Showing papers by "University of California published in 2004"

Tissue ablation with irreversible electroporation

Abstract: A new method for the ablation of undesirable tissue such as cells of a cancerous or non-cancerous tumor is disclosed. It involves the placement of electrodes into or near the vicinity of the undesirable tissue through the application of electrical pulses causing irreversible electroporation of the cells throughout the entire area of the undesirable tissue. The electric pulses irreversibly permeate the cell membranes, thereby invoking cell death. The irreversibly permeabilized cells are left in situ and are removed by the body immune system. The amount of tissue ablation achievable through the use of irreversible electroporation without inducing thermal damage is considerable.

Efflux-Mediated Drug Resistance in Bacteria

Abstract: Drug efflux pumps play a key role in drug resistance and also serve other functions in bacteria. There has been a growing list of multidrug and drug-specific efflux pumps characterized from bacteria of human, animal, plant and environmental origins. These pumps are mostly encoded on the chromosome, although they can also be plasmid-encoded. A previous article in this journal provided a comprehensive review regarding efflux-mediated drug resistance in bacteria. In the past 5 years, significant progress has been achieved in further understanding of drug resistance-related efflux transporters and this review focuses on the latest studies in this field since 2003. This has been demonstrated in multiple aspects that include but are not limited to: further molecular and biochemical characterization of the known drug efflux pumps and identification of novel drug efflux pumps; structural elucidation of the transport mechanisms of drug transporters; regulatory mechanisms of drug efflux pumps; determining the role of the drug efflux pumps in other functions such as stress responses, virulence and cell communication; and development of efflux pump inhibitors. Overall, the multifaceted implications of drug efflux transporters warrant novel strategies to combat multidrug resistance in bacteria.

The Political Salience of Cultural Difference: Why Chewas and Tumbukas Are Allies in Zambia and Adversaries in Malawi

Abstract: This paper explores the conditions under which cultural cleavages become politically salient. It does so by taking advantage of the natural experiment afforded by the division of the Chewa and Tumbuka peoples by the border between Zambia and Malawi. I document that, while the objective cultural differences between Chewas and Tumbukas on both sides of the border are identical, the political salience of the division between these communities is altogether different. I argue that this difference stems from the different sizes of the Chewa and Tumbuka communities in each country relative to each country's national political arena. In Malawi, Chewas and Tumbukas are each large groups vis-a-vis the country as a whole and, thus, serve as viable bases for political coalition-building. In Zambia, Chewas and Tumbukas are small relative to the country as a whole and, thus, not useful to mobilize as bases of political support. The analysis suggests that the political salience of a cultural cleavage depends not on the nature of the cleavage itself (since it is identical in both countries) but on the sizes of the groups it defines and whether or not they will be useful vehicles for political competition.

Resource pulses, species interactions and diversity maintenance in arid and semi-arid environments

Abstract: Arid environments are characterized by limited and variable rainfall that supplies resources in pulses. Resource pulsing is a special form of environmental variation, and the general theory of coexistence in variable environments suggests specific mechanisms by which rainfall variability might contribute to the maintenance of high species diversity in arid ecosystems. In this review, we discuss physiological, morphological, and life-history traits that facilitate plant survival and growth in strongly water-limited variable environments, outlining how species differences in these traits may promote diversity. Our analysis emphasizes that the variability of pulsed environments does not reduce the importance of species interactions in structuring communities, but instead provides axes of ecological differentiation between species that facilitate their coexistence. Pulses of rainfall also influence higher trophic levels and entire food webs. Better understanding of how rainfall affects the diversity, species composition, and dynamics of arid environments can contribute to solving environmental problems stemming from land use and global climate change.

Knowledge and Competence as Strategic Assets

Abstract: The firm is a repository for knowledge—the knowledge being embedded in business routines and processes. Distinctive processes undergird firm-specific assets and competences (defined as integrated clusters of firm-specific assets). The firm’s knowledge base includes its technological competences as well as its knowledge of customer needs and supplier capabilities. These competences reflect both individual skills and experiences as well as distinctive ways of doing things inside firms. The essence of the firm is its ability to create, transfer, assemble, integrate, and exploit knowledge assets. Knowledge assets underpin competences, and competences in turn underpin the firm’s product and service offerings to the market. Competitive advantage can be attributed not only to the ownership of knowledge assets and other assets complementary to them, but also to the ability to combine knowledge assets with other assets needed to create value.

