bluuebunny/crossref_metadata_2025 huggingface dataset:
Characterizing multiparty voice communication for multiplayer games
Authors: Papp Gabor , GauthierDickey Chris
Published: July 2008

Over the last few years, the number of game players using voice communication to talk to each other while playing games has increased dramatically. In fact, many modern games and game consoles have added voice support instead of expecting third-party companies to provide this technology. Unlike traditional voice-over-IP technology, where most conversations are between two people, voice communication in games often has 5 or more people talking together as they play.

We present the first measurement study on the characteristics of multiparty voice communications. Over a 3 month period, we measured over 7,000 sessions on an active multi-party voice communication server to quantify the characteristics of communication generated by game players, including overall server traffic, group sizes, sessions characteristics, and speaking (and silence) durations.
Performance analysis in the real world
Authors: Douceur John R.
Published: July 2008

What issues are on the minds of industrial performance analysts? Four representatives of world-class product organizations will describe their work at the front lines of measurement, modeling, and performance tuning. Topics will include performance engineering of middleware at IBM, tools for detecting false sharing in large-scale multiprocessors at Hewlett-Packard, kernel thread-scheduling performance in multiprocessors at Microsoft, and low-overhead instrumentation for profiling large-scale services at Google. Plenty of time will be available to ask questions about how to direct our research to have the greatest impact on industrial practice.
Empirical evaluation of querying mechanisms for unstructured wireless sensor networks
Authors: Ahn Joon , Kapadia Shyam , Pattem Sundeep , Sridharan Avinash , Zuniga Marco , Jun Jung-Hyun , Avin Chen , Krishnamachari Bhaskar
Published: July 2008

In the last few years, several studies have analyzed the performance of flooding and random walks as querying mechanisms for unstructured wireless sensor networks. However, most of the work is theoretical in nature and while providing insights into the asymptotic behavior of these querying mechanisms, does not account for the non-idealities faced by the network in real deployments. In this paper, we propose a 3-way handshake protocol as a reliable implementation of a random walk and compare its performance with flooding in real environments. The metrics considered are delay, reliability and transmission cost. Our initial results suggest that flooding is better suited for low-interference environments, while random walks might be a better option in networks with high interference. We also present possible research directions to improve the performance oflooding and random walks.
Stability and fairness of explicit congestion control with small buffers
Authors: Kelly Frank , Raina Gaurav , Voice Thomas
Published: July 2008

Rate control protocols that utilise explicit feedback from routers are able to achieve fast convergence to an equilibrium which approximates processor-sharing on a single bottleneck link, and hence such protocols allow short flows to complete quickly. For a network, however, processor-sharing is not uniquely defined but corresponds with a choice of fairness criteria, and proportional fairness has a reasonable claim to be the network generalization of processor-sharing.

In this paper, we develop a variant of RCP (rate control protocol) that achieves α-fairness when buffers are small, including proportional fairness as the case α = 1. At the level of theoretical abstraction treated, our model incorporates a general network topology, and heterogeneous propagation delays. For our variant of the RCP algorithm, we establish a simple decentralized sufficient condition for local stability.

An outstanding question for explicit congestion control is whether the presence of feedback based on queue size is helpful or not, given the presence of feedback based on rate mismatch. We show that, for the variant of RCP considered here, feedback based on queue size may cause the queue to be less accurately controlled.

A further outstanding question for explicit congestion control is the scale of the step-change in rate that is necessary at a resource to accommodate a new flow. We show that, for the variant of RCP considered here, this can be estimated from the aggregate flow through the resource, without knowledge of individual flow rates.
Censor networks
Authors: Raman Bhaskaran , Chebrolu Kameswari
Published: July 2008

This writeup presents a critique of the field of "Wireless Sensor Networks (WSNs)". Literature in this domain falls into two main, distinct categories: (1) algorithms or protocols, and (2) applicationcentric system design. A striking observation is that references across these two categories are minimal, and superficial at best. We argue that this is not accidental, and is the result of three main flaws in the former category of work. Going forward, an applicationdriven, bottom-up approach is required for meaningful articulation and subsequent solution of any networking issues in WSNs.
CRAWDAD
workshop 2007
Authors: Yeo Jihwang , Henderson Tristan , Kotz David
Published: July 2008

Wireless network researchers are hungry for data about how real users, applications, and devices use real networks under real network conditions.
CRAWDAD
, the Community Resource for Archiving Wireless Data at Dartmouth, is an NSF-funded project that is building a wireless network data archive for the research community. We host wireless data, and provide tools and documents to make it easy to collect and use wireless network data. We hope that this resource will help researchers to identify and evaluate real and interesting problems in mobile and pervasive computing. This report outlines the
CRAWDAD
project and summarizes the third
CRAWDAD
workshop, held at MobiCom 2007.
Open issues in organizing computer systems conferences
Authors: Mogul Jeffrey C. , Anderson Tom
Published: July 2008

