bluuebunny/crossref_metadata_2025 huggingface dataset:
Detection of bacterial contamination of platelet components: six years’ experience with the BacT/ALERT system
Authors: Munksgaard Lars , Albjerg Lene , Lillevang Søren T. , Gahrn‐Hansen Bente , Georgsen Jørgen
Published: July 2004

BACKGROUND:  Hemovigilance has shown that bacteria cause more fatalities than other infections together. Surveillance for detection of bacteria in platelets (PLTs) was initiated. Concomitantly, the storage period for PLTs was extended from 5 to 7 days to reduce cost.

STUDY DESIGN AND METHODS:  Analysis was performed of all cases of a positive signal in a screening procedure for contaminated PLTs taking into account results of confirmative cultures and results of culture from blood components including bacteria strains. Records were assessed from patients transfused with blood components issued before the screening culture became positive.

RESULTS:  Samples were collected from 22,057 PLT units. An initial reaction was seen in 84 (0.38%). Growth was confirmed in 70 of these. Of the associated PLT units, 26 had been issued or outdated at the time when the culture was found to be reactive, in 27 bacteria were found, and in 17 cultures were negative. The bacteria found were mainly from normal skin flora. Sixty‐six patients received 75 blood components issued before the screening system alarmed. None of these patients had a transfusion reaction reported. The outdating fell to less than 5 percent.

CONCLUSION:  A screening system for detection of bacterial contamination was implemented without increase in cost owing to extension of storage time to 7 days. Transfusion of several contaminated blood components was prevented.
Human parvovirus B19 in young male patients with hemophilia A: associations with treatment product exposure and joint range‐of‐motion limitation
Authors: Soucie J. Michael , Siwak Edward B. , Hooper W. Craig , Evatt Bruce L. , Hollinger F. Blaine ,   the Universal Data Collection Project Working Group
Published: July 2004

BACKGROUND:  To evaluate the risk of human parvovirus B19 (B19) transmission in recombinant antihemophilic factor, the seroprevalence among 798 two‐ to seven‐year‐old boys with hemophilia was compared. Also, data collected on joints were used to assess relations between B19 serostatus and joint range‐of‐motion (ROM) limitation.

STUDY DESIGN AND METHODS:  Staff at US hemophilia treatment centers collected data on product exposures and ROM of 10 joints and provided blood specimens as part of blood safety surveillance. Blood was tested for immunoglobulin G anti‐B19. Associations between B19 seropositivity and treatment products and joint ROM limitations were examined in multivariate analyses.

RESULTS:  Compared to children who received no product, the odds of B19 seropositivity were 0.8 (p = 0.5), 1.9 (p = 0.05), and 7.6 (p < 0.001) for those children who received recombinant antihemophilic factor only, both recombinant antihemophilic factor and plasma‐derived factor, and plasma‐derived factor only, respectively. Children who were anti‐B19 positive had an average 8° less overall ROM (p = 0.002) than those who were B19 antibody negative after adjustment for other risk factors.

CONCLUSION:  The risk of B19 transmission by recombinant antihemophilic factor is low. Previous B19 infection is associated with ROM limitations in very young male patients with hemophilia. Virus inactivation techniques effective against B19 and other nonenveloped viruses are needed.
Validation of BacT/ALERT plastic culture bottles for use in testing of whole‐blood‐derived leukoreduced platelet‐rich‐plasma‐derived platelets
Authors: Brecher M.E. , Hay S.N. , Rothenberg S.J.
Published: July 2004

BACKGROUND:  Bacterial detection of platelet (PLT)‐rich‐plasma (PRP)‐derived PLTs presents unique challenges for countries that do not allow pooling before storage. This study validated the BacT/ALERT for use in testing pooled PRP‐derived PLTs with nine contaminating organisms.

STUDY DESIGN AND METHODS:  Isolates of Bacillus cereus, Enterobacter cloacae, Escherichia coli, Klebsiella pneumoniae, Staphylococcus aureus, Staphylococcus epidermidis, Serratia marcescens, Streptococcus viridans, and Propionibacterium acnes were inoculated into two PRP‐derived PLT pools (target, 10 and 100 colony‐forming units [CFUs]/mL; actual recovered concentrations, 5 and 90 CFUs/mL). Four milliliters of each postbacterial inoculation sample was inoculated into both plastic aerobic and anaerobic bottles and 0.5 mL was plated onto blood agar.

RESULTS:  All organisms (excluding P. acnes) were detected in 8.2 to 22.0 and 7.6 to 20.3 hours (10 and 100 CFUs/mL, respectively) and the mean time to detection was 15.0 and 13.1 hours (10 and 100 CFUs/mL, respective). P. acnes was detected with the anaerobic bottles in a mean of 74.9 and 64.3 hours (10 and 100 CFUs/mL, respectively). With E. cloacae, E. coli, K. pneumoniae, S. marcescens, and S. viridans detection with the anaerobic bottles was faster or equivalent to the detection with the aerobic bottles. This was most notable with S. viridans where the anaerobic bottle was reactive on average 21.6 and 10.8 hours (10 and 100 CFUs/mL, respectively) faster than the aerobic bottle.

