The precipitation process for a concentration of CoTi of super-saturated solutions of Cu-0.50 at.% Co-0.45 at.% Ti (Cu-1 at.%
CoTi) was studied through differential scanning calorimetry (DSC) and microhardness measurements. The analysis of the calorimetric
curves between the environmental temperature and 900 K shows the presence of only one exothermic reaction attributed to the
formation of CoTi particles in the matrix of copper. The energy of activation estimated by using the modified Kissinger method
came out much lower than the corresponding to the diffusion of the cobalt and titanium in copper. We may attribute this fact
to the strong contribution of the vacancies introduced by quenching.
We used the formalism of Johnson-Mehl-Avrami (JMA) to assess the kinetic parameters. The energetic and kinetic evaluations
and the molar heats of precipitation obtained from the isochor of van’t Hoff allow us to infer that the reaction corresponds
to the formation of CoTi precipitates. The isothermal kinetics of precipitation reaction could be represented satisfactory
by an overall kinetic function based in a macroscopic parameter (Vickers hardness). The kinetic parameters obtained from microhardness
model are in agreements with those obtained from DSC traces.
Authors:B. Ramezanzadeh, M. Mohseni, H. Yari, and S. Sabbaghian
Biological resistance of coatings can be regarded as one of the main properties in automotive industries. This study aims
to investigate the effects of biological materials on the mechanical performance of an automotive clear coat. To this end,
two acrylic melamine clear coats containing different melamine cross-linker contents were used. In addition, biological resistance
of these clear coats were studied at two different ageing processes including pre-ageing and post-ageing which involve various
hot-cold, humid shockings and UV radiation of sunlight. By the aid of optical microscopy, micro Vickers and DMTA analyses,
different optical and mechanical properties such as micro hardness, Tg, cross-linking density and storage modulus were studied. Results revealed an inverse impact of both biological materials
to decrease the clear coats mechanical attributes. In addition, a complicated effect of ageing conditions was observed for
both clear coats exposed to these materials. It was shown that the coating having a higher mechanical properties and Tg even resulted in a lower biological resistance.
The acoustic response method is one of the most important dynamic methods used for assessment of the mechanical texture of different fruits and vegetables. The method is based on the mechanical excitation of the sample and the assessment of its resonant frequency. Different approaches are known for the interpretation of the vibration behavior of the samples having definite shapes. According to the most widely used interpretation, the stiffness of the sample (
) is dependent on the resonant frequency (
) and the mass (
) of the sample. The aim was to extend the acoustic response method to typically non-spherical samples (carrot, cucumber, etc.) to find a correct interpretation of the behavior of the sample and to introduce a stiffness coefficient suitable for characterization of the mechanical properties of a long shaped sample. According to Finite Element Modeling and experimental tests on carrot samples a close correlation was found between the resonant frequency and the effective length of the sample in a given shape range. A principally new stiffness coefficient was proposed for long shaped samples. It was found to be suitable for the characterization of the hardness of the vegetables in a wide size range.
Research was performed on the friction, wear and efficiency of plastic gears made of modern engineering polymers and their composites both in a clean environment (adhesive sliding surfaces) and in an environment contaminated with solid particles and dust (abrasive), with no lubrication at all. The purpose is to give a general view about the results of abrasive wear tests including seven soil types as abrasive media. At the first stage of the research silicious sand was applied between the meshing gears and the wear of plastic and steel gears was evaluated and analyzed from the point of different material properties (elongation at break, hardness, yield stress, modulus of elasticity) and its combinations. The different correlations between the experienced wear and material features are also introduced. At the second stage of the project the abrasive sand was replaced with different physical soil types. The abrasive wear of gears is plotted in the function of soil types. The results highlight on the considerable role of physical soil types on abrasive wear resistance and the conclusions contain the detailed wear resistance. The results offer a new tribology database for the operation and maintenance of agricultural machines with the opportunity of a better material selection according to the dominant soil type. This can finally result longer lifetime and higher reliability of wearing plastic/steel parts.
In this study, the influences of various pre-treatments and combined drying (CD) on the drying kinetics and quality parameters of sour cherry were investigated. Prior to freeze drying (FD), sour cherry was pre-treated by blanching in boiling water (100 °C, 3 and 6 min), immersion in sugar solution (20% w/w, 10 and 20 min) and blanching (100 °C) in sugar solution (20% w/w, 3 and 6 min). Freeze-drying of raw samples was taken as a control. Combined drying (CD) can be accomplished in two distinct ways: freeze drying assisted with hot-air drying application (FD-HAD) and hot-air drying followed by freeze drying (HAD-FD). The quality of the dried sour cherry was evaluated in terms of water activity, color, texture and rehydration. Our research results have shown that all of the pre-treatments can effectively reduce the freeze drying time, the best treatment methods are FD-HAD, HAD-FD and blanching in boiling water (6 min). CD involves much less drying time and energy consumption than conventional freeze drying methods. The highest values of hardness and rehydration were found in blanching in sugar solution with water at 100 °C for 6 min. The better color retention was observed for samples pre-treated with blanching in boiling water (6 min).
