4,183 research outputs found
Time-resolved charge detection in graphene quantum dots
We present real-time detection measurements of electron tunneling in a
graphene quantum dot. By counting single electron charging events on the dot,
the tunneling process in a graphene constriction and the role of localized
states are studied in detail. In the regime of low charge detector bias we see
only a single time-dependent process in the tunneling rate which can be modeled
using a Fermi-broadened energy distribution of the carriers in the lead. We
find a non-monotonic gate dependence of the tunneling coupling attributed to
the formation of localized states in the constriction. Increasing the detector
bias above 2 mV results in an increase of the dot-lead transition rate related
to back-action of the charge detector current on the dot.Comment: 8 pages, 6 figure
Automorphisms of the affine SU(3) fusion rules
We classify the automorphisms of the (chiral) level-k affine SU(3) fusion
rules, for any value of k, by looking for all permutations that commute with
the modular matrices S and T. This can be done by using the arithmetic of the
cyclotomic extensions where the problem is naturally posed. When k is divisible
by 3, the automorphism group (Z_2) is generated by the charge conjugation C. If
k is not divisible by 3, the automorphism group (Z_2 x Z_2) is generated by C
and the Altsch\"uler--Lacki--Zaugg automorphism. Although the combinatorial
analysis can become more involved, the techniques used here for SU(3) can be
applied to other algebras.Comment: 21 pages, plain TeX, DIAS-STP-92-4
LA DEMOCRAZIA INTERNA AI PARTITI POLITICI. BILANCI E PROSPETTIVE
The paper focuses on the internal democracy of the political parties, with particular attention to the concept of the " democratic method " governed by Article 49 of the Italian Constitution .
Empirical observation of the parties and scientific research underline a framework marked today by two general phenomena . On one hand, the continuing tendency of the Parties to "cartelization " and, on the other hand, the decreasing of the powers of the militants , the weakening of the structures and the personalization of the national and local structures.
In Italy, this scenario has to deal with article 49 of the Italian Constitution , an article that originally represented the will to overcome the neglect of the phenomenon of " political parties " , giving them constitutional significance , marking \u201cde facto\u201d a sharp break with the liberal Italy.
Today the Italian political parties are facing a crisis of legitimacy and authority, perhaps even greater than the one that dramatically changed the political landscape in the early nineties . Despite this, they still retain all the functions and policies of the previous decades and are still the fulcrum around which revolves the functioning of democratic institutions . This fact led some researchers to describe the situation as an Italian \u201cparty system without parties\u201d.
In particular, the controversy of the doctrine concerned the lack of interest of the Parties in the \u201cdemocratic method " included in Article 49 of the Italian Constitution .
Accepting therefore, the more widespread interpretation of the doctrine that extends the prescription of the " democratic method " even to the internal organization of the political Parties, we have focused on the status quo of the past and current Italian Party organizations through the study of the statutes of the major Parties and through a comparison beginning from some fundamental institutions.
The overall scenario is therefore focused on the political Parties that have little in common with the mass parties of the twentieth century and that, in the face of profound social changes , have not been able to introduce neither by laws nor by practice, new methods of democratic participation in political processes . Just to deal with the crisis of legitimacy caused by these events, it is now widely thought that it is necessary to pass a law governing the implementation of Art. 49 of the Constitution, including the concept of " democratic method " .
As we were writing ,however, an important innovation was introduced. By a decree of the Letta Government, approved by the government on December 13th , the possibility to access to the financial aid for political Parties becomes subject to compliance with the requirements of democracy and transparency. It\u2019s the first time ever.
Finally, we can also add a final reflection on the primaries, both those that are regulated via private law and those institutions regulated by public law. The primaries have strengths and weaknesses , but now it seems to be an essential tool in the processes to democratize the political Parties.
