Showing papers by "New York University published in 1992"

Statistical Power Analysis

Abstract: pression, Journal of Clinical Psychiatry, 51, 61-69 (1990). 11. L.R. Baxter, Jr., J.M. Schwartz, B.H. Guze, J.C. Mazziotta, M.P. Szuba, K. Bergman, A. Alazraki, C.E. Selin, H.K. Freng, P. Munford, and M.E. Phelps, Obsessive-compulsive disorder vs. Tourette's disorder: Differential function in subdivi sions of the neostriatum, paper presented at the an nual meeting of the American College of Neuropsy chopharmacology, San Juan, Puerto Rico (December 1991). 12. E.M. Reiman, M.E. Raichle, F.K. Butler, P. Herscovitch, and E. Robins, A focal brain abnormal ity in panic disorder, a severe form of anxiety, Na ture, 310, 683-685 (1984); E.M. Reiman, M.E. Ra ichle, E. Robins, F.K. Butler, P. Herscovitch, P. Fox, and J. Perlmutter, The application of positron emis sion tomography to the study of panic disorder, American Journal of Psychiatry, 143, 469-477 (1986); T.E. Nordahl, W.E. Semple, M. Gross, T.A. Mellman, M.B. Stein, P. Goyer, A.C. King, T.W. Uhde, and R.M. Cohen, Cerebral glucose metabolic differences in patients with panic disorder, Neuro psychopharmacology, 3, 261-272 (1990).

Imperial Eyes: Travel Writing and Transculturation

Abstract: 1st edition contents List of Illustrations Preface Introduction: Criticism in the contact zone Part I Science and sentiment, 1750-1800 Science, planetary consciousness, interiors Narrating the anti-conquest Anti-conquest II: The mystique of reciprocity Eros and Abolition Part II The reinvention of America, 1800-50 Alexander von Humboldt and the reinvention of America Reinventing America II: The capitalist vanguard and the exploratrices sociales Reinventing America/Reinventing Europe: Creole self-fashioning Part III Imperial Stylistics, 1860-1980 From the Victoria N'yanza to the Sheraton San Salvador Notes Index

Singularity detection and processing with wavelets

Abstract: The mathematical characterization of singularities with Lipschitz exponents is reviewed. Theorems that estimate local Lipschitz exponents of functions from the evolution across scales of their wavelet transform are reviewed. It is then proven that the local maxima of the wavelet transform modulus detect the locations of irregular structures and provide numerical procedures to compute their Lipschitz exponents. The wavelet transform of singularities with fast oscillations has a particular behavior that is studied separately. The local frequency of such oscillations is measured from the wavelet transform modulus maxima. It has been shown numerically that one- and two-dimensional signals can be reconstructed, with a good approximation, from the local maxima of their wavelet transform modulus. As an application, an algorithm is developed that removes white noises from signals by analyzing the evolution of the wavelet transform maxima across scales. In two dimensions, the wavelet transform maxima indicate the location of edges in images. >

Mass Customization: The New Frontier in Business Competition

Abstract: The article reviews the book “Mass Customization: The New Frontier in Business Competition,” by B. Joseph Pine II.

Lengthening the human mandible by gradual distraction.

Abstract: Lengthening of the mandible by gradual distraction was performed on four young patients (average age 78 months). The amount of mandibular bone lengthening ranged from 18 to 24 mm; one patient with Nager's syndrome underwent bilateral mandibular expansion. Following the period of expansion, the patients were maintained in external fixation for an average of 9 weeks to allow ossification. The patients were followed for a minimum of 11 months to a maximum of 20 months with clinical and dental examinations as well as photographic and radiographic documentation. The technique holds promise for early reconstruction of craniofacial skeletal defects without the need for bone grafts, blood transfusion, or intermaxillary fixation.

The Second National Acute Spinal Cord Injury Study.

