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In this study, single wire arc additive manufacturing (SWAAM) and multi wire arc additive manufacturing (MWAAM) were used to fabricate the TC11 alloy. Microstructure and mechanical properties of TC11 alloy were studied. The results showed that the microstructure of MWAAM TC11 alloy composed of aand ßphase, and the proportion of ßphase increased slightly than that of SWAAM TC11 sample. Compared with the SWAAM TC11 sample, the microhardness of MWAAM TC11 alloy sample increased from 382 to 407?HV, and average ultimate tensile strength of MWAAM TC11 alloy sample increased from 922.01 to 934.56?MPa. The results indicate that the addition of wires can significantly improve both manufacturing efficiency and mechanical properties of TC11 alloy components.

In this study, single wire arc additive manufacturing (SWAAM) and multi wire arc additive manufacturing (MWAAM) were used to fabricate the TC11 alloy. Microstructure and mechanical properties of TC11 alloy were studied. The results showed that the microstructure of MWAAM TC11 alloy composed of αand βphase, and the proportion of βphase increased slightly than that of SWAAM TC11 sample. Compared with the SWAAM TC11 sample, the microhardness of MWAAM TC11 alloy sample increased from 382 to 407 HV, and average ultimate tensile strength of MWAAM TC11 alloy sample increased from 922.01 to 934.56 MPa. The results indicate that the addition of wires can significantly improve both manufacturing efficiency and mechanical properties of TC11 alloy components.

Pulsed infrared irradiation is an alternative neural stimulation with the advantages of being non-contact, spatially precise and artifact-free. Although infrared neural stimulation (INS) is well characterized in the peripheral nervous system, research has been limited in the central nervous system (CNS), especially the near infrared with wavelength around 800nm. To establish feasibility of INS in the CNS, pulsed near infrared laser (λ=808nm, pulse duration=300–1000μs, radiant exposure=0.73–2.45J/cm2, fiber size=105μm, repetition rate=2Hz) was used to stimulate the primary visual cortex (V1) of anesthetized Long Evans (LE) rats and the near-infrared-evoked neural activities in V1 was recorded. The impact of the duration of infrared pulse on the intensity and the latency of evoked potentials was assessed. We found that V1 was activated by 808nm laser and the optical evoked potential (OEP) included a descending wave (D1) and an ascending wave (A1) after optical stimuli. Furthermore, with the increase of the stimulation pulse duration, both the amplitude of D1 and the latency of A1 were increased. The results from this paper will facilitate the applications of near infrared neural stimulation on central nervous system.

Electrospun poly(glycolide-co-lactide) (PLA10GA90, LA/GA ratio 10/90) biodegradable nanofiber membranes possessed very high surface area to volume ratios and were completely noncrystalline with a relatively lowered glass transition temperature. These characteristics led to very different structure, morphology, and property changes during in vitro degradation, which were examined systematically. A shrinkage study showed that the electrospun crystallizable but amorphous PLA10GA90 membranes exhibited a very small shrinkage percentage when compared with the electrospun membranes of noncrystallizable poly(lactide-co-glycolide) (PLA75GA25, LA/GA 75/25) and poly(d,l-lactide). Although the weight loss of electrospun PLA10GA90 membranes exhibited a similar degradation behavior as cast thin films, detailed studies showed that the structure and morphology changes in electrospun membranes followed different pathways during the hydrolytic degradation. After 1 day of degradation in buffer solution at 37 °C, electrospun PLA10GA90 membranes exhibited a sudden increase in crystallinity and glass transition temperature, due to the fast thermally induced crystallization process. The continuous increase in crystallinity and apparent crystal size, as well as the decrease in long period and lamellae thickness, indicated that the thermally induced crystallization was followed by a chain cleavage induced crystallization process. The mass loss rate was accelerated after 6 days of degradation. The increase in glass transition temperature during this period further confirmed that the degradation of PLA10GA90 nanofibers was initiated from the amorphous region within the lamellar superstructures. A mechanism of structure and morphology changes during in vitro degradation of electrospun PLA10GA90 nanofibers is proposed.

