bluuebunny/crossref_metadata_2025 huggingface dataset:
Two-handed virtual manipulation
Authors: Hinckley Ken , Pausch Randy , Proffitt Dennis , Kassell Neal F.
Published: July 2002

We discuss a two-handed user interface designed to support three-dimesional neurosurgical visualization. By itself, this system is a “point design,” an example of an advanced user interface technique. In this work, we argue that in order to understand why interaction techniques do or do not work, and to suggest possibilities for new techniques, it is important to move beyond point design and to introduce careful scientific measurement of human behavioral principles. In particular, we argue that the common-sense viewpoint that “two hands save time by working in parallel” may not always be an effective way to think about two-handed interface design because the hands do not necessarily work in parallel (there is a structure to two-handed manipulation) and because two hands do more than just save time over one hand (two hands provide the user with more information and can structure how the user thinks about a task). To support these claims, we present an interface design developed in collaboration with neurosurgeons which has undergone extensive informal usability testing, as well as a pair of formal experimental studies which investigate behavioral aspects of two-handed virtual object manipulation. Our hope is that this discussion will help others to apply the lessons in our neurosurgery application to future two-handed user interface designs.
Two methods for display of high contrast images
Authors: Tumblin Jack , Hodgins Jessica K. , Guenter Brian K.
Published: July 2002

High contrast images are common in night scenes and other scenes that include dark shadows and bright light sources. These scenes are difficult to display because their contrasts greatly exceed the range of most display devices for images. As a result, the image constrasts are compressed or truncated, obscuring subtle textures and details. Humans view and understand high contrast scenes easily, “adapting” their visual response to avoid compression or truncation with no apparent loss of detail. By imitating some of these visual adaptation processes, we developed methods for the improved display of high-contrast images. The first builds a display image from several layers of lighting and surface properties. Only the lighting layers are compressed, drastically reducing contrast while preserving much of the image detail. This method is practical only for synthetic images where the layers can be retained from the rendering process. The second method interactively adjusts the displayed image to preserve local contrasts in a small “foveal” neighborhood. Unlike the first method, this technique is usable on any image and includes a new tone reproduction operator. Both methods use a sigmoid function for contrast compression. This function has no effect when applied to small signals but compresses large signals to fit within an asymptotic limit. We demonstrate the effectiveness of these approaches by comparing processed and unprocessed images.
Constructing, organizing, and visualizing collections of topically related Web resources
Authors: Terveen Loren , Hill Will , Amento Brian
Published: July 2002

For many purposes, the Web page is too small a unit of interaction and analysis. Web sites are structured multimedia documents consisting of many pages, and users often are interested in obtaining and evaluating entire collections of topically related sites. Once such a collection is obtained, users face the challenge of exploring, comprehending and organizing the items. We report four innovations that address these user needs: (1) we replaced the Web page with the Websiteas the basic unit of interaction and analysis;(2) we defined a new informationstructure, theclan graph, that groups together sets of related sites; (3) we augment the representation of a site with asite profile, information about site structure and content that helps inform user evaluation of a site; and (4) we invented a new graph visualization, theauditorium visualization, that reveals important structural and content properties of sites within a clan graph. Detailed analysis and user studies document the utility of this approach. The clan graph construction algorithm tends to filter out irrelevant sites and discover additional relevant items. The auditorium visualization, augmented with drill-down capabilities to explore site profile data, helps users to find high-quality sites as well as sites that serve a particular function.
A New Pseudo-Random Number Generator
Authors: Rotenberg A.
Published: July 2002

Although the multiplicative congruential method for generating pseudo-random numbers is widely used and has passed a number of tests of randomness [1, 2], attempts have been made to find an additive congruential method since it could be expected to be faster. Tests on a Fibonacci sequence [1] have shown it to be unsatisfactory. The sequence
x

i
+1

= (2

a

+ 1)

x
i

+
c
(mod 2
35
) (1) has been tested on the IBM 704. In appendix I it is shown that the sequence generates the full period of 2
35
numbers for
a
≧ 2 and
c
odd. Similar results obtain for decimal machines. Since multiplication by a power of the base can be accomplished by shifting, which is comparable in speed to addition, this scheme requires essentially three additions. It takes 14 machine cycles on the IBM 704, compared to 28 for the multiplicative method, so that the saving is 168 μs/random number. The scheme has the further advantage that it does not destroy the multiplier-quotient register.

Some tests have been made on the randomness of this sequence for
a
= 7 and
c
= 1, and a summary of the results is given in appendix II, where now the random numbers are considered to lie in the interval (0, 1).

