Showing papers by "Cornell University published in 1972"

Thermodynamic Fluctuations in a Reacting System-Measurement by Fluorescence Correlation Spectroscopy

Abstract: The temporal correlations of thermodynamic concentration fluctuations have been measured in a chemically reactive system at equilibrium by observing fluctuations of the fluorescence of a reaction product. The experiment yields the chemical rate constants and diffusion coefficients and shows the coupling among them. Data are reported for binding of ethidium bromide to DNA.

Computation of channel capacity and rate-distortion functions

Abstract: By defining mutual information as a maximum over an appropriate space, channel capacities can be defined as double maxima and rate-distortion functions as double minima. This approach yields valuable new insights regarding the computation of channel capacities and rate-distortion functions. In particular, it suggests a simple algorithm for computing channel capacity that consists of a mapping from the set of channel input probability vectors into itself such that the sequence of probability vectors generated by successive applications of the mapping converges to the vector that achieves the capacity of the given channel. Analogous algorithms then are provided for computing rate-distortion functions and constrained channel capacities. The algorithms apply both to discrete and to continuous alphabet channels or sources. In addition, a formalization of the theory of channel capacity in the presence of constraints is included. Among the examples is the calculation of close upper and lower bounds to the rate-distortion function of a binary symmetric Markov source.

Critical Exponents in 3.99 Dimensions

Abstract: Critical exponents are calculated for dimension $d=4\ensuremath{-}\ensuremath{\epsilon}$ with $\ensuremath{\epsilon}$ small, using renormalization-group techniques. To order $\ensuremath{\epsilon}$ the exponent $\ensuremath{\gamma}$ is $1+\frac{1}{6}\ensuremath{\epsilon}$ for an Ising-like model and $1+\frac{1}{5}\ensuremath{\epsilon}$ for an $\mathrm{XY}$ model.

Scaling Theory for Finite-Size Effects in the Critical Region

Abstract: Critical phenomena in films of finite thickness are considered. A detailed scaling theory, with allowance for distinct exponents $\ensuremath{\lambda}$ and $\ensuremath{\theta}=\frac{1}{\ensuremath{ u}}$ for the critical-point shift and rounding, respectively, is confirmed by exact calculations on $d$-dimensional ferromagnetic spherical models and ideal Bose fluids with various boundary conditions. Isingmodel results and existing data on real helium films are consistent with the theory.

Critical Exponents for Long-Range Interactions

Abstract: Critical exponents for a $d$-dimensional system with an isotropic $n$-component order parameter and long-range attractive interactions decaying as $\frac{1}{{r}^{d+\ensuremath{\sigma}}} (\ensuremath{\sigma}g0)$ are derived, using the renormalization group approach, as power series in $\ensuremath{\epsilon}=2\ensuremath{\sigma}\ensuremath{-}dg0$ ($\ensuremath{\sigma}\ensuremath{ e}2$, fixed) or $\ensuremath{\Delta}\ensuremath{\sigma}=\ensuremath{\sigma}\ensuremath{-}\frac{1}{2}dg0$ ($d$ fixed) and, separately, to order $\frac{1}{n}$ for all $d$ and $\ensuremath{\sigma}\ensuremath{ e}2$. For $\ensuremath{\epsilon}l0$ the exponents have fixed ("classical") values; when $\ensuremath{\epsilon}=\ensuremath{\Delta}\ensuremath{\sigma}=0$ fractional powers of $\mathrm{ln}(\frac{\ensuremath{\Delta}T}{{T}_{c}})$ appear; when $\ensuremath{\sigma}g2$ the exponents assume their short-range values.

Earth and Mars: evolution of atmospheres and surface temperatures.

Abstract: Solar evolution implies, for contemporary albedos and atmospheric composition, global mean temperatures below the freezing point of seawater less than 2.3 aeons ago, contrary to geologic and paleontological evidence. Ammonia mixing ratios of the order of a few parts per million in the middle Precambrian atmosphere resolve this and other problems. Possible temperature evolutionary tracks for Earth and Mars are described. A runaway greenhouse efect will occur on Earth about 4.5 aeons from now, when clement conditions will prevail on Mars.

The influence of vegetational diversity on the population ecology of a specialized herbivore, Phyllotreta cruciferae (Coleoptera: Chrysomelidae).

Abstract: The population ecology of Phyllotreta cruciferae Goeze, a flea beetle which is an important pest of cole crops (Brassica oleracea) in central New York was studied in experimental gardens of differing vegetational diversity over a three year period. Adult beetles were more abundant on collards (B. oleracea var. acephala) grown in monocultures than on those grown adjacent to natural vegetation. The emergence of individuals forming the new annual generation was also greater in the pure stands. Predators and parasites appeared to have a negligible influence on the adult beetles in both habitats. Further experiments demonstrated that monocultures were colonized more rapidly and experienced greater feeding damage than stands in which collards had been interplanted with tomatoes and tobacco. Choice experiments in the laboratory showed that chemical stimuli given off by non-host plants (tomato, Lycopersicon esculentum, and ragweed, Ambrosia artemisiifolia) interfered with the host finding and feeding behaviour of P. cruciferae. These results indicate that vegetational diversity can exert a direct influence on populations of phytophagous insects.We conclude that the environmental capacity (Determination in Schwerdtfeger's terminology) of diverse natural communities is lower than that of natural or man-made monocultures. The "associational resistance" resulting from the higher taxonomic and microclimatic complexity of natural vegetation tends to reduce outbreaks of herbivores in diverse communities.

