Obliquely propagating ion-acoustic shock waves in a degenerate quantum plasma

A theoretical investigation has been carried out on the propagation of non-linear ion-acoustic shock waves (IASHWs) in a magnetized degenerate quantum plasma system composed of inertial non-relativistic positively charged light and heavy ions, inertialess non-relativistically or ultra-relativistically degenerate electrons and positrons. The reductive perturbation method has been employed to derive the Burgers' equation. It has been observed that under consideration, our plasma model supports only positive potential shock structure. It is also found that the amplitude and steepness of the IASHWs have been significantly modified by the variation of ion kinematic viscosity, oblique angle, number density, and charge state of the plasma species. The results of our present investigation will be helpful for understanding the propagation of IASHWs in white dwarfs and neutron stars.     

Quantitative analysis of specific target DNA oligomers using a DNA-immobilized packed-column system

Although a DNA-immobilized packed-column (DNA-packed column), which relies on sequence-dependent interactions of target DNA or mRNA (in the mobile phase) with DNA probes (on the silica particle) in a continuous flow process, could be considered as an alternative platform for quantitative analysis of specific DNA to DNA chip methodology, the performance in practice has not been satisfactory. In this study, we set up a more efficient quantitative analysis system based on a DNA-packed column by employing a temperature-gradient strategy and DMSO-containing mobile phase. Using a temperature-gradient strategy based on T _m values of probe/target DNA hybridizations and DMSO (5%)-containing mobile phase, we succeeded in the quantitative analysis of a specific complementary target distinguishable from non-complementary DNA oligomers or other similar DNA samples. In addition, two different target DNA oligomers even with similar T _m values were separated and detected quantitatively by using a packed column carrying two different DNA probes.     

Commensurability oscillations in NdBa2Cu3Oy single crystals

Commensurability between inter-vortex distance and crystal lattice constant is investigated by angular dependent magnetization in very pure twinned and twin-free NdBa₂ Cu₃ O_y single crystals. With increasing temperature the incommensurate states split up and become finally commensurate with half the vortex distance. These new commensurate states are related to a substructure of the intrinsic pinning potential within the unit cell and discussed with respect to temperature, field, anisotropy, and twin structure.     

Determining a 'safe' high-mass limit in matrix-assisted laser desorption/ionisation time-of-flight mass spectra of coal derived materials with reference to instrument noise

Three methods for determining a 'safe' estimate for high-mass limits of MALDI spectra of coal derived liquids were explored, using a sample of coal-tar pitch and its pyridine-insoluble fraction. Co-addition of increasing numbers of single-shot spectra (10, 30, 50 and 100 pulses) showed visually observable reductions in noise levels, consistent with robust and statistically meaningful signals. Three separate types of post-acquisition calculation were used to identify high-mass limits of the spectra. (i) A literature method indicated high-mass limits similar to those observed visually-as a shift from baseline at the highest masses, nearly 350 000 u for the coal tar pitch and about 390 000 u for its pyridine insoluble fraction. (ii) Comparing instrument signal with pre-selected multiples of the standard deviation, upper mass estimates of between 40-60 000 u for the coal-tar pitch and about 95 000 u for its pyridine-insoluble fraction were found. (iii) Calculation of the slope was used to identify 'lift-off' of the spectrum from baseline. The angle between the smoothed spectrum and the baseline was matched to a pre-selected value (e.g. 0.5 degrees and 1 degrees ). However, the arbitrary specification of the key parameter did not establish this last method on a firm basis. The choice of a criterion for estimating high-mass limits of MALDI spectra remains a semi-quantitative procedure; a reasonably conservative high-mass limit may be estimated by comparison of signal with five times the standard deviation. However, evaluation of size exclusion chromatograms of the present samples using polystyrene standards suggests that molecular mass distributions of pitch samples arrived at by MALDI mass spectrometry are, at least partly, determined by the limitations of available instruments. Copyright 1999 John Wiley & Sons, Ltd.     

Wide-bandwidth, tunable, multiple-pulse-width optical delays using slow light in cesium vapor

We demonstrate an all-optical delay line in hot cesium vapor that tunably delays 275 ps input pulses up to 6.8 ns and 740 input ps pulses up to 59 ns (group index of approximately 200) with little pulse distortion. The delay is made tunable with a fast reconfiguration time (hundreds of ns) by optically pumping out of the atomic ground states.     

Determination of oxygen triple isotope ratios of silicates without cryogenic separation of NF3- technique with application to analyses of technical O2 gas and meteorite classification

A novel technique is described to determine Delta'(17)O(TFL) with high accuracy and precision by using infrared (IR) laser fluorination with F(2) as the reaction gas. The technique includes precise monitoring of the intensity ratio of the (14)NF(2)+ (m/z 52) to O(2) signals. The correlation between the intensity of (14)NF(2) + and positive error in delta(17)O(VSMOW) allows correction of measured data to obtain reliable Delta'(17)O(TFL) values. The resultant error in Delta'(17)O(TFL) of a single measurement after correction is in the range of +/-0.06 per thousand, i.e. sufficiently small to permit the technique to be useful for meteorite classification. Our data for technical O(2), in combination with literature data, suggest a negative anomaly of tropospheric air O(2) with Delta'(17)O(TFL) = -0.344 +/- 0.015 per thousand (1sigma).     

