Influence of radiative interatomic collisions on an atom laser

We discuss the role of light absorption by pairs of atoms (radiative collisions) in the context of a model for an atom laser. The model is applied to the case of VSCPT cooling of metastable triplet helium. We show that, because of radiative collisions, for positive detuning of the driving light fields from an atomic resonance the operating conditions for the atom laser can only be marginally met. It is shown that the system only behaves as an atom laser if a very efficient sub-Doppler precooling mechanism is operative. In the case of negative frequency detuning the requirements on this sub-Doppler mechanism are less restricting, provided one avoids molecular resonances.Comment: 19 pages, 2 Postscript figure

Connecting species’ geographical distributions to environmental variables: range maps versus observed points of occurrence

Connecting the geographical occurrence of a species with underlying environmental variables is fundamental for many analyses of life history evolution and for modeling species distributions for both basic and practical ends. However, raw distributional information comes principally in two forms: points of occurrence (specific geographical coordinates where a species has been observed), and expert-prepared range maps. Each form has potential short-comings: range maps tend to overestimate the true occurrence of a species, whereas occurrence points (because of their frequent non-random spatial distribution) tend to underestimate it. Whereas previous comparisons of the two forms have focused on how they may differ when estimating species richness, less attention has been paid to the extent to which the two forms actually differ in their representation of a species’ environmental associations. We assess such differences using the globally distributed avian order Galliformes (294 species). For each species we overlaid range maps obtained from IUCN and point-of-occurrence data obtained from GBIF on global maps of four climate variables and elevation. Over all species, the median difference in distribution centroids was 234 km, and median values of all five environmental variables were highly correlated, although there were a few species outliers for each variable. We also acquired species’ elevational distribution mid-points (mid-point between minimum and maximum elevational extent) from the literature; median elevations from point occurrences and ranges were consistently lower (median −420 m) than mid-points. We concluded that in most cases occurrence points were likely to produce better estimates of underlying environmental variables than range maps, although differences were often slight. We also concluded that elevational range mid-points were biased high, and that elevation distributions based on either points or range maps provided better estimates

Spectral Signature Generalization and Expansion Can Improve the Accuracy of Satellite Image Classification

Conventional supervised classification of satellite images uses a single multi-band image and coincident ground observations to construct spectral signatures of land cover classes. We compared this approach with three alternatives that derive signatures from multiple images and time periods: (1) signature generalization: spectral signatures are derived from multiple images within one season, but perhaps from different years; (2) signature expansion: spectral signatures are created with data from images acquired during different seasons of the same year; and (3) combinations of expansion and generalization. Using data for northern Laos, we assessed the quality of these different signatures to (a) classify the images used to derive the signature, and (b) for use in temporal signature extension, i.e., applying a signature obtained from data of one or several years to images from other years. When applying signatures to the images they were derived from, signature expansion improved accuracy relative to the conventional method, and variability in accuracy declined markedly. In contrast, signature generalization did not improve classification. When applying signatures to images of other years (temporal extension), the conventional method, using a signature derived from a single image, resulted in very low classification accuracy. Signature expansion also performed poorly but multi-year signature generalization performed much better and this appears to be a promising approach in the temporal extension of spectral signatures for satellite image classification

Application of the Coupling Angle to Investigate Upper Limb Interjoint Coordination After Stroke

