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O-sulfated N-acetyl-d-galactosamine (GalNAc) residues in chondroitin sulfate (CS) play a crucial role in chondroitinase ABC I (cABC-I) activity. CSA containing mainly 4-O-monosulfated GalNAc was a good substrate for the enzyme, but not CSE containing mainly 4,6-O-disulfated GalNAc [GalNAc(4S,6S)]. Each CS isomer exhibits structural heterogeneity; CSE has di-sulfated disaccharide units and mono-sulfated disaccharide units. Disaccharide composition analysis of digested products revealed that mono-sulfated disaccharide units in CSE contributed to the enzyme reactivity. Although enough substrate (CSA) was present in mixtures of CSA and CSE for reaction, the reactivity was reduced depending on the amount of CSE in the mixture. These results suggested that CSE is not only resistant to enzyme digestion but also attenuates enzyme activity. To understand the mechanism of action, crystallography of cABC-I in complex with unsaturated CSE-disaccharide, ΔDi-(4,6)S, was performed. Both 4-O- and 6-O-sulfate groups in ΔDi-(4,6)S interact with Arg500, suggesting that there was a greater interaction between ΔDi-(4,6)S and Arg500 than between mono-sulfated disaccharides and Arg500. Besides, this interaction attenuated enzyme activity by interfering with a function of Arg500, which is the charge neutralization of the carboxy group of D-glucuronic acid (GlcA) residues in CS. When interacting with the CSE-disaccharide unit [GlcAβ1-3GalNAc(4S,6S)] in CS, cABC-I cannot interact with other CS-disaccharide units until it has digested the CSE-disaccharide unit. The low reactivity of cABC-I with CSE is attributable to two suggested factors: (a) resistance of E-units in CSE molecules to digestion by cABC-I, and (b) tendency of E-units in CSE molecules to attenuate cABC-I activity.

Retention durability, especially in the eye, is one of the most important properties of ophthalmic viscosurgical devices (OVDs) during ocular surgery. However, the information on the physical properties of OVDs is insufficient to explain their retention durability. The purpose of this study is to clarify the mechanism of OVD retention to improve understanding of the behavior of OVDs during ocular surgery. To elucidate the mechanism of OVD retention, we have developed a new test method for measuring repulsive force. As a result, the maximum repulsive force of OVDs was positively and well correlated with the retention durability of investigated OVDs. Consequently, we demonstrated that the repulsive force could be used as an index of retention durability on the ocular surface and in the eye. We directly compared the intraocular retention durability of three OVDs (Shellgan, Viscoat, and Opegan-Hi) in ex vivo porcine eyes. Opegan-Hi was immediately removed from the anterior chamber, but Shellgan and Viscoat remained largely in the anterior chamber as determined by fluorescence imaging. These results showed that the intraocular retention behavior of OVDs was similar to their ocular surface behavior in our previous report, suggesting that retention durability is dependent on the OVD itself. The retention durability of Shellgan seemed to be higher than that of Viscoat, and the maximum repulsive force of Shellgan was 1.35-fold higher than that of Viscoat. Therefore, the repulsive force might be a useful index for assessing the difference in the retention durability between OVDs such as Shellgan and Viscoat.

Objective: To investigate whether differences exist in the effectiveness/safety of a single session of Okada Purifying Therapy (OPT), a type of biofield therapy, among those from different ethnicity/cultures, and to analyze factors associated with the outcomes in a real-world setting. Design: Pre–post test design using convenience sampling methods. Setting: Home setting. Subjects: A total of 11,303 individuals aged 16 years or older from 14 different countries (>1000 individuals each from Japan, the United States, Thailand, Chile/Peru, and

