3 Gbit/s LED-based step index plastic optical fiber link using multilevel pulse amplitude modulation

Multilevel PAM is investigated for a LED-based SI-POF link. Using PAM-8, transmission at a record 3 Gbit/s is demonstrated for a maximum length of 25 m step index POF with offline post-receiver processing. © 2013 OSA.

Mode characteristics of semiconductor equilateral triangle microcavities with side length of 5-20 mu m

Semiconductor equilateral triangle microresonators (ETRs) with side length of 5, 10, and 20 mum are fabricated by the two-step inductively coupled plasma (ICP) etching technique. The mode properties of fabricated InGaAsP ETRs are investigated experimentally by photoluminescence (PL) with the pumping source of a 980-nm semiconductor laser and distinct peaks are observed in the measured PL spectra. The wavelength spacings of the distinct peaks agree very well with the theoretical longitudinal mode intervals of the fundamental transverse modes in the ETRs, which verifies that the distinct peaks are corresponding to the enhancement of resonant modes. The mode quality factors are calculated from the width of the resonant peaks of the PL spectra, which are about 100 for the ETR with side length of 20 mum.

A VSLMS Style Tap-length Learning Algorithm for Structure Adaptation

Compared with the ordinary adaptive filter, the variable-length adaptive filter is more efficient (including smaller., lower power consumption and higher computational complexity output SNR) because of its tap-length learning algorithm, which is able to dynamically adapt its tap-length to the optimal tap-length that best balances the complexity and the performance of the adaptive filter. Among existing tap-length algorithms, the LMS-style Variable Tap-Length Algorithm (also called Fractional Tap-Length Algorithm or FT Algorithm) proposed by Y.Gong has the best performance because it has the fastest convergence rates and best stability. However, in some cases its performance deteriorates dramatically. To solve this problem, we first analyze the FT algorithm and point out some of its defects. Second, we propose a new FT algorithm called 'VSLMS' (Variable Step-size LMS) Style Tap-Length Learning Algorithm, which not only uses the concept of FT but also introduces a new concept of adaptive convergence slope. With this improvement the new FT algorithm has even faster convergence rates and better stability. Finally, we offer computer simulations to verify this improvement.

Effect of alkyl group length on the conductivity in the 2,3,7,8,12,13,17,18-octakis(alkyl-thio)tetraazaporphyrins and redox properties of the metallooctakis(hexyl-thio)tetraazaporphyrins

A series of 2,3,7,8,12,13,17,18-octakis(alkyl-thio)tetraazaporphyrins (H(2)OATTAP) with different alkyl chain lengths have been synthesized. Cyclic voltammetry and differential pulse voltammetry have been used to investigate the effect of the controlled lengths of the eight peripheral thioether tails on the redox behavior of the molecules. The electrochemical reduction of octakis(hexyl-thio)tetraazaporphyrins, MOHTTAP (where M = Cu, Ni), was studied in 1,2-dichloroethane at a platinum electrode. The Cu derivative was oxidized in one single-electron-transfer step to yield a pi-cation radical and reduced in three single-electron-transfer steps to yield a pi-anion radical, dianion and trianion, respectively. For the Ni derivative, electron transfer reactions involving both the central metal atom and the macrocyclic ring were observed. Electron transfer pathways are proposed based upon voltammetric and in situ spectroelectrochemical results.

Surface plasmon polariton propagation across a gentle silver step

Surface plasmon polaritons (SPPs) are excited with light of wavelength lambda (1) = 632.8 nm on or near a gentle Ag/Ag step structure using focused beam, prism coupling and detected using a bare, sharpened fibre tip. The tip-sample separation is controlled by means of an evanescent optical field at wavelength lambda (2) = 543.5 nm in a photon scanning tunnelling microscope (PSTM). The SPP propagation properties are first characterised on both the thin and thick sections of the Ag film structure either side of the step, both macroscopically, using attenuated total reflection, and microscopically from the PSTM images; the two techniques yield very good agreement. It is found that the SPP propagation length is similar to 10-11 mum across the step in each direction (thick to thin and vice versa) as observed in the PSTM images. Thus, with reference to the propagation lengths of 14.2 and 11.7 mum for the thick and thin planar parts of the Ag film respectively, it is concluded that the SPPs negotiate the step reasonably successfully. Importantly, also, it is shown that images may be produced, displaying SPPs with either an artificially enhanced (similar to 15-20 mum) or truncated (5-8 mum) propagation length across the step. Consideration of such images leads us to suggest the possibility that the photon tunnelling occurs in a local water environment. (C) 2001 Elsevier Science B.V. All rights reserved.

