Showing papers by "Clemson University published in 2003"

Shaping agility through digital options: reconceptualizing the role of information technology in contemporary firms

Abstract: Agility is vital to the innovation and competitive performance of firms in contemporary business environments. Firms are increasingly relying on information technologies, including process, knowledge, and communication technologies, to enhance their agility. The purpose of this paper is to broaden understanding about the strategic role of IT by examining the nomological network of influences through which IT impacts firm performance. By drawing upon recent thinking in the strategy, entrepreneurship, and IT management literatures, this paper uses a multitheoretic lens to argue that information technology investments and capabilities influence firm performance through three significant organizational capabilities (agility, digital options, and entrepreneurial alertness) and strategic processes (capability-building, entrepreneurial action, and coevolutionary adaptation). We also propose that these dynamic capabilities and strategic processes impact the ability of firms to launch many and varied competitive actions and that, in turn, these competitive actions are a significant antecedent of firm performance. Through our theorizing, we draw attention to a significant and reframed role of IT as a digital options generator in contemporary firms.

How Massive Single Stars End Their Life

Abstract: How massive stars die-what sort of explosion and remnant each produces-depends chiefly on the masses of their helium cores and hydrogen envelopes at death. For single stars, stellar winds are the only means of mass loss, and these are a function of the metallicity of the star. We discuss how metallicity, and a simplified prescription for its effect on mass loss, affects the evolution and final fate of massive stars. We map, as a function of mass and metallicity, where black holes and neutron stars are likely to form and where different types of supernovae are produced. Integrating over an initial mass function, we derive the relative populations as a function of metallicity. Provided that single stars rotate rapidly enough at death, we speculate on stellar populations that might produce gamma-ray bursts and jet-driven supernovae.

Reduced drag coefficient for high wind speeds in tropical cyclones

Abstract: The transfer of momentum between the atmosphere and the ocean is described in terms of the variation of wind speed with height and a drag coefficient that increases with sea surface roughness and wind speed. But direct measurements have only been available for weak winds; momentum transfer under extreme wind conditions has therefore been extrapolated from these field measurements. Global Positioning System sondes have been used since 1997 to measure the profiles of the strong winds in the marine boundary layer associated with tropical cyclones. Here we present an analysis of these data, which show a logarithmic increase in mean wind speed with height in the lowest 200 m, maximum wind speed at 500 m and a gradual weakening up to a height of 3 km. By determining surface stress, roughness length and neutral stability drag coefficient, we find that surface momentum flux levels off as the wind speeds increase above hurricane force. This behaviour is contrary to surface flux parameterizations that are currently used in a variety of modelling applications, including hurricane risk assessment and prediction of storm motion, intensity, waves and storm surges.

Charge Transfer on the Nanoscale: Current Status

Abstract: This is the report of a DOE-sponsored workshop organized to discuss the status of our understanding of charge-transfer processes on the nanoscale and to identify research and other needs for progress in nanoscience and nanotechnology. The current status of basic electron-transfer research, both theoretical and experimental, is addressed, with emphasis on the distance-dependent measurements, and we have attempted to integrate terminology and notation of solution electron-transfer kinetics with that of conductance analysis. The interface between molecules or nanoparticles and bulk metals is examined, and new research tools that advance description and understanding of the interface are presented. The present state-of-the-art in molecular electronics efforts is summarized along with future research needs. Finally, novel strategies that exploit nanoscale architectures are presented for enhancing the efficiences of energy conversion based on photochemistry, catalysis, and electrocatalysis principles.

Locating the optic nerve in a retinal image using the fuzzy convergence of the blood vessels

Abstract: We describe an automated method to locate the optic nerve in images of the ocular fundus. Our method uses a novel algorithm we call fuzzy convergence to determine the origination of the blood vessel network. We evaluate our method using 31 images of healthy retinas and 50 images of diseased retinas, containing such diverse symptoms as tortuous vessels, choroidal neovascularization, and hemorrhages that completely obscure the actual nerve. On this difficult data set, our method achieved 89% correct detection. We also compare our method against three simpler methods, demonstrating the performance improvement. All our images and data are freely available for other researchers to use in evaluating related methods.

