Experiment Comparative Analysis of Feed Rate with Velocity Control in Cutting Mono Crystalline Silicon Using a Diamond Wire Saw.

Fixed-diamond abrasive wire saw cutting is one of the most common methods for cutting hard and brittle materials. This process has unique advantages including a narrow kerf and the ability to use a relatively small cutting force. In the cutting process, controlling the main process parameters can improve the processing efficiency, obtaining a better processing surface roughness. This work designs the PI controller (Proportional-Integral controller) based on the reciprocating wire saw cutting process. The control objects are the workpiece feed rate and wire saw velocity, and the control objective is the normal cutting force. For the control trials, several reference values of various normal cutting forces were chosen. The effects of feed rate and saw velocity on the cutting surface finish and cutting time were investigated in this work using wire saw cutting analysis on a square monocrystalline silicon specimen. The results of this study showed that under a constant applied force of 2.5 N, the optimal feed rate of the diamond wire through the specimen could reduce cutting time by 42% while achieving a 60% improvement in the measured surface finish. Likewise, optimal control of the wire saw velocity could reduce cycle time by 18% with a 45% improvement in the surface finish. Consequently, the feed speed control is more effective than the wire saw velocity.

Mathematical Modeling and Experimental Study of Cutting Force for Cutting Hard and Brittle Materials in Fixed Abrasive Trepanning Drill.

Hard and brittle materials have excellent physical and mechanical performance, which are widely applied in the fields of microelectronics and optoelectronics. However, deep-hole machining of hard and brittle materials is very difficult and inefficient due to the high hardness and brittleness of these materials. To improve the quality and efficiency of deep-hole machining of hard and brittle materials, according to the brittle crack fracture removal mechanism of hard and brittle materials and the cutting model of the trepanning cutter, an analytical cutting force prediction model of hard and brittle materials processed using a trepanning cutter is established. This experimental study of K9 optical glass machining shows that as the feeding rate increase, the cutting force increase, and as the spindle speed increase, the cutting force decrease. By comparing and verifying the theoretical and experimental values, the average errors of axial force and torque are 5.0% and 6.7%, respectively, and the maximum error is 14.9%. This paper analyzes the reasons for the errors. The results indicate that the cutting force theoretical model can be used to predict the axial force and torque of machining hard and brittle materials under the same conditions, which provides a theory for optimizing machining process parameters.

Experimental Study on the Influence of Wire-Saw Wear on Cutting Force and Silicon Wafer Surface.

Hard and brittle materials such as monocrystalline silicon still occupy an important position in the semiconductor industry, but hard and brittle materials are difficult to process because of their physical properties. Fixed-diamond abrasive wire-saw cutting is the most widely used method for slicing hard and brittle materials. The diamond abrasive particles on the wire saw wear to a certain extent, which affects the cutting force and wafer surface quality in the cutting process. In this experiment, keeping all the given parameters unchanged, a square silicon ingot is cut repeatedly with a consolidated diamond abrasive wire saw until the wire saw breaks. The experimental results show that the cutting force decreases with the increase in cutting times in the stable grinding stage. The wear of abrasive particles starts at the edges and corners, and the macro failure mode of the wire saw is fatigue fracture. The fluctuation of the wafer surface profile gradually decreases. The surface roughness of wafer is steady during the wear steady stage, and the large damage pits on the wafer surface are reduced in the whole process of cutting.

Fixed-Diamond Abrasive Wire-Saw Cutting Force Modeling Based on Changes in Contact Arc Lengths.

Monocrystalline silicon is widely used in the semiconductor market, but its hard and brittle physical properties make processing difficult. Fixed-diamond abrasive wire-saw (FAW) cutting is currently the most commonly used cutting method for hard and brittle materials due to advantages such as narrow cutting seams, low pollution, low cutting force and simple cutting process. During the process of cutting a wafer, the contact between the part and the wire is curved, and the arc length changes during the cutting process. This paper establishes a model of contact arc length by analyzing the cutting system. At the same time, a model of the random distribution of abrasive particles is established to solve the cutting force during the cutting process, using iterative algorithms to calculate cutting forces and chip surface saw marks. The error between the experiment and simulation of the average cutting force in the stable stage is less than 6%, and the errors with respect to the central angle and curvature of the saw arc on the wafer surface are less than 5% between the experiment and simulation. The relationship between the bow angle, contact arc length and cutting parameters is studied using simulations. The results show that the variation trend of the bow angle and contact arc length is consistent, increasing with an increase in the part feed rate and decreasing with an increase in the wire velocity.

