Chance Coincidence Research Articles

The Prevalence of Immature Respiratory Control in a Neonatal Population

Cot death could be the result of chance coincidence of an adventitious challenge and a baby ill-equipped to meet it. This work was designed to test the hypothesis that there is a subpopulation of babies who lack the appropriate responses to hypoxia and hypercapnia which would enable them to overcome the effects of, for instance, nasal obstruction. The responses of 630 babies to air mixtures which induced significant changes in ventilation in the overwhelming majority, were recorded in a short protocol in which both the addition and withdrawal of hypercapnia and of hypoxia were effected. The results of each test were placed in one of five categories; in 13.6% there was no response to hypoxia, and in 2% the ventilation fell in hypoxia to a significant degree. The study confirms the existence of a subgroup of normal babies with little defence to the respiratory loading of mild upper respiratory tract infections.

Amorphous materials at low temperatures: why are they so similar?

In addition to the well-known qualitative similarity of behavior of a wide range of amorphous materials, one dimensionless quantity, the reduced attenuation of transverse ultrasound, shows a quantitative universality whose explanation in terms of the standard “tunnelling two-level system” model would seem to require a totally unbelievable degree of chance coincidence. In addition, while the height of the “plateau” in the thermal conductivity is material-specific, the higher-temperature behavior is consistent with universal behavior. I sketch the outlines of a scenario which holds out hope of understanding these observations.

Analysis of mean lifetime for capture of neutrons in boron-loaded plastic scintillators

The commercial availability of boron-loaded organic scintillators has led to the development of neutron detectors that operate as “electronically” black, totally absorbing spectrometers. The key to the enhanced spectroscopy is the delayed capture of nearly thermalized neutrons by 10B that can occur within a few microseconds after the energy pulse from prompt proton recoils. Accurate information regarding the mean lifetime is important for correct setting of the timing logic of the detection system to obtain good neutron detection efficiency with a low chance coincidence rate. In this paper we present an analysis of the mean lifetime for neutron capture for the boron-loaded plastic BC454. Measurements of the capture time constant obtained with a 7.62 cm diameter, 10.16 cm long detector are compared with values computed with the time-dependent Monte Carlo neutron transport code MCNP. Additional analyses using MCNP examine the dependence of the mean lifetime on the boron concentration, the detector's dimensions and the incident neutron energy.

Greenlandic in comparison

Summary The first descriptive grammar of Greenlandic Eskimo was published in 1760 by Paul Egede, continuing the work of his father, Hans, and his missionary collaborator, Albert Top. Curiously, however, the comparative study of Greenlandic had already been inaugurated in 1745, when Marcus Wöldike (1699–1750), professor of theology at the University of Copenhagen, read a remarkable paper to the Kiøbenhavnske Selskab af Lœrdoms of Videnskabers Elskere, published next year in the proceedings of that Society. Based on information obtained from the Egedes, Wöldike presented a grammar of Greenlandic in summary form and compared Greenlandic to about two dozen other languages on some sixty phonological, morphological, and syntactic criteria. As it turned out, Greenlandic was rather similar to Hungarian, sharing with it a great many features (especially such as Hungarian did not share with European languages such as Icelandic, Norwegian, Danish, English, German, Irish, Welsh, Breton, Latin, Italian, French, Ancient Greek, and Slavonic) and showing preciously few differences. American languages, represented by Tupi, Carib, Huron, Natick, and Algonkin, were found to differ considerably from Greenlandic; and Hebrew, Arabic, and Turkish did not much better. Lapp and Finnish came out as close structural relatives of Hungarian – which amounted to the first published demonstration of the Finno-Ugric hypothesis, antedating Saj-novics’s of 1770 and Gyarmathi’s of 1799. For Wöldike the large-scale agreements especially between Greenlandic and Hungarian were no inexplicable chance coincidences. The explanation he suggested was not typological, drawing on necessary correlations of the structural features shared, but historical. Rather than positing a common Ursprache, as was and continued to be the fashion, however, he invoked diffusion within a Sprachbund, localized, somewhat vaguely, in Tartary, from where the Greenlanders and Hungarians (and Lapps and Finns too) had supposedly migrated to their present habitats.

Transverse momentum distributions and particle correlations from EMU05

Transverse momentum distributions and multi-particle correlations of charged particles in 200 GeV/AMU heavy-ion collisions are studied with the Magnetic-Interferometricr-Emulsion-Chamber (MAGIC) for central collision events in 16O + Pb and 32S + Pb interactions. The P T distribution of negative-charged particles below 1 GeV/c fits a single exponential, while that of positive particles contains additional contributions of both highand low-P T particles. The like-sign, two particle correlations indicate HBT interferences, while that of the unlike-sign pairs possibly suggests other components. The apparent, multi-particle, charge-sign clustering is studied with the run-test and with Monte Carlo simulations. Some of the data are consistent with chance coincidence and the HBT interference.

