After the production of the gradient coil of the magnetic resonance imaging system, electromagnetic field testing is required to verify whether the assembly accuracy meets the electromagnetic field requirements. Since the passive magnetic field B _z satisfies the Laplace ^,s equation and is a harmonic function, and according to the extreme value principle of harmonic function, the maximum or minimum values of B _z can only appear on the boundaries, so the observation points of the magnetic field are generally selected on the surface of the spherical imaging area. For superconducting magnets used for human body magnetic resonance imaging, a spherical area with a center diameter of 40~50 cm is generally selected as the shimming target area. Only the field value of the target area needs to be measured, and the spherical harmonic coefficients obtained after data processing are used to determine the magnetic field performance of the gradient coil. There are many testing principles and methods for electromagnetic fields, so there is no unified way and method in the field of commercial applications. This article is based on the Gauss-Legendre numerical integration, measures and analyzes the magnetic field performance of gradient coils by building a data acquisition system, and this article applies numerical analysis methods to calculate the spherical harmonic coefficients of the magnetic field using discrete test data, providing a feasible method for the production and testing of gradient coils.
Magnetic Resonance Imaging/methods* ; Magnetic Fields ; Electromagnetic Fields ; Equipment Design

The casting and curing of gradient coils in the production process is a relatively complex process. The chemical process similar to the black box model requires confirmation of the impact of each step of input on the output results, while the curing temperature and molding method affect the roundness and deformation of the gradient coils. The analysis of the curing temperature and demolding method of gradient coils has important practical significance for the formation and micro deformation of gradient coils. This article uses ANSYS finite element simulation software to analyze the thermal structural coupling and the specific performance of actual products. It has been found that the product quality is more stable under the heat conduction mode, and the roundness of the mold is better when placed vertically and waiting for temperature cooling before being demolding than when placed horizontally.

OBJECTIVE To investigate the correlation between gene polymorphisms and adverse drug reaction （ADR） and demands of opioids， aiming to guide personalized opioid analgesic therapy. METHODS The existing evidence-based medical data were adopted to identify gene loci related to the efficacy and ADR of opioid analgesics and select highly relevant single nucleotide polymorphism （SNP） for a clinical case-control study. The study cohort was divided into two evaluation groups： ADR assessment and drug demand assessment. The ADR assessment group included 254 cancer pain patients and was subdivided into the trial subgroup （with ADR） and the control subgroup （without ADR） based on the presence or absence of ADR following opioid usage； the two subgroups included 126 and 128 patients， respectively. The drug demand assessment group included a total of 120 cancer pain patients， who were divided into trial subgroup （equivalent to a daily dose of oral morphine ≥100 mg） and control subgroup （equivalent to a daily dose of oral morphine ＜100 mg） based on the different daily doses of opioid analgesics， with 60 patients in each subgroup. Polymorphism detection of SNP loci in these patients was performed using fluorescence in situ hybridization. SPSS 21.0 software and SNPStats genetic models were employed to compare genetic testing results between subgroups and conduct correlation analyses， aiming to evaluate the association of the selected SNP loci with opioid ADR and drug demand inclinical real-world cases. RESULTS The strongly correlated SNP loci identified were CYP2D6*10（rs1065852，C＞T）， CYP3A5*3（rs776746，A＞G），ABCB1（rs1045642，C＞T）and OPRM1（rs1799971，A＞G）. Genetic testing results indicated that the allele frequency distributions of these SNP loci conformed to Hardy-Weinberg equilibrium. Correlation analysis revealed that in the ADR assessment group， compared with control subgroup， the proportion of patients in trial subgroup with the AA genotype of OPRM1 （rs1799971， A＞G） was significantly higher （P＜0.05）； in the drug demand assessment group， compared with control subgroup， the proportion of patients in trial subgroup with the CC+CT genotype of ABCB1 （rs1045642， C＞T） was significantly higher （P＜0.05）. CONCLUSIONS The AA genotype of OPRM1 （rs1799971， A＞G） is associated with the occurrence of ADR following oxycodone use. Patients with the CC+ CT genotype of ABCB1（ rs1045642， C＞T） require higher doses of opioid analgesics.

Abstract E cigarette has become more and more popular among adolescents, and the awareness and use of e cigarettes among middle and high school students have shown a significant upward trend. E cigarette use is not only harmful to adolescent health, but also may become a gateway to other addictive substances. Individual characteristics, products features, environment and other factors were associated with e cigarette use among adolescents. The purpose of the review is to understand the current status and associated factors of adolescent e cigarette use, so as to provide scientific suggestions for the prevention of e cigarette use among adolescents.

The ban on addition of antibiotics in animal feed in China has made the search for new antibiotics substitutes, e.g. bacteriocin, a hot topic in research. The present study successfully isolated an antibacterial substance producing strain of Bacillus sp. from alpaca feces by agar diffusion method, using Escherichia coli, Salmonella enterica, Staphylococcus aureus, Staphylococcus epidermidis, Micrococcus luteus and Listeria monocytogenes as indicator bacteria. The isolated strain was named as B. licheniformis SXAU06 based on colony morphology, Gram staining and 16S rRNA gene sequence. The antibacterial substance was isolated and purified through a series of procedures including (NH4)2SO4 precipitation, chloroform extraction, molecular interception and SDS-PAGE analysis. Bioinformatics analysis of the LC-MS/MS data indicated that the antibacterial substance was a bacteriocin-like substance (BLIS) with an approximate molecular weight of 14 kDa, and it was designated as BLIS_SXAU06. BLIS_SXAU06 exhibited high resistance to treatment of proteinase K, high temperature, high acidity and alkalinity. BLIS_SXAU06 was heterologously expressed in E. coli and the recombinant BLIS_SXAU06 exhibited effective antibacterial activity against S. aureus, S. epidermidis, M. luteus, and L. monocytogenes, showing potential to be investigated further.
Animals ; Anti-Bacterial Agents/pharmacology* ; Bacillus licheniformis ; Bacteriocins/pharmacology* ; China ; Chromatography, Liquid ; Escherichia coli/genetics* ; Listeria monocytogenes ; RNA, Ribosomal, 16S ; Staphylococcus aureus ; Tandem Mass Spectrometry

