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Getting numbers is easy; getting numbers you can trust is hard. This practical guide by experimentation leaders at Google, LinkedIn, and Microsoft will teach you how to accelerate innovation using trustworthy online controlled experiments, or A/B tests. Based on practical experiences at companies that each run more than 20,000 controlled experiments a year, the authors share examples, pitfalls, and advice for students and industry professionals getting started with experiments, plus deeper dives into advanced topics for practitioners who want to improve the way they make data-driven decisions.Learn how to* Use the scientific method to evaluate hypotheses using controlled experiments * Define key metrics and ideally an Overall Evaluation Criterion* Test for trustworthiness of the results and alert experimenters to violated assumptions* Build a scalable platform that lowers the marginal cost of experiments close to zero* Avoid pitfalls like carryover effects and Twyman's law* Understand how statistical issues play out in practice
To provide scientific, theoretical support for the improvement of medical disaster training, we systematically analyzed the National Disaster Life Support (NDLS) Course and established a training curriculum with feedback based on the current status of disaster medicine in China.
The gray prediction model is applied to long-term forecast research on course effect. In line with the hypothesis, the NDLS course with feedback capability is more scientific and standardized.
The current training NDLS course system is suitable for Chinese medical disasters. After accepting the course training, audiences’ capabilities were enhanced. In the constructed GM (1,1) model prediction, the developing coefficients of the pretest and the posttest are 0.04 and 0.057, respectively. In light of the coefficient, the model is appropriate for the long-term prediction. The predicted results can be used as the basis for constructing training closed-loop optimization feedback. It can indicate that the course system has a good effect as well.
According to the constructed GM model, the NDLS course system is scientific, practical, and operational. The research results can provide reference for relevant departments and be used for the construction of similar training course systems.
This study compared the protective effect of sodium selenite (SS) and selenomethionine (SeMet) on heat stress (HS) invoked porcine IPEC-J2 cellular damage and integrate potential roles of corresponding selenoprotein. Cells were cultured at 37 oC until 80% conﬂuence, and then subjected to four different conditions for 24 h: at 37 oC (Control), 41.5 oC (HS), 41.5 oC supplied with 0.42 µmol Se/L SS (SS) or SeMet (SeMet). HS significantly decreased cell viability, up-regulated mRNA and protein levels of HSP70, and down-regulated mRNA and protein levels of tight junction-related proteins (CLDN-1 and ZO-1). HS induced cells injury was associated with the up-regulation (P < 0.05) of 6 inflammation-related genes and 14 selenoprotein encoding genes, and down-regulation (P < 0.05) of 2 inflammation-related genes and 5 selenoprotein encoding genes. Compared with the HS group, SS and SeMet supplementation resulted in an increase (P < 0.05) in cell viability, decreases (P < 0.05) mRNA expression of HSP70 and 6 inflammation-related genes, and rescue (P < 0.05) of mRNA and protein levels of CLDN-1 and ZO-1. SS and SeMet supplementation changes expressions of 19 selenoprotein encoding genes in cells affected by HS. Both Se supplementation significantly recovered the protein level of GPX1 and increased SELP in the IPEC-J2 cells under HS, respectively. In summary, Se supplementation alleviated the negative impact of HS on IPEC-J2 cells, and their cellular protective effect was associates with regulation expression of selenoproteins, SeMet exhibited a better protective effect.
This article examines the so-called “grid governance” scheme, a widely used grassroots governance strategy implemented in urban China in recent years. Drawing on data collected in multiple cities from 2011 to 2016, it analyses in what ways, and to what extent, the state employs the grid governance scheme to resolve neighbourhood conflicts and reinforce governance in Chinese urban middle-class neighbourhoods. The findings highlight complex interactions under the scheme among the residents, the state and market actors in neighbourhood governance, including the resident volunteers, residents’ social groups, residents’ committees and property management companies. By coopting middle-class resident volunteers, maximizing the existing political influence of the retired urban elites, and establishing Party organizations in middle-class residential communities, the grid governance scheme has become a major vehicle for resident mobilization and conflict resolution, and a key governance mechanism to reinforce the Party's leadership in middle-class neighbourhoods.
China's urbanization has revitalized grassroots governance under which millions of villagers have become increasingly keen to participate in grassroots elections and influence decision making in their village affairs. To maintain its political legitimacy over a rapidly transforming society, the authoritarian party-state has progressively promoted open, competitive grassroots elections in response to the increasing demand by villagers for more public participation. Based on in-depth field research in urbanizing villages in southern China, this article provides an empirical analysis of how the local state has adopted different interventionist strategies in elections to support villagers’ active participation while sustaining its direct leadership over daily village governance. Our findings explain why the recent development of open and transparent grassroots elections is reinforcing the ruling capacity of the socialist state rather than enhancing self-governance and grassroots democracy, although villagers now have more opportunities to defend their economic and social rights through elections.
