bluuebunny/crossref_metadata_2025 huggingface dataset:
Blue carbon stocks in Baltic Sea eelgrass (Zostera marina) meadows
Authors: Röhr Maria Emilia , Boström Christoffer , Canal-Vergés Paula , Holmer Marianne
Published: April 2016

Abstract. Although seagrasses cover only a minor fraction of the ocean seafloor, their carbon sink capacity account for nearly one-fifth of the oceanic carbon burial and thus play a critical structural and functional role in many coastal ecosystems. We sampled 10 eelgrass (Zostera marina) meadows in Finland and 10 in Denmark to explore the seagrass carbon stocks (Corg stock) and the carbon accumulation (Corg accumulation) in the Baltic Sea area. The study sites represent a gradient from sheltered to exposed locations in both regions to reflect expected minimum and maximum stocks and accumulation. The Corg stock integrated over the top 25 cm of the sediment averaged 627g C m−2 in Finland, while in Denmark the average Corg stock was over six times higher (4324 g C m−2). A conservative estimate of the total carbon pool in the regions ranged between 8.6–46.2 t ha−1. Our results suggest that the Finnish eelgrass meadows are minor carbon sinks compared to the Danish meadows, and that majority of the Corg produced in the Finnish meadows is exported. Similarly, the estimates for Corg accumulation in eelgrass meadows in Finland (< 0.002–0.033 t C y−1) were over two orders of magnitude lower compared to Denmark (0.376–3.636 Corg t y−1). Our analysis further showed that > 40 % of the variation in the Corg stocks was explained by sediment characteristics (density, porosity and silt content). In addition, the DistLm analysis showed, that root: shoot- ratio of Z. marina explained > 12 % and contribution of Z. marina detritus to the sediment surface Corg pool > 10 % of the variation in the Corg stocks, whereas annual eelgrass production explained additional 2.3 %. The mean monetary value for the present carbon storage and sequestration capacity of eelgrass meadows at Finland and Denmark, were 346 and 1862 € ha−1, respectively. We conclude that in order to produce reliable estimates on the magnitude of eelgrass Corg stocks, Corg accumulation and the monetary value of these services, more Blue Carbon studies investigating the role of sediment biogeochemistry, seascape structure, plant species architecture and hydrodynamic regime for seagrass carbon storage capacity are in urgent need.
Los factores determinantes del comportamiento innovador de las cooperativas: un análisis para el caso de Castilla y León
Authors: Peraza Castaneda Elías Humberto , Gómez García Jesús María , Aleixandre Mendizábal Guillermo
Published: April 2016

Las cooperativas tienen una larga trayectoria histórica en la economía española y han demostrado su capacidad para competir frente a las empresas tradicionales en el mercado. Para mantener esa capacidad, además de aprovechar las ventajas competitivas vinculadas con su idiosincrasia como empresas de la economía social, deben tener en consideración que la economía está crecientemente globalizada y, cada vez más, basada en el conocimiento, en especial, el de contenido tecnológico. Consecuencia de lo anterior, la capacidad innovadora aparece con un aspecto clave para hacer frente a sus competidores. En este artículo se caracteriza el comportamiento innovador de las cooperativas en Castilla y León y se analizan los factores internos y externos que afectan a su desempeño innovador, tomando como base los datos de una encuesta realizada a 581 cooperativas de la citada comunidad autónoma. Los resultados del análisis empírico realizado, que se lleva a cabo mediante regresión logística binaria multivariante sobre distintos tipos de innovación, permiten identificar la dimensión de las organizaciones, la existencia de planificación, las actividades de I+D y el capital humano como los principales factores determinantes.
STUDY OF THE FRIEDEL–CRAFT CO-CURING OF ETHYLENE–PROPYLENE–DIENE RUBBER AND STYRENE–BUTADIENE RUBBER
Authors: Estagy Sara , Movahed Saeed Ostad , Yazdanbakhsh Soheil , Nezhad Majid Karim
Published: April 2016

Polymer blends are mixtures of at least two macromolecular species, polymers, and/or copolymers. A good blend should have strong interphases between different parts of the constituent polymers. To improve adhesion and miscibility of EPDM and SBR in their blends, a Lewis acid, AlCl3, was used to form EPDM-g-SBR copolymer through Friedel–Craft reactions. The effects of blend AlCl3 content, the diene monomer content of the EPDM, the EPDM–SBR weight ratio in the blend, the room temperature aging of the blend, and the type of the oil in the blend on cross-link reactions were studied. The results showed that an increase in AlCl3 content, up to 2 phr in the formulation, was beneficial to ΔTorque (difference between minimum and maximum torque in cure trace) and cross-link density (CLD) values of the compounds. The viscosity of the blends played a key role on AlCl3 curing of the compounds. As a general rule, the ΔTorque and CLD values tended to increase with diene monomer content of the EPDM. A high reduction in ΔTorque values was observed after 3 months of aging at room temperature. The oil incorporation was beneficial to cure parameters in the following order: oleic acid, paraffin oil, no oil, and aromatic oil, respectively. The EPDM–SBR weight ratios of 50:50 and/or 60:40 were demonstrated to be desired blend ratios.
Using Universal Screening for Early Identification of Students at Risk: A Case Example from the Field
Authors: Donohue Peg , Goodman-Scott Emily , Jennifer Betters-Bubon
Published: April 2016

This study describes the benefits of systematic universal screening (US) for school counselors engaged in the creation of effective, multi-tiered systems of support that address academic, social, emotional, and behavioral student concerns. The authors used an action research framework to present a case example of one school district's pilot of US and the role of the school counselor in the identification of students in need of social-emotional support. This article discusses implications for school counselor collaboration with other school-based mental health professionals.
RELIGIOSIDADE E PROTAGONISMO DAS JUVENTUDES UNIVERSITÁRIAS
Authors: Peretti Clélia , Souza Alisson de , Passos Bruna Carolina dos
Published: April 2016

