The addition of suitable cross-linking agents with norbornene-based monomers has significant effects on the thermal properties
of the resulting polymers formed by olefin metathesis. Ethylidene norbornene (ENB) and endo-dicyclopentadiene (endo-DCPD) were mixed separately with various loadings of three different cross-linking agents and then polymerized with the addition
of Grubbs’ catalyst. The polymerization kinetics and resulting glass transition temperature (Tg) of the systems were evaluated by differential scanning calorimetry (DSC).
The addition of the first cross-linking agent, norbornadiene (CL-1), to both endo-DCPD and ENB resulted in decreasing glass transition temperatures with increasing concentrations. In contrast, the addition
of the other two cross-linking agents (CL-2 and CL-3), which were both custom synthesized bifunctional norbornyl systems,
to both endo-DCPD and ENB resulted in a monotonic increases in Tg with cross-linker concentration. By tailoring the loading of these custom cross-linking agents, the properties of these polymer
systems can be controlled for various applications, including self-healing composites.
The instantaneous elastic moduli for a nylon-6 monofilament were derived on strain recoveries right after creep, stress relaxation, and rapid elongation,Ec,Es andEe, respectively. It was found that during strain recoveryEs(>Ee) andEe increase monotonically with increasing load,m1, on the sample. The extrapolated value of Es atm1=0 g is almost equal to Young's modulus, 4.06 GPa. The value ofEc also increased with increasingm1, and atm1=600 g (1.93 t cm−2) reached about 14 GPa. The endothermic heat change right after creep, stress relaxation or rapid elongation,Q, was negligibly small. For comparison,Es,Ec andQ were also investigated for silicone rubber. It was found thatEs (53.8 M Pa at the draw ratioD=1.2) decreased abruptly atD=1.3. In the range ofD=1.4–1.9,Es was only 22.6 MPa. In the case of stress relaxation,Q increased with increasingD from 4 J mol−1 (atD=1.2) to 56 J mol−1 (atD=1.9). FurthermoreEc (5.58 MPa atm1=133.8 g (429.4 kg cm−2)) increased gradually with increasing m1 and attained 16.6 MPa atm1=548.4 g (1.76 t cm−2). In the case of creep,Q was in the range of 0–11.5 J mol−1 and larger when larger loads,m2 were removed during the later stages of creep.
Flow birefringence (FB) has been investigated in solutions of products of hydrolytic degradation of poly(naphthoyleneimide
benzimidazole) (PNIB) in 96% sulphuric acid PNIB solutions have previously been subjected to heating at various temperatures
from 65 to 120°C and then investigated at 22°C by FB and viscometry. A monotonic decrease in intrinsic viscosity and the molecular
weightM of thermal degradation products with increasing degradation temperature was detected. At the same time, the shear optical
coefficients in series of products with decreasingM first increases and then, at treatment temperatures exceeding 90°C, decreases with decreasing [ν] in accordance with decreasingM of the product. Possible reasons for the detected anomaly have been discussed.
, has been studied by the method of statistical thermal analysis (STA). It is shown that the melting temperature of solid
phase (Tm) increases non-monotonic from 970 °C due to rise in the preliminary melt overheating, and Tm reaches asymptotically 1010 °C. The equilibrium melting-crystallization temperature (
) has been defined as 989.2 °C. It is also found an extreme dependence of the melt supercooling on its overheating. The two
curves of irregular dependence of nucleation rate on melt supercooling have been plotted at different melt overheating.
The purpose of the study was to assess the effectiveness of meal replacement diets in body weight management and the impact on the body composition of working age people, when the participants purchased the products and followed the weight loss program outside the clinical trial.In weight loss programs (3.98±2.29 months), 79 participants (56 women, 23 men) lost an average of 10.19±6.1 kg of their body weight, 11.47±9.15 cm in the waist circumference, and 5.29±5.46 of the percentage of body fat. Replacing two meals a day was an effective way to loose weight because of its simplicity and convenience of use. The cost of the products and the monotony of the diet were the main causes of abandoning the diet. After the diet subjects were followed for an average of 11.28±8.1 months, and for the entire group of participants an average weight gain of 2.86±3.02 kg was observed compared to the minimum weight (31.5% of weight lost). Long-term maintenance was better in the subjects that replaced one meal a day, but is still a challenge and required further research.
