Fiber orientation and crimp level might control the auxetic effect of biological tissues

We propose an analytical micromechanical model for studying the lamellar-composite-like structure of fibrous soft tissue. The tissue under consideration is made up of several lamellae, and is designed to resemble the annulus fibrosus (AF) tissue or media layer of arterial tissue, for example. The collagen fibers are arranged in parallel in each lamella and the fiber orientation differs from one lamella to its neighbors. The parallel fibers in each lamella of AF tissue, for example, have been observed to have a crimped microstructure. The proposed model incorporates this quality, considering fiber waviness as a sinusoidal shape and taking into account the fiber dispersion in different layers, where both fiber and matrix are considered as solid phases. We find that collagen-fiber waviness and layer orientation have a significant influence on Poisson's ratio. The effective Poisson's ratio predicted by the proposed model demonstrates that the crimped collagen fiber microstructure might weaken the auxetic effect of fibrous soft tissue, which might explain why, as the literature suggests, the auxetic behavior is more difficult to observe than large Poisson's ratios. As opposed to the many studies that use the well-known hyperelastic fiber-based constitutive model, in which out-of-plane expansion is often observed, the present work explains the auxetic response found in modeling and in experimental data from the perspective of collagen fiber microstructure.

Validation of a new fluidic device for mechanical stimulation and characterization of microspheres: A first step towards cartilage characterization

Articular cartilage is made of chondrocytes surrounded by their extracellular matrix that can both sense and respond to various mechanical stimuli. One of the most widely used in vitro model to study cartilage growth is the model of mesenchymal stromal cells-derived cartilage micropellet. However, mechanical stimulation of micropellets has never been reported probably because of their small size and imperfect round shape. The objective of the study was to develop an original custom-made device allowing both the mechanical stimulation and characterization of cartilage micropellets. The fluidic-based device was designed for the concomitant stimulation or characterization of six microspheres placed into the conical wells of a tank. In the present study, the device was validated using alginate-, collagen- and crosslinked collagen-based microspheres. Different types and ranges of pressure signals (square, sinusoidal and constant) were applied. The mechanical properties of microspheres were equivalent to those determined by a conventional compression test. Accuracy, repeatability and reproducibility of all types of pressure signals were demonstrated even though square signals were less accurate and sinusoidal signals were less reproducible than the others. The interest of this new device lies in the reliability to mechanically stimulate and characterize microspheres with diameters in the range of 900 to 1500 μm. Mechanical stimulation can be performed on six microspheres in parallel allowing the mechanical and molecular characterization of the same group of cartilage micropellets. The device will be useful to evaluate the growth of cartilage micropellets under mechanical stimuli.

Pneumopathies graves liées au COVID-19 : facteurs prédictifs de mortalité après traitement par tocilizumab

Introduction

Matériels et méthodes

Résultats

Conclusion

Validation and deployment of the first Lidar based weather observation network in New York State: The NYS MesoNet Project

The number and quality of atmospheric observations used by meteorologists and operational forecasters are increasing year after year, and yet, consistent improvements in forecast skill remains a challenge. While contributing factors involving these challenges have been identified, including the difficulty in accurately establishing initial conditions, improving the observations at regional and local scales is necessary for accurate depiction of the atmospheric boundary layer (below 2km), particularly the wind profile, in high resolution numerical models. Above the uncertainty of weather forecasts, the goal is also to improve the detection of severe and extreme weather events (severe thunderstorms, tornadoes and other mesoscale phenomena) that can adversely affect life, property and commerce, primarily in densely populated urban centers.

This paper will describe the New York State Mesonet that is being deployed in the state of New York, USA. It is composed of 126 stations including 17 profiler sites. These sites will acquire continuous upper air observations through the combination of WINDCUBE Lidars and microwave radiometers. These stations will provide temperature, relative humidity & “3D” wind profile measurements through and above the planetary boundary layer (PBL) and will retrieve derived atmospheric quantities such as the PBL height, cloud base, momentum fluxes, and aerosol & cloud optical properties. The different modes and configurations that will be used for the Lidars are discussed. The performances in terms of data availability and wind accuracy and precision are evaluated. Several profiles with specific wind and aerosol features are presented to illustrate the benefits of the use of Coherent Doppler Lidars to monitor accurately the PBL.

