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Search Results: 1 - 10 of 422868 matches for " K. S. Troche "
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Doping of zigzag carbon nanotubes through the encapsulation of small fullerenes
K. S. Troche,V. R. Coluci,R. Rurali,D. S. Galv?o
Physics , 2006,
Abstract: In this work we investigated the encapsulation of C$_20$ and C$_30$ fullerenes into semiconducting carbon nanotubes to study the possibility of bandgap engineering in such systems. Classical molecular dynamics simulations coupled to tight-binding calculations were used to determine the conformational and electronic properties of carbon nanotube supercells containing up to 12 fullerenes. We have observed that C$_20$ fullerenes behave similarly to a p-type dopant while C$_30$ ones work as n-type ones. For larger diameter nanotubes, where fullerene patterns start to differ from the linear arrangements (peapods), the doping features are preserved for both fullerenes, but local disorder plays an important role and significantly alters the electronic structure. The combined incorporation of both fullerene types (hybrid encapsulation) into the same nanotube leads to a behavior similar to that found in electronic junctions in Silicon-based electronic devices. These aspects can be exploited in the design of nanoelectronic devices using semiconducting carbon nanotubes.
Research and Education in Basic Space Science: The Approach Pursued in the UN/ESA Workshops
H. M. K. Al-Naimiy,C. P. Celebre,K. Chamcham,H. S. P. de Alwis,M. C. P. de Carias,H. J. Haubold,A. E. Troche Boggino
Physics , 2000,
Abstract: Since 1990, the United Nations in cooperation with the European Space Agency is holding annually a workshop on basic space science for the benefit of the worldwide development of astronomy. These workshops have been held in countries of Asia and the Pacific (India, Sri Lanka), Latin America and the Caribbean (Costa Rica, Colombia, Honduras), Africa (Nigeria), Western Asia (Egypt, Jordan), and Europe (Germany, France). Additional to the scientific benefits of the workshops and the strengthening of international cooperation, the workshops lead to the establishment of astronomical telescope facilities in Colombia, Egypt, Honduras, Jordan, Morocco, Paraguay, Peru, Philippines, Sri Lanka, and Uruguay. The annual UN/ESA Workshops continue to pursue an agenda to network these astronomical telescope facilities through similar research and education programmes. Teaching material and hands-on astrophysics material has been developed for the operation of such astronomical telescope facilities in an university environment.
High-Level Language Production in Parkinson's Disease: A Review
Lori J. P. Altmann,Michelle S. Troche
Parkinson's Disease , 2011, DOI: 10.4061/2011/238956
Abstract: This paper discusses impairments of high-level, complex language production in Parkinson's disease (PD), defined as sentence and discourse production, and situates these impairments within the framework of current psycholinguistic theories of language production. The paper comprises three major sections, an overview of the effects of PD on the brain and cognition, a review of the literature on language production in PD, and a discussion of the stages of the language production process that are impaired in PD. Overall, the literature converges on a few common characteristics of language production in PD: reduced information content, impaired grammaticality, disrupted fluency, and reduced syntactic complexity. Many studies also document the strong impact of differences in cognitive ability on language production. Based on the data, PD affects all stages of language production including conceptualization and functional and positional processing. Furthermore, impairments at all stages appear to be exacerbated by impairments in cognitive abilities. 1. Introduction The current paper focuses on high-level, complex language production in Parkinson’s disease (PD), in which “high-level, complex language” is defined as production of language at the sentence- or discourse-level in contrast to single-word production. In comparison to the extensive literature on motor impairments affecting articulation and intelligibility of speech (e.g., [1–6]) and neuropsychological reports of impaired picture naming and verbal fluency in PD [7–13], the literature on complex language production is somewhat limited. However, those few reports converge on a few common themes. First, while information content has been assessed in a variety of ways, including clinical judgment [14], correct information units [15], propositional content [16], or specific mention of the actors in a picture and an appropriate action [17], the findings uniformly support reduced information content. Second, although examined in only a few studies, fluency seems to be impaired [17–19]. Interruptions of fluency take many forms, including abandoned utterances, long pauses between or in the middle of sentences, or filled and unfilled pauses. The studies agree that disruptions of fluency can be attributed to difficulties in the early stages of language production (e.g., conceptualization and formulation) as well as problems during motor programming and articulation [17–19]. Third, grammaticality has also been reported to be impaired [15–17, 20]. Finally, syntactic complexity may also be impaired although this
Atomistic Study of the Encapsulation of Diamondoids Inside Carbon Nanotubes
Karla S. Troche,Vitor R. Coluci,Douglas S. Galvao
Physics , 2007,
Abstract: The encapsulation of hydrogen-terminated nanosized diamond fragments (the so-called diamondoids) into armchair single walled carbon nanotubes with diameters in the range of 1.0 up to 2.2 nm has been investigated using classical molecular dynamics simulations. Diameter dependent molecular ordered phases were found for the encapsulation of adamantane (C10H16), diamantane (C14H20), and dihydroxy diamantane (C14H20O2). The same types of chiral ordered phases (double, triple, 4- and 5-stranded helices) observed for the encapsulation of C60 molecules were also observed for diamondoids. On the other hand, some achiral phases comprising layered structures were not observed. Our results also indicate that the modification of diamantane through functionalization with hydroxyl groups can lead to an enhancement of the packing of molecules inside the nanotubes compared to nonfunctionalized compounds. Comparisons to hard-sphere models are also presented revealing differences, specially when more asymmetrical diamondoids are considered. For larger structures (adamantane tetramers) we have not observed long-range ordering for nanotubes with diameters in the range of 1.49 to 2.17 nm but only a tendency to form incomplete helical structures.
