23,539 research outputs found
Experimental demonstration of phase-remapping attack in a practical quantum key distribution system
Unconditional security proofs of various quantum key distribution (QKD)
protocols are built on idealized assumptions. One key assumption is: the sender
(Alice) can prepare the required quantum states without errors. However, such
an assumption may be violated in a practical QKD system. In this paper, we
experimentally demonstrate a technically feasible "intercept-and-resend" attack
that exploits such a security loophole in a commercial "plug & play" QKD
system. The resulting quantum bit error rate is 19.7%, which is below the
proven secure bound of 20.0% for the BB84 protocol. The attack we utilize is
the phase-remapping attack (C.-H. F. Fung, et al., Phys. Rev. A, 75, 32314,
2007) proposed by our group.Comment: 16 pages, 6 figure
Implementation of two-party protocols in the noisy-storage model
The noisy-storage model allows the implementation of secure two-party
protocols under the sole assumption that no large-scale reliable quantum
storage is available to the cheating party. No quantum storage is thereby
required for the honest parties. Examples of such protocols include bit
commitment, oblivious transfer and secure identification. Here, we provide a
guideline for the practical implementation of such protocols. In particular, we
analyze security in a practical setting where the honest parties themselves are
unable to perform perfect operations and need to deal with practical problems
such as errors during transmission and detector inefficiencies. We provide
explicit security parameters for two different experimental setups using weak
coherent, and parametric down conversion sources. In addition, we analyze a
modification of the protocols based on decoy states.Comment: 41 pages, 33 figures, this is a companion paper to arXiv:0906.1030
considering practical aspects, v2: published version, title changed in
accordance with PRA guideline
Enzymatic activity of anthropogenic proto-organic soils in soilless farming
In soilless agriculture and horticulture coir is the more used substratum to grow plants because it is widely available
and more environmentally friendly than sphagnum or peat. In Italy, soilless agriculture concerns an area of about
1,000 hectares, particularly concentrated in Sicily. The southern coastal belt of this region is the area interested by
the most significant experiences in the application of techniques of soilless cultivation that, recently, has been used
also for growing table grapes.
Starting from the above consideration we suppose that the features of the coconut fiber underlay an evident transformation
and that even after few years of table grape cultivation, such organic material undergone to a transformation
that allows for the formation of a proto-organic soil (a proto-Histosol, we supposed). If this is true, we believe that,
in this case, to speak about soilless cultivation is for sure misleading for the common people, as we should define
this cultivation \u201con anthropogenic soils\u201d instead.
To fit the aims of this survey we used a big greenhouse devoted to soilless cultivation of table grape in a farm in
the Southern SicilyWe have considered the enzymatic activity that characterized the coconut fiber after 3 cycles of
cultivation of table grapes. We used as a control the coconut fiber that the farmer used to prepare pots for soilless
cultivation and coconut fiber of: 6 pots at the end of the first productive cycle 6 pots at the end of the second cycle
and 3 pots at the end of the third cycle. On these organic samples we investigated three enzymes, belonging to oxydoreductase
(catalase and dehydrogenase) and hydrolase (urease) classes. Statistical analysis of the investigated
enzymes was developed using IBM Statistic SPSS v20 by ANOVA, Tukey test HSD for p 0.01 and Multivariate
Statistical Analysis.
