A new benchmark of soft X-ray transition energies of Ne , CO 2 , and SF 6 : paving a pathway towards ppm accuracy.

Abstract: A key requirement for the correct interpretation of high-resolution X-ray spectra is that transition energies are known with high accuracy and precision. We investigate the K-shell features of Ne , CO 2 , and SF 6 gases, by measuring their photo ion-yield spectra at the BESSY II synchrotron facility simultaneously with the 1s-np fluorescence emission of He-like ions produced in the Polar-X EBIT. Accurate ab initio calculations of transitions in these ions provide the basis of the calibration. While the CO 2 result agrees well with previous measurements, the SF 6 spectrum appears shifted by ∼ 0.5 eV, about twice the uncertainty of the earlier results. Our result for Ne shows a large departure from earlier results, but may suffer from larger systematic effects than our other measurements. The molecular spectra agree well with our results of time-dependent density functional theory. We find that the statistical uncertainty allows calibrations in the desired range of 1-10 meV, however, systematic contributions still limit the uncertainty to ∼ 40-100 meV, mainly due to the temporal stability of the monochromator energy scale. Combining our absolute calibration technique with a relative energy calibration technique such as photoelectron energy spectroscopy will be necessary to realize its full potential of achieving uncertainties as low as 1-10 meV.

Global plant trait relationships extend to the climatic extremes of the tundra biome.

The majority of variation in six traits critical to the growth, survival and reproduction of plant species is thought to be organised along just two dimensions, corresponding to strategies of plant size and resource acquisition. However, it is unknown whether global plant trait relationships extend to climatic extremes, and if these interspecific relationships are confounded by trait variation within species. We test whether trait relationships extend to the cold extremes of life on Earth using the largest database of tundra plant traits yet compiled. We show that tundra plants demonstrate remarkably similar resource economic traits, but not size traits, compared to global distributions, and exhibit the same two dimensions of trait variation. Three quarters of trait variation occurs among species, mirroring global estimates of interspecific trait variation. Plant trait relationships are thus generalizable to the edge of global trait-space, informing prediction of plant community change in a warming world.

High-Precision Determination of Oxygen K_{α} Transition Energy Excludes Incongruent Motion of Interstellar Oxygen.

We demonstrate a widely applicable technique to absolutely calibrate the energy scale of x-ray spectra with experimentally well-known and accurately calculable transitions of highly charged ions, allowing us to measure the K-shell Rydberg spectrum of molecular O_{2} with 8 meV uncertainty. We reveal a systematic ∼450 meV shift from previous literature values, and settle an extraordinary discrepancy between astrophysical and laboratory measurements of neutral atomic oxygen, the latter being calibrated against the aforementioned O_{2} literature values. Because of the widespread use of such, now deprecated, references, our method impacts on many branches of x-ray absorption spectroscopy. Moreover, it potentially reduces absolute uncertainties there to below the meV level.

Traditional plant functional groups explain variation in economic but not size-related traits across the tundra biome.

AIM: Plant functional groups are widely used in community ecology and earth system modelling to describe trait variation within and across plant communities. However, this approach rests on the assumption that functional groups explain a large proportion of trait variation among species. We test whether four commonly used plant functional groups represent variation in six ecologically important plant traits. LOCATION: Tundra biome. TIME PERIOD: Data collected between 1964 and 2016. MAJOR TAXA STUDIED: 295 tundra vascular plant species. METHODS: We compiled a database of six plant traits (plant height, leaf area, specific leaf area, leaf dry matter content, leaf nitrogen, seed mass) for tundra species. We examined the variation in species-level trait expression explained by four traditional functional groups (evergreen shrubs, deciduous shrubs, graminoids, forbs), and whether variation explained was dependent upon the traits included in analysis. We further compared the explanatory power and species composition of functional groups to alternative classifications generated using post hoc clustering of species-level traits. RESULTS: Traditional functional groups explained significant differences in trait expression, particularly amongst traits associated with resource economics, which were consistent across sites and at the biome scale. However, functional groups explained 19% of overall trait variation and poorly represented differences in traits associated with plant size. Post hoc classification of species did not correspond well with traditional functional groups, and explained twice as much variation in species-level trait expression. MAIN CONCLUSIONS: Traditional functional groups only coarsely represent variation in well-measured traits within tundra plant communities, and better explain resource economic traits than size-related traits. We recommend caution when using functional group approaches to predict tundra vegetation change, or ecosystem functions relating to plant size, such as albedo or carbon storage. We argue that alternative classifications or direct use of specific plant traits could provide new insights for ecological prediction and modelling.

