Showing papers by "Harvard University published in 1982"
TL;DR: In this paper, the Bogoliubov equations were used to model the transmission and reflection of particles at the tunnel junction of normal-superconducting micro-constriction contacts, and a simple theory for the $I\ensuremath{-}V$ curves of normal superconducting contacts was proposed to describe the crossover from metallic to tunnel junction behavior.
Abstract: We propose a simple theory for the $I\ensuremath{-}V$ curves of normal-superconducting microconstriction contacts which describes the crossover from metallic to tunnel junction behavior. The detailed calculations are performed within a generalized semiconductor model, with the use of the Bogoliubov equations to treat the transmission and reflection of particles at the $N\ensuremath{-}S$ interface. By including a barrier of arbitrary strength at the interface, we have computed a family of $I\ensuremath{-}V$ curves ranging from the tunnel junction to the metallic limit. Excess current, generated by Andreev reflection, is found to vary smoothly from $\frac{4\ensuremath{\Delta}}{3e{R}_{N}}$ in the metallic case to zero for the tunnel junction. Charge-imbalance generation, previously calculated only for tunnel barriers, has been recalculated for an arbitrary barrier strength, and detailed insight into the conversion of normal current to supercurrent at the interface is obtained. We emphasize that the calculated differential conductance offers a particularly direct experimental test of the predictions of the model.
2,772 citations
TL;DR: In this article, a method for obtaining pure absorption phase spectra in four quadrants in a two-dimensional nuclear magnetic resonance spin exchange experiment is described, which results in a substantial increase in resolution and discrimination while maintaining a signal-to-noise ratio comparable to that of the usual magnitude spectrum.
2,539 citations
2,509 citations
Book•
01 Jan 1982TL;DR: Sandel as mentioned in this paper locates modern liberalism in the tradition of Kant, and focuses on its most influential recent expression in the work of John Rawls, tracing the limits of liberalism to the conception of the person that underlies it, and argues for a deeper understanding of community than liberalism allows.
Abstract: A liberal society seeks not to impose a single way of life, but to leave its citizens as free as possible to choose their own values and ends. It therefore must govern by principles of justice that do not presuppose any particular vision of the good life. But can any such principles be found? And if not, what are the consequences for justice as a moral and political ideal? These are the questions Michael Sandel takes up in this penetrating critique of contemporary liberalism. Sandel locates modern liberalism in the tradition of Kant, and focuses on its most influential recent expression in the work of John Rawls. In the most important challenge yet to Rawls' theory of justice, Sandel traces the limits of liberalism to the conception of the person that underlies it, and argues for a deeper understanding of community than liberalism allows.
2,308 citations
TL;DR: In this article, the Yang-Mills functional over a Riemann surface is studied from the point of view of Morse theory, and the main result is that this is a perfect 9 functional provided due account is taken of its gauge symmetry.
Abstract: The Yang-Mills functional over a Riemann surface is studied from the point of view of Morse theory. The main result is that this is a ‘perfect9 functional provided due account is taken of its gauge symmetry. This enables topological conclusions to be drawn about the critical sets and leads eventually to information about the moduli space of algebraic bundles over the Riemann surface. This in turn depends on the interplay between the holomorphic and unitary structures, which is analysed in detail.
2,298 citations
Book•
01 Jan 1982TL;DR: The third edition of Multinational Enterprise and Economic Analysis surveys the contributions that economic analysis has made to our understanding of why multinational enterprises exist and what consequences they have for the workings of the national and international economies.
Abstract: The third edition of Multinational Enterprise and Economic Analysis surveys the contributions that economic analysis has made to our understanding of why multinational enterprises exist and what consequences they have for the workings of the national and international economies. It shows how economic analysis can explain multinationals' activity patterns and how economics can shed conceptual light on problems of business policies and managerial decisions arising in practice. It addresses the welfare problems arising from multinationals' activities and the logic of governments' preferences and choices in their dealings with multinationals. Suitable for researchers, graduates and upper-level undergraduates. The third edition of this highly accessible book incorporates the many additions to our knowledge of multinationals accumulated in research appearing in the past decade.
2,274 citations
TL;DR: A procedure is derived for extracting the observed information matrix when the EM algorithm is used to find maximum likelihood estimates in incomplete data problems and a method useful in speeding up the convergence of the EM algorithms is developed.
Abstract: A procedure is derived for extracting the observed information matrix when the EM algorithm is used to find maximum likelihood estimates in incomplete data problems. The technique requires computation of a complete-data gradient vector or second derivative matrix, but not those associated with the incomplete data likelihood. In addition, a method useful in speeding up the convergence of the EM algorithm is developed. Two examples are presented.
2,145 citations
TL;DR: In this article, the role of the edge states in the quantized Hall conductance is discussed in the context of the general explanation of Laughlin's analysis and the existence of extended states in a weakly disordered two-dimensional system, when a strong magnetic field is present.
