Variations Of Tmax Research Articles

Source Rock Evaluation in The Lake Chad Area of the Bornu Basin, Nigeria

Source rock evaluation of the Lake Chad area of the Bornu Basin which contains a comparatively thicker sedimentary succession based on interpreted seismic and gravity data was undertaken in this study. A total of twenty-nine shale samples from three wells (Kutchali-1, Faltu-1 and Herwa-1) were analysed to arrive at the bulk geochemical properties, organic matter particles and vitrinite reflectance (VR) data of the strata penetrated by the wells. The Lake Chad area appears to contain the main ingredients required to make a rich source rock with over 96% of the total organic carbon (TOC) values being in the range of 0.63-2.88 wt% and over 95% having Tmax greater than 435°C in most of the sampled intervals. The variation of Tmax and VR with depth in the wells reveals irregular decreases or subtle decreasing trends that are suggestive of cooling in the basin’s thermal history probably as a result of uplift and erosion. The uplift could have been caused by epeirogenic movement or by folding related to the Santonian inversion witnessed by the West African Rift Subsystem. In terms of hydrocarbon generation potential, most of the samples have HI values greater than 50 mgHC/g TOC, but generally less than 200 mgHC/g TOC. These HI values suggest dominance of Type III with less Type II Kerogen; thus, a predominantly predominantly gas prone area. A study of some bulk geochemical parameters (TOC, Tmax and HI) of the three study wells has revealed that the succession penetrated by one of them (Faltu-1 well) contains several potential gas source intervals and two potential oil source intervals with the latter probably lying between 2500 m and 3000 m depth.

Bioenhanced sublingual tablet of drug with limited permeability using novel surfactant binder and microencapsulated polysorbate: In vitro/in vivo evaluation

Formulation of sublingual tablets of drugs with limited permeability poses a great challenge due to their poor absorption. In this study, bioenhanced sublingual tablets (BESTs) of zolmitriptan were prepared using novel surfactant binder (Pluronic® p123/Syloid® mixture) to enhance tablet disintegration and dissolution. Microencapsulated polysorbate 80 (Sepitrap™ 80) were included in the composition of BESTs to enhance the drug transport through the sublingual mucosa. Tablets were evaluated for in vitro/in vivo disintegration, in vitro dissolution and ex vivo permeation. Solubility studies confirmed that phosphate buffer; pH 6.8 could be used as dissolution medium for sublingual tablets of zolmitriptan. BEST-5 containing Pluronic® p123/Syloid® mixture and Sepitrap™ 80 exhibited the shortest in vitro/in vivo disintegration times (<30s), the highest dissolution at early time dissolution points and the highest enhancement of drug transport through mucosal membrane. The in vivo pharmacokinetic study using human volunteers showed a significant increase in the rate and extent of sublingual absorption with less variations of Tmax after sublingual administration of both BEST-5 and Zomig-ZMT ODT. Our results proposed that Pluronic® p123/Syloid® mixture and Sepitrap™ 80 could be promising for the development of sublingual tablets for rapid onset of action of drugs with limited permeability.

The Effect of Food on Cysteamine Bitartrate Absorption in Healthy Participants.

Treatment with cysteamine reduces the rate of progression to end-stage kidney disease in cystinosis. Although food is often taken with cysteamine to reduce associated gastrointestinal symptoms, this may alter the bioavailability of cysteamine. This is a prospective, randomized, 3-treatment study to determine the effects of fasting and high-fat/calorie and high-protein meals on cysteamine absorption in healthy adult controls. On 3 separate days, serial plasma cysteamine levels were measured after cysteamine bitartrate 500 mg was ingested while fasting and also 30 minutes after high-fat/calorie and high-protein diets. Gastrointestinal (GI) symptoms were also monitored. Eight participants (5 men) were enrolled. Cysteamine absorption, as measured by area under the cysteamine concentration-time curve (AUC0-∞ ) while fasted and following high-fat/calorie and high-protein meals, was 3618 ± 372 min·μM, 2799 ± 405 min·μM (P = .04 vs fasted), and 2457 ± 353 min·μM (P = .005), respectively, and the mean Cmax values for participants were 26.3 ± 3.5 μM, 22.4 ± 5.6 μM (P = .16 vs fasted), and 17.2 ± 2.6 μM (P = .036 vs fasted), respectively. Mild GI symptoms were reported in 3 participants. Cysteamine absorption may be decreased by 30% when taken with food as compared with the fasting state. Food causes wide variation in tmax and Cmax for cysteamine.

Anomalous temperature dependence of the magnetoresistance in Co/Cu multilayers

An anomalous temperature dependence of magnetoresistance (MR) of Co/Cu multilayer films witha ∼3 A thick magnetic layer has been established experimentally. The temperature of the MR maximum Tmax is shown to coincide with the Neel temperature. The variation of Tmax with the Cu layer thickness follows an oscillatory pattern.

Enrofloxacin serum bioactivity in bottlenose dolphins, Tursiops truncatus, following oral administration of 5 mg/kg in whole fish.

