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Variability in the light absorption coefficients of phytoplankton, nonalgal particles, and colored dissolved organic matter in a subtropical bay (Brazil)

Ferreira, Amabile; Ciotti, Áurea Maria; Giannini, Maria Fernanda Colo
Fonte: Hull Publicador: Hull
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
36.4%
This study characterized the variability in magnitudes and spectral shapes of the absorption coefficients of phytoplankton, detritus, and colored dissolved organic matter (CDOM) in a dynamic bay (Santos Bay) in southeastern Brazil in response to the contributions of the main estuarine channel and large tide variations, therefore in different time scales. Two strategies were adopted: (1) monthly year-round sampling in the estuarine channel and Santos Bay and (2) sampling in Santos Bay during spring/neap tides and cold/warm months. Chlorophyll-a concentration and CDOM absorption were higher during warm (wet) months, while the relative contribution of organic and inorganic particles was driven by neap/spring tide cycles. Salinity partially accounted for changes in optical variables, especially for CDOM absorption and total suspended matter (TSM) during cold months and neap tides, respectively. The spectral shapes of detritus and CDOM absorption showed relatively little variability for the entire dataset and were not considered feasible for monitoring purposes. The spectral shape of phytoplankton absorption (index of cell size) varied broadly, with no remarkable dependence on the sampling conditions. Comparison of absorption coefficients measured by the Quantitative Filter Technique (QFT) and Transmittance Reflectance (TR) method showed higher phytoplankton coefficients toward longer visible wavelengths (flatter spectra) and shallower slopes of detritus absorption yielded by the TR method. Our results also suggest that measurements at the near red spectral region result from not only scattering signals but also non-algal particle absorption.; ECOSAN and CIRSAN projects was supported by FAPESP (No. 03/09932-1 and No. 03/13747-5)...

Absorção de dióxido de carbono em soluções aquosas de aminas em uma coluna de parede molhada com promotor de película.; Carbon dioxide absorption in amines aqueous solutions in a wetted wall column with film promoter.

Rodriguez Flores, Henry Alexander
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 11/03/2011 PT
Relevância na Pesquisa
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O processo de absorção do CO2 em soluções aquosas de alcanolaminas foi estudado em uma coluna de parede molhada empregando-se uma tela metálica, de 28 mesh, como promotor de película e operando em contracorrente. As alcanolaminas testadas nos diferentes experimentos foram: monoetanolamina (MEA), 2-amino-2-metil-1-propanol (AMP) e piperazina (PZ). Os experimentos de absorção foram realizados nas soluções aquosas individuais da MEA e AMP; e, nas misturas MEA:AMP e AMP:PZ; visando avaliar a velocidade de absorção do CO2 em diferentes vazões do líquido, a saber: 3.10-7, 6.10-7 e 10.10-7 m3/s. O presente sistema de absorção foi caracterizado através da determinação dos principais parâmetros de transferência de massa: área interfacial efetiva, coeficiente de transferência individual da fase gasosa e o coeficiente volumétrico global médio de transferência de massa. Determinou-se a área interfacial efetiva da coluna, por meio da absorção do CO2 diluído em ar em uma solução aquosa de NaOH, para as diferentes vazões de líquido, sendo os resultados obtidos igual a 106, 126 e 144 m2/m3, respectivamente. O coeficiente volumétrico de transferência de massa da fase gasosa foi determinado por meio da absorção de SO2 diluído em ar em uma solução aquosa de NaOH. Os resultados experimentais mostram que o coeficiente volumétrico individual de transferência de massa e a área interfacial são função da vazão do líquido. As velocidades de absorção do CO2 diluído em ar...

