Facilitating entry into shea processing: a study of two interventions in northern Ghana

There is considerable potential for the shea industry (Vitellaria paradoxa) to contribute to the economic empowerment of women in the Sahel Region of sub-Saharan Africa. This article examines interventions in Ghana's Upper West Region at two different processing stages of the value chain, intended to facilitate women's participation in, and enhance the benefits accruing from, shea harvesting and processing. We use the responses of the nut pickers and butter processors to qualitative and quantitative field research undertaken in 2010 to explore the constraints facing women's market participation. Results showed that mechanisms to link butter producers to markets and to sources of credit were key for the development of the shea value chain in a way that retains value locally and benefits rural producers. Complementary services also facilitated participation in the butter chains. For women to benefit, the ability to negotiate and influence the terms of trade between producers and buyers is important. Such market initiatives and interventions must be considered in the context of time management of diverse livelihood strategies. Also, how financial management and benefit sharing occur within households is sure to interact with the willingness of women to participate in new shea opportunities

Kinetics and mechanism of protein tyrosine phosphatase 1B inactivation by acrolein

Human cells are exposed to the electrophilic [alpha],[beta]-unsaturated aldehyde acrolein from a variety of sources. The reaction of acrolein with functionally critical protein thiol residues can yield important biological consequences. Protein tyrosine phosphatases (PTPs) are an important class of cysteine-dependent enzymes whose reactivity with acrolein previously has not been well-characterized. These enzymes catalyze the dephosphorylation of phosphotyrosine residues on proteins via a phosphocysteine intermediate. PTPs work in tandem with protein tyrosine kinases to regulate a number of critically important mammalian signal transduction pathways. We find that acrolein is a potent time-dependent inactivator of the enzyme PTP1B (kinact = 0.02 [plus or minus] 0.005 s-1 and KI = 2.3 [plus or minus] 0.6 x 10-4 M). The enzyme activity does not return upon gel filtration of the inactivated enzyme, and addition of the competitive phosphatase inhibitor vanadate slows inactivation of PTP1B by acrolein. Together, these observations suggest that acrolein covalently modifies the active site of PTP1B. Mass spectrometric analysis reveals that acrolein modifies the catalytic cysteine residue at the active site of the enzyme. Aliphatic aldehydes such as glyoxal, acetaldehyde, and propanal are relatively weak inactivators of PTP1B under the conditions employed here. Similarly, unsaturated aldehydes such as crotonaldehyde and 3-methyl-2-butenal bearing substitution at the alkene terminus are poor inactivators of the enzyme. Overall, the data suggest that enzyme inactivation occurs via conjugate addition of the catalytic cysteine residue to the carbon-carbon double bond of acrolein. The results indicate that inactivation of PTPs should be considered as a possible contributor to the diverse biological activities of acrolein and structurally related α,β-unsaturated aldehydes

Monte Carlo energy and variance minimization techniques for optimizing many-body wave functions

We investigate Monte Carlo energy and variance minimization techniques for optimizing many-body wave functions. Several variants of the basic techniques are studied, including limiting the variations in the weighting factors which arise in correlated sampling estimations of the energy and its variance. We investigate the numerical stability of the techniques and identify two reasons why variance minimization exhibits superior numerical stability to energy minimization. The characteristics of each method are studied using a non-interacting 64-electron model of crystalline silicon. While our main interest is in solid state systems, the issues investigated are relevant to Monte Carlo studies of atoms, molecules and solids. We identify a robust and efficient variance minimization scheme for optimizing wave functions for large systems.Comment: 14 pages, including 7 figures. To appear in Phys. Rev. B. For related publications see http://www.tcm.phy.cam.ac.uk/Publications/many_body.htm

Development of outbred CD1 mouse colonies with distinct standardized gut microbiota profiles for use in complex microbiota targeted studies.

