bluuebunny/crossref_metadata_2025 huggingface dataset:
The regulation of oat coleoptile phosphoenolpyruvate carboxylase and malic enzyme activities by H+ and metabolites. Kinetic evidence for and against a metabolic pH-stat
Authors: Smith Ceredwyn E. , Bown Alan W.
Published: May 2008

Phosphoenolpyruvate carboxylase (EC 4.1.1.31) and malic enzyme (EC 1.1.1.40) activities in soluble protein extracts of Avena coleoptiles were investigated as functions of pH. The presence of malic enzyme activity was confirmed by radiochemical assays which identified the product of the forward reaction and spectrophotometric assays which demonstrated that reduction or oxidation of NADP required all the substrates and cofactors necessary for the forward or reverse reactions. In neither assay could NADP or Mn2+ be replaced by NAD or Mg2+. Activity was independent of pH (6.0 to 7.7) at malate concentrations less than 0.1 mM. At higher concentrations the pH increase raised activity by at least 100%, and substrate inhibition by malate resulted in activity at 0.97 mM malate which was less than that at 0.5 mM malate. The increase in malic enzyme activity with rising pH can be attributed to a decrease in substrate inhibition and a decrease in Km,app (Mn2+). pH increases between 7.0 and 7.6 increased Vmax and phosphoenolpyruvate limited phosphoenolpyruvate carboxylase (PEPC) activity by over 200%, and decreased the Km,app (Mg2+). Inhibition of PEPC and malic enzyme by various carboxylic acids and phosphorylated sugars decreased as the assay pH rose. The results are discussed in light of contrasting suggestions concerning the role of these enzymes in cytosol pH regulation.
Contenu en DNA nucléaire et cycles cellulaires dans le méristème apical du Fucus spiralis
Authors: Lecocq F. M. , Hallet J. N. , Reberteau R.
Published: May 2008

The mitotic indices and the nuclear DNA content of the cells of the meristematic apical zone of Fucus spiralis were investigated on young thalli 5,15, and 25 mm high. The apical cell exhibits a cell cycle with a prominent G2 phase whereas the segmental derivatives, the small cells of the promeristem and, the surrounding elongating cells are characterized by a preponderant G1 phase of their cycle.All the meristematic territories in the three sizes of plant studied show weak mitotic indices (0.5–1%). No significant difference is observed in the cycle features between the cells of the promeristem and the periapical zone of elongation. Hence, no change is seen in the mitotic activity of the cells which begin to differentiate. Certain similarities of structure and function among the shoot meristems of Cryptogams with a single apical cell are discussed.
Ecological studies of vesicular–arbuscular mycorrhizae in a barrier sand dune
Authors: Koske R. E. , Halvorson W. L.
Published: May 2008

An ecological survey of the vegetation of a barrier dune on the south coast of Rhode Island showed Ammophila breviligulata, Solidago sempervirens, Lathyrus japonicus, and Myrica pensylvanica to be the dominant plant species. All plants were mycorrhizal. Six species of vesicular–arbuscular (VA) fungi occurred in association with these plants, with Gigaspora gigantea and Acaulospora scrobiculata the most abundant. Also present were Gigaspora calospora, Glomus etunicatus, Glomus fasciculatus, and an undescribed species of Gigaspora. Spore densities and frequencies were measured in a transect across the dune and were compared with plant cover and physical factors (pH, soil moisture, organic matter, soil nutrients, chlorides, and sand grain size). Areas on the dune with greatest vegetation cover by Ammophila were associated with greatest spore densities and fungal diversity in the rhizosphere. For most plant species, maximum spore density occurred in the front half of the plant's distribution range, nearest the dune crest. There was little correlation between spore populations in the soil and physical characteristics, with the exception of sand grain size. The importance of considering VA mycorrhizae in sand dune stabilization programs is discussed.
Isoenzymes of the glycolytic and pentose-phosphate pathways during the development of the castor oil seed
Authors: Ireland Robert J. , Dennis David T.
Published: May 2008

Plastid and cytosolic isozymes of pyruvate kinase, hexose-phosphate isomerase, and 6-phosphogluconate dehydrogenase have been isolated and separated from seeds of the castor oil plant (Ricinus communis L.) at different stages of development. These enzymes can be detected 24 days after pollination, when the plastids contain 14% of the total cellular activities of both the pyruvate kinase and hexose-phosphate isomerase and 40% of the 6-phosphogluconate dehydrogenase activities. At this stage the seed consists mainly of nucellus, that is subsequently replaced by endosperm. The activities of the plastid isozymes increase faster than the cytosolic isozymes, until after 40 days, when endosperm fills the seed, the plastids contain 25% of the hexose-phosphate isomerase, 70% of the 6-phosphogluconate dehydrogenase, and 40% of the pyruvate kinase activities. The development of the plastid isozymes correlates with the increase in oil synthesis. This supports a central role for plastids in oil synthesis.
Two new fungal parasites of bdelloid rotifers
Authors: Barron G. L.
Published: May 2008

