Number Of Freeze Research Articles

Effects of Freeze−Thaw Cycles on Available Nitrogen Content in Soils of Different Crops

In order to study the effect of freeze−thaw cycles on the content of available nitrogen in soils of different crops and obtain an in-depth understanding of changes in soil fertility and soil environment in cold regions, a laboratory simulation experiment was conducted with different freeze−thaw times, temperature differences, and periods. The changes in available nitrogen concentrations in the 0–15 cm and 15–30 cm layers of corn, vegetable, and paddy soils were measured by the alkaline-hydrolysis diffusion method. The results were as follows. (1) The freeze−thaw process had significant effects on the available nitrogen content in the three soils. Under the treatment with different numbers of freeze−thaw cycles, the available nitrogen content in the 0–15 cm layers of corn soil, vegetable soil, and paddy soil reached the maximum values at the 8th, 1st, and 3rd freeze−thaw cycle, at 156.92 mg/kg, 479.17 mg/kg and 181.75 mg/kg, respectively; the available nitrogen content decreased slowly after reaching the maximum value. (2) Under the freeze−thaw temperature-difference treatment, the available nitrogen concentration in the 0–15 cm layers of corn soil, vegetable soil, and paddy soil reached the maximum value at a temperature difference of 30 °C, at 147 mg/kg, 476 mg/kg and 172.5 mg/kg, respectively, and the available nitrogen content of the 15–30 cm soil layers changed slightly. (3) Under different freeze−thaw periods, the magnitudes of the changes in soil available nitrogen concentration in 0–15 cm of corn soil and paddy soil were, in descending order, short-term freezing and long-term melting > long-term freezing and long-term melting > short-term freezing and short-term melting > long-term freezing and short-term melting. The soil available nitrogen concentration at different depths in the vegetable soil reached the maximum value under the treatment with long-term freezing and short-term melting. (4) The available nitrogen content of paddy soil under the high-water-content condition was higher than that of paddy soil under the low-water-content condition, and the change in available nitrogen content was more obvious under the high-water-content condition under different freeze−thaw period treatments; the opposite was true for corn soil and vegetable soil. Simulation studies on rapid changes in soil nitrogen content during tests that simulate winter freeze−thaw conditions are important for understanding crop growth, the application of nitrogen fertilizer in spring, and the prevention of surface-water pollution from agricultural runoff.

Experimental Study of Shear Strength of Loess under Freeze-thaw Cycles

In order to study the shear strength characteristics of loess under the action of freeze-thaw cycle, through the freeze-thaw test, straight shear test, to analyze the change rule of water content and freeze-thaw cycle on loess cohesion, internal friction angle and shear strength. The test results show that: loess cohesion gradually decreases with the increase of water content and the number of freeze-thaw cycles, when the freeze-thaw 7 times, the change of cohesion gradually tends to stabilize; the angle of internal friction decreases gradually with the increase of water content and the number of freeze-thaw cycles, but the rate of decrease is smaller than the rate of cohesion; the change of shear strength is affected by the cohesion more than the angle of internal friction, and the shear strength at different times of freezing and thawing increased linearly with the vertical stress, and the relationship equations between the shear strength and the water content and the number of freezing and thawing cycles were established.

Mechanical properties and damage modeling of unloaded marble under freezing and thawing with different temperature ranges

The seasonal freeze-thaw environment is a primary factor contributing to the deterioration of manually excavated disturbed rock masses on reservoir bank slopes in highland alpine areas. To investigate the mechanical properties and damage deterioration mechanism of excavation-unloading rock under seasonal freeze-thaw environment in cold region, the freeze-thaw cycle tests with different temperature difference levels (−10–10 °C, −15–25 °C, −20–40 °C) and different cycle times (0,10,20,30) were simulated for the triaxial unloading damaged marble. Then, the mechanical parameters of unloaded marble after freezing and thawing were obtained by uniaxial compression and triaxial compression tests, and the influence laws of temperature ranges, number of freezing and thawing cycles and confining pressure on the mechanical properties of unloaded marble were analyzed. Finally, the damage model of unloaded marble considering freeze-thaw action was established. The results show that the strength of unloaded marble is significantly weakened under the combined effect of F-T (freezing and thawing) and loading, and that the deterioration effect of the number of F-T cycles is stronger than that of the temperature ranges. The increase in the confining pressure increased the compressive strength and elastic modulus of the unloaded marble, and suppressed the damage of the unloaded marble after the freeze-thaw treatment. The porosity of the unloaded marble developed gradually and increased exponentially with the increase of the number of freeze-thaw cycles, the compressive strength and elastic modulus had a negative exponential relationship with the number of freeze-thaw cycles, and the shear strength parameter had a quadratic polynomial relationship with the number of freeze-thaw cycles. In addition, the softening mechanism of unloaded marble by natural water plays a key role in the process of freeze-thaw cycle, and the damage model considering freeze-thaw is established, and the theoretical curves are well matched with the experimental results. The outcomes of this study hold significant theoretical and engineering importance for evaluating the stability of excavated unloaded rock in highland alpine regions.

