2,332 research outputs found
Single donor ionization energies in a nanoscale CMOS channel
One consequence of the continued downwards scaling of transistors is the
reliance on only a few discrete atoms to dope the channel, and random
fluctuations of the number of these dopants is already a major issue in the
microelectonics industry. While single-dopant signatures have been observed at
low temperature, studying the impact of only one dopant up to room temperature
requires extremely small lengths. Here, we show that a single arsenic dopant
dramatically affects the off-state behavior of an advanced microelectronics
field effect transistor (FET) at room temperature. Furthermore, the ionization
energy of this dopant should be profoundly modified by the close proximity of
materials with a different dielectric constant than the host semiconductor. We
measure a strong enhancement, from 54meV to 108meV, of the ionization energy of
an arsenic atom located near the buried oxide. This enhancement is responsible
for the large current below threshold at room temperature and therefore
explains the large variability in these ultra-scaled transistors. The results
also suggest a path to incorporating quantum functionalities into silicon CMOS
devices through manipulation of single donor orbitals
Hepatitis C virus cell-cell transmission and resistance to direct-acting antiviral agents
Hepatitis C virus (HCV) is transmitted between hepatocytes via classical cell entry but also uses direct cell-cell transfer to infect neighboring hepatocytes. Viral cell-cell transmission has been shown to play an important role in viral persistence allowing evasion from neutralizing antibodies. In contrast, the role of HCV cell-cell transmission for antiviral resistance is unknown. Aiming to address this question we investigated the phenotype of HCV strains exhibiting resistance to direct-acting antivirals (DAAs) in state-of-the-art model systems for cell-cell transmission and spread. Using HCV genotype 2 as a model virus, we show that cell-cell transmission is the main route of viral spread of DAA-resistant HCV. Cell-cell transmission of DAA-resistant viruses results in viral persistence and thus hampers viral eradication. We also show that blocking cell-cell transmission using host-targeting entry inhibitors (HTEIs) was highly effective in inhibiting viral dissemination of resistant genotype 2 viruses. Combining HTEIs with DAAs prevented antiviral resistance and led to rapid elimination of the virus in cell culture model. In conclusion, our work provides evidence that cell-cell transmission plays an important role in dissemination and maintenance of resistant variants in cell culture models. Blocking virus cell-cell transmission prevents emergence of drug resistance in persistent viral infection including resistance to HCV DAAs
Fully gapped topological surface states in BiSe films induced by a d-wave high-temperature superconductor
Topological insulators are a new class of materials, that exhibit robust
gapless surface states protected by time-reversal symmetry. The interplay
between such symmetry-protected topological surface states and symmetry-broken
states (e.g. superconductivity) provides a platform for exploring novel quantum
phenomena and new functionalities, such as 1D chiral or helical gapless
Majorana fermions, and Majorana zero modes which may find application in
fault-tolerant quantum computation. Inducing superconductivity on topological
surface states is a prerequisite for their experimental realization. Here by
growing high quality topological insulator BiSe films on a d-wave
superconductor BiSrCaCuO using molecular beam epitaxy,
we are able to induce high temperature superconductivity on the surface states
of BiSe films with a large pairing gap up to 15 meV. Interestingly,
distinct from the d-wave pairing of BiSrCaCuO, the
proximity-induced gap on the surface states is nearly isotropic and consistent
with predominant s-wave pairing as revealed by angle-resolved photoemission
spectroscopy. Our work could provide a critical step toward the realization of
the long sought-after Majorana zero modes.Comment: Nature Physics, DOI:10.1038/nphys274
Culturally relevant multimedia materials for oral health education in an ethnic minority group
