bluuebunny/crossref_metadata_2025 huggingface dataset:
SINGULAR VALUE DECOMPOSITION AND MATRIX REORDERINGS IN QUANTUM INFORMATION THEORY
Authors: MISZCZAK JAROSŁAW ADAM
Published: July 2011

We review Schmidt and Kraus decompositions in the form of singular value decomposition using operations of reshaping, vectorization and reshuffling. We use the introduced notation to analyze the correspondence between quantum states and operations with the help of Jamiołkowski isomorphism. The presented matrix reorderings allow us to obtain simple formulae for the composition of quantum channels and partial operations used in quantum information theory. To provide examples of the discussed operations, we utilize a package for the Mathematica computing system implementing basic functions used in the calculations related to quantum information theory.
STUDIES OF TRANSPORT PROPERTIES OF RFe1-xNixO3 (x ≤ 0.5) WHERE R = Nd, Sm AND Gd
Authors: BASHIR ABIDA , IKRAM MOHD , KUMAR RAVI
Published: July 2011

We present here the electrical transport properties of RFe 1-x Ni x O 3 (x ≤ 0.5) where R = Nd , Sm and Gd and the correlation between these systems. The resistivity increases as the rare ion is changed from Nd to Sm . The resistivity increases from the magnitude of the order of 103 to 106 Ωcm at lower temperatures and from 10 to 105 Ωcm as the temperature is increased. Also, the resistivity decreases as the concentration of Ni is increased within the ensemble showing a semiconducting behavior. The resistivity data is fitted with the Greaves Variable Range Hopping model which fits in the intermediate range of temperatures. There is decrease in gap parameter, increase in conductivity and increase in the density of states at Fermi level which clarify that the correlation length in the conducting network increases with the increase in Ni substitution. The Debye temperature decreases as the Ni concentration increases and follows the same trend as the rare earth ion is replaced.
HALF-LIVES OF CLUSTER DECAY OF NEUTRON RICH NUCLEI IN TRANS-TIN REGION
Authors: SHIVA KUMARA SWAMY G. , UMESH T. K.
Published: July 2011

In this work, the logarithmic half-life [ log 10(T1/2)] values have been reported for the exotic decay of some neutron rich even–even parent nuclei (56≤Z≤64) accompanied by the emission of alpha-like and non-alpha-like clusters in the trans-tin region. These values were calculated by using the single line of universal curve (UNIV) for alpha and cluster radioactive decay as well as the universal decay law (UDL). The half-life values were also separately calculated by considering the interacting nuclear potential barrier as the sum of Coulomb and proximity potentials. The half-life values based on the three calculations mentioned above, were found to agree with one another within a few orders of magnitude. Possible conclusions are drawn based on the present study.
GENERALIZED HUGENHOLTZ–VAN HOVE THEOREM FOR MULTI-COMPONENT FERMI SYSTEMS WITH MULTI-BODY FORCES
Authors: NAYAK R. C. , PATTNAIK S.
Published: July 2011

We show here that the Hugenholtz–Van Hove theorem for an infinite Fermi system remains valid even with all possible multi-body interaction terms taken into account either separately or in any combination under Hartree–Fock approximation. We further extend the theorem to obtain its most generalized form that would hold good for any multi-component Fermi system.
STABILITY CRITERION OF A CLASS OF NEUTRAL NEURAL NETWORK WITH UNCERTAINTIES AND TIME-VARYING DELAY
Authors: TU JIANJUN , HE HANLIN
Published: July 2011

Under reasonable postulated conditions of time-varying delay, the stability of a class of neutral neural network is probed. Based on the proper construction of the Lyapunov functional, a new method of predicating the uniformly asymptotic stability of this kind of neutral network is presented. The criterion is based on the positive definite solutions of a Riccati equation and a discrete Lyapunov equation, and is converted to LMI problem. The validity of the criterion is also confirmed by the simulation.
Synthesis of chiral ruthenium and cobalt (meso-2-amidophenyl)porphyrins and their catalytic activity in cyclopropanation reactions
Authors: Raoul Nicolas , Gallo Emma , Rose Eric
Published: July 2011

The preparation of two chiral porphyrin ligands 7 and 9 and of their ruthenium and cobalt complexes is reported. These new complexes have been used as catalysts in cyclopropanation reactions. Both 7-Ru and 9-Ru complexes showed a catalytic activity in the enantiomeric cyclopropanation of α-methylstyrene by ethyldiazoacetate whereas amination of ethylbenzene by arylazide in the presence of 7-Ru or 9-Ru did not stop at the corresponding benzylamine stage but instead afforded the corresponding benzylimine.
Synthesis, structure and spectroscopic properties of a porphycene-ReI complex
Authors: Zhang Weina , Chang Yi , Wu Fan , Mack John , Kobayashi Nagao , Shen Zhen
Published: July 2011

