Showing papers by "Drexel University published in 2004"
Massachusetts Institute of Technology1, University of Pennsylvania2, Princeton University3, New York University4, Los Alamos National Laboratory5, Fermilab6, University of Chicago7, Ohio State University8, University of Arizona9, Drexel University10, Johns Hopkins University11, University of Pittsburgh12, Carnegie Mellon University13, New Mexico State University14, Spanish National Research Council15, University of Sussex16, University of Tokyo17, United States Department of the Navy18, University of Michigan19, Rochester Institute of Technology20, Pennsylvania State University21
TL;DR: In this paper, the authors measured cosmological parameters using the three-dimensional power spectrum P(k) from over 200,000 galaxies in the Sloan Digital Sky Survey (SDSS) in combination with WMAP and other data.
Abstract: We measure cosmological parameters using the three-dimensional power spectrum P(k) from over 200,000 galaxies in the Sloan Digital Sky Survey (SDSS) in combination with WMAP and other data. Our results are consistent with a "vanilla" flat adiabaticCDM model without tilt (ns = 1), running tilt, tensor modes or massive neutrinos. Adding SDSS information more than halves the WMAP-only error bars on some parameters, tightening 1� constraints on the Hubble parameter from h � 0.74 +0.18 −0.07 to h � 0.70 +0.04 −0.03, on the matter density from m � 0.25 ± 0.10 to m � 0.30 ± 0.04 (1�) and on neutrino masses from < 11 eV to < 0.6 eV (95%). SDSS helps even more when dropping prior assumptions about curvature, neutrinos, tensor modes and the equation of state. Our results are in substantial agreement with the joint analysis of WMAP and the 2dF Galaxy Redshift Survey, which is an impressive consistency check with independent redshift survey data and analysis techniques. In this paper, we place particular emphasis on clarifying the physical origin of the constraints, i.e., what we do and do not know when using different data sets and prior assumptions. For instance, dropping the assumption that space is perfectly flat, the WMAP-only constraint on the measured age of the Universe tightens from t0 � 16.3 +2.3
3,938 citations
TL;DR: Heuristics for reinvigorating the quest for validation in IS research via content/construct validity, reliability, manipulation validity, and statistical conclusion validity are suggested and new guidelines for validation and new research directions are offered.
Abstract: The issue of whether IS positivist researchers were validating their instruments sufficiently was initially raised fifteen years ago. Rigor in IS research is still one of the critical scientific issues facing the field. Without solid validation of the instruments that are used to gather data on which findings and interpretations are based, the very scientific basis of the profession is threatened. This study builds on four prior retrospectives of IS research that conclude that IS positivist researchers continue to face major barriers in instrument, statistical, and other forms of validation. It goes beyond these studies by offering analyses of the state-of-the-art of research validities and deriving specific heuristics for research practice in the validities. Some of these heuristics will, no doubt, be controversial. But we believe that it is time for the IS academic profession to bring such issues into the open for community debate. This article is a first step in that direction. Based on our interpretation of the importance of a long list of validities, this paper suggests heuristics for reinvigorating the quest for validation in IS research via content/construct validity, reliability, manipulation validity, and statistical conclusion validity. New guidelines for validation and new research directions are offered.
2,644 citations
TL;DR: The results indicate that spines individually follow Hebb's postulate for learning and suggest that small spines are preferential sites for long-term potentiation induction, whereas large spines might represent physical traces of long- term memory.
Abstract: Dendritic spines of pyramidal neurons in the cerebral cortex undergo activity-dependent structural remodelling that has been proposed to be a cellular basis of learning and memory. How structural remodelling supports synaptic plasticity, such as long-term potentiation, and whether such plasticity is input-specific at the level of the individual spine has remained unknown. We investigated the structural basis of long-term potentiation using two-photon photolysis of caged glutamate at single spines of hippocampal CA1 pyramidal neurons. Here we show that repetitive quantum-like photorelease (uncaging) of glutamate induces a rapid and selective enlargement of stimulated spines that is transient in large mushroom spines but persistent in small spines. Spine enlargement is associated with an increase in AMPA-receptor-mediated currents at the stimulated synapse and is dependent on NMDA receptors, calmodulin and actin polymerization. Long-lasting spine enlargement also requires Ca2+/calmodulin-dependent protein kinase II. Our results thus indicate that spines individually follow Hebb's postulate for learning. They further suggest that small spines are preferential sites for long-term potentiation induction, whereas large spines might represent physical traces of long-term memory.
