Physiological and Biochemical Parameters of Common Duckweed Lemna minor after the Exposure to Tetracycline and the Recovery from This Stress

In this study, the ability of Lemna minor L. to recover to normal growth, after being degraded in a tetracycline-containing medium, was extensively investigated. The plants were exposed to tetracycline (TC) at concentrations of 1, 2.5, and 10 mM. Subsequently, their physiological status was analysed against the following criteria: rate of plant growth; free radical accumulation; antioxidant enzyme activity; chlorophyll content; HSP70 protein content; cell membrane permeability, and mitochondrial activity. The study showed that duckweed can considerably recover from the damage caused by antibiotics, within a week of cessation of stress. Of the plant properties analysed, mitochondrial activity was the most sensitive to antibiotic-induced disturbances. After transferring the plants to a tetracycline-free medium, all plant parameters improved significantly, except for the mitochondrial activity in the plants grown on the medium containing the highest dose of tetracycline. In the plants treated with this antibiotic at the concentration of 10 mM, the proportion of dead mitochondria increased and was as high as 93% after one week from the beginning of the recovery phase, even after the transfer to the tetracycline-free medium.     

A new access to 2-phosphonothiophenes

2-Phosphonothiophenes are prepared via the reaction of β-chloroacroleins with diethyl mercaptomethylphosphonate.     

Magnesium tetraorganyl derivatives of group 13 metals as intermediate products in the synthesis of group 13 metal alkyls and aryls

Reactions of organomagnesium halides with group 13 metal halides lead to the formation of R₃M type compounds (R = alkyl, aryl; M = Al, Ga, In) and are considered as the simplest methods of R₃M compound syntheses. These seemingly simple reactions reveal a much more complex chemistry involving mixed magnesium-group 13 metal compounds. To elucidate the reaction course of reactions of organomagnesium halides with group 13 metal halides, we have studied reactions of R₃M with organomagnesium halides. The interaction of Et₃M with R¹MgX led to the formation of following products being mixtures of crystalline ionic complexes with the general composition of [Et_4-nR¹_nM]⁻[XMg (thf)₅]⁺·(thf): [Et_2.2Al(CH=CH₂)_1.8]⁻[BrMg (thf)₅]⁺·(thf) ( 1 ), [Et₃Ga(CH=CH₂)]⁻[BrMg (thf)₅]⁺·(thf) ( 2 ), [Et₄Al]⁻[BrMg (thf)₅]⁺·(thf) ( 3 ), [Et₄Ga]⁻[BrMg (thf)₅]⁺·(thf) ( 4 ), [Et_2.9Al(C₆H₅)_1.1]⁻[BrMg (thf)₅]⁺·(thf) ( 5 ), [Et_2.9Ga(C₆H₅)_1.1]⁻[BrMg (thf)₅]⁺·(thf) ( 6 ), [Et_3.4GaMe_0.6]⁻[IMg (thf)₅]⁺·(thf) ( 7 ) and [Et₄In]⁻[BrMg (thf)₅]⁺·(thf) ( 8 ). A comparison of the production course of group 13 metal trialkyls R₃M with a thermal decomposition of 1–8 products showed that reactions of MX₃ with RMgX (X = Br, I; R = alkyl, aryl) yield initially intermediate ionic compounds, which must then be thermally decomposed to obtain pure R₃M compounds. If group 13 metal bromides and iodides, and alkyl (aryl)magnesium bromides and iodides in thf are used, only intermediate products with the [R₄M]⁻[XMg (thf)₅]⁺·(thf) structure are formed.     

Temperature distributions in a periodically stratified layer with slant lamination

The paper deals with the two-dimensional stationary temperature distribution in a composite layer. The nonhomogenous body is assumed to be composed of periodically repeated two-layered laminae. The layering is inclined with an arbitrary angle to the boundary planes. The lower and upper boundary planes are assumed to be kept at given temperatures. The considered problem is solved within the framework of the homogenized model with microlocal parameters, where the continuity thermal conditions on interfaces are satisfied.     

On the rate allocation problem under co-existence of uncertain utility function parameters and uncertain link capacities

The allocation problem is considered for a computer communication network with network links being shared among multiple transmissions running at the same time. Typically, each transmission brings benefit to a network owner proportional to the transmission rate allowed. Since the link capacities are limited and the minimal rates defined by Quality of Service (QoS) requirements have to be preserved, the rate allocation problem is defined here as a problem of maximizing the overall benefit (utility) under capacity and QoS constraints. In this paper, we consider the uncertain version of the problem, in which unknown utility function parameters and unknown link capacities are treated as uncertain variables characterized by certainty distributions. We present a method for solving the problem in a unified way, with both uncertainties combined in a single certainty index.