@article{1748, abstract = {The authors apply selective wet chemical etching and atomic force microscopy to reveal the three-dimensional shape of SiGeSi (001) islands after capping with Si. Although the "self-assembled quantum dots" remain practically unaffected by capping in the temperature range of 300-450 °C, significant morphological changes take place on the Si surface. At 450 °C, the morphology of the capping layer (Si matrix) evolves toward an intriguing semifacetted structure, which we call a "ziggurat," giving the misleading impression of a stepped SiGe island shape.}, author = {Georgios Katsaros and Rastelli, Armando and Stoffel, Mathieu and Costantini, Giovanni and Schmidt, Oliver G and Kern, Klaus and Tersoff, Jerry and Müller, Elisabeth and Von Känel, Hans}, journal = {Applied Physics Letters}, number = {25}, publisher = {American Institute of Physics}, title = {{Evolution of buried semiconductor nanostructures and origin of stepped surface mounds during capping}}, doi = {10.1063/1.2405876}, volume = {89}, year = {2006}, } @article{17718, abstract = {The reionization history of the intergalactic medium at high redshift (z ≳ 6) was likely strongly shaped by several global feedback processes. Because the earliest ionizing sources formed at the locations of the rare density peaks, their spatial distribution was strongly clustered. Here we demonstrate that this clustering significantly boosts the impact of feedback processes operating at high redshift. We build a semianalytical model to include feedback and clustering simultaneously and apply this model to the suppression of star formation in minihalos due to photoionization. The model is built on the excursion-set-based formalism of Furlanetto, Zaldarriaga, and Hernquist, which incorporates the clustering of ionizing sources and which we here extend to include the suppression of star formation in minihalos. We find that clustering increases the mean H II bubble size by a factor of several, and it dramatically increases the fraction of minihalos that are suppressed by a factor of up to ~60 relative to a randomly distributed population. This enhanced suppression can significantly reduce the electron-scattering optical depth τ, as required by the 3 year data from the Wilkinson Microwave Anisotropy Probe. We argue that source clustering is likely to similarly boost the importance of a variety of other feedback mechanisms.}, author = {Kramer, Roban Hultman and Haiman, Zoltán and Oh, S. Peng}, issn = {0004-637X}, journal = {The Astrophysical Journal}, number = {2}, pages = {570--578}, publisher = {American Astronomical Society}, title = {{Feedback from clustered sources during reionization}}, doi = {10.1086/506906}, volume = {649}, year = {2006}, } @article{17727, abstract = {We report on i-band snapshot observations of 157 Sloan Digital Sky Survey (SDSS) quasars at 4-3.8 (3 sigma), assuming a break in the quasar luminosity function at M*_145=-24.5. This constraint is considerably stronger than the limit of beta>-4.63 obtained from the absence of lensing in four z>5.7 quasars. Such constraints are important for our understanding of the true space density of high-redshift quasars and the ionization state of the early universe.}, author = {Richards, Gordon T. and Haiman, Zoltán and Pindor, Bartosz and Strauss, Michael A. and Fan, Xiaohui and Eisenstein, Daniel and Schneider, Donald P. and Bahcall, Neta A. and Brinkmann, J. and Fukugita, Masataka}, issn = {0004-6256}, journal = {The Astronomical Journal}, number = {1}, pages = {49--54}, publisher = {American Astronomical Society}, title = {{A snapshot survey for gravitational lenses among z ≥ 4.0 quasars. II. Constraints on the 4.0 < z < 5.4 quasar population}}, doi = {10.1086/498063}, volume = {131}, year = {2006}, } @article{17730, abstract = {We model the spectra and surface brightness distributions for the Lyα radiation expected from protogalaxies that are caught in the early stages of their assembly. We use the results of a companion paper to characterize the radiation emerging from spherically collapsing gas clouds. We then modify these spectra to incorporate the effect of subsequent resonant scattering in the IGM. Using these models, we interpret a number of recent observations of extended Lyα blobs (LABs) at high redshift. We suggest, based