Quantitative localized proton-promoted dissolution kinetics of calcite using scanning electrochemical microscopy (SECM)

Scanning electrochemical microscopy (SECM) has been used to determine quantitatively the kinetics of proton-promoted dissolution of the calcite (101̅4) cleavage surface (from natural “Iceland Spar”) at the microscopic scale. By working under conditions where the probe size is much less than the characteristic dislocation spacing (as revealed from etching), it has been possible to measure kinetics mainly in regions of the surface which are free from dislocations, for the first time. To clearly reveal the locations of measurements, studies focused on cleaved “mirror” surfaces, where one of the two faces produced by cleavage was etched freely to reveal defects intersecting the surface, while the other (mirror) face was etched locally (and quantitatively) using SECM to generate high proton fluxes with a 25 μm diameter Pt disk ultramicroelectrode (UME) positioned at a defined (known) distance from a crystal surface. The etch pits formed at various etch times were measured using white light interferometry to ascertain pit dimensions. To determine quantitative dissolution kinetics, a moving boundary finite element model was formulated in which experimental time-dependent pit expansion data formed the input for simulations, from which solution and interfacial concentrations of key chemical species, and interfacial fluxes, could then be determined and visualized. This novel analysis allowed the rate constant for proton attack on calcite, and the order of the reaction with respect to the interfacial proton concentration, to be determined unambiguously. The process was found to be first order in terms of interfacial proton concentration with a rate constant k = 6.3 (± 1.3) × 10–4 m s–1. Significantly, this value is similar to previous macroscopic rate measurements of calcite dissolution which averaged over large areas and many dislocation sites, and where such sites provided a continuous source of steps for dissolution. Since the local measurements reported herein are mainly made in regions without dislocations, this study demonstrates that dislocations and steps that arise from such sites are not needed for fast proton-promoted calcite dissolution. Other sites, such as point defects, which are naturally abundant in calcite, are likely to be key reaction sites

Photodetachment study of He^- quartet resonances below the He(n=3) thresholds

The photodetachment cross section of He^- has been measured in the photon energy range 2.9 eV to 3.3 eV in order to investigate doubly excited states. Measurements were made channel specific by selectively detecting the residual He atoms left in a particular excited state following detachment. Three Feshbach resonances were found in the He(1s2p ^3P)+e^-(epsilon p) partial cross section: a ^4S resonance below the He(1s3s ^3S) threshold and two ^4P resonances below the He(1s3p ^3P) threshold. The measured energies of these doubly excited states are 2.959260(6) eV, 3.072(7) eV and 3.26487(4) eV. The corresponding widths are found to be 0.20(2) meV, 50(5) meV and 0.61(5) meV. The measured energies agree well with recent theoretical predictions for the 1s3s4s ^4S, 1s3p^2 ^4P and 1s3p4p ^4P states, respectively, but the widths deviate noticeably from calculations for 1s3p^2 ^4P and 1s3p4p ^4P states.Comment: 10 pages, 3 figures, LaTeX2e scrartcl, amsmath. Accepted by Journal of Physics B; minor changes after referee repor

Trauma and Trichotillomania: A Tenuous Relationship

Some have argued that hair pulling in trichotillomania (TTM) is triggered by traumatic events, but reliable evidence linking trauma to TTM is limited. However, research has shown that hair pulling is associated with emotion regulation, suggesting a connection between negative affect and TTM. We investigated the associations between trauma, negative affect, and hair pulling in a cross-sectional sample of treatment seeking adults with TTM (N=85). In the current study, participants’ self-reported traumatic experiences were assessed during a structured clinical interview, and participants completed several measures of hair pulling severity, global TTM severity, depression, anxiety, experiential avoidance, and quality of life. Those who experienced trauma had more depressive symptoms, increased experiential avoidance, and greater global TTM severity. Although the presence of a trauma history was not related to the severity of hair pulling symptoms in the past week, depressive symptoms mediated the relationship between traumatic experiences and global TTM severity. These findings cast doubt on the notion that TTM is directly linked to trauma, but suggest that trauma leads to negative affect that individuals cope with through hair pulling. Implications for the conceptualization and treatment of TTM are discussed

Group cognitive analytic music therapy: a quasi-experimental feasibility study conducted in a high secure hospital

This study conducted a feasibility patient preference quasi-experimental study of group cognitive analytic music therapy (G-CAMT) for mentally disordered offenders. Participants either chose or were randomised to 16 sessions of manualised G-CAMT (N = 10) plus treatment as usual (TAU) or TAU alone (N = 10). Self-rated and staff-rated outcomes were assessed at baseline, post-intervention and 8-weeks post-intervention. Residency was assessed at 2-year follow-up. Results indicate that G-CAMT was easily implemented; 9/10 participants completed G-CAMT and attendees had high satisfaction with the approach. Session attendance was high; 4/10 participants attended all sessions. At the 8-week follow-up, 3/9 G-CAMT participants had reliable reductions (i.e. statistically reliable pre to 8-week follow-up change results) in intrusive/possessive behaviours and fear of separation/abandonment. On the staff-rated outcome measure G-CAMT participants as a group were statistically significantly friendlier compared to TAU at 8-week follow-up (U = 0.50, p = 0.009, d = 1.92, CI 0.44 to 3.11). There were no differences between the arms in terms of residency outcomes at 2-year follow-up. The study is discussed in terms of G-CAMT’s theoretical grounding and high acceptability. The study is limited by its small sample size, but indicates the possibility of progressing onto a full trial

