Carrier induced refractive index change observed by a whispering gallery mode shift in GaN microrods

Vertical oriented GaNmicrorods were grown by metal organic vapor phase epitaxy with four different n type carrier concentration sections above 1019 cm amp; 8722;3 along the c axis. In cathodoluminescence investigations carried out on each section of the microrod, whispering gallery modes can be observed due to the hexagonal symmetry. Comparisons of the spectral positions of the modes from each section show the presence of an energy dependent mode shift, which suggest a carrier induced refractive index change. The shift of the high energy edge of the near band edge emission points out that the band gap parameter in the analytical expression of the refractive index has to be modified. A proper adjustment of the band gap parameter explains the observed whispering gallery mode shif

Maximizing Photoluminescence Extraction in Silicon Photonic Crystal Slabs

Photonic crystal modes can be tailored for increasing light matter interactions and light extraction efficiencies. These PhC properties have been explored for improving the device performance of LEDs, solar cells and precision biosensors. Tuning the extended band structure of 2D PhC provides a means for increasing light extraction throughout a planar device. This requires careful design and fabrication of PhC with a desirable mode structure overlapping with the spectral region of emission. We show a method for predicting and maximizing light extraction from 2D photonic crystal slabs, exemplifiedby maximizing silicon photoluminescence PL . Systematically varying the lattice constant and filling factor, we predict the increases in PL intensity from band structure calculations and confirm predictions in micro PL experiments. With the near optimal design parameters of PhC, we demonstrate more than 500 fold increase in PL intensity, measured near band edge of silicon at room temperature, an enhancement by an order of magnitude more than what has been reporte

INSTRUMENTO DE COMUNICAÇÃO DA SALA DE RECUPERAÇÃO ANESTÉSICA: AVALIAÇÃO E REESTRUTURAÇÃO

The authors propose a new instrument of communication to the anesthesia recovery room, in a governmental hospital in the state of São Paulo. Their objective is to improve the assistence given to the pacient, during the post anesthesic period, in order to have a more individualized treatment. Also it proposed to help the nurses who work on the surgical unities, the nurses staff, the anesthesiologist from surgical unities. These necessities came out from a survey carried out on the nursing field, with the people above related.Os autores propõem um novo instrumento de comunicação para a Sala de Recuperação Anestésica de um hospital governamental do Estado de São Paulo com o objetivo de melhorar a assistência prestada ao paciente no pós-anestésico tornando-a cada vez mais individualizada, preenchendo assim, as necessidades das enfermeiras que atuam nas unidades cirúrgicas, equipe de enfermeiras e anestesistas do Centro Cirúrgico e Recuperação Anestésica da referida instituição. Essas necessidades foram detectadas através de trabalhos de pesquisa de campo realizados com esses elementos. A nova ficha de Recuperação Anestésica foi estruturada a partir de dados já existentes associados às conclusões obtidas nos trabalhos de pesquisa mencionados e a uma crescente evolução na prestação de cuidados ao paciente nessa fase de alto risco da assitência. Essa ficha será testada e os resultados publicados posteriormente

Differential Inhibitory Effects of CysLT1 Receptor Antagonists on P2Y6 Receptor-Mediated Signaling and Ion Transport in Human Bronchial Epithelia

