Decrease In Isc Research Articles

Gasotransmitters do not prevent changes in transepithelial ion transport induced by hypoxia followed by reoxygenation.

How gaseous signalling molecules affect ion transport processes contributing to the physiological functions of the gastrointestinal tract under hypoxic conditions still needs to be clarified. The objective of the present study was to characterize the impact of gaseous signalling molecules on parameters of colonic ion transport during a hypoxia/reoxygenation cycle and the remaining secretory capacity of the epithelium after such a cycle. Short-circuit current (Isc) and tissue conductance (Gt) recordings in Ussing chamber experiments were performed on rat colon samples using CORM-2 (putative CO donor; 35 and 350 µM), sodium nitroprusside (NO donor; 100 µM), NaHS (fast H2S donor; 10- 1,000 µM), GYY 4137 (slowH2S donor; 50 µM) and Angeli's salt (HNO donor; 100 µM) as donors for gasotransmitters. Inhibition of endogenous synthesis of H2S was operated by inhibitors of cystathionin-γ-lyase, i.e.dl-propargylglycine (1 mM) or β-cyano-l-alanine (5 mM), and the inhibitor of cystathionine-β-synthase, amino-oxyacetate (5 mM). The fast gasotransmitter donors NaHS, sodium nitroprusside and Angeli's salt, administered 5 min before the onset of hypoxia, induced an increase in Isc. The response to the subsequently applied hypoxia was characterized by a decrease in Isc, which tended to be reduced only in the presence of the lowest concentration of NaHS (10 µM) tested. Reoxygenation resulted in a slow increase in Isc, which was unaffected by all donors or inhibitors tested. The stable acetylcholine derivative carbachol (50 µM) was administered at the end of each hypoxia/reoxygenation cycle to test the secretory capacity of the epithelium. Pretreatment of thetissue with the putative CO donor CORM-2 suppressed thesecretory response induced by carbachol. The same wasobserved when cystathionin-γ-lyase and cystathionin-γ-synthase were inhibited simultaneously. Under both conditions, Gt drastically increased suggesting an impaired tissue integrity. The present results demonstrate that none of the exogenous gasotransmitter releasing drugs significantly ameliorated the changes in epithelial ion transport during the hypoxia/reoxygenation cycle exvivo. In contrast, the putative CO donor CORM-2 exerted a toxic effect on the epithelium. The endogenous production of H2S, however, seems to have a protective effect on the mucosal integrity and the epithelial transport functions, which- when inhibited- leads to a loss of the secretory ability of the mucosa. This observation together with the trend for improvement observed with a low concentration of the H2S donor NaHS suggests a moderate protective role of low concentrations of H2S under hypoxic conditions.

Short Term Exposure of Sheep Tracheal Epithelium to Cigarette Smoke Extract Reduces ENaC Current: A Pilot Study.

Cigarette smoke has been shown to induce a phenotype in humans known as "acquired cystic fibrosis". This occurs because the cystic fibrosis transmembrane conductance regulator (CFTR) functions are impaired systemically due to the deleterious effects of smoke components. Elucidation of cigarette smoke effects on the tracheal epithelium is important. The aim of this study was to develop an ex vivo sheep tracheal model to investigate tracheal ion function. In this model, the epithelial sodium channel (ENaC) is inhibited after exposure to cigarette smoke extract (CSE) as a proof of principle. Tracheas were isolated from healthy sheep and the tracheal epithelium was surgically excised. Tissues were mounted in Ussing chambers and the short circuit current (Isc) was measured after incubation with 5% CSE in PBS or PBS alone for 30 min. The function of ENaC was investigated by the addition of amiloride (10-5M) apically. Western blot analysis was performed to assess differences in ENaC quantity after CSE exposure. Some specimens were stained with H&E for detection of histological alterations. The amiloride effect on normal epithelium led to a significant decrease in Isc [ΔI=33±5.92 μA/cm2; p<0.001 versus control experiments (ΔI=1.44±0.71 μA/cm2)]. After incubation with CSE, ENaC Isc was significantly reduced (ΔI=14.80±1.96 μA/cm2; p<0.001). No differences in αENaC expression were observed between CSE-exposed and normal tracheal epithelium. Histological images post CSE incubation revealed decreases in the height of the epithelium, with basal cell hyperplasia and loss of ciliated cells. Reduced ENaC inhibition by amiloride after CSE incubation could be due to alterations in the tracheal epithelium.

