Effect of Growth Phase on the Fatty Acid Compositions of Four Species of Marine Diatoms

The fatty acid compositions of four species of marine diatoms (Chaetoceros gracilis MACC/B13, Cylindrotheca fusiformis MACC/B211, Phaeodactylum tricornutum MACC/B221 and Nitzschia closterium MACC/B222), cultivated at 22 ℃± 1 ℃ with the salinity of 28 in f/2 medium and harvested in the exponential growth phase, the early stationary phase and the late stationary phase, were determined. The results showed that growth phase has significant effect on most fatty acid contents in the four species of marine diatoms. The proportions of 16:0 and 16:1n-7 fatty acids increased while those of 16:3n-4 and eicosapentaenoic acid (EPA) decreased with increasing culture age in all species studied. The subtotal of saturated fatty acids (SFA) increased with the increasing culture age in all species with the exception of B13. The subtotal of monounsaturated fatty acids (MUFA) increased while that of polyunsaturated fatty acids (PUFA) decreased with culture age in the four species of marine diatoms. MUFA reached their lowest value in the exponential growth phase, whereas PUFA reached their highest value in the same phase.

Relationship Study between the Alkaline Protease Production and the Growth Phases of <i>Pseudomonas aeruginosa</i>Isolated from Patients

This study was conducted in Diyala University Laboratories collaboration with the Directorate of Diyala Health. Occurrence of Pseudomonas aeruginosa was investigated in 161 samples from different clinical sources included Swabs from wounds, burns, ear, eye and samples from Urine and sputum which were collected from patients. Depending on the cultural and micro features and biochemical tests 49 isolated items of this bacteria have been diagnosed and all the isolates showed the proteolytic activity by using skim milk agar through forming clear zone around the growing colonies, and tested the isolates ability of alkaline protease production by quantitative methods, the local isolation P. aeruginosa AP3 had been selected based on the higher productivity of enzyme comparing to other isolates and thus it was used in the current study. Studied the relationship between the production of alkaline protease enzymes and growth phases of P. aeruginosa to determine the time of the enzyme production and the results showed that the local isolation P. aeruginosa AP3 began production of the enzyme in the later stages of the log phase and increased production significantly in the stationary phase reaching amaximum after 48 hours as estimated the enzyme activity 159.2 units/ml in the farm leaky and keep the enzyme fully functional almost in the stationary phase.

Thermodynamic Modeling and Phase Diagrams of Hexagonal and Cubic GaN Single-Crystal FilmGrowth by ECR-PEMOCVD Method

Based on thermodynamic equilibrium theory,a chemical equilibrium model for GaN g rowth is given in electron cyclotron resonance plasma enhanced metalorganic chem ical vapor deposition (ECR-PEMOCVD) system.Calculation indicates that the growt h driving force are functions of growth conditions:group Ⅲ input partial press ure,input Ⅴ/Ⅲ ratio,and growth temperature.Furthermore,the growth phase diag rams of hexagonal and cubic GaN film growth are obtained,which are consistent wi th our experimental conditions to some extent.Through analysis,it is explained t he reason that high temperature and high input Ⅴ/Ⅲ ratio are favorable for he xagonal GaN film growth.This model can be extended to the similar systems used f or GaN single-crystal film growth.

Global gene expression profiles for the growth phases of Trichophyton rubrum

Trichophyton rubrum （T. rubrum） is a common superficial fungus. Molecular and genetic studies of T. rubrum are still limited. In this paper, we report the global analysis of gene expression profiles at different growth phases using cDNA microarray technology. A total of 2044 differentially expressed genes were obtained and clustered into three expression patterns. Our data confirmed previous results that many mRNAs were pre-stored in the conidia of T. rubrum. Transcriptional profiling and function analysis showed that some glycolytic enzymes share similar expression patterns and may be coregulated during the transi- tion of growth phases. Some genes involved in small GTPase signaling pathways, and in cAMP-dependent and MAPK regulation pathways were induced in response to the growth dynamics of T. rubrum. Although the detailed biological roles of these Z rubrum genes are still unknown, our results suggest that these genes may be involved in regulation mechanisms in the life cycle of the fungus.

