bluuebunny/crossref_metadata_2025 huggingface dataset:
Temporal variation in cuckoldry and paternity in two sunfish species (Lepomis spp.) with alternative reproductive tactics
Authors: Neff Bryan D. , Clare Elizabeth L.
Published: April 2008

Male alternative reproductive tactics have been described in many mating systems. In fishes, these tactics typically involve a territorial male that defends a spawning site or nest and a parasitic male that uses sneaking or female mimicry to steal fertilizations from the territorial male. In this paper, we use molecular genetic markers to examine the success of males that adopt alternative reproductive tactics in two sunfishes, comprising the bluegill ( Lepomis macrochirus Rafinesque, 1819) and the pumpkinseed ( Lepomis gibbosus (L., 1758)). In sunfishes, the tactics are referred to as parental (territorial male) and cuckolder (parasitic male). We show that cuckoldry rates peak in the second trimester of the breeding season in bluegill, whereas cuckoldry rates are lowest during this period in pumpkinseed. We also show that paternity of parental male bluegill is positively correlated with body condition, but not body length or mass. No relationship between these phenotypic variables and paternity in pumpkinseed was found. We discuss the patterns of cuckoldry in relation to differences between the species in mating opportunities, parental male defence ability, and cuckolder density. Finally, we discuss how the paternity data can be used to differentiate between two mechanisms underlying the expression of alternative reproductive tactics, comprising the condition strategy and alternative strategies.
Exposure to high temperature influences the behaviour, physiology, and survival of sockeye salmon during spawning migration
Authors: Crossin G. T. , Hinch S. G. , Cooke S. J. , Welch D. W. , Patterson D. A. , Jones S. R.M. , Lotto A. G. , Leggatt R. A. , Mathes M. T. , Shrimpton J. M. , Van Der Kraak G. , Farrell A. P.
Published: April 2008

Since 1996, some populations of Fraser River sockeye salmon ( Oncorhynchus nerka Walbaum in Artedi, 1792) have begun spawning migrations weeks earlier than normal, and most perish en route as a result. We suspect that a high midsummer river temperature is the principal cause of mortality. We intercepted 100 sockeye during normal migration near a spawning stream and measured somatic energy and aspects of plasma biochemistry. Fish were then held at either 10 or 18 °C for 24 days. Before release, fish were biopsied again and implanted with acoustic transmitters. A group of biopsied but untreated control salmon were released at the same time. Sixty-two percent (8 of 13) of control salmon and 68% (21 of 31) of 10 °C salmon reached spawning areas. The 18 °C-treated fish were half as successful (35%; 6 of 17). During the holding period, mortality was 2 times higher and levels of Parvicapsula minibicornis (Kent, Whitaker and Dawe, 1997) infection were higher in the 18 °C-treated group than in the 10 °C-treated group. The only physiological difference between treatments was a change in gill Na+,K+-ATPase activity. This drop correlated negatively with travel times for the 18 °C-treated males. Reproductive-hormone levels and stress measures did not differ between treatments but showed significant correlations with individual travel times.
Altitude and temperature effects on the energetic cost of hover-feeding in migratory rufous hummingbirds,Selasphorus rufus
Authors: Welch, Kenneth C. , Suarez Raul K.
Published: April 2008

During migratory stopovers, rufous hummingbirds ( Selasphorus rufus (Gmelin, 1788)) can achieve high daily rates of net energy intake and mass gain while foraging at a range of elevations and ambient temperatures, despite the high energetic costs of hovering flight and thermoregulation. To gain insights into the factors affecting the energetic costs incurred during foraging, we captured migratory hummingbirds and measured their oxygen consumption rates during hover-feeding. Measurements were performed in situ where rufous hummingbirds forage as they migrate at several locations along a gradient in elevation and over the range of ambient temperatures normally experienced. Oxygen consumption rates during hover-feeding varied between the sexes and between juveniles and adults. These differences appeared to reflect differences in the power requirements for hovering flight in relation to variation in wing morphology. Decreasing ambient temperature and increasing elevation both significantly increased oxygen consumption rate during hover-feeding. The effects of these two environmental variables were additive, suggesting that hummingbird thermoregulatory requirements were not met by the additional heat produced by the higher metabolic rate necessary to support hovering flight at higher elevation. These results provide insight into the ways different foraging strategies may allow hummingbirds to maximize net energy intake.
Opportunistic exploitation of turtle eggs by Tripanurga importuna (Walker) (Diptera: Sarcophagidae)
Authors: Bolton R. M. , Marshall S. A. , Brooks R. J.
Published: April 2008