O artigo apresenta resultados de pesquisas realizadas com as juventudes sobre o perfil da religiosidade, o exercício da cidadania e dos direitos humanos entre os jovens. Objetivou-se conhecer o perfil da religiosidade e seus aspectos relevantes, mapear valores, dinâmicas e vivências religiosas e investigar o protagonismo entre os jovens universitários entre 18 e 29 anos. Os resultados mostram que as juventudes são objeto de estudos importante para o Brasil tanto pela crescente preocupação na construção de sua identidade quanto pela formação do futuro profissional. O perfil religioso vem se modificando com o aumento da mobilidade, com o crescente sincretismo e bricolagem religiosa. A intolerância e manipulação religiosa são o ponto de maior crítica e o principal problema entre os pesquisados. O protagonismo se revela através dos manifestos e do engajamento em projetos sociais que visem garantir os direitos fundamentais e a dignidade humana e deveres inerentes aos indivíduos.
A Research into Evaluation of Basketball Athletes’ Risk Perception Level
Authors: Karatas Ozgur
Published: April 2016

The aim of this study is to compare the risk perception levels of Basketball athletes in Turkish League teams according to some variables. In this research the “general screening model”, which is one of the descriptive screening methods, was used. While the population of the study consists of athletes actively engaged in the Turkish basketball league teams, its sampling consists of 229 athletes selected by chance and at random methods, which have been playing in different clubs. The questionnaire of Gok was used as a data tool in the study to perception of risk in sports. The difference between the risk perception levels according to the variables of gender, education level and years of playing basketball of the athletes who participated in the study were statistically significant. However, according to the variables of marital status and age of the athletes, the difference between the levels of risk perception statistically was not significant. Results showed that the average risk of female athletes were higher than the average risk of male athletes. The average risk of the athletes educated at high-school level were lower than the average risk of athletes educated at university and postgraduate level, average risk of athletes who play basketball between 1-5 years was lower than the average risk of athletes who play basketball between 6-10, 11-15, 16-20 and above 21 years. Basketball clubs, in order to be robust, should have professional managers in their club managements. Sports clubs should employ specialized advisors regarding the risks that players may encounter. In sports clubs, satisfaction of the players should be the first goal and expectations from them should be clearly specified. Sports clubs should also ask the players’ opinions when preparing strategic plans against the risk factors that may occur.
The Effect of Peer Teaching on Mathematics Academic Achievement of the Undergraduate Students in Oman
Authors: Abdelkarim Ra’ed , Abuiyada Reem
Published: April 2016

This study explored the effects of peer teaching on mathematics academic achievement of the undergraduate students in Oman. The sample of this study composed of (32) undergraduate female students enrolled in the course, “Mathematics for Social Sciences I” in Mathematics and Sciences Unit in Dhofar University in spring semester 2014-2015. The sample of the study was divided randomly into two groups, the first group was selected as experimental group (16) students and the other group was selected as control group (16) students. Both groups studied the same curriculum, same materials, and both groups had been taught by the same instructor. Data were collected by using, Mathematics Achievement Test (MACT) which was prepared by the researchers. In order to analyze data, researchers used mean, standard deviations, and Analysis of t-test. The result of the study found that peer teaching strategy is an active tool to increase the mathematical achievement. The study recommended the instructors and college professors to use peer teaching in order to improve the performance of the students in mathematics.
Does Problem-Based Learning Improve Problem Solving Skills?—A Study among Business Undergraduates at Malaysian Premier Technical University
Authors: Kadir Z. Abdul , Abdullah N. H. , Anthony E. , Salleh B. Mohd , Kamarulzaman R.
Published: April 2016

Problem-based Learning (PBL) approach has been widely used in various disciplines since it is claimed to improve students’ soft skills. However, empirical supports on the effect of PBL on problem solving skills have been lacking and anecdotal in nature. This study aimed to determine the effect of PBL approach on students’ problem solving skills using a quasi-experimental non-equivalent group pretest–posttest design. Fifty management students from a premier Technical University in Malaysia were assigned to experimental and control groups. In the experimental group, students were given four problems to be solved and their solutions of the problems given were assessed in terms of their accuracy and quality. Students in the control group received conventional classroom instructional design. Results indicate that students in the experimental group have better problem solving skills (z: -4.220, p: 0.001 for accuracy and z: -2.594, p: 0.009 for quality) compared to those who were not exposed to the PBL approach. This finding substantiates the use of PBL as an effective instructional tool to improve students’ problem solving abilities.
Academic Leadership in a Private University: An Iranian Case Study
Authors: Hamidifar Fatemeh , Ebrahimi Mansoureh
Published: April 2016

This study explores effective academic leadership as well as hindrances within Iran’s private higher educational institutions. The author employed a qualitative approach that utilized purposive sampling to collect and analyze data. Findings were categorized into three classes comprising the (i) setting of direction, (ii) organizational and (iii) staff development at three administrative levels: central office, branch office and faculty personnel. Obstacles confronting effective academic leadership were identified as (i) centralization of power; (ii) bureaucratic hierarchy; (iii) budgetary restraints; (iv) ineffective interaction including ineffectual communications as well as social, political and cultural interventions; and (v) unqualified staffing policies that eschewed meritocracy. This study reveals that the functional purview of an effective academic leader is to drive an institution’s vision forward towards achievement and define its mission and objectives. Moreover, it signifies an indispensable need for academic leadership development programs that incorporate, protect and support scientific management skills based on sound moral values, mutually established trust, collegial respect, and the application of transactional cum transformational governance methods in teaching, learning and research.
Academic Quality Assurance Variables in Nigerian Universities: Exploring Lecturers’ Perception
Authors: Obiekezie Eucharia O. , Ejemot-Nwadiaro Regina I. , Timothy Alexander E. , Essien Margaret I.
Published: April 2016