Selection and Evolution of Industry

Abstract: The evolution of industry depends on the selection mechanism, that is, the process of entry and exit of firms and the various factors influencing the entry and exit decisions. Three major factors are most important in the selection process. One is the evolutionary perspective which emphasizes the firm’s ability and competence to alter their market position and hence through strong increasing returns to scale, to alter the market structure significantly. Following the Schumpeterian theory of technological innovations the main source of such increasing returns is the cumulative aspect of innovations, where “size begets size” causes industrial dynamics to be characterized by nonlinear and path dependent processes, where random events like a new technical process may have lasting and irreversible effects on the dynamic evolution of the selection process. Secondly, firms differ significantly in their commitment and ability to innovate. Thus innovations in products and processes are largely endogenous to the firm through R&D investment and learning-by-doing. Thus vigorous innovation has been found to generate more competitive market structures, while innovations requiring large investment generally involve more concentration through large size firms. Also due to the cumulative nature of technological innovations firms that discover new technologies are able to maintain their lead even after the particular technology is obsolete.

Prostate Pathology of Genetically Engineered Mice: Definitions and Classification. The Consensus Report from the Bar Harbor Meeting of the Mouse Models of Human Cancer Consortium Prostate Pathology Committee

Abstract: The Pathological Classification of Prostate Lesions in Genetically Engineered Mice (GEM) is the result of a directive from the National Cancer Institute Mouse Models of Human Cancer Consortium Prostate Steering Committee to provide a hierarchical taxonomy of disorders of the mouse prostate to facilitate classification of existing and newly created mouse models and the translation to human prostate pathology. The proposed Bar Harbor Classification system is the culmination of three meetings and workshops attended by various members of the Prostate Pathology Committee of the Mouse Models of Human Cancer Consortium. A 2-day Pathology Workshop was held at The Jackson Laboratory in Bar Harbor, Maine, in October 2001, in which study sets of 93 slides from 22 GEM models were provided to individual panel members. The comparison of mouse and human prostate anatomy and disease demonstrates significant differences and considerable similarities that bear on the interpretation of the origin and natural history of their diseases. The recommended classification of mouse prostate pathology is hierarchical, and includes developmental, inflammatory, benign proliferative, and neoplastic disorders. Among the neoplastic disorders, preinvasive, microinvasive, and poorly differentiated neoplasms received the most attention. Specific criteria were recommended and will be discussed. Transitions between neoplastic states were of particular concern. Preinvasive neoplasias of the mouse prostate were recognized as focal, atypical, and progressive lesions. These lesions were designated as mouse prostatic intraepithelial neoplasia (mPIN). Some atypical lesions were identified in mouse models without evidence of progression to malignancy. The panel recommended that mPIN lesions not be given histological grades, but that mPIN be further classified as to the absence or presence of documented associated progression to invasive carcinoma. Criteria for recognizing microinvasion, for classification of invasive gland-forming adenocarcinomas, and for characterizing poorly differentiated tumors, including neuroendocrine carcinomas, were developed and are discussed. The uniform application of defined terminology is essential for correlating results between different laboratories and models. It is recommended that investigators use the Bar Harbor Classification system when characterizing new GEM models or when conducting experimental interventions that may alter the phenotype or natural history of lesion progression in existing models.

Social License and Environmental Protection: Why Businesses Go beyond Compliance

Abstract: This article examines the concept of the corporate “social license,” which governs the extent to which a corporation is constrained to meet societal expectations and avoid activities that societies (or influential elements within them) deem unacceptable, whether or not those expectations are embodied in law. It examines the social license empirically, as it relates to one social problem–environmental protection–and as it relates to one particular industry: pulp and paper manufacturing. It shows try the social license is important, the circumstances in which it may encourage companies to go “beyond compliance” with regulation, how its terms are monitored and enforced, and how it interacts with what we term the regulatory and economic licenses. Overall, this research demonstrates that corporate environmental behavior cannot be explained purely in terms of instrumental threats and moral obligations to comply with the law, and that the increasing incidence of “beyond compliance” corporate behavior can be better explained in terms of the interplay between social pressures and economic constraints.

