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‣ Estrutura latitudinal e temporal de assembleias de cnidários bentônicos em placas de recrutamento em dois portos da costa brasileira; Latitudinal and temporal structure of benthic cnidarians assemblages on recruitment panels in two harbors of the Brazilian coast

Fernandez, Marina de Oliveira
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 28/01/2013 Português
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Diferentes escalas espaciais, nas quais diferentes fatores variam, podem ser importantes em estudos da biodiversidade. Estrutura e dinâmica de comunidades marinhas epifaunais variam com a latitude, mas como essa variação muda ao longo do tempo é pouco estudada. Investigamos como a estrutura de assembleias de cnidários bentônicos em portos varia temporalmente em uma latitude tropical e uma subtropical e devido a fatores locais. No Brasil, estudamos recrutamento ao longo de quatro trimestres em duas áreas portuárias (Pecém a 3°32′S e Ilhabela a 23°46′S), e ao longo de dois anos em Ilhabela. Verificamos que (1) a riqueza de espécies segue o gradiente latitudinal, com assembleias de cnidários bentônicos mais ricas no Pecém, o local mais tropical; (2) a composição das assembleias varia muito ao longo do tempo, mas é mais constante na latitude tropical e parece ser uma consequência de maior variação sazonal da temperatura na latitude subtropical; (3) as abundâncias dos membros das assembleias de Ilhabela não são sazonalmente definidas; (4) cada local possui diferentes táxons que são mais importantes na estrutura da assembleia; (5) as assembleias em Ilhabela estão estruturadas conforme o microhabitat...

‣ The formal equations of the low latitude lower ionosphere and their applications

Zamlutti,Carlos José
Fonte: Sociedade Brasileira de Geofísica Publicador: Sociedade Brasileira de Geofísica
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/06/2005 Português
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The work presents two applications of the formal equations governing the behavior of the low latitude lower ionosphere comprised into a unique set. This set can be used for modeling purposes as well as to help the interpretation of most of the phenomena related to equatorial and low latitude dynamics. Furthermore coupling processes can also be analyzed combining ion transport and ion molecule chemistry to explain the connection between the circulation of the lower and upper portions of the range 100-200 km of altitude. Here the uses and interpretation of these equations to explain some controversial and intriguing questions as to the behavior of phenomena like sporadic E and intermediate layers are explored. It is shown, in particular, that the proposed set of equations is quite convenient in this respect.

‣ The influence of non-isothermal electrons and neutral wind structures on the doppler properties of vertical m-size field-aligned irregularities in the low latitude E-region

St.-Maurice,Jean-Pierre; Choudhary,Raj Kumar
Fonte: Sociedade Brasileira de Geofísica Publicador: Sociedade Brasileira de Geofísica
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/01/2007 Português
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Meter size irregularities are routinely studied with radars in the equatorial and low latitude regions. In both instances echoes from the E-region (90 to 120 km altitude) are a common occurrence. The resulting echoes are labeled as so-called Type I or Type II according to their spectral signature. In this paper we show that the phase velocity of Type I echoes increases with decreasing altitude owing to thermal feedback effects taking place in the growth process. We also show that Type II echoes can be influenced by atmospheric neutral winds to the point of revealing the presence of Kelvin- Helmholtz billows, as shown by a recently studied example taken from the Gadanki radar in India.

‣ Relationship between Latitude and Melanoma in Italy

Crocetti, Emanuele; Buzzoni, Carlotta; Chiarugi, Alessandra; Nardini, Paolo; Pimpinelli, Nicola
Fonte: International Scholarly Research Network Publicador: International Scholarly Research Network
Tipo: Artigo de Revista Científica
Publicado em 16/01/2012 Português
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Objective. Evaluate the ecological relationship between skin melanoma epidemiology and latitude in Italy. Methods. We used data from the Italian network of cancer registries (Airtum). In a Poisson model, we evaluated the effect on incidence, mortality, and survival of latitude, adjusting for some demographic, social, phenotypic, and behavioural variables. Results. Incidence increased in Italy by 17% for each degree of increase in latitude. The effect of latitude was statistically significantly present also adjusting for other variables (incidence rate ratio = 1.08). The effect of latitude on increasing mortality (mortality rate ratio = 1.27) and improving survival (relative excess risk of death = 0.93) was no longer present in the multivariate model. Conclusion. Melanoma incidence, mortality, and survival vary in Italy according to latitude. After adjustment for several confounders, incidence still grows with growing latitude. Presumably, latitude expresses other variables that might be related to individual susceptibility and/or local care.

