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In this work, three different nanoclays (1.44P, 1.34MN, and Cloisite 15A) were used to reinforce an injection grade poly(lactic acid) (PLA). The nanocomposites (NCs) were prepared using three different nanoclay concentration levels (1, 3, and 5 wt%) in a twin-screw extruder. To evaluate their mechanical performance (static and dynamic tests) and thermal properties, the respective samples were obtained by injection molding. Results showed that the three nanoclays significantly increased the tensile and flexural modulus of the injection grade PLA. The 1.34MN NCs also showed improvement in the tensile strength. An increment in flexural strength was obtained with 1.34MN and 1.44P nanoclays, while with nanoclay 15A, the flexural strength decreased. Additionally, the use of 5 wt% of 1.44P nanoclay allowed an increase in impact strength while using 1.34MN and 15A nanoclays, the impact strength was similar to the one observed for pure PLA. In general, mechanodynamic analysis results showed that storage modulus increased with nanoclay content; while thermogravimetric analysis indicated that none of the nanoclays has a significant effect over the degradation temperature of pure PLA. Differential scanning calorimetry results showed that the crystallinity of PLA is enhanced with nanoclay inclusion. For 1.34MN NCs, X-ray diffraction observations exposed that the mineral clay relative intensity peaks disappeared indicating nanoclay exfoliation, which contributes to the increase in tensile and flexural strength in the NCs. Nevertheless for 1.44P and 15A nanoclays, an increase in the interlayer distance (intercalation) was detected.

Se modelaron las condiciones de idoneidad ambiental asociada a la presencia de 370 especies de aves en la costa del Pacífico del estado de Guerrero. Con estos modelos se obtuvieron los patrones de riqueza, de endemismo y de acumulación de especies de las aves en riesgo de la región. Se utilizó un análisis de complementariedad para la avifauna residente y acuática y se empleó un análisis de parsimonia de endemismos con el fin de identificar sitios prioritarios para la conservación. El conocimiento de la avifauna de la región de estudio no es completo según el estimador de riqueza (ICE: 77% del total). Los patrones de distribución de la riqueza y el endemismo de las aves de la región estuvieron más concentrados hacia el centro oeste, en las áreas montañosas de la zona de estudio, excepto en la porción más occidental que también presentó un amplio número de especies en las partes bajas coincidiendo con algunos sistemas lacustres. El análisis de complementariedad para las aves terrestres identificó 6 celdas, el mismo número de celdas para las aves acuáticas, y que en ambos casos albergan en conjunto el 100% de las especies modeladas. El análisis de parsimonia encontró 2 áreas de endemismo y algunas celdas incluidas en estas fueron también identificadas con el método de complementariedad, por lo que el nivel de priorización es mayor. Las áreas de conservación identificadas indican una conectividad del centro al occidente del área de estudio, región que coincide con lo encontrado por otros estudios que utilizan especies importantes para la conservación.

In this study, high density polyethylene and polypropylene were blended and foamed using azodicarbonamide as a chemical blowing agent, zinc oxide as an accelerator, and Kraton D1102 as a compatibilizer. Gardner impact resistance of injection molded samples is reported as a function of blend composition for foamed and unfoamed samples. The results show that Kraton addition had negligible effect on impact strength of unfoamed samples while foamed samples were more resistant. A change in fracture behavior was also observed and related to the morphology of the material.

Blends of high density polyethylene and polystyrene were produced via ribbon extrusion to study the effect of post-extrusion conditions on the ribbon final dimensions and morphology. An experimental setup was designed to measure the stretching force as a function of draw ratio and water contact distance for blends of 3, 6 and 9% PS in HDPE. Numerical simulations of the non-isothermal process using Matlab were in good agreement with the experimental data only when both viscous and elastic effects are included. The results show that both draw ratio and water contact distance have a definite influence on the final dimensions of the ribbon and the stretching force. It was found that deformation of the dispersed phase increases with draw ratio, but decreases with water contact distance.