on the angular size, energetics, relatively shallow surface brightness profiles, and double-peaked spectra, that several of these LABs may be associated with collapsing protogalaxies. We suggest two follow-up observations to diagnose the presence of gas infall. High-S/N spectra of LABs should reveal a preferential flattening of the surface brightness profile at the red side of the line. Complementary imaging of the blobs at redshifted Hα wavelengths should reveal the intrinsic Lyα emissivity and allow its separation from radiative transfer effects. We show that Lyα scattering by infalling gas can reproduce the observed spectrum of the Steidel et al. LAB2 as accurately as a recently proposed outflow model. Finally, we find similar evidence for infall in the spectra of pointlike Lyα emitters. The presence of scattering by the infalling gas implies that the intrinsic Lyα luminosities and derived quantities, such as the star formation rate, in these objects may have been underestimated by about an order of magnitude.}, author = {Dijkstra, Mark and Haiman, Zoltán and Spaans, Marco}, issn = {0004-637X}, journal = {The Astrophysical Journal}, number = {1}, pages = {37--47}, publisher = {American Astronomical Society}, title = {{Lyα radiation from collapsing protogalaxies. II. Observational evidence for gas infall}}, doi = {10.1086/506244}, volume = {649}, year = {2006}, } @article{17733, abstract = {We use three-dimensional hydrodynamic simulations to investigate the effects of a transient photoionizing ultraviolet (UV) flux on the collapse and cooling of pregalactic clouds. These clouds have masses in the range 10^5 -10^7 M_sun, form at high redshifts (z>18), are assumed to lie within the short-lived cosmological HII regions around the first generation of stars. In addition, we study the combined effects of this transient UV flux and a persistent Lyman-Werner (LW) background from distant sources. In the absence of a LW background, we find that a critical specific intensity of J_UV ~ 0.1 x 10^-21 ergs s^-1 cm^-2 Hz^-1 sr^-1 demarcates a transition from net negative to positive feedback for the halo population. A weaker UV flux stimulates subsequent star formation inside the fossil HII regions, by enhancing the H_2 molecule abundance. A stronger UV flux significantly delays star-formation by reducing the gas density, and increasing the cooling time, at the centers of collapsing halos. At a fixed J_UV, the sign of the feedback also depends strongly on the density of the gas at the time of UV illumination. Regardless of the whether the feedback is positive or negative, we find that once the UV flux is turned off, its impact stars to diminish after ~30% of the Hubble time. In the more realistic case when a LW background is present, with J_LW > 0.01 x 10^-21 ergs s^-1 cm^-2 Hz^-1 sr^-1, strong suppression persists down to the lowest redshift (z=18) in our simulations. Finally, we find evidence that heating and photoevaporation by the transient UV flux renders the ~10^6 M_sun halos inside fossil HII regions more vulnerable to subsequent H_2 photo-dissociation by a LW background.}, author = {Mesinger, Andrei and Bryan, Greg L. and Haiman, Zoltán}, issn = {0004-637X}, journal = {The Astrophysical Journal}, number = {2}, pages = {835--851}, publisher = {American Astronomical Society}, title = {{Ultraviolet radiative feedback on high‐redshift protogalaxies}}, doi = {10.1086/506173}, volume = {648}, year = {2006}, } @article{17742, abstract = {The primordial gas in the earliest dark matter halos, collapsing at redshifts around z=20, with masses M_halo=10^6 M_sun, and virial temperatures T_vir<10^4K, relied on the presence of molecules for cooling. Several theoretical studies have suggested that gas contraction and star-formation in these minihalos was suppressed by radiative, chemical, thermal, and dynamical feedback processes. The recent measurement by the Wilkinson Microwave Anisotropy Probe (WMAP) of the optical depth to electron scattering, tau=0.09+/-0.03, provides the first empirical evidence for this suppression. The new WMAP result is consistent with vanilla models of reionization, in which ionizing sources populate cold dark matter (CDM) halos down to a virial temperature of T_vir=10^4K. On the other hand, we show that in order to avoid overproducing the optical depth, the efficiency for the production of ionizing photons in minihalos must have been about an order of magnitude lower than expected and lower than the efficiency in large halos that can cool via atomic hydrogen (T_vir > 10^4K). This conclusion is insensitive to assumptions about the efficiency of ionizing photon production in the large halos, as long as reionization ends by z=6, as required by the spectra of bright quasars at z<6. Our conclusion is strengthened if the clumping of the ionized gas evolves with redshift, as suggested by semi-analytical predictions and three-dimensional numerical simulations.