Waveguide design optimization for compact silicon photonic ferroelectric phase shifters.

In this paper, a new, to the best of our knowledge, design for a ferroelectric BaTiO3 cladded silicon photonic phase shifter with very small switching length for compact photonic integrated circuits (PICs) is proposed. The proposed design is based on the choice of a waveguide core with suitably slanted sidewalls in order to favor the desired polarization of ferroelectric cladding and to make guided modes spread toward the ferroelectric cladding with the consequence of further reduction in switching length compared to the conventional (rectangular core) structure. The proposed design also gives the additional benefit of having the identical switching length for both TE and TM modes with the same configuration. These results offer a viable strategy to realize compact non-volatile phase shifters for reconfigurable and programmable PICs.

Electron states in a silicon nanowire in the presence of surface potential and field.

In this paper, the energy states of electrons in a silicon nanowire are analytically calculated in the presence of a surface potential and an electric field, as in a nanowire field-effect transistor. The calculations are done for both partial and complete volume inversion and accumulation biasing conditions. Computations are performed for the <100> and <110> orientations of the silicon nanowire. The results show the effects of the surface potential, the electric field and the transverse dimensions of the nanowire on the electron energies and wavefunctions. Depending on the combinations of the surface potential and electric field, the energy level can increase, decrease or remain constant as the thickness of the nanowire increases. It is also observed that higher surface potentials can significantly change the energy states due to the increase of volume inversion/accumulation.

Electron emission from a semiconductor quantum ring under normally incident radiation.

In this paper we investigate the current density due to electrons emitted during normal irradiation of a toroidal quantum ring of a strongly degenerate wide-gap semiconductor. The computed results show that the current density increases in a step-like manner with increase in the incident photon energy. Increased current density can be obtained by reducing the dimensions of the ring. The threshold energy for photoemission becomes an oscillatory function of the cross-sectional radius, and can be used as an important tool for monitoring parameters such as the cross-sectional radius and doping density. The threshold energy is, however, independent of the circumference of the ring.

Laparoscopic bile duct injuries: spectrum at a tertiary-care center.

BACKGROUND AND PURPOSE: Laparoscopic cholecystectomy (LC) is associated with a higher incidence of bile duct injury than is open cholecystectomy. We reviewed our experiences with the management of laparoscopic bile duct injuries. PATIENTS AND METHODS: From October 1992 through August 1998, 34 patients with bile duct injuries (BDI) following LC were seen. The presentation, type of injury (Strasberg classification), management, and outcome were analyzed in these patients. RESULTS: Of the 16 patients who sustained injury at our center (type A [N = 9], D [N = 5], and E1 [N = 2]), in 14, the injury was detected during LC, and two patients manifested with postoperative bile leak. All patients had an excellent outcome at a median follow-up of 5.5 (range 1.9-8.0) years. Of the 18 patients who sustained injury elsewhere (type C [N = 1], D [N = 2], E [N = 14; 6 with external biliary fistula (EBF) and 8 with benign biliary stricture (BBS)], and not known [1]), 9 had EBF, 1 had biliary peritonitis, and 8 had BBS at the time of presentation. Of these 18 patients, 4 underwent early repair of the BDI before referral (repair over a T-tube [N = 2] and Roux-Y hepaticojejunostomy [N = 2]). Three of them developed restricture. One patient was referred to us within 12 hours of injury and had a successful repair over a T-tube. Two patients with early repair for lateral injury had an excellent outcome. Eleven patients with BBS underwent repair with an excellent (N = 10) or fair (N = 1) outcome at a median follow-up of 5.0 (2.0-6.2) years. Three patients were lost to follow-up. CONCLUSION: The spectrum of injuries sustained at LC at a tertiary-care center is different from that in the community hospitals. Missed injuries and attempts at repair in inexperienced hands result in serious sequelae of stricture formation and long-term morbidity.

Production and separation of carrier-free 145,146Eu from a CsNO3 target using a 16O beam.

Carrier free europium isotopes 145,146Eu have been produced by irradiating a CsNO3 target with an 80 MeV 16O beam. Radiochemical separation of the produced europium isotopes from the bulk target matrix of CsNO3 have effectively been done using HDEHP, the liquid cation exchanger.

Separation of carrier-free hafnium and lutetium radionuclides produced in 16O activated terbium metal target.

Charged particle activation with approximately 88 MeV 16O7+ beam on natural terbium metal foil leads to the production of the short lived carrier-free radioisotopes 170,171Ta and their corresponding daughter products 170,171Hf and 170,171Lu in the target matrix. Liquid-liquid extraction with HDEHP diluted in cyclohexane was carried out for the separation of 170,171Hf and 170,171Lu from the bulk terbium in an aqueous HCl medium.

Separation of carrier free 151,152Tb produced in 16O irradiated lanthanum oxide matrix.

Charged particle activation of natural La2O3 with approximately 78.5 MeV 16O results in the formation of carrier free 151,152Tb isotopes in the matrix. The liquid cation exchanger, HDEHP, has effectively been utilised as an extractant in the quantitative separation of the activation products from the bulk target matrix of lanthanum oxide.

Solvent extraction of gold.

The separation of gold by solvent extraction is reviewed.