Informational Herding and Optimal Experimentation

We show that far from capturing a formally new phenomenon, informational herding is really a special case of single-person experimentation -- and 'bad herds' the typical failure of complete learning. We then analyze the analogous team equilibrium, where individuals maximize the present discounted welfare of posterity. To do so, we generalize Gittins indices to our non-bandit learning problem, and thereby characterize when contrarian behaviour arises: (i) While herds are still constrained efficient, they arise for a strictly smaller belief set. (ii) A log-concave log-likelihood ratio density robustly ensures that individuals should lean more against their myopic preference for an action the more popular it becomes.Bayesian learning, value function, herding, experimentation, log concavity, Gittins index, team equilibrium

Informational Herding and Optimal Experimentation

We show that far from capturing a formally new phenomenon, informational herding is really a special case of single-person experimentation - and `bad herds' the typical failure of complete learning. We then analyze the analogous team equilibrium, where individuals maximize the present discounted welfare of posterity. To do so, we generalize Gittins indices to our non-bandit learning problem, and thereby characterize when contrarian behaviour arises: (i) While herds are still constrained efficient, they arise for a strictly smaller belief set. (ii) A log-concave log-likelihood ratio density robustly ensures that individuals should lean more against their myopic preference for an action the more popular it becomes.herding; optimal learning; experimentation; contrarianism

Effect of interpregnancy interval on outcomes of pregnancy after miscarriage : retrospective analysis of hospital episode statistics in Scotland

Peer reviewedPublisher PD

The First Population II Stars Formed in Externally Enriched Mini-halos

We present a simulation of the formation of the earliest Population II stars, starting from cosmological initial conditions and ending when metals created in the first supernovae are incorporated into a collapsing gas-cloud. This occurs after a supernova blast-wave collides with a nearby mini-halo, inducing further turbulence that efficiently mixes metals into the dense gas in the center of the halo. The gas that first collapses has been enriched to a metallicity of Z ~ 2e-5 Zsun. Due to the extremely low metallicity, collapse proceeds similarly to metal-free gas until dust cooling becomes efficient at high densities, causing the cloud to fragment into a large number of low mass objects. This external enrichment mechanism provides a plausible origin for the most metal-poor stars observed, such as SMSS J031300.36-670839.3, that appear to have formed out of gas enriched by a single supernova. This mechanism operates on shorter timescales than the time for low-mass mini-halos (M < 5e5 Msun) to recover their gas after experiencing a supernova. As such, metal-enriched stars will likely form first via this channel if the conditions are right for it to occur. We identify a number of other externally enriched halos that may form stars in this manner. These halos have metallicities as high as 0.01 Zsun, suggesting that some members of the first generation of metal-enriched stars may be hiding in plain sight in current stellar surveys.Comment: Accepted for publication in MNRAS. Minor updates and one additional figure. Movies and images available at http://www.roe.ac.uk/~brs/pop2prim

Ceramic-ceramic shell tile thermal protection system and method thereof

A ceramic reusable, externally applied composite thermal protection system (TPS) is proposed. The system functions by utilizing a ceramic/ceramic upper shell structure which effectively separates its primary functions as a thermal insulator and as a load carrier to transmit loads to the cold structure. The composite tile system also prevents impact damage to the atmospheric entry vehicle thermal protection system. The composite tile comprises a structurally strong upper ceramic/ceramic shell manufactured from ceramic fibers and ceramic matrix meeting the thermal and structural requirements of a tile used on a re-entry aerospace vehicle. In addition, a lightweight high temperature ceramic lower temperature base tile is used. The upper shell and lower tile are attached by means effective to withstand the extreme temperatures (3000 to 3200F) and stress conditions. The composite tile may include one or more layers of variable density rigid or flexible thermal insulation. The assembly of the overall tile is facilitated by two or more locking mechanisms on opposing sides of the overall tile assembly. The assembly may occur subsequent to the installation of the lower shell tile on the spacecraft structural skin

