3,654 research outputs found
New high performance digital memory devices fabricated with DNA and DNA-mimics
No full textWe report the first digital nonvolatile memory devices fabricated with DNA and DNA-mimicking brush polymers. Salmon testes and calf thymus DNA devices, as well as DNA-mimicking brush polymer devices revealed p-type unipolar write-once-read-many-times memory behaviors with low switching-on voltage and high ON/OFF current ratio. Such permanent memory characteristics were confirmed to originate from the charge trapping and hopping nature of nucleobase moieties. Overall, this study demonstrated that DNA and DNA-mimicking polymers are good candidate materials for the production of p-type permanent memory devices with high performance, high stability and low power consumption.111sciescopu
Clockwork graviton contributions to muon <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>g</mml:mi><mml:mo>−</mml:mo><mml:mn>2</mml:mn></mml:math>
No full textThe clockwork mechanism for gravity introduces a tower of massive graviton modes, clockwork gravitons, with a very compressed mass spectrum, whose interaction strengths are much stronger than those of massless gravitons. In this work, we compute the lowest order contributions of the clockwork gravitons to the anomalous magnetic moment, g-2, of muon in the context of an extra dimensional model with a five-dimensional Planck mass, M5. We find that the total contributions are rather insensitive to the detailed model parameters and are determined mostly by the value of M5. To account for the current muon g-2 anomaly, M5 should be around 0.2 TeV, and the size of the extra dimension has to be quite large, l5 10-7 m. For M5 1 TeV, the clockwork graviton contributions are too small to explain the current muon g-2 anomaly. We also compare the clockwork graviton contributions with other extra dimensional models such as Randall-Sundrum models or large extra dimensional models. We find that the leading contributions in the small curvature limit are universal, but the cutoff-independent subleading contributions vary for different background geometries and the clockwork geometry gives the smallest subleading contributions. © 2018 authors11Nsciescopu
Aligned natural inflation in the Large Volume Scenario
No full text© 2021, The Author(s).We embed natural inflation in an explict string theory model and derive observables in cosmology. We achieve this by compactifying the type IIB string on a Calabi-Yau orientifold, stabilizing moduli via the Large Volume Scenario, and configuring axions using D7-brane stacks. In order to obtain a large effective decay constant, we employ the Kim-Nilles-Peloso alignment mechanism, with the required multiple axions arising naturally from generically anisotropic bulk geometries. The bulk volumes, and hence the axion decay constants, are stabilized by generalized one-loop corrections and subject to various conditions: the Kähler cone condition on the string geometry; the convex hull condition of the weak gravity conjecture; and the constraint from the power spectrum of scalar perturbations. We find that all constraints can be satisfied in a geometry with relatively small volume and thus heavy bulk axion mass. We also covariantize the convex hull condition for the axion-dilaton-instanton system and verify the normalization of the extremal bound.11Nsciescopu
Low noise high performance 50nm T-gate metamorphic HEMT with cut-off frequency f<sub>T</sub> of 440 GHz for millimeterwave imaging receivers applications
No full textThe 50 nm m-HEMT exhibits extremely high f<sub>T</sub>, of 440GHz, low F<sub>min</sub> of 0.7 dB, associated gain of 13 dB at 26 GHz with an exceptionally high Id of 200 mA/mm and gm of 950 ms/mm at low noise biased point
Axion emission from supernova with axion-pion-nucleon contact interaction
No full textOpen Access ©The Authors. Article funded by SCOAP3 We examine the axion emission from supernovae with a complete set of relevant axion couplings including the axion-pion-nucleon contact interaction which was ignored in the previous studies. Two processes are affected by the axion-pion-nucleon contact interaction, pi(-) + p -> n + a and n + p -> n + p + a, and these processes can be the dominant source of axions for some region in the axion parameter space or in astrophysical conditions encountered inside supernovae. We find that the contact interaction can enhance the axion emissivity of pi(-) + p -> n + a by a factor of 2 - 4, while the effect on n + p -> n + p + a is not significant. We also discuss the relative importance of other pion-induced processes such as pi(0) + n -> n + a and pi(-) + pi(0) -> pi(-) + a.11Nsciescopu
Exploring the Universe with dark light scalars
No full textWe study the cosmology of the dark sector consisting of (ultra)light scalars. Since the scalar mass is radiatively unstable, a special explanation is required to make the mass much smaller than the UV scale. There are two well-known mechanisms for the origin of scalar mass. The scalar can be identified as a pseudo-Goldstone boson, whose shift symmetry is explicitly broken by nonperturbative corrections, like the axion. Alternatively, it can be identified as a composite particle like the glueball, whose mass is limited by the confinement scale of the theory because no scalar degree of freedom exists at high scales. In both cases, the scalar can be naturally light, but interaction behavior is quite different. The lighter the axion (glueball), the weaker (stronger) its interaction. As the simplest nontrivial example, we consider the dark axion whose shift symmetry is anomalously