Epithermal Neutron Beam Interference with Cardiac Pacemakers

Peer reviewe

First-principles study of adsorption, diffusion, and charge stability of metal adatoms on alkali halide surfaces

In this work we have performed first-principles calculations based on the spin-polarized density-functional theory for the adsorption and diffusion of Au, Ag, and Pb atoms on NaCl(001), KCl(001), and KBr(001) surfaces. We consider also the influence of adatom charge on the adsorption and diffusion. In order to characterize the different systems we explicitly calculate charge transfer between surface and adatom and consider the relative stability of the various charge states. Our results show that in general, apart from positively charged systems, the adatoms are weakly bound to the surface via orbital polarization and ionic interactions, and relatively little charge transfer occurs. Au and Ag adatoms are highly mobile on all surfaces, although they can be pinned by removal of an electron. In contrast, Pb adatoms are fairly immobile, and their mobility increases upon charging. Analysis of the charge stability suggests that Ag offers the potential of charge controlled mobility on insulators.Peer reviewe

High-resolution scanning force microscopy of gold nanoclusters on the KBr (001) surface

In this study we use a combination of dynamic scanning force microscopy experiments and first-principles simulations to study the imaging process of gold nanoclusters adsorbed on the (001) surface of KBr. In previous experiments atomic resolution was readily obtained on the KBr substrate. However, it was not possible to resolve atoms within the clusters themselves. This correlates with imaging simulations we present here using several different probable tip models: measurable contrast was readily achieved on the KBr surface and on the gold (001) surface, but simulations on the clusters demonstrated poor contrast for all tips. We further consider the role of cluster charging in the tip-surface interaction, and the role that surface defects play in the properties of adsorbed clusters.Peer reviewe

Calibration of a solid state nuclear track detector (SSNTD) with high detection threshold to search for rare events in cosmic rays

We have investigated a commercially available polymer for its suitability as a solid state nuclear track detector (SSNTD). We identified that polymer to be polyethylene terephthalate (PET) and found that it has a higher detection threshold compared to many other widely used SSNTDs which makes this detector particularly suitable for rare event search in cosmic rays as it eliminates the dominant low Z background. Systematic studies were carried out to determine its charge response which is essential before any new material can be used as an SSNTD. In this paper we describe the charge response of PET to 129Xe, 78Kr and 49Ti ions from the REX-ISOLDE facility at CERN, present the calibration curve for PET and characterize it as a nuclear track detector

The so-called dry laser cleaning governed by humidity at the nanometer scale

Illumination with single nanosecond pulses leads to the detachment of silica particles with 250nm radii from siliconsurfaces. We identify two laser-energy dependent cleaning regimes by time-of-flight particle-scattering diagnostics. For the higher energies, the ejection of particles is produced by nanoscale ablation due to the laser field enhancement at the particle-surface interface. The damage-free regime at lower energy is shown to be governed by the residual water molecules, which are inevitably trapped on the materials. We discuss the great importance that the humidity plays on the cleaning force and on the adhesion in the experiments.Peer reviewe

Imaging the real shape of nanoclusters in scanning force microscopy

A quantitative comparison between experiment and theory is given for the constant height mode imaging of metal nanoclusters in dynamic scanning force microscopy. We explain the fundamental mechanisms in the contrast formation with the help of the system Pd/MgO(001). The comparison shows that the shape and size of nanoclusters are precisely imaged due to the sharpness of the tip’s last nanometer. This quantitative comparison proves our previously proposed model for the contrast formation.Peer reviewe

Simulating atomic force microscopy imaging of the ideal and defected TiO2 (110) surface

In this study we simulate noncontact atomic force microscopy imaging of the TiO2 (110) surface using first-principles and atomistic methods. We use three different tip models to investigate the tip-surface interaction on the ideal surface, and find that agreement with experiment is found for either a silicon tip or a tip with a net positive electrostatic potential from the apex. Both predict bright contrast over the bridging oxygen rows. We then study the interaction of this tip with a bridging oxygen vacancy on the surface, and find that the much weaker interaction observed would result in vacancies appearing as dark contrast along the bright rows in images.Peer reviewe

Role of van der Waals forces in the adsorption and diffusion of organic molecules on an insulating surface