The serial correlation coefficient between one member of this sequence and the next is shown by Coveyou [3] to be approximately 0.8 per cent. By taking
a
= 9 this correlation coefficient can be reduced to approximately 0.2 per cent without increasing the time. Taking
a
= 21 would make this correlation very small but would require one more machine cycle on the IBM 704. Another way to reduce the correlation is to choose
c
such that the numerator in Coveyou's expression for the correlation coefficient is zero. This cannot be done exactly since it requires that
c
= (.5 ± √3/6)2

P

where
P
is the number of binary digits (excluding sign) in a machine word. However, a machine representation close to either of these numbers should be satisfactory. Some correlations with
c
= (.788
+
)2
35
and
a
= 7 were obtained and did not differ significantly from those given for
c
= 1 in the first section of appendix II.

The author wishes to thank R. R. Coveyou for communicating his results in advance of publication and Elizabeth Wetherell for carrying out the calculations.
On Ianov's Program Schemata
Authors: Rutledge J. D.
Published: July 2002

Ianov has defined a formal abstraction of the notion of program which represents the sequential and control properties of a program but suppresses the details of the operations. For these schemata he defines a notion corresponding to computation and defines equivalence of schemata in terms of it. He then gives a decision procedure for equivalence of schemata, and a deductive formalism for generating schemata equivalent to a given one. The present paper is intended, first as an exposition of Ianov's results and simplification of his method, and second to point out certain generalizations and extensions of it. We define a somewhat generalized version of the notion of schema, in a language similar to that used in finite automata theory, and present a simple algorithm for the equivalence problem solved by Ianov. We also point out that the same problem for an extended notion of schema, considered rather briefly by Ianov, is just the equivalence problem for finite automata, which has been solved, although the decision procedure is rather long for practical use. A simple procedure for generating all schemata equivalent to a given schema is also indicated.
Universality of Tag Systems with
P
= 2
Authors: Cocke John , Minsky Marvin
Published: July 2002

By a simple direct construction it is shown that computations done by Turing machines can be duplicated by a very simple symbol manipulation process. The process is described by a simple form of Post canonical system with some very strong restrictions.

This system is
monogenic
: each formula (string of symbols) of the system can be affected by one and only one production (rule of inference) to yield a unique result. Accordingly, if we begin with a single axiom (initial string) the system generates a simply ordered sequence of formulas, and this operation of a monogenic system brings to mind the idea of a machine.

The Post canonical system is further restricted to the “Tag” variety, described briefly below. It was shown in [1] that Tag systems are equivalent to Turing machines. The proof in [1] is very complicated and uses lemmas concerned with a variety of two-tape nonwriting Turing machines. The proof here avoids these otherwise interesting machines and strengthens the main result; obtaining the theorem with a best possible
deletion number P
= 2.

Also, the representation of the Turing machine in the present system has a lower degree of exponentiation, which may be of significance in applications.

These systems seem to be of value in establishing unsolvability of combinatorial problems.
Generation of Primes by a One-Dimensional Real-Time Iterative Array
Authors: Fischer Patrick C.
Published: July 2002

A construction is given of a one-dimensional iterative of finite-state sequential machines, which can generate in real time the binary sequence representing the set of prime numbers.
P-Complete Approximation Problems
Authors: Sahni Sartaj , Gonzalez Teofilo
Published: July 2002

For P-complete problems such as traveling salesperson, cycle covers, 0-1 integer programming, multicommodity network flows, quadratic assignment, etc., it is shown that the approximation problem is also P-complete. In contrast with these results, a linear time approximation algorithm for the clustering problem is presented.
FILL and FUNI
Authors: Long David E. , Iyer Mahesh A. , Abramovici Miron
Published: July 2002

In this paper, we first present an algorithm (FILL) to efficiently identify a large subset of illegal states in synchronous sequential circuits, without assuming a global reset mechanism. A second algorithm, FUNI, finds sequentially untestable faults whose detection requires some of the illegal states computed by FILL. Although based on binary decision diagrams (BDDs), FILL is able to process large circuits by using a new functional partitioning procedure. The incremental building of the set of illegal states guarantees that FILL will always obtain at least a partial solution. FUNI is a direct method that identifies untestable faults without using the exhaustive search involved in automatic test generation (ATG). Experimental results show that FUNI finds a large number of untestable faults up to several orders of magnitude faster than an ATG algorithm that targeted the faults identified by FUNI. Also, many untestable faults identified by FUNI were aborted by the test generator.
Computer technology and jobs: an impact assessment model
Authors: Weber Ron
Published: July 2002

A model is proposed that associates the impact of computer technology on a job, with the set of underlying characteristics that describe the activities performed on the job. An empirical test of the model has been undertaken. One thousand and thirty-five experts assessed the impact of computer technology that they believed would occur on 306 jobs over a three-year period. Job characteristics data was obtained from prior analyses of the jobs, using the Position Analysis Questionnaire (PAQ). Six job dimensions derived from analysis PAQ data were significant predictors of the technological impact ratings provided by the experts: engaging in physical activities; being aware of the work environment; performing clerical-related functions; working in an unpleasant or hazardous environment; performing service-related activities; and performing supervising, directing, and estimating functions.
A study of application program development techniques
Authors: Guimaraes Tor
Published: July 2002