High Fat High Sugar Diet Reduces Small Intestinal Secretion by Sex-Dependent Mechanisms.

The goal of this study was to determine the influence of high-fat high-sugar diet (Western diet) on intestinal function and subsequently to determine if there were any beneficial effects of exercise, genistein (a naturally occurring phytoestrogen) or both, on the intestine. We measured transepithelial short circuit current (Isc), across freshly isolated segments of jejunum from male and female C57Bl/6J mice randomly assigned to one of the following groups for the 12-week study duration: high-fat high-sugar diet (HFS), HFS with genistein (Gen), HFS with exercise (Ex), or HFS with both genistein and exercise (Gen+Ex) and compared them to lean controls. Genistein concentration was 600 mg genistein/kg diet. Exercise comprised of moderate intensity treadmill running (150 min per week). At the completion of the study, segments of jejunum were frozen for western blot determination of key proteins involved in secretory and absorptive functions, as well as senescence. Intestinal morphology was assessed. Serum cytokine assays were performed. Basal Isc was significantly decreased (by 70%, P<0.05) in HFS females and males versus leans. This decrease was partially mitigated by exercise in both sexes. In females, the HFS-induced decrease in Isc was attributed to a significant loss of CLC2, NKCC1 and CFTR expression whereas in males this was due to a significant loss of Na/K-ATPase, KCa and NKCC1 expression (indicating sex-dependent mechanisms). Exercise mitigated most of the loss of Isc in both sexes. Our data suggested that A2BR levels were dysregulated in HFS fed mice and that concomitant treatment with Gen or Gen+Ex prevented this disruption in females only. Inflammatory state was associated with body weight changes. Our data suggests that the reduced basal jejunal Isc in HFS mice is attributed to sex-dependent mechanisms and while exercise partially mitigated this, it's mechanism of action was unclear. Improved understanding of Western diet induced intestinal dysfunctions may allow for the development of novel drug targets to treat gastrointestinal disturbances in diabetic obesity.

High fat-high sugar diet induces sex-dependent effects on the small intestine

Background: Metabolic syndrome includes a plethora of symptoms ultimately leading to obesity and type 2 diabetes. Obesity has been linked to chronic gastrointestinal dysfunction (constipation, or diarrhea) and specifically females with high BMI have been associated with increased prevalence of diarrhea. We aimed to better understand the influence of high fat-high sugar diet (Western diet) on small intestinal function and to assess sex-dependent effects. Methods: We measured transepithelial short circuit current (Isc) a measure of chloride secretory function, across freshly isolated segments of jejunum from male and female C57Bl/6J mice fed a high fat high sugar diet (HFS) for 12 weeks, compared to lean controls. At the completion of the study, segments of jejunum were frozen for western blot determination of key proteins involved in secretory and absorptive functions and senescence. Intestinal morphology was assessed. Serum cytokine assays were performed. Results: Basal Isc was significantly decreased 70% ( P&lt;0.05) in HFS both females and males versus leans. In females, the HFS-induced decrease in Isc was attributed to a significant loss of CLC2, NKCC1 and CFTR expression whereas in males the decrease in Isc was due to a significant loss of Na/K-ATPase, KCa and NKCC1 expression (indicating interesting sex-dependent etiology). A2BR levels were also dysregulated in HFS fed male and female mice. Inflammatory state and shadowed body weight changes with feeding a western diet. Assessment of intestinal morphology and metabolic profile is being further evaluated. Conclusions: Our data suggests that the reduced basal jejunal Isc in HFS mice is attributed to sex-dependent mechanisms. Improved understanding of Western diet-induced intestinal dysfunctions may provide improved drug targets to treat gastrointestinal disturbances in obesity and diabetes. Midwestern Arizona Alzheimer’s Consortium and Diabetes Action Research and Education Foundation This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Soiling on PV performance influenced by weather parameters in Northern Nigeria

