bluuebunny/crossref_metadata_2025 huggingface dataset:
Songbird communities in a pyrogenic habitat mosaic
Authors: Stuart-Smith Kari , Adams Ian T. , Larsen Karl W.
Published: August 2002

Wildfires play a key role in shaping the boreal forest landscape, yet the
response of wildlife to the patchy mosaics they create is poorly understood.
We studied songbirds 5–6 years post-fire in a large burn (9600 ha) in
the boreal mixed wood forest of north-eastern Alberta. In the spring of 1995
and 1996 we estimated abundance of songbirds in four areas, each with four
replicate sites: unburned patches within the fire
(Isolates); burned patches
(Burns); patches that had been clear-cut prior to
burning by wildfire (Cut-Burns); and the unburned,
continuous forest adjacent to the burn (Peripherals). We
also sampled shrub-based arthropods with sweep-nets at each site. To
investigate the role of Isolates, we compared them to
Peripherals and to Burns. We
compared Cut-Burns to Burns to
examine the effect of logging prior to burning. In
general, Isolates supported higher numbers of species and
individuals than Peripherals, mainly due to higher
numbers of aerial-foraging birds. Isolates and
Burns had similar species richness and abundance, but
Burns supported more aerial foragers while
Isolates had more foliage
gleaners. Cut-Burns generally supported fewer individuals
than Burns, in particular fewer shrub-nesters, aerial
foragers, and neotropical migrants. More bird species reached their highest
densities in Burns than in any other area. Songbird
species richness and abundance were positively related to dry arthropod
biomass, with Burns and Isolates
having the highest arthropod biomass. These patterns indicated that, 5–6
years post-burn, the patchy mosaic created by this wildfire supported more
species than the mature forest surrounding the fire. Clear-cut logging prior
to burning resulted in a diminished songbird community compared to that found
in burned stands.
EQUIVALENCE OF MODULAR K AND ANOSOV DYNAMICAL SYSTEMS
Authors: NARNHOFER H. , THIRRING W.
Published: August 2002

We show that for modular dynamical systems the Anosov property and the existence of a refining subalgebra are equivalent. With some additional assumption they are also equivalent to the existence of an algebraic K-subsystem.
LIFSHITZ ASYMPTOTICS AND LOCALIZATION FOR RANDOM QUANTUM WAVEGUIDES
Authors: KLEESPIES FRANK , STOLLMANN PETER
Published: August 2002

We investigate a family of Dirichlet Laplacians on randomly dented or bulged strips in ℝ2; for this random quantum waveguide model, dense point spectrum with exponentially localized eigenfunctions near its fluctuation boundary at the bottom of the spectrum and Lifshitz asymptotics of the integrated density of states are established. For this purpose, multi-scale analysis in the quite abstract form of [21] is applied, and domain perturbations of the Laplacian are studied.
FOUR OBSERVATIONS ON n-TRIVIALITY AND BRUNNIAN LINKS
Authors: Stanford Theodore B.
Published: August 2002

Brunnian links have been known for a long time in knot theory, whereas the idea of n-triviality is a recent innovation. We illustrate the relationship between the two concepts with four short theorems.
THE SECOND SKEW-SYMMETRIC COHOMOLOGY GROUP AND SPATIAL EMBEDDINGS OF GRAPHS
Authors: NIKKUNI RYO
Published: August 2002

Let L(G) be the second skew-symmetric cohomology group of the residual space of a graph G. We determine L(G) in the case G is a 3-connected simple graph, and give the structure of L(G) in the case of G is a complete graph and a complete bipartite graph. By using these results, we determine the Wu invariants in L(G) of the spatial embeddings of the complete graph and those of the complete bipartite graph, respectively. Since the Wu invariant of a spatial embedding is a complete invariant up to homology which is an equivalence relation on spatial embeddings introduced in [12], we give a homology classification of the spatial embeddings of such graphs.
FINITE TYPE LINK HOMOTOPY INVARIANTS II: Milnor's $\bar\mu$-Invariants
Authors: MELLOR BLAKE
Published: August 2002

We define a notion of finite type invariants for links with a fixed linking matrix. We show that Milnor's link homotopy invariant [Formula: see text] is a finite type invariant, of type 1, in this sense. We also generalize this approach to Milnor's higher order [Formula: see text] invariants and show that they are also, in a sense, of finite type. Finally, we compare our approach to another approach for defining finite type invariants within linking classes.
HOMFLY Polynomials of Some Generalized Hopf Links
Authors: CHAN TAT-HUNG
Published: August 2002

The Hopf link, consisting of two unknots wrapped around each other, is the simplest possible nontrivial link with more than one component. We can generalize it to two bundles of "parallel" unknots wrapped around each other. In this paper, we show that when one of the two bundles has a fixed side, the HOMFLY polynomials of the links satisfy a system of recurrence equations. This leads to a procedure for computing explicit formulas for the HOMFLY polynomials.
THE THIRD POWER OF THE SMALE HORSESHOE INDUCES ALL LINK TYPES
Authors: KIN EIKO
Published: August 2002

