Diaspora remittances and investment : a derivation and measurement

This paper provides a theoretical framework and empirical evidence for assessing the impact remittances have on investment, saving, the interest and exchange rates in a small, open economy. The model shows that remittance inflows result in a currency that appreciates as the interest rate decreases, while the evidence confirms that remittances have a positive impact on investment. A poor business environment, the lack of corruption control and the absence of the rule of law can decrease investment. Commonwealth countries have a propensity to save and invest at relatively higher levels than other countries in the study; and political stability and the rule of law enhance this process. Remittances, however, reduce savings, making the country more remittance-dependent. Policy makers should therefore provide incentives that increase the use of remittances in investments that emphasize employment opportunities, and offer attractive medium and long term saving instruments to forestall the impact of a currency-appreciation.peer-reviewe

Photo-induced dynamics of the heme centers in cytochrome bc 1

The ultrafast response of cytochrome bc1 is investigated for the first time, via transient absorption spectroscopy. The distinct redox potentials of both c1- and b-hemes allow for a clear differentiation of their respective signals. We find that while the c1-heme photo-product exhibits the characteristics of a 5-coordinated species, the b-hemes presumably undergo photo-oxidation at a remarkably high quantum yield. The c1-heme iron–ligand recombination time is 5.4 ps, in agreement with previous reports on homologous cytochromes. The suggested photo-oxidized state of the b-hemes has a lifetime of 6.8 ps. From this short life-time we infer that the electron acceptor must be within van der Walls contact with the heme, which points to the fact that the axial histidine residue is the electron acceptor. The different heme-responses illustrate the flexibility of the c1-heme ligation in contrast to the more rigid b-heme binding, as well as the higher electronic reactivity of the b-hemes within the bc1 complex. This study also demonstrates the remarkable connection between the heme local environment and its dynamics and, therefore, biological functio

Effective index of refraction, optical rotation, and circular dichroism in isotropic chiral liquid crystals

This paper concerns optical properties of the isotropic phase above the isotropic-cholesteric transition and of the blue phase BP III. We introduce an effective index, which describes spatial dispersion effects such as optical rotation, circular dichroism, and the modification of the average index due to the fluctuations. We derive the wavelength dependance of these spatial dispersion effects quite generally without relying on an expansion in powers of the chirality and without assuming that the pitch of the cholesteric $P$ is much shorter than the wavelength of the light $\lambda$, an approximation which has been made in previous studies of this problem. The theoretical predictions are supported by comparing them with experimental spectra of the optical activity in the BP III phase.Comment: 15 pages and 7 figures. Submitted to PR

Upper critical fields and thermally-activated transport of Nd(O_0.7F_0.3)FeAs single crystal

We present measurements of the resistivity and the upper critical field H_c2 of Nd(O_0.7F_0.3)FeAs single crystals in strong DC and pulsed magnetic fields up to 45 T and 60 T, respectively. We found that the field scale of H_c2 is comparable to ~100 T of high T_c cuprates. H_c2(T) parallel to the c-axis exhibits a pronounced upward curvature similar to what was extracted from earlier measurements on polycrystalline samples. Thus this behavior is indeed an intrinsic feature of oxypnictides, rather than manifestation of vortex lattice melting or granularity. The orientational dependence of H_c2 shows deviations from the one-band Ginzburg-Landau scaling. The mass anisotropy decreases as T decreases, from 9.2 at 44K to 5 at 34K. Spin dependent magnetoresistance and nonlinearities in the Hall coefficient suggest contribution to the conductivity from electron-electron interactions modified by disorder reminiscent that of diluted magnetic semiconductors. The Ohmic resistivity measured below T_c but above the irreversibility field exhibits a clear Arrhenius thermally activated behavior over 4-5 decades. The activation energy has very different field dependencies for H||ab and H\perp ab. We discuss to what extent different pairing scenarios can manifest themselves in the observed behavior of H_{c2}, using the two-band model of superconductivity. The results indicate the importance of paramagnetic effects on H_c2(T),which may significantly reduce H_c2(0) as compared toH_c2(0)~200-300 T based on extrapolations of H_c2(T) near T_c down to low temperatures.Comment: 11 pages, 16 figure

Electron doped Ca10(Pt3As8)(Fe2As2)5 and Ca10(Pt4As8)(Fe2As2)5 - High Tc superconductors with skutterudite intermediary layers

