bluuebunny/crossref_metadata_2025 huggingface dataset:
Ultramafic-Rock-Hosted Vein Sepiolite Occurrences in the Ankara Ophiolitic Mélange, Central Anatolia, Turkey
Authors: Yalçin Hüseyin , Bozkaya Ömer
Published: April 2004

A 2 m thick brecciated zone containing magnesian minerals is present at the contact of tectonites and cumulates. Tectonites below this zone comprise serpentinized orthopyroxenite and serpentinite. An alteration zone with vein-type bedding comprises four different levels; from bottom to top they are: (1) green-brown serpentinite with dolomite (0.9 m), (2) light greenish-white dolomite with serpentine (0.5 m), (3) white dolomite with sepiolite (0.4 m), and (4) greenish-white dolomite with smectite-chlorite (0.2 m). The first level has a mineral association of serpentine + dolomite ± calcite ± aragonite, the second level consists of dolomite + serpentine ± calcite or dolomite + magnesite + serpentine, the third level comprises dolomite + sepiolite, and the fourth level is made up of dolomite + chlorite + smectite + serpentine. Dolomite, the main mineral of the alteration zone, occurs as coarse crystals (microsparitic-sparitic) in fractures and as small crystals (microsparitic-micritic) in the matrix, which includes serpentine and gabbro relics. Sepiolite developed at the edges and surfaces of dolomite and as fibrous forms in voids. Cumulate rocks above this zone comprise uralitic gabbros. The occurrences of magnesian minerals developed in three stages: the first stage was the serpentinization of olivine; the second stage was the dissolution of serpentine by groundwater and/or meteoric water containing carbon dioxide; and the last stage was the synthesis of neoformed minerals.
Synthesis of Birnessite from the Oxidation of Mn2+ by O2 in Alkali Medium: Effects of Synthesis Conditions
Authors: Feng Xiong Han , Liu Fan , Tan Wen Feng , Liu Xiang Wen
Published: April 2004

An O2 oxidation and freeze-dry procedure has been used to synthesize birnessite through the oxidation of Mn2+ in alkali media. The effects of O2 flow rate, the fluxion velocity of reaction suspension, the reaction temperature, pretreatment the reaction solutions with N2, and the hydration conditions on the purity of birnessite, the crystallinity, the ion-exchange properties, and the phase transformation of intermediate phases were examined. Buserite with a 1 nm basal spacing, produced after the oxidation, is transformed to 0.7 nm Na birnessite by complete freeze drying. Increasing the fluxion velocity of the reaction suspension and the O2 flow rate facilitated oxidation of Mn(OH)2. Prephase I (a phase related to hausmannite, γ-Mn3O4 (Luo and Suib, 1997; Luo et al., 1998), and feitknechtite (β-MnOOH) were formed as intermediates during the synthesis. Mechanical stirring was used to change the fluxion velocity of the reactive suspension. When the speed of stirring and the O2 flow rate were raised to 250 rpm and 3.0 L/min, respectively, or 450 rpm and 2.0 L/min, respectively, birnessite was the only phase in the final product. Irrespective of temperature in other reactions, pure birnessite was synthesized as long as the temperature during the initial mixing of the reaction solutions was maintained below 10°C. Increasing the reaction temperature led to a larger crystal size, better crystallinity and lower surface area. The pretreatment of solutions with N2 or O2 had little effect on the synthesis; synthesized birnessites had the same purity (100%) as, and similar crystallinity to, that of the no-pretreatment control. Dehydration of the buserite by freeze drying and heating at 60°C did not affect the production of birnessite; however, the latter caused partial loss of ion-exchange capacity with Mg2+. The pathways of the birnessite formation in this study might be:

(1)

Mn(OH)2 (amorphous) → feitknechtite → buserite → birnessite, and

(2)

Mn(OH)2 (amorphous) → prephase I → feitknechtite → buserite → birnessite

Mn(OH)2 existed in an X-ray amorphous state, not in the form of ‘pyrochroite’, during the synthesis.

The adopted conditions for synthesis of pure birnessite were NaOH to Mn molar ratio of 13.7, O2 flow rate of 2 L/min and oxidation for 5 h during vigorous stirring at 450 rpm at room temperature. The birnessite synthesized had a hexagonal platy morphology with good crystallinity, an average composition of Na0.25MnO2.07.0.66H2O, and a surface area of 38 m2/g.
A strategy for strengthening participatory technology development in agricultural and natural resources innovations systems: the case of Nepal
Authors: Gauchan D. , Joshi M. , Biggs S.
Published: April 2004

The underlying features of agricultural and natural resource research and technology systems operating in low-income countries have changed over the last couple of decades. New actors have emerged in the form of non-governmental and community-based organisations and private-sector agro-entrepreneurs
to take part in agricultural technology development and promotion - an area of activity which was generally the preserve of public institutions. This has resulted in the development of alternative institutional models for participatory technology development that involve new types of linkages
between actors. The shift of paradigm in the conceptualisation of agricultural and natural resource innovation systems has been occasioned by, amongst other things, changes in partner/client relationships and funding sources and mechanisms for science and technology systems at local, national
and international levels. Set against this background, the paper explores issues that the Nepal Agricultural Research Council (NARC) would need to consider while drawing up and developing new strategies for participatory technology development in Nepal.
Tonically Active Neurons in the Primate Caudate Nucleus and Putamen Differentially Encode Instructed Motivational Outcomes of Action
Authors: Yamada Hiroshi , Matsumoto Naoyuki , Kimura Minoru
Published: April 2004

