Showing papers by "University of Jena published in 1998"

Integration with respect to fractal functions and stochastic calculus. I

Abstract: The classical Lebesgue–Stieltjes integral ∫ b a fdg of real or complex-valued functions on a finite interval (a,b) is extended to a large class of integrands f and integrators g of unbounded variation. The key is to use composition formulas and integration-by-part rules for fractional integrals and Weyl derivatives. In the special case of Holder continuous functions f and g of summed order greater than 1 convergence of the corresponding Riemann–Stieltjes sums is proved. The results are applied to stochastic integrals where g is replaced by the Wiener process and f by adapted as well as anticipating random functions. In the anticipating case we work within Slobodeckij spaces and introduce a stochastic integral for which the classical Ito formula remains valid. Moreover, this approach enables us to derive calculation rules for pathwise defined stochastic integrals with respect to fractional Brownian motion.

Sympathetic activation triggers systemic interleukin-10 release in immunodepression induced by brain injury.

Abstract: The mechanism of immunodepression after brain injury is not yet clear. Here we demonstrate rapid systemic release of the immunoinhibitory cytokine interleukin-10, monocytic deactivation and a high incidence of infection in patients with 'sympathetic storm' due to acute accidental or iatrogenic brain trauma. In vitro studies showed that within minutes catecholamines trigger the secretion of interleukin-10 from unstimulated monocytes through a beta-adrenoreceptor-mediated, cAMP/protein kinase A-dependent pathway. We found that in a rat model of acute brain injury, the beta-receptor antagonist propranolol prevented the increase of interleukin-10 plasma levels. Rapid monocytic interleukin-10 release after sympathetic activation may represent a common pathway for immunodepression induced by stress and injury.

Postoperative plasma concentrations of procalcitonin after different types of surgery

Abstract: Objective: Procalcitonin (PCT) and C-reactive protein (CRP) plasma concentrations were measured after different types of surgery to analyze a possible postoperative induction of procalcitonin (PCT), which might interfere with the diagnosis of bacterial infection or sepsis by PCT. Design: PCT and CRP plasma levels as well as clinical symptoms of infection were prospectively registered preoperatively and 5 days postoperatively. Setting: University hospital, in-patient postoperative care. Patients: Hundred thirty patients were followed up; 117 patients with a normal postoperative course were statistically analyzed. Interventions: None. Measurements and results: PCT concentrations were moderately increased above the normal range in 32 % of patients after minor and aseptic surgery, in 59 % after cardiac and thoracic surgery, and in 95 % of patients after surgery of the intestine. In patients with an abnormal postoperative course, PCT was increased in 12 of 13 patients. CRP was increased in almost all patients. Conclusions: Postoperative induction of PCT largely depends on the type of surgery. Intestinal surgery and major operations more often increase PCT, whereas it is normal in the majority of patients after minor and primarily aseptic surgery. PCT can thus be used postoperatively for diagnostic means only when the range of PCT concentrations during the normal course of a certain type of surgery is considered and concentrations are followed up.

Fibrosarcomatous ("high-grade") dermatofibrosarcoma protuberans: clinicopathologic and immunohistochemical study of a series of 41 cases with emphasis on prognostic significance.

