bluuebunny/crossref_metadata_2025 huggingface dataset:
Commutativity analysis for XML updates
Authors: Ghelli Giorgio , Rose Kristoffer , Siméon Jérôme
Published: December 2008

An effective approach to support XML updates is to use XQuery extended with update operations. This approach results in very expressive languages which are convenient for users but are difficult to optimize or reason about. A crucial question underlying many static analysis problems for such languages, from optimization to view maintenance, is whether two expressions commute. Unfortunately, commutativity is undecidable for most existing XML update languages. In this article, we propose a conservative analysis for an expressive XML update language that can be used to determine commutativity. The approach relies on a form of path analysis that computes upper bounds for the nodes that are accessed or modified in a given expression. Our main result is a theorem that can be used to identify commuting expressions. We illustrate how the technique applies to concrete examples of query optimization in the presence of updates.
Kinetic and dynamic data structures for closest pair and all nearest neighbors
Authors: Agarwal Pankaj K. , Kaplan Haim , Sharir Micha
Published: December 2008

We present simple, fully dynamic and kinetic data structures, which are variants of a dynamic two-dimensional range tree, for maintaining the closest pair and all nearest neighbors for a set of
n
moving points in the plane; insertions and deletions of points are also allowed. If no insertions or deletions take place, the structure for the closest pair uses
O
(
n
log
n
) space, and processes
O
(
n
2
β

s
+2

(
n
)log
n
) critical events, each in
O
(log
2
n
) time. Here
s
is the maximum number of times where the distances between any two specific pairs of points can become equal, β

s

(
q
) = λ
s
(
q
)/
q
, and λ

s

(
q
) is the maximum length of Davenport-Schinzel sequences of order
s
on
q
symbols. The dynamic version of the problem incurs a slight degradation in performance: If
m
≥
n
insertions and deletions are performed, the structure still uses
O
(
n
log
n
) space, and processes
O
(
mn
β

s

+2(
n
)log
3
n
) events, each in
O
(log
3
n
) time.

Our kinetic data structure for all nearest neighbors uses
O
(
n
log
2
n
) space, and processes
O
(
n
2
β
2

s
+2

(
n
)log
3
n
) critical events. The expected time to process all events is
O
(
n
2
β

s
+2

2
(
n
) log
4
n
), though processing a single event may take Θ(
n
) expected time in the worst case. If
m
≥
n
insertions and deletions are performed, then the expected number of events is
O
(
mn
β
2

s
+2

(
n
) log
3
n
) and processing them all takes
O
(
mn
β
2

s
+2

(
n
) log
4
n
). An insertion or deletion takes
O
(
n
) expected time.
Algorithms for center and Tverberg points
Authors: Agarwal Pankaj K. , Sharir Micha , Welzl Emo
Published: December 2008

Given a set
S
of
n
points in R
3
, a point
x
in R
3
is called
center point of S
if every closed halfspace whose bounding hyperplane passes through
x
contains at least ⌈
n
/4⌉ points from
S
. We present a near-quadratic algorithm for computing the
center region
, that is the set of all center points, of a set of
n
points in R
3
. This is nearly tight in the worst case since the center region can have Ω(
n
2
) complexity.

We then consider sets
S
of 3
n
points in the plane which are the union of three disjoint sets consisting respectively of
n
red,
n
blue, and
n
green points. A point
x
in R
2
is called a
colored Tverberg point of S
if there is a partition of
S
into
n
triples with one point of each color, so that
x
lies in all triangles spanned by these triples. We present a first polynomial-time algorithm for recognizing whether a given point is a colored Tverberg point of such a 3-colored set
S
.
Distributed weighted vertex cover via maximal matchings
Authors: Grandoni Fabrizio , Könemann Jochen , Panconesi Alessandro
Published: December 2008

In this article, we consider the problem of computing a minimum-weight vertex-cover in an
n
-node, weighted, undirected graph
G
= (
V
,
E
). We present a fully distributed algorithm for computing vertex covers of weight at most twice the optimum, in the case of integer weights. Our algorithm runs in an expected number of
O
(log
n
+ log
Ŵ
) communication rounds, where
Ŵ
is the average vertex-weight. The previous best algorithm for this problem requires
O
(log
n
(log
n
+ log
Ŵ
)) rounds and it is not fully distributed.