To achieve a goal, animals procure immediately available rewards, escape from aversive events, or endure the absence of rewards. The neuronal substrates for these goal-directed actions include the limbic system and the basal ganglia. In the striatum, tonically active neurons (TANs), presumed cholinergic interneurons, were originally shown to respond to reward-associated stimuli and to evolve their activity through learning. Subsequent studies revealed that they also respond to aversive event-associated stimuli such as an airpuff on the face and that they are less selective to whether the stimuli instruct reward or no reward. To address this paradox, we designed a set of experiments in which macaque monkeys performed a set of visual reaction time tasks while expecting a reward, during escape from an aversive event, and in the absence of a reward. We found that TANs respond to instruction stimuli associated with motivational outcomes (312 of 390; 80%) but not to unassociated ones (51 of 390; 13%), and that they mostly differentiate associated instructions (217 of 312; 70%). We also found that a higher percentage of TANs in the caudate nucleus respond to stimuli associated with motivational outcomes (118 of 128; 92%) than in the putamen (194 of 262; 74%), whereas a higher percentage of TANs in the putamen respond to go signals for the lever release (112 of 262; 43%) than in the caudate nucleus (27 of 128; 21%), especially for an action expecting a reward. These findings suggest a distinct, pivotal role of TANs in the caudate nucleus and putamen in encoding instructed motivational contexts for goal-directed action planning and learning.
Survival of Developing Motor Neurons Mediated by Rho GTPase Signaling Pathway through Rho-Kinase
Authors: Kobayashi Kenta , Takahashi Masanori , Matsushita Natsuki , Miyazaki Jun-ichi , Koike Masato , Yaginuma Hiroyuki , Osumi Noriko , Kaibuchi Kozo , Kobayashi Kazuto
Published: April 2004

A variety of neurons generated during embryonic development survive or undergo programmed cell death (PCD) at later developmental stages. Survival or death of developing neurons is generally considered to depend on trophic support from various target tissues. The small GTPase Rho regulates diverse cellular processes such as cell morphology, cell adhesion, cell motility, and apoptosis. Rho-dependent serine–threonine protein kinase (Rho-kinase–ROK–ROCK), one of the effector proteins, transmits signals for some Rho-mediated processes. Here, we report thein vivorole of the Rho signaling pathway through Rho-kinase during development of motor neurons (MNs) in the spinal cord. We performed conditional expression of a dominant-negative form for RhoA (RhoA DN) or for Rho-kinase (Rho-K DN) in transgenic mice by using the Cre-loxPsystem to suppress the activity of these signaling molecules in developing MNs. Expression of RhoA DN reduced the number of MNs in the spinal cord because of increased apoptosis while preserving the gross patterning of motor axons. Expression of Rho-K DN produced developmental defects similar to those observed in RhoA DN expression. In addition, analysis of transgenic mice expressing Rho-K DN showed that the increased apoptosis of MNs was induced at the early embryonic stages before the initiation of PCD, and that MN death at the late embryonic stages corresponding to the period of PCD was moderately enhanced in the transgenic mice. These findings indicate that the Rho signaling pathway, primarily through Rho-kinase, plays a crucial role in survival of spinal MNs during embryogenesis, particularly at the early developmental stages.
Cognitive Correlates of White Matter Growth and Stress Hormones in Female Squirrel Monkey Adults
Authors: Lyons David M. , Yang Chou , Eliez Stephan , Reiss Allan L. , Schatzberg Alan F.
Published: April 2004

Neurobiological studies of stress and cognitive aging seldom consider white matter despite indications that complex brain processes depend on networks and white matter interconnections. Frontal and temporal lobe white matter volumes increase throughout midlife adulthood in humans, and this aspect of aging is thought to enhance distributed brain functions. Here, we examine spatial learning and memory, neuroendocrine responses to psychological stress, and regional volumes of gray and white matter determined by magnetic resonance imaging in 31 female squirrel monkeys between the ages of 5 and 17 years. This period of lifespan development corresponds to the years 18–60 in humans. Older adults responded to stress with greater increases in plasma levels of adrenocorticotropic hormone and modest reductions in glucocorticoid feedback sensitivity relative to young adults. Learning and memory did not differ with age during the initial cognitive test sessions, but older adults more often failed to inhibit the initial learned response after subsequent spatial reversals. Impaired cognitive response inhibition correlated with the expansion of white matter volume statistically controlling for age, stress hormones, gray matter, and CSF volumes. These results indicate that instead of enhancing cognitive control during midlife adulthood, white matter volume expansion contributes to aspects of cognitive decline. Cellular and molecular research combined with brain imaging is needed to determine the basis of white matter growth in adults, elucidate its functions during lifespan development, and provide potential new targets for therapies aimed at maintaining in humans cognitive vitality with aging.
SKCaChannels Mediate the Medium But Not the Slow Calcium-Activated Afterhyperpolarization in Cortical Neurons
Authors: Villalobos Claudio , Shakkottai Vikram G. , Chandy K. George , Michelhaugh Sharon K. , Andrade Rodrigo
Published: April 2004

Many neurons, including pyramidal cells of the cortex, express a slow afterhyperpolarization (sAHP) that regulates their firing. Although initial findings suggested that the current underlying the sAHP could be carried through SKCachannels, recent work has uncovered anomalies that are not congruent with this idea. Here, we used overexpression and dominant-negative strategies to assess the involvement of SKCachannels in mediating the current underlying the sAHP in pyramidal cells of the cerebral cortex.

