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Elementary treatments of Markov chains, especially those devoted to discrete-time and finite state-space theory, leave the impression that everything is smooth and easy to understand. This exposition of the works of Kolmogorov, Feller, Chung, Kato and other mathematical luminaries focuses on time-continuous chains but is not so far from being elementary itself. It reminds us once again that the first impression is false: an infinite, but denumerable state-space is where the fun begins. If you have not heard of Blackwell's example (in which all states are instantaneous), do not understand what the minimal process is, or do not know what happens after explosion, dive right in. But beware lest you are enchanted: 'There are more spells than your commonplace magicians ever dreamed of.'
We elaborate a general workflow of weighting-based survey inference, decomposing it into two main tasks. The first is the estimation of population targets from one or more sources of auxiliary information. The second is the construction of weights that calibrate the survey sample to the population targets. We emphasize that these tasks are predicated on models of the measurement, sampling, and nonresponse process whose assumptions cannot be fully tested. After describing this workflow in abstract terms, we then describe in detail how it can be applied to the analysis of historical and contemporary opinion polls. We also discuss extensions of the basic workflow, particularly inference for causal quantities and multilevel regression and poststratification.
Managing interactions between humans and wild elephants is a complex problem that is increasing as a result of agricultural and urban expansion into and alongside protected areas. Mitigating negative interactions requires the development of new tools to reduce competition and promote coexistence. Many studies have tested various mitigation techniques across elephant ranges in Africa and Asia, with varying levels of success. Recently, strobe lights have been suggested as a potential mitigation strategy in deterring African lions Panthera leo from kraals or bomas, but this technique has to date not been tested to reduce negative human–elephant interactions. Over a 2-year period (November 2016–June 2018), we tested the effectiveness of solar-powered strobe light barriers in deterring African elephants Loxodonta africana, in collaboration with 18 farmers in a community adjacent to the Chobe Forest Reserve and Chobe National Park in northern Botswana. Although elephants were more likely to pass by fields with solar-powered strobe light barriers (which was probably a result of selection bias as we focused on fields that had previously been damaged by elephants), they were less likely to enter these treatment fields than control fields without such barriers. Our findings demonstrate the efficacy of light barriers to reduce negative human–elephant interactions in rural communities.
The transition from defined benefit to defined contribution (DC) pension schemes has increased the interest in target annuitization funds that aim to fund a minimum level of retirement income. Prior literature has studied the optimal investment strategies for DC funds that provide minimum guarantees, but far less attention has been given to portfolio insurance strategies for DC pension funds focusing on retirement income targets. We evaluate the performance of option-based and constant proportion portfolio insurance strategies for a DC fund that targets a minimum level of inflation-protected annuity income at retirement. We show how the portfolio allocation to an equity fund varies depending on the member’s age upon joining the fund, displaying a downward trend through time for members joining the fund before ages in the mid-30s. We demonstrate how both portfolio insurance strategies provide strong protection against downside equity risk in financing a minimum level of retirement income. The option-based strategy generally leads to higher accumulated savings at retirement, whereas the constant proportion strategy provides better downside risk protection robust to equity market jumps/volatilities.
Which factors explain variation in the gendered composition of governing cabinets? To address this question, we transpose the idea of proportionality between legislative seat shares and cabinet seats shares from studies of the partisan composition of cabinets to studies of the gender composition of cabinets. Gamson's law identifies a strong association between the proportion of legislative seats a party contributes to a governing coalition and the proportion of seats the party receives in the cabinet. We attempt to gender Gamson's law. We develop a theory of why a gendered Gamson's logic should apply to cabinets in parliamentary systems. We test our intuition via analysis of a new dataset covering 18 OECD parliamentary systems from 1990 through early 2019. We find a strong relationship between the gendered distribution of seats in governing parties’ parliamentary delegations and the gendered distribution of seats in the cabinets those parties create.
Most clinical microbiology laboratories have replaced toxin immunoassay (EIA) alone with multistep testing (MST) protocols or nucleic acid amplification testing (NAAT) alone for the detection of C. difficile.
Study the effect of changing testing strategies on C. difficile detection and strain diversity.
A Veterans’ Affairs hospital.
