bluuebunny/crossref_metadata_2025 huggingface dataset:
Algorithm 781
Authors: Breinholt Greg , Schierz Christoph
Published: July 2002

An efficient algorithm for the generation of Hilbert's space-filling curve is given. The algorithm implements a recursive procedure that involves simple integer operations and quickly converges to the set of points that make the Hilbert curve. The algorithm is elegant, short, and considerably easier to implement than previous recursive and nonrecursive algorithms and can be efficiently implemented in all programming languages that have integer operations and allow recursion. The fundamental Hilbert shape (a line joining the four corners of a square) is represented by two variables with values of either 0 or 1. This coding technique could be successfully applied to the generation of other regular space-filling curves, such as the Peano curve.
The ARBAC97 model for role-based administration of roles
Authors: Sandhu Ravi , Bhamidipati Venkata , Munawer Qamar
Published: July 2002

In role-based access control (RBAC), permissions are associated with roles' and users are made members of roles, thereby acquiring the roles; permissions. RBAC's motivation is to simplify administration of authorizations. An appealing possibility is to use RBAC itself to manage RBAC, to further provide administrative convenience and scalability, especially in decentralizing administrative authority, responsibility, and chores. This paper describes the motivation, intuition, and formal definition of a new role-based model for RBAC administration. This model is called ARBAC97 (administrative RBAC '97) and has three components: URA97 (user-role assignment '97), RPA97 (permission-role assignment '97), and RRA97 (role-role assignment '97) dealing with different aspects of RBAC administration. URA97, PRA97, and an outline of RRA97 were defined in 1997, hence the designation given to the entire model. RRA97 was completed in 1998. ARBAC97 is described completely in this paper for the first time. We also discusses possible extensions of ARBAC97.
An improved third normal form for relational databases
Authors: Ling Tok-Wang , Tompa Frank W. , Kameda Tiko
Published: July 2002

In this paper, we show that some Codd third normal form relations may contain “superfluous” attributes because the definitions of transitive dependency and prime attribute are inadequate when applied to sets of relations. To correct this, an improved third normal form is defined and an algorithm is given to construct a set of relations from a given set of functional dependencies in such a way that the superfluous attributes are guaranteed to be removed. This new normal form is compared with other existing definitions of third normal form, and the deletion normalization method proposed is shown to subsume the decomposition method of normalization.
The Diclique Representation and Decomposition of Binary Relations
Authors: Haralick Robert M.
Published: July 2002

The binary relation is often a useful mathematical structure for representing simple relationships whose essence is a directed connection. To better aid in interpreting or storing a binary relation we suggest a diclique decomposition. A diclique of a binary relation
R
is defined as an ordered pair (
I, O
) such that
I
×
O
⊆
R
and (
I, O
) is maximal. In this paper, an algorithm is described for determining the dicliques of a binary relation; it is proved that the set of such dicliques has a nice algebraic structure. The algebraic structure is used to show how dicliques can be coalesced, the relationship between cliques and dicliques is discussed, and an algorithm for determining cliques from dicliques is described.
Algorithms for Scheduling Independent Tasks
Authors: Sahni Sartaj K.
Published: July 2002

The following job sequencing problems are studied: (i) single processor job sequencing with deadlines, (ii) job sequencing on
m
-identical processors to minimize finish time and related problems, (iii) job sequencing on 2-identical processors to minimize weighted mean flow time.

Dynamic programming type algorithms are presented to obtain optimal solutions to these problems, and three general techniques are presented to obtain approximate solutions for optimization problems solvable in this way. The techniques are applied to the problems above to obtain polynomial time algorithms that generate “good” approximate solutions.
A Methodology for LISP Program Construction from Examples
Authors: Summers Phillip D.
Published: July 2002

An automatic programming system, THESYS, for constructing recursive LISP programs from examples of what they do is described. The construction methodology is illustrated as a series of transformations from the set of examples to a program satisfying the examples. The transformations consist of (1) deriving the specific computation associated with a specific example, (2) deriving control flow predicates, and (3) deriving an equivalent program specification in the form of recurrence relations. Equivalence between certain recurrence relations and various program schemata is proved. A detailed description of the construction of four programs is presented to illustrate the application of the methodology.
The Cycle Time Distribution of Exponential Cyclic Queues
Authors: Chow We-Min
Published: July 2002

The cycle time distribution of a cyclic queue with two exponential servers is derived. Results show that when the population size
N
is large enough, the cycle time distribution is not sensitive to the ratio of service rates and asymptotically approaches an Erlangian distribution. If service rates are identical, however, the cycle time has an exact Erlangian distribution for any
N
.
A New Algorithm for Preemptive Scheduling of Trees
Authors: Gonzalez Teofilo F. , Johnson Donald B.
Published: July 2002

An algorithm which schedules forests of
n
tasks on
m
identical processors in
O
(
n
log
m
) time, offline, is given. The schedules are optimal with respect to finish time and contain at most
n
- 2 preemptions, a bound which is realized for all
n
. Also given is a simpler algorithm which runs in
O
(
nm
) time on the same problem and can be adapted to give optimal finish time schedules on-line for independent tasks with release times.
A polynomial time generator for minimal perfect hash functions
Authors: Sager Thomas J.
Published: July 2002

A perfect hash function PHF is an injection F from a set W of M objects into the set consisting of the first N nonnegative integers where N ⩾ M. If N = M, then F is a minimal perfect hash function, MPHF. PHFs are useful for the compact storage and fast retrieval of frequently used objects such as reserved words in a programming language or commonly employed words in a natural language.

