EPR detection of foods preserved with ionizing radiation

The applicability of the epr technique for the detection of dried vegetables, mushrooms, some spices, flavour additives and some condiments preserved with ionizing radiation is discussed. The epr signals recorded after exposure to gamma rays and to beams of 10 MeV electrons from linac are stable, intense and specific enough as compared with those observed with nonirradiated samples and could be used for the detection of irradiation. However, stability of radiation induced epr signals produced in these foods depends on storage condition.

No differences in shapes (spectral parameters) and intensities of the epr spectra recorded with samples exposed to the same doses of gamma rays (⁶⁰Co) and 10 MeV electrons were observed     

Influence of acidification on the optical properties and molecular composition of dissolved organic matter

Acidification is a common method for preserving dissolved organic matter (DOM) in natural water samples until sophisticated laboratory analyses can be performed. However, little is known about the effects of this practice on the composition and optical properties of DOM. In this study, the effects of acidification on DOM in porewater samples collected from the RL IV bog system of the Glacial Lake Agassiz Peatlands in northern Minnesota were characterized. Molecular composition was determined by ultrahigh resolution mass spectrometry and optical properties by UV absorption and three-dimensional fluorescence spectroscopy. Excitation–emission matrix fluorescence spectroscopy results indicate that the fluorescence properties of the peatland porewater DOM were sensitive to pH and that the observed changes were fluorophore dependent. Ultrahigh resolution Fourier transform ion cyclotron resonance mass spectrometry revealed the appearance of newly formed, oxygen-rich compounds upon acidification. The extent to which these oxygen-rich compounds were formed was also dependent on the composition of the DOM.     

Studies on the Structure and Properties of Cordierite Synthesized by Talc-Magnesite

Homogeneous cordierite has been synthesized at low cost by talc-magnesite and coal gangue as the main raw materials. The mechanism of synthesizing cordierite under such a com- posing system of raw materials, and the effect of temperature on the crystal cell parameters and microstructure and thermal expansion coefficient of cordierite crystal have been studied via testing methods of XRD, SEM, etc. The result shows that the homogeneous cordierite can be synthesized by the systematic composing materials of “talc-magnesite—coal gangue—talc” with heat pre- servation at 1350 ℃ for 1 h; as the keeping time is prolonged, Al3+ and Mg2+ in cordierite crystal are replaced by a few impurity ions such as Fe3+, Fe2+, etc., and the crystal cell parameters of cordierite present an increase trend; as the high-temperature heat preservation is prolonged, the content of glassy phase in the sample is increased, its density is improved, and its thermal expansion coeffi- cient presents an increase trend.     

热泵中定容水箱保温率的研究

提出定容水箱保温率的概念及其方程。为此,本实验对定容水箱自然冷却过程中各热力参数进行了测量。根据实验所测数据及相关公式推导,得到保温率方程的经验函数关系式。同时,通过对测量曲线和经验函数曲线的拟合,验证了定容水箱保温率方程。     

Effect of high pressure processing on the preservation of frozen and re-thawed sliced cod (Gadus morhua) and salmon (Salmo salar) fillets

Cod and salmon are both widely found in the seafood market, but those products are easily spoiled. This work reports on the investigation of the effects of three moderate pressure values (150, 300 and 450?MPa) applied for 5?min at 20°C on crude sliced cod and salmon fillets. It was found that high pressure processing (HPP) significantly reduced the microbial load during refrigerated storage for up to 14 days. As expected, the most effective treatment was 450?MPa because it inhibited microbial growth. This process affected the hardness, lightness, lipid oxidation, protein denaturation and oxidation. The fish muscle composition (lipid amount and protein profile) played a main role in the changes promoted by pressure. HPP permits the shelf life of the raw product at 4°C to be increased with minimal changes in the organoleptic characteristics and to enable crude consumption.     