Objective To evaluate different methods in detecting intraperitontal free cancer cells (IFCCs) in patients with gastric cancer and to clarify the relationship between positive IFCCs and short-term prognosis.Methods A total of 119 gastric cancer patients who underwent surgical treatment were enrolled.Peritoneal lavage was performed with 300-400 ml saline respectively at three points of time:immediately after abdominal cavity entry;when surgical operation was completed;when extensive intraoperative peritoneal lavage was done.The IFCCs were detected with methods of traditional centrifugal cytology,membrane cytology,ICC and RT-PCR.The survival curve of patients with gastric cancer was drawn using Kaplan-Meier method.Results The positive rate of PLC was 16.8％,20.7％ and 11.2％ respectively at 3 timepoints (P ＜ 0.05).The positive rates of ICC were 28.6％,38.8％ and 20.7％ respectively at 3 timepoints.The positive rates of RT-PCR were 39.3％,69.5％ and 50.8％ respectively at 3 time points.The positive rate of IFCCs detected through RT-PCR was higher than that of PLC and ICC (P ＜ 0.05).The short-term prognosis of patients with positive IFCCs was worse than those with negative results detected with any three method at the timg point immediately after opening the abdomen (P ＜ 0.05).At the timg point immediately after removing the tumors,the short-term prognosis of patients with positive IFCCs detected with PLC was worse (P ＜ 0.05).Conclusion The short-term prognosis was poor in patients with positive IFCCs.It is the best time to detect IFCCs before radical resection.Surgical procedures increase the risk of shedding of IFCCs.

Objective To investigate CT and MRI features of dermatofibrosarcoma protuberans (DFSP).Methods Totally 16 patients with DFSP confirmed by pathology were enrolled.Tumor morphology,CT and MRI imaging appearance (11 cases underwent plain and enhanced CT,5 cases underwent plain and enhanced MRI) were analyzed retrospectively.Results DFSP usually occurred in the skin of truck,head and neck,protruding from the skin surface in different extent.Some lesions even suspended out of the skin.The lesions were divided into nodular type (n=12) and diffuse type (n=4) according to their morphological appearance.The tumors usually demonstrated as iso-density or slightly low density solid mass compared to muscle on CT.On MRI,it usually demonstrated as low signal on T1WI and high signal on T2WI.Tumor blood supply was rich,and it usually showed progressively moderate to strong enhancement.The signs within DFSP include hanging sign (n=2),skin tail sign (n＝6),fascia tail sign (n=l),fat tail sign (n=4).Conclusion DFSP can be characterized by nodular or diffuse lesions,the manifestations of different form are slightly different,but still have a certain characteristic.

Objective To explore human cytomegalovirus UL97 mutations related to ganciclovir resistance in hematopoietic stem cell transplant (HSCT) recipients.Methods A total of 43 patients,including 24 males and 19 females,with an average age of 21 years old,who had HCMV DNAemia for more than two weeks after HSCT between 2008 and 2010 in Peking University People's Hospital,were included in this prospective study.UL97 GCV resistance mutations were investigated in 49 plasma specimens collected from those patients.GCV resistance mutations such as UL97 M460V/I,H520Q,A591V,A594V,L595S/F,and C603W,were analyzed by modified PCR-RFLP methods.UL97 mutations related to GCV resistance were assayed by the method of PCR-direct sequencing (PCR-DS).An amplified refractory mutation system real-time PCR (ARMS RT-PCR) was developed for the detection of UL97 A594V mutation.Results Eight known UL97 ganciclovir resistance mutations were not detected by PCR-RFLP and PCR-DS.Four new UL97 mutations like UL97 R494P,T502A,N558D,and G561S,were detected by PCR-DS.The ARMS RT-PCR for detecting of UL97 A594V was established successfully.The lower limit of detection of the method was at least 7.5 × 102 copies/ml combined with the use of nucleic acid extraction reagent.UL97 A594V resistance mutation was identified by the method of ARMS RT-PCR in two HSCT recipients.The rate of UL97 A594V mutation was 4.7％ (2/43) in HSCT recipients.Conclusion The ARMS RT-PCR assay represented a sensitive method for the identification of UL97 A594V mutation.

Objective To study the clinical characteristics of tuberculosis in oral and maxillofacial region,and to provide reference in early diagnosis and early treatment. Methods The clinical data of 132 patients were analyzed retrospectively. ResultsIn all cases, male to female ratio of 1∶1.69, the average age of 38.7 years, the group of 15 ～40year-old had higher incidence. Al1 parts of oral and maxillofacial region could be involved. In all 132 cases,107 cases were treated by surgery and drugs,25 cases by drugs only. Conclusion The local sign of tuberculosis in oral and maxillofacial region was atypical ,so it was likely to misdiagnosis. Definitive diagnosis relied on pathological examination. Operations played an important role in the cases of unifocal lymph nodes tuberculosis,oral mucosal tuberculosis, multifocal concentrated lymph nodes tuberculosis and salivary tuberculosis, while the therapy of multifocal sporadic lymph nodes tuberculosis and osseous tuberculosis should be relied on the medicine.

r diagnosing the disease to combine pathology, immunohistochemistry and SYT-SSX gene detection.