OGO-E space vehicle response to transient loading at Atlas booster engine cutoff

Computer program for OGO-E vehicle response analysis to transient loading during Atlas booster burnou

Convective overshooting and production of s-nuclei in massive stars during their core He-burning phase

With the "post-processing" technique we explore the role of the convective overshooting on the production of s-nuclei in stellar models of different initial mass and metallicity ($15 \leq M_{ZAMS}/M_{\odot} \leq 25$; $10^{-4} \leq Z \leq 0.02$), considering a range of values for the parameter $f$, which determines the overall efficiency of convective overshooting.We find enhancements in the production of s-nuclei until a factor $\sim 6$ (measured as the average overproduction factor of the 6 s-only nuclear species with $60\lesssim A\lesssim90$) in all our models of different initial mass and metallicity with $f$ in the range $0.01{-}0.035$ (i.e. models with overshooting) compared to the production obtained with "no-overshooting" models (i.e. models with the same initial mass and metallicity, but $f=10^{-5}$). Moreover the results indicate that the link between the overshooting parameter $f$ and the s-process efficiency is essentially monotonic in all our models of different initial mass and metallicity. Also evident is the higher s-process efficiency when we progressively increase for a given f value both the mass of the models from 15 M$_\odot$ to 25 M$_\odot$ and the Z value from 10$^{-4}$ to 0.02. We also briefly discuss the possible consequences of these results for some open questions linked to the s-process weak component efficiency, as well as a "rule of thumb" to evaluate the impact of the convective overshooting on the yields of a generation of stars.Comment: 12 pages, 6 figures, A&A accepted (corrected typos plus minor changes in order to fulfill the guidelines for A&A manuscripts

Spectroscopy of 13B via the 13C(t,3He) reaction at 115 AMeV

Gamow-Teller and dipole transitions to final states in 13B were studied via the 13C(t,3He) reaction at Et = 115 AMeV. Besides the strong Gamow-Teller transition to the 13B ground state, a weaker Gamow-Teller transition to a state at 3.6 MeV was found. This state was assigned a spin-parity of 3/2- by comparison with shell-model calculations using the WBP and WBT interactions which were modified to allow for mixing between nhw and (n+2)hw configurations. This assignment agrees with a recent result from a lifetime measurement of excited states in 13B. The shell-model calculations also explained the relatively large spectroscopic strength measured for a low-lying 1/2+ state at 4.83 MeV in 13B. The cross sections for dipole transitions up to Ex(13B)= 20 MeV excited via the 13C(t,3He) reaction were also compared with the shell-model calculations. The theoretical cross sections exceeded the data by a factor of about 1.8, which might indicate that the dipole excitations are "quenched". Uncertainties in the reaction calculations complicate that interpretation.Comment: 11 pages, 6 figure

Development of an approximate method for quantum optical models and their pseudo-Hermicity

An approximate method is suggested to obtain analytical expressions for the eigenvalues and eigenfunctions of the some quantum optical models. The method is based on the Lie-type transformation of the Hamiltonians. In a particular case it is demonstrated that $E\times \epsilon$ Jahn-Teller Hamiltonian can easily be solved within the framework of the suggested approximation. The method presented here is conceptually simple and can easily be extended to the other quantum optical models. We also show that for a purely imaginary coupling the $E\times \epsilon$ Hamiltonian becomes non-Hermitian but $P\sigma _{0}$-symmetric. Possible generalization of this approach is outlined.Comment: Paper prepared fo the "3rd International Workshop on Pseudo-Hermitian Hamiltonians in Quantum Physics" June 2005 Istanbul. To be published in Czechoslovak Journal of Physic

