bluuebunny/crossref_metadata_2025 huggingface dataset:
PI3K-Independent Function of PTEN
Authors: Gough Nancy R.
Published: November 2009

In worms, Eph destabilizes PTEN, which influences either PI3K or MAPK signaling to regulate life span and reproduction, respectively.
Alternative Means of Taming Yorkie
Authors: VanHook Annalisa M.
Published: November 2009

Hippo signaling may regulate Yorkie activity through a phosphorylation-independent mechanism.
Cdc20-APC in Synapse Formation
Authors: Ray L. Bryan
Published: November 2009

The ubiquitin ligase Cdc20-APC is required for proper synapse formation in the developing rat brain.
The Biochemistry of the All-Nighter
Authors: Ray L. Bryan
Published: November 2009

Loss of sleep inhibits signaling mechanisms underlying learning and memory.
Science Signaling
Podcast: 27 October 2009
Authors: Gorospe Myriam , VanHook Annalisa M.
Published: November 2009

Several microRNAs jointly regulate the abundance of the kinase MKK4 during replicative senescence.
P-REX2a Driving Tumorigenesis by PTEN Inhibition
Authors: Leslie Nick R.
Published: November 2009

The guanine exchange factor P-REX2 limits the lipid phosphatase activity of PTEN and is a potential oncogene.
To Co-Author or Not to Co-Author: How to Write, Publish, and Negotiate Issues of Authorship with Undergraduate Research Students
Authors: Burks Romi L. , Chumchal Matthew M.
Published: November 2009

The rewards associated with publishing with undergraduate students outweigh the challenges.
Special Delivery to the Lymph Node
Authors: Adler Elizabeth M.
Published: November 2009

Mast cell–derived particles provide a mechanism for the safe transport of signaling factors from inflamed tissues to the draining lymph nodes.
Self-Activating, but Still Regulated
Authors: Gough Nancy R.
Published: November 2009

Endogenous pseudophosphatases involved in the transition from oocyte to zygote inhibit kinase activity by “substrate trapping.”
Iron Sensor
Authors: Pickersgill Helen
Published: November 2009

A vertebrate hemerythrin domain in an E3 ubiquitin ligase complex senses and regulates cellular iron levels.
In with the TRP Channels: Intracellular Functions for TRPM1 and TRPM2
Authors: Patel Sandip , Docampo Roberto
Published: November 2009

Cationic channels of the TRP melastatin family are involved in pigmentation and oxidative stress responses.
Comparison of effects of a home exercise programme and a supervised exercise programme for the management of lateral elbow tendinopathy
Authors: Stasinopoulos D , Stasinopoulos I , Pantelis M , Stasinopoulou K
Published: November 2009

Background

Home and supervised exercise programmes consisting of stretching and eccentric exercises have been recommended for the management of lateral elbow tendinopathy (LET). No studies have examined their comparative efficacy effectiveness.

Objective

In this study, whether a home exercise programme is more successful than a supervised exercise programme in treating patients with LET was investigated.

Methods

Patients with unilateral LET for at least 4 weeks were included in this trial. They were sequentially allocated to receive either a home exercise programme or a supervised exercise programme five times a week for 12 weeks. The exercise programme consisted of slow progressive eccentric exercises of wrist extensors and static stretching of the extensor carpi radialis brevis tendon. Outcome measures were pain, using a visual analogue scale, and function, using a visual analogue scale and the pain-free grip strength. Patients were evaluated at baseline, at the end of treatment (week 12), and 3 months (week 24) after the end of treatment.

Results

70 patients met the inclusion criteria. At the end of treatment, there was a decline in pain and a rise in function in both groups compared with baseline (p<0.0005, paired t test). There were significant differences in the reduction of pain and the improvement of function between the groups at the end of treatment and at the 3-month follow up; the supervised exercise programme produced the largest effect (p<0.0005, independent t test).

Conclusions

Supervised exercise programme is superior to home exercise programme to reduce pain and improve function in patients with LET at the end of the treatment and at the follow-up. Further research is needed to confirm our results.
Disrupted working body schema of the trunk in people with back pain
Authors: Bray H , Moseley G L
Published: November 2009

Background

To test whether working body schema of the trunk is disrupted in people with back pain using a motor imagery task in which one decides whether a pictured model has their trunk rotated to the left or to the right. The authors hypothesised that chronic back pain is associated with reduced accuracy of left/right trunk rotation judgements.

Methods

21 Patients with back pain and 14 controls completed two tasks, each involving two trials of 40 images: a left/right hand judgement task, which was used as a control task, and the left/right trunk rotation judgement task. Two (task) × three (group: bilateral back pain, unilateral back pain and control) analyses of variance were undertaken on mean response time and accuracy.

Results

Response time was similar across participants and tasks (NS). Accuracy was not. The patients with bilateral back pain made more mistakes on the left/right trunk rotation task than patients with unilateral back pain, who in turn made more mistakes on that task than the controls (body part × group interaction; p<0.001). The mean (95% CI) accuracy for left/right trunk rotation judgements was 53.4% (44.5% to 62.3%) for the patients with bilateral back pain, 67.2% (60.2% to 74.1%) for the patients with unilateral back pain and 87% (75% to 98%) for the control participants. This pattern was not observed on the left/right-hand judgement task, on which all three groups made correct judgements about 83% of the time (NS).

