Quantum and Classical in Adiabatic Computation

Adiabatic transport provides a powerful way to manipulate quantum states. By preparing a system in a readily initialised state and then slowly changing its Hamiltonian, one may achieve quantum states that would otherwise be inaccessible. Moreover, a judicious choice of final Hamiltonian whose groundstate encodes the solution to a problem allows adiabatic transport to be used for universal quantum computation. However, the dephasing effects of the environment limit the quantum correlations that an open system can support and degrade the power of such adiabatic computation. We quantify this effect by allowing the system to evolve over a restricted set of quantum states, providing a link between physically inspired classical optimisation algorithms and quantum adiabatic optimisation. This new perspective allows us to develop benchmarks to bound the quantum correlations harnessed by an adiabatic computation. We apply these to the D-Wave Vesuvius machine with revealing - though inconclusive - results

Influence of Y2O3 addition on the mechanical and oxidation behaviour of carbon fibre reinforced ZrB2/SiC composites

The influence of Y2O3 addition on the microstructure, thermo-mechanical properties and oxidation resistance of carbon fibre reinforced ZrB2/SiC composites was investigated. Y2O3 reacted with oxide impurities present on the surface of ZrB2 and SiC grains and formed a liquid phase, effectively lowering the sintering temperature and allowing to reach full density at 1900 °C. The presence of a carbon source (fibres) led to additional reactions which resulted in the formation of new secondary phases such as yttrium boro-carbides. Mechanical properties were significantly enhanced compared to the un-doped composite. Further tests at high temperatures resulted in strength increase up to 700 MPa at 1500 °C which was attributed to stress relaxation. Oxidation tests carried out at 1500 °C and 1650 °C in air showed that the presence of the Y-based secondary phases enhanced the growth of ZrO2 grains, but offered limited protection to oxygen due to the lower availability of surficial SiO2 formed from SiC

Description of the topographical changes associated to the different stages of the DsbA catalytic cycle.

This paper provides a description of the surface topography of DsbA, the bacterial disulfide-bond forming enzyme, in the different phases of its catalytic cycle. Three representative states, that is, oxidized and reduced protein and a covalent complex mimicking the DsbA-substrate disulfide intermediate, have been investigated by a combination of limited proteolysis experiments and mass spectrometry methodologies. Protease-accessible sites are largely distributed in the oxidized form with a small predominance inside the thioredoxin domain. Proteolysis occurs even in secondary structure elements, revealing a significant mobility of the protein. Many cleavage sites disappear in the reduced form and most of the remaining ones appear with strongly reduced kinetics. The protein within the complex shows an intermediate behavior. This variation of flexibility in DsbA is probably the determining factor for the course of its catalytic cycle. In particular, the great mobility of the oxidized protein might facilitate the accommodation of its various substrates, whereas the increasing rigidity from the complexed to the reduced form could help the release of oxidized products. The formation of the complex between PID peptide and DsbA does not significantly protect the enzyme against proteolysis, reinforcing the results previously obtained by calorimetry concerning the weakness of their interaction. The few cleavage sites observed, however, are in favor of the presence of the peptide in the binding site postulated from crystallographic studies. As for the peptide itself, the proteolytic pattern and the protection effect exerted by DsbA could be explained by a preferential orientation within the binding site

Toughening effect of non-periodic fiber distribution on crack propagation energy of UHTC composites

Different configurations of continuous carbon fiber-reinforced ultrahigh temperature ceramics (UHTCs), by combining coatings and matrix, were produced via electrophoretic deposition (EPD) and slurry infiltration. The toughening of non-periodic fiber distribution induced by the EPD process was investigated through work of fracture analysis. The results show that a non-periodic fiber distribution results in toughness increase from 8 MPa√m to 11 MPa√m with respect to a periodic fiber distribution. This toughness improvement does not strongly affect the flexural strength, which is mainly related to the fiber volumetric amount. It is shown that the assembling of carbon fibers into bundles (i.e. by dispersing the fibers with a non-periodic distribution) increases the crack propagation energy dissipated on the crack-wake from 0.5 kJ/m2 to 1 kJ/m2, which can be mainly ascribed to the fiber/bundle pull-out. On the other hand, the energy dissipated on the crack-tip (as fiber/matrix debonding) is fiber distribution-independent and increases from 0.3 kJ/m2 to 0.4 kJ/m2 with increasing the fiber amount from 33 vol% to 40 vol%. Finally, WoF analysis is proposed as test to evaluate pull-out toughening instead of push-in and push-out tests

