BACKGROUND & AIMS: :The natural carotenoid crocetin has been reported to suppress phenotypes of an experimental myopia model in mice. We investigated the minimum effective dose to prevent myopia progression in a murine model. Three-week-old male mice (C57B6/J) were equipped with a -30 diopter (D) lens to induce myopia, and fed with normal chow, 0.0003%, or 0.001% of crocetin-containing chow. Changes in refractive errors and axial lengths (AL) were evaluated after three weeks. Pharmacokinetics of crocetin in the plasma and the eyeballs of mice was evaluated with specific high sensitivity quantitative analysis using liquid chromatography tandem mass spectrometry (LC-MS/MS) to determine the minimum effective dosage. A concentration of 0.001% of crocetin-containing chow showed a significant (p < 0.001) suppressive effect against both refractive and AL changes in the murine model. Meanwhile, there was no significant difference of AL change between the 0.0003% and the normal chow groups. The concentration of crocetin in the plasma and the eyeballs from mice fed with 0.001% crocetin-containing chow was significantly higher than control and 0.0003% crocetin-containing chow. In conclusion, we suggest 0.001% of crocetin-containing extract is the minimum effective dose showing a significant suppressive effect against both refractive and AL changes in the murine model.

背景与目标： : 据报道，天然类胡萝卜素crocetin可以抑制小鼠实验性近视模型的表型。我们研究了在鼠模型中预防近视进展的最小有效剂量。三周大的雄性小鼠 (C57B6/J) 配备有-30屈光度 (D) 晶状体以诱发近视，并饲喂正常的chow，0.0003% 或0.001% 的含有藏红花的chow。三周后评估屈光不正和轴向长度 (AL) 的变化。使用液相色谱串联质谱 (lc-ms/MS) 通过特定的高灵敏度定量分析评估了藏红花在小鼠血浆和眼球中的药代动力学，以确定最小有效剂量。在小鼠模型中，含有crocetin的chow浓度的0.001% 对屈光和AL变化均显示出显着的 (p < 0.001) 抑制作用。同时，0.0003% 组与正常组之间的AL变化无显着差异。用含有0.001% 的crocetin的chow喂养的小鼠的血浆和眼球中crocetin的浓度显着高于对照组和0.0003% 的crocetin的chow。总之，我们建议0.001% 含有crocetin的提取物是最小有效剂量，在小鼠模型中显示出对屈光和AL变化的显着抑制作用。

BACKGROUND & AIMS: BACKGROUND:Patients who have pain and dysfunction from glenohumeral arthritis associated with severe rotator cuff deficiency have few treatment options. The goal of this study was to retrospectively evaluate the short-term results of arthroplasty with use of the Reverse Shoulder Prosthesis in the management of this problem. METHODS:We report the results for sixty patients (sixty shoulders) with a rotator cuff deficiency and glenohumeral arthritis who were followed for a minimum of two years. Thirty-five patients had no previous shoulder surgery, whereas twenty-three had had either an open or arthroscopic rotator cuff repair, one had had a subacromial decompression, and one had had a biceps tendon repair. All patients were assessed preoperatively and postoperatively with the American Shoulder and Elbow Surgeons scoring system for pain and function and with visual analog scales for pain and function. They were also asked to rate their satisfaction with the outcome. The shoulder range of motion was measured preoperatively and postoperatively. RESULTS:The average age of the patients was seventy-one years. The average duration of follow-up was thirty-three months. All measures improved significantly (p < 0.0001). The mean total score on the American Shoulder and Elbow Surgeons system improved from 34.3 to 68.2; the mean function score, from 16.1 to 29.4; and the mean pain score, from 18.2 to 38.7. The score for function on the visual analog scale improved from 2.7 to 6.0, and the score for pain on the visual analog scale improved from 6.3 to 2.2. Forward flexion increased from 55.0 degrees to 105.1 degrees , and abduction increased from 41.4 degrees to 101.8 degrees . Forty-one of the sixty patients rated the outcome as good or excellent; sixteen were satisfied, and three were dissatisfied. There were a total of thirteen complications in ten patients (17%). Seven patients (12%) had eight failures, requiring revision surgery to another Reverse Shoulder Prosthesis in five patients (one shoulder had two revisions) and revision to a hemiarthroplasty in two patients because of deep infection. CONCLUSIONS:The data from this study suggest that arthroplasty with the Reverse Shoulder Prosthesis may be a viable treatment for patients with glenohumeral arthritis and a massive rotator cuff tear. However, future studies will be necessary to determine the longevity of the implant and whether it will provide continued improvement in function.