Monitoring and Quantifying Particles Emissions around Industrial Sites with Scanning Doppler Lidar

Scanning Coherent Doppler Lidars have been used over the last decade for measuring wind for applications in wind energy [1], meteorology [2] and aviation [3]. They allow for accurate measurements of wind speeds up to a distance of 10 km based on the Doppler shift effect of aerosols. The signal reflectivity (CNR or Carrier-to-Noise Ratio) profiles can also be retrieved from the strength of the Lidar signal. In this study, we will present the developments of algorithm for retrieving aerosol optical properties like the relative attenuated backscatter coefficient and the mass concentration of particles. The use of these algorithms during one operational trial in Point Samson, Western Australia to monitor fugitive emissions over a mine will be presented. This project has been initiated by the Australian Department of Environment Regulations to better determine the impact of the Port on the neighboring town. During the trial in Summer, the strong impact of turbulence refractive index on Lidar performances has been observed. Multiple methodologies have been applied to reduce this impact with more or less success. At the end, a dedicated setup and configuration have been established that allow to properly observe the plumes of the mine with the scanning Lidar. The Lidar data has also been coupled to beta attenuation in-situ sensors for retrieving mass concentration maps. A few case of dispersion of plumes will be presented showing the necessity to combine both the wind and aerosol data.

[Hypofractionated stereotactic radiotherapy for brain metastasis: Benefit of additional whole brain radiotherapy?]

PURPOSE

To study overall survival, risk of neurological death, local recurrence and development of new brain metastasis in patients treated for brain oligometastases with hypofractionated stereotactic radiotherapy with CyberKnife^®, according to the association or not with an additional whole brain irradiation.

PATIENTS AND METHODS

Institutional retrospective study of 102 patients treated for one to three brain metastasis: 76 with exclusive hypofractionated stereotactic radiotherapy and 26 with hypofractionated stereotactic radiotherapy and whole brain irradiation. Objectives were assessed and compared between these two groups according to the Kaplan-Meier method and Cox model.

RESULTS

Median follow-up was 18.8 months. There were no difference between exclusive hypofractionated stereotactic radiotherapy and hypofractionated stereotactic radiotherapy with whole brain irradiation for overall survival (respective median 21.5 and 20.1 months), risk of neurological death (respectively 9.2% and 15.4% at one year). At one year: the risk of cerebral progressive disease was greater in the group receiving exclusive hypofractionated stereotactic radiotherapy (respectively 43.4% vs. 26.2%, P=0.043), the risk of local recurrence was 25% versus 17.6% (P=0.28) and the development of new brain metastasis was 23.7% versus 11.5% (P=0.27). After salvage treatments, crude local control was similar in the two groups, respectively 78.6% and 73.5%. Whole brain irradiation has been avoided for 72.4% of patients in the group receving exclusive hypofractionated stereotactic radiotherapy.

CONCLUSION

Whole brain irradiation improves local control of brain metastatic disease in addition to hypofractionated stereotactic radiotherapy. Sparing whole brain irradiation for salvage treatments only does not affect overall survival or risk of neurological death in selected patients with favourable prognosis.

Rapid fabrication of micro-nanometric tapered fiber lens and characterization by a novel scanning optical microscope with submicron resolution

In numerous applications of optical scanning microscopy, a reference tapered fiber lens with high symmetry at sub-wavelength scale remains a challenge. Here, we demonstrate the ability to manufacture it with a wide range of geometry control, either for the length from several hundred nanometers to several hundred microns, or for the curvature radius from several tens of nanometers to several microns on the endface of a single mode fiber. On this basis, a scanning optical microscope has been developed, which allows for fast characterization of various sub-wavelength tapered fiber lenses. Focal position and depth of microlenses with different geometries have been determined to be ranged from several hundreds of nanometers to several microns. FDTD calculations are consistent with experimental results.

