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Search Results: 1 - 10 of 462998 matches for " A. Hoffmann "
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Journal of Central European Agriculture , 2007,
Abstract: The farm gate balance is well known from the environmental literature. This method is not suitable in every case to show the nutrient load for the environment of agricultural companies that is the reason why unit level internal nutrient balances are applied to express the level of nutrient pollution on the environment. These also help to determine the source of the pollution. With the survey of the nutrient flows within the farm we determine the keystones of nutrient management to control the nutrient load of the pollution sources. On the basis of the results and the controlled data of the unit level internal balances we make recommendations for the most appropriate environmental policy instrument to reduce the nutrient pollution.
Toxicity and feeding response of adult corn earworm (Lepidoptera: Noctuidae) to an organic spinosad formulation in sucrose solution  [PDF]
Juan D. López, Mohamed A. Latheef, Wesley C. Hoffmann
Advances in Entomology (AE) , 2014, DOI: 10.4236/ae.2014.21006
Abstract: Adult corn earworm, Helicoverpa zea (Boddie), feeds on plant exudates soon after emergence from pupa in their natural habitat, and thereafter disperses to suitable host plants for reproduction. The intent of this study was to determine if EntrustTM, an organic formulation of spinosad, could be used in a behavioral-based pest management strategy to control H. zea in organic farming systems. In the laboratory, we evaluated the response of the corn earworm to Entrust mixed with sugar solution relative to ingestion, toxicity and proboscis extension. The sucrose solution served as a feeding stimulant and simulated the plant exudate. Lethal concentration of Entrust (LC50 with 95% CLs) for male corn earworm captured in pheromone-baited traps was 0.48 (0.43 - 0.53) mgL-1 for 24 h response. Mean lethal time was 2.56 ± 0.13 h with ingestion of Entrust at 50 mg·L-1. A lethal dose of Entrust at 1000 mg·L-1 inhibited neither ingestion nor proboscis extension response of the insect. A detailed study of the adult corn earworm in the laboratory relative to toxicity after ingestion of Entrust indicates that the pesticide has potential to control the insect when used in an insecticidal bait formulation as part of an attract-and- kill system. Field studies are needed to support the conclusion.
Semiconductors as sensitisers for the radical addition of tertiary amines to electron deficient alkenes
Sini a Marinkovi ,Norbert Hoffmann
International Journal of Photoenergy , 2003, DOI: 10.1155/s1110662x03000308
Abstract: Using heterogeneous photocatalysis, the radical addition of tertiary amines with electron deficient alkenes can be performed in high yields (up to 98%) and high facial diastereoselectivity. The photochemical induced electron transfer process initiates the radical chain reaction and inorganic semiconductors like TiO2 and ZnS were used. According to the proposed mechanism, the reaction takes place at the surface of the semiconductor and the termination step results from an interfacial electron transfer from the conduction band to the oxoallyl radical intermediate. Frequently, semiconductors are used for the mineralisation of organic compounds in wastewater. However, in this case, they are used in organic synthesis. The process can be performed in a convenient way and is particularly interesting from the ecological and economical point of view. No previous functionalization of the tertiary amines is necessary for C ? C bond formation. Further on, the amines are used both as reactant and as solvent. The excess is recycled by distillation and the inexpensive sensitiser can be easily removed by filtration. In this way, products of high interest for organic synthesis are obtained by a diastereoselective radical reaction.
Outsmart your genes: How understanding your DNA will empower you to protect yourself against cancer, Alzheimer's, heart disease, obesity, and many other conditions
Andrea Hoffmann, Panagiotis A Tsonis
Human Genomics , 2011, DOI: 10.1186/1479-7364-5-5-516
Abstract: With a straightforward, readable text that combines entertaining anecdotes in lay terms with established medical facts, the author encourages the reader to take the initiative and become curious about his/her genetic make-up. In part this is due to the well-organised structure of the book, which partitions every topic of interest, such as the history of genetics, genetic screening and predictive medicine, how to execute genetic screening, parental and reproductive screening, as well as the screening of newborns, children and adults, and the corresponding interpretation regarding the risk of developing major diseases such as obesity, cardiovascular problems, Alzheimer's disease and cancers. Well-structured tables and a scheme that lists the prevalent genes and their genetic impact on a particular health issue, and potential lifestyle changes and treatment options for individuals with mutations in these genes, further help in understanding the notion of how to live a longer, better life in terms of one's complex individual genetic make-up. Besides tables, the book summarises essential take-home messages in fat print and contains boxes with anecdotes, including examples from the media, movie world and children's books/riddles, as well as evidence of historical and current genetics, which further underline and enlighten the main text in a humorous manner. Thus, some of the historical anecdotes, such as Mendel and his colleagues getting stung by his new cross-bred hive of bees, remain truly anecdotal.Regarding the science, the text uses numerous solid references to support the content. It includes a very detailed discussion about currently known genetic variations that determine genetic traits or disease states and gives examples of how changes in lifestyle or therapeutic interventions can positively affect a patient's quality of life. With this in mind, the book is well written for a reader who is seeking advice on genetic screening and its interpretation. Yet, the book
The role of hardness and roughness on the wear of different CoCrMo counterfaces on UHMWPE for artificial joints  [PDF]
Victor A. González-Mora, Michael Hoffmann, Rien Stroosnijder, F. Javier Gil
Journal of Biomedical Science and Engineering (JBiSE) , 2011, DOI: 10.4236/jbise.2011.410081
Abstract: Wear tests were carried out to study the effect of the hardness and roughness with various counterface materials on UHMWPE wear behaviour. The materials used as counterfaces were based on varieties of CoCrMo: 1) forged (hand-polished) CoCrMo, 2) forged (mass-finished) CoCrMo, and 3) cast (mass-finished) CoCrMo. Additionally, two coatings were proposed: 1) a CoCrMo coating applied to the forged CoCrMo alloy by means of physical vapour deposition (PVD), and 2) a ZrO2 coating applied to the forged CoCrMo alloy by means of plasma-assisted chemical vapour deposition (PACVD). The reciprocating pin-on-flat (RPOF) device for pin-on-disk wear testing was used for this study. The worn surfaces were observed using optical, atomic force and scanning electron microscopes.
