High-efficiency dielectric reflection gratings: design, fabrication, and analysis.

We report on reflection gratings produced entirely of dielectric materials. This gives the opportunity to enhance the laser damage threshold over that occurring in conventional metal gratings used for chirped-pulse-amplification, high-power lasers. The design of the system combines a dielectric mirror and a well-defined corrugated top layer to obtain optimum results. The rules that have to be considered for the design optimization are described. We optimized the parameters of a dielectric grating with a binary structure and theoretically obtained 100% reflectivity for the -1 order in the Littrow mounting for a 45 degrees angle of incidence. Subsequently we fabricated gratings by structuring a low-refractive-index top layer of a multilayer stack with electron-beam lithography. The multilayer system was fabricated by conventional sputtering techniques onto a flat fused-silica substrate. The parameters of the device were measured and controlled by light scatterometer equipment. We measured 97% diffraction efficiency in the -1 order and damage thresholds of 4.4 and 0.18 J/cm(2) with 5-ns and 1-ps laser pulses, respectively, at a wavelength of 532 nm in working conditions.

[Chondroma of the petrous bone. A contribution to differential skull base tumor diagnosis]. / Chondrom im Bereich des Felsenbeines. Ein Beitrag zur Differentialdiagnose der Schädelbasistumoren.

INTRODUCTION: Cartilaginous tumors of the mid-face and the skull base are rare. CASE REPORT: For the first time, a case report of a chondroma of the base of the ear in a 56-year-old woman is presented. In 1974 the patient developed a facial nerve paralysis while she was pregnant. Twenty-two years later the patient developed persistent headache and CT studies of the head were obtained, which showed an extensive tumorous lesion located at the base of the ear. A tumor was resected through an otoneurosurgical approach. The histological examination showed a chondroma. CONCLUSIONS: Even the rare diagnosis of a chondroma should be considered for a differential diagnosis of skull base tumors.

The fixed combination of collagen with components of fibrin adhesive-a new hemostypic agent in skull base procedures.

CSF leak still is one of the major sources of morbidity after extensive skull base procedures. Of the various standard closure techniques of traumatic or iatrogenic dural defects, none provides a really waterlight, persistent closure. Even the supplementary use of fluid fibrin glue did not substantially improve the rate of postoperative CSF leaks. The application of a collagen sheet covered with a fixed layer of solid components of a fibrin tissue glue (TachoComb(R)) overcomes the major drawbacks of dural sealing in skull base surgery. The dural defects of 58 patients undergoing extensive skull base procedures were sealed with this new hemostyptic agent. The series includes 44 patients undergoing primary surgery, 6 patients with traumatic or iatrogenic tears of venous sinuses, and 8 patients with postoperative leaks after previous skull base procedures in which other sealing methods were previously used. In the group of primary surgery, none of the patients had postoperative CSF leakage or venous rebleeding. One patient developed a delayed pneumatocephalus. All cases of patent CSF fistulas were resolved without any adjuvant therapy. Preliminary experience shows that the good sealing and hemostyptic performance of this new agent will considerably reduce the risk of postoperative CSF leak and infection after skull base procedures.

[Reconstruction of the soft palate with a microvascular radial flap]. / Rekonstruktion des weichen Gaumens mit dem mikro-vaskularisierten Radialislappen.

BACKGROUND: A new technique for reconstruction of the soft palate using a folded microvascularized radial forearm flap is described. PATIENTS: The method has been used in 16 patients to date. RESULTS: There was no loss of the transplant. Only three patients had unsatisfactory functional results with respect to speaking and swallowing. CONCLUSIONS: The presented technique enables a one-step reconstruction of the complete soft palate. The complication rate we experienced was low and the functional results were excellent.

[Bilateral Gradenigo syndrome--on the value of an integrated therapy concept including hyperbaric oxygenation and chronic destructive inflammation of the skull base]. / Gradenigo-Syndrom beidseits--Zum Stellenwert eines integrierten Therapiekonzepts unter Einschluss der hyperbaren Oxygenation bei chronisch-destruierenden Entzündungen der Schädelbasis.