For a maximal matching
M
in
G
, it is a well-known fact that any vertex-cover in
G
needs to have at least |
M
| vertices. Our algorithm is based on a generalization of this combinatorial lower-bound to the weighted setting.
Combinatorial dominance guarantees for problems with infeasible solutions
Authors: Berend Daniel , Skiena Steven S. , Twitto Yochai
Published: December 2008

The design and analysis of approximation algorithms for
NP
-hard problems is perhaps the most active research area in the theory of combinatorial algorithms. In this article, we study the notion of a
combinatorial dominance guarantee
as a way for assessing the performance of a given approximation algorithm. An
f
(
n
) dominance bound is a guarantee that the heuristic always returns a solution not worse than at least
f
(
n
) solutions. We give tight analysis of many heuristics, and establish novel and interesting dominance guarantees even for certain inapproximable problems and heuristic search algorithms. For example, we show that the maximal matching heuristic of VERTEX COVER offers a combinatorial dominance guarantee of 2

n

− (1.839 +
o
(1))

n

. We also give inapproximability results for most of the problems we discuss.
On the minimum common integer partition problem
Authors: Chen Xin , Liu Lan , Liu Zheng , Jiang Tao
Published: December 2008

We introduce a new combinatorial optimization problem in this article, called the
minimum common integer partition
(MCIP) problem, which was inspired by computational biology applications including ortholog assignment and DNA fingerprint assembly. A
partition
of a positive integer
n
is a multiset of positive integers that add up to exactly
n
, and an
integer partition
of a multiset
S
of integers is defined as the multiset union of partitions of integers in
S
. Given a sequence of multisets
S
1
,
S
2
, …,

S
k

of integers, where
k
≥ 2, we say that a multiset is a
common integer partition
if it is an integer partition of every multiset

S
i

, 1 ≤
i
≤
k
. The MCIP problem is thus defined as to find a common integer partition of
S
1
,
S
2
, …,

S
k

with the minimum cardinality, denoted as MCIP(
S
1
,
S
2
, …,

S
k

). It is easy to see that the MCIP problem is NP-hard, since it generalizes the well-known subset sum problem. We can in fact show that it is APX-hard. We will also present a 5/4-approximation algorithm for the MCIP problem when
k
= 2, and a 3
k
(
k
−1)/3
k
−2-approximation algorithm for
k
≥ 3.
On an infinite family of solvable Hanoi graphs
Authors: Azriel Dany , Solomon Noam , Solomon Shay
Published: December 2008

The Tower of Hanoi problem is generalized by placing pegs on the vertices of a given directed graph
G
with two distinguished vertices,
S
and
D
, and allowing moves only along arcs of this graph. An optimal solution for such a graph
G
is an algorithm that completes the task of moving a tower of any given number of disks from
S
to
D
in a minimal number of disk moves.

In this article we present an algorithm which solves the problem for two infinite families of graphs, and prove its optimality. To the best of our knowledge, this is the first optimality proof for an
infinite
family of graphs.

Furthermore, we present a unified algorithm that solves the problem for a wider family of graphs and conjecture its optimality.
MiniMax equilibrium of networked differential games
Authors: Cao Hui , Ertin Emre , Arora Anish
Published: December 2008

Surveillance systems based on wireless sensor network technology have been shown to successfully detect, classify and track evaders over a large area. State information collected via the sensor network also enables these systems to actuate mobile agents so as to achieve surveillance goals, such as target capture and asset protection. But satisfying these goals is complicated by the fact that the track information in a sensor network is routed to mobile agents through multihop wireless communication links and is thus subject to message delays and losses. Stabilization must also be considered in designing pursuer strategies so as to deal with state corruption as well as suboptimal evader strategies.

In this article, we formulate optimal pursuit control strategies in the presence of network effects, assuming that target track information has been established locally in the sensor network. We adapt ideas from the theory of differential games to networked games—including ones involving nonperiodic track updates, message losses and message delays—to derive optimal strategies, bounds on the information requirements, and scaling properties of these bounds. We show the inherent stabilization features of our pursuit strategies, both in terms of implementation as well as the strategies themselves.
Logarithmic keying
Authors: Elmallah Ehab S. , Gouda Mohamed G. , Kulkarni Sandeep S.
Published: December 2008

Consider a communication network where each process needs to securely exchange messages with its neighboring processes. In this network, each sent message is encrypted using one or more symmetric keys that are shared only between two processes: the process that sends the message and the neighboring process that receives the message. A straightforward scheme for assigning symmetric keys to the different processes in such a network is to assign each process
O
(
d
) keys, where
d
is the maximum number of neighbors of any process in the network. In this article, we present a more efficient scheme for assigning symmetric keys to the different processes in a communication network. This scheme, which is referred to as logarithmic keying, assigns
O
(log
d
) symmetric keys to each process in the network. We show that logarithmic keying can be used in rich classes of communication networks that include star networks, acyclic networks, limited-cycle networks, planar networks, and dense bipartite networks. In addition, we present a construction that utilizes efficient keying schemes for general bipartite networks to construct efficient keying schemes for general networks.
A general characterization of indulgence
Authors: Guerraoui R. , Lynch N.
Published: December 2008

An indulgent algorithm is a distributed algorithm that, besides tolerating process failures, also tolerates unreliable information about the interleaving of the processes. This article presents a general characterization of indulgence in an abstract computing model that encompasses various communication and resilience schemes. We use our characterization to establish several results about the inherent power and limitations of indulgent algorithms.
A programming model for concurrent object-oriented programs
Authors: Jacobs Bart , Piessens Frank , Smans Jan , Leino K. Rustan M. , Schulte Wolfram
Published: December 2008

