On Velocity Measurements in Non-Isothermal Turbulent Flows

Turbulent velocity measurements in non-isothermal flows are conventionally performed by constant current hot-wire anemometry. The procedure involved however is cumbersome, the output signals are nonlinear and more critically a continuous signal of velocity fluctuations is not provided. The method described here utilizes two orthogonal wires situated a fraction of a millimeter apart. The upstream wire is operated in a low overheat, constant-current compensated mode thus providing a signal proportional to temperature while the down-stream wire, practically unaffected by the thermal wake of the first wire is operated in the constant temperature mode. Compensation for the effects of local temperature on the downstream wire is accomplished by the temperature signal obtained from the first wire. Variations of Kramers\u27 law coefficients (both being functions of density and thermal conductivities) due to temperature variations are compensated through an analog circuit at the input of the logarithmic amplifiers of the linearizer. By this method, linear and separate signals of the velocity and local temperature are thus obtained simultaneously and continuously. Advantages accruing from this method are readily adapted to cross-wire configuration thus permitting direct measurements of momentum and heat transfer in turbulent heated flows

Preliminary pharmacological investigation of the ischuretic property and safety of a hydro-ethanolic extract of Amaranthus spinosis (Fam: Amaranthaceae)

Background: Ischuria is a health and social problem, having a negative impact on sufferers. This study therefore was a preliminary investigation of the ischuretic property and safety for use of a hydro-ethanolic extract of Amaranthus spinosus used traditionally in managing ischuria.Methods: Phytochemical screening, thin layer chromatography and high performance liquid chromatography were performed on the extract to establish fingerprints for identification. Acetylcholine, Nicotine, and the extract were applied to an isolated rat urinary bladder to ascertain contractile response. The possible receptor site(s) of action was also investigated using isolated rabbit jejunum, and guinea-pig ileum preparations. In-house observation, hematological analysis, and liver and kidney function tests were performed on Sprague-Dawley rats, in acute and sub-acute toxicity studies.Results: The extract had contractile effects on the rat urinary bladder (similar to acetylcholine and nicotine) and rabbit jejunum. Its contractile effect of the guinea-pig ileum was significantly inhibited by hexamethonium (77.50 ± 8.50 %; P ≤ 0.001) and to a lesser extent by mepyramine (49.2 ± 6.80 %; P ≤ 0.001) and Atropine (22.45 ± 5.22 %; P ≤ 0.01). The extract (80-800 mg kg-1) was not lethal and a 160 and 240 mg kg-1 dose had no adverse effect on blood, liver, kidney metabolic function.Conclusions: The hydro-ethanolic extract of Amaranthus spinosus has ischuretic activity possibly mediated via nicotinic, histaminic and muscarinic receptor stimulation and is safety to use in ischuria

Phase-Locked Spatial Domains and Bloch Domain Walls in Type-II Optical Parametric Oscillators

We study the role of transverse spatial degrees of freedom in the dynamics of signal-idler phase locked states in type-II Optical Parametric Oscillators. Phase locking stems from signal-idler polarization coupling which arises if the cavity birefringence and/or dichroism is not matched to the nonlinear crystal birefringence. Spontaneous Bloch domain wall formation is theoretically predicted and numerically studied. Bloch walls connect, by means of a polarization transformation, homogeneous regions of self-phase locked solutions. The parameter range for their existence is analytically found. The polarization properties and the dynamics of walls in one- and two transverse spatial dimensions is explained. Transition from Bloch to Ising walls is characterized, the control parameter being the linear coupling strength. Wall dynamics governs spatiotemporal dynamical states of the system, which include transient curvature driven domain growth, persistent dynamics dominated by spiraling defects for Bloch walls, and labyrinthine pattern formation for Ising walls.Comment: 27 pages, 16 figure

Taking up the cudgels against gay rights? Trends and trajectories in African Christian theologies on homosexuality

Against the background of the HIV epidemic and the intense public controversy on homosexuality in African societies, this article investigates the discourses of academic African Christian theologians on homosexuality. Distinguishing some major strands in African theology, that is, inculturation, liberation, women’s and reconstruction theology, the article examines how the central concepts of culture, liberation, justice, and human rights function in these discourses. On the basis of a qualitative analysis of a large number of publications, the article shows that stances of African theologians are varying from silence and rejection to acceptance. Although many African theologians have taken up the cudgels against gay rights, some “dissident voices” break the taboo and develop more inclusive concepts of African identity and African Christianity

