979 resultados para long-term change
Resumo:
We compared output from 3 dynamic process-based models (DMs: ECOSSE, MILLENNIA and the Durham Carbon Model) and 9 bioclimatic envelope models (BCEMs; including BBOG ensemble and PEATSTASH) ranging from simple threshold to semi-process-based models. Model simulations were run at 4 British peatland sites using historical climate data and climate projections under a medium (A1B) emissions scenario from the 11-RCM (regional climate model) ensemble underpinning UKCP09. The models showed that blanket peatlands are vulnerable to projected climate change; however, predictions varied between models as well as between sites. All BCEMs predicted a shift from presence to absence of a climate associated with blanket peat, where the sites with the lowest total annual precipitation were closest to the presence/absence threshold. DMs showed a more variable response. ECOSSE predicted a decline in net C sink and shift to net C source by the end of this century. The Durham Carbon Model predicted a smaller decline in the net C sink strength, but no shift to net C source. MILLENNIA predicted a slight overall increase in the net C sink. In contrast to the BCEM projections, the DMs predicted that the sites with coolest temperatures and greatest total annual precipitation showed the largest change in carbon sinks. In this model inter-comparison, the greatest variation in model output in response to climate change projections was not between the BCEMs and DMs but between the DMs themselves, because of different approaches to modelling soil organic matter pools and decomposition amongst other processes. The difference in the sign of the response has major implications for future climate feedbacks, climate policy and peatland management. Enhanced data collection, in particular monitoring peatland response to current change, would significantly improve model development and projections of future change.
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Recent paleoclimate studies provide strong evidence for an association between cosmogenic isotope production and Earth’s climate throughout the holecene. These isotopes are generated by the bombardment of Earth’s atmosphere by galactic cosmic rays, the fluxes of which vary in approximately inverse proportion to the total open magnetic flux of the Sun. This paper discusses how results from the Ulysses spacecraft allow us to quantify the open solar flux from observations of near-Earth interplanetary space and to study its long-term variations using the homogeneous record of geomagnetic activity. A study of the results and of their accuracy is presented. The two proposed mechanisms that could lead to the open solar flux being a good proxy for solar-induced climate change are discussed: the first is the modulation of the production of some types of cloud by the air ions produced by cosmic rays; the second is a variation in the total or spectral solar irradiance, in association with changes in the open flux. Some implications for our understanding of anthropogenic climate change are discussed.
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Recent studies of the variation of geomagnetic activity over the past 140 years have quantified the "coronal source" magnetic flux F-s that leaves the solar atmosphere and enters the heliosphere and have shown that it has risen, on average, by an estimated 34% since 1963 and by 140% since 1900. This variation of open solar flux has been reproduced by Solanki et al. [2000] using a model which demonstrates how the open flux accumulates and decays, depending on the rate of flux emergence in active regions and on the length of the solar cycle. We here use a new technique to evaluate solar cycle length and find that it does vary in association with the rate of change of F-s in the way predicted. The long-term variation of the rate of flux emergence is found to be very similar in form to that in F-s, which may offer a potential explanation of why F-s appears to be a useful proxy for extrapolating solar total irradiance back in time. We also find that most of the variation of cosmic ray fluxes incident on Earth is explained by the strength of the heliospheric field (quantified by F-s) and use observations of the abundance of the isotope Be-10 (produced by cosmic rays and deposited in ice sheets) to study the decrease in F-s during the Maunder minimum. The interior motions at the base of the convection zone, where the solar dynamo is probably located, have recently been revealed using the helioseismology technique and found to exhibit a 1.3-year oscillation. This periodicity is here reported in observations of the interplanetary magnetic field and geomagnetic activity but is only present after 1940, When present, it shows a strong 22-year variation, peaking near the maximum of even-numbered sunspot cycles and showing minima at the peaks of odd-numbered cycles. We discuss the implications of these long-term solar and heliospheric variations for Earth's environment.
