Showing papers by "University of Maryland, College Park published in 1974"

Lepton Number as the Fourth Color

Abstract: Universal strong, weak, and electromagnetic interactions of leptons and hadrons are generated by gauging a non-Abelian renormalizable anomaly-free subgroup of the fundamental symmetry structure $\mathrm{SU}{(4)}_{L}\ifmmode\times\else\texttimes\fi{}\mathrm{SU}{(4)}_{R}\ifmmode\times\else\texttimes\fi{}\mathrm{SU}({4}^{\ensuremath{'}})$, which unites three quartets of "colored" baryonic quarks and the quartet of known leptons into 16-folds of chiral fermionic multiplets, with lepton number treated as the fourth "color" quantum number. Experimental consequences of this scheme are discussed. These include (1) the emergence and effects of exotic gauge mesons carrying both baryonic as well as leptonic quantum numbers, particularly in semileptonic processes, (2) the manifestation of anomalous strong interactions among leptonic and semileptonic processes at high energies, (3) the independent possibility of baryon-lepton number violation in quark and proton decays, and (4) the occurrence of ($V+A$) weak-current effects.

Environmental Preservation, Uncertainty, and Irreversibility

Abstract: A number of recent contributions by economists have provided a clear insight into the causes of the varied forms of environmental deterioration, and have also suggested, implicitly or explicitly, policies for more efficient management of environmental as well as other resources.1 Yet, as Allen Kneese has pointed out in a review of empirical studies of pollution damages, “a general shortcoming of [these studies] has been that they have treated a stochastic or probabilistic phenomenon as being deterministic.”2 The purpose of this paper is to explore the implications of uncertainty surrounding estimates of the environmental costs of some economic activities. It is shown in particular that the existence of uncertainty will, in certain important cases, lead to a reduction in net benefits from an activity with environmental costs. In such cases the implication for an efficient control policy will generally involve some restriction of the activity.

Structural controllability

Abstract: The new concepts of "structure" and "structural controllability" for a linear time-invariant control system (described by a pair ( A,b )) are defined and studied. The physical justification of these concepts and examples are also given. The graph of a pair ( A,b ) is also defined. This gives another way of describing the structure of this pair. The property of structural controllability is reduced to a property of the graph of the pair ( A,b ). To do this, the basic concept of a "cactus" and the related concept of a "precactus" are introduced. The main result of this paper states that the pair ( A,b ) is structurally controllable if an only if the graph of ( A,b ) is "spanned by a cactus." The result is also expressed in a more conventional way, in terms of some properties of the pair ( A,b ).

Atmospheric concentrations and sources of trace metals at the South pole.

Abstract: The chemical composition of atmospheric particulate material collected at the geographic South Pole indicates that Al, Sc, Th, Sm, V, Mn, Eu, Fe, La, Ce, Co, Cr, Na, K, Mg, and Ca are derived from either crustal weathering or the ocean. The relatively volatile elements Zn, Cu, Sb, Se, Pb, and Br are apparently derived from other sources. Because of their volatility, vapor-phase condensation or a high-temperature dispersion source is suspected for these elements or their compounds.

Black hole in a uniform magnetic field

Abstract: Using the fact that a Killing vector in a vacuum spacetime serves as a vector potential for a Maxwell test field, we derive the solution for the electromagnetic field occurring when a stationary, axisymmetric black hole is placed in an originally uniform magnetic field aligned along the symmetry axis of the black hole. It is shown that a black hole in a magnetic field will selectively accrete charges until its charge becomes $Q=2{\mathrm{Bb}}_{0}J$, where ${B}_{0}$ is the strength of the magnetic field and $J$ is the angular momentum of the black hole. As a by-product of the analysis given here, we prove that the gyromagnetic ratio of a slightly charged, stationary, axisymmetric black hole (not assumed to be Kerr) must have the value $g=2$.

Should the History of Science Be Rated X?: The way scientists behave (according to historians) might not be a good model for students.