A new type of rhenium(I) tricarbonyl porphycene complex is reported based on a reaction between free-base 2,3,6,7,12,13,16,17-octaethylporphycene (H2OEPc) and Re(CO)5Cl . As is the case with tetraphenylporphyrin (TPP), a complex containing only one Re(CO)3 groups, which retains a pyrrole proton, can be isolated and characterized in addition to a bis- Re(I) complex. The ReI(HOEPc)(CO)3 complex was characterized by 1H NMR, 13C NMR, MS, IR, UV-visible, and MCD spectroscopy and cyclic voltammetry. A single crystal was successfully obtained, which enabled the determination of the X-ray structure.
A FACILE SYNTHESIS OF SHAPE- AND SIZE-CONTROLLED α-Fe2O3 NANOPARTICLES THROUGH HYDROTHERMAL METHOD
Authors: WANG GUANG-HUI , LI WEN-CUI , JIA KUN-MING , LU AN-HUI , FEYEN MATHIAS , SPLIETHOFF BERND , SCHÜTH FERDI
Published: July 2011

α- Fe 2 O 3 nanoparticles have wide-ranging applications such as in catalysis, sensoring, painting, etc. This is the reason to study their controlled synthesis. Here we have investigated the synthesis of uniform α- Fe 2 O 3 nanoparticles using amino acids as morphology control agents. The products were characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), thermogravimetry (TG) and differential thermal analysis (DTA). It was found that the type and the amount of amino acids as well as the reaction temperatures have significant influence on the shape and size of the obtained α- Fe 2 O 3 nanoparticles. The use of acidic amino acids (always contain C = O in the side chain) typically leads to the formation of α- Fe 2 O 3 nanoparticles with spindle shape. However, rhombohedrally shaped α- Fe 2 O 3 nanoparticles were formed in presence of basic amino acids (always contain - NH 2 in the side chain). Increasing the amount of amino acid generally results in α- Fe 2 O 3 nanoparticles with decreasing particle sizes.
ENHANCED GAS SENSING PROPERTIES OF p-TYPE TeO2 NANORODS FUNCTIONALIZED WITH Pd
Authors: KIM HYUNSU , PARK SUNGHOON , JIN CHANGHYUN , LEE CHONGMU
Published: July 2011

TeO2 nanorods functionalized with Pd were prepared by a three-step process comprising thermal evaporation of Te powders, Pd deposition by photo-reduction, and annealing. Sensors were fabricated by using the Pd -functionalized TeO2 nanorods. Scanning electron microscopy images exhibited that the nanorods with diameters in a range of 50–100 nm and lengths of a few micrometers were covered with the Pd nanoparticles with an average diameter of ~ 15 nm. Transmission electron microscopy and X-ray diffraction analysis revealed that the nanorods were monocrystalline simple tetragonal TeO2 . On the other hand, the nanoparticles on them were confirmed to be nanocrystalline face-centered cubic Pd . The multiple-networked TeO2 nanorod sensors exhibited a sensitivity of 3.13% at 100 ppm NO2 at 300°C, whereas the Pd -functionalized TeO2 nanorod sensors exhibited a sensitivity of 11.97% under the same condition. The recovery time of TeO2 nanorods was decreased considerably at every NO2 concentration by the Pd -functionalization even if the response time decreased or increased slightly depending upon the NO2 concentration. In addition, the origin of the enhancement of the sensing properties of the TeO2 nanorods by functionalization with Pd is discussed.
VECTOR FIELD AND INFLATION
Authors: KOH SEOKTAE
Published: July 2011

We have investigated if the vector field can give rise to an accelerating phase in the early universe. We consider a timelike vector field with a general quadratic kinetic term in order to preserve an isotropic background spacetime. The vector field potential is required to satisfy the three minimal conditions for successful inflation: i) ρ > 0, ii) ρ + 3P < 0, and iii) the slow-roll conditions. As an example, we consider a massive vector potential and a small-field type potential as in scalar driven inflation.
A system of interaction and structure IV
Authors: Burger Lutz Straß , Guglielmi Alessio
Published: July 2011

We study a system, called NEL, which is the mixed commutative/noncommutative linear logic BV augmented with linear logic's exponentials. Equivalently, NEL is MELL augmented with the noncommutative self-dual connective seq. In this article, we show a basic compositionality property of NEL, which we call
decomposition
. This result leads to a cut-elimination theorem, which is proved in the next article of this series. To control the induction measure for the theorem, we rely on a novel technique that extracts from NEL proofs the structure of exponentials, into what we call !-?-Flow-Graphs.
Unification and matching on compressed terms
Authors: Gascón Adrià , Godoy Guillem , Schmidt-Schauss Manfred
Published: July 2011

Term unification plays an important role in many areas of computer science, especially in those related to logic. The universal mechanism of grammar-based compression for terms, in particular the so-calledsingleton tree grammars (STGAs), have recently drawn considerable attention. Using STGs, terms of exponential size and height can be represented in linear space. Furthermore, the term representation by directed acyclic graphs (dags) can be efficiently simulated. The present article is the result of an investigation on term unification and matching when the terms given as input are represented using different compression mechanisms for terms such as dags and singleton tree grammars. We describe a polynomial time algorithm for context matching with dags, when the number of different context variables is fixed for the problem. For the same problem, NP-completeness is obtained when the terms are represented using the more general formalism of singleton tree grammars. For first-order unification and matching polynomial time algorithms are presented, each of them improving previous results for those problems.
A new benchmark for artificial intelligence
Authors: Kroeker Kirk L.
Published: July 2011

