Cosmic-ray and X-ray Heating of Interstellar Clouds and Protoplanetary Disks

Cosmic-ray and X-ray heating are derived from the electron energy loss calculations of Dalgarno, Yan and Liu for hydrogen-helium gas mixtures. These authors treated the heating from elastic scattering and collisional de-excitation of rotationally excited hydrogen molecules. Here we consider the heating that can arise from all ionization and excitation processes, with particular emphasis on the reactions of cosmic-ray and X-ray generated ions with the heavy neutral species, which we refer to as chemical heating. In molecular regions, chemical heating dominates and can account for 50 per cent of the energy expended in the creation of an ion pair. The heating per ion pair ranges in the limit of negligible electron fraction from about 4.3 eV for diffuse atomic gas, to about 13 eV for the moderately dense regions of molecular clouds and to about 18 eV for the very dense regions of protoplanetary disks. An important general conclusion of this study is that cosmic-ray and X-ray heating depends on the physical properties of the medium, i.e., on the molecular and electron fractions, the total density of hydrogen nuclei, and to a lesser extent on the temperature. It is also noted that chemical heating, the dominant process for cosmic-ray and X-ray heating, plays a role in UV irradiated molecular gas.Comment: 39 pages, accepted for publication in the Astrophysical Journa

Dry matter yields and hydrological properties of three perennial grasses of a semi-arid environment in east Africa

Enteropogon macrostachyus (Bush rye), Cenchrus ciliaris L. (African foxtail grass) and Eragrostis superba Peyr (Maasai love grass) are important perennial rangeland grasses in Kenya. They provide an important source of forage for domestic livestock and wild ungulates. These grasses have been used extensively to rehabilitate denuded patches in semi-arid environment of Kenya. This study investigated the dry matter yields and hydrological properties of the three grasses under simulated rainfall at three phenological stages; early growth, elongation and reproduction. Laboratory seed viability tests were also done. Hydrological properties of the three grasses were estimated using a Kamphorst rainfall simulator. Results showed that there was a significant difference (p > 0.05) in dry matter yields and soil hydrological properties at the different grass phenological stages. Generally, all the three grasses improved the soil hydrological properties with an increase in grass stubble height. C. ciliaris gave the best soil hydrological properties followed by E. macrostachyus and E. superba, respectively. E. macrostachyus recorded the highest seed viability percentage. C. ciliaris and E. superba were ranked second and third, respectively. C. ciliaris yielded the highest biomass production at the reproductive stage followed by E. superba and E. macrostachyus, respectively. (Résumé d'auteur

Contrast-enhanced computed tomography assessment of aortic stenosis

Abstract Objectives Non-contrast CT aortic valve calcium scoring ignores the contribution of valvular fibrosis in aortic stenosis. We assessed aortic valve calcific and non-calcific disease using contrast-enhanced CT. Methods This was a post hoc analysis of 164 patients (median age 71 (IQR 66–77) years, 78% male) with aortic stenosis (41 mild, 89 moderate, 34 severe; 7% bicuspid) who underwent echocardiography and contrast-enhanced CT as part of imaging studies. Calcific and non-calcific (fibrosis) valve tissue volumes were quantified and indexed to annulus area, using Hounsfield unit thresholds calibrated against blood pool radiodensity. The fibrocalcific ratio assessed the relative contributions of valve fibrosis and calcification. The fibrocalcific volume (sum of indexed non-calcific and calcific volumes) was compared with aortic valve peak velocity and, in a subgroup, histology and valve weight. Results Contrast-enhanced CT calcium volumes correlated with CT calcium score (r=0.80, p<0.001) and peak aortic jet velocity (r=0.55, p<0.001). The fibrocalcific ratio decreased with increasing aortic stenosis severity (mild: 1.29 (0.98–2.38), moderate: 0.87 (1.48–1.72), severe: 0.47 (0.33–0.78), p<0.001) while the fibrocalcific volume increased (mild: 109 (75–150), moderate: 191 (117–253), severe: 274 (213–344) mm3/cm2). Fibrocalcific volume correlated with ex vivo valve weight (r=0.72, p<0.001). Compared with the Agatston score, fibrocalcific volume demonstrated a better correlation with peak aortic jet velocity (r=0.59 and r=0.67, respectively), particularly in females (r=0.38 and r=0.72, respectively). Conclusions Contrast-enhanced CT assessment of aortic valve calcific and non-calcific volumes correlates with aortic stenosis severity and may be preferable to non-contrast CT when fibrosis is a significant contributor to valve obstruction

