bluuebunny/crossref_metadata_2025 huggingface dataset:
A Recurrent Solution of PH/M/c/N-Like and PH/M/c-Like Queues
Authors: Brandwajn Alexandre , Begin Thomas
Published: March 2012

We propose an efficient semi-numerical approach to compute the steady-state probability distribution for the number of requests at arbitrary and at arrival time instants in PH/M/c-like systems with homogeneous servers in which the inter-arrival time distribution is represented by an acyclic set of memoryless phases. Our method is based on conditional probabilities and results in a simple computationally stable recurrence. It avoids the explicit manipulation of potentially large matrices and involves no iteration. Owing to the use of conditional probabilities, it delays the onset of numerical issues related to floating-point underflow as the number of servers and/or phases increases. For generalized Coxian distributions, the computational complexity of the proposed approach grows linearly with the number of phases in the distribution.
A Fourier Approach for the Level Crossings of Shot Noise Processes with Jumps
Authors: Biermé Hermine , Desolneux Agnès
Published: March 2012

We use a change-of-variable formula in the framework of functions of bounded variation to derive an explicit formula for the Fourier transform of the level crossing function of shot noise processes with jumps. We illustrate the result in some examples and give some applications. In particular, it allows us to study the asymptotic behavior of the mean number of level crossings as the intensity of the Poisson point process of the shot noise process goes to infinity.
Optimal Control with Absolutely Continuous Strategies for Spectrally Negative Lévy Processes
Authors: Kyprianou Andreas E. , Loeffen Ronnie , Pérez José-Luis
Published: March 2012

In the last few years there has been renewed interest in the classical control problem of de Finetti (1957) for the case where the underlying source of randomness is a spectrally negative Lévy process. In particular, a significant step forward was made by Loeffen (2008), who showed that a natural and very general condition on the underlying Lévy process which allows one to proceed with the analysis of the associated Hamilton-Jacobi-Bellman equation is that its Lévy measure is absolutely continuous, having completely monotone density. In this paper we consider de Finetti's control problem, but with the restriction that control strategies are absolutely continuous with respect to the Lebesgue measure. This problem has been considered by Asmussen and Taksar (1997), Jeanblanc-Picqué and Shiryaev (1995), and Boguslavskaya (2006) in the diffusive case, and Gerber and Shiu (2006) for the case of a Cramér-Lundberg process with exponentially distributed jumps. We show the robustness of the condition that the underlying Lévy measure has a completely monotone density and establish an explicit optimal strategy for this case that envelopes the aforementioned existing results. The explicit optimal strategy in question is the so-called refraction strategy.
Motor axon exit from the mammalian spinal cord is controlled by the homeodomain protein Nkx2.9 via Robo-Slit signaling
Authors: Bravo-Ambrosio Arlene , Mastick Grant , Kaprielian Zaven
Published: March 2012

Mammalian motor circuits control voluntary movements by transmitting signals from the central nervous system (CNS) to muscle targets. To form these circuits, motor neurons (MNs) must extend their axons out of the CNS. Although exit from the CNS is an indispensable phase of motor axon pathfinding, the underlying molecular mechanisms remain obscure. Here, we present the first identification of a genetic pathway that regulates motor axon exit from the vertebrate spinal cord, utilizing spinal accessory motor neurons (SACMNs) as a model system. SACMNs are a homogeneous population of spinal MNs with axons that leave the CNS through a discrete lateral exit point (LEP) and can be visualized by the expression of the cell surface protein BEN. We show that the homeodomain transcription factor Nkx2.9 is selectively required for SACMN axon exit and identify the Robo2 guidance receptor as a likely downstream effector of Nkx2.9; loss of Nkx2.9 leads to a reduction in Robo2 mRNA and protein within SACMNs and SACMN axons fail to exit the spinal cord in Robo2-deficient mice. Consistent with short-range interactions between Robo2 and Slit ligands regulating SACMN axon exit, Robo2-expressing SACMN axons normally navigate through LEP-associated Slits as they emerge from the spinal cord, and fail to exit in Slit-deficient mice. Our studies support the view that Nkx2.9 controls SACMN axon exit from the mammalian spinal cord by regulating Robo-Slit signaling.
Neurula rotation determines left-right asymmetry in ascidian tadpole larvae
Authors: Nishide Kazuhiko , Mugitani Michio , Kumano Gaku , Nishida Hiroki
Published: March 2012

Tadpole larvae of the ascidian Halocynthia roretzi show morphological left-right asymmetry. The tail invariably bends towards the left side within the vitelline membrane. The structure of the larval brain is remarkably asymmetric. nodal, a conserved gene that shows left-sided expression, is also expressed on the left side in H. roretzi but in the epidermis unlike in vertebrates. We show that nodal signaling at the late neurula stage is required for stereotypic morphological left-right asymmetry at later stages. We uncover a novel mechanism to break embryonic symmetry, in which rotation of whole embryos provides the initial cue for left-sided expression of nodal. Two hours prior to the onset of nodal expression, the neurula embryo rotates along the anterior-posterior axis in a counterclockwise direction when seen in posterior view, and then this rotation stops when the left side of the embryo is oriented downwards. It is likely that epidermis monocilia, which appear at the neurula rotation stage, generate the driving force for the rotation. When the embryo lies on the left side, protrusion of the neural fold physically prevents it from rotating further. Experiments in which neurula rotation is perturbed by various means, including centrifugation and sandwiching between glass, indicate that contact of the left epidermis with the vitelline membrane as a consequence of neurula rotation promotes nodal expression in the left epidermis. We suggest that chemical, and not mechanical, signals from the vitelline membrane promote nodal expression. Neurula rotation is also conserved in other ascidian species.
XenopusNanos1 is required to prevent endoderm gene expression and apoptosis in primordial germ cells
Authors: Lai Fangfang , Singh Amar , King Mary Lou
Published: March 2012

