Graviton Absorption by Non-BPS Branes

We consider the behaviour of neutral non-BPS branes probed by scalars and gravitons. We show that the naked singularity of the non-BPS branes is a {\it repulson} absorbing no incoming radiation. The naked singularity is surrounded by an infinite potential well breaking the unitarity of the scattering S-matrix. We compute the absorption cross section which is infrared divergent. In particular this confirms that gravity does not decouple for the non-BPS branes.Comment: 13 pages, Late

Low-swing signaling for energy efficient on-chip networks

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2011.Cataloged from PDF version of thesis.Includes bibliographical references (p. 65-69).On-chip networks have emerged as a scalable and high-bandwidth communication fabric in many-core processor chips. However, the energy consumption of these networks is becoming comparable to that of computation cores, making further scaling of core counts difficult. This thesis makes several contributions to low-swing signaling circuit design for the energy efficient on-chip networks in two separate projects: on-chip networks optimized for one-to-many multicasts and broadcasts, and link designs that allow on-chip networks to approach an ideal interconnection fabric. A low-swing crossbar switch, which is based on tri-state Reduced-Swing Drivers (RSDs), is presented for the first project. Measurement results of its test chip fabricated in 45nm SOI CMOS show that the tri-state RSD-based crossbar enables 55% power savings as compared to an equivalent full-swing crossbar and link. Also, the measurement results show that the proposed crossbar allows the broadcast-optimized on-chip networks using a single pipeline stage for physical data transmission to operate at 21% higher data rate, when compared with the full-swing networks. For the second project, two clockless low-swing repeaters, a Self-Resetting Logic Repeater (SRLR) and a Voltage-Locked Repeater (VLR), have been proposed and analyzed in simulation only. They both require no reference clock, differential signaling, and bias current. Such digital-intensive properties enable them to approach energy and delay performance of a point-to-point interconnect of variable lengths. Simulated in 45nm SOI CMOS, the 10mm SRLR featured with high energy efficiency consumes 338fJ/b at 5.4Gb/s/ch while the 10mm VLR raises its data rate up to 16.OGb/s/ch with 427fJ/b.by Sunghyun Park.S.M

Proper incorporation of self-adjoint extension method to Green's function formalism : one-dimensional δ′\delta^{'}-function potential case

One-dimensional $\delta^{'}$-function potential is discussed in the framework of Green's function formalism without invoking perturbation expansion. It is shown that the energy-dependent Green's function for this case is crucially dependent on the boundary conditions which are provided by self-adjoint extension method. The most general Green's function which contains four real self-adjoint extension parameters is constructed. Also the relation between the bare coupling constant and self-adjoint extension parameter is derived.Comment: LATEX, 13 page

Birthweight and risk markers for type 2 diabetes and cardiovascular disease in childhood: the Child Heart and Health Study in England (CHASE).

AIMS/HYPOTHESIS: Lower birthweight (a marker of fetal undernutrition) is associated with higher risks of type 2 diabetes and cardiovascular disease (CVD) and could explain ethnic differences in these diseases. We examined associations between birthweight and risk markers for diabetes and CVD in UK-resident white European, South Asian and black African-Caribbean children. METHODS: In a cross-sectional study of risk markers for diabetes and CVD in 9- to 10-year-old children of different ethnic origins, birthweight was obtained from health records and/or parental recall. Associations between birthweight and risk markers were estimated using multilevel linear regression to account for clustering in children from the same school. RESULTS: Key data were available for 3,744 (66%) singleton study participants. In analyses adjusted for age, sex and ethnicity, birthweight was inversely associated with serum urate and positively associated with systolic BP. After additional height adjustment, lower birthweight (per 100 g) was associated with higher serum urate (0.52%; 95% CI 0.38, 0.66), fasting serum insulin (0.41%; 95% CI 0.08, 0.74), HbA1c (0.04%; 95% CI 0.00, 0.08), plasma glucose (0.06%; 95% CI 0.02, 0.10) and serum triacylglycerol (0.30%; 95% CI 0.09, 0.51) but not with BP or blood cholesterol. Birthweight was lower among children of South Asian (231 g lower; 95% CI 183, 280) and black African-Caribbean origin (81 g lower; 95% CI 30, 132). However, adjustment for birthweight had no effect on ethnic differences in risk markers. CONCLUSIONS/INTERPRETATION: Birthweight was inversely associated with urate and with insulin and glycaemia after adjustment for current height. Lower birthweight does not appear to explain emerging ethnic difference in risk markers for diabetes

Elaboration and characterization of Fe1–xO thin films sputter deposited from magnetite target

