bluuebunny/crossref_metadata_2025 huggingface dataset:
Scalable VPN routing via relaying
Authors: Kim Changhoon , Gerber Alexandre , Lund Carsten , Pei Dan , Sen Subhabrata
Published: July 2008

Enterprise customers are increasingly adopting MPLS (Multiprotocol Label Switching) VPN (Virtual Private Network) service that offers direct any-to-any reachability among the customer sites via a provider network. Unfortunately this direct reachability model makes the service provider's routing tables grow very large as the number of VPNs and the number of routes per customer increase. As a result, router memory in the provider's network has become a key bottleneck in provisioning new customers. This paper proposes Relaying, a scalable VPN routing architecture that the provider can implement simply by modifying the configuration of routers in the provider network, without requiring changes to the router hardware and software. Relaying substantially reduces the memory footprint of VPNs by choosing a small number of hub routers in each VPN that maintain full reachability information, and by allowing non-hub routers to reach other routers through a hub. Deploying Relaying in practice, however, poses a challenging optimization problem that involves minimizing router memory usage by having as few hubs as possible, while limiting the additional latency due to indirect delivery via a hub. We first investigate the fundamental tension between the two objectives and then develop algorithms to solve the optimization problem by leveraging some unique properties of VPNs, such as sparsity of traffic matrices and spatial locality of customer sites. Extensive evaluations using real traffic matrices, routing configurations, and VPN topologies demonstrate that Relaying is very promising and can reduce routing-table usage by up to 90%, while increasing the additional distances traversed by traffic by only a few hundred miles, and the backbone bandwidth usage by less than 10%.
Densification arising from sampling fixed graphs
Authors: Pedarsani Pedram , Figueiredo Daniel R. , Grossglauser Matthias
Published: July 2008

During the past decade, a number of different studies have identified several peculiar properties of networks that arise from a diverse universe, ranging from social to computer networks. A recently observed feature is known as network densification, which occurs when the number of edges grows much faster than the number of nodes, as the network evolves over time. This surprising phenomenon has been empirically validated in a variety of networks that emerge in the real world and mathematical models have been recently proposed to explain it. Leveraging on how real data is usually gathered and used, we propose a new model called Edge Sampling to explain how densification can arise. Our model is innovative, as we consider a fixed underlying graph and a process that discovers this graph by probabilistically sampling its edges. We show that this model possesses several interesting features, in particular, that edges and nodes discovered can exhibit densification. Moreover, when the node degree of the fixed underlying graph follows a heavy-tailed distribution, we show that the Edge Sampling model can yield power law densification, establishing an approximate relationship between the degree exponent and the densification exponent. The theoretical findings are supported by numerical evaluations of the model. Finally, we apply our model to real network data to evaluate its performance on capturing the previously observed densification. Our results indicate that edge sampling is indeed a plausible alternative explanation for the densification phenomenon that has been recently observed.
Xengine
Authors: Liu Alex X. , Chen Fei , Hwang JeeHyun , Xie Tao
Published: July 2008

XACML has become the de facto standard for specifying access control policies for various applications, especially web services. With the explosive growth of web applications deployed on the Internet, XACML policies grow rapidly in size and complexity, which leads to longer request processing time. This paper concerns the performance of request processing, which is a critical issue and so far has been overlooked by the research community. In this paper, we propose XEngine, a scheme for efficient XACML policy evaluation. XEngine first converts a textual XACML policy to a numerical policy. Second, it converts a numerical policy with complex structures to a numerical policy with a normalized structure. Third, it converts the normalized numerical policy to tree data structures for efficient processing of requests. To evaluate the performance of XEngine, we conducted extensive experiments on both real-life and synthetic XACML policies. The experimental results show that XEngine is orders of magnitude more efficient than Sun PDP, and the performance difference between XEngine and Sun PDP grows almost linearly with the number of rules in XACML policies. For XACML policies of small sizes (with hundreds of rules), XEngine is one to two orders of magnitude faster than the widely deployed Sun PDP. For XACML policies of large sizes (with thousands of rules), XEngine is three to four orders of magnitude faster than Sun PDP.
Epidemic live streaming
Authors: Bonald Thomas , Massoulié Laurent , Mathieu Fabien , Perino Diego , Twigg Andrew
Published: July 2008

Several peer-to-peer systems for live streaming have been recently deployed (e.g. CoolStreaming, PPLive, SopCast). These all rely on distributed, epidemic-style dissemination mechanisms. Despite their popularity, the fundamental performance trade-offs of such mechanisms are still poorly understood. In this paper we propose several results that contribute to the understanding of such trade-offs.