Base sequence- and <Emphasis Type="Italic">T</Emphasis><Subscript>m</Subscript>-dependent DNA oligomer separation by open tubular capillary columns carrying complementary DNA oligomers as probes

DNA chips prepared on a flat glass surface have unavoidable drawbacks when used for quantitative analysis. In an attempt to overcome this problem, we constructed an HPLC-type system suitable for quantitative analysis that enables base sequence- and T _m-dependent DNA oligomer separation in a flow system. A small open tubular capillary column (300-mm × 100-μm I.D.) was used. The DNA oligomers used as probes had an amino group at the 5′-end and were immobilized on the inner silica surface of the capillary column which had been sequentially treated with 3-aminopropyltriethoxysilane, butyltrimethoxysilane, and disuccinimidylglutarate. Using the combination of probe-immobilized column placed in a column oven equipped with temperature gradient function, a nano-flow-controllable pump, a small sample-loading injector, and a capillary-fitted UV detector, we succeeded in separating complementary and non-complementary DNA oligomers in specific and quantitative modes. We also designed a temperature gradient strategy for efficient separation of target DNA oligomers in DNA mixture samples. Using a column carrying two different probes with similar T _m values, their complementary target DNA oligomers were also separated and detected. The developed DNA open tubular capillary column system investigated in the present study could be further improved as an alternative tool to DNA chips to be used for the quantitative analysis of DNA or mRNA samples. Kamakshaiah Charyulu Devarayapalli and Seung Pil Pack contributed equally to this paper.     

Controlled incorporation of deuterium into bacterial cellulose

Isotopic enrichment has been widely used for investigating the structural and dynamic properties of biomacromolecules to provide information that cannot be carried out with molecules composed of natural abundance isotopes. A media formulation for controlled incorporation of deuterium in bacterial cellulose synthesized by Gluconacetobacter xylinus subsp. sucrofermentans is reported. The purified cellulose was characterized using Fourier Transform Infra-Red spectrophotometry and mass spectrometry which revealed that the level of deuterium incorporation in the perdeuterated cellulose was greater than 90 %. Small-angle neutron scattering analysis demonstrated that the overall structure of the cellulose was unaffected by the substitution of deuterium for hydrogen. In addition, by varying the amount of D-glycerol in the media it was possible to vary the scattering length density of the deuterated cellulose. A large disk model was used to fit the curves of bacterial cellulose grown using 0 and 100 % D-Glycerol yielding a lower bound to the disk radii, R _min = 1,132 ± 6 and 1,154 ± 3 Å and disk thickness, T = 128 ± 1 and 83 ± 1 Å for the protiated and deuterated forms of the bacterial cellulose, respectively. This agrees well with the scanning electron microscopy analysis which revealed stacked sheets in the cellulose pellicles. Controlled incorporation of deuterium into cellulose will enable new types of experiments using techniques such as neutron scattering to reveal information about the structure and dynamics of cellulose and its interactions with proteins and other (bio) polymers.     

A pulse-pileup correction procedure for rapid measurements of hydroxyl concentrations using picosecond time-resolved laser-induced fluorescence

The measurement of fluorescence lifetimes is important for determining minor-species concentrations in flames when using linear laser-induced fluorescence (LIF). Applications of LIF to turbulent flames require that the quenching rate coefficient be determined in less than ∼100 μs. Moreover, the measurement technique must be insensitive to the existence of relatively large backgrounds, such as occur from flame emission. To meet these goals, we have recently developed a rapid, gated photon-counting technique, termed LIFTIME. However, for ultimate application to turbulent time-series measurements, LIFTIME must be extended to photon count rates which unfortunately result in nonlinear discriminator operation. In this paper, a correction technique is derived to permit quantitative measurements of fluorescence lifetimes and concentrations at sampling rates up to 4 kHz. The technique was tested against liquid samples having a known lifetime and is further shown to reproduce previous hydroxyl concentration measurements in a series of laminar flames with total photon count rates of up to ∼35 million detected photoelectrons per second. The fluorescence lifetimes and hydroxyl concentrations are shown to be measured with ∼10% accuracy (68% confidence interval) for sampling times as low as 250 μs. Received: 9 October 1998 / Revised version: 30 December 1998 / Published online: 28 April 1999     

Optimal bounds for bilinear forms associated with linear equations

The construction of upper and lower bounds to the bilinear quantity g₀, f, where f is the solution of an operator equation Tf = f₀, requires either an approximation for f or one for T^?1. In this paper the question of “best” approximation of T^?1 by an operator of the form B = βI, where β is a real constant, is investigated for linear operators that are either self-adjoint or can be related by suitable manipulations to others that are. Particular attention is paid to a special operator, previously studied by Robinson, of importance in predicting the dynamic polarisabilities of quantum-mechanical systems.