Computers are unable to defeat the world's best Go players, but that may change with the application of a new strategy that promises to revolutionize artificial intelligence.
Life, translated
Authors: Greengard Samuel
Published: July 2011

The Holy Grail of language translation is to develop a machine-based system that can handle the task transparently and accurately.
Geography is alive and well in virtual teams
Authors: Cummings Jonathon N.
Published: July 2011

Just because a team is virtual, it doesn't mean geography is dead.
Storage strife
Authors: Neville-Neil George V.
Published: July 2011

Beware keeping data in binary format.
Computing without processors
Authors: Singh Satnam
Published: July 2011

Heterogeneous systems allow us to target our programming to the appropriate environment.
Should privacy impact assessments be mandatory?
Authors: Wright David
Published: July 2011

Privacy impact assessments should be integrated into the overall approach to risk management with other strategic planning instruments.

This article considers the issue of whether privacy impact assessments (PIAs) should be mandatory. I will examine the benefits and disadvantages of PIAs, the case for and against mandatory PIAs, and ultimately conclude they should be mandatory. Even if they are made mandatory, however, other factors, such as independent audits, must be taken into account to make them truly effective.
Cyberwarfare
Authors: Goel Sanjay
Published: July 2011

Perpetrators and victims usually act as if it never happened, while the evidence is designed to erase itself.

Cyberwarfare is a potent weapon in political conflicts, espionage, and propaganda. Difficult to detect a priori, it is often recognized only after significant damage has been done. Gaining offensive capability on the cyber battlefield figures prominently in the national strategies of many countries and is explicitly stated in the doctrines of several, including China, Russia, and the U.S. It is generally understood they are laying the groundwork for potential cyber conflicts by hacking the networks of adversaries and allies alike.
Rate vs. buffer size--greedy information gathering on the line
Authors: Rosén Adi , Scalosub Gabriel
Published: July 2011

We consider packet networks with limited buffer space at the nodes, and are interested in the question of maximizing the number of packets that arrive to destination rather than being dropped due to full buffers.

We initiate a more refined analysis of the throughput competitive ratio of admission and scheduling policies in the Competitive Network Throughput model [Aiello et al. 2005], taking into account not only the network size but also the buffer size and the injection rate of the traffic.

We specifically consider the problem of information gathering on the line, with limited buffer space, under adversarial traffic. We examine how the buffer size and the injection rate of the traffic affect the performance of the greedy protocol for this problem. We establish upper bounds on the competitive ratio of the greedy protocol in terms of the network size, the buffer size, and the adversary's rate, and present lower bounds which are tight up to constant factors. These results show, for example, that provisioning the network with sufficiently large buffers may substantially improve the performance of the greedy protocol in some cases, whereas for some high-rate adversaries, using larger buffers does not have any effect on the competitive ratio of the protocol.
The optimality of the online greedy algorithm in carpool and chairman assignment problems
Authors: Coppersmith Don , Nowicki Tomasz , Paleologo Giuseppe , Tresser Charles , Wu Chai Wah
Published: July 2011

We study several classes of related scheduling problems including the carpool problem, its generalization to arbitrary inputs and the chairman assignment problem. We derive both lower and upper bounds for online algorithms solving these problems. We show that the greedy algorithm is optimal among online algorithms for the chairman assignment problem and the generalized carpool problem. We also consider geometric versions of these problems and show how the bounds adapt to these cases.
Improved approximations for the hotlink assignment problem
Authors: Laber Eduardo , Molinaro Marco
Published: July 2011

Let
G
=(
V,E
) be a graph representing a Web site, where nodes correspond to pages and arcs to hyperlinks. In this context, hotlinks are defined as shortcuts (new arcs) added to Web pages of
G
in order to reduce the time spent by users to reach their desired information. In this article, we consider the problem where
G
is a rooted directed tree and the goal is minimizing the expected time spent by users by assigning at most
k
hotlinks to each node.

For the most studied version of this problem where at most one hotlink can be added to each node, we prove the existence of two FPTAS's which optimize different objectives considered in the literature: one minimizes the expected user path length and the other maximizes the expected reduction in user path lengths. These results improve over a constant factor approximation for the expected length and over a PTAS for the expected reduction, both obtained recently in Jacobs [2007]. Indeed, these FPTAS's are essentially the best possible results one can achieve under the assumption that
P
≠
NP
.

Another contribution we give here is a 16-approximation algorithm for the most general version of the problem where up to
k
hotlinks can be assigned from each node. This algorithm runs in
O
(|
V
| log |
V
|) time and it turns to be the first algorithm with constant approximation for this problem.
What the disability community can teach us about interactive crowdsourcing
Authors: Bigham Jeffrey P. , Ladner Richard E.
Published: July 2011

In this forum we will celebrate research that helps to successfully bring the benefits of computing technologies to children, older adults, people with disabilities, and other populations that are often ignored in the design of mass-marketed products.

