A new look at the critical community size for childhood infections

Quasi-stationarity and time to extinction are studied for the classic endemic model. Attention is restricted to the transition region in parameter space where the quasi-stationary distribution is non-normal. A new approximation of the marginal distribution of infected individuals in quasi-stationarity is presented. It leads to a simple explicit expression for an approximation of the critical community size in terms of model parameters.     

Dreams and revelations: A critical look at Kelsey.

After a seven-century lull in Christian scholarship about dreams, the mid-Twentieth Century saw the beginning of a growing effort to convince Christians dreams are a significant means of communication with God. This essay summarizes and criticizes Morton Kelsey's central argument concerning the Christian significance of dreams in his God, dreams, and revelation (1991). Kelsey's is a thoughtful version of the argument common to his colleagues. As such, it displays both the strengths and the weaknesses of the general position. It correctly reminds Christians of dreams' significance in their past. But if Kelsey means to offer a fully supported logical argument, that argument is not clear and even the most sympathetic restatement of it leaves it unsound. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A fresh look at the wolf-pack theory of companion-animal dog social behavior

A popular perspective on the social behavior of dogs in multiple-dog households sees the dogs' behavior as reflecting the sociobiological laws of the rigidly structured dominance hierarchy that has been described for wolf packs. This view suggests that aggression problems among dogs are natural expressions of conflict that arise whenever dominance status is in contention. One recommended solution has been for the owner to endorse and enforce a particular dominance hierarchy because, on the wolf pack model, aggression is minimized when the structure of the hierarchy is clear, strong, and stable. This article questions the validity of this perspective on 2 principal grounds. First, because it does not seem to occur in the wild, this article suggests the strong dominance hierarchy that has been described for wolves may be a by-product of captivity. If true, it implies that social behavior—even in wolves—may be a product more of environmental circumstances and contingencies than an instinctive directive. Second, because feral dogs do not exhibit the classic wolf-pack structure, the validity of the canid, social dominance hierarchy again comes into question. This article suggests that behavioral learning theory offers another perspective regarding the behavior of dogs and wolves in the wild or in captivity and offers an effective intervention for aggression problems.     

A critical look at some widely used estimators in mark-resighting experiments

1. For many species and circumstances, mark-resighting procedures constitute valid alternatives to capture-recapture methods. Indeed, resightings are generally cheaper to acquire than physically recapturing and rehandling the animals, especially when radiotelemetry or other tracking devices are available. 2. In order to estimate population abundance, the joint hypergeometric maximum likelihood estimator, the Minta-Mangel estimator and the Bowden estimator are implemented in noremark, software which has become very popular with biologists in the past decade. 3. In this paper, the basic assumptions regarding these widely applied procedures are delineated and discussed. A simulation study is performed in order to investigate the robustness of the estimators under failure of the assumptions. 4. Theoretical considerations and simulation results motivate the use of the Bowden estimator which, when marks are distributed quite evenly among groups, constitutes the sole reliable method, offering computational simplicity and robustness. On the other hand, if the marks are distributed unevenly, no mark-resighting procedure seems reliable. An application to a case study is considered.     

A critical look at the Treatise family-group classification of Conodonta: an exercise in eclecticism

The family-group classification of conodonts presented in the revised edition of the Treatise on Invertebrate Paleontology, Part W, Supplement 2, Conodonta, published in 1981, is shown to contain errors with regard to the International Code of Zoological Nomenclature. The classification lacks a concise philosophical and methodological foundation and exhibits very poor conceptualization of the taxa it recognizes. The classification is analyzed and discussed in terms of, among Linnkan taxonomists, generally accepted objectives and conventions with regard to the internal structure and phylogenetic message of a hierarchical natural classification. The obvious errors in terms of the ICZN are pointed out and corrected. As a demonstration of an alternative approach, a classification of the superfamilies Prioniodontacea, Hibbardellacea, and Icriodontacea is presented.     

