遗传密码和DNA序列的高维空间数字编码

二进制数字化编码是信息科学最基本的编码方式。用０（００）、１（０１）、２（１０）和３（１１）４个数码对４种碱基（Ｃ、Ｔ、Ａ、Ｇ）进行二进制数字编码,共有２４种可能的编码组合,其中８种满足碱基到补法则,它们是拓扑等价的。按碱基分子量大小排列的编码格式：０１２３／ＣＴＡＧ是最理想的编码格式。用二进制数对ＤＮＡ的字符序列进行编码,有以下优点：１）压缩信息冗余度,提高编码效率;２）可以对碱基的结构、功能基     

3S技术在哈尔滨市郊景观生态规划中的应用

利用哈尔滨市遥感数据资料,在RS、GIS 和GPS技术支持下,获取哈尔滨市郊景观格局现状及哈尔滨数字高程模型(DEM).选取平均斑块面积、景观优势度、平均坡度、平均海拔和破碎度因子对其进行综合分析,并借助 DEM 模型进行景观生态规划.结果表明,3S技术为典型景观类型的确定提供了科学依据;建立了市郊景观类型数据库,并生成景观类型专题图;土地利用现状和景观空间分布以及地形地貌和土地利用类型相结合.DEM和遥感影像的叠加,从大尺度上定性刻画市郊的景观生态规划,而景观生态规划和DEM 的叠加,更加直观地反映了市郊的景观结构,为提高区域生态功能,促进城乡一体化的健康发展提供科学依据.     

A Comparison between Teaching Methods in Secondary School Biology

The advent of cheaper SLR digital cameras and associated software has allowed the rapid creation of digital images. We explain three simple techniques that allow the generation of micrographs. A further technique is described that allows the production of an image from a full section of the microscope slide. Class sets of micrographs greatly enhance any discussion before or after the practical session.     

A comparative assessment of support vector regression,artificial neural networks,and random forests for predicting and mapping soil organic carbon stocks across an Afromontane landscape

Soil organic carbon (SOC) is a key indicator of ecosystem health, with a great potential to affect climate change. This study aimed to develop, evaluate, and compare the performance of support vector regression (SVR), artificial neural network (ANN), and random forest (RF) models in predicting and mapping SOC stocks in the Eastern Mau Forest Reserve, Kenya. Auxiliary data, including soil sampling, climatic, topographic, and remotely-sensed data were used for model calibration. The calibrated models were applied to create prediction maps of SOC stocks that were validated using independent testing data. The results showed that the models overestimated SOC stocks. Random forest model with a mean error (ME) of −6.5 Mg C ha⁻¹ had the highest tendency for overestimation, while SVR model with an ME of −4.4 Mg C ha⁻¹ had the lowest tendency. Support vector regression model also had the lowest root mean squared error (RMSE) and the highest R² values (14.9 Mg C ha⁻¹ and 0.6, respectively); hence, it was the best method to predict SOC stocks. Artificial neural network predictions followed closely with RMSE, ME, and R² values of 15.5, −4.7, and 0.6, respectively. The three prediction maps broadly depicted similar spatial patterns of SOC stocks, with an increasing gradient of SOC stocks from east to west. The highest stocks were on the forest-dominated western and north-western parts, while the lowest stocks were on the cropland-dominated eastern part. The most important variable for explaining the observed spatial patterns of SOC stocks was total nitrogen concentration. Based on the close performance of SVR and ANN models, we proposed that both models should be calibrated, and then the best result applied for spatial prediction of target soil properties in other contexts.     

The impact of PSA and digital rectal examination on the risk of prostate cancer specific mortality in men with a PSA level <2.5 ng/ml

IntroductionIt is unknown whether a normal range, diagnostic serum prostate specific antigen (PSA) level's influence on prostate cancer specific mortality (PCSM) is dependent upon digital rectal examination (DRE) findings.MethodsBetween 2004 and 2007, 9081 men diagnosed with non-palpable (T1c, N = 1710) or palpable (T2–T4, N = 7371) and non-metastatic prostate cancer (PC) were identified from surveillance, epidemiology, and end results data, selected based on pre-treatment PSA < 2.5 ng/ml. A multivariable competing risks regression model evaluated whether DRE findings interacted with PSA level in predicting risk of PCSM.ResultsAfter median follow-up of 2.83 years, 118 of 548 deaths (21.5%) were due to PC. Increasing diagnostic PSA was associated with increased risk of PCSM (AHR = 3.52; 95% CI: 1.25–9.89; P = .017) in men with T1c, Gleason score 7–10 PC, but decreased PCSM risk (AHR = 0.66; 95% CI: 0.52–0.83; P < .001) for men with T2–T4 PC and any Gleason score.DiscussionFor men with diagnostic PSA level <2.5 ng/ml and palpable PC, risk of early PCSM increases by 34% for a 1 point decrease in PSA from 2. This suggests the existence of clinically detectable, low PSA secreting disease with an elevated risk of early PCSM, highlighting the importance of the DRE in men with PC and normal range, diagnostic PSA.     