Results have shown significant differences in enzymes content and quality among coir tests. The use of the coco
fiber, as nutritive substratum under fertigation, has positively influenced the growing and proliferation of soil microbes
and thus enzymatic activity. In merely 3 productive cycles the stage of decomposition of the organic residues
changed highlighting a substantial evolution of such organic material
A validated energy model of a solar dish-Stirling system considering the cleanliness of mirrors
Solar systems based on the coupling of parabolic concentrating collectors and thermal engines (i.e. dish-Stirling systems) are among the most efficient generators of solar power currently available. This study focuses on the modelling of functioning data from a 32 kWe dish-Stirling solar plant installed at a facility test site on the University of Palermo campus, in Southern Italy. The proposed model, based on real monitored data, the energy balance of the collector and the partial load efficiency of the Stirling engine, can be used easily to simulate the annual energy production of such systems, making use of the solar radiation database, with the aim of encouraging a greater commercialisation of this technology. Introducing further simplifying assumptions based on our experimental data, the model can be linearised providing a new analytical expression of the parameters that characterise the widely used Stine empirical model. The model was calibrated against data corresponding to the collector with clean mirrors and used to predict the net electric production of the dish-Stirling accurately. A numerical method for assessing the daily level of mirror soiling without the use of direct reflectivity measures was also defined. The proposed methodology was used to evaluate the history of mirror soiling for the observation period, which shows a strong correlation with the recorded sequence of rains and dust depositions. The results of this study emphasise how desert dust transport events, frequent occurrences in parts of the Mediterranean, can have a dramatic impact on the electric power generation of dish-Stirling plants
The Megamaser Cosmology Project. III. Accurate Masses of Seven Supermassive Black Holes in Active Galaxies with Circumnuclear Megamaser Disks
Observations of HO masers from circumnuclear disks in active galaxies for
the Megamaser Cosmology Project allow accurate measurement of the mass of
supermassive black holes (BH) in these galaxies. We present the Very Long
Baseline Interferometry (VLBI) images and kinematics of water maser emission in
six active galaxies: NGC~1194, NGC~2273, NGC~2960 (Mrk~1419), NGC~4388,
NGC~6264 and NGC~6323. We use the Keplerian rotation curves of these six
megamaser galaxies, plus a seventh previously published, to determine accurate
enclosed masses within the central pc of these galaxies, smaller than
the radius of the sphere of influence of the central mass in all cases. We also
set lower limits to the central mass densities of between 0.12 and 60 ~pc. For six of the seven disks, the high central
densities rule out clusters of stars or stellar remnants as the central
objects, and this result further supports our assumption that the enclosed mass
can be attributed predominantly to a supermassive black hole. The seven BHs
have masses ranging between 0.76 and 6.510. The BH mass
errors are \%, dominated by the uncertainty of the Hubble constant.
We compare the megamaser BH mass determination with other BH mass measurement
techniques. The BH mass based on virial estimation in four galaxies is
consistent with the megamaser BH mass given the latest empirical value of
, but the virial mass uncertainty is much greater. MCP
observations continue and we expect to obtain more maser BH masses in the
future.Comment: 18 pages, 4 figures. This paper has been submitted to ApJ. An updated
version of this paper will be posted when it gets accepte
High performance liquid chromatographic determination of 2-furaldehyde and 5- hydroxymethyl-2-furaldehyde in fruit juices
A method for the determination of 2-furaldehyde (F) and 5-hydroxymethyl-2-furaldehyde (HMF) in fruit juices by high-performance liquid chromatography (HPLC) is described. The method is based on the formation of the 2,4-dinitrophenylhydrazones of carbonyl compounds and subsequent separation of these derivatives. Derivatization is carried out by utilizing an acidic solution of 2,4-dinitrophenylhydrazine in acetonitrile. Precipitation of the derivatives of carbonyl compounds is thus avoided; and direct injection of the sample into the HPLC system is allowed. The procedure offers a high specificity and a detection limit of the order of 10\u20138 mol/L. Recoveries of 95-98% are obtained from apple juice spiked at different levels with both analytes. The reproducibility (mean of six determinations) is \ub1 2% for F and \ub1 3% for HMF
High performance liquid chromatographic determination of 2-furaldehyde and 5-hydroxymethyl-2-furaldehyde in processes citrus juices
The occurrence of 2-furaldehyde (F) and 5-hydroxymethyl-2-furaldehyde (HMF) in processed citrus juices is an indication of quality deterioration. A close relationship between flavor changes and F content exists, while HMF can give rise to browning reactions. Both F and HMF are formed during heat processing or storage at improper temperatures. The detection of these compounds becomes more and more important as aseptic processing and packaging of citrus juices are becoming widespread. Aseptic packaging allows higher temperatures during distribution and storage to be employed without microbial spoilage, but off-flavors develop as citrus products are exposed to these conditions. In this paper a method of determination by high performance liquid chromatography (HPLC) is described. The method is based on the formation of the 2,4-dinitrophenylhydrazones of carbonyl compounds and subsequent reversed-phase separation of these derivatives. Derivatization is carried out by utilizing an acidic solution of 2,4-dinitrophenylhydrazine in acetonitrile. Precipitation of the derivatives of carbonyl compounds is thus avoided, and direct injection of the sample into the HPLC system is allowed. The determination offers a high specificity and a detection limit of the order of 10-8 mol/l for both analytes. Recoveries from an orange juice spiked at different levels are quantitative. Reproducibility data are presented
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