Showing papers by "New York University published in 1976"
TL;DR: In this paper, a least-square Wiener-Hopf minimization of an appropriately chosen cost functional is proposed to obtain an asymptotically stable and dynamical closed-loop configuration irrespective of whether the plant is proper, stable, or minimum phase.
Abstract: In many modern-day control problems encountered in the fluid, petroleum, power, gas and paper industries, cross coupling (interaction) between controlled and manipulated variables can be so severe that any attempt to employ single-loop controllers results in unacceptable performance. In all these situations, any workable control strategy most take into account the true multivariable nature of the plant and address itself directly to the design of a compatible multivariable controller. Any practical design technique most be able to cope with load disturbance, plant saturation, measurement noise, process lag, sensitivity and also incorporate suitable criteria delimiting transient behavior and steady-state performance. These difficulties, when compounded by the fact that many plants (such as chemical reactors) are inherently open-loop unstable have hindered the development of an inclusive frequency-domain analytic design methodology. However, a solution based on a least-square Wiener-Hopf minimization of an appropriately chosen cost functional is now available. The optimal controller obtained by this method guarantees an asymptotically stable and dynamical closed-loop configuration irrespective of whether or not the plant is proper, stable, or minimum-phase and also permits the stability margin of the optimal design to be ascertained in advance. The main purpose of this paper is to lay bare the physical assumptions underlying the choice of model and to present an explicit formula for the optimal controller.
1,276 citations
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TL;DR: In this paper, the authors describe how an organization can meet social and technological changes and reap advantage from them by forming a self-designing organization, where those who perform activities take primary responsibility for learning and for inventing new methods and nonparticipant designers restrict themselves to a catalytic role.
Abstract: This article prescribes how an organization can meet social and technological changes and reap advantage from them. Long-term viability maximizes in a self-designing organization, in which those who perform activities take primary responsibility for learning and for inventing new methods, and in which nonparticipant designers restrict themselves to a catalytic role. Designers can form such an organization by putting together processes, the generators of behaviors. Although complex interactions among processes make designers’ forecasts unreliable, people can mitigate serious future problems by keeping processes dynamically balanced. Six aphorisms caricature the desired balance: Cooperation requires minimal consensus; Satisfaction rests upon minimal contentment; Wealth arises from minimal affluence; Goals merit minimal faith; Improvement depends on minimal consistency; Wisdom demands minimal rationality.
814 citations
01 Jan 1976
TL;DR: The death rate per tumor cell due to immunological response is proportional to the total number of antigen-producing (tumor) cells; thus, the total death rate is quadratic.
Abstract: Let X(t) be the number of tumor cells at time t, and Pr{X(t) = n} = pn(t) is the density of X. A “birth”, i.e., an increase of one of the total population of cancer cells, can occur either by mutation of a normal cell caused by the action of the carcinogen, consisting of randomly (Poisson) distributed hits, or by reproduction of existing cancer cells. A death of a tumor cell occurs as an additive combination of non-immunological and immunological elements. Once a tumor is initiated by carcinogenic action, it undergoes a birth and death process with infinitesimal birth rate linear and infinitesimal death rate composed of a linear and a nonlinear term, the former due to non-immunological deaths, the latter to immunological feedback. The death rate per tumor cell due to immunological response is proportional to the total number of antigen-producing (tumor) cells; thus, the total death rate is quadratic. Although this assumes a very simple mechanism for the action of immunological feedback, it is nevertheless a first step.
565 citations
TL;DR: A new type of personal sampler for gases in air, originally reported from this laboratory, has been adapted to measurement of NO2, accurate, light, simple to use and have very good shelf life before and after sampling.
Abstract: A new type of personal sampler for gases in air, originally reported from this laboratory, has been adapted to measurement of NO2. The sampler depends on the transfer of NO2 by diffusion to a triethanolamine coated collector at the sealed end of a tube; the open end of the tube is exposed to the test environment. The devices are accurate, light, simple to use and have very good shelf life before and after sampling.
477 citations
TL;DR: In this article, an analytical feedback design technique is presented for single-input-output processes which are characterized by their rational transfer functions, and the design procedure accounts for the topological structure of the feedback system ensuring asymptotic stability for the closed-loop configuration.