THE USE OF VARIOUS BEHAVIORAL MODELS IN STUDYING THE RESPONSE OF RATS UNDER THE IMPACT OF NEGATIVE AEROIONS

The aim of the work was to evaluate the behavior of laboratory rats under the influence of negative air ions using various behavioral models. To create an excess of negative air ions, a Hippocrates ionizer (Enterprise Energia, Naberezhnye Chelny, Russia) was used. The exposure was carried out daily for 2 hours for 18-20 days. Wistar rats were used in the work. It was found that according to the open field test, under the influence of negative air ions, the level of indicators reflecting vertical and horizontal motor activity increased; decreased grooming rates and the number of bowel movements; the frequency of examination of holes increased. According to the elevated plus maze test, the number of visits to open and closed arms, hanging from open arms significantly increased with a simultaneous decrease in the frequency and duration of grooming, a decrease in the duration and number of freezes. The index of anxiety in the studies changed insignificantly. On the model of a black-and-white chamber, the time spent by rats in the dark and light compartments varied. The rats of the experimental group spent more time in the open space of the test, there was a significant increase in the exits and the duration of the time of looking out from the dark into the light compartments. In general, according to the behavioral models used, keeping animals in an environment enriched with air ions led to significant changes in the behavior of animals, increasing activity, emotional reactivity and stress resistance.

Incorporating 3D image analysis and response surface method to evaluate the effects of moisture damage on reinforced asphalt mixtures using glass and polypropylene fibers

• Incorporation of up to a certain amount of combined fibers can beneficially enhance load bearing capacity and reduce the proportion of broken aggregate. • Fibers can increase the total fracture energy (particularly post-peak G f ) and consequently reduce the fragility index by obstructing crack propagation. • Integration of fibers can improve mixtures' moisture susceptibility and reduce the negative effects of moisture damage. • The destructive impact of an increase in temperature is more dominant compared to the number of freeze and thaw cycles. • The combination of the response surface method and image analysis techniques exhibited a great capability to detect and quantify adhesion and cohesion failures. This paper evaluates the performance of fiber-reinforced mixtures subjected to moisture damage. Response Surface Method was used to design an experimental matrix based on the central composite design. The amounts of fibers, number of freeze and thaw cycles, and testing temperatures were considered as factors, while maximum load, stiffness, indirect tensile strength, CT index , fragility index, broken aggregate, and adhesion failure were regarded as the responses. Indirect tensile strength test and 3D image analysis were conducted to characterize mixtures’ fracture properties and moisture susceptibility, respectively. The results show that temperature exhibits the highest influence on mixtures’ mechanical properties as well as adhesion and cohesion failures. An increase in the number of freeze and thaw cycles deteriorated the mixtures’ performance. Although higher beneficial impacts of glass fiber were reported earlier, this study proved that the performance of the mixtures prepared with combined fibers is comparable with the previous study. This finding brings forth the advantage in cost reduction of reinforced mixtures production due to the replacement of part of the glass fiber with polypropylene fiber. In addition, it was found that a combination of utilized fibers up to approximately 0.2% by weight of aggregates exhibited beneficial impacts on load bearing capacity, indirect tensile strength, and proportion of broken aggregate while exceeding this amount was not favorable which was correlated to the jeopardizing of cohesion level between mixtures constituents. Moreover, it was observed that fibers slightly reduced the fragility index by obstructing crack propagation. It was finally concluded that a higher amount of fibers enhanced mixtures' moisture resistance and diminish the negative effects of freeze and thaw cycles.

