Optimisation of doped microcrystalline silicon films deposited at very low temperatures by Hot-Wire CVD

In this paper we present new results on doped μc-Si:H thin films deposited by hot-wire chemical vapour deposition (HWCVD) in the very low temperature range (125-275°C). The doped layers were obtained by the addition of diborane or phosphine in the gas phase during deposition. The incorporation of boron and phosphorus in the films and their influence on the crystalline fraction are studied by secondary ion mass spectrometry and Raman spectroscopy, respectively. Good electrical transport properties were obtained in this deposition regime, with best dark conductivities of 2.6 and 9.8 S cm -1 for the p- and n-doped films, respectively. The effect of the hydrogen dilution and the layer thickness on the electrical properties are also studied. Some technological conclusions referred to cross contamination could be deduced from the nominally undoped samples obtained in the same chamber after p- and n-type heavily doped layers.

Networks of people in specialty production: family firms in the iron and steel Wire industries in Spain (1870-2000)

Capital intensive industries in specialized niches of production have constituted solid ground for family firms in Spain , as evidenced by the experience of the iron and steel wire industries between 1870 and 2000. The embeddedness of these firms in their local and regional environments have allowed the creation of networks that, together with favourable institutional conditions, significantly explain the dominance of family entrepreneurship in iron and steel wire manufacturing in Spain, until the end of the 20 th century. Dominance of family firms at the regional level has not been not an obstacle for innovation in wire manufacturing in Spain, which has taken place even when institutional conditions blocked innovation and traditional networking. Therefore, economic theories about the difficulties dynastic family firms may have to perform appropriately in science-based industries must be questioned

Posterior vaginal wall repair with synthetic absorbable mesh: A new technique for and old procedure

The objective of this study was to assess the applicability of posterior wall repair with a synthetic absorbable mesh. Between January and September 1996, five posterior repairs using absorbable synthetic meshes were performed. Five posterior wall repairs in patients matched for age, parity, and rectocele degree were performed according to usual procedures during the same period, and were used as controls. No febrile morbidity, cuff or posterior vaginal wall infections, thrombophlebitis, rectal injury, or hemorrhagic complications were observed in the 10 women who entered the study. In summary, posterior wall repair can be easily performed with an absorbable soft tissue patch, theoretically preserving sexual activity, and probably offers better functional results with longer experience, thus providing a safe and useful procedure in sexually active women.

Consumer Advisory: Don’t Touch That Wire! Money Transfer Scams, August 2013

The Attorney General’s Consumer Protection Division receives hundreds of calls and consumer complaints every year. Follow these tips to avoid unexpected expense and disappointments. This record is about: Don’t Touch That Wire! Money Transfer Scams

Accuracy and predictability in use of AO three-dimensionally preformed titanium mesh plates for posttraumatic orbital reconstruction: a pilot study.

The aim of this study was to prospectively evaluate the accuracy and predictability of new three-dimensionally preformed AO titanium mesh plates for posttraumatic orbital wall reconstruction.We analyzed the preoperative and postoperative clinical and radiologic data of 10 patients with isolated blow-out orbital fractures. Fracture locations were as follows: floor (N = 7; 70%), medial wall (N = 1; 1%), and floor/medial wall (N = 2; 2%). The floor fractures were exposed by a standard transconjunctival approach, whereas a combined transcaruncular transconjunctival approach was used in patients with medial wall fractures. A three-dimensional preformed AO titanium mesh plate (0.4 mm in thickness) was selected according to the size of the defect previously measured on the preoperative computed tomographic (CT) scan examination and fixed at the inferior orbital rim with 1 or 2 screws. The accuracy of plate positioning of the reconstructed orbit was assessed on the postoperative CT scan. Coronal CT scan slices were used to measure bony orbital volume using OsiriX Medical Image software. Reconstructed versus uninjured orbital volume were statistically correlated.Nine patients (90%) had a successful treatment outcome without complications. One patient (10%) developed a mechanical limitation of upward gaze with a resulting handicapping diplopia requiring hardware removal. Postoperative orbital CT scan showed an anatomic three-dimensional placement of the orbital mesh plates in all of the patients. Volume data of the reconstructed orbit fitted that of the contralateral uninjured orbit with accuracy to within 2.5 cm(3). There was no significant difference in volume between the reconstructed and uninjured orbits.This preliminary study has demonstrated that three-dimensionally preformed AO titanium mesh plates for posttraumatic orbital wall reconstruction results in (1) a high rate of success with an acceptable rate of major clinical complications (10%) and (2) an anatomic restoration of the bony orbital contour and volume that closely approximates that of the contralateral uninjured orbit.

Computer-aided volume measurement of posttraumatic orbits reconstructed with AO titanium mesh plates: accuracy and reliability

PURPOSE: To prospectively evaluate the accuracy and reliability of "freehand" posttraumatic orbital wall reconstruction with AO (Arbeitsgemeinschaft Osteosynthese) titanium mesh plates by using computer-aided volumetric measurement of the bony orbits. METHODS: Bony orbital volume was measured in 12 patients from coronal CT scan slices using OsiriX Medical Image software. After defining the volumetric limits of the orbit, the segmentation of the bony orbital region of interest of each single slice was performed. At the end of the segmentation process, all regions of interest were grouped and the volume was computed. The same procedure was performed on both orbits, and thereafter the volume of the contralateral uninjured orbit was used as a control for comparison. RESULTS: In all patients, the volume data of the reconstructed orbit fitted that of the contralateral uninjured orbit with accuracy to within 1.85 cm3 (7%). CONCLUSIONS: This preliminary study has demonstrated that posttraumatic orbital wall reconstruction using "freehand" bending and placement of AO titanium mesh plates results in a high success rate in re-establishing preoperative bony volume, which closely approximates that of the contralateral uninjured orbit.