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1. Species’ distributions are likely to be affected by a combination of environmental drivers. We used a data set of 11 million species occurrence records over the period 1970–2010 to assess changes in the frequency of occurrence of 673 macro-moth species in Great Britain. Groups of species with different predicted sensitivities showed divergent trends, which we interpret in the context of land-use and climatic changes. 2. A diversity of responses was revealed: 260 moth species declined significantly, whereas 160 increased significantly. Overall, frequencies of occurrence declined, mirroring trends in less species-rich, yet more intensively studied taxa. 3. Geographically widespread species, which were predicted to be more sensitive to land use than to climate change, declined significantly in southern Britain, where the cover of urban and arable land has increased. 4. Moths associated with low nitrogen and open environments (based on their larval host plant characteristics) declined most strongly, which is also consistent with a land-use change explanation. 5. Some moths that reach their northern (leading edge) range limit in southern Britain increased, whereas species restricted to northern Britain (trailing edge) declined significantly, consistent with a climate change explanation. 6. Not all species of a given type behaved similarly, suggesting that complex interactions between species’ attributes and different combinations of environmental drivers determine frequency of occurrence changes. 7. Synthesis and applications. Our findings are consistent with large-scale responses to climatic and land-use changes, with some species increasing and others decreasing. We suggest that land-use change (e.g. habitat loss, nitrogen deposition) and climate change are both major drivers of moth biodiversity change, acting independently and in combination. Importantly, the diverse responses revealed in this species-rich taxon show that multifaceted conservation strategies are needed to minimize negative biodiversity impacts of multiple environmental changes. We suggest that habitat protection, management and ecological restoration can mitigate combined impacts of land-use change and climate change by providing environments that are suitable for existing populations and also enable species to shift their ranges.
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The purpose of this work is to verify the stability of the relationship between real activity and interest rate spread. The test is based on Chen (1988) and Osorio and Galea (2006). The analysis is applied to Chile and the United States, from 1980 to 1999. In general, in both cases the relationship was statistically significant in early 80s, but a break point is found in both countries during that decades, suggesting that the relationship depends on the monetary rule follow by the Central Bank.
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The aim of this thesis was to evaluate historical change of the landscape of Madeira Island and to assess spatial and temporal vegetation dynamics. In current research diverse “retrospective techniques”, such as landscape repeat photography, dendrochronology, and research of historical records were used. These, combined with vegetation relevés, aimed to gather information about landscape change, disturbance history, and vegetation successional patterns. It was found that landscape change, throughout 125 years, was higher in the last five decades manly driven by farming abandonment, building growth and exotic vegetation coverage increase. Pristine vegetation was greatly destroyed since early settlement and by the end of the nineteenth century native vegetation was highly devastated due to recurrent antropogenic disturbances. These actions also helped to block plant succession and to modify floristical assemblages, affecting as well as species richness. In places with less hemeroby, although significant growth of vegetation of lower seral stages was detected, the vegetation of most mature stages headed towards unbalance between recovery and loss, being also very vulnerable to exotic species encroachment. Recovery by native vegetation also occurred in areas formerly occupied by exotic plants and agriculture but it was almost negligible. Vegetation recovery followed the successional model currently proposed, attesting the model itself. Yet, succession was slower than espected, due to lack of favourable conditions and to recurrent disturbances. Probable tempus of each seral stage was obtained by growth rates of woody taxa estimated through dendrochronology. The exotic trees which were the dominant trees in the past (Castanea sativa and Pinus pinaster) almost vanished. Eucalyptus globulus, the current main tree of the exotic forest is being replaced by other cover types as Acacia mearnsii. The latter, along with Arundo donax, Cytisus scoparius and Pittosporum undulatum are currently the exotic species with higher invasive behaviour. However, many other exotic species have also proved to be highly pervasive and came together with the ones referred above to prevent native vegetation regeneration, to diminish biological diversity, and to block early successional phases delaying native forest recovery.
Resumo:
Statement of the problem. In selecting a disinfectant for dental prostheses, compatibility between the disinfectant and the type of denture base material must be considered to avoid adverse effects on the hardness of the acrylic resin.Purpose. This study investigated the hardness of 2 denture base resins after disinfection and long-term water immersion.Material and methods. Thirty-two disk-shaped specimens (13 mm in diameter and 8 mm thick) were fabricated from each resin (Lucitone 550 and QC-20), polished, stored in water at 37degreesC for 48 hours, and submitted to hardness tests (Vickers hardness number [VHN]) before disinfection. Disinfection methods included scrubbing with 4% chlorhexidine gluconate for 1 minute, immersion for 10 minutes in I of the tested disinfectant Solutions (n=8) (3.78% sodium perborate, 4% chlorhexidine gluconate, or 1% sodium hypochorite), and immersion in water for 3 minutes. The disinfection procedures were repeated 4 times, and 12 hardness measurements were made on each specimen. Control specimens (not disinfected) were stored in water for 56 minutes. Hardness tests (VHN) were also performed after 15, 30, 60, 90, and 120 days of storage in water. Statistical analyses of data were conducted with a repeated measures 3-way analysis of variance (ANOVA) and Tukey post-hoc test (alpha=.05).Results. Mean values +/- SD for Lucitone 550 (16.52 +/- 0.94 VHN) and QC-20 (9.61 +/- 0.62 VHN) demonstrated a significant (P<.05) decrease in hardness after disinfection, regardless of material and disinfectant solutions used (Lucitone 550: 15.25 +/- 0.74; QC-20: 8.09 +/- 0.39). However, this effect was reversed after 15 days of storage in water. Both materials exhibited a continuous increase (P<.05) in hardness values for up to 60 days of water storage, after which no significant change was observed.Conclusion. Within the limitations of this in vitro study, QC-20 and Lucitone 550 specimens exhibited significantly lower hardness values after disinfection regardless of the disinfectant solution used.