Fe K-edge X-ray absorption spectroscopy study of Pb(Fe2/3W 1/3)O3-PbTiO3 multiferroic ceramics

Mesquita, A.; Fraygola, B. M.; Mastelaro, V. R.; Eiras, J. A.
Fonte: Universidade Estadual Paulista Publicador: Universidade Estadual Paulista
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
36.4%
The present paper is a comprehensive study concerning Fe K-edge X-ray absorption spectroscopy (XAS) measurements, which were performed to characterize the local structure of (1 - x)Pb(Fe2/3W1/3)O 3-xPbTiO3 samples as a function of temperature and PbTiO3 content. Results obtained by the fits of extended X-ray absorption fine structure consist with rhombohedral symmetry for Pb(Fe 2/3W1/3)O3 composition at temperatures lower than room temperature. This result is in apparent disagreement with X-ray and neutron diffraction characterization which have been reported. This apparent disagreement is related to the fact that XAS probes the short-range order, whereas X-ray diffraction provides structural information about the average structure. Moreover, as the PbTiO3 content increases, a disorder has been detected at local structure of the FeO6 octahedron. Analysis of X-ray absorption near edge structure spectra did not show modifications in intensity nor energy of transitions. © 2013 American Institute of Physics.

High paracellular nutrient absorption in intact bats is associated with high paracellular permeability in perfused intestinal segments

Brun, Antonio; Price, Edwin R.; Gontero-Fourcade, Manuel N.; Fernandez-Marinone, Guido; Cruz-Neto, Ariovaldo P.; Karasov, William H.; Caviedes-Vidal, Enrique
Fonte: Company Of Biologists Ltd Publicador: Company Of Biologists Ltd
Tipo: Artigo de Revista Científica Formato: 3311-3317
ENG
Relevância na Pesquisa
36.4%
Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP); Processo FAPESP: 12/04610-5; Water-soluble nutrients are absorbed by the small intestine via transcellular and paracellular mechanisms. Based on a few previous studies, the capacity for paracellular nutrient absorption seems greater in flying mammals than in nonflying mammals, but there has been little investigation of the mechanisms driving this difference. Therefore, we studied three species each of bats (Artibeus lituratus, Sturnira lilium and Carollia perspicillata) and nonflying mammals (Akodon montensis, Mus musculus and Rattus norvegicus). Using standard pharmacokinetic techniques in intact animals, we confirmed the greater paracellular nutrient absorption in the fliers, comparing one species in each group. Then we conducted in situ intestinal perfusions on individuals of all species. In both approaches, we measured the absorption of 3OMD-glucose, a nonmetabolizable glucose analog absorbed both paracellularly and transcellularly, as well as L-arabinose, which has no mediated transport. Fractional absorption of L-arabinose was three times higher in the bat (S. lilium: 1.2 +/- 0.24) than in the rodent (A. montensis: 0.35 +/- 0.04), whereas fractional absorption of 3OMD-glucose was complete in both species (1.46 +/- 0.4 and 0.97 +/- 0.12...

Avaliação experimental da absorção de SO2 e estudo preliminar da absorção de NO em torre de nebulização; Experimental evaluation of SO2 absorption and preliminary study of NO absorption into a spray tower

Milene Costa Codolo
Fonte: Biblioteca Digital da Unicamp Publicador: Biblioteca Digital da Unicamp
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 23/06/2010 PT
Relevância na Pesquisa
36.42%
Este trabalho apresenta uma avaliação experimental da absorção de SO2 e um estudo preliminar da absorção de NO em uma torre de nebulização. O estudo experimental de absorção de SO2 foi realizado com solução de NaOH em diferentes condições de operação, variando a vazão de solução, vazão de gás e bicos pulverizadores de pressão. Assim, foi possível avaliar a influencia do tempo de residência do gás, da relação L/G e dos bicos pulverizadores de pressão. Além disso, analisa a absorção de SO2 ao longo da coluna, retirando amostras do interior da torre. O estudo experimental de absorção de NO na torre de nebulização avalia o desempenho de uma torre projetada para absorção de SO2 na absorção de NO. Os ensaios de absorção de NO foram realizados em meio ácido com soluções de peróxido de hidrogênio (H2O2) e de peróxido de hidrogênio (H2O2) com sulfato ferroso (FeSO4), em diferentes condições de operação, a fim de avaliar a influência do tempo de residência do gás, da relação L/G, da concentração de peróxido de hidrogênio e da presença de sulfato ferroso na solução. Além do estudo experimental, este trabalho apresenta um estudo teórico da absorção de SO2, utilizando dados provenientes do estudo experimental. As simulações realizadas mostraram a importância do diâmetro de gota...