2,295 citations
TL;DR: In this article, the authors integrate sociological and economic theories about institution-based trust to propose that the perceived effectiveness of three IT-enabled institutional mechanisms-specifically feedback mechanisms, third-party escrow services, and credit card guarantees-engender buyer trust in the community of online auction sellers.
Abstract: Institution-based trust is a buyer's perception that effective third-party institutional mechanisms are in place to facilitate transaction success. This paper integrates sociological and economic theories about institution-based trust to propose that the perceived effectiveness of three IT-enabled institutional mechanisms-specifically feedback mechanisms, third-party escrow services, and credit card guarantees-engender buyer trust in the community of online auction sellers. Trust in the marketplace intermediary that provides the overarching institutional context also builds buyer's trust in the community of sellers. In addition, buyers' trust in the community of sellers (as a group) facilitates online transactions by reducing perceived risk. Data collected from 274 buyers in Amazon's online auction marketplace provide support for the proposed structural model. Longitudinal data collected a year later show that transaction intentions are correlated with actual and self-reported buyer behavior. The study shows that the perceived effectiveness of institutional mechanisms encompasses both "weak" (market-driven) and "strong" (legally binding) mechanisms. These mechanisms engender trust, not only in a few reputable sellers, but also in the entire community of sellers, which contributes to an effective online marketplace. The results thus help explain why, despite the inherent uncertainty that arises when buyers and sellers are separated in time and in space, online marketplaces are proliferating. Implications for theory are discussed, and suggestions for future research on improving IT-enabled trust-building mechanisms are suggested.
1,950 citations
TL;DR: Allan R. Tunkel, Barry J. Hartman, Sheldon L. Kaplan, Bruce A. Kaufman, Karen L. Roos, W. Michael Scheld, and Richard J. Scheld are the authors of this study, which aims to contribute to the understanding of central nervous system disorders and its role in disease.
Abstract: Allan R. Tunkel, Barry J. Hartman, Sheldon L. Kaplan, Bruce A. Kaufman, Karen L. Roos, W. Michael Scheld, and Richard J. Whitley Drexel University College of Medicine, Philadelphia, Pennsylvania; Weill Cornell Medical Center, New York, New York; Baylor College of Medicine, Houston, Texas; Medical College of Wisconsin, Milwaukee; Indiana University School of Medicine, Indianapolis; University of Virginia School of Medicine, Charlottesville; and University of Alabama at Birmingham
1,835 citations
University of Pennsylvania1, New York University2, Princeton University3, Drexel University4, Ohio State University5, University of Chicago6, Johns Hopkins University7, University of Pittsburgh8, University of Arizona9, Fermilab10, University of Colorado Boulder11, Carnegie Mellon University12, University of Hawaii13, Apache Corporation14, Massachusetts Institute of Technology15, Spanish National Research Council16, University of Sussex17, University of Tokyo18, University of Michigan19, Rochester Institute of Technology20, Pennsylvania State University21
TL;DR: In this paper, the authors employed a matrix-based method using pseudo-Karhunen-Loeve eigenmodes, producing uncorrelated minimum-variance measurements in 22 k-bands of both the clustering power and its anisotropy due to redshift-space distortions.
Abstract: We measure the large-scale real-space power spectrum P(k) by using a sample of 205,443 galaxies from the Sloan Digital Sky Survey, covering 2417 effective square degrees with mean redshift z ≈ 0.1. We employ a matrix-based method using pseudo-Karhunen-Loeve eigenmodes, producing uncorrelated minimum-variance measurements in 22 k-bands of both the clustering power and its anisotropy due to redshift-space distortions, with narrow and well-behaved window functions in the range 0.02 h Mpc-1 < k < 0.3 h Mpc-1. We pay particular attention to modeling, quantifying, and correcting for potential systematic errors, nonlinear redshift distortions, and the artificial red-tilt caused by luminosity-dependent bias. Our results are robust to omitting angular and radial density fluctuations and are consistent between different parts of the sky. Our final result is a measurement of the real-space matter power spectrum P(k) up to an unknown overall multiplicative bias factor. Our calculations suggest that this bias factor is independent of scale to better than a few percent for k < 0.1 h Mpc-1, thereby making our results useful for precision measurements of cosmological parameters in conjunction with data from other experiments such as the Wilkinson Microwave Anisotropy Probe satellite. The power spectrum is not well-characterized by a single power law but unambiguously shows curvature. As a simple characterization of the data, our measurements are well fitted by a flat scale-invariant adiabatic cosmological model with h Ωm = 0.213 ± 0.023 and σ8 = 0.89 ± 0.02 for L* galaxies, when fixing the baryon fraction Ωb/Ωm = 0.17 and the Hubble parameter h = 0.72; cosmological interpretation is given in a companion paper.