A survey of application development techniques in 43 organizations identifies the methods and tools found most effective in application software development.
Programming semantics for multiprogrammed computations
Authors: Dennis Jack B. , Van Horn Earl C.
Published: July 2002

The semantics are defined for a number of meta-instructions which perform operations essential to the writing of programs in multiprogrammed computer systems. These meta-instructions relate to parallel processing, protection of separate computations, program debugging, and the sharing among users of memory segments and other computing objects, the names of which are hierarchically structured. The language sophistication contemplated is midway between an assembly language and an advanced algebraic language.
Algorithm 806: SPRNG
Authors: Mascagni Michael , Srinivasan Ashok
Published: July 2002

In this article we present background, rationale, and a description of the Scalable Parallel Random Number Generators (SPRNG) library. We begin by presenting some methods for parallel pseudorandom number generation. We will focus on methods based on parameterization, meaning that we will not consider splitting methods such as the leap-frog or blocking methods. We describe, in detail, parameterized versions of the following pseudorandom number generators: (i) linear congruential generators, (ii) shift-register generators, and (iii) lagged-Fibonacci generators. We briefly describe the methods, detail some advantages and disadvantages of each method, and recount results from number theory that impact our understanding of their quality in parallel applications. SPRNG was designed around the uniform implementation of different families of parameterized random number generators. We then present a short description of SPRNG. The description contained within this document is meant only to outline the rationale behind and the capabilities of SPRNG. Much more information, including examples and detailed documentation aimed at helping users with putting and using SPRNG on scalable systems is available at htt;//sprng.sc.fsu.edu. In this description of SPRNG we discuss the random-number generator library as well as the suite of tests of randomness that is an integral part of SPRNG. Random-number tools for parallel Monte Carlo applications must be subjected to classical as well as new types of empirical tests of randomness to eliminate generators that show defects when used in scalable envionments.
The use of an interactive information storage and retrieval system in medical research
Authors: Lucas Henry C.
Published: July 2002

This paper presents the results of a study of the use of an interactive computerized storage and retrieval system. A monitor built into the computer system provided usage data for the study. Additional data on user reactions were gathered from a questionnaire. The results show the important role played by frequently chosen laboratory reference leaders in influencing the use of this system. The implications of the study for the design of similar systems are discussed.
Value orientation of computer science students
Authors: Anderson Ronald E.
Published: July 2002

Technological and nontechnological value orientations are investigated with special attention to the complexity of value structures. Computer science students, who are closely associated with technology, contrast with social science students, who are often technologically aloof. This is confirmed by the value ratings of 313 students at the University of Minnesota in 1972. Computer science majors were found to have a more complex value structure than social science majors.
Economical encoding of commas between strings
Authors: Even S. , Rodeh M.
Published: July 2002

A method for insertion of delimiters between strings without using new symbols is presented. As the lengths of the strings increase, the extra cost, in terms of prolongation, becomes vanishingly small compared to the lengths of the strings.
Communicating sequential processes
Authors: Hoare C. A. R.
Published: July 2002

This paper suggests that input and output are basic primitives of programming and that parallel composition of communicating sequential processes is a fundamental program structuring method. When combined with a development of Dijkstra's guarded command, these concepts are surprisingly versatile. Their use is illustrated by sample solutions of a variety of a familiar programming exercises.
Formal requirements for virtualizable third generation architectures
Authors: Popek Gerald J. , Goldberg Robert P.
Published: July 2002

Virtual machine systems have been implemented on a limited number of third generation computer systems, e.g. CP-67 on the IBM 360/67. From previous empirical studies, it is known that certain third generation computer systems, e.g. the DEC PDP-10, cannot support a virtual machine system. In this paper, model of a third-generation-like computer system is developed. Formal techniques are used to derive precise sufficient conditions to test whether such an architecture can support virtual machines.
Comparison of several adaptive Newton-Cotes quadrature routines in evaluating definite integrals with peaked integrands
Authors: Hillstrom K. E.
Published: July 2002

This report compares the performance of five different adaptive quadrature schemes, based on Newton-Cotes (2
N
+ 1) point rules (
N
= 1, 2, 3, 4, 5), in approximating the set of definite integrals ∫
1
-1
(
x
2
+
p
2
)
-1
dx
with relative accuracy ε.
An experimental study on the role of touch in shared virtual environments
Authors: Basdogan Cagatay , Ho Chih-Hao , Srinivasan Mandayam A. , Slater Mel
Published: July 2002