Nanos is expressed in multipotent cells, stem cells and primordial germ cells (PGCs) of organisms as diverse as jellyfish and humans. It functions together with Pumilio to translationally repress targeted mRNAs. Here we show by loss-of-function experiments that Xenopus Nanos1 is required to preserve PGC fate. Morpholino knockdown of maternal Nanos1 resulted in a striking decrease in PGCs and a loss of germ cells from the gonads. Lineage tracing and TUNEL staining reveal that Nanos1-deficient PGCs fail to migrate out of the endoderm. They appear to undergo apoptosis rather than convert to normal endoderm. Whereas normal PGCs do not become transcriptionally active until neurula, Nanos1-depleted PGCs prematurely exhibit a hyperphosphorylated RNA polymerase II C-terminal domain at the midblastula transition. Furthermore, they inappropriately express somatic genes characteristic of endoderm regulated by maternal VegT, including Xsox17α, Bix4, Mixer, GATA4 and Edd. We further demonstrate that Pumilio specifically binds VegT RNA in vitro and represses, along with Nanos1, VegT translation within PGCs. Repressed VegT RNA in wild-type PGCs is significantly less stable than VegT in Nanos1-depleted PGCs. Our data indicate that maternal VegT RNA is an authentic target of Nanos1/Pumilio translational repression. We propose that Nanos1 functions to translationally repress RNAs that normally specify endoderm and promote apoptosis, thus preserving the germline.
Wiring through tunneling nanotubes – from electrical signals to organelle transfer
Authors: Abounit Saïda , Zurzolo Chiara
Published: March 2012

Tunneling nanotubes (TNTs) represent a subset of F-actin-based transient tubular connections that allow direct communication between distant cells. Recent studies have provided new insights into the existence of TNTs in vivo, and this novel mechanism of intercellular communication is implicated in various essential processes, such as development, immunity, tissue regeneration and transmission of electrical signals. TNTs are versatile structures known to facilitate the transfer of various cargos, such as organelles, plasma membrane components, pathogens and Ca2+. Recently, a new function of TNTs in the long-range transfer of electrical signals that involves gap junctions has been suggested. This indicates that different types of TNTs might exist, and supports the notion that TNTs might not be just passive open conduits but rather are regulated by gating mechanisms. Furthermore, TNTs have been found in different cell lines and are characterized by their diversity in terms of morphology. Here we discuss these novel findings in the context of the two models that have been proposed for TNT formation, and focus on putative proteins that could represent TNT specific markers. We also shed some light on the molecular mechanisms used by TNTs to transfer cargos, as well as chemical and electrical signals.
The microtubule poison vinorelbine kills cells independently of mitotic arrest and targets cells lacking the APC tumour suppressor more effectively
Authors: Klotz Daniel M. , Nelson Scott A. , Kroboth Karin , Newton Ian P. , Radulescu Sorina , Ridgway Rachel A. , Sansom Owen J. , Appleton Paul L. , Näthke Inke S.
Published: March 2012

Colorectal cancers commonly carry truncation mutations in the adenomatous polyposis coli (APC) gene. The APC protein contributes to the stabilization of microtubules. Consistently, microtubules in cells lacking APC depolymerize more readily in response to microtubule-destabilizing drugs. This raises the possibility that such agents are suitable for treatment of APC-deficient cancers. However, APC-deficient cells have a compromised spindle assembly checkpoint, which renders them less sensitive to killing by microtubule poisons whose toxicity relies on the induction of prolonged mitotic arrest. Here, we describe the novel discovery that the clinically used microtubule-depolymerizing drug vinorelbine (Navelbine) kills APC-deficient cells in culture and in intestinal tissue more effectively than it kills wild-type cells. This is due to the ability of vinorelbine to kill cells in interphase independently of mitotic arrest. Consistent with a role for p53 in cell death in interphase, depletion of p53 renders cells less sensitive to vinorelbine, but only in the presence of wild-type APC. The pro-apoptotic protein BIM (also known as BCL2L11) is recruited to mitochondria in response to vinorelbine, where it can inhibit the anti-apoptotic protein BCL2, suggesting that BIM mediates vinorelbine-induced cell death. This recruitment of BIM is enhanced in cells lacking APC. Consistently, BIM depletion dampens the selective effect of vinorelbine on these cells. Our findings reveal that vinorelbine is a potential therapeutic agent for colorectal cancer, but they also illustrate the importance of the APC tumour suppressor status when predicting therapeutic efficacy.
Kinetochores accelerate centrosome separation to ensure faithful chromosome segregation
Authors: Mchedlishvili Nunu , Wieser Samuel , Holtackers René , Mouysset Julien , Belwal Mukta , Amaro Ana C. , Meraldi Patrick
Published: March 2012

At the onset of mitosis, cells need to break down their nuclear envelope, form a bipolar spindle and attach the chromosomes to microtubules via kinetochores. Previous studies have shown that spindle bipolarization can occur either before or after nuclear envelope breakdown. In the latter case, early kinetochore–microtubule attachments generate pushing forces that accelerate centrosome separation. However, until now, the physiological relevance of this prometaphase kinetochore pushing force was unknown. We investigated the depletion phenotype of the kinetochore protein CENP-L, which we find to be essential for the stability of kinetochore microtubules, for a homogenous poleward microtubule flux rate and for the kinetochore pushing force. Loss of this force in prometaphase not only delays centrosome separation by 5–6 minutes, it also causes massive chromosome alignment and segregation defects due to the formation of syntelic and merotelic kinetochore–microtubule attachments. By contrast, CENP-L depletion has no impact on mitotic progression in cells that have already separated their centrosomes at nuclear envelope breakdown. We propose that the kinetochore pushing force is an essential safety mechanism that favors amphitelic attachments by ensuring that spindle bipolarization occurs before the formation of the majority of kinetochore–microtubule attachments.
The Evolution of Wireless near Infrared Spectroscopy Applications in Urology and Rationale for Clinical Use
Authors: Macnab Andrew John , Shadgan Babak , Stothers Lynn
Published: March 2012

