997 resultados para Permeability transition
Resumo:
Ambitious energy targets set by EU put pressures to increase share of renewable electricity supply in this and next decades and therefore, some EU member countries have boosted increasing renewable energy generation capacity by implementing subsidy schemes on national level. In this study, two different change approaches to increase renewable energy supply and increase self-sufficiency of supply are assessed with respect to their impacts on power system, electricity market and electricity generation costs in Finland. It is obtained that the current electricity generation costs are high compared to opportunities of earnings from present-day investor’s perspective. In addition, the growth expectations of consumptions and the price forecasts do not stimulate investing in new generation capacity. Revolutionary transition path is driven by administrative and political interventions to achieve the energy targets. Evolutionary transition path is driven by market-based mechanisms, such as market itself and emission trading scheme. It is obtained in this study that in the revolutionary transition path operation of market-based mechanisms is distorted to some extent and it is likely that this path requires providing more public financial resources compared to evolutionary transition path. In the evolutionary transition path the energy targets are not achieved as quickly but market-based mechanisms function better and investment environment endures more stable compared to revolutionary transition path.
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Electrokinetics has emerged as a potential technique for in situ soil remediation and especially unique because of the ability to work in low permeability soil. In electrokinetic remediation, non-polar contaminants like most organic compounds are transported primarily by electroosmosis, thus the process is effective only if the contaminants are soluble in pore fluid. Therefore, enhancement is needed to improve mobility of these hydrophobic compounds, which tend to adsorb strongly to the soil. On the other hand, as a novel and rapidly growing science, the applications of ultrasound in environmental technology hold a promising future. Compared to conventional methods, ultrasonication can bring several benefits such as environmental friendliness (no toxic chemical are used or produced), low cost, and compact instrumentation. It also can be applied onsite. Ultrasonic energy applied into contaminated soils can increase desorption and mobilization of contaminants and porosity and permeability of soil through developing of cavitation. The research investigated the coupling effect of the combination of these two techniques, electrokinetics and ultrasonication, in persistent organic pollutant removal from contaminated low permeability clayey soil (with kaolin as a model medium). The preliminary study checked feasibility of ultrasonic treatment of kaolin highly contaminated by persistent organic pollutants (POPs). The laboratory experiments were conducted in various conditions (moisture, frequency, power, duration time, initial concentration) to examine the effects of these parameters on the treatment process. Experimental results showed that ultrasonication has a potential to remove POPs, although the removal efficiencies were not high with short duration time. The study also suggested intermittent ultrasonication over longer time as an effective means to increase the removal efficiencies. Then, experiments were conducted to compare the performances among electrokinetic process alone and electrokinetic processes combined with surfactant addition and mainly with ultrasonication, in designed cylinders (with filtercloth separating central part and electrolyte parts) and in open pans. Combined electrokinetic and ultrasonic treatment did prove positive coupling effect compared to each single process alone, though the level of enhancement is not very significant. The assistance of ultrasound in electrokinetic remediation can help reduce POPs from clayey soil by improving the mobility of hydrophobic organic compounds and degrading these contaminants through pyrolysis and oxidation. Ultrasonication also sustains higher current and increases electroosmotic flow. Initial contaminant concentration is an essential input parameter that can affect the removal effectiveness.