Tripanurga importuna (Walker, 1849) is a sarcophagid fly whose larvae often occur in nests of freshwater turtles. We investigated this sarcophagid fly to determine whether it is an opportunistic scavenger or a potential predator of eggs, embryos, and hatchlings of the spiny softshell turtle ( Apalone spinifera (Lesueur, 1827)). Fly infestation of spiny softshell turtle nests can occur at any time between oviposition and hatching, but estimates based on larval size and development time, along with observations of adult fly activity, suggest that female sarcophagids deposit larvae over the nest primarily during hatching. Observed temperature variance within the turtle clutch mass and physiological and developmental differences among eggs may result in asynchronous hatching, and chemical cues associated with early hatching may attract adult flies. Egg position within the nest affects embryo hatching success independently of fly infestation while also affecting fly infestation. Tripanurga importuna is a habitat specialist able to find and develop in carrion buried in sand, but it is a food opportunist able to develop on other buried carrion as well as turtle eggs. Tripanurga importuna maggots in turtle nests preferentially scavenge necrotic tissue, including damaged turtle eggs, but will opportunistically prey upon live embryos and hatchlings under some circumstances.
Does habitat type modify group size in roe deer and red deer under predation risk by Iberian wolves?
Authors: Barja I. , Rosellini S.
Published: April 2008

We examined whether group size in red deer ( Cervus elaphus L., 1758) and roe deer ( Capreolus capreolus (L., 1758)) under predation risk by Iberian wolves ( Canis lupus L., 1758) is affected by the type of habitat in which the deer reside. We hypothesized that group size (i) would be larger in open than in closed habitats, since it is an antipredator response, and (ii) would vary more with habitat type in the species that had higher wolf predation rates. In the study area, wolves were the only predator of wild ungulates, with roe deer being the main target prey. We performed monthly transects along paths to observe the group size of red and roe deer. In roe deer, the mean group size was significantly higher in open than in closed habitats, serving as an antipredator response. However, in red deer, habitat type did not affect group size. The results indicate that under predation risk by wolves the habitat type influences the grouping behavior of roe deer but not red deer. Furthermore, compared with forests, heaths offer less protection from predators and species in this habitat would benefit from larger group sizes.
Small mammals in nests of cavity-nesting birds: Why should ornithologists study rodents?
Authors: Czeszczewik D. , Walankiewicz W. , Stańska M.
Published: April 2008

We analyze the frequency of occurrence of small mammals recorded in natural cavities and nest boxes in the Białowieża Forest (eastern Poland) and also describe some parameters of tree cavities. A total of 748 cavities and 60 nest boxes in primeval tree stands and 190 nest boxes in managed tree stands were monitored. Both cavities and nest boxes in primeval stands were occupied by mammals less often than nest boxes in managed stands (0.70%, 0.12%, and 1.26%, respectively). The following mammal species were recorded in natural cavities: Eurasian red squirrel ( Sciurus vulgaris L., 1758), forest dormouse ( Dryomys nitedula (Pallas, 1778)), yellow-necked mouse ( Apodemus flavicollis (Melchior, 1834)), and bats (Microchiroptera species). Three mammalian species were recorded in nest boxes: forest dormouse, fat dormouse ( Myoxus glis (L., 1766)), and yellow-necked mouse. The attractiveness of the boxes for mammals increases in managed forests, probably because of a shortage of natural cavities. We suggest that the role of rodents in the breeding ecology of cavity-nesters is underestimated, since studies on natural cavities are rather rare and the species identities of nest predators are most likely poorly recognized. To understand the breeding ecology of birds, ornithologists should study the population dynamics of mammals and the manner in which they use tree cavities and nest boxes.
Ruffed grouse brood habitat selection at multiple scales in Pennsylvania: implications for survival
Authors: Tirpak John M. , Giuliano William M. , Miller C. Allan
Published: April 2008

Declines in ruffed grouse ( Bonasa umbellus (L., 1766)) populations in the central and southern Appalachians may be linked to low brood survival. Therefore, managing for high-quality brood habitat could improve grouse numbers. Understanding how brood habitat selection affects survival and the spatial scale at which this occurs is therefore fundamental to developing effective habitat management strategies. From 1999–2002, we monitored 38 broods for 5 weeks post hatch and estimated utilization distributions (n = 28), site-scale habitat use (n = 21), and daily survival rate (mean = 0.966, range = 0.920–0.997, and n = 19). Relative to available habitat, broods selected sites with greater herbaceous ground cover and higher small (<2.5 cm diameter at breast height, DBH) stem densities and landscapes containing higher proportions of road and young deciduous forest. Herbaceous ground cover provided arthropod prey and concealment from predators and was a primary factor driving habitat selection. High stem densities and early successional habitats provided increased security, but were only used if adequate ground cover was present. Broods strongly selected roads and experienced higher survival near edges. However, higher road densities were associated with lower survival at the landscape scale. This pattern reflects the differential scale at which grouse and their predators respond to edge.
Heads up: sexual dimorphism in house crickets (Acheta domesticus)
Authors: Walker Sean E. , Roberts J. Andrew , Adame Israel , Collins Corey J. , Lim Daniel
Published: April 2008