1,734 citations
TL;DR: In this article, a four-dimensional scale of trust in the context of e-products and revalidates it in terms of services is presented, showing the influence of social presence on these dimensions of trust, especially benevolence, and its ultimate contribution to online purchase intentions.
Abstract: Reducing social uncertainty—understanding, predicting, and controlling the behavior of other people—is a central motivating force of human behavior. When rules and customs are not sufficient, people rely on trust and familiarity as primary mechanisms to reduce social uncertainty. The relative paucity of regulations and customs on the Internet makes consumer familiarity and trust especially important in the case of e-Commerce. Yet the lack of an interpersonal exchange and the one-time nature of the typical business transaction on the Internet make this kind of consumer trust unique, because trust relates to other people and is nourished through interactions with them. This study validates a four-dimensional scale of trust in the context of e-Products and revalidates it in the context of e-Services. The study then shows the influence of social presence on these dimensions of this trust, especially benevolence, and its ultimate contribution to online purchase intentions.
1,717 citations
TL;DR: A previously undescribed method progressively visualizing the evolution of a knowledge domain's cocitation network is introduced, demonstrating that a search for intellectual turning points can be narrowed down to visually salient nodes in the visualized network.
Abstract: This article introduces a previously undescribed method progressively visualizing the evolution of a knowledge domain's cocitation network. The method first derives a sequence of cocitation networks from a series of equal-length time interval slices. These time-registered networks are merged and visualized in a panoramic view in such a way that intellectually significant articles can be identified based on their visually salient features. The method is applied to a cocitation study of the superstring field in theoretical physics. The study focuses on the search of articles that triggered two superstring revolutions. Visually salient nodes in the panoramic view are identified, and the nature of their intellectual contributions is validated by leading scientists in the field. The analysis has demonstrated that a search for intellectual turning points can be narrowed down to visually salient nodes in the visualized network. The method provides a promising way to simplify otherwise cognitively demanding tasks to a search for landmarks, pivots, and hubs.
1,444 citations
Kevork N. Abazajian1, Jennifer K. Adelman-McCarthy2, Marcel A. Agüeros3, Sahar S. Allam4 +162 more•Institutions (41)
TL;DR: The second data release of the Sloan Digital Sky Survey (SDSS) as mentioned in this paper is the most recent data set to be publicly available, which consists of 3.5 million unique objects, 367,360 spectra of galaxies, quasars, stars, and calibrating blank sky patches selected over 2627 deg2 of this area.
Abstract: The Sloan Digital Sky Survey (SDSS) has validated and made publicly available its Second Data Release. This data release consists of 3324 deg2 of five-band (ugriz) imaging data with photometry for over 88 million unique objects, 367,360 spectra of galaxies, quasars, stars, and calibrating blank sky patches selected over 2627 deg2 of this area, and tables of measured parameters from these data. The imaging data reach a depth of r ≈ 22.2 (95% completeness limit for point sources) and are photometrically and astrometrically calibrated to 2% rms and 100 mas rms per coordinate, respectively. The imaging data have all been processed through a new version of the SDSS imaging pipeline, in which the most important improvement since the last data release is fixing an error in the model fits to each object. The result is that model magnitudes are now a good proxy for point-spread function magnitudes for point sources, and Petrosian magnitudes for extended sources. The spectroscopy extends from 3800 to 9200 A at a resolution of 2000. The spectroscopic software now repairs a systematic error in the radial velocities of certain types of stars and has substantially improved spectrophotometry. All data included in the SDSS Early Data Release and First Data Release are reprocessed with the improved pipelines and included in the Second Data Release. Further characteristics of the data are described, as are the data products themselves and the tools for accessing them.