Abstract: In 1990, the Second National Acute Spinal Cord Injury Study reported that high-dosage methylprednisolone improves neurologic recovery in spinal-injured humans. The study showed that patients who received the drug within 8 hr after injury improved, whereas those who received the drug later did not. The drug significantly increased recovery even in severely injured patients who were admitted with no motor or sensory function below the lesion, contradicting a long-held dogma that such patients would not recover. Some researchers, however, have questioned the stratification of the patient population, the use of summed neurologic change scores, and the absence of functional assessments. The stratification by injury severity and treatment time was planned a priori and based on objective criteria. Detailed analyses revealed no differences between groups attributable to stratification or randomization. While multivariate analyses of the summed neurologic scores were used, the conclusions were corroborated by other analytical approaches that did not rely on summed scores. For example, treatment with methylprednisolone more than doubled the probability that patients would convert from quadriplegia or paraplegia to quadriparesis or paraparesis, analgesia to hypalgesia, and anesthesia to hypesthesia. The treatment also significantly improved neurologic scores in lumbosacral segments, indicating that beneficial effects were not limited to segments close to the lesion site. The treatment did not significantly affect mortality or morbidity. The study strongly suggests that methylprednisolone has significant beneficial effects in human spinal cord injury, that these effects occur only when the drug is given within 8 hr, and that it helps even in patients with severe spinal cord injuries. These conclusions have important implications for spinal cord injury care and research.

Production of the Alzheimer amyloid β protein by normal proteolytic processing

Abstract: The 4-kilodalton (39 to 43 amino acids) amyloid beta protein (beta AP), which is deposited as amyloid in the brains of patients with Alzheimer's diseases, is derived from a large protein, the amyloid beta protein precursor (beta APP). Human mononuclear leukemic (K562) cells expressing a beta AP-bearing, carboxyl-terminal beta APP derivative released significant amounts of a soluble 4-kilodalton beta APP derivative essentially identical to the beta AP deposited in Alzheimer's disease. Human neuroblastoma (M17) cells transfected with constructs expressing full-length beta APP and M17 cells expressing only endogenous beta APP also released soluble 4-kilodalton beta AP, and a similar, if not identical, fragment was readily detected in cerebrospinal fluid from individuals with Alzheimer's disease and normal individuals. Thus cells normally produce and release soluble 4-kilodalton beta AP that is essentially identical to the 4-kilodalton beta AP deposited as insoluble amyloid fibrils in Alzheimer's disease.

Learning by Knowledge-Intensive Firms

Abstract: Knowledge-intensive firms (KIFs) specialize in expertise, especially esoteric knowledge that few other firms possess. KIFs must keep their knowledge up-to-date, so they need to learn continually. However, their ability to satisfy clients depends on the close relations that some of KIFs' personnel develop with specific clients.

Learning by knowledge‐intensive firms*

Abstract: Knowledge-intensive firms (KIFs) specialize in expertise, especially esoteric knowledge that few other firms possess. KIFs must keep their knowledge up-to-date, so they need to learn continually. However, their ability to satisfy clients depends on the close relations that some of KIFs' personnel develop with specific clients.

The FGF family of growth factors and oncogenes.

Abstract: Publisher Summary The family of fibroblast growth factors (FGF) is the largest family of growth factors involved in soft–tissue growth and regeneration. The FGF family includes seven members that share a varying degree of homology at the protein level and appear to have a similar broad mitogenic spectrum. They are angiogenic and promote the proliferation of a variety of cells of mesodermal and neuroectodermal origin . Three members of the family–namely, K–FGF/HST, FGF–5, INT–2 are identified originally as oncogenes, while two additions, FGF–6 and keratinocyte growth factor (KGF), are isolated by sequence homology or factor purification and cloning. FGF was identified as an activity in pituitary extracts that stimulated the proliferation of 3T3 cells in mice. The two prototypes of basic and acidic protein structure, the FGF genes, and the expressions of FGF are also discussed. FGF consist of three exons, separated by two introns of variable length and FGF genes map on several chromosomes. The molecular regulation of FGF expression, FGF receptors, and their interaction with extracellular matrix is described. The oncogenic potential of FGF members and their involvement in tumors is also discussed. All possible mechanisms operating on the expression of FGFs and their receptors: transcriptional controls, posttranscriptional regulation involving alternative splicing, alternative translation starts resulting in proteins with different properties, and control affecting the secretion of these proteins are discussed.