Haptoglossa humicola (Oomycetes) and Tolypocladium trigonosporum (Hyphomycetes) are described as new endoparasites attacking rotifers, belonging to the genera Adineta and Philodina, in soil. In H. humicola the laterally biflagellate zoospores produce spherical cysts each of which then germinates to form a specialized injection cell. The host is attacked by means of rapid injection of a sporidium through the cuticle. Each sporidium produces a thallus inside the host which at maturity functions as a zoosporangium. In T. trigonosporum, after infection, a network of curved anastomosing fertile hyphae produces a loose shell around the encysted host. Conidia are not produced under water, but in air these fertile hyphae give rise to solitary or clustered phialides and triangulate conidia.
Analysis of seasonal succession of attached algae in a mountain stream, the North Alouette River, British Columbia
Authors: Wehr John D.
Published: May 2008

Seasonal succession of attached algae in the North Alouette River over 1 year is described and analyzed in relation to physicochemical characteristics. An attempt is made to consider quantitatively both diatom and nondiatom species using a multivariate method, principal coordinates analysis (P-Co-A).Stream water was slightly acidic and nutrient poor, the order of dominance in anions being SO42− > SiO2 > Cl− > NO3− > PO43− and metals plus ammonium [Formula: see text]. P-Co-A of seasonal succession revealed a cyclic pattern with sequences of gradual and abrupt changes in species composition. Flow, temperature, Cl−, and SO42−, which fluctuated abruptly, were significantly correlated with most of the seasonal change in species summarized by P-Co-A. A smaller amount of the variation, which was more smoothly patterned, correlated with fluxes in dissolved cations. Methods of enumeration and analysis used, although not sensitive to differences in absolute abundance of algal populations, were useful in describing successional patterns in species composition, where both macrophyte and microphyte forms were encountered.Major species tended to wax and wane seasonally, but exhibited long periods of overlap. Such a pattern supports one idea from the "river continuum concept," that generally species are merely shifting along temporal and spatial axes, while the total exclusion or absence of a population is indeed rare. It is suggested that this form of community structure differs from that typically understood for plant succession.
Nitrogen assimilation and dissimilation in five genotypes of Brachiaria spp.
Authors: Pereira Pedro Antonio A. , Döbereiner Johanna , Neyra Carlos A.
Published: May 2008

Five genotypes of Brachiaria spp. were planted in a field experiment with and without nitrate fertilization. Nitrogen metabolism was evaluated by measurements of nitrate reductase (NR) activity in leaves, nitrate accumulation in stems, and nitrogenase activity and dentrification in intact soil–plant cores. There were differences between genotypes in all parameters and a tendency was observed for genotypes with high NR activity and nitrate accumulation to have low nitrogenase activity and vice versa. Brachiaria radicans (Tanner grass) was representative for the first type and B. ruziziensis (CPI 30623) for the second. Denitrification reached 7% of the applied N within 63 h and was lowest in Tanner grass and highest in B. brizantha (FL 902-4). Brachiaria ruziziensis (CPI 30623) plants were able to withstand N stress better than B. radicans as a consequence, possibly, of differences in nitrogenase activity.
Cytochemical staining and in vitro activity of acid trimetaphosphatase in etiolated soybean hypocotyls
Authors: Stôssel P. , Lazarovits G. , Ward E. W. B.
Published: May 2008

Acid trimetaphosphatase has been used as a cytochemical marker for lysosomes in mammalian tissues. Application of the same technique, which employs glutaraldehyde as a fixative, to soybean hypocotyl tissues resulted in staining mainly of nuclei. Sodium fluoride, an effective phosphatase inhibitor, did not prevent but intensified nuclear staining. Nuclei were not stained in formaldehyde-fixed tissues; lead deposits occurred in vacuoles, but ultrastructural preservation was poor and the cytochemical response was inconsistent. Acid trimetaphosphatase activity was demonstrated readily in vitro in protein extracts of soybean tissues, and was strongly inhibited by sodium fluoride. Activity was much reduced in extracts from glutaraldehyde-fixed tissues but not in extracts from formaldehyde-fixed tissues in which it was similar to that in controls. It is concluded that nuclear staining for acid trimetaphosphatase is an artifact of glutaraldehyde fixation, and it is suggested that reports of nuclear staining of acid phosphatases in plant tissues should be interpreted with caution.
Resistance to arsenate toxicity in the blue-green alga Synechococcus leopoliensis
Authors: Budd K. , Craig Susan R.
Published: May 2008

Phosphate-limited growth of the blue-green alga Synechococcus leopoliensis was unaffected by arsenate at up to 200 μM. Phosphate uptake, during growth and also under nongrowing conditions, was not measurably affected by arsenate even at 50 × the phosphate concentration. Arsenate uptake was very low and was not influenced by light or by external phosphate. It is concluded that phosphate transport in Synechococcus is highly phosphate specific. The ecological aspects of this specificity are briefly discussed.
Les facteurs élévation et distance dans la structure et la productivité d'une communauté riveraine de macrophytes
Authors: Tessier Claude , Aubin Antoine , Chenevier Danièle
Published: May 2008

