Evaluation of onlay island flap technique in shallow urethral plate hypospadiasis

Background: Hypospadias is one of the most common congenital genital anomalies in males that necessitates to be operated early in infancy (when 6 to 9 months old). On the other hand, hypospadias is a challenging field of pediatric urology with multiple reconstruction techniques. A perfect hypospadias repair is supposed to return urethral continuity with sufficient caliber, eradicate phallus curvature, and supply an acceptable appearance with low complications. Objectives: This study aimed to evaluate the outcomes of using onlay island flap technique in the repair of hypospadias with shallow urethral plate. Patients and Methods: In this prospective study within June 2012 to December 2013, we performed onlay island flap procedure to repair hypospadias with shallow urethral plate measuring less than 6 millimeter. This technique was selected for all types of hypospadiasis except subcoronal type. Nesbit�s dorsal plication procedure was established for chordee. In cases with very small glans, urethroplasty was performed without glansplasty. Results: Twenty three patients with mean age of 30 (range 10 -60) months underwent onlay island flap repair; all had a shallow urethral plate < 6 mm, 3 had a very small glans, and 18 had chordee. Meatus was located in distal shaft in 5 cases, mid shaft in 8, proximal in 6 and penoscrotal type in 4 patients. Chordee was corrected with Nesbit�s dorsal plication in 16 cases. Complications were: meatal stenosis in 2 cases and urethrocutaneous fistula in 2 patients, all of which were repaired surgically. Mean follow up time was 13 (3 -20) months. All cases that had glansplasty have excellent esthetic appearance. Conclusions: This technique offers acceptable results regarding meatal stenosis, urethrocutaneous fistula and esthetic outcome. © 2016, Growth & Development Research Center

A novel carbon-nanotube gas sensor based on field ionization from branched nanostructures

Branched treelike carbon nanotubes were grown by plasma enhanced chemical vapor deposition method on a silicon wafer. Patterned structures of as grown nanostructures were used for the fabrication of a gas sensor, which operates based on the field ionization of various gases. The variations in the electrical resistivity and the emission current of the fabricated device are related to the chemisorption and field ionization mechanisms, respectively. The sensor is capable of gas detection at room temperature and at low pressures with working at low voltages. Different gases such as H2, O2, C2H2 and Ar have been used to examine the gas sensitivity characteristics of the fabricated sensors

Effects of plasma power on the growth of carbon nanotubes in the plasma enhanced chemical vapor deposition method

Effects of plasma power on the growth of the multi-wall carbon nanotubes (CNTs) are reported. CNTs were grown on the silicon wafers by plasma enhanced chemical vapor deposition (PECVD) method using a mixture of acetylene and hydrogen at the temperature of 650 °C. Plasma powers ranging from zero to 35 W were applied on the samples and the effects of different magnitudes of the plasma power on the growth direction of the CNTs were investigated. Regular vertically aligned nanotubes were obtained at plasma power of 25 W. In order to set on the plasma during the growth, electrical force was applied on the carbon ions. Nickel layer was used as a catalyst, and prior to the nanotubes growth step, it was treated by hydrogen plasma bombardment in order to obtain the Ni nano-islands. In this step, as the plasma power on the Ni layer was increased, the grain size of nickel nano-particles decreased, and hence, nanotubes of smaller diameter were obtained later on. At the last step some anomalous structures of agglomerated CNTs were obtained by controlling the plasma power. Samples were analyzed by scanning tunneling microscopy (STM) and scanning electron microscopy (SEM)

Evolution of high aspect ratio and nano-grass structures using a modified low plasma density reactive ion etching

We report a modified deep reactive ion etching method to realize high aspect ratio features and nano-grasses on silicon substrates. This etching technique uses sequential etching and passivation sub-cycles and it is based on three gases of H2, O2 and SF6 in the presence of rf-plasma. By adjusting the etching parameters such as the flows of various gases, the plasma power and duration of each cycle, the process can be controlled to obtain high aspect ratio vertical structures on silicon substrates. Features with aspect ratios of the order of 30–50 and heights of the order of 25–30 μm are obtained. On the other hand, one can program the etching parameters to achieve grass-full structures in desired places and with pre-designed patterns. The formation of nano-grass on silicon surface, improves its wetability with water and oil spills. This property has been used to entrap carbon nanotubes onto nano-structured surfaces in desired places

Study of bulk micromachining for 〈100〉 silicon

Anisotropic etching of silicon is achieved in the presence of ultra-violet exposure in a solution containing hydrofluoric/nitric/acetic acids (HNA). The HNA solution is typically used for polishing silicon and etching polysilicon due to its isotropic etching property. In the technique proposed in this paper which is called UV-HNA, the etching of silicon is enhanced in the direction determined by UV exposure. A mixture of HF/HNO3/CH3COOH with a relative composition of 1:15:5 seems suitable for revealing 〈111〉 planes with an etch rate of 10 μm/h at 35 °C. The bottom of the etched craters is hillock-free and etch rates as high as 60 μm/h can be achieved using higher concentration of HF acid in HNA solution. In the latter case the etching is more isotropic and mask undercut is observed. Also membranes with a depth of 400 μm are fabricated on n-type Si 〈100〉 with a thickness of 500 μm by means of standard 34 wt% solution of KOH at temperature of 60 °C. Problems encountered during the experiment, and their solutions are discussed and results of these experiments are reported

A Nickel–Gold Bilayer Catalyst Engineering Technique for Self-Assembled Growth of Highly Ordered Silicon Nanotubes (SiNT)

We report the growth of vertically aligned high-crystallinity silicon nanotube (SiNT) arrays on silicon substrate by means of a Ni–Au bilayer catalyst engineering technique. Nanotubes were synthesized through solid–liquid–solid method as well as vapor–liquid–solid. A precise evaluation utilizing atomic force microscopy and lateral force microscopy describes that the gold profile in Ni regions leads to the construction of multiwall SiNTs. The agreement of the structural geometry and stiffness of the obtained SiNTs with previous theoretical predictions suggest sp hybridization as the mechanism of tube formation. Apart from scanning electron and transmission electron microscopy techniques, photoluminescence spectroscopy (PL) has been conducted to investigate the formation of nanostructures. PL spectroscopy confirms the evolution of ultrafine walls of the silicon nanotubes, responsible for the observed photoemission properties