Decrease In Absorption Rate Research Articles

Valorization of waste plastic bags in manufacturing of binders for bituminous concretes for road coatings

In 2012, Beninese landfills have quantified more than 12,000 tons plastic wastes with more than 50% of bags. The non-biodegradable nature of plastic generated an unprecedented environmental nuisance. The search for suitable solution led opting for partial recycling through construction processes. This article is devoted to characterization of new bituminous binders built of 50/70 graded bitumen to which is incorporated powder from molten waste plastic bags at 250-280 °C for road coatings/pavement. The analyzed parameters are binder’s penetrability, softening point and adhesiveness, water absorption, and Marshall and Duriez stabilities of resulting bituminous concretes. The doped 50/70 graded bitumen, using plastic bags powder at 2-20% (wt/wt.mix), provided bituminous binders of better properties. The recorded results showed that the penetrability decreases when increasing plastic bags content, giving bituminous binders belonging to respective grades of 50/70, 40/60, 35/50, 30/45 and 20/30 followed by softening points increase. When the plastic bags content increased, better were these binders adhesivity. Similar trend was recorded for stability according to Duriez and Marshall on resulting bituminous concretes disclosing that the water absorption rate decrease. These obtained good performance characteristics should allow for significant reduction of the rapid degradation of classically coated roads, via extensive usage of waste plastic bags, then decongesting the established landfills here and there in Benin. Key words: Waste plastic bags, bituminous binder, penetrability, softening point, adhesivity, stability; subsidence, bituminous concretes, water absorption rate, compacity.

Simultaneous absorption of NOx and SO2 in oxidant‐enhanced limestone slurry

In this article, a study of simultaneous absorption kinetics of NOx and SO2 in oxidant‐enhanced limestone slurry using sodium chlorite as additives is presented. The laboratory‐scale experiments were performed in a double‐stirred tank reactor, and the effect of inorganic ions and operating parameters on absorption rates was investigated. The results indicate that NOx absorption rate shows a positive order with respect to NO (0.573), SO2 (0.278), and NaClO2 (0.194), whereas SO2 absorption rate shows a first order with respect to SO2 and zero order for both NO and NaClO2 under a typical limestone wet flue gas desulfurization operating condition. Higher pH leads to a decrease of NOx absorption rate but has no significant influence on SO2 absorption. The SO2 absorption rate decreases with the increase of temperature, whereas the NOx absorption rate remains nearly constant. S(IV) in the slurry reduces the NOx absorption rate dramatically and suppresses the SO2 absorption, whereas the presence of nitrate ions can increase the absorption rate of both SO2 and NOx. High concentration of Cl− has a positive effect on the SO2 absorption, whereas it has a negative effect on NOx absorption rate. Additionally, Mg2+ and F− have no impact on SO2 and NOx absorption rates. © 2013 American Institute of Chemical Engineers Environ Prog, 33: 1171–1179, 2014

Modulation of Interparticle Interactions and Specific Absorption Rate in Magnetomicelles through Changes in the Molecular Weight of the Hydrophobic Polymer Block

Magnetomicelles are amphiphilic block copolymer micelles, which contain magnetic nanoparticles in the core. Magnetomicelles have been proposed as magnetic fluid hyperthermia agents for cancer treatment. Magnetic interactions between nanoparticles within a micelle affect the amount of heat that they dissipate. Here, magnetomicelles are prepared varying the molecular weight of the core‐forming polymer block. The magnetomicelles are magnetically characterized in liquid suspensions and embedded in a polymer matrix. The results show that as the molecular weight of the core‐forming polymer block increases, both the interparticle magnetic interactions and specific absorption rate decrease. This is probably due to mixing between the polymer and the magnetic nanoparticles, which increases the interparticle distance.

