Facile Microwave Assisted Synthesis of Silver Nanostars for Ultrasensitive Detection of Biological Analytes by SERS

We report a very simple, rapid and reproducible method for the fabrication of anisotropic silver nanostars (AgNS) that can be successfully used as highly efficient SERS substrates for different bioanalytes, even in the case of a near-infra-red (NIR) excitation laser. The nanostars have been synthesized using the chemical reduction of Ag⁺ ions by trisodium citrate. This is the first research reporting the synthesis of AgNS using only trisodium citrate as a reducing and stabilizing agent. The key elements of this original synthesis procedure are rapid hydrothermal synthesis of silver nanostars followed by a cooling down procedure by immersion in a water bath. The synthesis was performed in a sealed bottom flask homogenously heated and brought to a boil in a microwave oven. After 60 s, the colloidal solution was cooled down to room temperature by immersion in a water bath at 35 °C. The as-synthesized AgNS were washed by centrifugation and used for SERS analysis of test molecules (methylene blue) as well as biological analytes: pharmaceutical compounds with various Raman cross sections (doxorubicin, atenolol & metoprolol), cell lysates and amino acids (methionine & cysteine). UV-Vis absorption spectroscopy, (Scanning) Transmission Electron Microscopy ((S)TEM) and Atomic Force Microscopy (AFM) have been employed for investigating nanostars’ physical properties.     

Comparison of a real-time PCR method with a culture method for the detection of Salmonella enterica serotype enteritidis in naturally contaminated environmental samples from integrated poultry houses

Conventional culture methods have traditionally been considered the "gold standard" for the isolation and identification of foodborne bacterial pathogens. However, culture methods are labor-intensive and time-consuming. A Salmonella enterica serotype Enteritidis-specific real-time PCR assay that recently received interim approval by the National Poultry Improvement Plan for the detection of Salmonella Enteritidis was evaluated against a culture method that had also received interim National Poultry Improvement Plan approval for the analysis of environmental samples from integrated poultry houses. The method was validated with 422 field samples collected by either the boot sock or drag swab method. The samples were cultured by selective enrichment in tetrathionate broth followed by transfer onto a modified semisolid Rappaport-Vassiliadis medium and then plating onto brilliant green with novobiocin and xylose lysine brilliant Tergitol 4 plates. One-milliliter aliquots of the selective enrichment broths from each sample were collected for DNA extraction by the commercial PrepSEQ nucleic acid extraction assay and analysis by the Salmonella Enteritidis-specific real-time PCR assay. The real-time PCR assay detected no significant differences between the boot sock and drag swab samples. In contrast, the culture method detected a significantly higher number of positive samples from boot socks. The diagnostic sensitivity of the real-time PCR assay for the field samples was significantly higher than that of the culture method. The kappa value obtained was 0.46, indicating moderate agreement between the real-time PCR assay and the culture method. In addition, the real-time PCR method had a turnaround time of 2 days compared with 4 to 8 days for the culture method. The higher sensitivity as well as the reduction in time and labor makes this real-time PCR assay an excellent alternative to conventional culture methods for diagnostic purposes, surveillance, and research studies to improve food safety.     

Cell-Permeable Succinate Rescues Mitochondrial Respiration in Cellular Models of Statin Toxicity

Statins are the cornerstone of lipid-lowering therapy. Although generally well tolerated, statin-associated muscle symptoms (SAMS) represent the main reason for treatment discontinuation. Mitochondrial dysfunction of complex I has been implicated in the pathophysiology of SAMS. The present study proposed to assess the concentration-dependent ex vivo effects of three statins on mitochondrial respiration in viable human platelets and to investigate whether a cell-permeable prodrug of succinate (complex II substrate) can compensate for statin-induced mitochondrial dysfunction. Mitochondrial respiration was assessed by high-resolution respirometry in human platelets, acutely exposed to statins in the presence/absence of the prodrug NV118. Statins concentration-dependently inhibited mitochondrial respiration in both intact and permeabilized cells. Further, statins caused an increase in non-ATP generating oxygen consumption (uncoupling), severely limiting the OXPHOS coupling efficiency, a measure of the ATP generating capacity. Cerivastatin (commercially withdrawn due to muscle toxicity) displayed a similar inhibitory capacity compared with the widely prescribed and tolerable atorvastatin, but did not elicit direct complex I inhibition. NV118 increased succinate-supported mitochondrial oxygen consumption in atorvastatin/cerivastatin-exposed platelets leading to normalization of coupled (ATP generating) respiration. The results acquired in isolated human platelets were validated in a limited set of experiments using atorvastatin in HepG2 cells, reinforcing the generalizability of the findings.     

