The effect of wall depletion on the rheology of microfibrillated cellulose water suspensions by optical coherence tomography

Rheology of microfibrillated cellulose (MFC) water suspensions was characterized with a rotational rheometer, augmented with optical coherence tomography (OCT). To the best of the authors’ knowledge, this is the first time the behavior of MFC in the rheometer gap was characterized by this real-time imaging method. Two concentrations, 0.5 and 1 wt% were used, the latter also with 10^?3 and 10^?2 M NaCl. The aim was to follow the structure of the suspensions in a rotational rheometer during the measurements and observe wall depletion and other factors that can interfere with the rheological results. The stepped flow measurements were performed using a transparent cylindrical measuring system and combining the optical information to rheological parameters. OCT allows imaging in radial direction from the outer geometry boundary to the inner geometry boundary making both the shear rate profile and the structure of the suspension visible through the rheometer gap. Yield stress and maximum wall stress were determined by start-up of steady shear and logarithmic stress ramp methods and they both reflected in the stepped flow measurements. Above yield stress, floc size was inversely proportional to shear rate. Below the yield stress, flocs adhered to each other and the observed apparent constant shear stress was controlled by flow in the depleted boundary layer. With higher ionic strength (10^?2 M NaCl), the combination of yield stress and wall depletion favored the formation of vertical, cylindrical, rotating floc structures (rollers) coupled with a thicker water layer originating at the suspension—inner cylinder boundary at low shear rates.     

Adsorption of Ni(II), Cu(II) and Cd(II) from aqueous solutions by amino modified nanostructured microfibrillated cellulose

The aim of the present study was to investigate the adsorption properties of aminopropyltriethoxysilane (APS) modified microfibrillated cellulose (MFC) in aqueous solutions containing Ni(II), Cu(II) and Cd(II) ions. The modified adsorbents were characterized using elemental analysis, Fourier transform infrared spectroscopy, SEM and zeta potential analysis. The adsorption and regeneration studies were conducted in batch mode using various different pH values and contact times. The maximum removal capacities of the APS/MFC adsorbent for Ni(II), Cu(II), and Cd(II) ions were 2.734, 3.150 and 4.195 mmol/g, respectively. The Langmuir, Sips and Dubinin-Radushkevich models were representative to simulate adsorption isotherms. The adsorption kinetics of Ni(II) Cu(II), and Cd(II) adsorption by APS/MFC data were modeled using the pseudo-first-order, pseudo-second-order and intra-particle diffusion kinetics equations. The results indicate that the pseudo-second-order kinetic equation and intra-particle diffusion model were adequate to describe the adsorption kinetics.     

Recoil-fission tagging of the transfermium nucleus 252No

An in-beam study of the transfermium nucleus ²⁵²No has been performed using the JUROSPHERE II array of germanium detectors coupled to the gas-filled recoil separator RITU. A new technique of recoil-fission tagging was used to extract tagged γ-ray data. Having significant spontaneous fission and α-decay branches, ²⁵²No is an ideal candidate for a comparative study. In a similar manner to α-decay tagging the fission events can be used to obtain γ-ray data. The recoil-fission tagged γ-ray spectrum showed a similar structure to the α-decay tagged γ-ray spectrum. By comparing the α-tagged and fission-tagged spectra and decay curves, it was shown that the spontaneous fission originates from the same initial state as the α decay. This extension of the tagging method allows in-beam spectroscopic data to be obtained from heavy nuclei with significant spontaneous-fission branches.     

Functional characterisation of Fab′-fragments self-assembled onto hydrophilic gold surfaces

Antibody Fab′-fragments have been immobilised on hydrophilic gold by direct self-assembly, and embedded in a matrix of non-ionic hydrophilic polymers, tris(hydroxymethyl)methylacrylamide, carrying lipoate terminal linking groups. Different polymers were synthesised, and co-adsorbed or post-adsorbed between the antibody fragments in order to optimise the antigen binding. Various factors were investigated that influence the activity of the immobilised Fab′-fragments for binding of the antigen, human IgG. The Fab′-fragments were immobilised in dense layers close to monolayer coverage, and the stoichiometric efficiency of immobilisation was up to 30%, with the human IgG also approaching monolayer coverage. The cleaning of the gold surface was a crucial factor in preservation of activity. Besides the usual treatment in hot ammonia/peroxide solution, hot DMSO appeared to be highly effective as a cleaning agent.     

