8 research outputs found
The influence of aluminium additions on titanium during machining through the application of a novel orthogonal cutting test method
No full textDue to the high production rates of civil aircraft the demands for increased rates of production through high speed machining are ever increasing. A lack of consistency in the current practices for determining `machinability' means that a bespoke trial is needed to ascertain whether a particular combination of material, tool and machining parameters yields a sufficiently beneficial outcome. The current approach of large scale trials, while effective, is inefficient and costly to OEMs. Most significantly, with the aerospace industries desire to build engines outside the capabilities of current alloys, conventional machining trials cannot be conducted on new alloys that have yet to reach production scale due to the material quantities required in large scale trials. With regard to titanium alloys, the majority of alloys contain some level of aluminium as a major addition.
A research programme has been undertaken to investigate the influence of aluminium on the sub-surface deformation of Ti-xAl binary alloys during high speed machining processes with a view to developing a testing method for determining `machinability'. Such a novel test method would fast track the current inefficient and uneconomical approach. Microstructural analysis of the region immediately below the machined surface has been performed for high speed milled material, focusing on quantifying the depth to which deformation occurs and the dominant plastic deformation mode by backscatter electron imaging and light microscopy. The influence of aluminium was measured through the penetration of the severe plastic deformation region and twin depth penetration and showed that the behaviour was parabolic, with Ti - 4 wt.\% Al showing the maximum level of deformation. The resultant plastic deformation from high speed milling also causes the near surface material to undergo a crystallographic reorientation, demonstrating characteristics of a simple shear process. Comparisons were made with a well established simple shear test method, axisymmetric compression testing, analysing the deformation behaviour, from high speed milling, with the mechanical behaviour of axisymmetric compressions. Use of work hardening principles, traditionally applied to FCC materials, were used to identify characteristics that exhibit trends comparable to those observed during high speed milling, in contrast to conventional mechanical behaviours such as yield stress. A novel orthogonal cut test was successfully developed to generate deformation behaviour from high speed milling and flow behaviour from axisymmetric compression tests in a single test method. This suggests the potential to incorporate `machinability' testing during alloy development rather then a final test once large scale production has commenced
The effect of morning or evening fasted cycling on gastrointestinal function and appetite and metabolic responses in healthy males with overweight
No full textCombining fasting with exercise may influence gastric emptying rate (GER) and provide benefits to weight management and metabolic health. Furthermore, the time of day in which exercise is performed may also influence these variables. The aim was to investigate if fasting or fed exercise at different times of the day would alter GER, appetite and metabolic responses. Twelve males with overweight completed four experimental trials in a randomised crossover fashion involving cycling exercise in the morning fasted (FASTED‐AM), evening fasted (FASTED‐PM) and after a standardised meal in the morning (FED‐AM) and evening (FED‐PM). GER of a semi‐solid meal was measured using the 13C‐breath test for 2 h. Appetite hormones, metabolic markers and subjective appetite were measured throughout, with energy intake (EI) monitored for the following 24 h. No difference was observed for GER between trials. No differences were seen between trials for appetite hormone responses except pancreatic polypeptide hormone incremental area under the curve (iAUC) was greater in FED‐PM compared to FASTED‐AM and FASTED‐PM (P < 0.05). Glucose concentrations were greater in the postprandial period of FASTED‐PM compared to all trials (P < 0.05). No differences in other metabolic marker responses were seen between trials. GER in individuals with overweight was not sensitive to a diurnal variation following fasted or fed exercise, and an acute bout of fasted exercise did not evoke compensatory effects on appetite responses or 24 h EI. Glucose control may be impaired with FASTED‐PM exercise. Future work is required to assess the long‐term impact of fasted exercise on gastrointestinal function, appetite regulation and metabolic health
Delocalization transition for the Google matrix