‣ Preference and Performance in Plant–Herbivore Interactions across Latitude–A Study in U.S. Atlantic Salt Marshes

Ho, Chuan-Kai; Pennings, Steven C.
Fonte: Public Library of Science Publicador: Public Library of Science
Tipo: Artigo de Revista Científica
Publicado em 22/03/2013 Português
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High-latitude plants are often more palatable to herbivores than low-latitude conspecifics. Does increased plant palatability lead to better herbivore performance? Our field and laboratory work investigated (A) whether high-latitude plants have traits indicating that they should be higher-quality foods for herbivores; (B) whether geographic differences in plant quality are more important than local adaptation of herbivores. We studied 3 plant species and 6 invertebrate herbivores in U.S. Atlantic Coast. Past studies had shown high-latitude individuals of these plants are more palatable than low-latitude conspecifics. We documented plant traits and herbivore performance (body size) in the field across latitude. We collected individuals from different latitudes for factorial (plant region x herbivore region) laboratory experiments, examining how herbivore performance was affected by plant region, herbivore region, and their interaction (i.e., local adaptation). Field surveys suggested high-latitude plants were likely of higher quality to herbivores. Leaf nitrogen content in all plant species increased toward high latitudes, consistent with lower leaf C/N and higher leaf chlorophyll content at high latitudes. Furthermore, leaf toughness decreased toward higher latitudes in 1 species. The body size of 4 herbivore species increased with latitude...

‣ Latitude, sunshine, and human lactase phenotype distributions may contribute to geographic patterns of modern disease: the inflammatory bowel disease model

Szilagyi, Andrew; Leighton, Henry; Burstein, Barry; Xue, Xiaoqing
Fonte: Dove Medical Press Publicador: Dove Medical Press
Tipo: Artigo de Revista Científica
Publicado em 27/05/2014 Português
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Countries with high lactase nonpersistence (LNP) or low lactase persistence (LP) populations have lower rates of some “western” diseases, mimicking the effects of sunshine and latitude. Inflammatory bowel disease (IBD), ie, Crohn’s disease and ulcerative colitis, is putatively also influenced by sunshine. Recent availability of worldwide IBD rates and lactase distributions allows more extensive comparisons. The aim of this study was to evaluate the extent to which modern day lactase distributions interact with latitude, sunshine exposure, and IBD rates. National IBD rates, national distributions of LP/LNP, and population-weighted average national annual ultraviolet B exposure were obtained, estimated, or calculated from the literature. Negative binomial analysis was used to assess the relationship between the three parameters and IBD rates. Analyses for 55 countries were grouped in three geographic domains, ie, global, Europe, and non-Europe. In Europe, both latitude and ultraviolet B exposure correlate well with LP/LNP and IBD. In non-Europe, latitude and ultraviolet B exposure correlate weakly with LP/LNP, but the latter retains a more robust correlation with IBD. In univariate analysis, latitude, ultraviolet B exposure, and LP/LNP all had significant relationships with IBD. Multivariate analysis showed that lactase distributions provided the best model of fit for IBD. The model of IBD reveals the evolutionary effects of the human lactase divide...