CONCLUSIONS:  This study validates the use of the BacT/ALERT system for the detection of bacteria in PRP‐derived PLTs in a pooled format. Overall, the use of the BacT/ALERT system allowed the detection of pooled PRP‐derived PLTs inoculated with nine bacteria at 10 and 100 CFUs per mL in 7.6 to 22.0 hours (excluding P. acnes).
Comparison of demographic and donation profiles and transfusion‐transmissible disease markers and risk rates in previously transfused and nontransfused blood donors
Authors: Wang B. , Higgins M.J. , Kleinman S. , Schreiber G.B. , Murphy E.L. , Glynn S.A. , Wright D.J. , Nass C.C. , Chang D. , Busch M.P. , Retrovirus Epidemiology Donor Study For The
Published: July 2004

BACKGROUND:  Increasing concern about transfusion transmission of variant Creutzfeldt‐Jakob disease has resulted in indefinite deferral of transfused donors in France and the UK. Little is known, however, about the impact of indefinite deferral of transfused donors on blood safety and availability in the US.

STUDY DESIGN AND METHODS:  Data were collected on allogeneic donations at five US blood centers during 1991 through 2000. Donation characteristics, prevalence, and incidence of human immunodeficiency virus (HIV), hepatitis B virus (HBV), and hepatitis C virus (HCV) were compared between transfused and nontransfused donors. Unreported deferrable risk (UDR) and reasons to donate were evaluated with data from a mail survey.

RESULTS:  Transfusion history was reported by 4.2 percent of donors. Prevalence and incidence of HIV and HBV were comparable between transfused and nontransfused donors. Although HCV incidence was similar in both groups, HCV prevalence was nearly three times higher in transfused than in nontransfused first‐time donors. UDR and reasons to donate were similar in the two groups, except transfused donors were less likely to donate for screening test results (odds ratio, 0.5; 95% confidence interval, 0.3‐0.8).

CONCLUSION:  Transfused and nontransfused donors had similar viral incidence and comparable UDR, suggesting that indefinite deferral of transfused donors would unlikely improve blood safety. Until more is known about the prevalence and transfusion transmissibility of emerging agents, indefinite deferral of previously transfused donors in the US does not appear warranted.
Collaborative Watershed Management: A View from the Grassroots
Authors: Lubell Mark
Published: July 2004

To date, research on collaborative watershed management has paid scant attention to the role of grassroots stakeholders, who are the people that actually use natural resources. This article argues cooperation from grassroots stakeholders is necessary for the success of collaborative management, and outlines three theoretical perspectives to explain cooperation. The validity of these theoretical perspectives is tested using a survey of farmer participation in the Suwannee River Partnership in Florida. The findings suggest farmers’ perceptions of policy effectiveness are largely driven by economic considerations, whereas participation in collaborative management is linked to social capital.
Policy Implementation and the Environmental Protection Agency: What Factors Influence Remediation at Superfund Sites?
Authors: Daley Dorothy M. , Layton David F.
Published: July 2004

Since the early 1990s, the Environmental Protection Agency (EPA) has struggled to make Superfund, the program that addresses the nation's worst hazardous waste sites, “faster, fairer, and more efficient.” Indeed, agency figures reflect substantial changes in recent years. Since 1993, over 500 Superfund sites have reached the “construction completion” stage in remediation. Comparatively, in the program's first 13 years, only 156 sites reached construction completion. This article explores why some Superfund sites are more likely to be remediated than others. We use survival analysis to empirically test three theoretical models of Superfund remedial progress: (1) Administrative Convenience/Transaction Costs; (2) Problem Severity; and (3) Political Pressure models. The results indicate that the EPA is more likely to tackle “easier” or low‐risk sites within the program, community involvement in Superfund is associated with decreased remedial progress, and remedial action is more likely to occur when political oversight is present.
The Race Gap in Student Achievement Scores: Longitudinal Evidence from a Racially Diverse School District
Authors: Bali Valentina A. , Alvarez R. Michael
Published: July 2004

Black and Hispanic students often display substantial gaps in test scores when compared to White students at all levels of education. In this article, we examine when and how the Black‐White and Hispanic‐White test score gaps develop in the early elementary grades in a California school district with a large minority population, where more than 80% of the students are Black or Hispanic. We use multivariate analysis to predict the annual reading and math test scores of a student cohort from first through fourth grade controlling for various school and family factors. We find that in this racially diverse school district achievement gaps do develop, for both Black and Hispanic students. However, in comparison to the Black‐White achievement gaps, the Hispanic‐White gaps develop later, in particular in math, and they are half the size of the Black‐White achievement gaps. The eventual widening of the gaps for Hispanic and Black students does not seem to be the result of minority students attending schools of less quality. Finally, in contrast to previous studies with fewer minorities, the estimated achievement gaps by the fourth grade are small.1
Is Greener Whiter? Voluntary Environmental Performance of Western Ski Areas
Authors: Rivera Jorge , De Leon Peter
Published: July 2004

