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Release Pattern (release + pattern)
Selected AbstractsInterferon-, differentially modulates the release of cytokines and chemokines in lipopolysaccharide- and pneumococcal cell wall-stimulated mouse microglia and macrophagesEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 11 2002Karl Georg Häusler Abstract During bacterial infections of the CNS, activated microglia could support leucocyte recruitment to the brain through the synthesis of cyto- and chemokines. In turn, invading leucocytes may feedback on microglial cells to influence their chemokine release pattern. Here, we analyzed the capacity of interferon-, (IFN,) to serve as such a leucocyte-to-microglia signal. Production of cyto- and chemokines was stimulated in mouse microglia cultures by treatments with lipopolysaccharide (LPS) from Gram-negative Escherichia coli or cell walls from Gram-positive Streptococcus pneumoniae (PCW). IFN, presence during the stimulation (0.1,100 ng/mL) modulated the patterns of LPS- and PCW-induced cyto- and chemokine release in a dose-dependent, potent and complex manner. While amounts of TNF, and IL-6 remained nearly unchanged, IFN, enhanced the production of IL-12, MCP-1 and RANTES, but attenuated that of KC, MIP-1, and MIP-2. Release modulation was obtained with IFN, preincubation (treatment of cells before LPS or PCW administration), coincubation and even delayed addition to an ongoing LPS or PCW stimulation. Together the changes observed for the microglial chemokine release under IFN, would shift the chemoattractive profile from favouring neutrophils to a preferential attraction of monocytes and T lymphocyte populations , as actually seen during the course of bacterial meningitis. The findings support the view of activated microglia as a major intrinsic source for an instant production of a variety of chemokines and suggest that leucocyte-derived IFN, could potentially regulate the microglial chemokine release pattern. [source] Lep d 2 polymorphisms in wild and cultured Lepidoglyphus destructor mitesFEBS JOURNAL, Issue 4 2003Liselotte Kaiser We have previously cloned, expressed and characterized two variants of the major allergen Lep d 2 from cultured Lepidoglyphus destructor mites. These variants, Lep d 2.0101 and Lep d 2.0201, differ at 13 amino acid positions. In this study we investigated Lep d 2 sequence diversity between wild and cultured mites. PCR, Southern blot and DNA sequence analysis revealed the presence of two different Lep d 2 genes, one with and one without an intron. In addition, two new variants of Lep d 2, Lep d 2.0102 and Lep d 2.0202, were found at different frequencies in wild and cultured mites. When we expressed the Lep d 2 variants and compared their IgE binding properties by ELISA inhibition, we found that Lep d 2.0102 was a more potent inhibitor than Lep d 2.0101, and to a lesser extent Lep d 2.0202 was more potent than Lep d 2.0201. Long-term cultures of peripheral blood mononuclear cells were used to assess the ability of the expressed Lep d 2 variants to induce cytokine release. Although cells from different individuals released different amounts of interferon-, and interleukin-5, no consistent cytokine release pattern could be linked to any specific Lep d 2 variant. In conclusion, we show that both cultured and wild Lepidoglyphus destructor mites contain the same pattern of polymorphism. Furthermore, this Lep d 2 sequence diversity seems not to have any significant impact on the allergens IgE binding or its ability to induce T cell cytokine release. [source] Core-Sheath Nanofibers Containing Colloidal Arrays in the Core for Programmable Multi-Agent DeliveryADVANCED MATERIALS, Issue 9 2009Eunmin Jo Polymeric core-sheath nanofibers consisting of polymeric sheath and arrays of colloids in the core are produced by one-step single-nozzle electrospinning. Loading different species of active agents in each colloid provides control over the release of each of the agents independently, which enables a programmed release pattern for multiple agents. [source] Elastic liposomes mediated transdermal delivery of an anti-hypertensive agent: Propranolol hydrochlorideJOURNAL OF PHARMACEUTICAL SCIENCES, Issue 1 2007Dinesh Mishra Abstract One major problem encountered in transdermal drug delivery is the low permeability of drugs through the skin barrier. In the present investigation ultradeformable lipid vesicles, that is, elastic liposomes were prepared incorporating propranolol hydrochloride for enhanced transdermal delivery. Elastic liposomes bearing propranolol hydrochloride were prepared by conventional rotary evaporation method and characterized for various parameters including vesicles shape and surface morphology, size and size distribution, entrapment