Dynamics of transient domain structures in nematic liquid crystals: The splay Fréedericksz transition

We discuss the dynamics of the transient pattern formation process corresponding to the splay Fréedericksz transition. The emergence and subsequent evolution of the spatial periodicity is here described in terms of the temporal dependence of the wave numbers corresponding to the maxima of the structure factor. Situations of perpendicular as well as oblique field-induced stripes relative to the initial orientation of the director are both examined with explicit indications of the time scales needed for their appearance and posterior development.

Ionic-covalent transition in titanium oxides

The nature of the chemical bond in three titanium oxides of different crystal structure and different formal oxidation state has been studied by means of the ab initio cluster-model approach. The covalent and ionic contributions to the bond have been measured from different theoretical techniques. All the analysis is consistent with an increasing of covalence in the TiO, Ti2O3, and TiO2 series as expected from chemical intuition. Moreover, the use of the ab initio cluster-model approach combined with different theoretical techniques has permitted us to quantify the degree of ionic character, showing that while TiO can approximately be described as an ionic compound, TiO2 is better viewed as a rather covalent oxide.

Transient dynamics of orientational fluctuations in the Fréedericksz transition

Transient dynamics of spatial fluctuations of the director field in the pure twist Fréedericksz transition is studied. A nonlinear calculation is presented. Anomalous transient fluctuations are shown. Different stages of evolution and the domain of validity of linear theories are discussed.

X-ray diffraction, thermal analysis, and Raman scattering study of K2BeF4 and comparation to other member of the (beta)-K2SO4 family with ferroelectric -paraelectric transition

Thermal analysis, powder diffraction, and Raman scattering as a function of the temperature were carried out on K2BeF4. Moreover, the crystal structure was determined at 293 K from powder diffraction. The compound shows a transition from Pna21 to Pnam space group at 921 K with a transition enthalpy of 5 kJ/mol. The transition is assumed to be first order because the compound shows metastability. Structurally and spectroscopically the transition is similar to those observed in (NH4)2SO4, which suggests that the low-temperature phase is ferroelectric. In order to confirm it, the spontaneous polarization has been computed using an ionic model.

A cryptic heterogametic transition revealed by sex-linked DNA markers in Palearctic green toads.

In sharp contrast to birds and mammals, most cold-blooded vertebrates have homomorphic (morphologically undifferentiated) sex chromosomes. This might result either from recurrent X-Y recombination (occurring e.g. during occasional events of sex reversal) or from frequent turnovers (during which sex-determining genes are overthrown by new autosomal mutations). Evidence for turnovers is indeed mounting in fish, but very few have so far been documented in amphibians, possibly because of practical difficulties in identifying sex chromosomes. Female heterogamety (ZW) has long been established in Bufo bufo, based on sex reversal and crossing experiments. Here, we investigate a sex-linked marker identified from a laboratory cross between Palearctic green toads (Bufo viridis subgroup). The F(1) offspring produced by a female Bufo balearicus and a male Bufo siculus were phenotypically sexed, displaying an even sex ratio. A sex-specific marker detected in highly reproducible AFLP genotypes was cloned. Sequencing revealed a noncoding, microsatellite-containing fragment. Reamplification and genotyping of families of this and a reciprocal cross showed B. siculus to be male heterogametic (XY) and suggested the same system for B. balearicus. Our results thus reveal a cryptic heterogametic transition within bufonid frogs and help explain patterns of hybrid fitness within the B. viridis subgroup. Turnovers of genetic sex-determination systems may be more frequent in amphibians than previously thought and thus contribute to the prevalence of homomorphic sex chromosomes in this group.