Two positivity preserving flux limited,second‐order numerical methods for a haptotaxis model

Two numerical methods for a one‐dimensional haptotaxis model, which exploit the use of van Leer flux limiter, are developed and analyzed. Sufficient conditions time step size and flux limiting are given for such formulation to ensure the non‐negativity of the discrete solution and second‐order accuracy in space. Another advantage is that we avoid solving large nonlinear systems of algebraic equations. The discrete preservation of total conservation of cell density, concentration, and logarithmic density is also verified for the numerical solution. Numerical results concerning accuracy, convergence rate, positivity, and conservation properties are presented and discussed. Similar approach could be applied efficiently in the corresponding two‐ and three‐dimensional problems. © 2012 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq 2013     

New open modified Newton Cotes type formulae as multilayer symplectic integrators

New modified open Newton Cotes integrators are introduced in this paper. For the new proposed integrators the connection between these new algorithms, differential methods and symplectic integrators is studied. Much research has been done on one step symplectic integrators and several of them have obtained based on symplectic geometry. However, the research on multistep symplectic integrators is very poor. Zhu et al. [1] studied the well known open Newton Cotes differential methods and they presented them as multilayer symplectic integrators. Chiou and Wu [2] studied the development of multistep symplectic integrators based on the open Newton Cotes integration methods. In this paper we introduce a new open modified numerical method of Newton Cotes type and we present it as symplectic multilayer structure. The new obtained symplectic schemes are applied for the solution of Hamilton’s equations of motion which are linear in position and momentum. An important remark is that the Hamiltonian energy of the system remains almost constant as integration proceeds. We have applied also efficiently the new proposed method to a nonlinear orbital problem and an almost periodic orbital problem.     

Existence and uniqueness of monotone and bounded solutions for a finite-difference discretization à la Mickens of the generalized Burgers–Huxley equation

Departing from a generalized Burgers–Huxley partial differential equation, we provide a Mickens-type, nonlinear, finite-difference discretization of this model. The continuous system is a nonlinear regime for which the existence of travelling-wave solutions has been established previously in the literature. We prove that the method proposed also preserves many of the relevant characteristics of these solutions, such as the positivity, the boundedness and the spatial and the temporal monotonicity. The main results provide conditions that guarantee the existence and the uniqueness of monotone and bounded solutions of our scheme. The technique was implemented and tested computationally, and the results confirm both a good agreement with respect to the travelling-wave solutions reported in the literature and the preservation of the mathematical features of interest.     

Molecular fluorescence analysis of rainwater: Effects of sample preservation

Very different filtration and preservation procedures may be found in the literature on the study of the rainwater dissolved organic fraction. Thus, the influence of sample filtration and preservation procedures on the fluorescence of rainwater dissolved organic matter (DOM) was studied in this work. Rainwater was filtered through different filters (quartz 0.22 μm or PVDF 0.45 μm) and excitation (λ_em = 415 nm) and synchronous (Δλ = 70 nm) fluorescence spectra were obtained at the same day of collection, or after preservation by refrigeration (1-7 days) or by freezing (1-4 weeks). The excitation-emission matrix (EEM) spectra of rainwater showed six types of fluorescent bands: two corresponding to humic-like bands, and four resembling proteins. Then, the excitation and synchronous spectra were chosen in order to monitor changes in the humic-like and protein-like bands, respectively. The filtration procedures adopted in this work did not affect the fluorescence properties of the rainwater samples. However, these properties were differently preserved by refrigeration or freezing: after refrigeration, filtered rainwater maintained the original fluorescent properties for at least 4 days, while after freezing fluorescent properties were not always preserved since it occurred a decrease of protein-like fluorescence intensity.     

Boundary-layer disturbances subjected to free-stream turbulence and simulation on bypass transition

The phenomena associated with the entrainment of free-stream turbulence(FST) into boundary-layer flows are relevant for a number of subjects.It has been believed that the continuous spectra of the Orr-Sommerfeld(O-S)/Squire equations describe the entrainment process,and thus they are used to specify the inlet condition in simulation of bypass transition.However,Dong and Wu(Dong,M.and Wu,X.On continuous spectra of the Orr-Sommerfeld/Squire equations and entrainment of free-stream vortical disturbances.Journal of Fluid Mechanics,732,616–659(2013)) pointed out that continuous spectra exhibit several non-physical features due to neglecting the non-parallelism.They further proposed a large-Reynolds-number asymptotic approach,and showed that the non-parallelism is a leading-order effect even for the short-wavelength disturbance,for which the response concentrates in the edge layer.In this paper,the asymptotic solution is verified numerically by studying its evolution in incompressible boundary layers.It is found that the numerical results can be accurately predicted by the asymptotic solution,implying that the latter is adequate for moderate Reynolds numbers.By introducing a series of such solutions as the inflow perturbations,the bypass transition is investigated via the direct numerical simulation(DNS).The transition processes,including the evolution of streaks,the amplification of secondary-instability modes,and the emergence of turbulent spots,agree with the experimental observations.