bluuebunny/crossref_metadata_2025 huggingface dataset:
Optimized image acquisition for breast tomosynthesis in projection and reconstruction space
Authors: Chawla Amarpreet S. , Lo Joseph Y. , Baker Jay A. , Samei Ehsan
Published: October 2009

Breast tomosynthesis has been an exciting new development in the field of breast imaging. While the diagnostic improvement via tomosynthesis is notable, the full potential of tomosynthesis has not yet been realized. This may be attributed to the dependency of the diagnostic quality of tomosynthesis on multiple variables, each of which needs to be optimized. Those include dose, number of angular projections, and the total angular span of those projections. In this study, the authors investigated the effects of these acquisition parameters on the overall diagnostic image quality of breast tomosynthesis in both the projection and reconstruction space. Five mastectomy specimens were imaged using a prototype tomosynthesis system. 25 angular projections of each specimen were acquired at 6.2 times typical single‐view clinical dose level. Images at lower dose levels were then simulated using a noise modification routine. Each projection image was supplemented with 84 simulated 3 mm 3D lesions embedded at the center of 84 nonoverlapping ROIs. The projection images were then reconstructed using a filtered backprojection algorithm at different combinations of acquisition parameters to investigate which of the many possible combinations maximizes the performance. Performance was evaluated in terms of a Laguerre–Gauss channelized Hotelling observer model‐based measure of lesion detectability. The analysis was also performed without reconstruction by combining the model results from projection images using Bayesian decision fusion algorithm. The effect of acquisition parameters on projection images and reconstructed slices were then compared to derive an optimization rule for tomosynthesis. The results indicated that projection images yield comparable but higher performance than reconstructed images. Both modes, however, offered similar trends: Performance improved with an increase in the total acquisition dose level and the angular span. Using a constant dose level and angular span, the performance rolled off beyond a certain number of projections, indicating that simply increasing the number of projections in tomosynthesis may not necessarily improve its performance. The best performance for both projection images and tomosynthesis slices was obtained for 15–17 projections spanning an angular arc of ∼45°—the maximum tested in our study, and for an acquisition dose equal to single‐view mammography. The optimization framework developed in this framework is applicable to other reconstruction techniques and other multiprojection systems.
A design methodology using signal‐to‐noise ratio for plastic scintillation detectors design and performance optimization
Authors: Lacroix Frédéric , Beddar A. Sam , Guillot Mathieu , Beaulieu Luc , Gingras Luc
Published: October 2009

Purpose

: The design of novel plastic scintillation detectors (PSDs) is impeded by the lack of a suitable framework to simulate and predict their performance. The authors propose to use the signal‐to‐noise ratio (SNR) to model the performance of PSDs that use charge‐coupled devices (CCDs) as photodetectors.

Methods

: In PSDs using CCDs, the SNR is inversely related to the normalized standard deviation of the dose measurement. Thus, optimizing the SNR directly optimizes the system's precision. In this work, a model of SNR as a function of the system parameters is derived for optical fiber‐based PSD systems. Furthermore, this proposed model is validated using experimental results. A formula for the efficiency of fiber coupling to CCDs is derived and used to simulate the performance of a PSD under varying magnifications.

Results

: The proposed model is shown to simulate the experimental performance of an actual PSD to a suitable degree of accuracy under various conditions.

Conclusions

: The SNR constitutes a useful tool to simulate the dosimetric precision of PSDs. Using the SNR model, recommendations for the design and optimization of PSDs are provided. Using the same framework, recommendations for non‐fiber‐based PSDs are also provided.
Projection space denoising with bilateral filtering and CT noise modeling for dose reduction in CT
Authors: Manduca Armando , Yu Lifeng , Trzasko Joshua D. , Khaylova Natalia , Kofler James M. , McCollough Cynthia M. , Fletcher Joel G.
Published: October 2009

Purpose:

To investigate a novel locally adaptive projection space denoising algorithm for low‐dose CT data.

Methods:

The denoising algorithm is based on bilateral filtering, which smooths values using a weighted average in a local neighborhood, with weights determined according to both spatial proximity and intensity similarity between the center pixel and the neighboring pixels. This filtering is locally adaptive and can preserve important edge information in the sinogram, thus maintaining high spatial resolution. A CT noise model that takes into account the bowtie filter and patient‐specific automatic exposure control effects is also incorporated into the denoising process. The authors evaluated the noise‐resolution properties of bilateral filtering incorporating such a CT noise model in phantom studies and preliminary patient studies with contrast‐enhanced abdominal CT exams.

Results:

On a thin wire phantom, the noise‐resolution properties were significantly improved with the denoising algorithm compared to commercial reconstruction kernels. The noise‐resolution properties on low‐dose (40 mA s) data after denoising approximated those of conventional reconstructions at twice the dose level. A separate contrast plate phantom showed improved depiction of low‐contrast plates with the denoising algorithm over conventional reconstructions when noise levels were matched. Similar improvement in noise‐resolution properties was found on CT colonography data and on five abdominal low‐energy (80 kV) CT exams. In each abdominal case, a board‐certified subspecialized radiologist rated the denoised 80 kV images markedly superior in image quality compared to the commercially available reconstructions, and denoising improved the image quality to the point where the 80 kV images alone were considered to be of diagnostic quality.

