Beyond the Born-Oppenheimer approximation: high-resolution overtone spectroscopy of H2D+ and D2H+

Transitions to overtone 2v2 and 2v3, and combination v2 + v3 vibrations in jet-cooled H2D+ and D2H+ molecular ions have been measured for the first time by high-resolution IR spectroscopy. The source of these ions is a pulsed slit jet supersonic discharge, which allows for efficient generation, rotational cooling, and high frequency (100 KHz) concentration modulation for detection via sensitive lock-in detection methods. Isotopic substitution and high-resolution overtone spectroscopy in this fundamental molecular ion permit a systematic, first principles investigation of Born–Oppenheimer "breakdown" effects due to large amplitude vibrational motion as well as provide rigorous tests of approximate theoretical methods beyond the Born–Oppenheimer level. The observed overtone transitions are in remarkably good agreement (<0.1 cm–1) with non-Born–Oppenheimer ab initio theoretical predictions, with small but systematic deviations for 2v2, 2v + 3v, and 2v3 excited states indicating directions for further improvement in such treatments. Spectroscopic assignment and analysis of the isotopomeric transitions reveals strong Coriolis mixing between near resonant 2v3 and 2v + 3v vibrations in D2H+. Population-independent line intensity ratios for transitions from common lower states indicate excellent overall agreement with theoretical predictions for D2H+, but with statistically significant discrepancies noted for H2D+. Finally, H2D+ versus D2H+ isotopomer populations are analyzed as a function of D2/H2 mixing ratio and can be well described by steady state kinetics in the slit discharge expansion

The influence of nectar sugar production on insect visitors to flowers of Brassica rapa L.

Non-Peer ReviewedThe purpose of this study was to determine if differing amounts of floral nectar sugar could affect the insect pollination of Brassica rapa L., a self-incompatible species. This knowledge could be directly applicable to crop-breeding programs interested in maintaining or enhancing the attractiveness of flowers to nectar-foraging visitors (possible pollinators). Several lines of rapid-cycling B. rapa were assayed (microcapillary nectar collection plus refractometry) for floral nectar-sugar production, and seed increases were made from plants selected on that basis. Both high and low nectar-producing plants were crossed reciprocally (high by high and low by low) in attempts to establish progenies distinct from each other. It appeared that reliably high and low nectar-yielding lines could be established. Outdoor insect visitation trials using high, intermediate, and low nectar-yielding lines of rapid-cycling plants of B. rapa in small plots resulted in more insects (especially flies and bees) visiting the high nectar-producing line, which in turn produced more seeds per silique

XTHs from Fragaria vesca: Genomic structure and transcriptomic analysis in ripening fruit and other tissues

Indexación: Scopus.Background: Fragaria vesca or 'woodland strawberry' has emerged as an attractive model for the study of ripening of non-climacteric fruit. It has several advantages, such as its small genome and its diploidy. The recent availability of the complete sequence of its genome opens the possibility for further analysis and its use as a reference species. Fruit softening is a physiological event and involves many biochemical changes that take place at the final stages of fruit development; among them, the remodeling of cell walls by the action of a set of enzymes. Xyloglucan endotransglycosylase/hydrolase (XTH) is a cell wall-associated enzyme, which is encoded by a multigene family. Its action modifies the structure of xyloglucans, a diverse group of polysaccharides that crosslink with cellulose microfibrills, affecting therefore the functional structure of the cell wall. The aim of this work is to identify the XTH-encoding genes present in F. vesca and to determine its transcription level in ripening fruit. Results: The search resulted in identification of 26 XTH-encoding genes named as FvXTHs. Genetic structure and phylogenetic analyses were performed allowing the classification of FvXTH genes into three phylogenetic groups: 17 in group I/II, 2 in group IIIA and 4 in group IIIB. Two sequences were included into the ancestral group. Through a comparative analysis, characteristic structural protein domains were found in FvXTH protein sequences. In complement, expression analyses of FvXTHs by qPCR were performed in fruit at different developmental and ripening stages, as well as, in other tissues. The results showed a diverse expression pattern of FvXTHs in several tissues, although most of them are highly expressed in roots. Their expression patterns are not related to their respective phylogenetic groups. In addition, most FvXTHs are expressed in ripe fruit, and interestingly, some of them (FvXTH 18 and 20, belonging to phylogenic group I/II, and FvXTH 25 and 26 to group IIIB) display an increasing expression pattern as the fruit ripens. Conclusion: A discrete group of FvXTHs (18, 20, 25 and 26) increases their expression during softening of F. vesca fruit, and could take part in cell wall remodeling required for softening in collaboration with other cell wall degrading enzymes.https://bmcgenomics.biomedcentral.com/articles/10.1186/s12864-017-4255-

Elemental patterns in Ni hyperaccumulating and non-hyperaccumulating ultramafic soil populations of Senecio coronatus

