Motion of a sphere through an aging system

We have investigated the drag on a sphere falling through a clay suspension that has a yield stress and exhibits rheological aging. The drag force increases with both speed and the rest time between preparation of the system and the start of the experiment, but there exists a nonzero minimum speed below which steady motion is not possible. We find that only a very thin layer of material around the sphere is fluidized when it moves, while the rest of suspension is deformed elastically. This is in marked contrast to what is found for yield-stress fluids that do not age.Comment: latex, 4 figure

Shopping malls as catalyst for sub-urban development in Ghana

The concentration of population in major cities is usually the consequence of the concentration of employment opportunities, goods and services in such cities. These goods and services act as pull factors to the regional population, especially from the suburban or rural areas, to densely populated cities. The resulting migration creates congestion of all kinds in the cities. Suburban communities are, thus, rendered unattractive for living. This situation is prevalent in Ghana where 75% of migrants into major cities are from suburban areas and the rate of urbanization is 4.1%. Decentralizing amenities to suburban areas would initiate re-distribution of population and thus development. This study investigated the possibility of using the Shopping Mall concept as catalyst to both help develop the suburbia and decongest cities in Ghana. The West Hills Mall at Dunkonah, a suburb near Accra was selected for the study. A mixed research method including  questionnaires, interviews, and observations was used for data collection. Out of a total of 1,642 house owners 328 were sampled and interviewed with questionnaire that delved into their origins, whether they are migrants, and the reasons behind their movement. The study concluded that shopping malls could act as catalysts for development.Keywords: Shopping Malls, Catalyst, Decongestion, Suburbanization, Amenitie

Mircorheology and jamming in a yield-stress fluid

Abstract We study the onset of a yield stress in a polymer microgel dispersion using a combination of particle-tracking microrheology and shear rheometry. On the bulk scale, the dispersion changes from a predominantly viscous fluid to a stiff elastic gel as the concentration of the microgel particles increases. On the microscopic scale, the tracer particles see two distinct microrheological environments over a range of concentrations-one being primarily viscous, the other primarily elastic. The fraction of the material that is elastic on the microscale increases from zero to one as the concentration increases. Our results indicate that the yield stress appears as the result of jamming of the microgel particles, and we infer a model for the small-scale structure and interactions within the dispersion and their relationship to the bulk viscoelastic properties

Starting a Laparoscopic Surgery Programme in the Second Largest Teaching Hospital in Ghana

Background: Komfo Anokye Teaching Hospital (KATH) is the second  largest hospital in Ghana. Two years have elapsed after performance of the first laparoscopic cholecystectomy.Objectives: To examine our experience and lessons learned.Design: Retrospective review.Setting: Komfo Anokye Teaching Hospital (KATH). Subjects: We reviewed leadership support, the role of a surgeon champion, training of physician and OR staff, influence of surgeons from outside Ghana and equipment status. The results of laparoscopic cholecystectomies performed from 2010-2012 were compared with information available from open cholecystectomies over the same period.Results: Evidence of leadership support included equipment purchase and invitation of outside experts yearly from 2008. A KATH surgeon champion was identified in 2010. A dedicated OR team received training and exhibited excellent ownership of equipment preparation. Since 2010, 25 laparoscopic cholecystectomies have been performed, 17 independently by a single surgeon. Average operative time was 1.41 hours and length of stay (LOS) 1.5 days. Conversion rate was 4.0%(1/25). Complication rate was 20.0%(5/25), none involving haemorrhage or injuries to bile ducts or bowel. Median patient satisfaction score was 5 on a scale of 1-5 where 5 is most satisfied. Complication rates and hospital stay were lower than for open cholecystectomy (20.0%vs34.5%, p>0.05 and 1.5days vs 6.6days, p<0.001 respectively). Operative times were on average 27min onger for laparoscopic cholecystectomy (p<0.01).Conclusion: Laparoscopic cholecystectomy at KATH has become a reality with less complications rates, shorter LOS, and trends towards improved patient satisfaction. Expanding laparoscopic surgery in Ghana requires its inclusion into residency training programmes and public education about its benefits for both patients and physicians

Evaluation of Credit Risk Management Practices in Societe Generale Ghana

The study evaluated the credit risk management strategies of SG-SSB Ghana. The research was an attempt to assess the extent to which the implementation of various credit risk management strategies by the bank has reduced the amount of non-performing loans. In order to answer the research objectives, the case study approach was employed where face-to face interview was conducted to collate the views of a senior credit officer at SG-SSB Ghana Ltd on credit risk management strategies. Besides, information on non-performing loans was obtained from administered questionnaires. The results from the study showed that SG-SSB has a clear, written guideline on credit risk management with the board of directors having an oversight responsibility for implementation. SG-SSB realigns the amount of credit within various sectors grouped into a credit portfolio depending on environmental factors such as political regime, macroeconomic strategy of political regimes, new and existing regulations and legislation, social concerns of operating markets and technological developments within the banking industry in Ghana.  The study recommends that SG-SSB should work in collaboration with credit reference bureau in the country to thoroughly investigate the past credit records of loan applicants so as to reduce the high rate of default

