Nitrous oxide, methane and carbon dioxide patterns and dynamics from an experimental pig mass grave.

The objective of the three-year study was to examine spatial and temporal patterns of fluxes and soil pore air concentrations of methane (CH4), carbon dioxide (CO2) and nitrous oxide (N2O) from an experimental mass grave located in a temperate environment. The mass grave (5×10m) contained twenty pig carcasses at a depth of approximately 1m was compared to a plot of the same dimensions containing only disturbed soil, as well as an undisturbed plot. Soil pore air CH4 concentrations were sub-ambient (<1.8ppm) except at 75 and 100cm depths at the mass grave in years 1 and 2 but decreased in year 3. The consumption of CH4 within the aerobic soil resulted in small negative fluxes at the soil surface. Soil pore air CO2 concentration showed an increase with depth in all three plots, with the largest increase (>100,000ppm at 1m) in the mass grave, though there was a marked decrease from years 1 to 3. Surface fluxes of CO2 showed strong seasonal variations, peaking in summer. Soil pore air N2O concentration showed major increases in the mass grave, compared to the other two plots with the pattern maintained over the three years, resulting in larger surface fluxes of N2O. To establish the role of the carcasses in N2O dynamics, we incubated a soil sample containing carcass material which resulted in fast rates of N2O production and consumption. The maintenance of elevated pore air concentration and surface flux of N2O throughout the 3 years suggests that this is a long-term pattern and likely the best of the three gases to use to detect graves. Thus, we suggest that measurement of soil pore air concentrations, especially of N2O, could be a simple and effective approach to help determine the location of clandestine graves.

The association of inadequate mid-pregnancy weight gain and preterm birth in twin pregnancies.

OBJECTIVE: To determine whether inadequate gestational weight gain in the second trimester in twin pregnancies is associated with an increased risk of preterm birth (PTB) at <32 weeks. STUDY DESIGN: Retrospective cohort study including 489 twin pregnancies delivered between 2001 and 2013. Rates of weight gain at different gestational ages were compared with Institute of Medicine guidelines. RESULT: An inadequate rate of weight gain at <20 weeks was not associated with PTB. Patients with inadequate rates of weight gain at 20 to 28 weeks had a higher risk of PTB at <32 weeks (37.6%) compared to those with adequate weight gain (15.2%) (P<0.001). In multivariate analysis, women with inadequate weight gain at 20 to 28 weeks were 2.8 times more likely to deliver at <32 weeks (95% confidence interval 1.65 to 4.81). CONCLUSION: Inadequate gestational weight gain at 20 to 28 weeks in twin pregnancies was the strongest predictor of PTB at <32 weeks. This represents an optimal time for interventions to improve weight gain and potentially decrease rates of PTB.

Nitrous oxide, methane and carbon dioxide dynamics from experimental pig graves.

Twelve pig carcasses were buried in single, shallow and deep (30 and 90 cm, respectively) graves at an experimental site near Ottawa, Ontario, Canada, with three shallow and three deep wrapped in black plastic garbage bags. An additional six carcasses were left at the surface to decompose, three of which were bagged. Six reference pits without remains were also dug. The objective of this three-year study was to examine the biogeochemistry and utility of nitrous oxide (N2O), methane (CH4) and carbon dioxide (CO2) in grave detection and whether grave depth or cadaver condition (bagged versus bare) affected soil pore air concentrations and emission of the three gases. Graves showed significantly higher (α=0.05) concentrations and surface fluxes of N2O and CO2 than reference pits, but there was no difference in CH4 between graves and reference pits. While CH4 decreased with depth in the soil profiles, N2O and CO2 showed a large increase compared to reference pits. Shallow graves showed significantly higher emissions and pore air concentrations of N2O and CO2 than deep graves, as did bare versus bagged carcasses.

Gaseous carbon dioxide and methane, as well as dissolved organic carbon losses from a small temperate wetland under a changing climate.