A Transgenic Mouse with a Deletion in the Collagenous Domain of Adiponectin Displays Elevated Circulating Adiponectin and Improved Insulin Sensitivity

Abstract: Adiponectin is a plasma protein expressed exclusively in adipose tissue. Adiponectin levels are linked to insulin sensitivity, but a direct effect of chronically elevated adiponectin on improved insulin sensitivity has not yet been demonstrated. We identified a dominant mutation in the collagenous domain of adiponectin that elevated circulating adiponectin values in mice by 3-fold. Adiponectinemia raised lipid clearance and lipoprotein lipase activity, and suppressed insulin-mediated endogenous glucose production. The induction of adiponectin during puberty and the sexual dimorphism in adult adiponectin values were preserved in these transgenic animals. As a result of elevated adiponectin, serum PRL values and brown adipose mass both increased. The effects on carbohydrate and lipid metabolism were associated with elevated phosphorylation of 5′-AMP-activated protein kinase in liver and elevated expression of peroxisomal proliferator-activated receptor γ2, caveolin-1, and mitochondrial markers in white adip...

Soil Water Content and Organic Carbon Availability Are Major Determinants of Soil Microbial Community Composition

Abstract: Exploration of environmental factors governing soil microbial community composition is long overdue and now possible with improved methods for characterizing microbial communities. Previously, we observed that rice soil microbial communities were distinctly different from tomato soil microbial communities, despite management and seasonal variations within soil type. Potential contributing factors included types and amounts of organic inputs, organic carbon content, and timing and amounts of water inputs. Of these, both soil water content and organic carbon availability were highly correlated with observed differences in composition. We examined how organic carbon amendment (compost, vetch, or no amendment) and water additions (from air dry to flooded) affect microbial community composition. Using canonical correspondence analysis of phospholipid fatty acid data, we determined flooded, carbon-amended (+C) microcosm samples were distinctly different from other +C samples and unamended (-C) samples. Although flooding without organic carbon addition influenced composition some, organic carbon addition was necessary to substantially alter community composition. Organic carbon availability had the same general effects on microbial communities regardless of whether it was compost or vetch in origin. In addition, flooded samples, regardless of organic carbon inputs, had significantly lower ratios of fungal to bacterial biomarkers, whereas under drier conditions and increased organic carbon availability the microbial communities had higher proportions of fungal biomass. When comparing field and microcosm soil, flooded +C microcosm samples were most similar to field-collected rice soil, whereas all other treatments were more similar to field-collected tomato soil. Overall, manipulating water and carbon content selected for microbial communities similar to those observed when the same factors were manipulated at the field scale.

Anticipating Words and Their Gender: An Event-related Brain Potential Study of Semantic Integration, Gender Expectancy, and Gender Agreement in Spanish Sentence Reading

Abstract: Recent studies indicate that the human brain attends to and uses grammatical gender cues during sentence comprehension. Here, we examine the nature and time course of the effect of gender on word-by-word sentence reading. Event-related brain potentials were recorded to an article and noun, while native Spanish speakers read medium- to high-constraint Spanish sentences for comprehension. The noun either fit the sentence meaning or not, and matched the preceding article in gender or not; in addition, the preceding article was either expected or unexpected based on prior sentence context. Semantically anomalous nouns elicited an N400. Gender-disagreeing nouns elicited a posterior late positivity (P600), replicating previous findings for words. Gender agreement and semantic congruity interacted in both the N400 window—with a larger negativity frontally for double violations—and the P600 window—with a larger positivity for semantic anomalies, relative to the prestimulus baseline. Finally, unexpected articles elicited an enhanced positivity (500–700 msec post onset) relative to expected articles. Overall, our data indicate that readers anticipate and attend to the gender of both articles and nouns, and use gender in real time to maintain agreement and to build sentence meaning.

Efflux and compartmentalization of zinc by members of the SLC30 family of solute carriers.

