CEP-stable tunable THz-emission originating from laser-waveform-controlled sub-cycle plasma-electron bursts.

We study THz-emission from a plasma driven by an incommensurate-frequency two-colour laser field. A semi-classical transient electron current model is derived from a fully quantum-mechanical description of the emission process in terms of sub-cycle field-ionization followed by continuum-continuum electron transitions. For the experiment, a CEP-locked laser and a near-degenerate optical parametric amplifier are used to produce two-colour pulses that consist of the fundamental and its near-half frequency. By choosing two incommensurate frequencies, the frequency of the CEP-stable THz-emission can be continuously tuned into the mid-IR range. This measured frequency dependence of the THz-emission is found to be consistent with the semi-classical transient electron current model, similar to the Brunel mechanism of harmonic generation.

Resonant metamaterial detectors based on THz quantum-cascade structures.

We present the design, fabrication and characterisation of an intersubband detector employing a resonant metamaterial coupling structure. The semiconductor heterostructure relies on a conventional THz quantum-cascade laser design and is operated at zero bias for the detector operation. The same active region can be used to generate or detect light depending on the bias conditions and the vertical confinement. The metamaterial is processed directly into the top metal contact and is used to couple normal incidence radiation resonantly to the intersubband transitions. The device is capable of detecting light below and above the reststrahlenband of gallium-arsenide corresponding to the mid-infrared and THz spectral region.

THz-driven nonlinear intersubband dynamics in quantum wells.

In this work, we demonstrate the direct observation of non-equilibrium intersubband dynamics in a modulation-doped multiple quantum well sample induced by intense terahertz pulses. The transmission spectra show a clear dependence on the incident THz field strength, which gives rise to a multitude of nonlinear optical effects that go beyond the standard textbook two-level description of light-matter interaction. Of special interest is thereby the multiple octave spanning bandwidth of the used single-cycle THz pulses, which allows the phase-locked coupling of adjacent intersubband transitions. Examples of this interaction include the efficient, coherent population transfer, the THz induced undressing of collective excitations, and the THz Stark effect.

Terahertz meta-atoms coupled to a quantum well intersubband transition.

We present a method of coupling free-space terahertz radiation to intersubband transitions in semiconductor quantum wells using an array of meta-atoms. Owing to the resonant nature of the interaction between metamaterial and incident light and the field enhancement in the vicinity of the metal structure, the coupling efficiency of this method is very high and the energy conversion ratio from in-plane to z field reaches values on the order of 50%. To identify the role of different aspects of this coupling, we have used a custom-made finite-difference time-domain code. The simulation results are supplemented by transmission measurements on modulation-doped GaAs/AlGaAs parabolic quantum wells which demonstrate efficient strong light-matter coupling between meta-atoms and intersubband transitions for normal incident electromagnetic waves.

Strong dissipation inhibits losses and induces correlations in cold molecular gases.

Atomic quantum gases in the strong-correlation regime offer unique possibilities to explore a variety of many-body quantum phenomena. Reaching this regime has usually required both strong elastic and weak inelastic interactions because the latter produce losses. We show that strong inelastic collisions can actually inhibit particle losses and drive a system into a strongly correlated regime. Studying the dynamics of ultracold molecules in an optical lattice confined to one dimension, we show that the particle loss rate is reduced by a factor of 10. Adding a lattice along the one dimension increases the reduction to a factor of 2000. Our results open the possibility to observe exotic quantum many-body phenomena with systems that suffer from strong inelastic collisions.

Atom-molecule Rabi oscillations in a Mott insulator.

We observe large-amplitude Rabi oscillations between an atomic and a molecular state near a Feshbach resonance. The experiment uses 87Rb in an optical lattice and a Feshbach resonance near 414 G. The frequency and amplitude of the oscillations depend on the magnetic field in a way that is well described by a two-level model. The observed density dependence of the oscillation frequency agrees with theoretical expectations. We confirmed that the state produced after a half-cycle contains exactly one molecule at each lattice site. In addition, we show that, for energies in a gap of the lattice band structure, the molecules cannot dissociate.

Inhibitor kappaB kinase is involved in the paracrine crosstalk between human fat and muscle cells.