The level of job performance, international comparability and competitiveness of Nigerian university graduates are burning issues. Consequently, the academic quality of Nigerian universities has come under severe criticism. Since university lecturers are key players in quality assurance in universities, this study explored their perceptions of variables important to quality assurance in Nigerian universities. Five hundred lecturers from public universities in the South-South geopolitical zone responded to a 25-item survey. Five research questions were framed and descriptive statistics were used in analysing and presenting the data. The result showed that lecturers perceived availability of adequate number of qualified staff, students’ attitude to study, early publication of students’ examination results, availability of well-equipped laboratories and workshops, and funding of tertiary education as the most important variables in academic quality assurance.
Alternative Frameworks of the Secondary School Students on the Concept of Condensation at Submicroscopic Level
Authors: Abdullah Nurdiana , Surif Johari , Ismail Syuhaida
Published: April 2016

The study was carried out to identify the alternative frameworks on the concept of condensation at submicroscopic level among secondary school students (N = 324). Data was collected by using the qualitative method through the Understanding Test on the Concept of Matter at Submicroscopic Level which consisted of 10 open-ended questions. The analysis of contents showed that the students’ alternative frameworks on the concept of condensation at submicroscopic level are divided into three categories namely the explanations with the alternative frameworks at submicroscopic level, the limited explanations at macroscopic level and no explanation. This article discussed the alternative frameworks of the first category only, namely the explanations with the alternative framework at submicroscopic level while the second and third categories are discussed in the second part of the article. In summary, some implications on the teachings are recommended in order to enhance the understanding of the students on the concept of condensation at the submicroscopic level.
School Climate of Educational Institutions: Design and Validation of a Diagnostic Scale
Authors: Becerra Sandra
Published: April 2016

School climate is recognized as a relevant factor for the improvement of educative processes, favoring the administrative processes and optimum school performance. The present article is the result of a quantitative research model which had the objective of psychometrically designing and validating a scale to diagnose the organizational climate of educational institutions.

This study had the participation of 549 teachers and directors from 42 primary and secondary educational establishments of Chile. Diverse procedures were applied for the validation of content and psychometric validation in the various stages of the investigation, obtaining an instrument composed by seven factors and made up of conceptually and statistically consistent items. The complete scale and its sub-scales show adequate reliability, and likewise an appropriate validity, constituting it an instrument of wide use for supporting the process of education administration, and to promote coexistence climates of appreciation and respect among the educational participants.

The complete scale and its subscales permits the understanding that the organizational climate of the educational center is not reduced to the teacher-student relationship, but rather contemplates the dynamic relationships between diverse players, establishing the importance of the joint action between teachers, directives, students, and parents, as well as revealing the importance of some structural organization variables which influence the daily perception of school climate.
МОНГОЛ ЧОНОГОНО (JURINEA MONGOLICA Maxim.) УРГАМЛЫН ФИТОХИМИ БОЛОН БИОЛОГИЙН ИДЭВХИЙН СУДАЛГАА
Authors: Думаа М , Солонго Т , Болортуяа М , Чүнсриймятав Г , Грүнер Маргит , Рэгдэл Д , Кноелкер Ханс-Иаохим
Published: April 2016

Монгол чоногоно (Jurinea mongolica Maxim.) ургамлын газрын дээд хэсгийн этилацетатын бүлэг ханднаас хиспидулин бодисыг цэврээр ялгаж, түүний молекулын бүтэц байгууламжийг масс спектрометр, 1Н, 13С болон хоёр хэмжээст цөмийн соронзон резонансын (ЦСР) спектроскопын аргаар таньж тодорхойлов. Тухайн ургамлын нийлбэр алкалоид, хлороформ, этилацетатын хандны куарум сенсинг механизмыг дарангуйлах (quorum sensing (QS) system) идэвх нь 30 мг/мл тунд 10.0 ± 0.0 мм, 15.5 ± 2.1 мм, 12.0 ± 4.24 мм; хлороформын хандны Staphylococcus aureus (S. aureus), Micrococcus luteus (M. luteus), Staphylococcus epidermidis (S. epidermidis) бактерийн эсрэг идэвх нь 10 мг/мл тундаа 11.4 мм, 13.12 мм, 15.16 мм байв. Харин тухайн ургамлын мутагенийг дарангуйлах идэвх нь петролейны эфир, хлороформ, этилацетат, н-бутанол, усан үлдэгдэл болон нийлбэр алкалоидод 8%, 62%, 46%, 7%, 44%, 59% байв. М. чоногоно ургамлын метанолын хандны нийлбэр фенолт нэгдлийн агууламж нь 14,1±0,3 мг/г, антиоксидант идэвх 3,6 ± 0,3 µг/мл (ABTS), 1,3 ± 0,1 µг/мл (DPPH) тус тус хэмжээтэй байв.
ЦЭЭНИЙН ТӨРЛИЙН УРГАМАЛ ДАХЬ ГОЛ НЭГДЛҮҮД
Authors: Пүрэвдорж Э , Одонтуяа Г
Published: April 2016