Combined wide-angle X-ray diffraction (WAXD) and small-angle X-ray scattering (SAXS) studies using synchrotron radiation were carried out to investigate the structural development during in-situ solution spinning of poly(p-phenylenebenzobisoxazole) (PBO) in poly(phosphoric acid) (PPA). WAXD patterns indicated that the structure in the extruded PBO/PPA dope before coagulation (in water) possessed lyotropic “biaxial nematic” nematic order involving PBO−PPA complex as the mesogenic unit. A different biaxial nematic order in pure PBO was found to develop immediately upon coagulation in water. When the coagulation time exceeded 30 min, the complex PBO/PPA structure completely disappeared, and well-oriented PBO crystals were formed. The meridian peaks exhibited long streaks, indicating a translational disorder of PBO molecules in the fiber direction. SAXS patterns of the PBO fiber after coagulation showed equatorial streaks with no further maxima observed, which is attributed to a microvoid structure.

On-line studies of structural and morphological changes during the heating and drawing process of isotactic polypropylene (iPP) fiber were carried out using synchrotron small-angle X-ray scattering (SAXS) and wide-angle X-ray diffraction (WAXD) techniques. A unique image analysis method was used to deconvolute the two-dimensional (2D) WAXD patterns into quantitative fractions of crystal, mesomorphic, and amorphous phases. Results showed that the α-form crystals were quite defective in the initial iPP fibers and were converted into the mesomorphic modification by drawing at room temperature. Corresponding 2D SAXS patterns showed that there was no obvious long period (i.e., no lamellar structure) in the mesophase of the iPP fiber. We postulate that the constituents of the mesophase in iPP fibers include oriented bundles of helical chains with random helical hands and perhaps oriented chains with no helical structures; both have only partial packing ordering. The formation of the mesophase is through the destruction of the lamellar crystalline phase probably by pulling chains out from crystals. The α-form crystals were not converted into the mesophase by drawing at high temperatures. At higher temperatures, the α-form crystals became perfect and the crystallinity increased when the fiber was drawn. However, the draw ratio showed an inverse effect. The increase in draw ratio had a minimal effect on the crystallinity, but the transformation from the amorphous phase to the mesophase became dominant.

On-line studies of structure and morphology changes in Kevlar 49 fibers during stretching were carried out using synchrotron simultaneous small-angle X-ray scattering (SAXS) and wide-angle X-ray diffraction (WAXD) techniques. A unique two-dimensional (2D) image analysis method was used to extract quantitative information of crystal, amorphous and mesomorphic fractions from 2D WAXD patterns. Results showed that about 20% of the fraction (mass) in the Kevlar 49 fiber was mesophase, 50% was crystalline and 30% was amorphous. There were transitions between crystal, amorphous and mesomorphic fractions during deformation. The crystal orientation was obtained in terms of the Herman's orientation function f2from the azimuthal scan of the (200) crystal reflection. The crystal orientation was found to be quite high in the Kevlar 49 fiber and increased with the stretch ratio. The fibril length and misorientation were also obtained from 2D SAXS patterns by using the Ruland method. Results showed that the fibril length decreased with the stretch ratio until 2.0% and then increased. The misorientation decreased with increasing stretch ratio.

In an attempt to study the functional role of the positively charged amino acids present in the S4 segment of hyperpolarization‐activated cyclic nucleotide‐gated cation (HCN) channels, we have introduced single and sequential amino acid replacements throughout this domain in the mouse type 2 HCN channel (mHCN2). Sequential neutralization of the first three positively charged amino acids resulted in cumulative shifts of the midpoint voltage activation constant towards more hyperpolarizing potentials. The contribution of each amino acid substitution was approximately −20 mV. Amino acid replacements to neutralize either the first (K291Q) or fourth (R300Q) positively charged amino acid resulted in the same shift (about −20 mV) towards more hyperpolarized potentials. Replacing the first positively charged amino acid with the negatively charged glutamic acid (K291E) produced a shift of approximately −50 mV in the same direction. None of the above amino acid substitutions had any measurable effect on the time course of channel activation. This suggests that the S4 domain of HCN channels critically controls the voltage dependence of channel opening but is not involved in regulating activation kinetics. No channel activity was detected in mutants with neutralization of the last six positively charged amino acids from the S4 domain, suggesting that these amino acids cannot be altered without impairing channel function.

