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At least 469 records · Page 26Linked to original sources
PubMed2003

A silicone-based wire-reinforced tracheal tube with a hemispherical bevel reduces nasal morbidity for nasotracheal intubation.

UNLABELLED: We tested the hypothesis that a silicone-based wire-reinforced tracheal tube with a hemispherical bevel is superior to a polyvinyl chloride (PVC)-based precurved tube with a conventional diagonal bevel for nasotracheal intubation. Eighty anesthetized paralyzed adults (ASA physical status I-II) requiring nasotracheal intubation for tonsillectomy were randomly allocated into two equal-sized groups for airway management with the silicone tracheal tube or PVC tracheal tube. Intubation was subdivided into three phases: 1). passage through the nose into the pharynx, 2). laryngoscope-guided passage into the glottic inlet, and 3). laryngoscope-guided passage into the trachea. A specific sequence of airway maneuvers was followed at each stage if it was unsuccessful. The number of attempts and intubation time were documented by an unblinded observer. The frequency of epistaxis and postoperative nasal complications was documented by blinded observers. There were no intubation failures. The number of attempts at pharyngeal (47 versus 56; P = 0.04) and tracheal (43 versus 55; P = 0.005) placement was smaller for the silicone tracheal tube, but the number of attempts at glottic placement was more (72 versus 49; P < 0.0001). Intubation time was similar. The frequency (32% versus 80%; P < 0.0001) and severity of epistaxis were less for the silicone tracheal tube. The total number of postoperative nasal symptoms was smaller for the silicone tracheal tube (10 versus 21; P < 0.05). We conclude that the pharyngeal and tracheal placement phases of nasotracheal intubation require fewer attempts with the silicone tracheal tube than the PVC tracheal tube but that the glottic placement phase requires more attempts. Nasal morbidity is less common with the silicone tracheal tube. IMPLICATIONS: The pharyngeal and tracheal placement phases of nasotracheal intubation require fewer attempts with a silicone-based wire-reinforced tracheal tube with a hemispherical bevel than with a polyvinyl chloride-based precurved tracheal tube with a conventional diagonal bevel, but the glottic placement phase requires more attempts. Nasal morbidity is less common with the silicone tracheal tube.

Adult↗
PubMed1999

Functionally adapted surfaces on a silicone keratoprosthesis.

BACKGROUND: Silicone intraocular lenses as well as silicone sponges and encircling bands on the bulbar surface are widely used and are well tolerated. The aim of this project is a new one-piece silicone keratoprosthesis with enhanced cell adhesion in the haptic region to optimize the keratoprosthesis stability. These investigations show how enhanced profileration of conjunctival fibroblasts and, therefore, improved tissue compatibility can be achieved by hydrophilizing and by protein immobilisation on a hydrophobic silicone surface. This allows a combination of desired chemical and mechanical properties of the silicone bulk material with surfaces of improved tissue compatibility. METHODS: Silicone foils with surface modifications of different kinds were tested. Experiments were done using cell cultures with murine fibroblasts L-929 and human conjuctival fibroblasts. Cytotoxicity assays were carried out with cells grown on the material in direct contact, as well as in indirect contact, with extracts (EN 30993-5). Viability stains by means of fluoresceindiacetate and ethidiumbromide together with morphology analyses by hemalaun-staining were performed. RESULTS: For the unmodified and modified foils themselves and their extracts any negative influence on cell cultures of murine and human cells could be excluded. There was a gradual improvement of cell morphology, spreading and proliferation dependent on the degree of surface modification. Covalently immobilised fibronectin showed the best results in contrast to adsorptive binding. CONCLUSIONS: Silicone surfaces can be modified chemically with bioactive proteins. These modifications are cell compatible and do not result in toxic reactions. The degree and type of silicone hydrophilization results in improved development of cell morphology, spreading and proliferation. Even better results are obtained after covalent binding of bioactive proteins like fibronectin. Improved biocompatibility with enhanced cellular overgrowth has been demonstrated in vitro for the modified silicone of the haptic region. We believe that this type of modification will help in reducing extrusion problems observed with former keratoprostheses.

Animals↗
PubMed2001

The effect of vitrectomy with silicone oil tamponade on intraocular pressure and anterior chamber morphology.

