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T Meier

Publications and source records attributed to T Meier.

At least 19 recordsLinked to original sources
PubMed2006

Characterization of disorder in semiconductors via single-photon interferometry.

The method of angular photonic correlations of spontaneous emission is introduced as an experimental, purely optical scheme to characterize disorder in semiconductor nanostructures. The theoretical expression for the angular correlations is derived and numerically evaluated for a model system. The results demonstrate how the proposed experimental method yields direct information about the spatial distribution of the relevant states and thus on the disorder present in the system.

Journal Article↗
PubMed2006

Electrical impedance tomography: changes in distribution of pulmonary ventilation during laparoscopic surgery in a porcine model.

BACKGROUND: Because of the creation of a pneumoperitoneum, impairment of ventilation is a common side-effect during laparoscopic surgery. Electrical impedance tomography (EIT) is a method with the potential for becoming a tool to quantify these alterations during surgery. We have studied the change of regional ventilation during and after laparoscopic surgery with EIT and compared the diagnostic findings with computed tomography (CT) scans in a porcine study. MATERIALS AND METHODS: After approval by the local animal ethics committee, six pigs were included in the study. Two laparoscopic operations were performed [colon resection (n=3) and fundoplicatio (n=3)]. The EIT measurements (6th parasternal intercostal space) were continuously recorded by an EIT prototype (EIT Evaluation Kit, Dräger Medical, Lübeck, Germany). To verify ventilatory alterations detected by EIT, a CT scan was performed postoperatively. RESULTS: Ventilation with defined tidal volumes was significantly correlated to EIT measurements (r2=0.99). After creation of the pneumoperitoneum, lung compliance typically decreased, which agreed well with an alteration of the distribution of pulmonary ventilation measured by EIT. Elevation of positive end-inspiratory pressure reopened non-aerated lung areas and showed a recovery of the regional ventilation measured by EIT. Additionally, we could detect pulmonary complications by EIT monitoring as verified by CT scans postoperatively. CONCLUSION: EIT monitoring can be used as a continuous non-invasive intraoperative monitor of ventilation to detect regional changes of ventilation and pulmonary complications during laparoscopic surgery. These EIT findings indicate that surgeons and anesthetists may eventually be able to optimize ventilation directly in the operating theatre.

Animals↗
PubMed2005

Microscopic analysis of the coherent optical generation and the decay of charge and spin currents in semiconductor heterostructures.

The coherent optical injection and temporal decay of spin and charge currents in semiconductor heterostructures is described microscopically, including excitonic effects, many-body Coulomb correlations, and the carrier LO-phonon coupling on the second-order Born-Markov level, as well as nonperturbative light-field-induced intraband and interband excitations. A nonmonotonic dependence of the currents on the intensities of the laser beams is predicted. Enhanced damping of the spin current relative to the charge current is obtained as a consequence of Coulomb scattering.

Journal Article↗
PubMed2005

Post-dural puncture headache in young adults: comparison of two small-gauge spinal catheters with different needle design.

BACKGROUND: To reduce the risk of post-dural puncture headache (PDPH) in continuous spinal anaesthesia, small-gauge spinal catheter systems with different techniques of dural perforation have been developed. METHODS: Two systems, the catheter through-needle technique (MicroCatheter, Portex, UK) and the catheter over-needle technique (22G Spinocath, B. Braun, Germany), were used in 18 young healthy volunteers (age 18-30 yr), who were enrolled in a neuroendocrinological investigation for analysis of neuropeptides in cerebrospinal fluid (CSF). After intermittent sampling of CSF (17 x 0.5 ml over 4 h), the catheter was removed and the development of PDPH and pain intensity were documented prospectively by the subjects in a standardized headache assessment (11-point numerical rating scale [NRS]). RESULTS: The study revealed a high overall incidence of PDPH (78%) with no significant differences between groups (P=0.26). However, the over-needle group showed a significantly shorter duration of PDPH (2.4 [SD 2.3] vs 5.1 [3.1] days, P=0.050) and lower maximum pain intensity (3.1 [2.9] vs 7.3 [3.4] NRS, P=0.014) than the through-needle group. CONCLUSIONS: The results demonstrate a potential benefit of the catheter over-needle technique for the reduction of the duration and intensity of PDPH.

Adolescent↗
PubMed2005

[Unclear intraoperative cardiorespiratory decompensation. Anaphylactic reaction?].