The Dynamics of Productivity in the Telecommunications Equipment Industry

Abstract: Technological change and deregulation have caused a major restructuring of the telecommunications equipment industry over the last two decades. We estimate the parameters of a production function for the equipment industry and then use those estimates to analyze the evolution of plant level productivity over this period. The restructuring involved significant entry and exit and large changes in the sizes of incumbents. Since firms' choices on whether to liquidate and on the quantities of inputs demanded should they continue depend on their productivity, we use an equilibrium model to suggest an estimation algorithm that takes into account the relationship between productivity on the one hand. and both input demand and survival on the other. A fully parametric version of the estimation algorithm would be both computationally burdensome and require a host of auxiliary assumptions. So we develop a semi parametric technique which is both consistent with a quite general version of the theoretical framework and easy to use. The algorithm produces markedly different estimates of both production function parameters and of productivity movements than traditional estimation procedures. We find an increase in the rate of industry productivity growth after deregulation. This in spite of the fact there was no increase in the average of the plants' rates of productivity growth, and there was actually a fall in our index of the efficiency of the allocation of variable factors conditional on the existing distribution of fixed factors. Deregulation was, however, followed by a reallocation of capital towards more productive establishments (by a down sizing, often shutdown. of unproductive plants and by disproportionate growth of productive establishments) which more than offset the other factors' negative impacts on aggregate productivity.

Survivorship Bias in Performance Studies

Abstract: Survivorship bias distorts results of virtually all current performance studies based on time series. Thus, researchers need to recognize and adjust for the presence of this bias. Not only does the bias affect the absolute performance measures; it also affects the relative rankings of managers over time.This presentation comes from the Blending Quantitative and Traditional Equity Analysis conference held in Boston, Massachusetts, on March 30-31, 1994.

Association of the Shc and Grb2/Sem5 SH2-containing proteins is implicated in activation of the Ras pathway by tyrosine kinases.

Abstract: THE mammalian shc gene encodes two overlapping, widely expressed proteins of 46 and 52K, with a carboxy-terminal SH2 domain that binds activated growth factor receptors, and a more amino-terminal glycine/proline-rich region1. These shc gene products (Shc) are transforming when overexpressed in fibroblasts1. Shc proteins become phosphorylated on tyrosine in cells stimulated with a variety of growth factors1, and in cells transformed by v-src (ref. 2), suggesting that they are tyrosine kinase targets that control a mitogenic signalling pathway. Here we report that tyrosine-phosphorylated She proteins form a specific complex with a non-phosphorylated 23K polypeptide encoded by the grb2/sem-5 gene3,4. The grb2/sem-5 gene product itself contains an SH2 domain, which mediates binding to Shc, and is implicated in activation of the Ras guanine nucleotide-binding protein by tyrosine kinases in both Caenorhabditis elegans and mammalian cells3,4. Consistent with a role in signalling through Ras, shc overexpression induced Ras-dependent neurite outgrowth in PC 12 cells. These results suggest that She tyrosine phosphorylation can couple tyrosine kinases to Grb2/Sem-5, through formation of a Shc-Grb2/Sem-5 complex, and thereby regulate the mammalian Ras signalling pathway.

The effect of the distance from the contact point to the crest of bone on the presence or absence of the interproximal dental papilla

Abstract: This study was designed to determine whether the distance from the base of the contact area to the crest of bone could be correlated with the presence or absence of the interproximal papilla in humans. A total of 288 sites in 30 patients were examined. If a space was visible apical to the contact point, then the papilla was deemed missing; if tissue filled the embrasure space, the papilla was considered to be present. The results showed that when the measurement from the contact point to the crest of bone was 5 mm or less, the papilla was present almost 100% of the time. When the distance was 6 mm, the papilla was present 56% of the time, and when the distance was 7 mm or more, the papilla was present 27% of the time or less.

The role of managerial learning and interpretation in strategic persistence and reorientation: An empirical exploration

Abstract: This study uses a managerial learning framework to build and test a model of the decisionmaking process that drives decisions to strategically reorient an organization. The model examines the effects of past performance, managerial interpretations, and top management team characteristics on the likelihood of strategic reorientation in two distinct environmental contexts. The results indicate that poor past performance, environmental awareness, top management team heterogeneity, and CEO turnover increased the likelihood of reorientation. There are some differences in the ways in which these variables affect reorientation across the two environmental contexts. Poor past performance was more strongly associated with reorientation in the stable environment than in the turbulent environment. The tendency to make external attributions for poor performance outcomes decreased the likelihood of reorientation in the turbulent environment, but not in the stable environment.

