High strain rate response of nanofiber interlayered structural composites

Nanofibrous interlayer toughening strategy for laminated composite materials typically demonstrated at quasi-static loading is here evaluated under high strain rate deformation. Carbon fiber reinforced composite laminates of (0/90)25s stacking sequence are interlayered by polystyrene-co-glycidyl methacrylate (P(St-co-GMA)) nanofibers which are chemically tuned for interfacial compatibility when embedded in epoxy matrix. The cubical composite specimens are cut and subjected to high strain-rate deformation via Split Hopkinson pressure bar testing. Specimens are hit at their through-the-thickness (stacking) and side-to-side (in-plane) directions. The change in the dissipation of energy due to altered interlaminar microstructure is monitored and reported. Enhancement in the capacity of the energy dissipation due to the nanofibrous interlayers is as high as 80% in-plane and 40% through thickness directions, depending on the strain rate. The results overall suggest that interlayer toughening strategy used in this work prevents the formation of critical matrix cracks that can cause the formation of instantaneous mode II delamination. Incorporation of the nanofibers without causing notable weight penalty effectively toug

FATIGUE STRENGTH OF ANTIBIOTIC-IMPREGNATED BONE CEMENT SAMPLES ON "DAY 0" AND "DAY 15"

WOS: 000329084300017Objective: In this study, we aimed to assses the maximum efficious amount of teicoplanin in a mixture of 40 g CMV3 bone cement mixture, through the fatigue strength factor calculations. Material and Method: Five different doses of teicoplanin (0 mg, 400 mg, 800 mg, 1600 mg ve 3200 mg) were added to 40 g CMV3 bone cement mixture using the third generation cementing technique, then "day 0" and "day 15" groups were formed. Samples that were obtained on day 0 and day 15, were tested through fatigue strength machine to determine the rotational compressive strengths, intake/pulling strengths and four-point bending strengths. Day 0 and day 15 samples were compared statistically according to their fatigue strength values against the varying concentrations of antibiotic mixtures while day samples served as controls. Results: The "day 15" group that had various proportions of antibiotic which release to the surrounding was' compared to "0 mg" control group. While a meaningful reduction could not be identified between 400 mg and 800 mg doses (p>0.05) meaningful (p<0.001) strength reduced was identified between 1600 and 3200 mg doses. Day 0 and day 15 groups "fatigue-treated was applied on equal terms and group 0, 400, and 800 mg of antibiotic mixed samples did not yield any meaningful resistance differences with four points test. However, there was a statistically significant difference between 1600 and 3200 mg of the samples mixed with antibiotics (p<0.0001, p<0.0002). Conclusion: From the fatigue strength aspect, we assesed that 800 mg teicoplanin, is the maximum "efficious" amount of dose that can be added to 40 g CMV3 bone cement mixture

Loop security and tensile properties of polyblend and traditional suture materials

Tensile and knot properties of new generation (polyblend) and traditional suture materials in orthopedic surgery were investigated in standard laboratory conditions. Study focused on Fiberwire No. 5 and 2, Ethibond No. 5, 2 and 00, Orthocord No. 2, MaxBraid No. 2, Prolene No. 0 and 00, PDS No. 0 and 00, and Vicryl No. 2, 0 and 00. A 27-cm suture loop was fastened with 10 knots for ten samples for each type. Test parameters were tensile load to failure, elongation at failure point and knot slippage, and volume of 10-fold knots. Results were compared using ANOVA test. Failure load of No. 5 Fiberwire (625.0 +/- A 30.0 N) was significantly higher compared to all other suture types. Tensile strengths of MaxBraid No. 2 (287 +/- A 11 N) was significantly stronger compared to two other No. 2 polyblend sutures types and Ethibond No. 5. Knot slippage of Fiberwire No. 5 (14 +/- A 1.9 mm) was significantly higher compared to all other suture types. Ethibond No. 2 (0.1 +/- A 0.3 mm) had the lowest knot slippage. Elongation at the failure point of Fiberwire No. 2 (5%) was significantly lower than all other suture types. Mean calculated knot volume of #5 Fiberwire (73 +/- A 6.9 mm(3)) was significantly higher compared to #5 Ethibond (53 +/- A 4.8 mm(3)). Results of the study proved presence of significant differences between tensile and knot properties of various suture types and sizes. Loop security of larger diameter sutures is not always higher than thinner sutures. Suture elongation and knot slippage are important failure modes for high-diameter sutures and short-suture loops

