Uniform line fillings

Deterministic fabrication of random metamaterials requires filling of a space with randomly oriented and randomly positioned chords with an on-average homogenous density and orientation, which is a nontrivial task. We describe a method to generate fillings with such chords, lines that run from edge to edge of the space, in any dimension. We prove that the method leads to random but on-average homogeneous and rotationally invariant fillings of circles, balls and arbitrary-dimensional hyperballs from which other shapes such as rectangles and cuboids can be cut. We briefly sketch the historic context of Bertrand's paradox and Jaynes' solution by the principle of maximum ignorance. We analyse the statistical properties of the produced fillings, mapping out the density profile and the line-length distribution and comparing them to analytic expressions. We study the characteristic dimensions of the space in between the chords by determining the largest enclosed circles and balls in this pore space, finding a lognormal distribution of the pore sizes. We apply the algorithm to the direct-laser-writing fabrication design of optical multiple-scattering samples as three-dimensional cubes of random but homogeneously positioned and oriented chords.Comment: 10 pages, 12 figures; v3: restructured paper, more references, more graph

Crystal-to-crystal transition of ultrasoft colloids under shear

Ultrasoft colloids typically do not spontaneously crystallize, but rather vitrify, at high concentrations. Combining in-situ rheo-SANS experiments and numerical simulations we show that shear facilitates crystallization of colloidal star polymers in the vicinity of their glass transition. With increasing shear rate well beyond rheological yielding, a transition is found from an initial bcc-dominated structure to an fcc-dominated one. This crystal-to-crystal transition is not accompanied by intermediate melting but occurs via a sudden reorganization of the crystal structure. Our results provide a new avenue to tailor colloidal crystallization and crystal-to-crystal transition at molecular level by coupling softness and shear

EFFECT OF ETHNIC CONFLICTS ON TEACHERS INSTRUCTIONAL PERFORMANCE IN PUBLIC SECONDARY SCHOOLS IN LOWER AREAS OF BARINGO COUNTY, KENYA

Teachers are the key persons involved in ensuring successful secondary education curriculum implementation. However, their ability to perform their instructional tasks is dictated by the environment they operate from. This paper looks at how ethnic conflicts affect teachers’ ability to perform their duties as expected in public secondary schools. The study was conducted in lowland areas of Baringo that have been experiencing inter-ethnic conflicts for a long period of time. The study used mixed method research methodology to collect qualitative and quantitative data. The respondents for the study consisted of 205 teachers, 22 principals and 88 BOM members from which a sample of 136 teachers, 26 BOM members and 22 principals were selected. The study collected data through questionnaire and interview schedule. The study found out that as a result of conflict, majority of teachers did not report to school on time while others failed to attend school completely for some days. This affected their capacity to teach and assess students in secondary schools. The study found out that there existed significant negative effect of ethnic conflicts on teacher instructional performance in public secondary schools in the lower areas of Baringo County, Kenya. The study recommends that schools need to offer psychological support to teachers through guidance and counselling in order to ensure teachers perform well in their duties. Teachers need to be housed in school through construction of teachers quarters.  Article visualizations

The educational and practical value of clinical audit in Greece: a pilot study by surgical interns. Is it time to adapt a structured way to improve quality in healthcare?

Objectives: Clinical audit is a great way of facilitating quality improvement in health services. Our aim is to describe the concept, clinical and educational benefits of clinical audit, as well as present a simple example that can be used as a guide for interns and medical students in Greece. We hope to raise awareness on the subject of quality improvement in our financially challenged healthcare system. Methods: The potential educational benefits of the clinical audit were defined and were set as the objectives of this study. It was assigned to a team of surgical interns to select a topic of their choice, conduct a clinical audit, under the necessary supervision, and present their findings. Finally a discussion between the professors and the interns took place in order to assess whether the objectives were actually achieved. Results: The interns completed the audit successfully. It was obvious that they managed to improve the initial area of weakness significantly and identify opportunities for further improvement. At the same time this kind of project help them acquire important educational competencies. Conclusions: Incorporating clinical audits in medical education proves helpful for interns and for the quality of healthcare offered. This is especially important as it underscores the need and provides the methodology for structural changes that are critical in health care systems facing the global financial crisis

Laparoscopic Cholecystectomy for Severe Acute Cholecystitis in a Patient with Situs Inversus Totalis and Posterior Cystic Artery

Situs inversus totalis is an inherited condition characterized by a mirror-image transposition of thoracic and abdominal organs. It often coexists with other anatomical variations. Transposition of the organs imposes special demands on the diagnostic and surgical skills of the surgeon. We report a case of a 34-year-old female patient presented with left upper quadrant pain, signs of acute abdomen, and unknown situs inversus totalis. Severe acute cholecystitis was diagnosed, and an uneventful laparoscopic cholecystectomy was performed. A posterior cystic artery was identified and ligated. Laparoscopic cholecystectomy is feasible in patients with severe acute calculus cholecystitis and situs inversus totalis; however, the surgeon should be alert of possible anatomic variations

