bluuebunny/crossref_metadata_2025_split huggingface dataset:
The serotoninergic system in Cryptomphalus aspersa. Immunocytochemical study with an anti‐5‐HT antiserum
Authors: Flores Vladimir , Brusco Alicia , Saavedra Jorge Pecci 
Published: May 2005

AbstractThis immunocytochemical study of 5‐HT neurons and fibers in the nervous system of C. aspersa corroborate previous findings and describe new 5‐HT neurons and their connections, mainly between the central nervous system and the tentacular sensory organs. We found a number of networks, fascicles, and neurons that show constant and symmetrical location. Three networks were found at the tip of the posterior tentacle: (1) underlying the olfactory epithelium, (2) in the neuropil of the tentacular ganglion (TG), and (3) in the ocular capsule. The TG also contains a ventral 5‐HT fascicle. A group of 30–40 serotoninergic fibers run through the tentacular connective from the postcerebrum to the tentacular ganglion. This 5‐HT fascicle has a lateral position in the postcerebrum (lateral fascicle of the postcerebrum) and a subcortical location in the procerebrum (subcortical fascicle of the procerebrum). The optic nerve also has a small group of 5‐HT fibers. Seven serotoninergic neurons were found in each cerebral ganglion: two giant neurons, one medium‐sized, and four small neurons. Three different types of fascicles are in the postcerebrum: (1) fascicles proceeding from the suboesophageal connectives, (2) a lateral fascicle, and (3) a commisural fascicle. Each cerebral ganglion region (pro‐, meso‐ and postcerebrum) has a 5‐HT network with a particular pattern of distribution and morphology. The suboesophageal ganglia show the highest concentration of 5‐HT neurons (large, medium‐size, and small neurons).
The kinematics of turnaround and retrograde axonal transport
Authors: Snyder R. E. 
Published: May 2005

AbstractRapid axonal transport of a pulse of 35S‐methionine‐labelled material was studied in vitro in the sensory neurons of amphibian sciatic nerve using a position‐sensitive detector. For 10 nerves studied at 23.0 ± 0.2°C it was found that a pulse moved in the anterograde direction characterized by front edge, peak, and trailing edge transport rates of (mm/d) 180.8 ± 2.2 (±SEM), 176.6 ± 2.3, and 153.7 ± 3.0, respectively. Following its arrival at a distal ligature, a smaller pulse was observed to move in the retrograde direction characterized by front edge and peak transport rates of 158.0 ± 7.3 and 110.3 ± 3.5, respectively, indicating that retrograde transport proceeds at a rate of 0.88 ± 0.04 that of anterograde. The retrograde pulse was observed to disperse at a rate greater than the anterograde. Reversal of radiolabel at the distal ligature began 1.49 ± 0.15 h following arrival of the first radiolabel. Considerable variation was seen between preparations in the way radiolabel accumulated in the end (ligature) regions of the nerve. Although a retrograde pulse was seen in all preparations, in 7 of 10 preparations there was no evidence of this pulse accumulating within less than 2–3 mm of a proximal ligature; however, accumulation was observed within less than 5 mm in all preparations.
Characterization and development of rotational behavior in Helisoma embryos: Role of endogenous serotonin
Authors: Diefenbach Thomas J. , Koehncke Niels K. , Goldberg Jeffrey I. 
Published: May 2005

AbstractCilia‐driven rotational behavior displayed by embryos of the pond snail Helisoma trivolvis was characterized in terms of its behavioral subcomponents, developmental changes, and response to exogenous serotonin. Rotation was found to be a complex behavior characterized by four parameters; rotational direction, rotation rate, rotational surges, and periods of inactivity. These parameters all exhibited characteristic developmental changes from embryonic stage E15 through stage E30. Notably, both rotation rate and frequency of rotational surges increased from stage E15 to E25 and declined to an intermediate level by stage E30. It appeared that the developmental increase in overall rotation rate was caused primarily by an increase in surge frequency, rather than an increase in the rate of nonsurge rotation. Immersion of embryos inserotonin‐containing pond water resulted in a dose‐dependent, reversible increase in rotation rate as well as a dose‐dependent, reversible decrease in surge frequency. The serotonin antagonist, mianserin, abolished the excitatory effect of exogenous serotonin. Furthermore, application of mianserin alone reduced rotation rate and virtually abolished rotational surges. Taken together, these pharmacological results suggest that endogenous serotonin is responsible for generating rotational surges. Given that early embryos contain only a single pair of serotonergic neurons (Goldberg and Kater, 1989) during the stages when rotational surges are expressed, these results also prompt the hypothesis that these neurons, embryonic neurons C1, act as cilioexcitatory motor neurons during embryonic development.
Nitric oxide and carbon monoxide as possible retrograde messengers in hgippocampal long‐term potentiation
Authors: Hawkins R. D. , Zhuo M. , Arancio O. 
Published: May 2005