The Workshop on Organizing Workshops, Conferences, and Symposia for Computer Systems (WOWCS) was organized to "bring together conference organizers (past, present, and future) and other interested people to discuss the issues they confront." In conjunction with WOWCS, we survey some previous publications that discuss open issues related to organizing computer systems conferences, especially concerning conduct and management of the review process. We also list some topics about which we wish WOWCS had received submissions, but did not; these could be good topics for future articles.
SIGCAS, CAS, HCI & sustainability
Authors: Davis Janet
Published: July 2008

Greetings from 35,000 feet! I am en route from my home in Grinnell, Iowa to Sydney, Australia to participate in a workshop on---oddly enough---environmental sustainability. Reducing negative environmental impacts is a current hot topic in my field of Human-Computer Interaction (HCI); indeed, so much so that I've seen at least one researcher (Bill Tomlinson of UC Irvine) reduce his carbon footprint by using iChat to remotely present a conference paper. Computing technology has a tremendous capacity both to make the problem worse and to help us make wiser choices.
Disseminating information via Web 2.0
Authors: Hardy Nazli
Published: July 2008

It is wonderful to connect with you and have the opportunity to interact on our shared interests in all aspects of our profession. As a brief introduction, my research interests are currently in network efficiency and security, as well as bioinformatics (biodiversity informatics), Internet programming (the use of Web 2.0 technologies to disseminate information) and certainly pedagogy in the CS curriculum. I am involved in endeavors to attract women in math and science, and to introduce applications of computer science to students in high school. My website provides more detailed information. As a relatively new faculty member, I am very interested to collaborate with colleagues in any of these endeavors. My contact information is below; I look forward to hearing from you. Regards, Nazli
Teaching social implications of computing
Authors: Harvey Brian
Published: July 2008

I'm Brian Harvey; I'm a Lecturer with Security of Employment in the EECS Department at the University of California at Berkeley. (The strange title means that I'm a full-time teacher, but basically tenured, although I'm not supposed to call it that. There aren't very many of us: 17 on the Berkeley campus.) My main teaching assignment is our first course for CS majors, based on the Abelson and Sussman text from MIT. But I also teach "Social Implications of Computers," a course that was retired along with the professor who first taught it, and that I campaigned unsuccessfully to revive for several years until ABET, our accrediting agency, won the battle for me by complaining about the lack of ethics in our curriculum.
Net neutrality, computing and social change
Authors: Schahczenski Celia
Published: July 2008

Hello. Net neutrality, preserving a free and open Internet, is a critical issue. An information revolution similar to the industrial revolution has occurred and Internet policies are being formed. "Non-discrimination" provisions like Net Neutrality have governed the nation's communications networks since 1930. However such a doctrine needs to be put into law. In the same way that National Public Radio and public television are publicly governed, an open net is critical for the continuation of democracy.
Prelude to a Division
Authors: Bhalla Needhi , Dernburg Abby F.
Published: July 2008

Accurate segregation of chromosomes during meiosis requires physical links between homologs. These links are usually established through chromosome pairing, synapsis, and recombination, which occur during meiotic prophase. How chromosomes pair with their homologous partners is one of the outstanding mysteries of meiosis. Surprisingly, experimental evidence indicates that different organisms have found more than one way to accomplish this feat. Whereas some species depend on recombination machinery to achieve homologous pairing, others are able to pair and synapse their homologs in the absence of recombination. To ensure specific pairing between homologous chromosomes, both recombination-dependent and recombination-independent mechanisms must strike the proper balance between forces that promote chromosome interactions and activities that temper the promiscuity of those interactions. The initiation of synapsis is likely to be a tightly regulated step in a process that must be mechanically coupled to homolog pairing.
Deleterious action of FA metabolites on ATP synthesis: possible link between lipotoxicity, mitochondrial dysfunction, and insulin resistance
Authors: Abdul-Ghani Muhammad A. , Muller Florian L. , Liu Yuhong , Chavez Alberto O. , Balas Bogdan , Zuo Pengou , Chang Zhi , Tripathy Devjit , Jani Rucha , Molina-Carrion Marjorie , Monroy Adriana , Folli Franco , Van Remmen Holly , DeFronzo Ralph A.
Published: July 2008

Insulin resistance is a characteristic feature of type 2 diabetes and obesity. Insulin-resistant individuals manifest multiple disturbances in free fatty acid (FFA) metabolism and have excessive lipid accumulation in insulin target tissues. Although much evidence supports a causal role for altered FFA metabolism in the development of insulin resistance, i.e., “lipotoxicity”, the intracellular mechanisms by which elevated plasma FFA levels cause insulin resistance have yet to be completely elucidated. Recent studies have implicated a possible role for mitochondrial dysfunction in the pathogenesis of insulin resistance in skeletal muscle. We examined the effect of FFA metabolites [palmitoyl carnitine (PC), palmitoyl-coenzyme A (CoA), and oleoyl-CoA] on ATP synthesis in mitochondria isolated from mouse and human skeletal muscle. At concentrations ranging from 0.5 to 2 μM, these FFA metabolites stimulated ATP synthesis; however, above 5 μM, there was a dose-response inhibition of ATP synthesis. Furthermore, 10 μM PC inhibits ATP synthesis from pyruvate. Elevated PC concentrations (≥10 μM) inhibit electron transport chain activity and decrease the mitochondrial inner membrane potential. These acquired mitochondrial defects, caused by a physiological increase in the concentration of FFA metabolites, provide a mechanistic link between lipotoxicity, mitochondrial dysfunction, and muscle insulin resistance.
Pax6 and Pdx1 are required for production of glucose-dependent insulinotropic polypeptide in proglucagon-expressing L cells
Authors: Fujita Yukihiro , Chui Jeannie W. Y. , King David S. , Zhang Tianjiao , Seufert Jochen , Pownall Scott , Cheung Anthony T. , Kieffer Timothy J.
Published: July 2008

Glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide-1 (GLP-1) are incretin hormones that play important roles in maintaining glucose homeostasis and are being actively pursued as novel therapeutic agents for diabetes. GIP is produced by dispersed enteroendocrine cells and interestingly at times is coexpressed with GLP-1. We sought to determine the factors that selectively define GIP- vs. GLP-1-expressing cells. We performed comparative immunostaining of Pax6 and Pdx1 in GIP- and GLP-1-secreting cells. We investigated whether Pax6 and Pdx1 activate the human GIP promoter in control IEC-6 cells and GIP-expressing STC-1 cells. EMSA was performed to assess the binding of these transcription factors to the GIP promoter. Pax6 and Pdx1 consistently colocalized in GIP-immunoreactive cells. Cells that coexpress GIP and GLP-1 were Pax6 and Pdx1 positive, whereas cells expressing only GLP-1 were Pax6 positive but did not express Pdx1. GIP promoter activity was enhanced in IEC-6 cells by exogenous Pax6 or Pdx1 and diminished in STC-1 cells by inhibition of endogenous Pax6 or Pdx1 by dominant-negative forms. Promoter truncation analysis revealed a major loss of promoter activity when the sequence between −184 to −145 bp was deleted. EMSA studies indicated that Pax6 and Pdx1 bind to this proximal sequence of the human GIP promoter. Our findings indicate that concomitant expression of Pax6 and Pdx1 is important for GIP expression. Our results also suggest that the presence of Pdx1 defines whether GLP-1-expressing gastrointestinal L cells also coexpress GIP.
Effects of glucagon-like peptide-1, yohimbine, and nitrergic modulation on sympathetic and parasympathetic activity in humans
Authors: Bharucha Adil E. , Charkoudian Nisha , Andrews Christopher N. , Camilleri Michael , Sletten David , Zinsmeister Alan R. , Low Phillip A.
Published: July 2008

Glucagon-like peptide-1 (GLP-1), an incretin, which is used to treat diabetes mellitus in humans, inhibited vagal activity and activated nitrergic pathways. In rats, GLP-1 also increased sympathetic activity, heart rate, and blood pressure (BP). However, the effects of GLP-1 on sympathetic activity in humans are unknown. Our aims were to assess the effects of a GLP-1 agonist with or without α2-adrenergic or -nitrergic blockade on autonomic nervous functions in humans. In this double-blind study, 48 healthy volunteers were randomized to GLP-1-(7-36) amide, the nitric oxide synthase (NOS) inhibitor N G-monomethyl-l-arginine acetate (l-NMMA), the α2-adrenergic antagonist yohimbine, or placebo (i.e., saline), alone or in combination. Hemodynamic parameters, plasma catecholamines, and cardiac sympathetic and parasympathetic modulation were measured by spectral analysis of heart rate. Thereafter, the effects of GLP-1-(7-36) amide on muscle sympathetic nerve activity (MSNA) were assessed by microneurography in seven subjects. GLP-1 increased ( P = 0.02) MSNA but did not affect cardiac sympathetic or parasympathetic indices, as assessed by spectral analysis. Yohimbine increased plasma catecholamines and the low-frequency (LF) component of heart rate power spectrum, suggesting increased cardiac sympathetic activity. l-NMMA increased the BP and reduced the heart rate but did not affect the balance between sympathetic and parasympathetic activity. GLP-1 increases skeletal muscle sympathetic nerve activity but does not appear to affect cardiac sympathetic or parasympathetic activity in humans.
Diencephalic Locomotor Region in the Lamprey—Afferents and Efferent Control
Authors: Ménard Ariane , Grillner Sten
Published: July 2008

In vertebrates, locomotion can be initiated by stimulation of the diencephalic locomotor region (DLR). Little is known of the different forebrain regions that provide input to the neurons in DLR. In the lamprey, it had been shown previously that DLR provides monosynaptic input to reticulospinal neurons, which in turn elicit rhythmic ventral root activity at the spinal level. To show that actual locomotor movements are produced from DLR, we use a semi-intact preparation in which the brain stem is exposed and the head fixed, while the body is left to generate actual swimming movements. DLR stimulation induced symmetric locomotor movements with an undulatory wave transmitted along the body. To explore if DLR is under tonic GABAergic input under resting conditions, as in mammals, GABAergic antagonists and agonists were locally administered into DLR. Injections of GABA agonists inhibited locomotion, whereas GABA antagonists facilitated the induction of locomotion. These findings suggest that GABAergic projections provide tonic inhibition that once turned off can release locomotion. Double-labeling experiments were carried out to identify GABAergic projections to the DLR. Populations of GABAergic projection neurons to DLR originated in the caudoventral portion of the medial pallium, the lateral and dorsal pallium, and the striatal area. These different GABAergic projection neurons, which also project to other brain stem motor centers, may represent the basal ganglia output to DLR. Moreover, electrical stimulation of striatum induced long-lasting plateau potentials in reticulospinal cells and associated locomotor episodes dependent on DLR being intact, suggesting that striatum may act via the basal ganglia output identified here.
Choosing Where to Attend and the Medial Frontal Cortex: An fMRI Study
Authors: Taylor Paul C. J. , Rushworth Matthew F. S. , Nobre Anna C.
Published: July 2008

