bluuebunny/crossref_metadata_2025 huggingface dataset:
Active downward propulsion by oyster larvae in turbulence
Authors: Fuchs Heidi L. , Hunter Elias J. , Schmitt Erika L. , Guazzo Regina A.
Published: December 2012

Oyster larvae (Crassostrea virginica) could enhance their settlement success by moving toward the seafloor in strong turbulence associated with coastal habitats. We characterized the behavior of individual oyster larvae in grid-generated turbulence by measuring larval velocities and flow velocities simultaneously using infrared particle image velocimetry. We estimated larval behavioral velocities and propulsive forces as functions of the kinetic energy dissipation rate ε, strain rate γ, vorticity ξ, and acceleration α. In calm water most larvae had near-zero vertical velocities despite propelling themselves upward (swimming). In stronger turbulence all larvae used more propulsive force, but relative to the larval axis, larvae propelled themselves downward (diving) instead of upward more frequently and more forcefully. Vertical velocity magnitudes of both swimmers and divers increased with turbulence, but the swimming velocity leveled off as larvae were rotated away from their stable, velum-up orientation in strong turbulence. Diving speeds rose steadily with turbulence intensity to several times the terminal fall velocity in still water. Rapid dives may require a switch from ciliary swimming to another propulsive mode such as flapping the velum, which would become energetically efficient at the intermediate Reynolds numbers attained by larvae in strong turbulence. We expected larvae to respond to spatial or temporal velocity gradients, but although the diving frequency changed abruptly at a threshold acceleration, the variation in propulsive force and behavioral velocity was best explained by the dissipation rate. Downward propulsion could enhance oyster larval settlement by raising the probability of larval contact with oyster reef patches.
Linkages between the life-history evolution of tropical and temperate birds and the resistance of their cells to oxidative and non-oxidative chemical injury
Authors: Jimenez Ana Gabriela , Harper James M. , Queenborough Simon A. , Williams Joseph B.
Published: December 2012

A fundamental challenge facing physiological ecologists is to understand how variation in life-history at the whole-organism level might be linked to cellular function. Thus, because tropical birds have higher annual survival and lower rates of metabolism, we hypothesized that cells from tropical species would have greater cellular resistance to chemical injury than cells from phylogenetically related temperate species. We cultured dermal fibroblasts from 26 tropical and 26 temperate species of birds and examined cellular resistance to cadmium, H2O2, paraquat, thapsigargin, tunicamycium, methane methylsulfonate, and UV light. By ANCOVA, which assumes each species as an independent data point, we found that the LD50 (values for the dose that killed 50% of test cells), from tropical birds were significantly higher for H2O2, and MMS. While, using a generalised least squares approach accounting for phylogenetic relationships among species to model LD50, we found that cells from tropical birds had greater tolerance for Cd, H2O2, paraquat, tunicamycin and MMS than cells from temperate birds. While for thapsigargin and UV light, tropical birds showed lower tolerance and no difference from temperate birds, respectively. These findings are consistent with the idea that natural selection has uniquely fashioned cells of long-lived tropical bird species to be more resistant to forms of oxidative and non-oxidative stress than cells from shorter-lived temperate species.
Characterization of genome methylation patterns in the desert locust Schistocerca gregaria
Authors: Falckenhayn Cassandra , Boerjan Bart , Raddatz Günter , Frohme Marcus , Schoofs Liliane , Lyko Frank
Published: December 2012

DNA methylation is a widely conserved epigenetic modification. The analysis of genome-scale DNA methylation patterns in various organisms suggested that major features of animal methylomes are widely conserved. However, based on the variation of DNA methyltransferase genes in invertebrates, it has also been proposed that DNA methylation could provide a molecular mechanism for ecological adaptation. We have now analyzed the methylome of the desert locust, Schistocerca gregaria, which represents an organism with a high degree of phenotypic plasticity. Using genome-scale bisulfite sequencing we show here that the S. gregaria methylome is characterized by CpG- and exon-specific methylation and thus shares two major features with other animal methylomes. In contrast to other invertebrates, however, overall methylation levels were substantially higher and a significant fraction of transposons was methylated. Additionally, genic sequences were densely methylated in a pronounced bimodal pattern, suggesting a role for DNA methylation in the regulation of locust gene expression. Our results thus uncover a unique pattern of genome methylation in locusts and provide an important foundation for investigating the role of DNA methylation in locust phase polyphenism.
Electric organ discharge diversity in the genusGymnotus: functional groups and electrogenic mechanisms
Authors: Rodríguez-Cattáneo Alejo , Aguilera Pedro , Cilleruelo Esteban , Crampton William G. R. , Caputi Angel A.
Published: December 2012

