Crude awakening: behind the surge in oil prices

The first few months of 2008 saw crude oil prices breach one barrier after another. They topped $100 a barrel for the first time on Feb. 19, then rose past$103.76 about two weeks later, surpassing the previous inflation-adjusted peak, established in 1980. In April and early May, oil prices pushed past $110 and then$120 a barrel and beyond. ; These milestones reflect a new era in oil markets. After the tumult of the early 1980s, prices remained relatively tame for two decades - in both real and nominal terms. This long stretch of stability ended in 2004, when oil topped $40 a barrel for the first time, then embarked on a steep climb that continued into this year. ; Modern economies run on oil, so it's important to understand how recent years - with their surging prices - differ from the preceding two decades. A good starting point is strong demand, which has pushed world oil markets close to capacity. New supplies haven't kept up with this demand, fueling expectations that oil markets will remain tight for the foreseeable future. A weakening dollar has put upward pressure on the price of a commodity that trades in the U.S. currency. And because a large share of oil production takes place in politically unstable regions, fears of supply disruptions loom over markets. ; These factors have fed the steady, sometimes swift rise of oil prices in recent years. Their persistence suggests the days of relatively cheap oil are over and the global economy faces a future of high energy prices. How they play out will shape oil markets - and determine prices - for years to come.Petroleum products - Prices ; Petroleum industry and trade ; Organization of Petroleum Exporting Countries ; Dollar, American

Generalised state spaces and non-locality in fault tolerant quantum computing schemes

We develop connections between generalised notions of entanglement and quantum computational devices where the measurements available are restricted, either because they are noisy and/or because by design they are only along Pauli directions. By considering restricted measurements one can (by considering the dual positive operators) construct single particle state spaces that are different to the usual quantum state space. This leads to a modified notion of entanglement that can be very different to the quantum version (for example, Bell states can become separable). We use this approach to develop alternative methods of classical simulation that have strong connections to the study of non-local correlations: we construct noisy quantum computers that admit operations outside the Clifford set and can generate some forms of multiparty quantum entanglement, but are otherwise classical in that they can be efficiently simulated classically and cannot generate non-local statistics. Although the approach provides new regimes of noisy quantum evolution that can be efficiently simulated classically, it does not appear to lead to significant reductions of existing upper bounds to fault tolerance thresholds for common noise models.Comment: V2: 18 sides, 7 figures. Corrected two erroneous claims and one erroneous argumen

Spin chains and channels with memory

In most studies of the channel capacity of quantum channels, it is assumed that the errors in each use of the channel are independent. However, recent work has begun to investigate the effects of memory or correlations in the error. This work has led to speculation that interesting non-analytic behaviour may occur in the capacity. Motivated by these observations, we connect the study of channel capacities under correlated error to the study of critical behaviour in many-body physics. This connection enables us the techniques of many-body physics to either completely solve or understand qualitatively a number of interesting models of correlated error. The models can display analogous behaviour to associated many-body systems, including `phase transitions'.Comment: V2: changes in presentation, some additional comments on generalisation. V3: In accordance with published version, most (but not all) details of proofs now included. A separate paper will shortly be submitted separately with all details and more result

A study to compare continuous epidural infusion and intermittent bolus of bupivacaine for postoperative analgesia following renal surgery

Background: Extradural administration of local anaesthetics, opioids or a combination of both is now a well-established technique for managing postoperative pain following upper abdominal, pelvic and thoracic procedures or orthopaedic procedures on the lower extremities. There are two techniques of administration of drugs via epidural catheter – one isby continuous infusion and the other is by intermittent boluses. At present there is controversy in the literature regarding the analgesic effects of the techniques.Methods: This study was conducted in a prospective, randomised manner on 60 patients of either sex of ASA class I or II, scheduled to undergo elective renal surgery. The general anaesthetic technique was standardised. The patients were divided randomly into two groups of 30 each. The patients in group 1 received a continuous infusion of 0.166% bupivacaine, while the patients in group 2 received intermittent boluses through epidural catheter. The efficacy of postoperative analgesia was assessed using pulmonary function tests up to 12 hours. The generated data were analysed statistically.Results: There were no significant changes in pulse rate and arterial pressure at different time intervals from the preoperative values. Respiratory rates in both the groups were found to be significantly higher than the preoperative values in the two groups (p < 0.05). Forced vital capacity (FVC) and peak exploratory flow rate (PEFR) were significantly lower than the preoperative values at all points in time in both groups, but the drop was greater in group 2 and pain scores on movement were also found to be significantly higher than those in group 1 at the times when the effect of the bupivacaine bolus was wearing off (p < 0.05). Pain scores at rest were found to be comparable in both groups postoperatively.Conclusions: We conclude that continuous infusion of bupivacaine (8.3 mg/h) provides better analgesia at rest and on movement than intermittent boluses, and is not associated with fluctuations in the level of analgesia. Incidences of adverse effects are similar and not insignificant with both schedules

