15 research outputs found
Electric Current Focusing Efficiency in Graphene Electric Lens
In present work, we theoretically study the electron wave's focusing
phenomenon in a single layered graphene pn junction(PNJ) and obtain the
electric current density distribution of graphene PNJ, which is in good
agreement with the qualitative result in previous numerical calculations
[Science, 315, 1252 (2007)]. In addition, we find that for symmetric PNJ, 1/4
of total electric current radiated from source electrode can be collected by
drain electrode. Furthermore, this ratio reduces to 3/16 in a symmetric
graphene npn junction. Our results obtained by present analytical method
provide a general design rule for electric lens based on negative refractory
index systems.Comment: 13 pages, 7 figure
Simulations of tubulin sheet polymers as possible structural intermediates in microtubule assembly
The microtubule assembly process has been extensively studied, but the
underlying molecular mechanism remains poorly understood. The structure of an
artificially generated sheet polymer that alternates two types of lateral
contacts and that directly converts into microtubules, has been proposed to
correspond to the intermediate sheet structure observed during microtubule
assembly. We have studied the self-assembly process of GMPCPP tubulins into
sheet and microtubule structures using thermodynamic analysis and stochastic
simulations. With the novel assumptions that tubulins can laterally interact in
two different forms, and allosterically affect neighboring lateral
interactions, we can explain existing experimental observations. At low
temperature, the allosteric effect results in the observed sheet structure with
alternating lateral interactions as the thermodynamically most stable form. At
normal microtubule assembly temperature, our work indicates that a class of
sheet structures resembling those observed at low temperature is transiently
trapped as an intermediate during the assembly process. This work may shed
light on the tubulin molecular interactions, and the role of sheet formation
during microtubule assembly.Comment: 43 pages, 13 figures. Submitted; PLoS ONE 200
Characterization of a Human Antibody Fragment Fab and Its Calcium Phosphate Nanoparticles that Inhibit Rabies Virus Infection with Vaccine
Recombinant antibody phage display technology has been used to mimic many aspects
of the processes that govern the generation and selection of high-affinity
natural human antibodies in the human immune system, especially for infectious
disease prophylaxis. An anti-rabies virus immunized phage-display Fab library
was constructed from peripheral blood lymphocytes from vaccinated volunteers.
The immunized antibody library, with a diversity of 6.7Γ108,
was used to select and produce antibodies that bound to rabies virus
glycoprotein. After five rounds of immobilized fixed rabies virion panning, four
unique DNA sequences were found in the higher binding clones, and only one,
Fab094, showed neutralization activity. Fab094 components were analyzed by
ELISA, immunoprecipitation and immunofluorescent staining. ELISA and
immunofluorescence showed that Fab094 bound specifically to rabies virions.
Immunoprecipitation and mass spectrometry showed that Fab094 reacted with rabies
virus glycoprotein. To improve the penetration power of Fab094 antibodies, we
developed Fab094 calcium phosphate nanoparticles (Fab094-CPNPs) and tested their
efficacy. The rapid fluorescent focus inhibition test indicated that the
neutralizing antibody titers of Fab094 and Fab094-CPNPs were reached at 200.17
IU/Kg and 246.12 IU/Kg, respectively. These findings were confirmed in vivo in a
Kunming mouse challenge model. Our results demonstrate that human Fab094 and
Fab094-CPNPs are efficacious candidate drugs to replace rabies immunoglobulin in
post-exposure prophylaxis (PEP)
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Simulations of tubulin sheet polymers as possible structural intermediates in microtubule assembly.