UV disinfection of Staphylococcus aureus in ballast water: Effect of growth phase on the disinfection kinetics and the mechanization at molecular level

This work aimed to study the inactivate kinetics of Staphylococcus aureus （S. aureus） in artificial seawater by ultraviolet radi- ation, establish relationships between model parameters and growth phases, and explain the mechanization of UV disinfection by molecular biological detection. Investigations were carried out for the validation of Chick-Watson, Collins-Selleck, Horn and Biphasic models when S. aureus was in stationary phase （t=14 h）. The results showed that the Biphasic kinetic model＇s R2 turned out to be the highest one （R2=0.9892） and RMSE was less than 0.5 （RMSE =0.2699）. The Biphasic kinetic model was better fit for ultraviolet disinfection than the other three models under the circumstance of this experiment and chosen to fit the ultraviolet disinfection curves for microorganisms at three growth phases. The sensitivity of microorganisms under ultraviolet radiation was in the following order： in exponential phase 〉 in stationary phase 〉 in lag phase by comparing the indexes of the Biphasic model （kl and x）. Besides, agarose gel electrophoresis was used in order to directly assess the damage to DNA of mi- croorganisms that were exposed to the different dose of UV irradiation. The results revealed that DNA damage caused by UV radiation was an important reason for the microorganism inactivation and as the UV dose increased, there was greater damage caused in DNA.

Growth phase dependent changes in the structure and protein composition of nucleoid in Escherichia coli

The genomic DNA of bacteria is highly compacted in a single or a few bodies known as nucleoids. Here, we have isolated Escherichia coli nucleoid by sucrose density gradient centrifugation. The sedimentation rates, structures as well as pro- tein/DNA composition of isolated nucleoids were then compared under various growth phases. The nucleoid structures were found to undergo changes during the cell growth; i. e., the nucleoid structure in the stationary phase was more tightly com- pacted than that in the exponential phase. In addition to factor for inversion stimulation （Fis）, histone-like nucleoid structuring protein （H-NS）, heat-unstable nucleoid protein （HU） and integration host factor （IHF） here we have identified, three new can- didates of E. coli nucleoid, namely DNA-binding protein from starved cells （Dps）, host factor for phage QJ3 （Hfq） and sup- pressor of taC phenotype A （StpA）. Our results reveal that the major components of exponential phase nucleoid are Fis, HU, H-NS, StpA and Hfq, while Dps occupies more than half of the stationary phase nucleoid. It has been known for a while that Dps is the main nucleoid-associated protein at stationary phase. From these results and the prevailing information, we propose a model for growth phase dependent changes in the structure and protein composition of nucleoid in E. coli.

Assembly and variation of root-associated microbiota of rice during their vegetative growth phase with and without lindane pollutant

Soil-derived microbiota associated with plant roots are conducive to plant growth and stress resistance.However,the spatio-temporal dynamics of microbiota in response to organochlorine pollution during the unstable vegetative growth phase of rice is not well understood.In this study,we focused on the rice(Oryza sativa L.)microbiota across the bulk soil,rhizosphere and endosphere compartments during the vegetative growth phase in two different soils with and without lindane pollutant.The results showed that the factors of growth time,soil types and rhizo-compartments had significant influence on the microbial communities of rice,while lindane mostly stimulated the construction of endosphere microbiota at the vegetative phase.Active rice root-soil-microbe interactions induced an inhibition effect on lindane removal at the later vegetative growth phase in rice-growth-dependent anaerobic condition,likely due to the root oxygen loss and microbial mediated co-occurring competitive electron-consuming redox processes in soils.Each rhizocompartment owned distinct microbial communities,and therefore,presented specific ecologically functional categories,while the moderate functional differences were also affected by plants species and residual pollution stress.This work revealed the underground micro-ecological process of microbiota and especially their potential linkage to the natural attenuation of residual organochlorine such as lindane.

Cellular Growth Dynamics Affects Allelopathic Activity in Coffee Cell Culture

Cellular growth dynamics and allelopathic activity in coffee cell cultures were examined as follows: First, we compared allelopathic activity of seven woody plant calli, Coffea canephora, Derris indica, Ficus carica L., Juniperus conferta, Prunus persica, Punica granatum, and Sonneratia ovata, using a modified “sandwich method bioassay” and found that coffee callus showed the strongest growth inhibition to lettuce seedling nearly 90% of hypocotyl and 96% of root. This coffee callus actively proliferated, with a 21-fold increase during five weeks of subculture, with a growth curve comprising two typical phases: a lag phase of 0 - 2 weeks of culture and an exponential phase of 3 - 5 weeks of culture. Allelopathic activity varied depending on the growth phase of the coffee callus. The strongest allelopathic activity was detected in 1 - 2-week-old callus showing nearly 100% inhibitory effect on lettuce seedling growth. As the allelopathic activity of coffee calli is extremely high, beyond the natural level in coffee leaves and green beans, we focused on analyzing the allelopathic activity of its aqueous extracts using high-performance liquid chromatography. Several prominent peaks, including two reference alkaloids, theobromine and caffeine, which are known allelochemicals in coffee plants, and three distinct unknown peaks were identified at 270 nm in coffee calli during the lag phase (1 - 2 weeks of culture). The higher value of the total phenolic content in the lag phase also suggested a key biosynthetic pathway in relation to the allelopathic activity of coffee callus will be activated in the lag phase.

