Oxidation of cellulose in pressurized carbon dioxide

This work presents first results upon oxidation of type II cellulose by nitrogen dioxide dissolved in carbon dioxide at high pressure. This reaction leads to oxidized cellulose, a natural-based bioresorbable fabric used for biomedical applications. The oxidation reaction takes place in a heterogeneous fluid–solid system. Kinetics of oxidation is presented here and effects of operating conditions such as pressure, temperature and initial moisture content of cellulose are investigated. Results are presented in terms of degree of oxidation of cellulose and quality of the final oxidized cellulose, which has been characterized using liquid-state and solid-state 13C NMR. The experimental results show the existence of possible secondary reactions which may lead to oxidized cellulose with insufficient mechanical strength. An attempt is made to evidence and understand the role of CO2 as a solvent in this system. Indeed, although supercritical CO2 appears to be a suitable candidate as a solvent for oxidation reactions, some inhibiting effect on nitrogen dioxide activity are observed in this case

Experimental pressure versus temperature isochoric – isoplethic curves for n-pentane – dimethyl ether, n-pentane – dimethyl ether – polybutadiene and n-pentane – dimethyl ether – polybutadiene– hydrogen at high pressures

Loci of isochoric - isoplethic experimental phase equilibrium data, were determined for the binary mixture dimethyl ether (DME) + n-pentane (C5); the ternary mixture: DME + C5 + polybutadiene (PB); and the quaternary mixture DME + C5 + PB + hydrogen (H2). Binary experiments were performed at varying overall density (ρ) and varying quantity of C5. Ternary experiments were performed at varying ρ and varying relative quantities of each light solvent. In the case of quaternary mixtures, the mass fraction of polymer was kept constant, and the amount of H2 and ρ were varied. The experimental data obtained for binary and ternary mixtures were correlated using the Perturbed-Chain Statistical Associating Fluid Theory (PC-SAFT) equation of state (EoS)

Reproductive health related complications of spinal cord injury among patients at a specialized center in Bangladesh

Background: Our objective was to find out the reproductive health related complications among spinal cord injury patients. Methods: A cross sectional study was conducted at the Center for the Rehabilitation of the Paralyzed (CRP) in Savar, Dhaka, Bangladesh from August 2017 to July 2018. A total of 289 patients, both indoor and outdoor, with spinal cord injury were randomly selected. The study aimed to examine reproductive health complications associated with spinal cord injury. Data was collected using a questionnaire and analyzed using SPSS version 20. Results: Among 220 (76.1%) were male and 69 (23.9%) were female. In 15-35 (68.1% and 91.2%), 47 (68.1%) participants had menstruation problem. 42.1% had autonomic dysreflexia and 57.9% had UTI as pregnancy related complications. In sexual activity 52% had difficulties having intercourse, 20% had difficulties to reach orgasm and 28% had dry sex. In male participants after SCI 70.5% had erection problem and 78.6% had ejaculation problem. Participants who had erection problem, most of their neurological level was thoracic level 84.51% and in case of ejaculation also their neurological level was thoracic level 81.50%. Conclusions: Awareness of sexuality and reproductive health after SCI has grown among healthcare professionals and individuals with spinal cord injuries. This recognition emphasizes the importance of open discussions, active listening, and education to enhance the quality of life for those affected by spinal cord injury

Validation and data characteristics of methane and nitrous oxide profiles observed by MIPAS and processed with Version 4.61 algorithm

The ENVISAT validation programme for the atmospheric instruments MIPAS, SCIAMACHY and GOMOS is based on a number of balloon-borne, aircraft, satellite and ground-based correlative measurements. In particular the activities of validation scientists were coordinated by ESA within the ENVISAT Stratospheric Aircraft and Balloon Campaign or ESABC. As part of a series of similar papers on other species [this issue] and in parallel to the contribution of the individual validation teams, the present paper provides a synthesis of comparisons performed between MIPAS CH4 and N2O profiles produced by the current ESA operational software (Instrument Processing Facility version 4.61 or IPF v4.61, full resolution MIPAS data covering the period 9 July 2002 to 26 March 2004) and correlative measurements obtained from balloon and aircraft experiments as well as from satellite sensors or from ground-based instruments. In the middle stratosphere, no significant bias is observed between MIPAS and correlative measurements, and MIPAS is providing a very consistent and global picture of the distribution of CH4 and N2O in this region. In average, the MIPAS CH4 values show a small positive bias in the lower stratosphere of about 5%. A similar situation is observed for N2O with a positive bias of 4%. In the lower stratosphere/upper troposphere (UT/LS) the individual used MIPAS data version 4.61 still exhibits some unphysical oscillations in individual CH4 and N2O profiles caused by the processing algorithm (with almost no regularization). Taking these problems into account, the MIPAS CH4 and N2O profiles are behaving as expected from the internal error estimation of IPF v4.61 and the estimated errors of the correlative measurements

The UV-A and visible solar irradiance spectrum: inter-comparison of absolutely calibrated, spectrally medium resolution solar irradiance spectra from balloon- and satellite-borne measurements

