Fully integrated hybrid silicon two dimensional beam scanner.

In this work we present the first fully-integrated free-space beam-steering chip using the hybrid silicon platform. The photonic integrated circuit (PIC) consists of 164 optical components including lasers, amplifiers, photodiodes, phase tuners, grating couplers, splitters, and a photonic crystal lens. The PIC exhibited steering over 23° x 3.6° with beam widths of 1° x 0.6°.

Heterogeneously integrated III-V-on-silicon multibandgap superluminescent light-emitting diode with 290 nm optical bandwidth.

A broadband superluminescent III-V-on-silicon light-emitting diode (LED) was realized. To achieve the large bandwidth, quantum well intermixing and multiple die bonding of InP on a silicon photonic waveguide circuit were combined for the first time, to the best of our knowledge. The device consists of four sections with different bandgaps, centered around 1300, 1380, 1460, and 1540 nm. The fabricated LEDs were connected on-chip in a serial way, where the light generated in the smaller bandgap sections travels through the larger bandgap sections. By balancing the pump current in the four LEDs, we achieved 292 nm of 3 dB bandwidth and an on-chip power of -8 dBm.

Hybrid III/V silicon photonic source with integrated 1D free-space beam steering.

A chip-scale optical source with integrated beam steering is demonstrated. The chip was fabricated using the hybrid silicon platform and incorporates an on-chip laser, waveguide splitter, amplifiers, phase modulators, and surface gratings to comprise an optical phased array with beam steering across a 12° field of view in one axis. Tuning of the phased array is used to achieve 1.8°(steered axis)×0.6°(nonsteered axis) beam width with 7 dB background suppression for arbitrary beam direction within the field of view.

Two-dimensional free-space beam steering with an optical phased array on silicon-on-insulator.

We demonstrate a 16-channel, independently tuned waveguide surface grating optical phased array in silicon for two dimensional beam steering with a total field of view of 20° x 14°, beam width of 0.6° x 1.6°, and full-window background peak suppression of 10 dB.

De-misting condensation on intraocular lenses.

BACKGROUND: Condensation occurs rapidly on intraocular lenses (IOLs), particularly silicone IOLs, after vitrectomy and fluid-air exchange in the presence of a posterior capsulotomy and severely limits the surgeon's view of the retina. This study investigated the value of heating contact lens irrigation fluid to prevent condensation on IOLs. DESIGN: An experimental in vitro study and a noncomparative interventional case series. PARTICIPANTS: Five control eyes had temperature measurements during fluid-air exchanges. Two patients with silicone IOLs and posterior capsulotomies underwent a vitrectomy involving a fluid-air exchange with heated contact lens fluid. METHODS: An in vitro model allowed monitoring of temperature and humidity changes during condensation formation on four different IOL materials. Adjusting variables to promote evaporation rather than condensation was achieved in vitro. In vivo, intraocular temperatures were measured at various stages of five vitrectomies involving a fluid-air exchange. Finally, in two in vivo cases a blood warmer was used to heat the accessory contact lens irrigation fluid during the vitrectomy and fluid-air exchange. MAIN OUTCOME MEASURES: Successful prevention of condensation on the silicone IOL during the fluid-air exchange. RESULTS: Anterior segment temperature influences the IOL temperature, such that when it is higher than the posterior segment temperature, condensation does not form and evaporation is promoted. In vivo the temperatures in the eye are hypothermic throughout the vitrectomy. At fluid-air exchange the posterior segment heats rapidly as irrigation ceases and low specific heat gas enters. Finally, in two in vivo cases with silicone IOLs, condensation was predicted then prevented by our intervention for the duration of the fluid-air exchange. CONCLUSIONS: Heating the anterior segment by conduction from warmed irrigation fluid flowing through the irrigating contact lens represents a cheap, noninvasive, and safe means to prevent condensation on IOL materials.

Phosphorylation- and activation-independent association of the tyrosine kinase Syk and the tyrosine kinase substrates Cbl and Vav with tubulin in B-cells.

Aggregation of the B-cell antigen receptor leads to the activation of the 72-kDa Syk protein-tyrosine kinase and the phosphorylation of tubulin on tyrosine. To explore the requirement of Syk catalytic activity for tubulin phosphorylation, tubulin was isolated from cytosolic fractions from anti-IgM-activated B-cells (DT40) that lacked endogenous Syk and immunoblotted with anti-phosphotyrosine antibodies. Tubulin was not tyrosine-phosphorylated in Syk- B-cells. Phosphorylation could be restored by the expression of wild-type, but not catalytically inactive, Syk. However, both catalytically inactive and wild-type Syk were capable of constitutive association with tubulin, indicating that tubulin phosphorylation is not required for this interaction. Anti-phosphotyrosine antibody immunoblotting of proteins adsorbed to colchicine-agarose revealed the presence of three major tubulin-associated phosphoproteins of 110, 90, and 74 kDa, the phosphorylation of which was dependent on Syk expression. The proteins of 110 and 90 kDa were identified as Cbl and Vav, two proto-oncogene products known to become prominently phosphorylated following receptor engagement. Both proteins were shown to be constitutively associated with tubulin.