Cloning, expression, and characterization of a membrane progestin receptor and evidence it is an intermediary in meiotic maturation of fish oocytes

Abstract: The structures of membrane receptors mediating rapid, nongenomic actions of steroids have not been identified. We describe the cloning of a cDNA from spotted seatrout ovaries encoding a protein that satisfies the following seven criteria for its designation as a steroid membrane receptor: plausible structure, tissue specificity, cellular distribution, steroid binding, signal transduction, hormonal regulation, and biological relevance. For plausible structure, computer modeling predicts that the protein has seven transmembrane domains, typical of G protein-coupled receptors. The mRNA (4.0 kb) is only detected in the brain and reproductive tissues on Northern blots. Antisera only detect the protein (40 kDa) in plasma membranes of reproductive tissues. The recombinant protein produced in an Escherichia coli expression system has a high affinity (Kd = 30 nM), saturable, displaceable, single binding site specific for progestins. Progestins alter signal transduction pathways, activating mitogen-activated protein kinase and inhibiting adenylyl cyclase, in a transfected mammalian cell line. Inhibition of adenylyl cyclase is pertussis toxin sensitive, suggesting the receptor may be coupled to an inhibitory G protein. Progestins and gonadotropin up-regulate both mRNA and protein levels in seatrout ovaries. Changes in receptor abundance in response to hormones and at various stages of oocyte development, its probable coupling to an inhibitory G protein and inhibition of progestin induction of oocyte maturation upon microinjection of antisense oligonucleotides are consistent with the identity of the receptor as an intermediary in oocyte maturation. These characteristics suggest the fish protein is a membrane progestin receptor mediating a “nonclassical” action of progestins to induce oocyte maturation in fish.

Kinematics and the implementation of an elephant's trunk manipulator and other continuum style robots.

Abstract: Traditionally, robot manipulators have been a simple arrangement of a small number of serially connected links and actuated joints. Though these manipulators prove to be very effective for many tasks, they are not without their limitations, due mainly to their lack of maneuverability or total degrees of freedom. Continuum style (i.e., continuous "back-bone") robots, on the other hand, exhibit a wide range of maneuverability, and can have a large number of degrees of freedom. The motion of continuum style robots is generated through the bending of the robot over a given section; unlike traditional robots where the motion occurs in discrete locations, i.e., joints. The motion of continuum manipulators is often compared to that of biological manipulators such as trunks and tentacles. These continuum style robots can achieve motions that could only be obtainable by a conventionally designed robot with many more degrees of freedom. In this paper we present a detailed formulation and explanation of a novel kinematic model for continuum style robots. The design, construction, and implementation of our continuum style robot called the elephant trunk manipulator is presented. Experimental results are then provided to verify the legitimacy of our model when applied to our physical manipulator. We also provide a set of obstacle avoidance experiments that help to exhibit the practical implementation of both our manipulator and our kinematic model. c2003 Wiley Periodicals, Inc.

Teasing, rejection, and violence: Case studies of the school shootings.

Abstract: Media commentators have suggested that recent school shootings were precipitated by social rejection, but no empirical research has examined this claim. Case studies were conducted of 15 school shootings between 1995 and 2001 to examine the possible role of social rejection in school violence. Acute or chronic rejection-in the form of ostracism, bullying, and/or romantic rejection-was present in all but two of the incidents. In addition, the shooters tended to be characterized by one or more of three other risk factors-an interest in firearms or bombs, a fascination with death or Satanism, or psychological problems involving depression, impulse control, or sadistic tendencies. Implications for understanding and preventing school violence are discussed.

Cell and organ printing 1: Protein and cell printers

Abstract: We have developed several devices for positioning organic molecules, molecular aggregates, cells, and single-cell organisms onto solid supports. These printers can create stable, functional protein arrays using an inexpensive technology. The cell printer allows us to create cell libraries as well as cellular assemblies that mimic their respective position in organs. The printers are derived from commercially available ink-jet printers that are modified to dispense protein or cell solutions instead of ink. We describe here the modifications to the print heads, and the printer hardware and software that enabled us to adapt the ink-jet printers for the manufacture of cell and protein arrays. The printers have the advantage of being fully automated and computer controlled, and allow for the high-throughput manufacture of protein and cell arrays.

An Examination of the Relationship between Leisure Activity Involvement and Place Attachment among Hikers Along the Appalachian Trail

Abstract: The place attachment construct has been used by leisure researchers and practitioners to refine our understanding of certain leisure behaviors for over two decades. Despite the construct's importan...