Abstract: An analytical feedback design technique is presented here for single-input-output processes which are characterized by their rational transfer functions. The design procedure accounts for the topological structure of the feedback system ensuring asymptotic stability for the closed-loop configuration. The plant or process being controlled can be unstable and/or nonminimum phase. The treatment of feedback sensor noise, disturbance inputs, and process saturation is another major contribution of this work. The cornerstone in the development is the selection of a performance index based on sound engineering considerations. It is these considerations, in fact, which ensure the existence of an optimal compensator for the system and make the performance index a natural one for the problem at hand.
464 citations
TL;DR: It is indicated that Langerhans cells may pick up antigen in skin and from there circulate to draining lymph nodes, thus carrying out a function analogous to macrophages, in this way they may exhibit antigen to lymphocytes both inskin and in lymph nodes.
462 citations
TL;DR: This paper extends the discussion of estimation of the parameters of a single tone from a finite number of noisy discrete-time observations to include several tones and derives the Cramér-Rao bounds.
Abstract: In a previous paper, we discussed estimation of the parameters of a single tone from a finite number of noisy discrete-time observations. In this paper, we extend the discussion to include several tones. The Cramer-Rao bounds are derived and their properties examined. Estimation algorithms are discussed and characterized.
383 citations
TL;DR: Evidence is presented which points to a functional role for the protein found on the surface of normal but not transformed cells as a mediator of the adhesion of fibroblasts to collagen and the name cell adhesion factor (CAF) is proposed for this protein.
Abstract: DEFECTS in cell behaviour associated with malignancy may be causally related to alterations in the plasma membrane of the cell on transformation1. Much interest has focused on a protein found on the surface of normal but not transformed cells 2–7. This protein, designated SF (ref. 5), LETS (ref. 8), band 1 (ref. 9), L1 (ref. 3) or CSP (ref. 10), is a glycoprotein7,9,11 with a molecular weight of 210,000–250,000 (refs 7, 8 and 12). It is present in the serum12 and is sensitive to removal from the surface of normal fibroblasts by low levels of trypsin2,3,9. Several biological properties of this protein have been described. Normal fibroblasts arrested in mitosis lack this protein8,9. As normal cells approach confluency, there is a quantitative increase in the amount of this protein present on the cell surface8,9, whereas confluent normal cells, stimulated by the addition of serum, have lowered levels8. In conflict with these results, implying a growth regulatory function, is the finding that stimulation of growth-arrested normal cells by thrombin leads to thymidine incorporation without a concomitant decrease in the levels of this protein13. We now present evidence which points to a functional role for the protein as a mediator of the adhesion of fibroblasts to collagen. The protein is probably identical to a serum factor previously reported to be necessary for the attachment of SV40-transformed 3T3 fibroblasts to collagen-coated dishes14. Based on this functional role, we propose the name cell adhesion factor (CAF) for this protein.
370 citations
TL;DR: Incubation of histidine requiring auxotrophs of the bacterium Salmonella typhimurium with malonaldehyde, a three-carbon dialdehyde, produced an increased number of revertants in specific strains, consistent with the cross-linking of bacterial DNA by mal onaldehyde leading to mutagenesis expressed through the error-prone repair system.
Abstract: Incubation of histidine requiring auxotrophs of the bacterium Salmonella typhimurium with malonaldehyde, a three-carbon dialdehyde, produced an increased number of revertants in specific strains. Mutagenesis was only observed in frameshift mutants with normal excision repair and did not occur in those base-pair substitution mutants tested. The results are consistent with the cross-linking of bacterial DNA by malonaldehyde leading to mutagenesis expressed through the error-prone repair system.
359 citations
TL;DR: Primates show a strong positive relationship between body weight and home range area, and primates living in social groups have much larger total home range than individual solitary mammals.
Abstract: Primates show a strong positive relationship between body weight and home range area. Dietary habits also influence home range area. Folivorous primates occupy smaller home range areas for their body weight than do frugivores and omnivores. Primates generally require smaller home range area per individual than solitary terrestrial mammals, but primates living in social groups have much larger total home range than individual solitary mammals. This trend may necessitate higher expenditures of energy in food-gathering or modifications in movement patterns.
346 citations
TL;DR: Experiments in which viable FA fibroblasts were exposed to a direct-acting mutagen or carcinogen for a period of 6 d, ensuring chronic exposure of the cells during one or more cell cycles, until increased cell density inhibited further cell division.
