STRENGTH TESTING OF STRIPPING CYLINDER’S TOOTH

A magnitude of a stripping tooth’s necessary strength is an important parameter for designing of reapers. Methodology and means of efforts’ measuring, appeared at stripping teeth, are suggested in the article so as they are necessary for strength calculations. As an example of this method, the definition of efforts, which appear at a tooth during stripping of winter wheat “Luchezar” variety with humidity 10.7% at the certain conditions, is used.

Etching Patterns of Self-Etching Primers in Relation to Shear Bond Strength on Unground Enamel Samples

It was the intention of the study to evaluate the etching effects of several self-etching primers on unground enamel and their relevance for shear bond strength testing. Seven self-etching primers (Clearfil SE, Futurabond NR, M-Bond, One Coat, Optibond, Transbond SEP+, Xeno III) and a conventional 35% phosphoric gel acid were applied to bovine incisors according to the manufacturer’s instructions. All specimens were analyzed by electron microscopy. A visual four-step grading was used for the characterization of the macroscopic (5000×) and microscopic (20,000×) etching patterns. In addition, shear bond strength for all the products was tested with an Instron 3344 after 1000 thermocycles between 5 °C and 55 °C. Statistical analysis was carried out using Kruskal–Wallis with Dunn’s post-test and Pearson’s correlation coefficient. Very strong etching patterns with well-defined prisms were found for the conventional etching, Transbond SEP+, and to a lesser degree, for Xeno III. Clearfil SE and Futurabond NR revealed moderate etching patterns, and M-Bond, One Coat, and Optibond revealed very weak etching patterns. The bond strength correlated well with the etching patterns. The highest shear strength was obtained with conventional etching and Transbond SEP+, followed by Clearfil SE. Moderate shear bond strengths were found for Xeno III, Futurabond NR, One Coat, and M-Bond, and the lowest were found with Optibond.

The Impact of Resistance Training on Gene Expression of IGF1 and Athletes’ Physiological Parameters

AIM: The purpose of this study was to verify the effect of a resistance training program for 8 weeks on IGF1, gene expression, and physical performance in male student-athletes. METHODS: The population of this study was 20 male students divided to two equal groups. The parameters estimated were IGF1, gene expression, and muscle strength testing. Blood was drawn to verify the concentration of the variables, using kits and Elisa method in addition to the PCR technique. RESULTS: The results revealed that a significant increase in IGF1, gene expression was different between students. Furthermore, muscle strength testing revealed significant changes. CONCLUSION: The results suggested that resistance training program may impact fitness and muscle strength as well the anabolic activity through IGF1 increase accompanied by varied gene expressions.

LIGHTWEIGHT MORTAR GEOPOLIMER BASED ON FLY ASH AND PALM ASH

This research discusses the use of alumunium powder in the manufacture of geopolymer mortar made from fly ash and palm ash, with the aim of knowing the optimal amount of alumunium powder mixture against the compressive strength of geopolymer mortar. The research method used experimental methods in the laboratory, to examine the compressive strength of different geopolymer mortar tests used in the form of cubes measuring 5 x 5 x 5 cm with a mixture composition of NaOH: Na2SiO3 = 1: 2.5, Activator: Precursor = 1: 1, Fine Aggregate: Precursor = 1.5: 1 Concentration of NaOH = 12 M for the ratio of fly ash use: palm ash = 75: 25% using alumunium powder as much as 0, 0.5, 0.75 and 1%. Mortar strength testing was carried out after 3, 7, 14, 21 and 28 days of maintenance The compressive strength results obtained in each composition of the geopolymer mortar mixture are for geopolymer mortar without a mixture of alumunium powder as large as Mpa, for geopolymer mortar with a mixture of alumunium powder as much as 0.5%, 0.75% and 1% have a compressive strength of 20.9 Mpa, 15.2 Mpa, 12.7 Mpa Dan 9,7 Mpa

Recent Advances in Magnesia Blended Cement Studies for Geotechnical Well Construction—A Review

