Characterization of spherically focused transducers using an ultrasonic measurement model approach

A new and computationally efficient method is developed for characterizing a spherically focused, ultrasonic transducer (and its accompanying test system). Procedures for determining the probe's effective radius, effective focal length, and system efficiency factor are described. Predicted responses that make use of these effective parameters are shown to correspond very well to measured responses for a number of different transducers.     

Stimulation of pancreatic growth by cholecystokinin is mediated by high affinity receptors on rat pancreatic acinar cells

Pancreatic acinar cells possess both high low affinity receptors for cholecystokinin. The cholecystokinin analog caerulein, which exerts a trophic effect on the rat pancreas, acts as an agonist at both types of receptors. In contrast, the synthetic analog CCK-JMV-180, which also acts as an agonist at high affinity receptors, opposes the action of caerulein on the low affinity receptors. We report that infusion of either caerulein or CCK-JMV-180 into rats increases [3H]-thymidine incorporation into pancreatic DNA and causes the pancreatic weight as well as content of DNA, RNA, and protein to increase. CCK-JMV-180 also stimulates in-vitro incorporation of [3H]-thymidine into DNA of cultured rat acini. The finding that both caerulein and CCK-JMV-180 exert the same trophic effect on pancreatic acinar cells indicates that this effect is mediated via high affinity acinar cell cholecystokinin receptors.     

Using simulation‐based experiments for software requirements engineering

We describe the use of simulation‐based experiments to assess the computer support needs of automation supervisors in the United States Postal Service (USPS). Because of the high cost of the proposed system, the inability of supervisors to articulate their computer support needs, and the infeasibility of direct experimentation in the actual work environment, we used a simulation to study end‐user decision making, and to experiment with alternative computer support capabilities. In Phase One we investigated differences between expert and novice information search and decision strategies in the existing work environment. In Phase Two, we tested the impact of computer support features on performance. The empirical results of the two experiments showed how to differentially support experts and novices, and the effectiveness of proposed information systems before they were built. The paper concludes by examining the implications of the project for the software requirements engineering community.     

Endothelin-1 infusion inhibits plasma insulin responsiveness in normal men

OBJECTIVES: Elevated plasma endothelin (ET)-1 levels have been described in insulin-resistant states such as syndrome X, obesity, non-insulin-dependent diabetes mellitus, and in some studies in essential hypertension. To investigate whether increases in circulating ET-1 to levels observed in insulin-resistant states can modulate insulin levels and/or insulin sensitivity in humans, we assessed these variables during low, non-pressor-dose ET-1 compared with placebo infusion. DESIGN: In a randomized, single blind, crossover design, 10 lean normotensive male subjects received either an intravenous infusion of subpressor doses of ET-1 dissolved in polygeline or a control infusion of polygeline only (placebo). Using dynamic assessment by the minimal model approach with the modified frequent sampling intravenous glucose tolerance test (FSIGT) the following and other parameters were measured: insulin sensitivity; acute insulin response to glucose (AIR(G)) calculated as the average of the three peak values between 2 and 5 min after injection of glucose from which the basal insulin levels were subtracted; the initial area under the curve (AUC(1-19)) from insulin values between time 0 and 19 min and the first-phase insulin secretion (phi1) from insulin kinetics parameters. RESULTS: ET-1 infusion reduced AIR(G) (to 34.85 +/- 4.27 compared with 49.3 +/- 6.9 microU/ml during placebo, P=0.017) and the acute C-peptide response to glucose (to 2.33 +/- 0.41 compared with 3.1 +/- 0.44 ng/ml, P=0.018), decreased plasma insulin levels during the FSIGT compared with placebo (analysis of variance P<0.0001) and decreased the AUC(1-19) (to 2.1 +/- 0.2 compared with 2.9 +/- 0.3 U/l per 20 min, P<0.01) while phi1 tended to be lower. S1 measured during ET-1 infusion was unaltered (11.11 +/- 1.91 x 10(-4) versus 10.88 +/- 2.11 10(-4)/min per mU per l, NS). CONCLUSIONS: These findings demonstrate that an increase in circulating ET-1 to levels observed in insulin-resistant states acutely diminishes the insulin secretory response but does not significantly modify insulin sensitivity.     

