Folding Resistance Research Articles

A small-molecule Nrf1 and Nrf2 activator mitigates polyglutamine toxicity in spinal and bulbar muscular atrophy.

Spinal and bulbar muscular atrophy (SBMA, also known as Kennedy's disease) is one of nine neurodegenerative disorders that are caused by expansion of polyglutamine-encoding CAG repeats. Intracellular accumulation of abnormal proteins in these diseases, a pathological hallmark, is associated with defects in protein homeostasis. Enhancement of the cellular proteostasis capacity with small molecules has therefore emerged as a promising approach to treatment. Here, we characterize a novel curcumin analog, ASC-JM17, as an activator of central pathways controlling protein folding, degradation and oxidative stress resistance. ASC-JM17 acts on Nrf1, Nrf2 and Hsf1 to increase the expression of proteasome subunits, antioxidant enzymes and molecular chaperones. We show that ASC-JM17 ameliorates toxicity of the mutant androgen receptor (AR) responsible for SBMA in cell, fly and mouse models. Knockdown of the Drosophila Nrf1 and Nrf2 ortholog cap 'n' collar isoform-C, but not Hsf1, blocks the protective effect of ASC-JM17 on mutant AR-induced eye degeneration in flies. Our observations indicate that activation of the Nrf1/Nrf2 pathway is a viable option for pharmacological intervention in SBMA and potentially other polyglutamine diseases.

The preparation and application of CTBN modified epoxy adhesive

Purpose – The purpose of this study is to investigate the effects of two epoxy ratio and carboxyl-terminated butadiene solid rubber (CTBN) content on adhesive and flexible copper clad laminate (FCCL) performance. The epoxy adhesive used for FCCL was prepared with epoxy resin of 901 and 6128 as matrix and CTBN as toughener. Design/methodology/approach – The epoxy adhesive was prepared with epoxy resin as matrix, CTBN as toughener and 4,4′-diamino diphenyl sulfone as curing agent in solvent of butanone by mechanical agitation. The adhesives were cast on the polyimide film; subsequently, the polyimide film was dried at 160°C for 3 min to remove the solvent. Then, it was laminated with copper foil at 180°C with the pressure of 12 MPa for 3 min. The FCCL was obtained after heating for 3 h in a vacuum oven at 160°C. The structure and dielectric properties of cured adhesive, surface morphology of peeling FCCL and mechanical properties of FCCL were determined. Findings – CTBN was found to react with the epoxy resin during the curing process, with the rubber phase being precipitated and dispersed in the epoxy matrix. The relative dielectric constant and the dielectric loss tangent slightly increased with increasing CTBN content. The peeling strength of FCCL increased accompanied by a decrease of folding resistance with the increase of 901 content. Further, with the addition of XNBR, the peel strength of FCCL increased, as well as the folding resistance of FCCL, but at a higher XNBR level of 20 weight per cent, the folding resistance of FCCL tended to decrease. Research limitations/implications – In the study reported here, the effects of different epoxy resin molecular weight and CTBN content were investigated. Results of this research could benefit in-depth understanding of the influence of epoxy resin molecular weight and CTBN content on adhesive performance and could further promote the development of epoxy adhesive. Practical implications – The adhesion of epoxy adhesive prepared from epoxy resin with different molecular weight and CTBN increased, leading to the increase in peeling strength and folding resistance of FCCL. Social implications – The peeling strength of FCCL increased as the adhesion strength of epoxy adhesive increased by adding CTBN, making FCCL widely applicable. Originality/value – The mechanical properties of epoxy adhesive were increased by adding CTBN. The effects of CTBN on the microstructure and properties of FCCL were discussed in detail.

Properties and paper sizing application of waterborne polyurethane emulsions synthesized with isophorone diisocyanate

In this work, a two-step synthesis methodology has been used to synthesize a series of waterborne polyurethane (WPU) emulsions with isophorone diisocyanate (IPDI), poly-caprolactone diol (PCL) and dimethylol propionic acid (DMPA) as monomers and ethylenediamine (EDA) as the chain extender, respectively. The influences of the NCO/OH molar ratio, DMPA content, chemicals-adding sequence, and acetone content on the physical properties of the resultant emulsions have been investigated in detail. The results show that the emulsion viscosity increases with an increase in the NCO/OH molar ratio or DMPA content whereas it declines sharply as the acetone amount increases. The emulsion particle size is seen to increase with the NCO/OH molar ratio but it decreases as the DMPA content increases. The chemicals-adding sequence is observed to strongly affect the particle size and viscosity of the resultant emulsions. For cast films, with an increase in the NCO/OH molar ratio, the elongation monotonically decreases while the tensile strength is seen to increase at first and then deceases. The film water absorption capacity is found to go up as the DMPA content increases. Furthermore, after sized with the emulsions, the paper water resistance is markedly improved and the 30s Cobb value is seen to decrease by 63% as compared to the unsized counterpart. The paper folding resistance and the tensile index are also improved to certain extents. For producing well-performed WPU emulsions for sizing paper sheets, an NCO/OH molar ratio of 1.6–1.8 and a DMPA content of 6.0–7.0 wt.% are preferably chosen.

