Endovenous laser ablation: the role of intraluminal blood

AbstractObjectiveIn this histological study, the role of the intraluminal blood during endovenous laser ablation was assessed.MethodsIn 12 goats, 24 lateral saphenous veins were treated with a 1500-nm diode laser. Four goats were treated in an anti-Trendelenburg position (group 1). The next four goats were treated in a Trendelenburg position (group 2) and the remaining four goats in the Trendelenburg position with additional injection of tumescent liquid (group 3). Postoperatively, the veins were removed after 1 week and sent for histological examination. We measured the number of perforations. Vein wall necrosis and the perivenous tissue destruction were quantified using a graded scale.ResultsThe ‘calculated total vein wall destruction’ was significantly higher in the third group (81.83%), as compared with groups one (61.25%) (p < 0.001) and two (65.92%) (p < 0.001). All three groups showed a significant difference in the perivenous tissue destruction scale (p < 0.001) with the lowest score occurring in the third group. Vein wall perforations were significantly more frequent in groups one and two as compared with the third group (T-test respectively p < 0.001, p = 0.02).ConclusionA higher intraluminal blood volume results in reduced total vein wall destruction. Injection of tumescent liquid prevents the perivenous tissue destruction and minimises the number of perforations

Strong spin relaxation length dependence on electric field gradients

We discuss the influence of electrical effects on spin transport, and in particular the propagation and relaxation of spin polarized electrons in the presence of inhomogeneous electric fields. We show that the spin relaxation length strongly depends on electric field gradients, and that significant suppression of electron spin polarization can occur as a result thereof. A discussion in terms of a drift-diffusion picture, and self-consistent numerical calculations based on a Boltzmann-Poisson approach shows that the spin relaxation length in fact can be of the order of the charge screening length.Comment: 4 pages, 3 figures, to be presented at PASPSI

High spatial resolution nanoslit SERS for single-molecule nucleobase sensing

Solid-state nanopores promise a scalable platform for single-molecule DNA analysis. Direct, real-time identification of nucleobases in DNA strands is still limited by the sensitivity and the spatial resolution of established ionic sensing strategies. Here, we study a different but promising strategy based on optical spectroscopy. We use an optically engineered elongated nanopore structure, a plasmonic nanoslit, to locally enable single-molecule surface enhanced Raman spectroscopy (SERS). Combining SERS with nanopore fluidics facilitates both the electrokinetic capture of DNA analytes and their local identification through direct Raman spectroscopic fingerprinting of four nucleobases. By studying the stochastic fluctuation process of DNA analytes that are temporarily adsorbed inside the pores, we have observed asynchronous spectroscopic behavior of different nucleobases, both individual and incorporated in DNA strands. These results provide evidences for the single-molecule sensitivity and the sub-nanometer spatial resolution of plasmonic nanoslit SERS

Low-loss singlemode PECVD silicon nitride photonic wire waveguides for 532-900 nm wavelength window fabricated within a CMOS pilot line

PECVD silicon nitride photonic wire waveguides have been fabricated in a CMOS pilot line. Both clad and unclad single mode wire waveguides were measured at lambda = 532, 780, and 900 nm, respectively. The dependence of loss on wire width, wavelength, and cladding is discussed in detail. Cladded multimode and singlemode waveguides show a loss well below 1 dB/cm in the 532-900 nm wavelength range. For singlemode unclad waveguides, losses < 1 dB/cm were achieved at lambda = 900 nm, whereas losses were measured in the range of 1-3 dB/cm for lambda = 780 and 532 nm, respectively

Characterization of PECVD Silicon Nitride Photonic Components at 532 and 900 nm Wavelength

Low temperature PECVD silicon nitride photonic waveguides have been fabricated by both electron beam lithography and 200 mm DUV lithography. Propagation losses and bend losses were both measured at 532 and 900 nm wavelength, revealing sub 1dB/cm propagation losses for cladded waveguides at both wavelengths for single mode operation. Without cladding, propagation losses were measured to be in the 1-3 dB range for 532 nm and remain below 1 dB/cm for 900 nm for single mode waveguides. Bend losses were measured for 532 nm and were well below 0.1 dB per 90 degree bend for radii larger than 10 mu m

Boosting the Figure Of Merit of LSPR-based refractive index sensing by phase-sensitive measurements

Localized surface plasmon resonances possess very interesting properties for a wide variety of sensing applications. In many of the existing applications only the intensity of the reflected or transmitted signals is taken into account, while the phase information is ignored. At the center frequency of a (localized) surface plasmon resonance, the electron cloud makes the transition between in- and out-of-phase oscillation with respect to the incident wave. Here we show that this information can experimentally be extracted by performing phase-sensitive measurements, which result in linewidths that are almost one order of magnitude smaller than those for intensity based measurements. As this phase transition is an intrinsic property of a plasmon resonance, this opens up many possibilities for boosting the figure of merit (FOM) of refractive index sensing by taking into account the phase of the plasmon resonance. We experimentally investigated this for two model systems: randomly distributed gold nanodisks and gold nanorings on top of a continuous gold layer and a dielectric spacer and observed FOM values up to 8.3 and 16.5 for the respective nanoparticles

Near-field interactions between metal nanoparticle surface plasmons and molecular excitons in thin-films: part I: absorption

In this and the following paper (parts I and II, respectively), we systematically study the interactions between surface plasmons of metal nanoparticles (NPs) with excitons in thin-films of organic media. In an effort to exclusively probe near-field interactions, we utilize spherical Ag NPs in a size-regime where far-field light scattering is negligibly small compared to absorption. In part I, we discuss the effect of the presence of these Ag NPs on the absorption of the embedding medium by means of experiment, numerical simulations, and analytical calculations, all shown to be in good agreement. We observe absorption enhancement in the embedding medium due to the Ag NPs with a strong dependence on the medium permittivity, the spectral position relative to the surface plasmon resonance frequency, and the thickness of the organic layer. By introducing a low index spacer layer between the NPs and the organic medium, this absorption enhancement is experimentally confirmed to be a near field effect In part II, we probe the impact of the Ag NPs on the emission of organic molecules by time-resolved and steady-state photoluminescence measurements