1,098 citations
TL;DR: Robotic surgery is still in its infancy and its niche has not yet been well defined, so its current practical uses are mostly confined to smaller surgical procedures.
Abstract: Robotic surgery is a new and exciting emerging technology that is taking the surgical profession by storm. Up to this point, however, the race to acquire and incorporate this emerging technology has primarily been driven by the market. In addition, surgical robots have become the entry fee for centers wanting to be known for excellence in minimally invasive surgery despite the current lack of practical applications. Therefore, robotic devices seem to have more of a marketing role than a practical role. Whether or not robotic devices will grow into a more practical role remains to be seen.
Our goal in writing this review is to provide an objective evaluation of this technology and to touch on some of the subjects that manufacturers of robots do not readily disclose. In this article we discuss the development and evolution of robotic surgery, review current robotic systems, review the current data, discuss the current role of robotics in surgery, and finally we discuss the possible roles of robotic surgery in the future. It is our hope that by the end of this article the reader will be able to make a more informed decision about robotic surgery before “chasing the market.”
1,014 citations
TL;DR: This work observed two objective neural correlates of insight: increased activity in the right hemisphere anterior superior temporal gyrus for insight relative to noninsight solutions and a sudden burst of high-frequency neural activity prior to insight solutions.
Abstract: People sometimes solve problems with a unique process called insight, accompanied by an “Aha!” experience. It has long been unclear whether different cognitive and neural processes lead to insight versus noninsight solutions, or if solutions differ only in subsequent subjective feeling. Recent behavioral studies indicate distinct patterns of performance and suggest differential hemispheric involvement for insight and noninsight solutions. Subjects solved verbal problems, and after each correct solution indicated whether they solved with or without insight. We observed two objective neural correlates of insight. Functional magnetic resonance imaging (Experiment 1) revealed increased activity in the right hemisphere anterior superior temporal gyrus for insight relative to noninsight solutions. The same region was active during initial solving efforts. Scalp electroencephalogram recordings (Experiment 2) revealed a sudden burst of high-frequency (gamma-band) neural activity in the same area beginning 0.3 s prior to insight solutions. This right anterior temporal area is associated with making connections across distantly related information during comprehension. Although all problem solving relies on a largely shared cortical network, the sudden flash of insight occurs when solvers engage distinct neural and cognitive processes that allow them to see connections that previously eluded them.
TL;DR: The findings 1 year after randomization to a low-carbohydrate diet versus a high-fat weight loss diet (conventional diet) in severely obese adults with a high prevalence of diabetes or the metabolic syndrome are reported.
Abstract: Participants on a low-carbohydrate diet had better results overall at 1 year than those on a low-fat, restricted-calorie diet Weight loss was the same in the 2 groups, but patients on the low-carb
TL;DR: Numerical simulations of the evolution and motion of stars within the clusters find that for MGG 11 dynamical friction leads to the massive stars sinking rapidly to the centre of the cluster, where they participate in a runaway collision.
Abstract: A luminous X-ray source is associated with MGG 11—a cluster of young stars ∼200 pc from the centre of the starburst galaxy M 82 (refs 1, 2). The properties of this source are best explained3,4 by invoking a black hole with a mass of at least 350 solar masses (350 M⊙), which is intermediate between stellar-mass and supermassive black holes. A nearby but somewhat more massive cluster (MGG 9) shows no evidence of such an intermediate-mass black hole1,3, raising the issue of just what physical characteristics of the clusters can account for this difference. Here we report numerical simulations of the evolution and motion of stars within the clusters, where stars are allowed to merge with each other. We find that for MGG 11 dynamical friction leads to the massive stars sinking rapidly to the centre of the cluster, where they participate in a runaway collision. This produces a star of 800–3,000 M⊙, which ultimately collapses to a black hole of intermediate mass. No such runaway occurs in the cluster MGG 9, because the larger cluster radius leads to a mass segregation timescale a factor of five longer than for MGG 11.
TL;DR: PLAGA nanofibers show potential as antibiotic delivery systems for the treatment of wounds and can be tailored to desired diameters through modifications in processing parameters, and that antibiotics such as cefazolin can be incorporated into these nan ofibers.