Juan Pablo Hourcade, Editor
A professional empiricist manifesto
Authors: Siegel David A. , Dray Susan M.
Published: July 2011

Evaluation and usability as a practice area has diversified its approaches, broadened the spectrum of UX issues it addresses, and extended its contribution into deeper levels of product-development decision making. This forum addresses conceptual, methodological, and professional issues that arise in the field's continuing effort to contribute robust information about users to product planning and design.

David Siegel and Susan Dray, Editors
JavaGI
Authors: Wehr Stefan , Thiemann Peter
Published: July 2011

The language JavaGI extends Java 1.5 conservatively by a generalized interface mechanism. The generalization subsumes retroactive and type-conditional interface implementations, binary methods, symmetric multiple dispatch, interfaces over families of types, and static interface methods. These features make certain coding patterns redundant, increase the expressiveness of the type system, and permit solutions to extension and integration problems with components in binary form, for which previously several unrelated extensions had been suggested.

This article explains JavaGI and motivates its design. Moreover, it formalizes a core calculus for JavaGI and proves type soundness, decidability of typechecking, and determinacy of evaluation. The article also presents the implementation of a JavaGI compiler and an accompanying run-time system. The compiler, based on the Eclipse Compiler for Java, offers mostly modular static typechecking and fully modular code generation. It defers certain well-formedness checks until load time to increase flexibility and to enable full support for dynamic loading. Benchmarks show that the code generated by the compiler offers good performance. Several case studies demonstrate the practical utility of the language and its implementation.
Probabilistic data exchange
Authors: Fagin Ronald , Kimelfeld Benny , Kolaitis Phokion G.
Published: July 2011

The work reported here lays the foundations of data exchange in the presence of probabilistic data. This requires rethinking the very basic concepts of traditional data exchange, such as solution, universal solution, and the certain answers of target queries. We develop a framework for data exchange over probabilistic databases, and make a case for its coherence and robustness. This framework applies to arbitrary schema mappings, and finite or countably infinite probability spaces on the source and target instances. After establishing this framework and formulating the key concepts, we study the application of the framework to a concrete and practical setting where probabilistic databases are compactly encoded by means of annotations formulated over random Boolean variables. In this setting, we study the problems of testing for the existence of solutions and universal solutions, materializing such solutions, and evaluating target queries (for unions of conjunctive queries) in both the exact sense and the approximate sense. For each of the problems, we carry out a complexity analysis based on properties of the annotation, for various classes of dependencies. Finally, we show that the framework and results easily and completely generalize to allow not only the data, but also the schema mapping itself to be probabilistic.
XPath evaluation in linear time
Authors: Bojańczyk Mikołaj , Parys Paweł
Published: July 2011

We consider a fragment of XPath 1.0, where attribute and text values may be compared. We show that for any unary query φ in this fragment, the set of nodes that satisfy the query in a document
t
can be calculated in time
O
(|φ|
3
|
t
|). We show that for a query in a bigger fragment with Kleene star allowed, the same can be done in time
O
(2

O

(|φ|)|t|) or in time
O
(|φ|
3
|t|log|t|). Finally, we present algorithms for binary queries of XPath, which do a precomputation on the document and then output the selected pairs with constant delay.
Toward a semantic granularity model for domain-specific information retrieval
Authors: Yan Xin , Lau Raymond Y.K. , Song Dawei , Li Xue , Ma Jian
Published: July 2011

Both similarity-based and popularity-based document ranking functions have been successfully applied to information retrieval (IR) in general. However, the dimension of semantic granularity also should be considered for effective retrieval. In this article, we propose a semantic granularity-based IR model that takes into account the three dimensions, namely similarity, popularity, and semantic granularity, to improve domain-specific search. In particular, a concept-based computational model is developed to estimate the semantic granularity of documents with reference to a domain ontology. Semantic granularity refers to the levels of semantic detail carried by an information item. The results of our benchmark experiments confirm that the proposed semantic granularity based IR model performs significantly better than the similarity-based baseline in both a bio-medical and an agricultural domain. In addition, a series of user-oriented studies reveal that the proposed document ranking functions resemble the implicit ranking functions exercised by humans. The perceived relevance of the documents delivered by the granularity-based IR system is significantly higher than that produced by a popular search engine for a number of domain-specific search tasks. To the best of our knowledge, this is the first study regarding the application of semantic granularity to enhance domain-specific IR.
On the stability and optimality of universal swarms
Authors: Zhou Xia , Ioannidis Stratis , Massoulie Laurent
Published: July 2011

Recent work on BitTorrent swarms has demonstrated that a bandwidth bottleneck at the seed can lead to the underutilization of the aggregate swarm capacity. Bandwidth underutilization also occurs naturally in mobile peer-to-peer swarms, as a mobile peer may not always be within the range of peers storing the content it desires. We argue in this paper that, in both cases, idle bandwidth can be exploited to allow content sharing across multiple swarms, thereby forming a universal swarm system. We propose a model for universal swarms that applies to a variety of peer-to-peer environments, both mobile and online. Through a fluid limit analysis, we demonstrate that universal swarms have significantly improved stability properties compared to individually autonomous swarms. In addition, by studying a swarm's stationary behavior, we identify content replication ratios across different swarms that minimize the average sojourn time in the system. We then propose a content exchange scheme between peers that leads to these optimal replication ratios, and study its convergence numerically.
Student mini-kernel project based on an FPGA board
Authors: Schiper André , Milosevic Zarko , Shahmirzadi Omid
Published: July 2011