Specifically, we prove that the so-called random peer, latest useful chunk mechanism can achieve dissemination at an optimal rate and within an optimal delay, up to an additive constant term. This qualitative result suggests that epidemic live streaming algorithms can achieve near-unbeatable rates and delays. Using mean-field approximations, we also derive recursive formulas for the diffusion function of two schemes referred to as latest blind chunk, random peer and latest blind chunk, random useful peer.

Finally, we provide simulation results that validate the above theoretical results and allow us to compare the performance of various practically interesting diffusion schemes terms of delay, rate, and control overhead. In particular, we identify several peer/chunk selection algorithms that achieve near-optimal performance trade-offs. Moreover, we show that the control overhead needed to implement these algorithms may be reduced by restricting the neighborhood of each peer without substantial performance degradation.
Noncooperative power control and transmission scheduling in wireless collision channels
Authors: Menache Ishai , Shimkin Nahum
Published: July 2008

We consider a wireless collision channel, shared by a finite number of mobile users who transmit to a common base station using a random access protocol. Mobiles are self-optimizing, and wish to minimize their individual average power investment subject to minimum-throughput demand. The channel state between each mobile and the base station is stochastically time-varying and is observed by the mobile prior to transmission. Given the current channel state, a mobile may decide whether to transmit or not, and to determine the transmission power in case of transmission. In this paper, we investigate the properties of the Nash equilibrium of the resulting game in multiuser networks.

We characterize the best-response strategy of the mobile and show that it leads to a "water-filling"-like power allocation. Our equilibrium analysis then reveals that one of the possible equilibria is uniformly best for all mobiles. Furthermore, this equilibrium can be reached by a simple distributed mechanism that does not require specific information on other mobiles' actions. We then explore some additional characteristics of the distributed power control framework. Braess-like paradoxes are reported, where the use of multiple power levels can diminish system capacity and also lead to larger per-user power consumption, compared to the case where a single level only is permitted.
Software-directed combined cpu/link voltage scaling fornoc-based cmps
Authors: Kandemir Mahmut , Ozturk Ozcan
Published: July 2008

Network-on-Chip (NoC) based chip multiprocessors (CMPs) are expected to become more widespread in future, in both high performance scientific computing and low-end embedded computing. For many execution environments that employ these systems, reducing power consumption is an important goal. This paper presents a software approach for reducing power consumption in such systems through compiler-directed voltage/frequency scaling. The unique characteristic of this approach is that it scales the voltages and frequencies of select CPUs and communication links in a coordinated manner to maximize energy savings without degrading performance. Our approach has three important components. The first component is the identification of phases in the application. The next step is to determine the critical execution paths and slacks in each phase. For implementing these two components, our approach employs a novel parallel program representation. The last component of our approach is the assignment of voltages and frequencies to CPUs and communication links to maximize energy savings. We use integer linear programming (ILP) for this voltage/frequency assignment problem. To test our approach, we implemented it within a compilation framework and conducted experiments with applications from the SPEComp suite and SPECjbb. Our results show that the proposed combined CPU/link scaling is much more effective than scaling voltages of CPUs or communication links in isolation. In addition, we observed that the energy savings obtained are consistent across a wide range of values of our major simulation parameters such as the number of CPUs, the number of voltage/frequency levels, and the thread-to-CPU mapping.
Traffic capacity of multi-cell WLANS
Authors: Bonald Thomas , Ibrahim Ali , Roberts James
Published: July 2008

Performance of WLANs has been extensively studied during the past few years. While the focus has mostly been on isolated cells, the coverage of WLANs is in practice most often realised through several cells. Cells using the same frequency channel typically interact through the exclusion region enforced by the RTS/CTS mechanism prior to the transmission of any packet.

In this paper, we investigate the impact of this interaction on the overall network capacity under realistic dynamic traffic conditions. Specifically, we represent each cell as a queue and derive the stability condition of the corresponding coupled queuing system. This condition is then used to calculate the network capacity. To gain insight into the particular nature of interference in multi-cell WLANs, we apply our model to a number of simple network topologies and explicitly derive the capacity in several cases. The results notably show that the capacity gain obtained by using M frequency channels can grow significantly faster than M, the rate one might intuitively expect. In addition to stability results, we present an approximate model to derive the impact of network load on the mean transfer rate seen by the users.
An independent H-TCP implementation under FreeBSD 7.0
Authors: Armitage Grenville , Stewart Lawrence , Welzl Michael , Healy James
Published: July 2008

