Polymorphisms in base excision repair genes: Breast cancer risk and individual radiosensitivity

Breast cancer(BC) is the most common cancer among women worldwide. The aetiology and carcinogenesis of BC are not clearly defined, although genetic, hormonal, lifestyle and environmental risk factors have been established. The most common treatment for BC includes breast-conserving surgery followed by a standard radiotherapy(RT) regimen. However, radiation hypersensitivity and the occurrence of RT-induced toxicity in normal tissue may affect patients' treatment. The role of DNA repair in cancer has been extensively investigated, and an impaired DNA damage response may increase the risk of BC and individual radiosensitivity. Single nucleotide polymorphisms(SNPs) in DNA repair genes may alter protein function and modulate DNA repair efficiency, influencing the development of various cancers, including BC. SNPs in DNA repair genes have also been studied as potential predictive factors for the risk of RT-induced side effects. Here, we review the literature on the association between SNPs in base excision repair(BER) genes and BC risk. We focusedon X-ray repair cross complementing group 1(XRCC1), which plays a key role in BER, and on 8-oxoguanine DNA glycosylase 1, apurinic/apyrimidinic endonuclease 1 and poly(ADP-ribose) polymerase-1, which encode three important BER enzymes that interact with XRCC1. Although no association between SNPs and radiation toxicity has been validated thus far, we also report published studies on XRCC1 SNPs and variants in other BER genes and RT-induced side effects in BC patients, emphasising that large well-designed studies are needed to determine the genetic components of individual radiosensitivity.

Compressive strength and frost heave resistance of different types of semi-rigid base materials after freeze-thaw cycles

Freeze-thaw damage is the most common disease of semi-rigid bases in cold regions, which may greatly affect the dura- bility of roadways. In this study, the compressive strength and frost resistance of four different types of semi-rigid bases （lime-fly ash-stabilized sand, cement-stabilized sand, lime-fly ash-stabilized gravel, and cement-stabilized gravel） are assessed by varying the materials content. Based on freeze-thaw and compressive strength tests, this paper presents the performance of the different materials, each having different physical properties, and the optimal amounts of materials contents are proposed.

Preliminary Studies on Base Substitutions and Repair of DNA Mismatch Damage Stimulated by Low Energy N^+ Ion Beam Implantation in Escherichia coli

Ever since the low energy N+ ion beam has been accepted that the mutation effects of ionizing radiation are attributed mainly to direct or indirect damage to DNA. Evidences based on naked DNA irradiation in support of a mutation spectrum appears to be consistent, but direct proof of such results in vivo are limited. Using mutS, dam and/or dcm defective Eschericha coli imitator strains, an preliminary experimental system on induction of in vivo mutation spectra of low energy N+ ion beam has been established in this study. It was observed that the mutation rates of rifampicin resistance induced by N+ implantation were quite high, ranging from 9.2 x 10~8 to 4.9× 10~5 at the dosage of 5.2×1014 ions/cm2. Strains all had more than 90-fold higher mutation rate than its spontaneous mutation rate determined by this method. It reveals that base substitutions involve in induction of mutation of low energy nitrogen ion beam implantation. The mutation rates of mutator strains were nearly 500-fold (GM2929), 400-fold (GM5864) and 6-fold larger than that of AB1157. The GM2929 and GM5864 both lose the ability of repair DNA mismatch damage by virtue of both dam and dcm pathways defective (GM2929) or failing to assemble the repair complex (GM5864) respectively. It may explain the both strains had a similar higher mutation rate than GM124 did. It indicated that DNA cytosine methylase might play an important role in mismatch repair of DNA damage induced by N+ implantation. The further related research were also discussed.

Laser repairing surface crack of Ni-based superalloy components

Surface crack of components of the cast nickel base superalloy was repaired with twin laser beams under proper technological conditions. One laser beam was used to melt the substrate material of crack, and the other to fill in powder material to the crack region. The experimental results show that the surface crack with the width of 0.1 ～ 0.3?mm could be repaired under the laser power of 3?kW and the scanning speed of 6 ～ 8?mm/s. The repaired deepness of crack region is below 6.5?mm. The microstructure of repaired region is the cellular crystal, columnar crystal dendrite crystal from the transition region to the top filled layer. The phases in repaired region mainly consisted of supersaturated α Co with plenty of Ni, some Cr and Al, Cr 23 C 6, Co 2B, Co Ni Mo, Ni 4B 3, TiSi and VSi. The hardness of filled layer in repaired region ranged from HV 0.2 450 to HV 0.2 500, and the hardness decreases gradually from the filled layer to joined zone.

Extracellular matrix based biomaterials for central nervous system tissue repair: the benefits and drawbacks

Functional repair of injured tissue in the adult central nervous system （CNS） still remains a big challenge for current biomed- ical research and its upcoming clinical translation. The axonal regeneration of the adult CNS is generally low, and it is addi- tionally restricted after injury by the presence of inhibitory mol- ecules, generated by the glial scar.