Deterministic and controllable photonic scattering media via direct laser writing

Photonic scattering materials, such as biological tissue and white paper, are made of randomly positioned nanoscale inhomogeneities in refractive index that lead to multiple scattering of light. Typically these materials, both naturally-occurring or man-made, are formed through self assembly of the scattering inhomogeneities, which imposes challenges in tailoring the disorder and hence the optical properties. Here, We report on the nanofabrication of photonic scattering media using direct laser writing with deterministic design. These deterministic scattering media consist of submicron thick polymer nanorods that are randomly oriented within a cubic volume. We study the total transmission of light as a function of the number density of rods and of the sample thickness to extract the scattering and transport mean free paths using radiative transfer theory. Such photonic scattering media with deterministic and controllable properties are model systems for fundamental light scattering in particular with strong anisotropy and offer new applications in solid-state lighting and photovoltaics.Comment: 18 pages, 9 figure

Effect of Multiphase Radiation on Coal Combustion in a Pulverized Coal jet Flame

The accurate modeling of coal combustion requires detailed radiative heat transfer models for both gaseous combustion products and solid coal particles. A multiphase Monte Carlo ray tracing (MCRT) radiation solver is developed in this work to simulate a laboratory-scale pulverized coal flame. The MCRT solver considers radiative interactions between coal particles and three major combustion products (CO2, H2O, and CO). A line-by-line spectral database for the gas phase and a size-dependent nongray correlation for the solid phase are employed to account for the nongray effects. The flame structure is significantly altered by considering nongray radiation and the lift-off height of the flame increases by approximately 35%, compared to the simulation without radiation. Radiation is also found to affect the evolution of coal particles considerably as it takes over as the dominant mode of heat transfer for medium-to-large coal particles downstream of the flame. To investigate the respective effects of spectral models for the gas and solid phases, a Planck-mean-based gray gas model and a size-independent gray particle model are applied in a frozen-field analysis of a steady-state snapshot of the flame. The gray gas approximation considerably underestimates the radiative source terms for both the gas phase and the solid phase. The gray coal approximation also leads to under-prediction of the particle emission and absorption. However, the level of under-prediction is not as significant as that resulting from the employment of the gray gas model. Finally, the effect of the spectral property of ash on radiation is also investigated and found to be insignificant for the present target flame

POROUS STRUCTURES AS ACTIVE MICROFLUIDIC COMPONENTS

Active control of droplet mobility through low cost tools is highly desirable in applications entailing microfluidics, Lab-on-Chip devices and pertinent technologies. Here, we present the design concepts of a versatile, low cost tool for dynamic droplet mobility manipulation, employing a scheme with backpressure application. Initially sticky open- or closed- channel fluidics with hydrophobic, porous walls are rendered slippery with the application of backpressure through the porous walls. Deliberate control of backpressure directs the wetting phenomena to the desired state. Operation parameters, and control system considerations are presented. Ultra-low backpressure values, are needed for channels with small cross-sections, which in turn are compatible with ultra-low energy demands

Sodium and potassium intake in healthy adults in Thessaloniki Greater Metropolitan Area—the salt intake in Northern Greece (SING) Study.

A reduction in population sodium (as salt) consumption is a global health priority, as well as one of the most cost-effective strategies to reduce the burden of cardiovascular disease. High potassium intake is also recommended to reduce cardiovascular disease. To establish effective policies for setting targets and monitoring effectiveness within each country, the current level of consumption should be known. Greece lacks data on actual sodium and potassium intake. The aim of the present study was therefore to assess dietary salt (using sodium as biomarker) and potassium intakes in a sample of healthy adults in northern Greece, and to determine whether adherence to a Mediterranean diet is related to different sodium intakes or sodium-to-potassium ratio. A cross-sectional survey was carried out in the Thessaloniki greater metropolitan area (northern Greece) (n = 252, aged 18–75 years, 45.2% males). Participants’ dietary sodium and potassium intakes were determined by 24-hour urinary sodium and potassium excretions. In addition, we estimated their adherence to Mediterranean diet by the use of an 11-item MedDietScore (range 0–55). The mean sodium excretion was 175 (SD 72) mmol/day, equivalent to 4220 (1745) mg of sodium or 10.7 (4.4) g of salt per day, and the potassium excretion was 65 (25) mmol/day, equivalent to 3303 (1247) mg per day. Men had higher sodium and potassium excretions compared to women. Only 5.6% of the sample had salt intake <5 g/day, which is the target intake recommended by the World Health Organization. Mean sodium-to-potassium excretion ratio was 2.82 (1.07). There was no significant difference in salt or potassium intake or their ratio across MedDietScore quartiles. No significant relationships were found between salt intake and adherence to a Mediterranean diet, suggesting that the perception of the health benefits of the Mediterranean diet does not hold when referring to salt consumption. These results suggest the need for a larger, nation-wide survey on salt intake in Greece and underline the importance of continuation of salt reduction initiatives in Greece