Studienerfolg in den Ingenieurwissenschaften

Langzeitstudenten, Studienabbrecher und mangelnder Ingenieurnachwuchs sind Themen, die seit einigen Jahren durch die Presse gehen. Eine differenzierte Studie an der Fachhochschule Aachen soll Aufschluss darüber geben, welchen Einfluss schulische Vorkenntnisse auf den Studienerfolg in den Ingenieurwissenschaften besitzen. Ein Schwerpunkt dieser Studie sind dabei die Grundkenntnisse im Fach Mathematik, die in der schulischen Mittelstufe erworben werden. Diese werden über einen Eingangstest erhoben. Zusätzlich werden Eingangsvoraussetzungen wie schulische Noten und Art des Schulabschlusses in die Studie mit einbezogen. Bisher haben 1389 Studienanfänger ihre Daten freiwillig für diese Studie zur Verfügung gestellt. Für den ersten Jahrgang liegt der Studienerfolg nach vier Semestern vor. In allen Untergruppen erweisen sich die Vorkenntnisse im Fach Mathematik als der Prädikator mit der höchsten Prognosefähigkeit für einen erfolgreichen Studienbeginn

Single Strand Annealing and ATP-independent Strand Exchange Activities of Yeast and Human DNA2: possible role in Ozaki fragment maturation

The Dna2 protein is a multifunctional enzyme with 5'-3' DNA helicase, DNA-dependent ATPase, 3' exo/endonuclease, and 5' exo/endonuclease. The enzyme is highly specific for structures containing single-stranded flaps adjacent to duplex regions. We report here two novel activities of both the yeast and human Dna2 helicase/nuclease protein: single strand annealing and ATP-independent strand exchange on short duplexes. These activities are independent of ATPase/helicase and nuclease activities in that mutations eliminating either nuclease or ATPase/helicase do not inhibit strand annealing or strand exchange. ATP inhibits strand exchange. A model rationalizing the multiple catalytic functions of Dna2 and leading to its coordination with other enzymes in processing single-stranded flaps during DNA replication and repair is presented

Das valas comuns aos direitos humanos: a descoberta dos desaparecimentos forçados na Espanha contemporânea

Este texto se baseia numa investigação de campo “multissituada” de sete anos sobre o impacto do ciclo mais recente de exumações de fossas comuns da Guerra Civil espanhola, levada a termo em diversos cenários: exumações, atos comemorativos, conferências acadêmicas sobre a memória, apresentações de livros, concertos musicais, retiros universitários, assembléias, diversas ONG, grupos de trabalho com apoio institucional, laboratórios forenses, exposições de arte, manifestações, etc. Explora a forma pela qual os discursos e conceitos transnacionais dos direitos humanos tem se convertido paulatinamente em guias fundamentais da ação de muitas das associações que promovem o que se conhece como “recuperação da memória histórica, na medida em que o debate tem ido crescendo, se sofisticando, institucionalizando e, finalmente, indo a juízo. Neste sentido, a sequência de informações da Anistia Internacional sobre o processo ou o auto ditado por Baltasar Garzón aos 16 de setembro de 2008, a controvérsia gerada por ele até sua inibição aos 18 de novembro de 2008 e os sucessos derivados do processo que se lhe abriu no Supremo Tribunal, tem atuado como catalisadores desta irrupção dos direitos humanos nos debates sobre a memória, através de figuras jurídicas como as dos “crimes contra a humanidade”, os “desaparecimentos forçados”, e outras.Peer reviewe

BLM–DNA2–RPA–MRN and EXO1–BLM–RPA–MRN constitute two DNA end resection machineries for human DNA break repair

Repair of dsDNA breaks requires processing to produce 3′-terminated ssDNA. We biochemically reconstituted DNA end resection using purified human proteins: Bloom helicase (BLM); DNA2 helicase/nuclease; Exonuclease 1 (EXO1); the complex comprising MRE11, RAD50, and NBS1 (MRN); and Replication protein A (RPA). Resection occurs via two routes. In one, BLM and DNA2 physically and specifically interact to resect DNA in a process that is ATP-dependent and requires BLM helicase and DNA2 nuclease functions. RPA is essential for both DNA unwinding by BLM and enforcing 5′ → 3′ resection polarity by DNA2. MRN accelerates processing by recruiting BLM to the end. In the other, EXO1 resects the DNA and is stimulated by BLM, MRN, and RPA. BLM increases the affinity of EXO1 for ends, and MRN recruits and enhances the processivity of EXO1. Our results establish two of the core machineries that initiate recombinational DNA repair in human cells