Abstract: When a conducting layer is placed in a strong perpendicular magnetic field, there exist current-carrying electron states which are localized within approximately a cyclotron radius of the sample boundary but are extended around the perimeter of the sample. It is shown that these quasi-one-dimensional states remain extended and carry a current even in the presence of a moderate amount of disorder. The role of the edge states in the quantized Hall conductance is discussed in the context of the general explanation of Laughlin. An extension of Laughlin's analysis is also used to investigate the existence of extended states in a weakly disordered two-dimensional system, when a strong magnetic field is present.
1,721 citations
TL;DR: The thresholds for several effects in picosecondlaser-induced phase transformation on silicon-crystal surfaces are calibrated with a simple technique for in situ measurements of pulsed Gaussian-beam spot sizes.
Abstract: A simple technique for in situ measurements of pulsed Gaussian-beam spot sizes is reported. This technique is particularly useful for measurements on highly focused beam spots. It can also be used for absolute calibration of the threshold-energy fluences for pulsed-laser-induced effects. The thresholds for several effects in picosecond-laser-induced phase transformation on silicon-crystal surfaces are calibrated with this technique.
1,509 citations
Posted Content•
TL;DR: In this article, the authors proposed a method to solve the problem of unstructured data in order to improve the quality of the data collected, but no abstract is available for this method.
Abstract: No abstract is available for this paper.
1,337 citations
TL;DR: The binomial effect size display (BESD) as mentioned in this paper is a commonly used method to measure the change in success rate (e.g., survival rate, improvement rate, etc.) attributable to a new treatment procedure.
Abstract: We introduce the binomial effect size display (BESD), which is useful because it is (a) easily understood by researchers, students, and lay persons; (b) widely applicable; and (c) conveniently computed. The BESD displays the change in success rate (e.g., survival rate, improvement rate, etc.) attributable to a new treatment procedure. For example, an r of .32, the average size of the effect of psychotherapy, is said to account for "only 10% of the variance"; however, the BESD shows that this proportion of variance accounted for is equivalent to increasing the success rate from 34% to 66%, which would mean, for example, reducing an illness rate or a death rate from 66% to 34%. Traditionally, behavioral researchers have concentrated on reporting significance levels of experimental effects. Recent years, however, have shown a welcome increase in emphasis on reporting the magnitude of experimental effects obtained (Cohen, 1977; Fleiss, 1969; Friedman, 1968, Glass, Note 1, Hays, 1973; Rosenthal, 1978; Rosenthal & Rubin, 1978; Smith & Glass, 1977).
Posted Content•
TL;DR: In this paper, the authors examine the implications of arbitrage in a market with many assets and show that if the covariance matrix of the asset returns has only K unbounded eigenvalues then there is an approximate factor structure and it is unique.
Abstract: We examine the implications of arbitrage in a market with many assets. The absence of arbitrage opportunities implies that the linear functionals that give the mean and cost of a portfolio are continuous; hence there exist unique portfolios that represent these functionals. These portfolios span the mean-variance efficient set. We resolve the question of when a market with many assets permits so much diversification that risk-free investment opportunities are available. Ross 112, 141 showed that if there is a factor structure, then the mean returns are approximately linear functions of factor loadings. We define an approximate factor structure and show that this weaker restriction is sufficient for Ross' result. If the covariance matrix of the asset returns has only K unbounded eigenvalues, then there is an approximate factor structure and it is unique. The corresponding K eigenvectors converge and play the role of factor loadings. Hence only a principal component analysis is needed in empirical work.
TL;DR: A cosmid derivative of the low copy-number broad host-range cloning vector pRK290, pLAFR1 is constructed, is 21.6 kb long, confers tetracycline resistance, contains a unique EcoRI site, and can be mobilized into and stably replicates within many Gram-negative hosts.
TL;DR: The following is the lecture delivered by the author in Stockholm on 8 December 1981 when he received the Nobel Prize in Medicine, which he shared with Roger Sperry and David H. Hubel.
Abstract: The following is the lecture delivered by the author in Stockholm on 8 December 1981 when he received the Nobel Prize in Medicine, which he shared with Roger Sperry and David H. Hubel The article is published here with permission from the Nobel Foundation and will also be included in the complete volume of Les Prix Nobel en 1981 as well as in the series Nobel Lectures (in English) lished by Elsevier.
TL;DR: Together analysis of DNA polymorphisms in the human β-globin gene cluster and in cloned β-genes has revealed the association of specific β-thalassaemia mutations and β-gene polymorphisms with particular flanking polymorphisms.