Let φ:D2→D2 be an orientation preserving homeomorphism of the disk into itself, and Φ= {φt}0≤t≤1 an isotopy with φ0=idD2 and φ1=φ. Then for a finite union of periodic orbits P of φ, the set [Formula: see text] is a link in D2×S1. We say that φ induces all link types (for Φ) if there exists a homeomorphism h of D2×S1 into a standardly embedded solid torus in the 3-sphere S3 such that any link L in S3 can be realized by a finite union of periodic orbits PL of φ so that L and [Formula: see text] are equivalent. We will show that the Smale horseshoe and its second power do not induce all link types, but its third power does induce all link types.
APPROXIMATING JONES COEFFICIENTS AND OTHER LINK INVARIANTS BY VASSILIEV INVARIANTS
Authors: KOFMAN ILYA , RONG YONGWU
Published: August 2002

We find approximations by Vassiliev invariants for the coefficients of the Jones polynomial and all specializations of the HOMFLY and Kauffman polynomials. Consequently, we obtain approximations of some other link invariants arising from the homology of branched covers of links.
Knotted Spheres and Graphs in Balls
Authors: Howards Hugh Nelson
Published: August 2002

Given a properly embedded graph Γ in a ball B and a punctured sphere Σ properly embedded in B-Γ we examine the conditions on Γ that are necessary to assure that Σ is boundary parallel.
Quantitative Geography: Representations, Practices, and Possibilities
Authors: Sheppard Eric
Published: August 2002

Representations of quantitative geography, both by practitioners and by others, have tended to associate quantification with empiricism, positivism, and the social and academic status quo. Qualitative geography, by contrast is represented as nonempiricist or postempiricist, sensitive to complexity, contextual, and capable of empowering nonmainstream academic approaches and social groups. Attempts to engage in debate between these positions rarely challenge this dualism, reproducing the representation of quantitative geography as logical positivism, and a dualism separating quantitative and qualitative geography. I argue that this dualism can be broken down, by deconstructing the underlying representation. I discuss why this representation came into existence and how it was stabilized; how close attention to the practices of quantitative geographers, and particularly to the evolution of these practices, reveals its inadequacies; and what new possibilities for quantitative practices emerge from this deconstruction. GIS, one of the recent manifestations around which representations of quantitative geography polarize, is used as a case study to illustrate these arguments. I pay particular attention to the question of the relevance of quantitative practices for an emancipatory human geography.
Dynamic Visual Perception of Dyslexic Children
Authors: Fischer Burkhart , Hartnegg Klaus , Mokler Annette
Published: August 2002

This study describes the capacity of children to detect fast changes of a small visual pattern. Three visual detection tasks for a group of normally reading ( N = 140) and another group of dyslexic children ( N = 366) in the age range of 7 to 16 years have been used. All three tasks require the detection of the fast changing orientation of a small pattern before it disappears. In one task, stationary fixation was required, because the orientation changes took place always at the same location. In the saccade condition, the pattern was displaced suddenly to one or the other side and a saccade was required to detect the orientation. In a third condition, a distractor was presented at one side shortly before the oriented pattern appeared at the opposite side. In this case, an antisaccade with respect to the distractor was required. In all three conditions, the dyslexic group as a whole performed significantly below the level of the control group. The performance improved with age in both groups. The differences between the test and control group were largest in the distractor condition. When compared with eye-movement performance in an antisaccade task, a parallel development of the performance of both tasks was observed in both groups. The study shows that a certain percentage of dyslexic children has difficulties in the perception of fast changing stimuli, a task presumably challenging the magnocellular system.
Visual Discomfort: The Influence of Spatial Frequency
Authors: Conlon Elizabeth , Lovegrove William , Barker Susan , Chekaluk Eugene
Published: August 2002

The response of different visual discomfort groups to a range of spatial frequencies at threshold and suprathreshold was investigated. In experiment 1, a paired-comparison task was conducted. The high visual discomfort group judged a spatial frequency of 4 cycles deg−1 as the most perceptually distorted and somatically unpleasant to view. The moderate and low visual discomfort groups judged 8 and 12 cycles deg−1 as more perceptually and somatically unpleasant to view than lower spatial frequencies. In experiment 2, the spatial contrast-sensitivity function (CSF) for the high visual discomfort group was depressed for spatial frequencies between 1 and 12 cycles deg−1 in comparison with the moderate and low visual discomfort groups. When these same spatial frequencies were modulated at 6 Hz, CSFs were the same for all groups. These results are discussed in relation to a failure of inhibition across spatial-frequency channels in the high visual discomfort group. This may be explained by a more generalised parvocellular system processing deficit. Possible similarities between some forms of migraine and visual discomfort are highlighted.
The Glare Effect and the Perception of Luminosity
Authors: Zavagno Daniele , Caputo Giovanni
Published: August 2002

