2,434 research outputs found
Production and Downstream Integration of 5-(Chloromethyl)furfural from Lignocellulose
The importance of reducing the strong dependence of the chemical industry on fossil feedstock is no longer a debate. Above-the-ground carbon is abundant, but scalable technologies to supply alternatives to fossil-fuel-derived chemicals and/or materials at the world scale are still not available. Lignocellulosic biomass is the most available carbon source, and a first requirement for its valorization is the complete saccharification of its sugar-bearing components. HCl-based technologies can achieve this at 20 °C and ambient pressure. These principles were disclosed in the 1920s, but the inability to economically separate sugars from acids impeded its commercialization. Avantium Chemicals B.V. developed a modern version of this “Bergius” highly concentrated acid hydrolysis, in which the saccharides in HCl are transformed into furanics without any prior purification, in particular, to 5-(chloromethyl)furfural (CMF). Saccharide conversion to CMF was developed by Mascal in the early 2000s. CMF is extracted in situ using immiscible organic solvents, allowing for an easy product separation. This study not only targets to investigate the viability and optimization of this integrated process but also aims to predict the outcome of the CMF formation reaction by applying design of experiment techniques from the hydrolyzed saccharides varying a broad range of reaction parameters
Tapered-amplified AR-coated laser diodes for Potassium and Rubidium atomic-physics experiments
We present a system of room-temperature extended-cavity grating-diode lasers
(ECDL) for production of light in the range 760-790nm. The extension of the
tuning range towards the blue is permitted by the weak feedback in the cavity:
the diodes are anti-reflection coated, and the grating has just 10%
reflectance. The light is then amplified using semiconductor tapered amplifiers
to give more than 400mW of power. The outputs are shown to be suitable for
atomic physics experiments with potassium (767nm), rubidium (780nm) or both, of
particular relevance to doubly-degenerate boson-fermion mixtures
MAD@VLT: Deep into the Madding Crowd of Omega Centauri
We present deep and accurate Near-Infrared (NIR) photometry of the Galactic
Globular Cluster (GC) Omega Cen. Data were collected using the Multi-Conjugate
Adaptive Optics Demonstrator (MAD) on VLT (ESO). The unprecedented quality of
the images provided the opportunity to perform accurate photometry in the
central crowded regions. Preliminary results indicate that the spread in age
among the different stellar populations in Omega Cen is limited.Comment: 6 pages, 3 figures, to appear in the Springer Astrophysics and Space
Science Proceedings, "Science with the VLT in the ELT era", ed. A. Moorwoo
Antenatal corticosteroid treatment for the prevention of peri-intraventricular haemorrhage in preterm newborns: a retrospective cohort study using transfontanelle ultrasonography
Objective: The objective of this study was to assess the correlation between antenatal corticosteroids and peri-intraventricular haemorrhage (PIVH) using transfontanelle ultrasonography, as well as to evaluate the risk factors for its incidence. Methods: We performed a retrospective cohort study using medical records of preterm newborns. The protocol for maternal corticoid administration for foetal lung maturation included dexamethasone 4 mg (intramuscular) 8/8 hours per 48 hours, with one cycle per week. The diagnosis of periintraventricular haemorrhage was based on transfontanelle ultrasonography, using the Papile's classification. The following risk factors for peri-intraventricular haemorrhage were assessed: birth weight, gestational age at delivery, type of delivery, newborn's sex, surfactant administration, premature rupture of membranes and previous history of infection during the current pregnancy. The student's t-test and chi-square test were used for statistical analysis. Results: Our sample population included 184 preterm newborns. Transfontanelle ultrasonography revealed peri-intraventricular haemorrhage in 32 (74.4%) and periventricular leukomalacia in 11 (25.6%) newborns. Grade I haemorrhage was found in 20 (62.5%), grade II in five (15.6%), and grade III in seven (21.8%) newborns, as in accordance with Papile's classification. Vaginal delivery (p = 0.010), birth weight <1500 g (p = 0.024), gestational age at delivery ≤32 weeks (p = 0.018), and previous history of infection during pregnancy (p = 0.013) were considered risk factors for peri-intraventricular haemorrhage in preterm newborns. Conclusion: Maternal corticoid administration for foetal lung maturation showed a protective effect against peri-intraventricular haemorrhage in preterm newborns. The risk factors for peri-intraventricular haemorrhage were determined
Coherent combining of high brightness tapered lasers in Master Oscillator Power Amplifier configuration
