Search

In X-ray macromolecular crystallography (MX), single-wavelength anomalous dispersion (SAD) and multi-wavelength anomalous dispersion (MAD) techniques are commonly used for obtaining experimental phases. For an MX synchrotron beamline to support SAD and MAD techniques it is a prerequisite to have a reliable, fast and well automated energy scan routine. This work reports on a continuous energy scan procedure newly implemented at the BioMAX MX beamline at MAX IV Laboratory. The continuous energy scan is fully automated, capable of measuring accurate fluorescence counts over the absorption edge of interest while minimizing the sample exposure to X-rays, and is about a factor of five faster compared with a conventional step scan previously operational at BioMAX. The implementation of the continuous energy scan facilitates the prompt access to the anomalous scattering data, required for the SAD and MAD experiments. [ABSTRACT FROM AUTHOR]

We consider the computability and complexity of decision questions for Probabilistic Finite Automata (PFA) with sub-exponential ambiguity. We show that the emptiness problem for strict and non-strict cut-points of polynomially ambiguous commutative PFA remains undecidable, implying that the problem is undecidable when inputs are from a letter monotonic language. We show that the problem remains undecidable over a binary input alphabet when the input word is over a bounded language, in the noncommutative case. In doing so, we introduce a new technique based upon the Turakainen construction of a PFA from a Weighted Finite Automaton which can be used to generate PFA of lower dimensions and of sub-exponential ambiguity. We also study freeness/injectivity problems for polynomially ambiguous PFA and study the border of decidability and tractability for various cases. [ABSTRACT FROM AUTHOR]

The problem of uniformly placing N points onto a sphere finds applications in many areas. For example, points on the sphere correspond to unit quaternions as well as to the group of rotations SO(3) and the online version of generating uniform rotations (known as "incremental generation") plays a crucial role in a large number of engineering applications ranging from robotics and aeronautics to computer graphics. An online version of this problem was recently studied with respect to the gap ratio as a measure of uniformity. The first online algorithm of Chen et al. was upper-bounded by 5.99 and later improved to 3.69, which is achieved by considering a circumscribed dodecahedron followed by a recursive decomposition of each face. In this paper we provide a more efficient tessellation technique based on the regular icosahedron, which improves the upper-bound for the online version of this problem, decreasing it to approximately 2.84. Moreover, we show that the lower bound for the gap ratio of placing at least three points is (1 + 5) / 2 ≈ 1.618 and for at least four points is no less than 1.726. [ABSTRACT FROM AUTHOR]

This paper draws upon digital recordings of Northern Ireland football fans singing in the stadium during all 10 qualifying matches for the 2016 UEFA European Football Championship. Supplemented by participant observation and interview data with 21 supporters themselves, the paper challenges assertions within the literature which focus upon the predominance of sectarian singing amongst a section of Northern Ireland football supporters. Although vocal manifestations of football fandom may initially appear to be randomly driven by irrational emotions, on the contrary, there is an underlying structure and sequence to fandom in the stadium in which certain factors promote collective singing at particular times. The paper identifies four key themes in particular: the timing in a match; whether or not a goal has been scored; if there is a lull or a break in play; and the use of musical instruments to encourage the wider collective to sing. We argue that it is important to understand the process by which collective singing occurs in the football stadium rather than fixating upon the alleged racist or sectarian psychopathology of the individuals involved. Such knowledge may assist in supporting those fan organisations that seek to challenge discriminatory behaviour in the stadium, particularly in the current context of the European (UEFA) and World football governing bodies (FIFA) punishing fans collectively, regardless of whether or not the majority in the stadium are opposed to what is being sung in their name. [ABSTRACT FROM AUTHOR]

We consider notions of freeness and ambiguity for the acceptance probability of Moore-Crutchfield Measure Once Quantum Finite Automata (MO-QFA). We study the injectivity problem of determining if the acceptance probability function of a MO-QFA is injective over all input words, i.e., giving a distinct probability for each input word. We show that the injectivity problem is undecidable for 8 state MO-QFA, even when all unitary matrices and the projection matrix are rational and the initial state vector is real algebraic. We also show undecidability of this problem when the initial vector is rational, although with a huge increase in the number of states. We utilize properties of quaternions, free rotation groups, representations of tuples of rationals as linear sums of radicals and a reduction of the mixed modification of Post's correspondence problem, as well as a new result on rational polynomial packing functions which may be of independent interest. [ABSTRACT FROM AUTHOR]

We show that the problem of determining if the identity matrix belongs to a finitely generated semigroup of 2 × 2 matrices from the General Linear Group GL 2 (Z) is solvable in NP. We extend this to prove that the membership problem is decidable in NP for GL 2 (Z) and for any arbitrary regular expression over matrices from the Special Linear group SL 2 (Z). We show that determining if a given finite set of matrices from SL 2 (Z) or the modular group PSL 2 (Z) generates a group or a free semigroup are decidable in NP. Previous algorithms, shown in 2005 by Choffrut and Karhumäki, were in EXPSPACE. Our algorithm is based on new techniques allowing us to operate on compressed word representations of matrices without explicit expansions. When combined with known NP -hard lower bounds, this proves that the membership problem over GL 2 (Z) is NP -complete, and the group problem and the non-freeness problem in SL 2 (Z) are NP -complete. 1 [ABSTRACT FROM AUTHOR]