Reasoning about multithreaded object-oriented programs is difficult, due to the nonlocal nature of object aliasing and data races. We propose a programming regime (or
programming model
) that rules out data races, and enables local reasoning in the presence of object aliasing and concurrency. Our programming model builds on the multithreading and synchronization primitives as they are present in current mainstream programming languages. Java or C# programs developed according to our model can be annotated by means of stylized comments to make the use of the model explicit. We show that such annotated programs can be formally verified to comply with the programming model. If the annotated program verifies, the underlying Java or C# program is guaranteed to be free from data races, and it is sound to reason locally about program behavior. Verification is modular: a program is valid if all methods are valid, and validity of a method does not depend on program elements that are not visible to the method. We have implemented a verifier for programs developed according to our model in a custom build of the Spec# programming system, and we have validated our approach on a case study.
Efficient constraint propagation engines
Authors: Schulte Christian , Stuckey Peter J.
Published: December 2008

This article presents a model and implementation techniques for speeding up constraint propagation. Three fundamental approaches to improving constraint propagation based on propagators as implementations of constraints are explored: keeping track of which propagators are at fixpoint, choosing which propagator to apply next, and how to combine several propagators for the same constraint.

We show how idempotence reasoning and events help track fixpoints more accurately. We improve these methods by using them dynamically (taking into account current variable domains to improve accuracy). We define priority-based approaches to choosing a next propagator and show that dynamic priorities can improve propagation. We illustrate that the use of multiple propagators for the same constraint can be advantageous with priorities, and introduce staged propagators that combine the effects of multiple propagators with priorities for greater efficiency.
Decomposing bytecode verification by abstract interpretation
Authors: Bernardeschi C. , Francesco N. De , Lettieri G. , Martini L. , Masci P.
Published: December 2008

Bytecode verification is a key point in the security chain of the Java platform. This feature is only optional in many embedded devices since the memory requirements of the verification process are too high. In this article we propose an approach that significantly reduces the use of memory by a serial/parallel decomposition of the verification into multiple specialized passes. The algorithm reduces the type encoding space by operating on different abstractions of the domain of types. The results of our evaluation show that this bytecode verification can be performed directly on small memory systems. The method is formalized in the framework of abstract interpretation.
A probabilistic language based on sampling functions
Authors: Park Sungwoo , Pfenning Frank , Thrun Sebastian
Published: December 2008

As probabilistic computations play an increasing role in solving various problems, researchers have designed probabilistic languages which treat probability distributions as primitive datatypes. Most probabilistic languages, however, focus only on discrete distributions and have limited expressive power. This article presents a probabilistic language, called λ
○
, whose expressive power is beyond discrete distributions. Rich expressiveness of λ
○
is due to its use of
sampling functions
, that is, mappings from the unit interval (0.0,1.0] to probability domains, in specifying probability distributions. As such, λ
○
enables programmers to formally express and reason about sampling methods developed in simulation theory. The use of λ
○
is demonstrated with three applications in robotics: robot localization, people tracking, and robotic mapping. All experiments have been carried out with real robots.
Verified interoperable implementations of security protocols
Authors: Bhargavan Karthikeyan , Fournet Cédric , Gordon Andrew D. , Tse Stephen
Published: December 2008

We present an architecture and tools for verifying implementations of security protocols. Our implementations can run with both concrete and symbolic implementations of cryptographic algorithms. The concrete implementation is for production and interoperability testing. The symbolic implementation is for debugging and formal verification. We develop our approach for protocols written in F#, a dialect of ML, and verify them by compilation to ProVerif, a resolution-based theorem prover for cryptographic protocols. We establish the correctness of this compilation scheme, and we illustrate our approach with protocols for Web Services security.
The aesthetics of emergence
Authors: Baljko Melanie , Tenhaaf Nell
Published: December 2008

In this article, we describe theaesthetics of emergence, which is our theoretical framework for an aesthetics of interaction and the underpinning ofLoFi, an interactive A-life artwork that we are developing. We provide a survey of relevant concepts from the A-life and new media research communities, and we establish threads of commonalities with the HCI research community and especially the subset of that community that emphasizes aspects of user experience other than those that are characterized by performance-based measures. We describe and discuss several exemplar A-life artworks that are drawn from the last decade of jury selections of the annual Vida Art and Artificial Life Competition, conducted by Fundación Telefonica. We conclude with a discussion of issues that are common to the A-life and HCI research communities.
Interfaces with the ineffable
Authors: Boehner Kirsten , Sengers Phoebe , Warner Simeon
Published: December 2008

