Topologically protected bound states in photonic parity-time-symmetric crystals.

Parity-time (PT)-symmetric crystals are a class of non-Hermitian systems that allow, for example, the existence of modes with real propagation constants, for self-orthogonality of propagating modes, and for uni-directional invisibility at defects. Photonic PT-symmetric systems that also support topological states could be useful for shaping and routing light waves. However, it is currently debated whether topological interface states can exist at all in PT-symmetric systems. Here, we show theoretically and demonstrate experimentally the existence of such states: states that are localized at the interface between two topologically distinct PT-symmetric photonic lattices. We find analytical closed form solutions of topological PT-symmetric interface states, and observe them through fluorescence microscopy in a passive PT-symmetric dimerized photonic lattice. Our results are relevant towards approaches to localize light on the interface between non-Hermitian crystals.

Radiation-loss management in modulated waveguides.

In this work, we discuss the management of radiation loss in photonic waveguides. As an experimental basis, we introduce a new technique of fabricating waveguides with tunable loss, which is particularly useful when implementing non-Hermitian (PT-symmetric) systems. To this end, we employ laser-written waveguides with a transverse sinusoidal modulation, which causes well-controllable radiation losses of almost arbitrary amount. Numerical simulations support our experimental findings. Our study shows that the radiation loss not only depends on the local waveguide curvature but also is influenced by interference effects. As a consequence, the loss is a nonmonotonous function of the bending parameters, such as period length.

Impact of loss on the wave dynamics in photonic waveguide lattices.

We analyze the impact of loss in lattices of coupled optical waveguides and find that, in such a case, the hopping between adjacent waveguides is necessarily complex. This results not only in a transition of the light spreading from ballistic to diffusive, but also in a new kind of diffraction that is caused by loss dispersion. We prove our theoretical results with experimental observations.

Photonic coherent state transfer with Hamiltonian dynamics.

We report the observation of near-perfect light wave transfer by emulating quantum state transfer on a lattice with Hamiltonian dynamics, i.e., time-dependent intersite couplings. The structure transferring a single waveguide excitation over 11 sites with a fidelity of 0.93 works for classical light as well as single photons. As our implementation of perfect quantum state transfer uses a photonic setting, we introduce polarization as a new degree of freedom to the transport protocol. We demonstrate rotation operations of up to 40° on polarization during state transfer.

Mobility transition from ballistic to diffusive transport in non-Hermitian lattices.

Within all physical disciplines, it is accepted that wave transport is predetermined by the existence of disorder. In this vein, it is known that ballistic transport is possible only when a structure is ordered, and that disorder is crucial for diffusion or (Anderson-)localization to occur. As this commonly accepted picture is based on the very foundations of quantum mechanics where Hermiticity of the Hamiltonian is naturally assumed, the question arises whether these concepts of transport hold true within the more general context of non-Hermitian systems. Here we demonstrate theoretically and experimentally that in ordered time-independent -symmetric systems, which are symmetric under space-time reflection, wave transport can undergo a sudden change from ballistic to diffusive after a specific point in time. This transition as well as the diffusive transport in general is impossible in Hermitian systems in the absence of disorder. In contrast, we find that this transition depends only on the degree of dissipation.

GABAergic and glycinergic inhibition modulate monaural auditory response properties in the avian superior olivary nucleus.