Ophthalmic viscosurgical devices (OVDs) are mainly divided into two general categories: cohesive and dispersive. Dispersive OVDs such as the 3% hyaluronic acid and 4% chondroitin sulfate (HA/CS) combination have excellent adhesion to ocular tissues and protect the corneal endothelium to a greater extent than cohesive OVDs. Herein, we summarize our recent findings regarding one of the properties of the HA/CS combination related to clinical performance. (i) The room temperature stability of OVDs and needle clogging by OVDs remain clinical issues. We demonstrated that adding d-sorbitol to the HA/CS combination preserved its viscosity, which was equivalent after 2 year-storage at room temperature to the viscosity of HA/CS combination stored under refrigeration for 2 years without d-sorbitol. Besides, the HA/CS combination with d-sorbitol could be used repeatedly without cleaning or replacing the needle, suggesting that the addition of d-sorbitol prevents drying and solidification of the OVD on the needle. (ii) Although it can be inferred from numerous studies that the tissue adhesion of OVDs influences their retention by the eye, little is known about the physical properties of OVDs that contribute to intraocular retention. To address this issue, we compared two types of adhesive forces, detachment force and repulsive force, for each OVD. Compared with other dispersive OVDs, the HA/CS combination showed higher values for both adhesive forces. These results suggest that adhesive forces may be used as an index of dispersive OVD retention in the eye.

Some bacteria produce non-sulfated chondroitin (CH). Accurate, rapid, and high throughput methods to quantify CH in fermented cultures helps to improve microbial breeding and fermentation conditions efficiently. In this study, highly sensitive methods to quantify bacterial CH were developed based on ELISA techniques. An assay using an anti-K4 antiserum successfully determined the concentration of fructosylated CH in the range from 9 to 800 ng/mL. The method also enabled the determination of CH concentration exceeding 9 μg/mL. To improve the assay sensitivity for CH, hyaluronan (HA) binding protein (HABP) was applied instead of a capture antibody. HABP was bound to CH, but not to chemically desulfated chondroitin sulfate or fructosylated CH. The quantification limit of CH was 18 μg/mL in the HA assay using HABP. Replacing the HA-coated microplate with a CH-coated microplate increased the sensitivity1000 times (assay range = 14 to 1000 ng/mL). Pretreatment with hyaluronidase enabled us to accurately quantify CH in samples mixed with HA.

The combination of 3% sodium hyaluronate (HA) and 4% sodium chondroitin sulfate (CS) is used as a dispersive ophthalmic viscosurgical device (OVD) during cataract surgery. For most OVDs containing HA, storage at 2–8 °C is recommended to preserve product characteristics. In order to develop a dispersive OVD that can be stored at room temperature, in this study, we searched additives which can stably maintain the viscosity, a key parameter of OVD, under preservation stability testing at 60 °C. The addition of D-sorbitol to a combination OVD, 3% HA and 4% CS, suppressed the reduction in viscosity compared with other OVDs with or without additives. The addition of D-sorbitol was also effective in improving the residual viscosity of the combination OVD after thermal treatment and light irradiation. Moreover, the OVD containing D-sorbitol can be stored at 25 °C with stably maintaining the initial viscosity for at least 24 months. In conclusion, the new dispersive OVD, 3% HA, 4% CS, and 0.5% D-sorbitol, can be stored at room temperature instead of under cold conditions and may represent an attractive option for clinical use because it is not necessary to bring the product to room temperature prior to use.

Objective: To investigate whether the frequency of the practice of each of diet, art, and biofield therapy influences improvement in quality of life (QOL), and to examine whether the simultaneous practice of all three components increasingly improves QOL in a real-world setting. Design: Pre–post-test design using convenience sampling methods. Setting: Home setting. Subjects: A total of 4681 individuals aged 16 years or older who answered the questionnaire appropriately. Intervention: Participants agreed to practice the three components daily and self-evaluated the frequency of their weekly practice for three consecutive months. At the beginning and end of the study, they completed the MOA quality-of-life questionnaire (10-item MOA quality-of-life questionnaire [MQL-10]). Outcome measures: Factors associated with the increase in MQL-10 scores for each component, and the relationship between the simultaneous practice of multiple components and the changes in MQL-10 scores were analyzed. Results: Frequent practice of the diet and/or art components was associated with an increase in the term-end MQL-10 score (p

