bluuebunny/crossref_metadata_2025 huggingface dataset:
White space networking with wi-fi like connectivity
Authors: Bahl Paramvir , Chandra Ranveer , Moscibroda Thomas , Murty Rohan , Welsh Matt
Published: August 2009

Networking over UHF white spaces is fundamentally different from conventional Wi-Fi along three axes: spatial variation, temporal variation, and fragmentation of the UHF spectrum. Each of these differences gives rise to new challenges for implementing a wireless network in this band. We present the design and implementation of Net7, the first Wi-Fi like system constructed on top of UHF white spaces. Net7 incorporates a new adaptive spectrum assignment algorithm to handle spectrum variation and fragmentation, and proposes a low overhead protocol to handle temporal variation. builds on a simple technique, called SIFT, that reduces the time to detect transmissions in variable channel width systems by analyzing raw signals in the time domain. We provide an extensive evaluation of the system in terms of a prototype implementation and detailed experimental and simulation results.
BCube
Authors: Guo Chuanxiong , Lu Guohan , Li Dan , Wu Haitao , Zhang Xuan , Shi Yunfeng , Tian Chen , Zhang Yongguang , Lu Songwu
Published: August 2009

This paper presents BCube, a new network architecture specifically designed for shipping-container based, modular data centers. At the core of the BCube architecture is its server-centric network structure, where servers with multiple network ports connect to multiple layers of COTS (commodity off-the-shelf) mini-switches. Servers act as not only end hosts, but also relay nodes for each other. BCube supports various bandwidth-intensive applications by speeding-up one-to-one, one-to-several, and one-to-all traffic patterns, and by providing high network capacity for all-to-all traffic.

BCube exhibits graceful performance degradation as the server and/or switch failure rate increases. This property is of special importance for shipping-container data centers, since once the container is sealed and operational, it becomes very difficult to repair or replace its components.

Our implementation experiences show that BCube can be seamlessly integrated with the TCP/IP protocol stack and BCube packet forwarding can be efficiently implemented in both hardware and software. Experiments in our testbed demonstrate that BCube is fault tolerant and load balancing and it significantly accelerates representative bandwidth-intensive applications.
Persona
Authors: Baden Randy , Bender Adam , Spring Neil , Bhattacharjee Bobby , Starin Daniel
Published: August 2009

Online social networks (OSNs) are immensely popular, with some claiming over 200 million users. Users share private content, such as personal information or photographs, using OSN applications. Users must trust the OSN service to protect personal information even as the OSN provider benefits from examining and sharing that information. We present Persona, an OSN where users dictate who may access their information. Persona hides user data with attribute-based encryption (ABE), allowing users to apply fine-grained policies over who may view their data. Persona provides an effective means of creating applications in which users, not the OSN, define policy over access to private data. We demonstrate new cryptographic mechanisms that enhance the general applicability of ABE. We show how Persona provides the functionality of existing online social networks with additional privacy benefits. We describe an implementation of Persona that replicates Facebook applications and show that Persona provides acceptable performance when browsing privacy-enhanced web pages, even on mobile devices.
Safe and effective fine-grained TCP retransmissions for datacenter communication
Authors: Vasudevan Vijay , Phanishayee Amar , Shah Hiral , Krevat Elie , Andersen David G. , Ganger Gregory R. , Gibson Garth A. , Mueller Brian
Published: August 2009

This paper presents a practical solution to a problem facing high-fan-in, high-bandwidth synchronized TCP workloads in datacenter Ethernets---the TCP incast problem. In these networks, receivers can experience a drastic reduction in application throughput when simultaneously requesting data from many servers using TCP. Inbound data overfills small switch buffers, leading to TCP timeouts lasting hundreds of milliseconds. For many datacenter workloads that have a barrier synchronization requirement (e.g., filesystem reads and parallel data-intensive queries), throughput is reduced by up to 90%. For latency-sensitive applications, TCP timeouts in the datacenter impose delays of hundreds of milliseconds in networks with round-trip-times in microseconds.

Our practical solution uses high-resolution timers to enable microsecond-granularity TCP timeouts. We demonstrate that this technique is effective in avoiding TCP incast collapse in simulation and in real-world experiments. We show that eliminating the minimum retransmission timeout bound is safe for all environments, including the wide-area.
Using a groupware system in CS1 to engage introverted students
Authors: Townsend Gloria Childress
Published: August 2009

Concern with declining numbers of computer science majors leads educators to examine recruitment and retention factors in Computer Science I (CS1), in order to increase the number of students entering the undergraduate computer science pipeline. The literature reveals that introverted students dominate the CS1 classroom at a rate more than twice that of the general population and that the students perform better in the course as a group than extraverts do. Therefore, increasing the comfort level and engagement of introverted students seems practical - as well as thoughtful. The author of this paper hypothesizes that encouraging students to use an anonymous submission feature in a groupware system will increase the comfort of shy students who are reluctant to engage in the CS1 classroom. A study reveals a significant difference between a group of students who used the same groupware system without instruction regarding the groupware system's anonymous feature and a treatment group of students who received instruction and were encouraged to use the anonymous feature. The project also uncovers several significant correlations among students' responses to various items in the survey instrument.
Learning from and with peers
Authors: Sondergaard Harald
Published: August 2009