This study analyzes the initial implementation of the Sustainable Slopes Program a voluntary environmental initiative established by the U.S. National Ski Areas Association in partnership with federal and state government agencies. Our findings indicate that participation of western ski areas in the Sustainable Slopes Program is related to institutional pressures in the form of enhanced federal oversight and higher state environmental demands exerted by state agencies, local environmental groups and public opinion. The analysis also suggests that, despite these institutional pressures, participant ski areas appear to be correlated with lower third‐party environmental performance ratings. This behavior seems to reflect the lack of specific institutional mechanisms to prevent opportunism in the current design of the Sustainable Slopes Program. That is, the program does not involve specific environmental standards, lacks third‐party oversight, and does not have sanctions for poor performance.
KINETICS, MICROSTRUCTURE AND STRAIN IN GaN THIN FILMS GROWN VIA PENDEO-EPITAXY
Authors: ROSKOWSKI A. M. , PREBLE E. A. , EINFELDT S. , MIRAGLIA P. M. , SCHUCK J. , GROBER R. , DAVIS R. F.
Published: July 2004

Maskless pendeo-epitaxy involves the lateral and vertical growth of cantilevered "wings" of material from the sidewalls of unmasked etched forms. Gallium Nitride films grown at 1020°C via metalorganic vapor phase epitaxy on GaN / AlN /6 H - SiC (0001) substrates previously etched to form [Formula: see text]-oriented stripes exhibited similar vertical [0001] and lateral [Formula: see text] growth rates, as shown by cross-sectional scanning electron microscopy. Increasing the temperature increased the growth rate in the latter direction due to the higher thermal stability of the [Formula: see text] surface. The [Formula: see text] surface was atomically smooth under all growth conditions with a root mean square (RMS)=0.17 nm. High resolution X-ray diffraction and atomic force microscopy of the pendeo-epitaxial films confirmed transmission electron microscopy results regarding the significant reduction in dislocation density in the wings. This result is important for the properties of both optoelectronic and microelectronic devices fabricated in III-Nitride structures. Measurement of strain indicated that the wing material is crystallographically relaxed as evidenced by the increase in the c-axis lattice parameter and the upward shift of the E2 Raman line frequency. A strong D°X peak at 3.466 eV was also measured in the wing material. However, tilting of the wings of ≤0.15° occurred due to the tensile stresses in the stripes induced by the mismatch in the coefficients of thermal expansion between the GaN and the underlying substrate.
STRAIN OF GaN LAYERS GROWN USING 6H-SiC(0001) SUBSTRATES WITH DIFFERENT BUFFER LAYERS
Authors: EINFELDT S. , REITMEIER Z. J. , DAVIS R. F.
Published: July 2004

Gallium nitride films of increasing thickness have been grown on either AlN or AlGaN substrates. The state of stress of these biaxially stressed layers gradually changed from compression to tension with regard to both their average strain and their local strain along the [0001] growth direction. The components of both the compressive and tensile stresses are caused by the mismatch in lattice parameters between the GaN and the buffer layer and the mismatch in the coefficients of thermal expansion between GaN and SiC , respectively. The compressive stress is partially relieved within the first 20 nm in the GaN film grown on the AlN buffer layer. The relief of the remaining stress follows an exponential dependence on the thickness of the GaN layer with values for the characteristic decay length of 0.24 μm and 0.64 μm for the AlN and AlGaN buffer layer, respectively. The relaxation mechanism is discussed in terms of the formation of misfit dislocations via surface undulations.
GROWTH OF THICK GaN FILMS AND SEEDS FOR BULK CRYSTAL GROWTH
Authors: TAVERNIER P. R. , ETZKORN E. V. , CLARKE D. R.
Published: July 2004

The essential steps required to create thick GaN films and seed crystals for bulk crystal growth are described. These include the growth of low dislocation density GaN films by hydride vapor phase epitaxy and the separation of films from their growth substrates. Also addressed are issues of processing thin and thick films to create compliant layer substrates for thick film HVPE growth and chemical mechanical polishing methods to enhance surface morphology and remove material damage free. Growth of both gallium and nitrogen polar films is discussed with key issues identified regarding polarity inversion during growth and impurity incorporation along the -c growth direction. These are illustrated with examples that emphasize the growth of material with low threading dislocation density.
CRACKING OF GaN FILMS
Authors: ETZKORN E. V. , CLARKE D. R.
Published: July 2004