Abstract: All of the members of this family are thought to facilitate zinc efflux from the cytoplasm either into various intracellular compartments (endosomes, secretory granules, synaptic vesicles, Golgi apparatus, or trans-Golgi network) or across the plasma membrane. Thus, these transporters are thought to help maintain zinc homeostasis and facilitate transport of zinc into specialized intracellular compartments. Counterparts of the SLC30 family are found in all organisms. Most of the members of this class are predicted to have 6 transmembrane domains with both N- and C-termini on the cytoplasmic side of the membrane. Expression of rodent Znt1, Znt2 or Znt4 cDNAs in mammalian cells can confer resistance to zinc toxicity. Loss of function of the mouse Znt1 is embryonic lethal, loss of mouse Znt3 prevents accumulation of zinc in synaptic vesicles, nonfunctional mouse Znt4 (lethal milk) results in zinc-deficient milk, and Znt5-null mice display bone abnormalities and heart failure. No mutations in human counterparts of any of the members of the SLC30 family have been described.

Cryptographic Hash-Function Basics: Definitions, Implications, and Separations for Preimage Resistance, Second-Preimage Resistance, and Collision Resistance

Abstract: We consider basic notions of security for cryptographic hash functions: collision resistance, preimage resistance, and second-preimage resistance. We give seven different definitions that correspond to these three underlying ideas, and then we work out all of the implications and separations among these seven definitions within the concrete-security, provable-security framework. Because our results are concrete, we can show two types of implications, conventional and provisional, where the strength of the latter depends on the amount of compression achieved by the hash function. We also distinguish two types of separations, conditional and unconditional. When constructing counterexamples for our separations, we are careful to preserve specified hash-function domains and ranges; this rules out some pathological counterexamples and makes the separations more meaningful in practice. Four of our definitions are standard while three appear to be new; some of our relations and separations have appeared, others have not. Here we give a modern treatment that acts to catalog, in one place and with carefully-considered nomenclature, the most basic security notions for cryptographic hash functions.

Thresholds, memory, and seasonality: understanding pulse dynamics in arid/semi-arid ecosystems

Abstract: Changes in resource availability can alter the functioning of ecosystems, especially with regard to both population dynamics and the cycling of organic matter and nutrients. At perhaps one end of the spectrum, arid and semi-arid ecosystems represent an extreme in which essential resource availability (e.g., water) is discontinuously available and the availability of these resources impact the ecosystem as discreet pulse events interspersed among long periods of limited resource availability. The objective of the special section that follows is to contribute to our understanding of how pulsed events shape population dynamics, species interactions, and ecosystem processes in arid and semi-arid ecosystems. There has been a renewed interest in recent years in the relationships between precipitation and ecosystem processes in arid and semi-arid lands. For many years, studies focused on the effects of mean precipitation, averaged at annual, seasonal, or monthly time scales. These studies suggested broad-scale relationships between precipitation amounts and seasonal distribution and the productivity of ecosystems (Le Houerou 1984; Le Houerou et al. 1988), or the plant functional type composition of water-limited systems (e.g., Neilson 1995; Smith et al. 1997). Though some researchers asked questions about the effects of single rainfall events early on (e.g., Went and Westergaard 1949; Beatley 1974; Sala and Lauenroth 1982), this perspective received wider attention only in the last decade, in part through the development of stable isotope tracer methods in plant ecology (e.g., Caldwell et al. 1985; Ehleringer et al. 1991; Lin et al. 1996). More recently, studies also have begun to focus on intra-seasonal precipitation patterns, asking whether variability in rainfall event size, frequency, and timing alone affect the biological processes in water-limited ecosystems (e.g., Goldberg and Novoplansky 1997; Knapp et al. 2002; Schwinning et al. 2003). With a view to addressing these questions, an international workshop was held at the University of Arizona in Tucson, USA (http://ag.arizona.edu/research/schwinn/ workshop.html). This special issue contains both peerreviewed synthesis papers that were generated through the collaboration of workshop participants, as well as original research contributions related to pulse dynamics in arid and semi-arid ecosystems. A generation ago, two major paradigms for understanding rainfall effects in water-limited ecosystems were published: (1) the pulse-reserve paradigm of Noy-Meir (1974) and co-workers, and (2) Walter’s (1971) two-layer soil water-partitioning model. Our understanding has advanced significantly since then, moving from the largely conceptual paradigms to an invariably more complex body of data and theory. Reynolds et al. (2004) critically review both paradigms, concluding that the accurate description of soil moisture dynamics is pivotal for addressing the dynamics of primary production and soil water partitioning. While Walter (1971) envisioned water partitioning in vertical space to govern major patterns of plant functional type distribution, Ehleringer et al. (1991) and Lin et al. (1996) have provided strong evidence of this spatial partitioning. Evidence is mounting that partitioning over time may be at least as important (Reynolds et al. 2004; Schwinning et al. 2004a, b). However, the consequences of the hydraulic redistribution of water for species S. Schwinning (*) School of Natural Resources, University of Arizona, Biological Sciences East 325, Tucson, AZ, 85721 e-mail: schwinn@Ag.arizona.edu

