Characterization of the Mixtures of Gompertz Distributions by Conditional Expectation of Order Statistics

The mixtures of Gompertz random variables (Gompertz , 1825) X₁ and X₂ are identified in terms of relations between the conditional expectation of [exp (αX_2:2) — exp (αX_1:2)]^k given X_1:2 and the hazard rate function of the distribution, k is a positive integer and α < 0. Here X_1:2 and X_2:2 denote the corresponding order statistics. In addition, we also mention some related theorems to characterize the mixtures of Gompertz distributions. Finally, when the sample size is n, the above results are also valid and we also give an application to Multi-Hit models of carcinogenesis (Parallel Systems).     

On the effect of a therapy able to modify both the growth rates in a Gompertz stochastic model

A Gompertz-type diffusion process characterized by the presence of exogenous factors in the drift term is considered. Such a process is able to describe the dynamics of populations in which both the intrinsic rates are modified by means of time-dependent terms. In order to quantify the effect of such terms the evaluation of the relative entropy is made. The first passage time problem through suitable boundaries is studied. Moreover, some simulation results are shown in order to capture the dependence of the involved functions on the parameters. Finally, an application to tumor growth is presented and simulation results are shown.     

The Meta‐Nudge – A Response to the Claim That the Use of Nudges During the Informed Consent Process is Unavoidable

Richard Thaler and Cass Sunstein, in Nudge: Improving Decisions About Health, Wealth, and Happiness, assert that rejecting the use nudges is ‘pointless’ because ‘[i]n many cases, some kind of nudge is inevitable’. Schlomo Cohen makes a similar claim. He asserts that in certain situations surgeons cannot avoid nudging patients either toward or away from consenting to surgical interventions. Cohen concludes that in these situations (assuming surgeons believe that surgery is the best option for their patients), nudging patients toward consenting to surgical interventions is (at the very least) uncriticizable or morally permissible. I call this argument: The Unavoidability Argument. In this essay, I will respond to Cohen's use of the unavoidability argument in support of using nudges during the process of informed consent. Specifically, I argue that many so‐called ‘unavoidable nudges’ are, in fact, avoidable. Although my argument is directed toward Cohen's use of the unavoidability argument, it is applicable to the unavoidability argument more generally.     

The Concept of Additivity of Drug Combinations in the Case of Quantal Response

The concept of additivity of drug combinations is widely accepted in pharmacology and toxicology. Up to now, no general statistical methods to test that property are available. The present paper gives a mathematical formulation of additivity, a method to fit dose response surfaces under additivity assumption and a statistical test.     

Dietary restriction of rodents decreases aging rate without affecting initial mortality rate – a meta‐analysis

Dietary restriction (DR) extends lifespan in multiple species from various taxa. This effect can arise via two distinct but not mutually exclusive ways: a change in aging rate and/or vulnerability to the aging process (i.e. initial mortality rate). When DR affects vulnerability, this lowers mortality instantly, whereas a change in aging rate will gradually lower mortality risk over time. Unraveling how DR extends lifespan is of interest because it may guide toward understanding the mechanism(s) mediating lifespan extension and also has practical implications for the application of DR. We reanalyzed published survival data from 82 pairs of survival curves from DR experiments in rats and mice by fitting Gompertz and also Gompertz–Makeham models. The addition of the Makeham parameter has been reported to improve the estimation of Gompertz parameters. Both models separate initial mortality rate (vulnerability) from an age‐dependent increase in mortality (aging rate). We subjected the obtained Gompertz parameters to a meta‐analysis. We find that DR reduced aging rate without affecting vulnerability. The latter contrasts with the conclusion of a recent analysis of a largely overlapping data set, and we show how the earlier finding is due to a statistical artifact. Our analysis indicates that the biology underlying the life‐extending effect of DR in rodents likely involves attenuated accumulation of damage, which contrasts with the acute effect of DR on mortality reported for Drosophila. Moreover, our findings show that the often‐reported correlation between aging rate and vulnerability does not constrain changing aging rate without affecting vulnerability simultaneously.     

On the Use of Ranks in Combined Estimates in Quantal Bioassays

If {U_i} i = 1, …, k is a sequence of binary responses of n_i subjects at each of k successive dose levels x_i, there is the problem of the statistical treatment of the observed proportions P_i = U_i/ni when neither the probit nor the logit transformation may be assumed. This paper considers the use of the midranks of the responses for point and interval estimation of relative potency in the case of parallel line assay in particular. More generally the problem of combining the results of several independent estimates using ranks is discussed. Several examples illustrate the method.     

