bluuebunny/crossref_metadata_2025 huggingface dataset:
Colony size, density and distribution of the leaf‐cutting ant, Acromyrmex octospinosus (Reich) in cultivated fields
Authors: LEWIS T.
Published: August 2010

Fields of citrus, cacao and rubber in Trinidad were surveyed to measure the number and density of nests of Acromyrmex octospinosus. The greatest density (=153 nests/ha) was in an undisturbed field of young cacao; in established crops density ranged from 3–36 nests/ha.

Mounds of new nests appeared throughout the year, but most often 4–10 months after the main nuptial flights. Nests reached maximum size, with up to 17 holes, about three years after foundation.

The ratio of workers to brood was between 5 and 9: 1 for most of the year but it increased to 27: 1 as the sexuals developed. A medium‐large colony produced 200–300 queens and males/year; the largest single nest contained about 14,000 individuals.

The average intake of leaf fragments into laboratory nests was 1 fragment/6.5 individuals. It increased to 1 fragment/2.1 individuals when sexuals were present. Foragers collecting from fields of established cacao preferred flowers to leaves.

In fields with crops planted on cambered beds, nests were concentrated on the dry edges of drains in the dry season, but they were moved to drier ground in the wet season. Nests were aggregated in 13 of the 16 fields examined, the remaining three fields were exceptionally well drained.

In newly planted cacao an estimated 6—17% of plants were defoliated and destroyed. In established cacao ants collected about 3000 flowers/ha each day. Laboratory data suggest that ants could defoliate about 25 three‐year old citrus trees in a year.
Observations on the vertical distribution of soil Oribatei in a woodland soil
Authors: PANDE Y. D. , BERTHET P.
Published: August 2010

The vertical distribution of Oribatei in a black pine plantation soil was studied in situ using the soil sectioning technique.

Oribatei were most abundent in the upper 3 cm due to the greater abundance of suitable food in this region.

Larger species were usually confined to the upper layers but some smaller species were also abundant in this region.

A correlation between the size of the species and their penetration was not found to be statistically significant.

Nested analysis of variance showed seasonal redistribution in some species.

The vertical distribution of individual species is discussed, and partially explained.
Leucocytozoön musculi, sp. n., a Parasitic Protozoon from the Blood of. White Mice
Authors: Porter Annie
Published: August 2010

The forms of L. musculi here described occur in the mononuclear and transitional leucocytes of white mice.

 The free trophozoites in the plasma are gregariniform or reniform vermicules, the average size being 10.9μ long and 5.1μ broad (cf. Pl. XXXIX. figs. 1–12).

 The free trophozoites sooner or later enter leucocytes of the host and grow at the expense of the nucleus of the leucocyte (cf. Karyolysus among the Hæmogregarines). A thin cytocyst is formed probably by the host‐cell around the parasite (Pl XXXIX. figs. 16, 17).

 Endoglobular forms are on the average 8μ long by 5μ broad (cf. Pl. XXXIX. figs. 15, 16, 17).

 Schizogony takes place in the bone‐marrow. An endoglobular trophozoite rounds itself off and becomes a schizont, breaking up into merozoites, each about 4.4μ long and .8μ broad (Pl. XXXIX. fig. 20). This again suggests affinities with Karyolysus, judging by Labbé's figures of schizogony in Karyolysus.

 Two parasites may sometimes occur within one host‐cell. Two such forms suggesting the beginning of association are shown in PL XXXIX. figs. 21, 22.

Differentiation into male and female forms could not be made out with certainty, though some parasites were shorter, broader, and more granular than others.

 Vermicules were found in the gut and Malpighian tubules of lice, ectoparasitic upon the mice, but unfortunately no evidence of a sexual cycle in the louse was obtainable. Perhaps the lice merely act as mechanical agents in the transfer of the parasites among the mice.

 The parasites are found in smears from the heart and liver in abundance. They are less numerous in spleen and kidney smears, also in the bone‐marrow and peripheral circulation. They were not abundant in the latter.

 No Trypanosomas were seen in the infected mice.

 The movements of the vermicules or trophozoites of this parasite in the blood‐plasma of its Vertebrate host are fully described in section VI. of this memoir.
The External Morphology and Life‐history of the Coccid Bug,Orthezia urticœLinn.
Authors: Sikes Enid K.
Published: August 2010

All stages of the Coccid Bug,O. urticœ, were collected and bred in the laboratory to investigate the number of instars and the morphology.

The first and second instar larvæ are sexually indistinguishable. The male has two larval, two nymphal, and a winged adult stage. The female has three larval and a wingless adult stage.

Breeding and growth take place rapidly between May and the end of August. The males attain the adult stage in March, and are found in very small numbers until the middle of June. The females begin to form their brood‐sacs in May or June, and reproduce throughout the summer months. From the beginning of September to the end of January the insects hibernate.

The occurrence ofO. urticøEin its different instars is summed up in the table see (p. 303), from the events noted during the time I have had the Coccids under observation.