The importance of evolutionary history in studies of plant physiological ecology: examples from cerrados and forests of central Brazil
Hoffmann, William A.;Franco, Augusto C.;
Brazilian Journal of Plant Physiology , 2008, DOI: 10.1590/S1677-04202008000300008
Abstract: studies that compare physiology, anatomy, and ecology across species have offered some of the best insight into adaptation and evolutionary constraints in plants. as a result, the comparative approach has become increasingly used in studies of plant physiological ecology. the high species diversity of brazilian biomes provides many excellent opportunities for comparative plant ecophysiology, and could be better exploited for understanding the evolution of plant form and function. in this paper we emphasize the importance of considering phylogenetic information for the design and analysis of comparative studies, relying on examples from comparisons of woody plants from cerrado and gallery (riparian) forests. the use of congeneric species pairs, each containing one cerrado species and one forest species of the same genus, greatly improves statistical power while assuring phylogenetic independence, an essential condition for inference in comparative studies. for example, in a study of seedlings of nine cerrado species and nine forest species, when we ignore phylogenetic relationships, it is not be possible to conclude that cerrado and forest species differ with regard to leaf area ratio (lar), specific leaf area (sla), or seedling height. if, however, we use the generic groupings to account for phylogenetic effects, then we find that seedlings of savanna species have lower lar, sla, and seedling height. much of the phylogenetic inertia observed for these traits appears related to the fact that these traits are all strongly correlated with seed mass, which has been previously shown to be strongly conserved phylogenetically. these examples emphasize the importance of phylogenetic information in comparative studies.
Varia??o geográfica em Corydoras paleatus (Jenyns) (Siluriformes, Callichthyidae) do sul do Brasil
Shibatta, Oscar A.;Hoffmann, Ana C.;
Revista Brasileira de Zoologia , 2005, DOI: 10.1590/S0101-81752005000200010
Abstract: the species corydoras paleatus (jenyns, 1842) is widely distributed in southern brazil, occurring from rio grande do sul to the north of paraná state. studies related to this species populations are considered important once this fish is distributed in a region with great anthropogenic interference and also because its economic importance, given that this species is commercialised as ornamental fish. in the present study sixteen morphometric characters and six meristic characters were used for morphological evaluation in populations of tibagi and igua?u river basins (paraná) and lagoa dos quadros (rio grande do sul). in spite of the number of lateral plates being more variable in specimens from igua?u river, the overlap of plates and fin rays counts did not allow a safe discrimination of populations. however, principal components analysis allowed to differentiate populations by the allometric growth of the morphometric characters. besides, the sample from rio igua?u was morphometrically discriminated of those from tibagi river and lagoa dos quadros in the first canonical axis, while these two populations were separated in the second axis. the intraspecific variation, observed in this species, clearly shows that population morphometric analysis can be useful in the analysis of biological diversity of a given region. the morphometric differences and the geographical isolation are indicating that those populations are subject to different selective processes.