Eight adult bottlenose dolphins Tursiops truncatus (six male, two female) were employed in a single-dose study of orally administered enrofloxacin dosed at 5 mg/kg body weight. Blood samples were obtained from all animals at 0, 2, 4, 8, 12 and 24 h following administration of the dose in the animals morning ration of fish. Serum antimicrobial activity concentrations (SAAC) were determined using bioassay. The mean elimination half-life (t1/2) of enrofloxacin and its major metabolites was 6.4+/-2.0 h with a range of 3-9.4 h. The time of maximal serum concentration (tmax) occurred at approximately 4 h with a range of 2-8 h following a single oral dose of 5 mg/kg. This variation in tmax most likely resulted from individual differences in absorption because of variations in the storage and digestion of the fish ration containing the drug dose within the compartmentalized cetacean stomach.

Visual Markers of Maximum Grain Dry Weight Accumulation in Winter Wheat

Visual indicators that coincide with the time of maximum grain dry weight accumulation (tmax) in hard red winter wheat (Triticum aestivum L.) have not been confirmed. Our objective was to evaluate various potential visual markers of tmax for a range of cultivars in typical Great Plains environments. Spikes of uniform maturity from five hard red winter and one soft white winter wheat cultivars were harvested throughout grain filling and divided into upper, middle, and bottom portions to determine grain dry weights. For each cultivar‐year combination, tmax values for each spike portion and the entire spike were calculated using polynomial models derived from splined regression analysis. These values were compared with various visual traits observed at each harvest. There was no significant variation in tmax among the three spike portions. Complete loss of green color from the flag leaf blade and sheath preceded tmax by several days in all cultivars; green color in the node below the peduncle persisted 2 to 6 d beyond tmax. Complete loss of green color from the rachis, glumes, and the crease of kernels occurred within 1 d of tmax in all cases. The same was true for loss of awn color, except for the soft white winter cultivar, in which green color loss from awns occurred 2 d before tmax. Thus, color loss from most portions of the spike should serve as accurate indicators of tmax for hard red winter wheat in central Great Plains environments.

Double-tracer study of the fine regional blood-brain glucose transfer in the rat by computer-assisted autoradiography.

Glucose is transported from blood to brain tissue by facilitated diffusion of limited capacity. The regional variation of the glucose transport capacity is not known in detail because methods used previously have been too gross to detect fine regional differences. Therefore, it is not known to what extent the glucose transport capacity varies in proportion to regional blood flow and metabolic rate. To resolve this question, we used double-tracer, dual-label autoradiography to measure blood-brain glucose clearance and blood flow simultaneously in hypo-, normal, and hyperglycemic rats. From the values of glucose clearance and blood flow at various plasma glucose levels, we calculated the affinity constant and maximal transport capacity of the glucose transport system. The transport capacity (Tmax) varied in approximate proportion to the blood flow and, by inference, the metabolic rate. In contrast, the affinity constant (Kt) did not vary systematically between the regions (mean value 7.1 mM). The variation of Tmax from 270 to 890 mumol hg-1 min-1 reflected a parallel variation of total regional capillary length and surface. We conclude from the study that the cerebral capillary is a fixed unit, i.e., that the number of glucose transporters per unit of capillary surface area is the same in all regions. Regional differences are the result of different capillary densities in the regions of the brain.

Isobaric thermal behavior of glasses during uniform cooling and heating: Dependence of the characteristic temperatures on the relative contributions of temperature and structure to the rate of recovery. II. A one‐parameter model approach

AbstractIsobaric variations of the characteristic temperatures Tg and Tmax, obtained on uniform cooling and heating of glasses, are investigated in terms of their dependence on the relevant experimental variables, using a single retardation time model. The corresponding partial derivatives of Tg and Tmax are derived as functions of the partition parameter x (ranging between zero and unity), which determines the relative contributions of temperature and structure to the retardation time. It is shown that the variation of Tg with the cooling rate is independent of x. In contrast, Tmax critically depends on x, and its value as well as those of its three partial derivatives are linear functions of x−1. The variations of Tmax are analyzed in terms of a set of reduced variables, leading to simple reduction rules between any two of the experimental variables when the third is kept invariant. The reduction rules are further substantiated by investigating the behavior of glasses in two‐step thermal cycles, which result in a unique set of inter‐relationships between any pair of the partial derivatives of Tmax, whatever the value of x. The results are discussed in terms of their relevance to the behavior of real glasses.

Distribution of the Maximum Temperature for Growth Among Yeasts

The maximum temperature for growth (Tmax) was determined for 594 yeast strains belonging to 112 species of the genera Candida, Torulopsis, Hansenula, Pichia, Metschnikowia and Leucosporidium. Less than 2% of the strain population was psychrophilic having Tmax values below 24 C. More than 98% consisted of mesophilic strains with Tmax values ranging from 26 to 48 C, the highest frequency being in the 34-38 C range. No thermophilic yeasts were encountered. The intraspecific variation of Tmax in 41 species of which more than five strains each were studied did not exceed a range of 5 degrees C in 76% of the species, the highest frequency pertaining to the range of 3 degrees C. Analysis of the T.ma variation in the seven species of which more than 15 strains were available brought further evidence that in most yeasts Tmax is fixed on the species level within a narrow range of temperatures.