It has been argued that the very high transition temperatures of the highest Tc cuprate superconductors are facilitated by enhanced CuO2 plane coupling through the (Bi,Tl,Hg)-O intermediary layers. Whether enhanced coupling through intermediary layers can also influence Tc in the iron arsenide superconductors has never been tested due the lack of appropriate systems for study. Here we report the crystal structures and properties of two iron arsenide superconductors, Ca10(Pt3As8)(Fe2As2)5 (the 10-3-8 phase) and Ca10(Pt4As8)(Fe2As2)5 (the 10-4-8 phase). Based on -Ca-(PtnAs8)-Ca-Fe2As2- layer stacking, the most important difference in the structures lies in the structural and electronic characters of the intermediary platinum arsenide layers. Electron doping through partial substitution of Pt for Fe in the Fe2As2 layers leads to Tc of 11 K in the 10-3-8 phase and 25 K in the 10-4-8 phase. Using the chemical concepts of Zintl ion electron counting and the stability of Pt in the 5d8 configuration we argue that the dramatic difference in Tc arises because the intermediary layer is semiconducting in the 10-3-8 phase but metallic in the 10-4-8 phase, leading to enhanced interlayer coupling in the 10-4-8 phase. The results suggest that metallic intermediary layers may offer a new road to higher Tc in iron arsenide superconductors

Systematic Study on Fluorine-doping Dependence of Superconducting and Normal State Properties in LaFePO1-xFx

We have investigated the fluorine-doping dependence of lattice constants, transports and specific heat for polycrystalline LaFePO1-xFx. F doping slightly and monotonically decreases the in-plane lattice parameter. In the normal state, electrical resistivity at low temperature is proportional to the square of temperature and the electronic specific heat coefficient has large value, indicating the existence of moderate electron-electron correlation in this system. Hall coefficient has large magnitude, and shows large temperature dependence, indicating the low carrier density and multiple carriers in this system. Temperature dependence of the upper critical field suggests that the system is a two gap superconductor. The F-doping dependence of these properties in this system are very weak, while in the FeAs system (LaFeAsO), the F doping induces the large changes in electronic properties. This difference is probably due to the different F-doping dependence of the lattice in these two systems. It has been revealed that a pure effect of electron doping on electronic properties is very weak in this Fe pnictide compound.Comment: 8 pages, 5 figures, accepted for publication in J. Phys. Soc. Jp

Influence of substitutional disorder on the electrical transport and the superconducting properties of Fe1+z_{1+z}Te1−x−y_{1-x-y}Sex_{x}Sy_{y}

We have carried out an investigation of the structural, magnetic, transport and superconducting properties of Fe$_{1+z}$Te$_{1-x-y}$Se$_x$S$_y$ ceramic compounds, for $z=0$ and some specific Se (0$\leq$ x $\leq$ 0.5) and S (0 $\leq$ y $\leq$0.12) contents. The incorporation of Se and S to the FeTe structure produces a progressive reduction of the crystallographic parameters as well as different degrees of structural disorder associated with the differences of the ionic radius of the substituting cations. In the present study, we measure transport properties of this family of compounds and we show the direct influence of disorder in the normal and superconductor states. We notice that the structural disorder correlates with a variable range hopping conducting regime observed at temperatures $T >$ 200 K. At lower temperatures, all the samples except the one with the highest degree of disorder show a crossover to a metallic-like regime, probably related to the transport of resilient-quasi-particles associated with the proximity of a Fermi liquid state at temperatures below the superconducting transition. Moreover, the superconducting properties are depressed only for that particular sample, in accordance to the condition that superconductivity is affected by disorder when the electronic localization length $\xi_L$ becomes smaller than the coherence length $\xi_{SC}$.Comment: 23 pages, 9 figure

Alcohol use and mental health conditions among Black college males: Do those attending postsecondary minority institutions fare better than those at primarily White institutions?

While there is a sizeable body of research examining the association between alcohol use and mental health conditions among college students, there are sparse investigations specifically focusing on these associations among Black college students. This is concerning given Black college students face different stressors compared with their non-Black peers. Black males appear especially at risk, exhibiting increased susceptibility to mental health issues and drinking in greater quantities and more frequently than Black females. This investigation examined the association between alcohol consumption and mental health conditions among Black men attending institutions of higher education in the United States and sought to determine differences between Black men attending predominantly White institutions (PWIs) compared with those attending postsecondary minority institutions. Final sample included 416 Black men, 323 of which attended a PWI. Data were from the National College Health Assessment. Black men attending a PWI reported significantly greater levels of alcohol consumption and significantly more mental health conditions. Attendance at a minority-serving institution was associated with fewer mental health conditions among Black men. Future studies should seek to replicate these findings and conduct culturally sensitive and gender-specific research examining why Black men at PWIs report greater alcohol consumption and more mental health conditions than their peers attending postsecondary minority institutions.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/163991/1/Barry et al_Alcohol Use and Mental Health.pdfDescription of Barry et al_Alcohol Use and Mental Health.pdf : Main articl