Fabrication of Robust Reference Tips and Reference Electrodes for Kelvin Probe Applications in Changing Atmospheres.

The scanning Kelvin probe (SKP) is a versatile method for the measurement of the Volta potential difference between a sample and the SKP-tip (ΔψsampleSKP-tip). Based on suitable calibration, this technique is highly suited for the application in corrosion science due to its ability to serve as a very sensitive noncontact and nondestructive method for determining the electrode potential, even at buried interfaces beneath coatings or on surfaces covered by ultrathin electrolyte layers, which are not accessible by standard reference electrodes. However, the potential of the reference (i.e., the SKP-tip) will be influenced by variations of the surrounding atmosphere, resulting in errors of the electrode potential referred to the sample. The objective of this work is to provide a stable SKP-tip which can be used in different or changing atmosphere, e.g., within a wide range of relative humidity (approximately 0-99%-rh) or varying O2 partial pressure, without showing a change of its potential (note that the work functions measured in non-UHV atmospheres are electrochemical in nature [Hausbrand et al. J. Electrochem. Soc. 2008, 155 (7), C369-C379], and hence in the following we will refer to the potential of the SKP-tip instead of its work function). In that regard, the SKP-tip is in a first approach modified with self-assembled monolayers (SAMs) in order to create a hydrophobic barrier between the metallic surface and the surrounding atmosphere. The changes in potential upon varying relative humidity (ΔErh) of different bare metallic substrates are quantified, and it is shown that these potential differences cannot be minimized by SAMs. On the contrary, the ΔErh increases for every examined material system modified with SAMs. The major explanation for this observation is the dipole layer at the interface metal|SAM, causing an interfacial adsorption of water molecules even in a preferred orientation of their dipole moments, which leads to a changed work function and consequently to the correlated electrode potential. However, thin paraffin coatings were found to lead to a strongly reduced ΔErh, finally validated with novel robust Ag/Ag+ reference electrodes. It is also shown that nickel as SKP-tip material is seemingly more stable in varying atmospheric conditions compared to widely used Ni/Cr, stainless steel, or gold as SKP-tip material.

Element-resolved corrosion analysis of stainless-type glass-forming steels.

Ultrathin passive films effectively prevent the chemical attack of stainless steel grades in corrosive environments; their stability depends on the interplay between structure and chemistry of the constituents iron, chromium, and molybdenum (Fe-Cr-Mo). Carbon (C), and eventually boron (B), are also important constituents of steels, although in small quantities. In particular, nanoscale inhomogeneities along the surface can have an impact on material failure but are still poorly understood. Addressing a stainless-type glass-forming Fe50Cr15Mo14C15B6 alloy and using a combination of complementary high-resolution analytical techniques, we relate near-atomistic insights into increasingly inhomogeneous nanostructures with time- and element-resolved dissolution behavior. The progressive elemental partitioning on the nanoscale determines the degree of passivation. A detrimental transition from Cr-controlled passivity to Mo-controlled breakdown is dissected atom by atom, demonstrating the importance of nanoscale knowledge for understanding corrosion.

European proficiency study with control serum for the tumor marker CA 19-9 measured on different test systems.

BACKGROUND: Reliable and precise CA 19-9 testing is required for the long-term follow-up of patients with pancreatic carcinoma during therapy. The aim of this longitudinal proficiency study was to evaluate the comparability, linearity, and precision of CA 19-9 determinations performed in different laboratories using currently available test systems under routine conditions. METHODS: During the one year study period, 15 laboratories applied 7 different tests and included a liquid BIOREF control serum with pancreatic carcinoma derived CA 19-9 in their routine testing and quality control procedures. The results were collected centrally and evaluated statistically. RESULTS: The comparability of CA 19-9 results is limited especially when different tests are used, albeit, some tests show a good correlation: The CA 19-9 values obtained by different laboratories using different test systems vary up to a factor of 2. The precision of CA 19-9 determinations was acceptable in most laboratories with coefficients of variation ranging between very low 3.2% and high 17.8%. The imprecision was slightly increased when automatic dilution procedures of the analysers were used. CONCLUSIONS: The comparability of CA 19-9 test results must be improved. The precision is acceptable in most cases. In order to monitor key performance parameters, every laboratory should participate in external quality assessment schemes and should perform a routine internal quality control with a control serum independent from the test kit manufacturer.