Comet-like mineralogy of olivine crystals in an extrasolar proto-Kuiper belt

Some planetary systems harbour debris disks containing planetesimals such as asteroids and comets. Collisions between such bodies produce small dust particles, the spectral features of which reveal their composition and, hence, that of their parent bodies. A measurement of the composition of olivine crystals (Mg(2-2x)Fe(2x)SiO(4)) has been done for the protoplanetary disk HD 100546 (refs 3, 4) and for olivine crystals in the warm inner parts of planetary systems. The latter compares well with the iron-rich olivine in asteroids (x ≈ 0.29). In the cold outskirts of the β Pictoris system, an analogue to the young Solar System, olivine crystals were detected but their composition remained undetermined, leaving unknown how the composition of the bulk of Solar System cometary olivine grains compares with that of extrasolar comets. Here we report the detection of the 69-micrometre-wavelength band of olivine crystals in the spectrum of β Pictoris. Because the disk is optically thin, we can associate the crystals with an extrasolar proto-Kuiper belt a distance of 15-45 astronomical units from the star (one astronomical unit is the Sun-Earth distance), determine their magnesium-rich composition (x = 0.01 ± 0.001) and show that they make up 3.6 ± 1.0 per cent of the total dust mass. These values are strikingly similar to those for the dust emitted by the most primitive comets in the Solar System, even though β Pictoris is more massive and more luminous and has a different planetary system architecture.

Direct functionalization of an optical fiber by a plasmonic nanosensor

We explore a rapid route for fabricating silver nanoparticles (NPs) at the end of an optical fiber. The size and number of silver NPs can be controlled by varying the exposure doses. The effect of the refractive index of different solvents on the extinction spectra have been studied as a proof of concept of a fiber integrated plasmon-based sensor.

Abstract 690: Selection of resistance by anticancer drugs is not responsible for alterations in membrane micro-fluidity: A study by Fluorescence Correlation Micro-Spectroscopy

Expression of P-glycoprotein (P-gp), the multidrug resistance (MDR) 1 gene product, can lead to MDR in tumors. Previous studies on multidrug-resistant cells have suggested changes in membrane fluidity associated with P-gp expression in drug-selected resistant cells. However, Aleman and co-workers have shown that, in MDR1 transfected cells, expression of P-gp has little effect on membrane fluidity and the changes in this parameter observed in drug-selected cells must reflect other host adaptations to drug selection. In this study and the other reported on drug-selected resistant cells, membrane fluidity has been measured using fluorescent membrane probes and fluorescence anisotropy or electron spin resonance on cell population samples (Aleman et al. Cancer Res. 2003 63:3084-91).

Here, we propose to explore the plasma membrane microfluidity by using the fluorescent membrane probe DiA and fluorescence correlation micro-spectroscopy (FCM-S) on a single living cell and nanometer scale. By using the fluorescent membrane probe DiA and FCM-S to explore the plasma membrane micro-fluidity, we have previously shown a decrease in plasma membrane micro-fluidity in LR73R cells (the Chinese hamster ovarian LR73 cells transfected with MDR1 cDNA; Boutin et al., J Biomed Opt. 2009 14: 034030). Moreover, a strategy using flow cytometry and calcein-AM functional fluorescence-activated cell sorting permitted us to select two cell populations from LR73R cells expressing distinct levels of P-gp function. In this case, we were able to observe distinct level of membrane micro-fluidity in the two populations. Cells showing high level of calcein-AM uptake presented a higher membrane micro-fluidity. In contrast, the FCM-S yielded opposite data when we compared the membrane micro-fluidity of several parental cell lines (MCF7, KB3.1, LR73, ME-SSA) and their resistant counterparts which have been selected in the presence of anticancer drugs.

