Shapiro steps in a superconducting film with an antidot lattice

Shapiro voltage steps at voltages V_n=nV_0 (n integer) have been observed in the voltage-current characteristics of a superconducting film with a square lattice of perforating microholes (antidots)in the presence of radiofrequent radiation. These equidistant steps appear at the second matching field H_2 when the flow of the interstitial vortex lattice in the periodic potential created by the antidots and the vortices trapped by them, is in phase with the applied rf frequency. Therefore, the observation of Shapiro steps clearly reveals the presence of mobile intersitial vortices in superconducting films with regular pinning arrays. The interstitial vortices, moved by the driving current, coexist with immobile vortices strongly pinned at the antidots.Comment: 6 pages text, 3 EPS figures, RevTeX, accepted for publication in PRB Rapid Communication

Modelling, Design And Diagnostics For A Photoionised Plasma Experiment

Photoionised plasmas are common in astrophysical environments and new high resolution spectra from such sources have been recorded in recent years by the Chandra and XMM-Newton satellites. These provide a wealth of spectroscopic information and have motivated recent efforts aimed at obtaining a detailed understanding of the atomic-kinetic and radiative characteristics of photoionised plasmas. The Z-pinch facility at the Sandia National Laboratories is the most powerful terrestrial source of X-rays and provides an opportunity to produce photoionised plasmas in a well characterised radiation environment. We present modelling work and experimental design considerations for a forthcoming experiment at Sandia in which X-rays from a collapsing Z-pinch will be used to photoionise low density neon contained in a gas cell. View factor calculations were used to evaluate the radiation environment at the gas cell; the hydrodynamic characteristics of the gas cell were examined using the Helios-CR code, in particular looking at the heating, temperature and ionisation of the neon and the absorption of radiation. Emission and absorption spectra were also computed, giving estimates of spectra likely to be observed experimentally

Canine Motor Neuron Disease: A View from the Motor Unit

This chapter is from the book Motor Neurobiology of the Spinal Cord, which provides a description of the recent conceptual and technical advances in the field. It provides a description of the new experimental tools available for investigating the neuronal properties that allow populations of spinal cord neurons to control muscles responsible for limb movements and posture. It covers topics ranging from genetics to kinematics and examines cells, tissues, or whole animals in species ranging from fish to humans that are normal, injured, or diseased. By integrating data derived from many new approaches, you\u27ll learn about how spinal cord circuits operate under a variety conditions and about new and exciting inroads being made in motor neurobiology of the spinal cord. Motor Neurobiology of the Spinal Cord elucidates concepts and principles relevant to function and structure throughout the nervous system and presents information about changes induced by injury and disease

Canine Motor Neuron Disease: A View from the Motor Unit

This chapter is from the book Motor Neurobiology of the Spinal Cord, which provides a description of the recent conceptual and technical advances in the field. It provides a description of the new experimental tools available for investigating the neuronal properties that allow populations of spinal cord neurons to control muscles responsible for limb movements and posture. It covers topics ranging from genetics to kinematics and examines cells, tissues, or whole animals in species ranging from fish to humans that are normal, injured, or diseased. By integrating data derived from many new approaches, you\u27ll learn about how spinal cord circuits operate under a variety conditions and about new and exciting inroads being made in motor neurobiology of the spinal cord. Motor Neurobiology of the Spinal Cord elucidates concepts and principles relevant to function and structure throughout the nervous system and presents information about changes induced by injury and disease

Evolutionary perspectives into placental biology and disease

AbstractIn all mammals including humans, development takes place within the protective environment of the maternal womb. Throughout gestation, nutrients and waste products are continuously exchanged between mother and fetus through the placenta. Despite the clear importance of the placenta to successful pregnancy and the health of both mother and offspring, relatively little is understood about the biology of the placenta and its role in pregnancy-related diseases. Given that pre- and peri-natal diseases involving the placenta affect millions of women and their newborns worldwide, there is an urgent need to understand placenta biology and development. Here, we suggest that the placenta is an organ under unique selective pressures that have driven its rapid diversification throughout mammalian evolution. The high divergence of the placenta complicates the use of non-human animal models and necessitates an evolutionary perspective when studying its biology and role in disease. We suggest that diversifying evolution of the placenta is primarily driven by intraspecies evolutionary conflict between mother and fetus, and that many pregnancy diseases are a consequence of this evolutionary force. Understanding how maternal–fetal conflict shapes both basic placental and reproductive biology – in all species – will provide key insights into diseases of pregnancy

Canine Motor Neuron Disease: A View from the Motor Unit

This chapter is from the book Motor Neurobiology of the Spinal Cord, which provides a description of the recent conceptual and technical advances in the field. It provides a description of the new experimental tools available for investigating the neuronal properties that allow populations of spinal cord neurons to control muscles responsible for limb movements and posture. It covers topics ranging from genetics to kinematics and examines cells, tissues, or whole animals in species ranging from fish to humans that are normal, injured, or diseased. By integrating data derived from many new approaches, you\u27ll learn about how spinal cord circuits operate under a variety conditions and about new and exciting inroads being made in motor neurobiology of the spinal cord. Motor Neurobiology of the Spinal Cord elucidates concepts and principles relevant to function and structure throughout the nervous system and presents information about changes induced by injury and disease