BACKGROUND: Cysteinyl leukotriene (CysLT) is one of the proinflammatory mediators released by the bronchi during inflammation. CysLTs exert their biological effects via specific G-protein-coupled receptors. CysLT(1) receptor antagonists are available for clinical use for the treatment of asthma. Recently, crosstalk between CysLT(1) and P2Y(6) receptors has been delineated. P2Y receptors are expressed in apical and/or basolateral membranes of virtually all polarized epithelia to control the transport of fluid and electrolytes. Previous research suggests that CysLT(1) receptor antagonists inhibit the effects of nucleotides acting at P2Y receptors. However, the detailed molecular mechanism underlying the inhibition remains unresolved. METHODOLOGY/PRINCIPAL FINDINGS: In this study, western blot analysis confirmed that both CysLT(1) and P2Y(6) receptors were expressed in the human bronchial epithelial cell line 16HBE14o-. All three CysLT(1) antagonists inhibited the uridine diphosphate (UDP)-evoked I(SC), but only montelukast inhibited the UDP-evoked [Ca(2+)](i) increase. In the presence of forskolin or 8-bromoadenosine 3'5' cyclic monophosphate (8-Br-cAMP), the UDP-induced I(SC) was potentiated but was reduced by pranlukast and zafirlukast but not montelukast. Pranlukast inhibited the UDP-evoked I(SC) potentiated by an Epac activator, 8-(4-Chlorophenylthio)-2'-O-methyladenosine-3',5'-cyclic monophosphate (8-CPT-2'-O-Me-cAMP), while montelukast and zafirlukast had no such effect. Pranlukast inhibited the real-time increase in cAMP changes activated by 8-CPT-2'-O-Me-cAMP as monitored by fluorescence resonance energy transfer imaging. Zafirlukast inhibited the UDP-induced I(SC) potentiated by N(6)-Phenyladenosine-3',5'-cyclic monophosphorothioate, Sp-isomer (Sp-6-Phe-cAMP; a PKA activator) and UDP-activated PKA activity. CONCLUSIONS/SIGNIFICANCE: In summary, our data strongly suggest for the first time that in human airway epithelia, the three specific CysLT(1) receptor antagonists exert differential inhibitory effects on P2Y(6) receptor-coupled Ca(2+) signaling pathways and the potentiating effect on I(SC) mediated by cAMP and Epac, leading to the modulation of ion transport activities across the epithelia

β-Catenin is involved in alterations in mitochondrial activity in non-transformed intestinal epithelial and colon cancer cells

BACKGROUND: Alteration in respiratory activity and mitochondrial DNA (mtDNA) transcription seems to be an important feature of cancer cells. Leukotriene D(4) (LTD(4)) is a proinflammatory mediator implicated in the pathology of chronic inflammation and cancer. We have shown earlier that LTD(4) causes translocation of beta-catenin both to the mitochondria, in which it associates with the survival protein Bcl-2 identifying a novel role for beta-catenin in cell survival, and to the nucleus in which it activates the TCF/LEF transcription machinery. METHODS: Here we have used non-transformed intestinal epithelial Int 407 cells and Caco-2 colon cancer cells, transfected or not with wild type and mutated (S33Y) beta-catenin to analyse its effect on mitochondria activity. We have measured the ATP/ADP ratio, and transcription of the mtDNA genes ND2, ND6 and 16 s in these cells stimulated or not with LTD(4). RESULTS: We have shown for the first time that LTD(4) triggers a cellular increase in NADPH dehydrogenase activity and ATP/ADP ratio. In addition, LTD(4) significantly increased the transcription of mtDNA genes. Overexpression of wild-type beta-catenin or a constitutively active beta-catenin mutant mimicked the effect of LTD(4) on ATP/ADP ratio and mtDNA transcription. These elevations in mitochondrial activity resulted in increased reactive oxygen species levels and subsequent activations of the p65 subunit of NF-kappaB. CONCLUSIONS: The present novel data show that LTD(4), presumably through beta-catenin accumulation in the mitochondria, affects mitochondrial activity, lending further credence to the idea that inflammatory signalling pathways are intrinsically linked with potential oncogenic signals

Enhanced Light–Matter Interactions in Graphene-Covered Gold Nanovoid Arrays

The combination of graphene with noble-metal nanostructures is currently being explored for strong light-graphene interaction enhanced by plasmons. We introduce a novel hybrid graphene-metal system for studying light-matter interactions with gold-void nanostructures exhibiting resonances in the visible range. Strong coupling of graphene layers to the plasmon modes of the nanovoid arrays results in significant frequency shifts of the underlying plasmon resonances, enabling more than 30% absolute light absorption in a single layer of graphene and up to 700-fold enhancement of the Raman response of the graphene. These new perspectives enable us to verify the presence of graphene on gold-void arrays and the enhancement even allows us to accurately quantify the number of layers. Experimental observations are further supported by numerical simulations and perturbation-theory analysis. The graphene gold-void platform is beneficial for sensing of molecules and placing R6G dye molecules on top of the graphene, we observe a strong enhancement of the R6G Raman fingerprints. These results pave the way toward advanced substrates for surface-enhanced Raman scattering (SERS) with potential for unambiguous single-molecule detection on the atomically well-defined layer of graphene.Comment: 17 pages including 5 figure

Observation of strongly enhanced photoluminescence from inverted cone shaped silicon nanostuctures