Numerical Study on Mechanical Properties of the Freezing–Thawing Cycle of Tailings Based on Particle Discrete Element Method

To study the effects of the number of freezing–thawing cycles (F-T cycles), the dry density, and the average particle diameter on the mechanical properties of tailings, the calibration laws of the fine-scale parameters in the discrete particle element numerical simulation software PFC2D(Particle Flow Code) were first tested, and then pre-experiments were conducted in the form of orthogonal tests. Finally, according to the results of the pre-experiments and the analysis of the pre-experimental results by SPSS (Statistical Product Service Solutions) software, uniaxial tests were carried out for different numbers of freeze–thaw cycles, different dry densities, and different average particle sizes. The tailings specimens were subjected to uniaxial compression simulations. The results showed that (1) the uniaxial compressive strength of the tailings specimens decreased with each freeze–thaw cycle, and stabilized after seven freeze–thaw cycles. (2) With a greater number of freeze–thaw actions, the porosity of the tailings increased after freeze–thawing. The peak of porosity was much higher than that of the models with fewer than seven freeze–thaw actions. (3) The contact number of tailings specimens showed a significant decrease after the number of freeze–thaw cycles reached seven. However, the amount of exposure was not the main factor affecting the strength of tailings (4). As the number of freeze–thaws increased, the tailings model was more prone to stress concentration. Previously, PFC software has been applied to tailings simulation studies, and this study verifies the feasibility of this method. This research is able to offer a reference for studying the mechanical property changes of tailings in the cold highland area.

Ameliorating Effects of Soil Aggregate Promoter on the Physicochemical Properties of Solonetzes in the Songnen Plain of Northeast China

Freeze–thaw cycles cause serious soil erosion, which makes the prevention, control and management of solonetzic lands in the Songnen Plain challenging. The use of soil-aggregate-promoter (SAP) is highly favoured because of its energy-saving and efficient characteristics; however, SAP is rarely used in the improvement of solonetzic soil in cold regions. To fill this gap, we studied the effects of different experimental conditions on the physicochemical properties of solonetzes; the investigated conditions included the number of laboratory-based freeze–thaw cycles (with 0, 1, 3, and 5 cycles), initial moisture content (0%, 18%, 24%, and 30%) and SAP application amount (0 g/m2, 0.75 g/m2, 1.125 g/m2, and 1.5 g/m2). The results showed the following: (1) The soil pH value decreased significantly as the SAP application rate increased, and the effect of the initial moisture content and number of freeze–thaw cycles on soil pH was not significant. (2) SAP effectively reduced the soil electrical conductivity (EC), but a certain threshold was apparent, and the factors studied had significant effects on EC. (3) SAP effectively optimised the soil macroaggregates content and inhibited the damage posed by freeze–thaw cycles to the soil structure. These results provide an important theoretical basis for the effective prevention and control of solonetzes in the Songnen Plain of Northeast China.

The Effects of Particle Gradation on Salinized Soil in Arid and Cold Regions

Particle size grading impacts salt-frost heaving and dissolution collapse events of salinized soil on northwestern China’s arid and cold region highways. However, the influencing mechanisms remain unclear and the impact of varying particle size grading needs further investigation. Hence, this study focused on these effects and the number of freeze–thaw cycles on the characteristic changes in highway salinized soil in arid and cold regions. Three soil columns with different gradations were prepared to explore the gradation and the number of freeze–thaw cycle affects on salinized soil’s salt-frost heaving and dissolution collapse characteristics. The multi-functional physical simulation platform conducted multiple freeze–thaw cyclic tests in the laboratory. Test results confirmed significant and conclusive effects of gradation and the number of freeze–thaw cycles on salinized soil’s salt-frost heaving and dissolution collapse behaviors. Poorly graded salinized soil with high coarse particle content caused repeated freeze and thaw engineering hazards, significantly affecting salinized soil’s displacement and deformation behaviors during freezing. Contrarily, an increased range of fine particles more easily involved the characteristics of salinized soil during thawing. Therefore, the fourth freeze–thaw cycle was a crucial time node. After four freeze–thaw cycles, the displacement and deformation of original salinized soil and B-grade salinized soil samples (poorly graded with high fine particle content) tended to be stable. In contrast, the displacement and deformation of A-grade salinized soil samples (poorly graded with high coarse particle content) increased the growth rate. The present research results contribute to in-depth knowledge of the effects of gradation and freeze–thaw cycles on the characteristics of salinized soil in northwestern China, providing excellent referenced data support for the prevention and control of highway salinized soil failures and other engineering projects in arid and cold regions of northwest China.