Incontinencia fecal en adultos mayores
Remes- Troche, José Maía;Sáenz, Pablo;Ria?o, Daniela;Valdovinos, Miguel ángel;Mercado, Mauricio;Gutiérrez Robledo, Luis Miguel;Valdés, Pedro;
Revista de investigación clínica , 2004,
Abstract: fecal incontinence (fi) is a devastating condition that affects quality of life. age and gender are related with the prevalence of fi. in adults, prevalence varies from 2% to 7%. it is more frequent in women than in men (3:1) and is more prevalent in elderly patients. there are no studies in mexico that evaluate the frequency of fi in adults older than 60 years. aim. to investigate the fi frequency, severity and associated factors in patients ≥ 60 years. patients and methods. three groups of patients were included: a) group i: consecutive outpatients patients from the gastroenterology and geriatrics clinics of the incmnsz; b) group ii: incmnsz inpatients admitted due to a non-related condition with fi; c) group iii: reyna sofia nursing home residents (nhr) in mexico city. a structured questionnaire was used to obtain demographic data, comorbidity and associated factors with fi. grade of fi was assessed with the wexner scale. results. 159 patients were included, 89 (56%) were women. mean age was 75 years (range 59-98). there were 54 patients in group i, 50 in group ii and 55 in group iii. overall frequency of fi was 33% (n = 53). frequency of fi was 26% in group i, 20% in group ii and 53% in group iii. sixty six percent (n = 35) of the fi cases were female. neuropsychiatric disorders were associated to fi in 29 patients (54%) and diabetes mellitus in 17 (32%). eighty percent of patients wore disposable pads for fi. urinary incontinence was associated to fi in 31 (58%). thirteen (24%) patients had mild fi, 20 (38%) moderate, and 20 (38%) severe fi. the severity score for fi was lower in groups i and ii (8.1 y 9.7) than in group iii (18, p = 0.001). age in patients with mild fi was significantly lower (73 years) than in patients with severe fi (83y, p = 0.01). conclusions. fi in patients older than 60 years old is a very common condition. fi was more frequent and severe in women, in nhr and in those with neuropsychiatric disorders. urinary incontinence was associated i
Utilización de bisfosfonatos en las enfermedades de los huesos Use of bisphosponates in bone-related diseases
María Isabel Reyes Tur,Yenilen Troche Concepción
Revista Cubana de Farmacia , 2012,
Abstract: Los bifosfonatos son medicamentos que ayudan a fortalecer los huesos, reducen el riesgo de fracturas y dolor en los que han sido debilitados por el cáncer metastásico. Estos disminuyen la reabsorción ósea de modo general por vía oral; por vía intravenosa se suelen utilizar como tratamiento coadyuvante de algunos tipos de cáncer y, por ende, es necesario tener presente los efectos adversos asociados a su uso. El presente trabajo tiene como objetivo realizar una revisión bibliográfica sobre este grupo de fármacos, los cuales se emplean en el tratamiento de las enfermedades relacionadas con los huesos, para esto se efectuó una búsqueda en la que se utilizaron algunas de las bases de datos disponibles en la web tales como Google, Scirus y Medline durante los últimos 10 a os. Se concluye que los bifosfonatos inhiben la reabsorción ósea mediada por osteoclastos y debido a este mecanismo de acción se han empleado en el tratamiento de la osteoporosis. Bisphosphonates are drugs that help to fortify bones, reduce the risk of fractures and relieve pain in those patients who suffered metastatic cancer. These drugs generally decrease bone reabsorption when orally administered; they are also intravenously used as coadjuvant to treat certain types of cancer, hence, it is necessary to take into account the adverse effects associated to their use. This paper presented a literature review about this group of drugs for the treatment of bone-related diseases, to this end, some available databases in Google, Scirus and Medline for the last 10 years were used. It was concluded that bisphosphonates inhibit osteoclast-mediated bone reabsorption, and based on this mechanism of action, they are prescribed for the treatment of osteoporosis.