To investigate how we orient our spatial attention, previous studies have recorded neural activity while participants are instructed where to attend. Here we contrast this classical instructed attention condition with a novel condition in which the focus of voluntary attention is not specified by the experimenter but rather is freely chosen by the participant. Central cues prompted fixating participants either to choose which of two peripheral spatial locations to covertly attend or formed an instruction. Either type of cueing initiated selective attention demonstrated behaviorally by enhanced performance at a visual detection task in comparison to a separate divided attention condition. We used functional magnetic resonance imaging to measure which areas were more active during choice than instruction. Choosing where to attend activated a large cluster of medial frontal cortical regions similar to those that have been previously implicated in the free selection of overt action. We then addressed a potential confound in contrasting choice with instruction: participants may remember their behavior more when choosing. In a separate block, and interleaved with choice trials, “memory” trials were introduced in which participants were instructed to remember where they had attended on the previous trial. The presupplementary eye fields and lateral frontal eye fields were specialized for choice-guided attentional orienting over and above any memory confound. This evidence suggests a common mechanism may underlie free selection, whether for covert attention or overt saccades.
A Neural Correlate of Motivational Conflict in the Superior Colliculus of the Macaque
Authors: Isoda Masaki , Hikosaka Okihide
Published: July 2008

Behavior is controlled by both external instructions and internal motives, but the actions demanded by each may be different. A common consequence of such a conflict is a delay in decision making and subsequent motor responses. It is unknown, however, what neural mechanisms underlie motivational conflict and associated response delay. To answer this question, we recorded single-neuron activity in the superior colliculus (SC) as macaque monkeys performed a visually guided, asymmetrically rewarded saccade task. A peripheral spot of light at one of two opposing positions was illuminated to indicate a saccade target. In a given block of trials, one position was associated with a big reward and the other with a small reward. The big-reward position was alternated across blocks. Behavioral analyses revealed that small-reward trials created a conflict between the instructed saccade to one position and the internally motivated, yet invalid saccade to the opposite position. We found that movement neurons in the SC temporally exhibited bursting activity after the appearance of the small-reward target opposite their movement field. This transient activity predicted the amount of response delay for upcoming saccades. Our data suggest that motivational conflict activates movement neurons in both colliculi, thereby delaying saccade initiation through intercollicular inhibitory interactions.
Noxious Lingual Stimulation Influences the Excitability of the Face Primary Motor Cerebral Cortex (Face MI) in the Rat
Authors: Adachi K. , Murray G. M. , Lee J.-C. , Sessle B. J.
Published: July 2008

The mechanisms whereby orofacial pain affects motor function are poorly understood. The aims were to determine whether 1) lingual algesic chemical stimulation affected face primary motor cerebral cortex (face MI) excitability defined by intracortical microstimulation (ICMS); and 2) any such effects were limited to the motor efferent MI zones driving muscles in the vicinity of the noxious stimulus. Ketamine-anesthetized Sprague–Dawley male rats were implanted with electromyographic (EMG) electrodes into anterior digastric, masseter, and genioglossus muscles. In 38 rats, three microelectrodes were located in left face MI at ICMS-defined sites for evoking digastric and/or genioglossus responses. ICMS thresholds for evoking EMG activity from each site were determined every 15 min for 1 h, then the right anterior tongue was infused (20 μl, 120 μl/h) with glutamate (1.0 M, n = 18) or isotonic saline ( n = 7). Subsequently, ICMS thresholds were determined every 15 min for 4 h. In intact control rats ( n = 13), ICMS thresholds were recorded over 5 h. Only left and right genioglossus ICMS thresholds were significantly increased (≤350%) in the glutamate infusion group compared with intact and isotonic saline groups ( P < 0.05). These dramatic effects of glutamate on ICMS-evoked genioglossus activity contrast with its weak effects only on right genioglossus activity evoked from the internal capsule or hypoglossal nucleus. This is the first documentation that intraoral noxious stimulation results in prolonged neuroplastic changes manifested as a decrease in face MI excitability. These changes appear to occur predominantly in those parts of face MI that provide motor output to the orofacial region receiving the noxious stimulation.
Expression profiling reveals heightened apoptosis and supports fiber size economy in the murine muscles of mastication
Authors: Evans Marianna , Morine Kevin , Kulkarni Cyelee , Barton Elisabeth R.
Published: July 2008

