Enhancing Mechanical and Corrosion Properties of AISI 420 with Titanium-Nitride Reinforcement through High-Power-Density Selective Laser Melting Using Two-Stage Mixed TiN/AISI 420 Powder.

This study investigates the effect of laser volume energy density (VED) on the properties of AISI 420 stainless steel and TiN/AISI 420 composite manufactured by selective laser melting (SLM). The composite contained 1 wt.% TiN and the average diameters of AISI 420 and TiN powders were 45 µm and 1 µm, respectively. The powder for SLMing the TiN/AISI 420 composite was prepared using a novel two-stage mixing scheme. The morphology, mechanical, and corrosion properties of the specimens were analyzed, and their correlations with microstructures were investigated. The results showed that the surface roughness of both SLM samples decreases with increasing VED, while relative densities greater than 99% were achieved at VEDs higher than 160 J/mm3. The SLM AISI 420 specimen fabricated at a VED of 205 J/mm3 exhibited the highest density of 7.7 g/cm3, tensile strength (UTS) of 1270 MPa, and elongation of 3.86%. The SLM TiN/AISI 420 specimen at a VED of 285 J/mm3 had a density of 7.67 g/cm3, UTS of 1482 MPa, and elongation of 2.72%. The microstructure of the SLM TiN/AISI 420 composite displayed a ring-like micro-grain structure consisting of retained austenite on the grain boundary and martensite in the grain. The TiN particles strengthened the mechanical properties of the composite by accumulating along the grain boundary. The mean hardnesses of the SLM AISI 420 and TiN/AISI 420 specimens were 635 and 735 HV, respectively, which exceeded previously reported results. The SLM TiN/AISI 420 composite exhibited excellent corrosion resistance in both 3.5 wt.% NaCl and 6 wt.% FeCl3 solutions, with a resulting corrosion rate as low as 11 µm/year.

Effects of Laser Spot Size on the Mechanical Properties of AISI 420 Stainless Steel Fabricated by Selective Laser Melting.

The purpose of this study is to investigate the effects of laser spot size on the mechanical properties of AISI 420 stainless steel, fabricated by selective laser melting (SLM), process. Tensile specimens were built directly via the SLM process, using various laser spot diameters, namely 0.1, 0.2, 0.3, and 0.4 mm. The corresponding volumetric energy density (EV) is 80, 40, 26.7, and 20 J/mm3, respectively. Experimental results indicate that laser spot size is an important process parameter and has significant effects on the surface roughness, hardness, density, tensile strength, and microstructure of the SLM AISI 420 builds. A large laser spot with low volumetric energy density results in balling, un-overlapped defects, a large re-heated zone, and a large sub-grain size. As a result, SLM specimens fabricated by the largest laser spot diameter of 0.4 mm exhibit the roughest surface, lowest densification, and lowest ultimate tensile strength. To ensure complete melting of the powder and melt pool stability, EV of 80 J/mm3 proves to be a suitable laser energy density value for the given SLM processing and material system.

Effects of Build Direction on the Mechanical Properties of a Martensitic Stainless Steel Fabricated by Selective Laser Melting.

Mechanical properties and microstructure are investigated for a martensitic stainless steel (AISI 420) fabricated by selective laser melting (SLM) in three build directions. The tensile specimens built by SLM are classified into three groups. Group A is horizontally built in the thickness direction, Group B is horizontally built in the width direction, and Group C is vertically built in the length direction. The loading direction in tensile test is parallel to the build direction of Group C, but perpendicular to that of Groups A and B. Experimental results indicate build direction has significant effects on the residual stress, hardness, and tensile properties of SLM builds. Microstructural analyses indicate the as-fabricated SLM AISI 420 builds exhibit elongated cells and acicular structures which are composed of martensite and retained austenite phases growing along the build direction. Such anisotropy in the microstructure leads to anisotropic mechanical properties as Group C specimens (length direction) exhibit greater yield stress, ultimate tensile stress, and elongation than the specimens of Groups A (thickness direction) and B (width direction). The residual compressive stress in the gauge section also contributes to the superior tensile properties of Group C (length direction), as compared to Groups A (thickness direction) and B (width direction), which exhibit residual tensile stress in the gauge section.