Study on Test Methods for Mechanical Properties of Semi-rigid Base Cores of In-service Pavements

Compressive strength and compressive resilience modulus are two important parameters to measure the mechanical properties of semi-rigid base.The test methods of semi-rigid base cores are different from those of the laboratory samples in terms of sample acquisition,sample selection and humidity requirements.Core-drilling location,size of core sample,smoothness and humidity conditions were analyzed.The test methods of compressive strength and compressive resilience modulus were proposed.The research results show that compressive strength of lime fly-ash stabilized gravels base has a tendency of increasing during a long period.The compressive resilience modulus increases significantly with compressive strength of semi-rigid base.The compressive resilience modulus generally is 3-4 times than the recommended range of asphalt pavement design specifications.The fluctuation range of compressive resilience modulus is obviously higher than the compressive strength.The compressive resilience modulus is more sensitive to the construction variability.The overall trend between the compressive resilience modulus and the back-calculation modulus is consistent.FWD(falling weight deflectometer)back-calculation modulus can reflect the stiffness and bearing capacity of asphalt pavement.

Evidence for Base Substitutions and Repair of DNA Mismatch Damage Induced by Low Energy N^+ Ion Beam Implantation in E. coli

Ever since the low energy N + ion beam has been accepted, the mutations of ionizing radiation are attributable mainly to avoidance of DNA damages repair. Evidences based on in vivo proof results are limited. Using the E.coli wild type and mutator strains, the mutant frequencies suggest that base substitutions in rpoB gene are induced by the N + implantation. A highly conserved region is selected to get the direct evidence for base substitutions by sequence of the high fidelity PCR amplification products in mutants. Most of the mutants (90.9%, 40/44) have at least one base substitution in the amplification region. The evidences for CG to TA (55%, 22/40), AT to GC (20%, 8/40) and TA to CG (5%, 2/40) transitions are identified. The transversions are AT to TA (15%, 6/40) and GC to CG (5%, 2/40). It is suggested that DNA cytosine methylase might play an important role in mismatch repair of DNA damage induced by N + implantation by analysis of the mutant frequencies of mutator strains.

Numerical analysis of reflective cracking and fatigue lives of semi-rigid pavement structures using ABAQUS and FE-SAFE

In order to compare the impact of thickness of different layers on fatigue lives of different semi-rigid asphalt pavement structures, the mechanical results from finite element models in ABAQUS are incorporated with the fatigue results from fatigue models in FE-SAFE to calculate the mechanical response and fatigue lives of semi-rigid pavement structures under heavy traffic loads. Then the influences on fatigue lives caused by the changes in the thickness of layers in pavement structures are also evaluated. The numerical simulation results show that the aggregated base and the large stone porous mixture （LSPM） base have better anti-cracking performance than the conventional semi-rigid base. The appropriate thickness range for the aggregated layer in the aggregated base is 15 to 18 cm. The thickness of the LSPM layer in the LSPM base is recommended to be less than 15 cm.

Research on China's high-grade highway design index of asphalt pavement with granular base

Based on the 2006 Chinese asphalt pavement deflection value design index, we used KENLAYER Pavement Analysis and Design software and lstOpt statistical analysis software to can-y on the nonlinear regression, this paper establish high-grade highway design equations for the compressive slrain of soil sub-base top （CSSBT） and the radial compressive stress of semi-rigid base top （RCSRBT）. The correlation coefficients inspection standard to get precise proof, which means that our granular base design equations have high credibility and can be used in the Chinese design index of asphalt pavement with granular base （APGB）.

Optimal replacement policy of products with repair-cost threshold after the extended warranty

The reliability of the product sold under a warranty is usually maintained by the manufacturer during the warranty period. After the expiry of the warranty, however, the consumer confronts a problem about how to maintain the reliability of the product. This paper proposes, from the consumer's perspective, a replacement policy after the extended warranty, under the assumption that the product is sold under the renewable free replacement warranty (RFRW) policy in which the replacement is dependent on the repair-cost threshold. The proposed replacement policy is the replacement after the extended warranty is performed by the consumer based on the repair-cost threshold or preventive replacement (PR) age, which are decision variables. The expected cost rate model is derived from the consumer's perspective. The existence and uniqueness of the optimal solution that minimizes the expected cost rate per unit time are offered. Finally, a numerical example is presented to exemplify the proposed model.