Fertigung einer universellen Hüftprothesenpfanne mittels Hochdruckblechumformung

In recent years, the use of hip prostheses has become a routine procedure. The use of total hip replacement has evolved in recent years to a routine procedure. Despite this experience, it always comes back to complications. Especially the migration or loosening of the acetabular component because of the artificial load adaptive bone remodeling is still a current problem. This is due to the changing mechanical situation after the implantation of the prosthesis. Another problem is the high bone loss during implantation, which complicates a revision of the prosthesis. One solution is the use of patient‐specific prostheses. So far, the use of these prostheses is limited due to the time‐consuming and cost‐intensive production. The overall objective of the presented project in this publication is the development and establishment of an innovative concept for the production of patient‐specific hip prosthesis made of titanium plates by sheet metal forming. The idea of this concept involves the development of a two‐stage process. First of all a standardized hip prosthesis is made by high‐pressure sheet metal forming and then individually in the second step. This publication contains the derivation of the standard prosthesis. For this purpose, a design methodology was generated, based on the so‐called agglomerative clustering. In addition, presents the results of the numerical preliminary design of the first stage of the process and the tool developed concept in the course of this paper.     

Platinentechnologie auf dem Vormarsch

ProdukteHeraeus Sensor-Nite

Platinentechnologie auf dem Vormarsch     

Weidmüller Ein-Bolzen-Klemme

ProdukteW-Reihe Gem?ss en 50 124-1

Weidmüller Ein-Bolzen-Klemme     

Frequency security constrained short-term unit commitment

In island grids and weakly interconnected power systems, a loss of a large proportion of generation will cause the system frequency to fall dramatically. In order to ensure a stable operation with the lowest impact on the system, the disturbed power balance must be equalized within a short specified time by activating the seconds reserve of on-line units or by load shedding or both. This paper presents a frequency security constrained short-term scheduling. The procedure commits and optimizes units, calculates necessary seconds reserve capability, and allocates them among the available on-line units to provide emergent frequency regulation following a loss of generation. By means of the low-pressure pre-heater interruption (LPHI) implemented into thermal power plants, seconds reverse provision is increased. Thus, load shedding caused by insufficient availability of seconds reserve can be avoided. A case study on typical island systems with a large number of different units is demonstrated using the proposed procedure. Results from the study validated robust performance of the proposed procedure that minimizes fuel costs while maintaining frequency security condition.     

Successful term pregnancy after Mustard operation for transposition of the great arteries

Transposition of the great arteries is a complex cardiac malformation with poor prognosis without surgical correction. Since the introduction of surgical procedures such as the intra-auricular reorientation of the venous return (Mustard procedure), an increasing number of patients may reach adulthood and experience pregnancy. Because long-term complications after the Mustard operation include systemic heart failure, arrhythmias, venous return stenosis and pulmonary edema, hemodynamic changes during pregnancy and delivery may potentially engender life-threatening complications in these patients. We report the case of a 24-year-old primigravida who underwent a Mustard procedure at the age of 2 years for transposition of the great vessels, and who carried out a full-term pregnancy. The pregnancy was uneventful until the 34th week, when the woman developed signs of moderate right ventricular failure and frequent episodes of accelerated junctional rhythm. Digitalisation improved symptoms and elicited return to normal sinus rhythm. The patient delivered at term by elective cesarean section, under close hemodynamic monitoring.     

Investigations onNb/Al-AlO x -Al/Nb proximity tunneling junctions for X-ray detection

A new Nb/Al-AlO_x-Al/Nb trilayer process using a movable mechanical slit for junction-detector applications is described. Best junctions have a quality factor of 42 mV with a Josephson current density of 1200 A/cm ² at 4.2 K. The temperature dependence of the sub-gap current in the range of 0.45 to 4.2 K has been measured. Deviations from the thermally activated behavior due to imperfections in the tunneling barrier are observed. We compare our simple method with the usual whole wafer processes and we discuss the influence of proximity effects in these junctions in terms of the models proposed by Golubov et al. and by McMillan.