Improving SNR and B1 transmit field for an endorectal coil in 7 T MRI and MRS of prostate cancer

Higher magnetic field strengths like 7 T and above are desirable for MR spectroscopy given the increased spectral resolution and signal to noise ratio. At these field strengths, substantial nonuniformities in B(1)(+/-) and radiofrequency power deposition become apparent. In this investigation, we propose an improvement on a conventionally used endorectal coil, through the addition of a second element (stripline). Both elements are used as transceivers. In the center of the prostate, approximately 40% signal to noise ratio increase is achieved. In fact, the signal to noise ratio gain obtained with the quadrature configuration locally can be even greater than 40% when compared to the single loop configuration. This is due to the natural asymmetry of the B(1)(+/-) fields at high frequencies, which causes destructive and constructive interference patterns. Global specific absorption rate is reduced by almost a factor of 2 as expected. Furthermore, approximately a 4-fold decrease in local specific absorption rate is observed when normalized to the B(1) values in the center of the prostate. Because of the 4-fold local specific absorption rate decrease obtained with the dual channel setup for the same reference B(1) value (20 μT at 3.5 cm depth into the prostate) as compared to the single loop, the transmission power B(1) duty cycle can be increased by a factor 4. Consequently, when using the two-element endorectal coil, the radiofrequency power deposition is significantly reduced and radiofrequency intense sequences with adiabatic pulses can be safely applied at 7 T for (1)H magnetic resonance spectroscopy and MRI in the prostate. Altogether, in vivo (1)H magnetic resonance spectroscopic imaging of prostate cancer with a fully adiabatic sequence operated at a minimum B(1)(+) of 20 μT shows insensitivity to the nonuniform transmit field, while remaining within local specific absorption rate guidelines of 10 W/kg.

Population Pharmacokinetic and Concentration-QTc Models for Moxifloxacin: Pooled Analysis of 20 Thorough QT Studies

To increase our understanding of important subject characteristics and design variables affecting the performance of oral moxifloxacin in thorough QT studies, population pharmacokinetic and concentration-QTc models were developed by pooling data from 20 studies. A 1-compartment model with first-order elimination described the pharmacokinetics. Absorption delay was modeled using 8 transit compartments. Mean (95% confidence interval) values for oral clearance, apparent volume of distribution, the first-order absorption rate constant, and mean transit time were 11.7 (11.5-11.9) L/h, 147 (144-150) L, 1.9 (1.7-2.1) 1/h, and 0.3 (0.28-0.34) hours, respectively. Overencapsulating the moxifloxacin tablet increased mean transit time by 138% and delayed time to maximum concentration by 0.5 hours but had a minimal effect on overall exposure. Administration with food decreased absorption rate constant by 27%. Women had higher moxifloxacin exposure compared with men, which was explained by lower body weights. A linear model described the concentration-QTc relationship with a mean slope of 3.1 (2.8-3.3) milliseconds per µg/mL moxifloxacin. Mean slopes for individual studies ranged from 1.6 to 4.8 milliseconds per µg/mL. Hysteresis between moxifloxacin plasma concentrations and QTc was modest, and incorporating this delay did not result in a different slope (3.3 milliseconds per µg/mL). There were no differences in slope estimates between men and women or among race categories.

Numerical simulation on vapor absorption by wavy lithium bromide aqueous solution films

Numerical simulation has been made on heat and mass transfer of vapor absorption by wavy lithium bromide aqueous solution films. The velocity fields and interface positions are obtained by VOF model. Solitary waves are generated by periodically disturbed inflow boundary. Based on these, the temperature and concentration fields are obtained with a stationary interface shape. The effect of solitary waves on the heat and mass transfer across the film is investigated. It is shown that due to the mixing of circulation and stretch of large film thickness, the gradient of concentration and absorption rate decrease for solitary wave region. The region of capillary waves shows a significant amount of absorption enhancement. The percentage of absorption for the different regions is quantified.

Non-ionic surfactants and membrane transport of thioridazine in goldfish

Polysorbate 80, which has been widely used in studies of the effects of surfactants on drug absorption, increases the rate of absorption of some drugs at concentrations near its critical micelle concentration (cmc). To determine whether all non-ionic surfactants were capable of inducing this effect, the effects of six commercial non-ionic surfactants on thioridazine absorption in goldfish have been compared with the effect of polysorbate 80. The reciprocal death time (T-1) determined when the fish were immersed in the solution under study was the index of absoprtion rate used. Not all surfactants tested increased T-1. Cremophor EL (polyoxyethylated castor oil), Atlas G1295 (a polyoxyethylene fatty glyceride), Atlas G1300 (a polyoxyethylene glyceride ester) had no effect below their cmc's. Those surfactants that did increase T-1 [polysorbate 80 (a polyoxyethylene lanolin derivative), G2162 (a polyoxyethylene oxypropylene monosterate) and Renex 650 (a polyoxyethylene alkyl aryl ether)] display the concentration-dependent behaviour reported previously - a decrease in absorption rate when the surfactant concentration is increased above its cmc. The factor determining whether or not the surfactant will increas absorption rate appears to be the configuration of the surfactant molecule rather than its hydrophile-lipophile balance or its surface activity.