efficiency, elasticity, turbidity, and in vitro drug release. In vitro flux, enhancement ratio (ER), and release pattern of propranolol hydrochloride were calculated for transdermal delivery. In vivo study conducted on male albino rats (Sprague Dawley) was also taken as a measure of performance of elastic liposomal, liposomal, and plain drug solution. The better permeation through the skin was confirmed by confocal laser scanning microscopy (CLSM). Results indicate that the elastic liposomal formulation for transdermal delivery of propranolol hydrochloride provides better transdermal flux, higher entrapment efficiency, ability as a self-penetration enhancer and effectiveness for transdermal delivery as compared to liposomes. © 2006 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 96:145,155, 2007 [source] Preparation and characterization of quercetin-loaded polymethyl methacrylate microcapsules using a polyol-in-oil-in-polyol emulsion solvent evaporation methodJOURNAL OF PHARMACY AND PHARMACOLOGY: AN INTERNATI ONAL JOURNAL OF PHARMACEUTICAL SCIENCE, Issue 12 2007Dong-Hwan Lee Flavonoids and related compounds exhibit a wide range of useful pharmacological properties but present challenges related to their stability and solubility in commonly available solvents. In this study, polymethyl methacrylate (PMMA) microcapsules were prepared using a novel polyol-in-oil-in-polyol (P/O/P) emulsion solvent evaporation method as a means of stabilizing the flavonoids, using quercetin as a model flavonoid drug. The morphology of the microcapsules was evaluated using a scanning electron microscope, revealing a spherical shape with a smooth surface. The cross-section image of the PMMA microcapsules prepared with an amphiphilic polymer in the inner polyol phase showed that the microcapsule was filled with several submicron microspheres. The mean diameter varied from 1.03 ± 0.12 ,m to 2.39 ± 0.42 ,m, and the encapsulation efficiency ranged from 12.7% to 26.9%. When free quercetin was stored at 42°C, the residual quercetin content gradually decreased to 18% over 28 days as a result of oxidation. However, when encapsulated in PMMA microcapsules with an amphiphilic polymer in the inner polyol phase, the residual quercetin content decreased to just 82%. In-vitro release studies indicated a sustained release pattern throughout the 36-h study. The release kinetics of the microcapsules with an amphiphilic polymer followed a diffusion-controlled mechanism and the microcapsule without amphiphilic polymer followed an anomalous diffusion behaviour. This study suggests that the novel P/O/P emulsion solvent evaporation method can be applied to the encapsulation of flavonoids. [source] Development of a robust once-a-day glipizide matrix systemJOURNAL OF PHARMACY AND PHARMACOLOGY: AN INTERNATI ONAL JOURNAL OF PHARMACEUTICAL SCIENCE, Issue 6 2007Shahla Jamzad The robustness of a new hydroxypropylmethylcellulose (HPMC) based modified release glipizide (10 mg) formulation was studied. The tablet formulations were prepared by dry blending the ingredients and direct compression, incorporating a range of release modifying agents up to ± 20% w/w relative to an optimized formulation. The dissolution was assessed in 900 mL pH 6.8 buffer at 75 rev min,1 paddle speed. Calculated difference and similarity factors (f1 and f2) and results of analysis of variance suggest that the overall release profiles were similar. Compositional changes up to ± 20% w/w and a reduction of drug dose to half did not change the general release pattern of this low dose/pH-dependent drug in a significant way. It is concluded that the drug release from the developed matrix systems is highly dependent on the kinetics of hydration and erosion, and that the proposed compositional changes within ± 20% w/w did not alter this relationship. The particulate systems used were characterized by determining the Carr index, Hausner ratio and the rheological properties using a texture analyser. Results indicate that the release is reproducible and the system has potential for successful scale-up operation, while complying with recommended Food and Drug Administration guidelines "Scale Up and Post Approval Changes". [source] Effect of surfactant on fabrication and characterization of paclitaxel-loaded polybutylcyanoacrylate nanoparticulate delivery systemsJOURNAL OF PHARMACY AND PHARMACOLOGY: AN INTERNATI ONAL JOURNAL OF PHARMACEUTICAL SCIENCE, Issue 7 2003Amitava Mitra ABSTRACT The feasibility of applying biodegradable polybutylcyanoacrylate (PBCA) nanoparticulate delivery systems (NDSs) for the controlled release of paclitaxel was investigated. Paclitaxel-loaded and unloaded PBCA-NDSs containing various surfactants (dextran 70, cholesterol, polyvinyl alcohol and lecithin) were prepared by anionic