Discussion

Chronic back pain is associated with disruption of the working body schema of the trunk. This might be an important contributor to motor control abnormalities seen in this population.
LORENTZIAN SYMMETRIC THREE-SPACES AND THE CLASSIFICATION OF THEIR PARALLEL SURFACES
Authors: CALVARUSO G. , VAN DER VEKEN J.
Published: November 2009

We describe a global model for Lorentzian symmetric three-spaces admitting a parallel null vector field, and classify completely the surfaces with parallel second fundamental form in all Lorentzian symmetric three-spaces. Interesting differences arise with respect to the Riemannian case studied in [2]. Our results complete the classification of parallel surfaces in all three-dimensional Lorentzian homogeneous spaces.
CERTAIN APERIODIC AUTOMORPHISMS OF UNITAL SIMPLE PROJECTIONLESS C*-ALGEBRAS
Authors: SATO YASUHIKO
Published: November 2009

Let G be an inductive limit of finite cyclic groups, and A be a unital simple projectionless C*-algebra with K1(A) ≅ G and a unique tracial state, as constructed based on dimension drop algebras by Jiang and Su. First, we show that any two aperiodic elements in Aut (A)/ WInn (A) are conjugate, where WInn (A) means the subgroup of Aut (A) consisting of automorphisms which are inner in the tracial representation.

In the second part of this paper, we consider a class of unital simple C*-algebras with a unique tracial state which contains the class of unital simple A𝕋-algebras of real rank zero with a unique tracial state. This class is closed under inductive limits and crossed products by actions of ℤ with the Rohlin property. Let A be a TAF-algebra in this class. We show that for any automorphism α of A there exists an automorphism ᾶ of A with the Rohlin property such that ᾶ and α are asymptotically unitarily equivalent. For the proof we use an aperiodic automorphism of the Jiang-Su algebra.
A SUB-PRODUCT CONSTRUCTION OF POINCARÉ–EINSTEIN METRICS
Authors: ROD GOVER A. , LEITNER F.
Published: November 2009

Given any two Einstein (pseudo-)metrics, with scalar curvatures suitably related, we give an explicit construction of a Poincaré–Einstein (pseudo-)metric with conformal infinity the conformal class of the product of the initial metrics. We show that these metrics are equivalent to ambient metrics for the given conformal structure. The ambient metrics have holonomy that agrees with the conformal holonomy. In the generic case the ambient metric arises directly as a product of the metric cones over the original Einstein spaces. In general the conformal infinity of the Poincaré metric we construct is not Einstein, and so this describes a class of non-conformally Einstein metrics for which the (Fefferman–Graham) obstruction tensor vanishes.
STUDY ON A SORT OF CONTROLLABLE NONLINEAR LEFT-HANDED MATERIALS
Authors: ZHANG HONG XIN , ZHAO LAN , LU YING HUA
Published: November 2009

In this paper, three kinds of controllable nonlinear left-handed materials (DNLHMs) are proposed and analyzed, which are designed by introducing inductors and capacitors into the traditional nonlinear left-handed materials (NLHMs) as inhomogeneous doped elements. Due to such changes, several new transmission properties have been presented through finite-difference time-domain (FDTD) simulations. These have brought new features to our DNLHMs. On one hand, the original passband in the traditional nonlinear left-handed material is narrowed after introducing inductors. In addition, a new passband, which does not exist in doped linear LHMs, is generated. On the other hand, through introducing capacitors, the original passband of the nonlinear left-handed material can be shifted, resonance frequency can be changed, and a new passband can be generated. When capacitors and inductors are introduced simultaneously, the material properties, such as the number of passbands, the characteristic resonance frequency, and the bandwidth, can also be changed. Noting these characteristics, the values of the introduced inductors and capacitors are varied to investigate the spectrum changes of DNLHMs. Then, a series of controllable properties of the DNLHMs can be retrieved. And more importantly, the designed DNLHMs give the adjustability of suppressing high harmonics, which is not possible in the past materials.
NONLINEAR OPTICAL ABSORPTION IN ORDERED Au NANOPARTICLE ARRAYS
Authors: SHEN XIANGHUA , LIU CHENGYOU , SHEN HONG
Published: November 2009

Ordered Au nanoparticle arrays were fabricated on fused quartz substrates using nanosphere lithography. Linear and nonlinear optical properties of triangular Au nanoparticle arrays were investigated. Two LSPR peaks due to the surface plasmon resonance of Au particles were observed. The nonlinear optical properties were measured using the Z-scan technique at a wavelength of 532 nm and pulse duration of 10 ns. The nanoparticle arrays exhibit distinct nonlinear absorption saturation behavior, the absorption coefficient was determined to be –3.5 × 103 (cm/GW).
ENERGY EXCHANGE OF INTERACTING DISSIPATIVE OPTICAL BULLETS IN DISSIPATIVE SYSTEM
Authors: ZHENG LANG , TANG YI
Published: November 2009

