Search

Исследована кинематика ротационной схемы правки шлифовальных кругов вращающимся алмазным кругом чашечной формы. На примерах шлифования высокопористыми кругами из кубического нитрида бора на керамических связках деталей из жаропрочных никелевых и титановых сплавов и высоколегированных сталей показаны преимущества такой правки в сравнении с правкой обтачиванием алмазными карандашами. Досліджено кінематику ротаційної схеми правки шліфувальних кругів алмазним кругом чашечної форми, що обертається. На прикладах шліфування високопористими кругами з кубічного нітриду бору на керамічних зв’язках деталей з жароміцних нікелевих і титанових сплавів і високолегованих сталей показано її переваги порівняно з правкою обточуванням алмазними олівцями. Studied rotational kinematics scheme dressing of grinding wheels by rotating diamond cup. Examples of highly porous grinding wheels of cubic boron nitride ceramic ligaments parts of heat-resistant nickel alloys and titanium alloys and alloyed steels shown its advantages in comparison to edit the turning of diamond pencils.

Meiotic gene conversion has a major impact on genome diversity. Both crossovers and non-exchange conversions cluster into distinct recombination-active regions that we call hotspots. Hotspot analysis in humans has focused on the description of crossover profiles and only few hotspots had been tested for crossover and non-exchange gene conversion. Therefore, very little was known about the frequency and distribution of non-exchange conversions and how well they correlate with crossing over. Six extremely active recombination hotspots were analysed by using small pool PCR approaches on sperm DNA to detect both types of recombinant molecules. Non-exchange conversions were detectable and arose at high frequencies (0.01-0.47%) per sperm, in addition to crossovers (0.2-0.70%). Conversion tracts were short and their distribution defined a steep conversion gradient, centred at the peak of crossover activity and probably marking the zone of recombination initiation. It was also observed that non-exchange gene conversion and crossover frequencies were positively correlated, not just between men at the same hotspot but equally when compared across several hotspots. On average, non-exchange gene conversions spanning a marker close to the centre of the hotspot occurred at 50% of the crossover frequency. Hotspot regulation in cis had been described previously to results in different initiation efficiencies between interacting haplotypes. Preferential initiation on a more active haplotype, in turn leads to the overtransmission of alleles from the less active haplotype. Additional hotspots that showed a phenomenon of biased gene conversion were described in this study, with crossovers and non-exchange gene conversions influenced to the same degree. More unusually, biased gene conversion specifically affecting non-exchange events was also observed at two hotspots. Here single SNP heterozygosities appear responsible for triggering the bias in cis. Crossovers were not affected, which may provide evidence for distinct crossover and non-crossover pathways operating at human hotspots. Inter-individual differences in recombination frequencies between men at a given hotspot established PRDM9 as major trans-regulator of hotspot activity. PRDM9 regulation was characterised at two hotspots activated by specific sets of PRDM9 variants. At both hotspots a sequence motif, proposed to be the PRDM9 binding site in vitro, was not found to be responsible for hotspot activation as had been predicted previously. Curiously, better motif matches were not correlated with higher crossover frequencies, and PRDM9 can in fact activate hotspot without the proposed binding motif.