Many species are sexually dimorphic because of differential selection on each sex. In many species, males tend to have exaggerated traits or larger body size compared with females. In house crickets ( Acheta domesticus L., 1758), the males defend resources and compete for mates by engaging in a striking visual display sequence that includes mandible flaring, where males spread their mandibles wide open. This behavior presumably acts only in males as a visual signal of body size and as an indicator of the willingness to fight, as females do not exhibit this behavior. We tested the hypothesis that sex differences in the signals used for aggressive interactions will lead to sex differences in the morphology of the head in house crickets. To test this hypothesis we made linear measurements of body and head sizes on males and females and utilized geometric morphometric methods to reconstruct sex differences in shape. We also compared the total pigmented area of the faces of males and females. Males had larger heads with proportionally more pigmented area than females and there were significant shape differences. In addition, allometric relationships between head size and body size indicated that head size increases faster than body size in males. Geometric morphometric analysis indicated that the shape differences result in an exaggeration of the mandibular area in males compared with females. These data suggest that the differential selection acting on males and females can lead to differences in size, shape, and pigmentation related to signal structure and function.
Individual variation affects departure rate from the natal pond in an ephemeral pond-breeding anuran
Authors: Chelgren Nathan D. , Rosenberg Daniel K. , Heppell Selina S. , Gitelman Alix I.
Published: April 2008

Frogs exhibit extreme plasticity and individual variation in growth and behavior during metamorphosis, driven by interactions of intrinsic state factors and extrinsic environmental factors. In northern red-legged frogs ( Rana aurora Baird and Girard, 1852), we studied the timing of departure from the natal pond as it relates to date and size of individuals at metamorphosis in the context of environmental uncertainty. To affect body size at metamorphosis, we manipulated food availability during the larval stage for a sample (317) of 1045 uniquely marked individuals and released them at their natal ponds as newly metamorphosed frogs. We recaptured 34% of marked frogs in pitfall traps as they departed and related the timing of their initial terrestrial movements to individual properties using a time-to-event model. Median age at first capture was 4 and 9 days postmetamorphosis at two sites. The rate of departure was positively related to body size and to date of metamorphosis. Departure rate was strongly negatively related to time elapsed since rainfall, and this effect was diminished for smaller and later metamorphosing frogs. Individual variation in metamorphic traits thus affects individuals’ responses to environmental variability, supporting a behavioral link with variation in survival associated with these same metamorphic traits.
SINGULAR FERMI SURFACES II: THE TWO-DIMENSIONAL CASE
Authors: FELDMAN JOEL , SALMHOFER MANFRED
Published: April 2008

We consider many-fermion systems with singular Fermi surfaces, which contain Van Hove points where the gradient of the band function k ↦ e(k) vanishes. In a previous paper, we have treated the case of spatial dimension d ≥ 3. In this paper, we focus on the more singular case d = 2 and establish properties of the fermionic self-energy to all orders in perturbation theory. We show that there is an asymmetry between the spatial and frequency derivatives of the self-energy. The derivative with respect to the Matsubara frequency diverges at the Van Hove points, but, surprisingly, the self-energy is C1 in the spatial momentum to all orders in perturbation theory, provided the Fermi surface is curved away from the Van Hove points. In a prototypical example, the second spatial derivative behaves similarly to the first frequency derivative. We discuss the physical significance of these findings.
CASE DETECTION AND DIRECT OBSERVATION THERAPY STRATEGY (DOTS) IN NIGERIA: ITS EFFECT ON TB DYNAMICS
Authors: OKUONGHAE DANIEL , AIHIE VINCENT
Published: March 2008

This paper addresses the synergy between case detection and the implementation of DOTS in Nigeria in the control of tuberculosis using a deterministic model which incorporates many of the essential biological and epidemiological features of TB as well as DOTS surveillance and implementation parameters for Nigeria. The model differentiated between individuals who progress to the "primary" latent stage when they got infected for the first time and those who progress to the "secondary" latent class depending on whether they failed treatment or due to self-cure. The model was shown to have a locally asymptotically stable disease free equilibrium where the reproduction number was less than unity. However, it was also shown that the model is capable of exhibiting the backward bifurcation phenomenon, where the stable disease free equilibrium co-exists with a stable endemic equilibrium where the reproduction number is less than unity. We saw that increasing the case detection parameter actually reduces the backward bifurcation range. For smaller exogenous re-infection values, increasing the case detection parameter could totally eliminate the bifurcation range. Uncertainty and sensitivity analysis using the Latin hypercube sampling technique was also carried out on the parameters as well as the reproduction number and the results showed that there were three parameters that were highly influential in determining the magnitude of the reproduction number; of the three, only one, the case detection parameter, was highly influential in reducing the magnitude of the reproduction number. Results from the numerical simulation and qualitative analysis showed that DOTS expansion in Nigeria must include significant increase in case detection rates, otherwise the impressive cure rates under DOTS will pale into insignificance with the rise in the number of undetected infectious persons and the number of "secondary" latent cases.

