Accumulation of endogenous and exogenous nucleic acids in “Touch DNA” components on hands

Successful forensic DNA profiling from handled items is increasingly routine in casework. This “touch DNA” is thought to contain both cellular and acellular nucleic acid sources. However, there is little clarity on the origins or characteristics of this material. The cellular component consists of anucleate, terminally differentiated corneocytes (assumed to lack DNA), and the occasional nucleated cell. The acellular DNA source is fragmentary, presumably cell breakdown products. This study examines the relative contributions each component makes to the hand-secretions (endogenous) and hand-accumulations (exogenous) by recovering rinses from the inside and outside of worn gloves. Additionally, cellular and acellular DNA was measured at timepoints up to 2 h after hand washing, both with and without interim contact. Microscopic examination confirmed cell morphology and presence of nucleic acids. Following the novel application of a hair keratinocyte lysis method and plasma-DNA fragment purification to hand rinse samples, DNA profiles were generated from both fractions. Exogenous cell-free DNA is shown to be a significant source of touch DNA, which reaccumulates quickly, although its amplifiable nuclear alleles are limited. Endogenous DNA is mostly cellular in origin and provides more allelic information consistently over time.     

The Jahn-Teller effect in the lower electronic states of benzene cation. III. The ground-state vibrations of C6H6+ and C6D6+

New mass analyzed threshold ionization (MATI) spectra of the molecules C(6)H(6) (+) and C(6)D(6) (+) have been collected using tunable vacuum ultraviolet (VUV) single photon excitation from the neutral ground state and also using two-photon excitation through the 6(1) vibration of the (1)B(2u) S(1) state. Emphasis was placed on obtaining accurate relative intensities of the vibrational lines in order to use this information in the vibronic analysis. The MATI spectra collected from VUV (S(0) originating state), triplet (T(1)), and resonant two photon (S(1)) excitation schemes were compared with Jahn-Teller calculations employing the classical model of Longuet-Higgins and Moffitt to obtain the Jahn-Teller coupling parameters of 3 of the 4 linearly active modes (e(2g) modes 6-9 in Wilson's notation). Franck-Condon factors, including the effects of geometry changes, were calculated from the vibronic wave functions and used to identify the lines in the various spectra. It is found that most of the lines with substantial intensity can be understood using only the modes 1, 6, 8, and 9. Weaker peaks are due to various non-e(2g) modes, but these do not derive intensity through Jahn-Teller coupling. When the effects of geometry change were included, simulations of the spectra from the calculated vibrational energies and intensities were close to the experimental spectra. This verifies the applicability of the model to the understanding of the vibrational structure of this type of molecule, but some variations indicate directions for further improvement of the model.     

Stereochemical leakage mechanisms for tricarbonyl(dienyl)iron cations

ψ-Endo to ψ-exo leakage during solvolysis of a ψ-endo-dienol—Fe(CO)₃ dinitrobenzoate ester does not proceed via a syn, syn-cis-dienyl—Fe(CO)₃ cation. The most probable leakage mechanism involves non-stereospecific ionization of the dinitrobenzoate ester. syn,syn-cis-Dienyl—Fe(CO)₃ cations are formed from ψ-exo-dienol—Fe(CO)₃ complex during chromatography on grade I neutral alumina.     

Heat load of a GaAs photocathode in an SRF electron gun

A great deal of effort has been made over the last decades to develop a better polarized electron source for high energy physics. Several laboratories operate DC guns with a gallium arsenide photocathode, which yield a highly polarized electron beam. However, the beam's emittance might well be improved by using a superconducting radio frequency (SRF) electron gun, which delivers beams of a higher brightness than that from DC guns because the field gradient at the cathode is higher. SRF guns with metal and CsTe cathodes have been tested successfully. To produce polarized electrons, a Gallium-Arsenide photo-cathode must be used: an experiment to do so in a superconducting RF gun is under way at BNL. Since a bulk gallium arsenide (GaAs) photocathode is normal conducting, a problem arises from the heat load stemming from the cathode. We present our measurements of the electrical resistance of GaAs at cryogenic temperatures, a prediction of the heat load and verification by measuring the quality factor of the gun with and without the cathode at 2 K. We simulate heat generation and flow from the GaAs cathode using the ANSYS program. By following the findings with the heat load model, we designed and fabricated a new cathode holder (plug) to decrease the heat load from GaAs.     