PHEMTO: the polarimetric high energy modular telescope observatory

Based upon dual focusing techniques, the Polarimetric High-Energy Modular Telescope Observatory (PHEMTO) is designed to have performance several orders of magnitude better than the present hard X-ray instruments, in the 1–600 keV energy range. This, together with its angular resolution of around one arcsecond, and its sensitive polarimetry measurement capability, will give PHEMTO the improvements in scientific performance needed for a mission in the 2050 era in order to study AGN, galactic black holes, neutrons stars, and supernovae. In addition, its high performance will enable the study of the non-thermal processes in galaxy clusters with an unprecedented accuracy.Open access funding provided by Istituto Nazionale di Astrofisica within the CRUI-CARE Agreement

Changements techniques et dynamique d’innovation agricole en Afrique Sahelienne: le cas du Zaï mécanisé au Burkina Faso et de l’introduction d’une cactée en Ethiopie

En Afrique, 45% du territoire est situé dans des régions où l’agriculture pluviale est fragilisée par les sécheresses récurrentes. Au Burkina Faso, la dégradation des sols peut être limitée grâce à la technique du Zaï, technique manuelle traditionnelle très exigeante en main d’œuvre (300h/ha). La mécanisation de l'opération permet de passer à 40h/ha. L’amélioration de la technique touche aujourd’hui plusieurs centaines de fermes et d’artisans dans une vingtaine de villages du nord du Burkina Faso. Une cactée (Opuntia ficus-indica Mill) originaire du Mexique a été introduite accidentellement il y a moins de 20 ans en dans la province aride du Tigray au le nord de l’Ethiopie. Dans un délai très court, des modes de culture, d’utilisation et de transformation des différents produits de Opuntia ont fait l’objet d’améliorations techniques permettant d’améliorer l’alimentation humaine et animale et les revenus en période de soudure (juillet-septembre). Ces progrès ont été, au départ, initiés par la recherche agricole locale mais une rapide montée en puissance a été opérée grâce à une collaboration multi acteurs impliquant notamment les utilisateurs de ces techniques notamment les agriculteurs eux mêmes. Les deux expériences ont été présentées à la conférence AIDA : « Agricultural Innovation in Dryland Africa » (http://inco-aida.cirad.fr ) tenue à Accra (Ghana), 22-24 janvier 2007, qui a permis un premier inventaire d’études de cas d’amélioration agricole en Afrique sahélienne. Le principal enseignement de la conférence, illustré par ces deux études de cas, est que dans les conditions d’une grande variabilité spatiale et temporelle des facteurs environnementaux et humains, l’innovation agricole est un processus dynamique, complexe et interactif, en rupture avec les démarches linéaires de transfert de technologie majoritairement pratiqués depuis 40 ans. Les méthodes et les approches qui permettent d’intégrer cette complexité sont aujourd’hui au centre des débats afin de permettre l’appropriation par les acteurs donc accroitre l’impact des améliorations technologiques et leur pérennisation dans des contextes où les marges de manœuvre économique et climatiques sont très réduites.In Africa, 45% of the land is located in regions where rainfed agriculture is weakened by recurrent droughts. In Burkina Faso, soil degradation can be limited by the Zaï technique, which is a very labour-intensive traditional, manual technique (300 h/ha). By mechanizing the operation it only takes 40 h/ha. Today, several hundred farms and craftsmen in around twenty villages in northern Burkina Faso are benefiting from the improved technique. A cactus (Opuntia ficus-indica Mill), which originates from Mexico, was accidentally introduced less than 20 years ago in the arid province of Tigray in northern Ethiopia. Within a very short time, ways of growing, using and processing the different products derived from Opuntia have been technically developed, leading to better human and animal nutrition, and income during lean periods (July-September). At the outset, this progress was initiated by local agricultural research, but it was rapidly boosted by multi stakeholder collaboration, notably involving users of the techniques, particularly farmers themselves. These two cases were presented at the AIDA conference (Agricultural Innovation in Dryland Africa) (http://inco-aida.cirad.fr ) held in Accra (Ghana), 22-24 January 2007, which enabled the first inventory of agricultural improvement case studies in Sahelian Africa. The main lesson learnt from the conference, illustrated by these two case studies, was that under conditions of considerable spatial and temporal variability in environmental and human factors, agricultural innovation is a dynamic, complex and interactive process and a complete break from the linear technology transfer approaches mostly taken in the last 40 years. Today, the methods and approaches whereby this complexity can be integrated are at the heart of the debate, so that technological improvements can be appropriated by the stakeholders, their impact increased, and their durability ensured in contexts with very little economic and climatic room for manoeuvre

