In the current work we present a detailed analysis of the chiral molecule pulegone, which is a constituent of essential oils, using broadband rotational spectroscopy. Two conformers are observed ...under the cold conditions of a molecular jet. We report an accurate experimentally determined structure for the lowest energy conformer. For both conformers, a characteristic splitting pattern is observed in the spectrum, resulting from the internal rotation of the two non‐equivalent methyl groups situated in the isopropylidene side chain. The determined energy barriers are 1.961911(46) kJ mol−1 and 6.3617(12) kJ mol−1 for one conformer, and 1.96094(74) kJ mol−1 and 6.705(44) kJ mol−1 for the other one. Moreover, a cluster of the lowest energy conformer with one water molecule is reported. The water molecule locks one of the methyl groups by means of a hydrogen bond and some secondary interactions, so that we only observe internal rotation splittings from the other methyl group with an internal rotation barrier of 2.01013(38) kJ mol−1. Additionally, the chirality‐sensitive microwave three‐wave mixing technique is applied for the differentiation between the enantiomers, which can become of further use for the analysis of essential oils.
And yet it moves: Two conformers of pulegone and their internal dynamics, resulting from the two non‐equivalent methyl groups, were observed and analyzed using microwave spectroscopy in the gas phase. This leads to accurate experimental structures for the lowest energy conformer and its cluster with water. The internal rotation of one of the methyl groups is hindered upon complexation with water. Additionally, the microwave three‐wave mixing technique was applied for the differentiation between the enantiomers of pulegone.
Three Iberian mountain ranges encompassed glaciers during the Little Ice Age (LIA): the Pyrenees, Cantabrian Mountains, and Sierra Nevada. The gradual warming trend initiated during the second half ...of the 19th century promoted the progressive shrinking of these glaciers, which completely melted during the first half of the 20th century in the Cantabrian mountains and Sierra Nevada and reduced by 80% of their LIA extent in the Pyrenees. In these formerly glaciated environments, the transition between glacial and periglacial conditions results in an accelerated paraglacial readjustment, with very active geomorphic processes. Cirque walls generate a large amount of sediments through rock‐falls and slides. LIA moraines, devoid of vegetation and composed of highly unstable sediments, are being intensely mobilized by slope processes. Inside the moraines, the shrinking of LIA glaciers favoured the development of buried ice patches, with permafrost‐related landforms, small periglacial features generated by solifluction, and cryoturbation processes and remarkable hydrological changes. Present‐day morphodynamics is mostly related to seasonal frost, though patches of permafrost have formed in contact with the buried ice, undergoing a process of degradation because it is not balanced with present‐day climate. This is reflected in the occurrence of multiple collapses and subsidence of the debris cover where the frozen bodies sit. Next to the small glaciated environments in the highest Pyrenean massifs, there is a permafrost belt undergoing also rapid geomorphic changes. Based on the observed processes, we discuss spatio‐temporal patterns of paraglacial readjustment in Iberian mountains and compare it with other midlatitude mountain environments.
Research exploring the development and outcome of COVID-19 infections has led to the need to find better diagnostic and prognostic biomarkers. This cross-sectional study used targeted metabolomics to ...identify potential COVID-19 biomarkers that predicted the course of the illness by assessing 110 endogenous plasma metabolites from individuals admitted to a local hospital for diagnosis/treatment. Patients were classified into four groups (≈ 40 each) according to standard polymerase chain reaction (PCR) COVID-19 testing and disease course: PCR-/controls (i.e., non-COVID controls), PCR+/not-hospitalized, PCR+/hospitalized, and PCR+/intubated. Blood samples were collected within 2 days of admission/PCR testing. Metabolite concentration data, demographic data and clinical data were used to propose biomarkers and develop optimal regression models for the diagnosis and prognosis of COVID-19. The area under the receiver operating characteristic curve (AUC; 95% CI) was used to assess each models' predictive value. A panel that included the kynurenine: tryptophan ratio, lysoPC a C26:0, and pyruvic acid discriminated non-COVID controls from PCR+/not-hospitalized (AUC = 0.947; 95% CI 0.931-0.962). A second panel consisting of C10:2, butyric acid, and pyruvic acid distinguished PCR+/not-hospitalized from PCR+/hospitalized and PCR+/intubated (AUC = 0.975; 95% CI 0.968-0.983). Only lysoPC a C28:0 differentiated PCR+/hospitalized from PCR+/intubated patients (AUC = 0.770; 95% CI 0.736-0.803). If additional studies with targeted metabolomics confirm the diagnostic value of these plasma biomarkers, such panels could eventually be of clinical use in medical practice.
