bluuebunny/crossref_metadata_2025 huggingface dataset:
Leadership Curriculum and Materials Used by High School Agricultural Science Teachers: A National Study of the Pre-LifeKnowledge Days
Authors: A. Christian Morgan  , Nicholas E. Fuhrman  , Diana L. King  , Frank B. Flanders  , Rick D. Rudd
Published: March 2013

Agricultural science programs have provided many opportunities for leadership education through classroom, supervised agricultural experience (SAE), and FFA Organization activities. Past studies have focused on leadership developed through activities such as career development events (CDE), SAE activities, FFA Organization conventions, and other intra-curricular activities; however, little research has focused on the type of leadership curriculum and materials used to teach leadership in agricultural science classrooms. This study used a qualitative survey to determine what leadership curriculum and materials were being used by agricultural science teachers to teach leadership prior to the release of the LifeKnowledge curriculum. To understand the impact of LifeKnowledge in follow-up studies, a baseline must first be established for comparison. This study found that agricultural science instructors used a wide variety of curriculum and resources to teach leadership. The most popular resources being used were text books and state provided curriculum materials; however, no single curriculum was used by the majority of participants. Some participants indicated using curriculum and resources to teach leadership which contained little, if any, leadership content. Agricultural science instructors may have mixed views on the definition of the term “leadership,” therefore additional research is needed to determine how agricultural science instructors define leadership and the methods they use to build leadership skills in their students.
Teacher Behaviors Contributing to Student Content Engagement: A Socially Constructed Consensus of Undergraduate Students in a College of Agriculture
Authors: Estepp Christopher M. , Roberts T. Grady
Published: March 2013

Students in colleges of agriculture will face a dynamically changing workplace. In order to learn the skills needed to succeed in such an environment, students must be cognitively engaged in the college classroom. Engagement with instructional content is a precursor to learning, and teachers in colleges of agriculture must shift towards using more learner-centered, engaging instructional methods. The purpose of this qualitative study was to explore college of agriculture students’ perspectives of specific teacher behaviors contributing to cognitive engagement. A focus group methodology was applied using the Student Content Engagement (SCE) framework to guide the interviews. The SCE framework consists of four constructs that must be in place for cognitive engagement to occur: subject matter content level, occasion for processing, physiological readiness, and motivation. Results of the study showed a multitude of teacher variables contributed to student content engagement and many of the findings were consistent with prior research about effective teaching. What is more, teacher immediacy was discovered as a consistent theme throughout all of the constructs. We concluded that teacher immediacy might be a construct for consideration in the SCE framework.
Identification and Validation of Agricultural Hazardous Occupations Order Certification Program Instructor Criteria and Competencies
Authors: Snyder Shannon , French Brian , Field William , Tormoehlen Roger , Ess Daniel
Published: March 2013

The USDA/NIFA has awarded funding to Land Grant Institutions to conduct and enhance the Hazardous Occupations Safety Training in Agriculture (HOSTA) program.# The HOSTA program is designed to provide relevant educational opportunities in an effort to reduce the frequency and severity of farmrelated injuries to all youth who work in agricultural production and to meet the current training requirements of the Agricultural Hazardous Occupations Order (AgHOs) for non-exempt youth. The Cooperative Extension Service and secondary school agricultural science and business programs are designated by the AgHOs as the only entities eligible to conduct and affirm completion of certification training. However, the law does not identify the minimum core competencies necessary for instructors and there are currently no evidence-based criteria to assess the preparedness of individuals who provide instruction to youth seeking AgHOs certification. One of the objectives of the current HOSTA project at Purdue University is to identify and validate prescribed criteria and desired core competencies for instructors who conduct certification training. This paper summarizes the findings of the validation process and reports on the core criteria and competencies identified.
A 20-Year Comparison of Teachers’ Agricultural Mechanics Laboratory Management Competency
Authors: McKim Billy R. , Saucier P. Ryan
Published: March 2013

Agricultural mechanics laboratory management skills are essential for school-based agriculture teachers who instruct students in an agricultural mechanics laboratory (Bear & Hoerner, 1986). McKim and Saucier (2011) suggested the frequency and severity of accidents that occur in these laboratories can be reduced when these facilities are managed by educators who are competent and knowledgeable in the area of laboratory safety and facility management. This study investigated changes in Missouri agriculture teachers’ perceived agricultural mechanics laboratory management competency from 1989 to 2008, percent changes between 1989 and 2008 and effect size were used to describe changes in importance and ability of the selected competencies. Results indicated that teachers in 2008 had more teaching experience than their predecessors, less university semester credit hours of agricultural mechanics instruction, taught courses with greater student enrollment in laboratories that had less workingspace per student. Further, teachers’ perceptions of the importance of agricultural mechanics laboratory management competencies had a negligible change. However, the changes in teachers’ perceived ability to perform development, writing, and planning competencies were notable.
An Analysis of FFA Chapter Demographics as Compared to Schools and Communities
Authors: Lawrence Shannon , Rayfield John , Morre Lori L. , Outley Corliss
Published: March 2013

This descriptive study was a special project for the National FFA Organization to determine the demographic makeup of rural, suburban, urban, and randomly selected at-large FFA chapters from the four national FFA regions. Summary data for this study revealed that gender in selected FFA chapters was 55% male and 45% female. Eighty percent of FFA members were reported to be White while the respective communities were 54% White. Rural FFA chapters had the highest percentage of FFA members in relation to their agricultural education course enrollments. Urban chapters reported more than half (52%) of their agricultural education students were FFA members. The majority of agricultural education teachers are White males. The demographic characteristics of FFA chapters in relation to their respective schools and communities provide a snapshot of today’s agricultural education programs and FFA chapters. Furthermore, this research could help identify strategies to move FFA chapters toward a more parallel representation of the schools and communities in which they exist
High accuracy measurements of dry mole fractions of carbon dioxide and methane in humid air
Authors: Rella C. W. , Chen H. , Andrews A. E. , Filges A. , Gerbig C. , Hatakka J. , Karion A. , Miles N. L. , Richardson S. J. , Steinbacher M. , Sweeney C. , Wastine B. , Zellweger C.
Published: March 2013