The cracking of GaN films and the associated cracking of substrates are described. The geometry, structure, and evolution of fracture demonstrate that GaN films crack under tensile stress during growth and are subsequently overgrown and partially healed. The film cracks channel along the (1010) GaN planes and also extend a distance of ~5 μm into the sapphire substrate. These incipient cracks in the substrate form a set of initial flaws that leads to complete fracture through the sapphire during cooling for sufficiently thick films. Each stage of this cracking behavior is well described by a fracture mechanics model that delineates a series of critical thicknesses for the onset of cracking that are functions of the film and substrate stresses, thicknesses, and elastic properties. Similar cracking behavior is found to occur independently of the choice of substrate between sapphire and SiC and is traced to a tensile stress generation mechanism early in the growth process, such as that provided by island coalescence. Cracking is the dominant stress relief mechanism, as opposed to dislocation generation or diffusion, because of the island growth mode and because of optimized growth temperatures at or below the brittle-to-ductile transition. Lateral epitaxial overgrowth (LEO) of GaN is shown to minimize substrate fracture even though film cracking remains unaffected. This effect explained in terms of the limits placed on the initial extent of insipient substrate cracks due to the LEO geometry.
HIGH FIELD TRANSPORT IN AlN
Authors: COLLAZO RAMON , SCHLESSER RAOUL , SITAR ZLATKO
Published: July 2004

The energy distribution of electrons transported through intrinsic AlN was directly measured as a function of applied field and AlN film thickness. The electron energy distribution featured kinetic energies higher than that of completely thermalized electrons. Transport through films thicker than 95 nm at an applied field between 200 kV/cm and 350 kV/cm occurred as steady-state hot electron transport following a Maxwellian energy distribution with a characteristic carrier temperature. At higher fields (470 kV/cm), intervalley scattering was evidenced by a multi-component energy distribution featuring a second peak at the energy position of the first satellite valley. Velocity overshoot was observed in films thinner than 95 nm and at fields greater than 510 kV/cm. In this case, a symmetric energy distribution centered at an energy above the conduction band minimum was measured, indicating that the drift component of the electron velocity was on the order of the "thermal" component. A transient transport length of less than 80 nm was deduced from these observations.
INSULATED GATE III-N HETEROSTRUCTURE FIELD-EFFECT TRANSISTORS
Authors: SIMIN G. , ASIF KHAN M. , SHUR M. S. , GASKA R.
Published: July 2004

Unique materials properties of GaN -based semiconductors that make them promising for high-power high-temperature applications are high electron mobility and saturation velocity, high sheet carrier concentration at heterojunction interfaces, high breakdown field, and low thermal impedance (when grown over SiC or bulk AlN substrates). The chemical inertness of nitrides is another key property. An AlGaN / GaN Heterostructure Field Effect Transistor (HFET) has been a topic of intensive investigations since the first report in 1991 [1]. Several groups demonstrated high power operation of AlGaN / GaN HFETs at microwave frequencies [2,3,4], including a 100 W output power single chip amplifier developed by Cree, Inc. and devices with 100 GHz cut-off frequency reported in [5]. However, in spite of impressive achievements, the potential of nitride based HFETs has not been fully realized as yet. The RF powers expected from the fundamental properties of nitride based materials significantly exceed the experimental data. One of the key problems limiting the HFETs RF characteristics is high gate leakage currents causing DC and RF parameter degradation. When the gate voltage goes positive the forward leakage current shunts the gate-channel capacitance and thus limits the maximum device current. When the gate voltage is negative, high voltage drop between the gate and the drain causes premature breakdown and thus limits maximum applied drain voltage. In addition, gate leakage currents increase the device sub-threshold currents, which decrease the achievable amplitude of the RF output. These limitations become even more severe at high ambient temperatures. The characteristics of III-N HFETs can be considerably improved by implementing a new approach, which results from the demonstration of good quality of SiO 2/ AlGaN and Si 3 N 4/ AlGaN interfaces. This approach opens up a way to fabricate insulated gate heterostructure field-effect transistors (IGHFETs), which have the gate leakage currents several orders of magnitude below those of regular HFETs, and exhibit better linearity and higher channel saturation currents. In this chapter, we describe design, characterization and applications of these novel devices.
ETCHED APERTURE GaN CAVET THROUGH PHOTOELECTROCHEMICAL WET ETCHING
Authors: GAO YAN , BEN-YAACOV ILAN , MISHRA UMESH , HU EVELYN
Published: July 2004

We describe the fabrication of the CAVET (Current Aperture Vertical Electron Transistor) by Photoelectrochemical (PEC) formation of a current aperture. Etch process is quite naturally critical to the achievement of the etched aperture in CAVET. We provide some background on that etch process, and the subsequent modification and optimization of the process for CAVET fabrication.
A NEW EINSTEIN–HILBERT-TYPE ACTION AND A SUPERON-GRAVITON MODEL (SGM) OF NATURE
Authors: SHIMA KAZUNARI , TSUDA MOTOMU , SAWAGUCHI MANABU
Published: July 2004

A nonlinear supersymmetric (NLSUSY) Einstein–Hilbert (EH)-type new action for the unity of nature is obtained by performing Einstein gravity analogue geometrical arguments in high symmetry spacetime inspired by NLSUSY. The new action is unstable and breaks down spontaneously into the EH action with matter in ordinary Riemann spacetime. All elementary particles except the graviton are composed of the fundamental fermion "superon" (the Nambu–Goldstone (NG) fermion of NLSUSY) and regarded as the eigenstates of SO(10) super-Poincaré (SP) algebra, called the superon-graviton model (SGM) of nature. Some phenomenological implications for low energy particle physics and cosmology are discussed. The linearization of NLSUSY including N=1 SGM action is attempted explicitly to obtain the linear SUSY local field theory, which is equivalent and renormalizable.
THE KLEIN–GORDON EQUATION WITH A COULOMB PLUS SCALAR POTENTIAL IN D DIMENSIONS
Authors: MA ZHONG-QI , DONG SHI-HAI , GU XIAO-YAN , YU JIANG , LOZADA-CASSOU M.
Published: July 2004