Abstract: Wound healing is a complex process that often requires treatment with antibiotics. This article reports the initial development of a biodegradable polymeric nanofiber-based antibiotic delivery system. The functions of such a system would be (a) to serve as a biodegradable gauze, and (b) to serve as an antibiotic delivery system. The polymer used in this study was poly(lactide-co-glycolide) (PLAGA), and nanofibers of PLAGA were fabricated with the use of the electrospinning process. The objective of this study was to determine the effect of fabrication parameters: orifice diameter (needle gauge), polymer solution concentration, and voltage per unit length, on the morphology and diameter of electrospun nanofibers. The needle gauges studied were 16 (1.19 mm), 18 (0.84 mm), and 20 (0.58 mm), and the range of polymer solution concentration studied was from 0.10 g/mL to 0.30 g/mL. The effect of voltage was determined by varying the voltage per unit electrospinning distance, and the range studied was from 0.375 kV/cm to 1.5 kV/cm. In addition, the mass per unit area of the electrospun nanofibers as a function of time was determined and the feasibility of antibiotic (cefazolin) loading into the nanofibers was also studied. The results indicate that the diameter of nanofibers decreased with an increase in needle gauge (decrease in orifice diameter), and increased with an increase in the concentration of the polymer solution. The voltage study demonstrated that the average diameter of the nanofibers decreased with an increase in voltage. However, the effect of voltage on fiber diameter was less pronounced as compared to polymer solution concentration. The results of the areal density study indicated that the mass per unit area of the electrospun nanofibers increased linearly with time. Feasibility of drug incorporation into the nanofibers was demonstrated with the use of cefazolin, a broad-spectrum antibiotic. Overall, these studies demonstrated that PLAGA nanofibers can be tailored to desired diameters through modifications in processing parameters, and that antibiotics such as cefazolin can be incorporated into these nanofibers. Therefore, PLAGA nanofibers show potential as antibiotic delivery systems for the treatment of wounds.
TL;DR: The genomic structure of NIPBL is characterized and it is found that it is widely expressed in fetal and adult tissues and facilitates enhancer-promoter communication and regulates Notch signaling and other developmental pathways in Drosophila melanogaster.
Abstract: Cornelia de Lange syndrome (CdLS; OMIM 122470) is a dominantly inherited multisystem developmental disorder characterized by growth and cognitive retardation; abnormalities of the upper limbs; gastroesophageal dysfunction; cardiac, ophthalmologic and genitourinary anomalies; hirsutism; and characteristic facial features. Genital anomalies, pyloric stenosis, congenital diaphragmatic hernias, cardiac septal defects, hearing loss and autistic and self-injurious tendencies also frequently occur. Prevalence is estimated to be as high as 1 in 10,000 (ref. 4). We carried out genome-wide linkage exclusion analysis in 12 families with CdLS and identified four candidate regions, of which chromosome 5p13.1 gave the highest multipoint lod score of 2.7. This information, together with the previous identification of a child with CdLS with a de novo t(5;13)(p13.1;q12.1) translocation, allowed delineation of a 1.1-Mb critical region on chromosome 5 for the gene mutated in CdLS. We identified mutations in one gene in this region, which we named NIPBL, in four sporadic and two familial cases of CdLS. We characterized the genomic structure of NIPBL and found that it is widely expressed in fetal and adult tissues. The fly homolog of NIPBL, Nipped-B, facilitates enhancer-promoter communication and regulates Notch signaling and other developmental pathways in Drosophila melanogaster.
TL;DR: In this article, a method for producing a nanoporous carbide-derived carbon composition with a tunable pore structure and a narrow pore size is presented. But the method is not suitable for the use of nanoporous carbon.
Abstract: The present invention provides a method for producing a nanoporous carbide-derived carbon composition with a tunable pore structure and a narrow pore size. Also provided are compositions prepared by the method.
TL;DR: In this article, the authors fabricated polycrystalline bulk samples of Ti 3 Al 1.1 C 1.8 by reactively hot isostatically pressing a mixture of titanium, graphite, and Al 4 C 3 powders at a pressure of 70 MPa and temperature of 1400°C for 16 h.
