154 research outputs found
Growth direction determination of a single RuO2 nanowire by polarized Raman spectroscopy
The dependence of band intensities in the Raman spectrum of individual single-crystal ruthenium dioxide (RuO2) nanowires on the angle between the plane of polarization of the exciting (and collected) light and the long axis of the nanowire, is shown to be a simple, complementary technique to high resolution transmission electron microscopy (HRTEM) for determining nanowire growth direction. We show that excellent agreement exists between what is observed and what is predicted for the polarization angle dependence of the intensities of the nanowires' E-g (525 cm(-1)) and the B-2g (714 cm(-1)) Raman bands, only by assuming that the nanowires grow along the (001) crystallographic direction, as confirmed by HRTEM.open9
Quantum computation of stopping power for inertial fusion target design
Stopping power is the rate at which a material absorbs the kinetic energy of
a charged particle passing through it -- one of many properties needed over a
wide range of thermodynamic conditions in modeling inertial fusion implosions.
First-principles stopping calculations are classically challenging because they
involve the dynamics of large electronic systems far from equilibrium, with
accuracies that are particularly difficult to constrain and assess in the
warm-dense conditions preceding ignition. Here, we describe a protocol for
using a fault-tolerant quantum computer to calculate stopping power from a
first-quantized representation of the electrons and projectile. Our approach
builds upon the electronic structure block encodings of Su et al. [PRX Quantum
2, 040332 2021], adapting and optimizing those algorithms to estimate
observables of interest from the non-Born-Oppenheimer dynamics of multiple
particle species at finite temperature. Ultimately, we report logical qubit
requirements and leading-order Toffoli costs for computing the stopping power
of various projectile/target combinations relevant to interpreting and
designing inertial fusion experiments. We estimate that scientifically
interesting and classically intractable stopping power calculations can be
quantum simulated with roughly the same number of logical qubits and about one
hundred times more Toffoli gates than is required for state-of-the-art quantum
simulations of industrially relevant molecules such as FeMoCo or P450
APOE-ε4 synergizes with sleep disruption to accelerate Aβ deposition and Aβ-associated tau seeding and spreading
Alzheimer\u27s disease (AD) is the most common cause of dementia. The APOE-ε4 allele of the apolipoprotein E (APOE) gene is the strongest genetic risk factor for late-onset AD. The APOE genotype modulates the effect of sleep disruption on AD risk, suggesting a possible link between apoE and sleep in AD pathogenesis, which is relatively unexplored. We hypothesized that apoE modifies Aβ deposition and Aβ plaque-associated tau seeding and spreading in the form of neuritic plaque-tau (NP-tau) pathology in response to chronic sleep deprivation (SD) in an apoE isoform-dependent fashion. To test this hypothesis, we used APPPS1 mice expressing human APOE-ε3 or -ε4 with or without AD-tau injection. We found that SD in APPPS1 mice significantly increased Aβ deposition and peri-plaque NP-tau pathology in the presence of APOE4 but not APOE3. SD in APPPS1 mice significantly decreased microglial clustering around plaques and aquaporin-4 (AQP4) polarization around blood vessels in the presence of APOE4 but not APOE3. We also found that sleep-deprived APPPS1:E4 mice injected with AD-tau had significantly altered sleep behaviors compared with APPPS1:E3 mice. These findings suggest that the APOE-ε4 genotype is a critical modifier in the development of AD pathology in response to SD
The Operator Product Expansion of N=4 SYM and the 4-point Functions of Supergravity
We give a detailed Operator Product Expansion interpretation of the results
for conformal 4-point functions computed from supergravity through the AdS/CFT
duality. We show that for an arbitrary scalar exchange in AdS(d+1) all the
power-singular terms in the direct channel limit (and only these terms) exactly
match the corresponding contributions to the OPE of the operator dual to the
exchanged bulk field and of its conformal descendents. The leading logarithmic
singularities in the 4-point functions of protected N=4 super-Yang Mills
operators (computed from IIB supergravity on AdS(5) X S(5) are interpreted as
O(1/N^2) renormalization effects of the double-trace products appearing in the
OPE. Applied to the 4-point functions of the operators Ophi ~ tr F^2 + ... and
Oc ~ tr FF~ + ..., this analysis leads to the prediction that the double-trace
composites [Ophi Oc] and [Ophi Ophi - Oc Oc] have anomalous dimension -16/N^2
in the large N, large g_{YM}^2 N limit. We describe a geometric picture of the
OPE in the dual gravitational theory, for both the power-singular terms and the
leading logarithms. We comment on several possible extensions of our results.Comment: 42 page
Attacking Recommender Systems with Augmented User Profiles
Recommendation Systems (RS) have become an essential part of many online
services. Due to its pivotal role in guiding customers towards purchasing,
there is a natural motivation for unscrupulous parties to spoof RS for profits.
