High-resolution summer temperature reconstruction from Lake Silvaplana based on in-situ reflectance spectroscopy

Annually laminated (varved) sediments of proglacial Lake Silvaplana (46 ̊27’N, 9 ̊48’E, 1791 m a.s.l., Engadine, eastern Swiss Alps) provide an excellent archive for quantitative high-resolution (seasonal – annual) reconstruction of high- and lowfrequency climate signals back to AD 1580. The chronology of the core is based on varve counting, Cs-137, Pb-210 and event stratigraphy. In this study we present a reconstruction based on in-situ reflectance spectroscopy. In situ reflectance spectroscopy is known as a cost- and time-effective non destructtive method for semi-quantitative analysis of pigments (e.g., chlorines and carotenoids) and of lithoclastic sediment fractions. Reflectance-dependent absorption (RDA) was measured with a Gretac Macbeth spectrolino at 2 mm resolution. The spectral coverage ranges from 380 nm to 730 nm at 10 nm band resolution. In proglacial Lake Silvaplana, 99% of the sediment is lithoclastic prior to AD 1950. Therefore, we concentrate on absorption features that are characteristic for lithoclastic sediment fractions. In Lake Silvaplana, two significant correlations that are stable in time were found between RDA typical for lithoclastics and meteorological data: (1) the time series R 570 /R 630 (ratio between RDA at 570 nm and 630 nm) of varves in Lake Silvaplana and May to October temperatures at nearby station of Sils correlate highly significantly (calibration period AD 1864 – 1951, r = 0.74, p < 0.01 for 5ptsmoothed series; RMSE is 0.28 ̊C, RE = 0.41 and CE = 0.38), and (2) the minimum reflectance within the 690nm band (min690) data correlate with May to October (calibration period AD 1864 – 1951, r = 0.68, p < 0.01 for 5pt-smoothed series; RMSE = 0.22 ̊C, RE = 0.5, CE = 0.31). Both proxy series (min690nm and R 570 /R 630 values) are internally highly consistent (r = 0.8, p < 0.001). In proglacial Lake Silvaplana the largest amount of sediment is transported by glacial meltwater. The melting season spans approximately from May to October, which gives us a good understanding of the geophysical processes explaining the correlations between lithoclastic proxies and the meteorological data. The reconstructions were extended back to AD 1580 and show a broad corresponddence with fully independent reconstructions from tree rings and documentary data.

Clinical, histologic, and immunohistochemical analyses of feline squamous cell carcinoma in situ

Actinic keratosis (AK) and Bowenoid in situ carcinoma (BISC) are two distinct forms of in situ squamous cell carcinoma in felines. They usually occur on different locations and present with specific clinical and histologic features. However, in some cases, these diseases cannot be distinguished either clinically or histopathologically. The aim of the present study was to determine the accuracy of diagnosis based on clinical or histologic criteria alone, and whether immunohistochemistry for papillomavirus or p53 can improve the accuracy of diagnosis. A series of in situ squamous cell carcinoma cases (n = 45) were selected according to their location and initial histologic classification and subsequently classified as AK (n = 22) or BISC (n = 23) according to the clinical criteria and were reevaluated histologically by 2 dermatopathologists. All BISC cases and most of the AK cases (n = 15) were confirmed histologically. In 7 cases clinically classified as AK, this diagnosis was not unanimously confirmed histologically because of the presence of overlapping features. P53 immunoreactivity was observed in 11/14 (79%) confirmed AK cases and in 4/22 (18%) BISC cases, while papillomavirus antigen was not detected in any confirmed AK case but was detected in 11/23 (48%) BISC cases. It was concluded that BISC can usually be reliably diagnosed histologically. The histologic diagnosis of lesions clinically suggestive of AK might sometimes be difficult. Results of immunohistochemistry for p53 and papillomavirus antigen were supportive for a role of sun exposure and papillomavirus in the pathogenesis of AK and BISC, respectively.

Electro-oxidation of Au(1 1 1) in contact with aqueous electrolytes: New insight from in situ vibration spectroscopy

We carried out a comprehensive study of Au(1 1 1) oxidation–reduction in the presence of (hydrogen-) sulfate ions on ideally smooth and stepped Au(S)[n(1 1 1)-(1 1 1)] single crystal electrodes using cyclic voltammetry, in situ scanning tunneling microscopy (STM) and vibration spectroscopy, such as surface-enhanced infrared absorption spectroscopy (SEIRAS) and shell-isolated nanoparticle-enhanced Raman spectroscopy (SHINERS). Surface structure changes and the role of surface defects in the potential regions of double layer charging and gold oxidation/reduction are discussed based on cyclic voltammetry and in situ STM data. SEIRAS and SHINERS provide complementary information on the chemical nature of adsorbates. In particular, the potential-dependent formation and stability ranges of adsorbed sulfate, hydroxide-species and of gold surface oxide could be resolved in detail. Based on our experimental observations, we proposed new and extended mechanisms of gold surface oxidation and reduction in 1.0 M H2SO4 and 1.0 M Na2SO4.