Temperate forests can contain large numbers of wetlands located in areas of low relief and poor drainage. These wetlands can make a large contribution to the dissolved organic carbon (DOC) load of streams and rivers draining the forests, as well as the exchange of methane (CH4) and carbon dioxide (CO2) with the atmosphere. We studied the carbon budget of a small wetland, located in Kejimkujik National Park, Nova Scotia, Canada. The study wetland was the Pine Marten Brook site, a poor fen draining a mixed hardwood-softwood forest. We studied the loss of DOC from the wetland via the outlet stream from 1990 to 1999 and related this to climatic and hydrologic variables. We added the DOC export information to information from a previously published model describing CH4 and CO2 fluxes from the wetland as a function of precipitation and temperature, and generated a new synthesis of the major C losses from the wetland. We show that current annual C losses from this wetland amount to 0.6% of its total C mass. We then predicted that under climate changes caused by a doubling of atmospheric CO2 expected between 2040 and 2050, total C loss from the wetland will almost double to 1.1% of total biomass. This may convert this wetland from what we assume is currently a passive C storage area to an active source of greenhouse gases.

Fetal weight prediction by thigh volume measurement with three-dimensional ultrasonography.

OBJECTIVE: To evaluate the usefulness and accuracy of a simple method of predicting fetal weight by measuring fetal thigh volume with three-dimensional ultrasonography. METHODS: In 84 pregnant women, fetuses without structural or chromosomal anomalies were studied prospectively and cross-sectionally. Biparietal diameter (BPD), abdominal circumference (AC), and femur length (FL) were measured by two-dimensional ultrasound. Fetal thigh volume was measured by three-dimensional ultrasound, using three cross-sectional images of femur, from proximal, middle, and distal parts of femur diaphysis. Infants were delivered within 48 hours after ultrasound examinations. RESULTS: Modified thigh volume measurements using three cross-sectional images of femur by three-dimensional ultrasound were correlated strongly with birth weight (R(2) = 0.921, P <.001). Using linear and polynomial regression, we calculated a new best-fit formula: Birth weight (g) = 165.32 + 28.78 x modified thigh volume (mL). The mean and standard deviation of the residual were 121.8 and 110.4, respectively, in three-dimensional formulas, which were significantly smaller than those of two-dimensional formulas. CONCLUSION: Thigh volume measurement using three cross-sectional images of femur by three-dimensional ultrasound was simple, and there was better accuracy with this method than with two-dimensional ultrasound methods for predicting fetal weight during the third trimester of pregnancy.

Utility of minor ultrasonographic markers in the prediction of abnormal fetal karyotype at a prenatal diagnostic center.

OBJECTIVE: This study was undertaken to assess the value of minor ultrasonographic markers in predicting significant karyotypic abnormalities. STUDY DESIGN: A total of 2743 fetuses (14-24 weeks' gestation) prospectively underwent a detailed ultrasonographic survey before genetic amniocentesis. Criteria for 8 minor ultrasonographic markers were established. Odds ratios for significant karyotypic abnormalities in the presence of minor ultrasonographic markers were calculated with the chi(2) and Fisher exact tests. RESULTS: Of the fetuses, 14.6% had a single minor ultrasonographic marker, 2.1% had >/=2 minor ultrasonographic markers, and 2.7% had >/=1 major ultrasonographic abnormality. One hundred four fetuses (3.8%) had an abnormal karyotype. Compared with a normal ultrasonographic examination result a single minor ultrasonographic marker increased the risk of karyotypic abnormality 5.7-fold (95% confidence interval, 3.5-9.3), whereas multiple minor markers increased the risk of an abnormal karyotype 12-fold (95% confidence interval, 5.5-26.5). When they were identified ultrasonographically in isolation, echogenic bowel, 2-vessel umbilical cord, echogenic intracardiac foci, choroidal separation, and choroid plexus cysts were statistically associated with an abnormal karyotype. When minor markers were identified in clusters of >/=2, echogenic bowel, short femur, 2-vessel umbilical cord, echogenic intracardiac foci, and mild ventriculomegaly were significantly predictive of karyotypic abnormality. With respect to the a priori aneuploidy risk of 1:26 and the a priori Down syndrome risk of 1:50, a normal ultrasonographic examination result reduced the risks to 1:67 and 1:120, respectively. The use of minor ultrasonographic markers in addition to major ultrasonographic abnormalities increased the detection of karyotypic abnormality from 27.9% to 68.3%. For trisomy 21 the sensitivity rose from 16.4% to 67. 3%. CONCLUSIONS: Significant karyotypic abnormality risk assessment by ultrasonography was greatly enhanced by the addition of minor ultrasonographic markers. Further, clusters of minor ultrasonographic markers greatly increased the likelihood of karyotypic abnormality compared with a single minor marker. A completely normal ultrasonographic examination result reduced the risk of an abnormal karyotype by 62%. Inclusion of minor ultrasonographic markers in the genetic sonogram in a high-risk population will allow the detection of 68% of fetuses with karyotypic abnormalities with a false-positive rate of 17%.

