Effects of a spin-flavour dependent interaction on light-flavoured baryon helicity amplitudes

This paper is a continuation of previous work about the effects of a phenomenological flavour dependent force in a relativistically covariant constituent quark model based on the Salpeter equation on the structure of light-flavoured baryon resonances. Here the longitudinal and transverse helicity amplitudes as studied experimentally in the electro-excitation of nucleon- and $\Delta$ resonances are calculated. In particular the amplitudes for the excitation of three and four star resonances as calculated in a previous model $\mathcal A$ are compared to those of the novel model $\mathcal C$ as well as to existing and partially new experimental data such as e.g. determined by the CB-ELSA collaboration. A brief discussion of some improvements to model $\mathcal C$ is given after the introduction.Comment: 21 pages, 58 figure

Spin and Flavour dependent Interactions within a Quark Model for Baryons

Within the framework of a relativistic covariant quark model the effects of two novel quark interactions on the light-flavoured baryon mass spectra as well as on a multitude of observables, such as electroweak form factors, helicity amplitudes, decay amplitudes, magnetic moments and charge radii, are studied. This quark model is based on the so-called Bethe-Salpeter equation, which describes bound-state systems in quantum field theory. After a brief summary of the basic ingredients of the quark model, we discuss the results published so far. Then we introduce two different forms for alternative interactions. This is the major subject of this thesis: In addition to the so-called confinement potential and an instanton-induced 't Hooft interaction a novel spin-flavour dependent interaction motivated by pseudoscalar meson-exchange is introduced. Thereby we assume, that pseudoscalar octet and singlet mesons interact with quarks via pseudoscalar coupling. Assuming a short-range Gaussian potential in coordinate space, we introduce only three additional model parameters: The octet and singlet-coupling strength as well as the range of this interaction. It is found, that this additional spin-flavour dependent interaction leads to a better description of the light-flavoured baryon mass spectra than has been obtained so far. It also improves the description of the electroweak form factors and helicity amplitudes as well as of the other observables mentioned above. A second interaction is studied, which corresponds to a modification of the spin dependence of the confinement potential by introducing specific spin-spin and tensor contributions. This modified confinement potential was used in combination with the instanton-induced 't Hooft interaction and with the novel spin-flavour dependent interaction as well. Although not superior to the results found with the new spin-flavour dependent interaction as mentioned above, also for models with a modified confinement potential a, compared to the previous results, improved description of both the spectra and electroweak observables was found

DAC-Less amplifier-less generation and transmission of QAM signals using sub-volt silicon-organic hybrid modulators

We demonstrate generation and transmission of optical signals by directly interfacing highly efficient silicon-organic hybrid (SOH) modulators to binary output ports of a field-programmable gate array. Using an SOH Mach-Zehnder modulator (MZM) and an SOH IQ modulator we generate ON-OFF- keying and binary phase-shift keying signals as well as quadrature phase-shift keying and 16-state quadrature amplitude modulation (16QAM) formats. Peak-to-peak voltages amount to only 0.27 V-pp for driving the MZM and 0.41 V-pp for the IQ modulator. Neither digital-to-analog converters nor drive amplifiers are required, and the RF energy consumption in the modulator amounts to record-low 18 fJ/bit for 16QAM signaling

10 GBd modulator directly driven by an FPGA without electrical amplification

Using standard single-ended FPGA outputs with 270 mV(pp) we demonstrate 10GBd OOK and BPSK transmission by directly driving a low-voltage silicon-organic hybrid ( SOH) modulator. The scheme does not require electronic driver amplifiers, which paves the way to energy-efficient photonic-electronic integration

Bromus mollis

Angiosperm

Small Mammals from Troia VIII, Environment and Taphonomy

The following article deals with a sample of small mammals recovered from a levelling fill situated to the southwest of the Lower Sanctuary, and dated to about 550 B.C. The position of the bones within the pit and the condition of their surfaces indicate that they were probably piled up by an owl. The identified species perfectly fit into the environment, which has been reconstructed based on archaeozoological and -botanical investigations, they must have led a contented life in the man-made landscape and the grassland of Troia and its surroundings. An interesting aspect to be mentioned is the general absence of the black rat (Rattus rattus) within the sample as well as in the cultural layers of Troia up to at least the archaic period. It is likely that these animals had not yet reached the Mediterranean by that time.Der vorliegende Beitrag beschäftigt sich mit einem in die archaische Phase von Troia datierten Kleinsäugerfundkomplex. Die Probe stammt aus dem Verfüllmaterial, das im Zuge von Planierungsarbeiten zwischen 550 und 500 v. Chr. südwestlich des Unteren Heiligtums eingebracht wurde. Zustand und Lage der Knochen deuten darauf hin, dass die Akkumulation von einer Eule zusammengetragen wurde. Die festgestellten Arten fügen sich gut in die bereits mit Hilfe vorangegangener archäozoologischer und -botanischer Untersuchungen rekonstruierte Umwelt, sie dürften sich auf dem Kultur- und Grasland in und rund um Troia sehr wohl gefühlt haben. Bemerkenswert ist die Abwesenheit der Hausratte (Rattus rattus) sowohl in der Probe als auch allgemein in den Kulturschichten von Troia, was darauf hinweisen könnte, dass diese Art die Mittelmeerküste zumindest bis zur archaischen Phase noch nicht erreicht hatte