Pyramidal cells of layer V exhibit robust AHP currents composed of two kinetically and pharmacologically distinguishable currents known as the medium AHP current (ImAHP) and the slow AHP current (IsAHP).ImAHPis blocked by the SKCachannel blockers apamin and bicuculline, whereasIsAHPis resistant to these agents but is inhibited by activation of muscarinic receptors. To test for a role for SKCachannels, we overexpressed KCa2.1 (SK1) and KCa2.2 (SK2), the predominant SKCasubunits expressed in the cortex, in pyramidal cells of cultured brain slices. Overexpression of KCa2.1 and KCa2.2 resulted in a fourfold to fivefold increase in the amplitude ofImAHPbut had no detectable effect onIsAHP. As an additional test, we examinedIsAHPin a transgenic mouse expressing a truncated SKCasubunit (SK3-1B) capable of acting as a dominant negative for the entire family of SKCa–IKCachannels. Expression of SK3-1B profoundly inhibitedImAHPbut again had no discernable effect onIsAHP. These results are inconsistent with the proposal that SKCachannels mediateIsAHPin pyramidal cells and indicate that a different potassium channel mediates this current.
Intermediate-Term Memory for Site-Specific Sensitization inAplysiaIs Maintained by Persistent Activation of Protein Kinase C
Authors: Sutton Michael A. , Bagnall Martha W. , Sharma Shiv K. , Shobe Justin , Carew Thomas J.
Published: April 2004

Recent studies of long-term synaptic plasticity and long-term memory have demonstrated that the same functional endpoint, such as long-term potentiation, can be induced through distinct signaling pathways engaged by different patterns of stimulation. A critical question raised by these studies is whether different induction pathways either converge onto a common molecular mechanism or engage different molecular cascades for the maintenance of long-term plasticity. We directly examined this issue in the context of memory for sensitization in the marine molluskAplysia. In this system, training with a single tail shock normally induces short-term memory (<30 min) for sensitization of tail-elicited siphon withdrawal, whereas repeated spaced shocks induce both intermediate-term memory (ITM) (>90 min) and long-term memory (>24 hr). We now show that a single tail shock can also induce ITM that is expressed selectively at the trained site (site-specific ITM). Although phenotypically similar to the form of ITM induced by repeated trials, the mechanisms by which site-specific ITM is induced and maintained are distinct. Unlike repeated-trial ITM, site-specific ITM requires neither protein synthesis nor PKA activity for induction or maintenance. Rather, the induction of site-specific ITM requires calpain-dependent proteolysis of activated PKC, yielding a persistently active PKC catalytic fragment (PKM) that also serves to maintain the memory in the intermediateterm temporal domain. Thus, two unique forms of ITM that have different induction requirements also use distinct molecular mechanisms for their maintenance.
Optical Quantal Analysis Indicates That Long-Term Potentiation at Single Hippocampal Mossy Fiber Synapses Is Expressed through Increased Release Probability, Recruitment of New Release Sites, and Activation of Silent Synapses
Authors: Reid Christopher A. , Dixon Don B. , Takahashi Michiko , Bliss Tim V. P. , Fine Alan
Published: April 2004

It is generally believed that long-term potentiation (LTP) at hippocampal mossy fiber synapses between dentate granule and CA3 pyramidal cells is expressed through presynaptic mechanisms leading to an increase in quantal content. The source of this increase has remained undefined but could include enhanced probability of transmitter release at existing functional release sites or increases in the number of active release sites. We performed optical quantal analyses of transmission at individual mossy fiber synapses in cultured hippocampal slices, using confocal microscopy and intracellular fluorescent Ca2+indicators. Our results indicate that LTP is expressed at functional synapses by both increased probability of transmitter release and recruitment of new release sites, including the activation of previously silent synapses here visualized for the first time.
Direct Interaction of Adenosine with the TRPV1 Channel Protein
Authors: Puntambekar Preeti , Van Buren Jeremy , Raisinghani Manish , Premkumar Louis S. , Ramkumar Vickram
Published: April 2004

Vanilloid receptor 1 (TRPV1), a nonspecific cation channel expressed primarily in small sensory neurons, mediates inflammatory thermal pain sensation. The function and expression of TRPV1 are enhanced during inflammation and certain neuropathies, leading to sustained hyperalgesia. Activation of TRPV1 in the spinal cord and periphery promotes release of adenosine, which produces analgesia by activating A1and A2Aadenosine receptor (AR) on central and peripheral neurons. This study provides evidence of a direct interaction of AR analogs with TRPV1. Adenosine analogs inhibit TRPV1-mediated Ca2+entry in human embryonic kidney (HEK293) cells stably expressing TRPV1 (HEK/TRPV1) and DRG neurons. This inhibition was independent of A2AAR activation. Specific binding of [3H]resiniferatoxin (RTX) in plasma membrane preparations was inhibited byCGS21680, an A2AAR agonist. Similar degrees of inhibition were observed with both agonists and antagonists of ARs. Adenosine analogs inhibited [3H]RTX binding to affinity-purified TRPV1, indicative of a direct interaction of these ligands with the receptor. Furthermore, specific capsaicin-sensitive binding of [3H]CGS21680 was observed inXenopusoocyte membranes expressing TRPV1. Capsaicin-induced inward currents in DRG neurons were inhibited by adenosine and agonist and antagonist of A2AAR at nanomolar concentrations. Increasing the concentrations of capsaicin reversed the inhibitory response to capsaicin, suggesting a competitive inhibition at TRPV1. Finally, exposure of HEK/TRPV1 cells to capsaicin induced an ∼2.4-fold increase in proapoptotic cells that was abolished by adenosine analogs. Together, these data suggest that adenosine could serve as an endogenous inhibitor of TRPV1 activity by directly interacting with the receptor protein.
Perirhinal Cortex Supports Delay Fear Conditioning to Rat Ultrasonic Social Signals
Authors: Lindquist Derick H. , Jarrard Leonard E. , Brown Thomas H.
Published: April 2004