Near infrared (NIR) spectroscopy is an established non-invasive optical technique for measuring changes in haemoglobin concentration occurring in the microcirculation in real time. NIR spectroscopy parameters reflect change in tissue haemodynamics and oxygenation and can contribute important physiologic insights when used alone or interpreted in parallel with other conventional measurements. The broad use of NIR spectroscopy in research is not matched by clinical applications; reasons include limitations inherent to the technique, using instruments designed for research at the bedside, ambiguity regarding what NIR spectroscopy measures, deficiencies of early algorithms, and understandable expectations by clinicians that NIR spectroscopy data are reproducible and specific enough for clinical decision making. Such issues could be addressed by appropriate collaboration where clinicians drive the questions which NIR spectroscopy is to answer, researchers contribute to monitoring methodology, device design and data analysis/algorithms and both groups utilise physiologic knowledge and practical lessons learned from prior NIR spectroscopy studies when interpreting data. NIR spectroscopy applications in urology are recent and offer clear opportunities for clinicians and researchers to collaborate. Urology is a field where current clinical investigations are limited in terms of the physiologic information they provide and because the principal test used for evaluation of the many people who have problematic lower urinary tract dysfunction is invasive in nature. Hence the rationale for non-invasive transcutaneous optical monitoring of the bladder during voiding as, when the organ contracts, changes in oxygenated and deoxygenated haemoglobin occur which allow haemodynamic variations and alterations in oxygen supply and demand to be inferred. Different patterns of change are evident in healthy and diseased tissue; these patterns reflect the effects of physiologic events observed using NIR spectroscopy to study other tissues and provide novel insights into the causation of voiding dysfunction. This review of the evolution of a wireless methodology for bladder studies includes examples of effective clinician researcher collaboration, reveals how miniature NIR spectroscopy devices make monitoring in ambulant subjects straightforward and makes possible studies in special populations such as children and patients with spinal cord injury. Hence, such wireless devices represent an advance of relevance in urology and an opportunity to expand research in other fields and progress with translation of NIR spectroscopy into other relevant clinical arenas.
Near Infrared Brain and Muscle Oximetry: From the Discovery to Current Applications
Authors: Ferrari Marco , Quaresima Valentina
Published: March 2012

In the early 1960s, Norris introduced near infrared (NIR) spectroscopy (700–2500 nm) as an analytical technique for agricultural products. In 1977, Jöbsis founded in vivo medical NIR spectroscopy, reporting that the relatively high degree of transparency of brain tissue in the NIR spectral window (700–1000 nm) enables safe real-time non-invasive detection of regional haemoglobin oxygenation using trans-illumination spectroscopy. In order to place current medical NIR spectroscopy in its proper perspective, this review provides a snapshot of the roots of the discovery and the early years of medical NIR spectroscopy research and development. Starting in 1992, the opportunity of measuring quantitatively, by different NIR spectroscopy techniques, regional oxy-haemoglobin saturation by NIR oximetry, it is possible to monitor brain/muscle reserve capacity following tissue oxygen extraction in different pathophysiological conditions. This review reports the status of the current commercial oximeters (including wireless instrumentation) and their main clinical and physiological applications. In the last decade, NIR spectroscopy brain oximetry has obtained significant clinical relevance as suggested by the more than 10,000 instruments sold and the high number of related scientific publications. The most relevant clinical application is represented by the evaluation of cerebral oxy-haemoglobin saturation during adult cardiac surgery and cardiopulmonary bypass. Many commercial oximeters are presently available. However, their relatively poor precision and the lack of standardisation amongst the different instruments suggest that further technological advances are required before NIR spectroscopy oximetry can be adopted more widely under the “guidelines” of regulatory authorities.
Application of near Infrared Spectroscopy in Evaluating Cerebral and Muscle Haemodynamics during Exercise and Sport
Authors: Bhambhani Yagesh
Published: March 2012

Near infrared (NIR) spectroscopy is a non-invasive optical technique that has been used to evaluate cerebral and muscle haemodynamic responses during exercise in situ. Its ease of use, portability, relatively low cost, along with the capability of evaluating cardiorespiratory responses simultaneously, has made it a useful technique to study exercise performance in a more holistic manner. The evidence indicates that there are systematic changes in the muscle and cerebral haemodynamic responses which are coincident with the respiratory gas exchange alterations occurring at the lactate and respiratory compensation thresholds during incremental exercise. During the Wingate (anaerobic) test, the peak oxygen uptake and degree of muscle deoxygenation is comparable to that attained during maximal incremental exercise, implying that there is a large aerobic component during a short duration of intense anaerobic exercise. Studies that have measured cerebral and muscle NIR spectroscopy simultaneously during dynamic whole body exercise support the hypotheses that at exercise intensities above the respiratory compensation threshold: (i) the accessory respiratory muscles compromise oxygen availability to the muscles directly involved in exercise, thereby contributing to fatigue and (ii) there is a systematic decline in cerebral oxygenation until exercise is terminated, thereby supporting the possibility of a supraspinal component to fatigue. Research pertaining to the application of NIR spectroscopy on cerebral and muscle haemodynamics under hypoxic conditions has indicated that the reductions in maximal exercise and aerobic capacity cannot be explained solely on the basis of these acute changes. Additionally, the improvements in maximal and submaximal exercise performance subsequent to endurance, interval and simulated hypoxic training programmes can occur independently of any alterations in cerebral and muscle haemodynamics. Wireless NIR spectroscopy is a useful technique to evaluate sport performance in the field setting and will evolve as an important method for designing and implementing training methods for this purpose.
Time-Domain Broadband near Infrared Spectroscopy of the Female Breast: A Focused Review from Basic Principles to Future Perspectives
Authors: Pifferi Antonio , Farina Andrea , Torricelli Alessandro , Quarto Giovanna , Cubeddu Rinaldo , Taroni Paola
Published: March 2012