Objective: Interjoint coordination after stroke is affected, which limits the use of the upper limb. Current methods to determine interjoint coordination lack the ability to visualize and quantify the movement. Therefore we investigated if the coupling angle can be used to visualize and interpret upper limb interjoint coordination following a stroke. Methods: Seven chronic stroke patients trained six weeks with an assistive home-training system (MERLIN). Kinematic outcomes, i.e. elbow and shoulder range of motion, movement duration, and angle-angle plots were determined in a retrieving task. Interjoint coordination between elbow flexion and shoulder abduction angles was expressed as the coupling angle phases and the number of phase transitions: proximal/distal joint leading phase, in-phase and anti-phase. Comparisons were made within sides: pre-test versus post-test, and between sides: most-affected (MA) versus least-affected (LA). Results: Smaller elbow flexion angles were found PreMA versus PreLA, and smaller shoulder abduction angles in PostMA versus PostLA. A general coordination pattern was revealed on the LA side, but not on the MA side. A trend showed less phase transitions at the MA side after training, suggesting a smoother movement. Quantification of the movement phases indicated more involvement of the shoulder joint involvement in the MA side during pre-test. After training, these differences were not apparent, which might reveal an increased independent control of the elbow joint. Conclusions: The coupling angle and the movement phases provide a promising tool to investigate post-stroke interjoint coordination patterns. Significance: A new visualisation of the interjoint coordination may benefit rehabilitation of stroke survivors. Registration: This trial was registered at the Netherlands Trial Register (NL7535) https://www.trialregister.nl/trial/7535.</p

Double disadvantage: a case control study on health-related quality of life in children with sickle cell disease

<p>Abstract</p> <p>Background</p> <p>Low health-related quality of life (HRQoL) of children with sickle cell disease (SCD) may be associated with consequences of the disease, or with the low socio-economic status (SES) of this patient population. The aim of this study was to investigate the HRQoL of children with SCD, controlling for SES by comparing them to healthy siblings (matched for age and gender), and to a Dutch norm population.</p> <p>Methods</p> <p>The HRQoL of 40 children with homozygous SCD and 36 healthy siblings was evaluated by the KIDSCREEN-52. This self-report questionnaire assesses ten domains of HRQoL. Differences between children with SCD and healthy siblings were analyzed using linear mixed models. One-sample t-tests were used to analyze differences with the Dutch norm population. Furthermore, the proportion of children with SCD with impaired HRQoL was evaluated.</p> <p>Results</p> <p>In general, the HRQoL of children with SCD appeared comparable to the HRQoL of healthy siblings, while children with SCD had worse HRQoL than the Dutch norm population on five domains (Physical Well-being, Moods & Emotions, Autonomy, Parent Relation, and Financial Resources). Healthy siblings had worse HRQoL than the Dutch norm population on three domains (Moods & Emotions, Parent Relation, and Financial Resources). More than one in three children with SCD and healthy siblings had impaired HRQoL on several domains.</p> <p>Conclusion</p> <p>These findings imply that reduced HRQoL in children with SCD is mainly related to the low SES of this patient population, with the exception of disease specific effects on the physical and autonomy domain. We conclude that children with SCD are especially vulnerable compared to other patient populations, and have special health care needs.</p

Adiabatically changing the phase-space density of a trapped Bose gas

We show that the degeneracy parameter of a trapped Bose gas can be changed adiabatically in a reversible way, both in the Boltzmann regime and in the degenerate Bose regime. We have performed measurements on spin-polarized atomic hydrogen in the Boltzmann regime demonstrating reversible changes of the degeneracy parameter (phase-space density) by more than a factor of two. This result is in perfect agreement with theory. By extending our theoretical analysis to the quantum degenerate regime we predict that, starting close enough to the Bose-Einstein phase transition, one can cross the transition by an adiabatic change of the trap shape.Comment: 4 pages, 3 figures, Latex, submitted to PR