There are many different approaches to student peer assessment. In this paper I lay out the pedagogical philosophy behind my own use of student peer reviews. These should not only be seen as adding to the amount of formative feedback in a class, nor are they only about the development of certain higher-order cognitive skills. Properly aligned with an overall assessment strategy, peer reviewing can help build a stronger learning community. I describe such a strategy and my experience using PRAZE, an online tool for student peer reviewing, as well as students' response to the tool and its use.
Using game creation for teaching computer programming to high school students and teachers
Authors: Al-Bow Mohammed , Austin Debra , Edgington Jeffrey , Fajardo Rafael , Fishburn Joshua , Lara Carlos , Leutenegger Scott , Meyer Susan
Published: August 2009

In this paper we describe a two-week residential summer game camp for rising 9th and 10th grade students and a four-week high school teacher professional development course. We present survey results that indicate our approach results in increased computer programming knowledge and self-confidence for both students and teachers. Our project aims to use a holistic game creation approach to increase student interest in computer science by directly teaching to students in a summer camp, instructing the teachers during a 4-week professional development course, and finally by supporting teachers as they use our curriculum in their high schools.
What were they thinking?
Authors: Pargas Roy P. , Bryfczynski Samuel
Published: August 2009

This paper describes GraphPad, a web-based software tool designed not only to help an instructor of a CS2 or CS7 (data structures) course deliver content and assess student performance, but also to provide an instructor with the unique ability to observe and understand how students solve problems by replaying the students' solutions. GraphPad works with Tablet PCs or PCs with attached WACOM tablets. We describe how GraphPad enables an instructor to: establish a temporary network with the instructor's Tablet as server and the students' Tablets as clients, broadcast instructions and collect student Ink responses, evaluate student submissions and distribute evaluations with a single button-click, use student submissions as examples to guide lecture, and save student submissions in a database. The saved submissions may be replayed and reviewed individually, tagged for errors, and analyzed statistically. We are currently using GraphPad almost daily in a data structures course. A long term goal is to analyze data collected by GraphPad to help understand the thought process of computer science students for the purpose of identifying students at risk early in order to provide intervention assistance.
Anchor garden
Authors: Miura Motoki , Sugihara Taro , Kunifuji Susumu
Published: August 2009

We propose Anchor Garden (AG), an interactive workbench software for learning fundamentals of data structures with the concepts of type, variable, object, and their relations in a strongly typed object-oriented programming language (OOPL) such as Java or C#. Learners can approach the basic data-handling concepts of OOPLs by direct manipulation of graphical models in AG. In addition, the learner can correlate his/her manipulation and notation of source code because AG automatically generates appropriate source-code corresponding to this manipulation. Experimental results showed a tendency of a learning effect with AG and high correlations between concept understanding and programming ability. Thus, AG has the potential to enhance the programming ability of novice programmers.
Improving the mental models held by novice programmers using cognitive conflict and jeliot visualisations
Authors: Ma Linxiao , Ferguson John , Roper Marc , Ross Isla , Wood Murray
Published: August 2009

Recent research has found that many novice programmers often hold non-viable mental models of basic programming concepts which can limit their potential to develop appropriate programming skills. Previous work by the authors suggests that a teaching model that integrates cognitive conflict and program visualisation can help novices formulate appropriate mental models. This paper first outlines a 'concepts roadmap' that provides an ordered approach to learning programming concepts allowing students to build on fundamental base knowledge. It then reports the results of a series of studies investigating the use of the Jeliot visualisation tool as the visualisation component of the proposed learning model when applied to these concepts. The findings include: the ease with which Jeliot can be tailored to visualise a range of concepts using a variety of examples; the Jeliot visualisation of object reference was too complex for CS1 students; further evidence that CS1 students struggle to develop appropriate understanding of a range of key programming concepts; and, further evidence that an integrated cognitive conflict/visualisation strategy can help students develop an appropriate understanding of key programming concepts.
The professor on your PC
Authors: Gal-Ezer Judith , Vilner Tamar , Zur Ela
Published: August 2009

The Open University of Israel, a distance education institution with open admissions, offers a study system that was primarily based on written material. When we designed the new CS1 course in 2005, shifting from C++ to Java, we also switched from a course based on written material, to one based on videotaped lectures, which the students watch on PCs. Shifting to Java is an enormous challenge, however, we were also concerned about the new study method. Therefore, we conducted a study to determine how the students respond to the new and different environment, in terms of both learning and technical operation. The findings show that this method of study is at least as efficient as the previous one. The students' attitude to the new study method was positive and supportive of the new approach.
INSPIRED broadening participation
Authors: Doerschuk Peggy , Liu Jiangjiang , Mann Judith
Published: August 2009

The Increasing Student Participation in Research Development Program ('INSPIRED') is designed to increase participation of women and underrepresented minorities in computing. It is a comprehensive program whose goals are to attract, retain and transition these students into careers or advanced study in computing. This paper focuses on the program's first year experience, including the results of a formal assessment of the program's effectiveness. It describes the strategies used to attain the goals and the rationale for using these strategies. It also includes lessons learned for the benefit of those who are considering adopting these strategies at their institutions.
A music context for teaching introductory computing
Authors: Misra Ananya , Blank Douglas , Kumar Deepak
Published: August 2009

