Centrality dependence of rapidity spectra of negative pions in 12 C+12 C and 12 C+181 Ta collisions at 4.2 GeV/c per nucleon

The centrality dependences of the experimental rapidity as well as transversemomentumversus rapidity spectra of negative pions were analyzed quantitatively in ¹²C+¹²C and ¹²C+¹⁸¹Ta collisions at 4.2 GeV/c per nucleon using fitting the pion spectra by Gaussian distribution function. The experimental results were compared systematically with the predictions of the Quark-Gluon-String Model (QGSM) adapted to intermediate energies.     

Synthesis of New 1,2,3‐Triazole Derivatives Possessing 4H‐Pyran‐4‐one Moiety by 1,3‐Dipolar Cycloaddition Reaction of Azidomethyl Phenylpyrone with Various Alkynes

A series of new 1,2,3‐triazole derivatives were synthesized by 1,3‐dipolar cycloaddition reaction of 2‐(4‐azidomethylphenyl)‐6‐phenyl‐4H‐pyran‐4‐one with different alkynes in 40–71% yields. In the case of terminal alkynes, the reaction was proceeded in the presence of Cu(I) catalyst. The structure of the synthesized compounds were confirmed by FTIR, ¹H‐NMR, and ¹³C‐NMR spectroscopy and elemental analysis.     

Guanidinum Chloride as Dehydrocyclization Agent in the Synthesis of 2‐Fuctionalized (4H)‐3,1‐Benzoxazine‐4‐ones

A facile and expedient route for the synthesis of 2‐ethoxy‐ and 2‐(ethylcarboxylate)‐(4H)‐3,1‐benzoxazine‐4‐ones is described using guanidinium chloride as a safe and convenient dehydrocyclization agent. High yields of the products obtain under mild reaction conditions without need to use of any catalyst and with easy work‐up of the reaction mixture.     

Synthesis of new 4-aroyl-pyrano[c]chromenes via a one-pot,three-component reaction based on aryl glyoxals

A new library of pyrano[c]chromenes containing an aroyl group has been synthesized by a novel multicomponent process involving the reaction of various aryl glyoxals with 4-hydroxycoumarin and malononitrile. The reactions were catalyzed efficiently by ammonium dihydrogen phosphate to yield the desired products in good to excellent yields.     

DFT study of 1-, 4-, and 5-substituted 2-oxo-1,2,3,4-tetrahydropyrimidines: substituent steric and electronic effects,and ring flipping

Steric and the electronic effects caused by the substituents in the 1-, 4-, and 5-positions of substituted 2-oxo-1,2,3,4-tetrahydropyrimidines were investigated using density functional theory at the B3LYP/6-31++G(d,p) level. Results of this study show that the heterocyclic ring adopts a pseudo-boat conformation, in which the C₄ and N₁ atoms are deviated from ring planarity. The C₄-substituent occupies a pseudo-axial position and the space orientation of the substituent depends on the type and position of the additional substituent in this aryl group. The heights of the C₄ and N₁ atoms from the boat plane and the orientation of 5-CO moiety toward the heterocyclic ring depend on the electronic and steric effects of the substituents in the various positions. Ring flip calculations for 4-phenyl substituent explain the extreme steric effect caused by the substituent in the 1-position. These calculations indicate the more favored pseudo-axial orientation of the phenyl group over the equatorial orientation.     

Substituent effect on the tautomerism of 5-acetyl-2-methoxydihydropyrimidines: experimental NMR and computational DFT studies

Some selected 5-acetyl-2-methoxydihydropyrimidines (DHPMs) are synthesized and the electronic effect of the substituent on the 4-position of the heterocyclic ring on the ratio of the possible tautomeric forms is investigated using dynamic NMR experiments. The results of this study indicate that these compounds coexist in two tautomeric 1,4- and 3,4-forms in the solution and their tautomeric ratios depend on the electronic nature of the additional substituent on the 4-phenyl substituent, the nature of solvent used for NMR study and also on the temperature. B3LYP/6–31 ++G** computational studies in the gas and solution phases elucidate the effect of the additional substituent on the phenyl ring on the structural, electronic and bonding characteristics of the tautomeric forms in these compounds. Furthermore, solvation of these DHPMs determines the relative stabilities of the two tautomers in the solution phase, which cannot be probed by model solvents adopted in SCRF calculations.     

