The Effect of Fe Addition on Microstructure, Mechanical Properties and Electric Conductivity of the As-Cast Al-Mg-Si Alloys.

Fe is considered as one of the most harmful trace elements among impurities in aluminum and its alloys due to its influence of the mechanical properties especially in elongation. It is therefore essential that the Fe content is controlled to improve quality and the toughness of aluminum alloy castings. Since demand for high strength aluminum alloy casting was significantly increased in electro materials and devices, automotive and airplane industries, it is necessary to characterize the effect of Fe and set the tolerable amount of Fe content in aluminum alloys. Al6061 alloys were prepared with compositions of 0.36, 0.45, 0.58, 0.65, 0.75, 0.81 and 0.91 wt.% Fe. Solidification characteristics were analyzed by CALPHAD (Pandat software) method. Mechanical properties such as hardness, tensile strength, elongation and fatigue strength were evaluated and compared with different Fe contents. Al13Fe4 phase increased with increasing as Fe content, however, other phases, α-AlFeSi and Mg2Si, showder a slight decrease. The higher the Fe content, the lower the electrical conductivity of the alloy due to the severe distortion of the Al matrix. As Fe content was more than specification of Al6061 alloy, 0.7 wt.%, the mechanical properties, especially, hardness and elongation were greatly influenced. The hardness is attributed to the poor densification and angular-shaped Al13Fe4 phases unevenly distributed in the α-Al matrix.

Reliability of Processing Map and Influence of Sigma Phase Precipitation on Hot Workability of Duplex Stainless Steel.

The hot deformation characteristics of an UNS No. S32205 grade duplex stainless steel with nitrogen content of 0.17 ms% was studied over the ranges of temperature from 800 to 1200 °C and strain rates from 0.001 to 1.0 s-1 at the total strain of 0.5 by the hot compression test to draw the processing map. The obtained map was discussed in combinations of microstructural observations and TEM analysis. The optimum hot working region is the temperatures from 950 to 1200 °C regardless of the strain rates without cracks and sigma precipitates.

A Fatal Adverse Effect of Barbiturate Coma Therapy: Dyskalemia.

The management guideline for traumatic brain injury (TBI) recommends high-dose barbiturate therapy to control increased intracranial pressure refractory to other therapeutic options. High-dose barbiturate therapy, however, may cause many severe side effects; the commonly recognized ones include hypotension, immunosuppression, hepatic dysfunction, renal dysfunction, and prolonged decrease of cortical activity. Meanwhile, dyskalemia remains relatively uncommon. In this study, we report the case of a hypokalemic patient with severe rebound hyperkalemia, which occurred as a result of barbiturate coma therapy administered for TBI treatment.

Cranioplasty Using a Modified Split Calvarial Graft Technique in Cleidocranial Dysplasia.

Cleidocranial dysplasia is a well-documented rare autosomal dominant skeletal dysplasia characterized by hypoplastic/aplastic clavicles, brachycephalic skull, patent sutures and fontanelles, midface hypoplasia, and abnormalities of dentition. Patients with cleidocranial dysplasia often complain about undesirable esthetic appearance of their forehead and skull. Notwithstanding many studies of molecular, genetics and skeletal abnormalities of this congenial disorder, there have been very few written reports of cranioplasty involving cleidocranial dysplasia. Thus, we report a rare case of successful cranioplasty using a modified split calvarial graft technique in patient with cleidocranial dysplasia.

An Improved One-Stage Operation of Cranioplasty and Ventriculoperitoneal Shunt in Patient with Hydrocephalus and Large Cranial Defect.

OBJECTIVE: The risk of complications is high for patients with a large cranial defect and hydrocephalus, undergoing cranioplasty and ventriculoperitoneal (VP) shunt operation. The purpose of this study is to examine retrospectively such cases with complications and contrive an operative technique to reduce complications. METHODS: Nineteen patients underwent cranioplasty and VP shunt operation due to large cranial defects and hydrocephalus. These patients were divided into two groups: Group A with 10 patients who underwent staged-operations, and Group B with 9 patients who underwent one-stage operation. Their complications in each group were retrospectively reviewed. Another five patients underwent a one-stage operation with temporary occlusion of the distal shunt catheter to improve on the technique and were categorized as Group C. Complications in these groups were compared and analyzed. RESULTS: The results of the data analysis revealed that complications related to anesthesia (40%) and those related to antibiotic prophylaxis (30%) were high in Group A, while non-infectious delayed complications (45%) and perioperative complications such as intracranial hematoma (33%) were high in Group B. However, for patients in Group C, it showed less complication with the operative technique devised by these authors, as opposed to two previous procedures. CONCLUSION: In patients with hydrocephalus and a large cranial defect, complications arising from existing one-stage operation or staged-operations can be reduced by implementing the technique of "one-stage operation with temporary occlusion of the distal shunt catheter."

Use of the sundt clip graft in a previously coiled internal carotid artery blister-like aneurysm.

Owing to the focal wall defect covered with thin fibrous tissues, an aneurysm arising from the dorsal wall of the internal carotid artery (ICA) is difficult to manage either surgically or endovascularly and is often associated with high morbidity and mortality. Unfortunately, the definitive treatment modality of such highly risky aneurysm has not yet been demonstrated. Upon encountering the complex intracranial pathophysiology of such a highly precarious aneurysm, a neurosurgeon would be faced with a challenge to decide on an optimal approach. This is a case of multiple paraclinoid aneurysms including the ICA dorsal wall aneurysm, presented with spontaneous subarachnoid hemorrhage. With respect to treatment, direct clipping with a Sundt graft clip was performed after multiple endovascular interventions had failed. This surgical approach can be a treatment modality for a blood blister-like aneurysm after failed endovascular intervention(s).

Comparative Analysis of Cervical Lateral Mass Screw Insertion among Three Techniques in the Korean Population by Quantitative Measurements with Reformatted 2D CT Scan Images: Clinical Research.

OBJECTIVE: Our purpose of this study is to compare insertion angles and screw lengths from Roy-Camille, Magerl, and our designed method for cervical lateral mass screw fixation in the Korean population by quantitative measurement of reformatted two dimensional (2D) computed tomography (CT) images. METHODS: We selected thirty Korean patients who were evaluated with thin section CT scans and reconstruction program to obtain reformatted 2D-CT images of the transversal plane passing the cranio-caudal angle using three different techniques. We measured the minimum angle to avoid vertebral artery (VA) injury, the ideal angle and depth for bicortical screwing of cervical lateral mass. Morphometric measurements of the lateral masses from C3-C7 were also taken. RESULTS: In all three techniques, the mean safety angles from the VA were less than 8 degrees and the necessary depth of the screw was about 14 mm for safety to the VA and for the bicortical purchase. In our designed technique, the mean beta angles of each level from C3 to C7 were 29.0, 29.8, 29.5, 26.3, and 23.9 degrees, respectively. CONCLUSION: Results of this study and data from the literature indicate that differences may exist between the Korean and Western people in the length and angle for ideal lateral mass screw fixation. In addition, our technique needs further cadaveric and clinical study for safety and efficacy for being performed as alternative method for cervical lateral mass fixation.