The Lyophilization of Dispersed Systems: Influence of Freezing Process,Freezing time,Freezing Temperature and RBCs Concentration on RBCs Hemolysis

ABSTRACT

In this work, we studied the influence of different parameters controlling cooling stage on biological dispersed system injury. The human red blood cell (RBCs) was chosen as work model. The study examined the influence of two freezing processes on RBCs hemolysis, one process producing big crystals, the other producing small crystals. Using both processes, we examined the effect of freezing temperature, freezing time, and RBCs concentration on injuries to RBCs. Freezing damage was assessed by the hematocrite measure before freezing and after thawing. The process producing a small number of big ice crystals (Pa) seems—in relation to the one producing a large number of small ice crystals (Pb)—to be less traumatic for the RBC, although the two are not statistically different. Freezing temperature and freezing time influence the preservation of RBCs. At 0 and ?20°C there were high preservation and total hemolysis, respectively. At ?5°C and ?10°C, the RBC hemolysis depends on freezing temperature and freezing time. The RBCs hemolysis rates increases when freezing time increases and when freezing temperature decreases. The rates of RBCs preserved decreases with RBCs concentration some with either the freezing process used (Pa or Pb). More, an accentuation of the difference between the two used freezing processes on RBCs hemolysis was retrieved. The analysis of the conductivity evolution within the RBCs suspension frozen showed that the destruction of the RBCs is had essentially to the solution effects. When the crystallization eutectic takes place, the RBCs are already completely destroyed.     

Synthesis of well dispersed, regular shape ZnO nanorods: effect of pH, time and temperature

In this paper we presented a systematic study on the morphological variation of ZnO nanostructure by varying the pH of precursor solution, reaction time and reaction temperature via cetyl trimethylammonium bromide-assisted hydrothermal method. The phase and structural analysis was carried out by X-ray diffraction, showed the formation of single phase ZnO with hexagonal wurtzite structure in all the specimens. Morphological and structural analysis was carried out by scanning electron microscopy and transmission electron microscopy showed that the shape of ZnO nanorods were greatly influenced by pH of precursor precipitate while size was affected by reaction time as well as temperature. The selected area diffraction pattern showed that the as synthesized ZnO nanorods were single crystalline in nature and preferentially grow along [0001] direction. A plausible growth mechanism of as prepared ZnO nanostructures was discussed in detail. Furthermore, the optical property of as prepared ZnO nanostructures was studied by photoluminescence spectroscopy.     

The effect of salt concentration on the freezing point of meat simulants

Accurate data on the initial freezing point of cured meat is required to predict freezing rates or identify optimal slicing temperatures. However, little data was found in the literature. Experiments were therefore carried out using the ‘Karlsruhe test substance’ (‘Tylose’) with varying salt concentrations as a cured meat substitute. Initial freezing points were −1.4, −3.1, −4.1, −5.2 and −6.3 °C at salt contents of 0.5, 2, 3, 4 and 5 kg salt/100 kg sample, respectively. These values were within ±0.5 °C of published values for cured pork and within ±0.9 °C of theoretical predictions. Modifying the salt content of Tylose is therefore a simple way of determining the initial freezing point of cured lean meats, and Tylose modified in this way can be used to simulate the freezing of cured meat.     

Cure progress in epoxy systems: dependence on temperature and time

We have developed an analytical formula for the cure progress of epoxy systems as a function of both time t and temperature T. Complex viscosity η* or the storage modulus G′ are used as the measures of the cure progress. The equation is based on the shape of the isothermal viscosity vs. time curves typically found for thermoset systems; temperature dependence of the isothermal parameters is established, resulting in a single equation. The equation has been tested for two vastly different thermoset epoxy systems and found to provide reliable predictive capabilities. The equation seems applicable for predicting curing progress of most thermoset systems, without a limitation to epoxies. Moreover, the equation can be used for discriminating accurate experimental results from less accurate ones.     