The compatibilizing effect of the ionomer, poly(styrene-co-sodium acrylate) (PSSAc), on immiscible blends of polystyrene (PS)/polyamide 6 (PA6) was studied by mechanical tests and scanning electron microscopy. The PSSAc acts as an effective compatibilizer because both the deformation at break (%) obtained by tensile stress–strain tests and the impact rupture energy are larger in blends containing small amounts of PSSAc. The morphologies of the fractured surfaces produced by tensile stress–strain tests of blends with or without the ionomer confirm that PSSAc increases the interfacial adhesion between PS and PA6 phases. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 2545–2551, 2004

In this work, the compatibilization of polystyrene-and-nylon 6 mixtures with the ionomer, poly(styrene-co-sodium acrylate), is investigated. The ionomer was synthesized by emulsion polymerization. Scanning electron microscopy reveals that an appreciable size reduction of the dispersed phase is achieved in the whole composition range, when small amounts of the ionomer were added. IR spectroscopy and water absorption tests disclose that a chemical reaction occurs between the carboxylic group of the ionomer and the terminal amine group of the polyamide 6, which allows the compatibilization process. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91:1736–1745, 2004

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Amorphous carbon nitride thin films were prepared in a dual ion beam sputtering (DIBS) system. The N/C atomic concentration ratio ranged between 0.3 and 0.5 as determined by quantitative X-ray photoelectron spectroscopy (XPS) of the surface. Fourier Transform Infrared spectroscopy (FT–IR), XPS and X-ray Absorption Spectroscopy (XAS) were used to obtain information about the different types of bonding present in the films. The hardness and the Young's modulus of the samples were determined by nanoindentation measurements. The hardness varied in the range 15–30GPa with Young's modulus between 170 and 250GPa. In order to explain the measured hardness, some of the films are considered as heterogeneous, in good agreement with the XPS, FT–IR and XAS data.

1. In the unanesthetized spinal cord of the cat, simultaneous intracellular recordings were made from two motoneurons belonging to the gastronemius motor nucleus. 2. Supramaximal iterative stimulation of small branches of the gastrocnemius nerve produced monosynaptic EPSPs (Ia EPSPs) of varying amplitude superimposed on a fluctuating base line. 3. In most cases the variance of the motoneuron membrane potential was increased above base-line levels with a time course approximately matching the Ia EPSP. This suggests that Ia EPSP fluctuations are greater than can be accounted for by the base-line fluctuations alone. 4. For a given series of Ia EPSPs, the smaller responses in the series had about the same decay phase as the larger EPSPs, suggesting that most of the Ia EPSP fluctuations were not due to systematic changes in postsynaptic conductances produced by ongoing activity, but rather to a presynaptic mechanism. 5. Simultaneous recording from two motoneurons showed that base-line fluctuations were positively correlated. In most cases, however, there was an additional increased correlation above base-line levels resembling the time course of the Ia EPSPs, indicating positive correlation between EPSP fluctuations which is attributed to a presynaptic mechanism. 6. Conditioning volleys to group I muscle afferents or to low-threshold cutaneous afferents reduced the variance of the Ia EPSPs and also their correlation in motoneuron pairs, often without changing the mean Ia EPSPs. 7. It is concluded that, in the unanesthetized spinal cord, in addition to the random process which governs transmitter release intrinsic to a given synaptic terminal, there is another stochastic process affecting, in a correlated manner, transmitter release in large sets of Ia synaptic terminals. Most likely, the correlation in transmitter release is achieved by membrane potential fluctuations imposed on the Ia terminal arborizations by ongoing activity of the segmental mechanism mediating primary afferent depolarization. 8. The effects of such a correlating influence on cell firing behavior have been analyzed. The results suggest that this mechanism, referred to as control by presynaptic correlation, is able to modulate the information transmitted from Ia fibers to motoneurons.

1. In the unanesthetized spinal cord, conditioning stimulation of low-threshold afferents (below 1.3 times threshold strength) in the biceps semitendinosus (BST) nerve often reduced the peak amplitude of the monosynaptic Ia EPSPs evoked in gastrocnemius motoneurons without affecting the monosynaptic component of the EPSPs evoked by stimulation of the ipsilateral ventral funiculus (VF) in the thoracic cord. 2. Volleys to the BST nerve comprising higher threshold afferents (usually above 1.4 times threshold strength) reduced the peak amplitude of the monosynaptic Ia and VF EPSPs and shortened their falling phase. 3. Conditioning volleys to low-threshold cutaneous afferents often increased the Ia-EPSP peak amplitude, sometimes without affecting the monosynaptic component of the VF EPSP. 4. In most cases the Ia nd VF monosynaptic EPSPs elicited in a given motoneuron summated nonlinearly. The amount of nonlinear summation between Ia and VF monosynaptic EPSPs was often reduced by low-threshold BST conditioning volleys. These observations suggest that in many instances, both species of fibers end in "electrotonically close" synaptic loci over the motoneuron surface. Therefore, amplitude changes of monosynaptic Ia EPSPs produced by conditioning afferent volleys without concomitant changes of monosynaptic VF EPSPs do not appear to result from postsynaptic remote conductance changes and may be attributed to a presynaptic mechanism. 5. At the time of occurrence of the Ia and VF monosynaptic EPSP the variance of the motoneuron membrane potential may be increased above base-line levels with a time course approximately matching the EPSP itself. Conditioning stimulation of BST afferents usually reduced Ia EPSP variance, often without affecting or even increasing the variance of the monosynaptic VF EPSPs. These observations provide additional evidence that Ia EPSP variability is introduced, at least in part, through the segmental pathways mediating primary afferent depolarization. 6. The possibility of a differential control of the information flow transmitted through two independent channels converging on a given cell ensemble is discussed.