The purpose of this study is to evaluate the usefulness of the rheological properties and adhesive force of ophthalmic viscosurgical devices (OVDs) as parameters for understanding and identifying the surgical behavior of cohesive and dispersive OVDs. The apparent viscosity, and the storage and loss moduli (dynamic rheological parameters) of 50% chondroitin sulfate (CS), 3% sodium hyaluronate (HA), Shellgan (the combination of 3% HA and 4% CS), Opegan (1% HA with a low molecular mass) and Opegan-Hi (1% HA with a high molecular mass) were obtained with a rheometer. The adhesive force of each sample was measured by using a texture analyzer. Opegan-Hi showed a solid-like behavior, while 50% CS showed a fluid-like behavior from their apparent viscosity and dynamic rheological parameters. Shellgan, 3% HA, and Opegan exhibited similar rheological properties and intermediate characteristics between Opegan-Hi and 50% CS, although their respective values were slightly different. Among these OVD samples, the adhesive force was higher in the order of 50% CS > Shellgan, 3% HA > Opegan > Opegan-Hi. The adhesive force of dispersive OVDs tended to be higher than that of cohesive OVDs, which correlated well with the removal times of OVDs from the eye that have previously been reported. In conclusion, we demonstrated that cohesive OVDs and dispersive OVDs have particular rheological and adhesive properties that can be applied to identify both types. These parameters obtained in this study provide useful information for a greater understanding and prediction of the behavior of OVDs in the eye during surgery.

Suzuki [Automatica, 2016, 67, 33–45] solves the optimal, finitely iterative, three-regime switching problem for investing in a mean-reverting asset that follows an Ornstein–Uhlenbeck price process and find explicit solutions. The remarkable feature of this model is that the investor can explicitly take either a long, short or square position and can switch the position, with transaction costs, during the investment period. We run empirical simulations of such multiple-regime switching models. There are very few such attempts in the existing literature because it is difficult to find, first, an explicit solution to the problem and second, appropriate financial assets that follow the artificial stochastic process required by the mathematical model. According to the Monte Carlo simulations of the optimal pair-trading strategy, the mean daily Sharp ratio is more than 2.3, whereas the mean Sharp ratio for the historical simulation of the ‘stub’ pairs (combinations of parent/subsidiary companies) is 0.6886. We ...

Ophthalmic viscosurgical devices (OVDs), mainly containing sodium hyaluronate (HA), are used in cataract surgeries to protect the cornea endothelium. In this study, the rheological properties of 9 launched products (containing 1% HA) were evaluated. The molecular weights (MWs) of HA estimated based on intrinsic viscosity varied widely, between 1100-2500 kDa, and showed a particular value for each product. Of the 9 products, 6 are classified as cohesive OVDs and their product specifications show the same value for intrinsic viscosity (25-45 dL/g), with high MW HA (>2000 kDa); however, the MW of each HA showed a particular value (2200-2500 kDa) within the range of the product specification. As with the MW of HA, apparent viscosity and dynamic rheological parameters showed particular values for each OVD. The product Opegan-Hi exhibited the highest value of apparent viscosity at low shear rate, and a solid-like behavior among the OVDs. In a questionnaire survey among 198 cataract surgeons, 42% of surgeons had experienced a difference in ability to maintain the depth of anterior chamber during surgery among the different cohesive OVDs used. This suggested that surgeons select OVD properties based on surgical procedure and patient cases. In conclusion, we demonstrated that each OVD has particular rheological properties within the range of the product specification defined by the intrinsic viscosity. The results might provide useful information for surgeons in their selection of OVDs based on their experience.

Agradecimentos: The authors gratefully acknowledge the Brazilian research funding agencies National Council for Scientific and Technological Development (CNPq), São Paulo Research Foundation (FAPESP), and the Coordination of Superior Level Staff Improvement (CAPES). We are also in debt to Eder Conde Vieira and the Children’s Cancer Hospital Boldrini (Campinas, Brazil) for providing access to the MRI facilities, and to Prof. Dr. Rubens Caram for providing access to his laboratory facilities Abstract: This study compared Zr-Mo alloys with commercial metallic biomaterials. It was observed that the Zr-Mo alloys exhibited favourable mechanical properties, particularly the Zr-10Mo alloy, which showed the highest strength to Young's modulus ratio among all evaluated metals. These alloys also exhibited the lowest magnetic susceptibilities, which are important for magnetic resonance imaging (MRI). However, both Zr- and Ti-based metals yielded comparable artifacts. It was concluded that the magnetic susceptibility must differ considerably to afford significantly improved MRI quality owing to the increased importance of non-susceptibility-related artifacts when comparing materials with relatively similar magnetic susceptibilities CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO - CNPQ FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO - FAPESP COORDENAÇÃO DE APERFEIÇOAMENTO DE PESSOAL DE NÍVEL SUPERIOR - CAPES Aberto