Absorption of Manganese and Iron in a Mouse Model of Hemochromatosis

Kim, Jonghan; Buckett, Peter D.; Wessling-Resnick, Marianne
Fonte: Public Library of Science Publicador: Public Library of Science
Tipo: Artigo de Revista Científica
EN_US
Relevância na Pesquisa
36.4%
Hereditary hemochromatosis, an iron overload disease associated with excessive intestinal iron absorption, is commonly caused by loss of HFE gene function. Both iron and manganese absorption are regulated by iron status, but the relationships between the transport pathways of these metals and how they are affected by HFE-associated hemochromatosis remain poorly understood. Loss of HFE function is known to alter the intestinal expression of DMT1 (divalent metal transporter-1) and Fpn (ferroportin), transporters that have been implicated in absorption of both iron and manganese. Although the influence of HFE deficiency on dietary iron absorption has been characterized, potential effects on manganese metabolism have yet to be explored. To investigate the role of HFE in manganese absorption, we characterized the uptake and distribution of the metal in Hfe−/− knockout mice after intravenous, intragastric, and intranasal administration of 54Mn. These values were compared to intravenous and intragastric administration of 59Fe. Intestinal absorption of 59Fe was increased and clearance of injected 59Fe was also increased in Hfe−/− mice compared to controls. Hfe−/− mice displayed greater intestinal absorption of 54Mn compared to wild-type Hfe+/+ control mice. After intravenous injection...

Intestinal calcium absorption in men with spinal osteoporosis

Need, A.; Morris, H.; Horowitz, M.; Scopacasa, F.; Nordin, B.
Fonte: Universidade de Adelaide Publicador: Universidade de Adelaide
Tipo: Artigo de Revista Científica
Publicado em //1998 EN
Relevância na Pesquisa
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OBJECTIVE: To investigate the role of serum 1,25-dihydroxyvitamin D (1,25D) in the decreased calcium absorption found in men with osteoporosis. DESIGN: Prospective study of patients referred to a university teaching hospital clinic for investigation of possible osteoporosis. PATIENTS: Male patients referred for investigation for osteoporosis, from 1981 to 1995, because of specific risk factors or radiological suspicion of osteoporosis. Men with vertebral compression fractures were compared with those without. MEASUREMENTS: Height and weight, radiocalcium absorption, serum 1,25D and fasting urinary calcium and hydroxyproline excretion. RESULTS: The men with vertebral fractures had higher fasting urinary hydroxyproline excretion (P = 0.003) and lower calcium absorption (P = 0.002) than the men without. Calcium absorption was positively related to 1,25D in both groups but the estimated calcium absorption at zero 1,25D was lower in the osteoporotic than the normal group. 1,25D was lower in the osteoporotic group than in the normal group. However this difference could only explain about half of the difference in calcium absorption between the groups. CONCLUSIONS: Calcium absorption is low in men with osteoporosis. About half of the deficit is due to low serum 1...

Effect of perimenopause on calcium absorption: a longitudinal study

Wishart, J.; Scopacasa, F.; Horowitz, M.; Morris, H.; Need, A.; Clifton, P.; Nordin, B.
Fonte: Parthenon Publishing Group Publicador: Parthenon Publishing Group
Tipo: Artigo de Revista Científica
Publicado em //2000 EN
Relevância na Pesquisa
36.41%
OBJECTIVE: Cross-sectional studies suggest that the rise in calcium requirement at the menopause may be attributable, at least in part, to a fall in intestinal calcium absorption. The aim of the present study was to determine the effect of the menopause on intestinal calcium absorption and the relationship between any change in calcium absorption and serum calcitriol. METHODS: Radiocalcium absorption and serum calcitriol were measured in 72 women aged 47.3 (standard error, SE 0.19) years who were initially premenopausal (as judged by menstrual history and serum follicle stimulating hormone (FSH)) and again 18 months later. RESULTS: Calcium absorption fell at the second visit from 0.72 (0.029)/h to 0.64 (0.029)/h (p = 0.003). Serum calcitriol had also fallen at the second visit from 124 (4.2) pmol/l to 111 (4.0) pmol/l (p = 0.007). At that visit, serum FSH exceeded the premenopausal reference range in 11 subjects and the menstrual cycle had become irregular in 24 of them. In the 11 women with raised FSH at the second visit, radiocalcium absorption fell from 0.85/h (0.097) at baseline to 0.57/h (0.049) (p = 0.008), but only from 0.70/h (0.028) to 0.65/h (0.033) (not significant) in the remaining 61. Similarly, radiocalcium absorption fell significantly (p = 0.003) in the 24 women with irregular menses...

