331 research outputs found
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)
- …