A review of near infrared (NIR) spectroscopy of the female breast performed using time domain broadband systems is presented, summarising the key studies performed at Politecnico di Milano. The time domain approach, based on pulsed tunable lasers and single-photon detection, makes it possible to uncouple absorption from scattering contributions and to derive tissue optical properties in vivo non-invasively. The basic tissue absorbers in the 600–1100 nm range are discussed, together with the interpretation of the scattering spectra. Inter- and intra-subject variations in breast optical properties are addressed based on in vivo measurements on different women and on the same subject as a function of the menstrual cycle phase and of the measurement geometry. Results demonstrate that a specific breast type can be identified for each woman, ultimately related to the water, lipid and collagen content and to the scattering properties. As an example of the application of spectroscopy-derived information, we discuss the non-invasive optical detection of breast density as an important risk factor for breast cancer, envisaging an attractive contribution of NIR spectroscopy to the fight against breast cancer on both a medical diagnostics and research level.
Enforcement Costs: Some Humanitarian Alternatives to Stronger Patent Rights
Authors: Trotter Andrew
Published: March 2012

Diseases that cause comparatively few problems in developed countries kill millions of people in the Third World each year. In many cases, people die because they cannot afford the medication needed to save their lives. In others, there are simply no drugs available because there are no wealthy western patients to justify pharmaceutical companies investing in a cure. This reveals a deep-seated problem within the patent system and the pharmaceutical industry that emphasises markets and profits at the expense of health and global welfare. Global efforts have seen substantial improvements in access to medicines in isolated areas, but with international agreements driving towards stronger patent protection and the expiry date for the TRIPS grace period fast approaching, it is time to consider alternatives which will allow the patent system to work for the humanitarian cause rather than against it. This paper considers two such problems in the patent system and pharmaceutical industry – prohibitive pricing and misdirected incentives – to offer a mode of regulation and enforcement that will support both a viable pharmaceutical industry and the human right to health and medication.
The Productivity of Information Technology Investments: New Evidence from IT Labor Data
Authors: Tambe Prasanna , Hitt Lorin M.
Published: March 2012

This paper uses newly collected panel data that allow for significant improvements in the measurement and modeling of information technology (IT) productivity to address some longstanding empirical limitations in the IT business value literature. First, we show that using generalized method of moments–based estimators to account for the endogeneity of IT spending produces coefficient estimates that are only about 10% lower than unadjusted estimates, suggesting that the effects of endogeneity on IT productivity estimates may be relatively small. Second, analysis of the expanded panel suggests that (a) IT returns are substantially lower in midsize firms than in Fortune 500 firms; (b) they materialize more slowly in large firms—in midsize firms, unlike in larger firms, the short-run contribution of IT to output is similar to the long-run output contribution; and (c) the measured marginal product of IT spending is higher from 2000 to 2006 than in any previous period, suggesting that firms, and especially large firms, have been continuing to develop new, valuable IT-enabled business process innovations. Furthermore, we show that the productivity of IT investments is higher in manufacturing sectors and that our productivity results are robust to controls for IT labor quality and outsourcing levels.
Wundermittel Medien? Medienbeziehungen der britischen und deutschen Militärführung in der ersten Hälfte des 20. Jahrhunderts
Authors: Götter Christian
Published: March 2012

Zu Beginn des 20. Jahrhunderts entwickelten die Militärs in Deutschland und Großbritannien ihre Medienstrategien von einem stark auf die Medien reagierenden Ansatz hin zur Umsetzung eigener, aktiver Ziele. Dazu gehörte der Versuch, ganze Bevölkerungen in ihrem Denken und Handeln zu beeinflussen. Derartige Ziele wurden in der Folge gerade dann als machbar eingestuft, wenn militärische Situationen aussichtslos schienen. Beispiele hierfür bilden unbewegliche Fronten im Ersten Weltkrieg ebenso wie die militärische Schwäche Großbritanniens im Vergleich zur Sowjetunion im beginnenden Kalten Krieg. Wann immer jedoch begrenzte Ressourcen die Militärs vor die Entscheidung zwischen Medienstrategien und etablierten militärischen Vorgehensweisen stellten, entschieden sie sich für die Letzteren.
Nachrichten aus der Forschung
Authors: Sabanci Zeynep , Detering Nicolas , Töppel Roman , Ziemann Benjamin , Bresselau von Bressensdorf Agnes
Published: March 2012

Zeynep Sabancı: Ottoman Military Technology and Armaments Policy (1870-1918)

Nicolas Detering: "Populäre Kriegslyrik im Ersten Weltkrieg". Bericht des Studientages des Deutschen Volksliedarchivs in Zusammenarbeit mit der School of Language & Literature des Freiburg Institute for Advanced Studies (FRIAS), 4. bis 5. März 2011 in Freiburg

Roman Töppel: "Kolloquium zur Geschichte der Waffen-SS". Tagung des Deutschen Komitees für die Geschichte des Zweiten Weltkrieges und des Instituts für Geschichte der Universität Würzburg, 6. bis 7. Mai 2011 in Würzburg

