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Search Results: 1 - 10 of 90980 matches for " Peter Yang "
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Effect of a rotating frame on preventing bead aggregation in a microfluidic device  [PDF]
Jie Yang, Peter B. Howell, Nastaran Hashemi
Advances in Bioscience and Biotechnology (ABB) , 2012, DOI: 10.4236/abb.2012.35078
Abstract: Varying bead concentrations over the course of experiments have been reported by many scientists. A new device was designed and fabricated to eliminate bead aggregation in a syringe pump prior to flowing through a microchannel. We have molded the effects of rotation in the absence of longitudinal flow by evenly populating the cross section of a syringe with particles, then tracking their movement due to rotation, gravity, and centripetal forces. We have shown both experimentally and numerically that the concentration of the beads remains constant over the course of experiments once the rotational device is used. However, the concentration of the beads drops significantly once no rotation is applied during the experiment.
Encapsulation of gold nanoparticles into self-assembling protein nanoparticles
Yang Yongkun,Burkhard Peter
Journal of Nanobiotechnology , 2012, DOI: 10.1186/1477-3155-10-42
Abstract: Background Gold nanoparticles are useful tools for biological applications due to their attractive physical and chemical properties. Their applications can be further expanded when they are functionalized with biological molecules. The biological molecules not only provide the interfaces for interactions between nanoparticles and biological environment, but also contribute their biological functions to the nanoparticles. Therefore, we used self-assembling protein nanoparticles (SAPNs) to encapsulate gold nanoparticles. The protein nanoparticles are formed upon self-assembly of a protein chain that is composed of a pentameric coiled-coil domain at the N-terminus and trimeric coiled-coil domain at the C-terminus. The self-assembling protein nanoparticles form a central cavity of about 10 nm in size, which is ideal for the encapsulation of gold nanoparticles with similar sizes. Results We have used SAPNs to encapsulate several commercially available gold nanoparticles. The hydrodynamic size and the surface coating of gold nanoparticles are two important factors influencing successful encapsulation by the SAPNs. Gold nanoparticles with a hydrodynamic size of less than 15 nm can successfully be encapsulated. Gold nanoparticles with citrate coating appear to have stronger interactions with the proteins, which can interfere with the formation of regular protein nanoparticles. Upon encapsulation gold nanoparticles with polymer coating interfere less strongly with the ability of the SAPNs to assemble into nanoparticles. Although the central cavity of the SAPNs carries an overall charge, the electrostatic interaction appears to be less critical for the efficient encapsulation of gold nanoparticles into the protein nanoparticles. Conclusions The SAPNs can be used to encapsulate gold nanoparticles. The SAPNs can be further functionalized by engineering functional peptides or proteins to either their N- or C-termini. Therefore encapsulation of gold nanoparticles into SAPNs can provide a useful platform to generate a multifunctional biodevices.
Are there really phase transitions in 1-d heat conduction models?
Lei Yang,Peter Grassberger
Physics , 2003,
Abstract: Recently, it has been claimed (O. V. Gendelman and A. V. Savin, Phys. Rev. Lett. {\bf 84}, 2381 (2000); A.V.Savin and O.V.Gendelman, arXiv: cond-mat/0204631 (2002)) that two nonlinear classical 1-d lattice models show transitions, at finite temperatures, where the heat conduction changes from being finite to being infinite. These are the well known Frenkel-Kontorova (FK) model and a model for coupled rotators. For the FK model we give strong theoretical arguments why such a phase transition is not to be expected. For both models we show numerically that the effects observed by Gendelman {\it et al.} are not true phase transitions but are rather the expected cross-overs associated to the conductivity divergence as $T\to 0$ and (for the FK model) $T\to\infty$.
Indomethacin for post-endoscopic retrograde cholangiopancreatography pancreatitis prophylaxis: Is it the magic bullet?
Dennis Yang,Peter V Draganov
World Journal of Gastroenterology , 2012, DOI: 10.3748/wjg.v18.i31.4082
Abstract: Acute pancreatitis is a common complication of endoscopic retrograde cholangiopancreatography (ERCP). Pancreatic duct stent insertion after ERCP has been widely accepted as the standard of care for the prevention of this complication in high-risk patients. Unfortunately, the placement of pancreatic stents requires higher level of endoscopic expertise and is not always feasible due to anatomic considerations. Therefore, effective non-invasive pharmacologic prophylaxis remains appealing, particularly if it is inexpensive, easily administered, has a low risk side effect profile and is widely available. There have been multiple studies evaluating potential pharmacologic candidates for post-ERCP pancreatitis (PEP) prophylaxis, most of them yielding disappointing results. A recently published large, multi-center, randomized controlled trial reported that in high risk patients a single dose of rectal indomethacin administered immediately after the ERCP significantly decreased the incidence of PEP compare to placebo.