Morphological development of the homopolymer, poly(glycolide), PGA; its random copolymers, poly(glycolide-co-lactide), PGA-co-PLA (5:95 and 90:10) and segmented block copolymer, poly(glycolide-co-caprolactone), PGA-co-PCL (75:25) during isothermal crystallization was studied using simultaneous small-angle X-ray scattering (SAXS) and wide-angle X-ray diffraction (WAXD) techniques with synchrotron radiation. It was found that the lamellar morphology could best describe the superstructure of these polymers. During crystallization, both average long period (L) and lamellar thickness (lc) exhibited notable decreases with time, which were attributed to the mechanism of secondary crystallization in the form of lamellar-stacks insertion. Both values of Land lcwere found to increase with temperature. In the chosen crystallization temperature range (100–200°C), homopolymer PGA exhibited the fastest crystallization rate and the lowest values of Land lc, probably due to the largest degree of supercooling. As a result, in copolymers with higher content of PGA, the crystallization rate increased and the values of Land lcdecreased. The value of amorphous layer thickness (la) was the highest in PGA-co-PLA (5:95), but those in PGA, PGA-co-PLA (90:10) and PGA-co-PCL (75:25) were about the same. In addition, the values of L, lcand the crystallinity were the highest in PGA-co-PLA (5:95). Corresponding degrees of crystallinity in PGA homopolymer and PGA-co-PCL (75:25) and PGA-co-PLA (90:10) copolymers were relatively low.

The changes of crystal structure and morphology in poly(glycolide), PGA, homopolymer and poly(glycolide-co-l-lactide), PGA-co-PLA, (90/10) random copolymer during in vitro degradation were investigated by gel permeation chromatography (GPC), wide-angle X-ray diffraction (WAXD), and small-angle X-ray scattering (SAXS). GPC results showed that the molecular weight and polydispersity decreased significantly during the first 2 weeks of degradation. In contrast, the mass degree of crystallinity, φmc, determined from WAXD showed an Avrami-like behavior in both polymers, increasing rapidly within the first 2 weeks and gradually reaching a plateau value. The effect of degradation on the crystal unit cell dimensions was noticeable and anisotropic, which may reflect the process of crystal perfection in vitro. Corresponding SAXS results also showed that the long period (L), lamellar thickness (lc), and amorphous layer thickness (la) from the crystal lamellar stacks all decreased appreciably in both PGA and PGA-co-PLA samples during the first 3 weeks of degradation. By comparing molecular weight and lamellar thickness results, we conclude that the fully degraded chain fragments have an average length of about 3 times the crystal thickness. On the basis of these results, we propose that degradation proceeds through the combined processes of chain scission and cleavage-induced crystallization in the amorphous regions via two pathways. (1) The degradation occurs in the amorphous gaps between the crystal lamellar stacks, where the amorphous chains are broken leading to greater mobility to form new crystal lamellar stacks with thinner thickness. This process significantly reduces the averaged values of L, lc, and la. (2) The degradation process also occurs in the amorphous layer domain between the adjacent lamellae within the lamellar stacks, where chain scission causes the rapid decrease in polydispersity.

The effects of Ro 40-5967, a nondihydropyridine Ca++ channel blocker, on low-voltage activated (T-type) and high-voltage activated (L-type) Ca++ channels were compared. L-type barium currents were measured in Chinese hamster ovary cells stably transfected with the alpha 1 subunit of the class Cb Ca++ channel. T-type barium currents were investigated in human medullary thyroid carcinoma cells. The Ba++ currents of human medullary thyroid carcinoma cells were transient, activated at a threshold potential of -50 mV with the maximum at -14 +/- 3.2 mV and blocked by micromolar Ni++. The T- and L-type current inactivated with time constants of 33.4 +/- 4.1 and 416 +/- 26 msec at maximum barium currents, respectively. Ro 40-5967 inhibited reversibly the T- and L-type currents with IC50 values of 2.7 and 18.6 microM, respectively. The inhibition of the L-type current was voltage-dependent, whereas that of the T-type current was not. Ro 40-5967 blocked T-type current already at a holding potential of -100 mV. The different types of block, i.e., voltage-dependent vs. tonic block, may contribute to the pharmacological profile of Ro 40-5967 in intact animals.

