Boundary Integral Equations and the Dirichlet Problem

The standard boundary element method applied to a problem with Dirichlet boundary conditions leads to a Fredholm integral equation of the first kind. A stable second kind equation results from a hypersingular equation formulation of the problem, obtained by differentiating the original boundary integral statement. The evaluation of the hypersingular integral requires that the coefficient function multiplying the hypersingular kernel be differentiable. For two dimensional problems, Overhauser elements are a very convenient basis set for obtaining the necessary smoothness. Test calculations with the Laplace equation demonstrate (a) the stability of the hypersingular approach for the Dirichlet problem and (b) that the hypersingular approach yields results that are more accurate than those obtained with the standard approach

Metal Insulator transition at B=0 in p-SiGe

Observations are reported of a metal-insulator transition in a 2D hole gas in asymmetrically doped strained SiGe quantum wells. The metallic phase, which appears at low temperatures in these high mobility samples, is characterised by a resistivity that decreases exponentially with decreasing temperature. This behaviour, and the duality between resistivity and conductivity on the two sides of the transition, are very similar to that recently reported for high mobility Si-MOSFETs.Comment: 4 pages, REVTEX with 3 ps figure

Metal Dicyanamides as Efficient and Robust Water-Oxidation Catalysts

Non-oxide cobalt-based water-oxidation electrocatalysts have received attention recently for their relative ease of preparation, they are stable both in acidic and basic media, and they have higher turnover frequencies than cobalt oxides. Recent studies show that one of the main bottlenecks in the implementation of non-oxide systems to water splitting is the low number of active metal sites, which is in the order of nmol cm−2. Herein, a new series of non-oxide water-oxidation catalysts has been introduced to the field. Cobalt dicyanamides are observed to have around four times higher surface active sites and better catalytic performances than cyanide-based systems. Long-term catalytic studies (70 h) at an applied potential of 1.2 V and electrochemical studies performed in solutions in pH values of 3.0–12.0 indicate that the compounds are robust and retain their structures even under harsh conditions. Moreover, the addition of Ni impurities to cobalt dicyanamides is a feasible method to improve their catalytic activities. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinhei

A somatic origin of homologous Robertsonian translocations and isochromosomes

One t(14q14q), three t(15q15q), two t(21q21q), and two t(22q22q) nonmosaic, apparently balanced, de novo Robertsonian translocation cases were investigated with polymorphic markers to establish the origin of the translocated chromosomes. Four cases had results indicative of an isochromosome: one t(14q14q) case with mild mental retardation and maternal uniparental disomy (UPD) for chromosome 14, one t(15q15q) case with the Prader-Willi syndrome and UPD(15), a phenotypically normal carrier of t(22q22q) with maternal UPD(22), and a phenotypically normal t(21q21q) case of paternal UPD(21). All UPD cases showed complete homozygosity throughout the involved chromosome, which is supportive of a postmeiotic origin. In the remaining four cases, maternal and paternal inheritance of the involved chromosome was found, which unambiguously implies a somatic origin. One t(15q15q) female had a child with a ring chromosome 15, which was also of probable postmeiotic origin as recombination between grandparental haplotypes had occurred prior to ring formation. UPD might be expected to result from de novo Robertsonian translocations of meiotic origin; however, all de novo homologous translocation cases, so far reported, with UPD of chromosomes 14, 15, 21, or 22 have been isochromosomes. These data provide the first direct evidence that nonmosaic Robertsonian translocations, as well as isochromosomes, are commonly the result of a mitotic exchange

The European Registered Toxicologist (ERT) : Current status and prospects for advancement

Acknowledgements We would like to thank the participants of the five workshops in which the issues presented in this paper were discussed and the revised guidelines prepared, as well as the EUROTOX Executive Committee and the societies of toxicology of Sweden, the Netherlands, Switzerland, Austria and France for their support which allowed the workshops to take place.Peer reviewedPostprin

Razine antinuklearnoga antitijela i reumatoidnoga faktora u radnika izloženih silicijevu dioksidu

