816 research outputs found
Phase-Coherent Dynamics of a Superconducting Flux Qubit with Capacitive-Bias Readout
We present a systematic study of the phase-coherent dynamics of a
superconducting three-Josephson-junction flux qubit. The qubit state is
detected with the integrated-pulse method, which is a variant of the pulsed
switching DC SQUID method. In this scheme the DC SQUID bias current pulse is
applied via a capacitor instead of a resistor, giving rise to a narrow
band-pass instead of a pure low-pass filter configuration of the
electromagnetic environment. Measuring one and the same qubit with both setups
allows a direct comparison. With the capacitive method about four times faster
switching pulses and an increased visibility are achieved. Furthermore, the
deliberate engineering of the electromagnetic environment, which minimizes the
noise due to the bias circuit, is facilitated. Right at the degeneracy point
the qubit coherence is limited by energy relaxation. We find two main noise
contributions. White noise is limiting the energy relaxation and contributing
to the dephasing far from the degeneracy point. 1/f-noise is the dominant
source of dephasing in the direct vicinity of the optimal point. The influence
of 1/f-noise is also supported by non-random beatings in the Ramsey and spin
echo decay traces. Numeric simulations of a coupled qubit-oscillator system
indicate that these beatings are due to the resonant interaction of the qubit
with at least one point-like fluctuator, coupled especially strongly to the
qubit.Comment: Minor changes. 21 pages, 15 figure
Fisheries Statistics for Lake Victoria, Tanzania
This research article published by Springer Nature Switzerland AG., 2017Time series fisheries statistics data mainly from Frame Surveys, Catch Assessment Surveys and Fisheries Annual Statistics Reports for Lake Victoria from 1967–2016 were collected from the Fisheries Development Division in Tanzania. These surveys and reports comprised relevant information and data on fish catches and fishing effort. The data were analysed and used to describe variations and trends in the number of fishers, number of fishing crafts, fish weight, catch per boat, total number of gillnets, beach seines, longline hooks, outboard and inboard engines. Frame Survey results showed an increasing trend in the number of fishers and fishing crafts, with the highest number of fishers and fishing crafts being 109,397 and 31,773, respectively in 2016. Longline hooks increased from 2,200,901 in 2000 to 8,163,119 hooks in 2016. In general, the catch per unit effort (CPUE) for all species was high at 39 mt/boat/year in 1967 and decreased to 8 mt/boat/year in 2014. However, CPUE for Lates niloticus has increased since the late 1980s, with the highest CPUE of 19.22 mt/boat/year being recorded in 1995, and from 2000 it decreased gradually to 7 mt/boat/year in 2014. As the fisheries statistics show an increase in fishing pressure over the years, it is evident that there is a sign of overfishing. For that matter, effective fisheries management is needed for the three riparian states to safeguard the sustainable use of fishery resources in the lake and to provide data that can be used in the evaluation of the fisheries objectives
Linking Genotype and Phenotype of Saccharomyces cerevisiae Strains Reveals Metabolic Engineering Targets and Leads to Triterpene Hyper-Producers
Background: Metabolic engineering is an attractive approach in order to improve the microbial production of drugs. Triterpenes is a chemically diverse class of compounds and many among them are of interest from a human health perspective. A systematic experimental or computational survey of all feasible gene modifications to determine the genotype yielding the optimal triterpene production phenotype is a laborious and time-consuming process. Methodology/Principal Findings: Based on the recent genome-wide sequencing of Saccharomyces cerevisiae CEN.PK 113-7D and its phenotypic differences with the S288C strain, we implemented a strategy for the construction of a beta-amyrin production platform. The genes Erg8, Erg9 and HFA1 contained non-silent SNPs that were computationally analyzed to evaluate the changes that cause in the respective protein structures. Subsequently, Erg8, Erg9 and HFA1 were correlated with the increased levels of ergosterol and fatty acids in CEN.PK 113-7D and single, double, and triple gene over-expression strains were constructed. Conclusions: The six out of seven gene over-expression constructs had a considerable impact on both ergosterol and beta-amyrin production. In the case of beta-amyrin formation the triple over-expression construct exhibited a nearly 500% increase over the control strain making our metabolic engineering strategy the most successful design of triterpene microbial producers
Ginzburg-Landau theory of superconductors with short coherence length
We consider Fermions in two dimensions with an attractive interaction in the
singlet d-wave channel of arbitrary strength. By means of a
Hubbard-Stratonovich transformation a statistical Ginzburg-Landau theory is
derived, which describes the smooth crossover from a weak-coupling BCS
superconductor to a condensate of composite Bosons. Adjusting the interaction
strength to the observed slope of H_c2 at T_c in the optimally doped high-T_c
compounds YBCO and BSCCO, we determine the associated values of the
Ginzburg-Landau correlation length xi and the London penetration depth lambda.