OBJECTIVE: Adipose tissue is now considered as an endocrine and secretory organ, and some adipocyte factors are thought to play a major role in the induction of insulin resistance in skeletal muscle. Here we tested the hypothesis that the crosstalk between fat and muscle involves activation of inhibitor kappaB Kinase (IKK) in the myocytes. MEASUREMENTS: Adipocyte-conditioned culture medium was added to the muscle cells overnight, or human fat and muscle cells were kept in co-culture. Insulin signalling was subsequently analysed in the myocytes. Involvement of IKK was assessed using I229, a highly specific inhibitor of the IKK complex. RESULTS: Adipocyte-conditioned medium strongly inhibited insulin-induced serine phosphorylation of Akt in myocytes with a rapid parallel activation of the nuclear factor kappaB pathway in these cells. Conditioned medium lacking the perturbation of insulin signalling did not activate NF-kappaB. Insulin signalling to Akt was completely abrogated under co-culture conditions. The IKK inhibitor I229 did not affect protein expression of Akt, but fully restored insulin action in myocytes subjected to co-culture. CONCLUSION: These data show that the release of fat cell factors may rapidly induce insulin resistance in human skeletal muscle cells. This process appears to be mediated by an IKK/NF-kappaB dependent pathway. We suggest that inhibitors of IKK would be of use to counteract the negative crosstalk between fat and muscle.

Primary reconstruction for spinal infections.

Primary reconstruction using bone grafts and instrumentation for spinal infections remains controversial. Between 1991 and 1993, 27 infections of the spinal column were treated at the Department of Neurosurgery of the University of Florida. Of the 27 cases 20 (six cervical, eight thoracic, and six lumbar spine) required surgical debridement and spinal reconstruction to maximize eradication of the infection and maintenance of spinal alignment. All of the cervical and lumbar cases were caused by bacterial infections, and two of eight thoracic cases were caused by tuberculous infections. Spinal arthrodesis was performed in all cases: interbody grafts were used in 18 procedures and posterolateral onlay grafts in 14. Interbody grafts were autologous in 10 cases (six rib and four iliac crest) and allograft in eight (six fibular and two humerus). All of the posterolateral onlay grafts were autologous (three rib and 11 iliac crest). Spinal instrumentation was used in 15 cases: four with Caspar plates and 11 with posterior segmental fixation (five hook/rod constructs and six screw/rod constructs). Seventeen of 20 patients achieved improved clinical status postoperatively and 18 of 20 showed radiographic evidence of bone fusion. Antibiotic drugs were administered parenterally for an average of 6 weeks followed by a 3-month course of oral antibiotic medications. Tuberculous infections were treated for 1 year with antibiotic therapy. The average follow-up period was 37 months from surgery and 31 months after completion of treatment with antibiotic drugs. The authors conclude that primary arthrodesis and instrumentation can be performed in acute spinal infections; however, successful management depends on aggressive debridement of infectious foci and prolonged treatment with parenteral antibiotic drugs.

Posterolateral approach to intradural extramedullary thoracic tumors.

Six ventrally located intradural thoracic tumors were successfully resected through the posterolateral approach. This approach allows direct visualization of the ventral and dorsal boundaries of the tumor with minimal manipulation of the spinal cord. Compared to the traditional laminectomy, the operative time is increased but visualization of the tumor and spinal cord is markedly improved. Compared to the transthoracic approach, the posterolateral approach has fewer potential complications and eliminates the necessity of vertebrectomy. Neurological improvement occurred in all six patients. It is believed that this approach offers significant advantages for the treatment of ventrally located intradural thoracic tumors, and should be considered an alternative to the transthoracic approach.

Thoracic disc herniations.

