X-ray photoelectron spectroscopy for resistance-capacitance measurements of surface structures

Cataloged from PDF version of article.In x-ray photoemission measurements, differential charging causes the measured binding energy difference between the Si 2p of the oxide and the silicon substrate to vary nonlinearly as a function of the applied external do voltage stress, which controls the low-energy electrons going into and out of the sample. This nonlinear variation is similar to the system where a gold metal strip is connected to the same voltage stress through an external 10 Mohm series resistor and determined again by x-ray photoelectron spectroscopy (XPS). We utilize this functional resemblance to determine the resistance of the 4 nm SiO2 layer on a silicon substrate as 8 Mohm. In addition, by performing time-dependent XPS measurements (achieved by pulsing the voltage stress), we determine the time constant for charging/discharging of the same system as 2.0 s. Using an equivalent circuit, consisting of a gold metal strip connected through a 10 Mohm series resistor and a 56 nF parallel capacitor, and performing time-dependent XPS measurements, we also determine the time constant as 0.50 s in agreement with the expected value (0.56 s). Using this time constant and the resistance (8.0 Mohm), we can determined the capacitance of the 4 nm SiO2 layer as 250 nF in excellent agreement with the calculated value. Hence, by application of external do and pulsed voltage stresses, an x-ray photoelectron spectrometer is turned into a tool for extracting electrical parameters of surface structures in a noncontact fashion. (c) 2005 American Institute of Physics

X-ray photoelectron spectroscopic analysis of Si nanoclusters in SiO 2 matrix

We investigated silicon nanoclusters Si(nc) in a SiO2 matrix prepared by the plasma-enhanced chemical vapor deposition technique, using X-ray photoelectron spectroscopy (XPS) with external voltage stimuli in both static and pulsed modes. This method enables us to induce an additional charging shift of 0.8 eV between the Si2p peaks of the oxide and the underlying silicon, both in static and time-resolved modes, for a silicon sample containing a 6 nm oxide layer. In the case of the sample containing silicon nanoclusters, both Si2p peaks of Si(nc) and host SiO2 undergo a charging shift that is 1 order of magnitude larger (> 15 eV), with no measurable difference between them (i.e., no differential charging between the silicon nanoclusters and the oxide matrix could be detected). By use of a measured Auger parameter, we estimate the relaxation energy of the Si(nc) in the SiO2 matrix as -0.4 eV, which yields a -0.6 eV shift in the binding energy of the Si(nc) with respect to that of bulk Si in the opposite direction of the expected quantum size effect. This must be related to the residual differential charging between the silicon nanoclusters and the oxide host. Therefore, differential charging is still the biggest obstacle for extracting size-dependent binding energy shifts with XPS when one uses the oxide peak as the reference. © 2006 American Chemical Society

Vertical muscle transposition augmented with lateral fixation (Foster) suture for Duane syndrome and sixth nerve palsy

PurposeTo report the postoperative results of full-tendon vertical rectus transposition (VRT) augmented with lateral fixation suture for the treatment of type 1 Duane syndrome and sixth nerve palsy and to determine whether there was a decrease in the effect of the Foster suture over time.MethodsThis retrospective, consecutive case series included patients who underwent a full-tendon VRT transposition with lateral fixation for type 1 Duane syndrome or sixth nerve palsy. The primary outcome measures included deviation, abnormal head posture(AHP), abduction deficiency, and postoperative binocular single visual field (BSVF).ResultsEighty-seven patients (87 eyes: 40 eyes with Duane syndrome and 47 eyes with sixth nerve palsy) were included in this study. In Duane syndrome patients, the deviation was reduced by a mean of 95%, the AHP was eliminated in 86% of patients, the abduction was improved by 42%, and a useful BSVF of ∼67% of normal was achieved at 1 year post operation. In sixth nerve palsy patients, the deviation was reduced by 99%, the abduction was improved by 59%, and a useful BSVF of ∼71% of normal was achieved at 1 year post operation. In both groups, the improvements in deviation angle and abduction were stable postoperatively. Sixteen patients needed reoperation for undercorrection.ConclusionVRT surgery with posterior fixation is an effective treatment method for complete sixth nerve palsy and Duane syndrome with esotropia, AHP, and abduction deficiency. The procedure carries a small risk of reoperation for undercorrection. The effect of the Foster suture did not decline over time. © 2013 Macmillan Publishers Limited. All rights reserved

Efficacy of sub-Tenon's block using an equal volume of local anaesthetic administered either as a single or as divided doses. A randomised clinical trial