Abstract: Polycrystalline bulk samples of Ti 3 Al 1.1 C 1.8 have been fabricated by reactively hot isostatically pressing a mixture of titanium, graphite, and Al 4 C 3 powders at a pressure of 70 MPa and temperature of 1400°C for 16 h. The hot isostatically pressed samples are predominantly single phase (containing ∼4 vol% Al 2 O 3 ), fully dense, and have a grain size of ∼25 μm. This carbide is similar to Ti 3 SiC 2 , with which it is isostructural, and has an unusual combination of properties. It is relatively soft (Vickers hardness of ∼3.5 GPa) and elastically stiff (Young's modulus of 297 GPa and shear modulus of 124 GPa); yet, it is lightweight (density of 4.2 g/cm 3 ) and easily machinable. The room-temperature electrical resistivity is 0.35 ± 0.03 μΩ.m and decreases linearly as the temperature decreases. The temperature coefficient of resistivity is 0.0031 K -1 . The coefficient of thermal expansion, in the temperature range of 25°-1200°C, is 9.0 (± 0.2) x 10 -6 K -1 . The room-temperature compressive and flexural strengths are 560 ± 20 and 375 ± 15 MPa, respectively. In contrast to flexure, where the failure is brittle, the failure in compression is noncatastrophic and is accompanied by some plasticity. The origin of that plasticity is believed to be the formation of a shear band that is oriented at an angle of ∼45° to the applied load. Ti 3 Al 1.1 C 1.8 also is a highly damage-tolerant material; a 10-kg-load Vickers indentation made in a bar 1.5 mm thick reduces the postindentation flexural strength by ∼7%. This material also is quite resistant to thermal shock. At temperatures of >1000°C, the deformation in compression is accompanied by significant plasticity and very respectable ultimate compressive stresses (200 MPa at 1200°C).
TL;DR: This review paper focuses on RSM activities since 1989, and discusses current areas of research and mention some areas for future research.
Abstract: The original work in response surface methodology (RSM) has been widely used in the chemical and process industries. Recent years have seen more widespread use and new developments in RSM. RMS activities since 1989 are reviewed, and areas of current and..
TL;DR: Observations suggest that cell death mechanisms may be representative of a continuum between apoptotic and necrotic pathways, and whether apoptosis may serve a protective role in the injured brain.
Abstract: Neuronal and glial cell death and traumatic axonal injury contribute to the overall pathology of traumatic brain injury (TBI) in both humans and animals. In both head-injured humans and following experimental brain injury, dying neural cells exhibit either an apoptotic or a necrotic morphology. Apoptotic and necrotic neurons have been identified within contusions in the acute post-traumatic period, and in regions remote from the site of impact in the days and weeks after trauma, while degenerating oligodendrocytes and astrocytes have been observed within injured white matter tracts. We review and compare the regional and temporal patterns of apoptotic and necrotic cell death following TBI and the possible mechanisms underlying trauma-induced cell death. While excitatory amino acids, increases in intracellular calcium and free radicals can all cause cells to undergo apoptosis, in vitro studies have determined that neural cells can undergo apoptosis via many other pathways. It is generally accepted that a shift in the balance between pro- and anti-apoptotic protein factors towards the expression of proteins that promote death may be one mechanism underlying apoptotic cell death. The effect of TBI on cellular expression of survival promoting-proteins such as Bcl-2, Bcl-xL, and extracellular signal-regulated kinases, and death-inducing proteins such as Bax, c-Jun N-terminal kinase, tumor-suppressor gene, p53, and the calpain and caspase families of proteases are reviewed. In light of pharmacologic strategies that have been devised to reduce the extent of apoptotic cell death in animal models of TBI, our review also considers whether apoptosis may serve a protective role in the injured brain. Together, these observations suggest that cell death mechanisms may be representative of a continuum between apoptotic and necrotic pathways.
TL;DR: In this article, the authors present evidence that busy outside directors are associated with weak corporate governance based on a sample of U.S. industrial firms from 1989 to 1995, showing that when a majority of outside directors serve on three or more boards, firms exhibit lower market-to-book ratios as well as weaker operating profitability.
