397 research outputs found
Improvement of Native Perennial Forage Plants for Sustainability of Mediterranean Farming Systems
The amount of water available to agriculture in the Mediterranean is declining because of increasing population pressure and greater incidence of drought. Therefore, the efficiency of the use of water for agricultural production must be maximized and, in this context, perennial forage species have a number of advantages in comparison to the predominantly-used annuals. They can utilize water throughout the whole year besides being able to halt rangeland degradation, restore soil fertility and enhance forage production, thereby contributing to greater sustainability of rain-fed agricultural systems in the southern European Union and North Africa. Despite these advantages, the small size of individual national markets has so far worked against the development of a viable forage industry based on perennials. By adopting a multi-national approach and targeting the key breeding objectives of superior drought-resistance and water-use efficiency (WUE), an European Commission-funded project aims to produce commercially cultivars of a number of species of broad regional interest and adaptation
Dissolution and gettering of iron during contact co-firing
The dissolution and gettering of iron is studied during the final fabrication step of multicrystalline silicon solar cells, the co-firing step, through simulations and experiments. The post-processed interstitial iron concentration is simulated according to the as-grown concentration and distribution of iron within a silicon wafer, both in the presence and absence of the phosphorus emitter, and applying different time-temperature profiles for the firing step. The competing effects of dissolution and gettering during the short annealing process are found to be strongly dependant on the as-grown material quality. Furthermore, increasing the temperature of the firing process leads to a higher dissolution of iron, hardly compensated by the higher diffusivity of impurities. A new defect engineering tool is introduced, the extended co-firing, which could allow an enhanced gettering effect within a small additional tim
The Potential for Summer-Dormant Perennial Grasses in Mediterranean and Semi-Arid Pastures
In rain-fed Mediterranean and semi-arid areas, herbage production of perennial grasses depends on their ability to grow efficiently during the rainy seasons and to persist over the dry summer. A key survival strategy in these harsh conditions is summer dormancy (Volaire, 2002). Within the species Dactylis glomerata L., two cultivars (cvs.), contrasting in this trait, were compared in order to analyse their suitability in terms of yield and survival in these environments
Extended skyrmion lattice scattering and long-time memory in the chiral magnet FeCoSi
Small angle neutron scattering measurements on a bulk single crystal of the
doped chiral magnet FeCoSi with =0.3 reveal a pronounced effect
of the magnetic history and cooling rates on the magnetic phase diagram. The
extracted phase diagrams are qualitatively different for zero and field cooling
and reveal a metastable skyrmion lattice phase outside the A-phase for the
latter case. These thermodynamically metastable skyrmion lattice correlations
coexist with the conical phase and can be enhanced by increasing the cooling
rate. They appear in a wide region of the phase diagram at temperatures below
the -phase but also at fields considerably smaller or higher than the fields
required to stabilize the A-phase
Magnetic Fluctuations, Precursor Phenomena and Phase Transition in MnSi under Magnetic Field
The reference chiral helimagnet MnSi is the first system where skyrmion
lattice correlations have been reported. At zero magnetic field the transition
at to the helimagnetic state is of first order. Above , in a region
dominated by precursor phenomena, neutron scattering shows the build up of
strong chiral fluctuating correlations over the surface of a sphere with radius
, where is the pitch of the helix. It has been suggested that
these fluctuating correlations drive the helical transition to first order
following a scenario proposed by Brazovskii for liquid crystals. We present a
comprehensive neutron scattering study under magnetic fields, which provides
evidence that this is not the case. The sharp first order transition persists
for magnetic fields up to 0.4 T whereas the fluctuating correlations weaken and
start to concentrate along the field direction already above 0.2 T. Our results
thus disconnect the first order nature of the transition from the precursor
fluctuating correlations. They also show no indication for a tricritical point,
where the first order transition crosses over to second order with increasing
magnetic field. In this light, the nature of the first order helical transition
and the precursor phenomena above , both of general relevance to chiral
magnetism, remain an open question
Universality of the helimagnetic transition in cubic chiral magnets: Small angle neutron scattering and neutron spin echo spectroscopy studies of FeCoSi
We present a comprehensive Small Angle Neutron Scattering (SANS) and Neutron
Spin Echo Spectroscopy (NSE) study of the structural and dynamical aspects of
the helimagnetic transition in FeCoSi with = 0.30. In contrast
to the sharp transition observed in the archetype chiral magnet MnSi, the
transition in FeCoSi is gradual and long-range helimagnetic
ordering coexists with short-range correlations over a wide temperature range.