Investigating virtual environments has become an increasingly interesting research topic for engineers, computer and cognitive scientists, and psychologists. Although there have been several recent studies focused on the development of multimodal virtual environments (VEs) to study human-machine interactions, less attention has been paid to human-human and human-machine interactions in shared virtual environments (SVEs), and to our knowledge, no attention paid at all to what extent the addition of haptic communication between people would contribute to the shared experience. We have developed a multimodal shared virtual environment and performed a set of experiments with human subjects to study the role of haptic feedback in collaborative tasks and whether haptic communication through force feedback can facilitate a sense of being and collaborating with a remote partner. The study concerns a scenario where two participants at remote sites must cooperate to perform a joint task in an SVE. The goals of the study are (1) to assess the impact of force feedback on task performance, (2) to better understand the role of haptic communication in human-human interactions, (3) to study the impact of touch on the subjective sense of collaborating with a human as reported by the participants based on what they could see and feel, and (4) to investigate if gender, personality, or emotional experiences of users can affect haptic communication in SVEs. The outcomes of this research can have a powerful impact on the development of next-generation human-computer interfaces and network protocols that integrate touch and force feedback technology into the internet, development of protocols and techniques for collaborative teleoperation such as hazardous material removal, space station.
PSBLAS
Authors: Filippone Salvatore , Colajanni Michele
Published: July 2002

Many computationally intensive problems in engineering and science
give rise to the solution of large, sparse, linear systems of equations. Fast and efficient methods for their soltion are very important because these systems usually occur in the innermost loop of the computational scheme. Parallelization is often necessary to achieve an acceptable level of performance. This paper presents the design, implementation, and interface of a library of Basic Linear Algebra Subroutines for sparse matrices (PSBLAS) which is specifically tailored to distributed-memory computers. PSBLAS enables easy, efficient, and portable implementations of parallel iterative solvers for linear systems. The interface keeps in view a Single Program Multiple Data programming model on distributed-memory machines. However, the architecture of the library does not exclude an implementation in different paradigms, such as those based on the shared-memory model.
COMIT
Authors: Yngve Victor H.
Published: July 2002

The documentation of COMIT reflects the conviction that adequate user manuals are as much a part of a successful problem-oriented language system as is the compiler itself. Without adequate manuals, a language could not be easily learned or used, and much of the convenience that is implicit in the idea of a problem-oriented language would be lost. The COMIT manuals are thus as user-oriented as the language itself.
RECOL—a retrieval command language
Authors: Climenson W. D.
Published: July 2002

An interrogation scheme is described for the retrieval and manipulation of data file records. The language of the interrogation scheme allows for
selecting
file records with the use of logical condition statements,
defining
record classes,
associating
file records,
editing
printed output, and
summarizing
the results of the above operations. Some examples of a typical file application and the more significant features of a particular machine implementation are given.
Automatic graders for programming classes
Authors: Hollingsworth Jack
Published: July 2002

Fifteen months ago the first version of an “automatic grader” was tried with a group of twenty students taking a formal course in programming. The first group of twenty programs took only five minutes on the computer (an IBM 650). With such a satisfactory beginning, the grader was then used for the entire course with this group of students and have been used at Rensselaer ever since. For all exercises, the average time spent on the computer has run from half a minute to a minute for each student. In general only an eighth as much computer time is required when the grader is used as is required when each student is expected to run his own program, probably less than a third as much staff time, and considerably less student time. The grader easily justifies itself on economic grounds. It accomplishes more than savings in time and money; it makes possible the teaching of programming to large numbers of students. This spring we had 80 students taking a full semester course in programming; over 120 are expected next spring. We could not accommodate such numbers without the use of the grader. Even though the grader makes the teaching of programming to large numbers of students possible and economically feasible, a most serious question remains, how well did the students learn? After fifteen months, our experience leads us to believe that students learn programming not only as well but probably better than they did under the method we did use—laboratory groups of four or five students. They are not as skilled in machine operation, however, since they get only a brief introduction to it late in the course. After learning programming, very little time is needed for each student to become at least an adequate machine operator. Students seem to like the grader and are not reluctant to suggest improvements!
Multimodal error correction for speech user interfaces
Authors: Suhm Bernhard , Myers Brad , Waibel Alex
Published: July 2002

Although commercial dictation systems and speech-enabled telephone voice user interfaces have become readily available, speech recognition errors remain a serious problem in the design and implementation of speech user interfaces. Previous work hypothesized that switching modality could speed up interactive correction of recognition errors. This article presents multimodal error correction methods that allow the user to correct recognition errors efficiently without keyboard input. Correction accuracy is maximized by novel recognition algorithms that use context information for recognizing correction input. Multimodal error correction is evaluated in the context of a prototype multimodal dictation system. The study shows that unimodal repair is less accurate than multimodal error correction. On a dictation task, multimodal correction is faster than unimodal correction by respeaking. The study also provides empirical evidence that system-initiated error correction (based on confidence measures) may not expedite error correction. Furthermore, the study suggests that recognition accuracy determines user choice between modalities: while users initially prefer speech, they learn to avoid ineffective correction modalities with experience. To extrapolate results from this user study, the article introduces a performance model of (recognition-based) multimodal interaction that predicts input speed including time needed for error correction. Applied to interactive error correction, the model predicts the impact of improvements in recognition technology on correction speeds, and the influence of recognition accuracy and correction method on the productivity of dictation systems. This model is a first step toward formalizing multimodal interaction.
Modeling software design diversity
Authors: Littlewood Bev , Popov Peter , Strigini Lorenzo
Published: July 2002