A key requirement for IETF recognition of new TCP algorithms is having an independent, interoperable implementation. This paper describes our BSD-licensed implementation of H-TCP within FreeBSD 7.0, publicly available as a dynamically loadable kernel module. Based on our implementation experience we provide a summary description of the H-TCP algorithm to assist other groups build further interoperable implementations. Using data from our live testbed we demonstrate that our version exhibits expected H-TCP behavior, and describe a number of implementation-specific issues that influence H-TCP's dynamic behavior. Finally, we illustrate the actual collateral impact on path latency of using H-TCP instead of NewReno. In particular we illustrate how, compared to NewReno, H-TCP's cwnd growth strategy can cause faster fluctuations in queue sizes at, yet lower median latency through, congestion points. We believe these insights will prove valuable predictors of H-TCP's potential impact if deployed in consumer end-hosts in addition to specialist, high-performance network environments.
Empirical evaluation of hash functions for multipoint measurements
Authors: Henke Christian , Schmoll Carsten , Zseby Tanja
Published: July 2008

A broad spectrum of network measurement applications demand passive multipoint measurements in which data from multiple observation points has to be correlated. Examples are the passive measurement of one-way delay or the observation of the path that a packet takes through a network. Nevertheless, due to high data rates and the need for fine granular measurements, the resource consumption for passive measurements can be immense. Furthermore, the resource consumption depends on the traffic in the network, which usually is highly dynamic. Packet and flow-selection methods provide a solution to reduce and control the resource consumption for passive measurements. In order to apply such techniques to multipoint measurements the selection processes need to be synchronized. Hash-based selection is a deterministic packet selection based on a hash function computed on selected parts of the packet content. This selection decision is consistent throughout the network and enables packet tracing and the measurement of delay between network nodes. Because the selection is based on deterministic function it can introduce bias which leads to wrong estimation of traffic characteristics. In this paper we define a set of quality criteria and select methods to investigate which hash function is most suitable for hash-based packet selection. We analyze 23 non-cryptographic and 2 cryptographic hash functions. Experiments are performed with real traffic traces from different networks. Based on the results we recommend 2 fast hash functions which show low bias and sample a representative subset of the population.
Message-efficient dissemination for loop-free centralized routing
Authors: Peterson Haldane , Sen Soumya , Chandrashekar Jaideep , Gao Lixin , Guerin Roch , Zhang Zhi-Li
Published: July 2008

With steady improvement in the reliability and performance of communication devices, routing instabilities now contribute to many of the remaining service degradations and interruptions in modern networks. This has led to a renewed interest in centralized routing systems that, compared to distributed routing, can provide greater control over routing decisions and better visibility of the results. One benefit of centralized control is the opportunity to readily eliminate transient routing loops, which arise frequently after network changes because of inconsistent routing states across devices. Translating this conceptual simplicity into a solution with tolerable message complexity is non-trivial. Addressing this issue is the focus of this paper. We identify when and why avoiding transient loops might require a significant number of messages in a centralized routing system, and demonstrate that this is the case under many common failure scenarios. We also establish that minimizing the number of required messages is NP-hard, and propose a greedy heuristic that we show to perform well under many conditions. The paper's results can facilitate the deployment and evaluation of centralized architectures by leveraging their strengths without incurring unacceptable overhead.
Examining the data on computer ethics in the classroom
Authors: Spradling Carol
Published: July 2008

I currently serve on the ACM Education Council as the representative for SIGCAS. I have taught in a Computer Science/Information Systems department at a small midwestern university for approximately 20 years, where I mainly teach courses on computer ethics, databases, programming and multimedia.
PPAR‐γ: Therapeutic Potential for Multiple Sclerosis
Authors: Drew Paul D. , Xu Jihong , Racke Michael K.
Published: June 2008

The role of peroxisome proliferator‐activated receptors (PPARs) in altering lipid and glucose metabolism is well established. More recent studies indicate that PPARs also play critical roles in controlling immune responses. We and others have previously demonstrated that PPAR‐γ agonists modulate the development of experimental autoimmune encephalomyelitis (EAE), an animal model of multiple sclerosis (MS). This review will discuss the cellular and molecular mechanisms by which these agonists are believed to modulate disease. The therapeutic potential of PPAR‐γ agonists in the treatment of multiple sclerosis will also be considered.
Rechtsgeschichtliches Zur Hinrichtung Des Zebedäiden Jakobus (APGxii,2)
Authors: Blinzler Josef
Published: June 2008

Die Apostelgeschichte berichtet von der Hinrichtung des Zebedäiden Jakobus nur in einer auffallend knappen Notiz (xii 2) 1). Auch die Kommentare pflegen darüber nicht viel Worte zu verlieren. Und doch gibt der Text dem rechtsgeschichtlich interessierten Leser zu einigen Überlegungen Anlaß.
Classification of Cyclone Tracks over the Apennines and the Adriatic Sea
Authors: Horvath Kristian , Lin Yuh-Lang , Ivančan-Picek Branka
Published: July 2008

