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We prove that sums of length about
of Hecke eigenvalues of automorphic forms on
do not correlate with
-periodic functions with bounded Fourier transform. This generalizes the earlier results of Munshi and Holowinsky–Nelson, corresponding to multiplicative Dirichlet characters, and applies, in particular, to trace functions of small conductor modulo primes.
Integration of photonic devices on silicon (Si) substrates is a key method in enabling large scale manufacturing of Si-based photonic–electronic circuits for next generation systems with high performance, small form factor, low power consumption, and low cost. Germanium (Ge) is a promising material due to its pseudo-direct bandgap and its compatibility with Si-CMOS processing. In this article, we present our recent progress on achieving high quality germanium-on-silicon (Ge/Si) materials. Subsequently, the performance of various functional devices such as photodetectors, lasers, waveguides, and sensors that are fabricated on the Ge/Si platform are discussed. Some possible future works such as the incorporation of tin (Sn) into Ge will be proposed. Finally, some applications based on a fully monolithic integrated photonic–electronic chip on an Si platform will be highlighted at the end of this article.
We demonstrate that the second-Stokes output from a diamond Raman laser, pumped by a femtosecond Ti:Sapphire laser, can be used to efficiently excite red-emitting dyes by two-photon excitation at 1,080 nm and beyond. We image HeLa cells expressing red fluorescent protein, as well as dyes such as Texas Red and Mitotracker Red. We demonstrate the potential for simultaneous two-color, two-photon imaging with this laser by using the residual pump beam for excitation of a green-emitting dye. We demonstrate this for the combination of Alexa Fluor 488 and Alexa Fluor 568. Because the Raman laser extends the wavelength range of the Ti:Sapphire laser, resulting in a laser system tunable to 680–1,200 nm, it can be used for two-photon excitation of a large variety and combination of dyes.
Wellbeing (WB) is a major topic of research across several scientific disciplines, partly driven by its strong association with psychological and mental health. Twin-family studies have found that both genotype and environment play an important role in explaining the variance in WB. Epigenetic mechanisms, such as DNA methylation, regulate gene expression, and may mediate genetic and environmental effects on WB. Here, for the first time, we apply an epigenome-wide association study (EWAS) approach to identify differentially methylated sites associated with individual differences in WB. Subjects were part of the longitudinal survey studies of the Netherlands Twin Register (NTR) and participated in the NTR biobank project between 2002 and 2011. WB was assessed by a short inventory that measures satisfaction with life (SAT). DNA methylation was measured in whole blood by the Illumina Infinium HumanMethylation450 BeadChip (HM450k array) and the association between WB and DNA methylation level was tested at 411,169 autosomal sites. Two sites (cg10845147, p = 1.51 * 10−8 and cg01940273, p = 2.34 * 10−8) reached genome-wide significance following Bonferonni correction. Four more sites (cg03329539, p = 2.76* 10−7; cg09716613, p = 3.23 * 10−7; cg04387347, p = 3.95 * 10−7; and cg02290168, p = 5.23 * 10−7) were considered to be genome-wide significant when applying the widely used criterion of a FDR q value < 0.05. Gene ontology (GO) analysis highlighted enrichment of several central nervous system categories among higher-ranking methylation sites. Overall, these results provide a first insight into the epigenetic mechanisms associated with WB and lay the foundations for future work aiming to unravel the biological mechanisms underlying a complex trait like WB.
Emergency physicians are leaders in the ‘‘free open-access meducation’’ (FOAM) movement. The mandate of FOAM is to create open-access education and knowledge translation resources for trainees and practicing physicians (e.g., blogs, podcasts, and vodcasts). Critics of FOAM have suggested that because such resources can be easily published online without quality control mechanisms, unreviewed FOAM resources may be erroneous or biased. We present a new initiative to incorporate open, expert, peer review into an established academic medical blog. Experts provided either pre- or postpublication reviews that were visible to blog readers. This article outlines the details of this initiative and discusses the potentially transformative impact of this educational innovation.
The minimum roman dominating problem (denoted by γR(G),
the weight of minimum roman dominating function of graph G) is a variant of the very
well known minimum dominating set problem (denoted by γ(G), the
cardinality of minimum dominating set of graph G). Both problems remain NP-Complete when restricted
to P5-free graph class [A.A. Bertossi,
Inf. Process. Lett. 19 (1984) 37–40; E.J. Cockayne,
et al. Discret. Math. 278 (2004) 11–22]. In this paper we
study both problems restricted to some subclasses of P5-free graphs.
