V-substituted In2S3: an intermediate band material with photocatalytic activity in the whole visible light range

We proposed in our previous work V-substituted In2S3 as an intermediate band (IB) material able to enhance the efficiency of photovoltaic cells by combining two photons to achieve a higher energy electron excitation, much like natural photosynthesis. Here this hyper-doped material is tested in a photocatalytic reaction using wavelength-controlled light. The results evidence its ability to use photons with wavelengths of up to 750 nm, i.e. with energy significantly lower than the bandgap (=2.0 eV) of non-substituted In2S3, driving with them the photocatalytic reaction at rates comparable to those of non-substituted In2S3 in its photoactivity range (λ ≤ 650 nm). Photoluminescence spectra evidence that the same bandgap excitation as in V-free In2S3 occurs in V-substituted In2S3 upon illumination with photons in the same sub-bandgap energy range which is effective in photocatalysis, and its linear dependence on light intensity proves that this is not due to a nonlinear optical property. This evidences for the first time that a two-photon process can be active in photocatalysis in a single-phase material. Quantum calculations using GW-type many-body perturbation theory suggest that the new band introduced in the In2S3 gap by V insertion is located closer to the conduction band than to the valence band, so that hot carriers produced by the two-photon process would be of electron type; they also show that the absorption coefficients of both transitions involving the IB are of significant and similar magnitude. The results imply that V-substituted In2S3, besides being photocatalytically active in the whole visible light range (a property which could be used for the production of solar fuels), could make possible photovoltaic cells of improved efficiency.

Reflectancia multiespectral (visible e inferarrojo cercano) y composición de las cromitas. Datos preliminares

Se aborda por primera vez la relación entre el espectro VNIR de reflectancia especular y los parámetros composicionales del grupo de las espinelas, particularmente cromita

Optoelectronic property analysis of MCrO4 (M=Ba, Sr) with a response to visible light irradiation

Ternary MCrO4 (M = Ba, Sr) semiconductors are materials with a variety of photocatalyst and optoelectronic applications. We present detailed microscopic analyses based on first principles of the structure, the electronic properties and the optical absorption in which the difference between symmetrically non-equivalent atoms has been considered. The high absorption coefficients of these materials are split into chemical species contributions in accordance with the symmetry. The high optical absorption in these materials is mainly because of the Cr–O inter-species transitions.

Optical images of visible and invisible percepts in the primary visual cortex of primates

We optically imaged a visual masking illusion in primary visual cortex (area V-1) of rhesus monkeys to ask whether activity in the early visual system more closely reflects the physical stimulus or the generated percept. Visual illusions can be a powerful way to address this question because they have the benefit of dissociating the stimulus from perception. We used an illusion in which a flickering target (a bar oriented in visual space) is rendered invisible by two counter-phase flickering bars, called masks, which flank and abut the target. The target and masks, when shown separately, each generated correlated activity on the surface of the cortex. During the illusory condition, however, optical signals generated in the cortex by the target disappeared although the image of the masks persisted. The optical image thus was correlated with perception but not with the physical stimulus.

Chronic morphine induces visible changes in the morphology of mesolimbic dopamine neurons.

The mesolimbic dopamine system, which arises in the ventral tegmental area (VTA), is an important neural substrate for opiate reinforcement and addiction. Chronic exposure to opiates is known to produce biochemical adaptations in this brain region. We now show that these adaptations are associated with structural changes in VTA dopamine neurons. Individual VTA neurons in paraformaldehyde-fixed brain sections from control or morphine-treated rats were injected with the fluorescent dye Lucifer yellow. The identity of the injected cells as dopaminergic or nondopaminergic was determined by immunohistochemical labeling of the sections for tyrosine hydroxylase. Chronic morphine treatment resulted in a mean approximately 25% reduction in the area and perimeter of VTA dopamine neurons. This reduction in cell size was prevented by concomitant treatment of rats with naltrexone, an opioid receptor antagonist, as well as by intra-VTA infusion of brain-derived neurotrophic factor. In contrast, chronic morphine treatment did not alter the size of nondopaminergic neurons in the VTA, nor did it affect the total number of dopaminergic neurons in this brain region. The results of these studies provide direct evidence for structural alterations in VTA dopamine neurons as a consequence of chronic opiate exposure, which could contribute to changes in mesolimbic dopamine function associated with addiction.

Action spectra for phytochrome A- and B-specific photoinduction of seed germination in Arabidopsis thaliana.

We have examined the seed germination in Arabidopsis thaliana of wild type (wt), and phytochrome A (PhyA)- and B (PhyB)-mutants in terms of incubation time and environmental light effects. Seed germination of the wt and PhyA-null mutant (phyA) was photoreversibly regulated by red and far-red lights of 10-1,000 micromol m-2 when incubated in darkness for 1-14 hr, but no germination occurred in PhyB-null mutant (phyB). When wt seeds and the phyB mutant seeds were incubated in darkness for 48 hr, they synthesized PhyA during dark incubation and germinated upon exposure to red light of 1-100 nmol m-2 and far-red light of 0.5-10 micromol m-2, whereas the phyA mutant showed no such response. The results indicate that the seed germination is regulated by PhyA and PhyB but not by other phytochromes, and the effects of PhyA and PhyB are separable in this assay. We determined action spectra separately for PhyA- and PhyB-specific induction of seed germination at Okazaki large spectrograph. Action spectra for the PhyA response show that monochromatic 300-780 nm lights of very low fluence induced the germination, and this induction was not photoreversible in the range examined. Action spectra for the PhyB response show that germination was photoreversibly regulated by alternate irradiations with light of 0.01-1 mmol m-2 at wavelengths of 540-690 nm and 695-780 nm. The present work clearly demonstrated that PhyA photoirreversibly triggers the germination upon irradiations with ultraviolet, visible and far-red light of very low fluence, while PhyB controls the photoreversible effects of low fluence.

