Fabrication and operation of a two-dimensional ion-trap lattice on a high-voltage microchip

Microfabricated ion traps are a major advancement towards scalable quantum computing with trapped ions. The development of more versatile ion-trap designs, in which tailored arrays of ions are positioned in two dimensions above a microfabricated surface, will lead to applications in fields as varied as quantum simulation, metrology and atom–ion interactions. Current surface ion traps often have low trap depths and high heating rates, because of the size of the voltages that can be applied to them, limiting the fidelity of quantum gates. Here we report on a fabrication process that allows for the application of very high voltages to microfabricated devices in general and use this advance to fabricate a two-dimensional ion-trap lattice on a microchip. Our microfabricated architecture allows for reliable trapping of two-dimensional ion lattices, long ion lifetimes, rudimentary shuttling between lattice sites and the ability to deterministically introduce defects into the ion lattice

GABA Receptors and the Pharmacology of Sleep

Current GABAergic sleep-promoting medications were developed pragmatically, without making use of the immense diversity of GABAA receptors. Pharmacogenetic experiments are leading to an understanding of the circuit mechanisms in the hypothalamus by which zolpidem and similar compounds induce sleep at α2βγ2-type GABAA receptors. Drugs acting at more selective receptor types, for example, at receptors containing the α2 and/or α3 subunits expressed in hypothalamic and brain stem areas, could in principle be useful as hypnotics/anxiolytics. A highly promising sleep-promoting drug, gaboxadol, which activates αβδ-type receptors failed in clinical trials. Thus, for the time being, drugs such as zolpidem, which work as positive allosteric modulators at GABAA receptors, continue to be some of the most effective compounds to treat primary insomnia

Imbalance of ionic conductances contributes to diverse symptoms of demyelination

Fast axonal conduction of action potentials in mammals relies on myelin insulation. Demyelination can cause slowed, blocked, desynchronized, or paradoxically excessive spiking that underlies the symptoms observed in demyelination diseases. The diversity and timing of such symptoms are poorly understood, often intermittent, and uncorrelated with disease progress. We modeled the effects of demyelination (and secondary remodeling) on intrinsic axonal excitability using Hodgkin–Huxley and reduced Morris–Lecar models. Simulations and analysis suggested a simple explanation for the breadth of symptoms and revealed that the ratio of sodium to leak conductance, gNa/gL, acted as a four-way switch controlling excitability patterns that included spike failure, single spike transmission, afterdischarge, and spontaneous spiking. Failure occurred when this ratio fell below a threshold value. Afterdischarge occurred at gNa/gL just below the threshold for spontaneous spiking and required a slow inward current that allowed for two stable attractor states, one corresponding to quiescence and the other to repetitive spiking. A neuron prone to afterdischarge could function normally unless it was switched to its “pathological” attractor state; thus, although the underlying pathology may develop slowly by continuous changes in membrane conductances, a discontinuous change in axonal excitability can occur and lead to paroxysmal symptoms. We conclude that tonic and paroxysmal positive symptoms as well as negative symptoms may be a consequence of varying degrees of imbalance between gNa and gL after demyelination. The KCNK family of gL potassium channels may be an important target for new drugs to treat the symptoms of demyelination

Measurements of SOx, NOx and aerosol species on Bermuda

During August 1982 and January and February 1983, General Motors Research Laboratories operated an air monitoring site on the southwest coast of Bermuda. The data show that the levels of the NOx and SOx species reaching Bermuda are determined by the direction of the air flow. The highest levels of sulfate (mean = 4.0 [mu]g m-3), nitric acid (126 ppt) and other species are observed when air masses arrive from the northeastern United States while the lowest levels (sulfate = 1.1 [mu]g m-3; nitric ACID = 41 ppt) occur during air flow from the SE direction. With westerly air flow, increases in many anthropogenic constituents such as particulate sulfate, lead, elemental carbon, sulfur dioxide, nitrogen dioxide, nitric acid and ozone are observed. These species are generally the lowest during SE winds which bring high concentrations of soil- and crustal-related aerosol species. The source of this crustal material appears to be the Sahara Desert. On the average, the levels of anthropogenic constituents are higher in winter because of frequent intrusions of N American air masses. Conversely, the levels of crustal materials are higher in summer when the SE flow is more prevalent.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/26456/1/0000544.pd