背景与目标：

BACKGROUND & AIMS: BACKGROUND:Although hemorrhagic shock decreases the minimum alveolar concentration (MAC) of inhaled anesthetics, it minimally alters the electroencephalographic (EEG) effect. Hemorrhagic shock also induces the release of endorphins, which are naturally occurring opioids. We tested whether the release of such opioids might explain the decrease in MAC. METHODS:Using the dew claw-clamp technique in 11 swine, we determined the isoflurane MAC before hemorrhage, after removal of 30% of the estimated blood volume (21 mL/kg of blood over 30 min), after fluid resuscitation using a volume of hydroxyethylstarch equivalent to the blood withdrawn, and after IV administration of 0.1 mg/kg of the mu-opioid antagonist naloxone. RESULTS:Hemorrhagic shock decreased the isoflurane MAC from 2.05% +/- 0.28% to 1.50% +/- 0.51% (P = 0.0007). Fluid resuscitation did not reverse MAC (1.59% +/- 0.53%), but additional administration of naloxone restored it to control levels (1.96% +/- 0.26%). The MAC values decreased depending on the severity of the shock, but the alterations in hemodynamic variables and metabolic changes accompanying fluid resuscitation or naloxone administration did not explain the changes in MAC. CONCLUSIONS:Consistent with previous reports, we found that hemorrhagic shock decreases MAC. In addition, we found that naloxone administration reversed the effect on MAC, and we propose that activation of the endogenous opioid system accounts for the decrease in MAC during hemorrhagic shock. Such an activation would not be expected to materially alter the EEG, an expectation consistent with our previous finding that hemorrhagic shock minimally alters the EEG.

背景与目标：

BACKGROUND & AIMS: :An effective indexing scheme for clusters that enables fast structure comparison and congruence check is desperately desirable in the field of mathematics, artificial intelligence, materials science, etc. Here we introduce the concept of minimum vertex-type sequence for the indexing of clusters on square lattice, which contains a series of integers each labeling the vertex type of an atom. The minimum vertex-type sequence is orientation independent, and it builds a one-to-one correspondence with the cluster. By using minimum vertex-type sequence for structural comparison and congruence check, only one type of data is involved, and the largest amount of data to be compared is n pairs, n is the cluster size. In comparison with traditional coordinate-based methods and distance-matrix methods, the minimum vertex-type sequence indexing scheme has many other remarkable advantages. Furthermore, this indexing scheme can be easily generalized to clusters on other high-symmetry lattices. Our work can facilitate cluster indexing and searching in various situations, it may inspire the search of other practical indexing schemes for handling clusters of large sizes.

背景与目标： : 在数学，人工智能，材料科学等领域，迫切需要一种有效的集群索引方案，该方案可实现快速的结构比较和同余检查。在这里，我们介绍了最小顶点类型序列的概念，用于在方格上对簇进行索引，其中包含一系列整数，每个整数标记原子的顶点类型。最小顶点类型序列是方向无关的，它与集群建立了一对一的对应关系。通过使用最小顶点类型序列进行结构比较和同余检查，仅涉及一种类型的数据，要比较的最大数据量为n对，n为簇大小。与传统的基于坐标的方法和距离矩阵方法相比，最小顶点类型序列索引方案具有许多其他显着优势。此外，这种索引方案可以很容易地推广到其他高对称晶格上的簇。我们的工作可以促进在各种情况下对集群进行索引和搜索，这可能会激发寻找其他实用的索引方案来处理大型集群。