The microtubule assembly process has been extensively studied, but the underlying molecular mechanism remains poorly understood. The structure of an artificially generated sheet polymer that alternates two types of lateral contacts and that directly converts into microtubules, has been proposed to correspond to the intermediate sheet structure observed during microtubule assembly. We have studied the self-assembly process of GMPCPP tubulins into sheet and microtubule structures using thermodynamic analysis and stochastic simulations. With the novel assumptions that tubulins can laterally interact in two different forms, and allosterically affect neighboring lateral interactions, we can explain existing experimental observations. At low temperature, the allosteric effect results in the observed sheet structure with alternating lateral interactions as the thermodynamically most stable form. At normal microtubule assembly temperature, our work indicates that a class of sheet structures resembling those observed at low temperature is transiently trapped as an intermediate during the assembly process. This work may shed light on the tubulin molecular interactions, and the role of sheet formation during microtubule assembly
Prognostic significance of white blood cell to platelet ratio in delayed cerebral ischemia and long-term clinical outcome after aneurysmal subarachnoid hemorrhage
ObjectivesThe ratio of white blood cell to platelet count (WPR) is considered a promising biomarker in some diseases. However, its prediction of delayed cerebral ischemia (DCI) and prognosis after aneurysmal subarachnoid hemorrhage (aSAH) has not been studied. The primary objective of this study was to investigate the predictive value of WPR in DCI after aSAH and its impact on 90-day functional outcome.Materials and methodsThis study retrospectively analyzed the data of blood biochemical parameters in 447 patients with aSAH at early admission. Univariate and multivariate analyses were used to determine the risk factors for DCI. According to multivariate analysis results, a nomogram for predicting DCI is developed and verified by R software. The influence of WPR on 90-day modified Rankin score (mRS) was also analyzed.ResultsAmong 447 patients with aSAH, 117 (26.17%) developed DCI during hospitalization. Multivariate logistic regression analysis showed that WPR [ORβ=β1.236; 95%CI: 1.058β1.444; pβ=β0.007] was an independent risk factor for DCI. The receiver operating characteristic (ROC) curve analysis was used to evaluate the predictive ability of WPR for DCI, and the cut-off value of 5.26 (AUC 0.804, 95% CI: 0.757β0.851, pβ<β0.001). The ROC curve (AUC 0.875, 95% CI: 0.836β0.913, pβ<β0.001) and calibration curve (mean absolute errorβ=β0.017) showed that the nomogram had a good predictive ability for the occurrence of DCI. Finally, we also found that high WPR levels at admission were closely associated with poor prognosis.ConclusionWPR level at admission is a novel serum marker for DCI and the poor prognosis after aSAH. A nomogram model containing early WPR will be of great value in predicting DCI after aSAH
Constrained-Spherical Deconvolution Tractography in the Evaluation of the Corticospinal Tract in Glioma Surgery
Introduction: Tractography has demonstrated utility for surgical resection in the setting of primary brain tumors involving eloquent white matter (WM) pathways. Methods: Twelve patients with glioma in or near eloquent motor areas were analyzed. The motor status was recorded before and after surgery. Two different tractography approaches were used to generate the motor corticospinal tract (CST): Constrained spherical deconvolution probabilistic tractography (CSD-Prob) and single tensor deterministic tractography (Tens-DET). To define the degree of disruption of the CST after surgical resection of the tumor, we calculated the percentage of the CST affected by surgical resection, which was then correlated with the postoperative motor status. Moreover, the fractional anisotropy (FA), mean diffusivity (MD), axial diffusivity (AD), and radial diffusivity (RD) of the CST generated by the CSD-Prob and the Tens-DET was measured and compared between the ipsilesional and contralesional side. Results: The CST was identified in all patients and its trajectory was displaced by the tumor. Only the CSD-Prob approach showed the CST with the characteristic fan-like projections from the precentral gyrus to the brainstem. Disruption of the CST was identified in 6/6 with postoperative motor deficit by CSD-Prob approach and in 5/6 in the Tens-DET. The degree of disruption was significantly associated with the motor deficit with the CSD-Prob approach (rho = β0.88, p = 0.021). However, with the Tens-DET approach the CST disruption did not show significant association with the motor function (rho = β0.27, p = 0.6). There was a significant decrease in FA (p = 0.006) and a significant increase in MD (p = 0.0004) and RD (p = 0.005) on the ipsilesional CST compared with the contralesional CST only with the CSD-Prob approach. Conclusion: CSD-Prob accurately represented the known anatomy of the CST and provided a meaningful estimate of microstructural changes of the CST affected by the tumor and its macrostructural damage after surgery. Newer surgical planning stations should include advanced models and algorithms of tractography in order to obtain more meaningful reconstructions of the WM pathways during glioma surgery.ISSN:2296-875
Kaplan-Meier survival curves for Kunming mouse after rabies virus challenge.
<p>Kunming mice (17 groups of eight mice, 10β12 g) were infected with
100LD<sub>50</sub>/0.05 ml rabies virus CVS-11. Three hours later,
prophylaxis was initiated with vaccine (diluted with PBS; Chiron Behring
Vaccines) alone, single antibody (Fab094 or Fab094-CPNPs) alone, vaccine
plus HRIG (20 IU/kg; Taibang Ltd., China), or vaccine plus 40, 32, 20, 2
or 0.5 IU/kg single monoclonal antibody (Fab094 or Fab094-CPNPs). As a
negative control, one group was treated with PBS. On day 7, mice were
vaccinated with rabies vaccine again, except for the negative control
group. The mice were examined daily for clinical signs of rabies and
death. The mice were maintained and evaluated at up to 28 days after
infection. The mice were monitored twice daily and were killed when
clinical signs of rabies appeared. Kaplan-Meier survival curves are
shown for days 0β15. The mice were monitored until day 28 after
treatment (no additional deaths occurred between days 16 and 28).</p