Identification of the pathological prion protein allotypes in scrapie-infected heterozygous bank voles (Clethrionomys glareolus) by high-performance liquid chromatography-mass spectrometry

Cerebral formation of the pathological isoform of the prion protein (PrP) is a crucial molecular event in prion diseases. The bank vole (Clethrionomys glareolus) is a rodent species highly susceptible to natural scrapie. The PrP gene of bank vole is polymorphic (Met/Ile) at codon 109. Here we show that homozygous 109Met/Met voles have incubation times shorter than heterozygous 109Met/Ile voles after experimental challenge with three different scrapie isolates. An HPLC-MS/MS method was optimized and applied to investigate whether in heterozygous animals both PrP allotypes are able to undergo pathological conversion. The results demonstrate that both allotypes of the prion protein participate to pathological deposition.     

The crystal structure of 3-methyluracil from X-ray powder diffraction data

The crystal structure of 3-methyluracil has been determined ab initio by conventional monochromatic X-ray powder diffraction data. The crystal data are: orthorombic, a=6.6294(1), b=13.1816(3), c=6.53938(9) (Å), V=571.45(3) (ų), space group Pbnm, Z=8. The structure was solved by direct methods and the final Rietveld refinement converged to R_p=0.0398, R_wp=0.0528, R_Bragg=0.0294. The crystal structure exhibits endless chains of planar molecules, connected via head-to-tail N-H?O hydrogen bonds.     

Error rates for M-ary noncoherent FSK in impulsive reverberation noise

It is shown that reverberation noise for primary acoustic scattering in the ocean has an integral representation and that a canonical model for its analysis can be found. Exact values of error rates for M-ary noncoherent FSK for correlation receivers in such noise are given. Comparison with the well known Gaussian case is also made.     

Two Dimensions Residual Stresses Analysis Through Incremental Groove Machining Combined with Electronic Speckle Pattern Interferometry

In this study a new residual stress determination method in two directions simultaneously is presented. This method is based on stresses relaxation in a groove that is machined incrementally. The residual stresses relaxation occurs simultaneously from both the depth and the length of the groove. Thus, measuring the surface strain field generated by the relaxation enables to determine the stress gradient both along the depth and the length of the groove. To measure the surface strain in a direction perpendicular to the groove, a digital speckle pattern interferometer is used. This method is suitable when the residual stress field in the structure varies in the depth as well as along the surface of the part, like for example in a welded structure. The method is tested here on an aluminium plate in which a central band has been shot peened.     

On the Development of the VIPAR Polymer Gel Dosimeter for Three-Dimensional Dose Measurements

Summary: The new polymer gel dosimeter, based on the modification of the VIPAR gel composition, is described for the purpose of radiation dose distribution measurement in radiotherapy. It features increased concentration of the two VIPAR substrates: N-vinylpyrrolidone (8%) and gelatine (7.5%) (N,N′-methylenebisacrylamide was maintained at 4%), and the addition of copper sulphate (0.0008%) and ascorbic acid (0.007%) in order to facilitate the preparation through elimination of the need for deoxygenation of the gel. Following the exposure to ionizing radiation, polymerisation and cross-linking of the new gel monomers occurs retaining the spatial distribution of absorbed dose and causing opacity of the gel. Quantitative parameters of the new gel dose response were studied using magnetic resonance imaging to relate polymerisation induced physicochemical changes of the gel to dose. The dose threshold is found significantly lower than that of the original VIPAR gel. The linear part of measured spin-spin relaxation rate R₂(D) ( = 1/T₂(D)) reaches up to 35 Gy. Its slope and an intercept are slightly higher relative to the original VIPAR. The efficiency of the new polymer gel-magnetic resonance imaging dosimeter was also tested for dose verification of a 3D dose distribution planned by a commercially available treatment planning software (Eclipse External Beam v.6.5) and delivered by a 6 MV medical linear accelerator. The new polymer gel is proposed to be called, VIPAR^nd (after VIPAR-normoxic-double).     

Locally optimum detection in moving average non-Gaussian noise

Detection algorithms that are locally optimum Bayes, and also asymptotically optimum, are developed for both coherent and incoherent signaling for arbitrary interference and signal waveforms when the dependence in the noise samples is represented by a moving-average model. This leads to receiver structures, which are prewhitened versions of the locally optimum detectors in the independent case. A probability-of-error expression (in the ideal-observer symmetric case), the processing gain, and the minimum-detectable signal are derived in both cases. These demonstrate, by means of an expression comparing performance between this and the independent case, that for the same large sample size (n≫1), an improvement in performance is always achieved when the noise samples are dependent, without any additional complexity in receiver structure     

Diversity for binary noncoherent frequency shift keying in impulsive reverberation noise

The error rate in active sonar is given for binary non-coherent frequency shift keying (FSK) in slow and non-selective Rayleigh fading (multipath) and additive non-Gaussian reverberation noise. The improvement achieved by using time-diversity is derived from the expression for the probability of error. It is shown that for error probabilities of the order of 10?5 the improvement factor is 10 dB.     

Certification of total arsenic in blood and urine standard reference materials by radiochemical neutron activation analysis and inductively coupled plasma-mass spectrometry

Radiochemical neutron activation analysis (RNAA) was used to measure arsenic at four levels in standard reference material (SRM) 955c Toxic Elements in Caprine Blood and at two levels in SRM 2668 Toxic Elements in Frozen Human Urine for the purpose of providing mass concentration values for certification. Samples were freeze-dried prior to analysis followed by neutron irradiation for 3 h at a fluence rate of 1 × 10¹⁴ cm^?2 s^?1. After sample dissolution in perchloric and nitric acids, arsenic was separated from the matrix either by retention on hydrated manganese dioxide (urine) or by extraction into zinc diethyldithiocarbamate in chloroform (blood). ⁷⁶As was quantified by gamma-ray spectroscopy. Differences in chemical yield and counting geometry between samples and standards were monitored by measuring the count rate of a ⁷⁷As tracer added before sample dissolution. RNAA results were combined with inductively coupled plasma-mass spectrometry values from National Institute of Standards and Technology and collaborating laboratories to provide certified values of 10.81 ± 0.54 and 213.1 ± 0.73 μg/L for SRM 2668 Levels I and II, and certified values of 21.66 ± 0.73, 52.7 ± 1.1, and 78.8 ± 4.9 μg/L for SRM 955c Levels II–IV, respectively. Because of discrepancies between values obtained by different methods for SRM 955c Level I, an information value of <5 μg/L was assigned for this material.     

Particle filtering to combat inter-carrier interference in mobile communications

This paper deals with the effect of the Doppler spread in a mobile communication system. The Doppler effect in a moving mobile is computed by predicting the mobile velocity via particle filtering, an instance of Sequential Monte Carlo (SMC) filtering. By calculating the Doppler spread in the receiver and adjusting the transmitter in the appropriate frequency, the performance of communication systems, such as Orthogonal frequency division multiplexing (OFDM) which suffer from loss of orthogonality due to frequency offset, can be improved. Moreover, it is shown that, via performance comparison of OFDM between the compensated and un-compensated for Doppler shift cases, a substantial improvement (O(10⁻¹)) can be achieved in terms of Bit-Error-Rate (BER) for expectedly large values of Signal to Noise Ratio (SNR)