BACKGROUND & AIMS: OBJECTIVE:The aim of this study was to assess sensitivity and specificity of surrogate physical ability tests as predictors of criterion firefighting task performance and to identify corresponding minimum muscular strength and endurance standards. METHODS:Fifty-one (26 male; 25 female) participants completed three criterion tasks (ladder lift, ladder lower, ladder extension) and three corresponding surrogate tests [one-repetition maximum (1RM) seated shoulder press; 1RM seated rope pull-down; repeated 28 kg seated rope pull-down]. Surrogate test standards were calculated that best identified individuals who passed (sensitivity; true positives) and failed (specificity; true negatives) criterion tasks. RESULTS:Best sensitivity/specificity achieved were 1.00/1.00 for a 35 kg seated shoulder press, 0.79/0.92 for a 60 kg rope pull-down, and 0.83/0.93 for 23 repetitions of the 28 kg rope pull-down. CONCLUSIONS:These standards represent performance on surrogate tests commensurate with minimum acceptable performance of essential strength-based occupational tasks in UK firefighters.

背景与目标：

BACKGROUND & AIMS: Rice et al. [Hear. Res. 58, 132-152 (1992)] classified directional properties of the cat's head-related transfer function (HRTF) into three frequency domains. Low frequencies (< 5 kHz) display a broad azimuth-sensitive spectral peak that establishes interaural level differences, mid frequencies (5-18 kHz) are marked with a single deep spectral notch that changes in frequency as a function of both azimuth and elevation, and high frequencies (18-50 kHz) exhibit a complex pattern of peaks and notches that shows extensive but less systematic changes with sound location. Spectral cues conveyed by the mid frequencies of broadband sounds are important in tasks that require cats to identify the actual location of acoustic stimuli [Huang and May, J. Acoust. Soc. Am. (in press)]. The present study investigates how directional cues conveyed by the mid- and high-frequency spectrum of the HRTF influence the cat's ability to discriminate between sound locations. Thresholds for spatial acuity were measured as minimum audible angles (MAAs) [Mills, J. Acoust. Soc. Am. 30, 237-246 (1958)] at positive azimuths in the interaural horizontal plane and at positive and negative elevations in the median vertical plane. The frequency domain of the noise burst had little effect on MAAs in the horizontal plane, but removal of high-frequency spectral information significantly increased thresholds at positive and negative elevations in the median plane. These results suggest that cats are sensitive to directional properties of the HRTF at frequencies above 18 kHz and may use this information to detect small changes in sound source elevation.

背景与目标： Rice等人 [Hear. Res.58,132-152 (1992)] 将猫的头部相关传递函数 (HRTF) 的方向性质分类为三个频域。低频 (< 5 kHz) 显示了一个宽的方位角敏感频谱峰值，该峰值建立了耳间电平差，中频 (5-18 kHz) 用单个深频谱陷波标记，该陷波频率随方位角和仰角的变化而变化，高频 (18-50 kHz) 表现出复杂的峰值和缺口模式，显示出广泛但较少的系统变化与声音位置。宽带声音的中频传达的频谱提示在需要猫识别声刺激的实际位置的任务中很重要 [Huang和May，J. Acoust. Soc. Am. (印刷中)]。本研究调查了HRTF的中频谱和高频频谱传达的方向提示如何影响猫区分声音位置的能力。空间敏锐度的阈值测量为最小可听角 (MAAs) [Mills，J. Acoust. Soc. Am. 30, 237-246 (1958)]，在耳间水平面中的正方位和正负高程中的垂直平面。噪声突发的频域对水平面中的MAAs几乎没有影响，但是去除高频频谱信息会显着增加中值平面中的正负高程处的阈值。这些结果表明，cats对高于18 kHz的频率下HRTF的方向特性敏感，并且可以使用此信息来检测声源高程的微小变化。