Abstract. Traditional techniques for measuring the mole fractions of greenhouse gases in the well-mixed atmosphere have required dry sample gas streams (dew point < −25 °C) to achieve the inter-laboratory compatibility goals set forth by the Global Atmosphere Watch programme of the World Meteorological Organisation (WMO/GAW) for carbon dioxide (±0.1 ppm in the Northern Hemisphere and ±0.05 ppm in the Southern Hemisphere) and methane (±2 ppb). Drying the sample gas to low levels of water vapour can be expensive, time-consuming, and/or problematic, especially at remote sites where access is difficult. Recent advances in optical measurement techniques, in particular cavity ring down spectroscopy, have led to the development of greenhouse gas analysers capable of simultaneous measurements of carbon dioxide, methane and water vapour. Unlike many older technologies, which can suffer from significant uncorrected interference from water vapour, these instruments permit accurate and precise greenhouse gas measurements that can meet the WMO/GAW inter-laboratory compatibility goals (WMO, 2011a) without drying the sample gas. In this paper, we present laboratory methodology for empirically deriving the water vapour correction factors, and we summarise a series of in-situ validation experiments comparing the measurements in humid gas streams to well-characterised dry-gas measurements. By using the manufacturer-supplied correction factors, the dry-mole fraction measurements have been demonstrated to be well within the GAW compatibility goals up to a water vapour concentration of at least 1%. By determining the correction factors for individual instruments once at the start of life, this water vapour concentration range can be extended to at least 2% over the life of the instrument, and if the correction factors are determined periodically over time, the evidence suggests that this range can be extended up to and even above 4% water vapour concentrations.
Long-term trends in ocean plankton production and particle export between 1960–2006
Authors: Laufkötter C. , Vogt M. , Gruber N.
Published: March 2013

Abstract. We analyse long-term trends in marine primary and particle export production and their link to marine phytoplankton community composition over the period 1950–2006 using a hindcast simulation of the ocean component of the Community Climate System Model to which the Biogeochemical Elemental Cycling Model had been coupled. In our simulation, global primary and export production decreased by 6% and 7%, respectively over the last 50 yr. These changes go along with a 8% decrease in small phytoplankton biomass and 5% decrease in zooplankton biomass. Diatom biomass decreases by 3% with strong temporal and spatial variability. Strongest decreases in primary and export production occured in the Western Pacific, where increased stratification leads to a decrease in total phytoplankton and a decrease in diatom fraction. This causes decreases in zooplankton biomass and a lower export efficiency. Strong phytoplankton composition changes occur in the Southern Ocean and North Atlantic, where increased wind stress leads to stronger mixing, which reduces the biomass of small phytoplankton, while diatoms profit from higher nutrient inputs and lower grazing pressure. The relative fraction of diatoms correlates positively with the export efficiency (r = 0.8) in most areas except the Northern Pacific and Antarctic Circumpolar Current, where the correlation is negative (r = −0.5). However, long-term trends in global export efficiency are ultimately driven by decreases in small phytoplankton and consequent decreases in coccolithophore biomass.
The influence of climate change on flood risks in France – first estimates and uncertainty analysis
Authors: Dumas P. , Hallegatte S. , Quintana-Seguì P. , Martin E.
Published: March 2013

Abstract. This paper proposes a methodology to project the possible evolution of river flood damages due to climate change, and applies it to mainland France. Its main contributions are (i) to demonstrate a methodology to investigate the full causal chain from global climate change to local economic flood losses; (ii) to show that future flood losses may change in a very significant manner over France; (iii) to show that a very large uncertainty arises from the climate downscaling technique, since two techniques with comparable skills at reproducing reference river flows give very different estimates of future flows, and thus of future local losses. The main conclusion is thus that estimating future flood losses is still out of reach, especially at local scale, but that future national-scale losses may change significantly over this century, requiring policy changes in terms of risk management and land-use planning.
Mechanisms of AMOC variability simulated by the NEMO model
Authors: Stepanov V. N. , Haines K.
Published: March 2013

Abstract. We have investigated dominant mechanisms of the Atlantic Meridional Overturning Circulation (AMOC) variability at 26.5° N (without the Ekman component) on monthly timescales using 1° and 1/4° NEMO model data. All data were detrended and the seasonal cycle removed. The spatial lead-lag correlations of different hydrodynamic fields with the AMOC time series were calculated. The analysis shows that the AMOC depends on the strength of wind over the North Atlantic on different time scales. At ∼ 1 yr the January–June difference of mean sea level pressure between high and mid-latitudes in the North Atlantic defines (according to different model runs) 35–50% of the annual AMOC variability. At interannual time scales ∼ 4 yr after strong (weak) winds over the North Atlantic the AMOC transport becomes higher (lower) by means of an increase (a decrease) in deep water formation in the North Atlantic subpolar gyre. The analysis of the 1/4° NEMO model shows that about 30% of the AMOC variability is due to density changes in the top 1000 m in the Labrador and Irminger seas occurring about 4 yr early.
How Does Heart Rate Variability Biofeedback Work? Resonance, the Baroreflex, and Other Mechanisms
Authors: Lehrer Paul
Published: March 2013