Freeze–thaw and thermal cycle durability of pervious concrete with different aggregate sizes and water–cement ratios

ABSTRACT Use of pervious concrete (PC) for permeable pavements can help avoid urban waterlogging and urban heat islands. However, PC typically has low strength and poor durability owing to its special porous structure. The purpose of this study was to understand the influence of aggregate size and water–cement ratio (w/c) on PC under different environmental conditions (freeze–thaw and thermal cycles). The experiment designed a PC made with five aggregate sizes (3–5 mm, 5–7 mm, 7–9 mm, 9–11 mm, 11–13 mm) and five w/c values (0.21, 0.25, 0.29, 0.33, 0.37). The mass loss, compressive strength and life of all mixtures were tested under freeze–thaw and thermal cycles. Results indicated that aggregate size and w/c were identified as important factors determining the properties of PC and were evaluated using survival analysis to determine the optimal mixture. As the number of freeze–thaw cycles increased, mass loss and risk of damage increased while compressive strength decreased. As the number of thermal cycles increased, mass loss increased and compressive strength first increased and then decreased. After thermal cycling, high w/c had better frost resistance, contrary to the results for direct freezing–thawing.

An adaptive prediction method for mechanical properties deterioration of sandstone under freeze\u2013thaw cycles: a case study of Yungang Grottoes

Due to the location of the Yungang Grottoes, freeze–thaw cycles contribute significantly to the degradation of the mechanical properties of the sandstone. The factors influencing the freeze–thaw cycle are classified into two categories: external environmental conditions and the inherent properties of the rock itself. Since the parameters of rock properties are inherent to each rock, the effect of rock properties on freeze–thaw degradation cannot be investigated by the control variates method. An adaptive multi-output gradient boosting decision trees (AMGBDT) algorithm is proposed to fit nonlinear relationships between mechanical properties and physical factors. The hyperparameters in the GBDT algorithm are set as variables, and the Sequential quadratic programming (SQP) algorithm is applied to solve the hyperparameter optimization, which means finding the maximum Score. The case study illustrates that the AMGBDT algorithm can precisely determine the effect of each independent factor on the output. The patterns of mechanical properties are similar when the number of freeze–thaw cycles and porosity are used as variables separately and when both are used simultaneously. The uniaxial compressive strength decay rate is positively correlated with the number of freeze–thaw cycles and porosity. The modulus of elasticity is negatively correlated with the number of freeze–thaw cycles and porosity. The results show that the number of freeze–thaw cycles is the main factor influencing the freeze–thaw cycling action, and the porosity is minor. In addition, the fitting accuracy of the AMGBDT algorithm is generally higher than neural networks (NN) and random forests (RF). Studying the influence of porosity and other rock properties on the freeze–thaw cycle will help to understand the failure mechanism of rock freeze–thaw cycles.

Durability assessment of soft clay soil stabilized with halloysite nanotubes

In this study the compressive strength and durability of soft clay soil stabilized with halloysite nanotubes are investigated. Halloysite nanotubes are novel 1D natural nanomaterials which are widely used in reinforcing polymer, pollution remediation, and as nanoreactors for biocatalyst. The wide use of halloysite nanotubes is due to their high aspect ratio, appropriate mechanical strength, high thermal stability, nature-friendly and cost-effectiveness. However, the use of halloysite nanotubes as a stabilizing agent for improving the durability of soil is not clear. In this research, halloysite nanotubes was used in the amounts of 2%, 5% and 10% by the weight of dried soil. Unconfined compressive strength, wet/dry cycles and freeze/thaw cycles tests were performed to evaluate the strength and durability of stabilized soft clay soil. Experimental results showed that halloysite nanotubes considerably improves the compressive strength and durability of soft clay soil. The optimum amount of halloysite nanotubes for soil stabilizing in terms of compressive strength and durability was 5%. The compressive strength of soft clay increased as much as 129% by applying 5% halloysite nanotubes. Also, the specimen containing 5% halloysite nanotubes showed the least strength loss after wet/dry and freeze/thaw cycles. The soil sample containing 5% halloysite nanotubes lost 20% of its initial compressive strength after 8 cycles of freezing and thawing, while the soil sample without any halloysite content lost 100% of its compressive strength after the same number of freezing and thawing. Based on the obtained results, the use of halloysite nanotubes in order to enhance the strength and durability of soft clay is strongly recommended.

