Lattice-Dynamic Treatment of Vibrational and Elastic Properties of Cotunnite-Type ZrO2 and HfO2: Comparison with Ambient Pressure Polymorphs

The results of the joint lattice-dynamical model treatment of the vibrational and elastic properties of the cotunnite-type zirconia and hafnia are presented. The model is capable of reproducing the frequencies of the Raman-active vibrations, and provides their symmetry assignment. Also it predicts the position of the infrared-active bands. The model successfully describes the elastic properties of the low-pressure polymorphs, but could not reproduce the bulk modulus of OII-ZrO₂ of 332 GPa obtained from a volume-pressure dependence. The current results give an estimate of the bulk modulus of 254 GPa.     

Ferroelasticity in a metal–organic framework perovskite; towards a new class of multiferroics

A metal–organic framework perovskite, [(CH₂)₃NH₂][Mn(HCOO)₃], exhibits a weakly first order ferroelastic phase transition at ～272 K, from orthorhombic Pnma to monoclinic P2₁/n, and a further transition associated with antiferromagnetic ordering at ～8.5 K. The main structural changes, through the phase transition, are orientational ordering of the azetidium groups and associated changes in hydrogen bonding. In marked contrast to conventional improper ferroelastic oxide perovskites, the driving mechanism is associated with the X-point of the cubic Brillouin zone rather than being driven by R- and M-point octahedral tilting. The total ferroelastic shear strain of up to ～5% is substantially greater than found for typical oxide perovskites, and highlights the potential of the flexible framework to undergo large relaxations in response to local structural changes. Measurements of elastic and anelastic properties by resonant ultrasound spectroscopy show some of the characteristic features of ferroelastic materials. In particular, acoustic dissipation below the transition point can be understood in terms of mobility of twin walls under the influence of external stress with relaxation times on the order of ～10^?7 s. Elastic softening as the transition is approached from above is interpreted in terms of coupling between acoustic modes and dynamic local ordering of the azetidium groups. Subsequent stiffening with further temperature reduction is interpreted in terms of classical strain–order parameter coupling at an improper ferroelastic transition which is close to being tricritical. By way of contrast, there are no overt changes in elastic or anelastic properties near 9 K, implying that any coupling of the antiferromagnetic order parameter with strain is weak or negligible.     

Telomere Length in Metaphase Chromosomes of Human Triploid Zygotes

The human lifespan is strongly influenced by telomere length (TL) which is defined in a zygote—when two highly specialised haploid cells form a new diploid organism. Although TL is a variable parameter, it fluctuates in a limited range. We aimed to establish the determining factors of TL in chromosomes of maternal and paternal origin in human triploid zygotes. Using Q-FISH, we examined TL in the metaphase chromosomes of 28 human triploid zygotes obtained from 22 couples. The chromosomes’ parental origin was identified immunocytochemically through weak DNA methylation and strong hydroxymethylation in the sperm-derived (paternal) chromosomes versus strong DNA methylation and weak hydroxymethylation in the oocyte-derived (maternal) ones. In 24 zygotes, one maternal and two paternal chromosome sets were identified, while the four remaining zygotes contained one paternal and two maternal sets. For each zygote, we compared mean relative TLs between parental chromosomes, identifying a significant difference in favour of the paternal chromosomes, which attests to a certain “imprinting” of these regions. Mean relative TLs in paternal or maternal chromosomes did not correlate with the respective parent’s age. Similarly, no correlation was observed between the mean relative TL and sperm quality parameters: concentration, progressive motility and normal morphology. Based on the comparison of TLs in chromosomes inherited from a single individual’s gametes with those in chromosomes inherited from different individuals’ gametes, we compared intraindividual (intercellular) and interindividual variability, obtaining significance in favour of the latter and thus validating the role of heredity in determining TL in zygotes. A comparison of the interchromatid TL differences across the chromosomes from sets of different parental origin with those from PHA-stimulated lymphocytes showed an absence of a significant difference between the maternal and paternal sets but a significant excess over the lymphocytes. Therefore, interchromatid TL differences are more pronounced in zygotes than in lymphocytes. To summarise, TL in human zygotes is determined both by heredity and parental origin; the input of other factors is possible within the individual’s reaction norm.     

Comparative Coreflood Studies for Precipitation and Adsorption Squeeze with PPCA as the Scales Inhibitor

Comparative adsorption and precipitation squeezes carried out on field core materials demonstrate that significant lifetime enhancement is achievable for precipitation squeeze with respect to more conventional adsorption squeeze. Coreflood tests have been carried out under reservoir conditions (135°C) employing a poly-phosphinocarboxylate (PPCA) as the scales inhibitor. Field treatment simulations, carried out starting from coreflood data and considering the characteristics of a North Sea formation taken as the reference, confirmed the higher performance, in term of squeeze lifetime, of the precipitation squeeze with respect to adsorption. The results pointed out the importance of choosing the appropriate formulation once the operative conditions are known, in order to promote the inhibitor precipitation into the formation. Some implications of these results for the optimization of the precipitation squeeze technology for field applications, with particular emphasis to formation damage, are also discussed.     