The generality of the automatic attitude activation effect.

Abstract: Fazio, Sanbonmatsu, Powell, and Kardes (1986) demonstrated that Ss were able to evaluate adjectives more quickly when these adjectives were immediately preceded (primed) by attitude objects of similar valence, compared with when these adjectives were primed by attitude objects of opposite valence. Moreover, this effect obtained primarily for attitude objects toward which Ss were presumed to hold highly accessible attitudes, as indexed by evaluation latency. The present research explored the generality of these findings across attitude objects and across procedural variations. The results of 3 experiments indicated that the automatic activation effect is a pervasive and relatively unconditional phenomenon. It appears that most evaluations stored in memory, for social and nonsocial objects alike, become active automatically on the mere presence or mention of the object in the environment.

Microdomains of High Calcium Concentration in a Presynaptic Terminal

Abstract: Increases in intracellular calcium concentration are required for the release of neurotransmitter from presynaptic terminals in all neurons. However, the mechanism by which calcium exerts its effect is not known. A low-sensitivity calcium-dependent photoprotein (n-aequorin-J) was injected into the presynaptic terminal of the giant squid synapse to selectively detect high calcium concentration microdomains. During transmitter release, light emission occurred at specific points or quantum emission domains that remained in the same place during protracted stimulation. Intracellular calcium concentration microdomains on the order of 200 to 300 micromolar occur against the cytoplasmic surface of the plasmalemma during transmitter secretion, supporting the view that the synaptic vesicular fusion responsible for transmitter release is triggered by the activation of a low-affinity calcium-binding site at the active zone.

A steepest descent method for oscillatory Riemann-Hilbert problems

Abstract: In this announcement we present a general and new approach to analyzing the asymptotics of oscillatory Riemann-Hilbert problems. Such problems arise, in particular, in evaluating the long-time behavior of nonlinear wave equations solvable by the inverse scattering method. We will restrict ourselves here exclusively to the modified Korteweg de Vries (MKdV) equation, $$y_t-6y^2y_x+y_{xxx}=0,\qquad -\infty

Cox-Type Regression Analysis for Large Numbers of Small Groups of Correlated Failure Time Observations

Abstract: The Cox regression model has been used extensively to analyze survival data. For data that consist of large numbers of small groups of correlated failure time observations, we show that the standard maximum partial likelihood estimate of the regression coefficient in the Cox model is still consistent and asymptotically normal. However, the corresponding standard variance-covariance estimate may no longer be valid due to the dependence among members in the groups. In this article, a correct variance-covariance estimate that takes account of the intra-group correlation is proposed. Power comparisons are performed to show the advantage of the new proposal. Examples are provided for illustration.

Nitric oxide, an endothelial cell relaxation factor, inhibits neutrophil superoxide anion production via a direct action on the NADPH oxidase.

Abstract: Nitric oxide provokes vasodilation and inhibits platelet aggregation. We examined the effect of nitric oxide on superoxide anion production by three sources: activated intact neutrophils, xanthine oxidase/hypoxanthine, and the NADPH oxidase. Nitric oxide significantly inhibited the generation of superoxide anion by neutrophils exposed to either FMLP (10(-7)M) or PMA (150 ng/ml) (IC50 = 30 microM). To determine whether the effect of nitric oxide on the respiratory burst was due to simple scavenging of O2+, kinetic studies that compared effects on neutrophils and the cell-free xanthine oxidase system were performed. Nitric oxide inhibited O2+ produced by xanthine oxidase only when added simultaneously with substrate, consistent with the short half-life of NO in oxygenated solution. In contrast, the addition of nitric oxide to neutrophils 20 min before FMLP resulted in the inhibition of O2+ production, which suggests formation of a stable intermediate. The effect of nitric oxide on the cell-free NADPH oxidase superoxide-generating system was also examined: The addition of NO before arachidonate activation (t = -6 min) significantly inhibited superoxide anion production. Nitric oxide did not inhibit O2+ when added at NADPH initiation (t = 0). Treatment of the membrane but not cytosolic component of the oxidase was sufficient to inhibit O2+ generation. The data suggest that nitric oxide inhibits neutrophil O2+ production via direct effects on membrane components of the NADPH oxidase. This action must occur before the assembly of the activated complex.