A Study on the Influence of Process Parameters on the Workpiece Surface Quality in the Cutting of Hard and Brittle Materials with Trepanning Drill.

Hard and brittle materials have excellent physical and mechanical properties and are widely used in the fields of microelectronics and optoelectronics. However, due to their high hardness and brittleness, the machining quality of a workpiece struggles to meet the requirements of practical applications. In order to improve the surface quality of deep-hole machining of hard and brittle materials, this article analyzes the formation mechanism of surface roughness and the exit-chipping width during the drilling machining of hard and brittle materials and establishes a mathematical prediction model for the surface roughness and the exit-chipping width of hard and brittle materials using a trepanning cutter. The experimental study on K9 optical glass machining shows that the surface roughness of the workpiece and the exit-chipping width increase with the increase in feed rate, and decrease with the increase in rotational speed. Through comparison and verification between theoretical and experimental values, the average errors of workpiece surface roughness and the exit-chipping width are 13.15% and 6.73%, respectively. This article analyzes the reasons for the errors. The results indicate that the theoretical model proposed in this article can be used to predict the surface roughness and the exit-chipping width of hard and brittle materials processed under the same conditions, providing a theoretical basis to optimize process parameters to improve the surface quality of the workpiece.

Snare-assisted flexible endoscope in trans-gastric endoscopic gallbladder-preserving surgery: A pilot animal study.

BACKGROUND: Natural orifice transluminal endoscopic surgery (NOTES) gallbladder-preserving surgery by flexible endoscopy is an emerging technology. However, the gallbladder fails to obtain traction and positioning functions during the operation. AIM: To evaluate the feasibility and safety of a new surgical method, "snare-assisted pure NOTES gallbladder-preserving surgery". METHODS: Eight miniature pigs were randomly divided into the experimental group [NOTES gallbladder-preserving surgery using the snare device, snare assisted (SA)] and the control group (NOTES gallbladder-preserving surgery without using the snare device, NC), with four cases in each group. The differences between the two groups of animals in operating time, operating workload, complications, adverse events, white blood cells, and liver function were determined. RESULTS: No differences were found in the surgical success rate, gallbladder incision closure, white blood cell count, or liver function between the two groups. The total operating time, gallbladder incision blood loss, gallbladder disorientation time, gallbladder incision closure time, and workload scores on the National Aeronautics and Space Administration-Task Load Index were significantly reduced in the SA group (P < 0.05). CONCLUSION: These results indicated that snare-assisted pure NOTES gallbladder-preservation surgery using standard endoscopic instruments reduced the difficulty of operation, shortened operation time, and did not increase complications in pigs. A new method for pure NOTES gallbladder-preservation surgery was provided.

Landscape pattern change and its correlation with influencing factors in semiarid areas, northwestern China.

The West Liaohe Plain (WLP) is a typical crop-pastoral ecotone of the semiarid area in Northwestern, China. Land use/cover change (LUCC) of the WLP might endanger this ecosystem, triggering long-lasting environmental concerns. LUCC data for China (1980-2020) and hydrometeorological data were analyzed to reveal factors contributing to change and explore sustainable development opportunities. The results show that characteristics of the main land-use types in the WLP have changed significantly, especially cultivated land area, which increased by 15.2% and 6.79% during the periods 1980-1995 and 2000-2020, respectively. Response relationships were observed due to natural (precipitation, temperature, and runoff) and anthropogenic (economy) factors and LUCC. Between 2000 and 2020, the impact of anthropogenic factors on cultivated land was stronger than on grassland at the class and landscape level, using the landscape indices which were selected, including percent of landscape (PLAND), number of patches (NP), largest patch index (LPI), and Shannon's evenness index (SHEI). Expansion of cultivated land from 1990 to 1995 was not only related to anthropogenic factors but also to hydrological & climatic factors. The results of this study have the potential to influence sustainable land resource development.

Mechanical Behavior Investigation of 4H-SiC Single Crystal at the Micro-Nano Scale.