Previous studies describe six factors accounting for interspecific diversity of electric organ discharge (EOD) waveforms in Gymnotus. At the cellular level, three factors determine the locally generated waveforms: (1) electrocyte geometry and channel repertoire; (2) the localization of synaptic contacts on electrocytes surfaces; (3) electric activity of electromotor axons preceding the discharge of electrocytes. At the organismic level, three factors determine the integration of the EOD as a behavioral unit: (4) the distribution of different types of electrocytes and specialized passive tissue forming the electric organ (EO); (5) the neural mechanisms of electrocyte discharge coordination, (6) post-effector mechanisms. Here, we reconfirm the importance of the first five of these factors based on comparative studies of a wider diversity of Gymnotus than previously investigated. Additionally, we report another aspect of Gymnotus. The central region of the EO (which has the largest weight on the conspecific-received field) usually exhibits a negative-positive-negative pattern where the delay between the early negative and positive peaks (determined by neural coordination mechanisms) matches the delay between the positive and late negative peaks (determined by electrocyte responsiveness). Because delays between peaks typically determine the peak power frequency, this matching implies a co-evolution of neural and myogenic coordination mechanisms in determining the spectral specificity of the intraspecific communication channel. Finally, we define four functional species-groups based on EO/EOD structure. The first three exhibit a heterogeneous EO in which double-innervated electrocytes are responsible for a main triphasic complex. Group I species exhibit a characteristic cephalic extension of the EO. Group II species exhibit an early positive component of putative neural origin, and strong EO auto-excitability. Group III species exhibit an early, slow, negative wave of abdominal origin, and variation in EO auto-excitability. Representatives of Group IV generate a unique waveform comprising a main positive peak followed by a small, load-dependent negative component.
The influence of photosynthesis on host intracellular pH in scleractinian corals
Authors: Laurent Julien , Tambutté Sylvie , Tambutté Éric , Allemand Denis , Venn Alexander
Published: December 2012

The regulation of intracellular pH is a fundamental aspect of cell physiology that has received little attention in reef building corals and symbiotic cnidarians. Here, we investigated the hypothesis that dynamic changes in the pHi of coral host cells are controlled by the photosynthetic activity of the coral’s dinoflagellate symbionts. Using live cell imaging and the pH sensitive dye SNARF-1, we tracked pH in symbiont-containing and symbiont-free cells isolated from the reef coral Stylophora pistillata. We characterized the response of coral pHi in the presence of a photosynthetic inhibitor, the dynamics of coral pHi during light exposure and how pHi values vary on exposure to a range of irradiance levels lying within the coral's photosynthesis-irradiance (PI) response curve. Our results demonstrate that increases in coral pHi are dependent on photosynthetic activity of intracellular symbionts and that pHi recovers under darkness to pHi values that match symbiont-free cells. Furthermore, we show that the timing of the pHi response is governed by irradiance level and that pHi increases to irradiance-specific steady state values. Minimum steady state values of pHi 7.05±0.05 were obtained under darkness and maximum values of 7.46±0.07 under saturating irradiance. As changes in pHi affect organism homeostasis there is a need for continued research into acid/base regulation in symbiotic corals. More generally, these results represent the first characterization of photosynthesis-driven pHi changes in animal cells.
Pitfalls in invertebrate proteasome assays
Authors: Götze Sandra , Bose Aneesh , Abele Doris , Sokolova Inna , Saborowski Reinhard
Published: December 2012

The ubiquitin-proteasome system controls a variety of essential intracellular processes through directed protein turnover. The invertebrate proteasome has recently gained increasing interest with respect to central physiological processes and pathways in different taxa. A pitfall in proteasome-activity assays, represented by the trypsin-like, the chymotrypsin-like, or the caspase-like site, lies in the fact that most commonly-used experimental substrates are susceptible to degradation by non-proteasomal proteolytic enzymes, which can lead to erroneous interpretation of activity data obtained. Through the use of a proteasome-specific inhibitor, epoxomicin, we could show that the shares of proteasomal and non-proteasomal activities in the degradation of a model polypeptide substrate for the chymotrypsin-like activity vary considerably between invertebrate taxa. Crustacean muscle tissue and hemocytes showed almost exclusively proteasomal activity. In yeast, approximately 90% of total proteolytic activity can be attributed to the proteasome. In contrast, proteasomal activity comprises only 20-60% of the total proteolytic activity in bivalve tissues. These results reveal that, without verification of the shares of proteasomal and non-proteasomal activities in crude extracts through the use of highly specific inhibitors, common proteasomal enzyme assays should be used and interpreted with caution.
Two-way Linkage Photoisomerization of [Ru(2,2′:6′,2′′-terpyridine)(6-{(methylsulfinyl)methyl}picolinate)]BF4
Authors: Suzuki Shoko , Sakamoto Ryota , Nishihara Hiroshi
Published: December 2012

