Characterization of Deformability of Spheroidal Cementite by Residual Stress Measurement

This article deals with the characterization of the mechanical behaviors of spheroidized carbon steels, which contain ferrite and spheroidal cementite. The aim of the study is to identify the deformation behaviors of cementite particles by x-ray diffraction and to correlate them to the residual stress state evolution. The stress state evolutions for both phases during an in situ 4-point bending test and after a uniaxial tensile test that have been well followed by x-ray diffraction. After each tensile loading, optical observation is made to correlate the determined residual stress state with the microstructure. The coupling of techniques helps us to characterize the deformation evolution of spheroidal cementite in the carbon steel: at the initial state, the cementite shows the same elastic behavior as the ferrite; at the next state, the ferrite begins to deform plastically but the cementite deforms elastically; then, plastic relaxation occurs in the ferrite while the cementite still deforms elastically until finally breaking.     

Effect of friction stir processing on microstructure of laser clad cobalt-based alloy

(The microstructural refinement of cobalt-based alloy (Stellite No. 6) by laser cladding and friction stir processing (FSP) was studied. A nanometer-sized microstructure consisting of fine carbide (particle size: 100–200 nm) and a grain (grain size: 150–250 nm) was successfully fabricated by the FSP on the laser clad cobalt-based alloy. The nanostructured cobalt-based alloy (Stellite No. 6) had an extremely high hardness of about 750 HV.     

Modeling the trajectory of window flames with regard to flow attachment to the adjacent wall

A model for predicting the trajectory of window flame ejected from a fire compartment was formulated incorporating the effect of wall above the opening. Based on the observation in the reduced scale experiments, window flames were divided into the following categories with regard to its trajectory configuration: the flow which ascends almost vertically up after ejection maintaining a certain separation from the wall; and the flow which ascends upward after ejection and gradually approaches to the wall in the downstream. In the model, trajectories of these flows were approximated by cubic polynomials whose coefficients were given as functions of a dimensionless parameter F*. The parameter F* was derived from the conservation equation of momentum which incorporates the effect of pressure gradient across the ascending flows. Critical condition for the occurrence of flow attachment was described as a proportion of the maximum separation from the wall versus the opening width. Trajectories predicted by the proposed model were then compared with the measurement data which indicated reasonable agreements.     

Focal calcium monitoring with targeted nanosensors at the cytosolic side of endoplasmic reticulum

Ca²⁺ distribution is spatially and temporally non-uniform inside cells due to cellular compartmentalization. However, Ca²⁺ sensing with small organic dyes, such as fura-2 and fluo-4, has been practically applied at a single cell level where the averaged signal from freely diffusing dye molecules is acquired. In this study, we aimed to target azide-functionalized fura-2 (N₃-fura-2) to a specific site of subcellular compartments to realize focal Ca²⁺ sensing. Using scAVD (single-chain avidin)–biotin interaction and a copper-free click reaction system, we linked N₃-fura-2 to specifically-targeted scAVD protein fused with a red fluorescent protein mCherry, so that Ca²⁺ sensors conjugated with four N₃-fura-2 dyes with dibenzocyclooctyne (DBCO)-PEG4-biotin as a linker were generated at subcellular compartments in living cells. In cytoplasm, N₃-fura-2 showed a prolonged retention period after binding to scAVD. Furthermore, the reacted N₃-fura-2 was retained inside cells even after free dyes were washed out by methanol fixation. When scAVD was overexpressed on endoplasmic reticulum (ER) membranes, N₃-fura-2 was accumulated on ER membranes. Upon histamine stimulation, which increases cytosolic Ca²⁺ concentration, ER-localized N₃-fura-2 successfully sensed the Ca²⁺ level changes at the cytosolic side of ER membrane. Our study demonstrated specific targeting of N₃-fura-2 to subcellular compartments and the ability of sensing focal Ca²⁺ level changes with the specifically targeted Ca²⁺ sensors.     

High-throughput analysis of ligand-induced internalization of β2-adrenoceptors using the coiled-coil tag-probe method

Receptor internalization is a useful indicator of the activity of ligands. The N-terminus of the β(2)-adrenergic receptor expressed on the cell surface was labeled with fluorophores using a novel coiled-coil labeling system. Endocytosis of the receptors was automatically detected using a fluorescence image analyzer by evaluating (1) translocation of the receptor from cell-surface to intracellular regions and (2) acidification in endosomes. Both parameters increased upon agonist stimulation in a dose-dependent manner. The extent of endocytosis was significantly dependent on the agonist used, indicating the presence of a biased signaling for endocytosis. The receptor antagonists can also be screened by competitive inhibition of agonist-induced endocytosis. The image analysis approach has proven to be useful for high-throughput characterization and screening of GPCR ligands.     

Physician-received scatter radiation with angiography systems used for interventional radiology: comparison among many X-ray systems

Radiation protection for interventional radiology (IR) physicians is very important. Current IR X-ray systems tend to use flat-panel detectors (FPDs) rather than image intensifiers (IIs). The purpose of this study is to test the hypothesis that there is no difference in physician-received scatter radiation (PRSR) between FPD systems and II systems. This study examined 20 X-ray systems in 15 cardiac catheterisation laboratories (11 used a FPD and 9 used an II). The PRSR with digital cineangiography and fluoroscopy were compared among the 20 X-ray systems using a phantom and a solid-state-detector electronic pocket dosemeter. The maximum PRSR exceeded the minimum PRSR by ~12-fold for cineangiography and ~9-fold for fluoroscopy. For both fluoroscopy and digital cineangiography, the PRSR had a statistically significant positive correlation with the entrance surface dose (fluoroscopy, r = 0.87; cineangiography, r = 0.86). There was no statistically significant difference between the average PRSR of FPDs and IIs during either digital cineangiography or fluoroscopy. There is a wide range of PRSR among the radiography systems evaluated. The PRSR correlated well with the entrance surface dose of the phantom in 20 X-ray units used for IR. Hence, decreasing the dose to the patient will also decrease the dose to staff.     

Solution Property and Irradiation Effect of Random Copolypeptides Composed of Ala and Pro Residues

Summary Poly(proline) and random copolypeptide composed of Pro and Ala residues were synthesized, and their solution properties and molecular conformation were investigated. Aqueous solutions of the polypeptide were irradiated with γ-rays above the transition temperature. It was shown that the transition temperature of the aqueous solution of the copolypeptide is influenced by Ala-residue content and γ-ray irradiation.     

Heat regulating strategy in numerical control end milling for hard metal machining

The trend in die/mold manufacturing at present is towards the hard machining at high speed to replace the electron discharge machining. Failure forms of the A1TiN-coated micro-grain carbide endmill when used for the machining of/IS SKD61 (HRC 53), a widely used material in die/mold manufacturing, are investigated. The endmill shows a characteristic that tool life decreases greatly due to the chipping when overload occurs or the rapid increase of wear when over-heat accumulation in cutting edges. As a consequence of the investigation, a strategy to regulate heat generation in the end milling process is proposed. This is accomplished by controlling the cutting arc length, i.e. the length of each flute engaging workpiece in a cutting cycle. Case studies on the slot end milling and comer rounding are conducted. The results show that the proposed strategy suggests the optimal tool path as well as the optimal pitch between successive tool paths under the cutting time criterion.