Vibration analysis of rotating systems with open and breathing cracks

This paper is concerned with vibration analysis of rotating systems containing cracks. The flexibility matrix of cracked element is calculated with modified integration limits which is more accurate than conventional methods. The effect of this modification on the coefficients of flexibility matrix is presented for a simple rotor system containing open crack. To model the crack breathing behavior, a new finite element approach is introduced and implemented. Then, the dynamic response of a rotor with a breathing crack is evaluated by using the frequency/time domain approach (short time Fourier transform). The ability of short time Fourier transform to detect small cracks is investigated and compared with the transient response. The results provide a possible basis for an on-line monitoring system.     

Electrodeposition iron target for the cyclotron production of 55Co in labeling proteins

Natural iron electrodeposition on copper substrate was studied with the aim of production of cobalt-55 radionuclide. ⁵⁵Co seems well suited for PET imaging due to its high abundance of positron decay (I _β+ = 76%), its relatively long half-life (T _1/2 = 17.5 h) and its mean positron energy (E _avg = 570 keV). The electrodeposition experiments were carried out by chloride bath. Operating parameters such as pH, temperature, current density and amount of the electrolyte components are also optimized. The optimum conditions of the iron electrodeposition were follows: 8 g/L FeCl₂, 2 g/L CaCl₂, pH = 1, DC current density of 21.3 A/dm² with a bath temperature of 75 °C temperature and 20% current efficiency. SEM photomicrographs demonstrated fine-grained structure of the deposit obtained from the optimum bath. The electroplated iron-target was irradiated with 29.5 MeV protons at current of 100 μA for 1 h and yields of about 31.25 MBq/μAh were experimentally obtained.     

3D printed titanium micro-bore columns containing polymer monoliths for reversed-phase liquid chromatography

The potential of 3D selective laser melting (SLM) technology to produce compact, temperature and pressure stable titanium alloy chromatographic columns is explored. A micro bore channel (0.9 mm I.D. × 600 mm long) was produced within a 5 × 30 × 30 mm titanium alloy (Ti–6Al–4V) cuboid, in form of a double handed spiral. A poly(butyl methacrylate-co-ethyleneglycoldimethacrylate) (BuMA-co-EDMA) monolithic stationary phase was thermally polymerised within the channel for application in reversed-phase high-performance liquid chromatography. The prepared monolithic column was applied to the liquid chromatographic separation of intact proteins and peptides. Peak capacities of 69–76 (for 6–8 proteins respectively) were observed during isothermal separation of proteins at 44 °C which were further increased to 73–77 using a thermal step gradient with programmed temperature from 60 °C to 35 °C using an in-house built direct-contact heater/cooler platform based upon matching sized Peltier thermoelectric modules. Rapid temperature gradients were possible due to direct-contact between the planar metal column and the Peltier module, and the high thermal conductivity of the titanium column as compared to a similar stainless steel printed column. The separation of peptides released from a digestion of E.coli was also achieved in less than 35 min with ca. 40 distinguishable peaks at 210 nm.     

On the symmetry and topology of plasmonic eigenmodes in heptamer and hexamer nanocavities

Plasmonics is expected to play a key role in nanotechnology, leading to intriguing routes in many engineering and biological applications. Recently, it has been realized that toroidal resonances could be an alternative to electric and magnetic resonances, which have governed the innovation of plasmonic applications so far. In a previous contribution, we proved the existence of toroidal moments in an oligomeric void-plasmonic structure [1]. In this article, we investigate the role of topology and symmetry in decomposing the various dipolar, quadrupolar, and toroidal moments, using energy-filtering transmission electron microscopy supported by three-dimensional finite-difference time-domain method simulations. The consequences of changing the topology on the toroidal character are discussed by comparing results obtained from nanoholes forming heptamer and hexamer nanocavity systems that were drilled into a thin silver film.     

Epoxy-based monoliths for capillary liquid chromatography of small and large molecules

A versatile epoxy-based monolith was synthesised by polycondensation polymerisation of glycidyl ether 100 with ethylenediamine using a porogenic system consisting of polyethylene glycol, M _w?=?1000, and 1-decanol. Polymerisation was performed at 80 °C for 22 h. A simple acid hydrolysis of residual epoxides resulted in a mixed diol-amino chemistry. The modified column was used successfully for hydrophilic interaction liquid chromatography (HILIC) of small molecule probes such as nucleic acid bases and nucleosides, benzoic acid derivatives, as well as for peptides released from a tryptic digest of cytochrome c. The mixed-mode chemistry allowed both hydrophilic partitioning and ion-exchange (IEX) interactions to contribute to the separation, providing flexibility in selectivity control. Residual epoxide groups were also exploited for incorporating a mixed IEX chemistry. Alternatively, the surface chemistry of the monolith pore surface rendered hydrophobic via grafting of a co-polymerised hydrophobic hydrogel. The inherent hydrophilicity of the monolith scaffold also enabled high performance separation of proteins under IEX and hydrophobic interaction modes and in the absence of non-specific interactions.     

A variance bound for a general function of independent noncommutative random variables

The main purpose of this paper is to establish a noncommutative analogue of the Efron-Stein inequality, which bounds the variance of a general function of some independent random variables. Moreover, we state an operator version including random matrices, which extends a result of D. Paulin et al., [Ann. Probab. 44(5) (2016), 3431–3473]. Further, we state a Steele type inequality in the framework of noncommutative probability spaces.