Optimal Design of Ferronickel Slag Alkali-Activated Material for High Thermal Load Applications Developed by Design of Experiment

The development of an optimal low-calcium alkali-activated binder for high-temperature stability based on ferronickel slag, silica fume, potassium hydroxide, and potassium silicate was investigated based on Mixture Design of Experiment (Mixture DOE). Mass loss, shrinkage/expansion, and compressive and flexural strengths before and after exposure to a high thermal load (900 °C for two hours) were selected as performance markers. Chemical activator minimization was considered in the selection of the optimal mix to reduce CO₂ emissions. Unheated 42-day compressive strength was found to be as high as 99.6 MPa whereas the 42-day residual compressive strength after exposure to the high temperature reached 35 MPa (results pertaining to different mixes). Similarly, the maximum unheated 42-day flexural strength achieved was 8.8 MPa, and the maximum residual flexural strength after extreme temperature exposure was 2.5 MPa. The binder showed comparable properties to other alkali-activated ones already studied and a superior thermal performance when compared to Ordinary Portland Cement. A quantitative X-ray diffraction analysis was performed on selected hardened mixes, and fayalite was found to be an important component in the optimal formulation. A life-cycle analysis was performed to study the CO₂ savings, which corresponded to 55% for economic allocation.     

The Influence of Multiple Mechanical Recycling of Particleboards on Their Selected Mechanical and Physical Properties

This is a bridge between circular economy issues and wood-based panels technology, especially particleboards. Because these composites contain a significant amount of non-wood raw material (10–12% thermoset resin, high hardness laminates, among others), their mechanical recycling leads to an uncontrollable reduction in produced particle size. This problem can be especially significant since the particleboards can be intended for multiple recycling due to the shortening of their service life. This research aimed to produce particles in the cycle of multiple re-milling particleboards and evaluate the selected properties of the produced particles and particleboards. Thus, the response to the following scientific problem can be given: what factors qualitatively and quantitatively influence the properties of the particleboards produced by multi-re-milled particles? The novelty of this research is the approach to recycling the raw materials from particleboards in fully controlled conditions, providing the characterization of produced particles and producing particleboards with close-to-industrial parameters, and, finally, evaluating the features of produced particleboards in the light of raw materials used. The results confirmed that subsequent mechanical recycling of particleboards, where the other panels are made entirely of second-milling particles, leads to an unprofitable and unacceptable reduction in the mechanical properties of the panels. The physical parameters, such as thickness swelling and water absorption, are improved, but this can be the result of increased content of chemical ingredients, which negatively influence the hygienic features of panels (emission of formaldehyde and total volatile organic compounds—TVOC). Further research should be directed towards estimating the optimal addition of mechanically recycled particles to particleboard production.     

Comparative Life Cycle Assessment of Asphalt Mixtures Using Composite Admixtures of Lignin and Glass Fibers

Lignin and glass fiber were used as additives to improve the quality of road pavements and minimize moisture damage and cracking at low temperatures on asphalt pavement, according to a previous laboratory study. The aim of this paper is to make a significant contribution to the environmental assessment of the construction of road pavements using four types of asphalt mixtures based on the life cycle assessment (LCA) methodology according to the requirements of ISO 14040, considering the impact of raw material extraction, asphalt mixture manufacturing, transportation, and wearing surface construction. The results of the environmental assessment showed that all studied asphalt mixtures do not offer any improvement in all impact categories, and three modified asphalt mixtures have a slight negative effect in all impact categories. The composite mixture has the highest negative effect of the studied three modified asphalt mixtures in all categories except in the marine aquatic ecotoxicity potential category and freshwater aquatic ecotoxicity potential category, where the lignin modified asphalt mixture has the highest negative effect in these two categories but has the best environmental impacts on most of other impact categories. Furthermore, the negative effect caused by composite asphalt mixtures is minimal and thus can be used to improve the overall performance of asphalt pavement.     

