71 research outputs found
Dielectric relaxation dynamics of high-temperature piezoelectric polyimide copolymers
Polyimide co-polymers have been prepared based on different diamines as co-monomers:
a diamine without CN groups and a novel synthesized diamine with two CN groups
prepared by polycondensation reaction followed by thermal cyclodehydration. Dielectric
spectroscopy measurements were performed and the dielectric complex function, ac
conductivity and electric modulus of the co-polymers were investigated as a function of
CN group content in the frequency range from 0.1 Hz to 107
Hz at temperatures from 25
to 260 °C.
For all samples and temperatures above 150ºC, the dielectric constant increases with
increasing temperature due to increaseing conductivity. The α-relaxation is just detected
for the sample without CN groups, being this relaxation overlapped by the electrical
conductivity contributions in the remaining samples. For the copolymer samples and the
polymer with CN groups an important Maxwell-Wagner-Sillars contribution is detected.
The mechanisms responsible for the dielectric relaxation, conduction process and electric
modulus response have been discussed as a function of the CN groups content present in
the samples.This work was supported by FEDER through the COMPETE Program and by the Portuguese Foundation for Science and Technology (FCT) in the framework of the Strategic Project PESTC/FIS/UI607/2011 and grants SFRH/BD/ 62507/2009 (A.C.L.) SFRH/BD/68499/2010 (C.M.C.). The authors also thank funding from “Matepro – Optimizing Materials and Processes”, ref. NORTE-07-0124-FEDER-000037”, co-funded by the “Programa Operacional Regional do Norte” (ON.2 – O Novo Norte), under the “Quadro de Referência Estratégico Nacional” (QREN), through the “Fundo Europeu de Desenvolvimento Regional” (FEDER). RSS acknowledge the support of the Spanish Ministry of Economy and Competitiveness through the project MAT2012-38359-C03-01 (including the FEDER financial support). Authors also thank the Basque Country Government for financial support (ACTIMAT project, ETORTEK Program, IE13-380, and Ayudas para Grupos de Investigación del Sistema Universitario Vasco Program, IT718-13)
Hepatitis B Vaccine Antibody Response and the Risk of Clinical AIDS or Death
Whether seroresponse to a vaccine such as hepatitis B virus (HBV) vaccine can provide a measure of the functional immune status of HIV-infected persons is unknown.This study evaluated the relationship between HBV vaccine seroresponses and progression to clinical AIDS or death. (HR 3.40; 95% CI, 1.39–8.32).
Comparative genomic analysis of six new-found integrative conjugative elements (ICEs) in Vibrio alginolyticus
A Low T Regulatory Cell Response May Contribute to Both Viral Control and Generalized Immune Activation in HIV Controllers
HIV-infected individuals maintaining undetectable viremia in the absence of therapy (HIV controllers) often maintain high HIV-specific T cell responses, which has spurred the development of vaccines eliciting HIV-specific T cell responses. However, controllers also often have abnormally high T cell activation levels, potentially contributing to T cell dysfunction, CD4+ T cell depletion, and non-AIDS morbidity. We hypothesized that a weak T regulatory cell (Treg) response might contribute to the control of viral replication in HIV controllers, but might also contribute to generalized immune activation, contributing to CD4+ T cell loss. To address these hypotheses, we measured frequencies of activated (CD38+ HLA-DR+), regulatory (CD4+CD25+CD127dim), HIV-specific, and CMV-specific T cells among HIV controllers and 3 control populations: HIV-infected individuals with treatment-mediated viral suppression (ART-suppressed), untreated HIV-infected “non-controllers” with high levels of viremia, and HIV-uninfected individuals. Despite abnormally high T cell activation levels, controllers had lower Treg frequencies than HIV-uninfected controls (P = 0.014). Supporting the propensity for an unusually low Treg response to viral infection in HIV controllers, we observed unusually high CMV-specific CD4+ T cell frequencies and a strong correlation between HIV-specific CD4+ T cell responses and generalized CD8+ T cell activation levels in HIV controllers (P≤0.001). These data support a model in which low frequencies of Tregs in HIV controllers may contribute to an effective adaptive immune response, but may also contribute to generalized immune activation, potentially contributing to CD4 depletion
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The Soft X-ray Imager (SXI) on the SMILE Mission
The Soft X-ray Imager (SXI) is part of the scientific payload of the Solar wind Magnetosphere Ionosphere Link Explorer (SMILE) mission. SMILE is a joint science mission between the European Space Agency (ESA) and the Chinese Academy of Sciences (CAS) and is due for launch in 2025. SXI is a compact X-ray telescope with a wide field-of-view (FOV) capable of encompassing large portions of Earth’s magnetosphere from the vantage point of the SMILE orbit. SXI is sensitive to the soft X-rays produced by the Solar Wind Charge eXchange (SWCX) process produced when heavy ions of solar wind origin interact with neutral particles in Earth’s exosphere. SWCX provides a mechanism for boundary detection within the magnetosphere, such as the position of Earth’s magnetopause, because the solar wind heavy ions have a very low density in regions of closed magnetic field lines. The sensitivity of the SXI is such that it can potentially track movements of the magnetopause on timescales of a few minutes and the orbit of SMILE will enable such movements to be tracked for segments lasting many hours. SXI is led by the University of Leicester in the United Kingdom (UK) with collaborating organisations on hardware, software and science support within the UK, Europe, China and the United States
The Soft X-ray Imager (SXI) on the SMILE Mission
The Soft X-ray Imager (SXI) is part of the scientific payload of the Solar wind Magnetosphere Ionosphere Link Explorer (SMILE) mission. SMILE is a joint science mission between the European Space Agency (ESA) and the Chinese Academy of Sciences (CAS) and is due for launch in 2025. SXI is a compact X-ray telescope with a wide field-of-view (FOV) capable of encompassing large portions of Earth’s magnetosphere from the vantage point of the SMILE orbit. SXI is sensitive to the soft X-rays produced by the Solar Wind Charge eXchange (SWCX) process produced when heavy ions of solar wind origin interact with neutral particles in Earth’s exosphere. SWCX provides a mechanism for boundary detection within the magnetosphere, such as the position of Earth’s magnetopause, because the solar wind heavy ions have a very low density in regions of closed magnetic field lines. The sensitivity of the SXI is such that it can potentially track movements of the magnetopause on timescales of a few minutes and the orbit of SMILE will enable such movements to be tracked for segments lasting many hours. SXI is led by the University of Leicester in the United Kingdom (UK) with collaborating organisations on hardware, software and science support within the UK, Europe, China and the United States
A Polymeric Liquid Membrane Electrode Responsive to 3,3′,5,5′-Tetramethylbenzidine Oxidation for Sensitive Peroxidase/Peroxidase Mimetic-Based Potentiometric Biosensing
The Athena X-ray Integral Field Unit: a consolidated design for the system requirement review of the preliminary definition phase
Instrumentatio
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