polymerization. The effects of surfactant (1% w/v), surfactant combination (1% w/v each), and surfactant concentration (0.05, 1.0 and 2.5% w/v) on PBCA-NDSs were evaluated and characterized by particle size, zeta potential, entrapment efficiency, and in-vitro paclitaxel release kinetics. The physicochemical characteristics of PBCA-NDSs incorporated with various surfactants were significantly improved compared with PBCA-NDS without any surfactant, by decreasing particle size at least 3-fold as well as by increasing the zeta potential up to 18-fold to minimize the agglomeration of nanoparticles. Moreover, PBCA-NDSs incorporated with various surfactants demonstrated higher entrapment efficiency of paclitaxel. Results from the in-vitro release kinetic studies indicated that a more controlled biphasic zero-order release pattern of paclitaxel was observed for PBCA-NDSs incorporated with various surfactants. Compared with dextran 70 and polyvinyl alcohol, the naturally occurring lipids, lecithin and cholesterol, indicated greater advantages in improving the physicochemical properties of PBCA-NDSs, in terms of smaller particle size, higher zeta potential and better drug entrapment efficiency, and better controlled release of paclitaxel, in terms of lower release rate and prolonged action from PBCA-NDSs. [source] Antibiotics modulate the stimulated cytokine response to endotoxin in a human ex vivo, in vitro modelACTA ANAESTHESIOLOGICA SCANDINAVICA, Issue 9 2006S. Ziegeler Background:, Sepsis may lead to the suppression of stimulated cytokine release after Gram-negative stimuli, correlating with a fatal outcome. Treatment of sepsis includes adequate therapy with antibiotics. The aim of this study was to investigate the role of antibiotics in the modulation of the lipopolysaccharide (LPS)-stimulated cytokine response of human monocytes. Methods:, In this ex vivo, in vitro study, whole blood samples were taken from 10 healthy volunteers, stimulated with LPS in the presence or absence of various antibiotics (penicillin, amoxicillin, cefuroxime, ceftazidime, cefotaxime, piperacillin/tazobactam, imipenem/cilastatin, gentamicin, netilmicin, ciprofloxacin, vancomycin) and cultured for 24 h. Thereafter, tumor necrosis factor-, (TNF-,) and interleukin-10 (IL-10) were measured in the supernatants by enzyme-linked immunosorbent assay (ELISA). Furthermore, CD14 and HLA-DR expression on monocytes was assessed using flow cytometry. Results:, All cephalosporins decreased LPS-stimulated IL-10 release. Cefuroxime and cefotaxime also decreased the expression density of the LPS recognition molecule CD14 on monocytes. An increase in LPS-stimulated IL-10 release was observed with vancomycin. A suppression of LPS-stimulated TNF-, and IL-10 release was observed in the presence of ciprofloxacin. Conclusion:, These results indicate a modulation of the expression density of CD14 on monocytes, together with a shift from a balanced to an inflammatory cytokine release pattern, by cefuroxime and cefotaxime. Vancomycin changes the response to an anti-inflammatory release pattern. After ciprofloxacin, a profound unresponsiveness of immune-competent cells to LPS stimulation is observed. Because of the critical role of a balanced innate immune response, these data may be of importance for the selection of antibiotics in septic patients. [source] Nitrogen in diamond-free ureilite Allan Hills 78019: Clues to the origin of diamond in ureilitesMETEORITICS & PLANETARY SCIENCE, Issue 8 2002V. K. Rai A small amount of amorphous carbon combusting at ,500 °C carries most of the noble gases, while the major carbon phase consisting of large crystals of graphite combusts at ,800 °C, and is almost noble-gas free. Nitrogen on the other hand is present in both amorphous carbon and graphite, with different ,15N signatures of ,21%o and +19%o, respectively, distinctly different from the very light nitrogen (about ,100%o) of ureilite diamond. Amorphous carbon in ALH 78019 behaves similar to phase Q of chondrites with respect to noble gas release pattern, behavior towards oxidizing acids as well as nitrogen isotopic composition. In situ conversion of amorphous carbon or graphite to diamond through shock would require an isotopic fractionation of 8 to 12% for nitrogen favoring the light isotope, an unlikely proposition, posing a severe problem for the widely accepted shock origin of ureilite diamond. [source] Long-term streptozotocin-induced diabetes alters prostanoid production in rat aorta and mesenteric bedAUTONOMIC & AUTACOID PHARMACOLOGY, Issue 4 2006H. A. Peredo Summary 1 Vascular disease is a major cause of mortality and morbidity in chronic diabetes mellitus. 2 Prostanoids, metabolites of arachidonic acid, include vasoactive substances produced and released from the vascular wall. Alterations in prostanoid production have been reported in the vasculature of diabetic humans and experimental animals. 