bluuebunny/crossref_metadata_2025_split huggingface dataset:
Honeybee navigation: distance estimation in the third dimension
Authors: Dacke M. , Srinivasan M. V. 
Published: February 2007

SUMMARY
Honeybees determine distance flown by gauging the extent to which the image of the environment moves in the eye as they fly towards their goal. Here we investigate how this visual odometer operates when a bee flies along paths that include a vertical component. By training bees to fly to a feeder along tunnels of various three-dimensional configurations, we find that the odometric signal depends only upon the total distance travelled along the path and is independent of its three-dimensional configuration. Hence, unlike walking desert ants, which measure the distance travelled in the horizontal plane whilst traversing undulating terrain, flying bees simply integrate the image motion that is experienced on the way to the goal, irrespective of the direction in which the image moves across the eyes. These findings raise important questions about how honeybee recruits navigate reliably to find the food sources that are advertised by scouts.
Response properties of primary afferents supplying Eimer's organ
Authors: Marasco Paul D. , Catania Kenneth C. 
Published: February 2007

SUMMARYThe mole's nose is covered with mechanosensory structures called Eimer's organs. Each organ contains Merkel cell-neurite complexes, Paciniform corpuscles and intraepidermal free nerve endings. The function of Eimer's organ has been the subject of speculation since the 1800s, but responses from the afferents have never been investigated. Our goal was to explore the function of Eimer's organ by recording primary afferent responses to a range of mechanosensory stimuli. Unit activity from the trigeminal ganglion was recorded from coast (Scapanus orarius) and star-nosed (Condylura cristata) moles, while stimulating the nose with a Chubbuck mechanosensory stimulator, a piezo-electric sweeping stimulator, and hand-held probes. Stimuli included static indentations, sinusoidal displacements,different indentation velocities, displacement amplitudes, and directional stimuli across the skin. Receptive fields were small, sometimes restricted to single Eimer's organs. Responses were consistent with a slowly adapting Merkel cell-neurite complex-like receptor class and a dynamically sensitive Pacinian-like rapidly adapting class. A second rapidly adapting class was hypothesized to represent activity of prominent free nerve endings within a central cell column. Some receptors were most sensitive to stimuli applied in particular directions across the skin. Most receptors relayed mechanosensory input with high temporal fidelity. In addition some receptors were tuned to respond best when stimulated at a velocity matching the velocity of the nose during foraging. These results support the hypothesis that Eimer's organ functions to detect small surface features and textures by encoding and integrating deflection information for multiple Eimer's organs during brief touches.
A computational investigation of the three-dimensional unsteady aerodynamics ofDrosophilahovering and maneuvering
Authors: Ramamurti Ravi , Sandberg William C. 
Published: February 2007

SUMMARYThree-dimensional unsteady computations of the flow past a fruit fly Drosophila under hovering and free flight conditions are computed. The kinematics of the wings and the body of the fruit fly are prescribed from experimental observations. The computed unsteady lift and thrust forces are validated with experimental results and are in excellent agreement. The unsteady aerodynamic origin of the time-varying yaw moment is identified. The differences in the kinematics between the right and the left wings show that subtle change in the stroke angle and deviation angle can result in the yaw moment for the turning maneuver. The computed yaw moment reaches a peak value at the beginning of the maneuver and remains positive throughout the remainder of the maneuver. The origin of the yaw moment is investigated by computing the center of pressures on each wing and the individual moment arms. This investigation leads to the conclusion that it is the forward force and a component of the lift force that combine to produce the turning moment while the side force alone produces the restoring torque during the maneuver. The vorticity shed from the wing's leading edge and the tips show a loop like structure that during stroke reversals pinches off into Λ-like structures that have not been previously observed in the wakes of flapping fliers.
Escape behavior and neuronal responses to looming stimuli in the crabChasmagnathus granulatus(Decapoda: Grapsidae)
Authors: Oliva Damián , Medan Violeta , Tomsic Daniel 
Published: February 2007