Abstract: We present evidence that busy outside directors are associated with weak corporate governance based on a sample of U.S. industrial firms from 1989 to 1995. When a majority of outside directors serve on three or more boards, firms exhibit lower market-to-book ratios as well as weaker operating profitability. Appointments of busy outside directors appear unrelated to company performance, but such directors are more likely to depart boards following poor firm performance. When a majority of outside directors are busy, the sensitivity of CEO turnover to performance is significantly lower than when a majority of outside directors are not busy. Investors applaud departures of busy outside directors, and this effect is more pronounced for firms where the departure results in the majority of the remaining outside directors being not busy. When directors become busy as a result of acquiring an additional board seat, firms where they serve as directors experience negative abnormal returns.
TL;DR: In this paper, methods of multivariate analysis, 2nd Ed. (2nd Ed., 2nd ed. 2004) are used to perform multivariate analyses on a set of tasks.
Abstract: (2004). Methods of Multivariate Analysis, 2nd Ed. Journal of Quality Technology: Vol. 36, No. 1, pp. 125-126.
TL;DR: There are at least two rhythms below 50 Hz that are separately modulated by antiparkinsonian medication: one at low frequencies and one in the beta range, consistent with the hypothesis of multiple oscillating systems.
TL;DR: In this paper, the authors examined how various characteristics of the board of directors and other governance features affected the occurrence of U.S. corporate fraud in the 1978-2001 period and found that board composition and the structure of a board's oversight committees are significantly correlated with the incidence of corporate fraud.
Abstract: The study reported here examined how various characteristics of the board of directors and other governance features affected the occurrence of U.S. corporate fraud in the 1978–2001 period. The findings suggest that board composition and the structure of a board's oversight committees are significantly correlated with the incidence of corporate fraud. In the sample, as the number of independent outside directors increased on a board and in the board's audit and compensation committees, the likelihood of corporate wrongdoing decreased.
TL;DR: A comprehensive program of lifestyle modification induces loss of approximately 10% of initial weight in 16 to 26 weeks, as revealed by a review of recent randomized controlled trials, including the Diabetes Prevention Program.
Abstract: A comprehensive program of lifestyle modification induces loss of ∼10% of initial weight in 16 to 26 weeks, as revealed by a review of recent randomized controlled trials, including the Diabetes Prevention Program. Long-term weight control is facilitated by continued patient-therapist contact, whether provided in person or by telephone, mail, or e-mail. High levels of physical activity and the consumption of low-calorie, portion-controlled meals, including liquid meal replacements, can also help maintain weight loss. Additional studies are needed of the effects of macronutrient content (e.g., low-fat vs. low-carbohydrate diets) on long-term changes in weight and health. Research also is needed on effective methods of providing comprehensive weight loss control to the millions of Americans who need it.
Posted Content•
TL;DR: In this article, the authors show that the counterintuitive finding in prior literature that disclosure triggers litigation could be driven by the endogeneity between disclosure and litigation, and they find no evidence that disclosure potentially deters certain types of litigation.
Abstract: Securities litigation poses large costs to firms. The risk of litigation is heightened when firms have unexpectedly large earnings disappointments. Previous literature presents mixed evidence on whether voluntary disclosure of the bad news prior to regularly scheduled earnings announcements deters or triggers litigation. We show that the counterintuitive finding in prior literature that disclosure triggers litigation could be driven by the endogeneity between disclosure and litigation. Using a simultaneous equations methodology, we find no evidence that disclosure triggers litigation. In fact, consistent with economic arguments, our evidence suggests that disclosure potentially deters certain types of litigation.
TL;DR: The ability of cultured rat MSC to undergo in vitro osteogenesis, chondrogenesis, and adipogenesis is confirmed, demonstrating differentiation of these cells to three mesenchymal cell fates, and changes in morphology upon addition of the chemical induction medium were caused by rapid disruption of the actin cytoskeleton.