The case of a 30-year-old female with bilateral Gradenigo's syndrome is presented in order to detail commonly applied therapy. In particular, the importance of a comprehensive therapeutic approach is emphasized that includes such adjuvant therapeutic options as hyperbaric oxygenation and the administration of specific immunoglobulins. Indications, therapeutic benefits and limitations of treatment modalities are discussed in relationship to current concepts of therapy.

Light scattering from the volume of optical thin films: theory and experiment.

A theoretical model is presented that describes the volume scattering in thin optical films, particularly in typical columnar structures. It is based on a first-order perturbation theory that concerns the fluctuation of the dielectric permittivity in the film. For evaporated PbF(2) films that show a pronounced columnar morphology, angular as well as total integrated scattering measurements at lambda = 633 nm have been performed on a special layer design to suppress roughness-induced scattering. A comparison of the predicted theoretical and the measured experimental values leads to such structural parameters as packing density and the evolutionary exponent of the columns.

[Use of glass ionomer cement in surgery of the incus-stapedial joint. An initial report of experiences]. / Uber die Verwendung von Glasionomerzement in der Chirurgie am kleinen Gelenk. Ein erster Erfahrungsbericht.

Chronic inflammations of the middle ear are characterised by perforation of the tympanic membrane as well as hearing loss, due to disintegration in the incudostapedial joint. Usually the perforation is easily restored by means of available modern procedures; on the other hand, failure of the reconstruction of the ossicular chain, especially of the incudostapedial joint, is not uncommon. Hence, the improvement of hearing capacity is transitory, since later, due to scars, graft lateralisation results in a dislocation of the primarily reconstructed ossicular chain. The patient's hearing capacity is then as poor as it has been before surgery. The aim of this study is to demonstrate the ways of satisfactory reconstruction of the incudostapedial joint by means of glass-ionomer cement: 1. Scar tissue connecting the ossicles in slight defects of the incudostapedial joint can be stabilised by glass-ionomer cement leading to a reasonable sound transmission. 2. If the incus has to be removed in case of a more serious defect, the columella can be properly fixed to the stapes by means of glass-ionomer cement without the risk of scar-induced lateralisation. 3. The fixation of the stapes prosthesis' wire loop to the incus can be effectively achieved by glass-ionomer cement.

Cysteine analogues potentiate glucose-induced insulin release in vitro.

In rat pancreatic islets, cysteine analogues, including glutathione, acetylcysteine, cysteamine, D-penicillamine, L-cysteine ethyl ester, and cysteine-potentiated glucose (11.1 mM) induced insulin secretion in a concentration-dependent manner. Their maximal effects were similar and occurred at approximately 0.05, 0.05, 0.1, 0.5, 1.0, 1.0 mM, respectively. At substimulatory glucose levels (2.8 mM), insulin release was not affected by these compounds. In contrast, thiol compounds, structurally different from cysteine and its analogues, such as mesna, tiopronin, meso-2,3-dimercaptosuccinic acid (DMSA), dimercaprol (BAL), beta-thio-D-glucose, as well as those cysteine analogues that lack a free-thiol group, including L-cystine, cystamine, D-penicillamine disulfide, S-carbocysteine, and S-carbamoyl-L-cysteine, did not enhance insulin release at stimulatory glucose levels (11.1 mM); cystine (5 mM) was inhibitory. These in vitro data indicate that among the thiols tested here, only cysteine and its analogues potentiate glucose-induced insulin secretion, whereas thiols that are structurally not related to cysteine do not. This suggests that a cysteine moiety in the molecule is necessary for the insulinotropic effect. For their synergistic action to glucose, the availability of a sulfhydryl group is also a prerequisite. The maximal synergistic action is similar for all cysteine analogues tested, whereas the potency of action is different, suggesting similarity in the mechanism of action but differences in the affinity to the secretory system.