Within a cooperative program for the elaboration of a Latin American Map of Atmospheric Corrosion, weathering steel and mild steel samples were exposed to the Antarctic atmosphere and the corrosion products analyzed by ICEMS, XPS and XRD. Superparamagnetic α-FeOOH was the main corrosion product after 24 h of exposure. Cl− ions are found on the surface of the corroded samples by XPS.

1. Monosynaptic excitatory post‐synaptic potentials (e.p.s.p.s) were recorded from medial (m.g.) and lateral gastrocnemius (l.g.) motoneurones in the cat 2‐30 weeks after crushing the m.g. nerve.

1. Monosynaptic excitatory post‐synaptic potentials (e.p.s.p.s.) were recorded from triceps surae motoneurones of the cat 2‐8 months after section of the medial gastrocnemius nerve whose regeneration into the muscle was prevented. In other animals, the cut nerve was reunited to the muscle with a post‐denervation delay varying from 2 to 6 months, and the e.p.s.p.s were recorded 2 months later. The e.p.s.p.s were evoked by stimulation of the medial gastrocnemius nerve central to the site of the section or reunion. 2. The mean amplitudes of the e.p.s.p.s decreased with time after nerve section, virtually disappearing by the eighth post‐operative month. The decrement of the e.p.s.p. amplitude occurred more quickly in soleus motoneurones than in medial or lateral gastrocnemius motoneurones. 3. The e.p.s.p.s evoked in medial or lateral gastrocnemius motoneurones from the cut medial gastrocnemius nerve returned to normal levels 2 months after reunion of the cut nerve even following a post‐denervation delay of 6 months. However, in soleus motoneurones the e.p.s.p. recovery was incomplete. 4. The degree of functional motor reinnervation of the medial gastrocnemius muscle depended upon the post‐denervation delay preceding the reunion operation. With a delay of 6 months before the reunion, the muscle showed no or only weak contractions in response to nerve stimulation. 5. Axotomized medial gastrocnemius motoneurones showed a significant decrease in conduction velocity and significant increase in the amplitude of overshoot of action potentials. The changes persisted even when the cut nerve was reunited to the muscle 2‐6 months after denervation. 6. When the cut medial gastrocnemius nerve was reunited to the muscle 4 months after denervation, most of the sensory fibres, tested 2 months later, failed to respond to muscle stretch. 7. It is concluded that recovery of monosynaptic e.p.s.p.s following reconnexion of the cut nerve with its muscle does not require recovery of muscle activity, full restoration of sensory activity or the recovery of normal motoneurone properties. 8. It is also suggested that the degree to which central synaptic efficacy declines and recovers following section and regeneration of a peripheral nerve depends partly upon the type of motoneurone (fast phasic or slow tonic) with which the sensory fibres form synaptic connexions.

1. The fast‐twitch flexor digitorum (the lateral head; equivalent to the flexor hallucis longus) and slow‐twitch soleus muscles of the cat were denervated, and the two nerves immediately reunited to one or the other muscle. Contraction times of the dually reinnervated muscle were examined 9 weeks post‐operatively in response to separate stimulation of its own and the foreign nerve. Over a 5 week period before the terminal experiment, a variety of artificial activity patterns was imposed on the two nerves.

The emulsion copolymerization of styrene and sodium acrylate is reported using either a water-soluble initiator (potassium persulfate, or KPS), or an oil-soluble one [2,2-azoisobutyronitrile (AIBN)]. Reaction rates are fast with both KPS and AIBN. With KPS, conversions >90% are achieved in 50 min, with AIBN, conversions reach 85% in 100 min. Particle size, measured by quasielectric light scattering (QLS), increases with conversion. Particle size in final latices is ~ 70–80 nm. Copolymer formation is confirmed by infrared (IR) spectroscopy, plasma emission spectroscopy (PES), and scanning electron microscopy (SEM). IR and PES indicate that mainly sodium acrylate reacts at the beginning of the reaction and then styrene is incorporated in the copolymer backbone. The copolymer produced with KPS contains more sodium acrylate than the one made with AIBN. These differences can be explained in terms of the reactivities and partitioning (local concentrations) of the monomers and of the type of initiator used. Thermomechanical analysis (TMA) of the copolymers reveals two transitions: one at ~ 100°C, which is due to the glass transition temperature (Tg) of polystyrene blocky segments in the copolymer, and another one at higher temperatures, which is associated to the Tg of segments composed of alternated sodium acrylate and styrene units. The higher-temperature transition shifts to lower values as the reaction proceeds because these segments become richer in styrene. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 66: 879–889, 1997

