Strain-Rate Dependence of Tensile Behavior in Commercial-Grade Tungsten-Effect of Recrystallization Condition.

The tensile deformation behavior of double-forged (DF-W) and recrystallized (RX-W) commercial-grade tungsten was investigated at 700 °C. With increasing strain rate, the dominant dynamic recrystallization (DRX) mechanism changes from continuous dynamic recrystallization (CDRX) to discontinuous dynamic recrystallization (DDRX). For DF-W, pre-existing sub-grains promote CDRX and associated a high-DRX fraction, resulting in reduced post-necking strain under a static condition. With increasing strain rate, a shift in the restoration mechanism from CDRX to DDRX contributes to the enhanced ductility in DF-W, while RX-W shows enhanced flow hardening without a loss of ductility. These results suggest that the strain-rate dependence of mechanical behavior depends on the initial microstructure.

Effect of Ti Content on the Microstructure and High-Temperature Creep Property of Cast Fe-Ni-Based Alloys with High-Al Content.

The cast Fe-Ni-based austenitic heat-resistant alloys with 4.5 wt% Al and varying Ti content were developed for high-temperature application. With increase in Ti content, strength of model alloys increased gradually at 700 °C and 750 °C. At 750 °C, alloys with 35Ni-(2~4)Ti composition showed a significant increase in creep rupture life compared to 30Ni-1Ti alloy, attributed to the increase in γ'-Ni3(Al,Ti) precipitates due to higher Ni and Ti content. Among the 35Ni-(2~4)Ti alloys, increasing Ti content from 2 to 4 wt% gradually increased the creep rupture life in the as-cast condition. The creep rupture life was improved after solution annealing treatment, however, the beneficial effect of higher Ti content was not evident for 35Ni-(2~4)Ti alloys. After solution annealing, interdendritic phases were partially dissolved, but coarse B2-NiAl phases were formed. The size and amount of coarse B2-NiAl phases increased with Ti content. In the creep-tested specimens, creep void nucleation and crack propagation were observed along the coarse B2-NiAl phases, especially for high-Ti alloys. Therefore, the beneficial effect of the increase in γ'-Ni3(Al,Ti) precipitates for high-Ti alloys on creep property was limited due to the detrimental effect of the presence of coarse B2-NiAl phases.

Measurement of Fracture Toughness of Pure Tungsten Using a Small-Sized Compact Tension Specimen.

The evaluation of fracture toughness of pure tungsten is essential for the structural integrity analysis in a fusion reactor. Therefore, the accurate quantification of fracture toughness of tungsten alloys is needed. However, due to the inherent brittleness of tungsten, it is difficult to introduce a sharp fatigue pre-crack needed for the fracture toughness test. In this study, a novel fatigue pre-cracking method was developed and applied to the small-sized disc-type compact tension (DCT) specimens of double-forged pure tungsten. To overcome the brittleness and poor oxidation resistance, a low-frequency tensile fatigue pre-cracking was performed at 600 °C in Ar environment, which resulted in the introduction of a sharp pre-crack to DCT specimens. Then, fracture toughness tests were conducted at room temperature (RT), 400 °C, and 700 °C in air and Ar gas environments using as-machined and pre-cracked DCT specimens. At RT and 400 °C, the test environment and crack tip radius did not affect the fracture toughness measurement. However, at 700 °C, the Ar gas environment and the presence of a sharp fatigue pre-crack resulted in a decrease in the measured fracture toughness. Thus, it was suggested that, for the conservative fracture toughness measurement of pure tungsten, fatigue pre-cracking and fracture toughness test should be performed in an inert environment, especially for high-temperature tests.

Can A Sudden Sensorineural Hearing Loss Occur Due to Miliary Tuberculosis?

Miliary tuberculosis is a severe form of tuberculosis resulting from dissemination of Mycobacterium tuberculosis bacilli. Since symptoms appearing in patients due to miliary TB are diverse and atypical, depending on the site of invasion, early diagnosis and treatment are important. A paradoxical response of tuberculosis is a rare phenomenon and it can be a clinical difficulty to treatment especially when involving the central nervous system. We present a case report with a review of related literature about the patient who developed sudden hearing loss due to tuberculosis infection in vestibulocochlear area.

The structural changes of upper airway and newly developed sleep breathing disorders after surgical treatment in class III malocclusion subjects.

