Growth and yield responses of snap bean to mixtures of carbon dioxide and ozone.

Elevated CO2 concentrations expected in the 21st century can stimulate plant growth and yield, whereas tropospheric O3 suppresses plant growth and yield in many areas of the world. Recent experiments showed that elevated CO2 often protects plants from O3 stress, but this has not been tested for many important crop species including snap bean (Phaseolus vulgaris L.). The objective of this study was to determine if elevated CO2 protects snap bean from O3 stress. An O3-tolerant cultivar (Tenderette) and an O3-sensitive selection (S156) were exposed from shortly after emergence to maturity to mixtures of CO2 and O3 in open-top field chambers. The two CO2 treatments were ambient and ambient with CO2 added for 24 h d(-1) resulting in seasonal 12 h d(-1) (0800-2000 h EST) mean concentrations of 366 and 697 microL L(-1), respectively. The two O3 treatments were charcoal-filtered air and nonfiltered air with O3 added for 12 h d(-1) to achieve seasonal 12 h d(-1) (0800-2000 h EST) mean concentrations of 23 and 72 nL L(-1), respectively. Elevated CO2 significantly stimulated growth and pod weight of Tenderette and S156, whereas elevated O3 significantly suppressed growth and pod weight of S156 but not of Tenderette. The suppressive effect of elevated O3 on pod dry weight of S156 was approximately 75% at ambient CO2 and approximately 60% at elevated CO2 (harvests combined). This amount of protection from O3 stress afforded by elevated CO2 was much less than reported for other crop species. Extreme sensitivity to O3 may be the reason elevated CO2 failed to significantly protect S156 from O3 stress.

Laparoscopic cholecystectomy in patients with early cirrhosis.

Traditionally, cholecystectomy in cirrhotic patients has been reserved for patients with severe biliary disease, because of the high morbidity and mortality in cirrhotic patients undergoing this procedure. Laparoscopic cholecytectomy (LC) was originally contraindicated in cirrhotic patients because of the associated portal hypertension and coagulopathy. This study examined the safety of LC in Child's class A patients.A review was conducted of all patients with cirrhosis who underwent cholecystectomy at our hospital between 1990 and 1998.Fifteen patients with cirrhosis had their gallbladder removed laparoscopically during that time period. All patients were Child's class A. The average age was 59 (range, 36-85). The operative indications included acute cholecystitis (5 patients), biliary pacreatitis (4 patients), biliary colic (5 patients), and cholangitis (1 patients). Six patients had known cirrhosis, and 9 were examined intraoperatively. The average operative time was 105 minutes. None of the patients required a blood transfusion. No intraoperative or postoperative complications occurred. No deaths occurred. Postoperative stay was 3 days or less in all but 3 patients.These results compare favorably to other published studies from outside of the United States. Based on our findings, we believe LC can be performed safely in patients with class A cirrhosis.

On a simplified model of the renal medulla.

A set of equations that approximate the central core model of the human kidney are solved. It is noted that the solution indicates a limit to the increase in solute concentration in the descending limb of Henle for a given metabolic pump term. Comparison is made with the results of an alternative theory, and numerical results are presented for the increase in solute concentration in the descending limb of Henle.

Modelling transient heat transfer through the skin and a contact material.

Two thermal models of the skin and superficial tissues are described, both of which incorporate the thermal effects of subcutaneous and dermal blood flow through temperature-dependent heat sources. The model which represents the dermal blood flow as the perfusion of a region of finite thickness gives rise to purely numerical solutions for the transient temperatures. Representing the dermal blood flow by a heat generating surface gives rise to a model which yields explicitly analytical expressions. Although these analytical expressions require numerical integration techniques to finally evaluate them, they are of a form which allows temperature values to be derived more efficiently than by the purely numerical method. Both models are used to predict the time-dependent temperature profiles resulting from the interaction between the tissues and thermally passive materials in intimate contact with the skin surface. The predictions of the two models are compared and the limitations of the analytical model highlighted.

Interaction of tobacco etch or tobacco vein mottling virus and ozone on biomass changes in burley tobacco.

Burley tobacco is susceptible to several different types of virus diseases that suppress plant growth and development. Two viruses, tobacco etch virus (TEV) and tobacco vein mottling virus (TVMV), are particularly damaging to burley. Burley tobacco cultivars resistant to these two viruses are currently being developed. Some of these cultivars also show differential sensitivity to ozone (O3). Recent field observations have suggested that burley tobacco infected with TEV and TVMV was more sensitive to O3 than non-virus-infected tobacco. Experiments were designed to identify interactions between O3 and each of the two virus diseases. Three cultivars, Burley 21, Burley 49, and Greeneville 131, which were differentially sensitive to O3 and both virus diseases, were grown in a charcoal-filtered greenhouse environment. Tobacco plants of each cultivar were inoculated with TEV or TVMV, and virus infected and virus-free plants were exposed to 0.0, 0.05, 0.2, and 0.4 ppm O3 (1 ppm of O3 is equivalent to 1960 microg m(-3)), 3h day(-1), 5 days week(-1) for 3 weeks in continuous-stirred tank reactor exposure chambers in the greenhouse. Exposures were begun after systemic virus symptoms were expressed in inoculated plants. The suppression of lead and stem dry weight by increasing O3 concentrations was less in TEV-infected burley cultivars than in noninfected burley cultivars. Tobacco vein mottling virus infection enhanced biomass suppression by O3 on Burley 21 and on Greeneville 131, but not on Burley 49. Thus, the interactions with O3 were dependent on specific virus-cultivar combinations.

Modeling transient heat transfer through the skin and superficial tissues--1: Surface insulation.

Two models of transient heat transfer through the skin and superficial tissues are presented. One model comprises a finite slab and semi-infinite slab, representing the epidermis and subdermal tissues, respectively, and a heat-generating interface representing the thermal effect of blood flow through the dermis. A model is also considered where the three tissue regions are represented more conventionally by three finite slabs. A transient problem arising from surface insulation is examined and analytical solutions derived from the first model are compared with numerical solutions derived from the second.