Resumo:
The influence of voltage on the conductance of toad skin was studied to identify the time course of the activation/deactivation dynamics of voltage-dependent Cl- channels located in the apical membrane of mitochondrion-rich cells in this tissue. Positive apical voltage induced an important conductance inhibition which took a few seconds to fully develop and was instantaneously released by pulse inversion to negative voltage, indicating a short-duration memory of the inhibiting factors. Sinusoidal stimulation at 23.4 mM [Cl-] showed hysteresis in the current versus voltage curves, even at very low frequency, suggesting that the rate of voltage application was also relevant for the inhibition/releasing effect to develop. We conclude that the voltage modulation of apical Cl- permeability is essentially a fast process and the apparent slow components of activation/deactivation obtained in the whole skin are a consequence of a gradual voltage build-up across the apical membrane due to voltage sharing between apical and basolateral membranes
Resumo:
High magnesium concentration inhibits the effect of arginine vasopressin (AVP) on smooth muscle contraction and platelet aggregation and also influences hepatocyte AVP receptor binding. The aim of this study was to determine the role of magnesium concentration [Mg2+] in AVP-stimulated water transport in the kidney collecting duct. The effect of low and high peritubular [Mg2+] on the AVP-stimulated osmotic water permeability coefficient (Pf) was evaluated in the isolated perfused rabbit cortical collecting duct (CCD). Control tubules bathed and perfused with standard Ringer bicarbonate solution containing 1 mM Mg2+ presented a Pf of 223.9 ± 27.2 µm/s. When Mg2+ was not added to the bathing solution, an increase in the AVP-stimulated Pf to 363.1 ± 57.2 µm/s (P<0.05) was observed. An elevation of Mg2+ to 5 mM resulted in a decrease in Pf to 202.9 ± 12.6 µm/s (P<0.05). This decrease in the AVP-stimulated Pf at 5 mM Mg2+ persisted when the CCDs were returned to 1 mM Mg2+, Pf = 130.2 ± 20.3 µm/s, and was not normalized by the addition of 8-[4-chlorophenylthio]-adenosine 3',5'-cyclic monophosphate, a cAMP analogue, to the preparation. These data indicate that magnesium may play a modulatory role in the action of AVP on CCD osmotic water permeability, as observed in other tissues.
Resumo:
The excretion ratio of lactulose/mannitol in urine has been used to assess the extension of malabsorption and impairment of intestinal permeability. The recovery of lactulose and mannitol in urine was employed to evaluate intestinal permeability in children with and without diarrhea. Lactulose and mannitol probes were measured using high-performance liquid chromatography with pulsed amperometric detection (HPLC-PAD). Two groups of solutions containing 60 µM sugars were prepared. Group I consisted of glucosamine, mannitol, melibiose and lactulose, and group II of inositol, sorbitol, glucose and lactose. In the study of intra-experiment variation, a sample of 50 µl from each group was submitted to 4 successive determinations. The recovered amounts and retention times of each sugar showed a variation <2 and 1%, respectively. The estimated recovery was >97%. In the study of inter-experiment variation, we prepared 4 independent samples from groups I and II at the following concentrations: 1.0, 0.3, 0.1, 0.03 and 0.01 mM. The amounts of the sugars recovered varied by <10%, whereas the retention times showed an average variation <1%. The linear correlation coefficients were >99%. Retention (k'), selectivity (a) and efficiency (N) were used to assess the chromatographic conditions. All three parameters were in the normal range. Children with diarrhea presented a greater lactulose/mannitol ratio compared to children without diarrhea.
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Although gap junction channels are still widely viewed as large, non-specific pores connecting cells, the diversity in the connexin family has led more attention to be focused on their permeability characteristics. We summarize here the current status of these investigations, both published and on-going, that reveal both charge and size selectivity between gap junction channels composed of different connexins. In particular, this review will focus on quantitative approaches that monitor the expression level of the connexins, so that it is clear that differences that are seen can be attributed to channel properties. The degree of selectivity that is observed is modest compared to other channels, but is likely to be significant for biological molecules that are labile within the cell. Of particular relevance to the in vivo function of gap junctions, recent studies are summarized that demonstrate that the connexin phenotype can control the nature of the endogenous traffic between cells, with consequent effects on biological effects of gap junctions such as tumor suppression.
Resumo:
Angiotensin-(1-7) (Ang-(1-7)) increased osmotic water permeability in the isolated toad skin, a tissue with functional properties similar to those of the distal mammalian nephron. Concentrations of 0.1 to 10 µM were effective, with a peak at 20 min. This effect was similar in magnitude to that of frog skin angiotensin II (Ang II) and oxytocin but lower than that of human Ang II and arginine-vasotocin. The AT2 angiotensin receptor antagonist PD 123319 (1.0 µM) fully inhibited the response to 0.1 µM Ang-(1-7) but had no effect on the response to Ang II at the same concentration. The specific receptor antagonist of Ang-(1-7), A-779, was ineffective in blocking the response to Ang-(1-7) and to frog skin Ang II. The AT1 receptor subtype antagonist losartan, which blocked the response to frog skin Ang II, was ineffective in blocking the response to Ang-(1-7). The present results support the view of an antidiuretic action of Ang-(1-7) in the mammalian nephron.