No full text4 pages, 5 figures. Research done at http://www.quantware.ups-tlse.fr/International audienceWe study the localization properties of eigenvectors of the Google matrix, generated both from the World Wide Web and from the Albert-Barabasi model of networks. We establish the emergence of a delocalization phase for the PageRank vector when network parameters are changed. In the phase of localized PageRank, a delocalization takes place in the complex plane of eigenvalues of the matrix, leading to delocalized relaxation modes. We argue that the efficiency of information retrieval by Google-type search is strongly affected in the phase of delocalized PageRank
A hamiltonian to obtain a global frequency analysis of all the vibrational bands of ethane
No full textThe interest in laboratory spectroscopy of ethane stems from the desire to understand the methane cycle in the atmospheres of planets and their moons and from the importance of ethane as a trace species in the terrestrial atmosphere. Solar decomposition of methane in the upper part of these atmospheres followed by a series of reactions leads to a variety of hydrocarbon compounds among which ethane is often the second most abundant species. Because of its high abundance, ethane spectra have been measured by Voyager and Cassini in the regions around 30, 12, 7, and 3 m. Therefore, a complete knowledge of line parameters of ethane is crucial for spectroscopic remote sensing of planetary atmospheres. Experimental characterization of torsion-vibration states of ethane lying below 1400 cm have been made previously \footnote{N. Moazzen-Ahmadi and J. Norooz Oliaee, J. Quant. Spectrosc. Radiat. Transfer, submitted.}, but extension of the Hamiltonian model for treatment of the strongly perturbed \nub{8} fundamental and the complex band system of ethane in the 3 micron region requires careful examination of the operators for many new torsionally mediated vibration-rotation interactions. Following the procedures outlined by Hougen \footnote{J.T. Hougen, Can. J. Phys., 42, 1920 (1964)}{} \footnote{J. T. Hougen, Can. J. Phys., 43, 935 (1965)}, we have re-examined the transformation properties of the total angular momentum, the translational and vibrational coordinates and momenta of ethane, and for vibration-torsion-rotation interaction terms constructed by taking products of these basic operators. It is found that for certain choices of phase, the doubly degenerate vibrational coordinates with and symmetry can be made to transform under the group elements in such a way as to yield real matrix elements for the torsion-vibration-rotation couplings whereas other choices of phase may require complex algebra. In this talk, I will discuss the construction of a very general torsion-vibration-rotation Hamiltonian for ethane, as well as the prospect for using such a Hamiltonian to obtain a global frequency analysis (based in large part on an extension of earlier programs and ethane fits from our laboratory) of all the vibrational bands of ethane at or below the 3-micron region.Made available in DSpace on 2017-01-26T21:39:12Z (GMT). No. of bitstreams: 3
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Previous issue date: 2016-06-2
GC–MS characterisation and biological activity of essential oils from different vegetative organs of <i>Plectranthus barbatus</i> and <i>Plectranthus caninus</i> cultivated in north Italy
No full text<div><p>Essential oils (EOs) from the roots, stems and leaves of <i>Plectranthus barbatus</i> (A) and <i>Plectranthus</i><i>caninus</i> (B), cultivated in north Italy, were obtained by steam distillation and chemically characterised by gas chromatography–mass spectrometry. The highest yields were obtained from roots (268.15 and 673.60 mg/kg from A and B), followed by leaves (64.34 and 26.65 mg/kg) and stems (19.76 and 18.63 mg/kg). A total of 128 structures were identified in A and 121 in B. Fe<sup>++</sup> chelating and antiradical activities (DPPH and ABTS) were evaluated: root and stem EOs showed the strongest activities, while EOs from leaves did not show relevant activities. All EOs were tested for their <i>in vitro</i> antimicrobial activity, showing optimal growth-inhibition in antibiogram (∅>35 mm) and MIC tests (32–64 μg/mL) against <i>Candida albicans</i>, while EOs from leaves of both species showed a good activity (25 < ∅ < 34 mm, MIC 64–128 μg/mL) against <i>Escherichia coli</i>.</p></div
黒質の神経メラニンと被殻のドパミントランスポーターにおける加齢の影響
No full text【目的】MRIで測定した黒質の神経メラニンと、PETで測定したドパミントランスポー
ター(DAT)における加齢の影響調べる。【対象および方法】若年健常者7例（23±2歳
）と高齢健常者5例(67±7歳)を対象とし、 3テスラMRIでT1強調FSEにて, 第4脳室底
に垂直に脳幹の14スライス（2.5mm厚）を撮像した。円形の関心領域を上小脳脚交差
部(DS)と黒質(SN)に置き、両部位の信号比[(SSN-SDS)/S<SUB
>DS*100]を求めて神経メラニンの指標とした。[18F]PE2Iを静脈投
与し、PETにて90分間ダイナミック撮像した。小脳皮質を参照領域としてSimplified
reference tissue model解析して被殻の結合能を求めた。【結果】黒質の神経メラニ
ンの信号比は若年健常者で24.0±2.7、高齢健常者で26.9±2.4で、高齢健常者で高い
傾向がみられた（p ＜ 0.09）。一方、被殻のDAT結合能は若年健常者で4.19±0.50、
高齢健常者で2.26±0.43であり、高齢健常者で低下していた（p ＜ 0.0001）。【結
論】黒質線条体ニューロンは加齢とともに神経メラニンの含有量が増加し、一方、機
能は低下すると考えられた。第52回日本核医学会学術総会conference objec
