Composite Surface Model Research Articles

Landscape features influencing gene flow and connectivity of an endangered passerine.

Dispersal of individuals and gene flow are crucial aspects to maintain genetic diversity and viability of populations, especially in the case of threatened species. Landscape composition and structure may facilitate or limit individual movement within and among populations. We used a landscape genetics approach to assess the connectivity patterns of the threatened Dupont's lark (Chersophilus duponti subsp. duponti), considering their genetic patterns and the landscape features associated with its gene flow in Spain. We analysed the genetic relatedness based on 11 species-specific polymorphic microsatellites on 416 Dupont's lark individuals sampled across peninsular Spain between 2017 and 2019, covering most of the European distribution of the species. To assess the relationship between the landscape composition and the species gene flow, we estimated genetic distance at the individual level (Dps). Next, we built a set of environmental surfaces from two time periods (years 1990 and 2018), based on factors such as land use and topography, influencing individuals' movement. We then obtained resistance surfaces from an optimization process on landscape variables. Landscape genetics analyses were done for single and composite surface models for each year separately. Our findings from both time points show that scatter or mosaic-structured vegetation composed by low agricultural and tree cover and high presence of sclerophyllous shrubs favoured Dupont's lark dispersal, while dense and continuous tree cover, as well as areas of intensive agriculture, were limiting factors. Our results suggest the importance of steppe habitat patches for the species' establishment and dispersal. In addition, our results provide key information to develop conservation measures, including conserving and restoring steppe habitats as scattered and/or mosaic-structured vegetation that could warrant the connectivity and persistence of Dupont's lark populations.

Interaction between surfactants of different classes and nanofiltration membranes

The presence of surfactants in aquatic environments may alter the water quality parameters. Nanofiltration is a promising technique that can separate surfactants from water with high rejections. Nevertheless, negative charges on nanofiltration membranes could facilitate the occurrence of electrostatic interactions between the charged surfactants and the surface of these membranes, increasing the membrane-fouling tendency. In this work, the interaction of surfactants commonly found in residential laundry wastewater with membranes used in nanofiltration was investigated. For this purpose, the surface, and transport properties of four commercial membranes were analyzed. The zeta potential of the NF90 membrane in the presence of individual and mixture of surfactants was performed to evaluate the effect of adsorption of these surfactants on the performance of the membrane. Additionally, a central composite rotatable design (CCDR) and response surface model were applied to investigate the simultaneous effect of the initial concentration of CTAB and SDS ([CTAB + SDS]0) and pH on the NF90 permeate fluxes and rejections. It was shown that surfactant adsorption varies with the type of surfactant and membrane. Moreover, adsorption played an important role in NF90 membrane fouling, mainly for the cationic surfactant in individual solutions and in the mixture of surfactants. Besides adsorption, pore blocking may have affected the performance of nanofiltration for higher concentrations of surfactants. Finally, by the application of the central composite rotatable design (CCDR), it was possible to find the best conditions of pH and initial concentration of surfactants for achieving higher fluxes and rejections by the NF90 membrane.

Evaluation of a Chaotrope and Kosmotrope in the Multivariate Optimization of PHW-ATPE of Solasodine from Leaves of Solanum mauritianum.

A hyphenated pressurized hot water—aqueous two-phase extraction (PHW-ATPE) method was applied to extract solasodine from Solanum mauritianum (S. mauritianum). A central composite design (CCD) was applied to determine the optimal conditions for the extraction of solasodine. The parameters evaluated included the percentage concentration of salt (NaCl or Na2CO3) and temperature. The fit of the central composite design response surface model for PHW-ATPE to the data generated a model with a good quadratic fit (R2 = 0.901). The statistically significant (p < 0.05) parameters, such as the linear and quadratic effects of the concentration of salt (%) powder, had a significant impact on the extraction of solasodine. The application of multiply charged salts such as Na2CO3 (kosmotrope) was shown to be a comparably better extractant of solasodine than NaCl (chaotrope) due to the salting-out effect. The optimized conditions for extraction of solasodine with NaCl or Na2CO3 were a temperature of 80 °C at a salt concentration of 20%. The maximum extraction of solasodine was 300.79 mg kg−1 and 162.34 mg kg−1 for Na2CO3 and NaCl, respectively.

