Behavior of Spherical Particles at Low Reynolds Numbers in a Fluctuating Translational Flow. Preliminary Experiments

The behavior of small spheres in non-steady translational flow has been studied experimentally' for values of Reynolds nunber from 0 to 3000. The aim of the work was to improve our quantitative understanding of particle transport in turbulent gaseous media, a process of extreme importance in powerplants and energy transfer mechanisms. Particles, subjected to strong sinusoidal oscillations parallel to the direction of steady translation, were found to have changes in average drag coefficient depending upon their translational Reynolds number, the frequency and amplitude of the oscillations. When the Reynolds number based on the sphere diameter was les s than 200, the synunetric translational oscillation had negligible effect on the aver age particle dr ago For Reynolds numbers exceeding 300, the effective drag coefficient was significantly increased in a particular frequency range. For example, an increase in drag coefficient of 25 per cent was observed at a Reynolds nwnber of 3000 when the amplitude of the oscillation was 2 per cent of the sphere diazneter and the disturbance frequency was approximately the Strouhal frequency. The occurrence of the maximum effect at frequencies between one and two times the Stroubal frequency strongly suggests non-linear interaction between wake vortex shedding and the oscillation in translational motions. Flow visualization studies support this suggestion

Simulating Cortical Feedback Modulation as Changes in Excitation and Inhibition in a Cortical Circuit Model.

Cortical feedback pathways are hypothesized to distribute context-dependent signals during flexible behavior. Recent experimental work has attempted to understand the mechanisms by which cortical feedback inputs modulate their target regions. Within the mouse whisker sensorimotor system, cortical feedback stimulation modulates spontaneous activity and sensory responsiveness, leading to enhanced sensory representations. However, the cellular mechanisms underlying these effects are currently unknown. In this study we use a simplified neural circuit model, which includes two recurrent excitatory populations and global inhibition, to simulate cortical modulation. First, we demonstrate how changes in the strengths of excitation and inhibition alter the input-output processing responses of our model. Second, we compare these responses with experimental findings from cortical feedback stimulation. Our analyses predict that enhanced inhibition underlies the changes in spontaneous and sensory evoked activity observed experimentally. More generally, these analyses provide a framework for relating cellular and synaptic properties to emergent circuit function and dynamic modulation

Overcoming migration during giant planet formation

In the core accretion model, gas giant formation is a race between growth and migration; for a core to become a jovian planet, it must accrete its envelope before it spirals into the host star. We use a multizone numerical model to extend our previous investigation of the "window of opportunity" for gas giant formation within a disk. When the collision cross-section enhancement due to core atmospheres is taken into account, we find that a broad range of protoplanetary disks posses such a window.Comment: 4 pages, 3 figs, accepted to ApJ