Optimizing glutaraldehyde crosslinking of collagen: effects of time,temperature and concentration as measured by shrinkage temperature

Glutaraldehyde (GA) crosslinking (fixation) of collageneous tissues is a widely used method for the preparation of implantible tissues to be used as biomaterials. In an attempt to optimize the fixation process, experiments were carried out with two types of collagen (native collagen membrane and synthetic collagen sheet) to study the effect on crosslinking of temperature, GA concentration and fixation time. Secondly, stimulation of GA diffusion was studied and finally, a procedure of low T-presoaking followed by brief exposure to high temperatures was investigated. As a measure of the degree of crosslinking the shrinkage temperature (T _s) was determined. Temperature (20°C or 45°C), concentration (0.1% or 1.0%) or fixation time (4 or 24 h) were found to be positively correlated with the T _s of the collagen sheets. Whereas untanned collagen exhibits a T _s of around 60°C, short-term (1 or 5 min), high-temperature (50°C) fixation with a 0.1% GA solution caused the shrinkage temperature to increase to 72°C and 85.1°C, respectively. Fixation with 0.01% GA for 5 min at 50°C appeared equally effective as 1 min with 0.1% GA (T _s=70°C). Microwave irradiation showed to be slightly more effective in enhancing the crosslinking process compared with conventional heating. Surprisingly, at any combination of temperature, concentration and fixation periods of 4 h or 24 h, an increased T _s towards the central regions of the collagen was observed. Soaking the samples at 20°C (1 h) or at 0°C (3 h) with subsequent short-time heating to 45°C caused an almost equal rise in T _s throughout the collagen samples and is therefore recommended for preparing implantable tissues.     

预氧化时间和温度对聚丙烯腈纤维预氧化的影响

通过在线监测聚丙烯腈(PAN)纤维在预氧化过程中热收缩行为,结合纤维预氧化前后性能变化,考察了时间和温度对预氧化的影响.实验结果表明:温度和时间作用不同,即温度作用不能用时间代替.温度在预氧化过程中起决定性作用,要得到较高的环化度,预氧化温度必须超过240℃.     

The influence of dispositional mindfulness on safety behaviors: A dual process perspective

Based on the dual process model of human cognition, this study investigated the influence of dispositional mindfulness on operators’ safety behaviors and its boundary conditions. In a sample of 212 nuclear power plant control room operators, it was found that both safety compliance and safety participation behaviors were positively influenced by dispositional mindfulness as measured by the 14-item Freiburg Mindfulness Inventory. This effect was still positive after controlling for age, intelligence, work experience and conscientiousness. Moreover, two boundary conditions were identified: the impact of dispositional mindfulness of safety behaviors was stronger among operators who were either more experienced or more intelligent. Theoretically, the framework we used to understand the benefit of mindfulness on safety behaviors has been proved to be useful. Practically, it provides a new and valid criterion that could be used in operators’ selection and training program to improve organizational safety.     

Effects of time,temperature and curing on the stiffness of epoxy laminating systems

Relative creep moduli of a series of epoxy laminating resins were found to be the same in uniaxial tension and in torsion when measured under loads of short duration. However, their tensile creep moduli decreased with time and temperature at different rates, changing their relative stiffness. For one typical resin the short-term tensile and shear moduli decreased with cure temperature reaching minima and then increased slightly. Deflection temperature under load determined by standard tests correlated inversely with the short-term tensile modulus for the typical resin considered and failed to provide a basis for determining the relative stiffness of the different resin systems.     

工艺参数对真空吸铸TiAl基合金连杆铸造过程的影响

本文利用底漏式真空吸铸方法制备TiAl合金汽车发动机连杆铸件,并研究了吸铸工艺参数对铸造过程的影响.分别采用了金属型芯金属模具、陶瓷芯金属模具以及陶瓷型壳进行性吸铸实验,研究了不同的吸铸参数对连杆铸件的成形性影响.得到了TiAl合金底漏式真空吸铸的优化工艺参数,初步获得了形状完整的连杆件.     

