The Cretaceous Continental Intercalaire in central Algeria: subsurface evidence for a fluvial to aeolian transition and implications for the onset of aridity on the Saharan Platform.

The Lower Cretaceous Continental Intercalaire of North Africa is a terrestrial to shallow marine continental wedge deposited along the southern shoreline of the Neotethys Ocean. Today it has a wide distribution across the northern Sahara where it has enormous socio-economic importance as a major freshwater aquifer. During the Early Cretaceous major north-south trending basement structures were reactivated in response to renewed Atlantic rifting and in Algeria, faults along the El Biod-Hassi Messaourd Ridge appear to have been particularly important in controlling thickness patterns of the Lower Cretaceous Continental Intercalaire. Subsurface data from the Krechba gas field in Central Algeria shows that the Lower Cretaceous stratigraphy is subdivided into two clear parts. The lower part (here termed the In Salah Formation) is a 200 m thick succession of alluvial deposits with large meandering channels, clearly shown in 3D seismic, and waterlogged flood basins indicated by lignites and gleyed, pedogenic mudstones. The overlying Krechba Formation is a 500 m thick succession of quartz-dominated sands and sandstones whose microstructure indicates an aeolian origin, confirming earlier observations from outcrop. These interbed with brick red, highly oxidised mudstones representing deposition in temporary lakes or lagoons under an arid climate. The switch from fluvial to aeolian sedimentation at Krechba on the Saharan Platform occurred in the late Aptian and Albian and is thus synchronous to a comparable change observed by previous authors in Lower Cretaceous non-marine deposits of NE Spain. This was probably driven by a combination of sea-level fall and the northward shift of global arid belts into western Neotethys caused by oceanic rifting between Africa and South America

Exact Z2Z^2 scaling of pair production in the high-energy limit of heavy-ion collisions

The two-center Dirac equation for an electron in the external electromagnetic field of two colliding heavy ions in the limit in which the ions are moving at the speed of light is exactly solved and nonperturbative amplitudes for free electron-positron pair production are obtained. We find the condition for the applicability of this solution for large but finite collision energy, and use it to explain recent experimental results. The observed scaling of positron yields as the square of the projectile and target charges is a result of an exact cancellation of a nonperturbative charge dependence and holds as well for large coupling. Other observables would be sensitive to nonperturbative phases.Comment: 4 pages, Revtex, no figures, submitted to PR

Long-Term Monitoring of Post-Stroke Plasticity After Transient Cerebral Ischemia in Mice Using In Vivo and Ex Vivo Diffusion Tensor MRI

We used a murine model of transient focal cerebral ischemia to study: 1) in vivo DTI long-term temporal evolution of the apparent diffusion coefficient (ADC) and diffusion fractional anisotropy (FA) at days 4, 10, 15 and 21 after stroke 2) ex vivo distribution of a plasticity-related protein (GAP-43) and its relationship with the ex vivo DTI characteristics of the striato-thalamic pathway (21 days)

Heritability assessment of cartilage metabolism. A twin study on circulating procollagen IIA N-terminal propeptide (PIIANP)

SummaryObjectiveThe aim of this investigation was to estimate the heritability of circulating collagen IIA N-terminal propeptide (PIIANP) by studying mono- and dizygotic healthy twin pairs at different age and both genders.Design598 monozygotic (MZ) and dizygotic (DZ) twin individuals aged 18–59 years were recruited from the Danish Twin Registry. PIIANP was measured by competitive ELISA. The similarity of circulating PIIANP among MZ and DZ twins was assessed by intraclass correlations according to traits. The heritability was estimated by variance component analysis accounting for additive and dominant genetic factors as well as shared and non-shared environment but ignoring epistasis (genetic inter-locus interaction) and gene–environment interaction.ResultsThe intraclass correlation of PIIANP in MZ and DZ twins was 0.69 (0.60–0.76) and 0.46 (0.34–0.58) respectively indicating a significant genetic impact on PIIANP in serum. Additive genetic effects explained 45% (21–70%), shared environment 24% (7–53%) and non-shared environment 31% (24–39%) of the total variance. The heritability estimate did not differ across ages and between genders.ConclusionsThe study shows that approximately 45% of the collagen IIA synthesis as assessed by the collagen IIA N-terminal propeptide in serum is attributable to genetic effectors while individual and shared environment account for 24% and 31% respectively. The heritability does not differ between genders or according to age

Focused very high-energy electron beams as a novel radiotherapy modality for producing high-dose volumetric elements

