Censored linear model in high dimensions

Censored data are quite common in statistics and have been studied in depth in the last years [for some references, see Powell (J Econom 25(3):303–325, 1984), Murphy et al. (Math Methods Stat 8(3):407–425, 1999), Chay and Powell (J Econ Perspect 15(4):29–42, 2001)]. In this paper, we consider censored high-dimensional data. High-dimensional models are in some way more complex than their low-dimensional versions, therefore some different techniques are required. For the linear case, appropriate estimators based on penalised regression have been developed in the last years [see for example Bickel et al. (Ann Stat 37(4):1705–1732, 2009), Koltchinskii (Bernoulli 15:799–828, 2009)]. In particular, in sparse contexts, the \(l_1\)-penalised regression (also known as LASSO) [see Tibshirani (J R Stat Soc Ser B 58:267–288, 1996), Bühlmann and van de Geer (Statistics for high-dimensional data. Springer, Heidelberg, 2011) and reference therein] performs very well. Only few theoretical work was done to analyse censored linear models in a high-dimensional context. We therefore consider a high-dimensional censored linear model, where the response variable is left censored. We propose a new estimator, which aims to work with high-dimensional linear censored data. Theoretical non-asymptotic oracle inequalities are derived.     

Exponentially Accurate Approximations for Dirichlet Problems with Discontinuous data

A method to obtain exponentially accurate approximations to solutions for Dirichlet problems with discontinuous boundary data for Laplace's equation in two dimensions is presented and discussed. Model problems with circular or rectangular boundaries, whose solutions can be obtained by separation of variables involving Fourier series, are discussed in detail. First, the boundary data g is expressed as the sum of a singular function S_M, which is a certain linear combination of specially constructed singular basis functions {S_n}, and a function, namely, g-s_M, which is much smoother than the original data. The function S_M is constructed so that its discontinuities, and those of its first M derivatives, coincide with the corresponding discontinuities of g. The solution u to the boundary-value problem is then expressed as the sum of a linear combination of the harmonic extensions { _n} of {S_n}, and a function v, which satisfies the boundary condition v=g-S_M. Since the boundary data for v has at least M continuous derivatives, the partial sum approximations for v obtained by separation of variables converge much faster than the corresponding partial sum approximations for u. Formally, by letting N, the number of terms retained in the solution for v, be proportional to M, a sequence of approximations can be constructed which converges to u exponentially in the maximum norm, as M . In particular, this implies that, when g is discontinuous, the unwanted effects of the Gibbs phenomenon can be completely overcome! The method is illustrated by several examples, and some possible applications to related problems are discussed.     

近70年内蒙古呼和浩特城市演化的形态特征及影响因素剖析

城市演化的形态特征及其影响因素分析对于城市生态环境治理及国土空间管控具有重要的应用价值。然而,目前对城市形态特征演化过程的长期识别,尤其对北疆地区及少数民族地区的研究仍显不足。以呼和浩特市为例,基于遥感影像、土地利用/覆盖数据集和城市不透水面与绿地空间组分数据集等信息,利用地理统计方法,分析了1949~2018年城市扩展时空特征以及21世纪以来的城市土地覆盖变化,揭示了城市演化的影响因素,进一步探讨了城市规划在城市演化过程中的作用。研究表明：70年间,呼和浩特市区城市土地面积以“减速—保持—加速”的扩展特征增长了67.62倍,在形态上呈现“填充式—圈层式—单轴线外延—双轴线外延”模式。2000年以来,呼和浩特市区城市不透水面比例呈“先上升后下降”的趋势,城市绿地空间比例则呈现“波动上升”的趋势。国家西部大开发战略、城市总体规划等相关规划政策,以及经济因素是影响呼和浩特市城市演化的重要因素。本研究可为呼和浩特市以及北疆少数民族地区的城市可持续发展提供重要的参考。     

Low-loss electron beam transport in a high-power, electrostatic free-electron maser

At the FOM Institute for Plasma Physics “Rijnhuizen”, The Netherlands, the commissioning of a high-power, electrostatic free-electron maser is in progress. The design target is the generation of 1 MW microwave power in the frequency range 130–260 GHz. The foreseen application of this kind of device is as a power source for electron cyclotron applications on magnetically confined plasmas.

The device is driven by a high-power electron beam. For long-pulse operation a low loss current is essential. A 3-A electron beam has been accelerated to energies ranging from 1.35 to 1.7 MeV and transported through the undulator at current losses below 0.02%. Further, it was shown that the beam line accepts an electron energy variation of 5% with fixed beam optics. This is essential for rapid tuning of the microwave frequency, over 10%.

Electron beam simulations have shown to be remarkably accurate both for the prediction of the lens settings and for the intercepted current. The operational settings of the beam line which give the highest current transmission are within a few percent of the simulated values.     

Stereotaxy reduces cost of brain tumor resection

BACKGROUND: Health care professionals are under increasing pressure to contain the cost of health care. Simultaneously, medical technology continues to advance. Medical institutions must therefore consider the costs and benefits before using a new technology. Using a direct costing system, we determined the cost efficacy of stereotaxy applied to the resection of brain mass lesions. METHODS: Twenty-nine patients underwent a stereotactically guided craniotomy and brain tumor resection. Fifteen of them underwent general and fourteen received local anesthesia. Twelve other patients, comprising a historical reference group, underwent a standard craniotomy and brain tumor resection under general anesthesia. costs were determined for every hospital charge item in all patients. Cost efficiency was then compared between the two groups. RESULTS: Patients treated stereotactically incurred additional costs in frame placement and neuroimaging. These costs were offset by savings in operating room time, patient acuity, length of stay, respiratory care, and medications. Savings were greatest for patients who had local anesthesia. Overall, patients treated by stereotactic craniotomy had a total hospitalization cost of $8,495.19, whereas those treated with standard craniotomy incurred a cost of $11,365.23 (p < 0.001). CONCLUSION: Stereotaxy is cost effective for the surgical treatment of brain tumors. Accurate estimates of cost can justify the use of medical technology. Directly measured cost data is a useful index for any cost containment program.     

A look at today's behavior therapists.

Studied questionnaire responses of 45 members of the Association for Advancement of Behavior Therapy in order to develop a profile of characteristics and practices of behavior therapists. Findings indicate that behavior therapists are apparently becoming more flexible in their attitudes and practices and more eclectic. Most Ss have not had personal therapy, use a variety of behavioral techniques, and treat a wide range of adjustment disorders and a diverse set of clients. (13 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Direct measurements of genital responding.

Discusses methods of measuring genital responding in males and females. Advantages and disadvantages of various types of strain gauges, vaginal blood flow monitors, and photoplethysmography are considered, and extragenital measures (e.g., breast volume, EEGs, and muscle tension) are described. (PsycINFO Database Record (c) 2010 APA, all rights reserved)