Proteomic analysis of a toxic dinoflagellate Alexandrium catenella under different growth phases and conditions

Alexandrium is a widely spread dinoflagellate genus throughout many regions of the world,which not only causes the harmful algal blooms(HABs) but also results in the paralytic shellfish poisoning(PSP) throughout the world.This study compared protein profiles of A.catenella grown under different growth phases and conditions using a proteomic approach,and identified the differentially expressed proteins.The results showed that the expressions of proteins identified in three different regions of the gels,the groups 1,2 and 3 proteins,varied significantly with the growth phases and conditions.Group 1 proteins and six Group 2 proteins were highly expressed at the initial,exponential and stationary growth phases,eight Group 2 proteins were highly expressed only at the initial phase,and Group 3 proteins were highly expressed at the exponential and/or stationary phases.However,all these proteins were expressed at low levels or were barely visible at the dissipation phase.The expressions of groups 1 and 2 proteins were low or barely visible in various growth conditions except in continuous darkness they were highly expressed.Group 3 proteins,on the other hand,were overexpressed in continuous illumination and expressed at low levels or barely visible in continuous darkness or under nitrate-starvation.The data from MALDI-TOF-TOF mass spectrometry demonstrated that these differentially expressed proteins were associated with macromolecular biosynthesis,photosynthesis,tRNA synthesis and DNA stability,stress response and cell division regulation.Synthetase was the major component of the altered proteins.This is one of the first comprehensive proteomic study of a dinoflagellate,A.catenella,that provides a fundamental understanding of the proteins involved in A.catenella growth and response to environmental stresses,and potential physiological indicator proteins related to growth and environmental stress have been identified.

A numerical study on pattern selection in crystal growth by using anisotropic lattice Boltzmann-phase field method

Pattern selection during crystal growth is studied by using the anisotropic lattice Boltzmann-phase field model.In the model,the phase transition,melt flows,and heat transfer are coupled and mathematically described by using the lattice Boltzmann(LB)scheme.The anisotropic streaming-relaxation operation fitting into the LB framework is implemented to model interface advancing with various preferred orientations.Crystal pattern evolutions are then numerically investigated in the conditions of with and without melt flows.It is found that melt flows can significantly influence heat transfer,crystal growth behavior,and phase distributions.The crystal morphological transition from dendrite,seaweed to cauliflower-like patterns occurs with the increase of undercoolings.The interface normal angles and curvature distributions are proposed to quantitatively characterize crystal patterns.The results demonstrate that the distributions are corresponding to crystal morphological features,and they can be therefore used to describe the evolution of crystal patterns in a quantitative way.

Numerical Simulation of Two-Dimensional Dendritic Growth Using Phase-Field Model

In this article, we study the phase-field model of solidification for numerical simulation of dendritic crystal growth that occurs during the casting of metals and alloys. Phase-field model of solidification describes the physics of dendritic growth in any material during the process of under cooling. The numerical procedure in this work is based on finite difference scheme for space and the 4th-order Runge-Kutta method for time discretization. The effect of each physical parameter on the shape and growth of dendritic crystal is studied and visualized in detail.

Monte Carlo study on abnormal growth of Goss grains in Fe-3%Si steel induced by second-phase particles

The selective abnormal growth of Goss grains in magnetic sheets of Fe-3%Si （grade Hi-B） induced by second-phase particles （AlN and MnS） was studied using a modified Monte Carlo Ports model. The starting microstructures for the simulations were generated from electron backscatter diffraction （EBSD） orientation imaging maps of recrystallized samples. In the simulation, second-phase particles were assumed to be randomly distributed in the initial microstructures and the Zener drag effect of particles on Goss grain boundaries was assumed to be selectively invalid because of the unique properties of Goss grain boundaries. The simulation results suggest that normal growth of the matrix grains stagnates because of the pinning effect of particles on their boundaries. During the onset of abnormal grain growth, some Goss grains with concave boundaries in the initial microstructure grow fast abnormally and other Goss grains with convex boundaries shrink and eventually disappear.

3D anisotropy simulation of dendrites growth with phase field method

The anisotropy problem of 3D phase-field model was studied,and various degrees of anisotropy were simulated by numerical calculation method.The results show that with the change of interface anisotropy coefficients,from smooth transition to the appearance of angle,equilibrium crystals shape morphology has a critical value,and 3D critical value is 0.3.The growth of dendrites is stable and the interface is smooth when it is less than critical value;the interface is unstable,rolling edge appears and the growth is discontinuous when it is more than critical value.With the increase of anisotropy coefficients,the dendrites grow faster under the same condition.