Heart rate variability biofeedback is known to have multiple effects on the cardiovascular system, the respiratory system, and emotional reactivity. This paper reviews the origins of work on heart rate variability biofeedback, and mechanisms for its various effects, including direct effects on the baroreflex system and gas exchange efficiency, as well as indirect effects on emotional reactivity and possibly inflammatory activity. Resonance in the cardiovascular system is explained, as well as ways that heart rate variability biofeedback stimulates these resonance effects, through interactions between respiratory sinus arrhythmia and the baroreflex system. Relationships of these mechanisms to various clinical applications of heart rate variability biofeedback are explored, as are future extensions of biofeedback to the vascular tone baroreflex.
Leptospira spp. Prevalence in Small Mammal Populations in Cotonou, Benin
Authors: Houemenou G. , Ahmed A. , Libois R. , Hartskeerl R. A.
Published: March 2013

The aim of this study was to assess the Leptospira prevalence in small animals in Cotonou, the capital of Benin. Rodents and shrews were captured in urban and periurban settings and determined as species of the genera Rattus, Mastomys, and Crocidura. Kidney specimens of 90 animals were examined using a real-time PCR assay specific for leptospires that belong to pathogenic species. Leptospiral DNA was amplified from kidney tissues ranging from 13.3% (8/60) in Rattus rattus to 100.0% (1/1) in Crocidura spp. with an average of 18.9% (17/90) of the animals caught at 15 locations. Clade-specific Taqman PCR on 10 samples placed six of these within clade 1 comprising the species L. kirschneri, L. interrogans, L. meyeri, and L. noguchii and four within clade 2 consisting of species L. weilii, L. alexanderi, L. borgpetersenii, and L. santarosai. Phylogenetic analysis of partial sequences of the amplicons of seven samples of these 10 samples revealed that four of the clade 1 samples could equally be assigned to L. interrogans and L. kirschneri and three samples from clade 2 belonged to L. borgpetersenii. Results presented in the paper indicate that small mammals present a major public health risk for acquiring leptospirosis in Cotonou, Benin and will contribute to a raised awareness amongst health care workers and decision makers and hence promote appropriate clinical management of cases.
Preparation for Cardiopulmonary Resuscitation in Medical Schools in Australia: A Survey of Current Practice
Authors: Barton Peter J. M. , Beveridge Andrew A. , Jones Kay M.
Published: March 2013

Introduction. Cardiopulmonary resuscitation (CPR) is acknowledged worldwide as a stressful clinical activity for all young doctors. The extent of standardisation of preparation for CPR within Australian curricula is unknown. Recent trends in the UK suggest the emergence of a common endpoint, Immediate Life Support (ILS) certification. The support for a similar shared endpoint in Australia is unknown. Methodology. A telephone questionnaire survey about the preparation for teaching CPR to medical students was undertaken in all Australian medical schools in early 2012; 88% of schools replied. Results. The majority favoured early basic CPR training. There was marked variation in how schools taught advanced CPR and how CPR competence was assessed. Only one school considered their graduates to be less than well prepared for CPR and all schools agreed that a common endpoint was desirable. Discussion. There is broad support for Immediate Life Support as a common end in resuscitation competence. Medical schools where students are prepared for a rural placement on graduation may still require a higher standard of competence.
A paired-comparison intervention to improve quality of medical records
Authors: Esposito Sergio , Pelullo Concetta P , Agozzino Erminia , Attena Francesco
Published: March 2013

Background: To evaluate the quality of medical record (MR) compilation in the Teaching Hospital of the Second University of Naples, Italy, after a controlled intervention for quality improvement. Methods: From the 66 wards of the Teaching Hospital, we selected eight homogeneous pairs of wards, matched for similar typology. For each pair, we randomized a ward to undergo a training course about correct compilation of MRs (treated group) and considered the remaining ward as a control (untreated group). For each section of MR we evaluated completeness and clarity of handwriting and presence and clarity of signature. Results: In general, the worst result in both groups was the absence of signature in the daily diary (76.6% in the treated group and 94.4% in the untreated group). The greatest differences between the two groups were detected in the compilation of the daily diary (absent/incomplete in 1.9% of the treated group compared with 21.9% of the untreated group; relative risk [RR] = 11, 95% confidence interval [CI] = 5.1-26.4) and the physical examination section (absent/incomplete in 2.8% of the treated group compared with 21.3% of the untreated group; RR = 7.5; 95% CI = 3.8-14.8). Conclusions: Comparison between the treated and untreated groups shows that there is a significant improvement in compilation of several sections of the MRs in the treated group. However, the results obtained were only partially satisfactory because of the poor quality of MR compilation in both groups.
Quest of Urban Growth Monitoring from Myth to Reality
Authors: Sheeba Afsar  , Syed Jamil Hassan Kazmi  , Sumaiya Bano
Published: March 2013

The Earth's surface is changing rapidly, mainly because of the anthropogenic interventions. At many point of times, these changes are local, regional, national, and even global in scale, interconnected both horizontally and vertically. Some changes have natural causes, such as earthquakes or floods. Other changes, such as urban expansion, agricultural intensification, resource extraction, and water resources development are examples of human-induced change that have significant impacts upon people, the economy and resources. As the urban growth in the world as major element of change, the appraisal and monitoring of these areas is a matter of great concern for a quality life of human beings. For this purpose, an appropriate and instantaneous technology is required to monitor the unwanted change. Hence, the main objective of this paper is to monitor the spatial extension of urban growth of the Metropolitan Karachi during 1955-2010 using different data sets and series of satellite imageries. In addition to that the growth corridors have also determined both in terms of magnitude and direction. The spatial change detected through successive satellite imageries has revealed a gigantic change from 1955 to 2010. The averageannual growth rate of the Metropolis has taken place at an outstanding 13.35 %. It has been also found that the increase in urban growth has been noted towards the East and West of the city mainly but due to rapid expansion of housing schemes in north-eastern part of the city an enormous urban growth has taken place there as well. The paper has also revealed the utility of the Geo-Informatics for the monitoring of urban growth.
Sugar promotes vegetative phase change in Arabidopsis thaliana by repressing the expression of MIR156A and MIR156C
Authors: Yang Li , Xu Mingli , Koo Yeonjong , He Jia , Poethig R Scott
Published: March 2013