Electrically Tunable Selective Reflection of Light from Ultraviolet to Visible and Infrared by Heliconical Cholesterics

Acknowledgements This work was supported by NSF DMR-1410378 and DMR-1121288. We thank V. Borshch for helping with preparation of illustrations, to Y. K. Kim for the help in experiments, V. A. Belyakov and S. V. Shiyanovskii for useful discussions.

Small Town America Under the “Lights:” Contemporary Images of Rural America in the Series Friday Night Lights

Author: Heather K. Smith Title: Small Town America Under the “Lights:” Contemporary Images of Rural America in the Series Friday Night Lights Advisor: Rodney Buxton Degree Date: August 2015 ABSTRACT What is Small Town America? The answer to this varies based on a person’s experiences. This is not always from real-world exposure, but often vicariously through television. For some, television is the only opportunity to create a perception for such areas. For others, television could reinforce or sway their perceptions of Small Town America. Therefore, a comprehension of the identity for Small Town America broadcasted through the small screen is important. This research utilized the theory of semiotics to analyze cinematography and mise-en-scene in the opening credits of Friday Night Lights to unearth the themes and overarching ideology for Small Town America conveyed by the series. A modern depiction of rural America that played on considered “traditional values” arose. Unexpectedly, the research also unveiled the inability for an “authentic” or cohesive identity for Small Town America, or any person, location or group for that matter, to exist.

El desarrollo del pensamiento visible en la enseñanza de la Historia en alumnos de Magisterio

Se trata de una propuesta didáctica basada en el diseño de nuevas estrategias de enseñanza y aprendizaje, consistente en la elaboración de una programación de la asignatura de Didáctica de las Ciencias Sociales: Historia, en la que la teoría y la práctica están totalmente integradas de manera que la realización de la práctica suponga un avance más eficaz en el conocimiento y aprendizaje teórico. Para ello se ha utilizado una metodología activa, fundamentada en el desarrollo del pensamiento visible, en dónde el alumno es el sujeto sobre el que descansa toda la responsabilidad de su propio aprendizaje, pero siempre bajo la supervisión y colaboración del docente. También se ha incluido una batería de cuestiones sobre la docencia en la enseñanza de la Historia que inducen a la reflexión y al debate. De igual manera se ha modificado el modelo de evaluación, de forma que ésta sea formativa, no sumativa, y en la que el alumnado demuestra no solo su conocimiento, sino su saber hacer utilizando una gran variedad de instrumentos que le facilitan su planteamiento didáctico como futuro docente y su capacidad para ser consciente de su propio pensamiento, haciéndolo más visible para él mismo y para los demás.

Relative Concerns on Visible Consumption: A Source of Economic Distortions

Do relative concerns on visible consumption give rise to economic distortions? We re-examine the question posited by Arrow and Dasgupta (2009) building upon their general framework but recognizing that relative concerns can only apply to visible goods (e.g., cars, clothing, jewelry) and that households consume both visible and non-visible goods. Contrary to Arrow and Dasgupta (2009), the answer to this question turns to be always affirmative: the competitive equilibrium will always be different than the socially optimal one, since individuals do not take into account the negative externality they exert on others through the consumption of the visible good, while the social planner does. If one invokes separability assumptions, then the steady state competitive equilibrium consumption of non-visible goods will be strictly lower than the socially optimal one.

The ‘Visible Hand’ of the ECB’s Quantitative Easing. CEPS Working Document No. 407/May 2015

Quantitative easing à la ECB has produced so far an impact on long-term nominal rates through ex ante channels: signalling channels, term duration channels, and risk premia channels. The term duration channel will also lead to a lengthening of the average maturity of government debts, with possible implications for fiscal policy. The ECB’s determination to buy government bonds in a fragmented market with a low net supply may also produce an ex post impact, during the actual asset purchases, but less on nominal rates and more on financial plumbing, as recent volatility suggests. As the effects of scarce supply in collateral markets are felt, repo rates remain well below zero. Lower supply and limited re-usability of high quality collateral, capped by regulatory requirements, is a constraint on market liquidity and compresses dealers’ balance sheets. By keeping a depressed yield curve and asset prices high, QE may also accelerate the consolidation of both traditional and capital-market based (dealer) bank business models. What is less clear is how these changing business models will interact with the sharp rise of the asset management industry in the aftermath of the crisis, which raises questions about the implications for global collateral flows and deposit-like funding channels.

Implementazione di sistemi per visible light communication su Raspberry Pi

Grazie all'enorme sviluppo dei LED, le comunicazioni tramite luce visibile stanno acquisendo sempre maggiore importanza. Obiettivo di questa tesi è implementare su schede a basso costo (come Rasperry Pi) un sistema di trasmissione e ricezione basato appunto sulla visible light communication. Dopo un primo tentativo di trasferire il codice OpenVLC, sviluppato dal centro di ricerca spagnolo IMDEA Network, su Rasperry Pi, si è deciso di intraprendere una nuova strada e si è implementato un trasmettitore VLC in Simulink di Matlab e una prima bozza di ricevitore che sfrutta la SPI (serial-parallel interface). I primi risultati mostrano il corretto funzionamento del sistema anche se con data rate molto basse. Sviluppi futuri prevederanno l'ottimizzazione del sistema.