Exposure to benzene, toluene, ethylbenzene, and xylene (BTEX) at Nigeria's petrol stations: a review of current status, challenges and future directions.

Introduction: In Nigeria, because of increasing population, urbanization, industrialization, and auto-mobilization, petrol is the most everyday non-edible commodity, and it is the leading petroleum product traded at the proliferating Nigeria's petrol stations (NPSs). However, because of inadequate occupational health and safety (OHS) regulatory measures, working at NPSs exposes petrol station workers (PSWs) to a large amount of hazardous benzene, toluene, ethylbenzene, and xylene (BTEX) compounds. Methods: Studies on BTEX exposures among Nigerian PSWs are scarce. Thus, constraints in quantifying the health risks of BTEX limit stakeholders' ability to design practical risk assessment and risk control strategies. This paper reviews studies on the OHS of Nigerian PSWs at the NPSs. Results: Although knowledge, attitude, and practices on OHS in NPSs vary from one Nigeria's study setting to another, generally, safety practices, awareness about hazards and personal protective equipment (PPE), and the use of PPE among PSWs fell below expectations. Additionally, air quality at NPSs was poor, with a high content of BTEX and levels of carbon monoxide, hydrogen sulfide, particulate matter, and formaldehyde higher than the World Health Organization guideline limits. Discussion: Currently, regulatory bodies' effectiveness and accountability in safeguarding OHS at NPSs leave much to be desired. Understanding the OHS of NPSs would inform future initiatives, policies, and regulations that would promote the health and safety of workers at NPSs. However, further studies need to be conducted to describe the vulnerability of PSWs and other Nigerians who are occupationally exposed to BTEX pollution. More importantly, controlling air pollution from hazardous air pollutants like BTEX is an essential component of OHS and integral to attaining the Sustainable Development Goals (SDG) 3, 7, and 11.

Instrumentation for quantitative analysis of volatile compounds emission at elevated temperatures. Part 2: Analysis of carbon fibre reinforced epoxy composite.

We have investigated the release of gases and volatile organic compounds (VOCs) from a carbon fibre reinforced epoxy composite matrix used in aircraft structural components. Analysis was performed at several temperatures both up to and above the recommended operating temperature (121 °C) for the material, to a maximum of 250 °C. Gas chromatography-mass spectrometry (GC-MS) combined with thermal desorption (TD-GC-MS) was used to identify and quantify VOCs, and in parallel real-time gas detection with commercial off-the-shelf (COTS) gas sensors. Under hydrocarbon free air, CO, SO2, NO, NO2 and VOCs (mainly aldehydes, ketones and a carboxylic acid) were detected as the gaseous products released during the thermal exposure of the material up to 250 °C, accompanied by increased relative humidity (4%). At temperatures up to 150 °C, gas and volatile emission was limited.

Instrumentation for quantitative analysis of volatile compounds emission at elevated temperatures. Part 1: Design and implementation.

A novel suite of instrumentation for the characterisation of materials held inside an air-tight tube furnace operated up to 250 °C has been developed. Real-time detection of released gases (volatile organic compounds (VOCs), CO2, NO, NO2, SO2, CO and O2) was achieved combining commercial off-the-shelf (COTS) gas sensors and sorbent tubes for further qualitative and semi-quantitative analysis by gas chromatography-mass spectrometry coupled to thermal desorption (TD-GC-MS). The test system was designed to provide a controlled flow (1000 cm3 min-1) of hydrocarbon free air through the furnace. The furnace temperature ramp was set at a rate of 5 °C min-1 with 10 min dwell points at 70 °C, 150 °C, 200 °C and 250 °C to allow time for stabilisation and further headspace sampling onto sorbent tubes. Experimental design of the instrumentation is described here and an example data set upon exposure to a gas sample is presented.

Faecal volatile biomarkers of Clostridium difficile infection.