‣ Análise e comparaçao dos resultados de observaçoes obtidas com teodolitos Wild T-2 e T-4 para determinaçao da latitude astronômica de segunda ordem

Campos, Milton de Azevedo; Hatschbach, Fernando
Fonte: Universidade Federal do Paraná Publicador: Universidade Federal do Paraná
Tipo: Dissertação Formato: 126 p.; application/pdf
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Resumos em portugues e ingles; Orientador: Fernando Hatschbach; Dissertaçao (mestrado) -Universidade Federal do Paraná. Curso de Pós-Graduaçao em Ciencias Geodésicas; Resumo: Esta dissertação trata da comparação e analise dos resultados obtidos em determinações, a nível de segunda ordem, realizadas com equipamentos específicos para observações de 2ª ordem (teodolito com leitura direta de 1") e específicos para observações de 1ª ordem (teodolito com leitura direta de 0,1"), procurando verificar se há ou não conveniência em se utilizar equipamento mais sofisticado do que o necessário, quando se dispõe de toda a gama de teodolitos, em determinações com precisão adrede estabelecida. O autor pretendia, a princípio, realizar observações para a determinação do meridiano astronômico (pelo método de Estrelas Próximas ou em Elongação), da hora local (pelo método de Zinger) e da latitude astronômica (pelo método de Horrebow-Talcott simplificado, conhecido no Brasil por método de Sterneck), porém, devido às condições atmosféricas adversas em Curitiba (dez noites úteis em cento e um dias), restringiu as observações somente para a determinação da latitude astronômica.; Abstract: This essay deals with the comparison and analysis of results obtained in second order accuracy determinations...

‣ Characterizing the effects of latitude and freeze-thaw treatment on culturable soil bacterial communities: Can ice-nucleating bacteria be preferentially recovered?

Xu, John
Fonte: Quens University Publicador: Quens University
Tipo: Tese de Doutorado Formato: 22576640 bytes; application/msword
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Cycles of freezing and thawing are among the most challenging environmental stresses for bacteria. Certain strains of bacteria actively induce the freezing of water at high subzero temperatures. The adaptive function of bacterial ice-nucleation is unclear, and the theory that it could confer freeze-tolerance is not well tested. Soils at higher latitudes in North America may undergo a greater number of freeze-thaw cycles. And while there is evidence that certain strains of ice-nucleating bacteria could be ubiquitously dispersed, the increased freeze-thaw stress at higher latitudes may select for freeze-tolerance traits. This study aimed to determine whether culturable bacterial community size varies with latitude, whether freeze-thaw selection differentially affects culturable community sizes across latitudes, and whether freeze-thaw selection preferentially selects for ice-nucleating bacteria. Freeze-thaw treatment decreased viabilities of culturable bacterial communities, but did not appear to result in the preferential recovery of ice-nucleating bacteria. Bacterial communities sampled from different latitudes varied in freeze-thaw tolerance, with no latitudinal trend, suggesting site-specific resilience due to other factors. Comparisons of colony morphologies suggest that culturable soil communities change after freeze-thaw treatment...

‣ The high prevalence of vitamin D insufficiency across Australian populations is only partly explained by season and latitude

van der Mei, Ingrid A F; Ponsonby, Anne-Louise; Engelsen, Ola; Pasco, Julie A; McGrath, John J; Eyles, Daryl W; Blizzard, Leigh; Dwyer, Terence; Lucas, Robyn; Jones, Graeme
Fonte: Universidade Nacional da Austrália Publicador: Universidade Nacional da Austrália
Tipo: Journal article; Published Version Formato: 8 pages
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BACKGROUND: Inadequate sun exposure and dietary vitamin D intake can result in vitamin D insufficiency. However, limited data are available on actual vitamin D status and predictors in healthy individuals in different regions and by season. METHODS: We compared vitamin D status [25-hydroxyvitamin D ; 25(OH) D] in people < 60 years of age using data from cross-sectional studies of three regions across Australia: southeast Queensland (27°S ; 167 females and 211 males) , Geelong region (38°S ; 561 females) , and Tasmania (43°S ; 432 females and 298 males) . RESULTS: The prevalence of vitamin D insufficiency (≤ 50 nmol/L) in women in winter/spring was 40.5% in southeast Queensland, 37.4% in the Geelong region, and 67.3% in Tasmania. Season, simulated maximum daily duration of vitamin D synthesis, and vitamin D effective daily dose each explained around 14% of the variation in 25(OH) D. Although latitude explained only 3.9% of the variation, a decrease in average 25(OH) D of 1.0 (95% confidence interval, 0.7–1.3) nmol/L for every degree increase in latitude may be clinically relevant. In some months, we found a high insufficiency or even deficiency when sun exposure protection would be recommended on the basis of the simulated ultraviolet index. CONCLUSION: Vitamin D insufficiency is common over a wide latitude range in Australia. Season appears to be more important than latitude...

