Quantifying BTEX in aqueous solutions with potentially interfering hydrocarbons using a partially selective sensor array.

Partially selective gold nanoparticle sensors have the sensitivity and selectivity to discriminate and quantify benzene, toluene, ethylbenzene, p-xylene and naphthalene (BTEXN) at concentrations relevant to the US Environmental Protection Agency. In this paper we demonstrate that gold nanoparticle chemiresistors can do so in the presence of 16 other hydrocarbons and that they did not reduce the discriminating power of the array. A two-level full factorial designed experiment was performed on unary, binary, ternary, quaternary, quinary combinations of BTEXN analytes with and without the possibly interfering hydrocarbons. The nominal component concentration of the mixtures was 100 µg L(-1), equivalent to approximately 100 parts per billion (ppb). Concentrations predicted with the random forests method had an average root mean square error of 10-20% of the component concentrations. This level of accuracy was achieved regardless of whether or not the 16 possibly interfering hydrocarbons were present. This work shows that the sensitivity and selectivity of gold nanoparticles chemiresistor sensors towards BTEXN analytes are not unduly affected by the other hydrocarbons that are expected to be present at a petroleum remediation site.

Demonstration of nonlinear absorption in Au semi-continuous film by electrical measurement.

We have demonstrated the nonlinear absorption at 532 nm wavelength in an Au semi-continuous film (SF) resulting from smearing of the Fermi distribution and diffusion of conduction electrons into the substrate. The Au SF was irradiated by a pulsed laser with 8 ns pulse width at 532 nm in near resonance with the interband transition of the Au. We determined the temperature increase in the SF for different intensities by electrical measurement. We calculated the temperature increase by using a 1D heat transport equation; comparing the results of the calculation with measured values for the temperature increase, revealed the nonlinear absorption in the Au SF. We employed this deviation from linear behaviour to determine the nonlinear absorption coefficient.

Physical and chemical characterization of dentin surface following treatment with NovaMin technology.

OBJECTIVE: The aim of this study was to characterize, in vitro, the mode of action of calcium sodium phosphosilicate (NovaMin) in occluding dentin tubules for the purpose of treating dentin hypersensitivity. METHODS: Calcium sodium phosphosilicate (CSPS) was combined with artificial saliva on surfaces of prepared dentin discs. The layer formed was initially examined by a scanning electron microscope (SEM). Focused ion beam (FIB) milling was used to make bulk cross-sections and thin film lamellae. Low kV scanning transmission electron microscopy (STEM), energy dispersive x-ray spectroscopy (EDS), and selected area electron diffraction were then used to characterize, chemically and structurally, the layer formed and the material occluding the tubules. Experiments were also performed to assess the suitability of using an environmental scanning electron microscope (ESEM) in wet mode to follow the transition from CSPS to hydroxyapatite. RESULTS: SEM imaging showed that a layer was formed on the treated dentin samples, and that this layer occluded tubules. Chemical and structural analysis of this material showed that it was hydroxyapatite-like. The wet mode ESEM experiments demonstrated that this technique has the potential to follow the transition from CSPS to the crystalline hydroxyapatite material. CONCLUSION: The use of modern imaging and analysis techniques has demonstrated, in vitro, the reaction of CSPS from an amorphous material to a crystalline hydroxyapatite-like material. These experiments confirmed an occlusion mode of action for CSPS for the treatment of dentin hypersensitivity.

Thermoelectrics in an array of molecular junctions.

The room temperature thermoelectric properties of a three-dimensional array of molecular junctions are calculated. The array is composed of n-doped silicon nanoparticles where the surfaces are partially covered with polar molecules and the nanoparticles are bridged by trans-polyacetylene molecules. The role of the polar molecules is to reduce the band bending in the n-doped silicon nanoparticles and to shift the electronic resonances of the bridging molecules to the nanoparticle conduction band edges where the molecular resonances act as electron energy filters. The transmission coefficients of the bridging molecules that appear in the formulas for the Seebeck coefficient, the electrical conductance, and the electronic thermal conductance, are calculated using the nonequilibrium Green's function technique. A simple tight-binding Hamiltonian is used to describe the bridging molecules, and the self-energy term is calculated using the parabolic conduction band approximation. The dependencies of the thermoelectric properties of the molecular junctions on the silicon doping concentration and on the molecule-nanoparticle coupling are discussed. The maximal achievable thermoelectric figure of merit ZT of the array is estimated as a function of the phononic thermal conductance of the bridging molecules and the doping of the nanoparticles. The power factor of the array is also calculated. For sufficiently small phononic thermal conductances of the bridging molecules, very high ZT values are predicted.

Vascular endothelial growth factor is produced by peritoneal fluid macrophages in endometriosis and is regulated by ovarian steroids.

Angiogenesis is important in the pathophysiology of endometriosis, a condition characterized by implantation of ectopic endometrium in the peritoneal cavity. Vascular endothelial growth factor (VEGF) is a potent angiogenic factor involved in physiological and pathological angiogenesis, and elevated levels of VEGF are found in peritoneal fluid of patients with endometriosis. Our aim was to investigate the site of expression and regulation of VEGF in endometriosis. VEGF immunoreactivity was found in tissue macrophages present in ectopic endometrium and in activated peritoneal fluid macrophages. Macrophage activation was highest in women with endometriosis, and media conditioned by peritoneal fluid macrophages from these women caused a VEGF-dependent increase in endothelial cell proliferation above that seen from normal women. Peritoneal fluid macrophages secreted VEGF in response to ovarian steroids, and this secretion was enhanced after activation with lipopolysaccharide. Peritoneal fluid macrophages expressed receptors for steroid hormones. VEGF receptors flt and KDR (kinase domain receptor) were also detected, suggesting autocrine regulation. During the menstrual cycle, expression of flt was constant but that of KDR was increased in the luteal phase, at which time the cells migrated in response to VEGF. KDR expression and the migratory response were significantly higher in patients with endometriosis. This study demonstrates that activated macrophages are a major source of VEGF in endometriosis and that this expression is regulated directly by ovarian steroids.