An in-situ surface electrochemistry approach toward whole-cell studies: Charge transfer between Geobacter sulfurreducens and electrified metal/electrolyte interfaces through linker molecules

Electrochemical reactivity and structure properties of electrogenic bacteria, Geobacter sulfurreducens (Gs) were studied to explore the heterogeneous electron transfer at the bacteria/electrode interface using electrochemical and in-situ spectroscopic techniques. The redox behavior of Gs adsorbed on a gold electrode, which is modified with a ω-functionalized self-assembled monolayer (SAM) of alkanethiols, depends strongly on the terminal group. The latter interacts directly with outermost cytochromes embedded into the outer membrane of the Gs cells. The redox potential of bacterial cells bound electrostatically to a carboxyl-terminated SAM is close to that observed for bacteria attached to a bare gold electrode, revealing a high electronic coupling at the cell/SAM interface. The redox potentials of bacterial cells adsorbed on amino- and pyridyl-terminated SAMs are significantly different suggesting that the outermost cytochromes changes their conformation upon adsorption on these SAMs. No redox activity of Gs was found with CH3-, N(CH3)3+- and OH-terminated SAMs. Complementary in-situ spectroscopic studies on bacteria/SAMs/Au electrode assemblies were carried out to monitor structure changes of the bacterial cells upon polarization. Spectro-electrochemical techniques revealed the electrochemical turnover of the oxidized and reduced states of outer membrane cytochromes (OMCs) in Gs, providing evidence that the OMCs are responsible for the direct electron transfer to metal electrodes, such as gold or silver, during the electricity production. Furthermore, we observed spectroscopic signatures of the native structure of the OMCs and no conformational change during the oxidation/reduction process of the microorganisms. These findings indicate that the carboxyl-anchoring group provides biocompatible conditions for the outermost cytochromes of the Gs, which facilitate the heterogeneous electron transfer at the microorganism/electrode interface.

Ferrocene-terminated alkanethiol self-assembled monolayers: An electrochemical and in situ surface-enhanced infra-red absorption spectroscopy study

The effect of anions on the redox behavior and structure of 11-ferrocenyl-1-undecanethiol (FcC11) monolayers (SAM) on Au(1 1 1) single crystal and Au(1 1 1-25 nm) thin film electrodes was investigated in 0.1 M solutions of HPF6, HClO4, HBF4, HNO3, and H2SO4 by cyclic voltammetry (CV) and in situ surface-enhanced infrared reflection-absorption spectroscopy (SEIRAS). We demonstrate that the FcC11 redox peaks shift toward positive potentials and broaden with increasing hydrophilicity of the anions. In situ surface-enhanced IR-spectroscopy (SEIRAS) provided direct access for the incorporation of anions into the oxidized adlayer. The coadsorption of anions is accompanied by the penetration of water molecules. The latter effect is particularly pronounced in aqueous HNO3 and H2SO4 electrolytes. The adlayer permeability increases with increasing hydrophilicity of the anions. We also found that even the neutral (reduced) FcC11 SAM is permeable for water molecules. Based on the property of interfacial water to reorient upon charge inversion, we propose a spectroscopic approach for estimating the potential of zero total charge of the FcC11-modified Au(1 1 1) electrodes in aqueous electrolytes.

In Situ SHINERS at Electrochemical Single-Crystal Electrode/Electrolyte Interfaces: Tuning Preparation Strategies and Selected Applications

We have studied Au(55 nm)@SiO2 nanoparticles (NPs) on two low-index phases of gold and platinum single crystal electrodes in ClO4– and SO42– ion-containing electrolytes by both electrochemical methods and in-situ shell-isolated nanoparticle enhanced Raman spectroscopy (SHINERS). We showed the blocking of the electrode with surfactants originating from the synthesis of as-prepared SHINERS NPs. We introduce an efficient procedure to overcome this problem, which provides a fundamental platform for the application of SHINERS in surface electrochemistry and beyond. Our method is based on a hydrogen evolution treatment of the SHINERS-NP-modified single-crystal surfaces. The reliability of our preparation strategy is demonstrated in electrochemical SHINERS experiments on the potential-controlled adsorption and phase formation of pyridine on Au(hkl) and Pt(hkl). We obtained high-quality Raman spectra on these well-defined and structurally carefully characterized single-crystal surfaces. The analysis of the characteristic A1 vibrational modes revealed perfect agreement with the interpretation of single-crystal voltammetric and chronoamperometric experiments. Our study demonstrates that the SHINERS protocol developed in this work qualifies this Raman method as a pioneering approach with unique opportunities for in situ structure and reactivity studies at well-defined electrochemical solid/liquid interfaces.

