988 research outputs found
Torque Ripple Minimization in a Switched Reluctance Drive by Neuro-Fuzzy Compensation
Simple power electronic drive circuit and fault tolerance of converter are
specific advantages of SRM drives, but excessive torque ripple has limited its
use to special applications. It is well known that controlling the current
shape adequately can minimize the torque ripple. This paper presents a new
method for shaping the motor currents to minimize the torque ripple, using a
neuro-fuzzy compensator. In the proposed method, a compensating signal is added
to the output of a PI controller, in a current-regulated speed control loop.
Numerical results are presented in this paper, with an analysis of the effects
of changing the form of the membership function of the neuro-fuzzy compensator.Comment: To be published in IEEE Trans. on Magnetics, 200
Neurobiology and clinical implications of lucid dreaming
Several lines of evidence converge to the idea that rapid eye movement sleep (REMS) is a good model to
foster our understanding of psychosis. Both REMS and psychosis course with internally generated perceptions and lack of rational judgment, which is attributed to a hyperlimbic activity along with hypofrontality. Interestingly, some individuals can become aware of dreaming during REMS, a particular experience
known as lucid dreaming (LD), whose neurobiological basis is still controversial. Since the frontal lobe
plays a role in self-consciousness, working memory and attention, here we hypothesize that LD is associated with increased frontal activity during REMS. A possible way to test this hypothesis is to check
whether transcranial magnetic or electric stimulation of the frontal region during REMS triggers LD.
We further suggest that psychosis and LD are opposite phenomena: LD as a physiological awakening
while dreaming due to frontal activity, and psychosis as a pathological intrusion of dream features during
wake state due to hypofrontality. We further suggest that LD research may have three main clinical
implications. First, LD could be important to the study of consciousness, including its pathologies and
other altered states. Second, LD could be used as a therapy for recurrent nightmares, a common symptom
of depression and post-traumatic stress disorder. Finally, LD may allow for motor imagery during dreaming with possible improvement of physical rehabilitation. In all, we believe that LD research may clarify
multiple aspects of brain functioning in its physiological, altered and pathological states
Chemistry and antigerminative activity of essential oils and monoterpenoids from Mediterranean plants
The Mediterranean flora is characterized by the abundance of aromatic plants. The feature differentiating these plants from all others, in spite of the fact that they belong to many different families, is the production of chemically related secondary compounds, the low molecular weight and volatile isoprenoids. This remarkable presence of aromatic species is important in determining the allelopathic potential within this ecosystem. Such plants make a significant contribution to phryganic Mediterranean ecosystems both in terms of species number and biomass. Thus, the essential oils play an important role in this ecological context. Mediating various processes in the frame of an ecosystem, they become indirectly beneficial to the plants, considering their involvement in processes of adaptative character in Mediterranean ecosystem .
For this reason, our research group carried out a series of studies on the possible allelopathic properties of aromatic plants that, being rich in active principles, are considered a primary source of potential allelochemicals.The focus of this overview is direct to have an overall idea about the chemistry and antigerminative activity of essential oils of some Mediterranean aromatic plants and their main constituent
Escala de aceitação do teste pré-sintomático: Estudo de validação com uma amostra de pessoas em risco para a doença de Machado-Joseph
Este artigo apresenta um estudo de validação da Escala de Aceitação do
Teste Pré-Sintomático, realizado com uma amostra de pessoas em risco para a doença
de Machado-Joseph.
Este estudo visou testar a estabilidade e a reprodutibilidade da estrutura factorial
original da escala e apurar as suas características psicométricas. Avaliámos, ainda, a
convergência da escala com um outro instrumento de avaliação psicológica.
Os resultados revelaram uma estrutura composta por 18 itens e diferenciada em três
factores, que contribuem com 51,6% para a variância total explicada, e cujos
coeficientes alfa de Cronbach (Factor 1=0,85; Factor 2=0,76; Factor 3=0,60) atestam
a adequada consistência interna do instrumento. A escala não foi influenciada pelas
variáveis sexo, idade e grau de instrução e as respostas não foram, aparentemente,
determinadas pelo desejo de agradar a terceiros, aspecto que constitui um indicador
acrescido da validade de construto da escala. Detectámos, ainda, uma associação
estatisticamente significativa entre a adesão ao teste pré-sintomático e as atitudes em
relação aos médicos e à medicina.
Em suma, a escala apresenta qualidades psicométricas bastante satisfatórias, o que
favorece a sua aplicabilidade a amostras de pessoas em risco para doenças
neurogenéticas de início tardio e que disponham de teste pré-sintomático. ------ ABSTRACT ------ This paper presents a study on the validation of the Pre-Symptomatic
Testing Acceptance Scale, undertaken with a sample of at-risk subjects for Machado-
Joseph disease.
The present study has aimed to test the stability and reproducibility of the original
factorial structure of the scale and to check its psychometric characteristics. We have
still evaluated the convergence of the scale with another instrument of psychological
evaluation.
The results have shown a structure composed of 18 items and differentiated in three
factors that have contributed with 51.6% to the total explained variance and its Cronbach
alpha coefficient (Factor 1=.85; Factor 2=.76; Factor 3=.60) prove the adequate internal
consistency of the instrument. The scale has not been influenced by the variables gender,
age, schooling level, and the answers have not apparently been determined by the desire to please other people, which constitutes a further indicator of the scale construct validity.