Fluorescence in the Outer Atmospheres of Red Giant Stars

The outer atmosphere of a cool red giant star is an ideal locale for the operation of line fluorescence processes. Low plasma densities imply low rates of collisional de-excitation and thus allow radiative decay of levels populated by selective radiative pumping. There are many strong sources of line radiation (i.e. possible pumps) and numerous possible upward transitions from highly populated low-lying levels of abundant elements such as Fe II, thus providing many chance coincidences between potential pumps and lines to be pumped. These conditions ensure that many of the chromospheric emission features observed in the UV spectrum of such a star are affected by fluorescence. Many of the observed emission features originate from energy levels populated solely by radiative fluorescent excitation, including strong lines of S I, O I, CO, Ni II, Si I, Fe I and Fe II, as well as weaker lines from Cr II and Co II. Important pumps active in these atmospheres include hydrogen Lyman alpha, and individual lines of 0 I, C I, Si II, Fe II, and Mg II. In the case of Fe II, there are many additional features arising from upper levels whose populations, although primarily maintained by collisions, are also significantly affected by radiative fluorescent excitation. In fact, there may be virtually no level in Fe II not affected to one degree or another by direct decays or cascades down from levels populated by fluorescence, driven either by Lyman alpha or, in some cases, by lines of Fe II itself (“self-fluorescence“).

Optimum time for gamma-gamma coincidence measurements of decaying sources

Assuming that the true and chance coincidences between the two energy-selected radiations are measured simultaneously, the measurement time is optimized with respect to the initial activity of the decaying source and its half-life as well as with respect to the steady activity of the interfering background radiation.

An X-ray survey for pre-main-sequence stars in the Taurus-Auriga and Perseus molecular cloud complexes

Seventy-five fields from the Einstein X-Ray Observatory IPC detector between 3h and 5h right ascension and 15 deg and 35 deg declination are examined to search for X-ray-emitting low-mass pre-main-sequence (PMS) stars. Six such stars were previously found; they appear to be similar to T Tauri stars but without dense circumstellar envelopes or winds. Finding charts are presented for 59 X-ray sources that may be PMS stars. While some are likely to be spurious X-ray sources, chance coincidences with unrelated stars, or non-PMS stellar sources such as RS CVn type binaries, approximately half are probably X-ray-selected PMS stars.

Schumpeterian Analysis, Supply-Side Economics And Macroeconomic Policy In The 1920S

Economists who are passionately determined not to admit that policies answering to their social and moral vision, particularly fiscal policies of anticapitalist tendency, can possibly interfere with the working of the economic system, will no doubt hold that there was mere chance coincidence between that sociopolitical pattern and the economic results achieved in this country during the twenties, and between the different setup and the different results in England or Germany … we cannot, however, neglect the possible inference to the contrary. [J.S.Schumpeter, 1939, p. 289]

X-ray emission possibly coincident with the radio tail of PKS 0301 - 123

X-ray, radio, and optical observations are reported for a very poor cluster of galaxies containing the radio source PKS 0301 - 123. A long, 100,000 second X-ray observation using the Einstein Observatory's IPC resulted in the serendipitous discovery of a peculiar extended X-ray morphology associated with the poor cluster. The X-ray emission is extended in the same direction and is approximately the same length as the radio-tailed source, PKS 0301 - 123, which was mapped at 6 and 20 cm with the VLA. Optical redshift observations with the KPNO IIDS on the 2.1 m telescope confirm the identification of the X-ray and radio emission with the poor cluster at z = 0.1. It is argued that the X-ray extension is unlikely to be a chance coincidence of a background source projected onto the foreground cluster. Therefore, four possible mechanisms which might physically link the X-ray and radio emission are considered: thermal bremsstrahlung from a cluster with a flattened potential well; inverse Compton scattering of the relativistic electrons in the radio source, X-ray synchrotron radiation; and heating the cluster gas by the turbulent wake of the radio galaxy. The prospects for future observations of such X-ray/radio coincidences are briefly discussed.

Gamma-ray burster recurrence time scales

In the decade since gamma-ray bursters (GRBs) were discovered by Klebesadel et al. (1973), many models have been proposed to explain the GRB phenomenon. A difficulty is related to the small number of predictions which would make it possible to evaluate the models. One verifiable prediction is the recurrence time scale, tau-gamma. One method to measure tau-gamma is to look for possible cases of recurrence as indicated by overlapping error boxes. The analysis considered in the present investigation is composed of three procedures. One of these involves a search through known error regions for cases where the error regions overlap. In addition, the number of overlaps expected by chance coincidence alone has been determined, and a calculation has been performed regarding the number of overlaps which are expected due to recurrence for various assumed tau-gamma and luminosity functions.

