Measurements of Transient Phenomena with Digital Oscilloscopes

In this paper, the effects of sampling upon rise time measurements with a digital oscilloscope are considered. In particular, the use of linear interpolation for estimating signal rise times is discussed, and its effects are analyzed for various step signals. A simple expression is derived, which accurately models the sampling and linear interpolation contributions to the overall rise time measurement error. Using these results, a correction formula is proposed, and its applicability is discussed

FEM Applied to Hydrodynamic Bearing Design

The present chapter is aimed to provide the theoretical foundation of FEM mass- and energy-conserving models as well as to report their application to the ThermoHydroDynamic (THD) and/or ThermoElastoHydroDynamic (TEHD) analysis of different bearing types. Author\u2019s original contributions to the simulation methods are explained. They include the FEM groove-mixing theory, the SUPG stabilization of the conservation equations and the "quasi-3D" approach to the thermal problem. The theoretical construct is useful to enable the analysts to manage the models and to understand the responses. The application examples are relevant to both journal and axial bearings with fixed and tilting pads, in order to demonstrate the high flexibility of the method. With few modifications the presented method can be applied to the design of several types of bearings in both steady and dynamic loading conditions. The scope of the paper is anyway limited to the analysis of steadily-loaded bearings working in laminar lubrication regime

Comparative Analysis of Bearings for Micro-GT: An Innovative Arrangement

Microgas turbines are a widespread technology in cogenerative and propulsion applications. Bearings are a key factor in their design and development. The aim of the present research work is the development of the support system for a typical microturbine intended for power generation. To this goal, the present chapter defines the typical requirements of the machine and, afterward, describes the different technologies available to develop the support system of a reliable microturbine. Conventional (rolling element and oil-film) supports and cutting-edge (magnetic, aerodynamic, and aerostatic) bearings are reviewed. Particularly, their suitability to the operating conditions is compared by means of a literature review and elaboration of the relevant data. By analyzing all this information, a new concept for the design of a micro-GT support system is devised. Instead of using a single type of bearing as usual, the new system includes different types in order to take advantage of the best characteristics of each one and, simultaneously, to minimize the effects of the relevant flaws. The innovative support system requires a suitable bearing arrangement, which is compared with the conventional ones. The conceptual design of the innovation is completed by a discussion of its advantages, drawbacks, and prospective improvements

A new record of Craspedacusta sowerbii, Lankester 1880 (Cnidaria, Limnomedusae) in Northern Italy

A new record of the freshwater jellyfish Craspedacusta sowerbii in Northern Italy is reported. The medusae bloom occurred in a small oligo-mesotrophic artificial lake during July, 2009. At the time of sampling, the medusae were all immature, reached low density and showed feeding preference towards the Daphnia complex of species, the most abundant zooplanktonic species in the lake. Negative feeding selectivity towards small Rotifera was demonstrated. The occasional occurrence of a C. sowerbii bloom in this lake suggests the distribution range of this species may be largely underestimated, and its potential impact on the zooplankton community remains unknown

Aggregation of the Acylphosphatase from Sulfolobus solfataricus: the folded and partially unfolded states can both be precursors for amyloid formation.

Protein aggregation is associated with a number of human pathologies including Alzheimer's and Creutzfeldt-Jakob diseases and the systemic amyloidoses. In this study, we used the acylphosphatase from the hyperthermophilic Archaea Sulfolobus solfataricus (Sso AcP) to investigate the mechanism of aggregation under conditions in which the protein maintains a folded structure. In the presence of 15-25% (v/v) trifluoroethanol, Sso AcP was found to form aggregates able to bind specific dyes such as thioflavine T, Congo red, and 1-anilino-8-naphthalenesulfonic acid. The presence of aggregates was confirmed by circular dichroism and dynamic light scattering. Electron microscopy revealed the presence of small aggregates generally referred to as amyloid protofibrils. The monomeric form adopted by Sso AcP prior to aggregation under these conditions retained enzymatic activity; in addition, folding was remarkably faster than unfolding. These observations indicate that Sso AcP adopts a folded, although possibly distorted, conformation prior to aggregation. Most important, aggregation appeared to be 100-fold faster than unfolding under these conditions. Although aggregation of Sso AcP was faster at higher trifluoroethanol concentrations, in which the protein adopted a partially unfolded conformation, these findings suggest that the early events of amyloid fibril formation may involve an aggregation process consisting of the assembly of protein molecules in their folded state. This conclusion has a biological relevance as globular proteins normally spend most of their lifetime in folded structures

Phylogenetic relationships and revision of the genus Blastomussa (Cnidaria: Anthozoa: Scleractinia) with description of a new species