Efficient Distributed Skylining for Web Information Systems

Abstract: Though skyline queries already have claimed their place in retrieval over central databases, their application in Web information systems up to now was impossible due to the distributed aspect of retrieval over Web sources. But due to the amount, variety and volatile nature of information accessible over the Internet extended query capabilities are crucial. We show how to efficiently perform distributed skyline queries and thus essentially extend the expressiveness of querying today’s Web information systems. Together with our innovative retrieval algorithm we also present useful heuristics to further speed up the retrieval in most practical cases paving the road towards meeting even the real-time challenges of on-line information services. We discuss performance evaluations and point to open problems in the concept and application of skylining in modern information systems. For the curse of dimensionality, an intrinsic problem in skyline queries, we propose a novel sampling scheme that allows to get an early impression of the skyline for subsequent query refinement.

Detecting Public Network Attacks Using Signatures and Fast Content Analysis

Abstract: Network worms or viruses are a growing threat to the security of public and private networks and the individual computers that make up those networks. A content sifting method if provided that automatically generates a precise signature for a worm or virus that can then be used to significantly reduce the propagation of the worm elsewhere in the network or eradicate the worm altogether. The content sifting method is complemented by a value sampling method that increases the throughput of network traffic that can be monitored. Together, the methods track the number of times invariant strings appear in packets and the network address dispersion of those packets including variant strings. When an invariant string reaches a particular threshold of appearances and address dispersion, the string is reported as a signature for suspected worm.

Dimethylation of histone H3 lysine 9 is a critical mark for DNA methylation and gene silencing in Arabidopsis thaliana.

Abstract: The Arabidopsis KRYPTONITE gene encodes a member of the Su(var)3-9 family of histone methyltransferases. Mutations of kryptonite cause a reduction of methylated histone H3 lysine 9, a loss of DNA methylation, and reduced gene silencing. Lysine residues of histones can be either monomethylated, dimethylated or trimethylated and recent evidence suggests that different methylation states are found in different chromatin domains. Here we show that bulk Arabidopsis histones contain high levels of monomethylated and dimethylated, but not trimethylated histone H3 lysine 9. Using both immunostaining of nuclei and chromatin immunoprecipitation assays, we show that monomethyl and dimethyl histone H3 lysine 9 are concentrated in heterochromatin. In kryptonite mutants, dimethyl histone H3 lysine 9 is nearly completely lost, but monomethyl histone H3 lysine 9 levels are only slightly reduced. Recombinant KRYPTONITE can add one or two, but not three, methyl groups to the lysine 9 position of histone H3. Further, we identify a KRYPTONITE-related protein, SUVH6, which displays histone H3 lysine 9 methylation activity with a spectrum similar to that of KRYPTONITE. Our results suggest that multiple Su(var)3-9 family members are active in Arabidopsis and that dimethylation of histone H3 lysine 9 is the critical mark for gene silencing and DNA methylation.

Microbial community utilization of recalcitrant and simple carbon compounds: impact of oak-woodland plant communities

Abstract: Little is known about how the structure of microbial communities impacts carbon cycling or how soil microbial community composition mediates plant effects on C-decomposition processes. We examined the degradation of four 13C-labeled compounds (starch, xylose, vanillin, and pine litter), quantified rates of associated enzyme activities, and identified microbial groups utilizing the 13C-labeled substrates in soils under oaks and in adjacent open grasslands. By quantifying increases in non-13C-labeled carbon in microbial biomarkers, we were also able to identify functional groups responsible for the metabolism of indigenous soil organic matter. Although microbial community composition differed between oak and grassland soils, the microbial groups responsible for starch, xylose, and vanillin degradation, as defined by 13C-PLFA, did not differ significantly between oak and grassland soils. Microbial groups responsible for pine litter and SOM-C degradation did differ between the two soils. Enhanced degradation of SOM resulting from substrate addition (priming) was greater in grassland soils, particularly in response to pine litter addition; under these conditions, fungal and Gram + biomarkers showed more incorporation of SOM-C than did Gram – biomarkers. In contrast, the oak soil microbial community primarily incorporated C from the added substrates. More 13C (from both simple and recalcitrant sources) was incorporated into the Gram – biomarkers than Gram + biomarkers despite the fact that the Gram + group generally comprised a greater portion of the bacterial biomass than did markers for the Gram – group. These experiments begin to identify components of the soil microbial community responsible for decomposition of different types of C-substrates. The results demonstrate that the presence of distinctly different plant communities did not alter the microbial community profile responsible for decomposition of relatively labile C-substrates but did alter the profiles of microbial communities responsible for decomposition of the more recalcitrant substrates, pine litter and indigenous soil organic matter.