Auditory information can reach the lateral nucleus of the amygdala (LA) through a monosynaptic thalamic projection or a polysynaptic cortical route. The polymodal input from the perirhinal cortex (PR) is a major informational gateway to the LA and nearby structures. Pretraining PR lesions impair fear conditioning to a context, but there have been no reports that they cause deficits in delay conditioning to an auditory cue. The direct subcortical projection to the LA seems sufficient to support delay conditioning to a tone conditional stimulus (CS). We examined the effect of PR lesions on delay conditioning to two different tone conditional stimuli (4 and 22 kHz tones; both 10 sec duration) and two different rat ultrasonic vocalization (USV) conditional stimuli (10 sec of “22 kHz USVs”). The two USV conditional stimuli were multi-call segments that were recorded (digitized at 100 kHz) from two different rats. One USV CS was a continuous sequence of eight calls, and the other was a portion of a continuous sequence of six calls. PR lesions significantly impaired conditioning to both USV conditional stimuli and to the training context but had no significant effect on conditioning to either tone CS. The role of PR in fear conditioning appears not to be determined by whether the conditional stimuli serve as contexts or cues, but instead by the nature or complexity of the stimuli or stimulus configurations. These cue-specific effects of PR lesions are suggested to reflect differences in the stimulus features that are encoded in the two CS pathways to the LA.
Identification and Characterization of Heterogeneous Neuronal Injury and Death in Regions of Diffuse Brain Injury: Evidence for Multiple Independent Injury Phenotypes
Authors: Singleton Richard H. , Povlishock John T.
Published: April 2004

Diffuse brain injury (DBI) is a consequence of traumatic brain injury evoked via rapid acceleration–deceleration of the cranium, giving rise to subtle pathological changes appreciated best at the microscopic level. DBI is believed to be comprised by diffuse axonal injury and other forms of diffuse vascular change. The potential, however, that the same forces can also directly injure neuronal somatain vivohas not been considered. Recently, while investigating DBI-mediated perisomatic axonal injury, we identified scattered, rapid neuronal somatic necrosis occurring within the same domains. Moving on the premise that these cells sustained direct somatic injury as a result of DBI, we initiated the current study, in which rats were intracerebroventricularly infused with various high-molecular weight tracers (HMWTs) to identify injury-induced neuronal somatic plasmalemmal disruption. These studies revealed that DBI caused immediate, scattered neuronal somatic plasmalemmal injury to all of the extracellular HMWTs used. Through this approach, a spectrum of neuronal change was observed, ranging from rapid necrosis of the tracer-laden neurons to little or no pathological change at the light and electron microscopic level. Parallel double and triple studies using markers of neuronal degeneration, stress, and axonal injury identified additional injured neuronal phenotypes arising in close proximity to, but independent of, neurons demonstrating plasmalemmal disruption. These findings reveal that direct neuronal somatic injury is a component of DBI, and diffuse trauma elicits a heretofore-unrecognized multifaceted neuronal pathological change within the CNS, generating heterogeneous injury and reactive alteration within both axons and neuronal somata in the same domains.
Cocaine Self-Administration Produces a Progressive Involvement of Limbic, Association, and Sensorimotor Striatal Domains
Authors: Porrino Linda J. , Lyons David , Smith Hilary R. , Daunais James B. , Nader Michael A.
Published: April 2004

The primate striatum is composed of limbic, cognitive, and sensorimotor functional domains. Although the effects of cocaine have generally been associated with the ventral striatum, or limbic domain, recent evidence in rodents suggests the involvement of the dorsal striatum (cognitive and sensorimotor domains) in cocaine self-administration. The goals of the present studies were to map the topography of the functional response to cocaine throughout the entire extent of the striatum of monkeys self-administering cocaine and determine whether this response is modified by chronic exposure to cocaine. Rhesus monkeys were trained to self-administer 0.3 mg/kg per injection cocaine for 5 d (initial stages;n= 4) or 100 d (chronic stages;n= 4) and compared with monkeys trained to respond under an identical schedule of food reinforcement (n= 6). Monkeys received 30 reinforcers per session, and metabolic mapping was conducted at the end of the 5th or 100th self-administration session. In the initial phases of cocaine exposure, self-administration significantly decreased functional activity in the ventral striatum, but only in very restricted portions of the dorsal striatum. With chronic cocaine self-administration, however, the effects of cocaine intensified and spread dorsally to include most aspects of both caudate and putamen. Early experiences with cocaine, then, involve mainly the limbic domain, an area that mediates motivational and affective functions. In contrast, as exposure to cocaine continues, the impact of cocaine impinges progressively on the processing of sensorimotor and cognitive information, as well as the affective and motivational information processed in the ventral striatum.
Corticotrophin Releasing Factor-Induced Synaptic Plasticity in the Amygdala Translates Stress into Emotional Disorders
Authors: Rainnie Donald G. , Bergeron Richard , Sajdyk Tammy J. , Patil Madhvi , Gehlert Donald R. , Shekhar Anantha
Published: April 2004

