Standoff detection of chemical and biological threats using laser-induced breakdown spectroscopy

Laser-induced breakdown spectroscopy (LIBS) is a promising technique for real-time chemical and biological warfare agent detection in the field. We have demonstrated the detection and discrimination of the biological warfare agent surrogates Bacillus subtilis (BG) (2% false negatives, 0% false positives) and ovalbumin (0% false negatives, 1% false positives) at 20 meters using standoff laser-induced breakdown spectroscopy (ST-LIBS) and linear correlation. Unknown interferent samples (not included in the model), samples on different substrates, and mixtures of BG and Arizona road dust have been classified with reasonable success using partial least squares discriminant analysis (PLS-DA). A few of the samples tested such as the soot (not included in the model) and the 25% BG:75% dust mixture resulted in a significant number of false positives or false negatives, respectively. Our preliminary results indicate that while LIBS is able to discriminate biomaterials with similar elemental compositions at standoff distances based on differences in key intensity ratios, further work is needed to reduce the number of false positives/negatives by refining the PLS-DA model to include a sufficient range of material classes and carefully selecting a detection threshold. In addition, we have demonstrated that LIBS can distinguish five different organophosphate nerve agent simulants at 20 meters, despite their similar stoichiometric formulas. Finally, a combined PLS-DA model for chemical, biological, and explosives detection using a single ST-LIBS sensor has been developed in order to demonstrate the potential of standoff LIBS for universal hazardous materials detection.     

An analytical approach for physical modeling of hot-carrier induced degradation

We develop an analytical model for hot-carrier degradation based on a rigorous physics-based TCAD model. The model employs an analytical approximation of the carrier acceleration integral (calculated with our TCAD approach) by a fitting formula. The essential features of hot-carrier degradation such as the interplay between single-and multiple-electron components of Si–H bond dissociation, mobility degradation during interface state build-up, as well as saturation of degradation at long stress times are inherited. As a result, the change of the linear drain current can be represented by the analytical expression over a wide range of stress conditions. The analytical model can be used to study the impact of device geometric parameters on hot-carrier degradation.     

Antioxidant capacity and total phenolics of <Emphasis Type="Italic">Cyphostemma digitatum</Emphasis> before and after processing: use of different assays

In the framework of standardisation of new healthy food sources, this paper aimed to study the total phenolics and the antioxidant power of Cyphostemma digitatum (Vitaceae) in water and ethanol extracts, using 96-well micro plates with BMG FLUOstar Optima micro plate reader. Total phenolics by Folin–Ciocalteu method in the water extracts were significantly lower after processing, decreasing from 1.41 ± 0.06 g GAE/100 g in the raw leaves to 0.80 ± 0.08 g GAE/100 g in the processed sample; the ethanol extract revealed the same trend with higher values, decreasing from 1.95 ± 0.03 to 1.56 ± 0.12 g GAE/100 g. The antioxidant capacity was elucidated by four methods: TEAC, DPPH, FRAP and ORAC. No or very weak correlations were found between antioxidant assays and total phenolics; this confirms that the antioxidant capacity could be attributed to other molecules. The ORAC assay proved to be more powerful than the other assays; it showed 103.3 ± 2.5 mmol/100 g Trolox equivalents in the raw leaves ethanol extract and 91.9 ± 3.0 mmol/100 g in the processed sample. ORAC assay showed the opposite for the water extract where the antioxidant capacity increased from 16.7 ± 0.2 to 41.7 ± 2.7 mmol/100 g Trolox equivalents after processing, which could be attributed to new water-soluble compounds generated in the consumed form.     

Microcavity-integrated graphene photodetector

There is an increasing interest in using graphene (1, 2) for optoelectronic applications. (3-19) However, because graphene is an inherently weak optical absorber (only ≈2.3% absorption), novel concepts need to be developed to increase the absorption and take full advantage of its unique optical properties. We demonstrate that by monolithically integrating graphene with a Fabry-Pérot microcavity, the optical absorption is 26-fold enhanced, reaching values >60%. We present a graphene-based microcavity photodetector with responsivity of 21 mA/W. Our approach can be applied to a variety of other graphene devices, such as electro-absorption modulators, variable optical attenuators, or light emitters, and provides a new route to graphene photonics with the potential for applications in communications, security, sensing and spectroscopy.     