Benjamin Ziemann: "Unthinking the Imaginary War. Intellectual Reflections of the Nuclear Age, 1945-1990". Internationale Tagung am Deutschen Historischen Institut London, 4. bis 6. November 2010

Agnes Bresselau von Bressensdorf: "Der KSZE-Prozess. Internationale Politik und gesellschaftliche Transformation (1975-1989/90)". Tagung des Instituts für Zeitgeschichte in München, 21. bis 23. Oktober 2010
Variations of serum testosterone levels in prostate cancer patients under LH-releasing hormone therapy: an open question
Authors: Reis Leonardo Oliveira
Published: March 2012

The hypothesis ‘the lower the better when achieving castration levels of testosterone’ is based on the data from second-line hormonal manipulation and its molecular basis, and on better oncological results reported for lower castration levels in prostate cancer (PCa) patients, including those achieved with maximal androgen blockade. In this regard, the equivalence of surgical and different pharmacological castrations has been controversial. The modified amino acid structure that makes LH-releasing hormone (LHRH) analogs more potent than LHRH, and the method of delivering the analogs impacts on bioavailibility and potentially causes differences in androgen levels and in its final oncological efficacy. In addition to this, there is a myriad of circumstances, such as those related to ethnic variations and co-morbidities, which uniquely impact on the pharmacological approach in a highly heterogeneous population of castration-resistant prostate cancer (CRPC) patients. Ineffective testosterone suppression through hormonal escape is currently poorly recognized and may result in increased PCa mortality. Until now, the optimal serum testosterone level in patients under castration, and the impact of its variations in patients under LHRH therapy, remain open questions and have been merged to a broad spectra of patients who are highly heterogeneous. This heterogeneity relates to a number of mechanisms regarding response to treatment, which influences the biology of the relapsing tumor and the sensitivity to subsequent therapies in the individual patient. The rationale to achieve testosterone levels below 20–50 ng/dl warrant further investigation as these levels have recently rescued CRPC patients. In the last few years and months, important advancements in prostate cancer treatment have been achieved. Nevertheless, these advances are measured in a few months of additional survival and under high costs, not available to most of the world population, compared with the benefits of hormonal manipulation that are measured in years, there is a huge potential for accessible and durable effect expansion and optimization of treatment, particularly with the current tendency of a more individual approach.
Desmatamento no sul do estado de Roraima: padrões de distribuição em função de projetos de assentamento do INCRA e da distância das principais rodovias (BR-174 e BR-210)
Authors: Barni Paulo Eduardo , Fearnside Philip Martin , Graça Paulo Maurício L. de A.
Published: March 2012

O desmatamento na Amazônia representa, atualmente, um dos principais problemas ambientais do Brasil. A contenção deste processo requer políticas públicas baseadas no entendimento das forças que controlam, aceleram e desaceleram a perda de floresta. Para avaliar ocorrências de desmatamento no sul do Estado de Roraima foram utilizados dois buffers de 20 km de largura subdivididos em oito faixas de 2500 metros ao longo das duas principais rodovias da região: BR-174 e BR-210 em um ambiente de Sistema de Informações Geográficas - SIG. O período analisado foi entre 2001 e 2007, sendo utilizados dados de desmatamento do PRODES e análises visuais em imagens TM Landsat 5. Também foram utilizados arquivos shapefile da malha viária e de Projetos de Assentamento (PAs) do Sul do Estado de Roraima, junto com observações de campo. Os resultados mostraram que os desmatamentos do período estão fortemente relacionados com a disponibilidade de estradas e com o número de famílias dentro dos PAs. O desmatamento foi maior na área da BR-210 pela presença na região de grandes proprietários e invasões de terras. O pólo madeireiro, situado à margem da BR-174, pode ter influenciado na formação de pequenas áreas de desmatamento na região de Rorainópolis. A exploração madeireira predatória e novas ocupações de terras estão acontecendo de forma rápida e desordenada. Este quadro indica forte potencial para a perda de floresta em Roraima caso o fluxo de migração para esta área aumentar, como seria esperado se Roraima for conectada ao "Arco do Desmatamento" pela reabertura da Rodovia BR-319, ligando Manaus a Porto Velho.
Análise do potencial de imagem TerraSAR-X para mapeamento temático no sudoeste da Amazônia brasileira
Authors: Garcia César Edwin , Santos João Roberto dos , Mura José Claudio , Kux Hermann Johann Henrich
Published: March 2012

O presente trabalho tem como objetivo analisar o potencial de imagens SAR polarimétricas do sensor TerraSAR-X, no modo StripMap, para mapear o uso e cobertura da terra na região sudoeste da Amazônia brasileira. No procedimento metodológico imagens de amplitude nas polarizações A HH e A VV, A derivada da matriz de covariância, bem como da entropia A Entropia derivada da decomposição de alvos por auto-valores fizeram parte, de forma individual ou combinada, do conjunto de dados investigados. Na classificação das imagens foram empregados dois classificadores: um baseado nas funções estatísticas de máxima verossimilhança (MAXVER); e outro, o método contextual (Context). Os resultados temáticos dessas classificações foram avaliados através da matriz de confusão e pelo índice Kappa. De forma sintetizada pode-se afirmar que as componentes A e A Entropia, têm significativa contribuição no procedimento classificatório, sobretudo pelo método Context, cujo desempenho alcançou com 78% de exatidão global e índice Kappa de 0,70.
Os Hesperiidae (Lepidoptera, Hesperioidea) da RPPN Klagesi, Santo Antônio do Tauá, Pará, Brasil: nova contribuição para o conhecimento da biodiversidade da área de endemismo Belém
Authors: Mielke Olaf H. H. , Carneiro Eduardo , Casagrande Mirna M.
Published: March 2012

