More on continuously Urysohn spaces

We study the properties of weakly continuously Urysohn and continuously Urysohn spaces. We show that being a (weakly) continuously Urysohn space is not a multiplicative property, and that this property is not preserved under perfect maps. However, being a weakly continuously Urysohn space is preserved under perfect open maps. By using the scattering process, we show that the class of protometrizable spaces is also contained in the class of continuously Urysohn space. We also give a characterization of the continuously Urysohn property for well-ordered spaces, and prove that a paracompact locally continuously Urysohn ordered space is continuously Urysohn.     

Synthesis and electrochemistry of tetrakis(7-coumarinthio-4-methyl)-phthalocyanines,and preparation of their cinnamic acid and sodium cinnamate derivatives

Novel water soluble free-base, Zn(II) and Co(II) metallo phthalocyanines with four cinnamic acid moieties were prepared from the corresponding tetrakis(7-coumarinthio-4-methyl)-phthalocyanine by the lactone ring opening reaction. The new compounds were purified and characterized by elemental analysis, ¹H NMR, Maldi-TOF, FT-IR and UV–Vis spectral data. Cyclic and differential pulse voltammetry and in situ spectroelectrochemistry of the 2,9,16,23-tetrakis(7-coumarinthio-4-methyl) substituted free-base 1a, Zn(II) 1b and Co(II) 1c phthalocyanines, employed as the starting compounds have been studied. This allowed us not only to identify metal- and phthalocyanine ring-based redox processes of the complexes, but also the effect of aggregation on these processes.     

Spin currents and magnetoresistance of graphene-based magnetic junctions

Using the tight-binding approximation and the nonequilibrium Green’s function approach, we investigate the coherent spin-dependent transport in planar magnetic junctions consisting of two ferromagnetic (FM) electrodes separated by a graphene flake (GF) with zigzag or armchair interfaces. It is found that the electron conduction strongly depends on the geometry of contact between the GF and the FM electrodes. In the case of zigzag interfaces, the junction demonstrates a spin-valve effect with high magnetoresistance (MR) ratios and shows negative differential resistance features for a single spin channel at positive gate voltage. In the case of armchair interfaces, the current-voltage characteristics behave linearly at low bias voltages and hence, both spin channels are in on state with low MR ratios.     

Preparation of an Electrochromatographic Stationary Phase Using a New Polymethacrylate Monolith with Chloropropyl Functionality

A new reactive capillary monolith as an alternative to the commonly employed glycidyl methacrylate-based stationary phases in capillary electrochromatography (CEC) applications was synthesized and post-functionalized with charge-bearing groups. For this purpose, a hydrophilic capillary monolith with reactive 3-chloro-2-hydroxypropyl moiety was first obtained by the copolymerization of a new methacrylate-based monomer, 3-chloro-2-hydroxypropyl methacrylate (HPMA-Cl), with a methacrylic crosslinking agent, ethylene glycol dimethacrylate (EDMA). The presence of 3-chloro-2-hydroxypropyl functionality in poly(HPMA-Cl-co-EDMA) monolith allowed the synthesis of monoliths carrying strongly ionizable anionic, cationic or neutral groups such as sulfonic acid, quaternary ammonium or octadecyl, respectively, via simple and single-stage reactions. In the present study, a reactive poly(HPMA-Cl-co-EDMA) capillary monolith was functionalized with sodium bisulfite (NaHSO₃) to have a strongly ionizable sulfonic acid group on the monolith. The resulting monolith providing cathodic electroosmotic flow in CEC was successfully used for the separation of phenol derivatives. The theoretical plate numbers up to 63,000 plates/column were achieved. The results showed that a new promising, reactive support that could be functionalized with different chromatographic ligands for different chromatographic applications was obtained in the study.     

Synthesis of some novel 3,4,5-trisubstituted triazole derivatives bearing quinoline ring and evaluation of their antimicrobial activity