Distinctions between craniofacial and axial muscles exist from the onset of development and throughout adulthood. The masticatory muscles are a specialized group of craniofacial muscles that retain embryonic fiber properties in the adult, suggesting that the developmental origin of these muscles may govern a pattern of expression that differs from limb muscles. To determine the extent of these differences, expression profiling of total RNA isolated from the masseter and tibialis anterior (TA) muscles of adult female mice was performed, which identified transcriptional changes in unanticipated functional classes of genes in addition to those attributable to fiber type. In particular, the masseters displayed a reduction of transcripts associated with contractile and cytoskeletal load-sensing and anabolic processes, and heightened expression of genes associated with stress. Associated with these observations was a significantly smaller fiber cross-sectional area in masseters, significantly elevated load-sensing signaling (phosphorylated focal adhesion kinase), and increased apoptotic index in masseters compared with TA muscles. Based on these results, we hypothesize that masticatory muscles may have a fundamentally different strategy for muscle design, compared with axial muscles. Specifically there are small diameter fibers that have an attenuated ability to hypertrophy, but an increased propensity to undergo apoptosis. These results may provide insight into the molecular basis for specific muscle-related pathologies associated with masticatory muscles.
Involvement of T1R3 in calcium-magnesium taste
Authors: Tordoff Michael G. , Shao Hongguang , Alarcón Laura K. , Margolskee Robert F. , Mosinger Bedrich , Bachmanov Alexander A. , Reed Danielle R. , McCaughey Stuart
Published: July 2008

Calcium and magnesium are essential for survival but it is unknown how animals detect and consume enough of these minerals to meet their needs. To investigate this, we exploited the PWK/PhJ (PWK) strain of mice, which, in contrast to the C57BL/6J (B6) and other inbred strains, displays strong preferences for calcium solutions. We found that the PWK strain also has strong preferences for MgCl2and saccharin solutions but not representative salty, sour, bitter, or umami taste compounds. A genome scan of B6 × PWK F2mice linked a component of the strain difference in calcium and magnesium preference to distal chromosome 4. The taste receptor gene, Tas1r3, was implicated by studies with 129.B6ByJ- Tas1r3 congenic and Tas1r3 knockout mice. Most notably, calcium and magnesium solutions that were avoided by wild-type B6 mice were preferred (relative to water) by B6 mice null for the Tas1r3 gene. Oral calcium elicited less electrophysiological activity in the chorda tympani nerve of Tas1r3 knockout than wild-type mice. Comparison of the sequence of Tas1r3 with calcium and saccharin preferences in inbred mouse strains found 1) an inverse correlation between calcium and saccharin preference scores across primarily domesticus strains, which was associated with an I60T substitution in T1R3, and 2) a V689A substitution in T1R3 that was unique to the PWK strain and thus may be responsible for its strong calcium and magnesium preference. Our results imply that, in addition to its established roles in the detection of sweet and umami compounds, T1R3 functions as a gustatory calcium-magnesium receptor.
Expression of genes involved in excitatory neurotransmission in anoxic crucian carp (Carassius carassius) brain
Authors: Ellefsen Stian , Sandvik Guro K. , Larsen Helene K. , Stensløkken Kåre-Olav , Hov Dag Are S. , Kristensen Tom A. , Nilsson Göran E.
Published: July 2008

The crucian carp, Carassius carassius, survives months without oxygen. During anoxia it needs to keep energy expenditure low, particularly in the brain, with its high rate of ATP use related to neuronal activity. This could be accomplished by reducing neuronal excitability through altered expression of genes involved in excitatory neurotransmission. Through cloning and the use of a recently developed real-time RT-PCR approach, with an external RNA control for normalization, we investigated the effect of 1 and 7 days of anoxia (12°C) on the expression of 29 genes, including 8 3-hydroxy-5-methyl-4-isoxazole propionate (AMPA) receptor subunits, 6 N-methyl-d-aspartate (NMDA) receptor subunits, 7 voltage-gated sodium and calcium channels, 4 glutamate transporters, and 4 genes involved in NMDA receptor-mediated neuroplasticity. The subunits of the majority of the gene families had expression profiles similar to those observed in the mammalian brain and showed remarkably stable expression during anoxia. This suggests that the genes may have similar functions in crucian carp and mammals, and that the excitatory abilities of the crucian carp brain are retained during anoxia. Although the data generally argue against profound neural depression (“channel arrest”), NMDA receptor subunit (NR) expression showed features that could mediate reduced neural excitability. Primarily, the NR2 subunit expression, which was dominated by NR2B and NR2D, resembled that seen in hypoxia-tolerant neonatal rats, and decreased anoxic expression of NR1, NR2C, and NR3A indicated reduced numbers of functional NMDA receptors. We also report the full-length sequence of crucian carp NR1 mRNA and a novel NR1 splice cassette introducing an N-glycosylation site into the extracellular S1S2 domain.
Ancient and modern duplication events and the evolution of stearoyl-CoA desaturases in teleost fishes
Authors: Evans Helen , De Tomaso Tony , Quail Mike , Rogers Jane , Gracey Andrew Y. , Cossins Andrew R. , Berenbrink Michael
Published: July 2008