Study on environment modeling and electromagnetic scattering characteristics in mountainous areas

ABSTRACT This paper proposed a modeling method to describe the environmental structure of mountainous areas by using the composite rough surface model, and the electromagnetic (EM) scattering characteristics of the composite rough surfaces are studied. Based on the Monte Carlo method and Gaussian spectral function, the rough surface of the terrestrial environment is generated. And the inverse tangent function is introduced to weighted rough surfaces with different statistical properties, making rough surfaces join smoothly. On this basis, geometric models of rough surfaces of three typical mountainous environments, valley, hillside, and ridge, are established. The shooting and bouncing ray (SBR) method is used to calculate the EM scattering characteristics. Due to the multiple reflections of EM waves, the idea of ray-density normalization (RDN) is introduced to improve the EM flow on triangular facets illuminated by multiple rays. Finally, the effects of different slope angles, surface roughness, and incident wave angles on the EM scattering characteristics are discussed to provide some useful conclusions. The simulation results show that the rough surface with a certain slope will greatly change the scattering characteristics of the whole environment and make the spatial distribution of scattering energy show a new characteristic.

Effect of Microwave-Assisted Aqueous Two-Phase Extraction of α-Solanine from S. retroflexum and Analysis on UHPLC-qTOF-MS

Abstract A new, fast and efficient method, hyphenated microwave-assisted aqueous two-phase extraction (MA-ATPE) was applied in the extraction of α-solanine from Solanum retroflexum. This environmentally friendly extraction method applied water and ethanol as extraction solvents. Central composite design (CCD) was performed which included numerical parameters such as time, mass of plant powder and microwave power. The categorical factors included the chaotrope — NaCl or the kosmotrope — Na2CO3. Fitting the central composite design response surface model to the data generated a quadratic model with a good fit (R2 = 0.920). The statistically significant (p &lt; 0.05) parameters such as time and mass of plant powder were influential in the extraction of α-solanine. Quantification of α-solanine was achieved using a robust and sensitive feature of the ultra-high performance quadrupole time of flight mass spectrometer (UHPLC-qTOF-MS), multiple reaction monitoring (MRM). The optimized condition for the extraction of α-solanine in the presence of NaCl and Na2CO3 was a period of 1 min at a mass of 1.2 g using a microwave power of 40%. Maximal extraction of α-solanine was 93.50 mg kg−1 and 72.16 mg kg−1 for Na2CO3 and NaCl, respectively. The synergistic effect of salting-out and microwave extraction was influential in extraction of α-solanine. Furthermore, the higher negative charge density of the kosmotrope (Na2CO3) was responsible for its greater extraction of α-solanine than chaotrope (NaCl). The shorter optimal extraction times of MA-ATPE make it a potential technique that could meet market demand as it is a quick, green and efficient method for removal of toxic metabolites in nutraceuticals.

Chitosan based co-processed excipient for improved tableting

Chitosan is a multipurpose polymer with immense utility in pharmaceutical drug delivery systems. Low density, poor flowability and inadequate compression characteristics have limited its use as a tablet excipient. To address these limitations, a new tri-component excipient system composed of chitosan, mannitol and crospovidone was developed using spray drying technique. Mannitol was utilized for its ability to act as a bulking agent and to harness its unique characteristics such as a low hygroscopicity, strong inertness towards other excipients, whereas crospovidone was used as the disintegrant. Central composite response surface model was employed to obtain optimum combination of these components. Resulting coprocessed excipient showed remarkable improvement in density and flowability as confirmed by SeDeM diagram expert system. Heckel and Kawakita analysis predicted superior compression features of developed excipient for tableting. Furthermore, the applicability of developed excipient was studied by formulating paracetamol tablet as a model formulation by direct compression. Co-process excipient consisting of 50% chitosan, 43% mannitol and 6.5% crospovidone provided tablets with desired hardness of 100 N having disintegration time less than 25 s. Therefore, developed multifunctional coprocessed excipient exhibited promising results with potential for scale up and wide applicability in drug delivery.