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The activity of cytoplasmic and mitochondrial phosphoenolpyruvate carboxykinase (PEPCK) in kidney and liver, and in vivo gluconeogenic activity, were determined during different phases of prolonged fasting in quails. The fasting-induced changes in the activity of kidney cytoplasmic PEPCK were positively correlated with the changes in gluconeogenesis. Both activities increased at the initial phase (I) of fasting to levels 65% to 100% higher than fed values, and decreased during the protein-sparing period (phase II), although remaining higher than in fed birds. At the catabolic final phase (III) both kidney cytoplasmic PEPCK activity and gluconeogenesis increased markedly, attaining levels 115% to 150% higher than fed values. The activity of liver cytoplasmic PEPCK, present in appreciable amounts in quails, did not change during phases I and II of fasting, but increased to levels 60% higher than fed values at the final phase (III). Plasma glucose levels at phase III did not differ significantly from those at phases I and II. In both kidney and liver the activity of the mitochondrial PEPCK was not significantly affected by fasting. The data suggest that the kidney cytoplasmic PEPCK is the main enzyme responsible for gluconeogenesis adjustments during food deprivation in quails, and that this function is complemented at the final phase by enzyme present in liver cytosol.
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1. The aim of the present study was to examine the effects of long-term nitric oxide (NO) blockade on contractions of the rat ileum induced by muscarinic agonists.2. Male Wistar rats received the NO synthesis inhibitor N (G) -nitro-l-arginine methyl ester (l-NAME; 20 mg/rat per day) in drinking water for 7, 15, 30 and 60 days. Concentration-responses curves to methacholine and carbachol were obtained and pEC(50) values were calculated. Saturation binding assays were performed in membranes prepared from rat ileum after 60 days of l-NAME treatment and the dissociation constant (K-D ) and maximal number of binding sites (B-max ) were determined by Scatchard analysis.3. The NO synthase activity of the ileum was markedly reduced in all l-NAME-treated groups. At 60 days after l-NAME treatment, a significant increase in the potency of methacholine (fourfold) and carbachol (threefold) was observed. In binding studies, we found a significant increase in B-max for [(3) H]-quinuclidinyl benzilate of approximately 57% in the l-NAME treated group without any significant change in K-D values. The contractile response to methacholine was not modified by the soluble guanylate cyclase inhibitor 1H-[1,2,4]oxadiazolo-[4,3-a]quinoxalin-1-one (3 mumol/L). No morphological alterations in the rat ileum were observed in l-NAME-treated rats.4. Our findings suggest that treatment with l-NAME for 60 days induces a marked increase in the potency of methacholine and carbachol, as well as an increase in receptor number in the rat ileum.
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Groups of Wistar rats were fed with ration doped with uranyl nitrate at concentration A ranging from 0.5 to 100 ppm, starting after the weaning period and lasting until the postpuberty period when the animals were sacrificed. Uranium in the ashes of bones was determined by neutron activation analysis. It was found that the uranium concentration in the bones. as a function of A, exhibits a change in its slope at similar to20 ppm-a probable consequence of the malfunctioning of kidneys. The uranium transfer coefficient was obtained and an analytical expression was fitted into the data. thus allowing extrapolation down to low doses. Internal and localized doses were calculated. Absorbed doses exceeded the critical dose. even for the lowest uranium dosage.
Resumo:
1. To study the long term course of passive Heymann nephritis (PHN), 42 adult male Wistar rats were injected with rabbit anti-FX1A serum (PHN group) and 42 rats received normal rabbit serum (control group). Two animals from each group were sacrificed 2 weeks after the inoculation and 10 animals each from the control and PHN groups were sacrificed 4, 13, 25 and 53 weeks later.2. The PHN group exhibited a significant elevation in 20-h proteinuria which lasted from the first week (control group, 9.19 +/- 0.87; PHN group, 25.3 +/- 2.66) to the 25th week (control group, 22.6 +/- 2.15; PHN group, 66.7 +/- 10.4) except for week 17. From week 29 to week 53 there was no statistical difference between the 2 groups.3. Light microscopy showed no difference between the kidneys of PHN and control rats. Immunofluorescence microscopy in PHN rats showed granular deposition of autologous and heterologous IgG on the glomerular basement membrane (GBM), whose intensity and pattern did not change during 53 weeks of observation.4. When examined by electron microscopy the glomeruli of PHN rats showed: a) electron-dense deposits which were initially subepithelial and homogeneous and later intramembranous, granular and often surrounded by an electron-transparent halo; b) focal thickening of the GBM at the sites of intramembranous deposits; c) effacement of podocytes located close to the deposits; d) penetration of the podocytes into the GBM associated with the deposits; e) presence of osmiophilic granules in the cytoplasm of the podocyte located inside the GBM similar to the granules of the deposits next to them. The association of the penetration of the podocytes into the GBM with the deposits and the presence of the osmiophilic granules inside the foot process have not been described previously in PHN.5. The results suggest that the podocytes play a role in the clearing of intramembranous deposits in PHN.