Small-scale patterns in snowmelt timing affect gene flow and the distribution of genetic diversity in the alpine dwarf shrub Salix herbacea.

Current threats to biodiversity, such as climate change, are thought to alter the within-species genetic diversity among microhabitats in highly heterogeneous alpine environments. Assessing the spatial organization and dynamics of genetic diversity within species can help to predict the responses of organisms to environmental change. In this study, we evaluated whether small-scale heterogeneity in snowmelt timing restricts gene flow between microhabitats in the common long-lived dwarf shrub Salix herbacea L. We surveyed 273 genets across 12 early- and late-snowmelt sites (that is, ridges and snowbeds) in the Swiss Alps for phenological variation over 2 years and for genetic variation using seven SSR markers. Phenological differentiation triggered by differences in snowmelt timing did not correlate with genetic differentiation between microhabitats. On the contrary, extensive gene flow appeared to occur between microhabitats and slightly less extensively among adjacent mountains. However, ridges exhibited significantly lower levels of genetic diversity than snowbeds, and patterns of effective population size (Ne) and migration (Nem) between microhabitats were strongly asymmetric, with ridges acting as sources and snowbeds as sinks. As no recent genetic bottlenecks were detected in the studied sites, this asymmetry is likely to reflect current meta-population dynamics of the species dominated by gene flow via seeds rather than ancient re-colonization after the last glacial period. Overall, our results suggest that seed dispersal prevents snowmelt-driven genetic isolation, and snowbeds act as sinks of genetic diversity. We discuss the consequences of such small-scale variation in gene flow and diversity levels for population responses to climate change.

Increased spring freezing vulnerability for alpine shrubs under early snowmelt.

Alpine dwarf shrub communities are phenologically linked with snowmelt timing, so early spring exposure may increase risk of freezing damage during early development, and consequently reduce seasonal growth. We examined whether environmental factors (duration of snow cover, elevation) influenced size and the vulnerability of shrubs to spring freezing along elevational gradients and snow microhabitats by modelling the past frequency of spring freezing events. We sampled biomass and measured the size of Salix herbacea, Vaccinium myrtillus, Vaccinium uliginosum and Loiseleuria procumbens in late spring. Leaves were exposed to freezing temperatures to determine the temperature at which 50% of specimens are killed for each species and sampling site. By linking site snowmelt and temperatures to long-term climate measurements, we extrapolated the frequency of spring freezing events at each elevation, snow microhabitat and per species over 37 years. Snowmelt timing was significantly driven by microhabitat effects, but was independent of elevation. Shrub growth was neither enhanced nor reduced by earlier snowmelt, but decreased with elevation. Freezing resistance was strongly species dependent, and did not differ along the elevation or snowmelt gradient. Microclimate extrapolation suggested that potentially lethal freezing events (in May and June) occurred for three of the four species examined. Freezing events never occurred on late snow beds, and increased in frequency with earlier snowmelt and higher elevation. Extrapolated freezing events showed a slight, non-significant increase over the 37-year record. We suggest that earlier snowmelt does not enhance growth in four dominant alpine shrubs, but increases the risk of lethal spring freezing exposure for less freezing-resistant species.

Alpine cushion plants inhibit the loss of phylogenetic diversity in severe environments.