Abstract: INDIVIDUALS with certain genetic syndromes associated with chromosome damage show markedly increased incidence of cancer1. In one such syndrome, Fanconi's anaemia (FA), chromosomal breakage and rearrangement has been found in lymphocytes and fibroblasts2,3 years before the development of malignant tumours. There is some evidence that cells from FA patients are especially sensitive to oncogenic agents. FA fibroblasts are abnormally susceptible to SV40 transformation4, and lymphocytes from patients show increased chromosome aberrations after exposure to ionising radiation5, or to alkylating agents6,7. In these reports, however, evaluation was based on cells which entered metaphase during brief and possibly toxic exposures to chemicals. We report here experiments in which FA fibroblasts were exposed to a direct-acting mutagen or carcinogen for a period of 6 d, ensuring chronic exposure of the cells during one or more cell cycles, until increased cell density inhibited further cell division. After subculture we could then assay chromosome damage in cells capable of entering a new cycle of cell division after removal from the chemical. We found that viable FA fibroblasts showed increases in chromosome aberrations after exposure to the mutagen or carcinogen at concentrations that had no effect in other cell strains tested. Since fibroblasts can be maintained in serial passage, their use in this protocol makes it possible to examine residual and possibly lasting effects of the treatment.
TL;DR: From a series of 2,594 patients undergoing open-heart surgery, 39 patients had sternal or costochondral infections, most of which were associated with a number of predisposing factors: prolonged perfusion time, excessive postoperative bleeding, depressed cardiac output in the postoperative period, and a history of re-exploration for the control of hemorrhage.
TL;DR: A generalization of the Lax-Wendroff method is presented in this article, which bears the same relationship to the two-step Richtmyer method as the KreissOliger scheme does to the leapfrog method.
Abstract: A generalization of the Lax-Wendroff method is presented. This generalization bears the same relationship to the two-step Richtmyer method as the KreissOliger scheme does to the leapfrog method. Variants based on the MacCormack method are considered as well as extensions to parabolic problems. Extensions to two dimensions are analyzed, and a proof is presented for the stability of a Thommentype algorithm. Numerical results show that the phase error is considerably reduced from that of second-order methods and is similar to that of the Kreiss-Oliger method. Furthermore, the (2, 4) dissipative scheme can handle shocks without the necessity for an artificial viscosity.
TL;DR: A class of three-space-dimensional soliton solutions is given in this paper, which are made of scalar fields and are of a nontopological nature; the necessary conditions for having such soliton solution are (I) the conservation of an additive quantum number, say Q, and (II) the presence of a neutral (Q = 0) scalar field.
Abstract: A class of three-space-dimensional soliton solutions is given; these solitons are made of scalar fields and are of a nontopological nature. The necessary conditions for having such soliton solutions are (I) the conservation of an additive quantum number, say Q, and (II) the presence of a neutral (Q = 0) scalar field. It is shown that there exist two critical values of the additive quantum number, Q/sub C/ and Q/sub S/, with Q/sub C/ smaller than Q/sub S/. Soliton solutions exist for Q > Q/sub C/. When Q > Q/sub S/, the lowest soliton mass is Qm; never and Q/sub S/, the soliton mass is > Qm; nevertheless, the lowest-energy soliton solution can be shown to be always classically stable, though quantum-mechanically metastable. The canonical quantization procedures are carried out. General theorems on stability are established, and specific numerical results of the soliton solutions are given. (AIP)
TL;DR: The role of Langerhans cells in contact allergic hypersensitivity reactions has been reviewed in this paper, which suggests that these cells may be involved not only in the contact allergic reactions but also in other immunologic reactions, particularly in cell-mediated reactions in the skin.
TL;DR: The distribution of particles in the paranodal region of the axolemma suggests that the large intramembranous particles do not have free access to the axoglial junctional portion of the membrane and therefore the movement of such particles may occur primarily in the membrane of the ‘groove’ spiraling through this portion of The freeze-fracture technique.