Resumo:
The aim of this caring science thesis is to deepen the understanding for the long-term ill adolescents care. In particular it aims to reach a better understanding of transition in health care, with a focus on how young people perceive health care. The goal is to build a model, a consistent theoretical framework that makes it possible to listen to the adolescent´s own voice, providing a better understanding of what good care consists in from their point of view. This Master's thesis consists of a literature overview on the concept of transition and a themed interview with young patients regarding transition of health care. The overall issue is 1. What is good care during the transition according to the adolescents themselves? 2. How does transition affect the young people's health and lives? The theoretical perspective of this thesis lies in the caring science tradition that has been developed at the Åbo Akademi University department of caring science with the caritative nursing theory as a basis. The epistemological and ontological assumptions are based on the caritative nursing theory, which in itself is ethical. Understanding of the concept of transition is based on A. Meleis transitions theory. The methodological approach is hermeneutical. The theme interview has been analyzed by using S. Kvales method. The material consists of a thematic interview with 10 long-term ill adolescents, about their views of the care received. This thesis research even in how NOBABs standards appears in the litterature as well as how they are implemented from the point of view of young people. The findings of this thesis shows that good care for the adolescent is a true presence with the young and an understanding of the direction in which the young move toward during the transition of care. Good care for an adolescent consists in being recognized as a person who is seen, known, appreciated and understood. Good care for the young involves recognizing her strength and joy of life including the contrast she experiences between health and suffering. To recognize their personal strength and courage supports the adolescents during the process of transitions of care Good care for the young involves responsibility for the individual person and humility in approaching her, giving attention to her view of life and aspirations. Openness and humility in the approach lays the foundation for a trusting relation during the transition of care. A unified theoretical framework is needed to promote the long-term ill adolescents care during transition of care. When the young and her individual needs is the centerpiece of healthcare creates this the basis for empowering care that supports the young in her quest for health. This master thesis adds a given model to the long-term ill adolescents` healthcare.
Resumo:
The objective of the present study was to assess intestinal permeability in patients with infection caused by Strongyloides stercoralis. Twenty-six patients (16 women and 10 men), mean age 45.9, with a diagnosis of strongyloidiasis were evaluated. For comparison, 25 healthy volunteers (18 women and 7 men), mean age 44.9, without digestive disorders or intestinal parasites served as normal controls. Intestinal permeability was measured on the basis of urinary radioactivity levels during the 24 h following oral administration of chromium-labeled ethylenediaminetetraacetic acid (51Cr-EDTA) expressed as percentage of the ingested dose. The urinary excretion of 51Cr-EDTA was significantly reduced in patients with strongyloidiasis compared to controls (1.60 ± 0.74 and 3.10 ± 1.40, respectively, P = 0.0001). Intestinal permeability is diminished in strongyloidiasis. Abnormalities in mucus secretion and intestinal motility and loss of macromolecules could explain the impaired intestinal permeability.
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The objective of this Master’s Thesis is to find individuals’ inducements that assist innovation adoption in the framework of sustainable food system. The purpose of the thesis is to examine the reasons why individuals adopt sustainable approaches, and furthermore, to see by what means the transition to the more sustainable food system could be accelerated. The study’s focal point is on the micro level, even if the wider purpose is to accelerate the holistic change of food system in the near future. The study consists of a literature review and a qualitative research, which is actualized with semi-structured interviews. The results indicate that individuals adopt innovations based on their strong intrinsic motivation. The main inducements were environment-related and health-related aspects, and individual’s deep connection to the countryside. The effect of social circle and doing good actions with the consuming behavior were also highlighted. Strongest barriers to innovation adoption seem to be price sensitivity, lack of easiness, and lack of interest in food. The findings indicate also that the most significant means that could ease the individuals’ decision to adopt an innovation are health-related aspects, educating and learning, environmental aspects, and decreasing the prices. Although the theoretical part of the study highlights the effect of positive reinforcement, the empirical part neglects it.
