Effective-medium theory of elastic waves in random networks of rods.

We formulate an effective medium (mean field) theory of a material consisting of randomly distributed nodes connected by straight slender rods, hinged at the nodes. Defining wavelength-dependent effective elastic moduli, we calculate both the static moduli and the dispersion relations of ultrasonic longitudinal and transverse elastic waves. At finite wave vector k the waves are dispersive, with phase and group velocities decreasing with increasing wave vector. These results are directly applicable to networks with empty pore space. They also describe the solid matrix in two-component (Biot) theories of fluid-filled porous media. We suggest the possibility of low density materials with higher ratios of stiffness and strength to density than those of foams, aerogels, or trabecular bone.

[Thoracic and thoraco-lumbar discs herniations: diagnosis and therapeutic management]. / Les hernies discales thoraciques et thoraco-lombaires: prise en charge diagnostique et therapeutique.

Summary Management of symptomatic thoracic disc hemiations is difficult because of their polymorphic symptomatology and hardness to join the intervertebral thoracic disc surgically. The objective of this study was first to show the difficult diagnosis of these discal herniations and their posterior approach particularities; secondly, to analyse our results and compare them with those of the literature. This retrospective study analyses a four patients series operated between January 1997 and march 2003 using intraoperative somatosensory evoked potentials. All of them had before surgical management, a lumbar Xray or a MRI. The average postoperative follow-up was seven months. All patients were males with a mean age of 39.5 years old (extremes: 22-59). They had systematisation of their lumboradiculalgia, leading to an average delayed diagnosis of 10 months. The disc herniation was paramedian in three cases, median in one,. It was in T10-T11 in one case, in T11-T12 in two and in T12-L1 in one. All the patients were operated on with a posterior approach, recording the intraoperative somatosensory evoked potentials. Disc herniation was resected in three cases. Functional results were satisfactory (no pains for three patients) in the follow-up period of seven months. Every patient presenting with an atypical lumboradiculalgia must have a spine MRI to diagnose the symptomatic thoracic disc herniation. Surgery has good results if technical details are used respecting the threatened spinal cord.

Pharmacokinetics and hemostatic effects of saruplase in patients with acute myocardial infarction: comparison of infusion, single-bolus, and split-bolus administration.

Saruplase, or unglycosylated, single-chain urokinase-type plasminogen activator (scu-PA) selectively activates fibrin-bound plasminogen, and is subsequently converted to its two-chain derivative tcu-PA (urokinase) by plasmin. The efficacy of a 20 mg IV bolus followed by an infusion of 60 mg over 1 hour (standard regimen) has been demonstrated in acute myocardial infarction (AMI). The Bolus Administration of Saruplase in Europe (BASE) study compared the efficacy of standard therapy, single bolus (80 mg), and split bolus (2 x 40 mg at 30-minute intervals) in AMI. In a substudy of BASE, the pharmacokinetics of total u-PA activity (amidolytic activity after plasmin treatment), high molecular weight (HMW) u-PA antigen, and tcu-PA activity were compared in patients receiving standard therapy (n = 4), single bolus (n = 4), or split bolus (n = 5). Total u-PA activity and HMW u-PA antigen were similar. The maximum concentration (C(max,), mean +/- SD) of total u-PA activity was 2.2 +/- 0.3 microg/mL after standard therapy, 16.3 +/- 3.9 microg/mL after single bolus, and 8.2 +/- 1.6 ug/mL after split bolus. The area under the concentration versus time curve (AUC) values of total u-PA activity were 1.7 +/- 0.1 microg/mL*h (standard therapy), 4.0 +/- 0.9 microg/mL*h (bolus), and 3.0 +/- 0.7 microg/mL*h (split bolus). The dominant initial half-lives (t(1/2) alpha) were 7.1 +/- 1.1 minutes (standard), 8.8 +/- 0.8 minutes (bolus), and 5.1 +/- 2.1 minutes (split bolus). Maximum plasma concentrations of of tcu-PA activity were observed at 5.2 +/- 7 minutes (standard), 21 +/- 10 minutes (bolus), and 42 +/- 2 minutes (split bolus). C(max) was lowest after standard therapy (0.6 +/- 0.3 microg/mL), highest after bolus (4.2 +/- 2.2 microg/mL), and approximately twice as high as standard therapy after split bolus (1. 3 +/- 0.8 microg/mL). After standard therapy the mean fibrinogen concentration decreased gradually from approximately 300 mg/dL to 70 mg/dL at 90 and 120 minutes. After a single bolus the fibrinogen concentration decreased below the limit of quantification within 30 minutes and remained there for at least 120 minutes. Directly after the second 40 mg dose of the split bolus, the fibrinogen levels had an accelerated and more pronounced decrease to approximately 65 mg/dL at 90 and 120 minutes. A single bolus results in very high early total u-PA activity, which accelerates the appearance of tcu-PA activity and fibrinogen consumption. The pharmacokinetics and hemostatic effects of the split-bolus regimen are more comparable with those of standard therapy.

Porter's generic strategies, discontinuous environments, and performance: a longitudinal study of changing strategies in the hospital industry.

