Time Intervals Of Day Research Articles

Estimation of bloodstain deposition time within a 24-h day-night cycle with rhythmic mRNA based on a machine learning algorithm

Estimating the time that bloodstains are left at a crime scene can provide invaluable evidence for law enforcement investigations, including determining the time of the crime, linking the perpetrator to the crime scene, narrowing the pool of possible suspects, and verifying witness statements. There have been some attempts to estimate the time since deposition of bloodstains, i.e., how much time has passed since the bloodstain was left at a crime scene. However, most studies focus on the time interval of days. As far as we know, previous study have been conducted to estimate the deposition time of blood within a 24-h day-night cycle. To date, there is a lack of studies on whether rhythmic mRNA of blood is suitable for bloodstain samples. In this study, we estimated the bloodstain deposition time within a 24-h day-night cycle based on the expression of messenger RNAs (mRNAs) by real-time quantitative polymerase chain reaction. Bloodstain samples were prepared from eight individuals at eight time points under real and uncontrolled conditions. Four mRNAs expressed rhythmically and were used to construct a regression model using the k-nearest neighbor (KNN) algorithm, resulting in a mean absolute error of 3.92 h. Overall, using the rhythmic mRNAs, a machine learning model was developed which has allowed us to predict the deposition time of bloodstains within the 24-h day-night cycle in East Asian populations. This study demonstrates that mRNA biomarkers can be used to estimate the bloodstain deposition time within a 24-h period. Furthermore, rhythmic mRNA biomarkers provide a potential method and perspective for estimating the deposition time of forensic traces in forensic investigation. Case samples in forensic analysis are usually limited or degraded, so the stability and sensitivity of rhythmic biomarkers need to be further investigated.

Enzymatic fingerprinting reveals specific xyloglucan and pectin signatures in the cell wall purified with primary plasmodesmata.

Plasmodesmata (PD) pores connect neighbouring plant cells and enable direct transport across the cell wall. Understanding the molecular composition of these structures is essential to address their formation and later dynamic regulation. Here we provide a biochemical characterisation of the cell wall co-purified with primary PD of Arabidopsis thaliana cell cultures. To achieve this result we combined subcellular fractionation, polysaccharide analyses and enzymatic fingerprinting approaches. Relative to the rest of the cell wall, specific patterns were observed in the PD fraction. Most xyloglucans, although possibly not abundant as a group, were fucosylated. Homogalacturonans displayed short methylated stretches while rhamnogalacturonan I species were remarkably abundant. Full rhamnogalacturonan II forms, highly methyl-acetylated, were also present. We additionally showed that these domains, compared to the broad wall, are less affected by wall modifying activities during a time interval of days. Overall, the protocol and the data presented here open new opportunities for the study of wall polysaccharides associated with PD.

Patterns of Fatal Explosion Accidents in China

Explosion accidents usually lead to serious fatality and disability. To investigate the patterns of Fatal Explosion Accidents (FEA), a database containing 1835 FEA that happened in China during 2001–2018 was built. Statistical analysis was made based on the year, month, time interval of day, day of week, province, type of accident, place of occurrence and severity of accident. The result shown that, (1) FEA were more likely to occur in November; (2) 08: 00-10: 00 and 14: 00-16: 00 were two time intervals of frequent accident occurrence; (3) hazardous chemical FEA mostly happened on Tuesday and Wednesday, whereas pressurized container FEA often happened on Saturday; (4) coal mine gas FEA still accounted for a dominant proportion with the highest fatality rate. In addition, the correlation was measured by calculating Cramer’s coefficients, which indicated that the severities and types of FEA were significantly correlated with month. To be specific, (1) major and extraordinarily serious FEA were more likely to occur in November; (2) most of gas FEA were observed in April; (3) gunpowder and dust FEA happened most commonly in May; (4) more fireworks FEA happened in November. The patterns found in this study will provide explosion accident prevention and control with references.

