Classification of Parameter-Dependent Quantum Integrable Models, Their Parameterization, Exact Solution, and Other Properties

We study general quantum integrable Hamiltonians linear in a coupling constant and represented by finite NxN real symmetric matrices. The restriction on the coupling dependence leads to a natural notion of nontrivial integrals of motion and classification of integrable families into Types according to the number of such integrals. A Type M family in our definition is formed by N-M nontrivial mutually commuting operators linear in the coupling. Working from this definition alone, we parameterize Type M operators, i.e. resolve the commutation relations, and obtain an exact solution for their eigenvalues and eigenvectors. We show that our parameterization covers all Type 1, 2, and 3 integrable models and discuss the extent to which it is complete for other types. We also present robust numerical observation on the number of energy level crossings in Type M integrable systems and analyze the taxonomy of types in the 1d Hubbard model.Comment: 41 pages, 4 figures, 1 tabl

Thermoelectric prospects of nanomaterials with spin-orbit surface bands

Nanostructured composites and nanowire arrays of traditional thermoelectrics like Bi, Bi(1-x)Sb(x) and Bi(2)Te(3) have metallic Rashba surface spin-orbit bands featuring high mobilities rivaling that of the bulk for which topological insulator behavior has been proposed. Nearly pure surface electronic transport has been observed at low temperatures in Bi nanowires with diameter around the critical diameter, 50 nm, for the semimetal-to semiconductor transition. The surface contributes strongly to the thermopower, actually dominating for temperatures T < 100 K in these nanowires. The surface thermopower was found to be -1 T microvolt/(K^2), a value that is consistent with theory. We show that surface electronic transport together with boundary phonon scattering leads to enhanced thermoelectric performance at low temperatures of Bi nanowire arrays. We compare with bulk n-BiSb alloys, optimized CsBi(4)Te(6) and optimized Bi(2)Te(3). Surface dominated electronic transport can be expected in nanomaterials of the other traditional thermoelectrics.Comment: 18 pages, 3 figure

Agro-climatic and hydrological characterization of selected watersheds in northern Ghana

United States Agency for International Developmen

Connecting with home, keeping in touch : physical and virtual mobility across stretched families in sub-Saharan Africa.

There is a long history of migration among low-income families in sub-Saharan Africa, in which (usually young, often male) members leave home to seek their fortune in what are perceived to be more favourable locations. While the physical and virtual mobility practices of such stretched families are often complex and contingent, maintaining contact with distantly located close kin is frequently of crucial importance for the maintenance of emotional (and possibly material) well-being, both for those who have left home and for those who remain. This article explores the ways in which these connections are being reshaped by increasing access to mobile phones in three sub-Saharan countries – Ghana, Malawi and South Africa – drawing on interdisciplinary, mixed-methods research from twenty-four sites, ranging from poor urban neighbourhoods to remote rural hamlets. Stories collected from both ends of stretched families present a world in which the connectivities now offered by the mobile phone bring a different kind of closeness and knowing, as instant sociality introduces a potential substitute for letters, cassettes and face-to-face visits, while the rapid resource mobilization opportunities identified by those still at home impose increasing pressures on migrant kin

Podoconiosis in East and West Gojam Zones, Northern Ethiopia

Background: Podoconiosis is a neglected tropical disease (NTD) that is prevalent in red clay soil-covered highlands of tropical Africa, Central and South America, and northern India. It is estimated that up to one million cases exist in Ethiopia. This study aimed to estimate the prevalence of podoconiosis in East and West Gojam Zones of Amhara Region in northern Ethiopia. Methodology/Principal Findings: A cross-sectional household survey was conducted in Debre Eliyas and Dembecha woredas (districts) in East and West Gojam Zones, respectively. The survey covered all 17,553 households in 20 kebeles (administrative subunits) randomly selected from the two woredas. A detailed structured interview was conducted on 1,704 cases of podoconiosis identified in the survey. Results: The prevalence of podoconiosis in the population aged 15 years and above was found to be 3.3% (95% CI, 3.2% to 3.6%). 87% of cases were in the economically active age group (15–64 years). On average, patients sought treatment five years after the start of the leg swelling. Most subjects had second (42.7%) or third (36.1%) clinical stage disease, 97.9% had mossy lesions, and 53% had open wounds. On average, patients had five episodes of acute adenolymphangitis (ALA) per year and spent a total of 90 days per year with ALA. The median age of first use of shoes and socks were 22 and 23 years, respectively. More men than women owned more than one pair of shoes (61.1% vs. 50.5%; x2 = 11.6 p = 0.001). At the time of interview, 23.6% of the respondents were barefoot, of whom about two-thirds were women. Conclusions: This study showed high prevalence of podoconiosis and associated morbidities such as ALA, mossy lesions and open wounds in northern Ethiopia. Predominance of cases at early clinical stage of podoconiosis indicates the potential for reversing the swelling and calls for disease prevention interventions