The solutions of the Klein–Gordon equation with a Coulomb plus scalar potential in D dimensions are exactly obtained. The energy E(n,l,D) is analytically presented and the dependence of the energy E(n,l,D) on the dimension D is analyzed in some detail. The positive energy E(n,0,D) first decreases and then increases with increasing dimension D. The positive energy E(n,l D)(l≠0) increases with increasing dimension D. The dependences of the negative energies E(n,0,D) and E(n,l,D)(l≠0) on the dimension D are opposite to those of the corresponding positive energies E(n,0,D) and E(n,l,D)(l≠0). It is found that the energy E(n,0,D) is symmetric with respect to D=2 for D∈(0,4). It is also found that the energy E(n,l,D)(l≠0) is almost independent of the angular momentum quantum number l for large D and is completely independent of the angular momentum quantum number l if the Coulomb potential is equal to the scalar one. The energy E(n,l D) is almost overlapping for large D.
SOME CHARACTERISTICS OF6LiAND7LiISOTOPES INTERACTIONS WITH EMULSION NUCLEI AT 3.7–4.5AGeV/c
Authors: EL-NADI M. , UZHINSKII V. V. , SHERIF M. M. , ABD-ELSALAM A. , EL-NAGDY M. S. , YASIN M. N. , ALI-MOUSA N. , EL-SHARKAWY S. , JILANY M. A. , ABD-ELHALIM S. M.
Published: July 2004

Experimental data are presented on the multiplicities of the charged secondaries of the various types in the interactions of6Li and7Li projectile isotopes with the target nuclei in nuclear emulsion at 4.5 A GeV / c and 3.7 A GeV / c , respectively. A systematic comparison using the corresponding values of4He – Em interactions is made. The results are discussed in the frameworks of the cascade evaporation, "wounded" nucleons, and generalized Andersson–Otterlund–Stenlund (AOS) models.
DESCRIPTION OF DRIP-LINE NUCLEI WITHIN THE RELATIVISTIC MEAN FIELD PLUS BCS APPROACH
Authors: YADAV H. L. , KAUSHIK M. , TOKI H.
Published: July 2004

Recently, it has been demonstrated, considering Ni and Ca isotopes as prototypes, that the relativistic mean-field plus BCS (RMF+BCS) approach wherein the single particle continuum corresponding to the RMF is replaced by a set of discrete positive energy states for the calculation of pairing energy provides a good approximation to the full relativistic Hartree–Bogoliubov (RHB) description of the ground state properties of drip-line neutron rich nuclei. The applicability of the RMF+BCS approach even for the drip-line nuclei is essentially due to the fact that the main contribution to the pairing correlations for the neutron rich nuclei is provided by the low-lying resonant states, in addition to the contributions coming from the states close to the Fermi surface. In order to show the general validity of this approach we present the results of our detailed calculations for the ground state properties of the chains of isotopes of O, Ca, Ni, Zr, Sn and Pb nuclei. The TMA force parameter set has been used for the effective mean-field Lagrangian with nonlinear terms for the sigma and omega mesons. Further, to check the validity of our treatment for different mean-field descriptions, calculations have also been carried out for the NL-SH force parametrization usually employed for the description of drip-line nuclei. Comprehensive results for the two neutron separation energy, rms radii, single particle pairing gaps and pairing energies etc. are presented. In particular, the Ca isotopes are found to exhibit distinct features near the neutron drip line whereby it is found that further addition of neutrons causes a rapid increase in the neutron rms radius with almost no increase in the binding energy, indicating the occurrence of halos. This is mainly caused by the pairing correlations and results in the existence of bound states of extremely neutron rich exotic nuclei. Similar characteristics, though less pronounced, are also exhibited by neutron rich Zr isotopes. A comparison of these results with the available experimental data and with the recent continuum relativistic Hartree–Bogoliubov (RCHB) calculations amply demonstrates the validity and usefulness of this fast RMF+BCS approach for the description of nuclei including those near the drip-lines.
Insights on outsourcing
Authors: Marcus Aaron
Published: July 2004

What's in it for us? For them? Where are we headed?
The 18th British HCI Group annual conference
Authors: Campbell Marisa
Published: July 2004

The 18th British HCI Group Annual Conference

September 6-10, 2004

Leeds Metropolitan University, UK
Incremental elaboration of scenario-based specifications and behavior models using implied scenarios
Authors: Uchitel Sebastian , Kramer Jeff , Magee Jeff
Published: July 2004

