Monitoring of Carbon Fiber-Reinforced Old Timber Beams via Strain and Multiresonant Acoustic Emission Sensors.

This paper proposes the monitoring of old timber beams with natural defects (knots, grain deviations, fissures and wanes), reinforced using carbon composite materials (CFRP). Reinforcement consisted of the combination of a CFRP laminate strip and a carbon fabric discontinuously wrapping the timber element. Monitoring considered the use and comparison of two types of sensors: strain gauges and multi-resonant acoustic emission (AE) sensors. Results demonstrate that: (1) the mechanical behavior of the beams can be considerably improved by means of the use of CFRP (160% in bending load capacity and 90% in stiffness); (2) Acoustic emission sensors provide comparable information to strain gauges. This fact points to the great potential of AE techniques for in-service damage assessment in real wood structures.

Effect of Location, Clone, and Measurement Season on the Propagation Velocity of Poplar Trees Using the Akaike Information Criterion for Arrival Time Determination.

The purchase price of any forest plantation depends on the quality of its raw wood, and specifically, variables such as density, orientation of the fibers, bending strength, and bending MoE (Modulus of Elasticity). The elastic waves propagation velocity has become one of the most popular parameters to evaluate the wood in standing trees. This study had two objectives: (1) Show how this velocity is clearly affected by the clone, the location of the crop, and the measurement season of poplar crops; and (2) apply the Akaike information criterion to determinate the arrival time of the waves, on the basis of the entropy of the signals recorded by the piezoelectric sensors placed on the trunk of the tree.

Pine Beams Retrofitted with FRP and Poplar Planks: Mechanical Behavior.

The paper presents an experimental analysis of the bending behavior of pine beams (Pinus Sylvester) retrofitted with fiber reinforced plastic (FRP) and poplar planks used as external covering. Poplar wood was chosen because of its rapid growth in planted forests, its homogeneity and attributes for sustainable local development, and high CO2 absorption rate. Vibration tests were also conducted in order to evaluate the stiffness in a non-destructive way and compare it with that obtained by means of the destructive tests. Three types of reinforcement were compared, namely: basalt fabric (FB), carbon fabric (FC) and carbon laminate (LC). In addition, some pine beams were reinforced only with poplar planks and used as control specimens in order to evaluate the improvement provided by the FRP. It was observed that a strong delamination preceded the final breakage of beam. Moreover, the results indicated that stiffness is provided mainly by the poplar plank and not by the FRP, as was expected.

Presence of pituitary adenylate cyclase-activating polypeptide (PACAP) defines a subpopulation of hypothalamic POMC neurons.

Several lines of evidence support a role for pituitary adenylate cyclase-activating polypeptide (PACAP) in the regulation of energy balance. In the present study, we have used fluorescent in situ hybridization and immunohistochemistry to investigate in detail the cellular localization and chemical content of PACAP mRNA- and peptide-containing neuronal cell bodies in the mediobasal hypothalamus of the rat. PACAP mRNA-containing cell bodies were demonstrated in high numbers in the ventromedial hypothalamic nucleus (VMH) and in lower numbers in the arcuate nucleus (Arc). In colchicine-treated rats, PACAP immunoreactivity was demonstrated in many cell bodies of the VMH and several cell bodies of the ARC. Double-labeling revealed that PACAP immunoreactivity was present in approximately 20% of pro-opiomelanocortin (POMC) neurons in the ventrolateral Arc as shown by presence of alpha-melanocyte-stimulating hormone (alpha-MSH), but not in agouti-related peptide (AgRP)-containing neurons in the ventromedial aspect of the Arc. PACAP immunoreactivity was also colocalized with the vesicular acetylcholine transporter (VAChT; a marker for cholinergic neurons) in Arc POMC neurons. Brainstem POMC neurons in the commissural part of the solitary tract nucleus were devoid of PACAP immunoreactivity. However, several VAChT-positive neurons in the dorsal motor nucleus of the vagus nerve were also PACAP immunoreactive, whereas VAChT-positive neurons of the motor nucleus of the hypoglossal nerve were PACAP-negative. The results show presence of PACAP with alpha-MSH in a subpopulation of hypothalamic POMC neurons and point further to the neurochemical heterogeneity of hypothalamic, but not brainstem, POMC neurons.

