Transition temperature data obtained as a function of particle density in the 4 He-Vycor system are compared with recent theoretical calculations for 3D Bose condensed systems. In the low density dilute Bose gas regime we find, in agreement with theory, a positive shift in the transition temperature of the form ∆T /T0 = γ(na 3 ) 1/3 . At higher densities a maximum is found in the ratio of Tc/T0 for a value of the interaction parameter, na 3 , that is in agreement with path-integral Monte Carlo calculations.PACS numbers: 03.75. Fi, 05.30.Jp, The role of interparticle interactions in the determination of the properties of low density Bose-Einstein condensed (BEC) systems has been a topic of interest for many years. In spite of a long history of theoretical investigation [1] dating back to the 1950s, elementary questions such as the possible shift in the transition temperature, T c , with density and interaction strength have remained unsettled until the recent past. In the case of the repulsive interactions in the dilute Bose gas, there has now emerged a consensus [2] [3] [4] that T c will be an increasing function of the interaction parameter, na 3 , where a is the hard sphere diameter and n the particle density. This may seem a surprising result, since it is well known that in the case of liquid 4 He the superfluid transition occurs at a temperature well below the transition temperature, T 0 , for an ideal Bose gas with the same particle mass and number density. Moreover, a number of the earlier calculations [5] had found that the transition temperature would be reduced as a consequence of interparticle interaction.Motivated by the recent theoretical work in this area, we have examined the dependence of the transition temperature on superfluid particle number for the 4 He-Vycor system. In our early work with this system we demonstrated, for the first time in 1983 [6], an experimental realization of the weakly interacting or "dilute" Bose gas. The lowest density achieved in these experiments was on the order of 2 × 10 18 per cm 3 . This is sufficiently low to provide a region of overlap, in terms of the interaction parameter, with the values of na 3 , currently accessible to the BEC systems realized with 87 Rb [7] or 23 Na [8] atoms confined within magnetic or optical traps. In the case of Bose condensed atomic hydrogen [9] the small swave scattering length and limits on the particle density, set by recombination, restrict this system to values of na 3 several orders of magnitude below the values that can be achieved with Bose-condensed Na, Rb or He.For questions such as the effect on T c of increasing the interaction parameter, the 4 He-Vycor system offers advantages over the BEC systems of trapped atomic gases, because in the Vycor case, the interaction parameter can be varied continuously from the low-density, weakly interacting limit to the strongly interacting regime currently inaccessible with the alkali vapor systems. Further, working with the 4 He-Vycor system allows much larger sample sizes, on the order...
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A network of filaments formed primarily by the abundant cytoskeletal protein actin gives animal cells their shape and elasticity. The rheological properties of reconstituted actin networks have been studied by tracking micron-sized probe beads embedded within the networks. We investigate how microrheology depends on surface properties of probe particles by varying the stickiness of their surface. For this purpose, we chose carboxylate polystyrene (PS) beads, silica beads, bovine serum albumin (BSA) -coated PS beads, and polyethylene glycol (PEG) -grafted PS beads, which show descending stickiness to actin filaments, characterized by confocal imaging and microrheology. Probe size dependence of microrheology is observed for all four types of beads. For the slippery PEG beads, particle-tracking microrheology detects weaker networks using smaller beads, which tend to diffuse through the network by hopping from one confinement "cage" to another. This trend is reversed for the other three types of beads, for which microrheology measures stiffer networks for smaller beads due to physisorption of nearby filaments to the bead surface. We explain the probe size dependence with two simple models. We also evaluate depletion effect near nonadsorption bead surface using quantitative image analysis and discuss the possible impact of depletion on microrheology. Analysis of these effects is necessary in order to accurately define the actin network rheology both in vitro and in vivo.
We present Falcon, an interactive, deterministic, and declarative data cleaning system, which uses SQL update queries as the language to repair data. Falcon does not rely on the existence of a set of pre-defined data quality rules. On the contrary, it encourages users to explore the data, identify possible problems, and make updates to fix them. Bootstrapped by one user update, Falcon guesses a set of possible SQL update queries that can be used to repair the data. The main technical challenge addressed in this paper consists in finding a set of SQL update queries that is minimal in size and at the same time fixes the largest number of errors in the data. We formalize this problem as a search in a lattice-shaped space. To guarantee that the chosen updates are semantically correct, Falcon navigates the lattice by interacting with users to gradually validate the set of SQL update queries. Besides using traditional one-hop based traverse algorithms (e.g., BFS or DFS), we describe novel multi-hop search algorithms such that Falcon can dive over the lattice and conduct the search efficiently. Our novel search strategy is coupled with a number of optimization techniques to further prune the search space and efficiently maintain the lattice. We have conducted extensive experiments using both real-world and synthetic datasets to show that Falcon can effectively communicate with users in data repairing
Field emitter tips can now be fabricated with radii of curvature of the order of nm or even the size of a single atom. To include these geometric effects, we have calculated the field emission tunneling currents for hyperboloidal and conical free-electron tip models using geometry-dependent image interactions and bias fields. The numerical results can be fitted by an equation of the form J=AV2 exp(−B/V−C/V2), where A, B, and C are constants depending on material and geometric parameters. The calculated results, plotted as log J/V2 vs 1/V, do not exhibit the straight line behavior predicted by the Fowler–Nordheim model for field emission from a planar surface. Furthermore, the calculated current densities are dramatically enhanced for both the hyperboloidal (rt=10 nm) and conical (cone half-angle=70°) emitter models. In addition, field emission energy distributions for both models are significantly different from that of the Fowler–Nordheim planar model.
