Jet fuel toxicity: skin damage measured by 900-MHz MRI skin microscopy and visualization by 3D MR image processing

The toxicity of jet fuels was measured using noninvasive magnetic resonance microimaging (MRM) at 900-MHz magnetic field. The hypothesis was that MRM can visualize and measure the epidermis exfoliation and hair follicle size of rat skin tissue due to toxic skin irritation after skin exposure to jet fuels. High-resolution 900-MHz MRM was used to measure the change in size of hair follicle, epidermis thickening and dermis in the skin after jet fuel exposure. A number of imaging techniques utilized included magnetization transfer contrast (MTC), spin-lattice relaxation constant (T1-weighting), combination of T2-weighting with magnetic field inhomogeneity (T2*-weighting), magnetization transfer weighting, diffusion tensor weighting and chemical shift weighting. These techniques were used to obtain 2D slices and 3D multislice–multiecho images with high-contrast resolution and high magnetic resonance signal with better skin details. The segmented color-coded feature spaces after image processing of the epidermis and hair follicle structures were used to compare the toxic exposure to tetradecane, dodecane, hexadecane and JP-8 jet fuels. Jet fuel exposure caused skin damage (erythema) at high temperature in addition to chemical intoxication. Erythema scores of the skin were distinct for jet fuels. The multicontrast enhancement at optimized TE and TR parameters generated high MRM signal of different skin structures. The multiple contrast approach made visible details of skin structures by combining specific information achieved from each of the microimaging techniques. At short echo time, MRM images and digitized histological sections confirmed exfoliated epidermis, dermis thickening and hair follicle atrophy after exposure to jet fuels. MRM data showed correlation with the histopathology data for epidermis thickness (R²=0.9052, P<.0002) and hair root area (R²=0.88, P<.0002). The toxicity of jet fuels on skin structures was in the order of tetradecane>hexadecane>dodecane. The method showed a sensitivity of 87.5% and a specificity of 75%. By MR image processing, different color-coded skin structures were extracted and 3D shapes of the epidermis and hair follicle size were compared. In conclusion, high-resolution MRM measured the change in skin epidermis and hair follicle size due to toxicity of jet fuels. MRM offers a three-dimensional spatial visualization of the change in skin structures as a method of toxicity evaluation and for comparison of jet fuels.     

Comparison of Some Soft Unplasticized Cast Polyurethane Rubbers

Different types of unplasticized cast polyurethanes with hardness around 60 Shore A have been compared. The tensile properties, tear strength, resistance to hydrolysis, and swelling in solvents and water were examined. The influence of composition on the properties of cast polyurethanes prepared from a polyadipate polyol and diisocyanates, including the effect of a range of fillers, was investigated in detail. Fumed silica, fumed alumina, and carbon black significantly increased the hardness and tensile strength of the rubber, whereas kaolin and talc gave small increases. Ground silica, calcite, and rutile had no effect. No significant increases in tensile strength were obtained with silane and titanate coupling agents with a fumed silica filler. The rate of hydrolysis or extent of swelling in xylene was unchanged by fillers.     

Two-dimensional series evaluations via the elliptic functions of Ramanujan and Jacobi

We evaluate in closed form, for the first time, certain classes of double series, which are remindful of lattice sums. Elliptic functions, singular moduli, class invariants, and the Rogers?CRamanujan continued fraction play central roles in our evaluations.     

Kinetic Resolution of Piperazine-2-Carboxamide by Leucine Aminopeptidase. An Application in the Synthesis of the Nucleoside Transport Blocker (-) Draflazine

The resolution of N-t-Boc-piperazine carboxamide 5 proceeded smoothly in the presence of leucine aminopeptidase to produce acid (S)-1 and amide (R)-5 with good optical purity. Sequential alkylation and functional group manipulation of carboxamide (S)-5 provided the known nucleoside transport blocker draflazine (-) 2.     

Efficient Radical Coupling of Organobromides Using Dimanganese Decacarbonyl

Wurtz-type radical coupling of a variety of allylic and benzylic bromides was observed on irradiation with dimanganese decacarbonyl in excellent yield (77-99%). Efficient cross-coupling of two different bromides was also readily achieved.     

Assigning routes and wavelengths for collaboration over optical networks

The Routing and Wavelength Assignment problem is investigated in the context of collaboration where tools are shared and used simultaneously over a fiber optic network. Both online and offline versions are discussed, with and without using time as a parameter for scheduling purposes, and including the case where the network is used to carry time-multiplexed traffic. Also, the problem of rescheduling a blocked demand is studied. Several solutions based on Integer Linear Programs (ILP) and heuristics are proposed, implemented and their performance compared. The offline case is solved using two types of ILPs: link and path formulations. ILPs are also proposed for the online problem in addition to heuristic algorithms. While the link formulations give optimal solutions, they take a long time to solve and thus they can only be used for small problems. Path formulations and heuristics scale better but at the expense of optimality. The online approach is recommended when the resort to an offline approach is forbidden by the size of the problem.     

Presidential Communication About Marginalized Groups: Applying a New Analytic Framework in the Context of the LGBT Community

Scholars have long observed that presidential communication about a marginalized group can help shape that group's reality. Yet most analyses of such communication focus on a relatively small number of texts, making it difficult to identify important changes over time and analyze factors that might explain those changes. The present study proposes an analytic framework that specifies 4 measurable parameters of presidential communication about marginalized groups, as well as 4 explanatory factors. We use this framework to analyze the census of presidents' formal communications about the LGBT community. Results highlight presidents' limited communicative engagement with the LGBT community and the roles that political party, rhetorical context, public opinion, and sociocultural touchstones play in explaining presidential communication about this important group.     

Graphs with at most one crossing

The crossing number of a graph $G$ is the least number of crossings over all possible drawings of $G$. We present a structural characterization of graphs with crossing number one.