A study of the structural, optical and electrical properties of synthetic and natural melanin by means of X-ray diffraction, absorption and photocurrent techniques is reported. The model of the ...natural melanin film as a network of nano-aggregates of polymeric units based on the indolic structure is proposed to explain the X-ray diffraction results. The shape of the absorption spectra is similar to that of amorphous and disordered semiconductors, with a very strong, broad band UV and visible absorption and an optical gap value of about 0.5 eV. Photosensitivity to sun spectra has been demonstrated by photoconductivity measurements of synthetic melanin pellets under AM1 light source illumination.
Natural and synthetic melanin have been investigated by means of optical, electrical and photoelectronic measurements. Optical measurements evidence absorption curves which allow to estimate optical ...gap for synthetic melanin, by using Tauc’s method. Dark conductivity and photoconductivity measurements were performed as a function of temperature and for different duration of thermal treatments. It has been evidenced that both quantities are thermally activated and thermal treatments play a very important role as far as gap states are concerned.
Three types of CdS thin films, one undoped and two n-doped, have been grown on the quartz substrates by pulsed laser deposition technique. The two n-doped films have been deposited by laser ablating ...a home-made target obtained by mixing CdS and metallic Indium powders with two different concentrations of In powder weight (1 and 5%). The films were grown highly oriented along the (002) direction of the hexagonal phase. Raman spectra show that the LO peak broadens as the Indium doping increases, due to the increase of compositional disorder. Band filling effects characterize the absorption spectra of the heavily doped films: in particular, the band gap of the doped films presents an evident blue-shift with respect to the undoped film, due to Burstein-Moss effect. Photoluminescence spectra show the intrinsic radiative recombinations persisting up to room temperature.
Undoped CdSe and CdSe:Zn thin films have been grown on silicon substrate by using pulsed laser deposition technique. The electrical, structural and optical properties have been investigated. The ...films grow crystalline and highly oriented. Electrical measurements show that they are n-type doped. The reflectivity and photoluminescence are consistent and point out that the undoped CdSe film present excitonic features at low temperature, differently from CdSe:Zn films, whose spectral features are related to band–band transition. The luminescence efficiency of CdSe:Zn persists up to room temperature, whereas the luminescence of undoped CdSe is scarcely visible above 250
K.
Objective
The commercially available C-Port distal anastomotic device (Food and Drug Administration cleared in 2007) is an automated miniature vascular stapler that performs the coronary anastomosis. ...This prospective multicenter registry sought to evaluate midterm patency using this device compared with hand-sewn grafts.
Methods
Patients receiving at least one C-Port anastomosis during coronary artery bypass grafting surgery were enrolled at eight sites. Of the 117 patients enrolled, 78 patients (67%) with 104 C-Port vein grafts completed the study to patency assessment via computed tomography angiography. Clinical follow-up and index graft patency (Gated 64-slice computed tomography scan) were performed at least 12 months postoperatively. The primary efficacy endpoint was patency compared with the peer-reviewed results from the PRoject of Ex-vivo Vein graft ENgineering via Transfection IV (PREVENT IV) trial.
Results
The patient population was consistent with the PREVENT IV placebo cohort. The mortality at 12 months was 0.85% (1/117). The major cardiac morbidity rate was 3.4% (4/117). The C-Port vein graft occlusion rate was 16.3% (17/104) compared with 26.6% (597/2242) in the PREVENT IV trial (P = 0.011). Within this study, C-Port graft occlusion rates were not significantly different from the hand-sewn grafts (P = 0.821).
Conclusions
The C-Port device is safe and effective in creating the distal anastomosis with equivalent patency rates to hand-sewn grafts at 12 months. When compared with hand-sewn anastomoses from a recent large prospective trial, the C-Port device demonstrated a statistically significant reduction in midterm graft occlusion. Further studies are required to evaluate its effect in less invasive coronary surgery.