Nutrients shape the growth, maturation, and aging of plants and animals. In plants, the juvenile to adult transition (vegetative phase change) is initiated by a decrease in miR156. In Arabidopsis, we found that exogenous sugar decreased the abundance of miR156, whereas reduced photosynthesis increased the level of this miRNA. This effect was correlated with a change in the timing of vegetative phase change, and was primarily attributable to a change in the expression of two genes, MIR156A and MIR156C, which were found to play dominant roles in this transition. The glucose-induced repression of miR156 was dependent on the signaling activity of HEXOKINASE1. We also show that the defoliation-induced increase in miR156 levels can be suppressed by exogenous glucose. These results provide a molecular link between nutrient availability and developmental timing in plants, and suggest that sugar is a component of the leaf signal that mediates vegetative phase change.
Organic Light‐Emitting Diodes with 30% External Quantum Efficiency Based on a Horizontally Oriented Emitter
Authors: Kim Sei‐Yong , Jeong Won‐Ik , Mayr Christian , Park Young‐Seo , Kim Kwon‐Hyeon , Lee Jeong‐Hwan , Moon Chang‐Ki , Brütting Wolfgang , Kim Jang‐Joo
Published: March 2013

High‐efficiency phosphorescent organic light‐emitting diodes (OLEDs) doped with Ir(ppy)2(acac) [bis(2‐phenylpyridine)iridium(III)‐acetylacetonate] in an exciplex forming co‐host have been optically analyzed. This emitter has a preferred orientation with the horizontal to vertical dipole ratio of 0.77:0.23 as compared to 0.67:0.33 in the isotropic case. Theoretical analysis based on the orientation factor (Θ, the ratio of the horizontal dipoles to total dipoles) and the photoluminescence quantum yield (qPL) of the emitter predicts that the maximum external quantum efficiency (EQE) of the OLEDs with this emitter is about 30%, which matches very well with the experimental data, indicating that the electrical loss of the OLEDs is negligible and the device structure can be utilized as a platform to demonstrate the validity of optical modeling. Based on the results, the maximum EQE achievable for a certain emitting dye in a host can be predicted by just measuring qPL and Θ in a neat film on glass without the need to fabricate devices, which offers a universal plot of the maximum EQE as a function of qPL and Θ.
Membrane‐based ethylene/ethane separation: The upper bound and beyond
Authors: Rungta Meha , Zhang Chen , Koros William J. , Xu Liren
Published: March 2013

Ethylene/ethane separation via cryogenic distillation is extremely energy‐intensive, and membrane separation may provide an attractive alternative. In this paper, ethylene/ethane separation performance using polymeric membranes is summarized, and an experimental ethylene/ethane polymeric upper bound based on literature data is presented. A theoretical prediction of the ethylene/ethane upper bound is also presented, and shows good agreement with the experimental upper bound. Further, two ways to overcome the ethylene/ethane upper bound, based on increasing the sorption or diffusion selectivity, is also discussed, and a review on advanced membrane types such as facilitated transport membranes, zeolite and metal organic framework based membranes, and carbon molecular sieve membranes is presented. Of these, carbon membranes have shown the potential to surpass the polymeric ethylene/ethane upper bound performance. Furthermore, a convenient, potentially scalable method for tailoring the performance of carbon membranes for ethylene/ethane separation based on tuning the pyrolysis conditions has also been demonstrated. © 2013 American Institute of Chemical Engineers AIChE J, 59: 3475–3489, 2013
Diffusion and performance of fragranced products: Prediction and validation
Authors: Teixeira Miguel A. , Rodríguez Oscar , Rodrigues Alírio E.
Published: March 2013

The design of fragranced products is a combination of art, technology, and scientific knowledge, although the former still predominates in the industry. For that reason, a theoretical model to assess their performance considering the release and diffusion together with the predicted odor intensity over time and distance from the source was developed and validated. Diffusion profiles were experimentally measured in a diffusion tube, similar to the Stefan tube, and predicted with a model for pure fragrance chemicals, binary, quaternary, and multicomponent (11 chemicals) mixtures. A very good agreement between our purely predictive model and experimental concentration data was observed. Fragrance concentrations in air were then converted into odor intensities using models from psychophysics, making it possible to evaluate the evolution of the odor with time and distance using a performance plot. Accordingly, the performance of these mixtures was modeled and experimentally validated, which constitutes a landmark for fragrance design. © 2013 American Institute of Chemical EngineersAIChE J, 59: 3943–3957, 2013
Recurring and Generalized Visceroptosis in Ehlers–Danlos Syndrome Hypermobility Type
Authors: Dordoni Chiara , Ritelli Marco , Venturini Marina , Chiarelli Nicola , Pezzani Lidia , Vascellaro Annalisa , Calzavara‐Pinton Piergiacomo , Colombi Marina
Published: March 2013

Visceroptosis is described in several heritable connective tissue disorders, including the hypermobility type of Ehlers–Danlos syndrome (hEDS), a.k.a. joint hypermobility syndrome (JHS). Clinical features of hEDS comprise joint hypermobility, mild skin hyperextensibility, joint instability complications, chronic joint/limb pain, and positive family history. Uterine and rectal prolapse has been reported in nulliparous women. We report on a family with two patients with hEDS. The proposita, a 38‐year‐old woman, present bilateral kidney prolapse requiring three nephropexies, gastric ptosis treated with gastropexy and Billroth I gastrectomy, and liver prolapse treated with a non‐codified hepatopexy procedure. Radiological evaluation also showed ovarian and heart prolapse. To our knowledge this is the first case of multiple visceral ptoses in hEDS. Visceral prolapse may lead to severe morbidity, affecting quality of life and a high rate of relapses after surgical procedures. Further investigations are needed to understand the molecular basis of the disease and retrospective studies on surgical outcomes, presentation of case series can be effective in order to offer a better treatment and prevention for hEDS patients. © 2013 Wiley Periodicals, Inc.
Analysis of De Novo HOXA13 Polyalanine Expansions Supports Replication Slippage Without Repair in Their Generation
Authors: Owens Kailey M. , Quinonez Shane C. , Thomas Peedikayil E. , Keegan Catherine E. , Lefebvre Nanci , Roulston Diane , Larsen Christine A. , Stadler H. Scott , Innis Jeffrey W.
Published: March 2013