3 The aim of the present work was to study the influence of three different periods of long-term streptozotocin-induced diabetes, 30, 120 and 180 days in the production of prostanoids in the thoracic aorta and in the mesenteric vascular bed of the rat. The prostanoids released to the incubation medium by the tissues were extracted and measured by reversed-phase HPLC. 4 In the diabetic groups, body weight was reduced and glycaemia was increased when compared with the corresponding non-diabetic controls. 5 In the aorta, 30 days of diabetes did not modify the prostanoid release pattern, meanwhile 120 and 180 days of incubation decreased prostacyclin (PGI2) production. In the mesenteric bed, at 30 days the release of the vasodilators PGI2 and prostaglandin (PGE2) and the vasoconstrictor thromboxane (TXA2) was reduced. At 120 days the vasodilators were reduced and at 180 days such reduction was joined by an increase of the release of vasoconstrictor metabolites. 6 Thirty days of diabetes did not modify the PGI2/TXA2 ratio in the aorta or mesenteric bed. On the other hand, 120 and 180 days of diabetes reduced significantly the ratio when compared with the corresponding controls. 7 In conclusion, the mesenteric bed, a resistance vascular bed, seems to be more sensitive than the aorta, a conductance vessel, to the effects of diabetes on prostanoid production. The observed effects contribute to a displacement of the balance of prostanoid release in favour of the vasoconstrictor metabolites, a phenomenon that could be related to the vascular complications of diabetes mellitus. [source] Polyethylenimine-coated albumin nanoparticles for BMP-2 deliveryBIOTECHNOLOGY PROGRESS, Issue 4 2008Sufeng Zhang Abstract Nanoparticle (NP)-based delivery has gained importance for improving the potency of therapeutic agents. The bovine serum albumin (BSA) NPs, obtained by a coacervation process, was modified by electrostatic adsorption of cationic polyethylenimine (PEI) to NP surfaces for delivery of bone-inducing growth factor, bone morphogenetic protein-2 (BMP-2). Different concentrations of PEI were utilized for coating BSA NPs to stabilize the colloidal system and to control the release of BMP-2. The NPs were characterized by size and zeta potential measurements, as well as by Scanning Electron Microscopy and Atomic Force Microscopy. The encapsulation efficiency was typically >90% in all NP preparations. In vitro release kinetics showed that the PEI concentration used for coating the NPs efficiently controlled the release of BMP-2, demonstrating a gradual slowing, sustained release pattern during a 10-day study period. The bioactivity of the encapsulated BMP-2 and the toxicity of the NPs were examined by the alkaline phosphatase (ALP) induction assay and the MTT assay, respectively, using C2C12 cells. The results indicated that PEI was the primary determinant of NP toxicities, and BSA NPs coated with 0.1 mg/mL PEI demonstrated tolerable toxicity, retained the bioactivity of BMP-2, and efficiently slowed the release rate of BMP-2. We conclude that BMP-2 encapsulated in BSA NPs might be an efficient way to deliver the protein for in vivo bone induction. [source] Regeneration patterns and persistence of the fog-dependent Fray Jorge forest in semiarid Chile during the past two centuriesGLOBAL CHANGE BIOLOGY, Issue 1 2008ALVARO G. GUTIÉRREZ Abstract The persistence of rainforest patches at Fray Jorge National Park (FJNP) in semiarid Chile (30°40,S), a region receiving approximately 147 mm of annual rainfall, has been a source of concern among forest managers. These forests are likely dependent on water inputs from oceanic fog and their persistence seems uncertain in the face of climate change. Here, we assessed tree radial growth and establishment during the last two centuries and their relation to trends in climate and canopy disturbance. Such evaluation is critical to understanding the dynamics of these semiarid ecosystems in response to climate change. We analyzed forest structure of six forest patches (0.2,22 ha) in FJNP based on sampling within 0.1 ha permanent plots. For the main canopy species, the endemic Aextoxicon punctatum (Aextoxicaceae), we used tree-ring analysis to assess establishment periods, tree ages, growing trends and their relation to El Niño Southern Oscillation (ENSO), rainfall, and disturbance. The population dynamics of A. punctatum can be described by a continuous regeneration mode. Regeneration of A. punctatum was sensitive to different canopy structures. Growth release patterns suggest the absence of large scale human impact. Radial growth and establishment of A. punctatum were weakly correlated with rainfall