Studies indicate that the gut microbiota (GM) can significantly influence both local and systemic host physiologic processes. With rising concern for optimization of experimental reproducibility and translatability, it is essential to consider the GM in study design. However, GM profiles can vary between rodent producers making consistency between models challenging. To circumvent this, we developed outbred CD1 mouse colonies with stable, complex GM profiles that can be used as donors for a variety of GM transfer techniques including rederivation, co-housing, cross-foster, and fecal microbiota transfer (FMT). CD1 embryos were surgically transferred into CD1 or C57BL/6 surrogate dams that varied by GM composition and complexity to establish four separate mouse colonies harboring GM profiles representative of contemporary mouse producers. Using targeted 16S rRNA amplicon sequencing, subsequent female offspring were found to have similar GM profiles to surrogate dams. Furthermore, breeding colonies of CD1 mice with distinct GM profiles were maintained for nine generations, demonstrating GM stability within these colonies. To confirm GM stability, we shipped cohorts of these four colonies to collaborating institutions and found no significant variation in GM composition. These mice are an invaluable experimental resource that can be used to investigate GM effects on mouse model phenotype

Variational quantum Monte Carlo calculations for solid surfaces

Quantum Monte Carlo methods have proven to predict atomic and bulk properties of light and non-light elements with high accuracy. Here we report on the first variational quantum Monte Carlo (VMC) calculations for solid surfaces. Taking the boundary condition for the simulation from a finite layer geometry, the Hamiltonian, including a nonlocal pseudopotential, is cast in a layer resolved form and evaluated with a two-dimensional Ewald summation technique. The exact cancellation of all Jellium contributions to the Hamiltonian is ensured. The many-body trial wave function consists of a Slater determinant with parameterized localized orbitals and a Jastrow factor with a common two-body term plus a new confinement term representing further variational freedom to take into account the existence of the surface. We present results for the ideal (110) surface of Galliumarsenide for different system sizes. With the optimized trial wave function, we determine some properties related to a solid surface to illustrate that VMC techniques provide standard results under full inclusion of many-body effects at solid surfaces.Comment: 9 pages with 2 figures (eps) included, Latex 2.09, uses REVTEX style, submitted to Phys. Rev.

Functional Approach to Quantum Decoherence and the Classical Final Limit

For a wide set of quantum systems it is demonstrated that the quantum regime can be considered as the transient phase while the final classical statistical regime is a permanent state. A basis where exact matrix decoherence appears for these final states is found. The relation with the decoherence of histories formalism is studied. A set of final intrinsically consistent histories is found.Comment: 20 pages. Phys. Rev A in press 200

Hydration and blood volume effects on human thermoregulation in the heat: Space applications

Astronauts exposed to prolonged weightlessness will experience deconditioning, dehydration, and hypovolemia which all adversely affect thermoregulation. These thermoregulatory problems can be minimized by several countermeasures that manipulate body water and vascular volumes. USARIEM scientists have extensively studied dehydration effects and several possible countermeasures including hyperhydration, plasma and erythrocyte volume expansion. This paper reviews USARIEM research into these areas

Current-Induced Effective Magnetic Fields in Co/Cu/Co Nanopillars

We present a method to measure the effective field contribution to spin-transfer-induced interactions between the magnetic layers in a trilayer nanostructure, which enables spin-current effects to be distinguished from the usual charge-current-induced magnetic fields. This technique is demonstrated on submicron Co/Cu/Co nanopillars. The hysteresis loop of one of the magnetic layers in the trilayer is measured as a function of current while the direction of magnetization of the other layer is kept fixed, first in one direction and then in the opposite direction. These measurements show a current-dependent shift of the hysteresis loop which, based on the symmetry of the magnetic response, we associate with spin-transfer. The observed loop-shift with applied current at room temperature is reduced in measurements at 4.2 K. We interprete these results both in terms of a spin-current dependent effective activation barrier for magnetization reversal and a spin-current dependent effective magnetic field. From data at 4.2 K we estimate the magnitude of the spin-transfer induced effective field to be $\sim 1.5 \times 10^{-7}$ Oe cm$^2$/A, about a factor of 5 less than the spin-transfer torque.Comment: 6 pages, 4 figure

Local environment can enhance fidelity of quantum teleportation

We show how an interaction with the environment can enhance fidelity of quantum teleportation. To this end, we present examples of states which cannot be made useful for teleportation by any local unitary transformations; nevertheless, after being subjected to a dissipative interaction with the local environment, the states allow for teleportation with genuinely quantum fidelity. The surprising fact here is that the necessary interaction does not require any intelligent action from the parties sharing the states. In passing, we produce some general results regarding optimization of teleportation fidelity by local action. We show that bistochastic processes cannot improve fidelity of two-qubit states. We also show that in order to have their fidelity improvable by a local process, the bipartite states must violate the so-called reduction criterion of separability.Comment: 9 pages, Revte