Optical,electrochemical, and sensing properties of polyfluorenes bearing thiazole or oxazole and triphenylamine in the main chain

Polyfluorenes bearing thiazole (PFTH) or oxazole (PFOX) heterocyclic units as well as triphenylamine (TPA) in the main chain were synthesized. The ratio of thiazole or oxazole/TPA in the polymer chain varies from 100/0 to 25/75. The optical properties of polymers depend on thiazole or oxazole contents. Cyclic voltammetry reveals that thiazole or oxazole hinder the oxidation of polymers and only polymers with TPA show reversible oxidation. The Electron Affinities do not practically depend on composition of the polymer chain. The sensing properties of polymers PFTH100 and PFOX100 are investigated toward several cations and anions. Polymers detect two analytes, Fe²⁺ and Hg²⁺. PL quenching shows linear response to Fe²⁺ in wide concentration region 1–800 μΜ. I^? anions quench the emission of polymers. Hg²⁺ turns on the emission of the polymer/I^? complex at concentrations as low as 1 μM. Enhancement of polymer/I^? emission exhibits linear response to Hg²⁺ concentration. PFTH100 is able to detect Fe²⁺ and Hg²⁺ that coexist in a solution. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55 , 243–254     

Iron(III) chemistry with ferrocene-1,1'-dicarboxylic acid (fdcH2): an Fe7 cluster with an oxidized fdc(-) ligand

The synthesis and properties are reported of a new Fe(7) cluster obtained from the reaction of ferrocene-1,1'-dicarboxylic acid (fdcH(2)) with FeCl(2)·4H(2)O in MeOH under ambient light conditions. The compound is the mixed-anion salt [Fe(7)O(3)(OMe)(fdc)(6)(MeOH)(3)][FeCl(4)]Cl(2) (1; 8Fe(III)), containing six (fdc(n-)) groups as peripheral ligands. The cation of 1 has virtual C(3) symmetry and contains a central [Fe(4)(μ(3)-O)(3)(μ(3)-OMe)](5+) cubane unit whose three oxide ions each become μ(4) by attaching to a fourth Fe atom outside the cubane. The resulting [Fe(7)(μ(3)-O(3))(μ(3)-OMe)](14+) core is surrounded by six fdc(n-) (n = 1, 2) groups, which divide into two sets by virtual symmetry. The blue color of the complex suggested that some of these ligands are in their oxidized fdc(-) ferricenium (Fe(III)) state, and various data point to there being one fdc(-) ligand in the compound, the initial example of the group acting as a ligand in inorganic chemistry. Variable-temperature, solid-state DC and AC susceptibility measurements reveal the cation to be antiferromagnetically coupled, as expected for high-spin Fe(III), and to have an S = 2 ground state, consistent with an S = (5)/(2) Fe(7) inner core coupled antiferromagnetically to the one paramagnetic fdc(-) (S = (1)/(2)) ligand. Complex 1 displays multiple reductions and oxidations when investigated by electrochemistry in MeCN. (57)Fe Mo?ssbauer spectroscopy supports the presence of only five fdc(2-) ligands, but cannot resolve the signals from the various Fe(III) sites.     

On the student evaluation of university courses and faculty members’ teaching performance

Trying to determine higher education quality, one gets quickly to one of its significant dimensions, namely the quality of faculty members’ teaching. The latter and, overall, the quality of any university course should be certainly evaluated by their recipients, namely students. In this paper we develop a statistical framework based on Statistical Quality Control mainly, which can be used in order to exploit student evaluations as much as possible. More specifically we present two directions of data monitoring and analysis; the one uses control charts and the other hypotheses testing. The results that can be raised through both directions are crucial for any decision maker.     

Statistical and Criticality Analysis of the Lower Ionosphere Prior to the 30 October 2020 Samos (Greece) Earthquake (M6.9), Based on VLF Electromagnetic Propagation Data as Recorded by a New VLF/LF Receiver Installed in Athens (Greece)

In this work we present the statistical and criticality analysis of the very low frequency (VLF) sub-ionospheric propagation data recorded by a VLF/LF radio receiver which has recently been established at the University of West Attica in Athens (Greece). We investigate a very recent, strong (M6.9), and shallow earthquake (EQ) that occurred on 30 October 2020, very close to the northern coast of the island of Samos (Greece). We focus on the reception data from two VLF transmitters, located in Turkey and Israel, on the basis that the EQ’s epicenter was located within or very close to the 5th Fresnel zone, respectively, of the corresponding sub-ionospheric propagation path. Firstly, we employed in our study the conventional analyses known as the nighttime fluctuation method (NFM) and the terminator time method (TTM), aiming to reveal any statistical anomalies prior to the EQ’s occurrence. These analyses revealed statistical anomalies in the studied sub-ionospheric propagation paths within ~2 weeks and a few days before the EQ’s occurrence. Secondly, we performed criticality analysis using two well-established complex systems’ time series analysis methods—the natural time (NT) analysis method, and the method of critical fluctuations (MCF). The NT analysis method was applied to the VLF propagation quantities of the NFM, revealing criticality indications over a period of ~2 weeks prior to the Samos EQ, whereas MCF was applied to the raw receiver amplitude data, uncovering the time excerpts of the analyzed time series that present criticality which were closest before the Samos EQ. Interestingly, power-law indications were also found shortly after the EQ’s occurrence. However, it is shown that these do not correspond to criticality related to EQ preparation processes. Finally, it is noted that no other complex space-sourced or geophysical phenomenon that could disturb the lower ionosphere did occur during the studied time period or close after, corroborating the view that our results prior to the Samos EQ are likely related to this mainshock.     