Embora a região Belém seja uma das áreas mais exploradas da Amazônia com coletas desde o século XVIII, grande parte das informações se encontra dispersa em coleções internacionais, o que dificulta a reunião de dados e interpretações biogeográficas. Visando ampliar o conhecimento da fauna de lepidópteros da região, o presente estudo levantou uma lista de 225 espécies de Hesperiidae encontradas na RPPN Klagesi durante aproximadamente 24 anos de amostragens esporádicas, embora mais freqüentemente na última década. São adicionadas 113 espécies previamente não relacionadas para a região, a qual passa a ser a área de maior riqueza conhecida de Hesperiidae dentre todas as regiões de endemismo da Amazônia brasileira até então inventariadas. No entanto, o conhecimento da diversidade de Hesperiidae em outras áreas de endemismo é tão restrito, que a riqueza de espécies deve ser utilizada apenas como indicador de esforço amostral ao invés de inferências biogeográficas. Três das regiões de endemismo ainda não apresentam nenhum inventário de fauna (Xingú, Napo e Imeri), enquanto as demais são reconhecidas por um ou poucos inventários. Portanto, para que a lepidopterofauna amazônica seja realmente conhecida e utilizada em estudos de biogeografia e conservação, são necessários esforços direcionados nestas regiões ainda totalmente desconhecidas ou mesmo a reunião de informações sobre coletas já realizadas, cujo material se encontra disperso em coleções pelo mundo.
Distribuição de mercúrio total em sedimentos da plataforma continental Amazônica: Brasil
Authors: Siqueira Gilmar W. , Aprile Fabio M.
Published: March 2012

Este estudo foi desenvolvido na Plataforma Continental do Amazonas (PCA) com o objetivo de determinar os níveis de Hg total no sedimento de fundo, e assim contribuir como matriz ambiental indicadora para o plano geral de gerenciamento costeiro na região norte do Brasil. Foram amostrados 20 pontos entre maio e junho dos anos de 1999 a 2002, 2005 e 2007. Os resultados indicam não haver evidências de atividades antrópicas relacionadas à contaminação de mercúrio na região. Os teores encontrados variaram entre 0,047 e 0,166 mg kg-1 com média 0,085±0,026 mg kg-1, estando dentro do intervalo de "background" referido para os rios amazônicos não contaminados, que é de 0,05 a 0,28 mg kg-1. As concentrações de Hg no sedimento, especialmente no sedimento lamoso, mostraram uma estreita dependência com os teores de argila (material fino) e matéria orgânica, corroborando mecanismos geoquímicos importantes na dinâmica do metal. A maior adsorção do mercúrio pode estar associada ao aumento dos teores de compostos (óxidos e hidróxidos) de ferro, alumínio, manganês e os minerais primários e secundários formadores das rochas da bacia de drenagem amazônica.
Qualidade da castanha-do-brasil do comércio de Rio Branco, Acre
Authors: Álvares Virgínia de Souza , Castro Izabela Miranda de , Costa David Aquino da , Lima Angélica Costa de , Madruga Ailson Luiz Sudan
Published: March 2012

Este trabalho teve como objetivo avaliar a qualidade de castanhas-do-brasil beneficiadas e comercializadas em Rio Branco, Acre. Foram analisadas amostras das três marcas de castanha encontradas no mercado local quanto às variáveis: atividade de água, teor de umidade, contagem total de fungos filamentosos, quantificação de Aspergillus flavus e de A. parasiticus, bem como quantificação de aflatoxinas B1, B2, G1 e G2. As castanhas do comércio se encontravam com um teor de umidade e atividade de água adequados, o que pode ter sido responsável pela baixa contaminação por fungos e por aflatoxinas. Quanto a estas micotoxinas, as amostras estão de acordo com o recomendado pela Anvisa, podendo ser esta uma consequência da grande divulgação no Estado do uso de Boas Práticas no manejo da castanha.
Síntese do piperonal a partir do óleo essencial de pimenta longa (Piper hispidinervium C. DC.)
Authors: Cremasco Marco Aurélio , Braga Nazareno de Pina
Published: March 2012

O óleo essencial de pimenta longa (Piper hispidinervum C. DC) é rico em safrol, tornando-o suscetível à reação de isomerização para a obtenção de cis, trans-isosafrol. O presente artigo apresenta a etapa de eletroxidação dos isômeros cis, trans-isosafrol advindos da isomerização direta do óleo essencial de pimenta longa, apresentando 99,7% de conversão em isosafrol glicol, o qual é sujeito à oxidação com conversão de 99% em piperonal, este apresentando 84,9% de pureza.
Heparina e K3EDTA como anticoagulantes para tambaqui (Colossoma macropomum Cuvier, 1816)
Authors: Pádua Santiago Benites de , Pilarski Fabiana , Sakabe Róberson , Dias-Neto José , Chagas Edsandra Campos , Ishikawa Márcia Mayumi
Published: March 2012

