The filter paper partition chromatographic method for the quantitative determination of total ascorbic acid is used for determination of human blood ascorbic acid. The percentage recovery is 101-102%. A comparison is made of this method with Roe-Kuether colorimetric method and photoelectric titration method for the total ascorbic acid determination. The results indicate that 2-ketogulonic acid is not present in human plasma.

It has been proved chromatographically that the substances in human urine interfere 2,6-dichlorophenol indophenol visual titration method are mainly thiosulfates, cysteine and an unknown substance with Rf of 0.5 (Rf of ascorbic acid = 0.28). Ketonic substances present in urine interfere the ascorbic acid estimation with 2,4-dinitrophenylhydrazine colorimetric method. The amount of these interfering substances present in human urine is usually high, so that erroneous results are obtained with both methods, even in the case of large amount of ascorbic acid in the sample.Formaldehyde at pH 2.0 can not condense with ascorbic acid quantitatively, so that the results obtained by formaldehyde condensation method are considerably lower than that obtained with Kuo and Chen's filter paper partition chromatographic method.Our results indicate that the last mentioned method is the most convenient and accurate one for the quantitative analysis of ascorbic acid in urine.

Iodine was used as an oxidant instead of brimine in the 2,4-dinitro-phenylhydrazine method for the determination of total ascorbic acid content in vegetables. The excess of iodine was removed with a small amount of crystalline thiourea. This process of oxidation was simple, safe and rapid.With this modified method, the ascorbic acid content of 18 vegetables were determined. The ascorbic acid values thus obtained with iodine were sometimes slightly lower than those with bromine, but were higher than those with paper chromatographic method.

(1) The contents of total ascorbic acid in 129 kinds of vegetables and fruits in Kaifeng were determined by means of both Kuo-Chen's paper ch-romatographic method and Schaffert-Kingsley's 2,4-dinitrophenyIhydrazine colorimetric method.(2) Our results indicated that the 2,4-dinitrophenylhydrazine colorimetric method was not specific in determining the total amount of ascorbic acid contents in acid extracts of vegetables and fruits and thus usually gave false results. Such extracts must be first separated from interfering substances before determination. Kuo and Chen's paper chromatog-raphic method is most suitable for this purpose.

Objective To investigate the clinical effects and postoperative complications of arthrotomy and arthroscopy in repair of 170 menisci in 168 cases.Methods One hundred and sixty-eight patients with meniscus injury were repaired by arthrotomy or arthroscopy.They were 121 males and 47 females.There were 77 left knees and 91 right knees;117 medial menisci and 53 lateral ones.Their average age was 25.5?8.4 years old.Arthro- scopic repair methods included puncture and grinding,bio-absorbable meniscus arrow fixation,Outside-In suturing, Inside-Out suturing,Elite scuff instrument repairing,T-Fix fixation and FasT-Fix fixation techniques.The clinical results were assessed on the basis of symptoms,physical signs,Tegner scores and Lysholm scores of the cases. Postoperative complications were also investigated.Re-arthroscopic exploration was done for patients with obvious symptoms and physical signs.Results The average folluw-up time was 49.3?28.8 months.Their mean pre- operative Tegner score was 3.3?2.3,and their postoperative one 6.8?2.1 (P＜0.05).Their preoperative Lysholm score was 30.1?18.2,and their postoperative one 87.5?22.5 (P＜0.01).There were significant differences in Tegner and Lysholm scores before operation and after operation.Ninety-eight repaired menisci were rated as excellent(57.7%),57 as good (33.5%),10 as fair (5.9%),and five as poor (2.9%).The total ex- cellent and good result was 91.2%.Of the 19 patients with obvious symptoms and physical signs,re-arthroscopic exploration found no healing in five and partial healing in six.Postoperative complications included pain at the Outside-In suture nodes in three cases,referred pain at posterior articular capsule resulted from failed Outside-In meniscus anterior horn suturing in one case,and twinge at the meniscus arrow site in the posterior capsule in five cases.No serious lesion occurred at blood vessels or nerves.The postoperative complication incidence was 5.3%. Conclusion The eight methods of arthrotomy and arthroscopy to repair injured menisci investigated in our study can have a high successful rate and low perioperative and postoperative risk.

Objective:To investigate the application value of shear wave elastography (SWE) and real-time tissue elastography (RTE) in differential diagnosis of thyroid Amereican College Radiology (ACR) TR5 nodules.Methods:Patients who underwent ultrasound examination at the Fourth Affiliated Hospital of Harbin Medical University from August 2018 to June 2019 diagnosed as ACR TR5 nodules were surveyed, and received SWE and RTE examinations to evaluate the nodules hardness. The receiver operating characteristic curve (ROC curve) was drawn to obtain the best diagnostic cutoff value for the Young's modulus maximum (Emax) of the benign and malignant thyroid ACR TR5 nodules using SWE technique; using the 5-point method, the elasticity score (ES) was used to evaluate the benign and malignant ACR TR5 nodules by RTE technology, and the pathological results were regarded as "gold standard". The accuracy, sensitivity, specificity, positive predictive value, and negative predictive value of SWE, RTE and two elastography techniques in differential diagnosis of benign and malignant thyroid ACR TR5 nodules were compared.Results:A total of 65 patients were enrolled, with a total of 73 ACR TR5 nodules. The optimal Emax threshold for differential diagnosis of ACR TR5 nodules by SWE technology was 41.8 kPa, and 32 malignant nodules and 41 benign ones were determined. Of the 73 ACR TR5 nodules using RTE technology, 38 had ES scores of 1 to 3 and 35 had ES scores of ≥4. Pathological results showed that among 73 thyroid ACR TR5 nodules, benign nodules accounted for 45.21% (33/73), malignant nodules accounted for 54.79% (40/73). The sensitivity, specificity, accuracy, positive predictive value and negative predictive value of SWE, RTE and two elastography techniques for differential diagnosis of benign and malignant thyroid ACR TR5 nodules were 72.50%, 77.50%, 87.50%; 90.91%, 87.88%, 87.88%; 80.82%, 82.19%, 87.67%; 90.63%, 88.57%, 89.24% and 73.17%, 76.32%, 85.29%.Conclusions:Ultrasound elastography of two different imaging principles of SWE and RTE is an effective method for differential diagnosis of benign and malignant thyroid ACR TR5 nodules. The combination of the two is more advantageous.

