Publications

Cigarette smokers on average weigh less than nonsmokers. However, among smokers, those who smoke the most weigh the most. To better understand the effects of nicotine on body weight, we investigated the pharmacodynamics of intravenous nicotine and cigarette smoking in low-level smokers (10 or fewer cigarettes per day) and high-level smokers (15 to 30 cigarettes per day). Cigarette smoking and intravenous nicotine increased heart rate and energy expenditure in most smokers. The effects of intravenous nicotine and smoking were of similar magnitude, confirming that the effects of smoking are mediated by nicotine. Nicotine produced a slightly greater increase in heart rate in low-level versus high-level smokers, but energy expenditure increased to a much greater extent in low-level versus high-level smokers. The plots of plasma nicotine concentration versus responses suggest development of acute tolerance to both heart rate acceleration and increased energy expenditure in low-level smokers; high-level smokers show a similar pattern of tolerance for heart rate but show only a brief increase in energy expenditure and a hysteresis curve consistent with either rapid development of tolerance or no effect. Thus there is evidence of differential development or rate of loss of tolerance to cardiovascular versus metabolic effects of nicotine in low-level versus high-level smokers. Pharmacodynamic differences between low-level and high-level smokers may explain, at least in part, the unusual relationship between cigarette consumption and body weight.

Abstract We have studied synchronization mechanism in locally coupled nonlinear oscillators. Here, synchronization takes place by passive coupling based on a reaction–diffusion process. We will compare this mechanism with basic synchronization techniques, showing their similarities and specific properties. In addition to synchronization, passive and local coupling can also ‘awaken’ non‐oscillating cell circuits and trigger oscillation, provided that cells are locally active. This result resembles Turing's and Smale's works showing that locally communicating simple elements can produce very different patterns even if separate elements do not show any activity. This property will be demonstrated for two second‐order cells and also for a large ensemble of oscillatory cells. In latter case, the network of oscillatory cells exhibits very sophisticated spatio‐temporal waves, e.g. spiral waves. Copyright © 2008 John Wiley & Sons, Ltd.

Na-ion batteries have attracted growing attention due to the high abundance and low cost of Na compared with Li. As a promising category of cathode materials for Na-ion batteries, layered oxides have been widely studied. Among the rich diversity of structure, emphasis has been mainly focused on O3 and P2-phases (in Delmas’ denotion 1 . ) Several layered oxides have been studied recently, NaMnO 2 2 , NaNiO 2 3 , Na x CoO 2 4 , Na 2/3 Mn 1/2 Fe 1/2 O 2 5 , etc. For most O3-type oxides, the reversible capacity is limited to 120 mAh/g, corresponding to 0.5 Na per formula unit, while for most P2-type oxides, the reversible capacity is about 160 mAh/g which is equivalent to ≈ 0.67Na extracted and intercalated during cycling. We synthesized a series of O3- and P2-type compounds with the same transition metal components via solid-state reaction and carried out a comparative study between the O3 and P2 structure. Besides performance, we evaluated the structure/valence transition and Na + mobility. The structural transitions during Na + intercalation/deintercalation are similar for most reported O3-type oxides with an O3-P3 transition, while the P2 phases usually experience more reversible phase transitions, accompanied by stacking faults. We carried out in-situ XRD observation to study the structure evolution of our new O3- and P2-type materials. The valence evolution of the transition metals in O3- and P2-type materials was evaluated. A good understanding of the valence evolution of transition metals in layered oxides will benefit the design and tailoring of this category of materials.

Entrevista realizada a Loïc Wacquant, publicada en <i>KX-Magazine</i> (Sofía, Bulgaria, 2001), cuyo texto fue gentilmente cedido por el autor a la revista.

The diagnosis of acute stress disorder (ASD) was introduced to describe initial trauma reactions that predict chronic posttraumatic stress disorder (PTSD). This review outlines and critiques the rationales underpinning the ASD diagnosis and highlights conceptual and empirical problems inherent in this diagnosis. The authors conclude that there is little justification for the ASD diagnosis in its present form. The evidence for and against the current emphasis on peritraumatic dissociation is discussed, and the range of biological and cognitive mechanisms that potentially mediate acute trauma response are reviewed. The available evidence indicates that alternative means of conceptualizing acute trauma reactions and identifying acutely traumatized people who are at risk of developing PTSD need to be considered.

