1,264 research outputs found
Counterfactual Quantum Cryptography
Quantum cryptography allows one to distribute a secret key between two remote
parties using the fundamental principles of quantum mechanics. The well-known
established paradigm for the quantum key distribution relies on the actual
transmission of signal particle through a quantum channel. This paper shows
that the task of a secret key distribution can be accomplished even though a
particle carrying secret information is not in fact transmitted through the
quantum channel. The proposed protocols can be implemented with current
technologies and provide practical security advantages by eliminating the
possibility that an eavesdropper can directly access the entire quantum system
of each signal particle.Comment: 19 pages, 1 figure; a little ambiguity in the version 1 removed;
abstract, text, references, and appendix revised; suggestions and comments
are highly appreciate
Many Rivers to Cross: Evaluating the Benefits and Limitations of Strategic Environmental Assessment for the Koshi River Basin
This paper assesses the value of using Strategic Environmental Assessment (SEA) to account for the spatially and temporally diverse and diffuse impacts of hydropower development in South Asiaâs Koshi basin. A policy and practice review and key stakeholder interviews identified opportunities for SEA to improve existing planning procedures, but also barriers to effective adoption. Whilst stakeholders are interested in employing SEA to evaluate cumulative impacts, institutional blockages and an economic development imperative for power generation leave little space for consideration of alternative scenarios as part of SEA. The analysis is conducted through the formulation and application of a conceptual framework for SEA best practice which is then used to identify priority next-steps for SEA in the region
Liquid metals as electrodes in polymer light emitting diodes
We demonstrate that liquid metals can be used as cathodes in light emitting diodes (pLEDs). The main difference between the use of liquid cathodes and evaporated cathodes is the sharpness of the metalâpolymer interface. Liquid metal cathodes result in significantly sharper metalâorganic interfaces than vapor deposited cathodes, due to the high surface energy of the metals. The sharper interface in pLEDs with liquid metal cathodes is observed by neutral impact collision ion scattering spectroscopy and low energy ion scattering spectroscopy measurements. The influence of interface sharpness on device performance was studied by comparing currentâvoltage-light characteristics of devices with OC1C10 paraphenylenevinylene (PPV) as electroluminescent polymer and indium tin oxide (ITO) as hole injection electrode, and different cathodes. Comparison of devices using a liquid Ga cathode and an evaporated Al cathode showed that light emission for the liquid Ga cathode is two orders of magnitude larger than for the evaporated Al cathode, and that the external light efficiency is increased by an order of magnitude. Since the work function of Ga and Al is nearly the same, the poor performance for evaporated Al LEDs is attributed to the formation of an interfacial layer where Al has diffused into, and reacted with, the PPV. This interfacial layer has poor electrical conduction compared to pure PPV, and contains quenching sites which reduce light emission. Low work function liquid metal cathodes were studied by using liquid Ca and Ba amalgams. The improved performance of liquid amalgam pLEDs is attributed to the different structure of the metalâpolymer interface. The enormous increase in light and current through the amalgam devices compared to those using pure Hg demonstrate that less than 1 ML of a metal with a low work function at the polymer-cathode interface can have a dramatic effect on the performance of the devices. Devices with a liquid Ca amalgam cathode showed an increase of the current (by 50%) and brightness (80%) compared to devices with an evaporated Ca cathode, which is ascribed to reduced diffusion of Ca into the emissive PPV laye
The effect of Fe atoms on the adsorption of a W atom on W(100) surface
We report a first-principles calculation that models the effect of iron (Fe)
atoms on the adsorption of a tungsten (W) atom on W(100) surfaces. The
adsorption of a W atom on a clean W(100) surface is compared with that of a W
atom on a W(100) surface covered with a monolayer of Fe atoms. The total energy
of the system is computed as the function of the height of the W adatom. Our
result shows that the W atom first adsorbs on top of the Fe monolayer. Then the
W atom can replace one of the Fe atoms through a path with a moderate energy
barrier and reduce its energy further. This intermediate site makes the
adsorption (and desorption) of W atoms a two-step process in the presence of Fe
atoms and lowers the overall adsorption energy by nearly 2.4 eV. The Fe atoms
also provide a surface for W atoms to adsorb facilitating the diffusion of W
atoms. The combination of these two effects result in a much more efficient
desorption and diffusion of W atoms in the presence of Fe atoms. Our result
provides a fundamental mechanism that can explain the activated sintering of
tungsten by Fe atoms.Comment: 9 pages, 2 figure
Demographic, Behavioral and Perceptual Comparisons of the U.S. Visitor Experience with Group Package Tours and Free Independent Travel to China
U.S. visitor demand for the China travel experience is anticipated to rise significantly through 2105, causing the Chinese government to employ 100 million service providers over the next six years and raising concern about service delivery and perceptions of the on-site China experience. In an effort to better understand these issues concerning U.S. visitors, this study investigated two specific types of U.S. travelers to China: Group Package Tour (GPT) visitors and Free Independent Travel (FIT) visitors. Results indicated that GPT visitors were more likely to be older and have higher household income than FIT visitors. Four trip-related characteristics of GPT and FIT visitors were found to be significantly different, with GPT visitors showing higher levels of satisfaction with the overall China on-site travel experience
Limits of Binaries That Can Be Characterized by Gravitational Microlensing
Due to the high efficiency of planet detections, current microlensing planet
searches focus on high-magnification events. High-magnification events are
sensitive to remote binary companions as well and thus a sample of
wide-separation binaries are expected to be collected as a byproduct. In this
paper, we show that characterizing binaries for a portion of this sample will