The impact of the COVID-19 pandemic on deaf adults, children and their families in Ghana

This paper investigates the impact of the COVID-19 pandemic on deaf adults, children, and their families in Ghana, focusing on issues of inclusion. We ask what it takes to ‘make cities and human settlements inclusive, safe, resilient and sustainable’ (United Nations Strategic Development Goal 11) for deaf people in the context of the global pandemic in a low-resource context. The exceptional challenge to inclusion posed by COVID-19 is examined in terms of issues for deaf children and their families, and from the point of view of deaf adults in advocacy and support organisations. The pivotal language and communication issues are shown through a bioecological analysis that illuminates the interdependent dynamics of development and context, and their influence on access to, and understanding of, crucial information. It is argued that the global crisis of COVID-19 exposes and deepens issues of societal exclusion for deaf adults, children, and their families, and provokes wider questions about what inclusion means, and how it can be realised, in different cultural contexts

A Fermi-degenerate three-dimensional optical lattice clock

Strontium optical lattice clocks have the potential to simultaneously interrogate millions of atoms with a high spectroscopic quality factor of $4 \times 10^{-17}$. Previously, atomic interactions have forced a compromise between clock stability, which benefits from a large atom number, and accuracy, which suffers from density-dependent frequency shifts. Here, we demonstrate a scalable solution which takes advantage of the high, correlated density of a degenerate Fermi gas in a three-dimensional optical lattice to guard against on-site interaction shifts. We show that contact interactions are resolved so that their contribution to clock shifts is orders of magnitude lower than in previous experiments. A synchronous clock comparison between two regions of the 3D lattice yields a $5 \times 10^{-19}$ measurement precision in 1 hour of averaging time.Comment: 19 pages, 4 figures; Supplementary Material

Realizing spin squeezing with Rydberg interactions in a programmable optical clock

Neutral-atom arrays trapped in optical potentials are a powerful platform for studying quantum physics, combining precise single-particle control and detection with a range of tunable entangling interactions. For example, these capabilities have been leveraged for state-of-the-art frequency metrology as well as microscopic studies of entangled many-particle states. In this work, we combine these applications to realize spin squeezing - a widely studied operation for producing metrologically useful entanglement - in an optical atomic clock based on a programmable array of interacting optical qubits. In this first demonstration of Rydberg-mediated squeezing with a neutral-atom optical clock, we generate states that have almost 4 dB of metrological gain. Additionally, we perform a synchronous frequency comparison between independent squeezed states and observe a fractional frequency stability of $1.087(1)\times 10^{-15}$ at one-second averaging time, which is 1.94(1) dB below the standard quantum limit, and reaches a fractional precision at the $10^{-17}$ level during a half-hour measurement. We further leverage the programmable control afforded by optical tweezer arrays to apply local phase shifts in order to explore spin squeezing in measurements that operate beyond the relative coherence time with the optical local oscillator. The realization of this spin-squeezing protocol in a programmable atom-array clock opens the door to a wide range of quantum-information inspired techniques for optimal phase estimation and Heisenberg-limited optical atomic clocks.Comment: 13 pages, 4 figures; Supplementary Informatio

Childbearing and Economic Work: The Health Balance of Women in Accra, Ghana

Objectives: This study aims to investigate (1) whether the health of working women with young children differs from that of working women without young children, and (2) which social factors mediate the relationship between economic and maternal role performance and health among mothers with young children. Methods: The analyses uses panel data from 697 women present in both waves of the Women's Health Study for Accra (WHSA-I and WHSA-II); a community based study of women aged 18 years and older in the Accra Metropolitan Area of Ghana conducted in 2003 and 2008-2009. Change in physical and mental health between the survey waves is compared between women with a biological child alive at WHSA-II and born since WHSA-I and women without a living biological child at WHSA-II born in the interval. To account for attrition between the two survey waves selection models were used with unconditional change score models being used as the outcome model. Results: We found in our sample of working women that those who had a child born between WHSA-I and WHSA-II who was still alive at WHSA-II did not experience a change in mental or physical health different from other women. Among working women with young children, educational status, relationship to the household head and household demography were associated with change in mental health at the 5 % level, whilst migration status and household demography was associated with change in physical health scores. Conclusion: The results suggest there are no health penalties of combining work and childbearing among women with young children in Accra, Ghana