Background: Facial symmetry is a fundamental goal of plastic surgery, yet some asymmetry is inherent in any face. Three-dimensional photogrammetry allows for rapid, reproducible, and quantitative facial measurements. With this tool, the authors investigated the relationship between age and facial symmetry. Methods: The authors imaged normal subjects using three-dimensional photogrammetry. Facial symmetry was calculated by identifying the plane of maximum symmetry and the root-mean-square deviation. Regression analysis was used to assess the relationship between age and symmetry. Subgroup analyses were performed among facial thirds. Results: The authors imaged 191 volunteers with an average age of 26.7 ± 22.2 years (range, 0.3 to 88 years). Root-mean-square deviation of facial symmetry clustered between 0.4 and 1.3 mm (mean, 0.8 ± 0.2 mm). The authors found a significant positive correlation between increasing age and asymmetry (p < 0.001; r = 0.66). The upper, middle, and lower facial third’s average root-mean-square deviations were 0.5 ± 0.2 mm (range, 0.2 to 1.2 mm), 0.6 ± 0.2 mm (range, 0.2 to 1.4 mm), and 0.6 ± 0.2 mm (range, 0.2 to 1.2 mm), respectively. Asymmetry also increased with age across all facial thirds (p < 0.001). Conclusions: Facial asymmetry increases with age in each facial third, with a greater asymmetry and increase in asymmetry in the lower two-thirds. Contributing factors may include asymmetric skeletal remodeling along with differential deflation and descent of the soft tissues. The observed correlation between increasing facial asymmetry and age may be a useful guide in plastic surgery to produce age-matched features.
Background: Mixed results exist regarding the benefit of orthobiologic injections. The purpose of this study was to assess the variability in costs for platelet-rich plasma (PRP) and stem cell (SC) injections and evaluate for variables that influence pricing. Hypothesis: There will be significant variability in the cost of PRP and SC injections throughout the United States. Study Design: Descriptive epidemiology study. Level of Evidence: Level 3. Methods: Calls were made to 1345 orthopaedic sports medicine practices across the United States inquiring into the availability of PRP or SC knee injections and associated costs. In addition to pricing, the practice type, number of providers, and population and income demographics were recorded. Univariate statistical analyses were used to identify differences in availability and cost between variables. Results: Of the contacted offices that provided information on both PRP and SC availability (n = 1325), 268 (20.2%) offered both treatments, 550 (41.5%) offered only PRP injections, 20 (1.5%) offered only SC injections, and 487 (36.8%) did not offer either treatment. The mean ± SD cost of a PRP injection was $707 ± $388 (range, $175-$4973), and the mean cost of an SC injection was $2728 ± $1584 (range, $300-$12,000). Practices offering PRP and SC injections tended to be larger (PRP, 12.0 physicians per practice vs. 8.1 [ P < 0.001]; SC, 13.6 vs 9.7 [ P < 0.001]). Practices that offered PRP injections were located in areas with higher median household income ( P = 0.047). Variables associated with higher cost of PRP injections included city population ( P < 0.001) and median income of residents ( P < 0.001). Conclusion: While the majority of sports medicine practices across the United States offer some type of orthobiologic injection, there exists significant variability in the cost of these injections. Clinical Relevance: This study demonstrates the significant variability in costs of orthobiologic injections throughout the country, which will allow sports medicine physicians to appreciate the value of these injections when counseling patients on available treatment options.
High-quality large 1T phase of TiX 2 (X = Te, Se, and S) single crystals have been grown by chemical vapor transport using iodine as a transport agent. The samples are characterized by compositional and structural analyses, and their properties are investigated by Raman spectroscopy. Several phonon modes have been observed, including the widely reported A 1g and Eg modes, the rarely reported Eu mode (∼183 cm−1 for TiTe2, and ∼185 cm−1 for TiS2), and even the unexpected K mode (∼85 cm−1) of TiTe2. Most phonons harden with the decrease of temperature, except that the K mode of TiTe2 and the Eu and “A 2u /Sh” modes of TiS2 soften with the decrease of temperature. In addition, we also found phonon changes in TiSe2 that may be related to charge density wave phase transition. Our results on TiX 2 phonons will help to understand their charge density wave and superconductivity.
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