Abstract: The fibrosarcomatous variant of dermatofibrosarcoma protuberans (FS-DFSP) represents an uncommon form of DFSP, in which the prognostic influence of the fibrosarcomatous component is still debated. We analyzed the clinicopathologic and immunohistochemical features in a series of 41 patients. Patient age ranged from 8 to 87 years (median, 48 years), and 19 patients were female. Twenty five lesions were seen on the trunk, 6 on the upper limbs, and 4 on the lower limbs, and five neoplasms were located in the head/neck region; in one case, exact anatomic site was unknown. Twenty seven tumors involved purely dermal and subcutaneous tissues, in 10 cases, deeper structures were also involved, 1 case arose in the breast, and, in 3 cases, it was impossible to define exact depth of the lesion. Preoperative duration ranged from 1 month to 60 years (median, 3 years). Twenty six tumors were excised locally with clear margins, 7 were treated by wide excision, 3 by incomplete excision, and, in 4 patients, the lesion was shelled out. In one case, exact treatment was unknown. In addition, radiotherapy was administered in three cases and chemotherapy in one case. Histologically, the lesions showed areas of typical, low-grade DFSP adjacent to fibrosarcomatous areas. In four cases, a previously ordinary DFSP recurred as pure fibrosarcoma, in two cases, local recurrence of FS-DFSP showed features of ordinary DFSP. Fibrosarcomatous change was more common in the primary (de novo) lesions than in recurrent lesions (3.6:1). Proportion of fibrosarcoma varied between 70% of tumor tissue in 21 cases. An abrupt transition between both components was seen in 19 cases. The fibrosarcomatous component showed focal necrosis in seven cases and showed a higher mitotic rate in comparison with ordinary DFSP areas (mean, 13.4 versus 2.3 mitoses in 10 high-power fields). Additional histologic features included progression to pleomorphic sarcoma in 2 recurrent cases, melanin-pigmented cells (Bednar FS-DFSP) in 1 case, focal myxoid change in 13 cases, plaque or keloidlike hyalinization in 3 cases, and myoid bundles and nodules in 9 cases. Immunohistochemically, tumor cells in DFSP areas stained positively for CD34, whereas, in FS-DFSP areas, only 15 out 33 cases were positive for CD34. Follow-up in 34 of 41 patients (mean, 90 months; median, 36 months) revealed local recurrence in 20 patients (58%) (recurrence occurred in 5 patients on two or more occasions). Metastases (5 lung, 1 bone, and 1 soft tissue) were seen in 5 patients (14.7%), and 2 patients have died of tumor to date (5.8%). Necrosis, high mitotic rate (> 10 mitoses per 10 high-power fields), and presence of pleomorphic areas in FS-DFSP tended to be related with poor clinical outcome, but no statistically significant association was detected. Fibrosarcomatous change in DFSP represents a form of tumor progression in DFSP and is associated with a significantly more aggressive clinical course than in ordinary DFSP, indicating a possible need for treatment intensification in such cases.

Bifurcation of Lipid and Protein Kinase Signals of PI3Kγ to the Protein Kinases PKB and MAPK

Abstract: Phosphoinositide 3-kinases (PI3Ks) activate protein kinase PKB (also termed Akt), and PI3Kgamma activated by heterotrimeric guanosine triphosphate-binding protein can stimulate mitogen-activated protein kinase (MAPK). Exchange of a putative lipid substrate-binding site generated PI3Kgamma proteins with altered or aborted lipid but retained protein kinase activity. Transiently expressed, PI3Kgamma hybrids exhibited wortmannin-sensitive activation of MAPK, whereas a catalytically inactive PI3Kgamma did not. Membrane-targeted PI3Kgamma constitutively produced phosphatidylinositol 3,4, 3,4,5-trisphosphate and activated PKB but not MAPK. Moreover, stimulation of MAPK in response to lysophosphatidic acid was blocked by catalytically inactive PI3Kgamma but not by hybrid PI3Kgammas. Thus, two major signals emerge from PI3Kgamma: phosphoinositides that target PKB and protein phosphorylation that activates MAPK.

Adaptive AR modeling of nonstationary time series by means of Kalman filtering

Abstract: An adaptive on-line procedure is presented for autoregressive (AR) modeling of nonstationary multivariate time series by means of Kalman filtering. The parameters of the estimated time-varying model can be used to calculate instantaneous measures of linear dependence. The usefulness of the procedures in the analysis of physiological signals is discussed in two examples: first, in the analysis of respiratory movement, heart rate fluctuation, and blood pressure, and second, in the analysis of multichannel electroencephalogram (EEG) signals. It was shown for the first time that in intact animals the transition from a normoxic to a hypoxic state requires tremendous short-term readjustment of the autonomic cardiac-respiratory control. An application with experimental EEG data supported observations that the development of coherences among cell assemblies of the brain is a basic element of associative learning or conditioning.