[Current TNM system of the UICC/AJCC : the prognostic significance for differentiated thyroid carcinoma]. / Aktuelles TNM-System der UICC/AJCC : Prognostische Bedeutung beim differenzierten Schilddrüsenkarzinom.

BACKGROUND: The aim of study was an evaluation of prognostic factors of the current TNM version (UICC/AJCC 2009, 7th revision) for differentiated thyroid carcinoma (DTC). PATIENTS AND METHODS: A total of 368 patients with DTC (papillary thyroid carcinoma [PTC] n = 269, follicular thyroid carcinoma [FTC] n = 99) were included. Disease-specific survival (DSS) was calculated based on the different TNM stages (mean follow-up 60 ± 37.5 months). RESULTS: When compared to patients with FTC, PTC patients had smaller tumors (diameter 19 mm versus 33 mm), more often lymph node metastases (40.9% versus 9.1%) but less frequent distant metastases (2.6 versus 13.1%) and poorly differentiated variants (PDTC 3.0% versus 8.1%). The 5-year and 10-year DSS for PTC versus FTC were 97.3% versus 91.5% and 96.2% versus 91.5% (p = 0.086), respectively. When comparing different TNM categories between well-differentiated PTC and FTC, no statistically significant differences were found but PDTCs, had a significantly worse DSS. CONCLUSIONS: The current TNM system is a sufficient tool for predicting DSS in well-differentiated PTC. In FTC, the extent of capsular and vascular invasion should also be considered. The implementation of a specific TNM system for PDTC needs to be confirmed in further studies.

Multicentre evaluation of performance of C-reactive protein analysis over a one-year period.

This communication deals with a longitudinal evaluation of C-reactive protein (CRP) analysis during a one-year period using a single lot of liquid control sera (3 levels) (BIOREF-CRP levels 1, 2 and 3) in different laboratories. A total of 652 sets of data were returned from 20 participating laboratories using 13 different reagent-measuring device combinations. The use of the control materials was defined in a standard operating procedure. Data was returned to the organizers on a monthly basis and questions could be asked or problems presented during the evaluation period. Although the performance of different reagents varied, the control materials were shown to be stable over the whole of the evaluation period when stored at 4-7 degrees C in a refrigerator/cold room. Typical problems were encountered, examples of which are presented here in graphical and tabular form.

Experimental observation of temporal soliton molecules.

A bound state of temporal solitons in optical fibers is predicted numerically and demonstrated experimentally. It is appropriately described as a pair of bright solitons, bound together by a dark soliton. This structure exists only in dispersion-managed fiber and is different from bound solitons in fiber lasers.

Effects of a combination of rhGH and metformin on adiponectin levels in patients with metabolic syndrome.

Adiponectin is a recently discovered adipocytokine that correlates negatively with body mass index and body fat. In patients with GH deficiency, treatment with recombinant human growth hormone (rhGH) reduces body fat mass and thus may also have a favorable effect in patients with metabolic syndrome, and would also be expected to increase adiponectin levels. However, due to its diabetogenic effect, rhGH treatment also bears an increased risk for the development of type 2 diabetes mellitus. We conducted a 18-month randomized, double-blind, placebo-controlled study to assess the effect of rhGH in combination with metformin (MGH) in 14 obese men (7 MGH; 7 Metformin+Placebo, 54 +/- 2 years, BMI 33.0 +/- 1.2 kg/m(2)) with mildly elevated fasting plasma glucose (FPG) at screening (6.1-8.0 mmol/l). All patients received metformin (850 mg twice daily) for treatment of type 2 diabetes mellitus/impaired glucose tolerance, either alone or in combination with rhGH (daily dose 9.5 mug/kg body weight). Glucose disposal rate (GDR) was measured using the euglycemic hyperinsulinemic clamp technique, and body composition was measured by DEXA at 0 and 18 months. After 18 months, the mean adiponectin concentration increased by 32 +/- 11 % (p = 0.018) in the MGH group and did not change in the MP group (- 10 +/- 13 %; p = n. s.). The difference in relative changes in adiponectin levels between the two groups after 18 months was statistically significant (p = 0.026). Improvement in insulin sensitivity (GDR) correlated positively with adiponectin levels (r = 0.73; p = 0.004). In conclusion, the additional administration of rhGH increased adiponectin levels in patients with metabolic syndrome, indicating its potential role in adiponectin-associated insulin sensitivity alterations.

