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Search Results: 1 - 10 of 144789 matches for " Benedict F. Malele "
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The contribution of ineffective urban planning practices to disaster and disaster risks accumulation in urban areas: the case of former Kunduchi quarry site in Dar es Salaam, Tanzania
Benedict F. Malele
Jàmbá : Journal of Disaster Risk Studies , 2009, DOI: 10.4102/jamba.v2i1.14
Abstract: This study examined the link between urban planning practices and disaster risks. The study used the former Kunduchi Quarry Site within the City of Dar es Salaam to demonstrate how laxity in enforcing the laid down planning rules, regulations and procedures facilitates the accumulation and occurrence of disaster risks and disasters in urban areas. This undermines one of the central roles of urban planning, which is to protect the lives of people from disaster risks and disasters. In exploring this, the study specifically focused on understanding the rules, regulations and procedures of planning in Tanzania; the extent to which they are followed and, where they are not followed, their implications for disaster risks and disasters; the coping initiatives adopted by local communities to reduce risks and their level of success or failure; and finally the drawing of lessons and recommendations for disaster risk reduction in urban areas. Strongly emerging from this study is the finding that although planning rules and regulations do exist, they are not enforced. As a result urban communities suffer from disaster risks and disasters caused by unregulated activities. The study analyzed the coping initiatives that urban communities apply to reduce disaster risks in their areas. It noted that, while a range of “coping” responses could be observed, these are not lasting solutions to the disaster risks being faced. Sustainable solutions seem to be known by the local community but they are not adopted for fear of compromising or undermining their existing livelihood strategies.
Plankton- Based Assessment of the Trophic State of Three Tropical Lakes  [PDF]
Benedict Obeten Offem, Ezekiel Olatunji Ayotunde, Gabriel Ujong Ikpi, F. B. Ada, S. N. Ochang
Journal of Environmental Protection (JEP) , 2011, DOI: 10.4236/jep.2011.23034
Abstract: In developing countries, lakes being important sources of water supply and fishing are vulnerable to anthropogenic impact, yet knowledge of their trophic state in relation to changes in species composition, and environmental variables, are limited. This study is aimed at assessing the trophic status of lakes by monthly sampling of three lakes located along the floodplain of Cross River, Nigeria between January 2008 and December 2009. Samples were analyzed for water quality parameters, zooplankton and phytoplankton composition and distribution. Results were subjected to community structure analysis using trophic state index, species richness and diversity indexes. Essential primary productivity nutrients, nitrates, sulphates and phosphates were highest in Ejagham Lake, and lowest in Ikot Okpora Lake. Dominant phytoplankton species Oscillatoria lacustria (Cyanophyceae), Cyclotella operculata (Bacilliarophyceae) and zooplankton Keratella tropica, Keratella quadrata, Filinia longiseta, Branchionus anguillaris and Trichocerca pusilla (rotifers) all typical of eutrophic communities were recorded in high densities in Ejagham Lake in both dry and wet seasons while Cladocerans, Bosmina longirostris and Moina micrura and copepods considered indicators of oligotrophy and mesotrophy were recorded in large numbers in Ikot Okpora and Obubra Lakes respectively. Higher values of species richness, Evenness and Shannon-Wiener diversity index for both phytoplankton and zooplankton, were recorded in Ejagham Lake during the dry season than wet. Also values of the Trophic state index were generally highest at the Ejagham Lake in the savanna region of the floodplain and lowest at Ikot Okpora in the forest region of the floodplain. Forest region is therefore a limiting factor in the productivity of lakes in the tropics.