[Ru(tpy)(picSO)]BF4 (tpy: 2,2′:6′,2′′-terpyridine, picSO: 6-[(methylsulfinyl)methyl]picolinate) undergoes profound linkage isomerization behavior between stable S-bound and metastable O-bound isomers. S-[RuII(tpy)(picSO)]BF4 experiences photoisomerization to O-[RuII(tpy)(picSO)]BF4 upon irradiation with 436 nm light, whereas the back reaction is triggered with 546 nm light. Electrochemical linkage isomerization also takes place.
Unprecedented High Local Charge-carrier Mobility in P3HT Revealed by Direct and Alternating Current Methods
Authors: Yasutani Yoshihiro , Saeki Akinori , Fukumatsu Takahiro , Koizumi Yoshiko , Seki Shu
Published: December 2012

The impacts of solvent and thermal annealing on the mobility and photogeneration efficiency of free charge carriers in regioregular poly(3-hexylthiophene) were investigated by flash-photolysis time-resolved microwave conductivity measurements, transient absorption spectroscopy of the perylenediimide radical anion, and photocurrent measurements of a comb-type interdigitated electrode. A respectable high mobility of 0.62 cm2 V−1 s−1 was found as a three-dimensional value, highlighting the unprecedented electronic nature of the conjugated polymer.
Synthesis of a Base-stabilized (Chlorogermyl)metallogermylene and Its Photochemical Conversion to a (Chlorogermyl)germylyne Complex
Authors: Tashita Shin-ya , Watanabe Takahito , Tobita Hiromi
Published: December 2012

An NHC-stabilized (chlorogermyl)metallogermylene [Cp(CO)3WGe{GeCl(Mes)2}(MeIiPr)] (NHC: N-heterocyclic carbene, MeIiPr: 1,3-diisopropyl-4,5-dimethylimidazol-2-ylidene, Mes: mesityl) was synthesized by the reaction of [Na(dme)2][CpW(CO)3] (dme: 1,2-dimethoxyethane) with (chlorogermyl)chlorogermylene [GeCl{GeCl(Mes)2}(MeIiPr)]. Irradiation to a solution of the metallogermylene with an Hg lamp afforded an NHC-stabilized (chlorogermyl)germylyne complex [Cp(CO)2W≡Ge{GeCl(Mes)2}(MeIiPr)].
Effect of Noise and Redundant Auditory Alarm Signal on Semiconductor Production Operators' Response to Machine Downtime
Authors: Ocampo Lanndon A. , Clark Eppie E. , Liggayu Alaine
Published: December 2012

This paper investigates the effect of noise and the effect of a redundant impulsive auditory alarm signal on production operators' response to machine downtime in a semiconductor manufacturing system. Machine uptime is essential for productive and efficient production system and therefore downtime calls for an immediate response. Given a higher machine-to-man ratio, there is a difficulty in achieving quick response to machine downtime. For this end, ergonomic tower lamps with visual and auditory displays are used in most semiconductor manufacturing system to alert production operators and therefore minimize response time. The results of this study showed that a less noisy environment enhances operators' response to machine downtime. This proves literatures' claim on the limited capacity of human perception to achieve sharper focus on tasks when noise is present. Furthermore, the results also proved that a redundant auditory alarm signal aside from visual alarm at moderately high to high noise exposure; 85–90 dBA and >90 dBA, respectively, does not improve responses as discussed by literatures. It could be, as literatures say, that on persistent exposure to alarm signals beyond permissible noise level of 85 dBA, production operators may experience alarm fatigue phenomenon - a state of failing to hear the signals. Thus, redundant auditory alarm signals are only added costs and can further increase ambient noise which may, in effect, possibly induce health-related problems.
Simplified Method for Critical Elastic Distortional Buckling of Cold-Formed Steel C and Z Sections
Authors: Law KiamHai , Zhao Yang , Yan Weiming , Yu Cheng
Published: December 2012

The Direct Strength Method (DSM) is a recently adopted design approach by the North American Specifications for Cold-Formed Steel Structural Members (AISI S100) for calculating the nominal strength of cold-formed steel (CFS) sections. The critical elastic buckling load shall be obtained in order to employ the DSM in computing the nominal strength of CFS members. The AISI S100 provides simplified methods for determining the critical elastic distortional buckling load. However it is found that the AISI S100 simplified methods are over conservative for the industrial standard C and Z sections in the U.S. This paper presents revised simplified methods for calculating the critical elastic distortional buckling loads of typical CFS C and Z sections in bending and axial compression loading respectively. The new methods yield more accurate results but similar computation cost compared to the existing methods. The new methods can be added to the DSM methodologies for designing CFS members.
Bond Behavior of Reinforcement in Conventional and Self-Compacting Concrete
Authors: Aslani Farhad , Nejadi Shami
Published: December 2012

