To understand the thermodynamic behaviors of the borate-containing system, the solid–liquid equilibrium data (solubilities, density, and refractive index) of quinary aqueous solution composed of lithium, potassium, rubidium, magnesium, and borate at 323.15 K were determined by using the isothermal dissolution method. The crystalloid forms of the solid phase were confirmed by the X-ray diffraction method. Results show that four single salts Li2B4O7·3H2O, K2B4O7·4H2O, RbB5O8·4H2O, and MgB4O7·9H2O were formed at 323.15 K in the quinary invariant point, with no double salt or solid solution found. Under the condition of Li2B4O7 saturation, the crystallization region of MgB4O7·9H2O occupied the largest crystallization region, and the salt K2B4O7·4H2O had the smallest region. Among the four salts, the crystalline regions of the salts MgB4O7·9H2O and RbB5O8·4H2O changed obviously at 323.15 and 348.15 K, that of MgB4O7·9H2O enlarged at 323.15 K, and those of RbB5O8·4H2O and K2B4O7·4H2O decreased.
We use variation of test scores measuring closely related skills to isolate peer effects. The intuition for our identification strategy is that the difference in closely related scores eliminates factors common to the performance in either test while retaining idiosyncratic test specific variation. Common factors include unobserved teacher and group effects as well as test invariant ability and factors relevant for peer group formation. Peer effects work through idiosyncratic shocks which have the interpretation of individual and test specific ability or effort. We use education production functions as well as restrictions on the information content of unobserved test taking ability to formalize our approach. An important implication of our identifying assumptions is that we do not need to rely on randomized group assignment. We show that our model restrictions are sufficient for the formulation of linear and quadratic moment conditions that identify the peer effects parameter of interest. We use Project STAR data to empirically measure peer effects in kindergarten through third grade classes. We find evidence of highly significant peer effects with magnitudes that are at the lower end of the range of estimates found in the literature.
The phase equilibrium and physicochemical properties(density,conductivity and pH value)of the ternary system NaVO_3—Na_3PO_4—H_2O were studied at 298 K by the isothermal dissolution method.According to the determined data,the phase diagram and composition-proerties-composition diagram were plotted.The isothermal solubility diagram of the ternary system consists of two univariant curves,one invariant point B,and two crystallization regions for salt Na_3 PO4·8H_2O and NaVO_3,respectively.No double salt or solid solution is formed.Physicochemical properties(density,conductivity and pH value)regularly change with the composition of solution.
This paper presents the experimental data of metastable phase equilibrium of Li~+/Cl~-,CO_3~(2-),B_4O_7~(2-)-H_2O quaternary system at 298 K for Zhabuye salt lake in Tibet,from which the metastable phase diagram and physicochechemical properties(density,pH value,conductivity and refractive index) vs composition diagram is drawn.This quaternary system is a simple evtonic type,no double saltor solid solution is formed.The isotherm diagram consists of one invariant point,three univariant curves and three crystallization fields corresponding to Li_2B_4O_7·3H_2O,Li_2CO_3 and LiCl·H_2O salt.
The stable-phase equilibria of the aqueous quaternary system K+, Rb+, Cs+//SO42––H2O was investigated at T = 323.2 K using the isothermal dissolution equilibrium method. The solubility, density, and refractive index of equilibrium solutions were determined using the chemical/instrument analysis method, the specific gravity bottle method, and the WYA Abbe refractometer, respectively. The solid phases were identified by using X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results reveal that besides three single salts (K2SO4, Rb2SO4, and Cs2SO4), three complete solid solutions are formed in this system at 323.2 K, namely, [(Kx, Rb1–x)2SO4], [(Kx, Cs1–x)2SO4], and [(Rbx, Cs1–x)2SO4], increasing the difficulty of separation potassium from the solution composed of rubidium, cesium, and sulfate. The stable-phase diagram of the quaternary system K+, Rb+, Cs+//SO42––H2O at T = 323.2 K consists of four invariant points, nine univariant curves, and six crystallization regions. The sequence of the size of the salt crystal region is [(Kx, Rb1–x)2SO4] > [(Kx, Cs1–x)2SO4] > K2SO4 > [(Rbx, Cs1–x)2SO4] > Rb2SO4 > Cs2SO4. The phase diagrams at different temperatures (T = 298.2 K and T = 323.2 K) show that temperature is an important factor affecting salt crystallization, especially for the solid solution. As the temperature increases, the crystallization region of [(Kx, Cs1–x)2SO4] conspicuously decreases, whereas the crystallization regions of [(Kx, Rb1–x)2SO4] and [(Rbx, Cs1–x)2SO4] increase slightly.