Processing of G4 DNA by Dna2 Helicase/nuclease and RPA provides insights into the mechanism of Dna2/RPA substrate recognition

The polyguanine-rich DNA sequences commonly found at telomeres and in rDNA arrays have been shown to assemble into structures known as G quadruplexes, or G4 DNA, stabilized by base-stacked G quartets, an arrangement of four hydrogen-bonded guanines. G4 DNA structures are resistant to the many helicases and nucleases that process intermediates arising in the course of DNA replication and repair. The lagging strand DNA replication protein, Dna2, has demonstrated a unique localization to telomeres and a role in de novo telomere biogenesis, prompting us to study the activities of Dna2 on G4 DNA-containing substrates. We find that yeast Dna2 binds with 25-fold higher affinity to G4 DNA formed from yeast telomere repeats than to single-stranded DNA of the same sequence. Human Dna2 also binds G4 DNAs. The helicase activities of both yeast and human Dna2 are effective in unwinding G4 DNAs. On the other hand, the nuclease activities of both yeast and human Dna2 are attenuated by the formation of G4 DNA, with the extent of inhibition depending on the topology of the G4 structure. This inhibition can be overcome by replication protein A. Replication protein A is known to stimulate the 5'- to 3'-nuclease activity of Dna2; however, we go on to show that this same protein inhibits the 3'- to 5'-exo/endonuclease activity of Dna2. These observations are discussed in terms of possible roles for Dna2 in resolving G4 secondary structures that arise during Okazaki fragment processing and telomere lengthening

Accurate time dependent wave packet calculations for the N+ OH reaction

We present accurate quantum calculations of state-to-state cross sections for the N OH → NO H reaction performed on the ground 3A′′ global adiabatic potential energy surface of Guadagnini [J. Chem. Phys. 102, 774 (1995)10.1063/1.469191. The OH reagent is initially considered in the rovibrational state v 0, j 0 and wave packet calculations have been performed for selected total angular momentum, J 0, 10, 20, 30, 40,120. Converged integral state-to-state cross sections are obtained up to a collision energy of 0.5 eV, considering a maximum number of eight helicity components, = 0.7. Reaction probabilities for J = 0 obtained as a function of collision energy, using the wave packet method, are compared with the recently published time-independent quantum mechanical one. Total reaction cross sections, state-specific rate constants, opacity functions, and product state-resolved integral cross-sections have been obtained by means of the wave packet method for several collision energies and compared with recent quasi-classical trajectory results obtained with the same potential energy surface. The rate constant for OH(v 0, j 0) is in good agreement with the previous theoretical values, but in disagreement with the experimental data, except at 300 K. © 2011 American Institute of Physics. © 2011 American Institute of Physics.Partial financial support from the Scientific and Technological Research Council of TURKEY (TUBITAK) (Project No. TBAG-109T447) and Firat University Scientific Research Projects Unit (FUBAP-1775) is gratefully acknowledged. Wave packet computations have also been done on the High Performance and Grid Computing Center (TR-Grid) machine at ULAKBIM/TURKEY. O.R. acknowledges the fi- nancial support of Ministerio de Ciencia e Innovación (Spain) under Grant No. CSD2009-00038.Peer Reviewe

Филлофаги древесных растений рода Ulmus в защитных насаждениях аридной зоны

Главными лесообразующими породами насаждений на урбанизированных территориях аридной зоны являются ильмовые (сем. Ulmaceae - более 70% всего дендросостава). Ухудшению их санитарного состояния активно способствуют листогрызущие вредители. Особой вредоносностью и регулярностью локальных очагов среди них отличаются Xanthogaleruca luteola (Müller, 1766), Cladius ulmi (Linnaeus, 1758) и Aproceros leucopoda (Takeuchi, 1939), последний- инвайдер. Деструктивное влияние этих вредителей на отдельные виды ильмовых неравнозначно.Elms are the main tree species of plantations in urban areas of the arid zone (Fam. Ulmaceae represents more than 70% of tree composition). Leaf-eating pests actively contribute to the deterioration of their sanitary condition.Xanthogaleruca luteola (Müller, 1766), Cladius ulmi (Linnaeus, 1758), and Aproceros leucopoda (Takeuchi, 1939) have a special harmfulness as well as the regularity of the local centers among all the pests. The last-mentioned species is invider. The destructive effect of those pests on certain types of elm plants are uneven