Our data are not in agreement with previous published data and demonstrates clearly that alterations that can affect drug-selected cells do not induce any changes in membrane fluidity. Moreover, micro-analysis of cell membrane could allow to more precise measurements of membrane fluidity.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 690. doi:10.1158/1538-7445.AM2011-690

Integration of polymer microlens array at fiber bundle extremity by photopolymerization

We present a novel route to directly integrate an array of microlenses at the extremity of an optical fiber bundle. The method is based on photopolymerization at the end of the fiber. The method is based on the control of exposure dose and volume of the deposited droplet of photopolymerizable formulation. Optical properties of the integrated microlenses are discussed on the basis of FDTD calculations.

Applications of Optoelectrochemical Impedance Measurements on Electrolyte/Dielectric/Semiconductor Structure:Cartographic Analysis

The use of a weak modulated illumination with above-bandgap light energy as a probe scanning a Electrolyte/Dielectric/Semiconductor structure under electrochemical potentiostatic polarization gives an opportunity to obtain qualitative cartographies of different electrical parameters characterizing the Semiconductor/Dielectric interface.

Off-Resonant Optical Excitation of Gold Nanorods: Nanoscale Imprint of Polarization Surface Charge Distribution

We report on the nanoscale optical characterization of gold nanorods irradiated out of their plasmonic resonance. Our approach is based on the reticulation of a photopolymerizable formulation locally triggered by enhanced electromagnetic fields. The tiny local field enhancement stems from the surface polarization charges associated with the electric field discontinuity at the metal/dielectric interface. This allows us to get a nanoscale signature of the spatial distribution of the surface charge density in metallic nanoparticles irradiated off-resonance.

Bidimensional near-field sampling spectrometry

We report on a concept of compact optical Fourier-transform spectrometer based on bidimensional (2D) spatial sampling of a confined interferogram. The spectrometer consists of a nanostructured glass surface on which two light beams interfere in total internal reflection. Subwavelength spatial sampling of the interferogram near field is achieved by introducing a tilt angle between a 2D array of optical nanoantennas and the interferogram pattern. The intensity distribution of the scattered light is recorded on a 2D CCD camera, and a one-dimensional Fourier transform of the interferogram is used to recover the input light spectrum. Experimental results show a wide spectral bandwidth in the visible range, down to 380 nm, with spectral resolution of 1.6 nm around 780 nm.

Real-space observation of spectral degeneracy breaking in a waveguide-coupled disk microresonator

We report on the real-space observation of resonant frequency splitting in a high-Q waveguide-coupled silicon-on-insulator microdisk resonator. Phase sensitive near-field analysis reveals the stationary nature of the two resonant states, and spectral investigations clearly show their orthogonality. These measurements emphasize the role of the coupling waveguide in this splitting phenomenon. The symmetry of the two stationary whispering gallery modes is clearly observed and is found to follow the axial symmetry of the waveguide-coupled microdisk as it has been reported by earlier theoretical predictions.

Warm water vapour in the sooty outflow from a luminous carbon star

The detection of circumstellar water vapour around the ageing carbon star IRC +10216 challenged the current understanding of chemistry in old stars, because water was predicted to be almost absent in carbon-rich stars. Several explanations for the water were postulated, including the vaporization of icy bodies (comets or dwarf planets) in orbit around the star, grain surface reactions, and photochemistry in the outer circumstellar envelope. With a single water line detected so far from this one carbon-rich evolved star, it is difficult to discriminate between the different mechanisms proposed. Here we report the detection of dozens of water vapour lines in the far-infrared and sub-millimetre spectrum of IRC +10216 using the Herschel satellite. This includes some high-excitation lines with energies corresponding to approximately 1,000 K, which can be explained only if water is present in the warm inner sooty region of the envelope. A plausible explanation for the warm water appears to be the penetration of ultraviolet photons deep into a clumpy circumstellar envelope. This mechanism also triggers the formation of other molecules, such as ammonia, whose observed abundances are much higher than hitherto predicted.

