Application of the needle optimization technique to the design of optical coatings

The authors' experience with the application of the needle optimization technique to the design of optical coating is summarized. A physical interpretation of the technique is provided, and its main features are identified. Guidelines on the application of the needle optimization technique to various types of design problems are given.     

Two-dimensional finite-difference time-domain simulation for rewritable optical disk surface structure design

A novel two-dimensional finite-difference time-domain simulation for treating the interaction of a focused beam with a rewritable optical disk is detailed and experimentally validated. In this simulation, the real material properties of the rewritable multilayer stack and the aperiodic nature of the disk topography are considered. Excellent agreement is obtained between calculated and measured push-pull tracking servosignals for magneto-optical disks with pregrooves and infinite-length preformat pits. To demonstrate the utility of the simulation as a design tool, the design process for a 0.9-μm track pitch, continuous, composite servoformat magneto-optical disk is given.     

Antireflection coatings for UV radiation obtained by molecular-beam deposition

We have developed fluoride antireflection (AR) coatings on MgF(2) substrates for a wavelength of 248 nm by molecular-beam deposition. Transmission and laser-induced damage threshold of the samples were measured and atomic force microscope (AFM) investigations were carried out. We compare a 14-layer design for AR coatings with sublayer thicknesses of 12 nm with a conventional two-layer design with quarter-wavelength thicknesses. The laser-induced damage threshold of the 14-layer coating is slightly higher than that of the two-layer coating. The AFM surface images show that the 14-layer coating has a smoother surface than the two-layer coating.     

A microstructural investigation of NiAl/Ni-Si-B/NiAl transient liquid phase bonds

Microstructural development during transient liquid-phase bonding of cast polycrystalline near-stoichiometric NiAl (B2 compound, -phase) was investigated using cross-sectional transmission electron microscopy. Bonds made using Ni-4.5 wt % Si-3.2 wt % B (AWS designation BNi-3) interlayers in the form of melt-spun foils were studied. Microstructural changes in the joint region and surrounding substrates were examined as a function of holding time at temperatures of 1065 and 1150°C. The transformation of the substrate -phase to L1₀-type martensite due to aluminium transfer to the joint has been discussed, and the formation of L1₂ type ( structure) layers at the joint-substrate interfaces considered. The nature of the isothermal solidification process has also been discussed and the changes, with holding time at the bonding temperature, in the character of the residual eutectic examined. The formation of M₂₃X₆-type borides within both the joint and surrounding substrates was also considered.     

Mechanosynthesis of Nd-Fe-B alloys

A mechanical alloying technique has been applied for Nd-Fe-B alloy synthesis from the mixture of neodymium, iron and Fe-B powders. The direct formation of Nd₂Fe₁₄B phase ( phase) was not observed, but an Nd-Fe multilayer structure was formed during the milling process. Annealing of milled powders at 1023 K for 1 h resulted in magnet formation. The dependence of the magnetic properties on milling time was observed. For the applied milling device and parameters, the optimum milling time proved to be 4 h and the coercive force reached a value of about 1000 kAm^–1.     

A comparison of strain relief behaviour of In x Ga1− x As alloy on GaAs (001) and (110) substrates

A comparative study on the strain relief behaviour of epitaxially grown In _x Ga_{1 – x} As (where 0.1 × 1) alloys on GaAs (001) and (110) were carried out using transmission electron microscopy (TEM) and high resolution X-ray diffraction (XRD). Three different strain relief mechanisms related to the formation of misfit dislocations (MDs) were observed. The dominant strain relief process can be a single mechanism or a combination of two of the three mechanisms depending on the substrate orientation and the in content.     