Recoil Beta Tagging: Application to the study of odd-odd near proton drip line nuclei, 74Rb and 78Y

We present a study of low-spin states in ⁷⁴Rb and ⁷⁸Y using the new technique of Recoil Beta Tagging. This yielded new information on ⁷⁴Rb and has provided the first evidence for non-isomeric T= 1 states in ⁷⁸Y.     

Laterally-corrugated ridge-waveguide distributed feedback lasers at 980 nm

The paper presents a simulation-based analysis of laterally-corrugated ridge-waveguide distributed feedback semiconductor lasers emitting at 980 nm. The simulations were performed using software developed in-house and the PICS3D software package from Crosslight Software Inc. The effects of the corrugation geometry, phase-shift section, and mirror reflectivities on single longitudinal mode operation are discussed. The lasers, designed along the guidelines derived from the simulation results, were fabricated by using molecular beam epitaxy for wafer growth and low-cost nano-imprint lithography. They exhibited stable single-mode operation with up to 50 dB side-mode suppression ratio.     

Affinity,Speciation, and Molecular Features of Copper(II) Complexes with a Prion Tetraoctarepeat Domain in Aqueous Solution: Insights into Old and New Results

Characterization of the copper(II) complexes formed with the tetraoctarepeat peptide at low and high metal‐to‐ligand ratios and in a large pH range, would provide a breakthrough in the interpretation of biological relevance of the different metal complexes of copper(II)‐tetraoctarepeat system. In the present work, the potentiometric, UV/Vis, circular dichroism (CD), and electron paramagnetic resonance (EPR) studies were carried out on copper(II) complexes with a PEG‐ylated derivative of the tetraoctarepeats peptide sequence (Ac‐PEG₂₇‐(PHGGGWGQ)₄‐NH₂) and the peptide Ac‐(PHGGGWGQ)₂‐NH₂. Conjugation of tetraoctarepeat peptide sequence with polyethyleneglycol improved the solubility of the copper(II) complexes. The results enable a straightforward explanation of the conflicting results originated from the underestimation of all metal–ligand equilibria and the ensuing speciation. A complete and reliable speciation is therefore obtained with the released affinity and binding details of the main complexes species formed in aqueous solution. The results contribute to clarify the discrepancies of several studies in which the authors ascribe the redox activity of copper(II)‐tetraoctarepeat system considering only the average effects of several coexisting species with very different stoichiometries and binding modes.     

Multistimuli-responsive hydrogels of poly(2-acrylamido-2-methyl-1-propanesulfonic acid) containing graphene

Nanocomposite hydrogels of poly(2-acrylamido-2-methyl-1-propanesulfonic acid) containing graphene were prepared by radical polymerization. Their swelling properties in response to ionic strength and electrical stimuli were assessed. Graphene was obtained through an easy and convenient method lately developed by our research group, which consists in the exfoliation of graphite by sonicating it in a proper solvent medium. It was found that the graphene content influences the swelling properties of hydrogels; in particular, those containing graphene swell more than the filler-free ones; graphene content influences also the swelling ratio variation between the swollen and deswollen states.     

Isonicotinoylhydrazothiazoles and isonicotinoyl‐N4‐substituted thiosemicarbazides: Synthesis,characterization, and anti‐mycobacterial activity

Differently substituted isonicotinoylhydrazothiazoles and isonicotinoyl‐N⁴‐substituted thiosemi‐carbazides have been prepared and characterized by means of elemental analysis, ¹H‐NMR, ¹³C‐NMR, and Mass spectrometry. All the synthesised compounds have been screened in order to evaluate their antimycobacterial activity in vitro. Some of the new compounds showed activity towards M. tuberculosis H37R and M. Marinum in the millimolar range.