Pulsed mode of a negative corona in nitrogen: I. Experiment

The pulsed mode of a negative corona discharge in air has long been known; however, in electropositive gases, this mode has not been previously observed. This paper presents the results from a systematic study of a newly discovered pulsed mode of a negative corona in nitrogen over a wide range of experimental parameters. The conditions under which the pulsed mode is realized are described in detail. The dynamic characteristics of current pulses are determined. The shapes and parameters of current pulses in nitrogen and air are compared.     

An optical method for investigating the microwave absorption characteristics of DNA and other biomolecules in solution

Direct determination of the microwave absorption characteristics of biological molecules in solution by an optical heterodyne technique is described. A visibly transparent sample is irradiated in a spatially nonuniform manner with pulsed microwaves, and the spatial variation in temperature increase measured by detecting the phase chirp impressed on a single-frequency He-Ne laser beam passing through the heated region. Results for several liquids and solutions such as water, methanol, various saline solutions, and solutions of DNA and DNA sodium salt in water are described. Where direct comparison is possible the results agree very well with published values. A significant increase in the absorption of DNA solutions compared with pure water has been observed that is consistent with microwave absorption by the longitudinal mode of the double helix.     

Microanalysis of beta-cyclodextrin and glucosyl-beta-cyclodextrin in human plasma by high-performance liquid chromatography with pulsed amperometric detection.

High-performance liquid chromatography with pulsed amperometric detection was applied to the determination of beta-cyclodextrin (beta-CD) and glucosyl (G)-beta-CD in human plasma. They were well resolved from each other and from background components of plasma on a polymer-based reversed-phase column with 0.6% acetonitrile aqueous solution containing 1 mM sodium hydroxide as an eluent. The samples in the effluent were detected with a pulsed amperometric detector after postcolumn alkalization. The detection limits of beta-CD and G-beta-CD in plasma at a signal-to-noise ratio of 3 were 11 and 5 pmol, respectively.     

Pulsed mode of a negative corona in nitrogen: II. Numerical calculations

A simplified model of a cathode sheath sustained by electron avalanches is presented. The model is used to calculate the pulsed mode of a negative corona in nitrogen in order to establish the physical picture of the processes occurring in a pulsed corona. The most important point is that, in the pulsed mode, both the averaged and dynamic current-voltage characteristics of a glow cathode sheath are found to have a negative slope. Lowering the degree to which the glow cathode sheath is subnormal (by sharply reducing the sheath area) or switching on additional ionization mechanisms (e.g., stepwise ionization) that force the cathode sheath to evolve into a prearc spot causes the negative slopes of the averaged and dynamic current-voltage characteristics of the sheath to become more gradual and even positive, thereby stabilizing the discharge current.     

Changes in the Antibacterial Activity of Benzylpenicillin Exposed to a Pulsed High-Intensity Magnetic Field

Biophysics - An increase in the antibacterial effect of the benzylpenicillin sodium salt that was irradiated with pulsed magnetic field at certain parameters (H intensity, f frequency, and n number...     

Analysis of bile acids and their conjugates using high-pH anion-exchange chromatography with pulsed amperometric detection

Bile acids and their conjugated forms may be separated by anion-exchange chromatography in alkaline media (0.9 M sodium acetate, 0.1 M sodium hydroxide, 15% v/v acetonitrile) on a CarboPac PA-100 column. The efflient was monitored at high sensitivity, with detection limits of less than 10 μM, using a pulsed amperometric detector. Free bile acids and their glyco- and tauro-conjugated forms were separated and detected within 40 min under isocratic conditions.     

The effects of pulsed 860 MHz radiofrequency radiation on the promotion of neurogenic tumors in rats

In a previous study, this laboratory reported a statistically nonsignificant trend for shortened latency of ethylnitrosourea (ENU)-induced brain tumors in Sprague-Dawley rats exposed to an 860 MHz pulsed radiofrequency (RF) signal. The present study was designed to investigate further any promoting effect of the pulsed RF signal on latency and other characteristics of neurogenic tumors in the progeny of pregnant rats treated with 6.25 or 10 mg/kg ENU. The resulting 1080 offspring were randomized equally by number, sex and ENU dose into pulsed RF, sham and cage control groups. The rats were exposed to the pulsed RF signal 6 h per day 5 days per week; the sham-exposed group was similarly confined for the same periods, and the cage controls were housed in standard cages. An essentially equal number of rats from each group were killed humanely every 30 days between the ages of 171 and 325 days; 32 rats died and 225 rats were killed when they were moribund. Postmortem examinations on the 1080 rats revealed 38 spinal cord tumors, 191 spinal nerve tumors, 232 cranial nerve tumors, and 823 brain tumors. A methodical study of the tumor characteristics disclosed no evidence that exposure to the pulsed RF signal affected the incidence, malignancy, volume, multiplicity, latency or fatality associated with any kind of neurogenic tumor.     