Relation between calcium absorption and serum calcitriol in normal men: evidence for age-related intestinal resistance to calcitriol

Scopacasa, F.; Wishart, J.; Horowitz, M.; Morris, H.; Need, A.
Fonte: Nature Publishing Group Publicador: Nature Publishing Group
Tipo: Artigo de Revista Científica
Publicado em //2004 EN
Relevância na Pesquisa
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OBJECTIVE: To obtain information on the causes of age-related bone loss in men and the concomitant decline in calcium absorption. DESIGN: Cross-sectional study. SETTING: Adelaide, South Australia, Australia. SUBJECTS: A total of 95 healthy, Caucasian men (age range 27-87 y). RESULTS: Calcium absorption declined with age (r=-0.46, P<0.0001), as did 24-h urine calcium, phosphate and creatinine (r>-0.21, P<0.05 for all); serum calcitriol and 25 hydroxyvitamin D did not change with age. Calcium absorption was related to serum calcitriol (r=0.20, P=0.05). An inverse relation between the residual deviations in calcium absorption, after allowing for its dependence on calcitriol, and age (F=5.4, P<0.005) was observed. The 24-h urinary calcium, phosphate and creatinine were all related to calcium absorption (r>0.41, P<0.0001). Forearm bone density fell with age (r=-0.45, P<0.0001) but was not related to calcium absorption, or markers of bone turnover. CONCLUSIONS: In healthy Caucasian males (i) calcium absorption falls, but serum calcitriol does not change with age, (ii) the relation between calcium absorption and serum calcitriol changes with age, indicative of an intestinal resistance to calcitriol and (iii) calcium absorption is a significant determinant of 24-h urinary calcium excretion.; F Scopacasa...

Relationships between intestinal calcium absorption, serum vitamin D metabolites and smoking in postmenopausal women

Need, A.; Kemp, A.; Giles, N.; Morris, H.; Horowitz, M.; Nordin, B.
Fonte: Springer-Verlag London Ltd Publicador: Springer-Verlag London Ltd
Tipo: Artigo de Revista Científica
Publicado em //2002 EN
Relevância na Pesquisa
36.42%
Smoking has been associated with low bone density, fractures and poor intestinal calcium absorption. Calcium absorption is a critical factor in calcium balance in postmenopausal women but the mechanisms causing decreased absorption efficiency in postmenopausal smokers are controversial and poorly defined. We performed a cross-sectional study of 405 postmenopausal women attending a clinic for the management of osteoporosis to compare intestinal calcium absorption efficiency, serum vitamin D metabolites and parathyroid hormone levels in postmenopausal women who had never smoked, who were smokers previously or who were current smokers, to examine the relationships between these variables in smokers. Two hundred and fifty-two of the women had never smoked, 79 had smoked previously and 74 were current smokers. The hourly fractional rate of calcium absorption was similar in non-smokers and those who had previously smoked. Radiocalcium absorption was less in the 74 smokers compared with the 331 non-smokers [0.60 (0.29 SD) vs 0.71 (0.27); p = 0.004], as were serum calcitriol (p50.001) and parathyroid hormone (PTH) (p50.01). There was no difference in the relationship between calcium absorption and serum calcitriol between smokers (r = 0.38) and non-smokers (r = 0.28); hence the impaired calcium absorption in the smokers was almost entirely attributable to suppression of the PTH– calcitriol endocrine axis. In postmenopausal women smoking is associated with a reduction in calcium absorption efficiency due to suppression of the PTH– calcitriol axis. This impairment of calcium absorption could lead to accelerated bone loss and limit the usefulness of dietary calcium supplementation.; A. G. Need...

