Influence of culture medium composition on the micropropagation of Thymus tauricus Klokov et Des.-Shost.

Thymus tauricus Klokov et Des.-Shost. is a perennial dwarf shrub of the Lamiaceae family. This plant has anti-inflammatory, antispasmodic, analgesic and antiseptic properties. The use of biotechnological methods makes it possible to increase the efficiency of traditional methods of breeding and seed production. Our investigation aimed to study the influence of the culture medium composition on the explants morphogenesis at 1-2th stages of Thymus tauricus clonal micropropagation. When comparing three cytokinins, the best explants development was revealed on culture media containing kinetin. Both high vitrification rate of microshoots (31.2-90.2%) and formation of small shoots were observed on media supplemented with BAP or TDZ. The most effective culture medium at the introduction stage is MS with 1.0 mg/l kinetin and 1.0 mg/l GA3 or 1.0 mg/l kinetin. On this medium, on average, 8.4-10.1 microshoots per explant and shoots length of 1.9 cm were obtained. It was found that the optimal culture medium at the actually propagation stage is MS with 1.0 mg/l Kin or 1.0 mg/l kinetin and 0.5 mg/l IAA, on which the multiplication index 26.9-28.5 were obtained. Induction of rhizogenesis with a frequency of 30.2-94.4% and a root length of 1.6-3.0 cm was noted on culture media for the second stage of clonal micropropagation. The results of the studies are the basis for development T. tauricus clonal micropropagation method.

The Corrosion Propagation Stage of Stainless-Steel Reinforced Concrete: A Review

Stainless steel (SS) reinforcement is increasingly used to control corrosion of reinforced concrete in aggressive marine and deicing salt service. It is well established that the chloride threshold of SS is greater than that of plain steel (PS) rebar, yielding substantially increased duration of the corrosion initiation stage. Much less known, however, is if there is a similar benefit to the duration of the corrosion propagation stage (tp). Thus, credit for increased tp in durability forecasts for SS use tends to be conservatively limited. To reduce that uncertainty the literature was gleaned for the few instances where SS reinforcement had reached, and preferably completed, the corrosion propagation stage. Particular attention was given to actual structural service experience, outdoor tests, and realistic laboratory conditions. Only a single case of actual service in a structure was found for which tp could be estimated, albeit indirectly. The result suggests a tp of several decades for the case of austenitic Cr-Ni rebar in marine service. Outdoor tests without unnatural acceleration showed a few cases where tp was reached, but only for straight Cr ferritic alloys which showed some limited improvement over tp for PS. With the additional insight from laboratory tests, it was concluded that SS rebar made with high pitting resistant grades, and thoroughly descaled, had a positive outlook for propagation stage durations that substantially exceed those of PS rebar. Quantification of that improvement is much in need of further field and laboratory assessment.

In vitro propagation of the genus Echinacea Moench representatives

The regenerative capacity of Echinacea hybrid cultivar Mama Mia and the selected somaclonal variegated variant at the propagation and rooting stages was compared. The influence of the 6-BAP concentration in the MS culture medium on the microrosette formation at the propagation stage was studied. The highest morphogenetic potential of the selected form in comparison with the cultivar Mama Mia was found. It was shown that ½ MS culture medium supplemented with 0.3 mg/L IAA was the optimal medium for effective development of the root system of the genus Echinacea representatives at the rooting stage.

The investigation of low-cycle fatigue crack propagation of 16 Mn eccentric bar based on the acoustic emission technique

Compared to the traditional cropping technology, low-cycle fatigue cropping can reduce load and improve cross-section quality. Geometric factors of V-shaped notch and processing parameters (such as load amplitude and load frequency) influence the cropping efficiency and section quality. By changing the factors, the sufficient efficiency of cropping and quality of cross-section get together. However, the influences of material defects, geometric parameters, loading frequency and other factors are different in each stage of the whole cropping process. If the effects of the parameters on the each stage of cropping process are clear, the higher productivity and the better cross-section quality will be obtained by applying suitable parameter on each stage of cropping process. To investigate the effects of eccentric ratio on each stage of low –cycle fatigue cropping process, a suitable monitoring method is needed. This study proposes acoustic emission (AE) technique to detect the low-cycle fatigue cropping process of 16 Mn eccentric bar (The bar prefabricated eccentric notches. The prefabricated notch improve the efficiency of cropping). The parameters of signals such as counts and kurtosis during the low–cycle fatigue process are obtained. According to the counts changes over time, the process of the 16 Mn metal bar cropping can be divided into three stages: the crack initiation stage, the crack propagation stage, and the fracture stage. Based on the cumulative counts, the eccentric ratio’s influence on the time of each cropping process stage is obtained. The time of the crack initiation stage and the final fracture stage doesn’t increase with the eccentric ratio. The time of the propagation stage influenced by the eccentric ratio greatly. Besides, the eccentric ratio’s influence on the cross-section quality is studied by using an advanced optical microscope system. The cross-section quality was influenced by the eccentric ratio significantly. The results of the paper indicate the acoustic emission (AE) monitoring technique is a useful method to detect the process of low-cycle fatigue cropping. Especially, it provide effective information to investigate the effects of the notch eccentric ratio during the low-cycle fatigue cropping process. The eccentric ratio’s effects on each stage of low-cycle fatigue cropping process offer guidance to improve low-stress fatigue cropping efficiency and cross-section quality.