Polyalanine repeat expansion diseases are hypothesized to result from unequal chromosomal recombination, yet mechanistic studies are lacking. We identified two de novo cases of hand‐foot‐genital syndrome (HFGS) associated with polyalanine expansions in HOXA13 that afforded rare opportunities to investigate the mechanism. The first patient with HFGS was heterozygous for a de novo nine codon polyalanine expansion. Haplotype investigation showed that the expansion arose on the maternally inherited chromosome but not through unequal crossing over between homologs, leaving unequal sister chromatid exchange during mitosis or meiosis or slipped mispairing as possible explanations. The asymptomatic father of the second patient with HFGS was mosaic for a six codon polyalanine expansion. Multiple tissue PCR and clonal analysis of paternal fibroblasts showed only expansion/WT and WT/WT clones, and haplotype data showed that two unaffected offspring inherited the same paternal allele without the expansion, supporting a postzygotic origin. Absence of the contracted allele in the mosaic father does not support sister chromatid exchange in the origin of the expansion. Mosaicism for HOXA13 polyalanine expansions may be associated with a normal phenotype, making examination of parental DNA essential in apparently de novo HFGS cases to predict accurate recurrence risks. We could not find an example in the literature where unequal sister chromatid exchange has been proven for any polyalanine expansion, suggesting that the principal mechanism for polyalanine expansions (and contractions) is slipped mispairing without repair or that the true frequency of unequal sister chromatid exchange involving these repeats is low. © 2013 Wiley Periodicals, Inc.
(BeDABCO)2Pd2Cl6 (1‐benzyl‐4‐aza‐1‐azoniabicyclo[2.2.2]octane chloride) as a highly active catalytic system for the Stille cross‐coupling reaction under microwave irradiation
Authors: Hajipour Abdol R. , Najafi Narges , Rafiee Fatemeh
Published: March 2013

An efficient catalytic system using (BeDABCO)2Pd2Cl6 was developed for the Stille cross‐coupling reaction. The substituted biaryls were produced in excellent yields in short reaction times using a catalytic amount of this catalyst in DMF at 120 °C. The ionic character of homogeneous catalyst and microwave irradiation and also DMF as microwave‐active polar solvent gave higher yields and shorter reaction times than conventional heating. Benzyl DABCO as an efficient ligand and also a quaternary ammonium salt had an efficient stabilizing effect on the Pd(0) species. Copyright © 2013 John Wiley & Sons, Ltd.
Synthesis, characterization and 1,3‐butadiene polymerization behaviors of cobalt complexes bearing 2‐pyrazolyl‐substituted 1,10‐phenanthroline ligands
Authors: Wang Baolin , Gong Dirong , Bi Jifu , Dai Quanquan , Zhang Chunyu , Hu Yanming , Zhang Xuequan , Jiang Liansheng
Published: March 2013

A series of cobalt(II) complexes containing tridentate 2‐pyrazolyl‐substituted 1,10‐phenanthroline ligands (L) with the general formula [LCoCl2] have been successfully synthesized and fully identified by IR spectroscopy, elemental analysis and mass spectroscopy. Cobalt complexes Co4–Co8 were further confirmed by X‐ray crystallographic analysis, and all the complexes adopted distorted trigonal pyramid geometries around the cobalt center. In combination with methylaluminoxane, the complexes exhibit high cis‐1,4‐selectivity for 1,3‐butadiene polymerization. The catalytic activities of the complexes mainly depend on the nature of the substituent and its position at the pyrazolyl ring of the ligand. Complexes having a bulkier substituent on the pyrazolyl ring of the ligand show lower catalytic activity and the incorporation of electron‐withdrawing substituent enhances the activity. Polymerization behaviors were almost not affected with varying [Al]/[Co] ratio, but both activity and the cis‐1,4 content decrease slightly as polymerization temperature increasing. Copyright © 2013 John Wiley & Sons, Ltd.
Student injuries in the dissecting room
Authors: Cornwall Jon , Davies Tilman M. , Lees David
Published: March 2013

Cadaver dissection is the first opportunity for many students to practice handling human tissue and is their first exposure to the occupational hazards involved with this task. Few studies examine dissection room injuries to ascertain the dangers associated with dissecting. We performed a retrospective cohort analysis of dissection room injuries from four student cohorts over an eleven‐year period (2001–2011), including second‐year medical students, third‐year medical students, second‐year dental students, and third‐year science students. Injury data included activity causing injury, object responsible, and injury site. A total of 163 injuries during 70,039 hours of dissection were recorded, with 66 in third‐year medical students, 42 in second‐year medical students, 36 in third‐year science students, and 16 in second‐year dental students. The overall rate was 2.87 injuries per 1,000 dissection hours, with second‐year medical students most frequently injured (5.5 injuries per 1,000 hours); third‐year medical students were least frequently injured (1.3 injuries per 1,000 hours). A significant difference in injury rates between student groups indicated a higher than expected injury rate to second‐year medical students and lower than expected rates to third‐year medical students. Injury rates increased for most groups between 2001–2006 and 2007–2011 periods. Most injuries (79%) were from scalpel cuts to the finger or thumb. This study provides injury rates for dissection room injuries to students, indicating differences in injury frequency between cohorts and an increase in injury rate over time. As scalpel cuts were the most likely injury mechanism, targeting scalpel handling with preventative strategies may reduce future injury risk. Anat Sci Educ 6: 404–409. © 2013 American Association of Anatomists.
Berechnung aktiv absorbierender Schalldämpfer in Lüftungskanälen
Authors: Krüger J.
Published: March 2013