The process of electrochemical deposited hydroxyapatite coatings on biomedical titanium at room temperature

Calcium phosphate (CaP) ceramics, especially hydroxyapatite (HA), have received much attention and have been clinically applied in orthopaedics and dentistry due to their excellent biocompatibility. Among several methods for preparing HA coating, electrochemical deposition is a relatively new and possible process. However, documented electrochemical processes were conducted at elevated temperature. In this study, uniform HA coatings have been directly deposited on titanium at room temperature. X-ray diffractometry (XRD) results demonstrated that dicalcium phosphate dihydrate (CaHPO₄·2H₂O, DCPD) was the main component of the coating deposited at lower current densities (1 and 5 mA/cm²). HA structure was obtained at current density above 10 mA/cm² and remained stable after heat treatment at 100–600 °C for 1 h. Part of HA phase was transformed into β-TCP and became a biphasic calcium phosphate coating after annealing at 700 °C. Scratch tests showed that HA coating was not scraped off until a shear stress of 106.3 MPa. Coatings deposited at room temperature exhibited stronger adhesion than those at elevated temperature. HA coating revealed a dense inner layer and rough surface morphology which could fulfill the requisition of implant materials and be adequate to the attachment of bone tissue.     

Alkaline activation of metakaolin and calcium hydroxide mixtures: influence of temperature,activator concentration and solids ratio

Metakaolin is a highly reactive metastable clay that reacts with alkaline solutions forming a cementitious material with high mechanical performance. This material fixes alkalis as structural components.When metakaolin activation is carried out with highly concentrated alkaline solutions in the presence of calcium hydroxide, the main reaction product is a sodium aluminosilicate similar to that obtained when metakaolin is activated in the absence of calcium hydroxide. Additionally, the formation of CSH gel as a secondary product is also observed.The rate of polymer formation is influenced by parameters such as curing temperature, alkali concentration, initial solids content, etc. When the activator concentration increases, a delay in polymer formation is produced, whereas temperature accelerates its formation. The solids ratio (metakaolin/Ca(OH)₂) does not influence the rate of aluminosilicate formation, but it is demonstrated that larger product precipitation is produced when the solids ratio increases.     

The effect of pH, temperature and concentration on electrooxidation of phenol

The electrochemical oxidation of phenol on Pt electrode has been investigated in 1M NaOH and 0.5M H2SO4 solutions at different temperature and different phenol concentration. A simplified mechanism for the electrochemical oxidation of phenol is proposed which includes a selective oxidation parallel with PtO(x) formation. Activation energy, which was obtained from the experimental data, was almost same in studied mediums. This means that electrooxidation mechanism for phenol must be same. Other thermodynamic values such as DeltaS, DeltaH were calculated from the experimental data.     

The influence of dielectric media on nano-structured tungsten carbide (WC) powder synthesized by electro-discharge process

In this investigation, nano-structured tungsten carbide (WC) powder has been synthesized using electro discharge process with tungsten and graphite electrodes submerged in two different dielectrics (kerosene and deionized water). The effect of input parameters (current and pulse duration) in the electro discharge process on the amount of powder production, structure, phases, morphological properties, and size distribution of particles were studied. The obtained results illustrated that, in the majority of setup settings, the amount of nano-structured powder in the kerosene was noticed to be approximately four times greater than the amount of powder produced in deionized water dielectric. Furthermore, it was observed that the particle size in kerosene dielectric (10–30 nm) was smaller than the particle size in deionized water (30–80 nm). According to XRD patterns, WC_1−x phase in kerosene and W₂C phase in deionized water were the main phases of synthesized powder. After producing WC_1−x and W₂C, both powders were put into the carburization operation under the Nitrogen gas to produce WC phase.     

