Vf Values Research Articles

Study of the effects of PR toxin, mycophenolic acid and roquefortine C on in vitro gas production parameters and their stability in the rumen environment

SUMMARYMoulds belonging to Penicillium section roqueforti are common contaminants of feedstuffs and produce several mycotoxins that can cause health hazards when ingested by farm animals. Among these, PR toxin (PR), mycophenolic acid (MY) and roquefortine C (RC) have been frequently detected in forages, particularly silages. The aims of the current trials were to study the effects of the presence of pure mycotoxins on in vitro rumen fermentation parameters and to assess their stability in the rumen environment. Two successive in vitro gas production experiments were carried out: a central composite design with four replications of central point (CCD) and a completely randomized design with a fully factorial arrangement of treatments (FFD). In CCD, the effects of PR, MY and RC concentrations in diluted rumen fluid (i.e. 0·01, 0·30, 1·01, 1·71 and 2·00 μg of each mycotoxin/ml) were tested. Gas volume produced after 48 h of incubation (Vf) decreased linearly as concentrations of RC and MY in diluted rumen fluid increased, with marginal effects similar for two mycotoxins, being respectively −14·6 and −13·4 ml/g organic matter (OM) for each 1·0 μg/ml of increment in mycotoxin concentration. Similarly, total volatile fatty acid (VFA) production decreased quadratically as concentrations of RC and MY increased, with marginal effects about two times higher for MY than RC, being −4·22 and −2·62 mmol/l for each 1·0 μg/ml of increment in mycotoxin concentration. With respect to maximum Vf (i.e. 410·6 ml/g OM) and VFA (98·06 mmol/l) values estimated by the model, decreases of 13·6 and 15·2% were obtained when incubating the highest RC and MY concentrations, respectively. The PR did not interfere with rumen fermentation pattern and it was not recovered after 48 h of incubation, whereas the stabilities of MY and RC in rumen fluid were similar and on average equal to about 50%. On the basis of CCD results, a second experiment (FFD) was carried out in which only effects of MY and RC concentrations (i.e. 0, 0·67, 1·33 and 2·00 μg of each mycotoxin/ml of diluted rumen fluid) were tested. Data from FFD showed Vf decreased linearly when concentrations of MY and RC increased, with marginal effect two-folds higher for MY than for RC (−11·1 ml/g OM and −6·7 ml/g OM, respectively). Similar marginal effects of MY and RC in decreasing VFA production were recorded: −2·38 and −2·86 mmol/l for each 1·0 μg/ml of increment in mycotoxin concentration, respectively. At the highest RC and MY tested concentrations, Vf and VFA decreased by 8·7 and 10·7%, respectively, over maximum estimated values. In FFD, the average amounts of MY and RC recovered in rumen fluid after 48 h of incubation were 79·0 and 40·6%, respectively. In conclusion, the MY and RC from standards interfered with rumen microorganisms at relatively low levels and were partially stable in the rumen environment after 48 h of incubation. These findings suggested that MY and RC could interfere with digestive processes and might represent a potential risk for ruminants fed diets containing feeds contaminated by mycotoxins produced by P. roqueforti.

Assessing floating treatment wetlands nutrient removal performance through a first order kinetics model and statistical inference

A floating treatment wetland (FTW) is an ecological approach which seeks to reduce point and nonpoint source pollution in receiving waters. This technology has received increasing attention recently. Subsequent studies were conducted at worldwide locations; despite these efforts, reliable estimates of the FTW performance remains a significant research gap. This paper describes the development of a robust and simplified integrated FTW (i-FTW) model that includes uncertainty. The performance of FTWs was separated from other treatment processes ongoing within their respective water bodies. This approach facilitates generalization of the model and allowing parameters to adjust to each applied water body characteristic. A bootstrap method was incorporated to estimate uncertainty and generate more robust predictions of performance.Water concentration time series data were described by a first order kinetics i-FTW model that generates an FTW performance parameter: FTW apparent uptake velocity (vf). A comprehensive literature search of i-FTW studies was conducted to collect total phosphorus (TP) and total nitrogen (TN) concentrations data. The vf values were calculated from these studies and estimated using a bootstrap percentile method. The best estimation of median and expected range with 95% confidence interval of the vf were 0.048 (0.018–0.059) and 0.027 (0.016–0.040)m/day for TP and TN, respectively. The goodness of fit (R2) of the i-FTW model on water concentration time series data of the i-FTW experiments was 0.92±0.30 for TP and 0.86±0.38 for TN data (mean±SD). This model provides insights into compartmental treatments of i-FTW systems and serves as a preliminary tool to select extent of FTW coverage when designing an i-FTW system. Further research to resolve limitations of model application is suggested.

