Improving antibiotic prescribing for children in the resource-poor setting.

Antibiotics are a critically important part of paediatric medical care in low- and middle-income countries (LMICs), where infectious diseases are the leading cause of child mortality. The World Health Organization estimates that >50% of all medicines are prescribed, dispensed or sold inappropriately and that half of all patients do not take their medicines correctly. Given the rising prevalence of antimicrobial resistance globally, inappropriate antibiotic use is of international concern, and countries struggle to implement basic policies promoting rational antibiotic use. Many barriers to rational paediatric prescribing in LMICs persist. The World Health Organization initiatives, such as 'Make medicines child size', the Model List of Essential Medicines for Children and the Model Formulary for Children, have been significant steps forward. Continued strategies to improve access to appropriate drugs and formulations, in conjunction with improved evidence-based clinical guidelines and dosing recommendations, are essential to the success of such initiatives on both a national and an international level. This paper provides an overview of these issues and considers future developments that may improve LMIC antibiotic prescribing

RR Lyrae Variables in M33. I. Evidence For a Field Halo Population

We present observations of RR Lyrae variables in the Local Group late-type spiral galaxy M33. Using the Advanced Camera for Surveys on the Hubble Space Telescope, we have identified 64 ab-type RR Lyraes in M33. We have estimated reddenings for these stars based on their minimum light V-I colors and metallicities based on their periods. From the distributions of these properties, we conclude that the RR Lyraes belong to two populations - one associated with the halo of M33 and the other with its disk. Given that RR Lyraes are produced by populations older than ~10 Gyr, this suggests that not only does the field halo of M33 contain an old component, but so does its disk. This is one of the best pieces of evidence for the existence of a halo field component in M33. Using a relation between RR Lyrae absolute magnitude and metallicity (Mv(RR) = 0.23[Fe/H] + 0.93), we estimate a mean distance modulus of = 24.67 +/- 0.08 for M33. This places M33 approximately 70 kpc beyond M31 in line-of-sight distance.Comment: 20 pages, 17 figures, accepted for publication in The Astronomical Journa

Blunting the Spike: the CV Minimum Period

The standard picture of CV secular evolution predicts a spike in the CV distribution near the observed short-period cutoff P_0 ~ 78 min, which is not observed. We show that an intrinsic spread in minimum (`bounce') periods P_b resulting from a genuine difference in some parameter controlling the evolution can remove the spike without smearing the sharpness of the cutoff. The most probable second parameter is different admixtures of magnetic stellar wind braking (at up to 5 times the GR rate) in a small tail of systems, perhaps implying that the donor magnetic field strength at formation is a second parameter specifying CV evolution. We suggest that magnetic braking resumes below the gap with a wide range, being well below the GR rate in most CVs, but significantly above it in a small tail.Comment: 5 pages, 4 figures; accepted for publication in MNRA

Determination of S17 from 8B breakup by means of the method of continuum-discretized coupled-channels

The astrophysical factor for 7Be(p,\gamma)8B at zero energy, S17(0), is determined from an analysis of 208Pb(8B, p+7Be)208Pb at 52 MeV/nucleon by means of the method of continuum-discretized coupled-channels (CDCC) taking account of all nuclear and Coulomb breakup processes. The asymptotic normalization coefficient (ANC) method is used to extract S17(0) from the calculated breakup-cross-section. The main result of the present paper is S17(0)=20.9 +2.0/-1.9 eV b. The error consists of 8.4% experimental systematic error and the error due to the ambiguity in the s-wave p-7Be scattering length. This value of S17(0) differs from the one extracted with the first-order perturbation theory including Coulomb breakup by dipole transitions: 18.9 +/- 1.8 eV b. It turns out that the difference is due to the inclusion of the nuclear and Coulomb-quadrupole transitions and multi-step processes of all-order in the present work. The p-7Be interaction potential used in the CDCC calculation is also used in the ANC analysis of 7Be(p,\gamma)8B. The value of S17(0)=21.7 +0.62/-0.55 eV b obtained is consistent with the previous one obtained from a precise measurement of the p-capture reaction cross section extrapolated to zero incident energy, S17(0)=22.1 +/- 0.6 (expt) +/- 0.6 (theo) eV b, where (theo) stands for the error in the extrapolation. Thus, the agreement between the values of S17(0) obtained from direct 7Be(p,\gamma)8B and indirect 8B-breakup measurements is significantly improved.Comment: 13 pages, 9 figures, published in PR

Avian malaria co-infections confound infectivity and vector competence assays of Plasmodium homopolare.

Currently, there are very few studies of avian malaria that investigate relationships among the host-vector-parasite triad concomitantly. In the current study, we experimentally measured the vector competence of several Culex mosquitoes for a newly described avian malaria parasite, Plasmodium homopolare. Song sparrow (Melospiza melodia) blood infected with a low P. homopolare parasitemia was inoculated into a naïve domestic canary (Serinus canaria forma domestica). Within 5 to 10 days post infection (dpi), the canary unexpectedly developed a simultaneous high parasitemic infection of Plasmodium cathemerium (Pcat6) and a low parasitemic infection of P. homopolare, both of which were detected in blood smears. During this infection period, PCR detected Pcat6, but not P. homopolare in the canary. Between 10 and 60 dpi, Pcat6 blood stages were no longer visible and PCR no longer amplified Pcat6 parasite DNA from canary blood. However, P. homopolare blood stages remained visible, albeit still at very low parasitemias, and PCR was able to amplify P. homopolare DNA. This pattern of mixed Pcat6 and P. homopolare infection was repeated in three secondary infected canaries that were injected with blood from the first infected canary. Mosquitoes that blood-fed on the secondary infected canaries developed infections with Pcat6 as well as another P. cathemerium lineage (Pcat8); none developed PCR detectable P. homopolare infections. These observations suggest that the original P. homopolare-infected songbird also had two un-detectable P. cathemerium lineages/strains. The vector and host infectivity trials in this study demonstrated that current molecular assays may significantly underreport the extent of mixed avian malaria infections in vectors and hosts

Does gravity cause load-bearing bridges in colloidal and granular systems?

We study structures which can bear loads, "bridges", in particulate packings. To investigate the relationship between bridges and gravity, we experimentally determine bridge statistics in colloidal packings. We vary the effective magnitude and direction of gravity, volume fraction, and interactions, and find that the bridge size distributions depend only on the mean number of neighbors. We identify a universal distribution, in agreement with simulation results for granulars, suggesting that applied loads merely exploit preexisting bridges, which are inherent in dense packings

Low-energy quenching of positronium by helium

Very low-energy scattering of orthopositronium by helium has been investigated for simultaneous study of elastic cross section and pick-off quenching rate using a model exchange potential. The present calculational scheme, while agrees with the measured cross section of Skalsey et al, reproduces successfully the parameter ^ 1Z_{\makebox{eff}}, the effective number of electrons per atom in a singlet state relative to the positron. Together with the fact that this model potential also leads to an agreement with measured medium energy cross sections of this system, this study seems to resolve the long-standing discrepancy at low energies among different theoretical calculations and experimental measurements.Comment: 4 latex pages, 3 postscript figure