Sniffing out Endodontic Pain: Use of an Intranasal Analgesic in a Randomized Clinical Trial

Introduction Orofacial pain is a common encounter in dentistry (affecting 12% of the population) and is a primary reason for patients seeking emergency care. Dentists often prescribe oral analgesics, which have disadvantages of decreased absorption rates and delayed onset. Intranasal (IN) delivery takes advantage of a large surface area of mucosal tissue for rapid absorption. The purpose of this study was to evaluate the efficacy of IN ketorolac for endodontic pain using a randomized, double-blind, placebo-controlled parallel design study. Methods Twenty-two patients presenting with moderate to severe endodontic pain were selected to receive IN treatment with placebo (n = 11) or ketorolac (n = 11) 30 minutes before endodontic treatment was started and immediately after the completion of endodontic treatment. Baseline pain levels were recorded before IN treatment. Pain levels were also recorded at 15 and 30 minutes after the initial IN dosing (before endodontic treatment); 30 minutes after completion of endodontic treatment; and 4, 8, and 12 hours after the initial IN spray. Primary analysis was a repeated-measures analysis of variance. Results IN ketorolac alone or with endodontic treatment showed significantly better pain relief compared with IN placebo spray alone or with endodontic treatment at 30 minutes after the first or second intranasal dose and at 4 hours after the first intranasal dose ( P = .03). Conclusions These results suggest that IN ketorolac may provide a novel and efficacious method for pain relief in endodontic pain patients.

Rapidly dissolving formulations for quick absorption during pain episodes: Ibuprofen

Pain or its associated trauma impairs oral absorption of drugs due, perhaps, to a diminished disintegration and dissolution rate secondary to suppression of the vagal nervous system. We first examined whether ibuprofen absorption is impaired on suppressing vagus nerve activity in a rat model. Secondly, we examined if ibuprofen absorption in rats during vagal suppression and in humans experiencing dental pain is improved by enhancing disintegration and dissolution rate of the administered formulation. Vagal suppression was achieved in rats by administering 20 mg/kg propantheline i.p. 2 h and 1 h before gastric gavage of 20 mg/kg ibuprofen as small crushed pieces of a regular release and a fast-dissolving ibuprofen caplets. In humans, after surgical removal of wisdom teeth and emergence of pain, 2 A 200 mg ibuprofen as regular released (n = 14) and fast-dissolving (n = 12) caplets were administered. Serial blood sample were collected for bioavailability studies. Vagal suppression resulted in significantly decreased absorption rate of ibuprofen enantiomers following administration of the regular release but not after fast-dissolving formulation. Human dental pain was associated with significantly slower absorption of ibuprofen enantiomers from the regular released as compared with the fast-dissolving caplets. Within the first hour post-dose the area under the plasma drug concentration-time curve was raised to 2.7-fold (p < 0.05) after the fast-dissolving as compared with the regular release formulations. There was a 1-h difference in the peak concentration time (tmax) between the two caplets. Impaired drug absorption appears to be due to slow disintegration and dissolution encountered during pain episodes.

Structure and activity relationships for amine based CO 2 absorbents—I

A study to determine the structure and activity relationships of various amine based CO 2 absorbents was performed in which, the absorption of pure CO 2 at atmospheric pressure was measured to assess the total absorption rate and capacities. Results showed that an increase in chain length between the amine and different functional groups in the absorbent structure, result in a decrease of absorption rate whereas, the absorption capacity was increased in most absorbents.