In this study, a polycrystalline composite diamond (PCD) was adopted instead of a single crystal diamond as a burnishing tool. At first, EDM machinability was compared between two kinds of PCDs (10μm grain size), i.e. standard PCD (S-PCD) and electrically conductive PCD (EC-PCD (which was made of boron doped diamond particles). EDM machining time to make a hemispherical shape was 17 minutes for EC-PCD and 37 minutes for S-PCD. Further experiments were conducted with EC-PCD of different grain sizes such as 2μm and 5μm. As a result, the smaller the grain size of EC-PCD the higher the machining efficiency was. Surface roughness values of the EC-PCD after finish EDM were Rz=1.7μm for EC-PCD010, Rz=1.4μm for EC-PCD005, and Rz=1.2μm for EC-PCD002. As a result of burnishing a carbon steel bar (S45C, φ30mm) with the EC-PCD tool, the surface roughness value after machining was improved from 10μm to 1μm.

Use of a tool driven by a spin turning method on a 5 axis turning center has an advantage in suppressing a tool wear in the external turning of hard-to-machine materials. However, it is important not easy to control a radial runout of the tool periphery in the spin turning. In this research, a simple rod shaped tungsten carbide was applied as a rotating tool to the turning of a hardened steel workpiece (HRC63). In addition, on-machine grinding method was proposed as a measure to minimize a radial runout of the rotating tool. With this technique, a well suited rake angle, relief angle or chip breaker profile could be easily given to the tool. In spin turning of the hardened steel with a WC rod tool, roughness value of the worked surface was reduced and tool wear was suppressed in comparison with the turning without tool rotation. In addition, it was shown that correction of the tool runout and forming of the tool rake face could be done on the machine.

The authors have been conducting a research to apply strong alkali ion water (pH12 or so) to a working fluid for material removal processing. This is to cope with various problems relating to the existing water-soluble working fluid such as coolant putridity and the associated deterioration of factory environments and increased disposal costs of working fluids as well as to improve machining efficiency and tool life. In this study, the strong alkali ion water was applied to the tapping (M10) of stainless steel (SUS440C). As a result, use of the strong alkali ion water was found to contribute to the tool life improvement.

This chapter focuses on the Japanese attempt to digitalise government management. The case discussed is a mechanism commonly known as the “My Number” system, a Social Security and Tax Numbering system utilised in Japan. In the Japanese political and administrative context, the introduction of the “My Number” system is thought to be one of the steps to alleviate the current problem of harmonised information sharing among and between public agencies. Hence, the introduction of this system was part of the government’s efforts to reform and improve the quality of public management, as in the Japanese political environment the digitalisation of government has been an essential segment of administrative reform. It was also believed that the introduction of e-government and other digital tools would enhance transparency and accountability of public administration. Furthermore, it was also thought that digitalisation would help reduce the cost of running the government and the administration. Against this background, the chapter attempts to explore and examine the “My Number” system from three perspectives. First, it assesses the history of digitalisation attempts in Japan. Second, it examines several shortcomings inherent in the numbering system currently in place. And, third, it looks at the government system of personnel management, as the current system is considered an impediment in realising the digitalisation of government services and in improving the quality of public services provided. In sum, the chapter utilises the introduction of the “My Number” system in order to describe the problems that the central government bureaucracy has been facing in the era of digitalisation and the causes behind them.