We measured the tamponading effect of silicone oil, saline and air after vitrectomy, on intraocular pressure and aqueous humor outflow in 85 patients with highly proliferative retina and vitreous changes. Silicone oil as retinal tamponading agent after vitrectomy was used in 45 patients, and saline or air in 39 patients. The mean intraocular pressure measured at one month after treatment was greatly elevated in patients with silicone oil tamponade as compared to those with saline or air tamponade. At 6 and 12 months examinations, mean intraocular pressures were compared in these two groups of patients. Gonioscopy revealed silicone oil emulsification and presence of emulsified bubbles in the anterior chamber in 22.22% of patients, and narrowing of the chamber angle in several patients with silicone oil tamponade. Intraocular pressure elevation following vitrectomy with silicone oil tamponade was found to be of transient rather than permanent nature, since it regressed after silicone oil removal. This transient elevation was due to silicone oil tendency to emulsify. Silicone oil bubbles changed the morphology of the anterior chamber angle and fine trabecular structures by creating a barrier to aqueous humor outflow.

Air↗
PubMed2002

[Evaluation of silicone oil removal from eyes treated with retinotomy].

PURPOSE: Long-term silicone oil tamponade may resulting late complications. The aim of our study is to find out the results of silicone oil removal in eyes treated with retinotomy. MATERIAL AND METHODS: Between January 1991 and December 1999 37 patients (37 eyes) were given silicone oil removal after retinotomy. The indications for vitrectomy with silicone oil tamponade and retinotomy were: rhegmatogenous retinal detachment (78.4%) and trauma (21.6%). Completion retinal attachment within at least 3 months without reproliferations indicated for silicone oil removal. RESULTS: With a minimum of 6 months process follow-up the retina was attached in 36 cases (97.3%). 29 (78.4%) eyes achieving final visual acuity 1/50 or better. Visual acuity remained unchanged in 64.9% cases. Minimal visual acuity 5/50 was achieved in 47.1% of eyes with retinotomy size smaller than 180 ae and in 40% of eyes with retinotomy size 180ae-360ae. Visual acuity at least 1/50 was achieved in 72.2% of eyes where silicone oil tamponade remained shorter than 6 months and in 84.2% when longer than 6 months. CONCLUSIONS: Silicone oil removal leads to the stabilisation of visual acuity in majority of eyes. Final visual acuity does not correlate with either the retinotomy size or with the duration of silicone oil tamponade. Risk of retinal redetachment after silicone oil removal in eyes treated with retinotomy may result in similar symptom as in eyes treated without retinotomy.

Adult↗
PubMed2004

[Silicone and latex urinary catheters cytotoxicity on primary cultured rabbit urothelial cells].

UNLABELLED: In everyday urological practice, the use of urinary catheters creates problems such as epithelial hyperplasia, edema or erosion. THE AIM: of this study is estimation of the toxicity of latex and silicone urinary catheters on primary cultured rabbit urothelial cells (PRUCC) was compared. MATERIALS AND METHODS: Primary cultured rabbit urothelial cells (PRUC) were characterized for their proliferation, qualitative evaluation and quantitative measurement of cytokeratins. In the first kind of cytotoxic assay included exposition of the PRUC cells on liquid extracts of latex and silicone. Cytotoxicity of 1, 5, 10, 20, 50% dilution and pure extract was evaluated after 24 h. Additionally for 1% solution observation was extended up to 3 days. The second cytotoxic assay was based on the close contact between the catheter surface and cells. In direct contact test, latex and silicon catheters samples covered cultured cells. Trypan blue exclusion assay was used to measure cell viability. Cells were counted using inverted microscope with camera. RESULTS: 1, 5, 10 and 20% of silicon extracts did not affect cell viability while 5% of latex catheter extracts did. There was no difference in cytotoxicity when PRUC cells had been exposed to 1% dilutions of both silicone and latex catheters extracts after 3-days observation. 50% dilution and pure latex and silicone urinary catheters extracts appears to be highly toxic on PRUC. Direct contact test confirmed high toxicity of latex and silicone catheters on PRUC. CONCLUSIONS: We confirmed latex and silicone on PRUC to be very toxic with direct contact. Using extract test the properties of silicone seemed to be slightly better. Authors postulate using catheters covered with hydrogenic gel in every day urological practice.

