Model based evaluation of a contaminant plume development under aerobic and anaerobic conditions in 2D bench-scale tank experiments.

The influence of transverse mixing on competitive aerobic and anaerobic biodegradation of a hydrocarbon plume was investigated using a two-dimensional, bench-scale flow-through laboratory tank experiment. In the first part of the experiment aerobic degradation of increasing toluene concentrations was carried out by the aerobic strain Pseudomonas putida F1. Successively, ethylbenzene (injected as a mixture of unlabeled and fully deuterium-labeled isotopologues) substituted toluene; nitrate was added as additional electron acceptor and the anaerobic denitrifying strain Aromatoleum aromaticum EbN1 was inoculated to study competitive degradation under aerobic /anaerobic conditions. The spatial distribution of anaerobic degradation was resolved by measurements of compound-specific stable isotope fractionation induced by the anaerobic strain as well as compound concentrations. A fully transient numerical reactive transport model was employed and calibrated using measurements of electron donors, acceptors and isotope fractionation. The aerobic phases of the experiment were successfully reproduced using a double Monod kinetic growth model and assuming an initial homogeneous distribution of P. putida F1. Investigation of the competitive degradation phase shows that the observed isotopic pattern cannot be explained by transverse mixing driven biodegradation only, but also depends on the inoculation process of the anaerobic strain. Transient concentrations of electron acceptors and donors are well reproduced by the model, showing its ability to simulate transient competitive biodegradation.

Slow rhythmic oscillations of blood pressure, intracranial pressure, microcirculation, and cerebral oxygenation. Dynamic interrelation and time course in humans.

BACKGROUND AND PURPOSE: Various biological signals show nonpulsatile, slow rhythmic oscillations. These include arterial blood pressure (aBP), blood flow velocity in cerebral arteries, intracranial pressure (ICP), cerebral microflow, and cerebral tissue PO2. Generation and interrelations between these rhythmic fluctuations remained unclear. The aim of this study was to analyze whether stable dynamic interrelations in the low-frequency range exist between these different variables, and if they do, to analyze their exact time delay. METHODS: In a clinical study, 16 comatose patients with either higher-grade subarachnoid hemorrhage or severe traumatic brain injury were examined. A multimodal digital data acquisition system was used to simultaneously monitor aBP, flow velocity in the middle cerebral artery (FVMCA), ICP, cerebral microflow, and oxygen saturation in the jugular bulb (SjO2). Cross-correlation as a means to analyze time delay and correlation between two periodic signals was applied to a time series of 30 minutes' duration divided into four segments of 2048 data points (approximately 436 seconds) each. This resulted in four cross-correlations for each 30-minute time series. If the four cross-correlations were consistent and reproducible, averaging of the original cross-correlations was performed, resulting in a representative time delay and correlation for the complete 30-minute interval. RESULTS: Reproducible cross-correlations and stable dynamic interrelations were found between aBP, FVMCA, ICP, and SjO2. The mean time delay between aBP and ICP was 6.89 +/- 1.90 seconds, with a negative correlation in 81%. A mean time delay of 1.50 +/- 1.29 seconds (median, 0.85 seconds) was found between FVMCA and ICP, with a positive correlation in 94%. The mean delay between ICP and SjO2 was 9.47 +/- 2.21 seconds, with a positive correlation in 77%. Mean values of aBP and ICP did not influence the time delay and dynamic interrelation between the different parameters. CONCLUSIONS: These results strongly support Rosner's theory that ICP B-waves are the autoregulatory response of spontaneous fluctuations of cerebral perfusion pressure. There is casuistic evidence that failure of autoregulation significantly modifies time delay and the correlation between aBP and ICP.

Respiratory-dependent laser-Doppler flux motion in different skin areas and its meaning to autonomic nervous control of the vessels of the skin.

The aim of this study is to evaluate and quantify the respiratory dependency of cutaneous laser-Doppler flux motion in two variable innervated sites of the upper extremity (the proximal volar forearm and the fingertip) by using a computer-supported system. Various spontaneous (6-17/ min) and externally triggered (12 or 6/min) respiratory frequencies were used for comparative frequency analysis of the laser-Doppler flux signal. Further, an index (MIRSF) was determined as an indicator of the correlation between flux motion and respiration. The MIRSF is defined as the ratio of the power spectrum of the LDF signal at the specific respiratory frequency divided by the time-averaged LDF for that time period. The MIRSF enables a comparison of different intra- and interindividual flux values. A very high correlation was seen between the respiratory frequency and the MIRSF during spontaneous respiration in the skin of the proximal volar forearm; the lower the spontaneous respiratory frequency, the higher the MIRSF. However, this correlation could not be found in the results of the fingertip. The presence of a constant and therefore externally triggered respiratory frequency increased the modulations of the LDF at both measurement locations. While triggered respiration produced a decline in the taLDF of the fingertip, the taLDF of the forearm was unaffected. Considering the different innervation and hydrostatic effects the results lead to the following conclusion: the finger vessels are richly innervated with adrenoceptors which causes alpha 1-mediated vasoconstriction. In contrast to the vessels of the fingers those of the forearm seem to be under andrenergic as well as cholinergic control. Hydrostatic components appear to be more prevalent in the volar forearm site.