MRCI studies on ground and excited states of CBr

Potential curves and spectroscopic constants for a large number of doublet and quartet states of CBr were obtained by multireference configuration interaction calculations, using valence triple-zeta basis sets with polarization and diffuse functions. Besides the X²Π ground state, 1⁴Σ^?, 1²Δ and 2²Σ⁺ have been found to be stable. Spectroscopic constants calculated for 1²Δ are in excellent agreement with experimental values obtained by Dixon and Kroto in 1963. Their observed predissociation of one component of 1²Δ can be explained by the crossing of the 1²Δ potential near equilibrium by 1²Σ⁺. The 1²Σ⁺ state is calculated to have a shallow long-range minimum at 2.31?Å. The dissociation energy of X²Π is calculated to be 3.43?eV. An observed T _e of 4.97?eV for 2²Σ⁺ agrees with the theoretical value. Several Rydberg states of the 2π→Ryd and 3σ→Ryd series, starting at T _e ?=?5.25?eV, were identified. Photodissociation of CBr by sunlight, important in the ozone cycle, can occur via direct dissociation of the ground state, or by excitation to 1²Δ followed by predissociation. Most dissocative repulsive states lie at higher energies, and are not expected to participate in the photodisscociation of CBr.     

The ionization potential and ground state cation vibrational structure of 1,4-dioxane

The Mass Analyzed Threshold Ionization (MATI) spectrum of 1,4-dioxane has been collected using a one-photon vacuum-ultraviolet (VUV) excitation scheme that is produced via four-wave difference mixing of two pulsed dye lasers. The ionization potential (IP) is 73 062±4 cm⁻¹, approximately 575 cm⁻¹ lower than previously reported values. The vibrational structure seen in the cation ground state agrees very well with the ab initio line positions, as determined by density functional theory calculations. Only vibrations of a_g symmetry are seen in this spectrum, in line with expectations derived from consideration of orbital symmetries.     

Radiological dose assessment of naturally occurring radioactive materials in concrete building materials

Previous studies have shown that the natural radioactivity contained in building materials have significantly influenced the dose rates in dwelling. Exposure to natural radiation in building has been of concerned since almost 80 % of our daily live are spend indoor. Thus, the aim of the study is to assess the radiological risk associated by natural radioactivity in soil based building materials to dwellers. A total of 13 Portland cement, 46 sand and 43 gravel samples obtained from manufacturers or bought directly from local hardware stores in Peninsular of Malaysia were analysed for their radioactivity concentrations. The activity concentrations of ²²⁶Ra, ²³²Th and ⁴⁰K in the studied building materials samples were found to be in the range of 3.7–359.3, 2.0–370.8 and 10.3–1,949.5 Bq kg^?1 respectively. The annual radiation dose rates (μSv year^?1) received by dwellers were evaluated for 1 to 50 years of exposure using Resrad-Build Computer Code based on the activity concentration of ²²⁶Ra, ²³²Th and ⁴⁰K found in the studied building material samples. The rooms modelling were based on the changing parameters of concrete wall thickness and the room dimensions. The annual radiation dose rates to dwellers were found to increase annually over a period of 50 years. The concrete thicknesses were found to have significantly influenced the dose rates in building. The self-absorption occurred when the concrete thickness was thicker than 0.4 m. Results of this study shows that the dose rates received by the dwellers of the building are proportional to the size of the room. In general the study concludes that concrete building materials; Portland cements, sands, and gravels in Peninsular of Malaysia does not pose radiological hazard to the building dwellers.