Abstract: I suggest that the teacher who wants to indoctrinate his students in the traditional role of the scientist as a neutral fact finder should not use historical materials of the kind now being prepared by historians of science: they will not serve his purposes. He may wish to follow the advice of philosopher J. C. C. Smart, who recently suggested that it is legitimate to use fictionalized history of science to illustrate one's pronouncements on scientific method (56). On the other hand, those teachers who want to counteract the dogmatism of the textbooks and convey some understanding of science as an activity that cannot be divorced from metaphysical or esthetic considerations may find some stimulation in the new history of science. As historian D. S. L. Cardwell has argued (57, p. 120): . . . [I]f the history of science is to be used as an educational discipline, to inculcate an enlightened and critical mind, then the Whig view . . . cannot do this. For it must emphasize the continuities, the smooth and successive developments from one great achievement to the next and so on; and in doing so it must automatically endow the present state of science with all the immense authority of history. He suggests that the critical mind might be inhibited by seeing the present as the inevitable, triumphant product of the past. The history of science could aid the teaching of science by showing that "such puzzling concepts as force, energy, etc., are man-made and were evolved in an understandable sequence in response to acutely felt and very real problems. They were not handed down by some celestial textbook writer to whom they were immediately self-evident" (57, p. 120). The past may give some hints on how to survive the most recent recurrence of public hostility to science. Rather than blaming historians such as Kuhn for encouraging antiscientific attitudes, as one physicist did in a public address in 1972 (58), one might consider this criticism of the older style of science history, published in 1940 by W. James Lyons (59, p. 381): The historians of science are responsible, it would appear, for the unpopularity of science among those most acutely affected by the depression. In their clamor to enhance the scientific tradition, and hoard for science all credit for the remarkable and unprecedented material advances which studded the century and a quarter preceding 1930, these historians have been more enthusiastic than accurate . . . science emerged [in the popular mind] as the most prominent force responsible for making this modern world so startlingly different from all preceding ages. Thus when, for many people, the modern world, in spite of all its resources, began to slip from its role of "best of all imaginable worlds," science came in for a proportionate share of blame. Had a more accurate picture of the part science has played been presented, science would not now be the object of so much suspicion and resentment. In more recent times, hostility to science has been intensified by the image of the "objective," robot-like scientist lacking emotions and moral values. If the new approach to the history of science really does give a more realistic picture of the behavior of scientists, perhaps it has a "redeeming social significance." Then, rather than limiting the conception of science to the strict pattern allowed by traditional local standards, one might try to change those standards in such a way as to reflect the freedom that the boldest natural philosophers have always exercised.

Digital Straight Line Segments

Abstract: It is shown that a digital arc S is the digitization of a straight line segment if and only if it has the "chord property:" the line segment joining any two points of S lies everywhere within distance 1 of S. This result is used to derive several regularity properties of digitizations of straight line segments.

Patterns in pattern recognition: 1968-1974

Abstract: This paper selectively surveys contributions to major topics in pattern recognition since 1968. Representative books and surveys pattern recognition published during this period are listed. Theoretical models for automatic pattern recognition are contrasted with practical,, design methodology. Research contributions to statistical and structural pattern recognition are selectively discussed, including contributions to error estimation and the experimental design of pattern classifiers. The survey concludes with a representative set of applications of pattern recognition technology.

Narrow-band multiple-coupled cavity synthesis

Abstract: A synthesis procedure of identical narrow-band high-Q cavities is presented. The procedure handles multiple couplings in a noncascaded form by synthesizing coupling impedances in one step. Necessary and sufficient conditions for realizability of singly and doubly terminated networks are obtained. An example of a sixth-order elliptic function waveguide filter is included.

Effect of Viscosity on Bacterial Motility

Abstract: The behavior of a number of motile flagellated bacteria toward viscosity characteristics of their fluid environments was observed. All showed an increase in velocity (micrometers per second) in more viscous solutions. Velocity reached a maximum at a characteristic value, however, and thereafter decreased with higher viscosities. Peritrichously flagellated bacteria had maximum velocities at higher viscosities than polarly flagellated bacteria. Effects of temperature, and possible utilization of chemical constituents in the viscous solutions, were studied and found to be negligible factors under the experimental conditions used. Different agents produced the same phenomenon, thus indicating that there probably were no chemically induced metabolic effects. Loss of available water and the possibility of a variable energy supply to the flagellar propulsive system were considered but are believed minimal. Theoretically derived thermodynamic equations were utilized and suggest that the conformation of the flagellar helix affects efficiency of propulsion. Such a relationship between helix waveform and velocity was experimentally observed with Thiospirillum jenese.

A Threshold Selection Technique

Abstract: Threshold selection for picture segmentation is relatively easy when the frequency distribution of gray levels in the picture is strongly bimodal, with the two peaks comparable insize and separated by a deep valley. This report describes a method of handling cases in which the peaks are very unequal in size and the valley is broad. A Laplacian operation is applied to the picture to determine points that lie on or near the edges of objects. Threshold selection becomes easier when the frequency distribution of gray levels of these points is used.

On the poisson equation with intersecting interfaces

Abstract: The interface problem is considered for the Poisson equation in two independent variables, The interface curves, along which jump conditions are prescribed, are allowed to intersect, The second derivatives of solutions of the interface problem are shown to lie in a certain "twisted" Soboiev space. The solution operator is shown to be a closed, densely defined, operator in L2 whose domain can be determined exactly

Rotating cylinders and the possibility of global causality violation

Abstract: In 1936 van Stockum solved the Einstein equations ${G}_{\ensuremath{\mu}\ensuremath{ u}}=\ensuremath{-}8\ensuremath{\pi}{T}_{\ensuremath{\mu}\ensuremath{ u}}$ for the gravitational field of a rapidly rotating infinite cylinder. It is shown that such a field violates causality, in the sense that it allows a closed timelike line to connect any two events in spacetime. This suggests that a finite rotating cylinder would also act as a time machine.