BACKGROUND & AIMS: :Recent research indicates that the standard Minimum Enclosing Ball (MEB) or the center-constrained MEB can be used for effective training on large datasets by employing the core vector machine (CVM) or generalized CVM (GCVM). However, for another extensively-used MEB, i.e., MEB with total soft margin (T-MEB for brevity), we cannot directly employ the CVM or GCVM to realize its fast training for large datasets due to the fact that the involved inequality constraint is violated. In this paper, a fast learning algorithm called FL-TMEB for scaling up T-MEB is presented. First, FL-TMEB slightly relaxes the constraints in TMEB such that it can be equivalent to the corresponding center-constrained MEB, which can be solved with the corresponding Core Set (CS) by CVM. Then, with the help of the sub-optimal solution theorem about T-MEB, FL-TMEB attempts to obtain the extended core set (ECS) by including the neighbors of some samples in the CS into the ECS. Finally, FL-TMEB takes the optimal weights of ECS as the approximation solution of T-MEB. Experimental results on UCI and USPS datasets demonstrate that the proposed method is effective.

背景与目标： : 最近的研究表明，通过采用核向量机 (CVM) 或广义CVM (GCVM)，标准最小封闭球 (MEB) 或中心约束MEB可以用于大型数据集的有效训练。但是，对于另一种广泛使用的MEB，即具有总软裕度的MEB (为了简洁起见，T-MEB)，由于所涉及的不等式，我们无法直接使用CVM或GCVM来实现其对大型数据集的快速训练约束被违反。本文提出了一种用于扩展t-meb的快速学习算法fl-tmeb。首先，fl-tmeb稍微放松了TMEB中的约束，使得它可以等效于相应的中心约束MEB，这可以通过CVM用相应的核集 (CS) 求解。然后，借助关于t-meb的次优解定理，fl-tmeb尝试通过将CS中某些样本的邻居包含到ECS中来获得扩展核心集 (ECS)。最后，fl-tmeb将ECS的最优权重作为t-meb的近似解。在UCI和USPS数据集上的实验结果表明，该方法是有效的。

BACKGROUND & AIMS: BACKGROUND:This study aimed to estimate the minimum effective anaesthetic concentrations of lidocaine required to block the femoral nerve under ultrasound (US) guidance in 90% (MEAC90) of patients. METHODS:A minimum of 45 patients who had undergone knee arthroscopy were included in this observational study. All the patients received US-guided sciatic, obturator, and femoral nerve blocks. The femoral nerve block was performed using 15 ml of lidocaine. The lidocaine concentration given to a patient was determined by the response of the previous patient (a biased-coin design up-down sequential method). If a patient had a negative response, the lidocaine concentration was increased by 0.1% w/v in the next patient. If a patient had a positive response, the next patient was randomized to receive the same lidocaine concentration (with a probability of 0.89) or to receive a concentration 0.1% w/v less (with a probability of 0.11). A positive response was defined as complete sensory and motor block. The patients' responses were analysed to calculate the mean MEAC90. RESULTS:Fifty-two patients were required to complete the study; 45 had a positive response and seven had a negative response. The mean MEAC90 was estimated to be 0.93% w/v [95% confidence interval (CI), 0.8-1.03%]. Lidocaine 0.93% w/v was estimated to produce a successful block in 89% (95% CI, 78-100%) of patients. CONCLUSIONS:Perineural injection of 15 ml of lidocaine 0.93% w/v under US guidance could provide successful femoral nerve block in 90% of patients.

背景与目标：

BACKGROUND & AIMS: :Balanced minimum evolution is a distance-based criterion for the reconstruction of phylogenetic trees. Several algorithms exist to find the optimal tree with respect to this criterion. One approach is to minimize a certain linear functional over an appropriate polytope. Here we present polytopes that allow a similar linear programming approach to finding phylogenetic networks. We investigate a two-parameter family of polytopes that arise from phylogenetic networks, and which specialize to the Balanced Minimum Evolution polytopes as well as the Symmetric Travelling Salesman polytopes. We show that the vertices correspond to certain level-1 phylogenetic networks, and that there are facets or faces for every split. We also describe lower bound faces and a family of faces for every dimension.