The photovoltaic device's economic and environmental merits have made it the most suitable clean energy alternative to help developing countries achieve the SDG-7. However, the low efficiency of the device, which is undergoing massive study across the globe, there is another omnipresent factor, such as surface soiling that has a deleterious effect on a solar cell's performance, which is influenced by wind speed/direction, humidity and temperature. This study investigates the impact of dust on four PV types (Monocrystalline Silicon, Polycrystalline Silicon, Cadmium Telluride and amorphous Silicon) in a city with two large commissioned and one massive solar farm under construction considering wind, humidity, rain, temperature and dust particles under extreme conditions. Low iron glass coupons were also exposed in seasonal, monthly, and annual categories to determine optical losses, soiling rates, and deposition mass. Accumulated dust particles on the surface of the coupon were subjected to SEM/EDX imaging to identify the deposited minerals' morphology. The findings reveal a massive performance decline due to soiling on all exposed modules with a most significant ISC decrease recorded about 73% on a-Si and least about 65% of the Si modules in one year without cleaning and a total of seventeen months exposure. The outcome shows significant losses recorded, where a yield loss of 78.3% and efficiencies decline of 78% for amorphous Si, 77% and 77% for cadmium telluride, 70% and 71% for polycrystalline and 68.6% and 71% for the monocrystalline Si module. A wide variation of performance losses was recorded between months and seasons in 2021, and the dry season presented the most alarming rates. The optical loss results validated the above output performance losses with a similar trend. The particle characterisation reveals that mineral particles > PM10 size with opaque and translucent morphology were the main constituent of dust formation on the examined coupons. It is recommended to study various mitigation techniques and use the correct one in an optimal cycle, which is cost-effective, which could restore and maintain the installation's optimal efficiency.

The investigation of PV systems quantum efficiency in various irradiation condition

We confirm the importance of the angle of incidence of direct solar radiation on external quantum efficiency of solar mini-modules consisting of the following closed structure: silicon solar cells with antireflective coating (Si + ARC1)/EVA (ethylene–vinyl acetate) foil /glass with or without antireflective coating (ARC2). The results are consistent with a proposed model of an optical module with a specific architecture.A study of the electrical parameters of photovoltaic modules as a function of the angle of incidence of radiation was carried out using a solar class AAAA simulator. The changes in short circuit current Isc were calculated relative to Isc for the module fully illuminated by light perpendicular to the surface. A decrease in Isc was recorded for modules containing textured glass or Flat glass. The use of antireflective coating ARC2 on glass in module structure increases external quantum efficiency and photogeneration current under AM1.5 global spectrum at 1000 W/m2 light intensity at temperature 25 °C, mainly for the angle of incidence of 35°.

Potential‐induced degradation in photovoltaic modules composed of interdigitated back contact solar cells in photovoltaic systems under actual operating conditions

AbstractPolarization‐type potential‐induced degradation (PID‐p) of photovoltaic (PV) modules composed of n‐type interdigitated back contact (IBC) solar cells can decrease the performance of the PV modules under positive potential conditions. The purpose of this study is to observe and describe the reduction and stabilization of the electrical performance of every PV module installed in an operating PV system with the progress of the PID‐p over a time duration of 6 years. The direct current circuit of the investigated PV system is not grounded. Therefore, all the PV strings are under floating potential conditions. The results show that the performance of the n‐type IBC PV modules exhibits a two‐step degradation. In the first step of degradation, the PV performance at positive potential decreases with increasing the PV module potential, whereas the PV modules at negative potential show little performance degradation. The PV performance reduction due to PID‐p is mainly caused by the decreases in both open‐circuit voltage (VOC) and short circuit current (ISC). A PV performance reduction, which principally arises from the decrease in ISC, is observed at every PV module in the PV strings regardless of the PV module potential in the second step of degradation. Therefore, solar cell manufacturers who produce n‐type IBC, as well as those producing passivated emitters and rear totally diffused solar cells, are advised that processes to prevent the PID‐p are required.

