Ozone (O3) soundings have been performed on Easter Island or Rapa Nui (27 8S, 109 8W, 51 m a.s.l.) since 1994 as part of the Global Atmospheric Watch Programme of the World Meteorological ...Organization. In this work, we analyze 260 soundings compiled over the period 19942014, and make the data available for the international community. We characterize O3 profiles over this remote area of the Pacific by means of statistical analyses that consider, on the one hand, a traditional climatology that describes the data in terms of seasonal cycles based on monthly averages and, on the other hand, a process-oriented analysis based on self-organizing maps. Our analyses show the influence of both tropical and subtropical/mid-latitude air masses at Rapa Nui. The former occurs in summer and fall when convective conditions prevail, and the latter in late winter and spring when subsiding conditions are recurrent. The occurrence of stratospheric intrusions in late winter and spring in connection with deep troughs and the presence of the subtropical jet stream is also apparent in the data set. The tropospheric ozone column is in good agreement with the corresponding data derived from satellites but with a systematic overestimate of summer and fall values. There is evidence of an upward trend in ozone near the surface, which suggests the impact of local pollution. We look forward to an enhancement of the Rapa Nui observing site, given its location that offers a privileged position to observe climate change over the sparsely sampled and vast South Pacific Ocean.
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 2009.
Cataloged from PDF version of thesis.
Includes bibliographical references (p. ...133-142).
In this thesis, we study observationally the variation of upper level cloud fraction with sea surface temperature in tropical oceanic regions. We also explore the consequences of a cloud feedback, arising from variations in the coverage of thin upper level clouds, in the climate of the Archean using a simple radiative-convective model that includes the effect of the variations in the area of thin cirrus clouds. First, we look at the variation in area of upper level clouds using TRMM VIRS (Tropical Rainfall Measuring Mission, Visible Infrared Sounder) data. We quantify the effect of methodological choices on the magnitude of the observed correlations between upper level cloud cover and SST. We discuss several methodological choices that might contribute to the relatively small signals found by previous researchers (- 0%/K to 2%/K) , namely, the classification of cloudy regions into convective updrafts and anvil, the use of cloud weighted SST, and the truncation and sampling error with respect to the evolution of mesoscale convective systems. All of these contribute to some extent to the weakness of signal. We show that the coarse sampling of orbital satellites can introduce biases in the estimation of the signal. Our observational evidence shows a negative correlation between the upper level cloud fraction normalized by convection and sea surface temperatures. We also study the relation between local sea surface temperature (SST) and convective precipitation fraction and stratiform rainfall area from radar observations of precipitation, using data from the Kwajalein atoll ground-based radar as well as the precipitation radar on board of the Tropical Rainfall Measurement Mission (TRMM satellite).
(cont.) We find that the fraction of convective precipitation increases with SST at a rate of about 6 to 12%/K and the area of stratiform rainfall normalized by total precipitation decreases with SST at rates between -5 to -28%/K. These relations are observed to hold for different regions over the tropical oceans and also for different periods of time. Correlations are robust to outliers and to undersampled precipitation regions. Kwajalein results are relatively insensitive to the parameters in the stratiform-convective classification algorithm. Quantitative differences between the results obtained using the two different radars could be explained by the smoothing in the reflectivity of convective regions due to the relatively large pixel size of the TRMM precipitation radar compared to the size of the convective clouds. We discuss how this observations can be interpreted as an increase in the efficiency of precipitation with temperature in mesoscale convective systems in the tropics. Finally, we explore the consequences of a negative feedback mediated through tropical cirrus clouds in the climate of the Archean, and the possibility that this feedback could explain the so-called faint young sun paradox. We assume that rates of change in the area of detrainment cloud (from the observational estimates) are characteristic also for thin cirrus clouds that have a net positive cloud radiative forcing. We find that global mean surface temperatures above freezing can indeed be found for luminosities larger than about 0.8 (corresponding to - 2.9 Ga and nearly complete tropical cirrus coverage).