For political Parties to recover authority, it is necessary, therefore , to interfere with force in the mechanisms used to regulate the internal democracy organization . While it now seems that legislative intervention designed to regulate certain processes is necessary, it is understood that it needs to be accompanied by some self-regulatory experiments of the political Parties , so that the statutes are freely available to introduce the willingness to "open " the Party and to encourage the members of the Parties to make decisions
A neutron scattering study of the interplay between structure and magnetism in Ba(FeCo)As
Single crystal neutron diffraction is used to investigate the magnetic and
structural phase diagram of the electron doped superconductor
Ba(FeCo)As. Heat capacity and resistivity measurements have
demonstrated that Co doping this system splits the combined antiferromagnetic
and structural transition present in BaFeAs into two distinct
transitions. For =0.025, we find that the upper transition is between the
high-temperature tetragonal and low-temperature orthorhombic structures with
( K) and the antiferromagnetic transition occurs at
K. We find that doping rapidly suppresses the
antiferromagnetism, with antiferromagnetic order disappearing at . However, there is a region of co-existence of antiferromagnetism and
superconductivity. The effect of the antiferromagnetic transition can be seen
in the temperature dependence of the structural Bragg peaks from both neutron
scattering and x-ray diffraction. We infer from this that there is strong
coupling between the antiferromagnetism and the crystal lattice
Characterization of Flow Dynamics in the Pulmonary Bifurcation of Patients With Repaired Tetralogy of Fallot: A Computational Approach
The hemodynamic environment of the pulmonary bifurcation is of great importance for
adult patients with repaired tetralogy of Fallot (rTOF) due to possible complications in the
pulmonary valve and narrowing of the left pulmonary artery (LPA). The aim of this study
was to computationally investigate the effect of geometrical variability and flow split on
blood flow characteristics in the pulmonary trunk of patient-specific models. Data from
a cohort of seven patients was used retrospectively and the pulmonary hemodynamics
was investigated using averaged and MRI-derived patient-specific boundary conditions
on the individualized models, as well as a statistical mean geometry. Geometrical analysis
showed that curvature and tortuosity are higher in the LPA branch, compared to the right
pulmonary artery (RPA), resulting in complex flow patterns in the LPA. The computational
analysis also demonstrated high time-averaged wall shear stress (TAWSS) at the outer
wall of the LPA and the wall of the RPA proximal to the junction. Similar TAWSS patterns
were observed for averaged boundary conditions, except for a significantly modified
flow split assigned at the outlets. Overall, this study enhances our understanding about
the flow development in the pulmonary bifurcation of rTOF patients and associates
some morphological characteristics with hemodynamic parameters, highlighting the
importance of patient-specificity in the models. To confirm these findings, further studies
are required with a bigger cohort of patients
Contribution of oxygen extraction fraction to maximal oxygen uptake in healthy young men
We analysed the importance of systemic and peripheral arteriovenous O2 difference (a- v− O2 and a-vf O2 difference, respectively) and O2 extraction fraction for maximal oxygen uptake ( V˙ O2max ). Fick law of diffusion and the Piiper and Scheid model were applied to investigate whether diffusion vs perfusion limitations vary with V˙ O2max . Articles (n=17) publishing individual data (n=154) on V˙ O2max , maximal cardiac output ( Q˙ max ; indicator-dilution or Fick method), a- v− O2 difference (catheters or Fick equation) and systemic O2 extraction fraction were identified. For the peripheral responses, group-mean data (articles: n=27; subjects: n=234) on leg blood flow (LBF; thermodilution), a-vf O2 difference and O2 extraction fraction (arterial and femoral venous catheters) were obtained. Q˙ max and two-LBF increased linearly by 4.9-6.0 L·min-1 per 1 L·min-1 increase in V˙ O2max (R2 =0.73 and R2 =0.67, respectively; both P<0.001). The a- v− O2 difference increased from 118-168 mL·L-1 from a V˙ O2max of 2-4.5 L·min-1 followed by a reduction (second-order polynomial: R2 =0.27). After accounting for a hypoxemia-induced decrease in arterial O2 content with increasing V˙ O2max (R2 =0.17; P<0.001), systemic O2 extraction fraction increased up to ~90% ( V˙ O2max : 4.5 L·min-1 ) with no further change (exponential decay model: R2 =0.42). Likewise, leg O2 extraction fraction increased with V˙ O2max to approach a maximal value of ~90-95% (R2 =0.83). Muscle O2 diffusing capacity and the equilibration index Y increased linearly with V˙ O2max (R2 =0.77 and R2 =0.31, respectively; both P<0.01), reflecting decreasing O2 diffusional limitations and accentuating O2 delivery limitations. In conclusion, although O2 delivery is the main limiting factor to V˙ O2max , enhanced O2 extraction fraction (≥90%) contributes to the remarkably high V˙ O2max in endurance-trained individuals
Scintillating double beta decay bolometers
We present the results obtained in the development of scintillating Double
Beta Decay bolometers. Several Mo and Cd based crystals were tested with the
bolometric technique. The scintillation light was measured through a second
independent bolometer. A 140 g CdWO_4 crystal was run in a 417 h live time
measurement. Thanks to the scintillation light, the alpha background is easily
discriminated resulting in zero counts above the 2615 keV gamma line of
Thallium 208. These results, combined with an extremely easy light detector
operation, represent the first tangible proof demonstrating the feasibility of
this kind of technique.Comment: 15 pages, 8 figure
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