Overall, the study shows that increasing the case detection rate will not only lower the backward bifurcation range, in the presence of exogenous re-infection, but could also lower the reproduction number, reducing the severity of the TB epidemic. This is possible as far as the current impressive treatment success rates under DOTS in Nigeria is sustained.
Voice and Data Solutions (India)
Authors: Mishra Sumita , Gupta Rajen K.
Published: April 2008

VDS Inc., based in California, US, was founded by three Indian entrepreneurs in January 2000. The company provided VoIP (Voice over Internet Protocol) solutions to wireless, wire line and cable service providers in the US, Europe, and recently, Asia. VDS India, based in Noida, India, was established in September 2000 as the offshore product development base of VDS Inc. The product portfolio of VDS Inc. was steadily growing and gaining recognition in the industry. As a result, the product development base in India was becoming more important than ever. A new CEO, David Joseph was appointed in October 2003 to head VDS India. To standardize work processes to cope with growth in demand and to control attrition rates, David undertook initiatives such as the establishment of a human resources team, setting up of a technical documentation team, the tightening of team processes pertaining to induction and job allocation, and the initiation of organizational processes of employee performance appraisals.

David noticed that changes were not easy to implement. Outsourcing of the human resources team and problems of coordination between the technical documentation team and the engineers posed major challenges to David. Integration of communication and information with VDS Inc. also was another area of concern. The case is useful for the examination of human elements in the implementation process.
Whether or Not to Disinvest: The Case of Gujarat State Fertilizers & Chemicals Limited
Authors: Dholakia Ravindra H. , Gandhi Shailesh
Published: April 2008

India became independent in 1947. Its central planning model emphasized the development of core sectors of Indian economy through Public Sector Undertakings (PSUs). PSUs played an active role in economic development for more than four decades. The process of liberalization and globalization began in 1991. The Central and State Governments initiated process of disinvestment and decontrol in various PSUs. Gujarat State Fertilizers & Chemicals Limited (GSFC) was one of such PSUs. It was promoted in 1962 by the State Government of Gujarat (GoG) with its 49% equity share, as a joint sector fertilizer company. The objective of the Government was to promote agricultural growth by providing chemical fertilizers and other inputs along with extension services to the farmers. Over the years, it diversified into industrial products. It was also instrumental in promotion of other PSUs in Gujarat through equity participation. It had a strong brand image among the farmers.

In 2004, GoG appointed an Expert Committee (EC) to review the performance and sustainability of various PSUs in the State of Gujarat including GSFC and to recommend whether or not the Government should continue to hold its investment in them. The task of EC in providing recommendations on GSFC was very challenging because GSFC incurred losses for the first time during 2000–1 to 2002–3 since its inception but showed dramatic turnaround in 2003–4 and further improved its financial performance in 2004–5 and 2005–6. EC had to reassess the developmental role of GSFC and the need for GoG to continue its involvement. It had to assess the sustainability of improved financial performance in future and decide whether or not GoG should disinvest its stake.
CONGENITAL SCOLIOSIS ASSOCIATED WITH COEXISTENT SPLIT CORD MALFORMATION (SCM) AND INTRAMEDULLARY TERATOMA: REPORT OF A CASE
Authors: Ye Qibin , Li Duanming
Published: March 2008

A 9-year-old girl with congenital scoliosis, split cord malformation (SCM), and intramedullary teratoma was reported at the authors' institution. She had undergone three surgical corrections of the scoliosis without recognition of the existing teratoma, which was only revealed in a subsequent operative exploration of the spinal canal due to progressive neurological deficiency. The SCM was at the T9 level, and the teratoma at levels T10–T12. The teratoma was removed and the scoliotic curve was further corrected. These procedures resulted in restoring normal neurological function. This case shows that congenital scoliosis may coexist with other intraspinal deformities, and may be left unnoticed. Magnetic resonance imaging (MRI) is considered as a valuable means for the diagnosis of intraspinal teratoma.
OPTIMAL CREDIT RATINGS
Authors: HERZOG SEBASTIAN , KOZIOL CHRISTIAN , THABE TIM
Published: April 2008

In this paper, we show that an individual optimal credit rating exists for firms and empirically test whether firms strive to achieve their optimal rating. For this purpose, we consider the structural model by Leland [12], which balances the benefits of debt in the form of the tax-deductibility of interest payments against bankruptcy costs in order to obtain the optimal rating. Testable implications for both firms which have implemented their optimal rating and firms with non-optimal ratings are deduced. An empirical test with 420 firms contained in the S&P 500 Index indicates that all factors which theoretically drive optimal ratings also affect the observed rating in the predicted way. In line with our theory, observed ratings can be considerably better explained if, in addition to the traditional factors such as leverage and firm size, a proxy for bankruptcy costs and the default probability related to the optimal rating is considered. These findings suggest that U.S. firms contained in the S&P 500 Index strive to achieve their optimal credit ratings.
UTILIZING LOCAL CONTEXT FOR EFFECTIVE INFORMATION RETRIEVAL
Authors: SIDDIQUI TANVEER J. , TIWARY UMA SHANKER
Published: April 2008