A variety of approaches have emerged in HCI that grapple with the ineffable, ill-defined, and idiosyncratic nature of aesthetic experience. The most straightforward approach is to transform the ineffable aspects of these experiences into precise representations, producing systems that are well-defined and testable but may miss the fullness of the experienced phenomenon. But without formal models and codified methods, how can we design and evaluate for a phenomenon we aren't sure can be adequately captured? In this article, we present a case study of a system for reflection and awareness of emotional presence that was, in a sense, lived into being. Through system design, use, and evaluation we recount how the system evolved into something that enhanced rather than impoverished the sympathetic awareness of another. In discussing the strategies and results of the case study, we examine what it means for the HCI community to not only design for aesthetic experiences but also bring aesthetics into the practice of HCI.
Performing perception—staging aesthetics of interaction
Authors: Dalsgaard Peter , Hansen Lone Koefoed
Published: December 2008

In interaction design for experience-oriented uses of technology, a central facet of aesthetics of interaction is rooted in the user's experience of herself “performing her perception.” By drawing on performance (theater) theory, phenomenology and sociology and with references to recent HCI-work on the relation between the system and the performer/user and the spectator's relation to this dynamic, we show how the user is simultaneously operator, performer and spectator when interacting. By engaging with the system, she continuously acts out these three roles and her awareness of them is crucial in her experience. We argue that this 3-in-1 is always already shaping the user's understanding and perception of her interaction as it is staged through her experience of the object's form and expression. Through examples ranging from everyday technologies utilizing performances of interaction to spatial contemporary artworks, digital as well as analogue, we address the notion of the performative spectator and the spectating performer. We demonstrate how perception is also performative and how focus on this aspect seems to be crucial when designing experience-oriented products, systems and services.
Towards a theory of user judgment of aesthetics and user interface quality
Authors: Hartmann Jan , Sutcliffe Alistair , Angeli Antonella De
Published: December 2008

The article introduces a framework for users' design quality judgments based on Adaptive Decision Making theory. The framework describes judgment on quality attributes (usability, content/functionality, aesthetics, customisation and engagement) with dependencies on decision making arising from the user's background, task and context. The framework is tested and refined by three experimental studies. The first two assessed judgment of quality attributes of websites with similar content but radically different designs for aesthetics and engagement. Halo effects were demonstrated whereby attribution of good quality on one attribute positively influenced judgment on another, even in the face of objective evidence to the contrary (e.g., usability errors). Users' judgment was also shown to be susceptible to framing effects of the task and their background. These appear to change the importance order of the quality attributes; hence, quality assessment of a design appears to be very context dependent. The third study assessed the influence of customisation by experiments on mobile services applications, and demonstrated that evaluation of customisation depends on the users' needs and motivation. The results are discussed in the context of the literature on aesthetic judgment, user experience and trade-offs between usability and hedonic/ludic design qualities.
Tangled interaction
Authors: Redström Johan
Published: December 2008

This is an analysis and exploration of a basic aesthetic issue in interaction design: how an ambition to design strong and persistent relations between appearance and functionality, evident in approaches such as tangible user interfaces, in crucial ways in which conflicts with the ways miniaturization of technology have changed the relation between the object's surface and its internal complexity. To further investigate this issue, four conceptual design experiments are presented exploring the expressiveness and aesthetic potential of overloading the object's surface by adding several layers of interaction, thus creating a kind of tangled interaction.
Get Real about Realtime
Authors: Neville-Neil George
Published: December 2008

I’m working on a networked system that has become very sensitive to timing issues. When the system was first developed the bandwidth requirements were well within the tolerance of off-the-shelf hardware and software, but in the past three years things have changed. The data stream has remained the same but now the system is being called on to react more quickly to events as they arrive. The system is written in C++ and runs on top of Linux. In a recent project meeting I suggested that the quickest route to decreasing latency was to move to a realtime version of Linux, since realtime operating systems are designed to provide the lowest-latency services to applications. Our code already runs on Linux, so it should be a no-brainer to switch to realtime Linux and reap the rewards of lower latency.
Eventually Consistent
Authors: Vogels Werner
Published: December 2008

At the foundation of Amazon’s cloud computing are infrastructure services such as Amazon’s S3 (Simple Storage Service), SimpleDB, and EC2 (Elastic Compute Cloud) that provide the resources for constructing Internet-scale computing platforms and a great variety of applications. The requirements placed on these infrastructure services are very strict; they need to score high marks in the areas of security, scalability, availability, performance, and cost effectiveness, and they need to meet these requirements while serving millions of customers around the globe, continuously.
Improving Performance on the Internet
Authors: Leighton Tom
Published: December 2008

When it comes to achieving performance, reliability, and scalability for commercial-grade Web applications, where is the biggest bottleneck? In many cases today, we see that the limiting bottleneck is the middle mile, or the time data spends traveling back and forth across the Internet, between origin server and end user.
Thinking issues
Authors: Clear Tony
Published: December 2008

Critiquing the negative consequences of journal impact factor measurement on software engineering researchers, Offut has noted the amount of time many of us spend measuring and observed that "measurement is very difficult" [1]. Then proceeding to critique our measurements in the teaching context he asserted, "We assign students grades in classes (a process once described as 'an inadequate report of an inaccurate judgment by a biased and variable judge of the extent to which a student has attained an undefined level of mastery of an unknown proportion of an indefinite amount of material')" [1].