A low-cost [$30 (U.S. dollars)] consumer grade GPS receiver with a sideways-mounted antenna has been applied to measure tidal water levels at a mesotidal coastal site using an interferometric reflectometry approach. The proofof- concept system was installed approximately 16m above mean sea level in close proximity to a conventional bubbler tide gauge that provided validation data. The received signal-to-noise ratios (SNR) for the satellites in view were recorded for several months during two successive years and the observed frequencies of the interferometric oscillations used to calculate the difference in elevation between the receiver and the water surface. Comparisons with concurrent and historic in situ tide gauge data at the site initially helped to identify a calibration issue with the in situ gauge. The GPSbased measurements were shown to be in excellent agreement with the corrected in situ gauge, exhibiting a root-meansquare difference of 5.7 cm over a tidal range exceeding 3m at spring tides and a daily averaged RMS of 1.7 cm. The SNR data from the low-cost GPS receivers are shown to provide significantly higher-quality data for this purpose compared with high-end geodetic grade receivers at similar sites. This low-cost, widely available technology has the potential to be applied globally for monitoring water levels in a wide variety of circumstances and applications that would otherwise be cost or situation prohibitive. It could also be applied as an independent cross check and quality control measure for conventional water-level gauges. [ABSTRACT FROM AUTHOR]

We consider several language-theoretic aspects of various notions of unique decipherability (or unique factorization) in formal languages. Given a language L at some position within the Chomsky hierarchy, we investigate the language of words UD (L) in L ⁎ that have unique factorization over L. We also consider similar notions for weaker forms of unique decipherability, such as numerically decipherable words ND (L) , multiset decipherable words MSD (L) and set decipherable words SD (L). Although these notions of unique factorization have been considered before, it appears that the languages of words having these properties have not been positioned in the Chomsky hierarchy up until now. We show that UD (L) , ND (L) , MSD (L) and SD (L) need not be context-free if L is context-free. In fact ND (L) and MSD (L) need not be context-free even if L is finite, although UD (L) and SD (L) are regular in this case. We show that if L is context-sensitive, then so are UD (L) , ND (L) , MSD (L) and SD (L). We also prove that the membership problem (resp., emptiness problem) for these classes is PSPACE-complete (resp., undecidable). We finally determine upper and lower bounds on the length of the shortest word of L ⁎ not having the various forms of unique decipherability into elements of L. [ABSTRACT FROM AUTHOR]

This paper demonstrates the application of marine radar and a newly developed waterline mapping technique to the continued surveillance and monitoring of inter- and intra-annual intertidal morphological change, thus capturing new detail on coastal system behaviours. Marine radar data from 2006 to 2009 are used to create a sequence of waterline elevation surveys that show clear morphological evolution of two different sites in the Dee estuary, UK. An estimate of volumetric change was made at two locations: West Hoyle sandbank and the NW Wirral beach. Both sites exhibited a similar cyclic pattern of volumetric change, with lowest volumes in autumn and winter, respectively. The average beach elevations above Admiralty Chart Datum clearly reflect the observed change in sediment volume, with reduced elevations in winter and increased elevations in summer, suggesting a trend of high-energy storm waves in autumn and winter that remove sediment and simultaneously moderate the vertical dimension of bedforms in the intertidal area. Data at this temporal and spatial scale are not easily obtainable by other current remote sensing techniques. The use of marine radar as a tool for quantifying coastal change over seasonal and event timescales in complex hydrodynamic settings is illustrated. Specifically, its unique application to monitoring areas with dynamic morphology or that is vulnerable to erosion and/or degradation by storm events is exemplified. [ABSTRACT FROM AUTHOR]

We study variants of a recently introduced hybrid system model, called a Hierarchical Piecewise Constant Derivative (HPCD). These variants (loosely called Restricted HPCDs) form a class of natural models with similarities to many other well known hybrid system models in the literature such as Stopwatch Automata, Rectangular Automata and PCDs. We study the complexity of reachability and mortality problems for variants of RHPCDs and show a variety of results, depending upon the allowed powers. These models form a useful tool for the study of the complexity of such problems for hybrid systems, due to their connections with existing models. We show that the reachability problem and the mortality problem are co-NP-hard for bounded 3-dimensional RHPCDs (3-RHPCDs). Reachability is shown to be in PSPACE, even for n -dimensional RHPCDs. We show that for an unbounded 3-RHPCD, the reachability and mortality problems become undecidable. For a nondeterministic variant of 2-RHPCDs, the reachability problem is shown to be PSPACE-complete. [ABSTRACT FROM AUTHOR]