Care of patients with potential CDI can involve isolation and use of antibiotics, often before a definitive diagnosis is available, impacting healthcare resource and contributing to antibiotic resistance. There is anecdotal evidence that the faeces of CDI patients have a distinctive odour, while it is well-established that changes in the gut microbiota are associated with changes in the volatile organic compounds (VOC) produced. A total of twenty-four candidate volatile biomarkers were identified from a review of the literature including in vitro, animal and human studies. Using thermal desorption-gas chromatography-time-of flight mass spectrometry (TD-GC-ToFMS), VOC emission rates were determined on stored frozen stool samples from 53 CDI-positive and 53 CDI-negative patients with unexplained diarrhoea which had previously been diagnosed using enzymatic and nucleic acid amplification tests. Sample preparation was limited to placement of a subsample in an appropriate container. Compounds exhibiting a statistically significant difference (p < 0.05) in emission rate between the CDI-positive and-negative groups and a corresponding area under the receiver-operator characteristic curve (ROC) >0.7 were considered potentially indicative of CDI. Seven compounds were so identified: propan-1-ol (ROC 0.75), 3-methylbutanal (ROC 0.84), ethyl propionate (ROC 0.81), hexanoic acid (ROC 0.73), 4-methylphenol (ROC 0.81), dodecane (ROC 0.80) and indole (ROC 0.85). A number of potential volatile biomarkers of CDI can be sampled rapidly and with little prior preparation from faecal samples of patients with diarrhoea. Of these 4-methylphenol (p-cresol) is of particular interest as it has been anecdotally linked to CDI and is closely related to the biology and virulence of Clostridium difficile. This approach shows promise for the rapid, point-of-care diagnosis of CDI with good sensitivity and specificity.

Lifetime Stability and Microstructure Properties of Cr/B4C X-ray Reflective Multilayer Coatings.

This paper demonstrates that highly reflective Cr/B4C multilayer interference coatings with nanometric layer thicknesses, designed to operate in the soft X-ray photon energy range, have stable reflective performance for a period of 3 years after deposition. The microstructure and chemical composition of layers and interfaces within Cr/B4C multilayers is also examined, with emphasis on the B4C-on-Cr interface where a significant diffusion layer is formed and on the oxide in the top B4C layer. Multiple characterization techniques (X-ray reflectivity at different photon energies, X-ray photoelectron spectroscopy, transmission electron microscopy, electron diffraction and X-ray diffraction) are employed and the results reveal a consistent picture of the Cr/B4C layer structure.

In Situ Real-Time Radiographic Study of Thin Film Formation Inside Rotating Hollow Spheres.

Hollow spheres with uniform coatings on the inner surface have applications in optical devices, time- or site-controlled drug release, heat storage devices, and target fabrication for inertial confinement fusion experiments. The fabrication of uniform coatings, which is often critical for the application performance, requires precise understanding and control over the coating process and its parameters. Here, we report on in situ real-time radiography experiments that provide critical spatiotemporal information about the distribution of fluids inside hollow spheres during uniaxial rotation. Image analysis and computer fluid dynamics simulations were used to explore the effect of liquid viscosity and rotational velocity on the film uniformity. The data were then used to demonstrate the fabrication of uniform sol-gel chemistry derived porous polymer films inside 2 mm inner diameter diamond shells.

Analysis of volatile organic compounds of bacterial origin in chronic gastrointestinal diseases.

BACKGROUND: The aim of this study was to determine whether volatile organic compounds (VOCs) present in the headspace of feces could be used to diagnose or distinguish between chronic diseases of the gastrointestinal tract and apparently healthy volunteers. METHODS: A total of 87 people were recruited, divided between 4 categories: healthy volunteers (n = 19), Crohn's disease (n = 22), ulcerative colitis (n = 20), and irritable bowel syndrome (n = 26). They each supplied fecal samples before, and except for the healthy volunteers, after treatment. Fecal samples were incubated in a sample bag with added purified air at 40°C and headspace samples were taken and concentrated on thermal sorption tubes. Gas chromatography-mass spectrometry then desorbed and analyzed these. The concentrations of a selection of high-abundance compounds were determined and assessed for differences in concentration between the groups. RESULTS: Crohn's disease samples showed significant elevations in the concentrations of ester and alcohol derivates of short-chain fatty acids and indole compared with the other groups; indole and phenol were elevated in ulcerative colitis and irritable bowel syndrome but not at a statistically significant level. After treatment, the levels of many of the VOCs were significantly reduced and were more similar to those concentrations in healthy controls. CONCLUSIONS: The abundance of a number of VOCs in feces differs markedly between Crohn's disease and other gastrointestinal conditions. Following treatment, the VOC profile is altered to more closely resemble that of healthy volunteers.