This paints a rather dismal picture of the grading process? Yet as computing educators can we really refute this argument?
Upsilon Pi Epsilon
Authors: Popyack Jeffrey
Published: December 2008

Greetings! This year has been very active and exciting for Upsilon Pi Epsilon. Between hosting the UPE National Convention at SIGCSE 2008 to our continuing sponsorship of the ACM International Computer Programming Contest and supporting another outstanding group of scholarship winners, things have been quite busy.
Math counts
Authors: Henderson Peter B.
Published: December 2008

Interesting how the term "software correctness" keeps popping up in this column. What is correct software, and can it be achieved -- if so how? The Math CountS columns strive to provide some insights into answering the latter question. One example I used in my entry level classes was developing the software for a heart pacemaker. Pushing the popular develop and test analogy to its limit, the pacemaker developer would test the system on a patient. If problems arose, e.g., death, then debug and test again. Finding agreeable test candidates would be a key to this approach ** SMILE *.
Colorful challenges
Authors: Ginat David
Published: December 2008

The current issue's new challenge involves the development of two sequence processing algorithms. The naïve challenge solutions require repeated "passes" over the sequence. The problem-solver's challenge is to reduce the number of passes as much as possible, perhaps even into only one pass.

Following the presentation of the new challenge, we present the solution of the previous column's Separating Between Foes challenge. The elegant solution of this challenge embeds an approach that is useful and employed in various algorithmic tasks.
The Monash museum of computing history
Authors: Ainsworth A. Barbara , Sheard Judithe , Avram Chris
Published: December 2008

Introduction to the Monash Museum of Computing History, Monash University, Victoria, Australia. Part I of this series described the development of the Museum. This article gives a description of the current holdings of the Museum and the permanent display.
Another outlook on linear recursion
Authors: Yang Feng-Jen
Published: December 2008

Recursion is a well known hurdle for computer science beginners. This powerful problem solving technique challenges both instructors and students on how to convey and learn this skill correctively and efficiently. In this paper, I presented an analogy-based approach to expound the theoretical detail of linear recursion.
Use of MATLAB in teaching the fundamentals of random variables
Authors: Jovanovic-Dolecek Gordana , Fernandez-Vazquez Alfonso
Published: December 2008

The way engineering is being taught has changed in recent years with the introduction of commercial and educational software thus allowing a better understanding of the subject matter and increased teaching efficiency. This paper presents the educational software package designed to work in PCs and provides an attractive way to introduce the fundamentals of random variables. The software can be used as a complement to theoretical classes or alone as a self-study tool. The package was implemented in MATLAB and uses MATLAB™ tool "makeshow" which allows the students to create interactive slideshows without building their own graphic interface. The software is easy to use and is in accordance with the established standards, mouse operations, icon menus, etc. The demos include Probability Density Function (PDF), and Cumulative Distribution Function (CDF), normal, lognormal, exponential, Rayleigh and Rician random variables. The package also demonstrates how to generate the desired random sequence, how to examine its characteristics and how to estimate its PDF and CDF.
Labs@Home
Authors: Seeling Patrick
Published: December 2008

In this publication, we introduce the Labs@Home framework, which enables students to conduct laboratory elements of courses on their personal computing equipment. A major benefit of this approach is that students are able to progress through assignments at a time and pace of their choice, before submitting the results to the instructor for review. The introduced framework is based on capturing differences between versions of the virtual machines and exchanging these between instructor and students. We are currently implementing several parts of the framework and expect to evaluate its implementation in the near future.
Fostering individual learning
Authors: Yadin Aharon , Or-Bach Rachel
Published: December 2008

In this paper we describe an instructional tactic that promotes individual learning. The tactic was developed to cope with the relatively high IS students' failing rate and to support the development of effective learning habits (to be used in collaboration contexts as well). The learning process is based on a unique individual assignments design for a Computer Organization and Programming course. The accompanying study revealed encouraging quantitative and qualitative results. Overall student's failing rate decreased by 59% and an increase in students' motivation and learning accountability was observed. We conclude with a discussion regarding the results and their implications.
Computing educators oral history project
Authors: Almstrum Vicki L. , Applin E. Anne G. , Owens Barbara Boucher , Adams Elizabeth , Barker Lecia J. , Impagliazzo John , Joseph Patricia A. , Kahlon Amardeep , Last Mary Z. , Lawrence Andrea , Young Alison
Published: December 2008