Mapping the morphology of intertidal areas is a logistically challenging, time consuming and expensive task due to their large expanse and difficulties associated with access. A technique is presented here that uses standard marine navigational radar operating at X-band frequency. The method uses a series of time-exposure radar images over the course of a two-week tidal cycle to identify the elevation of the wetting and drying transitions at each pixel in the radar images, thereby building up a morphological map of the target intertidal area. This “Temporal Waterline” method is applied to a dataset acquired from Hilbre Island at the mouth of the Dee Estuary, UK, spanning March 2006 to January 2007. The radar gathered data with a radial range of 4 km and the resulting elevation maps describe the intertidal regions of that area. The results are compared with airborne LiDAR data surveyed over the same area and within the radar survey time period. The residual differences show good agreement across large areas of beach and sandbanks, with concentrations of poor estimations around points that are shadowed from the radar or likely to suffer from pooling water. This paper presents the theoretical framework of the method and demonstrates its stability and accuracy. The Temporal Waterline radar method is aimed at providing a useful tool for the monitoring and operational management of coastlines. [ABSTRACT FROM AUTHOR]

We consider a variant of the mortality problem: given k × k matrices A 1 , ... , A t , do there exist nonnegative integers m 1 , ... , m t such that A 1 m 1 ⋯ A t m t equals the zero matrix? This problem is known to be decidable when t ≤ 2 but undecidable for integer matrices with sufficiently large t and k. We prove that for t = 3 this problem is Turing-equivalent to Skolem's problem and thus decidable for k ≤ 3 (resp. k = 4) over (resp. real) algebraic numbers. Consequently, the set of triples (m 1 , m 2 , m 3) for which the equation A 1 m 1 A 2 m 2 A 3 m 3 equals the zero matrix is a finite union of direct products of semilinear sets. For t = 4 we show that the solution set can be non-semilinear, and thus there is unlikely to be a connection to Skolem's problem. We prove decidability for upper-triangular 2 × 2 rational matrices by employing powerful tools from transcendence theory such as Baker's theorem and S-unit equations. [ABSTRACT FROM AUTHOR]

The author critiques the conventional understanding of live electronic music through empirical research on his own DJ practice and investigates others working in the field. In reviewing the opinions of theorists and practitioners in both the live electronic music genre and DJ-ing he argues against the body/machine dialectic that has determined much of the thinking in the former. The author forms a notion of the DJ as a real-time composer working beyond traditional binary distinctions who brings the human body and machine into a mutual relationship. Through practice-led research he charts an investigation beginning in physical human gesture and culminating in digital machine repetition. He concludes that mechanical and digital repetition do not obscure human agency in the production of live works and that this concern is imaginary. The text is supported by audio examples which appear as supplementary material accessible online via the article's Supplementary tab on the Taylor & Francis website (http://www.tandfonline.com/loi/gcmr). [ABSTRACT FROM PUBLISHER]

We show that several problems concerning probabilistic finite automata of a fixed dimension and a fixed number of letters for bounded cut-point and strict cut-point languages are algorithmically undecidable by a reduction of Hilbert's tenth problem. We then consider the set of so called 'F-Problems' (emptiness, infiniteness, containment, disjointness, universe and equivalence) and show that they are also undecidable for bounded (non-)strict cut-point languages on probabilistic finite automata. For a finite set of matrices $\{M_1, M_2, \ldots ,M_k\} \subseteq \mathbb{Q}^{t \times t}$, we then consider the decidability of computing the maximal spectral radius of any matrix in the set $X = \{M^{j_1}_1 M^{j_2}_2 \cdot M^{j_k}_k \vert j_1, j_2,\ldots, j_k \geq 0\}$, which we call a bounded matrix language. Using an encoding of a probabilistic finite automaton shown in the paper, we prove the surprising result that determining if the maximal spectral radius of a bounded matrix language is less than or equal to one is undecidable, but determining whether it is strictly less than one is in fact decidable (which is similar to a result recently shown for quantum automata). [ABSTRACT FROM AUTHOR]

Most computational problems for matrix semigroups and groups are inherently difficult to solve and even undecidable starting from dimension three. The questions about the decidability and complexity of problems for two-dimensional matrix semigroups remain open and are directly linked with other challenging problems in the field. In this paper we study the computational complexity of the problem of determining whether the identity matrix belongs to a matrix semigroup (the Identity Problem) generated by a finite set of 2 × 2 integral unimodular matrices. The Identity Problem for matrix semigroups is a well-known challenging problem, which has remained open in any dimension until recently. It is currently known that the problem is decidable in dimension two and undecidable starting from dimension four. In particular, we show that the Identity Problem for 2 × 2 integral unimodular matrices is NP-hard by a reduction of the Subset Sum Problem and several new encoding techniques. An upper bound for the nontrivial decidability result by C. Choffrut and J. Karhumäki is unknown. However, we derive a lower bound on the minimum length solution to the Identity Problem for a constructible set of instances, which is exponential in the number of matrices of the generator set and the maximal element of the matrices. This shows that the most obvious candidate for an NP algorithm, which is to guess the shortest sequence of matrices which multiply to give the identity matrix, does not work correctly since the certificate would have a length which is exponential in the size of the instance. Both results lead to a number of corollaries confirming the same bounds for vector reachability, scalar reachability and zero in the right upper corner problems. [ABSTRACT FROM AUTHOR]