The productivity of macrophytes has been studied in three different zones of Lake Saint-Pierre, Québec: terrestrial, semiaquatic, and aquatic. From the data collected, six vegetation units can be defined. The productivity (grams per square metre) of each unit is as follows: Calamagrostis canadensis, 528; Phalaris arundinacea, 1096; Sparganium eurycarpum, 508; Scirpusfluviatilis, 436; Scirpus acutus, 284; Vallisneria americana, 138. The vegetation distribution is described as a function of elevation and distance from the shore. The results are compared with available data in the literature.
Interaction of mycorrhizal infection, phosphorus level, and moisture stress in growth of field corn
Authors: Hetrick B. A. Daniels , Hetrick J. A. , Bloom J.
Published: May 2008

Field corn from four locations sampled through the growing season was colonized by mycorrhizal fungi despite fairly high (56 μg/g) soil phosphorus fertilities. The mycorrhizal fungi indigenous to these sites were also assessed and Glomus spp. were found to predominate in all but one soil wherein Cigaspora spp. were most common. Adequately watered greenhouse corn exposed to a range of phosphorus fertilities and inoculated with Glomus mosseae showed increased growth in sand amended with 15.0 or 22.5 ppm KH2PO4 over noninoculated controls. Growth of plants amended with 30.0 ppm KH2PO4, however, was smaller suggesting high fertility parasitism by the endophyte. In contrast, no mycorrhizal response was observed on plants exposed to cyclic drought stress, even though root colonization in draughted plants was greater than that observed in adequately watered plants at the lower phosphorus levels. Thus it appears that G. mosseae was unable to measurably improve the drought tolerance of corn and, in addition, any nutritional benefit from the fungus appears to be lost under drought stress.
Ecological interaction of little bluestem and vesicular–arbuscular mycorrhizal fungi
Authors: Dickman Laura A. , Liberta Anthony E. , Anderson Roger C.
Published: May 2008

The percentage of vesicular–arbuscular mycorrhizal (VAM) colonization of little bluestem (Schizachyrium scoparium) (Michx.) Nash.) and VAM spore populations in the rhizosphere of little bluestem from four prairie areas in Illinois were studied. At Goose Lake Prairie, a significant positive correlation (r = 0.77, p < 0.01) was found between soil moisture and density of VAM spores, but soil moisture and percent VAM colonization were not significantly correlated at any of its sites. Percentage of VAM colonization tended to be higher at study areas where little bluestem was a dominant species. However, spore numbers and abundance of little bluestem tended to be inversely related. Colonization decreased from May to July at all areas and this trend frequently continued into September. Month of sample collection had no significant effect on spore numbers except at Reavis Hill Prairie. The endophyte isolated at all areas was Glomus fasciculatum (Thaxter sensu Gerd.) Gerd. & Trappe. Other species, such as Gigaspora heterogama (Nicol. & Gerd.) Gerd. & Trappe and Acaulospora laevis Gerd. & Trappe, were more restricted in their distribution.
Stenomyelon from the Upper Tournaisian of the Montagne Noire (France)
Authors: Meyer-Berthaud Brigitte
Published: May 2008

Stenomyelon bifasciculare nov. sp. is described from the Tournaisian of the Montagne Noire. Represented by six fragments of stems measuring 25 to 40 mm in diameter, these fossil axes bear swollen petiole bases separated by short internodes. Anatomically, they are characterized by a mixed stele with eccentrically mesarch protoxylem poles, secondary xylem with tracheids pitted on all walls, petiolar traces of Kalymma type, and few sclerotic nests in the cortex. The divergence of a pair of leaf traces from each rib of the stele has given the taxon its specific epithet. This feature is new for the genus. Stenomyelon bifasciculare is more distinctive than the Scottish and American taxa described to date. Except for Stenomyelon heterangioides, in which this character is doubtful, no sympodia from which leaf traces diverge are recognized in any Stenomyelon, including Stenomyelon bifasciculare; protoxylem maturation has no cauline expression. This character is suggested as the most important one to define the genus.
Dormancy of apple embryos. Are starch and reserve protein changes related to dormancy breaking?
Authors: Bouvier-Durand Michelle , Dawidowicz-Grzegorzewska Alina , Thévenot Claudine , Come Daniel
Published: May 2008

During cold stratification of apple seeds both dormancy removal and initiation of the germination process occur. To characterize these two processes and to dissociate them from each other, two different cold treatments were used. One of them (cold treatment within the fruits) excluded the germination process, the other corresponded to classical stratification. Control treatments at moderate temperature were also applied. Starch accumulated in the radicle during breaking of embryo dormancy by stratification, whereas it disappeared when dormancy was broken inside the fruits. The comparison of starch changes at 0 and at 20 °C also showed that these changes cannot be related to dormancy release. Moreover, no proteolysis occurred whether dormancy was broken or not. Proteolysis observed during stratification of the embryos seemed to be linked to their imbibition (the first step of the germination). These data refute previous observations on this problem; they demonstrate that neither starch variations nor reserve protein changes can be related to breaking of embryo dormancy.
Embryogenèse somatique a partir de cultures issues de protoplastes foliaires de Ranunculus sceleratus
Authors: Dorion N. , Godin B. , Bigot C.
Published: May 2008

