The Natural Experiment

Many of you, reading the title of this report, probably felt a certain confusion about this new, unusual term natural experiment. To dispel this quite natural confusion, let me say immediately that I am proposing this term to designate special investigatory techniques situated somewhere between external, objective observation, on the one hand, and a man-devised laboratory experiment (at present referred to as a psychological experiment), on the other. These original techniques, different from both the first and the second, are actually not completely new and unusual but, on the contrary, are well known to every one of you in their rudimentary form. Considered in more detail, they might perhaps be of considerable interest both theoretically and practically. It is for this reason that I decided to propose a new term to designate them. One cannot, of course, in such a brief report attempt to outline all the possible applications of this method to all the phenomena to which it could be applied; hence, I shall focus on an area that is more familiar to me and, moreover, seems to be especially suited for conducting a natural experiment, namely, research on personality or individuality.     

Morris Water Maze Experiment

The Morris water maze is widely used to study spatial memory and learning. Animals are placed in a pool of water that is colored opaque with powdered non-fat milk or non-toxic tempera paint, where they must swim to a hidden escape platform. Because they are in opaque water, the animals cannot see the platform, and cannot rely on scent to find the escape route. Instead, they must rely on external/extra-maze cues. As the animals become more familiar with the task, they are able to find the platform more quickly. Developed by Richard G. Morris in 1984, this paradigm has become one of the "gold standards" of behavioral neuroscience.Open in a separate windowClick here to view.^{(29M, flv)}     

Experiment specific expression patterns

The differential analysis of genes between microarrays from several experimental conditions or treatments routinely estimates which genes change significantly between groups. As genes are never regulated individually, observed behavior may be a consequence of changes in other genes. Existing approaches like co-expression analysis aim to resolve such patterns from a wide range of experiments. The knowledge of such a background set of experiments can be used to compute expected gene behavior based on known links. It is particularly interesting to detect previously unseen specific effects in other experiments. Here, a new method to spot genes deviating from expected behavior (PAttern DEviation SCOring--Padesco) is devised. It uses linear regression models learned from a background set to arrive at gene specific prediction accuracy distributions. For a given experiment, it is then decided whether each gene is predicted better or worse than expected. This provides a novel way to estimate the experiment specificity of each gene. We propose a validation procedure to estimate the detection of such specific candidates and show that these can be identified with an average accuracy of about 85%.     

The Pinwheel Experiment Revisited

The critical point hypothesis explains the origin of some cardiac arrhythmias, and the bidomain model describes electrical stimulation of the heart. In this paper, the critical point hypothesis is combined with the bidomain model. The result is four new predictions about the pinwheel experiment, a fundamental experiment in cardiac electrophysiology. These are: (1) The duration of the vulnerable period during cathodalS₂stimulation is longer for anS₁wavefront propagating perpendicular to the fibers than for anS₁wavefront propagating parallel to the fibers. (2) For anodalS₂stimulation with theS₁wavefront propagating parallel to the fibers, the vulnerable period splits into two periods with an “invulnerable period” between them. (3) For anodalS₂stimulation with theS₁wavefront propagating perpendicular to the fibers, the vulnerable period consists of only one period. (4) A previously suggested mechanism for the upper limit of vulnerability (S₂is so strong that the entire tissue is depolarized by an amount greater thanS*) is no longer applicable.     

The International Joint Experiment ISTTOK

The 3rd International Joint Experiment has been carried out on ISTTOK following the last RUSFD (technical meeting on Research Using Small Fusion Devices) conference, held at Lisbon, in the scope of the IAEA Coordinated Research Project. This program has allowed a great knowledge interchange among the “small” fusion devices community and, in particular, in the development of common work-programs. This communication gives an overview of the impact of such activities. The JE have proved to be a very useful applied forum to share knowledge and to initiate young scientists in some fields of tokamak operation and diagnostics. Many of the ISTTOK 2008 relevant results were obtained under this scope.     

Experiment in Progressive Patient Care

A successful experiment is described in providing total progressive patient care in a small hospital. This was based on dividing ward services into nursing and “hotel” services, the latter being provided by a housekeeping team. Patients were divided into three categories according to the amount of nursing care needed, and two wards were converted, one into an intensive care unit, the other into a homeward bound unit, with high and low nurse/patient ratios respectively.