Resumo:
Tämä työ tutkii ja tarkastelee transitio-kokeilua ravinnetaloudessa. Transitio-kokeilu on toimintatutkimusprojekti, joka toteutetaan systeemisen muutoksen ajattelun mukaisesti alhaalta ylöspäin. Ravinnetalous määritetään tarkemmin työn kautta sekä analysoidaan monitaso-perspektiivin näkökulmasta. Ravinnetalous on terminä varsin tuntematon ja tarvitsee enemmän tunnettavuutta laajemman yleisön edessä. Transitio-areenan ja transitio-visioiden kehittäminen ovat työn keskipisteessä, koska ne ovat tärkeimpiä vaiheita transition alkuvaiheessa. Joukko sidosryhmätoimijoita osallistuu transitio areenaan sekä visioiden jatkokehittelyyn. Visio(t) luodaan ensisijaisesti backcasting-menetelmällä, jota myös täydennetään tavanomaisella ennustamisella. Backcasting- menetelmä on osin osallistava ja siinä käytetään ravinteiden planeettarajoja kvantitatiivisina pääperiaatteina, minkä tuloksena myös visiot ovat osin kvantitatiivisia. Transitio areenan kokoaminen ja fasilitointi aiheuttavat hankalia kysymyksiä, jotka tarvitsevat jatko-tutkimusta. Alhaalta-ylöspäin organisoitu transitio-arena houkuttelee niche-toimijoita, mutta epäonnistuu sitouttamaan julkisen vallan toimijoita. Toimintamallin voimasuhteet, politiikka ja transition vakiinnuttaminen tulisivat olla jatko-toimenpiteinä niin tutkimuksessa kuin toiminnassakin.
Resumo:
The aims of the study were to assess the validity of a clinical dental fear question (Short Dental Fear Question, SDFQ) and an instrument measuring interaction between adolescents and dental staff (Patient Dental Staff Interaction Questionnaire, PDSIQ). Also, adolescents’ subjective perception of interaction with dental staff, the association with adolescents’ dental fear and sense of coherence as well as a multi-professional small-group intervention model for decreasing high dental fear were assessed. The study sample comprised Finnish adolescents in transition to early adulthood, aged 18–26 years (n = 777, n = 773, n = 5), except for a sample of 15-year-old adolescents (n = 27). Dental fear, sense of coherence (SOC) and the adolescents’ perceived interaction with dental staff were assessed with questionnaires. The principles of fear treatment such as gradual exposure, relaxation, encouragement and cornerstones of the reteaming method based on a solution-focused framework to maintain motivation and peer support were used to decrease fear in the intervention study. The SDFQ was found to be a valid dental fear instrument and the PDSIQ a valid interaction instrument with five factors of interaction retrieved: ‘kind atmosphere and mutual communication’, ‘roughness’, ‘insecurity’, ‘trust and safety’, and ‘shame and guilt’. Highly fearful young adults more often perceived their interaction with dental staff as negative, more often felt insecure and had a weaker sense of coherence compared to their peers with no to moderate dental fear. The results of the intervention study showed that young adults’ high dental fear decreased and their commitment to dental treatment increased. The SDFQ is clinically feasible and informative instrument in measuring dental fear. Knowledge of the level of fear enables dental staff to better consider an adolescent’s fear. Dental staff should be aware that a supportive interaction style, creating trust and safety, is especially beneficial for highly dentally fearful young adults. A weak SOC may affect young adults’ high dental fear in that they would not have enough tools to manage their fear. A multi-professional small therapeutic group seems to increase fearful young adults’ resources for confronting dental treatment.
Resumo:
T84 is an established cell line expressing an enterocyte phenotype whose permeability properties have been widely explored. Osmotic permeability (P OSM), hydraulic permeability (P HYDR) and transport-associated net water fluxes (J W-transp), as well as short-circuit current (I SC), transepithelial resistance (R T), and potential difference (deltaV T) were measured in T84 monolayers with the following results: P OSM 1.3 ± 0.1 cm.s-1 x 10-3; P HYDR 0.27 ± 0.02 cm.s-1; R T 2426 ± 109 omega.cm², and deltaV T 1.31 ± 0.38 mV. The effect of 50 µM 5,6-dichloro-1-ethyl-1,3-dihydro-2H-benzimidazol-2-one (DCEBIO), a "net Cl- secretory agent", on T84 cells was also studied. We confirm the reported important increase in I SC induced by DCEBIO which was associated here with a modest secretory deltaJ W-transp. The present results were compared with those reported using the same experimental approach applied to established cell lines originating from intestinal and renal epithelial cells (Caco-2, LLC-PK1 and RCCD-1). No clear association between P HYDR and R T could be demonstrated and high P HYDR values were observed in an electrically tight epithelium, supporting the view that a "water leaky" barrier is not necessarily an "electrically leaky" one. Furthermore, the modest secretory deltaJ W-transp was not consistent with previous results obtained with RCCD-1 cells stimulated with vasopressin (absorptive fluxes) or with T84 cells secreting water under the action of Escherichia coli heat stable enterotoxin. We conclude that, while the presence of aquaporins is necessary to dissipate an external osmotic gradient, coupling between water and ion transport cannot be explained by a simple and common underlying mechanism.