Mechanism and rate of glucose absorption differ between an Australian honeyeater (Meliphagidae) and a lorikeet (Loridae)

Napier, K.; McWhorter, T.; Fleming, P.
Fonte: Company of Biologists Ltd Publicador: Company of Biologists Ltd
Tipo: Artigo de Revista Científica
Publicado em //2008 EN
Relevância na Pesquisa
36.4%
Efficient mechanisms of glucose absorption are necessary for volant animals as a means of reducing mass during flight: they speed up gut transit time and require smaller volume and mass of gut tissue. One mechanism that may be important is absorption via paracellular (non-mediated) pathways. This may be particularly true for nectarivorous species which encounter large quantities of sugar in their natural diet. We investigated the extent of mediated and non-mediated glucose absorption in red wattlebirds Anthochaera carunculata (Meliphagidae) and rainbow lorikeets Trichoglossus haematodus (Loriidae) to test the hypothesis that paracellular uptake accounts for a significant proportion of total glucose uptake in these species. We found that routes of glucose absorption are highly dynamic in both species. In lorikeets, absorption of L-glucose (non-mediated uptake) is slower than that of D-glucose (mediated and non-mediated uptake), with as little as 10% of total glucose absorbed by the paracellular pathway initially (contrasting previous indirect estimates of 0%). Over time, however, more glucose may be absorbed via the paracellular route. Glucose absorption by both mediated and non-mediated mechanisms in wattlebirds occurred at a faster rate than in lorikeets...

Mechanistic bases for differences in passive absorption

Lavin, S.; McWhorter, T.; Karasov, W.
Fonte: Company of Biologists Ltd Publicador: Company of Biologists Ltd
Tipo: Artigo de Revista Científica
Publicado em //2007 EN
Relevância na Pesquisa
36.41%
Increasing evidence indicates that small birds have more extensive non-mediated, paracellular intestinal absorption of hydrosoluble compounds than do mammals, although studies have not employed uniform methodologies or demonstrated differences at the tissue level. The mechanistic bases behind apparent species differences are poorly understood. We show using uniform methodology at the whole-animal level that intact, unanesthetized pigeons had significantly higher absorption of L-arabinose and L-rhamnose, two water-soluble compounds used to measure paracellular absorption, than similarly sized laboratory rats. The species differences were also evident using perfused isolated loops of duodenum, showing that the difference in paracellular absorption occurred at the tissue level, even when D-glucose absorption rates (transcellular+paracellular) were similar between the two species. The greater absorption of these probes in pigeons could not be explained by mediated uptake of the putative paracellular probes, or by increased nominal surface area, increased villus area or increased number of tight junctions. Rats and pigeons had comparable absorption of larger probes, which is consistent with similar effective pore size of the tight junction between enterocytes. The elimination of these mechanistic explanations might suggest that pigeon intestine has relatively higher paracellular solvent drag...

Glucose absorption and gastric emptying in critical illness

Chapman, M.; Fraser, R.; Matthews, G.; Russo, A.; Bellon, M.; Besanko, L.; Jones, K.; Butler, R.; Chatterton, B.; Horowitz, M.
Fonte: Current Science Ltd Publicador: Current Science Ltd
Tipo: Artigo de Revista Científica
Publicado em //2009 EN
Relevância na Pesquisa
36.44%
Introduction: Delayed gastric emptying occurs frequently in critically ill patients and has the potential to adversely affect both the rate, and extent, of nutrient absorption. However, there is limited information about nutrient absorption in the critically ill, and the relationship between gastric emptying (GE) and absorption has hitherto not been evaluated. The aim of this study was to quantify glucose absorption and the relationships between GE, glucose absorption and glycaemia in critically ill patients. Methods: Studies were performed in nineteen mechanically ventilated critically ill patients and compared to nineteen healthy subjects. Following 4 hours fasting, 100 ml of Ensure, 2 g 3-Omethyl glucose (3-OMG) and ⁹⁹mTc sulphur colloid were infused into the stomach over 5 minutes. Glucose absorption (plasma 3- OMG), blood glucose levels and GE (scintigraphy) were measured over four hours. Data are mean ± SEM. A P-value < 0.05 was considered significant. Results Absorption of 3-OMG was markedly reduced in patients (AUC₂₄₀: 26.2 ± 18.4 vs. 66.6 ± 16.8; P < 0.001; peak: 0.17 ± 0.12 vs. 0.37 ± 0.098 mMol/l; P < 0.001; time to peak; 151 ± 84 vs. 89 ± 33 minutes; P = 0.007); and both the baseline (8.0 ± 2.1 vs. 5.6 ± 0.23 mMol/l; P < 0.001) and peak (10.0 ± 2.2 vs. 7.7 ± 0.2 mMol/l; P < 0.001) blood glucose levels were higher in patients; compared to healthy subjects. In patients; 3-OMG absorption was directly related to GE (AUC₂₄₀; r = -0.77 to -0.87; P < 0.001; peak concentrations; r = -0.75 to -0.81; P = 0.001; time to peak; r = 0.89-0.94; P < 0.001); but when GE was normal (percent retention 240 < 10%; n = 9) absorption was still impaired. GE was inversely related to baseline blood glucose...