In the external morphology it is noticeable that there is a breaking‐up in the wax plates to coincide with the segmentation of the insect, and extra intermediate blocks are cut off from the originally‐placed main blocks. The glandular setæ become more numerous from the first to fourth instar of the female, and the outline of the insect becomes almost circular, the abdomen shortening considerably in the adult stage. The male nymph of the third and fourth instars possesses external wing‐stumps on the mesothorax, and an indication of metathoracic halteres is seen on the fourth instar nymph. The adult male has a pair of mesothoracic wings, but flies very little and only lives for a few days.
REMARKS ON THE STOMACH AND THE SYSTEMATIC POSITION OF THE TYLOPODA
Authors: BOHLKEN HERWART
Published: August 2010

The differences in the anatomy of the stomachs of the Tylopoda and the typical Ruminantia are shown. To be mentioned especially are the glandular sacs of tylopods and the differences in structure of the oesophageal groove. It seems likely that the Tylopoda and the Ruminantia have acquired the faculty of ruminating independently one from the other. The similarity of the stomachs is intorpretocl as a result of parallel development arid not as a result of a close relationship of the two groups. In the system of Artiodactyla t, lie Tj‐lopoda should be distinguished from the Ruminantia.
COMMUNICATIONS BETWEEN THE FACIAL AND TRIGEMINAL NERVES IN CERTAIN MAMMALS
Authors: BOWDEN R. E. M. , MAHRAN Z. Y. , GOODING M. R.
Published: August 2010

The modes of division and branching of the extrapetrous part of the facial nerve and the presence or absence of communications between its branches and between it and the trigeminal nerve and cervical plexus were studied in nineteen mammalian species. Communications between the facial and derivatives of the mandibular division of the trigeminal were found invariably, but were inconstant in the case of the two other divisions and of the cervical plexus.

The possible functional significance of the observations is discussed.
CONTINUOUS BREEDING IN THREE SPECIES OF TROPICAL ASCIDIAN
Authors: GOODBODY IVAN
Published: August 2010

The breeding season of three ascidians in Jamaica has been studied by counting the number of newly settled individuals each week on microscope slides suspended in the sea. Settlement occurs throughout the year with greatest numbers in autumn and early winter. These peaks cannot at present be correlated with any specific environmental influence.
ON THE FOOD OF THE BROWN TROUT OF LLYN TEGID
Authors: BALL J. N.
Published: August 2010

The composition of the diet of Llyn Tegid trout has been determined by analysing the stomach contents, using the volume, number and occurrence methods. All three methods yield comparable results, but the volume method is the most satisfactory. The trout is an indiscriminate carnivore. The relative extent to which different animals are eaten depends mainly on their numerical representation in the fauna, though their size, habits and mobility are probably also important. In Llyn Tegid, Gammarus pulex formed 24 per cent by volume of the total food consumption. Other important animals were the caddis larvae Limnephilus lunatus and Potamophylax stellatus, the mayflies Ephemera danica (especially the sub‐imago) and Leptophlebia marginata (nymph) and the isopod Asellus meridianus. Seasonal changes in the diet were considerable and appeared to be largely the result of seasonal changes in the availability of the different food organisms. From October to April, the trout fed mainly on bottom‐living organisms, and from May to September on animals caught at the surface. The mean volume of food eaten increased greatly in summer to a mid‐summer peak more than eight times the winter level. This was probably due to seasonal physiological changes in the trout and to a spring and summer increase in the amount of available food. A comparison of the caddis larvae eaten by the two fishes indicates that the trout is a more superficial feeder than the grayling. It is suggested that this reduces competition for food between the two species. In accordance with the findings of other workers, the trout appeared to avoid eating corixids. No important change in feeding‐habits with size was found within the size‐range covered by the samples (88–344 mm.), all the trout being in the insect‐feeding stage.
RESPIRATORY FUNCTION OF THE SWIMBLADDER OF NOTOPTERUS (LACÉPÈDE)
Authors: DEHADRAI PADMAKAR V.
Published: August 2010

Some aspects of the anatomy, histology and physiology of the swimbladder of Notopterus have been studied, with special reference to its behaviour in aerial respiration.

The large swimbladder with a wide pneumatic duct is reported to function as an accessory respiratory organ. Circulation of blood is modified to discharge this function. The network of blood capillaries covered by a single layer of epithelium apparently facilitates the diffusion of gases between the blood and the swimbladder.

Notopterus is able to survive for long periods in foul water, if allowed to reach the surface to take in air. There is a regular exchange of gases between the cavity of the swimbladder and the exterior.

The frequency and extent of aquatic and aerial respiration in Notopterus under different conditions have been determined. They throw considerable light on the double respiratory mechanism in the fish.

Under normal condition, the mean value of oxygen is 11 per cent and that of carbon dioxide 3 per cent in the “alveolar air” of the swimbladder. The result of analysis of gases from the swimbladder of Notopterus under adverse experimental conditions clearly establishes the remarkable capacity of the swimbladder of the fish to function as an efficient respiratory organ.

The presence of a high percentage of carbon dioxide (6.5 per cent) in the swimbladder is of interest and suggests high resistance of the blood of the fish to carbon dioxide.

