711 research outputs found
Preroughening, Diffusion, and Growth of An FCC(111) Surface
Preroughening of close-packed fcc(111) surfaces, found in rare gas solids, is
an interesting, but poorly characterized phase transition. We introduce a
restricted solid-on-solid model, named FCSOS, which describes it. Using mostly
Monte Carlo, we study both statics, including critical behavior and scattering
properties, and dynamics, including surface diffusion and growth. In antiphase
scattering, it is shown that preroughening will generally show up at most as a
dip. Surface growth is predicted to be continuous at preroughening, where
surface self-diffusion should also drop. The physical mechanism leading to
preroughening on rare gas surfaces is analysed, and identified in the step-step
elastic repulsion.Comment: Revtex + uuencoded figures, to appear in Physical Review Letter
FUT8-directed core fucosylation of N-glycans is regulated by the glycan structure and protein environment
FUT8 is an essential a-1, 6-fucosyltransferase that fucosylates the innermost GlcNAc of N-glycans, a process called core fucosylation. In vitro, FUT8 exhibits substrate preference for the biantennary complex N-glycan oligosaccharide (G0), but the role of the underlying protein/peptide to which N-glycans are attached remains unclear. Here, we explored the FUT8 enzyme with a series of N-glycan oligosaccharides, N-glycopeptides, and an Asn-linked oligosaccharide. We found that the underlying peptide plays a role in fucosylation of paucimannose (low mannose) and high-mannose N-glycans but not for complex-type N-glycans. Using saturation transfer difference (STD) NMR spectroscopy, we demonstrate that FUT8 recognizes all sugar units of the G0 N-glycan and most of the amino acid residues (Asn-X-Thr) that serve as a recognition sequon for the oligosaccharyltransferase (OST). The largest STD signals were observed in the presence of GDP, suggesting that prior FUT8 binding to GDP-ß-l-fucose (GDP-Fuc) is required for an optimal recognition of N-glycans. We applied genetic engineering of glycosylation capacities in CHO cells to evaluate FUT8 core fucosylation of high-mannose and complex-type N-glycans in cells with a panel of well-characterized therapeutic N-glycoproteins. This confirmed that core fucosylation mainly occurs on complex-type N-glycans, although clearly only at selected glycosites. Eliminating the capacity for complex-type glycosylation in cells (KO mgat1) revealed that glycosites with complex-type N-glycans when converted to high mannose lost the core Fuc. Interestingly, however, for erythropoietin that is uncommon among the tested glycoproteins in efficiently acquiring tetra-antennary N-glycans, two out of three N-glycosites obtained Fuc on the high-mannose N-glycans. An examination of the N-glycosylation sites of several protein crystal structures indicates that core fucosylation is mostly affected by the accessibility and nature of the N-glycan and not by the nature of the underlying peptide sequence. These data have further elucidated the different FUT8 acceptor substrate specificities both in vitro and in vivo in cells, revealing different mechanisms for promoting core fucosylation.
Revisiting the Performance of the Modular Clock Algorithm for Distributed Blind Rendezvous in Cognitive Radio Networks
Abstract. We reexamine the modular clock algorithm for distributed blind rendezvous in cognitive radio networks. It proceeds in rounds. Each round consists of scanning twice a block of generated channels. The modular clock algorithm inspired the creation of the jump-stay ren-dezvous algorithm. It augments the modular clock with a stay-on-one-channel pattern. This enhancement guarantees rendezvous in one round. We make the observation that as the number of channels increases, the significance of the stay-on-one-channel pattern decreases. We revisit the performance analysis of the two-user symmetric case of the modular clock algorithm. We compare its performance with a random and the jump-stay rendezvous algorithms. Let m be the number of channels. Let p be the smallest prime number greater than m. The expected time-to-rendezvous of the random and jump-stay algorithms are m and p, respectively. Theis et al.’s analysis of the modular clock algorithm con-cludes a maximum expected time-to-rendezvous slightly larger than 2p time slots. Our analysis shows that the expected time-to-rendezvous of the modular clock algorithm is no more than 3p/4 time slots.