(cont.) For luminosities smaller than 0.8, even though global mean surface temperatures are below freezing, tropical mean temperatures are still above freezing, indicating the possibility of a partially ice-free earth for the Early Archean. While it is feasible for tropical cirrus to completely eliminate the paradox, it is similarly possible for tropical cirrus to reduce the amounts of other greenhouse gases needed for solving the paradox and therefore easing the constraints on CO 2 and CH4 that appear to be in disagreement with geological evidence.
by Roberto F. Rondanelli.
Ph.D.
Mesoscale Wind Regimes in Chile at 30°S Kalthoff, Norbert; Bischoff-Gauß, Inge; Fiebig-Wittmaack, Melitta ...
Journal of applied meteorology,
09/2002, Letnik:
41, Številka:
9
Journal Article
Odprti dostop
In November of 1999, four permanent surface stations were installed in the vicinity of the surface ozone monitoring station on the summit of the Cerro Tololo (2200 m MSL) in Chile at 30°S. These ...stations were used to study the atmospheric flow conditions, which are important for the interpretation of the ozone measurements at Cerro Tololo. In addition, radiosonde ascents were performed in March of 2000 near the coast and about 60 km inland. Different wind regimes were distinguished. Above 4 km MSL, large-scale westerly winds prevailed, while northerly winds were observed in a band along the coastline between 2- and 4-km-MSL height. The upper boundary of the northerly wind regime corresponded to the mean height of the Andes mountain range. This wind regime resulted from the westerly winds being blocked and forced to flow in parallel to the Andes (when Froude number is less than 1). The phenomenon was also confirmed by model simulations. Seasonally varying, thermally induced valley winds and a sea breeze developed below the northerly wind regime. In summer, the valley winds reached the Cerro Tololo. Diurnal variation of the top boundary of the valley winds also influenced the lower boundary of the northerly wind regime, which was less than 2 km MSL during the night and greater than 2 km MSL during the day. Thus, this observational and modeling study has shown that in summer the baseline ozone monitoring site at Cerro Tololo can be contaminated by polluted air that is transported from the plains by the thermally induced wind systems.
Sarcopenia has been recognized as a muscle disease, with adverse consequences on health. Updated recommendations, aimed at increasing awareness of sarcopenia and its accompanying risks, have been ...produced to urge the early detection and treatment of this disease. Recommended treatment is based on an individually tailored resistance exercise training program, the optimization of protein intake using high-quality protein sources (i.e., whey protein) in order to provide a high amount of essential amino acids-particularly leucine-and addressing vitamin D deficiency/insufficiency. The purpose of this review is to collate and describe all of the relevant efficacy studies carried out with a muscle-targeted oral nutritional supplementation (MT-ONS)-namely a whey-protein-based, leucine- and vitamin D-enriched formula aimed at optimizing their intake and satisfying their requirements-in different patient populations and clinical settings in order to determine if there is enough evidence to recommend prescription for the treatment of sarcopenia or its prevention in high-risk patient populations. Trials using a MT-ONS with or without a concomitant physical exercise program were systematically searched (up to June 2021), and those addressing relevant endpoints (muscle mass, physical performance and function) were critically reviewed. In total, 10 articles providing efficacy data from eight trials were identified and narratively reviewed. As far as older patients with sarcopenia are concerned, MT-ONS has been pertinently tested in six clinical trials (duration 4-52 weeks), mostly using a high-quality randomized controlled trial design and demonstrating efficacy in increasing the muscle mass and strength, as well as the physical performance versus iso-caloric placebo or standard practice. Consistent results have been observed in various clinical settings (community, rehabilitation centers, care homes), with or without adjunctive physical exercise programs. A positive effect on markers of inflammation has also been shown. A muscle-protein-sparing effect, with benefits on physical performance and function, has also been demonstrated in patients at risk of losing skeletal muscle mass (three trials), such as older patients undergoing weight loss or intensive rehabilitation programs associated with neurological disability (Parkinson's disease). MT-ONS has demonstrated not only a significant efficacy in clinical variables, but also a positive impact on healthcare resource consumption in the rehabilitation setting (length of stay and duration of rehabilitation). In summary, MT-ONS, alone or in association with an appropriate exercise program, is an effective therapy for older patients with sarcopenia and should be offered as a first-line treatment, not only to improve clinical outcomes but also to reduce healthcare resource consumption, particularly in patients admitted to a rehabilitation center.