Virginia Woolf as a literary critic

Thesis (Ph.D.)--Boston UniversityAlthough the novels of Virginia Woolf have received some measure of appraisal in recent years, critics have all but neglected her literary criticism. It is the purpose of this dissertation to study her achievement in detail; to discover the general critical principles underlying a body of writing hostile to systematization; and to reveal the particular insights that inform her work. Since Virginia Woolf was a creature of her age, as well as one of its foremost interpreters, I have duly noted relevant historical and environmental factors. Because of the occasional identity of aimsand ideas in both her critical and creative work, I have not hesitated to draw upon her novels to verify or bolster certain viewpoints. Reminiscences by friends suggest the infinite variety and completeness of Virginia Woolf's complex personality, and reveal a mind both logical and intuitive, practical and poetic. Her informal education consisted mainly of the unrestricted use of her father's library, her duties as a publisher's reader, and her membership in the Bloomsbury Group--an exchange center which served her as a forum for the discussion of everything that mattered to her in life and art. Although the "Bloomsburians" did not have enough in common, as far as specific doctrines and practices were concerned, to justify their inclusion within a "school," they did evoke and crystallize a general attitude towards artistic, philosophical, and political problems. Virginia Woolf was the centre or this coterie; and, in varying degrees, she exemplified many or its characteristics. Typical of her writing is a reluctance to utter certainties, and a disbelief in the power of the human mind to solve difficult problems. Sir Leslie Stephen's scepticism strengthened his belief in rationalism; his daughter's scepticism led her to suspect the intellectual processes that had engendered it. She preferred the intuitive approach to reality rather than the intellectual, since it harmonized with her poetic, feminine apperception of life and its values. It is not wholly accurate, however, to call her anti-intellectual. What she attacks is the predominance of intellect, rather than the intellect itself; and, in her critiques and novels, she often expresses reverence for learning and the joy of working with the brain. Voicing the spiritual dilemma of her milieu, Virginia Woolf rejected the orthodox Christian position. She was shocked by the disparity between the simple teachings of Christ and the accretions through the ages or dogma, wealth, and pomp of the Church; and she abhorred those aspects of Christianity which glorified pain, asceticism, and death. But she did not break completely with religion, and in her delineation of "Christian" characters she grows less bitter and satirical and more compassionate and understanding. Her attitude towards religion, however, accounted for the great gap in her critical sympathies: despite her enormous range of interests, she either slights or completely ignores devotional writers and religious poets. Determined to write as a woman and explore her femininity, Virginia Woolf continues the revolt or women as a spiritual suffragist. By her intense advocacy of intellectual and cultural as well as political emancipation, she emerges as one or the greatest feminists or the century. Much of her critical work deals with women writers and their special problems: the frustration of talent, the difficulty of self-expression in the face of masculine malevolence, the "feminine" creative state of mind, and the peculiarly "feminine" provinces of literature. Since her discernment of the essential qualities of feminine modes of thought and apprehension led to some of the fresh and brilliant insights of her critiques, feminism must be accepted as a salutary, fructifying force in her intellectual and artistic perspectives. Mrs. Woolf was not only a woman; she was also a lady, aristocratic in temper, ever sensitive to social distinctions, blood, and royalty. Yet she had the courage to transcend her prejudices even as she stated them. Hardly the "escapist" cut off from reality, she was a patrician with a strong sense of social responsibility who had the rare honesty to admit that her interest in the oppressed was based less on genuine sympathy than on abstract justice and reason. She envisioned the end of class distinctions and a society that would pool, not segregate its possessions. This interest in communal experience is a basic element of her social and literary philosophy. She was an internationalist, politically as well as artistically, who believed that the cooperative instincts of mankind are as deeply rooted as the competitive. In an age torn between democratic and totalitarian tensions, the artist, she felt, was forced to take part in politics because his own survival and the survival of his art were at stake. While many of her contemporaries were flirting with, or openly espousing, fascist doctrines, she was denouncing the surging threat to society. Despite an unrelenting classconsciousness, Mrs. Woolf showed a will to expedite the processes of democracy, and an affirmation of belief that out of struggle will come the triumph of the creative forces of life once again. The next major section of this paper deals with the interrelations of the artist, the milieu, and the tradition. Virginia Woolf looked upon literature as a corporate, composite production of author and public, subject to innumerable fluctuations in the environment. She believed in a genuine literary tradition, in the unity and continuity of literature, in a past altered by the present as much as the present is directed by the past. No tradition, for her, was wholly valid, however, unless it was rooted in contemporary life as much as in the past. She conceived of the Georgian period as a transitional age without a common pattern of belief. She realized the difficulty of creating significant art in an unstable civilization and the need of the artist to adumbrate within the work itself his own philosophic and artistic background. Thus, she was able to understand and explain the Georgian rebellion against literary convention and the adoption of new techniques. Despite her awareness of the dependence of art upon life, her conception of art was hardly utilitarian or moralistic. Origins, in her criticism, are subordinated to value. Favoring the esthetic approach to literature, she evinced a passionate interest in the nature of artistic creation. She is forever obsessed by the difficulty of expression, the agony of creation, and the frustration and failure that precede the final triumph. The creative act is more than a process