Abstract

Some new 3,4,5-trisubstituted 1,2,4-triazole derivatives were synthesized and studied for their antimicrobial activity. The lead compounds were obtained starting from 8-hydroxyquinoline and ethyl 2-chloroacetate. The obtained ester compound (1) first reacted with hydrazine hydrate (2) then with phenyl isothiocyanate (3). Ring closure by KOH led to 3-mercapto-1,2,4-triazole derivative (4). Lastly, it reacted with 2-chloro-N-(substituted (benzo)/thiazole)acetamide derivatives to obtain the final compounds (5a–j). The structural elucidation of the compounds was performed by ¹H NMR and ¹³C NMR spectroscopy and high resolution mass spectrometry techniques and elemental analysis. The synthesized compounds were investigated for their antimicrobial activities against seven bacteria and four fungi. As a result of the activity studies, it was observed that compounds N-(6-nitrobenzothiazol-2-yl)-2-[[4-phenyl-5-((quinolin-8-yloxy)methyl)-4H-1,2,4-triazol-3-yl]thio]acetamide (5a) and N-(6-fluorobenzothiazol-2-yl)-2-[[4-phenyl-5-((quinolin-8-yloxy)methyl)-4H-1,2,4-triazol-3-yl]thio]acetamide (5d) were the most active molecules. Also, the antifungal activity of the compounds was found to be higher than their antibacterial activity although lower than the standard drug’s potential. Additionally, the physicochemical properties of the compounds were calculated which were evaluated to be at a suitable range for oral administration.     

Use of amberlite XAD-7HP for the separation of Mn(II) and Mn(VII) in waters

A simple method is proposed for the determination and speciation of Mn(II) and Mn(VII) in waters utilizing a macroporous resin, Amberlite XAD-7HP. The batch method was employed and flame atomic absorption spectrometry was used in all determinations. Amberlite XAD-7HP resin was shown to retain Mn(VII) between pH 4 and 12. If the solution contains only one of the species, either Mn(II) or Mn(VII), the resin behaves selectively depending on the pH of the solution. The elution from the sorbent was realized using K₂C₂O₄ in HNO₃. The efficiency of the method was checked via spike recovery experiments. The proposed method was successfully applied to industrial wastewater samples and quantitative recoveries (≥96.0%) confirmed the accuracy of the method.     

β-Hydroxyamide derivatives of salicylic acid as organocatalysts for enantioselective reductions of prochiral ketones

In order to find the most effective catalyst for the enantioselective reduction of a prochiral ketone, a series of novel β-hydroxyamide derivatives of salicylic acid and chiral amino alcohols were synthesized. Different substituted prochiral ketones have been reduced in high yield (up to 99%) and the corresponding secondary alcohols are formed with good enantiomeric excess (up to 86%). The mechanism of this type of catalyst can be explained by considering the reaction mechanism for the CBS catalyst.     

Three-dimensional modeling of thermo-mechanical finite element analysis in edge-pumped composite Yb:YAG/YAG thin-disk laser

A study of the thermo-mechanical analysis in edge-pumped composite Yb:YAG disk laser is presented. A three-dimensional model of disk and cooling system was created in ANSYS software. Heat load density applied on active medium was 14.6% of power absorption density. Temperature, stress and strain analysis showed a uniform distribution in the upper surface and maximum in the center. Finally, optimum heat exchanger coefficient and temperature of cooling system were obtained by comparing with different analyses and results.     

Click-chemistry for surface modification of monodisperse-macroporous particles

In this study, click chemistry was proposed as a tool for tuning the surface hydrophilicity of monodisperse-macroporous particles in micron-size range. The monodisperse-porous particles carrying hydrophobic or hydrophilic molecular brushes on their surfaces were obtained by the proposed modification. Hydrophilic poly(glycidyl methacrylate-co-ethylene dimethacrylate), poly(GMA-co-EDM) particles were hydrophobized by the covalent attachment of poly(octadecyl acrylate-co-propargyl acrylate), poly(ODA-co-PA) copolymer onto the particle surface via triazole formation by click chemistry. In the second part, Hydrophobic poly(4-chloromethylstyrene-co-divinylbenzene), poly(CMS-co-DVB) particles were hydrophilized by the covalent attachment of poly(vinyl alcohol), PVA onto their surface also via triazole formation by click chemistry. The presence of PVA and poly(ODA-co-PA) copolymer on the corresponding particles was shown by FTIR-DRS. After click-coupling reactions applied for both hydrophobic poly(CMS-co-DVB) and hydrophilic poly(GMA-co-EDM) particles, the marked changes in surface polarity were shown by contact angle measurements. Protein adsorption characteristics of plain and modified particles were investigated for both materials. In the isoelectric point of albumin, the non-specific albumin adsorption decreased from 225 to 80 mg/g by grafting PVA onto the poly(CMS-co-DVB) beads. On the other hand, the non-specific albumin adsorption onto the plain poly(GMA-co-EDM) beads increased from 50 to 400 mg/g by the covalent attachment of poly(ODA-co-PA) copolymer onto the bead-surface via click chemistry. The protein adsorption behavior was efficiently regulated by the covalent attachment of appropriate molecular brushes onto the surfaces of selected particles. The results indicated that "click chemistry" was an efficient tool for controlling the polarity of monodisperse-macroporous particles.