"Quantum Interference with Slits" Revisited

Marcella [arXiv:quant-ph/0703126] has presented a straightforward technique employing the Dirac formalism to calculate single- and double-slit interference patterns. He claims that no reference is made to classical optics or scattering theory and that his method therefore provides a purely quantum mechanical description of these experiments. He also presents his calculation as if no approximations are employed. We show that he implicitly makes the same approximations found in classical treatments of interference and that no new physics has been introduced. At the same time, some of the quantum mechanical arguments Marcella gives are, at best, misleading.Comment: 11 pages, 3 figure

Quantum Chaos of Bogoliubov Waves for a Bose-Einstein Condensate in Stadium Billiards

We investigate the possibility of quantum (or wave) chaos for the Bogoliubov excitations of a Bose-Einstein condensate in billiards. Because of the mean field interaction in the condensate, the Bogoliubov excitations are very different from the single particle excitations in a non-interacting system. Nevertheless, we predict that the statistical distribution of level spacings is unchanged by mapping the non-Hermitian Bogoliubov operator to a real symmetric matrix. We numerically test our prediction by using a phase shift method for calculating the excitation energies.Comment: minor change, 4 pages, 4 figures, to appear in Phys. Rev. Let

Sumo-dependent substrate targeting of the SUMO protease Ulp1

<p>Abstract</p> <p>Background</p> <p>In the yeast <it>Saccharomyces cerevisiae</it>, the essential small ubiquitin-like modifier (SUMO) protease Ulp1 is responsible for both removing SUMO/Smt3 from specific target proteins and for processing precursor SUMO into its conjugation-competent form. Ulp1 localizes predominantly to nuclear pore complexes but has also been shown to deconjugate sumoylated septins at the bud-neck of dividing cells. How Ulp1 is directed to bud-neck localized septins and other cytoplasmic deconjugation targets is not well understood.</p> <p>Results</p> <p>Using a structure/function approach, we set out to elucidate features of Ulp1 that are required for substrate targeting. To aid our studies, we took advantage of a catalytically inactive mutant of Ulp1 that is greatly enriched at the septin ring of dividing yeast cells. We found that the localization of Ulp1 to the septins requires both SUMO and specific structural features of Ulp1's catalytic domain. Our analysis identified a 218-amino acid, substrate-trapping mutant of the catalytic domain of Ulp1, Ulp1(3)^(C580S), that is necessary and sufficient for septin localization. We also used the targeting and SUMO-binding properties of Ulp1(3)^(C580S)to purify Smt3-modified proteins from cell extracts.</p> <p>Conclusions</p> <p>Our study provides novel insights into how the Ulp1 SUMO protease is actively targeted to its substrates <it>in vivo </it>and <it>in vitro</it>. Furthermore, we found that a substrate-trapping Ulp1(3)^(C580S)interacts robustly with human SUMO1, SUMO2 and SUMO2 chains, making it a potentially useful tool for the analysis and purification of SUMO-modified proteins.</p

Regional Corn Planting Date Recommendations for Iowa

Corn is planted earlier every year and thisis one important component in maximizing grain yield. In 2009, 47% of the statewide corn crop was planted by approximately April 26. This was four days earlier than the previous 5-year average (USDA NASS, 2009). Earlier planting dates are attributed to several causes: larger acreage per producer, less spring tillage, advancements in hybrids, increased tile drainage, and improved seed treatments. The start of corn planting is generally related to the date when the soil temperature reaches 50°F (10°C) or greater

Manipulation of graphene's dynamic ripples by local harmonic out-of-plane excitation

With use of carefully designed molecular dynamics simulations, we demonstrate tuning of dynamic ripples in free-standing graphene by applying a local out-of-plane sinusoidal excitation. Depending on the boundary conditions and external modulation, we show control of the local dynamic morphology, including flattening and stable rippling patterns. In addition to studying the dynamic response of atomically thin layers to external time-varying excitation, our results open intriguing possibilities for modulating their properties via local dynamic morphology control