背景与目标： : 平衡最小进化是系统发育树重建的基于距离的标准。存在几种算法来找到与此标准相关的最佳树。一种方法是在适当的多胞形上最小化某个线性函数。在这里，我们介绍了允许类似的线性编程方法来寻找系统发育网络的多面体。我们研究了由系统发育网络产生的两个参数的多面体家族，这些多面体专门针对平衡的最小进化多面体以及对称的旅行推销员多面体。我们证明顶点对应于某些level-1系统发育网络，并且每个分裂都有小面或面。我们还描述了每个维度的下限面和一系列面。

BACKGROUND & AIMS: :In the eight years since phylogenomics was introduced as the intersection of genomics and phylogenetics, the field has provided fundamental insights into gene function, genome history and organismal relationships. The utility of phylogenomics is growing with the increase in the number and diversity of taxa for which whole genome and large transcriptome sequence sets are being generated. We assert that the synergy between genomic and phylogenetic perspectives in comparative biology would be enhanced by the development and refinement of minimal reporting standards for phylogenetic analyses. Encouraged by the development of the Minimum Information About a Microarray Experiment (MIAME) standard, we propose a similar roadmap for the development of a Minimal Information About a Phylogenetic Analysis (MIAPA) standard. Key in the successful development and implementation of such a standard will be broad participation by developers of phylogenetic analysis software, phylogenetic database developers, practitioners of phylogenomics, and journal editors.

背景与目标： : 自从将系统发育基因组学作为基因组学和系统发育学的交叉点引入以来的八年中，该领域提供了有关基因功能，基因组历史和生物关系的基本见解。随着产生全基因组和大转录组序列集的分类单元的数量和多样性的增加，系统发育基因组学的效用正在增长。我们断言，通过开发和完善用于系统发育分析的最低报告标准，将增强比较生物学中基因组和系统发育观点之间的协同作用。受到有关微阵列实验 (MIAME) 标准的最低信息开发的鼓舞，我们提出了类似的路线图，用于开发有关系统发育分析 (MIAPA) 标准的最低信息。成功开发和实施此类标准的关键将是系统发育分析软件开发人员，系统发育数据库开发人员，系统发育基因组学从业人员和期刊编辑的广泛参与。

BACKGROUND & AIMS: :Efforts to increase patient safety and satisfaction, a critical concern for health providers, require periodic evaluation of all factors involved in the provision of GI endoscopy services. We aimed to develop guidelines on minimum staffing requirements and scope of practice of available staff for the safe and efficient performance of GI endoscopy. The recommendations in this guideline were based on a systematic review of published literature, results from a nationwide survey of endoscopy directors, along with the expert guidance of the American Society for Gastrointestinal Endoscopy (ASGE) Standards of Practice Committee members, ASGE Practice Operation Committee members, and the ASGE Governing Board.

背景与目标： : 努力提高患者的安全性和满意度，这是卫生提供者的一个关键问题，需要定期评估提供GI内窥镜检查服务所涉及的所有因素。我们旨在制定有关最低人员配备要求和可用人员的执业范围的指南，以确保GI内窥镜检查的安全有效。本指南中的建议基于对已发表文献的系统回顾，对内窥镜检查主任的全国调查结果，以及美国胃肠内窥镜学会 (ASGE) 实践委员会成员，ASGE实践操作委员会成员和ASGE理事会的专家指导。

BACKGROUND & AIMS: :Low density materials can control plasma properties of laser absorption, which can enhance quantum beam generation. The recent practical extreme ultraviolet light (EUV) is the first industrial example of laser plasma source with low density targets. Here we propose an easy-handling target source based on a hollow sub-millimeter microcapsule fabricated from polyelectrolyte cationic and anionic surfactant on air bubbles. The lightweight microcapsules acted as a scaffold for surface coating by tin (IV) oxide nanoparticles (22-48%), and then dried. As a proof of concept study, the microcapsules were ablated with a Nd:YAG laser (7.1 × 1010 W/cm2, 1 ns) to generate 13.5 nm EUV relatively directed to laser incidence. The laser conversion efficiency (CE) at 13.5 nm 2% bandwidth from the tin-coated microcapsule (0.8%) was competitive compared with bulk tin (1%). We propose that microcapsule aggregates could be utilized as a potential small scale/compact EUV source, and future quantum beam sources by changing the coating to other elements.

