Dynamical screening in hot systems away from (chemical) equilibrium

Within the Closed Time Path Formalism of Thermal Field Theory we calculate the hard photon emission rate as well as the collisional energy-loss rate for a quark-gluon plasma away from chemical equilibrium. Mass singularities are shown to be dynamically screened within HTL-resummed perturbation theory also away from equilibrium. Additional (pinch) singularities are absent and well defined results are obtained.Comment: Talk given at the Japanese Workshop on Thermal Quantum Field Theories and their Applications, Kyoto, Japan, 25.-27. August 1999, 6 page

Dynamical screening away from equilibrium: hard photon production and collisional energy loss

We investigate the production rate for hard real photons and the collisional energy loss in the quark-gluon plasma away from chemical equilibrium. Applying the Hard-Thermal-Loop resummation scheme away from equilibrium, we can show that Landau damping provides dynamical screening for both fermion and boson exchange present in the two quantities.Comment: 5 pages RevTeX, 2 figures, remarks for clarification and one reference added, typos correcte

A Slavnov-Taylor identity and equality of damping rates for static transverse and longitudinal gluons in hot QCD

A Slavnov-Taylor identity is derived for the gluon polarization tensor in hot QCD. We evaluate its implications for damping of gluonic modes in the plasma. Applying the identity to next to the leading order in hard-thermal-loop resummed perturbation theory, we derive the expected equality of damping rates for static transverse and longitudinal (soft) gluons. This is of interest also in view of deviating recent reports of $\gamma_t(p=0)\neq\gamma_l(p=0)$ based on a direct calculation of $\gamma_l(p=0)$.Comment: 13 pages, 1 figure, LaTe

Intravenous thrombolysis for acute ischaemic stroke: from randomised clinical trials to daily practice

In the Netherlands, as in most Western countries, stroke is a major contributor to the total burden of disease, with an estimated 39,600 hospital admissions, 9,000 deaths, and approximately 241,600 people living with the consequences of a stroke in 2009.1 Fortunately, improvements are observed, stroke mortality is declining; due to a both declines in incidence of stroke as well as in case fatality.2,3 New treatments like thrombolysis for acute ischaemic stroke are highly effective, but the main cause of increased survival rates after stroke is a better coordination of care, through widespread implementation of stroke units.4,5 Thrombolysis refers to the breakdown of blood clots by stimulating fibrinolysis. In 1995 a large American study on the effectiveness of thrombolysis with intravenous alteplase (recombinant tissue plasminogen activator, rTPA) for patients with acute ischaemic stroke was published. Patients treated with intravenous alteplase had a better functional outcome at three months.6 However two European trials (MAST I and MAST E) had unfavourable results and the ECASS I had inconclusive results.7-9 The higher complication rate was attributed to a too high dose of thrombolytic and the lack of improvement was attributed to the extended time window of 6 hours. In 1998 the ECASS II trial was published, but it also showed inconclusive results.10 A few years later in 2000 the Cochrane Review (including all the trials mentioned above) was published and showed that thrombolytic therapy appears to result in a significant net reduction in the proportion of dependency or death. The relative reduction in risk of poor outcome, defined as a modified Rankin Score >2, was 17.5% (95% CI: 7 to 26%).11 The scepticism about treatment with rTPA gradually declined. Steadily but slowly, more and more hospitals started to treat acute ischaemic stroke patients with thrombolysis, but in daily practice, several circumstances and causes put a constraint on the number of patients who could be treated, the most important cause being the narrow time window for treatment. Taking that narrow time window into account, it was estimated that up to 24% of the stroke patients presenting at the emergency care might be eligible for thrombolysis. 12 In 2002-2003 however, the rate of thrombolysis in Dutch hospitals varied between 1% and 8%, with a few exceptions.13 Clearly, improvements could be made. In addition, concern about bleeding complications remained an issue. A European license for alteplase was provided on the condition that safety and effectiveness would be monitored in a European registry. This resulted in the Safe Implementation of Thrombolysis in Stroke-Monitoring Study (SITS-MOST)