Cyclones that appear in the Adriatic Sea basin strongly influence the climate and weather conditions in the area. In particular, apart from the usually mild climate, cyclone activity in the Adriatic and the central Mediterranean Sea provide both the main hydrological forcing and the trigger mechanisms for a range of extreme weather phenomena. Therefore, a basic understanding of the cyclogenesis over the Adriatic Sea is essential. In particular, the classification of different types of cyclogenesis in the area is fundamental because it will help the understanding and prediction of the relevant weather phenomena. In this study, based on the analysis of the 4-yr (2002–05) operational European Centre for Medium-Range Weather Forecasts T511 dataset, various types of cyclone tracks are classified and the mesocyclogenesis areas in the vicinity of the Adriatic Basin are isolated. This analysis indicates that the following four types of cyclogenesis over the Adriatic Sea can be identified: 1) type A: cyclones connected with preexisting Genoa cyclones [with two subcategories, (A-I) continuous track: Genoa cyclones crossing over the Apennines to the Adriatic Sea, and (A-II) discontinuous track: new surface cyclones generated over the Adriatic Sea under the influence of a parent cyclone generated in the Gulf of Genoa (Genoa cyclones) and moving toward the Adriatic but blocked by the Apennines]; 2) type B: cyclones developed in situ over the Adriatic Sea without any connections with other preexisting cyclones in the surrounding area; 3) type AB: mixed types A and B cyclones, including cases where two cyclones coexist and stride over the Apennines (twin or eyeglass cyclones); and 4) type C: cyclones moving from the Mediterranean Sea, but not from the Gulf of Genoa (non-Genoa cyclones) [with 2 subcategories: (C-I) continuous track: a non-Genoa cyclone is able to cross over the Apennines to the Adriatic Sea continuously, and (C-II) discontinuous track: a non-Genoa cyclone is blocked by the Apennines and a new surface cyclone is generated over the Adriatic Sea]. The relevant dynamics of the above types of cyclones are discussed along with characteristics of the cyclones and their synoptic situations at the lower and upper troposphere.
Comparison of WRF Model-Simulated and MODIS-Derived Cloud Data
Authors: Otkin Jason A. , Greenwald Thomas J.
Published: July 2008

In this study, the ability of different combinations of bulk cloud microphysics and planetary boundary layer (PBL) parameterization schemes implemented in the Weather Research and Forecasting Model to realistically simulate the wide variety of cloud types associated with an extratropical cyclone is examined. An ensemble of high-resolution model simulations was constructed for this case using four microphysics and two PBL schemes characterized by different levels of complexity. Simulated cloud properties, including cloud optical thickness, cloud water path, cloud-top pressure, and radiative cloud phase, were subsequently compared to cloud data from three Moderate Resolution Imaging Spectroradiometer (MODIS) overpasses across different portions of the domain. A detailed comparison of the simulated datasets revealed that the PBL and cloud microphysics schemes both exerted a strong influence on the spatial distribution and physical properties of the simulated cloud fields. In particular, the low-level cloud properties were found to be very sensitive to the PBL scheme while the upper-level clouds were sensitive to both the microphysics and PBL schemes. Overall, the simulated cloud properties were broadly similar to the MODIS observations, with the most realistic cloud fields produced by the more sophisticated parameterization schemes.
Response of a Subtropical Stratocumulus-Capped Mixed Layer to Climate and Aerosol Changes
Authors: Caldwell Peter , Bretherton Christopher S.
Published: June 2008

In this paper, an idealized framework based on a cloud-topped mixed layer model is developed for investigating feedbacks between subtropical stratocumulus (Sc) and global warming. The two principal control parameters are Sc-region sea surface temperature (SST) and intertropical convergence zone (ITCZ) SST (which controls the temperature and mean subsidence profiles above the Sc). The direct effect of CO2 doubling (leaving all other parameters fixed) is tested and found to somewhat reduce liquid water path; discussion of this effect on the SST-change simulations is included. The presence of a cold boundary layer is found to significantly affect the temperature and subsidence rate just above cloud top by enhancing lower-tropospheric diabatic cooling in this region. A simple representation of this effect (easily generalizable to a more realistic boundary layer model) is developed.

Steady-state solutions are analyzed as a function of local and ITCZ SST. Two climate change scenarios are considered. The first scenario is an equal increase of local and ITCZ SSTs. In this case, predicted boundary layer depth and cloud thickness increase. This is found in a simplified context to result from subsidence and entrainment decreases due to increased static stability in a warmer climate. In the second case, local SST change is diagnosed from a surface energy balance under the assumption that ocean heat transport remains unchanged. In this case, predicted boundary layer depth decreases. Cloud continues to thicken with rising ITCZ SST, but at a rate much reduced in comparison to the equal-warming scenario. This cloud shading feedback keeps SST in the Sc region nearly constant as the ITCZ SST increases.