背景与目标： : 低密度材料可以控制激光吸收的等离子体特性，从而可以增强量子束的产生。最近实用的极紫外光 (EUV) 是具有低密度目标的激光等离子体源的第一个工业示例。在这里，我们提出了一种易于处理的目标源，该源基于由聚电解质阳离子和阴离子表面活性剂在气泡上制成的空心亚毫米微胶囊。轻质微胶囊用作通过氧化锡 (IV) 纳米颗粒 (22-48%) 进行表面涂覆的支架，然后干燥。作为概念研究的证明，用Nd:YAG激光 (7.1  ×   1010  W/cm2，1  ns) 烧蚀微胶囊，以产生相对针对激光入射的13.5 nm nm EUV。与块状锡 (1%) 相比，来自锡包被的微胶囊 (0.8%) 在13.5  nm 2% 带宽下的激光转换效率 (CE) 具有竞争力。我们建议通过将涂层更改为其他元素，可以将微胶囊聚集体用作潜在的小规模/紧凑型EUV源和未来的量子束源。

BACKGROUND & AIMS: AIMS:The direct posterior approach with subperiosteal dissection of the paraspinal muscles from the vertebrae is considered to be the standard approach for the surgical treatment of adolescent idiopathic scoliosis (AIS). We investigated whether or not a minimally-invasive surgery (MIS) technique could offer improved results. METHODS:Consecutive AIS patients treated with an MIS technique at two tertiary centres from June 2013 to March 2016 were retrospectively included. Preoperative patient deformity characteristics, perioperative parameters, power of deformity correction, and complications were studied. A total of 93 patients were included. The outcome of the first 25 patients and the latter 68 were compared as part of our safety analysis to examine the effect of the learning curve. RESULTS:In the first 25 cases, with a mean follow-up of 5.6 years (standard deviation (SD) 0.4), the mean preoperative major Cobb angle was 57.6° (SD 9.8°) and significantly corrected to mean 15.4° (SD 5.6°, 73% curve correction). The mean preoperative T5-T12 was 26.2 (SD 12.8) and significantly increased to mean 32.9 (SD 8.3). Both frontal and sagittal plane correction was conserved two years after surgery. The rate of perioperative complications was 12% and three further complications occurred (three deep delayed infection). In the latter cases, 68 patients were included with a mean follow-up time of three years (SD 0.6). The mean preoperative major Cobb angle was 58.4° (SD 9.2°) and significantly corrected to mean 20.4° (SD 7.3°).The mean preoperative T5-T12 kyphosis was 26.6° (SD 12.8°) and was significantly increased to mean 31.4° (SD 8.3°). Both frontal and sagittal correction was conserved two years after surgery. The perioperative (30 day) complication rate was 1.4%. Two (2.9%) additional complications occurred in two patients. CONCLUSION:MIS for AIS is associated with a significant correction of spine deformity in the frontal and sagittal planes, together with low estimated blood loss and short length of stay. The perioperative complication rate seems to be lower compared with the standard open technique based on the literature data. The longer-term safety of MIS for AIS needs to be documented with a larger cohort and compared with the standard posterior approach. Cite this article: Bone Joint J 2020;102-B(4):506-512.

