942 resultados para light feedback


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Nocturnal bees in the genus Megalopta Smith, 1853 are generally collected using artificial light sources. However, between 1993 and 2000, a total of 946 females (no males were captured) were captured using aromatic baits commonly used for orchid bees (Euglossini) in five localities in Bauru region, São Paulo, Brazil. Aromatic compounds used in bait traps were: benzyl acetate, eucalyptol, eugenol, skatole, methyl salicylate, and vanillin. The Megalopta species collected were: M. guimaraesi (71.2% of total number of specimens), M. amoena (28.1%), and M. aegis (0.6%). Using the data from these traps, we showed that there was a positive and significant correlation between the abundance of individuals and meteorological factors, rainfall and temperature. Bees were more commonly collected in the spring (September to December) and summer (December to March) than in the autumn and winter, the latter characterized for being a drier and colder period. Variations in the abundance were also detected among localities and years. The most attractive compounds were eugenol (54%), methyl salicylate (22%), and eucalyptol (16%). The ability to detect smells may have an important role in searching for flowers during dim-light conditions. We suggest the use of aromatic compounds in future studies on the biology of Megalopta in the Neotropical region.

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The Iowa State Patrol appreciates your assistance and compliance with these guidelines and laws to ensure the safety of the public and Iowa law enforcement.

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El present projecte analitza el panorama de la premsa tradicional espanyola a partir dels anys 60 fins als últims dies. El treball proposa un estudi sobre la tendència dels periòdics cap a una cultura light caracteritzada per la seva levitat i la creixent aposta per l'espectacle. Així mateix, es reflexiona sobre el grau d'importància de les relacions públiques com a fonts informatives per als mitjans de comunicació. Aquest escenari mediàtic es posa en pràctica contrastant una varietat de portades de l'ABC i El País a partir del seu primer punt de trobada.

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Immune-endocrine interplay may play a major role in the pathogenesis of endometriosis. In the present study, we have investigated the interaction between macrophage migration inhibitory factor (MIF), a major pro-inflammatory and growth-promoting factor markedly expressed in active endometriotic lesions, and estradiol (E(2)) in ectopic endometrial cells. Our data showed a significant increase of MIF protein secretion and mRNA expression in endometriotic cells in response to E(2). MIF production was blocked by Fulvestrant, an estrogen receptor (ER) antagonist, and induced by ERα and ERβ selective agonists propyl-pyrazole-triol (PPT) and diarylpropionrile (DPN), respectively, thus demonstrating a specific receptor-mediated effect. Cell transfection with MIF promoter construct showed that E(2) significantly stimulates MIF promoter activity. Interestingly, our data further revealed that MIF reciprocally stimulates aromatase protein and mRNA expression via a posttranscriptional mRNA stabilization mechanism, that E(2) itself can upregulate aromatase expression, and that inhibition of endogenous MIF, using MIF specific siRNA, significantly inhibits E(2)-induced aromatase. Thus, the present study revealed the existence of a local positive feedback loop by which estrogen acts directly on ectopic endometrial cells to upregulate the expression of MIF, which, in turn, displays the capability of inducing the expression of aromatase, the key and rate-limiting enzyme for estrogen synthesis. Such interplay may have a considerable impact on the development of endometriosis.

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Aquest treball és la culminació de les pràctiques realitzades al sincrotró ALBA. Situat a Cerdanyola del Vallès, ALBA és un accelerador de 3a generació que permet emmagatzemar un feix d'electrons confinat de fins a 400 mA a 3GeV d'energia, amb l'objectiu d'obtenir llum a partir dels girs provocats al feix. Els sincrotrons moderns com el d'ALBA, el que pretenen és aconseguir un major control i estabilitat de la llum. Per aconseguir-ho, cal que el feix d'electrons que creen la llum estigui controlat al màxim i la seva òrbita sigui estable. Amb aquest objectiu els sincrotrons estant implementant sistemes de Fast Orbit FeedBack (FOFB) o sistemes realimentats de correcció ràpida de l'òrbita, per realitzar correccions d'almenys 100Hz que estabilitzin el feix d'electrons amb menys d'un 10% de l'amplada del feix (5-10μm). El treball exposa el desenvolupament d'una part del sistema de correcció ràpida de l'òrbita dels electrons (FOFB) que s'està duent a terme al sincrotró ALBA. Concretament, s’han revisat els estudis previs realitzats durant la fase de disseny del sincrotró, s’han recalculat funcions de transferència i retards de tots els elements involucrats al sistema. També s’han realitzat simulacions per confirmar la viabilitat del sistema amb les noves dades i finalment s’ha desenvolupat part de la unitat de control determinant el Hardware i s'ha adquirit dades que permetran analitzar el soroll de l'òrbita que en futurs treballs determinaran millor l'algorisme de la unitat de control.