Formation and Growth Kinetics of Intermediate Phases in Ni-Al Diffusion Couples

Formation and growth of the intermediate phases in the Ni-Al diffusion couples prepared by pouring technique were investigated. Electron probe microanalysis, scanning electron microscopy and X-ray diffraction were used to characterize the product phases in the joints. The results show that two intermediate phases form in the sequence of NiAl3 and Ni2Al3 during solidification. After annealed, Ni2Al3 and NiAl3 still exist in the joints of the couples. The reasons for the formation of Ni2Al3 and NiAl3, as well as the absence of NiAl, Ni5Al3 and Ni3Al were discussed, respectively. The growth kinetics of both product phase layers indicates that their growth obeys the parabolic rate law. The activation energies and frequency factors for NiAl3 and Ni2Al3 phases were also calculated according to the Arrhenius equation.

Analysis on high-temperature oxidation and growth stress of iron-based alloy using phase field method

High-temperature oxidation is an important property to evaluate thermal protection materials. However, since oxidation is a complex process involving microstructure evolution, its quantitative analysis has always been a challenge. In this work, a phase field method （PFM） based on the thermodynamics theory is developed to simulate the oxidation behavior and oxidation induced growth stress. It involves microstructure evolution and solves the problem of quantitatively computational analysis for the oxidation behavior and growth stress. Employing this method, the diffusion process, oxidation performance, and stress evolution axe predicted for Fe-Cr-A1-Y alloys. The numerical results agree well with the experimental data. The linear relationship between the maximum growth stress and the environment oxygen concentration is found. PFM provides a powerful tool to investigate high-temperature oxidation in complex environments.

Phase-field simulation of dendritic growth for binary alloys with complicate solution models

A phase-field method for simulation of dendritic growth in binary alloys with complicate solution models was studied. The free energy densities of solid and liquid used to construct the free energy of a solidification system in the phase-field model were derived from the Calphad thermodynamic modeling of phase diagram. The dendritic growth of Ti-Al alloy with a quasi-sub regular solution model was simulated in both an isothermal and a non-isothermal regime. In the isothermal one, different initial solute compositions and melt temperatures were chosen. And in the non-isothermal one, release of latent heat during solidification was considered. Realistic growth patterns of dendrite are derived. Both the initial compositions and melt temperatures affect isothermal dendritic morphology and solute distributions much, especially the latter. Release of latent heat will cause a less developed structure of dendrite and a lower interfacial composition.

Phase-field simulation of dendritic growth in a binary alloy with thermodynamics data

This paper simulates the dendrite growth process during non-isothermal solidification in the Al-Cu binary alloy by using the phase-field model. The heat transfer equation is solved simultaneously. The thermodynamic and kinetic parameters are directly obtained from existing database by using the Calculation of Phase Diagram （CALPHAD） method. The effects of the latent heat and undercooling on the dendrite growth, solute and temperature profile during the solidification of binary alloy are investigated. The results indicate that the dendrite growing morphologies could be simulated realistically by linking the phase-field method to CALPHAD. The secondary arms of solidification dendritic are better developed with the increase of undercooling. Correspondingly, the tip speed and the solute segregation in solid-liquid interface increase, but the tip radius decreases.

Phase field modeling of dendrite growth

Single dendrite and multi-dendrite growth for Al-2 mol pct Si alloy during isothermal solidification are simulated by phase field method. In the case of single equiaxed dendrite growth, the secondary and the necking phenomenon can be observed. For multi-dendrite growth, there exists the competitive growth among the dendrites during solidification. As solidification proceeds, growing and coarsening of the primary arms occurs, together with the branching and coarsening of the secondary arms. When the diffusion fields of dendrite tips come into contact with those of the branches growing from the neighboring dendrites, the dendrites stop growing and being to ripen and thicken.

Numerical Simulations of Equiaxed Dendrite Growth Using Phase Field Method

Phase field method offers the prospect of being able to perform realistic numerical experiments on dendrite growth in a metallic system. In this paper, the equiaxed dendrite evolution during the solidification of a pure material was numerically simulated using the phase field model. The equiaxed dendrite growth in a two-dimensional square domain of undercooled melt (nickel) with four-fold anisotropy was simulated. The phase field model equations was solved using the explicit finite difference method on a uniform mesh. The formation of various equiaxed dendrite patterns was shown by a series of simulations, and the effect of anisotropy on equiaxed dendrite morphology was investigated.

Grain growth simulation with the second phase particle pinning for heat-affected zone of microalloyed steel welds

The second phase particle dispersed in microalloyed steel has different effects on grain growth depending on their size and volume fiaction of the second phase particles which will change during welding thermal cycles. The particle coarsening and dissolution kinetics model was analyzed for continuous heating and cooling. In addition, based on experimental data, the coupled equation of grain growth was established by introducing limited size of grain growth with the consideration of the second phase particles pinning effects. Using Monte Carlo method based on experimental data model, the grain growth simulation for heat-affected zone of microalloyed steel welds was achieved. The calculating results were well in agreement with that of experiments.