The biochemically important interconversion process between aldoses and ketoses is assumed to take place via 1,2‐enediol or 1,2‐enediolate intermediates, but such intermediates have never been ...isolated. The current work was undertaken in an attempt to detect the presence of the 1,2‐enediol structure of glycolaldehyde in alkaline medium, actually a 1,2‐enediolate, and to try to clarify the scarce data existing about both the formation of deprotonated enediol and the aldo‐enediolate equilibrium. The Raman spectra of neutral and basic solutions were recorded as a function of time for eleven days. Several bands associated with the presence of the enediolate were observed in alkaline medium. Glycolaldehyde exists as three different structures in aqueous solution at neutral pH, that is, hydrated aldehydes, aldehydes and dimers, with a respective ratio of approximately 4:0.25:1. Additionally, the formation of Z‐enediolate forms takes place at basic pH, together with an increase in the concentration of aldehyde species, such as 2‐oxoethan‐1‐olate, and a decrease in the concentrations of the hydrated aldehyde and dimeric forms. The theoretical ratio of ≈1.5:1 for aldehyde:Z‐enediolate reproduces the experimental Raman spectrum in basic medium, with an additional contribution of the previously mentioned ratio between the hydrated aldehyde and dimeric forms. Finally, Raman spectroscopy allowed us to monitor the enolization of this carbohydrate model and conclude that aldo‐enediol tautomerism—formally aldo‐enediolate—happens when a suitable amount of basic species is added.
The Raman spectra of neutral and basic solutions of glycolaldehyde are recorded as a function of time. Three different structures are present in neutral aqueous solution (i.e. hydrated aldehydes, aldehydes, and dimers) whereas Z‐enediolate forms are observed at basic pH, together with an increase in the concentration of aldehyde species and a decrease in the concentrations of the hydrated aldehyde and dimeric forms.
In this study we analyzed the spatial distribution, temporal variability and trends in reference evapotranspiration (ET0) in Spain from 1961 to 2011. Twelve methods were analyzed to quantify ET0 from ...quality controlled and homogeneous series of various meteorological variables measured at 46 meteorological stations. Some of the models used are temperature based (e.g., Thornthwaite, Hargreaves, Linacre), whereas others are more complex and require more meteorological variables for calculation (e.g., Priestley–Taylor, Papadakis, FAO–Blaney–Criddle). The Penman–Monteith equation was used as a reference to quantify ET0, and for comparison among the other methods applied in the study. No major differences in the spatial distribution of the average ET0 were evident among the various methods. At annual and seasonal scales some of the ET0 methods requiring only temperature data for calculation provided better results than more complex methods requiring more variables. Among them the Hargreaves (HG) equation provided the best results, at both the annual and seasonal scales. The analysis of the temporal variability and trends in the magnitude of ET0 indicated that all methods show a marked increase in ET0 at the seasonal and annual time scales. Nevertheless, results obtained suggested substantial uncertainties among the methods assessed to determine ET0 changes, due to differences in temporal variability of the resulting time series, but mainly for the differences in the magnitude of change of ET0 and its spatial distribution. This suggests that ET0 trends obtained by means of methods that only require temperature data for ET0 calculations should be evaluated carefully under the current global warming scenario.
•Methods having limited data requirements were found to be highly reliable in reproducing average ET0 values.•A general positive increase in ET0 is observed in Spain using various methods.•Analysis of the magnitude of change in ET0 suggested substantial uncertainties among the methods assessed.•ET0 changes obtained by means of methods that only require temperature data should be evaluated carefully.
•Transhumance is the main deforestation factor in the subalpine belt.•The Middle Ages is the period when deforestation progressed the most.•Deforestation of the subalpine belt induced strong erosion ...processes.•Transhumance has reorganized the altitudinal distribution of forests.•Scientists from various fields provide a holistic view on mountain deforestation.