Studies on the characterization of the sodium-potassium transport adenosinetriphosphatase: Nuclear magnetic resonance studies of 23Na binding to the purified and partially purified enzyme

²³Sodium binding to a partially purified beef brain and purified dogfish rectal gland (sodium + potassium)-activated adenosinetriphosphatase (NaK ATPase) has been studied by pulsed nmr. In both preparations addition of ATP (in the absence of Mg) increased the amount of Na bound to the enzyme protein. In the less-pure brain preparation there was some binding of Na to the protein in the absence of ATP but in the purer preparation from the rectal gland there was little or no binding without ATP. With the dogfish enzyme, potassium readily displaced bound sodium. The K_D for sodium determined by nmr agreed closely with that determined kinetically. This, coupled with the fact that the dogfish enzyme required ATP for sodium binding suggests that the sodium detected by nmr in this preparation is due to binding at its specific site(s).     

Use of high-performance anion exchange chromatography with pulsed amperometric detection for O-glycan determination in yeast

O-glycosylation is a post-translational protein modification that occurs in all eukaryotes. Yeasts have received increasing attention as a host for therapeutic protein production because of their ability to secrete high levels of recombinant protein. Because yeasts such as Pichia pastoris have been shown to O-glycosylate some proteins with varying effects on protein function, it is important to elucidate the nature of this modification. Methods that characterize O-glycosylation on a qualitative and quantitative basis are thus important when considering yeast as a host for therapeutic protein production. This protocol describes the release of O-glycans from a protein sample by -elimination under alkaline conditions using sodium borohydride and sodium hydroxide. The released O-linked oligosaccharides are subsequently processed and then separated by high-performance anion exchange chromatography with pulsed amperometric detection (HPAEC-PAD). An estimation of O-glycan molar occupancy and average O-mannose chain length is ultimately derived. This protocol requires approximately 3 d for completion. This method provides an assessment of O-glycosylation and allows one to correlate the effect of O-glycosylation on protein properties.     

Pulsed microwave induced light, sound, and electrical discharge enhanced by a biopolymer

Intense flashes of light were observed in sodium bicarbonate and hydrogen peroxide solutions when they were exposed to pulsed microwave radiation, and the response was greatly enhanced by a microwave-absorbing, biosynthesized polymer, diazoluminomelanin. A FPS-7B radar transmitter, operating at 1.25 GHz provided pulses of 5.73 +/- 0.09 micros in duration at 10.00 +/- 0.03 pulses/s with 2.07 +/- 0.08 MW forward power (mean +/- standard deviation), induced the effect but only when the appropriate chemical interaction was present. This phenomenon involves acoustic wave generation, bubble formation, pulsed luminescence, ionized gas ejection, and electrical discharge. The use of pulsed microwave radiation to generate highly focused energy deposition opens up the possibility of a variety of biomedical applications, including targeting killing of microbes or eukaryotic cells. The full range of microwave intensities and frequencies that induce these effects has yet to be explored and, therefore, the health and safety implications of generating the phenomena in living tissues remain an open question.     

Haematological and physiological responses of brook charr, to untreated and limestone-neutralized acid mine drainage

Brook charr, Salvelinus fontinalis , exhibited depressed plasma sodium and elevated plasma glucose concentrations in untreated acid mine drainage effluent (AMD), at two dilutions. Plasma sodium and glucose concentrations remained stable in treated AMD, pulsed, fluidized beds of limestone and carbon-dioxide pre-treatment of influent, and in AMD-free water. Results indicate that effluents produced by this treatment system were not toxic to these fish, despite still containing moderate concentrations of manganese (3–4 mg l^-1 following dilution in exposure systems), and provide justification for field deployment and further biological testing of this treatment in the field.     

Coaxial microwave plasma source

Physical principles underlying the operation of a pulsed coaxial microwave plasma source (micro-wave plasmatron) are considered. The design and parameters of the device are described, and results of experimental studies of the characteristics of the generated plasma are presented. The possibility of application of this type of plasmatron in gas-discharge physics is discussed.     

Multiphoton stimulation of neurons

We pulsed the activation of neurons using a femtosecond laser. Pyramidal neurons are depolarized and fire action potentials when high intensity mode-locked infrared light irradiates somatic membranes and axon initial segments. This depolarization is reversible, does not occur with CW laser light, and appears to be due to multiphoton excitation. We describe two regimes of multiphoton optical stimulation. Low intensity, long duration laser irradiation produces a sustained depolarization, insensitive to sodium channel blockers yet sensitive to antioxidants. On the other hand, high intensity, short duration irradiation can induce fast depolarizations, which appear due to different mechanism. The combination of multiphoton stimulation and optical probing could enable systematic analysis of circuits.     

Gas phase hydrogen/deuterium exchange reactions of peptide ions in a quadrupole ion trap mass spectrometer

Hydrogen/deuterium exchange reactions of protonated and sodium cationized peptide molecules have been studied in the gas phase with a MALDI/quadrupole ion trap mass spectrometer. Unit-mass selected precursor ions were allowed to react with deuterated ammonia introduced into the trap cell by a pulsed valve. The reactant gas pressure, reaction time, and degree of the internal excitation of reactant ions were varied to explore the kinetics of the gas phase isotope exchange. Protonated peptide molecules exhibited a high degree of reactivity, some showing complete exchange of all labile hydrogen atoms. On the contrary, peptide molecules cationized with sodium exhibited only very limited reactivity, indicating a vast difference between the gas phase structures of the two ions. © 1997 Wiley-Liss Inc.     