and ENSO. If water limits forests patch persistence, patches are likely dependent on the combination of fog and rain water inputs. Forest patches have regenerated continuously for at least 250 years, despite large fluctuations in rainfall driven by ENSO and a regional decline in rainfall during the last century. Because of the positive influence on fog interception, forest structure should be preserved under any future climate scenario. Future research in FJNP should prioritize quantifying the long-term trends of fog water deposition on forests patches. Fog modeling is crucial for understanding the interplay among physical drivers of water inputs under climate change. [source] ,1 Adrenoreceptors Mediate The Stimulatory Effects of Oestrogen On Stress-Related Hypothalamic-Pituitary-Adrenal Activity in The Female RatJOURNAL OF NEUROENDOCRINOLOGY, Issue 1 2004V. Viau Abstract Variation in challenge-induced adrenocorticotropin hormone (ACTH) release over the oestrous cycle occurs in response to fluctuations in circulating concentrations of oestrogen and progesterone. However, how these ovarian steroids interact to regulate the principal ACTH cosecretagogues, corticotropin-releasing hormone (CRH) and arginine vasopressin is not understood. Here, we measured median eminence CRH and vasopressin content in intact cycling female rats, and in ovariectomized (OVX) females steroid-replaced in a manner that approximates the relative release patterns of oestrogen and progesterone seen over the oestrous cycle. Intact cycling females showed significantly higher median eminence CRH and vasopressin concentrations during proestrous and oestrous compared to the diestrous phase. In OVX rats, a single 10 µg injection of oestrogen failed to mimic this increase in median eminence CRH and vasopressin. However, this dose significantly elevated CRH and vasopressin content in OVX rats previously exposed to diestrous concentrations of oestrogen and progesterone. Moreover, oestrogen priming enhanced restraint-induced depletion of CRH and vasopressin from the median eminence, but only against a background of low oestrogen and progesterone replacement. Oestrogen-induced elevations in median eminence vasopressin (but not CRH) content were reduced by peripheral administration of the ,1 adrenoreceptor antagonist prazosin. Finally, plasma ACTH concentrations following central injection of the ,1 receptor agonist, phenylephrine, were significantly higher in rats during proestrous compared to diestrous. These results indicate that the stimulatory effect of oestrogen on both the expression and stress-induced release of ACTH cosecretagogues is exerted only against a background of low oestrogen and progesterone levels, and is mediated, in part, via the ,1 adrenoreceptor. [source] Feasibility study of aerosolized prostaglandin E1 microspheres as a noninvasive therapy for pulmonary arterial hypertensionJOURNAL OF PHARMACEUTICAL SCIENCES, Issue 4 2010Vivek Gupta Abstract This study was designed to test the feasibility of polymeric microspheres as an inhalable carrier for prostaglandin E1 (PGE1) for treatment of pulmonary arterial hypertension. Poly(lactic- co -glycolic acid) (PLGA) microspheres were prepared by a double emulsion,solvent evaporation method. Six different microspheric formulations were prepared using two different blends of PLGA (50:50 and 85:15) and varying concentrations of polyvinyl alcohol (PVA) in the external aqueous phase (EAP). The particles were characterized for morphology, size, aerodynamic diameter, entrapment efficiency, release patterns, and metabolic stability. Pulmonary absorption was studied in a rat model, and safety of the formulations was evaluated by measuring cytotoxicity in Calu-3 cells and assessing injury markers in bronchoalveolar lavage (BAL) fluid. Both actual particle size and aerodynamic diameter of the formulations decreased with increasing PVA concentration. The mass median aerodynamic diameter of the particles was within the respirable range. Entrapment efficiency increased with increasing PVA concentration; PLGA 85:15 showed better entrapment due to hydrophobic interactions with the drug. Compared to intravenously administered PGE1, microspheres prepared with PLGA 85:15 produced a 160-fold increase in the half-life of PGE1 following pulmonary administration. Although plain PGE1 showed rapid degradation in rat lung homogenate, PGE1 entrapped in the particles remained intact for about 8,h. Optimized formulations were demonstrated to be safe, based on analysis of cytotoxicity and lung-injury markers in BAL fluid. Overall, the data suggest that microspheric PGE1 formulations have the potential to be used as a noninvasive and controlled-release alternative to the current medications used for treatment of pulmonary arterial