AbstractWe have been investigating the hypothesis that the membrane‐permeant molecules nitric oxide (NO) and carbon monoxide(CO) may act as retrograde messengers during long‐term potentiation (LTP). Inhibitors of either NO synthase or heme oxygenase, the enzyme that produces CO, blocked induction of LTP in the CA1 region of hippocampal slices. Brief application of either NO or CO to slices produced a rapid and long‐lasting increase in the size of synaptic potentials if, and only if, the application occurred at the same time as weak tetanic stimulation of the presynaptic fibers. The long‐term enhancement by NO or CO was spatially restricted to synapses from active presynaptic fibers and appeared to involve mechanisms utilized by LTP, occluding the subsequent induction of LTP by strong tetanic stimulation. The enhancement by No or CO was not blocked by the NMDA receptor blocker APV, suggesting that NO and CO act downstream for the NMDA receptor. In other systems, both NO and CO produce many of their effects by activation of soluble guanylyl cyclase nd cGMP‐dependent protein kinase. An inhibitor of soluble guabylyl cyclase blocked the induction of normal LTP. Conversely, membrane‐permeabel analog 8‐Br‐cGMP produced a rapid onset and long‐lasting synaptic enhancement if, and only if, it was applied at the same time as weak presynaptic stimulation. Similarly, two inhibitors of cGMP‐dependent protein kinase blocked the induction of normal LTP, and a selective activator of cGMP‐dependent protein kinase produced activity‐dependent long‐lasting synaptic enhancement. 8‐Br‐cGMP also produced and activity‐dependent, long‐lasting increase in the amplitude of evoked synaptic current between pairs of hippocampal neurons in dissociated cell culture. In addition, 8‐Br‐cGMP, like NO, produced a long‐lasting increase in the frequency of spontaneous miniature synaptic currents. These results are consistent with the hypothesis that NO and CO, either alone or in combination, serve as retrograde messengers that produce activity‐dependent presynaptic enhancement, perhaps by stimulating soluble guanbylyl cyclase and cGMP‐dependent protein kinase, during LTP in hippocampus. 1994 John Wiley & Sons, Inc.
The negative ion mass spectra of mixtures of sulphur and organic compounds. II—the formation of [C5H5 + Sn]− from the mixture of sulphur and ferrocene
Authors: Hirata Yukio , Matsumoto Kozo , Takeuchi Tsugio 
Published: May 2005

AbstractThe negative ion mass spectra of ferrocene and of a mixture of ferrocene with sulphur were studied. In the spectrum of the mixture, characteristic peaks of [C5H5 + Sn]− (n = 1, 2, 3 etc.) were observed. The structures of these ions are discussed.
Mass spectrometry of some triphenylcyclopropenium salts. Competition between dimerisation and adduct formation
Authors: Györösi Peter , Hvistendahl Georg , Undheim Kjell 
Published: May 2005

AbstractThe triphenylcyclopropenium chloride, bromide and iodide evaporate in the mass spectrometer mainly as the covalent cation‐halide adduct, the fluoroborate as the corresponding fluoride adduct and boron trifluoride. In addition di‐3,3′‐triphenylcyclopropene is formed, presumably via triphenylcyclopropenyl radicals.
Dual mechanisms for the fragmentation of 1‐benzoylbenzotriazole upon electron impact
Authors: Yamada Shuzo , Kamiyama Yojiro , Ohashi Mamoru 
Published: May 2005

AbstractThe electron impact induced fragmentation of 1‐benzoylbenzotriazole has been studied by 13C labelling experiments. It has been found that the loss of CO from the [M  N2]+˙ ions proceeds by two routes; about 78% of the ions decompose via the molecular ions of the corresponding thermal fragmentation product, 2‐phenylbenzoxazole, and 22% via those of the corresponding photochemical fragmentation product, 6‐phenanthridone.
Mass spectral rearrangements of N,N‐bis(4′‐arylthio‐2′‐butynyl)anilines and N,N‐bis(4′‐arylsulfonyl‐2′‐butynyl)anilines
Authors: Thyagarajan B. S. , Glaspy Phillip E. , Brown Peter 
Published: May 2005

