50 research outputs found
Composition, Structure and Mechanical Properties of Industrially Sputtered Ta–B–C Coatings
Ta–B–C coatings were non-reactively sputter-deposited in an industrial batch coater from a single segmented rotating cylindrical cathode employing a combinatorial approach. The chemical composition, morphology, microstructure, mechanical properties, and fracture resistance of the coatings were investigated. Their mechanical properties were linked to their microstructure and phase composition. Coatings placed stationary in front of the racetrack of the target and those performing a 1-axis rotation around the substrate carousel are compared. Utilization of the substrate rotation has no significant effect on the chemical composition of the coatings deposited at the same position compared to the cathode. Whereas the morphology of coatings with corresponding chemical composition is similar for stationary as well as rotating samples, the rotating coatings exhibit a distinct multilayered structure with a repetition period in the range of nanometers despite utilizing a non-reactive process and a single sputter source. All the coatings are either amorphous, nanocomposite or nanocrystalline depending on their chemical composition. The presence of TaC, TaB, and/or TaB2 phases is identified. The crystallite size is typically less than 5 nm. The highest hardness of the coatings is associated with the presence of larger grains in a nanocomposite structure or formation of polycrystalline coatings. The number, density, and length of cracks observed after high-load indentation is on par with current optimized commercially available protective coatings
Waveguide grating mirror in a fully suspended 10 meter Fabry-Perot cavity
We report on the first demonstration of a fully suspended 10m Fabry-Perot
cavity incorporating a waveguide grating as the coupling mirror. The cavity was
kept on resonance by reading out the length fluctuations via the
Pound-Drever-Hall method and employing feedback to the laser frequency. From
the achieved finesse of 790 the grating reflectivity was determined to exceed
99.2% at the laser wavelength of 1064\,nm, which is in good agreement with
rigorous simulations. Our waveguide grating design was based on tantala and
fused silica and included a ~20nm thin etch stop layer made of Al2O3 that
allowed us to define the grating depth accurately during the fabrication
process. Demonstrating stable operation of a waveguide grating featuring high
reflectivity in a suspended low-noise cavity, our work paves the way for the
potential application of waveguide gratings as mirrors in high-precision
interferometry, for instance in future gravitational wave observatories
Michelson interferometer with diffractively-coupled arm resonators in second-order Littrow configuration
Michelson-type laser-interferometric gravitational-wave (GW) observatories
employ very high light powers as well as transmissively- coupled Fabry-Perot
arm resonators in order to realize high measurement sensitivities. Due to the
absorption in the transmissive optics, high powers lead to thermal lensing and
hence to thermal distortions of the laser beam profile, which sets a limit on
the maximal light power employable in GW observatories. Here, we propose and
realize a Michelson-type laser interferometer with arm resonators whose
coupling components are all-reflective second-order Littrow gratings. In
principle such gratings allow high finesse values of the resonators but avoid
bulk transmission of the laser light and thus the corresponding thermal beam
distortion. The gratings used have three diffraction orders, which leads to the
creation of a second signal port. We theoretically analyze the signal response
of the proposed topology and show that it is equivalent to a conventional
Michelson-type interferometer. In our proof-of-principle experiment we
generated phase-modulation signals inside the arm resonators and detected them
simultaneously at the two signal ports. The sum signal was shown to be
equivalent to a single-output-port Michelson interferometer with
transmissively-coupled arm cavities, taking into account optical loss. The
proposed and demonstrated topology is a possible approach for future
all-reflective GW observatory designs
Diffractively coupled Fabry-Perot resonator with power-recycling
We demonstrate the optical coupling of two cavities without light
transmission through a substrate. Compared to a conventional coupling
component, that is a partially transmissive mirror, an all-reflective coupler
avoids light absorption in the substrate and therefore associated thermal
problems, and even allows the use of opaque materials with possibly favourable
mechanical and thermal properties. Recently, the all-reflective coupling of two
cavities with a low-efficiency 3-port diffraction grating was theoretically
investigated. Such a grating has an additional (a third) port. However, it was
shown that the additional port does not necessarily decrease the bandwidth of
the coupled cavities. Such an all-reflective scheme for cavity coupling is of
interest in the field of gravitational wave detection. In such detectors light
that is resonantly enhanced inside the so-called power-recycling cavity is
coupled to (kilometre-scale) Fabry-Perot resonators representing the arms of a
Michelson interferometer. In order to achieve a high sensitivity over a broad
spectrum, the Fabry-Perot resonators need to have a high bandwidth for a given
(high) power build-up. We realized such an all-reflective coupling in a
table-top experiment. Our findings are in full agreement with the theoretical
model incorporating the characteristics of the 3-port grating used, and
therefore encourage the application of all-reflective cavity couplers in future
gravitational wave detectors
Pismenost nakon decentralizacije. Nudi li Mreža novi oblik pismenosti?