Determining the road traffic accident hotspots using GIS-based temporal-spatial statistical analytic techniques in Hanoi, Vietnam

ABSTRACT This study applied GIS-based statistical analytic techniques to investigate the influence of accident Severity Index (SI) on temporal-spatial patterns of accident hotspots related to the specific time intervals of day and seasons. Road Traffic Accident (RTA) data in 3 years (2015 − 2017) in Hanoi, Vietnam were used to analyze and test this approach. Firstly, the RTA data were divided into four seasons in accordance with Hanoi’s weather conditions and the time intervals such as the daytime, nighttime, or peak hours. Then, the Kernel Density Estimation (KDE) method was applied to analyze hotspots according to the time intervals and seasons. Finally, the results were presented by using the comap technique. This study considered both analyses with and without SI. The accident SI measures the seriousness of an accident. The approach method is to give higher weights to the more serious accidents, but not with the extremely high values calculated on a direct rate to the accident expenditures. The results showed that both analyses determined the relatively similar hotspots, but the rankings of some hotspots were quite different due to the integration of SI. It is better to take into account SI in determining RTA hotspots because the gained results are more precise and the rankings of hotspots are more accurate. From there, the traffic authorities can easily understand the causes behind each accident and provide reasonable solutions to solve the most dangerous hotspots in case of limited budget and resources appropriately. This is also the first study about this issue in Vietnam, so the contribution of the article will help the traffic authorities easily solve this problem not only in Hanoi but also in other cities.

The pre-analytical stability of 25-hydroxyvitamin D: Storage and mixing effects.

BackgroundThere is an increasing demand for serum 25‐OH VitD testing globally, and this has led to the greater use of automated immunoassays. These may be more prone to non‐specific interference, that is thought to be related to pre‐analytical stability of biological samples. We have investigated the changes in serum 25‐OH VitD concentrations that are caused by storage and mixing conditions, and if such changes are statistical, or clinically important.MethodsBlood samples were collected into plain tubes from 31 healthy donors. After separation, serum samples were stored at −20°C and analysis was carried out with and without mixing (vortexing) at different time intervals of days (0, 1, 2, 3, 4, 5, 15, and 30). All samples were analyzed using a chemiluminescent immunoassay.ResultsMean serum 25‐OH VitD concentrations for subsequent days of storage compared with day 0 showed a significant time effect (P < .05) except for the samples on day 1 (P = .654) in non‐vortexed samples and day 2 (P = .087), 5 (P = .118) and 30 (P = .118) in vortexed samples. Comparing values for vortexed and non‐vortexed samples on the same day, serum 25‐OH VitD showed a significant difference on days 1 (P = .003), 4 (P = .037), 5 (P = .002), and 30 (P = .025). However, the maximum change value was 8.85% which was less than the known total allowable error (TEa) and reference change value (RCV) for serum 25‐OH VitD.Conclusion25‐OH VitD is pre‐analytically stable after long‐term sample storage at −20°C and can be analyzed without vortexing. This may be beneficial for both research and diagnostic laboratories.

Evaluation of Tacrolimus Levels and Risk of Acute Graft-Versus-Host Disease in Allogeneic Hematopoietic Stem Cell Transplant