Bimaxillary surgery is the traditional treatment of choice for correcting class III malocclusion which is reported to cause an alteration of oropharyngeal structures and upper airway narrowing that might be a predisposing factor for obstructive sleep apnea (OSA). This study aimed to analyze sleep parameters in class III malocclusion subjects and ascertain the prevalence of snoring or OSA following bimaxillary surgery.A total of 22 patients with Le Fort I osteotomy and mandibular setback for class III malocclusion were prospectively enrolled. All patients received endoscopic examination, cephalometry, 3-dimensional computed tomography (3D-CT), and sleep study twice at 1 month before and 3 months after surgery.The patient population consisted of 5 males and 17 females with a mean body mass index of 22.5 kg/m and mean age of 22.1 years. No patients complained of sleep-related symptoms, and the results of sleep study showed normal values before surgery. Three patients (13%) were newly diagnosed with mild or moderate OSA and 6 patients (27%) showed increased loudness of snoring (over 40 dB) after bimaxillary surgery. According to cephalometric analysis and 3D-CT results, the retropalatal and retroglossal areas were significantly narrowed in class III malocclusion patients, showing snoring and sleep apnea after surgery. In addition, the total volume of the upper airway was considerably reduced following surgery in the same patients.Postoperative narrowing of the upper airway and a reduction of total upper airway volume can be induced, and causes snoring and OSA in class III malocclusion subjects following bimaxillary surgery.

Clinical implication of cervical vestibular evoked myogenic potentials in benign paroxysmal positional vertigo.

OBJECTIVES: To evaluate the value of cervical vestibular evoked myogenic potential (cVEMP) as a prognostic factor for benign paroxysmal positional vertigo (BPPV). METHODS: We reviewed 65 patients with BPPV who underwent cVEMP. Patients were divided into two groups according to resistance to the repositioning maneuver. Univariable and multivariable analyses were performed with age, gender, affected semicircular canal, affected side and cVEMP parameters to find the associated factors for resistance to the repositioning maneuver. RESULTS: From univariable analysis, cVEMP interaural amplitude difference (IAD) ratio, the affected semicircular canal and the affected side showed a better association (p<0.10) with resistance to the repositioning maneuver. With multivariable analysis, decreased cVEMP IAD ratio at the affected side (⩽-25%) (p=0.043, OR=4.934) and the posterior semicircular canal (p=0.049, OR=3.780) remained as associated factors. CONCLUSIONS: Decreased cVEMP IAD ratio at the affected side is associated with resistance to the repositioning maneuver. BPPV patients with decreased cVEMP IAD ratio at the affected side have a higher likelihood of their BPPV persisting after a single repositioning maneuver. SIGNIFICANCE: cVEMP test may provide a prognosis of BPPV. A decreased cVEMP IAD ratio at the affected side may be prognostic of BPPV not resolving after a single repositioning maneuver.

Impact of control of blood glucose level during treatment of sudden deafness in diabetics: relationship with prognosis.

The objective of this study is to investigate the impact of control of blood glucose level during treatment of sudden deafness. A retrospective study was performed involving 197 patients from January, 2011 to September, 2015. All patients were administrated prednisolone (Pharmaprednisolone tab®, 5 mg/T; KoreaPharma) p.o under the following regimen: 60 mg/day for 4 days, 40 mg/day for 2 days, 30 mg/day for 1 day, 20 mg/day for 1 day, and 10 mg/day for 2 days. During treatment, pure tone audiometry and blood glucose level were investigated for each patient and the results were statistically analyzed. Mean hearing improvement was 19.2 dB for the non-diabetes group and 24.8 dB for the diabetes group. The greater improvement for diabetics was not statistically significant (p = 0.146). Hearing improvement was 25.1 dB for subjects with mean blood glucose <200 mg/dl and 24.6 dB for subjects with mean blood glucose >200 mg/dl; the difference was not statistically significant (p = 0.267). Mean blood glucose level was 200.8 mg/dl for subjects with hearing improvement >20 dB and 181.8 mg/dl for subjects with hearing improvement <20 dB; the difference was not statistically significant (p = 0.286). Control of blood glucose level during treatment of sudden deafness does not have a direct effect on prognosis.

Cholesteatoma of Maxillary Sinus: What Is the Best Surgical Approach?

Cholesteatoma is a relatively common disease entity within the middle ear or mastoid cavity but cholesteatoma of the paranasal sinuses is a rare diseases entity, especially in the maxillary sinus. As the authors recently experienced a patient of maxillary sinus cholesteatoma, the authors tried to review all the literatures previously reported on the "Cholesteatoma of the maxillary sinus." The aim of this study was to describe authors' recent experience and review previously reported patients of cholesteatoma of the maxillary sinus. Additionally, it is to describe the clinical features focusing on the computed tomography findings and to elucidate which approach may be best for complete excision. The authors thoroughly reviewed 10 patient reports written in English regarding the cholesteatoma of maxillary sinus which have been published since the 1980s. Based on authors' review, the authors suggest some conclusions. First, the diagnosis of cholesteatoma, although rare, should be considered for any slowly expansile lesion of the maxillary sinus. Second, there was no specific computed tomography finding that was helpful for the diagnosis of maxillary sinus cholesteatoma. Last, the surgical approach to cholesteatoma of the maxillary sinus should be chosen to allow visibility and complete removal according to the size, location, and extent of diseases.