Abstract: The plasma membrane of myelinated axons in the frog brain has been examined by the freeze-fracture technique. The cytoplasmic leaflet of the axolemma contains numerous randomly distributed particles in nodal and internodal regions but relatively fewer particles in the axoglial junctional portion of the paranodal region. Particle distribution is even less uniform in the outer leaflet of the axolemma, which contains a low concentration of particles in the internodal region and a relatively high concentration at the node of Ranvier (approximately 1200 particles mum-2). The nodal particles tend to be larger than most intramembranous particles, approaching 200 A diameter. The paranodal region of the leaflet is virtually devoid of such particles except in the narrow helical 'groove' which faces extracellular clefts between terminating glial processes. In places this pathway widens to form 'lakes' up to approximately 0.3 mum2 area which contain large numbers of large particles resembling those at the node. The concentration of particles at the node is in the same range as the concentration of sodium channels estimated to be in this region and it is suggested on the basis of their location and concentration that these particles represent ionophores. The distribution of particles in the paranodal region suggests that the large intramembranous particles do not have free access to the axoglial junctional portion of the membrane and therefore the movement of such particles along the paranodal region of the membrane may occur primarily in the membrane of the 'groove' spiraling through this portion of the axolemma. Such a restriction in surface area for particle movements on either side of the node of Ranvier could result in trapping of particles at the node and thus contribute to their concentration in the nodal axolemma.
TL;DR: This chapter discusses the functions of IgA antibodies and presents many interesting and important problems related to IgA that remain to be solved.
Abstract: Publisher Summary Immunoglobulin A (IgA) is the principal class of immunoglobulin in most external secretions It is made by plasma cells in glands and mucous membranes that face the external environment The secretory form of IgA, known as secretory IgA, has distinctive antigenic and structural characteristics due to the presence of an extra polypeptide chain, the secretory component This chapter emphasizes the maturation of IgA during ontogeny; synthesis and assembly of IgA; IgA cell cycle; thymus dependency of IgA; and disorders of IgA production The chapter discusses the functions of IgA antibodies Commitment of an immunocyte to the production of IgA is the terminal step in a differentiation process that begins with a cell bearing IgM on its surface On balance, the evidence favors a direct switch from IgM to IgA Much of the IgA secreted by the plasma cells in exocrine glands and mucous membranes is dimeric The fully assembled secretory IgA molecule is the synthetic product of two distinct types of cell, both of which reside locally in the mucous membrane or gland As is the case with IgG and IgE, the secretion of IgA is thymus dependent In humans, thymic dysfunction is often associated with diminished IgA The chapter also presents many interesting and important problems related to IgA that remain to be solved
TL;DR: It is concluded that nitinol alloy is sufficiently compatible with dog tissue to warrant further investigation of its potential as a biomaterial.
Abstract: The biocompatibility of nitinol alloy as a potential implant material was investigated through in vivo studies on beagles. A high-purity alloy was fabricated into prototype bone plates and implanted into the femurs of beagles. Commercial cobalt-chromium (Co-Cr) alloy bone plates served as reference controls, an additional control data were obtained from beagles subjected to "sham" operations. The bone plates were removed from the animals and examined after exposures of 3, 6, 12, and 17 months. There was no evidence of either localized or of general corrosion on the surfaces of the bone plates and screws. Gross clinical, radiological, and morphological observations of the tissue at the implantation sites during the autopsies uncovered no signs of adverse tissue reactions resulting from the implants. Histological analyses were performed on samples of muscle and bone adjacent to the implantation sites, and of tissues removed from such organs as the liver, spleen, brain, and kidneys. No significant differences were noted between samples taken from controls and those taken from dogs exposed to the implants. Neutron activation analyses were carried out on suitable samples. The analysis data suggest that there is no metallic contamination in the organs due to the implants; however, there does appear to be some chromium contamination from the Co-Cr alloy implants in the adjacent bone. On the basis of the totality of the data, it is concluded that nitinol alloy is sufficiently compatible with dog tissue to warrant further investigation of its potential as a biomaterial.
TL;DR: The activities of a colony-stimulating factor (CSF), which stimulates granulocyte-macrophage colony formation by mouse hemopoietic cells, and macrophage growth factor (MGF),which stimulates proliferation of activated peritoneal macrophages, have been demonstrated by various criteria to reside in the same molecular species.
Abstract: The activities of a colony-stimulating factor (CSF), which stimulates granulocyte-macrophage colony formation by mouse hemopoietic cells, and macrophage growth factor (MGF), which stimulates proliferation of activated peritoneal macrophages, have been demonstrated by various criteria to reside in the same molecular species. These criteria include occurrence in various sources and copurification of the activities in mouse L-cell-conditioned medium as well as the biological, physicochemical, and antigenic properties of the activities of L-cell-conditioned medium. CSF and MGF activities of L-cell-conditioned medium are ascribable to a glycoprotein of mol wt approximately 60,000 which migrates electrophoretically with alpha-globulin. Human urinary CSF, which also possesses MGF activity, has similar properties and can be neutralized by antiserum to highly purified L-cell medium CSF. A procedure is described for the partial purification of material from L-cell medium that has activity at 1 ng/ml in both MGF and CSF assays.