Zielsetzung: Analyse der webbasierten ophthalmologischen Lernprogramme, welche von den Internetseiten der Universitäts-Augenkliniken in Deutschland angeboten werden. Methodik: Im Januar 2010 wurden in dieser prospektiven Studie alle 36 Internetseiten deutscher Universitäts-Augenkliniken besucht. Dabei wurde das angebotene Aus-, Weiter- und Fortbildungsangebot für Studierende und Ärzte quantitativ und qualitativ evaluiert. Ergebnisse: Die Homepages aller Kliniken waren zum Zeitpunkt der Besuche erreichbar. 28 Internetseiten hielten Informationen zur Aus-, Weiter- oder Fortbildung für Studierende und Ärzte vor. Eine Seite beinhaltete nur Angebote für Studenten, 3 ausschließlich für Ärzte. Auf 4 Seiten wurde für beide Zielgruppen kein Angebot gemacht. Das Angebot umfasste Informationen zu aktuellen Veranstaltungen wie ärztlichen Fortbildungen oder Lehrveranstaltungen für Studierende, weiter wurden Skripte oder ähnliches Material zum download bereitgestellt. Auf 9 Seiten wurden komplexe e-learning-Plattformen aufgefunden, welche sich einem bestimmten Thema im Rahmen einer logisch-didaktischen Gliederung widmen. Trotz der umfangreichen Möglichkeiten, welches das Web 2.0 bietet, wurden viele denkbare Hilfsmittel nur selten bereitgestellt. Die Aktualität des Angebots war nicht immer zu ermitteln, oft lag die letzte Aktualisierung lange zurück. Auf einer Seite war als letzte Aktualisierung der Fallsammlung das Jahr 2004 angegeben. Schlussfolgerung: Von den Homepages der Augenabteilungen deutscher Universitätskliniken werden 9 funktionsfähige e-learning-Applikationen zur Verfügung gestellt. Zwei weitere Kliniken verweisen auf ein Projekt der Deutschen Ophthalmologischen Gesellschaft. Das Angebot zeigt eine erhebliche Variation in Quantität und Qualität. In keinem Fall wird die Möglichkeit der Anrechnung des Besuchs dieser Programme auf die studentische Ausbildung (z.B. OSCE-Credits) oder die ärztliche Weiter- oder Fortbildung, z.B. in Form von CME-Punkten, genutzt. Der Mangel an modernen, technischen wie didaktischen Anforderungen genügenden Lernapplikationen ist alarmierend, wird doch ein wesentliches Kommunikations- und damit Lehr und Lernmedium von deutschen Universitäts-Augenkliniken nur zu einem kleinen Teil genutzt., GMS Zeitschrift für Medizinische Ausbildung; 28(3):Doc43; ISSN 1860-3572

A microsystem based microimplant with an optically powered single-channel stimulator was designed and developed as test system for an epi-retinal vision implant. Biostability of the hybrid assembly and the encapsulation materials were evaluated in pilot experiments in chronic implantations in a cat animal model. The implant was fabricated on a flexible polyimide substrate with integrated platinum electrode, interconnection lines, and contact pads for hybrid integration of electronic components. The receiver part was realized with four photodiodes connected in series. A parylene C coating was deposited on the electronic components as insulation layer. Silicone rubber was used to encapsulate the electronics in the shape of an artificial intraocular lens to allow proper implantation in the eye. Pilot experiments showed the biostability of the encapsulation approach and full electric functionality of the microimplant to generate stimulation currents over the implantation period of three months in two cats. In one cat, electrical stimulation of the retina evoked neuronal responses in the visual cortex and indicated the feasibility of the system approach for chronic use.

Background The role of copy number variation of the CCL3L1 gene, encoding MIP1α, in contributing to the host variation in susceptibility and response to HIV infection is controversial. Here we analyse a sub-Saharan African cohort from Tanzania and Ethiopia, two countries with a high prevalence of HIV-1 and a high co-morbidity of HIV with tuberculosis. Methods We use a form of quantitative PCR called the paralogue ratio test to determine CCL3L1 gene copy number in 1134 individuals and validate our copy number typing using array comparative genomic hybridisation and fiber-FISH. Results We find no significant association of CCL3L1 gene copy number with HIV load in antiretroviral-naïve patients prior to initiation of combination highly active anti-retroviral therapy. However, we find a significant association of low CCL3L1 gene copy number with improved immune reconstitution following initiation of highly active anti-retroviral therapy (p = 0.012), replicating a previous study. Conclusions Our work supports a role for CCL3L1 copy number in immune reconstitution following antiretroviral therapy in HIV, and suggests that the MIP1α -CCR5 axis might be targeted to aid immune reconstitution.