The paper describes a mini-kernel project in the context of a Concurrent Programming course. The goal of the project is to implement Java monitors and interrupt handling. The platform for the project is an FPGA board developed initially at EPFL for Computer Architecture courses.
Exploring schema repositories with schemr
Authors: Chen Kuang , Kannan Akshay , Madhavan Jayant , Halevy Alon
Published: July 2011

Schemr is a search engine for users to search for and visualize schemas in a metadata repository. Users may search by keywords and by example, using schema fragments as query terms. Schemr uses a novel search algorithm, based on a combination of text search and schema matching techniques, coupled with a structurally-aware scoring metric. Schemr presents search results in a GUI that allows users to explore which elements match and how well they do. The GUI supports interactions, including panning, zooming, layout and drilling-in. This paper introduces Schemr as a new component of the information integration toolbox and discusses its benefits in several applications.
Affiliation analysis of database publications
Authors: Aumüller David , Rahm Erhard
Published: July 2011

We analyze the author affiliations of database publications to determine the main institutions contributing research results in our field. We consider the publications of the last decade (2000'2009) that appeared in the top conferences SIGMOD and VLDB and in the VLDBJ and TODS journals. We determine the top affiliations in terms of number of papers and aggregate the numbers at the levels of entire countries and continents. Further, we analyze to which degree authors from different affiliations and countries cooperate on jointly authored papers, and study the development over time. We also consider the number and size of affiliations of different countries.
Gem #66
Authors: Briot Emmanuel
Published: July 2011

Most GPS features are accessible through menus and contextual menus. However, for maximum efficiency most users prefer to use keyboard shortcuts. Although GPS comes with a number of predefined shortcuts, you might want to adapt them to your own habits, especially if you are moving from a previous editor.
Gem #71
Authors: Kuo Dean , Wallenburg Angela
Published: July 2011

In the previous Gem in this series we saw how to deal with improper initialization in SPARK, based on source code from Tokeneer. In this Gem, we show how to identify ineffective statements.
Gem #73
Authors: Kuo Dean , Wallenburg Angela
Published: July 2011

In the previous Gem in this series, we saw how to validate input in SPARK, based on source code from Tokeneer. In this Gem, we show how the SPARK Toolset can verify application-specific safety and security properties.
Gem #73
Authors: Kuo Dean , Wallenburg Angela
Published: July 2011

In the previous Gem in this series, we saw how the SPARK Toolset can verify application-specific safety and security properties, based on source code from Tokeneer. In this Gem, we show how to deal with overflow errors.
Dynamic cache contention detection in multi-threaded applications
Authors: Zhao Qin , Koh David , Raza Syed , Bruening Derek , Wong Weng-Fai , Amarasinghe Saman
Published: July 2011

In today's multi-core systems, cache contention due to true and false sharing can cause unexpected and significant performance degradation. A detailed understanding of a given multi-threaded application's behavior is required to precisely identify such performance bottlenecks. Traditionally, however, such diagnostic information can only be obtained after lengthy simulation of the memory hierarchy.

In this paper, we present a novel approach that efficiently analyzes interactions between threads to determine thread correlation and detect true and false sharing. It is based on the following key insight: although the slowdown caused by cache contention depends on factors including the thread-to-core binding and parameters of the memory hierarchy, the amount of data sharing is primarily a function of the cache line size and application behavior. Using memory shadowing and dynamic instrumentation, we implemented a tool that obtains detailed sharing information between threads without simulating the full complexity of the memory hierarchy. The runtime overhead of our approach --- a 5x slowdown on average relative to native execution --- is significantly less than that of detailed cache simulation. The information collected allows programmers to identify the degree of cache contention in an application, the correlation among its threads, and the sources of significant false sharing. Using our approach, we were able to improve the performance of some applications up to a factor of 12x. For other contention-intensive applications, we were able to shed light on the obstacles that prevent their performance from scaling to many cores.
Rethink the virtual machine template
Authors: Wang Kun , Rao Jia , Xu Cheng-Zhong
Published: July 2011

Server virtualization technology facilitates the creation of an elastic computing infrastructure on demand. There are cloud applications like server-based computing and virtual desktop that concern startup latency and require impromptu requests for VM creation in a real-time manner. Conventional template-based VM creation is a time consuming process and lacks flexibility for the deployment of stateful VMs. In this paper, we present an abstraction of VM substrate to represent generic VM instances in miniature. Unlike templates that are stored as an image file in disk, VM substrates are docked in memory in a designated VM pool. They can be activated into stateful VMs without machine booting and application initialization. The abstraction leverages an arrange of techniques, including VM miniaturization, generalization, clone and migration, storage copy-on-write, and on-the-fly resource configuration, for rapid deployment of VMs and VM clusters on demand. We implement a prototype on a Xen platform and show that a server with typical configuration of TB disk and GB memory can accommodate more substrates in memory than templates in disk and stateful VMs can be created from the same or different substrates and deployed on to the same or different physical hosts in a cluster without causing any configuration conflicts. Experimental results show that general purpose VMs or a VM cluster for parallel computing can be deployed in a few seconds. We demonstrate the usage of VM substrates in a mobile gaming application.
Dolly
Authors: Cecchet Emmanuel , Singh Rahul , Sharma Upendra , Shenoy Prashant
Published: July 2011