Empirical Relationship Between the Doppler Centroid Derived From X-Band Spaceborne InSAR Data and Wind Vectors

One of the challenges in ocean surface current retrieval from synthetic aperture radar (SAR) data is the estimation and removal of the wave-induced Doppler centroid (DC). This article demonstrates empirically the relationship between the dc derived from spaceborne X-band InSAR data and the ocean surface wind and waves. In this study, we analyzed over 300 TanDEM-X image pairs. It is found that the general characteristics of the estimated dc follow the theoretically expected variation with incidence angle, wind speed, and wind direction. An empirical geophysical model function (GMF) is fit to the estimated dc and compared to existing models and previous experiments. Our GMF is in good agreement (within 0.2 m/s) with other models and data sets. It is found that the wind-induced Doppler velocity contributes to the total Doppler velocity with about 15% of the radial wind speed. This is much larger than the sum of the contributions from the Bragg waves (~0.2 m/s) and the wind-induced drift current (~3% of wind speed). This indicates a significant (dominant) contribution of the long wind waves to the SAR dc. Moreover, analysis of dual-polarized data shows that the backscatter polarization ratio ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$PR=\sigma ^{0}_{VV}/\sigma ^{0}_{HH}$ </tex-math></inline-formula> ) and the dc polarization difference ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$PD={|dc_{VV}|-|dc_{HH}|}$ </tex-math></inline-formula> ) are systematically larger than 1 and smaller than 0 Hz, respectively, and both increase in magnitude with incidence angle. The estimated PR and PD are compared to other theoretical and empirical models. The Bragg scattering theory-based (pure Bragg and composite surface) models overestimate both PR and PD, suggesting that other scattering mechanisms, e.g., wave breaking, are involved. In general, it is found that empirical models are more consistent with both backscatter and Doppler data than theory-based models. This motivates a further improvement of SAR dc GMFs.

An Improved Two-Scale Model for Electromagnetic Backscattering From Sea Surface

Based on composite rough surface and stochastic multiscale models, an improved two-scale model (TSM) is proposed. Different from the classical TSM, the proposed method adopts the integral equation method (IEM) to replace the small perturbation method (SPM) for calculating the contribution from small-scale roughness. Kirchhoff approximation (KA) is still kept in the model to calculate the contribution from large-scale roughness. Because the IEM has wider application range than the SPM, the proposed model exhibits a higher accuracy and has a wider application range in terms of sea surface roughness compared with the classical TSM. Usually, the classical TSM is sensitive to the cutoff wavenumber. The proposed model adopts an adaptive cutoff wavenumber instead of choosing a cutoff wavenumber in the classical TSM. The effectiveness of the proposed model is demonstrated through comparisons with the simulation results of multilevel fast multipole algorithm (MLFMA) and the measured results. Different roughness at different frequencies is analyzed as well.

A Remote Sensing Based Integrated Approach to Quantify the Impact of Fluvial and Pluvial Flooding in an Urban Catchment

Pluvial (surface water) flooding is often the cause of significant flood damage in urban areas. However, pluvial flooding is often overlooked in catchments which are historically known for fluvial floods. In this study, we present a conceptual remote sensing based integrated approach to enhance current practice in the estimation of flood extent and damage and characterise the spatial distribution of pluvial and fluvial flooding. Cockermouth, a town which is highly prone to flooding, was selected as a study site. The flood event caused by named storm Desmond in 2015 (5-6/12/2015) was selected for this study. A high resolution digital elevation model (DEM) was produced from a composite digital surface model (DSM) and a digital terrain model (DTM) obtained from the Environment Agency. Using this DEM, a 2D flood model was developed in HEC-RAS (v5) 2D for the study site. Simulations were carried out with and without pluvial flooding. Calibrated models were then used to compare the fluvial and combined (pluvial and fluvial) flood damage areas for different land use types. The number of residential properties affected by both fluvial and combined flooding was compared using a combination of modelled results and data collected from Unmanned Aircraft Systems (UAS). As far as the authors are aware, this is the first time that remote sensing data, hydrological modelling and flood damage data at a property level have been combined to differentiate between the extent of flooding and damage caused by fluvial and pluvial flooding in the same event. Results show that the contribution of pluvial flooding should not be ignored, even in a catchment where fluvial flooding is the major cause of the flood damages. Although the additional flood depths caused by the pluvial contribution were lower than the fluvial flood depths, the affected area is still significant. Pluvial flooding increased the overall number of affected properties by 25%. In addition, it increased the flood depths in a number of properties that were identified as being affected by fluvial flooding, in some cases by more than 50%. These findings show the importance of taking pluvial flooding into consideration in flood management practices. Further, most of the data used in this study was obtained via remote sensing methods, including UAS. This demonstrates the merit of developing a remote sensing based framework to enhance current practices in the estimation of both flood extent and damage.

