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Search Results: 1 - 10 of 5954 matches for " Roger ARNOLD "
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Analytic Trajectories for Mobility Edges in the Anderson Model
Wolfram T. Arnold,Roger Haydock
Physics , 2002, DOI: 10.1103/PhysRevB.66.155121
Abstract: A basis of Bloch waves, distorted locally by the random potential, is introduced for electrons in the Anderson model. Matrix elements of the Hamiltonian between these distorted waves are averages over infinite numbers of independent site-energies, and so take definite values rather than distributions of values. The transformed Hamiltonian is ordered, and may be interpreted as an itinerant electron interacting with a spin on each site. In this new basis, the distinction between extended and localized states is clear, and edges of the bands of extended states, the mobility edges, are calculated as a function of disorder. In two dimensions these edges have been found in both analytic and numerical applications of tridiagonalization, but they have not been found in analytic approaches based on perturbation theory, or the single-parameter scaling hypothesis; nor have they been detected in numerical approaches based on scaling or critical distributions of level spacing. In both two and three dimensions the mobility edges in this work are found to separate with increasing disorder for all disorders, in contrast with the results of calculation using numerical scaling for three dimensions. The analytic trajectories are compared with recent results of numerical tridiagonalization on samples of over 10^9 sites. This representation of the Anderson model as an ordered interacting system implies that in addition to transitions at mobility edges, the Anderson model contains weaker transitions characterized by critical disorders where the band of extended states decouples from individual sites; and that singularities in the distribution of site energies, rather than its second moment, determine localization properties of the Anderson model.
短周期尾巨桉能源林生物量与能量特征研究
周群英?,陈少雄?,韩斐扬?,Roger ARNOLD
热带亚热带植物学报 , 2013, DOI: 10.3969/j.issn.1005–3395.2013.01.006
Abstract: 为开发和利用尾巨桉能源林,通过测量1~4年生植株的叶片、树枝、树根、树干和树皮的热值和生物量,对短周期尾巨桉能源林的生物量和能量特征进行了研究。结果表明,尾巨桉叶片、树枝、树干、树根、树皮和林分生物量均随林龄增加而增加,叶片、树枝、树皮生物量占单株总生物量的比例逐年减小,而树干则呈逐年升高趋势。1~4年生尾巨桉单株和林分的生物量分别为4.32~66.29kg和10.68~153.33thm-2。生物量的结构特征表明,尾巨桉林分在第4年开始郁闭,生长以增加树干的生物量为主。尾巨桉各组分的平均干质量热值为17.23~20.56kjg-1,且差异极显著(p<0.01),以叶片的值最高、树皮的最低;同一组分不同林龄的热值差异不显著(p>0.05)。1~4年生尾巨桉的单株和林分能量现存量为81.61~1255.22mj和201.83~2903.32gjhm-2,其变化趋势及大小排列顺序与生物量相同。因此,对尾巨桉能源林可以4年短周期进行经营。
Studies on Biomass and Energy Characteristics of Short Rotation Energy Plantations of Eucalyptus urophylla×E. grandis
短周期尾巨桉能源林生物量与能量特征研究

ZHOU Qun-ying,CHEN Shao-xiong,HAN Fei-yang,Roger ARNOLD,
周群英
,陈少雄,韩斐扬,Roger ARNOLD

热带亚热带植物学报 , 2013,
Abstract: In order to development and utilization of Eucalyptus urophylla × E. grandis plantation, biomass and calorific values of 1- to 4-year-old E. urophylla × E. grandis were determined to reveal biomass and energy characteristics of Eucalyptus at different ages. The results showed that the biomass of leaves, branches, stem, roots, bark and total biomass increased with increasing age. The ratio of leaf, branch and bark biomass to total biomass decreased with age, while the ratio of stem biomass to total biomass increased. Biomass of 1- to 4-yearold individual and stands ranged from 4.32 to 66.29 kg, and 10.68 to 153.33 t hm-2, respectively. Biomass structure characteristics revealed that Eucalyptus plantation began to closure at the 4th year, and stem growth was dominant. Gross calorific values had significant difference (P<0.01) among five components, such as leaf, branch, root, stem and bark, with ranged from 17.23 kJ g-1 for bark to 20.56 kJ g-1 for leaf, those of the same component had no significant differences among different ages (P>0.05). The retained energy of 1- to 4-year-old individual and stands ranged from 81.61 to 1255.22 MJ and 201.83 to 2903.32 GJ hm-2, respectively, the change trend and orders of components were the same as biomass. Therefore, it suggested that E. urophylla × E. grandis energy plantation could manage with short rotation for 4 years.