Elevated Plasma Levels but Decreased Platelet-Associated Expression of LIGHT in Patients with Acute Atherothrombotic Stroke  [PDF]
Guangzhi Liu, Yang He, Tingting Yang, Hong Jiang, Yajuan Xiang, Qi Zhang, Xiangjun He, Peter Hjelmstrom, Xuguang Gao
World Journal of Neuroscience (WJNS) , 2014, DOI: 10.4236/wjns.2014.44042
Abstract: Background: As a member of the tumor necrosis factor superfamily (TNFSF), LIGHT (TNFSF14) is expressed by a variety of immune cells and exists in membrane-bound and soluble forms. Recently, LIGHT was found to be associated with platelets and released upon activation. Activation of endothelia cells by recombinant LIGHT protein results in pro-inflammatory and pro-thrombotic changes. Several studies have reported increased plasma levels of LIGHT in patients with stroke and cardiovascular diseases. However, the form-associated roles of LIGHT in ischemic atherosclerotic stroke remain unclear. Mater?als and Methods: In this study, the platelet LIGHT expression and soluble LIGHT protein were analyzed by flow cytometry and enzyme-linked immunosorbent assay (ELISA) in peripheral blood of patients with acute ischemic atherosclerotic stroke, asymptomatic carotid stenosis (ACS) and normal controls. RESULTS: During the initial 24 h after onset, the stroke patients had decreased LIGHT expression on their platelets (5.9% ± 4.9%) and increased plasma LIGHT levels (36.1 ± 21.0 pg/ml) as compared with normal controls (9.5% ± 3.0%, p < 0.05; 20.4 ± 13.4 pg/ml, p < 0.05). Moreover, the platelet LIGHT expression correlated with total plaque area in the stroke patients (r = 0.4572, p = 0.0247). Conclus?ons: The dysregulated LIGHT expression reflects a persistent chronic inflammatory
Allosteric Transitions of Supramolecular Systems Explored by Network Models: Application to Chaperonin GroEL
Zheng Yang,Peter Májek,Ivet Bahar
PLOS Computational Biology , 2009, DOI: 10.1371/journal.pcbi.1000360
Abstract: Identification of pathways involved in the structural transitions of biomolecular systems is often complicated by the transient nature of the conformations visited across energy barriers and the multiplicity of paths accessible in the multidimensional energy landscape. This task becomes even more challenging in exploring molecular systems on the order of megadaltons. Coarse-grained models that lend themselves to analytical solutions appear to be the only possible means of approaching such cases. Motivated by the utility of elastic network models for describing the collective dynamics of biomolecular systems and by the growing theoretical and experimental evidence in support of the intrinsic accessibility of functional substates, we introduce a new method, adaptive anisotropic network model (aANM), for exploring functional transitions. Application to bacterial chaperonin GroEL and comparisons with experimental data, results from action minimization algorithm, and previous simulations support the utility of aANM as a computationally efficient, yet physically plausible, tool for unraveling potential transition pathways sampled by large complexes/assemblies. An important outcome is the assessment of the critical inter-residue interactions formed/broken near the transition state(s), most of which involve conserved residues.
