Efficient computation of hashes

The sequential computation of hashes at the core of many distributed storage systems and found, for example, in grid services can hinder efficiency in service quality and even pose security challenges that can only be addressed by the use of parallel hash tree modes. The main contributions of this paper are, first, the identification of several efficiency and security challenges posed by the use of sequential hash computation based on the Merkle-Damgard engine. In addition, alternatives for the parallel computation of hash trees are discussed, and a prototype for a new parallel implementation of the Keccak function, the SHA-3 winner, is introduced

DEVELOPMENT OF (Na + -K + )-ATPase IN RAT CEREBRUM: CORRELATION WITH Na + -DEPENDENT PHOSPHORYLATION AND K + - para NITROPHENYLPHOSPHATASE 1

The activities of (Na + K + )-ATPase and its proposed partial reactions, K + - p NPPase and Na + -dependent phosphorylation, all increase tenfold relative to microsomal protein between 5 days prior to birth and 60 days postnatally in NaI-treated rat cerebral microsomes, and all reach half of their adult values between the fifth and tenth postnatal day. These increases are concurrent with the most rapid changes in cerebral wet weight. Increases in the amount of the related phosphorylatable polypeptide during development. as estimated by densitometry of Coomassie-stained polyacrylamide gels after electrophoresis of constant amounts of microsomal protein dissolved in sodium dodecylsulfate, parallel the increments in levels of Na + -dependent phosphorylation. The fraction of total phosphorylation that is Na + -dependent increases steadily during development. suggesting a precursor role for some of the Na + -independent fraction. The results are consistent with a single biosynthetic control for the enzymatic sites critical to the partial reactions of (Na + -K + )-ATPase. No changes in turnover number or affinity for substrate or ligands were found during development. Little similarity was noted among the age-related changes of Mg 2+ -ATPase activity. Mg 2+ -paranitrophenylphosphatase activity, and Na + -independent phosphorylation levels. The most rapid changes in (Na + -K + )-ATPase take place during the period corresponding to glial proliferation and neuronal arborization.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/66087/1/j.1471-4159.1978.tb06577.x.pd

DEVELOPMENT OF (Na + -K + )-ATPase IN RAT HINDBRAIN: INCREMENTS IN PARALLEL WITH Na + -DEPENDENT PHOSPHORYLATION AND K + - p NITROPHENYLPHOSPHATASE 1

Rat hindbrain NaI-enriched microsomal (Na + -K + )-ATPase activity, K + - p NPPase activity, and Na + -dependent steady-state phosphorylation levels all increase approx 10-fold relative to microsomal protein between 5 days prenatally and 60 days postnatally. These activities, as well as the mean wet weight of the hindbrain, are at half of their 60 day values shortly after the 10th postnatal day. For all ages, these hindbrain activities average over twice those found in the forebrain in a companion paper (Bertoni & Siegel, 1978). Increases during development in the amount of the related phosphorylatable polypeptide, estimated by densitometry of stained polyacrylamide gels containing fixed amounts of microsomal protein dissolved in SDS, are in agreement with increases in steady state levels of Na + -dependent phosphorylation. The fraction of total phosphorylation that is Na + -dependent rises steadily during development consistent with, but not obligatorily due to, a conversion of some of the previously Na + -independent portion. Mg2 + -ATPase and Mg 2+ - p NPPase activities and steady-state Na + ,-independent phosphorylation levels do not increase in parallel during development. These observations add further support to the proposed partial reaction scheme for (Na + - K + )-ATPase. The major increments in (Na + -K + )-ATPase occur simultaneously with the deposition of specialized plasma membranes, particularly in the molecular layer of the cerebellum, as described in previous studies of rat hind brain.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/65622/1/j.1471-4159.1979.tb00386.x.pd

Hysteresis and spin phase transitions in quantum wires in the integer quantum Hall regime

We demonstrate that a split-gate quantum wire in the integer quantum Hall regime can exhibit electronic transport hysteresis for up- and down-sweeps of a magnetic field. This behavior is shown to be due to phase spin transitions between two different ground states with and without spatial spin polarization in the vicinity of the wire boundary. The observed effect has a many-body origin arising from an interplay between a confining potential, Coulomb interactions and the exchange interaction. We also demonstrate and explain why the hysteretic behavior is absent for steep and smooth confining potentials and is present only for a limited range of intermediate confinement slopes.Comment: submitted to PR