Percutaneous versus Open Achilles Tendon Repair: A Case-Control Study  [PDF]
Benedict Schrinner, Michael Zellner, Christian B?uml, Bernd Füchtmeier, Franz Müller
Surgical Science (SS) , 2016, DOI: 10.4236/ss.2016.78047
Abstract: Purpose: We investigated whether percutaneous suturing of Achilles tendon ruptures showed better results and superiority in terms of clinical outcomes when compared to open suturing. Methods: We conducted a case-control study. Between 2009 and 2014, we performed surgical revisions of closed acute Achilles tendon ruptures in our hospital in 146 patients, of which 71 patients (2012-2014) received percutaneous suturing using Dresden instruments, and 75 patients (2009-2012) underwent open suturing. After a minimum period of 1 year post surgery, we performed clinical follow-up in 25 patients of each of the groups using the AOFAS hind foot score and the SF-12 questionnaire. Furthermore, we implemented a clinical questionnaire with a reference population of 200 healthy individuals. Results: Mean age in the total population of 146 patients was 47 years (range 21 to 83 years) at the time of surgery. The duration of the surgical procedure with percutaneous suturing was significantly shorter (24 versus 43 minutes, p < 0.0001), the complication rate was significantly lower (2.81% versus 10.7%, p < 0.0001), and the time of hospitalisation was significantly shorter (3 versus 4 days, p < 0.0001) when compared to open suturing. During follow-up, no significant differences between the two groups were observed in terms of descriptive parameters. Furthermore, ultrasound examinations of both follow-up populations did not show any significant difference. From a clinical perspective, the good to very good results achieved with open suturing (as measured with the AOFAS hind foot score and the SF-12 questionnaire) have not been significantly improved with percutaneous suturing. The additional use of a new clinical score (with the reference population) demonstrated good to very good consistency with the established scores. Conclusion: In our population, percutaneous Achilles tendon suturing showed significantly lower complication rates and significantly shorter procedure times when compared to open
L1 and HERV-W retrotransposons are hypomethylated in human ovarian carcinomas
Laura Menendez, Benedict B Benigno, John F McDonald
Molecular Cancer , 2004, DOI: 10.1186/1476-4598-3-12
Abstract: In the genome of differentiated somatic human cells, it is estimated that ~80% of all CpG dinucleotides are methylated [1]. Methylation of CpG dinucleotides located in or near promoter regions is typically associated with transcriptional repression [e.g, [2]]. Most retrotransposons, satellite DNA sequences, imprinted genes, X-chromosome inactivated genes, and many genes that are expressed tissue-specifically and that are transcriptionally silenced in differentiated human cells are associated with highly methylated (hypermethylated) CpG dinucleotides [3,4]. In contrast, CpG dinucleotides associated with the promoter regions of genes normally expressed in differentiated human cells, including tumor suppressor genes and genes involved in DNA repair and apoptosis, are associated with under-methylated (hypomethylated) CpG dinucleotides [e.g, [5]]. A number of recent studies have demonstrated that dramatic changes in these characteristic patterns of methylation are typically associated with cellular transformation [3]. For example, wide-spread (global) hypomethylation of up to 25% of CpG dinucleotides normally methylated in differentiated cells has been shown to be characteristic of many cancer cells, including those isolated from prostate, liver, ovarian and breast carcinomas [6]. In many instances, these increases in levels of global hypomethylation have been observed to be correlated with an increase in more localized patterns of hypermethylation associated with a subset of genes that includes tumor suppressor genes and other genes involved in DNA repair and apoptosis. The consequent reduction in expression of these genes is believed to initiate a cascade of events leading to cellular transformation [7].Relatively little is currently known concerning the specific targets of global increases in hypomethylation associated with cellular transformation, although they frequently include repetitive sequences located in proximity to centromeres [8]. One major class of middle
Quantum rings with time dependent spin-orbit coupling: Rabi oscillations, spintronic Schrodinger-cat states, and conductance properties
Peter Foldi,Mihaly G. Benedict,Orsolya Kalman,F. M. Peeters
Physics , 2009, DOI: 10.1103/PhysRevB.80.165303
Abstract: The strength of the (Rashba-type) spin-orbit coupling in mesoscopic semiconductor rings can be tuned with external gate voltages. Here we consider the case of a periodically changing spin-orbit interaction strength as induced by sinusoidal voltages. In a closed one dimensional quantum ring with weak spin-orbit coupling, Rabi oscillations are shown to appear. We find that the time evolution of initially localized wave packets exhibits a series of collapse and revival phenomena. Partial revivals -- that are typical in nonlinear systems -- are shown to correspond to superpositions of states localized at different spatial positions along the ring. These "spintronic Schrodinger-cat sates" appear periodically, and similarly to their counterparts in other physical systems, they are found to be sensitive to environment induced disturbances. The time dependent spin transport problem, when leads are attached to the ring, is also solved. We show that the "sideband currents" induced by the oscillating spin-orbit interaction strength can become the dominant output channel, even in the presence of moderate thermal fluctuations and random scattering events.
