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Abstract BACKGROUND: The suppression of the growth hormone (GH) on an oral glucose tolerance test (OGTT) has been accepted as the most reliable parameter for determining remission of acromegaly. OBJECTIVE: To evaluate the role of immediate postoperative GH level and 1-week postoperative OGTT as early predictive tools of long-term surgical remission. METHODS: One hundred ninety-four acromegalic patients who received transsphenoidal tumor resection and were followed up for > 1.5 years (3.80 ± 0.17 years) with at least 3 postoperative OGTTs were evaluated. Level of GH was measured 2, 6, 12, 18, 24, 48, and 72 hours postoperatively, and an OGTT was performed 1 week after surgery, every 6 months for the first 3 years, and annually thereafter. RESULTS: One hundred seventy-seven patients underwent gross total resection; long-term remission was achieved in 153. The GH level at 24 hours after surgery showed the highest predictive power for long-term remission. Long-term remission was maintained in 125/127 (98.4%) patients who had nadir GH levels < 1.0 μg/L on an early postoperative OGTT. However, when nadir GH levels were > 1.0 μg/L on an early postoperative OGTT, long-term remission was observed in 28 patients (28 of 67, 41.8%) in a delayed fashion. One-week postoperative OGTT had a sensitivity of 81.7% and specificity of 95.1% for predicting remission. CONCLUSION: Immediate postoperative GH level is a very good predictor of long-term outcome in acromegaly. One-week postoperative OGTT is also a good predictor with high specificity. These findings may provide critical information for the determination of adjuvant treatment after surgery.

We reviewed the research and developments in the field of fatigue failure, focusing on very-high cycle fatigue (VHCF) of metals, alloys, and steels. We also discussed ultrasonic fatigue testing, historical relevance, major testing principles, and equipment. The VHCF behavior of Al, Mg, Ni, Ti, and various types of steels were analyzed. Furthermore, we highlighted the major defects, crack initiation sites, fatigue models, and simulation studies to understand the crack development in VHCF regimes. Finally, we reviewed the details regarding various issues and challenges in the field of VHCF for engineering metals and identified future directions in this area.

In this work, we have investigated the role of high-energy ball milling (HEBM) on the evolution of microstructure, thermal, and wetting properties of an Sn-0.7Cu alloy. We ball-milled the constituent Sn and Cu powders in eutectic composition for 45 h. The microstructural studies were carried out using optical and scanning electron microscopy. The melting behavior of the powder was examined using differential scanning calorimetry (DSC). We observed a considerable depression in the melting point of the Sn-0.7Cu alloy (≈7 °C) as compared to standard cast Sn-0.7Cu alloys. The resultant crystallite size and lattice strain of the ball-milled Sn-0.7Cu alloy were 76 nm and 1.87%, respectively. The solderability of the Sn-0.7Cu alloy was also improved with the milling time, due to the basic processes occurring during the HEBM.

The reliability of terminal–substrate bonding in power modules for electric vehicles (EVs) was investigated by evaluating the effects of bonding method and substrate surface finish on the microstructural and mechanical properties of the joint. Ceramic substrates with bare Cu, electroless Ag, or electroless Ni-immersion Au surface finishes were bonded to Cu terminals by reflow soldering or ultrasonic welding. The interfacial intermetallic compound layers of the reflow-soldered joints exhibited varying compositions and morphologies according to the substrate surface finish, leading to differences in the shear strengths of the terminal joints. In contrast, the ultrasonic-welded joints did not exhibit any significant differences in morphology according to surface finish. Therefore, an electron backscatter diffraction analysis was conducted to observe the ultrasonic-welded joints in more detail. The results indicated that ultrasonic welding caused dynamic recrystallization (DRX) at the interface between the Cu terminal and ceramic substrate, resulting in grain refinement, and that the bare Cu substrate exhibited greater DRX than the other substrates. Consequently, both the bonding method and substrate surface finish were determined to significantly affect the mechanical properties of the power module terminal bond. This study is expected to contribute valuable insights to inform the improvement of terminal bonding for power modules, especially in EV applications.

The objective of the present research is to develop new admixed lubricants which can be used for high-density sintered iron when processed using warm die and warm compaction. Depending on various lubricants, the effect of compaction temperature on the ejection behavior and sintered properties was studied. Lubricants were prepared by mixing of Zn-stearate and ethylene bis stearamide (EBS) in various compositions. The iron powders blended with lubricants were compacted under the pressure of 700 MPa at various temperatures. The green compacts were sintered at 1120°C for 30 min. Microstructure, density, hardness, and transverse rupture strength of sintered materials with different lubricants were investigated in detail.