This report expands upon the work started by an ITiCSE 2005 Working Group, which established the groundwork for collecting and analyzing the oral histories of computing educators and provided a foundation for the Computing Educators Oral History Project (CEOHP). The main charge for the Working Group during ITiCSE 2008 was to begin analyzing the interviews already included in CEOHP. As part of the process of exploring analysis approaches, we revisited the status of CEOHP and what had been learned since 2005. We report on analytical procedures for using the interviews as research data and as the basis for informational, motivational resources. We describe techniques and software tools we investigated for qualitative (thematic) analysis of this rich set of personal histories. The analysis allowed themes to emerge naturally from the interviews and suggested specific areas for further investigation. The report describes plans, including procedural updates, archival options, web portal needs, legal and ethical issues, target groups, and publication targets. We conclude with a discussion of future challenges for CEOHP.
Manipulation of Host Behavior by Parasitic Insects and Insect Parasites
Authors: Libersat Frederic , Delago Antonia , Gal Ram
Published: December 2008

Parasites often alter the behavior of their hosts in ways that are ultimately beneficial to the parasite or its offspring. Although the alteration of host behavior by parasites is a widespread phenomenon, the underlying neuronal mechanisms are only beginning to be understood. Here, we focus on recent advances in the study of behavioral manipulation via modulation of the host central nervous system. We elaborate on a few case studies, in which recently published data provide explanations for the neuronal basis of parasite-induced alteration of host behavior. Among these, we describe how a worm may influence the nervous system of its cricket host and manipulate the cricket into committing suicide by jumping into water. We then focus on Ampulex compressa, which uses an Alien-like strategy for the sake of its offspring. Unlike most venomous hunters, this wasp injects venom directly into specific cerebral regions of its cockroach prey. As a result of the sting, the cockroach remains alive but immobile, but not paralyzed, and serves to nourish the developing wasp larva.
Floral Isolation, Specialized Pollination, and Pollinator Behavior in Orchids
Authors: Schiestl Florian P. , Schlüter Philipp M.
Published: December 2008

Floral isolation is a form of prepollination reproductive isolation mediated by floral morphology (morphological isolation) and pollinator behavior (ethological isolation). Here we review mechanisms and evolutionary consequences of floral isolation in various pollination systems. Furthermore, we compare key features of floral isolation, i.e., pollinator sharing and specialization in pollination, in different orchid pollination systems. In orchid pollination, pollinator sharing is generally low, indicating strong floral isolation. The pollinators’ motivation to visit flowers (specifically) can be due to both foraging or reproductive behavior. In both types of behavior, innate preferences for floral signals can be quickly overruled by learning. In pollination systems in which reproductive behavior of pollinators triggers flower visits, lower pollinator sharing was evident compared with systems with foraging behavior, probably because pollinators displaying reproductive behavior show higher fidelity in their visitation patterns. Orchids pollinated through reproductive behavior also use fewer pollinators than orchids pollinated through foraging behavior. No association between specialization and pollinator sharing was found. Thus, generalized pollination does not impede floral isolation, as orchids with many pollinators may nonetheless have low pollinator sharing. Specialization in pollination was, however, linked to orchid species richness in our analysis. Flower size, spur, and column morphology are most important for morphological isolation, and floral scent is most important for ethological isolation. These traits may be based on few genes, implying that floral isolation can be brought about by few genes of large effect.
Subcutaneous transplantation of embryonic pancreas for correction of type 1 diabetes
Authors: Gunawardana Subhadra C. , Benninger Richard K. P. , Piston David W.
Published: December 2008

Islet transplantation is a promising therapeutic approach for type 1 diabetes. However, current success rates are low due to progressive graft failure in the long term and inability to monitor graft development in vivo. Other limitations include the necessity of initial invasive surgery and continued immunosuppressive therapy. We report an alternative transplantation strategy with the potential to overcome these problems. This technique involves transplantation of embryonic pancreatic tissue into recipients’ subcutaneous space, eliminating the need for invasive surgery and associated risks. Current results in mouse models of type 1 diabetes show that embryonic pancreatic transplants in the subcutaneous space can normalize blood glucose homeostasis and achieve extensive endocrine differentiation and vascularization. Furthermore, modern imaging techniques such as two-photon excitation microscopy (TPEM) can be employed to monitor transplants through the intact skin in a completely noninvasive manner. Thus, this strategy is a convenient alternative to islet transplantation in diabetic mice and has the potential to be translated to human clinical applications with appropriate modifications.
Myocardial FFA metabolism during rest and atrial pacing in humans
Authors: Bergman Bryan C. , Tsvetkova Tatiana , Lowes Brian , Wolfel Eugene E.
Published: December 2008