Resumo:
Pharmacological evidence indicates that the basolateral nucleus of the amygdala (BLA) is involved in the mediation of inhibitory avoidance but not of escape behavior in the elevated T-maze test. These defensive responses have been associated with generalized anxiety disorder (GAD) and panic disorder, respectively. In the present study, we determined whether the BLA plays a differential role in the control of inhibitory avoidance and escape responses in the elevated T-maze. Male Wistar rats (250-280 g, N = 9-10 in each treatment group) were pre-exposed to one of the open arms of the maze for 30 min and 24 h later tested in the model after inactivation of the BLA by a local injection of the GABA A receptor agonist muscimol (8 nmol in 0.2 µL). It has been shown that a prior forced exposure to one of the open arms of the maze, by shortening latencies to withdrawal from the open arm during the test, improves the escape task as a behavioral index of panic. The effects of muscimol in the elevated T-maze were compared to those caused by this GABA agonist in the avoidance reaction generated in the light/dark transition test. This defensive behavior has also been associated with GAD. In the elevated T-maze, intra-BLA injection of muscimol impaired inhibitory avoidance (control: 187.70 ± 14.90 s, muscimol: 37.10 ± 2.63 s), indicating an anxiolytic effect, without interfering with escape performance. The drug also showed an anxiolytic effect in the light/dark transition test as indicated by the increase in the time spent in the lighted compartment (control: 23.50 ± 2.45 s, muscimol: 47.30 ± 4.48 s). The present findings point to involvement of the BLA in the modulation of defensive responses that have been associated with GAD.
Resumo:
In this work emission, optical, electrical and magnetic properties of the d- and f- elements doped zinc selenide crystals were investigated within a wide temperature range. Doping was performed in various technological processes: during the growth by chemical vapor transport method; by thermal diffusion from the Bi or Zn melt. Concentration of the doping impurity in the crystals was controlled by amount of the dopant in the source material or by its concentration in the doping media. Special interest in the work was paid to the influence of the different concentrations of Cr and Yb impurities on ZnSe crystals’ properties, correlations between observed effects and similarities with the Ni, Mn and Gd dopants are analysed. Possibility of formation of the excitons bound to the doping d-ions was shown. In contrast to this, it was observed that f-elements do not bound excitons, but prevent formation of excitons bound to some uncontrolled impurities. A mechanism of Cr doping impurity interaction with background impurities and zinc selenide structural defects was proposed based on experimental data. An assumption about resonant energy transfer between double charged chromium ions and complexes based on crystals’ vacancy defects was made. A correlation between emission and magnetic properties of the d- ions doped samples was established. Based on this correlation a mechanism explaining the concentration quench of the emission was proposed. It was found that f-ions bind electrically active shallow and deep donor and acceptor states of background impurity to electrically neutral complexes. This may be observed as “purification” of ZnSe crystals by doping with the rare-earth elements, resulting i tendency of the properties of f-ion doped crystals to the properties of intrinsic crystals, but with smaller concentration of uncontrolled native and impurity defects. A possible interpretation of this effect was proposed. It was shown that selenium substituting impurities decrease efficiency of the Yb doping. Based on this experimental results an attempt to determine ytterbium ion surroundings in the crystal lattice was made. It was shown that co-doping of zinc selenide crystals with the d- and f- ions leads to the combination of the impurities influence on the material’s properties. On the basis of obtained data an interaction mechanism of the d- and f-elements co-dopants was proposed. Guided by the model of the ytterbium ion incorporation in the selenide sublattice of the ZnSe crystals, an assumption about stabilization of single charged chromium ions in the zinc sublattice crystal nodes, by means of formation of the local charge compensating clusters, was made.