‣ Ecologic analysis of some immune-related disorders, including type 1 diabetes, in Australia: latitude, regional ultraviolet radiation, and disease prevalence

Staples, Judith A; Ponsonby, Anne-Louise; Lim, Lynette; McMichael, Anthony
Fonte: Universidade Nacional da Austrália Publicador: Universidade Nacional da Austrália
Tipo: Journal article; Published Version Formato: 6 pages
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The apparent immune-suppressive effect of ultraviolet radiation (UVR) has suggested that this environmental exposure may influence the development of immune-related disorders. Self-reported prevalence rates of type 1 diabetes mellitus, rheumatoid arthritis (RA) , eczema/dermatitis, and asthma, from the 1995 Australian National Health Survey, were therefore examined by latitude and ambient level of UVR. A positive association of type 1 diabetes mellitus prevalence was found with both increasing southern latitude of residence (r = 0.77 ; p = 0.026) and decreasing regional annual ambient UVR (r = -0.80 ; p = 0.018) ; a 3-fold increase in prevalence from the northernmost region to the southernmost region was evident. In contrast, asthma correlated negatively with latitude (r = -0.72 ; p = 0.046) , although the change in asthma prevalence from the north to the south of Australia was only 0.7-fold. For both RA and eczema/dermatitis, there were no statistically significant associations between latitude/UVR and disease prevalence. These ecologic data provide some support for a previously proposed beneficial effect of UVR on T-helper 1-mediated autoimmune disorders such as type 1 diabetes. The inverse association of type 1 diabetes prevalence with UVR is consistent with that previously reported for another autoimmune disease...

‣ Interstation correlation of high-latitude lower-stratosphere gravity wave activity: Evidence for planetary wave modulation of gravity waves over Antarctica

Innis, J.; Klekociuk, A.; Vincent, R.
Fonte: Amer Geophysical Union Publicador: Amer Geophysical Union
Tipo: Artigo de Revista Científica
Publicado em //2004 Português
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Four years of operational radiosonde balloon flights, from three Australian stations in eastern Antarctica (Casey, 66.3°S, 110.0°E; Davis, 68.6°S, 78.0°E; and Mawson, 67.6°S, 62.9°E) are analyzed to derive lower-stratosphere (12–20 km altitude) gravity wave information from perturbations in wind and temperature. Gravity wave activity and seasonal behavior was found to be similar to that seen in earlier studies from Antarctica. Interstation comparisons of zonal wind and gravity wave activity showed very high correlations throughout the entire data set, between Mawson and Davis stations (∼600 km distant), with a lag near 0.5 days. The correlations between Casey and Davis (1400 km apart) were lower but still significant, with a lag near 1 day. There is no significant correlation between stratospheric gravity wave activity and surface winds. Our results suggest a pattern of winds and waves moving eastward over the stations with a speed near 15 m s−1. As this is comparable to planetary wave speeds, we interpret our results as being evidence for a significant planetary wave–induced modulation of the zonal wind and the gravity wave field, although we are unable to identify the mechanism by which this operates. Our work suggests that the high-latitude lower-stratosphere gravity wave fields are relatively uniform on spatial scales of 500–1000 km and on timescales of around 0.5–1 days.; Innis...