The air‐breathing habit of Notopterus is probably a secondary adaptation to its life in ponds and puddles under tropical conditions.
ULTRASONIC EMISSIONS OF THE LESSER HORSESHOE BAT RHINOLOPHUS HIPPOSIDEROS (BECH.)
Authors: KAY L. , PICKVANCE T. J.
Published: August 2010

The ultrasonic emissions of both adult and juvenile Lesser Horseshoe bats have been studied. Two features were observed:—The range of frequencies used by adult bats when congregated in a crowd of 60 or more does not exceed 3 Kc/s, even though their frequency of emission is of the order of 113 Kc/s. The baby bats can make sounds of echo‐location type within 3 days of birth; they open their mouths to do so when disturbed and the frequency of the sound at first is about 30 kc/s. Erratic variations in frequency take place during development.
Cerebellar lipid differences between R6/1 transgenic mice and humans with Huntington’s disease
Authors: Denny Christine A. , Desplats Paula A. , Thomas Elizabeth A. , Seyfried Thomas N.
Published: August 2010

J. Neurochem. (2010) 115, 748–758.

Huntington’s disease (HD) is a progressive neurodegenerative disorder characterized by motor, psychiatric, and cognitive abnormalities. In this present study, we tested whether abnormal motor behavior in a mouse model of HD, the R6/1 transgenic (Tg) mice, was associated with changes in cerebellar lipid composition and gene expression. We report altered motor behavior, which was associated with abnormal expression of glycosyltransferase genes in the cerebellum of R6/1 Tg mice. Cerebellar wet weight and total ganglioside concentration was significantly lower in R6/1 Tg mice than in wild‐type (Wt) mice. Furthermore, the Purkinje cell‐enriched ganglioside LD1 and the granule cell‐enriched ganglioside GD1a were significantly lower in R6/1 Tg mice than in Wt mice. The myelin‐enriched lipid sulfatides was also reduced in the cerebellum of R6/1 Tg mice. In contrast to the R6/1 Tg mice, total cerebellar ganglioside concentration did not differ between HD and control subjects. However, expression of several cerebellar glycosyltransferases genes was significantly less in HD subjects than in control subjects. Our findings indicate that the R6/1 Tg mice have severe cerebellar glycosphingolipid (GSL) abnormalities that may account, in part, for their abnormal motor behavior. Although the cerebellar lipid abnormalities found in the R6/1 Tg mice were not found in these HD subjects, the R6/1 Tg mice may be useful for evaluating the role of GSLs in cerebellar development.
Denture Marking—Patient Preference of Various Methods
Authors: Richmond Raymond , Pretty Iain A.
Published: August 2010

Abstract:  Dental forensic organizations world wide have recommended that dental prostheses should be labeled with at least the patient's (wearer's) name and preferably with further unique identifiers such as social security number. A range of methods are available and the purpose of this study was to determine, via the means of a visual questionnaire, which are the most preferable to those patients who wear complete dentures. One hundred edentulous patients attending the Manchester Dental Hospital were shown a range of denture labeling methods and asked to rank these according to their preference. The most preferred method was that of an embedded radio frequency identification microchip (38% rated this as first) and the second was an inclusion technique using onion paper (24% rated this as first). The least preferred method was the use of a groove cut into the denture flange with 71% of patients rating this as the poorest in terms of esthetics. The study demonstrates that the method of denture labeling is important to patients and to ensure that denture labeling is performed routinely esthetic preferences must be considered.
TOWARD A COMMON‐FACTORS APPROACH TO SUPERVISION
Authors: Morgan Michael M. , Sprenkle Douglas H.
Published: August 2010

Despite the proliferation of supervision models, there is no evidence to suggest that any one model of supervision is in any way superior to any other. Many in the field have called for models that can bridge the various theoretical approaches to clinical supervision, and identify the essential elements of supervision. This article briefly explores the range of existing supervision models, and suggests a rationale for seeking factors common across the various models. The authors highlight the development of a new supervision model that synthesizes current thinking about supervision into three dimensions. The three dimensions are defined, and resulting supervisory roles explored. Implications for supervision practice, research, and training are discussed.
Quantitative Fault Tolerant Control Design for a Leaking Hydraulic Actuator
Authors: Karpenko Mark , Sepehri Nariman
Published: August 2010

This paper documents the design of a low-order, fixed-gain, controller that can maintain the positioning performance of an electrohydraulic actuator operating under variable load with a leaking piston seal. A set of linear time-invariant equivalent models of the faulty hydraulic actuator is first established, in the frequency domain, by Fourier transformation of acceptable actuator input-output responses. Then, a robust position control law is synthesized by quantitative feedback theory to meet the prescribed design tolerances on closed-loop stability and reference tracking. The designed fault tolerant controller uses only actuator position as feedback, yet it can accommodate nonlinearities in the hydraulic functions, maintain robustness against typical parametric uncertainties, and maintain the closed-loop performance despite a leakage fault that can bypass up to 40% of the rated servovalve flow across the actuator piston. To demonstrate the utility of the fault tolerant control approach in a realistic application, the experimental fault tolerant hydraulic system is operated as a flight surface actuator in the hardware-in-the-loop simulation of a high-performance jet aircraft.
Output Saturation in Electric Motor Systems: Identification and Controller Design
Authors: Kong Kyoungchul , Kniep Helge C. , Tomizuka Masayoshi
Published: August 2010

