Biomedical subjects

G Thalhammer

Publications and source records attributed to G Thalhammer.

6 recordsLinked to original sources

PubMed2006

Repulsively bound atom pairs in an optical lattice.

Throughout physics, stable composite objects are usually formed by way of attractive forces, which allow the constituents to lower their energy by binding together. Repulsive forces separate particles in free space. However, in a structured environment such as a periodic potential and in the absence of dissipation, stable composite objects can exist even for repulsive interactions. Here we report the observation of such an exotic bound state, which comprises a pair of ultracold rubidium atoms in an optical lattice. Consistent with our theoretical analysis, these repulsively bound pairs exhibit long lifetimes, even under conditions when they collide with one another. Signatures of the pairs are also recognized in the characteristic momentum distribution and through spectroscopic measurements. There is no analogue in traditional condensed matter systems of such repulsively bound pairs, owing to the presence of strong decay channels. Our results exemplify the strong correspondence between the optical lattice physics of ultracold bosonic atoms and the Bose-Hubbard model-a link that is vital for future applications of these systems to the study of strongly correlated condensed matter and to quantum information.

Journal Article↗

PubMed2006

Long-lived Feshbach molecules in a three-dimensional optical lattice.

We have created and trapped a pure sample of Feshbach molecules in a three-dimensional optical lattice. Compared to previous experiments without a lattice, we find dramatic improvements such as long lifetimes of up to 700 ms and a near unit efficiency for converting tightly confined atom pairs into molecules. The lattice shields the trapped molecules from collisions and, thus, overcomes the problem of inelastic decay by vibrational quenching. Furthermore, we have developed an advanced purification scheme that removes residual atoms, resulting in a lattice in which individual sites are either empty or filled with a single molecule in the vibrational ground state of the lattice.

Journal Article↗

PubMed2005

Atom-molecule dark states in a Bose-Einstein condensate.

We have created a dark quantum superposition state of a Rb Bose-Einstein condensate and a degenerate gas of Rb2 ground-state molecules in a specific rovibrational state using two-color photo-association. As a signature for the decoupling of this coherent atom-molecule gas from the light field, we observe a striking suppression of photo-association loss. In our experiment the maximal molecule population in the dark state is limited to about 100 Rb2 molecules due to laser induced decay. The experimental findings can be well described by a simple three mode model.

Journal Article↗

PubMed2004

Tuning the scattering length with an optically induced Feshbach resonance.

We demonstrate optical tuning of the scattering length in a Bose-Einstein condensate as predicted by Fedichev et al. [Phys. Rev. Lett. 77, 2913 (1996)]. In our experiment, atoms in a 87Rb condensate are exposed to laser light which is tuned close to the transition frequency to an excited molecular state. By controlling the power and detuning of the laser beam we can change the atomic scattering length over a wide range. In view of laser-driven atomic losses, we use Bragg spectroscopy as a fast method to measure the scattering length of the atoms.

Journal Article↗

PubMed2004

Arthralgia and digital clubbing in a child: hypertrophic osteoarthropathy with inflammatory pseudotumour of the lung.

Arthralgia in childhood is an unspecific symptom. One rare cause of arthralgia is hypertrophic osteoarthropathy associated with digital clubbing. We present a child where hypertrophic osteoarthropathy led to the rare diagnosis of an inflammatory pseudotumour of the lung. In a 12-year-old girl with arthralgia and digital clubbing, a chest radiograph disclosed a large round mass in the right upper lobe, and the following chest computed tomography scan showed a large solid homogenous, round, well marginated lesion with little contrast enhancement. A lobectomy of the right upper lobe was performed, and histological examination showed an inflammatory pseudotumour. The postoperative course was without problems: arthralgia and digital clubbing disappeared.

Arthralgia↗

PubMed1976

Antipsychotic drugs and dopamine-mediated responses in Aplysia neurons.

The effect of antipsychotic drugs was tested on responses to micro-electrophoretically applied dopamine, acetylcholine and 5-hydroxytryptamine in identified neurons of the marine gastropod Aplysia californica. Fluphenazine was able to depress the response to DA in concentration of 10 muM, with 100 muM DA-responses of many neurons were blocked completely. Thioridazine (10 and 100 muM) and haloperidol (50 muM) were also effective in depressing DA-responses, while the non-antipsychotic phenothiazines mepazine (10 and 100 muM) and promethazine (100 muM) had only a slight action on DA-receptors. ACh- and 5-HT-responses were slightly affected only by high concentrations after long lasting perfusion. The investigated drugs had no persistent or only an insignificant effect on resting membrane potential and amplitude of action potentials of the neurons. With haloperidol depolarizing afterpotentials leading to double discharges were observed in some neurons. In a few instances spontaneous EPSPs disappeared with the DA-response under the influence of anti-psychotic drugs. The results render a direct neurophysiological evidence for the blockade of DA-receptors by antipsychotic drugs in correspondence to their clinical efficacy and agree with data from clinical observations and obtained in neurochemical, behavioral and indirect neurophysiological experiments.

Acetylcholine↗