The impression of self-luminosity in the glare effect was studied in two experiments. In experiment 1 the target (CS) was set to the highest luminance of the field and subjects were asked to adjust the luminance ramp of the inducers (R) against five backgrounds (B) to the point where they began to see CS as self-luminous. It was found that there is a linear relationship between background and luminance ramp. Another group of subjects carried out the same task in experiment 2, but this time CS and R were linked together so that CS would always have the same luminance as the highest luminance level of R, as adjustments were performed. It was found that: (i) adjustments were always lower than the highest luminance available; (ii) the linear relationship between background and luminance ramp was confirmed; (iii) observers reported a compelling impression of self-luminous grays. Data are discussed in relation to Bonato and Gilchrist's model for the perception of luminosity. The authors advance the hypothesis that luminance ramps are used at an early stage of encoding for the perception of luminosity.
Haptic Perception of the Horizontal by Blind and Low-Vision Individuals
Authors: Heller Morton A , Brackett Deneen D , Scroggs Eric , Allen Angela C , Green Shavonda
Published: August 2002

We examined haptic perception of the horizontal in visually impaired people. Blind people (late blind and congenitally blind), persons with very low vision, and blindfolded sighted individuals felt raised-line drawings of jars at four angles. They had to demonstrate their understanding that water remains horizontal, despite jar tilt, by selecting the correct raised-line drawing given four choices. Low-vision subjects, with near perfect scores, performed significantly better than the other groups of subjects. While the late-blind and blindfolded sighted subjects performed slightly better than the congenitally blind participants, the difference between the late-blind and congenitally blind groups was nonsignificant. The performance of the congenitally blind subjects indicates that visual experience is not necessary for the development of an understanding that water level stays horizontal, given container tilt.
The Integration of Orientation Information in the Motion Correspondence Problem
Authors: Prince Simon , Offen Shani , Cumming Bruce G , Eagle Richard A
Published: August 2002

We examine how differently oriented components contribute to the discrimination of motion direction along a horizontal axis. Stimuli were two-frame random-dot kinematograms that were narrowband filtered in spatial frequency. On each trial, subjects had to state whether motion was to the left or the right. For each stimulus condition, Dmax (the largest displacement supporting 80% correct direction discrimination performance) was measured. In experiment 1, Dmax was measured for orientationally narrowband stimuli as a function of their mean orientation. Dmax was found to increase as the orientation of the stimuli became closer to the axis of motion. Experiment 2 used isotropic stimuli in which some orientation bands contained a coherent motion signal, and some contained only noise. When the noise band started at vertical orientations and increased until only horizontal orientations contained a coherent motion signal, Dmax increased slightly. This suggests that near-vertical orientations interfere with motion perception at large displacements when they contain a coherent motion signal. When the noise band started at horizontal and increased until only vertical orientations contained the motion signal, Dmax decreased steadily. This implies that Dmax depends at least partly on the most horizontal motion signal in the stimulus. These results were contrasted with two models. In the first, the visual system utilises the most informative orientations (nearest horizontal). In the second, all available orientations are used equally. Results supported an intermediate interpretation, in which all orientations are used but more informative ones are weighted more heavily.
Last but Not Least
Authors: Kitaoka Akiyoshi , Pinna Baingio , Brelstaff Gavin
Published: August 2002

New variations of the spiral illusion are demonstrated. They include spiral illusions of the Café Wall illusion and the Zöllner illusion, as well as other new orientation illusions. Thus the spiral illusion is not limited to the Fraser illusion. We discuss the role that detectors of spirals in a higher visual area might play in the spiral illusion.
Distance Perception within near Visual Space
Authors: Viguier Alain , Clément Gilles , Trotter Yves
Published: August 2002

We investigated the perception of distance of visual targets with constant size and luminance presented between 20 and 120 cm from subjects' eyes. When retinal disparity cues were present, the subjects could reproduce very accurately the distance of a seen reference in this area. When only extraretinal information was available, distance perception was still correct for distances of 40 cm or less. However, distances beyond 60 cm were underestimated. When forced to evaluate the distance between a reference and themselves, eg when evaluating the absolute distance or half the distance or twice the distance of a reference, subjects used an egocentric plane of reference located on average 10.4 cm in front of their eyes. Measurements of binocular eye movements indicated a clear relationship between vergence angle and target distance. The egocentric plane of reference at 10.4 cm also corresponds to the maximum achievable vergence. These results suggest that ocular convergence can be used as a reliable cue for distance within the arm's reaching space.
Identification of Visual Stimuli is Improved by Accompanying Auditory Stimuli: The Role of Eye Movements and Sound Location
Authors: Doyle Melanie C , Snowden Robert J
Published: August 2002

Can auditory signals influence the processing of visual information? The present study examined the effects of simple auditory signals (clicks and noise bursts) whose onset was simultaneous with that of the visual target, but which provided no information about the target. It was found that such a signal enhances performance in the visual task: the accessory sound reduced response times for target identification with no cost to accuracy. The spatial location of the sound (whether central to the display or at the target location) did not modify this facilitation. Furthermore, the same pattern of facilitation was evident whether the observer fixated centrally or moved their eyes to the target. The results were not altered by changes in the contrast (and therefore visibility) of the visual stimulus or by the perceived utility of the spatial location of the sound. We speculate that the auditory signal may promote attentional ‘disengagement’ and that, as a result, observers are able to process the visual target sooner when sound accompanies the display relative to when visual information is presented alone.
Perceptual Learning without Feedback and the Stability of Stereoscopic Slant Estimation
Authors: van Ee Raymond
Published: August 2002