The superior olivary nucleus (SON) is the primary source of inhibition in the avian auditory brainstem. While much is known about the role of inhibition at the SON's target nuclei, little is known about how the SON itself processes auditory information or how inhibition modulates these properties. Additionally, the synaptic physiology of inhibitory inputs within the SON has not been described. We investigated these questions using in vivo and in vitro electrophysiological techniques in combination with immunohistochemistry in the chicken, an organism for which the auditory brainstem has otherwise been well characterized. We provide a thorough characterization of monaural response properties in the SON and the influence of inhibitory input in shaping these features. We found that the SON contains a heterogeneous mixture of response patterns to acoustic stimulation and that in most neurons these responses are modulated by both GABAergic and glycinergic inhibitory inputs. Interestingly, many SON neurons tuned to low frequencies have robust phase-locking capability and the precision of this phase locking is enhanced by inhibitory inputs. On the synaptic level, we found that evoked and spontaneous inhibitory postsynaptic currents (IPSCs) within the SON are also mediated by both GABAergic and glycinergic inhibition in all neurons tested. Analysis of spontaneous IPSCs suggests that most SON cells receive a mixture of both purely GABAergic terminals, as well as terminals from which GABA and glycine are coreleased. Evidence for glycinergic signaling within the SON is a novel result that has important implications for understanding inhibitory function in the auditory brainstem.

Analysing the robustness of cellular rhythms.

Autonomous oscillations at the cellular level are important for various timing and signalling functions. The rhythms depend on environmental influences in a specific manner. In particular, the period of some rhythms has been shown to be very robust to certain environmental factors whereas other rhythms show a high sensitivity towards these factors. It is discussed that the robustness of the systems towards environmental changes results from underlying design principles. However, a comparison of robustness properties of different rhythms is lacking. Here we analyse the sensitivity of the oscillatory period with respect to parameter variations in models describing oscillations in calcium signalling, glycolysis and the circadian system. By comparing models for the same and different rhythms it is shown that the sensitivity depends on the oscillatory mechanism rather than the details of the model description. In particular, we find models of calcium oscillations to be very sensitive, those for glycolytic oscillations intermediately sensitive and models for circadian rhythms very robust. The results are discussed with respect to the temperature dependency of the rhythms. The question of what impact design principles have on the robustness of an oscillator, is addressed more explicitly by a direct comparison of systems with positive and negative feedback regulation for various reaction chain lengths. We find that the systems with negative feedback are more robust than corresponding systems with positive feedback. An increase in the length of the reaction chain under regulation leads to a decrease in sensitivity.

[Correlation between ear canal resonance and tympanic membrane impedance in relation to age and body mass and postmortem changes]. / Untersuchung über Korrelation von Gehörgangsresonanz und Trommelfellimpedanz bezüglich Alter und Körpermassen sowie Veränderungen nach Todeseintritt.

The human temporal bone preparation is an acknowledged model for research of the physical processes affecting the outer ear canal and eardrum. Changes affecting the oscillation and resonance behavior of the tympanic membrane and ear canal between death and temporal bone preparation presently exist in only a few studies. Since the influence of age and physique, as well as the width of ear canal on the ear canal resonance may be important, we prepared two separate studies to analyze these questions. The goal of our first test series involved children and was devised to determine if changes in the outer auditory canal resonances differed according to age. In so doing, canal resonance was recorded with a real ear measurement system. Further, we recorded middle ear pressure, impedance of the tympanic membrane, ear canal volume, height, weight and surface of the body, head and ear size. We found a significant decrease in the resonance frequency of the outer ear which was age-dependent and was 2.75 kHz in the 7-year-old child. In a separate study we wanted to know if results found in the postmortem temporal bone reflected in vivo relationships. A tympanometer and real ear measurement system was used to test the resonance behavior of the auditory canal as well as the vibration of the eardrum in dependence on temperature and the time after death for 9 h. We then proved the absence of significant changes in the auditory canal and eardrum oscillation in this time period before possible postmortem changes occurred. Our findings show that the method of bone preservation after its preparation is decisive for the validity of measurements in the isolated human temporal bone.

[Intraoperative calorimetry in aortic bifurcation reconstruction]. / Intraoperative Kalorimetrie bei Aortengabelrekonstruktion.