OBJECTIVE: Changes in generic strategies in response to discontinuous environments have been relatively ignored in the management literature. This study reports an examination of the relationships between Porter's (1980) generic strategies, discontinuous environments, and performance. DATA SOURCES: Archival data for 1984 and 1988 were collected for 172 acute care hospitals in Florida in order to test these relationships. STUDY DESIGN: To examine fully the performance impact of changes in strategy in a discontinuous environment, a longitudinal research design that identified a firm's strategy at two points in time, 1984 and 1988, was used. PRINCIPAL FINDINGS: Results indicate that firms with a proper strategy environment fit performed the highest, firms that did not change their strategy had no change in performance, and firms that changed their strategy toward a proper strategy environment showed an increase in performance. CONCLUSION: Findings support the notion that hospitals with appropriate strategy-environment combinations will exhibit higher performance.

Cardiopulmonary effects of direct venous CO2 insufflation in ewes. A model for CO2 hysteroscopy.

In order to mimic the delivery of CO2 into the pelvic circulation during sustained hysteroscopic surgery, direct insufflation of CO2 was done into the femoral vein of six anesthetized ewes. Following the establishment of baseline values in each animal, cardiac output, pulmonary arterial pressure (Ppa), pulmonary arterial wedge pressure (Ppw), arterial pH and gas levels, and ECG changes were recorded at ten-minute intervals. CO2 was delivered into the femoral circulation for 30 minutes. Following the experiment, measurements were repeated during a 20-minute recovery period. Ppa and Ppw increased significantly during the experiment but returned to baseline values after 70 minutes. Cardiac output, which increased significantly, remained high after the same period and was paralleled by cardiac rate. There was no significant change in systemic blood pressure or arterial oxygenation. Only at the highest flow rate were there observable changes in PCO2, accompanied by mild acidosis. One of the six animals displayed premature ventricular contractions at the inception of the highest flow rate. Since the delivery rate of CO2 per kilogram of body weight clearly exceeded that generally used in human hysteroscopic surgery (35-100 mL/min), these experimental results suggest that CO2, when employed as a distension modality in hysteroscopic surgery, displays a wide margin of safety.

A cluster analysis of Million Clinical Multiaxial Inventory (MCMI) profiles: more about a taxonomy of alcoholic subtypes.

MCMI and MMPI data were obtained from 125 male veteran alcoholic inpatients. MCMI profiles were classified into five relatively homogeneous subgroups by a hierarchical clustering technique. One-way ANOVAs were calculated for each of the MMPI scales; patients were classified according to MCMI group membership. Results showed that conceptually meaningful clusters exist among MCMI profiles, that statistically significant relationships exist between MCMI profiles and MMPI scale scores, and that these relationships are consistent with trends reported in the literature. The study provides additional support for the idea that a potentially useful taxonomy exists for alcoholics and suggests that the MCMI could be a useful tool in subsequent research on understanding and treating different patterns of alcoholism.

Ego identity status, conformity behavior, and personality in late adolescence.

Three related studies were completed to test the predictive relation among identity status, personality, and conformity behavior. The investigations were undertaken to replicate the earlier research findings of Toder and Marcia (1973). As predicted in Study 1, personality differences were found for both sexes. However, no relation was observed between identity status and conformity on the Asch task. Study 2 was completed to confirm the reliability of the identity status measure. Finally, in Study 3 four measures of conformity behavior (peer assessments, an experimental task, two self-report scales) were completed by college students of diffusion, foreclosure, moratorium, and identity-achievement statuses. Diffusion students were most influenced by peer pressure conformity, whereas identity-achievement students were most likely to report engaging in conformity behavior for achievement gains. Although earlier research by Toder and Marcia (1973) was not replicated via the Asch conformity task, the third study does support a predicted relation between identity and conformity behavior.

A practical classification of the risk factor in restorative surgery of the fallopian tube.

PIP: Microsurgical techniques are being developed which will soon be utilized in the following 3 areas: 1) restoration of fertility by using existing tissue; 2) restoration of fertility through graphed tissue; and 3) creation of laboratory models for the study of sperm and/or ovum and zygote transport. As the techniques of sterilization reversal are perfected, the demand rate for tubal sterilization will rise. Standard evaluations should be adopted in order to assess success rates (i.e., pregnancies following reversal procedures). Once these standards are established, it should be possible for the infertility surgeon to classify his/her risks, e.g., acceptable, moderate, poor, and unacceptable cases. There seems to be a requisite length of remaining tube for the procedure to end in success. Any evaluation of the surgery should include a ratio of the eventual uterine pregnancies: eventual ectopic pregnancies.^ieng

Pregnancy following segmental isthmic reversal of the rabbit oviduct.

Microsurgical reversal of a segment of rabbit proximal tubal isthmus has been followed by normal pregnency in the first two animals to undergo the procedure. Establishment of pregnancy despite radical modification of the oviduct furnishes the opportunity to gain new insights into the mechanisms controlling tubal ovum transport and emphasizes the evolving feasibility and importance of tuboplastic microsurgery both as a research tool and clinical procedure.