Design, optimization and in vitro-in vivo evaluation of smart nanocaged carrier delivery of multifunctional PEG-chitosan stabilized silybin nanocrystals

This study explored the feasibility of using smart nanocaged carrier technology for the delivering of multifunctional mPEG-chitosan stabilized silybin nanocrystals and to enhancing the long-term stability, dissolution velocity and bioavailability of the water insoluble drugs. The methoxypoly(ethylene glycol)-b-poly(ε-caprolactone) (mPEG-b-PCL), as nanocaged carrier, was modified with propargyl and azide group and confirmed by FTIR. The methoxypolythylene glycol-grafted chitosan (PEG-CS), as multifunctional stabilizer, were applied for the silybin nanocrystals formulation. Two silybin nanocrystals formulations (PEG-CS nanocrystals and nanocaged nanocrystals) were prepared using anti-solvent precipitation method and optimized by central composite design-response surface model. The transmission electron microscopy, scanning electron microscopy and atomic force microscope revealed small and uniformed morphology. The crystalline state of the nanocrystals was confirmed by X-ray powder diffraction and differential scanning calorimetry. The drug structure was confirmed by Fourier transform infrared spectroscopy. During the long term stability study, the nanocaged nanocrystals were presented remarkable stability. Compared with the silybin solution, the nanocaged nanocrystals and the PEG-CS nanocrystals drug delivery system also exhibited 5.54 and 2.58 fold increasing in the AUC, respectively. Thus, the nanocaged nanocrystals technology with excellent stability, improved dissolution velocity and relative bioavailability was recommended as an efficient and feasible approach for water insoluble drugs delivery.

Effects of multiple environmental factors on the growth and extracellular organic matter production of Microcystis aeruginosa: a central composite design response surface model.

In this study, statistically designed experiments using response surface methodology were conducted on Microcystis aeruginosa. A central composite design response surface model was established to investigate the multiple effects of various physical and chemical factors (total nitrogen, total phosphorus, temperature, and light intensity) on algal density and extracellular organic matter. The results of the experiments reveal that nitrate and phosphate had significant interactive effects on algal density, both iron and light intensity had synergic effects on the production of microcystins (MC-LR) and extracellular polysaccharides (EPS), and light intensity and nitrite had clear interactive effects on EPS release. Results did not show significant interactive effects on extracellular dissolved organic carbon (DOC) production. The contribution of extracellular dissolved organic matter of Microcystis aeruginosa during the logarithmic phase was further identified using a three-dimensional excitation emission matrix (3-DEEM). This study contributes to our theoretical knowledge of the prediction and analysis of M. aeruginosa growth and extracellular organic matter production.

Experimental investigation of cooling characteristics in wet grinding using heat pipe grinding wheel

High grinding temperature restricts the machining efficiency and precision of some aeronautical difficult-to-machine materials. Aiming to enhance heat exchange with the grinding zone and reduce grinding temperature, heat pipe grinding wheel (HPGW) provides a novel method through improving the thermal conductivity of grinding wheel assisted by heat pipe. In this paper, the structure of HPGW is introduced and the workpiece temperature and energy partition in wet grinding using HPGW based on a wheel-fluid composite surface model is analyzed. Wet grinding experiments including creep feed grinding, high-speed shallow grinding and high-efficiency deep grinding (HEDG) are carried to investigate the cooling characteristics of HPGW according to the workpieces of titanium alloy Ti-6A1-6 V and Inconel 718. Compared with using the traditional grinding wheel, the results show that using HPGW in creep feed grinding and HEDG can maintain a lower grinding temperature and avoid the burnout under a relatively high removal rate, but cooling effect of HPGW is not obviously different from the traditional grinding wheel in high-speed shallow grinding due to a small heat input at the evaporator of HPGW.