Asia Minor bluegrass (Polypogon fugax Nees ex Steud.) is a problem grass weed of winter crops in China, where a population has become resistant to aryloxyphenoxypropionate (APP) herbicides. The mechanism of resistance is due to an Ile-2041-Asn mutation of the ACCase gene. Screen house experiments were conducted to study the growth, fecundity characteristics, and competitive ability of this aryloxyphenoxypropionate-resistant (APP-R) biotype compared with a susceptible (APP-S) biotype. When grown under noncompetitive conditions, the APP-R P. fugax developed more rapidly than the APP-S plants, with earlier tiller and panicle emergence and seed shedding; the APP-R P. fugax set seeds nearly 12 d earlier than the APP-S biotype. APP-R and APP-S biotypes had similar aboveground dry weight before the flowering stage. Fecundity of the APP-R biotype was similar to the APP-S biotype (8.57 g seeds plant−1 and 0.17 g seeds panicle−1 versus 8.22 g seeds plant−1 and 0.13 g seeds panicle−1, respectively). Ultimately, the relatively slower-developing APP-S P. fugax had 50% more shoot dry weight than the APP-R plants. Relative competitiveness among the APP-R and APP-S P. fugax biotypes was investigated through replacement series experiments. No difference in competitive ability was measured between APP-R and APP-S biotypes on the basis of shoot dry weight before the tillering stage. These results indicate that there is no apparent fitness penalty for the APP-R P. fugax. The shorter growth cycle of APP-R with no apparent fitness penalty suggests that growers will need begin weed control earlier and possibly include vegetative crops with an even shorter growth cycle in their rotations.
We aimed to investigate the association between plasma retinol and incident cancer among Chinese hypertensive adults. We conducted a nested case–control study, including 231 patients with incident cancer and 231 matched controls during a median 4·5-year follow-up of the China Stroke Primary Prevention Trial. There was a significant, inverse association between retinol levels and digestive system cancer (per 10 μg/dl increases: OR 0·79; 95 % CI 0·69, 0·91). When compared with participants in the first quartile of retinol (< 52·3 μg/dl), a significantly lower cancer risk was found in participants in quartile 2–4 ( ≥ 52·3 μg/dl: OR 0·31; 95 % CI 0·13, 0·71). However, there was a U-shaped association between retinol levels and non-digestive system cancers where the risk of cancers decreased (although not significantly) with each increment of plasma retinol (per 10 μg/dl increases: OR 0·89; 95 % CI 0·60, 1·31) in participants with retinol < 68·2 μg/dl, and then increased significantly with retinol (per 10 μg/dl increase: OR 1·65; 95 % CI 1·12, 2·44) in participants with retinol ≥ 68·2 μg/dl. In conclusion, there was a significant inverse dose–response association between plasma retinol and the risk of digestive system cancers. However, a U-shaped association was observed between plasma retinol and the risk of non-digestive cancers (with a turning point approximately 68·2 μg/dl).
We herein report an experimental study on the morphological evolution of a vortex ring formed inside a liquid pool after it is impacted and penetrated by a coalescing drop of the same liquid. The dynamics of the penetrating vortex ring along with the deformation of the pool surface has been captured using simultaneous high-speed laser induced fluorescence and shadowgraph techniques. It is identified that the motion of such a vortex ring can be divided into three stages, during which inertial, capillary and viscous effects alternatingly play dominant roles to modulate the penetration process, resulting in linear, non-monotonic and decelerating motion in these three stages respectively. Furthermore, we also evaluate the relevant time and length scales of these three stages and subsequently propose a unified description of the downward motion of the penetrating vortex ring. Finally, we use the experimental data for a range of drop diameters and impact speeds to validate the proposed scaling.
With rapid urbanization worldwide, most people now live in cities, but the effects of urbanization on knowledge about the natural environment is not well studied. Due to the importance of Cymbidium to Chinese traditional culture, we tested how urbanization influences the distribution of orchid knowledge across various knowledge domains at risk of loss due to declining orchid populations. Participants in the Cymbidium trade were interviewed in three distinct urbanization-level jurisdictions in Sichuan, China: Puge (low urbanization), Huili (moderate urbanization) and Chengdu (high urbanization). Using photographic cue-cards of nine Cymbidium taxa, we assessed aggregate and specific knowledge held by 91 orchid collectors/traders across the urbanization gradient. Contrary to expectations, we found that urbanization and orchid knowledge were positively related, but this varied by knowledge type, with moderate urbanization showing significantly higher knowledge in two domains. Our findings suggest that a generalizable understanding of how urbanization affects knowledge must account for differences in knowledge types and geographic/cultural scales, with implications for biocultural diversity conservation in an increasingly urban world.
