bluuebunny/crossref_metadata_2025 huggingface dataset:
Community, edaphic, and historical analysis of mixed oak forests of the Ridge and Valley Province in central Pennsylvania
Authors: Nowacki Gregory J. , Abrams Marc D.
Published: October 2008

Fifty-nine mixed oak stands in the Ridge and Valley Province of central Pennsylvania were sampled to evaluate the potential for oak replacement by later successional species or oak stability across a diverse landscape. Using species importance, stands were separated into four groups along detrended correspondence analysis axes 1 and 2. Betulalenta L.–Quercusprinus L.–Quercusrubra L. and Q. prinus–Q. rubra groups occurred on sandstone-based Inceptisols and Ultisols on ridges, whereas mixed–Quercus and Quercusalba L. groups were representative of limestone-based Alfisols on valley floors. Quercus species dominated the overstory of all groups; however, the understories mainly comprised shade-adapted Acerrubrum L., Acerpensylvanicum L., and (or) B. lenta on the xeric ridges and A. rubrum and Prunusserotina Ehrh. in the mesic valleys. The presettlement forests consisted of Quercus, Pinus, and Castaneadentata (Marsh.) Borkh. on the ridges and Quercus, Pinus, and Carya in the valleys. Comparisons between presettlement and present-day forests indicate that Pinusstrobus L. and C. dentata have declined dramatically, whereas Quercus species have increased. Changes in disturbance patterns following European settlement (e.g., the charcoal iron industry) initially favored Quercus expansion, followed later by increases in Acer, Prunus, and Betula. Under existing conditions where large-scale disturbances from fire or logging are minimal, Quercus species are expected to decline slowly in importance, being replaced by Acer, Prunus, and (or) Betula species regardless of site moisture relations. Thus, mixed oak forests do not appear to represent a prominent edaphic climax in the region, despite the long history of oak domination.
Physiological changes induced in birch seedlings by sublethal applications of glyphosate
Authors: Stasiak M.A. , Hofstra G. , Fletcher R.A.
Published: October 2008

Sublethal (0–2.1 kg/ha) effects of glyphosate were evaluated on white birch (Betulapapyrifera Marsh.) seedlings grown outdoors and under controlled-environment conditions. Leaf fluorescence, photosynthetic pigments, ethylene, and changes in the shikimic acid pathway were used as indicators of these effects. Leaf fluorescence steadily increased in treated birch seedlings for 9 days, indicating decreased photosynthetic efficiency. After this period, a gradual decline occurred, suggesting recovery of the photosystems. Chlorophyll a and b levels decreased within 4 days of application, whereas carotenoid content increased. Treated seedlings exhibited increased ethylene production compared with control seedlings. Shikimic acid levels increased 10-fold within 24 h of application, even at 1% of the field rate, and were still elevated in the spring of the following year. Gallic acid, another compound on the shikimic acid pathway, also increased in treated seedlings. Of the several parameters measured, glyphosate had the greatest effect on shikimic acid and differences occurred long before visual injury was observed. Shikimic acid level showed responses to low concentrations of glyphosate that produced no visible symptoms.
Estimating seed crops of conifer and hardwood species
Authors: McDonald Philip M.
Published: October 2008

Cone, acorn, and berry crops of ponderosa pine (Pinusponderosa Dougl. ex Laws. var. ponderosa), sugar pine (Pinuslambertiana Dougl.), Douglas-fir (Pseudotsugamenziesii (Mirb.) Franco), California white fir (Abiesconcolor var. lowiana (Gord.) Lemm.), incense-cedar (Libocedrusdecurrens Torr.), California black oak (Quercuskelloggii Newb.), tan oak (Lithocarpusdensiflorus (Hook. & Arn.) Rehd.), and Pacific madrone (Arbutusmenziesii Pursh) were evaluated over a 24-year period (1958–1981) from an area in northern California by an easy to use visual crop rating system. Seed-trap data, also for 24 years, were gathered for four conifer species. Together, these data provide the wild-land manager with knowledge on seed-crop quantity, quality, and timing. The visual rating system involves visually estimating the amount of fruit in trees and the proportion of trees with fruit, and ranking the crop by species. Regressions of sound seed and total seed on seed-crop rating are provided for the two species with the most seed crops: ponderosa pine and Douglas-fir. Regressions were significant at the 1% level, and coefficients of determination ranged from 0.58 to 0.76.
Factors affecting recruitment of Pinuspungens in the southern Appalachian Mountains
Authors: Williams Charles E. , Johnson W. Carter
Published: October 2008