Subclinical peripheral arterial disease in renal transplantation.

BACKGROUND: Peripheral arterial disease (PAD) is a common finding in patients at various stages of chronic kidney disease; however, there has only been a limited amount of data that have been published regarding the prevalence and associated risk factors of subclinical PAD in renal transplant recipients. METHODS: The authors cross sectionally investigated the prevalence of PAD using ankle-brachial index (ABI) in 304 renal transplant recipients with no previous diagnosis of PAD. Patients were considered to have subclinical PAD when ABI <0.9. The authors also determined the associated risk factors for subclinical PAD. RESULTS: The mean age of the 304 patients was 53 years, and 30 patients (9.9%) had a history of atherosclerotic event (including past cardiovascular and cerebrovascular events). Twenty-five of the 304 patients (8%) had ABI <0.9 and 1 had (0.3%) ABI >1.3. Compared to patients with normal ABI, a history of atherosclerotic events is the only independent risk factor for patients with subclinical PAD (P = 0.0468). CONCLUSIONS: Subclinical PAD is an inadvertent issue in renal transplant patients, especially those with a history of atherosclerotic events. Further research is needed on the long-term clinical impact and optimal treatment of subclinical PAD among renal transplant patients.

Community-acquired urinary tract infection in kidney transplantation: risk factors for bacteremia and recurrent infection.

BACKGROUND/PURPOSE: Urinary tract infection (UTI) is the most common type of infectious complication among kidney transplant patients. However, the antibiotic susceptibility of causative microorganisms and risk factors for concomitant bacteremia and recurrent infection are rarely discussed. METHODS: This was a retrospective cohort review of kidney transplant recipients who had received follow-up in the past 10 years at the Chung-Shan Medical University (Taichung, Taiwan). Only community-acquired and symptomatic UTIs were included in this study. RESULTS: During the 53 ± 22 months of follow-up, 99 patients developed 167 episodes of UTI. Forty-two (25%) episodes had concomitant bacteremia. Escherichia coli was the most common causative microorganism, and strains with resistance to multiple commonly used empirical antibiotics began to emerge. The independent risk factors for UTI with concomitant bacteremia in multivariate analysis were immunosuppression with tacrolimus (adjusted odds ratio [AOR] 3.17; 95% confidence interval [CI] 1.29-7.75; P = 0.011) and baseline serum creatinine level >1.3 mg/dL before first UTI (AOR 2.55; 95% CI 1.02-6.36; P = 0.045). However, there were no factors that were significantly associated with recurrent infection. CONCLUSION: From this study, we found that E coli tends to have resistance to commonly used empirical antibiotics in this modern era and that patients who use the immunosuppressant tacrolimus and have baseline serum creatinine level >1.3 mg/dL before their first UTI have a tendency to suffer from concomitant bacteremia and even sepsis.

Glutathione S-transferase M1 gene polymorphism is associated with susceptibility to impaired long-term allograft outcomes in renal transplant recipients.

BACKGROUND: Despite improved post-transplantation care, progress in long-term kidney allograft survival of diabetic renal transplant recipients (pre-DM RTR) is worse than that of non-diabetic recipients (non-DM). We hypothesized that there are other potential risk factors, that predispose RTR to adverse renal allograft outcomes. METHODS: A total of 323 transplant recipients who underwent renal transplantation between March 2000 and January 2008 were recruited. The composite end-point consisted of serum creatinine (SCr) doubling, graft failure, and death. Baseline clinical data were recorded, and polymerase chain reaction-restriction fragment length polymorphism measurements of interleukin (IL)-4, IL-10, IL-23, glutathione S-transferase (GST)A1, GSTM1, and GSTP1 polymorphisms were determined. The risk factors for developing the primary outcome were analyzed among these clinical and genetic factors. RESULTS: Within a mean follow-up of 71.1 ± 24 months, there were 43 (13.3 %) patients with the primary outcome. Stepwise multivariate Cox regression analysis was used to determine the risk factors for the primary outcome of RTR. Renal transplant recipients who possessed the GSTM1 null genotype had a 2.2-fold risk (95 % CI: 1.10-4.40; P = 0.026) of developing the primary outcome. Additionally, RTR that had DM before transplantation (aHR: 3.31; 95 % CI: 1.77-6.20; P = 0.0002) or changes in SCr 6 to 12 months after transplantation (aHR: 2.83; 95 % CI: 1.29-6.19; P = 0.0095) had an increased risk of developing the primary outcome. CONCLUSIONS: In addition to the adverse role played by DM, the GSTM1 null genotype also has an unfavorable influence on the long-term allograft outcome of RTR.