The resulting dimensionless ratio k_F xi(0) approx 5-8 and the Ginzburg-Landau
parameter kappa=lambda xi approx 90-100 agree well with the experimentally
observed values. These parameters indicate that the optimally doped materials
are still on the weak coupling side of the crossover to a Bose regime.Comment: 12 pages, RevTeX, 6 postscript figures, resubmitted with minor
changes in section III, to appear in Physical Review
Co-management of Lake Victoria Fisheries
This research article published by Springer Nature Switzerland AG., 2017There have been concerns about the declining fish catches and fisheries ecosystem health for a number of fisheries including Lake Victoria. Consequently, a co-management system has been introduced as a means of, among others, reversing the declining catches. It is hypothesized that non-involvement of fishers in the management of the lake’s fisheries is a major reason for the ever-decreasing catches. This chapter discusses this particular management regime and its application in the lake’s fisheries. The analysis is based on data collected by the Fisheries Division since co-management was introduced in the lake in 1998. The chapter traces the lake’s fishery management since the pre-colonial to the post-colonial period. It presents the aim and rationale for managing the lake’s fishery, the structure of the management and roles of governors. It also analyses trends in illegal fishing practices as well as enforcement performance. The argument here is that co-management has helped in bringing on board fishers and this has enabled laws and regulations to be implemented in a much better way than they were under a central-command system. The chapter subsequently concludes that the involvement of fishing communities in the management of fisheries has created a forum for the exchange of ideas, knowledge and experience on the resources. This strategy has made the communities understand the importance of compliance to the law and regulations and effective management measures
Fluxoid dynamics in superconducting thin film rings
We have measured the dynamics of individual magnetic fluxoids entering and
leaving photolithographically patterned thin film rings of the underdoped
high-temperature superconductor BiSrCaCuO, using a
variable sample temperature scanning SQUID microscope. These results can be
qualitatively described using a model in which the fluxoid number changes by
thermally activated nucleation of a Pearl vortex in, and transport of the Pearl
vortex across, the ring wall.Comment: 9 pages, 10 figures, fixed typo
Temperature and magnetic-field dependence of the conductivity of YBaCuO films in the vicinity of superconducting transition: Effect of Tc-inhomogeneity
Temperature and magnetic field dependences of the conductivity of YBaCuO
films in the transition region are analyzed taking into account spatial
inhomogeneity in transition temperature, Tc.
(i) An expression for the superconducting contribution to conductivity,
\sigma_s(T,H,Tc), of a homogeneous superconductor for H<<Hc2(T=0) is obtained
using the solution of the Ginzburg-Landau equation in form of perturbation
expansions [S.Ullah, A.T.Dorsey, PRB 44, 262 (1991)].
(ii) The error in \sigma_s(T,H,Tc) occurring due to the presence of
Tc-inhomogeneity is calculated and plotted on an H-T plane diagram. These
calculations use an effective medium approximation and a Gaussian distribution
of Tc.
(iii) Measuring the temperature dependences of a voltage, induced by a
focused electron beam, we determine spatial distributions of the critical
temperature for YBaCuO microbridges with a 2 micron resolution. A typical
Tc-distribution dispersion is found to be approximately 1K. For such
dispersion, error in \sigma_s(T,H,Tc) due to Tc-inhomogeneity exceeds 30% for
magnetic fields H < 1 T and temperatures |T-Tc| < 0.5 K.
(iv) Experimental R(T,H) dependences of resistance are well described by a
numerical solution of a set of Kirchoff equations for the resistor network
based on the measured spatial distributions of Tc and the expression for
\sigma_s(T,H,Tc).Comment: REVTeX, 12 pages including 7 figures, resubmitted to Phys. Rev.