of self-examination; it is the artist's function to make people see, to communicate his vision and illuminate experience. The artist creates shape out of chaos, imposes a coherent form on the intractable material of life, and makes of the moment something permanent. Some of the attributes of esthetic experience that Mrs. Woolf considers are unconsciousness, or impersonality, detachment, integrity, and suggestion. The writer, in achieving his created reality, must transform his insights and perceptions into something which transcends the individual. He must have integrity, the courage to keep faith with his personal vision, his inner necessity and sincerity. Mrs. Woolf views imaginative literature as a potential, a stimulus, and not a terminal experience, which demands from the reader his active participation. Other recurring themes or her criticism are the unity and interraction of the arts, and, more particularly, their "purity." She condemned the subordination of art to alien disciplines and the deliberate inculcation of doctrine; but she had no objection to the presence of ethics, politics, or metaphysics, if they were implicit within the framework of the object or art itself and were burned up, or "consumed," by the form. Virginia Woolf's assumption of the role or the "common" or lay reader was motivated by the will to dissociate herself from the arid and abortive criticism of dogmatic academicians end specialists. Her criticism is as little concerned with schools and movements, the tracing of influences, and the derivation of styles as with close textual analysis, Empsonian ambiguities, and esoteric critical jargon. Suspicious or fixed labels and settled hierarchies, she eliminates by her disregard the jungle of secondary authorities and commentaries, and communicates her own untainted response to the originals. The exposition of methodology matters much less to her than the degree of the critic's engagement with a particular work on a particular occasion. She prefers synthesis to abstract analysis, demonstration to definition, the communication of her personal impressions to the formal declaration of critical principles. Emotionally and intellectually involved in the work of art, she attempts to insinuate herself into the writer's mind, in order to master his perspective and his "angle of vision." Her impressions are seldom vague and irresponsible. Hers is an impressionism recollected in tranquillity, disciplined and refined, and modified by a traditional sense of balance. Conjuring up the very "feel" and atmosphere of a book, she singles out its essential quality, and communicates it with joy. intensity, and immediacy. Because she not only reveals an author's quality but reproduces it in some form or framework of her own, her critical essays have some of the individuality and intensity of works of art. The forms and techniques she uses may be classified roughly as follows: criticism by evocation of the spirit and atmosphere of an age or a writer's environment; criticism by psychological portraitures of individual writers; criticism by direct appraisal of the book itself; and criticism by discussion of literary genres and the theory of writing. Very often two, three, or all of these methods--historical, biographical, ppychologioal, and esthetic--overlap and are fused in a single essay. Preceding an analysis of Mrs. Woolf critiques of novelists is a consideration of the general principles underlying her conception, in fiction, of reality, character, poetic capability, and form. Virginia Woolf was a self-conscious artist who tried to frame her own esthetic and justify the use of new forms devised to deal with new areas of conscious and subconscious experience. She rejected philosophic and esthetic naturalism, and substituted a view of reality demanded by the modern complexity of vision that crystallized, by and large, the artistic credo of a whole new generation. For her, reality is intangible, almost indefinable, and must be grasped intuitively with the aid of symbol and image. It is the "luminous halo" that surrounds consciousness; and it is the novelist's function to express and communicate the elusive nature of this "halo" and this "semi-transparent envelope" by recording, with utmost fidelity, the atoms of impressions that impinge upon the consciousness. Mrs. Brown, Virginia Woolf's symbol of character, is also a symbol of reality. She is less an individual than an abstract idea of human nature. She is not a clearly defined, continuous personality. Mrs. Woolf rejected the omniscient summing up of characters whose identity she considered neither constant nor limited. She favored fluidity rather tha.n fixity of personality. She preferred, also, fiction that was rich in poetic values, for a novel, she felt, gained in intensity and reality through the controlled expression of poetic feeling. Her notion of poetry is not limited to its lyrical aspects. She is concerned about those characteristic of poetry common to all imaginative literature. Among the poetic powers are ambiguity, the use of symbol with its fund of infinite suggestion, and the ability of the novelist to create a new world and force us to cede our own perspective and adopt his particular ordering of the elements of the novel--man, nature, God. Nor could the novel attain its highest expression without careful formal organization. Form is another aspect of the novelist's power to force the reader along his road and see what he sees. Form is achieved when the emotions are placed in the right relations to each other. It is a shaping power, an architectural quality, that should focus, not distract, the reader's attention. In great art, she felt, vision and expression, form and content, are indivisible. In the final third of this dissertation the general principles and methods of Virginia Woolf's criticism are illustrated in her critiques of writers of the last three centuries. Studied in detail are novelists from Defoe to D. H. Lawrence, and the poets Chaucer, Spenser, Donne, and Elizabeth Barrett Browning. She expressed some profound insights about Greek and Elizabethan drama, the function ofthe plot and the chorus in Greek tragedy, the differences of play and novel, and the art or Shakespeare, Congreve, and Chekhov. The thesis ends with a consideration of Mrs. Woolf's theory or biography as well as or her own biographical essays, in which she often illuminates the work of art itself by establishing the figure or the artist. In the light or this extensive study or Virginia Woolf's achievement, she emerges, I believe, as one of the most distinguished critics of the twentieth century, and certainly as the greatest woman critic of all centuries in English literature