The impact of depression on self-care activities and health care utilization among people with diabetes in Taiwan.

Using cross-sectional analyses of a nationally representative community sample (n=1260), we found that in people with diabetes, depression was associated with lower rates of reducing or quitting smoking and alcohol, less exercise, less regular lifestyle, but more health care utilization and a higher rate of foot care.

Assessing the impact of polysomy-17 on HER2 status and the correlations of HER2 status with prognostic variables (ER, PR, p53, Ki-67) in epithelial ovarian cancer: a tissue microarray study using immunohistochemistry and fluorescent in situ hybridization.

Although HER2 overexpression and Her2 amplification have been noted in breast and a variety of human cancers, we report here for the first time the impact of polysomy-17 on HER2 status and the correlations between HER2 status and other prognostic factors in patients with epithelial ovarian cancers (EOC).We analyzed HER2, estrogen receptor (ER), progesterone receptor (PR), p53, and Ki-67 protein overexpressions by immunohistochemistry (IHC) and determined Her2 gene amplification by fluorescence in situ hybridization (FISH) in 27 tissue microarray samples from EOC patients.We achieved 100% positive concordance (3/3) and 100% negative concordance (19/19) between HER2 testing by IHC and FISH. Both the total Her2 gene copies and FISH scores increased significantly in a stepwise order through the negative, equivocal, and positive HER2 IHC result categories in all 27 cases (P=0.001, P=0.001), and still increased significantly in 18 nonpolysomy-17 cases (P=0.007 and 0.013) after the exclusion of 9 polysomy-17 cases. HER2 protein expression is inversely correlated with both ER (P=0.002) and PR expressions (P=0.046). Her2 gene amplification is inversely correlated with ER expression (P=0.007) but not with PR expression (P=0.106).This study showed extremely high positive and negative concordances between Her2 FISH and HER2 IHC assays. Polysomy-17 is insufficient for causing a significant impact on the relationship between HER2 testing by IHC and FISH in EOC. ER and PR expressions were inversely correlated with HER2 protein expression. In addition, ER but not PR expression is inversely correlated with Her2 gene amplification.

Comparison of renal function and other health outcomes in vegetarians versus omnivores in Taiwan.

Renal disease is one of the top 10 leading causes of death, and the incidence of end-stage renal disease in Taiwan is the highest in the world. Many dietitians consider the diet of plant origin consumed by vegans to be 'lighter' and 'more healthful' than the diet of both plant and animal origin consumed by omnivores. Dietary protein has significant effects on renal functions. The study explored the effects of both the diets on renal functions. The study subjects included 102 Buddhist nun vegetarians and an equal number of matched control group (omnivores). A cross-sectional study was performed to investigate the effects of the diet of plant origin and the diet of both plant and animal origin on renal functions. There was no difference in the renal functions between the two groups. However, systolic blood pressure, blood urea nitrogen, serum sodium, glucose, cholesterol levels, and urinary specific gravity were lower in the vegetarian group. Although these results were compatible with general concepts regarding diet of plant origin, after adjusting for age, the duration of intake of this diet had no effect on the renal functions. Based on the findings, it is concluded that the renal functions, in terms of the estimated glomerular filtration rate, were not different between the vegetarians and the omnivores.

Clustering of unconventional cardiovascular risk factors among Taiwanese hemodialysis patients.