AbstractThe title compounds display unusual modes of fragmentation under electron impact. One of the dominant modes is the concerted elimination of the two arylthio and arylsulfonyl moieties followed by further extrusion of the C6H4 unit as a cumulene. No elimination of SO2 is observed from any of the sulfones nor an expulsion of the C4H4 fragment. Such behavior contrasts strikingly with that of 1,4‐diarylsulfonyl‐2‐butynes and of the 1,6‐diarylsulfonyl‐2,4‐hexadiynes.
Fast atom bombardment mass spectra of involatile monophosphonated and mixed sulphonated/monophosphonated azo dyestuffs
Authors: Monaghan John J. , Barber Michael , Bordoli Robert S. , Sedgwick R. Donald , Tyler Andrew N. 
Published: May 2005

AbstractFast atom bombardment mass spectra of a range of involatile monophosphonated and mixed sulphonated/monophosphonated azo dyestuffs are presented. Good spectra are obtained and the fragmentations are discussed with special reference to the ions formed by cleavage of the azo linkage. The negative ion spectra are shown to be superior in terms of signal to background and structural information to those obtained in the positive ion mode. The results are compared with those obtained from sulphonated azo dyestuffs.
Photodissociation of gaseous [C4H5N]+˙ ions
Authors: Weger E. , Brand W. A. , Levsen K. 
Published: May 2005

AbstractThe photodissociation of [C4H5N]+˙ ions generated by ionization of pyrrole (1), allyl cyanide (2), crotonitrile (3), cyclopropyl cyanide (4) and methacrylonitrile (5) has been studied using ion beam techniques. At least four different stable ion structures have been distinguished, which is in contrast to earlier CAD studies. In addition it has been shown that [C2H3N]+˙ fragment ions formed by dissociative ionization of the same precursors have structures which are distinct from that of ionized acetonitrile.
Mass spectra of 17ξ‐hydroxy‐5ξ‐androstane C(3) ketone and C(3ξ) alcohol isomers
Authors: Jackson Chung‐Ja Choi , Templeton John F. , Reimer Mark L. J. , Westmore John B. 
Published: May 2005

AbstractPositive ion electron impact mass spectral data for the four isomeric 17ξ‐hydroxy‐17ξ‐methyl‐5ξ‐androstane C(3) ketones and the eight isomeric C(3ξ) alcohols are reported. In contrast to earlier reports, no general correlation was observed between the [MH2O]+˙/[M]+˙ ratio and the configuration at C(17). The ratios of the intensity of several fragment ions to that of the molecular ion do differentiate between the 5α‐ and 5β‐isomers in both C(3) ketones and alcohols, the extent of fragmentation being greater for 5β‐steroids. All of these fragments probably involve elimination of a water molecule at some stage in their formation. Elimination of water is also enhanced for 3α‐ v. 3β‐hydroxysteroids, particularly in a 5β‐isomer.
The question of cyclic versus acyclic ions: The structure of [C10H12]+˙ gas phase ions
Authors: Dass Chhabil , Gross Michael L. 
Published: May 2005

AbstractThe extent of isomerization of acyclic and cyclic gas phase radical cations of composition [C10H12]+˙ has been investigated by using collisionally activated dissociation spectroscopy. Both electron and charge exchange ionizaiton were employed to form the ions with various internal energies. The [C10H12]+˙ ions investigated consisted of ionized phenylbutenes, ring‐substituted methyl derivatives of allylbenzene and phenylpropene, 1‐methyl‐2‐isopropenylbenzene, benzylcyclopropane, phenylcyclobutane, tetralin and 1‐methylindan. The 1‐methylindan and tetralin radical cations are the most stable of the C10H12 isomeric radical ions. The [C10H12]+˙ formed from acyclic olefins having the double bond in conjugation with the aromatic ring retain the initial structure to a significant extent. However, ions derived from olefins with the double bond out of conjugation with the benzene ring preferentially cyclize to stable five‐ and six‐membered cyclic ions. Ring opening of small‐ring cyclic ions, such as ionized benzylcyclopropane and phenylcyclobutane, occurs, followed by ring closure to the tetralin radical cation.
Adduct ion formation by metal complexes under methane negative chemical ionization conditions
Authors: Dillow G. W. , Gregor I. K. , Guilhaus M. 
Published: May 2005