Input saturation is a well-known nonlinearity in mechanical control systems; it constrains the maximum acceleration, which results in the limitation of the system response time. Input saturation has been considered in controller design in various ways, e.g., antiwindup control. In addition to the input, the state variables of mechanical systems are often subjected to saturation. For example, the maximum angular velocity of electric motor systems is limited by the maximum voltage provided to the motor windings. In the case of electronically commutated motors (i.e., brushless dc motors), the maximum speed is additionally constrained by limitations of the servo amplifier output. If gears are utilized, further constraints are introduced due to resonances in ball bearings and/or velocity dependent friction. Although such factors are significant in practice, they have not been fully considered in controller design. This paper investigates the input and output saturations, and presents how they may be considered in the controller design; a Kalman filter, a PID controller, and a disturbance observer are designed, taking input/output saturations into consideration. A case study is provided to verify the proposed methods.
Robust Fuzzy Tracking Control Design for a Class of Nonlinear Stochastic Markovian Jump Systems
Authors: Huang Ran , Lin Yan , Lin Zhongwei
Published: August 2010

This paper deals with the problem of robust fuzzy tracking control design for a class of nonlinear stochastic Itô-type systems with Markovian jumps. Considering the fuzzy approximation errors as norm-bounded uncertainties, we derive two sufficient conditions for the nonlinear stochastic robust fuzzy tracking control in terms of coupled matrix inequalities, which ensure the globally asymptotical stability in probability and L2 property for the augmented system, respectively. Then, a systematic algorithm is developed to construct the robust fuzzy tracking controller by reformulating the coupled matrix inequalities into two intertwined linear matrix inequalities (LMIs). Finally, a simulation example is presented to illustrate the design procedure.
Combined Controller for Test System of High Capacity Hydraulic Pump
Authors: Meng Wenjun , Suhling Jeffrey C.
Published: August 2010

A combined controller (CT-PBC) by contact task control (CTC) with passivity based controller (PBC) is introduced to control test system of high capacity hydraulic pump (HCHP) to measure its properties. It is compared with a vector controller; a torque feedback based combined controller, and two neural network controllers. The results gained from comparing and analyzing these controllers show that under different outlet pressures of HCHP, CT-PBC has good stability and robustness, which meet the requirements to test HCHP. CT-PBC is also simpler and better than other controllers in general.
Dynamic Thermomechanical Modeling of a Wet Shape Memory Alloy Actuator
Authors: Ertel Joel D. , Mascaro Stephen A.
Published: August 2010

This paper presents combined thermal and mechanical models of a wet shape memory alloy (SMA) wire actuator. The actuator consists of a SMA wire suspended concentrically in a compliant tube. Actuation occurs as hot and cold water that are alternately pumped through the tube to contract and extend the wire, respectively. The thermomechanical model presented in this paper accounts for the nonuniform temperature change of the SMA wire due to alternating the temperature of the flow along the wire. The thermal portion of the model consists of analysis of the heat transfer between the fluid and the SMA wire. Heat loss to the environment and the temperature change of the fluid through the actuator are taken into account. Based on this analysis, the temperature of the wire at segments along its length can be determined as a function of time. The mechanical portion of the model approximates the strain-martensite fraction and martensite fraction-temperature relationships. By combining the thermal and mechanical models, the displacement of the wire can be determined as a function of time. The combined thermomechanical model will be useful for predicting the performance of wet SMA actuators in a variety of applications.
Legionella
Hijacks Rab
Authors: Hurtley Stella M.
Published: August 2010

An intracellular bacterial pathogen interferes with host cell membrane trafficking.
PTIP in Immunoglobulin Switching
Authors: Mueller Kristen L.
Published: August 2010

A factor that regulates chromatin accessibility and recombination during immunoglobulin rearrangements is identified.
Bridging the Synaptic Cleft: Lessons from Orphan Glutamate Receptors
Authors: Schmid Sabine M. , Hollmann Michael
Published: August 2010

Three proteins act as a transsynaptic bridge at a major type of cerebellar synapse.
Efficacy of Intracellular Activated Promoters for Generation ofSalmonella-Based Vaccines
Authors: Xu Xin , Husseiny Mohamed I. , Goldwich Andreas , Hensel Michael
Published: August 2010

