Regenerative converter for PWM AC drives

Since the PWM induction motor drive has become the industrial drive of choice, applications involving four-quadrant operation for AC drives have become more common. To satisfy such applications, a regenerative AC/DC converter that is robust is needed to allow bidirectional power flow between the load and power distribution system. A robust technology that is well understood is the 6 SCR converter operating in the inverting mode. However, the typical 6 SCR converter will either limit the maximum DC bus voltage or require a step-up transformer. The proposed regenerative converter allows the SCR power structure to operate as a synchronous line commutator, while a two-transistor series/shunt chopper, with a power resistor, controls the regenerative power flow, and offers an emergency braking capability. In addition, SCR commutation is accomplished by the line voltage and diversion of bus current. Both simulation and experimental results are given     

Efficacy of low-dose dopamine in preventing amphotericin B nephrotoxicity in bone marrow transplant patients and leukemia patients

This study evaluated the efficacy of low-dose dopamine for prevention of amphotericin B-induced nephrotoxicity in autologous bone marrow transplant and leukemia patients. Seventy-one patients undergoing cytoreductive therapy who required amphotericin B were randomly assigned in an unblinded fashion to a group receiving continuous-infusion low-dose dopamine (3 microgram/kg/min) or a group receiving no dopamine. Amphotericin B was dosed at 0.5 or 1.0 mg/kg/day based on computerized tomography scan results or presence of positive blood cultures. No patient received saline boluses. The rate of nephrotoxicity, severity as graded by Southwest Oncology Group toxicity criteria, and time to each grade of nephrotoxicity were compared between the two groups. Eighty percent of the no-dopamine group and 66.7% of the dopamine group developed nephrotoxicity, defined as a 1.5-fold or greater increase in baseline serum creatinine level (P = 0.20). No statistical difference was noted at any grade of nephrotoxicity between the two groups. Thirty-four percent of patients in the no-dopamine group versus 17.6% in the dopamine group had a 2.5-fold or greater increase in serum creatinine level, which was not statistically significant (P = 0.0888). Ten patients developed grade IV nephrotoxicity and were withdrawn from the study, 7 in the no-dopamine group and 3 in the dopamine group (P = 0.19). The time to each grade of nephrotoxicity was also not significantly different for the two groups. Eleven adverse drug reactions were reported in the dopamine group in comparison to one in the no-dopamine group. Thus, dopamine offers little in the way of prevention of nephrotoxicity associated with amphotericin B therapy. Although the significance of drug reactions in the dopamine group is not clearly established due to lack of cardiac monitoring in the no-dopamine group, dopamine therapy is not without complications.     

Prototypic typology and the Borderline Personality Disorder.

Based on interview data from 76 18–45 yr old outpatients, the implications of a prototypic rather than a classical model of personality-disorder classification were demonstrated for DSM-III Axis II Borderline Personality Disorder (BPD). Heterogeneity of membership is described, and conditional probabilities are used to demonstrate the relative efficiency of single diagnostic criteria and combinations of criteria and the degree of overlap among BPD and other personality disorders. The conditional probability approach can be used to determine empirically the covariation of symptoms and to link the study of prototypicality to the individual patient rather than to the group. (17 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of leader behaviors on subordinate performance and satisfaction: A laboratory experiment with student employees.

Four groups of 12 participants were hired to code videotaped group interactions using the Bales coding system (R. F. Bales, 1950). Each of the 4 groups experienced different leader behaviors of either high or low consideration in conjunction with either high or low initiating structure. Results indicate that subordinates did not perceive the leader manipulations as different but that these manipulations caused differences in quantity and quality of work. (17 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of soil moisture stress on monoterpenes in loblolly pine

Monoterpene composition of xylem oleoresin in pole-size loblolly pine (Pinus taeda L.) was different between moisture-stressed and -unstressed trees during two test years. -Pinene concentration increased in stressed trees whereas -pinene, myrcene, and limonene decreased. Variations in camphene concentration with soil moisture stress were inconclusive. It increased with moisture stress in one test year and decreased in stressed trees during the other test year.     

Octave-bandwidth microwave FET doubler

A microwave MESFET circuit which doubles the frequency of an input signal in the 4 to 8 GHz band is described. The circuit consists of a class C amplifier/phase-shifter combination followed by a single-stage band-reject amplifier. In the 8?16 GHz output band, an average conversion loss of 3 dB with fundamental rejection greater than 12 dB was achieved.     

Lubrication of Ball Bearings with Volatile Organic Compounds

A new approach to vapor lubrication describing materials for wide temperature range and long term operation has been established by experiments that use high-speed rolling element bearings as test specimens. Several possibilities for the process of vapor lubrication are projected. In addition the effect of carrier gas composition as well as metal substrate alloying element or cladding component is demonstrated for a variety of volatile organic compounds. The significance of dispersion techniques for the volatile compounds carried by nitrogen gas is shown by experiments conducted for naphthalene.