Estimation of corrosion resistance of curing mixtures based on coal-bearing rocks from Western Donbass

Purpose. Substantiation of possible use of coal-bearing rocks as a replacement for a part of the filler in the preparation of shotcrete for lining of mine workings in the conditions of mineralized mine water. Methods. The research is based on carrying out corrosion testing of concrete specimens by dipping them into mine water. Chemical analysis of mine waters composition has been completed. A scanning microscope was used to study the state of concrete specimens microstructure. Findings. A comparative analysis was conducted to evaluate of the cement rock resistance to mineralized water, depending on the composition of the starting components for the grouting and shotcrete mixtures is carried out. The change in the chemical composition of mine water after soaking concrete specimens in it is defined. Photographs of concrete specimens microstructure after soaking in ordinary and mineralized water for 6 and 8 months are shown. Originality. Curing mixtures based on coal-bearing rocks from Western Donbass are mineralized water resistant and can act as a quality protection from aggressive water filtrationdue to the properties of rocks used as a filler. Practical implications. The results can be used for the rational choice of the composition of the concrete mixture with the replacement of filler part with mine rock. That will enhance the long-term stability of the mine working lined by these compositions.Мета. Обґрунтування можливості використання вуглевміщуючих порід у якості заміни частини заповнювача в процесі приготування бетону для кріплення гірничих виробок в умовах мінералізованих шахтних вод. Методика. Робота базується на проведенні корозійних випробувань бетонних зразків шляхом занурення їх у шахтну воду. Виконано хімічний аналіз складу шахтних вод. Використаний растровий мікроскоп для дослідження стану мікроструктури бетонних зразків. Результати. Виконано порівняльний аналіз оцінки стійкості цементного каменю до впливу мінералізованої води залежно від складу вихідних компонентів для тампонажних, торкрет-бетонних і набризкбетонних сумішей. Визначено зміну хімічного складу шахтної води після витримки у ній бетонних зразків. Наведено фотографії мікроструктури бетонних зразків після витримки у нормальних умовах та мінералізованої води протягом 6 і 8 місяців. Наукова новизна. Твердіючі суміші на основі вуглевміщуючих порід Західного Донбасу достатньо стійкі до впливу мінералізованих вод та є якісною протифільтраційною завісою завдяки властивостям порід, використаних у якості заповнювача. Практична значимість. Отримані результати можуть бути використані для раціонального підбору складу бетонної суміші із заміною частини заповнювача шахтної породою, що дозволить підвищити тривалу стійкість гірничої виробки, закріпленої з використанням даних складів.Цель. Обоснование возможности использование углевмещающих пород в качестве замены части заполнителя в процессе приготовления бетона для крепления горных выработок в условиях минерализованных шахтных вод. Методика. Работа базируется на проведении коррозионных испытаний бетонных образцов путем погружения их в шахтную воду. Выполнен химический анализ состава шахтных вод. Использован растровый микроскоп для исследования состояния микроструктуры бетонных образцов. Результаты. Выполнен сравнительный анализ оценки устойчивости цементного камня к воздействию минерализованной воды в зависимости от состава исходных компонентов для тампонажных, торкрет-бетонных и набрызгбетонных смесей. Определено изменение химического состава шахтной воды после выдержки в ней бетонных образцов. Представлены фотографии микроструктуры бетонных образцов после выдержки в нормальных условиях и минерализованной воде в течение 6 и 8 месяцев. Научная новизна. Твердеющие смеси на основе углевмещающих пород Западного Донбасса устойчивы к влиянию минерализованных вод и являются качественной противофильтрационной завесой благодаря свойствам пород, использованных в качестве заполнителя. Практическая значимость. Полученные результаты могут быть использованы для рационального подбора состава бетонной смеси с заменой части заполнителя шахтной породой, что позволит повысить длительную устойчивость горной выработки, закрепленной с использованием данных составов.The authors express their gratitude to the administration of the Department of Construction, Geotechnics and Geomechanics of the National Mining University (Dnipropetrovsk, Ukraine), represented by O. Shashenko and A. Solodiankin, as well as to all those who helped in carrying out works related to preparation of this paper