Misconceptions in geography held by high school seniors

Thesis (M.A.)--Boston University, 1948. This item was digitized by the Internet Archive

Injective choosability of subcubic planar graphs with girth 6

An injective coloring of a graph G is an assignment of colors to the vertices of G so that any two vertices with a common neighbor have distinct colors. A graph G is injectively k-choosable if for any list assignment L, where |L(v)| ≥ k for all v ∈ V(G), G has an injective L-coloring. Injective colorings have applications in the theory of error-correcting codes and are closely related to other notions of colorability. In this paper, we show that subcubic planar graphs with girth at least 6 are injectively 5-choosable. This strengthens the result of Lužar, Škrekovski, and Tancer that subcubic planar graphs with girth at least 7 are injectively 5-colorable. Our result also improves several other results in particular cases

Positional cloning of the PIS mutation in goats and its impact on understanding mammalian sex-differentiation

In goats, the PIS (polled intersex syndrome) mutation is responsible for both the absence of horns in males and females and sex-reversal affecting exclusively XX individuals. The mode of inheritance is dominant for the polled trait and recessive for sex-reversal. In XX PIS-/- mutants, the expression of testis-specific genes is observed very precociously during gonad development. Nevertheless, a delay of 4–5 days is observed in comparison with normal testis differentiation in XY males. By positional cloning, we demonstrate that the PIS mutation is an 11.7-kb regulatory-deletion affecting the expression of two genes, PISRT1 and FOXL2 which could act synergistically to promote ovarian differentiation. The transcriptional extinction of these two genes leads, very early, to testis-formation in XX homozygous PIS-/- mutants. According to their expression profiles and bibliographic data, we propose that FOXL2 may be an ovary-differentiating gene, and the non-coding RNA PISRT1, an anti-testis factor repressing SOX9, a key regulator of testis differentiation. Under this hypothesis, SRY, the testis-determining factor would inhibit these two genes in the gonads of XY males, to ensure testis differentiation

L’élevage dans les exploitations françaises

Dans le secteur de l’élevage des ruminants, en France, la forte diversité des systèmes de production est tour à tour considéré comme synonyme de facteur de richesse pour la typicité des produits et de contraintes pour l’organisation de certaines filières. À l’aide d’éclairages quantitatifs issus du traitement des recensements agricoles et qualitatifs en provenance du dispositif des Réseaux d’élevage (réseaux de fermes de référence), les principales tendances d’évolution de cette diversité sont étudiées pour les exploitations laitières, bovines et ovines. Ces évolutions résultent d’une interaction entre les projets des éleveurs toujours marqués par une aspiration à la parité avec les autres catégories socioprofessionnelles (et de plus en plus en matière de conditions de travail) et les caractéristiques de leur environnement dont certaines évoluent de façon permanente (politiques agricoles, filières et marchés) tandis que d’autres délimitent le champ des possibles (potentialités du milieu). Le poids des politiques agricoles et de leurs évolutions paraît très important. Face aux effets attendus du découplage qui pourrait accentuer les avantages des systèmes de production dominants, une politique de développement rural décentralisée pourrait favoriser une diversité de réponses à des enjeux locaux intégrant plus explicitement des dimensions environnementales et sociales associées à la fonction de production.In livestock sector, in France, the strong diversity of production systems is regarded in turn as factor of richness for the products typicity and as constraints for some market organizations and chains of distribution. Using quantitative approach with treatment of agricultural census and qualitative experience from Réseaux d’Elevage (networks of reference farms), the main tendencies of evolution of this diversity are studied for dairy, bovine and ovine farms. These evolutions result from an interaction between projects of stockbreeders always marked by an aspiration for parity with the other social and economic categories (and more and more as regards working conditions) and characteristics of their environment. Some of these characteristics evolve in a permanent way (agricultural policies, chains and markets) while others delimit the field of possible (potentialities of the land). The weight of agricultural policies and their evolutions appears very important. Decoupling is expected to accentuate the advantages of dominant production systems. A decentralized policy of rural development could support a diversity of answers to local stakes integrating more explicitly environmental and social dimensions associated with the production function

