6,461 research outputs found
Quantum Key Distribution using Continuous-variable non-Gaussian States
In this work we present a quantum key distribution protocol using
continuous-variable non-Gaussian states, homodyne detection and post-selection.
The employed signal states are the Photon Added then Subtracted Coherent States
(PASCS) in which one photon is added and subsequently one photon is subtracted.
We analyze the performance of our protocol, compared to a coherent state based
protocol, for two different attacks that could be carried out by the
eavesdropper (Eve). We calculate the secret key rate transmission in a lossy
line for a superior channel (beam-splitter) attack, and we show that we may
increase the secret key generation rate by using the non-Gaussian PASCS rather
than coherent states. We also consider the simultaneous quadrature measurement
(intercept-resend) attack and we show that the efficiency of Eve's attack is
substantially reduced if PASCS are used as signal states.Comment: We have included an analysis of the simultaneous quadrature
measurement attack plus 2 figures; we have also clarified some point
Semiclassical Tunneling of Wavepackets with Real Trajectories
Semiclassical approximations for tunneling processes usually involve complex
trajectories or complex times. In this paper we use a previously derived
approximation involving only real trajectories propagating in real time to
describe the scattering of a Gaussian wavepacket by a finite square potential
barrier. We show that the approximation describes both tunneling and
interferences very accurately in the limit of small Plank's constant. We use
these results to estimate the tunneling time of the wavepacket and find that,
for high energies, the barrier slows down the wavepacket but that it speeds it
up at energies comparable to the barrier height.Comment: 23 pages, 7 figures Revised text and figure
Geometric combinatorial algebras: cyclohedron and simplex
In this paper we report on results of our investigation into the algebraic
structure supported by the combinatorial geometry of the cyclohedron. Our new
graded algebra structures lie between two well known Hopf algebras: the
Malvenuto-Reutenauer algebra of permutations and the Loday-Ronco algebra of
binary trees. Connecting algebra maps arise from a new generalization of the
Tonks projection from the permutohedron to the associahedron, which we discover
via the viewpoint of the graph associahedra of Carr and Devadoss. At the same
time that viewpoint allows exciting geometrical insights into the
multiplicative structure of the algebras involved. Extending the Tonks
projection also reveals a new graded algebra structure on the simplices.
Finally this latter is extended to a new graded Hopf algebra (one-sided) with
basis all the faces of the simplices.Comment: 23 figures, new expanded section about Hopf algebra of simplices,
with journal correction
Combination Effect of Ozone and Heat Treatment for the Color Reduction in Sugarcane Juice
We have been studied the mechanism of color reduction of sugarcane juice as a new innovative technology to crystal sugar production as a substitute for sulfur use, which was related to health problems. This work evaluated the effect of ozonation on sugarcane juice in two different conditions, heated and non-heated juice. The samples in both conditions were ozonized for 120 min in a stainless-steel batch reactor, connected to an ozonation system with constant flow (17.3 mg O3/min). Ozonation did not change the values ​​of reducing sugars (RS) and the apparent sucrose content (POL); however, the color rate ICUMSA showed significant decrease for the heated juice, but there was no response to ozonation in the non-heated juice. These responses represent a key point to the industry, which during the clarification process, heats the juice before the sulfitation. The settling should become more efficient after ozonation (results not shown), showing great potential to use this technology in production systems because of the optimization of reaction parameters for color reduction ICUMSA in sugarcane juice. Keywords: Ozone, Clarification, Sugarcane, ICUMSA, UFLC/ELSD
Analysing tactics in architectural patterns
We present an approach to analyse the application of tactics in architectural patterns. We define and illustrate the approach by resorting to Archery, a language for specifying, analysing and verifying architectural patterns. The approach consists of characterising the design principles of an architectural pattern as constraints, expressed in the language, and then, establishing a refinement relation based on their satisfaction. The application of tactics preserving refinement preserves the original design principles expressed themselves as constraints for the architectural pattern. The paper’s focus on fault-tolerance tactics, and identifies a set of requirements for a semantic framework characterising them. Model transformations to represent their application are discussed and illustrated through two case studies.FC