We describe myro.chuck, a Python module for controlling music synthesis, and its applications to teaching introductory computer science. The module was built within the Myro framework using the ChucK programming language, and was used in an introductory computer science course combining robots, graphics and music. The results supported the value of music in engaging students and broadening their view of computer science.
Xen worlds
Authors: Anderson Benjamin R. , Joines Amy K. , Daniels Thomas E.
Published: August 2009

The Xen Worlds project at Iowa State University was designed to provide a virtualized lab environment for the Information Assurance program. The large number of off-campus students, and a desire for high levels of security, drove many of the requirements for the Xen Worlds environment. Some of the requirements established for the project were: The environment needed to be equally accessible and easy to use for both on- and off-campus students. It needed to be isolated from the outside world and other students. The system had to be equally usable for students with limited computing and network resources. Costs had to be kept to a minimum.

The Xen Worlds environment has now been used to support several courses at both the undergraduate and graduate level. This virtual environment was equally accessible to on- and off-campus students on a 24/7 basis and supported numerous assignments in support of established curriculum requirements. Finally, surveys of students who used the Xen Worlds environment show that students have a favorable view of the project and view it as a useful and convenient learning tool.
Generalised diagram revision tools with automatic marking
Authors: Thomas Pete , Waugh Kevin , Smith Neil
Published: August 2009

In this paper, we describe an approach to the generalisation of tools for teaching and learning the skills associated with modelling with diagrams. We have implemented two revision tools that automatically mark and provide feedback on students' attempts at constructing diagrammatic models of given scenarios in different domains. The similarities between these tools and diagrams in other domains suggest that it might be possible to generalise both the marking algorithm and the drawing editor in such a way that new revision tools could be easily generated for new domains. This paper briefly describes the existing revision tools and our approach to automatic marking of diagrams, and discusses how we are approaching the generalisation of our work for application in other domains.
Video courseware for teaching operating systems with Windows
Authors: Hwang Seung-won
Published: August 2009

Operating systems, being one of the most complex pieces of source code, are often an intimidating subject for both instructors and students. Recently, Microsoft released teaching materials on Windows for operating system curricula, to complement traditional Unix-based instructional operating systems. Such materials have been reported to boost student learning by enhancing the relevance and diversity of courses, while the lack of "hands-on" guidance materials has been reported as hindrance. To complement lacking, we created video courseware to walk students through the Windows source code and help them get ready for large-scale developments on Windows kernel.
Design patterns to support teaching of automata theory
Authors: Merceron Agathe
Published: August 2009

Deterministic finite automata (DFA) are taught in courses like "formal foundations of computer science". It is quite a challenge to get students interested and proficient in that field. This contribution presents a set of design patterns to help teachers teach and students learn the design of DFA.
Peer assessments using the moodle workshop tool
Authors: Dooley John F.
Published: August 2009

In this Tip, we describe our experiences over the past four years in using the Workshop tool in the Moodle Learning Management System (LMS) to allow students to do peer assessments of student written journal article reviews. In our junior-level Software Development course, students are required to read and review several journal articles, producing a written review of 2-4 pages. Students are then required to use the Workshop tool to read and assess the work of several of their peers using an instructor-supplied rubric. In this Tip we describe the Workshop tool, how it is set up for student use, and the results of several experiences with this approach.
Running a programming contest in an introductory computer science course
Authors: Rosenbloom Arnold
Published: August 2009

We describe how to run a motivating in-class competition for an Introductory Computer Science course. We outline the students background, the problems, the motivation and the materials needed to run the competition.
The attributes of task difficulty in informatics in secondary education
Authors: Schlueter Kirsten , Brinda Torsten
Published: August 2009

In the poster, the first results of an empirical study in progress are presented. The study is directed to modeling the competence requirements of tasks in informatics. Initially the focus is on the relevance of a catalog of criteria affecting the task difficulty, where relevance is supposed to mean the practicability as well as the interrelation between criteria and competence requirements.
Guided learning via diagnostic feedback to question responses
Authors: Palmer-Brown Dominic , Draganova Chrisina , Wee-Lee Sin
Published: August 2009

This work in progress investigates the potential of automatically generated diagnostic feedback for guided learning in formative assessments to enhance the students' understanding and interactive learning experience. A method that integrates an on-line Multiple Choice Questions (MCQs) system with a neural network based data analysis is developed.
Long-term software projects development
Authors: Haberman Bruria , Yehezkel Cecile
Published: August 2009

The "Computer Science, Academia and Industry" extra-curricular program has been running at the Davidson Institute of Science Education for the past few years. The program, designed especially for high-school students majoring in computer science, aims to bridge the gap between the school and "real world" of computing.
Introducing the interactive whiteboard in computer science teaching
Authors: Cassapu Anita
Published: August 2009

In our presentation, we will share our experience in using interactive whiteboards in CS secondary high school class, in order to promote the learning processes and to motivate students to elect CS studies by using this rich-technology environment.
Masters degrees in computing
Authors: Cassel Lillian N. , Davies Gordon , Seidman Stephen
Published: August 2009