There is limited in vivo data in humans evaluating myocardial fat utilization during increased heart work. This study was done to determine myocardial free fatty acid (FFA) metabolism during rest and atrial pacing, which increases cardiac work without changing arterial substrate concentration. We studied seven healthy men and women (age = 49.7 ± 3.9 yr, BMI = 23.4 ± 1.1 kg/m2, V̇o2max= 35.5 ± 3.0 ml·kg−1·min−1, ejection fraction = 68 ± 3%). After 3 days of dietary control, coronary sinus, femoral arterial and venous, and peripheral venous catheters were placed. Subjects received [13C]bicarbonate followed by a continuous infusion of [1-13C]palmitate through the end of the study. Arterial and coronary sinus blood sampling and measurements of resting coronary sinus blood flow were made during rest and atrial pacing to 120 beats/min. MV̇o2increased ( P < 0.05) from rest to atrial pacing. Coronary sinus FFA concentration was significantly lower than arterial through rest and atrial pacing ( P = 0.007). Isotopically measured myocardial palmitate uptake increased significantly from rest to atrial pacing ( P = 0.03). Approximately one-third of palmitate delivery was extracted by the myocardium during rest and atrial pacing. Myocardial V13CO2production and palmitate oxidation increased significantly from rest ( P < 0.01) to atrial pacing. Net glycerol balance was significantly greater than zero during rest ( P = 0.04) but not different from zero during atrial pacing ( P = 0.13). These data suggest that myocardial lipid uptake and oxidation increase with greater heart work during atrial pacing, with a similar relative proportion of fat oxidation to total myocardial energy expenditure.
Changes of the plasma metabolome during an oral glucose tolerance test: is there more than glucose to look at?
Authors: Zhao Xinjie , Peter Andreas , Fritsche Jens , Elcnerova Michaela , Fritsche Andreas , Häring Hans-Ulrich , Schleicher Erwin D. , Xu Guowang , Lehmann Rainer
Published: December 2008

The oral glucose tolerance test (oGTT) is a common tool to provoke a metabolic challenge for scientific purposes, as well as for diagnostic reasons, to monitor the kinetics of glucose and insulin. Here, we aimed to follow the variety of physiological changes of the whole metabolic pattern in plasma during an oGTT in healthy subjects in a nontargeted reversed-phase ultra performance liquid chromatography coupled to electrospray ionization quadrupole time of flight mass spectrometric metabolomics approach. We detected 11,500 metabolite ion masses/individual. Applying multivariate data analysis, four major groups of metabolites have been detected as the most discriminating oGTT biomarkers: free fatty acids (FFA), acylcarnitines, bile acids, and lysophosphatidylcholines. We found in detail 1) a strong decrease of all saturated and monounsaturated FFA studied during the oGTT; 2) a significant faster decline of palmitoleate (C16:1) and oleate (C18:1) FFA levels than their saturated counterparts; 3) a strong relative increase of polyunsaturated fatty acids in the fatty acid pattern at 120 min; and 4) a clear decrease in plasma C10:0, C12:0, and C14:1 acylcarnitine levels. These data reflect the switch from β-oxidation to glycolysis and fat storage during the oGTT. Moreover, the bile acids glycocholic acid, glycochenodeoxycholic acid, and glycodeoxycholic acid were highly discriminative, showing a biphasic kinetic with a maximum of a 4.5- to 6-fold increase at 30 min after glucose ingestion, a significant decrease over the next 60 min followed by an increase until the end of the oGTT. Lysophosphatidylcholines were also increased significantly. The findings of our metabolomics study reveal detailed insights in the complex physiological regulation of the metabolism during an oGTT offering novel perspectives of this widely used procedure.
Central Fos expression and conditioned flavor avoidance in rats following intragastric administration of bitter taste receptor ligands
Authors: Hao Shuzhen , Dulake Michelle , Espero Elvis , Sternini Catia , Raybould Helen E. , Rinaman Linda
Published: December 2008

G protein-coupled receptors that signal bitter taste (T2Rs) are expressed in the mucosal lining of the oral cavity and gastrointestinal (GI) tract. In mice, intragastric infusion of T2R ligands activates Fos expression within the caudal viscerosensory portion of the nucleus of the solitary tract (NTS) through a vagal pathway (Hao S, Sternini C, Raybould HE. Am J Physiol Regul Integr Comp Physiol 294: R33–R38, 2008). The present study was performed in rats to further characterize the distribution and chemical phenotypes of brain stem and forebrain neurons activated to express Fos after intragastric gavage of T2R ligands, and to determine a potential behavioral correlate of this central neural activation. Compared with relatively low brain stem and forebrain Fos expression in control rats gavaged intragastrically with water, rats gavaged intragastrically with T2R ligands displayed significantly increased activation of neurons within the caudal medial (visceral) NTS and caudal ventrolateral medulla, including noradrenergic neurons, and within the lateral parabrachial nucleus, central nucleus of the amygdala, and paraventricular nucleus of the hypothalamus. A behavioral correlate of this Fos activation was evidenced when rats avoided consuming flavors that previously were paired with intragastric gavage of T2R ligands. While unconditioned aversive responses to bitter tastants in the oral cavity are often sufficient to inhibit further consumption, a second line of defense may be provided postingestively by ligand-induced signaling at GI T2Rs that signal the brain via vagal sensory inputs to the caudal medulla.
Slow Recovery From Excitation of Thalamic Reticular Nucleus Neurons
Authors: Yu Xiong-Jie , Xu Xin-Xiu , Chen Xi , He Shigang , He Jufang
Published: December 2008

