Pine bark tannin foams were prepared for the first time. The high reactivity of pine tannins in relation to other tannins induced the change in the tannin foam formulations in order to coordinate ...foam resin hardening, reaction exotherm and solvent blowing allowing the formation of a rigid foam. Pine tannin foams with and without formaldehyde were prepared. Their characteristics were tested as regards stress–strain curves, thermal conductivity, Young's modulus, compression strength, densification, densification rate and energy absorbed under compression. Mostly, properties the pine tannin foams with formaldehyde have properties similar to mimosa tannin foams, in some cases slightly lower and in others slightly higher. Pine tannin foams without formaldehyde showed lower mechanical strength and more elastic behaviour. Display omitted
► Pine bark tannin foams were prepared with and without formaldehyde for the first time. ► High reactivity tannin induced change in foam formulations to coordinate foam resin hardening, reaction exotherm and solvent blowing. ► Stress–strain curves, thermal conductivity, E-modulus, compression strength and energy adsorbed, densification and its rate, were tested. ► Pine tannin foams have properties similar to mimosa tannin foams. ► Pine tannin foams without formaldehyde showed lower mechanical strength and more elastic behaviour.
Pine bark tannin foams were prepared for the first time. The high reactivity of pine tannins in relation to other tannins induced the change in the tannin foam formulations in order to coordinate foam resin hardening, reaction exotherm and solvent blowing allowing the formation of a rigid foam. Pine tannin foams with and without formaldehyde were prepared. Their characteristics were tested as regards stress–strain curves, thermal conductivity, Young's modulus, compression strength, densification, densification rate and energy absorbed under compression. Mostly, properties the pine tannin foams with formaldehyde have properties similar to mimosa tannin foams, in some cases slightly lower and in others slightly higher. Pine tannin foams without formaldehyde showed lower mechanical strength and more elastic behaviour.
Integration of Spin Torque Nano-Oscillators STNO's in conventional microwave circuits means that the devices have to meet certain specifications. One of the most important criteria is the phase ...noise, being the key parameter to evaluate the performance and define possible applications. Phase locking several oscillators together has been suggested as a possible means to decrease phase noise and consequently, the linewidth. In this work we present experiments, numerical simulations and an analytic model to describe the effects of thermal noise in the injection locking of a tunnel junction based STNO. The analytics show the relation of the intrinsic parameters of the STNO with the phase noise level, opening the path to tailor the spectral characteristics by the magnetic configuration. Experiments and simulations demonstrate that in the in-plane magnetized structure, while the frequency is locked, much higher reference currents are needed to reduce the noise by phase locking. Moreover, our analysis shows that it is possible to control the phase noise by the reference microwave current (I
) and that it can be further reduced by increasing the bias current (I
) of the oscillator, keeping the reference current in feasible limits for applications.
► Formaldehyde-free pine and procyanidin tannin/furanic foams are prepared by a new approach. ► These foams are prepared by using alternative non-toxic, non-volatile aldehydes: glyoxal or ...glutaraldehyde. ► These foams thermal conductivity, cell size and mechanical compressive strength were tested. ► Glyoxal can completely substitute formaldehyde to prepare such foams with good properties but not glutaraldehyde.
Rigid foams based on tannin extracted form Pinus radiata bark have been recently developed and present many advantages for use as an insulation material instead of synthetic foams. Formaldehyde-free, in reality any-ldehyde-free pine tannin foams have been developed but present lower mechanical resistance undergoing compression. In this work, formaldehyde-free pine tannin/furanic rigid foams are prepared by a new approach, namely using alternative non-toxic, non-volatile aldehydes as hardeners: glyoxal or glutaraldehyde. Physical properties – thermal conductivity, cell size – and mechanical – compressive strength – are tested. It was found that glyoxal can completely substitute formaldehyde to prepare foams with good properties for insulation whereas glutaraldehyde is not suitable for the purpose because of its lower reactivity with pine tannins.
•Open cells tannin–furanic foams give excellent acoustic insulation.•At frequencies equal and higher than 1000Hz coefficients of acoustic absorption were 0.7–0.97.•The acoustic absorption coefficient ...was lower 0.4–0.6 at lower frequencies (250–500Hz).•The thicker is the sample the better is the absorption at frequencies under 1000Hz.•The more open cells foams of higher porosity, and lower resistivity perform slightly better.•The artifice of adding perforations to the foams according to the double porosity concept is not needed for these foams.
Open cells structure tannin–furanic foams prepared using two different types of tannins have been shown to give good sound absorption/acoustic insulation characteristics at medium and high frequencies (1000–4000Hz) with coefficients of acoustic absorption of 0.85–0.97. Their acoustic absorption coefficient was lower 0.40–0.60 at lower frequencies (250–500Hz). Compared with commercial foams, tannin–furanic foams have the same typical behavior of light porous materials. The more open-cell is the material the better is its sound absorption. Thicker samples absorb better at medium frequencies for all types of porous material tested.