Optical Bloch oscillations in waveguide arrays

Abstract: We show that optical Bloch oscillations can emerge in waveguide arrays with linearly varying propagation constants. The existence of localized modes (Wannier-Stark states) with equidistant wave-number spacing (Wannier-Stark ladder) that do not undergo diffraction is analytically proved. The evolution of arbitrary initial excitations is described, and potential applications are suggested.

Three-dimensional quantization of the electromagnetic field in dispersive and absorbing inhomogeneous dielectrics

Abstract: A quantization scheme for the phenomenological Maxwell theory of the full electromagnetic field in an inhomogeneous three-dimensional, dispersive and absorbing dielectric medium is developed. The classical Maxwell equations with spatially varying and Kramers-Kronig consistent permittivity are regarded as operator-valued field equations, introducing additional current- and charge-density operator fields in order to take into account the noise associated with the dissipation in the medium. It is shown that the equal-time commutation relations between the fundamental electromagnetic fields $\hat E$ and $\hat B$ and the potentials $\hat A$ and $\hat \phi$ in the Coulomb gauge can be expressed in terms of the Green tensor of the classical problem. From the Green tensors for bulk material and an inhomogeneous medium consisting of two bulk dielectrics with a common planar interface it is explicitly proven that the well-known equal-time commutation relations of QED are preserved.

Experimental cranial pain elicited by capsaicin: a PET study

Abstract: Using a positron emission tomography (PET) study it was shown recently that in migraine without aura certain areas in the brain stem were activated during the headache state, but not in the headache free interval. It was suggested that this brain stem activation is inherent to the migraine attack itself and represents the so called `migraine generator'. To test this hypothesis we performed an experimental pain study in seven healthy volunteers, using the same positioning in the PET scanner as in the migraine patients. A small amount of capsaicin was administered subcutaneously in the right forehead to evoke a burning painful sensation in the first division of the trigeminal nerve. Increases of regional cerebral blood flow (rCBF) were found bilaterally in the insula, in the anterior cingulate cortex, the cavernous sinus and the cerebellum. Using the same stereotactic space limits as in the above mentioned migraine study no brain stem activation was found in the acute pain state compared to the pain free state. The increase of activation in the region of the cavernous sinus however, suggests that this structure is more likely to be involved in trigeminal transmitted pain as such, rather than in a specific type of headache as was suggested for cluster headache.

Low-Grade Myofibroblastic Sarcoma: Analysis of 18 Cases in the Spectrum of Myofibroblastic Tumors