During anaesthesia a patient is exposed to a variety of substances, all of which could lead to anaphylactic reactions. In addition, other drugs may exert clinical side-effects by non-immunological mechanisms, e.g. by direct stimulation of the release of histamine by mast cells. Initially, the observed symptoms, such as hypotension or tachycardia, may be misunderstood by the anaesthetist, leading to a possible delay in diagnosis and subsequent treatment of the anaphylactic event. Cardiac ischemia and lung embolisms are important differential diagnoses that often cannot be definitely ruled out during the acute situation and that have to be followed up once the patient has been stabilised. We report a case of anaphylactic reaction after the administration of ampicillin which required treatment and ventilation in the intensive care unit. Despite an accurate determination of serum tryptase levels, the diagnosis of an anaphylactic reaction to ampicillin was eventually confirmed by skin testing. During anaesthesia, anaesthetists should consider anaphylaxis when unforeseen symptoms such as bronchospasm, haemodynamical instability and/or flush arise. In cases of unexpected reactions, patients should undergo allergological follow-up to prevent fatal re-exposure.

Aged↗
PubMed2005

[Risk factors for back pain in children and adolescents].

Factors that have led to the increasing prevalence of back pain amongst children and adolescents living in industrialized nations are mostly unknown. The following literature review was aimed at determining the risk factors for back pain amongst children and adolescents. We searched both PUBMED and MEDLINE between the years 1985 and 2003 for the keywords "children or adolescents" and "back pain". Only data published in original articles were used. The risk for suffering back pain is influenced by physical, behavioural, emotional and social factors. The effects of physical activity, sitting, muscle status, weight of schoolbags, exercise, television and computer use, as well as age and gender on the development of back pain in children and adolescents were examined. Associations between continuous or recurring back pain and psychosocial factors (lifestyle, emotional factors, social relationships) could be demonstrated. There was no relationship between changes of the spine seen by radiological tests and the development of chronic back pain. Longitudinal epidemiological studies are urgently needed to delineate the risk factors for the development as well as the natural history of chronic back pain in the young.

Adolescent↗
PubMed2005

Sensitivity of a new commercial enzyme-linked immunospot assay (T SPOT-TB) for diagnosis of tuberculosis in clinical practice.

Diagnosis of active and latent tuberculosis (TB) remains a challenge; however, over the last few years, a new approach based on detecting Mycobacterium tuberculosis-specific T cells has shown much promise. In particular, there is substantial published evidence showing that the detection of ESAT-6- and CFP-10-specific T cells using the ex vivo enzyme-linked immunospot technique is a marked improvement over the existing tuberculin skin test. This technique, which detects gamma interferon-producing T cells, is now available as the commercial assay T SPOT-TB (Oxford Immunotec, Oxford, UK). In the present study, the usefulness of the T SPOT-TB test for diagnosis of TB in "real-world" clinical practice was investigated. Ninety patients of a southern German referral centre for TB with confirmed or suspected TB were randomly selected for this study. The results of the T SPOT-TB test were compared with the results of conventional diagnostic tools. The T SPOT-TB test detected 70 of 72 patients with pulmonary or extrapulmonary TB, indicating a sensitivity of 97.2% (95% confidence interval, 90.3-99.7). For 45 of these patients, tuberculin skin test (TST) results were also available. Only 40 (89%) of these 45 patients were positive in the TST compared to all 45 (100%) in the T SPOT-TB test (p=0.056). Among 12 of 90 patients for whom active TB disease was ruled out, the T SPOT-TB test was negative for 11 (92%), allowing the rapid exclusion of TB in patients suspected to have active TB disease. The T SPOT-TB test is a sensitive assay for detection of TB and represents a useful addition to the diagnostic algorithm available for detecting TB in low-incidence settings.

Adult↗
PubMed2004

Five-wave-mixing spectroscopy of ultrafast electron dynamics at a si(001) surface.

The optically induced electron dynamics at a Si(001) surface is studied using a five-wave-mixing setup which measures the diffracted second-harmonic intensity induced by three ultrashort (13 fs) laser pulses. Depending on the time ordering of the pulses, this technique is capable of monitoring the temporal evolution of photoexcited one- or two-photon coherences, or populations. For a particular pulse sequence, the experiments show a delayed rise and a decay of the diffracted signal intensity on time scales of 50 and 250 fs, respectively. This response can be described by optical Bloch equations by including rapid scattering of the photoexcited carriers in the D(down) band of Si(001).