Salmonella entericais a versatile vaccine carrier for heterologous antigens. One strategy for vaccine antigen delivery is the use of live attenuatedS. entericastrains that translocate heterologous antigens into antigen-presenting cells by means of type III secretion systems (T3SS). The feasibility of this approach has been demonstrated in various experimental vaccination studies. The efficacy of recombinant live vaccines is critically influenced by the optimal level of attenuation and many other factors. For the rational design of approaches involving translocation by T3SS, additional parameters are the level of expression of the heterologous antigens and the selection of carrier proteins for the delivery of antigens to desirable subcellular compartments of the target cell. We deployed theSalmonellapathogenicity island 2 (SPI2)-encoded T3SS for antigen delivery. The SPI2-T3SS and effector proteins are encoded by members of the large SsrAB regulon, including promoters with highly variable strength of expression. We investigated the effect of variousin vivo-activated promoters of the SsrAB regulon on the efficacy of recombinantSalmonellavaccines. We observed that the use of promoters with higher strength results in greater synthesis of recombinant antigens and greater stimulation of T-cell responses in cell culture assays for the stimulation of T cells by the model antigen ovalbumin. In contrast, in vaccination experiments, promoters with a low level of expression resulted in the induction of higher amounts of T cells reactive to the model antigen listeriolysin. These results demonstrate that high-level expression of heterologous antigens does not necessarily result in optimal stimulation of immune responses.
VALUING CALLABLE AND PUTABLE REVENUE-PERFORMANCE-LINKED PROJECT BACKED SECURITIES
Authors: DONG FENG , CHIARA NICOLA , VECER JAN
Published: August 2010

Public owners face a constant demand for developing new projects and for funding the renewal, maintenance and operation of existing infrastructure projects. One way to raise capitals to provide new financial resources to constrained budgets is to securitize a stream of revenue cash flows from a portfolio of mature infrastructure projects. We present a new type of PBS, the revenue performance-linked project backed securities (PBS), with embedded call and put options. In this new PBS setting, risks for issuers and buyers can be confined within a cut-off area. This risk hedging feature is expected to facilitate the trading of such products.
PeerReview
Authors: Haeberlen Andreas , Kouznetsov Petr , Druschel Peter
Published: August 2010

We describe PeerReview, a system that provides accountability in distributed systems. PeerReview ensures that Byzantine faults whose effects are observed by a correct node are eventually detected and irrefutably linked to a faulty node. At the same time, PeerReview ensures that a correct node can always defend itself against false accusations. These guarantees are particularly important for systems that span multiple administrative domains, which may not trust each other.PeerReview works by maintaining a secure record of the messages sent and received by each node. The record isused to automatically detect when a node's behavior deviates from that of a given reference implementation, thus exposing faulty nodes. PeerReview is widely applicable: it only requires that a correct node's actions are deterministic, that nodes can sign messages, and that each node is periodically checked by a correct node. We demonstrate that PeerReview is practical by applying it to three different types of distributed systems: a network filesystem, a peer-to-peer system, and an overlay multicast system.
Attested append-only memory
Authors: Chun Byung-Gon , Maniatis Petros , Shenker Scott , Kubiatowicz John
Published: August 2010

Researchers have made great strides in improving the fault tolerance of both centralized and replicated systems against arbitrary (Byzantine) faults. However, there are hard limits to how much can be done with entirely untrusted components; for example, replicated state machines cannot tolerate more than a third of their replica population being Byzantine. In this paper, we investigate how minimal trusted abstractions can push through these hard limits in practical ways. We propose Attested Append-Only Memory (A2M), a trusted system facility that is small, easy to implement and easy to verify formally. A2M provides the programming abstraction of a trusted log, which leads to protocol designs immune to equivocation -- the ability of a faulty host to lie in different ways to different clients or servers -- which is a common source of Byzantine headaches. Using A2M, we improve upon the state of the art in Byzantine-fault tolerant replicated state machines, producing A2M-enabled protocols (variants of Castro and Liskov's PBFT) that remain correct (linearizable) and keep making progress (live) even when half the replicas are faulty, in contrast to the previous upper bound. We also present an A2M-enabled single-server shared storage protocol that guarantees linearizability despite server faults. We implement A2M and our protocols, evaluate them experimentally through micro- and macro-benchmarks, and argue that the improved fault tolerance is cost-effective for a broad range of uses, opening up new avenues for practical, more reliable services.
Relevance heuristics for program analysis
Authors: McMillan K. L.
Published: August 2010

Relevance heuristics allow us to tailor a program analysis to a particular property to be verified. This in turn makes it possible to improve the precision of the analysis where needed, while maintaining scalability. In this talk I will discuss the principles by which SAT solvers and other decision procedures decide what information is relevant to a given proof. Then we will see how these ideas can be exploited in program verification using the method of Craig interpolation. The result is an analysis that is finely tuned to prove a given property of a program. At the end of the talk, I will cover some recent research in this area, including the use of interpolants for verifying heap-manipulating programs.
Caml trading
Authors: Minsky Yaron M.
Published: August 2010

Jane Street Capital is a successful proprietary trading company that has shifted from developing software in mainstream programming languages to developing software almost entirely in OCaml, a statically typed functional programming language that has only modest industrial use. The scope of the enterprise is small but growing: Jane Street now has over 20 OCaml programmers that have collectively written hundreds of thousands of lines of OCaml code. OCaml is used for building everything from trading systems to research infrastructure to user interfaces to systems administration tools. This talk will discuss the motivations behind Jane Street's adoption of OCaml, and why we think that statically typed functional programming languages are such a good fit for the world of trading and finance.
Much ado about two (pearl)
Authors: Voigtländer Janis
Published: August 2010