SUMMARYBehavioral responses to looming stimuli have been studied in many vertebrate and invertebrate species, but neurons sensitive to looming have been investigated in very few animals. In this paper we introduce a new experimental model using the crab Chasmagnathus granulatus, which allows investigation of the processes of looming detection and escape decision at both the behavioral and neuronal levels. By analyzing the escape response of the crab in a walking simulator device we show that: (i) a robust and reliable escape response can be elicited by computer-generated looming stimuli in all tested animals; (ii) parameters such as distance, speed, timing and directionality of the escape run, are easy to record and quantify precisely in the walking device; (iii) although the magnitude of escape varies between animals and stimulus presentations, the timing of the response is remarkably consistent and does not habituate at 3 min stimulus intervals. We then study the response of neurons from the brain of the crab by means of intracellular recordings in the intact animal and show that: (iv) two subclasses of previously identified movement detector neurons from the lobula (third optic neuropil) exhibit robust and reliable responses to the same looming stimuli that trigger the behavioral response; (v) the neurons respond to the object approach by increasing their rate of firing in a way that closely matches the dynamics of the image expansion. Finally, we compare the neuronal with the behavioral response showing that: (vi) differences in the neuronal responses to looming, receding or laterally moving stimuli closely reflect the behavioral differences to such stimuli; (vii) during looming, the crab starts to run soon after the looming-sensitive neurons begin to increase their firing rate. The increase in the running speed during stimulus approach faithfully follows the increment in the firing rate, until the moment of maximum stimulus expansion. Thereafter, the neurons abruptly stop firing and the animal immediately decelerates its run. The results are discussed in connection with studies of responses to looming stimuli in the locust.
Tracking of biogenic hydrodynamic trails in harbour seals (Phoca vitulina)
Authors: Schulte-Pelkum N. , Wieskotten S. , Hanke W. , Dehnhardt G. , Mauck B. 
Published: February 2007

SUMMARYFor seals hunting in dark and murky waters one source of sensory information for locating prey consists of fish-generated water movements,which they can detect using their highly sensitive mystacial vibrissae. As water movements in the wake of fishes can persist for several minutes,hydrodynamic trails of considerable length are generated. It has been demonstrated that seals can use their vibrissae to detect and track hydrodynamic trails generated artificially by miniature submarines. In the present study, we trained a harbour seal to swim predefined courses, thus generating biogenic hydrodynamic trails. The structure of these trails was measured using Particle Image Velocimetry. A second seal was trained to search for and track the trail after the trail-generating seal had left the water. Our trail-following seal was able to detect and accurately track the hydrodynamic trail, showing search patterns either mostly congruent with the trail or crossing the trail repeatedly in an undulatory way. The undulatory trail-following search pattern might allow a seal to relocate a lost trail or successfully track a fleeing, zigzagging prey fish.
Getting the jump on skeletal muscle disuse atrophy: preservation of contractile performance in aestivatingCyclorana alboguttata(Günther 1867)
Authors: Symonds Beth L. , James Rob S. , Franklin Craig E. 
Published: February 2007

SUMMARYProlonged immobilisation or unloading of skeletal muscle causes muscle disuse atrophy, which is characterised by a reduction in muscle cross-sectional area and compromised locomotory function. Animals that enter seasonal dormancy, such as hibernators and aestivators, provide an interesting model for investigating atrophy associated with disuse. Previous research on the amphibian aestivator Cyclorana alboguttata (Günther 1867)demonstrated an absence of muscle disuse atrophy after 3 months of aestivation, as measured by gastrocnemius muscle contractile properties and locomotor performance. In this study, we aimed to investigate the effect of aestivation on iliofibularis and sartorius muscle morphology and contractile function of C. alboguttata over a longer, more ecologically relevant time-frame of 9 months. We found that whole muscle mass, muscle cross-sectional area, fibre number and proportions of fibre types remained unchanged after prolonged disuse. There was a significant reduction in iliofibularis fibre cross-sectional area (declined by 36% for oxidative fibre area and 39% for glycolytic fibre area) and sartorius fibre density (declined by 44%). Prolonged aestivation had little effect on the isometric properties of the skeletal muscle of C. alboguttata. There was a significant reduction in the isometric contraction times of the relatively slow-twitch iliofibularis muscle, suggesting that the muscle was becoming slower after 9 months of aestivation (time to peak twitch increased by 25%, time from peak twitch to half relaxation increased by 34% and time from last stimulus to half tetanus relation increased by 20%). However, the results of the work-loop analysis clearly demonstrate that, despite changes to muscle morphology and isometric kinetics, the overall contractile performance and power output levels of muscles from 9-month aestivating C. alboguttata are maintained at control levels.
Light habitats and the role of polarized iridescence in the sensory ecology of neotropical nymphalid butterflies (Lepidoptera: Nymphalidae)
Authors: Douglas Jonathan M. , Cronin Thomas W. , Chiou Tsyr-Huei , Dominy Nathaniel J. 
Published: February 2007