Our research focuses on the use of local context through relation matching to improve retrieval effectiveness. An information retrieval (IR) model that integrates relation and keyword matching has been used in this work. The model takes advantage of any existing relational similarity between documents and query to improve retrieval effectiveness. It gives high rank to a document in which the query concepts are involved in similar relationships as in the query, as compared to those in which they are related differently. A conceptual graph (CG) representation has been used to capture relationship between concepts. A simplified form of graph matching has been used to keep our model computationally tractable. Structural variations have been captured during matching through simple heuristics. Four different CG similarity measures have been proposed and used to evaluate performance of our model. We observed a maximum improvement of 7.37% in precision with the second CG similarity measure. The document collection used in this study is CACM-3204. CG similarity measure proposed by us is simple, flexible and scalable and can find application in many IR related tasks like information filtering, information extraction, question answering, document summarization, etc.
A NEW APPROACH FOR TEXT SIMILARITY USING ARTICLES
Authors: ATLAM ELSAYED
Published: April 2008

Conventional approaches to text analysis and information retrieval which measured document similarity by considering all information in texts are relatively inefficiency for processing large text collections in heterogeneous subject areas. Previous researches showed that evidence from passage can improve retrieval results. But it also raised questions about how passage is defined, how they can be ranked efficiently, and what is their proper rule in long structure documents. Moreover, the frequency of "the" with important sentence is efficiently to summarize the text by dexterity way. We previously proposed an approach for extracting sentences which including article "the" by some restrict rules to carry out effectiveness passages. Based on previous approaches, this paper presents a new Passage SIMilarity (P-SIM) measurements between documents based on effectiveness passages after extracting them using article "the". Moreover, our new approach showing that this method is more efficient than traditional methods. Also, Recall and Precision are achieved by 92.6% and 97.5% respectively, depending on extracted passages. Furthermore, Recall and Precision significantly improved by 38.3% and 44.2% over the traditional method. The proposed methods are applied to 3,990 articles from the large tagged corpus.
CATEGORIZATION OF DISASTER DECISION SUPPORT NEEDS FOR THE DEVELOPMENT OF AN INTEGRATED MODEL FOR DMDSS
Authors: ASGHAR SOHAIL , ALAHAKOON DAMMINDA , CHURILOV LEONID
Published: April 2008

The wide variety of disasters and the large number of activities involved have resulted in the demand for separate Decision Support System (DSS) models to manage different requirements. The modular approach to model management is to provide a framework in which to focus multidisciplinary research and model integration. A broader view of our approach is to provide the flexibility to organize and adapt a tailored DSS model (or existing modular subroutines) according to the dynamic needs of a disaster. For this purpose, the existing modular subroutines of DSS models are selected and integrated to produce a dynamic integrated model focussed on a given disaster scenario. In order to facilitate the effective integration of these subroutines, it is necessary to select the appropriate modular subroutine beforehand. Therefore, subroutine selection is an important preliminary step towards model integration in developing Disaster Management Decision Support Systems (DMDSS). The ability to identify a modular subroutine for a problem is an important feature before performing model integration. Generally, decision support needs are combined, and encapsulate different requirements of decision-making in the disaster management area. Categorization of decision support needs can provide the basis for such model selection to facilitate effective and efficient decision-making in disaster management. Therefore, our focus in this paper is on developing a methodology to help identify subroutines from existing DSS models developed for disaster management on the basis of needs categorization. The problem of the formulation and execution of such modular subroutines are not addressed here. Since the focus is on the selection of the modular subroutines from the existing DMDSS models on basis of a proposed needs classification scheme.
COLLABORATIVE PLANNING IN SUPPLY CHAINS BY LAGRANGIAN RELAXATION AND GENETIC ALGORITHMS
Authors: NIE LANSHUN , XU XIAOFEI , ZHAN DECHEN
Published: April 2008

A collaborative planning framework combining the Lagrangian Relaxation method and Genetic Algorithms is developed to coordinate and optimize the production planning of the independent partners linked by material flows in multiple tier supply chains. Linking constraints and dependent demand constraints were added to the monolithic Multi-Level, multi-item Capacitated Lot Sizing Problem (MLCLSP) for supply chains. Model MLCLSP was Lagrangian relaxed and decomposed into facility-separable sub-problems based on the separability of it. Genetic Algorithms was incorporated into Lagrangian Relaxation method to update Lagrangian multipliers, which coordinated decentralized decisions of the facilities in supply chains. Production planning of independent partners could be appropriately coordinated and optimized by this framework without intruding their decision authorities and private information. This collaborative planning schema was applied to a large set problem in supply chain production planning. Experimental results show that the proposed coordination mechanism and procedure come close to optimal results as obtained by central coordination in terms of both performance and robustness.
ANALYTICAL AND NUMERICAL MODELING METHODS FOR IMPEDANCE ANALYSIS OF SINGLE CELLS ON-CHIP
Authors: SUN TAO , GREEN NICOLAS G. , MORGAN HYWEL
Published: March 2008

Electrical impedance spectroscopy (EIS) is a noninvasive method for characterizing the dielectric properties of biological particles. The technique can differentiate between cell types and provide information on cell properties through measurement of the permittivity and conductivity of the cell membrane and cytoplasm. In terms of lab-on-a-chip (LOC) technology, cells pass sequentially through the microfluidic channel at high speed and are analyzed individually, rather than as traditionally done on a mixture of particles in suspension. This paper describes the analytical and numerical modeling methods for EIS of single cell analysis in a microfluidic cytometer. The presented modeling methods include Maxwell's mixture theory, equivalent circuit model and finite element method. The difference and advantages of these methods have been discussed. The modeling work has covered the static case — an immobilized cell in suspension and the dynamic case — a moving cell in the channel.
Linking questions and evidence
Authors: Tenenberg Josh , McCartney Robert
Published: April 2008

