Isolation of anaerobic, extremely thermophilic, sulphur metabolising archaebacteria from New Zealand hot springs

Enrichments of New Zealand geo-thermal samples, initiated in anaerobic sulphur-containing media and incubated at temperatures above 85°C, yielded rod and coccal shaped organisms which possessed archaebacterial characteristics. Pure cultures were isolated and characterised. Five of the seven isolates, which were rod-shaped organisms and did not have an obligate requirement for sulphur respiration, were similar to Ther-moproteus sp. but had more neutral pH optima for growth. Three of these five Thermoproteus sp. were obligate heterotrophs, which has not previously been reported. The two coccal isolates had an obligate requirement for sulphur as an electron acceptor and were similar to Desulfurococcus sp. but again with more neutral pH optima for growth

Flow-induced dilation of skeletal muscle feed arteries: relevance to exercise hyperemia

During exercise, an increase in blood flow to working skeletal muscle is accomplished by dilation of arteries and arterioles supplying the muscle. Arterioles, located within contracting muscle, are exposed to dilatory metabolites released by the muscle; however, the mechanism by which feed arteries, located external to the muscle, dilate is still unknown. One potential mechanism for feed artery dilation is flow-induced dilation, occurring when arteries dilate in response to increased vascular wall shear stress. Shear stress is the frictional force between blood and the arterial wall, which increases when blood flow velocity increases. Data from previous in vitro experiments (8) indicate that flow-induced dilation in rat soleus feed arteries occurs at blood flow levels that are far less than normal resting blood flow in conscious rats. This data led to the conclusion that flow-induced dilation was not a plausible mechanism to explain the increase in blood flow during exercise. Furthermore, the soleus muscle is primarily composed of slow-oxidative fibers and used in maintaining posture; thus, it receives a substantial amount of blood flow at rest. We sought to test whether flow-induced dilation could contribute to exercise hyperemia in rat extensor digitorum longus muscle, primarily composed of fast-glycolytic fibers, and rat gastrocnemius, a muscle of mixed fiber type (4). The differences in fiber type of each muscle may be a factor in how the feed arteries dilate during exercise. The purpose of this study was to determine if flow-induced dilation potentially contributes to exercise hyperemia in rat extensor digitorum longus and gastrocnemius muscle feed arteries, EDLFA and GFA, respectively. In this study, blood flow was induced through the arteries and corresponding flow measurements (µl/min) were collected. The flow values were used to calculate intraluminal wall shear stress in the arteries and then compared to calculated in vivo shear stress values from previously published studies (1,2,3,7,10,11,12,13,14,15). We hypothesized that flow-induced dilation in GFA and EDLFA occurs at shear stress values lower than the shear stress normally present in non-exercising rats. This would preclude flow-induced dilation from causing the dilation of feed arteries to gastrocnemius and EDL muscles in exercise

A versatile high resolution objective for imaging quantum gases

We present a high resolution objective lens made entirely from catalog singlets that has a numerical aperture of 0.36. It corrects for aberrations introduced by a glass window and has a long working distance of 35mm, making it suitable for imaging objects within a vacuum system. This offers simple high resolution imaging for many in the quantum gas community. The objective achieves a resolution of 1.3{\mu}m at the design wavelength of 780nm, and a diffraction-limited field of view of 360{\mu}m when imaging through a 5mm window. Images of a resolution target and a pinhole show quantitative agreement with the simulated lens performance. The objective is suitable for diffraction-limited imaging on the D2 line of all the alkalis by changing only the aperture diameter, retaining numerical apertures above 0.32. The design corrects for window thicknesses of up to 15mm if the singlet spacings are modified

Relative intensity squeezing by four-wave mixing with loss: an analytic model and experimental diagnostic

Four-wave mixing near resonance in an atomic vapor can produce relative intensity squeezed light suitable for precision measurements beyond the shot-noise limit. We develop an analytic distributed gain/loss model to describe the competition of mixing and absorption through the non-linear medium. Using a novel matrix calculus, we present closed-form expressions for the degree of relative intensity squeezing produced by this system. We use these theoretical results to analyze experimentally measured squeezing from a $^{85}$Rb vapor and demonstrate the analytic model's utility as an experimental diagnostic.Comment: 10 pages, 5 figure

Effect of Patterned Slip on Micro and Nanofluidic Flows

We consider the flow of a Newtonian fluid in a nano or microchannel with walls that have patterned variations in slip length. We formulate a set of equations to describe the effects on an incompressible Newtonian flow of small variations in slip, and solve these equations for slow flows. We test these equations using molecular dynamics simulations of flow between two walls which have patterned variations in wettability. Good qualitative agreement and a reasonable degree of quantitative agreement is found between the theory and the molecular dynamics simulations. The results of both analyses show that patterned wettability can be used to induce complex variations in flow. Finally we discuss the implications of our results for the design of microfluidic mixers using slip.Comment: 13 pages, 12 figures, final version for publicatio

Precise wavefunction engineering with magnetic resonance

Controlling quantum fluids at their fundamental length scale will yield superlative quantum simulators, precision sensors, and spintronic devices. This scale is typically below the optical diffraction limit, precluding precise wavefunction engineering using optical potentials alone. We present a protocol to rapidly control the phase and density of a quantum fluid down to the healing length scale using strong time-dependent coupling between internal states of the fluid in a magnetic field gradient. We demonstrate this protocol by simulating the creation of a single stationary soliton and double soliton states in a Bose-Einstein condensate with control over the individual soliton positions and trajectories, using experimentally feasible parameters. Such states are yet to be realized experimentally, and are a path towards engineering soliton gases and exotic topological excitations.Comment: 8+ pages, 3 figures; revised parameters and added section about optimisation of adiabatic, finite-duration pulses and analytic resolution limi