SUMMARYThe exploitation of polarized light may increase perceived visual contrast independent of spectrum and intensity and thus have adaptive value in forest habitats, where illumination varies greatly in brightness and spectral properties. Here we investigate the extent to which Costa Rican butterflies of the family Nymphalidae exhibit polarized wing reflectance and evaluate the types of habitats in which the trait is commonly found. We also examine the degree of polarized reflectance of wing patterns in representative species belonging to the nymphalid subfamilies Charaxinae, Heliconiinae, Morphinae and Nymphalinae. Polarized reflectance was evaluated using museum specimens illuminated with a light source that simulated the spectrum of ambient sunlight and viewed through a polarized filter. Of the 144 species examined,75 species exhibited polarized reflectance patterns. These species were significantly more likely to occupy forest habitats than open habitats. A concentrated changes test performed on a phylogeny of the Nymphalidae, with the Papilionidae as an outgroup, provides further support for the correlated evolution of polarized iridescence and life in a forest light environment. These results are consistent with the hypothesis that the production and detection of polarized light may have adaptive communicative value in those species inhabiting forest habitats with complex light conditions. The potential utility of polarized iridescence and iridescent wing coloration within differing ambient spectral environments is discussed to provide a basis for future investigation of the polarized light ecology of butterflies.
Larval feeding duration affects ecdysteroid levels and nutritional reserves regulating pupal commitment in the yellow fever mosquitoAedes aegypti(Diptera: Culicidae)
Authors: Telang Aparna , Frame Laura , Brown Mark R. 
Published: February 2007

SUMMARYWhat little is known about the endocrine regulation of mosquito development suggests that models based on Lepidoptera and Drosophila may not apply. We report on basic parameters of larval development and the commitment to metamorphosis in the yellow fever mosquito Aedes aegypti that are affected by varying the length of feeding time for last instar larvae. A critical mass for pupal commitment was achieved after 24 h of feeding by last instars, also the age at which tissue production and hemolymph titers of ecdysteroids are increasing. A greater proportion of last instars successfully pupated and eclosed as adults as the length of their feeding time increased. Less than 24 h of feeding time resulted in last instars that were developmentally arrested; these larvae tolerated starvation conditions for up to 2 weeks and retained the capacity to pupate if re-fed. Starvation tolerance may be a common trait among container-inhabiting species, and this period is an important factor to be considered for vectorial capacity and control measures. To distinguish cues for metamorphosis related to a larva's nutritional status versus its age, newly molted last instars were fed for different periods of time but sampled at the same age; ecdysteroid levels,body mass and nutrient reserves were then measured for each group. Our data suggest that metamorphic capacity is dependent on a larva's nutritional condition and not just the age at which ecdysteroid titers increase. Last instars that have fed for a particular length of time may initiate their metamorphic molt when both threshold levels of nutrient reserves and ecdysteroid titer have been met. Future studies will lead to a conceptual model specific for the nutritional and hormonal regulation of mosquito post-embryonic development. This model should facilitate the exploitation of current and novel insect growth regulators that are among favored strategies for vector population suppression.
Quantitative Structure–Property Relationship Prediction of the Half-Wave Potential for Substituted Nitrobenzenes in Five Nonaqueous Solvents
Authors: Fatemi Mohammad Hossein , Hadjmohammadi Mohammad Reza , Kamel Kamyar , Biparva Poriya 
Published: February 2007