Laser multi-layer cladding of Mg-based alloys

By laser multi-layer cladding using a pulsed Nd-YAG irradiation the thickness of the cladding zone Mg-based alloys(ZM2 and ZM5) can reach about 1.0 mm.The microstructure of the substrate and the cladding zone was studied using optical microscope, scanning electron microscopy(SEM), X-ray diffractometry(XRD) and micro hardness analysis. It is observed that constituent of ZM5 alloy is δ+Mg 17Al 12, that of ZM2 alloy is α+MgZn+Mg 9Ce. That of cladding layer ZM2 alloy(L-ZM2) is Mg+Mg 2Zn 11+MgCe; while that of the cladding layer ZM5 alloy(L-ZM5) is Mg+Mg 32(Al, Zn) 49. The hardness of the cladding area can be increased to values above HV127. Very fine uniform microstructure and the produced new phases of nanometer/sub-micrometer order were obtained. Now, many repaired Mg-based alloy components have been passed by flying test in outside field.

Global Genome Nucleotide Excision Repair Proteins Rhp7p and Rhp41p Are Involved in Abasic Site Repair of <i>Schizosaccharomyces pombe</i>

The roles of nucleotide excision repair (NER) proteins in removing UV-induced lesions are well defined. There are two distinct NER pathways: global genome NER (GG-NER) and transcription-coupled NER. In human GG-NER, two heteromeric protein complexes, DDB1-DDB2 and XPC-RAD23, are responsible for initial lesion recognition. Here, we examined the genetic interactions between GG-NER and base excision repair (BER) genes during abasic (AP) site repair of Schizosaccharomyces pombe. Mutants of rhp7 (rhp7-rhp16 are functional homologs of DDB1-DDB2) and rhp41 (XPC homolog) were moderately sensitive to methyl methanesulfonate and slightly to sodium bisulfite. Nth1p most actively cleaves the AP site in S. pombe. Deletion of rhp7 or rhp41 from nth1&#916 cells greatly increased their sensitivity to alkylation and deamination, indicating that Rhp7p and Rhp41p are involved in repair of the AP sites generated by the action of DNA glycosylase. Induction of rhp7 and rhp16 genes by different types of DNA damage supports the ability of GG-NER to remove non-bulky lesions. Therefore, GG-NER activity not only targets bulky DNA helix-distorting lesions, but can also efficiently remove AP sites synergistically with BER.

Dural Graft-Induced Fibrotic Mass Twelve Years after Successful Treatment of Skull Base Non-Hodgkin Lymphoma Mimicking Recurrence: Case Report and Literature Review

Non-Hodgkin lymphoma involving the skull base is a very rare tumour. The role of surgery for these patients remains controversial, as is the use of dural graft for CSF leak repair. With an increasing incidence of CNS lymphoma, more atypical presentations are reported. It is, therefore, important to include lymphoma in the differential diagnosis of skull base lesions as long-term remission is achievable for such patients, as shown in our case. Dural graft used for CSF leak repair could present with delayed complication mimicking tumour recurrence. Relevant published literature is reviewed.

Cancer Prohibitor-Telomeric DNA Repair Pathways

Telomeres are DNA-protein structures that form protective caps at the end of eukaryotic chromosomes,safeguarding the chromosomes from degradation and maintaining the genomic integrity.When DNA damage occurs,the cell will activate its repair system to fix the errors to prevent cancer.There are three major molecular mechanisms of DNA repair:base excision repair(BER),nucleotide excision repair(NER),and mismatch repair(MMR).In this review article,we discuss the three canonical repair pathways at the telomeres and their functions in cancer prevention and therapy.

关于色漆双Base工艺的导入和应用研究

对车身色漆双基(Base)工艺的颜色开发和应用过程中的重难点课题进行提炼、分析和研究,在导入初期首先对色漆双Base工艺与普通单Base工艺的不同进行了对比分析,再对匹配色漆双Base工艺的一个典型案例(赤焰红颜色)的特性进行分析,并确定了色漆双Base工艺生技性测试要点和应用阶段会出现的难点课题,主要为B立柱色差、补漆加修困难和部品对色3个重难点课题,之后对颜色开发的不同阶段进行了针对性施策。重点梳理了色漆双Base工艺的开发的应用要点、难点解析及有效对策。

11例侧颅底罕见肿瘤的临床分析

目的总结以耳科症状为首发的侧颅底原发肿瘤的临床表现、影像学特点及诊疗方案,为临床诊疗积累经验。方法回顾性总结11例侧颅底肿瘤患者的临床资料,对其影像学表现、手术入路及术后随访结果进行分析。结果11例患者肿瘤侵犯范围主要包括颞骨鳞部、颞下窝、颞颌关节、中颅窝底、中耳等。采用颞下窝联合入路完整切除肿瘤,封闭外耳道。术后患者均无严重并发症。术后病理:弥漫性腱鞘巨细胞瘤3例,巨细胞修复性肉芽肿1例,软骨肉瘤1例,副神经节瘤1例,岩尖部胆脂瘤2例,面神经鞘瘤3例,均属于罕见肿瘤。8例随访超过1 a,1例复发,7例无复发,3例随访时间未超过1 a,随访时间内情况良好。结论高分辨颞骨CT及增强MRI对侧颅窝底肿瘤的病变范围和性质有良好的鉴别意义,术前仔细阅片可有效提高诊断率。针对肿瘤侵犯范围制定个性化手术方案。