Journal Article↗
PubMed2004

[Reduction of chronic pain for non-postherpetic peripheral neuropathies after topical treatment with a lidocaine patch].

INTRODUCTION: To clarify whether the therapeutic indication for a lidocaine patch to treat postherpetic neuralgia can be extended to include other focal peripheral neuropathic pain syndromes, we performed a subgroup analysis of a placebo-controlled, double-blind randomized study. METHODS: The study included 16 patients with focal peripheral painful neuropathies of non-herpetic origin, pain intensity > or =40 mm (VAS), and a stable pain medication. The patients received either the lidocaine patch 5% for 1 week or a placebo patch for 12 h daily according to a crossover design. Persistent pain, mechanical allodynia, and adverse events were assessed daily by the patients. Additionally, the pain perception test, the list of physical complaints, the depression test, and the health-related quality of life (SF-36) were used. Of the enrolled patients, 12 were statistically analyzed. RESULTS: Persistent pain was reduced by the lidocaine patch almost significantly and allodynia was reduced significantly in comparison to the placebo patch. Scores for physical complaints improved significantly with the lidocaine patch. Only mild focal skin irritations occurred. CONCLUSIONS: As an adjuvant medication, the lidocaine patch is effective and safe for reducing chronic pain and physical complaints in focal non-herpetic neuropathies.

Administration, Topical↗
PubMed2001

The central plug in the reconstituted undecameric c cylinder of a bacterial ATP synthase consists of phospholipids.

The isolated rotor cylinder of the ATP synthase from Ilyobacter tartaricus was reconstituted into two-dimensional crystalline arrays. Atomic force microscopy imaging indicated a central cavity on one side of the rotor and a central plug protruding from the other side. Upon incubation with phospholipase C, the plug disappeared, but the appearance of the surrounding c subunit oligomer was not affected. This indicates that the plug consists of phospholipids. As the detergent-purified c cylinder is completely devoid of phospholipids, these are incorporated into the central hole from one side of the cylinder during the reconstitution procedure.

Fusobacterium↗
PubMed2001

ATP synthase: constrained stoichiometry of the transmembrane rotor.

Recent structural data suggest that the number of identical subunits (c or III) assembled into the cation-powered rotor of F1F0 ATP synthase depends on the biological origin. Atomic force microscopy allowed individual subunits of the cylindrical transmembrane rotors from spinach chloroplast and from Ilyobacter tartaricus ATP synthase to be directly visualized in their native-like environment. Occasionally, individual rotors exhibit structural gaps of the size of one or more subunits. Complete rotors and arch-shaped fragments of incomplete rotors revealed the same diameter within one ATP synthase species. These results suggest the rotor diameter and stoichiometry to be determined by the shape of the subunits and their nearest neighbor interactions.

ATP Synthetase Complexes↗
PubMed2001

[Interscalene plexus block. Anatomic requirements--anesthesiologic and operative aspects].

The interscalene brachial plexus block with and without a catheter has become an indispensable method for anaesthesia and analgesia in shoulder surgery. Not only thorough knowledge of anatomy, but also accurate indication assessment and discussion with the surgeon regarding the location of access, is essential for the successful practice of this technique. Important and practical tips for implementation should especially help the less experienced, with special emphasis on correct positioning of the patient for surgery to avoid iatrogenic neural damage. Preoperative counselling of inevitable side-effects of the technique enhances the patient's acceptance and satisfaction.

Brachial Plexus↗
PubMed2001

[Comparison of severity of chronic pain in patients differing in pain diagnosis: an analysis by means of the Mainz Pain Staging System].

INTRODUCTION: Testing the validity of the Mainz Pain Staging System (MPSS) is often carried out by pain classification according to chronic stage. It is assumed that pain syndromes distribute equally over the chronic stages. This analysis was carried out to answer three questions: Do different pain syndromes vary in chronicity, do the four axes of the MPSS differ between pain syndromes, and are there any specific item responses with respect to a pain syndrome? METHODS: 406 patients with different pain diagnoses were included in this analysis. Patients were chosen from the PAIN-Documentation-System of the pain outpatients' department of the Medical University of Luebeck. The pain score according to MPSS had been assessed, and a diagnosis attributed according to the Multidimensional Classification of Pain (MASK). RESULTS: Pain diagnoses do differ in pain chronification. Patients with headache showing the lowest chronification, and patients with back pain describing the most severe chronification, formed the extreme patient groups. Further analysis using the axes of the MPSS demonstrate different sensitivity with respect to pain syndromes, i. e. intake of drugs being the least sensitive and aspects of time being the most sensitive axes. Statistical analysis using configural frequency analysis indicated a relation between pain syndromes and specific item responses. CONCLUSION: Using pain stages of the MPSS as an experimental factor in studies of pain, it is imperative either to control pain syndromes or to confine to a single pain syndrome, to avoid confusion between pain syndromes and severity of pain chronification.