We have also observed a meaningful statistic association between adherence to the presymptomatic
testing and attitudes in relation to doctors and medicine.
In conclusion, the scale presents fairly satisfactory psychometric qualities, which
enables its applicability to samples of at-risk people for other late onset neurogenetic
diseases with pre-symptomatic testing
Asymptotic entanglement in a two-dimensional quantum walk
The evolution operator of a discrete-time quantum walk involves a conditional
shift in position space which entangles the coin and position degrees of
freedom of the walker. After several steps, the coin-position entanglement
(CPE) converges to a well defined value which depends on the initial state. In
this work we provide an analytical method which allows for the exact
calculation of the asymptotic reduced density operator and the corresponding
CPE for a discrete-time quantum walk on a two-dimensional lattice. We use the
von Neumann entropy of the reduced density operator as an entanglement measure.
The method is applied to the case of a Hadamard walk for which the dependence
of the resulting CPE on initial conditions is obtained. Initial states leading
to maximum or minimum CPE are identified and the relation between the coin or
position entanglement present in the initial state of the walker and the final
level of CPE is discussed. The CPE obtained from separable initial states
satisfies an additivity property in terms of CPE of the corresponding
one-dimensional cases. Non-local initial conditions are also considered and we
find that the extreme case of an initial uniform position distribution leads to
the largest CPE variation.Comment: Major revision. Improved structure. Theoretical results are now
separated from specific examples. Most figures have been replaced by new
versions. The paper is now significantly reduced in size: 11 pages, 7 figure
Pseudo-Hermitian continuous-time quantum walks
In this paper we present a model exhibiting a new type of continuous-time
quantum walk (as a quantum mechanical transport process) on networks, which is
described by a non-Hermitian Hamiltonian possessing a real spectrum. We call it
pseudo-Hermitian continuous-time quantum walk. We introduce a method to obtain
the probability distribution of walk on any vertex and then study a specific
system. We observe that the probability distribution on certain vertices
increases compared to that of the Hermitian case. This formalism makes the
transport process faster and can be useful for search algorithms.Comment: 13 page, 7 figure
Eficiência da ureia revestida com polímeros, na produtividade de milho safrinha.
Em regiões tropicais e principalmente, sob cultivo em sistema de plantio direto, as perdas de N, na forma de NH3, por volatilização aliada à baixa disponibilidade hídrica, estão entre as principais causas de baixa produtividade de milho safrinha. Breda et al. (2010), constataram maior eficiência na utilização de ureia revestida com polímeros, em relação à redução das perdas de NH3 ocasionadas por volatilização. Consequentemente, ocasionando um melhor aproveitamento deste nutriente pelas plantas, podendo gerar incremento de produtividade. Em sistemas de plantio direto, onde há um maior acúmulo de resíduos vegetais na superfície do solo, as perdas de N, na forma de NH3, são maiores em relação a outros sistemas de cultivo, como por exemplo, o plantio convencional (VIERO, 2011). Contudo, o sistema plantio direto na palha, nos proporciona inúmeras vantagens em relação ao cultivo convencional, como por exemplo, menor suscetibilidade a erosão, controle de temperatura do solo, equilíbrio da micro e macro biota do solo, melhor conservação de água, dentre outras. Levando-nos a buscar alternativas eficientes para o seu manejo, principalmente na safrinha, onde estes benefícios são essenciais para o sucesso da lavoura. Diante do disposto acima, o objetivo deste estudo foi, avaliar o efeito da adubação nitrogenada protegida com polímeros, em plantas de milho cultivadas sob sistema de plantio direto, em regime de safrinha.Disponível em: http://www.cpao.embrapa.br/cds/milhosafrinha2013/PDF/61.pdf. Acesso em 18 dez. 2013
Neurobiology and clinical implications of lucid dreaming
Article history: a b s t r a c t Several lines of evidence converge to the idea that rapid eye movement sleep (REMS) is a good model to foster our understanding of psychosis. Both REMS and psychosis course with internally generated perceptions and lack of rational judgment, which is attributed to a hyperlimbic activity along with hypofrontality. Interestingly, some individuals can become aware of dreaming during REMS, a particular experience known as lucid dreaming (LD), whose neurobiological basis is still controversial. Since the frontal lobe plays a role in self-consciousness, working memory and attention, here we hypothesize that LD is associated with increased frontal activity during REMS. A possible way to test this hypothesis is to check whether transcranial magnetic or electric stimulation of the frontal region during REMS triggers LD. We further suggest that psychosis and LD are opposite phenomena: LD as a physiological awakening while dreaming due to frontal activity, and psychosis as a pathological intrusion of dream features during wake state due to hypofrontality. We further suggest that LD research may have three main clinical implications. First, LD could be important to the study of consciousness, including its pathologies and other altered states. Second, LD could be used as a therapy for recurrent nightmares, a common symptom of depression and post-traumatic stress disorder. Finally, LD may allow for motor imagery during dreaming with possible improvement of physical rehabilitation. In all, we believe that LD research may clarify multiple aspects of brain functioning in its physiological, altered and pathological states
- …