Responses to repeated auditory stimuli were examined in 103 neurons in the auditory region of the thalamic reticular nucleus (TRN) and in 20 medial geniculate (MGB) neurons of anesthetized rats. A further six TRN neurons were recorded from awake rats. The TRN neurons showed strong responses to the first trial and weak responses to the subsequent trials of repeated auditory stimuli and electrical stimulation of the MGB and auditory cortex when the interstimulus interval (ISI) was short (<3 s). They responded to the second trial when the interstimulus interval was lengthened to ≥3 s. These responses contrasted to those of MGB neurons, which responded to repeated auditory stimuli of different ISIs. The TRN neurons showed a significant increase in the onset auditory response from 9.5 to 76.5 Hz when the ISI was increased from 200 ms to 10 s ( P < 0.001, ANOVA). The duration of the auditory-evoked oscillation was longer when the ISI was lengthened. The slow recovery of the TRN neurons after oscillation of burst firings to fast repetitive stimulus was a reflection of a different role than that of the thalamocortical relay neurons. Supposedly the TRN is involved in the process of attention such as attention shift; the slow recovery of TRN neurons probably limits the frequent change of the attention in a fast rhythm.
Vibration Response Imaging as a New Tool for Interventional-Bronchoscopy Outcome Assessment: A Prospective Pilot Study
Authors: Becker Heinrich D. , Slawik Matthias , Miyazawa Teruomi , Gat Merav
Published: December 2008

Background: In many patients, the benefit of interventional bronchoscopy cannot be appropriately objectified. Objectives: We investigated a new technique, vibration response imaging (VRI), for breathing sound mapping to determine whether it could provide additional, valuable objective qualitative and quantitative information in central airway obstruction (CAO) and patient outcome following interventional bronchoscopy. Methods: VRI images from 83 patients with suspected central airway stenosis and 25 healthy volunteers were evaluated by two raters blinded to the subjects’ status. Qualitative and quantitative dynamic and static features were documented for the final assessment of images as normal or abnormal and changes after the intervention. As a secondary goal, stenosis location was also evaluated and compared to bronchoscopic findings. Treatment outcome analysis (improved vs. not improved) was performed by comparing baseline and follow-up images in 64 evaluations of interventional bronchoscopy. VRI measurements of treatment outcome were compared to standard tests, i.e. dyspnea score, pulmonary function testing (PFT, i.e. FEV1, FVC and FEV1/FVC), chest X-ray/computed tomography and bronchoscopy, the latter being considered the gold standard). Results: There was 95% (115/121) agreement between raters and clinical assessment in distinguishing between normal and abnormal images. The sensitivity and specificity of VRI were 97 and 88%, respectively. The accuracy of VRI in locating the pathology compared to bronchoscopy was 85% (17/20) for tracheal and 88% (51/58) for bronchial obstruction; overall accuracy was 83%. Correct detection of the affected side in bronchial obstructions was 88%. The overall accuracy of VRI in defining the outcome of interventional bronchoscopy was 84%. Conclusions: Obstruction location and procedure outcome were reliably identified according to specific patterns of lung images. VRI proved at least as good as standard tests in locating CAO and has the potential for becoming a valuable complementary tool in evaluating treatment outcome in patients with CAO. If our results are confirmed by further studies, VRI may replace PFT or imaging procedures in cases in which such tests cannot be performed or are not readily available at the time of the intervention.
The Association between Self-Rated Health Status and Increasing Age among Older Japanese Living in a Rural Community over a 6-Year Period: A Longitudinal Data Analysis
Authors: Ishizaki Tatsuro , Yoshida Hideyo , Suzuki Takao , Shibata Hiroshi
Published: December 2008

Background: Although previous longitudinal studies reported that changes in self-rated health (SRH) status were not explained by aging of population, they do not adequately adjust for potential confounding factors of SRH status. Objective: It was the aim of our study to examine the association of SRH status with increasing age among older individuals in a Japanese community during a 6-year period, 1994 through 2000. Methods: We conducted a community-based prospective cohort study. Subjects were a total of 710 men and women, ranging in age from 67 to 91 years at the beginning of the 1994 survey. Independent variables potentially associated with SRH were obtained from interview surveys conducted in 1994, 1996, 1998 and 2000. The dependent variable was SRH status obtained at each survey. Results: Univariate analysis showed no significant trends in the proportions of subjects with good SRH over time. However, analyses using the generalized estimating equations methodology revealed that aging was significantly associated with a small increase in the proportion of participants with good SRH, after adjusting for potential confounders. The analysis also revealed that factors contributing to good SRH included independence in activities of daily living and instrumental activities of daily living, as well as absence of the following: recent hospitalization history, chronic medical conditions, current complaints of pain and depressive symptomatology. Conclusion: This study demonstrated that after adjusting for negative confounders, aging was independently associated with a small but significant increase in the proportion of older individuals with good SRH.