抑制性整合野细胞的对比度响应函数研究

采用细胞外记录的方法,在单独刺激经典感受野(classical receptive field,CRF)或同时刺激CRF和感受野外区域(extra-receptive field,ERF)的情况下,测量了猫初级视觉皮层细胞的对比度响应函数。当刺激所用的中心和外周运动光栅的参数一致时,与仅刺激CRF相比,强的ERF抑制使对比度响应函数动态区增加,响应增益和对比度增益降低。当中心和外周光栅的方位相差90度时,与方位参数一致的情况相比,大部分细胞的ERF抑制减弱,对比度响应函数的动态区减小,对比度增益和响应增益增加;少数细胞的ERF对CRF的作用从抑制变为易化,其对比度响应函数的动态区与只刺激CRF相比还要小,而对比度增益和响应增益还要大。揭示了初级视觉皮层细胞的抑制型整合野在CRF和ERF图像的方位及对比度差异检测中的作用机制。     

The Use of Ultrasound for the Degradation of Pollutants in Water: Aquasonolysis – A Review

The degradation of organic compounds in water is the subject of a number of fundamental and applied investigations. Aquasonolysis of organic compounds is an advanced technology for the purification of contaminated water. The process is based on the phenomenon of acoustic cavitation. Dominant reactions of volatile compounds are: cavitative high‐temperature gas‐phase reactions and thermal‐oxidative decay in bubbles. Nonvolatile compounds are mainly decomposed by OH radicals in the aqueous solution (sonolytical cleavage of water). This article reviews mechanisms and kinetics of pollutant decomposition in water and discusses the influence of different experimental parameters. An overview of the application spectrum of aquasonolysis is provided, analyzing results gathered in experiments completed in our group as well as results reported in the literature.     

The role of the CD39–CD73–adenosine pathway in liver disease

Extracellular adenosine triphosphate (ATP) is a danger signal released by dying and damaged cells, and it functions as an immunostimulatory signal that promotes inflammation. The ectonucleotidases CD39/ectonucleoside triphosphate diphosphohydrolase‐1 and CD73/ecto‐5′‐nucleotidase are cell‐surface enzymes that breakdown extracellular ATP into adenosine. This drives a shift from an ATP‐driven proinflammatory environment to an anti‐inflammatory milieu induced by adenosine. The CD39–CD73–adenosine pathway changes dynamically with the pathophysiological context in which it is embedded. Accumulating evidence suggests that CD39 and CD73 play important roles in liver disease as critical components of the extracellular adenosinergic pathway. Recent studies have shown that the modification of the CD39–CD73–adenosine pathway alters the liver's response to injury. Moreover, adenosine exerts different effects on the pathophysiology of the liver through different receptors. In this review, we aim to describe the role of the CD39–CD73–adenosine pathway and adenosine receptors in liver disease, highlighting potential therapeutic targets in this pathway, which will facilitate the development of therapeutic strategies for the treatment of liver disease.     

Review – Treatment of Helicobacter pylori infection 2020

This review summarizes important studies regarding Helicobacter pylori therapy published from April 2019 to April 2020. The main themes that emerge involve studies assessing antibiotic resistance, and there is also growing momentum behind the utility of vonoprazan as an alternative to proton pump inhibitor (PPI) therapy and also bismuth‐based regimens as a first‐line regimen. Antibiotic resistance is rising wherever it is being assessed, and clarithromycin resistance in particular has reached a point where it may no longer be a viable therapy without previous testing in many regions of the world. The evidence for the efficacy of a bismuth‐based quadruple therapy as a first‐line therapy is now very clearly established, and there is substantial evidence that it is the best performing first‐line therapy. The utility of vonoprazan as an alternative to PPI therapy, especially in resistant and difficult‐to‐treat groups, has also been considered in great detail this year, and it may offer an opportunity in the near future to reduce the problem of antibiotic resistance.     

典型草原区鹰隼类密度对啮齿动物密度的数值响应

捕食者与猎物的关系是动物生态学研究的热点之一,捕食者应对猎物密度的变化往往呈现出特定的数值响应特征。为研究典型草原区鹰隼类对其猎物——啮齿动物密度变化的数值响应关系,于2005年7月在内蒙古自治区锡林郭勒盟阿巴嘎旗白音图嘎苏木选取15个实验样地,采用标准夹线法调查了啮齿类密度,同时采用目视方法调查了鹰隼类密度。本次实验共捕获鼠类2 675只,主要为布氏田鼠(Lasiopodomys brandtii),观察到鹰隼类活动450只次。回归分析结果表明,鼠类密度和鹰隼类密度的数值反应关系符合S型曲线,可用Gompertz方程W=22.765 e-3.735 e-0.078 t来拟合,拟合优度R2达0.984,表明鼠类密度对鹰隼类密度有显著影响,验证了Holling所提出的脊椎动物捕食者和猎物数量关系属于S型反应曲线的观点。从本文的结果看,鹰隼类数量对鼠类数量的反应可分为三个阶段:(1)平缓期,随着鼠类密度的逐渐增加,鹰隼类活动频次增长非常缓慢;(2)快速反应期,当鼠类密度达到5只/hm2时,鹰隼类活动频次随鼠类密度的增加迅速增长,期间出现一个增长拐点值;(3)稳定平台期,当鼠类的密度达到40只/hm2左右时,鼠类密度虽然继续增加,但鹰隼类活动频次保持稳定,不再增加。本研究可为草原鼠害的天敌控制方法提供参考。     