This pearl develops a statement about parallel prefix computation in the spirit of Knuth's 0-1-Principle for oblivious sorting algorithms. It turns out that 0-1 is not quite enough here. The perfect hammer for the nails we are going to drive in is relational parametricity.
Semantics of transactional memory and automatic mutual exclusion
Authors: Abadi Martín , Birrell Andrew , Harris Tim , Isard Michael
Published: August 2010

Software Transactional Memory (STM) is an attractive basis for the development of language features for concurrent programming. However, the semantics of these features can be delicate and problematic. In this paper we explore the tradeoffs between semantic simplicity, the viability of efficient implementation strategies, and the flexibilityof language constructs. Specifically, we develop semantics and type systems for the constructs of the Automatic Mutual Exclusion (AME) programming model; our results apply also to other constructs, such as atomic blocks. With this semantics as a point of reference, we study several implementation strategies. We model STM systems that use in-place update, optimistic concurrency, lazy conflict detection, and roll-back. These strategies are correct only under non-trivial assumptions that we identify and analyze. One important source of errors is that some efficient implementations create dangerous 'zombie' computations where a transaction keeps running after experiencing a conflict; the assumptions confine the effects of these computations.
The intensional content of Rice's theorem
Authors: Asperti Andrea
Published: August 2010

The proofs of major results of Computability Theory like Rice, Rice-Shapiro or Kleene's fixed point theorem hidemore information of what is usually expressed in theirrespective statements. We make this information explicit, allowing to state stronger, complexity theoretic-versions of all these theorems. In particular, we replace the notion of extensional set of indices of programs, by a set of indices of programs having not only the same extensional behavior but also similar complexity (Complexity Clique). We prove, under very weak complexity assumptions, that any recursive Complexity Clique is trivial, and any r.e. Complexity Clique is an extensional set (and thus satisfies Rice-Shapiro conditions). This allows, for instance, to use Rice's argument to prove that the property of having polynomial complexity is not decidable, and to use Rice-Shapiro to conclude that it is not even semi-decidable. We conclude the paper with a discussion of "complexity-theoretic" versions of Kleene's Fixed Point Theorem.
A logical account of pspace
Authors: Gaboardi Marco , Marion Jean-Yves , Della Rocca Simona Ronchi
Published: August 2010

We propose a characterization of PSPACE by means of atype assignment for an extension of lambda calculus with a conditional construction. The type assignment STA
B
is an extension of STA, a type assignment for lambda-calculus inspired by Lafont's Soft Linear Logic.

We extend STA by means of a ground type and terms for booleans. The key point is that the elimination rule for booleans is managed in an additive way. Thus, we are able to program polynomial time Alternating Turing Machines. Conversely, we introduce a call-by-name evaluation machine in order tocompute programs in polynomial space. As far as we know, this is the first characterization of PSPACE which is based on lambda calculusand light logics.
Back to the future
Authors: Lahiri Shuvendu , Qadeer Shaz
Published: August 2010

This paper takes a fresh look at the problem of precise verification of heap-manipulating programs using first-order Satisfiability-Modulo-Theories (SMT) solvers. We augment the specification logic of such solvers by introducing the Logic of Interpreted Sets and Bounded Quantification for specifying properties of heap-manipulating programs. Our logic is expressive, closed under weakest preconditions, and efficiently implementable on top of existing SMT solvers. We have created a prototype implementation of our logic over the solvers Simplify and Z3 and used our prototype to verify many programs. Our preliminary experience is encouraging; the completeness and the efficiency of the decisionprocedure is clearly evident in practice and has greatly improved the user experience of the verifier.
A theory of platform-dependent low-level software
Authors: Nita Marius , Grossman Dan , Chambers Craig
Published: August 2010

The C language definition leaves the sizes and layouts of types partially unspecified. When a C program makes assumptions about type layout, its semantics is defined only on platforms (C compilers and the underlying hardware) on which those assumptions hold. Previous work on formalizing C-like languages has ignored this issue, either by assuming that programs do not make such assumptions or by assuming that all valid programs target only one platform. In the latter case, the platform's choices are hard-wired in the language semantics.

In this paper, we present a practically-motivated model for a C-like language in which the memory layouts of types are left largely unspecified. The dynamic semantics is parameterized by a platform's layout policy and makes manifest the consequence of platform-dependent (i.e., unspecified) steps. A type-and-effect system produces a layout constraint: a logic formula encoding layout conditions under which the program is memory-safe. We prove that if a program type-checks, it is memory-safe on all platforms satisfying its constraint.