Exoskeleton technology has made significant advances during the last decade, resulting in a considerable variety of solutions for gait assistance and rehabilitation. The mechanical design of these ...devices is a crucial aspect that affects the efficiency and effectiveness of their interaction with the user. Recent developments have pointed towards compliant mechanisms and structures, due to their promising potential in terms of adaptability, safety, efficiency, and comfort. However, there still remain challenges to be solved before compliant lower limb exoskeletons can be deployed in real scenarios. In this review, we analysed 52 lower limb wearable exoskeletons, focusing on three main aspects of compliance: actuation, structure, and interface attachment components. We highlighted the drawbacks and advantages of the different solutions, and suggested a number of promising research lines. We also created and made available a set of data sheets that contain the technical characteristics of the reviewed devices, with the aim of providing researchers and end-users with an updated overview on the existing solutions.
Recent developments in unmanned aerial vehicles (UAV) and structure from motion (SfM) algorithms have shown reliable results for retrieving snow depth distribution. However, their ability to obtain ...accurate results usually relies on deploying and measuring the exact position of ground control points (GCP) for georeferencing the information. Commercial UAVs can now provide real time kinematic (RTK) positioning of the images with centimetric accuracy. Nonetheless, their operational applicability for observing snow distribution in highly heterogeneous mountain areas has not been evaluated. This study presents a complete assessment of the reliability of snow depth observations from a fixed‐wing UAV working in RTK mode with an RGB camera. During the 2018–2019 season, seven field campaigns (13 UAV flights) were undertaken covering 0.48 km2 in complex alpine terrain in the Pyrenees. The UAV observations obtained under different light conditions and flight block configurations (altitude and image overlaps) in the same day were evaluated with terrestrial laser scanner acquisitions. Two SfM processing options of the UAV images were also compared. When the study area received direct solar light, the results were comparable to previous studies that had used GCPs, with an average root mean squared error of 0.19 m and an average absolute snow volume discrepancy lower than 4%. However, when large areas were under shadow from the terrain, or solar light was affected by clouds, the estimated error tripled. The quality of the snow depth maps was little affected by the snow covered area and the flight mission configurations.
Key Points
Under good lighting conditions results were comparable to previous studies that had used ground control points, with an average root mean squared error of 0.19 m
When large areas were under shadow from the terrain, or solar light was affected by clouds, the estimated error increased noticeably
Unmanned aerial vehicles with real time kinematic positioning allow a fast acquisition of snow distribution over large areas dramatically reducing the exposure to nature hazards
The temporal concentration of snowfalls has direct implications on the management of water resources as well as on the economic activity of mountain areas, conditioning, for example, the seasonal ...performance of ski resorts. This work uses the daily concentration index (CI) for analysing the frequency concentration of snowfalls in the Iberian Peninsula Mountain ranges. First, we provide a spatiotemporal analysis of the CI patterns and trends for the 1980–2014 period. Subsequently, we determine the atmospheric circulation patterns that control the CI variability. In addition, we determine the geographical and low‐frequency climate modes that control the CI for this mid‐latitude area. In addition, we have estimated the partial dependence relationship between the CI and several geographical factors by fitting a multiple linear regression. The results from these analyses show that elevation as well as the distance from the Atlantic are the main geographical pattern that controls the CI in the Iberian Peninsula Mountain ranges. These geographical factors also reflect the role of the main atmospheric circulation patterns in the Iberian Peninsula in controlling the spatial dynamics of the CI. The Cantabrian, Iberian, and northern slopes of the Pyrenees show the lowest CI due to their exposition to northern and Atlantic circulation weather types. On the contrary, the highest CI values are found in the southern and eastern slopes of the Pyrenees, eastern slopes of Sierra Nevada, and southern slopes of the Central system. Trend analysis shows a slight increase of CI in the Central system and in the western Sierra Nevada. However, eastern Sierra Nevada, Cantabrian, Central, and Iberian show a downward CI trend. CI is principally driven by the East‐Atlantic/Western Russia pattern and the North Atlantic Oscillation (NAO) in the Cantabrian, Iberian, and northern slopes of the Central range. The CI values in the Pyrenees show a different relationship with the Western Mediterranean Oscillation (WeMO) depending on whether it is the southern or the northern slope. In addition, the positive phase of the NAO oscillation controls the higher values of CI for the whole Pyrenees, especially in the mid‐south part. Finally, in Sierra Nevada the CI dynamics are controlled mostly by the WeMO.