The mincycle algorithm for finding PHFs executes with an expected time complexity that is polynomial in M and has been used successfully on sets of cardinality up to 512. Given three pseudorandom functions h
0
, h
1
, and h
2
, the mincycle algorithm searches for a function g such that F(w) = (h
0
(w) + g ° h
1
(w) + g ° h
2
(w)) mod N is a PHF.
Incorporation of units into programming languages
Authors: Karr Michael , Loveman David B.
Published: July 2002

The issues of how a programming language might aid in keeping track of physical units (feet, sec, etc.) are discussed. A method is given for the introduction of relationships among units (a watt is volts*amps, a yard is three feet) and subsequent automatic conversion based upon these relationships. Various proposals for syntax are considered.
Protection and the control of information sharing in multics
Authors: Saltzer Jerome H.
Published: July 2002

The design of mechanisms to control the sharing of information in the Multics system is described. Five design principles help provide insight into the tradeoffs among different possible designs. The key mechanisms described include access control lists, hierarchical control of access specifications, identification and authentication of users, and primary memory protection. The paper ends with a discussion of several known weaknesses in the current protection mechanism design.
Simultaneous events and lookahead in simulation protocols
Authors: Jha Vikas , Bagrodia Rajive
Published: July 2002

A discrete event simulation model may contain several events that have the same timestamp, referred to as simultaneous events. In general, the results of a simulation depend on the order in which simultaneous events are executed. Simulation languages and protocols use different, sometimes ad hoc, tie-breaking mechanisms to order simulataneous events. As a result, it may be impossible to reproduce the results of a simulation model across different simulators. This article presents a systematic analysis of the lookahead requirements for sequential and parallel simulation protocols, utilizing the process-oriented world view, with respect to their abililty to execute models with simultaneous events in a deterministic order. In particular, the article shows that most protocols, including the global event list protocol and commonly used parallel conservative and optimistic protocols, require that the simulation model provide some form of lookahead guarantee to enforce deterministc ordering of simultaneous events. The article also shows that the lookahead requirements for many protocols can be weakened if the model allows simultaneous events to be processed in a nondeterministic order. Finally, the lookahead properties that must be satisfied by a model in order for its execution to make guaranteed progress are derived using various simulation protocols.
The “Plankalkül” of Konrad Zuse
Authors: Bauer F. L. , Wössner H.
Published: July 2002

Plankalkül was an attempt by Konrad Zuse in the 1940's to devise a notational and conceptual system for writing what today is termed a program. Although this early approach to a programming language did not lead to practical use, the plan is described here because it contains features that are standard in today's programming languages. The investigation is of historical interest; also, it may provide insights that would lead to advancements in the state of the art. Using modern programming terminology, the Plankalkül is presented to the extent it has been possible to reconstruct it from the published literature.
A graph formulation of a school scheduling algorithm
Authors: Salazar A. , Oakford R. V.
Published: July 2002

The problem classically titled “The Examination Schedule Problem” takes various forms in the literature. Most of these formulations can be presented in the terminology of classical Network Theory. One such formulation is: Given a nondirected network, partition its nodes into a minimal number of subsets such that no two members of the same subset are connected by an arc.

An obvious lower limit to this number is the size of the largest strongly connected subgraph. Kirchgassner proved that an upper limit is this size plus one.

One logical extension of the previous work is the introduction of variable length examinations where W(I) is the number of periods for exam I. The object of this paper is to generalize the definition of largest strongly connected subgraph to include the weighting of nodes, to present an approximate algorithm which usually finds the largest strongly connected subgraph, and to discuss the application of this algorithm to the solution of school scheduling and exam scheduling problems.
Algorithm 488: A Gaussian pseudo-random number generator
Authors: Brent Richard P.
Published: July 2002

The algorithm calculates the exact cumulative distribution of the two-sided Kolmogorov-Smirnov statistic for samples with few observations. The general problem for which the formula is needed is to assess the probability that a particular sample comes from a proposed distribution. The problem arises specifically in data sampling and in discrete system simulation. Typically, some finite number of observations are available, and some underlying distribution is being considered as characterizing the source of the observations.
Fortran Tausworthe pseudorandom number generator
Authors: Payne W. H.
Published: July 2002