The adsorption and diffusion of 3,4,9,10-perylene-tetracarboxylic-dianhydride (PTCDA) molecules on a nanostructured KBr (001) surface were investigated by combining noncontact atomic force microscopy (NC-AFM) and first-principles calculations. Atomically resolved measurements demonstrate trapping of PTCDA molecules in intentionally created rectangular monolayer-deep substrate pits and a preferential adsorption at kink sites. In order to understand the experimental results, we found that it was essential to include a first-principles treatment of the van der Waals interactions. We show that at some sites on the surface, 85% of the molecular binding is provided by van der Waals interactions, and in general it is always the dominant contribution to the adsorption energy. It also qualitatively changes molecular diffusion on the surface. Based on the specificity of the molecular interaction at kink sites, the species of the imaged ionic sublattice in the NC-AFM measurements could be identified.Peer reviewe

Transumbilical versus lateral transabdominal removal of benign adnexal masses in laparoscopic surgery-A randomized trial

Objective: In laparoscopic adnexal surgery the conventional method of removing a mass from the abdominal cavity in Finland is through a 10-mm-wide lateral abdominal port. The larger the lateral trocar, the greater the risk of pain, complications and delayed recovery. Here, we assumed that adnexal mass removal through a 10-mm umbilical port together with 5-mm side trocars would decrease the postoperative need of analgesics when compared with removal through a 10-mm lateral abdominal port. Study design: Women scheduled for laparoscopic surgery of a benign adnexal mass were invited to participate. The participants were randomized into two groups: removal via the transumbilical (TO) (n = 21) or lateral transabdominal (TA) (n= 21) route. General anesthesia and use of local anesthetics were standardized. The amount of postoperative opioid (oxycodone) and visual analog scale (VAS) scores for pain were the primary outcome measures. Secondary outcome measures were nausea/vomiting (VAS evaluation), time to discharge, peri- and postoperative complications, surgeons' opinions of the alternative methods and patients' satisfaction, evaluated via a questionnaire sent six months postoperatively. Results: There were no significant differences in the use of opioids or median pain-VAS scores between the groups during the first 24 h postoperatively. However, in the TU group the amount of women with very low pain-VAS scores (0-1) during the whole 12-h follow-up time was significantly greater than in the TA group (4 vs. 0 women p=0.04). The amounts of nausea and vomiting, and median times to discharge were similar in both groups. There were no major complications. Conclusions: Both transumbilical and transabdominal routes of abdominal mass removal during laparoscopy were feasible and safe. However, the transumbilical route resulted in more women with very low pain-VAS scores. (C) 2017 Elsevier B.V. All rights reserved.Peer reviewe

A comparative cohort study of Duhamel and Endorectal Pullthrough for Hirschsprung's Disease

Background: There are limited data available to compare outcomes between surgical approaches for Hirschsprung’s disease. Duhamel and endorectal pull-through (ERPT) are two of the most common procedures performed worldwide. // Methods: Objective outcomes were compared between contemporary cohorts (aged 4–32 years) after Duhamel or ERPT using case–control methodology. Data were collected using prospectively administered standardized questionnaires on bowel and bladder function and quality of life (Pediatric Quality of Life Inventory, Short form 36 and Gastrointestinal Quality of Life Index). Patients were compared in two age groups (18 years and younger and older than 18 years) and reference made to normative control data. Multivariable analysis explored factors associated with poor outcomes. // Results: Cohorts were well matched by demographics, disease characteristics and incidence of postoperative complications (120 patients who underwent Duhamel versus 57 patients who had ERPT). Bowel function scores were similar between groups. Patients who underwent Duhamel demonstrated worse constipation and inferior faecal awareness scores (P < 0.01 for both age groups). Recurrent postoperative enterocolitis was significantly more common after ERPT (34 versus 6 per cent; odds ratio 15.56 (95 per cent c.i. 6.19 to 39.24; P < 0.0001)). On multivariable analysis, poor bowel outcome was the only factor significantly associated with poor urinary outcome (adjusted odds ratio 6.66 (95 per cent c.i. 1.74 to 25.50; P = 0.006)) and was significantly associated with markedly reduced quality of life (QoL) in all instruments used (P < 0.001 for all). There were no associations between QoL measures and pull-through technique. // Conclusion: Outcomes from Duhamel and ERPT are good in the majority of cases, with comparable bowel function scores. Constipation and impaired faecal awareness were more prevalent after Duhamel, with differences sustained in adulthood. Recurrent enterocolitis was significantly more prevalent after ERPT. Clustering of poor QoL and poor functional outcomes were observed in both cohorts, with seemingly little effect by choice of surgical procedure in terms of QoL