The concentration index (CI) aids in understanding implications on water resources management and economic activity, such as ski resort performance. Lower CI values, associated with more regular snowfalls, are found in the Cantabrian, Iberian, and northern slopes of the Pyrenees.
Snow patterns in ice-free areas of Greenland play important roles in ecosystems. Within a changing climate, a comprehensive understanding of the snow responses to climate change is of interest to ...anticipate forthcoming dynamics in these areas. In this study, we analyze the future snowpack evolution of a polar maritime Arctic location, Qeqertarsuaq (Disko Island, Central-Western Greenland). A physically-based snow model (FSM2) is validated and forced with CMIP6 projections for SSP2–4.5 and SSP5–8.5 greenhouse gasses emission scenarios, using two models: CanESM5 and MIROC6. The future snowpack evolution is assessed through four key seasonal (October to May) snow climate indicators: snow depth, snow days, snowfall fraction and ablation rate. Comparison against the observed air temperature for the reference climate period demonstrates superior accuracies for MIROC6 SSP2.4–5, with anomalies at 19 %, compared to CanESM5 SSP5.8–5 (25 %) and CanESM5 SSP2.4–5 (78 %). In terms of precipitation, CanESM5 SSP2.4–5 and SSP2.4–5 exhibit smaller anomalies against the observed data (5 %) in contrast to MIROC6 SSP2.4–5 (15 %) and MIROC6 SSP2.8–5 (17 %). Results demonstrate distinct snowpack responses to climate change depending on the model and emission scenario. For CanESM5, seasonal snow depth anomalies with respect to the reference period range from – 38 % (SSP2–4.5, 2040–2050 period) to – 74 % (SSP5–8.5, 2090–2100 period). MIROC6 projects lower snowpack reductions, with a decrease ranging from – 38 % (SSP2–4.5, 2040–2050 period) to – 57 % (SSP5–8.5, 2090–2100 period). Similar reductions are anticipated for snowfall and snow days. Changes in the snowpack evolution are primarily driven by positive trends in downwelling longwave radiation and air temperature. The projected increase in precipitation by the mid to late 21st century will lead to more frequent rain-on-snow events, intensifying snowpack melting. These findings help enhance the comprehension of future snow dynamics in the ice-free zones of Greenland, as well as the associated hydrological and ecological changes.
Display omitted
•CMIP6 projections anticipate significant reductions in snowpack.•MIROC6 projected winter snowfall increases for SSPS4–8.5 scenario.•Snow reductions are driven by temperature and downwelling longwave radiation.•Snow cover depletion has a key impact on hydrological and ecological system.