Aktiv absorbierende Wandauskleidungen ermöglichen besonders dann effektive Lösungen zur Bedämpfung tieffrequenter Schallfelder, wenn der dafür zur Verfügung stehende Platz begrenzt ist. Dies trifft auch auf das Gebiet der Schalldämpfung in Kanälen zu. Darüber hinaus gestattet die Kaskadierung einzelner aktiver Schalldämpferkassetten (ASDK) die flächige Auskleidung von Wänden eines schallführenden Kanals. Damit können die ASDK den geometrischen Bedingungen und Dämpfungsanforderungen des jeweiligen Einsatzes speziell angepaßt werden, was für die praktische Anwendung von enormer Bedeutung ist. Im Unterschied zu den bekannten aktiven Schalldämpfern nach der Feedforward‐Methode erlaubt die Betrachtung der Wandimpedanz wie Berechnung der Schalldämpfung in Kanälen. Auf Grundlage der theoretischen Methoden zur Berechnung passiver Auskleidungen und eines Netzwerkmodells zur Beschreibung der Eingangsimpedanz der ASDK kann daher eine gezielte Auslegung dieser aktiven Schalldämpfer erfolgen. In der vorliegenden Arbeit wird auf die Berechnung der Schalldämpfung von aktiv absorbierenden Wandauskleidungen und im Vergleich dazu auf die im Labor erzielten Schalldämpfungen eingegangen.
Denkmalgeschützte Fassaden in Eisenhüttenstadt ‐ wärmeschutztechnisch aufgebessert ‐ Innendämmsysteme und infrarotreflektierende Beschichtungen
Authors: Stopp H. , Strangfeld P. , Kramer M.
Published: March 2013

Die Sanierung ostdeutscher sowie osteuropäischer Städte und Dörfer ist eine Last und Chance von volkswirtschaftlicher Größenordnung. Daneben enthält die wärmeschutztechnische Aufbesserung denkmalgeschützter Fassaden mit ihrem sozialen wie technischen Bezug für die Entscheidungsträger ein nicht zu unterschätzendes Konfliktpotential. Auf und in der baulichen Hülle mit ihren oft kapillaraktiven Strukturen herrscht ein ausgeprägt komplexes Geschehen gekoppelter Wärme‐ und Feuchtetransportvorgänge. Am Beispiel des Flächendenkmals Eisenhüttenstadt wird die hygrothermische Wirksamkeit von Innendämmsystemen auch unter Hinzunahme infrarotverspiegelnder Außenanstriche demonstriert und diskutiert. Als Wärmedämmstoffe für die Innendämmung kommen Calciumsilikat und ein hochwärmedämmender Porenbeton zum Einsatz. Die Reduzierung des Wärmedurchganges während der Heizperiode kann in mitteleuropäischen Breiten durch infrarotreflektierende Beschichtungen bei Vertikalflächen bis zu etwa 10 % betragen. Derzeit bleibt dies aber durch eine permanente Verschmutzung und zeitweise Feuchtefilmbildung eher eine theoretische Größe. Messungen belegen zudem, daß nicht alle auf dem Markt befindlichen Anstriche ihren Aussagen hinsichtlich einer Energieeffizienz gerecht werden.
Transparenter Brandschutz ‐ Die Gläserne Manufaktur in Dresden
Authors: Kiel M.
Published: March 2013

Die Gläserne Manufaktur in Dresden stellt sich mit der Kombination von Nutzungen als brandschutztechnisch besonders anspruchsvolles Projekt dar. Das Ziel der Transparenz wird dabei erreicht durch Anordnung von Abstandsflächen im Gebäude, gezielte Wärmeableitung im Bereich von Übergängen und durch gestufte Anforderungen an die Feuerwiderstandsdauer von Brandschutzverglasungen. Die auftretenden Sonderprobleme zur Auslegung der Löschanlagen und der Rauchabzugsanlagen wurden auf experimenteller Grundlage sowie numerisch durch verschiedene Simulationsrechnungen gelöst. Die Qualitätssicherung in der Ausführungsphase ist Voraussetzung für eine mängelfreie Abnahme und sichert das sinnvolle Zusammenwirken aller Brandschutzeinrichtungen mit der übrigen Haustechnik.
Hygrothermische Eignung von Außenwänden in verschiedenem Außenklima am Beispiel von zweischaligem Mauerwerk
Authors: Hens H.
Published: March 2013

In den meisten Handbüchern über den Hochbau wird das vorherrschende Klima in dem Land, in welchem das Buch geschrieben wurde, als Referenzklima angenommen. In einem kühlen oder kalten Klima ist das Heizen die Hauptanforderung und eine gute Wärmedämmung sehr wichtig. Dagegen stellt in einem heißen aber trockenen Klima die Temperaturdämpfung die größte Herausforderung dar. Dadurch verschiebt sich das Gewicht auf Massivbauweise, beschattete Fenster und Nachtlüftung. Schließlich wird in einem heißen und feuchten Klima die Klimatisierung entscheidend; nicht nur eine gute Wärmedämmung sondern auch ein effizienter Sonnenschutz helfen, den Energieverbrauch zu reduzieren. Das Außenklima wirkt sich aber auch auf das Wärme‐, Luft‐ und Feuchteverhalten der Außenwände sowie auf damit verbundene Aspekte der Dauerhaftigkeit aus. Dieser Beitrag bezieht sich auf eine zweischalige Wand als exemplarischer Fall. In kühlen, regnerischen Klimaten bewähren sich diese hervorragend. Wenn der Entwurf korrekt und die Bauausführung fachgerecht ausgeführt sind, stellt diese Bauweise eine risikolose Wahl dar. Unter heißen und feuchten Klimabedingungen, wo die Kühlung eine umgekehrte Tauwasserbildung bewirken kann, kann selbst eine gut konstruierte und fachgerecht gebaute zweischalige Wand mit Kerndämmung zu einem Problemfall werden.
Brandverhalten von Bauprodukten und Bauarten ‐ Umsetzung der Europäischen Normung in das nationale Regelwerk (Stand Februar 2001)
Authors: Becker W. , Sommer Th.
Published: March 2013