Hypoxia attenuate ionic transport in the isolated gill epithelium of Carcinus maenas.

The gills are osmorespiratory organs of aquatic organisms and the prime target of environmentally induced hypoxia. We have studied the impact of severe hypoxia (0.5mg O2/L) on the ionic transport across posterior gills of Carcinus maenas acclimated to 12ppt seawater (DSW). The short-circuit current (Isc) across hemilamellae from gills i.e. active ion transport was studied in micro Ussing chambers. Hypoxia induced by deoxygenation of the basolateral side, and not the apical side, resulted in time-dependent inhibition of Isc and full recovery of Isc after reoxygenation. Exposure of the crabs to severe 7h hypoxia decreased the specific activity of Na+,K+-ATPase in the gills by 36%. Full recovery of enzyme activity occurred in fasted crabs after 3days of reoxygenation. The intensity of Western blotting bands was not different in the gills of oxygenated, hypoxic and reoxygenated crabs. The reversible, nonspecific blocker of K+ channels Cs and hypoxia inhibited over 90% of Isc which is after reoxygenation fully recovered. The specific blocker of Cl- channels NPPB [5-nitro-2-(3-phenylpropylamino)benzoic acid] blocked Isc by 68.5%. Only the rest of not inhibited Isc in aerated saline was blocked by hypoxia and recovered after reoxygenation. The activity of the antioxidant enzyme catalase was not changed during hypoxia and reoxygenation kept the high enzyme activity in the gills at the level of crabs acclimated to DSW. As a response to hypoxia the presence of 2mM H2O2 induce an initial slight transient decrease of Isc followed by a rise and after reoxygenation fully recovered Isc. Incubation of hemilamellae with the antioxidant derivative Trolox did not affect the inhibition of Isc by hypoxia.

Chamomile decoction modulates water, neutral NaCl and electrogenic ionic exchange in mice intestinal epithelium

Diarrhea is one of the major public health problems. In this study, the role of the decoction extract of Tunisian chamomile (Matricaria recutita) in the modulation of gastrointestinal motility, its antisecretory effects as well as its part in the regulation of the net ion fluxes transported across the epithelium (mainly Na+ and Cl-) were studied. Chamomile decoction extract (CDE) significantly inhibited the intestinal motility and the gastric emptying in a dose-dependent manner. The physiological study also showed that CDE had a direct effect on short-circuits current (Isc) intensity using bumetanide. These results suggested that this decrease in Isc using CDE could be interpreted as a reduction in electrogenic Cl- secretion together with a stimulation of neutral NaCl absorption. CDE can also modulate the gastric and intestinal motilities as well as the intestinal epithelium transport of water and electrolytes. Hence, this study confirmed that CDE is a potential beverage, due to the high amount of biologically active compounds that can prevent digestive diseases as well as maintain intestinal comfort.