In this paper, we study the shilling attack: a subsistent and profitable attack
where an adversarial party injects a number of user profiles to promote or
demote a target item. Conventional shilling attack models are based on simple
heuristics that can be easily detected, or directly adopt adversarial attack
methods without a special design for RS. Moreover, the study on the attack
impact on deep learning based RS is missing in the literature, making the
effects of shilling attack against real RS doubtful. We present a novel
Augmented Shilling Attack framework (AUSH) and implement it with the idea of
Generative Adversarial Network. AUSH is capable of tailoring attacks against RS
according to budget and complex attack goals, such as targeting a specific user
group. We experimentally show that the attack impact of AUSH is noticeable on a
wide range of RS including both classic and modern deep learning based RS,
while it is virtually undetectable by the state-of-the-art attack detection
model.Comment: CIKM 2020. 10 pages, 2 figure
Inhibition of Non-Homologous End Joining Repair Impairs Pancreatic Cancer Growth and Enhances Radiation Response
Pancreatic ductal adenocarcinoma (PDAC) is amongst the deadliest of human cancers, due to its late diagnosis as well as its intense resistance to currently available therapeutics. To identify mechanisms as to why PDAC are refractory to DNA damaging cytoxic chemotherapy and radiation, we performed a global interrogation of the DNA damage response of PDAC. We find that PDAC cells generally harbor high levels of spontaneous DNA damage. Inhibition of Non-Homologous End Joining (NHEJ) repair either pharmacologically or by RNAi resulted in a further accumulation of DNA damage, inhibition of growth, and ultimately apoptosis even in the absence of exogenous DNA damaging agents. In response to radiation, PDAC cells rely on the NHEJ pathway to rapidly repair DNA double strand breaks. Mechanistically, when NHEJ is inhibited there is a compensatory increase in Homologous Recombination (HR). Despite this upregulation of HR, DNA damage persists and cells are significantly more sensitive to radiation. Together, these findings support the incorporation of NHEJ inhibition into PDAC therapeutic approaches, either alone, or in combination with DNA damaging therapies such as radiation
The Long-Baseline Neutrino Experiment: Exploring Fundamental Symmetries of the Universe
The preponderance of matter over antimatter in the early Universe, the
dynamics of the supernova bursts that produced the heavy elements necessary for
life and whether protons eventually decay --- these mysteries at the forefront
of particle physics and astrophysics are key to understanding the early
evolution of our Universe, its current state and its eventual fate. The
Long-Baseline Neutrino Experiment (LBNE) represents an extensively developed
plan for a world-class experiment dedicated to addressing these questions. LBNE
is conceived around three central components: (1) a new, high-intensity
neutrino source generated from a megawatt-class proton accelerator at Fermi
National Accelerator Laboratory, (2) a near neutrino detector just downstream
of the source, and (3) a massive liquid argon time-projection chamber deployed
as a far detector deep underground at the Sanford Underground Research
Facility. This facility, located at the site of the former Homestake Mine in
Lead, South Dakota, is approximately 1,300 km from the neutrino source at
Fermilab -- a distance (baseline) that delivers optimal sensitivity to neutrino
charge-parity symmetry violation and mass ordering effects. This ambitious yet
cost-effective design incorporates scalability and flexibility and can
accommodate a variety of upgrades and contributions. With its exceptional
combination of experimental configuration, technical capabilities, and
potential for transformative discoveries, LBNE promises to be a vital facility
for the field of particle physics worldwide, providing physicists from around
the globe with opportunities to collaborate in a twenty to thirty year program
of exciting science. In this document we provide a comprehensive overview of
LBNE's scientific objectives, its place in the landscape of neutrino physics
worldwide, the technologies it will incorporate and the capabilities it will
possess.Comment: Major update of previous version. This is the reference document for
LBNE science program and current status. Chapters 1, 3, and 9 provide a
comprehensive overview of LBNE's scientific objectives, its place in the
landscape of neutrino physics worldwide, the technologies it will incorporate
and the capabilities it will possess. 288 pages, 116 figure
The Rapid ASKAP Continuum Survey I: Design and First Results
The Rapid ASKAP Continuum Survey (RACS) is the first large-area survey to be
conducted with the full 36-antenna Australian Square Kilometre Array Pathfinder
(ASKAP) telescope. RACS will provide a shallow model of the ASKAP sky that will
aid the calibration of future deep ASKAP surveys. RACS will cover the whole sky
visible from the ASKAP site in Western Australia, and will cover the full ASKAP
band of MHz. The RACS images are generally deeper than the existing
NRAO VLA Sky Survey (NVSS) and Sydney University Molonglo Sky Survey (SUMSS)
radio surveys and have better spatial resolution. All RACS survey products will
be public, including radio images (with arcsecond resolution) and
catalogues of about three million source components with spectral index and
polarisation information. In this paper, we present a description of the RACS
survey and the first data release of 903 images covering the sky south of
declination made over a 288 MHz band centred at 887.5 MHz.Comment: 24 pages, 17 figures, 4 tables. For associated data see
https://data.csiro.au/collections/domain/casdaObservation/results/PRAS110%20-%20The%20Rapid%20ASKAP%20Continuu
Genome Sequences of Streptomyces Phages Amela and Verse
This article describes Amela and Verse, two Streptomyces phages isolated by enrichment on Streptomyces venezuelae (ATCC 10712) from two different soil samples
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