Bayesian Learning and Predictability in a Stochastic Nonlinear Dynamical Model

Bayesian inference methods are applied within a Bayesian hierarchical modelling framework to the problems of joint state and parameter estimation, and of state forecasting. We explore and demonstrate the ideas in the context of a simple nonlinear marine biogeochemical model. A novel approach is proposed to the formulation of the stochastic process model, in which ecophysiological properties of plankton communities are represented by autoregressive stochastic processes. This approach captures the effects of changes in plankton communities over time, and it allows the incorporation of literature metadata on individual species into prior distributions for process model parameters. The approach is applied to a case study at Ocean Station Papa, using Particle Markov chain Monte Carlo computational techniques. The results suggest that, by drawing on objective prior information, it is possible to extract useful information about model state and a subset of parameters, and even to make useful long-term forecasts, based on sparse and noisy observations

A fuzzy approach to aggregating military assessments

AbstractFuzzy set matrix operations in the form of a computer-aided decision tool are applied to the management problem of aggregating assessments upward through successive layers of a hierarchy. The particular problem addressed concerns the production of a worldwide assessment of military command and control at the global level based on an assessment of capabilities three hierarchical levels below. The program works directly with colors indicating the operational readiness state of the capability. Linguistic variables form a large portion of the data base. Extensive capability exists to link the global assessment with stored information on budgetary decisions identified by the software. The fuzzy set approach described is new in the defense community. The article provides an overview of the methodology and is not a detailed discussion

The Correspondence of Fr Matthew Gaughren OMI (1888-1890)

Em meados de 1888, o padre Matthew Gaughren (1843-1914) foi enviado à Argentina por seu superior, o O.M.I. provincial da Grã-Bretanha, a uma “expedição de mendicância”, que visava arrecadar dinheiro entre os colonos irlandeses para diminuir a dívida da igreja de Nossa Senhora da Graça em Tower Hill. No entanto, Gaughren mudou as prioridades de sua missão na América do Sul e apelou à comunidade de língua inglesa para apoiar os imigrantes irlandeses vindos de Cork, em fevereiro de 1889, no navio a vapor Dresden, e enviados a uma malfadada colônia irlandesa em Napostá, próxima ao porto de Bahía Blanca. Seu pensamento e sua luta são revelados nas cartas a seguir, coletadas de diversos arquivos, que agora estão sendo publicadas, a maioria delas pela primeira vez, em sua forma completa.In mid-1888, Fr Matthew Gaughren (1843-1914) was sent to Argentina by his superior, the O.M.I. provincial in Great Britain, on a “begging expedition”, which aimed at collecting money among the Irish settlers to lessen the debt upon the church of Our Lady of Grace at Tower Hill. However, Gaughren changed the priorities of his mission in South America and appealed to the English-speaking community to support the Irish immigrants who arrived in Buenos Aires in February 1889 on the Dresden steamer ship from Cork and were sent to an ill-fated Irish Colony in Napostá, near the port of Bahía Blanca. His thinking and his struggle are revealed in the following letters, collected from various archival sources, which are now being published, most of them for the first time, in their complete form