Cost-effectivness in a DRG system for two-step exchange of infected total joint arthroplasty

The costs related to the treatment of infected total joint arthroplasties represent an ever groving burden to the society. Different patient-adapted therapeutic options like débridement and retention, 1- or 2-step exchange can be used. If a 2-step exchange is used we have to consider short (2-4 weeks) or long (>4-6 weeks) interval treatment. The Swiss DRG (Diagnose related Groups) determines the reimboursement the hopsital receives for the treatment of an infected total arthroplasty. The review assesses the cost-effectiveness of hospitalisation practices linked to surgical treatment in the two-stage exchange of a prosthetic-joint infection. The aim of this retrospectiv study is to compare the economical impact between a short (2 to 4 weeks) versus a long (6 weeks and above) interval during a two-satge procedure to determine the financial impact. Retrospectiv study of the patients with a two-stage procedure for a hip or knee prosthetic joint infection at CHUV hospital Lausanne (Switzerland) between 2012 and 2013. The review analyses the correlation between the interval length and the length of the hospital stay as well as with the costs and revenues per hospital stay. In average there is a loss of 40′000 Euro per hospitalisation for the treatment of prosthetic joint infection. Revenues never cover all the costs, even with a short interval procedure. This economical loss increases with the length of the hospital stay if a long-term intervall is choosen. The review explores potential for improvement in reimbourement practices and hospitalisation practices in the current Swiss healthcare setting. There should be alternative setups to decrease the burden of medical costs by a) increase the reimboursment for the treatment of infected total joints or by b) splitting the hospital stay with partners (rapid transfer after first operation from center hospital to level 2 hospital and retransfer for second operation to center) in order to increase revenues.

Tomographic imaging of molecular orbitals in length and velocity form

Recently Itatani et al. [Nature 432, 876 (2004)] introduced the new concept of molecular orbital tomography, where high harmonic generation (HHG) is used to image electronic wave functions. We describe an alternative reconstruction form, using momentum instead of dipole matrix elements for the electron recombination step in HHG. We show that using this velocity-form reconstruction, one obtains better results than using the original length-form reconstruction. We provide numerical evidence for our claim that one has to resort to extremely short pulses to perform the reconstruction for an orbital with arbitrary symmetry. The numerical evidence is based on the exact solution of the time-dependent Schrödinger equation for 2D model systems to simulate the experiment. Furthermore we show that in the case of cylindrically symmetric orbitals, such as the N2 orbital that was reconstructed in the original work, one can obtain the full 3D wave function and not only a 2D projection of it. Vor kurzem führten Itatani et al. [Nature 432, 876 (2004)] das Konzept der Molelkülorbital-Tomographie ein. Hierbei wird die Erzeugung hoher Harmonischer verwendet, um Bilder von elektronischen Wellenfunktionen zu gewinnen. Wir beschreiben eine alternative Form der Rekonstruktion, die auf Impuls- statt Dipol-Matrixelementen für den Rekombinationsschritt bei der Erzeugung der Harmonischen basiert. Wir zeigen, dass diese "Geschwindigkeitsform" der Rekonstruktion bessere Ergebnisse als die ursprüngliche "Längenform" liefert. Wir zeigen numerische Beweise für unsere Behauptung, dass man zu extrem kurzen Laserpulsen gehen muss, um Orbitale mit beliebiger Symmetrie zu rekonstruieren. Diese Ergebnisse basieren auf der exakten Lösung der zeitabhängigen Schrödingergleichung für 2D-Modellsysteme. Wir zeigen ferner, dass für zylindersymmetrische Orbitale wie das N2-Orbital, welches in der oben zitierten Arbeit rekonstruiert wurde, das volle 3D-Orbital rekonstruiert werden kann, nicht nur seine 2D-Projektion.

