Electrohydrodynamic instability of two superposed fluids in normal electric fields

AbstractWe consider the linear stability of two unbounded fluids that are separated by a plane interface, and stressed by initially perpendicular uniform electric field. On each side of the interface there is a Coquette flow. The fluids have different viscosities, densities, and electrical properties and surface tension acts at the interface. The linear stability of the flow is analyzed by deriving the exact dispersion relation in terms of the Airy functions and their integrals, and solving it numerically and asymptotically to find marginal stability curves. The stability of the system depends on ten parameters: the ratio of viscosities, ratio of the densities, surface tension, gravity, ratio of the permitivities, two conductivities, two equilibrium electric fields and velocity of the upper fluid in the unperturbed motion. We investigate the electric charge relaxation effects on the stability of the flow by considering various limiting cases. We also examine the effects of finite charge relaxation times

Pattern of Fatal Injuries in Addis Ababa, Ethiopia: A One-year Audit

Background: Injury continues to account for a large number of clients attending emergency department in Addis Ababa. Reliable information on causes of death is essential to the development of health policies for prevention and control. The aim of this atudy was to identify the pattern and common causes of fatal injuriesMethods: This is prospective study analyses autopsy data related to fatal injuries handled by Menilik II Hospital between July1, 2006 –June 30, 2007. (Sene 24, 1998 - Sene 23, 1999)Results: A total of 2107 cases were analyzed. The victims were mostly male and the most vulnerable age group was found to be 15-44 years. Accidents versus homicide and accident versus suicide ratio was 1.8:1 and 5:1 respectively. Road traffic accidents were the most frequent causes of accident related death. Main means of homicide was hit by blunt or sharp object or firearm. More than 90% of victims who committed suicide use hanging or poisoning.Ninety percent of deaths occur with in 24 hours of the injury and only 105 (5%) died from the second day on wards. Eighty one percents of this patients had never received any medical care (either pre-hospital or hospital level).Conclusion: Road traffic accidents accounted for most causes of injury related deaths. Significant proportion of patients had no access to emergency medical care. The findings strongly suggest that more aggressive, regulatory, educational, and rapid emergency treatment is necessary to address the large number of injury related death

Pattern of injuries in Addis Ababa, Ethiopia: A one-year descriptive study

Background: Globally, trauma is recognized as one of the most life threatening public health problems. Traumatic injuries account for 12% of the global burden of diseases and are the third most important cause of overall mortality. This study was aaimed at assessing the burden of injuries in Addis Ababa, Ethiopia.Methods: A one-year (July 2005-June 2006) retrospective descriptive audit of injuries in a public health facility of Addis Ababa using external causes of injury codes on district health information system.Results: During the study period there were 40,752 out-patient department visits, of which 956 were hospitalizations with 35 deaths occurring as a results of injury which accounted for 27% of all emergency and 3% of all regular visits, 5% of all hospitalizations and 3% of deaths. The patients were predominantly young males. Even though falls were the commonest causes of unintentional injury, road traffic injuries were the main burden of the health facility being the commonest cause among young male and also accounted for 61% of injury related admission, 52% of injury related death, and leading cause of repeated visits. A total of 44% of unintentional injuries were categorized under ‘other accidental causes’, only 6 deaths were reported in the out patient department, and the conditions of one third of the patients at discharge were not recorded.Conclusion: The injury, especially road traffic injury, is the burden for health facility; there is a need for improving the way injuries are recorded and compiled

Synthesis of Ethylene Glycol Diesters as Bio-Lubricant from Jatropha Methyl Esters