Subjects were examined for practice effects in a stereoscopic slant-estimation task involving surfaces that comprised a large portion of the visual field. In most subjects slant estimation was significantly affected by practice, but only when an isolated surface (an absolute disparity gradient) was present in the visual field. When a second, unslanted, surface was visible (providing a second disparity gradient and thereby also a relative disparity gradient) none of the subjects exhibited practice effects. Apparently, stereoscopic slant estimation is more robust or stable over time in the presence of a second surface than in its absence. In order to relate the practice effects, which occurred without feedback, to perceptual learning, results are interpreted within a cue-interaction framework. In this paradigm the contribution of a cue depends on its reliability. It is suggested that normally absolute disparity gradients contribute relatively little to perceived slant and that subjects learn to increase this contribution by utilizing proprioceptive information. It is argued that—given the limited computational power of the brain—a relatively small contribution of absolute disparity gradients in perceived slant enhances the stability of stereoscopic slant perception.
Processing Time of Contour Integration: The Role of Colour, Contrast, and Curvature
Authors: Beaudot William H A , Mullen Kathy T
Published: August 2002

We investigated the temporal properties of the red-green, blue – yellow, and luminance mechanisms in a contour-integration task which required the linking of orientation across space to detect a ‘path’. Reaction times were obtained for simple detection of the stimulus regardless of the presence of a path, and for path detection measured by a yes/no procedure with path and no-path stimuli randomly presented. Additional processing times for contour integration were calculated as the difference between reaction times for simple stimulus detection and path detection, and were measured as a function of stimulus contrast for straight and curved paths. We found that processing time shows effects not apparent in choice reaction-time measurements. (i) Processing time for curved paths is longer than for straight paths. (ii) For straight paths, the achromatic mechanism is faster than the two chromatic ones, with no difference between the red – green and blue – yellow mechanisms. For curved paths there is no difference in processing time between mechanisms. (iii) The extra processing time required to detect curved compared to straight paths is longest for the achromatic mechanism, and similar for the red – green and blue – yellow mechanisms. (iv) Detection of the absence of a path requires at least 50 ms of additional time independently of chromaticity, contrast, and path curvature. The significance of these differences and similarities between postreceptoral mechanisms is discussed.
Beyond Junctions: Nonlocal form Constraints on Motion Interpretation
Authors: McDermott Josh , Weiss Yair , Adelson Edward H
Published: August 2002

Because of the aperture problem, local motion measurements must be combined across space. However, not all motions should be combined. Some arise from distinct objects and should be segregated, and some are due to occlusion and should be discounted because they are spurious. Humans have little difficulty ignoring spurious motions at occlusions and correctly integrating object motion, and are evidently making use of form information to do so. There is a large body of theoretical and empirical evidence supporting the importance of form processes involving junctions in the way motion is integrated. To assess the role of more complex form analysis, we manipulated nonlocal form cues that could be varied independently of local junctions. Using variants on diamond and plaid stimuli used in previous studies, we found that manipulations distant from the junctions themselves could cause large changes in motion interpretation. Nonlocal information often overrides the integration decisions that would be expected from local cues. The mechanisms implicated appear to involve surface segmentation, amodal completion, and depth ordering.
Fire-climate relationships and long-lead seasonal wildfire prediction for Hawaii
Authors: Chu Pao-Shin , Yan Weiping , Fujioka Francis
Published: August 2002

We examined statistical relationships between the seasonal Southern
Oscillation Index (SOI) and total acreages burned (TAB) and the number of
fires in the Hawaiian Islands. A composite of TAB during four El
Niño/Southern Oscillation (ENSO) events reveals that a large total
of acres burned is likely to occur from spring to summer in the year following
an ENSO event. The correlation is most significant between the TAB in summer
and the SOI of the antecedent winter. This relationship provides a potential
for long-lead (i.e. 2 seasons in advance) prediction of wildfire activity in
the Hawaiian Islands.
Logistic regression is applied to predict events of large acreages burned by
wildfires. The goodness of predictions is measured by specificity,
sensitivity, and correctness using a cross-validation method. A comparison of
prediction skill for four major islands in Hawaii is made using the summer TAB
as the response variable and the preceding winter SOI as the predictor
variable. For predicting the probability of events (sensitivity), results
indicate rather successful skills for the islands of Oahu and Kauai, but less
so for Maui and Hawaii. It is more difficult to predict non-events
(specificity), with the exception of Oahu. As a result, only Oahu has a high
overall correctness rate among the four islands tested.
Evaluation of Nixtamalized Corn Hulls as Fiber Source in Baking Products
Authors: Soto-Mendívil E. A. , Vidal-Quintanar R. L.
Published: August 2002

Texture and acceptability of tortillas and muffins prepared with 20, 25, and 30% (w/w) and cookies with 15, 22, and 30% (w/w) of nixtamalized corn hulls (NCH), as substitution for flour were evaluated. With up to 25% of substitution the three products were well-accepted by the sensory panel. Texture, flavor, and chewiness were the leading characteristics in the products. The dough stickiness was not affected by NCH ( p< 0.05), but tortillas became less rollable as the level of NCH substituted increased. NCH gives an excellent performance in tortillas, muffins, and cookies and 20–25% of NCH is a feasible level of substitution.
Effect of Formulation Parameters on Optical and Frictional Properties of Tubular Water Quenched Polypropylene Films
Authors: Crosby C. R. , Chatterjee A. M.
Published: August 2002