AbstractNegative chemical ionization mass spectrometry is used as a probe to examine reactions between hydrocarbon radicals and metal complexes in the gas phase. The methane negative chemical ionization mass spectra of 27 complexes of cobalt(II), nickel(II) and copper(II) in the presence of O4, O2N2 and N4 donor atom sets are characterized by two dominant series of adduct ions of the form [M + CnH2n]− and [M + CnH2n+1]− at m/z values above the molecular ion, [M]−. Insertion of the CH radical into the ligand followed by radical/radical recombination and electron capture is proposed as the major mechanism leading to the formation of [M + CnH2n]− adduct ions. A second pathway involves ligand substitution by CnH2n+1 radicals concomitant with H elimination and electron capture. Oxidative addition at the metal followed by ionization is suggested as the principal pathway for the formation of [M + CnH2n+1]− adduct ions.
Does the dieckmann condensation occur in the gas phase?
Authors: Raftery Mark J. , Bowie John H. 
Published: May 2005

AbstractBurinsky and Cooks1 have reported that deprotonated dimethyl adipate eliminates methanol via a gas‐phase Dieckmann condensation. This is in contrast to the behaviour of simple methyl ester enolates which lose MeOH by a different mechanism, e.g. MeOCOC̄HCH2R → [MeO(OCCHCH2R)] → OCCHC̄HR + MeOH. Evidence is presented which supports the Dieckmann mechanism for adipates. For example, MeOCOC̄(Me)CH2CH2CD(Me)CO2Me should eliminate MeOD in a Dieckmann condensation, but MeOH by the alternative mechanism outlined above. Experimentally, MeOD is lost exclusively. Similarly, MeOCOC̄DCH2CH2C(Me)2CO2Me also loses MeOD, consistent with a Dieckmann process.
Ring opening of the molecular ion of 5(4H)‐oxazolone
Authors: Császár Attila G. , Somogyi Árpád , Pócsfalvi Gabriella , Traldi Pietro 
Published: May 2005

AbstractQuantum chemical calculations were carried out at several theoretical levels (semi‐empirical, MNDO; ab initio, 3–21G SCF, 6–311G** SCF and DZP CISD) to investigate the ring‐opening process of and the loss of CO from the molecular ion of 5(4H)‐oxazolone. The ring‐opening process is predicted to be slightly endothermic and the loss of CO from the open‐ring molecular ion to be slightly exothermic. Detailed population analysis calculations suggest the weakening of the lactonic CO bond in the closed‐ring molecular ion and weak carbon—carbon and nitrogen—(formy)—carbon bonds in the open form. Both the open‐ring molecular ion and the [M–CO]+· ion are suggested to be of distonic type.
The viscoelastic behavior of the principal compliance matrix of a unidirectional graphite/epoxy composite
Authors: Morris D. H. , Brinson H. F. , Yeow Y. T. 
Published: May 2005

AbstractA testing program was conducted to determine the time‐temperature response of the principal compliances of a unidirectional graphite/epoxy composite. It is shown that two components of the compliance matrix are time and temperature independent. In addition, the compliance matrix is found to be symmetric for the viscoelastic composite. The time‐temperature superposition principle is used to determine shift factors. It is shown that shift factors are independent of fiber orientation for fiber angles that vary from 10 to 90° with respect to the load direction.
Improved epoxy‐amine matrices for composites
Authors: McLean P. D. , Garton A. , Stevenson W. T. K. , Macphee K. E. 
Published: May 2005

AbstractThe physical and mechanical properties of epoxy‐amine matrices can be improved by the use of additives known as epoxy fortifiers. The tensile strength of a typical aminecured epoxy increased from 82 MPa to 123 MPa, the tensile modulus form 2.5 GPa to 4.1 GPa, and the tensile test specimens also failed in a ductile fashion. The improvements in matrix properties translated into improved performance for filament‐wound and cloth‐reinforced composites. For example, the transverse moduli and compression strengths of carbon fiber/epoxy filament‐wound tubes and plates increased at least 20 percent with the addition of fortifiers, while the compression strength of glass cloth/epoxy laminates increased by up to 41 percent.
Blends containing liquid crystalline polymers: Preparation and properties of melt‐drawn fibers, unidirectional prepregs, and composite laminates
Authors: Dutta D. , Weiss R. A. , Kristal K. 
Published: May 2005

AbstractThis paper discusses the effect of melt drawing on the mechanical properties and morphology of liquid crystalline polymer (LCP) and thermoplastic polymer blends. Extruded fibers and films of LCP/polymer blends were melt drawn to develop uniaxial orientation of the dispersed LCP phase. The longitudinal modulus increased with increasing draw. The increase in modulus was due to higher aspect ratio of the LCP fibrils and improved molecular orientation of the LCP chains within the fibrils. Laminated composites were prepared using the extruded sheets as prepregs. The mechanical properties and the coefficient of thermal expansion (CTE) of the prepreg and the laminates agreed well with predictions from conventional composite lamination theories.
Thermodynamic behavior of solid polymers in uniaxial deformation
Authors: Lyon R. E. , Farris R. J. 
Published: May 2005