Cloud computing platforms are becoming increasingly popular for e-commerce applications that can be scaled on-demand in a very cost effective way. Dynamic provisioning is used to autonomously add capacity in multi-tier cloud-based applications that see workload increases. While many solutions exist to provision tiers with little or no state in applications, the database tier remains problematic for dynamic provisioning due to the need to replicate its large disk state. In this paper, we explore virtual machine (VM) cloning techniques to spawn database replicas and address the challenges of provisioning shared-nothing replicated databases in the cloud. We argue that being able to determine state replication time is crucial for provisioning databases and show that VM cloning provides this property. We propose Dolly, a database provisioning system based on VM cloning and cost models to adapt the provisioning policy to the cloud infrastructure specifics and application requirements. We present an implementation of Dolly in a commercial-grade replication middleware and evaluate database provisioning strategies for a TPC-W workload on a private cloud and on Amazon EC2. By being aware of VM-based state replication cost, Dolly can solve the challenge of automated provisioning for replicated databases on cloud platforms.
Fast and space-efficient virtual machine checkpointing
Authors: Park Eunbyung , Egger Bernhard , Lee Jaejin
Published: July 2011

Checkpointing, i.e., recording the volatile state of a virtual machine (VM) running as a guest in a virtual machine monitor (VMM) for later restoration, includes storing the memory available to the VM. Typically, a full image of the VM's memory along with processor and device states are recorded. With guest memory sizes of up to several gigabytes, the size of the checkpoint images becomes more and more of a concern.

In this work we present a technique for fast and space-efficient checkpointing of virtual machines. In contrast to existing methods, our technique eliminates redundant data and stores only a subset of the VM's memory pages. Our technique transparently tracks I/O operations of the guest to external storage and maintains a list of memory pages whose contents are duplicated on non-volatile storage. At a checkpoint, these pages are excluded from the checkpoint image.

We have implemented the proposed technique for paravirtualized as well as fully-virtualized guests in the Xen VMM. Our experiments with a paravirtualized guest (Linux) and two fullyvirtualized guests (Linux, Windows) show a significant reduction in the size of the checkpoint image as well as the time required to complete the checkpoint. Compared to the current Xen implementation, we achieve, on average, an 81% reduction in the stored data and a 74% reduction in the time required to take a checkpoint for the paravirtualized Linux guest. In a fully-virtualized environment runningWindows and Linux guests, we achieve a 64% reduction of the image size along with a 62% reduction in checkpointing time.
Fast restore of checkpointed memory using working set estimation
Authors: Zhang Irene , Garthwaite Alex , Baskakov Yury , Barr Kenneth C.
Published: July 2011

In order to make save and restore features practical, saved virtual machines (VMs) must be able to quickly restore to normal operation. Unfortunately, fetching a saved memory image from persistent storage can be slow, especially as VMs grow in memory size. One possible solution for reducing this time is to lazily restore memory after the VM starts. However, accesses to unrestored memory after the VM starts can degrade performance, sometimes rendering the VM unusable for even longer. Existing performance metrics do not account for performance degradation after the VM starts, making it difficult to compare lazily restoring memory against other approaches. In this paper, we propose both a better metric for evaluating the performance of different restore techniques and a better scheme for restoring saved VMs.

Existing performance metrics do not reflect what is really important to the user -- the time until the VM returns to normal operation. We introduce the time-to-responsiveness metric, which better characterizes user experience while restoring a saved VM by measuring the time until there is no longer a noticeable performance impact on the restoring VM. We propose a new lazy restore technique, called working set restore, that minimizes performance degradation after the VM starts by prefetching the working set. We also introduce a novel working set estimator based on memory tracing that we use to test working set restore, along with an estimator that uses access-bit scanning. We show that working set restore can improve the performance of restoring a saved VM by more than 89% for some workloads.
Fine-grained user-space security through virtualization
Authors: Payer Mathias , Gross Thomas R.
Published: July 2011

This paper presents an approach to the safe execution of applications based on
software-based fault isolation
and
policy-based system call authorization
. A running application is encapsulated in an additional layer of protection using dynamic binary translation in user-space. This virtualization layer dynamically recompiles the machine code and adds multiple dynamic security guards that verify the running code to protect and contain the application.

The binary translation system redirects all system calls to a policy-based system call authorization framework. This interposition framework validates every system call based on the given arguments and the location of the system call. Depending on the user-loadable policy and an extensible handler mechanism the framework decides whether a system call is allowed, rejected, or redirect to a specific user-space handler in the virtualization layer.

