Raman signatures of classical and quantum phases in coupled dots: A theoretical prediction

We study electron molecules in realistic vertically coupled quantum dots in a strong magnetic field. Computing the energy spectrum, pair correlation functions, and dynamical form factor as a function of inter-dot coupling via diagonalization of the many-body Hamiltonian, we identify structural transitions between different phases, some of which do not have a classical counterpart. The calculated Raman cross section shows how such phases can be experimentally singled out.Comment: 9 pages, 2 postscript figures, 1 colour postscript figure, Latex 2e, Europhysics Letters style and epsfig macros. Submitted to Europhysics Letter

Siren songs or path to salvation? Interpreting the visions of web technology at a UK regional newspaper in crisis, 2006-11

A 5-year case study of an established regional newspaper in Britain investigates journalists about their perceptions of convergence in digital technologies. This research is the first ethnographic longitudinal case study of a UK regional newspaper. Although conforming to some trends observed in the wider field of scholarship, the analysis adds to skepticism about any linear or directional views of innovation and adoption: the Northern Echo newspaper journalists were observed to have revised their opinions of optimum Web practices, and sometimes radically reversed policies. Technology is seen in the period as a fluid, amorphous entity. Central corporate authority appeared to diminish in the period as part of a wider reduction in formalism. Questioning functionalist notions of the market, the study suggests cause and effect models of change are often subverted by contradictory perceptions of particular actions. Meanwhile, during technological evolution, the ‘professional imagination’ can be understood as strongly reflecting the parent print culture and its routines, despite pioneering a new convergence partnership with an independent television company

Direct visualization of the magnetostructural phase transition in nanoscale FeRh thin films using differential phase contrast imaging

To advance the use of thermally activated magnetic materials in device applications it is necessary to examine their behavior on the localized scale operando conditions. Equiatomic FeRh undergoes a magnetostructural transition from an antiferromagnetic (AF) to a ferromagnetic (FM) phase above room temperature (∼350–380 K), and hence is considered a very desirable material for the next generation of nanomagnetic or spintronic devices. For this to be realized, we must fully understand the intricate details of the AF to FM transition and associated FM domain growth on the scale of their operation. Here we combine in situ heating with a comprehensive suite of advanced transmission electron microscopy techniques to investigate directly the magnetostructural transition in nanoscale FeRh thin films. Differential phase contrast imaging visualizes the stages of FM domain growth in both cross-sectional and planar FeRh thin films as a function of temperature. Small surface FM signals are also detected due to interfacial strain with the MgO substrate and Fe deficiency after HF etching of the substrate, providing a directional bias for FM domain growth. Our work provides high resolution imaging and quantitative measurements throughout the transition, which were previously inaccessible, and offers fundamental insight into their potential use in magnetic devices

Phase boundary exchange coupling in the mixed magnetic phase regime of a Pd-doped FeRh epilayer

Spin-wave resonance measurements were performe in the mixed magnetic phase regime of a Pd-doped FeRh epilayer that appears as the first-order ferromagnetic-antiferromagnetic phase transition takes place. It is seen that the measured value of the exchange stiffness is suppressed throughout the measurement range when compared to the expected value of the fully ferromagnetic regime, extracted via the independent means of a measurement of the Curie point, for only slight changes in the ferromagnetic volume fraction. This behavior is attributed to the influence of the antiferromagnetic phase: inspired by previous experiments that show ferromagnetism to be most persistent at the surfaces and interfaces of FeRh thin films, we modelled the antiferromagnetic phase as forming a thin layer in the middle of the epilayer through which the two ferromagnetic layers are coupled up to a certain critical thickness. The development of this exchange stiffness is then consistent with that expected from the development of an exchange coupling across the magnetic phase boundary, as a consequence of a thickness dependent phase transition taking place in the antiferromagnetic regions and is supported by complimentary computer simulations of atomistic spin-dynamics. The development of the Gilbert damping parameter extracted from the ferromagnetic resonance investigations is consistent with this picture

Not All Fabrics Are Created Equal: Exploring eFPGA Parameters for IP Redaction

Semiconductor design houses rely on third-party foundries to manufacture their integrated circuits (ICs). While this trend allows them to tackle fabrication costs, it introduces security concerns as external (and potentially malicious) parties can access critical parts of the designs and steal or modify the intellectual property (IP). Embedded field-programmable gate array (eFPGA) redaction is a promising technique to protect critical IPs of an ASIC by redacting (i.e., removing) critical parts and mapping them onto a custom reconfigurable fabric. Only trusted parties will receive the correct bitstream to restore the redacted functionality. While previous studies imply that using an eFPGA is a sufficient condition to provide security against IP threats like reverse-engineering, whether this truly holds for all eFPGA architectures is unclear, thus motivating the study in this article. We examine the security of eFPGA fabrics generated by varying different FPGA design parameters. We characterize the power, performance, and area (PPA) characteristics and evaluate each fabric’s resistance to Boolean satisfiability (SAT)-based bitstream recovery. Our results encourage designers to work with custom eFPGA fabrics rather than off-the-shelf commercial FPGAs and reveals that only considering a redaction fabric’s bitstream size is inadequate for gauging security

Galaxy And Mass Assembly: Galaxy Zoo spiral arms and star formation rates

Understanding the effect spiral structure has on star formation properties of galaxies is important to complete our picture of spiral structure evolution. Previous studies have investigated connections between spiral arm properties and star formation, but the effect that the number of spiral arms has on this process is unclear. Here, we use the Galaxy And Mass Assembly (GAMA) survey paired with the citizen science visual classifications from the Galaxy Zoo project to explore galaxies’ spiral arm number and how it connects to the star formation process. We use the votes from the GAMA-Kilo Degree Survey Galaxy Zoo classification to investigate the link between spiral arm number and stellar mass, star formation rate, and specific star formation rate (sSFR). We find that galaxies with fewer spiral arms have lower stellar masses and higher sSFRs, while those with more spiral arms tend towards higher stellar masses and lower sSFRs, and conclude that galaxies are less efficient at forming stars if they have more spiral arms. We note how previous studies’ findings may indicate a cause for this connection in spiral arm strength or opacity

The Longitudinal association Between Sexual Violence Victimization and Sexual Risk Behavior in adolescence

Being a victim of sexual violence (SV) is generally believed to be associated with subsequent sexual risk behavior (SRB) during adolescence. While this assumption makes intuitive sense, it is based on methodologically limited research, including a reliance on cross-sectional data. to address this gap in research, we test whether experiencing SV victimization in early adolescence is associated with self-reported SRB approximately two years later. The sample comprised 4,618 youth (58% female; 52% Hispanic; 39% Black) attending 44 schools in the southern United States. Self-reported data were collected using an audio computer-assisted self-interview (ACASI). Baseline data were collected when students were in 7th or 8th grade and follow-up data were collected approximately 24 months later when students were in 9th or 10th grade. Indices of SRB included behaviors related to oral, vaginal, and anal sex (e.g., number of partners, number of times without a condom). Girls, but not boys, who reported SV victimization at baseline reported engaging more frequently in all oral and vaginal SRBs at 24 month follow-up compared to their non-victimized female counterparts. Additionally, girls reporting SV victimization reported more anal sex partners than non-victimized girls. Girls who are victims of SV engage in significantly more SRB by early high school placing them at greater risk to contract STIs and become pregnant. Victims of SV should be screened for SRB and provided access to the appropriate resources. Teen pregnancy and STI prevention planning should consider SV victimization in their strategy planning