Différenciation des trajectoires professionnelles liée à la transition à la parentalité en Suisse

Les travaux qui se sont intéressés à l'hypothèse des avantages et désavantages cumulatifs (ADC) dans la perspective du parcours de vie montrent comment, au sein d'une même cohorte, des différences initiales pour une caractéristique déterminée (sexe, statut social, santé) contribuent à structurer des trajectoires de vie différenciées. La plupart de ces études se concentrent sur l'empan de vie sans mesurer l'effet que des transitions particulières jouent dans ce processus. Dans cet article nous nous centrons sur la transition à la parentalité pour montrer que le type d'insertion professionnelle des partenaires avant cette transition explique la différenciation subséquente de leurs trajectoires professionnelles. Abstract Life course studies focusing on the cumulated advantages and disadvantages (CAD) hypothesis indicate that initial differences in a specific characteristic (sex, social status, or health) have an impact on intracohort differentiation. Most of these studies consider an entire life course and do not focus on specific transitions as a key moment for differentiation. In this article, the researchers focus on the transition to parenthood, showing that variations in occupational participation of both partners before the birth of a first child explain how professional trajectories differentiate after the birth of the child. Zusammenfassung Die Arbeiten, die sich für die Hypothese der kumulierten Vor- und Nachteile in einer Lebenslaufperspektive interessiert haben, zeigen, wie anfängliche Unterschiede bezüglich bestimmter Charakteristiken (Geschlecht, sozialer Status, Gesundheit) innerhalb einer Kohorte zur Strukturierung unterschiedlicher Lebensläufe beitragen. Die meisten dieser Studien konzentrieren sich auf den Gesamtlebenslauf, ohne die Effekte spezifischer biographischer Übergänge zu messen. In diesem Artikel beschränken wir uns auf den biographischen Übergang zur Elternschaft. Wir zeigen auf, wie die Erwerbssituation der Partner vor diesem Übergang die nachfolgende Differenzierung ihrer Berufsverläufe beeinflusst.

Plant architecture of Paspalum vaginatum schwartz modified by nitrate and ammonium nutrition

Paspalum vaginatum Schwartz plants were grown under greenhouse conditions in a continuous-flow hydroponic culture, containing NO3- or NH4+or NH4NO3 as nitrogen source. After 30 days, the size of aerial biomass and root system decreased significantly when plants were supplied with NH4+as exclusive nitrogen source. Compared to NO3- treatment, reducing and non-reducing sugars were decreasing together with a significant increase in amino acids content. NH4+-nutrition caused tillers to grow toward an orthogravitropic position (average angle of 68° with respect to the horizontal), and with NO3--nutrition, tillers tended to become diagravitropic (average angle of 23°). With NH4NO3 all the parameters measured had values in between those of the other two sources. Thus, the morphologic differences among plants growing in NO3- or NH4+ nutrition confirm the hypothesis that nitrogen source determines the growth habit of tillers in P. vaginatum by modulating the endogenous levels of reducing-non-reducing sugars.

7Ni-O chemical interaction and the transition temperature of Ni-doped Bi2Sr2Ca1Cu2O8

We find that even very low Ni doping levels of high-quality Bi2Sr2Ca1Cu2O8 single crystals strongly affect the transition temperature T(c). We also observed that T(c) is not related to the total Ni concentration, but only to that of Ni engaged in NiO-type bonds. By controlling the temperature during crystal growth, one can modify the relative weight of Ni in NiO-type bonds with respect to other configurations-and therefore T(c).

Estimating potassium nutrition of Norway spruce with needle analysis during different seasons

Tiivistelmä: Kuusen neulasanalyyttinen kaliumravitsemuksen arviointi eri vuodenaikoina

The meaning of marriage for men during the transition to fatherhood : the Swiss context

In Europe, Switzerland presents an unusual pattern of marriage with a very high proportion of couples who begin to cohabit without being married, but with a very low proportion of nonmarital births. A lot of couples marry before the conception of the child or during the pregnancy. In this article we focus on the point of view of men vis-agrave-vis the marriage and its meanings. Qualitative investigations show that men strongly desire marriage for several reasons, from their desire to participate in child rearing to the fear of having their paternity denied by Swiss institutions

Nutrition & Wellness Programs for Older Iowans, June 20, 2012

Older Iowans are independent and want to stay that way – even in tough times. Good health is important to staying independent. Food Assistance can help you buy the groceries you need to stay healthy. Everyone deserves a nutritious meal. Food Assistance can help you buy foods that taste good and are good for you! Stay well for yourself and for your family. Call 2-1-1 and get connected to the Food Assistance office that serves your community. They can help you apply for an EBT card. The people who work in the Food Assistance Program really do care about your family’s health. Food Assistance is not a hand out . . . it’s a helping hand.