Spontaneous Shortening Research Articles

Shortening of the radiation pulse from a plasma relativistic microwave generator in numerical calculations with plasma simulation by the particle-in-cell method

Spontaneous shortening of radiation pulses of Cherenkov microwave generators based on the interaction of a high-current relativistic electron beam with preliminarily generated plasma was studied in a numerical model. Microwave pulse shortening is caused by the appearance of a gradually expanding region near the collector, from which plasma is expelled by an electrostatic field of relativistic electrons. The absence of plasma results in a severalfold decrease in the plasma wave reflectance from the collector and violation of generator self-excitation conditions. The microwave emission duration increases with the plasma ion mass.

Les allongements digitaux par distraction progressive

The authors report their experience of digital lengthening and analyze the indications and results of 12 cases performed over 13 years in the plastic and reconstructive surgery service of the Kassab institute. Distraction was performed using a mini-orthofix device. In majority of cases, the procedure was performed on young people, manual workers and victims of industrial accidents. The lengthened osseous segment was the 1st metacarpal in 7 cases, the proximal phalanx of the index in 3 cases, the 3rd metacarpal once and the proximal phalanx of the middle finger in one case. Gradual distraction at the rate of 0.25 to 0.5 mm/day was carried out in 10 cases using the procedure of "callotasis". In 2 cases the distraction was performed at a rate of 1 mm/day followed by bone graft. Callotasis allowed us to obtain an average lengthening of 17 mm (61.5%) in distraction of the phalanx, and 26 mm (63.3%) in distraction of the first metacarpal. This technique avoids the spontaneous shortening observed after the use of bone graft alone. Complications are relatively frequent but had little influence on the final result.

Cervical length at 11–14 weeks' and 22–24 weeks' gestation evaluated by transvaginal sonography, and gestational age at delivery

To compare cervical length measurements obtained at 11 to 14 weeks and 22 to 24 weeks of gestation in an unselected group of pregnant women and to correlate the measurements with time of delivery. This was a prospective study involving 529 pregnant women attending for routine antenatal care who underwent transvaginal scans at 11-14 weeks and 22-24 weeks for evaluation of cervical length. The mean cervical length was calculated at both stages of gestation and lengths were compared between groups which delivered at term or prematurely, this being defined as delivery before 37 completed weeks of gestation. The mean cervical lengths at 11-14 and 22-24 weeks were, respectively, 42.4 mm and 38.6 mm. Cervical length at 11-14 weeks was not significantly different between the groups which delivered at term (42.7 mm) and preterm (40.6 mm). However, at the 22-24-week evaluation, cervical length was significantly shorter in the group which had a preterm delivery than in that which had a term delivery (26.7 mm and 39.3 mm, respectively; P = 0.0001). In the group of women with a previous history of one or more preterm deliveries, there was a greater shortening in cervical length from the first to the second evaluation than there was in the group of women with no previous history of preterm delivery. This shortening was also more pronounced in the group which delivered prematurely (from 40.6 mm to 26.7 mm) than in that which delivered at term (from 42.7 mm to 39.3 mm). There is a spontaneous shortening in the pregnant cervix from the first to the second trimester of pregnancy. The shortening is more rapid in pregnant women who deliver prematurely and who have a history of previous preterm delivery.

S-band vircator with electron beam premodulation based on compact pulse driver with inductive energy storage

This paper describes an S-band vircator system with electron beam premodulation, built on the base of the MARINA compact high-voltage pulser with inductive energy storage. The peak microwave output was /spl sim/1 GW with /spl sim/5% power efficiency and 50-ns full-width at half-maximum. The microwave frequency was constant during the pulse as determined by the resonator. Substantial spontaneous shortening of the microwave pulse was observed. Possible mechanisms for this phenomenon are discussed and supported by three-dimensional KARAT simulations.

A method for isolating smooth muscle cells from pig urinary bladder with low concentrations of collagenase and papain: the relation between calcium concentration and isolated cell length.

The present study describes a method for isolating single smooth muscle cells from pig urinary bladder using a continuous resuspension device. Low concentrations of collagenase and papain were sufficient to obtain a high yield of viable smooth muscle cells, which remained viable for about 3-4 h as tested with fluorescein diacetate. Addition of fetal calf serum increased the lifespan of the isolated cells and the percentage of contractile smooth muscle cells, but caused spontaneous shortening of the cells. The length and volume of the isolated smooth muscle cells depended on the calcium concentration used in the isolation buffer solution. The isolated muscle cells were apparently relaxed if a calcium concentration less than 1.0 mmol/l was used in the isolation medium. In higher calcium concentrations the isolated cells were significantly shorter, probably as a result of a contraction caused by mechanical stimulation of the cells during the isolation procedure.

Synthesis of extended acyclic azathienes. Crystal and molecular structure of two compounds, Ar(SNSN) nSiMe 3 (Ar  2-O 2NC 6H 4; n  1,2)

The 1:1 reaction of (Me 3SiNSN) 2S with ArSCl gives Ar(SNSN) 2SiMe 3, while the 1:2 reaction gives (ArSN) 2S and (SN) 4 if Ar = Ph, and (ArSNSN) 2S if Ar = nitrophenyl. Thus, the aromatic nitro groups inhibit spontaneous shortening of azathiene chains of (ArSNSN) 2S, but they do not stabilize the compounds containing a chain of 17 alternating nitrogen and sulphur atoms [Ar(SNSN) 2SiMe 3 + SCl 2, 2:1] which are shortened to (ArSNSN) 2S. As shown by X-ray structure analysis, the configuration of the azathiene chains in the compounds Ar(SNSN) n SiMe 3 (Ar = 2- O 2NC 6H 4; n = 1, 2) is similar to that of (SN) x macromolecules: Z, E, n = 1; Z, E, Z, E, n = 2. At n = 1 the molecule is planar, at n = 2 (the longest oligomer azathiene chain with established real geometry) the non-hydrogen atoms lie on the cylindrical surface with a radius of ca 50 Å.