Intermediate computations in an “Extremely Portable Random Number Generator” by J. B. Kruskal [
Comm. ACM 12
, 2 (Feb. 1969), 93-94] exceed 15 bits plus sign. This is a severe limitation since the majority of small computers uses a 16 bit (15 bits plus sign) word or less. ASA standard FORTRAN compilers for these machines are readily available. Fortunately, a linearly recurring sequence generator [2] can be written in somewhat “portable” ASA Standard FORTRAN which will produce maximum length [2** (word size of computer - 1) -1] pseudorandom numbers for common 12, 16, 18, 24, and 32 bit computers, to mention only a few. Following Kendall's algorithm and notation presented by Whittlesey for a
p
-bit computer:
p
= 12,
N
= 11,
M
= 2;
p
= 16,
N
= 15,
M
= 1, 4, or 7;
p
= 18,
N
= 17,
M
= 3, 5, or 6;
p
= 24,
N
= 23,
M
= 5 or 9; and
p
= 32,
N
= 31,
M
= 3, 6, 7, or 13.
Threaded code
Authors: Bell James R.
Published: July 2002

The concept of “threaded code” is presented as an alternative to machine language code. Hardware and software realizations of it are given. In software it is realized as interpretive code not needing an interpreter. Extensions and optimizations are mentioned.
Concurrent control with “readers” and “writers”
Authors: Courtois P. J. , Heymans F. , Parnas D. L.
Published: July 2002

The problem of the mutual exclusion of several independent processes from simultaneous access to a “critical section” is discussed for the case where there are two distinct classes of processes known as “readers” and “writers.” The “readers” may share the section with each other, but the “writers” must have exclusive access. Two solutions are presented: one for the case where we wish minimum delay for the readers; the other for the case where we wish writing to take place as early as possible.
Dynamic planar convex hull operations in near-logarithmic amortized time
Authors: Chan Timothy M.
Published: July 2002

We give a data structure that allows arbitrary insertions and deletions on a planar point set
P
and supports basic queries on the convex hull of
P
, such as membership and tangent-finding. Updates take
O
(log
1+ε
n
) amori tzed time and queries take
O
(log
n
time each, where
n
is the maximum size of
P
and ε is any fixed positive constant. For some advanced queries such as bridge-finding, both our bounds increase to
O
(log
3/2
n
). The only previous fully dynamic solution was by Overmars and van Leeuwen from 1981 and required
O
(log
2
n
) time per update and
O
(log
n
) time per query.
A fast procedure for generating normal random variables
Authors: Marsaglia G. , MacLaren M. D. , Bray T. A.
Published: July 2002

A technique for generating normally distributed random numbers is described. It is faster than those currently in general use and is readily applicable to both binary and decimal computers.
A chaotic asynchronous algorithm for computing the fixed point of a nonnegative matrix of unit spectral radius
Authors: Lubachevsky Boris , Mitra Debasis
Published: July 2002

Given a nonnegative, irreducible matrix P of spectral radius unity, there exists a positive vector π such that π = πP. If P also happens to be stochastic, then π gives the stationary distribution of the Markov chain that has state-transition probabilities given by the elements of P. This paper gives an algorithm for computing π that is particularly well suited for parallel processing. The main attraction of our algorithm is that the timing and sequencing restrictions on individual processors are almost entirely eliminated and, consequently, the necessary coordination between processors is negligible and the enforced idle time is also negligible.

Under certain mild and easily satisfied restrictions on P and on the implementation of the algorithm, x(.), the vectors of computed values are proved to converge to within a positive, finite constant of proportionality of π. It is also proved that a natural measure of the
projective
distance of x(.) from π vanishes geometrically fast, and at a rate for which a lower bound is given. We have conducted extensive experiments on random matrices P, and the results show that the improvement over the parallel implementation of the synchronous version of the algorithm is substantial, sometimes exceeding the synchronization penalty to which the latter is always subject.
Abstract computability and algebraic specification
Authors: Tucker J. V. , Zucker J. I.
Published: July 2002

Abstract computable functions are defined by abstract finite deterministic algorithms on many-sorted algebras. We show that there exist finite universal algebraic specifications that specify uniquely (up to isomorphism) (i) all abstract computable functions on any many-sorted algebra; (ii) all functions effectively approximable by abstract computable functions on any metric algebra. We show that there exist universal algebraic specifications for all the classically computable functions on the set ℝ of real numbers. The algebraic specifications used are mainly bounded universal equations and conditional equations. We investigate the initial algebra semantics of these specifications, and derive situations where algebraic specifications precisely define the computable functions.
Experimental investigation of an interior search method within a simplex framework
Authors: Mitra Gautam , Tamiz Mehrdad , Yadegar Joseph
Published: July 2002

A feasible direction method for solving Linear Programming (LP) problems, followed by a procedure for purifying a non-basic solution to an improved extreme point solution have been embedded within an otherwise simplex based optimizer. The algorithm is designed to be hybrid in nature and exploits many aspects of sparse matrix and revised simplex technology. The interior search step terminates at a boundary point which is usually non-basic. This is followed by a series of minor pivotal steps which lead to a basic feasible solution with a superior objective function value. It is concluded that the procedures discussed in this article are likely to have three possible applications, which are

(i) improving a non-basic feasible solution to a superior extreme point solution,

(ii) an improved starting point for the revised simplex method, and

(iii) an efficient implementation of the multiple price strategy of the revised simplex method.
The evaluation of program-based software test data adequacy criteria
Authors: Weyuker E. J.
Published: July 2002