     The synthesis of ethylene glycol diesters as bio-lubricant was achieved via Trans- esterification reaction of Jatropha Methyl Ester (JME).The experimental strategy consists from two Transesterification reaction steps.At first step,Jatropha oil was extracted and characterized and then converted into JME. Then JME was converted to biolubricant at 120oC, molar ratio of ethylene glycol to JME was 1:3.5 through 2.5 hr. and sodium meth-oxide was used as a catalyst was 0.8% w/w of total reactants. The physicochemical properties of the bio-lubricant were investigated. Kinematic viscosity at 40 oC was 16 cSt, kinematic viscosity at 100 oC was 4.54 cSt, viscosity index was 195.83 and the pour point was 18oC.FTIR spectrum for JME to confirm the ester group was 1741cm-1while for bio-lubricant was 1743cm-1.It was found that the synthesis bio-lubricant data agree with petroleum base lubricant that reported by previouswork investigation. ملخص الدراسة       تم اصطناع استرات الايثلين جلايكول الثنائية كزيت تزييت حيوي عن طريق  تفاعل الاسترة التحويلية لاسترات ميثيل الجاتروفا. استراتيجية التجربة اشتملت على خطوتين من تفاعل الاسترة التحويلية. الخطوة  الاولي تم استخلاص زيت الجاتروفا حيث تم دراسة خصائصه ثم حول الى استرات ميثيل الجاتروفا. حولتاسترات ميثيل الجاتروفا الى الزيت الحيوي عند درجة حرارة 120م◦ وذلك بنسبة مولية للايثلينجلايكول الى استرات ميثيل الجاتروفا (3.5:1)وكان زمن التفاعل 2.5 ساعة باستخدام ميثو اكسيد الصوديوم كعامل حفاز بنسبة 0.8% من الوزن الكلي للمتفاعلات. درست الخصائص الفيزيوكيميائية للزيت الحيوي مثل اللزوجة الكاينماتيكية عند 40 م◦ هي 16 سنتي ستوك ، واللزوجة الكينماتيكية عند100 م◦ هي 4.54 سنتي ستوك ، ومعامل اللزوجة هو 195.83 ، ونقطة الانسكاب هي 18 م◦. وايضا تم إجراء التحليل الطيفي بواسطة الاشعة تحت الحمراء لاستراتجاتروفا الميثيل  للتأكد من مجموعة الاستر كان عند طول موجي 1741 سم-1 بينما الطول الموجي للزيت الحيوي 1743 سم-1. وجد ان نتائج الزيت الحيوي الذي تم اصطناعه  تتفق مع نتائج زيت الاساس البترولي في الدراسات السابقة. &nbsp

Novel SCN9A mutations underlying extreme pain phenotypes: unexpected electrophysiological and clinical phenotype correlations.

The importance of NaV1.7 (encoded by SCN9A) in the regulation of pain sensing is exemplified by the heterogeneity of clinical phenotypes associated with its mutation. Gain-of-function mutations are typically pain-causing and have been associated with inherited erythromelalgia (IEM) and paroxysmal extreme pain disorder (PEPD). IEM is usually caused by enhanced NaV1.7 channel activation, whereas mutations that alter steady-state fast inactivation often lead to PEPD. In contrast, nonfunctional mutations in SCN9A are known to underlie congenital insensitivity to pain (CIP). Although well documented, the correlation between SCN9A genotypes and clinical phenotypes is still unclear. Here we report three families with novel SCN9A mutations. In a multiaffected dominant family with IEM, we found the heterozygous change L245 V. Electrophysiological characterization showed that this mutation did not affect channel activation but instead resulted in incomplete fast inactivation and a small hyperpolarizing shift in steady-state slow inactivation, characteristics more commonly associated with PEPD. In two compound heterozygous CIP patients, we found mutations that still retained functionality of the channels, with two C-terminal mutations (W1775R and L1831X) exhibiting a depolarizing shift in channel activation. Two mutations (A1236E and L1831X) resulted in a hyperpolarizing shift in steady-state fast inactivation. To our knowledge, these are the first descriptions of mutations with some retained channel function causing CIP. This study emphasizes the complex genotype-phenotype correlations that exist for SCN9A and highlights the C-terminal cytoplasmic region of NaV1.7 as a critical region for channel function, potentially facilitating analgesic drug development studies.J.J.C. and A.M.H. were supported by an MRC Research Career Development fellowship. F.M.G., F.R., and E.C.E. were supported by Wellcome Trust Senior Fellowships WT088357/Z/09/Z and WT084210/Z/07/Z and MRC Grant MC_UU_12012/3. C.G.W. was supported by the Cambridge Biomedical Research Campus.This is the final published version. It first appeared at http://www.jneurosci.org/content/35/20/7674.short

Stochastic excitation of acoustic modes in stars

For more than ten years, solar-like oscillations have been detected and frequencies measured for a growing number of stars with various characteristics (e.g. different evolutionary stages, effective temperatures, gravities, metal abundances ...). Excitation of such oscillations is attributed to turbulent convection and takes place in the uppermost part of the convective envelope. Since the pioneering work of Goldreich & Keely (1977), more sophisticated theoretical models of stochastic excitation were developed, which differ from each other both by the way turbulent convection is modeled and by the assumed sources of excitation. We review here these different models and their underlying approximations and assumptions. We emphasize how the computed mode excitation rates crucially depend on the way turbulent convection is described but also on the stratification and the metal abundance of the upper layers of the star. In turn we will show how the seismic measurements collected so far allow us to infer properties of turbulent convection in stars.Comment: Notes associated with a lecture given during the fall school organized by the CNRS and held in St-Flour (France) 20-24 October 2008 ; 39 pages ; 11 figure

