Optimal cloning of single photon polarization by coherent feedback of beam splitter losses

Light fields can be amplified by measuring the field amplitude reflected at a beam splitter of reflectivity R and adding a coherent amplitude proportional to the measurement result to the transmitted field. By applying the quantum optical realization of this amplification scheme to single photon inputs, it is possible to clone the polarization states of photons. We show that optimal cloning of single photon polarization is possible when the gain factor of the amplification is equal to the inverse squareroot of 1-R.Comment: 10 pages, including 1 figure, extended from letter to full paper, to be published in New Journal of Physic

The art of spacecraft design: A multidisciplinary challenge

Actual design turn-around time has become shorter due to the use of optimization techniques which have been introduced into the design process. It seems that what, how and when to use these optimization techniques may be the key factor for future aircraft engineering operations. Another important aspect of this technique is that complex physical phenomena can be modeled by a simple mathematical equation. The new powerful multilevel methodology reduces time-consuming analysis significantly while maintaining the coupling effects. This simultaneous analysis method stems from the implicit function theorem and system sensitivity derivatives of input variables. Use of the Taylor's series expansion and finite differencing technique for sensitivity derivatives in each discipline makes this approach unique for screening dominant variables from nondominant variables. In this study, the current Computational Fluid Dynamics (CFD) aerodynamic and sensitivity derivative/optimization techniques are applied for a simple cone-type forebody of a high-speed vehicle configuration to understand basic aerodynamic/structure interaction in a hypersonic flight condition

The US current account deficit : how did it come about and what are the policy implications

One of the most remarkable characteristics of the world economy today is the enormous, ever worsening US balance of payments current account deficit, which reached a record level of 5.7 p.c. of GDP in 2004. This has given rise to concerns in academic and political circles regarding the sustainability of the current situation and the potential dangers for the global economy of a sudden, disorderly adjustment. The size of the US current account deficit is not only unprecedented in American post-war history, but it also seems to be exceptional from an international perspective. Moreover, the US deficit contrasts with a surplus in virtually every other region and the problem has consequently taken on a global dimension. The increase in the US current account deficit recorded in the nineties reflects an internal American shortfall in savings. Whereas the private savings-investment equilibrium was restored in 2002 and 2003, the same period saw a huge deficit in the public sector budget. The start of the new millennium brought notable changes in the way the US current account deficit was financed since investments by Asian public authorities in American government debt instruments largely took over the position previously occupied by European private foreign direct investments and investments in equities. It is sometimes put forward that the US, unlike other countries facing similar circumstances, is safeguarded from an attack on its currency because of its prominent role in the international financial system. According to an influential school of thought in economic literature, the current international system can even be seen as a “revived” Bretton Woods system. Indeed, a number of East-Asian countries, including China, use a fixed or quasi-fixed exchange rate against the dollar, which brings to mind an informal dollar standard. Although this set of circumstances has undoubtedly offered various regions in the world a number of mutual benefits during recent years, these exchange rate relations may nevertheless have caused some distortions in US spending, whereas Asian countries have to deal with a growing exchange rate risk on their official reserves. Different scenarios are conceivable to deal with the global imbalances. The results of model simulations show the huge effort required to significantly reduce the US current account deficit which highlights the scale of the problem, emphasising the need for simultaneous economic policy measures in the different economies involved. The concern over global imbalances and the development of exchange rates also feature prominently on the agenda of international forums such as the G7 or G20 meetings. In the statements issued at those meetings, the need for a common approach to tackle the global imbalances is given priority and the belief that excessive exchange rate volatility is not desirable is underlined.current account imbalances, United States current account, financial flows into the United States, international monetary system

Transonic aerodynamic and aeroelastic characteristics of a variable sweep wing

The flow over the B-1 wing is studied computationally, including the aeroelastic response of the wing. Computed results are compared with results from wind tunnel and flight tests for both low-sweep and high-sweep cases, at 25.0 deg. and 67.5 deg., respectively, for selected transonic Mach numbers. The aerodynamic and aeroelastic computations are made by using the transonic unsteady code ATRAN3S. Steady aerodynamic computations compare well with wind tunnel results for the 25.0 deg. sweep case and also for small angles of attack at the 67.5 deg. sweep case. The aeroelastic response results show that the wing is stable at the low sweep angle for the calculation at the Mach number at which there is a shock wave. In the higher sweep case, for the higher angle of attack at which oscillations were observed in the flight and wind tunnel tests, the calculations do not show any shock waves. Their absence lends support to the hypothesis that the observed oscillations are due to the presence of leading edge separation vortices and are not due to shock wave motion as was previously proposed

The major human AP endonuclease (Ape1) is involved in the nucleotide incision repair pathway