Oxygen uptake (VO2) and carbon dioxide elimination (VCO2) can be measured with an indirect calorimeter, this method is well established in routine monitoring of ICU patients to evaluate metabolic state as a reflection of stress. In various experimental studies it was demonstrated that anaesthetics can influence whole-body metabolism. The purpose of this study was to examine whether indirect calorimetry can be used intraoperatively during routine anaesthesia and whether presumable changes in metabolism can be detected immediately. Abdominal aortic cross-clamping changes circulation, nutritional supply of the lower extremities and thus VO2 and VCO2. We therefore used this operation for our study. METHOD. Eleven patients, mean age 64 years, undergoing reconstruction of the aortic bifurcation, were studied. After premedication with piritramid and atropine, total intravenous anaesthesia (TIVA) was performed with fentanyl and midazolam after an induction with thiopental. Patients were ventilated with a Servo-Ventilator 900 D and a constant FiO2 of 0.5, without N2O. Routine monitoring consisted of ECG, pulsoximetry, CVP and continuous AP. VO2 and VCO2 were measured with a Deltatrac (Datex), and data were registered every minute. For statistical evaluation we used a Wilcoxon-Ranksum test for matched pairs, p < 0.05 was considered significant. Data from specific time (5 min after intubation, 5 min before clamping; 5, 10 and 15 min after clamping, before declamping and 5 and 10 min after declamping and at the end of surgery) were calculated. In addition to absolute values, we compared the measured VO2 and VCO2 to baseline (5 min before clamping = MP2). RESULTS. Mean operating time was 139 min +/- 37; aortic cross-clamping time for the first extremity was 38 min and 55 min for the second. As expected, there was a significant decrease in VO2 (90% of baseline) and VCO2 (75% of baseline) during aortic cross-clamping. After declamping VO2 again rose to 110% of baseline, or to 103% for the second limb. VCO2 increased to only 90% and 82%, respectively. At the end of surgery VO2 reached baseline, whereas VCO2 remains at 83%. The respiratory quotient VCO2: VO2 was markedly reduced from 0.95 +/- 0.156 to 0.73 +/- 0.06 during surgery. The Deltatrac showed every change in VO2 without delay; changes in VCO2 seem to occur somewhat retarded. DISCUSSION. Aortic cross-clamping leads to a marked decrease in VO2 and VCO2 reflecting the temporary reduction in whole-body metabolism. Declamping results in a compensatory rise, especially in VO2. VCO2 seems to increase less after declamping, perhaps due to the CO2 pool of the organism or to a change in metabolism from carbohydrate to mainly fat oxidation. The results of this study demonstrate that indirect calorimetry can easily be performed during anaesthesia and surgery. Preconditions are a non-rebreathing system without airleak, constant FiO2 < 0.6 and no use of nitrous oxide.

Renal cell carcinoma extending into the vena cava: surgical approach, technique and results.

OBJECTIVE: To describe the technique and results of a thoraco-abdominal approach to removing the caval thombi in patients with renal cell carcinoma extending into the vena cava. PATIENTS AND METHODS: Between 1970 and 1990 35 patients presenting with renal cell carcinoma extending into the vena cava were treated at the Department of Urology, Innsbruck. Twenty-three of these patients underwent radical tumour nephrectomy including cavotomy and thrombectomy or caval resection. A transabdominal approach had been used in this department for radical tumour nephrectomy including cavotomy and thrombectomy or caval resection until 1987. Since 1988, a thoraco-abdominal approach has been employed. In group I patients the approach was via the seventh intercostal space, whereas in group II and III patients the thoraco-abdominal incision was made through the fifth intercostal space. In the present study the anatomy of the thoraco-abdominal approach is described. RESULTS: Tumour staging and grading yielded stage T3b in 15 patients (grade I, 1; grade II, 6; grade III, 8); another eight patients with stage T3b were found to have metastatic disease (N1, 6; N2, 2; M1, 3). On the basis of the extension of the caval thrombus the patients were classified as follows: group I, 16; group II, 3; group III, 4. In T3b N0 M0 patients the 5-year-survival rate was 62.5%, while in patients with positive lymph nodes the mean survival rate was 15.5 months. CONCLUSION: Our results suggest that the thoracoa-abdominal approach is the method of choice for the safe removal of renal cell carcinomas associated with caval thombi. If resection of the caval tumour is complete, prognosis is dependent on known factors, such as tumour invasion, nodal involvement and distant metastases rather than the extension of the tumour thrombus. An aggressive approach is not warranted in patients with nodal involvement and/or distant metastases, as it does not improve survival.