Following preliminary experiments, studies on isolation and culture of Ranunculus sceleratus L. leaf protoplasts were performed to specify conditions inducing embryogenesis. The best developmental stage for obtaining protoplasts was the second unfolded leaf; protoplasts were incubated in cellulase Onozuka R 10 (0.1%), Driselase (0.05%), Macerozyme R 10 (0.02%), glucose (8.9%), and Murashige and Skoog major salts (×0.5) or calcium chloride (220 mg/L), yielding 8 × 105 viable protoplasts per leaf; the best inoculum has 35 × 103 protoplasts/mL, protoplasts were cultured in 1-naphthaleneacetic acid (NAA) (3 mg/L), 6-benzylaminopurine (1 mg/L), modified Heller's micronutrients, Morel's vitamins, calcium nitrate (400 mg/L), and glutamine (100 mg/L). Although survival of protoplasts was as high as 80%, only 3% of the cells divide after 3 weeks. After subculturing the suspensions embryogenesis proceeded rapidly. Use of NAA (3 mg/L) or spreading cell cultures on solid medium delays the process. Following induction, cultures become habituated; continuous embryogenesis results from the differentiation of secondary embryos arising directly from primary embryo epidermis. The capacity for embryogenesis, however, diminishes after several subcultures, particularly if media are supplemented with growth regulators. Although growth of many embryos is inhibited, most plantlets subsequently develop normally. Thus, while we have demonstrated embryogenic capacity in suspension cultures derived from mesophyll protoplasts, direct development of somatic embryos from protoplasts remains to be shown.
Alpine plants of phytogeographic interest on northwestern Vancouver Island
Authors: Ogilvie R. T. , Ceska A.
Published: May 2008

Forty-four alpine taxa of phytogeographic interest are reported for seven mountain peaks on northwestern Vancouver Island, and their distribution is discussed. These taxa include two of the Queen Charlotte Islands endemics, two of the Olympic Peninsula endemics, one new record for North America, five new records for Vancouver Island, and a number of disjuncts. The relation of the alpine flora of the Vancouver Island Ranges to other mountain systems and phytogeographic evidence for nonglaciated refugia on Vancouver Island are discussed.
Anatomical analysis of the development and distribution of Rhizobium infections in soybean roots
Authors: Calvert Harry E. , Pence Mark K. , Pierce Margaret , Malik Nasir S. A. , Bauer Wolfgang D.
Published: May 2008

Roots of young soybean (Glycine max (L.) Merr.) seedlings inoculated with Rhizobium japonicum Kirchner USDA 110 ARS were examined in serial sections by light microscopy to ascertain the extent of infection. The location of each infection site was established in relation to the zones of root and root hair development at the time of inoculation. Each infection locus was classified as to its relative state of differentiation using a developmental scale encompassing the first 10 days of nodule development. Both the initiation and maturation of Rhizobium infections were found to be governed by the acropetal development of host root hairs. Regions of the root where mature root hairs were present at the time of inoculation were not susceptible to Rhizobium infection. Infections developed most frequently in root hairs which emerged shortly after inoculation. Many infections formed on the root but relatively few developed into nodules. Most infection loci which formed infection threads stopped developing at stages prior to meristem formation. A high proportion of the infection loci were pseudoinfections, i.e., localized areas of cortical cell division without infection thread formation. The maturation of infections in younger regions of the root was suppressed by prior exposure of older regions of the root to rhizobia. Development was suppressed at stages after meristem formation but before nodule emergence.
Uptake and translocation of benzyladenine by elm shoots cultured in vitro
Authors: Biondi S. , Canciani L. , Bagni N.
Published: May 2008

The rate of uptake of 8-[14C]benzyladenine by Ulmus campestris L. (elm) shoots cultured in vitro was extremely rapid during the first 30–60 min of incubation. Total radioactivity, both in methanol extracts and in the pellet, continued to increase up to the 15th day in culture when shoots were transferred to a basal medium. After transfer, the 14C extracted and that remaining in the pellet diminished significantly, especially in the former, while only a small amount of radioactivity was released into the medium, suggesting that some 14C must have been released as 14CO2. A possible pathway leading to CO2 formation is described. Activated charcoal in the basal medium did not affect the loss of activity from the tissue. Benzyladenine was translocated into the upper half of the shoots quite rapidly (within 30 min) and benzyladenine degradation into a metabolite which cochromatographed with adenine was already detectable after 2 h in the lower half and 6 h in the upper half of the shoots. Throughout the 24-h feeding period, uptake was more rapid than degradation. By day 5, however, benzyladenine levels in the tissue were decreasing rapidly, reaching almost zero by day 15. In parallel, there was a transient increase in what is assumed to be adenine levels; the levels of products which cochromatographed with adenosine and adenine nucleotide were measured only during the 24-h feeding period and remained low throughout.
The primary vascular system and medullary bundle structure of Phytolacca dioica (Phytolaccaceae)
Authors: Kirchoff Bruce K. , Fahn Abraham
Published: May 2008