Applying Flax FRP in an Innovative Closed-Shape Stirrup for Concrete Beams

Under the background of climate change, the steel industry is considered one of the least eco-friendly industries. Flax fiber-reinforced polymer (FFRP) is an emerging sustainable alternative to steel reinforcement bar; however, its application is much restricted due to its interior material properties. This paper proposed a novel way to form closed-shape stirrups with FFRP, which is suitable for replacing steel stirrups. A multi-disciplinary investigation was conducted concerning the structural and environmental performance of FFRP stirrups in reinforced concrete (RC) beams. Seven specimens were tested under a three-point bending load. The FFRP stirrups substantially increased the shear capacity and ultimate vertical displacement by 77% and 74%, respectively, and shifted brittle failure to ductile failure. The closed-shape stirrups avoided the stress concentration and increased the utilization of FFRP tensile capacity to over 80%. Decreasing the spacing of FFRP stirrups effectively increased the shear capacity and ductility; increasing the width or layer of FFRP stirrups improved ductility only. A life cycle assessment (LCA) was later performed to evaluate and compare the environmental performance of steel, FFRP, and carbon FRP stirrups. As compared to carbon FRP and steel ones, FFRP stirrups substantially decreased the global warming and fossil depletion potential by over 60%. The main contributors to the environmental impacts of FFRP stirrups were the heavy metal released into the water and terrestrial environment during the cultivation process.     

Cement-Matrix Composites Using CFRP Waste: A Circular Economy Perspective Using Industrial Symbiosis

This study aims to provide a mitigation strategy for reducing the economic and environmental impacts of carbon fiber wastes deriving from automotive industry. Recycling and reuse in the construction industry is proposed, according to an industrial symbiosis within a circular economy perspective. Specifically, the process consists of repurposing carbon fiber reinforced polymer (CFRP) scraps/waste into new cement-matrix composites, for which the resulting benefits, in terms of mechanical and environmental performance, are herein described. An experimental campaign, starting with a specific heat treatment of CFRP sheets and an accurate dimensional distribution analysis of the short carbon fibers, is presented. The influence of the fiber content and length on both the workability and the mechanical performance of cement-based carbon fiber reinforced mortars is also evaluated. A reduced amount of either sand or cement (up to 8% and 12.8% in volume, respectively) is also considered in the mix design of the fiber reinforced mortars and derives from the substitution of the sand or binder with an equivalent volume of CFRP fibers. The results show a satisfactory increase in compressive and flexural strength in the range 10–18% for the samples characterized by a volume fraction of fibers of approximately 4% and having a 2–5 mm length. Finally, a life cycle assessment (LCA, 14040/14044) was carried out to quantify the environmental burden reductions associated with the implementation of the proposed symbiotic scheme.     

Performance Evaluation and Structure Optimization of Low-Emission Mixed Epoxy Asphalt Pavement

Epoxy asphalt concrete (EAC) has excellent properties such as high strength, outstanding thermal stability, and great fatigue resistance, and is considered to be a long-life pavement material. Meanwhile, the low initial viscosity of the epoxy components provides the possibility to reduce the mixing temperature of SBS-modified asphalt. The purpose of this study is to verify the feasibility of low-emission mixing of SBS-modified epoxy asphalt and to compare the mechanical responses in several typical structures with EAC, in order to perform structure optimization for practical applications of EAC. In this paper, the Brookfield rotational viscosity test was conducted to investigate the feasibility of mixing SBS-modified epoxy asphalt at a reduced temperature. Subsequently, the dynamic modulus tests were carried out on EAC to obtain the Prony series in order to provide viscoelastic parameters for the finite element model. Six feasible pavement structures with EAC were proposed, and a finite element method (FEM) model was developed to analyze and compare the mechanical responses with the conventional pavement structure. Additionally, the design life was predicted and compared to comprehensively evaluate the performance of EAC structures. Finally, life cycle assessment (LCA) on carbon emissions was developed to explore the emission reduction effect of the epoxy asphalt pavement. The results indicate that the addition of epoxy components could reduce the mixing temperature of SBS-modified asphalt by 30 °C. The proper use of EAC can significantly improve the mechanical condition of the pavement and improve its performance and service life. It is recommended to choose S5 (with EAC applied in the middle-lower layer) as the optimal pavement structure, whose allowable load repetitions to limit fatigue cracking were more than 1.7 times that of conventional pavements and it has favorable rutting resistance as well. The LCA results show that in a 25-year life cycle, the carbon emissions of epoxy asphalt pavements could be reduced by 29.8% in comparison to conventional pavements.     