The tubular water quenched (TWQ) process is commonly used to convert polypropylene (PP) into unoriented films in Asian, Mideast and other markets. The key requirements for TWQ films are (1) good optics (e.g. low haze) and (2) good openability. This study reports the effects of antiblock and slip additives in UNIPOL® PP homopolymer on these key film properties.
Fatty Acid Changes in High Oleic Acid Sunflower Oil during Successive Deep-Fat Fryings of Frozen Foods
Authors: Cuesta C. , Romero A. , Sánchez-Muniz F. J.
Published: August 2002

High oleic acid sunflower oil (HOSO) is a monounsaturated oil that is being extensively used in frying. The level of total altered fatty acids and the fatty acid pattern of a fryer oil was used to evaluate the alteration of a HOSO used 20 times to fry various frozen foods with frequent replenishment (FR) or without replenishment (NR) with fresh oil during the frying. In addition, the levels of total altered fatty acids and the fatty acid composition of the fat extracted from the fried potatoes after numerous fryings were determined and compared to those of the corresponding fryer oils. Altered fatty acids increased linearly through 20 fryings within FR and NR in the frying oil and also in the fat extracted. Although differences were not quantitatively relevant, changes tended to be higher in the extracted fat, and in the NR modality as a consequence of oil renovation and fat exchange between the frying oil and the potatoes. The decrease in the oleic acid content in the oil was more pronounced ( p< 0.001) in NR than in FR method, and more (at least p< 0.01) in the oils than in the corresponding extracted fats. Nevertheless, other fatty acids remained quite stable and similar or increased during frying, by both methods. These results suggest that total fatty acid alteration measure is a useful tool for frying assessments, and that they must be related not only to the degradation of unsaturated fatty acids but also to migrations of some fatty acids from the frozen prefried foods to the fryer oil as revealed by composition of the fat extracted from the fried potatoes.
Flashover for Bus Fires from Empirical Equations
Authors: Chow W. K.
Published: August 2002

Flashover for local bus fires is discussed using the heat balance equation. Empirical equations on the air intake rates through the opening, heat release rate of the fire, and heat lost rate through the compartment wall are reviewed and applied. The possibility of flashover is studied by plotting the heat lost through the bus envelope and the heat generated by a fire against the air temperature rise in the bus compartment. The heat release rate curve of the fire was computed with the aid of a two-layer zone model. Heat losses through the bus envelope with different materials are compared. It is further confirmed that thermal conducting materials with higher heat loss would have lower chance to flashover.
Measurement and Prediction of Thermal Conductivity of Open Cell Rigid Polyurethane Foam
Authors: Tao Wei-Han , Hsu Hung-Che , Chang Chih-Chen , Hsu Chuan-Liang , Lin Yung-Sen
Published: August 2002

The objectives of this research are to develop, for water-blown open cell rigid polyurethane foam, a theoretical model based on Maxwell’s equation (taking into account conduction in the solid and gas phases), and to establish Rosseland’s diffusion equation (taking into account radiation across the cell-gas spaces, but excluding convection) to predict the thermal conductivity of the polyurethane foam. The physical properties performances of the open cell rigid PU foam were experimentally investigated. The mean deviations of thermal conductivities data between the theoretical calculations of this model, compared with experiment data obtained from the ASTM C518 method, are within 3% to 8% within the mean temperatures from 4°C to 32°C, respectively.
Distributed Sensing and Shape Control of Piezoelectric Bimorph Mirrors
Authors: Martin Jeffrey W. , Redmond James M. , Barney Patrick S. , Henson Tammy D. , Wehlburg Joseph C. , Main John A.
Published: August 2002

Meeting the long term needs of the remote sensing community requires the development of large aperture space-based optical systems to achieve dramatic improvements in resolution and sensitivity. It is possible that ultralarge apertures will be obtained using deployable thin film mirror technology, yet many technological barriers must be overcome to make this approach viable. This paper summarizes an initial research effort into the development of piezoelectric thin film mirrors that can be actively shaped using electric fields applied by an electron flux at selected locations. Recent progress is described in the key areas of mirror figure sensing methods, electron gun excitation, and shape control algorithm development.
Rechargeable Lithium Batteries for Powering Piezoelectric Devices
Authors: Salloux Kurt , Lim James , Dunn Bruce , Chaplya Pavel M. , Carman Gregory P.
Published: August 2002

A new, rechargeable, thick-film, polymer electrolyte, lithium battery using a high-energy density cathode material (vanadium pentoxide aerogel, 350 mAh/g) has been tested in a pulse-discharge mode of operation. Three separate 12 volt batteries were pulse-discharged through a piezoelectric stack actuator. Since motion rectification devices such as linear motors operate at elevated frequencies, the batteries were pulse-discharged at 10, 100, and 500 Hz. Multiple cycle, charge/discharge data is presented for the three batteries tested in this study. Additionally, a 6 volt battery was fabricated and used to power a piezoelectric actuator patch (chirp source) that was part of a damage detection system.
Influence of the Selection of the Suture Material on the Mechanical Behavior of a Biomaterial to be Employed in the Construction of Implants. Part 2: Porcine Pericardium
Authors: Páez J. M. García , Carrera A. , Herrero E. Jorge , Millán I. , Rocha A. , Cordón A. , Sainz N. , Mendez J. , Castillo-Olivares J. L.
Published: August 2002

