Oblique ion collection in the drift-approximation: how magnetized Mach-probes really work

The anisotropic fluid equations governing a frictionless obliquely-flowing plasma around an essentially arbitrarily shaped three-dimensional ion-absorbing object in a strong magnetic field are solved analytically in the quasi-neutral drift-approximation, neglecting parallel temperature gradients. The effects of transverse displacements traversing the magnetic presheath are also quantified. It is shown that the parallel collection flux density dependence upon external Mach-number is $n_\infty c_s \exp[-1 -(M_{\parallel\infty}- M_\perp\cot\theta)]$ where $\theta$ is the angle (in the plane of field and drift velocity) of the object-surface to the magnetic-field and $M_{\parallel\infty}$ is the external parallel flow. The perpendicular drift, \M_\perp, appearing here consists of the external \E\wedge\B drift plus a weighted sum of the ion and electron electron diamagnetic drifts that depends upon the total angle of the surface to the magnetic field. It is that somewhat counter-intuitive combination that an oblique (transverse) Mach probe experiment measures.Comment: Revised version following refereeing for Physics of Plasma

Aplastic Anemia Complicating Orthotopic Liver Transplantation for Non-A, Non-B Hepatitis

Aplastic anemia developed in 9 of 32 patients (28 percent) undergoing orthotopic liver transplantation for acute non-A, non-B hepatitis, at one to seven weeks after the procedure. No patient previously had evidence of hematologic dysfunction or conditions known to be associated with aplastic anemia. No other cases of aplastic anemia were identified among 1463 patients undergoing liver transplantation for all other indications at the four centers participating in the study (chi-square = 415, P<0.001; 95 percent confidence interval for the incidence of aplastic anemia after transplantation for non-A, non-B hepatitis, 13 to 44 percent, vs. 0.00 to 0.13 percent for all other indications). The operative and postoperative treatment of these patients was not otherwise different, indicating that the aplastic anemia was a complication of the hepatitis, not of the transplantation procedure. Four of the nine patients died of complications due to infections. Three of the surviving patients have been followed for less than six months, one for one year, and one for two years. The two patients followed the longest have recovered marrow function to an appreciable degree, and two of the others have evidence of early recovery. We conclude that patients undergoing orthotopic liver transplantation for non-A, non-B hepatitis are at a high risk for the development of aplastic anemia. (N Engl J Med 1988; 319:393–6.) © 1988, Massachusetts Medical Society. All rights reserved

Dynamics of the edge transport barrier at plasma biasing on the CASTOR tokamak

A clear and reproducible transition to a regime with an improved particle confinement is routinely observed on the CASTOR tokamak, if the biasing electrode is inserted deep enough into the plasma (r/a ~ 0.5) and biased up to +250V. The steepening of the radial profiles of the plasma density and potential demonstrate the formation of a transport barrier just inside the last closed flux surface. Fast relaxations of the edge plasma parameters, with a frequency of about 10 kHz, are observed when the average radial electric field within the barrier prevails values of about 20 kV/m. A detailed analysis of the spatial-temporal behavior of these relaxations is presented.На токамаке CASTOR устойчиво наблюдается отчетливый и воспроизводимый переход в режим с улучшенным удержанием частиц при достаточно глубоком введении в плазму (r/a - 0,5) электрода, на который подаётся смещение до +250 В. У кручение радиальных профилей плотности плазмы и потенциала свидетельствуют об образовании транспортного барьера сразу внутри последней замкнутой магнитной поверхности. Наблюдаются быстрые релаксации параметров краевой плазмы с частотой около 10 кГц, когда среднее радиальное электрическое поле внутри барьера превышает значение около 20 кВ/м. Приводится обстоятельный анализ пространственно-временного поведения этих релаксаций.На токамаці CASTOR стійко спостерігається чіткий та відтворений перехід до режиму з поліпшеним утриманням частинок при достатньо глибокому введенні у плазму (r/a ~ 0,5) електрода, на який подано зміщення до +250 В. Радіальні профілі густини плазми та потенціалу стають більш крутими, що свідчить про створення потенціального бар'єру зразу усередині останньої замкненої магнітної поверхні. Спостерігаються швидкі релаксації параметрів крайової плазми з частотою порядку 10 кГц, коли середнє радіальне електричне поле усередині бар'єра перевищує значення приблизно 20 кВ/м. Надається докладний аналіз просторово-часової поведінки цих релаксацій

Efficient QTL detection for nonhost resistance in wild lettuce: backcross inbred lines versus F2 population

In plants, several population types [F2, recombinant inbred lines, backcross inbred lines (BILs), etc.] are used for quantitative trait locus (QTL) analyses. However, dissection of the trait of interest and subsequent confirmation by introgression of QTLs for breeding purposes has not been as successful as that predicted from theoretical calculations. More practical knowledge of different QTL mapping approaches is needed. In this recent study, we describe the detection and mapping of quantitative resistances to downy mildew in a set of 29 BILs of cultivated lettuce (L. sativa) containing genome segments introgressed from wild lettuce (L. saligna). Introgression regions that are associated with quantitative resistance are considered to harbor a QTL. Furthermore, we compare this with results from an already existing F2 population derived from the same parents. We identified six QTLs in our BIL approach compared to only three in the F2 approach, while there were two QTLs in common. We performed a simulation study based on our actual data to help us interpret them. This revealed that two newly detected QTLs in the BILs had gone unnoticed in the F2, due to a combination of recessiveness of the trait and skewed segregation, causing a deficit of the wild species alleles. This study clearly illustrates the added value of extended genetic studies on two different population types (BILs and F2) to dissect complex genetic traits

SAM levels, gene expression of SAM synthetase, methionine synthase and ACC oxidase, and ethylene emission from N. suaveolens flowers

S′adenosyl-l-methionine (SAM) is a ubiquitous methyl donor and a precursor in the biosynthesis of ethylene, polyamines, biotin, and nicotianamine in plants. Only limited information is available regarding its synthesis (SAM cycle) and its concentrations in plant tissues. The SAM concentrations in flowers of Nicotiana suaveolens were determined during day/night cycles and found to fluctuate rhythmically between 10 and 50 nmol g−1 fresh weight. Troughs of SAM levels were measured in the evening and night, which corresponds to the time when the major floral scent compound, methyl benzoate, is synthesized by a SAM dependent methyltransferase (NsBSMT) and when this enzyme possesses its highest activity. The SAM synthetase (NsSAMS1) and methionine synthase (NsMS1) are enzymes, among others, which are involved in the synthesis and regeneration of SAM. Respective genes were isolated from a N. suaveolens petal cDNA library. Transcript accumulation patterns of both SAM regenerating enzymes matched perfectly those of the bifunctional NsBSMT; maximum mRNA accumulations of NsMS1 and NsSAMS1 were attained in the evening. Ethylene, which is synthesized from SAM, reached only low levels of 1–2 ppbv in N. suaveolens flowers. It is emitted in a burst at the end of the life span of the flowers, which correlates with the increased expression of the 1-aminocyclopropane-1-carboxylate oxidase (NsACO)