Assessment of radiolabeled d-glucose and the nonmetabolizable analog 3-O-methyl-d-glucose as tools for in vivo absorption studies

McWhorter, T.; Green, A.; Karasov, W.
Fonte: Univ Chicago Press Publicador: Univ Chicago Press
Tipo: Artigo de Revista Científica
Publicado em //2010 EN
Relevância na Pesquisa
36.4%
3-O-methyl-D-glucose has been extensively used as a proxy for d-glucose uptake. This nonmetabolizable analog has lower affinity for transporters, potentially leading to underestimates of glucose absorption rates as well as overestimates of the nutritional significance of passive uptake. Here we sought to precisely quantify the bias, if any, incurred when using 3-O-methyl-D-glucose by comparing relative absorption rates with D-glucose in vivo in a seasonally frugivorous bird, the American robin. By simultaneously administering these D-glucose probes with L-glucose--the latter absorbed only via nonmediated mechanisms and the former absorbed by both mediated and nonmediated mechanisms--using common pharmacokinetic procedures, we were able to estimate the nutritional significance of paracellular uptake in this species. The relative absorption rate of 3-O-methyl-D-glucose calculated over the initial absorptive phase was not significantly different from that of D-glucose, indicating that the former provides reasonable estimates of glucose absorption rates in vivo. The ratio of L-glucose to D-glucose cumulative fractional absorption indicates that around 60% of total glucose absorption in American robins is paracellular and showed no apparent bias in using 3-O-methyl-D-glucose when averaged over the entire initial absorptive phase. Although the absorption and elimination kinetics of radiolabeled D-glucose were appropriate for pharmacokinetic analysis in this study...

Enhancement of coir fiber normal incidence sound absorption coefficient

Fouladi, M.; Nor, M.; Ayub, M.; Ghassem, M.
Fonte: World Scientific Publ Co Pte Ltd Publicador: World Scientific Publ Co Pte Ltd
Tipo: Artigo de Revista Científica
Publicado em //2012 EN
Relevância na Pesquisa
36.42%
Coir fiber from coconut husk is an important agricultural waste in Malaysia. The porous structure of fiber makes it an eligible material for acoustical absorption. In previous studies at Universiti Kebangsaan Malaysia, single layer coir fiber showed low acoustical absorption in medium and low frequencies; e.g. absorption coefficient of a 20 mm industrial prepared coir fiber sample was below 0.3 for frequencies less than 1.5 kHz. Current research was initiated to improve the shortcoming by mixing industrial prepared coir fiber with air gap layers. Analyzes were based on two approaches, namely; Delany–Bazley with acoustic transmission analysis (ATA) and Allard elastic model with transfer matrix analysis. Experimental measurements were conducted in impedance tube to validate the analytical results. Outcomes described that Delany–Bazley-ATA technique was an approximate solution showing overall absorption path without giving any accurate information about the peaks and resonances. Allard method took the elasticity of material into account and transfer matrices were able to characterize the whole structure as a combination of single layers. Results were close to experimental values and predicted the path and resonances very well. Further analyzes were conducted by Allard method and derived that having a fiber layer backed by an air gap was better than leaving the same gap in between that layer. The explanation was that...

