Robust Inference for Univariate Proportional Hazards Frailty Regression Models

We consider a class of semiparametric regression models which are one-parameter extensions of the Cox [J. Roy. Statist. Soc. Ser. B 34 (1972) 187-220] model for right-censored univariate failure times. These models assume that the hazard given the covariates and a random frailty unique to each individual has the proportional hazards form multiplied by the frailty. The frailty is assumed to have mean 1 within a known one-parameter family of distributions. Inference is based on a nonparametric likelihood. The behavior of the likelihood maximizer is studied under general conditions where the fitted model may be misspecified. The joint estimator of the regression and frailty parameters as well as the baseline hazard is shown to be uniformly consistent for the pseudo-value maximizing the asymptotic limit of the likelihood. Appropriately standardized, the estimator converges weakly to a Gaussian process. When the model is correctly specified, the procedure is semiparametric efficient, achieving the semiparametric information bound for all parameter components. It is also proved that the bootstrap gives valid inferences for all parameters, even under misspecification. We demonstrate analytically the importance of the robust inference in several examples. In a randomized clinical trial, a valid test of the treatment effect is possible when other prognostic factors and the frailty distribution are both misspecified. Under certain conditions on the covariates, the ratios of the regression parameters are still identifiable. The practical utility of the procedure is illustrated on a non-Hodgkin's lymphoma dataset.Comment: Published by the Institute of Mathematical Statistics (http://www.imstat.org) in the Annals of Statistics (http://www.imstat.org/aos/) at http://dx.doi.org/10.1214/00905360400000053

Analisis Terhadap Perlunya Penyesuaian Laporan Keuangan Historis (Conventional Accounting) Menjadi Berdasarkan Tingkat Harga Umum (General Price Level Accounting)

Generally, in conventional accounting, financial statements are based on the historical cost principle that assumes that prices (monetery unit) are stable. Conventional accounting recognizes neither changes in the general price level nor changes in the specific price level. Consequently, if there are any changes in purchasing power such as in inflation period, the historical financial statement are not economically relevant and also income is usually overstated, and the fixed assets are usually understated. Actually, there are several methods on accounting for the effect of changing prices, such as constant accounting, current value accounting, and general price level accounting. General price level accounting will do restatement the components of financial statement to be a rupiah on a similar level of purchasing power, but without changes in accounting principles which using on conventional accounting. In practice, the controversy concerning the relevance of general price level accounting has been continuing. Pros and cons general price level accounting will be presented on this paper. Also the result of two researches concerning the influence of applied general price level accounting on the financial statement will be compared as considerations whether the general price level adjustment is necessary needed

Electric‐field dependence of interband transitions in In_(0.53)Ga_(0.47)As/In_(0.52)Al_(0.48)As single quantum wells by room‐temperature electrotransmittance

Room‐temperature electrotransmittance has been used in order to investigate the interband excitonic transitions in a 250‐Å‐thick In_(0.53)Ga_(0.47)As/In_(0.52)Al_(0.48)As single‐quantum‐well system as a function of an externally applied electric field. Parity forbidden transitions, involving conduction‐band states with quantum numbers up to n=5, which become more pronounced at high electric fields were observed. The ground‐state and the forbidden transitions showed a significant red shift due to the quantum confined Stark effect. A comparison with previously reported results on thinner InGaAs/InAlAs quantum wells indicated that the wide‐well sample exhibits the largest shift, as expected from theory. Despite the appreciable Stark shift, the rather large, field‐induced linewidth broadening and the relatively low electric field at which the ground‐state exciton is ionized poses limitations on using this wide‐quantum‐well system for electro‐optic applications

Limits of flexural wave absorption by open lossy resonators: reflection and transmission problems

The limits of flexural wave absorption by open lossy resonators are analytically and numerically reported in this work for both the reflection and transmission problems. An experimental validation for the reflection problem is presented. The reflection and transmission of flexural waves in 1D resonant thin beams are analyzed by means of the transfer matrix method. The hypotheses, on which the analytical model relies, are validated by experimental results. The open lossy resonator, consisting of a finite length beam thinner than the main beam, presents both energy leakage due to the aperture of the resonators to the main beam and inherent losses due to the viscoelastic damping. Wave absorption is found to be limited by the balance between the energy leakage and the inherent losses of the open lossy resonator. The perfect compensation of these two elements is known as the critical coupling condition and can be easily tuned by the geometry of the resonator. On the one hand, the scattering in the reflection problem is represented by the reflection coefficient. A single symmetry of the resonance is used to obtain the critical coupling condition. Therefore the perfect absorption can be obtained in this case. On the other hand, the transmission problem is represented by two eigenvalues of the scattering matrix, representing the symmetric and anti-symmetric parts of the full scattering problem. In the geometry analyzed in this work, only one kind of symmetry can be critically coupled, and therefore, the maximal absorption in the transmission problem is limited to 0.5. The results shown in this work pave the way to the design of resonators for efficient flexural wave absorption

