Fabrication of coupled graphene-nanotube quantum devices.

We report on the fabrication and characterization of all-carbon hybrid quantum devices based on graphene and single-walled carbon nanotubes. We discuss both carbon nanotube quantum dot devices with graphene charge detectors and nanotube quantum dots with graphene leads. The devices are fabricated by chemical vapor deposition growth of carbon nanotubes and subsequent structuring of mechanically exfoliated graphene. We study the detection of individual charging events in the carbon nanotube quantum dot by a nearby graphene nanoribbon and show that they lead to changes of up to 20% of the conductance maxima in the graphene nanoribbon, acting as a well performing charge detector. Moreover, we discuss an electrically coupled graphene-nanotube junction, which exhibits a tunneling barrier with tunneling rates in the low GHz regime. This allows us to observe Coulomb blockade on a carbon nanotube quantum dot with graphene source and drain leads.

[Subretinal transplantation of confluent pigment epithelium: a novel device for non-traumatic tissue handling]. / Subretinale Transplantation von konfluentem Pigmentepithel: Ein neues Instrument zur atraumatischen Gewebeaufnahme.

BACKGROUND: Subretinal transplantation of pigment epithelium may be a therapeutic option in the treatment of age-related macular degeneration. Suspensions of pigment epithelial cells as well as confluent cell layers are being considered. METHODS: We developed a surgical device which permits to load living tissue, without exerting mechanical stress to the cells themselves, and to deliver it precisely onto the subretinal target site. RESULTS: After having been grown to confluency on extracellular matrix, the tissue can be fixed on a cannulated spoon by creating a vacuum on its undersurface. The spoon is connected to a silicone tube attached to a syringe. The syringe is used to produce a vacuum which is delivered to the tissue through the perforated surface of the spoon. After directing the spoon into the subretinal space, the tissue can be discharged by releasing the vacuum. CONCLUSIONS: In previous studies large cannulas have been used for injecting coherent cell layers underneath the retina. This technique frequently resulted in major distortion of the tissue. Furthermore, correct apico-basal orientation of the tissue often could not be achieved. We present a novel concept of a device which exerts vacuum to the entire underside of the graft allowing to hold it in position without distorting it. By releasing the vacuum, the graft can be positioned in the site of RPE atrophy. (Patent Reg. No. 29819018.4, München, Germany, 1998).

[Endoscope-assisted fixation of condylar fractures of the mandible]. / Endoskop-gestützte Fixation von Gelenkfortsatzfrakturen des Unterkiefers.

The reduction and plate osteosynthesis of condylar fractures often require a wide extraoral approach with the risk of facial nerve palsy. The endoscopic technique is an alternative. Seven condylar fractures were operated on under endoscopic control. In three patients a newly developed device for endoscopically controlled plate application was clinically tested for osteosynthesis. In two cases fracture healing was achieved. In the third case the plate had to be removed early due to insufficient screw fixation. The new device and the application technique are described in detail. This technique may be helpful in further minimizing trauma surgery.

[Endoscopically controlled fixation of condylar fractures]. / Endoskop-gestützte Fixation von Gelenkfortsatzfrakturen des Unterkiefers.

The reduction and plate osteosynthesis of condylar fractures often require a wide extraoral approach with the risk of facial nerve palsy. The endoscopic technique is an alternative. Seven condylar fractures were operated on under endoscopic control. In three patients a newly developed device for endoscopically controlled plate application was clinically tested for osteosynthesis. In two cases fracture healing was achieved. In the third case the plate had to be removed early due to insufficient screw fixation. The new device and the application technique are described in detail. This technique may be helpful in further minimizing trauma surgery.

[Resorption of progesterone through the intact skin of the breast in comparison with other body regions]. / Zur Resorption von Progesteron durch die intakte Haut der Brust im Vergleich zu anderen Körperregionen.

In healthy female volunteers the percutaneous absorption of progesterone from an ointment is studied comparing the absorption in the breast skin and that of other regions (thigh, abdomen). Before and certain times after the application progesterone serum levels are measured. A significant increase of mean serum levels (1 to 1.9 ng/ml) ist observed after application to the breast, while it is missing after application to other sites. Individual values of progesterone levels show a distinct peak after 30-120 min following application to the breast, while it lacks in three cases following other application. Serum peaks do not depend on the skin thickness as determined by ultrasound measurement. Percutaneous treatment with progesterone obviously is easier to perform using the breast skin than that of other regions.

Treatment of oligozoospermia by tamoxifen: no evidence for direct testicular action.

The improvement of impaired spermatogenesis by tamoxifen is well documented. The antiestrogen seems to act via an enhancement of gonadotropin release from the hypophysis, but there is evidence for a direct testicular effect. Thus we studied the serum levels of gonadotropins and steroid hormones in 22 patients with idiopathic oligozoospermia. To study the direct testicular effect, we tested the response of 5 normal males to hCG prior to and after the application of tamoxifen. FSH levels showed a continuous increase in the patients during the three months of treatment, while the stimulation by LH-RH was not altered. In the case of LH the basal as well the stimulated levels increased. Mean levels of testosterone, 17-hydroxyprogesterone, androstenedione and estradiol increased significantly during treatment. Sperm counts of patients were found to be considerably higher after three months. In the normal males no differences in steroid levels as a response to hCG with and without tamoxifen treatment occurred. Our results give evidence, that the hormonal changes occurring under tamoxifen treatment are not due to a direct testicular effect.

Serum levels of testosterone precursors, testosterone and estradiol in 10 animal species.

Blood levels of testosterone precursors, i.e. pregnenolone, progesterone, 17 alpha-hydroxyprogesterone, androstendione, DHEA, and delta 5-androstendiol as well as testosterone and estradiol are measured in 10 animals each of 10 different species. The determination is done by radioimmunoassay with steroidspecific antibodies. Precursors of the delta 5-pathway (DHEA, androstendiol) are low in the red deer, dog, cat, rat and guinea pig. Precursors of the delta 4-pathway (progesterone, 17-hydroxprogesterone, androstendione) are lower in the bull, boar, ram, stallion and rabbit thus indicating a predominance of different pathways in the animal species studied herein. Pregnenolone concentrations are of equal height in all animals, testosterone is lowest in the cat and stallion. In the latter species the estradiol/testosterone ratio is spectacular high.