Self-compacting concrete (SCC) can be placed under its own weight without compaction. In addition, it is cohesive enough to be handled without segregation and bleeding. Modification in the mix design of SCC can have a significant influence on the material's mechanical properties. Therefore, it is important to investigate whether all of the assumptions about conventional concrete (CC) design structures also valid for SCC construction. Bond behavior between concrete and reinforcement is a primary factor in the design of reinforced concrete structures. This study presents a bond strength model based on the experimental results from eight recent investigations of SCC and CC. In addition, the proposed model, code provisions, and empirical equations and experimental results from recent studies on the bond strength of SCC and CC are compared. The comparison is based on the measured bond between reinforcing steel and concrete utilizing the pullout test on the embedded bars at various heights in the mock-up structural elements to assess the top-bar effect on single bars in small prismatic specimens by conducting beam tests. The investigated varying parameters on bond strength are the: steel bar diameter, concrete compressive strength, concrete type, curing age of the concrete, and height of the embedded bar along the formwork.
Numerical Modeling of Limiting Oxygen Index Apparatus for Film Type Fuels
Authors: Kumar Amit , T'ien James S.
Published: December 2012

A detailed three-dimensional numerical model is used to compute the flow pattern and the flame behavior of thin solid fuels in a rectangular column that resembles a standard Limiting Oxygen Index (LOI) device. The model includes full Navier-Stokes equations for mixed buoyant-forced flow and finite rate combustion and pyrolysis reactions so that the sample LOI can be computed to study the effect of feeding flow rate, sample width and gravity levels. In addition to the above parameters, the sample location in the column and the column cross-sectional area are also investigated on their effect on the ambient air entrainment from the top.
Transient Evolution of Strain and Curvature in Flames Developing from Kernels
Authors: Reddy Harinath , Abraham John
Published: December 2012

Achieving reliable ignition in lean-burn natural gas engines is a challenge. To provide insight into the processes involved, direct simulations are carried out to study the influence of varying flow fluctuation scales on flames developing from kernels. This study is conducted at elevated temperature and pressure conditions relevant to lean-burn natural gas engines. The transient evolution of strain and curvature during kernel development is studied. It is observed that both strain and curvature reach statistically steady values in distinct characteristic times. The time period is about four flow time scales for strain rate and about two and a half flow time scales for curvature, respectively, and these scales are found to be independent of flow fluctuation scales and laminar flame speed of the mixture when the initial kernel diameter is larger than the integral length scale of the flow field.
Aerodynamic Performance of a Gun Launched Micro Air Vehicle
Authors: Gnemmi Patrick , Meder Kevin , Rey Christian
Published: December 2012

The study deals with the prediction of the aerodynamic performance of the Gun Launched Micro Air Vehicle (GLMAV) platform by using the ANSYS CFX code. A first step consisted of the validation of the numerical simulation on a two-bladed rotor, which has a diameter of 0.20 m. This micro-rotor model is the perfect reproduction at a scale of 1:10 of the rotor bench that ISL had studied in the nineties. The validation was made by the comparison of the computed thrust and torque with the measured ones. These results proved the ability of the ANSYS CFX code to predict the flow field around MAV rotors and gave us confidence for further computations. The second step consisted of an analysis of the grid convergence for the single rotor of the GLMAV platform. Finally, by using the experience gained from all previous computational investigations, the computation of aerodynamic performance of the two coaxial 0.25-m diameter counter-rotating rotors of the GLMAV was carried out in hover flight.
Exploratory Structural Investigation of a Hawkmoth-Inspired MAV's Thorax
Authors: Demasi Luciano , Palazotto Anthony N. , Hollenbeck Alex , Cavallaro Rauno
Published: December 2012

Manduca Sexta present excellent flight performances which make this insect an ideal candidate for bio-inspired engineered micro air vehicles. The actual insect presents an energetically very efficient thorax-wing flight system which needs to be fully understood for an effective design of artificial flying machines. This work discusses a preliminary finite element model which simulates the thorax-wing system and the muscles involved in the flapping motion. Both upstroke and downstroke conditions are statically analyzed with the application of load sets that simulate the contractions of the dorso-ventral and dorso-longitudinal muscles (indirect flight). Comparison with commercial software and experimental results is also presented and discussed.
Innovation in UK companies. An Evaluation of the Implementation of Best Practice in Front End Innovation Processes and Methodologies
Authors: Trotter Patrick , Vaughan Jason
Published: December 2012