Towards an agent-based framework for online after-sales services

The multi-agent paradigm for building intelligent systems has gradually been accepted by researchers and practitioners in the research field of artificial intelligence. There are also attempts of adapting agents and agent-based systems for creating industrial applications and providing e-services. In this paper, we present an attempt to use agents for constructing an online after-sale services system. The system is decomposed into four major cooperative agents, and in which each agent concentrates on particular aspects in the system and expresses intelligence by using various techniques. The proposed agent-based framework for the system is presented at both the micro-level and the macro-level according to the Gaia methodology. UML notations are also used to represent some software design models. As the result of this, agents are implemented into a framework for which exploits Case-Based Reasoning (CBR) technique to fulfil real life on-line services' diagnoses and tasks

Oxygen isotopes in Molluscan shell: applications in environmental archaeology

Oxygen isotope geochemistry of Molluscan shell is an essential part of environmental archaeology and over the last decade has contributed significantly to the understanding of the past inhabitants of our planet. From the analysis of collected (and disposed of) shells we can gain information on environmental data from the species assemblages and also from the shell chemistry. In particular, intra-seasonal information can be gained from shells by analysing the isotope composition of the shell from successive growth increments. Here, we describe some of the recent developments in the use of oxygen isotopes in environmental archaeology. In particular, we consider preservation and sampling and describe how δ18O can provide us with information on seasonal climate, season of collection as well as changes in global climate

Selective inhibition of bacterial topoisomerase I

The present invention provides novel bisbenzimidazole compounds and methods of using the compounds as antibacterial agents

Exploring Language Learning Motivation among Primary EFL Learners

The present study examined factors contributing to motivation of young EFL learners. Specifically, it explored learners’ attitudes and purposes for studying English, and how their perceptions of social support (teacher, family, peers) and that of the formal learning environment (learning tasks and class activities) varied at different levels of motivation. In total, 23 grade six students who studied at a Macau primary school completed a 10-item open-ended questionnaire. Findings revealed that most of the participants were highly motivated and learned English for both instrumental (e.g., for work and travel) and integrative (e.g., wanting to integrate within the target language culture) reasons. Most respondents reported that they viewed their teachers positively, which may explain why most of them also had a positive view of studying English despite indicating that their family expected them to get high grades on exams, and that most of their classmates perceived studying English negatively. Unsurprisingly, participants also reported that games and songs were their favored activities because they increased their intrinsic motivation to learn. The results of this study suggest that young learner motivation may be largely influenced by the learning environment (as opposed to family or peer social relationships), notably the positive relationship with the teacher and the types of learning activities employed to achieve learning aims

An experimental evaluation of the use of Δ13C as a proxy for palaeoatmospheric CO2

Understanding changes in atmospheric CO2 over geological time via the development of well constrained and tested proxies is of increasing importance within the Earth sciences. Recently a new proxy (identified as the C3 proxy) has been proposed that is based on the relationship between CO2 and carbon isotope discrimination (Δ13C) of plant leaf tissue. Initial work suggests that this proxy has the capacity to deliver accurate and potentially precise palaeo-CO2 reconstructions through geological time since the origins of vascular plants (∼450 Mya). However, the proposed model has yet to be fully validated through independent experiments. Using the model plant Arabidopsis thaliana exposed to different watering regimes and grown over a wide range of CO2 concentrations (380, 400, 760, 1000, 1200, 1500, 2000 and 3000ppm) relevant to plant evolution we provide an experimental framework that allows for such validation. Our experiments show that a wide variation in Δ13C as a function of water availability is independent of CO2 treatment. Validation of the C3 proxy was undertaken by comparing growth CO2 to estimates of CO2 derived from Δ13C. Our results show significant differences between predicted and observed CO2 across all CO2 treatments and water availabilities, with a strong under prediction of CO2 in experiments designed to simulate Cenozoic and Mesozoic atmospheric conditions (≥1500ppm). Further assessment of Δ13C to predict CO2 was undertaken using Monte Carlo error propagation. This suite of analysis revealed a lack of convergence between predicted and observed CO2. Collectively these findings suggest that the relationship between Δ13C and CO2 is poorly constrained. Consequently the use of Δ13C as a proxy to reconstruct palaeoatmospheric CO2 is of limited use as the estimates of CO2 are not accurate when compared to known growth conditions