hypertension that are administered by continuous infusion or require multiple inhalations. © 2009 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 99: 1774,1789, 2010 [source] Aerial seed bank dynamics and seedling emergence patterns in two annual Mediterranean AsteraceaeJOURNAL OF VEGETATION SCIENCE, Issue 3 2010F. Bastida Abstract Question: We explored the functional significance of seasonal aerial seed banks in two coexisting, heterocarpic annual Asteraceae with dormant (Chrysanthemum coronarium) and non-dormant (Anacyclus radiatus) achenes. We hypothesised that the plant achene pool is a significant component of total seed reserves, and that within-season seedling emergence timing is shaped by achene release patterns. Location: SW Spain. Methods: In an observational study, we established temporal achene release patterns. We also quantified the aerial and soil achene pools throughout the release season, and assessed seedling emergence timing. Sowing experiments were used to explore the influence of achene release dynamics on emergence timing, and to establish achene morph-specific patterns of between-year distribution of germination. Results: Achene release extended from late spring to late autumn (Chrysanthemum), or from early autumn to early winter (Anacyclus). Within species, achene morphs differed in release timing. Only in Chrysanthemum, a small achene fraction seemed to persist in the soil, and between-year germination distribution differed among morphs. In coexisting populations, the Anacyclus plant achene pool was an order of magnitude higher than the soil pool throughout the release season, whereas in Chrysanthemum both pools were of the same magnitude during autumn. Within-year seedling emergence was significantly staggered beneath parent plants compared with the pattern resulting solely from the germination response in soil, with the exception of Chrysanthemum in one of the two study years. Conclusions: Results suggest that seasonal aerial seed banks are effective within-season, risk-reducing traits in ruderal Mediterranean habitats characteristic of the study species. [source] Controlled Delivery Achieved with Bi-Layer Matrix Devices Produced by Co-Injection MouldingMACROMOLECULAR BIOSCIENCE, Issue 8 2004Cláudia M. Vaz Abstract Summary: The aim of this study was to design new soy protein-based bi-layered co-injection moulded matrix systems aimed to achieve controlled drug delivery. The devices consisted of a drug-free outer layer (skin) and a drug-containing core. The systems overcame the inherent disadvantage of non-linear release associated with diffusion-controlled single-layer matrix devices by providing additional releasing area with time to compensate for the decreasing release rate. As expected, the bi-layer devices presented a significant decrease in drug release rate when compared with a correspondent single layer matrix system. The skin thickness and the degree of crosslinking of the core appeared to be very important tools to tailor the release patterns. Furthermore, due to the amphoteric nature of the soy protein, the developed devices evidenced a pH-dependent behaviour. The mechanisms of drug release were also elucidated at two different pH values: i) pH 5.0, near the isoelectric point of soy (low matrix solubility); and ii) pH 7.4, physiological pH (high matrix solubility). Consequently, changing the release medium from pH 5.0 to pH 7.4 after two hours, led to an abrupt increase in drug release and the devices presented a typical controlled drug delivery profile: slow release/fast release. These evidences may provide for the development of individual systems with different release onsets that in combination may exhibit drug releases at predetermined times in a pre-programmed way. Another possibility is the production of three-layer devices presenting bimodal release profiles (fast release/slow release/fast release) by similar technologies. Scanning electron micrograph of a developed bi-layer device. [source] The Flask model: emergence of nutrient-recycling microbial ecosystems and their disruption by environment-altering ,rebel' organismsOIKOS, Issue 7 2007Hywel T. P. Williams Here we introduce a new model of life,environment interaction, which simulates an evolving microbial community in a ,Fask' of liquid with prescribed inputs of nutrients. The flask is seeded with a clonal population of ,microbes' that are subject to mutation on genetic loci that determine their nutrient uptake patterns, release patterns, and their effects on, and response to, other environmental variables. In contrast to existing models of life-environment interaction, notably Daisyworld, what benefits the individual organisms is decoupled from their ,global' (system-level) effects. A robust property of the model is the