Phytolacca dioica has a primary vascular system which includes medullary bundles. The primary structure of these bundles is composite, consisting of two to four collateral vascular strands with their phloem poles oriented toward a common center. A cambium is formed between the xylem and phloem of the strands and extends to enclose the phloem of the whole bundle. After a period of cambial activity the medullary bundles become amphivasal. As is typical of species with helical phyllotaxy, the primary vascular system is organized into sympodia. The medullary bundles form the distal portions of the median leaf traces and continue in a medullary position for the number of nodes equal to the denominator of the phyllotactic fraction characterizing a given stem. As a medullary bundle passes out into a leaf, two or three vascular strands pass inward from the vascular cylinder to form a new medullary bundle. The number of medullary bundles in a stem is, thus, maintained. Variations of this pattern occur in the basal regions of juvenile shoots and in the basal and apical regions of adult flowering shoots. The relationship between leaf arrangement and the passing of vascular strand into the pith is discussed and a new classification of vascular systems with medullary bundles is proposed.
Inland spruce cone rust, Chrysomyxa pirolata, in Pyrola asarifolia and cones of Picea glauca, and morphology of the spore stages
Authors: Sutherland Jack R. , Hopkinson Sarah J. , Farris S. H.
Published: May 2008

Intact and sectioned specimens were examined by using a light and a scanning electron microscope to determine the presence and spore morphology of inland spruce cone rust, Chrysomyxa pirolata Wint., in Pyrola asarifolia Michx. plants and in white spruce, Picea glauca (Moench) Voss, cones. Field observations of rust development and sporulation were made throughout the year. The microscope studies confirmed that C. pirolata is systemic and perennial in shoots and connecting rhizomes of P. asarifolia, indicating that one mode of fungus spread is between plants originating from the same rhizome. Sometimes, hyphae of C. pirolata occurred only at the nodes along part of a rhizome connecting diseased P. asarifolia plants. Spring-collected buds from diseased P. asarifolia contained C. pirolata mycelium, but the fungus was not evident externally on current growth until the following spring. However, all leaves, especially those produced in the current year, on these plants were more upright and their upper surface less shiny. In some years, all P. asarifolia leaves in a locality bore mostly uredinia or telia; at other times about equal numbers of both were present on each leaf. About 6 weeks after telial production, spermogonia appeared on nearby spruce cones and about 4 weeks later these cones bore aeciospores on most scales of the systemically infected cones. Fruiting bodies and spores for each stage of the life cycle of the fungus are illustrated.
Applying computational tools to predict gaze direction in interactive visual environments
Authors: Peters Robert J. , Itti Laurent
Published: May 2008

Future interactive virtual environments will be “attention-aware,” capable of predicting, reacting to, and ultimately influencing the visual attention of their human operators. Before such environments can be realized, it is necessary to operationalize our understanding of the relevant aspects of visual perception, in the form of fully automated computational heuristics that can efficiently identify locations that would attract human gaze in complex dynamic environments. One promising approach to designing such heuristics draws on ideas from computational neuroscience. We compared several neurobiologically inspired heuristics with eye-movement recordings from five observers playing video games, and found that human gaze was better predicted by heuristics that detect outliers from the global distribution of visual features than by purely local heuristics. Heuristics sensitive to dynamic events performed best overall. Further, heuristic prediction power differed more between games than between different human observers. While other factors clearly also influence eye position, our findings suggest that simple neurally inspired algorithmic methods can account for a significant portion of human gaze behavior in a naturalistic, interactive setting. These algorithms may be useful in the implementation of interactive virtual environments, both to predict the cognitive state of human operators, as well as to effectively endow virtual agents in the system with humanlike visual behavior.
XPath satisfiability in the presence of DTDs
Authors: Benedikt Michael , Fan Wenfei , Geerts Floris
Published: May 2008

We study the satisfiability problem associated with XPath in the presence of DTDs. This is the problem of determining, given a query
p
in an XPath fragment and a DTD
D
, whether or not there exists an XML document
T
such that
T
conforms to
D
and the answer of
p
on
T
is nonempty. We consider a variety of XPath fragments widely used in practice, and investigate the impact of different XPath operators on the satisfiability analysis. We first study the problem for negation-free XPath fragments with and without upward axes, recursion and data-value joins, identifying which factors lead to tractability and which to NP-completeness. We then turn to fragments with negation but without data values, establishing lower and upper bounds in the absence and in the presence of upward modalities and recursion. We show that with negation the complexity ranges from PSPACE to EXPTIME. Moreover, when both data values and negation are in place, we find that the complexity ranges from NEXPTIME to undecidable. Furthermore, we give a finer analysis of the problem for particular classes of DTDs, exploring the impact of various DTD constructs, identifying tractable cases, as well as providing the complexity in the query size alone. Finally, we investigate the problem for XPath fragments with sibling axes, exploring the impact of horizontal modalities on the satisfiability analysis.
Efficient core computation in data exchange
Authors: Gottlob Georg , Nash Alan
Published: May 2008