Rad će postaviti pitanje nudi li danas Mreža alat za “osnaživanje čitatelja”, kako je najavljivala hipertekstualna teorija devedesetih. Interaktivnost kao “prirodan” oblik pismenosti postala je ideologem razumijevanja elektroničke pismenosti. No je li danas uistinu riječ o demokratizaciji čitanja-pisanja putem odabira smjera, “kretanja” virtualnim prostorom teksta? Rad će naglasiti razliku između Web 2.0 žanrova i koncepcije hiperteksta te razliku tekstualne i vizualne pismenosti. Ono što ćemo ovdje nazvati “topografskom proizvodnošću” bitno se razlikuje od “distributivne proizvodnosti” kakvu danas susrećemo na Mreži. Mreža nije orijentirana isključivo na proizvodnju virtualnog dérivea, trodimenzionalnog prostora kretanja, već je riječ prvenstveno o komunikacijskom kanalu. Umjesto topografije, za Mrežu će biti ključno povezivanje bilo kojih dviju točaka i uspostavljanje kanala “distribucije”. Temelj distributivne strukture jesu mrežni protokoli, prvenstveno TCP/IP protokol koji omogućava peer-to-peer, izravnu komunikaciju dvaju računala. Kanali neovisne distribucije postojali su i ranije, prvenstveno u polju alternativnih ili opozicijskih kultura u obliku DIY praksi, no domet njihove distributivne mreže bio je slab. Mreža je kanal do sada nezamislive fleksibilne distribucije, nehijerarhijski kanal koji (digitalnoj) proizvodnji pripaja dodatnu vrijednost. Politička, ekonomska i kulturalna pitanja redefinirana su arhitekturom te protokolima koji tu arhitekturu definiraju. Protokoli su pravila koja su podređena socijalnom konsenzusu. U tom smislu politička teorija novih medija mora napustiti mit “osnaživanja čitatelja” i krenuti prema složenom tipu materijalne analize ili analize arhitekture te socijalnih pravila koja tu arhitekturu definiraju. Proizvodno-distribucijski subjekti i tekstovi naseljavaju sve mrežne komunikacijske kanale. Bloganje, Twitteranje, Facebookanje, Flickeranje, YouTubanje naših života dio je procesa lifestreama. Dio je ontologije elektroničkog identiteta ultimativni zahtjev za menadžeriranjem života koji se provodi translacijom identitetskih varijabli na Mrežu
Roflumilast in moderate-to-severe chronic obstructive pulmonary disease treated with longacting bronchodilators: two randomised clinical trials
Background Patients with chronic obstructive pulmonary disease (COPD) have few options for treatment. The efficacy and safety of the phosphodiesterase-4 inhibitor roflumilast have been investigated in studies of patients with moderate-to-severe COPD, but not in those concomitantly treated with longacting inhaled bronchodilators. The effect of roflumilast on lung function in patients with COPD that is moderate to severe who are already being treated with salmeterol or tiotropium was investigated. Methods In two double-blind, multicentre studies done in an outpatient setting, after a 4-week run-in, patients older than 40 years with moderate-to-severe COPD were randomly assigned to oral roflumilast 500 mu g or placebo once a day for 24 weeks, in addition to salmeterol (M2-127 study) or tiotropium (M2-128 study). The primary endpoint was change in prebronchodilator forced expiratory volume in 1s (FEV(1)). Analysis was by intention to treat. The studies are registered with ClinicalTrials.gov, number NCT00313209 for M2-127, and NCT00424268 for M2-128. Findings In the salmeterol plus roflumilast trial, 466 patients were assigned to and treated with roflumilast and 467 with placebo; in the tiotropium plus roflumilast trial, 371 patients were assigned to and treated with roflumilast and 372 with placebo. Compared with placebo, roflumilast consistently improved mean prebronchodilator FEV(1) by 49 mL (p<0.0001) in patients treated with salmeterol, and 80 mL (p<0.0001) in those treated with tiotropium. Similar improvement in postbronchodilator FEV(1) was noted in both groups. Furthermore, roflumilast had beneficial effects on other lung function measurements and on selected patient-reported outcomes in both groups. Nausea, diarrhoea, weight loss, and, to a lesser extent, headache were more frequent in patients in the roflumilast groups. These adverse events were associated with increased patient withdrawal. Interpretation Roflumilast improves lung function in patients with COPD treated with salmeterol or tiotropium, and could become an important treatment for these patients
Richard Hancox
The authors discuss Hancox's films which delineate the contradictions between personal memories and the collective construction of Canadian regional identity. 25 bibl. ref