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Search Results: 1 - 10 of 191357 matches for " D. Cogan "
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Lattice Operators and Topologies
Eva Cogan
International Journal of Mathematics and Mathematical Sciences , 2009, DOI: 10.1155/2009/474356
Abstract: Working within a complete (not necessarily atomic) Boolean algebra, we use a sublattice to define a topology on that algebra. Our operators generalize complement on a lattice which in turn abstracts the set theoretic operator. Less restricted than those of Banaschewski and Samuel, the operators exhibit some surprising behaviors. We consider properties of such lattices and their interrelations. Many of these properties are abstractions and generalizations of topological spaces. The approach is similar to that of Bachman and Cohen. It is in the spirit of Alexandroff, Frolík, and Nöbeling, although the setting is more general. Proceeding in this manner, we can handle diverse topological theorems systematically before specializing to get as corollaries as the topological results of Alexandroff, Alo and Shapiro, Dykes, Frolík, and Ramsay.
Um modelo de reconcilia??o de dados para o custeio baseado-em-atividades (ABC)
Cogan, Samuel;
Revista de Administra??o de Empresas , 1999, DOI: 10.1590/S0034-75901999000200006
Abstract: cost structure changes, due to new production technologies, to major diversification needed because of business competitivity, and to cost reduction, have motivated the development programmes of new cost management techniques that allocate indirect costs to each product more precisely. in this context, activity-based costing/activity- based management (abc/abm) is considered as one of the most important techniques that have emerged in the last few years to provide accurate estimates for indirect expenses that each product consumes. nevertheless, some difficulties to obtain some costs remain, even when using abc. this happens not only due to the impossibility to measure costs with adequate accuracy, but also due to the fact that the investments made to measure some costs exceed the benefits to be obtained. in order to address this problem, the present work provides a business cost flow framework utilizing data reconciliation used in chemical process networks to determine indirect costs, incorporating accurate information concerning some of the costs. the model developed utilizes non-linear programming.
THEORY OF CONSTRAINTS VERSUS OTHER COSTING METHODS: A MATTER OF SHORT OR LONG TERM TEORIA DAS RESTRI ES VERSUS OUTROS MéTODOS DE CUSTEIO: UMA QUEST O DE CURTO OU DE LONGO PRAZO
Samuel Cogan
Revista Universo Contábil , 2007,
Abstract: The Theory of Constraints (TOC) and Activity-based Costing (ABC), although opposite in their basic foundations, can concur in integration studies which attempt to show that these methods applied together perform better when compared to their individual use. As for that integration, a group of authors (CAMPBELL,1992; MAcARTHUR, 1993; HOLMEN, 1995; FRITZSCH, 1997) defends an idea of the difference between these two methodologies being a matter of the time horizon: TOC used in the short term and ABC in the long term. The present article’s objective is to show, through a numeric illustration, considerations of that group of studies. Therefore, the TOC decision making is compared with other costing methods: Absorption Costing, Activity-based Costing and Variable Costing. The data analysis permits to confirm that TOC has produced a better result than the other techniques, in the short term. In the long term, however, when idle capacities can be exploited fully in the absence of internal constraints, ABC proved to be the technique that leads to the best result. Keywords: Integration. Theory of Constraints. Activity-based Costing. A Teoria das Restri es (TOC) e o Custeio Baseado em Atividades (ABC), embora opostos em seus fundamentos básicos, podem se conciliar em estudos de integra o que buscam mostrar que juntos s o superiores à sua abordagem individual. No que se refere a essa integra o, um grupo de autores (CAMPBELL,1992; MAcARTHUR, 1993; HOLMEN, 1995; FRITZSCH, 1997) defende que a diferen a entre essas duas metodologias é uma quest o de horizonte de tempo: a Teoria das Restri es para o curto prazo e o Custeio Baseado em Atividades para o longo prazo. O presente artigo tem por objetivo mostrar, através de uma ilustra o numérica, as considera es desse grupo de estudos. Para tanto, a tomada de decis o da Teoria das Restri es é comparada com outros métodos de custeio: Custeio por Absor o Tradicional, Custeio Baseado em Atividades e o Custeio Variável. A análise dos dados obtidos permite confirmar que a Teoria das Restri es apresentou resultado melhor que as demais técnicas no curto prazo. No longo prazo, contudo, em que as capacidades n o usadas podem ser utilizadas em sua plenitude, n o existindo, pois, restri es internas, o Custeio Baseado em Atividades mostrou ser a técnica que conduz ao melhor resultado. Palavras-chave: Integra o. Teoria das Restri es. Custeio Baseado em Atividades.
