Hydrostatic lubrication with cryogenic fluids

The paper presents a computational procedure that can be useful in assessing the main performance parameters (load, flow rate, attitude angle) of hydrostatic journal bearings, without resorting to full numerical computing. The procedure is based on the ‘lumped resistance method’, which has been extended to take into account turbulence and inertia effects. Comparison with available experimental data shows a pretty reasonable agreement, in spite of the approximations that have been introduced. The procedure has been used to design a number of bearings that have been tested in order to study the possible replacement of rolling bearings in cryogenic turbopumps.     

A “Probe-Lift” MOS-Capacitor Technique for Measuring Very Low Oxide Leakage Currents and Their Effect on Generation Lifetime Extraction

A new method for precisely measuring low gate oxide currents by measuring the charge leaking through the oxide in a pulsed metal oxide semiconductor capacitor (MOS-C) is presented. Using basic equipment, it is possible to measure currents less than 10 fA/cm² . The relevant theory is developed to use these capacitance-time data to extract an approximate leakage current and the effect on the extracted generation lifetime. The technique is simple and requires the same equipment used for pulsed MOS-C generation lifetime measurements. Experimental results are presented, which are consistent with theory.     

Space anthropology: physical and cultural adaptation in outer space

Humans are the product of biologic and cultural adaptation to our Planet achieved over million years of Primates and Hominids species evolution which has led us to a specific development of intelligence, speech, and manual capability. Interface usability mainly depends on human characteristics that are also modified by variations in the environment. In outer space, body shapes may be different, things may not be in the expected place and models of conventional social relationships may be hardly transferred to prolonged missions. The process known as exaptation, according to which traits developed by a species as a response to a specific need are later “recycled” with new functions in a different environment, will be considered. Biologic and cultural built-in mechanisms belonging to our past cannot be left out in the analysis of design and man–machine interface in the Outer Space.     

On a non-Markov neuronal model and its approximations

Single neuron's activity modeling is considered with reference to some earlier contributions in which a non-Markov Gaussian process is assumed to describe the time course of the neuron's membrane potential. After re-formulating the problem in a rigorous framework and pinpointing the limits of validity of such a model, the available results on the firing probability density are compared with those obtained by us by means of an ad hoc numerical algorithm implemented for the leaky integrator diffusion firing model and with some data constructed by a simulation procedure of non-Markov Gaussian processes with pre-assigned covariances. Throughout this paper, the notion of 'correlation time' plays a fundamental role for the neuronal coding process modeling.     

Fabrication of biocompatible monolithic microchannels with high pressure‐resistance using direct polymerization of PEG‐modified PMMA

Withstanding high pressures in polymeric microchannels is an important requirement for many biological applications. Here, a simple direct polymerization through a polyester photomask is applied to obtain monolithic polyethylene glycol (PEG)‐modified poly(methyl methacrylate) (PMMA) (PEGMA) microchannels, showing the ability to withstand pressure up to 12 MPa in burst pressure tests. The ability of withstanding high pressures is observed to increase with increasing ratio between the thickness of the cover polymer layer forming the microchannel lid and the width of the microchannel. A simplified finite element modeling model of the burst pressure test is set up to interpret the experimental findings. The outcomes of the modeling activity, along with direct scanning electron microscopy observation of the fracture surfaces, confirm the effectiveness of the polymerization method for the production of monolithic PEGMA microchannels. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 41031.     

H-bonding driven assembly of colloidal Au nanoparticles on nanostructured poly(styrene-b-ethylene oxide) block copolymer templates

A facile, cost-effective, and general solution-based “bottom-up” method for nanopatterning dense arrays of colloidal Au nanoparticles (NPs) has been developed. The organization of the NPs has been successfully achieved onto a microphase-separated poly(styrene-block-ethylene oxide) (PS-b-PEO) block copolymer (BCP) thin film which acts as structural template. The NP assembly process occurs by incubating the BCP films in dispersions of the ex situ synthesized Au NPs, not requiring any chemical pre-treatment or activation step of the copolymer surface, and has demonstrated to be distinctively controlled by multiple, cooperative, and selective hydrogen bonding interactions between hydroxyl functionalities of the capping molecules coating the Au NP surface and the hydrophilic PEO block. The effect of incubation time and concentration of NPs on the selectivity of the assembly has been investigated by atomic force and scanning electron microscopy. The results show that the BCP pattern is preserved after decoration with the Au NPs. The fabricated nanopatterns are good candidates for nanostructure integration in sensing and optoelectronic applications, as well as in memory devices and photonic systems. Moreover, the proposed immobilization protocol represents a model system that can be extended to other NPs having different compositions and surface chemistries.     

Myrtle hydroalcoholic extracts obtained from different selections of Myrtus communis L.

Hydroalcoholic extracts obtained from myrtle berries of five different selections were studied to obtain unique clones. During the typical 40 day maceration period, dry matter, pH, colour, and anthocyanins, were analyzed. Variability among myrtle selections was observed both in fresh berries (yield berries/plant, weight of the berries, number and weight of seeds per berry) and in the hydroalcoholic extract physical–chemical characteristics (dry matter, colour intensity, tint and anthocyanins). Reversed-phase high performance liquid chromatography (RP-HPLC) analysis with photodiode array detection (PDA) was used for anthocyanins characterization in myrtle hydroalcoholic extracts. Anthocyanin qualitative composition was the same in all selections, but varied strongly in its total amount. D was the selection with the characteristics most suitable for industrial use.     

Fabrication of Sealed µ‐Channels Through a Fast and Reliable Photopolymerization Process

Sealed microchannels and simple microfluidic networks with good efficiency and controlled quality of the structures were developed from a photocurable and PCR‐compatible material based on a PEG–methacrylate oligomers mixture. The influence of UV exposure time and of conversion degree on microchannel geometry were studied to obtain structures with controlled depth, vertical sidewalls, and good reproducibility. The roughness inside channels was as low as 50–100 nm, less than that typical of alternative LOC prototyping techniques such as micromilling. Efficient channel sealing was also achieved without using a different sealing material. Surface smoothness and hydrophilicity (static contact angle below 60°) allow spontaneous water flow inside the channels by capillarity without need of surface treatments.