762 research outputs found
Theory of the optical properties of non-absorbing compensated cholesteric liquid crystals
A theory is developed of the optical properties of a non-absorbing compensated cholesteric liquid crystal. It is shown that the Mauguin-de Vries equation fails when the pitch becomes very large. Theoretical curves are presented of the dependence of the rotatory power on pitch for different values of the sample thickness. The results are in agreement with the observed variation of the rotatory power of a compensated cholesteric mixture with temperature
Evidence for structural and electronic instabilities at intermediate temperatures in -(BEDT-TTF)X for X=Cu[N(CN)]Cl, Cu[N(CN)]Br and Cu(NCS): Implications for the phase diagram of these quasi-2D organic superconductors
We present high-resolution measurements of the coefficient of thermal
expansion of the quasi-twodimensional
(quasi-2D) salts -(BEDT-TTF)X with X = Cu(NCS), Cu[N(CN)]Br
and Cu[N(CN)]Cl. At intermediate temperatures (B), distinct anomalies
reminiscent of second-order phase transitions have been found at
K and 45 K for the superconducting X = Cu(NCS) and Cu[N(CN)]Br salts,
respectively. Most interestingly, we find that the signs of the uniaxial
pressure coefficients of are strictly anticorrelated with those of
. We propose that marks the transition to a spin-density-wave
(SDW) state forming on minor, quasi-1D parts of the Fermi surface. Our results
are compatible with two competing order parameters that form on disjunct
portions of the Fermi surface. At elevated temperatures (C), all compounds show
anomalies that can be identified with a kinetic, glass-like
transition where, below a characteristic temperature , disorder in the
orientational degrees of freedom of the terminal ethylene groups becomes frozen
in. We argue that the degree of disorder increases on going from the X =
Cu(NCS) to Cu[N(CN)]Br and the Cu[N(CN)]Cl salt. Our results
provide a natural explanation for the unusual time- and cooling-rate
dependencies of the ground-state properties in the hydrogenated and deuterated
Cu[N(CN)]Br salts reported in the literature.Comment: 22 pages, 7 figure
Integrating sexual and reproductive health into health system strengthening in humanitarian settings: a planning workshop toolkit to transition from minimum to comprehensive services in the Democratic Republic of Congo, Bangladesh, and Yemen.
BackgroundPlanning to transition from the Minimum Initial Service Package for Sexual and Reproductive Health (SRH) toward comprehensive SRH services has been a challenge in humanitarian settings. To bridge this gap, a workshop toolkit for SRH coordinators was designed to support effective planning. This article aims to describe the toolkit design, piloting, and final product.MethodsAnchored in the Health System Building Blocks Framework of the World Health Organization, the design entailed two complementary and participatory strategies. First, a collaborative design phase with iterative feedback loops involved global partners with extensive operational experience in the initial toolkit conception. The second phase engaged stakeholders from three major humanitarian crises to participate in pilot workshops to contextualize, evaluate, validate, and improve the toolkit using qualitative interviews and end-of-workshop evaluations. The aim of this two-phase design process was to finalize a planning toolkit that can be utilized in and adapted to diverse humanitarian contexts, and efficiently and effectively meet its objectives. Pilots occurred in the Democratic Republic of Congo for the Kasai region crisis, Bangladesh for the Rohingya humanitarian response in Cox's Bazar, and Yemen for selected Governorates.ResultsResults suggest that the toolkit enabled facilitators to foster a systematic, participatory, interactive, and inclusive planning process among participants over a two-day workshop. The approach was reportedly effective and time-efficient in producing a joint work plan. The main planning priorities cutting across settings included improving comprehensive SRH services in general, healthcare workforce strengthening, such as midwifery capacity development, increasing community mobilization and engagement, focusing on adolescent SRH, and enhancing maternal and newborn health services in terms of quality, coverage, and referral pathways. Recommendations for improvement included a dedicated and adequately anticipated pre-workshop preparation to gather relevant data, encouraging participants to undertake preliminary study to equalize knowledge to partake fully in the workshop, and enlisting participants from marginalized and underserved populations.ConclusionCollaborative design and piloting efforts resulted in a workshop toolkit that could support a systematic and efficient identification of priority activities and services related to comprehensive SRH. Such priorities could help meet the SRH needs of communities emerging from acute humanitarian situations while strengthening the overall health system
Cytoplasmic Poly(A) Binding Protein-1 Binds to Genomically Encoded Sequences Within Mammalian mRNAs
The functions of the major mammalian cytoplasmic poly(A) binding protein, PABPC1, have been characterized predominantly in the context of its binding to the 3′ poly(A) tails of mRNAs. These interactions play important roles in post-transcriptional gene regulation by enhancing translation and mRNA stability. Here, we performed transcriptome-wide CLIP-seq analysis to identify additional PABPC1 binding sites within genomically encoded mRNA sequences that may impact on gene regulation. From this analysis, we found that PABPC1 binds directly to the canonical polyadenylation signal in thousands of mRNAs in the mouse transcriptome. PABPC1 binding also maps to translation initiation and termination sites bracketing open reading frames, exemplified most dramatically in replication-dependent histone mRNAs. Additionally, a more restricted subset of PABPC1 interaction sites comprised A-rich sequences within the 5′ UTRs of mRNAs, including Pabpc1 mRNA itself. Functional analyses revealed that these PABPC1 interactions in the 5′ UTR mediate both auto- and trans-regulatory translational control. In total, these findings reveal a repertoire of PABPC1 binding that is substantially broader than previously recognized with a corresponding potential to impact and coordinate post-transcriptional controls critical to a broad array of cellular functions
Two- and three-dimensional magnetic correlations in the spin-1/2 square-lattice system Zn2VO(PO4)2
The magnetic correlations in the quasi-two dimensional spin-1/2
square-lattice system Zn2VO(PO4)2 have been investigated by neutron diffraction
technique. A long-range antiferromagnetic (AFM) ordering below 3.75 K (TN) has
been observed with a reduced moment of 0.66(2) {\mu}B per V ion at 1.5 K. In a
given ab plane, the AFM spin arrangement is N\'eel type and the AFM layers are
coupled ferromagnetically along the c axis. Remarkably, we have observed a pure
2D short-range AFM ordering in the ab plane above TN. Interestingly, the
coexistence of diffuse magnetic scattering and three dimensional
antiferromagnetic Bragg peaks has been found below TN, indicating the presence
of spin-waves as confirmed by our calculation using the linear spin-wave
theory. The observed results are discussed in the light of existing theory for
a two-dimensional spin-1/2 square-lattice system.Comment: 19 PAGES, 8 FIGURES, Accepted for publication in Physical Review B
201
Substitution Effect by Deuterated Donors on Superconductivity in -(BEDT-TTF)Cu[N(CN)]Br
We investigate the superconductivity in the deuterated BEDT-TTF molecular
substitution system
-[(h8-BEDT-TTF)(d8-BEDT-TTF)]Cu[N(CN)]Br, where h8
and d8 denote fully hydrogenated and deuterated molecules, respectively.
