Factors Affecting Flow-Mediated Vasodilatation in Hemodialysis Patients

Clinical manifestation of overt vascular disease may be preceded for years by endothelial dysfunction. Objective: This study was undertaken to evaluate endothelial function in ESRD patients and correlation between endothelial function and clinical and biochemical parameters. Methods: 32 stable ESRD patients (male : female = 16 : 16, average age: 55.2 ± 13.0) on hemodialysis were included. A 10‐MHz ultrasound transducer was used to image the brachial artery. Brachial artery diameter was measured, and reactive hyperemia was induced by inflation to 250 mmHg for 5 min and then deflation of a pneumatic cuff. After release of the cuff, brachial artery diameter was measured. Results: In the entire study population and non‐diabetic group, the %FMD (% flow‐mediated dilatation, % change of brachial artery diameter between before and after cuff inflation) did not show any significant correlation with duration of dialysis, age, hypertension, albumin, CRP, total cholesterol, LDL and HDL cholesterol, and triglyceride. However, the %FMD of diabetic patients was lower than that of non‐diabetics. Among the patients with diabetes, the group of patients with FMD of <5.2% showed significant lower serum albumin and significantly higher ln(CRP) levels compared to the group of patients with FMD ≥5.2%. The %FMD showed significant positive correlation with serum albumin level and significant negative correlation with ln(CRP) in diabetic patients. Conclusion: These findings suggest that endothelial dysfunction, estimated by FMD, was significantly more prominent in diabetic ESRD, especially with low serum albumin and high CRP levels.     

Clinical Characteristics of Upper Gastrointestinal Bleeding in Hemodialysis Patients

Upper gastrointestinal bleeding (UGIB) frequently occurs in hemodialysis (HD) patients. But, clinical characteristics of UGIB in HD patients are not well reported yet.
Objective:  This study was designed to compare the clinical characteristics of UGIB between HD patients and normal population with intact renal function.
Methods:  This study enrolled 24 HD patients with UGIB. Age- and sex-matched 26 patients with UGIB and normal renal function were selected as control group during the same period. Of the cases with UGIB, esophageal variceal bleedings due to liver cirrhosis were excluded in this study. We investigated the results of treatment and UGIB-associated mortality for 3 months after the event and then compared previous gastrointestinal (GI) symptoms (Sx), endoscopic findings, treatment results, and mortality between HD patients and control.
Results:  The results are summarized in the table.  

     

Cirrhosis Ameliorates Renal Osteodystrophy in Patients on Regular Hemodialysis

Cirrhosis (Cir) is often associated with chronic renal failure (CRF) in Egyptian patients on regular hemodialysis (RHD). This is largely attributed to hepatosplenic schistosomiasis and concomitant Hepatitis C viral infection. As the liver has a major role in vitamin D3 activation, we designed this study to envisage the impact of Cir on renal osteodystrophy (ROD). It included 130 consecutive age‐ and gender‐matched subjects in 4 categories. Group I: 39 patients (34 male and 5 female; mean age 48.8 years) with Cir normal renal function; group II: 37 patients (30 male and 7 female; mean age 49.0 years) with CRF and normal liver function, on RHD for a mean duration of 6 ± 3.9 years; group III: 41 patients (30 male and 11 female; mean age 50.7 years) with CRF and concomitant Cir, stable on RHD for a mean duration of 7.0 ± 4.0 years; and group IV: 16 normal volunteers (13 male and 3 female; mean age 46.3 years). The prevalence of diabetes as well as previous infection with schistosomiasis was similar in all patient groups and that of HCV infection was alike in groups I and III. In all subjects, conventional parameters of liver and renal function were tested; in addition to measurement of serum total protein, albumin, calcium, phosphate, total and bone‐specific alkaline phosphatase (B‐ALP), parathormone (PTH), 5‐hydroxycholecalciferol (5HD), 1,25‐dihydroxycholecalciferol (1,25HD), Cross Laps (CXL) as a marker of bone resorption, and aminoterminal propeptide of type I procollagen (PINP) as a measure of bone formation. Bone mineral density (BMD) was measured by either Dual Energy X‐ray Absorptiometry (DEXA) or Computerized Tomography (CT). Group II patients displayed the typical CRF profile comprising hypocalcemia, hyperphosphatemia, increased total and bone‐specific alkaline phosphatases, high PTH and 25HD, low 1,25HD, increased PINP as well as CXL, and generally decreased BMD. Cir (Group III) significantly (p value at least <0.5) modified this profile in several aspects: it checked hypocalcemia (mean 8.8 vs. 7.9 mg/dL in groups II and III, respectively), hyperphosphatemia (5.15 vs. 4.9 mg/dL), and the elevation of B‐ALP (62 vs. 30.5 μg/L) and PTH (89 vs. 78 pg/mL). It lowered the serum level of 25HD (18.7 vs. 13.7 ng/mL), augmented the deficiency of 1,25HD (13.4 vs. 8.0 pg/mL), did not appreciably affect the increase in bone formation (PINP 77.9 vs. 75.5 ng/mL), but ameliorated its excessive resorption (CXL 21 860 vs. 30 328 pmol/L) noticed in group II. This was associated with amelioration of the dialysis‐associated osteopenia (70 vs. 33.5%) and increased incidence of osteosclerosis (30 vs. 61%), as measured by bone mineral density. Conclusion: Our data indicate that Cir ameliorates ROD through decreased bone resorption. This is associated with better tolerance to 1,25HD deficiency, which initiates the cascade of hypocalcemia, hyperparathyroidism, and increased bone resorption in CRF. Such tolerance may reflect upregulation of vitamin D receptors as a consequence of the humoral perturbation supervening in Cir, involving IGF‐1, estrogens, or other vitamin D metabolites as 24,25 HD.     

