Lagrangian motion, coherent structures, and lines of persistent material strain.

Lagrangian motion in geophysical fluids may be strongly influenced by coherent structures that support distinct regimes in a given flow. The problems of identifying and demarcating Lagrangian regime boundaries associated with dynamical coherent structures in a given velocity field can be studied using approaches originally developed in the context of the abstract geometric theory of ordinary differential equations. An essential insight is that when coherent structures exist in a flow, Lagrangian regime boundaries may often be indicated as material curves on which the Lagrangian-mean principal-axis strain is large. This insight is the foundation of many numerical techniques for identifying such features in complex observed or numerically simulated ocean flows. The basic theoretical ideas are illustrated with a simple, kinematic traveling-wave model. The corresponding numerical algorithms for identifying candidate Lagrangian regime boundaries and lines of principal Lagrangian strain (also called Lagrangian coherent structures) are divided into parcel and bundle schemes; the latter include the finite-time and finite-size Lyapunov exponent/Lagrangian strain (FTLE/FTLS and FSLE/FSLS) metrics. Some aspects and results of oceanographic studies based on these approaches are reviewed, and the results are discussed in the context of oceanographic observations of dynamical coherent structures.

Variation in blood lead and hematocrit levels during pregnancy in a socioeconomically disadvantaged population.

Lead is a long-recognized human toxicant that crosses the placenta. Fetal sensitivity to environmental agents can vary with stage of development; therefore, how maternal blood lead levels change during pregnancy and how fetal exposure is influenced provide useful knowledge. In this study, the authors describe longitudinal changes in blood lead levels during the course of pregnancy in a sample of socioeconomically disadvantaged pregnant women. The women were recruited early in pregnancy when they sought care at one of two obstetrics clinics in Albany, New York. Maternal blood lead levels changed between the 1st and 2nd trimesters, from 1.99 microg/dl to 1.69 microg/dl (hematocrit corrected, 1.70-1.62); between the 2nd and 3rd trimester from 1.78 microg/dl to 1.86 microg/dl (hematocrit corrected, 1.65-1.72); and between 3rd trimester and delivery from 1.80 microg/dl to 2.17 microg/dl (hematocrit corrected, 1.70-1.86). These changes were statistically significant and were corrected for secular trends. The rate of change per day in lead levels averaged -36.6% from trimester 1 to trimester 2, 18.3% from trimester 2 to trimester 3, and -40.8% from trimester 3 to delivery. The patterns in our study were consistent with the patterns reported in a few other longitudinal studies of change in lead level during pregnancy. Findings reveal significant associations between maternal blood lead levels and both hematocrit and trimester of pregnancy. Clinicians who interpret test results should take into account the dynamics of these variables when determining appropriate care for both mother and neonate.

Home heparin therapy used in a pregnant patient with a mechanical heart valve prosthesis.

The optimal anticoagulation therapy for pregnant patients with a mechanical valve prosthesis is uncertain, but teratogenic effects and the high incidence of fetal loss associated with dicumarol derivatives limit the use of these agents as anticoagulants in this setting. A patient with a mechanical valve prosthesis, in the first trimester of pregnancy, stopped taking her warfarin because of personal fears about teratogenicity. Prosthetic valve thrombosis developed, and she required redo mitral valve replacement. Another mechanical prosthesis was inserted without maternal or fetal injury. The patient was maintained on continuous home, intravenous, high-dose heparin therapy for the remainder of her pregnancy. This therapy resulted in a successful pregnancy and delivery without valve thrombosis, hemorrhagic events, or maternal or fetal compromise.

Effect of labor on lymphocyte subsets in full-term neonates.

PROBLEM: To determine the effect of labor on lymphocyte subsets in full-term neonates. METHOD OF STUDY: Cord blood obtained at delivery from full-term neonates, six born vaginally and six born by elective Cesarean section, was analyzed for lymphocyte subsets. Monoclonal antibodies, immunofluorescence, and flow cytometry were utilized to determine the lymphocyte phenotype frequencies in these neonates. These frequencies were compared by mode of delivery and to adult peripheral blood reference ranges using a two-tailed Student's t-test, P < 0.05. RESULTS: A profile of significantly elevated T (CD2, CD3) and helper cells (CD4) and depressed Natural Killer cells (CD16, CD56) is characteristic of term Cesarean section neonates. Significantly depressed frequency of T cells (CD2, CD3) and helper T cells (CD4) and elevated Natural Killer cells (CD16, CD56) is characteristic of vaginally delivered neonates. CONCLUSIONS: The mode of delivery affects the lymphocyte subset frequencies in full-term neonates.

The computerization of industrial hygiene records.

A program for computerizing the results of industrial hygiene monitoring data has been developed and implemented. The methodology and approaches taken in data collection, retrieval, and utilization are presented.