Model sensitivity to aerosol indirect effects is also considered by varying the assumed droplet concentration. The resulting change in liquid water path is small, suggesting a weaker dependence on second indirect effect than found in previous studies.
Virtual Field Campaigns on Deep Tropical Convection in Climate Models
Authors: Mapes Brian , Bacmeister Julio , Khairoutdinov Marat , Hannay Cecile , Zhao Ming
Published: June 2008

High-resolution time–height data over warm tropical oceans are examined, from three global atmosphere models [GFDL’s Atmosphere Model 2 (AM2), NCAR’s Community Atmosphere Model, version 3 (CAM3), and a NASA Global Modeling and Assimilation Office (GMAO) model], field campaign observations, and observation-driven cloud model outputs. The character of rain events is shown in data samples and summarized in lagged regressions versus surface rain rate. The CAM3 humidity and cloud exhibit little vertical coherence among three distinct layers, and its rain events have a short characteristic time, reflecting the convection scheme’s penetrative nature and its closure’s concentrated sensitivity to a thin boundary layer source level. In contrast, AM2 rain variations have much longer time scales as convection scheme plumes whose entrainment gives them tops below 500 hPa interact with humidity variations in that layer. Plumes detraining at model levels above 500 hPa are restricted by cloud work function thresholds, and upper-tropospheric humidity and cloud layers fed by these are detached from the lower levels and are somewhat sporadic. With these discrete entrainment rates and instability thresholds, AM2 also produces some synthetic-looking noise (sharp features in height and time) on top of its slow rain variations. A distinctive feature of the NASA model is a separate anvil scheme, distinct from the main large-scale cloud scheme, fed by relaxed Arakawa–Schubert (RAS) plume ensemble convection (a different implementation than in AM2). Its variability is rich and vertically coherent, and involves a very strong vertical dipole component to its tropospheric heating variations, of both signs (limited-depth convective heating and top-heavy heating in strong deep events with significant nonconvective rain). Grid-scale saturation events occur in all three models, often without nonconvective surface rain, causing relatively rare episodes of large negative top-of-atmosphere cloud forcing. Overall, cloud forcing regressions show a mild net positive forcing by rain-correlated clouds in CAM3 and mild net cooling in the other models, as the residual of large canceling shortwave and longwave contributions.
Intraseasonal Land–Atmosphere Coupling in the West African Monsoon
Authors: Taylor Christopher M.
Published: June 2008

Via its impact on surface fluxes, subseasonal variability in soil moisture has the potential to feed back on regional atmospheric circulations, and thereby rainfall. An understanding of this feedback mechanism in the climate system has been hindered by the lack of observations at an appropriate scale. In this study, passive microwave data at 10.65 GHz from the Tropical Rainfall Measuring Mission satellite are used to identify soil moisture variability during the West African monsoon. A simple model of surface sensible heat flux is developed from these data and is used, alongside atmospheric analyses from the European Centre for Medium-Range Weather Forecasting (ECMWF), to provide a new interpretation of monsoon variability on time scales of the order of 15 days. During active monsoon periods, the data indicate extensive areas of wet soil in the Sahel. The impact of the resulting weak surface heat fluxes is consistent in space and time with low-level variations in atmospheric heating and vorticity, as depicted in the ECMWF analyses. The surface-induced vorticity structure is similar to previously documented intraseasonal variations in the monsoon flow, notably a westward-propagating vortex at low levels. In those earlier studies, the variability in low-level flow was considered to be the critical factor in producing intraseasonal fluctuations in rainfall. The current analysis shows that this vortex can be regarded as an effect of the rainfall (via surface hydrology) as well as a cause.
North Atlantic Hurricanes Contributed by African Easterly Waves North and South of the African Easterly Jet
Authors: Chen Tsing-Chang , Wang Shih-Yu , Clark Adam J.
Published: June 2008

A majority of tropical cyclones in the North Atlantic develop from African easterly waves (AEWs), which originate along both the southern and northern flanks of the midtropospheric African easterly jet (AEWS and AEWn, respectively). The purpose of this note is to identify the contribution of AEWSs and AEWns to North Atlantic tropical cyclones that develop from AEWs. Applying a manual backtracking approach to identify the genesis locations of AEWS, it was found that the population ratio of tropical cyclones formed from AEWSs to those formed from AEWns is 1:1.2. Because the population ratio of AEWSs to AEWns is 1:2.5, the conversion rate of the former AEWS to tropical cyclones is twice as effective as the latter waves. In addition, it was found that AEWns travel farther and take longer to transform into tropical cyclones than AEWSs, which is likely because the AEWns are drier and shallower than AEWSs. An analysis of various terms in the moisture and vorticity budgets reveals that the monsoon trough over West Africa provides moisture and enhances low-level vorticity for both AEWns and AEWSs as they move off the West African coast. The monsoon trough appears to be of particular importance in supplying AEWns with enough moisture so that they have similar properties to AEWSs after they have traveled a considerable westward distance across the tropical Atlantic.
Current-Induced Modulation of the Ocean Wave Spectrum and the Role of Nonlinear Energy Transfer
Authors: Tamura Hitoshi , Waseda Takuji , Miyazawa Yasumasa , Komatsu Kosei
Published: June 2008