Effect of freeze\u2013thaw cycle on physical and mechanical properties and damage characteristics of sandstone

Rock deterioration under freeze–thaw cycles is a concern for in-service tunnel in cold regions. Previous studies focused on the change of rock mechanical properties under unidirectional stress, but the natural rock mass is under three dimensional stresses. This paper investigates influences of the number of freeze–thaw cycle on sandstone under low confining pressure. Twelve sandstone samples were tested subjected to triaxial compression. Additionally, the damage characteristics of sandstone internal microstructure were obtained by using acoustic emission (AE) and mercury intrusion porosimetry. Results indicated that the mechanical properties of sandstone were significantly reduced by freeze–thaw effect. Sandstone’ peak strength and elastic modulus were 7.28–37.96% and 6.38–40.87% less than for the control, respectively. The proportion of super-large pore and large pore in sandstone increased by 19.53–81.19%. We attributed the reduced sandstone’ mechanical properties to the degenerated sandstone microstructure, which, in turn, was associated with increased sandstone macropores. The macroscopic failure pattern of sandstone changed from splitting failure to shear failure with an increasing of freeze–thaw cycles. Moreover, the activity of AE signal increased at each stage, and the cumulative ringing count also showed upward trend with the increase of freeze–thaw number.

Behavioral analysis of anxiolytic action of phenazepam in conditions of an acute psychogenic stress (predator presentation) in Danio rerio

We studied the effect of benzodiazepine anxiolytic phenazepam after the predator presentation to Danio rerio. The test of novelty was used: the fish was placed first in a beaker with a dissolved pharmacological substance (or H2O) and then into a novel tank for 6 min, where the trajectory, the path length, the number of movements to the upper part of the novel tank, the number and time of the pattern of freezing were measured. It is shown that, in response to the novelty of tank, the fish are reacted by submerging to the bottom, increasing the frizing, and reducing the number of movements to the upper half of the novel tank. After phenazepam administration, the fish were not only in the lower, but also in the upper part of the novel tank. The average path length did not change significantly in the range of doses used. The number and time of the frizing, as well as the time spent in the lower part of the novel tank, decreased more than 2 times compared to the control group of animals and showed a dose-dependent effect. The number of movements to the upper part of the novel tank for the experiment increased significantly from 1 in the control to 57 after phenazepam in a dose of 1 mg/l. At the same time, the number of movements of fish to the upper part of the novel tank significantly increased more than 2 times from 3th min of the experiment with the use of phenazepam in a dose of 1 mg/l. Predator presentation (Hypsophrys nicaraguensis) caused an increase in the number of freezing (temporary immobilization) and a decrease in the length of the trajectory of movement in the novel tank as compared with the Danio rerio control group. Phenazapam at a dose of 1 mg/l removed the effects of a predator, while exhibiting a typical effect: the number of movements to the upper part of the tank during the experiment significantly increased to 30; the time at the bottom of the tank was halved. It was concluded that the novelty stress test and the test with a predator are highly sensitive for studying anxiety-phobic reactions in Danio rerio.

Strategies for cryopreservation of testicular cells and tissues in cancer and genetic diseases.

