2,951 research outputs found
Impact of boundaries on fully connected random geometric networks
Many complex networks exhibit a percolation transition involving a
macroscopic connected component, with universal features largely independent of
the microscopic model and the macroscopic domain geometry. In contrast, we show
that the transition to full connectivity is strongly influenced by details of
the boundary, but observe an alternative form of universality. Our approach
correctly distinguishes connectivity properties of networks in domains with
equal bulk contributions. It also facilitates system design to promote or avoid
full connectivity for diverse geometries in arbitrary dimension.Comment: 6 pages, 3 figure
Role of microenvironment in the mixed Langmuir-Blodgett films
This paper reports the pi-A isotherms and spectroscopic characteristics of
mixed Langmuir and Langmuir-Blodgett (LB) films of non-amphiphilic carbazole
(CA) molecules mixed with polymethyl methacrylate (PMMA) and stearic acid (SA).
pi-A isotherm studies of mixed monolayer and as well as also the collapse
pressure study of isotherms definitely conclude that CA is incorporated into
PMMA and SA matrices. However CA is stacked in the PMMA/SA chains and forms
microcrystalline aggregates as is evidenced from the scanning electron
micrograph picture. Nature of these aggregated species in the mixed LB films
has been revealed by UV-Vis absorption and fluorescence spectroscopic studies.
The presence of two different kinds of band systems in the fluorescence spectra
of the mixed LB films have been observed. This may be due to the formation of
low dimensional aggregates in the mixed LB films. Intensity distribution of
different band system is highly sensitive to the microenvironment of two
different matrices as well as also on the film thicknessComment: 11 pages, 5 figure
Coronary computed tomography angiography in dialysis patients undergoing pre-renal transplantation cardiac risk stratification
Background: This study addresses the safety, feasibility, and interpretability of coronary
computed tomography angiography (CCTA) in excluding significant coronary artery disease
in end-stage renal disease patients on dialysis undergoing pre-renal transplant cardiac risk
evaluation.
Methods: Twenty nine patients (55.5 ± 10.2 years) undergoing cardiac risk assessment
prior to renal transplantation, underwent research CCTA with calcium scoring and formed
the study group. All CCTAs were performed using retrospective acquisition, with beta-blockade
provided one hour prior to scanning.
Results: No major complications occurred in this group up to 30 days after CCTA. Of the
total of 374 segments interpreted by both readers, only 36 (10%) were uninterpretable by both
readers. Of these, 31 (86%) were from distal segments or branches. On a segmental level, there
was 95% concordance between both readers for < 50% stenosis detection. Only three out of
28 (11%) CCTAs were deemed uninterpretable. Ten patients (36%) had zero calcium score,
despite being on dialysis with no evidence of obstructive coronary artery disease by CCTA.
Conclusions: CCTA is feasible and safe in end-stage renal disease dialysis patients with the
advent of 64-slice CCTA. Despite significant calcium burden, there was excellent inter-observer
agreement at segment level for the left main and all three proximal-mid coronary
arteries in excluding obstructive coronary artery disease (> 50% stenosis). (Cardiol J 2010;
17, 4: 349-361
Full-dose PET Synthesis from Low-dose PET Using High-efficiency Diffusion Denoising Probabilistic Model
To reduce the risks associated with ionizing radiation, a reduction of
radiation exposure in PET imaging is needed. However, this leads to a
detrimental effect on image contrast and quantification. High-quality PET
images synthesized from low-dose data offer a solution to reduce radiation
exposure. We introduce a diffusion-model-based approach for estimating
full-dose PET images from low-dose ones: the PET Consistency Model (PET-CM)
yielding synthetic quality comparable to state-of-the-art diffusion-based
synthesis models, but with greater efficiency. There are two steps: a forward
process that adds Gaussian noise to a full dose PET image at multiple
timesteps, and a reverse diffusion process that employs a PET Shifted-window
Vision Transformer (PET-VIT) network to learn the denoising procedure
conditioned on the corresponding low-dose PETs. In PET-CM, the reverse process
learns a consistency function for direct denoising of Gaussian noise to a clean
full-dose PET. We evaluated the PET-CM in generating full-dose images using
only 1/8 and 1/4 of the standard PET dose. Comparing 1/8 dose to full-dose
images, PET-CM demonstrated impressive performance with normalized mean
absolute error (NMAE) of 1.233+/-0.131%, peak signal-to-noise ratio (PSNR) of
33.915+/-0.933dB, structural similarity index (SSIM) of 0.964+/-0.009, and
normalized cross-correlation (NCC) of 0.968+/-0.011, with an average generation
time of 62 seconds per patient. This is a significant improvement compared to
the state-of-the-art diffusion-based model with PET-CM reaching this result 12x
faster. In the 1/4 dose to full-dose image experiments, PET-CM is also