Spatial variation in biodiversity loss across China under multiple environmental stressors
Biodiversity is essential for the maintenance of ecosystem health and delivery of the Sustainable Development Goals. However, the drivers of biodiversity loss and the spatial variation in their impacts are poorly understood. Here, we explore the spatial-temporal distributions of threatened and declining ("biodiversity-loss") species and find that these species are affected by multiple stressors, with climate and human activities being the fundamental shaping forces. There has been large spatial variation in the distribution of threatened species over China's provinces, with the biodiversity of Gansu, Guangdong, Hainan, and Shaanxi provinces severely reduced. With increasing urbanization and industrialization, the expansion of construction and worsening pollution has led to habitat retreat or degradation, and high proportions of amphibians, mammals, and reptiles are threatened. Because distributions of species and stressors vary widely across different climate zones and geographical areas, specific policies and measures are needed for preventing biodiversity loss in different regions
A Statistical Study on Photospheric Magnetic Nonpotentiality of Active Regions and Its Relationship with Flares during Solar Cycles 22-23
A statistical study is carried out on the photospheric magnetic
nonpotentiality in solar active regions and its relationship with associated
flares. We select 2173 photospheric vector magnetograms from 1106 active
regions observed by the Solar Magnetic Field Telescope at Huairou Solar
Observing Station, National Astronomical Observatories of China, in the period
of 1988-2008, which covers most of the 22nd and 23rd solar cycles. We have
computed the mean planar magnetic shear angle (\bar{\Delta\phi}), mean shear
angle of the vector magnetic field (\bar{\Delta\psi}), mean absolute vertical
current density (\bar{|J_{z}|}), mean absolute current helicity density
(\bar{|h_{c}|}), absolute twist parameter (|\alpha_{av}|), mean free magnetic
energy density (\bar{\rho_{free}}), effective distance of the longitudinal
magnetic field (d_{E}), and modified effective distance (d_{Em}) of each
photospheric vector magnetogram. Parameters \bar{|h_{c}|}, \bar{\rho_{free}},
and d_{Em} show higher correlation with the evolution of the solar cycle. The
Pearson linear correlation coefficients between these three parameters and the
yearly mean sunspot number are all larger than 0.59. Parameters
\bar{\Delta\phi}, \bar{\Delta\psi}, \bar{|J_{z}|}, |\alpha_{av}|, and d_{E}
show only weak correlations with the solar cycle, though the nonpotentiality
and the complexity of active regions are greater in the activity maximum
periods than in the minimum periods. All of the eight parameters show positive
correlations with the flare productivity of active regions, and the combination
of different nonpotentiality parameters may be effective in predicting the
flaring probability of active regions.Comment: 20 pages, 5 figures, 4 tables, accepted for publication in Solar
Physic
Thermobiological Characteristics of Pikas, Rabbits and Rats
Animals are provided by nature with biological defense mechanisms against the deleterious effects of the environment. Three different animal species: pikas, rabbits and rats were compared in their thermobiological characteristics. Results revealed significant dissimilarities of the characteristics of pikas from both rabbits and rats that they called morphologically and physiologically unique. Compared to the two, these animals have relatively high body temperature and absence of circadian rhythm in core body temperature. These probably explain the non-manifestation of thermal panting and salivation which are evidences of the absence of natural heat losing ability in these animals. Since 1975 up to the present blood glucose has never been studied in pikas. Thus, in this experiment, this substance was determined to explain some biochemical related peculiarities in these animals. Findings revealed a low blood glucose level in pika in contrast to the rats but relatively similar to that of the rabbits. Conclusively, pikas have peculiarities which enable them to exist in environments with low temperature. It seems that blood glucose does not bear any relationship with this physiological nature. The same characteristics make them different from Lagomorpha and other lower animals
P-wave excited baryons from pion- and photo-induced hyperon production
We report evidence for , , ,
, , and , and find
indications that might have a companion state at 1970\,MeV. The
controversial is not seen. The evidence is derived from a
study of data on pion- and photo-induced hyperon production, but other data are
included as well. Most of the resonances reported here were found in the
Karlsruhe-Helsinki (KH84) and the Carnegie-Mellon (CM) analyses but were
challenged recently by the Data Analysis Center at GWU. Our analysis is
constrained by the energy independent scattering amplitudes from either
KH84 or GWU. The two amplitudes from KH84 or GWU, respectively, lead to
slightly different branching ratios of contributing resonances but the
debated resonances are required in both series of fits.Comment: 22 pages, 28 figures. Some additional sets of data are adde
Time-Dependent CP Violation Effects in Partially Reconstructed Decays
We report measurements of time-dependent decay rates for decays and extraction of CP violation parameters related to .
We use a partial reconstruction technique, whereby signal events are identified
using information only from the primary pion and the charged pion from the
decay of the . The analysis uses of data
accumulated at the resonance with the Belle detector at the KEKB
asymmetric-energy collider. We measure the CP violation parameters
and .Comment: 15 pages, 5 figures. To appear in Physics Letters
An Integrated TCGA Pan-Cancer Clinical Data Resource to Drive High-Quality Survival Outcome Analytics
For a decade, The Cancer Genome Atlas (TCGA) program collected clinicopathologic annotation data along with multi-platform molecular profiles of more than 11,000 human tumors across 33 different cancer types. TCGA clinical data contain key features representing the democratized nature of the data collection process. To ensure proper use of this large clinical dataset associated with genomic features, we developed a standardized dataset named the TCGA Pan-Cancer Clinical Data Resource (TCGA-CDR), which includes four major clinical outcome endpoints. In addition to detailing major challenges and statistical limitations encountered during the effort of integrating the acquired clinical data, we present a summary that includes endpoint usage recommendations for each cancer type. These TCGA-CDR findings appear to be consistent with cancer genomics studies independent of the TCGA effort and provide opportunities for investigating cancer biology using clinical correlates at an unprecedented scale. Analysis of clinicopathologic annotations for over 11,000 cancer patients in the TCGA program leads to the generation of TCGA Clinical Data Resource, which provides recommendations of clinical outcome endpoint usage for 33 cancer types
Search for direct production of charginos and neutralinos in events with three leptons and missing transverse momentum in √s = 7 TeV pp collisions with the ATLAS detector
A search for the direct production of charginos and neutralinos in final states with three electrons or muons and missing transverse momentum is presented. The analysis is based on 4.7 fb−1 of proton–proton collision data delivered by the Large Hadron Collider and recorded with the ATLAS detector. Observations are consistent with Standard Model expectations in three signal regions that are either depleted or enriched in Z-boson decays. Upper limits at 95% confidence level are set in R-parity conserving phenomenological minimal supersymmetric models and in simplified models, significantly extending previous results
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