Analysis of hybrid layer thickness, resin tag length and their correlation with microtensile bond strength using a total etch adhesive to intact dentin.

The objective of this study was to evaluate the use of a two-step total etch and rinse adhesive, the correlation between the hyybrid layer thickness (HL) and bond strength (BS), and between resin tag length (RT) and bond strength in the same teeth, and also to evaluate the fracture patterns of the tested specimens. Ten human molars were used for the restorative procedure and then sectioned in two halves (mesio-distally). The materials used were Adper Single Bond 2, 3M ESPE, Ultra etch gel, Ultradent and Filtek Z250, 3M ESPE. One half were utilized to measure the HL thickness and RT length through light microscopy analysis (400x), and the other half was subject to a microtensile test to measure the BS. The fractured surfaces were analyzed by scanning electron microscopy and fracture patterns classified. The Pearson correlation test was applied (p = 0.05). The results of the analyses of each specimen then were correlated: mean HL thickness = 4.39 (0.48) microm, mean length of RT = 9.94 (1.69) microm, mean BS = 23.98 (10.24) MPa. A statistically significant correlation between HL thickness and bond strength was found (r = 0.93). The two step etch and rinse adhesive system, showed a strong correlation between HL thickness and bond strength. The most common fractures were adhesive, followed by cohesive in resin.

Influence of the hybrid layer thickness and resin tag length on microtensile bond strength.

The purpose of this study was to evaluate the correlation between the hybrid layer thickness/resin tag length and the microtensile bond strength of conventional two-step adhesive system, when applied to healthy dentinal tissue. After performing the restorative adhesive procedures and tooth extractions, ten specimens were sectioned in the mesiodistal direction. One section was used for microscopic analysis of the resin tag lengths and the hybrid layer thickness, while the other was used for the microtensile bond strength test (0.5 mm/min). The fractured surface was classified according to the fracture pattern, under a stereoscopic microscope at 40x magnification. Data obtained were submitted to analysis using one-way ANOVA and Pearson's Correlation test (alpha=0.05). The means corresponding to the hybrid layer thickness, resin tag lengths and the microtensile test were 2.68 microm, 6.43 microm and 16.23 MPa, respectively. There was no correlation between the means of the values obtained for the microtensile test, and those presented by the hybrid layer (r2=0.40, p>0.05) and resin tags (r2=0.21, p>0.05). The microtensile bond strength of the conventional two-step adhesive system Adper Single Bond 2 did not depend on the thickness of the hybrid layer and length of resin tags.

Measurement of the K + - pi + pi - e + - (-) v e form factors and of the pi pi scattering length a 0 0

The quark condensate is a fundamental free parameter of Chiral Perturbation Theory ($chi PT$), since it determines the relative size of the mass and momentum terms in the power expansion. In order to confirm or contradict the assumption of a large quark condensate, on which $chi PT$ is based, experimental tests are needed. In particular, the $S$-wave $pipi$ scattering lengths $a_0^0$ and $a_0^2$ can be predicted precisely within $chi PT$ as a function of this parameter and can be measured very cleanly in the decay $K^{pm} to pi^{+} pi^{-} e^{pm} stackrel{mbox{tiny(---)}}{nu_e}$ ($K_{e4}$). About one third of the data collected in 2003 and 2004 by the NA48/2 experiment were analysed and 342,859 $K_{e4}$ candidates were selected. The background contamination in the sample could be reduced down to 0.3% and it could be estimated directly from the data, by selecting events with the same signature as $K_{e4}$, but requiring for the electron the opposite charge with respect to the kaon, the so-called ``wrong sign'' events. This is a clean background sample, since the kaon decay with $Delta S=-Delta Q$, that would be the only source of signal, can only take place through two weak decays and is therefore strongly suppressed. The Cabibbo-Maksymowicz variables, used to describe the kinematics of the decay, were computed under the assumption of a fixed kaon momentum of 60 GeV/$c$ along the $z$ axis, so that the neutrino momentum could be obtained without ambiguity. The measurement of the form factors and of the $pipi$ scattering length $a_0^0$ was performed in a single step by comparing the five-dimensional distributions of data and MC in the kinematic variables. The MC distributions were corrected in order to properly take into account the trigger and selection efficiencies of the data and the background contamination. The following parameter values were obtained from a binned maximum likelihood fit, where $a_0^2$ was expressed as a function of $a_0^0$ according to the prediction of chiral perturbation theory: f'_s/f_s = 0.133+- 0.013(stat)+- 0.026(syst) f''_s/f_s = -0.041+- 0.013(stat)+- 0.020(syst) f_e/f_s = 0.221+- 0.051(stat)+- 0.105(syst) f'_e/f_s = -0.459+- 0.170(stat)+- 0.316(syst) tilde{f_p}/f_s = -0.112+- 0.013(stat)+- 0.023(syst) g_p/f_s = 0.892+- 0.012(stat)+- 0.025(syst) g'_p/f_s = 0.114+- 0.015(stat)+- 0.022(syst) h_p/f_s = -0.380+- 0.028(stat)+- 0.050(syst) a_0^0 = 0.246+- 0.009(stat)+- 0.012(syst)}+- 0.002(theor), where the statistical uncertainty only includes the effect of the data statistics and the theoretical uncertainty is due to the width of the allowed band for $a_0^2$.