Cryopreservation of testicular cells and tissues is useful for the preservation and restoration of fertility in pre-pubertal males expecting gonadotoxic treatment for cancer and genetic diseases causing impaired spermatogenesis. A number of freezing and vitrification protocols have thus been tried and variable results have been reported in terms of cell viability spermatogenesis progression and the production of fertile spermatozoa. A few studies have also reported the production of live offspring from cryopreserved testicular stem cells and tissues in rodents but their replication in large animals and human have been lacking. Advancement in in vitro spermatogenesis system has improved the possibility of producing fertile spermatozoa from the cryopreserved testis and has reduced the dependency on transplantation. This review provides an update on various cryopreservation strategies for fertility preservation in males expecting gonadotoxic treatment. It also discusses various methods of assessing and ameliorating cryoinjuries. Newer developments on in vitro spermatogenesis and testicular tissue engineering for in vitro sperm production from cryopreserved SSCs and testicular tissue are also discussed.

Experiment on the Effect of Freezing–Thawing Cyclic on Mechanical Properties of Solidified Sludge

The solidification technology of sludge can effectively solve the problem of environmental pollution and resource shortage. Whereas, the current study lacks the exploration of the durability of solidified sludge. The freeze–thaw cycle test and the moisture transfer test were carried out to test the freeze–thaw resistance and the failure mechanism of the solidified sludge. The results showed that the content of fly ash has a significant effect on the freeze–thaw cycle of the mechanical properties of the solidified sludge. The stress–strain relationship of different dosage samples tends to approach the number of freeze–thaw cycles increases. The stress–strain curve of the samples under all confining pressures is strain-hardening type, which failure mode is ductile failure. The incorporation of fly ash can improve the failure strength and cohesion of cement–lime solidified soil, and gradually increase with the increase of fly ash content. The freeze–thaw cycle test is carried out under the closed system. The moisture in the sample migrates under the temperature load, causing the water content to increase and decrease the partition distribution. The sample with lower fly ash content has smaller static pressure density, which is beneficial to water migration. And increasing the range of water increase zone, the effect of the sample on the freeze–thaw cycle is relatively small. However, the influence of the number of freeze–thaw cycles on the internal friction angle of each soil sample depends largely on the distribution of water in the soil sample, it does not appear regular changes. During the freezing and thawing process, the effects of fly ash content and water redistribution on the mechanical properties of the solidified sludge are simultaneous. In short, the samples with different ratios and freeze–thaw cycles have different factors influencing the change of strength.

Investigation of Changes in Quality Indicators of Agro-Industry Products During

Quality control is an integral part of production process and sales and one of the main means conformity of the products in line with established requirements.Meat products belong to the category of the most valuable food products. Freezing is a low-temperature preservation method. It provides the development of microbiological processes and a sharp reduction in the rate of enzymatic and physical-chemical reactions sacrificing the quality of the product.There are some methods for evaluating the quality of meat products. One of the promising methods of complex research in this area is the impedance method. An important property of biological tissues is the dependence of their conductivity and relative permittivity on the current frequency. There is a dependence of frequency on electrical resistance dependency in the same way.Its electrical characteristics also undergo changes, given that the cellular structure of meat changes during freezing. These changes are caused by the cell membranes destruction. As a result, the conditions for the passage of electrons and ions inside the meat change.Impedancometry offers a wide range of possibilities for determining the meat freshness, the storage conditions correctness, compliance with technological modes of processing meat raw materials, in particular, the number of freezes that meat raw materials have undergone.The bioimpedance meter will allow you to set the standard indicators typical for each type of meat, exceeding which would serve as evidence of the unsuitability of meat as a food.

Effect of environmental factors on performance of jointed concrete pavements

This study investigated the distress conditions of test sections of concrete pavement that have been used for more than the design life of 20 years. The study was performed using data from a highway pavement management system. To determine the effects of distress and environmental factors, weather data were analysed for the test sections. Regression models were developed for five types of distress: longitudinal cracks, asphalt patching, concrete patching, durability cracks and longitudinal spalling. The influence of environmental factors was analysed, such as the days with temperature below zero, number of freeze and thaw cycles, average relative humidity and the amount of de-icing salt consumed. Using these models, the amount of distress was predicted and compared with the actual amount of distress. The predicted amount of distress was similar to the actual amount of distress, indicating that the models were properly developed. Using the results of this study, the distress of aging concrete pavement could be reduced by managing the environmental factors more appropriately.

