A mutant of Neurospora crassa deficient in cytochrome c heme lyase activity cannot import cytochrome c into mitochondria

The nuclear cyt-2-1 mutant of Neurospora crassa is characterized by a gross deficiency of cytochrome c (Bertrand, H., and Collins, R. A. (1978) Mol. Gen. Genet. 166, 1-13). The mutant produces mRNA that can be translated into apocytochrome c in vitro. Apocytochrome c is also synthesized in vivo in cyt-2-1, but it is rapidly degraded and thus does not accumulate in the cytosol. Mitochondria from wild-type cells bind apocytochrome c made in vitro from either wild-type or cyt-2-1 mRNA and convert it to holocytochrome c. This conversion depends on the addition of heme by cytochrome c heme lyase and is coupled to translocation of cytochrome c into the intermembrane space. Mitochondria from the cyt-2-1 strain are deficient in the ability to bind apocytochrome c. They are also completely devoid of cytochrome c heme lyase activity. These defects explain the inability of the cyt-2-1 mutant to convert apocytochrome c to the holo form and to import it into mitochondria

What could be learnt from Positronium for Quarkonium?

In order to fulfill Low's theorem requirements, a new lowest order basis for bound state decay computations is proposed, in which the binding energy is treated non-perturbatively. The properties of the method are sketched by reviewing standard positronium decay processes. Then, it is shown how applying the method to quarkonia sheds new light on some longstanding puzzles.Comment: 12 pages, 10 figures. Talk given at the ETH Workshop on Positronium Physics, May 30-31, 2003, Zurich, Switzerlan

Solar neutrino interactions: Using charged currents at SNO to tell neutral currents at Super-Kamiokande

In the presence of flavor oscillations, muon and tau neutrinos can contribute to the Super-Kamiokande (SK) solar neutrino signal through the neutral current process \nu_{\mu,\tau} e^{-}\to \nu_{\mu,\tau} e^{-}. We show how to separate the \nu_e and \nu_{\mu,\tau} event rates in SK in a model independent way, by using the rate of the charged current process \nu_e d \to p p e^{-} from the Sudbury Neutrino Observatory (SNO) experiment, with an appropriate choice of the SK and SNO energy thresholds. Under the additional hypothesis of no oscillations into sterile states, we also show how to determine the absolute ^{8}B neutrino flux from the same data set, independently of the \nu_e survival probability.Comment: 14 pages (RevTeX), incl. 3 figures (epsf), submitted to Phys. ReV.

Enhancing the Critical Current of a Superconducting Film in a Wide Range of Magnetic Fields with a Conformal Array of Nanoscale Holes

The maximum current (critical current) a type-II superconductor can transmit without energy loss is limited by the motion of the quantized magnetic flux penetrating into a superconductor. Introducing nanoscale holes into a superconducting film has been long pursued as a promising way to increase the critical current. So far the critical current enhancement was found to be mostly limited to low magnetic fields. Here we experimentally investigate the critical currents of superconducting films with a conformal array of nanoscale holes that have non-uniform density while preserving the local ordering. We find that the conformal array of nanoscle holes provides a more significant critical current enhancement at high magnetic fields. The better performance can be attributed to its arching effect that not only gives rise to the gradient in hole-density for pinning vortices with a wide range of densities but also prevent vortex channeling occurring in samples with a regular lattice of holes.Comment: 5 pages, 3 figure

Gluonic and leptonic decays of heavy quarkonia and the determination of αs(mc)\alpha_s(m_c) and αs(mb)\alpha_s(m_b)

QCD running coupling constant $\alpha_s(m_c)$ and $\alpha_s(m_b)$ are determined from heavy quarkonia $c\overline{c}$ and $b\overline{b}$ decays. The decay rates of $V\rightarrow 3g$ and $V\rightarrow e^+ e^-$ for $V=J/\psi$ and $\Upsilon$ are estimated by taking into account both relativistic and QCD radiative corrections. The decay amplitudes are derived in the Bethe-Salpeter formalism, and the decay rates are estimated by using the meson wavefunctions which are obtained with a QCD-inspired inter-quark potential. For the $V\rightarrow 3g$ decay we find the relativistic correction to be very large and to severely suppress the decay rate. Using the experimental values of ratio R_g\equiv \frac {\Gamma (V\longrightarrow 3g)}% {\Gamma (V\longrightarrow e^{+}e^{-})}\approx 10,~32 for $V=J/\psi, ~\Upsilon$ respectively, and the calculated widths , we find $\alpha_{s}(m_c)=0.29\pm 0.02$ and $\alpha_s(m_b)=0.20\pm 0.02$. These values for the QCD running coupling constant are substantially enhanced, as compared with the ones obtained without relativistic corrections, and are consistent with the QCD scale parameter $\Lambda_{\overline {MS}}^{(4)}$. We also find that these results are mainly due to kinematic corrections and not sensitive to the dynamical models.Comment: 15 pages in Late