Staining of endothelial cells and macrophages in atherosclerotic lesions with human heat-shock protein-reactive antisera.

Our previous epidemiological studies have shown that levels of serum antibodies against mycobacterial heat-shock protein (hsp) 65 correlate positively with carotid atherosclerosis in subjects aged 40 to 79 years. To determine whether these high-titer sera also react with homologous human hsp60 and/or cell components of atherosclerotic lesions, we selected 15 human sera samples, each with high or low titers to recombinant mycobacterial hsp65, and investigated their reactivity with human arterial lesion components by immunoblotting and immunofluorescence techniques. All five higher-titer sera against hsp65 reacted with a 60-kDa band of atherosclerotic lesion proteins and human recombinant hsp60 on Western blots. Pooled sera with low antibody titers to hsp65 diluted similarly as high-titer sera did not show reactivity with atherosclerotic lesion and media proteins. By immunohistochemistry and immunofluorescence with human immunoglobulin G isolated from different sera, labeled with biotin, and visualized with a streptavidin conjugate, positive staining was observed in sections of fatty streaks and atherosclerotic plaques of carotid arteries, and weak staining was observed in the normal intima. Double immunofluorescence identified the majority of positively stained cells as macrophages, endothelial cells, and a few smooth muscle cells. In summary, serum antibodies against hsp65 cross-react with the human 60-kDa homologue present in high levels in atherosclerotic lesions and are mainly reacting with macrophages and endothelial cells, supporting our concept of a possible involvement of humoral-mediated immune reaction against hsp60 in atherogenesis.

Immunology of atherosclerosis. Demonstration of heat shock protein 60 expression and T lymphocytes bearing alpha/beta or gamma/delta receptor in human atherosclerotic lesions.

Our previous work revealed the presence of a great number of activated T lymphocytes in early human atherosclerotic lesions, and we were able to induce atherosclerosis in normocholesterolemic rabbits by immunization with Mycobacterium tuberculosis heat-shock protein (HSP) 65. We hypothesized this latter phenomenon to arise from cross-reactivity of mycobacterial HSP 65 with the endogenously expressed homologous 60-kd form of this stress protein. To study HSP 60 expression and the phenotype of intima infiltrating T lymphocytes relative to the T cell receptor (TCR) in human atherosclerotic lesions, specimens of aorta, carotid arteries, and internal mammary arteries and veins, as well as saphenous veins and vena cava from 27 subjects, aged 23 to 80 years, were examined using immunohistochemical and immunofluorescence techniques on serial frozen tissue sections. HSP 60 was detected on endothelium, smooth muscle cells, and/or mononuclear cells of all carotid and aortic specimens, whereas vessels of smaller diameter, serving as reference specimens for normal intima without atherosclerotic lesions and mononuclear infiltration, showed no detectable expression of this stress protein. Furthermore, although the majority of CD3+ cells within the mononuclear cell infiltrates of atherosclerotic lesions bear the alpha/beta TCR, a considerable portion also consisted of gamma/delta TCR+ cells. Thus, 9.7% of T cells in the transition zone between normal intima and fatty streaks carry the gamma/delta TCR, a proportion that decreases to 6.6% and 4.3% in fatty streaks and atherosclerotic plaques, respectively. We conclude that the intensity of HSP 60 expression correlates positively with the atherosclerotic severity and that most lymphocytes participating in atherogenesis bear the alpha/beta TCR, although gamma/delta TCR+ cells are also enriched in atherosclerotic lesions. Expression of HSP 60 by intimal cells, caused, eg, by hemodynamic shear forces, may be responsible for recruitment of HSP-sensitized T cells, thus leading to the induction of an initiating inflammatory process in atherosclerosis. Other risk factors, such as high serum cholesterol levels, contribute to the final outcome of the disease.