Relationship of Hypoalbuminemia to Multiple Clinical Factors in Hemodialysis Patients

Research shows that low albumin is correlated with higher morbidity and mortality in the dialysis population. The reasons for this are multi‐factorial and may be related to inadequate protein intake, infection and sepsis, inadequate dialysis, or catabolism of uremia. USRDS data show that ESRD Network 16 tends to have lower albumins compared to other ESRD Networks. Objective: To evaluate albumin status of HD patients at Puget Sound Kidney Centers, Everett, WA (ESRD Network 16) and identify potential factors that may put patients at risk of hypoalbuminemia. Methods: Clinical and biochemical data were collected for 3 months on 221 HD patients. Data included serum albumin (bromcresol purple), calcium, phosphorus, CO₂, Hct, % saturation, ferritin, PTH, BUN, Kt/V, URR, nPCR, hours of HD treatment, interdialytic fluid weight gains, DW changes, incidence of infection and hospitalization, catheter use for dialysis access, presence of diabetes and other co‐morbidities, dialyzer reuse, social/psychological status, and use of nutrition supplements. All biochemical data were collected after the longest interdialytic period and analyzed at the same reference laboratory. Data were averaged for each patient for the 3 months and correlations between parameters were determined using Chi‐square analysis. Results: 25% of all patients had albumins <3.2 g/dL (reference range for normal population 3.5–5.0 g/dL). Patients with lower albumins were significantly more likely to have DM (p < 0.02), use catheters for HD access (p < 0.001), had infections during the previous month (p < 0.001), been hospitalized during the previous month (p < 0.002), have co‐morbid issues (p < 0.001), and use nutrition supplements (p < 0.002). No other factors were significantly correlated with lower albumin. Conclusion: Factors other than nutrition seem to be related to hypoalbuminemia. This study has prompted improved protocols for catheter care and use, infection control, and early intervention for nutrition supplement use. Increased screening and monitoring at‐risk patients (those with diabetes and other co‐morbid conditions) has resulted in improved patient care.     

Role of Genetic Factors in Vascular Access Thrombosis in Hemodialysis Patients

Vascular access thrombosis is a frequent complication in hemodialysis (HD) patients. Genetic mutations, inflammation, and changes in the vascular wall are some factors that are thought to increase thrombosis risk. In this study, we tested for possible relationships between vascular thrombosis and some known thrombophilic mutation/polymorphisms in coagulation factors [factor V Leiden (FVL), prothrombin (Pt) G20210A, methylene tetrahydrofolate reductase (MTHFR C677T), factor XIII (F-XIII) Val34Leu, alpha-fibrinogen (AF) Thr312Ala, factor VII (F-VII) R353Q] and angiotensin I converting enzyme (ACE) gene in our HD patients. Patients who had experienced at least 3 episodes of AVF thrombosis composed of the study group, and patients who had never encountered this complication composed of the control group. None of the patients in either group had a history of diabetes mellitus, atherosclerosis, dialysis-related amyloidosis, or vasculitis. In order to find the frequency of F-XIII Val34Leu, AF Thr312Ala, and F-VII R353Q polymorphisms in our population, we also searched persons without renal disease or history of thrombosis (normal group). Results are summarized in Table. There was a tendency toward thrombotic mutation/polymorphisms in the study group for FVL, Pt G20210A, ACE I/D, and AF Thr312Ala. We suggest that patients who develop recurrent AVF thrombosis should be screened for the above-mentioned factors and investigated for other possible risk factors. This screening would allow more effective focus on prophylaxis.  