Behavior modeling has proved to be successful in helping uncover design flaws of concurrent and distributed systems. Nevertheless, it has not had a widespread impact on practitioners because model construction remains a difficult task and because the benefits of behavior analysis appear at the end of the model construction effort. In contrast, scenario-based specifications have a wide acceptance in industry and are well suited for developing first approximations of intended behavior; however, they are still maturing with respect to rigorous semantics and analysis tools.This article proposes a process for elaborating system behavior that exploits the potential benefits of behavior modeling and scenario-based specifications yet ameliorates their shortcomings. The concept that drives the elaboration process is that of
implied scenarios
. Implied scenarios identify gaps in scenario-based specifications that arise from specifying the global behavior of a system that will be implemented component-wise. They are the result of a mismatch between the behavioral and architectural aspects of scenario-based specifications. Due to the partial nature of scenario-based specifications, implied scenarios need to be validated as desired or undesired behavior. The scenario specifications are then updated accordingly with new positive or negative scenarios. By iteratively detecting and validating implied scenarios, it is possible to incrementally elaborate the behavior described both in the scenario-based specification and models. The proposed elaboration process starts with a message sequence chart (MSC) specification that includes basic, high-level and negative MSCs. Implied scenario detection is performed by synthesis and automated analysis of behavior models. The final outcome consists of four artifacts: (1) an MSC specification that has been evolved from its original form to cover important aspects of the concurrent nature of the system that were under-specified or absent in the original specification, (2) a behavior model that captures the component structure of the system that, combined with (3) a constraint model and (4) a property model that provides the basis for modeling and reasoning about system design.
Expressing and optimizing sequence queries in database systems
Authors: Sadri Reza , Zaniolo Carlo , Zarkesh Amir , Adibi Jafar
Published: July 2004

The need to search for complex and recurring patterns in database sequences is shared by many applications. In this paper, we investigate the design and optimization of a query language capable of expressing and supporting efficiently the search for complex sequential patterns in database systems. Thus, we first introduce SQL-TS, an extension of SQL to express these patterns, and then we study how to optimize the queries for this language. We take the optimal text search algorithm of Knuth, Morris and Pratt, and generalize it to handle complex queries on sequences. Our algorithm exploits the interdependencies between the elements of a pattern to minimize repeated passes over the same data. Experimental results on typical sequence queries, such as double bottom queries, confirm that substantial speedups are achieved by our new optimization techniques.
Evaluating top-
k
queries over web-accessible databases
Authors: Marian Amélie , Bruno Nicolas , Gravano Luis
Published: July 2004

A query to a web search engine usually consists of a list of keywords, to which the search engine responds with the best or "top"
k
pages for the query. This top-
k
query model is prevalent over multimedia collections in general, but also over plain relational data for certain applications. For example, consider a relation with information on available restaurants, including their location, price range for one diner, and overall food rating. A user who queries such a relation might simply specify the user's location and target price range, and expect in return the best 10 restaurants in terms of some combination of proximity to the user, closeness of match to the target price range, and overall food rating. Processing top-
k
queries efficiently is challenging for a number of reasons. One critical such reason is that, in many web applications, the relation attributes might not be available other than through external web-accessible form interfaces, which we will have to query repeatedly for a potentially large set of candidate objects. In this article, we study how to process top-
k
queries efficiently in this setting, where the attributes for which users specify target values might be handled by external, autonomous sources with a variety of access interfaces. We present a sequential algorithm for processing such queries, but observe that any sequential top-
k
query processing strategy is bound to require unnecessarily long query processing times, since web accesses exhibit high and variable latency. Fortunately, web sources can be probed in parallel, and each source can typically process concurrent requests, although sources may impose some restrictions on the type and number of probes that they are willing to accept. We adapt our sequential query processing technique and introduce an efficient algorithm that maximizes source-access parallelism to minimize query response time, while satisfying source-access constraints. We evaluate our techniques experimentally using both synthetic and real web-accessible data and show that parallel algorithms can be significantly more efficient than their sequential counterparts.
Proxy-based acceleration of dynamically generated content on the world wide web
Authors: Datta Anindya , Dutta Kaushik , Thomas Helen , Vandermeer Debra , Ramamritham Krithi
Published: July 2004

As Internet traffic continues to grow and websites become increasingly complex, performance and scalability are major issues for websites. Websites are increasingly relying on dynamic content generation applications to provide website visitors with dynamic, interactive, and personalized experiences. However, dynamic content generation comes at a cost---each request requires computation as well as communication across multiple components.To address these issues, various dynamic content caching approaches have been proposed. Proxy-based caching approaches store content at various locations outside the site infrastructure and can improve website performance by reducing content generation delays, firewall processing delays, and bandwidth requirements. However, existing proxy-based caching approaches either (a) cache at the page level, which does not guarantee that correct pages are served and provides very limited reusability, or (b) cache at the fragment level, which is associated with several design-level and runtime scalability issues. To address these issues, several back-end caching approaches have been proposed, including query result caching and fragment level caching. While back-end approaches guarantee the correctness of results and offer the advantages of fine-grained caching, they neither address firewall delays nor reduce bandwidth requirements.In this article, we present an approach and an implementation of a dynamic proxy caching technique which combines the benefits of both proxy-based and back-end caching approaches, yet does not suffer from their above-mentioned limitations. Our dynamic proxy caching technique allows granular, proxy-based caching in highly dynamic scenarios, accessible outside the site infrastructure. We present two possible configurations for our dynamic proxy caching technique: (1) a
reverse proxy
configuration, and (2) a
forward proxy
configuration. Analysis of the performance of our approach indicates that it is capable of providing significant reductions in bandwidth. We have deployed our proposed dynamic proxy caching technique at a major financial institution. The results of this implementation indicate that our technique is capable of providing up to 3x reductions in bandwidth and response times in real-world dynamic Web applications when compared to existing caching solutions.
The impact of Internet use on the other side of the digital divide
Authors: Jackson Linda A. , von Eye Alexander , Barbatsis Gretchen , Biocca Frank , Fitzgerald Hiram E. , Zhao Yong
Published: July 2004