This special issue features a set of papers recently published in the 3rd International Workshop on Computing Education Research (ICER'07). The papers were selected because they closely meet the publication criteria for ACM/JERIC: stemming from computing education practice, grounded in relevant literature, containing analysis of primary empirical data collected to support specific claims, and providing implications for practice. In addition, the diverse set of research methods used demonstrates how empirical methods can be chosen to serve the specific questions of interest, whether for purposes of research or for improvement of teaching practice. This set of papers can therefore serve as examplars and resources for the educator wishing to develop a wider range of tools for probing issues of teaching and learning within the classroom.
Uncovering student values for hiring in the software industry
Authors: Chinn Donald , Vandegrift Tammy
Published: April 2008

This article provides an analysis of student responses to an exercise used in a computer ethics and a software engineering course to raise awareness of issues related to hiring, including issues of professional responsibility and diversity. Students from two different universities were asked to evaluate four candidates for two positions in a fictitious software company. They then developed a set of criteria for evaluation and constructed an argument to support their choices. After discussing their choice with others in the class, students could change their hiring decisions. Students' hiring criteria were coded using emergent categories, inferences in the arguments were coded according to the criteria, and reasons for changing hiring decisions were coded. Students considered criteria that fell into five areas: technical skills, soft skills, personal traits, previous employment, and career/job considerations. Reasons for changing hiring choices included previous experience, diversity considerations, people skills, leadership skills, and reaching consensus. The article also reports inferences students made about the job candidates.
No sorting? better searching!
Authors: Franceschini Gianni , Grossi Roberto
Published: April 2008

Questions about order versus disorder in systems and models have been fascinating scientists over the years. In computer science, order is intimately related to sorting, commonly meant as the task of arranging keys in increasing or decreasing order with respect to an underlying total order relation. The sorted organization is amenable for searching a set of
n
keys, since each search requires Θ(log
n
) comparisons in the worst case, which is optimal if the cost of a single comparison can be considered a constant. Nevertheless, we prove that disorder implicitly provides more information than order does. For the general case of searching an array of multidimensional keys whose comparison cost is proportional to their length (and hence which cannot be considered a constant), we demonstrate that “suitable” disorder gives better bounds than those derivable by using the natural lexicographic order.

We start from previous work done by Andersson et al. [2001], who proved that Θ(
k
log log
n
/log log(4 +
k
log log
n
/log
n
) +
k
+ log
n
) character comparisons (or probes) comprise the tight complexity for searching a plain sorted array of
n
keys, each of length
k
, arranged in lexicographic order. We describe a novel
permutation
of the
n
keys that is different from the sorted order. When keys are kept “unsorted” in the array according to this permutation, the complexity of searching drops to Θ(
k
+ log
n
) character comparisons (or probes) in the worst case, which is
optimal
among all possible permutations, up to a constant factor. Consequently, disorder carries more information than does order; this fact was not observable before, since the latter two bounds are Θ(log
n
) when
k
=
O
(1). More implications are discussed in the article, including searching in the bit-probe model.
Thin heaps, thick heaps
Authors: Kaplan Haim , Tarjan Robert Endre
Published: April 2008

The Fibonacci heap was devised to provide an especially efficient implementation of Dijkstra's shortest path algorithm. Although asyptotically efficient, it is not as fast in practice as other heap implementations. Expanding on ideas of Høyer [1995], we describe three heap implementations (two versions of
thin heaps
and one of
thick heaps
) that have the same amortized efficiency as Fibonacci heaps, but need less space and promise better practical performance. As part of our development, we fill in a gap in Høyer's analysis.
Randomized minimum spanning tree algorithms using exponentially fewer random bits
Authors: Pettie Seth , Ramachandran Vijaya
Published: April 2008

For many fundamental problems there exist randomized algorithms that are asymptotically optimal and are superior to the best-known deterministic algorithm. Among these are the minimum spanning tree (MST) problem, the MST sensitivity analysis problem, the parallel connected components and parallel minimum spanning tree problems, and the local sorting and set maxima problems. (For the first two problems there are provably optimal deterministic algorithms with unknown, and possibly superlinear, running times.) One downside of the randomized methods for solving these problems is that they use a number of random bits linear in the size of input. In this article we develop some general methods for reducing exponentially the consumption of random bits in comparison-based algorithms. In some cases we are able to reduce the number of random bits from linear to nearly constant, without affecting the expected running time.