Clean synthesis and antibacterial activities of spiro[pyrimido[4,5-b]quinoline-5,5'-pyrrolo[2,3-d]pyrimidine]-pentaones

A simple, clean and efficient method for the synthesis of spiro[pyrimido[4,5-b]quinoline-5,5'-pyrrolo[2,3-d]pyrimidine]-pentaone derivatives by condensation reaction of 6-amino-uracils and isatins in aqueous media is reported. These products were evaluated in vitro for their antibacterial activities.     

Comparison of Pulsed and Continuous Wave Diode Laser at 940 nm on the Viability and Migration of Gingival Fibroblasts

Gingival fibroblasts have critical roles in oral wound healing. Photobiomodulation (PBM) has been shown to promote mucosal healing and is now recommended for managing oncotherapy-associated oral mucositis. This study examined the effects of the emission mode of a 940 nm diode laser on the viability and migration of human gingival fibroblasts. Cells were cultured in a routine growth media and treated with PBM (average power 0.1 W cm⁻², average fluence 3 J cm⁻², every 12 h for six sessions) in one continuous wave and two pulsing settings with 20% and 50% duty cycles. Cell viability was assessed using MTT, and digital imaging quantified cell migration. After 48 and 72 h, all treatment groups had significantly higher viability (n = 6, P < 0.05) compared with the control. The highest viability was seen in the pulsed (20% duty cycle) group at the 72-h time point. PBM improved fibroblast migration in all PBM-treated groups, but differences were not statistically significant (n = 2, P > 0.05). PBM treatments can promote cell viability in both continuous and pulsed modes. Further studies are needed to elucidate the optimal setting for PBM-evoked responses for its rationalized use in promoting specific phases of oral wound healing.     

Investigation of fragrance stability used in the formulation of cosmetic and hygienic products using headspace solid‐phase microextraction by nanostructured materials followed by gas chromatography with mass spectrometry

A new composite coating of polypyrrole and sodium lauryl ether sulfate was electrochemically prepared on a stainless‐steel wire using cyclic voltammetry. The application and performance of the fiber was evaluated for the headspace solid‐phase microextraction of a fragrance in aqueous bleach samples followed by gas chromatography combined with mass spectrometry to assess the fragrance stability in this kind of household cleaning product. To obtain a stable and efficient composite coating, parameters related to the coating process such as scan rate and numbers of cycles were optimized using a central composite design. In addition, the effects of various parameters on the extraction efficiency of the headspace solid‐phase microextraction process such as extraction temperature and time, ionic strength, sample volume, and stirring rate were investigated by experimental design methods using Plackett–Burman and Doehlert designs. The optimum values of 53°C and 28 min for sample temperature and time, respectively, were found through response surface methodology. Results show that the combination of polypyrrole and sodium lauryl ether sulfate in a composite form presents desirable opportunities to produce new materials to study fragrance stability by headspace solid‐phase microextraction.     

Comparison of solidification of floating drop and homogenous liquid–liquid microextractions for the extraction of two plasticizers from the water kept in PET‐bottles

Two approaches based on solidification of floating drop microextraction (SFDME) and homogenous liquid–liquid microextraction (HLLE) were compared for the extraction and preconcentration of di‐(2‐ethylhexyl) phthalate (DEHP) and di‐(2‐ethylhexyl) adipate (DEHA) from the mineral water samples. In SFDME, a floated drop of the mixture of acetophenone/1‐undecanol (1:8) was exposed on the surface of the aqueous solution and extraction was permitted to occur. In HLLE, a homogenous ternary solvent system was used by water/methanol/chloroform and the phase separation phenomenon occurred by salt addition. Under the optimal conditions, the LODs for the two target plasticizers (DEHA and DEHP), obtained by SFDME–GC‐FID and HLLE–GC‐FID, were ranged from 0.03 to 0.01 μg/L and 0.02 to 0.01 μg/L, respectively. HLLE provided higher preconcentration factors (472.5‐ and 551.2‐fold) within the shorter extraction time as well as better RSDs (4.5–6.9%). While, in SFDME, high preconcentration factors in the range of 162–198 and good RSDs in the range of 5.2–9.6% were obtained. Both methods were applied for the analysis of two plasticizers in different water samples and two target plasticizers were found in the bottled mineral water after the expiring time and the boiling water was exposed to a polyethylene vial.