Polymerase chain reaction amplification of DNA from aged blood stains: quantitative evaluation of the "suitability for purpose" of four filter papers as archival media

In collaboration with the Armed Forces Institute of Pathology's Department of Defense DNA Registry, the National Institute of Standards and Technology recently evaluated the performance of a short tandem repeat multiplex with dried whole blood stains on four different commercially available identification card matrixes. DNA from 70 stains that had been stored for 19 months at ambient temperature was extracted or directly amplified and then processed using routine methods. All four storage media provided fully typeable (qualitatively identical) samples. After standardization, the average among-locus fluorescence intensity (electropherographic peak height or area) provided a suitable metric for quantitative analysis of the relative amounts of amplifiable DNA in an archived sample. The amounts of DNA in Chelex extracts from stains on two untreated high-purity cotton linter pulp papers and a paper treated with a DNA-binding coating were essentially identical. Average intensities for the aqueous extracts from a paper treated with a DNA-releasing coating were somewhat lower but also somewhat less variable than for the Chelex extracts. Average intensities of directly amplified punches of the DNA-binding paper were much larger but somewhat more variable than the Chelex extracts. Approximately 25% of the observed variation among the intensity measurements is shared among the four media and thus can be attributed to intrinsic variation in white blood count among the donors. All of the evaluated media adequately "bank" forensically useful DNA in well-dried whole blood stains for at least 19 months at ambient temperature.     

Ultrasonic determination of the superconducting energy gap in high-purity tantalum

Ultrasonic attenuation measurements as a function of temperature were made for sound propagating along the [100], [110], and [111] crystal directions of Ta single-crystal specimens. Sound frequencies from 180 to 500 MHz were used with single crystals having residual resistance ratios up to 3866. For the three propagation directions used, the superconducting energy gap had an average value of 1.77kT _c , which was within the experimental error for the three separate values of the gap parameter.     

Cumulative size effects in electrical conductivity of thin semi-metal films

In the general framework of conduction models for monocrystalline and polycrystalline metal films, analytical expressions are derived for the electrical conductivity of semi-metal films. The existence of two cumulative size effects is thus predicted. These new equations agree with those previously derived in a special case of energy dependence of the relaxation time.     

Impact of high pressure treatment on the structure of montmorillonite

The modification of sodium montmorillonite after a high pressure pasteurization treatment was followed by X-ray diffraction, FTIR spectroscopy and thermogravimetric analysis. Regardless of the treatment intensity (300 and 800 MPa), the structure of montmorillonite was clearly modified. Such changes should be taken into consideration when binging montmorillonite–polymer nanocomposites into contact with food.     

Concomitant use of liquid–liquid batch and continuous plug flow reactors for kinetic model discrimination. Application to the Rh/TPPTS catalysed reduction of the C–C double bond in dimethylitaconate

The biphasic catalytic reduction of the C–C double bond of dimethylitaconate with a water soluble rhodium/triphenylphosphinetrisulphonated sodium salt (TPPTS) complex is investigated. Kinetic studies in a well-mixed batch reactor provide kinetics parameters and an activation energy of 71 kJ mol⁻¹ but cannot discriminate between a first order or a complex kinetic model within the range of substrate concentration where the approximation of linear liquid/liquid partition is respected. Catalytic tests in the centrifugal partition chromatograph (CPC) reactor under steady-state operations in chemical regime and plug flow mode allow discriminating the kinetic models, the complex kinetic rate law being preferred.     

Cold Compaction and Solid-State Sintering of WC-Co-Based Structures: Experiments and Modeling

Cold compaction (200-1900 MPa) and sintering (1250°-1350°C) of cermets based on WC-Co were experimentally studied using die compaction, cold isostatic pressing, sintering, and creep tests. Two different-sized WC powders were used. The cobalt content varied over a range of 10-30 wt%. Cold-compaction behavior has been described by using a Cam-Clay model. Die-wall friction was measured by using green powder compacts that had different aspect ratios. Friction coefficients were 0.28-0.85, depending on the WC particle size and cobalt content. Simple constitutive equations have been used to model the high-temperature behavior (sintering and creep). The constitutive equations were implemented in a finite-element program to model the compaction, ejection, and sintering of bilayer structures that had different cobalt contents. The model can represent the effect of die-wall friction on the average density, as well as deformation inside the green compact. Density gradients were generated; they were revealed during sintering, because the compact does not deform homogeneously. Simulation also can be used to evaluate deformations that are induced by sintering.     

Variable energy positron beam study of Xe-implanted uranium oxide

Doppler broadening of annihilation gamma-line combined with a slow positron beam was used to measure the momentum density distribution of annihilating pair in a set of sintered UO₂ samples. The influence of surface polishing, of implantation with 800-keV ¹³⁶Xe²⁺ at fluences of 1 × 10¹⁵ and 1 × 10¹⁶ Xe cm^?2, and of annealing were studied by following the changes of the momentum distribution shape by means of S and W parameters. The program used for this purpose was VEPFIT. At the two fluences in the stoichiometric as-implanted UO₂, formation of Xe bubbles was not detected. The post-implantation annealing and over-stoichiometry in the as-implanted sample caused Xe precipitation and formation of Xe bubbles.