Temperature variation of ferromagnetic relaxation in the 3 d transition metals

Abstract: We report measurements on the ferromagnetic resonance in single-crystal specimens of hcp Co, Ni, and Fe. The linewidth data have been analyzed to obtain the temperature dependence of the ferromagnetic relaxation frequency $\ensuremath{\lambda}$. These temperature dependences can be qualitatively understood in terms of recent theories. On the other hand, it turns out that in some cases $\ensuremath{\lambda}$ is essentially constant over wide ranges of temperature. This behavior is unexplained at present.

Adjacency in digital pictures

Abstract: Let S be a subset of a digital picture, and let s be the complement of S. It is well known that the connected components of S and s, under the relation “is adjacent to,≓ form a tree, and algorithms for constructing this tree have been devised. The main purpose of this paper is to prove that the components do form a tree, and in the process, to provide a basis for proving the validity of the tree-constructing algorithms.

Characterizations of Reducible Flow Graphs

Abstract: It is established that if G is a reducible flow graph, then edge (n, m) is backward (a back latch) if and only if either n = m or m dominates n in G. Thus, the backward edges of a reducible flow graph are unique.Further characterizations of reducibility are presented. In particular, the following are equivalent: (a) G = (N, E, n0) is reducible. (b) The “dag” of G is unique. (A dag of a flow graph G is a maximal acyclic flow graph which is a subgraph of G.) (c) E can be partitioned into two sets E1 and E2 such that E1 forms a dag D of G and each (n, m) in E2 has n = m or m dominates n in G. (d) Same as (c), except each (n, m) in E2 has n = m or m dominates n in D. (e) Same as (c), except E2 is the back edge set of a depth-first spanning tree for G. (f) Every cycle of G has a node which dominates the other nodes of the cycle.Finally, it is shown that there is a “natural” single-entry loop associated with each backward edge of a reducible flow graph.

The diffusive idealization of charged particle transport in random magnetic fields

Abstract: The transport of charged particles diffusing in a random magnetic field parallel to a relatively large guiding field is presented. The same coefficient of diffusion is obtained by three methods. Two corrections must be added to the expression in which the diffusive flux is proportional to the gradient of the density. Explicit expressions are given for a characteristic time and a characteristic length which describe the corrections. The well known divergence of the coefficient of diffusion, which is implied by the quasilinear analysis of pitch angle scattering, does not occur if the scattering rate is finite at 90 deg pitch angle. This effect is illustrated by formulas which give the coefficient of diffusion when the quasilinear expression is perturbed by a variable amount of isotropic scattering.

Stabilization of electron streams in type III solar radio bursts

Abstract: It is shown that the electron streams that give rise to Type 3 solar radio bursts are stable and will not be decelerated while propagating out of the solar corona. The stabilization mechanism depends on the parametric oscillating two stream instability. Radiation is produced near the fundamental and second harmonic of the local electron plasma frequency. Estimates of the emission at the second harmonic indicate that the wave spectra created by the oscillating two stream instability can account for the observed intensities of Type 3 bursts.

Solar flux and its variations

Abstract: Data on the solar irradiance as derived from a number of sources are presented An attempt was made to bring these data onto a uniform scale Summation of fluxes at all wavelengths yields a figure of 1357826 per sq m for the solar constant Estimates are made of the solar flux variations due to flares, active regions (slowly varying component), solar rotation and the 11-year cycle Solar activity does not produce a significant variation in the value of the solar constant Nevertheless, variations in the X-ray and extreme ultraviolet portions of the solar flux may be several orders of magnitude during solar activity, especially at times of major flares It is well established that these short wavelength flux enhancements cause significant changes in the terrestrial ionosphere

The Effects of Other Fish On the Reproductive Behavior of the Male Cyprinodon Variegatus (Pisces: Cyprinodontidae)

Abstract: This study was conducted to investigate the effects of both inter- and intraspecific intruders on the reproductive behavior of Cyprinodon variegatus. Field observations suggested that the highly aggressive male Cyprinodon prefer to chase their own species, then Fundulus heteroclitus, followed by Lucania parva and Gambusia affinis last. In a series of laboratory experiments, in which dominant males were given various combinations of uni-specific and hetero-specific groups to chase, strong evidence was produced for the chase preferences predicted from field observations. The effects of intruders on the spawning behavior of the male were also recorded. In the field the female entered the male's territory, spawned an average of four times and then left. A female spent approximately 20 seconds in the male's territory. While other fish did interrupt spawning, only neighboring territorial males actually interfered physically. This interference occurred if the spawning pair ventured too close to the border (approximately seven cm). In the laboratory conspecific intruders significantly reduced both the number of spawns and the total duration of contacting (i.e., a side-by-side position of the pair, occurring just before spawning). These intruders also increased the probability of long spawning intervals following other long intervals. At the same time, intruders caused the pair to produce relatively more short intervals. Thus, when other Cyprinodon males were present, the pair had a tendency to perform a clustering of spawns which was separated by several long intervals. This resembled the field situation in which a female entered, spawned several times and quickly left. This study suggests that the effects of other interacting fish should be considered when analyzing reproductive behavior. The observation of laboratory fish in isolated pairs may produce misleading results as to the evolution and/or maintenance of behavior.