By using the three-dimensional complex Ginzburg–Landau equation with the cubic-quintic nonlinearity, the energy exchange of stable dissipative optical bullets is investigated for bullets launched with zero velocities and with non-zero velocities numerically in dissipative system. It is found that there are two primary factors in the energy exchange process: (i) the relative phase of dissipative optical bullets, which is crucial for energy exchange between bullets, and (ii) the initial velocities of them, which influence interaction and energy exchange between bullets and external source greatly. In addition, some interesting phenomena accompanied by energy exchange, such as asymmetric lateral deflection, bullet fusion and bullet disappearance, are also demonstrated.
ALL-OPTICAL TERAHERTZ OPTICAL ASYMMETRIC DEMULTIPLEXER (TOAD) BASED BINARY COMPARATOR: A PROPOSAL
Authors: CHATTOPADHYAY TANAY
Published: November 2009

Comparator determines whether a number is greater than, equals to or less than another number. It plays a significant role in fast central processing unit in all-optical scheme. In all-optical scheme here 1-bit binary comparator is proposed and described by Terahertz Optical Asymmetric Demultiplexer (TOAD) based interferometric switch. Simulation result by Mathcad-7 is also given. Cascading technique of building up the n-bit binary comparator with this 1-bit comparator block is also proposed here.
LASER ACTION IN DYE DOPED LIQUID CRYSTALS: FROM PERIODIC STRUCTURES TO RANDOM MEDIA
Authors: DE LUCA A. , BARNA V. , FERJANI S. , CAPUTO R. , VERSACE C. , SCARAMUZZA N. , BARTOLINO R. , UMETON C. , STRANGI G.
Published: November 2009

The birefringence and natural ability to form periodic structures make cholesteric liquid crystalline (CLC — chiral nematics) materials particularly attractive as 1D photonic band gap systems. If a CLC is doped with dye fluorescent molecules, in such a way that the maximum peak of fluorescence matches one of the edges of the selective stop band, laser action is expected at that spectral position. By confining the helical super-structure of chiral liquid crystals in polymeric micro-cavity channels, a tunable microcavity laser array was achieved. In multiple scattering systems, the propagation of the light waves is quite different, as optical scattering may induce a phase transition in the photon transport behavior. Beyond a critical scattering level, the system makes a transition into a strongly localized state and light transmission is inhibited. This effect can be used as a photon trapping mechanism to obtain laser action in the presence of a gain medium. Random lasing modes come from interference effects which survive in disordered systems and open a particular chapter in the study of the interplay between localization and amplification. Here, experiments performed on systems having different order degree and confinement are presented and possible technological implications are discussed.
THE EFFECT OF DECAY-INDUCED INTERFERENCE ON THE PHASE CONTROL OF THE OPTICAL BISTABILITY (OB)
Authors: SAHRAI M. , KHERADMAND R. , SALAHSHOUR N. , MAHMOUDI M.
Published: November 2009

This paper studies the optical bistability in a degenerate three-level Λ-type atomic system in a unidirectional optical ring cavity. The effect of quantum interference on the phase control of the optical bistabilty is then discussed. It is shown that the optical bistability changes with the intensity of coupling and the rate of an incoherent pumping field. The possibility of creating an optical multistability (OM) by the intensity of coupling field relative phase between the applied fields, and the rate of an incoherent pump field has also been discussed.
Generalized Halton sequences in 2008
Authors: Faure Henri , Lemieux Christiane
Published: November 2009

Halton sequences have always been quite popular with practitioners, in part because of their intuitive definition and ease of implementation. However, in their original form, these sequences have also been known for their inadequacy to integrate functions in moderate to large dimensions, in which case (
t
,
s
)-sequences such as the Sobol' sequence are usually preferred. To overcome this problem, one possible approach is to include permutations in the definition of Halton sequences—thereby obtaining
generalized Halton sequences
—an idea that goes back to almost thirty years ago, and that has been studied by many researchers in the last few years. In parallel to these efforts, an important improvement in the upper bounds for the discrepancy of Halton sequences has been made by Atanassov in 2004. Together, these two lines of research have revived the interest in Halton sequences. In this article, we review different generalized Halton sequences that have been proposed recently, and compare them by means of numerical experiments. We also propose a new generalized Halton sequence which, we believe, offers a practical advantage over the surveyed constructions, and that should be of interest to practitioners.
FISTE
Authors: Feng Benjamin Zhong Ming , Huang Changcheng , Devetsikiotis Michael
Published: November 2009

The goal of traffic engineering is to achieve a target Quality of Service (QoS) while maximizing network utilization. While determining the QoS for end-to-end paths in a network under self-similar traffic models is difficult, end-to-end network performance analysis is still essential in providing QoS to networks such as Virtual Private Networks (VPN) and Peer-to-Peer (P2P) networks. The Fast Importance Sampling based Traffic Engineering (FISTE) approach proposed in this article is a prediction-based approach that maps the ingress traffic levels of a network to the QoS of end-to-end path(s) in the network. Because FISTE is a hybrid of simulation analysis and closed-form analysis, it can treat a complex network as a black box. When we combined Simulated Annealing (SA) with FISTE, the resulting approach can provide a traffic engineering solution so that multiple end-to-end QoS requirements are satisfied while the network resource utilization is maximized. FISTE originated from the concept of Importance Sampling (IS), and our approach differs from the previous Importance Sampling based approaches since this is the first time that IS is applied to multi-queue systems under Fractional Gaussian Noise (FGN) input and traffic engineering.
Random variate generation for exponentially and polynomially tilted stable distributions
Authors: Devroye Luc
Published: November 2009