Factors affecting the establishment and recruitment of seedlings of the Appalachian endemic Pinuspungens Lamb were studied in pine–oak forests of dry, southwesterly mountain slopes in southwestern Virginia, United States. Recruitment of P. pungens was not limited by seedfall from serotinous cones or by postdispersal seed predation. Total viable seedfall ranged from 35 000 to 69 000 seeds/ha in 1988 and was concentrated in the spring and summer months. Low availability of suitable seedling habitat strongly limited recruitment of P. pungens seedlings. The distributions of habitat variables for P. pungens seedlings and random points in the forest overlapped little, indicating that suitable microsites were relatively rare. Seedlings occurred in microsites characterized by shallow pine litter, low ground and canopy covers, and larger nearest neighbor distances than occurred at random. Summer drought also contributed to low seedling survivorship, particularly in young seedlings. Our results suggest that optimal recruitment and population maintenance of P. pungens in pine–oak forests is unlikely in the absence of fire.
Winter injury to subalpine red spruce: influence of prior vigor and effects on subsequent growth
Authors: Peart David R. , Poage Nathan J. , Jones Matthew B.
Published: October 2008

We assessed the relationship between prior vigor and severity of winter injury to trees and saplings of red spruce (Picearubens Sarg.) at Mount Moosilauke, New Hampshire. Severity of injury was quantified as percent foliar damage on current-year needles after severe injury in the winter of 1988–1989. There was no relationship between severity of injury and prior crown condition. There was only a weak tendency for trees with high live crown ratios to be less damaged than trees with proportionally smaller crowns. Severity of winter injury was not correlated with prior growth rates in the 1-, 2-, or 5-year periods preceding injury, for either trees (radial growth) or saplings (extension growth). However, crown condition of trees and saplings deteriorated significantly following injury. For both trees and saplings, prior growth and subsequent growth were positively correlated for the 1- and 2-year periods before and after the winter injury event. Effects of winter injury on growth in 1989 and 1990 were analyzed using growth ratios (subsequent growth relative to prior growth) to avoid ambiguity resulting from individual differences in growth rates. Severity of winter injury had no effect on growth ratios in the 1- or 2-year periods following winter injury. Although no effects on growth were detected following a single winter injury event, it remains plausible that successive, severe episodes of winter injury could reduce growth and increase mortality risk in red spruce.
Role of oregano on bacterial enzymes in 1,2-dimethylhydrazine-induced experimental colon carcinogenesis
Authors: Srihari T. , Balasubramaniyan V. , Nalini N.
Published: October 2008

Colon cancer incidence is higher in developed countries than in developing countries. We determined the effect of oregano ( Origanum vulgare L.) on fecal bacterial enzyme activities in 1,2-dimethylhydrazine (DMH)-induced experimental colon carcinogenesis in rats. Male Wistar albino rats were divided into 6 groups and all animals were fed with a high-fat diet (20% fat in the diet). Group 1 served as control and group 2 animals received 60 mg·kg–1body weight (b.w.) oregano daily for 15 weeks. To induce colon cancer, DMH (20 mg·kg–1b.w.) was injected subcutaneously once a week for the first 4 weeks (groups 3–6). In addition, oregano was administered at 20, 40, or 60 mg·kg–1b.w. each day orally for the entire 15 weeks (groups 4–6). We analyzed the fecal bacterial enzyme activities and found it to be significantly higher in the group treated with DMH alone than in the control group. Oregano supplementation at all 3 doses significantly suppressed the bacterial enzyme activities and modulated oxidative stress significantly compared with the unsupplemented DMH-treated group. Results of our present investigation therefore revealed that oregano markedly inhibited DMH-induced colon carcinogenesis and that the optimal dose of 40 mg·kg–1b.w. was more effective than either the higher or lower doses.
Reduction of asymmetric dimethylarginine in the protective effects of rutaecarpine on gastric mucosal injury
Authors: Liu Ying-Zi , Zhou Yuan , Li Dai , Wang Li , Hu Gao-Yun , Peng Jun , Li Yuan-Jian
Published: October 2008

Our recent study has shown that asymmetric dimethylarginine (ADMA) plays an important role in facilitating gastric mucosal injury by multiple factors. To explore whether the protection of rutaecarpine against gastric mucosal injury is related to reduction of ADMA content, a model of ethanol-induced gastric mucosal injury in rats was selected for this study. The ulcer index, the content of ADMA and NO, and the activity of dimethylarginine dimethylaminohydrolase (DDAH) in gastric tissues were measured in vivo after pretreatment with rutaecarpine. The in vitro effect of rutaecarpine on the release of calcitonin gene-related peptide (CGRP) and NO from isolated gastric tissues was also determined. The results showed that ethanol significantly increased the ulcer index, decreased the DDAH activity and the NO level, and elevated the ADMA level, which was attenuated by pretreatment with rutaecarpine (0.6 mg/kg or 1.2 mg/kg). In the isolated gastric tissues, rutaecarpine significantly increased the release of both CGRP and NO; the release of NO, but not CGRP, was abolished in the presence of l-NAME (10−4 mol/L). The present results suggest that rutaecarpine protects the gastric mucosa against injury induced by ethanol and that the gastroprotection of rutaecarpine is related to reduction of ADMA levels through stimulating the release of CGRP.
Leonurus sibiricusinduces nitric oxide and tumor necrosis factor-α in mouse peritoneal macrophages
Authors: An Hyo-Jin , Rim Hong-Kun , Lee Jong-Hyun , Suh Se-Eun , Lee Ji-Hyun , Kim Na-Hyung , Choi In-Young , Jeong Hyun-Ja , Kim Il Kwang , Lee Ju-Young , An Nyeon-Hyoung , Kim Hyung-Ryong , Um Jae-Young , Kim Hyung-Min , Hong Seung-Heon
Published: October 2008

