4,316 research outputs found

    Correlation Effects on Transport Through Few-Electrons Systems

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    We study lateral tunneling through a quantum box including electron-electron interactions in the presence of a magnetic field which breaks single particle degeneracies. The conductance at zero temperature as a function of the Fermi energy in the leads consists of a set of peaks related to changing by one the electron occupancy in the box. We find that the position and heights of the peaks are controlled by many-body effects. We compute the conductance up to 8 electrons for several cases where correlation effects dominate. In the range of intermediate fields spin selection rules quench some peaks. At low and high fields the behavior of the conductance as a function of the number of electrons is very different due to big changes in the many-body ground state wavefunctions.Comment: 9 pages, 2 postscript figures, Latex 3.1

    The development of live attenuated cold-adapted influenza virus vaccine for humans

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    A procedure to attenuate live influenza virus of type A and type B was developed using adaptation of the virus to grow at 25°C (cold adaptation; ca). Through a series of stepwise passages, two stable mutants were obtained and designated as ‘Master’ strains, one for type A influenza virus (A/Ann Arbor/6/60-H2N2) and one for type B influenza virus (B/Ann Arbor/1/66). These mutants were used in genetic reassortment using either the classical method or more recently described reverse genetics to update the relevant surface antigens of the circulating strains of influenza virus. The derivation is based on the concept of 6/2 where 6 signifies the six internal genes of the master strain and 2 refers to the two genes coding for the two surface glycoproteins HA and NA of the circulating influenza virus. The advantages of this vaccine were demonstrated to be (1) proper level of attentuation, (2) non-transmissibility, (3) genetic stability, (4) presence of the ca and ts markers and (5) immunogenicity involving both local and the cell-mediated immune responses. The clinical trials in infants, children, adults and elderly have provided the necessary data for eventual licensing of this vaccine. The ease of administration (intranasal) safety and high efficacy make this vaccine suitable to prevent influenza virus infection in all age groups. Copyright © 1999 John Wiley & Sons, Ltd.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/35147/1/252_ftp.pd

    Team Spirit: How Three Libraries Are Working to Support Health Sciences Libraries in Liberia

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    This poster presentation is a collaborative effort of librarians from Lamar Soutter Library, University of Massachusetts Medical School; Himmelfarb Health Sciences Library, The George Washington University; and Louis Stokes Health Sciences Library, Howard University. International medicine initiatives often occur through institution specific efforts. Yet information needs extend across borders and institutions. Three American health sciences libraries have united to support the development of health sciences libraries in Liberia. While separate schools will support undergraduate and graduate medical education initiatives, the libraries are working together to bring current information resources to all health care professionals

    Interventions targeted at women to encourage the uptake of cervical screening

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    BACKGROUND World-wide, cervical cancer is the second most common cancer in women. Increasing the uptake of screening, alongside increasing informed choice is of great importance in controlling this disease through prevention and early detection. OBJECTIVES To assess the effectiveness of interventions aimed at women, to increase the uptake, including informed uptake, of cervical cancer screening. SEARCH STRATEGY We searched the Cochrane Gynaecological Cancer Group Trials Register, Cochrane Central Register of Controlled Trials (CENTRAL), Issue 1, 2009. MEDLINE, EMBASE and LILACS databases up to March 2009. We also searched registers of clinical trials, abstracts of scientific meetings, reference lists of included studies and contacted experts in the field. SELECTION CRITERIA Randomised controlled trials (RCTs) of interventions to increase uptake/informed uptake of cervical cancer screening. DATA COLLECTION AND ANALYSIS Two review authors independently abstracted data and assessed risk of bias. Where possible the data were synthesised in a meta-analysis. MAIN RESULTS Thirty-eight trials met our inclusion criteria. These trials assessed the effectiveness of invitational and educational interventions, counselling, risk factor assessment and procedural interventions. Heterogeneity between trials limited statistical pooling of data. Overall, however, invitations appear to be effective methods of increasing uptake. In addition, there is limited evidence to support the use of educational materials. Secondary outcomes including cost data were incompletely documented so evidence was limited. Most trials were at moderate risk of bias. Informed uptake of cervical screening was not reported in any trials. AUTHORS' CONCLUSIONS There is evidence to support the use of invitation letters to increase the uptake of cervical screening. There is limited evidence to support educational interventions but it is unclear what format is most effective. The majority of the studies are from developed countries and so the relevance to developing countries is unclear.Output Type: Revie