‣ An archaic crested plesiosaur in opal from the Lower Cretaceous high-latitude deposits of Australia

Kear, B.; Schroeder, N.; Lee, M.
Fonte: The Royal Society Publicador: The Royal Society
Tipo: Artigo de Revista Científica
Publicado em //2006 Português
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Umoonasaurus demoscyllus gen. et sp. nov. is a new small-bodied (approx. 2.5m) pliosauroid plesiosaur from the Lower Cretaceous (Aptian–Albian) of southern Australia. It is represented by several partial skeletons (one with a near complete skull is the most complete opalized vertebrate fossil yet known), and is unique in having large crests on the skull midline and above the orbits. Umoonasaurus is surprisingly archaic despite its relatively late age (approx. 115Myr ago)—being simultaneously the most basal (primitive) and last surviving rhomaleosaurid. Notably, it lacks the ‘pliosauromorph’ features (large head, short neck, gigantism) typically characterizing many more derived Jurassic rhomaleosaurids; thus, reinforcing the suspected convergent evolution of the ‘pliosauromorph’ hypercarnivore body plan. Umoonasaurus inhabited an Early Cretaceous high-latitude (approx. 70°S) inland seaway subject to seasonally near-freezing climatic conditions. This extreme environment supported a diverse range of plesiosaur taxa, suggesting that these marine reptiles might have possessed adaptations (e.g. heightened metabolic levels) to cope with cold-water temperatures. Indeed, survival of ancient endemic lineages such as Umoonasaurus is a common phenomenon in Australian Cretaceous vertebrate assemblages and might have been facilitated by isolation in low-temperature high-latitude regions.; Benjamin P. Kear...

‣ Electrodynamics of the low-latitude ionosphere

Riley, Peter
Fonte: Universidade Rice Publicador: Universidade Rice
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We have undertaken a study of the low and mid latitude ionospheric electric field pattern, during both magnetospherically quiet and active periods. Our analysis can be conveniently split into two parts. i.In an effort to study the penetration of magnetospheric electric fields to low latitudes, we have compared Jicamarca F-region vertical drifts for 10 radar-observation periods with the auroral boundary index (ABI). The ABI is the latitude of the equatorward edge of the diffuse aurora at local midnight, as estimated from precipitating-electron fluxes measured from DMSP spacecraft. The periods occurred in the interval January 1984 to June 1991 inclusive and each lasted between 2 and 5 days. We focus on periods that occurred in September 1986, March 1990, and June 1991. In the post-midnight sector, where we expect the penetration to be strongest, we found many examples of correlation; specifically, associated with an ionospheric updraft (implying an eastward electric field) is a strong poleward motion of the auroral boundary. However, we also found a significant number of cases where there was little or no correlation. We conclude that there is only mediocre agreement between the observed Sudden Postmidnight Ionospheric Events (SPIEs) and the ABI. These SPIEs have also been compared with other magnetospheric parameters...

‣ Seismic-stratigraphic analysis of shelf-margin delta/slope fan and basin floor fan on high-latitude and middle-latitude margins (Ross Sea, Weddell Sea and Alabama/West Florida shelf): Paleoclimatic and eustatic implications

Bart, Philip John
Fonte: Universidade Rice Publicador: Universidade Rice
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This dissertation consists of three chapters describing seismic stratigraphic studies in three very different continental margin settings. The first chapter discusses the northwestern Ross Sea, the second discusses the southeastern Weddell Sea and the third discusses the Alabama/west Florida margin. The purpose was to investigate stratigraphic relationships between deposition during glacial periods (i.e., eustatic lowstands) and interglacial periods (i.e., eustatic highstands) on high-latitude and low-latitude margins. The high-latitude Antarctic margin is of particular interest because it is over-deepened and surrounds a continent that is free of melt-water. Because of these factors, the shelf/shelf-edge were not subaerially exposed and fluvially incised during eustatic lowstands. Seismic-stratigraphic analysis of the southeastern Weddell and northwestern Ross Sea margins shows that sediments were sequestered in pre-existing glacial troughs or upper-slope fans, at the mouth of glacial troughs. Locations of trough fans and trough mouth fans were strongly controlled by the location of ice streams. This point-source component of stratal architecture contrasts with the implicit line-source assumption that dominates recent thinking of Antarctic stratal development. Point-sourced trough mouth fans are relatively stable features...