This paper offers an in-depth analysis of the different security guarantees and a performance analysis of libdetox, a prototype of the full protection platform. The combination of
software-based fault isolation
and
policy-based system call authorization
imposes only low overhead and is therefore an attractive option to encapsulate and sandbox applications to improve host security.
Minimal-overhead virtualization of a large scale supercomputer
Authors: Lange John R. , Pedretti Kevin , Dinda Peter , Bridges Patrick G. , Bae Chang , Soltero Philip , Merritt Alexander
Published: July 2011

Virtualization has the potential to dramatically increase the usability and reliability of high performance computing (HPC) systems. However, this potential will remain unrealized unless overheads can be minimized. This is particularly challenging on large scale machines that run carefully crafted HPC OSes supporting tightly-coupled, parallel applications. In this paper, we show how careful use of hardware and VMM features enables the virtualization of a large-scale HPC system, specifically a Cray XT4 machine, with < = 5% overhead on key HPC applications, microbenchmarks, and guests at scales of up to 4096 nodes. We describe three techniques essential for achieving such low overhead: passthrough I/O, workload-sensitive selection of paging mechanisms, and carefully controlled preemption. These techniques are forms of symbiotic virtualization, an approach on which we elaborate.
Hybrid binary rewriting for memory access instrumentation
Authors: Roy Amitabha , Hand Steven , Harris Tim
Published: July 2011

Memory access instrumentation is fundamental to many applications such as software transactional memory systems, profiling tools and race detectors. We examine the problem of efficiently instrumenting memory accesses in x86 machine code to support software transactional memory and profiling. We aim to automatically instrument all shared memory accesses in critical sections of x86
binaries
, while achieving overhead close to that obtained when performing manual instrumentation at the source code level.

The two primary options in building such an instrumentation system are static and dynamic binary rewriting: the former instruments binaries at link time before execution, while the latter binary rewriting instruments binaries at runtime. Static binary rewriting offers extremely low overhead but is hampered by the limits of static analysis. Dynamic binary rewriting is able to use runtime information but typically incurs higher overhead. This paper proposes an alternative: hybrid binary rewriting. Hybrid binary rewriting is built around the idea of a persistent instrumentation cache (PIC) that is associated with a binary and contains instrumented code from it. It supports two execution modes when using instrumentation: active and passive modes. In the active execution mode, a dynamic binary rewriting engine (PIN) is used to intercept execution, and generate instrumentation into the PIC, which is an on-disk file. This execution mode can take full advantage of runtime information. Later, passive execution can be used where instrumented code is executed out of the PIC. This allows us to attain overheads similar to those incurred with static binary rewriting.

This instrumentation methodology enables a variety of static and dynamic techniques to be applied. For example, in passive mode, execution occurs directly from the original executable save for regions that require instrumentation. This has allowed us to build a low-overhead transactional memory profiler. We also demonstrate how we can use the combination of static and dynamic techniques to eliminate instrumentation for accesses to locations that are thread-private.
GABA reverse transport by the neuronal cotransporter GAT1: influence of internal chloride depletion
Authors: Bertram Simone , Cherubino Francesca , Bossi Elena , Castagna Michela , Peres Antonio
Published: July 2011

The role of intracellular ions on the reverse GABA transport by the neuronal transporter GAT1 was studied using voltage-clamp and [3H]GABA efflux determinations in Xenopus oocytes transfected with heterologous mRNA. Reverse transport was induced by intracellular GABA injections and measured in terms of the net outward current generated by the transporter. Changes in various intracellular ionic conditions affected the reverse current: higher concentrations of Na+ enhanced the ratio of outward over inward transport current, while a considerable decrease of the outward current and a parallel reduction of the transporter-mediated GABA efflux were observed after treatments causing a diminution of the intracellular Cl− concentration. Particularly interesting was the impairment of the reverse transport observed after depletion of internal Cl− generated by the activity of a coexpressed K+-Cl− exporter KCC2. This finding suggests that reverse GABA transport may be physiologically regulated during early neuronal development, similarly to the functional alterations seen in GABA receptors caused by KCC2 activity.
Kinetics of hyperosmotically stimulated Na-K-2Cl cotransporter in Xenopus laevis oocytes
Authors: Delpire Eric , Gagnon Kenneth B.
Published: July 2011

A detailed study of hypertonically stimulated Na-K-2Cl cotransport (NKCC1) in Xenopus laevis oocytes was carried out to better understand the 1 K+:1 Cl− stoichiometry of transport that was previously observed. In this study, we derived the velocity equations for K+ influx under both rapid equilibrium assumptions and combined equilibrium and steady-state assumptions and demonstrate that the behavior of the equations and curves in Lineweaver-Burke plots are consistent with a model where Cl− binds first, followed by Na+, a second Cl−, and then K+. We further demonstrate that stimulation of K+ movement by K+ on the trans side is an intrinsic property of a carrier that transports multiple substrates. We also demonstrate that K+ movement through NKCC1 is strictly dependent upon the presence of external Na+, even though only a fraction of Na+ is in fact transported. Finally, we propose that the larger transport of K+, as compared with Na+, is a result of the return of partially unloaded carriers, which masks the net 1Na+:1K+:2Cl− stoichiometry of NKCC1. These data have profound implications for the physiology of Na-K-2Cl cotransport, since transport of K-Cl in some conditions seems to be uncoupled from the transport of Na-Cl.
Endothelium-derived GM-CSF influences expression of oncostatin M
Authors: Elbjeirami Wafa M. , Donnachie Elizabeth M. , Burns Alan R. , Smith C. Wayne
Published: July 2011