As a measure to perform a burnishing process easily on an NC lathe, the authors propose a new method using a flank face positioned in a few millimeters lower part of the nose cutting edge of a tool. In the experiment, giving a fixed depth of burnishing (t=1, 2 and 4μm/pass), the carbon steel workpiece (S45C) of φ30mm which had been turned at V=200m/min and f=0.15mm/rev was burnished by predefined number of times. As a result, the surface roughness improved in nearly proportion to the total depth of burnishing and the roughness value of Rz≈10μm measured after turning could be improved to Rz≈2.5μm. Utilizing the feed control with an accuracy level of micron meters of the NC lathe, an attempt to control the dimensional accuracy of the workpiece diameter in the order of micron meters was also made. As a result, the workpiece radius came down constantly by 0.6~0.8 times in proportion to the tool depth of burnishing (t=1μm/pass), which reveals that the dimensional accuracy of the workpiece diameter could be controlled by the proposed burnishing process utilizing a fixed depth of burnishing system. Using the same burnishing process, circularity of the workpiece Δr could be improved to Δr≈2μm from Δr≈4μm measured after turning.

In our previous research, precise groove machining could be achieved on a cemented carbide workpiece by utilizing a combined method of EDM and grinding using only a single tool, i.e. a rotary PCD disc tool acting as an electrode for EDM and as a wheel for grinding. In this study, the authors applied this method to forming a 3D shape on a cemented carbide workpiece. Firstly, an EC-PCD disc-shaped tool of φ33.4mm was mounted on a spindle of the EDM machine vertically to the workpiece. And the tool was rotated to make a spherical concave on the workpiece by EDM. The surface roughness of the workpiece was Rz=6.4μm and no electrode wear resulted at all. Secondly, the EDMed surface was ground with the same PCD tool. As a result, the improved surface roughness of Rz=1.7μm was obtained on the workpiece maintaining the precise tool profile and dimension.

For the purpose of improving the electric discharge machinability of PCD, the authors have proposed a method using an electrode made of a specific transition metal which is easy to react with diamond. As a result, Ti, Nb, Ta, Mo, and W among various reactive metals brought very high efficiency, higher than 3 times of existing electrode materials (Cu, CuW) in the EDM of PCD. It was thought that the higher removal efficiency was due to the material properties such as mixing enthalpy between transition metal atom and carbon atom and a crystal structure of body centered cubic (bcc) lattice.

Chondroitin sulfate E (CSE) is a polysaccharide containing mainly disaccharide units of D-glucuronic acid (GlcA) and 4,6-O-disulfated N-acetyl-D-galactosamine (GalNAc) residues (E-unit) in the amount of ∼ 60%. CSE is involved in many biological and pathological processes. In this study, we established new monoclonal antibodies, termed E-12C and E-18H, by using CSE that contained more than 70% of E-units as an immunogen. These antibodies recognized CSE but not other CSs isomers or dermatan sulfate (DS). We evaluated the reactivities of the antibodies to 6-O-sulfated CSA (6S-CSA) and DS (6S-DS) that possessed ∼ 60% of GalNAc (4S, 6S) moieties in their structures. Neither of the antibodies reacted with 6S-DS. The antibodies strictly distinguished the structural difference of GlcA and L-iduronic acid in the polysaccharide. Binding affinities of the antibodies were determined by a surface plasmon resonance assay using CSE and 6S-CSA. The binding affinities were strongly associated with the molecular weight of CSE and the E-unit content of 6S-CSA. Moreover, we demonstrated that the antibodies are applicable to histochemical analysis. In conclusion, the new anti-CSE monoclonal antibodies specifically recognize the E-unit of CSE. The antibodies will become useful tools for the investigation of the biological and pathological significance of CSE.

Iduronic acid (IdoA) is a critical component of heparan sulfate in its interaction with functional proteins. Heparosan-N-sulfate-glucuronate 5-epimerase (HNSG-5epi) converts d-glucuronic acid (GlcA) residues in N-sulfated heparosan (NS-heparosan), as an intermediate in heparan sulfate biosynthesis, to IdoA. In the present study, the authors discovered a different 5-epimerase, designated HG-5epi (heparosan-glucuronate 5-epimerase), that is involved in acharan sulfate biosynthesis and possesses novel substrate specificity. A candidate cDNA of HG-5epi was cloned from the cDNA library of Achatina fulica. The cloned cDNA contained a whole coding region that predicts a type II transmembrane protein composed of 601 amino acid residues. The amino acid sequence of HG-5epi is homologous to that of HNSG-5epi. Recombinant HG-5epi was expressed in insect cells and its enzymatic properties characterized. As expected, HG-5epi epimerizes GlcA residues in heparosan, but not in NS-heparosan. Conversion of IdoA to GlcA was also catalyzed by HG-5epi when completely desulfated N-acetylated heparin was used as the substrate, indicating a reversible reaction mechanism. At equilibrium of the epimerization, the proportion of IdoA in the reaction product reached up to 30% of total hexuronic acid. To our knowledge, this is the first report to describe an enzyme that catalyzes the epimerization of non-sulfated heparosan. This new enzyme may be applied to the study of synthetic heparan sulfate-related polysaccharides having certain biological and pharmacological activities. In addition, a new method using anion-exchange HPLC connected to a post-column fluorescent labeling system was developed for analyzing hexuronic acid isomers.