Numerical simulations were performed to investigate current-induced modulation of the spectral and statistical properties of ocean waves advected by idealized and realistic current fields. In particular, the role of nonlinear energy transfer among waves in wave–current interactions is examined. In this type of numerical simulation, it is critical to treat the nonlinear transfer function (Snl) properly, because a rigorous Snl algorithm incurs a huge computational cost. However, the applicability of the widely used discrete interaction approximation (DIA) method is strictly limited for complex wave fields. Therefore, the simplified RIAM (SRIAM) method is implemented in an operational third-generation wave model. The method approximates an infinite resonant quadruplet with 20 optimized resonance configurations. The performance of the model is assessed by applying it to fetch-limited wave growth and wave propagation against a shear current. Numerical simulations using the idealized current field revealed that the Snl retained spectral form by redistributing the refracted wave energy; this suggests that energy concentration due to ray focusing is dispersed via the self-stabilization effect of nonlinear transfer. A hindcast simulation using wind and current reanalysis data indicated that the difference in the average monthly wave height was substantial and that instantaneous wave–current interactions were highly sensitive to small current structures. Spectral shape was also modulated, and the spatial distributions of the directional bandwidth with or without current data were completely different. Moreover, the self-stabilization effect of the Snl was also confirmed in a realistic situation. These results indicate that a realistic representation of the current field is crucial for high-resolution wave forecasting.
CAPE and Convective Events in the Southwest during the North American Monsoon
Authors: Adams David K. , Souza Enio P.
Published: June 2008

The relationship between atmospheric stability, measured as CAPE, and deep precipitating convection has been widely studied but is not definitive. In the maritime tropics, CAPE and precipitation are usually inversely correlated. In continental convection (i.e., midlatitude and tropical), no consistent relationship has been found. In this study of the semiarid Southwest, a moderate positive correlation exists, approaching 0.6. Correlations based on radiosonde data are found to be sensitive to the parcel level of origin. The strongest correlations are found by modifying the preconvective morning sounding with the maximum reported surface temperature, assuming well-mixed adiabatic layers to the level of free convection with pseudoadiabatic ascent. These results show that the upper bounds on parcel instability correlate best with precipitation. Furthermore, the CAPE–precipitation relationship is argued to depend on the convective regime being considered. The North American monsoon convective regime requires essentially only moisture advection interacting with the strong surface sensible heating over complex topography. Elimination of strong convective inhibition through intense surface sensible heating in the presence of sufficient water vapor leads to the positive CAPE–precipitation relationship on diurnal time scales. These results are discussed in light of contradictory results from other continental and maritime regions, which demonstrate negative correlations.
Understanding Satellite-Observed Mountain-Wave Signatures Using High-Resolution Numerical Model Data
Authors: Feltz W. F. , Bedka K. M. , Otkin J. A. , Greenwald T. , Ackerman S. A.
Published: June 2008

Prior work has shown that pilot reports of severe turbulence over Colorado often occur when complex interference or crossing wave patterns are present in satellite water vapor imagery downstream of the Rocky Mountains. To improve the understanding of these patterns, a high-resolution (1-km) Weather Research and Forecasting (WRF) model simulation was performed for an intense mountain-wave event that occurred on 6 March 2004. Synthetic satellite imagery was subsequently generated by passing the model-simulated data through a forward radiative transfer model. Comparison with concurrent Moderate Resolution Imaging Spectroradiometer (MODIS) water vapor imagery demonstrates that the synthetic satellite data realistically captured many of the observed mesoscale features, including a mountain-wave train extending far downstream of the Colorado Front Range, the deformation of this wave train by an approaching cold front, and the substantially warmer brightness temperatures in the lee of the major mountain ranges composing the Colorado Rockies. Inspection of the model data revealed that the mountain waves redistributed the water vapor within the lower and middle troposphere, with the maximum column-integrated water vapor content occurring one-quarter wavelength downstream of the maximum ascent within each mountain wave. Due to this phase shift, the strongest vertical motions occur halfway between the locally warm and cool brightness temperature couplets in the water vapor imagery. Interference patterns seen in the water vapor imagery appear to be associated with mesoscale variability in the ambient wind field at or near mountaintop due to flow interaction with the complex topography. It is also demonstrated that the synergistic use of multiple water vapor channels provides a more thorough depiction of the vertical extent of the mountain waves since the weighting function for each channel peaks at a different height in the atmosphere.
Beneath the Surface of the Therapeutic Interaction: the Psychoanalytic Method in Modern Dress
Authors: Bucci Wilma , Maskit Bernard
Published: July 2008