The ACM Education Board, the Education Activities Board of the IEEE Computer Society, representatives of the Association for Information Systems and the British Computer Society have joined forces to investigate the state of Masters degree programs in computing. This joint effort intends to document the variety and common features of programs throughout the United States and Europe. This poster is a status report on that project and an opportunity for interested individuals to add information about their programs to this work.
Inducing student interaction in a virtual environment
Authors: Tirado Felipe , Bustos Alfonso , Miranda Alejandro , Del Bosque Ana Elena
Published: August 2009

In this paper we are reporting on an experimental research study. The study employed a mixed teaching procedure (traditional classroom -face to face- and virtual classroom). The purpose of the study was to induce student interactions in a virtual environment. The aim was to develop a series of specific skills by means of collaborative online work including collective essays and digital presentations.
Keeping the pace in CS-1 through the use of CMS
Authors: Kültür Can
Published: August 2009

In this poster, it is aimed to share the experience of using course management systems (CMS) in a CS-1 course. The aim was to focus on the individual needs of students while learning programming. Creating a social online environment for solving exercises and sharing solutions seemed to be effective to support instructors as well as students.
Visual examples of recursion
Authors: Stephenson Ben
Published: August 2009

Because recursion is generally introduced early in the curriculum, the range of problems that can be used to motivate its study is limited. We describe three interesting visual problems that use recursion effectively. Each problem demonstrates the utility of recursion in an engaging way while being appropriate for students nearing the end of CS1.
Concurrency and parallelism in the computing ontology
Authors: Cassel Lillian , LeBlanc Richard , McGettrick Andrew , Wrinn Michael
Published: August 2009

This poster will describe ongoing work to modify the Computing Ontology to incorporate issues of parallelism and concurrency, motivated by recent developments in computer hardware design.
Regulation of HSP60 and the role of MK2 in a new model of severe experimental pancreatitis
Authors: Li Yong-Yu , Ochs Stephanie , Gao Zhi-Rong , Malo Antje , Chen Chang-Jie , Lv Shuai , Gallmeier Eike , Göke Burkhard , Schäfer Claus
Published: August 2009

The objective of this study was to investigate the role of MAPKAP kinase 2 (MK2) and heat shock protein (HSP) HSP60 in the pathogenesis of a new model of severe acute pancreatitis (AP). MK2 plays a significant role in the regulation of cytokines. It has been shown that induction and expression of several HSPs can protect against experimental pancreatitis. Interplay between both systems seems of high interest. Mice with a homozygous deletion of the MK2 gene were used. Severe AP was induced by combined intraperitoneal injections of cerulein with lipopolysaccharide (LPS). Severity of AP was assessed by biochemical markers and histology. The serum IL-6 and lung myeloperoxidase (MPO) levels were determined for assessing the extent of systemic inflammatory response. Expression of HSP25, HSP60, HSP70, and HSP90 was analyzed by Western blotting. Repeated injections of cerulein alone or cerulein plus LPS (Cer+LPS) resulted in local inflammatory responses in the pancreas and corresponding systemic inflammatory changes with pronounced severity in the Cer+LPS group. Compared with the C57Bl wild-type mice, the MK2−/− mice presented with significant milder pancreatitis and attenuated responses of serum amylase and trypsinogen activity. Furthermore, serum IL-6 was decreased as well as lung MPO activity. Injection of LPS alone displayed neither pancreatic inflammatory responses nor alterations of pancreatic enzyme activities but evidently elevated serum IL-6 levels and increased lung MPO activity. In contrast hereto, in the MK2−/− mice, these changes were much milder. Increased expression of HSP25 and HSP60 occurred after induction of AP. Especially, HSP60 was robustly elevated after Cer+LPS treatment, in both MK2−/− and wild-type mice. Thus the homozygous deletion of the MK2 gene ameliorates the severity of acute pancreatitis and accompanying systemic inflammatory reactions in a new model of severe acute pancreatitis. Our data support the hypothesis that MK2 participates in the multifactorial regulation of early inflammatory responses in AP, independently of the regulation of stress proteins like HSP25 and HSP60 and most likely due to its effect on cytokine regulation.
Experimental and theoretical ventricular electrograms and their relation to electrophysiological gradients in the adult rat heart
Authors: Weber dos Santos Rodrigo , Nygren Anders , Otaviano Campos Fernando , Koch Hans , Giles Wayne R.
Published: August 2009

The electrical activity of adult mouse and rat hearts has been analyzed extensively, often as a prerequisite for genetic engineering studies or for the development of rodent models of human diseases. Some aspects of the initiation and conduction of the cardiac action potential in rodents closely resemble those in large mammals. However, rodents have a much higher heart rate and their ventricular action potential is triangular and very short. As a consequence, an interpretation of the electrocardiogram in the mouse and rat remains difficult and controversial. In this study, optical mapping techniques have been applied to an in vitro left ventricular adult rat preparation to obtain patterns of conduction and action potential duration measurements from the epicardial surface. This information has been combined with previously published mathematical models of the rat ventricular myocyte to develop a bidomain model for action potential propagation and electrogram formation in the rat left ventricle. Important insights into the basis for the repolarization waveform in the ventricular electrogram of the adult rat have been obtained. Notably, our model demonstrated that the biphasic shape of the rat ventricular repolarization wave can be explained in terms of the transmural and apex-to-base gradients in action potential duration that exist in the rat left ventricle.
Pulmonary effects of keratinocyte growth factor in newborn rats exposed to hyperoxia
Authors: Franco-Montoya Marie-Laure , Bourbon Jacques R. , Durrmeyer Xavier , Lorotte Stéphanie , Jarreau Pierre-Henri , Delacourt Christophe
Published: August 2009