Natural history of brachial plexus neuropathy. Report on 99 patients.

Abstract: A clinical analysis of 99 patients with brachial plexus neuropathy (BPN) and the outcome of 84 of these patients are presented. The disease may involve the upper, the lower, or the entire plexus; the involvement may be complete or incomplete, and it may often be bilateral. Although the etiologic factor or factors remain unknown, our studies support the contention that this form of neuropathy is a clinical entity with, in most cases, a fairly typical pattern of symptoms and signs. The overall prognosis is excellent despite the severity and extent of the lesion. There is no apparent difference in the clinical aspects and recovery rates between patients who had antecedent immunizations and those who did not. While improvement may begin in one to two months, complete functional recovery may not be achieved for up to three years or longer in some cases.

Feynman graph expansion for critical exponents

Abstract: The critical exponents $\ensuremath{\gamma}$, $\ensuremath{\eta}$ and the "crossover index" $\ensuremath{\phi}$ are computed for generalized classical Heisenberg models with $n$ internal degrees of freedom as an exact expansion in $\ensuremath{\epsilon}=4\ensuremath{-}d$ ($d$ is the number of space dimensions). Results are obtained to order ${\ensuremath{\epsilon}}^{2}$ for $\ensuremath{\gamma}$ and to order ${\ensuremath{\epsilon}}^{3}$ for $\ensuremath{\eta}$. The results to this order for the three-dimensional Ising case ($n=\ensuremath{\epsilon}=1$) are $\ensuremath{\gamma}=1.244$ and $\ensuremath{\eta}=0.037$.

Evidence for a New Phase of Solid He 3

Abstract: Measurements of the melting pressure of a sample of ${\mathrm{He}}^{3}$ containing less than 40-ppm ${\mathrm{He}}^{4}$ impurities, self-cooled to below 2 mK in a Pomeranchuk compression cell, indicate the existence of a new phase in solid ${\mathrm{He}}^{3}$ below 2.7 mK of a fundamentally different nature than the anticipated antiferromagnetically ordered state. At lower temperatures, evidence of possibly a further transition is observed. We discuss these pressure measurements and supporting temperature measurements.

Homogeneous Dynamical Conductivity of Simple Metals

Abstract: Within the jellium model the zero wave vector, frequency-dependent conductivity is expressed in terms of a regular memory function. This quantity is calculated in lowest order in the impurity concentration and the electron-phonon coupling, thus yielding a reasonable approximation for the conductivity valid in the complete frequency regime. The standard results for the static conductivity including vertex corrections are reproduced. Deviations from Drude's formula a because of spin-flip scattering in a magnetic field, because of resonance scattering, because of phonon creation at low temperatures, and because of breaking of the screening cloud attached to charged impurities are discussed.

Canine distemper virus

Abstract: Distemper is not a very precise description of a disease entity, and the Oxford Dictionary lists a vast number of different meanings for the word “distemper”: “It argues sickness and distemper in the mind as well as in the body” In connection with dogs it has been applied for centuries for “that fatal disorder proper to the canine race called par excellence, the distemper” Besides rabies, canine distemper (CD) is the only virus disease in dogs with a high mortality rate It has a worldwide distribution and only few dogs in isolated areas remain without contact with the virus According to some reports (Kirk, 1922; Geiger, 1939) CD made its first appearance in Europe in Spain in 1761, introduced from either Asia or Peru From Spain it spread to all European countries within the same century Jenner, well known for his development of a successful smallpox vaccine, made its first accurate description in 1809

An Experimental Analysis of the Parameters of Bird Song Eliciting Species Recognition