Authors:Pál Jakusch, Tímea Kocsis, Ilona Kovácsné Székely, and István Gábor Hatvani
The aim of the present study is to extend the applicability of MRI measurements similar to those used in human diagnostics to the examination of water barriers in living plants, thus broadening their use in natural sciences. The cucumber, Cucumis sativus, and Phillyrea angustifolia, or false olive, were chosen as test plants. The MRI measurements were carried out on three samples of each plant in the same position vis-a-vis the MRI apparatus using a Siemens Avanto MRI scanner. Two different relaxation times were employed, T1, capable of histological mapping, and T2, used for the examination of water content. In the course of the analysis, it was found that certain histological formations and branching cause modifications to the intensity detected with relaxation time T2. Furthermore, these positions can also be found in T1 measurements. A monotonic correlation (cucumber: ρ = 0.829; false olive: ρ = –0.84) was observed between the T1 and T2 measurements. In the course of the statistical analysis of the signal intensities of the xylems it was concluded that they cannot be regarded as independent in a statistical sense; these changes rather depend on the anatomic structure of the plant, as the intensity profile is modified by nodes, leaves and branches. This serves as a demonstration of the applicability of MRI to the measurement of well know plant physiological processes. The special parametrization required for this equipment, which is usually used in human diagnostics, is also documented in the present study.
This paper presents a method for measuring indoor radon concentrations using a commercially available air-purifying respirator
filter as a component of the radon monitor. The filter used was Survivair’s NIOSH (National Institute for Occupational Health
and Safety)-approved 100800 model. The method is based on the diffusion of radon gas into the activated carbon of the filter
and the measurement of the radioactive daughters resulting from the radon decay. The photopeaks of the 214Bi daughter gamma rays (0.609 MeV) were analyzed with a Hyper-Pure Germanium (HPGe) detector and a multichannel system. A
monotonically increasing and very close to linear response relation between the integrated area under the 214Bi photopeak and the radon concentration of the activated carbon was found. A well-defined relation held for radon levels
ranging from 15 to 4,700 Bq/m3. This procedure results in highly reproducible and reliable measurements of indoor radon levels. Interesting applications
include the investigation of radiological accidents involving radon and the retrospective measuring of indoor radon concentrations
by analyzing the filters of the respirators worn by personnel working during the relevant period.
At a given surfactant-surfactant ratio, the enthalpies of transfer ΔH (W→W+S) of pentanol 0.03m from water to sodium dodecylsulfate (NaDS)-dodecyldimethylamine oxide-water mixtures as functions of the surfactants mixture
concentration (mt) were determined. ForXNaDS=0.9, ΔH (W→W+S) increases monotonically withmt such as observed for pure surfactants. ForXNaDS=0.12 and 0.3, ΔH (W→W+S) increases withmt up to 0.12m beyond which it decreases withmt. AtXNaDS=0.6, two monotonic curves can be distinguished in the ΔH (W→W+S)vs. mt trend. Experimental data were fitted through an equation previously reported for additives in pure surfactants derived by
assuming the pseudo-phase transition model for the micellization and a mass action model for the distribution of the additive
between the aqueous and the micellar phases. This method did permit to simultaneously obtain the distribution constant of
the alcohol between the aqueous and the micellar phase (and, then, the standard free energy of transfer) and its enthalpy
of transfer from the aqueous to the micellar phases. By combining these properties the standard entropies of transfer were
calculated. From these results, the excess properties of pentanol in the mixed micelles were calculated as a function of the
mixture composition. The excess enthalpies and entropies are positive and compensate with each other leading to null values
for the excess free energies in the whole range of the mixed micelles composition.