Abstract: Bone marrow stromal cells (MSC), which represent a population of multipotential mesenchymal stem cells, have been reported to undergo rapid and robust transformation into neuron-like phenotypes in vitro following treatment with chemical induction medium including dimethyl sulfoxide (DMSO; Woodbury et al. [2002] J. Neurosci. Res. 96:908). In this study, we confirmed the ability of cultured rat MSC to undergo in vitro osteogenesis, chondrogenesis, and adipogenesis, demonstrating differentiation of these cells to three mesenchymal cell fates. We then evaluated the potential for in vitro neuronal differentiation of these MSC, finding that changes in morphology upon addition of the chemical induction medium were caused by rapid disruption of the actin cytoskeleton. Retraction of the cytoplasm left behind long processes, which, although strikingly resembling neurites, showed essentially no motility and no further elaboration during time-lapse studies. Similar neurite-like processes were induced by treating MSC with DMSO only or with actin filament-depolymerizing agents. Although process formation was accompanied by rapid expression of some neuronal and glial markers, the absence of other essential neuronal proteins pointed toward aberrantly induced gene expression rather than toward a sequence of gene expression as is required for neurogenesis. Moreover, rat dermal fibroblasts responded to neuronal induction by forming similar processes and expressing similar markers. These studies do not rule out the possibility that MSC can differentiate into neurons; however, we do want to caution that in vitro differentiation protocols may have unexpected, misleading effects. A dissection of molecular signaling and commitment events may be necessary to verify the ability of MSC transdifferentiation to neuronal lineages.
TL;DR: The proposed two-point model is able to account for four interesting aspects of steering behavior: curve negotiation with occluded visual regions, corrective steering after a lateral drift, lane changing, and individual differences.
Abstract: When steering down a winding road, drivers have been shown to use both near and far regions of the road for guidance during steering. We propose a model of steering that explicitly embodies this idea, using both a 'near point' to maintain a central lane position and a 'far point' to account for the upcoming roadway. Unlike control models that integrate near and far information to compute curvature or more complex features, our model relies solely on one perceptually plausible feature of the near and far points, namely the visual direction to each point. The resulting parsimonious model can be run in simulation within a realistic highway environment to facilitate direct comparison between model and human behavior. Using such simulations, we demonstrate that the proposed two-point model is able to account for four interesting aspects of steering behavior: curve negotiation with occluded visual regions, corrective steering after a lateral drift, lane changing, and individual differences.
TL;DR: It is proved that for controllable quantum systems with no constraints placed on the controls, the only allowed extrema of the transition probability landscape correspond to perfect control or no control.
Abstract: A large number of experimental studies and simulations show that it is surprisingly easy to find excellent quality control over broad classes of quantum systems. We now prove that for controllable quantum systems with no constraints placed on the controls, the only allowed extrema of the transition probability landscape correspond to perfect control or no control. Under these conditions, no suboptimal local extrema exist as traps that would impede the search for an optimal control. The identified landscape structure is universal for all controllable quantum systems of the same dimension when seeking to maximize the same transition probability, regardless of the detailed nature of the system Hamiltonian. The presence of weak control field noise or environmental decoherence is shown to preserve the general structure of the control landscape, but at lower resolution.
TL;DR: In this article, the authors presented a catalog of 1,172,157 quasar candidates selected from the photometric imaging data of the Sloan Digital Sky Survey (SDSS).
Abstract: We present a catalog of 1,172,157 quasar candidates selected from the photometric imaging data of the Sloan Digital Sky Survey (SDSS). The objects are all point sources to a limiting magnitude of i = 21.3 from 8417 deg2 of imaging from SDSS Data Release 6 (DR6). This sample extends our previous catalog by using the latest SDSS public release data and probing both ultraviolet (UV)-excess and high-redshift quasars. While the addition of high-redshift candidates reduces the overall efficiency (quasars:quasar candidates) of the catalog to ~80%, it is expected to contain no fewer than 850,000 bona fide quasars, which is ~8 times the number of our previous sample and ~10 times the size of the largest spectroscopic quasar catalog. Cross-matching between our photometric catalog and spectroscopic quasar catalogs from both the SDSS and 2dF survey yields 88,879 spectroscopically confirmed quasars. For judicious selection of the most robust UV-excess sources (~500, 000 objects in all), the efficiency is nearly 97%—more than sufficient for detailed statistical analyses. The catalog's completeness to type 1 (broad-line) quasars is expected to be no worse than 70%, with most missing objects occurring at z < 0.7 and 2.5 < z < 3.0. In addition to classification information, we provide photometric redshift estimates (typically good to Δz ± 0.3 [2σ]) and cross-matching with radio, X-ray, and proper-motion catalogs. Finally, we consider the catalog's utility for determining the optical luminosity function of quasars and are able to confirm the flattening of the bright-end slope of the quasar luminosity function at z ~ 4 as compared to z ~ 2.