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The present study aimed to estimate the prevalence of elderly using potentially inappropriate medications (PIM) and with occurrence of potentially hazardous drug interactions (PHDI), to identify the risk factors for the prescription of PIM and to evaluate the impact of pharmaceutical intervention (PI) for the prescription of safer therapeutic alternatives. Therefore, a cross-sectional study was performed in a long-term care facility in São Paulo State, between December/2010 and January/2011. The medical records of the patients >= 60 years old who took any drugs were consulted to assess the pharmacotherapeutic safety of the medical prescriptions, in order to identify PIM and PHDI, according to the Beers (2003) and World Health Organization criteria, respectively. PI consisted of a guidance letter to the physician responsible for the institution, with the suggestions of safer equivalent therapeutics. Approximately 88% of the elderly took at least one drug, and for 30% of them the PIM had been prescribed. Most of the PIM identified (53.4%) act on the central nervous system. Among the 13 different DI detected, 6 are considered PHDI. Polypharmacy was detected as a risk factor for PIM prescription. After the PI there was no change in medical prescriptions of patients who had been prescribed PIM or PHDI. The data suggests that PI performed by letter, as the only interventional, method was ineffective. To contribute it a wide dissemination of PIM and PHDI among prescriber professionals is necessary for the selection of safer treatment for elderly. Additionally, a pharmacist should be part of the health care team in order to help promote rational use of medicines.
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Starvation is a physiologic stress and can significantly alter the structure of hepatic cells. This work aims to detect morphological changes in mice hepatocyte under starvation physiologic stress, based on silver staining technique. Fourteen 21 day old male mice (Mus musculus) were used, 5 as control, 5 submitted to 72 hours of starvation, and 4 were refed during 72 hours after 72 hours of starvation. After liver imprint, 15 nuclei per mouse and their respective nucleoli were outlined in millimetric paper and their areas were obtained. The results, in mm2, were transformed into μm2. The number of nucleoli per nuclei were also counted. After starvation, a statistically significant rise in nuclear and nucleolar areas occurred and no significant increase in the number of nucleoli was observed. The refeeding caused a partial recovery of the nuclear area, no significant change in the nucleolar area and a statistically significant increase in the number of nucleoli. Therefore, starvation can be considered as a modifier agent of the chromatinic structure, leading to an increase of the nuclear and nucleolar areas probably due to an increment of RNA and protein synthesis. The recovery of the stress (refeeding) did not presented a decrease of nucleolar area and evidenced a nucleoli fragmentation, probably to increase more the protein synthesis and/or due to its cycle during the interphase.
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The combined periodontalrestorative approach (that is, a connective tissue graft for root coverage and NCCL restoration with RMGI cement) has demonstrated significant root coverage and a good esthetic outcome. In some cases, though, the color of an RMGI restoration can change over time, compromising esthetics. In this situation, applying composite resin over an RMGI restoration can be a conservative approach to satisfy the patient's esthetic complaint. Long-term observation is necessary to evaluate the stability of the results and establish the success of this approach over time.
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Sacroiliac joint (SIJ) pain is responsible for up to 40% of all cases of lumbar back pain. Objective Report the long-term efficacy of radiofrequency denervation for sacroiliac joint pain at six, twelve and eighteen months. Method Third-two adults’ patients with sacroiliac join pain diagnosis were included for a prospective study. Primary outcome measure was pain intensity on the Numeric Rating Scale (NRS). Secondary outcome measure was Patient Global Impression of Change Scale (PGIC). Results Short-term pain relief was observed, with the mean NRS pain score decreasing from 7.7 ± 1.8 at baseline to 2.8 ± 1.2 at one month and to 3.1 ± 1.9 at six months post-procedure (p < 0.001). Long-term pain relief was sustained at twelve and eighteen months post-procedure, with NRS pain remaining at 3.4 ± 2.1 and 4.0 ± 2.7, respectively. Conclusion Radiofrequency denervation of the SIJ can significantly reduce pain in selected patients with sacroiliac syndrome.