Nothing lasts forever - a critical look at sustained remission

Remission is key to prevent progression of rheumatoid arthritis, but it is still rarely seen in clinical practice, not to speak of sustained remission, which is the best possible disease outcome of rheumatoid arthritis. New strategies and recommendations focus on achievement of remission, but it is unclear how long remission can actually be maintained in clinical practice. A study by Prince and colleagues gives insights into this question, and raises some other questions for the future.Remission of rheumatoid arthritis (RA): not so long ago this concept was illusory and far out of reach for rheumatologists. In fact, there was also little scientific interest, as the main focus of RA therapy was to prevent severe disability, which was evident in a good portion of patients until even the 1990s. It can easily be appreciated that things have changed by looking at the trend over time in the scientific interest in remission of RA: if one simply pulls publications on ''rheumatoid arthritis'' and compares those including the term ''remission'' with those including the term ''therapy'', it is striking that when comparing the number of publications in the year 1980 with the respective number in 2010, the indexed articles increased 4.4-fold when the term ''therapy'' was used, and 15-fold with the term ''remission'' (Figure ​(Figure1).1). The current article on sustainment of remission by Prince and colleagues [1] thus hits a very timely topic.Open in a separate windowFigure 1Studies on remission in rheumatoid arthritis. The graph shows the disproportional increase of studies on remission of rheumatoid arthritis (light bars) when compared to studies of treatment of rheumatoid arthritis (dark bars) over the years.In recent years, particularly the treat to target concept has engaged therapy towards reaching the goal of remission in patients with RA [2], and this has also been reflected in recent management recommendations for RA by the European League Against Rheumatism (EULAR) [3], and finally culminated in the publication of new remission criteria by the American College of Rheumatology (ACR) and EULAR [4]. Throughout the years, a central question in the definition of remission has been whether it should be at a single point in time or should include a time perspective. The most recent decision on this in the aforementioned ACR/EULAR remission criteria was the former.This single time point definition of remission may sound contradictory to the concept of RA being a progressive and destructive disease, and disease activity over time being the most robust predictor of such progression. On a closer look, and considering the treat to target approach, it begins to make more sense: as long as remission at a single point in time is not reached, treatment needs to be adapted. There is no doubt, however, that achieving remission is just the beginning of therapeutic success in RA: years ago, for example, in their definition of remission, the US Food and Drug Administration had adopted the concept of reaching a good state without radiographic progression [5], and this concept can similarly be found in some of the most recent clinical trials.Still, little definite is known about how often sustained remission can be achieved, and what then the minimum time requirements would be. The current paper by Prince and colleagues provides insights into the question of maintenance of remission, troubling insights in fact, as they conclude that only about half of individuals in remission at a single time point (by any instrument) remain in remission at a subsequent measurement a year later. Among those losing the remission status, only one in four patients was able to regain the remission status subsequently.Another aspect of the data, as can be deduced from the Kaplan-Meier plots in the pulication of Prince and colleagues [1], is the fact that the greatest loss of remission status occurred after a single remission visit, and once remission was seen on two subsequent visits, the chance of remaining in remission became much higher. This matches other reports on the fact that frequency of remission in patients in a typical outpatient setting drops from approximately 40% if a single random visit is looked at to about 20% if two subsequent visits in remission are required [6]. Van der Kooij and colleagues [7] used the data from the BeST trial and further showed that the longer and the better a good clinical state is maintained, the greater the likelihood of remaining in that state.One limitation in the present study remains the fact that the remission status has been determined only on an annual basis. RA is a fluctuating disease, and the fluctuating disease activity over time, even when overall levels were low, had been shown to be a risk factor for radiographic progression, the prevention of which is a core structural target of RA treatment [8]. Since no data are available about the time points between the annual assessments, nor radiographic data, not all the final questions can be answered by Prince and colleagues.In fact, there are many other questions around this topic, some of which may even sound a bit heretical, such as: ''Why remission?'' Particularly when biological drugs are used, reaching remission may not always be necessary: it has been shown for tumour necrosis factor-α inhibitors that structural progression is abrogated even if some levels of disease activity remain [9,10]. Recently, this has also been shown for interleukin-6 receptor blockade [11] and it remains to be seen if this is the case also for other biologic modes of action, such as inhibition of co-stimulation or B-cell-directed therapy. This supports the single point in time approach to remission as discussed above, which for some patients in some circumstances may even only need to be low disease activity [3].In summary, we can conclude that we have come a long way, and the road remains ahead of us. Sustained remission is an ambitious goal for patients with RA, and with the current article we have learned that it is only infrequently seen. At the same time we have also noticed the developments in therapies and therapeutic strategies in the past decades, and extrapolating this to the future, it may be more than timely to start thinking about sustainment of remission, its definition as an outcome measure of successful treatment, and eventually also its definition in regards to the right timing of a therapeutic withdrawal.     

Specialist registration: a critical look at the proposals of the Merrison report.

In the general euphoria over the many views in the Merrison Report that the profession welcomed too little attention has been paid to what has been said about specialist registration. The report contains several basic confusions and a serious misunderstanding of the nature of specialist medical training and practice. It makes several cardinal errors in thinking that some notorious problems related to NHS staffing are also related to a lack of an effective specialist register, and it shows how the creation of such a register would largely destroy the authority of the colleges and faculties. Nowhere in the report is there any convincing argument to show that specialist registration would confer advantages sufficient to outweigh the disadvantages. To let specialist registration in the UK slip in on the irrelevant coat tails of EEC requirements would be a grave dereliction of the long-term interests of medical practice and patient care. The General Medical Council is holding a conference in which this topic is to be discussed on 24 February 1976 and it is still not too late for the profession to think again on this topic.     

A first look at biosensors

This is a very elementary guide to biosensors, outlining the principles of operation of some optoelectronic and current measuring biosensors. Factors which can influence successful translation to the marketplace are addressed.