5,892 research outputs found
Principles of Discrete Time Mechanics: II. Classical field Theory
We apply the principles discussed in an earlier paper to the construction of
discrete time field theories. We derive the discrete time field equations of
motion and Noether's theorem and apply them to the Schrodinger equation to
illustrate the methodology. Stationary solutions to the discrete time
Schrodinger wave equation are found to be identical to standard energy
eigenvalue solutions except for a fundamental limit on the energy. Then we
apply the formalism to the free neutral Klein Gordon system, deriving the
equations of motion and conserved quantities such as the linear momentum and
angular momentum. We show that there is an upper bound on the magnitude of
linear momentum for physical particle-like solutions. We extend the formalism
to the charged scalar field coupled to Maxwell's electrodynamics in a gauge
invariant way. We apply the formalism to include the Maxwell and Dirac fields,
setting the scene for second quantisation of discrete time mechanics and
discrete time Quantum Electrodynamics.Comment: 23 pages, LateX, To be published in J.Phys.A: Math.Gen: contact email
address: [email protected]
Inkjet Printing of Graphene
The optimization of inkjet printing graphene using a Fujifilm Dimatix Inkjet printer, is described in this study. The number of printing passes were varied, and relatively uniform lines were obtained. The printing parameter considerations and optimized printing parameters for graphene are also discussed
Yohimbine-Induced Amygdala Activation in Pathological Gamblers: A Pilot Study
Rationale and Objectives: There is evidence that drug addiction is associated with increased physiological and psychological responses to stress. In this pilot functional magnetic resonance imaging (fMRI) study we assessed whether a prototype behavioral addiction, pathological gambling (PG), is likewise associated with an enhanced response to stress. Methods: We induced stress by injecting yohimbine (0.2–0.3 mg/kg, IV), an alpha-2 adrenoceptor antagonist that elicits stress-like physiological and psychological effects in humans and in laboratory animals, to four subjects with PG and to five non-gamblers mentally healthy control subjects. Their fMRI brain responses were assessed along with subjective stress and gambling urges ratings. Results: Voxelwise analyses of data sets from individual subjects, utilizing generalized linear model approach, revealed significant left amygdala activation in response to yohimbine across all PG subjects. This amygdala effect was not observed in the five control individuals. Yohimbine elicited subjective stress ratings in both groups with greater (albeit not statically significantly) average response in the PG subjects. On the other hand, yohimbine did not induce urges to gamble
Principles of Discrete Time Mechanics: I. Particle Systems
We discuss the principles to be used in the construction of discrete time
classical and quantum mechanics as applied to point particle systems. In the
classical theory this includes the concept of virtual path and the construction
of system functions from classical Lagrangians, Cadzow's variational principle
applied to the action sum, Maeda-Noether and Logan invariants of the motion,
elliptic and hyperbolic harmonic oscillator behaviour, gauge invariant
electrodynamics and charge conservation, and the Grassmannian oscillator. First
quantised discrete time mechanics is discussed via the concept of system
amplitude, which permits the construction of all quantities of interest such as
commutators and scattering amplitudes. We discuss stroboscopic quantum
mechanics, or the construction of discrete time quantum theory from continuous
time quantum theory and show how this works in detail for the free Newtonian
particle. We conclude with an application of the Schwinger action principle to
the important case of the quantised discrete time inhomogeneous oscillator.Comment: 35 pages, LateX, To be published in J.Phys.A: Math.Gen. Basic
principles stated: applications to field theory in subsequent papers of
series contact email address: [email protected]
Targeting Dysregulation of Metalloproteinase Activity in Osteoarthritis
Metalloproteinases were first identified as collagen cleaving enzymes and are now appreciated to play important roles in a wide variety of biological processes. The aberrant activity and dysregulation of the metalloproteinase family are linked to numerous diseases including cardiovascular and pulmonary diseases, chronic wounds, cancer, fibrosis and arthritis. Osteoarthritis (OA) is the most prevalent age-related joint disorder that causes pain and disability, but there are no disease-modifying drugs available. The hallmark of OA is loss of articular cartilage and elevated activities of matrix-degrading metalloproteinases are responsible. These enzymes do not exist in isolation and their activity is tightly regulated by a number of processes, such as transcription, proteolytic activation, interaction with their inhibitors, cell surface and extracellular matrix molecules, and endocytic clearance from the extracellular milieu. Here, we describe the functions and roles of metalloproteinase family in OA pathogenesis. We highlight recent studies that have illustrated novel mechanisms regulating their extracellular activity and impairment of such regulations that lead to the development of OA. We also discuss how to stop or slow down the degenerative processes by targeting aberrant metalloproteinase activity, which may in future become therapeutic interventions for the disease