Most of our results are obtained by adjusting or reorganizing existing randomized algorithms to work well with a pairwise or
O
(1)-wise independent sampler. The prominent exception, and the main focus of this article, is a linear-time randomized minimum spanning tree algorithm that is
not
derived from the well-known Karger-Klein-Tarjan algorithm. In many ways it resembles more closely the deterministic minimum spanning tree algorithms based on soft heaps. Further, using our algorithm as a guide, we present a unified view of the existing “nongreedy” minimum spanning tree algorithms. Concepts from the Karger-Klein-Tarjan algorithm, such as
F
-lightness, MST verification, and sampled graphs, are related to the concepts of edge corruption, subgraph contractibility, and soft heaps, which are the basis of the deterministic MST algorithms of Chazelle and Pettie-Ramachandran.
A faster and simpler fully dynamic transitive closure
Authors: Roditty Liam
Published: April 2008

We obtain a new fully dynamic algorithm for maintaining the transitive closure of a directed graph. Our algorithm maintains the transitive closure matrix in a total running time of
O
(
mn
+ (
ins
+
del
) ·
n
2
), where
ins
(
del
) is the number of insert (delete) operations performed. Here
n
is the number of vertices in the graph and
m
is the
initial
number of edges in the graph. Obviously, reachability queries can be answered in constant time. The algorithm uses only
O
(
n
2
) time which is essentially optimal for maintaining the transitive closure matrix. Our algorithm can also support path queries. If
v
is reachable from
u
, the algorithm can produce a path from
u
to
v
in time proportional to the length of the path. The best previously known algorithm for the problem is due to Demetrescu and Italiano [2000]. Their algorithm has a total running time of
O
(
n
3
+ (
ins
+
del
) ·
n
2
). The query time is also constant. In addition, we also present a simple algorithm for directed acyclic graphs (DAGs) with a total running time of
O
(
mn
+
ins
·
n
2
+
del
). Our algorithms are obtained by combining some new ideas with techniques of Italiano [1986, 1988], King [1999], King and Thorup [2001] and Frigioni et al. [2001]. We also note that our algorithms are extremely simple and can be easily implemented.
Rectangular layouts and contact graphs
Authors: Buchsbaum Adam L. , Gansner Emden R. , Procopiuc Cecilia M. , Venkatasubramanian Suresh
Published: April 2008

Contact graphs of isothetic rectangles unify many concepts from applications including VLSI and architectural design, computational geometry, and GIS. Minimizing the area of their corresponding
rectangular layouts
is a key problem. We study the area-optimization problem and show that it is NP-hard to find a minimum-area rectangular layout of a given contact graph. We present
O
(
n
)-time algorithms that construct
O
(
n
2
)-area rectangular layouts for general contact graphs and
O
(
n
log
n
)-area rectangular layouts for trees. (For trees, this is an
O
(log
n
)-approximation algorithm.) We also present an infinite family of graphs (respectively, trees) that require Ω(
n
2
) (respectively, Ω(
n
log
n
))area.

We derive these results by presenting a new characterization of graphs that admit rectangular layouts, using the related concept of
rectangular duals
. A corollary to our results relates the class of graphs that admit rectangular layouts to
rectangle-of-influence drawings
.
Approximate distance oracles for geometric spanners
Authors: Gudmundsson Joachim , Levcopoulos Christos , Narasimhan Giri , Smid Michiel
Published: April 2008

Given an arbitrary real constant ε > 0, and a geometric graph
G
in
d
-dimensional Euclidean space with
n
points,
O
(
n
) edges, and constant dilation, our main result is a data structure that answers (1 + ε)-approximate shortest-path-length queries in constant time. The data structure can be constructed in
O
(
n
log
n
) time using
O
(
n
log
n
) space. This represents the first data structure that answers (1 + ε)-approximate shortest-path queries in constant time, and hence functions as an approximate distance oracle. The data structure is also applied to several other problems. In particular, we also show that approximate shortest-path queries between vertices in a planar polygonal domain with “rounded” obstacles can be answered in constant time. Other applications include query versions of
closest-pair
problems, and the efficient computation of the approximate dilations of geometric graphs. Finally, we show how to extend the main result to answer (1 + ε)-approximate shortest-path-length queries in constant time for geometric spanner graphs with
m
= ω(
n
) edges. The resulting data structure can be constructed in
O
(
m
+
n
log
n
) time using
O
(
n
log
n
) space.
Hierarchical bin buffering
Authors: Lemire Daniel , Kaser Owen
Published: April 2008

For a massive I/O array of size
n
, we want to compute the first
N
local moments, for some constant
N
. Our simpler algorithms partition the array into consecutive ranges called bins, and apply not only to local-moment queries, but also to algebraic queries. With
N
buffers of size √
n
, time complexity drops to
O
(√
n
). A more sophisticated approach uses hierarchical buffering and has a logarithmic time complexity (
O
(
b
log

b

n
)), when using
N
hierarchical buffers of size
n
/
b
. Using overlapped bin buffering, we show that only one buffer is needed, as with wavelet-based algorithms, but using much less storage.
The psychology of security
Authors: West Ryan
Published: April 2008

Why do good users make bad decisions?
The business of open source
Authors: Watson Richard T. , Boudreau Marie-Claude , York Paul T. , Greiner Martina E. , Wynn Donald
Published: April 2008

