Paired atom laser beams created via four-wave mixing

A method to create paired atom laser beams from a metastable helium atom laser via four-wave mixing is demonstrated. Radio frequency outcoupling is used to extract atoms from a Bose Einstein condensate near the center of the condensate and initiate scattering between trapped and untrapped atoms. The unequal strengths of the interactions for different internal states allows an energy-momentum resonance which leads to the creation of pairs of atoms scattered from the zero-velocity condensate. The resulting scattered beams are well separated from the main atom laser in the 2-dimensional transverse atom laser profile. Numerical simulations of the system are in good agreement with the observed atom laser spatial profiles, and indicate that the scattered beams are generated by a four-wave mixing process, suggesting that the beams are correlated.Comment: 5 pages, 3 figure

A multi-modal data resource for investigating topographic heterogeneity in patient-derived xenograft tumors.

Patient-derived xenografts (PDXs) are an essential pre-clinical resource for investigating tumor biology. However, cellular heterogeneity within and across PDX tumors can strongly impact the interpretation of PDX studies. Here, we generated a multi-modal, large-scale dataset to investigate PDX heterogeneity in metastatic colorectal cancer (CRC) across tumor models, spatial scales and genomic, transcriptomic, proteomic and imaging assay modalities. To showcase this dataset, we present analysis to assess sources of PDX variation, including anatomical orientation within the implanted tumor, mouse contribution, and differences between replicate PDX tumors. A unique aspect of our dataset is deep characterization of intra-tumor heterogeneity via immunofluorescence imaging, which enables investigation of variation across multiple spatial scales, from subcellular to whole tumor levels. Our study provides a benchmark data resource to investigate PDX models of metastatic CRC and serves as a template for future, quantitative investigations of spatial heterogeneity within and across PDX tumor models

Context-Bounded Analysis For Concurrent Programs With Dynamic Creation of Threads

Context-bounded analysis has been shown to be both efficient and effective at finding bugs in concurrent programs. According to its original definition, context-bounded analysis explores all behaviors of a concurrent program up to some fixed number of context switches between threads. This definition is inadequate for programs that create threads dynamically because bounding the number of context switches in a computation also bounds the number of threads involved in the computation. In this paper, we propose a more general definition of context-bounded analysis useful for programs with dynamic thread creation. The idea is to bound the number of context switches for each thread instead of bounding the number of switches of all threads. We consider several variants based on this new definition, and we establish decidability and complexity results for the analysis induced by them

A Theoretical Treatment of the Steady-Flow, Linear, Crossed-Field, Direct-Current Plasma Accelerator for Inviscid, Adiabatic, Isothermal, Constant-Area Flow

The theory is developed from the individual equations of motion of the three components of the plasma. The effect of the ion cyclotron angle (omega tau), which is the product of the ion cyclotron frequency and the ion mean free time between collisions with neutral particles and which is proportional to the axial component of the ion slip velocity, on both Joule heating rate and accelerator length is included in the results and is shown to be small only for values of about 10(exp -3) radian or less

Report of the panel on geopotential fields: Gravity field, section 8

The objective of the Geopotential Panel was to develop a program of data acquisition and model development for the Earth's gravity and magnetic fields that meet the basic science requirements of the solid Earth and ocean studies. Presented here are the requirements for gravity information and models through the end of the century, the present status of our knowledge, data acquisition techniques, and an outline of a program to meet the requirements

Singular Modes of the Electromagnetic Field

We show that the mode corresponding to the point of essential spectrum of the electromagnetic scattering operator is a vector-valued distribution representing the square root of the three-dimensional Dirac's delta function. An explicit expression for this singular mode in terms of the Weyl sequence is provided and analyzed. An essential resonance thus leads to a perfect localization (confinement) of the electromagnetic field, which in practice, however, may result in complete absorption.Comment: 14 pages, no figure

Calculation of the photoionization with de-excitation cross sections of He and helium-like ions

We discuss the results of the calculation of the photoionization with de-excitation of excited He and helium-like ions Li$^{+}$ and B$^{3+}$ at high but non-relativistic photon energies $\omega$. Several lower $^{1}S$ and $^{3}S$ states are considered. We present and analyze the ratios $R_{d}^{+\ast}$ of the cross sections of photoionization with de-excitation, $\sigma_{(d)}^{+\ast}(\omega)$, and of the photo-ionization with excitation, $\sigma ^{+\ast}(\omega)$. The dependence of $R_{d}^{+\ast}$ on the excitation of the target object and the charge of its nucleus is presented. Apart to theoretical interest, results obtained can be verified using such long living excited state as $2^{3}S$ of He.Comment: 10 pages, 6 table