We develop exact random variate generators for the polynomially and exponentially tilted unilateral stable distributions. The algorithms, which generalize Kanter's method, are uniformly fast over all choices of the tilting and stable parameters. The key to the solution is a new distribution which we call Zolotarev's distribution. We also present a novel double rejection method that is useful whenever densities have an integral representation involving an auxiliary variable.
Corrigendum
Authors: Ghosh Soumyadip , Henderson Shane G.
Published: November 2009

This note corrects an error in Ghosh and Henderson [2003].
A generalized minimum cost
k
-clustering
Authors: Levin Asaf
Published: November 2009

We consider the problems of set partitioning into
k
clusters with minimum total cost and minimum of the maximum cost of a cluster. The cost function is given by an oracle, and we assume that it satisfies some natural structural constraints. That is, we assume that the cost function is monotone, the cost of a singleton is zero, and we assume that for all
S
∩ S′ ≠ ∅ the following holds
c
(
S
) +
c
(
S
′) ≥
c
(
S
∪
S
′). For the problem of minimizing the maximum cost of a cluster we present a (2
k
− 1)-approximation algorithm for
k
≥ 3, a 2-approximation algorithm for
k
= 2, and we also show a lower bound of
k
on the performance guarantee of any polynomial-time algorithm. For the problem of minimizing the total cost of all the clusters, we present a 2-approximation algorithm for the case where
k
is a fixed constant, a (4
k
− 3)-approximation where
k
is unbounded, and we show a lower bound of 2 on the approximation ratio of any polynomial-time algorithm. Our lower bounds do not depend on the common assumption that
P
≠
NP
.
Bootstrapping a hop-optimal network in the weak sensor model
Authors: Farach-Colton Martin , Fernandes Rohan J. , Mosteiro Miguel A.
Published: November 2009

Sensor nodes are very weak computers that get distributed at random on a surface. Once deployed, they must wake up and form a radio network. Sensor network bootstrapping research thus has three parts: One must model the restrictions on sensor nodes; one must prove that the connectivity graph of the sensors has a subgraph that would make a good network; and one must give a distributed protocol for finding such a network subgraph that can be implemented on sensor nodes.

Although many particular restrictions on sensor nodes are implicit or explicit in many papers, there remain many inconsistencies and ambiguities from paper to paper. The lack of a clear model means that solutions to the network bootstrapping problem in both the theory and systems literature all violate constraints on sensor nodes. For example, random geometric graph results on sensor networks predict the existence of subgraphs on the connectivity graph with good route-stretch, but these results do not address the degree of such a graph, and sensor networks must have constant degree. Furthermore, proposed protocols for actually finding such graphs require that nodes have too much memory, whereas others assume the existence of a contention-resolution mechanism.

We present a formal Weak Sensor model that summarizes the literature on sensor node restrictions, taking the most restrictive choices when possible. We show that sensor connectivity graphs have low-degree subgraphs with good
hop-stretch
, as required by the Weak Sensor model. Finally, we give a Weak Sensor model-compatible protocol for finding such graphs. Ours is the first network initialization algorithm that is implementable on sensor nodes.
All maximal independent sets and dynamic dominance for sparse graphs
Authors: Eppstein David
Published: November 2009

We describe algorithms, based on Avis and Fukuda's reverse search paradigm, for listing all maximal independent sets in a sparse graph in polynomial time and delay per output. For bounded degree graphs, our algorithms take constant time per set generated; for minor-closed graph families, the time is
O
(
n
) per set, and for more general sparse graph families we achieve subquadratic time per set. We also describe new data structures for maintaining a dynamic vertex set
S
in a sparse or minor-closed graph family, and querying the number of vertices not dominated by
S
; for minor-closed graph families the time per update is constant, while it is sublinear for any sparse graph family. We can also maintain a dynamic vertex set in an arbitrary
m
-edge graph and test the independence of the maintained set in time
O
(√m) per update. We use the domination data structures as part of our enumeration algorithms.
A linear-time algorithm to find a separator in a graph excluding a minor
Authors: Reed Bruce , Wood David R.
Published: November 2009

Let
G
be an
n
-vertex
m
-edge graph with weighted vertices. A pair of vertex sets
A
,
B
⊆
V
(
G
) is a 2/3
-separation
of
order
|
A
∩
B
| if
A
∪
B
=
V
(
G
), there is no edge between
A
−
B
and
B
−
A
, and both
A
−
B
and
B
−
A
have weight at most 2/3 the total weight of
G
. Let ℓ ∈ Z
+
be fixed. Alon et al. [1990] presented an algorithm that in
O
(
n
1/2
m
) time, outputs either a
K
ℓ
-minor of
G
, or a separation of
G
of order
O
(
n
1/2
). Whether there is a
O
(
n
+
m
)-time algorithm for this theorem was left as an open problem. In this article, we obtain a
O
(
n
+
m
)-time algorithm at the expense of a
O
(
n
2/3
) separator. Moreover, our algorithm exhibits a trade-off between time complexity and the order of the separator. In particular, for any given ϵ ∈ [0,1/2], our algorithm outputs either a
K
ℓ
-minor of
G
, or a separation of
G
with order
O
(
n
(2−ϵ)/3
in
O
(
n
1 + ϵ
+
m
) time. As an application we give a fast approximation algorithm for finding an independent set in a graph with no
K
ℓ-minor.
Enumeration of isolated cliques and pseudo-cliques
Authors: Ito Hiro , Iwama Kazuo
Published: November 2009

In this article, we consider
isolated
cliques and
isolated
dense subgraphs. For a given graph
G
, a vertex subset
S
of size
k
(and also its induced subgraph
G
(
S
)) is said to be
c
-isolated if
G
(
S
) is connected to its outside via less than
ck
edges. The number
c
is sometimes called the
isolation factor
. The subgraph appears more isolated if the isolation factor is smaller. The main result in this work shows that for a fixed constant
c
, we can enumerate all
c
-isolated maximal cliques (including a maximum one, if any) in linear time.