基于互动语言学的英语择优修正构式研究

英语择优修正构式在交际、翻译和二语习得中有举足轻重的作用。本文以互动语言学为视角,以“与其(说)A,不如(说)B”为典型个案,采用定性分析与定量分析相结合、宏观研究与微观研究相结合的方法,分别从语表、语义和语用角度研究,重点研究英语的择优修正构式在开启话题、传情达意、强调重点、给足面子、转换话题和总结话题这几个方面的语用价值。

耳后沟带蒂皮瓣修复联合循证护理对难治性耳前瘘管反复感染患儿疗效及美学效果观察

目的探讨耳后沟带蒂皮瓣修复联合循证护理在难治性耳前瘘管反复感染患儿瘘管修复的可行性及优势。方法随机将2020年2月~2022年1月收治的83例反复感染耳前瘘管患儿分为观察组(42例)和对照组(41例),两组患儿均实施耳前瘘管切除术,对照组耳前瘘管切除后直接周围皮肤减张拉拢缝合;观察组耳前瘘管切除后游离耳后沟皮瓣带蒂翻转至耳前缝合,术后配合循证护理。观察两组术后并发症、切口愈合程度、疗效及美学效果。结果两组患儿均顺利完成手术,对照组术后并发症发生率为19.51%,明显高于观察组2.38%,差异有统计学意义(χ2=4.651,P=0.031)。观察组切口Ⅰ期愈合率高于对照组,Ⅱ期愈合率低于对照组,差异均具有统计学意义(P<0.05)。随访1年,两组患儿耳前瘘管均痊愈,治愈率均为100%,但观察组平均愈合时间为(11.63±3.24)d,明显较对照组(19.25±4.81)d短,差异具有统计学意义(t=8.483,P=0.000)。观察组美学满意度为100%,明显高于对照,85.37%,差异有统计学意义(χ2=4.623,P=0.032)。结论耳后沟带蒂皮瓣修复难治性耳前瘘管反复感染创面安全、可靠,联合循证护理可有效降低术后并发症发生率,促进切口愈合和皮瓣存活,缩短治疗时间,提高美学效果。

低温养护对环氧树脂基砂浆早期性能的影响及机理

环氧树脂基砂浆是一种快速修补材料,为研究低温养护条件对环氧树脂基砂浆工作性能及早期力学性能的影响,构建了全过程低温环境,分别进行了抗压强度、抗折强度、流动度、凝结时间以及内部温度测试,分析了环氧树脂基砂浆的微观结构。结果表明:环氧树脂基砂浆性能受养护温度影响较大,当养护温度为0℃时,流动度仅为112 mm,但随着温度升高流动度增长较快;低温养护使得砂浆内部热效应减弱,延缓了凝结时间;早期强度也损失显著,0℃时,砂浆养护1 d才形成强度,说明低温环境大大减慢了体系的固化速度。微观分析表明低温养护导致砂浆内部结构疏松,裂缝及孔隙增多,说明固化反应不完全,从而降低了砂浆的性能。当养护温度为20℃时,砂浆内部结构较为致密,宏观结构也表现出较高强度。

超声振动对激光修复镍基高温合金晶粒特征及其缺陷的影响

目的研究超声振动对激光修复镍基高温合金梯形槽修复区显微组织及力学性能的影响,为实现高温合金的高质量激光增材修复提供参考。方法以镍基高温合金为基体和修复材料,并将超声振动引入激光增材修复过程中。采用光学显微镜,对比分析有无超声振动时梯形槽修复区的显微组织结构;采用电子背散射衍射(EBSD)、扫描电镜(SEM)、能谱仪(EDS)等设备,表征不同超声功率下梯形槽修复区的晶粒取向、析出相分布和元素组成;结合试验研究与机理分析,揭示超声振动对修复区晶粒特征和缺陷的影响规律。结果超声振动减少了梯形槽修复区底角的缺陷,修复区一次枝晶间距平均值由6.74μm减至3.38μm,晶粒平均尺寸由58.4μm降至50.2μm,等轴晶占比由46.6%增至63.4%,Laves相析出含量减少。当超声功率为4000 W时,梯形槽修复区的平均显微硬度为256.2HV0.2,相较于无超声振动时提高了17.7HV0.2。结论在超声振动作用下,梯形槽底角的熔合不良缺陷得到抑制,一次枝晶间距减小,长条状Laves相转变为颗粒状Laves相,且随着超声功率的增大,梯形槽修复区的平均显微硬度逐渐增大。