The influence of local environment on the aging and mortality ofAedes aegypti (L.): Case study in Fortaleza‐CE,Brazil

It is generally assumed that the daily probability of survival of mosquitoes is independent of age. To test this assumption we have conducted a three‐year experimental fieldwork study (2005–2007) at Fortaleza‐CE in Brazil, determining daily survival rates of the dengue vector Aedes aegypti (L.). Survival rates of adult Ae. aegypti may be age‐dependent and the statistical analysis is a sensitive approach for comparing patterns of mosquito survival. The mosquito survival data were better fit by a Weibull survival function than by the more traditionally used Gompertz or logistic survival functions. Gompertz, Weibull, or logistic survival functions often fit the survival, and the tails of the survival curves usually appear to fall between the values predicted by the three functions. We corroborate that the mortality of Ae. aegypti in semi‐natural conditions may no more be considered as a constant phenomenon during the life of adult mosquitoes but varies according to the age and environmental conditions under a tropical climate. This study estimates the variability in the survival rate of Ae. aegypti and environmental factors that are related to such variability. The statistical analysis shows that the fitting ability, concerning the hazard function, was in decreasing order: Seasonal Cox, the three‐parameter Gompertz, and the three‐parameter Weibull, that was similar to the three‐parameter logistic. The advantage of using the Cox model is that it is convenient for exploring the relationship between survival and several explanatory variables. The Cox model has the advantage of preserving the variable in its original quantitative form and of using a maximum of information. The survival analyses indicate that mosquito mortality is both age‐ and environment‐dependent.     

Raising the Barriers to Access to Medicines in the Developing World – The Relentless Push for Data Exclusivity

Since the adoption of the WTO‐TRIPS Agreement in 1994, there has been significant controversy over the impact of pharmaceutical patent protection on the access to medicines in the developing world. In addition to the market exclusivity provided by patents, the pharmaceutical industry has also sought to further extend their monopolies by advocating the need for additional ‘regulatory’ protection for new medicines, known as data exclusivity. Data exclusivity limits the use of clinical trial data that need to be submitted to the regulatory authorities before a new drug can enter the market. For a specified period, generic competitors cannot apply for regulatory approval for equivalent drugs relying on the originator's data. As a consequence, data exclusivity lengthens the monopoly for the original drug, impairing the availability of generic drugs. This article illustrates how the pharmaceutical industry has convinced the US and the EU to impose data exclusivity on their trade partners, many of them developing countries. The key arguments formulated by the pharmaceutical industry in favor of adopting data exclusivity and their underlying ethical assumptions are described in this article, analyzed, and found to be unconvincing. Contrary to industry's arguments, it is unlikely that data exclusivity will promote innovation, especially in developing countries. Moreover, the industry's appeal to a property rights claim over clinical test data and the idea that data exclusivity can prevent the generic competitors from ‘free‐riding’ encounters some important problems: Neither legitimize excluding all others.     

Investigations of different chemiluminescent peaks in H2O2–SCN−–Cu2+–OH−–luminol flow system

In the H₂O₂–SCN^?–Cu²⁺–OH^?–luminol oscillatory system of chemiluminescence, the effects of the ingredient concentrations, temperature, flow rate and complexing agent on the oscillatory dynamics were investigated in a continuous‐flow stirred tank reactor (CSTR). The dynamical structure of two peaks during a period was discussed in detail. By addition of EDTA to the oscillating system, the peak I height decreased sharply while the peak II height was little affected, and the period kept constant. This may be due to the fast reaction between Cu(II) and EDTA and the highly stable complex Cu(II)–EDTA. From the experimental study and mechanism analysis, the chemiluminescent peak I corresponds to Cu(II) → Cu(I) transformation and the peak II corresponds to the Cu(I) → Cu(II) transformation process. The key species involving in the two‐transformation process are inferred to be superoxide radical and hydroxyl radical. Copyright © 2010 John Wiley & Son, Ltd.