Electrodynamic Radiation Reaction and General Relativity

We argue that the well-known problem of the instabilities associated with the self-forces (radiation reaction forces) in classical electrodynamics are possibly stabilized by the introduction of gravitational forces via general relativity

Does the continuum theory of dynamic fracture work?

We investigate the validity of the Linear Elastic Fracture Mechanics approach to dynamic fracture. We first test the predictions in a lattice simulation, using a formula of Eshelby for the time-dependent Stress Intensity Factor. Excellent agreement with the theory is found. We then use the same method to analyze the experiment of Sharon and Fineberg. The data here is not consistent with the theoretical expectation.Comment: 4 page

Effects of substrate and mycorrhizal inoculum on stem segment cuttings of Pterocarpus erinaceus Poir. (Fabaceae) in the Guinean savannah highlands of Cameroon

Pterocarpus erinaceus Poir is a woody species of the Sudano-Guinean to Sudano-Sahelian zones with very high food, medicinal and commercial potential leading to the overexploitation. This study aimed to contribute to the domestication of this species using stem segment cuttings. The sand/sawdust and black soil/sawdust substrates were inoculated with 0.10, and 20 g of mycorrhizae. The split plot with 4 repetitions was used as the experimental method and set at 10 cuttings per unit. The experience revealed that the appropriate substrate and dose of mycorrhizae for the budding of stem segment cuttings (SSC) were the sand/sawdust mixture (25.00 ± 18.34 %) and 10 g (23.75 ± 5.63 %) respectively. Satisfactory result was recorded in 10 g (4.18 ± 2.52 cm) dose of mycorrhizae for the height of the aerial axes with abundant number of leaves per aerial observed in the sand/sawdust substrate (2.36 ± 0.48). Concerning the rooting ability of the cuttings, adequate substrate for the number of newly formed roots is the sand/sawdust mixture (25.00 ± 18.34 %) while the dose of 10 g of mycorrhizae favoured the appearance of roots (23.75 ± 14.07 %). The best substrate for the length of newly formed roots is the sand/sawdust mixture (10.64 ± 7.14 cm) and 10 g of mycorrhizae improved the length (9.82 ± 6.40 cm) for Senegal rosewood. Given the above results, we can admit that the improvement of certain parameters (budding, rooting) in P. erinaceus is possible by vegetative propagation

Bighead soup for lunch

French version available in IDRC Digital Library: Potage de carpe au menuSpanish version available in IDRC Digital Library: Carpas para Malasia y el Sudeste Asiátic

Potage de carpe au menu

Version anglaise disponible dans la Bibliothèque numérique du CRDI: Bighead soup for lunchVersion espagnole disponible dans la Bibliothèque numérique du CRDI: Carpas para Malasia y el Sudeste Asiátic

The status of GEO 600

The GEO 600 laser interferometer with 600m armlength is part of a worldwide network of gravitational wave detectors. GEO 600 is unique in having advanced multiple pendulum suspensions with a monolithic last stage and in employing a signal recycled optical design. This paper describes the recent commissioning of the interferometer and its operation in signal recycled mode

Phenomenology of the Lense-Thirring effect in the Solar System

Recent years have seen increasing efforts to directly measure some aspects of the general relativistic gravitomagnetic interaction in several astronomical scenarios in the solar system. After briefly overviewing the concept of gravitomagnetism from a theoretical point of view, we review the performed or proposed attempts to detect the Lense-Thirring effect affecting the orbital motions of natural and artificial bodies in the gravitational fields of the Sun, Earth, Mars and Jupiter. In particular, we will focus on the evaluation of the impact of several sources of systematic uncertainties of dynamical origin to realistically elucidate the present and future perspectives in directly measuring such an elusive relativistic effect.Comment: LaTex, 51 pages, 14 figures, 22 tables. Invited review, to appear in Astrophysics and Space Science (ApSS). Some uncited references in the text now correctly quoted. One reference added. A footnote adde

Coherent Compton scattering on light nuclei in the delta resonance region

Coherent Compton scattering on light nuclei in the delta resonance region is studied in the impulse approximation and is shown to be a sensitive probe of the in-medium properties of the delta resonance. The elementary amplitude on a single nucleon is calculated from the unitary K-matrix approach developed previously. Modifications of the properties of the delta resonance due to the nuclear medium are accounted for through the self-energy operator of the delta, calculated from the one-pion loop. The dominant medium effects such as the Pauli blocking, mean-field modification of the nucleon and delta masses, and particle-hole excitations in the pion propagator are consistently included in nuclear matter.Comment: 30 pages, 11 figures, accepted for publication in Phys. Rev.

EXPLORE: A Prospective, Multinational, Natural History Study of Patients with Acute Hepatic Porphyria with Recurrent Attacks

BACKGROUND AND AIMS: Acute hepatic porphyria comprises a group of rare genetic diseases caused by mutations in genes involved in heme biosynthesis. Patients can experience acute neurovisceral attacks, debilitating chronic symptoms, and long-term complications. There is a lack of multinational, prospective data characterizing the disease and current treatment practices in severely affected patients. APPROACH AND RESULTS: EXPLORE is a prospective, multinational, natural history study characterizing disease activity and clinical management in patients with acute hepatic porphyria who experience recurrent attacks. Eligible patients had a confirmed acute hepatic porphyria diagnosis and had experienced ≥3 attacks in the prior 12 months or were receiving prophylactic treatment. A total of 112 patients were enrolled and followed for at least 6 months. In the 12 months before the study, patients reported a median (range) of 6 (0-52) acute attacks, with 52 (46%) patients receiving hemin prophylaxis. Chronic symptoms were reported by 73 (65%) patients, with 52 (46%) patients experiencing these daily. During the study, 98 (88%) patients experienced a total of 483 attacks, 77% of which required treatment at a health care facility and/or hemin administration (median [range] annualized attack rate 2.0 [0.0-37.0]). Elevated levels of hepatic δ-aminolevulinic acid synthase 1 messenger ribonucleic acid levels, δ-aminolevulinic acid, and porphobilinogen compared with the upper limit of normal in healthy individuals were observed at baseline and increased further during attacks. Patients had impaired quality of life and increased health care utilization. CONCLUSIONS: Patients experienced attacks often requiring treatment in a health care facility and/or with hemin, as well as chronic symptoms that adversely influenced day-to-day functioning. In this patient group, the high disease burden and diminished quality of life highlight the need for novel therapies. (Hepatology 2020;71:1546-1558)