A hybrid method for electromagnetic scattering from target above composite rough surface of ground and near sea in adjacent region

ABSTRACTThis paper proposes a hybrid method for computing electromagnetic scattering from target above composite rough surface of ground and near sea in adjacent region. First, a kind of composite rough surface for simulating ground and near sea in adjacent region is modeled by utilizing the Monte Carlo method, in which the ground region is modeled by adopting Gauss spectral function; the near sea region is modeled by adopting JONSWAP spectral function combined with shallow coefficient; diverse weighted inverse tangent functions are introduced to structure different boundaries and connect regions. Second, aiming at fast and accurately computing composite scattering from target above this kind of composite rough surface, a hybrid method with several acceleration strategies is proposed by combining adaptive iterative physical optics (AIPO) with method of equivalent currents (MEC), in which MEC meliorates edge diffraction. Finally, some examples verify the validation of the proposed hybrid method showing that: this hybrid method is an effective tool for analyzing the composite scattering characteristics of target above practical environment during radar detection and SAR imaging, and we also give the composite scattering from target above composite rough surface with different incident angle, shape of boundary and statistic parameters. Moreover, composite scattering from different targets above this kind of composite rough surface model is studied in order to provide some useful conclusions.

In vitro and in vivo evaluation of targeting tumor with folate-based amphiphilic multifunctional stabilizer for resveratrol nanosuspensions

Resveratrol (RSV) nanosuspensions, with long term stability and targeting delivery ability, were designed and demonstrated by in vitro and in vivo model. The folate modified distearoylphosphatidyl ethanolamine-polyethylene glycol (DSPE-PEG-FA), as target delivery carrier, was synthesized and confirmed by FTIR and 1H NMR. D-α-tocopherol polyethylene glycol 1000 succinate (TPGS) and DSPE-PEG-FA used as stabilizers formed two RSV nanosuspensions (RSV-NA and RSV-NB), which were prepared by anti-solvent precipitation method and optimized by central composite design-response surface model (CCD-RSM). The morphology of RSV nanosuspensions showed flake shapes and spherical shapes by SEM. And the distribution of particles was uniform by TEM and AFM. The two RSV nanosuspensions displayed an amorphous state, by XRPD and DSC determination. At room temperature, the optimum RSV nanosuspensions showed long term stability for 20days. The cell proliferation and morphology study revealed that the RSV nanosuspensions significantly enhanced the in vitro cytotoxicity against A549 cells in a dose- and time-dependent manner. The recommended safe concentration was 5μM for in vitro study. In vivo studies of the two nanosuspensions also displayed higher antitumor efficacy by reduced tumor volume and weight. Compared with the saline group, the tumor inhibition ratio of the RSV-NA was 61.53±18.36% and RSV-NB was 64.61±21.13%. The mice weight of the RSV-NA group and RSV-NB group was also maintained constant increasing. These results demonstrated that TPGS and DSPE-PEG-FA could be used as stabilizers for stable RSV nanosuspensions formulation with the potentiality for targeting delivery to human alveolar carcinoma cells with high stability and efficacy.

The effect of temperature and methanol–water mixture on pressurized hot water extraction (PHWE) of anti-HIV analogoues from Bidens pilosa

