Two primary methods of proving gas flow meters

Methods for determining mass flow rates of gases for use in calibrating gas flowmeter

Crack nucleation using combined crystal plasticity modelling, high-resolution digital image correlation and high-resolution electron backscatter diffraction in a superalloy containing non-metallic inclusions under fatigue

A crystal plasticity finite-element model, which explicitly and directly represents the complex microstructures of a non-metallic agglomerate inclusion within polycrystal nickel alloy, has been developed to study the mechanistic basis of fatigue crack nucleation. The methodology is to use the crystal plasticity model in conjunction with direct measurement at the microscale using high (angular) resolution-electron backscatter diffraction (HR-EBSD) and high (spatial) resolution-digital image correlation (HR-DIC) strain measurement techniques. Experimentally, this sample has been subjected to heat treatment leading to the establishment of residual (elastic) strains local to the agglomerate and subsequently loaded under conditions of low cyclic fatigue. The full thermal and mechanical loading history was reproduced within the model. HR-EBSD and HR-DIC elastic and total strain measurements demonstrate qualitative and quantitative agreement with crystal plasticity results. Crack nucleation by interfacial decohesion at the nickel matrix/agglomerate inclusion boundaries is observed experimentally, and systematic modelling studies enable the mechanistic basis of the nucleation to be established. A number of fatigue crack nucleation indicators are also assessed against the experimental results. Decohesion was found to be driven by interface tensile normal stress alone, and the interfacial strength was determined to be in the range of 1270–1480 MPa

Quantum information processing with trapped ions

Experiments directed towards the development of a quantum computer based on trapped atomic ions are described briefly. We discuss the implementation of single qubit operations and gates between qubits. A geometric phase gate between two ion qubits is described. Limitations of the trapped-ion method such as those caused by Stark shifts and spontaneous emission are addressed. Finally, we describe a strategy to realize a large-scale device.Comment: Article submitted by D. J. Wineland ([email protected]) for proceeding of the Discussion Meeting on Practical Realisations of Quantum Information Processing, held at the Royal Society, Nov. 13,14, 200

Intestinal volvulus in the pump twin of a twin reversed arterial perfusion (TRAP) sequence after laser therapy at 18 weeks: a case report

Background: Twin reversed arterial perfusion sequence is a rare and potentially lethal condition affecting approximately 1% of monochorionic twin pregnancies and 1 in 35,000 pregnancies overall. An apparently normal (pump) twin perfuses its severely malformed cotwin with deoxygenated blood via retrograde flow in direct arterioarterial anastomoses between the umbilical arteries of each twin. Fetal intestinal volvulus is a rare condition usually manifesting after birth. We report a unique case of twin reversed arterial perfusion sequence in association with intestinal volvulus in the surviving pump twin. Case presentation: A 32-year-old Hispanic primigravida was referred to our clinic after a fetoscopy procedure of laser photocoagulation of anastomoses at 18 weeks of gestation. Follow up scans in the ex-pump twin revealed dilated bowel loops and a typical “whirlpool sign” at 26 weeks of gestation, and intrauterine intestinal volvulus was suspected. At 29 weeks of gestation, preterm premature rupture of membranes occurred, and an emergency cesarean section was performed. The newborn was diagnosed in the early neonatal period with intestinal perforation. The diagnosis was postnatally confirmed by surgery and histopathology. Conclusions: The type of fetal intervention and late gestational age of the procedure increase the risk of complications. This case alerts health providers to be vigilant in the follow-up of patients with complicated monochorionic pregnanciesBackground: Twin reversed arterial perfusion sequence is a rare and potentially lethal condition affecting approximately 1% of monochorionic twin pregnancies and 1 in 35,000 pregnancies overall. An apparently normal (pump) twin perfuses its severely malformed cotwin with deoxygenated blood via retrograde flow in direct arterioarterial anastomoses between the umbilical arteries of each twin. Fetal intestinal volvulus is a rare condition usually manifesting after birth. We report a unique case of twin reversed arterial perfusion sequence in association with intestinal volvulus in the surviving pump twin. Case presentation: A 32-year-old Hispanic primigravida was referred to our clinic after a fetoscopy procedure of laser photocoagulation of anastomoses at 18 weeks of gestation. Follow up scans in the ex-pump twin revealed dilated bowel loops and a typical “whirlpool sign” at 26 weeks of gestation, and intrauterine intestinal volvulus was suspected. At 29 weeks of gestation, preterm premature rupture of membranes occurred, and an emergency cesarean section was performed. The newborn was diagnosed in the early neonatal period with intestinal perforation. The diagnosis was postnatally confirmed by surgery and histopathology. Conclusions: The type of fetal intervention and late gestational age of the procedure increase the risk of complications. This case alerts health providers to be vigilant in the follow-up of patients with complicated monochorionic pregnancie