Using mouse peritoneal macrophages, we have examined the mechanism by which Leonurus sibiricus (LS) regulates nitric oxide (NO) production. When LS was used in combination with recombinant interferon-γ (rIFN-γ), there was a marked cooperative induction of NO production; however, LS by itself had no effect on NO production. The increased production of NO from rIFN-γ plus LS-stimulated cells was almost completely inhibited by pretreatment with pyrrolidine dithiocarbamate (PDTC), an inhibitor of nuclear factor κB. Furthermore, treatment of peritoneal macrophages with rIFN-γ plus LS caused a significant increase in tumor necrosis factor-α (TNF-α) production. PDTC also decreased the effect of LS on TNF-α production significantly. Because NO and TNF-α play an important role in immune function and host defense, LS treatment could modulate several aspects of host defense mechanisms as a result of stimulation of the inducible nitric oxide synthase.
RICCION AS A COSMIC DARK MATTER CANDIDATE AND LATE COSMIC ACCELERATION
Authors: SRIVASTAVA S. K. , SINHA K. P.
Published: October 2008

In the past few years, a possibility is investigated, where curvature itself behaves as a source of dark energy. So, it is natural to think whether curvature can produce dark matter too. It is found that, at classical level, higher-derivative gravity yields curvature inspired particles namely riccions.31 Here, it is probed whether riccion can be a possible source of dark matter. Further, it is found that the late universe accelerates. Here, it is interesting to see that acceleration is obtained from curvature without using any dark energy source of exotic matter.
ACCELERATING UNIVERSE WITH MODIFIED FRIEDMANN EQUATION
Authors: AL-RAWAF A. S.
Published: October 2008

In this paper we propose a specific modification for Friedmann equation which leads during the matter-dominated era to a Cardassian type model, with the usual two undetermined parameters but with an important difference however, the usual parameter B which is constant in the Cardassian model becomes a function of time in this model. We found that although the model leads to acceleration at recent epoch. The acceleration values are more moderate than in the usual Cardassian model because B(t) is a reducing function of time. The model further leads to an increase in the abundance of light element during nucleosynthesis. We use the difference between the predicted and measured values of big bang nucleosynthesis of helium to obtain a value for n and B(t).
NEW PORPHYRIN ADDUCT OF FULLERENE-C60: A PROMISING NANOTOOL FOR MEDICINAL USE IN THE HEART MUSCLE HYPOXIA CASES
Authors: AMIRSHAHI NIMA , ALYAUTDIN RENAD N. , SARKAR SAEED , REZAYAT SEYED M. , ORLOVA MARINA A. , TRUSHKOV IGOR V. , BUCHACHENKO ANATOLY L. , KUZNETSOV DMITRY A.
Published: October 2008

This is a first case ever reported on the fullerene-based low toxic nanocationite particles (porphyrin adducts of cyclohexl fullerene- C60) designed for targeted delivery of the paramagnetic magnesium stable isotope to the heart muscle providing a sharp clinical effect close to about 80% recovery of the tissue hypoxia symptoms in less than 24 h after a single injection (0.03–0.1 LD50). A whole principle of this therapy is novel:25Mg2+-magnetic isotope effect selectively stimulates the ATP over-production in the oxygen-depleted cell due to25Mg2+released by nanoparticles. Being membranotropic cationites, these "smart nanoparticles" release the over-activating paramagnetic cations only in response to the metabolic acidic shift. The resulting positive changes in the heart cell energy metabolism may help to prevent and/or treat the local myocardial hypoxic disorders and, hence, to protect the heart muscle from a serious damage in a vast variety of the hypoxia-caused clinical situations including both Doxorubicin and 1-methylnicotineamide cardiotoxic side effects. Both pharmacokinetics and pharmacodynamics of the drug proposed makes it suitable for safe and efficient administration in either single or multi-injection (acute or chronic) therapeutic schemes.
Macrodynamic Cooperative Complexity of Information Dynamics
Authors: Lerner Vladimir S.
Published: October 2008

The introduced concept and measure of macrocomplexity (MC) arise in an irreversible macrodynamic cooperative process and determine the process components ability to assemble into an integrated system.

MC serves as a common indicator of the origin of the cooperative complexity measured by the specific entropy speed per assembled volume, rather than the entropy, as it has been accepted before. The MC cooperative mechanism is studied using the variation principle (VP) of information macrodynamics (IMD), applied to a complex system with the macrolevel dynamics and random microlevel stochastics and different forms of physical and virtual transitions of information. This principle describes a transition from a local unstable process movement to a local stable process — the former is associated with the current influx of information that precedes cooperation, and the latter is continued after the cooperation with incoming information and its accumulation. This transition enables the production of the cooperative phenomena and, in particular, the contributions from different superimposing processes, which are measured by the MC. MC, arising as an indicator of these phenomena at the unification (or decomposition) of the system processes, is defined by the invariant information measure, allowing for both analytical formulation and computer evaluation. An optimal multi-dimensional consolidation process, satisfying the VP, forms the information hierarchical network (IN) consisting of the model eigenvalues sequential cooperation in triples.