Бид монгол оронд ургадаг Цээнийн төрлийн Цагаан цээнэ (Paeonia lactiflora Pall.) ба Ягаан цээнэ (Paeonia anomala L.)-н газрын дээд хэсэг, цэцэг, үндэсний химийн бүрэлдэхүүн, найрлагыг харьцуулан анх удаа судалж тэдгээрт кверцетин (1), кемпферол (2), кемпферол-3-O-β-D-глюкопиранозид (3) этилгаллат (4), галлын хүчил (5), 1,2,3,4,6-пентагаллоил-O-β-D-глюкопираноз (6), паеонифлорин (7) зонхилдог болохыг тогтоолоо. Эдгээрээс нэгдэл 1-г Цагаан цээнэ болон Ягаан цээнэ, нэгдэл 3-г Ягаан цээнээс тус тус анх удаа ялгав.Дээрх хоёр зүйл Цээнийн эмийн түүхий эдэд энгийн фенол (4, 5), таннин (6) болон монотерпений гликозид (7) харьцангуй их байгаа нь тэдгээрийг ялгаж, бүтэц байгууламжийг тодорхойлох явцад тогтоогдлоо. Харин флавоноидын уламжлалын нэгдэл нь (1, 2, 3) бусад ангиллын нэгдлээс бага боловч газрын дээд хэсэгт зонхилж байна.Цагаан цээнийн газрын дээд хэсэгт нэгдэл 3 (0.108%), 4 (0.216%), 6 (0.165%) их байгаа бол Ягаан цээнийхэд 4 (0.361%), 6 (0.386%) and 7 (0.725%) зонхилж их хэмжээтэй байна. Мөн эдгээр нэгдэл нь Ягаан цээнийн цэцгэнд их илэрч байв. Дээрх хоёр зүйл Цээнийн үндсэнд флавоноидын төрлийн нэгдлүүд илрээгүй бол харин аль алинд нь нэгдэл 4, 7 маш их хэмжээтэй агуулагдаж байна.Цээнийн төрлийн дээрх хоёр зүйлийн химийн бүрэлдэхүүн, найрлагыг харьцуулан судалсан ажил урьд өмнө байгаагүй тул тэдгээрт зонхилон агуулагддаг биологийн идэвхт нэгдлүүдийн тоо хэмжээг эмийн түүхий эд тус бүрт нь анх тодорхойлсон нь шинжлэх ухааны шинэ мэдээлэл болж байна. Энэ нь эдгээр ургамлын ямар эд, эрхтэнг эм, хүнс, гоо сайхны бүтээгдэхүүний түүхий эд болгон ашиглаж болохыг илэрхийлж буй үнэ цэнэтэй суурь мэдээлэл болохын зэрэгцээ практик ач холбогдолтой юм.
Body side-specific control of motor activity during turning in a walking animal
Authors: Gruhn Matthias , Rosenbaum Philipp , Bockemühl Till , Büschges Ansgar
Published: April 2016

Animals and humans need to move deftly and flexibly to adapt to environmental demands. Despite a large body of work on the neural control of walking in invertebrates and vertebrates alike, the mechanisms underlying the motor flexibility that is needed to adjust the motor behavior remain largely unknown. Here, we investigated optomotor-induced turning and the neuronal mechanisms underlying the differences between the leg movements of the two body sides in the stick insect Carausius morosus. We present data to show that the generation of turning kinematics in an insect are the combined result of descending unilateral commands that change the leg motor output via task-specific modifications in the processing of local sensory feedback as well as modification of the activity of local central pattern generating networks in a body-side-specific way. To our knowledge, this is the first study to demonstrate the specificity of such modifications in a defined motor task.
One-step fabrication of nanostructure-covered microstructures using selective aluminum anodization based on non-uniform electric field
Authors: Park Yong Min , Kim Byeong Hee , Seo Young Ho
Published: April 2016

This paper presents a selective aluminum anodization technique for the fabrication of microstructures covered by nanoscale dome structures. It is possible to fabricate bulging microstructures, utilizing the different growth rates of anodic aluminum oxide in non-uniform electric fields, because the growth rate of anodic aluminum oxide depends on the intensity of electric field, or current density. After anodizing under a non-uniform electric field, bulging microstructures covered by nanostructures were fabricated by removing the residual aluminum layer. The non-uniform electric field induced by insulative micropatterns was estimated by computational simulations and verified experimentally. Utilizing computational simulations, the intensity profile of the electric field was calculated according to the ratio of height and width of the insulative micropatterns. To compare computational simulation results and experimental results, insulative micropatterns were fabricated using SU-8 photoresist. The results verified that the shape of the bottom topology of anodic alumina was strongly dependent on the intensity profile of the applied electric field, or current density. The one-step fabrication of nanostructure-covered microstructures can be applied to various fields, such as nano-biochip and nano-optics, owing to its simplicity and cost effectiveness.
Electronic Waste Awareness and Management in the Municipality of Tuburan, Cebu, Philippines
Authors: Asendiente-Bajao Naomi , Pepino Mario , Celeste Noel , Sarucam Jae-an , C. Brigoli Helen , Pontillas Pedrito C.
Published: April 2016

