Weighing designs to detect a single counterfeit coin

In this article, we discuss at length a combinatorial problem which has been of historic interest. It has appeared as a puzzle in several different versions with varying degrees of difficulty. It can be simply stated as follows: We are given a number of coins which are otherwise identical except that there may be at most one fake coin among them which is either slightly heavier or slightly lighter than the other genuine coins. Using only a two-pan weighing balance, we must devise a weighing scheme to identify the counterfeit coin and determine whether it is heavier or lighter (or declare that all coins are normal). We construct both sequential and non-sequential (that is, simultaneously declared) weighing plans for any given number of coins containing at most one fake coin using the minimum number of weighings needed.     

Comparison of computed tomography and chest radiography in the detection of rib fractures in abused infants

PURPOSE: Chest radiographs (CXR) are the standard method for evaluating rib fractures in abused infants. Computed tomography (CT) is a sensitive method to detect rib fractures. The purpose of this study was to compare CT and CXR in the evaluation of rib fractures in abused infants. METHODS: This retrospective study included all 12 abused infants identified from 1999 to 2004 who had rib fractures and both CXR and CT (8 abdomen CTs, 4 chest CTs). CT exams had been performed for clinical indications, and were obtained within one day of the CXR. Studies were reviewed by two pediatric radiologists to determine the number, locations, and approximate ages of the rib fractures. A total of 225 ribs were completely (192) or partially (33) seen by CT, and the matched ribs on CXR were used for the analysis. RESULTS: The mean patient age was 2.5 months (1.2-5.6), with seven females and five males. While 131 fractures were visualized by CT, only 79 were seen by CXR (p<.001). One patient had fractures only seen by CT. There were significantly (p<.05) more early subacute (24 vs. 4), subacute (47 vs. 26), and old fractures (4 vs. 0) seen by CT than by CXR. Anterior (42 vs. 11), anterolateral (21 vs. 12), posterolateral (9 vs. 3) and posterior (39 vs. 24) fractures were better seen by CT than by CXR (p<.01). Bilateral fractures were detected more often by CT (11) than by CXR (6). CONCLUSIONS: While this study group is small, these findings suggest that CT is better than CXR in visualizing rib fractures in abused infants.     

Unanticipated problems in the United States child protection system

While the United States child protection system is widely recognized as probably the most sophisticated and wide-ranging in the world, it nevertheless has some inherent problems. This article addresses some of the negative effects of mandatory reporting and the lack of fit of a short-term crisis intervention treatment approach for a substantial proportion of the protective services population. Reporting may have detrimental effects on the client-reporter relationship. Further, over half of the cases investigated are not substantiated. Of concern are the impact on innocent families of being investigated and the waste of scarce worker resources on investigation. While some protective services families are well suited to a crisis intervention model, a large number are multiproblem families who are always in crisis and families with chronic problems for whom crisis intervention is totally inadequate. Furthermore, because of high caseload size, workers are often not available to intervene after they have investigated the case. The problems described have been exacerbated by funding cutbacks under the current United States administration. The child protection system, along with other social welfare programs, is at risk for being dismantled by the Reagan administration.     

Ugandan adolescents’ sources,interpretation and evaluation of sexual content in entertainment media programming

Although mounting evidence in Western nations indicates that entertainment media influence young people’s sexual socialisation, virtually no research has addressed the topic in sub-Saharan Africa. The present study employed 14 focus groups of Ugandan high school students to identify media through which they were exposed to sexual content, how they interpreted and evaluated that content, and how they compared its influence with that of parents, schools and religious institutions. Participants most often mentioned TV, followed by print media and Internet as sources of sexual material. Media were said to present discrepant messages regarding the timing of sexual debut, with international programming urging early sexual debut and local programming described as urging young people to delay sex. Young people spoke of turning to ssengas and kojjas for sexual advice, and a number of boys suggested pornography could also be educational. Both local and international programming was interpreted as conveying views of men as sex driven and women as submissive in sex and relationships. Participants expressed the belief that sexual media content had a negative impact on young people. Most nevertheless assessed these messages as more influential than other sources of sexual socialisation.     

Behaviour and misbehaviour of Latino children in a time of zero tolerance: mothers' views

Thirty‐eight Latin American mothers with young children tell of their perceptions of school discipline and comportment issues and talk of their children's encounters with ‘zero tolerance’ legislation, and related rules for conduct, implemented by the local school boards. The purpose of this exploratory study is to understand: (a) parents' views of and concern about disciplinary practices at school; (b) parents' ideas about the connection between home and school discipline; and (c) parents' understanding of the officially prescribed consequences of behaviour identified as non‐tolerable. Implications of the findings are discussed with regard to professional practice.     

Know your personal computer

This article surveys personal computing with the IBM personal computer as a platform to discuss details of hardware.     

Cars beyond Otto's internal combustion engines

Road transportation as an important requirement of modern society is presently faced with restrictions in mainly two respects, namely the ever tightening emission legislation as well as the availability of petroleum fuels, and as a consequence the fuel cost. But in any review of power sources for future road transport vehicles, the performance of the existing internal combustion engine is likely to be the yardstick against which other power sources will be compared. The power sources most likely to provide favourable comparison are those, which can display comparable range and speed, long and reliable life and manufactured at a cost comparable to petrol engine. A vehicle which fails in any of these requirements is unlikely to achieve anything but a niche market share. This article is an appraisal of a variety of proposed electrochemical systems, viz. rechargeable batteries, fuel cells and supercapacitors, for an electric car. It is surmised that a viable electric car could be powered with a fuel cell to provide power for cruising and climbing coupled in parallel with a supercapacitor/battery bank to deliver additional short-term burst-power during acceleration. A K Shukla is a Professor at the Solid State and Structural Chemistry Unit, Indian Institute of Science, Bangalore. His current research interests are in materials electrochemistry with special emphasis on batteries, fuel cells and supercapacitors.     

Know your personal computer

This article surveys system software organization in personal computers using the IBM personal computer software. Details of the hierarchical levels of the system software organization are explained.