Als Grundlage für die Verwirklichung des europäischen Binnenmarktes im Bausektor wurde im Dezember 1989 die Bauprodukten‐Richtlinie (BPR) erlassen. Mit ihr wurden u. a. die Regeln für die Verwendbarkeits‐ und Übereinstimmungsmachweise für Bauprodukte festgelegt. Weiterhin gibt die BPR den Rahmen für die wesentlichen Anforderungen an Bauprodukte vor, u. a. auch hinsichtlich des Brandschutzes.
Vereinfachter brandschutztechnischer Nachweis für Bauteile bei lokal begrenzten Bränden in großen Räumen
Authors: Hosser D. , Dehne M.
Published: March 2013

In diesem Beitrag wird ein vereinfachtes brandschutztechnisches Nachweisverfahren vorgestellt, das auf experimentell abgesicherten analythischen Ansätzen und Eingangsdaten beruht und insbesondere bei lokal begrenzten Bränden anwendbar ist. In diesem Anwendungsbereich ist es aufwendigeren Brandsimulationsmodellen nach dem internationalen Stand der Technik ebenbürtig, da es dieselben Grundlagen verwendet. Die für eine Bauteilbemessung benötigten Temperaturzeitverläufe lassen sich ohne aufwendige Simulationsrechnungen mit Hilfe nachvollziehbar physikalischer Zusammenhänge berechnen und leicht überprüfen. Die Anwendung des Verfahrens wird anhand eines Beispieles dokumentiert.
Theoretische Ermittlung der in der Praxis erreichbaren Genauigkeit von Luftdichtheitsmessungen, Teil I: Einführung, Grundlagen und Modellbildung
Authors: Geißler A.
Published: March 2013

Anhand von rechnerischen Simulationen von Luftdichtheitsmessungen wird untersucht, welchen Einfluß die Veränderung der Druckverteilung um ein Gebäude infolge von Windanströmung und Temperaturunterschied auf die Meßgenauigkeit hat. Durch umfangreiche Parametervariationen wird die zu erwartende Größenordnung des windinduzierten Meßfehlers rechnerisch abgeschätzt. Angenommene Windgeschwindigkeiten vor Ort von etwa 3 m/s führen zu einer zusätzlichen Unsicherheit im ermittelten Volumenstrom bei 50 Pa Druckdifferenz von ca. 3 %. Dies ist vergleichbar mit der durch den Einsatz von Standard‐Differenzdrucksensoren oder auch durch den Bediener zu erwartenden Unsicherheit. Bei Windgeschwindigkeiten von bis zu 4,7 m/s ist der zu erwartende zusätzliche Fehler im Bereich von ca. 7 %, und entspricht damit ungefähr der gesamten Meßunsicherheit bei Windstille. Eine ungünstige Lage bzw. umgebende Bebauung des untersuchten Gebäudes, eine ungünstige Leckageverteilung und eine unglückliche Wahl der Anzahl und Lage externer Druckentnahmestellen können zu deutlich größeren zusätzlichen Unsicherheiten von ca. 10 % bei 3 m/s und bis über 40 % bei 4,7 m/s führen.
Thermisches Verhalten, Heiz‐ und Kühlenergiebedarf eines Modellgebäudes mit beweglicher Wärmedämmung unter verschiedenen Klimabedingungen
Authors: Krainer A. , Lah M. T.
Published: March 2013

Der Beitrag stellt die parametrische Analyse des dynamischen thermischen Verhaltens eines Gebäudes mit beweglicher Wärmedämmung unter echten klimatischen Bedingungen dar. Mit der dynamisch‐flexiblen Gebäudehülle soll eine optimale thermische Behaglichkeit im Innenraum erreicht und gleichzeitig der Energiebedarf für Heizung und Kühlung gesenkt werden. Das thermische Verhalten des Gebäudes auf eine bewegliche Wärmedämmung unter echten klimatischen Bedingungen wird beschrieben. Hierzu werden Innenlufttemperaturen und Energiebedarf für Heizung und Kühlung bei echten klimatischen Bedingungen im März und Juli verfolgt, wobei die globale Solarstrahlung und Außenlufttemperaturen berücksichtigt werden. Die Ergebnisse werden bei allen Fensterorientierungen analysiert. Die Simulationen wurden mit dem mathematischen Modell KAMRA durchgeführt. Abmessungen des Modellgebäudes sind: Raumhöhe = 2,5 m, Raumbreite = 4,0 m und Raumtiefe = 3,0 m.
Beispiele zur U‐Wert‐Berechnung nach der neuen Norm DIN EN ISO 6946
Authors: Palecki S. , Wehling M.
Published: March 2013