Determinstic Generation of a Quantum Dot-Confined Triexciton and its Radiative Decay via Three-Photon Cascade
E. R. Schmidgall,I. Schwartz,L. Gantz,D. Cogan,S. Raindel,D. Gershoni
Physics , 2014, DOI: 10.1103/PhysRevB.90.241411
Abstract: Semiconductor quantum dots (QDs) have potential applications in quantum information processing due to the fact that they are potential on-demand sources of single and entangled photons. Generation of polarization-entangled photon pairs was demonstrated using the biexciton-exciton radiative cascade. One obvious way to increase the number of quantum correlated photons that the QDs emit is to use higher-order multiexcitons, in particular the triexciton. Towards achieving this goal, we first demonstrate deterministic generation of the QD-confined triexciton in a well-definedcoherent state and then spectrally identify and directly measure a three-photon radiative cascade resulting from the sequential triexciton-biexciton-exciton radiative recombination.
All-Optical Depletion of Dark Excitons from a Semiconductor Quantum Dot
E. R. Schmidgall,I. Schwartz,D. Cogan,L. Gantz,T. Heindel,S. Reitzenstein,D. Gershoni
Physics , 2015, DOI: 10.1063/1.4921000
Abstract: Semiconductor quantum dots are considered to be the leading venue for fabricating on-demand sources of single photons. However, the generation of long-lived dark excitons imposes significant limits on the efficiency of these sources. We demonstrate a technique that optically pumps the dark exciton population and converts it to a bright exciton population, using intermediate excited biexciton states. We show experimentally that our method considerably reduces the DE population while doubling the triggered bright exciton emission, approaching thereby near-unit fidelity of quantum dot depletion.
Deterministic Coherent Writing of a Long-Lived Semiconductor Spin Qubit Using One Ultrafast Optical Pulse
I. Schwartz,D. Cogan,E. R. Schmidgall,L. Gantz,Y. Don,M. Zielinski,D. Gershoni
Physics , 2015, DOI: 10.1103/PhysRevB.92.201201
Abstract: We use one single, few-picosecond-long, variably polarized laser pulse to deterministically write any selected spin state of a quantum dot confined dark exciton whose life and coherence time are six and five orders of magnitude longer than the laser pulse duration, respectively. The pulse is tuned to an absorption resonance of an excited dark exciton state, which acquires non-negligible oscillator strength due to residual mixing with bright exciton states. We obtain a high fidelity one-to-one mapping from any point on the Poincar\'e sphere of the pulse polarization to a corresponding point on the Bloch sphere of the spin of the deterministically photogenerated dark exciton.