Wax Diffusivity: Is It a Physical Property or a Pivotable Parameter?

In order to predict wax deposition problems the key parameter is the wax diffusion coefficient. While it is quite easy to find measured diffusivity values for well-defined compounds at quite low concentrations, very few experimental data are available for wax diffusivity in oil. Most of the literature data are estimated by interpolating experimental data obtained by loop tests and then they are affected by a noticeable uncertainty. In fact this parameter collects the whole uncertainty of the test and the paradoxical situation is that the key parameter ends to be the most error-affected or to be used as a pivotable parameter in “predictive” models. This article describes an experimental procedure to determine the overall diffusivity coefficient of waxes into the oil; the main advantage of this technique is that it allows the direct measure of diffusivity on the oil. Besides it is a very simple and straightforward technique. Results obtained were used to gain insight into the deposition process; the conclusion was that, due to the counter-intuitive diffusivity dependence on temperature, it is likely that noncompositional models available at present are structurally incorrect.     

Sensitivity of static noise margins to random dopant variations in 6-T SRAM cells

The random dopant induced fluctuations of static noise margins (SNM) in 6-T SRAM cells are analyzed by using the formalism of doping sensitivity functions, which show how sensitive the SNM are to variations of the doping concentration at different locations inside the cell. The technique presented in this article is based on a full circuit perturbation theory at the level of each device transport model. It provides important information for the design and optimization of SNM and can capture correlation effects of doping fluctuations inside the same semiconductor device and between more devices. The bias points and the magnitude of random dopant induced fluctuations are computed by solving the Poisson, current continuity, and density–gradient equations for all the devices self-consistently (mixed-mode simulation). Simulation results for a well scaled SRAM cell with 30 nm channel length transistors show that the most sensitive regions to doping fluctuations extend for approximately 10 nm below the oxide/semiconductor interface and are located in the middle of the conduction channels for both the p-channel and n-channel transistors. It is apparent that random dopant induced fluctuations can significantly impinge on the yield and reliability of SRAM circuits and constitute a fundamental limit for further scaling unless these devices are properly optimized.     

Nonlocality as well as rejection of realism are only sufficient (but non-necessary!) conditions for violation of Bell’s inequality

In this review we remind the viewpoint that violation of Bell’s inequality might be interpreted not only as an evidence of the alternative - either nonlocality or “death of reality” (under the assumption the quantum mechanics is incomplete). Violation of Bell’s type inequalities is a well known sufficient condition of probabilistic incompatibility of random variables - impossibility to realize them on a single probability space. Thus, in fact, we should take into account an additional interpretation of violation of Bell’s inequality - a few pairs of random variables (two-dimensional vector variables) involved in the EPR-Bohm experiment are incompatible. They could not be realized on a single Kolmogorov probability space. Thus, one can choose between: (a) completeness of quantum mechanics; (b) nonlocality; (c) “ death of reality”; (d) non-Kolmogorovness. In any event, violation of Bell’s inequality has a variety of possible interpretations. Hence, it could not be used to obtain the definite conclusion on the relation between quantum and classical models.     

Crack growth retardation following the application of an overload cycle using a strip-yield model

Experiments have shown that the application of an overload cycle can act to retard crack growth and even potentially lead to crack arrest. This paper describes a new method for investigating fatigue crack growth after the application of an overload cycle under plane stress conditions. The developed method is based on the concept of plasticity-induced crack closure and utilises the distributed dislocation technique and a modified strip-yield model. The present results are compared to previous experimental data for several materials. A good agreement is found, with the predictions showing the same trends in the various stages of post-overload crack growth.     

Parameters of cache systems based on a Zipf-like distribution

The object of this paper is to explain a system of Internet traffic caching. The task is to create an analytical model of a cache system linking its size with other parameters by boundary conditions. A definition of a dynamic cache model is introduced. The parameters of a cache system are calculated using the Zipf's first law and Zipf-like distribution. The correspondence between size of a cache system and aggregated bandwidth of external links is derived.     

High-speed,high-sensitivity,gated surface profiling with closed-loop optical coherence topography

We describe and experimentally demonstrate a novel (to our knowledge) surface profiling technique, for which we propose the term closed-loop optical coherence topography. This technique is a scanning beam, servo-locked variation of low-coherence interferometry. It allows for the sub-wavelength-resolution tracking of a weakly scattering macroscopic-scale surface, with the surface profile being directly output by the controlling electronics. The absence of significant real-time computational overhead makes the technique well suited to high-speed tracking. The use of a micrometer-scale coherence gate efficiently suppresses signals arising from structures not associated with the surface. These features make the technique particularly well suited to real-time surface profiling of in vivo, macroscopic biological surfaces.