Improving the strength of adhesively bonded joints through the introduction of various surface treatments

The aim of this paper is to model an interface adhesion and failure mechanism of single lap joints, subjected to tensile loading, focusing on the effects of various surface treatments, including surface characterization parameters, such as surface roughness and contact angle of adherend surfaces. The applied surface treatments are sandblasting, etching, anodic oxidation and hybrid processes. The influence of surface treatment techniques and conditions on single lap joint strength and interfacial properties is investigated by performing a static tensile test. A numerical approach, which is a cohesive zone model, is implemented using ABAQUS? and introduced to create a correlation between maximum interface traction and surface processing parameters, such as surface roughness and work of adhesion. As a result of experiments, an etching plus sanding process was found to provide the best single lap joint performance (8726 N), having surface roughness of Ra = 2.93 μm and work of adhesion, W_a = 119.4 mJ/m². Based on numerical solutions, a correlation between maximum interface traction and type of surface treatment process has been established, taking certain assumptions into consideration.     

Cation deficiency associated with the chemical exfoliation of lithium cobalt oxide

Compositional changes associated with the chemical exfoliation of lithium cobalt oxide, a layered transition metal oxide, are discussed. Starting from a layered bulk structure, lithium cobalt oxide can undergo chemical exfoliation through a two-step method: treatment with a protic acid, then treatment with tetramethylammonium hydroxide (this intercalates the layered structure and yields exfoliated nanosheets). This work provides an in-depth analysis of compositional and structural changes occurring to the powder upon the first step to exfoliation, treatment with acid, revealing variations in vacancies and valence changes depending on the conditions used. Through coupled analysis of X-ray photoelectron spectroscopy, X-ray diffraction, UV-Vis absorption spectroscopy, and inductively coupled plasma-optical emission spectroscopy data, we illustrate that both lithium and cobalt ions are diffusing out the structure along with the dissolution of full unit cells. As such, nanosheets accessed from the bulk by this exfoliation process should not be considered simply as divisions of the original unit cell. This work provides fundamental insights on the stability of LiCoO₂ and the exfoliation of layered transition metal oxides, beyond the access of individual nanosheets, and is vital to determining structure-property relationships of chemically exfoliated nanosheets (eg, changes in valency which dictate catalytic activity, magnetic susceptibility, etc).     

Isothermal crystallization kinetics and mechanical properties of polycaprolactone composites with zinc oxide,oleic acid,and glycerol monooleate

The isothermal crystallization and mechanical behavior of polycaprolactone (PCL) with zinc oxide (ZnO) with oleic acid and glycerol monooleate (GMO) were studied. Theoretical melting points calculated by the Flory–Huggins and Thompson–Gibbs models were thoroughly compared with differential scanning calorimetry experimental observations. The isothermal crystallization kinetic parameters by Avrami analysis showed that crystallization was controlled by nucleation, crystal growth was spherical, and the nucleation type changed between thermal and athermal nucleation. X‐ray diffraction showed that when the additives were used together both the crystal thickness and the degree of crystallinity increased. A multiple‐response regression analysis was made with the ZnO, oleic acid, and GMO concentrations as variables and the crystallinity as output. Interaction parameters by the Pukanzky model were calculated from the tensile strength at the yield point and indicated that the addition of oleic acid or GMO improved the interface between the ZnO particles and PCL. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 1259‐1275, 2013     

Hydrogen effects in a dual-phase microalloy steel

A dual-phase steel containing niobium, vanadium and titanium as microalloying elements was tested for hydrogen embrittlement (HE). The susceptibility to HE was observed to be closely related to the microstructural state. Hydrogenated specimens intercritically annealed at relatively low temperatures to develop martensite islands in a ferrite matrix basically exhibited quasi-cleavage fracture with some ductile dimpling. The mode of fracture in charged specimens quenched from higher intercritical annealing temperatures was predominantly intergranular fracture along prior austenite grain boundaries and cracking of martensite laths. The detrimental role of residual stresses, retained austenite and microalloying carbides in the process of HE is discussed.     