Acute lung injury and compromised alveolar development characterize bronchopulmonary dysplasia (BPD) of the premature neonate. High levels of keratinocyte growth factor (KGF), a cell-cell mediator with pleiotrophic lung effects, are associated with low BPD risk. KGF decreases mortality in hyperoxia-exposed newborn rodents, a classic model of injury-induced impaired alveolarization, although the pulmonary mechanisms of this protection are poorly defined. These were explored through in vitro and in vivo approaches in the rat. Hyperoxia decreased by 30% the rate of wound closure of a monolayer of fetal alveolar epithelial cells, due to cell death, which was overcome by recombinant human KGF (100 ng/ml). In rat pups exposed to >95% O2 from birth, increased viability induced by intraperitoneal injection of KGF (2 μg/g body wt) every other day was associated with prevention of neutrophil influx in bronchoalveolar lavage (BAL), prevention of decreases in whole lung DNA content and cell proliferation rate, partial prevention of apoptosis increase, and a markedly increased proportion of surfactant protein B-immunoreactive cells in lung parenchyma. Increased lung antioxidant capacity is likely to be due in part to enhanced CAAT/enhancer binding protein α expression. By contrast, KGF neither corrected changes induced by hyperoxia in parameters of lung morphometry that clearly indicated impaired alveolarization nor had any significant effect on tissue or BAL surfactant phospholipids. These findings evidence KGF alveolar epithelial cell protection, enhancing effects on alveolar repair capacity, and anti-inflammatory effects in the injured neonatal lung that may account, at least in part, for its ability to reduce mortality. They argue in favor of a therapeutic potential of KGF in the injured neonatal lung.
Procoagulant alveolar microparticles in the lungs of patients with acute respiratory distress syndrome
Authors: Bastarache Julie A. , Fremont Richard D. , Kropski Jonathan A. , Bossert Frederick R. , Ware Lorraine B.
Published: August 2009

Coagulation and fibrinolysis abnormalities are observed in acute lung injury (ALI) in both human disease and animal models and may contribute to ongoing inflammation in the lung. Tissue factor (TF), the main initiator of the coagulation cascade, is upregulated in the lungs of patients with ALI/acute respiratory distress syndrome (ARDS) and likely contributes to fibrin deposition in the air space. The mechanisms that govern TF upregulation and activation in the lung are not well understood. In the vascular space, TF-bearing microparticles (MPs) are central to clot formation and propagation. We hypothesized that TF-bearing MPs in the lungs of patients with ARDS contribute to the procoagulant phenotype in the air space during acute injury and that the alveolar epithelium is one potential source of TF MPs. We studied pulmonary edema fluid collected from patients with ARDS compared with a control group of patients with hydrostatic pulmonary edema. Patients with ARDS have higher concentrations of MPs in the lung compared with patients with hydrostatic edema (25.5 IQR 21.3–46.9 vs. 7.8 IQR 2.3–27.5 μmol/l, P = 0.009 by Mann-Whitney U-test). These MPs are enriched for TF, have procoagulant activity, and likely originate from the alveolar epithelium [as measured by elevated levels of RAGE (receptor for advanced glycation end products) in ARDS MPs compared with hydrostatic MPs]. Furthermore, alveolar epithelial cells in culture release procoagulant TF MPs in response to a proinflammatory stimulus. These findings suggest that alveolar epithelial-derived MPs are one potential source of TF procoagulant activity in the air space in ARDS and that epithelial MP formation and release may represent a unique therapeutic target in ARDS.
How can an inert gas counterbalance a NMDA-induced glutamate release?
Authors: Vallee Nicolas , Rostain Jean-Claude , Risso Jean-Jacques
Published: August 2009

Previous neurochemical studies performed in rats have revealed a decrease of striatal dopamine and glutamate induced by inert gas narcosis. We sought to establish the hypothetical role of glutamate and its main receptor, the N-methyl-d-aspartate (NMDA) receptor, in this syndrome. We aimed to counteract the nitrogen narcosis-induced glutamate and dopamine decreases by stimulating the NMDA receptor in the striatum. We used bilateral retrodialysis on awake rats, submitted to nitrogen under pressure (3 MPa). Continuous infusion of 2 mM of NMDA under normobaric conditions (0.01 MPa) ( n = 8) significantly increased extracellular average levels of glutamate, aspartate, glutamine, and asparagine by 241.8%, 292.5%, 108.3%, and 195.3%, respectively. The same infusion conducted under nitrogen at 3 MPa ( n = 6) revealed significant lower levels of these amino acids ( n = 8/6, P > 0.001). In opposition, the NMDA-induced effects on dopamine, dihydrophenylacetic acid (DOPAC), and homovanillic acid (HVA) levels were statistically not affected by the nitrogen at 3 MPa exposure ( n = 8/6, P > 0.05). Dopamine was increased by >240% on average. HVA was decreased (down to 40%), and there was no change in DOPAC levels, in both conditions. Results highlight that the NMDA receptor is not directly affected by nitrogen under pressure as indicated by the elevation in NMDA-induced dopamine release under hyperbaric nitrogen. On the other hand, the NMDA-evoked glutamate increase is counteracted by nitrogen narcosis. No improvement in motor and locomotor disturbances was observed with high striatal concentration in dopamine. Further experiments have to be done to specify why the striatal glutamate pathways, in association with the inhibition of its metabolism, only are affected by nitrogen narcosis in this study.
Marginal DCS events: their relation to decompression and use in DCS models
Authors: Howle Laurens E. , Weber Paul W. , Vann Richard D. , Campbell Mark C.
Published: August 2009