Animals↗
PubMed2004

Effect of chemical treatment of silicon gel on tissue compatibility.

BACKGROUND: Silicon gel is unfavourable for cell attachment and growth. This study was to study if pretreating the surface of silicon gel with chemical agents affects the proliferation of epithelial cells. METHODS: Silicon gel was made and treated with either mixed acid solution (containing 232 g/dm(3) of H(2)SO(4) and 8 g/dm(3) of K(2)Cr(2)O(7)) or 300 cm(3)/dm(3) peroxide for 5, 10, and 15 minutes or 10, 15, and 20 minutes, respectively. The cultured corneal epithelial cells were seeded onto those silicon gels and kept for 13 days. Immunohistochemical investigations were then carried out for integrin (alpha 6 or beta 4) and actin. RESULTS: Growth of the epithelial cells in silicon gels treated with mixed acid solution for 10 minutes and 15 minutes was much significant than that in the untreated gels. After a 12-hour culture, a small number of corneal epithelial cells were proliferated on the surface of the silicon gels that had been treated with peroxide for 15 minutes. After a 3-day culture, those cells were further proliferated and fused together. The corneal epithelial cells did not grow well in the silicon gels treated with peroxide for 10 or 20 minutes. Immunostaining revealed the expression of actin and integrin alpha 6 or beta 4 on the silicon gels that were treated with mixed acid solution for 10 minutes or peroxide for 15 minutes. CONCLUSION: Silicon gels treated either with mixed acid solution for 10 or 15 minutes or with peroxide for 15 minutes improves cell proliferation.

Animals↗
PubMed2004

Simple technique for silicone intubation in congenital nasolacrimal duct obstruction.

OBJECTIVE: To propose a simple and low cost technique of using the simple materials in the operating room for silicone intubation in case of nasolacrimal duct obstruction in children after failed probing. METHOD: The study was a consecutive case series. Three patients with congenital nasolacrimal duct obstruction aged 42, 51 and 72 months were referred to the authors. Their symptoms persisted after probing twice with or without infracture inferior turbinate. The authors decided to insert a silicone tubing by using an 18-gauge, intravascular catheter as a channel to place a silicone tubing into the nasolacrimal system. Success was defined as a complete resolution of symptoms and signs (tearing, crusting, discharge, regurgitation on pressure over the lacrimal sac) after silicone intubation. RESULTS: All three patients were free of symptoms and signs after insertion of silicone tubing and an average 5.5 months (9, 6, 1.5 months) after removal of the silicone tubing. There were no intraoperative complications. No unplanned silicone tubing removal was needed and also no complications associated with silicone stent, such as punctal erosion, corneal erosion or granuloma formation occurred. CONCLUSION: This simple and low cost technique using an intravascular catheter as a channel to place the silicone tubing into the nasolacrimal system in case of congenital nasolacrimal duct obstruction in children works well. This new technique is not only inexpensive but also effortless with no complications.

Catheterization↗
PubMed2006

[Calcification on the posterior surface of an implanted silicone intraocular lens in a patient with asteroid hyalosis].

BACKGROUND: Calcification on the surface of the hydrogel intraocular lens (IOL) has been reported, but the mechanism of the surface calcification is not fully understood. We report a case of surface calcification on an implanted silicone IOL. The purpose of our study was to examine the clinical and ultrastructural findings associated with the late surface calcification of a silicone IOL. CASE: A 70-year-old Japanese man had undergone cataract surgery in his left eye, with uneventful phacoemulsification and silicone IOL (Allergan SI-55 NB) implantation with the manufacturer's cartridge and injector. He was referred again 29 months later with blurred vision, glare sensitivity, and decreased vision in his left eye. He was diagnosed as having aftercataract. Although YAG laser capsulotomy was performed, the opacity on the posterior surface gradually increased. The opacity was located mainly within the capsulotomy window on the posterior surface of the lens, although the patient maintained good visual acuity. LV : 0.2 (1.0 x S-2.0 D). The lens was removed 46 months after the initial surgery. Scanning electron microscopy (SEM) showed membranous deposits on the posterior optical surface of the silicone lens. There were high levels of phosphoric acid (P) and calcium (C) confirming calcification of the silicone IOL. Asteroid hyalosis was observed in the fellow eye of the patient. CONCLUSION: This is the first report of surface calcification of a silicone IOL in Japan. Although the mechanism of the calcification has not been determined, careful clinical follow-up of patients implanted with silicone lenses is necessary to determine if this phenomenon is rare and sporadic or if it may be more widespread. Since 5 similar cases of calcification in silicone lenses with accompanying asteroid hyalosis have been reported in other countries, we can conclude that silicone lens implantation in eyes with asteroid hyalosis should be avoided.