Interventions to attenuate the adverse effects of age-related loss of skeletal muscle and function include increased physical activity and nutritional supplementation.
This study tested the ...hypothesis that nutritional supplementation with whey protein (22 g), essential amino acids (10.9 g, including 4 g leucine), and vitamin D 2.5 μg (100 IU) concurrent with regular, controlled physical activity would increase fat-free mass, strength, physical function, and quality of life, and reduce the risk of malnutrition in sarcopenic elderly persons.
A total of 130 sarcopenic elderly people (53 men and 77 women; mean age: 80.3 y) participated in a 12-wk randomized, double-blind, placebo-controlled supplementation trial. All participants concurrently took part in a controlled physical activity program. We examined body composition with dual-energy X-ray absorptiometry, muscle strength with a handgrip dynamometer, and blood biochemical indexes of nutritional and health status, and evaluated global nutritional status, physical function, and quality of life before and after the 12 wk of intervention.
Compared with physical activity and placebo, supplementation plus physical activity increased fat-free mass (1.7-kg gain, P < 0.001), relative skeletal muscle mass (P = 0.009), android distribution of fat (P = 0.021), handgrip strength (P = 0.001), standardized summary scores for physical components (P = 0.030), activities of daily living (P = 0.001), mini nutritional assessment (P = 0.003), and insulin-like growth factor I (P = 0.002), and lowered C-reactive protein (P = 0.038).
Supplementation with whey protein, essential amino acids, and vitamin D, in conjunction with age-appropriate exercise, not only boosts fat-free mass and strength but also enhances other aspects that contribute to well-being in sarcopenic elderly. This trial was registered at clinicaltrials.gov as NCT02402608.
Several studies have described a strong correlation between diet, weight loss, and gut microbiota composition. The aim of this review was to evaluate the potential effects of energy-restricted diets, ...namely very low calorie diets (VLCDs), very low calorie ketogenic diets (VLCKDs), and very low carbohydrate diets (VLCarbDs), on the composition of the gut microbiota in humans. We performed a literature search using the following terms (with their abbreviations or acronyms): "very low calorie diet", "very low calorie ketogenic diet", "very low carbohydrate diet", and "gut microbiota". Our search strategy retrieved nine eligible studies. Overall, VLCDs and VLCarbDs affected the Bacteroidetes to Firmicutes ratio in obese patients, leading to a reduction in short-chain fatty acid production by fecal microbiota associated with Clostridial cluster XIVa. This reduction particularly affected
and
, the two most abundant butyrate-producing bacteria in human feces. VLCKDs preserved the core fecal microbiome, but altered the composition of fecal microbial populations in relation to the plasma metabolome and fecal bile acid composition. In particular, VLCKD-induced weight loss resulted in a reduction in
and
, an increase in
and
while not all studies show a decrease in
. Although very few studies have analyzed the effects of VLCarbDs and VLCDs on gut microbiota, significant diet-induced changes in fecal microbiota composition have been observed. Further studies are needed.
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Antifreezing activity is a phenomenon of great significance in food industry that affects the quality of frozen foods. As a solution, ice-binding proteins, more specifically ...antifreeze proteins, have been used to mitigate recrystallization. However, knowledge about the mechanism of ice recrystallization and the influence of antifreeze proteins is scarce.
In this work, model homopeptides of three amino acids (proline, arginine and lysine) were studied by means of differential scanning calorimetry through the determination of their thermal hysteresis activity, to see the influence of several factors on their secondary structure. It was found that model homopeptides formed polyproline II type secondary structure that was more stable at low temperature. In addition, thermal hysteresis activity was higher for peptides of intermediate lengths and for proline homopeptides.
The study of homopeptides sheds light on the mechanism of antifreeze activity and will allow the design of new molecules with antifreeze properties to be used in diverse biotechnological fields.
How to cite: Rojas R, Aróstica M, Carvajal-Rondanelli P, et al. Relationship between type II polyproline helix secondary structure and thermal hysteresis activity of short homopeptides. Electron J Biotechnol 2022;59. https://doi.org/10.1016/j.ejbt.2022.08.003.
