Contribution of the finite volume point dilution method for measurement of groundwater fluxes in a fractured aquifer.

Measurement of groundwater fluxes is the basis of all hydrogeological study, from hydraulic characterization to the most advanced reactive transport modeling. Usual groundwater flux estimation with Darcy's law may lead to cumulated errors on spatial variability, especially in fractured aquifers where local direct measurement of groundwater fluxes becomes necessary. In the present study, both classical point dilution method (PDM) and finite volume point dilution method (FVPDM) are compared on the fractured crystalline aquifer of Ploemeur, France. The manipulation includes the first use of the FVPDM in a fractured aquifer using a double packer. This configuration limits the vertical extent of the tested zone to target a precise fracture zone of the aquifer. The result of this experiment is a continuous monitoring of groundwater fluxes that lasted for more than 4 days. Measurements of groundwater flow rate in the fracture (Q(t)) by PDM provide good estimates only if the mixing volume (V(w)) (volume of water in which the tracer is mixed) is precisely known. Conversely, the FVPDM allows for an independent estimation of V(w) and Q(t), leading to better precision in case of complex experimental setup such as the one used. The precision of a PDM does not rely on the duration of the experiment while a FVPDM may require long experimental duration to guarantees a good precision. Classical PDM should then be used for rapid estimation of groundwater flux using simple experimental setup. On the other hand, the FVPDM is a more precise method that has a great potential for development but may require longer duration experiment to achieve a good precision if the groundwater fluxes investigated are low and/or the mixing volume is large.

Interaction forces between a deformable air bubble and a spherical particle of tuneable hydrophobicity and surface charge in aqueous solutions.

Interaction forces between an air bubble and a spherical particle of moderate and tuneable surface charge density and hydrophobicity in aqueous solutions were measured using atomic force microscopy. Bitumen coated silica spheres were used as model particles of tuneable charge density and hydrophobicity due to pH-dependent ionisation of carboxylic acids at bitumen-water interfaces. The measured force profiles showed a long-range repulsion prior to jump into contact, indicating the rupture of intervening liquid film between the bitumen and bubble surfaces. The long-range repulsive force increased with increasing pH. The measured force profiles were analysed by adopting the model originally developed by White and co-workers to account for deformation and change in shape of bubbles before rupture of the intervening liquid film. Satisfactory agreement between the theory and measured force profiles was obtained, showing the suitability of the model to describe the measured interaction forces. The model was then used to study the physical parameters on the particle-bubble interaction forces prior to three phase contact line (TPCL) formation. The hydrophobic decay length, surface potential and size of bubble and probe particles, and ionic strength of the medium (KCl concentration) were found to have a strong influence on the predicted force profiles.

Synchronization of chaotic networks with time-delayed couplings: an analytic study.

Networks of nonlinear units with time-delayed couplings can synchronize to a common chaotic trajectory. Although the delay time may be very large, the units can synchronize completely without time shift. For networks of coupled Bernoulli maps, analytic results are derived for the stability of the chaotic synchronization manifold. For a single delay time, chaos synchronization is related to the spectral gap of the coupling matrix. For networks with multiple delay times, analytic results are obtained from the theory of polynomials. Finally, the analytic results are compared with networks of iterated tent maps and Lang-Kobayashi equations, which imitate the behavior of networks of semiconductor lasers.

Zero lag synchronization of chaotic systems with time delayed couplings.

Zero-lag synchronization (ZLS) between chaotic units, which do not have self-feedback or a relay unit connecting them, is experimentally demonstrated for two mutually coupled chaotic semiconductor lasers. The mechanism is based on two mutual coupling delay times with certain allowed integer ratios, whereas for a single mutual delay time ZLS cannot be achieved. This mechanism is also found numerically for mutually coupled chaotic maps where its stability is analyzed using the Schur-Cohn theorem for the roots of polynomials. The symmetry of the polynomials allows only specific integer ratios for ZLS. In addition, we present a general argument for ZLS when several mutual coupling delay times are present.

On chaos synchronization and secure communication.

Chaos synchronization, in particular isochronal synchronization of two chaotic trajectories to each other, may be used to build a means of secure communication over a public channel. In this paper, we give an overview of coupling schemes of Bernoulli units deduced from chaotic laser systems, different ways to transmit information by chaos synchronization and the advantage of bidirectional over unidirectional coupling with respect to secure communication. We present the protocol for using dynamical private commutative filters for tap-proof transmission of information that maps the task of a passive attacker to the class of non-deterministic polynomial time-complete problems.

Feedbacks between hydrological heterogeneity and bioremediation induced biogeochemical transformations.