‣ A comparison of high-latitude ionospheric propagation predictions from Advanced Prophet 4.0 with measured data

Gikas, Stefanos S.
Fonte: Monterey, California: Naval Postgraduate School Publicador: Monterey, California: Naval Postgraduate School
Tipo: Tese de Doutorado Formato: ix, 81 p. ill.
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Approved for public release; distribution is unlimited.; Progress in computers during the past two decades has sparked the development of many useful high frequency (HF) ionospheric propagation prediction codes. The high-latitude (polar) ionosphere still remains as the most difficult propagation region to predict. A 'Non centric database of collected high-latitude signal and noise measurements was obtained during 1988 and 1989 by the University of Leicester, UK The Advanced Prophet 4.0 HF Ionospheric Propagation Prediction Code was exercised and compared to a portion of the 'Non centric database, for a transmitter at Clyde River, Canada and a receiver at Leicester, U.K. The Prophet predictions were better during winter months than during summer months. Overall, 70% of the signal strength data from Prophet 4.0 were between -20 dB and +20 dB error, compared to the measured data.; Lieutenant, Hellenic Navy

‣ A comparison of high-latitude ionosphere propagation predicitions from AMBCOM with measured data

Wilson, David J.
Fonte: Monterey, California. Naval Postgraduate School Publicador: Monterey, California. Naval Postgraduate School
Tipo: Tese de Doutorado Formato: 104 p.
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Approved for public release; distribution is unlimited.; This thesis examines the performance of SRI's Ambient Communications (AMBCOM) model for high latitude propagation prediction. It is one in a series of studies, conducted at the Naval Postgraduate School, to establish the relative merits of several computer-based propagation prediction models using a standard set of measured data. AMBCOM modeled the propagation path between a transmitter located in the polar cap region and several midlatitude receiver sites. Model predictions were matched to measured data obtained during two high- latitude communication experiments (campaigns). The absolute difference between model signal-to-noise ratio (SNR) and measured SNR was considered as error. Error statistics were accumulated to show the distribution of the error by campaign and frequency. The percentage, by frequency, of matched AMBCOM predictions in reference to total predictions for a given frequency was considered a measure of AMBCOM performance. AMBCOM exhibited small absolute values of average error, i.e., 7-11 dB, and high percentages of matched records. The average error was typically distributed between -20 and +20 dB. Unfortunately, these are only relative measures of model performance. The site antenna and environmental data used to model high latitude campaigns were estimated not measured...

‣ Influence of altitude, latitude and season of collection (Bergmann's Rule) on the dimensions of Lutzomyia intermedia (Lutz & Neiva, 1912) (diptera, psychodidae, phlebotominae)

Marcondes,Carlos Brisola; Lozovei,Ana Leuch; Falqueto,Aloisio; Brazil,Reginaldo P; Galati,EAB; Aguiar,GM; Souza,NA
Fonte: Instituto Oswaldo Cruz, Ministério da Saúde Publicador: Instituto Oswaldo Cruz, Ministério da Saúde
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/09/1999 Português
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The influence of altitude and latitude on some structure sizes of Lutzomyia intermedia was noted; several structures of insects collected in higher localities were greater, according to Bergmann's rule. This influence was more remarkable in two localities of the State of Espírito Santo, probably due to greater differences in altitude. Comparing insects from different latitudes, more differences were noted in comparisons of insects from low altitude localities than in those of material from higher altitudes. The small number of differences between insects collected in July and in December does not indicate a defined influence of season and temperature on the size of adults. The possible epidemiological implications of these variations are discussed.