Data exchange deals with inserting data from one database into another database having a different schema. Fagin et al. [2005] have shown that among the universal solutions of a solvable data exchange problem, there exists—up to isomorphism—a unique most compact one, “the core”, and have convincingly argued that this core should be the database to be materialized. They stated as an important open problem whether the core can be computed in polynomial time in the general setting where the mapping between the source and target schemas is given by source-to-target constraints that are arbitrary tuple generating dependencies (tgds) and target constraints consisting of equality generating dependencies (egds) and a weakly acyclic set of tgds. In this article, we solve this problem by developing new methods for efficiently computing the core of a universal solution. This positive result shows that data exchange based on cores is feasible and applicable in a very general setting. In addition to our main result, we use the method of hypertree decompositions to derive new algorithms and upper bounds for query containment checking and computing cores of arbitrary database instances. We also show that computing the core of a data exchange problem is fixed-parameter intractable with respect to a number of relevant parameters, and that computing cores is NP-complete if the rule bodies of target tgds are augmented by a special predicate that distinguishes a null value from a constant data value.
The worst-case execution-time problem—overview of methods and survey of tools
Authors: Wilhelm Reinhard , Engblom Jakob , Ermedahl Andreas , Holsti Niklas , Thesing Stephan , Whalley David , Bernat Guillem , Ferdinand Christian , Heckmann Reinhold , Mitra Tulika , Mueller Frank , Puaut Isabelle , Puschner Peter , Staschulat Jan , Stenström Per
Published: May 2008

The determination of upper bounds on execution times, commonly called worst-case execution times (WCETs), is a necessary step in the development and validation process for hard real-time systems. This problem is hard if the underlying processor architecture has components, such as caches, pipelines, branch prediction, and other speculative components. This article describes different approaches to this problem and surveys several commercially available tools
1
and research prototypes.
Trends in the living room and beyond
Authors: Bernhaupt Regina , Obrist Marianna , Weiss Astrid , Beck Elke , Tscheligi Manfred
Published: May 2008

In this article we present the findings of two ethnographic studies embedded into two broader projects on interactive television in the home environment. Based on previous research on the home context and inspired by ongoing trends around interactive television, we explored basic concepts, such as the extended home, and new interaction techniques, in particular those related to future developments of the remote control. For the two studies we also developed two variations of the cultural probes method: creative probing and playful probing. This methodological approach proved to be appropriate for gathering in-depth data on participants' opinions, attitudes, and ideas in a way favorable to the participants. Overall, our results support existing research data on user media behavior and expectations and show trends in and beyond the living room, concerned with personalization, privacy, and security as well as communication.
Feature synthesized EM algorithm for image retrieval
Authors: Li Rui , Bhanu Bir , Dong Anlei
Published: May 2008

As a commonly used unsupervised learning algorithm in
Content-Based Image Retrieval
(CBIR),
Expectation-Maximization
(EM) algorithm has several limitations, including the curse of dimensionality and the convergence at a local maximum. In this article, we propose a novel learning approach, namely
Coevolutionary Feature Synthesized Expectation-Maximization
(CFS-EM), to address the above problems. The CFS-EM is a hybrid of
coevolutionary genetic programming
(CGP) and EM algorithm applied on partially labeled data. CFS-EM is especially suitable for image retrieval because the images can be searched in the synthesized low-dimensional feature space, while a kernel-based method has to make classification computation in the original high-dimensional space. Experiments on real image databases show that CFS-EM outperforms
Radial Basis Function Support Vector Machine
(RBF-SVM), CGP,
Discriminant-EM
(D-EM) and
Transductive-SVM
(TSVM) in the sense of classification performance and it is computationally more efficient than RBF-SVM in the query phase.
Audio keywords generation for sports video analysis
Authors: Xu Min , Xu Changsheng , Duan Lingyu , Jin Jesse S. , Luo Suhuai
Published: May 2008

Sports video has attracted a global viewership. Research effort in this area has been focused on semantic event detection in sports video to facilitate accessing and browsing. Most of the event detection methods in sports video are based on visual features. However, being a significant component of sports video, audio may also play an important role in semantic event detection. In this paper, we have borrowed the concept of the “keyword” from the text mining domain to define a set of specific audio sounds. These specific audio sounds refer to a set of game-specific sounds with strong relationships to the actions of players, referees, commentators, and audience, which are the reference points for interesting sports events. Unlike low-level features, audio keywords can be considered as a mid-level representation, able to facilitate high-level analysis from the semantic concept point of view. Audio keywords are created from low-level audio features with learning by support vector machines. With the help of video shots, the created audio keywords can be used to detect semantic events in sports video by Hidden Markov Model (HMM) learning. Experiments on creating audio keywords and, subsequently, event detection based on audio keywords have been very encouraging. Based on the experimental results, we believe that the audio keyword is an effective representation that is able to achieve satisfying results for event detection in sports video. Application in three sports types demonstrates the practicality of the proposed method.
Multimedia streaming using multiple TCP connections
Authors: Tullimas Sunand , Nguyen Thinh , Edgecomb Rich , Cheung Sen-ching
Published: May 2008