Background Achieving therapeutic tacrolimus blood concentrations is crucial for decreasing the risk of developing acute graft-versus-host-disease (aGvHD) in allogeneic hematopoietic stem cell transplant (aHSCT) patients. Studies have suggested that tacrolimus levels in the first 1-2 weeks may affect the risk of aGVHD but therapeutic goals are not well established. This study explores tacrolimus levels and risk of GVHD during that time frame. Methods This study is a retrospective cohort single center chart review performed with 348 consecutive adult patients who received an aHSCT and were followed for at least 100 days post-transplant for aGvHD development. Patients that received a transplant from a cord blood or participated in aGvHD prophylaxis clinical trials were excluded. The primary endpoint was aGvHD grades II - IV incidence. Serum tacrolimus levels were evaluated from days -1 to +100 post-transplant. Serum tacrolimus levels were divided into time intervals of days 0 - 7 and days 0 - 14 post-transplant. Receiver operator characteristic curves (ROC) were used to quantify serum tacrolimus levels as predictors of aGvHD grades II-IV. Using the ROC analysis and Youden's Index, optimal cutpoints in the tacrolimus level distribution for the individual time intervals were assessed. From this, patients were analyzed based on whether they achieved mean tacrolimus serum levels below the cutpoint (low group) or if they achieved a mean tacrolimus level above the cutpoint (high group). Results Within the URD group during days 0-7 post-transplant, the low group and high group demonstrated a mean tacrolimus level of 11.3 and 14.5 respectively, with significantly less aGVHD observed in the high group (38% vs 57.2%, p = 0.021). In respect to days 0-14, the low group and high group demonstrated a mean tacrolimus level of 10.4 and 13 respectively, again with significantly less aGVHD in the high group (35.6% vs 57.3%, p = 0.012). Within the RD group during days 0-7 post-transplant, the low group and high group demonstrated a mean tacrolimus level of 10.9 and 13.7 respectively, also with significantly less aGVHD in the high group (21.7% vs 38.7%, p = 0.042). In respect to days 0-14, the low and high group demonstrated a mean tacrolimus level of 10.2 and 13.1 respectively. However, there was not a significant difference in aGVHD (25.7% vs 35.9%, p = 0.272). Conclusion Higher levels of tacrolimus in the first 2 weeks after allogeneic stem cell transplant appear to correlate with a lower incidence of grade II-IV aGVHD. Higher levels in both weeks 1 and 2 were associated with a 37% reduction in the URD group while higher levels in week 1 were associated with a 44% in the RD group. While larger studies would help to clarify more specific ranges, this data suggests that target tacrolimus levels should be 14-15 ng/ml in the first 2 weeks post allogeneic transplant to decrease rates of grade II-IV aGVHD.

Fatal accident patterns of building construction activities in China

Fatal accidents occur frequently in building construction activities due to inherently hazardous nature. This paper aims to explore the fatal accident patterns in China’s building construction activities by using frequency analysis, correlation coefficient analysis and variance analysis. The data presented in this study come from short reports of accidents published by the Ministry of Housing and Urban-Rural Development. The results are obtained by analyzing the factors related to month, day of week, time interval of day, province, type of accident, and severity of accident. It’s mainly found that more fatal accidents occur (1) in July and August, (2) on Monday and (3) during the time intervals 10:00–11:00 and 15:00–16:00, and excessive laboring hours still exist in building construction activities. It’s also notable that relatively underdeveloped provinces have experienced higher mortality rate per hundred million yuan of gross domestic product in the building industry, especially Qinghai, Hainan and Heilongjiang. Moreover, fall is the predominant type of fatal accidents, accounting for more than 55% overall. There exists the significant correlation between the types of accidents and the severities of accidents, and each collapse and hoisting damage can cause more fatalities compared to other types. The corresponding recommendations are ultimately put forward to prevent fatal accidents of building construction activities. The patterns found in this paper can provide valuable direction for formulating accident prevention strategies.

383 Fever and Leukocytosis as a Predictor of DCI After SAH

Abstract INTRODUCTION Aneurysmal subarachnoid hemorrhage (SAH) is associated with significant morbidity and mortality. Delayed cerebral ischemia (DCI) is a major cause for poor outcome after SAH. Cerebral vasospasm is the primary driver of DCI, and the largest independent contributor to poor outcome after SAH. Prior studies have reported an association between fever and leukocytosis, and cerebral vasospasm. In this study, we assessed the utility of fever and/or leukocytosis to predict DCI after SAH. METHODS We performed a retrospective analysis of 187 SAH patients. Univariate and multivariate logistic regression was performed to identify potential risk factors for three different endpoints - (a) Mild, Moderate, or Severe Angiographic Vasospasm, (b) Moderate or Severe Angiographic Vasospasm, and (c) Symptomatic DCI. Multiple independent variables including age, Hunt-Hess grade, modified Fisher grade, fever (T&gt;/= 38.0 °C), WBC &gt;/= 10, WBC &gt;/= 15, fever and WBC &gt;/= 10, fever and WBC &gt;/= 15 were examined over the course of each hospital stay. RESULTS &gt;Presence of fever and/or leukocytosis were both significant predictors of symptomatic DCI. In addition, number of days with fever following aneurysm rupture was strongly associated with angiographic vasospasm, while number of days with WBC&gt;/= 15 was strongly associated with symptomatic DCI. When these variables were combined, number of days with concurrent fever and WBC&gt;/= 10 was an independent predictor of angiographic vasospasm, and number of days with concurrent fever and WBC&gt;/= 15 was an independent predictor of both angiographic vasospasm and symptomatic DCI. Time intervals of Day 0–3 and Day 3–7 after aneurysm rupture had the highest odds ratios for angiographic vasospasm. CONCLUSION Patients with aneurysmal SAH who had higher number of days with fever and/or leukocytosis after aneurysm rupture were more likely to have angiographic vasospasm and symptomatic DCI. Presence of fever and/or leukocytosis may have utility in assessing the risk of DCI following SAH.