Paradigms for computational nucleic acid design

The design of DNA and RNA sequences is critical for many endeavors, from DNA nanotechnology, to PCR‐based applications, to DNA hybridization arrays. Results in the literature rely on a wide variety of design criteria adapted to the particular requirements of each application. Using an extensively studied thermodynamic model, we perform a detailed study of several criteria for designing sequences intended to adopt a target secondary structure. We conclude that superior design methods should explicitly implement both a positive design paradigm (optimize affinity for the target structure) and a negative design paradigm (optimize specificity for the target structure). The commonly used approaches of sequence symmetry minimization and minimum free‐energy satisfaction primarily implement negative design and can be strengthened by introducing a positive design component. Surprisingly, our findings hold for a wide range of secondary structures and are robust to modest perturbation of the thermodynamic parameters used for evaluating sequence quality, suggesting the feasibility and ongoing utility of a unified approach to nucleic acid design as parameter sets are refined further. Finally, we observe that designing for thermodynamic stability does not determine folding kinetics, emphasizing the opportunity for extending design criteria to target kinetic features of the energy landscape

Thermodynamic Analysis of Interacting Nucleic Acid Strands

Motivated by the analysis of natural and engineered DNA and RNA systems, we present the first algorithm for calculating the partition function of an unpseudoknotted complex of multiple interacting nucleic acid strands. This dynamic program is based on a rigorous extension of secondary structure models to the multistranded case, addressing representation and distinguishability issues that do not arise for single-stranded structures. We then derive the form of the partition function for a fixed volume containing a dilute solution of nucleic acid complexes. This expression can be evaluated explicitly for small numbers of strands, allowing the calculation of the equilibrium population distribution for each species of complex. Alternatively, for large systems (e.g., a test tube), we show that the unique complex concentrations corresponding to thermodynamic equilibrium can be obtained by solving a convex programming problem. Partition function and concentration information can then be used to calculate equilibrium base-pairing observables. The underlying physics and mathematical formulation of these problems lead to an interesting blend of approaches, including ideas from graph theory, group theory, dynamic programming, combinatorics, convex optimization, and Lagrange duality

Nieuwsbrief Bloeiend Bedrijf #1

Bloeiend Bedrijf is een samenwerkingsverband van bedrijven in de akkerbouw en veehouderij die aan de slag gaan met akkerranden voor nuttige biodiversiteit. Inhoud: -Bloeiend Bedrijf van start! -Boeren aan de slag met Biodiversiteit -Zaadmengsels kiezen en inzaaien -Aanleg en beheer van de akkerrand -Functionele agrobiodiversiteit (FAB) -Administratie -Scouting: nuttige insecten herkennen -Nuttige akkerranden -Kennisuitwisselin

Resonant decay of parity odd bubbles in hot hadronic matter

We investigate the decay of metastable states with broken CP-symmetry which have recently been proposed by Kharzeev, Pisarski and Tytgat to form in hot hadronic matter. We consider the efficiency of the amplification of the $\eta'$-field via parametric resonance, taking the backreaction into account. For times of the order $t\approx 10 fm$, we find a particle density of about $0.7/fm^3$ and a correlation length of $\xi_{max}\approx 2.5 fm$. The corresponding momentum spectra show a non-thermal behaviour.Comment: 11 pages latex file with 4 gif - figures. Uses elsart.cls (included

Bloeiend Bedrijf van start!

Eerste nieuwsbrief van Bloeiend Bedrijf. Bloeiend Bedrijf is een samenwerkingsverband ondersteund door 17 agrarische natuurverenigingen (ANV’s), Veelzijdig Boerenland, het Louis Bolk Instituut, BoerenNatuur en de Natuurweide. Bloeiend Bedrijf richt zich op de aanleg en het beheer van akkerranden voor functionele biodiversiteit, met de nadruk op het bevorderen van natuurlijke vijanden van landbouwplagen