In recent years, multimedia applications over the Internet become increasingly popular. However, packet loss, delay, and time-varying bandwidth of the Internet have remained the major problems for multimedia streaming applications. As such, a number of approaches, including network infrastructure and protocol, source and channel coding, have been proposed to either overcome or alleviate these drawbacks of the Internet. In this article, we propose the MultiTCP system, a receiver-driven, TCP-based system for multimedia streaming over the Internet. Our proposed algorithm aims at providing resilience against short term insufficient bandwidth by using multiple TCP connections for the same application. Our proposed system enables the application to achieve and control the desired sending rate during congested periods, which cannot be achieved using traditional TCP. Finally, our proposed system is implemented at the application layer, and hence, no kernel modification to TCP is necessary. We analyze the proposed system, and present simulation and experimental results to demonstrate its advantages over the traditional single-TCP-based approach.
A scalable and extensible segment-event-object-based sports video retrieval system
Authors: Tjondronegoro Dian , Chen Yi-Ping Phoebe , Joly Adrien
Published: May 2008

Sport video data is growing rapidly as a result of the maturing digital technologies that support digital video capture, faster data processing, and large storage. However, (1) semi-automatic content extraction and annotation, (2) scalable indexing model, and (3) effective retrieval and browsing, still pose the most challenging problems for maximizing the usage of large video databases. This article will present the findings from a comprehensive work that proposes a scalable and extensible sports video retrieval system with two major contributions in the area of sports video indexing and retrieval. The first contribution is a new sports video indexing model that utilizes semi-schema-based indexing scheme on top of an Object-Relationship approach. This indexing model is scalable and extensible as it enables gradual index construction which is supported by ongoing development of future content extraction algorithms. The second contribution is a set of novel queries which are based on XQuery to generate dynamic and user-oriented summaries and event structures. The proposed sports video retrieval system has been fully implemented and populated with soccer, tennis, swimming, and diving video. The system has been evaluated against 20 users to demonstrate and confirm its feasibility and benefits. The experimental sports genres were specifically selected to represent the four main categories of sports domain: period-, set-point-, time (race)-, and performance-based sports. Thus, the proposed system should be generic and robust for all types of sports.
Algorithm 875
Authors: Benson Steven J. , Ye Yinyu
Published: May 2008

DSDP implements the dual-scaling algorithm for semidefinite programming. The source code for this interior-point algorithm, written entirely in ANSI C, is freely available under an open source license. The solver can be used as a subroutine library, as a function within the Matlab environment, or as an executable that reads and writes to data files. Initiated in 1997, DSDP has developed into an efficient and robust general-purpose solver for semidefinite programming. Its features include a convergence proof with polynomially bounded worst-case complexity, primal and dual feasible solutions when they exist, certificates of infeasibility when solutions do not exist, initial points that can be feasible or infeasible, relatively low memory requirements for an interior-point method, sparse and low-rank data structures, extensibility that allows applications to customize the solver and improve its performance, a subroutine library that enables it to be linked to larger applications, scalable performance for large problems on parallel architectures, and a well-documented interface and examples of its use. The package has been used in many applications and tested for efficiency, robustness, and ease of use.
An authentication and validation mechanism for analyzing syslogs forensically
Authors: Monteiro Steena D. S. , Erbacher Robert F.
Published: May 2008

This research proposes a novel technique for authenticating and validating syslogs for forensic analysis. This technique uses a modification of the Needham Schroeder protocol, which uses nonces (numbers used only once) and public keys. Syslogs, which were developed from an event-logging perspective and not from an evidence-sustaining one, are system treasure maps that chart out and pinpoint attacks and attack attempts. Over the past few years, research on securing syslogs has yielded enhanced syslog protocols that focus on tamper prevention and detection. However, many of these protocols, though efficient from a security perspective, are inadequate when forensics comes into play. From a legal perspective, any kind of evidence found at a crime scene needs to be validated. In addition, any digital forensic evidence when presented in court needs to be admissible, authentic, believable, and reliable [4]. Currently, a patchy log on the server side and client side cannot be considered as formal authentication of a wrong doer [5]. This paper presents a method that ties together, authenticates, and validates all the entities involved in the crime scene---the user using the application, the system that is being used, and the application being used on the system by a user. This means that instead of merely transmitting the header and the message, which is the standard syslog protocol format, the syslog entry along with the user fingerprint, application fingerprint, and system fingerprint are transmitted to the logging server. The assignment of digital fingerprints and the addition of a challenge response mechanism to the underlying syslogging mechanism aim to validate generated syslogs forensically.
A normality based method for detecting kernel rootkits
Authors: Wampler Doug , Graham James H.
Published: May 2008

Rootkits are stealthy, malicious software that allow an attacker to gain and maintain control of a system, attack other systems, destroy evidence, and decrease the chance of detection. Existing detection methods typically rely on
a priori
knowledge and operate by either (a) saving the system state before infection and comparing this information post infection, or (b) installing a detection program before infection. This approach focuses on detection using reduced
a priori
knowledge in the form of general knowledge of the statistical properties of broad classes of operating system/architecture pairs.