Based on our theory, we have implemented a tool that discovers unportable layout assumptions in C programs. Our approach should generalize to other kinds of platform-dependent assumptions.
Extensible encoding of type hierarchies
Authors: Alavi Hamed Seiied , Gilbert Seth , Guerraoui Rachid
Published: August 2010

The
subtyping test
consists of checking whether a type
t
is a descendant of a type
r
(Agrawal et al. 1989). We study how to perform such a test efficiently, assuming a
dynamic
hierarchy when new types are inserted at run-time. The goal is to achieve time and space efficiency, even as new types are inserted. We propose an
extensible
scheme, named
ESE
, that ensures (1) efficient insertion of new types, (2) efficient subtyping tests, and (3) small space usage. On the one hand ESE provides comparable test times to the most efficient existing static schemes (e.g.,Zibin et al. (2001)). On the other hand, ESE has comparable insertion times to the most efficient existing dynamic scheme (Baehni et al. 2007), while ESE outperforms it by a factor of 2-3 times in terms of space usage.
A type-theoretic foundation for programming with higher-order abstract syntax and first-class substitutions
Authors: Pientka Brigitte
Published: August 2010

Higher-order abstract syntax (HOAS) is a simple, powerful technique for implementing object languages, since it directly supports common and tricky routines dealing with variables, such as capture-avoiding substitution and renaming. This is achieved by representing binders in the object-language via binders in the meta-language. However, enriching functional programming languages with direct support for HOAS has been a major challenge, because recursion over HOAS encodings requires one to traverse lambda-abstractions and necessitates programming with open objects.

We present a novel type-theoretic foundation based on contextual modal types which allows us to recursively analyze open terms via higher-order pattern matching. By design, variables occurring in open terms can never escape their scope. Using several examples, we demonstrate that our framework provides a name-safe foundation to operations typically found in nominal systems. In contrast to nominal systems however, we also support capture-avoiding substitution operations and even provide first-class substitutions to the programmer. The main contribution of this paper is a syntax-directed bi-directional type system where we distinguish between the data language and the computation language together with the progress and preservation proof for our language.
Minimizing leakage power of sequential circuits through mixed-

V
t

flip-flops and multi-

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t

combinational gates
Authors: Kim Jaehyun , Oh Chungki , Shin Youngsoo
Published: August 2010

The current use of multi-

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t

to control leakage power targets combinational gates, even though sequential elements such as flip-flops and latches also contribute appreciable leakage. We can, nevertheless, apply multi-

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t

to flip-flops, but few can take advantage of high-

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t

, which causes abrupt changes in timing. We combine low- and high-

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at the transistor level to design mixed-

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t

flip-flops with reduced leakage, an unchanged footprint, and a small increase in either setup time or clock-to-Q delay, but not both. An allocation algorithm for two

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t

s determines the

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t

(mixed, high, or low) of each flip-flop and the

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t

of each combinational gate (high or low) in a sequential circuit. Experiments with 65-nm technology show an average leakage saving of 42% compared to conventional multi-

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t

approaches; the leakage of flip-flops alone is cut by 78%. This saving is largely unaffected by die-to-die or within-die process variations, which we show through simulations. Standard deviation of leakage caused by process variation is also reduced due to less use of low-

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t

devices. We also extend our approach to three

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t

s, and obtain a further 14% reduction in leakage.
Using stuck-at tests to form scan-based tests for transition faults in standard-scan circuits
Authors: Pomeranz Irith , Reddy Sudhakar M.
Published: August 2010

In enhanced-scan circuits, a two-pattern test <

t
i

,

t
j

> for a transition fault can be obtained by using a test

t
j

that detects a stuck-at fault, and preceding it by a test

t
i

that activates another stuck-at fault. Thus, test generation for transition faults can be done by combining pairs of stuck-at tests. This provides an alternative to deterministic test generation, as well as reduces the test storage requirements for transition fault tests. We study the possibility of generating scan-based tests for transition faults in standard-scan circuits in a similar way, by combining pairs of stuck-at tests. Since it is not always possible to obtain a standard-scan test that is equivalent to a two-pattern test <

t
i

,

t
j

> based on stuck-at tests

t
i

and

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j

, it is not always possible to guarantee that the combination of

t
i

and

t
j

will detect a transition fault. To compensate for this, it is necessary to try combinations of different stuck-at test pairs, resulting in an increased simulation effort to compute effective standard-scan tests. Our focus in this work is on reducing this simulation effort by reducing the number of stuck-at test pairs that need to be considered.
Improved approximate string matching and regular expression matching on Ziv-Lempel compressed texts
Authors: Bille Philip , Fagerberg Rolf , Gørtz Inge Li
Published: August 2010

We study the approximate string matching and regular expression matching problem for the case when the text to be searched is compressed with the Ziv-Lempel adaptive dictionary compression schemes. We present a time-space trade-off that leads to algorithms improving the previously known complexities for both problems. In particular, we significantly improve the space bounds, which in practical applications are likely to be a bottleneck.
Admission control to minimize rejections and online set cover with repetitions
Authors: Alon Noga , Azar Yossi , Gutner Shai
Published: August 2010

We study the admission control problem in general networks. Communication requests arrive over time, and the online algorithm accepts or rejects each request while maintaining the capacity limitations of the network. The admission control problem has been usually analyzed as a benefit problem, where the goal is to devise an online algorithm that accepts the maximum number of requests possible. The problem with this objective function is that even algorithms with optimal competitive ratios may reject almost all of the requests, when it would have been possible to reject only a few. This could be inappropriate for settings in which rejections are intended to be rare events.