We consider the nature and utility of marginal decompression sickness (DCS) events in fitting probabilistic decompression models to experimental dive trial data. Previous works have assigned various fractional weights to marginal DCS events, so that they contributed to probabilistic model parameter optimization, but less so than did full DCS events. Inclusion of fractional weight for marginal DCS events resulted in more conservative model predictions. We explore whether marginal DCS events are correlated with exposure to decompression or are randomly occurring events. Three null models are developed and compared with a known decompression model that is tuned on dive trial data containing only marginal DCS and non-DCS events. We further investigate the technique by which marginal DCS events were previously included in parameter optimization, explore the effects of fractional weighting of marginal DCS events on model optimization, and explore the rigor of combining data containing full and marginal DCS events for probabilistic DCS model optimization. We find that although marginal DCS events are related to exposure to decompression, empirical dive data containing marginal and full DCS events cannot be combined under a single DCS model. Furthermore, we find analytically that the optimal weight for a marginal DCS event is 0. Thus marginal DCS should be counted as no-DCS events when probabilistic DCS models are optimized with binomial likelihood functions. Specifically, our study finds that inclusion of marginal DCS events in model optimization to make the dive profiles more conservative is counterproductive and worsens the model's fit to the full DCS data.
Intracoronary intermedin 1–47 augments cardiac perfusion and function in anesthetized pigs: role of calcitonin receptors and β-adrenoreceptor-mediated nitric oxide release
Authors: Grossini Elena , Molinari Claudio , Mary David A. S. G. , Uberti Francesca , Caimmi Philippe Primo , Vacca Giovanni
Published: August 2009

Systemic intermedin (IMD)1–47 administration has been reported to result in vasodilation and marked hypotension through calcitonin-related receptor complexes. However, its effects on the coronary circulation and the heart have not been examined in vivo. The present study was therefore planned to determine the primary in vivo effect of IMD1–47 on coronary blood flow and cardiac function and the involvement of the autonomic nervous system and nitric oxide (NO). In 35 anesthetized pigs, IMD1–47, infused into the left anterior descending coronary artery at doses of 87.2 pmol/min, at constant heart rate and arterial blood pressure, augmented coronary blood flow and cardiac function. These responses were graded in a further five pigs by increasing the infused dose of IMD1–47 between 0.81 and 204.1 pmol/min. In the 35 pigs, the blockade of cholinergic receptors (intravenous atropine, 5 pigs), α-adrenoceptors (intravenous phentolamine, 5 pigs), and β1-adrenoceptors (intravenous atenolol, 5 pigs) did not abolish the cardiac response to IMD1–47, the effects of which were prevented by blockade of β2-adrenoceptors (intravenous butoxamine, 5 pigs), NO synthase (intracoronary Nω-nitro-l-arginine methyl ester, 5 pigs), and calcitonin-related receptors (intracoronary CGRP8–37/AM22–52, 10 pigs). In porcine coronary endothelial cells, IMD1–47 induced the phosphorylation of endothelial NO synthase and NO production through cAMP signaling leading to ERK, Akt, and p38 activation, which was prevented by the inhibition of β2-adrenoceptors, calcitonin-related receptor complexes, and K+channels. In conclusion, IMD1–47 primarily augmented coronary blood flow and cardiac function through the involvement of calcitonin-related receptor complexes and β2-adrenoreceptor-mediated NO release. The intracellular signaling involved cAMP-dependent activation of kinases and the opening of K+channels.
Cyclooxygenase and thromboxane/prostaglandin receptor contribute to aortic endothelium-dependent dysfunction in aging female spontaneously hypertensive rats
Authors: Graham Drew A. , Rush James W. E.
Published: August 2009