competitive, achieving an NMAE 1.058+/-0.092%, PSNR of 35.548+/-0.805dB, SSIM
of 0.978+/-0.005, and NCC 0.981+/-0.007 The results indicate promising low-dose
PET image quality improvements for clinical applications
Full Connectivity: Corners, edges and faces
We develop a cluster expansion for the probability of full connectivity of
high density random networks in confined geometries. In contrast to percolation
phenomena at lower densities, boundary effects, which have previously been
largely neglected, are not only relevant but dominant. We derive general
analytical formulas that show a persistence of universality in a different form
to percolation theory, and provide numerical confirmation. We also demonstrate
the simplicity of our approach in three simple but instructive examples and
discuss the practical benefits of its application to different models.Comment: 28 pages, 8 figure
KELT-3b: A Hot Jupiter Transiting a V=9.8 Late-F Star
We report the discovery of KELT-3b, a moderately inflated transiting hot
Jupiter with a mass of 1.477 (-0.067, +0.066) M_J, and radius of 1.345 +/-
0.072 R_J, with an orbital period of 2.7033904 +/- 0.000010 days. The host
star, KELT-3, is a V=9.8 late F star with M_* = 1.278 (-0.061, +0.063) M_sun,
R_* = 1.472 (-0.067, +0.065) R_sun, T_eff = 6306 (-49, +50) K, log(g) = 4.209
(-0.031, +0.033), and [Fe/H] = 0.044 (-0.082, +0.080), and has a likely proper
motion companion. KELT-3b is the third transiting exoplanet discovered by the
KELT survey, and is orbiting one of the 20 brightest known transiting planet
host stars, making it a promising candidate for detailed characterization
studies. Although we infer that KELT-3 is significantly evolved, a preliminary
analysis of the stellar and orbital evolution of the system suggests that the
planet has likely always received a level of incident flux above the
empirically-identified threshold for radius inflation suggested by Demory &
Seager (2011).Comment: 12 pages, 12 figures, accepted to Ap
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Reprogramming human T cell function and specificity with non-viral genome targeting.
Decades of work have aimed to genetically reprogram T cells for therapeutic purposes1,2 using recombinant viral vectors, which do not target transgenes to specific genomic sites3,4. The need for viral vectors has slowed down research and clinical use as their manufacturing and testing is lengthy and expensive. Genome editing brought the promise of specific and efficient insertion of large transgenes into target cells using homology-directed repair5,6. Here we developed a CRISPR-Cas9 genome-targeting system that does not require viral vectors, allowing rapid and efficient insertion of large DNA sequences (greater than one kilobase) at specific sites in the genomes of primary human T cells, while preserving cell viability and function. This permits individual or multiplexed modification of endogenous genes. First, we applied this strategy to correct a pathogenic IL2RA mutation in cells from patients with monogenic autoimmune disease, and demonstrate improved signalling function. Second, we replaced the endogenous T cell receptor (TCR) locus with a new TCR that redirected T cells to a cancer antigen. The resulting TCR-engineered T cells specifically recognized tumour antigens and mounted productive anti-tumour cell responses in vitro and in vivo. Together, these studies provide preclinical evidence that non-viral genome targeting can enable rapid and flexible experimental manipulation and therapeutic engineering of primary human immune cells
Isolation of HIV-1-Neutralizing Mucosal Monoclonal Antibodies from Human Colostrum
BACKGROUND: Generation of potent anti-HIV antibody responses in mucosal compartments is a potential requirement of a transmission-blocking HIV vaccine. HIV-specific, functional antibody responses are present in breast milk, and these mucosal antibody responses may play a role in protection of the majority of HIV-exposed, breastfeeding infants. Therefore, characterization of HIV-specific antibodies produced by B cells in milk could guide the development of vaccines that elicit protective mucosal antibody responses. METHODS: We isolated B cells from colostrum of an HIV-infected lactating woman with a detectable neutralization response in milk and recombinantly produced and characterized the resulting HIV-1 Envelope (Env)-specific monoclonal antibodies (mAbs). RESULTS: The identified HIV-1 Env-specific colostrum mAbs, CH07 and CH08, represent two of the first mucosally-derived anti-HIV antibodies yet to be reported. Colostrum mAb CH07 is a highly-autoreactive, weakly-neutralizing gp140-specific mAb that binds to linear epitopes in the gp120 C5 region and gp41 fusion domain. In contrast, colostrum mAb CH08 is a nonpolyreactive CD4-inducible (CD4i) gp120-specific mAb with moderate breadth of neutralization. CONCLUSIONS: These novel HIV-neutralizing mAbs isolated from a mucosal compartment provide insight into the ability of mucosal B cell populations to produce functional anti-HIV antibodies that may contribute to protection against virus acquisition at mucosal surfaces
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