835 research outputs found
Experimental Data on Stagnation-Point Gas Injection Cooling on a Hemisphere-Cone in a Hypersonic Arc Tunnel
Exploratory tests were made to determine the reduction of heat transfer resulting from ejection of gases at the stagnation point on a hemisphere-cone at a nominal Mach number of about 9 and at stagnation enthalpies up to 1600 BTU per pound. Helium, nitrogen, and argon gases were used as coolants. The ratio of mass flow of coolant to the mass flow of air swept out by the model projected area was less than 0.20 in all cases. The experimental heat-transfer data were normalized by the calculated stagnation-point values based on test conditions in the tunnel and are presented as a function of the surface distance from the stagnation point. The variation of shock standoff distances with mass flow and volumetric flow of the gaseous ejectants is presented along with photographs of the luminous flow field of the model during tests
The Roots of Controls on Pennsylvania\u27s General Assembly: Benjamin Rush\u27s 1777 Observations
Facteurs de variation du poids vif et de lâĂ©tat corporel du zĂ©bu Arabe en zone soudanienne du Tchad
Lâobjectif de cette Ă©tude a Ă©tĂ© de dĂ©terminer les effets saisonniers sur lâĂ©volution du poids et de la note dâĂ©tat corporel (NEC) des zĂ©bus arabes du Tchad. Durant les cinq saisons liĂ©es au calendrier fourrager, des mensurations et des notations dâĂ©tat corporel ont Ă©tĂ© effectuĂ©es sur des bovins mĂąles et femelles. Les mesures barymĂ©triques ont concernĂ© le pĂ©rimĂštre thoracique. La NEC a Ă©tĂ© dĂ©terminĂ©e par palpation de la rĂ©gion lombaire de lâanimal. Lâalternance saisonniĂšre a provoquĂ© de grandes variations de poids et de lâĂ©tat corporel des animaux qui ont Ă©tĂ© notĂ©es selon le sexe et lâĂąge. La variabilitĂ© des performances pondĂ©rales (2,2 ± 16 kg Ă 64 ±24 kg) et dâĂ©tat corporel des animaux, obtenue Ă partir des facteurs individuels (sexe ou Ăąge) et saisonniers (disponibilitĂ© fourragĂšre), a montrĂ© que ce sont les animaux dâĂąge supĂ©rieur Ă 6 ans qui ont perdu plus de poids en saison sĂšche. Les femelles de 3-6 ans (64 ± 44,8 kg) et les mĂąles de 2-3 ans (54 ± 43 kg) ont montrĂ© les fluctuations pondĂ©rales les plus significatives en saison des pluies. Afin de minimiser les risques et maximiser la production en Ă©levage extensif, des amĂ©liorations dans la conduite des animaux ont Ă©tĂ© proposĂ©es.Mots clĂ©s : Variations fourragĂšres - Poids - Etat corporel - ZĂ©bu arabe - Tcha
Pratiques d'Ă©levage dans les exploitations bovines allaitantes conduites sur pĂąturage dans les Hauts de la RĂ©union
Dans les Hauts de la RĂ©union, lâĂ©levage bovin constitue la principale activitĂ© agricole. LâĂ©levage naisseur «professionnel» reprĂ©sente 8828 vaches mĂšres pour 497 exploitations. Ce sont des exploitations de taille modeste (18 vaches mĂšres en moyenne) dont les performances animales sont en-deçà de leurs homologues mĂ©tropolitaines. Lâobjectif de lâĂ©tude est dâanalyser les pratiques des Ă©leveurs naisseurs et dâen faire le lien avec les performances obtenues afin dâidentifier des voies dâamĂ©lioration potentielles. Pour cela, 10 Ă©leveurs ont fait lâobjet dâun suivi de 1999 Ă 2002, qui Ă©tait fondĂ© sur lâĂ©valuation des performances des animaux et sur lâenregistrement des pratiques des Ă©leveurs en particularisant lâallotement, la gestion du pĂąturage et la complĂ©mentation alimentaire. Cet article montre que les pratiques sont variĂ©es et conditionnĂ©es par des objectifs de production diffĂ©rents: stratĂ©gies de maximisation des performances ou du chargement, simplification de la conduite.Cattle farming is the main agricultural activity in the Highlands of the Reunion Island. "Professional" suckling farming represents 8828 cows for 497 farms. They are modest sized farms (18 cows on the average) whose animal performances are lower than their metropolitan counterparts. The aim of the study was to analyse the practices of the suckling farmers with the purpose of improving their management. We carried out herd monitoring on 10 farms from 1999 to 2002 within this framework. This monitoring was based on the measurement of animal performances and on the recording of the farmers' practices in terms of livestock and grazing management. This article presents the analysis carried out on 3 categories of practices: the allotment, grazing management and supplementation. There are various practices underlain by different socioeconomic objectives. Thus, strategies can be founded on the maximisation of the animal performances, the stocking rate or simplification of the management
Exposure to Maternal Diabetes Is Associated With Early Abnormal Vascular Structure in Offspring
Aim/hypothesis: In utero exposure to maternal diabetes increases the risk of developing hypertension and cardiovascular disorders during adulthood. We have previously shown that this is associated with changes in vascular tone in favor of a vasoconstrictor profile, which is involved in the development of hypertension. This excessive constrictor tone has also a strong impact on vascular structure. Our objective was to study the impact of in utero exposure to maternal diabetes on vascular structure and remodeling induced by chronic changes in hemodynamic parameters.
