Development of a miniature calorimeter for identification and detection of explosives and other energetic compounds

The development of versatile systems capable of providing rapid, portable, and inexpensive detection of explosives and energetic compounds are critically needed to offer enhanced levels of protection against current and future threats to homeland security, as well as satisfying a wide range of applications in the fields of forensic analysis, emergency response, and industrial hazards analysis. Calorimetric techniques have been largely overlooked in efforts to develop advanced chemical analysis technology, largely because of limitations associated with the physical size of the instruments and the relatively long timescales (>30 min) required to obtain a result. This miniaturized calorimeter circumvents these limitations, thereby creating a first-of-its-kind system allowing thermal analysis to be performed in a portable format that can be configured for use in a variety of field operations with a significantly reduced response time (approximately 2 min). Unlike current explosives detectors, this system is based on calorimetric techniques that are inherently capable of providing direct measurements of energy release potential and therefore do not depend on prior knowledge of familiar compounds.     

Increasing the potency of a cytotoxin with an arginine graft

Variants and homologs of bovine pancreatic ribonuclease (RNase A) can exhibit cytotoxic activity. This toxicity relies on cellular internalization of the enzyme. Residues Glu49 and Asp53 form an anionic patch on the surface of RNase A. We find that replacing these two residues with arginine does not affect catalytic activity or affinity for the cytosolic ribonuclease inhibitor (RI) protein. This 'arginine graft' does, however, increase toxicity towards human cancer cells. Appending a nonaarginine domain to this cationic variant results in an additional increase in cytotoxicity, providing one of the most cytotoxic known variants of RNase A. These findings correlate the potency of a ribonuclease with its deliverance of ribonucleolytic activity to the cytosol, and indicate a rational means to enhance the efficacy of ribonucleases and other cytotoxic proteins.     

Electronic and structural characteristics of zinc-blende wurtzite biphasic homostructure GaN nanowires

We report a new biphasic crystalline wurtzite/zinc-blende homostructure in gallium nitride nanowires. Cathodoluminescence was used to quantitatively measure the wurtzite and zinc-blende band gaps. High-resolution transmission electron microscopy was used to identify distinct wurtzite and zinc-blende crystalline phases within single nanowires through the use of selected area electron diffraction, electron dispersive spectroscopy, electron energy loss spectroscopy, and fast Fourier transform techniques. A mechanism for growth is identified.     

Evaluation of pretreatment strategies for near-infrared spectroscopy calibration development of unground and ground compound feedingstuffs

Chemometric procedures are usually applied to near-infrared (NIR) spectra in order to obtain prediction models. These procedures include the application of different combinations of spectral mathematical pretreatments for the improvement of calibrations and the selection of the best model on the basis of validation results. In this work, we used an automatic routine to obtain calibrations for unground and ground compound feedingstuffs (N=354 samples), including 49 combinations of pretreatments (first and second derivatives, an auto scaling procedure, detrending and two versions of multiplicative scatter correction). Calibrations for crude fiber and crude protein were developed without elimination of outliers and with 2 or 9 maximum passes of elimination of outliers. Validation statistics were highly influenced by the pretreatments used, as a combined result of their ability to improve the detection of outliers and the model adjustment. The standard error of prediction (SEP) values ranged from 0.61 to 1.27 for crude protein (CP) and from 0.74 to 1.33 for crude fiber (CF). In spite of the fact that validation statistics did not show a clear distribution pattern, some combinations of pretreatments provided consistently better results.     

CoCrPt/Ti perpendicular media onto nanostructured polymer templates

The fabrication and the study of the magnetic properties of CoCrPt/Ti nanostructures produced by sputtering onto ordered polymer templates are reported here. Samples exhibit a significant out-of-plane component of the magnetization higher than for planar films, and it is stronger for the thicker CoCrPt films, and for nanostructured films with the shorter period ordering. The shape of the polymeric templates plays an important role for the determination of magnetic easy-axis. Magnetic Force Microscopy images of the samples show a single magnetic domain structure with high out-of-plane anisotropy for the samples with longer ordering (480 nm period).     

Surface enhanced Raman scattering spot tests: a new insight on Feigl's analysis using gold nanoparticles

Traditional Feigl's spot tests can be greatly improved with the aid of gold nanoparticles and Raman probes, by monitoring the changes in the surface enhanced Raman scattering (SERS) of the analytes directly applied on a filter paper previously impregnated with the selective organic reagent. As a proof of concept, diphenylthiocarbazone (dithizone) was treated with citrate stabilized gold nanoparticles and employed in paper spot tests for a variety of transition and heavy metal ions. Below 10(-5) mol L(-1), only mercury(II) ions were able to displace the dithizone molecules from the "coordination shell" of the gold nanoparticles, leading to a systematic decay of the Raman signals. Because of the huge enhancement of the dithizone vibrational peaks, the SERS spot tests allowed the detection of picograms of Hg(2+) ions.     