Marine radars mounted on ships can provide remarkable insights into ocean behaviour from distances of several kilometres, placing other in situ observations and the environment around a ship into a wider oceanographic context. It has been known for some time that it is possible to map shallow water bathymetry and currents using radar image sequences recorded from shore based stations. However, a long standing question from military and hydrographic communities has been whether such techniques can be applied to radar data collected by moving vessels. If so, this presents the possibility of mapping large areas of shallow or coastal seas (albeit with a somewhat coarse horizontal resolution of 50-100 m) prior to the surveying vessel actually having to travel into potentially uncharted or dangerous shallow water areas. Trial sets of radar data were recorded by the Canadian Forces Auxiliary Vessel Quest using a Wamos radar digitiser connected to a Decca navigation radar during a number of deployments around Nova Scotia in 2008 and 2009. Georeferencing corrections derived from the existing ship navigation systems were sufficient to allow the application of the existing depth inversion analysis designed for static radar installations. This paper presents the results of bathymetry analyses of two datasets recorded from CFAV Quest while the vessel was travelling at speeds of up to 14 knots. The bathymetry derived from the radar data compare favourably with independent surveys and with the on-board echo sounder to depths of approximately 50 m. [ABSTRACT FROM AUTHOR]

In this paper we study several closely related fundamental problems for words and matrices. First, we introduce the Identity Correspondence Problem (ICP): whether a finite set of pairs of words (over a group alphabet) can generate an identity pair by a sequence of concatenations. We prove that ICP is undecidable by a reduction of Post's Correspondence Problem via several new encoding techniques. In the second part of the paper we use ICP to answer a long standing open problem concerning matrix semigroups: "Is it decidable for a finitely generated semigroup S of integral square matrices whether or not the identity matrix belongs to S?". We show that the problem is undecidable starting from dimension four even when the number of matrices in the generator is 48. From this fact, we can immediately derive that the fundamental problem of whether a finite set of matrices generates a group is also undecidable. We also answer several questions for matrices over different number fields. Apart from the application to matrix problems, we believe that the Identity Correspondence Problem will also be useful in identifying new areas of undecidable problems in abstract algebra, computational questions in logic and combinatorics on words. [ABSTRACT FROM AUTHOR]

Abstract: We study decidability and complexity questions related to a continuous analogue of the Skolem-Pisot problem concerning the zeros and nonnegativity of a linear recurrent sequence. In particular, we show that the continuous version of the nonnegativity problem is NP-hard in general and we show that the presence of a zero is decidable for several subcases, including instances of depth two or less, although the decidability in general is left open. The problems may also be stated as reachability problems related to real zeros of exponential polynomials or solutions to initial value problems of linear differential equations, which are interesting problems in their own right. [ABSTRACT FROM AUTHOR]

Research on noise shows that a variety of effects including stress, annoyance, and performance decrements exist for certain types of sounds. Noise interferes with cognitive ability by overloading the attentional system or simply distracting from efficient encoding or rehearsal, but very little research has extended those findings to recreation or natural environments such as those found in national parks. By exposing participants to one of four soundscape conditions-control, natural, natural with voices, and natural with ground traffic-the current project tested the effect of sound conditions on the recognition and recall of factual information presented whereas viewing scenes of national parks. Both the natural with voices and natural with ground traffic conditions caused significant decreases in memory scores while the natural condition showed no differences from the control condition. Implications for sound management strategies are discussed in the context of current legislation and recent field research. Avenues for future research to clarify the mode of memory interference are discussed. [ABSTRACT FROM AUTHOR]

Alzheimer's disease can be particularly devastating to those who are caring for their loved one with the condition. There have been recent calls for the tailoring of caregiving interventions to examine outcome differences between groups of caregivers and the reporting of effectiveness via longitudinal and specific outcomes. The purpose of this study was to examine 3 interventions (psychoeducational training, a respite voucher-type grant, or their combination) while looking for possible group differences. A total of 367 caregivers participated in the study. Participants completed surveys and questionnaires before the intervention and at a 6-month follow-up. Positive outcomes were found, including lower depression scores, increased support service use, and increased support group usage. Possible effectiveness of the 3 types of interventions and variation among caregiver characteristics are discussed along with implications for future research. [ABSTRACT FROM AUTHOR]

We show a reduction of Hilbert's tenth problem to the solvability of the matrix equation $X_1^{i_1}X_2^{i_2}\cdots X_k^{i_k} = Z$ over non-commuting integral matrices, where Z is the zero matrix, thus proving that the solvability of the equation is undecidable. This is in contrast to the case whereby the matrix semigroup is commutative in which the solvability of the same equation was shown to be decidable in general. The restricted problem where k = 2 for commutative matrices is known as the "A-B-C Problem" and we show that this problem is decidable even for a pair of non-commutative matrices over an algebraic number field. [ABSTRACT FROM AUTHOR]

Abstract: We examine computational problems on quaternion matrix and rotation semigroups. It is shown that in the ultimate case of quaternion matrices, in which multiplication is still associative, most of the decision problems for matrix semigroups are undecidable in dimension two. The geometric interpretation of matrix problems over quaternions is presented in terms of rotation problems for the 2- and 3-sphere. In particular, we show that the reachability of the rotation problem is undecidable on the 3-sphere and other rotation problems can be formulated as matrix problems over complex and hypercomplex numbers. [Copyright &y& Elsevier]

