2,993 research outputs found
Three-potential formalism for the three-body scattering problem with attractive Coulomb interactions
A three-body scattering process in the presence of Coulomb interaction can be
decomposed formally into a two-body single channel, a two-body multichannel and
a genuine three-body scattering. The corresponding integral equations are
coupled Lippmann-Schwinger and Faddeev-Merkuriev integral equations. We solve
them by applying the Coulomb-Sturmian separable expansion method. We present
elastic scattering and reaction cross sections of the system both below
and above the threshold. We found excellent agreements with previous
calculations in most cases.Comment: 12 pages, 3 figure
Experimental investigation of the radial structure of energetic particle driven modes
Alfv\'en eigenmodes (AEs) and energetic particle modes (EPMs) are often
excited by energetic particles (EPs) in tokamak plasmas. One of the main open
questions concerning EP driven instabilities is the non-linear evolution of the
mode structure. The aim of the present paper is to investigate the properties
of beta-induced AEs (BAEs) and EP driven geodesic acoustic modes (EGAMs)
observed in the ramp-up phase of off-axis NBI heated ASDEX Upgrade (AUG)
discharges. This paper focuses on the changes in the mode structure of
BAEs/EGAMs during the non-linear chirping phase. Our investigation has shown
that in case of the observed down-chirping BAEs the changes in the radial
structure are smaller than the uncertainty of our measurement. This behaviour
is most probably the consequence of that BAEs are normal modes, thus their
radial structure strongly depends on the background plasma parameters rather
than on the EP distribution. In the case of rapidly upward chirping EGAMs the
analysis consistently shows shrinkage of the mode structure. The proposed
explanation is that the resonance in the velocity space moves towards more
passing particles which have narrower orbit widths.Comment: submitted to Nuclear Fusio
Analysis and Design of Computer Networks Using a Web-Based DSS
Analyzing the performance of computer networks to improve their overall performance requires accounting for a large variety of inputs and operating characteristics, such as packet flow rates and sizes, device capabilities and interconnection capacities. A decision support system to analyze these multiple simultaneous variables is presented to assist network developers. Network architectures and demand patterns are accounted for and the underlying model that analyzes these patterns is discussed. A web based approach was utilized which has resulted in an accessible and scalable analytical tool
Cavity optomechanics with stoichiometric SiN films
We study high-stress SiN films for reaching the quantum regime with
mesoscopic oscillators connected to a room-temperature thermal bath, for which
there are stringent requirements on the oscillators' quality factors and
frequencies. Our SiN films support mechanical modes with unprecedented products
of mechanical quality factor and frequency reaching Hz. The SiN membranes exhibit a low optical absorption
characterized by Im at 935 nm, representing a 15 times
reduction for SiN membranes. We have developed an apparatus to simultaneously
cool the motion of multiple mechanical modes based on a short, high-finesse
Fabry-Perot cavity and present initial cooling results along with future
possibilities.Comment: 4 pages, 5 figure
dUTPase based switch controls transfer of virulence genes in order to preserve integrity of the transferred mobile genetic elements
dUTPases ubiquitously regulate cellular dUTP levels to preserve
genome integrity. Recently, several other cellular processes were
reported to be controlled by dUTPases including the horizontal
transfer of Staphylococcus aureus pathogenicity islands (SaPI).
SaPIs are mobil genetic elements that encode virulence enhancing
factors e.g. toxins. Here, phage dUTPases were proposed to
counteract the repressor protein (Stl) and promote SaPI excision
and transfer. A G protein-like mechanism was proposed which is
unexpected in light of the kinetic mechanism of dUTPase.
Here we investigate the molecular mechanism of SaPI transfer
regulation, using numerous dUTPase variants and a wide range
of in vitro methods (steady-state and transient kinetics, VIS and
fluorescence spectroscopy, EMSA, quartz crystal microbalance,
X-ray crystallography).
Our results unambiguously show that Stl inhibits the enzymatic
activity of dUTPase in the nM concentration range and
dUTP strongly inhibits the dUTPase: Stl complexation. These
results identify Stl as a highly potent dUTPase inhibitor protein
and disprove the G protein-like mechanism. Importantly, our
results clearly show that the dUTPase:dUTP complex is inaccessible
to the Stl repressor. Unlike in small GTPases, hydrolysis of
the substrate nucleoside triphosphate (dUTP in this case) is
required prior to the interaction with the partner (Stl repressor in
this case). We propose that dUTPase can efficiently interact with
Stl and induce SaPI excision only if the cellular dUTP level is low (i.e. when dUTPase resides mainly in the apo enzyme form)
while high dUTP levels would inhibit SaPI transfer. This mechanism
may serve the preservation of the integrity of the transferred
SaPI genes and links the well-known metabolic role of
dUTPases to their newly revealed regulatory function in spread
of virulence factors
Current advances in digital cognitive assessment for preclinical Alzheimer\u27s disease
There is a pressing need to capture and track subtle cognitive change at the preclinical stage of Alzheimer\u27s disease (AD) rapidly, cost-effectively, and with high sensitivity. Concurrently, the landscape of digital cognitive assessment is rapidly evolving as technology advances, older adult tech-adoption increases, and external events (i.e., COVID-19) necessitate remote digital assessment. Here, we provide a snapshot review of the current state of digital cognitive assessment for preclinical AD including different device platforms/assessment approaches, levels of validation, and implementation challenges. We focus on articles, grants, and recent conference proceedings specifically querying the relationship between digital cognitive assessments and established biomarkers for preclinical AD (e.g., amyloid beta and tau) in clinically normal (CN) individuals. Several digital assessments were identified across platforms (e.g., digital pens, smartphones). Digital assessments varied by intended setting (e.g., remote vs. in-clinic), level of supervision (e.g., self vs. supervised), and device origin (personal vs. study-provided). At least 11 publications characterize digital cognitive assessment against AD biomarkers among CN. First available data demonstrate promising validity of this approach against both conventional assessment methods (moderate to large effect sizes) and relevant biomarkers (predominantly weak to moderate effect sizes). We discuss levels of validation and issues relating to usability, data quality, data protection, and attrition. While still in its infancy, digital cognitive assessment, especially when administered remotely, will undoubtedly play a major future role in screening for and tracking preclinical AD
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