be difficult due to the degeneracy of the binary-lensing parameters. This
degeneracy arises because the perturbation induced by the binary companion is
well approximated by the Chang-Refsdal lensing for binaries with separations
greater than a certain limit. For binaries composed of equal mass lenses, we
find that the lens binarity can be noticed up to the separations of
times of the Einstein radius corresponding to the mass of each lens. Among
these binaries, however, we find that the lensing parameters can be determined
only for a portion of binaries with separations less than times of
the Einstein radius.Comment: 5 pages, 3 figures, 1 tabl
Recent advances in the intellectual property landscape of filamentous fungi
For centuries, filamentous fungi have been used in the making of food and beverages, and for decades for the production of enzymes and pharmaceuticals. In the last decades, the intellectual property (IP) landscape for fungal technology has seen an ever increasing upward trend, introducing new and promising applications utilising fungi. In this review, we highlight fungi-related patent applications published during the last 5\ua0years (2015â2020), identify the key players in each field, and analyse future trends.\ua0New developments in the field of fungal technology include the increased use of filamentous fungi as a food source (mycoprotein), using fungi as biodegradable materials, in wastewater treatment, in integrated biorefineries and as biological pest agents. Biotechnology companies in Europe and the US are currently leading when it comes to the number of patents in these areas, but Asian companies and research institutes, in particular in China, are becoming increasingly important players, for example in pesticide formulation and agricultural practices
Properties of Central Caustics in Planetary Microlensing
To maximize the number of planet detections, current microlensing follow-up
observations are focusing on high-magnification events which have a higher
chance of being perturbed by central caustics. In this paper, we investigate
the properties of central caustics and the perturbations induced by them. We
derive analytic expressions of the location, size, and shape of the central
caustic as a function of the star-planet separation, , and the planet/star
mass ratio, , under the planetary perturbative approximation and compare the
results with those based on numerical computations. While it has been known
that the size of the planetary caustic is \propto \sqrt{q}, we find from this
work that the dependence of the size of the central caustic on is linear,
i.e., \propto q, implying that the central caustic shrinks much more rapidly
with the decrease of compared to the planetary caustic. The central-caustic
size depends also on the star-planet separation. If the size of the caustic is
defined as the separation between the two cusps on the star-planet axis
(horizontal width), we find that the dependence of the central-caustic size on
the separation is \propto (s+1/s). While the size of the central caustic
depends both on and q, its shape defined as the vertical/horizontal width
ratio, R_c, is solely dependent on the planetary separation and we derive an
analytic relation between R_c and s. Due to the smaller size of the central
caustic combined with much more rapid decrease of its size with the decrease of
q, the effect of finite source size on the perturbation induced by the central
caustic is much more severe than the effect on the perturbation induced by the
planetary caustic. Abridged.Comment: 5 pages, 4 figures, ApJ accepte
Microlensing Detections of Planets in Binary Stellar Systems
We demonstrate that microlensing can be used for detecting planets in binary
stellar systems. This is possible because in the geometry of planetary binary
systems where the planet orbits one of the binary component and the other
binary star is located at a large distance, both planet and secondary companion
produce perturbations at a common region around the planet-hosting binary star
and thus the signatures of both planet and binary companion can be detected in
the light curves of high-magnification lensing events. We find that identifying
planets in binary systems is optimized when the secondary is located in a
certain range which depends on the type of the planet. The proposed method can
detect planets with masses down to one tenth of the Jupiter mass in binaries
with separations <~ 100 AU. These ranges of planet mass and binary separation
are not covered by other methods and thus microlensing would be able to make
the planetary binary sample richer.Comment: 5 pages, two figures in JPG forma
Modelling the chemically aged and mixed aerosols over the eastern central Atlantic Ocean â potential impacts
Detailed information on the chemical and physical properties of aerosols is important for assessing their role in air quality and climate. This work explores the origin and fate of continental aerosols transported over the Central Atlantic Ocean, in terms of chemical composition, number and size distribution, using chemistry-transport models, satellite data and in situ measurements. We focus on August 2005, a period with intense hurricane and tropical storm activity over the Atlantic Ocean. A mixture of anthropogenic (sulphates, nitrates), natural (desert dust, sea salt) and chemically aged (sulphate and nitrate on dust) aerosols is found entering the hurricane genesis region, most likely interacting with clouds in the area. Results from our modelling study suggest rather small amounts of accumulation mode desert dust, sea salt and chemically aged dust aerosols in this Atlantic Ocean region. Aerosols of smaller size (Aitken mode) are more abundant in the area and in some occasions sulphates of anthropogenic origin and desert dust are of the same magnitude in terms of number concentrations. Typical aerosol number concentrations are derived for the vertical layers near shallow cloud formation regimes, indicating that the aerosol number concentration can reach several thousand particles per cubic centimetre. The vertical distribution of the aerosols shows that the desert dust particles are often transported near the top of the marine cloud layer as they enter into the region where deep convection is initiated. The anthropogenic sulphate aerosol can be transported within a thick layer and enter the cloud deck through multiple ways (from the top, the base of the cloud, and by entrainment). The sodium (sea salt related) aerosol is mostly found below the cloud base. The results of this work may provide insights relevant for studies that consider aerosol influences on cloud processes and storm development in the Central Atlantic region
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