DYNAMICS OF HEAVY VIBRATING MACHINES TAKING INTO ACCOUNT INSTABILITY IN TIME OF THEIR PARAMETERS

Underground mining of uranium ores consists of several technological processes, one of the most important of which is the release of broken rock from the working excavation zone and loading it into transportation vehicles. The issue of increasing the intensity of production requires a simultaneous increase in the productivity of all production processes, including the production of mineral raw materials. At the same time, it is necessary to create both a high-performance and a safe process. This problem is successfully solved by the use of vibration machines with elastic links made of elastomeric materials, which, along with an increase in productivity, can reduce energy consumption and the number of freezes. An integrated approach was used, which includes analytical studies and results of industrial tests of vibratory feeders for underground mining and delivery of uranium ores and building materials. On the basis of the developed algorithm and synergistic model of fatigue microfracture of rubber links in vibratory feeder, mathematical equations were obtained, which made it possible to describe dynamics of feeders with time-depending parameters; when solving the integro-differential equation of the oscillatory system, the dependence of the amplitude characteristics of the feeder on the time of its operation is obtained. An original algorithm and synergistic model were developed, and on their basis, a mathematical apparatus was created, which allowed determining change of amplitude of vibratory feeder oscillations during its operation. On the basis of analytical calculations, a method was developed and introduced for predicting changes of parameters change of oscillation amplitudes of vibratory feeder used for underground mining and feeding of uranium ores.

Validation and assessment of preanalytical factors of a fluorometric in vitro assay for glucocerebrosidase activity in human cerebrospinal fluid

Lysosomal dysfunction is an emerging feature in the pathology of Parkinson’s disease and Dementia with Lewy bodies. Mutations in the GBA gene, encoding the enzyme Glucocerebrosidase (GCase), have been identified as a genetic risk factor for these synucleinopathies. As a result, there has been a growing interest in the involvement of GCase in these diseases. This GCase activity assay is based on the catalytic hydrolysis of 4-methylumbelliferyl β-d-glucopyranoside that releases the highly fluorescent 4-methylumbelliferyl (4-MU). The final assay protocol was tested for the following parameters: Lower limit of quantification (LLOQ), precision, parallelism, linearity, spike recovery, number of freeze–thaw events, and sample handling stability. The GCase activity assay is within acceptable criteria for parallelism, precision and spike recovery. The LLOQ of this assay corresponds to an enzymatic activity of generating 0.26 pmol 4-MU/min/ml. The enzymatic activity was stable when samples were processed and frozen at − 80 °C within 4 h after the lumbar puncture procedure. Repetitive freeze–thaw events significantly decreased enzyme activity. We present the validation of an optimized in vitro GCase activity assay, based on commercially available components, to quantify its enzymatic activity in human cerebrospinal fluid and the assessment of preanalytical factors.

Factors affecting stability of plasma brain-derived neurotrophic factor

Circulating concentrations of brain-derived neurotrophic factor (BDNF) have been linked to cancer, neuropsychiatric, diabetes, and gynecological disorders. However, factors influencing plasma storage and subsequent BDNF quantification are incompletely understood. Therefore, the anticoagulant used in plasma separator tubes, storage-time, storage-temperature, and repeated freeze–thaw cycles on circulating BDNF concentrations was evaluated. Peripheral blood samples were collected from healthy women (n = 14) and men (n = 10) recruited prospectively from McMaster University (August 2014). Blood was collected from the cubital vein into plasma separator tubes containing five different anticoagulant systems [K2EDTA, Li-Hep, Li-Hep (gel), Na-Hep, Na-Hep (glass)], and placed on ice for transport to the lab for centrifugation. Plasma samples (n = 16) collected in K2EDTA tubes from women recruited to a previous study (April 2011 to December 2012) were used to determine the effect of multiple freeze–thaw cycles. Plasma BDNF was quantified using a commercially available ELISA kit. Plasma concentrations of BDNF were significantly affected by the type of plasma separator tube, storage-time, and number of freeze–thaw cycles. Storage temperature (− 20 vs. − 80 °C) did not significantly affect the quantity of BDNF measured as mean BDNF concentrations generally fell within our calculated acceptable change limit up to 6 months in the freezer. Our results suggest that for quantification of circulating BDNF blood collected in K2EDTA tubes and plasma stored up to 6 months at either − 20 or − 80 °C produces reproducible results that fall within an acceptable range. However, plasma samples stored beyond 6 months and repeated freeze–thaw cycles should be avoided.