In earlier work, a preliminary set of axioms for software test data adequacy was introduced in order to formalize properties which should be satisfied by any good program-based adequacy criterion. Here, we extend this work by augmenting the set with additional axioms which substantially strengthen the set. In doing so, we rule out several types of unsuitable notions of adequacy.
Automatic determination of grain size for efficient parallel processing
Authors: McCreary Carolyn , Gill Helen
Published: July 2002

The authors propose a method for automatic determination and scheduling of modules from a sequential program.
A graph partitioning algorithm by node separators
Authors: Liu Joseph W. H.
Published: July 2002

A heuristic graph partitioning scheme is presented to determine effective node separators for undirected graphs. An initial separator is first obtained from the minimum degree ordering, an algorithm designed originally to produce fill-reducing orderings for sparse matrices. The separator is then improved by an iterative strategy based on some known results from bipartite graph matching. This gives an overall practical scheme in partitioning graphs. Experimental results are provided to demonstrate the effectiveness of this heuristic algorithm on graphs arising from sparse matrix applications.
Constrained nonlinear least squares: an exact penalty approach with projected structured quasi-Newton updates
Authors: Mahdavi-Amiri Nezam , Bartels Richard H.
Published: July 2002

This paper is concerned with the development, numerical implementation, and testing of an algorithm for solving constrained nonlinear least squares problems. The algorithm is an adaptation of the least squares case of an exact penalty method for solving nonlinearly constrained optimization problems due to Coleman and Conn. It also uses the ideas of Nocedal and Overton for handling quasi-Newton updates of projected Hessians, those of Dennis, Gay, and Welsch for approaching the structure of nonlinear least squares Hessians, and those of Murray and Overton for performing line searches. This method has been tested on a selection of problems listed in the collection of Hock and Schittkowski. The results indicate that the approach taken here is a viable alternative for least squares problems to the general nonlinear methods studied by Hock and Schittkowski.
N-Fold inspection: a requirements analysis technique
Authors: Martin Johnny , Tsai W. T.
Published: July 2002

N-fold inspection uses traditional inspections of the user requirements document (URD) but replicates the inspection activities using N independent teams. A pilot study was conducted to explore the usefulness of N-fold inspection during requirements analysis. A comparison of N-fold inspection with other development techniques reveals that N-fold inspection is a cost-effective method for finding faults in the URD and may be a valid technique in the development of mission-critical software systems.
P-uniform circuit complexity
Authors: Allender Eric W.
Published: July 2002

Much complexity-theoretic work on parallelism has focused on the class NC, which is defined in terms of logspace-uniform circuits. Yet P-uniform circuit complexity is in some ways a more natural setting for studying feasible parallelism. In this paper, P-uniform NC (PUNC) is characterized in terms of space-bounded AuxPDAs and alternating Turing Machines with bounded access to the input. The notions of general-purpose and special-purpose computation are considered, and a general-purpose parallel computer for PUNC is presented. It is also shown that NC = PUNC if all tally languages in P are in NC; this implies that the NC = PUNC question and the NC = P question are both instances of the ASPACE(
S
(
n
)) = ASPACE,TIME(
S
(
n
),
S
(
n
)

o
(1)

) question. As a corollary, it follows that NC = PUNC implies PSPACE = DTIME(2

no
(1)

).
HOMOLOGY-DEPENDENT GENE SILENCING IN PLANTS
Authors: Meyer P. , Saedler H.
Published: July 2002

▪ Abstract  Homology-dependent gene silencing phenomena in plants have received considerable attention, especially when it was discovered that the presence of homologous sequences not only affected the stability of transgene expression, but that the activity of endogenous genes could be altered after insertion of homologous transgenes into the genome. Homology-mediated inactivation most likely comprises at least two different molecular mechanisms that induce gene silencing at the transcriptional or posttranscriptional level, respectively. In this review we discuss different mechanistic models for plant-specific inactivation mechanisms and their relationship with repeat-specific silencing phenomena in other species.
POSTTRANSLATIONAL ASSEMBLY OF PHOTOSYNTHETIC METALLOPROTEINS
Authors: Merchant Sabeeha , Dreyfuss Beth Welty
Published: July 2002

▪ Abstract  The assembly of chloroplast metalloproteins requires biochemical catalysis. Assembly factors involved in the biosynthesis of metalloproteins might be required to synthesize, chaperone, or transport the cofactor; modify or chaperone the apoprotein; or catalyze cofactor-protein association. Genetic and biochemical approaches have been applied to the study of the assembly of chloroplast iron-sulfur centers, cytochromes, plastocyanin, and the manganese center of photosystem II. These have led to the discovery of NifS-homologues and cysteine desulfhydrase for iron-sulfur center assembly, six loci (CCS1–CCS5, ccsA) for c-type cytochrome assembly, four loci for cytochrome b6assembly (CCB1–CCB4), the CtpA protease, which is involved in pre-D1 processing, and the PCY2 locus, which is involved in holoplastocyanin accumulation. New assembly factors are likely to be discovered via the study of assembly-defective mutants of Arabidopsis, cyanobacteria, Chlamydomonas, maize, and via the functional analysis of candidate cofactor metabolizing components identified in the genome databases.
C4 GENE EXPRESSION
Authors: Sheen Jen
Published: July 2002