Neurotoxicant-induced animal models of Parkinson’s disease: understanding the role of rotenone, maneb and paraquat in neurodegeneration

Abstract: The etiologic basis of Parkinson's disease (PD), the second most common age-related neurodegenerative disorder, is unknown. Recent epidemiological and experimental studies indicate that exposure to environmental agents, including a number of agricultural chemicals, may contribute to the pathogenesis of this disorder. Animal models are important tools in experimental medical science for studying the pathogenesis and therapeutic intervention strategies of human diseases. Since many human disorders do not arise spontaneously in animals, characteristic functional changes have to be mimicked by neurotoxic agents. Recently, agricultural chemicals, when administrated systemically, have been shown to reproduce specific features of PD in rodents, thus opening new routes for the development of animal models for this disorder. In addition to a brief historical overview of the toxin-induced PD models, this study provides a detailed description of exiting models in which Parkinsonism is initiated via the exposure of animals to such agricultural chemicals as rotenone, paraquat, and maneb. Suggested neurotoxicity mechanisms of these chemicals are considered, and the major lessons learned from the analysis of pesticide-induced PD models are discussed.

Bargaining and Learning While Fighting

Abstract: Much of the existing formal work on war models the decision to go to war as a game-ending, costly lottery. This article relaxes this assumption by treating war as a costly process during which the states run the risk of military collapse. The model also allows for uncertainty over either the cost of fighting or the distribution of power. The analysis makes four contributions to the growing costly-process literature: (i) the present model provides a more general treatment of the learning process that occurs when states are uncertain about the distribution of power, (ii) it explicitly compares the bargaining and learning processes for the two different sources of uncertainty, (iii) it suggests a way to empirically distinguish wars arising from these two sources, and (iv) it shows that the equilibrium dynamics of informational accounts of war may be quite sensitive to the underlying bargaining environment through which information is conveyed.

Age-dependent effects of nicotine on locomotor activity and conditioned place preference in rats

Abstract: Most adult smokers start smoking during their adolescence. This adolescent initiation may be due to multiple factors, but little evidence is available regarding whether their brains are differentially sensitive to the addictive effects of nicotine during adolescence. To test the hypothesis that adolescents are more sensitive than adults to nicotine’s rewarding actions. An unbiased, counterbalanced, place-conditioning procedure was used to examine drug-induced reward and locomotor activity. Early adolescent (postnatal day 28), late adolescent (P38) and adult (P90) rats received either saline or nicotine (0.125, 0.25 or 0.5 mg/kg, s.c.) and were tested for place conditioning. During early adolescence, a single nicotine injection (0.5 mg/kg) induced significant conditioned place preference (CPP). In contrast, during late adolescence or adulthood, nicotine did not induce CPP after either one or four conditioning trials. Initial locomotor responses to acute nicotine administration during the first conditioning trial also differed with age, with no effect at P28, but substantial inhibitory responses at all doses studied (0.125–0.5 mg/kg) at later ages. Although not differing in their initial locomotor response to nicotine, there was a significantly greater tolerance/sensitization during the second and subsequent drug exposures in late adolescents than in adults. These findings provide evidence that adolescent brain is differentially sensitive to both the acute and repeated effects of nicotine relative to adult brain. Furthermore, there are significant differences in nicotine sensitivity between early and late phases of adolescence.