Spark Plasma Sintering As a Solid-State Recycling Technique: The Case of Aluminum Alloy Scrap Consolidation

Recently, “meltless” recycling techniques have been presented for the light metals category, targeting both energy and material savings by bypassing the final recycling step of remelting. In this context, the use of spark plasma sintering (SPS) is proposed in this paper as a novel solid-state recycling technique. The objective is two-fold: (I) to prove the technical feasibility of this approach; and (II) to characterize the recycled samples. Aluminum (Al) alloy scrap was selected to demonstrate the SPS effectiveness in producing fully-dense samples. For this purpose, Al alloy scrap in the form of machining chips was cold pre-compacted and sintered bellow the solidus temperature at 490 °C, under elevated pressure of 200 MPa. The dynamic scrap compaction, combined with electric current-based joule heating, achieved partial fracture of the stable surface oxides, desorption of the entrapped gases and activated the metallic surfaces, resulting in efficient solid-state chip welding eliminating residual porosity. The microhardness, the texture, the mechanical properties, the microstructure and the density of the recycled specimens have been investigated. An X-ray computed tomography (CT) analysis confirmed the density measurements, revealing a void-less bulk material with homogeneously distributed intermetallic compounds and oxides. The oxide content of the chips incorporated within the recycled material slightly increases its elastic properties. Finally, a thermal distribution simulation of the process in different segments illustrates the improved energy efficiency of this approach.     

Analysis of Mechanical Properties Related to Fiber Length of Closed-Loop-Recycled Offcuts of a Thermoplastic Fiber Composites (Organo Sheets)

Increasing demand for energy-efficient means of transport has steadily intensified the trend towards lightweight components. Thermoplastic glass fiber composites (organo sheets) play a major role in the production of functional automotive components. Organo sheets are cut, shaped and functionalized by injection molding to produce hybrid components, such as those used in car door modules. The cutting process produces a considerable amount of production waste, which has thus far been thermally recycled. This study develops a closed mechanical recycling process and analyzes the different steps of the process. The offcuts were shredded using two shredding methods and implemented directly in the injection-molding process. Using tensile tests and impact bending tests, the material properties of the recycled materials were compared with the virgin material. In addition, fiber length degradation via the injection-molding process and the influence of the waterjet-cutting process on the mechanical properties are investigated. Recycled offcuts are both comparable to new material in terms of mechanical properties and usability, and are also economically and ecologically advantageous. Recycling polypropylene waste with glass fiber reinforcement in a closed loop is an effective way to reduce industrial waste in a sustainable and economical production process.     

