Enrichment exercises in spelling for grades two, three, and four

Thesis (Ed.M.)--Boston Universit

A lattice mesoscopic model of dynamically heterogeneous fluids

We introduce a mesoscopic three-dimensional Lattice Boltzmann Model which attempts to mimick the physical features associated with cage effects in dynamically heterogeneous fluids. To this purpose, we extend the standard Lattice Boltzmann dynamics with self-consistent constraints based on the non-local density of the surrounding fluid. The resulting dynamics exhibits typical features of dynamic heterogeneous fluids, such as non-Gaussian density distributions and long-time relaxation. Due to its intrinsically parallel dynamics, and absence of statistical noise, the method is expected to compute significantly faster than molecular dynamics, Monte Carlo and lattice glass models.Comment: 4 pages, 3 figures, to appear in Phys. Rev. Let

Transport Phenomena and Structuring in Shear Flow of Suspensions near Solid Walls

In this paper we apply the lattice-Boltzmann method and an extension to particle suspensions as introduced by Ladd et al. to study transport phenomena and structuring effects of particles suspended in a fluid near sheared solid walls. We find that a particle free region arises near walls, which has a width depending on the shear rate and the particle concentration. The wall causes the formation of parallel particle layers at low concentrations, where the number of particles per layer decreases with increasing distance to the wall.Comment: 14 pages, 14 figure

Sedimentation and Flow Through Porous Media: Simulating Dynamically Coupled Discrete and Continuum Phases

We describe a method to address efficiently problems of two-phase flow in the regime of low particle Reynolds number and negligible Brownian motion. One of the phases is an incompressible continuous fluid and the other a discrete particulate phase which we simulate by following the motion of single particles. Interactions between the phases are taken into account using locally defined drag forces. We apply our method to the problem of flow through random media at high porosity where we find good agreement to theoretical expectations for the functional dependence of the pressure drop on the solid volume fraction. We undertake further validations on systems undergoing gravity induced sedimentation.Comment: 22 pages REVTEX, figures separately in uudecoded, compressed postscript format - alternatively e-mail '[email protected]' for hardcopies

Realization of a Knill-Laflamme-Milburn C-NOT gate -a photonic quantum circuit combining effective optical nonlinearities

Quantum information science addresses how uniquely quantum mechanical phenomena such as superposition and entanglement can enhance communication, information processing and precision measurement. Photons are appealing for their low noise, light-speed transmission and ease of manipulation using conventional optical components. However, the lack of highly efficient optical Kerr nonlinearities at single photon level was a major obstacle. In a breakthrough, Knill, Laflamme and Milburn (KLM) showed that such an efficient nonlinearity can be achieved using only linear optical elements, auxiliary photons, and measurement. They proposed a heralded controlled-NOT (CNOT) gate for scalable quantum computation using a photonic quantum circuit to combine two such nonlinear elements. Here we experimentally demonstrate a KLM CNOT gate. We developed a stable architecture to realize the required four-photon network of nested multiple interferometers based on a displaced-Sagnac interferometer and several partially polarizing beamsplitters. This result confirms the first step in the KLM `recipe' for all-optical quantum computation, and should be useful for on-demand entanglement generation and purification. Optical quantum circuits combining giant optical nonlinearities may find wide applications across telecommunications and sensing.Comment: 6pages, 3figure

Notions and subnotions in information structure

Three dimensions can be distinguished in a cross-linguistic account of information structure. First, there is the definition of the focus constituent, the part of the linguistic expression which is subject to some focus meaning. Second and third, there are the focus meanings and the array of structural devices that encode them. In a given language, the expression of focus is facilitated as well as constrained by the grammar within which the focus devices operate. The prevalence of focus ambiguity, the structural inability to make focus distinctions, will thus vary across languages, and within a language, across focus meanings

A data mining approach to the SAR values over large MR image repositories

Purpose: In magnetic resonance imaging, the radiofrequency energy absorption arises as one of the main safety concerns, being mainly related with increased body temperature. Monitoring radiofrequency absorption is achieved by the estimation of specific absorption rate (SAR), whose implementation lies on equipment manufacturers, which in turn are not totally enlightening about its calculus. This work presents an exploratory approach of whole-body SAR values stored in DICOM metadata aiming to find correlation with body weight, body mass index (BMI), gender and pulse sequences for abdominal/pelvic (17.812 series) and head (29.907 series) studies. Methods and Materials: All studies were acquired in a 3 Tesla scanner with high-performance gradients. Data were extracted using Dicoogle, a DICOM metadata mining tool. Several DICOM tags were analysed (e.g. patient weight, height, gender, sequence name). For each study type, specifically weighted pulse sequences were related with weight, BMI and gender through boxplot diagrams, statistical and effect size analysis. Results: SAR limits were never exceeded. Generally, SAR values tended to decrease with increasing body weight and BMI values for abdominal/pelvic studies. On the other hand, head studies showed different trends regarding distinct pulse sequences. SAR values tend to be higher in male individuals (p<0,05). As expected, turbo spin echo sequences present the highest SAR values. The values found for echo gradient spoiled sequence (FLASH) were also high. Conclusion: It is confirmed that SAR estimates are related with the analysed variables. An individual examination of pulse sequences is recommended to observe trends regarding weight, BMI or gender.publishe

Integrated silicon qubit platform with single-spin addressability, exchange control and robust single-shot singlet-triplet readout

Silicon quantum dot spin qubits provide a promising platform for large-scale quantum computation because of their compatibility with conventional CMOS manufacturing and the long coherence times accessible using $^{28}$Si enriched material. A scalable error-corrected quantum processor, however, will require control of many qubits in parallel, while performing error detection across the constituent qubits. Spin resonance techniques are a convenient path to parallel two-axis control, while Pauli spin blockade can be used to realize local parity measurements for error detection. Despite this, silicon qubit implementations have so far focused on either single-spin resonance control, or control and measurement via voltage-pulse detuning in the two-spin singlet-triplet basis, but not both simultaneously. Here, we demonstrate an integrated device platform incorporating a silicon metal-oxide-semiconductor double quantum dot that is capable of single-spin addressing and control via electron spin resonance, combined with high-fidelity spin readout in the singlet-triplet basis.Comment: 10 pages, 4 figure

Hydrodynamic Spinodal Decomposition: Growth Kinetics and Scaling Functions

We examine the effects of hydrodynamics on the late stage kinetics in spinodal decomposition. From computer simulations of a lattice Boltzmann scheme we observe, for critical quenches, that single phase domains grow asymptotically like $t^{\alpha}$, with $\alpha \approx .66$ in two dimensions and $\alpha \approx 1.0$ in three dimensions, both in excellent agreement with theoretical predictions.Comment: 12 pages, latex, Physical Review B Rapid Communication (in press