Exploring factors influencing the social impact of Internet use.
High-tech forensics
Authors: Harrison Warren , Heuston George , Mocas Sarah , Morrissey Mark , Richardson John
Published: July 2004

An Oregon police department successfully enlists tech-savvy citizens to serve as police reserve specialists.
Universities marginalize online courses
Authors: Schell George P.
Published: July 2004

Why should faculty members develop online courses if the effort may be detrimental to their promotion or tenure?
ERP in China
Authors: Martinsons Maris G.
Published: July 2004

How and why the same software system implementation can produce fundamentally different results.
Investor perceptions of traditional and online channels
Authors: Strader Troy J. , Ramaswami Sridhar N.
Published: July 2004

How should financial service firms, online and off, adjust their customer-acquisition and -service strategies to reflect investors' changing expectations?
The field of programmers myth
Authors: Denning Peter J.
Published: July 2004

The persistent public image of computing as a field of programmers has become a costly myth. Reversing it is possible but not easy.
Is telemedicine the panacea for Sub-Saharan Africa's medical nightmare?
Authors: Mbarika Victor W. A.
Published: July 2004

"Ever since my eye swelled up, I've gone to church to pray for a cure...I always knew He would send a way to make me better---I just didn't know it was going to be from London,"
says Anna Mobutsu, a 23-year-old farm laborer, who cannot imagine journeying farther than a bus ride from her home in the small African town of Nelspruit. An illiterate single parent with a 7-year-old and an elderly mother to support on about $56 a month, Anna does not even own a TV to introduce her to a world beyond her own.
"But this afternoon I went to London"
[2].
Improving partial parsing based on error-pattern analysis for a Korean grammar-checker
Authors: Kang Mi-Young , Yoon Aesun , Kwon Hyuk-Chul
Published: July 2004

The main aim of this work is to make improvements to Mirine 2.2, a Korean grammar-checker that takes Korean language properties into account and to develop a system that satisfies user expectations. Particular attention is given to processing Korean texts that may contain users' grammatical and practical errors. In order to treat these errors efficiently, the system includes methods based on asymmetric relations from which partial parsing and the potential governing relationship are derived, implying the starting point for checking, the direction for parsing, and the limits of the scope for parsing.To organize partial parsing efficiently, the system requires an appropriate knowledge base. As its essential prerequisites, this study (a) considers the factors from which the various error types encountered while parsing various Korean texts arise; (b) extracts general patterns from the linguistic or extra-linguistic factors obtained in this manner; and (c) demonstrates how the system, based on a linguistic analysis, procures an adequate knowledge base for partial parsing to satisfy end-users. Mirine 2.2 achieves an F-measure of about 0.80 in detecting unknown erroneous words; an F-measure of about 0.98 when not considering unknown words; and 98.94% precision in correcting erroneous words.
Resolution of referring expressions in a Korean multimodal dialogue system
Authors: Kim Harksoo , Seo Jungyun
Published: July 2004

Referring expressions in multimodal dialogues have different aspects compared to those in language-only dialogues. They often refer to the items signified by either a gesture or visual means. In this article we classify referring expressions into two types (i.e., a deictic reference and an anaphoric reference), and propose two general methods to resolve these referring expressions. One method is a simple mapping algorithm that can find items referred with/without pointing gestures on a screen. The other is the centering algorithm with a dual cache model, to which Walker's centering algorithm is extended for a multimodal dialogue system. The extended algorithm is appropriate for resolving various anaphoric references in a multimodal dialogue. In the experiments, the proposed system correctly resolved 376 out of 405 referring expressions in 40 dialogues (0.54 referring expressions per utterance) showing 92.84 percent correctness.
Web services for the people
Authors: Treese Win
Published: July 2004

I don't know about you, but sometimes I have trouble remembering when my library books are due. Of course, it can get complicated with several people in the family checking out books and more than one library account. A long time ago, when all you checked out of a library were books, they usually had the same due date. Books were due every two weeks like clockwork. But libraries have changed. Besides books, you can get CDs, DVDs, rental books, audio tapes, and more, each with its own lending period. How to keep track?
Nonclairvoyant scheduling to minimize the total flow time on single and parallel machines
Authors: Becchetti Luca , Leonardi Stefano
Published: July 2004