Quantitative analysis of localized surface plasmons based on molecular probing

We report on the quantitative characterization of the plasmonic optical near-field of a single silver nanoparticle. Our approach relies on nanoscale molecular molding of the confined electromagnetic field by photoactivated molecules. We were able to directly image the dipolar profile of the near-field distribution with a resolution better than 10 nm and to quantify the near-field depth and its enhancement factor. A single nanoparticle spectral signature was also assessed. This quantitative characterization constitutes a prerequisite for developing nanophotonic applications.

Note: Multiscale scanning probe microscopy

Combining the nanoscopic and macroscopic worlds is a serious challenge common to numerous scientific fields, from physics to biology. In this paper, we demonstrate nanometric resolution over a millimeter range by means of atomic-force microscopy using metrological stage. Nanometric repeatability and millimeter range open up the possibility of probing components and materials combining multiscale properties i.e., engineered nanomaterials. Multiscale probing is not limited to atomic-force microscopy and can be extended to any type of scanning probe technique in nanotechnology, including piezoforce microscopy, electrostatic-force microscopy, and scanning near-field optical microscopy.

Abstract 3537: P-glycoprotein expression level is responsible for alterations in plasma membrane microfluidity as probed by fluorescence correlation spectroscopy

Expression of P-glycoprotein (P-gp), the multidrug resistance (MDR) 1 gene product, leads to MDR in tumors. By using the fluorescent membrane probe DiA and Fluoresence Correlation Spectroscopy (FCS) to explore the plasma membrane microfluidity, we have previousely shown a showed a decrease in plasma membrane microfluidity in LR73R cells (the Chinese hamster ovarian LR73R cells transfected with MDR1 cDNA) (1).

In the present study, and in order to study the relationship between membrane microfluidity and the level of P-gp expression, a strategy using flow cytometry and calcein-AM functional fluorescence-activated cell sorting permitted us to select two cell populations from LR73R cells expressing distinct levels of P-gp (P4 “lower calcein-AM uptake” and P5 “higher calcein-AM uptake”). Data obtained on the cytotoxic effects of doxorubicin (DOX) showed clearly that P4 cells were 10-fold resistant to DOX than P5 cells. A direct correlation between the sensitivity of the cells to DOX and the calcein-AM uptake was observed. In addition, intranuclear DOX measurements using microspectrofluorometry showed a decrease in nuclear accumulation of DOX in P4 cells when compared to P5 cells. This was in agreement with the functional calcein-AM uptake assay.

By using the fluorescent membrane probe DiA FCS analysis, we explored the membrane microfluidity in P4 and P5 cells. We show that P5 cells presented an increase in membrane fluidity when compared to P4 cells. LR73 cells presented the highest microfluidity when compared to P4 and P5 cells. This was in agreement with the previous published data (1) and demonstrate also that the microfluidity of the plasma membrane is strongly related to the level of Pgp expression.

(1) Boutin C, Roche Y, Millot C, Deturche R, Royer P, Manfait M, Plain JM, Jeannesson P, Millot JM, Jaffiol R. High heterogeneity of plasma membrane microfluidity in multidrug-resistant cancer cells. J Biomed Opt. 2009 14(3): 034030.

Note: This abstract was not presented at the AACR 101st Annual Meeting 2010 because the presenter was unable to attend.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 3537.

Spatially controlled synthesis of silver nanoparticles and nanowires by photosensitized reduction

The present paper reports on the spatially controlled synthesis of silver nanoparticles (NPs) and silver nanowires by photosensitized reduction. In a first approach, direct photogeneration of silver NPs at the end of an optical fiber was carried out. Control of both size and density of silver NPs was possible by changing the photonic conditions. In a further development, a photochemically assisted procedure allowing silver to be deposited at the surface of a polymer microtip was implemented. Finally, polymer tips terminated by silver nanowires were fabricated by simultaneous photopolymerization and silver photoreduction. The silver NPs were characterized by UV-visible spectroscopy and scanning electron microscopy.