Efficient Instantiations of Tweakable Blockciphers and Refinements to Modes OCB and PMAC

Abstract: We describe highly efficient constructions, XE and XEX, that turn a blockcipher \(E: \mathcal{K} \times \{0, 1 \}^{n} \rightarrow \{0, 1 \}^{n}\) into a tweakable blockcipher \({E}: \mathcal{K} \times \mathcal{T} \times \{0, 1 \}^{n} \rightarrow \{0, 1 \}^{n}\) having tweak space \(\mathcal{T} = \{0, 1 \}^{n} \times \mathbb{I}\) where \(\mathbb{I}\) is a set of tuples of integers such as \(\mathbb{I} = [..2^{n/2}] \times [0..10]\). When tweak T is obtained from tweak S by incrementing one if its numerical components, the cost to compute \({E}^{T}_{K}(M)\) having already computed some \({E}^{S}_{K}(M')\) is one blockcipher call plus a small and constant number of elementary machine operations. Our constructions work by associating to the i th coordinate of \(\mathbb{I}\) an element \(\alpha_{i} \epsilon \mathbb{F}^{*}_{2}n\) and multiplying by α i when one increments that component of the tweak. We illustrate the use of this approach by refining the authenticated-encryption scheme OCB and the message authentication code PMAC, yielding variants of these algorithms that are simpler and faster than the original schemes, and yet have simpler proofs. Our results bolster the thesis of Liskov, Rivest, and Wagner [10] that a desirable approach for designing modes of operation is to start from a tweakable blockcipher. We elaborate on their idea, suggesting the kind of tweak space, usage-discipline, and blockcipher-based instantiations that give rise to simple and efficient modes.

Parameter Analysis of the Differential Model of Hysteresis

Abstract: The extended Bouc-Wen differential model is one of the most widely accepted phenomenological models of hysteresis in mechanics. It is routinely used in the characterization of nonlinear damping and in system identification. In this paper, the differential model of hysteresis is carefully re-examined and two significant issues are uncovered. First, it is found that the unspecified parameters of the model are functionally redundant. One of the parameters can be eliminated through suitable transformations in the parameter space. Second, local and global sensitivity analyses are conducted to assess the relative sensitivity of each model parameter. Through extensive Monte Carlo simulations, it is found that some parameters of the hysteretic model are rather insensitive. If the values of these insensitive parameters are fixed, a greatly simplified model is obtained.

Oviposition habitat selection in response to risk of predation in temporary pools: mode of detection and consistency across experimental venue

Abstract: Natural selection should favor females that avoid ovipositing where risk of predation is high for their progeny. Despite the large consequences of such oviposition behavior for individual fitness, population dynamics, and community structure, relatively few studies have tested for this behavior. Moreover, these studies have rarely assessed the mode of detection of predators, compared responses in prey species that vary in vulnerability to predators, or tested for the behavior in natural habitats. In an outdoor artificial pool experiment, we tested the oviposition responses of two dipteran species, Culiseta longiareolata (mosquito) and Chironomus riparius (midge), to the hemipteran predator, Notonecta maculata. Both dipteran species have similar life history characteristics, but Culiseta longiareolata larvae are highly vulnerable to predation by Notonecta, while Chironomus riparius larvae are not. As their vulnerabilities would suggest, Culiseta longiareolata, but not Chironomus riparius, strongly avoided ovipositing in pools containing Notonecta. An experiment in natural rock pools assessing oviposition by Culiseta longiareolata in response to Notonecta maculata yielded an oviposition pattern highly consistent with that of the artificial pool experiment. We also demonstrated that the cue for oviposition avoidance by Culiseta longiareolata was a predator-released chemical: Notonecta water (without Notonecta replenishment) repelled oviposition for 8 days. Oviposition avoidance and mode of detection of the predator have important implications for how to assess the true impact of predators and for the use of commercially produced kairomones for mosquito control.

Nanowire array and nanowire solar cells and methods for forming the same

Abstract: Homogeneous and dense arrays of nanowires are described. The nanowires can be formed in solution and can have average diameters of 40-300 nm and lengths of 1-3 μm. They can be formed on any suitable substrate. Photovoltaic devices are also described.

Dependability and Its Threats: A Taxonomy

Abstract: This paper gives the main definitions relating to dependability, a generic concept including as special case such attributes as reliability, availability, safety, confidentiality, integrity, maintainability, etc. Basic definitions are given first. They are then commented upon, and supplemented by additional definitions, which address the threats to dependability (faults, errors, failures), and the attributes of dependability. The discussion on the attributes encompasses the relationship of dependability with security, survivability and trustworthiness.