A key problem in explaining the mountain landscapes of the Mediterranean region is the relationship between the development of transhumance (seasonal movement of livestock over long distances) and deforestation of the subalpine and upper montane belts at 1350–2200 m above sea level (m a.s.l.). We examined this relationship in the Central Southern Pyrenees using information from multiple proxies—archaeology, pollen analysis, lacustrine sedimentation patterns, historical documents, and geomorphology. Although there is evidence of forest clearing since the Neolithic, and we can infer the presence of shepherds and livestock in mountain areas based on archaeological sites and pollen analysis in some lacustrine records, there is no strong evidence for transhumance between the Ebro Depression and the Pyrenees during the Prehistory. Instead, we found evidence of transterminance (seasonal movement of livestock over short distances) during this time. Growth of human populations and the establishment of large-scale markets favored longer livestock movements during the Roman period, although we only have indirect information on this for other areas of the Iberian Peninsula and the Mediterranean region. A few documents indicate the occurrence of transhumance during the Early Middle Ages, whereas all other proxies indicate a general expansion of livestock and transhumance during the 12th and 13th centuries. This coincides with the Christian conquest of the Central Ebro Depression by the Aragon Kingdom, the organization of large wool markets in Western Europe, and the exemptions conferred by the kings of Aragon to herders in the city of Saragossa. This led to rapid deforestation, in that forests were rapidly logged or burned to expand the summer grasslands. During this period, written documents indicate many conflicts between people in the villages and valleys for control of summer grasslands, pollen analyses show a rapid decline of arboreal pollen, and geomorphology studies indicate greatly increased sedimentation rates following deforestation, suggesting intense erosion. Transhumance has declined since the end of the 18th century, and particularly throughout the 20th century, and this has led to tree re-colonization of less accessible and marginal areas. The hydrological and geomorphological consequences of these recent events are important topics for future studies.
Industry 4.0 is in continuous technological growth that benefits all sectors of industry and society in general. This article reviews the Digital Twin (DT) concept and the interest of its application ...in photovoltaic installations. It compares how other authors use the DT approach in photovoltaic installations to improve the efficiency of the renewable energy generated and consumed, energy prediction and the reduction of the operation and maintenance costs of the photovoltaic installation. It reviews how, by providing real-time data and analysis, DTs enable more informed decision-making in the solar energy sector. The objectives of the review are to study digital twin technology and to analyse its application and implementation in PV systems.
The presence of a seasonal snowpack determines the hydrology, geomorphology and ecology of wide parts of the Iberian Peninsula, with strong implications for the economy, transport and risk ...management. Thus, reliable information on snow is necessary from a scientific and operational point of view. This is the case of the Iberian Peninsula where, lack of observation has impeded proper analysis of snowpack duration, magnitude and interannual variability. In this study, we present the first snow climatology of the entire Iberian Peninsula. The scarcity of in situ observations has been overcome, using a newly developed remote sensing snow database from MODIS satellite sensors for the period 2000–2014 and a physically based snow model (Factorial Snow Model—FSM), driven by a regional atmospheric model (Weather Research and Forecast model—WRF) over the Iberian Peninsula for the period 1980–2014. The snowpack of the main mountain areas (Pyrenees, Cantabrian, Central, Iberian range and Sierra Nevada) are described, estimated from the generated databases. The information has been processed using a k‐means cluster algorithm, looking for similarities in snow indices at different elevation bands. Results show four different types of snowpack in terms of depth, duration and interannual variability, lying over different elevation bands in the different ranges, proving the variability of the snowpack over Iberia. Analyses reveal areas characterized by ephemeral snowpacks, while in some sectors snowpack lasts, on average, 198 days per year with 3.02 m of peak snow depth. The coefficient of variation of interannual peak snow depth oscillated between 35.2 and 162.4%. All the analysed indices show that at common elevations the Cantabrian range and the Pyrenees host the deepest and longest lasting snowpacks, followed by the Central and Iberian ranges. The Sierra Nevada exhibits the shortest, shallowest snowpack and more year‐to‐year variability.
First snow climatoly of the Iberian Peninsula workflow. The data come from downscaled reanalysis data and satellite remote sensing. The results describe the spatio‐temporal variability of the snowpack over Iberia. Snow Climatology of Iberian Peninsula Workflow
To know the vertical distribution of air temperature is complex, and this is necessary for different applications. The main explanatory variable of air temperature is elevation above sea level, whose ...relationship with air temperature is measured by air temperature lapse rates (LRs). LRs can vary considerably spatiotemporally due to a wide spectrum of geographical, environmental, and other atmospheric factors. Our study presents the first comprehensive assessment of spatiotemporal changes of LRs over the Tropical Andes. Our study is focused on the Peruvian and Ecuadorian Andes, divided in two subregions by the parallel 9.5° (i.e., north and south). Maximum and minimum air temperatures were employed from 115 quality checked weather stations, for the period 1994–2011. Maximum (LRmax) and minimum (LRmin) air temperature lapse rates have been calculated for the whole study period. The effects of seasonality, humidity content and ENSO on the variability of LRs have been analysed. Results show that LRs have large spatiotemporal variability, since references values of LRmax range from −3.57 (South, dry season) to −4.77 (North, wet season), and LRmin range from −3.78 (North, dry season) to −4.93°C·km−1 (South, dry season), in function of season and subregion. Results indicate that the ENSO phases contribute significantly to the variability of southern subregion LRs. This study also presents that minimum air temperatures were more unpredictable than maximum air temperatures in terms of error and uncertainty, as a consequence of the larger spatial variability of nocturnal air temperatures, mainly influenced by local topography. In conclusion, this work goes deeper into the need to obtain precise LRs adapted to the study region, and shows that the use of standard LR values can cause significant failures in modelling air temperature in regions of complex terrain, such as the Andes.