Aged↗
PubMed1990

Silicone: a critical review.

The response of biologic systems to implanted foreign materials is subject to a lesion of variables. Each type of implant must be individually evaluated in a specific application and host. Pure DMPS polymer injected into subcutaneous tissues behaves in a specific and characteristic way. An analysis of the behavior of other types of implants in other applications will not necessarily reveal insights applicable to the behavior of liquid silicone. Most adverse case reports relate to injected fluids of unknown purity or identity used in inappropriate volumes in poorly chosen anatomical sites. It is ironic that pure DMPS in small volumes, a theoretically ideal combination, is so mistrusted. However, liquid silicone's sinful potential was easy to predict. It was cheap, available, easy to use, and, when injected in large volumes, produced instant and financially profitable results. Moreover, a welter of confusing titles, "authorized investigators" and "medical grade silicone" coupled with sensationally adverse reports detailing a criminal misuse of this modality led to draconian measures banning its use and made a meaningful analysis of true incidence and type of side effects following its use nearly impossible to assess. The advocates' position that liquid silicone is safe when used properly cannot be refuted. Only a handful of serious adverse reactions can be documented following its use; however, the concept that pure DMPS polymer can, even in expert hands, occasionally produce immunologically mediated adverse effects is equally irrefutable. This concept is supported by the following evidence: 1. Minor idiosyncratic and granulomatous reactions occurring in 1 in 10,000 are reported in association with a nidus of infection or as a consequence of allergic events. 2. At least one serious inflammatory reaction occurred in a patient afflicted with both autoimmune disease and concurrent infection. These reactions are best understood in the broader context of tissue responses to all classes of implanted foreign material, and they are most easily understood in the narrow context of autoimmune disease after injection of implantable paraffin, silicone, and possibly "silicone polymers." "Certain authors speculate that silicone acting as a primary antigen is not likely," however, silicone acting as an adjuvant associated with a subclinical infection as an antigen source may be the cause of adjuvant disease. A careful review of published anecdotal and personal experience involving the use of 350 centistoke pure dimethypolysiloxane fluid (liquid silicone) for soft-tissue augmentation in small volumes (and in large volumes for facial hemiatrophy) suggests that the bias against its proper use is unfounded.(ABSTRACT TRUNCATED AT 400 WORDS)

Dermatologic Surgical Procedures↗
PubMed1987

Usefulness and limit of silicone in management of complicated retinal detachment.

Among various substances used for intraocular tamponade in the treatment of vitreous opacity and complicated retinal detachment, silicone oil is superior to hyaluronic acid or sulfur hexafluoride. Its low gravity and hydrophobic nature permit good tamponade effect to be obtained and its high transparency allows us to detect remnant vitreous traction in the far periphery and/or retinal tears. Furthermore, preretinal membrane can be peeled off easily after silicone oil removal. The hydrophobic nature of silicone prevents clouding due to postoperative hemorrhage and fibrin reaction. It should also be stressed that intravitreal silicone oil suppresses iridial rubeosis or prevents its development. However, the use of silicone has limitations, since it gives rise to various complications that include pupillary block glaucoma, secondary glaucoma, cataract formation and corneal complications including band-shaped keratopathy. Pupillary block in aphakic eyes can be prevented by placing peripheral iridectomy at the 6 o'clock position, since silicone is lighter than water. After silicone injection, glaucoma is more often seen in diabetic aphakic eyes than in phakic or nondiabetic eyes. On the other hand, corneal complications were less frequent in diabetic than in nondiabetic eyes; in nondiabetic eyes the complications were more frequent in aphakic than in phakic eyes. Due to possible complications, silicone should be removed after a certain follow-up period, during which time detection and management of the causes of redetachment of the retina are possible due to the high transparency of silicone.