‣ Seasonal variation in suicidal deaths in Chile: Its relationship to latitude

Valeria, Claudio; Medina, Bárbara; Heerlein, Andrés
Fonte: KARGER Publicador: KARGER
Tipo: Artículo de revista
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Background: Studies in the northern and southern hemispheres consistently identified seasonal influences on monthly and semester suicide distribution. The variations of sunlight exposure in zones of increasing latitude has been suggested as one of the most plausible explanations for this phenomenon. Some recent studies in the northern hemisphere could not find seasonal asymmetries of suicides. The current study examines the monthly, seasonal and semester distribution of suicidal deaths in Chile and the influence of seasons in zones of low latitude as compared with regions of high or very high latitude, trying to determine if a seasonal pattern still exists in a country of the southern hemisphere. Methods: Monthly, seasonal and semester suicidal data over the period 1995-1999 were examined for the whole sample and for gender-specific subgroups in Chile. Four different latitudinal zones were analyzed separately, in order to investigate the effect of the photoperiod on suicide distribution. Results were analyzed by chi(2) tests for multinomials, as an overall measure of deviation. Results: We found a significant unimodal springtime peak for both genders in the global territory. Among the 4,710 male and 829 female suicides reported in this period there were no gender differences in the seasonal pattern of suicidal deaths. When divided into four different latitudinal zones...

‣ Variação da aceleração da gravidade com a latitude e altitude; Variation of the gravity acceleration with the latitude and altitude

Lopes, Wilson; USJT - São Paulo
Fonte: Imprensa Universitária - UFSC Publicador: Imprensa Universitária - UFSC
Tipo: info:eu-repo/semantics/article; info:eu-repo/semantics/publishedVersion; Formato: application/pdf
Publicado em 08/01/2009 Português
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http://dx.doi.org/10.5007/2175-7941.2008v25n3p561Propõe-se, neste trabalho, uma equação para o módulo do vetor aceleração da gravidade, variando com a latitude e altitude. Para essa finalidade, foram usados os seguintes valores para a aceleração da gravidade, ao nível do mar: no equador, g0 = 9,7803 m/s2 e, na latitude de 450, gP = 9,8062 m/s2. O perfil terrestre foi assumido como sendo um elipsóide de revolução, achatado nos pólos, e a aceleração da gravidade variando com a altitude, em relação ao nível do mar, foi considerada também dependente da latitude.; The propose of this work is an equation for the module of the acceleration vector of the gravity, varying with the latitude and altitude. For this purpose, the following values of the gravity acceleration were used, at the sea level: in the equator, g0 = 9,7803 m/s2, and in the latitude of 450, gP = 9,8062 m/s2. The terrestrial profile were assumed as being a revolution ellipsoid, flattened in the poles, and the acceleration of the gravity varying with the altitude, at sea level, was considered dependent of the latitude too.

‣ A comparison of two cases of low-latitude thundersnow

DOLIF NETO,G.; MARKET,P. S.; BECKER,A. E.; PETTEGREW,B.; MELICK,C.; SCHULTZ,C.; BUCKLEY,P. I.; CLARK,J. V.; LUPO,A. R.; HOLLE,R.; DEMETRIADES,N.; BARBIERI,C. E.
Fonte: Centro de Ciencias de la Atmósfera, UNAM Publicador: Centro de Ciencias de la Atmósfera, UNAM
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/07/2009 Português
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Two cases of low-latitude snow with lightning are studied to determine their characteristics. Both cases had synoptic-scale origins, but also featured smaller-scale influences (e. g. orographic lift and elevated instability). The first event occurred in the Southern Hemisphere and was a late winter case that developed under the influence of underlying orography. Lightning was plentiful in that event (94 cloud-to-ground flashes in the region), but snow accumulations were not significant. Lightning flashes of negative polarity dominated this case, with a mean peak amplitude of -43.2 kA. The second event was a Northern Hemisphere case of elevated convection, with frontogenesis beneath an extended layer of potential instability. Appreciable lightning occurred with this event as well (706 cloud-to-ground flashes in the region), and snow accumulations were significant over a broad area. Lightning flashes of negative polarity dominated this case also, with a mean peak amplitude of -23.7 kA. Each of these events is worthy of further scrutiny, as studies of such storms do not appear often in the literature. Indeed, such warm, subtropical regions are often unprepared for the effects of just a little snow or ice accumulation. Future forecasters can anticipate better such anomalous events by looking for these broad features: 1) significant and well-defined synoptic-scale weather systems at low latitudes...