Argon-laser iridoplasty in the management of uveitis-induced acute angle-closure glaucoma.

PURPOSE: To report the use of argon laser iridoplasty in the management of uveitic acute angle-closure glaucoma. METHODS: Interventional case report. RESULTS: A 46-year-old man developed uveitic acute angle-closure glaucoma with an intraocular pressure (IOP) of 65 mmHg. After unsuccessful attempts with medical treatment and two laser peripheral iridotomies, iridoplasty allowed to break posterior synechiae, open the angle, and reduce the IOP within a few hours. CONCLUSIONS: Argon laser iridoplasty allowed rapid reduction of IOP and prevented the need for emergency surgery. Therefore, the authors stipulate that it is a viable management option in active uveitic acute angle-closure glaucoma.

Late removal of retrievable caval filters.

The advent of retrievable caval filters was a game changer in the sense, that the previously irreversible act of implanting a medical device into the main venous blood stream of the body requiring careful evaluation of the pros and cons prior to execution suddenly became a "reversible" procedure where potential hazards in the late future of the patient lost most of their weight at the time of decision making. This review was designed to assess the rate of success with late retrieval of so called retrievable caval filters in order to get some indication about reasonable implant duration with respect to relatively "easy" implant removal with conventional means, i.e., catheters, hooks and lassos. A PubMed search (www.pubmed.gov) was performed with the search term "cava filter retrieval after 30 days clinical", and 20 reports between 1994 and 2013 dealing with late retrieval of caval filters were identified, covering approximately 7,000 devices with 600 removed filters. The maximal duration of implant reported is 2,599 days and the maximal implant duration of removed filters is also 2,599 days. The maximal duration reported with standard retrieval techniques, i.e., catheter, hook and/or lasso, is 475 days, whereas for the retrievals after this period more sophisticated techniques including lasers, etc. were required. The maximal implant duration for series with 100% retrieval accounts for 84 days, which is equivalent to 12 weeks or almost 3 months. We conclude that retrievable caval filters often become permanent despite the initial decision of temporary use. However, such "forgotten" retrievable devices can still be removed with a great chance of success up to three months after implantation. Conventional percutaneous removal techniques may be sufficient up to sixteen months after implantation whereas more sophisticated catheter techniques have been shown to be successful up to 83 months or more than seven years of implant duration. Tilting, migrating, or misplaced devices should be removed early on, and replaced if indicated with a device which is both, efficient and retrievable.

Acoustic transport of charge and spins in GaAs-based heterostructures

Report for the scientific sojourn carried out at the Paul Drude Institut für Festkörperelektronik of the Stanford University, USA, from 2010 to 2012. The objective of this project is the transport and control of electronic charge and spin along GaAs-based semiconductor heterostructures. The electronic transport has been achieved by taking advantage of the piezolectric field induced by surface acoustic waves in non-centrosymmetric materials like GaAs. This piezolectric field separates photogenerated electrons and holes at different positions along the acoustic wave, where they acummulate and are transported at the same velocity as the wave. Two different kinds of structures have been studied: quantum wells grown along the (110) direction, both intrinsic and n-doped, as well as GaAs nanowires. The analysis of the charge acoustic transport was performed by micro-photoluminescence, whereas the detection of the spin transport was done either by analyzing the polarization state of the emitted photoluminescence or by Kerr reflectometry. Our results in GaAs quantum wells show that charge and spin transport is clearly observed at the non-doped structures,obtaining spin lifetimes of the order of several nanoseconds, whereas no acoutically induced spin transport was detected for the n-doped quantum wells. In the GaAs nanowires, we were able of transporting successfully both electrons and holes along the nanowire axis, but no conservation of the spin polarization has been observed until now. The photoluminescence emitted by these structures after acoustic transport, however, shows anti-bunching characteristics, making this system a very good candidate for its use as single photon emitters.

Intracellular nanomanipulation by a photonic-force microscope with real-time acquisition of a 3D stiffness matrix.

A traditional photonic-force microscope (PFM) results in huge sets of data, which requires tedious numerical analysis. In this paper, we propose instead an analog signal processor to attain real-time capabilities while retaining the richness of the traditional PFM data. Our system is devoted to intracellular measurements and is fully interactive through the use of a haptic joystick. Using our specialized analog hardware along with a dedicated algorithm, we can extract the full 3D stiffness matrix of the optical trap in real time, including the off-diagonal cross-terms. Our system is also capable of simultaneously recording data for subsequent offline analysis. This allows us to check that a good correlation exists between the classical analysis of stiffness and our real-time measurements. We monitor the PFM beads using an optical microscope. The force-feedback mechanism of the haptic joystick helps us in interactively guiding the bead inside living cells and collecting information from its (possibly anisotropic) environment. The instantaneous stiffness measurements are also displayed in real time on a graphical user interface. The whole system has been built and is operational; here we present early results that confirm the consistency of the real-time measurements with offline computations.