Electrical conductivity of Ca-substituted lanthanum manganites

The physico-chemical properties of substituted perovskites materials have been analyzed with the aim of studying the relationships between structure and properties in this class of materials. Investigations were carried out into the effect of substitution in lanthanum manganites La_1–xCa_xMnO₃ (x = 0; 0.05; 0.1; 0.15) materials obtained through sol-gel method followed by heat treatment at low temperatures and X-ray diffraction, into the surface area thereof, as well as into transmission electron microscopy for purposes of morpho-structural characterization. The results indicated a well-crystallized Pm-3m perovskite-type structure, and 20 nm average crystallite sizes for all samples. By means of complex impedance measurements in the 20 Hz–2 MHz frequency range, the electrical conductivity was determined at temperatures between 30 °C and 120 °C; the results showed that the conductivity obeys a Jonscher's universal law. It was found that below 10 kHz, the dc component of the conductivity increases with temperature for all samples, indicating that electrical conduction processes are activated thermally, in agreement with Mott's variable-range hopping (VRH) model; the model parameters (hopping distance and hopping energy) were also determined. In the high frequency range (f > 200 kHz) the ac conductivity is attributed to charge carriers hopping between the nearest neighboring states, in agreement with the correlated barrier hopping (CBH) model. Using this model, the energy band gap values: 0.364 eV, 0.372 eV and 0.424 eV of the substituted samples were found.     

Synthesis and Optical Studies of Superconducting MgB2 Thin Films

Synthesis and optical transmission of MgB₂ thin films on optically transparent glass are reported. In the 400–1000 nm regime as deposited films show high metallic reflectivity and very little transmission. After deposition, the films were annealed ex situ and rendered superconducting with T _c of 38 K, approaching that of the bulk material. The reaction conditions where quite soft ∼10 min at 550°C. The optical absorption coefficient, α and photon energy, E followed a Tauc-type behavior, = _T (E - E_g )(\alpha E)^{1/2} = \beta _T (E - E_{\rm g} ). The band gap (E _g) was observed to peak at 2.5 eV; but, the slope parameter β _T behaved monotonically with reaction temperature. Our results indicate that an intermediate semiconducting phase is produced before the formation of the superconducting phase; also optical measurements provide valuable information in monitoring the synthesis of MgB₂ from its metallic constituents. In addition these films have interesting optical properties that may be integrated into optoelectronics.     

Reduced Order Observer for Linear Time-Invariant Multivariable Systems with Unknown Inputs

This paper presents the design of a new reduced order observer to estimate the state for a class of linear time-invariant multivariable systems with unknown inputs. The proposed design approach is a combination of the approaches proposed by Hou and Muller (IEEE Trans. Autom. Control 37:871–875, 1992) and Boubaker (Int. J. Autom. Control Syst. Eng. 5:45–51, 2005); matrix decompositions, state transformations, and substitutions based on coordinate changes are used. It is shown that the problem of reduced order observers for linear systems with unknown inputs can be reduced to a standard one (the unknown input vector will not interfere in the observer equations). The effectiveness of the suggested design algorithm is illustrated by a numerical example (aircraft lateral motion), and, for the same aircraft dynamics, we compare our new observer with other already existing observers from the existence conditions and dynamic characteristics point of view; the superiority of the new designed observer is demonstrated.     

Computer-based engineering of thermostabilized antibody fragments

We used the molecular modeling program Rosetta to identify clusters of amino acid substitutions in antibody fragments (scFvs and scAbs) that improve global protein stability and resistance to thermal deactivation. Using this methodology, we increased the melting temperature (T_m) and resistance to heat treatment of an antibody fragment that binds to the Clostridium botulinum hemagglutinin protein (anti-HA33). Two designed antibody fragment variants with two amino acid replacement clusters, designed to stabilize local regions, were shown to have both higher T_m compared to the parental scFv and importantly to retain full antigen binding activity after 2 hr of incubation at 70°C. The crystal structure of one thermostabilized scFv variants was solved at 1.6 Å and shown to be in close agreement with the RosettaAntibody model prediction.     

欧洲内部电力市场中对用户群的电费率开发

由于欧洲议会 96/92 EC的指示 ,欧洲正在引入供电竞争。如果供电公司能开发出有区别的电价和服务工作的一揽子规定 (以下按原文直译为费率 -服务包 )奉献给用户群 ,那么电力市场的自由化将使用户得益。新出现和快速变化的营业对供电商代表一种挑战性的新的市场机会。适用于竞争市场条件的新的费率和服务工作的快速设计提出走一条非传统的途径。供电商与用户合作开发的负荷测量工程所产生的实验性的响应费率 ,可能有助于将新的费率 -服务产物迅速推向市场。这些产物包括用于热力储存、自动发电用户所发的电力、实时定价和动态费率以及各种“绿色费率”的创新的费率 -服务包。