AbstractNickel hyperaccumulation can defend plants against herbivores and pathogens. However, variability in plant tissue elemental concentrations in space and time will influence the effectiveness of this defense. We investigated a South African Ni hyperaccumulator, Senecio coronatus Thunb. (Harv.), for variation in nine elements (Ni plus Ca, Cu, Fe, K, Mg, Mn, P and Zn) between populations and between above-ground and below-ground plant organs (leaves, roots). Plant material was collected from four populations growing on ultramafic soils in the vicinity of Badplaas, Mpumalanga Province, South Africa. Concentrations of Ca, Cu, Fe, K, Mg, Mn, Ni, P and Zn were determined in dry-ashed samples. Two-way analysis of variance of data for each element revealed considerable variation in S. coronatus plant chemistry. Leaf concentrations of all elements except Cu were generally greater than root concentrations. Population-level variation was found for Ca, Fe, Mn, P, Ni and Zn, and of these all but P showed significant two-way interactions as well. Significant positive correlations were found between some pairs of elements: in hyperaccumulator roots (Ni–Ca, K–Mg), non-hyperaccumulator roots (Fe–Mn, Fe–Zn, Fe–Cu, Cu–Zn), hyperaccumulator leaves (P–Mg, P–Fe, P–Mn, Fe–Mg) and non-hyperaccumulator leaves (P–Mn, P–Ca, Ca–Mn). Two populations hyperaccumulated Ni in leaves (means of 12,000 and 8800 μg Ni/g) whereas the others did not (means of 120 and 130 μg Ni/g). Such extreme population-level variation in Ni accumulation ability is unusual among Ni hyperaccumulator species: its physiological basis and possible consequences for plant elemental defense deserve further investigation

On the stability of the primordial closed string gas

We recast the study of a closed string gas in a toroidal container in the physical situation in which the single string density of states is independent of the volume because energy density is very high. This includes the gas for the well known Brandenberger-Vafa cosmological scenario. We describe the gas in the grandcanonical and microcanonical ensembles. In the microcanonical description, we find a result that clearly confronts the Brandenberger-Vafa calculation to get the specific heat of the system. The important point is that we use the same approach to the problem but a different regularization. By the way, we show that, in the complex temperature formalism, at the Hagedorn singularity, the analytic structure obtained from the so-called F-representation of the free energy coincides with the one computed using the S-representation.Comment: 20 pages and 1 figure. The final version that appeared in JHE

Mechanical properties of tungsten alloys with Y2O3 and titanium additions

In this research the mechanical behaviour of pure tungsten (W) and its alloys (2 wt.% Ti–0.47 wt.% Y2O3 and 4 wt.% Ti–0.5 wt.% Y2O3) is compared. These tungsten alloys, have been obtained by powder metallurgy. The yield strength, fracture toughness and elastic modulus have been studied in the temperature interval of 25 °C to 1000 °C. The results have shown that the addition of Ti substantially improves the bending strength and toughness of W, but it also dramatically increases the DBTT. On the other hand, the addition of 0.5% Y2O3, is enough to improve noticeably the oxidation behaviour at the higher temperatures. The grain size, fractography and microstructure are studied in these materials. Titanium is a good grain growth inhibitor and effective precursor of liquid phase in HIP. The simultaneous presence of Y2O3 and Ti permits to obtain materials with low pores presenc

Hydrothermal Surface-Wave Instability and the Kuramoto-Sivashinsky Equation

We consider a system formed by an infinite viscous liquid layer with a constant horizontal temperature gradient, and a basic nonlinear bulk velocity profile. In the limit of long-wavelength and large nondimensional surface tension, we show that hydrothermal surface-wave instabilities may give rise to disturbances governed by the Kuramoto-Sivashinsky equation. A possible connection to hot-wire experiments is also discussed.Comment: 11 pages, RevTex, no figure

Low energy collective excitations in a superfluid trapped Fermi gas

We study low energy collective excitations in a trapped superfluid Fermi gas, that describe slow variations of the phase of the superfluid order parameter. Well below the critical temperature the corresponding eigenfrequencies turn out to be of the order of the trap frequency, and these modes manifest themselves as the eigenmodes of the density fluctuations of the gas sample. The latter could provide an experimental evidence of the presence of the superfluid phase.Comment: 5 pages, REVTeX, referencies correcte

Return to work and workplace activity limitations following total hip or knee replacement

SummaryObjectiveTotal hip (THR) and knee (TKR) replacements increasingly are performed on younger people making return to work a salient outcome. This research evaluates characteristics of individuals with early and later return to work following THR and TKR. Additionally, at work limitations pre-surgery and upon returning to work, and factors associated with work limitations were evaluated.Methods190 THR and 170 TKR of a total 931 cohort participants were eligible (i.e., working or on short-term disability pre-surgery). They completed questionnaires pre-surgery and 1, 3, 6 and 12 months post-surgery that included demographics, type of occupation, and the Workplace Activity Limitations Scale (WALS).Results166 (87%) and 144 (85%) returned to work by 12 months following THR and TKR, respectively. Early (1 month) return to work was associated with, male gender, university education, working in business, finance or administration, and low physical demand work. People with THR returned to work earlier than those with TKR. For both groups, less pain and every day functional limitations were associated with less workplace activity limitations at the time return to work.ConclusionsThe majority of individuals working prior to surgery return to work following hip or knee replacement for osteoarthritis (OA) and experience fewer limitations at work than pre-surgery. The changing workforce dynamics and trends toward surgery at younger ages mean that these are important outcomes for clinicians to assess. Additionally, this is important information for employers in understanding continued participation in employment for people with OA

Stress inversions to forecast magma pathways and eruptive vent location

When a batch of magma reaches Earth\u2019s surface, it forms a vent from which volcanic products are erupted. At many volcanoes, successive batches may open vents far away from previous ones, resulting in scattered, sometimes seemingly random spatial distributions. This exposes vast areas to volcanic hazards and makes forecasting difficult. Here, we show that magma pathways and thus future vent locations may be forecast by combining the physics of magma transport with a Monte Carlo inversion scheme for the volcano stress history. We validate our approach on a densely populated active volcanic field, Campi Flegrei (Italy), where we forecast future vents on an onshore semi-annular belt located between 2.3 and 4.2 km from the caldera center. Our approach offers a mechanical explanation for the vent migration over time at Campi Flegrei and at many calderas worldwide and may be applicable to volcanoes of any type