▪ Abstract  C4 plants, including maize, Flaveria, amaranth, sorghum, and an amphibious sedge Eleocharis vivipara, have been employed to elucidate the molecular mechanisms and signaling pathways that control C4 photosynthesis gene expression. Current evidence suggests that pre-existing genes were recruited for the C4 pathway after acquiring potent and surprisingly diverse regulatory elements. This review emphasizes recent advances in our understanding of the creation of C4 genes, the activities of the C4 gene promoters consisting of synergistic and combinatorial enhancers and silencers, the use of 5′ and 3′ untranslated regions for transcriptional and posttranscriptional regulations, and the function of novel transcription factors. The research has also revealed new insights into unique or universal mechanisms underlying cell-type specificity, coordinate nuclear-chloroplast actions, hormonal, metabolic, stress and light responses, and the control of enzymatic activities by phosphorylation and reductive processes.
Stem Cell Bioengineering
Authors: Zandstra Peter W. , Nagy Andras
Published: July 2002

▪ Abstract  Tissue engineering and cellular therapies, either on their own or in combination with therapeutic gene delivery, have the potential to significantly impact medicine. Implementation of technologies based on these approaches requires a readily available source of cells for the generation of cells and tissues outside a living body. Because of their unique capacity to regenerate functional tissue for the lifetime of an organism, stem cells are an attractive “raw material” for multiple biotechnological applications. By definition they are self-renewing because on cell division they can generate daughter stem cells. They are also multipotent because they can differentiate into numerous specialized, functional cells. Recent findings have shown that stem cells exist in most, if not all, tissues, and that stem cell tissue specificity may be more flexible than originally thought. Although the potential for producing novel cell-based products from stem cells is large, currently there are no effective technologically relevant methodologies for culturing stem cells outside the body, or for reproducibly stimulating them to differentiate into functional cells. A mechanistic understanding of the parameters important in the control of stem cell self-renewal and lineage commitment is thus necessary to guide the development of bioprocesses for the ex vivo culture of stem cells and their derivates.
Molecular Population Genetics of Social Insects
Authors: Pamilo Pekka , Gertsch Pia , Thorén Peter , Seppä Perttu
Published: July 2002

The life of social insects centers around sedentary colonies that can include individuals belonging to different patrilines or matrilines, with a turnover of reproductives. The colony is a scene for both cooperation and conflicts, and the conceptual framework for the evolution of social life and colony organization is provided by the kin selection theory. Variable molecular markers make it possible to dissect kinship within colonies, identifying patrilines and matrilines and estimating genetic relatednesses. Such markers have been used to test hypotheses on social conflicts between queens and workers (split sex ratio hypothesis), among workers (worker policing hypothesis), and among reproductive females (skew hypothesis). The data from several species of ants, bees, and wasps indicate that workers can obtain information on the genetic heterogeneity of their colonies and use that information to manipulate reproductive decisions. The social structure of colonies and the mode of colony founding affect the population-wide dispersal of sexuals. Populations with multi-queen colonial networks have limited dispersal; females stay in their natal colonies, and mating flights can be restricted. As a result, coexisting queens tend to be related to each other, maintaining the genetic integrity of colonies, and populations become spatially differentiated to an extent that can lead even to socially driven speciation.
ENDANGERED MUTUALISMS: The Conservation of Plant-Pollinator Interactions
Authors: Kearns Carol A. , Inouye David W. , Waser Nickolas M.
Published: July 2002

▪ Abstract  The pollination of flowering plants by animals represents a critical ecosystem service of great value to humanity, both monetary and otherwise. However, the need for active conservation of pollination interactions is only now being appreciated. Pollination systems are under increasing threat from anthropogenic sources, including fragmentation of habitat, changes in land use, modern agricultural practices, use of chemicals such as pesticides and herbicides, and invasions of non-native plants and animals. Honeybees, which themselves are non-native pollinators on most continents, and which may harm native bees and other pollinators, are nonetheless critically important for crop pollination. Recent declines in honeybee numbers in the United States and Europe bring home the importance of healthy pollination systems, and the need to further develop native bees and other animals as crop pollinators. The “pollination crisis” that is evident in declines of honeybees and native bees, and in damage to webs of plant-pollinator interaction, may be ameliorated not only by cultivation of a diversity of crop pollinators, but also by changes in habitat use and agricultural practices, species reintroductions and removals, and other means. In addition, ecologists must redouble efforts to study basic aspects of plant-pollinator interactions if optimal management decisions are to be made for conservation of these interactions in natural and agricultural ecosystems.
Consequences of Evolving With Bacterial Symbionts: Insights from the Squid-Vibrio Associations
Authors: Margaret J McFall-Ngai
Published: July 2002