Cataract↗
PubMed1996

Bladder neck reconstruction: long-term followup of reconstruction with omentum and silicone sheath.

PURPOSE: In 1986 we reported the placement of a silicone sheath sandwiched between layers of omentum around a newly reconstructed bladder neck. We now present long-term followup of 94 cases of silicone sheath bladder neck reconstruction. MATERIALS AND METHODS: A total of 94 silicone sheaths was placed in 84 patients between August 1983 and October 1992. We retrospectively reviewed our results and divided the reconstructions into 3 groups according to modifications in surgical technique. We report the results of each modification and current recommendations for use. RESULTS: Each sequential modification of silicone sheath bladder neck reconstruction significantly reduced the risk of erosion from 100%, 32% and 7%, respectively (p < 0.05). Erosion was independent of patient age, sex, pathological condition or whether bladder neck reconstruction was a repeat procedure. Patients who had silicone sheath erosion did not have different continence or loss of urethral continuity than those with no erosion. In 13 patients (16%) artificial sphincter placement was clearly facilitated by the silicone sheath. CONCLUSIONS: Modifications in the surgical technique of silicone sheath placement around a reconstructed bladder neck have resulted in a decrease in the erosion rate to 7%. The primary benefit of silicone sheath placement is ease of subsequent sphincter placement. Currently we reserve silicone sheath placement for a small subset of patients who are most likely to benefit from subsequent artificial sphincter placement.

Adolescent↗
PubMed1996

Role of blood components in ocular silicone oil emulsification. Studies on an in vitro model.

PURPOSE: To develop an in vitro model for silicone oil emulsification and to explore the blood components involved in this process. METHODS: The capacity of various blood components to support silicone oil (1000 CS) emulsification was studied by applying 0.5 ml oil on top of 0.5 ml saline containing various blood components. Each tube was sonicated for 150 seconds and centrifuged at 5000 g for 20 minutes. Three phases were noted in the tube: At the top was clear silicone oil, in the middle was emulsified silicone oil, and at the bottom was aqueous solution. The tubes were photographed, and the percentage of the phase length containing emulsified silicone oil (middle) of the total length of the three phases was calculated from the projected image of each tube. RESULTS: Emulsified silicone oil in plasma or serum was initiated after 100 seconds of sonication and quickly reached maximum (approximately 80%) at 120 seconds. The size of these oil droplets prepared in vitro was 0.0467 +/- 0.028 mm, closely resembling that observed in oil samples removed from a patient's anterior chamber (0.038 +/- 0.018 mm). Under these conditions, silicone oil emulsified in the presence of whole blood cells occurred only at a concentration of 120 micrograms protein/ml; in the presence of red blood cell membranes, it occurred at a concentration of 60 micrograms protein/ml. Lipoprotein-deficient serum failed to support emulsification; however, samples of high-density lipoprotein and low-density lipoprotein supported this process. Purified high-density lipoprotein-apolipoproteins supported oil emulsification. The addition of phosphatidylcholine further enhanced this process, but phosphatidylcholine alone failed to support emulsification. CONCLUSIONS: A simple and fast in vitro model to study factors affecting silicone oil emulsification was developed. Using this model, red blood cell membranes, plasma lipoproteins, and purified HDL-apolipoproteins supported silicone oil emulsification. Lipids did not, but they had the capacity to enhance the apolipoprotein-supported emulsification.

Blood Cells↗
PubMed1998

[Usefulness of different silicone oils for intraocular tamponade].

PURPOSE: This paper presents the influence of different silicone oils on surgical results achieved after pars plana vitrectomy and silicone oil tamponade. MATERIAL AND METHODS: Pars plana vitrectomy and silicone oil tamponade were used for the treatment of 141 eyes with proliferative Vitreoretinopathy, diabetic retinopathy and posttraumatic retinal detachment. In group I (23 eyes), group II (26 eyes), group III (32 eyes) and group IV (60 eyes) following silicone oils were used, respectively: highly purified silicone oil with viscosity 5000 mPa(x)s, 1000 mPa(x)s, cosmetically purified silicone oil with viscosity 3690 mPa(x)s and 1000 mPa(x)s. RESULTS: The achieved results did not show any statistically significant differences according to anatomical and functional results and early and late postoperative complications between the analysed groups. Compared to other groups, highly purified silicone oil with viscosity 5000 mPa(x)s did not show any emulsification. CONCLUSIONS: The achieved results show that different silicone oils can be successfully used for intraocular tamponade. Highly purified silicone oil with viscosity 5000 mPa(x)s is most biocompatible.