The current paper presents a literature review on the studies of incorporation of magnesia (magnesium oxide) into Portland cement material from the geotechnical well construction perspective. Starting with a comparison of application conditions between civil construction and geotechnical well cementing, this work reviewed the Portland cement categorizations, magnesia manufacturing routes at first. Then, the physical-chemical-mechanical properties were investigated which includes the reactivity of magnesia, expansion influence from its hydration, and carbonation/dehydroxylation of magnesia blended Portland cement. The development of cement material hydration modeling methods is also summarized. Moreover, the experimental characterization methods have also been elucidated including composition determination, particle size analysis, volumetric variation measurement, compressive strength testing, shear-bond strength testing, transition state analysis, etc. Meanwhile, the results and conclusions were extracted from the literature. Through this route, a comprehensive understanding of the scientific research progress on magnesia blended Portland cement development for geotechnical well construction is derived. Additionally, it is concluded that incorporating magnesia into Portland cement can provide benefits for this material utilization in geotechnical well constructions provided the reasonable tuning among the characteristics of magnesia, the downhole surrounding conditions, and the formulation of the cement slurry. Satisfying these pre-conditions, the effective expansion not only mitigates the micro-annulus issues but also increases the shear bonding strength at the cementing interfaces. Moreover, the caustic magnesia introduction into Portland cement has the potential advantage on carbon dioxide geological sequestration well integrity compared with the Portland cement sheath without it because of the denser in-situ porous matrix evolvement and more stable carbon fixation features of magnesium carbonate. However, since the impact of magnesia on Portland cement strongly depended on its properties (calcination conditions, particle size, reactivity) and the aging conditions (downhole temperature, pressure, contacting medium), it should be noted that some extended research is worth conducting in the future such as the synchronized hydration between magnesia and Portland cement, the dosage limit of caustic magnesia in Portland cement in terms of CO2 sequestration and the corresponding mechanical properties analysis, and the hybrid method (caustic magnesia, Portland cement, and other supplementary cementitious materials) targeting the co-existence of the geothermal environment and the corrosive medium scenario.

The Association between Radiologic Severity of Rotator Cuff Pathology and Supraspinatus Weakness on Biomechanical Assessment (229)