Conclusions:

The results demonstrate that bilateral filtering incorporating a CT noise model can achieve a significantly better noise‐resolution trade‐off than a series of commercial reconstruction kernels. This improvement in noise‐resolution properties can be used for improving image quality in CT and can be translated into substantial dose reduction.
Identification of Optimal Renal Dosage Adjustments for Traditional and Extended-Infusion Piperacillin-Tazobactam Dosing Regimens in Hospitalized Patients
Authors: Patel N. , Scheetz M. H. , Drusano G. L. , Lodise T. P.
Published: October 2009

This study examined the effect of various levels of renal impairment on the probability of achieving free drug concentrations that exceed the MIC for 50% of the dosing interval (50%fT > MIC) for traditional and extended-infusion piperacillin-tazobactam (TZP) dosing strategies. It also identified optimal renal dosage adjustments for traditional and extended-infusion dosing schemes that yielded probability of target attainment (PTA) and exposure profiles that were isometric to those of the parent regimens. Data from 105 patients were analyzed using the population pharmacokinetic modeling program BigNPAG. To assess the effect of creatinine clearance (CLCR) on overall clearance, TZP clearance was made proportional to the estimated CLCR. A Monte Carlo simulation (9,999 subjects) was performed for the traditional dosing scheme (4.5 g infused during 30 min every 6 h) and the extended-infusion TZP dosing scheme (3.375 g infused during 4 h every 8 h). The fraction of simulated subjects who achieved 50%fT > MIC was calculated for the range of piperacillin MICs from 0.25 to 32 mg/liter and stratified by CLCR. The traditional TZP regimen displayed the greatest variability in PTA across MIC values, especially for MIC values exceeding 4 mg/liter, when stratified by CLCR. In contrast, the PTA for the extended-infusion TZP regimen exceeded ≥80% for MIC values of ≤8 mg/liter across all CLCRstrata. All regimens were associated with suboptimal PTA for MIC values of ≥32 mg/liter irrespective of the CLCR. The CLCRadjustments for traditional and extended-infusion TZP dosing regimens should be considered at a CLCRof ≤20 ml/min.
Pharmacometrics-Based Dose Selection of Levofloxacin as a Treatment for Postexposure Inhalational Anthrax in Children
Authors: Li Fang , Nandy Partha , Chien Shuchean , Noel Gary J. , Tornoe Christoffer W.
Published: October 2009

Levofloxacin was recently (May 2008) approved by the U.S. Food and Drug Administration as a treatment for children following inhalational exposure to anthrax. Given that no clinical trials to assess the efficacy of a chosen dose was conducted, the basis for the dose recommendation was based upon pharmacometric analyses. The objective of this paper is to describe the basis of the chosen pediatric dose recommended for the label. Pharmacokinetic (PK) data from 90 pediatric patients receiving 7 mg/kg of body weight levofloxacin and two studies of 47 healthy adults receiving 500 and 750 mg/kg levofloxacin were used for the pharmacometric analyses. Body weight was found to be a significant covariate for levofloxacin clearance and the volume of distribution. Consistently with developmental physiology, clearance also was found to be reduced in pediatric patients under 2 years of age due to immature renal function. Different dosing regimens were simulated to match adult exposure (area under the concentration-time curve from 0 to 24 h at steady state, maximum concentration of drug in serum at steady state, and minimum concentration of drug in serum at steady state) following the approved adult dose of 500 mg once a day. The recommended dose of 8 mg/kg twice a day was found to match the exposure of the dose approved for adults in a manner that permitted confidence that this dose in children would achieve efficacy comparable to that of adults.
A Single Mutation in Enzyme I of the Sugar Phosphotransferase System Confers Penicillin Tolerance to
Streptococcus gordonii
Authors: Bizzini A. , Entenza J. M. , Michielin O. , Arnold I. , Erni B. , Moreillon P.
Published: October 2009

Tolerance is a poorly understood phenomenon that allows bacteria exposed to a bactericidal antibiotic to stop their growth and withstand drug-induced killing. This survival ability has been implicated in antibiotic treatment failures. Here, we describe a single nucleotide mutation (
tol1
) in a tolerant
Streptococcus gordonii
strain (Tol1) that is sufficient to provide tolerance in vitro and in vivo. It induces a proline-to-arginine substitution (P483R) in the homodimerization interface of enzyme I of the sugar phosphotransferase system, resulting in diminished sugar uptake. In vitro, the susceptible wild-type (WT) and Tol1 cultures lost 4.5 and 0.6 log
10
CFU/ml, respectively, after 24 h of penicillin exposure. The introduction of
tol1
into the WT (WT P483R) conferred tolerance (a loss of 0.7 log
10
CFU/ml/24 h), whereas restitution of the parent sequence in Tol1 (Tol1 R483P) restored antibiotic susceptibility. Moreover, penicillin treatment of rats in an experimental model of endocarditis showed a complete inversion in the outcome, with a failure of therapy in rats infected with WT P483R and the complete disappearance of bacteria in animals infected with Tol1 R483P.
Antifungal Activity of Colistin against
Mucorales
Species
In Vitro
and in a Murine Model of
Rhizopus oryzae
Pulmonary Infection
Authors: Ben-Ami Ronen , Lewis Russell E. , Tarrand Jeffrey , Leventakos Konstantinos , Kontoyiannis Dimitrios P.
Published: October 2009