The MC of such an optimal cooperative triplet structure is measured by the IN triplet code (as an algorithm of the minimal program, which evaluates the IN hierarchical structure by the triplet information contributions in bits of information). The distributed IN allows for the automatic arrangement and measurement of the MC-local complexities in a multi-dimensional cooperative process, taking into account the MC time-space locations and mutual dependencies, and providing the MC hierarchical invariant information measure by quantity and quality in the triplet code. The MC is connected to Kolmogorov (K) complexity, which measures a deterministic order over a stochastic disorder by a minimal program. The MC specific consists of providing a computable complexity measure of a cooperative dynamic irreversible process, as an opposite to the K incomputability.
Post-rift compressional reactivation potential of passive margins and extensional basins
Authors: Cloetingh Sierd , Beekman Fred , Ziegler Peter A. , van Wees Jan-Diederik , Sokoutis Dimitrios
Published: October 2008

Poly-phase deformation of a compressional nature is a common feature in the post-rift evolution of passive margins and rifts. The compressional mode of deformation in these sedimentary basins, originally formed by extension in an intraplate setting, is characterized by a spectrum of spatial wavelengths spanning several tens of kilometres up to several hundreds of kilometres. The actual mode of compressional deformation appears to be strongly affected by the rheological structure of the underlying lithosphere, the level of the regional intraplate stress field, and the geometry of the rifted basin configuration prior to late-stage compressional reactivation. The interplay of plumes and intraplate compressional deformation can lead to temporal transitions from basin inversion to lithospheric folding. These modes of deformation lead to substantial differential vertical motions, late-stage anomalies in subsidence and uplift patterns. The development of innovative combinations of numerical and analogue modelling techniques is the key to differentiating different modes of compressional deformation of passive margins and extensional basins.
Present-day stresses, seismicity and Neogene-to-Recent tectonics of Australia's ‘passive’ margins: intraplate deformation controlled by plate boundary forces
Authors: Hillis Richard R. , Sandiford Mike , Reynolds Scott D. , Quigley Mark C.
Published: October 2008

Neogene-to-Recent deformation is widespread on and adjacent to Australia's ‘passive’ margins. Elevated historical seismic activity and relatively high levels of Neogene-to-Recent tectonic activity are recognized in the Flinders and Mount Lofty Ranges, the SE Australian Passive Margin, SW Western Australia and the North West Shelf. In all cases the orientation of palaeostresses inferred from Neogene-to-Recent structures is consistent with independent determinations of the orientation of the present-day stress field.

Present-day stress orientations (and neotectonic palaeostress trends) vary across the Australian continent. Plate-scale stress modelling that incorporates the complex nature of the convergent plate boundary of the Indo-Australian Plate (with segments of continent–continent collision, continent–arc collision and subduction) indicates that present-day stress orientations in the Australian continent are consistent with a first-order control by plate-boundary forces. The consistency between the present-day, plate-boundary-sourced stress orientations and the record of deformation deduced from neotectonic structures implicates plate boundary forces in the ongoing intraplate deformation of the Australian continent.

Deformation rates inferred from seismicity and neotectonics (as high as 10
−16
s
−1
) are faster than seismic strain rates in many other ‘stable’ intraplate regions, suggestive of unusually high stress levels imposed on the Australian intraplate environment from plate boundary interactions many thousands of kilometres distant. The spatial overlap of neotectonic structures and zones of concentrated historical seismicity with ancient fault zones and/or regions of enhanced crustal heat flow indicates that patterns of active deformation in Australia are in part, governed, by prior tectonic structuring and are also related to structural and thermal weakening of continental crust. Neogene-to-Recent intraplate deformation within the Australian continent has had profound and under-recognized effects on hydrocarbon occurrence, both by amplifying some hydrocarbon-hosting structures and by inducing leakage from pre-existing traps due to fault reactivation or tilting.
Evidence for kilometre-scale Neogene exhumation driven by compressional deformation in the Irish Sea basin system
Authors: Holford Simon P. , Green Paul F. , Turner Jonathan P. , Williams Gareth A. , Hillis Richard R. , Tappin David R. , Duddy Ian R.
Published: October 2008