The Energy-Scaling Approach to Phase-Ordering Growth Laws

We present a simple, unified approach to determining the growth law for the characteristic length scale, $L(t)$, in the phase ordering kinetics of a system quenched from a disordered phase to within an ordered phase. This approach, based on a scaling assumption for pair correlations, determines $L(t)$ self-consistently for purely dissipative dynamics by computing the time-dependence of the energy in two ways. We derive growth laws for conserved and non-conserved $O(n)$ models, including two-dimensional XY models and systems with textures. We demonstrate that the growth laws for other systems, such as liquid-crystals and Potts models, are determined by the type of topological defect in the order parameter field that dominates the energy. We also obtain generalized Porod laws for systems with topological textures.Comment: LATeX 18 pages (REVTeX macros), one postscript figure appended, REVISED --- rearranged and clarified, new paragraph on naive dimensional analysis at end of section I

African Communitarianism and Difference

There has been the recurrent suspicion that community, harmony, cohesion, and similar relational goods as understood in the African ethical tradition threaten to occlude difference. Often, it has been Western defenders of liberty who have raised the concern that these characteristically sub-Saharan values fail to account adequately for individuality, although some contemporary African thinkers have expressed the same concern. In this chapter, I provide a certain understanding of the sub-Saharan value of communal relationship and demonstrate that it entails a substantial allowance for difference. I aim to show that African thinkers need not appeal to, say, characteristically Euro-American values of authenticity or autonomy to make sense of why individuals should not be pressured to conform to a group’s norms regarding sex and gender. A key illustration involves homosexuality

The Household Water Insecurity Experiences (HWISE) Scale: comparison scores from 27 sites in 22 countries

Abstract Household survey data from 27 sites in 22 countries were collected in 2017–2018 in order to construct and validate a cross-cultural household-level water insecurity scale. The resultant Household Water Insecurity Experiences (HWISE) scale presents a useful tool for monitoring and evaluating water interventions as a complement to traditional metrics used by the development community. It can also help track progress toward achievement of Sustainable Development Goal 6 ‘clean water and sanitation for all’. We present HWISE scale scores from 27 sites as comparative data for future studies using the HWISE scale in low- and middle-income contexts. Site-level mean scores for HWISE-12 (scored 0–36) ranged from 1.64 (SD 4.22) in Pune, India, to 20.90 (7.50) in Cartagena, Colombia, while site-level mean scores for HWISE-4 (scored 0–12) ranged from 0.51 (1.50) in Pune, India, to 8.21 (2.55) in Punjab, Pakistan. Scores tended to be higher in the dry season as expected. Data from this first implementation of the HWISE scale demonstrate the diversity of water insecurity within and across communities and can help to situate findings from future applications of this tool

Practicing Imperfect Forgiveness

Forgiveness is typically regarded as a good thing - even a virtue - but acts of forgiveness can vary widely in value, depending on their context and motivation. Faced with this variation, philosophers have tended to reinforce everyday concepts of forgiveness with strict sets of conditions, creating ideals or paradigms of forgiveness. These are meant to distinguish good or praiseworthy instances of forgiveness from problematic instances and, in particular, to protect the self-respect of would-be forgivers. But paradigmatic forgiveness is problematic for a number of reasons, including its inattention to forgiveness as a gendered trait. We can account for the values and the risks associated with forgiving far better if we treat it as a moral practice and not an ideal

The isimodeni style: traditional beadwork, Zulu trinket or, South African sartorial tradition on Durban’s Golden Mile?

Beadwork is a well-documented aspect of the socio-political culture of isiZulu-speaking groupings in Southern Africa. Whilst scholarship on beadwork deals largely with the denotative and connotative value it offers wearers, this article’s contribution relates both to its commodification and apolitical value by confronting a general assumption that a beadwork style known as isimodeni (modern beadwork), produced as a trinket for tourists along Durban’s racially stratified Golden Mile since the 1960s, is an authentic representation of a Zulu material culture. The paper probes how traditional beadwork and rickshaw rides (with both highly decorated carts and pullers) were earmarked by tourism officials of the time as commodities that could serve a demand for colourful exoticism and accessible “Zulu” culture. Methodologically, the article draws on the visual analysis of beaded artefacts and photographs, in addition to ethnographic data derived from unstructured interviews with beadworkers on the Durban beachfront, to examine how a beadwork tradition transformed into a “Zulu” tourism commodity, and then transmuted into a nationalised form of ethnic identity and sartorial tradition