With the plant terpenoids were discovered and applied in Human life, the researches on terpenoid biosynthesis were paid more attentions. Terpene synthases catalyse the biosynthesis of monoterpenes, sesquiterpenes and diterpenes with the GPP, FPP and GGPP as substrates, respectively. This paper summarized the present study situation in the catalyze mechanism, clone strategy and terpene bio-engineering of plant terpene synthase.
The phase equilibria of ternary systems Li2SO4 + Na2SO4 + H2O and Na2SO4 + K2SO4 + H2O at 303.2 K were investigated by using the isothermal dissolution method. The solubility, density, and refractive index of the systems were measured. There are two ternary invariant points and three crystallization regions corresponding to Li2SO4·3Na2SO4·12H2O, Li2SO4·H2O, and Na2SO4·10H2O in the system Li2SO4 + Na2SO4 + H2O at 303.2 K. There are two ternary invariant points and three crystallization regions corresponding to Na2SO4·10H2O, Na2SO4·3K2SO4, and K2SO4 in the system Na2SO4 + K2SO4 + H2O at 303.2 K. By comparing the phase diagrams of the ternary system Li2SO4 + Na2SO4 + H2O at different temperatures, one can find that the existence form of double salt changes from Li2SO4·3Na2SO4·12H2O to Li2SO4·Na2SO4. By comparing the phase diagrams of the ternary system Na2SO4 + K2SO4 + H2O at different temperatures, the double salt Na2SO4·3K2SO4 was not found at 273.2 K, while it was formed at 303.2 and 313.2 K. Meanwhile, the thermodynamic data of these two systems at 303.2 K were fitted by the Pitzer–Simonson–Clegg model, and the calculated values agree well with the experimental values.
In this study, a targeted analytical method was developed for measuring multiple mono/di-chloropropanols containing 3-chloro-1,2-propanediol(3-MCPD), 2-chloro-1,3-propanediol(2-MCPD), 1,3-dichloro-2-propanol(1,3-DCP), and 2,3-dichloro-1-propanol(2,3-DCP) in food contact papers. This method was demonstrated as an accurate and sensitive technique for detecting multiple chlopropanols with satisfactory recoveries (95.4%-109%), and the limits of detection (LOD) and quantification (LOQ) were achieved at 2 μg kg -1 , and 6 μg kg -1 , respectively. A total of 126 food contact papers collected in China were investigated for their occurrence and potential health risk. The results indicated chloropropanols were widely detected in water extract of food contact papers, while 50.0% samples were non-compliant with the regulatory limits. Both highest detection frequency and concentration of chloropropanols were observed in kitchen papers where mean concentration of 3-MCPD and 1,3-DCP in water extract was 201.9 μg L -1 , and 12.5 μg L -1 , respectively. 3-MPCD and 1,3-MPCD were found to be the predominant chloropropanols with mean concentration of 49.2 μg L -1 and 6.1 μg L -1 in water extract, respectively, while the concentration of 2-MCPD and 2,3-DCP were relatively low. 3-MPCD was significantly responsible for high concentration of chloropropanols at level above 40 μg kg -1 . The estimated daily intake for typical exposure consumer (Mean) and high-exposure consumer (P75, P95) to 3-MCPD are greater than 10% of tolerable daily intake(TDI) establlised by European Food Safety Authority (EFSA), suggesting the release of 3-MCPD from food contact papers pose a potential health risk to certain groups of consumers.
'/%3e%3cuse xlink:href='%23a' transform='rotate(23.036 .093 25.536)'/%3e%3cuse xlink:href='%23a' transform='rotate(45.87 1.273 16.18)'/%3e%3cuse xlink:href='%23a' transform='rotate(69.945 .996 12.078)'/%3e%3cuse xlink:href='%23a' transform='rotate(20.66 -19.689 31.932)'/%3e%3c/svg%3e)