Authors:Magda Michalik, Maja Surmacka, Monika Stalmach, Grażyna Wilczek, Teresa Kowalska, and Mieczysław Sajewicz
In the search for biocompatible and biodegradable natural products, much attention of biomedical engineering experts is attracted by spider web (also known as spider silk). Apart from its biocompatibility and biodegradability, the key feature of spider silk is its extraordinary tensile strength, in many cases surpassing that of steel or Kevlar. Although spider silk (unlike that produced by the silk worms) cannot be produced on a mass scale, it can serve as a structural template to be imitated by the organic chemists. The main building blocks of the spider silk proteins, spidroins, are the non-polar and hydrophobic α-amino acids, and the most abundant among them are l-glycine and l-alanine. In this study, we investigated an impact of cadmium chloride (CdCl2) as a toxic anthropogenic environmental pollutant on quantitative levels of glycine, alanine, histidine, and phenylalanine in spider silk produced by the female Steatoda grossa spider kept for the periods of 4 weeks and 12 months, respectively, on cadmium-enriched diet. Quantification of this dietary effect was carried out with the aid of thin-layer chromatography, using silica gel as the stationary phase and 2-butanol- acetone-glacial acetic acid–water, 7:7:2:4 (v/v) as the mobile phase. First, the calibration curves were established for the standards of the four α-amino acids of interest (for glycine, y = 369.8x + 175.9 [r = 0.990]; for alanine, y = 725.8x + 175.3 [r = 0.985]; for histidine, y = 117.7x + 272.4 [r = 0.990]; for phenylalanine, y = 198.0x + 143.0 [r = 0.995]). Then, these four α-amino acids were quantified in the spider webs of the control spiders and those held on the cadmium- enriched diet. With all four α-amino acids of interest, their respective levels were in the range of 100 to 200 μg α-amino acid per 1 mg spider silk. The observed differences between the α-amino acid contents in the control web silk and in those produced by the cadmium fed spiders were rather insignificant and, in most cases, within the range of the experimental error. Thus, a general conclusion was drawn as to an apparent resistance of the S. grossa spider species to the environmental cadmium pollution.
Authors:I. S. Aji, E. S. Zainudin, A. Khalina, S. M. Sapuan, and M. D. Khairul
other composites was a little higher than the temperature at which HDPE concluded decomposition. Kenaf composite on its own showed initial thermal resistance, but above 240 °C, a sharp increase in decomposition occurred. This could be as a result of
Authors:Éva Sárdi, Eszter Szarka, Gábor Csilléry, and János Szarka
Plant resistance breeding has, so far, been based on specific resistance genes which regulate hypersensitive reaction, resulting in fast tissue destruction. Hungarian researchers have, however, discovered the existence of the
general defense system
), which regulates a completely different plant defense reaction. This manifests itself in tissue thickening through cell enlargement. We have studied the biochemical background of these different plant defense processes by OPLC, a forced-flow version of planar chromatography. We also exploited some basic well-known advantages of planar chromatography which made its application suitable and favorable in our experiments. As a result of analysis of time-dependent changes in carbohydrate compounds, we confirmed pathological and symptomatological observations that plants have both general and specific defense systems. These two systems have different roles and strategies in excluding pathogens, but together constitute the complete disease resistance of plants.
Authors:M. Kweon, L. Haynes, L. Slade, and H. Levine
Thermal analysis was used to deduce the mechanism of resistance to enzymatic digestion by starches and to account for the extent of resistance at different enzymolysis reaction temperatures. Thermalanalysis was also used to determine the most productive treatment temperature for exploration of the effects of heat-moisture treatment of starches on their subsequent chemical and physical behavior, including enzyme digestibility. The starches were selected according to an experimental design based on a nontraditional description of genetically varied corn starches. As a result, each functional response to heat moisture treatments of the starches adjusted to different moisture contents could be assigned to the relevant causative structural factor in the experimental design.
The accelerated thermal degradation of low-density polyethylene (LDPE) was studied in air at atmospheric pressure and temperatures
of 70, 80, 90 and 100C. The changes in elongation at break, traction resistance and density as a result of accelerated thermooxidative
degradation were followed. Thermal analysis curves (TG, DTG and DTA) of non-aged and thermally aged LDPE were recorded, and
the thermal analysis results were compared with those relating to the variations in the elongation at break, the traction
resistance and the density as a consequence of accelerated thermal aging.
Authors:A. Amaya, J. Píriz, N. Tancredi, and T. Cordero
Char and tar derived from pyrolysis of Uruguayan Eucalyptus wood has been evaluated as raw materials for the preparation of
high mechanical resistance activated carbon pellets. Thermogravimetric analysis was used as the main technique for studying
tar and char pyrolysis in N2 and CO2 atmospheres, and to determine the best conditions for CO2 activation of the carbon pellets. Results indicated that activated carbon pellets with high surface area and good mechanical
resistance were obtained by CO2 gasification at 1098 K. Pellets properties can be explained as due to the independent contribution of each component.
Authors:J. Chruściel, Grażyna Janowska, P. Rybiński, and L. Ślusarski
Thermal properties, ageing
resistance and flammability of peroxide vulcanizates of butadiene-acrylonitrile
rubber Perbunan NT 1845 (NBR) of Bayer, modified in bulk and on a surface
with synthesized hybrid functional poly(methylsiloxanes) were investigated.
The derivatographic, DSC, oxygen index and FTIR methods were applied. It was
stated that addition of poly(methylsiloxanes) caused distinct increase of
ageing resistance and of NBR vulcanizates and decrease of their thermal decomposition
rate and flammability, providing self-extinguishing samples. The mechanism
of addition reactions of Si–H bond to multiple bonds of NBR has been
To study the corrosion resistance of metals and alloys,
an analysis system needs to be able to simulate the harsh environments to
which these materials are subjected. The system must also collect data from
metal and alloy samples at elevated temperatures over long periods of time
(typically days). Thermogravimetric analyzers (TGs) are well accepted systems
for both corrosion studies and long-term elevated temperature studies. However,
until now, TGs could conduct either corrosion studies or long-term studies,
but not both. This paper presents a TG system specifically designed to satisfy
the requirements of long-term corrosion resistance studies of metals and alloys.