Si, dans le cas du radiodiagnostic, les limites de dose individuelles ne s'appliquent pas à l'exposition des patients, l'optimisation de la radioprotection peut, par contre, jouer un rôle important. L'utilisation du principe d'optimisation a guidé ce projet visant à améliorer, en Chine, la protection des patients lors de la pratique du radiodiagnostic médical. Notre enquête, réalisée dans les régions de Sichuan, Shandong et Pékin (Chine), a évalué la situation actuelle de la protection des patients. Les doses aux patients ont été classées en dose réelle, dose justifiée et dose optimisée afin d'évaluer séparément l'influence des facteurs de gestion et d'équipement. Les résultats démontrent l'urgente nécessité de résoudre un certain nombre de problèmes dans la protection contre les rayons X. Cet article indique, toutefois, que les perspectives de réduction des doses sont encourageantes si des dispositions adéquates sont adoptées. Ainsi, une bonne gestion, sans changement radical des équipements actuels, peut réduire les doses en fluoroscopie et radiographie pulmonaires, respectivement, de 40 à 18 %, la révision de certains équipements de 82,4 et 66 %, et de 80 % dans les examens du tractus gastrointestinal avec repas baryté. L'utilisation de la radiographie pulmonaire au lieu de la fluoroscopie associée à d'autres dispositions peut aboutir à une réduction de 91,7 %. Une analyse de cette optimisation montre que ces dispositions sont conformes au principe d'optimisation de la radioprotection.

Nickel-doped Al2O3 (sapphire) crystals have been studied using optical absorption and transmission electron microscopy. After reduction at elevated temperatures in a hydrogen atmosphere, these crystals exhibit a dark colouration. Our results indicate that the colouration is due to Mie scattering from precipitates resulting from the reduction process. Analytical transmission electron microscopy techniques revealed the presence of metallic precipitates and identified them as Al3Ni. The precipitate distribution is very inhomogeneous.

The microstructure in C49-TiSi2 crystals has been studied by high-resolution electron microscopy (HREM) and electron microdiffraction. HREM images show that the crystals of C49-TiSi2 were heavily faulted on (010) planes, with a displacement of ½(a+c). In addition, 90d`domains exist, which relate to the faults with a displacement of ½(a+c). There are two types of 90d`domain boundary parallel to (100) or (001) plane. Type I has a sharp interface and type II has a transition zone between [100] and [001] domains, which may be explained in the light of the richness and dilution of Si atoms at the boundaries. New structures have been found which depend on the arrangement sequence of the layers with a displacement of ½(a+c) along the [010] direction of C49-TiSi2. The structure P has the Cmmm space group and the same cell dimension as C49-TiSi2, with ap//a49, bp//b49 and cp//c49. The structure S, a superstructure of TiSi2, is formed with one unit cell of C49-TiSi2 overlapping another unit cell with a displacement of ½(a+c). The formation of the two structures is discussed.

The cDNA of three variants of a cyclic nucleotide-gated (CNG) channel modulatory subunit (CNG4c-CNG4e) has been cloned. CNG4c, CNG4d, and CNG4e differ slightly from each other within an amino-terminal sequence that was originally reported as part of the bovine retinal glutamic acid-rich protein (GARP). The core region of CNG4 is homologous to the second subunit of the human rod photoreceptor channel (hRCNC2b), suggesting that both proteins are alternatively spliced products of the bovine and human homologue of the same gene. CNG4 transcripts are present in retina, testis, kidney, heart, and brain. Expression of CNG4 in HEK293 cells did not lead to detectable currents. Coexpression of CNG4 with the principal subunit of the bovine testis CNG channel (CNG3) resulted in currents which differed in several aspects from that induced by CNG3 alone. The heterooligomeric CNG3/CNG4 and the homooligomeric CNG3 channels were modified by Ca2+-calmodulin and some calmodulin antagonists. The results suggest that CNG4 forms functional heterooligomeric channels with CNG3 in vitro and probably also in intact tissues.

Veratridine modification of Na current was examined in single dissociated ventricular myocytes from late-fetal rats by applying pulses to -30 mV for 50 ms every 2 or 5 s from a holding potential of -100 mV (20 degrees C) and measuring amplitude, Itail, and time constant, tau tail, of the post-repolarization inward tail current induced by the alkaloid. Increasing the pH of a 30 microM veratridine superfusate from 7.3 to 8.3 (which increases the fraction of uncharged veratridine molecules from 0.5 to 5% while decreasing that of protonated molecules from 99.5 to 95%) increased Itail by a factor of 2.5 +/- 0.5 (mean +/- SEM; n = 3). Switching from 100 microM veratridine superfusate at pH 7.3 to 10 microM at pH 8.3 did not affect the size of Itail (n = 4). Intracellular (pipette) application of 100 microM veratridine at pH 7.3 or 8.3 produced small Itail's suggesting transmembrane loss of alkaloid. If this was compensated for by simultaneous extracellular application of 100 microM veratridine at a pH identical to intracellular pH, Itail (measured relative to the maximum amplitude induced by a combination of 100 microM veratridine and 1 microM BDF 9145 in the same cell) at pHi 7.3 did not significantly differ from that at pHi 8.3 (84 +/- 4 vs. 70 +/- 6%; n = 3 each). Results from six control cells and five cells subjected to extra- and/or intracellularly increased viscosity by the addition of 0.5 or 1 molal sucrose showed that increasing intracellular viscosity 1.6- and 2.5-fold increased tau tail 1.5- and 2.3-fold, respectively, while a selective 2.5-fold increase of extracellular viscosity did not significantly affect tau tail.(ABSTRACT TRUNCATED AT 250 WORDS)