In more detail, we show that, for a given graph
G
of
n
vertices and
m
edges, and a positive real number
c
, all
c
-isolated maximal cliques can be enumerated in time
O
( c
4
2
2c
m
). From this, we can see that: (1) if
c
is a constant, all
c
-isolated maximal cliques can be enumerated in linear time, and (2) if
c
=
O
(log
n
), all
c
-isolated maximal cliques can be enumerated in polynomial time. Moreover, we show that these bounds are tight. That is, if
f
(
n
) is an increasing function not bounded by any constant, then there is a graph of
n
vertices and
m
edges for which the number of
f
(
n
)-isolated maximal cliques is superlinear in
n
+
m
. Furthermore, if
f
(
n
) = ω(log
n
), there is a graph of
n
vertices and
m
edges for which the number of
f
(
n
)-isolated maximal cliques is superpolynomial in
n
+
m
.

We next introduce the idea of pseudo-cliques. A
pseudo-clique
having an average degree α and a minimum degree β, denoted by
PC
(α,β), is a set
V
′ ⊆
V
such that the subgraph induced by
V
′ has an average degree of at least α and a minimum degree of at least β. This article investigates these, and obtains some cases that can be solved in polynomial time and some other cases that have a superpolynomial number of solutions. Especially, we show the following results, where
k
is the number of vertices of the isolated pseudo-cliques: (1) For any ϵ > 0 there is a graph of
n
vertices for which the number of 1-isolated
PC
(
k
- (log
k
)
1 + ϵ
,
k
/(log
k
)
1 + ϵ
) is superpolynomial, and (2) there is a polynomial-time algorithm which enumerates all
c
-isolated
PC
(
k
- log
k
,
k
/log
k
), for any constant
c
.
A linear algorithm for computing convex hulls for random lines
Authors: Berend Daniel , Braverman Vladimir
Published: November 2009

Finding the convex hull of
n
points in the plane requires
O
(
n
log
n
) time in general. In Devroye and Toussaint [1993] and Golin et al. [2002] the problem of computing the convex hull of the intersection points of
n
lines was considered, where the lines are chosen randomly according to two various models. In both models, linear-time algorithms were developed. Here we improve the results of Devroye and Toussaint [1993] by giving a universal algorithm for a wider range of distributions.
Polynomial constraint satisfaction problems, graph bisection, and the Ising partition function
Authors: Scott Alexander D. , Sorkin Gregory B.
Published: November 2009

We introduce a problem class we call Polynomial Constraint Satisfaction Problems, or PCSP. Where the usual CSPs from computer science and optimization have real-valued score functions, and partition functions from physics have monomials, PCSP has scores that are arbitrary multivariate formal polynomials, or indeed take values in an arbitrary ring.

Although PCSP is much more general than CSP, remarkably, all (exact, exponential-time) algorithms we know of for 2-CSP (where each score depends on at most 2 variables) extend to 2-PCSP, at the expense of just a polynomial factor in running time. Specifically, we extend the reduction-based algorithm of Scott and Sorkin [2007]; the specialization of that approach to sparse random instances, where the algorithm runs in polynomial expected time; dynamic-programming algorithms based on tree decompositions; and the split-and-list matrix-multiplication algorithm of Williams [2004].

This gives the first polynomial-space exact algorithm more efficient than exhaustive enumeration for the well-studied problems of finding a maximum bisection of a graph, and calculating the partition function of an Ising model. It also yields the most efficient algorithm known for certain instances of counting and/or weighted Maximum Independent Set. Furthermore, PCSP solves both optimization and counting versions of a wide range of problems, including all CSPs, and thus enables samplers including uniform sampling of optimal solutions and Gibbs sampling of all solutions.
Control-flow integrity principles, implementations, and applications
Authors: Abadi Martín , Budiu Mihai , Erlingsson Úlfar , Ligatti Jay
Published: November 2009

Current software attacks often build on exploits that subvert machine-code execution. The enforcement of a basic safety property, control-flow integrity (CFI), can prevent such attacks from arbitrarily controlling program behavior. CFI enforcement is simple and its guarantees can be established formally, even with respect to powerful adversaries. Moreover, CFI enforcement is practical: It is compatible with existing software and can be done efficiently using software rewriting in commodity systems. Finally, CFI provides a useful foundation for enforcing further security policies, as we demonstrate with efficient software implementations of a protected shadow call stack and of access control for memory regions.
Maintaining control while delegating trust
Authors: Etalle Sandro , Winsborough William H.
Published: November 2009

We introduce the use, monitoring, and enforcement of integrity constraints in trust management-style authorization systems. We consider what portions of the policy state must be monitored to detect violations of integrity constraints. Then, we address the fact that not all participants in a trust-management system can be trusted to assist in such monitoring, and show how many integrity constraints can be monitored in a conservative manner so that trusted participants detect and report if the system enters a policy state from which evolution in unmonitored portions of the policy could lead to a constraint violation.
Compromising anonymous communication systems using blind source separation
Authors: Zhu Ye , Bettati Riccardo
Published: November 2009

We propose a class of anonymity attacks to both wired and wireless anonymity networks. These attacks are based on the blind source separation algorithms widely used to recover individual signals from mixtures of signals in statistical signal processing. Since the philosophy behind the design of current anonymity networks is to mix traffic or to hide in crowds, the proposed anonymity attacks are very effective.