Summary Myocardial lesions induced by isoproterenol (ISP) are similar to those of human “coagulative myocytolysis” or “myofibrillar degeneration”. The localization of tritiated ISP in the damaged myocardium of rats has been recently described. Since H3-ISP was noted in “grooves” along the sarcolemma of ischemic and necrotic fibers, an action on the membrane with exaggerated calcium inflow was suggested. For this reason, the quantity of 45Ca in rats treated with ISP was studied. Thirty rats were given 5 µCi of 45Ca. Twenty (Group B) of them were also given ISP 10 mg/kg. Animals were killed at 1 h after the injections. The hearts were sectioned transversally and autoradiography was performed. Serial sections were examined to localize the 45Ca, and its topographic distribution. In Group A (injected only with 45Ca) the myocardium showed + of 45Ca (600 dots in a field × 400) inside the fibers. In Group B (injected also with ISP) 45Ca was deposited +++ (more than 1,200 dots) and related to extensive myocytolysis. These findings confirm that the crucial point in the ISP-induced lesions is the increase of calcium inflow, and if the pathogenesis of human myocytolysis is related to catecholamine effects pharmacological measures may be adopted to prevent these myocardial lesions.

1. Monosynaptic excitatory post‐synaptic potentials (e.p.s.p.s) were recorded from triceps surae motoneurones in the cat following section or chronic conduction block of the medial gastrocnemius (m.g.) nerve with tetrodotoxin (TTX) or after daily stimulation of the sciatic nerve. 2. The mean maximum amplitudes of homonymous and heteronymous monosynaptic e.p.s.p.s evoked by stimulation of the mg. nerve were reduced significantly between 1 and 2 weeks after section of the muscle nerve. The mean amplitudes of monosynaptic e.p.s.p.s produced in the same motoneurones by afferent volleys from the intact synergists showed no significant alterations. 3. Reduction of the amplitude of monosynaptic e.p.s.p.s. evoked by the sectioned m.g. afferent volleys was not prevented by daily stimulation of the sciatic nerve. The chronic stimulation of the sciatic nerve did not increase the amplitude of monosynaptic e.p.s.p.s evoked by stimulation of the intact, lateral gastrocnemius (l.g.) or soleus nerve. 4. Chronic conduction block of the intact m.g. nerve with TTX cuffs for 2 weeks resulted in a significant increase in the homonymous e.p.s.p. amplitude. The amplitude of the heteronymous e.p.s.p.s evoked in the same m.g. motoneurones by stimulation of the intact l.g. or soleus nerve showed no significant changes. 5. It is concluded that decreased central synaptic transmission following section of the peripheral nerve is not due to elimination of impulse activity (disuse) of the sensory input and that prolonged disuse of the sensory fibres causes an increase, rather than a decrease, in central synaptic efficacy.

1. The soleus muscle of adult cats was fixed in a shortened or lengthened position for 2 weeks by immobilizing the leg with a plaster cast. To eliminate the effects of reflex activity arising from the muscle, the lumbosacral dorsal roots were sectioned on the side of leg immobilization.