Pharmacokinetic evaluation and studies on the clinical efficacy of guar gum‐–based oral drug delivery systems of albendazole and albendazole‐β‐cyclodextrin for colon‐targeting in human volunteers

AbstractThe present investigation assessed the in vivo properties of the guar gum–based colon‐targeted matrix tablets of albendazole‐β‐cyclodextrin (KA), albendazole matrix tablet (GA), and an immediate‐release albendazole tablet (CA) in humans. A single oral dose was administered in healthy human volunteers and a completely randomized, two‐way, three‐period crossover design was adopted. The data were statistically analyzed and a value of P&lt;0.05 was considered statistically significant. In healthy human volunteers, guar gum colon‐targeted tablets showed delayed tmax and absorption time, decreased absorption rate constant, and unaltered t1/2indicating that albendazole is not released in stomach and small intestine, but is delivered to the colon, resulting in a slow absorption of the drug and making the drug available for local action in the colon. The increase in Cmax and AUC0‐∞ of KA shows that the bioavailability of albendazole in humans could be definitely improved by complexing the drug with β‐cyclodextrin. Furthermore, an open, parallel, single‐blind clinical study was conducted in patient volunteers who had helminthiasis. Clinical studies showed that the guar gum colon‐targeted tablets could reduce eggs per gram faster than conventional tablets could, resulting in improved clinical symptoms, Hb content, and decreased total count as compared to conventional tablets of albendazole. The investigation shows that albendazole, when complexed with β‐cyclodextrin, improves in vivo bioavailability of the drug and colon targeting using guar gum ensures drug delivery in the colonic fluids, and therefore improves clinical efficacy in human beings with helminthiasis. Drug Dev. Res. 67:154–165, 2006. © 2006 Wiley‐Liss, Inc.

Effect of viscous additives on drug absorption from the liver surface in rats using phenol red as a model

The purpose of this study is to obtain information that can be used to improve controlled release and residence time of drugs on the liver surface. Using carboxymethylcellulose sodium salt (CMC-Na) and polyvinyl alcohol (PVA), we examined the effect of viscous formulations on the absorption of phenol red as a model. In the presence of 3% CMC-Na or 15% PVA, the maximum plasma concentration of phenol red decreased after application to the rat liver surface using a cylindrical glass cell. The absorption ratios in 6 h calculated from the remaining amount of phenol red in the glass cell were 68.6, 60.5 and 48.7% (control: 73.1%) in the presence of 1 or 3% CMC-Na and 15% PVA, respectively. As a result of the reduction in the absorption ratio, the amount of phenol red excreted into the bile and urine in 6 h was decreased by the addition of the viscous additives. The decrease in absorption rate was characterized by a pharmacokinetic analysis of the plasma concentration profile. The change in absorption rate differed between the viscous additives, reflecting the result of the in vitro release experiment. Accordingly, the possibility that the drug absorption rate from the liver surface can be altered by viscous additives was suggested to have a promising prospect for therapeutic use.

Inclusion complexation of amide-typed local anesthetics with β-cyclodextrin and its derivatives. III. Biopharmaceutics of bupivacaine-SBE7- βCD complex following percutaneous sciatic nerve administration in rabbits

The effect of a new modified β-cyclodextrin derivative, sulfobutylether7- β-cyclodextrin (SBE7- βCD) on the biopharmaceutics of local anesthetic bupivacaine (BVC) was studied in a rabbit sciatic model. Phase-solubility study revealed the formation of a 1:1 complex of the Al type between BVC and SBE7- βCD, with an apparent stability constant of 149±7 M −1. Then, BVC hydrochloride (BVC-HCl) and BVC complexed with SBE7- βCD (BVC-SBE7- βCD) were administered around the sciatic nerve both as solutions, in a randomized cross-over design in six New Zealand rabbits. The plasma concentrations of BVC, the onset and duration of motor blockade were evaluated. For the dose of BVC injected (5 mg in 2.5 ml), complexation with SBE7- βCD led to a decrease in the maximum plasma concentration ( C max) of BVC, while the time to reach C max ( T max) was increased. Complexation also delayed the onset of motor block and did not modify its duration. This decrease in absorption rate of BVC following complex administration was confirmed by Loo-Riegleman absorption analysis. The effect of SBE7- βCD concerned mainly the faster absorption phase, responsible for side effects, but had also an impact on the slower phase, even if not stastistically significant, shown by a flip-flop in the elimination constant. Complexation may be useful to improve the therapeutic index of local anesthetics, allowing greater amounts of drug to be injected in order to prolong nerve blockade.