The flow separation attack proposed for wired anonymity networks can separate the traffic in a mix network. Our experiments show that this attack is effective and scalable. By combining the flow separation method with frequency spectrum matching, a passive attacker can derive the traffic map of the mix network. We use a nontrivial network to show that the combined attack works.

The proposed anonymity attacks for wireless networks can identify nodes in fully anonymized wireless networks using collections of very simple sensors. Based on a time series of counts of anonymous packets provided by the sensors, we estimate the number of nodes with the use of principal component analysis. We then proceed to separate the collected packet data into traffic flows that, with help of the spatial diversity in the available sensors, can be used to estimate the location of the wireless nodes. Our simulation experiments indicate that the estimators show high accuracy and high confidence for anonymized TCP traffic. Additional experiments indicate that the estimators perform very well in anonymous wireless networks that use traffic padding.
Automated termination proofs for logic programs by term rewriting
Authors: Schneider-Kamp Peter , Giesl Jürgen , Serebrenik Alexander , Thiemann René
Published: November 2009

There are two kinds of approaches for termination analysis of logic programs: “transformational” and “direct” ones. Direct approaches prove termination directly on the basis of the logic program. Transformational approaches transform a logic program into a Term Rewrite System (TRS) and then analyze termination of the resulting TRS instead. Thus, transformational approaches make all methods previously developed for TRSs available for logic programs as well. However, the applicability of most existing transformations is quite restricted, as they can only be used for certain subclasses of logic programs. (Most of them are restricted to
well-moded
programs.) In this article we improve these transformations such that they become applicable for
any
definite logic program. To simulate the behavior of logic programs by TRSs, we slightly modify the notion of rewriting by permitting infinite terms. We show that our transformation results in TRSs which are indeed suitable for
automated
termination analysis. In contrast to most other methods for termination of logic programs, our technique is also sound for logic programming
without occur check
, which is typically used in practice. We implemented our approach in the termination prover AProVE and successfully evaluated it on a large collection of examples.
Tableau-based decision procedures for logics of strategic ability in multiagent systems
Authors: Goranko Valentin , Shkatov Dmitry
Published: November 2009

We develop an incremental tableau-based decision procedure for the alternating-time temporal logic ATL and some of its variants. While running within the theoretically established complexity upper bound, we believe that our tableaux are practically more efficient in the average case than other decision procedures for ATL known so far. Besides, the ease of its adaptation to variants of ATL demonstrates the flexibility of the proposed procedure.
The formal system λδ
Authors: Guidi Ferruccio
Published: November 2009

The formal system λδ is a typed λ-calculus that pursues the unification of terms, types, environments, and contexts as the main goal. λδ takes some features from the Automath-related λ-calculi and some from the pure type systems, but differs from both in that it does not include the Π construction while it provides for an abbreviation mechanism at the level of terms. λδ enjoys some important desirable properties such as the confluence of reduction, the correctness of types, the uniqueness of types up to conversion, the subject reduction of the type assignment, the strong normalization of the typed terms, and, as a corollary, the decidability of type inference problem.
ON MODELINGA model of mobile community
Authors: Rhee Youngho , Lee Juyeon
Published: November 2009

Editor's Note: This article proposes several models of community, including a model of "mobile community"---an extension of physical community merged with online community. The authors also provide examples of how these models have contributed to the development of community applications in their work at Samsung.
---Hugh Dubberly
Learning Business Through Scenarios
Authors: Schank Roger C.
Published: November 2009

In his latest column, Roger Schank explains how a new series of soon-to-launch, story-based business courses came to be, and outlines the content and scenarios of the seven storylines that make up the curriculum. In future columns, after the course launches, he will comment on whether they are working as planned.
Global megatrends and the web
Authors: Singh Nitish , Bartikowski Boris P. , Dwivedi Yogesh K. , Williams Miachael D.
Published: November 2009

Proactive companies analyze global megatrends to anticipate and leverage future opportunities in the marketplace. Limited body of academic research ex-ists to facilitate global megatrends forecasting. The objective of this paper is to identify important global megatrends that are being facilitated by the rise of the World Wide Web. An attempt is also made to explore how these global megatrends are leading to the emergence of various global consumer trends. This thought-piece identifies three major global mega-trends, namely Globalization, Rise of Networks and Open Innovation, which are being facilitated by the global expansion of the web.
Organizational readiness and the adoption of electronic business
Authors: Kollmann* Tobias , Kuckertz Andreas , Breugst Nicola
Published: November 2009

