A Back-reaction Induced Lower Bound on the Tensor-to-Scalar Ratio

There are large classes of inflationary models, particularly popular in the context of string theory and brane world approaches to inflation, in which the ratio of linearized tensor to scalar metric fluctuations is very small. In such models, however, gravitational waves produced by scalar modes cannot be neglected. We derive the lower bound on the tensor-to-scalar ratio by considering the back-reaction of the scalar perturbations as a source of gravitational waves. These results show that no cosmological model that is compatible with a metric scalar amplitude of $\approx 10^{-5}$ can have a ratio of the tensor to scalar power spectra less than $\approx 10^{-8}$ at recombination and that higher-order terms leads to logarithmic growth for r during radiation domination. Our lower bound also applies to non-inflationary models which produce an almost scale-invariant spectrum of coherent super-Hubble scale metric fluctuations.Comment: 5 pages, version 3, minor changes from version

Knowledge and practice of exclusive breastfeeding among women with children aged between 9 and 12 months in Al-Sabah Children Hospital, Juba, South Sudan

Introduction: Breastfeeding is an important tool for preventing childhood illnesses, and obesity, and hypertension later on in life, and it reduces the cost of food for the family and the country. Appropriate practices that support exclusive breastfeeding in the first six months reduce childhood morbidity and mortality.Methodology: 384 mothers with children aged 9 to 12 months attending the immunization and paediatric outpatient clinics were interviewed. Statistical Package for Social Sciences (SPSS) was used for data handling. Descriptive statistics and univariate logistic regression were used to analyse the data.Results: The majority of mothers were aged between 21 – 25 years (43.5%), had 2 - 4 children (55.5%) and primary education (48.2%). Most mothers had started breastfeeding within the first hour of delivery (76.8%), and knew that breastfeeding was nutritious to the baby. Parity and mother`s level of education were significant factors associated with exclusive breastfeeding (p<0.05). There was no statistically significant association between occupation, age of the mother, mode of delivery and exclusive breastfeeding (p>0.05). There was no statistical difference in rate of exclusive breastfeeding in mothers attending the OPD and the immunization clinic (p value=0.09).Conclusion: Most mothers knew the benefits and definitions of exclusive  breastfeeding. The early measures supporting breastfeeding are well practiced. Parity and mothers` education significantly affected exclusive breastfeeding.Keys words: Exclusive breast feeding, child, nutritio

Instability of antiferromagnetic magnons in strong fields

We predict that spin-waves in an ordered quantum antiferromagnet (AFM) in a strong magnetic field become unstable with respect to spontaneous two-magnon decays. At zero temperature, the instability occurs between the threshold field $H^*$ and the saturation field $H_c$. As an example, we investigate the high-field dynamics of a Heisenberg antiferromagnet on a square lattice and show that the single-magnon branch of the spectrum disappears in the most part of the Brillouin zone.Comment: RevTeX, 4 pages, 3 figures, accepted to PR

Do clinicians adhere to practice guidelines? A descriptive study at a referral hospital in Kenya

Background: Clinical guidelines when implemented correctly have shown to improve disease outcomes. This study describes utilization of Kenya National guidelines in managing ante partum haemorrhage (APH) in 3rd trimester.Objective: To describe adherence to clinical guideline in management of antepartum haemorrhage at Garissa Provincial General Hospital Design: Crossectional mixed methods studySetting: Garissa Provincial General HospitalSubjects: Medical records of patients managed for APH between 2002 and 2012 and Key Informant Interviews (KIIs) of Health workers.Results: 36.1% of the cases assessed were managed with strict adherence to guidelines. 90% of health care workers had high levels of awareness of the existence of guidelines and sited utilization challenges attributed to resource inadequacies.Conclusion: Clinicians are skilled on APH guidelines, but adherence levels are still low. Therefore, continuous appraisal of clinical practices, availing equipment, facilities and supplies to reinforce adherence is recommended

Gauge invariant Boltzmann equation and the fluid limit

This article investigates the collisionless Boltzmann equation up to second order in the cosmological perturbations. It describes the gauge dependence of the distribution function and the construction of a gauge invariant distribution function and brightness, and then derives the gauge invariant fluid limit.Comment: 36 page

Density growth in Kantowski-Sachs cosmologies with cosmological constant

In this work the growth of density perturbations in Kantowski-Sachs cosmologies with a positive cosmological constant is studied, using the 1+3 and 1+1+2 covariant formalisms. For each wave number we obtain a closed system for scalars formed from quantities that are zero on the background and hence are gauge-invariant. The solutions to this system are then analyzed both analytically and numerically. In particular the effects of anisotropy and the behaviour close to a bounce in the cosmic scale factor are considered. We find that typically the density gradient in the bouncing directions experiences a local maximum at or slightly after the bounce.Comment: 33 pages, 17 picture

How close can an Inhomogeneous Universe mimic the Concordance Model?