International audienceWithin the framework of the ENVISAT/-SCIAMACHY satellite validation, solar irradiance spectra are absolutely measured at moderate resolution in the UV/visible spectral range (in the UV from 316.7–418 nm and the visible from 400–652 nm at a full width half maximum resolution of 0.55 nm and 1.48 nm, respectively) from aboard the azimuth-controlled LPMA/DOAS balloon gondola at around 32 km balloon float altitude. After accounting for the atmospheric extinction due to Rayleigh scattering and gaseous absorption (O3, and NO2), the measured solar spectra are compared with previous observations. Our solar irradiance is +1.6% larger than the re-calibrated Kurucz et al. (1984) solar spectrum (Fontenla et al., 1999, called MODTRAN 3.5) in the visible spectral range (435–650 nm), +1.5% larger in the (370–415 nm) wavelength interval, but -4% smaller in the UV spectral range (316.7–370 nm), when the Kurucz spectrum is convolved to the spectral resolution of our instrument. The same comparison with the SOLSPEC solar spectrum (Thuillier et al., 1997, 1998a, b) confirms the somewhat larger solar irradiance (+1.7%) measured by the balloon instrument from 435–500 nm, but not from 500–650 nm, where the SOLSPEC is -1.3% lower than MODTRAN 3.5. Comparison of the SCIAMACHY solar spectrum from channels 1 to 4 (– re-calibrated by the University of Bremen –) with MODTRAN 3.5 indicates an agreement of +0.2% in the visible spectral range (435–585 nm). With this calibration, the SCIAMACHY solar spectrum is congruent with the balloon observations (-1%) in the 316.7–370 nm wavelength range, but both are up to -5%/-3% smaller than MODTRAN 3.5 and SOLSPEC, respectively. In agreement with findings of Skupin et al. (2002) our study emphasizes that the present ESA SCIAMACHY level 1 calibration is systematically +15% larger in the considered wavelength intervals when compared to all available other solar irradiance measurements

Diode-pumped, ion-exchanged Er/Yb waveguide laser at 1.5µm in phosphorus-free silicate glass

We demonstrate the first diode-pumped, planar ErNb waveguide laser. The device was fabricated by thallium-exchange in a phosphorus-free silicate glass. Lasing was achieved with a low threshold of 15 mW, indicating the absence of the severe backtransfer effects previously reported in Er/Yb bulk laser silicate glasses

Determination of mass transfer coefficients in high-pressure two-phase flows in capillaries using Raman spectroscopy

This study presents a method for the experimental determination of local volumetric mass transfer coefficients kLaL in a high-pressure two-phase flow of water (H2O) and carbon dioxide (CO2) in a micro-capillary using Raman spectroscopy. H2O and CO2 are continuously and co-currently fed at high pressure (8, 9 and 10 MPa) and moderate temperature (303 K) into a fused silica micro-capillary. A segmented two-phase flow is obtained therein and the fraction of CO2 in the water-rich phase is measured in-situ at different points along the capillary using Raman spectroscopy. A modified Henry’s law is used to compute the equilibrium compositions of the water-rich phase at the desired pressure and temperature. A mixture density model is used to convert the fraction of CO2 in the water-rich phase into a CO2 concentration. The volumetric liquid mass transfer coefficient is computed at various axial locations along the capillary, from the contacting zone to the end of the capillary. Experimentally derived kLaL values range between 2.10−3 and 5.10−3 s−1

Anomalously high uniform upconversion in an erbium-doped waveguide amplifier

The performance of a planar Er3+-doped ion-exchanged waveguide is compared to a detailed model, including uniform upconversion estimated from spectral measurements. A discrepancy between experiment and theory requires a much higher level of uniform upconversion than predicted. We consider possible explanations for this anomaly

Balloon-borne stratospheric BrO measurements: comparison with Envisat/SCIAMACHY BrO limb profiles

International audienceFor the first time, results of four stratospheric BrO profiling instruments, are presented and compared with reference to the SLIMCAT 3-dimensional chemical transport model (3-D CTM). Model calculations are used to infer a BrO profile validation set, measured by 3 different balloon sensors, for the new Envisat/SCIAMACHY (ENVIronment SATellite/SCanning Imaging Absorption spectroMeter for Atmospheric CHartographY) satellite instrument. The balloon observations include (a) balloon-borne in situ resonance fluorescence detection of BrO (Triple), (b) balloon-borne solar occultation DOAS measurements (Differential Optical Absorption Spectroscopy) of BrO in the UV, and (c) BrO profiling from the solar occultation SAOZ (Systeme d'Analyse par Observation Zenithale) balloon instrument. Since stratospheric BrO is subject to considerable diurnal variation and none of the measurements are performed close enough in time and space for a direct comparison, all balloon observations are considered with reference to outputs from the 3-D CTM. The referencing is performed by forward and backward air mass trajectory calculations to match the balloon with the satellite observations. The diurnal variation of BrO is considered by 1-D photochemical model calculation along the trajectories. The 1-D photochemical model is initialised with output data of the 3-D model with additional constraints on the vertical transport, the total amount and photochemistry of stratospheric bromine as given by the various balloon observations. Total [Bry]=(20.1±2.5) pptv obtained from DOAS BrO observations at mid-latitudes in 2003, serves as an upper limit of the comparison. Most of the balloon observations agree with the photochemical model predictions within their given error estimates. First retrieval exercises of BrO limb profiling from the SCIAMACHY satellite instrument on average agree to around 20% with the photochemically-corrected balloon observations of the remote sensing instruments (SAOZ and DOAS). An exception is the in situ Triple profile, in which the balloon and satellite data mostly does not agree within the given errors. In general, the satellite measurements show systematically higher values below 25 km than the balloon data and a change in profile shape above about 25 km