Abstract: Combined analysis of DNA polymorphisms in the human β-globin gene cluster and in cloned β-genes has revealed the association of specific β-thalassaemia mutations and β-gene polymorphisms with particular flanking polymorphisms. A systematic study of cloned genes identified several new mutations, one of which possibly affects transcription. The strategy used may be applicable to other diseases of single-copy genes.
TL;DR: The nucleotide sequence of twoBacillus subtilis promoters (veg andtms) that are utilized by the principal form of B. subtilIS RNA polymerase found in vegetative cells is determined and sequences are compared to those of several previously reported Bacillus promoters.
Abstract: We have determined the nucleotide sequence of twoBacillus subtilis promoters (veg andtms) that are utilized by the principal form ofB subtilis RNA polymerase found in vegetative cells (σ55-RNA polymerase) and have compared our sequences to those of several previously reportedBacillus promoters Hexanucleotide sequences centered approximately 35 (the “-35” region) and 10 (the “-10” region) base pairs upstream from theveg andtms transcription startpoints (and separated by 17 base pairs) corresponded closely to the consensus hexanucleotides (TTGACA and TATAAT) attributed toEscherichia coli promoters Conformity to the preferred -35 and -10 sequences may not be sufficient to promote efficient utilization byB subtilis RNA polymerase, however, since three promoters (veg, tms andE coli tac) that conform to these sequences and that are utilized efficiently byE coli RNA polymerase were used with highly varied efficiencies byB subtilis RNA polymerase
TL;DR: Monoclonal antibodies were prepared to anti-HLA-DR cytolytic T lymphocytes (CTLs) and screened for inhibition of CTL-mediated killing, suggesting that these molecules participate in the C TL-target cell interaction.
Abstract: Monoclonal antibodies were prepared to anti-HLA-DR cytolytic T lymphocytes (CTLs) and screened for inhibition of CTL-mediated killing. Binding of monoclonal antibodies to four types of molecules, LFA-1, LFA-2, LFA-3, and HLA-DR, inhibited killing, suggesting that these molecules participate in the CTL-target cell interaction. The antigens were characterized by immunoprecipitation, crosslinking, NaDodSO4/polyacrylamide gel electrophoresis, and immunofluorescence flow cytometry. The LFA-1 antigen contains alpha and beta polypeptide chains of Mr 177,000 and 95,000 that are noncovalently associated in an alpha 1 beta 1 structure. It is present on both B and T lymphocytes and marks subpopulations that differ in quantitative expression. Human LFA-1 appears to be the homologue of mouse LFA-1. Human LFA-2 is of Mr 49,000 with a minor component of Mr 36,000. It is expressed on CTL lines but not on a B-cell line and in peripheral blood preferentially on T lymphocytes. Human LFA-3 is of Mr 60,000 and is expressed on both B and T lymphocytes.
TL;DR: Results indicate that the transforming genes of these human tumor cell lines are the cellular homologs of two retroviral transforming genes.
Abstract: Blot hybridization analysis indicated that NIH 3T3 mouse bladder transformed by high molecular weight DNAs of a human bladder and a human lung carcinoma cell line contained new sequences homologous, respectively, to the transforming genes of Harvey (rasH) and Kirsten (rasK) sarcoma viruses. The unique ras sequences were present in multiple independent NIH cell lines transformed in both primary and secondary transfection assays and corresponded to ras sequences normally present in human DNAs. The ras gene product was expressed in NIH cells transformed by bladder carcinoma DNAs and in the human bladder carcinoma cell lines at levels 2- to 4-fold greater than the level observed in nontransformed NIH 3T3 cells. These results indicate that the transforming genes of these human tumor cell lines are the cellular homologs of two retroviral transforming genes.
TL;DR: The detected myoelectric signals have been decomposed into their constituent motor‐unit action potential trains using a recently developed technique and recorded from the human deltoid and first dorsal interosseous muscles.
Abstract: 1. The electrical activity of up to eight concurrently active motor units has been recorded from the human deltoid and first dorsal interosseous (f.d.i.) muscles. The detected myoelectric signals have been decomposed into their constituent motor-unit action potential trains using a recently developed technique.
2. Concurrently active motor unit behaviour has been examined during triangular force-varying isometric contractions reaching 40 and 80% of maximal voluntary contraction (m.v.c.). Experiments were performed on four normal subjects and three groups of highly trained performers (long-distance swimmers, powerlifters and pianists).
3. Results revealed a highly ordered recruitment and decruitment scheme, based on motoneurone excitability, in both muscles and in all subject groups.
4. Differences were observed between the initial (recruitment) and final (decruitment) firing rates in each muscle. These parameters were invariant with respect to the force rates studied, although some differences were observed among subject groups.
5. In general, firing rates of f.d.i. motor units increased steadily with increasing force (up to 80% m.v.c.). The firing rates of deltoid motor units rose sharply just after recruitment and then increased only slightly thereafter.