Toward molecular wire: Synthesis, crystal, molecular, and π‐electronic structure of 1,7‐bis(aryl)‐1,3,5,7‐tetraaza‐2,4,6‐trithia‐1,2,5,6‐heptatetraenes

AbstractThe title compounds were obtained by the reaction of 1‐aryl‐3‐trimethylsilyl‐1,3‐diaza‐2‐thiaallenes with dichloromonosulfane or 1‐aryl‐4‐(1‐phtalimidyl)‐1,3‐diaza‐2,4‐dithia‐1,2‐butadienes in the presence of CsF. The latter route also afforded nonsymmetric derivatives. In contrast, the reaction of N,N,N′,N′‐tetrakis(trimethylsilyl)diaminosulfane with S,S‐dichloro‐N‐aryliminosulfuranes (1:2) led to 1,3‐bis(aryl)‐1,3‐diaza‐2‐thiaallenes and cyclotetra(azathiene). As shown by the X‐ray structure analysis, the molecule of the title compound with Ar = Ph is planar, with configuration of the azathiene chain being similar to that of poly(azathiene) (SN)x. The MNDO calculations indicate that most of the π‐MOs of this compound, including the frontier ones, are delocalized throughout the whole molecule. The data obtained confirm the possibility of creating molecular wire for molecular electronic devices on the basis of extended acyclic azathienes. An attempt to synthesize more extended compounds than the title ones resulted in spontaneous shortening of their azathiene chains.

STUDIES OF CONTROLLED REPERFUSION AFTER ISCHEMIA: XI. Reperfusate composition: Interaction of marked hyperglycemia and marked hyperosmolarity in allowing immediate contractile recovery after four hours of regional ischemia

This study tests the hypothesis that improved muscle salvage after prolonged ischemia (4 hours) occurs when the substrate-enriched blood cardioplegic solution is markedly hyperglycemic (greater than 400 mg/dl) and markedly hyperosmotic (greater than 400 mOsm). Thirty-five dogs underwent 4 hours of occlusion of the left anterior descending coronary artery and reperfusion during total vented bypass with substrate-enriched blood cardioplegic solution, in which the glucose concentration and osmolarity were varied in relation to one another. Spontaneous systolic shortening recovered consistently (31 +/- 6%) only when glucose was greater than 400 mg/dl and osmolarity was greater than 400 mOsm. The least recovery occurred (only one of six dogs recovering spontaneous shortening) when cardioplegic glucose was greater than 400 mg/dl and osmolarity was greater than 400 mOsm. Regional segments reperfused with our standard substrate-enriched blood cardioplegic solution had lower transmural flow rates following reperfusion (56 versus 87 ml/100 gm/min, p less than 0.05), markedly reduced mitochondrial State 3 and State 4 respiration in epicardial and endocardial muscle (p less than 0.05), and the most extensive histochemical evidence of damage (63% area of nonstaining versus area at risk, p less than 0.05). We conclude that markedly increased levels of osmolarity (greater than 400 mOsm) and glucose (greater than 400 mg/dl) improve the capacity of substrate-enriched blood cardioplegic solution to salvage myocardium after prolonged ischemia.

The role of augmented Hageman factor (factor XII) titers in the cold-promoted activation of factor VII and spontaneous shortening of the prothrombin time in women using oral contraceptives.

Spontaneous shortening of the Thrombotest time and an increase in factor VII activity after cold storage of plasma in plastic vials have been described in the plasma of women using OCAs. The phenomenon if CPA is dependent on the presence of HF (factor XII) and is associated with increased plasma kallikrein activity and the disappearance of C1-INH activity. In the present study, spontaneous CPA and shortening of the prothrombin time were observed in 66% of women using OCAs. The prothrombin time was inversely related to factor VII activity and HF coagulant titer, whereas factor VII activity was strongly associated with the titer of HF. The addition of purified HF to normal plasma to a degree observed in OCA users promoted CPA generation and shortening of the prothrombin time. In contrast, reduction of the HF coagulant titer in the plasma of OCA users to a normal level prevented the rise in factor VII activity and shortening of the prothrombin time after cold storage. These data indicate that a high titer of HF, such as that observed in OCA users, is needed for the spontaneous CPA and add support to evidence linking the extrinsic and intrinsic pathways of clotting. The relationship of this in vitro phenomenon to the pathogenesis of thrombosis in women using OCAs is presently unclear. (J Lab Clin Med 99:363, 1982.)

Observations on the spontaneous motility of human uterine muscle in vitro

1.1. The capacity of human uterine muscle for spontaneous shortening was found to decrease with age, and the activity of myometrial samples from old, postmenopausal women was characterized by relatively rapid, feeble contraction waves.2.2. Myometrial samples excised from uteri with secretory endometria exhibited a slower rate of spontaneous motility than did those from uteri in the proliferative phase. Muscle shortening, however, was found to be unaffected by the ovarian cycle.3.3. Repeated pregnancies and labors, the presence of leiomyomas else-where in the uterus, sedatives, analgesics and anesthetic agents administered at the time of operation, as well as race, were found to be of no statistical significance as factors influencing the spontaneous motility of myometrial strips excised from the nongravid human uterus.4.4. Muscle samples removed from gravid uteri (from 2 months' gestation until term) exhibited no statistical differences in regard to motility, when compared with tissues from the nongravid viscus.5.5. In a limited number of tests, myometrial tissues from patients with primary uterine inertia exhibited a significantly reduced muscle shortening with increased frequency of contraction when compared with “normal” tissues from both nongravid and gravid uteri.