Simultaneous determination of mycotoxin in commercial coffee

Mycotoxins are secondary metabolites produced by filamentous fungi that usually contaminate food products. Coffee is a natural product susceptible to mycotoxin contamination. The present study evaluates the presence of nivalenol, deoxynivalenol, T-2 and HT-2 Toxin, diacetoxyscirpenol, aflatoxin B₁, aflatoxin B₂, aflatoxin G₁, aflatoxin G₂, fumonisin B₁, fumonisin B₂, ochratoxin A, zearalenone, enniatin A, enniatin A₁, enniatin B, enniatin B₁, and beauvericin in coffee samples, using liquid chromatography tandem mass spectrometry (LC-MS/MS). The results show that zearalenone was not present in any sample. In the positive samples the contents of fumonisins ranged from 58.62 to 537.45 μg/kg, emerging mycotoxins ranged from 0.10 to 3569.92 μg/kg, aflatoxins ranged from 0.25 to 13.12 μg/kg, and trichothecenes, excepting nivalenol, ranged from 5.70 to 325.68 μg/kg. Nivalenol presented the highest concentrations, from 0.40 to 25.86 mg/kg. Ochratoxin A ranged from 1.56 to 32.40 μg/kg, and five samples exceeded the maximum limit established by the European Commission.     

Fatigue crack growth in SiC particulates reinforced Al matrix graded composite

The SiC/Al graded composite was fabricated by powder metallurgy processing and its fatigue crack growth behavior was studied. The volume percentage of SiC particulates was distributed from 5 to 30% layer by layer on the cross section. Since the aluminium was dissolved together, there was no evident interface between the two layers with different volume fraction of SiC particulates. Fatigue crack growth was in direction of from 5 to 30% SiC layers under sinusoidal wave-form. The retardation of fatigue crack growth was found when crack propagated from low volume fraction of SiC to high volume fraction of SiC. The crack deflection and branching between two layers were observed, which decreased crack growth rates. In view of crack tip driving force, the plasticity mismatch between the layers shielded crack tip driving force, i.e. decreased the effective J-integral at the tip of the crack as the plastic zone of the crack tip spread from the weaker material into the stronger material.     

Fracture toughness of short carbon fibre reinforced thermoplastic polyimide

The fracture toughness testing of short fibre reinforced thermoplastic materials were performed. Materials tested were the polyimide resin and also that reinforced with 20 wt% or 30 wt% short carbon fibre. For introducing the initial crack, the tapping method, the sliding method and the bridge indentation method were examined. Among them, the sliding method was found to be effective for every case. The fracture tests were conducted by the three-point bending test with several loading rates. Stable crack growth was observed for the neat material while unstable fracture occurred for the reinforced materials. The critical values of the stress intensity factor at crack initiation were greater for the reinforced materials than for the neat resin. The fracture toughness of the 30 wt% reinforced material was independent of loading rate while that of 20 wt% reinforced material increased with loading rate. In order to investigate the fracture mechanisms, fractographic observations were also performed.     

Chemical leaching and magnetic properties of non-equilibrium Al(Co–Cu) powders produced by rod milling

We report upon the chemical leaching and magnetic properties of nanoscale crystalline Al_0.6(Co₂₅Cu₇₅)_0.4 alloy powders produced by rod milling. X-Ray diffractometry (XRD), transmission electron microscopy, differential scanning calorimetry, vibrating sample magnetometry, and superconducting quantum interference device magnetometry were used to characterize the as-milled and leached specimens. After 400 h of milling, only the b.c.c. phase of the intermetallic compound γ-Al_3.892Cu_6.10808 was detected by XRD. After annealing the leached specimen at 600 °C for 1 h, the nanoscale crystalline phase was transformed into the f.c.c. Cu phase, and this was accompanied by a change in the magnetic properties. The peaks of the magnetization shifted towards lower temperature with increasing external field. The temperature behavior at T_f (45 K) for direct current (d.c.) magnetic susceptibility measurements was quite different for field cooling and zero-field cooling. After cooling the leached specimen from 800 °C, magnetization increased gradually.     

ASYMPTOTIC PROPERTIES OF THE SAMPLE AUTOCORRELATIONS AND PARTIAL AUTOCORRELATIONS OF A MULTIPLICATIVE ARIMA PROCESS

Abstract. We shall investigate the asymptotic behaviour of the sample autocorrelations and partial autocorrelations of a multiplicative ARIMA process and derive their limiting distributions. Some simulations are presented to illustrate the results obtained.     

Containerless solidification of highly undercooled mullite melts: Crystal growth behavior and microstructure formation

A mullite (3Al₂O₃·2SiO₂) sample has been levitated and undercooled in an aero-acoustic levitator, so as to investigate the solidification behavior in a containerless condition. Crystal-growth velocities are measured as a function of melt undercoolings, which increase slowly with melt undercoolings up to 380 K and then increase quickly when undercoolings exceed 400 K. In order to elucidate the crystal growth and solidification behavior, the relationship of melt viscosities as a function of melt undercoolings is established on the basis of the fact that molten mullite melts are fragile, from which the atomic diffusivity is calculated via the Einstein-Stokes equation. The interface kinetics is analyzed when considering atomic diffusivities. The crystal-growth velocity vs melt undercooling is calculated based on the classical rate theory. Interestingly, two different microstructures are observed; one exhibits a straight, faceted rod without any branching with melt undercoolings up to 400 K, and the other is a feathery faceted dendrite when undercoolings exceed 400 K. The formation of these morphologies is discussed, taking into account the contributions of constitutional and kinetic undercoolings at different bulk undercoolings.     

Microbial Sensors for the Detection of Fish Freshness

A microbial sensor system consisting of immobilized living spoilage-causing bacterium, Alteromonas putrefaciens, and an oxygen electrode was prepared and applied to the continuous determination of fish freshness. Fish freshness was expressed as a ratio of A/B, where A is the current decrease of the microbial sensor obtained by the application of l0–50 μL fish extract and B is the current decrease by the equivalent volume of culture medium. Freshness of bluefin tuna and yellowtail meats stored in ice for up to 2 weeks was determined by both the proposed and the conventional K value enzyme sensor method. Good comparative results were obtained. One assay could be completed within 13 min.