Experimental study of relationship between average isotopic fractionation factor and evaporation rate

Isotopic fractionation is the basis of tracing the water cycle using hydrogen and oxygen isotopes. Isotopic fractionation factors in water evaporating from free water bodies are mainly affected by temperature and relative humidity, and vary significantly with these atmospheric factors over the course of a day. The evaporation rate (E) can reveal the effects of atmospheric factors. Therefore, there should be a certain functional relationship between isotopic fractionation factors and E. An average isotopic fractionation factor (α*) was defined to describe isotopic differences between vapor and liquid phases in evaporation with time intervals of days. The relationship between α* and E based on the isotopic mass balance was investigated through an evaporation pan experiment with no inflow. The experimental results showed that the isotopic compositions of residual water were more enriched with time; α* was affected by air temperature, relative humidity, and other atmospheric factors, and had a strong functional relation with E. The values of α* can be easily calculated with the known values of E, the initial volume of water in the pan, and isotopic compositions of residual water.

Visual Disorders in Optic Neuromyelitis: Report of Two Cases

Optic neuromyelitis is a disease caused by autoimmune disruption of the aquaporin 4 channels of central nervous system, whose involvement is more frequent over the spinal cord and optic nerves as well as in specific areas of the brain. Optic neuritis in optic neuromyelitis can occur simultaneously with transverse myelitis or separated by a variable time interval of days or even years. It may be unilateral or bilateral and could occur in recurrent forms. We describe a 35-year-old woman with visual loss due to acute bilateral optic neuritis and a 46-year-old woman with unilateral optic neuritis that were admitted at the neuro- ophthalmology service of the Cuban Ophthalmology Institute last year. Both were treated with intravenous methylprednisole for five days. Three month later neurologic symptoms appeared, a magnetic resonance imaging was performed and the optic neuromyelitis diagnosis was confirmed. We show the results of the neuro-ophthalmology studies before and three month after the treatment.

Analytical ecological epidemiology: exposure–response relations in spatially stratified time series

AbstractAn important task of environmental research is the investigation of a possible causal relationship between exposure and the frequency of a biologic trait. Major industrial accidents provide examples where the exposure status of large populations may change considerably within relatively short time intervals of days or weeks (e.g. Seveso herbicide plant explosion, Chernobyl Nuclear Power Plant catastrophe). Therefore, purely temporal change‐points may be tested in time series of appropriate public health indicators (e.g. mortality, morbidity, sex ratio at birth). If, in addition, the spatial contamination is strong and variable enough and can be identified with sufficient precision at the level of regional units (e.g. districts), then a spatial‐temporal approach makes sense. This essentially means that a global time trend model is adjusted for region‐specific trend functions, allowing for local or global temporal jumps or broken sticks (change‐points) at certain points in time. The local jump heights may be tested for associations with local exposure (exposure–response relation), and all other characteristics in the data that vary with locality and in time are automatically accounted for, thus minimizing confounding. Spatial‐temporal approaches may help to strengthen the evidence of possible causal relationships. As an example, the human sex ratio at birth in several European countries before and after the Chernobyl Nuclear Power Plant accident was investigated. A long‐term chronic impact of radioactive fallout on the secondary sex ratio has been found. Copyright © 2008 John Wiley &amp; Sons, Ltd.