Stearoyl-CoA desaturases (SCDs) are key enzymes of fatty acid biosynthesis whose regulation underpins responses to dietary, thermal, and hormonal treatment. Although two isoforms are known to exist in the common carp and human and four in mouse, there is no coherent view on how this gene family evolved to generate functionally diverse members. Here we identify numerous new SCD homologs in teleost fishes, using sequence data from expressed sequence tag (EST) and cDNA collections and genomic model species. Phylogenetic analyses of the deduced coding sequences produced only partially resolved molecular trees. The multiple SCD isoforms were, however, consistent with having arisen by an ancient gene duplication event in teleost fishes together with a more recent duplication in the tetraploid carp and possibly also salmonid lineages. Critical support for this interpretation comes from comparison across all vertebrate groups of the gene order in the genomic environments of the SCD isoforms. Using syntenically aligned chromosomal fragments from large-insert clones of common carp and grass carp together with those from genomically sequenced model species, we show that the ancient and modern SCD duplication events in the carp lineage were each associated with large chromosomal segment duplications, both possibly linked to whole genome duplications. By contrast, the four mouse isoforms likely arose by tandem duplications. Each duplication in the carp lineage gave rise to differentially expressed SCD isoforms, either induced by cold or diet as previously shown for the recent duplicated carp isoforms or tissue specific as demonstrated here for the ancient duplicate zebrafish isoforms.
3D Space‐Time Visualization of Player Behaviour in Pervasive Location‐Based Games
Authors: Coulton Paul , Bamford Will , Cheverst Keith , Rashid Omer
Published: July 2008

Location‐based games not only offer new experiences for the players, but also present new challenges for researchers in terms of analyzing player behaviour. Whilst many ethnographical studies have presented useful qualitative insights into this area, there is the potential to both improve support for these studies and to provide more effective representations of the quantitative data that can often be extracted from the game itself in a manner that enables greater understanding. In this paper, we illustrate how combined spatial and temporal information can be represented using the human geographers′ technique of space-time paths to provide 3D visualizations of a player′s or players′ movement. Our analysis of a particular location‐based game shows how a richer understanding of overall game play is obtained and highlights the possibilities for using the technique for a whole range of location‐based services to provide a more complete view of complexities of journeys. Further, we discuss how these techniques can be utilized more generally by ethnographers who study the behaviour of mobile actors.
Neutrophil and Monocyte CD64 and CD163 Expression in Critically Ill Neonates and Children with Sepsis: Comparison of Fluorescence Intensities and Calculated Indexes
Authors: Groselj-Grenc Mojca , Ihan Alojz , Derganc Metka
Published: July 2008

Objective. To evaluate the expression of CD64 and CD163 on neutrophils and monocytes in SIRS with/without sepsis and to compare the diagnostic accuracy of CD64 and CD163 molecules expression determined as (1) mean fluorescence intensities (MFI) of CD64 and CD163; and (2) the ratio (index) of linearized MFI to the fluorescence signal of standardized beads. Patients and methods. Fifty‐six critically ill neonates and children with systemic inflammatory response syndrome (SIRS) and suspected sepsis, classified into two groups: SIRS with sepsis (n = 29) and SIRS without sepsis (n = 27). Results. CD64 and CD163 MFI measured on neutrophils and monocytes were elevated in patients with SIRS with sepsis. Diagnostic accuracy of indexes was equal to diagnostic accuracy of MFI for CD64 on neutrophils (0.833 versus 0.854 for day 0 and 0.975 versus 0.983 for day 1) and monocytes (0.811 versus 0.865 for day 0 and 0.825 versus 0.858 for day 1), and CD163 on neutrophils (0.595 versus 0.655 for day 0 and 0.677 versus 0.750 for day 1), but not for CD163 on monocytes. Conclusion. CD64 MFI, CD163 MFI, CD64 indexes for neutrophils and monocytes, and CD163 index for neutrophils can all be used for discrimination of SIRS and sepsis in critically ill neonates and children. CD64 index for neutrophils, however, is superior to all other markers.
Mechanisms of Nanoindentation on Multiwalled Carbon Nanotube and Nanotube Cluster
Authors: Liu Ling , Cao Guoxin , Chen Xi
Published: July 2008

Nanoindentation is a promising technique for deducing the elastic property of carbon nanotubes (CNTs). The paper presents an atomistic study on the nanoindentation mechanisms of single‐walled and multiwalled CNTs and CNT clusters, through which the deformation characteristics are linked with CNT elastic stiffness. The assembly of individual single‐walled CNTs (SWCNTs) into multiwalled CNTs (MWCNTs) and CNT clusters would significantly increase the buckling resistance in terms of withstanding the indentation load. Reverse analysis algorithms are proposed to extract the CNT stiffness by utilizing the indentation force‐depth data measured from the prebuckling regimes. The numerical studies carried out in this paper may be used to guide the nanoindentation experiments, explain and extract useful data from the test, as well as stimulate new experiments.
Applications of Fixed Point Theorems in the Theory of Generalized IFS
Authors: Mihail Alexandru , Miculescu Radu
Published: July 2008