BackgroundPressurized hot water extraction (PHWE) technique has recently gain much attention for the extraction of biologically active compounds from plant tissues for analytical purposes, due to the limited use of organic solvents, its cost-effectiveness, ease-of-use and efficiency. An increase in temperature results in higher yields, however, issues with degradation of some metabolites (e.g. tartrate esters) when PHWE is conditioned at elevated temperatures has greatly limited its use. In this study, we considered possibilities of optimizing PHWE of some specific functional metabolites from Bidens pilosa using solvent compositions of 0, 20, 40 and 60 % methanol and a temperature profile of 50, 100 and 150 °C.ResultsThe extracts obtained were analyzed using UPLC-qTOF-MS/MS and the results showed that both temperature and solvent composition were critical for efficient recovery of target metabolites, i.e., dicaffeoylquinic acid (diCQA) and chicoric acid (CA), which are known to possess anti-HIV properties. It was also possible to extract different isomers (possibly cis-geometrical isomers) of these molecules. Significantly differential (p ≤ 0.05) recovery patterns corresponding to the extraction conditions were observed as recovery increased with increase in methanol composition as well as temperature. The major compounds recovered in descending order were 3,5-diCQA with relative peak intensity of 204.23 ± 3.16 extracted at 50 °C and 60 % methanol; chicoric acid (141.00 ± 3.55) at 50 °C and 60 % methanol; 4,5-diCQA (108.05 ± 4.76) at 150 °C and 0 % methanol; 3,4-diCQA (53.04 ± 13.49) at 150 °C and 0 % methanol; chicoric acid isomer (40.01 ± 1.14) at 150 °C and 20 % methanol; and cis-3,5-diCQA (12.07 ± 5.54) at 100 °C and 60 % methanol. Fitting the central composite design response surface model to our data generated models that fit the data well with R2 values ranging from 0.57 to 0.87. Accordingly, it was possible to observe on the response surface plots the effects of temperature and solvent composition on the recovery patterns of these metabolites as well as to establish the optimum extraction conditions. Furthermore, the pareto charts revealed that methanol composition had a stronger effect on extraction yield than temperature.ConclusionUsing methanol as a co-solvent resulted in significantly higher (p ≤ 0.05) even at temperatures as low as 50 °C, thus undermining the limitation of thermal degradation at higher temperatures during PHWE.

Optimization of environmental parameters for Nannochloropsis salina growth and lipid content using the response surface method and invading organisms

Algae biofuel has the potential to replace fossil fuels. However, cultivation and productivity of target algae need improvement, while controlling undesired organisms that can lower the efficiency of production systems. A central composite design and response surface model were utilized to predict cultivation optima of marine microalga, Nannochloropsis salina, under a suite of environmental parameters. The effects of salinity, pH, and temperature and their interactions were studied on maximum sustainable yield (MSY, a measure for biomass productivity), lipid content of N. salina, and invading organisms. Five different levels of each environmental predictor variable were tested. The environmental factors were kept within ranges that had previously been determined to allow positive N. salina growth (14.5–45.5 PSU; pH 6.3–9.7; 11–29 °C). The models created for this experiment showed that N. salina’s MSY and lipid content are not strongly affected over the broad range of salinity and temperature values. Calculated optima levels were 28 PSU/20 °C for MSY and 14.5 PSU/20 °C for lipid accumulation, but neither value significantly influenced the model. However, pH was the most important factor to influence algae productivity, and pH optimum was estimated around 8. Both MSY and lipid content were strongly reduced when pH deviated from the optimum. Occurrence of invading organisms seemed stochastic, and none of the environmental factors studied significantly influenced abundance. In conclusion, pH should be kept around 8 for maximum productivity of N. salina. Temperature and salinity should be kept around 20 °C and 28 PSU; however, moderate variations are not too much of a concern and might enhance lipid content of N. salina.

A novel method of dynamic characteristics analysis of machine tool based on unit structure

A novel approach, which can be used for dynamic characteristics analysis of machine tools based on unit structure (US), is reported in this paper. The concepts of unit structures for design of machine tools are defined. In order to satisfy the dynamic characteristics requirement of high natural frequency and light-weight of US, a design method of multi-disciplinary optimization of NSGA-II about unit structures driven by natural frequency and mass is developed. Through analyzing the unit structures, key factors affecting the natural frequency and mass are extracted, and the mathematical models of natural frequency and mass about unit structures are also established by using central composite design and response surface model. The goal of high natural frequency and light-weight is reached by using the multi-objective genetic algorithms. The Pareto optimal set is also obtained. The dynamic behavior of US is investigated by the experimental modal analysis. To show the efficiency of the proposed novel method, the example of YKW51250 gear shaping machine bed is used. Through optimization of NSGA-II about US of YKW51250 machine bed, the natural frequency of YKW51250 gear shaping machine bed is increased by 30.4% and its mass decreased by 5.2% comparing with the original design. By studying the dynamic characteristics of the simplified machine tools bed, useful laws are obtained, and these laws can be used in primary design of NC machine tools structures. The optimal method based on US can be also applied to the dynamic optimal design of machine tools and other similar equipments.

