Search

Copyright of Canadian Veterinary Journal / Revue Vétérinaire Canadienne is the property of Canadian Veterinary Medical Association and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Low-modulus β-type Ti-45Nb alloy is a promising implant material due to its good mechanical biocompatibility, non-toxicity, and outstanding corrosion resistance. Its excellent chemical stability brings new challenges to chemical surface modification treatments, which are indispensable for both osteogenesis and antibacterial performance. Coatings containing metal ions as anti-microbial agents can be an effective way to reduce implant-associated infections caused by bacterial biofilm. Gallium ion (Ga3+) has the potential to reduce bacterial viability and biofilm formation on implant surfaces. In this study, a novel two-step process has been proposed for Ga3+ incorporation in hydroxyapatite (HAP) to develop bioactive and antibacterial surfaces on Ti-45Nb alloy. For the generation of bioactive surface states, HAP electrodeposition was conducted, followed by wet chemical immersion treatments in gallium nitrate (1 mM). Different buffers such as phosphate, sodium bicarbonate, ammonium acetate, and citrate were added to the solution to maintain a pH value in the range of 6.5–6.9. Coating morphology and HAP phases were retained after treatment with gallium nitrate, and Ga3+ ion presence on the surface up to 1 wt.% was confirmed. Combining Ga and HAP shows great promise to enable the local delivery of Ga3+ ions and consequent antibacterial protection during bone regeneration, without using growth factors or antibiotics. [ABSTRACT FROM AUTHOR]

Selective laser melting (SLM) of biodegradable metallic materials offers a great potential for manufacturing customized implants. Herein, SLM processing of a novel Fe–30Mn–1C–0.02S twinning‐induced plasticity (TWIP) alloy and the resulting structural, mechanical, and corrosion properties are presented. The occurring rapid solidification results in a fine‐grained austenitic microstructure with mainly homogeneous element distribution, which is investigated by scanning electron microscopy (SEM) combined with energy‐dispersive X‐ray spectroscopy (EDX) and electron backscatter diffraction (EBSD) as well as X‐ray diffraction (XRD). By processing the alloy via SLM, significantly higher strengths under tensile and compressive load in comparison with those for the as‐cast counterpart and a 316L reference steel are achieved. Electrochemical corrosion tests in a simulated body fluid (SBF) indicate a moderate corrosion activity, and a beneficial uniform degradation is shown in immersion tests in SBF. Regarding the envisaged application for vascular implants, SLM‐processed stent prototypes out of the novel alloy are presented and a first functionality test is shown. [ABSTRACT FROM AUTHOR]

Abstract: Small indium (In) additions up to 5 wt % to the beta‐type Ti‐40Nb alloy effectively improve its mechanical biofunctionality. The impact on its biocompatibility is addressed in this work. Comparative electrochemical polarization studies and inductively coupled plasma optical emission spectrometry analyses were conducted in Tris‐buffered saline (on the basis of 150 mM NaCl) with pH 7.6 and 2.0 at 310 ± 1 K with Ti‐6Al‐4V as reference. The metal ion releases from beta‐type alloys were generally very low, for example, those of In3+ ions from (Ti‐40Nb)‐4In specimens were below 6 × 10−7 mmol/cm2. X‐ray photoelectron spectroscopy revealed the passivation mainly by Ti‐ and Nb‐oxides with traces of In‐oxides as the dominating surface process. In vitro studies demonstrate a better human bone marrow stromal cells (hBMSC) activity on the beta‐type alloys in comparison to CP‐Ti (grade 2), which is mainly due to their high Nb content. At 24 h after seeding on (Ti‐40Nb)‐4In the metabolic activity of hBMSC was 1.5‐fold higher and after 11 days, the tissue non‐specific alkaline phosphatase activity was 1.8‐fold higher relative to values for CP‐Ti. Surface treatments, like chemical etching or plasma oxidation, change the surface topography and the thickness and composition of the oxide layers, but they are not effective in further improving the cell response. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 106B: 1686–1697, 2018. [ABSTRACT FROM AUTHOR]

The diffusion model is one of the most prominent response time models in cognitive psychology. The model describes evidence accumulation as a stochastic process that runs between two boundaries until a threshold is hit, and a decision is made. The model assumes that information accumulation follows a Wiener diffusion process with normally distributed noise. However, the model's assumption of Gaussian noise might not be the optimal description of decision making. We argue that Lévy flights, incorporating more heavy-tailed, non-Gaussian noise, might provide a more accurate description of actual decision processes. In contrast to diffusion processes, Lévy flights are characterized by larger jumps in the decision process. To further examine this proposal, we compare the fit of the basic diffusion model and the full diffusion model (including inter-trial variability of starting-point, drift rate and non-decisional processes) to the fit of a simple and a complex version of a Lévy flight model. In the latter model, the heavy-tailedness of noise distributions was estimated by an additional free stability parameter alpha. Participants completed 500 trials of a color discrimination task and 400 trials of a lexical decision task. Results indicate that a complex Lévy flight model -including inter-trial variability parameters and alpha- shows the best fit in both tasks. Importantly, alpha-values correlated across tasks, indicating a trait-like nature of this parameter.