Because of the protean nature of thoracic disc disease, surgeons should maintain a high order of suspicion of a thoracic disc herniation in the patient with unexplained localized back or torso pain and sensorimotor deficits. These patients should have MR imaging performed as a screening test, and, if suspicious for a thoracic disc herniation, confirmatory myelogram and postmyelogram CT imaging. Though the natural history is anecdotal, there appears to be a tendency for myelopathic symptoms and signs to be progressive, warranting surgical intervention. For radicular dysfunction or localized back pain, a conservative therapeutic plan is recommended. If intractable pain is demonstrated, and the diagnosis is certain, then surgical intervention is recommended. Once surgical intervention is recommended the surgical approach needs to be individualized according to the surgeon's skills and experience and the specifics of the patient's pathology. Appropriate surgical decision-making depends on an understanding of the variety of surgical options and their advantages and disadvantages, and an understanding of the biomechanical factors of the spine of the individual patient. Surgical concepts important to successful thoracic disc removal are (1) minimal spinal cord manipulation, (2) preservation of the neurovascular supply whenever possible, (3) minimal manipulation of the intercostal nerve, and (4) preservation of maximal bony and ligamentous attachments allowable for adequate exposure. Lastly it is recommended that the posterior longitudinal ligament be removed to ensure complete spinal cord decompression.

Lateral parascapular extrapleural approach to the upper thoracic spine.

The upper thoracic vertebrae are difficult to approach surgically because of the narrowing of the thoracic inlet, the proximity of the brachial plexus, and the parascapular shoulder musculature. A novel lateral parascapular extrapleural approach to the upper thoracic vertebrae is described. The parascapular shoulder musculature (trapezius, levator scapulae, and rhomboid muscles) is reflected off the spinous processes to the scapula as a musculocutaneous flap, preserving the neurovascular supply. The paraspinal musculature is mobilized and retracted, and the upper dorsal ribs are removed with caution to avoid injury to the C-8 and T-1 nerve roots. The rami communicantes are transected, and the sympathetic chain is displaced anterolaterally. The T2-4 vertebrae can be approached unobstructed. The T-1 nerve root obstructs posterolateral access to the T-1 vertebra, necessitating an inferolateral approach underneath the T-1 nerve root axilla. Four patients with compressive myelopathy from upper thoracic vertebral metastases underwent neural decompression, vertebral reconstruction, and posterior spinal fixation with this approach. Their postoperative neurological status was either unchanged or improved. Complications included radiographic pleural effusion and superficial wound dehiscence; one patient required posterior spinal reinstrumentation for progressive kyphosis. One patient developed pneumonia 7 days postoperatively which was unresponsive to appropriate treatment. It is believed that the anatomical limitations to this region have been overcome, and that excellent exposure of the T1-4 vertebrae for neural decompression and vertebral reconstruction can be performed safely. A major advantage is that posterior spinal fixation can be carried out simultaneously.

Cerebellar mutism after posterior fossa surgery.

A large midline posterior fossa medulluloblastoma and a cerebellar arteriovenous malformation with associated clot were moved with postoperative mutism. Mutism was immediate and resolved into an ataxic dysarthria with residual mild dysarthria at 3 months. The literature is reviewed, and the clinicopathological and neurophysiological data of cerebellar function in speech are discussed. Acute injury to the midportion of the cerebellum with or without dentate nuclear involvement can cause a spectrum of speech disturbances. The more widespread the injury to the midportion of the cerebellum with dentate nuclei involvement the greater the risk of developing postoperative mutism.

[Clinical interpretation of retinal circulatory measurements. II. Blood flow]. / Klinische Interpretation retinaler Durchblutungsmessungen. II. Blutfluss.

Beginning as early as the mid-4th decade of life, an age-dependent reduction in retinal blood flow has to be considered an essential risk factor for disorders of retinal microcirculation. Blood flow measurements are a valuable, but not the sole criterion of microcirculatory disorders. While in retinal occlusive diseases blood flow is a valuable indicator of the severity of microcirculatory disorders, the latter can also occur in the presence of normal and elevated blood flow values. Shifts of the metabolic activity of the retina and changes in the metabolic activity of the retina and changes in the metabolic conditions have to be taken into account when a clinical interpretation is given.

Reviewing results of psychological tests in a patient group.

Believing that much helpful information from psychological test results was not being transmitted to patients, psychologists on a teaching ward at a Veterans Administration hospital began holding group sessions to explain the results of psychological tests to patients. Attendance was voluntary, but 96 per cent of the patients who were tested in a one-year period attended, an average of four or five each session. The psychologist described routine tests and how the results were used and then presented individual test results, giving practical illustrations of the findings and emphasizing patients' strengths and coping styles. Scores from questionnaires administered to patients after they completed the tests and at the end of the group session showed that their attitudes toward tests became more positive after the group session, and that they felt that hearing their own and others' test results had been helpful.