Instability strips of SPB and beta Cephei stars: the effect of the updated OP opacities and of the metal mixture

The discovery of $\beta$ Cephei stars in low metallicity environments, as well as the difficulty in theoretically explaining the excitation of the pulsation modes observed in some $\beta$ Cephei and hybrid SPB-$\beta$ Cephei pulsators, suggest that the ``iron opacity bump'' provided by stellar models could be underestimated. We analyze the effect of uncertainties in the opacity computations and in the solar metal mixture, on the excitation of pulsation modes in B-type stars. We carry out a pulsational stability analysis for four grids of main-sequence models with masses between 2.5 and 12 $\rm M_\odot$ computed with OPAL and OP opacity tables and two different metal mixtures. We find that in a typical $\beta$ Cephei model the OP opacity is 25% larger than OPAL in the region where the driving of pulsation modes occurs. Furthermore, the difference in the Fe mass fraction between the two metal mixtures considered is of the order of 20%. The implication on the excitation of pulsation modes is non-negligible: the blue border of the SPB instability strip is displaced at higher effective temperatures, leading to a larger number of models being hybrid SPB-$\beta$ Cephei pulsators. Moreover, higher overtone p-modes are excited in $\beta$ Cephei models and unstable modes are found in a larger number of models for lower metallicities, in particular $\beta$ Cephei pulsations are also found in models with Z=0.01.Comment: Accepted for publication in MNRAS Letter

Some are more equal than others : the role of ‘keystone’ species in the degradation of recalcitrant substrates

Peer reviewedPublisher PD

Non-Markovian effect on the quantum discord

We study the non-Markovian effect on the dynamics of the quantum discord by exactly solving a model consisting of two independent qubits subject to two zero-temperature non-Markovian reservoirs, respectively. Considering the two qubits initially prepared in Bell-like or extended Werner-like states, we show that there is no occurrence of the sudden death, but only instantaneous disappearance of the quantum discord at some time points, in comparison to the entanglement sudden death in the same range of the parameters of interest. It implies that the quantum discord is more useful than the entanglement to describe quantum correlation involved in quantum systems.Comment: 5 pages, 5 figure

Neutrino oscillations in de Sitter space-time

We try to understand flavor oscillations and to develop the formulae for describing neutrino oscillations in de Sitter space-time. First, the covariant Dirac equation is investigated under the conformally flat coordinates of de Sitter geometry. Then, we obtain the exact solutions of the Dirac equation and indicate the explicit form of the phase of wave function. Next, the concise formulae for calculating the neutrino oscillation probabilities in de Sitter space-time are given. Finally, The difference between our formulae and the standard result in Minkowski space-time is pointed out.Comment: 13 pages, no figure

A compact robotic device for upper-limb reaching rehabilitation

This paper presents a compact linear-motion robotic device for upper-extremity reaching rehabilitation. Starting from conceptual design, the paper describes electronic circuit design and program development. The work develops a prototype that provides active and passive rehabilitation training. In active training, subjects actively move their arm with assistive or resistive force from the device to finish predefined displacement and force profiles. In passive training, subjects remain passive while the device moves the limb following the pre-defined displacement profile. Engineering specifications with adequate safety factor are determined and standard electronic and readily available mechanical components are exploited to keep the total cost low

Engineering PET-degrading enzymes for biorecycling and bioremediation

Plastics, due to their inert properties and resistance to biodegradation, have been ravaging ecosystems worldwide and are especially harmful to aquatic wildlife. Plastics in the environment wear and tear into micron sized particles, termed microplastics, which are ingested and/or affect organisms at every level of the food chain. Recently, microplastics have been reported in human feces, and their potential health hazards remain unknown. In 2010, 4.8-12.7 million metric tons entered the oceans due to mismanagement and leakage, with an additional 31 million metric tons when terrestrial and freshwater ecosystems are considered. Both food and water supplies are likely contaminated with microplastics, and we need technologies to decrease formation of microplastics and remove these particulates from the environment. One of the most synthesized plastics is poly(ethylene terephthalate) (PET), an aromatic polyester with extremely low degradation rates. Due to the huge negative environmental impact of PET products, efficient recycling strategies need to be designed to “close the loop”’ to reduce dependence on petroleum feedstocks and decrease economic loss through single-use practices. The recent discovery of a PET-consuming bacteria Ideonella sakaiensis and its PET hydrolases has shown potential for enzyme-mediated recycling and bioremediation. Here, we present preliminary characterization of the catalytic rate of the newly discovered PETase and its behaviour over time, with perspective into future engineering potential for the enzyme for use in industrial processes

Surgical treatment and outcome of 195 cases of non acute subdural haematoma at the Youndé Central Hospital: The need for landmarked burr holes

Background Chronic subdural hematoma (CSDH) is frequent neurosurgical pathology but many issues related to the surgical procedure are still discussed.Objective To present our experience in the treatment of Non Acute Subdural Hematoma (NASH). Methodology This retrospective study included patients operated for NASH at the Yaoundé Central Hospital from January 2000 to September 2008. Surgery consisted of one burr hole (92.4%), 2 burr holes (3.6%), trephine or craniotomy (4%). All patients underwent per operative irrigation, a 48 hour-postoperative drainage and supine position. The burr hole was performed at the thickest point of the hematoma which in most cases corresponded to the intersection between the superior temporal line and the coronal suture. Results One hundred and ninety five consecutive patients were included: 155 males and 40 females. The mean age was 55 years. The past medical history revealed head injury (81.5%), alcoholism (12.9%), epilepsy (4.1%) or anticoagulation therapy (1.5%). The collection was unilateral (72.8%), bilateral (26.7%) or interhemispheric (1 case). On CT scan, the lesion was hypodense (79.9%), isodense (17.4%) or mixed (2.7%). The mortality rate was 2.5% while the recurrence rate was 3.7% after a 6 to 9 months follow-up period. The main recurrence factor was the inappropriate location of the burr hole.Conclusion One burr hole drainage is an effective and safe method for the treatment of NASH. The location of the burr hole is an important factor of recurrence. There is a need for Landmarked burr holes