Magnetic-Field Effects on Donor Impurity States in a Quantum Well  [PDF]
Arnold Abramov
World Journal of Condensed Matter Physics (WJCMP) , 2012, DOI: 10.4236/wjcmp.2012.24031
Abstract: Green’s function technique is used to obtain the solution of Shredinger equation for impurity states in a quantum well (QW) under the magnetic field. Binding energy of impurity states is defined as poles of the wave function. We studied effects of the magnetic field magnitude and impurity position on the binding energy. The calculations were performed for both ground and excited states. The dependences of binding energies versus impurity position and magnetic field are presented for GaAs/Al0.3Ga0.7As QW.
Creativity, Wicked Problems and the Contemporary PhD  [PDF]
Josie Arnold
Open Journal of Social Sciences (JSS) , 2016, DOI: 10.4236/jss.2016.48019
Abstract: In this paper, I survey the challenges the creative and contemporary PhD make to the academy. I look at the scholarship entailed in creative production and in identifying and working with wicked problems as having similar attributes contributing to the need to create new PhD models. Traditionally, the PhD has been a preparation for a career in the academy, with scholars undertaking it so as to show their capacity to identify a research gap in their area, to develop a research question from that and to build a major and new contribution to knowledge in a written submission of some 100,000 words. This traditional model is based upon the certainties of scholarship within enlightenment ideals of science. These have delivered us great strides in many areas of medicine and science and have also come, because of their productivity, to dominate the arts, particularly the social sciences and psychology. Whilst its value should not be debased, this enlightenment model has been challenged from such different areas of scholarship as creative production and wicked problems. The core ideas in this paper are how we might utilise creativity and emerging ideas of wicked problems to debate the importance of understanding the contemporary PhD.
Elucidation of the outer membrane proteome of Salmonella enterica serovar Typhimurium utilising a lipid-based protein immobilization technique
Darren Chooneea, Roger Karlsson, Vesela Encheva, Cath Arnold, Hazel Appleton, Haroun Shah
BMC Microbiology , 2010, DOI: 10.1186/1471-2180-10-44
Abstract: In this study, 54 outer membrane proteins, were identified with two or more peptide hits using a multi-step digest approach. Out of these 28 were lipoproteins, nine were involved in transport and three with enzyme activity These included the transporters BtuB which is responsible for the uptake of vitamin B12, LamB which is involved in the uptake of maltose and maltodextrins and LolB which is involved in the incorporation of lipoproteins in the outer membrane. Other proteins identified included the enzymes MltC which may play a role in cell elongation and division and NlpD which is involved in catabolic processes in cell wall formation as well as proteins involved in virulence such as Lpp1, Lpp2 and OmpX.Using a multi-step digest approach the LPI? technique enables the incorporation of a multi-step protease work flow ensuring enough sequence coverage of membrane proteins subsequently leading to the identification of more membrane proteins with higher confidence. Compared to current sub-cellular fractionation procedures and previous published work, the LPI? technique currently provides the widest coverage of outer membrane proteins identified as demonstrated here for Salmonella Typhimurium.The Gram-negative bacterial pathogen Salmonella enterica serovar Typhimurium (S. Typhimurium) is a leading cause of human gastroenteritis worldwide. It has the ability to infect a broad range of hosts such as poultry, pigs, cattle, rodents and human and the severity of disease is sometimes determined by the type of host infected [1]. For example in mice S. Typhimurium exhibits symptoms similar to those of human typhoid, while in humans it causes classical non-typhoidal gastroenteritis [2,3].The genome of S. Typhimurium contains a large number of prominent genes that code for virulence factors which are non-existent in non-pathogenic strains. Regions of the genome that code for these virulence factors are known as pathogenicity islands. S. Typhimurium possesses two major islands, wh
A simple electric circuit for teaching onedimensional characterization of piezoelectric plates
F. J. Arnold,L. L. Bravo-Roger,M. S. Gon?alves,M. Grilo
Latin-American Journal of Physics Education , 2011,
Abstract: This work presents a method based on elementary concepts of electric network for characterization of piezoceramics. A simplified version of Mason’s equivalent circuit is obtained applying basic theorems of electricity. The methodology employed to simplify the circuit is mandatorily presented in the issues addressed in introductory courses of electric circuits. The experimental development can be performed in laboratories for the teaching activities without further specific equipment. Using this methodology stimulates students because it is performed on devices very employed in technological application. Furthermore, it facilitates the understanding of physical principles present in the study of piezoelectric elements.