The amygdala is involved in the associative processes for both appetitive and aversive emotions, and its function is modulated by stress hormones. The neuropeptide corticotrophin releasing factor (CRF) is released during stress and has been linked to many stress-related behavioral, autonomic, and endocrine responses. In the present study, nonanxiety-inducing doses of a potent CRF type 1 and 2 receptor agonist, urocortin (Ucn), was infused locally into the basolateral amygdala (BLA) of rats. After 5 daily injections of Ucn, the animals developed anxiety-like responses in behavioral tests. Intravenous administration of the anxiogenic agent sodium lactate elicited robust increases in blood pressure, respiratory rate, and heart rate. Furthermore, in the absence of any additional Ucn treatment, these behavioral and autonomic responses persisted for >30 d. Whole-cell patch-clamp recordings from BLA neurons of these hyper-reactive animals revealed a pronounced reduction in both spontaneous and stimulation-evoked IPSPs, leading to a hyperexcitability of the BLA network. This Ucn-induced plasticity appears to be dependent on NMDA receptor and subsequent calcium–calmodulin-dependent protein kinase II (CaMKII) activation, because it is blocked by pretreatment with NMDA receptor antagonists and by coadministration of CaMKII inhibitors. Our results show for the first time a stress peptide-induced behavioral syndrome that can be correlated with cellular mechanisms of neural plasticity, a novel mechanism that may explain the etiological role of stress in several chronic psychiatric and medical disorders.
Amphibious water‐soluble copolymer. I. Its synthesis and dispersing ability on barium titanate
Authors: Chen Lung‐Pin , Ying Kuo‐Liang , Hsu Kung‐Chung
Published: April 2004

An amphibious water‐soluble copolymer, polyacrylamide/(α‐N,N‐dimethyl‐N‐acryloyloxyethyl) ammonium ethanate (PAAM/DAAE), was synthesized and used as a dispersion agent for BaTiO3 particles. PAAM/DAAE was prepared from acrylamide and (α‐N,N‐dimethyl‐N‐acryloyloxyethyl) ammonium ethanate under basic conditions through a free‐radical polymerization. The structure of this copolymer was verified with IR and 1H‐NMR spectra. The dispersing effects of PAAM/DAAE were examined through the measurement of the viscosity and sedimentation of BaTiO3 suspensions and the green density. The results indicated that this copolymer could uniformly disperse the particles, reduce the viscosity, stabilize the suspensions, and produce high‐density green compacts. In comparison with a commercial dispersant, the ammonium salt of poly(methylacrylic acid), PAAM/DAAE was clearly more effective. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 2232–2239, 2004
Thermal stability of native polybutylene terephthalate
Authors: Shelgaev V. N. , Mikitaev A. K. , Lomakin S. M. , Zaikov G. E. , Koverzanova E. V.
Published: April 2004

The thermal and thermooxidative stability of polybutylene terephthalate (PBTP), synthesized in the presence of the optimal stabilizing system, has been investigated. The basic products of PBTP degradation and the regularities of their formation in the temperature regime close to the temperature regimes of its processing were determined. The investigations conducted allowed recommendations to be made on the temperature regimes of PBTP processing because even a small excess of the chosen temperature (265°C) leads to polymer chain fragmentation. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 2351–2356, 2004
Sound absorption properties of thermally bonded nonwovens based on composing fibers and production parameters
Authors: Lee Youn Eung , Joo Chang Whan
Published: April 2004

This article reviews the noise absorption capacity of thermally bonded nonwovens in the range of audible frequencies (125–2500 Hz). First, we focus on the effects of the properties of the fibers, which constitute nonwovens, on the sound absorption properties, and then we consider the web orientation angle of nonwovens. We also investigate a composite model of the sound absorption properties of nonwovens, including the surface roughness and panel vibration. We have used an impedance tube interferometer, which provides the normal incidence sound absorption coefficient of materials, for the determination of the noise absorption properties of nonwovens produced under different conditions. The noise absorption capacity of nonwovens depends primarily on the thickness and surface characteristics of specimens, but the effects of the fiber contents are only marginal. Interestingly, when there is a panel in front of nonwovens, the noise absorption capacity increases significantly at low and medium frequencies (250–1000 Hz). © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 2295–2302, 2004
Phosphonate‐containing bismaleimide resins. II. Preparation and characteristics of reactive blends of phosphonate‐containing bismaleimide and epoxy
Authors: Shu Wei‐Jye , Chin Wei‐Kuo , Chiu Hsiu‐Jung
Published: April 2004

Two kinds of phosphonate‐containing bismaleimide (BMI) monomers, phenyl‐(4,4′‐bismaleimidophenyl) phosphonate and ethyl‐(4,4′‐bismaleimido‐phenyl) phosphonate, were synthesized and added through blending to two epoxy systems for the study of their applications as reactive flame retardants. The thermal behaviors of the BMI monomers in both kinds of epoxy systems, bisphenol and phenol–novolac, were similar. An increase in the BMI contents increased the storage modulus and glass‐transition temperature but slightly reduced the mechanical strength of the epoxy blends. The pyrolysis models of both BMI blends in the two epoxy systems were quite alike. Although the initial pyrolysis temperatures of all the blending systems gradually decreased as the phosphorous content increased, the flame retardancy of all the phosphonate‐containing epoxy systems was promoted significantly by increasing contents of BMI. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 2375–2386, 2004
Tl(III) initiated polymerization of methyl methacrylate in micellar phase
Authors: Patra Manabendra , Behera Ajay K. , Behera Rajani K. , Sinha Bijoy K.
Published: April 2004