Initially, toxin EIA testing was replaced by an MST approach utilizing a glutamate dehydrogenase (GDH) and toxin EIA followed by tcdB NAAT for discordant results. After 18 months, MST was replaced by a NAAT-only strategy. Available patient stool specimens were cultured for C. difficile. Restriction endonuclease analysis (REA) strain typing and quantitative in vitro toxin testing were performed on recovered isolates.
Before MST (toxin EIA), 79 of 708 specimens (11%) were positive, and after MST (MST-A), 121 of 517 specimens (23%) were positive (P < .0001). Prior to NAAT-only testing (MST-B), 80 of the 490 specimens (16%) were positive by MST, and after NAAT-only testing was implemented, 67 of the 368 specimens (18%) were positive (P = nonsignificant). After replacing toxin EIA testing, REA strain group diversity increased (8, 13, 13, and 10 REA groups in the toxin EIA, MST-A, MST-B, and NAAT-only periods, respectively) and in vitro toxin concentration decreased. The average log10 toxin concentration of the isolates were 2.08, 1.88, 1.20 and 1.55 ng/mL for the same periods, respectively.
MST and NAAT had similar detection rates for C. difficile. Compared to toxin testing alone, they detected increased diversity of C. difficile strains, many of which were low toxin producing.
To determine the Final ICU Need in the 24 hours prior to ICU discharge for children with cardiac disease by utilising a single-centre survey.
A cross-sectional survey was utilised to determine Final ICU Need, which was categorised as “Cardiovascular”, “Respiratory”, “Feeding”, “Sedation”, “Systems Issue”, or “Other” for each encounter. Survey responses were obtained from attending physicians who discharged children (≤18 years of age with ICU length of stay >24 hours) from the Cardiac ICU between April 2016 and July 2018.
Measurements and results:
Survey response rate was 99% (n = 1073), with 667 encounters eligible for analysis. “Cardiovascular” (61%) and “Respiratory” (26%) were the most frequently chosen Final ICU Needs. From a multivariable mixed effects logistic regression model fitted to “Cardiovascular” and “Respiratory”, operations with significantly reduced odds of having “Cardiovascular” Final ICU Need included Glenn palliation (p = 0.003), total anomalous pulmonary venous connection repair (p = 0.024), truncus arteriosus repair (p = 0.044), and vascular ring repair (p < 0.001). Short lengths of stay (<7.9 days) had significantly higher odds of “Cardiovascular” Final ICU Need (p < 0.001). “Cardiovascular” and “Respiratory” Final ICU Needs were also associated with provider and ICU discharge season.
Final ICU Need is a novel metric to identify variations in Cardiac ICU utilisation and clinical trajectories. Final ICU Need was significantly influenced by benchmark operation, length of stay, provider, and season. Future applications of Final ICU Need include targeting quality and research initiatives, calibrating provider and family expectations, and identifying provider-level variability in care processes and mental models.
A wealth of research documents the rise of affective polarization, or the increasing disdain for the out-party in American politics. In this paper, we analyze ANES data from 1988 to 2016 to investigate the contribution of core value polarization to the phenomenon of out-party enmity. We find that greater differences in fundamental principles relate significantly to emotionally intense evaluations of the opposing party and its candidates, as well as the ideological out-group, independent of issue attitude extremity and the strength of one's partisan and ideological identities. Moreover, ANES panel data from 1992 to 1996 reveal that past value extremity promotes future affective polarization. These results are important for our understanding of the nature and extent of value-based polarization in American politics.
This reflection presents a discussion of some common measures of variability and how they are appropriately used in descriptive and inferential statistical analyses. We argue that confidence intervals (CIs), which incorporate these measures, serve as tools to assess both clinical and statistical significance.
Recent work on political divisions in the mass public has identified several manifestations of polarization linked to different types of attitudes, orientations, and behaviors. Of these, affective polarization and perceived polarization have attracted increasing attention, though we still know fairly little of the links between these variants of polarization. In this paper, we examine the association between affective and perceived polarization, with an aim toward disentangling any potential causal relationship between the two processes. Using two sets of nationally representative panel data from 1992 to 1996 and 2008 to 2009, we find evidence that affective polarization causes perceived polarization, and that perceived polarization is not related to future affective polarization. Stratifying the models by level of political information, we find that the strength and statistical significance of the relationships between past and future values of affective and perceived polarization are conditional on political sophistication: more sophisticated individuals exhibit stronger relationships.