This study represents a new generation of psychotherapy process research, using multiple perspectives on the data of the analytic situation, including impressions of the treating analyst, ratings of complete sessions by clinical judges, and objective linguistic measures. Computerized measures of language style developed in the framework of multiple code theory were applied to verbatim session recordings from a psychoanalytic case; the measures are illustrated in microanalyses of the process in two sessions. The results show agreement between the linguistic measures and clinical ratings based on a psychoanalytic perspective. The linguistic measures look beneath the surface of the therapeutic interaction by relying largely on lexical items of which clinicians are not likely to be explicitly aware, and enable a new perspective on the therapeutic discourse as seen in the graphic images of the microprocess. While the results of this study were limited to a single case, the automatized measures can be readily applied to large samples and in repeated single case designs. Two goals of process research, using measures such as those developed in this study, are discussed: to develop measures of mediating variables that can be used to identify specific treatment effects in comparative outcome studies; and, beyond this pragmatic aim, to assess development of capacities for self-exploration and self-regulation as psychoanalytic treatment goals.
Motivation Orientations, Academic Achievement, and Career Goals of Undergraduate Music Education Majors
Authors: Schmidt Charles P , Zdzinski Stephen F. , Ballard Dennis L.
Published: July 2008

This study is an examination of motivation orientations (mastery, intrinsic, cooperative, individual, competition, ego, approach success, avoid failure, hypercompetition, personal development competition) and musical self-concept in relation to measures of academic achievement and career goals of preservice music teachers. The research questions addressed (a) relations among motivation and self-concept variables and their underlying factors, and (b) relations between the motivation and self-concept variables and academic achievement, class level, sex, and immediate and long-term career goals. Participants were 148 undergraduate music education majors from three American universities. A survey was administered to measure the motivation constructs and to gather information concerning academic achievement, demographic variables, and career goals. Of the subjects surveyed, 69. 4 % reported public school teaching as an immediate career goal, and 49.3 % reported it as a long-term goal. Significantly greater numbers of women (62.7%) than men (3 7.3 %) indicated public school teaching as the long term goal. Means for self concept in music dif fered by university, while means for motivation and frequencies for career goals did not. Factor analysis revealed five factors: Competitive/Ego, Achieve Success/Avoid Failure, Cooperative vs. Individual, Intrinsic/Mastery, and Personal Development Competition. Significant but low correlations were found between Personal Development Competition and class level. Motivation and self-concept variables were not correlated with academic achievement variables and generally did not differ by sex or class level. Differences in motivation and musical self-concept by immediate and long-term career goal categories were nonsignificant.
Relationships among Conducting Quality, Ensemble Performance Quality, and State Festival Ratings
Authors: Price Harry E.
Published: July 2008

This study was the third in a series examining the relationships among conductors, ensembles' performances, and festival ratings. Participants (N = 51) were asked to score the quality of video-only conducting and parallel audio-only excerpts of performances at a state-level concert festival of nine bands, three each that had received ratings of Superior (I), Excellent (II), or Good (III). There was no significant difference among scores for conducting across festival ratings; however, there were significant differences among ensemble performance scores, with bands receiving Superior ratings scoring higher than those receiving ratings of Excellent or Good. No relationship was found between scores given conductors and their respective ensembles' performances. Participants were also asked to give reasons (N = 1, 393) for the scores. The comments were used to develop emergent themes based on what participants attended to, and trends were found regarding aspects of conducting and performances that had positive or negative influences.
Undergraduate Instrumental Music Education Majors' Approaches to Score Study in Various Musical Contexts
Authors: Lane Jeremy S.
Published: July 2008

Participants in the study (N = 21) engaged in two one-on-one interview sessions with the investigator. During each session, participants "thought out loud" as they studied one solo score and one full score of music by various composers. Interviews were conducted in an effort to assess preexisting knowledge of the music being studied and to assess participants' perceptions about score study. Results indicated three primary themes: (1) a lack of transfer of preexisting knowledge into certain score-study procedures, (2) an increase in specificity of verbal responses that seemed to correspond with education and experience, and (3) a lack of audible sound used during score preparation within full-score settings. Other findings suggest a contextual basis for score-study procedures and reflect changes in score-study patterns that seem influenced by experience and education.
The Effect of Articulation Style on Perception of Modulated Tempo
Authors: Geringer John M. , Madsen Clifford K. , MacLeod Rebecca B. , Droe Kevin
Published: July 2008