•Tannin-based foams were prepared with maritime pine (Pinus pinaster) tannin for the first time.•Gel time of maritime pine tannins and three aldehydes (formaldehyde, glyoxal, and glutaraldehyde) were ...measured under acid condition. Maritime pine tannins are highly purified and highly reactive in comparison with radiata crude tannins.•A non-ionic surfactant (castor oil ethoxylated) and a plasticizer (polyethylene 400) induced change in foam formulations to coordinate foam resin hardening, reaction exotherm and solvent blowing.
New formulations of procyanidin tannin-based foams have been developed for the first time with maritime pine (Pinus pinaster) tannins. These tannins have an extremely high reactivity which makes them difficult to use for traditional tannin-based foams. For this work, an equipment named FOAMAT was used to record simultaneously temperature, pressure, velocity and dielectric polarization during foaming. The results highlight the role of surfactant (castor oil ethoxylate) and plasticizer (Polyethylene glycol) during foam formation: polymerization, expansion, hardening, and shrinkage. In this work, foams density – and its physical properties – are either surfactant or plasticizer-controlled. With polyethylene glycol and castor oil ethoxylate, homogeneous microstructure foams were obtained but polyethylene glycol made the foams more elastic and improved their shrinkage.
Sequence analysis revealed phospholipase A2 (PLA2) motifs in capsid proteins of parvoviruses. Although PLA2 activity is not known to exist in viruses, putative PLA2s from divergent parvoviruses, ...human B19, porcine parvovirus, and insect GmDNV (densovirus from Galleria mellonella), can emulate catalytic properties of secreted PLA2. Mutations of critical amino acids strongly reduce both PLA2 activity and, proportionally, viral infectivity, but cell surface attachment, entry, and endocytosis by PLA2-deficient virions are not affected. PLA2 activity is critical for efficient transfer of the viral genome from late endosomes/lysosomes to the nucleus to initiate replication. These findings offer the prospect of developing PLA2 inhibitors as a new class of antiviral drugs against parvovirus infections and associated diseases.
Here we review current evidence in support of the cortical disconnection/cortical connectivity model of Alzheimer disease (AD) pathogenesis, a model which predicts that one of the first events in AD ...is damage to the entorhinal cortex and/or subiculum resulting in the disconnection of the hippocampal formation and neocortex, and the subsequent progression of the disease in a stepwise fashion along cortico-cortical connections. Much of the evidence for this model has been obtained from studies involving the limbic system where investigators have demonstrated a precise correspondence between established patterns of connectivity and the degenerative changes associated with AD. In addition, some studies of the distribution of neuritic plaques (NP) and neuro-fibrillary tangles (NFT) in the neocortex and subcortical structures have yielded corroborative data. The validity of the cortical disconnection/connectivity model in the neocortex remains to be established or refuted. We propose that testing of this model can be accomplished with systematic studies of the laminar and regional distribution of NP and NFT in a series of sequentially interconnected cytoarchitectural regions that also form part of two functional hierarchies--the paralimbic and occipitotemporal visual systems. To adequately control for variation between brains affected by AD, it is imperative that such studies be conducted in a large but varied population of AD cases exhibiting differences in several variables, including clinical and/or neuropathological severity of the disease, temporal duration of the disease, and clinical/neuropsychological profile. We believe that further understanding of the relationship between characteristic AD pathology and intrinsic anatomico-functional circuits will contribute not only to our comprehension of AD pathogenesis but also to our general knowledge of the human brain.
The twin-to-twin transfusion syndrome (TTS) results from an unbalanced blood supply through placental anastomoses in monochorionic twins. It induces growth restriction, renal tubular dysgenesis, and ...oliguria in the donor and visceromegaly and polyuria in the recipient. A better understanding of its pathophysiology could contribute to improving the management of TTS, which still carries a high perinatal mortality in both twins. As well as several other candidates, the renin-angiotensin system might be involved in TTS. To evaluate its role in the pathogenesis of the syndrome, we studied the kidneys of 21 twin pairs who died from TTS at 19 to 30 weeks, compared with 39 individuals in a control group, using light microscopy, immunohistochemistry, and in situ hybridization. The overexpression of the renin protein and transcript with frequent evidence of renin synthesis by mesangial cells was observed in the donor kidneys, presumably as a consequence of chronic renal hypoperfusion. This upregulation of renin synthesis might be beneficial to restore euvolemia. In severe cases of TTS, however, angiotensin-II-induced vasoconstriction acts as an additional deleterious factor by further reducing the renal blood flow in donors. In recipients, renin expression was virtually absent, possibly because it was down-regulated by hypervolemia. However, in addition to congestion and hemorrhagic infarction, there were severe glomerular and arterial lesions resembling those observed in polycythemia- or hypertension-induced microangiopathy. We speculate that fetal hypertension in the recipient might be partly mediated by the transfer of circulating renin produced by the donor, through the placental vascular shunts.
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