Single-shot electron bunch length measurements using a spatial electro-optical autocorrelation interferometer

A spatial, electro-optical autocorrelation (EOA) interferometer using the vertically polarized lobes of coherent transition radiation (CTR) has been developed as a single-shot electron bunch length monitor at an optical beam port downstream the 100 MeV preinjector LINAC of the Swiss Light Source. This EOA monitor combines the advantages of step-scan interferometers (high temporal resolution) [D. Mihalcea et al., Phys. Rev. ST Accel. Beams 9, 082801 (2006) and T. Takahashi and K. Takami, Infrared Phys. Technol. 51, 363 (2008)] and terahertz-gating technologies [U. Schmidhammer et al., Appl. Phys. B: Lasers Opt. 94, 95 (2009) and B. Steffen et al., Phys. Rev. ST Accel. Beams 12, 032802 (2009)] (fast response), providing the possibility to tune the accelerator with an online bunch length diagnostics. While a proof of principle of the spatial interferometer was achieved by step-scan measurements with far-infrared detectors, the single-shot capability of the monitor has been demonstrated by electro-optical correlation of the spatial CTR interference pattern with fairly long (500 ps) neodymium-doped yttrium aluminum garnet (Nd:YAG) laser pulses in a ZnTe crystal. In single-shot operation, variations of the bunch length between 1.5 and 4 ps due to different phase settings of the LINAC bunching cavities have been measured with subpicosecond time resolution.

Step-Wise Changes in Glacier Flow Speed Coincide With Calving and Glacial Earthquakes at Helheim Glacier, Greenland

Geodetic observations show several large, sudden increases in flow speed at Helheim Glacier, one of Greenland's largest outlet glaciers, during summer, 2007. These step-like accelerations, detected along the length of the glacier, coincide with teleseismically detected glacial earthquakes and major iceberg calving events. No coseismic offset in the position of the glacier surface is observed; instead, modest tsunamis associated with the glacial earthquakes implicate glacier calving in the seismogenic process. Our results link changes in glacier velocity directly to calving-front behavior at Greenland's largest outlet glaciers, on timescales as short as minutes to hours, and clarify the mechanism by which glacial earthquakes occur. Citation: Nettles, M., et al. (2008), Step-wise changes in glacier flow speed coincide with calving and glacial earthquakes at Helheim Glacier, Greenland, Geophys. Res. Lett., 35, L24503, doi: 10.1029/2008GL036127.