BACKGROUND: Cardiovascular disease (CAVD) is the most common cause of mortality for chronic hemodialysis (HD) patients, yet the risk factors for the events have not been well established. METHODS: We conducted a multicenter cross-sectional survey in 995 chronic HD patients recruited from 12 HD centers in Taiwan to investigate the prevalence of CAVD, including coronary heart disease (CHD), cerebrovascular disease (CVD), and peripheral vascular disease (PVD), and related them to 30 different parameters. RESULTS: The mean age of 995 patients (499 males/496 females) was 56.4 +/- 12.3 years, and average HD duration was 59.8 +/- 51.2 months. The prevalence rates of CHD, CVD, and PVD were 24.0, 6.0, and 5.3%, respectively. Results of our multivariate logistic regression analysis showed that out of the conventional CAVD risk factors, only old age and diabetes could be significantly associated with CAVD. Meanwhile, we found some novel clinical correlates, including low apolipoprotein A-I and creatinine for CHD, low uric acid for CVD, and low hematocrit and low diastolic blood pressure for PVD. Interestingly, left ventricular hypertrophy was found to be an independent correlate for all three: CHD, CVD, and PVD. CONCLUSIONS: Our study suggests that consideration of conventional cardiovascular risk factors as well as unconventional risk factors might better assess the risk for CAVD among HD patients.

Attitudes toward taking medication among outpatients with schizophrenia: cross-national comparison between Tokyo and Beijing.

OBJECTIVES: The aim of this study was to compare attitudes toward medication and associated factors for patients with schizophrenia in Japan and China. METHODS: Age-group matched samples were drawn from outpatients in Tokyo (N = 76) and Beijing (N = 76) according to the same inclusion/exclusion criteria. Psychotropic prescription and attitudes toward medication were measured using Drug Attitude Inventory-30 (DAI-30) and an original questionnaire regarding beliefs about psychiatric medication. Stepwise regression analysis of the DAI-30 data was performed for each group. RESULTS: Japanese subjects were prescribed significantly larger amounts of antipsychotics. Polypharmacy of antipsychotics and concurrent use of anticholinergics, anxiolytics, or hypnotics were more frequently found among subjects in Tokyo than among those in Beijing. However, subjects in Tokyo and Beijing had similar subjective responses to medication, subjective evaluation of side-effects, and complaints about overuse of psychotropics. Subjects in Tokyo complained less about physician's over-reliance on medication and were less concerned about medication cost than those in Beijing. In Tokyo, longer duration of illness and lower subjective distress caused by side effects predicted a more positive subjective response, while female gender, younger age, and lower Brief Psychiatric Rating Scale score were independently correlated with a better subjective response in Beijing. CONCLUSIONS: Subjective acceptance of multiple medications is greater for patients in Japan than those in China. Determinants of subjective response to medication varied between Japan and China.

Use of serum cystatin C to detect early decline of glomerular filtration rate in type 2 diabetes.

OBJECT: The estimation of serum cystatin C and its practical use for the estimation of the glomerular filtration rate (GFR) in diabetic patients has been previously demonstrated, however, those studies did not use the chronic kidney disease GFR staging. Therefore, we performed this study in type 2 diabetic patients with the aim to examine the usefulness of serum cystatin C to detect early decline of GFR using the staging of chronic kidney disease defined by the National Kidney Foundation. METHODS: A total of 102 Taiwanese type 2 diabetic patients were recruited from the Chung-Shan Medical University Hospital. Morning fasting blood and urine samples were obtained for basal metabolic parameters, serum creatinine, serum cystatin C, and albumin-creatinine ratio. GFR was determined by Cockcroft-Gault equation creatinine clearance (CG-CCr). RESULTS: Of the 102 type 2 diabetic patients, 67, 25, and 10 had normo-, micro-, and macroalbuminuria, respectively. Serum cystatin C was superior to serum creatinine in detecting early decline of GFR. The diagnostic accuracy of serum cystatin C was better than serum creatinine for stage 1 and 2 chronic kidney disease (CG-CCr cut-off value of 90 ml/min and 60 ml/min). Furthermore, serum cystatin C was also correlated with urine albumin excretion, which was not true with serum creatinine. CONCLUSIONS: These results suggest that serum cystatin C may be an alternative serum marker for the early identification of subjects with a slight reduction of renal function, and also it may be a marker for early glomerular dysfunction in type 2 diabetes.