Experimental demonstration of a technique to generate arbitrary quantum superposition states

Using a single, harmonically trapped $^9$Be$^+$ ion, we experimentally demonstrate a technique for generation of arbitrary states of a two-level particle confined by a harmonic potential. Rather than engineering a single Hamiltonian that evolves the system to a desired final sate, we implement a technique that applies a sequence of simple operations to synthesize the state

Cis-regulatory elements of the mitotic regulator, string/Cdc25

Mitosis in most Drosophila cells is triggered by brief bursts of transcription of string (stg), a Cdc25-type phosphatase that activates the mitotic kinase, Cdk1 (Cdc2). To understand how string transcription is regulated, we analyzed the expression of string-lacZ reporter genes covering approximately 40 kb of the string locus. We also tested protein coding fragments of the string locus of 6 kb to 31.6 kb for their ability to complement loss of string function in embryos and imaginal discs. A plethora of cis-acting elements spread over >30 kb control string transcription in different cells and tissue types. Regulatory elements specific to subsets of epidermal cells, mesoderm, trachea and nurse cells were identified, but the majority of the string locus appears to be devoted to controlling cell proliferation during neurogenesis. Consistent with this, compact promotor-proximal sequences are sufficient for string function during imaginal disc growth, but additional distal elements are required for the development of neural structures in the eye, wing, leg and notum. We suggest that, during evolution, cell-type-specific control elements were acquired by a simple growth-regulated promoter as a means of coordinating cell division with developmental processes, particularly neurogenesis.Dara A. Lehman; Briony Patterson, Laura A. Johnston; Tracy Balzer; Jessica S. Britton; Robert Saint and Bruce A. Edga

High resolution characterisation of microstructural evolution in Rbx_{x}Fe2−y_{2-y}Se2_{2} crystals on annealing

The superconducting and magnetic properties of phase-separated A$_x$Fe$_{2-y}$Se$_2$ compounds are known to depend on post-growth heat treatments and cooling profiles. This paper focusses on the evolution of microstructure on annealing, and how this influences the superconducting properties of Rb$_x$Fe$_2-y$Se$_2$ crystals. We find that the minority phase in the as-grown crystal has increased unit cell anisotropy (c/a ratio), reduced Rb content and increased Fe content compared to the matrix. The microstructure is rather complex, with two-phase mesoscopic plate-shaped features aligned along {113} habit planes. The minority phase are strongly facetted on the {113} planes, which we have shown to be driven by minimising the volume strain energy introduced as a result of the phase transformation. Annealing at 488K results in coarsening of the mesoscopic plate-shaped features and the formation of a third distinct phase. The subtle differences in structure and chemistry of the minority phase(s) in the crystals are thought to be responsible for changes in the superconducting transition temperature. In addition, scanning photoemission microscopy has clearly shown that the electronic structure of the minority phase has a higher occupied density of states of the low binding energy Fe3d orbitals, characteristic of crystals that exhibit superconductivity. This demonstrates a clear correlation between the Fe-vacancy-free phase with high c/a ratio and the electronic structure characteristics of the superconducting phase.Comment: 6 figures v2 is exactly the same as v1. The typesetting errors in the abstract have been correcte