`Faster than light' photons and rotating black holes

The effective action for QED in curved spacetime includes equivalence principle violating interactions between the electromagnetic field and the spacetime curvature. These interactions admit the possibility of superluminal yet causal photon propagation in gravitational fields. In this paper, we extend our analysis of photon propagation in gravitational backgrounds to the Kerr spacetime describing a rotating black hole. The results support two general theorems -- a polarisation sum rule and a `horizon theorem'. The implications for the stationary limit surface bounding the ergosphere are also discussed.Comment: Plain TeX, 12 pages, 1 figur

Plasma neuropeptide-Y levels, monoamine metabolism, electrolyte excretion and drinking behavior in children with attention-deficit hyperactivity disorder

Introduction: This study was conducted against a background of the following four points: a) increased drinking behavior in children with attention-deficit hyperactivity disorder (ADHD), b) the parallel between some behaviours associated with ADHD and with hypertension, c) the use of the spontaneously hypertensive rat as a model for ADHD, and d) similarities in the changes of neuropeptide-Y (NPY) and catecholamine in the studies of hypertension and drinking, Methods: Measures of NPY, catecholamines and electrolyte balance were compared in the plasma and urine of healthy children and those with ADHD. Drinking was monitored during three hours of neuropsychological tests over two days in 14 ADHD (mean 9.8 years-of-age) and 9 healthy children (10.6 years-of-age). Results: Patients drank 4 times more water and showed twice the levels of NPY in controls. In controls there were positive and in patients there were negative relationships for NPY with drinking and restless behavior. Patients' plasma levels of norepinephrine (NE) and epinephrine were slightly elevated, but urinary levels of NE and the serotonin metabolite were markedly increased. Urinary excretion rates for sodium (not potassium), phosphate and, especially calcium were decreased in patients. NPY levels were inversely related to calcium excretion and drinking inversely to sodium circulating (but positively with potassium and phosphate excretion). Conclusions: Increases of drinking and increased levels of circulating NPY in ADHD children and decreased electrolyte excretion may reflect a common disturbance in the homeostatic control of metabolism.This may contribute to the impairments of attentional and behavioural control typical of ADHD children

Light propagation in non-trivial QED vacua

Within the framework of effective action QED, we derive the light cone condition for homogeneous non-trivial QED vacua in the geometric optics approximation. Our result generalizes the ``unified formula'' suggested by Latorre, Pascual and Tarrach and allows for the calculation of velocity shifts and refractive indices for soft photons travelling through these vacua. Furthermore, we clarify the connection between the light velocity shift and the scale anomaly. This study motivates the introduction of a so-called effective action charge that characterizes the velocity modifying properties of the vacuum. Several applications are given concerning vacuum modifications caused by, e.g., strong fields, Casimir systems and high temperature.Comment: 13 pages, REVTeX, 3 figures, to appear in Phys. Rev.

Studies of the limit order book around large price changes

We study the dynamics of the limit order book of liquid stocks after experiencing large intra-day price changes. In the data we find large variations in several microscopical measures, e.g., the volatility the bid-ask spread, the bid-ask imbalance, the number of queuing limit orders, the activity (number and volume) of limit orders placed and canceled, etc. The relaxation of the quantities is generally very slow that can be described by a power law of exponent $\approx0.4$. We introduce a numerical model in order to understand the empirical results better. We find that with a zero intelligence deposition model of the order flow the empirical results can be reproduced qualitatively. This suggests that the slow relaxations might not be results of agents' strategic behaviour. Studying the difference between the exponents found empirically and numerically helps us to better identify the role of strategic behaviour in the phenomena.Comment: 19 pages, 7 figure

Color-Octet J/ψJ/\psi Production in the Υ\Upsilon Decay

The direct production rate of $\psi$ in the $\Upsilon$ decay is shown to be dominated by the process $\Upsilon \to ggg^*$ followed by $g^* \to \psi$ via the color-octet mechanism proposed recently to explain the anomalous prompt charmonium production at the Tevatron. We show that this plausibly dominant process has a branching ratio compatible with the experimental data. Further experimental study in this channel is important to test the significance of the color-octet component of $c\bar c$ pair inside the $\psi$ system.Comment: 20 pages, Standard LaTeX, 2 figures; a couple of new processes added, but conclusion unchange

Characteristics of Early-Onset vs Late-Onset Colorectal Cancer: A Review.

The incidence of early-onset colorectal cancer (younger than 50 years) is rising globally, the reasons for which are unclear. It appears to represent a unique disease process with different clinical, pathological, and molecular characteristics compared with late-onset colorectal cancer. Data on oncological outcomes are limited, and sensitivity to conventional neoadjuvant and adjuvant therapy regimens appear to be unknown. The purpose of this review is to summarize the available literature on early-onset colorectal cancer. Within the next decade, it is estimated that 1 in 10 colon cancers and 1 in 4 rectal cancers will be diagnosed in adults younger than 50 years. Potential risk factors include a Westernized diet, obesity, antibiotic usage, and alterations in the gut microbiome. Although genetic predisposition plays a role, most cases are sporadic. The full spectrum of germline and somatic sequence variations implicated remains unknown. Younger patients typically present with descending colonic or rectal cancer, advanced disease stage, and unfavorable histopathological features. Despite being more likely to receive neoadjuvant and adjuvant therapy, patients with early-onset disease demonstrate comparable oncological outcomes with their older counterparts. The clinicopathological features, underlying molecular profiles, and drivers of early-onset colorectal cancer differ from those of late-onset disease. Standardized, age-specific preventive, screening, diagnostic, and therapeutic strategies are required to optimize outcomes

Evaluation of coatings applied over corroded structural steel surfaces (FHWA-OK-90-03) 2722

Five coating systems were evaluated for use over corroded structural steel surfaces. The coatings were applied over both clean (non-corroded) steel panels and panels pre-corroded in a salt fog chamber. The coated panels were then exposed for 50 days in the salt fog chamber. Visual observations were made on a daily basis to obtain data on blister size, blister frequency, rust rating, and scribe rating. The coatings tested were: ( 1 ) Freecom, Corroseal FOC 54/55, an epoxy one-coat system, ( 2) DuPont, 25P/Imron, an epoxy base coat with a polyurethane top coat, ( 3 ) Praxis, Prax-Ten, a penetrant base coat and a concentrate top coat of metal alkyl sulfonates, (4) Tenemec, series 135/74, an epoxy base coat with a polyurethane top coat, and ( 5) Black Gold, a hydrocarbon sealer base coat with an aluminum flake top coat in a hydrocarbon and solvent binder. The best performing coating was the one supplied by DuPont. The Tnemec coating also performed well and ranked second. The Praxis coating ranked third. The poorest performing coating was Black Gold. The Corroseal coating performed better than Black Gold on the pre-corroded panels, but disbanded from the clean surfaces before the end of the testing period.Final Report July 1988-December 1989N