In a warmer climate, significant variations in the snow regime are expected. Thus, it is crucial to better understand present‐day snow cover regime, its duration and thickness, in order to anticipate ...future changes. This work presents the first characterization of snow patterns in the Catalan Pyrenees based on 11 snow stations located in high elevation areas (>2,000 m). Here, we examine spatio‐temporal evolution of the daily snow depth and new snow height (HN) since the earliest 2000s to 2020. In addition, we analyse the different synoptic patterns that cause HN events in the study area as well as the low frequency climate modes on the different stages of the snow season. Our results show evidence that the measured snow amount differs considerably between the western and the eastern Catalan Pyrenees independently of the considered elevation. While the eastern part has an average seasonal cumulative HN of 278 cm, the western sector gets almost twice (433 cm). Nonetheless, the onset of the snow melting does not show substantial differences, being primarily ruled by the elevation in both areas. The longest snow records (Núria, 1971 m) point to an increase of HN from 1985 to 2020, a trend which is also observed in most stations from 2000 to 2020. Nevertheless, some stations of the N western fringe record negative trends associated with the low frequency variability of the Western Mediterranean Oscillation (WeMO). Results also indicate that the NW Atlantic low‐pressure systems are the circulation weather types that provide more abundant HN in the majority of snow stations. The Atlantic advections are more frequent in autumn and winter, while the Mediterranean advections provide more intense and recurrent HN in spring. The atmospheric circulation is basically ruled by the East Atlantic/West Russia and the WeMO teleconnection patterns.
This work presents the first characterization of snow patterns in high elevation areas (>2,000 m) of the Catalan (SE) Pyrenees. We analyse the different synoptic patterns that cause new snow height events as well as the impact of the modes of low frequency climate. The longest snow records point to an increase of new snow height (from 1985 to 2020). Nevertheless, some stations of the N western fringe record negative trends associated with the frequency variability of the circulation weather types.
We report on a combined experimental and computational study of the chiral recognition of the amino acid serine in protonated form (L/D-SerH(+)), by the crown ether ...(all-S)-(18-crown-6)-2,3,11,12-tetracarboxylic acid (S-18c6H4). Infrared and vibrational circular dichroism spectroscopies (IR-VCD) are employed to characterize the chiroptical response of the complexes formed by S-18c6H4 with the L-SerH(+) and D-SerH(+) enantiomers in dried thin films obtained from aqueous solutions. The study focuses on vibrational modes directly related to the intermolecular hydrogen bonds between the crown ether derivative and serine, responsible for crown-serine binding, namely, the C═O and C-O stretching modes, and on the C-O-H bending mode, which yield intense IR and VCD signals in the range of wavenumbers 900-2000 cm(-1). The experimental spectra are analyzed in combination with a computational structural survey and optimization at different levels of density functional theory. The conformational landscape of the complexes is found to be primarily governed by a bowl-like structure of the crown ether host and a tripodal coordination of the protonated R-NH3(+) group of serine with the oxygen atoms of the central ether ring. Additionally, one or two of the carboxylic side groups of the crown ether interact with the -COH and -COOH groups of serine. Chiral selectivity is probed by recording the IR and VCD spectra of dried thin films obtained from aqueous solutions with equimolar concentrations of the two serine enantiomers and the macrocycle. The results demonstrate a marked chiral recognition of L-SerH(+) relative to D-SerH(+) by the S-18c6H4 substrate, which arises from the favorable host-guest coordination through H-bonds at optimum distances and collinear orientations, also involving a limited distortion of the crown ether backbone.
Monoterpenoids are biogenic volatile organic compounds that play a major role in atmospheric chemistry by participating in the formation of aerosols. In this work, the monoterpenoid (R)‐(+)‐limonene ...oxide (C10H16O) was characterized in the gas phase by Fourier‐transform microwave spectroscopy in a supersonic jet. Five conformers of limonene oxide, four equatorial and one axial considering the configuration of the isopropenyl group, were unambiguously identified from analysis of the rotational spectrum. The observed conformers include cis and trans forms, which are stabilized by a subtle balance of hydrogen bonds, dispersive interactions, and steric effects. Estimated conformational relative abundances surprisingly reveal that the abundance of the axial conformer is similar to that of some of the equatorial conformers. In addition, the potential energy surface was extensively explored by using density functional theory and ab initio methods.
Limonene oxide in the gas phase: Five conformers of limonene oxide, four equatorial and one axial considering the configuration of the isopropenyl group, are unambiguously identified in the gas phase by Fourier‐transform microwave spectroscopy. The axial conformer is, surprisingly, as abundant as some of the equatorial forms. The potential energy surface is extensively explored by using density functional theory and ab initio methods.
PDF