Three cadherin alleles associated with resistance to Bacillus thuringiensis in pink bollworm

Abstract: Evolution of resistance by pests is the main threat to long-term insect control by transgenic crops that produce Bacillus thuringiensis (Bt) toxins. Because inheritance of resistance to the Bt toxins in transgenic crops is typically recessive, DNA-based screening for resistance alleles in heterozygotes is potentially much more efficient than detection of resistant homozygotes with bioassays. Such screening, however, requires knowledge of the resistance alleles in field populations of pests that are associated with survival on Bt crops. Here we report that field populations of pink bollworm (Pectinophora gossypiella), a major cotton pest, harbored three mutant alleles of a cadherin-encoding gene linked with resistance to Bt toxin Cry1Ac and survival on transgenic Bt cotton. Each of the three resistance alleles has a deletion expected to eliminate at least eight amino acids upstream of the putative toxin-binding region of the cadherin protein. Larvae with two resistance alleles in any combination were resistant, whereas those with one or none were susceptible to Cry1Ac. Together with previous evidence, the results reported here identify the cadherin gene as a leading target for DNA-based screening of resistance to Bt crops in lepidopteran pests.

Corridor use by diverse taxa

Abstract: One of the most popular approaches for maintaining populations and con- serving biodiversity in fragmented landscapes is to retain or create corridors that connect otherwise isolated habitat patches. Working in large-scale, experimental landscapes in which open-habitat patches and corridors were created by harvesting pine forest, we showed that corridors direct movements of different types of species, including butterflies, small mam- mals, and bird-dispersed plants, causing higher movement between connected than between unconnected patches. Corridors directed the movement of all 10 species studied, with all corridor effect sizes .68%. However, this corridor effect was significant for five species, not significant for one species, and inconclusive for four species because of small sample sizes. Although we found no evidence that corridors increase emigration from a patch, our results show that movements of disparate taxa with broadly different life histories and functional roles are directed by corridors.

The Role of System Trust in Business-to-Consumer Transactions

Abstract: It has been argued that the buyer's trust of the vendor is a critical precursor to a transactional relationship in an e-commerce environment. This study uses an experimental survey to test a model that includes a number of factors such as trust mechanisms, "system trust," and vendor reputation. The results suggest that one trust mechanism, vendor guarantees, has a direct influence on system trust. Further, within e-commerce situations, system trust plays an important role in the nomological network by directly affecting trust in vendors and indirectly affecting attitudes and intentions to purchase. These results held in the case of both firms with and without an established reputation. The results demonstrate the importance of interventions such as self-reported vendor guarantees that affect system trust in enabling successful e-commerce outcomes.

Transport and cycling of iron and hydrogen peroxide in a freshwater stream: Influence of organic acids

Abstract: [1] An in-stream injection of two dissolved organic acids (phthalic and aspartic acids) was performed in an acidic mountain stream to assess the effects of organic acids on Fe photoreduction and H2O2 cycling. Results indicate that the fate of Fe is dependent on a net balance of oxidative and reductive processes, which can vary over a distance of several meters due to changes in incident light and other factors. Solution phase photoreduction rates were high in sunlit reaches and were enhanced by the organic acid addition but were also limited by the amount of ferric iron present in the water column. Fe oxide photoreduction from the streambed and colloids within the water column resulted in an increase in the diurnal load of total filterable Fe within the experimental reach, which also responded to increases in light and organic acids. Our results also suggest that Fe(II) oxidation increased in response to the organic acids, with the result of offsetting the increase in Fe(II) from photoreductive processes. Fe(II) was rapidly oxidized to Fe(III) after sunset and during the day within a well-shaded reach, presumably through microbial oxidation. H2O2, a product of dissolved organic matter photolysis, increased downstream to maximum concentrations of 0.25 μM midday. Kinetic calculations show that the buildup of H2O2 is controlled by reaction with Fe(II), but this has only a small effect on Fe(II) because of the small formation rates of H2O2 compared to those of Fe(II). The results demonstrate the importance of incorporating the effects of light and dissolved organic carbon into Fe reactive transport models to further our understanding of the fate of Fe in streams and lakes.

Cell and organ printing 2: Fusion of cell aggregates in three‐dimensional gels

Abstract: We recently developed a cell printer (Wilson and Boland, 2003) that enables us to place cells in positions that mimic their respective positions in organs. However, this technology was limited to the printing of two-dimensional (2D) tissue constructs. Here we describe the use of thermosensitive gels to generate sequential layers for cell printing. The ability to drop cells on previously printed successive layers provides a real opportunity for the realization of three-dimensional (3D) organ printing. Organ printing will allow us to print complex 3D organs with computer-controlled, exact placing of different cell types, by a process that can be completed in several minutes. To demonstrate the feasibility of this novel technology, we showed that cell aggregates can be placed in the sequential layers of 3D gels close enough for fusion to occur. We estimated the optimum minimal thickness of the gel that can be reproducibly generated by dropping the liquid at room temperature onto a heated substrate. Then we generated cell aggregates with the corresponding (to the minimal thickness of the gel) size to ensure a direct contact between printed cell aggregates during sequential printing cycles. Finally, we demonstrated that these closely-placed cell aggregates could fuse in two types of thermosensitive 3D gels. Taken together, these data strongly support the feasibility of the proposed novel organ-printing technology. Anat Rec Part A 272A:497–502, 2003. © 2003 Wiley-Liss, Inc.