Genetic analysis of milking ability in Lacaune dairy ewes

The milking ability of Lacaune ewes was characterised by derived traits of milk flow patterns, in an INRA experimental farm, from a divergent selection experiment in order to estimate the correlated effects of selection for protein and fat yields. The analysis of selected divergent line effects (involving 34 616 data and 1204 ewes) indicated an indirect improvement of milking traits (+17% for maximum milk flow and -10% for latency time) with a 25% increase in milk yield. Genetic parameters were estimated by multi-trait analysis with an animal model, on 751 primiparous ewes. The heritabilities of the traits expressed on an annual basis were high, especially for maximum flow (0.54) and for latency time (0.55). The heritabilities were intermediate for average flow (0.30), time at maximum flow (0.42) and phase of increasing flow (0.43), and low for the phase of decreasing flow (0.16) and the plateau of high flow (0.07). When considering test-day data, the heritabilities of maximum flow and latency time remained intermediate and stable throughout the lactation. Genetic correlations between milk yield and milking traits were all favourable, but latency time was less milk yield dependent (-0.22) than maximum flow (+0.46). It is concluded that the current dairy ewe selection based on milk solid yield is not antagonistic to milking ability

Specific cytogenetic labeling of bovine spermatozoa bearing X or Y chromosomes using fluorescent in situ hybridization (FISH)

X and Y specific probes were identified in order to apply the fluorescent in situ hybridization (FISH) technique to bovine spermatozoa. For Y chromosome detection, the BRY4a repetitive probe, covering three quarters of the chromosome, was used. For X chromosome detection, a goat Bacterial Artificial Chromosome (BAC) specific to the X chromosome of bovine and goats and giving a strong FISH signal was used. Each probe labeled roughly 45% of sperm cells. The hybridization method will be useful for evaluating the ratio of X- and Y- bearing spermatozoa in a sperm sample and consequently can be used to evaluate the efficiency of sperm sorting by different techniques such as flow cytometry

Ramial wood amendments (Piliostigma reticulatum) mitigate degradation of tropical soils but do not replenish nutrient exports

Restoring degraded soils to support food production is a major challenge for West African smallholders who have developed local innovations to counter further degradation. The objective of this study was to evaluate a local farmer's technique that uses ramial wood (RW) as soil amendment (Piliostigma reticulatum shrub). Three treatments were applied in an experimental plot in Burkina Faso: control (no amendment), low RW (3 Mg fresh mass·ha−1·yr−1), and high RW (12 Mg fresh mass·ha−1·yr−1). RW was chipped to <5‐cm pieces and either buried or mulched. Topsoil carbon (C), nitrogen (N), and phosphorus (P) in control and low‐RW treatments declined after 7 years of continuous sorghum cultivation. Use of high‐RW amendment stabilized soil C content while N and P declined, thus not replenishing nutrient exports. Net contribution to soil C in the layer measuring 0–15 cm was 15% of the applied C in the high‐RW amendments. Although biomass and grain yields were higher in high‐RW treatments, crop productivity declined throughout the experiment for all treatments. Termite casts on RW treatments evidenced the potential role of wood‐foraging termites in diluting the impact of RW on soil fertility build‐up and soil water content. We conclude that mitigating soil degradation under semiarid conditions in Burkina Faso would require large amounts of woody amendments, particularly if the level of termite activity is high. Additional nutrient sources would be needed to compensate for removal in exported products so that biomass and grain production can be stabilized or increased.Estación Experimental Agropecuaria BarilocheFil: Félix, Georges F. Wageningen University. Farming Systems Ecology; HolandaFil: Clermont-Dauphin, Cathy. Montpellier SupAgro- Centre de Coopération Internationale en Recherche Agronomique pour le Développement-Institut National de la Recherche Agronomique. Eco&Sols; FranciaFil: Hien, Edmond. Laboratoire Mixte International. Intensification Ecologique des Sols Cultivés en Afrique de l'Ouest; Burkina FasoFil: Groot, Jeroen C.J. Wageningen University. Farming Systems Ecology; HolandaFil: Penche, Aurelien. Laboratoire Mixte International. Intensification Ecologique des Sols Cultivés en Afrique de l'Ouest; Burkina FasoFil: Barthès, Bernard G. Universidad Montpellier; FranciaFil: Manlay, Raphaël J. AgroParisTech; FranciaFil: Tittonell, Pablo Adrian. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Bariloche; ArgentinaFil: Cournac, Laurent. Montpellier SupAgro- Centre de Coopération Internationale en Recherche Agronomique pour le Développement-Institut National de la Recherche Agronomique. Eco&Sols; Franci