Objectives: Many different magnetic resonance imaging (MRI)-based classifications are used to characterize rotator cuff supraspinatus pathology, ranging from mild tendinopathy to full-thickness tears. While MRIs are chiefly utilized to guide the need for and approach to operative management of supraspinatus pathology, the functional implications, if any, across the entire range of pathologies have not been defined. The purpose of this biomechanical study was to examine shoulder strength and function in patients presenting with presumptive supraspinatus pathology and to determine if these clinical parameters are correlated with radiologic severity. Methods: We prospectively enrolled 171 patients with suspected rotator cuff pathology disease and without apparent strength deficit on traditional rotator cuff physical examination (PE). Exclusion criteria were radiographically apparent glenohumeral OA, previously diagnosed rotator cuff tear of the affected shoulder, previously diagnosed adhesive capsulitis, prior ipsilateral shoulder surgery, injury to the ipsilateral hand or wrist, limited range of motion, and history or radiographic evidence of anterior or posterior shoulder dislocation. For both clinical (e.g. testing isotonic strength in patients with frank weakness yields unreliable strength measurements and provides little useful information) and ethical (e.g. to avoid causing pain to patients already experiencing significant shoulder pain) reasons, this study evaluating dynamic strength testing was strictly limited to patients with negative traditional, static PE tests. All patients underwent two bilateral shoulder strength tests using dynamometry; first, isometric strength was measured at 90 degrees of abduction and, second, isotonic strength was measured eccentrically from full abduction throughout the full range of motion until the arm was at the patient’s side. For both of these tests, the examiner placed the handheld dynamometer (Hoggan microFET® 3; Hoggan Scientific, LLC, Salt Lake City UT, USA) on the patient’s wrist, perpendicular to the arm, to measure the force applied along the arc. Absolute strength and symptomatic-to-asymptomatic arm (S/A) strength ratios were calculated. All patients were included in analyses of absolute strength measurements on strength testing; patients who had a history or clinical evidence of contralateral shoulder pathology were excluded from analyses of S/A strength ratios. Patients then underwent shoulder MRI, classifying supraspinatus findings into one of seven ordinal categories. The primary outcome was the relationship between the radiologic severity of supraspinatus pathology on MRI and the degree of rotator cuff strength deficit upon exam. Results were analyzed for both isotonic and isometric function. Results: The study cohort consisted of 171 patients (102 [59.6%] males, 69 [40.4%] females). The mean patient age (± 95% CI) was 52.0 ± 1.9 years. The mean symptom duration (± 95% CI) was 10.8 ± 2.9 months. MRI revealed: 26 (15.2%) instances of no supraspinatus pathology, 37 (21.6%) instances of tendinopathy, 17 (9.9%) instances of supraspinatus fraying, 39 (22.8%) partial thickness tears (PTTs), 13 (7.6%) high-grade PTTs, 12 (7.0%) focal full thickness tears (FTTs)/full-thickness perforations, and 27 (15.8%) FTTs. Isotonic strength : Increasing imaging severity was significantly associated with decreasing absolute strength during isotonic testing ( P=0.036, Table 1). Specifically, absolute strength measurements declined with increasingly severe imaging findings, from no tear [59.9 N], to tendinopathy [50.9 N], to fraying [48.2 N], to PTT [55.0 N], to high-grade PTT [48.9 N], to focal FTT/full thickness perforation [45.7 N], to FTT [44.2 N]. Similarly, increasing imaging severity was significantly associated with decreasing S/A strength ratios during isotonic testing ( P=0.022, Table 1). Isotonic S/A strength ratios declined with increasingly severe imaging findings, from no tear [91.9%], to tendinopathy [70.8%], to fraying [66.1%], to PTT [76.2%], to high-grade PTT [75.7%], to focal FTT/full thickness perforation [65.2%], to FTT [63.3%]. Isometric strength : In contrast to isotonic testing, increasing imaging severity was not significantly associated with decreased absolute strength measurements on isometric testing ( P=0.12, Table 2). Similar results were seen for isometric S/A ratio, as increasing imaging severity was not significantly associated with S/A strength ratio ( P=0.085, Table 2). Conclusions: Radiologic severity of supraspinatus pathology was correlated with dynamic clinical function across the full range of pathology, revealing the functional importance of these frequently-used classifications. The lower discriminatory ability of isometric measurements and higher strength measurements on isometric assessment may be related to a greater role of compensatory musculature in static testing. These biomechanical results support the need for future work investigating the utility of dynamic rotator cuff physical examination maneuvers.

MECHANICAL TESTING OF LAMINATED COMPOSITE MATERIALS FOR PROSTHETIC SOCKETS

The mechanical properties of the composite materials for prosthetic sockets are a key determinant of the quality and usability of prostheses. Our aim was to compare the existing materials used in production at our institution with some modified, potentially improved materials. We conducted an industrial experiment. The existing material (A) was compared with three newly produced materials that introduced changes in the lamination process: B1, where an infusion spiral tube was added; B2, where the resin was degassed; and B3, where a mesh and peel ply were used. The specimens underwent laboratory strength testing. The strength measurements were statistically analysed using one-way analysis of covariance (ANCOVA) that was adjusted for specimen thickness because of the observed negative correlation of thickness with strength. Material A had the highest bending strength, on average, but there were no statistically significant differences in the bending strength between the materials after adjusting for the specimen thickness (p = 0.941). Materials B1 and B2 exhibited statistically significantly lower tensile strengths than material A (p < 0.001). Material B3 had the lowest average tensile strength, but it could not be statistically distinguished from the others, because of the significantly larger average specimen thickness. The compressive strength was tested only for materials B1, B2 and B3; their averages did not differ statistically significantly (p = 0.291). Laboratory strength testing provided important insights into the differences between the various laminated composite prosthetics materials. We did not reach our initial goal to produce a better material, but we will continue our research and development in this field with a more systematic, technological approach.