Session GC - SEADDE Student GC Prevention Competition: abstract no. 3INTRODUCTION: In developed countries, the oral health of ethnic minority groups is often worse than that of the general public. In order to improve their oral health, the use of cultural relevant oral health education (OHE) materials delivered through multimedia approach is desirable. AIM: This project aimed to 1) design culturally relevant OHE materials; 2) deliver them through multimedia approach and 3) evaluate their usefulness in the Pakistani community in Hong Kong. MATERIALS AND METHOD: To gain a deep understanding on Pakistanis’ culture, lifestyles, oral health beliefs and the barriers for their access to dental service, a two-hour focus group discussion was conducted involving 9 Pakistani women. Two oral health pamphlets were designed. One focused on (a) causes, symptoms and signs, and preventive measures of tooth …postprin
Evaluation of the realism of an MRI simulator for stroke lesion prediction using convolutional neural network
Résumé en françai
The influence of PC6 on cardiovascular disorders: a review of central neural mechanisms
PC6 is a classic acupuncture point in traditional Chinese medicine. It is considered to be effective when treating cardiovascular disorders. In the present review the authors have focused on the neurophysiological bases of the effects of PC6 stimulation on cardiovascular mechanisms. Experimental studies have shown that the hypothalamic rostral ventrolateral medulla, arcuate nucleus and ventrolateral periaqueductal gray are involved in acupuncture attenuation of sympathoexcitatory cardiovascular reflex responses. This long-loop pathway also appears to contribute to the long-lasting, acupuncture-mediated attenuation of sympathetic premotor outflow and excitatory cardiovascular reflex responses. Acupuncture of PC6 modulates the activity in the cardiovascular system, an effect that may be attributed to attenuation of sympathoexcitatory cardiovascular reflex responses
Thermal Properties of Graphene, Carbon Nanotubes and Nanostructured Carbon Materials
Recent years witnessed a rapid growth of interest of scientific and
engineering communities to thermal properties of materials. Carbon allotropes
and derivatives occupy a unique place in terms of their ability to conduct
heat. The room-temperature thermal conductivity of carbon materials span an
extraordinary large range - of over five orders of magnitude - from the lowest
in amorphous carbons to the highest in graphene and carbon nanotubes. I review
thermal and thermoelectric properties of carbon materials focusing on recent
results for graphene, carbon nanotubes and nanostructured carbon materials with
different degrees of disorder. A special attention is given to the unusual size
dependence of heat conduction in two-dimensional crystals and, specifically, in
graphene. I also describe prospects of applications of graphene and carbon
materials for thermal management of electronics.Comment: Review Paper; 37 manuscript pages; 4 figures and 2 boxe
Molecular epidemiology of drug-resistant malaria in western Kenya highlands
<p>Abstract</p> <p>Background</p> <p>Since the late 1980s a series of malaria epidemics has occurred in western Kenya highlands. Among the possible factors that may contribute to the highland malaria epidemics, parasite resistance to antimalarials has not been well investigated.</p> <p>Methods</p> <p>Using parasites from highland and lowland areas of western Kenya, we examined key mutations associated with <it>Plasmodium falciparum </it>resistance to sulfadoxine – pyrimethamine and chloroquine, including dihydrofolate reductase (<it>pfdhfr</it>) and dihydropteroate synthetase (<it>pfdhps</it>), chloroquine resistance transporter gene (<it>pfcrt</it>), and multi-drug resistance gene 1 (<it>pfmdr1</it>).</p> <p>Results</p> <p>We found that >70% of samples harbored 76T <it>pfcrt </it>mutations and over 80% of samples harbored quintuple mutations (51I/59R/108N <it>pfdhfr </it>and 437G/540E <it>pfdhps</it>) in both highland and lowland samples. Further, we did not detect significant difference in the frequencies of these mutations between symptomatic and asymptomatic malaria volunteers, and between highland and lowland samples.</p> <p>Conclusion</p> <p>These findings suggest that drug resistance of malaria parasites in the highlands could be contributed by the mutations and their high frequencies as found in the lowland. The results are discussed in terms of the role of drug resistance as a driving force for malaria outbreaks in the highlands.</p
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