Quantum rings as electron spin beam splitters
Peter Foldi,Orsolya Kalman,Mihaly G. Benedict,F. M. Peeters
Physics , 2005, DOI: 10.1103/PhysRevB.73.155325
Abstract: Quantum interference and spin-orbit interaction in a one-dimensional mesoscopic semiconductor ring with one input and two output leads can act as a spin beam splitter. Different polarization can be achieved in the two output channels from an originally totally unpolarized incoming spin state, very much like in a Stern-Gerlach apparatus. We determine the relevant parameters such that the device has unit efficiency.
Interference induced preparation of spinpolarized electrons in a three-terminal quantum ring
Orsolya Kalman,Peter Foldi,Mihaly G. Benedict,F. M. Peeters
Physics , 2006, DOI: 10.1016/j.physe.2007.08.014
Abstract: We present an exact, analytic solution of the spin dependent quantum transport problem with spin-orbit interaction in a one-dimensional mesoscopic ring with one input and two output leads. We demonstrate that for appropriate parameters spatial interference in the ring leads to a behavior analogous to that of the Stern-Gerlach apparatus: different spin polarizations can be achieved in the two output channels from an originally totally unpolarized incoming spin state. It is shown that this requires an appropriate interference of states that carry oppositely directed currents. We find that spin polarization is possible for several geometries, including the case when the device is not symmetric with respect to the incoming lead. A clear connection is established between the Stern-Gerlach like property of the device and the relevant Aharonov-Casher phases in the loop geometry.
Dynamics of periodic anticrossings: Decoherence, pointer states and hysteresis curves
Peter Foldi,Mihaly G. Benedict,F. M. Peeters
Physics , 2007, DOI: 10.1103/PhysRevA.77.013406
Abstract: We consider a strongly driven two-level (spin) system, with a periodic external field that induces a sequence of avoided level crossings. The spin system interacts with a bosonic reservoir which leads to decoherence. A Markovian dynamical equation is introduced without relying on the rotating wave approximation in the system-external field interaction. We show that the time evolution of the two-level system is directed towards an incoherent sum of periodic Floquet states regardless of the initial state and even the type of the coupling to the environment. Analyzing the time scale of approaching these time-dependent pointer states, information can be deduced concerning the nature and strength of the system-environment coupling. The inversion as a function of the external field is usually multi-valued, and the form of these hysteresis curves is qualitatively different for low and high temperatures. For moderate temperatures we found that the series of Landau-Zener-St\"{u}ckelberg-type transitions still can be used for state preparation, regardless of the decoherence rate. Possible applications include quantum information processing and molecular nanomagnets.
Networks of quantum nanorings: programmable spintronic devices
Peter Foldi,Orsolya Kalman,Mihaly G. Benedict,F. M. Peeters
Physics , 2008, DOI: 10.1021/nl801858a
Abstract: An array of quantum rings with local (ring by ring) modulation of the spin orbit interaction (SOI) can lead to novel effects in spin state transformation of electrons. It is shown that already small (3x3, 5x5) networks are remarkably versatile from this point of view: Working in a given network geometry, the input current can be directed to any of the output ports, simply by changing the SOI strengths by external gate voltages. Additionally, the same network with different SOI strengths can be completely analogous to the Stern-Gerlach device, exhibiting spatial-spin entanglement.
Spintronic single qubit gate based on a quantum ring with spin-orbit interaction
Peter Foldi,Balazs Molnar,Mihaly G. Benedict,F. M. Peeters
Physics , 2004, DOI: 10.1103/PhysRevB.71.033309
Abstract: In a quantum ring connected with two external leads the spin properties of an incoming electron are modified by the spin-orbit interaction resulting in a transformation of the qubit state carried by the spin. The ring acts as a one qubit spintronic quantum gate whose properties can be varied by tuning the Rashba parameter of the spin-orbit interaction, by changing the relative position of the junctions, as well as by the size of the ring. We show that a large class of unitary transformations can be attained with already one ring -- or a few rings in series -- including the important cases of the Z, X, and Hadamard gates. By choosing appropriate parameters the spin transformations can be made unitary, which corresponds to lossless gates.
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