Adolescent↗
PubMed2003

Alkyl monolayer passivated metal-semiconductor diodes: 2: Comparison with native silicon oxide.

To understand the electrical properties at passivated metal-semiconductor interfaces, two types of mercury-insulator-silicon (n-type) junctions, Hg\C10H21-Si and Hg\SiO2-Si, were fabricated and their current-voltage and capacitance-voltage characteristics compared. Both of them exhibited near-ideal rectifying characteristics with an excellent saturation current at reverse bias, which is in contrast to the previously reported ohmic behavior of an unmodified mercury-silicon junction. The experimental results also indicated that the n-decyl monolayer passivated junction possesses a higher effective barrier height, a lower ideality factor (that is, closer to unity), and better reproducibility than that of native silicon oxide. In addition, the dopant density and build-in potential, extracted from capacitance-voltage measurements of these passivated mercury-silicon junctions, revealed that alkyl monolayer derivatization does not alter the intrinsic properties of the silicon substrate. The calculated surface state density at the alkyl monolayer\silicon interface is lower than that of the silicon oxide\silicon interface. The present study increases the possibility of using advanced organic materials as ultrathin insulator layers for miniaturized, silicon-based microelectronic devices.

Journal Article↗
PubMed2005

The feasibility of inert colloidal processing of silicon nanoparticles.

Silicon nanoparticles have important applications, including nonvolatile floating-gate memory devices. To prevent device performance variations, particle size and oxide thicknesses need to be controlled with a high degree of precision. Additionally, producing well-ordered, two-dimensional arrays of nanoparticles may require the exploitation of self-assembly techniques and colloidal forces, which in turn requires that silicon nanoparticles first come into contact with liquids. Until recently, aerosol silicon nanoparticle collection into liquid was assumed to be an inert process. Once formed, the silicon nanoparticle colloid was assumed to be inert. In fact, silicon nanoparticles produced in the aerosol phase by dilute silane pyrolysis and size classified with a differential mobility analyzer undergo a size reduction upon collection in ethylene glycol, water, and ethanol. Unclassified polydisperse silicon aerosol nanoparticles with an average diameter of 11 nm become monodisperse when collected in a colloid and have a final particle diameter of 2-5 nm. Further evidence suggests that silicon nanoparticles collected in ethanol react with the ethanol to produce tetraalkylorthosilicate-like species. Collections of aerosol silicon nanoparticles in degassed water do not show measurable differences between the aerosol and colloidal size distributions. This reduced reactivity to the solvent indicates that the presence of dissolved oxygen in the solvent may be responsible for the reactivity between the silicon nanoparticles and the solvent.

Journal Article↗
PubMed1998

Lens refilling with injectable silicone in rabbit eyes.

PURPOSE: To evaluate the technique of refilling the lens capsule with injectable silicone and assess the postoperative findings. SETTING: Jinshikai Medical Foundation, Nishi Eye Hospital, Osaka, Japan. METHODS: The lens capsules in the eyes of 16 rabbits weighing 1.5 to 2.0 kg were refilled with 0.2 mL of silicone polymer (about 66% bag volume) after endocapsular phacoemulsification through an upper minicircular capsulorhexis 1.5 to 1.8 mm in diameter. The capsule opening was sealed with a silicone plug to prevent leakage of the injected silicone. Main outcome measures were surgical success rate, inflammation, endothelial cell loss, refractive change after pilocarpine 4% instillation, and capsule opacification. RESULTS: The lens capsule could be refilled in 10 eyes. The failures were caused by capsule rupture during phacoemulsification (n = 3) and profuse leakage of the injected silicone. Silicone that leaked minimally during surgery was easily washed away. Silicone that leaked and polymerized in the anterior chamber postoperatively (n = 3) was easily removed by surgery the following day. Mean endothelial cell loss was 10.2% 1 month after surgery. Aqueous flare intensity was significantly lower on days 2 and 4 than after conventional intraocular lens implantation in a control group. The respective mean preoperative and postoperative refractions were 0.7 diopters (D) +/- 1.0 (SD) and 19.1 +/- 1.0 D and the mean change (difference between the refractions before and after topical application of pilocarpine 4%), -0.4 +/- 0.6 and 1.1 +/- 0.4 D (P < .01). Posterior capsule opacification (PCO) was noted after 3 weeks in all eyes. CONCLUSIONS: Lens capsule refilling and capsular plug use to prevent silicone leakage was shown to be feasible and avoided complications caused by leakage. Refractive changes suggest that the procedure could yield accommodation in primates> Although neodymium: YAG laser capsulotomy did not cause herniation of the injected silicone, PCO prevention is an essential issue in lens refilling because the capsulotomy may annul the attained accommodation.

