1,994 research outputs found
Finite Size Effects in Addition and Chipping Processes
We investigate analytically and numerically a system of clusters evolving via
collisions with clusters of minimal mass (monomers). Each collision either
leads to the addition of the monomer to the cluster or the chipping of a
monomer from the cluster, and emerging behaviors depend on which of the two
processes is more probable. If addition prevails, monomers disappear in a time
that scales as with the total mass , and the system reaches a
jammed state. When chipping prevails, the system remains in a quasi-stationary
state for a time that scales exponentially with , but eventually, a giant
fluctuation leads to the disappearance of monomers. In the marginal case,
monomers disappear in a time that scales linearly with , and the final
supercluster state is a peculiar jammed state, viz., it is not extensive.Comment: 18 pages, 8 figures, 45 reference
Aggregation kinetics at sedimentation: the impact of particles diffusion
We investigate the aggregation kinetics of sedimenting particles
theoretically and numerically, using the advection-diffusion equation.
Agglomeration, caused by both transport mechanisms (diffusion and advection),
is important for small particles, like primary ash or soot particles in
atmosphere, and large particles of equal or close size, where the advection
mechanism is weak. For small Peclet numbers, which quantify the relative
importance of diffusion and advection, we obtain the aggregation rates, as an
expansion in Peclet numbers. For large Peclet numbers we use purely ballistic
aggregation rates. Combining these results we obtain the rational approximant
for the whole range of Peclet numbers. We also compute the aggregation rates by
numerically solving the advection-diffusion equation. The results of the
numerical simulations are in excellent agreement with the analytical theory for
the studied Peclet numbers, varying by four orders of magnitude.Comment: 7 pages, 2 figures, 26 reference
Down Syndrome: Age-Dependence of PiB Binding in Postmortem Frontal Cortex Across the Lifespan
Beta-amyloid (Aβ) deposition in brain accumulates as a function of age in people with Down syndrome (DS) with subsequent development into Alzheimer disease neuropathology, typically by 40 years of age. In vivo imaging using the Pittsburgh Compound B (PiB) ligand has facilitated studies linking Aβ, cognition, and dementia in DS. However, there are no studies of PiB binding across the lifespan in DS. The current study describes in vitro 3H-PiB binding in the frontal cortex of autopsy cases with DS compared to non-DS controls. Tissue from 64 cases included controls (N=25) and DS (N=39). In DS, 3H-PiB binding was significantly associated with age. After age 40 years in DS, 3H-PiB binding rose dramatically along with increasing individual variability. 3H-PiB binding correlated with the amount of Aβ42. Using fixed frontal tissue and fluorescent 6-CN-PiB, neuritic and cored plaques along with extensive cerebral amyloid angiopathy (CAA) showed 6-CN-PiB binding. These results suggest that cortical PiB binding as shown by positron emission tomography imaging reflects plaques and CAA in DS brain
Tunneling through a multigrain system: deducing the sample topology from the nonlinear conductance
We study a current transport through a system of a few grains connected with
tunneling links. The exact solution is given for an arbitrarily connected
double-grain system with a shared gate in the framework of the orthodox model.
The obtained result is generalized for multigrain systems with strongly
different tunneling resistances. We analyse the large-scale nonlinear
conductance and demonstrate how the sample topology can be unambiguously
deduced from the spectroscopy pattern (differential conductance versus
gate-bias plot). We present experimental data for a multigrain sample and
reconstruct the sample topology. A simple selection rule is formulated to
distinguish samples with spectral patterns free from spurious disturbance
caused by recharging of some grains nearby. As an example, we demonstrate
experimental data with additional peaks in the spectroscopy pattern, which can
not be attributed to coupling to additional grains. The described approach can
be used to judge the sample topology when it is not guaranteed by fabrication
and direct imaging is not possible.Comment: 13 pages (including 8 figures
Pilot study of the safety and efficacy of angiogenic therapy in diabetic foot syndrome
BACKGROUND: The syndrome of diabetic foot remains the main cause of non-traumatic amputation of the lower extremity in the world. Even with the provision of comprehensive medical care in the conditions of a specialized center, 10-15% of patients do not succeed in healing the ulcerative defect due to the ischemic component. AIMS: The objective of this study is evaluation of safety and efficacy of pl-VEGF165 transfer in patients with neuroischemic type of diabetic foot syndrome. METHODS: The pilot study included 35 diabetic patients with neuroischemic foot ulcers (Wagner stage 1-2) who were not candidates for revascularization procedures (NCT02538705). The patients were closely monitored after repeated pl-VEGF165 intramuscular gene transfer (2,4 mg) at 1, 3, and 6 months after treatment. The primary efficacy endpoint was the surface area of the ulcers (sq.cm), the secondary endpoints were transcutaneous oxygen tension (Tcp02), ankle-brachial index (ABI), neuropathy disability score (NDS), neuropathy symptoms score (NSS), and Michigan neuropathy screening instrument (MNSI). Adverse events were monitored throughout the study. RESULTS: The use of pl-VEGF165 as part of complex treatment allowed to achieve wound healing in 65,7% of patients with chronic ulcerative defects, the safety of the target limb was 84%. Carrying out therapeutic angiogenesis as a part of the combined therapy ensured a reduction in the average area of the resistant to treatment defects from 3.6 [1.0; 7.05] cm2 to 0.0 [0.0;2.0] cm2 (p=0,001), which correlated with an increase in the TcPo2 index by 15% from 35 [29.5; 40.5] to 40.5 [36.0; 46.5] mm Hg (p= p=0,005) and in the ABI by 16% from 0.96 [0.82;1.08] to 1.11 [0.85; 1.24] (p=0,062). The decrease in the signs of diabetic neuropathy was determined - the scores of NSS scales and VAT decreased from 6,5 [5.75; 8.0) to 6.0 [5.25; 7.0] (p=0,004) and from 9.0 [8.0; 13.5] to 8.0 [7.0; 12.7] (p=0,001), respectively. No adverse effects associated with the use of pl-VEGF165 were recorded. CONCLUSIONS: Thus, preliminary results of the pilot study show that the use of pl-VEGF165 gene transfer in combination therapy allows for complete healing of neuroischemic diabetic foot ulcers in the majority of patients
Orientational mobility and relaxation spectra of dendrimers: Theory and computer simulation
Dark sectors 2016 Workshop: community report
This report, based on the Dark Sectors workshop at SLAC in April 2016,
summarizes the scientific importance of searches for dark sector dark matter
and forces at masses beneath the weak-scale, the status of this broad
international field, the important milestones motivating future exploration,
and promising experimental opportunities to reach these milestones over the
next 5-10 years
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