The diffusion model belongs to the class of sequential sampling models. Based on information about RT distributions from binary tasks, the model allows the separation of distinct processes underlying decision-making. With the present simulation study, we demonstrate that diffusion modeling has essential advantages over the mere analysis of behavioral variables such as accuracy rate or mean RT. Specifically, our results show that qualitatively different sets of diffusion model parameters can lead to the same pattern of these aggregated variables, which renders the interpretation of these measures ambiguous. Even apparently clear patterns of results can be based on completely different parameter sets, which reflect completely different cognitive processes. For example, if one group\IeC {\textquoteright }s performance (or performance in one experimental condition) is superior in both mean RT and accuracy rate (i.e., fast responses and few errors), this does not necessarily mean that in this group (or condition) information processing is faster (drift rate of the diffusion model). Accordingly, we conclude that the mere analysis of behavioral variables can result in false conclusions.

Objective To determine the effects of once-daily topical treatment with timolol maleate gel-forming solution ( GFS) on intraocular pressure ( IOP), pupil diameter ( PD), and heart rate ( HR) in normal cats and cats with feline primary congenital glaucoma ( FCG). Animals studied and procedures A single drop of timolol maleate 0.5% GFS was administered topically to one randomly assigned eye of 18 adult cats (8 normal, 10 FCG) at 8 am for 8 days; the opposite eye served as the untreated control. IOP was measured in both eyes ( OU) every 2 h ( PD and HR were measured every 4 h), for 14 h total, 1 day prior to and on days 1 and 8 of treatment. In a second treatment phase, a single drop of timolol was administered at 8 pm for 3 nights and IOP, PD, and HR were measured, as above, beginning at 8 am on day 4. Slit-lamp examinations were conducted prior to and after treatment phases. Comparisons of mean IOP, PD, and HR were made at each time point and between treated and untreated eyes by repeated-measures ANOVA and Tukey-Kramer post hoc test, with P < 0.05 considered significant. Results Timolol maleate 0.5% GFS had an inconsistent effect on IOP, with maximum IOP-lowering effect (mean = 5.6 mmHg, 17.4%) observed 6 h post-treatment in FCG. The drug caused significant miosis (from 4 to 8 h post-treatment), but had no effect on HR. Conclusion Once-daily application of timolol maleate 0.5% GFS may be of limited clinical benefit in the management of feline congenital glaucoma. [ABSTRACT FROM AUTHOR]

The low modulus β-type Ti-45Nb alloy is a promising new implant alloy due to its excellent mechanical biocompatibility and composition of non-toxic elements. The effect of surface treatments on the evolution of controlled topography and roughness was investigated by means of scanning electron microscopy and optical profilometry. Severe mechanical treatments, for example sand-blasting, or etching treatments in strongly oxidizing acidic solutions, like HF:HNO3 (4:1) or H2SO4:H2O2 (1:1) piranha solution were found to be very effective. In particular, the latter generates a nanopatterned surface topography which is expected to be promising for the stimulation of bone tissue growth. Compared to Ti and Ti-6Al-4V, the β-type Ti-45Nb alloy requires significantly longer etching durations due to the high chemical stability of Nb. Severe surface treatments alter the passive film properties, but do not deteriorate the outstanding corrosion resistance of the Ti-45Nb alloy in synthetic body fluid environments. The Ti-45Nb appears to have a lower apatite-formation ability compared to Ti. Etching with H2SO4:H2O2 (1:1) piranha solution inhibits apatite formation on Ti, but not on Ti-45Nb. © 2012 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2013. [ABSTRACT FROM AUTHOR]

Background: Electrocardiographic methods still provide the bulk of cardiovascular diagnostics. Cardiac ischemia is associated with typical alterations in cardiac biosignals that have to be measured, analyzed by mathematical algorithms and allegorized for further clinical diagnostics. The fast growing fields of biomedical engineering and applied sciences are intensely focused on generating new approaches to cardiac biosignal analysis for diagnosis and risk stratification in myocardial ischemia. Objectives: To present and review the state of the art in and new approaches to electrocardiologic methods for non-invasive detection and risk stratification in coronary artery disease (CAD) and myocardial ischemia; secondarily, to explore the future perspectives of these methods. Methods: In follow-up to the Expert Discussion at the 2008 Workshop on "Biosignal Analysis" of the German Society of Biomedical Engineering in Potsdam, Germany, we comprehensively searched the pertinent literature and databases and compiled the results into this review. Then, we categorized the state-of-the-art methods and selected new approaches based on their applications in detection and risk stratification of myocardial ischemia. Finally, we compared the pros and cons of the methods and explored their future potentials for cardiology. Results: Resting ECG, particularly suited for detecting ST-elevation myocardial infarctions, and exercise ECG, for the diagnosis of stable CAD, are state-of-the-art methods. New exercise-free methods for detecting stable CAD include cardiogoniometry (CGM); methods for detecting acute coronary syndrome without ST elevation are Body Surface Potential Mapping, functional imaging and CGM. Heart rate variability and blood pressure variability analyses, microvolt T-wave alternans and signal-averaged ECG mainly serve in detecting and stratifying the risk for lethal arrythmias in patients with myocardial ischemia or previous myocardial infarctions. Telemedicine and ambient-assisted living support the electrocardiological monitoring of at-risk patients. Conclusions: There are many promising methods for the exercise-free, non-invasive detection of CAD and myocardial ischemia in the stable and acute phases. In the coming years, these new methods will help enhance state-of-the-art procedures in routine diagnostics. The future can expect that equally novel methods for risk stratification and telemedicine will transition into clinical routine.