The relationship between attentional blink and psychometric intelligence: A fixed-links model approach
STEFAN J. TROCHE,KARL SCHWEIZER,THOMAS H. RAMMSAYER
Psychology Science Quarterly , 2009,
Abstract: Attentional blink (AB) denotes the impairment in identifying a target when this target follows a preceding target after about 150 to 500 msec. Several models explain AB and some studies suggest that more processes than only one are involved in AB. Therefore, confounding effects of these underlying processes might be the reason why previous studies could not observe a relationship between AB and psychometric intelligence. In the present study, fixed-links models were used to disentangle the processes underlying the performance of 66 female and 52 male volunteers on an AB task. In accordance with theoretical explanations of AB, three latent variables with loadings describing a linearly increasing, a linearly decreasing and a u-shaped trend described the data well. Psychometric intelligence was related to the latent variables reflected by the u-shaped (β = .30; p < .05) and the linearly increasing trends (β = .23; p < .05) but not to the latent variable reflected by the linearly decreasing trend (β = .10; n.s.). These results support the assumptions that more processes than only one are involved in AB. Decomposition of the underlying processes seems to be promising to investigate intelligence-related individual differences on this early level of information processing.
An investigation of volumetric and corpus callosum dimension to detect brain disorders  [PDF]
S. Prabakar, K. Porkumaran
Journal of Biomedical Science and Engineering (JBiSE) , 2012, DOI: 10.4236/jbise.2012.57047
Abstract: Alzheimer’s disease (AD), Mental retardation, Cerebral Palsy, and other Dementias are the neurogenerative brain disorders which are statistically proven that 2% - 3% of people affected in the world today. The proposed method considered the symptoms which stands distinct for Alzheimer’s disease. Many structural neuroimaging studies have found the atrophy of the Corpus Callosum (CC) and the decrease in brain volume in AD. The measurement, area has been extracted from the gradient mask of the image to characterize the local atrophy of the CC. The result showed decreased area of the CC in AD when compared to the control groups. The volume has also been calculated by volume rendering and voxel size measurement for the same set of control groups and was found to be reduced in the AD patients. These findings confirmed the pathology characteristics in AD of brain disorders. The system’s validity with respect to results obtained with conventional diagnosis has been examined and proved to offer better results.
New Practical Algebraic Public-Key Cryptosystem and Some Related Algebraic and Computational Aspects  [PDF]
S. K. Rososhek
Applied Mathematics (AM) , 2013, DOI: 10.4236/am.2013.47142
Abstract:

The most popular present-day public-key cryptosystems are RSA and ElGamal cryptosystems. Some practical algebraic generalization of the ElGamal cryptosystem is considered-basic modular matrix cryptosystem (BMMC) over the modular matrix ring M2(Zn). An example of computation for an artificially small number n is presented. Some possible attacks on the cryptosystem and mathematical problems, the solution of which are necessary for implementing these attacks, are studied. For a small number n, computational time for compromising some present-day public-key cryptosystems such as RSA, ElGamal, and Rabin, is compared with the corresponding time for the ВММС. Finally, some open mathematical and computational problems are formulated.

Assessment of Natural Radioactivity Levels and Radiation Dose Rate in Some Soil Samples from Historical Area, AL-RAKKAH, Saudi Arabia  [PDF]
K. S. Al Mugren
Natural Science (NS) , 2015, DOI: 10.4236/ns.2015.75027
Abstract: This study aims to determine the activity concentrations of naturally occurring, technically-enhanced levels of radiation and the gamma absorbed dose rates in soil samples collected across the land scape of historical area which discovered in east of Saudi Arabia at 2009 G, Called AL- RAKKAH. By using an HPGe detector gamma-ray spectrometer, the activity concentrations of 226Ra 232Th and 40K were found in surface soil samples ranged from 17. 4 ± 1.2 Bq/kg to 28.3 ± 2.3 Bq/kg with an average value of 23 ± 1.6 Bq/kg, ranging from 1.1 ± 1.8 Bq/kg to 81.0 ± 1.7 Bq/kg with the average value 20 ± 1.4 Bq/kg and from 218 ± 11 Bq/kg to 255 ± 18 Bq/kg, with the mean value of 233 ± 12 Bq/kg respectively. The mean radium equivalent (Raeq) and outdoor radiation hazard index (Hex) for the area under study were determined as 69.52 Bq/kg and 0.16 respectively. The total absorbed dose rate due to three primordial radionuclides lies in the range of 17.74 - 72.24 nGy·h-1 with a mean of 32.69 nGy·h-1, which yields total annual effective dose of 0.37 mSv·y-1. The measured values are comparable with other global radioactivity measurements and are found to be safe for public and environment. The baseline data of this type will almost certainly be of importance in making estimations of population exposure.
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