Simplest cosmological model with the scalar field II. Influence of cosmological constant

Continuing the investigation of the simplest cosmological model with the massive real scalar non-interacting inflaton field minimally coupled to gravity we study an influence of the cosmological constant on the behaviour of trajectories in closed minisuperspace Friedmann-Robertson-Walker model. The transition from chaotic to regular behaviour for large values of cosmological constant is discussed. Combining numerical calculations with qualitative analysis both in configuration and phase space we present a convenient classification of trajectories.Comment: 12 pages with 2 gif figures and 2 eps figures, mprocl.sty, To appear in International Journal of Modern Physics

Relic Gravitational Waves and Their Detection

The range of expected amplitudes and spectral slopes of relic (squeezed) gravitational waves, predicted by theory and partially supported by observations, is within the reach of sensitive gravity-wave detectors. In the most favorable case, the detection of relic gravitational waves can be achieved by the cross-correlation of outputs of the initial laser interferometers in LIGO, VIRGO, GEO600. In the more realistic case, the sensitivity of advanced ground-based and space-based laser interferometers will be needed. The specific statistical signature of relic gravitational waves, associated with the phenomenon of squeezing, is a potential reserve for further improvement of the signal to noise ratio.Comment: 25 pages, 9 figures included, revtex. Based on a talk given at "Gyros, Clocks, and Interferometers: Testing General Relativity in Space" (Germany, August 99

Aprendizagem de leitura por meio de um procedimento de discriminação sem erros (exclusão):: Uma replicação com pré-escolares

The present study investigated, with three preschoolers,the acquisition of reading (oral naming of textual stimuli) through ateaching program in which an exclusion procedure was embebed in orderto increase a repertoire of matching written words to spoken words. Theteaching program, which combines exclusion tasks, and equivalence andgeneralization tests, had been previously designed and evaluated. In theexclusion trials, two written words were simultaneously presented to thesubject; one was a new word and the other was a word that the subjecthad already learned to match to the corresponding spoken word. Thesubject was asked to point to the printed word corresponding to the wordspoken by the experimenter (oral sample). When the experimenterdictated the new word, the known word could function as a cue based onwhich the subject would reject the known word and select the new one.The teaching program involved the expansion of this matching repertoire,and evaluated 1) if the subject would leam to name the words previouslymatched. when presented with the printed stimulus alone, and 2) if hewould become able to present generalized reading when exposed to newwords composed by the rearrangement of syllables from the learnedwords. The results replicated previous studies with students with a history ofacademic failure: the subjects learned to read the training words andbegan to present generalized reading along the program. The occurrenceof generalized reading indicates that the subjects dominated themechanisms of analysis and synthesis involved in reading, that is, theirtextual behavior carne under the contrai of textual minimal units. Also, thespeed of generalization seems to be related to the amount of trainingrequired for the emergence of the reading of paired words. These resultsextend the generality of data on the effects of the exclusion procedure,establishing stimulus contrai by textual minimal units also with preschoolerswho did not have any experience with formal teaching of reading.O estudo investigou, com três pré-escolares, a aquisição de leitura por meio de um programa individualizado de ensino que emprega o procedimento de exclusão para ampliar o repertório de discriminações condicionais entre palavras ditadas (modelos) e palavras impressas (estímulos de escolha ou comparações). O programa, desenvolvido em um estudo prévio, combina passos de exclusão com testes de equivalência e de generalização. Nas tentativas de pareamento por exclusão, duas palavras impressas eram apresentadas simultaneamente ao sujeito: uma era uma palavra nova e a outra era uma palavra que o sujeito já havia aprendido a relacionar à palavra ditada correspondente. A tarefa do sujeito consistia em apontar a palavra impressa que correspondesse à palavra falada pelo experimentador (modelo oral); neste caso, quando a palavra nova era ditada, o sujeito podia excluir a palavra já conhecida, usando-a como pista para selecionar a palavra impressa nova. Pretendia-se verificar se, também com esta população, a expansão deste repertório de pareamentos favoreceria a aprendizagem de leitura (das palavras de treino) e sua generalização (diante de outras palavras, formadas por recombinações de sílabas contidas nas palavras já aprendidas). Os resultados replicaram os de estudos anteriores (com alunos que já tinham uma história académica mal-sucedida): os sujeitos aprenderam a ler as palavras de treino e passaram a apresentar leitura generalizada no decorrer do programa. A ocorrência de leitura generalizada indica que os sujeitos dominaram os mecanismos de análise e síntese envolvidos na leitura, isto é, seu comportamento textual passou a ser controlado por unidades textuais mínimas. Os dados indicam também que parece haver uma relação entre a dificuldade de aprender a ler as palavras de treino e a rapidez da generalização. Estes resultados estendem a generalidade dos efeitos do procedimento de exclusão no estabelecimento de controle de estímulos por unidades textuais mínimas para uma população ainda não exposta ao ensino formal de leitura

How digital is agriculture in a subset of countries from South America? Adoption and limitations

Digital agriculture (DA) can contribute solutions to meet an increase in healthy, nutritious, and affordable food demands in an efficient and sustainable way. South America (SA) is one of the main grain and protein producers in the world but the status of DA in the region is unknown. A systematic review and case studies from Brazil, Argentina, Uruguay, and Chile were conducted to address the following objectives: (1) quantify adoption of existing DA technologies, (2) identify limitations for DA adoption; and (3) summarise existing metrics to benchmark DA benefits. Level of DA adoption was led by Brazil and Argentina followed by Uruguay and at a slower rate, Chile. GPS guidance systems, mapping tools, mobile apps and remote sensing were the most adopted DA technologies in SA. The most reported limitations to adoption were technology cost, lack of training, limited number of companies providing services, and unclear benefits from DA. Across the case studies, there was no clear definition of DA. To mitigate some of these limitations, our findings suggest the need for a DA educational curriculum that can fulfill the demand for job skills such as data processing, analysis and interpretation. Regional efforts are needed to standardise these metrics. This will allow stakeholders to design targeted initiatives to promote DA towards sustainability of food production in the region