We aimed to examine the association between impaired proinsulin processing in pancreatic beta cells and type 2 diabetes mellitus in non-obese Japanese patients. Participants were divided into groups for normal glucose tolerance, prediabetes, and type 2 diabetes based on the oral glucose tolerance test (OGTT). Activities of prohormone convertase (PC) 1/3 and PC2 in fasting states were estimated. Multiple regression analysis was undertaken to ascertain if alteration of the activities of these enzymes contributes to the development of impaired glucose tolerance by comparison with HOMA-β and the oral disposition index (DI(O)). Overall, 452 subjects were included. PC1/3 activity tended to decrease in type 2 diabetes compared with normal glucose tolerance. PC2 activity showed no difference among the three groups. Decreased estimated PC1/3 activity was significantly associated with type 2 diabetes after adjustment for sex, age, creatinine, triglycerides, HOMA-β and DI(O). Odds ratios (95% CI) of PC1/3, HOMA-β, and DI(O) were 2.16 (1.12-4.19), 3.44 (1.82-6.52) and 14.60 (7.87-27.11), respectively. Furthermore, decreased PC1/3(≤1.7) combined with decreased HOMA-β (≤30) had a sensitivity of 73% and specificity of 62%. Decreased PC1/3 activity may be a useful measurement of beta-cell function alongside decreased HOMA-β or DI(O). A combined decrease in estimated fasting PC1/3 activity and HOMA-β measurement led to suspicion of type 2 diabetes in the non-obese Japanese population studied.

Context • Fibromyalgia (FM) is a disorder with an unknown etiology; symptoms include physical and psychological stress, widespread chronic pain, insomnia, and depression. Mind-body medicine and aerobic exercise have shown positive effects for symptom control. Several studies have reported positive effects for biofield therapy for FM, but when other studies have compared the treatment with a sham control, they have not found those beneficial effects. Objective • The study intended to examine the effects of a biofield therapy called Okada purifying therapy on patients' FM symptoms. Design • An open-label, self-controlled study was conducted with 2 groups of FM patients. Setting • The study was conducted at an integrative medicine clinic in Portugal. Participants • Twelve patients, aged 25 to 59 y, with symptoms of FM for the 3 mo before the study, participated. Participants agreed not to receive any new treatment other than the intervention throughout the study as a condition for participation. Intervention • Participants received 50 min of biofield therapy 2 ×/wk for 3 mo, either during the first half of the 6-mo study for group A or the second half for group B. The second half of the study was designated as a sham control for group A, and the first half of the study was designated as a sham control for group B. Outcome Measures • Measures included the Beck depression inventory (BDI), the fibromyalgia impact questionnaire (FIQ), the tender point index (TPI), and changes in the dosage of prescribed medication. Results • A significant change was observed for scores in the FIQ (P = .027), BDI (P = .027), and TPI (P = .027) in the second group of patients who received the intervention in the second half of the 6-mo study. Seven of 11 participants taking prescribed medications reduced their dosage. Conclusion • Biofield therapy may help reduce symptoms of depression, chronic widespread pain, and tenderness among patients suffering from FM. Larger studies with rigorous designs are required for further accurate evaluation.