During and after transendothelial migration, neutrophils undergo a number of phenotypic changes resulting from encounters with endothelium-derived factors. This report uses an in vitro model with human umbilical vein endothelial cells and isolated human neutrophils to examine the effects of two locally derived cytokines, granulocyte (G)-macrophage (M) colony-stimulating factor (GM-CSF) and G-CSF, on oncostatin M (OSM) expression. Neutrophils contacting activated HUVEC expressed and released increased amounts of oncostatin M (OSM), a proinflammatory cytokine known to induce polymorphonuclear neutrophil adhesion and chemotaxis. Neutrophil transendothelial migration resulted in threefold higher OSM expression and protein levels compared with nontransmigrated cells. Addition of anti-GM-CSF neutralizing antibody reduced OSM expression level but anti-G-CSF was without effect. GM-CSF but not G-CSF protein addition to cultures of isolated neutrophils resulted in a significant increase in OSM protein secretion. However, inhibition of β2 integrins by neutralizing antibody significantly reduced GM-CSF-induced OSM production indicating this phenomenon is adhesion dependent. Thus cytokine-stimulated endothelial cells can produce sufficient quantities of GM-CSF to influence in an adhesion-dependent manner, the phenotypic characteristics of neutrophils resulting in the latter's transmigration. Both transmigration and adhesion phenomenon lead to increased production of OSM by neutrophils that then play a major role in inflammatory response.
Decreased metalloprotease 9 induction, cardiac fibrosis, and higher autophagy after pressure overload in mice lacking the transcriptional regulator p8
Authors: Georgescu Serban P. , Aronovitz Mark J. , Iovanna Juan L. , Patten Richard D. , Kyriakis John M. , Goruppi Sandro
Published: July 2011

Left ventricular remodeling, including the deposition of excess extracellular matrix, is key to the pathogenesis of heart failure. The stress-inducible transcriptional regulator p8 is increased in failing human hearts and is required both for agonist-stimulated cardiomyocyte hypertrophy and for cardiac fibroblasts matrix metalloprotease-9 (MMP9) induction. In the heart, upregulation of autophagy is an adaptive response to stress and plays a causative role in cardiomyopathies. We have recently shown that p8 ablation in cardiac cells upregulates autophagy and that, in vivo, loss of p8 results in a decrease of cardiac function. Here we investigated the effects of p8 genetic deletion in mediating adverse myocardial remodeling. Unstressed p8−/− mouse hearts manifested complex alterations in the expression of fibrosis markers. In addition, these mice displayed elevated autophagy and apoptosis compared with p8+/+ mice. Transverse aortic constriction (TAC) induced left ventricular p8 expression in p8+/+ mice. Pressure overload caused left ventricular remodeling in both genotypes, however, p8−/− mice showed less cardiac fibrosis induction. Consistent with this, although MMP9 induction was attenuated in the p8−/− mice, induction of MMP2 and MMP3 were strikingly upregulated while TIMP2 was downregulated. Left ventricular autophagy increased after TAC and was significantly higher in the p8−/− mice. Thus p8-deletion results in reduced collagen fibrosis after TAC, but in turn, is associated with a detrimental higher increase in autophagy. These findings suggest a role for p8 in regulating in vivo key signaling pathways involved in the pathogenesis of heart failure.
In vivo real-time imaging of the liver with confocal endomicroscopy permits visualization of the temporospatial patterns of hepatocyte apoptosis
Authors: Goetz Martin , Ansems Jacqueline V. , Galle Peter R. , Schuchmann Marcus , Kiesslich Ralf
Published: July 2011

Apoptosis is a dynamic process of programmed cell death and is involved in multiple diseases. However, its mechanisms and sequence of events are still incompletely understood, partly because of the inability to visualize single cells continuously in vivo. The aim of the present study was to monitor hepatocyte apoptosis with confocal endomicroscopy in living rodents. In 73 anaesthetized mice, apoptotic liver injury was induced by injection of the CD95-agonistic antibody Jo2. Individual hepatocytes were followed for up to 240 min with a handheld confocal probe (FIVE1; Optiscan) providing 0.7 μm resolution (1,000-fold magnification). Different fluorescence staining protocols were used for cellular staining, vascular and cellular barrier function imaging, and caspase activation visualization. The time course of apoptosis could be visualized in vivo while liver perfusion and tissue integrity were maintained. In contrast to most ex vivo studies, initial cell swelling was observed that coincided with early defects in barrier function of sinusoids and hepatocytes. Cytoplasmic vesicle formation, nuclear condensation, cellular disintegration, and macrophage infiltration were captured sequentially. Labeling of caspases allowed molecular imaging. Our study allowed for the first time to continuously follow distinct morphological, functional, and molecular features of apoptosis in a solid organ in vivo and at high resolution. Intravital confocal microscopy may be a valuable tool to study the effects of therapeutic intervention on apoptosis in animal models and humans.