Waterborne polyurethane/poly(n-butyl acrylate-styrene) hybrid emulsions: Particle formation, film properties, and application

In this work, a hybrid synthesis technology has been used to fabricate waterborne polyurethane (WPU)/poly(n-butyl acrylate-styrene) (PBS) emulsions with dimethylol-propionic acid (DMPA) as chain extender. The influences of the PBS, styrene, and DMPA contents on the physical properties of the resultant emulsions and cast films have been investigated in detail using various characterization methods. The experimental results show that with an increase in the PBS or styrene content, the particle size in emulsions increases but the viscosity of the emulsions decreases and that the opposite applies for the DMPA content. For cast films, with an increase in the styrene or DMPA content, the tensile strength increases whereas the elongation decreases. The water absorption capacity of the film decreases with an increase in the styrene content or a decrease in the DMPA content. Furthermore, the emulsions synthesized have been used for paper sizing applications. The treated papers exhibit greatly improved water resistance, and the Cobb values at 30 and 60s are only 10.23 and 11.89%, respectively, of those of unsized papers. The other paper properties, such as gloss, smoothness, folding resistance, and burst strength, are also considerably improved.

Properties and Application of Waterborne Polyurethane/starch Composite Surface Sizing Agent

TDI as main isocyanate, IPDI as end-capping reagent, waterborne polyurethane (WPU) surface-sizing agent have been obtained by a pre–polymerization process. WPU were mixed with starch SSA in different proportion and a composite sizing agent obtained. It is indicated the water resistance, gloss and folding resistance of WPU/starch sized papers are much higher than starch sized papers. The ink absorption obviously decreases and the mechanical properties wholly increase. WPU/starch composite emulsions is a new kind of surface sizing agent having broad development prospects.

LuxR-type quorum-sensing regulators that are detached from common scents

The ability of LuxR-type proteins to regulate transcription is controlled by bacterial pheromones, N-acylhomoserine lactones (AHLs). Most LuxR-family proteins require their cognate AHLs for activity, and at least some of them require AHLs for folding and protease resistance. However, a few members of this family are able to fold, dimerize, bind DNA, and regulate transcription in the absence of AHLs; moreover, these proteins are antagonized by their cognate AHLs. Complexes between some of these proteins and their DNA binding sites are disrupted by AHLs in vitro. All such proteins are fairly closely related within the larger LuxR family, indicating that they share a relatively recent common ancestor. The 3' ends of the genes encoding these receptors invariably overlap with the 3' ends of the cognate AHL synthase genes, suggesting additional antagonism at the level of mRNA synthesis, stability or translation.

Propriedades mecânicas do cimento ósseo e da poliuretana de mamona com e sem catalisador

Avaliou-se o comportamento mecânico do polímero de mamona, tendo por variáveis o tempo de produção e a presença de catalisador, e utilizando como padrão comparativo o cimento ósseo (polimetilmetacrilato). Foram estabelecidos três grupos experimentais, de acordo com o tipo de corpo de prova (cilindro ou barra) e polímero utilizado, que foram posteriormente subdivididos em subgrupos conforme o tempo após produção, ou seja, 24, 48 e 72 horas. O ensaio de compressão analisou a carga máxima e a tensão e o ensaio de dobramento estudou o módulo de dobramento e a resistência. Estatisticamente não houve diferenças nos valores de resistência à compressão ou ao dobramento às 24, 48 e 72 horas após a produção do polimetilmetacrilato e da poliuretana, com ou sem catalisador. A poliuretana com catalisador foi a mais resistente nos ensaios de compressão, apresentando módulo de dobramento semelhante ao do polimetilmetacrilato e resistência ao dobramento superior à da poliuretana sem catalisador. Conclui-se que: o tempo não alterou as propriedades mecânicas dos compósitos avaliados; o catalisador melhorou o desempenho mecânico da poliuretana de mamona; na resistência mecânica à compressão, a poliuretana com catalisador suportou mais carga que o polimetilmetacrilato.

Effect of Shape and Application Process of Precipitated Calcium Carbonate on Optical and Mechanical Properties of Recycled Paper

ABSTRACT Recycled paper was made with Precipitated Calcium Carbonate (PCC) which is famous for alkaline mineral filler. Filling behavior, whiteness, opacity and mechanical property change according to shape of PCC. Calcite PCC was difficult to disperse and to be filled uniformly because calcite PCC hardly aggregated but it could improve tensile strength as its amount increases. A suitable filler to be filled in recycled paper was needle-like aragonite and it could increase folding resistance slightly when aragonite of 10 wt% against dried pulp mass was added. PCC already synthesized was not effective on improvement of optical property but a new process, In-situ process, developed whiteness and opacity because PCC nucleated on fiber surface and then diffused reflection happens on surface. Whiteness of recycled paper made by In-situ process was 64 which is 92% of standard presented by Korea Public Procurement Service.