Local fibrinolysis and perfusion in the treatment of priapism of the corpora cavernosa and corpus spongiosum.

A 69-year-old patient was referred with priapism of the corpora cavernosa and the corpus spongiosum. Blood aspiration, irrigation with heparin-saline solution and metaraminol injections proved unsuccessful. Surgical intervention was inadvisable in view of delayed coagulation. Complete detumescence was achieved after intracorporeal perfusion with streptokinase.

Graft replacement of post-traumatic thoracic aortic aneurysm: results without bypass or shunting.

From 1986 to 1991 13 cases of post-traumatic thoracic aneurysm were treated at our department. All patients had apparent thoracic injury at the time of trauma, and their mean age was 35 years. The mean time between trauma and operation was 3 years and six patients were asymptomatic. In all patients the diagnosis was made by computed tomography and angiography and all post-traumatic thoracic aneurysms were located at the aortic isthmus. No spinal cord protection by bypass or shunting was used during surgery and the clamp-and-repair method with a mean clamping time of 38 min was used in all 13 patients. No renal or neurological complications were observed postoperatively and there were no hospital deaths. The data of 202 patients who had been operated upon for post-traumatic thoracic aneurysms since 1981 have been reviewed with regard to the relationship between spinal cord protection and the incidence of postoperative paraplegia. Different methods of spinal cord protection were used in 121 patients resulting in paraplegia rate of 1.6%. In 81 patients the clamp-and-repair method was used and no case of paraplegia was observed in this group.

[Increasing value of the duplex scan in preoperative diagnosis of the carotid artery--is preoperative carotid angiography still sensible?]. / Die zunehmende Bedeutung des Duplex Scans in der präoperativen Carotisdiagnostik--ist die präoperative Carotisangiographie noch sinnvoll?

In effort to eliminate morbidity and costs, associated with arteriographic investigation, we increasingly perform Duplex Scan of the extracranial carotid artery prior to endarterectomy. 451 carotid reconstructions between 1986 and April 1991 were evaluated retrospectively. The percentage of patients undergoing carotid endarterectomy without angiography has increased from 21.1% to 92.8%. Angiography was associated with a combined neurologic morbidity rate of 3.0%. Perioperative outcome of patients and stratification by indication did not show any significant differences for both groups undergoing Duplex Scan alone and/or angiography. Diagnostic Carotid angiography should only be used selectively in patients showing distal internal carotid plaque, recurrent stenosis, symptomatic carotid occlusion or aortic arch disease.

Isolated iliac artery aneurysms.

Clinical and diagnostic data were collected from 22 men with iliac artery aneurysms treated surgically over a period of 22 years. Their ages ranged from 47 to 80 years (mean 64.0). Eight patients had multiple aneurysms. Thirty isolated iliac artery aneurysms were detected, 20 aneurysms (66.6%) located on the right and 10 (33.3%) on the left side. Twenty-six aneurysms were found in the common iliac artery (86.6%). Fifteen patients were symptomatic (68.2%); rupture occurred in five patients (22.7%), three of whom were initially asymptomatic. Thirteen of 17 patients whose aneurysms did not rupture had a palpable mass (76.4%), and three had bruits in the area of the aneurysm. All 22 patients were subjected to operative procedures. Seventeen patients operated upon electively survived, whereas only three patients who were operated upon after rupture survived. Graft interposition was the most common procedure. All 20 patients who survived after the operation were followed. Two died of myocardial infarction three and five years later, one of cancer six years later, and one of an unknown cause eight years after operation. Iliac artery aneurysms are extremely rare; their diagnosis is very difficult. The mortality rate is two times higher than in aortic aneurysms, once the diagnosis has been established. Therefore elective resection and arterial reconstruction are recommended.