脑卒中生存质量量表中译本信度和效度及敏感度的初步研究

目的　引进并修订了Williams等编制的脑卒中生存质量量表 (SS QOL) ,并在我国脑卒中人群中进行信度、效度和敏感度的初步研究。方法　信度检验用加权kappa系数和Cronbach’sα系数来评价。采用人为推理判断方法评价内容效度 ;以Rankin量表分级作为外在效标来评估辨别效度 ;采用聚类分析方法考核量表的结构效度 ;通过相关分析考察量表的效标效度。各领域敏感度通过标准化效应大小 (SES)来评估 91例患者。结果　 3个月时实际随访评定 80例。SS QOL中译本各领域的重测信度和评定者间信度的kappa系数均在 0 .82～ 1.0 0之间 ;内容一致信度的Cronbach’sα系数在 0 .76以上 ,显示了良好的信度。以Rankin量表为外在效标的分组中 ,得分具有显著差异 ,具有良好的辨别效度。通过聚类分析将 12个领域聚为 6类。除“社会角色 (0 .10 )”和“视力 (0 .17)”领域外 ,SS QOL中译本各领域均显示了与对应的“准金标准”呈适度的相关性 (相关系数 0 .30～ 0 .84 ,P <0 .0 0 1)。大多数领域显示了理想的敏感度。结论　SS QOL中译本在轻、中度脑卒中患者中具有良好的信度、效度及敏感度 ,可用于脑卒中结局测量。     

Effects of Recycled Rubber Particles Incorporated as Partial Sand Replacement on Fresh and Hardened Properties of Cement-Based Concrete: Mechanical,Microstructural and Life Cycle Analyses

Cement is one of the most valuable materials in today’s society, as it is used in most construction developments known to mankind. However, the energy intensive process and significant environmental impacts related to the production of Ordinary Portland Cement have shown the importance of searching for more sustainable materials. Concrete uses different aggregates added to the cement binder to lower, not only cost, but other factors like environmental burden, while maintaining good mechanical properties. This study analyzes the properties of fresh and hardened concrete incorporating recycled rubber to replace fine aggregate. Locally sourced 2 mm diameter rubber was incorporated in a regular strength concrete matrix into three different replacement levels, i.e., 3%, 5%, and 10%. Compression, tensile, flexural, and modulus of elasticity of hardened concrete were carried out in specimens aged 7, 14, and 28 days. In addition, non-destructive ultrasonic pulse velocity and rebound number tests were only performed on specimens aged 28 days. Once the tests were carried out, the fresh and hardened concrete properties were obtained. Similarly, the compressive and flexural strengths had the exact relationship between the values obtained. On the other hand, the modulus of elasticity tends to decrease due to the presence of the rubber. Consequently, it is recommended not to develop mix designs with more than 5% rubber because it is not meaningfully affected. The fine aggregate can be partially replaced by the rubber, keeping almost the same performance compared with sand-only counterparts. In addition, the life cycle assessment showed a reduction of up to 40% in the global warming potential. In fact, the 15% recycled rubber concrete mix has a climate change indicator of approximately 245 kg of CO₂ eq.     

Critical Influence of the Processing Route on the Mechanical Properties of Zirconia Composites with Graphene Nanoplatelets

Graphene-based nanostructures, used as potential reinforcement in ceramic composites, have a great tendency to agglomerate. This requires the use of homogenization techniques during the powder processing, posing the need to evaluate how these techniques affect the microstructure and the mechanical properties of the resulting composites. The influence of the processing route on the properties of 3YTZP (3 mol % yttria tetragonal zirconia polycrystals) ceramic composites with 10 vol % cost-effective GNP (graphene nanoplatelets) has been addressed. Four different powder processing routines combining ultrasonic powder agitation (UA) and planetary ball milling (PBM) in wet and dry media have been used and all the composites were densified by spark plasma sintering (SPS). The mechanical properties at room temperature in the macroscale have been assessed by Vickers indentations, four-point bending tests and the impulse-echo technique, while instrumented indentation was used to measure the hardness and Young’s modulus at the nanoscale. The application of dry-PBM enhances greatly the mechanical and electrical isotropy of the composites, slightly increases the hardness and lowers the elastic modulus, independently of the application of UA. The combination of UA and dry-PBM enhances the flexure strength by 50%, which is desirable for structural applications.     