Abstract: This project examined relationships among two dimensions of the “Big Five” personality factor theory (Costa & McCrae, 1992) and the conflict resolution styles of competing, collaborating, accommodating, and avoiding (Thomas & Kilmann, 1974). Some 288 students at Colorado State University participated. The Big Five personality measures of agreeableness (A) and extraversion (E) were significant predictors of all four conflict resolution style scores. These findings show that contemporary personality measures are significant predictors of conflict resolution styles. The findings suggest that personality measures may be helpful predictors of conflict resolution style preference in mediation and negotiation situations. [Copyright &y& Elsevier]

Abstract: In this paper we consider several reachability problems such as vector reachability, membership in matrix semigroups and reachability problems in piecewise linear maps. Since all of these questions are undecidable in general, we work on lowering the bounds for undecidability. In particular, we show an elementary proof of undecidability of the reachability problem for a set of 5 two-dimensional affine transformations. Then, using a modified version of a standard technique, we also prove that the vector reachability problem is undecidable for two (rational) matrices in dimension 11. The above result can be used to show that the system of piecewise linear functions of dimension 12 with only two intervals has an undecidable set-to-point reachability problem. We also show that the “zero in the upper right corner” problem is undecidable for two integral matrices of dimension 18 lowering the bound from 23. [Copyright &y& Elsevier]

The ATLAS detector at CERN's LHC will be exposed to proton-proton collisions at a rate of 40 MHz. To reduce the data rate, only potentially interesting events are selected by a three-level trigger system. The first level is implemented in custom-made electronics, with an output rate to less than 100 kHz. The second and third level are software triggers with a final output rate of 100 to 200 Hz. A system has been designed and implemented that holds and records the full configuration information of all three trigger levels at a centrally maintained location. This system provides fast access to consistent configuration information of the online trigger system for the purpose of data taking as well as to all parts of the of- fine trigger simulation. The use of relational database technology provides a means of reliable recording of the trigger configuration history over the lifetime of the experiment. In addition to the online system, tools for flexible browsing and manipulation of trigger configurations, and for their distribution across the ATLAS reconstruction sites have been developed. The usability of this design has been demonstrated in dedicated configuration tests of the ATLAS level-i Central Trigger and of a 600-node software trigger computing farm. Further tests on a computing cluster which is part of the final high level trigger system were also successful. [ABSTRACT FROM AUTHOR]

Nonviral gene delivery vectors now show good therapeutic potential: however, detailed characterization of the composition and macromolecular organization of such particles remains a challenge. This paper describes experiments to elucidate the structure of a ternary, targeted, lipopolyplex synthetic vector, the LID complex. This consists of a lipid component, Lipofectin (L) (1:1 DOTMA:DOPE), plasmid DNA (D), and a dual-function, cationic peptide component (I) containing DNA condensation and integrin-targeting sequences. Fluorophore-labeled lipid, peptide, and DNA components were used to formulate the vector, and the stoichiometry of the particles was established by fluorescence correlation spectroscopy (FCS). The size of the complex was measured by FCS, and the sizes of LID, L, LD, and ID complexes were measured by dynamic light scattering (DLS). Fluorescence quenching experiments and freeze—fracture electron microscopy were then used to demonstrate the arrangement of the lipid, peptide, and DNA components within the complex. These experiments showed that the cationic portion of the peptide, I, interacts with the plasmid DNA, resulting in a tightly condensed DNA—peptide inner core; this is surrounded by a disordered lipid layer, from which the integrin-targeting sequence of the peptide partially protrudes. [ABSTRACT FROM AUTHOR]

We consider decidability questions for the emptiness problem of intersections of matrix semigroups. This problem was studied by A. Markov [7] and more recently by V. Halava and T. Harju [5]. We give slightly strengthened results of their theorems by using a different matrix encoding. In particular, we show that given two finitely generated semigroups of non-singular upper triangular 3 × 3 matrices over the natural numbers, checking the emptiness of their intersections is undecidable. We also show that the problem is undecidable even for unimodular matrices over 3 × 3 rational matrices. [ABSTRACT FROM AUTHOR]

This study examined the effects of self-regulated learning (SRL) and epistemological beliefs (EB) on individual learner levels of academic achievement in Web-based learning environments while holding constant the effect of computer self-efficacy, reason for taking an online course, prior college academic achievement, and parental level of education. The study constituents included 201 undergraduate students enrolled in a variety of asyn chronous Web-based courses at a university in the southeastern United States. Data was collected via a Web-based questionnaire and subjected to the following analyses: separate exploratory factor analyses of the self-regulated learning and the epistemological beliefs question items, correlations between the independent variables and the dependent variable, and linear regression of final course grades with all the variables in the model. Analysis of the data revealed that three independent variables (prior academic achievement (GPA), expectancy for learning, and an interaction term based on the cross product of these two variables were significant predictors in the model of learning achievement in asynchronous online courses. Discussion of the study's predictive model follows. [ABSTRACT FROM AUTHOR]

Abstract: In this paper, we consider decidability questions that are related to the membership problem in matrix semigroups. In particular, we consider the membership of a given invertible diagonal matrix in a matrix semigroup and then a scalar matrix, which has a separate geometric interpretation. Both problems have been open for any dimensions and are shown to be undecidable in dimension 4 with integral matrices by a reduction of the Post Correspondence Problem (PCP). Although the idea of PCP reduction is standard for such problems, we suggest a new coding technique to cover the case of diagonal matrices. [Copyright &y& Elsevier]