Evaluation of the mean ice ratio as a function of temperature in a heterogeneous food: Application to the determination of the target temperature at the end of freezing

The freezing process is widely used in the food industry. In the 70s, French regulation authorities have created in collaboration with the food industry the concept of «surgélation» process with the objective of improving the image of high quality frozen foods. The process of “surgélation” which could be translated as “super freezing” corresponds to a freezing process for which a final temperature of −18 °C must be reached “as fast as possible”. This concept was proposed in opposition to a conventionally “freezing” process for which no specific freezing rate is expected and the final storage temperature can be of −12 °C only. The objective of this work is to propose a methodology to evaluate the mean amount of frozen ice in a complex food as a function of temperature and to deduce a target temperature that must be considered as the temperature for which the food may be considered as “frozen”. Based on the definition proposed by the IIF-IIR red book, this target temperature has been defined as the temperature for which 80% of the freezable water is frozen. A case study is proposed with a model food made of two constituents.     

The influence of modified zeolites as nucleating agents on crystallization behavior and mechanical properties of polypropylene

Polypropylene (PP) composites with unmodified and modified zeolites were prepared by melt blending in single-screw extruder. The modified zeolites, diethoxy (distearoyl) silane (DDS)–zeolite 13X (DDS-13X) and diethoxy (distearoyl) silane–zeolite 5A (DDS-5A), were obtained by grafting diethoxy (distearoyl) silane onto zeolite 13X and 5A, respectively. The influence of the unmodified and modified zeolites as nucleating agents on properties of polypropylene was investigated with X-ray diffraction (XRD), differential scanning calorimetry (DSC), polarized light microscopy (PLM), Vicat softening temperature (VST) and mechanical properties test. The XRD results revealed that zeolite 13X and DDS-13X had a great influence on nucleation of PP compared to zeolite 5A and DDS-5A. The DSC results showed that the addition of small amount of modified zeolites lead to increase in crystallization temperature (T_c), initial crystallization temperature (T_onset) and crystallinity (X_c) of PP composites compared to unmodified zeolites, especially, DDS-13X was more effective than DDS-5A, and the highest crystallinity X_c (50.48%) was observed in PP/0.3 wt.% DDS-13X, which was responsible to the higher tensile strength and flexural strength of PP/DDS-13X. The PP/DDS-5A, however, exhibited evident increase in flexural strength and a little change in tensile strength compared to pure PP. Moreover, as the addition amount of DDS-5A or DDS-13X up to 1 wt.%, the impact strength of both PP/DDS-5A and PP/DDS-13X reached 43 kJ/m², which was about 2.8 times greater than that of the pure PP (11.3 kJ/m²). These results were in good agreement with the spherulite morphology observed from PLM micrographs.     

The influence of Na on low temperature growth of CIGS thin film solar cells on polyimide substrates

The objective of this work is to study the influence of Na on the properties of Cu(In,Ga)Se₂ (CIGS) absorber layers and finished solar cell devices on polyimide substrates. For this study Na is added to 3-stage grown CIGS thin films by evaporation of a NaF precursor layer prior to the absorber deposition. The precursor layer modifies the CIGS growth kinetics. A stronger Ga-gradient and a decrease of grain size are observed when the Na content increases. An increase in V_oc for a higher Na concentration at a nominal growth temperature of T_sub,max = 500 °C during CIGS deposition is explained by a higher carrier density, as obtained by DLCP measurements. The higher carrier concentration for the higher Na content could be attributed to the reduction of a compensating donor. However, a low J_sc does not allow for an enhanced efficiency possibly due to a shorter depletion region, as observed by admittance spectroscopy, and effective diffusion length.     

Additive manufacturing of copper alloys: influence of process parameters and alloying elements

Owing to the physical properties of copper and its alloys it is challenging to achieve good surface quality and low porosity by the widely used laser-based additive manufacturing processes. This paper deals with the role of alloy composition, powder size and process parameters in additive manufacturing with laser beam melting machine (with power up to 100 W). Test parts were produced in pure copper and CuNiSi(Cr) alloys. The porosity was investigated as a function of different process parameters and powder size ranges. The effects of the alloy physical properties (reflectivity, thermal conductivity, melting range and surface tension) are discussed. Moreover, the effect of thermal treatment on the properties of CuNiSi parts was assessed in conventional two-step heat treatments.     