Atypical antipsychotics: Part II: Adverse effects, drug interactions, and costs.

OBJECTIVE: To compare the adverse effects, drug interactions, and costs of conventional and atypical agents, and to provide a summary of therapeutic guidelines. Part I compared the pharmacology, pharmacokinetics, and efficacy of atypical and conventional agents. DATA SOURCES: Information was retrieved from a MEDLINE English-language literature search from June 1986 to June 1998 and by review of references. Indexing terms included atypical antipsychotics, neuroleptics, clozapine, risperidone, olanzapine, sertindole, quetiapine, and ziprasidone. STUDY SELECTION: Comparative studies were selected when possible; placebo-controlled studies were included when data were limited on newer atypical antipsychotics. DATA EXTRACTION: Emphasis was placed on properly designed clinical trials that assessed dosage, expanded efficacy, enhanced adverse effect profile, and cost. DATA SYNTHESIS: Significant adverse effects are agranulocytosis with clozapine, dose-dependent extrapyramidal side effects (EPS) with risperidone, and neuroleptic malignant syndrome with clozapine and risperidone. Clinically relevant drug interactions may occur with clozapine-lorazepam, clozapine-fluvoxamine, and sertindole-quinidine. Newer atypical agents have high acquisition costs but may reduce noncompliance and rehospitalization rates. CONCLUSIONS: Risperidone or olanzapine are recommended as first-line agents for schizophrenia due to accumulating controlled trials and clinical experience. Quetiapine should be considered with partial response or if EPS develop, and clozapine is an option with treatment-refractory patients. Atypical agents may contribute to a better quality of life, but conventional neuroleptics are the first choice for strictly cost considerations.

Atypical antipsychotics. Part I: Pharmacology, pharmacokinetics, and efficacy.

OBJECTIVE: To compare the pharmacology, pharmacokinetics, and efficacy of the newer atypical antipsychotics with those of conventional agents and existing atypical agents. DATA SOURCES: Information was retrieved from a MEDLINE English-literature search from July 1986 to June 1998 and by review of references. Indexing terms included neuroleptics, atypical antipsychotics, clozapine, risperidone, olanzapine, sertindole, quetiapine, and ziprasidone. STUDY SELECTION: Comparative studies were selected when possible; placebo-controlled studies were included when data were limited on newer atypical antipsychotics. DATA EXTRACTION: Emphasis was placed on properly designed clinical trials that assessed dosage, expanded efficacy, enhanced adverse effect profile, and cost. DATA SYNTHESIS: Like other atypical antipsychotics, the newer agents have an enhanced 5-hydroxytryptophan/dopaminergic receptors (5-HT2/D2) affinity ratio and undergo extensive biotransformation. Risperidone and olanzapine demonstrate more favorable efficacy/adverse effect ratios than clozapine, sertindole, and conventional antipsychotics in nonrefractory and refractory schizophrenics. Future studies will more clearly define the role of quetiapine and ziprasidone in antipsychotic therapy. CONCLUSIONS: Data from controlled trials on efficacy and extrapyramidal side effects support risperidone or olanzapine as first-line agents for the treatment of schizophrenia. Pharmacologic and pharmacokinetic factors do not distinguish between agents sufficiently for drug selection.

Holographic interferometers with photorefractive recording media.

We discuss two types of holographic interferometer that contain photorefractive recording media. The first type contains two beams interacting in a photorefractive medium. The second type utilizes a single beam and relies on self-pumped phase conjugation from a photorefractive crystal to make phase changes appear as intensity changes. We show both theoretically and experimentally that the first type can be analyzed in a straightforward manner; however, the second type cannot be approximated as simply a special case of the first type, as one may näively suspect.

Maternal characteristics and risk of severe neonatal thrombocytopenia and intracranial hemorrhage in pregnancies complicated by autoimmune thrombocytopenia.