In vitro comparison of two different materials for the repair of urethan dimethacrylate denture bases

PURPOSE. The purpose of this in vitro study was to investigate the flexural properties of a recently introduced urethane dimethacrylate denture base material (Eclipse) after being repaired with two different materials. MATERIALS AND METHODS. Two repair groups and a control group consisting of 10 specimens each were generated. The ES group was repaired with auto-polymerizing polymer. The EE group was repaired with the Eclipse. The E group was left intact as a control group. A 3-point bending test device which was set to travel at a crosshead speed of 5 mm/min was used. Specimens were loaded until fracture occurred and the mean displacement, maximum load, flexural modulus and flexural strength values and standard deviations were calculated for each group and the data were statistically analyzed. The results were assessed at a significance level of P.05) was found between the mean values of Group ES and EE. There was a statistically significant positive relation (P<.01) between the displacement and maximum load of Group ES (99.5%), Group EE (94.3%) and Group E (84.4%). CONCLUSION. The more economic and commonly used self-curing acrylic resin can be recommended as an alternative repair material for Eclipse denture bases

Vibration characteristics of grafts for the tympanic membrane

Perforation of the tympanic membrane occurs frequently as a result of infection, external trauma, and high-level impulsive sound pressure, such as that associated with an explosion. Many different surgical techniques can be used to repair the tympanic membrane and ossicles. Clinical operations such as tympanoplasty are undertaken to repair the damaged tympanic membrane and ossicles, thus improving hearing and reducing the chance of infection. The membrane is repaired or replaced with the use of graft materials, either from the patient's body or from artificial sources. The selection of graft material is very important because, as much as possible, it must exhibit the same dynamic behavior as the natural membrane. To compare various allograft materials, investigators developed a model of the ear on which different graft materials can be replaced. Three different membrane materials-irradiated allograft dura (Tutoplast (R) Dura; IOP Inc., Costa Mesa, Calif), irradiated allograft fascia lata (Tutoplast Fascia Lata; IOP Inc.), and irradiated allograft fascia temporalis (Tutoplast Fascia Temporalis; IOP Inc.) - were used. Vibration responses of these membrane materials produced by defined sound signals with different frequencies were recorded by a small strain gauge; the spectra of sound for various corresponding input signals were recorded, and the results were compared with those of the sample graft material. Tutoplast Fascia Lata accomplished the best dynamic performance in vitro. Additional clinical and experimental data are needed, however, to determine which of these materials provides the best audiological and clinical performance

Biomechanical comparison of three different plate configurations for comminuted clavicle midshaft fracture fixation

Background: The aim of this study was to compare the fixation rigidity of anterior, anterosuperior, and superior plates in the treatment of comminuted midshaft clavicle fractures

Retention and surface changes of zirconia primary crowns with secondary crowns of different materials

To evaluate zirconia as a substitute for gold alloy in primary crowns facing secondary crowns manufactured with different materials, in terms of long-term retention force changes, wear, and phase transformation was aimed

Biomechanical analysis of multilevel discectomy and excision of posterior longitudinal ligament: An in vitro study in sheep

Aim: This experimental biomechanical study was performed to determine the effects of multilevel anterior cervical discectomy and excision of posterior longitudinal ligament (PLL) to stabilize the cervical spine using an in vitro animal model. Materials and Methods: Fifty fresh cadaveric C3-C6 sheep spine specimens were divided into five experimental groups: Group A was the control group; Group B, one-level discectomy; Group C, two- level discectomy, Group D, three-level discectomy, and Group E, three-level discectomy and excision of PLL, respectively. The specimens were subjected to non-destructive loads cycled from zero to five Newton-meter for flexion, extension, right and left lateral bending, and axial rotation on an electrohydraulic test machine. Load displacement curves were obtained via collected data using strain gauges. The values were obtained for all five groups, statistical differences were determined respectively (P < 0.05, ANOVA). Results: One- level discectomy was less stable than the control group, two-level discectomy was less stable than one-level discectomy and three-level discectomy was less stable than two-level discectomy, respectively (P < 0.05). Excision of PLL did not seem to affect stability (P > 0.05). Conclusion: Our data suggested that cervical discectomy decreases stability of sheep spine pieces