Probing Y-shaped DNA structure with time-resolved FRET

Self-assembly based on nucleic acid systems has become highly attractive for bottom-up fabrication of programmable matter due to the highly selective molecular recognition property of biomolecules. In this context, Y-shaped DNA (Y-DNA) provides an effective building block for forming unique self-assembled large-scale architectures. The dimension and growth of the nano- and microstructures depend significantly on the configurational stability of Y-DNA as a building block. Here we present structural studies of Y-DNA systems using a time-resolved FRET (F?rster resonance energy transfer) technique. A fluorophore (Alexa 488) and an acceptor (DABCYL) were placed at two different ends of Y-DNA, and the lifetime of the fluorophore was measured to probe the relative distance between the donor and acceptor. Our results confirmed different distances between the arms of the Y-DNA and highlighted the overall structural integrity of the Y-DNA system as a leading building block for molecular self-assembly. Temperature dependent lifetime measurements indicated configurational changes in the overall Y-DNA nanoarchitecture above 40 °C.     

Transfer of Salmonella Enteritidis to four types of surfaces after cleaning procedures and cross-contamination to tomatoes

The objectives of the present study were to evaluate the spread of Salmonella Enteritidis to different cutting boards (wood, triclosan-treated plastic, glass, and stainless steel) from contaminated poultry skin (5 log CFU/g) and then to tomatoes and to analyze the effect of different protocols used to clean these surfaces to control contamination. The following procedures were simulated: (1) no cleaning after handling contaminated poultry skin; (2) rinsing in running water; (3) cleaning with dish soap and mechanical scrubbing; and (4) cleaning with dish soap and mechanical scrubbing, followed by disinfection with hypochlorite. The pathogen was recovered from all surfaces following procedure 1, with counts ranging from 1.90 to 2.80 log, as well as from the tomatoes handled on it. Reduced numbers of S. Enteritidis were recovered using the other procedures, both from the surfaces and from the tomatoes. Counts were undetectable after procedure 4. From all surfaces evaluated, wood was the most difficult to clean, and stainless steel was the easiest. The use of hypochlorite as a disinfecting agent helped to reduce cross-contamination.     

Metabolic and production profiles of dairy cows in response to decreased nutrient density to increase physiological imbalance at different stages of lactation

Physiological imbalance (PI) is a situation in which physiological parameters deviate from the normal, and cows consequently have an increased risk of developing production diseases and reduced production or reproduction. Our objectives were to (1) determine the effect of stage of lactation and milk yield on metabolic and production responses of cows during a nutrient restriction period to experimentally increase PI; (2) identify major metabolites that relate to degree of PI; and (3) identify potential biomarkers in milk for on-farm detection of PI throughout lactation. Forty-seven Holstein cows in early [n=14; 49±22 d in milk (DIM); parity=1.6±0.5], mid (n=15; 159±39 DIM; parity=1.5±0.5), and late (n=18; 273±3 DIM; parity=1.3±0.5) lactation were used. Prior to restriction, all cows were fed the same total mixed ration ad libitum. All cows were then nutrient restricted for 4 d by supplementing the ration with 60% wheat straw to induce PI. After restriction, cows returned to full feed. Daily milk yield was recorded and composite milk samples were analyzed for fat, protein, lactose, citrate, somatic cells, uric acid, alkaline phosphatase, β-hydroxybutyrate (BHBA), and milk urea nitrogen. Blood was collected daily and analyzed for metabolites: nonesterified fatty acids (NEFA), BHBA, glucose, plasma urea nitrogen, and insulin. The revised quantitative insulin sensitivity check index (RQUICKI) was calculated for each cow. Liver biopsies collected before and during restriction were analyzed for triglycerides, glycogen, phospholipids, glucose, and total lipid content. A generalized linear mixed model was used to determine the effect of stage of lactation on responses during restriction. Regression analyses were used to examine the effect of pre-restriction levels on changes during restriction. Similar decreases in milk yield among groups indicate that the capacity of individual responses is dependent on milk yield but the coping strategies used are dependent on stage of lactation. Milk yield was a better predictor of feed intake than DIM. Plasma glucose decreased for all cows, and cows in early lactation had increased plasma BHBA, whereas cows in later lactation had increased NEFA during restriction. Milk citrate had the greatest increase (58%) during restriction for all cows. Results reported here identified metabolites (i.e., glucose, NEFA, BHBA, cholesterol) as predictors of PI and identified milk citrate as a promising biomarker for PI on farm.