Study of a hybrid photovoltaic-photochemical technology for meeting the needs of safe drinking water and electricity in developing countries: First field trial in rural Mexico

Developing countries have vast areas and large population groups where access to electricity and safe drinking water is still limited or inexistent. In Mexico, 1.1 million people do not have access to electricity, while more than 3 million people lack access to clean water. However, Mexico presents one of the best locations to exploit solar sources. Therefore, off-grid photovoltaic (PV) systems and solar water disinfection (SODIS) are two promising options to develop rural electrification and to improve the coverage of drinking water access. In this regard, the technology proposed consists of a hybrid photovoltaic and solar disinfection system (SolWat) that comprises a photovoltaic module and a water disinfection reactor fully integrated into a single unit. Its effectiveness was tested for the first time in a rural community of Oaxaca (Mexico), on the basis of natural climatic conditions and available drinking water sources. Main results showed that despite the meteorological conditions were not the most favourable, the strong solar irradiation conditions of Mexico allowed complete inactivation of E. coli and total coliforms after 3 h of sun exposure. Furthermore, although the SolWat PV module presented a decrease in ISC, the refrigeration effect of the water being purified on top of the PV cells compensated this loss. In conclusion, the present work confirms the feasibility of the SolWat system to contribute to mitigate the lack of access to safe drinking water and energy in developing countries, since under real operation conditions it was able to simultaneously produce clean water and electricity.

The Impact of Air Mass on the Performance of a Monocrystalline Silicon Solar Module in Kakamega

This paper investigates the outdoor performance of a 20 W monocrystalline silicon solar module in relation to air mass (AM) in Kakamega. Direct measurement of air mass and module output parameters from experimental setup was done in Kakamega at a location 0.28270 N and 34.7519 E. Experimental results showed a decrease in ISC and VOC with increasing AM. The maximum output power produced by the module reduced with an increase in AM. Maximum power was therefore seen to be produced at noon in this region. VOC increased from 19.47 to 20.04 then decreased to 19.49 V while ISC increased from 0.36 to 1.19 then decreased to 0.48A. It was observed that both the FF and of a monocrystalline solar module increase with increase in air mass. The module performed better during the afternoon than morning and evening hours with the peak performance observed close to AM 1.

Regulation of the Pore-Forming Activity of Cecropin A by Local Anesthetics

The influence of local anesthetics on the regulation of the channel-forming activity of the antimicrobial peptide cecropin A has been investigated. The mean current flowing through the single cecropin channels isc was determined, and steady-state transmembrane current induced by cecropin AI∞ was measured. It has been shown that the introduction of 1 mM of bupivacaine, benzocaine or 0.3 mM of tetracaine into the membrane bathing solution results in a decrease in isc and I∞. At the same time, the addition of 1 mM lidocaine or procaine to the membrane-bathing solutions does not lead to a significant change in isc and I∞. Comparison of the absolute values and the sign of the change in the boundary potential of negatively charged membranes and relative changes of isc and I∞ after addition of local anesthetics shows that neither parameter correlates with the membrane boundary potential. The results of studying the effect of tested local anesthetics on the phase transition of membrane lipids allow us to conclude that the observed changes of isc and I∞ are due to modulation of the elastic properties of the membrane.

Bis-(p-hydroxyphenyl)-pyridyl-2-methane (BHPM)-the active metabolite of the laxatives bisacodyl and sodium picosulfate-enhances contractility and secretion in human intestine in vitro.

Stimulant laxatives are widely used to treat constipation. We investigated in human small and large intestinal preparations the effects of bis-(p-hydroxyphenyl)-pyridyl-2-methane (BHPM), the active metabolite of the laxatives bisacodyl and sodium picosulfate on smooth muscle tone and epithelial secretion. Circular and longitudinal muscle tone of small or large intestinal preparations were recorded with isometric force transducers. Epithelial ion flux (ISC ) and tissue resistance was measured with Ussing chamber technique after apical and basolateral BHPM application to large intestinal mucosa/submucosa preparations. Studies were performed in macroscopically normal specimens from 79 patients. BHPM concentration-dependently (0.5-5μM) increased the tone of circular and longitudinal muscle from small to large intestine. The effect was strongest in large intestinal longitudinal muscle and smallest in small intestinal circular muscle. Increase in muscle tone was prevented by the L-type Ca++ channel blocker nifedipine but insensitive to the nerve blocker tetrodotoxin. Apical or basolateral BHPM concentration-dependently decreased or increased ISC, respectively. The KCa 1.1 (BK) channel blocker iberiotoxin reversed apical ISC decrease whereas tetrodotoxin reversed basolateral ISC increase. BHPM had no effect on tissue resistance or nerve-mediated secretory or muscle response with one exception: at the highest concentration basolateral BHPM reduced nerve-mediated secretion. BHPM enhanced mucosal secretion and muscle contractility. Results suggested that the laxative effect of BHPM was a consequence of the increase in muscle tone as well as an increased K+ secretion when acting luminally and a nerve-driven Cl- and HCO3- secretion once acting basolaterally after absorption.