Knowledge and perception of Ghanaian cocoa farmers on mirid control and their willingness to use forecasting systems

Annual losses of cocoa in Ghana to mirids are significant. Therefore, accurate timing of insecticide application is critical to enhance yields. However, cocoa farmers often lack information on the expected mirid population for each season to enable them to optimise pesticide use. This study assessed farmers’ knowledge and perceptions of mirid control and their willingness to use forecasting systems informing them of expected mirid peaks and time of application of pesticides. A total of 280 farmers were interviewed in the Eastern and Ashanti regions of Ghana with a structured open and closed ended questionnaire. Most farmers (87%) considered mirids as the most important insect pest on cocoa with 47% of them attributing 30-40% annual crop loss to mirid damage. There was wide variation in the timing of insecticide application as a result of farmers using different sources of information to guide the start of application. The majority of farmers (56%) do not have access to information on the type, frequency and timing of insecticides to use. However, respondents who are members of farmer groups had better access to such information. Extension officers were the preferred channel for information transfer to farmers with 72% of farmers preferring them to other available methods of communication. Almost all the respondents (99%) saw the need for a comprehensive forecasting system to help farmers manage cocoa mirids. The importance of accurate timing for mirid control based on forecasted information to farmer groups and extension officers was discussed

Burden of podoconiosis in poor rural communities in Guliso woreda, western Ethiopia

Background. Podoconiosis is an environmental lymphoedema affecting people living and working barefoot on irritant red clay soil. Podoconiosis is relatively well described in southern Ethiopia, but remains neglected in other parts of the Ethiopian highlands. This study aimed to assess the burden of podoconiosis in rural communities in western Ethiopia. Methodology/Principal Findings. A cross-sectional study was conducted in Gulliso woreda (district), west Ethiopia. A household survey in the 26 rural kebeles (villages) of this district was conducted to identify podoconiosis patients and to measure disease prevalence. A more detailed study was done in six randomly selected kebeles to describe clinical features of the disease, patients’ experiences of foot hygiene, and shoe wearing practice. 1,935 cases of podoconiosis were registered, giving a prevalence of 2.8%. The prevalence was higher in those aged 15 – 64 years (5.2%) and in females than males (prevalence ratio 2.6:1). 90.3% of patients were in the 15 – 64 year age group. In the detailed study, 335 cases were interviewed and their feet assessed. The majority of patients were farmers, uneducated, and poor. Two-third of patients developed the disease before the age of thirty. Almost all patients (97.0%) had experienced adenolymphangitis (ALA - red, hot legs, swollen and painful groin) at least once during the previous year. Patients experienced an average of 5.5 ALA episodes annually, each of average 4.4 days, thus 24 working days were lost annually. The incidence of ALA in podoconiosis patients was higher than that reported for filariasis in other countries. Shoe wearing was limited mainly due to financial problems. Conclusions. We have documented high podoconiosis prevalence, frequent adenolymphangitis and high disease-related morbidity in west Ethiopia. Interventions must be developed to prevent, treat and control podoconiosis, one of the core neglected tropical diseases in Ethiopia

Profile of cancer patients’ seen at Korle Bu teaching hospital in Ghana (A cancer registry review)

BACKGROUND: Though cancer has become a major source of morbidity and mortality globally, few countries in Sub Saharan Africa have data on cancer incidence. This study aims to describe the profile of cancers seen at the Korle Bu teaching hospital which is a major referral centre in Ghana for cancers and other health conditions. Data for the study was obtained from the cancer registry of the hospital and covered the period from January 2012 to December 2012. The public health unit actively collects data on all cancer cases presenting to any department/unit of the hospital to feed the cancer registry. RESULTS: A total of 1136 patients with cancer were studied. Their ages ranged from 1 year to 92 years with a mean of 52.3 ± 15.9 years and a median of 54 years. Patients were predominantly female (70.2%) and majority had attained secondary level of education or higher. The most prevalent cancers seen in men were those of prostate, pharynx and colorectal while in the females, the corresponding cancers were breast, cervix and uterus. CONCLUSIONS: Breast and prostate cancers were the commonest among females and males respectively who presented with cancer at the Korle Bu teaching hospital in 2012