Noninvasive continuous blood pressure control by pulse wave velocity.

A comparison of arterial pulse wave velocity (PWV) detected by ultrasonic Doppler probes and invasive blood pressure data was performed. For accurate assessment of PWV beat-to-beat detection of the pulse transit time (PTT) was performed by means of two 8 Mhz ultrasonic Doppler probes placed externally over the right brachial resp. radial artery, as a reference the continuous invasive blood pressure (IAP) of the contralateral radial artery was collected. Comparing the PWV associated blood pressure (APPWV) and IAP yielded a correlation coefficient of r = 0.86, and Bland-Altman plotting proved 95% (+/- 2 SEM) of APPWV values to differ within +/- 10 mm Hg from IAP. With this clinical study we found that beat-to-beat PWV measurement noninvasively, continuously and reliably monitors arterial blood pressure especially with respect to rapid blood pressure changes.

[Color-coded duplex ultrasound and laser Doppler flowmetry of finger tips of healthy probands]. / Farbkodierte Duplex-Sonographie und Laser-Doppler-Fluxmetrie in Fingerkuppen Gesunder.

In the study presented, color-coded duplex sonography (CCDS) and laser Doppler flux (LDF) signals from finger tips of 7 healthy individuals were recorded simultaneously. The aim of the study was to examine whether or not the results of a functional test ('deep inspiration') could also be observed with an ultrasonic Doppler. In the literature this test is known to provoke notable blood flow characteristics of the LDF ('inspiratory gasp'), a phenomenon which is caused by a sympathetically mediated vasoconstriction of acral vessels. With regard to the penetration depth of the LDF in skin it was of further interest to determine the distance between the surface of the skin and the vessels found near the surface. We found for CCDS parameters (color pixels/image; time-averaged flow velocity [TAV]; resistance index [RI]) as well as for LDF (flux [taLDF]) significant changes before versus after 'deep inspiration'. CCDS is a new diagnostic tool to visualize also very small vessels down to 0.2 mm, e.g. in finger tips. It should be evaluated which role this method may play in combination with functional tests in diagnostic handling, e.g. of patients with polyneuropathies or collagenoses.

[Respiration-dependence of cutaneous laser Doppler flow motion]. / Atemabhängigkeit kutaner Laser-Doppler-Fluxmotion.

The aim of this study was to show and to quantify the breath-dependency of cutaneous fluxmotion in the volar proximal forearm using a new computer-aided system. A meanflux-related index (MI) representing the intensity of the influence of respiration on fluxmotion was calculated. There was a good correlation between MI and the rate of respiration under spontaneous breathing: the lower the rate of respiration, the higher the value of MI. Prescribing a constant breathing rhythm amplifies this frequency-dependent effect. According to occurrence of low rates of respiration (< 12/min) also under physiological conditions the respiration should be simultaneously recorded while assessing fluxmotion.

Treatment of enchondromas of the hand with allograft bone.

We investigated whether cortico-cancellous allograft obtained from cadaveric banked bone is effective in the treatment of enchondroma of the hand. Twelve patients had 15 operations on 19 enchondromas using allograft bone. These patients were compared with 16 patients with enchondroma treated with autogenous iliac cancellous bone. The distribution of tumors was similar in both groups. There was no significant difference in the patient's age, their occupations, or whether the operation involved the dominant hand. In both groups, immobilization was maintained until clinical union was obtained. The duration of immobilization for both groups was identical. There were no recurrences, refractures, or complications in patients treated with allograft bone. The grafts incorporated and remodeled in all patients. We concluded that a allograft cortico-cancellous bone can be used effectively in the treatment of enchondromas of the hand. It is especially useful in the treatment of patients with multiple tumors.

Evaluation and diagnosis of cervical spine injuries: a review of the literature.

Cervical spine injuries pose devastating potential problems for surgeon and patient alike. This review will stress the early diagnosis of cervical spine injuries, with emphasis on early suspicion of injury. This review will focus on the radiology and types of lesions found with cervical spine injury.

The input impedance of the peripheral vascular termination in skeletal muscle.