Analysis of CDC social control measures using an agent-based simulation of an influenza epidemic in a city
Yong Yang, Peter M Atkinson, Dick Ettema
BMC Infectious Diseases , 2011, DOI: 10.1186/1471-2334-11-199
Abstract: An Individual Space-Time Activity-based Model (ISTAM) was applied to simulate the effectiveness of non-pharmaceutical control measures including: (1) refraining from social activities, (2) school closure and (3) household quarantine, for a hypothetical influenza outbreak in an urban area.Amongst the set of control measures tested, refraining from social activities with various compliance levels was relatively ineffective. Household quarantine was very effective, especially for the peak number of cases and total number of cases, with large differences between compliance levels. Household quarantine resulted in a decrease in the peak number of cases from more than 300 to around 158 for a 100% compliance level, a decrease of about 48.7%. The delay in the outbreak peak was about 3 to 17 days. The total number of cases decreased to a range of 3635-5403, that is, 63.7%-94.7% of the baseline value.When coupling control measures, household quarantine together with school closure was the most effective strategy. The resulting space-time distribution of infection in different classes of activity bundles (AB) suggests that the epidemic outbreak is strengthened amongst children and then spread to adults. By sensitivity analysis, this study demonstrated that earlier implementation of control measures leads to greater efficacy. Also, for infectious diseases with larger basic reproduction number, the effectiveness of non-pharmaceutical measures was shown to be limited.Simulated results showed that household quarantine was the most effective control measure, while school closure and household quarantine implemented together achieved the greatest benefit. Agent-based models should be applied in the future to evaluate the efficacy of control measures for a range of disease outbreaks in a range of settings given sufficient information about the given case and knowledge about the transmission processes at a fine scale.Since the beginning of the new millennium, epidemics of severe acute
Transient receptor potential (TRP) gene superfamily encoding cation channels
Zan Pan, Hua Yang, Peter S Reinach
Human Genomics , 2011, DOI: 10.1186/1479-7364-5-2-108
Abstract: The founding member of the transient receptor potential (TRP) protein superfamily was first described in Drosophila. In some of these flies, prolonged exposure to light only induced transient photoreceptor depolarisation, whereas in the wild type the response was sustained. This difference was attributed to mutant trp gene expression. Mammalian TRP homologues have been identified over the past 30 years since the initial trp description in Drosophila. The members of this superfamily constitute a large and very different collection of proteins that are expressed in many tissues and cell types [1]. This superfamily is conserved throughout evolution, from nematodes to humans [2]. They form non-selective monovalent and divalent cation channels with very variable Ca2+/Na+ permeability ratios. Some members are even impermeable for Ca2+, whereas others are highly Ca2+ permeable relative to monovalent cations. TRPV5 and -6 exhibit a Ca2+/Na+ permeability ratio of greater than 100 [3]. This variability is unique by comparison with most other ion channel families. In those cases, the differences in permeation properties within a single family are for the most part very much smaller [4]. TRPs are distinguished from one another based on differences in their primary amino acid sequence rather than ligand affinity or selectivity. This system of classification is used because their properties are heterogeneous and their regulation is complex. The common feature of TRP channels is that they comprise six putative transmembrane spanning domains and a cationpermeable pore formed by a short hydrophobic region between transmembrane domains 5 and 6. They assemble themselves as homo-or heterotetramers to form cation channels (Figure 1). These channels are activated by a remarkable assemblage of very diverse stimuli.Genetic ablation studies in worms, flies and mice indicate that TRPs serve as sensors to elicit responses to a variety of stimuli, ranging from temperature, osmotic pressure, ol
catena-Poly[[[(diethylenetriamine-κ3N,N′,N′′)copper(II)]-μ-cyanido-κ2C:N] perchlorate]
Peter W. R. Corfield,Sylvia C. Yang
Acta Crystallographica Section E , 2012, DOI: 10.1107/s1600536812023987
Abstract: The structure of the title salt, {[Cu(CN)(C4H13N3)]ClO4}n, is composed of copper-containing cations and perchlorate anions. The CuII atom shows a square-pyramidal coordination, with equatorial positions occupied by the cyanide C atom [Cu—C = 1.990 (3) ] and the N atoms of the diethylenetriamine ligand (average Cu—N = 2.033 ), while the axial position is occupied by the N atom of a c-glide-related cyanide group. The axial Cu—N distance of 2.340 (3) is longer than the equatorial distances, reflecting Jahn–Teller distortion. The CuII cations are linked by the cyanide groups into infinite chains along the c-axis direction. The refinement included a three-component disordered model for the perchlorate ion. Each minor site is stabilized by hydrogen bonds to N—H donors from four surrounding cations, while one O atom of the major perchlorate site forms hydrogen bonds to three of these cations.
Model Consistent Pseudo-Observations of Precipitation and Their Use for Bias Correcting Regional Climate Models
Peter Berg,Thomas Bosshard,Wei Yang
Climate , 2015, DOI: 10.3390/cli3010118
Abstract: Lack of suitable observational data makes bias correction of high space and time resolution regional climate models (RCM) problematic. We present a method to construct pseudo-observational precipitation data bymerging a large scale constrained RCMreanalysis downscaling simulation with coarse time and space resolution observations. The large scale constraint synchronizes the inner domain solution to the driving reanalysis model, such that the simulated weather is similar to observations on a monthly time scale. Monthly biases for each single month are corrected to the corresponding month of the observational data, and applied to the finer temporal resolution of the RCM. A low-pass filter is applied to the correction factors to retain the small spatial scale information of the RCM. The method is applied to a 12.5 km RCM simulation and proven successful in producing a reliable pseudo-observational data set. Furthermore, the constructed data set is applied as reference in a quantile mapping bias correction, and is proven skillful in retaining small scale information of the RCM, while still correcting the large scale spatial bias. The proposed method allows bias correction of high resolution model simulations without changing the fine scale spatial features, i.e., retaining the very information required by many impact models.
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