Large tracts of the NW European continental shelf and Atlantic margin have experienced kilometre-scale exhumation during the Cenozoic, the timing and causes of which are debated. There is particular uncertainty about the exhumation history of the Irish Sea basin system, Western UK, which has been suggested to be a focal point of Cenozoic exhumation across the NW European continental shelf. Many studies have attributed the exhumation of this region to processes associated with the early Palaeogene initiation of the Iceland Plume, whilst the magnitude and causes of Neogene exhumation have attracted little attention. However, the sedimentary basins of the southern Irish Sea contain a mid–late Cenozoic sedimentary succession up to 1.5 km in thickness, the analysis of which should permit the contributions of Palaeogene and Neogene events to the Cenozoic exhumation of this region to be separated. In this paper, an analysis of the palaeothermal, mechanical and structural properties of the Cenozoic succession is presented with the aim of quantifying the timing and magnitude of Neogene exhumation, and identifying its ultimate causes. Synthesis of an extensive apatite fission-track analysis (AFTA), vitrinite reflectance (VR) and compaction (sonic velocity and density log-derived porosities) database shows that the preserved Cenozoic sediments in the southern Irish Sea were more deeply buried by up to 1.5 km of additional section prior to exhumation which began between 20 and 15 Ma. Maximum burial depths of the preserved sedimentary succession in the St George's Channel Basin were reached during mid–late Cenozoic times meaning that no evidence for early Palaeogene exhumation is preserved whereas AFTA data from the Mochras borehole (onshore NW Wales) show that early Palaeogene cooling (i.e. exhumation) at this location was not significant. Seismic reflection data indicate that compressional shortening was the principal driving mechanism for the Neogene exhumation of the southern Irish Sea. Coeval Neogene shortening and exhumation is observed in several sedimentary basins around the British Isles, including those along the UK Atlantic margin. This suggests that the forces responsible for the deformation and exhumation of the margin may also be responsible for the generation of kilometre-scale exhumation in an intraplate sedimentary basin system located >1000 km from the most proximal plate boundary. The results presented here show that compressional deformation has made an important contribution to the Neogene exhumation of the NW European continental shelf.
Efficient IP table lookup via adaptive stratified trees with selective reconstructions
Authors: Pellegrini Marco , Fusco Giordano
Published: October 2008

IP address lookup is a critical operation for high-bandwidth routers in packet-switching networks, such as Internet. The lookup is a nontrivial operation, since it requires searching for the longest prefix, among those stored in a (large) given table, matching the IP address. Ever increasing routing table size, traffic volume, and links speed demand new and more efficient algorithms. Moreover, the imminent move to IPv6 128-bit addresses will soon require a rethinking of previous technical choices. This article describes a the new data structure for solving the IP table lookup problem christened the adaptive stratified tree (AST). The proposed solution is based on casting the problem in geometric terms and on repeated application of efficient local geometric optimization routines. Experiments with this approach have shown that in terms of storage, query time, and update time the AST is at a par with state of the art algorithms based on data compression or string manipulations (and often it is better on some of the measured quantities).
Better external memory suffix array construction
Authors: Dementiev Roman , Kärkkäinen Juha , Mehnert Jens , Sanders Peter
Published: October 2008

Suffix arrays are a simple and powerful data structure for text processing that can be used for full text indexes, data compression, and many other applications, in particular, in bioinformatics. However, so far, it has appeared prohibitive to build suffix arrays for huge inputs that do not fit into main memory. This paper presents design, analysis, implementation, and experimental evaluation of several new and improved algorithms for suffix array construction. The algorithms are asymptotically optimal in the worst case or on average. Our implementation can construct suffix arrays for inputs of up to 4-GB in hours on a low-cost machine. As a tool of possible independent interest, we present a systematic way to design, analyze, and implement
pipelined
algorithms.
Design and implementation trade-offs for wide-area resource discovery
Authors: Albrecht Jeannie , Oppenheimer David , Vahdat Amin , Patterson David A.
Published: October 2008

We describe the design and implementation of SWORD, a scalable resource discovery service for wide-area distributed systems. In contrast to previous systems, SWORD allows users to describe desired resources as a topology of interconnected groups with required intragroup, intergroup, and per-node characteristics, along with the utility that the application derives from specified ranges of metric values. This design gives users the flexibility to find geographically distributed resources for applications that are sensitive to both node and network characteristics, and allows the system to rank acceptable configurations based on their quality for that application.

Rather than evaluating a single implementation of SWORD, we explore a variety of architectural designs that deliver the required functionality in a scalable and highly available manner. We discuss the trade-offs of using a centralized architecture as compared to a fully decentralized design to perform wide-area resource discovery. To summarize our results, we found that a centralized architecture based on 4-node server cluster sites at network-peering facilities outperforms a decentralized DHT-based resource discovery infrastructure with respect to query latency for all but the smallest number of sites. However, although a centralized architecture shows significant promise in stable environments, we find that our decentralized implementation has acceptable performance and also benefits from the DHT's self-healing properties in more volatile environments. We evaluate the advantages and disadvantages of centralized and distributed resource discovery architectures on 1000 hosts in emulation and on approximately 200 PlanetLab nodes spread across the Internet.
A high-level clustering algorithm targeting dual V
dd
FPGAs
Authors: Mukherjee Rajarshi , Liu Song , Memik Seda Ogrenci , Mondal Somsubhra
Published: October 2008