▪ Abstract  The squid-vibrio light-organ symbioses, which have been under investigation for just over 10 years, offer the opportunity to decipher aspects of the dynamics of stable associations between animals and bacteria. The two best-studied partners, the Hawaiian sepiolid squid Euprymna scolopes and the marine luminous bacterium Vibrio fischeri, engage in the most common type of animal-bacterial association, i.e., between extracellular, gram-negative bacteria and animal epithelia. Similar to most such symbioses, the squid-vibrio relationship begins anew each generation when thehost animal acquires the symbiont from the surrounding environment. To establish a specific association, mechanisms have evolved to ensure recognition between the host and symbiont and the exclusion of other potential partnerships. Once the association has been established, the bacteria induce significant morphological changes in the host that result in a transition of the light organ from a form associated with initiation of the symbiosis to one characteristic of the mature, functional relationship.
FEDERAL FOSSIL FUEL SUBSIDIES AND GREENHOUSE GAS EMISSIONS: A Case Study of Increasing Transparency for Fiscal Policy
Authors: Koplow Doug , Dernbach John
Published: July 2002

▪ Abstract  Growing international pressure to curb greenhouse gas (GHG) emissions has focused attention on existing policies that may, either by design or by effect, subsidize fossil fuel production and consumption. This paper reviews existing studies of fossil fuel subsidies within the United States, as well as assessments of the potential impact of subsidy reform on GHG emissions. Evaluating the differences across the studies, it highlights the most important disparities in subsidy definition and valuation in order to clarify the conclusions that can be drawn from this body of work. We then present some of the tools used to provide transparency in environmental regulation. We conclude that many of these approaches can be used to improve the transparency of fiscal policy, with important benefits within the context of climate change and beyond.
Endocrine Insights into the Evolution of Metamorphosis in Insects
Authors: Truman James W. , Riddiford Lynn M.
Published: July 2002

▪ Abstract  This review explores the roles of ecdysone and juvenile hormone (JH) in the evolution of complete metamorphosis and how metamorphosis, in turn, has impacted endocrine signaling. JH is a key player in the evolution of metamorphosis because it can act on embryos from more basal insect groups to suppress morphogenesis and cause premature differentiation, functions needed for transforming the transitional pronymphal stage of hemimetabolous insects into a functional larval stage. In the ancestral condition, imaginal-related growth is then delayed until JH finally disappears during the last larval instar. In the more derived groups of the Holometabola, selective tissues have escaped this JH suppression to form early-growing imaginal discs. We discuss how complete metamorphosis may have influenced the molecular aspects of both ecdysone and JH signaling.
Renormalization-Group Analysis of Turbulence
Authors: Smith Leslie M. , Woodruff Stephen L.
Published: July 2002

▪ Abstract  The renormalization-group (RG) analysis of turbulence, based primarily on KG Wilson's coarse-graining procedure, leads to suggestive results for turbulence coefficients and models. Application of the method to turbulence evolved from the contributions of many authors and received widespread attention following the 1986 work of V Yakhot and SA Orszag. The Yakhot-Orszag method involves the basic renormalization-group scale-removal procedure, as well as additional hypotheses and approximations; their analysis is reviewed here with an attempt to clarify those approximations. Discussion of some related and subsequent literature is also included. Following the work of M Avellaneda and AJ Majda, a simpler version of the method is appplied to a model passive scalar problem wherein it is seen that, in certain cases, the RG method can recover exact results.
CERAMIC COMPOSITE INTERFACES:Properties and Design
Authors: Faber K. T.
Published: July 2002

▪ Abstract  Optimal design of the fiber-matrix interface in ceramic-matrix composites is the key to achieving desired composite performance. In this paper the interface-controlling parameters are described. Techniques for measuring interfacial properties are reported. Examples of interface design of both oxide and non-oxide types are illustrated.
InGaN-BASED LASER DIODES
Authors: Nakamura Shuji
Published: July 2002

▪ Abstract  Continuous-wave operation of InGaN multi-quantum-well (MQW) structure laser diodes (LDs) has been demonstrated at room temperature with output power up to 50 mW, operating temperature up to 100°C, emission wavelength of 400–420 nm, and a lifetime up to 300 h. InGaN MQW LDs with a lifetime of more than 1000 h are expected soon. Commercialization will begin in 1998 if research on the bluish-purple InGaN-based laser diodes continues to progress. The stimulated emission of the InGaN-based LDs originates from localized energy states of 100–250 meV depth, which are equivalent to quantum dot energy states, probably arising from from InGaN composition fluctuation in the InGaN well layers.
Materials for Non-Viral Gene Delivery
Authors: Segura Tatiana , Shea Lonnie D
Published: July 2002

▪ Abstract  Novel therapeutic strategies can be envisioned based on altering the expression level of target genes involved in cellular processes and disease progression; however, our ability to efficiently manipulate gene expression is limited. Non-viralbased gene therapy provides a relatively safe approach to increase or decrease the expression of a specific gene using DNA or antisense sequences; however, synthetic systems are required to direct plasmids and oligonucleotides to a specific tissue and to enhance cellular uptake and intracellular trafficking. Numerous materials are being developed that interact with DNA to enhance its properties (e.g. stability, charge density) and thus direct its biodistribution and facilitate cellular interactions. The development of synthetic delivery systems to manipulate gene expression efficiently is a powerful tool that will ultimately lead to novel therapeutic strategies for the treatment of numerous disorders.
OSMOADAPTATION BY RHIZOSPHERE BACTERIA
Authors: Miller Karen J. , Wood Janet M.
Published: July 2002