<p>Abstract</p> <p>Background</p> <p>Sub-Tenon's anaesthetic is effective and reliable in producing both akinesia and anaesthesia for cataract surgery. Our clinical experience indicates that it is sometimes necessary when absolute akinesia is required during surgery to augment the block with 1–2 ml of local anaesthetic. Hypothesis was that after first injection some of the volume injected may spill out and before second injection the effect of hyaluronidase has taken place and second volume injectate will have desired effect.</p> <p>Methods</p> <p>A prospective, randomised, control trial in which patients were randomly allocated to one of two groups. In group 1, single injection of 5 ml of local anaesthetic was injected. In group 2, 3 ml of the same anaesthetic solution was injected followed by application of gentle orbital pressure for 2 minutes. A further 2 ml of the same anaesthetic solution was injected through the same conjunctival incision. Measurement of movement in four quadrants of eye was done by the surgeon at 3 and 6 minutes. Intraocular pressure, chemosis, and subconjuctival haemorrhage were also measured.</p> <p>Results</p> <p>Significant differences at 3 minutes between groups for overall movement, medial, superior, and lateral quadrants occurred. At 6 minutes no significant group differences emerged for the overall movement or for any of four quadrants.</p> <p>Conclusion</p> <p>Single injection of local anaesthesia for sub-Tenon's block with mixture of lignocaine with adrenaline, bupivacaine and hyaluronidase was found to be superior to provide akinesia of ocular muscles compared to divided dose given by two injections. No difference in groups in terms of haemorrhage, chemosis, patient's satisfaction and intraocular pressure was found.</p> <p>Trial registration</p> <p>Trial registration no-ISRCTN73431052</p

Cytogenetical studies in five Atlantic Anguilliformes fishes

The order Anguilliformes comprises 15 families, 141 genera and 791 fish species. Eight families had at least one karyotyped species, with a prevalence of 2n = 38 chromosomes and high fundamental numbers (FN). The only exception to this pattern is the family Muraenidae, in which the eight species analyzed presented 2n = 42 chromosomes. Despite of the large number of Anguilliformes species, karyotypic reports are available for only a few representatives. In the present work, a species of Ophichthidae, Myrichthys ocellatus (2n = 38; 8m+14sm+10st+6a; FN = 70) and four species of Muraenidae, Enchelycore nigricans (2n = 42; 6m+8sm+12st+16a; FN = 68), Gymnothorax miliaris (2n = 42; 14m+18sm+10st; FN = 84), G. vicinus (2n = 42; 8m+6sm+28a; FN = 56) and Muraena pavonina (2n = 42; 6m+4sm+32a; FN = 52), collected along the Northeastern coast of Brazil and around the St Peter and St Paul Archipelago were analyzed. Typical large metacentric chromosomes were observed in all species. Conspicuous polymorphic heterochromatic regions were observed at the centromeres of most chromosomes and at single ribosomal sites. The data obtained for Ophichthidae corroborate the hypothesis of a karyotypic diversification mainly due to pericentric inversions and Robertsonian rearrangements, while the identification of constant chromosome numbers in Muraenidae (2n = 42) suggests a karyotype diversification through pericentric inversions and heterochromatin processes

Trocar-assisted, flanged sutureless scleral-fixated intraocular lens implantation combined with silicone oil injection after penetrating keratoplasty surgery

We describe a combined technique of trocar-assisted sutureless scleral-fixated intraocular lens implantation and silicone oil injection at the same session. Two 3 mm scleral tunnels were created 2 mm away from and parallel to the limbus with the 23-gauge vitrectomy trocars entering the sclera transconjunctivally at an angle of approximately 10° at the 3 o'clock and 9 o'clock meridians. After the 3-piece foldable IOL was delivered to the anterior chamber through the corneal incision, the tip of one of the IOL haptics was grasped with a 23-gauge serrated retinal forceps entered through the trocar located at the 3 o'clock meridian. Then the haptic was removed from the scleral tunnel together with the trocar out of the globe. The same procedure was applied to the other haptic. A transconjunctival secure 10-0 nylon suture was placed at the scleral tunnel entry site around the haptic. The ends of the haptics were cauterized to make a flange. The resultant flanges of the haptics were pushed back and fixed into the scleral tunnels. Perfluorooctane was taken out of the eye with vitreoretinal surgery and the silicone was injected into the eye to prevent hypotonia. No complications were seen intraoperatively or postoperatively. After 1-month follow-up period, IOL was seen stabilized

Is Duane retraction syndrome part of the VACTERL association?

Serpil Akar,1 Birsen Gokyigit,1 Isilay Kavadarli,2 Ahmet Demirok11Pediatric Ophthalmology and Strabismus Department, Prof Dr N Resat Belger Beyoglu Education and Research Eye Hospital, Istanbul, 2Department of Ophthalmology, Gaziantep, Kilis State Hospital, Kilis, TurkeyAbstract: We report here a patient with type 1 Duane&amp;rsquo;s retraction syndrome and multiple congenital abnormalities as a result of the VACTERL association. The presented combination of Duane&amp;rsquo;s retraction syndrome and the VACTERL association has not been reported in the literature. The present case was instructive for reviewing the continuous spectrum of ocular anomalies that accompany the VACTERL association.Keywords: Duane&amp;rsquo;s retraction syndrome, VACTERL association, combinatio