Role of disorder in the size-scaling of material strength

We study the sample size dependence of the strength of disordered materials with a flaw, by numerical simulations of lattice models for fracture. We find a crossover between a regime controlled by the fluctuations due to disorder and another controlled by stress-concentrations, ruled by continuum fracture mechanics. The results are formulated in terms of a scaling law involving a statistical fracture process zone. Its existence and scaling properties are only revealed by sampling over many configurations of the disorder. The scaling law is in good agreement with experimental results obtained from notched paper samples.Comment: 4 pages 5 figure

Development of UHTCMCs via water based ZrB2 powder slurry infiltration and polymer infiltration and pyrolysis

Cf/ZrB2-SiC ultra-high temperature composites were manufactured via aqueous slurry impregnation coupled with polymer infiltration and pyrolysis, using a allylhydrido polycarbosilane precursor. For the first time we used ultra-high modulus pitch-based carbon fibres for the PIP process, investigating three different architectures, 0/0°, 0/90°, and 2D. Microstructure, mechanical properties and oxidation resistance in air at 1650 °C were investigated. As expected, the mechanical properties showed the tendency to decrease with increase of the preforms complexity, due to the higher amount of flaws and residual stresses. For instance, the flexural strength was approaching 500 MPa for 0/0°, 370 MPa for 0/90° and 190 MPa for 2D. The materials showed an optimal resistance to oxidation at 1650 °C thanks to formation of a viscous borosilicate glass that guaranteed a self-healing functionality

Up to 4 × 192 LTE-A radio waveforms transmission in a point to multipoint architecture for massive fronthauling solutions

In this work, a novel point-to-multipoint fronthauling architecture based on the use of a Multi-Output Erbium Doped Fibre Amplifier (MO-EDFA), to deliver several digital signal processing (DSP) aggregated analogue radio waveforms, is proposed and experimentally analysed. The transmission of 4x192 20 MHz radio waveforms, according to the DSP-aggregated fronthauling (DSP-AF) Frequency Division Multiplexed (FDM) architecture originally proposed in [1]. Using the MO-EDFA, we are able to feed up to 24 remote radio head (RRH) units, experimentally demonstrating successful transmission over a link with up to 25 dB of optical path losses, including 37 km of single mode fibre

FMECA methodology applied to two pathways in an orthopaedic hospital in Milan.

INTRODUCTION: Adverse events pose a challenge to medical management: they can produce mild or transient disabilities or lead to permanent disabilities or even death; preventable adverse events result from error or equipment failure. METHODS: IRCCS Istituto Ortopedico Galeazzi implemented a clinical risk management program in order to study the epidemiology of adverse events and to improve new pathways for preventing clinical errors: a risk management FMECA-FMEA pro-active analysis was applied either to an existing clinical support pathway or to a new process before its implementation. RESULTS: The application of FMEA-FMECA allowed the clinical risk unit of our hospital to undertake corrective actions in order to reduce the adverse events and errors on high-risk procedure used inside the hospitals

Effect of PAN-based and pitch-based carbon fibres on microstructure and properties of continuous Cf/ZrB2-SiC UHTCMCs

In this paper the microstructure and mechanical properties of two different Cf/ZrB2-SiC composites reinforced with continuous PyC coated PAN-derived fibres or uncoated pitch-derived fibres were compared. Pitch-derived carbon fibres showed a lower degree of reaction with the matrix phase during sintering compared to PyC/PAN-derived fibres. The reason lies in the different microstructure of the carbon. The presence of a coating for PAN-derived fibres was found to be essential to limit the reaction at the fibre/matrix interface during SPS. However, coated bundles were more difficult to infiltrate, resulting in a less homogeneous microstructure. As far as the mechanical properties are concerned, specimens reinforced with coated PAN-derived fibres provided higher strengths and damage tolerance than uncoated pitch-derived fibres, due to the higher degree of fibre pull-out. On the other hand, the weaker fibre/matrix interface resulted in lower interlaminar shear, off-axis strength and ablation resistance

Reactive melt infiltration of carbon fibre reinforced ZrB2/B composites with Zr2Cu

The microstructure and mechanical properties of carbon fibre reinforced ZrB2 composites produced by slurry infiltration and consolidated by reactive melt infiltration were investigated. Fibres were preliminary infiltrated with ZrB2/B slurries with varying ZrB2/B ratios. Then the composites were infiltrated with Zr2Cu melt at 1200 °C under vacuum. Boron was chosen as the reactant phase, while raw ZrB2 was added as a filler to prevent excessive swelling. With increase of boron content the infiltration becomes more difficult due to the reaction of alloy and boron. The boron is completely converted to nano ZrB2 grains. Some ZrC is produced from the side reaction between Zr2Cu and the carbon fibre, resulting in reduction of fibre diameter. The flexural strength increased from 360 to 560 MPa with the increase of boron content, while KIc amounted to 10 MPa⋅m0.5 but was affected by large scatter. The mechanical behaviour was mostly dominated by matrix properties