Odd–even effect in biphenyl‐based symmetrical dimers with methylene spacer – evidence of the B4 phase

A series of 4‐decyloxy‐4′‐hydroxybiphenyl esters of α,ω‐alkanedicarboxylic acids containing two mesogenic units connected by a methylene spacer was synthesized. The mesogenic properties of the compounds were investigated by polarising optical microscopy, differential scanning calorimetry and X‐ray diffraction methods. A strong influence of the spacer length and its parity on the mesomorphic properties was found. A dramatic odd–even effect was observed for the clearing temperatures and entropies. Compounds with an even number of carbon atoms in the methylene spacer formed tilted smectic phases, whereas compounds with an odd number of carbon atoms in the spacer exhibited the B4 phase, characteristic of bent‐shaped molecules.     

Quantification of Saponins in Different Plant Parts of Lysimachia L. Species by validated HPTLC—Densitometric Method

JPC – Journal of Planar Chromatography – Modern TLC - Quantitative high-performance thin-layer chromatography (HPTLC) analysis of triterpene saponins in different parts of eight...     

Zinc oxide nanoparticles based microfluidic immunosensor applied in congenital hypothyroidism screening

In this article, we present an innovative approach for congenital hypothyroidism (CHT) screening. This pathology is the most common preventable cause of mental retardation, affecting newborns around the world. Its consequences could be avoided with an early diagnosis through the thyrotropin (TSH) level measurement. To accomplish the determination of TSH, synthesized zinc oxide (ZnO) nanobeads (NBs) covered by chitosan (CH), ZnO-CH NBs, were covalently attached to the central channel of the designed microfluidic device. These beads were employed as platform for anti-TSH monoclonal antibody immobilization to specifically recognize and capture TSH in neonatal samples without any special pretreatment. Afterwards, the amount of this trapped hormone was quantified by horseradish peroxidase (HRP)-conjugated anti-TSH antibody. HRP reacted with its enzymatic substrate in a redox process, which resulted in the appearance of a current whose magnitude was directly proportional to the level of TSH in the neonatal sample. The structure and morphology of synthesized ZnO-CH NBs were characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The calculated detection limits for electrochemical detection and the enzyme-linked immunosorbent assay procedure were 0.00087 μUI mL^?1 and 0.015 μUI mL^?1, respectively, and the within- and between-assay coefficients of variation were below 6.31 % for the proposed method. According to the cut-off value for TSH neonatal screening, a reasonably good limit of detection was achieved. These above-mentioned features make the system advantageous for routine clinical analysis adaptation.     

Modulated noisy biological dynamics: Three examples

Three examples of noisy biological dynamics modulated by a periodic signal are discussed. A minimal neuron model driven by stochastic noise and small periodic force show a firing statistic comparable with stochastic resonance as demonstrated in bistable systems. Similar results are obtained from responses to periodic vibrotactile stimulation on higher-order neuronal units of the somatosensory pathway. Finally, results from a bistable visual perception task exhibiting stochastic resonance are reported.     

Comparison of the Kalman filter and dedicated algorithms for processing data for solution equilibria,noise smoothing and calibration

The suitability of the Kalman filter for extracting acidity (protonation) constants from titration curves, for noise removal, and for multicomponent determinations in the presence of sample-related interferences is described. The performance of the algorithm is illustrated with simulated examples and checked by comparing the results with those obtained by dedicated methods (Savitzky-Golay and Fourier-transform procedures and the general standard-addition procedure). The ability of a combination of two Kalman filters as a fixed-interval smoother for noise removal is stressed.     

On the probability that finite spaces with random distances are metric spaces

For a set of 3 or 4 points we compute the exact probability that, after assigning the distances between these points uniformly at random from the set 1,…,n , the space obtained is metric. The corresponding results for random real distances follow easily. We also prove estimates for the general case of a finite set of points with uniformly random real distances.     

Cloud point extraction of mercury with PONPE 7.5 prior to its determination in biological samples by ETAAS

Cloud point extraction (CPE) has been used for the pre-concentration of mercury, after the formation of a complex with 2-(5-bromo-2-pyridylazo)-5-(diethylamino)-phenol (5-Br-PADAP), and later analysis by electrothermal atomic absorption spectrometry (ETAAS) using polyethyleneglycolmono-p-nonyphenylether (PONPE 7.5) as surfactant. The chemical variables affecting the separation step were optimized. Under the optimum conditions, i.e, pH 8.5, cloud point temperature 80 degrees C, 5-Br-PADAP=4x10(-5) mol L(-1), PONPE 7.5=0.2%, sample volume=1.0 mL, an enhancement factor of 22-fold was reached. The lower limit of detection (LOD) obtained under the optimal conditions was 0.01 microg L(-1). The precision for 10 replicate determinations at 2.0 microg L(-1) Hg was 4.0% relative standard deviation (R.S.D.). The calibration graph using the pre-concentration system for mercury was linear with a correlation coefficient of 0.9994 at levels near the detection limits up to at least 16 microg L(-1). The method was successfully applied to the determination of mercury in biological samples and in certified reference material (QC METAL LL3).     

Estimating the influence of finite instrumental resolution on elastic neutron scattering intensities from proteins

Recent experimental and simulation studies show that the fractional Ornstein-Uhlenbeck process describes well the single particle motions in internal protein dynamics. Here the authors use this model to estimate the influence of finite instrumental resolution on elastic neutron scattering intensities from hydrated protein powders. They give, in particular, an estimation of the attenuation factor for the observed atomic position fluctuations, assuming a Gaussian and a triangular resolution function.     

New ferrocenyl-chalcones and bichalcones: Synthesis and characterization

Ferrocenyl-chalcones and their bichalcone analogues were characterized by IR and NMR spectroscopy, as well as electrochemically. Their UV–visible spectra were recorded, and the electronic transitions were assigned by time-dependent DFT calculations. The single-crystal X-ray structures were determined for two ferrocenyl bichalcones.