Chains of temporal dark solitons in dispersion-managed fiber.

Attractive interaction of dark dispersion-managed (DM) solitons is observed numerically. For certain initial separations chains of bound dark DM solitons are found. The chains can have various lengths (up to 12 solitons are shown), and the nearest-neighbor separations can take several values-all the same or mixed.

Electroreduction of oxygen on octadecylmercaptan self-assembled monolayers.

The reduction of oxygen has been studied on octadecylmercaptan self-assembled monolayers adsorbed on gold substrates in borate buffer solutions with a rotating disc electrode. A great inhibition of the oxygen reduction and other electrochemical reactions by these monolayers has been found. However, after polarisation at -0.80 V(SHE) the protecting properties of the film against electron transfer reactions are lost, and a behaviour similar to bare gold is observed. Ex situ XPS indicates that the thiol monolayer has not been desorbed to a large extent during oxygen reduction. Disorders of the monolayer structure and desorption of thiol molecules are proposed as the main reasons for the accessibility of electrochemical reactions to the surface.

Adsorption of self-assembled monolayers of mercaptan on gold.

XPS and AES are suitable techniques for studying organic monolayers on metals if radiation doses are kept low. The adsorption of self-assembled (SA) mercaptan monolayers on gold is a process in two stages. The adsorption to near completeness is very rapid. However, the process of orientation of the carbon chains, which is responsible for the blocking of electrochemical reactions takes much longer, as could be shown by ARXPS (angle resolved X-ray photo electron spectroscopy). Adsorption under potential control allows electrochemical experiments during the adsorption process as e.g. the measurement of the capacity of the electric double layer. Furthermore the control of the potential guarantees sure that the metal/liquid interface is well defined during the adsorption process.

Investigation of the delamination of polymer films from galvanized steel with the Scanning Kelvinprobe.

The applicability of a new experimental technique - the Scanning Kelvinprobe - for the analysis of the delamination of polymer films from galvanized steel is discussed. Defect ions having direct access to the zinc/ polymer interface will diffuse along this interface, a process, which can be monitored by the Kelvinprobe in a very early state with a high local resolution. After incorporation of ions a galvanic element is formed, the local cathode being at the delamination front, where oxygen is reduced, and the local anode at the zinc coated defect. For the model polymer under investigation the interaction between the film and the substrate is weak and the rate determining step for the delamination is the diffusion of cations from the local anode to the local cathode. An exposure to a highly CO(2)-containing atmosphere before the delamination prolongs the incubation time of delamination. If there is no zinc layer at the defect, an anodic delamination mechanism occurs. Zinc is dissolved under the polymer film, while the steel surface is cathodically protected.

The use of microsatellites in zygosity diagnosis of twins.

Although numerous genetic and anthropological markers are available for determining zygosity of twins, there is still a need for a more practical and informative method in zygosity diagnosis. Dinucleotide repeats or other short repeats (microsatellites) are highly variable between individuals and offer a simple, fast, cheap, and exact approach for zygosity determination. The feasibility of a set of microsatellites to be used for this purpose is demonstrated.

Disseminated toxoplasmosis with sepsis in AIDS.

A 24-year-old woman with acquired immunodeficiency syndrome was admitted with septic fever of unknown origin and a 2-week history of diarrhea. Clinical diagnostic procedures did not reveal the cause of sepsis. Broad-spectrum antibiotics and intensive symptomatic therapy could not prevent progressive deterioration. The patient developed septic shock and consumptive coagulopathy and died 6 days after admission. Autopsy revealed disseminated infection with toxoplasma gondii and multiple organ manifestations. We conclude that disseminated toxoplasmosis should be considered in AIDS patients with septic disease of unknown origin. Extremely elevated lactate dehydrogenase may suggest disseminated toxoplasma gondii infection. New procedures such as polymerase chain reaction for detection of toxoplasmosis may be helpful diagnostic tools.