Sloth Hair as a Novel Source of Fungi with Potent Anti-Parasitic, Anti-Cancer and Anti-Bacterial Bioactivity
Sarah Higginbotham, Weng Ruh Wong, Roger G. Linington, Carmenza Spadafora, Liliana Iturrado, A. Elizabeth Arnold
PLOS ONE , 2014, DOI: 10.1371/journal.pone.0084549
Abstract: The extraordinary biological diversity of tropical forests harbors a rich chemical diversity with enormous potential as a source of novel bioactive compounds. Of particular interest are new environments for microbial discovery. Sloths – arboreal mammals commonly found in the lowland forests of Panama – carry a wide variety of micro- and macro-organisms on their coarse outer hair. Here we report for the first time the isolation of diverse and bioactive strains of fungi from sloth hair, and their taxonomic placement. Eighty-four isolates of fungi were obtained in culture from the surface of hair that was collected from living three-toed sloths (Bradypus variegatus, Bradypodidae) in Soberanía National Park, Republic of Panama. Phylogenetic analyses revealed a diverse group of Ascomycota belonging to 28 distinct operational taxonomic units (OTUs), several of which are divergent from previously known taxa. Seventy-four isolates were cultivated in liquid broth and crude extracts were tested for bioactivity in vitro. We found a broad range of activities against strains of the parasites that cause malaria (Plasmodium falciparum) and Chagas disease (Trypanosoma cruzi), and against the human breast cancer cell line MCF-7. Fifty fungal extracts were tested for antibacterial activity in a new antibiotic profile screen called BioMAP; of these, 20 were active against at least one bacterial strain, and one had an unusual pattern of bioactivity against Gram-negative bacteria that suggests a potentially new mode of action. Together our results reveal the importance of exploring novel environments for bioactive fungi, and demonstrate for the first time the taxonomic composition and bioactivity of fungi from sloth hair.
邓恩桉生长、木材密度和树皮厚度的遗传变异研究
罗建中,Roger,Arnold,项东云,谢耀坚,陈健波
林业科学研究 , 2009,
Abstract: 以广西桂林和柳州的邓恩桉种源/家系(6个种源53个家系)试验林为材料,对8.5年生胸径以及10.5年生胸径、树高、材积、木材密度和树皮厚度的遗传变异进行了研究,结果表明:10.5年生时,邓恩桉在桂林和柳州的平均单株材积分别为0.218、0.189 m3,平均木材密度分别为521.0、483.7 kg?m-3,树皮厚度分别为1.15、1.26 cm;10.5年生材积性状和木材密度在种源间差异不显著(P>0.10),10.5年生木材密度在家系间差异显著(P<0.05);树皮厚度在种源间、家系间差异均不显著(P>0.10)。除8.5年生胸径外,其他性状的试验地点与种源间交互作用不显著(P>0.10);8.5年生胸径、10.5年生树高、木材密度均存在显著的试验地点与家系间交互作用(P<0.05);10.5年生树皮厚在种源、家系水平上和地点均不存在显著的交互作用。8.5年生胸径、10.5年生胸径与树高的遗传力在0.128 9 - 0.234 5间,木材密度的遗传力为0.700 0 - 0.962 9,树皮厚度的遗传力为0.105 3 - 0.335 7。
Managing Ethical Risks and Crises: Beyond Legal Compliance  [PDF]
Diane Huberman Arnold, Keith Arnold, Vanessa J. Arnold
Beijing Law Review (BLR) , 2010, DOI: 10.4236/blr.2010.11001
Abstract: Recent interest in culture stems from its power to explain corporate and organizational failures. Such failures are both internal and external: accounting fraud, management misconduct, harassment and bullying in the workplace, racism, sexism, environmental issues, and health and safety concerns. Current theory holds that these failures are to be explained partly by the particular, poor organizational culture and unhealthy climate, poor leadership, and by the misdeeds of a few bad apples. When economic conditions are negative, organizations look to legislation, regulations, and codes, to reform their culture, and manage the risks of organizational failure. Both the compliance strategy, demanding obedience to laws, regulations and codes, and the integrity or values strategy, focusing on ethics training, education, tone at the top, and the hiring of employees with integrity and values, are the mainstay of recent legislation and regulations in North America and the European Union. We criticize the reliance on legislation, regulations and codes, the focus of a compliance solution which we find inadequate, ineffective, and unenforceable. We suggest reliance on a front-end, proactive and preventive program of best, precautionary practices, will better meet the challenge, in prosperity or poverty, of setting corporate culture on the right track.
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