Intradermal and subcutaneous leiomyosarcoma: a clinicopathological and immunohistochemical study of 41 cases

Superficial leiomyosarcomas are rare tumours. The lesions confined to the dermis, contrary to those involving the subcutis, have been reported to carry a favourable prognosis. A retrospective study of 41 consecutive cases of surgically treated intradermal and subcutaneous leiomyosarcomas was undertaken in order to determine the prognostic factors that may influence the survival of these patients. Seven tumours were predominantly intradermal and 34 involved the subcutaneous tissue. Fifty-four percent of the tumours were located in the lower extremities. All cases stained positively for smooth muscle antigen and 66% for desmin. The tumours were classified with regard to tumour grade I (low grade, 3%), II (intermediate, 12%), IIIA (high grade, 46%) and IIIB (high grade, 39%). In all patients, follow-up information was available. Mean follow-up time was 5 years. The patients with intradermal tumours were all alive without signs of recurrence, whereas 14 of those with leiomyosarcomas involving the subcutis have died with pulmonary metastases. Our study confirms that "pure" intradermal leiomyosarcomas independent of tumour grade behave in a benign fashion, probably due to small tumour size. Tumour size > or = 5 cm, deep localization with fascia involvement, and high malignancy grade (IIIB) were found to deteriorate survival based on a univariate analysis. However, in a multivariate analysis only tumour size was found to be an independent prognostic factor.     

An experimental micromechanics measurement technique for submicrometre domains

Orthogonal arrays of dots applied to surfaces can be used to directly measure microscopic strain fields. The spatial and strain resolution are both limited by the size of the dots placed on the surface. Two techniques using the beam of a scanning electron microscope (SEM) have been developed which make possible the placement of very fine dots with diameters of only 0.5 and 0.02 m, respectively, on the surface of the specimen, allowing local strain measurements on the scale of 0.2–10 m when specimens are loaded in the SEM. Measurements of strains fields around the tips of growing cracks in both polymers and polymeric composites are presented to illustrate the capabilities of the technique.     

Primary chronic polyarthritis of the knee joint

Rheumatoid arthritis is a chronic, multisystemic disease. The characteristic feature is persistent inflammatory synovitis. The knee joint is commonly involved with synovial hypertrophy, chronic effusion, and frequently ligamentous laxity. Pain and swelling behind the knee may be caused by extension of inflamed synovium into the popliteal space (Baker's cyst). Plain radiographs of the knee joint remain the basic radiological procedure, although early in the disease they might not provide significant changes. Sonography sufficiently reveals synovial fluid and Baker cysts, but cannot be recommended for evaluation of synovial proliferations or pannus formation. Computer tomography has only limited indications and may be used for the evaluation of subtle erosive lesions or the quantitation of osteoporotic changes. Magnetic resonance imaging has shown excellent visualization of cartilage, fluid, synovium and soft tissues and is the method of choice for the demonstration of early affection and the evaluation of pannus activity and therapy control. With administration of contrast agents (gadolinium), dynamic studies may demonstrate inflammatory activity. Modern MR sequences, such as T1 SE "fat sat" or magnetization transfer, further improve the discrimination of cartilage, pannus and synovial fluid.     

Quality assurance in coloscopy in private practice and the hospital. The Gastroenterology Quality Circle (GEQC) Munich

OBJECTIVE: As quality control in medicine is part of a doctor's professional duty, the "Munich Quality Circle" conducted a prospective feasibility study in which ten, previously defined, quality indicators were to be assessed. PATIENTS AND METHODS: Six specialised private practice groups and three specialised hospitals centers took part. Data on 2928 consecutive patients were collected by questionnaire and ten quality indicators assessed: concordance with the indication list; intestinal cleansing; premedication; duration and completeness of the study; sensation of pain; use of radiology; complications; diagnosis; and therapeutic intervention. RESULTS: Concordance with the indication list was present in 97.8% (range 93-100), premedication was given to 94.6% (77-100), midazolam to 77%. The proportion of patients who recorded no or only moderate pain correlated with the dose but not with the duration of advancing the coloscope. Mean time of advancing the instrument to the caecum was 8.0 min, the duration directly depending on the experience of the examiner. A mean time of less than 10 minutes was achieved only after more than 1200 examinations. The more a centre used fluoroscopic control the shorter the time of coloscopy. The examination was completed in 97.6% (92-99). There was no correlation between experience (assuming supervision) and dose of midazolam or frequency of fluoroscopy. CONCLUSIONS: Nowadays total coloscopy is a primary diagnostic method, but it needs an intensive learning phase. In clinical centers consequent supervision of less experienced examiners achieved comparable results to those with experience. Informative quality indicators for coloscopy can be documented with little cost.