emergence of ecosystems that tend toward a state where nutrients are efficiently utilised and differentially recycled, with a correlated increase in total population. Organisms alter the environment as a free ,by-product' of their growth, and their growth is constrained by adverse environmental effects. This introduces environmental feedback, which can disrupt the model ecosystems, even though there are no constraints on the conditions to which the organisms can theoretically adapt. ,Rebel' organisms can appear that grow rapidly by exploiting an under-utilised resource, but in doing so shift the environment away from the state to which the majority of the community are adapted. The result can be a population crash with lossof recycling, followed by later recovery, or in extreme cases, a total extinction of the system. Numerous runs of these ,flask' ecosystems show that tighter environmental constraints on growth make the system more vulnerable to internally generated ecosystem extinction. [source] Permeation of urea through various polyurethane membranesPEST MANAGEMENT SCIENCE (FORMERLY: PESTICIDE SCIENCE), Issue 11 2009Atsushi Watanabe Abstract BACKGROUND: Controlled-release systems using polymer membranes are very important in agriculture for labour-saving and effective delivery of pesticides and other agents. Polymer-coated granules are one of the most useful formulations, and a study of the factors for polymer design is necessary to achieve various release patterns. A permeation study using plain membranes was carried out in order to clarify parameters, and the results were compared with the release from polymer-coated granules. RESULTS: The permeation coefficient of urea through a plain polyurethane membrane decreased significantly as the urethane and alkyl side chain content increased. The glass transition temperature and crosslink density of the polyurethanes hardly influenced its permeability. The release rate from polyurethane-coated granules was also reduced by alkyl side chains. However, it was faster than that through a plain membrane because of capsule expansion by continuous water penetration and structural changes in the membrane. CONCLUSION: The release rate of urea through a polyurethane plain membrane and from polyurethane-coated granules can be controlled by changing the chemical properties of the membrane. In addition, physical properties such as the glass transition temperature Tg or crosslink density should be considered to assess the release profile from polyurethane-coated granules. Copyright © 2009 Society of Chemical Industry [source] Number of Follicular Waves and Their Effect on Pregnancy Rate in the CowREPRODUCTION IN DOMESTIC ANIMALS, Issue 2 2005HA Çelik Contents In the study, the relationship of follicular growth waves, oestradiol and pregnancy rates were investigated during oestrus cycle in cows. A total of 22, Brown Swiss cows (3,5 years old) were used for the study. The ovaries of animals were examined from sixth day of cycle to next oestrus by ultrasound. The follicles that were present in the ovarium were recorded. Follicular growth was observed every day by means of ultrasound examination. The blood samples were taken for analysis of oestradiol simultaneously with ultrasound examinations. The oestrus animals were inseminated. Each animal that inseminated was examined by ultrasound on day 28 after insemination for pregnancy diagnosis. Two follicular growth waves were observed in nine of 22 (40.9%), three waves in 13 of 22 (59.1%) animals. The oestradiol was found in the same concentration but in different release patterns between two and three waves animals. Pregnancy rate in cows with three and two follicular waves did not differ. In conclusion, emergence of three waves of follicular growth was higher in Brown Swiss cows, the analysis of oestradiol could be used for determination of the wave numbers and the animals with different waves may have had the same pregnancy rates. [source] Ensemble Measurement of Diffusion: Novel Beauty and EvidenceCHEMPHYSCHEM, Issue 15 2009Christian Chmelik Dr. Abstract Recording the evolution of concentration profiles in nanoporous materials opens a new field of diffusion research with particle ensembles. The technique is based on the complementary application of interference microscopy and IR micro-imaging. Combining the virtues of diffusion measurements with solids and fluids, it provides information of unprecedented wealth and visual power on transport phenomena in molecular ensembles. These phenomena include the diverging uptake and release patterns for concentration-dependent diffusivities, the mechanisms of mass transfer at the fluid,solid interface and opposing tendencies in local and global concentration evolution. [source] | ||||||||||||||||||||||