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Biomedical subjects

R A London

Publications and source records attributed to R A London.

8 recordsLinked to original sources
PubMed2000

Temperature distribution for combined laser hyperthermia-photodynamic therapy in the esophagus.

In recent years photodynamic laser therapy (PDT) has been tested in animal and clinical studies for treatment of esophageal cancer. In several animal experiments a synergistic effect was found by simultaneously applying PDT and hyperthermia (HT). In this paper an optical fibre system is described which can be used in the esophagus for combined PDT with a 1 W dye laser and HT with a 15 W Nd:YAG laser. A phantom was built simulating the geometry of the esophagus using cow muscle. The spatial temperature field during HT was measured versus irradiation time. The results were compared with calculations using a coupled Monte Carlo laser transport/finite difference heat transport model using the LATIS computer program. Measurements and calculations yield a realistic description of the temperature distribution during HT under various experimental conditions. The LATIS program allows the prediction of the effects of blood perfusion for in vivo situations. The results show that perfusion has considerable influence on the temperature field, reducing the effective depth in tissue for HT.

Animals↗
PubMed1998

Trends in single mothers' living arrangements from 1970 to 1995: correcting the current population survey.

I examine trends in single mothers' living arrangements using data from the 1970-1995 Current Population Surveys. I create a consistent trend by correcting a coding problem that stemmed from the misidentification of children living in multigenerational households before 1984. Revised estimates show that the number of single mothers in each of these years was undercounted by 200,000-300,000. All of these women were subfamily heads living with their parents, and the problem occurred disproportionately among teens and black women. The uncorrected trend falsely indicates a large increase in the share of single mothers living with their parents. In reality, there was little change in the percentage of single mothers living in this arrangement over the time period. However, the data indicate a large increase in the rate of cohabitation and a comparable decline in the rate of living independently among this population.

Adolescent↗
PubMed1997

Investigation of laser tissue welding dynamics via experiment and modeling.

An in vitro study of laser tissue welding mediated with a dye-enhanced protein solder was performed. Freshly harvested sections of porcine aorta were used for the experiments. Arteriotomies approximately 4 mm in length were treated using an 805 nm continuous-wave diode laser coupled to a 1-mm diameter fiber. Temperature histories of the surface of the weld site were obtained using a fiberoptic-based infrared thermometer. The experimental effort was complemented by the LATIS (LAser-TISsue) computer code, which numerically simulates the exposure of tissue to near-infrared radiation using coupled Monte Carlo, thermal transport, and mass transport models. Comparison of the experimental and simulated thermal results shows that the inclusion of water transport and evaporative losses in the model is necessary to determine the thermal distributions and hydration state in the tissue. The hydration state of the weld site was correlated with the acute weld strength.

Animals↗
PubMed1996

State abortion rates. The impact of policies, providers, politics, demographics, and economic environment.

This paper uses data on abortion rates by state from 1974-1988 to estimate two-stage least squares models with fixed state and year effects. Restrictions on Medicaid funding for abortion are correlated with lower abortion rates in-state and higher rates among nearby states. A maximal estimate suggests that 19-25% of the abortions among low-income women that are publicly funded do not take place after funding is eliminated. Parental notification laws for teen abortions do not significantly affect aggregate abortion rates. A larger number of abortion providers in a state increases the abortion rate, primarily through inducing cross-state travel.

Abortion, Legal↗
PubMed1986

Immersion anesthesia for extracorporeal shock wave lithotripsy. Review of two hundred twenty treatments.

Two hundred twenty extracorporeal shockwave lithotripsy (ESWL) treatments at the New York Hospital-Cornell Medical Center between September, 1984, and April, 1985, were reviewed with respect to anesthetic management. One hundred seventy-four treatments (79%) were performed under a regional anesthetic technique (RA), either with an indwelling epidural catheter (155 treatments), or with a single spinal injection (19 treatments). Forty-six treatments (21%) were performed under general anesthesia (GA). Ninety per cent of the patients were classified as ASA I or II. Hypotension during treatment, defined as blood pressure falls greater than 20 per cent of baseline mean arterial pressure, was recorded with 19.5 per cent of the regional anesthetic treatments (18.7% of the epidurals and 26.3% of the spinals) and 13.0 per cent of the general anesthetic treatments. Blood pressure falls were larger in the regional group than in the general group. The average recovery room stay was longer for the bupivacaine (0.25-0.5%) epidurals and the tetracaine (0.4%) spinals (252 min and 212.1 min, respectively) than for the lidocaine (1.5-2.0%) epidurals and the general anesthetics (101.7 min and 102.1 min, respectively). General anesthesia, with controlled ventilation, was advantageous in minimizing renal excursion and stone movement during treatment. Yet, in appropriately selected and sedated patients, regional anesthesia with continuous lidocaine epidural techniques was found to provide acceptable anesthesia for patients undergoing ESWL.

Adolescent↗
PubMed1982

Circulating immune complexes in idiopathic glomerular disease.

Circulating immune complexes (CIC) could be found in the majority of 271 sera from 131 patients with idiopathic minimal change, membranous and mesangial proliferative glomerulonephritis when a combination of CIC assays detecting different properties of CIC were used. In neither individual patients nor in any of the three groups as a whole did CIC levels reflect the state of the renal lesion. No correlation was found between the class of immunoglobulin in the CIC and that deposited in the kidney. With the exception of minimal change disease in which non-C1q binding IgG CIC predominated, a range of CIC was found in the patients examined. The pattern of CIC detected did not allow different forms of renal disease to be distinguished. IgA CIC could be found in mesangial proliferative glomerulonephritis both with and without IgA deposition and in some patients with membranous and minimal change disease, as well as in a high proportion of sera from 12 patients with the Henoch-Schönlein syndrome. CIC size was estimated in six patients, but only in one did a specific size of complex predominate. The CIC which may be found in the majority of sera from patients with idiopathic glomerulonepohritis provide little information of clinical value; no direct relationship can be demonstrated between the CIC found and the renal lesion.

Antigen-Antibody Complex↗