High-order multiphoton ionization photoelectron spectroscopy of NO

Photoelectron energy angular distributions of NO following three different high-order multiphoton ionization (MPI) schemes have been measured. The 3 + 3 resonantly enhanced multiphoton ionization (REMPI) via the A/sup 2/..sigma../sup +/ (v=O) level yielded a distribution of electron energies corresponding to all accessible vibrational levels (v/sup +/=O-6) of the nascent ion. Angular distributions of electrons corresponding to v/sup +/=O and v/sup +/=3 were significantly different. The 3 + 2 REMPI via the A/sup 2/..sigma../sup +/ (v=1) level produced only one low-energy electron peak (v/sup +/=1). Nonresonant MPI at 532 nm yielded a distribution of electron energies corresponding to both four- and five-photon ionization. Prominent peaks in the five-photon photoelectron spectrum (PES) suggest contributions from near-resonant states at the three-photon level. 4 refs., 3 figs

Near-Field Analysis of Rectangular Waveguide Probes Used for Imaging

Near-field microwave imaging of composite structures has received considerable attention recently. The success achieved on the experimental level motivated the development of a theoretical model to describe the high quality images obtained using near-field microwave imaging [1–4]. This theoretical model will also help in building an intuitive understanding of the behavior of the fields inside dielectric materials in the near-field of an open-ended rectangular waveguide probe. A near-field microwave image is the result of several factors such as probe type (example rectangular waveguide, circular waveguide or coaxial line), field properties (i.e. main lobe, sidelobes and half power beam width, etc.), geometrical and physical properties of both the defect and the material under inspection. Thus, in order to characterize a defect, the effect of all non-defect factors needs to be taken out of an image. One of the dominant non-defect factors which influences an image significantly is the radiator field properties. Thus, it is essential to formulate the properties of the fields radiating out of an open-ended rectangular waveguide in its near-field. This knowledge will aid in formulating the forward problem when imaging a defect, and will be used to solve the inverse problem for obtaining defect properties. In this paper fields radiating out of an open-ended rectangular waveguide, into an infinite half-space of a dielectric material, are calculated and used to explain some of the features observed in experimental near-field microwave images

Logics of Finite Hankel Rank

We discuss the Feferman-Vaught Theorem in the setting of abstract model theory for finite structures. We look at sum-like and product-like binary operations on finite structures and their Hankel matrices. We show the connection between Hankel matrices and the Feferman-Vaught Theorem. The largest logic known to satisfy a Feferman-Vaught Theorem for product-like operations is CFOL, first order logic with modular counting quantifiers. For sum-like operations it is CMSOL, the corresponding monadic second order logic. We discuss whether there are maximal logics satisfying Feferman-Vaught Theorems for finite structures.Comment: Appeared in YuriFest 2015, held in honor of Yuri Gurevich's 75th birthday. The final publication is available at Springer via http://dx.doi.org/10.1007/978-3-319-23534-9_1

Burrowing Behavior of a Deposit Feeding Bivalve Predicts Change in Intertidal Ecosystem State

Behavior has a predictive power that is often underutilized as a tool for signaling ecological change. The burrowing behavior of the deposit feeding bivalve Macoma balthica reflects a typical food-safety trade-off. The choice to live close to the sediment surface comes at a risk of predation and is a decision made when predation danger, food intake rates or future fitness prospects are low. In parts of the Dutch Wadden Sea, Macoma populations declined by 90% in the late 1990s, in parallel with large-scale mechanical cockle-dredging activities. During this decline, the burrowing depth of Macoma became shallow and was correlated with the population decline in the following year, indicating that it forecasted population change. Recently, there has been a series of large recruitment events in Macoma. According to the food-safety trade-off, we expected that Macoma should now live deeper, and have a higher body condition. Indeed, we observed that Macoma now lives deeper and that living depth in a given year forecasted population growth in the next year, especially in individuals larger than 14 mm. As living depth and body condition were strongly correlated in individuals larger than 14 mm, larger Macoma could be living deeper to protect their reproductive assets. Our results confirmed that burrowing depth signals impending population change and, together with body condition, can provide an early warning signal of ecological change. We suggest that population recovery is being driven by improved intertidal habitat quality in the Dutch Wadden Sea, rather than by the proposed climate-change related effects. This shift in ecosystem state is suggested to include the recovery of diatom habitat in the top layer of the sediment after cockle-dredging ended