Structural and optical investigation of semiconductor CdSe/CdS core-shell quantum dot thin films.

Highly luminescent CdSe/CdS core-shell nanocrystals have been assembled on indium tin oxide (ITO) coated glass substrates using a wet synthesis route. The physical properties of the quantum dots (QD) have been investigated using X-ray diffraction, transmission electron microscopy and optical absorption spectroscopy techniques. These quantum dots showed a strong enhancement in the near band edge absorption. The in situ luminescence behavior has been interpreted in the light of the quantum confinement effect and induced strain in the core-shell structure.

Highly luminescent inverted ZnS/CdS core/shell quantum dots.

Synthesis of highly luminescent and monochromatic inverted core-shell structures utilizing ZnS/CdS quantum dots (QDs) has been investigated. The core/shell quantum dots have been characterized using grazing angle X-ray diffraction (XRD), Transmission electron microscopy, Optical absorption and luminescence spectroscopy. The results suggested that passivation of surface states along with an increased localization of electron and hole in CdS shell layer, give rise to increased monochromaticity with higher quantum yield. The possibility of using the inverted core-shell structure as an additional parameter for tuning the color of luminescence has also been discussed.

Study of self-organized CdS Q-dots.

Self-organized cadmium sulfide quantum dots assembled using wet synthesis route on glass/ITO as well as Si(100) substrates have been investigated, using X-ray diffraction and transmission electron microscopy. The quantum dots have been shown to grow with a strong (111) orientation with narrow size distribution. Self-organized growth of the quantum dots was examined by high resolution imaging with an atomic force microscope. It is shown that increased self-organization is obtained on silicon substrate. The role of surfactant in imparting self-organization has been invoked to explain the observed morphological features. The as grown Q-dots exhibited size dependent blue shift in the absorption edge. The luminescence behavior of the quantum dots self-organized on glass/ITO as well as Si(100) substrate has also been examined. It is shown that substantial enhancement in luminescence yield is obtained for quantum dots grown on silicon substrate. A model to explain the observed luminescence enhancement has also been presented.

Self-organized ZnSe quantum dots: synthesis and characterization.

Self-organized ZnSe quantum dots (Q-ZnSe) were grown on indium tin oxide substrate using wet chemical technique without or in presence of copper and manganese dopants. The structural, morphological and luminescence properties of the as grown Q-dot films have been investigated, using X-ray diffraction, transmission electron microscopy, atomic force microscopy and optical and luminescence spectroscopy. Composition of the samples were analyzed using atomic absorption spectroscopy. The quantum dots have been shown to deposit in a compact, uniform and organized array on the indium tin oxide substrate. The size dependent blue shift in the experimentally determined absorption edge has been compared with the theoretical predictions based on the effective mass and tight binding approximations. It is shown that the experimentally determined absorption edges depart significantly from the theoretically calculated values. The photoluminescence properties of the undoped as well as doped Q-ZnSe have also been discussed.

Primary tuberculosis of tongue.

Primary tuberculosis of tongue is very rare with unusual presentation creating a diagnostic dilemma. We report a case of primary tuberculosis of tongue in a 49-year-old female patient. Tuberculosis was not suspected clinically and there was no other focus elsewhere in the body. Fine needle aspiration cytology was attempted but was inconclusive. The diagnosis was made after histopathological examination.

Maxillary and mandibular reconstruction in preparation for endosseous implants.

Bony and soft tissue deficiencies can deter esthetic, functional and prosthetic rehabilitation. Modern surgical techniques using bone or composite grafts to reconstruct or augment implant sites are reviewed.

Selective excitation of parabolic-index optical fibers by Gaussian beams.

Excitation coefficients of the guided modes of a parabolic-index optical fiber by narrow input Gaussian beams are calculated. The effects of beam offset, tilt, width, and wave-front curvature are examined. A wave-optical procedure for optimizing the input Gaussian beamwidth (to excite as few mode groups as possible) as a function of beam offset is presented and shown to be in agreement with a simple Fourier-optics optimization.

Design of efficient all-optical code-division multiplexing systems supporting multiple-bit-rate and equal-bit-rate transmissions.

We present the design of efficient all-optical code-division multiplexing (AOCDM) systems that can transmit multiple-bit-rate (MBR) data signals over a common optical fiber. This is achieved when the proposed strict optical orthogonal code (OOC) of autocorrelation and cross-correlation constraints of 1 are used but without performance degradation compared with the use of conventional OOC. We describe the design of various strict OOC's by employing the useful concept of slot distances, and methods of code construction are also presented. Moreover, we give the principle of MBR data transmissions in an AOCDM system. It is shown that AOCDM systems using the proposed OOC can effectively transmit multiuser MBR and equal-bit-rate (EBR) data with no increase of system complexity. In principle, optimal strict OOC's need the same or a slightly larger system bandwidth compared with optimal conventional OOC's for EBR operation, whereas the former can require a smaller system bandwidth and have a better system performance than the latter for MBR transmissions. A new, to our knowledge, family of strict OOC's is also introduced, whose code words can have nonconstant weights to support multiuser communications with different transmission quality. Furthermore, we design low-cost AOCDM transmitters that are based on an efficient gain-switching scheme that does not require an electro-optic intensity modulator to on-off modulate an optical clock pulse stream at each transmitter. The basic operation principle is also experimentally demonstrated.

Reconstruction of a complex midfacial defect with the folded fibular free flap and osseointegrated implants.

Refinements in microsurgical techniques, plate fixation, and osseointegration have changed the conceptual approach to midface reconstruction. Free tissue transfer has emerged as the ideal method of reconstructing complex midfacial defects. Single-stage bony restoration of the palate and orbital rim using the folded fibular osteocutaneous free flap is described. The fibular free flap is our first choice for reconstructing complex midfacial defects. The thin, soft, pliable tissue is ideal for intraoral and palatal reconstructions. The bone can be tailored precisely to fit any desired shape, and forms a sturdy support for both orbital and dental prostheses. With a single flap, rapid and reliable restoration of midfacial appearance, orbital support, and palatal function can be achieved.