A closure model with plumes I. The solar convection

Oscillations of stellar p modes, excited by turbulent convection, are investigated. We take into account the asymmetry of the up and downflows created by turbulent plumes through an adapted closure model. In a companion paper, we apply it to the formalism of excitation of solar p modes developed by Samadi & Goupil 2001. Using results from 3D numerical simulations of the upper most part of the solar convection zone, we show that the two-scale-mass-flux model (TFM) is valid only for quasi-laminar or highly skewed flows (Gryanik & Hartmann 2002). We build a generalized-Two-scale-Mass-Flux Model (GTFM) model which takes into account both the skew introduced by the presence of two flows and the effects of turbulence in each flow. In order to apply the GTFM to the solar case, we introduce the plume dynamics as modelled by Rieutord & Zahn (1995) and construct a Closure Model with Plumes (CMP). When comparing with 3D simulation results, the CMP improves the agreement for the fourth order moments, by approximatively a factor of two compared with the use of the quasi-normal approximation or a skewness computed with the classical TFM. The asymmetry of turbulent convection in the solar case has an important impact on the vertical-velocity fourth-order moment which has to be accounted for by models. The CMP is a significant improvement and is expected to improve the modelling of solar p-mode excitation.Comment: 13 pages, accepted for publication in A&

Pain-causing stinging nettle toxins target TMEM233 to modulate NaV1.7 function

Voltage-gated sodium (NaV) channels are critical regulators of neuronal excitability and are targeted by many toxins that directly interact with the pore-forming α subunit, typically via extracellular loops of the voltage-sensing domains, or residues forming part of the pore domain. Excelsatoxin A (ExTxA), a pain-causing knottin peptide from the Australian stinging tree Dendrocnide excelsa, is the first reported plant-derived NaV channel modulating peptide toxin. Here we show that TMEM233, a member of the dispanin family of transmembrane proteins expressed in sensory neurons, is essential for pharmacological activity of ExTxA at NaV channels, and that co-expression of TMEM233 modulates the gating properties of NaV1.7. These findings identify TMEM233 as a previously unknown NaV1.7-interacting protein, position TMEM233 and the dispanins as accessory proteins that are indispensable for toxin-mediated effects on NaV channel gating, and provide important insights into the function of NaV channels in sensory neurons

Exploring barriers to the use of formal maternal health services and priority areas for action in Sidama zone, southern Ethiopia.

In 2015 the maternal mortality ratio for Ethiopia was 353 per 100,000 live births. Large numbers of women do not use maternal health services. This study aimed to identify factors influencing the use of maternal health services at the primary health care unit (PHCU) level in rural communities in Sidama zone, south Ethiopia in order to design quality improvement interventions. We conducted a qualitative study in six woredas in 2013: 14 focus group discussions (FGDs) and 44 in-depth interviews with purposefully selected community members (women, male, traditional birth attendants, local kebele administrators), health professionals and health extension workers (HEWs) at PHCUs. We digitally recorded, transcribed and thematically analysed the interviews and FGDs using Nvivo. The 'three delay model' informed the analytical process and discussion of barriers to the use of maternal health services. Lack of knowledge on danger signs and benefits of maternal health services; cultural and traditional beliefs; trust in TBAs; lack of decision making power of women, previous negative experiences with health facilities; fear of going to an unfamiliar setting; lack of privacy and perceived costs of maternal health services were the main factors causing the first delay in deciding to seek care. Transport problems in inaccessible areas were the main contributing factor for the second delay on reaching care facilities. Lack of logistic supplies and equipment, insufficient knowledge and skills and unprofessional behaviour of health workers were key factors for the third delay in accessing quality care. Use of maternal health services at the PHCU level in Sidama zone is influenced by complex factors within the community and health system. PHCUs should continue to implement awareness creation activities to improve knowledge of the community on complications of pregnancy and benefits of maternal health services. The health system has to be responsive to community's cultural norms and practices. The mangers of the woreda health office and health centres should take into account the available budgets; work on ensuring the necessary logistics and supplies to be in place at PHCU