Investigation of Non-fully Similar Laws of Damage to an Arch Dam in Shaking Table Model Tests

In order to overcome the defect that the general shaking table test can’t clarify the scale relationship between the prototype structure and the scale model in the damaged area based on the fully similar laws, we derived a method that can analyze the relationship between the prototype structure and the scale model in the damaged area based on non-fully similar lows and verified it. We selected the appropriate material (the emulation concrete material, ECM), which has a good scale relationship with the prototype material in the elastic stage, the crack appearance stage, and crack propagation stage (damage stage). We proposed some similar ratios to reveal the similar relationship between the prototype structure and the scale model in the elastic stage, the crack appearance stage, and the crack propagation stage. Especially, we proposed two similar ratios: cr and hr (deduced by the fracture toughness similarity requirements and the fracture energy similarity requirements, respectively) which can well reflect the similar relationship between the prototype structure and the scale model in the damaged area. In order to verify these ratios, we compared the results of the prototype structure numerical simulation with those of the shaking table test of the scale model. The results show that hr has higher accuracy for predicting the relationship between the prototype structure and the scale model in the damaged area.

Peculiarities of in vitro propagation of gooseberry varieties

The article presents the results of the study on the morphogenesis peculiarities of Ribes uva-crispa L. varieties at all stages of in vitro cultivation and adaptation to ex vitro conditions. The optimal method of sterilization at the initiation stage to in vitro culture was established: consistent application of 2 % «Fundazole» solution with an exposure of 10-15 minutes, 70 % ethanol for 30 seconds and 7 % calcium hypochlorite for 5-7 minutes. The maximum number of viable gooseberry regenerants was obtained in the selection of initial explants during the beginning of active shoots growth (April – early May). The regeneration frequency was 70-80 %, depending on the variety. The optimal size of explants, the mineral and carbohydrate composition of the culture medium, and the cultivation conditions at the propagation stage were determined. The highest multiplication rate was characterized by varieties: Grushenka (6.1-6.7), Beryl (3.1-4.9) and Chernomor (3.5-4.5). It has been established that Quorin and Lepoivre culture medium was the most eff ective medium for the cultivation of the studied gooseberry varieties. As a source of carbohydrates, the use of sucrose at a concentration of 30 g/L was optimal. It was found eff ective to cultivate gooseberries for 20-25 days at a reduced temperature (16-18 °C) at the propagation stage. The efficiency of using 1.0 mg/l IBA at the rooting stage was revealed. The use of sphagnum as part of the soil substrate at the adaptation of gooseberry regenerants contributed to a high survival rate (97-100 %) in all substrate variants. The study of the infl uence of the composition of the soil substrate on the growth dynamics of regenerants showed that the adaptation of gooseberries was eff ectively carried out on a substrate consisting of peat and sphagnum.

The cover thickness design of concrete structures subjected to chloride ingress from RBDO solution technique

Diffusion is the principal transport mechanism of chloride ions into concrete pores. The chlorides trigger the reinforcements’ depassivation when its concentration at the concrete/reinforcement interface reaches the threshold level. Thus, the depassivation defines the initiation stage end and the propagation stage start. The structural safety reduces widely during the propagation stage because of the various deleterious mechanisms triggered by reinforcement’s corrosion. Therefore, the engineers should accurately predict and prevent the propagation stage start. The literature describes several models for evaluating the end of the initiation stage. However, few of them applies the Boundary Element Method (BEM) for this purpose, despite its known accuracy. Besides, enormous randomness affect the phenomenon. Thus, it is adequately handled solely in the probabilistic context. Optimisation techniques may be coupled in the problem modelling to propose adequate cover thickness values accounting for probabilities of failure. This study presents a Reliability-Based Design Optimisation (RBDO) approach for designing accurately the cover thickness of concrete structures subjected to chloride ingress. The BEM handles the diffusion modelling whereas the Monte Carlo simulation assesses the probabilities of failure. The RBDO is formulated in the context of Weighted Average Simulation Method (WASM), which requires only one assessment of the reliability analysis. It leads to a reliable and computationally efficient solution technique. The problem formulation and the implemented solution scheme are described herein. Moreover, one application is presented, in which the design results are interpreted properly.

Clonal micropropagation of Thymus vulgaris L.

Thymus vulgaris L. is one of the widely known spicy aromatic and medicinal plants. Thyme plant material is widely used in medicine, cooking and perfumery. To increase the efficiency of breeding and seed production, it is necessary to develop biotechnological techniques, in particular, clonal micropropagation. The aim of the research is to optimize the composition of culture media for the main stages of propagation in vitro and to select adaptation ex vitro conditions for the development of Thymus vulgaris. clonal micropropagation. The article presents the results of studies of explant morphometric parameters cultivated on 20 variants of culture media at firstsecond stages of micropropagation. It was found that the optimal culture medium at the introduction stage is MS medium with 1.0 mg/l Kin and 1.0 mg/l GA3, on which, on average, 2.2 microshoots per explant with a length of 1.9 cm were obtained. Both high vitrification rate of microshoots and formation of small shoots (0.6-0.9 cm) were observed on media supplemented with BAP or TDZ. The most effective culture medium at the proper propagation stage is MS with 1.0 mg/l Kin, on which 4.6 shoots per explant and the multiplication index 12.8 were obtained. It is advisable to root microshoots at the 3rd stage of micropropagation on MS culture medium supplemented with 1.0 mg/l IBA or 1.0 mg/l IAA. It has been shown that it is possible to obtain high plant survival rate (89.5%) during adaptation ex vitro, using a substrate consisting of peat and perlite (1:1).