The Influence of Incinerated Sewage Sludge as an Aggregate on the Selected Properties of Cement Mortars

In line with the trend of using waste raw materials in the technology of building materials, experimental studies of cement mortars containing various amounts of fine-grained waste aggregate were carried out. The waste aggregate was based on an incinerated municipal sewage sludge which was mechanically crushed to an appropriate grading. Chemical and physical properties of the waste aggregate are presented. Mortars with varying amounts of waste aggregate as a replacement for natural sand were prepared. Study determines compressive strength and flexural strength up to 56 days. Properties such as capillary action, air content and thermal conductivity were determined. The results of the tests has shown that the incinerated waste sludge can be used as a partial or total replacement for natural aggregate. In mortars with waste aggregate, a favorable relation between flexural and compressive strengths was observed, which translates into increased strength of the interfacial transition zone. A significant increase in water absorption was observed for mortars containing high amounts of waste aggregate, which is directly related to its porous structure. Conducted studied prove that the aggregate obtained from incineration of the municipal sewage sludge can a feasible alternative for natural aggregates in production of masonry and rendering mortars for construction purposes.     

Influence of Different Alloying Strategies on the Mechanical Behavior of Tool Steel Produced by Laser-Powder Bed Fusion

Additive manufacturing is a high-potential technique that allows the production of components with almost no limitation in complexity. However, one of the main factors that still limits the laser-based additive manufacturing is a lack of processable alloys such as carbon martensitic hardenable tool steels, which are rarely investigated due to their susceptibility to cold cracking. Therefore, this study aimed to expand the variety of steels for laser powder bed fusion (L-PBF) by investigating an alternative alloying strategy for hot work tool steel powder. In this study, a comprehensive investigation was performed on the powder and L-PBF processed specimen properties and their correlation with the existing defects. Cubical specimens were created using the following two alloying strategies by means of L-PBF: conventional pre-alloyed gas-atomized powder and a mixture of gas-atomized powder with mechanically crushed pure elements and ferroalloys. The influence of the particle parameters such as morphology were correlated to the defect density and resulting quasi-static mechanical properties. Micromechanical behavior and damage evolution of the processed specimens were investigated using in situ computed tomography. It was shown that the properties of the L-PBF processed specimens obtained from the powder mixture performs equal or better compared to the specimens produced from conventional powder.     

Deviations of the SLM Produced Lattice Structures and Their Influence on Mechanical Properties

Selective laser melting (SLM) is an additive manufacturing technology suitable for producing cellular lattice structures using fine metal powder and a laser beam. However, the shape and dimensional deviations occur on the thin struts during manufacturing, influencing the mechanical properties of the structure. There are attempts in the literature to describe the actual shape of the struts’ geometry, however, on a smaller data sample only, and there is a lack of a universal FEA material model applicable to a wider range of lattice structure diameters. To describe the actual dimensions of the struts, a set of lattice structures, with diameters ranging from 0.6 to 3.0 mm, were manufactured using SLM. These samples were digitized using micro-computed tomography (μCT) and fully analyzed for shape and dimensions. The results show large deviations in diameters of inscribed and circumscribed cylinders, indicating an elliptical shape of the struts. With increasing lattice structure diameter, the deviations decreased. In terms of the effect of the shape and dimensions on the mechanical properties, the Gaussian cylinder was found to describe struts in the diameter range of 1.5 to 3.0 mm sufficiently well. For smaller diameters, it is appropriate to represent the actual cross-section by an ellipse. The use of substitute ellipses, in combination with the compression test results, has resulted in FEA material model that can be used for the 0.6 to 3.0 mm struts’ diameter range. The model has fixed Young’s and tangential modules for these diameters and is controlled only by the yield strength parameter (YST).     

