Micromechanical modelling and simulation of chopped random fiber reinforced polymer composites with progressive debonding damage

The aim of the present paper is to provide a quantitative prediction of the elastic-damage behaviour of randomly oriented fiber polymer composites. A constitutive model based on micromechanical considerations is presented. The nucleation and growth of voids induced by progressive fiber debonding is combined with the constitutive relationship. Failure resulting of excessive damage accumulation is captured by a critical void volume criterion and a vanishing element technique. Experimentally, damage accumulation in random glass fiber–polyester composites was monitored by a videoextensometry technique able to control the local strain rate. Good agreement of model predictions with experimental data is pointed out. The model was implemented into a finite element program and numerical applications on composite structures (a tensile specimen and a plate containing a central hole) are presented to illustrate the capability of the approach. Digital image correlation method was also used to measure the full-field strain in a notched specimen under tensile loading. The simulated results compared favourably with those obtained from experiments.     

Regioselective One-Pot Synthesis,Biological Activity and Molecular Docking Studies of Novel Conjugates N-(p-Aryltriazolyl)-1,5-benzodiazepin-2-ones as Potent Antibacterial and Antifungal Agents

Novel 1,2,3-triazolo-linked-1,5-benzodiazepinones were designed and synthesized via a Cu(I)-catalyzed 1,3-dipolar alkyne-azide coupling reaction (CuAAC). The chemical structures of these compounds were confirmed by ¹H NMR, ¹³C NMR, HMBC, HRMS, and elemental analysis. The compounds were screened for their in vitro antibacterial and antifungal activities. Several compounds exhibited good to moderate activities compared to those of established standard drugs. Furthermore, the binding interactions of these active analogs were confirmed through molecular docking.     

Catalytic and biological valorization of a supramolecular mononuclear copper complex based 4‐aminopyridine

Hydrothermal reaction of copper bromide with 4‐aminopyridine in DMF solution yields a new mononuclear copper complex [Cu(C₅H₆N₂)₄]2Br.2(C₃H₇NO) abbreviated Cu‐4AP‐Br . The product was characterized, structurally, by single‐crystal X‐ray diffraction analysis and, thermally, by DSC‐ATG measurement. The inorganic–organic hybrid compound Cu‐4AP‐Br crystallizes in the centrosymmetric space group Pbcn, exhibiting a supramolecular network. Simultaneous DSC‐ATG analysis shows that this compound remains stable up to 100 °C and then performs a successive decompositions accompanied with endothermic peaks. The complex Cu‐4AP‐Br was applied as a catalyst in the Heck coupling reaction under ultrasonic irradiation in various reaction conditions. The yields, obtained for a short period of time, allow us to consider this complex, generating selectivity on the external position of styrene with a preference of the trans form over cis, as an excellent catalyst for this type of reaction. Interestingly, Cu‐4AP‐Br displayed important antibacterial (Gram‐positive and Gram‐negative) and antioxidant activities (β‐carotene bleaching inhibition, scavenging effect on DPPH free radical, and reducing power).     

Determination of 3J(H3í, Pi+1) and 3J(H5í/5i, Pi) coupling constants in 13C-labeled nucleic acids using constant-time HMQC.

A novel 1H-13C correlated two-dimensional experiment, CT-HMQC-J, for the measurement of three-bond proton-phosphorus coupling constants in 13C-labeled DNA is described. The experiment is based on the intensity difference of 1H-13C cross peaks in the presence and absence of the proton-phosphorus coupling interaction during the constant-time period in HMQC experiment. The 3J(H, P) coupling constants can be easily extracted from the intensity ratios of the two experiments. The method has been applied to a uniformly 13C, 15N-labeled d(GGAGGAT) 7-mer DNA sample. The proton-phosphorus coupling constants determined from CT-HMQC-J, together with the other three-bond coupling constants, are used to determine beta and epsilon torsion angles. The introduction of beta and epsilon restraints has improved the convergence as well as the quality of d(GGAGGAT) structure.     