The Indo-Pacific coral genus Blastomussa (Cnidaria: Anthozoa: Scleractinia) includes three species, i.e., B. merleti, B. wellsi, and B. loyae. Following the re-examination of relevant type material, other museum specimens, and the study of newly sampled corals, the genus is revised and the new species B. vivida is described. The new species differs from its congeners by being encrusting, having coralla with a cerioid corallite arrangement and much larger corallites. In vivo, the expanded polyp mantle is fleshy and characterised by bright, vivid colours. Specimens were sampled in New Caledonia, northern Papua New Guinea, Sabah (northern Malaysia), Brunei Darussalam and the east coast of Peninsular Malaysia. Additional records from Southeast Asia and the western Pacific were obtained through the study of museum collections and published illustrations of living animals in situ: Japan, Vietnam, Indonesia, Philippines, and Australia. The new species appears widespread and has so far been misidentified as B. wellsi, which has smaller corallites, less septa, and a phaceloid corallite arrangement. The phylogenetic relationships within the genus Blastomussa and with other genera were investigated by analyses of their nuclear and mitochondrial DNA. These other genera are Parasimplastrea, Plerogyra, Physogyra, all currently incertae sedis in the Robust clade of Scleractinia as a result of molecular coral systematics, and Nemenzophyllia, whose phylogenetic position is examined for the first time. Representatives of all these genera are characterised by fleshy polyps with well-developed and expandable mantles. They are all closely related and form a strongly supported clade. The results of the molecular analyses provide evidence for Blastomussa's monophyly and show that the new B. vivida is a distinct species, which is most closely related to B. wellsi. Furthermore, the only known extant species of the genus Parasimplastrea appears to be embedded within the Blastomussa clade, thus prompting its taxonomic revision. Because Blastomussa is closely related to the monospecific Nemenzophyllia, the affinities of their polyp and corallite morphology are discussed. Although polyp morphology and molecular data suggest that Blastomussa, Plerogyra, Physogyra, and Nemenzophyllia could constitute a new scleractinian family, the macro and micromorphology of their skeletons need to be examined before a family diagnosis can be formulated

Investigating the Effects of Mutations on Protein Aggregation in the Cell

The conversion of peptides and proteins into highly ordered and intractable aggregates is associated with a range of debilitating human diseases and represents a widespread problem in biotechnology. Protein engineering studies carried out in vitro have shown that mutations promote aggregation when they either destabilize the native state of a globular protein or accelerate the conversion of unfolded or partially folded conformations into oligomeric structures. We have extended such studies to investigate protein aggregation in vivo where a number of additional factors able to modify dramatically the aggregation behavior of proteins are present. We have expressed, in Escherichia coli cells, an E. coli protein domain, HypF-N. The results for a range of mutational variants indicate that although mutants with a conformational stability similar to that of the wild-type protein are soluble in the E. coli cytosol, variants with single point mutations predicted to destabilize the protein invariably aggregate after expression. We show, however, that aggregation of destabilized variants can be prevented by incorporating multiple mutations designed to reduce the intrinsic propensity of the polypeptide chain to aggregate; in the cases discussed here, this is achieved by an increase in the net charge of the protein. These results suggest that the principles being established to rationalize aggregation behavior in vitro have general validity for situations in vivo where aggregation has both biotechnological and medical relevance

Multi-phase and Multi-component CFD Analysis of a Load - Sensing Proportional Control Valve

The paper analyzes the flow through a directional control valve for load –sensing application by means of a multi-phase and multi-component CFD approach. Numerical modeling includes both cavitation and aeration; in particular, the Rayleigh-Plesset equation and the inertia controlled growth model for bubble formation are adopted. The effects of gas release and vapor formation as well as turbulence on the main valve metering characteristics are investigated. The results show a remarkable influence of the aeration phenomena on the recirculating zones downstream of the metering area and thus on the cavitation onset region

Folding and Aggregation Are Selectively Influenced by the Conformational Preferences of the α-Helices of Muscle Acylphosphatase

The native state of human muscle acylphosphatase (AcP) presents two alpha-helices. In this study we have investigated folding and aggregation of a number of protein variants having mutations aimed at changing the propensity of these helical regions. Equilibrium and kinetic measurements of folding indicate that only helix-2, spanning residues 55-67, is largely stabilized in the transition state for folding therefore playing a relevant role in this process. On the contrary, the aggregation rate appears to vary only for the variants in which the propensity of the region corresponding to helix-1, spanning residues 22-32, is changed. Mutations that stabilize the first helix slow down the aggregation process while those that destabilize it increase the aggregation rate. AcP variants with the first helix destabilized aggregate with rates increased to different extents depending on whether the introduced mutations also alter the propensity to form beta-sheet structure. The fact that the first alpha-helix is important for aggregation and the second helix is important for folding indicates that these processes are highly specific. This partitioning does not reflect the difference in intrinsic alpha-helical propensities of the two helices, because helix-1 is the one presenting the highest propensity. Both processes of folding and aggregation do not therefore initiate from regions that have simply secondary structure propensities favorable for such processes. The identification of the regions involved in aggregation and the understanding of the factors that promote such a process are of fundamental importance to elucidate the principles by which proteins have evolved and for successful protein design