Improved magic states distillation for quantum universality

Given stabilizer operations and the ability to repeatedly prepare a single-qubit mixed state rho, can we do universal quantum computation? As motivation for this question, "magic state" distillation procedures can reduce the general fault-tolerance problem to that of performing fault-tolerant stabilizer circuits. We improve the procedures of Bravyi and Kitaev in the Hadamard "magic" direction of the Bloch sphere to achieve a sharp threshold between those rho allowing universal quantum computation, and those for which any calculation can be efficiently classically simulated. As a corollary, the ability to repeatedly prepare any pure state which is not a stabilizer state (e.g., any single-qubit pure state which is not a Pauli eigenstate), together with stabilizer operations, gives quantum universality. It remains open whether there is also a tight separation in the so-called T direction.Comment: 6 pages, 5 figure

The geometric measure of entanglement for a symmetric pure state with positive amplitudes

In this paper for a class of symmetric multiparty pure states we consider a conjecture related to the geometric measure of entanglement: 'for a symmetric pure state, the closest product state in terms of the fidelity can be chosen as a symmetric product state'. We show that this conjecture is true for symmetric pure states whose amplitudes are all non-negative in a computational basis. The more general conjecture is still open.Comment: Similar results have been obtained independently and with different methods by T-C. Wei and S. Severini, see arXiv:0905.0012v

Effect of metabolic and antioxidant supplementation on sperm parameters in oligo-astheno-teratozoospermia, with and without varicocele: a double-blind placebo-controlled study

Since sperm require high energy levels to perform their specialised function, it is vital that essential nutrients are available for spermatozoa when they develop, capacitate and acquire motility. However, they are vulnerable to a lack of energy and excess amounts of reactive oxygen species, which can impair sperm function, lead to immotility, acrosomal reaction impairment, DNA fragmentation and cell death. This monocentric, randomised, double-blind, placebo-controlled trial investigated the effect of 6&nbsp;months of supplementation with l-carnitine, acetyl-l-carnitine and other micronutrients on sperm quality in 104 subjects with oligo- and/or astheno- and/or teratozoospermia with or without varicocele. In 94 patients who completed the study, sperm concentration was significantly increased in supplemented patients compared to the placebo (p&nbsp;=.0186). Total sperm count also increased significantly (p&nbsp;=.0117) in the supplemented group as compared to the placebo group. Both, progressive and total motility were higher in supplemented patients (p&nbsp;=.0088 and p&nbsp;=.0120, respectively). Although pregnancy rate was not an endpoint of the study, of the 12 pregnancies that occurred during the follow-up, 10 were reported in the supplementation group. In general, all these changes were more evident in varicocele patients. In conclusion, supplementation with metabolic and antioxidant compounds could be efficacious when included in strategies to improve fertility

Preclinical restenosis models and drug-eluting stents Still important, still much to learn

Percutaneous coronary intervention continues to revolutionize the treatment of coronary atherosclerosis. Restenosis remains a significant problem but may at last be yielding to technologic advances. The examination of neointimal hyperplasia in injured animal artery models has helped in our understanding of angioplasty and stenting mechanisms, and as drug-eluting stent (DES) technologies have arrived, they too have been advanced through the study of animal models.These models are useful for predicting adverse clinical outcomes in patients with DESs because suboptimal animal model studies typically lead to problematic human trials. Similarly, stent thrombosis in animal models suggests stent thrombogenicity in human patients. Equivocal animal model results at six or nine months occasionally have been mirrored by excellent clinical outcomes in patients. The causes of such disparities are unclear but may result from differing methods, including less injury severity than originally described in the models. Ongoing research into animal models will reconcile apparent differences with clinical trials and advance our understanding of how to apply animal models to clinical stenting in the era of DESs