Recent advanced power optimizations deployed in commercial FPGAs, laid out a roadmap towards FPGA devices that can be integrated into ultra low power systems. In this article, we present a high-level design tool to support the process of mapping an application onto a FPGA device with dual supply voltages. Our main contribution in this paper is an algorithm, which creates voltage scaling ready clusters by utilizing the timing slack available in the designs. We propose to first create clusters of CLBs within a given CLB-level netlist. This clustering algorithm intends to group chains of CLBs possessing similar amounts of timing slack along their critical path together. Once these clusters are identified, they are placed onto respective V
dd
partitions on the device. We have evaluated different dual V
dd
fabrics and the potential gain in power consumption is explored. When a subset of the logic blocks on the device can be driven by low V
dd
levels (either with a dedicated low V
dd
supply or with a programmable selection between low and high V
dd
levels for these blocks) this affects placement and routing. As a result the maximum frequency of the designs may be affected. In order to evaluate the overall impact of creating voltage islands, we measured the Energy-Delay Product for our benchmark designs. We observed that the Energy-Delay product can be decreased by 26.9% when the placement of the designs into different voltage levels is guided by our clustering algorithm.
System-level throughput analysis for process variation aware multiple voltage-frequency island designs
Authors: Garg Siddharth , Marculescu Diana
Published: October 2008

The increasing variability in manufacturing process parameters is expected to lead to significant performance degradation in deep submicron technologies. Multiple Voltage-Frequency Island (VFI) design styles with fine-grained, process-variation aware clocking have recently been shown to possess increased immunity to manufacturing process variations. In this article, we propose a theoretical framework that allows designers to quantify the performance improvement that is to be expected if they were to migrate from a fully synchronous design to the proposed multiple VFI design style. Specifically, we provide techniques to efficiently and accurately estimate the probability distribution of the execution rate (or throughput) of both single and multiple VFI systems under the influence of manufacturing process variations. Finally, using an MPEG-2 encoder benchmark, we demonstrate how the proposed analysis framework can be used by designers to make architectural decisions such as the granularity of VFI domain partitioning based on the throughput constraints their systems are required to satisfy.
A compiler approach to managing storage and memory bandwidth in configurable architectures
Authors: Baradaran Nastaran , Diniz Pedro C.
Published: October 2008

Configurable architectures offer the unique opportunity of realizing hardware designs tailored to the specific data and computational patterns of an application code. Customizing the storage structures is becoming increasingly important in mitigating the continuing gap between memory latencies and internal computing speeds. In this article we describe and evaluate a compiler algorithm that maps the arrays of a loop-based computation to internal storage structures, either RAM blocks or discrete registers. Our objective is to minimize the overall execution time while considering the capacity and bandwidth constraints of the storage resources. The novelty of our approach lies in creating a single framework that combines high-level compiler techniques with lower-level scheduling information for mapping the data. We illustrate the benefits of our approach for a set of image/signal processing kernels using a Xilinx Virtex™ Field-Programmable Gate Array (FPGA). Our algorithm leads to faster designs compared to the state-of-the-art
custom data layout
mapping technique, in some instances using less storage. When compared to hand-coded designs, our results are comparable in terms of execution time and resources, but are derived in a minute fraction of the design time.
Simulation-based verification using Temporally Attributed Boolean Logic
Authors: Panda S. K. , Roy Arnab , Chakrabarti P. P. , Kumar Rajeev
Published: October 2008

We propose a specification logic called Temporally Attributed Boolean (TAB) Logic for Assertion Based Verification, which allows us to: (i) represent assertions succinctly, (ii) incorporate data-orientation and (iii) associate timing to design intentions. TAB Logic allows us to write specifications functionally linking system variables from different temporal contexts. We present examples to show the motivation for this logic especially in the context of high level modeling of complex real time systems. We formally define TAB Logic, formulate the problem of verification on a simulation trace and present efficient algorithms to check TAB assertions, both offline and online. We present results of application of TAB Logic for Instruction Semantics and Bus Transaction Verification of a bus integrated pipelined processor core implementation. We also employ TAB Logic to validate the Interrupt mode behavior of the processor core implementation. Further, we show the utility of TAB Logic in fault detection. Finally, we demonstrate the applicability of TAB Logic in the domain of simulation based verification of analog circuits like Operational Amplifiers and DC-DC Converters. We finally discuss the limitations of TAB logic and conclude.
Optimal routing algorithms for rectilinear pin clusters in high-density multichip modules
Authors: Ozdal Muhammet Mustafa , Wong Martin D. F. , Honsinger Philip S.
Published: October 2008

As the circuit densities and transistor counts are increasing, the package routing problem is becoming more and more challenging. In this article, we study an important routing problem encountered in typical high-end MCM designs: routing within dense pin clusters. Pin clusters are often formed by pins that belong to the same functional unit or the same data bus, and can become bottlenecks in terms of overall routability. Typically, these clusters have irregular shapes, which can be approximated with rectilinear convex boundaries. Since such boundaries have often irregular shapes, a traditional escape routing algorithm may give unroutable solutions. In this article, we study how the positions of escape terminals on a convex boundary affect the overall routability. For this purpose, we propose a set of necessary and sufficient conditions to model routability outside a rectilinear convex boundary. Given an escape routing solution, we propose an optimal algorithm to select the maximal subset of nets that are routable outside the boundary. After that, we focus on an integrated approach to consider routability constraints (outside the boundary) during the actual escape routing algorithm. Here, we propose an optimal algorithm to find the best escape routing solution that satisfies all routability constraints. Our experiments demonstrate that we can reduce the number of layers by 17% on the average, by using this integrated methodology.
Unit-level test adequacy criteria for visual dataflow languages and a testing methodology
Authors: Karam Marcel R. , Smedley Trevor J. , Dascalu Sergiu M.
Published: October 2008