Mit der Herausgabe der neuen DIN EN ISO 6946, die den Teil 5 der DIN 4108 ersetzt, wurde eine modifizierte Berechnung des Wärmedurchgangskoeffizienten k ‐ neu U‐Wert ‐ eingeführt. Im Gegensatz zur bisherigen k‐Wert‐Bestimmung fließt bei dem veränderten Berechnungsansatz die Querleitung in inhomogenen Bauteilen mit ein. Dies wird in der Berechnung durch die Mittelung der Wärmedurchgangswiderstände der jeweiligen Schichten in horizontaler Richtung berücksichtigt, die, bezogen auf die Flächenanteile, den unteren Grenzwert des Wärmedurchgangskoeffizienten bilden. Aufgrund dieses veränderten Berechnungsansatzes wird also der U‐Wert ungünstiger angesetzt als der bisherige k‐Wert nach DIN 4108 Teil 5. Sinn und Zweck dieser Umstellung soll in erster Linie die präzisere und wirtschaftlichere Bemessung von Gebäuden sein, wie es auch in der Energieeinsparverordnung EnEV gefordert wird. Im Entwurf zur EnEV wird dieser neue Berechnungsansatz zur Anwendung kommen. Die Berechnung wird an einigen in der Praxis häufig vorkommenden Sparrendachkonstruktionen vorgestellt. Ziel ist es, den neuen Berechnungsalgorithmus für Anwender verständlicher zu machen.
Verkehrslärm im Urteil der Anwohner
Authors: Mehra Sch.‐R.
Published: March 2013

Um zu ermitteln, wie die Anwohner von Verkehrsstraßen die Lärmsituation ihrer Wohngebiete beurteilen, wurden Vorortbefragungen durchgeführt. Die drei untersuchten Wohngebiete lagen an unterschiedlich stark befahrenen Straßen und wiesen verschiedene Bebauungsformen und ‐dichten auf. Auch die Lage der Wohnorte bezüglich der Lärmquelle war nicht gleich. Die Befragungen zeigen jedoch überraschend ähnliche Ergebnisse.
Schimmelpilzbildung an Fenstereckpfeilern ‐ Überlagerung ungünstiger Einflußfaktoren
Authors: Bonk M. , Fechner O.
Published: March 2013

Schimmelpilzbildungen in Wohnräumen führten in den letzten Jahren vermehrt zu gerichtlichen Auseinandersetzungen. Die Auswertung eigener Untersuchungen hat gezeigt, daß sich die Ursachen konstruktionsbedingter bzw. nutzungsbedingter Schimmelpilzbildungen in etwa die Waage halten. Der folgende Schadensfall beschreibt einen konstruktionsbedingten Schimmelpilzbefall an einem auf den ersten Blick ausreichend gedämmten Bauteil, bei dem sich mehrere ungünstige Einflußfaktoren überlagern.
Energieeffizientes Bauen in Europa ‐ Erkenntnisse aus dem CEPHEUS‐Projekt
Authors: Feist W. , Schnieders J. , Pfluger R.
Published: March 2013

Im hier vorgestellten EU‐Demonstrationsprojekt wurden an 14 europäischen Standorten Passivhäuser gebaut und wissenschaftlich begleitet. Passivhäuser zeichnen sich durch sehr guten Wärmeschutz und hocheffiziente Lüftungswärmerückgewinnung aus. Die maximale Heizlast ist mit 10 W/m� so gering, daß eine Beheizung allein durch Erwärmung des Außenluftmassenstromes der Lüftungsanlagen ausreicht. Die Messungen in 113 Wohneinheiten ergaben standardisierte Heizwärmeverbrauchswerte von durchschnittlich 16 kWh/(m�a), diese liegen um mehr als 80 % unter dem Bedarf entwurfsgleicher Neubauten nach den jeweiligen Bauvorschriften. Die Bewohner äußern sich sehr positiv zur Behaglichkeit. Das beobachtete Nutzerverhalten beeinträchtigt die Zielerfüllung nicht, insbesondere konnte kein bedeutender Einfluß durch Fensterlüftung festgestellt werden. Die absolute Höhe der Streuung der individuellen Verbräuche nimmt mit besserem baulichen Standard ab; sie kann vor allem durch unterschiedliche Komfortansprüche erklärt werden. Die Verbrauchsunterschiede kompensieren sich im Mittel über eine ausreichend große Stichprobe. Die Validität der wärmetechnischen Gebäudesimulation und der numerischen Strömungsberechnung konnte durch Detailmessungen überprüft werden.
Kann Wachstum von Algen und Pilzen an wärmegedämmten Fassaden verhindert werden?
Authors: Nay M.
Published: March 2013

Algen und Pilze an wärmegedämmten Hausfassaden treiben seit einigen Jahren die betroffenen Hauseigentümer schier zur Verzweiflung, und die unerwünschten "Verzierungen" vermehren sich auch noch! Solche Fälle treten aus unerklärlichen Gründen sogar schon innerhalb der Gewährleistungsfristen auf und verursachen dann mindestens Ärger, manches Mal aber auch teure Streitfälle.
Schimmelpilzbedingter Mindesluftwechsel ‐ Ergebnisse einer Studie zur Raumluftqualität
Authors: Hartmann Th. , Reichel D. , Richter W.
Published: March 2013

Obwohl in der Wärmeschutzverordnung 1995 bereits vorgeschrieben, wird mit der Energieeinsparverordnung die Luftdichtheit aufgrund der vorgesehenen Bonifizierung ‐ auch für Gebäude ohne mechanische Lüftungsanlagen ‐ einen neuen Stellenwert erhalten. Parallel dazu führen Gebäudesanierungen zu ähnlichen Dichtheitsverhältnissen. Diese quasi "Hermetisierung" der Gebäude steht in formalem Widerspruch zu der Tatsache, daß heute schätzungsweise ca. 10 % der Haushalte einen problematischen Schimmelpilzbefall aufweisen, der u. a. auch auf unzureichende Durchlüftungsverhältnisse zurückgeführt werden kann. In einer unter Federführung der Technischen Universität Dresden erstellten Studie wird der Versuch unternommen, fundierte Aussagen zum notwendigen Mindestluftwechsel zu treffen und entsprechende Realisierungsmöglichkeiten praxisnah vorzustellen und einer Bewertung zu unterziehen.