Objective: To obtain the high-resolution dose distribution for the single source channel of Leksell 4C gamma knife. Methods: A parallel computing platform based on the Message Passing Interface (MPI) and Monte Carlo Code MCNPX was established. The ring-shaped detector and two pre-validated variance reduction techniques (emission direction-biased sampling of source and termination of electron tracking in partial structures) were adopted to derive the high-resolution dose distribution for the single source channel of Leksell 4C gamma knife. The effect of cut-off energy for both photon and electron on the accuracy of simulation outcomes was evaluated and statistically compared. Results: Compared with previous findings, the spatial resolution of the dose distribution for the single source channel obtained in this study was higher (radial resolution=0.1 mm) with less statistical error (<1%). The calculation time was acceptable (approximately 24 h). For the 4-, 8-, 14-and 18-mm variable collimators, the penumbra and full width at the half maximum (FWHM) for single side were 1.0, 1.1, 1.2, 1.3 mm and 2.2, 4.3, 7.3, 9.3 mm, respectively, which were consistent with previous studies. The difference of the simulation results was extremely small between different cut-off energy for photon (1 keV vs.10 keV). However, the simulation results significantly differ between 1 and 521 keV electronic cut-off energy. Conclusions The MCNPX parallel computing platform based on the MPI environment can be utilized to derive highly accurate dose distribution with high resolution in acceptable calculation time. The cut-off energy of the photon and electron should be cautiously set up during simulation.

Objective improve the accuracy of the measurement results by using the field output factor measurement method based on daisy-chaining.Methods The Varian Edge Accelerator 6 MV X-ray data were measured using the IBA CC13 ionization chamber, IBA CC01 ionization chamber, IBA Razor semiconductor detector , IBA EFD semiconductor detector and Gafchromic EBT 3 film , respectively. Results Compared with the daisy-chaining measurement method,the results obtained by the conventional measurement method using CC13 were smaller. The deviation value was 16. 71% in the 1 cm × 1 cm field. The measurement results in a larger field via CC01 were bigger with a deviation of 8. 39% in the 40 cm × 40 cm filed. The measurement results via Razor in a larger field were larger with a deviation of 9. 40% in the 40 cm × 40 cm field. The measurement results were similar between EFD and Razor with a deviation of 9. 14% in the 40 cm × 40 cm field. The results of the film measurement were equivalent to those obtained from the daisy-chaining method in a field of＞ 1 cm × 1 cm with a deviation within 1. 60%,whereas the deviation was increased to 3. 13% in the 1 cm× 1 cm field. The results were consistent with daisy-chaining measurement if the 3 cm × 3 cm or 4 cm × 4 cm fields were selected as the intermediate fields with the maximum deviation of 0. 29%. Conclusions For the detectors with changing response along with the field size,daisy-chaining measurement method can be utilized to extend the measurement range and improve the accuracy of the measurement results.

Objective The IAEA report No.483 describes the latest method of small field dosimetry.The field output factor measurement and correction methods are used to improve the accuracy and consistency of the measurement results for different type detectors.Methods The field output factors from 0.6 cm×0.6 cm to 10 cm× 10 cm were measured using IBA's CC13 ionization chamber,CC01 ionization chamber,PFD semiconductor detector,EFD semiconductor detector and Razor semiconductor detector,respectively.The field output correction factors were used to correct the measurement result.Results Compared with the corrected data,the results of ionization chamber are mainly affected by the volume averaging and the fluence perturbation effect,lead to the measurement result which is 4.70％ lower at 0.6 cm × 0.6 cm;The results of Shielded semiconductors are mainly affected by fluence perturbation effect,lead to the measurement result which is 4.80％ higher at 0.6 cm × 0.6 cm.The results of unshielded semiconductors are mainly affected by energy response and fluence perturbation effect,resulting in lower measurement results at the field size＞0.8 cm×0.8 cm,2.10％ lower at field size of 1.5 cm× 1.5 cm,higher measurement results at field size＜0.8 cm×0.8 cm and 1.1％ higher at field size of 0.6 cm×0.6 cm.Before the correction,the measurement results from different types of detectors are quite different,average standard deviation is 0.016 6.After the correction,the difference among the detectors is significantly reduced,average standard deviation is 0.006 6.Conclusions For detectors such as ionization chambers and semiconductors,the field output correction factors can be used to correct the output factors of the small field to improve the accuracy and consistency of the measurement results.