Maíz en baja densidad como estrategia para sortear ambientes limitantes

Frente a escenarios de alto riesgo climático y económico, la elección de la densidad de siembra en maíz tiene alto impacto en el costo del cultivo. El ajuste de la densidad de siembra en bajos niveles permite mantener un piso de rendimiento, mediante una mayor oferta de recursos por planta. El objetivo de este trabajo fue evaluar el rendimiento de híbridos de maíz con diferentes caracteres de plasticidad vegetativa y reproductiva bajo densidades de siembra contrastantes en fechas de siembra tardía en dos ambientes del oeste de la provincia de Entre Ríos.EEA ParanáFil: Maltese, Nicolás. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Paraná; ArgentinaFil: Melchiori, Ricardo Jose. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Paraná; ArgentinaFil: Kunzi, E.Y. Actividad Privada; ArgentinaFil: Modon, G. Universidad Nacional de Entre Ríos. Facultad de Ciencias Agropecuarias; ArgentinaFil: Karst, E. Universidad Nacional de Entre Ríos. Facultad de Ciencias Agropecuarias; ArgentinaFil: Novelli, Leonardo Esteban. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Paraná; Argentin

Smaller and better: The university of Michigan experience

This paper discusses several hierarchical and sequential reduction options, including Balderston's budgetary strategies and this author's curricular change options. The latter are based on data gathered in a 1979-80 survey of 46 states on patterns of program reduction. Having introduced various reduction categories, the paper then focuses on the institutional shrinkage process currently being implemented at the University of Michigan. Four specific strategies are being discussed: (1) across-the-board cuts, (2) reduction of nonacademic programs; (3) long-range faculty reduction procedures, and (4) program discontinuance. A host of potential problems regarding the elimination of academic programs is described. The paper concludes by providing several general recommendations for institutional shrinkage procedures.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/43589/1/11162_2004_Article_BF00992049.pd

Validation and psychometric evaluation of the Italian version of the Bergen–Yale Sex Addiction Scale

Excessive problematic sexual behavior in the form of compulsive sexual behavior disorder (CSBD), hypersexuality (HS), and sex addiction has gained increasing credibility in recent years and has led to the development of various psychometric instruments to assess such behavior. However, there is still considerable controversy over the operational definition of such concepts and whether they can be used interchangeably to describe the behavior. One recently developed tool is the Bergen–Yale Sex Addiction Scale (BYSAS) based on the “components model of addiction.” The present study validated the Italian version of the BYSAS. The BYSAS was administered to a large Italian-speaking sample of Italian adults [N = 1230, aged 18 to 67 years] along with psychometric instruments assessing the “Big Five” personality traits, self-esteem, depression, and two other measures of addictive sexual behavior (i.e., PATHOS and Shorter PROMIS Questionnaire–Sex Subscale). Confirmatory factorial analysis supported a one-factor solution. Furthermore, the scale had good internal consistency (Cronbach’s α = 0.787). The BYSAS was positively associated with extroversion, openness to experience, depression, and problematic sexual behavior, and negatively associated with self-esteem, conscientiousness, emotional stability, agreeableness, and age. Based on the findings, the BYSAS is a brief, psychometrically reliable and valid measure for assessing sex addiction among Italian adults

Parametrization of Born-Infeld Type Phantom Dark Energy Model

Applying the parametrization of dark energy density, we can construct directly independent-model potentials. In Born-Infeld type phantom dark energy model, we consider four special parametrization equation of state parameter. The evolutive behavior of dark energy density with respect to red-shift $z$, potentials with respect to $\phi$ and $z$ are shown mathematically. Moreover, we investigate the effect of parameter $\eta$ upon the evolution of the constructed potential with respect to $z$. These results show that the evolutive behavior of constructed Born-Infeld type dark energy model is quite different from those of the other models.Comment: 5 pages, 4 figures, Accepted for publication in Astrophysics & Space Scienc

Could Only Fermions Be Elementary?

In standard Poincare and anti de Sitter SO(2,3) invariant theories, antiparticles are related to negative energy solutions of covariant equations while independent positive energy unitary irreducible representations (UIRs) of the symmetry group are used for describing both a particle and its antiparticle. Such an approach cannot be applied in de Sitter SO(1,4) invariant theory. We argue that it would be more natural to require that (*) one UIR should describe a particle and its antiparticle simultaneously. This would automatically explain the existence of antiparticles and show that a particle and its antiparticle are different states of the same object. If (*) is adopted then among the above groups only the SO(1,4) one can be a candidate for constructing elementary particle theory. It is shown that UIRs of the SO(1,4) group can be interpreted in the framework of (*) and cannot be interpreted in the standard way. By quantizing such UIRs and requiring that the energy should be positive in the Poincare approximation, we conclude that i) elementary particles can be only fermions. It is also shown that ii) C invariance is not exact even in the free massive theory and iii) elementary particles cannot be neutral. This gives a natural explanation of the fact that all observed neutral states are bosons.Comment: The paper is considerably revised and the following results are added: in the SO(1,4) invariant theory i) the C invariance is not exact even for free massive particles; ii) neutral particles cannot be elementar