Este estudo avaliou a eficácia da heparina sódica e do EDTA tripotássico como anticoagulantes e seus efeitos sobre os parâmetros hematológicos de tambaqui (Colossoma macropomum). Foram utilizados dez indivíduos de tambaqui com médias de 384,9 ± 85,71 g de peso e 27,90 ± 2,10 cm de comprimento total para avaliação da heparina 5.000 UI e 100 UI, bem como do K3EDTA 10%. Foram analisados a inibição da coagulação por 10 h, eritrograma e teste de fragilidade osmótica dos eritrócitos. Os resultados foram submetidos à análise de variância e as médias comparadas pelo teste de Tukey (P < 0,05). Heparina 5000 UI, heparina 100 UI e K3EDTA 10% foram eficazes na prevenção da coagulação por mais de 10 h, no entanto o EDTA tripotássico causou hemólise desde os primeiros momentos. No eritrograma não foi observada diferença (P > 0,05) na contagem de eritrócitos, hematócrito, taxa de hemoglobina e CHCM, no entanto, houve aumento do VCM (P < 0,05) nas amostras acondicionados com K3EDTA 10%. Este anticoagulante causou incremento (P < 0,01) na fragilidade osmótica dos eritrócitos quando comparado com a heparina pura, heparina diluída, e grupo controle. A utilização da heparina como anticoagulante é mais apropriada para tambaqui (Colossoma macropomum), visto que foi eficiente na prevenção da coagulação por mais de 10 h, sem ocasionar hemólise, ou alterações nos parâmetros hematológicos e na fragilidade osmótica dos eritrócitos.
Record of the freshwater stingrays Potamotrygon brachyura and P. motoro (Chondrichthyes, Potamotrygonidae) in the lower Uruguay river, South America
Authors: Oddone María Cristina , Velasco Gonzalo , Charvet Patricia
Published: March 2012

Freshwater stingrays, or potamotrygonids, are restricted to Neotropical river drainages. These elasmobranchs are well adapted to freshwater environments and the number of described species gradually increases as further research is carried out. Some of the first studies on their systematics and natural history were carried out in the 1960s and 1970s in southern South America. However, there is no new published data on potamotrygonids from Uruguayan waters since then (except for local journal reports from sportive fishermen and specimens deposited in Uruguayan collections). The present study aims to record the recent occurrence of two species of potamotrygonids caught by sport fishermen, with comments on other published historical records for the same area. As many other elasmobranchs, these species have an important, but not always well understood, role in the Uruguayan rivers ecosystems.
Dos nuevas especies del grupo Drosophila onychophora (Diptera, Drosophilidae) en los bosques de Polylepis de Papallacta, Pichincha, Ecuador
Authors: Figuero María Luna , Rafael Violeta
Published: March 2012

A pesar de ser un país relativamente pequeño, Ecuador tiene una gran variedad de ecosistemas que han favorecido altos niveles de especiación. Uno de estos ecosistemas es el bosque de Polylepis. En estos bosques existe una gran diversidad de plantas, como las asteráceas (compuestas), cuyas flores hospedan una plétora de insectos, entre los que se encuentran las especies del grupo Drosophila onychophora. En este estudio, describimos dos nuevas especies de Drosophila recolectadas en un parche de bosque de Polylepis pauta en el Páramo de Papallacta a 4000 msnm. Ambas especies pertenecen al grupo D. onychophora: Drosophila yurag sp. nov. y Drosophila yuragshina sp. nov. Las dos especies presentan edeagos alargados, este carácter es propio de especies del grupo. Morfológicamente ambas especies son muy parecidas, la manera más fácil de distinguirlas consiste en la observación de las alas.
Escore tomográfico em pacientes com fibrose cística colonizados por Pseudomonas aeruginosa ou Staphylococcus aureus
Authors: Folescu Tania Wrobel , Marques Elizabeth de Andrade , Boechat Márcia Cristina Bastos , Daltro Pedro , Higa Laurinda Yoko Shinzato , Cohen Renata Wrobel Folescu
Published: March 2012

OBJETIVO: Comparar achados de TCAR em pacientes com fibrose cística (FC) colonizados cronicamente por Pseudomonas aeruginosa ou Staphylococcus aureus, empregando o escore de Bhalla modificado, e avaliar as confiabilidades intraobservador e interobservador do método. MÉTODOS: Estudo transversal retrospectivo incluindo 41 pacientes portadores de FC, 26 dos quais colonizados cronicamente por P. aeruginosa (grupo Pa) e 15 por S. aureus (grupo Sa). Dois radiologistas analisaram independentemente em duas ocasiões, as imagens de TCAR desses pacientes e aplicaram o escore de Bhalla modificado. As confiabilidades intra e interobservador foram avaliadas segundo o coeficiente de correlação intraclasse (CCI). RESULTADOS: Houve boa concordância intraobservador e interobservador (CCI > 0,8). Os resultados dos escores do grupo Pa foram mais elevados que os do grupo Sa para o observador 1 (média de 13,50 ± 3,90 e mediana de 13,5 vs. média de 5,0 ± 5,28 e mediana de 3,0) e para o observador 2 (média de 11,96 ± 5,07 e mediana de 12,0 vs. média de 5,07 ± 5,65 e mediana de 5,0). Alterações tomográficas, como bronquiectasias, espessamento das paredes brônquicas, formação de tampões mucosos, comprometimento de gerações de divisões brônquicas e padrão de atenuação em mosaico, foram mais prevalentes no grupo colonizado por P. aeruginosa. CONCLUSÕES: O escore de Bhalla modificado se mostrou reprodutível e confiável para a avaliação de TCAR e permitiu a diferenciação entre os pacientes incluídos nos dois grupos. Escores mais altos no grupo Pa evidenciaram maior comprometimento estrutural pulmonar nesse grupo.
Influenza pandêmica A (H1N1) 2009: fatores de risco para o internamento
Authors: Lenzi Luana , Mello Ângela Maron de , Silva Lineu Roberto da , Grochocki Mônica Holtz Cavichiolo , Pontarolo Roberto
Published: March 2012

