Invalid Method Research Articles

Bit-sequences: an adaptive cache invalidation method in mobile client/server environments

In this paper, we present Bit-Sequences (BS), an adaptive cache invalidation algorithm for client/server mobile environments. The algorithm uses adaptable mechanisms to adjust the size of the invalidation report to optimize the use of a limited communication bandwidth while retaining the effectiveness of cache invalidation. The proposed BS algorithm is especially suited for dissemination-based (or “server-push”-based) nomadic information service applications. The critical aspect of our algorithm is its self-adaptability and effectiveness, regardless of the connectivity behavior of the mobile clients. The performance of BS is analyzed through a simulation study that compares BS's effectiveness with that of a hypothetical optimal cache invalidation algorithm.

Scientifically valid leaching of coal conversion solid residues to predict environmental impact

The disposal of wastes from energy production, particularly solid wastes from coal conversion processes, requires a thorough understanding of both the waste and the environment. Environmentally responsible disposal requires an appreciation and understanding of all of the complex interactions that can occur between the waste and the environment. Additionally, the importance of site characterization cannot be overemphasized, since local geology plays such an important part in the transport and fate of potentially problematic trace elements and other contaminants. Waste characterization techniques must be scientifically valid, comprehensive, and thorough. The focus of this paper is on the importance of the selection and application of scientifically valid methods for characterizing wastes. Selection criteria for scientifically valid evaluation techniques for the characterization of coal conversion solid waste are discussed, and guidelines for selection are provided. The importance of understanding all possible environmental consequences must be considered, including water-to-waste and waste-to-waste interactions, as well as leachate-to-sediment interactions. The importance of the philosophical integration of all aspects of disposal, site characterization, and waste characterization are discussed. The application of scientifically invalid characterization methods or incomplete site characterization is poor science at best and can lead to false conclusions.

Antibiotic Therapy for Otitis Media With Effusion

CANTEKIN et al 1 have recently challenged our 1987 New England Journal of Medicine report 2 that in infants and children with otitis media with effusion (secretory otitis media), amoxicillin treatment modestly increased the likelihood of resolution. From reanalyses of our clinical trial data, Cantekin et al concluded instead that amoxicillin had been no more efficacious than placebo, and that otoscopic diagnoses in our trial had been biased. Further, they cited reports indicat[ing] that antimicrobial treatment is not effective even for acute otitis media. To arrive at these positions, Cantekin et al committed a series of methodological improprieties, invoked fallacious concepts and invalid assumptions, and inadequately represented the findings of cited studies. Space constraints preclude our discussing these fully, but the most important were the following: Post Hoc Use of an Altered and Invalid Method for Determining Outcome. —Our amoxicillin trial was conducted from 1981 through 1984. Its original protocol

Psychological factors in the irritable bowel syndrome.

This paper reviews recent psychological studies of patients with the irritable bowel syndrome (IBS) or 'functional abdominal pain'. Many studies have used unreliable or invalid methods of assessment and some have confused personality with treatable psychiatric illness. Reliable and valid measures have indicated that 40-50% of patients with recently diagnosed functional abdominal pain have demonstrable psychiatric illness; these patients have a worse prognosis than those who are psychologically normal. When psychiatric disorder is diagnosed in a patient with IBS there are three possibilities: (1) The patient may have developed abdominal and psychiatric symptoms simultaneously in which case treatment of the latter may relieve the bowel symptoms. (2) Psychiatric disorder may precipitate increased concern about bowel symptoms, and consequent attendance at the gastroenterology clinic, of those with chronic mild symptoms. In this case it is illness behaviour, rather than abdominal symptoms, that is caused by the anxiety/depression. (3) Those with chronic neurotic symptoms as part of their personality must be screened for organic disease if they have a fresh onset of bowel symptoms; but they are at high risk of becoming persistent clinic attenders. Further research is needed to clarify when psychological abnormalities play a role in the aetiology of IBS and when they are coincidental, but lead to illness behaviour. The role of psychological factors in the aetiology of the irritable bowel syndrome (IBS) is far from clear, but a review of the literature suggests that some consistent patterns are emerging in spite of methodological problems. There have been three major defects with studies that have linked IBS with neurotic symptomatology. First, the measurement of psychological factors has generally been imprecise. Second, most studies have considered IBS patients as a single group, without making allowance for differing symptom patterns. Third, conclusions have been drawn about hospital samples and extrapolated to all IBS subjects, without taking account of factors which affect consulting behaviour. Most studies have been concerned with psychological factors so these will be considered in most detail.

Effectiveness of community preventive programs on improving oral health.

Although sizable community efforts in the United States have been made to educate children and adults about periodontal disease and its control, valid inferences regarding their effectiveness cannot be made because, for the most part, invalid methods of evaluation have been used. Confusion about these methods may exist because there has been little conviction that the available methods of control will stop the progress of periodontal pathology. Many recommended oral hygiene practices are probably applicable only to certain motivated individuals. An effective, comprehensive community-program for the prevention of periodontal disease remains to be developed. It is unlikely that sufficient sums of money and personnel could be diverted from the budgets of lesser-developed countries to initiate mass oral hygiene programs. Therefore, it appears that, organized community efforts appear to be promising only for the control of dental caries. However, it must be remembered that community fluoridation may not be applicable in many countries. Therefore, new strategies and vehicles to bring fluorides to all segments of the world's population are needed.