Continuous flow production of cationic liposomes at high lipid concentration in microfluidic devices for gene delivery applications

Microfluidics is a powerful technology that allows the production of cationic liposomes by the hydrodynamic focusing method. We first studied a single hydrodynamic focusing (SHF) device, which uses a central stream in which lipids dispersed in ethanol are injected and hydrodynamically compressed by the two aqueous streams. The ethanol diffusion from the inner stream to the aqueous stream encourages the formation of the liposomes. To intensify the mass diffusion and increase the surface area between the two fluids, a second device was designed with double hydrodynamic focusing (DHF). We investigated the influence of fluid flow velocity (Vf), Flow Rate Ratio (FRR) and total lipid concentration (Clip) on the particle size of the CLs produced. The DHF microfluidic device had the ability of using higher Vf values than the SHF device, which resulted in a higher productivity level. Small Angle X-ray Scattering (SAXS) experiments were performed to structurally characterize the cationic liposomes produced by both microfluidic devices. The SAXS results revealed that both devices produce unilamellar cationic liposomes with a very small fraction of multilamellar liposomes; this finding is in agreement with the observations made in the analysis of the liposomes using Transmission Electron Microscopy (TEM). The biological efficacies of the cationic liposomes produced by both microfluidic devices were examined in vitro in HeLa cells, which confirmed their potential for gene delivery and vaccine therapy applications.

Enhancement of Output Power for GaN‐Based LEDs by Treatments of Ar Plasma on p‐GaN Surface

We successfully demonstrated that the Arplasmatreatment p‐GaN surface increased the contact resistance of ITO/P‐GaN serving as injection current deflection layer under the electrode pad. It was found that the Vf values of the two LEDs at 20 mA were approximately 3.3 V. Under a 20 mA current injection, it was found that output powers of conventional LED and Ar‐plasma‐treatment LED on p‐GaN surfaces were 9.8 and 11.08 mW, respectively. We can increase the output power of GaN LEDs in 13% due to current blocking on the surface of p‐GaN under the electrode pad by inserting the treatment with Ar plasma. It was also found that, after the reliability test for 72 hours the half lifetimes of conventional LEDs and LEDs with Ar‐plasma treatment on p‐GaN surface were about 49% and 55%, corresponding to the initial intensity, respectively.

Influence of Copper Volume Fraction on Tensile Strain/Stress Tolerances of Critical Current in a Copper-Plated DyBCO-Coated Conductor

The influence of the volume fraction (Vf) of copper, plated at room temperature over a DyBa2Cu3O7¹¤-coated conductor, on the tensile strain tolerance and stress tolerance of critical current at 77K was studied over a wide range of copper Vf values. The copper plating exerts a tensile stress during cooling because copper has a higher coefficient of thermal expansion than the substrate conductor. Before application of tensile strain, the copper plated at room temperature yielded at 77K when the copper Vf was lower than a critical value, and was in an elastic state at 77K when the copper Vf was higher than the critical value. The strain tolerance of critical current increased with increasing copper Vf due to an increase in thermally induced compressive strain in the substrate tape. The stress tolerance of critical current decreased with increasing copper Vf because copper is softer than the substrate tape. These results, together with the trade-off between strain tolerance and stress tolerance (i.e., stress tolerance decreases with increasing strain tolerance), were analyzed by modeling. The results show that the restriction imposed by the trade-off, which limits the ability to simultaneously obtain a high strain tolerance and a high stress tolerance, can be relaxed by strengthening the copper. [doi:10.2320/matertrans.MBW201201]