AbstractThe heat and work of uniaxial deformation were measured for two commercial polyurethane elastomers and a low density polyethylene using a new deformation calorimeter. Internal energy changes in the materials resulting from deformation were calculated from the difference between the heat and work according to the first law of thermodynamics. The elastomers were found to exhibit complete reversibility for small and large strain deformation cycles as determined from the absence of a permanent internal energy change, even though one of these undergoes strain‐induced crystallization and melting. The low density polyethylene behaves irreversibly even at small strains, and will store 30 percent of the deformation work as internal energy during drawing at room temperature.
Statistical entropy model for relaxation in stressed polymer glasses
Authors: Chow T. S. 
Published: May 2005

AbstractThe molecular kinetic theory near the glass transition, bused on the existence of free volume distribution, is extended to incorporate the effects of stress and stress rate. The fundamental equations for the volume relaxation and recovery in stressed amorphous polymers are derived in accordance with the balance of nonequilibrium statistical entropy. Using these kinetic equations, an earlier nonequilibrium criterion for the glass transition temperature, Tg, is generalized to include the effects of stress and stress rate. In contrast to the prevalent thinking toward free volume theories, an explicit expression between Tg and stress is developed and reveals that Tg does not continue to increase at all pressures but levels off to a “universal” asymptote at very high pressure (>10 K bars). The expression is applicable to any tension and compression stress conditions. A comparison between theory and experiment under constant stresses determines the activation volume tensor which reveals the molecular mechanism relating Tg and the plastic yield of glassy polymers.
A simple model of nonisothermal coextrusion
Authors: Nordberg M. E. , Winter H. H. 
Published: May 2005

AbstractA numerical method has been developed that takes the streamline finite difference method for modeling fully developed multilayer polymer flows and adds to it a simple means of accounting for nonisothermal conditions. In industrial practice, temperature control is often used to match material viscosities and, thereby, to avoid flow instabilities. By numerically calculating both viscosity ratios and normal stress difference ratios, the numerical method allows one to judge the relative stability of different flows and to choose an intelligent set of experiments when designing a coextrusion process. The algorithm has been successfully tested for a number of polymer melt constitutive equations in flows where the viscosity jumps no more than two orders of magnitude between fluids. Results for a rheologically well characterized polystyrene low‐density polyethylene system and for an industrially interesting high‐density polyethylene/Ultem system show that the common practice of matching zero‐shear viscosities is overly simplistic when interface shear rate, conduction, normal stress, and flow rate effects are taken into account.
Structural analysis and electrical properties of halogen substituted poly(paraphenylene)
Authors: Mertens R. , Krikor H. , Nagels P. , Callaerts R. , Remaut G. 
Published: May 2005

AbstractPoly(tetrafluoro‐p‐phenylene) was prepared by the modified Ullmann reaction. The average degree of polymerization was determined from electron impact mass spectrometry and was found to be n = 8. The structure of the polymer was studied using infrared, Raman, ultraviolet absorption spectroscopy and differential scanning calorimetry. Polymerization of 1,4‐diiodo‐2,3,5,6‐tetrafluorobenzene resulted in the disappearance of the characteristic C‐I vibrations and the appearance of new absorption bands in the infrared and Raman spectra. At room temperature poly(tetrafluorophenylene) is an insulator. Attempts to increase the dc conductivity on FeCl3 and sodium doping were unsuccessful until now.
Critical review of the molecular topology of semicrystalline polymers: The origin and assessment of intercrystalline tie molecules and chain entanglements
Authors: Seguela Roland 
Published: May 2005

AbstractIntercrystalline molecular connections in semicrystalline polymers have been the subject of numerous discussions and controversies. Nevertheless, there is one point of agreement: such intercrystalline tie molecules have a prime role in the mechanical and use properties of the materials, notably the resistance to slow crack growth. This article is a critical review of the mechanisms of generation of the tie molecules during the stage of crystallization and of the experimental and theoretical assessment of their concentration. Polyethylene and related materials are mainly studied. The contribution of chain entanglements is also discussed in parallel with tie molecules. Particular attention is paid to Huang and Brown's statistical approach, which appears to be the most appropriate one for predictive purposes and has aroused much interest from various authors. Attempts are made to provide solutions to the shortcomings of this model. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 1729–1748, 2005