The main objectives of the present study are to determine the time-dependent character of bedform dimensions and to assess the feasibility and reliability of dune-tracking techniques to estimate bedload transport in estuarine–marine conditions. A third additional aim is to evaluate the application of the Ribberink bedload transport formula for field conditions with a rippled bed. Field experiments were carried out on Spratt Sand, an intertidal shoal in the mouth of the Teign estuary, Devon, UK. In the framework of the COAST3D project, data of hydrodynamics, bedform development and sediment transport were collected over a period of a month. The presence of sediment on Spratt Sand turns out to be an important factor in the development of bedforms. As soon as sufficient sediment is available—a layer with a thickness of at least 0.20–0.30 m—ripples start to grow and develop into dunes. In general, an increase in bedform height is anticipated to result in an increase in bedload transport. However, the present study demonstrates that the development of dunes instead of ripples may lead to a reduction in migration rates, which, at the end, in reality causes a reduction in bedload transport. The presence of waves appears to be a critical factor to the applicability of the dune tracking technique. Dunes only start to migrate when wave orbital velocities exceed 0.3 m/s. Bedload transport by migrating dunes is generally in the order of 0–1.5 m2/s when orbital velocities remain below 0.7 m/s. Bedload transport increases by a factor 2 when wave orbital velocities reach values of 0.8–0.9 m/s. The increase in bedload transport is partly caused by the additional bed shear in the presence of waves. A second wave-generated mechanism is that stronger wave action reduces the effect of hiding which, under low wave–strong current conditions, suppresses sediment pick-up in the sand–gravel mixture.Application of the Ribberink bedload transport formula for conditions with a rippled bed and in case of unidirectional flows with superimposed oscillatory flows leads to a maximum difference between “measured” (dune-tracking) and computed bedload transport up to a factor 2. For low-energetic conditions, the difference is smaller and generally varies between 10% and 20%; for high-energetic conditions this figure amounts maximum 100%. [Copyright &y& Elsevier]

For over a century, authorities have recognized cultural and psychological benefits of preserving national parks and wilderness areas. Yet, with increases in visitation and mechanized travel, air and noise pollution are intruding more and more into preserved natural areas. Psychological research shows that humans can detect very low levels of these pollutants in natural and laboratory settings, that air and noise pollution detract from the enjoyment of the visitor experience, and that people place a high value on naturally quiet, pollution-free settings. This article discusses how psychological research is essential for a more complete understanding of the value and the influence of both visibility and quiet surroundings with a focus on applied, field-based research in national parks and wilderness areas. The article concludes with recommendations for future directions in research in these areas and argues that implications of psychological research results should be addressed in the natural resource policy-making process. [ABSTRACT FROM AUTHOR]

Aircraft overflight noise from helicopter tours is frequently encountered in such national parks as Grand Canyon, Hawaii Volcanoes, Haleakala, and Bryce Canyon. Noise is an environmental stressor and is associated with a variety of physiological and psychological effects, some of which are long-lasting. Psychologically, attributing a stressor to a nonhostile origin (e.g., a helicopter rescue mission) could mitigate stress effects. In this study, 200 undergraduates rated National Park scenes while exposed to either natural sounds (birds, brooks, wind), helicopter noise attributed to tourist overflights, helicopter noise attributed to backcountry maintenance operations, or helicopter noise attributed to the rescue of a back country hiker. Regardless of the source, 60 decibel (dB(A)) helicopter noise resulted in lower ratings of scenic beauty, solitude, tranquility, freedom, naturalness, and preference, and higher ratings of annoyance. These effects occurred across all types of scenery. Results suggest that park management-related overflight noise is just as disturbing as tourist aircraft noise, and that the impact of this noise is substantial across demographic variables and across types of vistas. [ABSTRACT FROM AUTHOR]

Nitrogen fertilization is a required production practice for cotton (Gossypium hirsutum L.) with risks arising from under- and overfertilization. Tissue testing for diagnosing N deficiencies in crops can use leaf blades and the total N concentration, but this practice has not been rigorously examined in cotton. The primary objective of these experiments was to determine the leaf-N concentration of the uppermost, fully mature leaf blade below which yield loss could be expected. Nitrogen-rate field experiments were conducted at 12 research station and farm sites in the Midsouth USA in Louisiana, Arkansas, Mississippi, and Alabama in 1996 and 1997. Leaf-blade total N concentrations associated with yield loss were 4.3% N at early bloom (R² = 0.50) and 4.1% N at mid-bloom (3 wk after early bloom, R² = 0.32). The likelihood of applying N when not needed could be reduced by lowering the early bloom critical value to 3.9%. Only 4% of all samples sufficient in N would have been incorrectly diagnosed N deficient at that critical value, but 44% of all deficient samples would have been misidentified as N sufficient. Reduced yields due to over application of N were evident in some samples with leaf N between 4.6 and 4.8% at early bloom. These concentrations were also common for N-sufficient plants, making accurate diagnoses of the over application of N unlikely. Our leaf-N critical values probably differ from previously established values because earlier values were derived via survey techniques and because faster fruiting cultivars may require higher leaf N. [ABSTRACT FROM AUTHOR]