The Comparative Assessment of Effects on the Power System and Environment of Selected Electric Transport Means in Poland

Currently, electric vehicles are a rapidly growing alternative to those with combustion engines and can contribute to reduction of CO₂ emissions in the transport sector, especially when the energy to power electric motors is predominantly derived from renewable sources. Until now, the comparison of environmental impact and influence of electric transport means on the power systems was not fully addressed in the case of Poland. The purpose of the study is to describe, analyse and assess electric vehicles (EV) operation against performance indicators in Poland, especially the influence of electric transport means (ETM) (electric cars, trams, trolley buses and buses) on power system and environment. The influence on the power system was investigated for the Polish National Powers system using the simulation of different scenarios of loads generated by EV charging. The energy demand of the National Power System and daily load variability indices were determined. Based on the data of ETM powers consumption and emissions of energy production, the emissions of harmful gases per one km and per one person were calculated, as well as the financial outlays for energy necessary to drive 1 km per 1 passenger. To assess and compare the environmental impact of the selected ETM life cycle, the life cycle assessment method was used. The results of environmental impacts were determined for selected assessment methods: CML 2 and IPCC 2013 GWP 100. The functional unit in this study is one selected ETM with a service life of 100,000 km. Comparison of trams, trolley buses, buses and electric passenger cars indicates that most beneficial are electric buses which do not need rails or overhead lines, thus investment costs are lower.     

Influence of Sequential CAD/CAM Milling on the Fitting Accuracy of Titanium Three-Unit Fixed Dental Prostheses

This study investigated the fitting accuracy of titanium alloy fixed dental prostheses (FDP) after sequential CAD/CAM (Computer Aided Design/Computer Aided Manufacturing) fabrication. A three-unit FDP model connecting mandibular second premolars and molars was prepared and scanned to fabricate titanium FDPs by CAD/CAM milling. A total of six FDPs were sequentially milled in one titanium alloy disk using a new set of burs every time (n = 4). The fitting accuracy of FDPs was mesiodistally evaluated by a silicone replica technique and the measurement was triplicated at four different locations: MO (marginal opening), MG (marginal gap), AG (axial gap), and OG (occlusal gap). Data were statistically analyzed using ANOVA and Tukey’s HSD test. The fitting accuracy of PMMA (polymethyl methacrylate) FDPs milled using the worn or new bur were evaluated by the same procedure (n = 6). The mean dimensions of titanium FDP for all measuring positions, except for AG, were significantly increased from the third milling. However, no difference was noted between the first FDP and the second FDP milled with the same set of burs. Severe edge chippings were observed in all milling burs. Detrimental effects of the worn burs on the fitting accuracy were demonstrated in the CAD/CAM-milled PMMA FDP. The results recommend proper changing frequency of cutting burs to achieve the quality of fit and predictable outcomes for dental CAD/CAM prostheses.     

Analysis of the Aggregate Production Process with Different Geometric Properties in the Light Fraction Separator

This article presents an analysis of separation results in a specially designed and activated light fraction separator used to remove impurities from mineral aggregates. Laboratory tests conducted on a quarter-technical scale involved performing experiments to ascertain the scope for adjusting the variable settings of the separator operating parameters. These include the frequency and amplitude of pulsation, the height of the heavy-product reception threshold, the size of water flow and variations in the grain size and shape of the feed. During the experiments, the degrees of chalcedonite and dolomite grain purification were studied within the range of grain size for the feed: (2.0–4.0 mm for small grains, 8.0–16.0 for coarse grains and 2.0–16.0 mm for a wide range of grain sizes). The effects of the separator were assessed based on the amount of organic impurities in each heavy product. In all experiments, very good results were obtained, because the percentage of impurities in the product after separation was below 1% in accordance with the assumed technological standard assumption. Regarding the obtained content of light impurities with the separator set to optimal operating parameters, the percentage of light impurities in the product content was reduced to below 0.1%, which meets the guidelines described according to applicable standards. Multi-variant analysis allowed the optimal operating ranges of the separator to be determined, producing refined aggregate in terms of grain size and shape. The final results were also linked to the performance of the device, and its model dependencies were also determined.     