Cyclooxygenase (COX)-derived vasoconstrictory prostanoids contribute to impaired endothelium-dependent vasorelaxation in aging male (m) spontaneously hypertensive rats (SHR); however, vasomotor responses in aging female (f) SHR and sex differences in aging SHR are unknown. Examining mechanisms governing dysfunction in aging fSHR will contribute to understanding sex-dependent vascular complications in advanced hypertension. Aortic endothelium-dependent relaxation dose responses (ACh) of 16- and 30-wk-old mSHR and fSHR and normotensive Wistar-Kyoto rats were examined in the absence (no drug control) and presence of COX inhibition [indomethacin (Indo)] and thromboxane/prostaglandin receptor inhibition (SQ-29548). No drug control-treated 16-wk mSHR exhibited considerable blunting of the peak relaxation response to ACh (e.g., 77 ± 4% relaxation to 10−5mol/l) vs. Wistar-Kyoto controls (89 ± 6%), and greater dysfunction occurred in 30-wk mSHR (63 ± 2%). Interestingly, ACh relaxations of fSHR were unimpaired at 16 wk (101 ± 2% to 10−5mol/l), but blunted in 30 wk (76 ± 4%). Indo and SQ-29548 restored robust ACh vasorelaxation in all groups (e.g., 113 ± 3 and 112 ± 3%, respectively, in Indo- and SQ-29548-treated 30-wk fSHR). Aortic COX-1 protein expression was elevated by 75% in 30-wk vs. 16-wk fSHR, whereas group-averaged ACh-stimulated aortic PGI2release (assessed as 6- keto-PGF1α) was 30% greater in 30-wk vs. 16-wk fSHR (9,926 ± 890 vs. 7,621 ± 690 pg·ml−1·mg dry wt−1), although this did not reach significance ( P = 0.0758). Dramatic deterioration of endothelium-dependent vasomotor function in fSHR across this age range involves COX and thromboxane/prostaglandin receptor, supporting a mechanism of impairment similar to that which occurs in aging mSHR.
Dynamic correction for parallel conductance, GP, and gain factor, α, in invasive murine left ventricular volume measurements
Authors: Porterfield John E. , Kottam Anil T. G. , Raghavan Karthik , Escobedo Daniel , Jenkins James T. , Larson Erik R. , Treviño Rodolfo J. , Valvano Jonathan W. , Pearce John A. , Feldman Marc D.
Published: August 2009

The conductance catheter technique could be improved by determining instantaneous parallel conductance (GP), which is known to be time varying, and by including a time-varying calibration factor in Baan's equation [α( t)]. We have recently proposed solutions to the problems of both time-varying GP and time-varying α, which we term “admittance” and “Wei's equation,” respectively. We validate both our solutions in mice, compared with the currently accepted methods of hypertonic saline (HS) to determine GP and Baan's equation calibrated with both stroke volume (SV) and cuvette. We performed simultaneous echocardiography in closed-chest mice ( n = 8) as a reference for left ventricular (LV) volume and demonstrate that an off-center position for the miniaturized pressure-volume (PV) catheter in the LV generates end-systolic and diastolic volumes calculated by admittance with less error ( P < 0.03) (−2.49 ± 15.33 μl error) compared with those same parameters calculated by SV calibrated conductance (35.89 ± 73.22 μl error) and by cuvette calibrated conductance (−7.53 ± 16.23 μl ES and −29.10 ± 31.53 μl ED error). To utilize the admittance approach, myocardial permittivity (εm) and conductivity (σm) were calculated in additional mice ( n = 7), and those results are used in this calculation. In aortic banded mice ( n = 6), increased myocardial permittivity was measured (11,844 ± 2,700 control, 21,267 ± 8,005 banded, P < 0.05), demonstrating that muscle properties vary with disease state. Volume error calculated with respect to echo did not significantly change in aortic banded mice (6.74 ± 13.06 μl, P = not significant). Increased inotropy in response to intravenous dobutamine was detected with greater sensitivity with the admittance technique compared with traditional conductance [4.9 ± 1.4 to 12.5 ± 6.6 mmHg/μl Wei's equation ( P < 0.05), 3.3 ± 1.2 to 8.8 ± 5.1 mmHg/μl using Baan's equation ( P = not significant)]. New theory and method for instantaneous GP removal, as well as application of Wei's equation, are presented and validated in vivo in mice. We conclude that, for closed-chest mice, admittance (dynamic GP) and Wei's equation (dynamic α) provide more accurate volumes than traditional conductance, are more sensitive to inotropic changes, eliminate the need for hypertonic saline, and can be accurately extended to aortic banded mice.
Underwater study of arterial blood pressure in breath-hold divers
Authors: Sieber Arne , L'Abbate Antonio , Passera Mirko , Garbella Erika , Benassi Antonio , Bedini Remo
Published: August 2009

Knowledge regarding arterial blood pressure (ABP) values during breath-hold diving is scanty. It derives from a few reports of measurements performed at the water's surface, showing slight or no increase in ABP, and from a single study of two simulated deep breath-hold dives in a hyperbaric chamber. Simulated dives showed an increase in ABP to values considered life threatening by standard clinical criteria. For the first time, using a novel noninvasive subaquatic sphygmomanometer, we successfully measured ABP in 10 healthy elite breath-hold divers at a depth of 10 m of freshwater (mfw). ABP was measured in dry conditions, at the surface (head-out immersion), and twice at a depth of 10 mfw. Underwater measurements of ABP were obtained in all subjects. Each measurement lasted 50–60 s and was accomplished without any complications or diver discomfort. In the 10 subjects as a whole, mean ABP values were 124/93 mmHg at the surface and 123/94 mmHg at a depth of 10 mfw. No significant statistical differences were found when blood pressure measurements at the water surface were compared with breath-hold diving conditions at a depth of 10 mfw. No systolic blood pressure values >140 mmHg or diastolic blood pressure values >115 mmHg were recorded. In conclusion, direct measurements of ABP during apnea diving showed no or only mild increases in ABP. However, our results cannot be extended over environmental conditions different from those of the present study.
Cornuside Attenuates Apoptosis and Ameliorates Mitochondrial Energy Metabolism in Rat Cortical Neurons
Authors: Jiang Wang-Lin , Chen Xi-Guang , Zhu Hai-Bo , Hou Jian , Tian Jing-Wei
Published: August 2009