The Quiet Period Goes out with a Bang

Abstract: We examine the expiration of the IPO quiet period, which occurs after the 25th calendar day following the offering. For IPOs during 1996 to 2000, we find that analyst coverage is initiated immediately for 76 percent of these firms, almost always with a favorable rating. Initiated firms experience a five-day abnormal return of 4.1 percent versus 0.1 percent for firms with no coverage. The abnormal returns are concentrated in the days just before the quiet period expires. Abnormal returns are much larger when coverage is initiated by multiple analysts. It does not matter whether a recommendation comes from the lead underwriter or not. COMPANIES PARTICIPATING in an initial public offering (IPO) face numerous regulatory restrictions that prohibit certain activities while the company is "in registration"After completion of an IPO, a firm is still considered to be in registration for an additional period of time. During this time, 25 days during our sample period which is termed the post-IPO "quiet" period, firms may make statements of fact regarding business developments and may respond to inquiries from analysts and shareholders regarding factual matters. However, U.S. Securities and Exchange Commission (SEC) regulations generally prohibit firms and their underwriters from publishing opinions concerning valuation and from making forward-looking statements regarding earnings, revenues, and similar items. The logic behind the SEC's quiet period regulations is that all material information should be contained in the prospectus. Although there is an extensive literature concerning equity IPOs, this paper appears to be the first to specifically examine events surrounding the end of the quiet period.1 For 1,611 IPOs over the period 1996 to 2000, we find that analyst coverage is initiated immediately 76 percent of the time following quiet period

Extending shelf-life of minimally processed apples with edible coatings and antibrowning agents

Abstract: Effect of edible coatings in combination with antibrowning agents on minimally processed apple slices was studied during storage at 3°C for 2 week. To control initial respiration rate of apple slices, edible coatings were applied to cut apples as semipermeable barriers against air. Initial respiration rate showed a decrease by 5% and 20% in carrageenan (0.5 g/100 mL)-coated and whey protein concentrate (5 g/100 mL)-coated apples, respectively, at 25°C. Edible coatings in combination with antibrowning agents effectively prolonged the shelf-life of minimally processed apple slices by 2 week when stored in packed trays at 3°C. Addition of various antibrowning agents to these coating solutions was advantageous in maintaining color during storage. Addition of CaCl 2 (1 g/100 mL) significantly inhibited the loss of firmness. These edible coatings in combination with antibrowning agents also showed positive sensory analysis results and beneficial reduction of microbial levels. WPC (5 g/100 mL) containing ascorbic acid (1 g/100 mL) plus CaCl 2 (1 g/100 mL) was the most effective preservation treatment in terms of sensory quality after 2 week.

Nonlinear coupling control laws for an underactuated overhead crane system

Abstract: In this paper, we consider the regulation control problem for an underactuated overhead crane system. Motivated by recent passivity-based controllers for underactuated systems, we design several controllers that asymptotically regulate the planar gantry position and the payload angle. Specifically, utilizing LaSalle's invariant set theorem, we first illustrate how a simple proportional-derivative (PD) controller can be utilized to asymptotically regulate the overhead crane system. Motivated by the desire to achieve improved transient performance, we then present two nonlinear controllers that increase the coupling between the planar gantry position and the payload angle. Experimental results are provided to illustrate the improved performance of the nonlinear controllers over the simple PD controller.

Large deflection dynamics and control for planar continuum robots

Abstract: This paper focuses on a class of robot manipulators termed "continuum" robots - robots that exhibit behavior similar to tentacles, trunks, and snakes. In previous work, we studied details of the mechanical design, kinematics, path-planning and small-deflection dynamics for continuum robots such as the Clemson "tentacle manipulator". In this paper, we discuss the dynamics of a planar continuum backbone section, incorporating a large-deflection dynamic model. Based on these dynamics, we formulate a vibration-damping setpoint controller, and include experimental results to illustrate the efficacy of the proposed controller.

