The chromatin remodeller ACF acts as a dimeric motor to space nucleosomes.

Evenly spaced nucleosomes directly correlate with condensed chromatin and gene silencing. The ATP-dependent chromatin assembly factor (ACF) forms such structures in vitro and is required for silencing in vivo. ACF generates and maintains nucleosome spacing by constantly moving a nucleosome towards the longer flanking DNA faster than the shorter flanking DNA. How the enzyme rapidly moves back and forth between both sides of a nucleosome to accomplish bidirectional movement is unknown. Here we show that nucleosome movement depends cooperatively on two ACF molecules, indicating that ACF functions as a dimer of ATPases. Further, the nucleotide state determines whether the dimer closely engages one or both sides of the nucleosome. Three-dimensional reconstruction by single-particle electron microscopy of the ATPase-nucleosome complex in an activated ATP state reveals a dimer architecture in which the two ATPases face each other. Our results indicate a model in which the two ATPases work in a coordinated manner, taking turns to engage either side of a nucleosome, thereby allowing processive bidirectional movement. This novel dimeric motor mechanism differs from that of dimeric motors such as kinesin and dimeric helicases that processively translocate unidirectionally and reflects the unique challenges faced by motors that move nucleosomes

Single-charge detection by an atomic precision tunnel junction

We demonstrate sensitive detection of single charges using a planar tunnel junction 8.5 nm wide and 17.2 nm long defined by an atomically precise phosphorus doping profile in silicon. The conductance of the junction responds to a nearby gate potential and also to changes in the charge state of a quantum dot patterned 52 nm away. The response of this detector is monotonic across the entire working voltage range of the device, which will make it particularly useful for studying systems of multiple quantum dots. The charge sensitivity is maximized when the junction is most conductive, suggesting that more sensitive detection can be achieved by shortening the length of the junction to increase its conductance

Aeroelasticity of a Generic Hypersonic Vehicle

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/76282/1/AIAA-2002-1209-307.pd

Hypersonic Aerothermoelastic Studies for Reusable Launch Vehicles

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/77241/1/AIAA-2004-1590-254.pd

Aeroelastic and Aerothermoelastic Vehicle Behavior in Hypersonic Flow

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/76797/1/AIAA-2005-3305-890.pd

Radio frequency reflectometry and charge sensing of a precision placed donor in silicon

We compare charge transitions on a deterministic single P donor in silicon using radio frequency reflectometry measurements with a tunnel coupled reservoir and DC charge sensing using a capacitively coupled single electron transistor (SET). By measuring the conductance through the SET and comparing this with the phase shift of the reflected RF excitation from the reservoir, we can discriminate between charge transfer within the SET channel and tunneling between the donor and reservoir. The RF measurement allows observation of donor electron transitions at every charge degeneracy point in contrast to the SET conductance signal where charge transitions are only observed at triple points. The tunnel coupled reservoir has the advantage of a large effective lever arm (~35%) allowing us to independently extract a neutral donor charging energy ~62 +/- 17meV. These results demonstrate that we can replace three terminal transistors by a single terminal dispersive reservoir, promising for high bandwidth scalable donor control and readout.Comment: 5 pages, 3 figures. Copyright (2015) American Institute of Physics. This article may be downloaded for personal use only. Any other use requires prior permission of the author and the American Institute of Physic

The Bridgwater Infant Welfare Centre, 1922-1939: from an authoritarian concern with 'welfare mothers' to a more inclusive community health project?

The infant welfare movement in Britain has received considerable scholarly attention but continues to generate controversy and debate. Many of the services began with nineteenth-century voluntary initiative but were later developed by local authorities. Critics have drawn attention to the limitations of such provision; arguing that it was predicated on unattractive assumptions about class and gender roles. Under this interpretation working-class mothers were viewed with suspicion and targeted for advice aimed at inculcating middle-class standards of childcare and housekeeping. This paper accepts that there was an authoritarian character to much of the early welfare work but suggests that over time this gave way to more inclusive approaches that sought to provide clients with the services that met their real rather than assumed needs. This paper reviews the recent historiography, develops an overview of national trends, and then takes a detailed look at the Bridgwater Infant Welfare Centre. The case study benefi ts from unusually comprehensive records and, by drawing on evidence from a small Somerset town, adds to our understanding of infant welfare work that has previously been developed from research on major urban centres.Wellcome Trust Fellowshi

A surface code quantum computer in silicon

The exceptionally long quantum coherence times of phosphorus donor nuclear spin qubits in silicon, coupled with the proven scalability of silicon-based nano-electronics, make them attractive candidates for large-scale quantum computing. However, the high threshold of topological quantum error correction can only be captured in a two-dimensional array of qubits operating synchronously and in parallel—posing formidable fabrication and control challenges. We present an architecture that addresses these problems through a novel shared-control paradigm that is particularly suited to the natural uniformity of the phosphorus donor nuclear spin qubit states and electronic confinement. The architecture comprises a two-dimensional lattice of donor qubits sandwiched between two vertically separated control layers forming a mutually perpendicular crisscross gate array. Shared-control lines facilitate loading/unloading of single electrons to specific donors, thereby activating multiple qubits in parallel across the array on which the required operations for surface code quantum error correction are carried out by global spin control. The complexities of independent qubit control, wave function engineering, and ad hoc quantum interconnects are explicitly avoided. With many of the basic elements of fabrication and control based on demonstrated techniques and with simulated quantum operation below the surface code error threshold, the architecture represents a new pathway for large-scale quantum information processing in silicon and potentially in other qubit systems where uniformity can be exploited

Two systems for empathy: a double dissociation between emotional and cognitive empathy in inferior frontal gyrus versus ventromedial prefrontal lesions

Recent evidence suggests that there are two possible systems for empathy: a basic emotional contagion system and a more advanced cognitive perspective-taking system. However, it is not clear whether these two systems are part of a single interacting empathy system or whether they are independent. Additionally, the neuroanatomical bases of these systems are largely unknown. In this study, we tested the hypothesis that emotional empathic abilities (involving the mirror neuron system) are distinct from those related to cognitive empathy and that the two depend on separate anatomical substrates. Subjects with lesions in the ventromedial prefrontal (VM) or inferior frontal gyrus (IFG) cortices and two control groups were assessed with measures of empathy that incorporate both cognitive and affective dimensions. The findings reveal a remarkable behavioural and anatomic double dissociation between deficits in cognitive empathy (VM) and emotional empathy (IFG). Furthermore, precise anatomical mapping of lesions revealed Brodmann area 44 to be critical for emotional empathy while areas 11 and 10 were found necessary for cognitive empathy. These findings are consistent with these cortices being different in terms of synaptic hierarchy and phylogenetic age. The pattern of empathy deficits among patients with VM and IFG lesions represents a first direct evidence of a double dissociation between emotional and cognitive empathy using the lesion method. Keywords: Emotional empathy; cognitive empathy; mirror neurons; inferior frontal gyrus; ventromedial prefrontal cortex Abbreviations: ANOVA = analysis of variance; BA = Brodmann area; EC = empathic concern scale; FS = fantasy scale; HC = healthy control; IFG = inferior frontal gyrus; IRI = Interpersonal Reactivity Index; MNS = mirror neuron system; PC = posterior lesion; PD = personal distress scale; PT = perspective-taking scale; ToM = Theory of Mind; VM = ventromedial prefrontal; WCST = Wisconsin Card Sorting Test