Möglichkeiten der simultanen Untersuchung von Freisetzung und Absorption schwer-wasserlöslicher Arzneistoffe aus festen oralen Darreichungsformen durch biorelevante in vitro Modelle; Possibilities for the simultaneous examination of dissolution and absorption of poorly water soluble active pharmaceutical ingredients from solid oral formulations through biorelevant in vitro models

Pfefferle, Martin Ludwig
Fonte: Universidade de Tubinga Publicador: Universidade de Tubinga
Tipo: Dissertação
DE_DE
Relevância na Pesquisa
36.42%
Vielen Arzneistoffen ist eine pH-abhängige schlechte Wasserlöslichkeit gemeinsam. Dies führt sowohl bei der Charakterisierung des Absorptionsverhaltens der Substanz, als auch bei der in vitro Charakterisierung der entwickelten Arzneiformen zu Problemen. Ziel der vorliegenden Arbeit ist es, Modelle zu entwickeln und zu qualifizieren, mit denen das Löslichkeitsverhalten von Arzneistoffen nach ihrer Freisetzung (Dissolution) simultan untersucht werden kann zur Simulation der Absorption des freigesetzten Stoffs. Bei der Entwicklung der Modelle wird Augenmerk auf hohe Biorelevanz, also einer möglichst exakten Abbildung der Verhältnisse im menschlichen gastrointestinalen Trakt gelegt, wodurch sich gute Rückschlüsse auf das in vivo Verhalten von Arzneistoff und –form ziehen lassen sollten. Weiterhin soll durch nahezu vollständige Automation für Anwenderfreundlichkeit und den Ausschluss von Fehlerquellen gesorgt werden. Um später Rückschlüsse zwischen experimentell ermittelten Daten und bereits zuvor gewonnenen Daten aus einer Humanstudie ziehen zu können (in vivo-in vitro Korrelation, IVIVC), müssen die Plasmaspiegeldaten in eine Form gebracht werden, die direkt mit in vitro Disolutionsversuchen verglichen werden kann. Die geschieht unter dem Einsatz der numerischen Dekonvolution...

Absorption of sugars in the Egyptian fruit bat (Rousettus aegyptiacus): a paradox explained

Tracy, C.; McWhorter, T.; Korine, C.; Wojciechowski, M.; Pinshow, B.; Karasov, W.
Fonte: Company of Biologists Ltd Publicador: Company of Biologists Ltd
Tipo: Artigo de Revista Científica
Publicado em //2007 EN
Relevância na Pesquisa
36.41%
Two decades ago D. J. Keegan reported results on Egyptian fruit bats (Rousettus aegyptiacus, Megachiroptera) that were strangely at odds with the prevailing understanding of how glucose is absorbed in the mammalian intestine. Keegan's in vitro tests for glucose transport against a concentration gradient and with phloridzin inhibition in fruit bat intestine were all negative, although he used several different tissue preparations and had positive control results with laboratory rats. Because glucose absorption by fruit bats is nonetheless efficient, Keegan postulated that the rapid glucose absorption from the fruit bat intestine is not through the enterocytes, but must occur via spaces between the cells. Thus, we hypothesized that absorption of water-soluble compounds that are not actively transported would be extensive in these bats, and would decline with increasing molecular mass in accord with sieve-like paracellular absorption. We did not presume from Keegan's studies that there is no Na+-coupled, mediated sugar transport in these bats, and our study was not designed to rule it out, but rather to quantify the level of possible non-mediated absorption. Using a standard pharmacokinetic technique, we fed, or injected intraperitonealy...

Is a 40 % Absorption of Iron from a Ferrous Ascorbate Reference Dose Appropriate to Assess Iron Absorption Independent of Iron Status?