Tectonic controls on the morphometry of alluvial fans around Danehkhoshk anticline, Zagros, Iran

Alluvial fans are important landforms where their morphology and morphometry reflect changes in tectonic, climate, base level, and drainage basin characteristics. Along the margins of tectonically active mountain ranges like the Zagros Mountains, alluvial fans are generally assumed to act as useful landforms for identifying the level of tectonic activity. The purpose of this paper is to evaluate the relationship between active tectonics and morphometric characteristics of alluvial fans around Danehkhoshk anticline in the Simply Folded Belt of Zagros. Morphometric characteristics of alluvial fans, such as area (FA), slope (SF) length of base (BF), width/length ratio (W/L), radius (R), sweep angle (SA) and entrenchment (E) as well as valley floor width-to-height ratio (Vf) and strata dips of anticline limbs (DAL), were measured. The study area was sub-divided into eight tectonic zones and then the mean values of the above-mentioned parameters were calculated in each zone. Result reveals that values of SA, BF and E are directly proportional to DAL. The poor relationships between catchment characteristics (slope and area) and fan parameters are probably due to extensive karstic landforms of catchments having complex hydrologic systems and, hence, result in complex catchment/fan relations. The highly entrenched fans with high sweep angles and long bases are characteristic of tectonically active fronts of Danehkhoshk anticline, having V-shaped valleys (higher Vf values), steep triangular facets and more rotated limbs (higher DAL values). Apart from the tectonic control on fan development, the fan head entrenchment and negative accumulation spaces on most alluvial fans can be attributed to decreased sediment load and discharge the drier the present-day climate regime.

Spatial analysis of morphometric indices: the case of Bolu pull-apart basin, western section of North Anatolian Fault System, Turkey

Advances in quality, acquisition and processing of high-resolution digital topography over the past decade have enabled geomorphologists to interpret topography in terms of tectonic processes in a quantitative and more objective way. This study defines the tectonic impact of the North Anatolian fault system (NAFS) on the evaluation and activity of the Bolu pull-apart basin using morphometric indices based on topographic maps. In this study, three different indices including valley floor width to height ratio (Vf), asymmetry factor (Af), and Stream Length Gradient Index (SL) are applied to the tectonic basin area. To detect the deviation from spatial randomness of applied indices, the weighted correlation coefficient Moran’s I is used, and results are interpreted at 99% confidence interval. According to the results, the tectonic impact of NAFS on the northern and western sides of the basin distinctly differs from one another. Clustered distribution of Vf and Af values on the southern side of the basin margin reveals that this side of the basin margin is tectonically more deformed compared with the northern side. The applied methodology reveals that the spatial analysis of the morphometric indices proved to be the effective tool in analyzing tectonic influence of the fault system on the opposite side of the basin margins.

Antibacterial effect of taurolidine (2%) on established dental plaque biofilm

Preliminary data have suggested that taurolidine may bear promising disinfectant properties for the therapy of bacterial infections. However, at present, the potential antibacterial effect of taurolidine on the supragingival plaque biofilm is unknown. To evaluate the antibacterial effect of taurolidine on the supragingival plaque biofilm using the vital fluorescence technique and to compare it with the effect of NaCl and chlorhexidine (CHX), 18 subjects had to refrain from all mechanical and chemical hygiene measures for 24h. A voluminous supragingival plaque sample was taken from the buccal surfaces of the lower molars and wiped on an objective slide. The sample was then divided into three equal parts and mounted with one of the three test or control preparations (a) NaCl, (b) taurolidine 2% and (c) CHX 0.2%. After a reaction time of 2min, the test solutions were sucked of. Subsequently, the plaque biofilm was stained with fluorescence dye and vitality of the plaque flora was evaluated under the fluorescence microscope (VF%). Plaque samples treated with NaCl showed a mean VF of 82.42 ± 6.04%. Taurolidine affected mean VF with 47.57 ± 16.60% significantly (p < 0.001, paired t test). The positive control CHX showed the lowest mean VF values (34.41 ± 14.79%; p < 0.001 compared to NaCl, p = 0.017 compared to taurolidine). Taurolidine possesses a significant antibacterial effect on the supragingival plaque biofilm which was, however, not as pronounced as that of CHX.