Photothermal colloid antibodies for shape-selective recognition and killing of microorganisms.

We have developed a class of selective antimicrobial agents based on the recognition of the shape and size of the bacterial cells. These agents are anisotropic colloid particles fabricated as negative replicas of the target cells which involve templating of the cells with shells of inert material followed by their fragmentation. The cell shape recognition by such shell fragments is due to the increased area of surface contact between the cells and their matching shell fragments which resembles antibody-antigen interaction. We produced such "colloid antibodies" with photothermal mechanism for shape-selective killing of matching cells. This was achieved by the subsequent deposition of (i) gold nanoparticles (AuNPs) and (ii) silica shell over yeast cells, which were chosen as model pathogens. We demonstrated that fragments of these composite AuNP/silica shells act as "colloid antibodies" and can bind to yeast cells of the same shape and size and deliver AuNPs directly onto their surface. We showed that after laser irradiation, the localized heating around the AuNPs kills the microbial cells of matching shape. We confirmed the cell shape-specific killing by photothermal colloid antibodies in a mixture of two bacterial cultures of different cell shape and size. This approach opens a number of avenues for building powerful selective biocides based on combinations of colloid antibodies and cell-killing strategies which can be applied in new antibacterial therapies.

Diversity and distribution of sulphate-reducing bacteria in human faeces from healthy subjects and patients with inflammatory bowel disease.

The relative abundance of different groups of sulphate-reducing bacteria (SRB) in faecal DNA collected before and after therapy from patients suffering from Crohn's disease (CD), irritable bowel syndrome (IBS) or ulcerative colitis (UC) has been compared with that from healthy controls. Growth tests revealed that SRB were not more abundant in samples from patients with CD before treatment than in the healthy control group. For most of the 128 samples available, these preliminary results were confirmed using degenerate PCR primers that amplify the dsrAB gene. However, some samples from patients with CD before treatment contained a growth inhibitor that was absent from IBS or UC samples. In-depth sequencing of PCR-generated dsrB fragments revealed that the diversity detected was surprisingly low, with only eight strains of SRB and the sulphite-reducing bacterium, Bilophila wadsworthia, detected above the 0.1% threshold. The proportion of the two major species detected, B. wadsworthia and Desulfovibrio piger, was as high as 93.5% of the total SRB population in the healthy control group and lower in all patient groups. Four previously undescribed species were found: it is impossible to predict whether they are sulphate or sulphite-reducing bacteria.

Breath acetone concentration decreases with blood glucose concentration in type I diabetes mellitus patients during hypoglycaemic clamps.

Conventional wisdom is that breath acetone may be markedly elevated in type 1 diabetes, but that this only occurs during poor blood glucose control and/or intercurrent illness. In contrast, little is known about breath acetone at more representative everyday blood glucose levels in diabetes. We used selected ion flow tube mass spectrometry to monitor the breath of eight patients with type 1 diabetes mellitus during 'insulin clamp' studies in which insulin and glucose were infused into patients to lower blood glucose levels in steps from normal values into the low glucose (hypoglycaemic) range. The concentration of acetone in breath and the blood sugar concentration of the patients were monitored at each blood glucose concentration. The blood glucose level at the start of the study was typically about 6 mM L(-1), whereas the breath acetone concentration at this blood glucose level was unexpectedly variable, ranging from 1 part-per-million to 21 ppm, in contrast to what was previously believed, i.e. that type 1 diabetes mellitus is characterized by high acetone levels. In all eight patients, the breath acetone declined linearly with blood glucose concentration.

An exploratory comparative study of volatile compounds in exhaled breath and emitted by skin using selected ion flow tube mass spectrometry.

Selected ion flow tube mass spectrometry (SIFT-MS) has been used to carry out a pilot parallel study on five volunteers to determine changes occurring in several trace compounds present in exhaled breath and emitted from skin into a collection bag surrounding part of the arm, before and after ingesting 75 g of glucose in the fasting state. SIFT-MS enabled real-time quantification of ammonia, methanol, ethanol, propanol, formaldehyde, acetaldehyde, isoprene and acetone. Following glucose ingestion, blood glucose and trace compound levels were measured every 30 min for 2 h. All the above compounds, except formaldehyde, were detected at the expected levels in exhaled breath of all volunteers; all the above compounds, except isoprene, were detected in the collection bag. Ammonia, methanol and ethanol were present at lower levels in the bag than in the breath. The aldehydes were present at higher levels in the bag than in breath. The blood glucose increased to a peak about 1 h post-ingestion, but this change was not obviously correlated with temporal changes in any of the compounds in breath or emitted by skin, except for acetone. The decrease in breath acetone was closely mirrored by skin-emitted acetone in three volunteers. Breath and skin acetone also clearly change with blood glucose and further work may ultimately enable inferences to be drawn of the blood glucose concentration from skin or breath measurements in type 1 diabetes.