In this paper we explore the relationship between average organizational readiness and actual electronic business (e-business) adoption at a national level. Several researchers have provided empirical evidence suggesting that an organization's readiness is one of the most important antecedents of e-business adoption; however, despite often comparable levels of organizational readiness, tremendous variations in the national level of e-business adoption can still be observed. We argue that cultural specifics can explain these variations to a great extent, and report results from a pan-European empirical study conducted among 14,065 enterprises from 29 different countries. Measuring culture by Hofstede's (2001) well-known cultural dimensions we are able to show that national culture significantly moderates the relationship of organizational readiness and e-business adoption. Power distance, masculinity, and uncertainty avoidance were found to exert a significant influence on the relation between organizational readiness and e-business-adoption. We suggest that decision makers interested in e-business consider these cultural effects prior to starting new initiatives.
Deficiency of electron transport chain in human skeletal muscle mitochondria in type 2 diabetes mellitus and obesity
Authors: Ritov Vladimir B. , Menshikova Elizabeth V. , Azuma Koichiro , Wood Richard , Toledo Frederico G. S. , Goodpaster Bret H. , Ruderman Neil B. , Kelley David E.
Published: November 2009

Insulin resistance in skeletal muscle in obesity and T2DM is associated with reduced muscle oxidative capacity, reduced expression in nuclear genes responsible for oxidative metabolism, and reduced activity of mitochondrial electron transport chain. The presented study was undertaken to analyze mitochondrial content and mitochondrial enzyme profile in skeletal muscle of sedentary lean individuals and to compare that with our previous data on obese or obese T2DM group. Frozen skeletal muscle biopsies obtained from lean volunteers were used to estimate cardiolipin content, mtDNA (markers of mitochondrial mass), NADH oxidase activity of mitochondrial electron transport chain (ETC), and activity of citrate synthase and β-hydroxyacyl-CoA dehydrogenase (β-HAD), key enzymes of TCA cycle and β-oxidation pathway, respectively. Frozen biopsies collected from obese or T2DM individuals in our previous studies were used to estimate activity of β-HAD. The obtained data were complemented by data from our previous studies and statistically analyzed to compare mitochondrial content and mitochondrial enzyme profile in lean, obese, or T2DM cohort. The total activity of NADH oxidase was reduced significantly in obese or T2DM subjects. The cardiolipin content for lean or obese group was similar, and although for T2DM group cardiolipin showed a tendency to decline, it was statistically insignificant. The total activity of citrate synthase for lean and T2DM group was similar; however, it was increased significantly in the obese group. Activity of β-HAD and mtDNA content was similar for all three groups. We conclude that the total activity of NADH oxidase in biopsy for lean group is significantly higher than corresponding activity for obese or T2DM cohort. The specific activity of NADH oxidase (per mg cardiolipin) and NADH oxidase/citrate synthase and NADH oxidase/β-HAD ratios are reduced two- to threefold in both T2DM and obesity.
Calorie restriction increases fatty acid synthesis and whole body fat oxidation rates
Authors: Bruss Matthew D. , Khambatta Cyrus F. , Ruby Maxwell A. , Aggarwal Ishita , Hellerstein Marc K.
Published: November 2009

Calorie restriction (CR) increases longevity and retards the development of many chronic diseases, but the underlying metabolic signals are poorly understood. Increased fatty acid (FA) oxidation and reduced FA synthesis have been hypothesized to be important metabolic adaptations to CR. However, at metabolic steady state, FA oxidation must match FA intake plus synthesis; moreover, FA intake is low, not high, during CR. Therefore, it is not clear how FA dynamics are altered during CR. Accordingly, we measured food intake patterns, whole body fuel selection, endogenous FA synthesis, and gene expression in mice on CR. Within 2 days of CR being started, a shift to a cyclic, diurnal pattern of whole body FA metabolism occurred, with an initial phase of elevated endogenous FA synthesis [respiratory exchange ratio (RER) >1.10, lasting 4–6 h after food provision], followed by a prolonged phase of FA oxidation (RER = 0.70, lasting 18–20 h). CR mice oxidized four times as much fat per day as ad libitum (AL)-fed controls (367 ± 19 vs. 97 ± 14 mg/day, P < O.001) despite reduced energy intake from fat. This increase in FA oxidation was balanced by a threefold increase in adipose tissue FA synthesis compared with AL. Expression of FA synthase and acetyl-CoA carboxylase mRNA were increased in adipose and liver in a time-dependent manner. We conclude that CR induces a surprising metabolic pattern characterized by periods of elevated FA synthesis alternating with periods of FA oxidation disproportionate to dietary FA intake. This pattern may have implications for oxidative damage and disease risk.
Potential role of autophagy in modulation of lipid metabolism
Authors: Kovsan Julia , Bashan Nava , Greenberg Andrew S. , Rudich Assaf
Published: November 2009

Autophagy is a major degradative pathway(s) by which intracellular components are delivered into the lysosomes. It is largely implicated in determining cell death and survival because it eliminates unnecessary, damaged, and/or potentially harmful cellular products and organelles and is an important source for nutrients and energy production under conditions of external nutrient deficiency. As such, autophagy has been suggested to contribute to the regulation of carbohydrate and protein metabolism during fasting. Recently, three papers implicated a role for autophagy in cellular lipid metabolism as well. This Perspectives article presents these novel findings in the context of prior studies on the role of autophagy and lysosomes in metabolic and energy regulation, discusses their points of agreement and opposing propositions, and outlines key outstanding questions.
The liver X-receptor gene promoter is hypermethylated in a mouse model of prenatal protein restriction
Authors: van Straten Esther M. E. , Bloks Vincent W. , Huijkman Nicolette C. A. , Baller Julius F. W. , Meer Hester van , Lütjohann Dieter , Kuipers Folkert , Plösch Torsten
Published: November 2009