Tracking the changing competitive conditions of the software industry.
A typology of complaints about eBay sellers
Authors: Gregg Dawn G. , Scott Judy E.
Published: April 2008

More could be done to reduce rising online fraud rates.
Missing links
Authors: Oshri Ilan , Kotlarsky Julia , Willcocks Leslie
Published: April 2008

Face-to-face meetings may be invaluable, but they are not a panacea for the challenges facing teams spread around the globe---managers must also prioritize activities before and after these meetings to help team members stay connected.
Knowledge management in small and medium-sized enterprises
Authors: Chan Ivy , Chao Chee-Kwong
Published: April 2008

A balanced combination of management support, technology, and organizational structural factors is necessary for successful knowledge management program implementation.
Demographic changes in IS research productivity and impact
Authors: Khalifa Mohamed , Ning Kathy
Published: April 2008

Always considered an area dominated by North American institutions, there are signs afoot that the globalization of IS research productivity is making moves, particularly in Asia and Europe.
Hacking your network's weakest link
Authors: Greiner Lynn
Published: April 2008

Wandering the halls of a security conference is an experience like nothing else.
Pittsburgh, Pennsylvania to host two international conferences in June, 2008
Authors: Shaffer Kelly
Published: April 2008

The city of Pittsburgh, Pennsylvania, will play host to two international conferences in June 2008. This former industrial Mecca will turn truly high-tech when JCDL 2008 and Hypertext 2008 take place! The conferences are being hosted by the School of Information Sciences at the University of Pittsburgh. JCDL (the Joint Digital Libraries Conference) will take place June 16--20, 2008. It is immediately followed by Hypertext 2008 on June 19--21, 2008. Together, the conferences will welcome more than 450 scholars, industry professionals, students, and researchers to Pittsburgh. It is not the first time that these two conferences have been presented together. Following our conference themes of "linking people and places" and "Bridging Culture, Bridging Technology," it is of interest to note that the ACM Hypertext and Digital Libraries conferences were co-located in Pittsburgh in 1998. This was extremely appropriate as the Hypertext Conference examines one of the core technologies that support the development and management of digital libraries. Soon after 1998, the Digital Libraries Conference evolved into the Joint Conference on Digital Libraries (JCDL), a stand-alone event. It is only fitting that Hypertext is again linked to JCDL in Pittsburgh ten years later.
Weakest precondition based verification tool that models spatial ordering
Authors: Bandyopadhyay Anup Kumar
Published: April 2008

Weakest precondition based method for specification and verification of geographically distributed system is described. For this purpose spatial predicates have been defined. A distributed mutual exclusion algorithm is proposed and is used to illustrate this verification tool.
TML
Authors: Foos Rüdiger , Bunse Christian , Höpfner Hagen , Zimmermann Torsten
Published: April 2008

Quality is a key property of modern software systems. In addition, to quality improvement strategies such as CMM or CMMI and manual checking approaches such as reviews or inspections, software testing is the major quality assurance activity in most projects. Literally speaking, software testing is nearly as essential as writing code itself. Due to its prominent role there are quite a number of commercial and open-source test tools available. However, the question remains if an organisation should rely on a single tool or if it should follow a more general strategy using several tools? Practical experience has shown that the latter strategy is more promising by covering multiple quality aspects that cannot be covered by a single tool, although it requires a means of communication between tools (i.e., a tool independent test language). This paper introduces a XML-based and test tool independent test modeling language that support creating general test cases. The language separates test logic from test tool specific code. Thus, a test case only has to be specified once and can then be executed by several test tools.
Complexity metrics for component-oriented software systems
Authors: Kharb Latika , Singh Rajender
Published: April 2008

Component-based software development (CBSD) has become one of the preferred streams for developing large and complex systems by integrating prefabricated software components that not only facilitates the process of software development but is also changing the ways for software professionals to develop software applications. Till today, numerous attempts have been made by several organizations, software development teams, developers as well as researchers to improve component-oriented software systems (COSS) through improved measurement tools and techniques i.e. through an effective metrics. Our paper is a simple attempt to work for the demand of an appropriate and relevant integration metrics for the measurement of complexity of a software component that could be used as one of the approaches for further guidance in component complexity measurement and problem reduction. We represented a component metrics as an instantiation of the integration complexity measurement which can then be evaluated using appropriate metric tools. The work presented in this paper introduces a perception of component-oriented software systems complexity and also defines some new complexity metrics.
ASM-based model of dynamic service update in OSGi
Authors: Wu Jiankun , Huang Linpeng , Wang Dejun
Published: April 2008

An ASM-based high level semantical model for service-oriented systems based on OSGi and supporting service dynamic updating is provided in this paper. The model not only provides the refinement methods but also gives the final model that specifies the constraint of OSGi. The resulting formal model can be applied in several ways. First, it enables checking or comparing existing systems based on OSGi to determine if they satisfy the dynamic updating demands and provide the necessary functionalities. Furthermore, it can serve as a basis for high level specification of a new system or components or updating constraint. Finally, the model is also useful in reasoning about the properties of service-oriented dynamic updating system based on OSGi.