Lecithin translational diffusion studied by pulsed nuclear magnetic resonance.

The translational diffusion coefficient of egg yolk and dilauroyl lecithin in optically isotropic phases containing sodium cholate has been measured using the pulsed NMR magnetic field gradient method. After a correction for geometrical factors the measured diffusion coefficient is found to agree well with previous determinations in phospholipid systems. The experimental data imply that the cubic mesophase of the lecithin-sodium cholate-water system contains continuous lipid aggregates. A possible model of the arrangement of the different amphiphile molecules in the cubic phase is discussed.     

Simultaneous analysis of homocysteine and methionine in plasma

The new isocratic cation exchange method separates up to eight different amino thiols. The separated sample components are detected electrochemically using a gold electrode and the integrated pulsed amperometry. The eluent composition is, for example, 0.15 M sodium perchlorate, 0.02 M perchloric acid and 5% acetonitrile. The report describes the optimization of chromatographic parameters such as column diameter and eluent composition. Quantitative performance is discussed for eight different amino thiols using standards. Also presented is a long term quantitative study for homocysteine and methionine in plasma samples. The preparation of plasma samples is simpler than with the previously reported version of the method. Only a reduction step is required, and neither column switching nor derivatization are necessary.     

Atmospheric-pressure electric discharge as an instrument of chemical activation of water solutions

Results of experimental studies and numerical simulations of physicochemical characteristics of plasmas generated in different types of atmospheric-pressure discharges (pulsed streamer corona, gliding electric arc, dielectric barrier discharge, glow-discharge electrolysis, diaphragmatic discharge, and dc glow discharge) used to initiate various chemical processes in water solutions are analyzed. Typical reactor designs are considered. Data on the power supply characteristics, plasma electron parameters, gas temperatures, and densities of active particles in different types of discharges excited in different gases and their dependences on the external parameters of discharges are presented. The chemical composition of active particles formed in water is described. Possible mechanisms of production and loss of plasma particles are discussed.     

神经递质3H-去甲肾上腺素释放与家蝇对拟除虫菊酯抗性的关系

在用K⁺去极化条件下,研究了溴氰菊酯和氯菊酯分别对敏感、抗溴氰菊酯和抗氯菊酯家蝇Musca domestica 品系脑突触体释放神经递质去甲肾上腺素的影响。结果表明：在用K⁺去极化后,神经递质去甲肾上腺素的释放在抗溴氰菊酯和抗氯菊酯家蝇品系中比敏感品系分别下降47.0%和51.0%;当用10^-5 mol/L溴氰菊酯预处理家蝇脑突触体,用K+去极化后对敏感、抗溴氰菊酯和抗氯菊酯家蝇品系释放去甲肾上腺素的加强作用分别提高80.3%、26.5%和70.5%;用10^-5 mol/L氯菊酯预处理3个家蝇品系的突触体对去甲肾上腺素释放均无加强作用。由此表明,家蝇对溴氰菊酯的抗性是与Na+通道的亲和性降低有关,而氯菊酯的抗性与Na+通道的亲和性关系不大。     

"Peroxidatic" form of cytochrome oxidase as studied by X-ray absorption spectroscopy

X-ray absorption spectroscopy shows pulsed oxidase to be similar to resting oxidase but to lack the sulfur bridge between iron and copper of active sites (Powers, L., Y. Ching, B. Chance, and B. Muhoberac, 1982, Biophys. J., 37[2, Pt. 2]: 403a. [Abstr.] ) The first shell ligands and bond lengths of the pulsed oxidase active site heme most clearly fit the ferric peroxidases from horseradish and yeast, and the pulsed oxidase cyanide compound resembles the low spin hemoprotein cyanide compounds. The structural results are consistent with an aquo or a peroxo form for pulsed oxidase as is also observed by optical studies. These structural and chemical data are consistent with a role for the pulsed forms in a cyclic peroxidatic side reaction in which the pulsed and pulsed peroxide compounds act as peroxide scavengers. The peroxidatic role of cytochrome oxidase in the nonsulfur bridged form suggests the renaming of the "oxygenated" or "pulsed" forms on a functional basis as "peroxidatic" forms of cytochrome oxidase.     

Sialic acids in gastropods.

The occurrence of N-acetylneuraminic acid and N-glycolylneuraminic acid residues in preparations of the slug Arion lusitanicus (Gastropoda) was determined by sodium dodecyl sulphate electrophoresis of the proteins followed by lectin blots stained with the sialic acid specific lectin from Maackia amurensis, by the sensitivity of this binding to sialidase from Clostridium perfringens, by specific fluorescent labelling of sialic acids with 1,2-diamino-4,5-methylenedioxybenzene, by the determination of the sensitivity to sialate-pyruvate-lyase, by co-migration with standards on high performance anion exchange chromatography with pulsed amperometric detection and by identification of the typical masses in the fragmentation patterns of the trimethylsilyl derivatives after gas chromatography. It is the first time sialic acids are identified in gastropods.