OBJECTIVE: The antenatal and intrapartum management of women with autoimmune thrombocytopenia is controversial. The current approach emphasizes an effort to identify maternal characteristics predictive of severe neonatal thrombocytopenia or to measure fetal platelet counts and perform cesarean section in patients considered to be at risk for neonatal intracranial hemorrhage. In the current study we review our experience with maternal autoimmune thrombocytopenia and neonatal outcome. STUDY DESIGN: Fifty-five pregnancies with autoimmune thrombocytopenia over a 10-year period in three major medical centers in San Diego, California, were evaluated. Maternal characteristics and neonatal outcomes were assessed and compared with those in other recent reports. Data were submitted to Fisher's exact (two-tailed), chi2, and Student t tests, with linear regression performed to analyze the association between variables. RESULTS: Maternal characteristics including platelet count, presence of antiplatelet antibody, antecedent history of autoimmune thrombocytopenia, and corticosteroid therapy were not predictive of severe neonatal thrombocytopenia. Maternal history of splenectomy was significantly correlated with fetal platelet counts <50 x 10(9)/L (odds ratio 5.63; 95% confidence interval 2.2 to 14.3). There were four neonates with severe neonatal thrombocytopenia (8%), and one who was delivered by cesarean section had intracranial hemorrhage. CONCLUSIONS: These findings, combined with others in the literature, confirm that severe neonatal thrombocytopenia is an infrequent complication of maternal autoimmune thrombocytopenia and is not reliably predicted by maternal characteristics. Intracranial hemorrhage is also a rare event and is not related to mode of delivery. Cesarean section should be reserved for obstetric indications only.

Clinical assessment of amniotic fluid.

Amniotic fluid volume estimation has become an integral part of fetal evaluation. Although the sonographic techniques clinically available are limited in their accuracy and predictive value, the careful performance of AFI measurements provide important and complementary clinical data on which to base management decisions in pregnancies at risk.

Fetal growth in diabetic pregnancy.

In summary, fetal macrosomia occurs in almost one third of diabetic pregnancies regardless of class. Abnormal fetal fat stores lead to difficult labor, dystocia, and birth injury as well as postnatal metabolic transition. The abnormal body fat distribution at birth may destine some of these infants to lifelong obesity. Abnormal fetal growth in diabetic pregnancy appears to occur with any elevations in maternal glucose levels, however modest. Detection of macrosomia is therefore a major goal of diabetic pregnancy management.

Nonlinear-optical Christiansen filter as an optical power limiter.

We have constructed an optical power limiter based on nonlinear induced scattering in a cell containing crushed glass and a mixture of acetone and carbon disulfide. For 30-ps-long laser pulses the transmitted energy saturates at a value of 6 microJ. We also present the results of a theoretical modeling study that shows how the operating characteristics of such a device can be optimized.

Staphylococcal septicemia and adult respiratory distress syndrome in pregnancy treated with extracorporeal carbon dioxide removal.

BACKGROUND: Septicemia in pregnancy may take an especially fulminant course. Adult respiratory distress syndrome (RDS) and disseminated intravascular coagulation (DIC) are associated life-threatening complications. Treatment consists of appropriate antibiotic coverage and supportive measures. CASE: A previously healthy 21-year-old woman presented at 26 weeks' gestation with staphylococcal sepsis of undetermined origin. Her course was complicated by the rapid onset of adult RDS, DIC, and multi-organ-system failure, resulting in preterm delivery. Despite maximal ventilatory support, her pulmonary status continued to deteriorate. She was treated ultimately with extracorporeal carbon dioxide removal and survived without serious sequelae. CONCLUSION: Extracorporeal carbon dioxide removal may improve survival in gravidas with adult RDS by decreasing the required airway pressures for ventilation, thus permitting pulmonary recovery.

Gestational diabetes mellitus: antenatal variables as predictors of postpartum glucose intolerance.