Traces of self-organisation and long-range memory in variations of environmental radon in soil: comparative results from monitoring in Lesvos Island and Ileia (Greece)

This paper addresses issues of self-affinity, long-memory and self-organisation in variations of radon in soil recorded in Lesvos Island, Greece. Several techniques were employed, namely (a) power-law wavelet spectral fractal analysis, (b) estimation of Hurst exponents through (b1) rescaled-range, (b2) roughness-length, (b3) variogram and (a), (c) detrended fluctuation analysis, (d) investigation of fractal dimensions and (e) analysis of five block entropies: (e1) Shannon entropy, (e2) Shannon entropy per letter, (e3) conditional entropy, (e4) Tsallis entropy, and (e5) normalised Tsallis entropy. Long-lasting antipersistency was identified during a period of anomalous radon variations following fractional Brownian modelling. Remaining variations did not exhibit analogous behaviour and followed fractional Gaussian modelling. Antipersistent power-law-beta-exponent-values between 1.5 and 2.0 were detected during anomalies. Persistent values were also found. Hurst exponents were mainly within 0 < H < 0.5. Some persistent exponents (0.5 < H < 1) were also observed. Fractal dimensions were within 1.5 < D < 2. Radon anomalies presented lower fractal dimensions. Shannon entropy ranged between 0.77 ≤ H(n) ≤ 2.38, Shannon entropy per letter, between 0.19 ≤ h ⁽ⁿ⁾ ≤ 0.59, conditional entropy, between 0.01 ≤ h _(n) ≤ 0.58, Tsallis entropy, between 0.55 ≤ S _q  ≤ 1.01 and normalised Tsallis entropy between, 0.98 ≤  $\hat{S}$  ≤ 5.42 (block-size n = 4). Entropies were lower during anomalies, indicating strong self-organisation. Persistency–antipersistency switching was observed, consistent with long-memory dynamics. Potential geological sources were discussed. The asperity-model was proposed. Findings were compared to results obtained under analogous methodologies in Ileia, Greece.     

Scale-up of Thermally Dried Kefir Production as Starter Culture for Hard-Type Cheese Making: An Economic Evaluation

This paper concerns the effect of thermal-drying methodology on the investment cost for dried kefir cells production in order to be used as starter culture in cheese manufacturing. Kefir cells were produced at pilot plant scale using a 250-L bioreactor and whey as the main substrate. Kefir cells were subsequently dried in a thermal dryer at 38?°C and used as a starter culture in industrial-scale production of hard-type cheeses. The use of thermally dried kefir as starter culture accelerated ripening of cheeses by increasing both lipolysis and fermentation rate as indicated by the ethanol, lactic acid, and glycerol formation. Additionally, it reduced coliforms and enterobacteria as ripening proceeded. This constituted the basis of developing an economic study in which industrial-scale production of thermally dried kefir starter culture is discussed. The industrial design involved a three-step process using three bioreactors of 100, 3,000, and 30,000 L for a plant capacity of 300 kg of thermally dried kefir culture per day. The cost of investment was estimated at 238,000 €, which is the 46% of the corresponding cost using freeze-drying methodology. Production cost was estimated at 4.9 €/kg of kefir biomass for a 300-kg/day plant capacity, which is the same as with the corresponding cost of freeze-dried cells. However, the estimated added value is up to 10.8?×?10⁹ € within the European Union.     

On the singular set,the resolvent and Fermi's Golden Rule for finite volume hyperbolic surfaces

Consider a finite volume hyperbolic surface. Under perturbation the spectrum of the Laplace operator is unstable but the singular set is stable. We characterize the singular set in terms of the resolvent of the Laplace operator and extend Fermi's Golden Rule to the case of multiple eigenvalues. the date of receipt and acceptance should be inserted later     

The settling of suspensions promoted by rigid buoyant particles

When substantial numbers of buoyant particles are mixed with a sedimenting suspension of heavy particles, the two types of solids undergo rapid lateral segregation from each other. Streams 3–5 mm in diameter containing the less populous species form and flow through a concentrated continuum suspension of the more populous species. This buoyancy driven convection results in greatly enhanced sedimentation rates. A theory is developed on the premise that streams move in plug flow with all resistance to motion confined to a thin lubricating layer at the strean-continuum interface. The model is compared with experimental data and is shown to account correctly for the effect of each system parameter on the observed settling rates.