For guiding optimal design and interpretation of in situ treatments that strongly perturb subsurface systems, knowledge about the spatial and temporal patterns of mass transport and reaction intensities are important. Here, a procedure was developed and applied to time-lapse concentrations of a conservative tracer (bromide), an injected amendment (acetate) and reactive species (iron(II), uranium(VI) and sulfate) associated with two field scale biostimulation experiments, which were conducted successively at the same field location over two years. The procedure is based on a temporal moment analysis approach that relies on a streamtube approximation. The study shows that biostimulated reactions can be considerably influenced by subsurface hydrological and geochemical heterogeneities: the delivery of bromide and acetate and the intensity of the sulfate reduction is interpreted to be predominantly driven by the hydrological heterogeneity, while the intensity of the iron reduction is interpreted to be primarily controlled by the geochemical heterogeneity. The intensity of the uranium(VI) reduction appears to be impacted by both the hydrological and geochemical heterogeneity. Finally, the study documents the existence of feedbacks between hydrological heterogeneity and remediation-induced biogeochemical transformations at the field scale, particularly the development of precipitates that may cause clogging end flow rerouting.

Synchronization of networks of chaotic units with time-delayed couplings.

A network of chaotic units is investigated where the units are coupled by signals with a transmission delay. Any arbitrary finite network is considered where the chaotic trajectories of the uncoupled units are a solution of the dynamic equations of the network. It is shown that chaotic trajectories cannot be synchronized if the transmission delay is larger than the time scales of the individual units. For several models the master stability function is calculated which determines the maximal delay time for which synchronization is possible.

Characterization of subsoil heterogeneity, estimation of grain size distribution and hydraulic conductivity at the Krauthausen test site using Cone Penetration Test.

A Cone Penetration Test (CPT) survey with a high spatial resolution was performed in order to investigate the stratigraphy as well as the spatial variability of various soil properties of the Krauthausen test site. Analyses of the CPT measurements showed the subsurface to be dominated by a planar layered structure. Variogram analysis of the various CPT parameters disclosed that within each layer the soil properties have an anisotropic spatial correlation structure. A correlation analysis of the measured CPT data and co-located grain size distributions from soil samples was performed. Since the correlation coefficients were greater equal to 0.7, a reliable empirical relationship between the data sets could be developed. Based on this empirical relationship grain size distributions were estimated at CPT locations. The statistical processing of estimated and measured grain size distributions with respect to their spatial correlation structure disclosed good agreement between the data sets. The estimated grain size distributions from CPT data were used to estimate the hydraulic conductivity in the aquifer. The results provide detailed information of the spatial heterogeneity of the hydraulic conductivity at Krauthausen test site. The validation of these results, using a prior investigation of hydraulic conductivity statistics, suggests the CPT a fast and inexpensive tool for the estimation of three dimensional hydraulic conductivity fields with sufficient accuracy.

[The treatment of carpal collapse: proximal row carpectomy or limited midcarpal arthrodesis? A comparative study]. / Der fortgeschrittene karpale Kollaps: Resektion der proximalen Handwurzelreihe (PRC) oder mediokarpale Teilarthrodese? Eine vergleichende Studie.

Between July 2000 and February 2002, 26 wrists were treated because of SLAC, SNAC and radiocarpal arthrosis after fracture of the distal radius. In 14 cases proximal row carpectomy (PRC) and in twelve cases limited midcarpal arthrodesis (LWF) was performed. Follow-up was after a mean time of 16.8 (PRC) and 13.7 months (LWF) on ten wrists each. There was one complication in the PRC group and two in the LWF group. In all cases significant reduction of extension/flexion was observed with a mean range of motion of 69 degrees (PRC) and 71 degrees (LWF). The reduction of pain postoperatively was almost identical in both groups. Comparing grip-strength to the unoperated hand, we measured 26 compared to 39 kg in the PRC group and 28 compared to 46 kg in the LWF group, respectively. The DASH-score for the LWF group was 30 points and therefore better than the 36 points for the PRC group.

[Sigmoidoperianal fistula associated with diverticulitis and Cul de Sac situation--diagnostics and therapy]. / Sigmoidoperianale Fistel durch Sigmadivertikulitis bei Cul de Sac-Syndrom--Diagnostik und Therapie.

We report on the case of a 64-year-old female patient who presented herself in our outpatient clinic because of a perianal fistula with recurrent abscesses. We describe the step diagnostics and the surgical treatment of the causal sigmoido-perianal fistula with diverticulitis and Cul de sac situation. Clinical examination, fistulography, colonoscopy and MRT were part of the precise representation and preparation for the high anterior rectosigmoidal resection with simultaneous rectopexy according to Sudeck which were performed without complications. The sigmoidoperianal fistula must be taken into account as a differential diagnosis of a recalcitrant high perianal fistula.

S-100b as a screening marker of the severity of minor head trauma (MHT)--a pilot study.