Applications of SNMS in archaeometry.

The recently developed High Frequency Mode HFM of electron gas SNMS allows investigations on insulating samples with the well known advantages of the SNMS Direct Bombardment Mode DBM for the analysis of conducting samples. HFM has been applied to analyses of different historic ceramic and glass samples in order to demonstrate the possibilities of SNMS in this field. It is shown that manufacturing places of ceramic samples could be distinguished by SNMS mass spectra ("fingerprints"). Furthermore questions of the constituents of colour remains on a painted ceramic ("Kaisermedaillon") could be answered by our SNMS analyses. SNMS investigations have been also applied to corrosion phenomena on different glass samples.

A cooling chain for studies of cryofixed biological specimens by scanning transmission electron microscopy and X-ray microanalysis.

A cooling chain is described which enables the transfer of frozen hydrated biological specimens (ultrathin cryosections as well as about 1 micrometer thick cultured cells) from a cryoultramicrotome into a scanning transmission electron microscope with a field emission gun. Transfer is done at 118 K, specimen temperature in the microscope is 165 K. Sublimation processes are controlled visually and by mass spectrometry. Electron micrographs and X-ray microanalytical spectra of cryofixed unstained tissue culture cells and rat liver tissue sections are described and discussed. Contamination of the specimen is much reduced by use of the cold stage.

Transmission of IBR/IPV virus in bovine semen: A case report.

The transmission of IBR/IPV virus in imported semen is reported. Some of the inseminated animals showed seroconversion and, in accordance with Swiss law, had to be eliminated. To avoid such cases in international sperm exchange, methods of detecting IBR/IPV virus need to be improved. In the longer term, AI centres must be established in which all bovine stock is seronegative for IBR/IPV.

ASIF External Fixation as a Means to Control Fracture Healing by Ring Force Measuring Box.

The development and clinical application of a force measurement device compatible with the ASIF external fixator are described. Use of the force ring measuring box not only confirms the mechanical stability of external fixation, but also appears useful in postoperative management of compressive forces at the fracture site.

[Development of habitual shoulder dislocation]. / Die Entwicklung zur habituellen Schulterluxation.

The starting point of the retrospective analysis of 177 primary dislocations was the question of frequency of habitual dislocations, the correlation between habitual dislocation and time of early immobilisation, as well as the search for additional statements which would result in a differentiated therapy. 18.1% habitual dislocations were seen to develop, mostly after immobilisation for less than three weeks. It is an interesting fact that the technique of immobilisation made no difference. We found that after the first even there was generally no loss in function, whereas 14.5% of the men and 34.3% of the women complained of severe subjective symptoms. The 12 patients who underwent an operation because of habitual dislocation suffered neither from dysfunction nor from painful movement, and no dislocation was found. The rate of habitual dislocation in our patients showed a lower rate of dislocation of the shoulder joint. We found 18.1% dislocations, whereas the literature showed an average quota of 30%. To improve the results we recommend a special X-ray technique following the first reposition. In the age group between 20 and 30 years, which is most susceptible, we also recommend arthrography and arthroscopy of the shoulder joint. To improve typical lesions, such as osseous rupture of the capsule or what is known as Hill-Sachs lesions, primary operation is discussed as an alternative treatment.

[The crossed-leg flap with the fixateur externe technic]. / Der gekreuzte Beinlappen mit der Fixateur-externe-Technik.

As an introduction statements from literature and own experience are used to show and evaluate the present possibilities for the coverage of skin and soft tissue defects. As a routine operation the stemmed cross-leg flap is further on indicated on the lower leg. For the immobilisation of the legs wer use the fixateur externe. This kind of fixation has got advantages compared to plaster casts: optimal position of the two lower legs to each other, a local and general handling of the nursing with only few problems and a subjective relief for the patient. Moreover, flaps and transplant base can be connected permanently and without tension during the operation by fine adjustment of the fixateur externe, while postoperative functional strains of the neighbouring joints are possible to a certain degree. The technique of assembling the fixateur externe, i.e. immobilisation of the legs by Schanz screws and the AO-tubular system is described in detail. The results of a collective of 21 patients with mostly infectious soft tissue defects after an osteomyelitis of the tibia were checked by control examinations. There were no disadvantages for the donor leg following the use of Schanz screws. According to the presented results the settling of cross-leg flaps has been improved by the fixateur-externe-technique. Together with other authors we can recommend this method.

[Rupture of the Achilles tendon--case report of a rare form of Achilles tendon damage]. / Achillessehnenlösung--Kasuistik einer seltenen Form der Achillessehnenschädigung.

The great increase in the number of persons engaged in sports in the 30-50 years age group has led to a marked increase in injuries of the tendon of Achilles. In this case there is tearing loose of the Achilles tendon; the bone and the tendon come apart, as in a rupture of Sharpey's fibres. The tack was made in webbing the tendon of Achilles with polydioxanone ligaments to the tuberosity of calcaneus. The question about prophylactic webbing of the degenerated tendon of Achilles on the other side has to be discussed. Assessment of this injury from the viewpoint of the accident insurance company is explained.