Arctic Wolf Attacks Scientist -- A Unique Canadian Incident

Recent biological studies have concluded that North American wolves are rarely dangerous to humans. To date the scientific literature contains only one well-documented account of a vicious wolf attack on a man, an incident that took place in northwestern Ontario in 1942. A much earlier attack, however, took place in February 1915 on the Coppermine River in Canada's Arctic. Though mentioned in two publications in the 1920s, this incident has escaped the scientists' notice and is reported again now with additional information. In this encounter a large white wolf ( Canis lupus mackenzii Anderson) entered the campsite of members of the 1913-18 Canadian Arctic Expedition and on discovery attacked one of the scientists. The incident is unique for three reasons: (1) the existence and reliability of eyewitness accounts of the attack in the unpublished diaries of two of the scientific members, one of whom was the wolf's victim; (2) the chance coincidence that the man who shot the wolf was a mammalogist responsible for collecting arctic specimens for the National Museum of Canada in Ottawa; and (3) the existence today, 70 years later, of the wolf mount in the museum's research collection. Key words: Arctic, wolf, Rudolph Anderson, Diamond Jenness, Frits Johansen, Canadian Arctic Expedition

Common lines in the rest-frame absorption-line spectra of QSOs?

Libbyet al. (1984) have studied the absorption-line data for 13 QSOs in the rest-frames of the QSOs. It is shown that the number of groups in which 5 lines or more lie within a wavelength interval of 1.0 A found by these authors is insignificantly different from that that would be expected from chance coincidences. Consequently, there is no evidence that the rest-frame wavelengths at which these groups occur have any special significance.

Predicted secondary structure and hydrophobic cores of T-cell (TCGF or IL-2) and platelet-derived growth factors as well as of transforming protein p28 sis of simian sarcoma virus are similar to those of interferons

Estimation of a content of secondary structures from amino acid composition of IL-2 (TCGF), PDGF and transforming protein p28 sis of simian sarcoma virus by means of the previously suggested nomograms (V. P. Zav'yalov and A. I. Denesyuk (1982) Immunol. Lett. 4, 7–14) allowed us to conclude that a dominant secondary structure of these proteins should be α-helix. Its content in PDGF and p28 sis was estimated to be ≈50%, and that in IL-2 to be 50–65%. The content of β-pleated structure in PDGF and p28 sis does not exceed 10%, and that in IL-2 is found to be 20–30%. In all the proteins investigated five α-helical segments can be distinguished, of which one of the surfaces contains clusters of bulky hydrophobic side chains. As the number of α-helical segments satisfying the principles of packing into a hydrophobic core as well as the overall length of a polypeptide chain of IL-2 and PDGF coincided with those for IFNs, it was decided to arrange α-helices of these proteins into a globular structure by analogy with IFNs (V. P. Zav'yalov and A. I. Denesyuk (1984) Doklady Akad Nauk S.S.S.R. 275, 242–246). In consequence, identical side chains of amino acid residues were found at 9 out of 29 positions in hydrophobic cores of IFN-β and IL-2, p28 sis (PDGF), respectively. Thus the homology of hydrophobic cores of the proteins compared is >30%. Probability of chance coincidences of amino acid residues in the hydrophobic cores of p28 sis (PDGF) and IFN-β is found to be 0.03, and that deduced from comparison of IL-2 and IFN-β is 0.05. It was concluded that IL-2, PDGF and p28 sis must have a three-dimensional structure generally similar to that of IFNs.

Half lives of the 482.2 keV and 615.3 keV levels in181Ta

The half lives of the excited levels at 482.2 keV and 615.3 keV in181Ta have been measured by the delayed coincidence technique. In the nanosecond time range (482.2 keV level) the most serious sources of errors are jitter, walk and drift phenomena. To minimize those the time pick-off has been defined carefully by means of modern fast timing detectors and electronics. In the microsecond time range (615.3 keV level) the ratio of true delayed coincidences to chance coincidences influences considerably the final accuracy of the half-life measurements. It has been reduced as much as possible. From a series of independent measurements half lives ofT 1/2=(10.67±0.05) ns andT 1/2=(17.64±0.14) μs have been deduced for the 482.2 keV and 615.3 keV levels, respectively. The results have been compared with other values published before.