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We hypothesised that, during occlusion inside granular aggregates of oxide-rich soils, the light fraction organic matter would undergo a strong process of decomposition, either due to the slow process of aggregate formation and stabilisation or due to digestion in the macro- and meso-fauna guts. This process would favour the accumulation of recalcitrant materials inside aggregates. The aim of this study was to compare the dynamics and the chemical composition of free and occluded light fraction organic matter in a natural cerrado vegetation (woodland savannah) and a nearby pasture (Brachiaria spp.) to elucidate the transformations during occlusion of light fraction in aggregates of a clayey Oxisol. Nuclear Magnetic Resonance of the 13C, with Cross Polarisation and Magic Angle Spinning (13C-CPMAS-NMR), and 13C/12C isotopic ratio were combined to study organic matter composition and changes in carbon dynamics, respectively. The occluded light fraction had a slower turnover than the free light fraction and the heavy fraction. Organic matter in the occluded fraction also showed a higher degree of decomposition. The results confirm that processes of soil organic matter occlusion in the typical "very fine strong granular" structure of the studied oxide-rich soil led to an intense transformation, selectively preserving stable organic matter. The small amount of organic material stored as occluded light faction, as well as its stability, suggests that this is not an important or manageable sink for sequestration of atmospheric CO2.

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Contribution of visual and nonvisual mechanisms to spatial behavior of rats in the Morris water maze was studied with a computerized infrared tracking system, which switched off the room lights when the subject entered the inner circular area of the pool with an escape platform. Naive rats trained under light-dark conditions (L-D) found the escape platform more slowly than rats trained in permanent light (L). After group members were swapped, the L-pretrained rats found under L-D conditions the same target faster and eventually approached latencies attained during L navigation. Performance of L-D-trained rats deteriorated in permanent darkness (D) but improved with continued D training. Thus L-D navigation improves gradually by procedural learning (extrapolation of the start-target azimuth into the zero-visibility zone) but remains impaired by lack of immediate visual feedback rather than by absence of the snapshot memory of the target view.

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Phytochromes are red/far-red photosensors that regulate numerous developmental programs in plants. Among them, phytochrome A (phyA) is essential to enable seedling de-etiolation under continuous far-red (FR) light, a condition that mimics the environment under a dense canopy. The ecological relevance of this response is demonstrated by the high mortality rate of phyA mutant plants that germinate in deep vegetational shade. phyA signaling involves direct interaction of the photoreceptor with phytochrome-interacting factors PIF1 and PIF3, members of the bHLH transcription factor family. Here we investigated the involvement of PIF4 and PIF5 in phyA signaling, and found that they redundantly control de-etiolation in FR light. The pif4 pif5 double mutant is hypersensitive to low fluence rates of FR light. This phenotype is dependent on FR light perception by phyA, but does not rely on alterations in the phyA level. Our microarray analysis shows that PIF4 and PIF5 are part of an inhibitory mechanism that represses the expression of some light-responsive genes in the dark, and that they are also needed for full expression of several growth-related genes in the light. Unlike PIF1 and PIF3, PIF4 and PIF5 are not degraded in response to FR light, indicating that they are light-regulated by a different mechanism. Our genetic analysis suggests that this is achieved through sequestration of these PIFs by the closely related bHLH transcription factor HFR1 (long hypocotyl in FR light).

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CD44 is the major cell-surface receptor for hyaluronan, which is implicated in cell-cell and cell-matrix adhesion, cell migration, and signaling. Studies have shown that CD44-dependent migration requires CD44 to be shed from the cell surface and that matrix metalloproteinase-mediated cleavage may provide an underlying mechanism. However, the full spectrum of proteases that may participate in CD44 shedding has yet to be defined. In this issue, Anderegg et al. demonstrate that ADAM10, but not ADAM17 or MMP14, mediates constitutive shedding of CD44 in human melanoma cells and that knockdown of ADAM10 blocks the antiproliferative activity of the soluble proteolytic cleavage product of CD44.

