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  • 1
    ISSN: 1432-2218
    Keywords: Hypercoagulability ; Laparoscopic cholecystectomy ; Deep-vein thrombosis ; Prophylaxis ; Heparin ; Intermittent pneumatic compression
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Patients who undergo laparoscopic cholecystectomy (LC) are operated on under general anesthesia, in a reverse Trendelenburg position, with 12–15-mmHg pneumoperitoneum. All of these factors can induce venous stasis of the legs, which may lead to postoperative deep-vein thrombosis (DVT). The objectives of this study were to assess the degree of hypercoagulability and to determine the rate of postoperative DVT in a group of 100 patients in whom LC was completed. Whole-blood thrombelastography (TEG) and plasma-activated partial thromboplastin time (PTT) determination were carried out preoperatively and on the 1st postoperative day. All patients received pre-, intra-, and postoperative graduated compression stockings and sequential pneumatic compression devices until fully ambulatory. Twenty-six percent of the patients with a risk score 〉4, or a postoperative TEG index 〉+5.0, received subcutaneous heparin (5,000 units b.i.d.), beginning in the postoperative period and continuing for 4 weeks as an outpatient. A complete venous duplex scan of both legs was performed on the 7th postoperative day, at the time of their office visit. Our results revealed significant postoperative hypercoagulability for the TEG index (P〈0.005) and for PTT (P〈0.05). One patient had an asymptomatic DVT (1%), and no side effects from the mechanical or pharmacological prophylaxis occurred in this series. These data suggest that the low incidence of thrombosis in the face of theoretical and laboratory evidence of postoperative hypercoagulability may reflect an effective prophylactic regime. Alternatively, the incidence of these thrombotic problems may be very low, or the sensitivity and timing of duplex scanning may be inadequate to identify asymptomatic venous thrombosis. Until further studies are done to resolve these issues, we feel that mechanical prophylaxis combined with selective low-dose heparin therapy is safe and effective in patients having laparoscopic cholecystectomy.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 59 (1986), S. 11-18 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Fully electromagnetic particle-in-cell simulations of Applied-B ion diodes have been performed using the magic code. These calculations indicate that Applied-B diodes can be nearly 100% efficient. Furthermore, the simulations exhibit an impedance relaxation phenomenon due to the buildup of electron space charge near the anode which causes a time-dependent enhancement of the ion emission above the Child–Langmuir value. This phenomenon may at least partially explain the rapidly decreasing impedance that has been observed in Applied-B ion diode experiments. The results of our numerical simulations will be compared to experimental data on Applied-B ion diodes and to analytic theories of their operation.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A new, large-area, high-uniformity, flash x-ray source that efficiently couples electrical energy to photon energy has been successfully constructed and tested on the 1-MV, 2-MA electron accelerator SPEED (short pulse experimental electron device). The source employs 18 individual blade diodes arranged in the configuration of a frustum. Each blade was magnetically isolated on the real-cathode side of an anode foil, but not on the virtual-cathode side. The operation of the diode was heavily diagnosed using 24 Rogowski coils, a vacuum voltage monitor, p-i-n diode detectors, an 80-element TLD array, and a fast-framing x-ray pinhole camera. The individual blade diodes were found to exhibit line pinching, end-to-end pinching, and minimal electron reflexing through the Ta anode foil, with a radiation yield that agreed with Monte Carlo simulations. The end-to-end pinch location could be controlled by tapering the anode–cathode gap. The impedance depended on only the smallest spacing, and was independent of pinch location.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 59 (1986), S. 725-730 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Beam extraction simulations for high-voltage, immersed source accelerators are compared with analytic theory and experiment. dynadisc, a new nonlinear beam propagation code, is described and applied to the initial few meters of propagation in 1 atm air. The dynadisc results indicate that filamentation is the fastest growing instability. The filamentation changes the beam current density profile from an annular to a quasi-uniform distribution.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: An improved understanding of the factors that control the axial focus of applied-B ion diodes was obtained from time-resolved diagnostics of ion-beam trajectories. This resulted in a new selection of anode shape that produced a proton focus of 1.3-mm diameter from a 4.5-cm-radius diode, which is a factor of 2 improvement over previous results. We have achieved a peak proton power density of 1.5±0.2 TW/cm2 on the 1-TW Proto I accelerator. The radial convergence of this proton beam, defined as the ratio of the anode diameter to focused beam FWHM, is 70. Time-resolved information about virtual cathode evolution, the self- and applied-magnetic-field bending, and the horizontal focus of the beam was also obtained. In addition, the diffusion of the magnetic field into the anode plasma is estimated by measuring the horizontal focal position as a function of time. Finally, we discuss the effects of gas cell scattering on the beam focus.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1072-8368
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Medicine
    Notes: [Auszug] We have determined the solution structure of NusB, a transcription antitermination protein from Escherichia coli. The structure reveals a novel, all α-helical protein fold. NusB mutations that cause a loss of function (NusB5) or alter specificity for RNA targets (NusB101) are localized to ...