•The assessment of obese participants must consider the analysis of body composition.•Very low calorie ketogenic diet preserves the fat-free mass during weight loss.•Branched chain amino acids and ...whey protein are useful in maintaining fat-free mass.•The assessment of vitamin D blood concentration is required for obese patients.
The loss of fat-free mass (FFM) that occurs during weight loss secondary to low-calorie diet can lead to numerous and deleterious consequences. We performed a review to evaluate the state of the art on metabolic and nutritional correlates of loss of fat free mass during low calorie diet and treatment for maintaining fat free mass.
This review included 44 eligible studies. There are various diet strategies to maintain FFM during a low-calorie diet, including adoption of a very low carbohydrate ketogenic diet (VLCKD) and taking an adequate amount of specific nutrients (vitamin D, leucine, whey protein).
Regarding the numerous and various low-calorie diet proposals for achieving weight loss, the comparison of VLCKD with prudent low-calorie diet found that FFM was practically unaffected by VLCKD. There are numerous possible mechanisms for this, involving insulin and the insulin-like growth factor-1–growth hormone axis, which acts by stimulating protein synthesis.
Considering protein and amino acids intake, an adequate daily intake of leucine (4 g/d) and whey protein (20 g/d) is recommended. Regarding vitamin D, if the blood vitamin D has low values (<30 ng/mL), it is mandatory that adequate supplementation is provided, specifically calcifediol, because in the obese patient this form is recommended to avoid seizure in the adipose tissue; 3 to 4 drops/d or 20 to 30 drops/wk of calcifediol are generally adequate to restore normal 25(OH)D plasma levels in obese patients.
Knowledge of past environmental and climatic conditions of lake ecosystems on Chiloé Island on a millennial scale is limited. Hence, this study fills a gap in our understanding of this part of ...southern Chile. The aim of this study was to reconstruct the environmental and climatic history of the last 1000 years of Lake Pastahué through a multi-proxy sediment core analysis. The 1-m-long core was subsampled every centimeter for the organic matter, magnetic susceptibility, grain-size distribution, and biological indicator (pollen, chironomids) analyses. The age model was constructed from 210Pb, 137Cs, and 14C activity. Pollen results revealed a North Patagonian forest composition represented by Nothofagus, Weinmannia, Drimys, Tepualia, Myrtaceae, Poaceae, and Pteridophyta. The abundance of Rumex and Pinus in the most recent part of the pollen assemblage reflects a clear anthropogenic impact. The sedimentological parameters and chironomid assemblage show similar variations, which highlight changes in the trophic state of the lake. The changes observed in all proxies suggest the influence of climate events such as the ‘Medieval Climate Anomaly’ (MCA) and ‘Little Ice Age’ (LIA). The variations observed since the beginning of the 20th century could be the result of the combined effect of anthropogenic activities and the increase in temperature recorded in south-central Chile and Patagonia.
Emerging literature suggests that diet plays an important modulatory role in rheumatoid arthritis (RA) because diet is an environmental factor that affects inflammation, antigen presentation, ...antioxidant defense mechanisms and gut microbiota. Patients with RA frequently ask their doctors about which diets to follow, and even in the absence of advice from their physicians, many patients are undertaking various dietary interventions.
Given this background, the aim of this review is to evaluate the evidence to date regarding the ideal dietary approach for management of RA in order to reduce the counteracting inflammation, and to construct a food pyramid for patients with RA. The pyramid shows that carbohydrates should be consumed every day (3 portions of whole grains, preferably gluten free), together with fruits and vegetables (5 portions; among which fruit, berries and citrus fruit are to be preferred, and among the vegetables, green leafy ones.), light yogurt (125 ml), skim milk (200 ml), 1 glass (125 ml) of wine and extra virgin olive oil; weekly, fish (3 portions), white meat (3 portions), legumes (2 portions) eggs (2 portions), seasoned cheeses (2 portions), and red or processed meats (once a week). At the top of the pyramid, there are two pennants: one green means that subjects with RA need some personalized supplementation (vitamin D and omega 3) and one red means that there are some foods that are banned (salt and sugar). The food pyramid allows patients to easily figure out what to eat.
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