Vitamin D and subsequent all-age and premature mortality: a systematic review
<br>Background:
All-cause mortality in the population < 65 years is 30% higher in Glasgow than in equally deprived Liverpool and Manchester. We investigated a hypothesis that low vitamin D in this population may be associated with premature mortality via a systematic review and meta-analysis.</br>
<br>Methods:
Medline, EMBASE, Web of Science, the Cochrane Library and grey literature sources were searched until February 2012 for relevant studies. Summary statistics were combined in an age-stratified meta-analysis.</br>
<br>Results:
Nine studies were included in the meta-analysis, representing 24,297 participants, 5,324 of whom died during follow-up. The pooled hazard ratio for low compared to high vitamin D demonstrated a significant inverse association (HR 1.19, 95% CI 1.12-1.27) between vitamin D levels and all-cause mortality after adjustment for available confounders. In an age-stratified meta-analysis, the hazard ratio for older participants was 1.25 (95% CI 1.14-1.36) and for younger participants 1.12 (95% CI 1.01-1.24).</br>
<br>Conclusions:
Low vitamin D status is inversely associated with all-cause mortality but the risk is higher amongst older individuals and the relationship is prone to residual confounding. Further studies investigating the association between vitamin D deficiency and all-cause mortality in younger adults with adjustment for all important confounders (or using randomised trials of supplementation) are required to clarify this relationship.</br>
Evaluation of α2-Integrin Expression as a Biomarker for Tumor Growth Inhibition for the Investigational Integrin Inhibitor E7820 in Preclinical and Clinical Studies
E7820 is an orally active inhibitor of α2-integrin mRNA expression, currently tested in phases I and II. We aimed to evaluate what levels of inhibition of integrin expression are needed to achieve tumor stasis in mice, and to compare this to the level of inhibition achieved in humans. Tumor growth inhibition was measured in mice bearing a pancreatic KP-1 tumor, dosed at 12.5–200 mg/kg over 21 days. In the phase I study, E7820 was administered daily for 28 days over a range of 0–200 mg, followed by a 7-day washout period. PK-PD models were developed in NONMEM. α2-Integrin expression measured on platelets, corresponding to tumor stasis at t = 21 in 50% and 90% of the mice (Iint,50, Iint,90) were calculated. It was evaluated if these levels of inhibition could be achieved in patients at tolerable doses. One hundred nineteen α2-Integrin measurements and 210 tumor size measurements were available from mice. The relationship between PK and α2-integrin expression was modeled using an indirect-effect model, subsequently linked to an exponential tumor growth model. Iinh,50 and Iinh,90 were 14.7% (RSE 7%) and 17.9% (RSE 8%). Four hundred sixty two α2-integrin measurements were available from 29 patients. Using the schedule of 100 mg qd (MTD), α2-integrin expression was inhibited more strongly than the Iint,50 and Iint,90 in greater than 95% and greater than 50% of patients, respectively. Moderate inhibition of α2-integrin expression corresponded to tumor stasis in mice, and similar levels could be reached in patients with the dose level of 100 mg qd
Micronutrient malnutrition and wasting in adults with pulmonary tuberculosis with and without HIV co-infection in Malawi
BACKGROUND: Wasting and micronutrient malnutrition have not been well characterized in adults with pulmonary tuberculosis. We hypothesized that micronutrient malnutrition is associated with wasting and higher plasma human immunodeficiency virus (HIV) load in adults with pulmonary tuberculosis. METHODS: In a cross-sectional study involving 579 HIV-positive and 222 HIV-negative adults with pulmonary tuberculosis in Zomba, Malawi, anthropometry, plasma HIV load and plasma micronutrient concentrations (retinol, α-tocopherol, carotenoids, zinc, and selenium) were measured. The risk of micronutrient deficiencies was examined at different severity levels of wasting. RESULTS: Body mass index (BMI), plasma retinol, carotenoid and selenium concentrations significantly decreased by increasing tertile of plasma HIV load. There were no significant differences in plasma micronutrient concentrations between HIV-negative individuals and HIV-positive individuals who were in the lowest tertile of plasma HIV load. Plasma vitamin A concentrations <0.70 μmol/L occurred in 61%, and zinc and selenium deficiency occurred in 85% and 87% respectively. Wasting, defined as BMI<18.5 was present in 59% of study participants and was independently associated with a higher risk of low carotenoids, and vitamin A and selenium deficiency. Severe wasting, defined as BMI<16.0 showed the strongest associations with deficiencies in vitamin A, selenium and plasma carotenoids. CONCLUSIONS: These data demonstrate that wasting and higher HIV load in pulmonary tuberculosis are associated with micronutrient malnutrition
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