LRmax and LRmin are weaker than the fixed Mean Environmental Lapse‐Rate (MELR −6.5°C·km−1).
The steepest lapse‐rates are registered in the wet season (October to May), with the exception of the LRmin in the South.
ENSO phenomenon influences the LR in the South significantly, whereas its effect is highly variable in the North.
This study extends knowledge of the evolution of glacier shrinkage in the Cocuy‐Güican Mountains since the maximum glacier extent of the Little Ice Age (LIA). Mass balance data for the Ritacuba ...Glacier since 2009 were acquired and compared with available data for the Conejeras Glacier (Los Nevados National Park). This study also investigated the hydrological significance of Colombian glaciers, which is still largely unknown because the available information is very limited. Glaciers in the Cocuy‐Güican Mountains covered 13.2 km2 in 2019 compared with 127.8 km2 during the maximum LIA, representing a shrinkage of 89.7%. Analysis of glacier cover observations made in 1955, 1994, 2010, and 2019 revealed that the rate of ice loss was greatest from 1994 to 2010 (0.59 km2 yr−1), and was then almost halved from 2010 to 2019 (0.34 km2 yr−1). This slowing of glacier retreat is consistent with the moderate negative mass balance measured for 2009–2019, and an accumulated loss of 1766 mm w.e. (mm water equivalent). The progressive confinement of glaciers to higher elevations, ice accumulation in topographic locations providing shelter from solar radiation, and an absence of recent marked climatic anomalies could explain why the Cocuy‐Güican glaciers have temporally reached a near equilibrium state conditions. This contrasts with the Conejeras Glacier, where 47,000 mm w.e. has been lost in the same period. The available data on runoff and isotope tracers of streamflow and precipitation suggest that precipitation rather than glacier melt water exerts primary control over the hydrological variability at high elevation sites.
Overweight and obesity have been steadily increasing in recent years and currently represent a serious threat to public health. Few human studies have investigated the relationship between polyphenol ...intake and body weight. Our aim was to assess the relationship between urinary polyphenol levels and body weight. A cross-sectional study was performed with 573 participants from the PREDIMED (Prevención con Dieta Mediterránea) trial (ISRCTN35739639). Total polyphenol levels were measured by a reliable biomarker, total urinary polyphenol excretion (TPE), determined by the Folin-Ciocalteu method in urine samples. Participants were categorized into five groups according to their TPE at the fifth year. Multiple linear regression models were used to assess the relationships between TPE and obesity parameters; body weight (BW), body mass index (BMI), waist circumference (WC), and waist-to-height ratio (WHtR). After a five years follow up, significant inverse correlations were observed between TPE at the 5th year and BW (β = -1.004; 95% CI: -1.634 to -0.375,
= 0.002), BMI (β = -0.320; 95% CI: -0.541 to -0.098,
= 0.005), WC (β = -0.742; 95% CI: -1.326 to -0.158,
= 0.013), and WHtR (β = -0.408; 95% CI: -0.788 to -0.028,
= 0.036) after adjustments for potential confounders. To conclude, a greater polyphenol intake may thus contribute to reducing body weight in elderly people at high cardiovascular risk.
Mountain glaciers have generally experienced an accelerated retreat over the
last 3 decades as a rapid response to current global warming. However,
the response to previous warm periods in the ...Holocene is not well-described
for glaciers of the southern Europe mountain ranges, such as the Pyrenees.
The situation during the Medieval Climate Anomaly (900–1300 CE) is
particularly relevant since it is not certain whether the southern European
glaciers just experienced significant ice loss or whether they actually
disappeared. We present here the first chronological study of a glacier
located in the Central Pyrenees (NE Spain), Monte Perdido Glacier (MPG),
carried out by different radiochronological techniques and a comparison with
geochemical proxies from neighbouring palaeoclimate records. The chronological
model evidences that the glacier persisted during the Roman period and the
Medieval Climate Anomaly. The apparent absence of ice in the past
∼ 600 years suggests that any ice accumulated during the
Little Ice Age has since ablated. This interpretation is supported by
measured concentrations of anthropogenic metals, including Zn, Se, Cd, Hg
and Pb, which have concentrations well below those typical of industrial-age ice measured at other glaciers in Europe. This study strengthens the general
understanding that warming of the past few decades has been exceptional for
the past 2 millennia.
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