The polymerization kinetics of methyl methacrylate (MMA) was studied, using Tl(III)‐cyclohexanone (CH) redox system as initiator, in the presence of emulsifier [i.e., sodium dodecyl sulfate (SDS), cetyltrimethylammonium bromide (CTAB), and thallium triacetate (TX‐100)] over a temperature range of 25–45°C. The effect of various concentrations of MMA, Tl(III), cyclohexanone, H+, and varying ionic strengths on the rate of polymerization, rate of Tl(III) consumption (−RTl), and the percentage of monomer conversion were examined in the presence of 0.015M SDS. The kinetic results of polymerization in the absence and presence of 0.015M SDS were compared in terms of overall activation energy (Ea) for the process. The viscosity‐average molecular weight (MV) of the polymers, obtained in the presence of varying concentrations of anionic surfactant (SDS), was also determined. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 2480–2485, 2004
Effects of water on the curing and properties of epoxy adhesive used for bonding FRP composite sheet to concrete
Authors: Wu Lixin , Hoa Suong V. , Ton‐That Minh‐Tan
Published: April 2004

When a concrete surface is contaminated by water due to rain, saline water, ground water, and water jetty treatment, water, alkalis, and other contaminants on the concrete surface may interact with an epoxy adhesive used for bonding fiber‐reinforced polymer composite sheets to concrete. This can influence both the curing rate and the degree of cure of the curing reaction. This in turn can affect the time required for field application. It can also influence the mechanical properties and durability of epoxy adhesives. In this paper, water effects on the curing and properties of two kinds of commercial adhesives were evaluated. Curing kinetics were studied using isothermal DSC analysis. Results showed that water accelerated the curing reaction. However, excess water offsets part of the accelerating effect. While water is typically considered to be harmful to properties of adhesives, it was seen that a small amount (less than 2%) of water improved degree of cure, mechanical properties, and durability of adhesives. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 2261–2268, 2004
Proton exchange membranes by grafting of styrene–acrylic acid onto FEP by preirradiation technique. II. Physicochemical properties of the membrane and its sulfonated derivatives
Authors: Phadnis Swati , Patri M. , Hande Varsha R. , Roychoudhury Suhasini , Deb P. C.
Published: April 2004

Poly(tetrafluoroethylene‐co‐haxafluoropropylene) (FEP)‐g‐styrene–acrylic acid and its sulfonated derivative membranes were prepared by graft copolymerization of styrene–acrylic acid onto FEP by using preirradiation of γ‐ray technique followed by sulfonation. The physiochemical properties such as ion exchange capacity, water uptake, ionic resistance of the grafted membranes, and their sulfonated derivatives were studied as a function of degree of grafting. These membranes on sulfonation gave acid base, indicating property. The membranes gave yellow color in acidic medium and purple color in alkali medium. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 2318–2325, 2004
Complexation of poly(dimethylsiloxane)/poly(methyl methacrylate‐co‐butyl acrylate‐co‐methacrylic acid) latex with poly(dimethylsiloxane)/poly(vinyl acetate‐co‐butyl acrylate) latex
Authors: Yang Mingjiao , Dan Yi
Published: April 2004

Two latices—the poly(dimethylsiloxane) (PDMS)/poly(methyl methacrylate‐co‐butyl acrylate‐co‐methacrylic acid) system (PA latex) and the PDMS/poly(vinyl acetate‐co‐butyl acrylate) system (PB latex)—were prepared by seeded emulsion polymerization, and PA/PB complex latices were obtained through the interparticle complexation of the PA latex with the PB latex. In addition, for the further study of the interparticle complexation of the PA latex with the PB latex, copolymer latices [PDMS/methyl methacrylate‐co‐butyl acrylate‐co‐vinyl acetate‐co‐methacrylic acid) (PC)] were prepared according to the monomer recipe of the complex latices and the polymerization process of the component latices. The properties of the obtained polymer latices and complex latices were investigated with surface‐tension, contact‐angle, and viscosity measurements. The mechanical properties of the coatings obtained from the latices were investigated with tensile‐strength measurements. The results showed that, in comparison with the two component latices (PA latex and PB latex) and the corresponding copolymer latices (PC latices), the PA/PB complex latices had lower surface tension, lower viscosities, and better wettability to different substrates. The tensile strengths of the coatings obtained from the complex latices were higher than the tensile strengths of the coatings from the two component latices and copolymer latices. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 2522–2527, 2004
Studies on poly(styrene‐co‐maleic anhydride)‐modified polyesteramide‐based anticorrosive coatings synthesized from a sustainable resource
Authors: Zafar Fahmina , Sharmin Eram , Ashraf S. M. , Ahmad Sharif
Published: April 2004