Soil quality and constraints in global rice production

We assessed soil quality in global rice production areas with the Fertility Capability Soil Classification (FCC) system adjusted to match the harmonized world soil database, established by the Food and Agriculture Organization and the International Institute for Applied Systems Analysis. We computed the distribution of 20 soil constraints, and used these to categorize soils as 'good', 'poor', 'very poor', or 'problem soil' for rice production. These data were then combined with data of global rice distribution to determine soil quality in the main rice production systems around the world. Most rice is grown in Asia (143.4. million. ha), followed by Africa (10.5. million. ha) and the Americas (7.2. million. ha). Globally, one-third of the total rice area is grown on very poor soils, which includes 25.6. million. ha of irrigated rice land, 18.5. million. ha in rainfed lowlands, and 7.5. million. ha of upland rice. At least 8.3. million. ha of rice is grown on problem soils, including saline, alkaline/sodic, acid-sulfate, and organic soils. Asia has the largest percentage of rice on good soils (47%) whereas rice production on good soils is much less common in the Americas (28%) and accounts for only 18% in Africa. The most common soil chemical problems in rice fields are very low inherent nutrient status (35.8. million. ha), very low pH (27.1. million. ha), and high P fixation (8.1. million. ha); widespread soil physical problems especially severe in rainfed environments are very shallow soils and low water-holding capacity. The results of the analysis can be used to better target crop improvement research, plant breeding, and the dissemination of stress-specific tolerant varieties and soil management technologies. © 2014 Elsevier B.V.S.M. Haefele, A. Nelson, R.J. Hijman

Atomic Deuterium Adsorbed on the Surface of Liquid Helium

We investigate deuterium atoms adsorbed on the surface of liquid helium in equilibrium with a vapor of atoms of the same species. These atoms are studied by a sensitive optical method based on spectroscopy at a wavelength of 122 nm, exciting the 1S-2P transition. We present a direct measurement of the adsorption energy of deuterium atoms on helium and show evidence for the existence of resonantly enhanced recombination of atoms residing on the surface to molecules.Comment: 6 pages 4 figure

NMR imaging of the soliton lattice profile in the spin-Peierls compound CuGeO_3

In the spin-Peierls compound CuGeO$_{3}$, the commensurate-incommensurate transition concerning the modulation of atomic position and the local spin-polarization is fully monitored at T=0 by the application of an external magnetic field ($H$) above a threshold value $H_{c}\simeq$ 13 Tesla. The solitonic profile of the spin-polarization, as well as its absolute magnitude, has been precisely imaged from $^{65}Cu$ NMR lineshapes obtained for $h=(H-H_{c})/H_{c}$ varying from 0.0015 to 2. This offers a unique possibility to test quantitatively the various numerical and analytical methods developed to solve a generic Hamiltonian in 1-D physics, namely strongly interacting fermions in presence of electron-phonon coupling at arbitrary band filling.Comment: 3 pages, 4 eps figures, RevTeX, submitted to Physical Review Lette

Quality of life and behavioral functioning in Dutch pediatric patients with hereditary spherocytosis

The objective of this study was to evaluate health-related quality of life (HRQoL) and behavioral functioning in pediatric patients with hereditary spherocytosis (HS). A cross-sectional study was conducted in 132 Dutch children and adolescents with HS and aged 8-18 years of whom 48 underwent splenectomy prior to the study. HRQoL was assessed using the KIDSCREEN-27, and behavioral functioning was evaluated using the strength and difficulties questionnaire (SDQ). Scores of pediatric patients with HS were compared to a Dutch norm population. Additionally, the effects of three factors were assessed: fatigue, self-image, and parents' perceived vulnerability (measured with the checklist individual strength, the self-perception profile for children and adolescents, and the child vulnerability scale). Both unsplenectomised and splenectomised pediatric patients reported lower HRQoL on the domain physical well-being (KIDSCREEN-27) compared to Dutch peers. For behavioral functioning, parents of both groups reported more emotional problems (SDQ) compared to the norm population. Pediatric patients with lower scores on physical well-being experienced more fatigue. The patients' perceived social acceptance and parents' perceived vulnerability appeared as determinants of emotional problems. Conclusion: Pediatric patients in the current study generally report few complaints, and the results suggest that these patients overall have a strong ability to cope with HS. Despite these few complaints, fatigue and parents' perceived vulnerability seem to be important determinants for lower HRQoL and more emotional problems. Therefore, screening on these factors could serve as an addition to the treatment of HS, to help pediatric patients who are at risk for lower HRQoL or more emotional problems