The incidence, prevention and treatment of malaria in India

The observations of the writer in the different districts led to the following conclusions with reference to the etiology, prophylaxis and treatment of malaria.The most important factors in the etiology of the disease were the canal irrigation, and the condition of the houses and forts. No material progress can be made in lowering the incidence of malaria in Central and 1orthem India until canal irrigation is controlled, and, if necessary, prohibited in the neighbourhood of towns. The condition of the habitations of all classes of people calls for great improvement. Old forts and barracks situated in malarious places should be pulled down and rebuilt on healtkrsites.As regards the prophylaxis of malaria in India the only measures which have a general application are those which aim at the destruction of the mosquito. General quininisation of the infected population is impracticable, and screening has only a limited application. In areas of low endemicity minor measures will suffice, if efficiently and thoroughly carried out. The small incidence of malaria should be no excuse for the relaxation of antimosquito measures. In regions of moderate and high endemicity major measures are usually necessary in addition; and of these drainage and the control of canal irrigation are the most important. Until these measures have been carried out screening has an important place in the prevention of malaria among Europeans and better class Indians. The screening of houses, barracks and forts is of small use unless the buildings themselves are in a sufficiently good state of repair to render such screening effective in excluding mosquitoes. On Frontier campaigns the use of bivouac nets and mos- quito-proof huts would do much to lessen the incidence of the disease. Prophylactic quinine has a definite place in the prevention of malaria in India. It is indicated particularly for administration to troops and Europeanson Frontier campaigns and in hyperendermic areas; and, though attacks of malaria may not be prevented by the use of prophylactic quinine under such circumstances, they are rendered less severe and are less liable to become pernicious. TheThe treatment of malaria is true prophylaxis and can be summarised in one word - quinine. The drug should be given by the mouth in ordinary cases. The maximum safe dose of quinine for India is 30 grains a._day and rest is essential while large doses are being taken. Quinine orally administered in the form of a Standard course does not prevent reinfection in hyperendermic areas. Intramuscular injections of cuinine are of use in the treatment of severe cases, and of those unable to take quinine orally, and in selected cases give good results. Intravenous injections are safe and effective in skilled hands and are indicated in pernicious cases and where a speedy effect is desired, but the method is unsuitable for general use in India. The transient effect of intravenous injections necessitates a supplementary course of oral quinine. Rectal injections of quinine are uncertain in their action, but have given good results under the supervision of the writer. Subcutaneous injections cannot be recommended. No drug treatment of malaria is successful unless the resistance of the patient is maintained or increased by rest, nourishing food, and general tonic treatment.The pernicious forms of the disease are most common in times of hardship and strain, as on active service. Cerebral cases are most likely to occur during the hot weather, and in subjects of latent malaria who are not taking quinine and are performing strenuous exertion in the heat of the day.Abdominal and pulmonary types of malaria are more prevalent during the autumn months. Benign tertian malaria is more resistant to quinine treatment than malignant tertian, and early diagnosis and early treatment of all cases is essential.The eradication of malaria in India can only be attained by constant and scientifically applied warfare against the mosquito. The malaria carrying anopheles of every district must be identified, their breeding places mapped out, and measures taken to destroy them. By general improvement of the housing conditions the possibility of the hibernation of adult mosquitoes will be lessened. As in other countries, education should hold a prominent place in the prevention of the disease. Coincident with general education a practical knowledge of malaria should be imparted to every scholar. The progress of education among the indigenous masses of India is necessarily slow, but it is proceeding gradually. The prophylactic measures adopted by the Europeans and educated Indians should form an object lesson to the uneducated classes. Agriculture should be encouraged and the conditions of the peasant improved; for agriculture scientifically carried out prevents malaria and the consequent prosperity of the agriculturalist renders him less liable to fall a victim to the disease. It is true that the wholesale eradication of malaria will take many years, out the time can be shortened and the incidence lessened by vhole- hearted efforts to prevent the disease. Antimalarial measures may seem costly, but the disease is still more costly, and antimalarial measures alone will render India, with its unlimited vealth and resources, a healthy and prosperous country

Constitutional Rights of Students, Their Families, and Teachers in the Public Schools

This article searches for resolutions of constitutional conflicts, not only between the state as public school administrator and individual students, parents, and teachers, but also among the competing constitutional demands of the individuals whose interests are affected by the system of public education. Part II of this article addresses the public interests and values in which the educational system is rooted. Part III identifies and discusses the first amendment rights at stake in public education: freedom of expression; the right to receive communication; freedom of religion; and the protection against establishment of religion and familial childrearing rights. Part IV contains an elaboration of measures that may be taken to protect or accommodate the individual constitutional rights at stake; considers the extent to which these measures may be applicable in the contexts of school libraries, textbooks and courses of instruction, teacher\u27s lectures and assignments, and extracurricular activities; and offers resolutions of the competing educational and constitutional claims in accordance with applicable case law

An evaluative study of the 1972-74 standards of quality and objectives for public schools in Virginia

On November 3, 1970, the voters of Virginia approved a new Constitution. Within Article VIII, the education article, was the constitutional provision for a new statewide program to seek to insure that an educational program of high quality is established and continually maintained throughout the Commonwealth. An important aspect of this program, The Standards of Quality and Objectives, was the directive that each school division develop systematic, multi-year plans to guide the quest for quality.;The purpose of this study was: (1) to determine whether progress has been made by Virginia\u27s school divisions toward reaching a major goal of the Standards of Quality and Objectives which has usually been stated as, The student will become competent in fundamental academic skills; (2) to examine the relationship between multi-year planning and the progress made toward reaching this goal; and (3) to examine the use of time-series data and analysis on unobtrusive measures to conduct a summative evaluation of a statewide educational program.;The population in this study consisted of all the public school divisions in the Commonwealth of Virginia. The twenty-one divisions comprising the sample were drawn from those divisions whose 1975-80 Five-Year School Improvement Plans were ranked as high, average, or low in overall quality on a rating instrument especially designed for this purpose in an earlier doctoral study. Two types of data were collected for these divisions. The first type included measures specifically identified in the 1972-74 Standards of Quality and Objectives. These included overageness in grades K-7, attendance in grades K-12, and scores on standardized tests of ability and achievement. The second type of data included unobtrusive measures, including retentions in grades 8-12, K-12, 11 and 4; overageness in grades 8-12, K-12, 11 and 4; attendance in grades K-7 and 8-12; high school graduates; and high school dropouts. The source of data was state records.;It was hypothesized that significant changes would occur in the levels of both types of measures during the 1972-74 period and that school divisions with multi-year plans rated high would have significantly higher levels of performance than those divisions with plans rated low. The archival data were organized in graphic and tabular form. The TSX and CORREL computer programs were used to test for significant differences in the levels of measures before and after the introduction of the Standards of Quality and Objectives. Insufficient data points existed to permit the use of the computer programs and the data were analyzed through visual inspection.;The following conclusions were drawn. Performance objectives regarding the measures stated in the Standards of Quality and Objectives were achieved. While improvements in performance did occur during and after the 1972-74 period, the historical trend preceding the introduction of the Standards of Quality and Objectives was such that one cannot assign causality for the changes to the Standards themselves. School divisions with multi-year plans rated high tended to perform better than those divisions with plans rated low.;Although statistical tests of significance were not possible, the consistent trends of the data, when examined as a time-series, led to the conclusion that the 1972-74 Standards of Quality and Objectives tended to reinforce trends that had been in evidence for several years. In addition, other variables, especially size, could have influenced the performance of school divisions