Lake ice phenology from AVHRR data for European lakes: An automated two-step extraction method

Several lake ice phenology studies from satellite data have been undertaken. However, the availability of long-term lake freeze-thaw-cycles, required to understand this proxy for climate variability and change, is scarce for European lakes. Long time series from space observations are limited to few satellite sensors. Data of the Advanced Very High Resolution Radiometer (AVHRR) are used in account of their unique potential as they offer each day global coverage from the early 1980s expectedly until 2022. An automatic two-step extraction was developed, which makes use of near-infrared reflectance values and thermal infrared derived lake surface water temperatures to extract lake ice phenology dates. In contrast to other studies utilizing thermal infrared, the thresholds are derived from the data itself, making it unnecessary to define arbitrary or lake specific thresholds. Two lakes in the Baltic region and a steppe lake on the Austrian–Hungarian border were selected. The later one was used to test the applicability of the approach to another climatic region for the time period 1990 to 2012. A comparison of the extracted event dates with in situ data provided good agreements of about 10 d mean absolute error. The two-step extraction was found to be applicable for European lakes in different climate regions and could fill existing data gaps in future applications. The extension of the time series to the full AVHRR record length (early 1980 until today) with adequate length for trend estimations would be of interest to assess climate variability and change. Furthermore, the two-step extraction itself is not sensor-specific and could be applied to other sensors with equivalent near- and thermal infrared spectral bands.

Transcripts from a single full-length cDNA clone of hepatitis C virus are infectious when directly transfected into the liver of a chimpanzee

We have succeeded in constructing a stable full-length cDNA clone of strain H77 (genotype 1a) of hepatitis C virus (HCV). We devised a cassette vector with fixed 5′ and 3′ termini and constructed multiple full-length cDNA clones of H77 in a single step by cloning of the entire ORF, which was amplified by long reverse transcriptase–PCR, directly into this vector. The infectivity of two complete full-length cDNA clones was tested by the direct intrahepatic injection of a chimpanzee with RNA transcripts. However, we found no evidence for HCV replication. Sequence analysis of these and 16 additional full-length clones revealed that seven clones were defective for polyprotein synthesis, and the remaining nine clones had 6–28 amino acid mutations in the predicted polyprotein compared with the consensus sequence of H77. Next, we constructed a consensus chimera from four of the full-length cDNA clones with just two ligation steps. Injection of RNA transcripts from this consensus clone into the liver of a chimpanzee resulted in viral replication. The sequence of the virus recovered from the chimpanzee was identical to that of the injected RNA transcripts. This stable infectious molecular clone should be an important tool for developing a better understanding of the molecular biology and pathogenesis of HCV.

The 9-cis-epoxycarotenoid cleavage reaction is the key regulatory step of abscisic acid biosynthesis in water-stressed bean

Abscisic acid (ABA), a cleavage product of carotenoids, is involved in stress responses in plants. A well known response of plants to water stress is accumulation of ABA, which is caused by de novo synthesis. The limiting step of ABA biosynthesis in plants is presumably the cleavage of 9-cis-epoxycarotenoids, the first committed step of ABA biosynthesis. This step generates the C15 intermediate xanthoxin and C25-apocarotenoids. A cDNA, PvNCED1, was cloned from wilted bean (Phaseolus vulgaris L.) leaves. The 2,398-bp full-length PvNCED1 has an ORF of 615 aa and encodes a 68-kDa protein. The PvNCED1 protein is imported into chloroplasts, where it is associated with the thylakoids. The recombinant protein PvNCED1 catalyzes the cleavage of 9-cis-violaxanthin and 9′-cis-neoxanthin, so that the enzyme is referred to as 9-cis-epoxycarotenoid dioxygenase. When detached bean leaves were water stressed, ABA accumulation was preceded by large increases in PvNCED1 mRNA and protein levels. Conversely, rehydration of stressed leaves caused a rapid decrease in PvNCED1 mRNA, protein, and ABA levels. In bean roots, a similar correlation among PvNCED1 mRNA, protein, and ABA levels was observed. However, the ABA content was much less than in leaves, presumably because of the much smaller carotenoid precursor pool in roots than in leaves. At 7°C, PvNCED1 mRNA and ABA were slowly induced by water stress, but, at 2°C, neither accumulated. The results provide evidence that drought-induced ABA biosynthesis is regulated by the 9-cis-epoxycarotenoid cleavage reaction and that this reaction takes place in the thylakoids, where the carotenoid substrate is located.