In immunosuppressed hosts, mucormycosis is a life-threatening infection with few treatment options. We studied the activity of colistin (polymyxin E) against
Mucorales
species
in vitro
and in a murine model of pulmonary
Rhizopus oryzae
infection. Colistin exhibited fungicidal activity
in vitro
against
Mucorales
spores and mycelia. At the colistin MIC, initial
R. oryzae
hyphal damage was followed by rapid regrowth; however, regrowth was prevented by combining colistin with a subinhibitory concentration of amphotericin B. Using electron microscopy and FM4-64 staining, we demonstrated that colistin disrupts
R. oryzae
cytoplasmic and vacuolar membranes, resulting in the leakage of intracellular contents. The prophylactic intranasal treatment of immunosuppressed mice with colistimethate significantly reduced the mortality rate and pulmonary fungal burden resulting from inhalational challenge with
R. oryzae
spores, whereas intraperitoneal colistimethate treatment had no effect. We conclude that colistin has modest
in vitro
and
in vivo
fungicidal activity against
Mucorales
spp. Further studies are warranted to assess the use of this drug in the prevention and treatment of mucormycosis.
Inhibition of B Virus (Macacine herpesvirus1) by Conventional and Experimental Antiviral Compounds
Authors: Krug P. W. , Schinazi R. F. , Hilliard J. K.
Published: October 2009

B virus infection of humans results in high morbidity and mortality in as many as 80% of identified cases. The main objective of this study was to conduct a comparative analysis of conventional and experimental antiviral drug susceptibilities of B virus isolates from multiple macaque species and zoonotically infected humans. We used a plaque reduction assay to establish the effective inhibitory doses of acyclovir, ganciclovir, and vidarabine, as well as those of a group of experimental nucleoside analogs with known anti-herpes simplex virus activity. Four of the experimental drugs tested were 10- to 100-fold more potent inhibitors of B virus replication than conventional antiviral agents. Drug efficacies were similar for multiple B virus isolates tested, with variations within 2-fold of the median effective concentration (EC50) for each drug, and each EC50was considerably lower than those for B virus thymidine kinase (TK) mutants. We observed no differences in the viral TK amino acid sequence between B virus isolates from rhesus monkeys and those from human zoonoses. Differences in the TK protein sequence between cynomolgus and pigtail macaque B virus isolates did not affect drug sensitivity except in the case of one compound. Taken together, these data suggest that future B virus zoonoses will respond consistently to conventional antiviral treatment. Further, the considerably higher potency of FEAU (2′-fluoro-5-ethyl-Ara-U) than of conventional antiviral drugs argues for its compassionate use in advanced human B virus infections.
Division of theSalmonella-Containing Vacuole and Depletion of Acidic Lysosomes inSalmonella-Infected Host Cells Are Novel Strategies ofSalmonella entericaTo Avoid Lysosomes
Authors: Eswarappa Sandeepa M. , Negi Vidya Devi , Chakraborty Sangeeta , Chandrasekhar Sagar B. K. , Chakravortty Dipshikha
Published: October 2009

Salmonellahas evolved several strategies to counteract intracellular microbicidal agents like reactive oxygen and nitrogen species. However, it is not yet clear howSalmonellaescapes lysosomal degradation. Some studies have demonstrated thatSalmonellacan inhibit phagolysosomal fusion, whereas other reports have shown that theSalmonella-containing vacuole (SCV) fuses/interacts with lysosomes. Here, we have addressed this issue from a different perspective by investigating if the infected host cell has a sufficient quantity of lysosomes to targetSalmonella. Our results suggest that SCVs divide along withSalmonella, resulting in a single bacterium per SCV. As a consequence, the SCV load per cell increases with the division ofSalmonellainside the host cell. This demands more investment from the host cell to counteractSalmonella. Interestingly, we observed thatSalmonellainfection decreases the number of acidic lysosomes inside the host cell bothin vitroandin vivo. These events potentially result in a condition in which an infected cell is left with insufficient acidic lysosomes to target the increasing number of SCVs, which favors the survival and proliferation ofSalmonellainside the host cell.
Detection of PCR products using self-reporting duplex mutation primers
Authors: Xia Q-F , Tu Z-G , Liu J-B , Qin X , Qian S-Y , Li P
Published: October 2009

A novel oligonucleotide probe, with duplex mutation primers, which comprised a normal reverse primer labelled with a fluorophore at its 5′-end and a single-base mismatched complementary oligonucleotide labelled with a quencher at its 3′-end, was designed. Its application in the detection of hepatitis B virus (HBV) DNA of serum was investigated; results were compared with those obtained using a commercial TaqMan kit. There was a good linear correlation in the range of 102∼107copies/ml (r2 = 0.999) with the method. Intra-experimental coefficients of variation (CVs) were 0.70%∼7.80%, and inter-experimental CVs were 0.78%∼9.02%, respectively. There was no significant difference of HBV genome number tested by the two methods (p<0.05) in 132 hepatitis B patients; HBV DNA was not detected in any serum samples of 20 healthy volunteers by the two methods.
An autopsy report on multiple system atrophy diagnosed immunohistochemically despite severe ischaemic damage: a new approach for investigation of medical practice associated deaths in Japan
Authors: Nakajima M , Kojima H , Takazawa Y , Yahagi N , Harada K , Takahashi K , Unuma K , Yoshida K
Published: October 2009