Chelator-buffered hydroponic solutions provide low and buffered free-metal concentrations and allow the easy calculation of nutrient species expected in these solutions. Some researchers suspect that the solutions allow plant uptake of chelates and that this uptake explains the failure of the free-ion activity model using these solutions. To determine the amount and method of chelate uptake, swiss chard was grown in solution culture in growth chambers for about three wks and then transferred to solutions containing 14C-EDTA, 14C-citrate, or 14C-L-histidine for a 21-hour assay. Much higher root and shoot 14C were found from treatments containing metabolites histidine (2706 097 shoot Bq 14C) or citrate (2241 953 shoot Bq 14C) than EDTA (280 110 shoot Bq 14C). Passive transpirational flow could explain all of the EDTA uptake, but active uptake would be required to explain most of the citrate and histidine uptake even assuming some adsorption of ligand bound to roots. Swiss chard grown in solutions with the same total EDTA concentrations, but different amounts of Fe bound to EDTA, had ≥3-fold differences in root and shoot 14C concentrations. In a second experiment, swiss chard roots removed more EDTA from solutions containing mostly M-EDTA0 than M-EDTA1- or M-EDTA2- (288 140, 245 051, and 192 559 Bq 14C, respectively) suggesting plant selectivity for EDTA and a non-apoplastic route of uptake or an effect resulting from root cell-wall adsorption. Results indicated buffering of metals by ligands allowed some ligand uptake with much more uptake occurring with metabolites citrate and histidine than EDTA. A passive or indiscriminate form of uptake does not appear to explain all EDTA uptake with a selectivity by swiss chard for M-EDTA complexes of lower charge. [ABSTRACT FROM AUTHOR]

The methanolysis of hydroxypropyl-p-nitrophenyl phosphate (HPNPP, 1) promoted by La(OTf)[sub 3] under buffered conditions was studied in methanol as a function of [sup s, sub s]pH at 25 °C. [sup 31]P NMR studies at -90 °C indicate that there are at least three La/1 complexes formed at [sup s, sub s]pH ≈ 5.3 of 1:1, 2:2. and 1:2 stoichiometry. Kinetic studies of the observed pseudo-first-order rate constants for the methanolysis of 1 as a function of [La[sup 3+]] at 4.5 < [sup s, sub s]pH < 10.5 indicate there are two general [sup s, sub s]pH regimes. In the low [sup s, sub s]pH regime between 4.5 and 7.6 the plots of k[sub obs] versus [La[sup 3+]] exhibit saturation behavior with very strong 1:1 binding, with a plateau rate constant that depends on [OCH[sub 3, sup -]]. The catalytically productive species is shown to be a 2:2 complex of La[sup 3+] and 1, where the phosphate is proposed to be doubly activated, thereby promoting the methoxide reaction by some 4.6 × 10[sup 10]-fold. In the high [sup s, sub s]pH regime from 7.9 to 10.5, 1:1. 2:2, and 2:1 LA[sup 3+]/1 complexes are formed with the La[sup 3+] coordinated in the form of [La[sup 3+](OCH[sub 3, sup -])][sub 1,2]. Throughout this [sup s, sub s]pH regime at high [La[sup 3+]], a saturation complex, (La[sup 3+]OCH[sub 3, sup -])[sub 2]/1, is formed that spontaneously decomposes with a rate constant of (5-10) × 10[sup -3] s[sup -1], leading to an acceleration of 10[sup 9]fold at [sup s, sub s]pH 8.0. [ABSTRACT FROM AUTHOR]

Pearl millet [Pennisetum glaucum (R) Br.] is a promising alternative grain crop for the Southeast and mid-South regions of the USA, but additional-N fertility information is needed to optimize its production. Identification of a critical tissue N level at early growth stages is necessary to determine the need for subsequent applications of N. Field experiments were conducted to determine the response of hybrid 'HGM 100' grain yield, protein yield, and shoot N concentration to N application rate and to determine the relationship of grain yield and protein yield with shoot N concentration at different growth stages. Grain yield response to N fertilizer applications from 0 to 168 kg ha[sup -1], in 34-kg increments, varied among five field environments ranging from sandy loam to silty clay loam soils and resulted in a moderately low correlation (r² = 0.36). Relative total protein yield was more consistent (r² = 0.67). Tissue N concentration of shoots harvested 44 ± 4 d after seeding [early boot(EB)] was related to relative grain yield (r² = 0.65). A critical N concentration of 31 g kg[sup -1] dry matter (dm), determined by regression and "old" Cate-Nelson procedures, resulted in optimum grain yield. On a per hectare basis, total relative protein yield also correlated moderately high with shoot tissue N concentration at EB (r² = 0.70). The use of Care-Nelson procedures determined a critical N concentration in shoot tissue at EB of 32 g kg[sup -1] dm. Determination of a critical N level at an earlier growth stage resulted in low correlations with yield parameters. On the basis of critical values at the EB stage, N amendments could possibly be applied in time to enhance some yield components, although the effective application window is narrow. [ABSTRACT FROM AUTHOR]

We examined the effects of trait driving anger, aggressive stimuli, and anonymity on aggressive driving behavior in a driving simulation task. High and low driving anger participants were randomly assigned to one of four conditions: (a) anonymous vs. identifiable driver; and (b) exposure to aggressive stimuli versus nonaggressive stimuli. Participants drove more aggressively when they were anonymous (d = .28) and exposed to aggressive stimuli (d = .05). Males drove more aggressively than did females (d = .06). No main or interaction effects were found for trait driving anger. Results suggest that situational factors affecting other forms of aggression are also important in aggressive driving. [ABSTRACT FROM AUTHOR]

Presents information on a study which explored some aspects of a psychometric scaling technique called paired comparison, which is used to evaluate decision-making strategies. Experimental design; Data collection and analysis; Results.