The world is now facing the great effect of the rapid growth of information technology. The electronic waste or E-waste has been the major contributor of solid waste throughout the globe that had caused the contamination of the global environment. Thus, this study assessed the electronic waste in the Municipality of Tuburan Cebu. Questionnaires were distributed to the 13 barangays in the municipality of Tuburan with simple questions answerable by “Yes” or “No”. There were 1,115 respondents (families) over 13 barangays in Tuburan, Cebu. Results showed that more than half of the respondents still need complete awareness about electronic waste, its composition, proper handling, and its effects to the environment. An alarming value shows that 721 or 64.66 percent of the 1,115 respondents said that there are no waste collectors in their area. This simply means that more than 50 percent of the total number of respondents would end up throwing and dumping their waste including E-waste; anywhere or in the open landfill. It shows that respondents need complete awareness about E-waste; particularly, the nature of electronic waste, proper handling, and the negative effects to the environment and their effects to the human health and other living animals. The absence of waste collectors in most barangays has created big impact to the surroundings already. Moreover, some respondents have thought that these E-wastes just mean nothing to the waste collectors. Waste collectors must be strictly assigned by the LGU to some specific areas to closely monitor and confine the waste disposal of each household. It will also be good if a separate collector for E-waste can be provided in each locality.
Tidal controls on the flow of ice streams
Authors: Rosier Sebastian H. R. , Gudmundsson G. Hilmar
Published: April 2016

The flow of many Antarctic ice streams is known to be significantly influenced by tides. In the past, modeling studies have implemented the tidal forces acting on a coupled ice stream/ice shelf system in a number of different ways, but the consequences that this has on the modeled response of ice streams to tides have, until now, not been considered. Here we investigate for the first time differences in model response that are only due to differences in the way tidal forcings are implemented. We find that attempts to simplify the problem by neglecting flexural stresses are generally not valid and forcing models with only changes in ocean back pressure will not capture either the correct amplitudes or length scale.
Can PDSI inform extreme precipitation?: An exploration with a 500 year long paleoclimate reconstruction over the U.S.
Authors: Steinschneider Scott , Ho Michelle , Cook Edward R. , Lall Upmanu
Published: April 2016

This study explores whether it is possible to reconstruct the frequency of extreme precipitation occurrence across the contiguous United States (CONUS) using the Living Blended Drought Atlas (LBDA), a 500 year paleoclimate reconstruction of the summer (June–August) Palmer Drought Severity Index (PDSI). We first identify regions of the country where the LBDA may reflect the occurrence of extremes based on their seasonality and contribution to total annual moisture delivery. Correlation measures are used to assess the relationship between the frequencies of extreme precipitation occurrence and both the instrumental monthly PDSI and the annual LBDA‐estimated PDSI. Extreme precipitation is found to account for a large portion of total precipitation west of the Mississippi River and clusters in particular seasons (winter and summer), supporting a strong relationship with the LBDA without much information loss from the instrumental PDSI data. Dimension reduction techniques are used to explore the joint spatiotemporal structure of extreme precipitation occurrence and LBDA across the country. The primary modes of variability of the LBDA and extreme precipitation occurrence relate remarkably well for a region centered over the southwest that exhibits an ENSO‐like time‐frequency structure. Generalized linear models (GLMs) are used to demonstrate the feasibility of reconstructing the annual extreme precipitation frequency over the 500 year prehistoric record at two sites in the southwest and Southern Plains. GLM‐based reconstructions show a high degree of structured variability in the likelihood of extreme precipitation occurrences over the prehistoric record.
Kalibrierung [Air Monitoring Methods in German language, 2016]
Authors: Hebisch R. , Ball M. , Breuer D. , Heckmann P. , Krämer W. , Maschmeier C.‐P. , Nitz G. , Riepe W. , Schuh C. , Hartwig Andrea ,   MAK Commission
Published: April 2016

Workplace measurements are intended to give information about kind and extent of workers' exposure during their activities with hazardous substances. For this purpose calibration is necessary to establish the relationship between a known concentration and the corresponding measuring signal resulting in reliable measuring results at a high level of quality. Therefore, calibration strongly influences accuracy and precision of the whole measuring procedure. Calibration is required for different tasks. During development of a measurement procedure the calibration range has to be determined, for which there must be a linear relationship between the concentration of the analyte and the response of the analytical procedure. Important analytical parameters such as limit of detection (LOD) and limit of quantification (LOQ) may also be determined using calibration procedures. Normally, calibration is needed for the quantification of hazardous substances from workplace measurements. In this case the composition of calibration solutions should be as near as possible to that of the collected samples. The calibrated concentration range should yield unambiguous analytical results. Traceability of the complete calibration procedure from the measuring result back to the typically used (certified) reference material must be ensured. This chapter describes how to perform calibration for different purposes and the possible sources of errors which have to be considered. Requirements for reference materials are also specified.
Ethylene glycol monomethyl ether and ethylene glycol monomethyl ether acetate[BAT Value Documentation, 2009]
Authors: Kaefferlein H. , Drexler H. , Hartwig A. ,   MAK Commission
Published: April 2016

Ethylene glycol monomethyl ether and ethylene glycol monomethyl ether acetate

In 2009, the German Commission for the Investigation of Health Hazards of Chemical Compounds in the Work Area has evaluated a BAT‐value for ethylene glycol monomethyl ether (2‐methoxyethanol, 2‐ME) and ethylene glycol monomethyl ether acetate (2‐methoxyethyl acetate, 2‐MEA), considering methoxyacetic acid in urine to characterize the internal exposure. Both substances have been designated with “H” (skin notation) and classified in pregnancy risk group B (MAK Value Documentation, Hartwig 2009). Available publications are described in detail.The most sensitive parameter for the effects of 2‐ME in humans is its influence on the erythropoetic system (haematotoxicity). The study by Shih et al. (2003) found clear haematological effects for the parameters haemoglobin, haematocrit and erythrocyte count for 2‐ME at mean arithmetic concentration of 57.7 ± 31.8 mg/g creatinine. Slight haematological effects could not be excluded with certainty at a mean arithmetic concentration of 24.6 ± 14.7 mg/g creatinine, while no effects were observed at a concentration of 13.5 ± 10.6 mg/g. In another study of this working group (Shih et al. 2000b), haematological effects were found at a mean geometric concentration of 20.0 ± 2.2 mg/g creatinine and 20.9 ± 2.2 mg/g creatinine compared with a non‐exposed control group. On the basis of these data available, a BAT‐value of 15 mg methoxyacetic acid/g creatinine was established. The sampling time is at the end of exposure or the end of the shift. Due to the long half‐life of 2‐ME or methoxyacetic acid (about 70 hours), an accumulation in the body during the working week has to be considered.
Saliva as a matrix for human biomonitoring in occupational and environmental medicine [Biomonitoring Methods, 2015]
Authors: Michalke B. , Rossbach B. , Göen T. , Schäferhenrich A. , Scherer G. , Hartwig A. ,   MAK Commission
Published: April 2016