Design diversity has been used for many years now as a means of achieving a degree of fault tolerance in software-based systems. While there is clear evidence that the approach can be expected to deliver some increase in reliability compared to a single version, there is no agreement about the extent of this. More importantly, it remains difficult to evaluate exactly how reliable a particular diverse fault-tolerant system is. This difficulty arises because assumptions of independence of failures between different versions have been shown to be untenable: assessment of the actual level of dependence present is therefore needed, and this is difficult. In this tutorial, we survey the modeling issues here, with an emphasis upon the impact these have upon the problem of assessing the reliability of fault-tolerant systems. The intended audience is one of designers, assessors, and project managers with only a basic knowledge of probabilities, as well as reliability experts without detailed knowledge of software, who seek an introduction to the probabilistic issues in decisions about design diversity.
A sufficient condition for backtrack-bounded search
Authors: Freuder Eugene C.
Published: July 2002

Backtrack search is often used to solve constraint satisfaction problems. A relationship involving the structure of the constraints is described that provides a bound on the backtracking required to advance deeper into the backtrack tree. This analysis leads to upper bounds on the effort required for solution of a class of constraint satisfaction problems. The solutions involve a combination of relaxation preprocessing and backtrack search. The bounds are expressed in terms of the structure of the constraint connections. Specifically, the effort is shown to have a bound exponential in the size of the largest biconnected component of the constraint graph, as opposed to the size of the graph as a whole.
A routine for converting regression algorithms into corresponding orthogonal regression algorithms
Authors: Ammann Larry , Van Ness John
Published: July 2002

The routine converts any standard regression algorithm (that calculates both the coefficients and residuals) into a corresponding
orthogonal
regression algorithm. Thus, a standard, or robust, or
L
1
regression algorithm is converted into the corresponding standard, or robust, or
L
1
orthogonal
algorithm. Such orthogonal procedures are important for three basic reasons. First, they solve the classical errors-in-variables (EV) regression problem. Standard
L
2
orthogonal regression, obtained by converting ordinary least squares regression, is the maximum likelihood solution of the EV problem under Gaussian assumptions. However, this
L
2
solution is known to be unstable under even slight deviations from the model. Thus this routine's ability to create
robust
orthogonal regression algorithms from robust ordinary regression algorithms will also be very useful in practice. Second, orthogonal regression is intimately related to principal components procedures. Therefore, this routine can also be used to create corresponding
L
1
, robust, etc., principal components algorithms. And third, orthogonal regression treats the
x
and
y
variables symmetrically. This is very important in many science and engineering modeling problems. Monte Carlo studies, which test the effectiveness of the routine under a variety of types of data, are given.
Effective transformations on infinite trees, with applications to high undecidability, dominoes, and fairness
Authors: Harel David
Published: July 2002

Elementary translations between various kinds of recursive trees are presented. It is shown that trees of either finite or countably infinite branching can be effectively put into one-one correspondence with infinitely branching trees in such a way that the infinite paths of the latter correspond to the “
P
-abiding” infinite paths of the former. Here
P
can be any member of a very wide class of properties of infinite paths. For many properties ??, the converse holds too. Two of the applications involve (a) the formulation of large classes of highly undecidable variants of classical computational problems, and in particular, easily describable domino problems that are III
1
1
-complete, and (b) the existence of a general method for proving termination of nondeterministic or concurrent programs under any reasonable notion of fairness.
FORTRAN codes for estimating the one-norm of a real or complex matrix, with applications to condition estimation
Authors: Higham Nicholas J.
Published: July 2002

FORTRAN 77 codes SONEST and CONEST are presented for estimating the 1-norm ( or the infinity-norm) of a real or complex matrix, respectively. The codes are of wide applicability in condition estimation since explicit access to the matrix,
A
, is not required; instead, matrix-vector products
Ax
and

A
T
x

are computed by the calling program via a reverse communication interface. The algorithms are based on a convex optimization method for estimating the 1-norm of a real matrix devised by Hager. We derive new results concerning the behavior of Hager's method, extend it to complex matrices, and make several algorithmic modifications in order to improve the reliability and efficiency.
A model curriculum for a liberal arts degree in computer science
Authors: Gibbs Norman E. , Tucker Allen B.
Published: July 2002

This report proposes developing a rigorous undergraduate curriculum for a B.A.-degree program in computer science. The curriculum is intended as a model not only for high-quality undergraduate colleges and universities, but also for larger universities with strong computer science programs in a liberal arts setting.
Learning to program and learning to think: what's the connection?
Authors: Mayer Richard E. , Dyck Jennifer L. , Vilberg William
Published: July 2002

