839 research outputs found
Stellenwert der minimal-invasiven Chirurgie beim primären und sekundären Hyperparathyroidismus
BACKGROUND: The standard surgical approach to treat primary (pHPT) and secondary hyperparathyroidism (sHPT) used to be a cervicotomy with exploration of all four parathyroid glands. This access has been challenged recently by the introduction of minimally invasive techniques in order to achieve superior cosmesic results and to reduce theatre time. We analyzed the advantages and morbidities of these surgical aproaches. PATIENTS AND METHODS: Between 1997 and 2006 a total of 123 patients (109 with pHPT and 14 with sHPT) underwent parathyroidectomy at the ENT Department in Luzern. Ultrasonographic scanning was performed on 74 patients (68%), szintigraphy in 8 patients (7%) and both scanning methods in 27 patients (25%). 103 patients were available for follow-up. The indications for each technique were reviewed and outcome measures included serum Calcium and parathyroid hormone levels. RESULTS: Sensitivity for preoperative ultrasonographic and scintigraphic scanning was 67% and 65% for identification of the correct quadrant and 74% and 71% for identification of the correct side. A bilateral exploration was performed until June 2001 for all patients. Thereafter, a minimally invasive approach was chosen for patients with pHPT, whereas patients with sHPT still require bilateral exploration. Adequate preoperative localization was a prerequisite for a minimally invasive technique. Mean postoperative serum Kalzium levels were within the normal range, independently of the surgical technique and disease. Two patients developed hypercalcemia after an initially successful operation. CONCLUSIONS: Review of the literature confirms the shift from bilateral exploration towards minimally invasive techniques. The incidence of persistent or recurrent disease as well as the rate of complications seems comparable. Operation time for minimally invasive techniques is reduced in the hands of an experienced surgeon. However, proper preoperative localization of the diseased parathyroid gland is not always possible and the expenses of intraoperative parathyroid hormone measures do not lower the overall costs. Considerable experience and a multidisiplinary approach (endocrinologist, surgeon, pathologist) is required to adopt efficient minimally invasive techniques. As for sHPT, bilateral exploration remains the treatment of choice
Possibilities for Measurement and Compensation of Stray DC Electric Fields Acting on Drag-Free Test Masses
DC electric fields can combine with test mass charging and thermal dielectric
voltage noise to create significant force noise acting on the drag-free test
masses in the LISA (Laser Interferometer Space Antenna) gravitational wave
mission. This paper proposes a simple technique to measure and compensate
average stray DC potentials at the mV level, yielding substantial reduction in
this source of force noise. We discuss the attainable resolution for both
flight and ground based experiments.Comment: To be published in Advances in Space Research, COSPAR 2002 conference
proceedings (6 pages, 3 figures
Measuring random force noise for LISA aboard the LISA Pathfinder mission
The LTP (LISA Testflight Package), to be flown aboard the ESA / NASA LISA
Pathfinder mission, aims to demonstrate drag-free control for LISA test masses
with acceleration noise below 30 fm/s^2/Hz^1/2 from 1-30 mHz. This paper
describes the LTP measurement of random, position independent forces acting on
the test masses. In addition to putting an overall upper limit for all source
of random force noise, LTP will measure the conversion of several key
disturbances into acceleration noise and thus allow a more detailed
characterization of the drag-free performance to be expected for LISA.Comment: 7 pages, 3 figures. To be published in Classical and Quantum Gravity
with the proceedings of the 2003 Amaldi Meetin
Measuring the LISA test mass magnetic proprieties with a torsion pendulum
Achieving the low frequency LISA sensitivity requires that the test masses
acting as the interferometer end mirrors are free-falling with an unprecedented
small degree of deviation. Magnetic disturbances, originating in the
interaction of the test mass with the environmental magnetic field, can
significantly deteriorate the LISA performance and can be parameterized through
the test mass remnant dipole moment and the magnetic susceptibility
. While the LISA test flight precursor LTP will investigate these effects
during the preliminary phases of the mission, the very stringent requirements
on the test mass magnetic cleanliness make ground-based characterization of its
magnetic proprieties paramount. We propose a torsion pendulum technique to
accurately measure on ground the magnetic proprieties of the LISA/LTP test
masses.Comment: 6 pages, 3 figure
Proposta de planejamento estratégico para a Embrapa Trigo.
Orientadora: Denise Michael dos Santos, Coorientador: Alvaro Augusto Dossa
Characterization of disturbance sources for LISA: torsion pendulum results
A torsion pendulum allows ground-based investigation of the purity of
free-fall for the LISA test masses inside their capacitive position sensor.
This paper presents recent improvements in our torsion pendulum facility that
have both increased the pendulum sensitivity and allowed detailed
characterization of several important sources of acceleration noise for the
LISA test masses. We discuss here an improved upper limit on random force noise
originating in the sensor. Additionally, we present new measurement techniques
and preliminary results for characterizing the forces caused by the sensor's
residual electrostatic fields, dielectric losses, residual spring-like
coupling, and temperature gradients.Comment: 11 pages, 8 figures, accepted for publication Classical and Quantum
Gravit
Avaliação das doses respostas do glifosato isolado e em misturas em biótipos resistente e sensíveis da espécie Conyza bonariensis.
A DFT study on secondary reaction pathways in the acid-catalysed Beckmann rearrangement of cyclohexanone oxime in aprotic solvent
Upper limits on stray force noise for LISA
We have developed a torsion pendulum facility for LISA gravitational
reference sensor ground testing that allows us to put significant upper limits
on residual stray forces exerted by LISA-like position sensors on a
representative test mass and to characterize specific sources of disturbances
for LISA. We present here the details of the facility, the experimental
procedures used to maximize its sensitivity, and the techniques used to
characterize the pendulum itself that allowed us to reach a torque sensitivity
below 20 fNm /sqrt{Hz} from 0.3 to 10 mHz. We also discuss the implications of
the obtained results for LISA.Comment: To be published in Classical and Quantum Gravity, special issue on
Amaldi5 2003 conference proceedings (10 pages, 6 figures
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