The Effect of Acidification and Magnetic Field on Emitter Clogging under Saline Water Application

Up to day, drip irrigation systems have reached to a high level of technology. But, these systems are not able to showtheir potential benefits, due to various reasons. Emitter clogging can affect distribution uniformity and the systemperformance, which has direct relationship with water quality. In this study five types of emitters with different nominaldischarges, with or without self-flushing system and with or without pressure compensating system were evaluatedunder three management schemes; untreated well water (S1), acidic treated water (S2) and magnetic treated water (S3)in order to reduce chemical clogging. Flow reduction rate, statistical uniformity coefficient (Uc), emission uniformitycoefficient (Eu) and variation coefficient of emitters’ performance in the field (Vf) were monitored. The emitterperformance indexes (Uc and Eu) decreased during the experiment due to emitter clogging. The Uc and Eu values indifferent management schemes confirmed that the acidification has better performance than the magnetic water in orderto control emitter clogging and keep high distribution uniformity. Regarding to Vf values, the priority of untreated andtreated water was as S2>S3>S1 for each emitter.

English

&nbsp; Apparent molar volumes (Vf) and viscosities (h) for 0.00005 to 0.0004 kg.mol-1(50 to 400&nbsp;mmol kg-1) aqueous methotrexate (MTX), gram (Gp) and soya bean (SBp) proteins, and similar compositions of Gp and SBp each in 50 to 400&nbsp;mmol kg-1&nbsp;aqueous MTX were determined at 298.15, 303.15 and 308.15K. The Vfvalues are positive except aqueous MTX and listed as SBp&nbsp;&gt;&nbsp;Gp&nbsp;&gt;&nbsp;MTX in aqueous and SBp &gt; Gp in MTX solutions, respectively. It infers weaker hydrophobic heteromolecular interaction of SBp in binary and ternary systems. The higher&nbsp;h&nbsp;values of SBp and Gp in MTX than those of aqueous MTX prove strengthening of hydrophobic interactions of proteins by MTX. It illustrates the conformational changes of proteins; slightly higher Vf&nbsp;values of SBp than of Gp. The MTX confirm higher structural activity in biological process. The Vf0&nbsp;of MTX increases with K and decrease with composition. But with compositions the values continuously decrease with lower magnitude. &nbsp; Key words:&nbsp;Density, Apparent molal volume, viscosity B coefficient, methotrexate, soya bean, gram protein.

Tectonic activity classes along the nahan thrust (NT) in nw sub-himalaya

Morphotectonic analysis using remote sensing images and GIS techniques have been utilized to identify areas experiencing rapid tectonic deformation and to estimate relative variations of tectonic activity along the mountain front in the Morni Hills, marked by the Nahan Thrust (NT) zone. The NT separates the Upper Morni Hills (UMH) from the highly dissected Lower Morni Hills (LMH). The digital elevation model (DEM) of the area draped with the satellite image was used to identify different geomorphic zones mainly based on altitude and dissection by streams. The NT is also marked by incising streams on the hanging wall block that become braided on the footwall block, across the NT, which can be very well picked on the satellite image. The topographic profiles drawn across the NT, using DEM show a sharp break in slope at the mountain front. Morphometric analysis of the mountain front was carried out determining mountain front sinuosity (Smf) derived from remote sensing images and valley floor/valley width ratio (Vf) indices obtained from topographic profiles using the DEM. The Smf values vary from 1.1 to 2.4 that are characteristic of low sinuosity mountain fronts. On the other hand, Vf values (0.1 to 0.33) are quite low. Both these indices indicate active uplift of the mountain front and consequent downcutting by streams in the hanging wall block. Further, using the Smf and Vf indices, two tectonic activity classes: 1 (active) and 2 (moderately active) are identified from the study area.