TL;DR: An algorithm for drawing pictures of three-dimensional objects, with surfaces made up of patches of quadric surfaces, is described, which can find the coordinates of points of even quartic (fourth-order) intersection curves, using equations of no more than second order.
Abstract: An algorithm for drawing pictures of three-dimensional objects, with surfaces made up of patches of quadric surfaces, is described. The emphasis of this algorithm is on calculating the intersections of quadric surfaces. A parameterization scheme is used. Each quadric surface intersection curve (QSIC) is represented as a set of coefficients and parameter limits. Each value of the parameter represents at most two points, and these may easily be distinguished. This scheme can find the coordinates of points of even quartic (fourth-order) intersection curves, using equations of no more than second order. Methods of parameterization for each type of QSIC are discussed, as well as surface bounding and hidden surface removal.
01 May 1976
TL;DR: (1976).
Abstract: (1976). Volatile Organic Compounds and Microorganisms. CRC Critical Reviews in Microbiology: Vol. 4, No. 4, pp. 333-382.
TL;DR: It was established that freshly isolated rod outer segments (ROS) could regenerate their rhodopsin almost completely from added 11- cis retinol, provided that NADP was also present, and that the ROS isomerase is specific for retinyl ester, which under normal circumstances can only be provided by the RPE.
TL;DR: The authors found that self-relevant words were read faster than neutral words, even though they had been matched for length, frequency, and part of speech, while the expected interaction of word content and presence of mirror and camera to produce longer color-naming latencies did not appear.
01 Jan 1976
TL;DR: In this paper, the transonic potential flow equation is derived from the Euler equations for inviscid compressible flow by introducing the assumption that the flow is irrotational, and the numerical procedure for actually computing a solution contains two main elements: the construction of a discrete approximation which converges to the solution of the continuous problem in the limit as the mesh width is reduced to zero.
Abstract: The development of relaxation methods to calculate transonic flows is discussed. Rather accurate predictions can be made for a number of flows of interest using the transonic potential flow equation, which may be derived from the Euler equations for inviscid compressible flow by introducing the assumption that the flow is irrotational. Once the choice of a mathematical model has been settled, the numerical procedure for actually computing a solution contains two main elements: the construction of a discrete approximation which converges to the solution of the continuous problem in the limit as the mesh width is reduced to zero, and the solution of the resulting set of nonlinear difference equations by a convergent iterative scheme. The choice of an appropriate coordinate system and its influence on the accuracy of the discrete approximation is discussed. Several applications of the general method are described.
TL;DR: In this paper, an analysis of several different indices of voting power reveals that the voting power of a member of a weighted voting body may increase, rather than decrease, when new members are added to the original body.
Abstract: An analysis of several different indices of voting power reveals that the voting power of a member of a weighted voting body may increase, rather than decrease, when new members are added to the original body. Real instances of this phenomenon, called the paradox of new members, are shown to have occurred when new states were added to the U.S. Electoral College and new countries to the European Community Council of Ministers. Conditions for the existence of the paradox, and probabilities of its occurrence in small and moderate-size voting bodies, are given. Efficient algorithms for the calculation of the voting power indices, based on generating functions, are also outlined.
TL;DR: The results suggest that alpha-tocopherol and beta-carotene are transported differently in the circulation and that the tissue storage and mobilization of these compounds are different.
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TL;DR: The tuberous breast deformity cannot usually be corrected satisfactorily by standard augmentation mammaplasty or mastopexy, but the two operative techniques described have been most helpful in dealing with this difficult problem.
TL;DR: In this article, the generalized Zimmermann identity relating normal products of different subtraction degrees is generalized to include arbitrary masses, ultraviolet regulators, and green functions with arbitrary numbers of normal products, providing the basis for the derivation of normal product field equations in models with zero-mass propagators.
TL;DR: In this paper, a general momentum-space subtraction procedure is proposed for the removal of both ultraviolet and infrared divergences of Feynman integrals, which allows one to define time-ordered Green functions, as tempered distributions, for a wide class of theories with zero-mass propagators.
Abstract: A general momentum-space subtraction procedure is proposed for the removal of both ultraviolet and infrared divergences of Feynman integrals. Convergence theorems are proved which allow one to define time-ordered Green functions, as tempered distributions, for a wide class of theories with zero-mass propagators.