Purpose: Human biomonitoring (HBM) implies the assessment of internal exposure to hazardous substances by measuring the substances, their metabolites or reaction products, as well as effect parameters in human body fluids. Along with blood, plasma and urine, saliva is of increasing interest as an alternative matrix for HBM.

Methods: This paper reviews studies that measure salivary background levels of hazardous substances, elevated levels after environmental or occupational exposure, as well as references which deal with physiological and toxicokinetic behaviour of saliva and salivary parameters, respectively.

Results: The studies revealed that the determination of biomarkers in saliva is a promising approach for HBM, even if only few substances showed a satisfying correlation with exposure data or established biomonitoring matrices such as blood, plasma and urine. Saliva has been proven to be particularly suitable for substances of low molecular weight such as organic solvents, selected pesticides, cotinine, and for some specific trace elements. Besides several advantages, serious problems and limitations were identified. Above all, the complex interactions between substance properties, sampling procedure, sample preparation, measurement techniques or individual factors, and the salivary analyte level are discussed.

Conclusions: A major conclusion of the review is that more scientific studies are needed in order to systematically collect data on parameters, influencing salivary analyte levels. Crucially required is a harmonisation of the sampling as well as the sample preparation techniques and procedures, which is indispensable to achieve an overall comparability and interpretability of salivary biomarker levels.
Chlorierte Biphenyle [MAK Value Documentation in German language, 2016]
Authors: Hartwig A. ,   MAK Commission
Published: April 2016

Chlorinated Biphenyls (PCB)

The German Commission for the Investigation of Health Hazards of Chemical Compounds in the Work Area has re‐evaluated the maximum concentration at the workplace (MAK value) of chlorinated biphenyls (PCB), considering all toxicity endpoints. Available publications are described in detail.

The Commission re‐evaluated the previous distinction of PCB in two groups: congeners with up to 3 and 4 or more chlorine atoms. Recent inhalation studies show that the lung is not expected to be the primary target organ of PCB 3 and PCB 11 but the liver. In feeding studies, Aroclor mixtures containing congeners with up to 3 chlorine atoms yield only liver adenomas but no carcinomas in rats, although some of these congeners are genotoxic. On the other hand, Aroclor mixtures with high amounts of congeners with 4 and more chlorine atoms lead to a high incidence of liver carcinomas in rats. Therefore, for congeners with up to 3 chlorine atoms, the genotoxicity is not decisive for the development of liver tumours but mainly the tumour promotion, which has also been shown for congeners with 4 and more chlorine atoms. The distinction between these two groups is therefore no longer retained and all PCBs are classified in Carcinogen Category 4. As a 4‐week inhalation study in rats with a PCB containing mainly congeners with up to 3 chlorine atoms does not give rise to toxicity at a concentration which is 35 times higher than the previous MAK value for congeners with 4 and more chlorine atoms, this MAK value of 0.003 mg/m3is now set for all PCB. The assignment to Peak Limitation Category II with an excursion factor of 8 is retained due to the critical systemic effects and to the long half‐life of PCB. The assignment to Pregnancy Risk Group B is retained, as damage to the embryo or foetus cannot be ruled out even when the MAK value is observed. The genotoxic potency in vivo is regarded as very low if the MAK value is observed, and all PCB are grouped into Germ Cell Mutagen Category 5.
Chlorinated Biphenyls [MAK Value Documentation, 2013]
Authors: Hartwig A. ,   MAK Commission
Published: April 2016

Toxic Effects and Mode of Action

Mechanism of Action

Toxicokinetics and Metabolism

Absorption, distribution and elimination

Metabolism

Effects in Humans

Single exposures

Repeated exposure

Local effects on skin and mucous membranes

Allergenic effects

Reproductive and developmental toxicity

Genotoxicity

Carcinogenicity

Animal Experiments and in vitro Studies

Acute toxicity

Subacute, subchronic and chronic toxicity

Local effects on skin and mucous membranes

Allergenic effects

Reproductive and developmental toxicity

Genotoxicity

Carcinogenicity

Manifesto (MAK value/classification)
tert‐Butyl acetate [MAK Value Documentation, 2014]
Authors: Hartwig A. ,   MAK Commission
Published: April 2016

The German Commission for the Investigation of Health Hazards of Chemical Compounds in the Work Area has re‐evaluated the maximum concentration at the workplace (MAK value) of
tert
‐butyl acetate, considering all toxicity endpoints. Available unpublished study reports and publications are described in detail. The critical effects of
tert
‐butyl acetate are irritation and systemic effects on the liver and kidneys, in addition neurotoxic effects in rats and mice. The subchronic NOAEC in mice is 100 ml/m
3
based on transient acute neurotoxic symptoms which can be used to calculate a MAK value of 50 ml/m
3
. This value also provides protection from irritation. As the critical effect is systemic, Peak Limitation Category II is assigned. The default excursion factor of 2 is set as no half‐life in blood is known, and it is not clear whether the clinical effects were caused by the substance itself or a metabolite. Damage to the embryo and foetus is unlikely if the MAK value for
tert
‐butyl acetate is observed taking into consideration the data for the metabolite
tert
‐butyl alcohol. Therefore
tert
‐butyl acetate has been classified in Pregnancy Risk Group C. Skin contact is not expected to contribute significantly to systemic toxicity.
tert
‐Butyl acetate is not genotoxic and carcinogenicity data are missing. Sensitization is not expected from the limited data.
Gold‐Catalyzed Cyclizations of Alkynyl Silyl Enol Ethers: An Easy Access to Bicyclo[3.2.1]octanone Derivatives
Authors: Carrër Amandine , Péan Christophe , Perron‐Sierra Françoise , Mirguet Olivier , Michelet Véronique
Published: April 2016