In active volcanic arcs such as the Andean volcanic mountain belt, magmatically sourced fluids are channeled through the brittle crust by faults and fracture networks. In the Andes, volcanoes, geothermal springs, and major mineral deposits have a spatial and genetic relationship with NNE trending, margin‐parallel faults and margin‐oblique, NW trending Andean Transverse Faults (ATF). The Tinguiririca and Planchón‐Peteroa volcanoes in the Andean Southern Volcanic Zone (SVZ) demonstrate this relationship, as their spatially associated thermal springs show strike alignment to the NNE oriented El Fierro Thrust Fault System. We constrain the fault system architecture and its interaction with volcanically sourced hydrothermal fluids using a combined magnetotelluric (MT) and seismic survey that was deployed for 20 months. High‐conductivity zones are located along the axis of the active volcanic chain, delineating fluids and/or melt. A distinct WNW trending cluster of seismicity correlates with resistivity contrasts, considered to be a reactivated ATF. Seismicity occurs below 4 km, suggesting activity is limited to basement rocks, and the cessation of seismicity at 9 km delineates the local brittle‐ductile transition. As seismicity is not seen west of the El Fierro fault, we hypothesize that this structure plays a key role in compartmentalizing magmatically derived hydrothermal fluids to the east, where the fault zone acts as a barrier to cross‐fault fluid migration and channels fault‐parallel fluid flow to the surface from depth. Increases in fluid pressure above hydrostatic may facilitate reactivation. This site‐specific case study provides the first three‐dimensional seismic and MT observations of the mechanics behind the reactivation of an ATF. In the Andean volcanic arc, margin‐parallel and blind oblique fault systems control volcanic, hydrothermal, and ore‐porphyry processesSubsurface conductivity structure and seismicity show a WNW trending active fault in the Andean Southern Volcanic ZoneResults show magmatic/hydrothermal fluids are compartmentalized by local faults and elevated fluid pressures promote fault reactivation

Eosinophilia of synovial fluid is an uncommon condition. The majority of the reported cases are associated to diseases such as rheumatoid arthritis, parasitic disease, hypereosinophilic syndrome, Lyme disease, and allergic processes as well as hemarthrosis and arthrography. Presently there are only four cases of eosinophilic synovitis with unknown cause. We are reporting a patient with oligoarthritis of the knees, massive eosinophilia, and Charcot-Leyden crystals in synovial fluid without associated cause. We review the clinical and biological features of eosinophilic synovitis and discuss its pathogenesis.

Anorectal manometry was performed in 32 neonates: 18 pre-term and 14 full-term infants, mean ages 6.1 and 7.1 days, respectively. The rectoanal inhibitory reflex (RAIR) was positive in 31 cases, and the relaxation waves produced by rectal distention were recorded along the anal canal and were directly related to the intensity of the stimulus. In the remaining patient the RAIR was negative due to Hirschsprung's disease. The length of the anal canal was 11.3 ± 2 mm in pre-term and 14.7 ± 2.9 mm in full-term infants (P < 0.001). These findings suggest that the presence of a RAIR is independent of the weight, gestational age, and birth age of the infant, and that anal canal length correlates with weight. We conclude that anorectal manometry in the neonatal period is a simple, reliable, and safe method of testing anorectal function, including the diagnosis of Hirschsprung's disease.

We report a patient with an anorectal malformation and an abnormal penis with an isolated prepuce, double glans, and two corpora cavernosa. A right main urethra opened into the bladder neck; the right meatus was hypospadiac. The proximal end of the left accessory urethra opened into the right prostatic urethra and the left meatus was orthotopic. Severe chordee and normal urinary flow through both meatuses were present. At the age of 4 years, the diphallus was corrected. Both corpora cavernosa were dissected and the urethra was reconstructed, lengthening the right urethra with a 2.5-cm fragment of left urethra as a free graft excised from the emergence point and joined to the main urethra pasteriorly. The right urethra, whose meatus was hypospadiac and lateral, was dissected until a medial course was obtained. The glans was reconstructed using the lateral aspect of each glans; both medial aspects were extirpated. To correct the urethral trajectory, the urethra was fixed to the tip of the glans. A penis with two corpora cavernosa, a single glans, and a complete urethra with a meatus at the tip of the glans was obtained. The prepuce was reconstructed from the dorsal redundant aspect. The postoperative course was satisfactory.We report a patient with an anorectal malformation and an abnormal penis with an isolated prepuce, double glans, and two corpora cavernosa. A right main urethra opened into the bladder neck; the right meatus was hypospadiac. The proximal end of the left accessory urethra opened into the right prostatic urethra and the left meatus was orthotopic. Severe chordee and normal urinary flow through both meatuses were present. At the age of 4 years, the diphallus was corrected. Both corpora cavernosa were dissected and the urethra was reconstructed, lengthening the right urethra with a 2.5-cm fragment of left urethra as a free graft excised from the emergence point and joined to the main urethra pasteriorly. The right urethra, whose meatus was hypospadiac and lateral, was dissected until a medial course was obtained. The glans was reconstructed using the lateral aspect of each glans; both medial aspects were extirpated. To correct the urethral trajectory, the urethra was fixed to the tip of the glans. A penis with two corpora cavernosa, a single glans, and a complete urethra with a meatus at the tip of the glans was obtained. The prepuce was reconstructed from the dorsal redundant aspect. The postoperative course was satisfactory.