Error control schemes for networks: An overview

In this paper, we investigate the issue of error control in wireless communication networks. We review the alternative error control schemes available for providing reliable end-to-end communication in wireless environments. Through case studies, the performance and tradeoffs of these schemes are shown. Based on the application environments and QoS requirements, the design issues of error control are discussed to achieve the best solution. This revised version was published online in June 2006 with corrections to the Cover Date.     

Electrochemical behavior of vanadium in EDTA

The use of chelating agents as cleaning chemicals to remove metal deposits is gaining interest. In this study the Electrochemical behavior of vanadium in EDTA, EA and EAC solutions was studied using AC impedance technique at different immersion time. The results indicate that the values of R_ct for EA solution are higher than that for EDTA and EAC. This may be due to the presence of ascorbic acid as reducing agent. The presence of surface film is confirmed by capacitance measurements. It is shown that the capacitance is time‐dependent. Generally, the capacitance decreases with immersion time and this can be discussed on the basis that the concentration of vanadium ions at the interface increases with immersion time.     

Tailoring structure-function and pharmacokinetic properties of single-chain Fv proteins by site-specific PEGylation

The utility of single-chain Fv proteins as therapeutic agentswould be realized if the circulating lives of these minimalantigen-binding polypeptides could be both prolonged and adjustable.We have developed a general strategy for creating tailored monoPEGylatedsingle-chain antibodies. Free cysteine residues were engineeredin an anti-TNF-     

Sol–gel derived composite from bioactive glass–polyvinyl alcohol

Investigation of novel biomaterials for bone engineering is based on the development of porous scaffolds, which should match the properties of the tissue that is to be replaced. These materials need to be biocompatible, ideally osteoinductive, osteoconductive, and mechanically well-matched. In the present paper, we report the preparation and characterization of hybrid macroporous scaffold of polyvinyl alcohol (PVA)/bioactive glass through the sol–gel route. Hybrids containing PVA (80, 70 and 60 wt%) and bioactive glass with composition 58SiO₂–33CaO–9P₂O₅ were synthesized by foaming a mixture of polymer solution and bioactive glass via sol–gel precursor solution. PVA with two different degree of hydrolysis (DH), 98.5% (high degree) and 80% (low degree) were also investigated, in order to evaluate the influence of residual acetate group present in polymer chain on the final structure and properties of 3D porous composite produced. The microstructure, morphology and crystallinity of the hybrid porous scaffolds were characterized by X-ray diffraction (XRD), Infrared Fourier Transform spectrometry (FTIR) and Scanning electron microscopy (SEM/EDX) analysis. In addition, specific surface area was assessed by B.E.T. nitrogen adsorption method and mechanical behavior was evaluated by compression tests. Preliminary cytotoxicity and cell viability were also performed by the MTT assay. VERO cell monolayers were grown in 96-well microtiter plates. The results have clearly showed that hybrid foams of polyvinyl alcohol/bioactive glass (PVA/BG) with interconnected macroporous 3D structure were successfully produced. All the tested hybrids of PVA/BG have showed adequate cell viability properties for potential biological applications.     

Rhodium‐Catalyzed [2+2+2] Cycloadditions of Diynes with Morita–Baylis–Hillman Adducts: A Stereoselective Entry to Densely Functionalized Cyclohexadiene Scaffolds

A rhodium‐catalyzed asymmetric synthesis of 5,5‐disubstituted cyclohexa‐1,3‐dienes has been achieved by [2+2+2] cycloaddition reactions between diynes and Morita–Baylis–Hillman (M‐B‐H) adducts as unsaturated substrates. Products containing two adjacent chiral centres (quaternary and tertiary, respectively) were obtained with complete diastereoselectivity and high enantioselectivity (84–97%) through a kinetic resolution of the M‐B‐H adduct. Furthermore, these highly substituted cyclohexadienes reacted with dienophiles to afford the corresponding Diels–Alder cycloadducts in good yields.