Biotic interactions can shape phylogenetic community structure (PCS). However, we do not know how the asymmetric effects of foundation species on communities extend to effects on PCS. We assessed PCS of alpine plant communities around the world, both within cushion plant foundation species and adjacent open ground, and compared the effects of foundation species and climate on alpha (within-microsite), beta (between open and cushion) and gamma (open and cushion combined) PCS. In the open, alpha PCS shifted from highly related to distantly related with increasing potential productivity. However, we found no relationship between gamma PCS and climate, due to divergence in phylogenetic composition between cushion and open sub-communities in severe environments, as demonstrated by increasing phylo-beta diversity. Thus, foundation species functioned as micro-refugia by facilitating less stress-tolerant lineages in severe environments, erasing a global productivity - phylogenetic diversity relationship that would go undetected without accounting for this important biotic interaction.

The consequences of complacency: managing the effects of unrecognized Charcot feet.

AIMS: Several authors have discussed an early prodromal state of neuroarthropathy (stage 0 Charcot) prior to the development of frank radiographic changes. However, very few reports are available that detail the outcomes of these patients. The purpose of this study was to report on the outcomes of patients with undetected early Charcot neuroarthropathy of the foot. METHODS: Twenty patients, from two health science centres, were diagnosed retrospectively with stage 0 Charcot neuroarthropathy and were managed after referral from outside facilities. We evaluated any complications, including ulcer formation, infection, progression into active Charcot neuroarthropathy and the need for surgical reconstruction. Patients who did not progress to an active Charcot neuroarthropathy (Group I) were compared with those (Group II) who did progress to the destructive phase. RESULTS: The diagnosis of Charcot neuroarthropathy was missed in 19 of 20 patients prior to referral. The average delay in treatment in Group I was 4.1±0.7 weeks compared with 8.7±6.8 weeks in Group II (Mann-Whitney U-test=24.5, n(1) =15, n(2) =7, P<0.05 two-tailed). Sixteen of 22 feet (72%) developed a complication during their treatment course. Group II experienced more complications than Group I (66.7% compared with 14.3%). Overall, eleven of 22 feet (50%) required surgical treatment; however, no patient required an amputation during the follow-up course. CONCLUSIONS: This study reveals that outcomes of stage 0 Charcot neuroarthropathy feet depend on proper recognition and early management. To reduce the rate of future complications for Charcot foot should be the goal of all treatment.

Spherical rotary piston machine as an artificial heart.

A positive displacement pump with six rotary pistons was proposed as an artificial heart. The pump's design was characterized by high symmetry and compactness. Thus, a spherical volume of 4 1/4 inch diameter sufficed for a pump delivering 10 L/min at 120 pulses/min with the pistons turning at 30 rpm. The pistons and four connecting gears were the only moving parts. The pump functions in two separate halves as left and right ventricles, with two of the six pistons each having inlet and outlet passages, and one of them replacing mitral and pulmonary valves with the other, tricuspid and aortic valves. The function of the intraventricular septum was provided by the other four pistons whose interiors also accommodated driving motors each capable of 0.4 Nm torque for a combined power of 5 watts. There were no stagnant regions in the pumping volume, and at all internal surfaces in contact with blood, there was periodic shear stress not exceeding approximately 300 Pa.

[Chondrodysplasia with macrocranium and mental retardation in 2 brothers]. / Chondrodysplasie avec macrocranie et retard mental chez deux frères.

Two cases of a very unusual bone dysplasia in two brothers are reported. Features included very severe dwarfism, with macrocrania and mental deficiency. Roentgenograms taken in early infancy were reminiscent of spondyloepiphyseal dysplasia congenital syndrome but the course was not suggestive of this diagnosis. The shafts of the long bones became increasingly narrow, whereas the metaphyses broadened and the epiphyses at the knee became extremely wide. Vertebral bodies were ovoid or trapezoidal. The skull was extremely large. Since two offspring of consanguineous parents were involved, this disease is certainly of genetic origin. Autosomal recessive transmission is likely, although X-linked transmission cannot be outruled.