冠状动脉CT造影对冠心病的临床诊断价值研究

目的：探讨研究冠状动脉CT造影检查对冠心病的临床诊断价值。方法：收集我院2012年1月至2013年10月共计70例临床怀疑为冠心病的患者,对这些患者分别进行冠状动脉CT造影检查和数字减影冠状动脉造影（DSA）检查,记录这两项检查所得结果及数据,以检查数据为基础对冠状动脉CT造影和数字减影冠状动脉造影检查的临床实验效果进行对比研究。结果：70例病人均可顺利完成以上两种检查,按照数字减影冠状动脉造影检查的标准,冠状动脉CT造影的敏感度为92.2%,特异度为97.4%、阳性预测率为90.5%、阴性预测率98%。结论：相对于数字减影冠状动脉造影检查,冠状动脉CT造影检查是一种更加安全、可靠、无创且更具临床指导意义的检测技术,因此可以推荐作为冠心病诊断的首选方法。     

EVIDENCE FOR MECHANOSENSITIVE TRANSMEMBRANE ION CHANNELS OF SMALL CONDUCTANCE IN MAGNETOTACTIC BACTERIA

To determine whether or not mechanosensitive (MS) ion channels are present in the magnetotactic bacterium Magnetospirillum magnetotacticum, techniques for spheroplast preparation in Escherichia coli were adapted for this bacterium. This resulted in the formation of 2–3-μm spheroplasts, which were used for patch clamp analysis. Ion channel activity in M. magnetotacticum was compared with that of the MS of small conductance (MscS) in E. coli. This comparison reveals the presence of MscS-like channels in M. magnetotacticum and, as this bacterium produces intracellular magnetite (Fe₃O₄) particles similar to those found in the human brain, provides a model for investigation of the effects of magnetic fields on MS ion channels in magnetite-bearing cells.     

乳腺三维断层技术结合乳腺超声对致密型乳腺病变的诊断价值

摘要 目的：探讨乳腺三维断层技术（DBT）结合乳腺超声(BUS)对致密型乳腺病变的诊断价值。方法：回顾分析2018年6月至2019年4月在我院就诊且有完整病理结果的149例致密型乳腺病变患者的影像资料,对比DBT、BUS两种检查方法的检出率;以病理结果为金标准,分析DBT、BUS、DBT联合BUS三种检查模式的诊断效能。结果：BUS对良性病变的检出率（97.87%）高于DBT（89.36%）,差异有统计学意义（x²=5.697,P＜0.05）;DBT与BUS对恶性病变的检出率分别为98.44%、95.31%,差异无统计学意义（x²=1.032,P>0.05）。DBT诊断致密型乳腺病变的敏感度为90.61%、特异度为93.55％、准确率为91.77％,BUS诊断致密型乳腺病变的敏感度为78.13%、特异度为89.36%、准确率为84.81%,DBT联合BUS诊断致密型乳腺病变的敏感度为95.31%、特异度为95.74%、准确率为95.57%。DBT联合BUS诊断致密型乳腺恶性病变的受试者工作特征曲线（ROC）的曲线下面积（AUC）为0.977,稍高于DBT的AUC（0.951）,明显高于BUS的AUC（0.885）。结论：BUS对良性病变的检出率显著高于DBT,DBT对致密型乳腺病变的诊断效能高于BUS,二者结合能提高病变的检出率与诊断效能。     

烟雾病5例临床分析

目的：研究烟雾病（moyamoya disease,MMD）的临床及影像学特征。方法：回顾性分析5例烟雾病患者,分析其临床及影像学特点。结果：本组病例既往均无阳性病史,中、青年起病,男性居多,均以缺血性脑血管病起病,肢体瘫痪不重,经颅多普勒（TCD）及头颅核磁改变明显,数字减影血管造影（DSA）检查均存在血管闭塞及侧支开放,烟雾血管网形成,1例MRA证实烟雾血管网形成。结论：对于无既往史的中、青年脑卒中患者,要考虑MMD的可能,需完善TCD、头核磁检寻找证据,最后完善数字减影血管造影确诊。