Wear of two artificial tooth materials in vivo: a 12-month pilot study.

STATEMENT OF PROBLEM: Wear of methacrylate artificial teeth resulting in vertical loss is a problem for both dentists and patients. PURPOSE: The purpose of this study was to quantify wear of artificial teeth in vivo and to relate it to subject and tooth variables. MATERIAL AND METHODS: Twenty-eight subjects treated with complete dentures received 2 artificial tooth materials (polymethyl methacrylate (PMMA)/double-cross linked PMMA fillers; 35%/59% (SR Antaris DCL, SR Postaris DCL); experimental 48%/46%). At baseline and after 12 months, impressions of the dentures were poured with improved stone. After laser scanning, the casts were superimposed and matched. Maximal vertical loss (mm) and volumetric loss (mm(3)) were calculated for each tooth and log-transformed to reduce variability. Volumetric loss was related to the occlusally active surface area. Linear mixed models were used to study the influence of the factors jaw, tooth, and material on adjusted (residual) wear values (alpha=.05). RESULTS: Due to drop outs (n=5) and unmatchable casts (n=3), 69% of all teeth were analyzed. Volumetric loss had a strong linear relationship to surface area (P<.001); this was less pronounced for vertical loss (P=.004). The factor showing the highest influence was the subject. Wear was tooth dependent (increasing from incisors to molars). However, these differences diminished once the wear rates were adjusted for occlusal area, and only a few remained significant (anterior versus posterior maxillary teeth). Another influencing factor was the age of the subject. CONCLUSIONS: Clinical wear of artificial teeth is higher than previously measured or expected. The presented method of analyzing wear of artificial teeth using a laser-scanning device seemed suitable.

Acute effects of transmyocardial laser revascularization on left-ventricular function: an haemodynamic and echocardiographic study.

While the lesions produced by transmyocardial laser revascularisation (TMLR) induce scar formation, it is important to determine whether this procedure can be deleterious for the left-ventricular function, which is already impaired by the underlying ischaemic process in some patients. Ten channels were drilled in the left lateral wall of the hearts of ten pigs (mean weight, 61 +/- 8.2kg) with a Holmium:YAG laser. Haemodynamic measurements and echocardiographic assessment of left-ventricular function were performed before the TMLR procedure, 5 and 30 min after, and lastly after 5 min of pacing at a rate increased by 30% of the baseline value. Echocardiographic assessment was in the short axis at the level of the laser channels, and included left-ventricular ejection fraction and segmental wall motility of the lasered area (scale 0-3:0 = normal 1 = hypokinesia, 2 = akinesia, 3 = dyskinesia). Values at 5 and 30 min were compared with baseline values; the difference was considered significant if p < 0.05. Haemodynamical values were stable throughout all the procedures. The ejection fraction showed a slight but significant decrease 5 min after the creation of the channels (60.4 +/- 6.8% vs 54 +/- 7.6%, p=0.02) and recovered at 30min. The segmental motility score of the involved areas increased to 1 after 5 min in five animals, and came back to 0 at 30 min except in one animal. Even with pacing no segmental dysfunction occurred. The reversibility of the segmental hypokinesia induced by TMLR, as well as the absence of pace-induced dysfunction 30 min after the procedure strongly suggest the inocuity of TMLR in this experimental set-up.

Análise do Desempenho de Amplificadores Ópticos Semiconductores Reflectivos em Redes Ópticas de Acesso da Próxima Geração

O constante crescimento de aplicações Internet têm vindo a contribuir para a necessidade do aumento de largura de banda na rede de acesso, o que fomenta a procura de novas soluções para redes de acesso de fibra óptica. Nesse contexto, soluções conhecidas como transmissores independentes do comprimento de onda (WIT wavelengthindependent transmitters) isto é, soluções para emissores que possam operar numa ampla gama de comprimentos de onda, poderão ser muito úteis. Sendo uma das mais promissoras o amplificador óptico semiconductor reflectivo (RSOA). Nesta dissertação foi implementado um modelo simplificado do RSOA que permite eficientemente determinar as suas características estáticas e dinâmicas. Foi também implementado um modelo de simulação, em Matlab, que permita estudar o desempenho de um sistema de comunicação por fibra óptica que utiliza RSOA e técnicas de modulação digital por desvio de fase com M estados (M-PSK M-ary Phase Shift Keying). Com o modelo de simulação foi avaliada qual a taxa de transmissão máxima atingível. A avaliação do desempenho foi feita através do cálculo da magnitude do vector erro (EVM Error Vector Magnitude), considerando os vários blocos implementados. Foi determinado o ponto óptimo de funcionamento do RSOA, sendo também avaliado do desempenho de sistema de transmissão, usando diferentes parâmetros do sinal M-PSK (M=4,16,64) com taxa de transmissão de 1Gbits/s e 10 Gbits/s considerando vários comprimentos de fibra óptica.