We investigated the effect of legato and staccato articulation styles on the perception of modulated tempos. Ninety music majors served as participants. Listeners heard music examples that had been selected from two pieces, each of which included staccato and legato passages. Excerpts were presented to listeners in three conditions of tempo modulation: gradual increases, gradual decreases, or no change. Modulations were produced in small increments so that listeners would not notice any abrupt change in tempo. Results indicated that articulation style and direction of modulation affected listener perception of tempo, and these two factors interacted significantly. All staccato stimuli were judged as increasing in tempo more than legato stimuli; however, differences between the two articulation styles were perceived as larger in tempo-increase examples compared to the no-change and tempo-decrease examples. Implications for performance practice and teaching are discussed.
The Tip of the Iceberg
Authors: Littlejohn Andrew
Published: July 2008

Teachers' informal discussions of learner motivation often emphasize the need to find ways to motivate learners, most usually through `fun' or `dynamic' activities. This paper starts from the assumption, however, that part of the work of the teacher is to avoid the demotivation of learners, and that there is a need to consider the overall structural organization of teaching and learning, not just the kinds of activities which learners do. The paper reviews four factors significant in affecting learner motivation: the locus of control, a sense of value and purpose, self-esteem, and feelings of success. These concepts are then used to interpret interview data from two school-aged learners. The causes of their apathetic reaction to English classes are explained by reference to these factors, as evidenced by how they describe the nature and purposes of the activities they do. They appear to see their classes as mainly consisting of `exercises', free of any memorable content. It is suggested that they experience their classes as `endlessly contemporary', with no clear sense of a past, present or future and that that, combined with a lack of involvement in classroom decisions, conspires to produce learners who simply comply because they are required to do so.
Destination Word of Mouth
Authors: Simpson Penny M. , Siguaw Judy A.
Published: July 2008

Recent research has identified identity salience and satisfaction as important variables affecting word-of-mouth communications in several contexts, such as university giving, retail environments, and leisure activities. Given these findings, these same variables may also be important in a tourism context, depending on the type of tourist. This study explores the effects of satisfaction and identity salience on word-of-mouth promotion and differences in these variables based on five different destination market segments, including tourists and local residents. The data indicate that satisfaction and identity salience are significant in predicting word-of-mouth promotions and that level of satisfaction and identity salience vary significantly depending on tourist type and resident type.
Italian School Psychology as Perceived by Italian School Psychologists
Authors: Trombetta Carlo , Alessandri Guido , Coyne Julia
Published: June 2008

International research in school psychology has suggested that Italy is among the remaining nations that have not generated systematic inquiry to clarify the practice of psychology in its schools. Italian school psychology has long been presumed to be nonexistent due to historical factors hindering its development and lack of local research readily available to a wider readership. The purpose of this study was to contribute to the growing knowledge base of Italian school psychology by presenting the findings of the first systematic nationwide research initiative targeted to gain an understanding of the profession. Surveys were collected from 1,251 schools and 690 school psychologists as respondents to obtain their perceptions of the profession. Characteristics, interface between the school and psychologist, professional practice, evaluation of professional practice and professional perceptions are discussed. Findings from this research initiative suggest that school psychology in Italy has followed a distinct evolution which has developed thus far into refined forms of consultation that are strongly correlated with relational ties between school psychologists and their schools. Implications for the training needs of school psychologists, the changing trends of interventions and areas of subsequent research are discussed.
The Effects of Cooperative Learning on Junior High School Students' Behaviours, Discourse and Learning During a Science-Based Learning Activity
Authors: Gillies Robyn M.
Published: June 2008

The study investigated the effects of structured and unstructured cooperating groups on students' behaviours, discourse and learning in junior high school. One hundred and sixty-four grade 9 students participated in the study. The students were videotaped as they worked in three to four person, mixed-gender and ability groups on a science-based categorization activity. The results show that the students in structured cooperating groups demonstrated more cooperative and helping behaviours such as giving more elaborated help and guided directions to assist understanding than their peers in the unstructured groups. Moreover, they demonstrated more complex thinking and problem-solving skills both in their discourse and their responses on the follow-up learning probe. These findings are discussed in the context of the importance of structuring cooperative learning experiences if students are to attain the benefits widely attributed to this approach to learning.
Applying Cognitive Behavioural Methods to Retrain Children's Attributions for Success and Failure in Learning
Authors: Toland John , Boyle Christopher
Published: June 2008

This study involves the use of methods derived from cognitive behavioural therapy (CBT) to change the attributions for success and failure of school children with regard to learning. Children with learning difficulties and/or motivational and self-esteem difficulties ( n = 29) were identified by their schools. The children then took part in twelve 30-minute group sessions with an educational psychologist, in which the children's attributions were retrained using methods derived from CBT. The intervention appeared to accelerate the children's progress in reading but not in spelling. Significant improvements in motivation and self-esteem were reported by the children and their parents. These changes were less apparent to the teachers. The findings point to a potentially fruitful way of offering additional intervention and support to children with learning difficulties and of increasing attainment. The cognitive behaviour methods complement more directly focused curricular work in a positive manner.