We describe robust algorithms that solve both problems restricted to (P5,(s,t)-net)-free graphs
in polynomial time. This result generalizes previous works for both problems, and improves
existing algorithms when restricted to certain families such as (P5,bull)-free
graphs. It turns out that the same approach also serves to solve problems for general
graphs in polynomial time whenever γ(G) and γR(G)
are fixed (more efficiently than naive algorithms). Moreover, the algorithms described are
extremely simple which makes them useful for practical purposes, and as we show in the
last section it allows to simplify algorithms for significant classes such as
Several Gigantopithecus faunas associated with taxonomically undetermined hominoid fossils and/or stone artifacts are known from southern China. These faunas are particularly important for the study of the evolution of humans and other mammals in Asia. However, the geochronology of the Gigantopithecus faunas remains uncertain. In order to solve this problem, a program of geochronological studies of Gigantopithecus faunas in Guangxi Province was recently initiated. Chuifeng Cave is the first studied site, which yielded 92 Gigantopithecus blacki teeth associated with numerous other mammalian fossils. We carried out combined ESR/U-series dating of fossil teeth and sediment paleomagnetic studies. Our ESR results suggest that the lower layers at this cave can be dated to 1.92 ± 0.14 Ma and the upper layers can be dated to older than 1.38 ± 0.17 Ma. Correlation of the recognized magnetozones to the geomagnetic polarity timescale was achieved by combining magnetostratigraphic, biostratigraphic and ESR data. The combined chronologies establish an Olduvai subchron (1.945–1.778 Ma) for the lowermost Chuifeng Cave sediments. We also analyzed the enamel δ13C values of the Gigantopithecus faunas. Our results show that southern China was dominated by C3 plants during the early Pleistocene and that the Gigantopithecus faunas lived in a woodland-forest ecosystem.
This study aims to explore the impact of different captions on second language (L2) learning in a computer-assisted multimedia context. A quasi-experimental design was adopted, and a total of thirty-two eighth graders selected from a junior high school joined the study. They were systematically assigned into four groups based on their proficiency in English; these groups were shown animations with English narration and one of the following types of caption: no captions (M1), Chinese captions (M2), English captions (M3), and Chinese plus English captions (M4). A multimedia English learning program was conducted; the learning content involved two scientific articles presented on a computer. To track the learning process, data on oral repetition were collected after each sentence or scene was played. A post-test evaluation and a semi-structured interview were conducted immediately after viewing. The results show that the effect of different captions in multimedia L2 learning with respect to vocabulary acquisition and reading comprehension depend on students’ L2 proficiency. With English and Chinese + English captions, learners with low proficiency performed better in learning English relative to those who did not have such captions. Students relied on graphics and animation as an important tool for understanding English sentences.
Probability Density Function (PDF) is often selected to couple chemistry with turbulence
for complex reactive flows since complex reactions can be treated without modeling
assumptions. This paper describes an investigation into the use of the particles
approximation of this transport equation approach applied to Homogeneous Charge
Compression Ignition (HCCI) combustion. The model used here is an IEM (Interaction by
Exchange with the Mean) model to describe the micromixing. Therefore, the fluid within the
combustion chamber is represented by a number of computational particles. Each particle
evolves function of the rate of change due to the chemical reaction term and the mixing
term. The chemical reaction term is calculated using a reduced mechanism of n-heptane
oxidation with 25 species and 25 reactions developed previously. The parametric study with
a variation of the number of particles from 50 up to 104 has been investigated
for three initial distributions. The numerical experiments have shown that the hat
distribution is not appropriate and the normal and lognormal distributions give the same
trends. As expected when the number of particles increases for homogenous mixture (i.e.
high turbulence intensity), the in-cylinder pressure evolution tends towards the
homogeneous curve. For both homogeneous and inhomogeneous (i.e. low turbulence intensity)
cases, we have found that 200 particles are sufficient to model correctly the system, with
a CPU time of a few minutes when a restriction of initial distribution is adopted.
Two dimensional Er3+-TeO2 thin film photonics crystals (PhCs) are fabricated. These PhCs demonstrate broadband enhancement of PL emission at near Infrared (NIR). The PhC structures are written by dual beam focused ion beam (FIB). Highly uniformed patterns with smooth surfaces are observed. A pattern resolution better than hundred nanometers is achieved. PhCs arrays with photonic lattice constants from 350 nm to 1700 nm are examined in order to optimize the PL extraction efficiency. Strong photoluminescence around 1530 nm is observed by 488-532 nm lasers pumping. A confocal microscopy with spectrometer is used to capture the broadband PL signals from individual PhC array.