     

快速和灵敏地分析常见氨基酸

利用基质辅助激光解吸电离飞行时间质谱(MALDI-TOF-MS)和电子轰击(EI)质谱法快速、灵敏地分析了常见的八种氨基酸。并讨论了在不同电离方式下这八种氨基酸的质谱行为,分析结果表明两种方法对测定氨基酸均具有独特之处。     

Survival of End-Stage Renal Disease Diabetic Patients on Hemodialysis

Purpose: To analyze survival and causes of mortality in end‐stage renal disease (ESRD) diabetic patients treated by hemodialysis. Methods: Data of 1203 ESRD hemodialyzed patients between 1975 and 2002 were analyzed, 116 patients were excluded and 1087 patients included in the study. We studied the prevalence of the diabetic nephropathy, the rate of survival and causes of death by comparing diabetic patients with a control group of patients without diabetes. Results: Among the 1087 patients requiring dialysis, 272 (25%) were diabetic and 815 non‐diabetic whose causal nephropathy was nephroangiosclerosis 32%, glomerulonephritis 15%, chronic interstitial nephropathy 14%, and others 14%. The diabetics were older at the beginning of dialysis than non‐diabetic patients: 60.33 ± 11.39 years vs. 52.23 ± 17.20 years, p < 0.001. Average time on dialysis is more important in non‐diabetic than diabetic group [5.90 ± 5.73 years vs. 2.71. ± 2.48 years, p < 0.001]. The rate of death was higher in diabetics than in control group [71.7% vs. 55.8%, respectively, p < 0.003]. The difference in survival between the two groups remains significant for the same age. Death caused by cardiovascular disorders is higher in diabetics (68.8%) than non‐diabetics (31.2%) (p < 0.05). Among death causes, stroke is the most frequent cause in diabetics (18.4% vs. 11.6%) in non‐diabetics, p < 0.05. Death by heart failure and infections is higher in diabetics but the difference is not statistically significant (12.3% in diabetics vs. 9.4% in non‐diabetics for heart failure and 13.8% vs. 11.4% for infections). Death due to neoplasms is higher in non‐diabetics (4.39% vs. 1.02% in diabetics, p < 0.05). Conclusion: In our cohort, mortality in diabetic patients is higher than in non‐diabetic patients. Cardio‐vascular disorders are the most cause of death in diabetics and above all stroke, whereas mortality due to neoplasms is higher in non‐diabetic patients. Diabetes is an important risk factor of mortality in hemodialysis patients.     

Effect of Vitamin E Dialyzer Membrane on Anemia in Hemodialysis Patients

Red blood cell (RBC) survival in patients on chronic maintenance hemodialysis (HD) has been reported to be shortened due to the oxidative damage of RBC membrane. The use of antioxidants might help in the control of anemia and reduce the erythropoietin (EPO) dose needed. Objective: The objective was to determine the effects of vitamin E‐bonded dialyzer membrane (VEM) on anemia and EPO requirements in chronic HD patients. Patients and methods: We prospectively studied 19 stable patients on HD (8 males, age 58.47, range 31–76 years) who were shifted from other dialyzer membranes to VEM for 6 months. At baseline they were given a mean dose of EPO of 90.6 ± 51 U kg^–1 BW^–1 week^–1. Clinical data, dry body weight corrected pre‐dialysis RBC, hemoglobin, reticulocytes, serum iron and ferritin, complete biochemistry, iPTH, and CRP were studied at 3 and 6 months, while therapy scheme was reevaluated monthly. Results: A significant rise, compared to the baseline, was found in hemoglobin and in RBC at 3 months of treatment (12.44 ± 1.16 g/dL vs. 11.2 ± 1.2 g/dL, p = 0.002; and 4.01 ± 0.53 × 10⁶/μL vs. 3.64 ± 0.5 × 10⁶/μL, p < 0.05) and at the end of follow‐up (12.17 ± 1.33 g/dL vs. 11.2 ± 1.2 g/dL, p < 0.05; and 4.03 ± 0.53 × 10⁶/μL vs. 3.64 ± 0.5 × 106/μL, p < 0.05). No significant change in serum iron and ferritin, reticulocytes, EPO dose used, iPTH, Kt/V, or CRP was found at the end of follow‐up compared to the baseline (68.8 ± 17 mg/dL vs. 67.9 ± 18 mg/dL, p = NS; 421 ± 296 mg/dL vs. 478 ± 359 mg/dL, p = NS; 3.76 ± 0.89 × 10⁴/μL vs. 3.82 ± 0.78 × 10⁴/μL, p = NS; 90.2 ± 53 U kg^–1 BW^–1 week^–1 vs. 90.6 ± 51 U kg^–1 BW^–1 week^–1, p = NS; 157 ± 43 pg/dL vs. 148 ± 56 pg/dL, p = NS; 1.21 ± 0.22 vs. 1.2 ± 0.17, p = NS; 7.15 ± 5.42 mg/L vs. 15.38 ± 29.8 mg/L, p = NS, respectively). Conclusions: Despite the small number of patients and the short time interval of treatment, an antioxidant effect of VEM apparently achieved early a better control of anemia in HD patients.     