Effect of some non-genetic factors on the growth of kids of the brown short-haired breed

The evaluation of effects of some non-genetic factors (sex, litter size, age of dams and year of study) on the growth of 85 kids of the Brown Short-haired breed was carried out in a period of two successive years. The analysis of the growth of all kids revealed that in the time interval from birth to Day 90 of age daily gain and final body weight were 181.3 g and 19.52 kg, respectively. As far as the effect of sex was concerned, the intensity of growth was significantly higher in males than in females (P &amp;le; 0.01) in all periods under study. From birth to Day 90, the respective daily gains of males and females were 200.6 g and 162.0 g. As far as the litter size was concerned, it was found out that daily gains of singles and triplets were higher than those of twins and that the differences between single kids and twins were significant (P &amp;le; 0.01) in all periods under study. Specifically, daily gains of single kids, twins and triplets in the time interval from birth to Day 90 were 201.4 g; 167.1 g and 175.6&amp;nbsp;g, respectively. The analysis of the effect of age of dams on daily gains revealed significant effects of this factor on daily gains in the time intervals of Day 30 &amp;ndash; Day 60; Day 60 &amp;ndash; Day 90; Day 30 &amp;ndash; Day 90 and from birth to Day 90 (P &amp;le; 0.05). With the exception of the period from birth to Day 30, the highest daily gains were recorded in kids of four-years-old dams in all other periods under study. In both years of study, all kids were reared under nearly identical conditions but the effect of year of study on the growth was significant. &amp;nbsp;

Phase synchronization in temperature and precipitation records

We study phase synchronization between atmospheric variables such as daily mean temperature and daily precipitation records. We find significant phase synchronization between records of Oxford and Vienna as well as between the records of precipitation and temperature in each city. To find the time delay in the synchronization between the records we study the time lag phase synchronization when the records are shifted by a variable time interval of days. We also compare the results of the method with the classical cross-correlation method and find that in certain cases the phase synchronization yields more significant results.

Multiband Optical Polarimetry of the BL Lacertae Object PKS 2155−304: Intranight and Long‐Term Variability

The polarized and total flux of the BL Lac object PKS 2155-304 were monitored intensively and simultaneously in the optical UBVRI bands with the Turin photopolarimeter at the CASLEO 2.15 m telescope during four campaigns in 1998 June, August, and November and 1999 August. The effective observation time amounted to ~47 hr. PKS 2155-304 showed a linear polarization percentage (P) usually ranging between 3% and 7% and a polarization position angle (P.A.) mainly between 70° and 120°. The highest temporal resolution of our observations, 15 minutes, is unprecedented for polarimetric monitoring of this source and has allowed us to detect amplitude variations of the linear polarization percentage from 6% to 7.5% in timescales of hours. In some nights the polarization percentage seems to increase toward shorter wavelengths; however, the polarized spectrum does not vary significantly with time. The most remarkable variability event occurred on 1998 June 18, when the degree of linear polarization decreased by more than a factor 2 in 1 day in all bands, while the P.A. rotated by 90°. This is consistent with the presence of two emission components, of different polarization degree and position angle. Intranight variability of P and P.A. can be interpreted with small-amplitude physical or geometrical changes within the jet. Measurements of the circular polarization over time intervals of days set upper limits of 0.2%. Simultaneous photometry taken with the Turin Photopolarimeter and with a CCD camera at Cordoba Astronomical Observatory did not show light variations correlated with those of the linearly polarized flux.

