Objective To research the effect of cavity under Bolus to anisotropic analytical algorithm (AAA) on calculation precision of dose in shallow tissue based on Monte Carlo method;Methods A 30 cm × 30 cm × 30 cm water phantom with the upper surface was constructed which was located at the source-axis distance (SAD) of the medical linear accelerator and the center as well as coincided with the central axis of the radiation field in Eclipse treatment panning system. Above the water phantom, a water film of 1 cm thick with or without different cavities was constructed or. AAA was used to calculate the dose distribution on the central axis and the x-axis of different depth of the water model with different cavities respectively. The accelerator model, the same water phantom and the water film were constructed and the dose distributions of the same positions were calculated with Geant4. Based on the Geant4 calculation result, the calculation precision of AAA with different cavity were compared;Results For cavities with area of 2 cm × 2 cm, if the thickness is smaller than 0.5 cm, the AAA calculation error is about 2%. with the cavity thickness increase, the AAA would overestimate the dose in the shallow area under the cavity. With the cavity area increase, the area where AAA overestimate the shallow dose gradually moved out until near the edge of the radiation field, and the calculation error on the central area gradually reduced until there is basically no error. Conclusions The shallow dose would be increased according to the cavity size when planning with AAA; If there are cavities with large volume, it is better to reposition.

Polyhydroxyalkanoate depolymerase (PHAD) can be used for the degradation and recovery of polyhydroxyalkanoate (PHA). In order to develop a PHAD with good stability under high temperature, PHAD from Thermomonospora umbrina (TumPHAD) was heterelogously expressed in Escherichia coli BL21(DE3). At the same time, a mutant A190C/V240C with enhanced stability was obtained via rational design of disulfide bonds. Characterization of enzymatic properties showed that the mutant A190C/V240C had an optimum temperature of 60 ℃, which was 20 ℃ higher than that of the wild type. The half-life at 50 ℃ was 7 hours, at 50 ℃ which was 21 times longer than that of the wild type. The mutant A190C/V240C was used for the degradation of polyhydroxybutyrate (PHB), one of the typical PHA. At 50 ℃, the degradation rate of PHB being treated for 2 hours and 12 hours was 2.1 times and 3.8 times higher than that of the wild type, respectively. The TumPHAD mutant A190C/V240C obtained in this study shows tolerance to high temperature resistance, good thermal stability and strong PHB degradation ability, which may facilitate the degradation and recovery of PHB.
Thermomonospora ; Actinomycetales ; Escherichia coli/genetics* ; Polyhydroxyalkanoates

We developed a method to construct a gene mutant pool in Pichia pastoris based on in vivo homologous recombination. It was an absolute PCR-dependent method (PDM) and could avoid the disadvantages of traditional mutant pool construction process such as long-experimental period, low pool capacity and inadequate abundance. The method consisted of four steps: (1) construction of recombinant expression plasmid of target gene; (2) design of long primers that have 40-70 bp of homology to expression vector fragments at both ends and amplification of target gene by error-prone PCR, DNA Shuffling or other methods; (3) PCR amplification of expression vectors fragments; (4) mixture of gene and vectors by appropriate mole ratio, electroporation, formation of expression cassette in vivo, homologous recombination with host genome and achievement of mutant pool. Screening from this library, we obtained mutants with improved enzyme activity, protein expression level and thermostability. In conclusion, PDM was very efficient and convenient with advantages of shortened pool construction cycle from 2 weeks to 3 days, enlarged pool capacity from the original 10(3)-10(4) to more than 10(5), with a positive rate of more than 95%.
Gene Library ; Genetic Vectors ; genetics ; Homologous Recombination ; genetics ; Mutation ; Pichia ; genetics ; Polymerase Chain Reaction ; methods

Objective: To evaluate annual skin equivalent dose and annual effective dose to consumers arising from three types of cloths samples containing naturally occurring radioactive material (NORM). Methods: Firstly, measurement of radioactivity in three types of cloths were made with γ-ray spectrometer. And then, theoretical exposure scenarios were simulated with Monte Carlo software to calculate organ dose and effective dose by using ICRP reference voxel male phantom. Finally, annual skin equivalent dose and effective dose to consumers from these cloths samples were evaluated. Results: In the wrapped and covered estimation models used in this study, sample mass ranged from 135 to 7 197 g, annual skin equivalent dose to consumers from these cloths samples from 155.41 to 9 028.61 μSv, and annual effective dose from 11.91 to 1 234.44 μSv. Conclusions NORM-added consumer products would cause some radiation hazard to human body.

Objective:To analyze tetanus antibody levels in healthy people in Henan Province and to provide reference data for the adjustment of tetanus vaccine immunization strategy.Methods:A total of 7 519 healthy people were selected using stratified sampling in Henan Province from 2020 to 2021. Serum samples were collected and tested for anti-tetanus toxoid IgG antibody (anti-TT) by ELISA. The positive rate (≥0.01 IU/ml), protection rate (≥0.1 IU/ml) and mean concentration (MC) of anti-TT were analyzed.Results:The overall positive rate, protection rate and MC of anti-TT among the 7 519 subjects were 70.33% (5 288/7 519), 37.07% (2 787/7 519) and 0.035 IU/ml, respectively. Both basic and booster tetanus vaccines were effective. The positive rate, protective rate and MC of anti-TT decreased from 99.63% (272/273), 82.05% (224/273) and 0.215 IU/ml in 6-year-olds to 64.22% (262/408), 21.57% (88/408) and 0.023 IU/ml in 16- to 19-year-olds, and further decreased to 40.97% (1 302/3 178), 5.48% (174/3 178) and 0.007 IU/ml in people ≥20 years old.Conclusions:The level of tetanus antibody decreased with age in healthy people in Henan Province. It was suggested that the sixth dose of tetanus vaccine should to be given at 16-20 years old.

Objective: To analyze the magnetic resonance imaging (MRI) radiomic performance of hypoxic area in nasopharyngeal carcinoma patients, aiming to provide a reference for identification and analysis of hypoxic area. Methods: The MRI-T₁, MRI-T₂, MRI-T₁+ and PET/CT images of 32 patients initially diagnosed with nasopharyngeal carcinoma were retrospectively analyzed. The gross tumor volume (GTV) of nasopharynx was countoured and the hypoxic areas (GTV-H) were identified by ¹⁸F-FMISO-PET images. The non-hypoxic areas (GTV-NH) were defined as the rest of areas removed GTV-H from GTV. The radiomic features of GTV-H and GTV-NH were extracted and compared. Results: The average volume of GTV-H and GTV-NH was (10.92±11.02) cm³ and (7.21±5.70) cm³, respectively. The maximum rate of change was 46% for intensity direct-global min (ID-GM) on MRI-T₁(P<0.05, AUC>0.7 and Youden index>0.5). The average rate of change was 136% for long run emphasis (LRE), long run high gray level emphasis (LRHGLE) and long run low gray level emphasis (LRLGLE) on MRI-T₂(P<0.05, AUC>0.7 and Youden index>0.5). The high change rates was greater than 90% on MRI-T₁+ (P<0.05, AUC>0.7 and Youden index>0.5) for ID-GM, LRE, LRHGLE and LRLGLE. Conclusions The hypoxic area of tumor target can be reflected by MRI radiomics on T₁/T₂/T₁+ . Quantifying and tracking the variations of these features can bring benefit to recognize the hypoxic area of nasopharyngeal carcinoma tumor target.