With the global economy facing its toughest test in over 60 years never has it been so important for companies, large and small, to innovate and grow. Whilst few business leaders would argue with this statement, research has highlighted the difficulty that businesses face in developing commercially successful, innovative products and services. It's well documented that between 80-90% of new product launches fail and whilst 80% of business leaders believe that innovation is important 65% are dissatisfied with their ability to innovate. To understand why successful, innovative products and services appears to be so elusive we conducted original research amongst a sample of UK based companies. The aim of the research was to identify how companies generate potential product ideas and what barriers they face in taking these ideas to the next stage of development. The results showed that whilst small and medium sized companies recognized the importance of innovation they did not have formal processes for generating ideas. In contrast all respondents from large companies reported that their organizations did have formal documented processes for innovation activities. Worryingly, all companies failed to use a sufficiently wide range of research tools to identify customers unmet needs. Another key area of the research was regarding barriers to innovation. Perhaps unsurprisingly, cost was considered to be the greatest barrier. Several of the other top and middle tier barriers to innovation were: lack of communication between departments; senior management; politics; poor decision making processes; and incomplete scientific or technical understanding. These barriers are directly rectifiable by putting specific transparent front end innovation processes in place. Although these problems are likely to differ between different industries the use of some innovation methodologies such as technical forecasting would help in the strategic decision making process. These findings suggest that both SMEs and large companies have gaps in the quality of their innovation systems which present a significant risk that the new products they develop may meet with commercial failure.
Information‐Guided Surgery of Intracranial Gliomas: Overview of an Advanced Intraoperative Technology
Authors: Muragaki Yoshihiro , Chernov Mikhail , Yoshimitsu Kitaro , Suzuki Takashi , Iseki Hiroshi , Maruyama Takashi , Tamura Manabu , Ikuta Soko , Nitta Masayuki , Watanabe Atsushi , Saito Taiichi , Okamoto Jun , Niki Chiharu , Hayashi Motohiro , Takakura Kintomo
Published: December 2012

The objective of this paper is to provide an overview of advanced information‐guided surgical management technology of intracranial gliomas implemented in Japan, represented by the Intelligent Operating Theater at the Tokyo Women’s Medical University, established in 2000, where more than 1000 patients with various intracranial pathology have received neurosurgical treatment with application of the intraoperative MRI, updated neuronavigation, and advanced neurophysiological and histopathological monitoring. Additionally, a dedicated computer‐based system for accumulating, storing, integrating, and analyzing various surgical data was developed, which provided an opportunity for adequate risk management and prediction of the surgical results. Application of these modalities and tools led to significant improvements in both surgical outcome and long‐term patients’ prognosis. Further technological developments, such as new therapeutic robot, dedicated laser, and high intensity focused ultrasound are currently under investigation. The final goal is to integrate all these devices and systems into comprehensive neurosurgical framework.
A Review of the Ergonomic Issues in the Laparoscopic Operating Room
Authors: Choi Sang D.
Published: December 2012

This review paper discusses the ergonomic challenges associated with laparoscopy in the operating room (OR) and summarizes the practical ergonomic solutions. The literature search was conducted in the fields of laparoscopy and applied ergonomics. Findings indicated that laparoscopic OR staff (surgeons, perioperative nurses and technicians) commonly experienced physical and mental ergonomic risks while working in prolonged static and awkward body positions. This study highlighted the need for more ergonomic interventions in OR environment in order to improve the efficiency of laparoscopy. Ergonomic solutions included utilizing adjustable equipment, placing computer peripherals in optimal locations, providing ergonomic instruments, and improving communication. Understanding the job‐ or task‐related ergonomic risks and hazards could help identify intervention requirements to meet the challenges associated with increased dependency on advanced high technology in the OR.
Reduction of Hospital Physicians′ Workflow Interruptions: A Controlled Unit‐Based Intervention Study
Authors: Weigl Matthias , Hornung Severin , Glaser Jürgen , Angerer Peter
Published: December 2012

Highly interruptive clinical environments may cause work stress and suboptimal clinical care. This study features an intervention to reduce workflow interruptions by re‐designing work and organizational practices in hospital physicians providing ward coverage. A prospective, controlled intervention was conducted in two surgical and two internal wards. The intervention was based on physician quality circles ‐ a participative technique to involve employees in the development of solutions to overcome work‐related stressors. Outcome measures were the frequency of observed workflow interruptions. Workflow interruptions by fellow physicians and nursing staff were significantly lower after the intervention. However, a similar decrease was also observed in control units. Additional interviews to explore process‐related factors suggested that there might have been spill‐over effects in the sense that solutions were not strictly confined to the intervention group. Recommendations for further research on the effectiveness and consequences of such interventions for professional communication and patient safety are discussed.
Quality Improvement in Hospitals: Identifying and Understanding Behaviors
Authors: Mazur Lukasz M. , McCreery John K. , Chen Shi-Jie (Gary)
Published: December 2012

