Mean flow instabilities of two-dimensional convection in strong magnetic fields

The interaction of magnetic fields with convection is of great importance in astrophysics. Two well-known aspects of the interaction are the tendency of convection cells to become narrow in the perpendicular direction when the imposed field is strong, and the occurrence of streaming instabilities involving horizontal shears. Previous studies have found that the latter instability mechanism operates only when the cells are narrow, and so we investigate the occurrence of the streaming instability for large imposed fields, when the cells are naturally narrow near onset. The basic cellular solution can be treated in the asymptotic limit as a nonlinear eigenvalue problem. In the limit of large imposed field, the instability occurs for asymptotically small Prandtl number. The determination of the stability boundary turns out to be surprisingly complicated. At leading order, the linear stability problem is the linearisation of the same nonlinear eigenvalue problem, and as a result, it is necessary to go to higher order to obtain a stability criterion. We establish that the flow can only be unstable to a horizontal mean flow if the Prandtl number is smaller than order , where B0 is the imposed magnetic field, and that the mean flow is concentrated in a horizontal jet of width in the middle of the layer. The result applies to stress-free or no-slip boundary conditions at the top and bottom of the layer

A Fetal-Maternal Shift of Blood Oxygen Affinity in an Australian Viviparous Lizard, Sphenomorphus quoyii (Reptilia, Scincidae)

Compared to adults, the oxygen affinity of blood from fetal Sphenomorphus quoyii is very much higher: P50 is approximately 70 Torr in adults and 30 Torr in nearly full term embryos (PC02= 17 Torr, T=34 degrees C). Following birth, oxygen affinity decreases gradually and adult values are approached after about 15 weeks, with the onset of winter retreat. Electrophoresis revealed a multiple hemoglobin system in both adults and embryos, but there were no apparent differences between them

Submillimeter Studies of Prestellar Cores and Protostars: Probing the Initial Conditions for Protostellar Collapse

Improving our understanding of the initial conditions and earliest stages of protostellar collapse is crucial to gain insight into the origin of stellar masses, multiple systems, and protoplanetary disks. Observationally, there are two complementary approaches to this problem: (1) studying the structure and kinematics of prestellar cores observed prior to protostar formation, and (2) studying the structure of young (e.g. Class 0) accreting protostars observed soon after point mass formation. We discuss recent advances made in this area thanks to (sub)millimeter mapping observations with large single-dish telescopes and interferometers. In particular, we argue that the beginning of protostellar collapse is much more violent in cluster-forming clouds than in regions of distributed star formation. Major breakthroughs are expected in this field from future large submillimeter instruments such as Herschel and ALMA.Comment: 12 pages, 9 figures, to appear in the proceedings of the conference "Chemistry as a Diagnostic of Star Formation" (C.L. Curry & M. Fich eds.

Atom--Molecule Coherence in a Bose-Einstein Condensate

Coherent coupling between atoms and molecules in a Bose-Einstein condensate (BEC) has been observed. Oscillations between atomic and molecular states were excited by sudden changes in the magnetic field near a Feshbach resonance and persisted for many periods of the oscillation. The oscillation frequency was measured over a large range of magnetic fields and is in excellent quantitative agreement with the energy difference between the colliding atom threshold energy and the energy of the bound molecular state. This agreement indicates that we have created a quantum superposition of atoms and diatomic molecules, which are chemically different species.Comment: 7 pages, 6 figure

Primary cutaneous melanoma of the breast: A case report

which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Background: Primary cutaneous melanoma of the breast is a very rare tumour, accounting for < 5 % of all malignant melanomas. Case presentation: A young lady was seen in the breast clinic for a skin lesion in the right breast. Clinical examination and investigations confirmed a diagnosis of a primary cutaneous melanoma of the breast. The lesion was excised and the patient made good recovery. She has shown no signs of local recurrence and is under regular follow-up in the dermatology clinic. Conclusion: This case is educational as it shows that the treatment of breast cutaneous melanoma is similar to that for any skin parts with surgery remaining the main therapeutic option. It also shows that mastectomy is unnecessary as it does not improve the results obtained by wide local excision of melanoma. Background Primary cutaneous melanoma rarely affects the breast, accounting for less than 5 % of all malignant melanomas