We introduce the notion of a generalized iterated function system (GIFS), which is a finite family of functions "Equation missing", where "Equation missing" is a metric space and "Equation missing". In case that "Equation missing" is a compact metric space and the functions "Equation missing" are contractions, using some fixed point theorems for contractions from "Equation missing" to "Equation missing", we prove the existence of the attractor of such a GIFS and its continuous dependence in the "Equation missing"'s.
h‐Stability of Dynamic Equations on Time Scales with Nonregressivity
Authors: Choi Sung Kyu , Goo Yoon Hoe , Koo Namjip
Published: July 2008

We study the h‐stability of dynamic equations on time scales,
without the regressivity condition on the right‐hand side of dynamic equations.
This means that we can include noninvertible difference equations into our
results.
Insulin Resistance: A Proinflammatory State Mediated by Lipid‐Induced Signaling Dysfunction and Involved in Atherosclerotic Plaque Instability
Authors: Montecucco Fabrizio , Steffens Sabine , Mach François
Published: July 2008

The dysregulation of the insulin‐glucose axis represents the crucial event in insulin resistance syndrome. Insulin resistance increases atherogenesis and atherosclerotic plaque instability by inducing proinflammatory activities on vascular and immune cells. This condition characterizes several diseases, such as type 2 diabetes, impaired glucose tolerance (IGT), impaired fasting glucose (IFG), obesity, hypertension, dyslipidemia, and other endocrinopathies, but also cancer. Recent studies suggest that the pathophysiology of insulin resistance is closely related to interferences with insulin‐mediated intracellular signaling on skeletal muscle cells, hepatocytes, and adipocytes. Strong evidence supports the role of free fatty acids (FFAs) in promoting insulin resistance. The FFA‐induced activation of protein kinase C (PKC) delta, inhibitor kappaB kinase (IKK), or c‐Jun N‐terminal kinase (JNK) modulates insulin‐triggered intracellular pathway (classically known as PI3‐K‐dependent). Therefore, reduction of FFA levels represents a selective target for modulating insulin resistance.
Silicon Carbide Emitter Turn-Off Thyristor
Authors: Wang Jun , Wang Gangyao , Li Jun , Huang Alex Q. , Melcher Jerry , Atcitty Stan
Published: July 2008

A novel MOS-controlled SiC thyristor device, the SiC emitter turn-off thyristor (ETO) is a promising technology for future high-voltage switching applications because it integrates the excellent current conduction capability of a SiC thyristor with a simple MOS-control interface. Through unity-gain turn-off, the SiC ETO also achieves excellent Safe Operation Area (SOA) and faster switching speeds than silicon ETOs. The world's first 4.5-kV SiC ETO prototype shows a forward voltage drop of 4.26 V at 26.5 A/cm2 current density at room and elevated temperatures. Tested in an inductive circuit with a 2.5 kV DC link voltage and a 9.56-A load current, the SiC ETO shows a fast turn-off time of 1.63 microseconds and a low 9.88 mJ turn-off energy. The low switching loss indicates that the SiC ETO could operate at about 4 kHz if 100 W/cm2 conduction and the 100 W/cm2 turn-off losses can be removed by the thermal management system. This frequency capability is about 4 times higher than 4.5-kV-class silicon power devices. The preliminary demonstration shows that the SiC ETO is a promising candidate for high-frequency, high-voltage power conversion applications, and additional developments to optimize the device for higher voltage (>5 kV) and higher frequency (10 kHz) are needed.
Emerin and the Nuclear Lamina in Muscle and Cardiac Disease
Authors: Holaska James M.
Published: July 2008

The human genome is contained within the nucleus and is separated from the cytoplasm by the nuclear envelope. Mutations in the nuclear envelope proteins emerin and lamin A cause a number of diseases including premature aging syndromes, muscular dystrophy, and cardiomyopathy. Emerin and lamin A are implicated in regulating muscle- and heart-specific gene expression and nuclear architecture. For example, lamin A regulates the expression and localization of gap junction and intercalated disc components. Additionally, emerin and lamin A are also required to maintain nuclear envelope integrity. Demonstrating the importance of maintaining nuclear integrity in heart disease, atrioventricular node cells lacking lamin A exhibit increased nuclear deformation and apoptosis. This review highlights the present understanding of lamin A and emerin function in regulating nuclear architecture, gene expression, and cell signaling and discusses putative mechanisms for how specific mutations in lamin A and emerin cause cardiac- or muscle-specific disease.
The Contribution of Ex–Tropical Cyclone Gert (1999) toward the Weakening of a Midlatitude Cyclogenesis Event
Authors: Agustí-Panareda Anna
Published: July 2008