broken by the hidden non-Abelian gauge symmetry. After the confinement of the gauge group, the dark axion and the dark glueball get masses and both form multicomponent dark matter. We carefully consider the effects of energy flow from the dark gluons to the dark axions and derive the full equations of motion for the background and the perturbed variables. The effect of the dark axion-dark gluon coupling on the evolution of the entropy and the isocurvature perturbations is also clarified. Finally, we discuss the gravothermal collapse of the glueball subcomponent dark matter after the halos form, in order to explore the potential to contribute to the formation of seeds for the supermassive black holes observed at high redshifts. With the simplified assumptions, the glueball subcomponent dark matter with the mass of 0.01-0.1 MeV and the axion main dark matter component with the decay constant f(a) = O(10(15)-10(16)) GeV and the mass of O(10(-14)-10(-18)) eV can provide a hint on the origin of the supermassive black holes at high redshifts.11Nsciescopu
Electro-chemo-mechanical studies of perovskite-structured mixed ionic-electronic conducting SrSn[subscript 1-x]Fe[subscript x]O[subscript 3-x/2+δ] part II: Electrical conductivity and cathode performance
No full textThe bulk electrical conductivity of the mixed ionic-electronic conducting perovskite-structured SrSn[subscript 1-x]Fe[subscript x]O[subscript 3-x/2+δ] (SSF) was measured to examine how changes in defect chemistry and electronic band structure associated with the substitution of Ti by Sn impact defect charge carrier density and ultimately electrode performance. These results complement a defect chemical model for SSF investigated and reported in Part I of this study. The electrical properties of SSF were found not to differ significantly from the corresponding composition in SrTi[subscript 1-x]Fe[subscript x]O[subscript 3-x/2+δ] (STF). It is believed that Fe dominates the character of the valence and conduction bands and thus governs the electronic properties in SSF. Though slightly shifted in energy due to the larger size of Sn, the defect equilibria and therefore the electrical conductivity of SSF were found to be largely dominated by Fe and thus differed only in a limited way from that in STF. Key kinetic parameters obtained include the migration enthalpy of oxygen vacancies (0.772 ± 0.204 eV), the activation energy of area-specific-resistance for oxygen exchange (1.65 ± 0.03 eV) and the magnitudes of electron (0.0002 ± 0.00005 cm2/V∙s) and hole (0.0037 ± 0.0015 cm[superscript 2]/V∙s) mobilities. Keywords: Mixed ionic electronic conductor, Cathode, Area specific resistance, Impedance spectroscopy, Perovskite oxid
Emotional experiences of medical students during cadaver dissection and the role of memorial ceremonies: a qualitative study
No full textAbstract Background It has been well reported that the emotional experiences of medical students in the gross anatomy laboratory could have significant impacts on their professional identity formation. This qualitative study aimed to investigate students’ emotions towards cadaver dissection and the educational role of memorial ceremonies. Methods A total of 37 students from eight teams were recruited in the team-based dissection course during two consecutive academic years (2016 and 2017) at one medical school. In focus group interviews, students were encouraged to express and discuss their emotions regarding cadaver dissection and memorial ceremonies. Results The participants described their apprehension and anxiety during their first encounter with cadavers that diminished through gradual exposure. Unfortunately, their positive emotions such as gratitude and responsibility also tended to decline under the pressure of excessive workloads and frequent examinations. Memorial ceremonies, including not only large-scale events but also daily rituals, had educational effects that they prevented the decline of students’ responsibility and respect during the dissection course. Conclusion Educators should assist medical students in overcoming their initial distress and maintaining respectful attitudes throughout the dissection course. Memorial ceremonies can be effective educational tools for fostering appropriate attitudes and ethical practice in the gross anatomy laboratory
Manipulating Resonances and Electron Confinement in Quantum Barriers
No full textthis paper, we choose the pressure as a continuous external parameter and study the coherent intereference e#ects that arise in multi-wave GaAs/Al x Ga 1-x As/ GaAs single-barrier structures. Since the electron wavefunction varies slowly on the lattice constant scale, we use the envelope function approach generalized to include -522- Manipulating Resonances and Electron Confinement in Quantum Barriers -- Chang Sub Kim et al. -523Fig. 1. Band-edge profile of the single barrier heterostructure, where a barrier width D = 18.4 nm (40 layers thickness) and a fraction x = 0.3 are assumed. For the chosen fraction, a direct band configuration is forme
Whole-genome sequence of Sunxiuqinia dokdonensis DH1T, isolated from deep sub-seafloor sediment in Dokdo Island
No full textAbstractSunxiuqinia dokdonensis DH1T was isolated from deep sub-seafloor sediment at a depth of 900m below the seafloor off Seo-do (the west part of Dokdo Island) in the East Sea of the Republic of Korea and subjected to whole genome sequencing on HiSeq platform and annotated on RAST. The nucleotide sequence of this genome was deposited into DDBJ/EMBL/GenBank under the accession LGIA00000000
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