OBJECTIVE: To determine whether antepartum variables can predict postpartum glucose intolerance. METHODS: Glucose tolerance was assessed 6 weeks postpartum in 94 of 238 women with gestational diabetes using a 2-hour, 75-g oral glucose tolerance test (GTT). Selected antepartum variables were analyzed for predictive ability for postpartum glucose intolerance. RESULTS: Of 238 patients, 94 (39%) returned for a GTT. Those returning and those not returning were similar in all variables. Postpartum glucose intolerance occurred in 34%: impaired glucose tolerance in 18%, overt diabetes in 16%. No single maternal, intrapartum, or neonatal variable was predictive of postpartum glucose intolerance in all cases. Predictive variables included: requirement for insulin (insulin versus diet: 25 versus 3% impaired glucose tolerance, 26 versus 0% diabetes; P = .001), poor glycemic control (any 2-hour postprandial blood sugar level of 150 mg/dL or higher: 34 versus 5% diabetes; P = .005), and the 50-g GTT value (200 mg/dL or higher: 32 versus 6% diabetes; P = .01). For insulin requirement, the relative risk (RR) was 17.28 (95% confidence interval [CI] 2.46-121.45), and for the above three variables combined, the RR was 19.68 (95% CI 2.88-134.2). When the insulin dose was at least 100 U/day, all patients had abnormal glucose tolerance postpartum (RR = 34.00, 95% CI 4.93-234.39). CONCLUSIONS: Postpartum glucose screening is not warranted for women at low risk who do not require insulin during pregnancy. The incidence of postpartum glucose intolerance in this group is very low. Women with risk factors should receive postpartum screening. Patients receiving at least 100 U/day of insulin have a 100% incidence of postpartum glucose intolerance.

Fetal electrolyte and acid-base responses to amnioinfusion: lactated Ringer's versus normal saline in the ovine fetus.

OBJECTIVE: We hypothesized that amnioinfusion with normal saline would increase fetal plasma sodium and chloride concentrations, resulting in a hyperchloremic acidosis, and that these alterations would not occur after amnioinfusion with lactated Ringer's solution. METHODS: Chronically catheterized fetal sheep (137 +/- 1 days' gestation; mean +/- SE) were divided into three groups: control (n = 8), infused with normal saline (n = 10), and infused with lactated Ringer's solution (n = 10). The protocol consisted of a 30-minute pre-infusion period, a 1-hour amnioinfusion, and a 1-hour recovery period. During amnioinfusion, warmed solution was infused at a rate of 100 mL/minute for 1 hour. Fetal plasma and amniotic fluid electrolyte concentrations and osmolalities were measured every 20 minutes. Statistical analysis was by analysis of variance and linear regression. RESULTS: Amniotic fluid electrolyte concentrations changed significantly (P < .001) in both amnioinfusion groups, resulting in amniotic fluid compositions that were essentially the same as the infused fluid 20 minutes after starting the amnioinfusion. Significant increases in fetal plasma Na+ and CI- concentrations (2-3 mEq/L) occurred in the normal-saline infusion group relative to both the control and lactated Ringer's groups (P < .001). The lactated Ringer's group demonstrated only a modest increase in plasma Na+ (P = .04) and no change in plasma Cl- concentration. Fetal arterial pH decreased (-0.015 U) in the normal-saline group, and the change in fetal pH was linearly related to the change in plasma Cl- concentration (r = -0.532, P = .004). CONCLUSIONS: Normal-saline amnioinfusion can significantly alter fetal plasma electrolyte concentrations and blood pH, whereas amnioinfusion with lactated Ringer's solution results in minimal changes in fetal electrolytes and acid-base balance. The fetal plasma changes that occur during saline infusion are in the physiologic but not the pathologic range.

Environmental controls on the photosynthesis and respiration of a boreal lichen woodland: a growing season of whole-ecosystem exchange measurements by eddy correlation.

Measurements of net ecosystem CO2 exchange by eddy correlation, incident photosynthetically active photon flux density (PPFD), soil temperature, air temperature, and air humidity were made in a black spruce (Picea mariana) boreal woodland near Schefferville, Quebec, Canada, from June through August 1990. Nighttime respiration was between 0.5 and 1.5 kg C ha-1 h-1, increasing with temperature. Net uptake of carbon during the day peaked at 3 kg C ha-1 h-1, and the daily net uptake over the experiment was 12 kg C ha-1 day-1. Photosynthesis dropped substantially at leaf-to-air vapor pressure deficit (VPD) greater than 7 mb, presumably as a result of stomatal closure. The response of ecosystem photosynthesis to incident PPFD was markedly non-linear, with an abrupt saturation at 600 µmol m-2 s-1. This sharp saturation reflected the geometry of the spruce canopy (isolated conical crowns), the frequently overcast conditions, and an increase in VPD coincident with high radiation. The ecosystem light-use efficiency increased markedly during overcast periods as a result of a more even distribution of light across the forest surface. A mechanistic model of forest photosynthesis, parameterized with observations of leaf density and nitrogen content from a nearby stand, provided accurate predictions of forest photosynthesis. The observations and model results indicated that ecosystem carbon balance at the site is highly sensitive to temperature, and relatively insensitive to cloudiness.