Synthesis and X-ray crystal structure determination of N-p-methylphenyl-4-benzoyl-3,4-diphenyl-2-azetidinone

The title compound, C₂₉H₂₃NO₂, has been characterized by single-crystal X-ray diffraction at two different temperatures (303 K and 120 K) and wavelengths (MoK _α and CuK _α). The non-centrosymmetric hexagonal crystal structure contains four-membered planar β-lactam ring with an unusually long C-C bond. The β-lactam ring is almost planar.     

Effects of different temperatures and additives on the metastable zone width precipitation kinetics of NaBO2

In this study, the sodium metaborate, which is applicable in various industrial areas, and its metastable zone width that is very important for its production by crystallization, and its nucleation are investigated to obtain the necessary thermodynamic parameters. The polythermal and isothermal method has been used for the measurement of metastable zone width. Metastable zone width of NaBO₂ has found at 9°C at average and cooling rate do not have any effect on it. In addition, the effect of sodium metaborate on the hydrogen storage capacity of sodium borohyride solutions that is known as one of the best hydrogen sources today is investigated at the various concentrations of sodium borohyride in the medium. Results have shown that three different areas emerged as the percentage of NaBH4 in the solution increased.     

Manganese(III) acetate-mediated synthesis of biaryls under microwave irradiation

Manganese(III) acetate (Mn(OAc)₃)-mediated synthesis of biaryls and heterobiaryls starting from arylboronic acid was developed under microwave irradiation in high yields. Microwaves were also used for the synthesis of Mn(OAc)₃ from KMnO₄ and acetic acid. Additional irradiation of this in situ generated Mn(OAc)₃ with arylboronic acids, which in turn furnished the biaryls in high yields in a one pot reaction. This is superior from the point of view of yield, short reaction time, sensitive functional group toleration, and more environmentally friendly than the reported methods with a minimum amount of benzene and thiophene as a reagent but not as a solvent.     

Nonlinear effects in proline–thiourea host–guest complex catalyzed aldol reactions in nonpolar solvents

An aldol reaction catalyzed by a proline–thiourea host–guest complex in a nonpolar solvent shows excellent nonlinear effects. This proline–thiourea system has the ability to form a hydrogen-bonding network. The enantiomeric excess of proline in a solution can be significantly enhanced by its incorporation with a urea molecule into its solid racemate. This suggests a general and facile route to homochirality, which may be involved in the origin of chirality on earth.     

Dielectric and proton conductivity studies in organic electrolytes based on 2-perfluoroalkyl-ethyl-azides

Intrinsically proton conducting organic electrolytes based on 2-perfluoroalkyl-ethyl-azides were synthesized via 1,3 cycloaddition between 2-perfluoroalkyl-ethyl-azide and alkynes. FT-IR, elemental analysis and NMR methods were used to characterize the resulting organic electrolytes. Thermal properties were analyzed with thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) and the morphology of the organic electrolytes was studied with X-ray diffraction (XRD). The effect of chain length on proton conductivity was investigated with impedance spectrometer. Dielectric constant and electrical modulus formalisms were analyzed and the maximum proton conductivity was measured as 10⁻² mS/cm at 180 °C.     

Admission control strategies for tandem Markovian loss systems

Motivated by communication networks, we study an admission control problem for a Markovian loss system comprised of two finite capacity service stations in tandem. Customers arrive to station 1 according to a Poisson process, and a gatekeeper, who has complete knowledge of the number of customers at both stations, decides whether to accept or reject each arriving customer. If a customer is rejected, a rejection cost is incurred. If an admitted customer finds that station 2 is full at the time of his service completion at station 1, he leaves the system and a loss cost is incurred. The goal is to find easy-to-implement policies that minimize long-run average cost per unit time. We formulate two intuitive, extremal policies and provide analytical results on their performances. We also present necessary and/or sufficient conditions under which each of these policies is optimal. Next, we show that for some states of the system it is always optimal to admit new arrivals. We also fully characterize the optimal policy when the capacity of each station is two and discuss some characteristics of optimal policies in general. Finally, we design heuristic admission control policies using these insights. Numerical experiments indicate that these heuristic policies yield near-optimal long-run average cost performance.     

Hyperharmonic series involving Hurwitz zeta function

We show that the sum of the series formed by the so-called hyperharmonic numbers can be expressed in terms of the Riemann zeta function. These results enable us to reformulate Euler's formula involving the Hurwitz zeta function. In additon, we improve Conway and Guy's formula for hyperharmonic numbers.     

Plasma treatment of polypropylene fabric for improved dyeability with soluble textile dyestuff

The impact of plasma treatment parameters on the surface morphology, physical-chemical, and dyeing properties of polypropylene (PP) using anionic and cationic dyestuffs were investigated in this study. Argon plasma treatment was used to activate PP fabric surfaces. Activated surfaces were grafted different compounds: 6-aminohexanoic acid (6-AHA), acrylic acid (AA), ethylendiamine (EDA), acryl amide (AAMID) and hexamethyldisiloxane (HMDS). Compounds were applied after the plasma treatment and the acid and basic dyeing result that was then observed, were quite encouraging in certain conditions. The possible formed oxidizing groups were emphasized by FTIR and ATR and the surface morphology of plasma treated PP fibers was also investigated with scanning electron microscopy (SEM).PP fabric could be dyed with acid and basic dyestuffs after only plasma treatment and plasma induced grafting, and fastnesses of the dyed samples were satisfactory.     

On values of the Riemann zeta function at positive integers

Lithuanian Mathematical Journal - We give new proofs of some known results on the values of the Riemann zeta function at positive integers and obtain some new theorems related to these values....