Nd:YAG Laser Welding of 5083 Aluminium Alloy using Filler Wire

High reflectivity and high thermal conductivity, high vapour pressure of alloyingelements as well as low liquid surface tension and low ionisation potential, make laser welding of aluminium and its alloys a demanding task.Problems that occur during welding are mainly process instabilities of the keyhole and the melt pool, increased plasma formation above the melt pool and loss of alloying elements. These problems lead to unwanted metallurgical defects like hot cracks and porosity in the weld bead andother problems concerning the shape and appearance of the weld bead. In order to minimise the defects and improve the weld quality, the process and beam parameters need to be carefully adjusted along with a consideration concerning the use of filler wire for the welding process. In this work the welding of 3,0 mm thick grade 5083 aluminium alloy plates using a 3,0 kW Nd:YAG laser with grade 5183 filler wire addition is investigated. The plates were welded as butt joints with air gap sizes 0,5 mm, 0,7mm and 1,0 mm. The analysis of the weld beads obtained from the weldedsamples showed that the least imperfections were produced with 0,7 mm air gaps at moderate welding speeds. The analysis also covered the calculation of the melting efficiency and the study of the shape of the weld bead. The melting efficiency was on average around 20 % for the melting process of the welded plates. The weld beads showed the characteristic V-shape of a laser weld and retained this shape during the whole series of experiments.

Comparison of three separate antiadhesive barriers for intraperitoneal onlay mesh hernia repair in an experimental model (Br J Surg 2011; 98: 442-449).

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The use of external mesh reinforcement to reduce intimal hyperplasia and preserve the structure of human saphenous veins.

The saphenous vein is the conduit of choice in bypass graft procedures. Haemodynamic factors play a major role in the development of intimal hyperplasia (IH), and subsequent bypass failure. To evaluate the potential protective effect of external reinforcement on such a failure, we developed an ex vivo model for the perfusion of segments of human saphenous veins under arterial shear stress. In veins submitted to pulsatile high pressure (mean pressure at 100 mmHg) for 3 or 7 days, the use of an external macroporous polyester mesh 1) prevented the dilatation of the vessel, 2) decreased the development of IH, 3) reduced the apoptosis of smooth muscle cells, and the subsequent fibrosis of the media layer, 4) prevented the remodelling of extracellular matrix through the up-regulation of matrix metalloproteinases (MMP-2, MMP-9) and plasminogen activator type I. The data show that, in an experimental ex vivo setting, an external scaffold decreases IH and maintains the integrity of veins exposed to arterial pressure, via increase in shear stress and decrease wall tension, that likely contribute to trigger selective molecular and cellular changes.

Implantación de un modelo de red abierta tipo mesh para propagar el acceso libre al servicio de biblioteca y contenidos abiertos

Implantación de un modelo de red abierta tipo mesh para propagar el acceso libre al servicio de biblioteca y contenidos abiertos.

Progress in a-Si:H/c-Si heterojunction emitters obtained by Hot-Wire CVD at 200°C

In this work, we investigate heterojunction emitters deposited by Hot-Wire CVD on p-type crystalline silicon. The emitter structure consists of an n-doped film (20 nm) combined with a thin intrinsic hydrogenated amorphous silicon buffer layer (5 nm). The microstructure of these films has been studied by spectroscopic ellipsometry in the UV-visible range. These measurements reveal that the microstructure of the n-doped film is strongly influenced by the amorphous silicon buffer. The Quasy-Steady-State Photoconductance (QSS-PC) technique allows us to estimate implicit open-circuit voltages near 700 mV for heterojunction emitters on p-type (0.8 Ω·cm) FZ silicon wafers. Finally, 1 cm 2 heterojunction solar cells with 15.4% conversion efficiencies (total area) have been fabricated on flat p-type (14 Ω·cm) CZ silicon wafers with aluminum back-surface-field contact.

Investigation of defect formation and electronic transport in microcrystalline silicon deposited by hot-wire CVD

We have investigated doped and undoped layers of microcrystalline silicon prepared by hot-wire chemical vapour deposition optically, electrically and by means of transmission electron microscopy. Besides needle-like crystals grown perpendicular to the substrate's surface, all of the layers contained a noncrystalline phase with a volume fraction between 4% and 25%. A high oxygen content of several per cent in the porous phase was detected by electron energy loss spectrometry. Deep-level transient spectroscopy of the crystals suggests that the concentration of electrically active defects is less than 1% of the undoped background concentration of typically 10^17 cm -3. Frequency-dependent measurements of the conductance and capacitance perpendicular to the substrate surface showed that a hopping process takes place within the noncrystalline phase parallel to the conduction in the crystals. The parasitic contribution to the electrical circuit arising from the porous phase is believed to be an important loss mechanism in the output of a pin-structured photovoltaic solar cell deposited by hot-wire CVD.

Studies on grain boundaries in nanocrystalline silicon grown by Hot-Wire CVD

The use of a tantalum wire in hot-wire chemical vapour deposition (HWCVD) has allowed the deposition of dense nanocrystalline silicon at low filament temperatures (1550 °C). A transition in the crystalline preferential orientation from (2 2 0) to (1 1 1) was observed around 1700 °C. Transmission electron microscopy (TEM) images, together with secondary ion mass spectrometry (SIMS) measurements, suggested that no oxidation occurred in materials obtained at low filament temperature due to the high density of the tissue surrounding grain boundaries. A greater concentration of SiH 3 radicals formed at these temperatures seemed to be responsible for the higher density.