A modified normality based approach proved effective in detecting kernel rootkits infecting the kernel via the system call target modification attack. This approach capitalizes on the discovery that system calls are loaded into memory sequentially, with the higher level calls, which are more likely to be infected by kernel rootkits loaded first, and the lower level calls loaded later. In the single case evaluated, the enyelkm rootkit, neither false positives nor false positives were indicated. The enyelkm rootkit was selected for analysis since it infects the Linux kernel via the system call target modification attack, which is the subject of this research.
Acquiring volatile operating system data tools and techniques
Authors: Sutherland Iain , Evans Jon , Tryfonas Theodore , Blyth Andrew
Published: May 2008

The current approach to forensic examination during search and seizure has predominantly been to pull the plug on the suspect machine and subsequently perform a post mortem examination on the storage medium. However, with the advent of larger capacities of memory, drive encryption and anti-forensics, this procedure may result in the loss of valuable evidence. Volatile data may be vital in determining criminal activity; it may contain passwords used for encryption, indications of anti-forensic techniques, memory resident malware which would otherwise go unnoticed by the investigator. This paper emphasizes the importance of understanding the potential value of volatile data and how best to collate forensic artifacts to the benefit of the investigation, ensuring the preservation and integrity of the evidence. The paper will review current methods for volatile data collection, assessing the capabilities, limitations and liabilities of current tools and techniques available to the forensic investigator.
Forensics examination of volatile system data using virtual introspection
Authors: Hay Brian , Nance Kara
Published: May 2008

While static examination of computer systems is an important part of many digital forensics investigations, there are often important system properties present only in volatile memory that cannot be effectively recovered using static analysis techniques, such as offline hard disk acquisition and analysis. An alternative approach, involving the live analysis of target systems to uncover this volatile data, presents significant risks and challenges to forensic investigators as observation techniques are generally intrusive and can affect the system being observed. This paper provides a discussion of live digital forensics analysis through virtual introspection and presents a suite of virtual introspection tools developed for Xen (VIX tools). The VIX tools suite can be used for unobtrusive digital forensic examination of volatile system data in virtual machines, and addresses a key research area identified in the virtualization in digital forensics research agenda [22].
The impact of full disk encryption on digital forensics
Authors: Casey Eoghan , Stellatos Gerasimos J.
Published: May 2008

The integration of strong encryption into operating systems is creating challenges for forensic examiners, potentially preventing us from recovering any digital evidence from a computer. Because strong encryption cannot be circumvented without a key or passphrase, forensic examiners may not be able to access data after a computer is shut down, and must decide whether to perform a live forensic acquisition. In addition, with encryption becoming integrated into the operating system, in some cases, virtualization is the most effective approach to performing a forensic examination of a system with FDE. This paper presents the evolution of full disk encryption (FDE) and its impact on digital forensics. Furthermore, by demonstrating how full disk encryption has been dealt with in past investigations, this paper provides forensics examiners with practical techniques for recovering evidence that would otherwise be inaccessible.
Computer forensics
in forensis
Authors: Peisert Sean , Bishop Matt , Marzullo Keith
Published: May 2008

Different users apply computer forensic systems, models, and terminology in very different ways. They often make incompatible assumptions and reach different conclusions about the validity and accuracy of the methods they use to log, audit, and present forensic data. In fact, it can be hard to say who, if anyone is right. We present several forensic systems and discuss situations in which they produce valid and accurate conclusions and also situations in which their accuracy is suspect. We also present forensic models and discuss areas in which they are useful and areas in which they could be augmented. Finally, we present some recommendations about how computer scientists, forensic practitioners, lawyers, and judges could build more complete models of forensics that take into account appropriate legal details and lead to scientifically valid forensic analysis.
Insulin Signaling in the Pancreatic β-Cell
Authors: Leibiger Ingo B. , Leibiger Barbara , Berggren Per-Olof
Published: May 2008

The appropriate function of insulin-producing pancreatic β-cells is crucial for the regulation of glucose homeostasis, and its impairment leads to diabetes mellitus, the most common metabolic disorder in man. In addition to glucose, the major nutrient factor, inputs from the nervous system, humoral components, and cell-cell communication within the islet of Langerhans act together to guarantee the release of appropriate amounts of insulin in response to changes in blood glucose levels. Data obtained within the past decade in several laboratories have revitalized controversy over the autocrine feedback action of secreted insulin on β-cell function. Although insulin historically has been suggested to exert a negative effect on β-cells, recent data provide evidence for a positive role of insulin in transcription, translation, ion flux, insulin secretion, proliferation, and β-cell survival. Current insights on the role of insulin on pancreatic β-cell function are discussed.