To simulate the effects of hot working parameters on microstructure and flow resistance during dynamic recrystallization (DRX) of a Ni–Cr–Mo-based C276 superalloy, a 2D mesoscopic model has been established using cellular automaton (CA) method. The isothermal hot compression tests were performed on a Gleeble 1500 thermal-mechanical simulator at the temperature range of 1273–1473 K and strain rate range of 0.001–5 s−1. The flow stress behaviors were then obtained and the microstructures of quenching specimen were observed after compression. Then the dislocation density evolution, nucleation and grain growth during hot compression were determined from experiments and integrated to the CA model. The topology of microstructure evolution and deformation resistance were calculated using the developed CA model and compared with the experimental ones. The CA simulation results show reasonable agreements with the experiments, implying the developed CA can capture the effects of processing parameters on the DRX behavior of C276 superalloy.
Persons with special needs are in an extremely vulnerable position where they are potentially subject to financial abuse by rogues. Unfortunately, policy makers and scholars have not given this problem sufficient consideration. Drawing from the Singapore experience, this chapter explores the financial planning mechanisms available to persons with special needs which currently exist through legislation and various government and non-profit initiatives. It then considers several case studies of financial abuse of persons with special needs to expose the potential systemic weaknesses in the current regime. The aim of the chapter is to provoke a conversation on how societies can do better by enacting laws and implementing schemes to prevent financial abuse of persons with special needs.
In recent decades, there has been significant growth in the capital market for mortality- and longevity-linked bonds. Therefore, modeling and forecasting the mortality indexes underlying these bonds have crucial implications for risk management in life insurance companies. In this paper, we propose a hierarchical reconciliation approach to constructing probabilistic forecasts for mortality bond indexes. We apply this approach to analyzing the Swiss Re Kortis bond, which is the first “longevity trend bond” introduced in the market. We express the longevity divergence index associated with the bond’s principal reduction factor (PRF) in a hierarchical setting. We first adopt time-series models to obtain forecasts on each hierarchical level, and then apply a minimum trace reconciliation approach to ensure coherence of forecasts across all levels. Based on the reconciled probabilistic forecasts of the longevity divergence index, we estimate the probability distribution of the PRF of the Kortis bond, and compare our results with those stated in Standard and Poor’s report on pre-sale information. We also illustrate the strong performance of the approach by comparing the reconciled forecasts with unreconciled forecasts as well as those from the bottom-up approach and the optimal combination approach. Finally, we provide first insights on the interest spread of the Kortis bond throughout its risk period 2010–2016.
For decades, fructose intake has been recognized as an environmental risk for metabolic syndromes and diseases. Here, we comprehensively examined effects of fructose intake on mice liver transcriptomes. Fructose supplemented water (34%; wt/vol) was fed to both male and female C57BL/6N mice at their free will for six weeks, followed by hepatic transcriptomics analysis. Based on our criteria, differentially expressed genes (DEGs) were selected and subjected to further computational analyses to predict key pathways and upstream regulator(s). Subsequently, predicted genes and pathways from the transcriptomics dataset were validated via quantitative RT-PCR analyses. As results, we identified 89 down-regulated and 88 up-regulated mRNAs in fructose-fed mice livers. These DEGs were subjected to bioinformatic analysis tools in which DEGs were mainly enriched in xenobiotic metabolic processes; further, in the Ingenuity Pathway Analysis software, it was suggested that the aryl hydrocarbon receptor (AhR) is an upstream regulator governing overall changes, while fructose suppresses the AhR signaling pathway. In our quantitative RT-PCR validation, we confirmed that fructose suppressed AhR signaling through modulating expressions of transcription factor (Arnt) and upstream regulators (Ncor2, and Rb1). Altogether, we demonstrated that ad libitum fructose intake suppresses the canonical AhR signaling pathway in C57BL/6N mice liver. Based on our current observations, further studies are warranted, especially with regard to the effects of co-exposure to fructose on 1) other types of carcinogens and 2) inflammation inducing agents (or even diets such as a high-fat diet), to find implications of fructose induced-AhR suppression.