A lot of workers in industries such as foundry, stonecutting, and sandblasting are exposed to higher than permissible levels of crystalline silica. Various alterations in humoral immune function have been reported in silicosis patients and workers exposed to silica dust. The aim of this study was to measure antinuclear antibody (ANA) and rheumatoid factor (RF) levels in foundry workers exposed to silica and to compare them with a control group without such exposure. ANA and RF were measured in 78 exposed and 73 non-exposed workers, and standard statistical methods were used to compare them. The two groups did not significantly differ in age and smoking. Mean work duration of the exposed and non-exposed workers was (14.9±4.72) years and (12.41±6.3) years, respectively. Ten exposed workers had silicosis. ANA was negative in all workers in either group. Its mean titer did not differ significantly between the exposed and control workers [(0.39±0.15) IU mL-1 vs. (0.36±0.17) IU mL-1, respectively]. RF was positive in two workers of each group. Other studies have reported an increase in ANA and RF associated with exposure to silica dust and silicosis. In contrast, our study suggests that exposure to silica dust does not increase the level of ANA and RF in exposed workers.Mnogi su radnici izloženi kristalnomu silicijevu dioksidu u razinama iznad dopuštenih. U oboljelih od silikoze i radnika izloženih prašinama koje sadržavaju silicijev dioksid zamijećen je niz oštećenja humoralne obrane. Budući da su radnici u ljevaonicama izloženi visokim razinama kristalnoga silicijeva dioksida, u njih bismo očekivali ovakve humoralne poremećaje. Cilj je ovog ispitivanja bio izmjeriti i usporediti razine antinuklearnih protutijela (ANA) i reumatoidnoga faktora (RF) u krvi radnika u ljevaonici izloženih silicijevu dioksidu i neizložene kontrolne skupine. ANA i RF izmjereni su u 78 izloženih radnika i 73 neizložena radnika te su uspoređeni s pomoću standardnih statističkih metoda. Dvije se skupine nisu bitno razlikovale u broju pušača i u dobi. Prosječna duljina radnog vijeka izloženih radnika bila je (14,9±4,72) godine, a neizloženih (12,41±6,3) godine. Deset izloženih radnika imalo je silikozu. Nalazi ANA bili su negativni u obje skupine radnika. Srednja vrijednost titra ANA iznosila je (0,39±0,15) IU mL-1 u izloženih ispitanika, a (0,36±0,17) IU mL-1 u kontrola, što je statistički zanemariva razlika. Nalaz RF-a bio je pozitivan u dva izložena te dva kontrolna radnika. Naše ispitivanje upućuje na to da prašine silicijeva dioksida ne uzrokuju porast razina ANA i RF-a u izloženih radnika

Contemporary management of primary parapharyngeal space tumors

The parapharyngeal space is a complex anatomical area. Primary parapharyngeal tumors are rare tumors and 80% of them are benign. A variety of tumor types can develop in this location; most common are salivary gland neoplasm and neurogenic tumors. The management of these tumors has improved greatly owing to the developments in imaging techniques, surgery, and radiotherapy. Most tumors can be removed with a low rate of complications and recurrence. The transcervical approach is the most frequently used. In some cases, minimally invasive approaches may be used alone or in combination with a limited transcervical route, allowing large tumors to be removed by reducing morbidity of expanded approaches. An adequate knowledge of the anatomy and a careful surgical plan is essential to tailor management according to the patient and the tumor. The purpose of the present review was to update current aspects of knowledge related to this more challenging area of tumor occurrence.Peer reviewe

Global Perspectives on Task Shifting and Task Sharing in Neurosurgery.

BACKGROUND: Neurosurgical task shifting and task sharing (TS/S), delegating clinical care to non-neurosurgeons, is ongoing in many hospital systems in which neurosurgeons are scarce. Although TS/S can increase access to treatment, it remains highly controversial. This survey investigated perceptions of neurosurgical TS/S to elucidate whether it is a permissible temporary solution to the global workforce deficit. METHODS: The survey was distributed to a convenience sample of individuals providing neurosurgical care. A digital survey link was distributed through electronic mailing lists of continental neurosurgical societies and various collectives, conference announcements, and social media platforms (July 2018-January 2019). Data were analyzed by descriptive statistics and univariate regression of Likert Scale scores. RESULTS: Survey respondents represented 105 of 194 World Health Organization member countries (54.1%; 391 respondents, 162 from high-income countries and 229 from low- and middle-income countries [LMICs]). The most agreed on statement was that task sharing is preferred to task shifting. There was broad consensus that both task shifting and task sharing should require competency-based evaluation, standardized training endorsed by governing organizations, and maintenance of certification. When perspectives were stratified by income class, LMICs were significantly more likely to agree that task shifting is professionally disruptive to traditional training, task sharing should be a priority where human resources are scarce, and to call for additional TS/S regulation, such as certification and formal consultation with a neurosurgeon (in person or electronic/telemedicine). CONCLUSIONS: Both LMIC and high-income countries agreed that task sharing should be prioritized over task shifting and that additional recommendations and regulations could enhance care. These data invite future discussions on policy and training programs