Experimental Comparison of Different Carbon Fiber Composites in Reinforcement Layouts for Wooden Beams of Historical Buildings.

This paper offers a detailed, quantitative and exhaustive experimental comparison in terms of mechanical properties of three different layouts of carbon composite materials (CFRP) used to strengthen existing old timber beams highly affected by diverse natural defects and biological attacks, testing the use of pultruded laminate attached on the tension side of the element (LR), CFRP fabrics totally U-shape wrapping the timber element (UR), and the combined use of both reinforcement solutions (UR-P). Moreover, unidirectional and bidirectional fabrics were considered and compared. Timber elements used for the experimental program were extracted from a recent rehabilitation of the roof of the current Faculty of Law building, University of Granada (Spain), catalogued as a historical edifice. Experimental results from bending tests show that in all cases reinforcement provides a clear improvement in terms of bending capacity and stiffness as compared with the control specimens (without reinforcement). However, improvements in terms of ductility differ considerably depending on the kind of layout.

Hypothalamic proopiomelanocortin (POMC) neurons have a cholinergic phenotype.

Neuronal networks originating in the hypothalamic arcuate nucleus play fundamental roles in the control of energy balance. Neuropeptide Y (NPY)-producing neurons in the arcuate nucleus stimulate food intake, whereas arcuate nucleus neurons that release the proopiomelanocortin (POMC)-derived peptide alpha-melanocyte-stimulating hormone (alpha-MSH) potently reduce food intake. Relatively little attention has been focused on classical neurotransmitters in regulation of food intake. Here, we have investigated the potential presence of acetylcholine (ACh) in NPY- and POMC-containing neuronal populations of the arcuate nucleus. Antisera to proteins required for cholinergic neurotransmission, including choline acetyltransferase (ChAT) and the vesicular acetylcholine transporter (VAChT), were employed in double-labeling immunohistochemical experiments. In colchicine-treated rats, ChAT- and VAChT-immunopositive cell bodies were located in the ventral aspect of the arcuate nucleus. ChAT and VAChT immunoreactivities were demonstrated in alpha-MSH- and cocaine- and amphetamine-regulated transcript (CART)-containing cell bodies of the arcuate nucleus, whereas cell bodies containing NPY or agouti-related peptide (AGRP) were distinct from VAChT-immunoreactive neuronal perikarya. VAChT immunoreactivity was also present in a large number of alpha-MSH-containing nerve fiber varicosities throughout the central nervous system. In the commissural part of the nucleus tractus solitarius, no alpha-MSH-containing cell bodies were found to have ChAT or VAChT immunoreactivity. The presence of markers for cholinergic neurotransmission in a subpopulation of hypothalamic POMC/CART neurons suggests co-release of ACh with peptides derived from the POMC precursor and CART. The results indicate a role for ACh in control of energy balance, mediating the effects of peripheral hormones such as leptin and insulin.

Neuregulins mediate calcium-induced glucose transport during muscle contraction.

Neuregulin, a growth factor involved in myogenesis, has rapid effects on muscle metabolism. In a manner analogous to insulin and exercise, neuregulins stimulate glucose transport through recruitment of glucose transporters to surface membranes in skeletal muscle. Like muscle contraction, neuregulins have additive effects with insulin on glucose uptake. Therefore, we examined whether neuregulins are involved in the mechanism by which muscle contraction regulates glucose transport. We show that caffeine-induced increases in cytosolic Ca2+ mediate a metalloproteinase-dependent release of neuregulins, which stimulates tyrosine phosphorylation of ErbB4 receptors. Activation of ErbB4 is necessary for Ca2+-derived effects on glucose transport. Furthermore, blockage of ErbB4 abruptly impairs contraction-induced glucose uptake in slow twitch muscle fibers, and to a lesser extent, in fast twitch muscle fibers. In conclusion, we provide evidence that contraction-induced activation of neuregulin receptors is necessary for the stimulation of glucose transport and a key element of energetic metabolism during muscle contraction.