Recently, spatially inhomogeneous cosmological models have been proposed as an alternative to the LCDM model, with the aim of reproducing the late time dynamics of the Universe without introducing a cosmological constant or dark energy. This paper investigates the possibility of distinguishing such models from the standard LCDM using background or large scale structure data. It also illustrates and emphasizes the necessity of testing the Copernican principle in order to confront the tests of general relativity with the large scale structure.Comment: 15 pages, 7 figure

Charting achievements: a two-year retrospective of the society for environmental geochemistry and health (SEGH) and the evolving strategies

Emerging from the shadow of the COVID-19 pandemic, it is time to ground ourselves and retrospectively assess the recent achievements of SEGH over the past years. This editorial serves as a comprehensive report on the progress made in comparison to the aspirations and goals set by the society's board in 2019 (Watts et al., Environ Geochem Health 42:343–347, 2019) (Fig. 1) and reflects on the state of the SEGH community as it reached its 50th anniversary at the close of 2021 (Watts et al. Environ Geochem Health 45:1165–1171, 2023). The focus lies on how the SEGH community navigated through the extraordinary challenges posed by the COVID-19 pandemic since early 2020, and to what extent the 2023 targets have been met

Antimicrobial resistance of Campylobacter isolates from small scale and backyard chicken in Kenya

Background Thermophilic Campylobacter species are a major cause of bacterial foodborne diarrhoea in humans worldwide. Poultry and their products are the predominant source for human campylobacteriosis. Resistance of Campylobacter to antibiotics is increasing worldwide, but little is known about the antibiotic resistance in Campylobacter isolated from chicken in Kenya. In this study, 35 suspected Campylobacter strains isolated from faeces and cloacal swabs of chicken were tested for their susceptibility to seven antibiotics using a broth microdilution assay and molecular biological investigations. Results Overall, DNA of thermophilic Campylobacter was identified in 53 samples by PCR (34 C. jejuni, 18 C. coli and one mix of both species) but only 35 Campylobacter isolates (31 C. jejuni and 4 C. coli) could be re-cultivated after transportation to Germany. Isolates were tested for their susceptibility to antibiotics using a broth microdilution assay. Additionally, molecular biological detection of antibiotic resistance genes was carried out. C. jejuni isolates showed a high rate of resistance to nalidixic acid, tetracycline and ciprofloxacin of 77.4, 71.0 and 71.0 %, respectively. Low resistance (25.8 %) was detected for gentamicin and chloramphenicol. Multidrug resistance in C. jejuni could be detected in 19 (61.3 %) isolates. Resistance pattern of C. coli isolates was comparable. Resistance to ciprofloxacin was confirmed by MAMA–PCR and PCR–RFLP in all phenotypically resistant isolates. The tet(O) gene was detected only in 54.5 % of tetracycline resistant C. jejuni isolates. The tet(A) gene, which is also responsible for tetracycline resistance, was found in 90.3 % of C. jejuni and in all C. coli isolates. Thirteen phenotypically erythromycin-resistant isolates could not be characterised by using PCR–RFLP and MAMA–PCR. Conclusions To the best of our knowledge, this study is the first report about resistance to antibiotics in thermophilic Campylobacter originating from chicken in Kenya. Campylobacter spp. show a high level of resistance to ciprofloxacin, nalidixic acid and tetracycline but also a remarkable one to chloramphenicol and gentamicin and they are multidrug resistant. Resistance to antibiotics is a global public health concern. In Kenya, resistance surveillance needs further attention in the future. Efforts to establish at least a National Laboratory with facilities for performing phenotypic and genotypic characterization of thermophilic Campylobacter is highly recommended