Animals↗
PubMed2004

Stereoselective synthesis of optically active disilanes and selective functionalization by the cleavage of silicon-naphthyl bonds with bromine.

Optically active disilanes with one chiral silicon center, (R)-1,2-dimethyl-1-(naphth-1-yl)-1,2,2-triphenyldisilane and (R)-1,2,2-trimethyl-2-(4-methoxynaphth-1-yl)-1-(naphth-1-yl)-1-phenyldisilane, were obtained by the reaction of (S)-methyl(naphth-1-yl)phenylchlorosilane (> 99% ee) with methyldiphenylsilyllithium or by the reaction of methyldiphenylchlorosilane with optically active (S)-methyl(naphth-1-yl)phenylsilyllithium and by the reaction of (S)-methyl(naphth-1-yl)phenylchlorosilane (> 99% ee) with dimethyl(4-methoxynaphth-1-yl)silyllithium. Under the optimized conditions, the reactions proceeded with almost complete inversion for the cholorosilanes and retention for the silyl anions. Optically active disilanes with two chiral centers, (1R,2R)-1,2-dimethyl-1,2-di(naphth-1-yl)-1,2-diphenyldisilane and (1S,2S)-1,2-di(4-methoxynaphth-1-yl)-1,2-dimethyl-1,2-diphenyldisilane, were obtained in high optical purity by the reactions of corresponding optically active halogenosilanes (Cl or F) with optically active silyllithiums. The silicon-silicon bond and the silicon-naphthyl bond of (R)-1,1,2-trimethyl-1,2-di(naphth-1-yl)-2-phenyldisilane and (1R,2R)-1,2-dimethyl-1,2-di(naphth-1-yl)-1,2-diphenyldisilane were cleaved without selectivity on bromination. The silicon-(4-methoxynaphth-1-yl) bond of (R)-1,2,2-trimethyl-2-(4-methoxynaphth-1-yl)-1-(naphth-1-yl)-1-phenyldisilane was regiospecifically cleaved, followed by the stereoselective cleavage of the remaining chiral silicon-naphthyl bond (94% inversion). Although the silicon-(4-methoxynaphth-1-yl) bonds of (1S,2S)-1,2-di(4-methoxynaphth-1-yl)-1,2-dimethyl-1,2-diphenyldisilane (> 99% ee) were regioselectively cleaved without silicon-silicon bond scission, remarkable racemization could not be avoided during the one-pot reaction.

Journal Article↗
PubMed2006

Photodissociation of metal-silicon clusters: encapsulated versus surface-bound metal.

Metal-silicon cluster cations of the form MSi(n)+ (M = Cu, Ag, Cr) are produced in a molecular beam with pulsed laser vaporization. These species are mass-selected in a reflectron time-of-flight spectrometer and studied with laser photodissociation at 532 and 355 nm. For the noble metals copper and silver, photodissociation of the n = 7 and 10 clusters proceeds primarily by the loss of metal atoms, indicating that the metal is not located within the interior of silicon cages, and that metal-silicon bonding is weaker than silicon-silicon bonding. Chromium-silicon clusters for n = 7 also lose primarily the metal atom, but at n = 15 and 16 these dissociate via the loss of silicon, producing smaller metal-silicon species. This behavior is consistent with stronger metal-silicon bonding and encapsulated metal structures, as suggested previously by theory. MSi6(+) cations are produced efficiently in all of these photodissociation processes, indicating that these species have enhanced stability compared to other small clusters. Improved values are obtained for the ionization potentials of Si7 and Si10.

Letter↗