Systematic and wide range ( = 0 -- 1) substitution can control chemical
pressure finely near the Mott boundary, which results in the modification of
the superconductivity. After cooling slowly, the increase of
observed up to 0.1 is evidently caused by the chemical pressure
effect. Neither reduction of nor suppression of
superconducting volume fraction is found below 0.5. This demonstrates
that the effect of disorder by substitution is negligible in the present
system. With further increase of , both and superconducting
volume fraction start to decrease toward the values in = 1.Comment: J. Phys. Soc. Jp
CeRuPO: A rare example of a Ferromagnetic Kondo lattice
We have determined the physical ground state properties of the compounds
CeRuPO and CeOsPO by means of magnetic susceptibility chi(T), specific heat
C(T), electrical resistivity rho(T), and thermopower S(T) measurements. chi(T)
reveals a trivalent 4f1 cerium state in both compounds. For CeRuPO a pronounced
decrease of rho(T) below 50K indicates the onset of coherent Kondo scattering
which is confirmed by enhanced S(T). The temperature and magnetic field
dependence of chi(T) and C(T) evidence ferromagnetic (FM) order at TC=15K.
Thus, CeRuPO seems to be one of the rare example of a FM Kondo lattice. In
contrast, CeOsPO shows antiferromagnetic order at TN=4.4K despite only minor
changes in lattice parameters and electronic configuration. Additional 31P NMR
results support these scenarios. LSDA+U calculations evidence a quasi two
dimensional electronic band structure, reflecting a strong covalent bonding
within the CeO and RuP layers and a weak ionic like bonding between the layers.Comment: accepted in Phys. Rev. B, high quality figures:
http://www.cpfs.mpg.de/~krellner
Biochemical characterization of Fusarium oxysporum f. sp. cubense isolates from India
The Fusarium wilt caused by Fusarium oxyspoum f. sp. cubense (Foc) is a major biotic constraint for banana production. The characteristics of F. oxyspoum f. sp. cubense isolates were investigated using electrophoretic studies of isozyme and whole-cell protein. The morphological characteristics of the isolates were very similar to each other. All the Foc isolates were pathogenic to banana cultivar 'Nanjangud Rasabale' but they did not induce any disease symptoms on cultivar 'Cavendish'. F. oxyspoum (Isolate 6) did not induce wilt symptoms on either 'Nanjangud' or 'Cavendish' cultivar. Isozyme banding patterns showed 46 scoreable markers and cluster analysis with UPGMA using genetic distance showed that the isolates belonged to three main groups. Group 1 contained isolates 1, 2, 4, 5, 7 and isolate 3 and 6 were placed in group 2 and 3. Results indicated that the estimated intra-specific variation may be more pronounced with isozyme analysis than with protein markers. The level of isozyme variability detected within F. oxysporum f.sp. cubense suggested that it is reliable, efficient and effective in determining genetic relationships among Foc isolates
Isotope effect in superconductors with coexisting interactions of phonon and nonphonon mechanisms
We examine the isotope effect of superconductivity in systems with coexisting
interactions of phonon and nonphonon mechanisms in addition to the direct
Coulomb interaction. The interaction mediated by the spin fluctuations is
discussed as an example of the nonphonon interaction. Extended formulas for the
transition temperature Tc and the isotope-effect coefficient alpha are derived
for cases (a) omega_np omega_D, where omega_np is
an effective cutoff frequency of the nonphonon interaction that corresponds to
the Debye frequency omega_D in the phonon interaction. In case (a), it is found
that the nonphonon interaction does not change the condition for the inverse
isotope effect, i.e., mu^* > lambda_ph/2, but it modifies the magnitude of
alpha markedly. In particular, it is found that a giant isotope shift occurs
when the phonon and nonphonon interactions cancel each other largely. For
instance, strong critical spin fluctuations may give rise to the giant isotope
effect. In case (b), it is found that the inverse isotope effect occurs only
when the nonphonon interaction and the repulsive Coulomb interaction, in total
effect, work as repulsive interactions against the superconductivity. We
discuss the relevance of the present result to some organic superconductors,
such as kappa-(ET)2Cu(NCS)2 and Sr2RuO4 superconductors, in which inverse
isotope effects have been observed, and briefly to high-Tc cuprates, in which
giant isotope effects have been observed.Comment: 4 pages, 2 figures, (with jpsj2.cls, ver.1.2), v2:linguistic
correction
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