HLA-DRB1*15 influences the development of brain tissue damage in early PPMS

OBJECTIVES To investigate whether (1) there were differences between HLA-DRB1*15-positive and -negative patients at baseline, and (2) HLA-DRB1*15-positive patients showed a greater development of brain and spinal cord damage, as assessed by MRI, and greater progression of disability, during a 5-year follow-up, compared with HLA-DRB1*15-negative patients. METHODS HLA-DRB1*15 typing was performed in 41 patients with primary progressive multiple sclerosis (PPMS) who were recruited within 5 years of symptom onset. All patients and 18 healthy controls were studied clinically and with MRI at baseline, and every 6 months for 3 years, and then at 5 years. Magnetization transfer ratio parameters and volumes for brain gray matter and normal-appearing white matter, brain T2 lesion load, and spinal cord cross-sectional area were obtained. Patient disability was assessed at each visit using the Expanded Disability Status Scale and Multiple Sclerosis Functional Composite subscores. RESULTS There were no significant differences between HLA-DRB1*15-positive and -negative patients at baseline. HLA-DRB1*15-positive patients showed a greater decline in brain magnetization transfer ratio for gray matter and normal-appearing white matter (both p = 0.005) than HLA-DRB1*15-negative patients over 5 years, while the same parameters did not change over time in healthy controls. HLA-DRB1*15-positive patients also showed a trend toward a faster increase in brain T2 lesion load than HLA-DRB1*15-negative patients (0.29 [95% confidence interval 0.20-0.38] vs 0.21 [0.13-0.30] mL/mo, p = 0.085) and higher T2 lesion volumes at all time points (average difference [95% confidence interval]: 10.58 mL [7.09-14.07], p < 0.001) during the follow-up, after adjusting for disease duration. CONCLUSIONS These findings suggest that HLA-DRB1*15 influences the progression of brain pathology in PPMS

Canonical description of ideal magnetohydrodynamic flows and integrals of motion

In the framework of the variational principle the canonical variables describing ideal magnetohydrodynamic (MHD) flows of general type (i.e., with spatially varying entropy and nonzero values of all topological invariants) are introduced. The corresponding complete velocity representation enables us not only to describe the general type flows in terms of single-valued functions, but also to solve the intriguing problem of the ``missing'' MHD integrals of motion. The set of hitherto known MHD local invariants and integrals of motion appears to be incomplete: for the vanishing magnetic field it does not reduce to the set of the conventional hydrodynamic invariants. And if the MHD analogs of the vorticity and helicity were discussed earlier for the particular cases, the analog of Ertel invariant has been so far unknown. It is found that on the basis of the new invariants introduced a wide set of high-order invariants can be constructed. The new invariants are relevant both for the deeper insight into the problem of the topological structure of the MHD flows as a whole and for the examination of the stability problems. The additional advantage of the proposed approach is that it enables one to deal with discontinuous flows, including all types of possible breaks.Comment: 16 page

Mode division multiplexing using an orbital angular momentum mode sorter and MIMO-DSP over a graded-index few-mode optical fibre

Mode division multiplexing (MDM)– using a multimode optical fiber’s N spatial modes as data channels to transmit N independent data streams – has received interest as it can potentially increase optical fiber data transmission capacity N-times with respect to single mode optical fibers. Two challenges of MDM are (1) designing mode (de)multiplexers with high mode selectivity (2) designing mode (de)multiplexers without cascaded beam splitting’s 1/N insertion loss. One spatial mode basis that has received interest is that of orbital angular momentum (OAM) modes. In this paper, using a device referred to as an OAM mode sorter, we show that OAM modes can be (de)multiplexed over a multimode optical fiber with higher than −15 dB mode selectivity and without cascaded beam splitting’s 1/N insertion loss. As a proof of concept, the OAM modes of the LP11 mode group (OAM−1,0 and OAM+1,0), each carrying 20-Gbit/s polarization division multiplexed and quadrature phase shift keyed data streams, are transmitted 5km over a graded-index, few-mode optical fibre. Channel crosstalk is mitigated using 4 × 4 multiple-input-multiple-output digital-signal-processing with &lt;1.5 dB power penalties at a bit-error-rate of 2 × 10−3

An improved geometric inequality via vanishing moments, with applications to singular Liouville equations

We consider a class of singular Liouville equations on compact surfaces motivated by the study of Electroweak and Self-Dual Chern-Simons theories, the Gaussian curvature prescription with conical singularities and Onsager's description of turbulence. We analyse the problem of existence variationally, and show how the angular distribution of the conformal volume near the singularities may lead to improvements in the Moser-Trudinger inequality, and in turn to lower bounds on the Euler-Lagrange functional. We then discuss existence and non-existence results.Comment: some references adde