Suitability of ccRSM as a tool to predict inactivation and its kinetics for Escherichia coli, Staphylococcus aureus and Pseudomonas fluorescens in homogenized milk treated by manothermosonication (MTS)

The application of ultrasound (US) technology (i.e. sonication) has been used as an alternative to thermal technologies to reduce the microbial population of foods and beverages. This approach can be used on its own or combined with pressure and temperature (i.e. manothermosonication (MTS)). Microbial inactivation kinetics by sonication remains unclear. In the present study, a central composite response surface model (ccRSM) was used in order to study the effects of temperature (20–52 °C), acoustic intensity (60–120 W/cm2) and treatment time (40–240 s) at a constant pressure (225 kPa) by MTS processing on microbial inactivation. Reductions of up to c. 1.6 log CFU/ml were achieved for Escherichia coli and Pseudomonas fluorescens. Lower inactivation values were reported for Staphylococcus aureus (1.05 log CFU/ml). These inactivation values were achieved using conditions of 36 °C, 90 W/cm2 and 240 s. Inactivation of E. coli by MTS (R2 = 0.90) was described by an exponential curve, whereas inactivation of S. aureus and P. fluorescens by MTS (R2 ≥ 0.73) were described by a linear trend. The coefficient of determination values were obtained following validation between the theoretical model and the experimental values. Statistical analysis showed that treatment time was the factor with greatest influence on microbial inactivation for all three microorganisms. The present study confirms the suitability of using ccRSM as a tool for investigating and predicting the inactivation of E. coli, S. aureus and P. fluorescens as a function of temperature, acoustic power and treatment time, and may also be useful for predicting inactivation of other microorganisms commonly found in raw milk.

COMPARISON OF THE TWO-SCALE AND THREE-SCALE MODELS FOR BISTATIC ELECTROMAGNETIC SCATTERING FROM OCEAN SURFACES

With rapid development of satellite technology in monitoring the ocean, a good understanding of the physical processes involved in the electromagnetic ocean-surface interaction is required. The composite surface models are usually applied in the analysis of the interaction, hence a systematical check of their region of validity is desirable. Based on a generalized minimal residual procedure which is right preconditioned (GMRES-RP) that we have recently developed which has demonstrated the desirable properties of a numerical algorithm: robust and e-cient, in this paper, for bistatic scattering from one dimensional ocean surfaces, we carry out a systematic assessment of the performance of the popular two-scale model and the advanced three-scale model under difierent conditions of ocean surface wind speeds, polarizations, frequencies, and incidence angles. It is found that the two-scale model in general captures the bistatic scattering pattern, yet the accuracy of geometrical optics (GO) for the large scale wave brings considerable impact on the overall accuracy. If the evaluation of the contribution of the large scale wave is instead using direct numerical integration for the corresponding Kirchhofi integral, impressive improvements are frequently observed, especially at low frequency (L and C bands) and low wind speed (3m/s). But care should be taken when apply two-scale method with numerical integration, since there are cases where visible discrepancy with method of moment (MoM) are observed. On the other hand, the three- scale model is found in very good agreement with MoM across the considered ocean surface wind speeds, polarizations, frequencies, and incidence angles, hence represents a much advanced model over the two-scale model.

Laboratory and Theoretical Studies on Doppler Spectra From Bound and Free Waves

There exist bound gravity-capillary waves that move at the speed of the dominate waves on the ocean surface, apart from free gravity-capillary waves that satisfy the linear dispersion relation. The radar Doppler spectra are hypothesized to be the weighted sum of two parts, one is attributed to free waves, and the other is attributed to bound waves. Based on the Bound\Free wave composite surface model (BF), a theoretical model to predict the Doppler bandwidths of bound and free waves is proposed in this paper. According to the nature and the phase distribution of bound and free waves, their Doppler bandwidths can be derived from ocean wave spectra. Meanwhile, the nonlinear motion of partial intermediate scale waves is considered. Besides, the experiments on microwave backscatter from surface waves are carried out in the wind-wave tank. General Gaussian curve fitting is used to separate and obtain the measured Doppler offsets and bandwidths of bound and free waves in the data processing. Compared with the experimental measurements at X-band and Ku-band, the model shows its applicability to predict the Doppler bandwidths of bound and free waves.