Rate limit for photoassociation of a Bose-Einstein condensate

We simulate numerically the photodissociation of molecules into noncondensate atom pairs that accompanies photoassociation of an atomic Bose-Einstein condensate into a molecular condensate. Such rogue photodissociation sets a limit on the achievable rate of photoassociation. Given the atom density \rho and mass m, the limit is approximately 6\hbar\rho^{2/3}/m. At low temperatures this is a more stringent restriction than the unitary limit of scattering theory.Comment: 5 pgs, 18 refs., 3 figs., submitted to Phys. Rev. Let

Sub-Natural-Linewidth Quantum Interference Features Observed in Photoassociation of a Thermal Gas

By driving photoassociation transitions we form electronically excited molecules (Na$_2^*$) from ultra-cold (50-300 $\mu$K) Na atoms. Using a second laser to drive transitions from the excited state to a level in the molecular ground state, we are able to split the photoassociation line and observe features with a width smaller than the natural linewidth of the excited molecular state. The quantum interference which gives rise to this effect is analogous to that which leads to electromagnetically induced transparency in three level atomic $\Lambda$ systems, but here one of the ground states is a pair of free atoms while the other is a bound molecule. The linewidth is limited primarily by the finite temperature of the atoms.Comment: 4 pages, 5 figure

Effects of increasing cannabis potency on adolescent health

Cannabis is the most prevalent illicit drug used by adolescents worldwide. Over the past 40 years, changes in cannabis potency through rising concentrations of Δ-9-tetrahydrocannabiol (THC), decreases in cannabidiol, or both, have occurred. Epidemiological and experimental evidence demonstrates that cannabis with high THC concentrations and negligible cannabidiol concentrations is associated with an increased risk of psychotic outcomes, an effect on spatial working memory and prose recall, and increased reports of the severity of cannabis dependence. However, many studies have failed to address cannabis use in adolescence, the peak age at which individuals typically try cannabis and probably the most vulnerable age to experience its harmful effects. In this Review, we highlight the influence that changing cannabis products have on adolescent health and the implications they carry for policy and prevention measures as legal cannabis markets continue to emerge worldwide.</p

Superposition of macroscopic numbers of atoms and molecules

We theoretically examine photoassociation of a non-ideal Bose-Einstein condensate, focusing on evidence for a macroscopic superposition of atoms and molecules. This problem raises an interest because, rather than two states of a given object, an atom-molecule system is a seemingly impossible macroscopic superposition of different objects. Nevertheless, photoassociation enables coherent intraparticle conversion, and we thereby propose a viable scheme for creating a superposition of a macroscopic number of atoms with a macroscopic number of molecules.Comment: 4 pages, 2 figs, to appear in Phys. Rev. Let

A performance evaluation of commercial fibrinogen reference preparations and assays for Clauss and PT-derived fibrinogen

The wide availability of fibrinogen estimations based on the prothrombin time (PT-Fg) has caused concern about the variability and clinical utility of fibrinogen assays. In a multi-centre study, we investigated fibrinogen assays using various reagents and analysers, Clauss assays generally gave good agreement, although one reagent gave 15-30% higher values in DIC and thrombolysis. Two commercial reference preparations had much lower potencies than the manufacturers declared, and plasma turbidity influenced parallelism in some Clauss assays, PT-Fg assays gave higher values than Clauss and showed calibrant dependent effects, the degree of disparity correlating with calibrant and test sample turbidity. Analyser and thromboplastin dependent differences were noted. The relationship between Clauss and PT-Fg assays was sigmoid, and the plateau of maximal PT-Fg differed by about 2 g/l between reagents. ELISA and immunonephelometric assays correlated well, but with a high degree of scatter. Antigen levels were higher than Clauss, but slightly lower than PT-Fg assays, which appeared to be influenced by degraded fibrinogen. Clauss assays are generally reproducible between centres, analysers and reagents, but PT-Fg assays are not reliable in clinical settings

Bisphosphonates regulate cell growth and gene expression in the UMR 106-01 clonal rat osteosarcoma cell line

Local growth of osteosarcoma involves destruction of host bone by proteolytic mechanisms and/or host osteoclast activation. Osteoclast formation and activity are regulated by osteoblast-derived factors such as the osteoclast differentiating factor, receptor activator of NF-κB ligand (RANKL) and the inhibitor osteoprotegerin (OPG). We have investigated the in vitro effects of bisphosphonates on a clonal rat osteosarcoma cell line. The aminobisphosphonate pamidronate was added to UMR 106-01 cell cultures (10−8M to 10−4M up to 5 days). The non-aminobisphosphonate clodronate was administered for the same time periods (10−6M to 10−2M). Cell proliferation, apoptosis and mRNA expression was assessed. Both agents inhibited cell proliferation in a time- and dose-dependent manner. ELISA analysis demonstrated an increase in DNA fragmentation although there was no significant dose-related difference between the doses studied. Bisphosphonate-treated cultures had a greater subpopulation of cells exhibiting morphological changes of apoptosis. Expression of mRNA for osteopontin and RANKL was down-regulated by both agents, while the expression of mRNA for alkaline phosphatase, pro-α1(I) collagen and OPG was not altered. Out in vitro work suggests the bisphosphonates not only have direct effects on osteosarcoma cell growth and apoptosis, but also, by altering the relative expression of osteoclast-regulating factors, they may inhibit the activity of osteoclasts and their recruitment. © 2001 Cancer Research Campaignhttp://www.bjcancer.co

Host-Imposed Copper Poisoning Impacts Fungal Micronutrient Acquisition during Systemic Candida albicans Infections

This work was supported by the European Research Council (http://erc.europa.eu/: STRIFE Advanced Grant ERC-2009-AdG-249793). A.J.P.B. was also supported by the UK Biotechnology and Biological Research Council (www.bbsrc.ac.uk: Research Grants BB/F00513X/1, BB/K017365/1), the UK Medical Research Council (www.mrc.ac.uk: Programme Grant MR/M026663/1; Centre Grant MR/ N006364/1), and the Wellcome Trust (www.wellcome.ac.uk: Strategic Award 097377)Peer reviewedPublisher PD

Dissipative Particle Dynamics with Energy Conservation

The stochastic differential equations for a model of dissipative particle dynamics with both total energy and total momentum conservation in the particle-particle interactions are presented. The corresponding Fokker-Planck equation for the evolution of the probability distribution for the system is deduced together with the corresponding fluctuation-dissipation theorems ensuring that the ab initio chosen equilibrium probability distribution for the relevant variables is a stationary solution. When energy conservation is included, the system can sustain temperature gradients and heat flow can be modeled.Comment: 7 pages, submitted to Europhys. Let

Daily-running exercise may induce incomplete energy intake compensation: a 7-day crossover trial

Understanding daily-exercise effects on energy balance is important. This study examined the effects of seven days of imposed exercise (EX) and no exercise (N-EX) on free-living energy intake (EI) and physical activity energy expenditure (PAEE) in nine men. Free-living EI was higher in EX compared with N-EX. Total and vigorous PAEE were higher, with PAEE in sedentary activities lower, during EX compared with N-EX. Daily-running (for 7 days) induced EI compensation of ~60% exercise-induced EE. Novelty bullet: • Daily running for seven days induced incomplete EI compensation accounting for~60% of the exercise-induced EE