Focusing on thinking skills that are cognitive components of programming—rather than on intellectual ability—can illuminate the relationship between learning a programming language and learning more about thinking processes.
Identity authentication based on keystroke latencies
Authors: Joyce Rick , Gupta Gopal
Published: July 2002

The variables that help make a handwritten signature a unique human identifier also provide a unique digital signature in the form of a stream of latency periods between keystrokes. This article describes a method of verifying the identity of a user based on such a digital signature, and reports results from trial usage of the system.
What is Anthropological Enlightenment? Some Lessons of the Twentieth Century
Authors: Sahlins Marshall
Published: July 2002

[Figure: see text]

▪ Abstract  A broad reflection on some of the major surprises to anthropological theory occasioned by the history, and in a number of instances the tenacity, of indigenous cultures in the twentieth century. We are not leaving the century with the same ideas that got us there. Contrary to the inherited notions of progressive development, whether of the political left or right, the surviving victims of imperial capitalism neither became all alike nor just like us. Contrary to the “despondency theory” of mid-century, the logical and historical precursor of dependency theory, surviving indigenous peoples aim to take cultural responsibility for what has been done to them. Across large parts of northern North America, even hunters and gatherers live, largely by hunting and gathering. The Eskimo are still there, and they are still Eskimo. Around the world the peoples give the lie to received theoretical oppositions between tradition and change, indigenous culture and modernity, townsmen and tribesmen, and other clichés of the received anthropological wisdom. Reports of the death of indigenous cultures—as of the demise of anthropology—have been exaggerated.
Environments and Environmentalisms in Anthropological Research: Facing a New Millennium
Authors: Little Paul E.
Published: July 2002

▪ Abstract  With the concept of environment as its organizing motif, this review focuses on two general fields of anthropological environmental research: ecological anthropology and the anthropology of environmentalism. Analysis of the complementary political and human ecology research programs is structured around four theoretical and methodological areas: transformations in the ecological paradigm, levels of analysis and articulation, the use of history, and the reemergence of space. Ethnographic analyses of the social forces of environmentalism point to civil society as an emerging and important protagonist with regard to environmental issues, and these social forces are reviewed within the categories of environmental movements, rights, territories, and discourses. A final prospective section looks at contemporary urban, viral, virtual, and warfare environments and postulates that the combination of empirical and political approaches can provide for anthropology an expanded role, one that has strong bioethical implications, in environmental debates and issues.
THE C2 OXIDATIVE PHOTOSYNTHETIC CARBON CYCLE
Authors: Tolbert N. E.
Published: July 2002

[Figure: see text]

▪ Abstract  The C2 oxidative photosynthetic carbon cycle plus the C3 reductive photosynthetic carbon cycle coexist. Both are initiated by Rubisco, use about equal amounts of energy, must regenerate RuBP, and result in exchanges of CO2 and O2 to establish rates of net photosynthesis, CO2 and O2 compensation points, and the ratio of CO2 and O2 in the atmosphere. These concepts evolved from research on O2 inhibition, glycolate metabolism, leaf peroxisomes, photorespiration, 18O2/16O2 exchange, CO2 concentrating processes, and a requirement for the oxygenase activity of Rubisco. Nearly 80 years of research on these topics are unified under the one process of photosynthetic carbon metabolism and its self-regulation.
MOLECULAR GENETIC ANALYSIS OF TRICHOME DEVELOPMENT IN ARABIDOPSIS
Authors: Marks M. David
Published: July 2002

▪ Abstract  Two basic questions in developmental biology are: How does a cell know when it should or should not differentiate, and once a cell is committed to differentiate, how is that process controlled? The first process regulates the arrangement or pattern of the various cell types, whereas the second makes cells functionally distinct. Together, these two processes define plant morphogenesis. Trichome development in Arabidopsis provides an excellent model to analyze these questions. First, trichome development in Arabidopsis is a relatively simple process. A single epidermal cell differentiates into a unicellular trichome. Second, this differentiation occurs in a nonrandom pattern on the plant surface. Finally, the process is amenable to genetic analysis because many mutations that affect trichome differentiation do not alter other aspects of plant development. Thus far, more than 20 genes affecting trichome development have been identified. This review examines the current state of our understanding of these genes.
The Supermassive Black Hole at the Galactic Center
Authors: Melia Fulvio , Falcke Heino
Published: July 2002