     

Magnetization transfer imaging of cortical bone in vivo using a zero echo time sequence in mice at 4.7 T: a feasibility study

Objective

To investigate the feasibility of magnetization transfer (MT) imaging in mice in vivo for the assessment of cortical bone.

Materials and methods

MT-zero echo time data were acquired at 4.7 T in six mice using MT preparation pulses with two different flip angles (FAs) and a series of ten different off-resonance frequencies (500–15000 Hz). Regions of interest were drawn at multiple levels of the femoral cortical bone. The MT ratio (MTR) was computed for each combination of FAs and off-resonance frequencies. T1 measurements were used to estimate the direct saturation (DS) using a Bloch equation simulation. Estimation of the absorption line width of cortical bone from T2* measurements was also performed.

Results

MTR values were higher using 3000° FA than 1000° FA. MTR values decreased toward higher off-resonance frequencies. Maximum mean MTR ± standard deviation (SD) of 58.57 ± 5.22 (range 50.44–70.61) was measured with a preparation pulse of 3000° and off-resonance frequency of 500 Hz. Maximum “true” MT effect was estimated at around 2–3 and 5 kHz, respectively, for 1000° and 3000° FA. Mean full width at half maximum ± SD of 577 ± 91 Hz was calculated for the absorption spectral line of the cortical bone.

Conclusion

MT imaging can be used for the assessment of cortical bone in mice in vivo. DS effects are negligible using preparation pulses with off-resonance frequencies greater than 3 kHz.

     

Relevance of cue reactivity to understanding alcohol and smoking relapse.

Several learning-based theories have been forwarded to account for the problem of drug relapse, including conditioned withdrawal, conditioned compensatory responding, appetitive motivational models, and social learning models. The various models are compared and evaluated against available evidence from studies with humans pertaining to alcohol and tobacco addiction. Studies that are reviewed focus primarily on the antecedents and consequences of alcohol and smoking relapse, as well as on reactions to cues that have been associated with prior drug ingestion, in an attempt to understand their motivational relevance. Problems in evaluating the various relapse models in humans are discussed. It is concluded that the appetitive model is better supported than the withdrawal model, and the compensatory model is least supported. Reactions to substance use stimuli may play an important role in alcohol and smoking relapse. Concepts drawn from the various theoretical models are linked tentatively in a schematic diagram of a hypothesized sequence of cognitive/affective, physiological, and behavioral events that lead to initial drug use after a period of abstinence (slip) and then to continued use (a relapse). The treatment implications of some of the cue reactivity models are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Aflatoxin (B1, B2, G1, and G2) Contamination in Rice of Mexico and Spain,from Local Sources or Imported

Rice is an important cereal but it is often contaminated with aflatoxins (AFs). The purpose of this study was to identify and quantify AF (B₁, B₂, G₁, and G₂) in 67 rice samples cultivated in Mexico and Spain, and from imported crops collected in 2008 and 2009. The methodology was validated, the rice samples were concentrated and purified with immunoaffinity columns and were quantified by high‐pressure liquid chromatography (HPLC). The average total AF (AFt) in the Spanish rice was 37.3 μg/kg, the range was from 1.6 to 1383 μg/kg, the most contaminated samples being from San Juan de Aznalfarache, Sevilla (AFt = 138.6 μg/kg), from Tortosa, Tarragona (AFt = 104.6 μg/kg), and Calasparra, Murcia (AFt = 103.9 μg/kg). The rice imported from France to Spain had AFt of 26.6 μg/kg and from Pakistan AFt of 18.4 μg/kg, showing less AF contamination than the local one. The rice which originated from Mexico contained (AFt = 16.9 μg/kg), and those imported from the United States (AFt = 14.4 μg/kg) and Uruguay (AFt = 15.6 μg/kg). The imported rice had better quality in terms of the presence of AFs.