In order to investigate the dynamic behaviour of the peripheral vessels of the arterial system, simultaneous pressure-flow measurements were made in the deep femoral artery of the rabbit at the same site. The input impedance calculated from the recorded pulses was regarded as representing the peripheral vascular termination in skeletal muscle and was expressed in terms of modulus and phase. The modulus decreases monotonously with increasing frequency while the phase angle is about -45 degrees in the low frequency range and becomes less negative with increasing frequency. This behaviour can be simulated by a model in which the inert mass of the pulsating blood, the elastic compliance of the blood vessels, and the frictional resistance to blood flow are taken into account. An essential result is that the model is provided with a considerable degree of elastic compliance, which means that the peripheral vessels as a whole possess an important compliance and do not behave like pure frictional resistances.

Malignant melanoma metastatic to the endometrium.

A case of malignant melanoma metastatic to the endometrium is presented along with a review of the literature on metastatic melanoma, showing its rarity. Malignant melanoma metastasizes to many sites, including the lung, bone, liver, skin, and pancreas. Four cases of melanoma metastatic to the endometrium have been reported. The purpose of the present report is to describe the clinical picture of another patient with malignant melanoma metastatic to the endometrium as well as the general histologic and prognostic features of the disease.

Rheological approaches of arteries.

A fundamental problem of haemodynamics lies in the description of the rheological properties of arteries. The time and history dependency of stress and strain, the nonlinearity of the stress-radius relationship, and the activity of vascular smooth muscle complicate or even prevent a complete mathematical characterization of the arterial wall mechanics. Due to this nonlinearity, dynamic investigations were hitherto performed in excised arteries in vitro by means of small sinusoidal changes of stress and radius at different stress levels in a wide frequency range. To allow an analysis of the dynamic rheological properties of arteries in vivo, we have developed a procedure which permits the separate determination of the elastic, the viscous, and the inertial forces acting on the arterial wall. The stress can be subdivided into an elastic stress which is a function of radius (r), a viscous stress which is a function of dr/dt, and an inertial stress which is a function of d2r/dt2. These stresses are formulated as polynomials. Under cyclic loading and unloading, hysteresis loops appear in the stress-radius diagrams of arteries. Since the elastic stress-radius diagram must be free from any loop, the coefficients of the viscous and the inertial stress can be found by a fitting procedure, using the criterion of loop elimination. Investigations were performed on exposed canine arteries in vivo. The main result was that the elastic stress-radius curve was markedly nonlinear at greater pulse pressures. The viscous wall behaviour, too, was nonlinear and depended mainly on the square of the vessel radius.

The contribution of the parallel and series elastic components to the dynamic properties of the rat tail artery under two different smooth muscle tones.

The dynamic elastic modulus (Ed) and the coefficient of wall viscosity (eta w) of the tail artery of normotensive rats were determined as functions of the circumferential wall stress under quasistatic and dynamic conditions. The experiments were performed under strong smooth muscle activation induced by norepinephrine, and during relaxation induced by papaverine. The following results were obtained. 1. Ed and eta w increase with increasing wall stress. At a given wall stress, Ed is virtually independent of frequency while eta w decreases markedly with increasing frequency. This behaviour of eta w is called thixotropy or pseudoplasticity. 2. In the wall stress range from 5--60 kPa the values of Ed, and in the wall stress range from 60--140 kPa those of eta w obtained under smooth muscle activation and during relaxation are virtually identical. 3. In the relaxed smooth muscle, the phase angles between sinusoidal pressure and radius changes area virtually independent of the mean wall stress at all frequencies. In the low stress range, the phase angles are greater at low frequencies in the activated state than in the relaxed state, decrease with increasing wall stress, and are virtually identical to the values under papaverine at high wall stresses. At high frequencies no dependence of the phase angles on the mean wall stress can be seen.

Mechanical properties of arteries.

UNLABELLED: For the description of the mechanical properties of the arterial wall, a number of different models and mathematical approaches of varying complexity have been used. Most investigations based on the elastomeric approach have been related to the elastic properties of arteries, while relatively little is known about the arterial wall viscosity (eta w) and its dependence on circumferential wall stress (sigma t) and smooth muscle tone. For this reason we have examined these relationships on segments of the abdominal aorta, the carotid artery, and the tail artery of normotensive rats in vitro under the condition of strong smooth muscle activation induced by norepinephrine (NE), and during smooth muscle relaxation induced by papaverine (PAP). RESULTS: 1. For the abdominal aorta, the quotient of the dynamic (Ed) and the quasistatic elastic modulus (ESt) increase from 1.5 to 2.1 under NE, and from 1.2 to 1.5 under PAP, for the carotid artery from 2.8 to 3.9 under NE, and from 1.3 to 1.4 under PAP, when sigma t increases from 10 to 120 kPa. For the tail artery, this quotient is 8.6 under NE and 1.9 under PAP in the low sigma t-range (5 to 60 kPa) and 12.1 under NE and 1.5 under PAP in the sigma t-range between 60 and 120 kPa. 2. For all three types of arteries, Ed and eta w increases with increasing sigma t. At a given sigma t, the values of Ed are virtually independent of frequency, while the values of eta w decrease markedly with increasing frequency. 3. The values of Ed and eta w, obtained under NE and PAP, are virtually identical for a given sigma t-range.