Silicon nanowires (SiNWs) attached to a wafer substrate are converted to inversely tapered silicon nanocones (SiNCs). After excitation with visible light, individual SiNCs show a 200-fold enhanced integral band-to-band luminescence as compared to a straight SiNW reference. Furthermore, the reverse taper is responsible for multifold emission peaks in addition to the relatively broad near-infrared (NIR) luminescence spectrum. A thorough numerical mode analysis reveals that unlike a SiNW the inverted SiNC sustains a multitude of leaky whispering gallery modes. The modes are unique to this geometry and they are characterized by a relatively high quality factor (Q similar to 1300) and a low mode volume (0.2 < (lambda/n(eff))(3) < 4). In addition they show a vertical out coupling of the optically excited NIR luminescence with a numerical aperture as low as 0.22. Estimated Purcell factors F-p proportional to Q/V-m of these modes can explain the enhanced luminescence in individual emission peaks as compared to the SiNW reference. Investigating the relation between the SiNC geometry and the mode formation leads to simple design rules that permit to control the number and wavelength of the hosted modes and therefore the luminescent emission peaks

High quality factor whispering gallery modes from self-assembled hexagonal GaN rods grown by metal-organic vapor phase epitaxy

Self-assembled GaN rods were grown on sapphire by metalorganic vapor phase epitaxy using a simple two-step method that relies first on a nitridation step followed by GaN epitaxy. The mask-free rods formed without any additional catalyst. Most of the vertically aligned rods exhibit a regular hexagonal shape with sharp edges and smooth sidewall facets. Cathodo-and microphotoluminescence investigations were carried out on single GaN rods. Whispering gallery modes with quality factors greater than 4000 were measured demonstrating the high morphological and optical quality of the self-assembled GaN rods. (C) 2012 Optical Society of Americ

Disentangling the effects of nanoscale structural variations on the light emission wavelength of single nano emitters InGaN GaN multi quantum well nano LEDs for a case study

The scattering in the light emission wavelength of semiconductor nano emitters assigned to nanoscale variations in strain, thickness, and composition is critical in current and novel nanotechnologies from highly efficient light sources to photovoltaics. Here, we present a correlated experimental and theoretical study of single nanorod light emitting diodes nano LEDs based on InGaN GaN multiquantum wells to separate the contributions of these intrinsic fluctuations. Cathodoluminescence measurements show that nano LEDs with identical strain states probed by non resonant micro Raman spectroscopy can radiate light at different wavelengths. The deviations in the measured optical transitions agree very well with band profile calculations for quantum well thicknesses of 2.07 2.72 nm and In fractions of 17.5 19.5 tightly enclosing the growth values. The nanorod surface roughness controls the appearance of surface optical phonon modes with direct implications on the design of phonon assisted nano LED devices. This work establishes a new, simple, and powerful methodology for fundamental understanding as well as quantitative analysis of the strain light emission relationship and surface related phenomena in the emerging field of nano emitter

Correlating internal stresses, electrical activity and defect structure on the micrometer scale in EFG silicon ribbons

In the present paper, we study the influence of defects through their stress fields on the electrical activity and residual stress states of as-grown edge-defined film-feed (EFG) multicrystalline silicon (mc-Si) ribbons. We apply a combination of micro-Raman spectroscopy, electron beam induced current, defect etching and electron backscatter diffraction techniques that enables us to correlate internal stresses, recombination activity and microstructure on the micrometer scale. The stress fields of defect structures are considered to be too small (several tens of MPa) to influence directly the electrical activity, but they can enhance it via stress-induced accumulation of metallic impurities. It is commonly found that not all recombination-active dislocations on grain boundaries (GBs) and within grains are accompanied by internal stresses. The reason for this is that dislocations interact with each other and tend to locally rearrange in configurations of minimum strain energy in which their stress fields can cancel partially, totally or not at all. The outcome is a nonuniform distribution of electrical activity and internal stresses along the same GB, along different GBs of similar character as well as inside the same grain and inside different grains of similar crystallographic orientations. Our work has implications for developing crystal growth procedures that may lead to reduced internal stresses and consequently to improved electrical quality and mechanical stability of mc-Si materials by means of controlled interaction between structural defects. (C) 2011 Elsevier B.V. All rights reserved