The efficient gold‐catalyzed cyclization reactions of alkynyl silyl enol ethers were successfully applied to the preparation of bicyclo[3.2.1]octanone derivatives. Accordingly, after optimization of the gold catalytic system, several bicyclic α,β‐unsaturated keto adducts were synthesized in good to excellent yields. The process followed a major 5‐exo cyclization via an anti addition of the silyl enol ether to the π‐activated intermediate, which was demonstrated by a deuterium incorporation experiment. A 6‐endo cyclization process was observed for a silyl enol ether bearing an electron‐donating aromatic group.

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Efficient Modular Synthesis of Isomeric Mono‐ and Bispyridyl[2.2]paracyclophanes by Palladium‐Catalyzed Cross‐ Coupling Reactions
Authors: Braun Carolin , Spuling Eduard , Heine Niklas B. , Cakici Murat , Nieger Martin , Bräse Stefan
Published: April 2016

Pyridyl‐substituted [2.2]paracyclophanes build a multifunctional structural motif that is useful in material chemistry, catalysis and for luminescent structures. Nonetheless, there is still a lack of general methods for the synthesis of these structures tolerating easily accessible bromides as well as different isomeric pyridyl groups. Hence the coupling of functionalized [2.2]paracyclophanes with various substituted and functionalized pyridyl derivatives was achieved using Stille, Suzuki and Kumada coupling conditions. Hereby the Stille coupling of a [2.2]paracyclophane is presented as a versatile reaction for the formation of heteromeric [2.2]paracyclophane‐containing biaryl structures.

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Gold Functionalized Platinum M12L24‐Nanospheres and Their Application in Cyclization Reactions
Authors: Leenders Stefan H. A. M. , Dürr Maximillian , Ivanović‐Burmazović Ivana , Reek Joost N. H.
Published: April 2016

Nanospheres can be formed by combining 24 bispyridinyl building blocks with a palladium or platinum precursor. These spheres can be functionalized on the inside with a gold(I) chloride complex leading to a high local concentration of gold(I) complexes. The high local concentration makes the neutral gold species an active catalyst. Furthermore, the platinum‐gold spheres can be post‐modified with a silver(I) salt to form cationic gold(I) catalysts. The platinum assemblies are demonstrated to be stable in the presence of various substrates and as a result several cyclization reactions have been carried out using these new spheres as catalysts. Higher conversions in a [4+2] cycloaddition are observed for the sphere catalyst compared to the mono‐nuclear analogues. Also the cyclization of 1,6‐enynes can be facilitated by the confined gold catalyst and high activity is observed in the activation of allenes. For the lactonization of alkynoic acids, a different selectivity is observed compared to a standard gold(I) complex, demonstrating that the high local concentration due to a confined space can induce other selectivity in catalysis.

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Gold‐Catalyzed Imination/Mannich Reaction Cascades of 3‐En‐1‐ynamides with Anilines and Aldehydes to Enable 1,5‐Nitrogen Functionalizations
Authors: Singh RahulKumar Rajmani , Liu Rai‐Shung
Published: April 2016

Gold‐catalyzed imination/Mannich reaction cascades on readily available 3‐en‐1‐ynamides enable the diastereoselective synthesis of 1,5‐iminoamino compounds in a one‐pot operation. The reactions work well with diversified 3‐en‐1‐ynamides, aldehydes and anilines with good to excellent diastereoselectivities. Our control experiments indicate gold‐catalyzed aminations of 3‐en‐1‐ynamides to yield α‐imino allylgold intermediates that react subsequently with iminiums to implement the Mannich reactions stereoselectively. The reactions proceed with anti‐selectivity for those 3‐en‐1‐ynamides bearing acyclic alkenes whereas syn‐selectivity is seen for their cycloalkene‐based analogues. An open‐transition state can satisfactorily rationalize these observed stereoselectivities based on an antiperiplanar conformation.

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Design and Synthesis of Alanine Triazole Ligands and Application in Promotion of Hydration, Allene Synthesis and Borrowing Hydrogen Reactions
Authors: Yang Yongchun , Qin Anni , Zhao Keyan , Wang Dawei , Shi Xiaodong
Published: April 2016

A new type of alanine triazole (ATA) ligand was found to be an efficient partner for the stabilization of gold(III), thus rendering improved stability and high catalytic activities in allene synthesis and hydration reactions through the 3,3′‐arrangement of propargyl esters and propargyl alcohols. In addition to Au(I), ATA‐gold(III) was also proven to be an effective catalyst in promoting the formation of allenes with high yields. Furthermore, alanine triazole ruthenium has exhibited excellent potential as a means to catalyze borrowing hydrogen of alcohols and amines, ketones and alcohols.