OBJETIVO: Avaliar os aspectos da influenza pandêmica A (H1N1) 2009 em pacientes hospitalizados a fim de identificar os fatores de risco para o internamento e, consequentemente, para o agravamento da doença. MÉTODOS: Estudo observacional e retrospectivo realizado entre março e dezembro de 2010. Os dados foram coletados a partir do Sistema Nacional de Agravos de Notificação do Ministério da Saúde. Foram incluídos somente os pacientes hospitalizados e não hospitalizados com confirmação laboratorial da infecção durante o período de estudo. As variáveis referentes às características demográficas e clínicas foram avaliadas estatisticamente a fim de comparar as taxas de internamento na presença ou na ausência desses fatores. Os fatores de risco foram identificados por regressão logística. RESULTADOS: Foram incluídos no estudo 4.740 pacientes com confirmação laboratorial da infecção. Desses, 1.911 foram internados, e 258 (13,5%) foram a óbito. Os fatores de risco para o internamento foram idade (faixa etária de 20 a 29 anos), etnia negra ou indígena, presença de algumas comorbidades (cardiopatias, pneumopatias, nefropatias, hemoglobinopatia, imunodepressão, diabetes, obesidade, puerpério e tabagismo), número alto de comorbidades associadas, e alguns sintomas (dispneia, diarreia, vômito, dor torácica, hemoptise, pneumonia e sibilos). Níveis maiores de escolaridade e uso precoce do oseltamivir foram relacionados a fatores de proteção. A hospitalização contribuiu para o aumento da sobrevida. CONCLUSÕES: O conhecimento das características epidemiológicas que podem estar associadas a internação, gravidade da doença e mortalidade podem ser úteis na adoção de medidas preventivas e no diagnóstico e tratamento precoce da doença, colaborando para a diminuição dos óbitos e da necessidade de hospitalização.
Preditores dos desfechos do tratamento da tuberculose
Authors: Orofino Renata de Lima , Brasil Pedro Emmanuel Americano do , Trajman Anete , Schmaltz Carolina Arana Stanis , Dalcolmo Margareth , Rolla Valéria Cavalcanti
Published: March 2012

OBJETIVO: Analisar os desfechos do tratamento da tuberculose e seus preditores. MÉTODOS: Estudo longitudinal de coorte de pacientes com tuberculose tratados entre 2004 e 2006 no Instituto de Pesquisa Evandro Chagas, na cidade do Rio de Janeiro. As razões de risco ajustadas (RRa) dos preditores foram estimadas. RESULTADOS: Foram incluídos 311 pacientes. As taxas de cura, de abandono, de mortalidade e de falha terapêutica foram, respectivamente, 72%, 19%, 6% e 2%. A troca de regime terapêutico por eventos adversos foi necessária em 8%. O alcoolismo (RRa, 0,30), uso do regime estreptomicina+etambutol+ofloxacina (SEO; RRa, 0,32), infecção por HIV sem tratamento antirretroviral (TARV; RRa, 0,36) e o uso do regime rifampicina+isoniazida+pirazinamida+etambutol (RRa, 0,58) reduziram a probabilidade de cura. A faixa etária mais jovem (RRa, 3,84) e o alcoolismo (RRa, 1,76) aumentaram a probabilidade do abandono. Não foi possível determinar as RRa para os demais desfechos devido a suas baixas prevalências. Entretanto, medidas do risco relativo (RR) identificaram os seguintes potenciais preditores do óbito: uso de esquema SEO (RR, 11,43), infecção pelo HIV sem TARV (RR, 9,64), forma clínica disseminada (RR, 9,09), ausência de confirmação bacteriológica (RR, 4,00), diabetes mellitus (RR, 3,94) e comportamento homo/bissexual (RR, 2,97). A baixa renda (RR, 11,70) foi potencial preditor para falha terapêutica, ao passo que infecção pelo HIV com uso de TARV (RR, 2,46) e forma clínica disseminada (RR, 3,57) foram potenciais preditores para troca do esquema por evento adverso. CONCLUSÕES: O esquema SEO deve ser utilizado transitoriamente quando possível. Os dados confirmam a importância de TARV e sugerem a necessidade de seu início precoce.
Ventilação mecânica com baixo volume corrente e estresse oxidativo em pulmões saudáveis de camundongos
Authors: Pires Karla Maria Pereira , Melo Adriana Correa , Lanzetti Manuella , Casquilho Natália Vasconcelos , Zin Walter Araújo , Porto Luís Cristóvão , Valença Samuel Santos
Published: March 2012

OBJETIVO: A ventilação mecânica (VM) por si própria pode contribuir diretamente para a lesão pulmonar. Assim, o objetivo do presente estudo foi investigar biomarcadores precoces relacionados ao equilíbrio oxidantes/antioxidantes, estresse oxidativo e inflamação causados por VM de curta duração em pulmões de camundongos saudáveis. MÉTODOS: Vinte camundongos C57BL/6 machos foram randomicamente divididos em dois grupos: VM, submetidos a VM com baixo volume corrente (V T, 6 mL/kg) por 30 min; e respiração espontânea (RE), utilizados como controles. Amostras de homogeneizados de pulmão foram testados quanto à atividade de enzimas antioxidantes, peroxidação lipídica e expressão de TNF-α. RESULTADOS: Comparados ao grupo RE, houve uma redução significativa na atividade de superóxido dismutase (≈35%; p < 0,05) e aumento da atividade de catalase (40%; p < 0,01), glutationa peroxidase (500%; p < 0,001) e mieloperoxidase (260%; p < 0,001), ao passo que a razão glutationa reduzida/glutationa oxidada foi menor (≈50%; p < 0,05), e houve um aumento na atividade de expressão de TNF-α no grupo VM. O dano oxidativo, analisado como peroxidação lipídica, também aumentou no grupo VM (45%; p < 0.05). CONCLUSÕES: Nossos resultados demonstraram que VM de curta duração com baixa V T pode contribuir diretamente para a lesão pulmonar, gerando estresse oxidativo e inflamação em pulmões de camundongos saudáveis.