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Humans spend one third of their life sleeping, then we could raise the basic question: Why do we sleep? Despite the fact that we still don't fully understand its function, we made much progress in understanding at different levels how sleep is regulated. One model suggests that sleep is regulated by two processes: a homeostatic process that tracks the need for sleep and by a circadian rhythm that determines the preferred time-of-day sleep occurs. At the molecular level circadian rhythms are a property of interlocking transcriptional regula-tors referred to as clock genes. The heterodimeric transcription factors BMAL1::CLOCK/NPAS2 drive the transcription of many target genes including the clock genes Cryptochome1 (Cry1), Cry2, Period1 (Per1), and Per2. The encoded CRY/PER proteins are transcriptional inhibitors of BMAL1::CLOCK/NPAS2 thereby providing negative feedback to their own transcription. These genes seem, however, also involved in sleep homeostasis because the brain expression of clock genes, es-pecially that of Per2, increase as a function of time-spent-awake and because mice lacking clock genes display altered sleep homeostasis. The aim of first part of my doctoral work has been to advance our understanding the link that exists between sleep homeostasis and circadian rhythms investigating a possible mechanism by which sleep deprivation could alter clock gene expression by quantifying DNA-binding of the core-clock genes BMAL1, CLOCK and NPAS2 to their target chromatin loci including the E-box enhancers of the Per2 promoter. We made use of chromatin immunoprecipitation (ChIP) and quantitative poly-merase chain reaction (qPCR) to show that DNA-binding of CLOCK and BMAL1 to their target genes changes as a function of time-of-day in both liver and cerebral cortex. We then performed a 6h sleep deprivation (SD) and observed a significant decrease in DNA-binding of CLOCK and BMAL1 to Dbp. This is consistent with a decrease in Dbp mRNA levels after SD. The DNA-binding of NPAS2 and BMAL1 to Per2 was similarly decreased following SD. However, SD has been previously shown to in-crease Per2 expression in the cortex which seems paradoxical. Our results demonstrate that sleep-wake history can affect the molecular clock machinery directly at the level of the chromatin thereby altering the cortical expression of Dbp and Per2, and likely other targets. However, the precise dy-namic relationship between DNA-binding and mRNA expression, especially for Per2, remains elusive. The second aim of my doctoral work has been to perform an in depth characterization of cir-cadian rhythmicity, sleep architecture, analyze the response to SD in full null-Per2 knock-out (Per2-/-) mice, and Per1-/- mice, as well as their double knock-out offspring (Per1,2-/-) and littermate wildtype (Wt) mice. The techniques used include locomotor activity recording by passive infrared (PIR) sen-sors, EEG/EMG surgery, recording, and analysis, and cerebral cortex extraction and quantification of mRNA levels by qPCR. Under standard LD12:12 conditions, we found that wakefulness onset, as well as the time courses of clock gene expression in the brain and corticosterone plasma levels were ad-vanced by about 2h in Per2-/- mice compared to Wt mice. When released under constant dark condi-tions almost all Per2-/- mice (97%) became arrhythmic immediately. From these observations, we conclude that while Per2-/- mice seem to be able to anticipate dark onset, this does not result from a self-sustained circadian clock. Our results suggest instead that the earlier onset of activity results from a labile, not-self sustained 22h rhythm linked to light onset suggesting the existence of a light-driven rhythm. Analyses of sleep under LD12:12 conditions revealed that in both Per2-/- and Per1,2-/- mice the same sleep phenotypes are observed compared to Wt mice: increased NREM sleep frag-mentation and inability to adequately compensate the loss of NREM sleep. That suggests a possible role of PER2 in sleep consolidation and recovery.

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The OLS estimator of the intergenerational earnings correlation is biased towards zero, while the instrumental variables estimator is biased upwards. The first of these results arises because of measurement error, while the latter rests on the presumption that the education of the parent family is an invalid instrument. We propose a panel data framework for quantifying the asymptotic biases of these estimators, as well as a mis-specification test for the IV estimator. [Author]

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An unusual case of localized amyloid light-chain (AL) amyloidosis and extramedullary plasmacytoma of the mitral valve is described. The worsening of a mitral regurgitation led to investigations and surgery. The valve presented marked distortion and thickening by type AL amyloid associated with a monotypic CD138+ immunoglobulin lambda plasma cell proliferation. Systemic staging showed a normal bone marrow and no evidence of amyloid deposition in other localizations. The patient's outcome after mitral valve replacement was excellent. To our knowledge, this is the first description of a localized AL amyloidosis as well as of a primary extramedullary plasmacytoma of the mitral valve.

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High quantum efficiency erbium doped silicon nanocluster (Si-NC:Er) light emitting diodes (LEDs) were grown by low-pressure chemical vapor deposition (LPCVD) in a complementary metal-oxide-semiconductor (CMOS) line. Erbium (Er) excitation mechanisms under direct current (DC) and bipolar pulsed electrical injection were studied in a broad range of excitation voltages and frequencies. Under DC excitation, Fowler-Nordheim tunneling of electrons is mediated by Er-related trap states and electroluminescence originates from impact excitation of Er ions. When the bipolar pulsed electrical injection is used, the electron transport and Er excitation mechanism change. Sequential injection of electrons and holes into silicon nanoclusters takes place and nonradiative energy transfer to Er ions is observed. This mechanism occurs in a range of lower driving voltages than those observed in DC and injection frequencies higher than the Er emission rate.

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The potential for application of silicon nitride-based light sources to general lighting is reported. The mechanism of current injection and transport in silicon nitride layers and silicon oxide tunnel layers is determined by electro-optical characterization of both bi- and tri-layers. It is shown that red luminescence is due to bipolar injection by direct tunneling, whereas Poole-Frenkel ionization is responsible for blue-green emission. The emission appears warm white to the eye, and the technology has potential for large-area lighting devices. A photometric study, including color rendering, color quality and luminous efficacy of radiation, measured under various AC excitation conditions, is given for a spectrum deemed promising for lighting. A correlated color temperature of 4800K was obtained using a 35% duty cycle of the AC excitation signal. Under these conditions, values for general color rendering index of 93 and luminous efficacy of radiation of 112 lm/W are demonstrated. This proof of concept demonstrates that mature silicon technology, which is extendable to lowcost, large-area lamps, can be used for general lighting purposes. Once the external quantum efficiency is improved to exceed 10%, this technique could be competitive with other energy-efficient solid-state lighting options. ©2011 Optical Society of America OCIS codes: (230.2090) Electro-optical devices; (150.2950) Illumination.