Visual dataflow languages (VDFLs), which include commercial and research systems, have had a substantial impact on end-user programming. Like any other programming languages, whether visual or textual, VDFLs often contain faults. A desire to provide programmers of these languages with some of the benefits of traditional testing methodologies has been the driving force behind our effort in this work. In this article we introduce, in the context of prograph, a testing methodology for VDFLs based on structural test adequacy criteria and coverage. This article also reports on the results of two empirical studies. The first study was conducted to obtain meaningful information about, in particular, the effectiveness of our all-Dus criteria in detecting a reasonable percentage of faults in VDFLs. The second study was conducted to evaluate, under the same criterion, the effectiveness of our methodology in assisting users to visually localize faults by reducing their search space. Both studies were conducted using a testing system that we have implemented in Prograph's IDE.
Evaluating the benefits of context-sensitive points-to analysis using a BDD-based implementation
Authors: Lhoták Ondřej , Hendren Laurie
Published: October 2008

We present Paddle, a framework of BDD-based context-sensitive points-to and call graph analyses for Java, as well as client analyses that use their results. Paddle supports several variations of context-sensitive analyses, including call site strings and object sensitivity, and context-sensitively specializes both pointer variables and the heap abstraction. We empirically evaluate the precision of these context-sensitive analyses on significant Java programs. We find that that object-sensitive analyses are more precise than comparable variations of the other approaches, and that specializing the heap abstraction improves precision more than extending the length of context strings.
Organizing and managing personal electronic files
Authors: Hicks B. J. , Dong A. , Palmer R. , Mcalpine H. C.
Published: October 2008

This article deals with the organization and management of the computer files handled by mechanical engineers on their personal computers. In engineering organizations, a wide variety of electronic files (documents) are necessary to support both business processes and the activities of design and manufacture. Whilst a large number of files and hence information is formally archived, a significant amount of additional information and knowledge resides in electronic files on personal computers. The widespread use of these personal information stores means that all information is retained. However, its reuse is problematic for all but the individual as a result of the naming and organization of the files. To begin to address this issue, a study of the use and current practices for managing personal electronic files is described. The study considers the fundamental classes of files handled by engineers and analyses the organization of these files across the personal computers of 40 participants. The study involves a questionnaire and an electronic audit. The results of these qualitative and quantitative elements are used to elicit an understanding of the practices and requirements of engineers for managing personal electronic files. A potential scheme for naming and organizing personal electronic files is discussed as one possible way to satisfy these requirements. The aim of the scheme is to balance the personal nature of data storage with the need for personal records to be shared with others to support knowledge reuse in engineering organizations. Although this article is concerned with mechanical engineers, the issues dealt with are relevant to knowledge-based industries and, in particular, teams of knowledge workers.
Information scraps
Authors: Bernstein Michael , Van Kleek Max , Karger David , schraefel m.c.
Published: October 2008

In this article we investigateinformation scraps—personal information where content has been scribbled on Post-it notes, scrawled on the corners of sheets of paper, stuck in our pockets, sent in email messages to ourselves, and stashed in miscellaneous digital text files. Information scraps encode information ranging from ideas and sketches to notes, reminders, shipment tracking numbers, driving directions, and even poetry. Although information scraps are ubiquitous, we have much still to learn about these loose forms of information practice. Why do we keep information scraps outside of our traditional PIM applications? What role do information scraps play in our overall information practice? How might PIM applications be better designed to accommodate and support information scraps' creation, manipulation and retrieval?

We pursued these questions by studying the information scrap practices of 27 knowledge workers at five organizations. Our observations shed light on information scraps' content, form, media, and location. From this data, we elaborate on the typical information scrap lifecycle, and identify common roles that information scraps play: temporary storage, archiving, work-in-progress, reminding, and management of unusual data. These roles suggest a set of unmet design needs in current PIM tools: lightweight entry, unconstrained content, flexible use and adaptability, visibility, and mobility.
Making it Real
Authors: McCartney Robert , Tenenberg Josh
Published: October 2008

Some have proposed that realistic problem situations are better for learning. This issue contains two articles that examine the effects of “making it real” in computer architecture and human-computer interaction.
An HCI Approach to Computing in the Real World
Authors: Yardi Sarita , Krolikowski Pamela , Marshall Taneshia , Bruckman Amy
Published: October 2008

We describe the implementation of a six-week course to teach Human-Computer Interaction (HCI) to high school students. Our goal was to explore the potential of HCI in motivating students to pursue future studies in related computing fields. Participants in our course learned to make connections between the types of technology they use in their daily lives and the design processes that went into creating these technologies. We suggest that by portraying computing through the lens of HCI, as an innovative, creative, and challenging field with authentic, real-world applications, we may be able to motivate students to become more interested in computing.
Torino (Italy) to host the 20th ACM Hypertext and Hypermedia Conference in June 2009
Authors: Cattuto Ciro , Menczer Filippo , Ruffo Giancarlo
Published: October 2008