The influence of API concentration on the roller compaction process: modeling and prediction of the post compacted ribbon,granule and tablet properties using multivariate data analysis

Objective: While previous research has demonstrated roller compaction operating parameters strongly influence the properties of the final product, a greater emphasis might be placed on the raw material attributes of the formulation. There were two main objectives to this study. First, to assess the effects of different process variables on the properties of the obtained ribbons and downstream granules produced from the rolled compacted ribbons. Second, was to establish if models obtained with formulations of one active pharmaceutical ingredient (API) could predict the properties of similar formulations in terms of the excipients used, but with a different API.

Materials and methods: Tolmetin and acetaminophen, chosen for their different compaction properties, were roller compacted on Fitzpatrick roller compactor using the same formulation. Models created using tolmetin and tested using acetaminophen. The physical properties of the blends, ribbon, granule and tablet were characterized. Multivariate analysis using partial least squares was used to analyze all data.

Results: Multivariate models showed that the operating parameters and raw material attributes were essential in the prediction of ribbon porosity and post-milled particle size. The post compacted ribbon and granule attributes also significantly contributed to the prediction of the tablet tensile strength.

Conclusions: Models derived using tolmetin could reasonably predict the ribbon porosity of a second API. After further processing, the post-milled ribbon and granules properties, rather than the physical attributes of the formulation were needed to predict downstream tablet properties. An understanding of the percolation threshold of the formulation significantly improved the predictive ability of the models.     

The influence of pH and bath composition on the properties of Ni-Co coatings synthesized by electrodeposition

Ni-Co coatings were produced on Cu substrates by electrodeposition from electrolytes with different pH values and different Co²⁺ concentration. The current efficiency increases from 52.1% to 81.2% with the pH increasing from 2.0 to 5.4. It is clearly observed that the content of cobalt in the deposited coatings gradually increases from 9.4% to 19.6% as the pH value varies from 2.0 to 5.4. The Co content in the deposited coatings increases from 16.5% to 72.7% as the molar ratio of CoSO₄/NiSO₄ varying from 1:5 to 1:2 in electrolyte. XRD patterns reveal that the structure of the coatings strongly depends on the Co content in the binary coatings. Both granular and dendritic crystals were investigated by SEM and the different crystallization behaviors were illustrated. The saturation magnetization of the coatings goes up from 96.36 kAm⁻¹ to 136.08 kAm⁻¹ with the pH value increasing from 2.0 to 5.4. The saturation magnetization (M_s) and coercivity (H_c) move up from 144.84 kAm⁻¹ and 15.27 kAm⁻¹ to 175.13 kAm⁻¹ and 125.20 kAm⁻¹ with the increase of Co in the electrolyte, respectively.     

The influence of pH,contact time,ionic strength,temperature, and fullerene on the adsorption of Cu(II) onto magnetic multi-walled carbon nanotubes

The influences of pH, contact time, absorbent dose, temperature and C₆₀(C(COOH)₂)_n on Cu(II) adsorption onto the magnetic multi-walled carbon nanotubes (MMWCNTs) were studied by batch technique. The dynamic process showed that the adsorption of Cu(II) onto MMWCNTs matched well with the pseudo-second-order kinetics model. The adsorption of Cu(II) onto MMWCNTs was dependent on pH values significantly, the adsorption percentage increased observably at pH 5.0–7.0, and then maintained a steady state with pH increased. Through simulating the adsorption isotherms by Langmuir, Freundlich and Dubini-Radushkevich models, respectively, it could be seen that the adsorption pattern of Cu(II) onto MMWCNTs was mainly surface complexation. The presence of C₆₀(C(COOH)₂)_n could enhance the adsorption content of Cu(II) onto MMWCNTs at low pH, but restrained that at higher pH.