Using a hydraulic stress simulator, the mechanical behavior of the porcine pericardium used in the construction of cardiac valve leaflets was characterized following the same procedure employed with calf pericardium in Part 1 of this study. One hundred fifty pairs of tissue samples were subjected to tensile testing to rupture. One of the two samples from each of 120 pairs (four series of 30 pairs each) was saturated with commercially available threads made of nylon, silk, Prolene or Gore-Tex, while the other sample in each of these pairs was left unsewn. The remaining 30 pairs were employed as controls in which neither of the two samples was subjected to suturing. The sutured tissue samples showed a significant decrease in tensile strength at rupture (range: 11.61 to 21.22 MPa) when compared with unsutured samples (range: 50.80 to 89.45 MPa; p < 0.01). When these results were compared with their equivalent in calf pericardium, no significant differences were observed (the mean values at rupture in calf pericardium ranged between 211.61 MPa and 26.04 MPa). Again, the application of morphological and mechanical selection criteria to ensure the homogeneity of the samples provided excellent fit with respect to the stress/strain curves.

The interaction of the different suture materials with the pericardial tissue was also assessed by comparing the mechanical behavior of the sutured samples with that of the control samples. At the working stress of a cardiac valve leaflet, 0.250 MPa, samples sewn with Gore-Tex were found to show the least difference in behavior with respect to the controls, indicating that this material presented the lowest degree of interaction with the pericardium. In conclusion, the suture clearly has deleterious effects on the resistance of both calf and porcine pericardium, which showed no statistically significant differences in terms of resistance to rupture when their respective sutured or unsutured samples were compared, except in the case of porcine pericardium sewn with silk, which presented lower resistance to rupture in all the zones studied. These findings suggest that the hypothesis that porcine pericardium is less resistant is erroneous.

The Gore-Tex suture also presented a lower degree of interaction with the porcine pericardium, with values similar to the working stress of a cardiac valve leaflet.

This methodology and the results should be evaluated in dynamic studies, such as fatigue testing, that not only confirm the resistance of the material but establish the durability of the samples being assayed.
Effect of Osmotic Solution Concentration, Temperature and Vacuum Impregnation Pretreatment on Osmotic Dehydration Kinetics of Apple Slices
Authors: Barat J. M. , Chiralt A. , Fito P.
Published: August 2002

Apple slices of 10mm thickness were osmotically dehydrated with sucrose–water solutions of 0.25, 0.35, 0.45, 0.55 and 0.65 (w/w) at 30, 40 and 50 C. Experimental conditions were atmospheric osmotic dehydration and pulsed vacuum osmotic dehydration, where 180 mbar were applied for the first five minutes. Experimental data were fitted to a mathematical model to obtain the kinetic parameters (De, K, k1, and k2). The influence of operation variables on water, solute concentration and weight net gain is discussed. No significant effect of osmotic solution concentration on effective diffusivity was observed, except with 0.25 w/w concentration osmotic solutions at 30 and 40 C. Under these conditions, the diffusion mechanism seemed to be hindered by some active cell transport due to the mild experimental conditions (low temperature and/or concentration). Vacuum impregnation has a strong influence on weight and solute concentration changes throughout the treatment. The effect of temperature on mass transfer kinetics was well predicted by Arrhenius equation.
Plastic/Rubber Blends of Ultrasonically Devulcanized GRT with HDPE
Authors: Hong Chang Kook , Isayev A. I.
Published: August 2002

Ground tire rubber (GRT) and ultrasonically devulcanized GRT (DGRT) were blended with high density polyethylene (HDPE) in a Brabender internal mixer and a twin screw extruder. The DGRT with curatives was mixed with HDPE (HDPE/RGRT) and dynamically revulcanized in an internal mixer and a twin screw extruder. Also, HDPE and GRT blends mixed earlier by using a twin screw extruder were passed through the ultrasonic devulcanization extruder, and dynamically revulcanized by means of the internal mixer and the twin screw extruder. In addition, mechanical properties, rheology and morphology as well as melting behavior of the blends were studied. The mechanical properties of the blends were improved by dynamic revulcanization. The blends mixed by using the twin screw extruder prior to devulcanization and devulcanized in the presence of HDPE matrix were found to have better tensile properties and impact strength. Effects of various mixing devices on rheology of blends were also studied. The viscosity of HDPE/RGRT blends increased in comparison with that of HDPE/DGRT blends. Thermal properties of the blends were also investigated indicating little effect on their melting behavior.
Comparison of the Instrumented Falling Weight Impact Response of Polypropylene Composites Reinforced by Continuous and Discontinuous Fiber Mats
Authors: Czigány T. , Karger-Kocsis J.
Published: August 2002

The temperature dependent instrumented falling weight impact (IFWI) behavior of glass mat reinforced thermoplastic polypropylene (GMT-PP) composites with continuous (GM-C) and discontinuous (GM-D) fiber mats were studied at three different temperatures: −40°C, room temperature (RT) and +90°C. Apart from the mat type the matrix viscosity and the fiber/matrix adhesion were also varied in the GMT-PP samples.

