429 research outputs found
On the Kramers-Kronig transform with logarithmic kernel for the reflection phase in the Drude model
We use the Kramers-Kronig transform (KKT) with logarithmic kernel to obtain
the reflection phase and, subsequently, the complex refractive index of a bulk
mirror from reflectance. However, there remains some confusion regarding the
formulation for this analysis. Assuming the damped Drude model for the
dielectric constant and the oblique incidence case, we calculate the additional
terms: phase at zero frequency and Blashke factor and we propose a reformulated
KKT within this model. Absolute reflectance in the s-polarization case of a
gold film is measured between 40 and 350 eV for various glancing angles using
synchrotron radiation and its complex refractive index is deduced using the
reformulated KKT that we propose. The results are discussed with respect to the
data available in the literature.Comment: 18 pages, piblished in j. Mod. Opt. 57, 1504 (2010
Cr/Sc multilayer radiator for parametric EUV radiation in "water-window" spectral range
The results of experimental investigation of parametric radiation generated by 5.7 MeV electrons in a multilayer structure consisting of 100 Cr/Sc bi-layers deposited on a Si3N4 membrane are presented. The multilayer structure was specially created for generation of parametric radiation with photon energy in "water-window" spectral rang
Thermal, mechanical and viscoelastic properties of citric acid-crosslinked starch/cellulose composite foams
In this work, biodegradable starch/cellulose composite foams were fabricated at 220 °C by compression moulding gelatinised starch containing cellulose fibres as a reinforcing agent and citric acid as a cross-linking agent. It was found that the stiffness, tensile strength, flexural strength, and hydrophobicity of the starch/cellulose composite foams increased, and water absorption capacity decreased with an increase in the concentration of citric acid. The tensile strength increased from 1.76 MPa for 0 % citric acid to 2.25 MPa for the starch/cellulose composite foam crosslinked with 5 % (w/w) citric acid. Similarly, the flexural modulus also increased from 445 MPa to 601.1 MPa, and the flexural strength from 3.76 MPa to 7.61 MPa, for the composite foam crosslinked with 5 % (w/w) citric acid. The crosslinked composite foams showed better thermal stability compared to the non-crosslinked composite foam. The resulting composite foams could be used as a biodegradable alternative to expanded polystyrene packaging
Investigation of the thermal stability of Mg/Co periodic multilayers for EUV applications
We present the results of the characterization of Mg/Co periodic multilayers
and their thermal stability for the EUV range. The annealing study is performed
up to a temperature of 400\degree C. Images obtained by scanning transmission
electron microscopy and electron energy loss spectroscopy clearly show the good
quality of the multilayer structure. The measurements of the EUV reflectivity
around 25 nm (~49 eV) indicate that the reflectivity decreases when the
annealing temperature increases above 300\degreeC. X-ray emission spectroscopy
is performed to determine the chemical state of the Mg atoms within the Mg/Co
multilayer. Nuclear magnetic resonance used to determine the chemical state of
the Co atoms and scanning electron microscopy images of cross sections of the
Mg/Co multilayers reveal changes in the morphology of the stack from an
annealing temperature of 305\degreee;C. This explains the observed reflectivity
loss.Comment: Published in Applied Physics A: Materials Science \& Processing
Published at
http://www.springerlink.com.chimie.gate.inist.fr/content/6v396j6m56771r61/ 21
page
Thermo-mechanical, morphological and water absorption properties of thermoplastic starch/cellulose composite foams reinforced with PLA