A mechanism for the antiinflammatory effects of corticosteroids: the glucocorticoid receptor regulates leukocyte adhesion to endothelial cells and expression of endothelial-leukocyte adhesion molecule 1 and intercellular adhesion molecule 1.

Abstract: Corticosteroids are the preeminent antiinflammatory agents although the molecular mechanisms that impart their efficacy have not been defined. The endothelium plays a critical role in inflammation by directing circulating leukocytes into extravascular tissues by expressing adhesive molecules for leukocytes [e.g., endothelial-leukocyte adhesion molecule 1 (ELAM-1) and intercellular adhesion molecule 1 (ICAM-1)]. We therefore determined whether corticosteroids suppress inflammation by inhibiting endothelial expression of adhesion molecules for neutrophils (polymorphonuclear leukocytes). Preincubation of endothelial cells with endotoxin [lipopolysaccharide (LPS), 1 microgram/ml] led to a 4-fold increase in subsequent adherence of polymorphonuclear leukocytes (P < 0.0001, n = 10) to endothelial cells, an increase that was markedly attenuated when endothelial cells were treated with dexamethasone (IC50 < 1 nM, P < 0.0001, n = 6 or 7) during preincubation with LPS. Moreover, the steroid receptor agonist cortisol (10 microM), but not its inactive metabolite tetrahydrocortisol (10 microM), diminished LPS-induced endothelial cell adhesiveness. Further evidence that the action of dexamethasone was mediated through ligation of corticosteroid receptors [human glucocorticoid receptors (hGRs)] was provided by experiments utilizing the steroid antagonist RU-486. RU-486 (10 microM), which prevents translocation of ligated hGR to the nucleus by inhibiting dissociation of hGR from heat shock protein 90, completely aborted the effect of dexamethasone on adhesiveness of endothelial cells (P < 0.0005, n = 3). Treatment of endothelial cells with LPS (1 microgram/ml) stimulated transcription of ELAM-1, as shown by Northern blot analysis, and expression of membrane-associated ELAM-1 and ICAM-1, as shown by quantitative immunofluorescence (both P < 0.001, n = 9). Dexamethasone markedly inhibited LPS-stimulated accumulation of mRNA for ELAM-1 and expression of ELAM-1 and ICAM-1 (IC50 < 10 nM, both P < 0.001, n = 4-9); inhibition of expression by dexamethasone was reversed by RU-486 (both P < 0.005, n = 4-6). As in the adhesion studies, cortisol but not tetrahydrocortisol inhibited expression of ELAM-1 and ICAM-1 (both P < 0.005, n = 3 or 4). In contrast, sodium salicylate (1 mM) inhibited neither adhesion nor expression of these adhesion molecules. These studies suggest that antagonism by dexamethasone of endotoxin-induced inflammation is a specific instance of the general biological principle that the glucocorticoid receptor is a hormone-dependent regulator of transcription.

Defensive Processing of Personally Relevant Health Messages

Abstract: Subectsfor whom a health threat was relvant or irrelevant were recruited and matched on prior beliefs in the health threat. Following exposure to either a low- or a high-threat message, high-relvance subjects were less likely to believe in the threat. Consistent with earlier work, no evidence was found to suggest that defensive inattention to the messages mediated subjects' final beliefs. Instead, processing measures suggested that highrelevance subects processed threatening parts of both messages in a biased fashion. The relationship between biased judgment and biased processing is discussed, as are the difficulties in documenting the latter

Selective transmission of human immunodeficiency virus type-1 variants from mothers to infants

Abstract: Multiple human immunodeficiency virus type-1 sequences from the V3 and V4-V5 regions of the envelope gene were analyzed from three mother-infant pairs. The infants' viral sequences were less diverse than those of their mothers. In two pairs, a proviral form infrequently found in the mother predominated in her infant. A conserved N-linked glycosylation site within the V3 region, present in each mother's sequence set, was absent in all of the infants' sequence sets. These findings demonstrate that a minor subset of maternal virus is transmitted to the infant.