Tropical Cyclone Gert (1999) experienced an extratropical transition while it merged with an extratropical cyclone upstream. The upstream extratropical cyclone had started to intensify before it merged with the transitioning tropical cyclone, and it continued intensifying afterward (12 hPa in 12 h, according to the Met Office analysis). The question addressed in this paper is the following: what was the impact of the transitioning tropical cyclone on this intensification of the upstream extratropical cyclone? Until now, in the literature, tropical cyclones that experience extratropical transition have been found to have either no impact or a positive impact on the development of extratropical cyclogenesis events. The positive impact involves either a triggering of the development of the extratropical cyclone or simply a contribution to its deepening. However, the case studied here proves to have a negative impact on the developing extratropical cyclone upstream by diminishing its intensification. Forecasts are performed with and without the tropical cyclone in the initial conditions. They show that when Gert is not present in the initial conditions, the peak intensity of the cyclone upstream occurs 9 h earlier and it is 10 hPa deeper than when Gert is present. Thus, Gert acts to weaken the development by contributing to the filling of the extratropical surface low upstream. Quasigeostropic (QG) diagnostics show that the negative impact on the extratropical development is linked to the fact that the transitioning tropical cyclone interacts with a warm front inducing a negative QG vertical velocity over the developing extratropical low upstream. This interpretation is consistent with other contrasting cases in which the transitioning tropical cyclone interacts with a cold front and induces a positive QG vertical velocity over the developing low upstream, thus enhancing its development. The results are also in agreement with idealized experiments in the literature that are aimed at studying the predictability of extratropical storms. These idealized experiments yielded similar results using synoptic-scale and mesoscale vortices as perturbations on warm and cold fronts.
Contributions of Mixed Physics versus Perturbed Initial/Lateral Boundary Conditions to Ensemble-Based Precipitation Forecast Skill
Authors: Clark Adam J. , Gallus William A. , Chen Tsing-Chang
Published: July 2008

An experiment is described that is designed to examine the contributions of model, initial condition (IC), and lateral boundary condition (LBC) errors to the spread and skill of precipitation forecasts from two regional eight-member 15-km grid-spacing Weather Research and Forecasting (WRF) ensembles covering a 1575 km × 1800 km domain. It is widely recognized that a skillful ensemble [i.e., an ensemble with a probability distribution function (PDF) that generates forecast probabilities with high resolution and reliability] should account for both error sources. Previous work suggests that model errors make a larger contribution than IC and LBC errors to forecast uncertainty in the short range before synoptic-scale error growth becomes nonlinear. However, in a regional model with unperturbed LBCs, the infiltration of the lateral boundaries will negate increasing spread. To obtain a better understanding of the contributions to the forecast errors in precipitation and to examine the window of forecast lead time before unperturbed ICs and LBCs begin to cause degradation in ensemble forecast skill, the “perfect model” assumption is made in an ensemble that uses perturbed ICs and LBCs (PILB ensemble), and the “perfect analysis” assumption is made in another ensemble that uses mixed physics–dynamic cores (MP ensemble), thus isolating the error contributions. For the domain and time period used in this study, unperturbed ICs and LBCs in the MP ensemble begin to negate increasing spread around forecast hour 24, and ensemble forecast skill as measured by relative operating characteristic curves (ROC scores) becomes lower in the MP ensemble than in the PILB ensemble, with statistical significance beginning after forecast hour 69. However, degradation in forecast skill in the MP ensemble relative to the PILB ensemble is not observed in an analysis of deterministic forecasts calculated from each ensemble using the probability matching method. Both ensembles were found to lack statistical consistency (i.e., to be underdispersive), with the PILB ensemble (MP ensemble) exhibiting more (less) statistical consistency with respect to forecast lead time. Spread ratios in the PILB ensemble are greater than those in the MP ensemble at all forecast lead times and thresholds examined; however, ensemble variance in the MP ensemble is greater than that in the PILB ensemble during the first 24 h of the forecast. This discrepancy in spread measures likely results from greater bias in the MP ensemble leading to an increase in ensemble variance and decrease in spread ratio relative to the PILB ensemble.
Analysis of the Wind Field Evolution Associated with the Extratropical Transition of Bonnie (1998)
Authors: Evans Clark , Hart Robert E.
Published: July 2008

Extratropical transition brings about a number of environmentally induced structural changes within a transitioning tropical cyclone. Of particular interest among these changes is the acceleration of the wind field away from the cyclone’s center of circulation along with the outward movement of the radial wind maximum, together termed wind field expansion. Previous informal hypotheses aimed at understanding this evolution do not entirely capture the observed expansion, while a review of the literature shows no formal work done upon the topic beyond analyzing its occurrence. This study seeks to analyze the physical and dynamical mechanisms behind the wind field expansion using model simulations of a representative transition case, North Atlantic Tropical Cyclone Bonnie of 1998. The acceleration of the wind field along the outer periphery of the cyclone is found to be a function of the net import of absolute angular momentum within the cyclone’s environment along inflowing trajectories. This evolution is shown to be a natural outgrowth of the development of isentropic conveyor belts and asymmetries associated with extratropical cyclones. Asymmetries in the outer-core wind field manifest themselves via the tightening and development of height and temperature gradients within the cyclone’s environment. Outward movement of the radial wind maximum occurs coincident with integrated net cooling found inside the radius of maximum winds. Tests using a secondary circulation balance model show the radial wind maximum evolution to be similar yet opposite to the response noted for intensifying tropical cyclones with contracting eyewalls.