}, author = {Haiman, Zoltán and Bryan, Greg L.}, issn = {0004-637X}, journal = {The Astrophysical Journal}, number = {1}, pages = {7--11}, publisher = {American Astronomical Society}, title = {{Was star formation suppressed in high‐redshift minihalos?}}, doi = {10.1086/506580}, volume = {650}, year = {2006}, } @article{17744, abstract = {We present Monte Carlo calculations of Lyman alpha (Lya) radiative transfer through collapsing gas clouds, representing proto-galaxies that are caught in the process of their assembly. Such galaxies produce Lya flux over an extended solid angle from a spatially extended Lya emissivity and/or from scattering effects. We study the effect of the gas distribution and kinematics, and of the Lya emissivity profile, on the emergent spectrum and surface brightness distribution. The emergent Lya spectrum is typically double-peaked and asymmetric. In practice, the blue peak is significantly enhanced and the red peak, in most cases, will be undetectable. The resulting effective blueshift, combined with scattering in the intergalactic medium, will render extended Lya emission from collapsing protogalaxies difficult to detect beyond redshift z=4. The surface brightness distribution is typically flat, and a strong wavelength dependence of its slope (with preferential flattening at the red side of the line) would be a robust indication that Lya photons are being generated (rather than just scattered) in a spatially extended region around the galaxy. We also find that for self-ionized clouds whose effective Lya optical depth is less than 10^3, infall and outflow models can produce nearly identical spectra and surface brightness distributions, and are difficult to distinguish from one another. The presence of deuterium with a cosmic abundance may produce a narrow but detectable dip in the spectra of systems with moderate hydrogen column densities, in the range 10^18-10^20 cm^-2. Finally, we present a new analytic solution for the emerging Lya spectrum in the limiting case of a static uniform sphere, extending previous solutions for static plane-parallel slabs.}, author = {Dijkstra, Mark and Haiman, Zoltán and Spaans, Marco}, issn = {0004-637X}, journal = {The Astrophysical Journal}, number = {1}, pages = {14--36}, publisher = {American Astronomical Society}, title = {{Lyα radiation from collapsing protogalaxies. I. Characteristics of the emergent spectrum}}, doi = {10.1086/506243}, volume = {649}, year = {2006}, } @article{17749, abstract = {We discuss the UV radiative feedback on high-redshift proto-galaxies.}, author = {Mesinger, Andrei and Haiman, Greg L. and Haiman, Zoltán}, issn = {1743-9213}, journal = {Proceedings of the International Astronomical Union}, number = {14}, pages = {269--269}, publisher = {Cambridge University Press}, title = {{UV radiative feedback on high-redshift proto-galaxies}}, doi = {10.1017/s1743921307010526}, volume = {2}, year = {2006}, } @article{17766, abstract = {It has been shown that in an idealized galaxy cluster survey, containing ≳10,000 clusters, statistical errors on dark energy and other cosmological parameters would be at the percent level. Furthermore, through ``self-calibration,'' parameters describing the mass-observable relation and cosmology could be simultaneously determined, although at a loss in accuracy by about an order of magnitude. Here we examine an alternative approach to self-calibration, in which a parameterized ab initio physical model is used to compute theoretical mass-observable relations from the cluster structure. As an example, we use a modified-entropy (``preheating'') model of the intracluster medium, with the history and magnitude of entropy injection