Active tectonic influence on the evolution of drainage and landscape: Geomorphic signatures from frontal and hinterland areas along the Northwestern Himalaya, India

The Kangra Re-entrant in the NW Himalaya is one of the most seismically active regions, falling into Seismic Zone V along the Himalaya. In 1905 the area experienced one of the great Himalayan earthquakes with magnitude 7.8. The frontal fault system – the Himalayan Frontal Thrust (HFT) associated with the foreland fold – Janauri Anticline, along with other major as well as secondary hinterland thrust faults, provides an ideal site to study the ongoing tectonic activity which has influenced the evolution of drainage and landscape in the region. The present study suggests that the flat-uplifted surface in the central portion of the Janauri Anticline represents the paleo-exit of the Sutlej River. It is suggested that initially when the tectonic activity propagated southward along the HFT the Janauri Anticline grew along two separate fault segments (north and south faults), the gap between these two fault and the related folds allowed the Sutlej River to flow across this area. Later, the radial propagation of the faults towards each other resulted in an interaction of the fault tips, which caused the rapid uplift of the area. Rapid uplift resulted in the disruption and longitudinal deflection of the Sutlej river channel. Fluvial deposits on the flat surface suggest that an earlier fluvial system flowed across this area in the recent past. Geomorphic signatures, like the sharp mountain fronts along the HFT in some places, as well as along various hinterland subordinate faults like the Nalagarh Thrust (NaT), the Barsar Thrust (BaT) and the Jawalamukhi Thrust (JMT); the change in the channel pattern, marked by a tight incised meander of the Beas channel upstream of the JMT indicate active tectonic movements in the area. The prominent V-shaped valleys of the Beas and Sutlej rivers, flowing across the thrust fronts, with Vf values ranging from <1.0–1.5 are also suggestive of ongoing tectonic activity along major and hinterland faults. This suggests that not only is the HFT system active, but also the other major and secondary hinterland faults, viz. the MBT, MCT, SnT, NaT, BaT, and the JMT can be shown to have undergone recent tectonic displacement.

Different Mechanisms of Free Fatty Acid Flip-Flop and Dissociation Revealed by Temperature and Molecular Species Dependence of Transport across Lipid Vesicles

The mechanism of free fatty acid (FFA) transport across membranes is a subject of intense investigation. We have demonstrated recently that flip-flop is the rate-limiting step for transport of oleic acid across phospholipid vesicles (Cupp, D., Kampf, J. P., and Kleinfeld, A. M. (2004) Biochemistry 43, 4473-4481). To better understand the nature of the flip-flop barrier, we measured the temperature dependence of a series of saturated and monounsaturated FFA. We determined the rate constants for flip-flop and dissociation for small (SUV), large (LUV), and giant (GUV) unilamellar vesicles composed of egg phosphatidylcholine. For all FFA and vesicle types, dissociation was faster than flip-flop, and for all FFA, flip-flop and dissociation were faster in SUV than in LUV or GUV. Rate constants for both flip-flop and dissociation decreased exponentially with increasing FFA size. However, only the flip-flop rate constants increased significantly with temperature; the barrier to flip-flop was virtually entirely due to an enthalpic activation free energy. The barrier to dissociation was primarily entropic. Analysis in terms of a simple free volume (V(f)) model revealed V(f) values for flip-flop that ranged between approximately 12 and 15 Angstroms(3), with larger values for SUV than for LUV or GUV. V(f) values increased with temperature, and this temperature dependence generated the enthalpic barrier to flip-flop. The barrier for dissociation and its size dependence primarily reflect the aqueous solubility of FFA. These are the first results to distinguish the energetics of flipflop and dissociation. This should lead to a better understanding of the mechanisms governing FFA transport across biological membranes.