Abstract: The clinicopathologic, immunohistochemical, and ultrastructural features of a seemingly distinctive low-grade spindle cell sarcoma showing myofibroblastic differentiation have been analyzed in a series of 18 patients. The age range of the patients (7 women and 11 men) was 19-72 years (median: 42 years). A painless, enlarging mass was the most common clinical presentation. Five tumors arose in the oral cavity (including four lesions in the tongue), four in the lower extremities and three in the upper extremities, four cases in the abdominal/pelvic cavity, and two on the trunk. Eight soft-tissue cases involved skeletal muscle, three cases were located in perifascial tissues, and two arose in subcutaneous tissue. Tumor size ranged from 1.4 to 17 cm (median: 4 cm); in six cases (of which four were abdominal/pelvic) the lesion was larger than 5 cm. All patients were treated surgically, and four received additional adjunctive therapy. Histologically, most cases were cellular lesions showing a diffusely infiltrative pattern, and were composed of spindle-shaped tumor cells arranged mainly in fascicles. Tumor cells had poorly defined, palely eosinophilic cytoplasm and fusiform nuclei, which were either tapering and wavy or plumper and vesicular with indentations and small inconspicuous nucleoli. Tumor cells were set in a collagenous matrix often with prominent hyalinization. Mild nuclear atypia was noted in 16 cases; in the other 2 cases, and in the metastases of one other lesion, a greater degree of nuclear atypia was seen. In all but one case, the mitotic rate ranged from 1 to 6 mitoses in 10 HPFs (mean: 2/10 HPFs); in a single case, there were more than 20 mitoses in 10 HPFs. Immunohistochemically, all cases stained positively for at least one myogenic marker; 12 cases were positive for desmin, 11 for alpha-smooth muscle actin, and 6 for muscle actin (HHF35). Seven neoplasms were desmin positive/ alpha-smooth-muscle actin negative, and five cases were desmin negative/alpha-smooth-muscle actin positive emphasizing the variable immunophenotype of myofibroblastic lesions. In addition, 7 of 10 tumors stained at least focally positive for fibronectin. Ultrastructural examination in five cases showed characteristic features of myofibroblasts. Follow-up in 11 patients (median: 29 months) revealed local recurrence in 2 cases, and multiple distant soft-tissue, intraosseous, and pulmonary metastases in one other patient. Low-grade myofibroblastic sarcoma seems to represent a distinct entity in the spectrum of low-grade myofibroblastic neoplasms and is distinguishable from fibromatosis, myofibromatosis, solitary fibrous tumor, fibrosarcoma, and leiomyosarcoma.

Mass Flow and Accretion through gaps in Accretion Discs

Abstract: We study the structure and dynamics of the gap created by a protoplanet in an accretion disc. The hydrodynamic equations for a flat, two-dimensional, non-selfgravitating protostellar accretion disc with an embedded, Jupiter sized protoplanet on a circular orbit are solved. To simulate possible accretion of mass onto the protoplanet we continually remove mass from the interior of the planet's Roche lobe which is monitored. Firstly, it is shown that consistent results independent on numerical issues (such as boundary or initial conditions, artificial viscosity or resolution) can be obtained. Then, a detailed parameter study delineates the influence of the disc viscosity and pressure on the magnitude of the accretion rate. We find that, even after the formation of a gap in the disc, the planet is still able to accrete more mass from the disc. This accretion occurs from regions of the disc which are radially exterior and interior to the planet's orbital radius. The rate depends on the magnitude of the viscosity and vertical thickness of the disc. For a disc viscosity alpha=10^{-3} and vertical thickness H/r=0.05 we estimate the time scale for the accumulation of one Jupiter mass to be of order hundred thousand years. For a larger(smaller) viscosity and disc thickness this accretion rate is increasing(decreasing). For a very small viscosity (alpha < 5 10^{-4}) the mass accretion rate through the gap onto the planet is markedly reduced, and the corresponding accretion time scale becomes larger than the viscous evolution time of the disc.

Responding to negative social identity: a taxonomy of identity management strategies

Abstract: Taken from literature on social identity theory and social comparison theory, 12 strategies of identity management were identified as possible responses to negative social identity. A taxonomy with two orthogonal axes is proposed as theoretical organization of these diverse strategies. While the first axis considers responses as being either individual or collective, the second axis refers to the distinction between behaviours and cognitions. It is assumed that the German unification process implied a lower status position of East Germans relative to West Germans on relevant comparison dimensions, and that East Germans have to deal with this threat to their identity. Hence, data of an East German sample are used to empirically systematize identity management strategies, and, thus, to test the proposed taxonomy. Results support the expected four-factor solution only for those strategies taken from social identity theory, while the responses derived from social comparison research build a fifth factor. In addition, the empirical assignments of strategies to cells of the taxonomy are only partly in line with the expected pattern. The empirical findings suggest some clarification and modifications of the proposed response taxonomy. The most important refers to a re-interpretation of the taxonomy's first axis, which now differentiates between responses according to the specific changes of the comparison parameters they imply. © 1998 John Wiley & Sons, Ltd.