In this paper, theoretical models of the critical indentation depth and critical force on brittle materials using cleavage strength and contact theory are proposed. A Berkovich indenter is adopted for nanoindentation tests on a 4H-SiC single crystal sample to evaluate its mechanical behaviors. The stages of brittle material deformation (elastic, plastic, and brittle) can be characterized by the load versus indentation depth curves through the nanoindentation test. The curve of the elastic deformation stage follows the Hertz contact theory, and plastic deformation occurs at an indentation depth of up to 10 nm. The mechanism of 4H-SiC single crystal cracking is discussed, and the critical indentation depth and critical force for the plastic-brittle transition are obtained through the occurrence of the pop-in point. This shows that the theoretical results have good coherence with the test results. Both the values of the elastic modulus and hardness decrease as the crack length increases. In order to obtain more accurate mechanical property values in the nanoindentation test for brittle materials such as SiC, GaN, and sapphire, an appropriate load that avoids surface cracks should be adopted.

The Diagnosis Performance of the TCM Syndromes of Irritable Bowel Syndrome by Gastroenterologists Based on Modified Simple Criteria Compared to TCM Practitioners: A Prospective, Multicenter Preliminary Study.

PURPOSE: Traditional Chinese medicine (TCM) including Chinese patent medicine has been widely used to treat irritable bowel syndrome (IBS). Syndrome differentiation is the essence of TCM. However, the diagnostic ability of gastroenterologists to detect TCM syndromes in IBS in China remains unknown. The aim of this study was to investigate the ability of gastroenterologists to diagnose the TCM syndromes of IBS based on modified simple criteria compared with TCM practitioners. METHODS: Patients meeting the Rome III criteria for IBS-D or IBS-C were recruited from six tertiary referral centers between January 2016 and December 2017. After learning the diagnosis criteria of the TCM syndromes in IBS, gastroenterologists first diagnosed the syndromes of the enrolled patients. Subsequently, the patients were diagnosed by TCM practitioners. The rate of agreement between the gastroenterologists and TCM practitioners was analyzed. In addition, demographic data and the distribution of TCM syndrome types in IBS were also analyzed. RESULTS: A total of 178 patients (93 males and 85 females), including 131 patients with IBS-D and 47 patients with IBS-C, were enrolled in this study. The rate of agreement of the syndrome diagnosis between the gastroenterologists and TCM practitioners was 84.3%. The diagnosis consistency rates among IBS-D patients and IBS-C patients were 87.0% and 76.5%, respectively. The most common TCM syndrome type in IBS-D patients was liver depression and spleen deficiency syndrome (27.5%), followed by spleen-yang deficiency syndrome (19.8%). Dryness and heat in intestine syndrome was the most common TCM syndrome in IBS-C patients (57.4%). CONCLUSIONS: Gastroenterologists had good diagnostic agreement with TCM practitioners for diagnosing TCM syndrome types in IBS after learning the diagnostic criteria. This knowledge can aid gastroenterologists in selecting suitable Chinese patent medicine to treat IBS.

Agreement of gastroenterologists in traditional Chinese medical differential diagnosis of functional dyspepsia compared with traditional Chinese medical practitioners: A prospective, multicenter study.

OBJECTIVE: To compare the performance of gastroenterologists major in western medicine in diagnosing traditional Chinese medicine (TCM) syndrome types of functional dyspepsia (FD), postprandial distress (PDS) and epigastric pain syndromes (EPS) based on the main symptoms, with that of traditional TCM practitioners in outpatient services. METHODS: Patients with PDS or EPS were enrolled in the study from six tertiary referral centers between January 2016 and December 2017. Their symptoms were first diagnosed by medical doctors, and then by the TCM practitioners. The diagnostic agreement between the gastroenterologists and the TCM practitioners was calculated. The patients' data and their types of FD syndrome were collected and analyzed. RESULTS: In total 160 patients, including 81 with PDS and 79 with EPS were enrolled. The total diagnostic consistency rate between the gastroenterologists and TCM practitioners was 86.3%, while that of PDS and EPS was 85.2% and 87.3%, respectively. The most common type of PDS diagnosed by TCM practitioners was liver-stomach disharmony syndrome (33.3%), spleen deficiency and qi-stagnation syndrome (33.3%), while that for EPS was liver-stomach disharmony syndrome (36.7%). CONCLUSIONS: Gastroenterologists had a high diagnostic agreement about the types of FD syndromes based on differential diagnosis of the main symptoms, compared with TCM practitioners. This may aid gastroenterologists in selecting Chinese medicine for FD-based on syndrome differentiation.

[The change of intestinal mucosa barrier in chronic severe hepatitis B patients and clinical intervention].