The osmolality of rhizosphere soil water is expected to be elevated in relation to bulk-soil water osmolality as a result of the exclusion of solutes by plant roots during water uptake, the release of plant root exudates, and the production of exopolymers by plant roots and rhizobacteria. In contrast, the osmolality of water within highly hydrated bulk soil is low (less than 50 Osm/kg); thus the ability to adapt to elevated osmolality is likely to be important for successful rhizosphere colonization by rhizobacteria. The present review focuses on the osmoadaptive responses of three gram-negative rhizobacterial genera: Rhizobium, Azospirillum, and Pseudomonas. Specifically, we examine the compatible solutes and osmoprotectants utilized by various species within these genera. The adaptation of rhizobacteria to hypoosmotic environments is also examined in the present review. In particular, we focus on the biosynthesis and accumulation of periplasmic glucans by rhizobacteria. Finally, the relationship between rhizobacterial osmoadaptation and selected plant-microbe interactions is considered.
CELLULAR AND MOLECULAR DETERMINANTS OF SYMPATHETIC NEURON DEVELOPMENT
Authors: Francis Nicole J. , Landis Story C.
Published: July 2002

▪ Abstract  The development of the sympathetic nervous system can be divided into three overlapping stages. First, the precursors of sympathetic neurons arise from undifferentiated neural crest cells that migrate ventrally, aggregate adjacent to the dorsal aorta, and ultimately differentiate into catecholaminergic neurons. Second, cell number is refined during a period of cell death when neurotrophic factors determine the number of neuronal precursors and neurons that survive. The final stage of sympathetic development is the establishment and maturation of synaptic connections, which for sympathetic neurons can include alterations in neurotransmitter phenotype. Considerable progress has been made recently in elucidating the cellular and molecular mechanisms that direct each of these developmental decisions. We review the current understanding of each of these, focusing primarily on events in the peripheral nervous system of rodents.
The Emergence of Modern Neuroscience: Some Implications for Neurology and Psychiatry
Authors: Cowan W. Maxwell , Harter Donald H. , Kandel Eric R.
Published: July 2002

One of the most significant developments in biology in the past half century was the emergence, in the late 1950s and early 1960s, of neuroscience as a distinct discipline. We review here factors that led to the convergence into a common discipline of the traditional fields of neurophysiology, neuroanatomy, neurochemistry, and behavior, and we emphasize the seminal roles played by David McKenzie Rioch, Francis O Schmitt, and especially Stephen W Kuffler in creating neuroscience as we now know it. The application of the techniques of molecular and cellular biology to the study of the nervous system has greatly accelerated our understanding of the mechanisms involved in neuronal signaling, neural development, and the function of the major sensory and motor systems of the brain. The elucidation of the underlying causes of most neurological and psychiatric disorders has proved to be more difficult; but striking progress is now being made in determining the genetic basis of such disorders as Alzheimer’s disease, amyotrophic lateral sclerosis, Parkinson’s disease, and a number of ion channel and mitochondrial disorders, and a significant start has been made in identifying genetic factors in the etiology of such disorders as manic depressive illness and schizophrenia. These developments presage the emergence in the coming decades of a new nosology, certainly in neurology and perhaps also in psychiatry, based not on symptomatology but on the dysfunction of specific genes, molecules, neuronal organelles and particular neural systems.
NEUTRINOMASS ANDOSCILLATION
Authors: Fisher Peter , Kayser Boris , McFarland Kevin S.
Published: July 2002

▪ Abstract  The question of neutrino mass is one of the major riddles in particle physics. Recently, strong evidence that neutrinos have nonzero masses has been found. Though tiny, these masses could be large enough to contribute significantly to the mass density of the universe. The evidence for nonvanishing neutrino masses is based on the apparent observation of neutrino oscillation—the transformation of a neutrino from one type or “flavor” to another. We explain the physics of neutrino oscillation and review and weigh the evidence that it actually occurs in nature. We discuss the constraints on neutrino mass from cosmology and from experiments with negative results. After presenting illustrative neutrino mass spectra suggested by the present data, we consider how experiments in the near and distant future can further illuminate the nature of neutrinos and their masses.
THE OPTIMAL RATIO OF FAT-TO-CARBOHYDRATE IN THE DIET
Authors: Grundy Scott M.
Published: July 2002