Role of fiberoptic bronchoscopy in conjunction with the use of double-lumen tubes for thoracic anesthesia : A prospective study

Abstract: Background Fiberoptic bronchoscopy has been recommended to verify the position of double-lumen tubes (DLT), but this remains controversial. The authors studied the role of bronchoscopy for placing and monitoring right- and left-sided DLTs after blind intubation and after positioning the patient. Methods Two hundred patients having thoracic surgery requiring DLT insertion were prospectively studied. "Blind" tracheal intubations were done with 163 left-sided and 37 right-sided disposable polyvinyl chloride Robertshaw tubes. Bronchoscopy was performed by a different anesthesiologist after intubation and conventional clinical verification of correct placement and after patient positioning for thoracotomy. A DLT was considered malpositioned when it had to be moved >0.5 cm to correct its position. Critical malpositions were those that might have affected patient safety or influenced the surgical procedure if left uncorrected. Results After "blind" DLT intubation, clinical evidence of malpositioning was found in 28 patients. This was confirmed by fiberoptic assessment. In 172 patients in whom placement was judged correct by clinical assessment, malpositioning was detected by bronchoscopy in 79 cases, 25 of which were critical. After patient positioning, DLTs were found to be displaced in 93 patients, 48 of which were critical. Right-sided DLTs were significantly more likely to be malpositioned than were left-sided DLTs. Two complications were related to unsatisfactory lung separation in the 200 patients studied. Conclusions After blind intubation and patient positioning, more than one third of DLTs required repositioning. Routine bronchoscopy is therefore recommended after intubation and after patient positioning.

A nuclear-encoded protein of prokaryotic origin is essential for the stability of photosystem II in Arabidopsis thaliana

Abstract: To understand the regulatory mechanisms underlying the biogenesis of photosystem II (PSII) we have characterized the nuclear mutant hcf136 of Arabidopsis thaliana and isolated the affected gene. The mutant is devoid of any photosystem II activity, and none of the nuclear- and plastome-encoded subunits of this photosystem accumulate to significant levels. Protein labelling studies in the presence of cycloheximide showed that the plastome-encoded PSII subunits are synthesized but are not stable. The HCF136 gene was isolated by virtue of its T-DNA tag, and its identity was confirmed by complementation of homozygous hcf136 seedlings. Immunoblot analysis of fractionated chloroplasts showed that the HCF136 protein is a lumenal protein, found only in stromal thylakoid lamellae. The HCF136 protein is produced already in dark-grown seedlings and its levels do not increase dramatically during light-induced greening. This accumulation profile confirms the mutational data by showing that the HCF136 protein must be present when PSII complexes are made. HCF136 homologues are found in the cyanobacterium Synechocystis species PCC6803 (slr2034) and the cyanelle genome of Cyanophora paradoxa (ORF333), but are lacking in the plastomes of chlorophytes and metaphytes as well as from those of rhodo- and chromophytes. We conclude that HCF136 encodes a stability and/or assembly factor of PSII which dates back to the cyanobacterial-like endosymbiont that led to the plastids of the present photosynthetic eukaryotes.

Kinematics and electromyography of lower limb muscles in overground and treadmill running.

Abstract: ■ Treadmills are often used in research to analyse kinematic and physiological variables. The success of transfering the results to overground running depends on the comparability of the values between the two situations. The aim of the present study was to compare the kinematics and muscle activities in overground and treadmill running. Ten male physical education students with experience in treadmill running were asked to run with a speed of 4.0 and 6.0 m/s both overground and on a Woodway treadmill. The 3D-kinematics of the limbs were studied using a two camera video tracking system. Additionally the surface EMG of six lower limb muscles and the pattern of ground contact of the right foot was registered. Both the activities of the leg muscles and several kinematic variables showed systematic changes from overground to treadmill running. On the treadmill the subjects favoured a type of running that provided them with a higher level of security. The swing amplitude of the leg, the vertical displacement and the variance in vertical and horizontal velocity were lower in treadmill running. The angle between shoe sole and ground at foot impact was also lower and the forward lean of the upper body was higher in running on the treadmill compared with the overground mode. Most of the subjects reduced their step length and increased stride frequency in treadmill running. Furthermore, the contact time in treadmill running was shorter than for overground running. The above mentioned kinematic variables were significantly different (p<0.05). The EMG patterns of the leg muscles were generally similar between overground and treadmill modes, but some minor differences could consistently be identified.