One of the fundamental roles of human imagination is to enable the representation of possible future events. Here, we survey some of the most critical abilities that this foresight supports: anticipating future emotions, setting and pursuing goals, preparing for threats, deliberately acquiring skills and knowledge, and intentionally shaping the future environment. Furthermore, we outline how metacognition bolsters human capacities even further by enabling people to reflect on and compensate for the natural limits of their foresight. For example, humans make contingency plans because they appreciate that their initial predictions may turn out to be wrong. We suggest that the processes involved in monitoring, controlling, and ultimately augmenting future-oriented imagination represent an important and understudied parallel of “metamemory” that should be called “metaforesight.”
While the Victorian ideal of the public park is well understood, we know less of how local governors sought to realize this ideal in practice. This article is concerned with park-making as a process – contingent, unstable, open – rather than with parks as outcomes – determined, settled, closed. It details how local governors bounded, designed and regulated park spaces to differentiate them as ‘spaces apart’ within the city, and how this programme of spatial governance was obstructed, frustrated and diverted by political, environmental and social forces. The article also uses this historical analysis to provide a new perspective on the future prospects of urban parks today.
Writing in the 1880s, Galton recognized that some healthy individuals lack visual imagery. This phenomenon has been relatively neglected since then. In 2015 we coined the term “aphantasia” to describe the lack of the mind’s eye, reporting on twenty-one individuals with a lifelong lack of imagery. Since then we have been contacted by many thousands of people lying at both the aphantasic and the hyperphantasic extremes of the vividness spectrum. Preliminary evidence suggests that lifelong aphantasia is associated variably with prosopagnosia and reduction in autobiographical memory; hyperphantasia is associated with synaesthesia. Over 50 percent of people with aphantasia report visual dreaming. In around 50 percent of our aphantasic participants, all modalities of imagery are affected, while in others some modalities of imagery are preserved. Aphantasia often runs in families. Functional imaging studies of imagery suggest a range of hypotheses for the neural correlates of aphantasia; the few functional imaging studies specifically examining imagery vividness point to positive correlations with brain activity in higher visual and memory-related areas. The study of aphantasia reminds us how easily invisible differences can escape detection. Visualization is only one of many ways of representing things in their absence, and individuals lacking visual imagery can be highly imaginative.
Coronavirus disease 2019 (COVID-19) has caused a global pandemic which has affected patients and healthcare systems around the world. Patients with underlying health conditions seem to be more severely affected. There are limited reports of patients with univentricular circulations and COVID 19; thus, we report a case of COVID-19 in a patient with a univentricular circulation.
Florpyrauxifen-benzyl and quizalofop were available for POST applications in 2018; however, little is known about the response of acetyl-CoA carboxylase (ACCase)-resistant rice cultivars and advanced lines to POST herbicides. A field study was conducted in 2017 and 2018 at Stoneville, MS, to characterize the response of ACCase-resistant rice cultivars and advanced lines to POST applications of florpyrauxifen-benzyl. The imidazolinone-resistant (IR) rice cultivars ‘CL163’ and ‘CLXL 745’, and ACCase-resistant rice cultivars, ‘PVL01’, ‘PVL013’, ‘PVL024-B’, ‘PVL038’, ‘PVL080’, and ‘PVL081’were treated with florpyrauxifen-benzyl at 0 (nontreated control for each cultivar) and 58 g ai ha-1 at the four-leaf to one-tiller (LPOST) growth stage. At 14 d after treatment (DAT), PVL01 was injured 5 to 6% greater than CLXL 745, PVL013, and PVL081; however, injury was ≤ 10% at that evaluation for all cultivars. Similarly, injury was ≤ 13% for all cultivars 28 DAT. Mature heights were reduced for all cultivars except PVL013 and PVL081. Rough rice yield was ≥ 100% of the control for all cultivars except PVL081, PVL013, and CL163. Results suggest that florpyrauxifen-benzyl can safely be applied POST to rice cultivars grown in Mississippi as well as ACCase-resistant cultivars that are currently under development.