Prenatal nutrition as influenced by the nutritional status of the mother has been identified as a determinant of adult disease. Feeding low-protein diets during pregnancy in rodents is a well-established model to induce programming events in offspring. We hypothesized that protein restriction would influence fetal lipid metabolism by inducing epigenetic adaptations. Pregnant C57BL/6J mice were exposed to a protein-restriction protocol (9% vs. 18% casein). Shortly before birth, dams and fetuses were killed. To identify putative epigenetic changes, CG-dinucleotide-rich region in the promoter of a gene (CpG island) methylation microarrays were performed on DNA isolated from fetal livers. Two hundred four gene promoter regions were differentially methylated upon protein restriction. The liver X-receptor (Lxr) alpha promoter was hypermethylated in protein-restricted pups. Lxr alpha is a nuclear receptor critically involved in control of cholesterol and fatty acid metabolism. The mRNA level of Lxra was reduced by 32% in fetal liver upon maternal protein restriction, whereas expression of the Lxr target genes Abcg5/ Abcg8 was reduced by 56% and 51%, respectively, measured by real-time quantitative PCR. The same effect, although less pronounced, was observed in the fetal intestine. In vitro methylation of a mouse Lxra-promoter/luciferase expression cassette resulted in a 24-fold transcriptional repression. Our study demonstrates that, in mice, protein restriction during pregnancy interferes with DNA methylation in fetal liver. Lxra is a target of differential methylation, and Lxra transcription is dependent on DNA methylation. It is tempting to speculate that perinatal nutrition may influence adult lipid metabolism by DNA methylation, which may contribute to the epidemiological relation between perinatal/neonatal nutrition and adult disease.
In Vivo Discharge Properties of Hypothalamic Paraventricular Nucleus Neurons With Axonal Projections to the Rostral Ventrolateral Medulla
Authors: Chen Qing-Hui , Toney Glenn M.
Published: November 2009

The hypothalamic paraventricular nucleus (PVN) and rostral ventrolateral medulla (RVLM) are key components of a neural network that generates and regulates sympathetic nerve activity (SNA). Although each region has been extensively studied, little is presently known about the in vivo discharge properties of individual PVN neurons that directly innervate the RVLM. Here extracellular recording was performed in anesthetized rats, and antidromic stimulation was used to identify single PVN neurons with axonal projections to the RVLM ( n = 94). Neurons were divided into two groups that had either unbranched axons terminating in the RVLM (i.e., PVN-RVLM neurons, n = 65) or collateralized axons targeting both the RVLM and spinal cord [i.e., PVN-RVLM/intermediolateral cell column (IML) neurons, n = 29]. Many PVN-RVLM (32/65, 49%) and PVN-RVLM/IML (17/29, 59%) neurons were spontaneously active. The average firing frequency was not different across groups. Spike-triggered averaging revealed that spontaneous discharge of most neurons was temporally correlated with renal SNA (PVN-RVLM: 12/21, 57%; PVN-RVLM/IML: 6/9, 67%). Time histograms triggered by the electrocardiogram (ECG) R-wave indicated that discharge of most cells was also cardiac rhythmic (PVN-RVLM: 25/32, 78%; PVN-RVLM/IML: 10/17, 59%). Raising and lowering arterial blood pressure to increase and decrease arterial baroreceptor input caused a corresponding decrease and increase in firing frequency among cells of both groups (PVN-RVLM: 9/13, 69%; PVN-RVLM/IML: 4/4, 100%). These results indicate that PVN-RVLM and PVN-RVLM/IML neurons are both capable of contributing to basal sympathetic activity and its baroreflex modulation.
Mechanisms of Modulation of AMPA-Induced Na+-Activated K+ Current by mGluR1
Authors: Nanou Evanthia , El Manira Abdeljabbar
Published: November 2009

Na+-activated K+ (KNa) channels can be activated by Na+ influx via ionotropic receptors and play a role in shaping synaptic transmission. In expression systems, KNa channels are modulated by G protein–coupled receptors, but such a modulation has not been shown for the native channels. In this study, we examined whether KNa channels coupled to AMPA receptors are modulated by metabotropic glutamate receptors (mGluRs) in lamprey spinal cord neurons. Activation of mGluR1 strongly inhibited the AMPA-induced KNa current. However, when intracellular Ca2+ was chelated with 1,2-bis(2-aminophenoxy)ethane- N,N,N′, N′-tetraacetic acid (BAPTA), the KNa current was enhanced by mGluR1. Activation of protein kinase C (PKC) mimicked the inhibitory effect of mGluR1 on the KNa current. Blockade of PKC prevented the mGluR1-induced inhibition of the KNa current, but did not affect the enhancement of the current seen in BAPTA. Together these results suggest that mGluR1 can differentially modulate AMPA-induced KNa current in a Ca2+- and PKC-dependent manner.