Coherence loss and revivals in atomic interferometry: A quantum-recoil analysis

The coherence effects induced by external photons coupled to matter waves inside a Mach-Zehnder three-grating interferometer are analyzed. Alternatively to atom-photon entanglement scenarios, the model considered here only relies on the atomic wave function and the momentum shift induced in it by the photon scattering events. A functional dependence is thus found between the observables, namely the fringe visibility and the phase shift, and the transversal momentum transfer distribution. A good quantitative agreement is found when comparing the results obtained from our model with the experimental data.Comment: 18 pages, 4 figure

Testing Report: Littleford-Day Dryer Operation: Dryer Operation Impacts of Proposed MIS Mitigation Changes

Pacific Northwest National Laboratory performed a series of tests using the Littleford Day 22-liter dryer during investigations that evaluated changes in the melter-feed composition for the Demonstration Bulk Vitrification System. During testing, a new melter-feed formulation was developed that improved dryer performance while improving the retention of waste salts in the melter feed during vitrification

Evaluation of West Valley High-Level Waste Tank Lay-Up Strategies

The primary objective of the task summarized in this paper was to demonstrate a methodology for evaluating alternative strategies for preclosure lay-up of the two high-level waste (HLW) storage tanks at the West Valley Demonstration Project (WVDP). Lay-up is defined as the period between operational use of tanks for waste storage and final closure. The U.S. Department of Energy (DOE) is planning to separate the environmental impact statement (EIS) for completion of closure of the WVDP into two separate EISs. The first EIS will cover only waste management and decontamination. DOE expects to complete this EIS in about 18 months. The second EIS will cover final decommissioning and closure and may take up to five years to complete. This approach has been proposed to expedite continued management of the waste and decontamination activities in advance of the final EIS and its associated Record of Decision on final site closure. Final closure of the WVDP site may take 10 to 15 years; therefore, the tanks need to be placed in a safe, stable condition with minimum surveillance during an extended lay-up period. The methodology developed for ranking the potential strategies for lay-up of the WVDP tanks can be used to provide a basis for a decision on the preferred path forward. The methodology is also applicable to determining preferred lay-up approaches at other DOE sites. Some of the alternative strategies identified for the WVDP should also be considered for implementation at the other DOE sites. Each site has unique characteristics that would require unique considerations for lay-up

Neutron-proton interaction in rare-earth nuclei: Role of tensor force

We investigate the role of the tensor force in the description of doubly odd deformed nuclei within the framework of the particle-rotor model. We study the rare-earth nuclei 174Lu, 180Ta, 182Ta, and 188Re using a finite-range interaction, with and without tensor terms. Attention is focused on the lowest K=0 and K=1 bands, where the effects of the residual neutron-proton interaction are particularly evident. Comparison of the calculated results with experimental data evidences the importance of the tensor-force effects.Comment: 8 pages, 5 figures, to be published on Physical Review

Modeling Early Stage Bone Regeneration With Biomimetic Electrospun Fibrinogen Nanofibers and Adipose-Derived Mesenchymal Stem Cells

The key events of the earliest stages of bone regeneration have been described in vivo although not yet modeled in an in vitro environment, where mechanistic cell-matrix-growth factor interactions can be more effectively studied. Here, we explore an early-stage bone regeneration model where the ability of electrospun fibrinogen (Fg) nanofibers to regulate osteoblastogenesis between distinct mesenchymal stem cells populations is assessed. Electrospun scaffolds of Fg, polydioxanone (PDO), and a Fg:PDO blend were seeded with adipose-derived mesenchymal stem cells (ASCs) and grown for 7-21 days in osteogenic differentiation media or control growth media. Scaffolds were analyzed weekly for histologic and molecular evidence of osteoblastogenesis. In response to osteogenic differentiation media, ASCs seeded on the Fg scaffolds exhibit elevated expression of multiple genes associated with osteoblastogenesis. Histologic stains and scanning electron microscopy demonstrate widespread mineralization within the scaffolds, as well as de novo type I collagen synthesis. Our data demonstrates that electrospun Fg nanofibers support ASC osteogenic differentiation, yet the scaffold itself does not appear to be osteoinductive. Together, ASCs and Fg recapitulate early stages of bone regeneration ex vivo and presents a prospective autologous therapeutic approach for bone repair