The emission enhancement factor and spectral dependent extraction ratio are analyzed to find the interaction between PL lightwave and PhC structures. By optimize the PhC structures, 1500 um-1560 um broadband PL is successfully converted between the PL emission layer and the external cavity. A 60 % enhancement of surface extraction efficiency is achieved when PhC with periodicity a=800 nm is applied. When photonic lattice constants a are smaller than the critical periodicity 600 nm, the PL light becomes confined inside the thin film layer. Simulation is also performed by two dimensional finite difference time domain (FDTD) calculation in order to explain the experimental observed anisotropic PL enhancements.
The broadband PL enhancement enables Er3+-TeO2 PhCs thin film as a potential light source for three dimensional integrated photonic circuits.
While health warnings are present on cigarette packs around the world, the nature of the warnings varies considerably between countries. In the United States, a small text warning citing the dangers of cigarette smoking is found on the side of all packs. This pilot study sought to determine whether graphic cigarette warning images, like those found in the United Kingdom and Canada, were better at decreasing cravings to smoke than existing text warnings found on cigarette packs in the United States. Twenty-five smokers seeking treatment to quit at a specialty tobacco treatment program were administered the Brief Questionnaire of Smoking Urges (QSU — BRIEF), a validated measure of craving, prior to and following exposure to cigarette pack warning images. The graphic cigarette warning images reduced cravings to smoke (6.20 point decrease) more than neutral images (3.36 point decrease) and current text warnings used in the United States (5.75 point decrease), although this difference was not statistically significant. Based on these pilot data, a larger study could further examine the effectiveness of graphic warning images and whether such warnings hold an advantage over the currently used text warnings.
A novel material design was developed by functionalizing a biocompatible hydrogel material with organic boundary lubricants. Polyvinyl alcohol was functionalized with varying molar ratios of 0.2, 0.5, and 1.0 moles of lauroyl chloride. Tribological and mechanical characterization was performed by means of nanofriction testing and nanoindentation to determine the influence of the hydrocarbon chains on the friction coefficient and elastic modulus of the hydrogels. It was found that fusing of the lubricant to the polymer material has a positive effect on the surface friction properties, yet an unfavorable effect on stiffness properties of the gel due to the processing method.
High mobility channel materials and new device structures will be needed to meet the power and performance specifications in future technology nodes. Therefore, the use of Ge and III/V materials and novel devices such as heterojunction TunnelFET’s is investigated for future CMOS applications. High-performance CMOS can be obtained by combining Ge pMOS devices with nMOS devices made on III/V compounds such as InGaAs. In all cases the key challenge is the electrical passivation of the interface between the high-k dielectric and the alternative channel materials.
Recent studies have demonstrated good electrical properties of the GeO2/Ge interface. Since the GeO2 layer is very hygroscopic, full in-situ processing of GeO2 formation and high-k deposition must be performed or other methods must be employed to stabilize the GeO2 layer. One of the most successful passivation techniques for Ge MOS gate stacks is a thin, epitaxial layer of Si. A lot of attention went into better understanding of this passivation and the effects of its optimization on various device characteristics. It was found that mobility and Vt trends in both pMOS and nMOS transistors can be explained based on defects located at the Si/SiO2 interface.
Unfortunately, III-V/oxide interfaces are not quite as robust and most interfaces present rather high densities of interface states. Although, considerable improvements have been realized in the reduction of the interface state density, further developments are required to obtain high performance MOS devices. To this purpose various passivation methods were critically evaluated. Simulations using Density Functional Theory reveal the possibility of using a thin amorphous layer made of GeOX to obtain an electrically unpinned gap. The major challenge resides in the control of the c-Ge thickness and the oxidation of this layer to avoid the diffusion of oxygen atoms at the Ge/GaAs(001) interface. Promising results are obtained by optimizing the surface preparation, high-k deposition and annealing cycle on In0.53Ga0.47As-Al2O3 interfaces. Self-aligned inversion channel n-MOSFETs fabricated on p-type In0.53Ga0.47As demonstrate inversion-mode operation with high drive current and a peak electron mobility of 3000 cm2/Vs.
Since ultimately the major showstopper on the scaling roadmap is not device speed, but rather power density, the introduction of these advanced materials will have to go together with the introduction of new device concepts. Novel structures such as heterojunction TunnelFET’s can fully exploit the properties of these new materials and provide superior performance at lower power consumption by virtue of their improved subthreshold behaviour. Vertical surround gate devices produced from nanowires allow the introduction of a wide range of materials on Si. This illustrates the possibilities that are created by the combination of new materials and devices to allow scaling of nanoelectronics beyond the Si roadmap.