Emission characteristics of laser-induced plasma using collinear long and short dual-pulse LIBS

The collinear long and short dual-pulse LIBS (DP-LIBS) was employed to clarify the emission characteristics from laser-induced plasma. The plasma was sustained and became stable by the long pulse-width laser with the pulse width of 60 μs under FR (free running) condition as an external energy source. Comparing the measurement results of stainless steel in air using SP-LIBS and DP-LIBS, the emission intensity was enhanced using DP-LIBS markedly. The temperature of plasma induced by DP-LIBS was maintained at higher temperature under different gate delay time and short pulse-width laser power conditions compared with these measured using SP-LIBS of short pulse width. Moreover, the variation rates of plasma temperature measured using DP-LIBS were also lower. The superior detection ability was verified by the measurement of aluminum sample in water. The spectra were clearly detected using DP-LIBS, whereas it cannot be identified using SP-LIBS of short pulse width and long pulse width. The effects of gate delay time and short pulse-width laser power were also discussed. These results demonstrate the feasibility and enhanced detection ability of the proposed collinear long and short DP-LIBS method

Detection of SARS-associated Coronavirus in Throat Wash and Saliva in Early Diagnosis

Early detection of SARS-CoV in throat wash and saliva suggests that these specimens are ideal for SARS diagnosis

Malignant phyllodes tumors display mesenchymal stem cell features and aldehyde dehydrogenase/disialoganglioside identify their tumor stem cells

INTRODUCTION: Although breast phyllodes tumors are rare, there is no effective therapy other than surgery. Little is known about their tumor biology. A malignant phyllodes tumor contains heterologous stromal elements, and can transform into rhabdomyosarcoma, liposarcoma and osteosarcoma. These versatile properties prompted us to explore their possible relationship to mesenchymal stem cells (MSCs) and to search for the presence of cancer stem cells (CSCs) in phyllodes tumors. METHODS: Paraffin sections of malignant phyllodes tumors were examined for various markers by immunohistochemical staining. Xenografts of human primary phyllodes tumors were established by injecting freshly isolated tumor cells into the mammary fat pad of non-obese diabetic-severe combined immunodeficient (NOD-SCID) mice. To search for CSCs, xenografted tumor cells were sorted into various subpopulations by flow cytometry and examined for their in vitro mammosphere forming capacity, in vivo tumorigenicity in NOD-SCID mice and their ability to undergo differentiation. RESULTS: Immunohistochemical analysis revealed the expression of the following 10 markers: CD44, CD29, CD106, CD166, CD105, CD90, disialoganglioside (GD2), CD117, Aldehyde dehydrogenase 1 (ALDH), and Oct-4, and 7 clinically relevant markers (CD10, CD34, p53, p63, Ki-67, Bcl-2, vimentin, and Globo H) in all 51 malignant phyllodes tumors examined, albeit to different extents. Four xenografts were successfully established from human primary phyllodes tumors. In vitro, ALDH(+) cells sorted from xenografts displayed approximately 10-fold greater mammosphere-forming capacity than ALDH(-) cells. GD2(+) cells showed a 3.9-fold greater capacity than GD2(-) cells. ALDH(+)/GD2(+)cells displayed 12.8-fold greater mammosphere forming ability than ALDH(-)/GD2(-) cells. In vivo, the tumor-initiating frequency of ALDH(+)/GD2(+) cells were up to 33-fold higher than that of ALDH(+) cells, with as few as 50 ALDH(+)/GD2(+) cells being sufficient for engraftment. Moreover, we provided the first evidence for the induction of ALDH(+)/GD2(+) cells to differentiate into neural cells of various lineages, along with the observation of neural differentiation in clinical specimens and xenografts of malignant phyllodes tumors. ALDH(+) or ALDH(+)/GD2(+) cells could also be induced to differentiate into adipocytes, osteocytes or chondrocytes. CONCLUSIONS: Our findings revealed that malignant phyllodes tumors possessed many characteristics of MSC, and their CSCs were enriched in ALDH(+) and ALDH(+)/GD2(+) subpopulations

Reduction in the Volumetric Wear of a Ball Polishing Tool Using Ultrasonic-Vibration-Assisted Polishing Process

Ultraprecision freeform polishing using a bonnet or a felt ball mounted on a polishing head plays an important role in the mold and lens production industries. The volumetric wear of a bonnet or a felt polishing ball is still a problem to be solved. The objective of this study was to develop an ultrasonic-vibration-assisted ball polishing process on a CNC machining center to improve the surface roughness of a STAVAX mold steel and to reduce the volumetric wear of the polishing ball. The optimal combination of the ultrasonic-vibration-assisted ball polishing parameters for a plane surface was determined by conducting the Taguchi L18 matrix experiments, ANOVA analysis, and verification experiments. The surface roughness of the polished specimens was improved from the burnished surface roughness of Ra 0.122 μm to Ra 0.022 μm. In applying the optimal plane surface ball burnishing and vibration-assisted spherical polishing parameters sequentially to a fine-milled and burnished aspherical lens surface carrier on a five-axis machining center, the surface roughness of Ra 0.014 μm was obtainable. The improvement in the volumetric wear of the polishing ball was about 62% using the vibration-assisted polishing process compared with the nonvibrated polishing process

Preliminary Development of an Automated Optical Inspection System for Quality Control of Circular Saw Inserts

Circular saw inserts are fundamental and high-value-added cutting tool inserts used for sawing, slot milling, and other related machining processes. In their mass production, sintered blanks are first made by powder metallurgy and then precisely form-ground to generate the geometric shapes and dimensions required for cutting action. In order to ensure quality in the production of circular saw inserts, the defects of sintered blanks and geometric accuracy of semi-products must be inspected before and after the form-grinding process, respectively. To this end, this paper presents the preliminary development of an automated optical inspection (AOI) system for quality control of circular saw inserts. A prototype system was designed and constructed in this study. Image processing procedures were then developed to perform the calibration process of the prototype system, defect detection of the sintered blanks, and geometric measurement of the form-ground semi-products. Experiments were conducted to inspect insert samples and test the feasibility of the developed prototype system. Preliminary experimental results verified the presented prototype system and image processing procedures as being able to inspect certain circular saw inserts for ensuring quality control.<br /