Changements techniques et dynamique d’innovation agricole en Afrique Sahelienne: le cas du Zaï mécanisé au Burkina Faso et de l’introduction d’une cactée en Ethiopie

In Africa, 45% of the land is located in regions where rainfed agriculture is weakened by recurrent droughts. In Burkina Faso, soil degradation can be limited by the Zaï technique, which is a very labour-intensive traditional, manual technique (300 h/ha). By mechanizing the operation it only takes 40 h/ha. Today, several hundred farms and craftsmen in around twenty villages in northern Burkina Faso are benefiting from the improved technique. A cactus (Opuntia ficus-indica Mill), which originates from Mexico, was accidentally introduced less than 20 years ago in the arid province of Tigray in northern Ethiopia. Within a very short time, ways of growing, using and processing the different products derived from Opuntia have been technically developed, leading to better human and animal nutrition, and income during lean periods (July-September). At the outset, this progress was initiated by local agricultural research, but it was rapidly boosted by multi stakeholder collaboration, notably involving users of the techniques, particularly farmers themselves. These two cases were presented at the AIDA conference (Agricultural Innovation in Dryland Africa) (http://inco-aida.cirad.fr ) held in Accra (Ghana), 22-24 January 2007, which enabled the first inventory of agricultural improvement case studies in Sahelian Africa. The main lesson learnt from the conference, illustrated by these two case studies, was that under conditions of considerable spatial and temporal variability in environmental and human factors, agricultural innovation is a dynamic, complex and interactive process and a complete break from the linear technology transfer approaches mostly taken in the last 40 years. Today, the methods and approaches whereby this complexity can be integrated are at the heart of the debate, so that technological improvements can be appropriated by the stakeholders, their impact increased, and their durability ensured in contexts with very little economic and climatic room for manoeuvre

The role of varietal traits in the adoption of improved dryland crop varieties: The case of pigeon pea in Kenya

This study uses a multivariate probit model and the Poisson regression to examine the role of varietal attributes in farmers’ adoption of improved pigeon pea (Cajanus cajan) varieties in Taita District, Kenya. It is based on data collected from 200 households stratified by adoption of improved pigeon pea varieties between April and May 2009. The study finds correlation in the decisions made by farmers to adopt different varieties, implying that using simple probit analysis could yield biased and inefficient results. The results further indicate that the major pigeon pea varietal traits driving rapid adoption are drought tolerance, pest tolerance, yield, ease of cooking, taste and price. Early maturity, a major focus of recent research, has no effect on farmers’ adoption decisions. These findings imply that developers of improved crop varieties should pay attention to consumption and market characteristics in addition to production traits to increase technology uptake and satisfy farmers’ multiple needs

Structural analysis of the bright monomeric yellow-green fluorescent protein mNeonGreen obtained by directed evolution.

International audienceUntil recently, genes coding for homologues of the autofluorescent protein GFP had only been identified in marine organisms from the phyla Cnidaria and Arthropoda. New fluorescent-protein genes have now been found in the phylum Chordata, coding for particularly bright oligomeric fluorescent proteins such as the tetrameric yellow fluorescent protein lanYFP from Branchiostoma lanceolatum. A successful monomerization attempt led to the development of the bright yellow-green fluorescent protein mNeonGreen. The structures of lanYFP and mNeonGreen have been determined and compared in order to rationalize the directed evolution process leading from a bright, tetrameric to a still bright, monomeric fluorescent protein. An unusual discolouration of crystals of mNeonGreen was observed after X-ray data collection, which was investigated using a combination of X-ray crystallography and UV-visible absorption and Raman spectroscopies, revealing the effects of specific radiation damage in the chromophore cavity. It is shown that X-rays rapidly lead to the protonation of the phenolate O atom of the chromophore and to the loss of its planarity at the methylene bridge