氨基酸改性聚乳酸共聚物的合成及降解研究进展

为了改善聚乳酸的降解速率,提高其与细胞的亲和性,氨基酸对聚乳酸的改性研究引起了人们的关注。综述了聚(乳酸-氨基酸)共聚物的各种合成路线及产物降解性能的研究进展。在聚乳酸(PLA)分子中引入氨基酸,可以使产物的大分子侧链获得氨基、羟基、羧基等活性基团。与PLA相比,此类聚合物的降解性能有所提高,具有两亲性和良好的细胞相容性,可用于药物缓释体系及组织工程。     

氨基酸分析方法的进展

氨基酸分析方法的研究是绿色工业、绿色农业和生命科学中的比较重要的课题.综述了氨基酸的分析方法,重点介绍了分析测定氨基酸的分光光度法、色谱法和电化学法,展望了氨基酸分析方法的发展趋势.     

Clinical Consequences of Intermittent Elevation of C-Reactive Protein Level in Hemodialysis Patients

The presence of persistently high C‐reactive protein (CRP) levels is well known to be associated with a state of inflammation, malnutrition, and erythropoietin resistance in hemodialysis (HD) population. Meanwhile, a substantial group of patients present with intermittent elevations of CRP levels, and its clinical consequences are unclear. We designed this study to compare the inflammatory and nutritional parameters and erythropoietin requirements in HD patients with persistent or intermittent CRP elevation and those with CRP levels in without. We included 100 HD patients [age: 48.4 ± 14.3 years; HD duration: 69.3 ± 49.0 months (minimum 12 months)]. The 6‐month retrospective clinical and laboratory data were retrieved from the patient records, and those with chronic inflammatory disease, malignancy, infectious complications, and surgery were excluded. The monthly determined CRP levels (at least 6 for each patient) were reviewed, and the patients were grouped according to their CRP levels as those with persistent (group 1), intermittent (at least one level of CRP 10 mg/L) (group 2), and those with CRP in normal ranges set by the laboratory (group 3). We compared the fibrinogen, ICAM‐1, VCAM‐1, albumin, prealbumin, normalized protein catabolic rate (nPCR), interdialytic weight gain (IDWG), and rHuEPO/kg/Hct results of the patient groups. The patient groups revealed significant differences in terms of fibrinogen (p < 0.001), albumin (p < 0.0001), prealbumin (p < 0.007), ICAM‐1 (p < 00.2) levels and nPCR (p < 0.03), IDWG (p < 0.02), and rHuEPO/kg/Hct (p < 0.03) values. Group 2 presented to be in risk of inflammation and malnutrition with a decrease in albumin levels and nPCR and presence of rHUEpo resistance when compared to patients in group 3. We conclude that, similar to HD patients with persistently high CRP levels, those with intermittent elevation of CRP must also be considered to be in a state of chronic inflammatory response associated with malnutrition and erythropoietin resistance. This signifies the importance of regulatory monitoring of CRP in HD population.     