A 60-year old man with a 10-year history of multiple system atrophy (MSA) was found in respiratory arrest. After 4 months of respiratory support with two episodes of septic shock, he died. Autopsy disclosed severe atrophy of the mesencephalon, brainstem, medulla oblongata and cerebellum. Gallyas–Braak, α-synuclein and ubiquitin-positive inclusions in the cytoplasm of glial cells were evident, despite the severe ischaemic damage due to respiratory arrest and subsequent respiratory support for 4 months. The cause of respiratory arrest was not identified, but could be explained by the natural history of MSA. The bereaved family, who had suspected malpractice, was satisfied with the explanation based on the investigation performed by eight expert doctors, one expert nurse, two coordinator nurses and two lawyers in the model project promoted by the Japanese government.
Use of an elastic stain to show venous invasion in colorectal carcinoma: a simple technique for detection of an important prognostic factor
Authors: Howlett C J , Tweedie E J , Driman D K
Published: October 2009

Background:

Venous invasion (VI) is an important prognostic factor in colorectal cancer; it is positively associated with visceral metastases and may affect the decision to treat with adjuvant therapy.

Aims:

To evaluate whether an elastic tissue (Movat) stain facilitates identification of VI, the number of Movat-stained blocks needed to detect VI, and whether VI identified with a Movat stain is prognostically equivalent to VI identified on H&E-stained slides.

Methods:

H&E-stained sections from colorectal carcinomas from the year 2000 (n = 92) were examined for VI and compared to Movat-stained slides. Clinical charts were reviewed to compare rates of metastases in VI-positive versus VI-negative patients.

Results:

With the Movat stain, VI was identified in 44% of cases previously categorised as negative (p<0.001) on review of H&E slides alone. One Movat-stained section was often sufficient to identify VI, with a statistically significant benefit to performing multiple stains if necessary. In H&E sections, two clues helped identify VI: the “unaccompanied artery” sign, where large arteries were seen without an accompanying vein; and the “protruding tongue” sign, where smooth tongues of tumour extended into pericolic/rectal fat. Metastases were present in 61% of cases positive for VI compared to 35% in VI-negative cases (p = 0.03). 45% of cases positive for intramural VI only developed metastases (p = 0.39), while 65% of cases positive for extramural VI only developed metastases (p = 0.03).

Conclusions:

Pathologists should look for morphological clues of VI in H&E stained sections; when VI is not apparent, an elastic tissue stain on all tumour blocks significantly improves identification of VI. Morphological clues include the “unaccompanied artery” and “protruding tongue” signs.
BOAT-SAIL VORONOI DIAGRAM AND ITS APPLICATION
Authors: NISHIDA TETSUSHI , SUGIHARA KOKICHI
Published: October 2009

A new generalized Voronoi diagram, called a boat-sail Voronoi diagram, is defined on the basis of the time necessary for a boat to reach on water surface with flow. A new concept called a boat-sail distance is introduced on the surface of water with flow, and it is used to define a generalized Voronoi diagram, in such a way that the water surface is partitioned into regions belonging to the nearest harbors with respect to this distance. The problem of computing this Voronoi diagram is reduced to a boundary value problem of a partial differential equation, and a numerical method for solving this problem is constructed. The method is a modification of a so-called fast marching method originally proposed for the eikonal equation. Computational experiments show the efficiency and the stableness of the proposal method. We also apply our equation to the shortest path problem and the simulation of the forest fire.
ACTIVE GALACTIC NUCLEI: SOURCES FOR ULTRA HIGH ENERGY COSMIC RAYS
Authors: BIERMANN P. L. , BECKER J. K. , CARAMETE L. , GERGELY L. , MARIŞ I. C. , MELI A. , DE SOUZA V. , STANEV T.
Published: October 2009

Ultra high energy cosmic ray events presently show a spectrum, which we interpret here as galactic cosmic rays due to a starburst, in the radio galaxy Cen A which is pushed up in energy by the shock of a relativistic jet. The knee feature and the particles with energy immediately higher in galactic cosmic rays then turn into the bulk of ultra high energy cosmic rays. This entails that all ultra high energy cosmic rays are heavy nuclei. This picture is viable if the majority of the observed ultra high energy events come from the radio galaxy Cen A, and are scattered by intergalactic magnetic fields across much of the sky.
FLARE DETECTION USING WAVELET DENOISING AND SWIFT BAT DATA FOR NEUTRINO MULTIMESSENGER STUDIES
Authors: MOVIT STEVEN M.
Published: October 2009

Theory predicts a neutrino signal is possible from jets from active galactic nuclei (AGN) if there is hadronic acceleration in the jets. Flaring activity in X-rays and γ-rays from blazars could indicate similar activity in neutrinos in the jets. Short duration flares, on the scale of hours, could allow for narrow time windows to be searched for a Neutrino signal above the background of atmospheric neutrinos. A wavelet technique will be run over orbit-by-orbit Swift BAT (Burst Alert Telescope) data to identify flaring periods to accurately determine start and end times. The wavelet technique is notable as it accounts for both uneven time sampling and varying error bars across a time series.
COSMIC RAYS ABOVE THE 2ND KNEE FROM CLUSTERS OF GALAXIES
Authors: MURASE KOHTA , INOUE SUSUMU , ASANO KATSUAKI
Published: October 2009