    PHOTOCHEMISTRY OF PHYCOBILIPROTEINS

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    Native PEC from the cyanobacterium, Mastigocladus laminosus, and its isolated α-subunit show photoreversibly photochromic reactions with difference-maxima around 502 and 570 nm in the spectral region of the α-84 phycoviolobilin chromophore. (b) Native PEC and its β-subunit show little if any reversible photochemistry in the 600–620 nm region, where the phycocyanobilin chromophores on the β-subunit absorb maximally, (c) Reversible photochemistry is retained in ureadenatured PEC at pH = 7.0 or pH ≤ 3. The difference maxima are shifted to 510 and 600 nm, and the amplitudes are decreased. An irreversible absorbance increase occurs around 670 nm (pH ≤ 3). (d) The amplitude of the reversible photoreaction difference spectrum is maximum in the presence of 4–5 M urea or 1 M KSCN, conditions known to dissociate phycobiliprotein aggregates into monomers. At the same time, the phycocyanobilin chromophore(s) are bleached irreversibly, (e) The amplitude becomes very small in high aggregates, e.g. in phycobilisomes. (f) In a reciprocal manner, the phototransformation of native PEC leads to a reversible shift of its aggregation equilibrium between trimer and monomer. The latter is favored by orange, the former by green light, (g) It is concluded that the phycoviolobilin chromophore of PEC is responsible for reversible photochemistry in PEC, and that there is not only an influence of aggregation state on photochemistry, but also vice versa an effect of the status of the chromophore on aggregation state. This could constitute a primary signal in the putative function as sensory pigment, either directly, or indirectly via the release of other polypeptides, via photodynamic effects, or the like

    Priority setting in developing countries health care institutions: the case of a Ugandan hospital

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    BACKGROUND: Because the demand for health services outstrips the available resources, priority setting is one of the most difficult issues faced by health policy makers, particularly those in developing countries. However, there is lack of literature that describes and evaluates priority setting in these contexts. The objective of this paper is to describe priority setting in a teaching hospital in Uganda and evaluate the description against an ethical framework for fair priority setting processes – Accountability for Reasonableness. METHODS: A case study in a 1,500 bed national referral hospital receiving 1,320 out patients per day and an average budget of US$ 13.5 million per year. We reviewed documents and carried out 70 in-depth interviews (14 health planners, 40 doctors, and 16 nurses working at the hospital). Interviews were recorded and transcribed. Data analysis employed the modified thematic approach to describe priority setting, and the description was evaluated using the four conditions of Accountability for Reasonableness: relevance, publicity, revisions and enforcement. RESULTS: Senior managers, guided by the hospital strategic plan make the hospital budget allocation decisions. Frontline practitioners expressed lack of knowledge of the process. Relevance: Priority is given according to a cluster of factors including need, emergencies and patient volume. However, surgical departments and departments whose leaders "make a lot of noise" are also prioritized. Publicity: Decisions, but not reasons, are publicized through general meetings and circulars, but this information does not always reach the frontline practitioners. Publicity to the general public was through ad hoc radio programs and to patients who directly ask. Revisions: There were no formal mechanisms for challenging the reasoning. Enforcement: There were no mechanisms to ensure adherence to the four conditions of a fair process. CONCLUSION: Priority setting decisions at this hospital do not satisfy the conditions of fairness. To improve, the hospital should: (i) engage frontline practitioners, (ii) publicize the reasons for decisions both within the hospital and to the general public, and (iii) develop formal mechanisms for challenging the reasoning. In addition, capacity strengthening is required for senior managers who must accept responsibility for ensuring that the above three conditions are met

    PARP-3 and APLF function together to accelerate nonhomologous end joining

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    PARP-3 is a member of the ADP-ribosyl transferase superfamily of unknown function. We show that PARP-3 is stimulated by DNA double-strand breaks (DSBs) in vitro and functions in the same pathway as the poly (ADP-ribose)-binding protein APLF to accelerate chromosomal DNA DSB repair. We implicate PARP-3 in the accumulation of APLF at DSBs and demonstrate that APLF promotes the retention of XRCC4/DNA ligase IV complex in chromatin, suggesting that PARP-3 and APLF accelerate DNA ligation during nonhomologous end-joining (NHEJ). Consistent with this, we show that class switch recombination in Aplf−/− B cells is biased toward microhomology-mediated end-joining, a pathway that operates in the absence of XRCC4/DNA ligase IV, and that the requirement for PARP-3 and APLF for NHEJ is circumvented by overexpression of XRCC4/DNA ligase IV. These data identify molecular roles for PARP-3 and APLF in chromosomal DNA double-strand break repair reactions
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