Positron annihilation and differential scanning calorimetry studies of plasticized poly(ethylene oxide)

Positron annihilation spectroscopy (PALS) and differential scanning calorimetry (DSC) measurements were performed in pure and plasticized poly(ethylene oxide) (PEO)–dioctyl phthalate (DOP) and (PEO)–ethylene carbonate (EC) systems. The plasticized PEO samples were prepared by co-dissolution and melting methods in the concentration range of 0–25wt% of plasticizer. The mean free volume hole size (Vf) values were calculated from the positron lifetime data. For the PEO–DOP it was observed an increase of the Vf values with increasing DOP concentration, while for PEO–EC system the Vf values remained constant. The relative concentration of vacancies showed to be not dependent on DOP concentration and for PEO–EC system it was observed a small decrease with the increase of EC concentration. The thermal behaviour characterized by DSC measurements showed variations of transition and melting temperatures as well as on the degree of crystallinity of PEO with plasticizer concentration. The PALS and DSC results clearly showed the presence of plasticization effect with DOP in opposite to the antiplasticization with EC. The compatibility limit of DOP in PEO was about 15wt% in the preparation conditions of these samples. The efficiency of plasticization was estimated from the slope of Vf curves for PEO–DOP systems.

Free volume-size dependence on temperature and average molecular-weight in poly(ethylene oxide) determined by positron annihilation lifetime spectroscopy

Positron lifetime measurements were carried out in a series of poly(ethylene oxide)—PEO—of different average molecular weights (Mw): 1000, 1500, 6000, 10,000, 300,000, and 4 M. The mean radius (R) and the mean free volume size (Vf) values were determined using a semiempirical equation that correlates the ortho-positronium (o-Ps) lifetime (τ3) and size of holes existing in the amorphous phases. The hole mean radius values determined at room temperature from lifetime spectra were found to be between 2.68 and 2.97 Å, and the hole volumes between 80 and 110 Å3. Free volume size evolution was studied with temperature variation until the melting temperature of the PEO samples. The degree of crystallinity and the melting temperatures were determined by Differential Scanning Calorimetry. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 219–226, 1999

Effect of interfacial phenomena on the thermal expansion behavior of rubber-toughened PMMA composites

The thermal expansion behavior of different types of rubber-toughened poly(methyl methacrylate) (PMMA) composites was determined over a wide range of temperatures and different filler-volume fractions. In a previous publication, the thermal expansion coefficients of particle-reinforced polymers were predicted by means of a theoretical model especially developed that takes into account the adhesion efficiency between the inclusions and the matrix material through the concept of the boundary interphase, that is, a layer between the matrix and the fillers that has a structure and properties different from those of the constituent phases. This layer was assumed to have varying properties. Predictions of the model were in good agreement with experimental results. In the present work, the same model was used in order to study the effect of interphase thickness on the thermal expansion behavior of onion-structure, rubber-modified, paniculate PMMA materials. It was found that the interphase volume-fraction Vi of these materials changes dramatically with the filler-volume fraction Vf . More precisely, at low Vf values, Vi increases, with Vf showing a maximum at a specific Vf value; at higher Vf values, it decreases. This kind of behavior was also previously observed in the case of metal-particle-reinforced resins and other types of particulates, but its explanation has been obscure until now.