背景与目标：

BACKGROUND & AIMS: :In metabolic network modification, we newly add enzymes or/and knock-out genes to maximize the biomass production with minimum side-effect. Although this problem has been studied for various problem settings via mathematical models including flux balance analysis, elementary mode, and Boolean models, some important problem settings still remain to be studied. In this paper, we consider the Boolean Reaction Modification (BRM) problem, where a host metabolic network and a reference metabolic network are given in the Boolean model. The host network initially produces some toxic compounds and cannot produce some necessary compounds, but the reference network can produce the necessary compounds, and we should minimize the total number of removed reactions from the host network and added reactions from the reference network so that the toxic compounds are not producible, but the necessary compounds are producible in the resulting host network. We developed integer linear programming (ILP)-based methods for BRM, and compared them with OptStrain and SimOptStrain. The results show that our method performed better for reducing the total number of added and removed reactions, while OptStrain and SimOptStrain performed better for optimizing the production of the target compound. Our developed software is freely available at "http://sunflower.kuicr.kyoto-u.ac.jp/~rogi/solBRM/solBRM.html ".

背景与目标： : 在代谢网络修饰中，我们新添加了酶或/和敲除基因，以最大程度地提高生物量产量，并减少副作用。尽管已经通过数学模型 (包括通量平衡分析，基本模式和布尔模型) 针对各种问题设置研究了此问题，但仍有一些重要的问题设置有待研究。在本文中，我们考虑布尔反应修改 (BRM) 问题，其中在布尔模型中给出了宿主代谢网络和参考代谢网络。主机网络最初产生一些有毒化合物，不能产生一些必要的化合物，但是参考网络可以产生必要的化合物，我们应该尽量减少从主机网络中去除的反应和从参考网络中添加的反应的总数，以使有毒化合物不可生产，但是必要的化合物在生成的主机网络中是可生产的。我们开发了基于整数线性规划 (ILP) 的BRM方法，并将其与OptStrain和SimOptStrain进行了比较。结果表明，我们的方法在减少添加和去除的反应总数方面表现更好，而OptStrain和SimOptStrain在优化目标化合物的生产方面表现更好。我们开发的软件可在 “http://sunflower.kuicr.kyoto-u.ac.jp/~ rogi/solBRM/solBRM.html” 免费获得。

BACKGROUND & AIMS: :Missing data is a very common problem in medical and social studies, especially when data are collected longitudinally. It is a challenging problem to utilize observed data effectively. Many papers on missing data problems can be found in statistical literature. It is well known that the inverse weighted estimation is neither efficient nor robust. On the other hand, the doubly robust (DR) method can improve the efficiency and robustness. As is known, the DR estimation requires a missing data model (i.e., a model for the probability that data are observed) and a working regression model (i.e., a model for the outcome variable given covariates and surrogate variables). Because the DR estimating function has mean zero for any parameters in the working regression model when the missing data model is correctly specified, in this paper, we derive a formula for the estimator of the parameters of the working regression model that yields the optimally efficient estimator of the marginal mean model (the parameters of interest) when the missing data model is correctly specified. Furthermore, the proposed method also inherits the DR property. Simulation studies demonstrate the greater efficiency of the proposed method compared with the standard DR method. A longitudinal dementia data set is used for illustration.

背景与目标： : 缺少数据是医学和社会研究中非常普遍的问题，尤其是在纵向收集数据时。有效利用观测数据是一个具有挑战性的问题。在统计文献中可以找到许多有关缺失数据问题的论文。众所周知，逆加权估计既不有效也不稳健。另一方面，双鲁棒 (DR) 方法可以提高效率和鲁棒性。众所周知，DR估计需要缺失数据模型 (即，用于观察到数据的概率的模型) 和工作回归模型 (即，用于给定协变量和替代变量的结果变量的模型)。由于当正确指定缺失数据模型时，DR估计函数对于工作回归模型中的任何参数均为零，因此，我们推导了工作回归模型参数估计器的公式，该公式可在正确指定缺失数据模型时得出边际均值模型 (感兴趣的参数) 的最佳有效估计器。此外，所提出的方法还继承了DR属性。仿真研究表明，与标准DR方法相比，该方法具有更高的效率。纵向痴呆症数据集用于说明。