Permeation of acetate across sheep ruminal epithelium is partly mediated by an anion channel

The present study pursued the question if an anion channel could be partly responsible for the transport of acetate in the isolated ovine ruminal epithelium. Using the Ussing chamber technique, changes of short-circuit current (Isc) induced by mucosal or serosal addition of acetate was investigated. To further evaluate the Isc changes induced by acetate the epithelia were preincubated with ouabain or 4,4′-diisothiocyano-2,2′-stilbenedisulfonic acid (DIDS). In addition, unidirectional flux rates of 14C-acetate were measured at different transepithelial potential difference (Vt). At Vt=0mV, acetate addition to the mucosal side of epithelia incubated in ouabain/DIDS free solution resulted in an Isc decrease, whereas application to the serosal side induced an Isc increase. Absolute Isc changes were significantly larger after serosal than after mucosal acetate addition. Ouabain pre-incubation abolished these side-specific differences. Pre-incubation with DIDS on the mucosal side inhibited the current induced by subsequent mucosal acetate addition in a voltage dependent manner, whereas serosal DIDS pre-incubation had no effect on acetate-induced changes of Isc. Mucosal-to-serosal acetate flux was partly voltage-dependent. The serosal-to-mucosal flux of acetate was not influenced by Vt. The asymmetric changes of Isc after acetate application and the Vt dependence of the DIDS inhibition on the mucosal side indicate a partly electrogenic transcellular permeation of acetate which includes an apically located acetate conductance. It is suggested that this conductance may be important for epithelial cell homeostasis.

Hyperosmolarity evokes histamine release from ileum mucosa by stimulating a cholinergic pathway

Changes in extracellular osmolarity lead to alteration in cellular volume. In the study, we examined the effects of hyperosmolarity on short-circuit currents (Isc) in the rat ileum using the Ussing chamber technique. Mucosal exposure to 20 mM glucose evoked a decrease of ISC in the rat ileum, which was antagonized by the stretch-activated channel blocker GdCl3, TTX and atropine, respectively. In contrast, it was not blocked by phlorizin, a Na+-glucose cotransporter SGLT1 inhibitor. Furthermore, the unabsorbed substances, such as sucrose, lactulose or urea, also induced a decrease of ISC in rat ileum. ELISA results revealed that 20 mM glucose stimulated the release of histamine from rat ileum mucosa, which was attenuated by TTX. In addition, the glucose-induced ISC was depressed by pyrilamine, a histamine H1 receptor blocker (H1 antagonist) whereas it was not affected by ranitidine (H2 antagonist), clobenpropit (H3 antagonists) or JNJ7777120 (H4 antagonist), respectively. The ion substitution experiments suggest that the changes of Na+ and HCO3− ion flux underlie the glucose-induced ISC. In conclusion, osmotic stimulus decreased the basal ISC of rat ileum by evoking histamine release from ileum mucosa. The changes of Na+ and HCO3− ion transport are involved in the glucose-evoked decrease of basal ISC.

Nitric oxide inhibition of NaCl secretion in the opercular epithelium of seawater-acclimated killifish, Fundulus heteroclitus.