Trait coping, state anger, perceived arousal, blood pressure, negative affect, and escape behavior were measured in a sample of 240 undergraduate males and females exposed to 1 of 4 foul-odor conditions or to a no-odor condition. Consistent with Baron and Bell's (1976) negative-affect--escape model, it was hypothesized that people exposed to noxious odors would experience increased negative affect and heightened motivation to escape the situation. Results showed that negative affect and motivation to escape, but not anger or arousal, increased significantly as odor became more noxious. In addition, anger and motivation to escape significantly predicted negative affect. Variances in anger and perceived arousal, but hot discomfort and escape, were accounted for mainly by trait coping styles and gender differences. Variances in discomfort and escape were accounted for mainly by odor alone. [ABSTRACT FROM AUTHOR]

Research has shown that helicopter noise from tourist flights is very common in some national parks and wilderness areas . At Grand Canyon National Park , air craft noise has been found to be as high as 76 dB (A) with as many as 43 noise events in a 20-minute period . The present study examined the influence of 40 dB (A) or 80 dB (A) helicopter noise on assessment of a popular Grand Canyon vista in a laboratory simulation. Participants (44 female and 36 male undergraduates) viewed 68 slides of scenic vistas and assessed them on naturalness, preference, and scenic beauty and evaluated dimensions of freedom, annoyance, solitude, and tranquility. Compared to a control condition of background natural sounds (e.g.,birds, brooks), noise conditions negatively impacted all dependent measures. Although the effects were most pronounced at the 80-dB level, even the 40-dB helicopter noise negatively impacted all dependent variables. Results suggest that helicopter noise interferes with the quality of the visitor experience and even affects the perceived aesthetic quality of landscapes. [ABSTRACT FROM AUTHOR]

Highlights a survey on the attitudes of United States college students regarding two contrasting paradigms of the US Space Program. Scientific use of space compared to its commercial exploitation; Use of the pair-comparison method to validate survey results.

Describes the relevance of literature on environmental psychology to the coping strategies used by a leukemia patient in adapting to psychological and physical isolation on a hospital bone marrow transplant unit and oncology unit. Difficulty of place attachment on the isolation unit and its evolution on the oncology unit; Power of a window with a natural view.

Examines the combined operation of feedback and punishment by factorially manipulating them in a shared resource dilemma. Research participants' harvesting of resources from a regenerating shared pool in a computer-assisted game; Occurrence of commons dilemma; Provision of an index of participants' awareness of the interdependency of their outcomes; Punishment's effect on harvesting efficiency.

Describes two computer simulation programs addressing the `commons dilemma' concept or the exploitation of resources. Computer application in commons dilemma research; Program actuation.

ABSTRACT. A commons dilemma arises when individuals sharing a resource act according to their short-term interests, resulting in the long term destruction of a renewable resource. This experiment was conducted to determine if interpersonal attraction impacts destructive commons dilemma behavior. Introductory psychology students (N = 135) participated in groups of three in a commons dilemma simulation. Using attitude similarity, four levels of interpersonal attraction were manipulated, ranging from very high to low to mixed attraction between group members. The results indicated that a high level of interpersonal mutual attraction improved harvesting efficiency, increased self-sacrificing, and extended the life of the commons. In addition, perceived trust among players increased as total harvests increased [ABSTRACT FROM AUTHOR]

Demand characteristics may influence claims that the color pink inhibits muscle strength whereas blue increases muscle strength. In Experiment 1, undergraduates (N = 59, 30 women, 29 men) were told either that the experimenters thought pink would increase and blue decrease strength or that blue would increase muscle strength and pink decrease muscle strength. A hand dynamometer assessed grip strength as subjects stared at each of 8 differently colored panels. Results indicated that men viewing the pink or orange panels had higher grip strength under pink-strengthen than under pink-weaken instructions. The reverse relationship was found for men viewing a green panel. For women, the pink-weaken instructions resulted in a higher grip strength than did the pink-strengthen instructions, regardless of actual color present. In Experiment 2, women in a no-instruction control condition had lower grip strength than women given the pink-weaken instructions. For men, the control (no-instruction) condition resulted in higher grip strength than the pink-weaken condition. Results of both studies suggest that men followed overt demand characteristics but that women reacted with increased intensity to any suggestion that a stereotypically feminine pink is associated with weakness. [ABSTRACT FROM AUTHOR]

Presets a study which examined the influence of seating arrangement and high ambient temperatures on interpersonal attraction and assessments of the environment. Method used in the study; Results; Discussion.