A type III porous-thermo-elastic problem with quasi-static microvoids

Meccanica - In this work we study, from the numerical point of view, a one-dimensional thermoelastic problem where the thermal law is of type III. Quasi-static microvoids are also assumed within...     

Dinuclear Cobalt(III) Complexes Showing a Co2O2 Metallacycle

The heptadentate Schiff base H₃L reacts with cobalt(II) acetate in methanol to form the discrete dinuclear complex Co₂L(OAc)₂(OMe)(H₂O)₂ ( 1 ·2H₂O). The reaction of 1 ·2H₂O with NMe₄OH·5H₂O in methanol gives rise to displacement of the acetate by methanolate groups, yielding Co₂L(OMe)₃(H₂O) ( 2 ·1H₂O). Recrystallizations of the Schiff base, 1 ·2H₂O and 2 ·H₂O in different solvents, produce single crystals of H₃L, 1 ·2.5H₂O and 2 ·2MeOH, respectively. The crystal structures of 1 ·2.5H₂O and 2 ·2MeOH show the cobalt atoms double bridged by and endogenous phenol oxygen atom and an exogenous methanolate oxygen donor, giving rise to Co₂O₂ cores with Co···Co distances of ca. 2.87 Å.     

The effect of octyl glucoside on the lamellar phase of diluted C12E4 and alcohol systems

A systematic study on phase behavior of the mixture of nonionic surfactants with alcohols at 30.0+/-0.1 degrees C was carried out. The total surfactant concentration was kept to 0.1 M varying the mole ratio of n-octyl beta-d-glucopyranoside (OG) and tetraethylene glycol monododecyl ether. Two uniphasic regions were found, the lamellar phase at low OG mole fraction and micelles at high OG mole fraction. The presence of OG favors the lamellae-micelle transition. Alkanols and benzyl alcohol were used as cosurfactants. The more hydrophobic alcohols (octanol and decanol) increase the OG content in the mixed bilayers. On the contrary, benzyl alcohol is not as favorable to the OG incorporation in the lamellar phase as in the mixed micelles. The L(3) phase has only been found as a uniphasic region with hexanol.     

Reactivity of 2-acylaminoacrylates with ketene diethyl acetal; [2 + 2] cycloadditions vs. tandem condensations

The reactivity of 2-acylaminoacrylates with ketene diethyl acetal can be modulated by means of thermal conditions to yield cyclobutanes for the preparation of protected beta-hydroxycyclobutane-alpha-amino acids, or catalytic conditions that yield cyclohexanes by tandem condensations to obtain interesting building blocks that are alternatives to Danishefsky's diene.     

Insights into the absorption of carbon dioxide by zinc substrates: isolation and reactivity of di- and tetranuclear zinc complexes

The heptadentate Schiff base H(3)L can react with zinc acetate to form the discrete dinuclear complex Zn(2)L(OAc)(H(2)O), 1.H(2)O. The reaction of 1.H(2)O with NMe(4)OH.5H(2)O both in air and under an argon stream has been investigated. On one hand, this reaction in air yields the tetranuclear complex (Zn(2)L)(2)(CO(3))(H(2)O)(6), 2.5H(2)O, by spontaneous absorption of adventitious carbon dioxide. This process can be reverted in an acetic acid medium, whereas the treatment of 2.5H(2)O with methanoic acid yields crystals of [Zn(2)L(HCOO)].0.5MeCN.1.25MeOH.2H(2)O, 3.0.5MeCN.1.25MeOH.2H(2)O. On the other hand, the interaction under an argon atmosphere of 1.H(2)O with NMe(4)OH.5H(2)O in methanol allows the isolation of the dinuclear complex Zn(2)L(OMe)(H(2)O)(4), 4.4H(2)O. Recrystallisations of 1.H(2)O, 2.5H(2)O and 4.4H(2)O, in different solvents, yielded single crystals of 1.MeCN.2.5H(2)O, 2.4MeOH and 4.3MeOH.H(2)O, respectively. The crystal structure of 2.4MeOH can be understood as resulting from an unusual asymmetric tetranuclear self-assembly from two dinuclear units, and shows three different geometries around the four zinc atoms.     

Families,experiments, and nature: Learning science through project-based learning

This study brings together the research focused on science education through project-based learning (PBL). This learning project was carried out in a rural learning community and an attempt was made to adapt to the natural resources of the area by organizing educational outings, experimental activities, and encouraging the participation of families. The overall objective is to test the effectiveness of applying the PBL teaching methodology for learning science in a rural learning community. The methodology used has been qualitative, specifically, the participating research has been used and the information has been compiled in a field notebook. The results show that the didactic proposal had good results; showing that, in conclusion, science teaching today should be inclined toward more innovative educational methodologies such as PBL.     

Ultrasound-assisted extraction of antimony and cobalt from inorganic environmental samples using a cup-horn sonoreactor prior to their determination by electrothermal-atomic absorption spectrometry

A simple, fast and reliable method is described for the quantitative extraction of Sb and Co from inorganic environmental matrices containing variable amounts of silicates prior to their determination by electrothermal-atomic absorption spectrometry. The method is based on the ultrasound-assisted extraction of both elements using the mixture 20% v/v HF + 20% v/v HNO₃ as extractant. The extraction procedure was carried out in closed Eppendorf vials immersed in a cup-horn sonoreactor for 20?min. Once extraction has been accomplished, the supernatant liquid is separated from the solid phase and subsequently transferred into the autosampler of the instrument. A two-level full factorial design (2⁴) was applied for screening optimisation of the variables influencing the ultrasonic extraction. These variables were: sonication time; amplitude of the ultrasound energy; nitric and hydrofluoric acid concentrations. MLDs were 0.20 and 0.06?µg?·?g^?1 for Sb and Co, respectively. Between-batch precision values, expressed as relative standard deviations (n?=?3), were less than 5.5 and 9.6% for Sb and Co, respectively. The method was evaluated using a wide variety of inorganic certified reference materials, such as SRM 2702 (Marine Sediment), SRM 2782 (Industrial Sludge), BCR 176R (Fly Ash), SRM 1633b (Coal Fly Ash) SRM 2710 (Montana Soil) and SRM 2711 (Montana Soil).