环保氨基酸型粘合剂的制备研究

以环氧氯丙烷为交联剂对骨胶进行化学改性得到环保氨基酸粘合剂.以初始粘度为指标,氢氧化钠用量、碱解时间、接枝共聚温度、环氧氯丙烷用量和接枝共聚时间为考察因素,做正交实验.结果表明氢氧化钠和环氧氯丙烷的加入量对粘度的影响最大,重点研究这两个因素,选出最佳合成工艺.通过热重分析对胶粘剂的热力学性能进行检测.所制得的粘合剂各项性能均达到GB 18583-2001和HG/T 2727-95要求,其中游离甲醛为0.01g/kg,剪切干强度为13.14MPa,远远高于标准要求.与传统改性相比,环保氨基酸粘合剂的凝固点为-5℃左右,常温呈液态,使用方便,应用范围更广.     

氨基酸离子液体对壳聚糖溶解性能的影响

合成了一系列氨基酸类离子液体,从中筛选出对溶解壳聚糖具有良好性能的离子液体——甘氨酸盐酸盐离子液体。在常温常压下考察了该离子液体1%～10%水溶液对壳聚糖的溶解能力,溶解壳聚糖能力最大能达到6.32%(质量分数,下同)。对离子液体重复使用5次后,溶解能力没有明显下降。采用X射线衍射(XRD)和红外光谱(FT-IR)对再生的壳聚糖进行表征,结果表明,壳聚糖在溶解过程中没有发生衍生化。甘氨酸盐酸盐离子液体水溶液是壳聚糖的良溶剂。     

Reaching Target Hemoglobin after Hospitalization for Incident Hemodialysis Patients

Introduction:  The Kidney Disease Outcomes Quality Initiative (K/DOQI) has established target hemoglobin (Hb) level of 11–12 g/dL for all dialysis patients. For patients who leave an inpatient hospitalization with an Hb under this target, it is hypothesized that several factors contribute to the length of time required to achieve an Hb of 11 g/dL after hospitalization.
Objective:  To identify factors contributing to a decreased likelihood of reaching this target Hb.
Methods:  Using the first hospitalization of patients who initiated HD in 1999 and who were regularly treated with EPO, we identified those with a mean Hb of less than 11 g/dL on EPO claims during the same month as their index hospitalization. Patients were then followed up to see how long it took them to achieve an Hb of 11 g/dL, censored at death, re-hospitalization, a switch of modality, or suspension of EPO treatment.
Results:  A total of 6050 HD patients were identified. 3 months after hospitalization, 70% had achieved 11 g/dL, and 12% had been censored. For the remaining patients who eventually reached 11 g/dL, the average number of additional months required was 2.69 (SE of 0.09). From proportional hazards regression on the time (in months) to achieving an Hb of 11 g/dL, factors that significantly decreased the likelihood of reaching a target Hb included: a diagnosis on the index hospitalization of CHF or hepatic disease, a low Hb prior to the hospitalization, a high dose of EPO prior to the hospitalization, and a longer hospital stay.
Conclusions:  Patients with anemia after hospitalization are at high risk of both persistent anemia and rehospitalization. It is important to address patient comorbidities, to ensure adequate medication usage, and to monitor patient progress to prevent hospitalizations and potential impact on Hb levels.     

Determination of Low Activity of Tritium-Labeled Amino Acids Using Simultaneously Flow Scintillation and Amino Acid Analyzers

The possibility of measuring a low activity of tritium-labeled amino acids in the eluate from Amino Acid Analyzer 835 (Hitachi, Japan) using a Radiomatic 150TR Flow Scintillation Analyzer (Packard Instrument Co., USA) was studied. Due to stepped variations of pH, ionic strength, and salt concentration in eluting solutions during amino acid separation and utilization of ninhydrin reagent in spectrophotometric measurements of amino acids, special selection of scintillation liquids was necessary. Six scintillation cocktails were tested: ZhS-8 (Reakhim, Ukraine), OptiPhase HiSafe 3 (Wallac Oy, EGGgr; Co., Finland), Hionic-Fluor, Ultima-Flo AP, Ultima-Flo M, and Ultima Gold (Packard Instrument Co., USA). It was found that Hionic-Fluor and Ultima-Flo AP cocktails are the most appropriate for flow measurements of tritium activity. Under optimal conditions the detection limit with Hionic-Fluor and Ultima-Flo AP was 150 and 100 decays min^{- 1} in the peak of amino acid, respectively. Such a high sensitivity allows utilization of the above analytical system for measurements of amino acid radioactivity to study the structure of proteins and protein complexes by tritium planigraphy.     