Home environment and cognitive development in the first 3 years of life: A collaborative study involving six sites and three ethnic groups in North America.

Attempted to examine the generalizability of environment/development relationships among 3 ethnic groups across the first 3 years of life. Social status did not show a consistent relationship to either quality of home environment or children's developmental status across the various groups. Results indicated a fairly consistent relationship between HOME scores and children's developmental status, although there were some ethnic and social status differences in the relationship. Measures of specific aspects of the child's home environment, such as parental responsivity and availability of stimulating play materials, were more strongly related to child developmental status than global measures of environmental quality such as SES. When the child's developmental status and early home environment were both very low, the likelihood of poor developmental outcomes was markedly increased compared with cases when only one was low. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Preformulation the Role of Moisture in Solid Dosage Forms

Moisture plays an important role in the individual stages of preformulation studies for solid dosage forms. Examples are given to demonstrate this

The first stage involves chemical tests with the pure active substance using a reliable storage scheme. Then compatibility testing between active and inactive substances is performed. Under the general heading of sorption tests, the determination of sorption isotherms using special apparatus and their correlation with the physical and chemical changes which occur in the samples are discussed. With the results of these tests it is often possible to influence the sorption properties of the finished dosage form, for example by selection of the excipients and the salt form of the active substance, or by deferring the point of ansorption

Finally, as an example of special tests used in pre-formulation, the development of compound preparations is described and the galenical pre-stages are discussed     

Virtual cystoscopy based on helical CT scan datasets: perspectives and limitations

The purpose of the study was to simulate cystoscopy based on three-dimensional helical CT scan datasets in real-time in patients with tumours of the urinary bladder. A helical CT scan with double detector technology was carried out pre-operatively in 11 patients with histologically confirmed carcinoma of the urinary bladder and one patient with chronic cystitis. A non-enhanced scan was first performed, followed by an examination in the early phase of contrast medium enhancement. Further images were acquired after adequate filling of the bladder with contrast medium, approximately 30 min after injection. These data were transferred to a separate graphic computer workstation and reconstructed. The results were then compared with the cystoscopic and histopathological findings. All tumours of the urinary bladder identified at fibreoptic cystoscopy were shown on virtual cystoscopy. The best reconstruction results were obtained from data acquired 30 min after injection of contrast medium. The ureteric orifices were not visualized at virtual cystoscopy. These data lead us to conclude that, at present, virtual cystoscopy has not reached the quality of fibreoptic examination and remains restricted to use in specific cases, for example patients with urethral strictures.     

Vorkommen von β-Phenylethylamin und seinen Derivaten in Kakao und Kakaoerzeugnissen

Zusammenfassung -Phenylethylamin wurde aus Kakaokernen und Schokoladen extrahiert und anhand GC/MS als Trifluoracetamid analysiert. Seine Konzentration steigt bei der Fermentation des Kakaos und sinkt während der Röstung und des Alkalisierens. Der Gehalt in Schokoladen hängt vom fettfreien Kakaoanteil ab. In Kakaopulver wurden erstmals Aldimine aus der Kondensation von Phenylethylamin mit Aldehyden gefunden, deren Hauptprodukt das N-Benzyliden--phenylethylamin (CAS 3240-95-7) darstellt.

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Occurrence of 2-phenylethylamine and its derivatives in cocoas and chocolates

Summary 2-Phenylethylamine was extracted from cocoa nibs and chocolates and analysed by coupled gas chromatography-mass spectroscopy. The amine concentration increases in fermentation of cocoa and decreased during roasting and alkalization. Its concentration in chocolates is dependent on non-fat cocoa contents. Previously unreported aldimines were found in cocoa powders, which arise from the condensation of phenylethylamine and aldehydes. The main component of these products isN-phenylmethyl-N-phenylmethylene amine (CAS 3240-95-7).