Showing papers by "University of Hamburg published in 1981"

On determining developmental stages in natural second language acquisition

Abstract: Research on Second Language (L2) Acquisition, over the past ten years, has undergone substantial changes by shifting its focus of interest away from an analysis of linguistic structures alone, concentrating more on the learner himself or, rather, on the process of learning. It had become obvious that one of the major shortcomings in contrastive studies as well as in the usual kind of error analysis is that they lack thorough investigation of factors which determine the kind of approach a learner may take to acquire a second language. This again implies that it is more fruitful to study the process of learning itself instead of merely analysing its outputs. It is by now widely accepted that the learner takes an active part in the learning process and does not merely get trapped in structural gaps which linguists may find when comparing the source language (the learner's L1) and the target language (L2).

Saccadic eye movement strategies in patients with homonymous hemianopia

Abstract: Infrared oculographic recordings from three patients with hemianopia due to an occipital lesion showed that these patients employed a consistent set of (presumably unconscious) compensatory strategies to find and fixate objects. For targets in the blind hemifield, patients at first used a staircase strategy consisting of a series of stepwise saccadic search movements. This is safe but slow. When retested later, one patient had adopted a more efficient strategy employing one large saccade calculated to overshoot the target. Other strategies for finding targets in the blind hemifield were employed in response to specific situations presented by our experiments: a predictive strategy using past experience to anticipate where the target would be found, and special strategies for recovering a lost target and for awaiting the reappearance of the target. To fixate targets in the seeing hemifield, our subjects undershot the target to prevent losing it in the blind hemifield, then held it off-fovea on the seeing side of the macula.

Low-drift fibre gyro using a superluminescent diode

Abstract: By using a superluminescent diode as the light source and a depolariser inside the fibre coil, a constant scale factor is achieved without using polarisation control elements. For long-term behaviour an RMS-bias drift of 10 degrees/h is obtained.

Bausteine von Oligosacchariden, XXX. Neue effektive β-Glycosidsynthese für Mannose-Glycoside Synthesen von Mannose-haltigen Oligosacchariden

Abstract: Es wird eine neue Methode zur selektiven Synthese von Oligosacchariden mit β-verknupfter Mannose-Einheit entwickelt, fur deren direkte Gewinnung es bisher kein Verfahren gab. Als Katalysator dient ein auf Al2O3 niedergeschlagenes Silbersilicat. Es werden die Trisaccharide β-D-Man-(14)α-D-Gal-(14)-L-Rha (20) und sowie das Tetrasaccharid 33 synthetisiert. Hierbei werden die Vorteile der Blocksynthese demonstriert. Building Units for Oligosaccharides, XXX. New Efficient β-Glycoside Synthesis of Mannose Glycosides Syntheses of Mannose Containing Oligosaccharides A new method was developed for the stereo selective synthesis of oligosaccharides containing a β-linked mannose-unit which were hitherto not available by direct synthesis. The glycoside synthesis is promoted by a silversilicate-catalyst which was precipitated on aluminium oxide. The trisaccharides 20 and 31 (see german summary) and the tetrasaccharide 33 were synthesized, demonstrating the advantages offered by block synthesis.

Intermediate-sized filament proteins (prekeratin, vimentin, desmin) in the normal parotid gland and parotid gland tumours

Abstract: Antibodies to different intermediate-sized filament proteins can distinguish cells and tissues of epithelial, mesenchymal, muscle, astrocytic and neural origin. Antibodies to prekeratin, vimentin and desmin have been used to distinguish cells of epithelial, mesenchymal and muscle origin in the normal human parotid gland, and in addition to study some common tumors of this gland. Prekeratin-positive and vimentin-positive cells are found among the tumor cells in the pleomorphic adenomas. In contrast the tumor cells of the mucoepidermoid tumors and squamous cell carcinomas are prekeratin-positive but vimentin-negative.

Microinjection of cloned retroviral genomes into mouse zygotes: integration and expression in the animal.

Abstract: Cloned genomic retroviral DNA is expressed in mouse zygotes after microinjection. The resulting virus integrated into the mouse genome at a single chromosomal site and was expressed in a tissue-specific manner. Our findings suggest that the chromosomal position of a viral genome influences its activation during development.

Temperature sensing by mode-mode interference in birefringent optical fibers.