Visual field defect is a major indication for surgery of pituitary adenoma, but visual outcome after surgery is difficult to predict. We developed a nomogram that predicts postoperative restoration of visual field defects in patients with pituitary adenoma. This study was a retrospective cohort investigation of patients who were treated for pituitary adenoma between January 2009 and December 2013. We enrolled 111 eyes of 57 patients who completed one ophthalmological evaluation preoperatively and at least two evaluations within 6 months after surgery. Serial changes in visual fields and retinal nerve fiber layer (RNFL) thickness were evaluated. Multiple logistic regression analysis was performed to select prognostic variables, and a nomogram to predict restoration of visual field defects was constructed. Visual field defects continuously improved until 3 months after surgery. However, average, superior, and inferior RNFL thickness continuously decreased until 6 months after surgery. Multiple logistic regression analysis revealed that worse preoperative visual field defect (p = 0.018), high MRI compression grade (p = 0.009), and inferior RNFL thinning (p = 0.011) were significantly associated with worse visual outcome. The nomogram that predicts the visual restoration showed an area under the receiver operating characteristic curve of 0.84. In conclusion, we developed a nomogram that predicted the restoration of visual field defects after removal of pituitary adenoma. This would allow tailored counseling of individual patients by precisely predicting visual recovery after surgery.

Pre-alloyed Astaloy CrLTM (Fe-1.5 wt% Cr-0.2 wt% Mo), a commercial Fe-based alloy powder for high strength powder metallurgy products, was sintered and hot forged with additions of 0.5 wt% C and 0~2 wt% Cu. To investigate the influence of various Cu contents, the microstructural evolution was characterized using density measurements, scanning electron microscope (SEM) and electron backscatter diffraction (EBSD). Transverse rupture strength (TRS) was measured for each composition and processing stage. The correlation between Cu additions and properties of sinter-forged Fe-Cr-Mo-C alloy was discussed in detail.

The solvothermal decomposition of iron complexes using the heat-up process enables monodisperse Fe3O4 nanoparticle synthesis. Here, we demonstrate that the high reduction potential capability of alkaline metal reagents in the reductive environment allows for pure magnetite phase formation at 200 °C, which is lower than that of typical synthetic method and offers highly crystalline superparamagnetic and ferrimagnetic nanostructures with the ability to control uniformity including spherical and cubic morphology with narrow size distributions. Our method involved reduction of the acetylacetonate and acetate anions to aldehyde and alcohol as an oxygen resource for iron oxide nucleation in an inert condition. For confirming the developed pure surface phase of alkaline metal reagent-assisted magnetite nanoparticle, the magnetic field-dependent shifting of blocking temperature was investigated. The degree of the exchange interaction between core spins and disordered surface spins is attributed to the ratio of core spins and disordered surface spins. The decrease in disordered surface spins deviation due to an enhanced pure phase of magnetite nanoparticles exhibited the negligible shift of the blocking temperature under differently applied external field, and it demonstrated that alkaline metal reagent-induced reductive conditions enable less formation of both disordered surface spins and biphasic nanostructures.

Extensive data exist regarding the success rates and long-term outcomes of transsphenoidal adenomectomy (TSA) of growth hormone (GH)-secreting pituitary tumors; however, few data exist regarding the extent of adenomectomy. To evaluate surgical outcomes for the treatment of GH-secreting pituitary adenomas with regard to the extent of adenomectomy. A retrospective study of 282 patients with GH-secreting pituitary tumors who underwent TSA. Three surgical paradigms (1, 2, and 3) were applied, all of which differed in extent of adenomectomy. All participants were evaluated with oral glucose tolerance tests (OGTTs) at 6-month intervals for 1.5 years and combined pituitary function tests at 1.5-year intervals after TSA. All surgeries were conducted by a single neurosurgeon at a single medical center. Biochemical remission was defined with insulinlike growth factor 1 and OGTT results. The overall surgical remission rates were 89%, 87%, 64%, 70%, and 50% (nadir GH <1 ng/mL on OGTTs: 96%, 95%, 73%, 84%, and 56%) for modified Hardy classifications I, II, IIIA, IIIB, and IV, respectively. The remission rates for modified Hardy classification I-IIIB improved to 42%, 68%, and 84% after application of surgical paradigms 1, 2, and 3, respectively (P = .002). Aggressive surgical resection did not worsen hypopituitarism. Among the 42 patients with modified Hardy classification IV, 24 (57%) achieved remission without recurrence after applying the aggressive paradigm 3 surgery. An aggressive surgical approach may be critical to managing GH-secreting pituitary adenomas and does not increase the risk of postoperative hypopituitarism. ACTH, corticotropinCPFT, combined pituitary function testCV, coefficient of variationGH, growth hormoneOGTT, oral glucose tolerance testPRL, prolactinTSA, transsphenoidal adenomectomyTSH, thyroid-stimulating hormone.

The objective of the present research is to develop the novel multi-compaction technology to produce hybrid structure in powder metallurgy (P/M) components using dissimilar Fe-based alloys. Two distinct powder alloys with different compositions were are used in this study: Fe-Cr-Mo-C pre-alloyed powder for high strength and Fe-Cu-C mixed powder for enhanced machinability and lower material cost. Initially, Fe-Cu-C was pre-compacted using a bar-shaped die with lower compaction pressure. The green compact of Fe-Cu-C alloy was inserted into a die residing a half of the die, and another half of the die was filled with the Fe-Cr-Mo-C powder. Then they subsequently underwent re-compaction with higher pressure. The final compact was sintered at 1120°C for 60 min. In order to determine the mechanical behavior, transverse rupture strength (TRS) and Vickers hardness of sintered materials were measured and correlated with density variations. The microstructure was characterized using optical microscope and scanning electron microscope to investigate the interfacial characteristics between dissimilar P/M alloys.