Enhancement and quenching regimes in metal-semiconductor hybrid optical nanosources

We report on the emission of hybrid nanosources composed of gold nanoparticles coupled with quantum dots. The emission relies on energy transfer from the quantum dots to gold nanoparticles which could be de-excited through radiative plasmon relaxation. The dependence of the emission efficiency is studied systematically as a function of the size of gold nanoparticles and interdistance between gold nanoparticles and quantum dots. We demonstrate a size-dependent transition between quenching and enhancement and a nonradiative energy transfer from the quantum dots to the gold nanoparticles.

Understanding near/far-field engineering of optical dimer antennas through geometry modification

Numerical investigations based on the boundary element method (BEM) have been carried out to two-dimensional (2-D) silver dimer nano-antennas of various geometries. The near-field and far-field properties are mainly determined by the local geometry at the gap and the global shape of the antenna shafts respectively. A hybrid dimer antenna, which mixes the geometry ingredients of the rod dimer and the bowtie, benefits in both near and far field. Using a microcavity representation, the resonance in dimer nano-antennas is explained in a common and semi-analytical manner. The plasmonic enhancement and the wavelength mismatching in the optical dimer antenna are naturally embodied in this model. The quality factor of the resonance, which can be influenced by the wavelength and the geometry, is discussed intuitively. The understanding presented in this work could guide the future engineering of the optical dimer antenna.

Tuning of an optical dimer nanoantenna by electrically controlling its load impedance

Optical antennas are elementary units used to direct optical radiation to the nanoscale. Here we demonstrate an active control over individual antenna performances by an external electrical trigger. We find that by an in-plane command of an anisotropic load medium, the electromagnetic interaction between individual elements constituting an optical antenna can be controlled, resulting in a strong polarization and tuning response. An active command of the antenna is a prerequisite for directing light wave through the utilization of such a device.

Multiscale model for photoinduced molecular motion in azo polymers

Light-induced isomerization processes in azobenzene-containing polymers produce mass transport that is of much interest for nanoscale imaging and lithography. Yet, despite the development of numerous models to simulate the mass transport mechanism, no model precisely describes all the experimental observations. We develop a new statistical approach that correctly reproduces light-driven mass motion in azobenzene-containing polymers with a high degree of accuracy. Comparisons with experiments show that our model predicts the nanoscale topographic modifications for many different incident field configurations, including optical near-fields produced by plasmonic structures with complex polarization states. In particular, the model allows the detailed molecular motions that lead to these topographic modifications to be identified.

High heterogeneity of plasma membrane microfluidity in multidrug-resistant cancer cells

Diffusion-time distribution analysis (DDA) has been used to explore the plasma membrane fluidity of multidrug-resistant cancer cells (LR73 carcinoma cells) and also to characterize the influence of various membrane agents present in the extracellular medium. DDA is a recent single-molecule technique, based on fluorescence correlation spectroscopy (FCS), well suited to retrieve local organization of cell membrane. The method was conducted on a large number of living cells, which enabled us to get a detailed overview of plasma membrane microviscosity, and plasma membrane micro-organization, between the cells of the same line. Thus, we clearly reveal the higher heterogeneity of plasma membrane in multidrug-resistant cancer cells in comparison with the nonresistant ones (denoted sensitive cells). We also display distinct modifications related to a membrane fluidity modulator, benzyl alcohol, and two revertants of multidrug resistance, verapamil and cyclosporin-A. A relation between the distribution of the diffusion-time values and the modification of membrane lateral heterogeneities is proposed.

Enhanced light coupling in sub-wavelength single-mode silicon on insulator waveguides

We report on NIR efficient end-coupling in single-mode silicon on insulator waveguides. Efficient coupling has been achieved using Polymer-Tipped Optical Fibers (PTOF) of adaptable radius of curvature (ROC). When compared with commercial micro lenses, systematic studies as a function of PTOF ROC, lead for subwavelength PTOF to a coupling factor enhancement as high as 2.5. This experimental behavior is clearly corroborated by radial FDTD simulations and an absolute coupling efficiency of about 50% is also estimated.