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Mild and Functional Group Tolerant Method for Tandem Palladium‐Catalyzed Carbocyclization–Coupling of ε‐Acetylenic β‐Ketoesters with Aryl Bromides and Chlorides
Authors: Chaładaj Wojciech , Domański Sylwester
Published: April 2016

We report a new protocol for the annulative difunctionalization of acetylenes via tandem carbocyclization–coupling of ε‐acetylenic β‐ketoesters with aryl and heteroaryl bromides and chlorides catalyzed by the palladium species derived from an air‐ and moisture‐stable palladacyclic precatalyst. In the tandem process, the palladium complex combines appropriate carbophilic Lewis acidity and redox activity to catalyze two mechanistically distinct reactions ‐ nucleophilic addition of the enolate to unactivated alkyne, followed by CC coupling.

We found that a broad range of electronically varied aryl and heteroaryl bromides and chlorides underwent this reaction with various ε‐acetylenic β‐ketoesters, providing corresponding substituted vinylidenecyclopentanes in high yield with excellent functional group tolerance.

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P450 BM3 Monooxygenase as an Efficient NAD(P)H‐Oxidase for Regeneration of Nicotinamide Cofactors in ADH‐Catalysed Preparative Scale Biotransformations
Authors: Holec Claudia , Neufeld Katharina , Pietruszka Jörg
Published: April 2016

Enzymatic oxidations of primary and secondary alcohols catalysed by nicotinamide dependent alcohol dehydrogenases on the preparative scale require cofactor regeneration systems. Of critical value from an economic and ecological perspective is the application of NAD(P)H‐oxidases, which utilise molecular oxygen as a cost‐effective, atom‐efficient and environmentally benign oxidant to regenerate the cofactor NAD(P)+. Herein, the P450 BM3 monooxygenase from Bacillus megaterium is presented as an NAD(P)H‐oxidase for the successful regeneration of both NADP+ and NAD+ on the preparative scale. This enzyme was exemplarily applied for ADH‐catalysed oxidative kinetic resolutions of racemic secondary alcohols and the desymmetrisation of a meso‐diol leading to enantiomerically enriched secondary alcohols in both cases. Furthermore, the ADH‐catalysed oxidation of a primary alcohol targeting the corresponding aldehyde was performed. The obtained results significantly broaden the scope of feasible oxidative biotransformations, thereby increasing the number of synthetic reactions complying with key challenges of a modern and sustainable chemistry such as mild reaction conditions, environmentally benign solvents, and biodegradable non‐toxic catalysts.

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Compatibility of PTB7 and [70]PCBM as a Key Factor for the Stability of PTB7:[70]PCBM Solar Cells
Authors: Bartesaghi Davide , Ye Gang , Chiechi Ryan C. , Koster L. Jan Anton
Published: April 2016

The rapid degradation of organic photovoltaic (OPV) devices compared to conventional inorganic solar cells is one of the critical issues that have to be solved in order to make OPV a competitive commercial technology. The understanding of the fundamental mechanisms that reduce the power conversion efficiency (PCE) over time is beneficial for the design of new materials with enhanced stability. This paper focuses on bulk heterojunction organic solar cells based on thieno [3,4‐b] thiophene‐alt‐benzodithiophene (PTB7) mixed with [6,6]‐phenyl‐C71‐butyric acid methyl esther ([70]PCBM). In spite of being promising in terms of PCE, devices based on this blend are unstable and have a short lifetime. When exposed to light in inert atmosphere, the PCE drops by 15% in less than 1 h and by 35% in 8 h; this degradation is induced by the ultraviolet (UV) part of the spectrum. This paper analyzes the effect induced by UV light on the transport of charges in PTB7:[70]PCBM. Contrary to expectations, the electron transport shows evidence of trapping, while the transport of holes appears unaffected. Furthermore, it is proven that the loss of PCE is due to a reaction between PTB7 and [70]PCBM, while the intrinsic instability of the polymer plays a marginal role.
Empowering Semi‐Transparent Solar Cells with Thermal‐Mirror Functionality
Authors: Kim Hoyeon , Kim Hui‐Seon , Ha Jaewon , Park Nam‐Gyu , Yoo Seunghyup
Published: April 2016

Device architectures for semi‐transparent perovskite solar cells are proposed that are not only highly efficient but also very effective in thermal‐mirror operation. With the optimal top transparent electrode design based on thin metal layer capped with a high‐index dielectric layer for selective transmittance in visible and high reflectance in near‐infrared (NIR) region, the proposed see‐through devices exhibit average power conversion efficiency as large as 13.3% and outstanding NIR rejection of 85.5%, demonstrating their great potential for ideal “energy‐generating and heat‐rejecting” solar windows that can make a smart use of solar energy.
Synthesis and Anti‐HIV Activity of 5′‐Homo‐2′,3′‐dideoxy‐2′,3′‐didehydro‐4′‐selenonucleosides (5′‐Homo‐4′‐Se‐d4 Ns)
Authors: Qu Shuhao , Kim Gyudong , Yu Jinha , Sahu Pramod K. , Choi Yoojin , Naik Siddhi D. , Jeong Lak Shin
Published: April 2016

On the hypothesis that one carbon homologation of 4′‐selenonucleosides might relieve the steric repulsion between cellular kinases and bulky selenium, 5′‐homo‐4′‐Se‐d4Ns, 3 a–e, as anti‐HIV agents were designed and synthesized stereoselectively from d‐gulonic γ‐lactone, with the conversion of 2′,3′‐diol into the olefin as the key step. The anti‐HIV activity of all synthesized compounds, 5′‐homo‐4′‐Se‐d4Ns, was toxicity‐dependent, unlike normal 4′‐Se‐d4Ns, which were inactive against HIV‐1. This result indicates that 5′‐homo‐4′‐Se‐d4Ns might be phosphorylated by cellular kinases as per the hypothesis.