hours in each session. Before and after dialysis, blood was taken for biochemical and liver function tests and to evaluate oxidative stress markers and measure Ca and pH levels.Results: There was a significant decrease in FRAP and GSH levels after dialysis compared to those before treatment. Dialysis caused an increase in pH and Ca levels compared to levels in control subjects after dialysis.Conclusion: In general, before dialysis, there is a balance between oxidants and antioxidants; however, due to higher levels of oxidants as well as the possible binding of antioxidants to the dialyzer membrane during dialysis, an imbalance occurs. The instability in the balance of oxidants and antioxidants may be the major cause of cellular oxidative damage found in HD patients. This study indicates that there is a significant level of oxidative stress in renal chronic patients and this stress is augmented by dialysis. Antioxidant therapy should be considered in these patients
Depositional environment of the Fort Member of the Jurasic Jaisalmer Formation (western Rajasthan, India), as revealed from lithofacies and grain-size analysis
Lithofacies and granulometric analysis were carried out to decipher the depositional environment of the Fort Member of the Jurassic Jaisalmer Formation. Based on field data nine lithofacies have been identified including trough cross-bedded sandstones, planar cross-bedded sandstones, matrix supported conglomerates, thinly bedded siltstone and sandstones, herringbone cross-bedded sandstones, wave rippled sandstones, laminated sandstones, hummocky cross-bedded sandstones, limestones and shales. Granulometric analysis of the sandstones samples has been carried out for their statistical and textural parameters. Bivariant plots of textural parameters such as graphic skewness versus graphic standard deviation and kewness versus standard deviation confirm the high energy (beach) origin of sandstones. These results suggest a wide spectrum of marine environments ranging from inner shelf to upper shoreface for the Fort Member sandstones
- …