Nitric oxide (NO) modulates epithelial ion transport pathways in mammals, but this remains largely unexamined in fish. We explored the involvement of NO in controlling NaCl secretion by the opercular epithelium of seawater killifish using an Ussing chamber approach. Pharmacological agents were used to explore the mechanism(s) triggering NO action. A modified Biotin-switch technique was used to investigate S-nitrosation of proteins. Stimulation of endogenous NO production via the nitric oxide synthase (NOS) substrate l-arginine (2.0 mmol l-1), and addition of exogenous NO via the NO donor SNAP (10-6 to 10-4moll-1), decreased the epithelial short-circuit current (Isc). Inhibition of endogenous NO production by the NOS inhibitor l-NAME (10-4moll-1) increased Isc and revealed a tonic control of ion transport by NO in unstimulated opercular epithelia. The NO scavenger PTIO (10-5moll-1) supressed the NO-mediated decrease in Isc, and confirmed that the effect observed was elicited by release of NO. The effect of SNAP on Isc was abolished by inhibitors of the soluble guanylyl cyclase (sGC), ODQ (10-6moll-1) and Methylene Blue (10-4moll-1), revealing NO signalling via the sGC/cGMP pathway. Incubation of opercular epithelium and gill tissues with SNAP (10-4moll-1) led to S-nitrosation of proteins, including Na+/K+-ATPase. Blocking of NOS with l-NAME (10-6moll-1) or scavenging of NO with PTIO during hypotonic shock suggested an involvement of NO in the hypotonic-mediated decrease in Isc Yohimbine (10-4moll-1), an inhibitor of α2-adrenoceptors, did not block NO effects, suggesting that NO is not involved in the α-adrenergic control of NaCl secretion.

Effect of potassium iodide on luminescent and photovoltaic properties of organic solar cells P3HT-PCBM

It has been investigated spectral-luminescence properties of polymer films, doped with potassium iodide (KI). Using of KI didn't lead to the gradual changes of optical density of polymer films and the range of band gap semiconductor polymer P3HT. The fluorescence intensity of P3HT decreased and changed by use of KI. Using of 1% KI in polymer leaded to decrease of fluorescence lifetime. Influence of heavy atom on photovoltaic effect of organic solar cells has been investigated. 1% of KI in polymer film leaded to decrease of Isc and slightly decrease of Uoc. Investigation shows that magnetic field does not affect on photovoltaic properties of cells P3HT-PCBM. Magnetic field increased of open circuit voltage and short circuit current of solar cells with 1% of KI. Study of electrical impedance of cells revealed the magnetic sensivity of solar cells with KI additives. The lifetime of free charge carriers increased in the magnetic field for solar cells with KI additives.

Performance Degradation of Various PV Module Technologies in Tropical Singapore

The performance of ten photovoltaic (PV) modules with nine different solar cell technologies (and one different module construction) is monitored in the tropical climate of Singapore. The types of modules included in this study are monocrystalline Si (glass-backsheet with frame and glass-glass without frame), heterojunction crystalline Si, monocrystalline Si back-contact, multicrystalline Si, double-junction “micromorph” Si, single-junction/double-junction amorphous Si, CdTe, and CIGS. Three years of outdoor monitoring data are used to extract degradation trends of the performance of the various modules. Statistical decomposition methods are used to extract trends for performance ratio (PR), short-circuit current (I SC ), open-circuit voltage (V OC ), and fill factor (FF). The degradation rates of the monocrystalline Si modules are found to be equal to or less than -0.8% per year, mainly contributed by the decrease in I SC . The multicrystalline Si module shows a slightly higher degradation rate of -1.0% per year. The amorphous Si, micromorph Si, and CdTe modules show degradation rates of around -2% per year. The CIGS module showed an exceptionally high degradation rate of -6% per year. The decrease in FF and VOC is found to be significant for all the thin-film modules but not for the crystalline silicon modules.