Polyesteramide (PEA) coating resin, synthesized from linseed oil, a sustainable resource, was found to show improved physicomechanical and acid‐resistance properties. To further improve these properties in terms of alkali resistance, scratch hardness, and thermal stability and to reduce the baking temperature, we have attempted to incorporate styrene into the polymer backbone through its copolymer with maleic anhydride. The structural elucidation of modified PEA resin (SCPEA) was carried out by FTIR, 1H‐NMR, and 13C‐NMR spectroscopes. The physicomechanical and chemical‐resistance properties were investigated by standard methods and thermal stability was investigated by thermogravimetric analysis method. A comparative study of these properties of PEA and SCPEA was carried out. It was observed that the SCPEA showed better properties than the reported one. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 2538–2544, 2004
New polyurethane cationomers with naphthyl and phenyltriazene pendants: Synthesis and properties
Authors: Buruiana Emil C. , Niculescu Violeta , Buruiana Tinca
Published: April 2004

Two new diols bearing triazene moiety, 1‐(α‐naphthyl)‐3,3‐di(2‐hydroxyethyl) triazene‐1 (NT‐D) and 1‐phenyl‐3,3‐di(2‐hydroxyethyl) triazene‐1 (PT‐D), were synthesized from aromatic amines and diethanolamine. These monomers were used as chain coextenders in the two‐step addition reaction between poly(tetramethylene oxide) diol, 2,4‐tolylene diisocyanate, and N‐methyldiethanolamine to obtain photosensitive polyurethanes of elastomer type. Triazene polyurethane cationomers with chlorine counterions were prepared via a quaternization reaction of the above polymers with benzyl chloride. All polyurethanes had a quantity of triazene units between 7.02 and 8.93 wt % polymer, and the content of ammonium quaternary groups in the cationic ones was of 30.56 meq/100 g naphthyl triazene polyurethane cationomer (PUC‐NT) and 30.19 meq/100 g phenyl triazene polyurethane cationomer (PUC‐PT), respectively. Photobehavior of the triazene units in all polymers under continuous Hg‐lamp irradiation was similar to that found for monomers, when both chromophores were transformed during UV irradiation. It is concluded that the PT‐D acts as a more efficient sensitizer in the UV light‐induced reaction but the photolysis in elastomeric films was lower than that observed in solution. The presence of quaternary ammonium structure on the same polymer backbone decreases the constant rates of photolysis. Because the triazene polyurethanes become crosslinked during UV irradiation could be assessed as potential negative‐resist polymers. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 2599–2605, 2004
Pore structure of water‐wettable hydrophobic resins based on divinylbenzene and methyl acrylate
Authors: Wei Jia , Zhao Xin , Yan Jun
Published: April 2004

Hydrophobic, but water‐wettable porous resins based on divinylbenzene (DVB) and methyl acrylate (MA) were prepared with a wide range of pore structures by suspension copolymerization under different conditions. By using purified DVB (98.8%), the specific surface area for the resulting MA/DVB resins could reach high values at high DVB levels, while these resins are wettable by direct contact with water. An increased content of MA significantly increases the porosity of the resins, whereas the solvating power of the porogen affects both pore structure and water‐wettability of the MA/DVB resins profoundly. Treating these MA/DVB resins with ferric chloride in the presence of dichloroethane gives products with larger surface areas and an enhanced water‐wettability. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 2681–2688, 2004
Studies of sulfonated polyethylene for biliary stent application
Authors: Peng Mei‐Chuan , Lin Jui‐Che , Chen Chiung‐Yu , Wu Jiunn‐Jong , Lin Xi‐Zhang
Published: April 2004

Palliative treatment for obstructive jaundice by endoscopic biliary stent insertion is a recent commonly used method. Unfortunately, stent reobstruction may occur within 3 to 6 months as a result of bacterial adhesion and formation of biofilm. Bacterial adhesion was postulated as the initial step of stent clogging and the bacterial enzyme activity of β‐glucuronidase led to the deposition of calcium bilirubinate. In this study, surface sulfonation of the polyethylene lumen was postulated to improve the patency of the biliary stent. Surface modification with sulfonated group formation was carried out with fuming sulfuric acid containing 20 wt % sulfuric trioxide (SO3). The reaction time varied from 1 to 3 h at room temperature. ATR‐FTIR and ESCA techniques showed that the surface amount of sulfonated functionalities increased with sulfonation time. The contact angle of the sulfonated PE, determined by the sessile drop technique, decreased compared to that of unmodified PE, but cannot be detected by the captive bubble method because of the high surface hydrophilicity. SEM micrographs indicated that the sulfonated PE inner lumen remained relatively smooth after extended sulfonation reaction. Adhesion of Escherichia coli to the sulfonated PE stents after 48‐h bile perfusion was about 10‐ to 20‐fold less than that to the unmodified PE, as observed by SEM and surface spreading method. These results indicated that the surface sulfonated groups could effectively decrease the adhesion of E. coli in human bile, probably attributable to the hydrophilic repellence between the bacterial cell membrane and sulfonated groups. This finding suggested that the sulfonated PE tubing could prolong the patency period of plastic stents and may be of great potential as a biliary stent in a real clinical setting. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 2450–2457, 2004
Temperature/pH‐sensitive comb‐type graft hydrogels composed of chitosan and poly(N‐isopropylacrylamide)
Authors: Lee Sang Bong , Ha Dong In , Cho Seong Kwan , Kim Seon Jeong , Lee Young Moo
Published: April 2004