Veratridine modification of Na current was examined in single dissociated ventricular myocytes from late-fetal rats. Extracellularly applied veratridine reduced peak Na current and induced a noninactivating current during the depolarizing pulse and an inward tail current that decayed exponentially (tau = 226 ms) after repolarization. The effect was quantitated as tail current amplitude, Itail (measured 10 ms after repolarization), relative to the maximum amplitude induced by a combination of 100 microM veratridine and 1 microM BDF 9145 (which removes inactivation) in the same cell. Saturation curves for Itail were predicted on the assumption of reversible veratridine binding to open Na channels during the pulse with reaction rate constants determined previously in the same type of cell at single Na channels comodified with BDF 9145. Experimental relationships between veratridine concentration and Itail confirmed those predicted by showing (a) half-maximum effect near 60 microM veratridine and no saturation up to 300 microM in cells with normally inactivating Na channels, and (b) half-maximum effect near 3.5 microM and saturation at 30 microM in cells treated with BDF 9145. Due to its known suppressive effect on single channel conductance, veratridine induced a progressive, but partial reduction of noninactivating Na current during the 50-ms depolarizations in the presence of BDF 9145, the kinetics of which were consistent with veratridine association kinetics in showing a decrease in time constant from 57 to 22 and 11 ms, when veratridine concentration was raised from 3 to 10 and 30 microM, respectively. As predicted for a dissociation process, the tail current time constant was insensitive to veratridine concentration in the range from 1 to 300 microM. In conclusion, we have shown that macroscopic Na current of a veratridine-treated cardiomyocyte can be quantitatively predicted on the assumption of a direct relationship between veratridine binding dynamics and Na current and as such can be successfully used to analyze molecular properties of the veratridine receptor site at the cardiac Na channel.

The intestinal mucosa forms a physical and metabolic barrier against the diffusion of pathogens, toxins and allergens from the lumen into the circulatory system. Compromising the barrier function of the intestinal mucosa increases host susceptibility to luminal antigens and pathogens, results in impaired host lipid metabolism by decreasing lipid transporter expression in epithelial cells. Methylation of the N6 position of adenosine (m6A) is the most prevalent internal mRNA modification in eukaryotes; it could act as the transcriptional brake of inflammatory response. However, whether the m6A modification participates in the regulation of lipid metabolism, especially in the regulating the expression of lipid transporter, is unknown. In this study, we used the E.coli K88 infected porcine intestinal epithelial cells, investigated the role of m6A in intestine inflammation response and how m6A regulated lipid transporter expression. The results showed that: (i) the ratio of m6A/A was significantly decreased after E.coli K88 infection (p < 0.05); (ii) the expression of m6A “readers” (YTHDF1, YTHDF2) was significantly increased after E.coli K88 infection (p < 0.01), whereas that of the “eraser” FTO and “writer” Mettl3 were not changed; (iii) the expression of lipid transporter (CD36, FATP4) was significantly decreased after E.coli K88 infection (p < 0.01); (iv) compared with normal porcine epithelial cells, the expression of lipid transporter in YTHDF1 deficiency epithelial cells did not decrease anymore after E.coli K88 infection. According to our results, the E.coli K88 infection caused intestinal inflammatory could impair the lipid transport in porcine intestinal epithelial cells in YTHDF1-dependent m6A pathway. The findings of this study provide valuable information for pig intestine health.

The phosphodiesterase inhibitors papaverine, theophylline and 3-isobutyl-1-methylxanthine (IBMX) reveal a negative inotropic effect of acetylcholine in cat ventricular heart muscle. This effect is unrelated to β-adrenoceptor stimulation and possibly mediated by the accumulation of cyclic GMP.

Review: 16 refs.