Sub-diffraction-limited multilayer coatings for the 0.3 numerical aperture micro-exposure tool for extreme ultraviolet lithography.

Multilayer coating results are discussed for the primary and secondary mirrors of the micro-exposure tool (MET): a 0.30 NA lithographic imaging system with a 200 microm x 600 microm field of view at the wafer plane, operating in the extreme ultraviolet (EUV) region at an illumination wavelength around 13.4 nm. Mo/Si multilayers were deposited by DC-magnetron sputtering on large-area, curved MET camera substrates. A velocity modulation technique was implemented to consistently achieve multilayer thickness profiles with added figure errors below 0.1 nm rms demonstrating sub-diffraction-limited performance, as defined by the classical diffraction limit of Rayleigh (0.25 waves peak to valley) or Marechal (0.07 waves rms). This work is an experimental demonstration of sub-diffraction- limited multilayer coatings for high-NA EUV imaging systems, which resulted in the highest resolution microfield EUV images to date.

Inflammation markers and erythrocyte sedimentation rate but not metabolic syndrome factor score predict coronary heart disease in high socioeconomic class males: the HDDRISC study.

OBJECTIVE: To evaluate prediction of coronary heart disease (CHD) by quantitative measures of the metabolic syndrome and inflammation in a cohort of high socio-economic status males. METHODS: Incident CHD was identified in a cohort of 649 male participants in a company health programme during a mean follow-up of 10.6 years. Using factor analysis, metabolic syndrome and sub-clinical inflammation scores were derived from baseline measurements, which included an oral glucose tolerance test-derived measure of insulin resistance. Factor scores were then included as predictor variables in a Cox regression analysis of incident CHD. RESULTS: Forty-two cases of definite CHD were identified on follow-up. The conventional risk factors, cigarette smoking, blood pressure, total cholesterol and low HDL cholesterol were clearly distinguished as significant predictors of incident CHD. Erythrocyte sedimentation rate was also an independent predictor (coefficient 0.0480, z score 2.39, p=0.017). The metabolic syndrome factor included insulin resistance, body mass index, serum triglycerides, glucose tolerance, serum uric acid and fasting plasma glucose. The inflammation factor included serum globulin, blood leukocyte count, low albumin, haemoglobin and cholesterol, but not erythrocyte sedimentation rate. The inflammation factor score was a significant predictor of CHD (coefficient 0.4601, z score 2.43, p=0.015) but the metabolic syndrome factor was not (coefficient 0.2488, z score 1.24, p=0.2). CONCLUSIONS: Erythrocyte sedimentation rate and a factor analysis-derived measure of sub-clinical inflammation were important in the development of CHD in this relatively low-risk group, but neither metabolic syndrome factor score nor its individual components predicted CHD.

Atomic-precision multilayer coating of the first set of optics for an extreme-ultraviolet lithography prototype system.

We present our results of coating a first set of optical elements for an extreme-ultraviolet (EUV) lithography system. The optics were coated with Mo-Si multilayer mirrors by dc magnetron sputtering and characterized by synchrotron radiation. Near-normal incidence reflectances above 65% were achieved at 13.35 nm. The run-to-run reproducibility of the reflectance peak wavelength was maintained to within 0.4%, and the thickness uniformity (or gradient) was controlled to within +/-0.05% peak to valley, exceeding the prescribed specification. The deposition technique used for this study is an enabling technology for EUV lithography, making it possible to fabricate multilayer-coated optics to accuracies commensurate with atomic dimensions.

Normal-incidence reflectance of optimized W /B(4) C x-ray multilayers in the range 1.4 nm < l > 2.4 nm.

We have fabricated W/B(4)C multilayers having periods in the range d = 0.8-1.2 nm and measured their soft-x-ray performance near normal incidence in the wavelength range 1.4