Relationship between Volatile Composition and Bioactive Potential of Vegetables and Fruits of Regular Consumption—An Integrative Approach
In recent years, there has been a growing interest in studying and exploring the potential
health benefits of foods, mainly from vegetables and fruits from regular intake. The presence of
secondary metabolites, namely polyphenols, carotenoids and terpenes, in certain food matrices
seems to contribute to their functional properties, expressed through an increased prevention in the
development of certain chronic diseases, namely coronary heart diseases, neurodegenerative diseases,
cancer and diabetes. However, some foods’ volatile secondary metabolites also present important
bioactive properties, although this is a poorly scientifically explored field. In this context, and in
order to explore the potential bioactivity of volatile metabolites in different vegetables and fruits from
regular consumption, the volatile composition was established using a green extraction technique,
solid phase microextraction in headspace mode (HS-SPME), combined with gas chromatography
tandem mass spectrometry (GC-MS). A total of 320 volatile metabolites, comprising 51 terpenic
compounds, 45 organosulfur compounds, 31 aldehydes, 37 esters, 29 ketones, 28 alcohols, 23 furanic
compounds, 22 hydrocarbons, 19 benzene compounds, 13 nitrogenous compounds, 9 carboxylic
acids, 7 ethers, 4 halogenated compounds and 3 naphthalene derivatives, were positively identified.
Each investigated fruit and vegetable showed a specific volatile metabolomic profile. The obtained
results revealed that terpenic compounds, to which are associated antimicrobial, antioxidant, and
anticancer activities, are the most predominant chemical family in beetroot (61%), orange carrot
(58%) and white carrot (61%), while organosulfur compounds (antiviral activity) are dominant
in onion, garlic and watercress. Broccoli and spinach are essentially constituted by alcohols and
aldehydes (enzyme-inhibition and antimicrobial properties), while fruits from the Solanaceae family
are characterized by esters in tamarillo and aldehydes in tomato.info:eu-repo/semantics/publishedVersio
Chemical fingerprint of free polyphenols and antioxidant activity in dietary fruits and vegetables using a non-targeted approach based on QuEChERS ultrasound-assisted extraction combined with UHPLC-PDA
Fruits and vegetables are considered a good source of antioxidants, which are beneficial in
protecting the human body against damage induced by free radicals and other reactive oxygen (ROS)
and nitrogen (RNS) species. In this work, we aimed to evaluate the integral antioxidant activity (AOA)
and determine individual polyphenols in fruits and vegetables of frequent consumption. For this
purpose, an innovative and high throughput analytical approach based on original QuEChERS assisted
by ultrasound extraction (USAE), instead of the manual agitation used in the classical procedure,
was optimized and implemented for the isolation of polyphenols. The total phenolic content (TPC),
flavonoids, anthocyanins, and betalains were evaluated using different spectrophotometric assays.
In addition, free radical scavenging by methods 2,2’-azinobis-(3-ethylbenzothiazoline-6-sulfonate)
(ABTS) and 2,20
-diphenyl-1-picrylhydrazyl (DPPH) and ferric reducing antioxidant power (FRAP)
were used to estimate the AOA of the investigated fruit and vegetable extracts. Red onion,
tamarillo, and beetroot were the samples with the highest AOA. The quantification and identification
of free low molecular weight polyphenols from QuEChERS-USAE extracts was carried out by
ultra-high-pressure liquid chromatography equipped with a photodiode array detection system
(UHPLC-PDA). Catechin was the most abundant polyphenol, followed by gentisic and ferulic acids,
mainly in the watercress sample. In relation to flavonols, quercetin and kaempferol were found mostly
in onion samples, and in small quantities in tomato and watercress. The improved analytical approach,
QuEChERS-USAE/UHPLC-PDA, offers an attractive alternative for the analysis of polyphenols from
fruit and vegetable samples, providing several advantages over traditional extraction techniques, in
terms of reproducibility, simplicity, low cost, analysis speed, and analytical performance.info:eu-repo/semantics/publishedVersio
Monitoramento das principais doenças do maracujazeiro, Passiflora edulis L., no estado do Pará.
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