Improving operational performance in hospitals is complicated, particularly if process improvement requires complex behavioral changes. Using single‐loop and double‐loop learning theory as a foundation, the purpose of this research is to empirically uncover key improvement behaviors and the factors that may be associated with such behaviors in hospitals. A two‐phased approach was taken to collect data regarding improvement behaviors and associated factors, and data analysis was conducted using methods proposed by grounded theorists. The contributions of this research are twofold. First, five key behaviors related to process improvement are identified, namely Quick Fixing, Initiating, Conforming, Expediting, and Enhancing. Second, based on these observed behaviors, a set of force field diagrams is developed to structure and organize possible factors that are important to consider when attempting to change improvement behaviors. This begins to fill the gap in the knowledge about what factors drive effective improvement efforts in hospital settings.
Application of Computer Simulation Modeling to Medication Administration Process Redesign
Authors: Huynh Nathan , Snyder Rita , Vidal Jose M. , Tavakoli Abbas S. , Cai Bo
Published: December 2012

The medication administration process (MAP) is one of the most high‐risk processes in health care. MAP workflow redesign can precipitate both unanticipated and unintended consequences that can lead to new medication safety risks and workflow inefficiencies. Thus, it is necessary to have a tool to evaluate the impact of redesign approaches in advance of their clinical implementation. This paper discusses the development of an agent‐based MAP computer simulation model that can be used to assess the impact of MAP workflow redesign on MAP performance. The agent‐based approach is adopted in order to capture Registered Nurse medication administration performance. The process of designing, developing, validating, and testing such a model is explained. Work is underway to collect MAP data in a hospital setting to provide more complex MAP observations to extend development of the model to better represent the complexity of MAP.
Passenger Profiling and Screening for Aviation Security in the Presence of Strategic Attackers
Authors: Cavusoglu Huseyin , Kwark Young , Mai Bin , Raghunathan Srinivasan
Published: December 2012

Passenger profiling enables the Transportation Security Administration to target costly inspection effort toward passengers that have an incentive to attack. On the other hand, critics point out that attackers may game the profiler by manipulating their attributes and behavior, making the profiler ineffective. We examine how passenger profiling impacts airport security operations when the profiler is vulnerable to gaming by attackers. We consider the no-profiling setup and two profiling setups. In the no-profiling setup, all passengers are sent through a screening device, and those that raise an alarm are physically inspected. In the first profiling setup, all classified attackers are physically inspected and classified normal passengers are sent through a screening device, and those that raise an alarm are physically inspected. In the second profiling setup, every passenger, regardless of the profiler's classification, is sent through a screening device and those that raise an alarm are inspected, but the screening devices are configured differently for classified attackers and classified normal passengers. We find that, regardless of the profiling setup, the optimal profiling setup performs at least as good as the no-profiling setup on key performance measures such as total expected security cost, inspection rate of normal passengers, and attacker detection rate even when the profiler is vulnerable to attackers' gaming. The benefit from profiling increases if the profiler becomes less vulnerable. Although neither profiling setup dominates the other on these performance measures, we find that each setup has different desirable properties.
An Empirical Analysis of Technical Efficiency: The Role of IT Intensity and Competition
Authors: Chang Young Bong , Gurbaxani Vijay
Published: December 2012

We analyze the impact of information technology (IT) on the technical efficiency of firms in the context of their observed competitive settings. Because competition can be a driver of efficiency and industries display varying degrees of competitiveness, firm-level efficiency is likely to display considerable heterogeneity. To shed light on these questions, we analyze the economic impact of IT on technical efficiency, a key component of efficiency, in heterogeneous competitive settings. Our study employs a number of econometric techniques, including a stochastic frontier and a generalized method of moments approach, on data from firms in a wide cross-section of industries. We find, after controlling for firm-level heterogeneity and potential endogeneity, that IT is positively associated with gains in technical efficiency but its impact is moderated by the degree of competition. Firms display large variation in their levels of technical efficiency partly because of the heterogeneous market competitiveness conditions they face. In more competitive industries, firms tend to deploy IT more intensively and use it more efficiently. Our study makes a distinct contribution relative to prior studies that have focused on the productivity impacts of IT while assuming perfect competition and not allowing for potential heterogeneity in firm-level efficiency. Overall, our results demonstrate that IT and competition are significant determinants of gains in technical efficiency and provide insight into how competition affects the returns to IT investment.
The Impact and Implications of On-Demand Services on Market Structure
Authors: Chen Pei-yu , Wu Shin-yi
Published: December 2012