International audienceImproved diode laser beam combining techniques are in strong demand for applications in material processing. Coherent beam combining (CBC) is the only combining approach that has the potential to maintain or even improve all laser properties, and thus has high potential for future systems. As part of our ongoing studies into CBC of diode lasers, we present recent progress in the coherent superposition of high-power single-pass tapered laser amplifiers. The amplifiers are seeded by a DFB laser at λ = 976 nm, where the seed is injected into a laterally single-mode ridge-waveguide input section. The phase pistons on each beam are actively controlled by varying the current in the ridge section of each amplifier, using a sequential hill-climbing algorithm, resulting in a combined beam with power fluctuations of below 1%. The currents into the tapered sections of the amplifiers are separately controlled, and remain constant. In contrast to our previous studies, we favour a limited number of individual high-power amplifiers, in order to preserve a high extracted power per emitter in a simple, low-loss coupling arrangement. Specifically, a multi-arm interferometer architecture with only three devices is used, constructed using 6 mm-long tapered amplifiers, mounted junction up on C-mounts, to allow separate contact to single mode and amplifier sections. A maximum coherently combined power of 12.9 W is demonstrated in a nearly diffraction-limited beam, corresponding to a 65% combining efficiency, with power mainly limited by the intrinsic beam quality of the amplifiers. Further increased combined power is currently sought
Hippocampal long-term potentiation is disrupted during expression and extinction but is restored after reinstatement of morphine place preference
Learned associations between environmental cues and morphine use play an important role in the maintenance and/or relapse of opioid addiction. Although previous studies suggest that context-dependent morphine treatment alters glutamatergic transmission and synaptic plasticity in the hippocampus, their role in morphine conditioned place preference (CPP) and reinstatement remains unknown. We investigated changes in synaptic plasticity and NMDAR expression in the hippocampus after the expression, extinction, and reinstatement of morphine CPP. Here we report that morphine CPP is associated with increased basal synaptic transmission, impaired hippocampal long-term potentiation (LTP), and increased synaptic expression of the NR1 and NR2b NMDAR subunits. Changes in synaptic plasticity, synaptic NR1 and NR2b expression, and morphine CPP were absent when morphine was not paired with a specific context. Furthermore, hippocampal LTP was impaired and synaptic NR2b expression was increased after extinction of morphine CPP, indicating that these alterations in plasticity may be involved in the mechanisms underlying the learning of drug–environment associations. After extinction of morphine CPP, a priming dose of morphine was sufficient to reinstate morphine CPP and was associated with LTP that was indistinguishable from saline control groups. In contrast, morphine CPP extinguished mice that received a saline priming dose did not show CPP and had disrupted hippocampal LTP. Finally, we found that reinstatement of morphine CPP was prevented by the selective blockade of the NR2b subunit in the hippocampus. Together, these data suggest that alterations in synaptic plasticity and glutamatergic transmission play an important role in the reinstatement of morphine CPP
Modal analysis and measurement of water cooling induced vibrations on a CLIC main beam quadrapole prototype
ECFA Detector R&D Panel, Review Report
Two special calorimeters are foreseen for the instrumentation of the very
forward region of an ILC or CLIC detector; a luminometer (LumiCal) designed to
measure the rate of low angle Bhabha scattering events with a precision better
than 10 at the ILC and 10 at CLIC, and a low polar-angle
calorimeter (BeamCal). The latter will be hit by a large amount of
beamstrahlung remnants. The intensity and the spatial shape of these
depositions will provide a fast luminosity estimate, as well as determination
of beam parameters. The sensors of this calorimeter must be radiation-hard.
Both devices will improve the e.m. hermeticity of the detector in the search
for new particles. Finely segmented and very compact electromagnetic
calorimeters will match these requirements. Due to the high occupancy, fast
front-end electronics will be needed. Monte Carlo studies were performed to
investigate the impact of beam-beam interactions and physics background
processes on the luminosity measurement, and of beamstrahlung on the
performance of BeamCal, as well as to optimise the design of both calorimeters.
Dedicated sensors, front-end and ADC ASICs have been designed for the ILC and
prototypes are available. Prototypes of sensor planes fully assembled with
readout electronics have been studied in electron beams.Comment: 61 pages, 51 figure
Measurement of shower development and its Moli\`ere radius with a four-plane LumiCal test set-up
A prototype of a luminometer, designed for a future e+e- collider detector,
and consisting at present of a four-plane module, was tested in the CERN PS
accelerator T9 beam. The objective of this beam test was to demonstrate a
multi-plane tungsten/silicon operation, to study the development of the
electromagnetic shower and to compare it with MC simulations. The Moli\`ere
radius has been determined to be 24.0 +/- 0.6 (stat.) +/- 1.5 (syst.) mm using
a parametrization of the shower shape. Very good agreement was found between
data and a detailed Geant4 simulation.Comment: Paper published in Eur. Phys. J., includes 25 figures and 3 Table
Performance of fully instrumented detector planes of the forward calorimeter of a Linear Collider detector
Detector-plane prototypes of the very forward calorimetry of a future
detector at an e+e- collider have been built and their performance was measured
in an electron beam. The detector plane comprises silicon or GaAs pad sensors,
dedicated front-end and ADC ASICs, and an FPGA for data concentration.
Measurements of the signal-to-noise ratio and the response as a function of the
position of the sensor are presented. A deconvolution method is successfully
applied, and a comparison of the measured shower shape as a function of the
absorber depth with a Monte-Carlo simulation is given.Comment: 25 pages, 32 figures, revised version following comments from
referee
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