Properties and Application Prospects of 1-(Vinyloxyalkoxy)propylene 2,3-Oxide Copolymers

Thermal stability, impact strength, folding resistance, and adhesion were studied for copolymers of vinyl chloride and 1-(vinyloxyalkoxy)propylene 2,3-oxides prepared in acetone and dimethyl sulfoxide.

Creasability testing by inclined rules — a base for standardized specification of paperboard

In die cutting manufacture of paperboard it is necessary to apply the correct creasing conditions, e.g. neither too small nor too big a rule height, in order to achieve sufficiently low folding resistance without any cracks along the folding lines. The most appropriate rule height for a given paperboard is usually determined by trying different rule heights in a series of very time consuming and costly trial and error tests. And, in practice, this procedure must be repeated for each major change in board quality. This report shows that an inclined crease rule, i.e. a rule having a gradually increasing rule height, can be used advantageously to rationalize such tests and to achieve much greater reliability. A folding line produced by such an inclined rule contains both the upper limit for the rule height, i.e. where cracks start to appear, and the lower limit, i.e. where the rule height is obviously too small, and the technical range for achieving a good creasing result is thus clarified in one single test. Illustrative data for two types of paperboard are given as well as some theoretical aspects of the concept of creasability. Considering that the described method not only rationalizes the testing work but also enables more reliable observations to be made than have been possible in the past, the method opens new potentials for effective research and development in the fields of converting, convertibility, die form design, etc. © 1997 John Wiley & Sons, Ltd.

Creasability testing by inclined rules — a base for standardized specification of paperboard

In die cutting manufacture of paperboard it is necessary to apply the correct creasing conditions, e.g. neither too small nor too big a rule height, in order to achieve sufficiently low folding resistance without any cracks along the folding lines. The most appropriate rule height for a given paperboard is usually determined by trying different rule heights in a series of very time consuming and costly trial and error tests. And, in practice, this procedure must be repeated for each major change in board quality. This report shows that an inclined crease rule, i.e. a rule having a gradually increasing rule height, can be used advantageously to rationalize such tests and to achieve much greater reliability. A folding line produced by such an inclined rule contains both the upper limit for the rule height, i.e. where cracks start to appear, and the lower limit, i.e. where the rule height is obviously too small, and the technical range for achieving a good creasing result is thus clarified in one single test. Illustrative data for two types of paperboard are given as well as some theoretical aspects of the concept of creasability. Considering that the described method not only rationalizes the testing work but also enables more reliable observations to be made than have been possible in the past, the method opens new potentials for effective research and development in the fields of converting, convertibility, die form design, etc. © 1997 John Wiley & Sons, Ltd.

The unique convertibility of paperboard

AbstractAlthough the tensile strength or bending stiffness of paperboard is high, in general the material possesses good fold, creasing or scoring properties. Both crease and fold resistance are surprisingly low, as is the rate of crack propagation along the deformation lines. The background to this characteristic is explained.It is shown experimentally that the folding resistance before and after creasing, MB and M' respectively, are strongly correlated with the (in plane) compression strength of the material, approximately according to MB ˜τBC · τ2 and M'/MB ˜ ϵBc, where t is the board thickness, τBC and ϵBc are the compression breaking stress and strain respectively.The strength in compression is several times lower than in tension, both in terms of stress and strain. Consequently, the manner in which the material yields, both in folding and in creasing fracture, originates from the compression regions, i.e. the concave parts of the deformation zone. The tension level at this time may only be 30–50% of its maximum. The breaking limit in tension is reached far later than in compression, and can effectively be ignored.Combined shear stresses (out of plane) of various magnitudes, applied during folding, do not change the relationships found. The material is insensitive to shear stress at least up to folding angles of 90°.Crack propagation along the cut, folded or creased lines is directly related to the in‐plane compression strength of the material, approximately according to l˜Lc−1(τBC/T87‐)2, where /is the crack length, τer is the tension breaking stress and τc‐1 is the brittleness characterized by the critical tensile span of the material, Lc.The rate of crack propagation is greatly reduced in comparison to materials with more equal compression and tension strength and can be as little as 75 or 90%, due to the actual strength ratio. Additionally, paperboard has a relatively high critical span length, Lc, of the same order as that of various synthetic fibre composites, which reduces crack propagation even further.It is necessary to keep the compression strength as low as possible in the development of paperboard; if compression strength needs to be raised, e.g. for end‐usability, tensile strength also needs to be increased, or brittleness reduced, at least in the outer layers of the material. If these adjustments are not made, the properties that make for good convertibility are degraded, according to the results presented.

The mechanical properties of latex‐treated papers

AbstractThe effect of the amount and type of latex on the mechanical properties of the paper‐polymer combinations is described in detail. The treatment with latex increases the wet and dry strength properties of the paper considerably, together with improving the folding and tearing resistance. If the polymer in latex is below its film‐forming temperature, however, the beneficial effects of latex treatment are absent. Limitations to varying the rheological properties of plasticpaper combinations are imposed by the comparatively inextensible nature of the paper matrix. Methods of improving the extensibility of paper, including the use of synthetic fiber papers, are discussed, and the time‐dependent nature of the properties are outlined.