Photoluminescence spectroscopy of trions in quantum dots: A theoretical description

We present a full configuration-interaction study of the spontaneous recombination of neutral and singly charged excitons (trions) in semiconductor quantum dots from weak- to strong-coupling regimes. We find that the enhancement of the recombination rate of neutral excitons with increasing dot size is suppressed for negative trions and even reversed for positive trions. Our findings agree with recent comprehensive photoluminescence experiments in self-assembled quantum dots [P. Dalgarno , Phys. Rev. B 77, 245311 (2008)] and confirm the major role played by correlations in the valence band. The effect of the temperature on the photoluminescence spectrum and that of the ratio between the electron and hole wave-function length scales are also described

Enhancement and anisotropy of electron Lande factor due to spin-orbit interaction in semiconductor nanowires

We investigate the effective Lande factor in semiconductor nanowires with strong Rashba spin-orbit coupling. Using the $\mathbf{k}\cdot\mathbf{p}$ theory and the envelope function approach we derive a conduction band Hamiltonian where the tensor $g^*$ is explicitly related to the spin-orbit coupling constant $\alpha_R$. Our model includes orbital effects from the Rashba spin-orbit term, leading to a significant enhancement of the effective Lande factor which is naturally anisotropic. For nanowires based on the low-gap, high spin-orbit coupled material InSb, we investigate the anisotropy of the effective Lande factor with respect to the magnetic field direction, exposing a twofold symmetry for the bottom gate architecture. The anisotropy results from the competition between the localization of the envelope function and the spin polarization of the electronic state, both determined by the magnetic field direction.Comment: 12 pages, 12 figure

The interpretation of the solutions of the Wheeler De Witt equation

We extract transition amplitudes among matter constituents of the universe from the solutions of the Wheeler De Witt equation. The physical interpretation of these solutions is then reached by an analysis of the properties of the transition amplitudes. The interpretation so obtained is based on the current carried by these solutions and confirms ideas put forward by Vilenkin.Comment: 11 pages, latex, no figure

Measuring out quasi-local integrals of motion from entanglement

Quasi-local integrals of motion are a key concept underpinning the modern understanding of many-body localisation, a phenomenon in which interactions and disorder come together. Despite the existence of several numerical ways to compute them—and in the light of the observation that much of the phenomenology of many properties can be derived from them—it is not obvious how to directly measure aspects of them in real quantum simulations; in fact, hard experimental evidence is still missing. In this work, we propose a way to extract the real-space properties of such quasi-local integrals of motion based on a spatially-resolved entanglement probe able to distinguish Anderson from many-body localisation from non-equilibrium dynamics. We complement these findings with a rigorous entanglement bound and compute the relevant quantities using tensor networks. We demonstrate that the entanglement gives rise to a well-defined length scale that can be measured in experiments

Local integrals of motion and the stability of many-body localisation in Wannier-Stark potentials

Many-body localisation in disordered systems in one spatial dimension is typically understood in terms of the existence of an extensive number of (quasi)-local integrals of motion (LIOMs) which are thought to decay exponentially with distance and interact only weakly with one another. By contrast, little is known about the form of the integrals of motion in disorder-free systems which exhibit localisation. Here, we explicitly compute the LIOMs for disorder-free localised systems, focusing on the case of a linearly increasing potential. We show that while in the absence of interactions, the LIOMs decay faster than exponentially, the addition of interactions leads to the formation of a slow-decaying plateau at short distances. We study how the localisation properties of the LIOMs depend on the linear slope, finding that there is a significant finite-size dependence, and present evidence that adding a weak harmonic potential does not result in typical many-body localisation phenomenology. By contrast, the addition of disorder has a qualitatively different effect, dramatically modifying the properties of the LIOMS.Comment: 21 pages, 14 figures, replaced with final versio

Directionality of acoustic phonon emission in weakly-confined semiconductor quantum dots

The direction of propagation of acoustic phonons emitted by electron relaxation in weakly confined, parabolic quantum dots charged with one or two electrons is studied theoretically. The emission angle strongly depends on the energy of the phonon, the dominant electron-phonon scattering mechanism (deformation potential or piezoelectric field), and the orbital symmetries of the initial and final electron states. This leads to different behaviors for phonons emitted by electrons relaxing between levels of single and coupled quantum dots. Our results establish the basis to control the direction of propagation of phonon modes triggered by transitions in quantum dot systems