It has been made clear that the EC-PCD composed of boron doped diamond particles improves the performance in the die sinking EDM and wire EDM in comparison with the existing standard PCD (S-PCD). However, the effect of the property improvement could not been evaluated quantitatively in the research reports in the past. Therefore, in this study, wire EDM cutting tests were conducted on the specimens of S-PCD and EC-PCD, in addition to the evaluation of cutting efficiency and cutting PCD surface, a detailed investigation of the cut surface properties of the PCD has been performed under the color 3D laser scanning microscope. In order to investigate effects of a grain size of the source diamond, EDM cutting experiments were conducted on the EC-PCD specimens of 4 different grain sizes. As a result, it was found that the cutting speed was higher in the case of EC-PCD than the case of S-PCD, e.g., by 20% and 40% respectively in the sample of 10μm and 25μm particle size. Also, in the case of the cut S-PCD surface, a groove due to the discharge is formed in the boundary of the tungsten carbide layer and the PCD layer. However, in the case of the cut EC-PCD surface, the groove did not appear in the boundary.

In order to cope with various problems associated with machining of PCD, development of a new PCD possessing excellent tool properties and good machinability at the same time has been demanded. From this point of view, the authors have developed a new PCD, “EC-PCD (Electrically Conductive PCD)”, composed of boron doped diamond particles in place of the standard non-conductive diamond. In this research, investigation into material properties of the newly developed EC-PCD is made. Through the tests, it was found that the boron doped diamond particles (the source material of the new PCD) had an electrical resistivity of 1.6×10-4Ω·m and the thermal conductivity after sintering was lower than that of the standard PCD. In addition, it was confirmed that the electrical conductivity of the source diamond particles of the EC-PCD had not been lost even under the condition of high temperature and high pressure during the manufacture. As a result of the heat test, EC-PCD’s high resistance to oxidation at high temperatures was confirmed showing no changes in the surface condition even at 675oC while the surface of the S-PCD was largely changed at the same temperature. One of the reasons for this is guessed to be that EC-PCD is hard to react with the cobalt contained as a catalyst metal. Further, it was found in the friction tests using a steel ball that the friction coefficient of the EC-PCD was 50% higher than that of S-PCD at the room temperature though it dropped by 10-30% at the temperature of 80oC.

In order to achieve a high efficient and high quality EDM of PCD, the authors have developed a new PCD having superior electrical conductivity by using boron diamond as a source material. On the other hand they applied a method to give ultrasonic vibrations to the electrode, and have made it clear that even the standard PCD could be machined at the similar level of efficiency to the cases of EDMing die steels and cemented carbides. With a purpose to obtain a good surface roughness on the PCD at high efficiency, various EDM conditions and methods were compared in this paper. Firstly, influence of discharge duration time was examined, and it was found that a shorter pulse duration time as te=0.5μs showed high efficiency and smaller electrode wear rate. Secondary, influence of bipolar pulse current method was examined, and it was found that the method effected higher efficiency but rather large amount of electrode wear resulted. Thirdly, ultrasonic assisted EDM was conducted, and it was found that the method showed superior result regarding efficiency and wear rate on both standard PCD and EC-PCD. A combination use of ultrasonic assisted and bipolar pulse current EDM methods was also attempted in this research. On the contrary to the expectation, efficiency and electrode wear rate became worse in EDM of standard and EC-PCD in comparison with other methods tested before.

Recent years, use of the strong alkali ion water produced by electrolyzing high purity water (RO water) with addition of a small amount of electrolyte (potassium carbonate) is becoming widely used as a substitutable cleaning liquid in place of organic solvent which is said to exert a bad influence on the environment. The authors have been conducting a research to apply this strong alkali ion water (pH12 or so) to a working fluid for material removal processing. This is to cope with various problems relating to the existing water-soluble working fluid such as coolant putridity and the associated deterioration of factory environments and increased disposal costs of working fluids as well as to improve machining efficiency and tool life. In this study, the authors would like to describe how the working fluid consisting of water-soluble lubricant diluted with the strong alkali ion water contributes to an improvement of the factory environment and verify experimentally that the said fluid could improve the tool life by 1.2 to several times. In addition, a factor contributing to the improvement of material removal characteristics has been found to be the fact that the friction resistance of the said fluid containing the strong alkali ion water is as low as 2/3~1/2 of that of the fluid diluted with the city water.