Lactation persistency: Insights from mammary cell proliferation studies

Abstract: A persistent lactation is dependent on maintaining the number and activity of milk secreting cells with advancing lactation. When dairy cows are milked twice daily, the increase in milk yield from parturition to peak lactation is due to increased secretory activity per cell rather than to accretion of additional epithelial cells. After peak lactation, declining milk yield is due to loss of mammary epithelial cells by apoptosis. During lactation, only 0.3% of mammary cells proliferate in a 24-h period. Yet this proliferative rate is sufficient to replace most mammary epithelial cells by the end of lactation. Management practices can influence lactation persistency. Administration of bovine somatotropin may enhance persistency by increasing cell proliferation and turnover, or by reducing the rate of apoptosis. Increased photoperiod may also increase persistency of lactation by mechanisms that are as yet undefined. Increased milking frequency during the first weeks of lactation increases milk yield, even after return to less frequent milking, with increases of approximately 8% over the entire lactation. A mammary cell proliferation response to frequent milking during early lactation appears to be involved. Conversely, advanced pregnancy, infrequent milking, and mastitis increase death of epithelial cells by apoptosis. Regulation of mammary cell renewal provides a key to increasing persistency. Investigations to characterize epithelial cells that serve as the proliferative population in the bovine mammary gland have been initiated. Epithelial cells that stain lightly in histological sections are evident through all phases of mammary development and secretion and account for nearly all proliferation in the prepubertal gland. Characterization of these cells may provide a means to regulate mammary cell proliferation and thus to enhance persistency, reduce the effects of mastitis, and decrease the necessity for a dry period.

A critical look at the bathtub curve

Abstract: This paper addresses some of the fundamental assumptions underlying the bathtub curve It is shown to be unlikely that any practical hazard function is decreasing near zero Great care should be taken in interpreting the hazard function, particularly in applying quality-control practices, such as burn-in or environmental-stress-screening to manufactured products

The Moderating Role of Place Attachment on the Relationship Between Attitudes Toward Fees and Spending Preferences

Abstract: The variable, place attachment, has recently been used by investigators to assist in understanding visitor responses to fee programs on public lands. This paper examines the relationship between place attachment (i.e., place identity and place dependence), attitudes toward paying fees, and visitor preferences for spending fee revenue within the context of social judgment theory. It was hypothesized that both place dependence and place identity would moderate the relationship between recreationists' attitudes toward the site's fee program and visitor support for spending revenue generated by the fee program in the areas of facilities and service development, environmental protection, and environmental education. Data were collected at Mono Basin Scenic Area over the summer of 1998. Results indicated that only place identity was a statistically significant moderator, such that it magnified the relationship between recreationists' attitudes toward the fee program and spending support. As place identity incre...

Challenges with fats and fatty acid methods.

Abstract: The content and chemical nature of lipids in feedstuffs is heterogeneous. It has long been known that ether extraction by the Weende procedure inadequately characterizes the fat content of feedstuffs, yet it remains the official method. Diethyl ether (or hexanes that are often used) extracts significant amounts of nonnutritive, nonsaponifiable lipids from forages, and often incompletely extracts lipids of nutritional value, especially fatty acids present as salts of divalent cations. Preextraction hydrolysis of insoluble fatty acid salts with acid releases these fatty acids, and this step is included in the official procedure for certain feedstuffs in the United Kingdom; however, acid hydrolysis increases analysis time and decreases precision. Acid hydrolysis also causes confusion as to the proper definition of the fat content of feedstuffs. A preferred method of fat analysis determines the total fatty acid concentration in feed samples by converting fatty acid salts, as well as the acyl components in all lipid classes, such as triacylglycerols, phospholipids, and sphingolipids, to methyl esters using a simple, direct one-step esterification procedure. Fatty acid methyl esters are then quantified by GLC, which provides information on both fatty acid quantity and profile in a single analysis. Adjustments in conditions and reagents may be necessary to overcome difficulty in quantitatively preparing esters from certain types of fatty acids and their derivatives in commercial fat supplements. After correction for glycerol content, analysis of oils by this procedure provides information on the content of nonsaponifiable material, such as chlorophyll, waxes, and indigestible polymers formed from heat- or oxidatively damaged fats. The correct description of feedstuffs for energy value of fats is the content of total fatty acids.

Cloud Microphysical Properties, Processes, and Rainfall Estimation Opportunities

Abstract: In this work the longstanding question of the connections between raindrop-size distributions (RDSDs) and radar reflectivity-rainfall rate (Z-R) relationships is revisited, this time from the combined approach of rain-forming physical processes that shape the RDSD, and a formulation of the RDSD into the simplest free parameters of the rain intensity R, rainwater content W, and median volume drop diameter D0. This is accomplished through a theoretical analysis, using a gamma RDSD, of D0-R and W-R relations implied by the coefficients and exponents in empirical Z-R relations. The results provide a means by which these Z-R relations can be classified. The most dramatic of these classifications involves the relation between D0 and W, which shows a remarkable ordering with the rain types.