as unknown input parameters. Using a Fisher matrix approach, we evaluate the expected simultaneous statistical errors on cosmological and cluster model parameters. We find that compared to a phenomenological parameterization of the mass-observable relation, our physical model yields significantly tighter constraints in both surveys and offers substantially improved synergy when the two surveys are combined. In a mock X-ray survey, we find statistical errors on the dark energy equation of state are a factor of 2 tighter than the phenomenological model, with Δw0 ~ 0.08 and its evolution, Δwa ≡ -Δdw/da ~ 0.23, with corresponding errors of Δw0 ~ 0.06 and Δwa ~ 0.17 from a mock Sunyaev-Zel'dovich (SZ) survey, both with Ncl ~ 2.2 × 104 clusters, while simultaneously constraining cluster model parameters to ≲10%. When the two surveys are combined, the constraints tighten to Δw0 ~ 0.03 and Δwa ~ 0.1, a 40% improvement over adding the individual experiment errors in quadrature and a factor of 2 improvement over the phenomenological model. This suggests that parameterized physical models of cluster structure would be useful when extracting cosmological constraints from SZ and X-ray cluster surveys.}, author = {Younger, Joshua D. and Haiman, Zoltán and Bryan, Greg L. and Wang, Sheng}, issn = {0004-637X}, journal = {The Astrophysical Journal}, number = {1}, pages = {27--42}, publisher = {American Astronomical Society}, title = {{Breaking cosmological degeneracies in galaxy cluster surveys with a physical model of cluster structure}}, doi = {10.1086/508646}, volume = {653}, year = {2006}, } @article{17776, abstract = {The gravitational waves (GW) emitted during the coalescence of supermassive black holes (SMBHs) in the mass range 10^4-10^7 M_sun will be detectable out to high redshifts with LISA. We calculate the size and orientation of the three-dimensional error ellipse in solid angle and redshift within which the LISA event could be localized using the GW signatures alone. We take into account uncertainties in LISA's measurements of the luminosity distance and direction to the source, in the background cosmology, in weak gravitational lensing magnification due to inhomogeneities along the line of sight, and potential source peculiar velocities. We find that weak lensing errors exceed other sources of uncertainties by nearly an order of magnitude. Under the plausible assumption that BH mergers are accompanied by gas accretion leading to Eddington-limited quasar activity, we then compute the number of quasars that would be found in a typical LISA error volume, as a function of BH mass and redshift. We find that low redshifts offer the best opportunities to identify quasar counterparts to cosmological standard sirens, and that the LISA error volume will typically contain a single near-Eddington quasar at z=1. This will allow a straightforward test of the hypothesis that BH mergers are accompanied by bright quasar activity and, if the hypothesis proves correct, will guarantee the identification of a unique quasar counterpart. This would yield unprecedented tests of the physics of SMBH accretion, and offer an alternative method to precisely constrain cosmological parameters.}, author = {Kocsis, Bence and Frei, Zsolt and Haiman, Zoltán and Menou, Kristen}, issn = {0004-637X}, journal = {The Astrophysical Journal}, number = {1}, pages = {27--37}, publisher = {American Astronomical Society}, title = {{Finding the electromagnetic counterparts of cosmological standard sirens}}, doi = {10.1086/498236}, volume = {637}, year = {2006}, } @article{17794, abstract = {We model the number of detectable supernovae (SNe) as a function of redshift at different flux thresholds, making use of the observed properties of local SNe, such as their light curves, fiducial spectra, and peak magnitude distributions. We assume that the star formation rate (SFR) at high redshift traces the formation rate of dark matter halos. We obtain a rate of 0.4-2.3 SNe arcmin^-2 yr^-1 at z ≳ 5 at the near-infrared (4.5 μm) flux density threshold of 3 nJy (achievable with the James Webb Space Telescope [JWST] in a 10^5 s integration). In a hypothetical 1 yr survey, it should be possible to detect up to several thousand SNe per unit redshift at z ~ 6. We discuss the possible application of such a large