Fluorescent In Situ hybridization: a new tool for the direct identification and detection of F. psychrophilum

F. psychrophilum is the causative agent of Bacterial Cold Water Disease (BCW) and Rainbow Trout Fry Syndrome (RTFS). To date, diagnosis relies mainly on direct microscopy or cultural methods. Direct microscopy is fast but not very reliable, whereas cultural methods are reliable but time-consuming and labor-intensive. So far fluorescent in situ hybridization (FISH) has not been used in the diagnosis of flavobacteriosis but it has the potential to rapidly and specifically detect F. psychrophilum in infected tissues. Outbreaks in fish farms, caused by pathogenic strains of Flavobacterium species, are increasingly frequent and there is a need for reliable and cost-effective techniques to rapidly diagnose flavobacterioses. This study is aimed at developing a FISH that could be used for the diagnosis of F. psychrophilum infections in fish. We constructed a generic probe for the genus Flavobacterium ("Pan-Flavo") and two specific probes targeting F. psychrophilum based on 16S rRNA gene sequences. We tested their specificity and sensitivity on pure cultures of different Flavobacterium and other aquatic bacterial species. After assessing their sensitivity and specificity, we established their limit of detection and tested the probes on infected fresh tissues (spleen and skin) and on paraffin-embedded tissues. The results showed high sensitivity and specificity of the probes (100% and 91% for the Pan-Flavo probe and 100% and 97% for the F. psychrophilum probe, respectively). FISH was able to detect F. psychrophilum in infected fish tissues, thus the findings from this study indicate this technique is suitable as a fast and reliable method for the detection of Flavobacterium spp. and F. psychrophilum.

Randomised in situ study on the efficacy of a tin/chitosan toothpaste on erosive-abrasive enamel loss

Tin is a notable anti-erosive agent, and the biopolymer chitosan has also shown demineralisation-inhibiting properties. Therefore, the anti-erosive/anti-abrasive efficacy of the combination of both compounds was tested under in situ conditions. Twenty-seven volunteers were included in a randomised, double-blind, three-cell crossover in situ trial. Enamel specimens were recessed on the buccal aspects of mandibular appliances, extraorally demineralised (6 × 2 min/day) and intraorally treated with toothpaste slurries (2 × 2 min/day). Within the slurry treatment time, one-half of the specimens received additional intraoral brushing (5 s, 2.5 N). The tested toothpastes included a placebo toothpaste, an experimental NaF toothpaste (1,400 ppm F(-)) and an experimental F/Sn/chitosan toothpaste (1,400 ppm F(-), 3,500 ppm Sn(2+), 0.5% chitosan). The percentage reduction of tissue loss (slurry exposure/slurry exposure + brushing) compared to placebo was 19.0 ± 47.3/21.3 ± 22.4 after use of NaF and 52.5 ± 30.9/50.2 ± 34.3 after use of F/Sn/chitosan. F/Sn/chitosan was significantly more effective than NaF (p ≤ 0.001) and showed good efficacy against erosive and erosive-abrasive tissue loss. This study suggests that the F/Sn/chitosan toothpaste could provide good protection for patients who frequently consume acidic foodstuffs.

Effect of a chitosan additive to a Sn(2+)-containing toothpaste on its anti-erosive/anti-abrasive efficacy-a controlled randomised in situ trial

OBJECTIVES It is well known that Sn(2+) is a notable anti-erosive agent. There are indications that biopolymers such as chitosan can enhance the effect of Sn(2+), at least in vitro. However, little information exists about their anti-erosive/anti-abrasive in situ effects. In the present in situ study, the efficacy of Sn(2+)-containing toothpastes in the presence or absence of chitosan was tested. METHODS Ten subjects participated in the randomised crossover study, wearing mandibular appliances with human enamel specimens. Specimens were extraorally demineralised (7 days, 0.5 % citric acid, pH 2.6; 6 × 2 min/day) and intraorally exposed to toothpaste suspensions (2 × 2 min/day). Within the suspension immersion time, one half of the specimens were additionally brushed intraorally with a powered toothbrush (5 s, 2.5 N). Tested preparations were a placebo toothpaste (negative control), two experimental toothpastes (F/Sn = 1,400 ppm F(-), 3,500 ppm Sn(2+); F/Sn/chitosan = 1,400 ppm F(-), 3,500 ppm Sn(2+), 0.5 % chitosan) and an SnF2-containing gel (positive control, GelKam = 3,000 ppm Sn(2+), 1,000 ppm F(-)). Substance loss was quantified profilometrically (μm). RESULTS In the placebo group, tissue loss was 11.2 ± 4.6 (immersion in suspension) and 17.7 ± 4.7 (immersion in suspension + brushing). Immersion in each Sn(2+)-containing suspension significantly reduced tissue loss (p ≤ 0.01); after immersion in suspension + brushing, only the treatments with GelKam (5.4 ± 5.5) and with F/Sn/chitosan (9.6 ± 5.6) significantly reduced loss [both p ≤ 0.05 compared to placebo; F/Sn 12.8 ± 6.4 (not significant)] CONCLUSION Chitosan enhanced the efficacy of the Sn(2+)-containing toothpaste as an anti-erosive/anti-abrasive agent. CLINICAL RELEVANCE The use of Sn(2+)- and chitosan-containing toothpaste is a good option for symptomatic therapy in patients with regular acid impacts.