Infección simultánea de ninfas de Ixodes ricinus por dos especies de Borrelia burgdorferi Sensu Lato: posibles implicaciones de las manifestaciones de clínicas

Los datos de estudios Europeos indican que en humanos, genoespecies particulares de Borrelia burgdorferi pueden asociarse con las manifestaciones clínicas específicas de la enfermedad de Lyme. Las infecciones por B. burgdorferi sensu stricto tienden a conducir a síntomas artríticos, mientras que las infecciones por B. garinii parecen ocasionar complicaciones neurológicas. Las manifestaciones cutáneas tardías (acrodermatitis) parecen estar asociadas con B. afzelii (1). Las manifestaciones clínicas mixtas han sido también descritas (2). Recientemente se ha demostrado, mediante el uso de la reacción en cadena de la polimerasa (PCR), que el DNA de más de una de las tres especies de Borrelia asociadas con la enfermedad de Lyme en Europa estaban presentes en los fluidos biológicos de los pacientes de enfermedad Lyme (3). Estos datos generan la pregunta en lo que concierne al crecimiento relativo de especies de Borrelia después de una mordedura por una garrapata dualmente infectada, la importancia clínica de la infección humana ocasionada por más de una de las especies de Borrelia, y el origen de estas infecciones múltiples. Este último punto evoca la siguiente pregunta: ¿Estas infecciones resultan de las mordeduras consecutivas por dos garrapatas infectadas o desde una única mordedura por una garrapata infectada por más de una especie?Facultad de Ciencias Veterinaria

Infección simultánea de ninfas de Ixodes ricinus por dos especies de Borrelia burgdorferi Sensu Lato: posibles implicaciones de las manifestaciones de clínicas

Los datos de estudios Europeos indican que en humanos, genoespecies particulares de Borrelia burgdorferi pueden asociarse con las manifestaciones clínicas específicas de la enfermedad de Lyme. Las infecciones por B. burgdorferi sensu stricto tienden a conducir a síntomas artríticos, mientras que las infecciones por B. garinii parecen ocasionar complicaciones neurológicas. Las manifestaciones cutáneas tardías (acrodermatitis) parecen estar asociadas con B. afzelii (1). Las manifestaciones clínicas mixtas han sido también descritas (2). Recientemente se ha demostrado, mediante el uso de la reacción en cadena de la polimerasa (PCR), que el DNA de más de una de las tres especies de Borrelia asociadas con la enfermedad de Lyme en Europa estaban presentes en los fluidos biológicos de los pacientes de enfermedad Lyme (3). Estos datos generan la pregunta en lo que concierne al crecimiento relativo de especies de Borrelia después de una mordedura por una garrapata dualmente infectada, la importancia clínica de la infección humana ocasionada por más de una de las especies de Borrelia, y el origen de estas infecciones múltiples. Este último punto evoca la siguiente pregunta: ¿Estas infecciones resultan de las mordeduras consecutivas por dos garrapatas infectadas o desde una única mordedura por una garrapata infectada por más de una especie?Facultad de Ciencias Veterinaria