L'application de la spectroscopie Raman en criminalistique pour l'analyse du colorant des fibres textiles en acrylique, coton et laine

RESUME La méthode de la spectroscopie Raman est une technique d'analyse chimique basée sur l'exploitation du phénomène de diffusion de la lumière (light scattering). Ce phénomène fut observé pour la première fois en 1928 par Raman et Krishnan. Ces observations permirent à Raman d'obtenir le Prix Nobel en physique en 1930. L'application de la spectroscopie Raman a été entreprise pour l'analyse du colorant de fibres textiles en acrylique, en coton et en laine de couleurs bleue, rouge et noire. Nous avons ainsi pu confirmer que la technique est adaptée pour l'analyse in situ de traces de taille microscopique. De plus, elle peut être qualifiée de rapide, non destructive et ne nécessite aucune préparation particulière des échantillons. Cependant, le phénomène de la fluorescence s'est révélé être l'inconvénient le plus important. Lors de l'analyse des fibres, différentes conditions analytiques ont été testées et il est apparu qu'elles dépendaient surtout du laser choisi. Son potentiel pour la détection et l'identification des colorants imprégnés dans les fibres a été confirmé dans cette étude. Une banque de données spectrale comprenant soixante colorants de référence a été réalisée dans le but d'identifier le colorant principal imprégné dans les fibres collectées. De plus, l'analyse de différents blocs de couleur, caractérisés par des échantillons d'origine inconnue demandés à diverses personnes, a permis de diviser ces derniers en plusieurs groupes et d'évaluer la rareté des configurations des spectres Raman obtenus. La capacité de la technique Raman à différencier ces échantillons a été évaluée et comparée à celle des méthodes conventionnelles pour l'analyse des fibres textiles, à savoir la micro spectrophotométrie UV-Vis (MSP) et la chromatographie sur couche mince (CCM). La technique Raman s'est révélée être moins discriminatoire que la MSP pour tous les blocs de couleurs considérés. C'est pourquoi dans le cadre d'une séquence analytique nous recommandons l'utilisation du Raman après celle de la méthode d'analyse de la couleur, à partir d'un nombre de sources lasers le plus élevé possible. Finalement, la possibilité de disposer d'instruments équipés avec plusieurs longueurs d'onde d'excitation, outre leur pouvoir de réduire la fluorescence, permet l'exploitation d'un plus grand nombre d'échantillons. ABSTRACT Raman spectroscopy allows for the measurement of the inelastic scattering of light due to the vibrational modes of a molecule when irradiated by an intense monochromatic source such as a laser. Such a phenomenon was observed for the first time by Raman and Krishnan in 1928. For this observation, Raman was awarded with the Nobel Prize in Physics in 1930. The application of Raman spectroscopy has been undertaken for the dye analysis of textile fibers. Blue, black and red acrylics, cottons and wools were examined. The Raman technique presents advantages such as non-destructive nature, fast analysis time, and the possibility of performing microscopic in situ analyses. However, the problem of fluorescence was often encountered. Several aspects were investigated according to the best analytical conditions for every type/color fiber combination. The potential of the technique for the detection and identification of dyes was confirmed. A spectral database of 60 reference dyes was built to detect the main dyes used for the coloration of fiber samples. Particular attention was placed on the discriminating power of the technique. Based on the results from the Raman analysis for the different blocs of color submitted to analyses, it was possible to obtain different classes of fibers according to the general shape of spectra. The ability of Raman spectroscopy to differentiate samples was compared to the one of the conventional techniques used for the analysis of textile fibers, like UV-Vis Microspectrophotometry (UV-Vis MSP) and thin layer chromatography (TLC). The Raman technique resulted to be less discriminative than MSP for every bloc of color considered in this study. Thus, it is recommended to use Raman spectroscopy after MSP and light microscopy to be considered for an analytical sequence. It was shown that using several laser wavelengths allowed for the reduction of fluorescence and for the exploitation of a higher number of samples.