Physiological and Pharmacological Properties of an Endogenous Sodium Pump Inhibitor

To investigate on Na+, K+ - ATPase behavior in chronic uremia, pre and postdialysis serum from 10 chronic dialysis patients and 10 healthy subjects was pooled and subjected to reverse phase C-18 HPLC. Only one fraction, isolated from pre and postdialysis sera, eluting at 28 min (F1), was found to display significant effects on electrophysiological and transepithelial 22Na flux pattern of rabbit distal colon mucosa mounted in Ussing type chambers; indeed, serosal addition of uremic F1 to colonic mucosa resulted in a slow, but constant, decline in short-circuit current (Isc) (ΔIsc=1.55±0.16 μEq h−1 cm−2, mean ± S.E.M., n=12, p<0.01) and transepithelial conductance (GT) (from 4.50±0.23 to 3.71±0.33 mS cm−2, p<0.01, n=12). Measurement of transepithelial 22Na fluxes in the presence of pre or postdialysis sera also showed a significant Na+ absorption rate decrease (from 1.3±0.22 to 0.48±0.30 μEq h−1 cm−2, mean ± S.E.M., n=4, p < 0.01), mainly due to a decrease in mucosal-to-serosal Na+ flux. By contrast, assays of peaks isolated from healthy sera did not inhibit Isc and transepithelial Na+ transport. The incubation of highly purified basolateral membranes with F1 for 1 min produced a ∼26% inhibition of Na+, K+-ATPase. These findings are consistent with the presence of an endogenous inhibitor of sodium pump activity in uremic plasma; it is of pharmacological interest in that it may participate in the development of unpredictable responsiveness to digitalis therapy in pathophysiologic states.

Modulation of Water and Solute Transport following Food Restriction in the Colons of the Levant Vole (Microtus guenteri) and the Mouse (Mus musculus)

The objective of the present study was to investigate putative interactions of reduced short chain fatty acid (SCFA) availability, induced by restricting food intake, with the absorption of electrolytes and water from the colons of two rodent species, the herbivorous Levant vole (Microtus guenteri) and an omnivorous laboratory mouse (Mus musculus). Following food restriction, cecal and colonic concentrations of acetate, propionate, and butyrate in the voles and mice were significantly reduced. Food restriction also reduced rates of water, SCFA, and sodium absorption from the perfused colon of the voles but had no effect on the mice. However, the exclusion of SCFAs from the perfusion solutions in the animals that were fed ad lib. decreased absorption rates of water and solutes in both voles and mice. Following food restriction, the exclusion of SCFAs had no effect on the absorption rates of water or of sodium in the voles, whereas in the laboratory mice, absorption rates of water and sodium decreased significantly. Ouabainsensitive ATPase activity in colon extracts of the food-restricted voles was 47% lower than that of the voles fed ad lib. In the mice, however, the change of the level of nutrition had no effect on the ouabain-sensitive ATPase activity. It is suggested that the capacity to adjust the rate of water absorption to the amount of fermentable substance in the intestine is of great advantage to a grazing herbivore that depends largely on the energy utilized by fermentation of cell-wall carbohydrates.

Modulation of the Endolymphatic Sac Function

A method for inducing a partial dysfunction of the endolymphatic sac and its effect was investigated. Acetazolamide as well as amiloride caused collapse of the lateral intercellular spaces in the endolymphatic sac epithelium and a subsequent mild endolymphatic hydrops. These changes indicate a decreased absorption rate of endolymph in the endolymphatic sac. Colchicine caused a disturbed secretory activity of the sac induced by glycerol. Animals treated with colchicine showed marked signs of inner ear malfunction after additional treatment with glycerol, which might indicate that the secretory activity in the sac is closely related to the regulation of inner ear fluid homeostasis and functional disturbance.