Abstract
Half-wave potentials (E1/2) are an important electrochemical property of organic compounds, which depends on both solute and solvent. In this work, a quantitative structure–property relationship (QSPR) study was carried out to predict the reduction E1/2 behavior of 15 substituted nitrobenzenes in five solvents, including acetonitrile, N,N-dimethylformamide, dimethyl sulfoxide, methanol, and tetrahydrofuran. For selection of the most relevant descriptors, a stepwise multiple linear regression (MLR) technique was used. Five descriptors that appeared in the MLR model were: minimum charges of the oxygen atom in the nitro group, Guttmann acceptor number of the solvent, dipole moment of solute, dipole moment of the solvent, and Hammet substitution constant (σ). The leave-one out cross validation method was used to evaluate the credibility of the model. Statistical parameters derived from this test are: R2 = 0.960, Q2 = 0.959, and SPREES = 0.046. These indicate the suitability of the constructed model.
Ab Initio and DFT Calculations on 2-Aminopyrimidine, 2-Amino-4,6-dichloropyrimidine, and Their Dimers
Authors: Hasanein Ahmed Abd El-gawad , Senior Samir Abd El-aziz 
Published: February 2007

Abstract
Optimum molecular geometries of 2-aminopyrimidine and 2-amino-4,6-dichloropyrimidine have been calculated by using MP2 and B3LYP methods with different extended basis sets. Dimer interactions for these two pyrimidine derivatives have been also investigated. Full geometry optimization at MP2 and B3LYP levels has been performed for the dimers. BSSE correction was made using the counterpoise method, and the H-bond energies have been calculated.
Synthesis, X-ray Structures, and Solution Properties of Vanadium(III) and -(IV) Complexes with N-(2-Hydroxyphenyl)-N-(2-pyridylmethyl)amine
Authors: Kanamori Kan , Kusajima Koji , Yachi Hiroyuki , Suzuki Honoh , Miyashita Yoshitaro , Okamoto Ken-ichi 
Published: February 2007

Abstract
New vanadium(III) and -(IV) complexes with N-(2-hydroxyphenyl)-N-(2-pyridylmethyl)amine (H2hppma) have been prepared, and their structures have been determined by X-ray crystallography. As for the vanadium(III) complex, the vanadium(III) center has a center of symmetry and adopts an ordinary octahedral structure, in which the H2hppma ligand coordinates as a monoanion (Hhppma) in a facial fashion. The vanadium(IV) complex with H2hppma has been determined to be an unusual non-oxo or bare vanadium(IV) complex. In this complex, the H2hppma ligand coordinates as a dianion (hppma) in a meridional fashion. Both complexes are fairly unstable in an aerobic solution and decompose to an oxovanadium(IV) complex.
Separation Characteristics of a Phosphatidylcholine-Coated ODS Column for Direct Sample Injection Analysis of Biological Fluid Samples
Authors: Hasegawa Takuya , Fukumoto Yasuharu , Ishise Jotaro , Hattori Ryota , Zhu Yanbei , Umemura Tomonari , Haraguchi Hiroki 
Published: February 2007

Abstract
An octadecylsilyl silica (ODS) column coated with phosphatidylcholine (PC) was prepared by using a dynamic coating method, and its separation characteristics were evaluated for direct sample injection analysis of biological fluids. First, fundamental separation behaviors of various kinds of large and small molecules/ions were examined by HPLC using the PC-coated ODS column with UV absorption detection, for which pure water was used as a mobile phase. In the experiments, proteins (large molecules) were rapidly eluted in the range of 2.07 min (dead time)–3.20 min, while small molecules, such as inorganic anions, amino acids, organic acids, and organic drugs, were eluted after 3.50 min. The fact that proteins and small molecules/ions were separated on the PC-coated ODS column suggested that the present column can be used for direct sample injection analysis of biological fluid samples, such as urine and blood serum. Thus, the PC-coated ODS column was used in the analysis of arsenic species in urine and in the analysis of nicotinamide, theophylline, tryptophan, and caffeine in a model blood serum solution without any sample pretreatment.
Morphology and Specific Surface Free Energies of Ruby Single Crystal Grown from Molybdenum Trioxide Flux Studied by Contact Angle of Liquid Droplets
Authors: Suzuki Takaomi , Iguchi Eiichi , Teshima Katsuya , Oishi Shuji 
Published: February 2007