F plasmid replication during the Escherichia coli division cycle was investigated by using the membrane-elution technique to produce cells labeled at different times during the division cycle and scintillation counting for quantitative analysis of radioactive plasmid DNA. The F plasmid replicated, like the minichromosome, during a restricted portion of the bacterial division cycle; i.e., F plasmid replication is cell-cycle specific. The F plasmid replicated at a different time during the division cycle than a minichromosome present in the same cell. F plasmid replication coincided with doubling in the rate of enzyme synthesis from a plasmid-encoded gene. When the cell cycle age of replication of the F plasmid was determined over a range of growth rates, the cell size at which the F plasmid replicated followed the same rules as did replication of the bacterial chromosome--initiation occurred when a constant mass per origin was achieved--except that the initiation mass per origin for the F plasmid was different from that for the chromosome origin. In contrast, the high-copy mini-R6K plasmid replicated throughout the division cycle.

An extraordinary downfield-shifted ²⁹ Si{¹ H} NMR signal is seen at δ=338.5 for the platinum silylene complex [(dippe)(H)Pt=SiMes₂ ][MeB(C₆ F₅ )₃ ] (2). This remarkably stable metal silylene complex was obtained from 1 in the first intramolecular 1,2-hydride migration from silicon to a transition metal. dippe=iPr₂ PCH₂ CH₂ PiPr₂ , Mes=2,4,6-Me₃ C₆ H₂ .

Summary General characterization of physical systems uses two aspects of data analysis methods: decomposition of empirical data to determine system parameters and reconstruction of the system attributes using these characteristic parameters. Spectral methods, involving a frequency-based representation of data, usually assume stationarity. These methods, therefore, extract only average information and, hence, are not suitable for analyzing data with isolated or deterministic discontinuities, such as faults or fractures in reservoir rocks or image edges in computer vision. Wavelet transforms provide a multiresolution framework for data representation. They are a family of basis functions that separate a function or a signal into distinct frequency packets that are localized in the time domain. Thus, wavelets are well suited for analyzing nonstationary data. In other words, a function or a discrete data set when transformed into a time-scale space using wavelets shows how it behaves at different scales of measurement. Because wavelets have compact support, it is easy to apply this transform to large data sets with minimal computations. We apply wavelet transforms to one-dimensional and twodimensional permeability data to determine the locations of layer boundaries and other discontinuities. By binning in the time-frequency plane with wavelet packets, permeability structures of arbitrary size are analyzed. Wavelets are also applied to scaling up spatially correlated heterogeneous permeability fields.

AbstractA study has been made of the susceptibility to hydrogen attack of a newly developed 3Cr–1 Mo–1Ni pressure-vessel steel, intended for use in coal-conversion vessels, following long-term exposure to high-pressure (14-17 MPa) gaseous hydrogen at 550 and 600°C; the results are compared to the behaviour of 2·25Cr–1Mo steel. To simulate the condition of both surface and mid-section locations of thick-section (400 mm) plate during commercial normalizing, oil quenched and slowly cooled (8 K min−1) structures were examined after tempering at 650 and 700°C, with respect to their strength, ductility, and impact toughness properties. Compared to unexposed samples, structures exposed to hydrogen were observed to show some softening (up to 20% reduction in yield stress) and ‘embrittlement’ (up to 22% reduction in upper-shelf Charpy energies and increases in the transition temperatures by 65–100 K), although there were no visible signs of major microstructural damage. Moreover, the behaviour of the oil-quenched and slow-cooled structures was largely similar. In comparison to 2·25Cr–1 Mo steel, which can become highly susceptible to hydrogen damage in the very slowly cooled state, the present 3Cr–1Mo–1Ni steel was found to have far superior resistance to hydrogen attack. This was attributed primarily to two factors: namely, the increased hardenability, which resulted from the absence of pro-eutectoid ferrite in as-cooled microstructures, and the accelerated kinetics in the carbide precipitation sequence, which resulted in the more rapid replacement of M3C by more stable, higher-alloyed carbides, such as M23C6.MST/95