Interferences in the density of two Bose-Einstein condensates consisting of identical or different atoms

The density of two initially independent condensates which are allowed to expand and overlap can show interferences as a function of time due to interparticle interaction. Two situations are separately discussed and compared: (1) all atoms are identical and (2) each condensate consists of a different kind of atoms. Illustrative examples are presented.     

Dark Energy： Relating the Evolutions of the Universe from the Past to the Future

Using the evolution history of the universe, one can make constraint on the parameter space of dynamic dark energy models. We discuss two different parameterized dark energy models. Our results further restrict the combined constraints obtained from supernova and the first-year Wilkinson-microwave-anisotropy-probe observations. From the allowed parameter space, it is found that our universe will experience an eternal acceleration. We also estimate the bound on the physically relevant regions both in the re-inflationary and inflationary phases.     

Polymer and biopolymer mediated self-assembly of gold nanoparticles

Gold nanoparticle-polymer composites are versatile and diverse functional materials, with applications in optical, electronic and sensing devices. This tutorial review focuses on the use of polymers to control the assembly of gold nanoparticles. Examples of synthetic polymers and biopolymers are provided, as well as applications of the composite materials in sensing and memory devices.     

Na(-) photolysis in THF: Charge transfer to solvent studied from the donors perspective in <10 fs detail

Two and three pulse photolysis experiments on terahydrofuran (THF) solutions of Na(-), utilizing hyperspectral probing, are described. The objective is to probe the extent and duration of energetic correlations between the primary charge transfer to solvent (CTTS) fragments which are an e(-) and Na(0). The latter is characterized by an intense visible absorption spectrum with fine structure reflecting the atom's immediate solvent environment. Pump-probe experiments with approximately 6 fs pulses show that for the majority of irradiated ions, the electron ejection and production of unperturbed Na(0) is effectively over in approximately 15 fs, with no precursors. Three pulse experiments further demonstrate this to be true for nearly all ions irradiated at 3 eV. Thus, the 400 nm data provide a detailed spectral record of the formation and subsequent solvation and polarization of neutral sodium bubbles in THF. Measures are presented for parametrizing the ensuing spectral evolution. In contrast, exciting at 1.5 eV, the red edge of the CTTS band leads to charge transfer with less than unity quantum efficiency. The complementary fraction of absorbing ions is photostable at 800 nm, presumably due to preferential solvent stabilization. Prompt secondary irradiation at 2 microm can complete ionization of that population leading to additional generation of Na(0) but exhibiting much more pronounced spectral structure. Thus, at low photon energies, a short lived correlated and bound electronic excited state is produced with significant yield. These results are discussed in terms of classical models for CTTS spectra, as well as more recent simulations and experiments concerning CTTS in this and other related systems.     

Exploring peptide‐functionalized alginate scaffolds for engineering cardiac tissue from human embryonic stem cell‐derived cardiomyocytes in serum‐free medium

Engineering human cardiac tissue is a promising solution for myocardial repair of injured hearts and for drug screening. Herein, we examined the capability of chemically defined alginate scaffolds to promote cardiac tissue regeneration from human embryonic stem cell‐derived cardiomyocytes (hESC‐CMs) in serum‐free, chemically defined medium. The cells were single seeded or coseeded with human dermal fibroblasts (HFs) in macroporous scaffolds made from pristine alginate or alginate modified with arginine‐glycine‐aspartate (RGD) peptide and heparin‐binding peptide (HBP). Our results show that the addition of fibroblasts to the 3‐D culture is indispensable for the formation of functional cardiac tissues and that the presence of RGD/HBP attached to the alginate matrix further improves its functionality. The engineered tissue displayed the typical fiber morphology with massive striation. An increase in contraction amplitude and calcium transients with time, together with a decrease in excitation threshold, indicated advancement toward tissue maturation. Our results thus point to the importance of co‐cultivating fibroblasts with hESCs‐CMs in chemically defined peptide‐functionalized alginate scaffolds and culture medium for regenerating functional cardiac tissue in vitro.     

Unified view on multiconfigurational time propagation for systems consisting of identical particles

We show that the successful and formally exact multiconfigurational time-dependent Hartree method (MCTDH) takes on a unified and compact form when specified for systems of identical particles (MCTDHF for fermions MCTDHB for bosons). In particular the equations of motion for the orbitals depend explicitly and solely on the reduced one- and two-body density matrices of the system's many-particle wave function. We point out that this appealing representation of the equations of motion opens up further possibilities for approximate propagation schemes.     

Semi-invariant Matrices over Finite Groups

The semi-center of an artinian semisimple module-algebra over a finite group G can be described using the projective representations of G. In particular, the semi-center of the endomorphism ring of an irreducible projective representation over an algebraically closed field has a structure of a twisted group algebra. The following group-theoretic result is deduced: the center of a group of central type embeds into the group of its linear characters.