▪ Abstract  A major issue in human nutrition is the optimal relation of carbohydrate-to-fat in the diet. According to some investigators, a high proportion of fat energy to total energy favors the development of several chronic diseases. Among these are obesity, coronary heart disease, diabetes, and cancer. The theory that a high proportion of fat relative to other nutrients promotes the development of obesity is founded on research with experimental animals and in human population surveys. This theory has been difficult to prove in prospective feeding studies in humans; therefore it remains a contentious issue. Regarding coronary heart disease, little evidence supports a claim that a high proportion of dietary fat predisposes to disease. On the other hand, strong evidence bolsters the claim that certain fatty acids raise the risk for coronary heart disease. These include saturated fatty acids and trans fatty acids, both of which raise serum cholesterol levels. In contrast, neither monounsaturated nor polyunsaturated fatty acids raise serum cholesterol levels and seemingly pose little risk for coronary disease. The relationship between dietary fat and type 2 diabetes is tied largely to the issue of obesity, because obesity is a major cause of diabetes. Although animal studies and epidemiological studies have implicated dietary fat as a factor in cancer, recent prospective epidemiological data in humans have cast doubt on the possibility of a strong relationship. In summary, clear evidence points to the need to reduce intakes of saturated and trans fatty acids in the diet. Beyond this change, a balanced ratio of unsaturated fatty acids to carbohydrate leading to fat intake of approximately 30% of total energy seems appropriate for the American public.
PROTEIN AND AMINO ACID METABOLISM DURING AND AFTER EXERCISE AND THE EFFECTS OF NUTRITION
Authors: Rennie Michael J. , Tipton Kevin D.
Published: July 2002

▪ Abstract  Sustained dynamic exercise stimulates amino acid oxidation, chiefly of the branched-chain amino acids, and ammonia production in proportion to exercise intensity; if the exercise is intense enough, there is a net loss of muscle protein (as a result of decreased protein synthesis, increased breakdown, or both); some of the amino acids are oxidized as fuel, whereas the rest provide substrates for gluconeogenesis and possibly for acid-based regulation. Protein balance is restored after exercise, but no hypertrophy occurs with habitual dynamic exercise. Resistance exercise causes little change in amino acid oxidation but probably depresses protein synthesis and elevates breakdown acutely. After exercise, protein synthesis rebounds for ≤48 h, but breakdown remains elevated, and net positive balance is achieved only if amino acid availability is increased. There is no evidence that habitual exercise increases protein requirements; indeed protein metabolism may become more efficient as a result of training.
BODYCOMPOSITION OF THEMALE ANDFEMALEREFERENCEINFANTS
Authors: Fomon Samuel J. , Nelson Steven E.
Published: July 2002

▪ Abstract  During infancy, especially early infancy, a substantial proportion of the requirements for energy and specific nutrients are those needed for growth. Knowledge of the body composition of a reference infant (body size and chemical composition at the 50th centile for age) permits an estimate of the growth needs of the infant. In this communication, we review efforts from the 1960s to the present at defining the composition of the male and female reference infants. We and others have demonstrated that accumulation of fat is remarkably rapid during the first 4 or 6 months of life. As a percentage of fat-free mass, water decreases throughout infancy whereas protein and minerals increase. However, the quantitative nature of these changes remains uncertain. After identifying the areas in which further data are needed, we conclude that the single most important area for further work is determining the relation of “bone mineral content” determined by dual energy X-ray absorptiometry to the osseous mineral content of the infant.
Somatic Gene Therapy in the Cardiovascular System
Authors: Baumgartner I , Isner JM
Published: July 2002

▪ Abstract  This review surveys a range of approaches using plasmid DNA encoding the 165-amino-acid isoform of vascular endothelial growth factor (phVEGF165) to therapeutically modulate micro- or macrovascular endothelial cells, focusing on strategies to augment postnatal collateral circulation in arterial insufficiency or to accelerate re-endothelialization after balloon angioplasty to prevent restenosis. We focus on intra-arterial and intramuscular/intramyocardial gene transfer of the VEGF165gene, the options that have been most thoroughly studied to date in patients. We review developmental and postnatal significance of the endothelial-cell-specific mitogen VEGF that has stimulated these studies and present limitations of current knowledge as well as challenges for the future.
ADVANCES IN THE MOLECULAR GENETIC ANALYSIS OF THE FLAX-FLAX RUST INTERACTION
Authors: Ellis Jeff , Lawrence Greg , Ayliffe Michael , Anderson Peter , Collins Nick , Finnegan Jean , Frost Donna , Luck Joanne , Pryor Tony
Published: July 2002

▪ Abstract  The L6 and M rust-resistance genes, representing two of the five rust-resistance gene loci in flax (Linum usitatissimum), have been cloned. The molecular data are fully consistent with earlier genetic data: the L locus is a single gene with multiple alleles expressing different rust resistance specificities, and the M locus is complex, containing an array of about 15 similar genes. Thus, while L6 and M resistance genes have 86% nucleotide identity, their locus structure is very different. These genes encode products belonging to the nucleotide binding site–leucine-rich repeat class of disease-resistance proteins. Analysis of alleles from the L locus and chimeric genes is providing evidence suggesting that important specificity determinants occur in the C-terminal half of the proteins, the region containing the leucine-rich repeats. The isolation and characterization of the rust (Melampsora lini) avirulence genes that correspond to the cloned rust-resistance genes is one of the major challenges remaining to the understanding of this system.