Expanded polystyrene foams are lightweight and cheap, but they have excellent strength and insulation properties. However, their inability to biodegrade in traditional landfill situations makes their disposal problematic. Starch, a polysaccharide, has the potential to replace synthetic thermoplastics for some applications but starch-based foams are hydrophilic, which limits their applications. In this work, polylactide (PLA), a sustainably derived and industrially compostable polymer, was added to starch/cellulose composite foams to enhance their water barrier properties. PLA powder at various weight % was mixed with moistened starch and cellulose mixture, and composite foams were prepared by compression moulding at 220 °C. The thermomechanical and viscoelastic properties of the produced foam materials were analysed by thermogravimetric analysis, dynamic mechanical thermal analysis, mechanical testing, and also by the 3-point compressive mechanical quasi-static testing. It was found that the tensile strength of the composite foams increased with an increase in the PLA loading, which increased from 2.50 MPa for 0% PLA to 3.27 MPa for 9.72% PLA loading. The flexural strength also increased from 345.91 kPa for the 0% PLA to 378.53 kPa for the composite foam containing 4.86% PLA; beyond which the flexural strength started decreasing with an increase in PLA loading. Similarly, the stiffness of the starch/cellulose composite also increased with an increase in PLA loading up to 4.86%, and further increase in PLA loading decreased the stiffness. The flexural modulus of the composite foams increased from 522 MPa for 0% PLA loading to 542.85 MPa for the 4.86% PLA loading. The thermal stability of the starch/cellulose composite foams also increased and the water absorbency decreased with the increased PLA loading
Anterolateral ligament reconstruction does not delay functional recovery, rehabilitation, and return to sport after anterior cruciate ligament reconstruction. A matched-pair analysis from the SANTI (Scientific ACL Network International) Study Group
Purpose: To determine whether the addition of an anterolateral ligament reconstruction (ALLR) resulted in delayed functional recovery (based on the Knee Santy Athletic Return to Sport [K-STARTS] score) at 6 months after anterior cruciate ligament reconstruction (ACLR). Methods: A retrospective analysis of prospectively collected data from consecutive pa- tients who underwent an ACLR between September 2017 and December 2020 was conducted. Patients who received an isolated hamstring autograft (isolated ACLR group) were propensity matched in a 1:1 ratio to patients who received a hamstring autograft ACLR combined with an ALLR (ACLR-ALLR group). Outcome measures included the Tegner Activity Scale and the K-STARTS testda validated composite return-to-sports test (including the Anterior Cruciate LigamenteReturn to Sport After Injury scale, Qualitative Assessment of Single-Leg Landing tool, limb symmetry index, and ability to change direction using the Modified Illinois Change of Direction Test). Results: The study included 111 matched pairs. At 6 months postoperatively, there were no significant differences between groups in the overall K-STARTS score (65.4 for isolated ACLR vs 61.2 for ACLR-ALLR, P 1⁄4 .087) or the Tegner Activity Scale score (3.7 for isolated ACLR vs 3.8 for ACLR-ALLR, P 1⁄4 .45). In addition, an evaluation of the subscales of the K-STARTS score revealed no disadvantage across the domains of neuromuscular control, limb symmetry index, agility, or psychological readiness to return to sport when an ALLR was performed. Conclusions: The addition of ALLR at the time of ACLR does not delay functional recovery. Spe- cifically, at 6 months postoperatively, there was no disadvantage in patients undergoing ALLR-ACLR, when compared with those undergoing isolated ACLR, with respect to neuromuscular control, limb symmetry indices (hop tests), agility, or psychological readiness to return to sport
Introduction of Zr in nanometric periodic Mg/Co multilayers
We study the introduction of a third material, namely Zr, within a nanometric
periodic Mg/Co structure designed to work as optical component in the extreme
UV (EUV) spectral range. Mg/Co, Mg/Zr/Co, Mg/Co/Zr and Mg/Zr/Co/Zr multilayers
are designed, then characterized in terms of structural quality and optical
performances through X-ray and EUV reflectometry measurements respectively. For
the Mg/Co/Zr structure, the reflectance value is equal to 50% at 25.1 nm and
45deg of grazing incidence and reaches 51.3% upon annealing at 200deg C.
Measured EUV reflectivity values of tri-layered systems are discussed in terms
of material order within a period and compared to the predictions of the
theoretical model of Larruquert. Possible applications are pointed out.Comment: 19 page
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