OBJECTIVE: To study the change of intestinal mucosa barrier in chronic severe hepatitis B patients and clinical intervention. METHOD: (1) 30 normal healthy controls and 60 chronic severe hepatitis B patients were enrolled in this study. The change of intestinal permeability was determined by urine lactulose/ mannitol ratio (L/M), and the serum diamine oxidase (DAO) was measured. (2) 60 chronic severe hepatitis B patients were randomly divided into two groups: the control group and the treated group, each group has 30 cases. Patients in the control group received standard treatment for 2 weeks, however, in addition to standard treatment, patients in the treated group also received glutamine 10g tid. Endotoxin (ET), DAO and L/M were compared between the two group. RESULTS: (1) Compared to healthy controls, the level of L/M and DAO was significantly increased in chronic severe hepatitis B patients (t = 2.762, P less than 0.01 or t = 6.326, P less than 0.01). (2) Compared to the control group, ET, DAO and L/M were significantly lower 2 weeks after treatment (F = 11.662, P less than 0.01; F = 12.699, P less than 0.01; F = 19.981, P less than 0.01). CONCLUSION: (1) There is an early intestinal mucosa barrier damage in chronic severe hepatitis B patients. (2) Compared to standard treatment, adding glutamine can reverse intestinal mucosa barrier damage.

The Diagnostic and Prognostic Value of miR-200c in Gastric Cancer: A Meta-Analysis.

BACKGROUND: The role of miR-200c in gastric cancer remains controversial. This study is aimed at clarifying the diagnostic and prognostic value of miR-200c in gastric cancer through a meta-analysis. METHODS: A comprehensive literature search of PubMed, Embase, and Ovid library databases was conducted. The studies included were those conducted before December 2017. The sensitivity and specificity, positive likelihood ratio (PLR), negative likelihood ratio (NLR), diagnostic odds ratio (DOR), and area under curve (AUC) were used to estimate the diagnostic value of miR-200c. Meanwhile, the pooled hazard ratio (HR) was used to estimate the prognostic value of miR-200c. RESULTS: For the diagnostic value of miR-200c, six studies that included 202 patients with gastric cancer and 250 normal controls were analyzed. The sensitivity, specificity, PLR, NLR, DOR, and AUC were 0.74, 0.66, 2.20, 0.40, 5.34, and 0.75, respectively. Subgroup analysis showed no significant difference in the type of the sample, method for testing miR-200c, and ethnicity among the patients. Meanwhile, for the prognostic value of miR-200c, seven studies comprising 935 patients with gastric cancer were analyzed. The pooled results showed that miR-200c expression was associated with overall survival (HR = 2.19) and disease-free survival (HR = 1.73), but not with progression-free survival (HR = 1.64) in patients with gastric cancer. There was no publication bias across the studies. CONCLUSIONS: Both serum and tissue miR-200c have moderate diagnostic accuracy in gastric cancer. miR-200c could also be used as a valuable indicator for predicting the prognosis of gastric cancer patients.

Differential diagnosis of Helicobacter pylori-associated gastritis with the linked-color imaging score.

BACKGROUND: Helicobacter pylori (H. pylori) infection in gastric mucosa is the main risk factor for gastric cancer. The purpose of this study was to assess the value of the linked-color imaging (LCI) score for the identification of H. pylori-associated gastritis. METHODS: A total of 358 patients were enrolled in the study. H. pylori was positive in 127 cases and negative in 231 cases. Redness of fundus glands, granular erosion, purple mucus (+) and mucus lake turbidity were investigated by the LCI mode of endoscopy. Logistic regression was used to screen the observation indexes and their relative partial regression coefficients, which were helpful for the differential diagnosis of H. pylori infection. Then, each observation index was scored according to the partial regression coefficient. RESULTS: Using a total scores of 3.5 as the cut-off value, the sensitivity and specificity were 83.8% and 99.5%, respectively, for the differential diagnosis of H. pylori gastritis. The area under the curve was 95.3%. CONCLUSIONS: The LCI score showed high sensitivity and specificity for the differential diagnosis of H. pylori-associated gastritis and is an effective method for identifying H. pylori infection in gastric mucosa.

A Randomized, Double-Blind, Multicenter, Placebo-Controlled Trial of Qi-Zhi-Wei-Tong Granules on Postprandial Distress Syndrome-Predominant Functional Dyspepsia.