Hamilton West, Christopher; Pizarro Aguirre, Fernando Dagoberto; Olivares, Manuel; Brito, Alex; Valenzuela Venegas, Carolina Paz
Fonte: Springer Publicador: Springer
Tipo: Artículo de revista
ES
Relevância na Pesquisa
36.42%
Artículo de publicación ISI; Although a 40%absorption of a standard reference dose corresponds to iron (Fe) absorption in borderline Fedeficient subjects, this percentage is currently applied to all subjects independent of Fe status: (a) to assess the use of the 40 % of Fe absorption of the reference dose (FeRD%) for subjects with iron-depleted stores (IDS), normal Fe status (NIS), Fe deficiency without anemia (IDWA), and Fe deficiency anemia (IDA) and (b) to explore relationships between Fe status biomarkers and FeRD%. Six hundred forty-six participants (582 women and 64 men) were selected from multiple Fe bioavailability studies and classified into four groups based on Fe status: NIS, IDS, IDWA, and IDA. All men were classified as normal. The absorption from FeRD% was calculated in each group and correlated with Fe status biomarkers. (a) Women with IDS absorbed 40 (18.9–84.7)% of the reference dose; (b) for male subjects with NIS, the absorption of the reference dose was 19 (9.8–36.1)%, while for females, absorption was observed as to be 34 (16.7–68.6)%. In the case of subjects with IDWA, a 43 (19.7–92.5)% absorption was observed, while subjects with IDA demonstrated 67 (45.2– 98.6)% absorption. Serum ferritin (SF) had the strongest inverse correlation with FeRD% (r =−0.41...

Experimental analysis of a solar absorption system with interior energy storage

Pastakkaya,Bilsay; Yamankaradeniz,Nurettin; Kaynakli,Omer; Coskun,Salih; Yamanakaradeniz,Recep
Fonte: Journal of Energy in Southern Africa Publicador: Journal of Energy in Southern Africa
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/01/2012 EN
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This study examines experimentally the cooling application of a solar absorption system with interior energy storage that uses two different auxiliary systems. The experiments were performed at Uludag University, Bursa, Turkey on the 3rd and 4th of August 2010 that had the approximately same average outdoor temperature, 31°C. A solar hot water was delivered via a 40 m2 array of flat plate solar collectors that drove a lithium chloride (LiCl) absorption heat pump with a cooling power peak of 20 kW. A solar-powered air conditioning system was designed for heating and cooling in a test room that had a total floor space of 30 m2. Chilled water produced in the evaporator was supplied to the fan coil units, and the heat of condensation and absorption was rejected by means of a wet cooling tower. An electric heater and an air source heat pump were used as auxiliary systems for the absorption cooling application for two different cases when the solar energy was insufficient. Temperature variations were recorded for the absorption machine components, the test room, and the outdoors. The cooling energy, thermal energy, and daily average coefficient of performance (COP) of the absorption system were calculated for two days. Solar absorption cooling was considered for two different auxiliary systems and is presented in this manuscript. The results showed that the daily average COP of the absorption system was 0.283 for Case 1 and 0.282 for Case 2. For both cases...

Absorption of unlabeled reduced iron of small particle size from a commercial source: A method to predict absorption of unlabeled iron compounds in humans

González,Horacio; Mendoza,Concepción; Viteri,Fernando E
Fonte: Sociedad Latinoamericana de Nutrición Publicador: Sociedad Latinoamericana de Nutrición
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/09/2001 EN
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The absorption of a commercial brand of small-particle reduced iron was evaluated in 10 normal subjects. For each subject, the hemoglobin incorporation method was used to measure the true absorption of 60 mg of iron from either ferrous sulfate or ferric ammonium citrate. The iron tolerance test (ITT) was also studied for these two compounds and for reduced iron. This procedure consisted of measuring the area under the curve of plasma iron elevations at specified times for 6 hours, or the peak plasma iron, corrected by the plasma iron disappearance rate obtained from measuring plasma iron at specified times for 4 hours after the slow intravenous injection of 0.4 mg of iron as ferric citrate. Only the ITT was used to measure the absorption of 60 mg of reduced iron. Reference dose iron ascorbate absorption was measured in each subject. The absorption of ferric ammonium citrate and reduced iron was expressed as percent of dose and also as absorption percent of that of ferrous sulfate. Mean % geometric "true absorptions" were 39.0 for reference dose, 10.4 for FeSO4 and 2.4 for ferric ammonium citrate. The later was 23% that of FeSO4. By ITT the mean geometric % absorptions were 7.9, 3.7 and 3.2 for FeSO4, ferric ammonium citrate and reduced iron respectively...