The dynamics of large gravity waves are known to be modified from the linear model by nonlinear physics. In this paper we analyse Eulerian surface elevation time histories measured from two sites, Lake George (Australia) and the North Sea, to examine how weak nonlinearity has modified the shape of extreme wave groups relative to linear theory. We analyse the asymmetry of the extreme wave groups and find that, on average, the wave in front of an extreme wave is smaller than the wave following it. We also observe a contraction in the envelope width of the wave group relative to linear theory. The departures from linear theory are strongly correlated with the steepness of the underlying sea state and are generally consistent with theoretical expectations, providing strong evidence that such nonlinear phenomena arise in naturally occurring water waves.
Apolipoprotein E (APOE) E4 is the main genetic risk factor for Alzheimer’s disease (AD). Due to the consistent association, there is interest as to whether E4 influences the risk of other neurodegenerative diseases. Further, there is a constant search for other genetic biomarkers contributing to these phenotypes, such as microtubule-associated protein tau (MAPT) haplotypes. Here, participants from the Ontario Neurodegenerative Disease Research Initiative were genotyped to investigate whether the APOE E4 allele or MAPT H1 haplotype are associated with five neurodegenerative diseases: (1) AD and mild cognitive impairment (MCI), (2) amyotrophic lateral sclerosis, (3) frontotemporal dementia (FTD), (4) Parkinson’s disease, and (5) vascular cognitive impairment.
Genotypes were defined for their respective APOE allele and MAPT haplotype calls for each participant, and logistic regression analyses were performed to identify the associations with the presentations of neurodegenerative diseases.
Our work confirmed the association of the E4 allele with a dose-dependent increased presentation of AD, and an association between the E4 allele alone and MCI; however, the other four diseases were not associated with E4. Further, the APOE E2 allele was associated with decreased presentation of both AD and MCI. No associations were identified between MAPT haplotype and the neurodegenerative disease cohorts; but following subtyping of the FTD cohort, the H1 haplotype was significantly associated with progressive supranuclear palsy.
This is the first study to concurrently analyze the association of APOE isoforms and MAPT haplotypes with five neurodegenerative diseases using consistent enrollment criteria and broad phenotypic analysis.
The third generation of the BeiDou navigation satellite system (BDS-3) is a global navigation system, and is expected to be in full operation by 2020. High-precision orbits are a precondition for BDS-3 to provide a highly accurate service, which needs a global tracking and monitoring capability for the operational satellites. However, it is difficult for BDS to construct global ground monitoring stations. Fortunately, Ka-band Inter-Satellite Link (ISL) antennae fitted to the BDS-3 satellites can be used to extend the visible arc of the Medium Earth Orbit (MEO) satellites and to enhance the ground stations for orbit determination. This paper analyses the ISL-enhanced orbit determination for eight BDS-3 satellites, using the data from ten Chinese domestic stations and 13 international Global Navigation Satellite System (GNSS) Monitoring and Assessment System (iGMAS) overseas stations. The results show that the Three-Dimensional (3D) position Root Mean Square (RMS) error of the Overlapping Orbit Differences (OODs) is approximately 1 m when only ten regional stations are used. When the ISL measurements are added, the 3D position RMS error is decreased to 0·5 m, and the accuracy of the 24-hour orbit prediction can also be improved from 2 m to 0·7 m, which is even better than that of the orbits determined using globally distributed stations. It can be expected that with the subsequent launch of BDS-3 satellites and the increasing number of ISLs, the advantage of the ISL enhanced orbit determination will become more significant.
In this work, a new phenylethylene derivative, named 2-((3,5-di(9H-carbazol-9-yl)phenyl)(p-tolyl)methylene)malononitrile (DCPTMM), is synthesized and characterized by 1H NMR, 13C NMR spectroscopies, mass spectrum, and X-ray crystallography. Its photophysical properties are systematically studied and the result illustrates that DCPTMM shows aggregation-induced emission (AIE). The X-ray single crystal diffraction shows that the individual structure of crystals is monoclinic system with space group symbol P21/c and presents a twisted propeller-type structure as well as the packing structure of crystals has multiple types of hydrogen bonds (C–H⋯π and C–H⋯N) formed between adjacent molecules, and there is no π–π interaction between the aromatic rings, which is the main reason for the formation of AIE. Nondoped OLED fabricated with DCPTMM as light emitting layer emits greenish yellow light with a maximum emission peak of 554 nm and has relatively good performance with a maximum current efficiency of 5.53 cd/A and a maximum brightness of 6936 cd/m2.