In nucleotide incision repair (NIR), an endonuclease nicks oxidatively damaged DNA in a DNA glycosylase-independent manner, providing the correct ends for DNA synthesis coupled to the repair of the remaining 5'-dangling modified nucleotide. This mechanistic feature is distinct from DNA glycosylase-mediated base excision repair. Here we report that Ape1, the major apurinic/apyrimidinic endonuclease in human cells, is the damage- specific endonuclease involved in NIR. We show that Ape1 incises DNA containing 5,6-dihydro-2'-deoxyuridine, 5,6-dihydrothymidine, 5-hydroxy-2'-deoxyuridine, alpha-2'-deoxyadenosine and alpha-thymidine adducts, generating 3'-hydroxyl and 5'-phosphate termini. The kinetic constants indicate that Ape1-catalysed NIR activity is highly efficient. The substrate specificity and protein conformation of Ape1 is modulated by MgCl2 concentrations, thus providing conditions under which NIR becomes a major activity in cell-free extracts. While the N-terminal region of Ape1 is not required for AP endonuclease function, we show that it regulates the NIR activity. The physiological relevance of the mammalian NIR pathway is discussed

Finite-Time Singularity Signature of Hyperinflation

We present a novel analysis extending the recent work of Mizuno et al. [2002] on the hyperinflations of Germany (1920/1/1-1923/11/1), Hungary (1945/4/30-1946/7/15), Brazil (1969-1994), Israel (1969-1985), Nicaragua (1969-1991), Peru (1969-1990) and Bolivia (1969-1985). On the basis of a generalization of Cagan's model of inflation based on the mechanism of ``inflationary expectation'' or positive feedbacks between realized growth rate and people's expected growth rate, we find that hyperinflations can be characterized by a power law singularity culminating at a critical time $t_c$. Mizuno et al.'s double-exponential function can be seen as a discrete time-step approximation of our more general nonlinear ODE formulation of the price dynamics which exhibits a finite-time singular behavior. This extension of Cagan's model, which makes natural the appearance of a critical time $t_c$, has the advantage of providing a well-defined end of the clearly unsustainable hyperinflation regime. We find an excellent and reliable agreement between theory and data for Germany, Hungary, Peru and Bolivia. For Brazil, Israel and Nicaragua, the super-exponential growth seems to be already contaminated significantly by the existence of a cross-over to a stationary regime.Comment: Latex 21 pages including 2 tables and 7 eps figure

Thermally latent water in a polymer matrix.

Possible phase transition of water in polymer-water systems has been understood (assumed) to be only either freezing/melting or nothing, without relation to whether the polymer was soluble in water or whether its water content was high or low. This general understanding of water structure has been structured on the basis of calorimetric analyses such as differential scanning calorimetry, DSC. DSC is one of the most frequently used methods to analyze the water structure in polymer-water systems because the data obtained are relatively easy to interpret. This easiness of interpretation, however, can be accepted only if based on the understanding stated above. Unexpectedly, results of the infrared spectroscopic analysis presented here completely denied the general understanding and provided definite evidence of the existence of all phase transitions among the three states of water in a polymer solid. Furthermore, the impossibility of detection of condensation, deposition, sublimation, and vaporization by calorimetric analysis was revealed

A New Method for Calculating Arrival Distribution of Ultra-High Energy Cosmic Rays above 10^19 eV with Modifications by the Galactic Magnetic Field

We present a new method for calculating arrival distribution of UHECRs including modifications by the galactic magnetic field. We perform numerical simulations of UHE anti-protons, which are injected isotropically at the earth, in the Galaxy and record the directions of velocities at the earth and outside the Galaxy for all of the trajectories. We then select some of them so that the resultant mapping of the velocity directions outside the Galaxy of the selected trajectories corresponds to a given source location scenario, applying Liouville's theorem. We also consider energy loss processes of UHE protons in the intergalactic space. Applying this method to our source location scenario which is adopted in our recent study and can explain the AGASA observation above 4 \times 10^{19} eV, we calculate the arrival distribution of UHECRs including lower energy (E>10^19 eV) ones. We find that our source model can reproduce the large-scale isotropy and the small-scale anisotropy on UHECR arrival distribution above 10^19 eV observed by the AGASA. We also demonstrate the UHECR arrival distribution above 10^19 eV with the event number expected by future experiments in the next few years. The interesting feature of the resultant arrival distribution is the arrangement of the clustered events in the order of their energies, reflecting the directions of the galactic magnetic field. This is also pointed out by Alvarez-Muniz et al.(2002). This feature will allow us to obtain some kind of information about the composition of UHECRs and the magnetic field with increasing amount of data.Comment: 10 pages, 8 figures, to appear in the Astrophysical Journa