In clusters of galaxies, accretion and merger shocks are potential accelerators of high energy protons, as well as intracluster active galactic nuclei. We discuss the possibility that protons from cluster shocks make a significant contribution to the observed cosmic rays in the energy range between the second knee at ~1017.5 eV and the ankle at ~1018.5 eV. The accompanying neutrino and gamma-ray signals could be detectable by upcoming telescopes such as IceCube/KM3Net and CTA, providing a test of this scenario as well as a probe of cosmic-ray confinement properties in clusters.
JOINT SEARCHES BETWEEN GRAVITATIONAL-WAVE INTERFEROMETERS AND HIGH-ENERGY NEUTRINO TELESCOPES: SCIENCE REACH AND ANALYSIS STRATEGIES
Authors: VAN ELEWYCK VERONIQUE , ANDO S. , ASO Y. , BARET B. , BARSUGLIA M. , BARTOS I. , CHASSANDE-MOTTIN E. , DI PALMA I. , DWYER J. , FINLEY C. , KEI K. , KOUCHNER A. , MARKA S. , MARKA Z. , ROLLINS J. , OTT C. D. , PRADIER T. , SEARLE A.
Published: October 2009

Many of the astrophysical sources and violent phenomena observed in our Universe are potential emitters of gravitational waves (GWs) and high-energy neutrinos (HENs). A network of GW detectors such as LIGO and Virgo can determine the direction/time of GW bursts while the IceCube and ANTARES neutrino telescopes can also provide accurate directional information for HEN events. Requiring the consistency between both, totally independent, detection channels shall enable new searches for cosmic events arriving from potential common sources, of which many extra-galactic objects.
GAMMA-RAY AND NEUTRINO SPECTRA IN GRBs
Authors: ASANO KATSUAKI
Published: October 2009

Gamma-ray bursts (GRBs) are the possible sources of ultra-high-energy cosmic rays (UHECRs), because of the extreme values of ultra-relativistic velocities and strong magnetic fields. In this paper we review the validity of GRBs as sources of UHECRs, and introduce our recent detailed studies of gamma-rays and neutrinos due to UHECRs utilizing comprehensive Monte Carlo codes. Future observations such as Fermi, ground-based telescopes and other facilities may provide constraints on the UHECR acceleration efficiency in GRBs. We also show a preliminary result of neutrino detection efficiency from a GRB with JEM-EUSO.
THE ROLE OF FAMILY START UPS IN THE EMERGENCE OF A SMALL BUSINESS SECTOR IN BULGARIA
Authors: FLETCHER DENISE , HELIENEK EMIL , ZAFIROVA ZVETA
Published: October 2009

It is widely reported that entrepreneurial activity has a significant role to play in transition economies such as Central and Eastern Europe but little is known about the role that the family unit plays in facilitating small business emergence in the former command economies. This is surprising given that the link between family and small business development has been widely researched in market economies. In this study, attention is drawn to the role that family relations and resources play in small business emergence. The study focuses on Bulgaria, a country in the Balkans with much cultural diversity and which became a European Union member in 2007–8. Analysis is undertaken of research material drawn from a survey of 69 small firms. 42% of the surveyed firms are two generation businesses involving the entrepreneur and children or parents. 35% of the businesses are three generation businesses involving the lead entrepreneur, parents, children and siblings. The remaining 33% are firms that are run by couples and/or siblings. This suggests that the family household is the key channel for (and of) small business formation. In neglecting the role of family start-ups, this gives a false understanding to the role that households and families sometimes contribute to the economy. At the same time, it is also partly because of this dependency on family relations and resources that small businesses become rooted in the 'informal economy' — an economy that is based on family favours and which it is difficult to break out of.
CONTINUOUS INNOVATION IN ENTREPRENEURIAL GROWTH COMPANIES: EXPLORING THE AMBIDEXTROUS STRATEGY
Authors: KOLLMANN TOBIAS , KUCKERTZ ANDREAS , STÖCKMANN CHRISTOPH
Published: October 2009

This paper applies ambidextrous management to entrepreneurial growth companies. Ambidexterity aims at overcoming organizational inertia that threatens organizational survival. The concept is typically applied to established corporations in order to cure existing inertia. However, ambidextrous management may also help to avoid the emergence of inertia in entrepreneurial growth companies. We therefore discuss ambidexterity against the background of entrepreneurial growth companies and reveal how it can be used to build sustainable organizations. Our reasoning is based on organization science and entrepreneurship theory; in doing so we derive two groups of theoretical propositions explaining the antecedents of emergence and the antecedents of success of ambidextrous management in entrepreneurial growth companies.
CONVEXITY CONDITIONS ON THE BOUNDARY OF A STATIONARY SPACETIME AND APPLICATIONS
Authors: BARTOLO ROSSELLA , GERMINARIO ANNA
Published: October 2009

We deal with the convexity of the boundary of a standard stationary spacetime L = M × ℝ. We obtain a characterization of this notion by means of Riemannian conditions involving a potential plus a magnetic field on M, where both are linked to the coefficients of the metric. Natural applications of our results concern geodesics having a prescribed parametrization proportional to the arc length, joining a point to a line and periodic, on non-complete manifolds, and in particular on Kerr spacetime.
SOME QUANTUM VERTEX ALGEBRAS OF ZAMOLODCHIKOV–FADDEEV TYPE
Authors: KAREL MARTIN , LI HAISHENG
Published: October 2009