sample of distant SNe as a probe of the epoch of reionization. By heating the intergalactic medium (IGM) and raising the cosmological Jeans mass, the process of reionization can suppress star formation in low-mass galaxies. This could have produced a relatively sharp drop in the SN rate around the redshift of reionization (zre). We quantify the detectability of this feature in future surveys of distant SNe by varying the redshift and duration of reionization, as well as its impact on the SFR in low-mass halos, which results in different redshifts, widths, and sizes of the drop in the expected SFR. We find that the drop can be detected out to zre ~ 13, as long as (1) the reionization history contains a relatively rapid feature that is synchronized over different regions to within Δz ≲ 1-3, (2) the star formation efficiency in halos that dominate reionization is epsilon* ~ 10%, and (3) reionization significantly suppresses the star formation in low-mass halos. Depending on the details of (1)-(3), this could be achieved with a survey lasting less than 2 weeks. Detecting this signature would also help elucidate the feedback mechanism that regulates reionization.}, author = {Mesinger, Andrei and Johnson, Benjamin D. and Haiman, Zoltán}, issn = {0004-637X}, journal = {The Astrophysical Journal}, number = {1}, pages = {80--90}, publisher = {American Astronomical Society}, title = {{The redshift distribution of distant supernovae and its use in probing reionization}}, doi = {10.1086/498294}, volume = {637}, year = {2006}, } @article{17807, abstract = {The first massive astrophysical black holes likely formed at high redshifts (z ≳ 10) at the centers of low mass (∼106 M⊙) dark matter concentrations. These black holes grow by mergers and gas accretion, evolve into the population of bright quasars observed at lower redshifts, and eventually leave the supermassive black hole remnants that are ubiquitous at the centers of galaxies in the nearby universe. The astrophysical processes responsible for the formation of the earliest seed black holes are poorly understood. The purpose of this review is to describe theoretical expectations for the formation and growth of the earliest black holes within the general paradigm of hierarchical cold dark matter cosmologies, and to summarize several relevant recent observations that have implications for the formation of the earliest black holes.}, author = {Haiman, Zoltán}, issn = {1387-6473}, journal = {New Astronomy Reviews}, number = {9-10}, pages = {672--676}, publisher = {Elsevier}, title = {{The formation of the first black holes and their host halos}}, doi = {10.1016/j.newar.2006.06.021}, volume = {50}, year = {2006}, } @article{17808, abstract = {Four recent observational results have challenged our understanding of high--redshift galaxies, as they require the presence of far more ultraviolet photons than should be emitted by normal stellar populations. First, there is significant ultraviolet emission from Lyman Break Galaxies (LBGs) at wavelenghts shorter than 912Å. Second, there is strong Lyman alpha emission from extended ``blobs'' with little or no associated apparent ionizing continuum. Third, there is a population of galaxies with unusually strong Lyman-alpha emission lines. And fourth, there is a strong HeII (1640 Å) emission line in a composite of LBGs. The proposed explanations for the first three observations are internally inconsistent, and the fourth puzzle has remained hitherto unexplained. Here we show that all four problems are resolved simultaneously if 10-30 percent of the stars in many galaxies at z ~ 3-4 are mainly primordial - unenriched by elements heavier than helium ('metals'). Most models of hierarchical galaxy formation assume efficient intra--galactic metal mixing, and therefore do not predict metal-free star formation at redshifts significantly below z ~5. Our results imply that micro-mixing of metals within galaxies is inefficient on a ~ Gyr time-scale, a conclusion that can be verified with higher resolution simulations, and future observations of the HeII emission line.