The Cassini Ion and Neutral Mass Spectrometer (INMS) Investigation

Abstract: The Cassini Ion and Neutral Mass Spectrometer (INMS) investigation will determine the mass composition and number densities of neutral species and low-energy ions in key regions of the Saturn system. The primary focus of the INMS investigation is on the composition and structure of Titan’s upper atmosphere and its interaction with Saturn’s magnetospheric plasma. Of particular interest is the high-altitude region, between 900 and 1000 km, where the methane and nitrogen photochemistry is initiated that leads to the creation of complex hydrocarbons and nitriles that may eventually precipitate onto the moon’s surface to form hydrocarbon—nitrile lakes or oceans. The investigation is also focused on the neutral and plasma environments of Saturn’s ring system and icy moons and on the identification of positive ions and neutral species in Saturn’s inner magnetosphere. Measurement of material sputtered from the satellites and the rings by magnetospheric charged particle and micrometeorite bombardment is expected to provide information about the formation of the giant neutral cloud of water molecules and water products that surrounds Saturn out to a distance of ~12 planetary radii and about the genesis and evolution of the rings.

Different Approaches to Risk Estimation in Portfolio Theory

Abstract: Some new performance measures may be regarded as alternatives to the most popular criterion for portfolio optimization, the Sharpe ratio. Analysis of some allocation problems here takes into consideration portfolio selection models based on different risk perceptions and sample paths of the final wealth process for each allocation problem. One new performance ratio seems to be suitable for some optimization problems, but we need a thorough classification of the set of performance measures that would be ideal for large classes of financial optimization problems.

Dormancy of Arabidopsis seeds and barley grains can be broken by nitric oxide

Abstract: Seeds of Arabidopsis thaliana (L.) Heynh. and grains of barley (Hordeum vulgare L.) were used to characterize the affects of nitric oxide (NO) on seed dormancy. Seeds of the C24 and Col-1 ecotypes of Arabidopsis are almost completely dormant when freshly harvested, but dormancy was broken by stratification for 3 days at 4°C or by imbibition of seeds with the NO donor sodium nitroprusside (SNP). This effect of SNP on dormancy of Arabidopsis seeds was concentration dependent. SNP concentrations as low as 25 μM reduced dormancy and stimulated germination, but SNP at 250 μM or more impaired seedling development, including root growth, and inhibited germination. Dormancy was also reduced when Arabidopsis seeds were exposed to gasses that are generated by solutions of SNP. Nitrate and nitrite, two other oxides of nitrogen, reduced the dormancy of Arabidopsis seeds, but much higher concentrations of these were required compared to SNP. Furthermore, the kinetics of germination were slower for seeds imbibed with either nitrate or nitrite than for seeds imbibed with SNP. Although seeds imbibed with SNP had reduced dormancy, seeds imbibed with SNP and abscisic acid (ABA) remained strongly dormant. This may indicate that the effects of ABA action on germination are downstream of NO action. The NO scavenger 2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3 oxide (cPTIO) strengthened dormancy of unstratified and briefly stratified Arabidopsis seeds. Dormancy of three cultivars of barley was also reduced by SNP. Furthermore, dormancy in barley grain was strengthened by imbibition of grain with cPTIO. The data presented here support the conclusion that NO is a potent dormancy breaking agent for seeds and grains. Experiments with the NO scavenger suggest that NO is an endogenous regulator of seed dormancy.

High speed spectral domain functional optical coherence tomography and optical doppler tomography for in vivo blood flow dynamics and tissue structure

Abstract: A system for tomographic imaging includes a source of at least partially coherent radiation, a frequency-swept laser source and an interferometer. The radiation in the interferometer is phase modulated at a modulation frequency for elimination of DC and autocorrelation noises as well as the mirror image. The interference fringes of the radiation backscattered from the sample into the interferometer are detected to obtain a spectral signal. The spectral signal of the detected backscattered interference fringes is transformed to obtain a location dependent signal at each pixel location in a data window. A tomographic image of the fluid flow in the data window is generated for display and of the structure of the scanned fluid flow sample in the data window from the location dependent signal is generated.