Quantitative Detection of µ Opioid Receptor: Western Blot Analyses Using µ Opioid Receptor Knockout Mice
Increasing evidence suggests that µ opioid receptor (MOP) expression is altered during the development of and withdrawal from substance dependence. Although anti-MOP antibodies have been hypothesized to be useful for estimating MOP expression levels, inconsistent MOP molecular weights (MWs) have been reported in studies using anti-MOP antibodies. In the present study, we generated a new anti-MOP antibody (N38) against the 1-38 amino acid sequence of the mouse MOP N-terminus and conducted Western blot analysis with wildtype and MOP knockout brain lysates to determine the MWs of intrinsic MOP. The N38 antibody detected migrating bands with relative MWs of 60-67 kDa in the plasma membrane fraction isolated from wildtype brain, but not from the MOP knockout brain. These migrating bands exhibited semi-linear density in the range of 3-30 µg membrane proteins/lane. The N38 antibody may be useful for quantitatively detecting MOP
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A Physically Based Correlation of Irradiation-Induced Transition Temperature Shifts for RPV Steels
The reactor pressure vessels (RPVs) of commercial nuclear power plants are subject to embrittlement due to exposure to high-energy neutrons from the core, which causes changes in material toughness properties that increase with radiation exposure and are affected by many variables. Irradiation embrittlement of RPV beltline materials is currently evaluated using Regulatory Guide 1.99 Revision 2 (RG1.99/2), which presents methods for estimating the shift in Charpy transition temperature at 30 ft-lb (TTS) and the drop in Charpy upper shelf energy (ΔUSE). The purpose of the work reported here is to improve on the TTS correlation model in RG1.99/2 using the broader database now available and current understanding of embrittlement mechanisms. The USE database and models have not been updated since the publication of NUREG/CR-6551 and, therefore, are not discussed in this report. The revised embrittlement shift model is calibrated and validated on a substantially larger, better-balanced database compared to prior models, including over five times the amount of data used to develop RG1.99/2. It also contains about 27% more data than the most recent update to the surveillance shift database, in 2000. The key areas expanded in the current database relative to the database available in 2000 are low-flux, low-copper, and long-time, high-fluence exposures, all areas that were previously relatively sparse. All old and new surveillance data were reviewed for completeness, duplicates, and discrepancies in cooperation with the American Society for Testing and Materials (ASTM) Subcommittee E10.02 on Radiation Effects in Structural Materials. In the present modeling effort, a 10% random sample of data was reserved from the fitting process, and most aspects of the model were validated with that sample as well as other data not used in calibration. The model is a hybrid, incorporating both physically motivated features and empirical calibration to the U.S. power reactor surveillance data. It contains two terms, corresponding to the best-understood radiation damage features, matrix damage and copper-rich precipitates, although the empirical calibration will ensure that all other damage processes that are occurring are also reflected in those terms. Effects of material chemical composition, product form, and radiation exposure are incorporated, such that all effects are supported by findings of statistical significance, physical understanding, or comparison with independent data from controlled experiments, such as the Irradiation Variable (IVAR) Program. In most variable effects, the model is supported by two or three of these different forms of evidence. The key variable trends, such as the neutron fluence dependence and copper-nickel dependence in the new TTS model, are much improved over RG1.99/2 and are well supported by independent data and the current understanding of embrittlement mechanisms. The new model includes the variables copper, nickel, and fluence that are in RG1.99/2, but also includes effects of irradiation temperature, neutron flux, phosphorus, and manganese. The calibrated model is a good fit, with no significant residual error trends in any of the variables used in the model or several additional variables and variable interactions that were investigated. The report includes a chapter summarizing the current understanding of embrittlement mechanisms and one comparing the IVAR database with the TTS model predictions. Generally good agreement is found in that quantitative comparison, providing independent confirmation of the predictive capability of the TTS model. The key new insight in the TTS modeling effort, that flux effects are evident in both low (or no) copper and higher copper materials, is supported by the IVAR data. The slightly simplified version of the TTS model presented in Section 7.3 of this report is recommended for applications
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