An Innovative Test Method for Tensile Strength of Concrete by Applying the Strut-and-Tie Methodology.

Tensile strength is one of the important mechanical properties of concrete, but it is difficult to measure accurately due to the brittle nature of concrete in tension. The three widely used test methods for measuring the tensile strength of concrete each have their shortcomings: the direct tension test equipment is not easy to set up, particularly for alignment, and there are no standard test specifications; the tensile strengths obtained from the test method of splitting tensile strength (American Society for Testing and Materials, ASTM C496) and that of flexural strength of concrete (ASTM C78) are significantly different from the actual tensile strength owing to mechanisms of methodologies and test setup. The objective of this research is to develop a new concrete tensile strength test method that is easy to conduct and the result is close to the direct tension strength. By applying the strut-and-tie concept and modifying the experimental design of the ASTM C78, a new concrete tensile strength test method is proposed. The test results show that the concrete tensile strength obtained by this proposed method is close to the value obtained from the direct tension test for concrete with compressive strengths from 25 to 55 MPa. It shows that this innovative test method, which is precise and easy to conduct, can be an effective alternative for tensile strength of concrete.

Nasopharyngeal branchial cleft cyst.

Second branchial cleft cysts are almost always located in the neck; thus, their presence in the nasopharynx is extremely rare. A 44-year-old man was referred to our department because a cystic mass was fortuitously found in the right lateral nasopharyngeal wall during transnasal esophagogastroscopy. He had suffered from intermittent right-sided nasal obstruction since childhood. T1- and T2-weighted magnetic resonance imaging revealed hyperintense signals. Marsupialization was performed by diode laser via an endoscopy-guided approach. No immediate postoperative complications occurred, and there was no recurrence 6 months following surgery. When a cystic lesion presents in the lateral nasopharynx, branchial cleft cyst should be considered in the differential diagnosis. In our experience, marsupialization by diode laser via an endoscopy approach is a safe and straightforward method of treating nasopharyngeal branchial cleft cyst, with no adverse effects.

Assessments of growth conditions on the production of cyanophycin by recombinant Escherichia coli strains expressing cyanophycin synthetase gene.

The synthesis of cyanophycin, a biodegradable polymer, is directed by cyanophycin synthetase. Polymerase chain reaction (PCR) cloned the gene cphA coding for cyanophycin synthetase from Synechocystis sp. PCC 6803 into pET-21b followed by transformation into two Escherichia coli hosts. The culture conditions for cyanophycin production were investigated, and the molecular weight and compositions of purified cyanophycin were analyzed. The results showed that E. coli BL21-CodonPlus(DE3)-RIL could produce 120 mg cyanophycin per gram dry cell weight in terrific medium. The purified cyanophycin consisted of insoluble and soluble forms at pH 7. The insoluble form had a higher molecular weight (20-32 kDa) than the soluble form (14-25 kDa). Both forms are composed of three major amino acids, aspartic acid, arginine, and lysine, and the insoluble form showed a higher arginine/lysine molar ratio (4.61 ± 0.31) than the soluble form (0.89 ± 0.05). In addition, the nitrogen sources could affect the yields of insoluble and soluble forms of cyanophycin. The medium containing additional lysine could enhance the proportion of the soluble form, but had little effect on the lysine and arginine percentages of both soluble and insoluble forms. The medium containing additional arginine slightly decreased the proportion of soluble form and altered its amino acid composition, with a minimal effect on the lysine and arginine percentages in the insoluble form.

Progressive dysphagia in an elderly male.

Dysphagia can result from a variety of causes, including central nervous and peripheral nervous system, myogenic, and structural disorders. A 76-year-old man underwent anterior cervical disketomy and fusion 10 years ago, with progressive dysphagia noted 2 years ago. Endoscopy showed an oropharyngeal tumor, and lateral plain film evaluation of the neck revealed a cervical plate extrusion. Removal of the instrumentation and tumor with primary closure of the pharyngeal perforation was performed, and dysphagia was resolved postoperatively. We report the case of an unusual presentation in the pharynx. We should not neglect this rare diagnosis, because it can progress to a life-threatening outcome.