Maternal smoking, birth weight, infant death, and the self-selection problem

Several aspects of the relationship between maternal smoking and birth weights of infants are discussed. No satisfactory explanation for Yerushalmy's results has been given other than that low birth weight appears to relate more to the smoker than to the smoking. Recent studies by Silverman support this position. The possibility that nicotine may induce a physiologic response that serves to alleviate bioenergetic deficiency in some individuals should not be overlooked. In this view, both smoking and low birth weight are symptoms of deficient maternal bioenergetic systems.

Use of uniform-field values of Townsend's α to predict current multiplication in nonuniform fields

Some earlier investigations had indicated that the amount of ionisation observed in nonuniform fields was more than that predicted by the use of uniform-field values of α/p to evaluate current multiplication. The reasons for this discrepancy between theory and experiment were attributed to the variation (> 2%) of electric-field intensity over an electron mean free path or to the nonequilibrium of electrons with fields at high E/p. The results and methods of previous investigators are considered and analysed in the paper, and the reasons for the apparent discrepancy are found to be due to the use of inappropriate values of α/p to evaluate the quantity exp ∫ αdx and due to invalid methods of analysis. A new method of analysis for nonuniform fields is proposed.

A Method of Evaluating Growth Stocks

IN THE PAST FEW YEARS the term company has been frequently used by Security Analysts and investors. Some of the characteristics ascribed to growth companies include: (1) rapid sales increase over an extended period of time; (2) new product development of an alert research department; (3) large capital expenditures; (4) high depreciation charges; (5) low dividend payments compared with earnings; (6) frequent stock dividends; and (7), above all, aggressive and able management. In short, if a company has several of the above attributes, it is usually accepted as a growth company. Consequently, its stock reflects the expectation of a continued growth of earnings by selling at a high priceearnings ratio. Further, as is often the case, Analysts become so bemused by a growth company that they often fail to study the basic factor: the growth rate of net income. It is believed that the growth rate of net income of a company should be calculated for a 10-year period. This can be compared profitably with similar companies in the same industry. In addition, it is possible by using the growth rate to project the past 10 years' earnings trend forward another 10 years and estimate the earnings of a company at that time. This would of course assume that the same rate of growth is maintained. While the projection of past records into the future earnings might seem to be an invalid method of estimating growth, it does serve as a tool for comparison of various securities. We will endeavor to show that it is useful to compare the estimated earnings of several companies in 1968 based on a formula, together with their prices at the end of 1959. An example might be taken of the growth rate of earning for International Business Machines Corporation for the years 1939-1948, as shown in Table L. Using Table l's correlation techniques, a measure can be found that shows the annual rate of earnings growth. Applying Glover's tables for the value of M or 5.67, see Table II, it will be seen that r equals 1.160. This means that the annual rate of increase of earnings of International Business Machines Corporation from 1939 to 1948 was about 16%. Since it is assumed that the Table II calculation was made in 1949, a time when the earnings for 10 years from 1939 through 1948 were available, it might be interesting to forecast the earnings for 1958. This can be done by selecting the equation to the simple exponential curve, as follows: y arx.

XV. The condensation of a perfect Bose-Einstein gas.—II

Abstract In an earlier paper formulae were given for the macroscopic behaviour of a perfect Bose-Einstein gas. In this paper formulae are given for the mean occupation numbers of the energy levels and for the fluctuations in these numbers. These formulae are in agreement with those obtained by earlier (invalid) methods.

The production of polarized X-rays

In theoretical studies of the interaction of X-rays and matter it is often necessary or convenient to deal first with a plane polarized beam of X-rays. In the laboratory such theoretical conditions cannot often be realized solely because of the extreme weakness of any beam of polarized X-rays normally available. It would appear, however, that some facts can be established only by actual use of polarized X-rays. For example, in order to establish that X-rays are scattered as if atoms were spherically symmetrical wholes, it would appear necessary to control both the direction of the electric vector, by using polarized X-rays, and the orientation of the atoms, by using a single crystal. The use of either a single crystal and ordinary X-rays with random orientation of the electric vector or the use of polarized X-rays with a crystal powder and random orientation of the crystals would appear to simulate the conditions of spherically symmetrical scattering. The technical difficulties of working with polarized X-rays are in all experiments very great. Inference as distinct from actual experiment is however an invalid method of establishing physical facts. In theoretical treatments of scattering of X-rays by crystals it is possible to derive results agreeing with those of experiments with unpolarized X-rays, by using postulates involving polarized X-rays. For example, an unpolarized beam can be treated as two polarized beams of equal amplitude, polarized one in the plane of incidence and one normal to it. The results are then recombined at the end. This purely mathematical device gives no facts about polarized X-rays and is in some circumstances in conflict with the experimental results of Mark and Szilard.