This is a continuation of a previous study of quantum vertex algebras of the Zamolodchikov–Faddeev type. In this paper, we focus our attention on the special case associated to diagonal unitary rational quantum Yang–Baxter operators. We prove that the associated weak quantum vertex algebras, if not zero, are irreducible quantum vertex algebras with a normal basis in a certain sense.
SCATTERING OPERATOR FOR NONLINEAR KLEIN–GORDON EQUATIONS
Authors: HAYASHI NAKAO , NAUMKIN PAVEL I.
Published: October 2009

We prove the existence of the scattering operator in [Formula: see text] in the neighborhood of the origin for the nonlinear Klein–Gordon equation with a power nonlinearity [Formula: see text] where [Formula: see text]μ ∈ C, n=1,2.
ON THE CONTROLLABILITY OF A COUPLED SYSTEM OF TWO KORTEWEG–DE VRIES EQUATIONS
Authors: MICU SORIN , ORTEGA JAIME H. , PAZOTO ADEMIR F.
Published: October 2009

This paper proves the local exact boundary controllability property of a nonlinear system of two coupled Korteweg–de Vries equations which models the interactions of weakly nonlinear gravity waves (see [10]). Following the method in [24], which combines the analysis of the linearized system and the Banach's fixed point theorem, the controllability problem is reduced to prove a nonstandard unique continuation property of the eigenfunctions of the corresponding differential operator.
CONTINUOUS TRACE C*-ALGEBRAS, GAUGE GROUPS AND RATIONALIZATION
Authors: KLEIN JOHN R. , SCHOCHET CLAUDE L. , SMITH SAMUEL B.
Published: October 2009

Let ζ be an n-dimensional complex matrix bundle over a compact metric space X and let Aζdenote the C*-algebra of sections of this bundle. We determine the rational homotopy type as an H-space of UAζ, the group of unitaries of Aζ. The answer turns out to be independent of the bundle ζ and depends only upon n and the rational cohomology of X. We prove analogous results for the gauge group and the projective gauge group of a principal bundle over a compact metric space X.
Deep data dives discover natural laws
Authors: Anthes Gary
Published: October 2009

Computer scientists have found a way to bootstrap science, using evolutionary computation to find fundamental meaning in massive amounts of raw data.
Implementing electronic medical records
Authors: Hoffmann Leah
Published: October 2009

Despite a number of challenges, patients' medical records are slowly making the transition to the digital age.
Economic and business dimensionsThe broadband price is not right
Authors: Greenstein Shane
Published: October 2009

Developing an effective pricing index is essential to understanding the value of broadband connectivity.
InterviewAn interview with Ping Fu
Authors: Cramblitt Bob , Fu Ping
Published: October 2009

Ping Fu, CEO of the digital shape sampling and processing company Geomagic, discusses her background, achievements, and challenges managing a company during a period of dynamic growth.
Communications surveillance
Authors: Diffie Whitfield , Landau Susan
Published: October 2009

As the sophistication of wiretapping technology grows, so too do the risks it poses to our privacy and security.
You don't know jack about software maintenance
Authors: Stachour Paul , Collier-Brown David
Published: October 2009

Long considered an afterthought, software maintenance is easiest and most effective when built into a system from the ground up.
Model checking
Authors: Clarke Edmund M. , Emerson E. Allen , Sifakis Joseph
Published: October 2009

Turing Lecture from the winners of the 2007 ACM A.M. Turing Award.

In 1981, Edmund M. Clarke and E. Allen Emerson, working in the USA, and Joseph Sifakis working independently in France, authored seminal papers that founded what has become the highly successful field of model checking. This verification technology provides an algorithmic means of determining whether an abstract model---representing, for example, a hardware or software design---satisfies a formal specification expressed as a temporal logic (TL) formula. Moreover, if the property does not hold, the method identifies a counterexample execution that shows the source of the problem.

The progression of model checking to the point where it can be successfully used for complex systems has required the development of sophisticated means of coping with what is known as the state explosion problem. Great strides have been made on this problem over the past 28 years by what is now a very large international research community. As a result many major hardware and software companies are beginning to use model checking in practice. Examples of its use include the verification of VLSI circuits, communication protocols, software device drivers, real-time embedded systems, and security algorithms.

The work of Clarke, Emerson, and Sifakis continues to be central to the success of this research area. Their work over the years has led to the creation of new logics for specification, new verification algorithms, and surprising theoretical results. Model checking tools, created by both academic and industrial teams, have resulted in an entirely novel approach to verification and test case generation. This approach, for example, often enables engineers in the electronics industry to design complex systems with considerable assurance regarding the correctness of their initial designs. Model checking promises to have an even greater impact on the hardware and software industries in the future.