The city of Torino, Italy, is to host for the first time the ACM Hypertext and Hypermedia Conference in 2009. Hypertext 2009, sponsored by ACM and SIGWEB, will be held from June 29th to July 1st at the Villa Gualino Convention Centre (www.villagualino.net), on the hills overlooking Torino. Professionals from academia, industry and the media will present innovative ideas and tools exploiting the wide range of links increasingly connecting people, information, communities, and structures. Hypertext 2009 has been scheduled immediately after the next User Modeling Conference in Trento (Italy), and researchers will have a great opportunity to attend both events with limited logistic effort.
Multilevel algorithms for linear ordering problems
Authors: Safro Ilya , Ron Dorit , Brandt Achi
Published: October 2008

Linear ordering problems are combinatorial optimization problems that deal with the minimization of different functionals by finding a suitable permutation of the graph vertices. These problems are widely used and studied in many practical and theoretical applications. In this paper, we present a variety of linear--time algorithms for these problems inspired by the Algebraic Multigrid approach, which is based on weighted-edge contraction. The experimental result for four such problems turned out to be better than every known result in almost all cases, while the short (linear) running time of the algorithms enables testing very large graphs.
An experimental study of point location in planar arrangements in CGAL
Authors: Haran Idit , Halperin Dan
Published: October 2008

We study the performance in practice of various point-location algorithms implemented in CGAL (the Computational Geometry Algorithms Library), including a newly devised
landmarks
algorithm. Among the other algorithms studied are: a naïve approach, a “walk along a line” strategy, and a trapezoidal decomposition-based search structure. The current implementation addresses general arrangements of planar curves, including arrangements of nonlinear segments (e.g., conic arcs) and allows for degenerate input (for example, more than two curves intersecting in a single point or overlapping curves). The algorithms use exact geometric computation and thus result in the correct point location. In our landmarks algorithm (a.k.a. jump & walk), special points, “landmarks,” are chosen in a preprocessing stage, their place in the arrangement is found, and they are inserted into a data structure that enables efficient nearest-neighbor search. Given a query point, the nearest landmark is located and a “walk” strategy is applied from the landmark to the query point. We report on various experiments with arrangements composed of line segments or conic arcs. The results indicate that compared to the other algorithms tested, the landmarks approach is the most efficient, when the overall (amortized) cost of a query is taken into account, combining both preprocessing and query time. The simplicity of the algorithm enables an almost straightforward implementation and rather easy maintenance. The generic programming implementation allows versatility both in the selected type of landmarks and in the choice of the nearest-neighbor search structure. The end result is an efficient point-location algorithm that bypasses the alternative CGAL implementations in most practical aspects.
Summarizing spatial data streams using ClusterHulls
Authors: Hershberger John , Shrivastava Nisheeth , Suri Subhash
Published: October 2008

We consider the following problem: given an on-line, possibly unbounded stream of two-dimensional (2D) points, how can we summarize its spatial distribution orshapeusing a small, bounded amount of memory? We propose a novel scheme, calledClusterHull, which represents the shape of the stream as a dynamic collection of convex hulls, with a total of at mostmvertices, wheremis the size of the memory. The algorithm dynamically adjusts both the number of hulls and the number of vertices in each hull to best represent the stream using its fixed-memory budget. This algorithm addresses a problem whose importance is increasingly recognized, namely, the problem of summarizing real-time data streams to enable on-line analytical processing. As a motivating example, consider habitat monitoring using wireless sensor networks. The sensors produce a steady stream of geographic data, namely, the locations of objects being tracked. In order to conserve their limited resources (power, bandwidth, and storage), the sensors can compute, store, and exchange ClusterHull summaries of their data, without losing important geometric information. We are not aware of other schemes specifically designed for capturing shape information in geometric data streams and so we compare ClusterHull with some of the best general-purpose clustering schemes, such as CURE,k-medians, and LSEARCH. We show through experiments that ClusterHull is able to represent the shape of two-dimensional data streams more faithfully and flexibly than the stream versions of these clustering algorithms.
Engineering multilevel overlay graphs for shortest-path queries
Authors: Holzer Martin , Schulz Frank , Wagner Dorothea
Published: October 2008

An overlay graph of a given graph
G
= (
V
,
E
) on a subset
S
⊆
V
is a graph with vertex set
S
and edges corresponding to shortest paths in
G
. In particular, we consider variations of the multilevel overlay graph used in Schulz et al. [2002] to speed up shortest-path computation. In this work, we follow up and present several vertex selection criteria, along with two general strategies of applying these criteria, to determine a subset
S
of a graph's vertices. The main contribution is a systematic experimental study where we investigate the impact of selection criteria and strategies on multilevel overlay graphs and the resulting speed-up achieved for shortest-path computation: Depending on selection strategy and graph type, a centrality index criterion, selection based on planar separators, and vertex degree turned out to perform best.