The increased inertia of very high-energy electrons (VHEEs) due to relativistic effects reduces scattering and enables irradiation of deep-seated tumours. However, entrance and exit doses are high for collimated or diverging beams. Here, we perform a study based on Monte Carlo simulations of focused VHEE beams in a water phantom, showing that dose can be concentrated into a small, well-defined volumetric element, which can be shaped or scanned to treat deep-seated tumours. The dose to surrounding tissue is distributed over a larger volume, which reduces peak surface and exit doses for a single beam by more than one order of magnitude compared with a collimated beam

Temperature dependence of the breakdown of the quantum Hall effect studied by induced currents

Copyright © 2004 The American Physical SocietyWe have developed a model of the high-current breakdown of the integer quantum Hall effect, as measured in contactless experiments using a highly-sensitive torsion balance magnetometer. The model predicts that, for empirically “low-mobility” samples (μ<75 m2 V−1 s−1), the critical current for breakdown should decrease with, and have a linear dependence on, temperature. This prediction is verified experimentally with the addition of a low-temperature saturation of the critical current at a temperature that depends on both sample number density and filling factor. It is shown that this saturation is consistent with quasielastic inter-Landau-level scattering when the maximum electric field in the sample reaches a large enough value. In addition we show how this model can be extended to give qualitative agreement with experiments on high-mobility samples

Many particle entanglement in two-component Bose-Einstein Condensates

We investigate schemes to dynamically create many particle entangled states of a two component Bose-Einstein condensate in a very short time proportional to 1/N where $N$ is the number of condensate particles. For small $N$ we compare exact numerical calculations with analytical semiclassical estimates and find very good agreement for $N \geq 50$. We also estimate the effect of decoherence on our scheme, study possible scenarios for measuring the entangled states, and investigate experimental imperfections.Comment: 12 pages, 8 figure

Non-Markovian entanglement dynamics in coupled superconducting qubit systems

We theoretically analyze the entanglement generation and dynamics by coupled Josephson junction qubits. Considering a current-biased Josephson junction (CBJJ), we generate maximally entangled states. In particular, the entanglement dynamics is considered as a function of the decoherence parameters, such as the temperature, the ratio $r\equiv\omega_c/\omega_0$ between the reservoir cutoff frequency $\omega_c$ and the system oscillator frequency $\omega_0$, % between $\omega_0$ the characteristic frequency of the %quantum system of interest, and $\omega_c$ the cut-off frequency of %Ohmic reservoir and the energy levels split of the superconducting circuits in the non-Markovian master equation. We analyzed the entanglement sudden death (ESD) and entanglement sudden birth (ESB) by the non-Markovian master equation. Furthermore, we find that the larger the ratio $r$ and the thermal energy $k_BT$, the shorter the decoherence. In this superconducting qubit system we find that the entanglement can be controlled and the ESD time can be prolonged by adjusting the temperature and the superconducting phases $\Phi_k$ which split the energy levels.Comment: 13 pages, 3 figure

The Cerenkov effect revisited: from swimming ducks to zero modes in gravitational analogs

We present an interdisciplinary review of the generalized Cerenkov emission of radiation from uniformly moving sources in the different contexts of classical electromagnetism, superfluid hydrodynamics, and classical hydrodynamics. The details of each specific physical systems enter our theory via the dispersion law of the excitations. A geometrical recipe to obtain the emission patterns in both real and wavevector space from the geometrical shape of the dispersion law is discussed and applied to a number of cases of current experimental interest. Some consequences of these emission processes onto the stability of condensed-matter analogs of gravitational systems are finally illustrated.Comment: Lecture Notes at the IX SIGRAV School on "Analogue Gravity" in Como, Italy from May 16th-21th, 201

GH safety workshop position paper: A critical appraisal of recombinant human GH therapy in children and adults

Recombinant human GH (rhGH) has been in use for 30 years, and over that time its safety and efficacy in children and adults has been subject to considerable scrutiny. In 2001, a statement from the GH Research Society (GRS) concluded that 'for approved indications, GH is safe'; however, the statement highlighted a number of areas for on-going surveillance of long-Term safety, including cancer risk, impact on glucose homeostasis, and use of high dose pharmacological rhGH treatment. Over the intervening years, there have been a number of publications addressing the safety of rhGH with regard to mortality, cancer and cardiovascular risk, and the need for long-Term surveillance of the increasing number of adults who were treated with rhGH in childhood. Against this backdrop of interest in safety, the European Society of Paediatric Endocrinology (ESPE), the GRS, and the Pediatric Endocrine Society (PES) convened a meeting to reappraise the safety of rhGH. The ouput of the meeting is a concise position statement