Quantifying the mineralization of contaminants using stable carbon isotope ratios

Current techniques used to monitor in situ degradation of organic contaminants require time intervals of days to months to measure significant changes in concentration. In addition, these methods are unable to monitor mineralization or measure absolute degradation of complex mixed wastes. The ability to continuously and definitively monitor mineralization (conversion to CO 2 and H 2O) would greatly enhance the ability to study the fate of contaminants. The objectives of this study were to show that in environments with appropriate background δ 13C signatures, simultaneous measurement of CO 2 production and δ 13C signatures of the produced CO 2 will allow both the quantification and qualification of contaminant mineralization. In laboratory microcosm studies the mineralization of hexadecane was monitored by both traditional 14C radiorespirometry techniques and by measuring the δ 13C ratio and total amount of produced CO 2. The total mass of hexadecane mineralized determined by each technique was statistically the same. More importantly, the first order rate constants calculated from the respective mineralization curves were virtually identical. These results indicate that stable carbon isotope ratios are an appropriate means of monitoring aerobic mineralization of contaminants in environments in which differences in δ 13C ratios exist between contaminant and natural organic matter.

Food intake and diet selection in sheep: the effect of manipulating the rates of digestion of carbohydrates and protein of the foods offered as a choice.

An experiment was designed to investigate whether the degree of synchrony between the rates of digestion of carbohydrates and N of foods offered as a choice would have an effect, through their consequences, on the short- and long-term diet selection of sheep. Four foods (RL, RH, SL and SH) with the same high metabolizable energy, and similar high metabolizable protein contents were made into pellets. Foods RL and RH were based on a rapidly fermentable carbohydrate source and foods SL and SH on a slowly fermentable carbohydrate source; within each source one food (RL or SL) had a low, and the other (RH or SH) a high, rumen-degradable protein (RDP) content. The foods within a carbohydrate source were offered either singly or as a choice (RL/RH or SL/SH) to eleven rumen-fistulated mature sheep. The design was two 3 x 3 Latin squares (replicated once) with 5-week periods; squares consisted of two single foods and their respective choice. Weeks 1, 3 and 5 were considered to be controls, and weeks 2 and 4 used for rumen infusions of either urea or fructose infused over 4 h (10.00-14.00 hours). Food intake (FI) and diet selections (DS) were recorded daily and every 2 h (08.00-16.00 hours) on days 2-5 of each week; rumen pH and NH3 concentrations were also measured during these time intervals of day 5. As expected, feeding treatment affected significantly the rumen measurements: rumen NH3 concentrations were higher on foods RH and SH, and rumen pH lowest on RL. Daily FI was lowest on treatments SL, and choice SL/SH. The mean daily proportion of the low-RDP food in the selected diet was lower when the carbohydrate source was rapidly (choice RL/RH) rather than slowly fermentable (choice SL/SH); this was consistent with the experimental hypothesis. Short-term infusions affected further rumen variables (in the expected directions), irrespective of feeding treatment. However, DS over the 4h infusion period were unaffected; these short-term DS were consistent with the ones selected over the longer term (daily). The results suggest that the long-term (daily) diet selection of sheep may be affected by the degree of synchrony of energy and protein to the rumen. The fact that diet selections were not altered further by short-term manipulations of these supplies might reflect inadequacies of the methodology (infusions) adopted here.

Volume transport in the Alaska Coastal Current

Nine moorings were deployed in three sections in the Shelikof Strait/Semidi Islands region of the Alaskan continental shelf during the period of August 1984 to July 1985. Analysis of the resulting current and bottom pressure data, together with surface wind, provides a new understanding of transport in the Alaska Coastal Current. Using current observations, mean volume transport through the Shelikof sea valley was computed to be 0.85 × 10 6 m 3 s −1, which is in good agreement with estimates of transport obtained from hydrographic data. Approximately 75% of this flux flowed seaward through the Shelikof sea valley, with the remainder flowing along the Alaska Peninsula. Data showed the expected increase of volume transport concomitant with maximum freshwater discharge in autumn. The greatest monthly mean transport, however, occurred in winter and was related to wind forcing. On time intervals of days, fluctuations in transport were often large (up to 3.0 × 10 6 m 3 s −1), and generally geostrophic ( r = 0.79). Some of these fluctuations resulted from convergence of flow caused by the complex interaction of storms with orography. Approximately half of the fluctuations in volume transport were accounted for by the alongshore wind.