It was established that the mat type is that parameter which controls the fracture and failure behavior. The high perforation impact resistance of GM-C compared to GM-D is due to an efficient stress redistribution via the continuous fibers and rovings within the mat. Effects of the matrix and interface variations could not be detected during IFWI. The testing temperatures also affected the IFWI characteristics marginally, especially in case of GM-C reinforced PP.
The Belt-Rib Concept: A Structronic Approach to Variable Camber
Authors: Campanile L. F. , Sachau D.
Published: August 2002

The belt-rib concept for lifting surfaces with variable camber evolved at DLR recently as one of the most promising solutions for the adaptive wing. With the belt-rib idea the adaptive wing issue is approached in a new way: instead of a “mechatronic” solution with hinges or linear bearings a “structronic” solution is chosen, where distributed flexibility allows the desired shape changes. The resulting system is not only easier to maintain due to the absence of wear, but also is structurally more reliable and substantially lighter.

The new concept evolves from the classical wing structure. The classical rib, which is in charge of the wing section’s stiffness, is replaced by a “belt rib,” which allows camber changes within given limits while leaving the remaining in-plane stiffness properties of the section widely unchanged.

The evolution of the belt-rib concept was accompanied by experimental tests on different prototypes. After a first development stage, in which mainly the system’s shape adaptability and the overall stiffness properties were investigated, further steps followed, focused on manufacturing, weight optimization and strength aspects.

Recent developments dealt with the construction of a model with solid-state hinges, realized as hybrid glass fiber-carbon-fiber reinforced composite structure. The model is actuated mechanically by cables, which can be replaced by multifunctional actuators—like shape memory wires—in the future.

The paper opens with an introduction about shape control of aerospace structures and variable camber in particular, in which the major advantages of a “structronic” approach with respect to classical solutions are discussed. Then the fundamentals of the belt-rib concept are sketched, with some significant results of the feasibility proof phase, followed by the description of the last developments. The conclusion summarizes the potential of a structronic approach to shape control with an outline of possible future work.
Application of Polyacrylate Rubber for High Performance Automotive Gaskets and Seals
Authors: Nakajima N. , DeMarco R. D.
Published: August 2002

Polyacrylate rubber compounds have been used for a number of years for manufacturing oil seals used in current high performance automotive engines. The work reported here was done at the time of the development of these engines, which required new sealing material. Polyacrylate rubber was already known to withstand the use temperature of 150°C with adequate oil resistance. The unknown was the mechanical performance, particularly the endurance at the service condition. A comparative study was undertaken with compounds prepared from polyacrylate and fluoro-rubber. The latter was already known to have adequate performance and, therefore, was the reference material of this study. The strategy was to conduct a minimum amount of work and to achieve the goal in the shortest time. The temperature dependence of modulus up to 200°C, high-speed deformation behavior with subsequent relaxation and endurance at 150°C indicated that polyacrylate rubber would give satisfactory performance.
Porous Foils Filled with Active Substances in Life Support Systems of Manned Space Flight
Authors: Rudolph H. , Hebestreit G. , Harzer D.
Published: August 2002

Within the framework of this project a CO2-absorbing material was developed. Approximately 2 m2 of this material would keep the exhaled air for 1 hour/one person clean. Additionally, a humidity adsorbing material was developed. At 98% relative humidity and 20°C, the developed moisture adsorbing material is able to adsorb between 80 and 90 wt.% moisture. After 10–15 h the adsorption is accomplished. The moisture-laden material can be regenerated within a short time.
The Year in Review: Cardiology
Authors: Sanoski Cynthia A.
Published: August 2002

Overall, the evolution of the management of a broad spectrum of cardiovascular disease states has occurred primarily as a result of randomized, controlled clinical trials that have been conducted and published over time. During the past two years, the results of numerous clinical trials have certainly had a significant impact on the ways in which practitioners have treated conditions such as chronic heart failure, cardiac arrhythmias, ischemic heart disease, dyslipidemias, and hypertension. This review article summarizes the results of several key clinical trials that evaluated various treatment strategies for these five cardiovascular disease states and attempts to provide insight as to how these findings can be incorporated into clinical practice.
Cell-Wall Degrading Enzymes in the Release of Grape Aroma Precursors
Authors: Ganga A. , Piñaga F. , Querol A. , Vallés S. , Ramón D.
Published: August 2002

The potential use of cell-wall degrading enzymes, such as xylanase and endoglucanase, for the release of nonvolatile aroma precursors during maceration of Chenin grapes was evaluated. Aroma precursor levels in must from enzymatically macerated grapes were greater than those detected in must obtained from control grapes macerated in the absence of added enzymes. Similar observations were also made regarding the terpene content (specially •-terpineol and nerol) of must aglycon moities. Fermentation of musts from non-enzymatically and enzymatically macerated grapes resulted in wines of similar chemical characteristics, although a clear increase in fruity aroma was sensorially detected in wines derived from enzymatically macerated grapes.
Energy Conversion in Shape Memory Alloy Heat Engine Part II: Simulation
Authors: Zhu J. J. , Liang N. G. , Huang W. M. , Liew K. M.
Published: August 2002