The dynamics are more complex than in MnSi and involve long relaxation times
with a stretched exponential relaxation which persists even under magnetic
field. These results in conjunction with an analysis of the hierarchy of the
relevant length scales show that the helimagnetic transition in
FeCoSi differs substantially from the transition in MnSi and
question the validity of a universal approach to the helimagnetic transition in
chiral magnets
Magnetic Fluctuations and Correlations in MnSi - Evidence for a Skyrmion Spin Liquid Phase
We present a comprehensive analysis of high resolution neutron scattering
data involving Neutron Spin Echo spectroscopy and Spherical Polarimetry which
confirm the first order nature of the helical transition and reveal the
existence of a new spin liquid skyrmion phase. Similar to the blue phases of
liquid crystals this phase appears in a very narrow temperature range between
the low temperature helical and the high temperature paramagnetic phases.Comment: 11 pages, 16 figure
The magnitude of nephron number reduction mediates intrauterine growth-restriction-induced long term chronic renal disease in the rat. A comparative study in two experimental models.
Intrauterine growth restriction (IUGR) is a risk factor for hypertension (HT) and chronic renal disease (CRD). A reduction in the nephron number is proposed to be the underlying mechanism; however, the mechanism is debated. The aim of this study was to demonstrate that IUGR-induced HT and CRD are linked to the magnitude of nephron number reduction, independently on its cause.
Systolic blood pressure (SBP), glomerular filtration rate (GFR), proteinuria, nephron number, and glomerular sclerosis were compared between IUGR offspring prenatally exposed to a maternal low-protein diet (9% casein; LPD offspring) or maternal administration of betamethasone (from E17 to E19; BET offspring) and offspring with a normal birth weight (NBW offspring).
Both prenatal interventions led to IUGR and a similar reduction in birth weight. In comparison to NBW offspring, BET offspring had a severe nephron deficit (-50% in males and -40% in females, p < 0.01), an impaired GFR (-33%, p < 0.05), and HT (SBP+ 17 mmHg, p < 0.05). Glomerular sclerosis was more than twofold higher in BET offspring than in NBW offspring (p < 0.05). Long-term SBP, GFR, and glomerular sclerosis were unchanged in LPD offspring while the nephron number was moderately reduced only in males (-28% vs. NBW offspring, p < 0.05).
In this study, the magnitude of nephron number reduction influences long term renal disease in IUGR offspring: a moderate nephron number is an insufficient factor. Extremely long-term follow-up of adults prenatally exposed to glucocorticoids are required
Experimental models of disseminated scedosporiosis with cerebral involvement
Scedosporium apiospermum is a soil fungus which can cause severe and often fatal cerebral infections in both immunocompetent patients in the event of near drowning and immunosuppressed patients such as lung transplant recipients. Because of the low susceptibility of this fungus to antifungal drugs, and the low permeability of the blood-brain barrier (BBB), therapeutic drug monitoring is necessary to reach an effective tissue concentration with limited side effects. Indeed, diffusion of the drug in the brain is dependent on several parameters, such as the integrity of the BBB and the activity of efflux pumps. To evaluate drug diffusion, two experimental models were developed in immunocompetent and immunosuppressed rats. Inocula were administered via the penile vein and a clinical scale (0-9) was established, based on weight and clinical and neurologic signs evaluated by the tail suspension test. Cerebral involvement was confirmed by magnetic resonance imaging and histologic examination of brain sections after hematoxylin-eosin-safran or silver staining. Voriconazole or posaconazole was given to the rats at doses ranging from 10 to 75 mg/kg/day via i.v. or oral routes, respectively. Whatever the immune status, the effective doses (defined by a doubling of the survival time and the absence of neurologic sequelae) were 30 mg/kg/day for voriconazole and 50 mg/kg/day for posaconazole. Overall, the results demonstrated that these models may constitute valuable tools for the performance of pharmacokinetic and pharmacodynamic studies for pharmacokinetic-pharmacodynamic modeling
Modèle murins de scédosporioase disséminée avec atteintes cérébrale (Scedosporium apiospermium)
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