Corpora compilation for prosody-informed speech processing

Language Resources and Evaluation - Research on speech technologies necessitates spoken data, which is usually obtained through read recorded speech, and specifically adapted to the research needs....     

Acute kidney injury after near drowning: The way from the beach to hemodialysis

Acute kidney injury (AKI) occurs in many different situations and may have a variable prognosis influenced by clinical setting, underlying cause, and comorbidity. This is important because of the high mortality and morbidity risk affecting many people around the world. Near‐drowning related AKI requiring hemodialysis is very seldom reported in literature. Although cardiovascular and respiratory disorders are more frequently seen after this entity, we aimed to emphasize this rare but dangerous complication in near‐drowning patients.     

Anticoagulation,delivered dose and outcomes in CRRT: The program to improve care in acute renal disease (PICARD)

Delivered dialysis dose by continuous renal replacement therapies (CRRT) depends on circuit efficacy, which is influenced in part by the anticoagulation strategy. We evaluated the association of anticoagulation strategy used on solute clearance efficacy, circuit longevity, bleeding complications, and mortality. We analyzed data from 1740 sessions 24 h in length among 244 critically ill patients, with at least 48 h on CRRT. Regional citrate, heparin, or saline flushes was variably used to prevent or attenuate filter clotting. We calculated delivered dose using the standardized Kt/V_urea. We monitored filter efficacy by calculating effluent urea nitrogen/blood urea nitrogen ratios. Filter longevity was significantly higher with citrate (median 48, interquartile range [IQR] 20.3–75.0 hours) than with heparin (5.9, IQR 8.5–27.0 hours) or no anticoagulation (17.5, IQR 9.5–32 hours, P < 0.0001). Delivered dose was highest in treatments where citrate was employed. Bleeding complications were similar across the three groups (P = 0.25). Compared with no anticoagulation, odds of death was higher with the heparin use (odds ratio [OR] 1.82, 95% confidence interval [CI] 1.02–3.32; P = 0.033), but not with citrate (OR 1.02 95% CI 0.54–1.96; P = 0.53). Relative to heparin or no anticoagulation, the use of regional citrate for anticoagulation in CRRT was associated with significantly prolonged filter life and increased filter efficacy with respect to delivered dialysis dose. Rates of bleeding complications, transfusions, and mortality were similar across the three groups. While these and other data suggest that citrate anticoagulation may offer superior technical performance than heparin or no anticoagulation, adequately powered clinical trials comparing alternative anticoagulation strategies should be performed to evaluate overall safety and efficacy.     

Electron emission from 57Fe nuclei excited with synchrotron radiation

The increase in cytosolic free Ca2+ concentration ([Ca2+]i) seen in submandibular cells of early postnatal rats following exposure to acetylcholine (ACh) is larger than in cells of adult rats. To elucidate possible reasons for this difference, we compared Ca2+ movements through Ca2+ pumps in both types of cells using Ca(2+)-sensitive fluorescent probe fura-2 and the radiotracer 45Ca2+. Ca2+ release induced by endoplasmic reticulum (ER) Ca(2+)-pump inhibitor thapsigargin (TG) was significantly smaller in neonatal cells than in adult cells, whereas the inositol 1,4,5-trisphosphate (IP3)-elicited Ca2+ release was comparable in both cell types. This suggests that although the size of the IP3-sensitive Ca2+ pool is adequate in immature cells, the activity of TG-sensitive Ca2+ pump in this pool is lower. The activity of the plasma membrane (PM) Ca(2+)-pump, measured by extrusion of 45Ca2+, was also significantly lower in immature cells. These results indicate that both ER and PM Ca2+ pumps may be functionally underdeveloped in immature cells, and that the enhanced increase of [Ca2+]i seen in response to ACh in immature cells may be partially, if not completely, due to a reduced capacity for removal of Ca2+ from the cytosol by active mechanisms.