▪ Abstract  The inner few parsecs at the Galactic Center have come under intense scrutiny in recent years, in part due to the exciting broad-band observations of this region, but also because of the growing interest from theorists motivated to study the physics of black hole accretion, magnetized gas dynamics, and unusual star formation. The Galactic Center is now known to contain arguably the most compelling supermassive black hole candidate, weighing in at a little over 2.6 million suns. Its interaction with the nearby environment, comprised of clusters of evolved and young stars, a molecular dusty ring, ionized gas streamers, diffuse hot gas, and a hypernova remnant, is providing a wealth of accretion phenomenology and high-energy processes for detailed modeling. In this review, we summarize the latest observational results and focus on the physical interpretation of the most intriguing object in this region—the compact radio source Sgr A*, thought to be the radiative manifestation of the supermassive black hole.
Chaos in the Solar System
Authors: Lecar Myron , Franklin Fred A. , Holman Matthew J. , Murray Norman W.
Published: July 2002

▪ Abstract  The physical basis of chaos in the solar system is now better understood: In all cases investigated so far, chaotic orbits result from overlapping resonances. Perhaps the clearest examples are found in the asteroid belt. Overlapping resonances account for its Kirkwood gaps and were used to predict and find evidence for very narrow gaps in the outer belt. Further afield, about one new “short-period” comet is discovered each year. They are believed to come from the “Kuiper Belt” (at 40 AU or more) via chaotic orbits produced by mean-motion and secular resonances with Neptune. Finally, the planetary system itself is not immune from chaos. In the inner solar system, overlapping secular resonances have been identified as the possible source of chaos. For example, Mercury, in 1012 years, may suffer a close encounter with Venus or plunge into the Sun. In the outer solar system, three-body resonances have been identified as a source of chaos, but on an even longer time scale of 109 times the age of the solar system. On the human time scale, the planets do follow their orbits in a stately procession, and we can predict their trajectories for hundreds of thousands of years. That is because the mavericks, with shorter instability times, have long since been ejected. The solar system is not stable; it is just old!
MITOCHONDRIAL DNA MAINTENANCE IN VERTEBRATES
Authors: Shadel Gerald S. , Clayton David A.
Published: July 2002

The discovery that mutations in mitochondrial DNA (mtDNA) can be pathogenic in humans has increased interest in understanding mtDNA maintenance. The functional state of mtDNA requires a great number of factors for gene expression, DNA replication, and DNA repair. These processes are ultimately controlled by the cell nucleus, because the requisite proteins are all encoded by nuclear genes and imported into the mitochondrion. DNA replication and transcription are linked in vertebrate mitochondria because RNA transcripts initiated at the light-strand promoter are the primers for mtDNA replication at the heavy-strand origin. Study of this transcription-primed DNA replication mechanism has led to isolation of key factors involved in mtDNA replication and transcription and to elucidation of unique nucleic acid structures formed at this origin. Because features of a transcription-primed mechanism appear to be conserved in vertebrates, a general model for initiation of vertebrate heavy-strand DNA synthesis is proposed. In many organisms, mtDNA maintenance requires not only faithful mtDNA replication, but also mtDNA repair and recombination. The extent to which these latter two processes are involved in mtDNA maintenance in vertebrates is also appraised.
Mammalian Caspases: Structure, Activation, Substrates, and Functions During Apoptosis
Authors: Earnshaw William C. , Martins Luis M. , Kaufmann Scott H.
Published: July 2002

▪ Abstract  Apoptosis is a genetically programmed, morphologically distinct form of cell death that can be triggered by a variety of physiological and pathological stimuli. Studies performed over the past 10 years have demonstrated that proteases play critical roles in initiation and execution of this process. The caspases, a family of cysteine-dependent aspartate-directed proteases, are prominent among the death proteases. Caspases are synthesized as relatively inactive zymogens that become activated by scaffold-mediated transactivation or by cleavage via upstream proteases in an intracellular cascade. Regulation of caspase activation and activity occurs at several different levels: (a) Zymogen gene transcription is regulated; (b) antiapoptotic members of the Bcl-2 family and other cellular polypeptides block proximity-induced activation of certain procaspases; and (c) certain cellular inhibitor of apoptosis proteins (cIAPs) can bind to and inhibit active caspases. Once activated, caspases cleave a variety of intracellular polypeptides, including major structural elements of the cytoplasm and nucleus, components of the DNA repair machinery, and a number of protein kinases. Collectively, these scissions disrupt survival pathways and disassemble important architectural components of the cell, contributing to the stereotypic morphological and biochemical changes that characterize apoptotic cell death.
GTPase-Activating Proteins for Heterotrimeric G Proteins: Regulators of G Protein Signaling (RGS) and RGS-Like Proteins
Authors: Ross Elliott M. , Wilkie Thomas M.
Published: July 2002