Cold acclimation of NaCl secretion in a eurythermic teleost: Mitochondrial function and gill remodeling

Active chloride secretion, measured as short-circuit current (Isc) in ionocytes of opercular epithelia (OE) in the eurythermic, euryoxic, and euryhaline killifish or mummichog (Fundulus heteroclitus) was studied in cold (5°C) and warm (20°C) acclimated fish to determine if homeoviscous adaptation aided chloride secretion in the cold. Isolated opercular epithelia were cooled from 30°C to 0.2°C for warm and cold acclimated fish; from 30 to 8°C, Isc decreased with Q10=1.68 for warm and Q10=1.56 for cold acclimated tissues. By Arrhenius plots, there is a critical temperature, 8°C, below which aerobic Isc decreased sharply (Q10=6.90 for warm and 4.23 for cold acclimated tissues), suggesting a shift in mitochondrial efficiency of oxidative phosphorylation. In anaerobic conditions (0.5mM NaCN; N2 saturation), chloride transport continued at a lower rate, and Isc decrease with cooling below 8°C was less pronounced (Q10=2.95 for warm and 3.08 for cold), suggesting a shift in transporter function in plasma membrane. Under anaerobic conditions, NaCl secretion at 20°C was reversibly inhibited by hypotonic shock, indicating normal regulation of transport. Chloride secretion in warm-acclimated fish was supported mostly (75% at 20°C) by aerobic metabolism, whereas that for cold-acclimated fish was lower (55% at 20°C), suggesting a greater reliance on anaerobic metabolism in the cold. Once acclimated to cold, ionocytes may be temporarily incapable of increasing their aerobic ATP supply, even when warmed to 30°C. In cold acclimated fish there was increased polyunsaturated fatty acid composition of gill epithelium (consistent with homeoviscous adaptation) and gill remodeling, wherein epithelial cells filled the interlamellar space (interlamellar cell mass, ILCM) by as much as 70%, thus increasing diffusion distance against passive ion gain. Most ionocytes in these thickened epithelial masses became taller, still connecting basal lamina with the environment, consistent with the continuing transport rates at low temperatures. Whereas the low aerobic scope of cold-acclimated fish and thickened gill epithelium is appropriate to winter inactivity, metabolic depression and anaerobiosis, the large aerobic scope of warm-acclimated fish favors active foraging at high temperatures.

Effects of non-steroidal estrogen diethylstilbestrol on pH and ion transport in the mantle epithelium of a bivalve Anodonta cygnea

Freshwater bivalves are used as sentinel organisms to detect pollutants effects in the aquatic environment due to their sedentary nature, filter-feeding behaviour. We aimed to determine the in vivo, ex vivo and in vitro influence of Diethylstilbestrol (DES), a widely used synthetic non-steroidal estrogen and endocrine disruptor, in Anodonta cygnea shell growth mechanisms. For that, in vivo exposure to DES (0.75μM) during 15 days, in vitro and ex vivo exposure of outer mantle epithelium (OME) cells to DES (0.75μM), were performed followed by study of short-circuit current (Isc), transepithelial potential (Vt) and transepithelial conductance (Gt) as well as identification of membrane transport systems and intracellular pH (pHi). Our results show that in vivo exposure to DES decreases in 30% the OME Isc and ex vivo addition of DES to the basolateral side of OME also induced Isc decrease. Several membrane transporters such as V-type ATPases, Na+/H+ exchangers, Na+–K+ pump, Na+-driven and Na+-independent HCO3−/Cl− transporters and Na+/HCO3− co-transporter were identified as responsible for pHi maintenance in OME and noteworthy, DES caused a pHi decrease in OME cells similar to the effect observed when OME cells were exposed to 4,4′-diisothiocyanostilbene disulfonic acid (DIDS), an inhibitor of several bicarbonate membrane transporters. The addition of DIDS after OME cells exposure to DES did not cause any alteration. We concluded that DES is able to modulate membrane ion transport and pHi in the OME of A. cygnea and that this effect seems to be due to inhibition of HCO3−/Cl− co-transporters present on the basolateral membrane.