Due to its neural tissue specificity S-100b is considered as a screening marker of cerebral injury in head trauma patients. However, the occurrence and relevance of an increased S-100b serum level in minor head trauma (MHT) is still debated. Therefore, the purpose of our study was to evaluate the diagnostic utility of S-100b measurements in a level I trauma center emergency room (ER). Eighty patients presenting with clinical symptoms of MHT (GCS score of 13-15, transitory loss of consciousness, amnesia, nausea) were prospectively recruited. Blood samples were drawn at 0 h, 6 h and 24 h after admission, and a cerebral computed tomography (CT) was performed. The reference group consisted of 10 patients with severe head injury (GCS score < 8), the control group of 20 healthy volunteers. Concentrations of S-100b in serum were determined by an immunoluminometric assay. The results were compared with the plasma levels of polymorphonuclear (PMN) elastase as an established general trauma marker. In the MHT group, the S-100b serum level revealed 1.26 +/- 0.57 ng/ml at study entry (73.46 +/- 47.53 min after trauma). In comparison, the S-100b concentration was significantly elevated in patients with severe head trauma (5.26 +/- 1.65 ng/ml, p = 0.009), but no significant difference became evident in relation to the control group (0.05 +/- 0.01 ng/ml). Starting values of PMN elastase in plasma amounted to 66.40 +/- 14.92 ng/ml in severe trauma, and to 60.52 +/- 10.75 ng/ml in MHT showing significant differences only in relation to the control group (23.36 +/- 1.53 ng/ml). When correlated with the severity of the later clinical course, the first S-100b measurements exhibited steadily increasing values as demonstrated in MHT outpatients (0.29 +/- 0.11 ng/ml), MHT in-hospital patients (0.70 +/- 0.19 ng/ml) and MHT intensive care unit patients (5.03 +/- 3.18 ng/ml). PMN elastase levels revealed no significant differences concerning the three MHT subgroups. Thus, in contrast to the general trauma marker PMN elastase, assessment of the specific neuroprotein S-100b early after traumatic insult appears to be a promising laboratory marker for the prognosis of the severity of brain injury in MHT patients. Nevertheless, further investigations are required to better understand its predictive value.

The influence of visual field disorders on visual identification tasks.

Visual identification of shapes, figures, objects and faces was tested in a group of 26 patients with homonymous field defects due to unilateral "posterior" brain damage. In addition, a search test was used for evaluation of the effect of visual field loss on visual information acquisition. Of the patients, 5 performed entirely normally, i.e. errorless and within age-matched time limits, in all tests. The majority of patients (n = 15) also performed correctly but required significantly more time than normals. In contrast, 6 patients showed a rather specific impairment in visual identification tasks. It is argued that visual field loss per se does not impair visual identification but may affect visual search and, thus, information acquisition. Visual identification may be impaired, however, if brain damage involves the inferotemporal cortex.

Theoretical conformational analysis of enkephalin analogues related to fluorescence and n.m.r. measurements in aqueous solution.

The properties related to non-radiative energy transfer of a number of enkephalin analogues with tryptophan substituted for phenylalanine in position 4 and n.m.r. 3JNH-C alpha H coupling constants of corresponding [Phe4]-enkephalin analogues are being derived from semi-empirical conformational energy. The molecules considered contain a glycyl, a D-alanyl or an L-alanyl as second residue; two of the compounds are N-methylated at position 4 or 5. The [Trp4]-enkephalin analogues and the corresponding [Phe4]-enkephalin analogues display nearly parallel affinities in the opiate receptor binding assay (Schiller et al. (1). The comparison of computed and experimental properties shows that an ensemble of conformers is a satisfactory representation of the state of these molecules in water.

The frequency distribution of the orientation factor of dipole-dipole interaction.

An analytical expression is derived for the frequency distribution of the orientation factor in the non-radiative transfer of electronic excitation energy.

Intramolecular energy transfer in molecules with a large number of conformations.

The equations representing the decay kinetics of fluorescence of a donor luminophore in the presence of an acceptor in the same flexible molecule are discussed. The assumption that distances between luminophores attached to chain ends are not correlated with the relative orientations of luminophores is tested by theoretical calculations for the unperturbed chains Tyr-(Ala)(n)-Tyr with n equal to 4 and 9. It appears that for these chains, in which the conformation is dominated by entropic factors, the above assumption is satisfactory even for chains with a small number of repeating units (n = 4).

Theoretical determination of helix-coil parameter sigma from a model of partly helical polypeptide chain.

The Zimm and Bragg parameter sigma is calculated numerically for poly(L-alanine), polyglycine, and the copolymers of L-alanine and glycine using the molecular theory of s and sigma as developed by Go, Go, and Scheraga in a modified formulation. In this formulation, sigma is obtained from the partition function of the whole chain in the helix-coil transition region and represents therefore the contributions from the ends of helical and coil sequences and from the interactions between atoms in a coil sequence with those in the neighboring helical sequence. When the parameter sigma is calculated numerically from a hard-sphere potential, it appears that steric intractions between atoms in the coil sequence with atoms in the neighboring helical sequence, which have been neglected in previous calculations, contribute significantly to the value of sigma. Owing to these interactions the entropy of the coil sequence as well as sigma decrease, but the decrease of sigma is larger in poly(L-alanine) than in polyglycine, because of the higher flexibility of the monomer in polyglycine. The numerical value of sigma for polyglycine compared with that of poly(L-alanine) might be overestimated however by the model presented here due to approximations inherent in the hard-sphere treatment and because only regular helical sequences are considered.