In this article, we consider preemptive online algorithms whose goal is to minimize the number of rejected requests. Each request arrives together with the path it should be routed on. We show an
O
(log
2
(
mc
))-competitive randomized algorithm for the weighted case, where
m
is the number of edges in the graph and
c
is the maximum edge capacity. For the unweighted case, we give an
O
(log
m
log
c
)-competitive randomized algorithm. This settles an open question of Blum et al. [2001]. We note that allowing preemption and handling requests with given paths are essential for avoiding trivial lower bounds.

The admission control problem is a generalization of the online set cover with repetitions problem, whose input is a family of
m
subsets of a ground set of
n
elements. Elements of the ground set are given to the online algorithm one by one, possibly requesting each element a multiple number of times. (If each element arrives at most once, this corresponds to the online set cover problem.) The algorithm must cover each element by different subsets, according to the number of times it has been requested.

We give an
O
(log
m
log
n
)-competitive randomized algorithm for the online set cover with repetitions problem. This matches a recent lower bound of Ω(log
m
log
n
) given by Korman [2005] (based on Feige [1998]) for the competitive ratio of any randomized
polynomial
time algorithm, under the
BPP
≠
NP
assumption. Given any constant ϵ > 0, an
O
(log
m
log
n
)-competitive deterministic bicriteria algorithm is shown that covers each element by at least (1 - ϵ)
k
sets, where
k
is the number of times the element is covered by the optimal solution.
Simultaneous source location
Authors: Andreev Konstantin , Garrod Charles , Golovin Daniel , Maggs Bruce , Meyerson Adam
Published: August 2010

We consider the problem of simultaneous source location: selecting locations for sources in a capacitated graph such that a given set of demands can be satisfied simultaneously, with the goal of minimizing the number of locations chosen. For general directed and undirected graphs we give an
O
(log
D
)-approximation algorithm, where
D
is the sum of demands, and prove matching Ω(log
D
) hardness results assuming
P
≠
NP
. For undirected trees, we give an exact algorithm and show how this can be combined with a result of Räcke to give a solution that exceeds edge capacities by at most
O
(log
2
n
log log
n
), where
n
is the number of nodes. For undirected graphs of bounded treewidth we show that the problem is still
NP
-hard, but we are able to give a PTAS with at most (1 + ϵ) violation of the capacities for arbitrarily small ϵ, or a (
k
+1) approximation with exact capacities, where
k
is the treewidth.
W4A 2010
Authors: Naftali Maia , Watanabe Willian , Sloan David
Published: August 2010

2010 saw the launch of the W4A student award scheme, generously supported by Google, to enable two of our most promising web accessibility research students to attend W4A --- the annual International Cross-Disciplinary Research Conference on Web Accessibility. This year's conference was held in Raleigh, North Carolina, on 26--27 April, and our two award winners were Maia Naftali (University of Buenos Aires, Argentina) and Willian Massani Watanabe (University of Sao Paulo, Brazil). Maia and Willian have kindly provided their reflections on the conference below.
Molecular Clouds in Nearby Galaxies
Authors: Fukui Yasuo , Kawamura Akiko
Published: August 2010

We present a review of spatially resolved giant molecular clouds (GMCs) in nearby galaxies, aiming at providing a template of GMC properties, which may be extrapolated to distant galaxies. We focus on the Magellanic system including the Large and Small Magellanic Clouds (LMC, SMC), M33, and a few dwarfs as observed in the J = 1–012CO transition at 2.6-mm wavelength. The X factor, a conversion factor of the12CO intensity to total molecular column density, and the GMC mass distribution, dN/dM, are similar among these galaxies, suggesting that GMCs share similar properties in the Local Group. The GMCs are classified into three types according to their level of star-formation activity and the types are interpreted in terms of evolution in 20–30 Myr rather than as three different generic types. A three-dimensional comparison including the velocity axis has revealed that GMCs in the LMC are associated with Hi envelopes. The Hi envelopes are probably gravitationally bound and may be infalling to increase the GMC mass via Hi-H2conversion. Recent submillimeter observations are revealing dense and warm clumps in GMCs, suggesting that the interior of a GMC also follows contraction leading to star formation on a similar timescale. Finally, we present an attempt to place these GMC properties among more distant galaxies and discuss future observational prospects.
Smoothed Particle Hydrodynamics in Astrophysics
Authors: Springel Volker
Published: August 2010

This review discusses smoothed particle hydrodynamics (SPH) in the astrophysical context, with a focus on inviscid gas dynamics. The particle-based SPH technique allows an intuitive and simple formulation of hydrodynamics that has excellent conservation properties and can be coupled to self-gravity with high accuracy. The Lagrangian character of SPH allows it to automatically adjust its resolution to the clumping of matter, a property that makes the scheme ideal for many application areas in astrophysics, where often a large dynamic range in density is encountered. We discuss the derivation of the basic SPH equations in their modern formulation, and give an overview about extensions of SPH developed to treat physics such as radiative transfer, thermal conduction, relativistic dynamics, or magnetic fields. We also briefly describe some of the most important applications areas of SPH in astrophysical research. Finally, we provide a critical discussion of the accuracy of SPH for different hydrodynamical problems, including measurements of its convergence rate for important classes of problems.