}, author = {Jimenez, Raul and Haiman, Zoltán}, issn = {0028-0836}, journal = {Nature}, number = {7083}, pages = {501--504}, publisher = {Springer Science and Business Media LLC}, title = {{Significant primordial star formation at redshifts z ≈ 3–4}}, doi = {10.1038/nature04580}, volume = {440}, year = {2006}, } @article{1796, abstract = {Drugs that block the entry of human immunodeficiency virus type 1 (HIV-1) into host cells abrogate the establishment of a productive infection and should ideally diminish the chances of HIV-1 developing resistance. This review will give an overview of the mechanism by which the envelope glycoprotein mediates HIV-1 entry and will summarize current drug developments.}, author = {Sandra Siegert and Schnierle, Peter and Schnierle, Barbara S}, journal = {Mini-Reviews in Medicinal Chemistry}, number = {5}, pages = {557 -- 562}, publisher = {Bentham Science Publishers}, title = {{Novel anti-viral therapy: Drugs that block HIV entry at different target sites}}, doi = {10.2174/138955706776876267}, volume = {6}, year = {2006}, } @article{18041, abstract = {Since it was first suggested1 that a single molecule might function as an active electronic component, a number of techniques have been developed to measure the charge transport properties of single molecules2,3,4,5,6,7,8,9,10,11,12. Although scanning tunnelling microscopy observations under high vacuum conditions can allow stable measurements of electron transport, most measurements of a single molecule bonded in a metal–molecule–metal junction exhibit relatively large variations in conductance. As a result, even simple predictions about how molecules behave in such junctions have still not been rigorously tested. For instance, it is well known13,14 that the tunnelling current passing through a molecule depends on its conformation; but although some experiments have verified this effect15,16,17,18, a comprehensive mapping of how junction conductance changes with molecular conformation is not yet available. In the simple case of a biphenyl—a molecule with two phenyl rings linked by a single C–C bond—conductance is expected to change with the relative twist angle between the two rings, with the planar conformation having the highest conductance. Here we use amine link groups to form single-molecule junctions with more reproducible current–voltage characteristics19. This allows us to extract average conductance values from thousands of individual measurements on a series of seven biphenyl molecules with different ring substitutions that alter the twist angle of the molecules. We find that the conductance for the series decreases with increasing twist angle, consistent with a cosine-squared relation predicted for transport through π-conjugated biphenyl systems13.}, author = {Venkataraman, Latha and Klare, Jennifer E. and Nuckolls, Colin and Hybertsen, Mark S. and Steigerwald, Michael L.}, issn = {1476-4687}, journal = {Nature}, number = {7105}, pages = {904--907}, publisher = {Springer Nature}, title = {{Dependence of single-molecule junction conductance on molecular conformation}}, doi = {10.1038/nature05037}, volume = {442}, year = {2006}, } @article{18042, abstract = {We have measured electron transport in small bundles of identical conducting molybdenum selenide nanowires where the number of weakly interacting one-dimensional chains ranges from 1 to 300. The linear conductance and current in these nanowires exhibit a power-law dependence on temperature and bias voltage, respectively. The exponents governing these power laws decrease as the number of conducting channels increase. These exponents can be related to the electron-electron interaction parameter for transport in multichannel 1D systems with a few defects.}, author = {Venkataraman, Latha and Hong, Yeon Suk and Kim, Philip}, issn = {1079-7114}, journal = {Physical Review Letters}, number = {7}, publisher = {American Physical Society}, title = {{Electron transport in m Multichannel one-dimensional conductor: Molybdenum selenide nanowires}}, doi = {10.1103/physrevlett.96.076601}, volume = {96}, year = {2006}, } @article{18043, abstract = {We measure the conductance of amine-terminated molecules by breaking Au point contacts in a molecular solution at room temperature. We find that the variability of the observed conductance for the diamine molecule−Au junctions is much less than the variability for diisonitrile− and dithiol−Au junctions. This narrow distribution enables unambiguous conductance measurements of single molecules. For an