The use of GaN as an alternative interlayer for stable passivation of gallium arsenide surface is investigated. To this aim remote N
2–H
2 plasma nitridation of the n-doped gallium arsenide surface ...has been performed. The exposure time to N
2–H
2 plasmas has been varied in order to form ultrathin GaN layers with different thickness. Gallium nitride layer thickness and composition analysis have been determined by in situ spectroscopic ellipsometry. The changes of the electronic properties of GaAs surface induced by nitridation process have been studied by means of DC and AC electrical characterizations on Schottky barrier diodes tailored on gallium nitride/gallium arsenide structure. The evidence of achievement of GaAs surface electronic passivation under short time plasma treatment will be provided.
Formulae describing the spatial distribution of radiation intensity in a thin semiconductor film on a relatively thick, transparent, parallel-sided substrate are given for the case of non-normal ...incidence of radiation. Internal reflection and interference of radiation in the film makes the radiation intensity very sensitive to geometrical and material parameters of the structure as well as to the wavelength, angle of incidence, and polarization of radiation. The influence of radiation wavelength range and uncertainties of film thickness and refractive index on the spatial distribution of radiation intensity is discussed. The presented formulae are useful in photoelectric and photoelectromagnetic investigations on thin-film semiconductors. They make the calculations about fifty times faster than those using the general equations.
Venous access for pectoral pacemaker and defibrillator lead placement can be compromised by venous occlusion due to previous pacing leads, access ports for medications such as chemotherapy, dialysis ...access, and other causes. On rare occasion, a femoral access is utilized for device placement. We report here a patient without venous access to the heart from either above or below due to retroperitoneal fibrosis. A bi-ventricular pacing-defibrillator was placed using a direct trans-atrial approach with good results. This minimally invasive approach to device placement may be useful in patients with poor venous access and avoids the placement of epicardial hardware.
The RD48 (ROSE) collaboration has succeeded to develop radiation hard silicon detectors, capable to withstand the harsh hadron fluences in the tracking areas of LHC experiments. In order to reach ...this objective, a defect engineering technique was employed resulting in the development of Oxygen enriched FZ silicon (DOFZ), ensuring the necessary O-enrichment of about 2×10
17 O/cm
3 in the normal detector processing. Systematic investigations have been carried out on various standard and oxygenated silicon diodes with neutron, proton and pion irradiation up to a fluence of 5×10
14
cm
−2 (1
MeV neutron equivalent). Major focus is on the changes of the effective doping concentration (depletion voltage). Other aspects (reverse current, charge collection) are covered too and the appreciable benefits obtained with DOFZ silicon in radiation tolerance for charged hadrons are outlined. The results are reliably described by the “Hamburg model”: its application to LHC experimental conditions is shown, demonstrating the superiority of the defect engineered silicon. Microscopic aspects of damage effects are also discussed, including differences due to charged and neutral hadron irradiation.
We investigated neurohumoral profiles and transmitter and neuroenzyme markers of cardiac autonomic innervation in control (unpaced) dogs and three groups of dogs with pacing-induced heart failure ...(paced, paced + beta-adrenergic blockade, and paced + cardiac denervation). Left ventricular ejection fraction decreased significantly and to a comparable extent in all paced groups. Pacing increased plasma norepinephrine (NE); increases in NE were not attenuated but instead tended to be exaggerated by treatment with propranolol or cardiac denervation. Atrial hypertrophy occurred in all paced groups compared with the control group. However, atrial and right ventricular hypertrophy were not as pronounced in the paced plus cardiac denervation group as in the paced and paced plus propranolol groups. Pacing also depleted neuropeptide Y and NE from all heart chambers; propranolol treatment did not modify these local tissue changes. Pacing caused selective depletion of neuroenzymes predominantly in the left ventricle; again, propranolol did little to modify these changes. In this study of paced animals with experimentally maintained cardiac dysfunction, failure to modify noradrenergic responses with intrapericardial cardiac denervation suggests that noncardiac sources contribute predominantly to high plasma NE. Failure to modify neurohumoral, neuropeptide, and neuroenzyme responses with beta-antagonist suggests this treatment has little practical direct influence on sympathetic vasomotor activity or neuronal function in heart failure.