The effect of calcium on gallbladder absorption

The absorption of water and electrolytes is an important physiologic function of the gallbladder which is altered during gallstone formation. Extracellular calcium and calcium channel antagonists are known to affect intestinal absorption, yet their effect on gallbladder absorption is less well defined. We, therefore, tested the hypothesis that changes in extracellular calcium or in calcium channels would alter gallbladder absorption. New Zealand white rabbit gallbladders were removed, filled with a modified Krebs buffer (Ca 2+ = 0.7 m M), and suspended in an oxygenated bath of the same buffer. Water absorption was determined gravimetrically by obtaining serial gallbladder weights at 10-min intervals. After a 40-min control period, the serosal bathing solution was changed to one of four experimental solutions ( n = 6 for each group): Ca 2+ = 0.25, 0.7, or 1.2 m M or Ca 2+ = 0.7 m M plus 0.1 m M verapamil. Absorption was determined during an 80-min experimental period with results expressed as the percentage change in gallbladder absorption compared to that of the control period. The 0.25, 0.7, and 1.2 m M Ca 2+ groups did not show a significant change in absorption rate from their respective control rates. However, the verapamil group did demonstrate a significant ( P < 0.05) decrease in absorption rate of −69 ± 8% by the end of the experimental period. These data demonstrate that verapamil inhibits gallbladder absorption while changes in serosal calcium concentration have no effect. We conclude that calcium channels and intracellular calcium may play an important role in modulating gallbladder absorption.

Responses of wild plants to nitrate availability

Two annual species of Bromus, an invader (B. hordeaceus, ex B. mollis) and a non-invader (B. intermedius), were grown for 28 days in growth chambers, at 5 and 100 μM NO 3- in flowing nutrient solution. No differences between the two species were observed at either NO 3- level, in terms of relative growth rate (RGR) or its components, dry matter partitioning, specific NO 3- absorption rate, nitrogen concentration, and other characteristics of NO 3- uptake and photosynthesis. The effects of decreasing NO 3- concentration in the solution were mainly to decrease the NO 3- concentration in the plants through decreased absorption rate, and to decrease the leaf area ratio through increased specific leaf mass and decreased leaf mass ratio. Organic nitrogen concentration varied little between the two treatments, which may be the reason why photosynthetic rates were not altered. Consequently, RGR was only slightly decreased in the 5-μM treatment compared to the 100-μM treatment. This is in contrast with other species, where growth is reduced at much higher NO 3- concentrations. These discrepancies may be related to differences in RGR, since a log-linear relationship was found between RGR and the NO 3- concentration at which growth is first reduced. In addition, a strong linear relationship was found between the RGR of these species and their maximum absorption rate for nitrate, suggesting that the growth of species with low maximum RGR may be partly regulated by nutrient uptake.

Safening effect of dimepiperate on root-growth inhibition in rice caused by bensulfuron methyl.

The effect of dimepiperate on herbicidal activity of root-applied BSM and also on its absorption, translocation and metabolism were investigated in rice plants. It was observed that dimepiperate significantly reduced the inhibition of root elongation caused by BSM. 14C-BSM was linearly absorbed by rice roots within 24 hours, but addition of dimepiperate caused a decrease of the rate of absorption. There were no differences detected in the rate of translocation of 14C-BSM from roots to shoots between BSM applied alone and in combination with dimepiperate. In shoots, more than 50% of incorporated 14C-radioactivity was found as metabolites, the major one being metabolite A (methyl=α-(4-hydroxy-6-methoxypyrimidin-2-ylcarbamoylsulfamoyl)-o-toluate). In roots, a large part of the 14C-radioactivity was detected in unchanged BSM. Dimepiperate addition increased the rate of matabolism of applied BSM, while metabolite A, B (methyl=α-(aminosulfonyl)-o-toluate), C (1 H-2, 3-benzothiazin-4-(3H)-one 2, 2-dioxide) and other metabolites, including those water soluble were produced in greater quantity. These results sugget that the decrease of absorption rate and the acceleration of metabolism rate by dimepiperate addition is a major factor in the safening action of dimepiperate against the phytotoxic activity of BSM in rice roots.

Effect of oxygen on the Mg-H reaction

Two identical samples of magnesium powder (purity, 99.58%) were hydrogenated at approximately 30 bar and 380 °C and dehydrogenated under vacuum at the same temperature about 500 times. The first sample was exposed to pure hydrogen (purity, 99.9999%) and the second was exposed to hydrogen containing 85 ppm O and 8 ppm H 2 O vapour. In both experiments a moderate overall reduction in the amount of hydrogen absorbed and desorbed was observed. This can be ascribed to a reduced absorption rate with increased number of cycles. The effect of oxygen was negligible, and this was confirmed by a precision absorption measurement performed after the cycling experiment. Despite the decreased absorption rate, which was mainly observed at higher degrees of reaction, little change in the desorption kinetics was observed.