6. Recruitment was found to be the major mechanism for generating extra force between 40 and 80% m.v.c. in the deltoid, while rate coding played the major role in the f.d.i.
7. The potential of rate coding for increasing force levels up to m.v.c. is discussed.
TL;DR: It is demonstrated that epidermal cells do move over a fibrin and fibronectin matrix during in vivo wound repair, as well as other factors regulating the attachment and directional migration of a regenerating epidermis in wound healing.
TL;DR: A functional extension of skin over the entire wound area is formed in about 4 weeks and no immunosuppression is used and infection, exudation, and rejection are absent.
Abstract: Prompt and long-term closure of full-thickness skin wounds is guinea pigs and humans is achieved by applying a bilayer polymeric membrane. The membrane comprises a top layer of a silicone elastomer and a bottom layer of a porous cross-linked network of collagen and glycosaminoglycan. The bottom layer can be seeded with a small number of autologous basal cells before grafting. No immunosuppression is used and infection, exudation, and rejection are absent. Host tissue utilizes the sterile membrane as a culture medium to synthesize neoepidermal and neodermal tissue. A functional extension of skin over the entire wound area is formed in about 4 weeks.
TL;DR: Despite the anomaly of migrations and the post-migratory positions of neurons in reeler, cohorts of cells formed at the same time in the two genotypes give rise to the same neuronal classes.
TL;DR: Protamine is shown to be a specific inhibitor of angiogenesis, which inhibits the capillary proliferation observed in embryogenesis, inflammation, certain immune reactions and the growth of solid tumours.
Abstract: Protamine is shown to be a specific inhibitor of angiogenesis. The compound inhibits the capillary proliferation observed in embryogenesis, inflammation, certain immune reactions and the growth of solid tumours.
TL;DR: In this paper, the authors discuss explicit soft breaking of global supersymmetry using superfield methods and show that dimension-two operators are soft while dimension-three operators are not and introduce quadratic divergences not present in unbroken theory.
TL;DR: The fact that yeast can recognize and use DNA ends from the distantly related organism Tetrahymena suggests that the structural features required for telomere replication and resolution have been highly conserved in evolution.
TL;DR: DNA's of various tumors induce transformation with high efficiencies, indicating that oncogenesis can involve dominant genetic alterations resulting in activation of cellular transforming genes.
Abstract: Cellular genes potentially capable of inducing oncogenic transformation have been identified by homology to the transforming genes of retroviruses and by the biological activity of cellular DNA's in transfection assays. DNA's of various tumors induce transformation with high efficiencies, indicating that oncogenesis can involve dominant genetic alterations resulting in activation of cellular transforming genes. The identification and characterization of cellular transforming genes and their possible involvement in naturally occurring cancers, is discussed.
TL;DR: The evidence reviewed here supports the hypothesis that variations occur to a large extent because of differences among physicians in their evaluation of patients or in their belief in the value of the procedures for meeting patient needs.
TL;DR: For both the slow-twitch soleus and the fast-twitch EDL and for all tetanus durations (up to 15 s), the extent of the initial chemical change was identical with the amount of recovery chemical resynthesis, showing that a biochemical energy balance existed in these muscles.
Abstract: The energy utilization associated with contraction was measured in isolated slow- and fast-twitch muscles of the mouse at 20 degrees C. The extent of this utilization was estimated from either the extent of high-energy phosphate splitting occurring during contraction (the initial chemical change, delta approximately P init) or from the extent of recovery resynthesis calculated from the observed oxygen consumption and lactate production occurring during the recovery period (recovery chemical resynthesis, delta approximately P rec). For short tetani, the cost to maintain isometric tension in the fast-twitch extensor digitorum longus (EDL) was approximately threefold greater than that in the slow-twitch soleus. With prolonged stimulation, however, the energy cost in the EDL diminished so that after 12 s of stimulation, the energy cost in the EDL was only 50% greater than that of the soleus. For both the slow-twitch soleus and the fast-twitch EDL and for all tetanus durations (up to 15 s), the extent of the initial chemical change was identical with the amount of recovery chemical resynthesis, showing that a biochemical energy balance existed in these muscles.
TL;DR: An expanded hierarchical theory would not be Darwinism, has strictly defined, but it would capture, in abstract form, the fundamental feature of Darwin's vision--direction of evolution by selection at each level.
Abstract: The essence of Darwinism lies in the claim that natural selection is a creative force, and in the reductionist assertion that selection upon individual organisms is the locus of evolutionary change. Critiques of adaptationism and gradualism call into doubt the traditional consequences of the argument for creativity, while a concept of hierarchy, with selection acting upon such higher-level "individuals" as demes and species, challenges the reductionist claim. An expanded hierarchical theory would not be Darwinism, has strictly defined, but it would capture, in abstract form, the fundamental feature of Darwin's vision--direction of evolution by selection at each level.