Comparative Serological Study for the Prevalence of Anti-MERS Coronavirus Antibodies in High- and Low-Risk Groups in Qatar

Infection with Middle East respiratory syndrome coronavirus (MERS-CoV) could be asymptomatic or cause mild influenza-like illness. Therefore, the prevalence of MERS-CoV infections in the general population could be underestimated, which necessitates active surveillance to determine the epidemiological importance of asymptomatic cases. The aim of this study is to evaluate the performance of various serological assays and to estimate the seroprevalence of anti-MERS-CoV antibodies in high- and low-risk groups in Qatar. A total of 4858 samples were screened, including 4719 samples collected from healthy blood donors (BD) over a period of five years (2012-2016), 135 samples from baseline case contacts (CC) collected from individuals in close contact with three positive PCR-confirmed patients (CP), and four samples from MERS-CoV CP. Initial screening using anti-MERS-CoV IgG (IgG rS1-ELISA kit) revealed ten reactive samples from BD (10/4719, 0.21%), one from CC (1/135, 0.74%), and three from CP (3/4, 75%). Samples from CP but not from BD were also reactive by whole-virus anti-MERS-CoV IgG (n=3/4) and IgM (n=1/4) indirect immunefluorescent tests (IIFT) and pseudoparticle neutralization test (ppNT). The reactive sample from CC was also confirmed by ppNT. Surprisingly, one out of thirteen (7.7%) randomly selected IgG rS1-ELISA-negative BD samples from the initial screening was reactive by the IgM-IIFT (but not by the IgG-IIFT) and was subsequently confirmed by ppNT. All IgG rS1-ELISA-reactive samples from BD exhibited considerable reactivity to the four circulating human coronaviruses (HKU1, OC43, 229E, and NL63). Cross-reactivity with SARS was only reported for samples from CP using IgG and IgM-IIFT. In conclusion, we report a low prevalence of anti-MERS antibodies in the general population, which coincides with the low number of all reported cases by the time of our study (2017) in Qatar (n=21). The false-positive results and the observed cross-reactivity between MERS-CoV and other circulating human coronavirus necessitate more detailed evaluation of available serological assays.

Determination of oxidation characteristics and decomposition kinetics of some Nigerian biomass

The oxidation characteristics and devolatilisation kinetics studies of palm kernel shell (Elaeis guineensis), African bush mango wood and shell (Irvingia wombolu), and African border tree wood (Newbouldia laevis), were carried out by the thermogravimetric method. A thermogravimetric analyser TA Q500 instrument was used at a heating rate of 30 °C.min-1 under oxidative conditions. It was observed that all the samples followed a two-stage structural decomposition between 200 °C and500 °C. The greatest mass loss rate occurred within the oxidation stage (200–375 °C) in all the samples. The ignition temperature of the samples ranged from 275–293 °C while their burnout temperatures ranged from 475–500 °C. During the oxidationstage, African bush mango shell was the most reactive sample, while palm kernel shell was the least. During the char combustion stage (375–500 °C), the reactivity of palm kernel shell was the highest. The average activation energy of the samples for the entire decomposition period are 140, 270, 131 and 231 kJ.mol-1 respectively. The biomass samples considered are thus suitable for combustion purposes for bioenergy production with minimal external energy input.

Case report and evaluation of the frequency of the prozone phenomenon in syphilis serology - an infrequent but important laboratory phenomenon

Background Treponema pallidum specific serology generally remains reactive for life. Therefore, the diagnosis of syphilis reinfection relies on clinical assessment and nontreponemal (reagin) serologic testing. The prozone phenomenon can lead to a falsely nonreactive rapid plasma reagin (RPR) assay result. Methods: We report a case of secondary syphilis in a HIV infected patient with a previous history of syphilis infection, where a falsely nonreactive RPR assay was associated with a delayed diagnosis of reinfection and infectious syphilis. The prozone phenomenon was detected in several of the patient’s serum samples collected around this time. We subsequently undertook a prospective evaluation for the prozone phenomenon in 3222 consecutive sera, which were assayed using the RPR assay for clinical purposes over a 10-month period. Results: The overall rate of the prozone phenomenon was 2 out of 3222 samples (0.06%; 95% confidence interval (CI): 0.02–0.22%) and the rate per reactive sample was 2 out of 397 (0.5%; 95% CI: 0.14–1.81%). Conclusion: Clinicians should request RPR testing at dilutions of sera when syphilis is suspected clinically and the RPR assay is nonreactive.

In situ and ex situ transmission electron microscopy investigation of Cu–Al–Cu–Ti reactive metallic multilayer coatings

Metallic multilayers of Cu/Al/Ti composition were studied by transmission electron microscopy (TEM) and plasmon energy-loss mapping as prototypes of nanoscale reactive multilayer systems with exothermic alloy formation in oxygen-free conditions. The selection and arrangement of alloy phases by the system during ex situ and in situ heating experiments were found to depend not only on temperature but strongly on the initial volume ratios of metals, and to a lesser degree on the dimensionality of the reactive sample. Here, a two-dimensional sample was represented by ex situ heating of the full multilayer structure, a one-dimensional sample refers to in situ heating of thin cross-sectional TEM specimens, while a zero-dimensional sample (or metallic dot-array) was obtained after cutting thin pillars using focused ion beams. Lamellar self-organized alternation between Heusler phase and Cu9Al4 was found.

LVSEM Surface Sampling, Preparation, Peak Overlap, Convergent Analysis and Covering up the FESTEM Aperture Charging Problem

Surfaces The majority of the SEM secondary electron signal (SE) comes from the first few (<2nm) nanometers of the surface. The quality of the outermost few atomic layers of an exposed and reactive sample can therefore have a profound effect on image contrast. With light elements and low voltages the SE signal is dominated by scattering at the point of incidence of the primary probe, but more generally there is a significant contribution to surface SE generation by primary electrons backscattered from deeper in the sample. With the advent of very low voltage EDS, and the application of more conventional surface science methods, we learn that even without a coating the surface of a sample may be atypical of the bulk (Fig. 1). Contamination of an otherwise clean surface occurs by transport of the sample through the air, leading to oxidation, hydrocarbon accumulation, and occasionally to rather more dramatic pyrophoric effects.

The effects of a linearly increasing ambient temperature on an exothermic reaction in a closed system

Thermal analysis in general, and differential scanning calorimetry in particular, offer rapid and automated techniques for studying exothermic decompositions. When reaction is not too complex, values for the exothermicities and Arrhenius parameters may be extracted. The basis of most mathematical treatments is not deep and quite commonly rests on analyses of ‘static’ situations, in which the responses to constant ambient temperatures are the starting point. In this paper we give an economical analysis of the dynamic process of heating a reactive sample continuously. The reduced variables of thermal explosion theory provide a compact representation of the standard case of a single reaction obeying a first-order rate law with an Arrhenius temperature dependence. An asymptotic treatment is used to refine the equations of mass and energy conservation to a practically important form. The natural variables that arise in this way lead to a model of the system in terms of the rate of the chemical reaction, rather than the more usual temperature of the sample. This new treatment leads to a clear and compact description of the behaviour of the reaction for all useful operating conditions. The well-known Kissinger relation normally derived from static treatments is seen to be relevant in this model, but care must be taken in choosing the precise physical quantities to which it relates.