Photoelectric device for the recording of diameter changes of opaque and transparent blood vessels in vitro.

A new photoelectric device for measuring blood vessel diameters is described. The principle of this device consists in locating the vessel within a beam of parallel light at right angles to the beam direction, and eliminating all light striking the vessel. Thus only the light passing by the side of the vessel determines the signal strength of a photocell. The elimination of the light by the vessel due to reflection, refraction, diffraction, or scattering, is achieved with the aid of a lens and pinhole representing a spatial filter. This arrangement is effective irrespective of whether the vessel is opaque or transparent. The resolving power of the device in measuring changes of outside diameter is better than 0.5 micrometer for vessels up to 3 mm in diameter. The upper frequency limit is 300 Hz (--3 dB). The application of the method is demonstrated by two examples of measurements obtained on a small muscular artery.

The mechanical properties of exposed human common carotid arteries in vivo.

In exposed common carotid arteries of 15 patients (36-74 years) undergoing neck surgery, the intra-arterial pressure (P) was recorded by means of a catheter-tip manometer and, at the same site, the external diameter (D) by means of a contact-free photoelectric device. On the average, the pulsatile diameter changes were 5.6% of the end-diastolic diameter at pulse pressures of about 50 mm Hg. Due to viscoelasticity, the P-D diagrams exhibited hysteresis loops. Using the criterion of loop elimination, an iterative procedure was applied which permitted, by the use of an appropriate computer program, the separation of the purely elastic and the purely viscous components of the P-D relationships. In all cases, the purely elastic P-D curves markedly deviated from linearity. The tangential elastic modulus (Et) and the pulse wave velocity (c) calculated from these curves were normalized by dividing these quantities by the respective end-diastolic values and plotted against the normalized external diameters. During each pulse cycle, Et increased, with increasing diameter, by a factor between 1.2 and 3.5, while c increased by a factor between 1.1 and 1.9 with reference to the respective end-diastolic values.

Separate determination of the pulsatile elastic and viscous forces developed in the arterial wall in vivo.

The viscoelastic behaviour of arteries in vivo is analyzed by separate representation of the purely elastic and the purely viscous properties, using natural pressure and diameter pulses of various dog arteries recorded under steady-state conditions. The circumferential wall stress (sigma) and the radius (r) of the mean wall layer are calculated as functions of time and the hysteresis of the sigma-r diagram is represented. The stress is regarded as the sum of an elastic stress (sigma el) which is a function of r, and a viscous stress (sigma vis) which is a function of dr/dt. Thus sigma el = sigma - sigma vis. Since the sigma el-r diagram must be free from hysteresis, the disappearance of the loop is the criterion that indicates that sigma el has been found. sigma vis is formulated as a second degree polynomial of dr/dt whose coefficients are determined using that criterion. The sigma el-r curve is always nonlinear and the elastic modulus increases with increasing radius. The sigma vis-dr/dt curve, too, is nonlinear. Its slope decreases with increasing dr/dt. The same applies to the wall viscosity (pseudoplastic behaviour). The nonlinear properties can be represented adequately by processing the experimental data in the time domain. Problems inherent in investigations based on the frequency domain, as reported in the literature, are pointed out.

[Principles of the genesis of pressure and flow pulse contours of the human carotid artery (author's transl)]. / Die Prinzipien der Entstehung der Druck- und Strompulsformen in der A. carotis communis des Menschen.

In order to clarify the genesis of the characteristic pressure and flow pulse contours of the common carotid artery of man, at first transcutaneous pulse recordings were carried out on healthy resting subjects during breathing of room air and of a mixture of 95% O2 and 5% CO2 (Carbogen). The latter was used to cause vasodilation of the cerebral resistance vessels and thus reducing the peripheral reflection coefficient. Secondly pulse constructions were performed by means of a theoretical inhomogeneous tube model using a digital computer. A side branch of this model represented the carotid artery. The pressure pulse of the aortic arch of the model was used as generating pulse for the carotid system. A satisfactory simulation of the carotid pressure and flow pulse contours under normal conditions and during peripheral vasodilation requires an intermediate reflection (positive for antegrade waves) at a site near the middle of the total transmission time of the carotid model system. The adequacy of the model is demonstrated by comparison of the recorded and constructed pulses.