Majority of the authors report elaboration of iron oxide thin films by reactive magnetron sputtering from an iron target with Ar–O2 gas mixture. Instead of using the reactive sputtering of a metallic target we report here the preparation of Fe1–xOthin films, directly sputtered froma magnetite target in a pure argon gas flow with a bias power applied. This oxide is generally obtained at very low partial oxygen pressure and high temperature.We showed that bias sputtering which can be controlled very easily can lead to reducing conditions during deposition of oxide thin film on simple glass substrates. The proportion of wustite was directly adjusted bymodifying the power of the substrate polarization. Atomic force microscopy was used to observe these nanostructured layers. Mössbauer measurements and electrical properties versus bias polarization and annealing temperature are also reported

Compositional Inversion Symmetry Breaking in Ferroelectric Perovskites

Ternary cubic perovskite compounds of the form A_(1/3)A'_(1/3)A''_(1/3)BO_3 and AB_(1/3)B'_(1/3)B''_(1/3)O_3, in which the differentiated cations form an alternating series of monolayers, are studied using first-principles methods. Such compounds are representative of a possible new class of materials in which ferroelectricity is perturbed by compositional breaking of inversion symmetry. For isovalent substitution on either sublattice, the ferroelectric double-well potential is found to persist, but becomes sufficiently asymmetric that minority domains may no longer survive. The strength of the symmetry breaking is enormously stronger for heterovalent substitution, so that the double-well behavior is completely destroyed. Possible means of tuning between these behaviors may allow for the optimization of resulting materials properties.Comment: 4 pages, two-column style with 3 postscript figures embedded. Uses REVTEX and epsf macros. Also available at http://www.physics.rutgers.edu/~dhv/preprints/index.html#sai_is

E-QED: Electrical Bug Localization During Post-Silicon Validation Enabled by Quick Error Detection and Formal Methods

During post-silicon validation, manufactured integrated circuits are extensively tested in actual system environments to detect design bugs. Bug localization involves identification of a bug trace (a sequence of inputs that activates and detects the bug) and a hardware design block where the bug is located. Existing bug localization practices during post-silicon validation are mostly manual and ad hoc, and, hence, extremely expensive and time consuming. This is particularly true for subtle electrical bugs caused by unexpected interactions between a design and its electrical state. We present E-QED, a new approach that automatically localizes electrical bugs during post-silicon validation. Our results on the OpenSPARC T2, an open-source 500-million-transistor multicore chip design, demonstrate the effectiveness and practicality of E-QED: starting with a failed post-silicon test, in a few hours (9 hours on average) we can automatically narrow the location of the bug to (the fan-in logic cone of) a handful of candidate flip-flops (18 flip-flops on average for a design with ~ 1 Million flip-flops) and also obtain the corresponding bug trace. The area impact of E-QED is ~2.5%. In contrast, deter-mining this same information might take weeks (or even months) of mostly manual work using traditional approaches

Structural and magnetic properties of Fe/ZnSe(001) interfaces

We have performed first principles electronic structure calculations to investigate the structural and magnetic properties of Fe/ZnSe(001) interfaces. Calculations involving full geometry optimizations have been carried out for a broad range of thickness of Fe layers(0.5 monolayer to 10 monolayers) on top of a ZnSe(001) substrate. Both Zn and Se terminated interfaces have been explored. Total energy calculations show that Se segregates at the surface which is in agreement with recent experiments. For both Zn and Se terminations, the interface Fe magnetic moments are higher than the bulk bcc Fe moment. We have also investigated the effect of adding Fe atoms on top of a reconstructed ZnSe surface to explore the role of reconstruction of semiconductor surfaces in determining properties of metal-semiconductor interfaces. Fe breaks the Se dimer bond formed for a Se-rich (2x1) reconstructed surface. Finally, we looked at the reverse growth i.e. growth of Zn and Se atoms on a bcc Fe(001) substrate to investigate the properties of the second interface of a magnetotunnel junction. The results are in good agreement with the theoretical and experimental results, wherever available.Comment: 7 pages, 8 figures, accepted for publication in PR

Ab initio study of ferroelectric domain walls in PbTiO3

We have investigated the atomistic structure of the 180-degree and 90-degree domain boundaries in the ferroelectric perovskite compound PbTiO3 using a first-principles ultrasoft-pseudopotential approach. For each case we have computed the position, thickness and creation energy of the domain walls, and an estimate of the barrier height for their motion has been obtained. We find both kinds of domain walls to be very narrow with a similar width of the order of one to two lattice constants. The energy of the 90-dergree domain wall is calculated to be 35 mJ/m^2, about a factor of four lower than the energy of its 180-degree counterpart, and only a miniscule barrier for its motion is found. As a surprising feature we detected a small offset of 0.15-0.2 eV in the electrostatic potential across the 90-degree domain wall.Comment: 12 pages, with 9 postscript figures embedded. Uses REVTEX and epsf macros. Also available at http://www.physics.rutgers.edu/~dhv/preprints/bm_dw/index.htm