1,721,326 research outputs found
Sensors for structural control applications using piezoelectric polymer film
No full textThesis (M.S.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 1990.Includes bibliographical references (leaves 124-135).by Simon Andrew Collins.M.S
Multi-axis analog adaptive feedforward cancellation of cryocooler vibration
No full textThesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 1994.Includes bibliographical references (p. 213-222).by Simon Andrew Collins.Ph.D
Spectroscopic studies of highly excited states of short-lived molecules
No full textMultiphoton ionisation (MPI) spectroscopy has been used to investigate the electronic structure of short-lived molecules in the gas-phase. Electronic transitions observed in the MPI spectra of the short-lived molecules studied were assigned by analysis of the rotational structure in the observed bands. In the main part of this work, the molecules chosen for study using MPI spectroscopy were NF and NC1, which are of interest as possible energy transfer agents in chemical laser systems. NF was produced by the rapid gas-phase reactions F+HN3→HF+N3 and F+N3→NF+N2, whilst NC1 was produced in a similar manner by the reactions F+N3→HF+N3 and C1+N3→NC1+N2.In the MPI spectrum of NF, two-photon resonant transitions were observed from the low-lying NF(a1Δ) state to 3dδ 1,3φ and 4dδ 1,3φ Rydberg states, in which the appearance of the formally forbidden 3φ ← a1Δ transition was rationalised in terms of a spin-orbit and S-uncoupling interaction in the excited state. In addition, two-photon transitions from NF(a1Δ) to a 1Σ and a perturbed 1Δ Rydberg state were observed. In the case of the 1Δ ← a1Δ transition the assignment of a perturbed 1Δ Rydberg upper state was tentative.In the MPI spectrum of NC1, two-photon resonant transitions from NCI(a1Δ) to 1Σ, 1Π, 1Σ, 3dδ 1φ, 1Σ and 4dδ 1φ Rydberg states were observed, in order of increasing transition energy. Two-photon resonant transitions from the NC1(X3Σ-) state to 3Π and 3Δ Rydberg states were also observed.Prior to this work, no states lying higher in energy than the b1Σ+ state for NC1 were known, whilst for NF only two Rydberg states (1Δ and 1Σ) were known at energies higher than the NF (b1Σ+) state. The observation of resolved bands involving triplet Rydberg states has allowed the determination of the first experimental values for the spin-orbit splitting in any state of NF and NC1.Finally, known two-photon resonant MPI transitions of atomic chlorine were used to measure the relative population of the C1(2P3/2) and C1(2P1/2) spin-orbit states resulting from the UV photolysis of HOC1, a species of importance in stratospheric ozone depletion. The results indicated a stronger preference for formation of ground state atomic (C1(2P3/2) than expected from statistical weights, and also that most of the energy available upon photolysis is converted into kinetic energy of the photofragments.</p
The clinical, immunological and diagnostic significance of the phenotype of circulating, malignant, B-lymphocyte clones
No full textTwo hundred and twelve cases of chronic, B-cell leukaemia were investigated by direct and indirect antibody rosette methods to determine the expression of the following surface antigens: MHC class II, MRBCr, CD1, CD3, CDS, CDS, CD9, CD10, CDllb, CD1 Ic, CD19, CD20, CD21, CD22, CD23, CD24, CD25, CD37, CD38, CD39, CDw40 and surface heavy- and light-chain type. The patient group was, in the main, histolog-ically defined and comprised 174 cases of chronic lymphocytic leukaemia (CLL), 19 of hairy cell leukaemia (HCL) and 9 each of leukaemia associated with centroblastic-centrocytic (CB-CC) and centrocytic (CC) lym-phoma.The diseases showed different but overlapping phenotypcs. These differences could be related, in part, to the point in normal B-cell development at which the malignancy arose. The phenotype of HCL was most characteristic while the phenotype of CC was sufficiently distinct to confirm that it was a separate disease but not to define its relation to normal B-cell development.The diseases had significant differences in their clinical features, im-munoglobulin levels and phenotype but no particular pattern was uniformly associated with any disease. Stcpwise, discriminant analysis showed that, using the clinical and phenotypic data together resulted in a more accurate discrimination between the disease than either data set used alone. The extent of expression of CDS, MRBCr, CD10 and CD38 were most useful in distinguishing between the diseases.Phentotypic heterogeneity was observed in each disease but could be assessed in most detail in CLL because of the larger number of cases. Multiple positive correlations were observed between the expression of pairs of antigens. No particular patterns were detectable linking these correlated pairs. Some cases of CLL had a phentotype similar to that of HCL suggesting that part of the heterogeneity was due to the degree of differentiation and activation of particular malignant clones.Cases of CLL with a total lymphocyte count less than 10 x 109/1 had more frequent expression of CD38 while those with isolated splenomegaly had more frequent expression of CD25 than other cases. This suggests that some of the clinical heterogeneity of CLL may be due to the homing behaviour of different lymphocyte clones which in turn may be mediated through cell surface antigens.Cases which expressed any of several antigens (notably MRBCr, CD20, CD23, CD39) on a small proportion of cells had more extensive disease, more advanced disease stage and a worse prognosis. Such cases also more frequently co-expressed slgD and slgM. Multivariate survival analysis showed that, after allowing for the effect of clinical parameters, only MRBCr and MHC class II expression had additional independent prognostic significance. The hypothesis is proposed that, during the course of CLL, the disease evolves with the development of more extensive disease, a fall in the frequency of expression of a number of antigens and a worsening prognosis. This may occur in association with prolymphocytoid transformation but is not necessarily caused by it.</p
Effectiveness of grade-control structures in reducing erosion along incised river channels: the case of Hotophia Creek, Mississippi
No full textHerein, we undertake a geomorphological analysis in which spatial and temporal trends of bed and bank erosion along an 18-km length of Hotophia Creek, Mississippi, are estimated for the period between 1961 and 2050. The evaluation was undertaken for two scenarios of channel response to channelization during 1961-1963. One scenario represents the 'actual' response of the channel and includes the effects of installing a series of grade-control structures (GCS) between 1980 and 1996, while the other represents a hypothetical scenario in which the channel is left to adjust naturally. This allows the effectiveness of GCS in reducing in-channel erosion to be assessed. The analysis relies on the availability of channel survey data to develop empirical bed and bank response models for each adjustment scenario, supplemented by bank stability modelling to predict future rates of bank erosion. Results indicate that channel erosion rates decline nonlinearly with respect to time since 1961, for both adjustment scenarios. However, by the year 2050, the ''with'' GCS adjustment scenario results in the cumulative removal of some 663,000 (9%) extra tonnes of sediment relative to the ''without'' GCS scenario. Most (63%) of this excess is derived from enhanced bed erosion during 1976-1985 and 1985-1992, with the remainder derived from increased bank erosion during 1985-1992. Detailed analysis of the patterns of erosion and deposition, and their association with the GCS, provides evidence to support the view that GCS installed along Hotophia Creek have, for the most part, been ineffective in reducing channel erosion rates. This is because the GCS were installed too late to prevent bed degradation, caused by the 1961-1963 channelization, migrating upstream. In addition, some structures have disrupted the downstream transmission of bed material from eroded reaches upstream, exacerbating bed degradation and bank erosion in incised reaches downstream
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Intelligent approaches to modelling and interpreting disc brake squeal data
No full textSIGLEAvailable from British Library Document Supply Centre-DSC:DXN043119 / BLDSC - British Library Document Supply CentreGBUnited Kingdo
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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