        ---
Moshe Y. Vardi, Editor-in-Chief
Predicting structured objects with support vector machines
Authors: Joachims Thorsten , Hofmann Thomas , Yue Yisong , Yu Chun-Nam
Published: October 2009

Machine Learning today offers a broad repertoire of methods for classification and regression. But what if we need to predict complex objects like trees, orderings, or alignments? Such problems arise naturally in natural language processing, search engines, and bioinformatics. The following explores a generalization of Support Vector Machines (SVMs) for such complex prediction problems.
Selectively retrofitting monitoring in distributed systems
Authors: Anandkumar Animashree , Bisdikian Chatschik , He Ting , Agrawal Dakshi
Published: October 2009

Current distributed systems carry legacy subsystems lacking sufficient instrumentation for monitoring the end-to-end business transactions supported by these systems. In the absence of instrumentation, only probabilistic monitoring is possible by using time-stamped log-records. Retro fitting these systems with expensive monitoring instrumentation provides high-granularity, precise tracking of transactions. Given a limited budget, local instrumentation strategies which maximize the effectiveness of monitoring transactions throughout the system are proposed. The operation of the end-to-end system is modeled by a queuing network;each queue represents a subsystem which produces time-stamped log-records as transactions pass through it. Two simple heuristics for instrumentation are proposed which become optimal under certain conditions. One heuristic selects states in the transition diagram for local instrumentation in the decreasing order of the load factors of their queues. Sufficient onditions for this load-factor heuristic to be optimal are proven using the notion of stochastic order. The other heuristic selects states in the transition diagram based on the approximated tracking accuracy of probabilistic monitoring at each state, which is shown to be tight at low arrival rates.
On modeling product advertisement in social networks
Authors: Zhao Bridge , Li y. K. , Lui John C.S. , Chiu Dah-Ming
Published: October 2009

Advertising via social networks is receiving more attention these days. Given a fixed investment (e.g., free samples), a company needs to find out the final probability that users will purchase the product. In this paper we characterize and model various influence mechanisms that govern the word-of-mouth spread of advertisements in large social networks. We use the local mean field (LMF) technique to analyze large scale networks wherein states of nodes can be changed by various influence mechanisms. Extensive simulations are carried out to validate the accuracy of our model, and the results also provide insights on designing advertising strategies.
A distributed data streaming algorithm for network-wide traffic anomaly detection
Authors: Liu Yang , Zhang Linfeng , Guan Yong
Published: October 2009

Nowadays, Internet has serious security problems and network failures that are hard to resolve, for example, botnet attacks, polymorphic worm/virus spreading, DDoS, and flash crowds. To address many of these problems, we need to have a network-wide view of the traffic dynamics, and more importantly, be able to detect traffic anomaly in a timely manner. To our knowledge, Principle Component Analysis (PCA)is the best-known spatial detection method for the network-wide traffic anomaly. However, existing PCA-based solutions have scalability problems in that they require
O
(
m
2
n
)running time and
O
(
mn
)space to analyze traffic measurements from
m
aggregated traffic flows within a sliding window of the length
n
. We propose a novel data streaming algorithm for PCA-based network-wide traffic anomaly detection in a distributed fashion. Our algorithm can archive
O
(
wn
log
n
)running time and
O
(
wn
)space at local monitors,and
O
(
m
2
log
n
)running time and
O
(
m
log
n
) space at Network Operation Center (NOC), where
w
denotes the maximum number of traffic flows at a local monitor.
What a mesh
Authors: Nandi Animesh , Bhattacharjee Bobby , Druschel Peter
Published: October 2009

Cooperative end-system multicast (CEM) is a promising paradigm for Internet video distribution. Several CEM systems have been proposed and deployed, but the tradeoffs inherent in the different designs are not well understood. In this work, we provide a common framework in which different CEM design choices can be empirically and systematically evaluated. Based on our results, we conjecture that all CEM systems must abide by a set of fundamental design constraints, which we express in a simple model. By necessity, existing system implementations couple the data- and control-planes and often use different transport protocols.
CZ
Authors: Malayeri Donna , Aldrich Jonathan
Published: October 2009

Multiple inheritance has long been plagued with the "diamond" inheritance problem, leading to solutions that restrict expressiveness, such as mixins and traits. Instead, we address the diamond problem directly, considering two difficulties it causes: ensuring a correct semantics for object initializers, and typechecking multiple dispatch in a modular fashion-the latter problem arising even with multiple interface inheritance. We show that previous solutions to these problems are either unsatisfactory or cumbersome, and suggest a novel approach: supporting multiple inheritance but forbidding diamond inheritance. Expressiveness is retained through two features: a "requires" construct that provides a form of subtyping without inheritance (inspired by Scala), and a dynamically-dispatched "super" call similar to that found in traits. Through examples, we illustrate that inheritance diamonds can be eliminated via a combination of "requires" and ordinary inheritance. We provide a sound formal model for our language and demonstrate its modularity and expressiveness.
Empirical assessment of object-oriented implementations with multiple inheritance and static typing
Authors: Ducournau Roland , Morandat Floréal , Privat Jean
Published: October 2009