BACKGROUND: Functional dyspepsia (FD) is a common upper gastrointestinal disorder worldwide, but the current treatments for FD are still unsatisfactory. The aims of this study were to investigate the efficacy and safety of Qi-Zhi-Wei-Tong granules in patients with postprandial distress syndrome (PDS)-predominant FD. METHODS: The study was conducted as a randomized, double-blinded, multicenter, placebo-controlled design in 197 patients with PDS. All participants received placebo treatment for 1 week. Patients whose total symptom score decreased by <50% after the placebo treatment were recruited into the 4-week treatment period, in which they were randomly assigned to be treated with either Qi-Zhi-Wei-Tong granules or placebo. The patients were then followed for 2 weeks without any treatment. Dyspeptic symptoms were scored at weeks 2 and 4 during the random treatment period and 2 weeks after the treatment. Anxiety and depression symptoms were also scored and compared. RESULTS: (1) The total effective rates in the Qi-Zhi-Wei-Tong granules group at weeks 2 and 4 during the random treatment period and 2 weeks after treatment were all significantly higher than those in the placebo group (38.82% vs. 8.75%, P < 0.001; 69.14% vs. 16.25%, P < 0.001; 77.65% vs. 21.25%, P < 0.001). (2) The total dyspeptic symptoms scores in the Qi-Zhi-Wei-Tong granules group at weeks 2 and 4 and 2 weeks after treatment were significantly lower than those in the placebo group. (3) The severity and frequency of each dyspeptic symptom at weeks 2 and 4 and the follow-up period were all significantly lower than those in the placebo group. (4) The anxiety scores in the Qi-Zhi-Wei-Tong granules group were significantly lower than those in the placebo group. (5) Qi-Zhi-Wei-Tong granules did not have more adverse effects than the placebo. CONCLUSION: Qi-Zhi-Wei-Tong granules offer significant symptomatic improvement in PDS with no more adverse effects than placebo. TRIAL REGISTRATION: https://clinicaltrials.gov/, NCT02460601.

Deanxit relieves symptoms in a patient with jackhammer esophagus: A case report.

Jackhammer (hypercontractile) esophagus presents with dysphagia and chest pain. Current treatments are limited. We describe a 60-year-old man who presented with dysphagia, chest pain and heartburn for a period of 1 year. His workup showed Barrett's esophagus on endoscopy and high-resolution manometry demonstrated jackhammer esophagus with esophagogastric junction outflow obstruction. The patient was treated with proton pump inhibitor and nifedipine but without resolution of his symptoms. He was followed up to assess the efficacy of treatment with deanxit (flupentixol + melitracen). Dysphagia and chest pain resolved during the therapeutic trial and efficacy was maintained on maintenance treatment without troublesome side effects.

Role of mast cell-miR-490-5p in irritable bowel syndrome.

AIM: To determine the functional role of miR-490-5p in mast cell proliferation and apoptosis, and in the mast cell tryptase/PAR-2 signal pathway. METHODS: The 3rd generation of lentivirus vector systems containing enhanced green fluorescent protein (EGFP) (Ruisai Inc., Shanghai, China), which acts as a reporter gene was used to construct the mmu-miR-490-5p lentivirus expression vector pEGFP-antagomiR-490-5p, and the lentivirus vector pEGFP-negative was used as a negative control. The stably transfected mast cell line p815 was then constructed. GFP positive cells were successfully transfected cells. We determined the expression of miR-490-5p in p815 mast cells before and after transfection using quantitative real-time PCR (qRT-PCR). In addition, after transduction with the lentivirus vectors, the role of miR-490-5p in mast cell proliferation and apoptosis was investigated using the CCK-8 assay and flow cytometry, respectively. The mRNA levels of tryptase and PAR-2 were detected by qRT-PCR and the protein levels were detected by Western blot. RESULTS: The inhibition of miR-490-5p expression promoted apoptosis and inhibited proliferation of p815 mast cells. The mRNA levels of tryptase and PAR-2 were significantly increased after transfection compared with the control group, tryptase (P = 0.721, normal vs null; P = 0.001, siRNA vs normal; P = 0.002, siRNA vs null) and PAR-2 (P = 0.027, siRNA vs null; P = 0.353, normal vs null; P = 0.105, siRNA vs normal). The protein levels of tryptase and PAR2 were slightly higher in the siRNA group than those in the control group, but the difference was not statistically significant (P > 0.05). CONCLUSION: miR-490-5p plays a vital role in the pathogenesis of irritable bowel syndrome by affecting mast cell proliferation and apoptosis; with down-regulation of miR-490-5p, the mRNA level of mast cell tryptase and PAR-2 increased, and the protein level increased, but the difference was not statistically significant.

Tryptase and Protease-Activated Receptor 2 Expression Levels in Irritable Bowel Syndrome.