The quasar PKS 0237-233: Chance coincidences and the alleged co redshift systems

It is shown that the number of redshifted CO absorption-line systems which are found in the spectrum of the quasar PKS 0237-233, using the rules of Varshalovich and Levshakov (1981), differ insignificantly from that that would be expected from chance coincidences. Consequently, the CO systems proposed by Varshalovich and Levshakov have no physical reality.

Momentum flux invariance in the solar wind

view Abstract Citations (18) References (2) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Momentum flux invariance in the solar wind Mullan, D. J. Abstract On the basis of data from the ISEE C satellite, the results of Steinitz and Eyni (1980), Eyni and Steinitz (1981), and Steinitz (1981) are corroborated. In addition, the scope is extended to another phase of the solar cycle when solar wind conditions are quite different. The temperature of the wind is seen to be related to the velocity in a way that alters with time. This indicates that the rate of energy deposition, or its distribution between thermal and kinetic forms, fluctuates during the solar cycle. On the other hand, the coefficients in the density-velocity relation have apparently remained unchanged between solar minimum and solar maximum conditions, thereby keeping the momentum flux remarkably constant. Barring the possibility of chance coincidence, the momentum flux in the solar wind may be even more invariant than Steinitz and Eyni suspected. This strengthens their conclusion that the momentum-flux invariance derives from initial constraints determining the evolution of the solar wind. Publication: The Astrophysical Journal Pub Date: September 1983 DOI: 10.1086/161296 Bibcode: 1983ApJ...272..325M Keywords: Momentum Transfer; Solar Wind Velocity; International Sun Earth Explorer 3; Invariance; Plasma Density; Plasma Temperature; Solar Physics full text sources ADS |

Half-life measurements of excited levels in the nanosecond and microsecond region

The application of the delayed-coincidence technique to accurate half-life measurements of excited levels in the nanosecond and microsecond region is described. In order to achieve an overall uncertainty of ⩽ 1% on the final values of the half lives a series of precautions depending on the time region have to be taken. In the nanosecond time range the most serious sources of errors are jitter, walk and drift phenomena. To minimize those the time pickoff has to be defined carefully by means of modern fast timing detectors and electronics. In the microsecond time range the ratio of true delayed coincidences to chance coincidences influences considerably the final accuracy of the half-life measurements. It must be the aim to reduce the chance-coincidence rate as much as possible. In both cases the analysis of the experimental data is of critical importance. The choice of the analysis region will be discussed. Time calibration and a careful consideration of system linearity, short- and long-term stability of the entire experimental system, are of great importance. Regular checks of these quantities performed during the measurements cycles allow estimates of the systematic uncertainties. The successful application of the experimental procedures mentioned above yielded the following half-life values for the 37.1-keV level in 121Sb (3.46 ± 0.03) ns, the 81-keV level in 133Cs (6.23 ± 0.03)ns, the 482.18-keV level in 181Ta (6.05 ± .012) μs 23.87-keV level in 119Sn (18.03 ± 0.07)ns, the 6.21-keV levelin 181Ta (6.05 ± 0.12) μs and the 615.25-keV level in 181Ta (17.64 ± 0.14) μs.

Near Infrared and Radio Observations of Distant Galaxies

This paper is concerned with the distant radio galaxies in a sample of bright sources selected at 178 MHz by Laing, Riley & Longair (1982). This sample is 96% complete for sources with θ < 10′ and the bias of the 3CR catalogue against sources of large angular size has also been reduced. Deep optical searches have located many candidate identifications, but the probability of a chance coincidence with an unrelated object is appreciable, especially in the faintest cases, unless the area to be searched is small. We have therefore mapped the sources with candidate identifications having V > 20, using the VLA at a wavelength of 6 cm (Laing, Owen & Puschell, in preparation), in order to search for radio cores. We have so far located cores in 16/23 sources and set 5σ upper limits of 0.6 mJy for the remainder. None of the cores had been detected previously. In all cases, the cores coincide with optical objects, although one source (3C 340) had been misidentified. Several ambiguities have now been resolved.

Electronics syteem for positron computerized tomography “positologica” dedicated to head studies

The design of an electronic system for a new positron camera for head studies is presented. The positron camera, adopting bismuth germanate crystals, was developed aiming at high spatial resolution by improvement of linear sampling with a detector arrangement with non-uniform spacing and rotation of the detector gantry. To improve image quality at high counting rates, false events can be eliminated by delayed coincidence circuits that record chance coincidences and by multipli-coincidence rejection circuits. The width of the delayed coincidence time window is exactly equal to that of the prompt coincidence time window which allows direct subtraction of chance coincidence events. Coincidence time windows are controlled by a single DC reference voltage. A rotary photo-coupler was developed that transmits signals from the rotary part of the gantry to the computer interface on the stationary part of the gantry.