Single scattering by red blood cells

Abstract: A highly diluted suspension of red blood cells (hematocrit 0.01) was illuminated with an Ar or a dye laser in the wavelength range of 458-660 nm. The extinction and the angle-resolved intensity of scattered light were measured and compared with the predictions of Mie theory, the Rayleigh-Gans approximation, and the anomalous diffraction approximation. Furthermore, empirical phase functions were fitted to the measurements. The measurements were in satisfactory agreement with the predictions of Mie theory. However, better agreement was found with the anomalous diffraction model. In the Rayleigh-Gans approximation, only small-angle scattering is described appropriately. The scattering phase function of erythrocytes may be represented by the Gegenbauer kernel phase function.

Positive–Negative Asymmetry in Social Discrimination

Abstract: Minimal group experiments showed that mere categorization of individuals into arbitrary social groups can be sufficient to elicit ingroup favouritism. This effect has been qualified by demonstrating a positive–negative asymmetry in social discrimination: categorization into minimal, laboratory groups was sufficient to elicit ingroup favouritism in allocations of positive stimuli, but not in allocations of negative ones. Different explanatory perspectives for this valence-specific asymmetry in intergroup behaviour were tested. An integrative perspective linking normative, cognitive and motivational aspects is proposed. This perspective also implies a critical analysis and re-framing of traditional theorizing on categorization effects in minimal intergroup situations.

Dispersion pre-compensation of 15 femtosecond optical pulses for high-numerical-aperture objectives

Abstract: The excitation efficiency in two-photon absorption (TPA) microscopy depends strongly — owing to the square dependence of the TPA fluorescence on the excitation intensity — on the temporal width of the excitation pulse. Because of their inherently large frequency bandwidth, ultrashort optical pulses tend to broaden substantially because of dispersion from propagation through the dispersive elements in the microscope. In this paper, the dispersion characteristics of a wide range of microscope objectives are investigated. It is shown that the induced dispersion can be pre-compensated in all cases for pulses as short as 15 fs. Because of the excellent agreement between the results from theoretical modelling and the experimental data, predictions of the possibility of dispersion control for microscope objectives in general, as well as for even shorter pulses, can be inferred. Since for TPA imaging the background due to single photon absorption processes and scattering is independent of the pulse width, proper dispersion pre-compensation — which minimizes the pulse duration at the focal point and hence maximizes the excitation efficiency — provides optimal image contrast in TPA microscopy.

Relationship Between Disease Activity and Serum Levels of Vitamin D Metabolites and PTH in Rheumatoid Arthritis