Copy-number variation in BMPR2 is not associated with the pathogenesis of pulmonary arterial hypertension
Jennifer A Johnson, Cindy L Vnencak-Jones, Joy D Cogan, James E Loyd, James West
BMC Medical Genetics , 2009, DOI: 10.1186/1471-2350-10-58
Abstract: 97 human DNA samples were obtained which included 24 patients with familial PAH, 18 obligate carriers (BMPR2 mutation positive), 20 sporadic PAH patients, and 35 controls. Two sets of primers were designed within the CNV, and two sets of control primers were designed outside the CNV. Quantitative PCR was performed to quantify genomic copies of CNV and control sequences.A CNV in BMPR2 was present in one African American negative control subject.We conclude that the CNV in intron 1 in BMPR2 is unlikely to play a role in the pathogenesis of either familial or sporadic PAH.NIH NCT00091546.Pulmonary arterial hypertension is a progressive disease characterized by obstruction of pre-capillary pulmonary arteries. Symptoms of PAH include fatigue and shortness of breath. Sustained pulmonary arterial hypertension eventually leads to right-sided heart failure and death. In 2000, mutations in BMPR2 (bone morphogenic protein receptor type 2) located on chromosome 2 were shown to cause familial PAH[1]. The BMPR2 gene spans 190 kb but encodes only a 4 kb transcript. It contains 13 exons and a large first intron composed of over 90 kb with frequent repetitive sequences. BMPR2 mutations are present in over 80% of patients diagnosed with familial PAH and are responsible for some cases of idiopathic PAH. Although the discovery of the BMPR2 mutation has enhanced our understanding of PAH, there are several important characteristics of the disease which remain unexplained. For example, the lifetime risk of developing PAH with the BMPR2 mutation is less than 20%, anticipation is observed, and there are both familial and sporadic patients without the BMPR2 mutation who develop PAH[2]. Recently, penetrance has been linked to levels of BMPR2; unaffected carriers (patients with a BMPR2 mutation who do not have PAH) have higher levels of wild-type BMPR2 allele transcript than patients with BMPR2 mutations and PAH[3]. This finding suggests that alterations of gene expression may be relevant to P
Determinisitic Writing and Control of the Dark Exciton Spin using Short Single Optical Pulses
I. Schwartz,E. R. Schmidgall,L. Gantz,D. Cogan,E. Bordo,Y. Don,M. Zielinski,D. Gershoni
Physics , 2014, DOI: 10.1103/PhysRevX.5.011009
Abstract: We demonstrate that the quantum dot-confined dark exciton forms a long-lived integer spin solid state qubit which can be deterministically on-demand initiated in a pure state by one optical pulse. Moreover, we show that this qubit can be fully controlled using short optical pulses, which are several orders of magnitude shorter than the life and coherence times of the qubit. Our demonstrations do not require an externally applied magnetic field and they establish that the quantum dot-confined dark exciton forms an excellent solid state matter qubit with some advantages over the half-integer spin qubits such as the confined electron and hole, separately. Since quantum dots are semiconductor nanostructures that allow integration of electronic and photonic components, the dark exciton may have important implications on implementations of quantum technologies consisting of semiconductor qubits.
Jóvenes contemporáneos: entre el trabajo emocional y estético en el mundo corporativo
Liuba, Kogan-Cogan
Boletín Científico Sapiens Research , 2012,
Abstract: In this research we examine the contemporary sociocultural context and its relationship with the corporal image that young women and males, students of the management and economic areas of a private university in Lima, consider “ideal”. Specifically, we focus on the type of corporal management that students consider to be important to help them gain access to the corporate environment in order to develop a successful career. That is, we want to know the meaning that young people who will form part of the political and economic elites of the country give to the relation between their bodies, super egos and their sociocultural environment. The results of this study are a product of two methodolog-ical approaches: the Q multivariable analysis allowed us to identify those factors that students of both sexes regarded to be important to manage their bodies as social capital. Then, we performed qualitative analysis of the information obtained in focus groups.
Failure of antibiotic treatment in microbial populations
Patrick De Leenheer,Nick Cogan
Quantitative Biology , 2008,
Abstract: The tolerance of bacterial populations to biocidal or antibiotic treatment has been well documented in both biofilm and planktonic settings. However, there is still very little known about the mechanisms that produce this tolerance. Evidence that small, non-mutant subpopulations of bacteria are not affected by antibiotic challenge has been accumulating and provides an attractive explanation for the failure of typical dosing protocols. Although a dosing challenge can kill all the susceptible bacteria, the remaining persister cells can serve as a source of population regrowth. We give a robust condition for the failure of a periodic dosing protocol for a general chemostat model, which supports the mathematical conclusions and simulations of an earlier, more specialized batch model. Our condition implies that the treatment protocol fails globally, in the sense that a mixed bacterial population will ultimately persist above a level that is independent of the initial composition of the population. We also give a sufficient condition for treatment success, at least for initial population compositions near the steady state of interest, corresponding to bacterial washout. Finally, we investigate how the speed at which the bacteria are wiped out depends on the duration of administration of the antibiotic. We find that this dependence is not necessarily monotone, implying that optimal dosing does not necessarily correspond to continuous administration of the antibiotic. Thus, genuine periodic protocols can be more advantageous in treating a wide variety of bacterial infections.
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