Scheduling a sequence of jobs released over time when the processing time of a job is only known at its completion is a classical problem in CPU scheduling in time sharing operating systems. A widely used measure for the responsiveness of the system is the average flow time of the jobs, that is, the average time spent by jobs in the system between release and completion.The Windows NT and the Unix operating system scheduling policies are based on the Multilevel Feedback algorithm. In this article, we prove that a randomized version of the Multilevel Feedback algorithm is competitive for single and parallel machine systems, in our opinion providing one theoretical validation of the goodness of an idea that has proven effective in practice along the last two decades.The randomized Multilevel Feedback algorithm (RMLF) was first proposed by Kalyanasundaram and Pruhs for a single machine achieving an
O
(log
n
log log
n
) competitive ratio to minimize the average flow time against the on-line adaptive adversary, where
n
is the number of jobs that are released. We present a version of RMLF working for any number
m
of parallel machines. We show for RMLF a first
O
(log
n
log
n
/
m
) competitiveness result against the oblivious adversary on parallel machines. We also show that the same RMLF algorithm surprisingly achieves a tight
O
(log
n
) competitive ratio against the oblivious adversary on a single machine, therefore matching the lower bound for this case.
Edge-disjoint routing in plane switch graphs in linear time
Authors: Hochstein Jan M. , Weihe Karsten
Published: July 2004

By a
switch graph
, we mean an undirected graph
G
= (
P
⊍
W
,
E
) such that all vertices in
P
(the
plugs
) have degree one and all vertices in
W
(the
switches
) have even degrees. We call
G
plane
if
G
is planar and can be embedded such that all plugs are in the outer face. Given a set (
s
1
,
t
1
), …,(
s
k
,
t

k

) of pairs of plugs, the problem is to find edge-disjoint paths
p
1
, …,
p

k

such that every
p

i

connects
s

i

with
t

i

. The best asymptotic worst-case complexity known so far is quadratic in the number of vertices. In this article, a linear, and thus asymptotically optimal, algorithm is introduced. This result may be viewed as a concluding "keystone" for a number of previous results on various special cases of the problem.
Trustworthy 100-year digital objects
Authors: Gladney Henry M.
Published: July 2004

In ancient times, wax seals impressed with signet rings were affixed to documents as evidence of their authenticity. A digital counterpart is a message authentication code fixed firmly to each important document. If a digital object is sealed together with its own audit trail, each user can examine this evidence to decide whether to trust the content---no matter how distant this user is in time, space, and social affiliation from the document's source.We propose an architecture and design that accomplish this: encapsulation of digital object content with metadata describing its origins, cryptographic sealing, webs of trust for public keys rooted in a forest of respected institutions, and a certain way of managing information identifiers. These means will satisfy emerging needs in civilian and military record management, including medical patient records, regulatory records for aircraft and pharmaceuticals, business records for financial audit, legislative and legal briefs, and scholarly works.This is true for any kind of digital object, independent of its purposes and of most data type and representation details, and provides every kind of user---information authors and editors, librarians and collection managers, and information consumers---with autonomy for implied tasks. Our prototype will conform to applicable standards, will be interoperable over most computing bases, and will be compatible with existing digital library software.The proposed architecture integrates software that is mostly available and widely accepted.
PocketLens
Authors: Miller Bradley N. , Konstan Joseph A. , Riedl John
Published: July 2004

Recommender systems using collaborative filtering are a popular technique for reducing information overload and finding products to purchase. One limitation of current recommenders is that they are not portable. They can only run on large computers connected to the Internet. A second limitation is that they require the user to trust the owner of the recommender with personal preference data. Personal recommenders hold the promise of delivering high quality recommendations on palmtop computers, even when disconnected from the Internet. Further, they can protect the user's privacy by storing personal information locally, or by sharing it in encrypted form. In this article we present the new PocketLens collaborative filtering algorithm along with five peer-to-peer architectures for finding neighbors. We evaluate the architectures and algorithms in a series of offline experiments. These experiments show that Pocketlens can run on connected servers, on usually connected workstations, or on occasionally connected portable devices, and produce recommendations that are as good as the best published algorithms to date.
Distributed content-based visual information retrieval system on peer-to-peer networks
Authors: King Irwin , Ng Cheuk Hang , Sia Ka Cheung
Published: July 2004

With the recent advances of distributed computing, the limitation of information retrieval from a centralized image collection can be removed by allowing distributed image data sources to interact with each other for data storage sharing and information retrieval. In this article, we present our design and implementation of DISCOVIR: DIStributed COntent-based Visual Information Retrieval system using the Peer-to-Peer (P2P) Network. We describe the system architecture and detail the interactions among various system modules. Specifically, we propose a Firework Query Model for distributed information retrieval, which aims to reduce the network traffic of query passing in the network. We carry out experiments to show the distributed image retrieval system and the Firework information retrieval algorithm. The results show that the algorithm reduces network traffic while increases searching performance.