Methods and Results: We used an animal model of rats exposed in utero to maternal hyperglycemia (DMO), which developed hypertension at 6 months of age. At a pre-hypertensive stage (3 months of age), we observed deep structural modifications of the vascular wall without any hemodynamic perturbations. Indeed, in basal conditions, resistance arteries of DMO rats are smaller than those of control mother offspring (CMO) rats; in addition, large arteries like thoracic aorta of DMO rats have an increase of smooth muscle cell attachments to elastic lamellae. In an isolated perfused kidney, we also observed a leftward shift of the flow/pressure relationship, suggesting a rise in renal peripheral vascular resistance in DMO compared to CMO rats. In this context, we studied vascular remodeling in response to reduced blood flow by in vivo mesenteric arteries ligation. In DMO rats, inward remodeling induced by a chronic reduction in blood flow (1 or 3 weeks after ligation) did not occur by contrast to CMO rats in which arterial diameter decreased from 428 ± 17 Όm to 331 ± 20 Όm (at 125 mmHg, p = 0.001). In these animals, the transglutaminase 2 (TG2) pathway, essential for inward remodeling development in case of flow perturbations, was not activated in low-flow (LF) mesenteric arteries. Finally, in old hypertensive DMO rats (18 months of age), we were not able to detect a pressure-induced remodeling in thoracic aorta.
Conclusions: Our results demonstrate for the first time that in utero exposure to maternal diabetes induces deep changes in the vascular structure. Indeed, the early narrowing of the microvasculature and the structural modifications of conductance arteries could be a pre-emptive adaptation to fetal programming of hypertension
DLX5/6 GABAergic Expression Affects Social Vocalization: Implications for Human Evolution
DLX5 and DLX6 are two closely related transcription factors involved in brain development and in GABAergic differentiation. The DLX5/6 locus is regulated by FoxP2, a gene involved in language evolution and has been associated with neurodevelopmental disorders and mental retardation. Targeted inactivation of Dlx5/6 in mouse GABAergic neurons (Dlx5/6VgatCre mice) results in behavioral and metabolic phenotypes notably increasing lifespan by 33%. Here, we show that Dlx5/6VgatCre mice present a hyper-vocalization and hyper-socialization phenotype. While only 7% of control mice emitted more than 700 vocalizations/10 min, 30% and 56% of heterozygous or homozygous Dlx5/6VgatCre mice emitted more than 700 and up to 1,400 calls/10 min with a higher proportion of complex and modulated calls. Hyper-vocalizing animals were more sociable: the time spent in dynamic interactions with an unknown visitor was more than doubled compared to low-vocalizing individuals. The characters affected by Dlx5/6 in the mouse (sociability, vocalization, skull, and brain shape..) overlap those affected in the "domestication syndrome". We therefore explored the possibility that DLX5/6 played a role in human evolution and "self-domestication"comparing DLX5/6 genomic regions from Neanderthal and modern humans. We identified an introgressed Neanderthal haplotype (DLX5/6-N-Haplotype) present in 12.6% of European individuals that covers DLX5/6 coding and regulatory sequences. The DLX5/6-N-Haplotype includes the binding site for GTF2I, a gene associated with Williams-Beuren syndrome, a hyper-sociability and hyper-vocalization neurodevelopmental disorder. The DLX5/6-N-Haplotype is significantly underrepresented in semi-supercentenarians (>105 years of age), a well-established human model of healthy aging and longevity, suggesting their involvement in the coevolution of longevity, sociability, and speech
Helium and carbon geochemistry of hydrothermal fluids from the North Fiji Basin spreading ridge (Southwest Pacific)
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