Assessment of the Life Cycle of a Wind and Photovoltaic Power Plant in the Context of Sustainable Development of Energy Systems

The conversion of kinetic energy from wind and solar radiation into electricity during the operation of wind and photovoltaic power plants causes practically no emissions of chemical compounds that are harmful to the environment. However, the production of their materials and components, as well as their post-use management after the end of their operation, is highly consumptive of energy and materials. For this reason, this article aims to assess the life cycle of a wind and photovoltaic power plant in the context of the sustainable development of energy systems. The objects of the research were two actual technical facilities—a 2 MW wind power plant and a 2 MW photovoltaic power plant, both located in Poland. The analysis of their life cycle was carried out on the basis of the LCA (life-cycle assessment) method, using the ReCiPe 2016 calculation procedure. The impact of the examined renewable energy systems was assessed under 22 impact categories and 3 areas of influence (i.e., human health, ecosystems, and resources), and an analysis was conducted for the results obtained as part of three compartments (i.e., air, water, and soil). The life cycle of the wind power plant was distinguished by a higher total potential negative environmental impact compared to the life cycle of the photovoltaic power plant. The highest levels of potential harmful impacts on the environment in both life cycles were recorded for areas of influence associated with negative impacts on human health. Emissions to the atmosphere accounted for over 90% of all emissions in the lifetimes of both the wind and the photovoltaic power plants. On the basis of the obtained results, guidelines were proposed for pro-ecological changes in the life cycle of materials and elements of the considered technical facilities for renewable energy sources, aimed at better implementation of the main assumptions of contemporary sustainable development (especially in the field of environmental protection).     

Influence of Strain Route Changes on the Microstructure and Mechanical Properties of CuZn36 Alloy during Cross Channel Extrusion CCE

This study evaluates the impact of changing the deformation routes of the extrusion process in a cross-shaped die (CCE) on the structure and properties of a CuZn36 alloy (% at.). Samples with dimensions of Ø8 × 36 mm were subjected to extrusion at room temperature according to two variants: straight extrusion in the A route (2-, 4-, 8- and 12-pass) and extrusion with interoperative rotation by 90° in the B_C route (2- and 4-pass). The improvement of strength properties was obtained as a result of grain fragmentation in the CCE process. Changes in the microstructure were observed using a light microscope, and mechanical properties were measured in the microhardness test and a static tensile test. The obtained results showed that the mechanical properties of the alloy depend on the number of passes and the material deformation route. This observation was related to the fragmentation of its structure and strengthening, which resulted in changes in its properties. The highest strength was characterized by the material pressed four times with the rotation of 90° (B_C route), whose properties were comparable and even slightly better than the material squeezed twelve times without rotation (A route).     

The Influence of Various Irradiances of Artificial Light, Twilight, and Moonlight on the Suppression of Pineal Melatonin Content in the Syrian Hamster

The purpose of the present studies using artificial light was to determine how the timing and duration of exposure influence the light-induced suppression of pineal melatonin levels in hamsters. An 8-min exposure to 0.186 microW/cm2 of cool white fluorescent light caused a continued depression of pineal melatonin even when animals were returned to darkness. In addition, the pineal gland does not appear to change its sensitivity to light throughout the night. A 20-min exposure to 0.019 microW/cm2 of cool white fluorescent light did not significantly suppress pineal melatonin during any time of the melatonin peak, whereas a 20-min exposure to 0.186 microW/cm2 was capable of always suppressing melatonin. Furthermore, increasing the duration of 0.019-microW/cm2 exposure to 30, 60, 120, or 180 min does not increase the capacity of this irradiance to depress melatonin. Similar to artifical light, natural light has a variable capacity for suppressing nocturnal levels of pineal melatonin. Twilight irradiances of 0.138 microW/cm2 or less did not suppress nocturnal melatonin whereas twilight irradiances of 3.0 microW/cm2 or greater did suppress pineal melatonin. A few animals did have lower melatonin after a 40-min exposure to full moonlight during July (0.045 microW/cm2) or January (0.240 microW/cm2). However, pineal melatonin levels remained high in the majority of animals exposed to full moonlight.