Bespoke magnetic field design for a magnetically shielded cold atom interferometer.

Quantum sensors based on cold atoms are being developed which produce measurements of unprecedented accuracy. Due to shifts in atomic energy levels, quantum sensors often have stringent requirements on their internal magnetic field environment. Typically, background magnetic fields are attenuated using high permeability magnetic shielding, with the cancelling of residual and introduction of quantisation fields implemented with coils inside the shield. The high permeability shield, however, distorts all magnetic fields, including those generated inside the sensor. Here, we demonstrate a solution by designing multiple coils overlaid on a 3D-printed former to generate three uniform and three constant linear gradient magnetic fields inside the capped cylindrical magnetic shield of a cold atom interferometer. The fields are characterised in-situ and match their desired forms to high accuracy. For example, the uniform transverse field, Bx, deviates by less than 0.2% over more than 40% of the length of the shield. We also map the field directly using the cold atoms and investigate the potential of the coil system to reduce bias from the quadratic Zeeman effect. This coil design technology enables targeted field compensation over large spatial volumes and has the potential to reduce systematic shifts and noise in numerous cold atom systems.

A portable magneto-optical trap with prospects for atom interferometry in civil engineering.

The high precision and scalable technology offered by atom interferometry has the opportunity to profoundly affect gravity surveys, enabling the detection of features of either smaller size or greater depth. While such systems are already starting to enter into the commercial market, significant reductions are required in order to reach the size, weight and power of conventional devices. In this article, the potential for atom interferometry based gravimetry is assessed, suggesting that the key opportunity resides within the development of gravity gradiometry sensors to enable drastic improvements in measurement time. To push forward in realizing more compact systems, techniques have been pursued to realize a highly portable magneto-optical trap system, which represents the core package of an atom interferometry system. This can create clouds of 107 atoms within a system package of 20 l and 10 kg, consuming 80 W of power.This article is part of the themed issue 'Quantum technology for the 21st century'.

Haemorrhage as a complication of extracorporeal pig liver perfusion: studies on mechanism and prevention.

The use of extracorporeal pig liver perfusion for temporary liver support has been followed not infrequently by major bleeding with a fall in coagulation factors and platelets, rather than a rise as hoped. In 18 experimental perfusions in which (125)I-labelled fibrinogen was used as a marker there was in every instance a significant loss of the fibrinogen into the fluid supporting the liver in the perfusion chamber. Further, in 11 of the perfusions there was an additional loss into liver substance, this being associated with a very rapid fall in (125)I fibrinogen and platelets content of the perfusion fluid. Damage to the sinusoids from ischaemic damage incurred during removal of the liver could explain both the direct loss of fibrinogen and, as a result of intravascular coagulation, the associated loss within the perfused liver. No correlation could be found with biochemical function, but it proved possible to assess haematological safety before connexion of the patient to the perfusion by a shortened (125)I fibrinogen test. This was done in three patients treated by five perfusions and in none was the thrombocytopenia or coagulation disturbance adversely affected.

Effects of haemoperfusion through charcoal or XAD-2 resin on an animal model of fulminant liver failure.

In a group of dogs in whom fulminant liver failure had been induced, perfusion of blood through activated charcoal resulted in a significantly longer survival than that of a similar group of dogs whose blood was not so treated. An otherwise progressive rise in blood ammonia concentration was halted in the treatment group. In another group of dogs with fulminant liver failure perfusion of blood through the resin Amberlite XAD-2 was associated with a fall in the serum bilirubin concentration and complete clearance from the blood of (14)C-labelled sodium glycocholate. Survival in this group of animals was not significantly prolonged. This was due at least in part to the occurrence of haemorrhage due to thrombocytopenia. Platelets adhere to the resin but do not adhere to the same degree to charcoal coated with a thin layer of polymer.

Early and intensive therapy of intravascular coagulation in acute liver failure.

Four consecutive patients, three with fulminant hepatic failure and one with a severe relapse of serum hepatitis, who showed evidence of intravascular coagulation, were treated intensively with heparin and fresh frozen plasma. Rapid correction of the coagulation disturbance was achieved, and all four patients recovered completely. The necessity for starting such treatment early in the course of the disease and before the onset of major gastrointestinal bleeding is stressed, and it is suggested that intravascular coagulation may act as an intermediary in the pathogenesis of the hepatic necrosis.