The lived experiences of late-adolescent female suicide survivors: ‘A part of me died’
Willem A. Hoffmann,Chris Myburgh,Marie Poggenpoel
Health SA Gesondheid , 2010, DOI: 10.4102/hsag.v15i1.493
Abstract: People’s thoughts often focus on the suicide victim immediately after a completed suicide. Yet, the real victims of such an event are those individuals who are left behind to cope with the aftermath of the suicide. This phenomenological psychological study explored the lived experiences of late-adolescent suicide survivors, particularly those negative experiences that seemed to worsen in the weeks and months after a significant other’s completed suicide. The research participants were five female late-adolescents (aged 17–22 years) who were recruited by means of purposive sampling at a South African tertiary institution and at youth camps. Data collection consisted of collage-facilitated, face-to-face phenomenological interviews. In addition, some participants provided documentary material in the form of personal diaries, letters and poems. The data analysis was conducted according to Giorgi’s phenomenological method. The following salient experiences emerged during the data analysis: guilt, self-blame, blaming others or God, anger, loss or restriction of ‘self’, depression, suboptimal behavioural coping patterns, changes in relationship dynamics, and suicidality. The results of this study can be used by mental health professionals and caregivers to support adolescent suicide survivors effectively, in the midst of their mourning. Opsomming Mense se gedagtes fokus meestal op die selfmoordslagoffer onmiddellik na ’n voltooide selfmoord. Tog is die werklike slagoffers die persone wat agterbly om die lewe na die selfmoord te hanteer. Hierdie fenomenologies-sielkundige studie het die geleefde belewenisse van laat-adolessente oorlewendes ondersoek, spesifiek daardie negatiewe belewenisse wat skynbaar erger word in die weke en maande na ’n betekenisvolle ander se voltooide selfmoord. Die navorsingsdeelnemers was vyf vroulike laat-adolessente (17–22 jaar oud) wat gewerf is deur middel van doelgerigte selektering by ’n Suid-Afrikaanse tersiêre instelling en jeugkampe. Data-insameling het geskied aan die hand van collage-gefasiliteerde, aangesig-tot-aangesig fenomenologiese onderhoude. Sommige deelnemers het addisionele dokumente in die vorm van persoonlike dagboeke, briewe en gedigte beskikbaar gestel vir data-analise. Die data is geanaliseer volgens Giorgi se fenomenologiese metode. Die volgende belewenisse het na vore getree tydens die data-analise: skuldgevoelens, self-blaam/spyt, blameer ander/God, woede, verlies/inperking van ‘self’, depressie, sub-optimale gedragshanteringspatrone, veranderinge in verhoudingsdinamika, en selfmoordneigings. Die resultate va
Neutron Back- and Front-Face Bragg Diffraction on a Thin Si Single Crystal Excited by Ultrasound  [PDF]
E. Raitman, V. Gavrilov, D. Mjasischev, Ju. Ekmanis, A. Hoser, T. Hoffmann
Journal of Modern Physics (JMP) , 2015, DOI: 10.4236/jmp.2015.61006
Abstract: In this research project, we measured and analyzed the spatial distribution of neutron beam Bragg diffracted from the front- and back-faces of thin Si single crystal undergoing on ultrasound excitation. For the perfect crystal, it is shown that when the acoustic wave amplitude is increased, the front-face peak position remains unchanged and its value grows linearly. The values of ultrasound wave amplitude were determined. The back-face peak becomes asymmetric and tends to disappear. New types of Pendellosung fringes in the center of the diffraction profiles were observed at the first time. It is supposed that in the perfect crystal this effect may be due to the appearance of the new “sonic” extinction length, depending on the amplitude of the ultrasonic wave. Thus, it leads to the new interference interactions between neutron wave and ultrasonic phonons. It is established that within the framework of the dynamical theory of the neutron scattering, some asymptotic models valid for the case of Laue geometry as well as Kato’s quasi-classical approximation can be applied in the case of Bragg geometry also. Good agreement between experimental data and the theory has been obtained.
Spiral and Taylor vortex fronts and pulses in axial through-flow
A. Pinter,M. Lücke,Ch. Hoffmann
Physics , 2003, DOI: 10.1103/PhysRevE.67.026318
Abstract: The influence of an axial through-flow on the spatiotemporal growth behavior of different vortex structures in the Taylor-Couette system with radius ratio eta=0.5 is determined. The Navier Stokes equations (NSE) linearized around the basic Couette-Poiseuille flow are solved numerically with a shooting method in a wide range of through-flow strengths Re and different rates of co- and counterrotating cylinders for toroidally closed vortices with azimuthal wave number m=0 and for spiral vortex flow with m=+1 and m=-1. For each of these three different vortex varieties we have investigated (i) axially extended vortex structures, (ii) axially localized vortex pulses, and (iii) vortex fronts. The complex dispersion relations of the linearized NSE for vortex modes with the three different m are evaluated for real axial wave numbers for (i) and over the plane of complex axial wave numbers for (ii,iii). We have also determined the Ginzburg-Landau amplitude equation (GLE) approximation in order to analyze its predictions for the vortex stuctures (ii,iii). Critical bifurcation thresholds for extended vortex structures are evaluated. The boundaries between absolute and convective instability of the basic state for vortex pulses are determined with a saddle-point analysis of the dispersion relations. Finally, the linearly selected front behavior of growing vortex structures is investigated. For the two front intensity profiles (increasing in positive or negative axial direction) we have determined front velocities, axial growth rates, and the wave numbers and frequencies of the unfolding vortex patterns with azimuthal wave numbers m=0, +1, -1, respectively.
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