Syk, activated by cross-linking the B-cell antigen receptor, localizes to the cytosol where it interacts with and phosphorylates alpha-tubulin on tyrosine.

Syk (p72syk) is a 72-kDa, nonreceptor, protein-tyrosine kinase that becomes tyrosine-phosphorylated and activated in B lymphocytes following aggregation of the B-cell antigen receptor. To explore the subcellular location of activated Syk, anti-IgM-activated B-cells were fractionated into soluble and particulate fractions by ultracentrifugation. Activated and tyrosine-phosphorylated Syk was found predominantly in the soluble fraction and was not associated with components of the antigen receptor. Similarly, the activated forms of Syk and its homolog, ZAP-70, were found in soluble fractions prepared from pervanadate-treated Jurkat T-cells. A 54-kDa protein that co-immunoprecipitated with Syk from the soluble fraction of activated B-cells was identified by peptide mapping as alpha-tubulin. alpha-Tubulin was an excellent in vitro substrate for Syk and was phosphorylated on a single tyrosine present within an acidic stretch of amino acids located near the carboxyl terminus. alpha-Tubulin was phosphorylated on tyrosine in intact cells following aggregation of the B-cell antigen receptor in a reaction that was inhibited by the Syk-selective inhibitor, piceatannol. Thus, once activated, Syk releases from the aggregated antigen receptor complex and is free to associate with and phosphorylate soluble proteins including alpha-tubulin.

Anterior spinal fusion with Zielke instrumentation for idiopathic scoliosis. A frontal and sagittal curve analysis in 36 patients.

The authors have reviewed the records of 36 patients with idiopathic scoliosis who underwent a single-stage anterior spinal fusion with Zielke instrumentation to determine if any adverse frontal or secondary sagittal deformities or changes in balance resulted from the surgery. Spontaneous correction of uninstrumented thoracic curves was noted in five patients with double-major curves, and frontal balance was maintained or improved after operation in all but four patients. Kyphosis was increased in the instrumented segments in all patients. In the uninstrumented segments, however, thoracic kyphosis and lumbar lordosis were decreased in all but five patients after operation, whereas overall sagittal balance was not adversely affected by the surgery in any patient.

The metal-backed patella. An invitation for failure?

Thirty-one cases of failed metal-backed patellar components requiring revision surgery are reviewed. Two modes of implant failure onset were noted. Within each group, delays in patient presentation and diagnosis of the failed component were encountered. The syndrome of the failed metal-backed patellar component is proposed. The authors conclude that: (1) more of these failures will be seen in the future; (2) this patient population needs appropriate counsel concerning the signs and symptoms of this syndrome as well as more frequent follow-up evaluations; (3) surgeons treating this complication should be prepared to revise all components; and (4) the use of metal-backed patellar components should be discontinued.

Closed intramedullary femoral shortening.

Twelve cases of adult anisomelia were treated with closed intramedullary femoral shortening. Follow-up was conducted at regular intervals until the osteotomy healed. This study reviewed hospital and office records, preoperative and postoperative roentgenograms, and telephone interviews of all patients. An average femoral shortening of 3.7 cm was attained; significant complications such as deep infection or nonunion did not occur. These results suggest that closed intramedullary shortening of the femur produces excellent results in cases of adult anisomelia.

Hospitals' direct liability for medical malpractice--implications for the medical staff.

Historically, hospital liability for the wrongful acts of physicians was based on the doctrine of vicarious liability-i.e., the physician was regarded as an employee or agent of the hospital. With the courts' growing recognition of most physicians as independent contractors, the doctrine of corporate or direct liability has emerged as the primary basis upon which courts now hold hospitals liable for failing to adequately monitor and control the standards of medical care and treatment offered within their walls. This article discusses eleven theories for imposing direct liability on hospitals and considers their impact on hospital-physician relations.

Infections of the heart complicating acute myocardial infarction.

Purulent pericarditis is a serious but uncommon disorder which rarely complicates acute myocardial infarction. We have described a patient who had fatal purulent pericarditis subsequent to Swan-Ganz catheterization, which was done to facilitate the management of left ventricular failure complicating acute myocardial infarction. Although rare, purulent pericarditis should be considered in the differential diagnosis of otherwise unexplained sepsis associated with myocardial infarction. The presence of a pericardial effusion may rapidly be confirmed by echocardiography, and diagnostic pericardiocentesis undertaken.