In this paper, a theoretical model proposed in Part I (Zhu et al., 2001a) is used to simulate the behavior of a twin crank NiTi SMA spring based heat engine, which has been experimentally studied by Iwanaga et al. (1988). The simulation results are compared favorably with the measurements. It is found that (1) output torque and heat efficiency decrease as rotation speed increase; (2) both output torque and output power increase with the increase of hot water temperature; (3) at high rotation speed, higher water temperature improves the heat efficiency. On the contrary, at low rotation speed, lower water temperature is more efficient; (4) the effects of initial spring length may not be monotonic as reported. According to the simulation, output torque, output power and heat efficiency increase with the decrease of spring length only in the low rotation speed case. At high rotation speed, the result might be on the contrary.
Medical Management Considerations for Patients With Lung Transplantation
Authors: Dupuis Robert E. , Taber David J. , Fann Amy L. , Lumbert Kevin P.
Published: August 2002

Lung transplantation has become an accepted modality for the treatment of end-stage lung disease. Adult and pediatric patients with a variety of lung diseases, including cystic fibrosis, chronic obstructive pulmonary disease, and idiopathic pulmonary fibrosis are candidates for lung transplantation. Lung transplantation can extend survival and improve quality of life for these patients. With the introduction of new immunosuppressive agents and enhanced surgical and medical care, both short- and long-term morbidity and mortality in these populations, although not as good as other transplant types, are improving. After lung transplantation, recipients continue to face a number of obstacles including post-operative complications, complex drug regimens, drug-induced toxicities, infection, and rejection. An understanding of the management and monitoring issues after lung transplantation is the focus of this review.
Fundamental Understanding of Piezoelectric Strain Sensors
Authors: Sirohi Jayant , Chopra Inderjit
Published: August 2002

This paper investigates the behavior of piezoelectric elements as strain sensors. Strain is measured in terms of the charge generated by the element as a result of the direct piezoelectric effect. Strain measurements from piezoceramic (PZT) and piezofilm (PVDF) sensors are compared with strains from a conventional foil strain gage and the advantages of each type of sensor are discussed, along with their limitations. The sensors are surface bonded to a beam and are calibrated over a frequency range of 5-500 Hz. Correction factors to account for transverse strain and shear lag effects due to the bond layer are analytically derived and experimentally validated. The effect of temperature on the output of PZT strain sensors is investigated. Additionally, design of signal conditioning electronics to collect the signals from the piezoelectric sensors is addressed. The superior performance of piezoelectric sensors compared to conventional strain gages in terms of sensitivity and signal to noise ratio is demonstrated.
Investigation of Flammability for Alternative Mixtures in Air Conditioner and Refrigeration Systems
Authors: Zhao Yang , Yie Li , Zhengguo Zhang
Published: August 2002

There may be some fire accidents related to flammability during the running of some refrigerating system if leakages appear. Because the alternative mixtures in the systems may have leaked and changed their composition, some of them may have possibly become weakly flammable. The theoretical calculation results based on CSD equation have been achieved that have not previously been reported. There are two most dangerous leakage position points and a most dangerous operating condition for flammable mixtures in refrigerating and air conditioner systems. We have found the ways and criteria to evaluate them according to the behaviors of the mixtures to prevent the fire and explosion accidents.
Adenosine Triphosphate and Derivatives as Freshness Indicators of Gilthead Sea Bream (Sparus aurata)
Authors: Huidobro, A. , Pastor A. , Tejada M.
Published: August 2002

Intensive production of farmed gilthead sea bream ( Sparus aurata) and the different slaughtering methods and postmortem treatments are prompting a need for early indicators to determine fish quality during chilled storage. Adenosine-5 -triphosphate (ATP) and derivatives and their relationship as Kvalue were measured in chilled whole and gutted gilthead sea bream killed by immersion in ice water, asphyxia, anesthesia followed by a blow to the head, or a blow to the head. ATP derivatives taken independently were not found to be useful indicators for this species. The evolution of Kvalue was linear but attained lower final values than in other species. No significant differences were found in relation to the method of slaughter or postmortem treatment.
Predicting Fatigue Life of Composite Laminates Subjected to Tension-Tension Fatigue
Authors: Caprino G.
Published: August 2002

A recent two-parameter model, successfully employed to predict the flexural fatigue lifetime of randomly oriented glass fibre reinforced plastics, is applied to experimental data available in the literature, concerning carbon fibre reinforced plastic-laminates subjected to tension-tension fatigue. It is shown that the model accurately reproduces not only the classical S-N curve, but also the probability of failure under assigned loading conditions, if its constants are calculated by a minimum number of experimental tests. However, the results also demonstrated that the proposed method fails in describing the residual strength decay with cycle evolution, resulting in very conservative estimates. This was unexpected, because the formula for fatigue life directly derives from a precise assumption on the law governing the strength degradation. From the results presented, it is concluded that the model must be considered as an empirical formula, yet efficient in predicting fatigue life.