Abstract: During the summers of I967 I968 and I969, I studied the acoustical communication system of the Indigo Bunting (Passerina cyanea) by means of playback experiments. Attention was directed to deciphering those properties of territorial song used in species identification. I tested the importance of different song parameters by exposing birds to recordings of normal and artificially modified vocalizations. The level of agonistic response exhibited by male territory holders was used as a bioassay of the effectiveness of the experimental song in allowing species recognition. The results indicate the following: I) Syntactical featues of song (the arrangement or order of notes (= figures) within the song) are not essential recognition cues. 2) Altering the rhythmic cadence of the song by lengthening or shortening the intervals between successive notes causes a marked reduction in male responsiveness. 3) The structure or morphology of the individual notes is also important in song identification. I hypothesize that notes must have a particular acoustical quality characterized by their covering a wide frequency range (mean = 4 kHz) in a short time interval (mean length = 0.18 seconds) and by their containing abrupt changes and reversals of pitch. A wide diversity of bunting note-types fit this description, and differences in details of their fine structure probably provide the variability necessary for permitting individual identification. 4) Only a small number of the acoustical cues potentially available are critical for species recognition. This high degree of feature extraction suggests that a) considerable redundancy is present in bunting song and, b) a large number of song parameters function in the conveyance of other (non-identification) messages. When these results are compared with data from other species of passerines (the Ovenbird, Seiurus aurocapillus, White-throated Sparrow, Zonotrichia albicollis, Wood Lark, Lullula arborea, and European Robin, Erithacus rubecula) several generalizations emerge: i) In all five species, recognition depends upon song features that are among the most constant and unvarying in the species repertoire. 2) Song characteristics that are constant in the repertoire of an individual bird but variable within a population are unimportant in species identification but often function in allowing recognition of specific individuals. 3) Those aspects of territorial song that are variable within an individuals's repertoire often convey information about the motivational state of the singer. While only a few vocal parameters are essential for identification in each of these species, the parameters serving this function cover the entire spectrum of morphological, temporal and syntactical features. One would like to be able to predict optimal physical structures for acoustical signals that convey recognition information. At present, too few studies have been conducted to make this possible. However, several speculations are advanced concerning the importance of behavioral and ecological factors such as population dispersion pattern, social organization, habitat structure, and the background sound environment.

Intrinsic fluctuations in a superconducting ring closed with a josephson junction.

Abstract: The distribution in the external flux at which a superconducting ring closed with a weak link admits a quantum of flux is determined assuming that the weak link can be treated as a Josephson junction. We find that this transition occurs at an appreciable fraction of the flux quantum from the theoretical critical external flux. To a first approximation the width of the distribution is proportional to the inductance of the ring and varies as ${T}^{\frac{2}{3}}{i}_{c}^{\ensuremath{-}\frac{1}{3}}$, where $T$ is the temperature and ${i}_{c}$ the critical current.

Nutritional and environmental interactions in the behavioral development of the rat: long-term effects.

Abstract: The behavioral effects of early malnutrition and early environmental isolation were observed in male rats. Dietary and environmental manipulations occurred during the first 7 weeks of life, after which followed a 10-week recovery period. On the basis of several different responses, it was found that the behavioral effects of early malnutrition were exaggerated by the environmental isolation. In most cases, the behavioral effects of early malnutrition were completely eliminated by supplying "additional stimulation" early in life. Two theoretical mechanisms are proposed to explain these findings.

Revegetation following Forest Cutting: Mechanisms for Return to Steady-State Nutrient Cycling.

Abstract: Dense stands of a woody, successional species, Prunus pensylvanica L., develop rapidly, with early closure of canopy and rapid attainment of high values of net annual production and nutrient accumulation. Such rapid growth following disturbance tends to minimize losses of nutrients from the ecosystem, thus promoting a return to steady-state cycling characteristic of a mature forest.

New Magnetic Phenomena in Liquid He 3 below 3 mK

Abstract: Magnetic measurements have been made on a sample of ${\mathrm{He}}^{3}$ in a Pomeranchuk cell. Below about 2.7 mK, the NMR line apparently associated with the liquid portion of the sample shifts continuously to higher frequencies during cooling. Below about 2 mK the frequency shift vanishes, and the magnitude of the liquid absorption drops abruptly to approximately \textonehalf{} its previous value. These measurements are related to the pressure phenomena reported by Osheroff, Richardson, and Lee.

Operator product expansions and composite field operators in the general framework of quantum field theory

Abstract: The short distance behavior of field operator products is analyzed. It is shown that under certain conditions operator product expansions can be derived which give complete information on the short distance behavior and lead to the construction of composite field operators.

Microsomal Drug Metabolizing Enzymes in Insects

Abstract: (1972). Microsomal Drug Metabolizing Enzymes in Insects. Drug Metabolism Reviews: Vol. 1, No. 1, pp. 153-227.

Ultraviolet Reflection of a Male Butterfly: Interference Color Caused by Thin-Layer Elaboration of Wing Scales

Abstract: Males of the butterfly Eurema lisa, like many other members of the family Pieridae, reflect ultraviolet light. The color is structural rather than pigmentary, and originates from optical interference in a microscopic lamellar system associated with ridges on the outer scales of the wing. The dimensions and angular orientation of the lamellar system conform to predictions based on physical measurement of the spectral characteristics, including "color shifts" with varying angles of incidence, of the reflected ultraviolet light. The female lacks such scales and is consequently nonreflectant. The ultraviolet dimorphism supposedly serves as the basis for sexual recognition in courtship.

Competition between an alga and an aquatic bacterium for phosphate1

Abstract: Competition for phosphate was studied in Scenedesmus sp. and Pseudomonas sp. grown in pure and mixed cultures. Algal growth was severely limited in the presence of bacteria, but the growth of bacteria was hardly affected by algae. The first sign of competition in mixed cultures (cessation of exponential algal growth) was always observed some time after the external phosphate had been exhausted. The faster growth rate of bacteria accounted for the suppressed growth of the algae in the mixed cultures. The first sign of competition in algae appeared when the concentration of surplus phosphorus within the algal cell dropped to a critical value near zero. The surplus phosphorus appeared to consist of three or all four inorganic polyphosphate fractions.