Cornuside, a secoiridoid glucoside compound, was isolated from the fruit of Cornus officinalis Sieb. et Zucc. The present study elucidates the effects of cornuside on cultured rat cortical neuron damage induced by oxygen-glucose deprivation. The results show that cornuside treatment obviously attenuates apoptosis and ameliorates mitochondrial energy metabolism in rat cortical neurons by increasing the cell survival rate, mitochondrial antioxidant enzyme activities, mitochondrial respiratory enzyme activity, mitochondrial respiratory control ratio and the ATP content, and by decreasing the mitochondrial malondialdehyde content, lactate dehydrogenase leakage rate, intracellular Ca2+ level and caspase-3 activity in a concentration-dependent manner. These findings indicate that cornuside has protective potential against cerebral ischemic injury, and its protective effects may be due to the suppression of intracellular Ca2+ elevation and caspase-3 activity, and improvements in mitochondrial energy metabolism and antioxidant properties.
Impact of Hyperlipidemia and Statins on Ischemic Stroke Outcomes after Intra-Arterial Fibrinolysis and Percutaneous Mechanical Embolectomy
Authors: Restrepo Lucas , Bang Oh Young , Ovbiagele Bruce , Ali Latisha , Kim Doojin , Liebeskind David S. , Starkman Sidney , Vinuela Fernando , Duckwiler Gary R. , Jahan Reza , Saver Jeffrey L.
Published: August 2009

Background: Endovascular recanalization therapies are an increasingly employed treatment strategy in acute cerebral ischemia. The determinants of the final clinical outcome after endovascular treatment have been understudied. We investigated the effects of hyperlipidemia and statins on acute ischemic stroke outcomes after endovascular procedures. Methods: An inquiry of a prospectively maintained stroke registry was conducted. Endovascular procedures were performed using recombinant tissue plasminogen activator, prourokinase or the Merci device within 12 hours after symptom onset. The analyzed outcomes were revascularization, hemorrhage and excellent functional outcome (Rankin score of 0–1 at 3 months). The analyses included χ2 and Wilcoxon rank sum, logistic regression (for multivariate analyses with binary outcomes) and linear regression (for continuous outcomes). Significance was set at p < 0.05. Results: We included 142 patients, 80% treated with intra-arterial fibrinolysis, 22% with percutaneous mechanical embolectomy and 27% treated with intravenous fibrinolysis prior to endovascular intervention. Age (OR = 0.956, 95% CI = 0.927–0.986, p = 0.0041), National Institutes of Health Stroke Scale (NIHSS) score on admission (OR = 0.881, 95% CI = 0.812–0.957, p = 0.0025) and history of hyperlipidemia (OR = 0.284, 95% CI = 0.08–0.99, p = 0.0478) were negatively associated with excellent functional outcome at 3 months. Every 50 mg/dl increment in the total cholesterol level resulted in 64% decrease in the odds of excellent functional outcome (OR = 0.36, 95% CI = 0.447–0.882, p = 0.0253). History of hyperlipidemia decreased the likelihood of neurological improvement (p = 0.0462) and was associated with a higher NIHSS score at 7 days or discharge. Statin use was related to an average 6.5-unit NIHSS decrease at discharge (p = 0.0168). Statins were not associated with increased frequency of recanalization or symptomatic intracerebral hemorrhage. Conclusions: History of hyperlipidemia may have a negative impact on the outcomes of acute ischemic stroke treated with intra-arterial fibrinolysis or percutaneous mechanical embolectomy. Statin use before and after these procedures may be related to better neurological outcomes. Larger prospective studies are needed to endorse these findings.
Thrombus Size and Doppler Embolic Signal Intensity
Authors: Martin Matthew J. , Chung Emma M.L. , Ramnarine Kumar V. , Goodall Alison H. , Naylor A. Ross , Evans David H.
Published: August 2009

Background: Migration of thrombus through the cerebral arteries is a common cause of stroke. Thrombus emboli can be detected non-invasively using Doppler ultrasound, but even where the embolus composition is known, there is currently no method for estimating the size of an embolus based on the returned ultrasound signal. Here we report the results of in vitro experiments investigating the relationship between size and embolic signal intensity for fresh thrombus emboli with a view to estimating the sizes of thrombi detected following carotid surgery. Method: Thrombi were formed from whole blood using the ‘Chandler loop’ method under flow conditions similar to those associated with arterial thrombus formation in vivo. A total of 390 Doppler embolic signals were then measured from 37 pieces of thrombus circulated in a pulsatile closed-flow circuit. The dimensions of each of the thrombi were measured before and after circulation using an optical microscope. Relationships between thrombus size and embolic signal properties were then investigated using standard statistical methods with a view to size estimation of thrombi during clinical monitoring. Results: Although embolic signals generally became more intense with increasing thrombus size, strong oscillations due to resonance effects were observed. Pearson tests revealed strong positive correlations between embolus diameter, signal intensity and duration (r > 0.8, p ≤ 0.01). Conclusions: This study provides experimental evidence supporting theoretical predictions relating Doppler embolic signal intensity to thrombus size. In our discussion, we tentatively suggest how this information might be used to size emboli in clinical practice.