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  • 7
    ISSN: 1432-2218
    Keywords: Ultrasound ; Localization ; Adhesions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Laparoscopic candidates with abdominal scars may have adhesions that result in visceral injury during trocar insertion. The purpose of this study was to evaluate the use of preoperative ultrasound mapping of abdominal wall adhesions, to provide safe initial laparoscopic access, and to guide the placement of subsequent trocars, facilitating adhesolysis when necessary. Thirty consecutive patients with previous abdominal surgery who were scheduled for laparoscopy underwent a preoperative ultrasonic examination of the abdominal wall using a 7-MHz linear ultrasound probe. Spontaneous viscera slide was measured during longitudinal scanning (normal=2–5 cm) and induced viscera slide was evaluated during longitudinal and transverse scanning (normal=1 cm or more) over the existing abdominal scar, the peri-umbilical region, and the remaining abdominal quadrants. Sixteen (53%) of 30 patients had adhesions under their scar and only four patients (25%) had umbilical adhesions. The 12 patients without umbilical adhesions all had successful closed cannulation while open cannulation at alternate sites was successful in the four individuals with umbilical adhesions. Blind umbilical needle cannulation was successfully done in all of the remaining 14 patients (47%) without visceral injury, including three patients (21%) with upper abdominal scars who were adhesion-free elsewhere. No adhesions were encountered that had not been preoperatively predicted by ultrasound. We conclude that examination of the abdominal wall with spontaneous and induced viscera slide, using ultrasound scanning, can reliably detect intraabdominal adhesions. The examination is best done on a highly selective basis by the operating surgeon to guide the location for initial trocar insertion and determine the type of abdominal wall cannulation in those individuals with previous abdominal scars.
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The three-dimensional particle-in-cell code quicksilver [Seidel et al., Computational Physics, edited by A. Tenner (World Scientific, Singapore, 1991), p. 475] has been used to study applied-B ion diodes. The impedance behavior of the diode in these simulations is in good agreement with both analytic theory and experiments at peak power. The simulations also demonstrate the existence of electromagnetic instabilities which induce divergence in the ion beam. Early in time, there is an instability at high frequency relative to the ion transit time τi, and the resulting beam divergence is low. However, later in time, the system makes a transition to an instability with a frequency close to 1/τi, and the ion beam divergence rises to an unacceptably high value. The transition is associated with the build-up of electron space charge in the diode, and the resulting increase in the beam current density enhancement (J/JCL). Using different schemes to inhibit the electron evolution, the transition has both been postponed and permanently eliminated, resulting in Li+1 ion beams with a sustained divergence of ∼10 mrad at an energy of ∼10 MeV.
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  • 9
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 61 (1987), S. 4970-4977 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We present the design of the high-voltage (30 MV) Applied-B ion diode that is now being tested on the PBFA-II accelerator at Sandia National Laboratories. This diode design is the first application of a new set of numerical design tools that have been developed over the past several years. Furthermore, this design represents significant departures from previous designs due to much higher voltage and the use of a nonprotonic ion, Li+. The higher voltage increases the magnetic field strength required to insulate the diode from 1 to 2 T of previous diodes to 3–7 T. This represents a very large increase in the magnetic field energy and the magnetic forces exerted on the field-coil structures. Our new design incorporates changes in the field-coil locations to significantly reduce the field energy and the forces on the field-coil structures. The use of nonprotonic ions introduces a new complication in that these ions will be stripped when they penetrate material, i.e., the gas cell membrane. The importance of current neutralization, charge-exchange reactions, and the conservation of canonical angular momentum are discussed in the context of designing light ion diodes suitable as drivers for inertial confinement fusion. We have simulated the performance of this diode design using the electromagnetic particle-in-cell code, magic. We find that the most sensitive point in the power flow is the transition from the self-magnetically insulated transmission line to the applied field region of the diode.
    Type of Medium: Electronic Resource
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