Somatic mutations at T-cell antigen receptor and glycophorin a loci in pediatric leukemia pateints following chemotherapy: comparison with HPRT locus mutation

Frequencies of somatic mutations in pediatric patients with leukemia were evaluated following intensive treatment at three different loci: the hypoxanthine-guanine phosphoribosyl transferase (HPRT)), T-cell antigen receptor (TCR), and glycophorin A (GPA) gene. Thirty-two children with acute lymphoblastic leukemia (ALL), nine children with acute myegenous leukemia (AML), and 20 age-matched healthy controls were inlcuded in the study of mutant frequencies (Mfs) at the HPRT and TCR loci. Among these patients and controls, individuals with heterozygous MN blood type, i.e., 14 children with ALL, three children with AML, and nine healthy controls, served for the further assessment of variant frequency (Vf) at the GPA locus. In ALL patients, geometric mean Mfs abd Vfs at these loci were significantly higher than in healthy controls. The high Mf value at the HPRT locus persisted for up to 8 years after the end of chemotherapy. On the other hand, the Mf values at the TCR locus and Vf values at the GPA locus declined gradually with time. IN AML patients, on the other hand, the geometric mean Mf only at the TCR locus was significantly higher than in the controls, albeit to a alosse degree than in ALL patients. These data suggest that anti-cancer therapy induced somatic mutations at various loci ans that ALL patients are more susceptible to mutagenic intervention than are AML patients.

Mechanical properties of natural rubber composites reinforced with cellulose fibers

The mechanical properties of natural rubber composites filled with cellulose short fibers were investigated with respect to fiber concentration and fiber orientation. Strong anisotropy caused by the fiber orientation was observed in the mechanical properties at high fiber loading. The ultimate tensile strength in the longitudinal direction to the fiber orientation had a minimum at Vf=12.5%, while the transverse strength decreased with Vf values. The logarithmic elongation at break decreased linearly with Vf, and the transverse elongation was higher than the longitudinal elongation. The modulus of the composite increased with fiber concentration, with semiempirical equation E=k/{1+[Vm/(1−Vm0.5)]} being valid for the transverse direction and the longitudinal direction at lower fiber loading. The longitudinal modulus was much higher than the transverse modulus. In order to improve adhesion between the fibers and matrix, polyallylacrylate was grafted on cellulose fibers, but grafting was ineffective on the mechanical properties of the composite. The dynamic viscoelastic properties of the natural rubber composite were also investigated. The dynamic modulus, E’, increased with increasing amounts of fiber concentration above the glass transition temperature. The loss modulus, E‘, had a peak at about −36 °C; which shifted to higher temperatures with increasing amounts of mixed fibers. The activation energy for glass transition of the composites was calculated at 198.6–228.6 kJ/mol, depending on fiber concentration for the longitudinal direction. The dynamic viscoelasticity in the transverse direction to the fiber orientation was not affected by filled fibers and the activation energy was 187.3 kJ/mol, approximately the same value as for the unfilled rubber vulcanizate.

Mechanical Properties of Natural Rubber Composites Reinforced with Cellulose Fibers

The mechanical properties of natural rubber composites filled with cellulose short fibers were investigated with respect to fiber concentration and fiber orientation. Strong anisotropy caused by the fiber orientation was observed in the mechanical properties at high fiber loading. The ultimate tensile strength in the longitudinal direction to the fiber orientation had a minimum at Vf=12.5%, while the transverse strength decreased with Vf values. The logarithmic elongation at break decreased linearly with Vf, and the transverse elongation was higher than the longitudinal elongation. The modulus of the composite increased with fiber concentration, with semiempirical equation E=k/{1+[Vm/(1−Vm0.5)]} being valid for the transverse direction and the longitudinal direction at lower fiber loading. The longitudinal modulus was much higher than the transverse modulus. In order to improve adhesion between the fibers and matrix, polyallylacrylate was grafted on cellulose fibers, but grafting was ineffective on the me...

Free Volume of Network‐Forming Oxide Glasses in the Systems P2O5‐(GeO2,TeO2,Sb2O3,V2O5)

The free‐volume fraction (Vf) defined by Simha and Boyer was measured for network‐forming oxide glasses in the systems P2O5‐(GeO2, TeO2,Sb2O3.V2O5). The Vf values varied from 0.06 to 0.25. The systems P2O5‐TeO2: and P2O5‐Sb2O3 have Vf∼0.1, which is near the magnitude of the free‐volume fraction for normal metaphosphate glasses and many organic high polymers.