Abstract
Contact angles of water and formamide droplets on a ruby crystal grown from MoO3 flux were determined. The specific surface free energies of the () and (0001) faces, calculated using the Fowkes approximation, were 48 ± 1 and 65 ± 1 mN m−1, respectively. The length of the normal lines from the center of the crystal to () and (0001) faces were 1.06 and 1.45 mm, respectively. The relationship between the specific surface free energy and the morphology of the crystal satisfies Wulff’s relationship.
1,1,4,4-Tetra(2-furyl, 2-thienyl, and 2-selenienyl)butatrienes: Synthesis, Properties, and Molecular Structures
Authors: Kurata Hiroyuki , Muro Seiji , Enomoto Tetsuya , Kawase Takeshi , Oda Masaji 
Published: February 2007

Abstract
Tetra(2-furyl, 2-thienyl, and 2-selenienyl)butatrienes and their derivatives have been prepared by dimerization of ate-type complexes derived from the corresponding 1,1-dichloro-2,2-diarylethenes using appropriate copper complexes in moderate to high yields. These new butatrienes are relatively stable crystalline substances with intense absorption bands at long wavelengths. The electronic properties of the substituents at the 5-position of aryl groups remarkably influence the wavelength of the longest absorption and the π-electron distribution of butatriene moiety. Their redox potentials, measured by cyclic voltammetry, have higher amphoteric redox properties than those of tetraphenylbutatriene. The crystal structures of tetrakis(5-trimethylsilyl)-substituted derivatives show the following two features: (1) the thiophene and selenole derivatives have pseudo-D2 structures, while the furan derivative has a C2 symmetric structure probably due to the counterbalance between the energy of conjugation and the nonbonded chalcogen–chalcogen interaction; (2) the central double bonds of these butatrienes are considerably short.
Photostimulated Crystal Lattice Change Induced by the Photochemical Ring-Opening Reaction of Diarylethene Molecules
Authors: Hamazaki Takuro , Matsuda Kenji , Kobatake Seiya , Irie Masahiro 
Published: February 2007

Abstract
Single crystals of the closed-ring isomer of the diarylethene derivative 1,2-bis(2-methyl-6-styryl-1-benzothiophen-3-yl)perfluorocyclopentene underwent a ring-opening reaction with high conversion while keeping their crystalline shape and transparency. Polar plots of the absorption anisotropy revealed that the closed-ring isomer in the crystal maintained an ordered alignment even at high conversion, and the transparency of the single crystal remained intact during photoreaction. X-ray crystal structural analysis showed that the length of the b axis of the unit cell increases as the photoreaction proceeds. The photostimulated crystal-lattice change is attributed to the rotational movement of the thiophene rings of the molecule during the photochemical ring-opening reaction.
Synthesis of Selenoketone–Platinum Complex
Authors: Shigetomi Toshiyuki , Shioji Kosei , Okuma Kentaro , Yokomori Yoshinobu 
Published: February 2007

Abstract
The synthesis of selenoketone–platinum complexes 3a–3c was achieved by reacting selenoketones 4 with (η2-ethylene)bis(triphenylphosphine)platinum(0) (1). 1,1,3,3-Tetramethylindan-2-selone–platinum complex 3b was determined by X-ray crystallographic analysis to be an η2-selenoketone–platinum complex. Interestingly, only one isomer of selenofenchone–platinum complex 3c was formed by this reaction.
Perrhenic Acid-Catalyzed Dehydration from Primary Amides, Aldoximes, N-Monoacylureas, and α-Substituted Ketoximes to Nitrile Compounds
Authors: Furuya Yoshiro , Ishihara Kazuaki , Yamamoto Hisashi 
Published: February 2007

Abstract
The dehydration reaction of primary amides is one of the most fundamental methods for the synthesis of nitriles, and the development of environmentally benign catalytic reaction processes is needed. We surveyed a variety of metal catalysts and found that perrhenic acid was extremely effective for the dehydration of not only primary amides but also aldoximes. Typically, 1 mol % of perrhenic acid gave the corresponding nitriles from amides or aldoximes under azeotropic reflux conditions with the removal of water in toluene or mesitylene. In addition, perrhenic acid is an extremely efficient catalyst for the Beckmann fragmentation of α-substituted ketoximes to functionalized nitriles. This new catalytic system can be applied to the gram-scale synthesis of nitriles without further modifications.