This paper considers on-demand services and its impact on market structure, firm profitability, and consumer welfare. The unique properties of on-demand services are the conversion of fixed costs to variable costs, removal of capacity constraint, and fast setup time (which enables quick entry by any firm at any time when there is opportunity), whereas privacy and security concerns and switching costs have been noted as the biggest barriers from adopting on-demand services. With a stylized model capturing these benefits and barriers to using on-demand services, we establish several results. First, we show that conversion of fixed cost to variable cost enables new and small firms to enter existing markets and leads to the creation of new markets. Second, we show that competition and the threat of new entrants can be an important driver of a firm's decision to switch to on-demand services. In addition, a firm's barriers to using on-demand services can influence another firm's entry decision. Third, we show that two identical firms may employ different technologies in equilibrium. Fourth, we show that fast setup time and removal of capacity constraint associated with on-demand services make it impossible for firms to make supranormal return and would lead to a perfect competitive market, even when there is only one firm, under very general conditions. Such a result still holds even when there exists an economy of scale (e.g., quantity discount) from using on-demand services. On the other hand, when there are barriers preventing firms from offering similar products and products are substantially differentiated, on-demand services can amplify this advantage of entry barriers by enabling firms to further increase prices and enhance their profitability. Therefore, contrary to the common belief that offering on-demand services is best for firms offering commodity products, we show on-demand services to be more profitable for firms with differentiated products.
How Is the Mobile Internet Different? Search Costs and Local Activities
Authors: Ghose Anindya , Goldfarb Avi , Han Sang Pil
Published: December 2012

We explore how Internet browsing behavior varies between mobile phones and personal computers. Smaller screen sizes on mobile phones increase the cost to the user of browsing for information. In addition, a wider range of offline locations for mobile Internet usage suggests that local activities are particularly important. Using data on user behavior at a (Twitter-like) microblogging service, we exploit exogenous variation in the ranking mechanism of posts to identify the ranking effects. We show that (1) ranking effects are higher on mobile phones suggesting higher search costs: links that appear at the top of the screen are especially likely to be clicked on mobile phones and (2) the benefit of browsing for geographically close matches is higher on mobile phones: stores located in close proximity to a user's home are much more likely to be clicked on mobile phones. Thus, the mobile Internet is somewhat less “Internet-like”: search costs are higher and distance matters more. We speculate on how these changes may affect the future direction of Internet commerce.
The Effect of Customers' Social Media Participation on Customer Visit Frequency and Profitability: An Empirical Investigation
Authors: Rishika Rishika , Kumar Ashish , Janakiraman Ramkumar , Bezawada Ram
Published: December 2012

In this study we examine the effect of customers' participation in a firm's social media efforts on the intensity of the relationship between the firm and its customers as captured by customers' visit frequency. We further hypothesize and test for the moderating roles of social media activity and customer characteristics on the link between social media participation and the intensity of customer-firm relationship. Importantly, we also quantify the impact of social media participation on customer profitability. We assemble a novel data set that combines customers' social media participation data with individual customer level transaction data. To account for endogeneity that could arise because of customer self-selection, we utilize the propensity score matching technique in combination with difference in differences analysis. Our results suggest that customer participation in a firm's social media efforts leads to an increase in the frequency of customer visits. We find that this participation effect is greater when there are high levels of activity in the social media site and for customers who exhibit a strong patronage with the firm, buy premium products, and exhibit lower levels of buying focus and deal sensitivity. We find that the above set of results holds for customer profitability as well. We discuss theoretical implications of our results and offer prescriptions for managers on how to engage customers via social media. Our study emphasizes the need for managers to integrate knowledge from customers' transactional relationship with their social media participation to better serve customers and create sustainable business value.
Social Ties and User Content Generation: Evidence from Flickr
Authors: Zeng Xiaohua , Wei Liyuan
Published: December 2012

The content created by the users of social networking sites has reached such high levels of quality and variety that it is comparable to that produced by professional agencies. Therefore, understanding what types of content users generate and the underlying motivational factors is vital to the success of the sites. The extant research on content generation has primarily focused on the amount of content and on how to encourage participation in content creation, and less attention has been paid to the content itself and how social relations affect the types of content that users upload. This study aims to empirically document the relationship between social ties and the similarities between the types of content that people create online. We collected a large data set from the photo-hosting website Flickr detailing the users' social relations over time in conjunction with their photo-uploading behavior. We found that around the time of the formation of a social tie, members of dyads began to upload more similar photos than they did before that time. After a social tie was formed, this similarity evolved in different ways in different subgroups of dyads. Whereas the similarity between photos uploaded by dyads experiencing notably different popularity levels on the site continued to grow, the dyads of users with similar levels of popularity gradually began to upload less similar photos. In cultural production, individuals appear to present themselves as unique; this feature is more salient when the social contacts are similar in popularity status. Photo-shooting behaviors have been found to exhibit the same patterns. Furthermore, we show that the most divergent uploading behavior is observed when a high-popularity user initiates a tie with a user with lower popularity. We use social psychological motivations to explain these results.
A Fluid Limit for an Overloaded X Model via a Stochastic Averaging Principle
Authors: Perry Ohad , Whitt Ward
Published: December 2012