Abstract: In several studies on patients with rheumatoid arthritis, an association of bone loss with a persistently high disease activity has been found. The aim of our study was to investigate the relation between disease activity and serum levels of vitamin D metabolites, parathyroid hormone (PTH), and parameters of bone turnover in patients with rheumatoid arthritis. A total of 96 patients (83 women and 13 men) were divided into three groups according to disease activity measured by serum levels of C-reactive protein (CRP). In the whole group, serum levels of 1,25-dihydroxyvitamin D3 (1,25(OH)2D3) (P < 0.001) and PTH (P < 0.05) were negatively correlated to disease activity. The urinary excretion of collagen crosslinks--pyridinoline (Pyd) (P < 0.001) and deoxypyridinoline (Dpd) (P < 0.05)--showed a positive correlation with disease activity. The inverse correlation between serum 1,25(OH)2D3 and disease activity was separately evident in patients with (P < 0.001) and without (P < 0.01) glucocorticoid treatment, in pre- (P < 0.01) and postmenopausal (P < 0.001) women, and in men (P < 0.01). 1,25(OH)2D3 and PTH serum levels were positively correlated to serum bone alkaline phosphatase (ALP) (P < 0.01). The results indicate that high disease activity in patients with rheumatoid arthritis is associated with an alteration in vitamin D metabolism and increased bone resorption. The decrease of 1,25(OH)2D3 levels in these patients may contribute to a negative calcium balance and inhibition of bone formation. Furthermore, low levels of 1,25(OH)2D3 as an endogenous immunomodulator suppressing activated T cells and the proliferation of cells may accelerate the arthritic process in rheumatoid arthritis.

Ion-beam induced damage and annealing behaviour in SiC

Abstract: The paper presents the damage accumulation in silicon carbide (SiC) as a function of the ion mass, the ion energy and the implantation temperature. A defect-interaction and amorphization model is used to analyse the dose dependence of defect production, as obtained by the various methods. The temperature dependence of the amorphization dose can be represented assuming a thermally enhanced annealing within the primary collision cascades. On the basis of such a model, a critical implantation temperature is obtained, which was found to vary with the ion mass and the implantation energy. The concurrent influence of implantation temperature and ion fluence on the resulting damage distribution in SiC is demonstrated. The damage annealing of ion implanted SiC is investigated for low, medium and high damage concentrations. The effect of the implantation temperature and the concentration of implanted atoms, both influencing the kind of defects obtained after implantation, on the annealing behaviour is analysed.

DQAsomes: a novel potential drug and gene delivery system made from Dequalinium.

Abstract: Purpose. Dequalinium, a drug known for over 30 years, is a dicationic amphiphile compound resembling bolaform electrolytes. The purpose of our work was to determine the state of aggregation of dequalinium in aqueous medium and to investigate both, its ability to bind DNA and its potential to serve as a novel non-viral transfection vector.

Rankings of Graphs

Abstract: A vertex (edge) coloring $\phi:V\rightarrow \{1,2,\ldots ,t\}$ ($\phi':E\rightarrow \{1,2,\ldots,$ $t\}$) of a graph G=(V,E) is a vertex (edge) t-ranking if, for any two vertices (edges) of the same color, every path between them contains a vertex (edge) of larger color. The {\em vertex ranking number} $\chi_{r}(G)$ ({\em edge ranking number} $\chi_{r}'(G)$) is the smallest value of t such that G has a vertex (edge) t-ranking. In this paper we study the algorithmic complexity of the {\sc Vertex Ranking} and {\sc Edge Ranking} problems. It is shown that $\chi_{r}(G)$ can be computed in polynomial time when restricted to graphs with treewidth at most k for any fixed k. We characterize the graphs where the vertex ranking number $\chi_{r}$ and the chromatic number $\chi$ coincide on all induced subgraphs, show that $\chi_{r}(G)=\chi (G)$ implies $\chi (G)=\omega (G)$ (largest clique size), and give a formula for $\chi_{r}'(K_n)$.

Laser-induced autofluorescence spectroscopy of dental caries.

Abstract: We studied spectral autofluorescence characteristics of dental caries. A wide range of carious lesions revealed characteristic emission of endogenous fluorophores with strong fluorescence bands in the red spectral region when excited with 407 nm line radiation of a krypton ion laser. Healthy hard dental tissue exhibited no emission bands in the red. The fluorescence spectra, fluorescence excitation spectra as well as the reflectance spectra of carious lesions were found to be typical for fluorescent porphyrins, mainly protoporphyrin IX. A possible source of these porphyrins within carious tissues is bacterial biosynthesis. Non-invasive sensitive in vivo caries detection by means of appropriate excitation sources and porphyrin fluorescence detectors should be possible.