▪ Abstract  GTPase-activating proteins (GAPs) regulate heterotrimeric G proteins by increasing the rates at which their α subunits hydrolyze bound GTP and thus return to the inactive state. G protein GAPs act allosterically on Gα subunits, in contrast to GAPs for the Ras-like monomeric GTP-binding proteins. Although they do not contribute directly to the chemistry of GTP hydrolysis, G protein GAPs can accelerate hydrolysis >2000-fold. G protein GAPs include both effector proteins (phospholipase C-β, p115RhoGEF) and a growing family of regulators of G protein signaling (RGS proteins) that are found throughout the animal and fungal kingdoms. GAP activity can sharpen the termination of a signal upon removal of stimulus, attenuate a signal either as a feedback inhibitor or in response to a second input, promote regulatory association of other proteins, or redirect signaling within a G protein signaling network. GAPs are regulated by various controls of their cellular concentrations, by complex interactions with Gβγ or with Gβ5 through an endogenous Gγ-like domain, and by interaction with multiple other proteins.
Cartilage Tissue Remodeling in Response to Mechanical Forces
Authors: Grodzinsky Alan J. , Levenston Marc E. , Jin Moonsoo , Frank Eliot H.
Published: July 2002

▪ Abstract  Recent studies suggest that there are multiple regulatory pathways by which chondrocytes in articular cartilage sense and respond to mechanical stimuli, including upstream signaling pathways and mechanisms that may lead to direct changes at the level of transcription, translation, post-translational modifications, and cell-mediated extracellular assembly and degradation of the tissue matrix. This review focuses on the effects of mechanical loading on cartilage and the resulting chondrocyte-mediated biosynthesis, remodeling, degradation, and repair of this tissue. The effects of compression and tissue shear deformation are compared, and approaches to the study of mechanical regulation of gene expression are described. Of particular interest regarding dense connective tissues, recent experiments have shown that mechanotransduction is critically important in vivo in the cell-mediated feedback between physical stimuli, the molecular structure of newly synthesized matrix molecules, and the resulting macroscopic biomechanical properties of the tissue.
HISTONE STRUCTURE AND THE ORGANIZATION OF THE NUCLEOSOME
Authors: Ramakrishnan V.
Published: July 2002

▪ Abstract  Chromatin structure is now believed to be dynamic and intimately related with cellular processes such as transcription. Over the past few years, high-resolution structures for the histones have become available. These structures and their implications for nucleosome organization are reviewed here.
Vacuolar Import of Proteins and Organelles From The Cytoplasm
Authors: Klionsky Daniel J. , Ohsumi Yoshinori
Published: July 2002

▪ Abstract  Many cellular processes require a balance between protein synthesis and protein degradation. The vacuole/lysosome is the main site of protein and organellar turnover within the cell due to its ability to sequester numerous hydrolases within a membrane-enclosed compartment. Several mechanisms are used to deliver substrates, as well as resident hydrolases, to this organelle. The delivery processes involve dynamic rearrangements of membrane. In addition, continual adjustments are made to respond to changes in environmental conditions. In this review, we focus on recent progress made in analyzing these delivery processes at a molecular level. The identification of protein components involved in the recognition, sequestration, and transport events has begun to provide information about this important area of eukaryotic cell physiology.
GEOLOGIC APPLICATIONS OF SEISMIC SCATTERING
Authors: Revenaugh Justin
Published: July 2002

▪ Abstract  Once disregarded as noise, scattered seismic waves are finding increasing application in subsurface imaging. This sea change is driven by the increasing density and quality of seismic recordings and advances in waveform modeling which, together, are allowing seismologists to exploit their unique properties. In addition to extensive application in the energy exploration industry, seismic scattering is now used to characterize heterogeneity in the lower continental crust and subcrustal lithosphere, to examine the relationship between crustal structure and seismogenesis, and to probe the plumbing of active volcanoes. In each application, the study of seismic scattering brings wavelength-scale structure into sharper focus and characterizes the short scale-length fabric of geology.
PRINCIPLES OF PHYLOGEOGRAPHY AS ILLUSTRATED BY FRESHWATER AND TERRESTRIAL TURTLES IN THE SOUTHEASTERN UNITED STATES
Authors: Walker DeEtte , Avise John C.
Published: July 2002

▪ Abstract  Geographic patterns in mtDNA variation are compiled for 22 species of freshwater and terrestrial turtles in the southeastern United States, and the results are employed to evaluate phylogeographic hypotheses and principles of genealogical concordance derived previously from similar analyses of other vertebrates in the region. The comparative molecular findings are interpreted in the context of intraspecific systematics for these taxa, the historical geology of the area, traditional nonmolecular zoogeographic information, and conservation significance. A considerable degree of phylogeographic concordance is registered with respect to (a) the configuration of intraspecific mtDNA subdivisions across turtle species, (b) the principal molecular partitions and traditional morphology-based taxonomic boundaries, (c) genetic patterns in turtles versus those described previously for freshwater fishes and terrestrial vertebrates in the region, and (d) intraspecific molecular subdivisions versus the boundaries between major zoogeographic provinces as identified by composite ranges of species in the Testudines. Findings demonstrate shared elements in the biogeographic histories of a diverse regional biota. Such phylogeographic concordances (and discordances) have ramifications for evolutionary theory as well as for the pragmatic efforts of taxonomy and conservation biology.