Chronic Disease↗
PubMed2001

Evidence for a diagnostic window in fourth generation assays for HIV.

BACKGROUND: The routine HIV screening essentially depends on the detection of HIV specific antibodies. However, HIV p24 antigen can be detected in individuals with recent HIV infection about 2-18 days prior to seroconversion. New fourth generation HIV screening assays combine the detection of anti-HIV antibodies with the simultaneous detection of HIV p24 antigen. This may result in a reduction of the diagnostic window after primary infection. OBJECTIVES: The performance of two novel fourth generation assays in routine diagnostic was evaluated. STUDY DESIGN: We compared two third generation, two fourth generation and one antigen HIV assays in a case with acute primary HIV infection. RESULTS: In our case, the HIV infection was detected 11 days earlier with the fourth generation assays compared to third generation assays. Interestingly, after the initial reactive results the fourth generation assays became negative resulting in a second diagnostic window. During this second diagnostic window neither third nor fourth generation HIV assays were reactive. This second diagnostic window was caused by the absence of HIV specific antibodies and the decline of HIV p24 antigen concentrations below the detection limits of the fourth generation assays. CONCLUSIONS: Fourth generation assays markedly improve the diagnosis of recent HIV infections but the possibility of a second diagnostic window must be considered.

Acute Disease↗
PubMed2001

Multiplicity in the high-frequency signals during the short-latency somatosensory evoked cortical activity in humans.

OBJECTIVE: Recent studies using electroencephalography or magnetoencephalography have shown that peripheral nerve stimulations produce short-latency high-frequency signals in the human somatosensory cortex. The present study tested whether they consist of more than one distinct type of signal. METHODS: Somatic evoked magnetic fields (SEFs) elicited by electrical stimulation of the median nerve were measured in 12 healthy volunteers. They were analyzed using a time-frequency analysis method based on Gabor filters and another based on autoregressive moving average, and also with bispectrum and bicoherence techniques and a new dispersion curve method. RESULTS: Signals in two separate high-frequency bands (200 and 600 Hz) were distinguished from the main signal in the low frequency (LF) range during the time period of N20m and P25m. The novel 200 Hz-band signal was seen reliably in those channels where the LF band signal was weak, so that the former was not masked by the latter. The 600 Hz signal consisted of two distinct components or parts (p1 and p2) in 10 out of 12 subjects, one peaking during ascending slope and the second during the descending slope of the N20m. The latency of the p1 was shorter than the latencies of the 200 Hz and LF signals according to the dispersion curve analysis. The inter-peak interval of p1 became shorter for later peaks in all 12 subjects. Bicoherence analysis revealed a significant phase coupling between the 200 and 600 Hz bands. CONCLUSIONS: There are three distinct types of signal during the time period of the short-latency cortical components of the SEF -- LF which gives rise to the commonly seen waveform of the SEF, the newly found 200 Hz signal and the 600 Hz signal which consists of two components. The possible origins of the high frequency signals are discussed in light of the new set of evidence found in the present study.

Adult↗
PubMed2001

Bacterial Na(+)-ATP synthase has an undecameric rotor.

Synthesis of adenosine triphosphate (ATP) by the F(1)F(0) ATP synthase involves a membrane-embedded rotary engine, the F(0) domain, which drives the extra-membranous catalytic F(1) domain. The F(0) domain consists of subunits a(1)b(2) and a cylindrical rotor assembled from 9-14 alpha-helical hairpin-shaped c-subunits. According to structural analyses, rotors contain 10 c-subunits in yeast and 14 in chloroplast ATP synthases. We determined the rotor stoichiometry of Ilyobacter tartaricus ATP synthase by atomic force microscopy and cryo-electron microscopy, and show the cylindrical sodium-driven rotor to comprise 11 c-subunits.

Bacteria, Anaerobic↗