We prove a many-server heavy-traffic fluid limit for an overloaded Markovian queueing system having two customer classes and two service pools, known in the call-center literature as the X model. The system uses the fixed-queue-ratio-with-thresholds (FQR-T) control, which we proposed in a recent paper as a way for one service system to help another in face of an unexpected overload. Under FQR-T, customers are served by their own service pool until a threshold is exceeded. Then, one-way sharing is activated with customers from one class allowed to be served in both pools. After the control is activated, it aims to keep the two queues at a prespecified fixed ratio. For large systems that fixed ratio is achieved approximately. For the fluid limit, or FWLLN (functional weak law of large numbers), we consider a sequence of properly scaled X models in overload operating under FQR-T. Our proof of the FWLLN follows the compactness approach, i.e., we show that the sequence of scaled processes is tight and then show that all converging subsequences have the specified limit. The characterization step is complicated because the queue-difference processes, which determine the customer-server assignments, need to be considered without spatial scaling. Asymptotically, these queue-difference processes operate on a faster time scale than the fluid-scaled processes. In the limit, because of a separation of time scales, the driving processes converge to a time-dependent steady state (or local average) of a time-varying fast-time-scale process (FTSP). This averaging principle allows us to replace the driving processes with the long-run average behavior of the FTSP.
A Cantor Set of Games with No Shift-Homogeneous Equilibrium Selection
Authors: Levy Yehuda
Published: December 2012

We construct a continuum of games on a countable set of players that does not possess a measurable equilibrium selection that satisfies a natural homogeneity property. The explicit nature of the construction yields counterexamples to the existence of equilibria in models with overlapping generations and in games with a continuum of players.
Approximate Linear Programming for Average Cost MDPs
Authors: Veatch Michael H.
Published: December 2012

We consider the linear programming approach to approximate dynamic programming with an average cost objective and a finite state space. Using a Lagrangian form of the linear program (LP), the average cost error is shown to be a multiple of the best fit differential cost error. This result is analogous to previous error bounds for a discounted cost objective. Second, bounds are derived for average cost error and performance of the policy generated from the LP that involve the mixing time of the Markov decision process (MDP) under this policy or the optimal policy. These results improve on a previous performance bound involving mixing times.
Temporal Work in Strategy Making
Authors: Kaplan Sarah , Orlikowski Wanda J.
Published: December 2012

This paper reports on a field study of strategy making in one organization facing an industry crisis. In a comparison of five strategy projects, we observed that organizational participants struggled with competing interpretations of what might emerge in the future, what was currently at stake, and even what had happened in the past. We develop a model of temporal work in strategy making that articulates how actors resolved differences and linked their interpretations of the past, present, and future so as to construct a strategic account that enabled concrete strategic choice and action. We found that settling on a particular account required it to be coherent, plausible, and acceptable; otherwise, breakdowns resulted. Such breakdowns could impede progress, but they could also be generative in provoking a search for new interpretations and possibilities for action. The more intensely actors engaged in temporal work, the more likely the strategies departed from the status quo. Our model suggests that strategy cannot be understood as the product of more or less accurate forecasting without considering the multiple interpretations of present concerns and historical trajectories that help to constitute those forecasts. Projections of the future are always entangled with views of the past and present, and temporal work is the means by which actors construct and reconstruct the connections among them. These insights into the mechanisms of strategy making help explain the practices and conditions that produce organizational inertia and change.
Learning from Customers: Individual and Organizational Effects in Outsourced Radiological Services
Authors: Clark Jonathan R. , Huckman Robert S. , Staats Bradley R.
Published: December 2012

The ongoing fragmentation of work has resulted in a narrowing of tasks into smaller pieces that can be sent outside the organization and, in many instances, around the world. This trend is shifting the boundaries of organizations and leading to increased outsourcing. Though the consolidation of volume may lead to productivity improvement, little is known about how this shift toward outsourcing influences learning by providers of outsourced services. When producing output, the content of the knowledge gained can vary from one unit to the next. One dimension along which output can vary—a dimension with particular relevance in outsourcing—is the end customer for whom it is produced. The performance benefits of such customer experience remain largely unexamined. We explore this dimension of volume-based learning in a setting where doctors at an outsourcing firm complete radiological reads for hospital customers. We examine more than 2.7 million cases read by 97 radiologists for 1,431 customers and find evidence supporting the benefits of customer-specific experience accumulated by individual radiologists. Additionally, we find that variety in an individual’s customer experience may increase the rate of individual learning from customer-specific experience for a focal task. Finally, we find that the level of experience with a customer for the entire outsourcing firm also yields learning and that the degree of customer depth moderates the impact of customer-specific experience at the individual level. We discuss the implications of our results for the study of learning as well as for providers and consumers of outsourced services.