Object-oriented languages involve a threefold tradeoff between runtime efficiency, expressiveness (multiple inheritance), and modularity, i.e. open-world assumption (OWA). Runtime efficiency is conditioned by both the
implementation technique
and
compilation scheme
. The former specifies the data structures that support method invocation, attribute access and subtype testing. The latter consists of the production line of an executable from the source code. Many implementation techniques have been proposed and several compilation schemes can be considered from fully global compilation under the closed-world assumption (CWA) to separate compilation with dynamic loading under the OWA, with midway solutions. This article reviews a significant subset of possible combinations and presents a systematic, empirical comparison of their respective efficiencies with
all other things being equal
. The testbed consists of the Prm compiler that has been designed for this purpose. The considered techniques include C++ subobjects, coloring, perfect hashing, binary tree dispatch and caching. A variety of processors were considered. Qualitatively, these first results confirm the intuitive or theoretical abstract assessments of the tested approaches. As expected, efficiency increases as CWA strengthens. From a quantitative standpoint, the results are the first to precisely compare the efficiency of techniques that are closely associated with specific languages like C++ and Eiffel. They also confirm that perfect hashing should be considered for implementing Java and .Net interfaces.
A type and effect system for deterministic parallel Java
Authors: Bocchino Robert L. , Adve Vikram S. , Dig Danny , Adve Sarita V. , Heumann Stephen , Komuravelli Rakesh , Overbey Jeffrey , Simmons Patrick , Sung Hyojin , Vakilian Mohsen
Published: October 2009

Today's shared-memory parallel programming models are complex and error-prone.While many parallel programs are intended to be deterministic, unanticipated thread interleavings can lead to subtle bugs and nondeterministic semantics. In this paper, we demonstrate that a practical
type and effect system
can simplify parallel programming by
guaranteeing deterministic semantics
with modular, compile-time type checking even in a rich, concurrent object-oriented language such as Java. We describe an object-oriented type and effect system that provides several new capabilities over previous systems for expressing deterministic parallel algorithms.We also describe a language called Deterministic Parallel Java (DPJ) that incorporates the new type system features, and we show that a core subset of DPJ is sound. We describe an experimental validation showing thatDPJ can express a wide range of realistic parallel programs; that the new type system features are useful for such programs; and that the parallel programs exhibit good performance gains (coming close to or beating equivalent, nondeterministic multithreaded programs where those are available).
Thorn
Authors: Bloom Bard , Field John , Nystrom Nathaniel , Östlund Johan , Richards Gregor , Strniša Rok , Vitek Jan , Wrigstad Tobias
Published: October 2009

Scripting languages enjoy great popularity due to their support for rapid and exploratory development. They typically have lightweight syntax, weak data privacy, dynamic typing, powerful aggregate data types, and allow execution of the completed parts of incomplete programs. The price of these features comes later in the software life cycle. Scripts are hard to evolve and compose, and often slow. An additional weakness of most scripting languages is lack of support for concurrency - though concurrency is required for scalability and interacting with remote services. This paper reports on the design and implementation of Thorn, a novel programming language targeting the JVM. Our principal contributions are a careful selection of features that support the evolution of scripts into industrial grade programs -
e.g.
, an expressive module system, an optional type annotation facility for declarations, and support for concurrency based on message passing between lightweight, isolated processes. On the implementation side, Thorn has been designed to accommodate the evolution of the language itself through a compiler plugin mechanism and target the Java virtual machine.
How a Java VM can get more from a hardware performance monitor
Authors: Inoue Hiroshi , Nakatani Toshio
Published: October 2009

This paper describes our sampling-based profiler that exploits a processor's HPM (Hardware Performance Monitor) to collect information on running Java applications for use by the Java VM. Our profiler provides two novel features: Java-level event profiling and lightweight context-sensitive event profiling. For Java events, we propose new techniques to leverage the sampling facility of the HPM to generate object creation profiles and lock activity profiles. The HPM sampling is the key to achieve a smaller overhead compared to profilers that do not rely on hardware helps. To sample the object creations with the HPM, which can only sample hardware events such as executed instructions or cache misses, we correlate the object creations with the store instructions for Java object headers. For the lock activity profile, we introduce an instrumentation-based technique, called ProbeNOP, which uses a special NOP instruction whose executions are counted by the HPM. For the context-sensitive event profiling, we propose a new technique called
CallerChaining
, which detects the calling context of HPM events based on the call stack depth (the value of the stack frame pointer). We show that it can detect the calling contexts in many programs including a large commercial application. Our proposed techniques enable both programmers and runtime systems to get more valuable information from the HPM to understand and optimize the programs without adding significant runtime overhead.
A concurrent dynamic analysis framework for multicore hardware
Authors: Ha Jungwoo , Arnold Matthew , Blackburn Stephen M. , McKinley Kathryn S.
Published: October 2009

Software has spent the bounty of Moore's law by solving harder problems and exploiting abstractions, such as high-level languages, virtual machine technology, binary rewriting, and dynamic analysis. Abstractions make programmers more productive and programs more portable, but usually slow them down. Since Moore's law is now delivering multiple cores instead of faster processors, future systems must either bear a relatively higher cost for abstractions or use some cores to help tolerate abstraction costs.

This paper presents the design, implementation, and evaluation of a novel concurrent, configurable dynamic analysis framework that efficiently utilizes multicore cache architectures. It introduces Cache-friendly Asymmetric Buffering (CAB), a lock-free ring-buffer that implements efficient communication between application and analysis threads. We guide the design and implementation of our framework with a model of dynamic analysis overheads. The framework implements exhaustive and sampling event processing and is analysis-neutral. We evaluate the framework with five popular and diverse analyses, and show performance improvements even for lightweight, low-overhead analyses.

Efficient inter-core communication is central to high performance parallel systems and we believe the CAB design gives insight into the subtleties and difficulties of attaining it for dynamic analysis and other parallel software.