A review of the origin and setting of tepees and their associated fabrics

ABSTRACTCarbonate hardgrounds often occur at the surface of shallow subtidal to supratidal, lacustrine, and subaerial carbonate shelf sediments. These are commonly disrupted and brecciated when the surface area of these crusts increases. In the subtidal environment, megapolygons form when cementation of the matrix causes the surface area of the hardgrounds to expand. Similar megapolygons form in the supratidal, lacustrine and subaerial settings when repeated incremental fracturing and fracture fill by sediment and/or cement also causes the area of the hardgrounds to expand. The arched up antiform margins of expansion megapolygons are known as tepees.The types of tepees found in the geological record include:(1) Submarine tepees which form in shallow carbonate‐saturated waters where fractured and bedded marine grainstones are bound by isopachous marine‐phreatic acicular and micritic cements. The surfaces of these brecciated crusts have undergone diagenesis and are bored. Unlike tepees listed below they contain no vadose pisolites or gravity cements;(2) Peritidal and lacustrine tepees are formed of crusts characterized by fenestral. pisolitic and laminar algal fabrics. This similarity in fabric makes these tepees of different origins difficult to separate. Peritidal tepees occur where the marine phreatic lens is close to the sediment surface and the climate is tropical. They are associated with fractured and bedded tidal flat carbonates. Their fracture fills contain geopetal asymmetric travertines of marine‐vadose origin and/or marine phreatic travertines and/or Terra rossa sediments. The senile form of these peritidal tepees are cut by labyrinthic dissolution cavities filled by the same material. Lacustrine tepees form in the margins of shallow salinas where periodic groundwater resurgence is common. They include groundwater tepees which form over evaporitic ‘boxwork’ carbonates, and extrusion tepees which also form where periodic groundwater resurgence occurs at the margins of shallow salinas, but the dominant sediment type is carbonate mud. These latter tepee crusts are coated and crosscut by laminated micrite; the laminae extend from the fractures downward into the underlying dolomitic micrite below the crust.Both peritidal and lacustrine tepees form where crusts experience alternating phreatic and vadose conditions, in time intervals of days to years. Cement morphologies reflect this and the crusts often contain gravitational, meniscus vadose cements as well as phreatic isopachous cement rinds.(3) Caliche tepees which are developed within soil profiles in a continental setting. They are formed by laminar crusts which contain pisolites, and fractures filled by micritic laminae, microspar, spar and Terra rossa. Most of the cements are gravitational and/or meniscoid.In ancient carbonates, when their cementation and diagenetic fabric can be interpreted, tepee structures can be used as environmental indicators. They can also be used to trace the evolution of the depositional and hydrological setting.

Column methodologies for determining sorption and biotransformation potential for chlorinated aliphatic compounds in aquifers

A method is described to measure the potential for sorption and biotransformation of halogenated compounds in aquifers. Glass columns, 40 cm in length and with a volume of 130 ml, were filled with aquifer material under conditions to avoid contamination from surface bacteria. Poorly sorted fluvial aquifer soils from three locations in the Bay area of San Francisco were used for evaluation. Gravel larger than 5 mm in diameter and a portion of the clay and silt fraction were removed during column filling. The columns were operated aerobically or anaerobically. The fluid within a column was periodically replaced within 15 minutes with new fluid of defined composition by syringe pump at time intervals of days to weeks. Initially, bromide was used to characterize flow through properties and to determine pore volume. Break-through curves for chlorinated aliphatic compounds allowed determination of sorption behaviour during fluid exchange. During the first several exchanges, and in the absence of biotransformation, added chlorinated aliphatics were removed significantly by sorption until a steady state was achieved. Through mass balance, the extent of sorption could be estimated. The ratio of sorbed mass to solution mass for the aquifer materials evaluated were 2.2 ± 1.0 for 1,1,1-trichloroethane (TCA) and 4.5 ± 1.5 for 1,1-dichloroethane (DCA) in the chloroorganic concentration range used of 50–150 μg/l. In an anaerobic column, biotransformation of TCA to DCA was demonstrated.