The electrochemical surface forces apparatus : the effect of surface roughness, electrostatic surface potentials, and anodic oxide growth on interaction forces, and friction between dissimilar surfaces in aqueous solutions

We present a newly designed electrochemical surface forces apparatus (EC-SFA) that allows control and measurement of surface potentials and interfacial electrochemical reactions with simultaneous measurement of normal interaction forces (with nN resolution), friction forces (with μN resolution), and distances (with Å resolution) between apposing surfaces. We describe three applications of the developed EC-SFA and discuss the wide-range of potential other applications. In particular, we describe measurements of (1) force–distance profiles between smooth and rough gold surfaces and apposing self-assembled monolayer-covered smooth mica surfaces; (2) the effective changing thickness of anodically growing oxide layers with Å-accuracy on rough and smooth surfaces; and (3) friction forces evolving at a metal–ceramic contact, all as a function of the applied electrochemical potential. Interaction forces between atomically smooth surfaces are well-described using DLVO theory and the Hogg–Healy–Fuerstenau approximation for electric double layer interactions between dissimilar surfaces, which unintuitively predicts the possibility of attractive double layer forces between dissimilar surfaces whose surface potentials have similar sign, and repulsive forces between surfaces whose surface potentials have opposite sign. Surface roughness of the gold electrodes leads to an additional exponentially repulsive force in the force–distance profiles that is qualitatively well described by an extended DLVO model that includes repulsive hydration and steric forces. Comparing the measured thickness of the anodic gold oxide layer and the charge consumed for generating this layer allowed the identification of its chemical structure as a hydrated Au(OH)3 phase formed at the gold surface at high positive potentials. The EC-SFA allows, for the first time, one to look at complex long-term transient effects of dynamic processes (e.g., relaxation times), which are also reflected in friction forces while tuning electrochemical surface potentials.

Classification of neural action potentials using mean shift clustering

 Understanding neural functions requires the observation of the activities of single neurons that are represented via electrophysiological data. Processing and understanding these data are challenging problems in biomedical engineering. A microelectrode commonly records the activity of multiple neurons. Spike sorting is a process of classifying every single action potential (spike) to a particular neuron. This paper proposes a combination between diffusion maps (DM) and mean shift clustering method for spike sorting. DM is utilized to extract spike features, which are highly capable of discriminating different spike shapes. Mean shift clustering provides an automatic unsupervised clustering, which takes extracted features from DM as inputs. Experimental results show a noticeable dominance of the features extracted by DM compared to those selected by wavelet transformation (WT). Accordingly, the proposed integrated method is significantly superior to the popular existing combination of WT and superparamagnetic clustering regarding spike sorting accuracy.

Snakes on an island: independent introductions have different potentials for invasion

Snakes introduced to islands can be devastating to naïve native fauna. However, introduced populations must establish before range expansion (invasion) can occur. The factors that can determine successful invasion are those associated with the introduction event (e.g., characteristics of the founding population), the location (e.g., suitable environment and prey availability) and the species (e.g. life history characteristics). Here, we collected morphometric, ecological and genetic data on the recently introduced California Kingsnake (Lampropeltis californiae) in Gran Canaria. We found that snakes occurring at two locations a few 10 s of km apart do not represent the same population. Genetic analyses confirmed significant genetic difference (FST = 0.184; Dest = 0.341), and that despite being inbred (Fis = 0.245–0.257) the populations had high levels of diversity (Ho = 0.485–0.490; allelic richness = 4.875–6.364). Snakes at the different Gran Canaria locations were significantly different in morphology (colouration, mass, length and age), fitness (egg production) and diet (rodents, skinks, lizards and geckos), supporting a hypothesis of separate founding groups in combination with local environmental heterogeneity leading to variation between these populations. We concluded that one population was more successful than the other in reproduction and recruitment, and may be having a greater impact on endemic reptiles. We recommend greater eradication effort for this population, as well as monitoring of local fauna at all locations to access the impact of predation.

The gut microbiota and inflammatory noncommunicable diseases: associations and potentials for gut microbiota therapies

Rapid environmental transition and modern lifestyles are likely driving changes in the biodiversity of the human gut microbiota. With clear effects on physiologic, immunologic, and metabolic processes in human health, aberrations in the gut microbiome and intestinal homeostasis have the capacity for multisystem effects. Changes in microbial composition are implicated in the increasing propensity for a broad range of inflammatory diseases, such as allergic disease, asthma, inflammatory bowel disease (IBD), obesity, and associated noncommunicable diseases (NCDs). There are also suggestive implications for neurodevelopment and mental health. These diverse multisystem influences have sparked interest in strategies that might favorably modulate the gut microbiota to reduce the risk of many NCDs. For example, specific prebiotics promote favorable intestinal colonization, and their fermented products have anti-inflammatory properties. Specific probiotics also have immunomodulatory and metabolic effects. However, when evaluated in clinical trials, the effects are variable, preliminary, or limited in magnitude. Fecal microbiota transplantation is another emerging therapy that regulates inflammation in experimental models. In human subjects it has been successfully used in cases of Clostridium difficile infection and IBD, although controlled trials are lacking for IBD. Here we discuss relationships between gut colonization and inflammatory NCDs and gut microbiota modulation strategies for their treatment and prevention. (J Allergy Clin Immunol 2015;135:3-13.)

Occurrence of anodic current and corrosion of steel in aqueous media under fluctuating cathodic protection potentials

Excursion of cathodic protection (CP) potential from the designed "safe" CP level resulting from various forms of electrical interference signals are observed rather frequently in industrial applications, in particular in the pipeline industry; however, the influence of such potential fluctuations on the corrosion behavior of steel under CP conditions does not yet appear to be fully understood. In this work, the effects of anodic transients that periodically shift the potential of a CP protected steel electrode from-1,200 mVAg/AgCl to-750 mVAg/AgCl on the corrosion of a steel electrode in aqueous media was investigated using square wave polarization. Anodic currents were measured that lasted for significant periods of time upon stepping the CP potential up to a less cathodic potential at various frequencies (1 h, 30 s, 10 s, 5 s, and 1 s). Part of such anodic currents is found to cause steel corrosion, and this is explained on the basis of understanding the Fe/H2O equilibrium.