Palm cryobanking

We describe the development of an efficient cryopreservation protocol for proembryogenic masses (PEMs) of date palm variety 'Barhee'. Proembryos were induced by inoculating small pieces of juvenile leaves on MS medium supplemented with 0.3 mg per liter 2,4-D. Application of these in vitro conditions led to true-to-type plants as observed after plant fructification. When compared to the standard vitrification protocol, the ultra-rapid droplet-vitrification technique proved to be superior. Sucrose preculture considerably increased post-cryopreservation recovery. The highest regeneration after cryogenic exposure reached 63.3 percent when PEMs were treated with PVS2 for 30 min at 0 degree C and 56.7 percent when PVS2 treatment lasted for 15 min at 25 degree C. The first signs of regrowth of cryopreserved PEMs were observed after 2 to 3 weeks. Cryopreservation did not affect the morphogenetic capacities of the plant material. Moreover, highly proliferating suspension cultures could be established from the cryopreserved material. The overall production of somatic embryos from 500 mg cryopreserved PEMs reached 1030 +/- 50 units after 1 month. The morphological study of date palms regenerated from cryopreserved material confirmed the stability of clonal material following cryopreservation.     

Synthesis and chemistry of new spiro‐Δ1‐pyrazoline

In explorations of syntheses and chemistry of spiroheterocycles, we found that the reaction of 2‐diazopropane with (E)‐α‐arylidenepyrrolin‐2‐one, (E)‐α‐arylidene‐γ‐butyrolactone, and (E)‐arylidene‐N‐arylsuccinimide derivatives produced spiro‐Δ¹‐pyrazolines. The photolysis of Δ¹‐pyrazolines has led to cyclopropanes. The structures of the obtained adducts have been assigned by means of spectroscopic measurements. J. Heterocyclic Chem., (2011).     

Experimental and DFT study of the conversion of ephedrine derivatives into oxazolidinones. Double SN2 mechanism against SN1 mechanism

Sulfonation of the N-Boc derivatives of 1,2-aminoalcohols, such as ephedrine, pseudoephedrine, norephedrine, norpseudoephedrine, thiomicamine, and chloramphenicol yields a mixture of the corresponding oxazolidinones with inversion (erythro derivatives) and/or retention of configuration (threo derivatives)at C5. We suggest a competition between two mechanisms: an intramolecular S_N2 process initiated by attack of the carbonyl oxygen of the Boc group to the benzylic carbon and the other one through a double S_N2 process. In the erythro derivatives the first mechanism is predominant, while in the threo derivatives both mechanisms have similar energy. This hypothesis is supported by theoretical calculations and additional experimental assays.     

Sequential MCR/Fisher indolization strategy for the construction of polycyclic carbazole derivatives

A one-pot method for the synthesis of novel polycyclic carbazole derivatives from readily available starting materials using a sequential multicomponent reaction/Fisher indolization strategy is described.     

On the coupled theory of thermo-magnetoelectroelasticity

Within the context of the coupled theory of thermo-magnetoelectroelasticity,we derive some variational principles which fully characterizethe solution of the boundary-initial-value problem. Then weestablish a reciprocity relation using a new method of proof,which involves two thermoelastic processes at different instants.We show that this relation can be used to obtain reciprocityand uniqueness theorems. The reciprocity theorem avoids boththe use of the Laplace transform and the incorporation of initialconditions into the equations of motion. The uniqueness theoremis derived without making restrictions on the positive definitenessof the elastic moduli or the conductivity tensor. There arealso no restrictions on piezoelectric moduli, piezomagneticmoduli and thermal coupling coefficients other than symmetryconditions. The results obtained are applicable for some specialcases which can be deduced from our model.     

Metal complexes stability constant determination by hyphenation of capillary electrophoresis with inductively coupled plasma mass spectrometry: The case of 1:1 metal-to-ligand stoichiometry

Nuclear energy development has raised new issues like radionuclides biogeochemistry. The modelling of their biochemical properties involves the accurate determination of thermodynamical data, like stability constants. This can be achieved by using hyphenated capillary electrophoresis (CE)–ICPMS and the method was applied successfully on 1:1 lanthanum–oxalate and uranyl–oxalate complexes. Several significant steps are discussed: choice of analytical conditions, electrophoretic mobility calculation, mathematical treatment of experimental data by using linear regressions, ligand concentration and ionic strength corrections. The following values were obtained with a good precision for lanthanum–oxalate and uranyl–oxalate complexes: log(K°(LaOxa⁺)) = 6.10 ± 0.10 and log(K°(UO₂Oxa)) = 6.40 ± 0.30, respectively, at infinite dilution. These values are consistent with the literature data, showing CE–ICPMS potential for metal complexes stability constants determination.