BACKGROUND/AIMS: Previous studies have revealed that mast cells (MCs) may activate the protease-activated receptors and release of neuropeptides involved in the pathogenesis of irritable bowel syndrome (IBS). The levels of proteaseactivated receptor 2 (PAR-2) and tryptase can contribute to understanding the pathogenesis of IBS. METHODS: Colonoscopic biopsies were performed of 38 subjects (20 with IBSdiarrhea [IBS-D], eight with IBS-constipation [IBS-C], and 10 healthy volunteers). The mRNA and protein levels of tryptase and PAR-2 were assessed by real-time PCR and Western blot. The levels of vasoactive intestinal peptide (VIP), substance P (SP), and calcitonin gene-related peptide (CGRP) were measured by immunohistochemistry, and MCs were counted by toluidine blue staining. RESULTS: Significant increases in the mRNA expression of tryptase (p<0.05, IBS-D, IBS-C vs control) and PAR-2 (p<0.05, IBS-D, IBS-C vs control) and in the tryptase protein level (p<0.05, IBS-D, IBS-C vs control) were detected in IBS. Elevations of MCs, CGRP, VIP and SP (p<0.05, IBS-D vs control) were observed for IBS-D only. CONCLUSIONS: Tryptase levels may upregulate the function of PAR- 2, resulting in the release of neuropeptide and they were correlated with clinical symptoms associated with IBS.

Antinociceptive property of tegaserod in a rat model of chronic visceral hypersensitivity.

OBJECTIVE: To establish a model of chronic visceral hypersensitivity in rats and to investigate the effect of tegaserod, a partial 5-hydroxytryptamine-4 receptor agonist, on visceral hypersensitivity. METHODS: Neonate Sprague-Dawley rats at 8-21 days after birth underwent colorectal distension once daily. Adult rats aged 8-10 postnatal weeks underwent colorectal distension and the abdominal withdrawal reflex (AWR) during the distension was determined. The AWR score was recorded before and after intraperitoneal administration of either tegaserod (treatment group: 0.3 mg/kg) or vehicle (control group). RESULTS: Changes in the AWR score were dependent on the pressure intensity of the colorectal distension (P < 0.01). At pressures of 40, 60 and 80 mmHg, the AWR scores in the model rats with visceral hypersensitivity were significantly higher than those recorded in the control group (1.95 +/- 0.16 vs 1.35 +/- 0.15, 2.82 +/- 0.12 vs 2.17 +/- 0.13, 3.20 +/- 0.14 vs 2.59 +/- 0.14, P < 0.01). Compared with the controls, tegaserod significantly decreased the AWR scores at the distension pressures of 40, 60 and 80 mmHg (1.95 +/- 0.50 vs 1.32 +/- 0.55, 3.05 +/- 0.48 vs 2.32 +/- 0.54, 3.25 +/- 0.63 vs 2.77 +/- 0.51, P < 0.05). CONCLUSIONS: Adult rats can develop chronic visceral hypersensitivity after transient colorectal mechanical irritation during their postnatal period. Tegaserod increases the pain threshold to noxious stimuli, suggesting an antinociceptive property in its effect on visceral hypersensitivity.

[Relationship between mutation at 1 573 fragment of TNF receptor II gene and keloid].

OBJECTIVE: To study the mutations at 1 573 fragment of TNF receptor II (TNFR-II) gene in patients with keloid. METHODS: The tissue DNA was extracted from 22 samples of keloids donated by 22 patients (6 males and 16 females, aged 18-53 years), and all keloids were examined and classified by pathologist. The peripheral blood DNA was extracted from the same patients as the control. PCR was used to amplify the 1 573 fragment of TNFR-II gene from the keloid tissue DNA and peripheral blood DNA. The PCR products were sequenced directly and then compared with the GeneBank data. RESULTS: All the concentration of the extracted DNA in trial were higher than 0.50 microg/microL and the purity (A260/A280) of the extracted DNA were higher than 1.5. It closed to the magnitude of the design DNA fragment by agarose gel electrophoresis examining, and corresponded with the test requirement. Mutations at 1 573 fragment of TNFR-II gene were detected in 13 out of 22 keloids. The mutation incidence was 59.1%. Among them, 9 had point mutation at codon 1 663, accounting 40.9%. No TNFR-II gene mutation was detected in all peripheral blood samples. There were significant difference between keloids DNA and peripheral blood DNA (P < 0.01). The mutations involved point mutation, deletion and insertion as well as multisite and multitype. CONCLUSION: There is a correlation between the mutation at 1 573 fragment of TNFR-II gene and keloid.