Comb‐type graft hydrogels, composed of chitosan and poly(N‐isopropylacrylamide) (PNIPAAm), were prepared to manifest rapid temperature and pH sensitivity. Instead of directly grafting the NIPAAm monomer onto the chitosan chain, semitelechelic PNIPAAm with carboxyl end group was synthesized by radical polymerization using 3‐mercaptopropionic acid as the chain‐transfer agent, and was grafted onto chitosan having amino groups. The comb‐type hydrogels were prepared with two different graft yields and grafting regions, such as surface‐ and bulk‐grafting, and then compared with a chitosan hydrogel. The synthesis of telechelic PNIPAAm and the formation of amide group were confirmed by using FTIR spectroscopy and gel permeation chromatography. Results from the water state and thermal stability revealed that the introduction of the PNIPAAm side chain disturbed the ordered arrangement of the chitosan molecule, resulting in an increase in the equilibrium water content. Comb‐type graft hydrogels showed rapid temperature and pH sensitivity because of the free‐ended PNIPAAm attached to the chitosan main chain and the chitosan amino group itself, respectively. In particular, the surface graft hydrogel maintained its dimension at low pH, although the chitosan main chain was not crosslinked, whereas chitosan and bulk graft hydrogel were dissolved as a result of the coating effect of pH‐independent PNIPAAm. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 2612–2620, 2004
Resistivity of conductive polymer–coated fabric
Authors: Lekpittaya Porntip , Yanumet Nantaya , Grady Brian P. , O'Rear Edgar A.
Published: April 2004

Preparation of conductive polymer–coated fabrics was carried out by admicellar polymerization. By this method, a thin layer of conductive polymers (polypyrrole, polyaniline, and polythiophene) was formed on cotton and polyester fabrics by a surfactant template. The effects of monomer concentration, oxidant to monomer ratio, and addition of salt on the resistivity of the resulting fabrics were studied. The results showed that the apparent surface and volume resistivity decreased with an increase in monomer concentration in the range 5–15 mM, but was not strongly dependent on the oxidant to monomer ratio over the range of 1 : 1 to 2 : 1. Addition of 0.5M salt was found to reduce the resistivity significantly. The lowest resistivity obtained was with polypyrrole‐coated fabric, with resistivity around 106 ohm. SEM micrographs of the treated fabric surface showed a filmlike polymer coating, confirming that the fabrics were successfully coated by admicellar polymerization. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 2629–2636, 2004
Syntheses and biodegradability of benzylated waste pulps and graft copolymers from PBzs and L‐lactic acid
Authors: Hadano Shingo , Maehara Seiji , Onimura Kenjiro , Yamasaki Hirohito , Tsutsumi Hiromori , Oishi Tutomu
Published: April 2004

Benzylated waste pulps (PBzs) were synthesized from treated waste pulp (Pulp), and benzyl chloride with phase transfer catalyst (PTC), and graft copolymers (PBz‐g‐LA) were synthesized from PBzs and L‐lactic acid (LA). Thermal properties, solubility, crystallinity, and biodegradability of the obtained PBzs and graft copolymers were investigated. PBzs with the degree of substitution (DS) higher than 1.5 showed Tg and Tm in DSC measurement. All PBz‐g‐LA exhibited no Tm. However, the graft copolymers obtained from lower DS PBzs having no Tg, exhibited Tg. The solubility of PBzs enhanced with increasing DS, and the crystallinity of PBzs reduced with increasing DS because of hydrophobicity and steric effect of benzyl groups. The solubility of graft copolymers was similar to that of original PBzs. Biodegradation tests for PBzs, Pulp, and graft copolymers were performed using cellulase in 0.1 M acetate buffer solution (pH 5.5) at 37°C. All samples showed biodegradability though the biodegradation rate decreased with increasing DS of PBz. In PBz‐g‐LA, the initial biodegradation rate was faster than that of original PBz because of hydrolysis of LA units. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 2658–2664, 2004
Nanocomposites of poly(vinyl chloride) and nanometric calcium carbonate particles: Effects of chlorinated polyethylene on mechanical properties, morphology, and rheology
Authors: Wu Dezhen , Wang Xiaodong , Song Yongzhi , Jin Riguang
Published: April 2004

Nanocomposites of poly(vinyl chloride) (PVC) and nano‐calcium carbonate (CaCO3) particles were prepared via melt blending, and chlorinated polyethylene (CPE) as an interfacial modifier was also introduced into the nanocomposites through preparing CPE/nano‐CaCO3 master batch. The mechanical properties, morphology, and rheology were studied. A moderate toughening effect was observed for PVC/nano‐CaCO3 binary nanocomposites. The elongation at break and Young's modulus also increased with increasing the nano‐CaCO3 concentration. Transmission electron microscopy (TEM) study demonstrated that the nano‐CaCO3 particles were dispersed in a PVC matrix uniformly, and a few nanoparticles agglomeration was found. The toughening effect of the nano‐CaCO3 particles on PVC could be attributed to the cavitation of the matrix, which consumed tremendous fracture energy. The notched Izod impact strength achieved a significant improvement by incorporating CPE into the nanocomposites, and obtained the high value of 745 J/m. Morphology investigation indicated that the nano‐CaCO3 particles in the PVC matrix was encapsulated with a CPE layer through preparing the CPE/nano‐CaCO3 master batch. The evaluation of rheological properties revealed that the introduction of nano‐CaCO3 particles into PVC resulted in a remarkable increase in the melt viscosity. However, the viscosity decreased with addition of CPE, especially at high shear rates; thus, the processability of the ternary nanocomposites was improved. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 2714–2723, 2004