Abstract: Fiber-optic sensors are described that utilize the mode–mode interference of the two orthogonal linear polarizations of the HE11 mode in strongly birefringent single-mode fibers. The sensitivities of various versions of these one-fiber interferometers are calculated. When fibers with high internal stress are used, the temperature sensitivity is reduced by only a factor of 50 compared with that of two-fiber interferometers while the pressure sensitivity is reduced by 7.3 × 103. Thus the cross sensitivity is reduced by a factor of 150.

Superspaces and supersymmetries

Abstract: A theory of graded Banach modules over a Banach-Grassmann algebra is developed and applied to differential geometry of super-manifolds. The explicit structure of superspaces carrying Poincare supersymmetry and extended supersymmetry, including central charges, is described.

Low-noise fiber-optic rotation sensing

Abstract: A major source of noise in fiber-optic Sagnac interferometers was identified to be the fluctuation of the phase of Rayleigh backscattering resulting from minute temperature variations and vibration. This noise can be reduced either by introducing a phase modulation into the fiber ring or by the use of a low-coherence source. A noise-equivalent rotation rate of 8 x 10(-4) deg/sec was achieved.

Immunocytochemical demonstration of filamentous structures in the parotid gland. Occurrence of keratin and actin in normal and tumoral parotid gland with special respect to the myoepithelial cells.

Abstract: The aim of this study was to analyze the filament distribution in the parotid gland and their tumors. A correlation to the histogenetic implications and histological properties was attempted. Normal rat and human parotid glands as well as pleomorphic adenomas and squamous cell carcinomas of this gland were examined by the indirect immunoperoxidase technique using antibodies to the keratin polypeptide of 67,000 dalton, and 55,000 dalton and anti-actin auto-antibodies.

Representation of Moving Rigid Objects Based on Visual Observations

Abstract: A single-camera algorithmic system can learn from observations of scenes with moving rigid objects.

Effect of abscisic acid on the transport of assimilates in barley

Abstract: The effect of abscisic acid (ABA) on assimilate transport in barley was investigated in two parallel experiments. First, the effect upon [14C]sucrose transport from the flag leaf to the ear of a single ABA application made at different stages of growth of the fruits was investigated; the effect was measured 24 h after treatment. Second, the effect of a single application of ABA made at the same stages of growth as above on grain weight of the mature plant was investigated. In both types of experiments ABA was applied once to the ear of different plants as an aqueous solution (10-3–10-5 M), one to five weeks after anthesis. [14C] sucrose was applied by means of agar blocks. Parallel to these experiments, the endogenous content of ABA was investigated in the developing grains. When ears were treated with ABA two or four weeks after anthesis, an increase of up to 70% in the 14C-transport from the flag leaf to the ear was observed within a 24-h period after treatment (short duration experiments). At these growth stages the endogenous concentrations of ABA were low. In sharp contrast, ABA, especially in a concentration of 10-3 M, decreased 14C-import from the flag leaf when applied three weeks after anthesis. At this stage the endogenous ABA content had reached its maximum. Long duration experiments with a single application of ABA to the car two weeks after anthesis resulted in a marked increase of weight per thousand kernels. ABA applications made earlier or later than two weeks after anthesis either reduced the grain weight or had no effect. It is concluded that ABA is involved in the regulation of assimilate transport from the leaves to the grains, possibly by influencing the unloading of sieve tubes in the ears. Promotion or inhibition of assimilate import by exogenously applied ABA may depend on the developmental stage of the grains and on the endogenous ABA level.

Discriminative ability and function of the immunobiological recognition system of the snailHelix pomatia

Abstract: The internal defense mechanism ofHelix pomatia discriminates between different types of foreign cells as demonstrated by determinations of their clearance rates. The rate of elimination is not dependent on the size of foreign cells but on their molecular surface properties. Circulating hemocytes are not involved in the first phase of the clearance event, which is characterized by an accumulation of nonself cells in the digestive gland, kidney and foot muscle ofHelix. Light microscopic studies of these organs reveal nonself cells to be attached to the membrane of cells lining hemolymph sinuses. The attachment of certain types of foreign cells is apparently mediated by opsonins as their clearance depends on the opsonin level of the hemolymph, whereas others are cleared without involvement of opsonizing molecules. Membrane bound molecules of the latter type of nonself cells seem to directly interact with carbohydrate-specific combining sites on the membranes of cells of the sinus walls, as their binding can be inhibited by N-acetyl-galactosamine, and N-acetyl-glucosamine.