alkane diamine series with 2−8 carbon atoms in the hydrocarbon chain, our results show a systematic trend in the conductance from which we extract a tunneling decay constant of 0.91 ± 0.03 per methylene group. We hypothesize that the diamine link binds preferentially to undercoordinated Au atoms in the junction. This is supported by density functional theory-based calculations that show the amine binding to a gold adatom with sufficient angular flexibility for easy junction formation but well-defined electronic coupling of the N lone pair to the Au. Therefore, the amine linkage leads to well-defined conductance measurements of a single molecule junction in a statistical study.}, author = {Venkataraman, Latha and Klare, Jennifer E. and Tam, Iris W. and Nuckolls, Colin and Hybertsen, Mark S. and Steigerwald, Michael L.}, issn = {1530-6992}, journal = {Nano Letters}, number = {3}, pages = {458--462}, publisher = {American Chemical Society}, title = {{Single-molecule circuits with well-defined molecular conductance}}, doi = {10.1021/nl052373+}, volume = {6}, year = {2006}, } @article{18044, abstract = {The conductance of molecular junctions, formed by breaking gold point contacts dressed with various thiol functionalized organic molecules, is measured at 293 K and at 30 K. In the presence of molecules, individual conductance traces measured as a function of increasing gold electrode displacement show clear steps below the quantum conductance steps of the gold contact. These steps are distributed over a wide range of molecule-dependent conductance values. Histograms constructed from all conductance traces therefore do not show clear peaks either at room or low temperatures. Filtering of the data sets by an objective automated procedure only marginally improves the visibility of such features. We conclude that the geometrical junction to junction variations dominate the conductance measurements.}, author = {Ulrich, Jochen and Esrail, Donna and Pontius, William and Venkataraman, Latha and Millar, David and Doerrer, Linda H.}, issn = {1520-5207}, journal = {The Journal of Physical Chemistry B}, number = {6}, pages = {2462--2466}, publisher = {American Chemical Society}, title = {{Variability of conductance in molecular junctions}}, doi = {10.1021/jp056455y}, volume = {110}, year = {2006}, } @article{18318, abstract = {Multidimensional scaling (MDS) is a generic name for a family of algorithms that construct a configuration of points in a target metric space from information about inter-point distances measured in some other metric space. Large-scale MDS problems often occur in data analysis, representation and visualization. Solving such problems efficiently is of key importance in many applications. In this paper we present a multigrid framework for MDS problems. We demonstrate the performance of our algorithm on dimensionality reduction and isometric embedding problems, two classical problems requiring efficient large-scale MDS. Simulation results show that the proposed approach significantly outperforms conventional MDS algorithms.}, author = {Bronstein, M. M. and Bronstein, Alexander and Kimmel, R. and Yavneh, I.}, issn = {1099-1506}, journal = {Numerical Linear Algebra with Applications}, number = {2-3}, pages = {149--171}, publisher = {Wiley}, title = {{Multigrid multidimensional scaling}}, doi = {10.1002/nla.475}, volume = {13}, year = {2006}, } @inproceedings{18320, abstract = {Presented here is the problem of recovering a dynamic image superimposed on a static background. Such a problem is ill-posed and may arise e.g. in imaging through semireflective media, in separation of an illumination image from a reflectance image, in imaging with diffraction phenomena, etc. In this work we study regularization of this problem in spirit of Total Variation and general sparsifying transformations.}, author = {Bronstein, Alexander and Bronstein, Michael M. and Zibulevsky, Michael}, booktitle = {6th International Conference on Independent Component Analysis and Signal Separation}, isbn = {9783540326304}, issn = {1611-3349}, location = {Charleston, SC, United States}, pages = {934--940}, publisher = {Springer Nature}, title = {{On separation of semitransparent dynamic images from static background}}, doi = {10.1007/11679363_116}, volume = {3889}, year = {2006}, }