A simple proof of the unconditional security of quantum key distribution

Quantum key distribution is the most well-known application of quantum cryptography. Previous proposed proofs of security of quantum key distribution contain various technical subtleties. Here, a conceptually simpler proof of security of quantum key distribution is presented. The new insight is the invariance of the error rate of a teleportation channel: We show that the error rate of a teleportation channel is independent of the signals being transmitted. This is because the non-trivial error patterns are permuted under teleportation. This new insight is combined with the recently proposed quantum to classical reduction theorem. Our result shows that assuming that Alice and Bob have fault-tolerant quantum computers, quantum key distribution can be made unconditionally secure over arbitrarily long distances even against the most general type of eavesdropping attacks and in the presence of all types of noises.Comment: 13 pages, extended abstract. Comments will be appreciate

Large optical gain from four-wave mixing instabilities in semiconductor quantum wells

Based on a microscopic many-particle theory, we predict large optical gain in the probe and background-free four-wave mixing directions caused by excitonic instabilities in semiconductor quantum wells. For a single quantum well with radiative-decay limited dephasing in a typical pump-probe setup we discuss the microscopic driving mechanisms and polarization and frequency dependence of these instabilities

Charmonium states in QCD-inspired quark potential model using Gaussian expansion method

We investigate the mass spectrum and electromagnetic processes of charmonium system with the nonperturbative treatment for the spin-dependent potentials, comparing the pure scalar and scalar-vector mixing linear confining potentials. It is revealed that the scalar-vector mixing confinement would be important for reproducing the mass spectrum and decay widths, and therein the vector component is predicted to be around 22%. With the state wave functions obtained via the full-potential Hamiltonian, the long-standing discrepancy in M1 radiative transitions of $J/\psi$ and $\psi^{\prime}$ are alleviated spontaneously. This work also intends to provide an inspection and suggestion for the possible $c\bar{c}$ among the copious higher charmonium-like states. Particularly, the newly observed X(4160) and X(4350) are found in the charmonium family mass spectrum as $M(2^1D_2)= 4164.9$ MeV and $M(3^3P_2)= 4352.4$ MeV, which strongly favor the $J^{PC}=2^{-+}, 2^{++}$ assignments respectively. The corresponding radiative transitions, leptonic and two-photon decay widths have been also predicted theoretically for the further experimental search.Comment: 16 pages,3 figure

Security proof of a three-state quantum key distribution protocol without rotational symmetry

Standard security proofs of quantum key distribution (QKD) protocols often rely on symmetry arguments. In this paper, we prove the security of a three-state protocol that does not possess rotational symmetry. The three-state QKD protocol we consider involves three qubit states, where the first two states, |0_z> and |1_z>, can contribute to key generation and the third state, |+>=(|0_z>+|1_z>)/\sqrt{2}, is for channel estimation. This protocol has been proposed and implemented experimentally in some frequency-based QKD systems where the three states can be prepared easily. Thus, by founding on the security of this three-state protocol, we prove that these QKD schemes are, in fact, unconditionally secure against any attacks allowed by quantum mechanics. The main task in our proof is to upper bound the phase error rate of the qubits given the bit error rates observed. Unconditional security can then be proved not only for the ideal case of a single-photon source and perfect detectors, but also for the realistic case of a phase-randomized weak coherent light source and imperfect threshold detectors. Our result on the phase error rate upper bound is independent of the loss in the channel. Also, we compare the three-state protocol with the BB84 protocol. For the single-photon source case, our result proves that the BB84 protocol strictly tolerates a higher quantum bit error rate than the three-state protocol; while for the coherent-source case, the BB84 protocol achieves a higher key generation rate and secure distance than the three-state protocol when a decoy-state method is used.Comment: 10 pages, 3 figures, 2 column