Building nonparametric nn-body force fields using Gaussian process regression

Constructing a classical potential suited to simulate a given atomic system is a remarkably difficult task. This chapter presents a framework under which this problem can be tackled, based on the Bayesian construction of nonparametric force fields of a given order using Gaussian process (GP) priors. The formalism of GP regression is first reviewed, particularly in relation to its application in learning local atomic energies and forces. For accurate regression it is fundamental to incorporate prior knowledge into the GP kernel function. To this end, this chapter details how properties of smoothness, invariance and interaction order of a force field can be encoded into corresponding kernel properties. A range of kernels is then proposed, possessing all the required properties and an adjustable parameter $n$ governing the interaction order modelled. The order $n$ best suited to describe a given system can be found automatically within the Bayesian framework by maximisation of the marginal likelihood. The procedure is first tested on a toy model of known interaction and later applied to two real materials described at the DFT level of accuracy. The models automatically selected for the two materials were found to be in agreement with physical intuition. More in general, it was found that lower order (simpler) models should be chosen when the data are not sufficient to resolve more complex interactions. Low $n$ GPs can be further sped up by orders of magnitude by constructing the corresponding tabulated force field, here named "MFF".Comment: 31 pages, 11 figures, book chapte

Health-care costs of losartan and candesartan in the primary treatment of hypertension

A recent study of two widely used angiotensin receptor blockers reported a reduced risk of cardiovascular events (−14.4%) when using candesartan compared with losartan in the primary treatment of hypertension. In addition to clinical benefits, costs associated with treatment strategies must be considered when allocating scarce health-care resources. The aim of this study was to assess resource use and costs of losartan and candesartan in hypertensive patients. Resource use (drugs, outpatient contacts, hospitalizations and laboratory tests) associated with losartan and candesartan treatment was estimated in 14 100 patients in a real-life clinical setting. We electronically extracted patient data from primary care records and mandatory Swedish national registers for death and hospitalization. Patients treated with losartan had more outpatient contacts (+15.6%), laboratory tests (+13.8%) and hospitalizations (+13.8%) compared with the candesartan group. During a maximum observation time of 9 years, the mean total costs per patient were 10 369 Swedish kronor (95% confidence interval: 3109–17 629) higher in the losartan group. In conclusion, prescribing candesartan for the primary treatment of hypertension results in lower long-term health-care costs compared with losartan

Circulating Cell-Free DNA in Dogs with Mammary Tumors: Short and Long Fragments and Integrity Index

Circulating cell-free DNA (cfDNA) has been considered an interesting diagnostic/prognostic plasma biomarker in tumor-bearing subjects. In cancer patients, cfDNA can hypothetically derive from tumor necrosis/apoptosis, lysed circulating cells, and some yet unrevealed mechanisms of active release. This study aimed to preliminarily analyze cfDNA in dogs with canine mammary tumors (CMTs). Forty-four neoplastic, 17 non-neoplastic disease-bearing, and 15 healthy dogs were recruited. Necrosis and apoptosis were also assessed as potential source of cfDNA on 78 CMTs diagnosed from the 44 dogs. The cfDNA fragments and integrity index significantly differentiated neoplastic versus non-neoplastic dogs (P<0.05), and allowed the distinction between benign and malignant lesions (P<0.05). Even if without statistical significance, the amount of cfDNA was also affected by tumor necrosis and correlated with tumor size and apoptotic markers expression. A significant (P<0.01) increase of Bcl-2 in malignant tumors was observed, and in metastatic CMTs the evasion of apoptosis was also suggested. This study, therefore, provides evidence that cfDNA could be a diagnostic marker in dogs carrying mammary nodules suggesting that its potential application in early diagnostic procedures should be further investigated