Pre‐ and Post Hemodialysis Procalcitonin Levels and Their Relationships with Immunoregulatory,Proinflammatory Cytokines in Chronic Hemodialysis Patients

Arteriosclerosis is characterized by stiffening of arteries. The incremental elastic modulus (Einc) measurement is a good marker of arterial wall stiffness. Arteriosclerosis is characterized by stiffening of arteries. Metabolic, inflammatory, and hemodynamic alterations cause structural changes and vascular complications in end‐stage renal disease. The aim of the present study was to evaluate the factors that may affect the development of arteriosclerosis by measurement of Einc in hemodialysis (HD) patients. Thirty‐two patients (16 men and 16 women) on chronic HD with a mean age of 42.2 ± 19.3 (range, 15–80) were included in the study. The carotid Einc was measured to determine arteriosclerosis by high‐resolution echo‐tracking system. Einc measurement was calculated from transcutaneous measurements of carotid arterial internal diameter and wall thickness and carotid pulse pressure. Common carotid compliance (CCC) and distensibility (CCD) were determined from changes in carotid artery diameter during systole and simultaneously measured carotid pulse pressure. Serum levels of calcium (Ca), phosphorus (P), parathormone (PTH), ferritin, C‐reactive protein (CRP), predialysis systolic blood pressure (SBP), predialysis diastolic blood pressure (DBP), pulse pressure (PP), age, HD duration, CCC, and CCD were correlated with Einc in all patients. A significant positive correlation was found between Einc and age (r = 0.40, p < 0.02), SBP (r = 0.39, p < 0.02), PP (r = 0.40, p < 0.02), Ca (r = 0.43, p < 0.01), CRP (r = 0.38, p < 0.02). As expected, Einc was correlated inversely with CCD (r = ?0.77, p < 0.0001). The correlation between Einc and HD duration, DBP, ferritin, P, PTH, and CCC was not significant. In conclusion, the stiffening of carotid artery in HD patients is related not only to hemodynamic changes (increased SBP and PP) but also to metabolic (increased Ca) and inflammatory (increased CRP) responses. Carotid Einc is an accepted independent risk factor for cardiovascular mortality. Because of the positive correlation between Einc and serum Ca, vitamin D and Ca‐containing P binder should be used carefully in HD patients.     

氨基酸离子液体清洁催化合成阿司匹林

以氨基酸为原料采用一步法合成了3种氨基酸离子液体,将其代替浓H2SO4用于催化乙酸酐和水杨酸的乙酰化反应,清洁合成阿司匹林。考察了离子液体种类及用量、原料配比、反应温度、时间等因素对合成阿司匹林的影响。结果表明,该离子液体对于合成阿司匹林具有良好的催化效果,在水杨酸20mmol、乙酸酐40mmol、谷氨酸硫酸盐离子液体([Glu]HSO4)2mmol、反应温度70℃、反应时间30min的条件下,阿司匹林分离产率可达84.8%。增大投料量,产率还会进一步升高,并且离子液体可重复使用。     

多元氨基酸共聚物的合成及性能表征

以本体聚合方法合成了可生物降解的多元氨基酸共聚物,并采用差示扫描量热分析(DSC)、热重(TGA)和X射线衍射(XRD)等手段对所合成的共聚物进行了表征.结果表明,所合成的多元氨基酸共聚物在常温下可微溶于某些非质子有机溶剂及质子强酸,提高温度可明显提高其溶解性;所合成共聚物为一种半结晶性聚合物,其结晶部分主要为6-氨基...     

氨基酸衍生环氧树脂的固化反应动力学

以天然氨基酸为起始材料,合成了一种具有双酚羟基官能团的环肽,并以此环肽为联酚合成了主链包含酰胺键、可生物降解的环氧树脂(AAEP)。用红外光谱(FT-IR)及核磁共振(1H-NMR1、3C-NMR)表征了AAEP的化学结构,测试结果表明,合成了预期的结构;用盐酸-丙酮法测算了环氧树脂的环氧值;用动态差示扫描量热(DSC)方法对这种新环氧树脂的固化动力学进行了详细的分析,固化反应存在两个明显的放热峰,对应的表观活化能分别为Ea1=53.38 kJ/mol,Ea2=62.58 kJ/mol(Kissinger方法)。     

氨基酸分析仪检测限的测量结果不确定度评定

本文结合实例,对氨基酸分析仪检测限的测量结果不确定度进行了分析评定。