Structural characterization of laser-treated Cr3C2-NiCr coatings

The interconnected porosity of the Cr3C2-NiCr coatings obtained by high-velocity oxy fuel spraying is detrimental in corrosion and wear resistance applications. Laser treatments allow sealing of their surfaces through melting and resolidification of a thin superficial layer. A Nd:YAG laser beam was used to irradiate Cr3C2-NiCr coatings either in the continuous wave mode or at different repetition rates in the pulsed one. Results indicated that high peak and low mean laser irradiances are not good, since samples presented deep grooves and an extensive crack network. At low peak and higher mean laser irradiances the surface was molten, and only a few shallow cracks were observed. The interconnected porosity was completely eliminated in a layer up to 80 m thick, formed by large Cr7C3 grains imbedded in a NiCr matrix.

Leukocyte-endothelial cell interaction is necessary for photodynamic therapy induced vascular permeabilization.

BACKGROUND AND OBJECTIVE: Photodynamic therapy (PDT) affects vascular barrier function and thus increases vessel permeability. This phenomenon may be exploited to facilitate targeted drug delivery and may lead to a new clinical application of photodynamic therapy. Here, we investigate the role of leukocyte recruitment for PDT-induced vascular permeabilization. STUDY DESIGN/MATERIAL AND METHODS: Fluorescein isothiocyanate dextran (FITC-D, 2,000 kDa) was injected intravenously 120 minutes after focal PDT on striated muscle in nude mice bearing dorsal skinfold chambers (Visudyne® 800 µg/kg, fluence rate 300 mW/cm2 , light dose of 200 J/cm2). Leukocyte interaction with endothelial cells was inhibited by antibodies functionally blocking adhesion molecules ("MABS-PDT" group, n = 5); control animals had PDT but no antibody injection (group "PDT", n = 7). By intravital microscopy, we monitored leukocyte rolling and sticking in real-time before, 90 and 180 minutes after PDT. The extravasation of FITC-D from striated muscle vessels into the interstitial space was determined in vivo during 45 minutes to assess treatment-induced alterations of vascular permeability. RESULTS: PDT significantly increased the recruitment of leukocytes and enhanced the leakage of FITC-D. Neutralization of adhesion molecules before PDT suppressed the rolling of leukocytes along the venular endothelium and significantly reduced the extravasation of FITC-D as compared to control animals (156 ± 27 vs. 11 ± 2 (mean ± SEM, number of WBC/30 seconds mm vessel circumference; P < 0.05) at 90 minutes after PDT and 194 ± 21 vs. 14 ± 4 at 180 minutes after PDT). In contrast, leukocyte sticking was not downregulated by the antibody treatment. CONCLUSION: Leukocyte recruitment plays an essential role in the permeability-enhancing effect of PDT.

Surface states in template synthesized tin oxide nanoparticles

Tin-oxide nanoparticles with controlled narrow size distributions are synthesized while physically encapsulated inside silica mesoporous templates. By means of ultraviolet-visible spectroscopy, a redshift of the optical absorbance edge is observed. Photoluminescence measurements corroborate the existence of an optical transition at 3.2 eV. The associated band of states in the semiconductor gap is present even on template-synthesized nanopowders calcined at 800°C, which contrasts with the evolution of the gap states measured on materials obtained by other methods. The gap states are thus considered to be surface localized, disappearing with surface faceting or being hidden by the surface-to-bulk ratio decrease.

Shot-noise suppression in Schottky barrier diodes

We give a theoretical interpretation of the noise properties of Schottky barrier diodes based on the role played by the long range Coulomb interaction. We show that at low bias Schottky diodes display shot noise because the presence of the depletion layer makes the effects of the Coulomb interaction negligible on the current fluctuations. When the device passes from barrier to flat band conditions, the Coulomb interaction becomes active, thus introducing correlation between different current fluctuations. Therefore, the crossover between shot and thermal noise represents the suppression due to long range Coulomb interaction of the otherwise full shot noise. Similar ideas can be used to interpret the noise properties of other semiconductor devices.

Influence of the (111) twinning on the formation of diamond cubic/diamond hexagonal heterostructures in Cu-catalyzed Si nanowires

The occurrence of heterostructures of cubic silicon/hexagonal silicon as disks defined along the nanowire (111) growth direction is reviewed in detail for Si nanowires obtained using Cu as catalyst. Detailed measurements on the structural properties of both semiconductor phases and their interface are presented. We observe that during growth, lamellar twinning on the cubic phase along the (111) direction is generated. Consecutive presence of twins along the (111) growth direction was found to be correlated with the origin of the local formation of the hexagonal Si segments along the nanowires, which define quantum wells of hexagonal Si diamond. Finally, we evaluate and comment on the consequences of the twins and wurtzite in the final electronic properties of the wires with the help of the predicted energy band diagram.