Authors:M. KARUNAKARAN, N. V. NAIR, H. S. RHO, and Y. H. LEE
Colletotrichum falcatum Went, the
causal agent of red rot of sugarcane produces a specialized infection structure
called appressorium, for penetrating the host. Environmental cues like surface
hydrophobicity and hardness tend to break the dormancy of the conidia and
initiate conidial germination. Conidial attachment is generally stronger on
hydrophobic surfaces, while hydrophilic surfaces do not permit conidial
attachment of C. falcatum. In vitro studies on conidial germination and
appressorium development were made to examine whether the Ca2+/calmodulin
dependent pathways are involved in appressorium formation in C. falcatum.
Effects of calcium chelator (EGTA), calcium channel blocker (methoxy
verampamil), calmodulin antagonists (chloropromazine, phenoxy benzamine and
W-7) and phospholipase C inhibitor (neomycin) were also examined to see whether
they can impair conidial germination and appressorium development. All these
chemicals were found to inhibit conidial germination and or appressorium
formation in C. falcatum. Chloropromazine and W-7 specifically inhibited
appressorium formation at the µM level. Exogenous addition of Ca2+
was found to restore the inhibition of conidial germination and appressorium
development by EGTA. These results suggest that the Ca2+/calmodulin signal
transduction pathway play an important role in the conidial morphogenesis and
appressorium development in C. falcatum.
Authors:S. Meenakshisundaram, S. Parthiban, G. Madhurambal, R. Dhanasekaran, and S. Mojumdar
1,10-Phenanthroline (Phen) as a new additive was added into the solutions of KH2PO4 (KDP) and NH4H2PO4 (ADP) in a small amount (∼2.5·10−3 M L−1). The crystals were grown from the aqueous solutions of pH ∼4.5 at constant temperature by solvent evaporation technique.
It leads to an increase in metastable zone width and assists the bulk growth process. The growth rate of crystals in the presence
of Phen decreases considerably with an increase in impurity concentration (∼2.5·10−2 M L−1). Not much variation is observed in FTIR and XRD of pure and doped ADP/KDP. It appears that the growth promoting effect (GPE)
of Phen is caused by the adsorption of the organic additive on the prism faces of ADP/KDP crystals. Higher optical transmittance
is observed in the presence of the dopant. Detailed microhardness studies of ADP crystals reveal the anisotropy in the hardness
behaviour. Scanning electron microscope (SEM) photographs exhibit the effectiveness of the impurity in changing the surface
morphology of ADP/KDP crystals. Contrary to expectations, Phen depresses the NLO efficiency of ADP/KDP, suggesting that the
molecular alignments in the presence of Phen results in cancellation effects disturbing the non-linearity.
Authors:Daniela Horvat, Zdenko Loncaric, Vladimir Vukadinovic, Georg Drezner, Blazenka Bertic, and Kresimir Dvojković
The effect of the N, P and K fertilisation on yield and quality parameters of cultivar Žitarka during two growing seasons (2002/03 and 2003/04) was studied. Fertilization increased yield, although only treatment with 200 kg N ha
yielded significantly higher than treatments with 80 kg N ha
. Protein content increased significantly (P<0.001) with the application of 80 kg N ha
, 120 kg N ha
and 160 kg N ha
. The highest N applications with 200 kg N ha
and 240 kg N ha
increased protein content on the same level as with 160 kg N ha
. Wet gluten and sedimentation value were also significantly (P<0.001) affected by N fertilizer treatments. Although increment of N fertilization increased values of these quality parameters, 120 kg N ha
, 160 kg N ha
and 200 kg N ha
treatments showed similar effect, while treatment with 240 kg N ha
resulted with significantly higher values. Gluten index increased only with applying 80 kg N ha
while the highest N levels (200 kg N ha
and 240 kg N ha
) showed dramatically gluten weakening. Considering grain hardness only treatment with 80 kg N ha
had significant (P<0.001) influence. Simultaneously, P and K did not affect grain yield and quality, neither comparing PK to controle, or N
Authors:G. Peymanpour, B. Sorkhilalehloo, K. Rezaei, G. Najafian, and B. Pirayeshfar
Ten different Iranian cultivars of bread wheat (Alamoot, Alvand, Arta, Bahar, Chamran, Darya, Dez, Pishtaz, Shahriar and Tajan) were examined for their bread-making properties. To determine the best wheat cultivar, several quality attributes such as protein content on a dry basis (PRT), wet gluten content (WGL), Zeleny (ZLN) and sodium dodecyl sulfate (SDS) sedimentation values, hardness of grain (HRD) and bread volume (BVOL) were measured. Additionally, high molecular weight glutenin subunits (HMW-GSs) and low molecular weight glutenin subunits (LMW-GSs) of the wheat cultivars were studied using sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE). Two alleles (2 + 12 and 5 + 10) were identified at HMW-GS Glu-D1 locus. Significant correlations were found between PRT and each of the following parameters: ZLN (r = 0.67), BVOL (r = 0.73), HRD (r = 0.71) and 5 + 10 subunit (r = 0.66). Also, correlation between BVOL and HRD (r = 0.67) and that between subunit 5 + 10 and BVOL (r = 0.71) were significant. Among HMW-GSs, 5 + 10 subunit had significant influence on bread-making qualities. Significant positive correlations were obtained for LMW-GSs with HRD and ZLN. Considering the traits such as PRT, HRD, SDS, WGL, ZLN, BVOL, HMW-GS (5 + 10) and LMW-GSs, it was concluded that Bahar was the best choice for making bread. Tajan was ranked as the second best cultivar using the HRD, SDS, ZLN, BVOL, HMW-GSs and LMW-GSs data.