ZTF-8 Interacts with the 9-1-1 Complex and Is Required for DNA Damage Response and Double-Strand Break Repair in the C. elegans Germline

Germline mutations in DNA repair genes are linked to tumor progression. Furthermore, failure in either activating a DNA damage checkpoint or repairing programmed meiotic double-strand breaks (DSBs) can impair chromosome segregation. Therefore, understanding the molecular basis for DNA damage response (DDR) and DSB repair (DSBR) within the germline is highly important. Here we define ZTF-8, a previously uncharacterized protein conserved from worms to humans, as a novel factor involved in the repair of both mitotic and meiotic DSBs as well as in meiotic DNA damage checkpoint activation in the C. elegans germline. ztf-8 mutants exhibit specific sensitivity to γ-irradiation and hydroxyurea, mitotic nuclear arrest at S-phase accompanied by activation of the ATL-1 and CHK-1 DNA damage checkpoint kinases, as well as accumulation of both mitotic and meiotic recombination intermediates, indicating that ZTF-8 functions in DSBR. However, impaired meiotic DSBR progression partially fails to trigger the CEP-1/p53-dependent DNA damage checkpoint in late pachytene, also supporting a role for ZTF-8 in meiotic DDR. ZTF-8 partially co-localizes with the 9-1-1 DDR complex and interacts with MRT-2/Rad1, a component of this complex. The human RHINO protein rescues the phenotypes observed in ztf-8 mutants, suggesting functional conservation across species. We propose that ZTF-8 is involved in promoting repair at stalled replication forks and meiotic DSBs by transducing DNA damage checkpoint signaling via the 9-1-1 pathway. Our findings define a conserved function for ZTF-8/RHINO in promoting genomic stability in the germline

Semiconductor nanoring lasers

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/98671/1/ApplPhysLett_98_201105.pd

Lasing in a metal-clad microring resonator

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/98661/1/ApplPhysLett_98_131107.pd

Nonvolatile memories using deep traps formed in HfO₂ by Nb ion implantation

We report nonvolatile memories (NVMs) based on deep-energy trap levels formed in HfO₂ by metal ion implantation. A comparison of Nb- and Ta-implanted samples shows that suitable charge-trapping centers are formed in Nb-implanted samples, but not in Ta-implanted samples. This is consistent with density-functional theory calculations which predict that only Nb will form deep-energy levels in the bandgap of HfO₂. Photocurrent spectroscopy exhibits characteristics consistent with one of the trap levels predicted in these calculations. Nb-implanted samples showing memory windows in capacitance–voltage (V) curves always exhibit current (I) peaks in I–V curves, indicating that NVM effects result from deep traps in HfO₂. In contrast, Ta-implanted samples show dielectric breakdowns during the I–V sweeps between 5 and 11 V, consistent with the fact that no trap levels are present. For a sample implanted with a fluence of 10¹³Nb cm⁻², the charge losses after 10⁴ s are ∼9.8 and ∼25.5% at room temperature (RT) and 85°C, respectively, and the expected charge loss after 10 years is ∼34% at RT, very promising for commercial NVMs

Effective Vortex Mass from Microscopic Theory

We calculate the effective mass of a single quantized vortex in the BCS superconductor at finite temperature. Based on effective action approach, we arrive at the effective mass of a vortex as integral of the spectral function $J(\omega)$ divided by $\omega^3$ over frequency. The spectral function is given in terms of the quantum-mechanical transition elements of the gradient of the Hamiltonian between two Bogoliubov-deGennes (BdG) eigenstates. Based on self-consistent numerical diagonalization of the BdG equation we find that the effective mass per unit length of vortex at zero temperature is of order $m (k_f \xi_0)^2$ ($k_f$=Fermi momentum, $\xi_0$=coherence length), essentially equaling the electron mass displaced within the coherence length from the vortex core. Transitions between the core states are responsible for most of the mass. The mass reaches a maximum value at $T\approx 0.5 T_c$ and decreases continuously to zero at $T_c$.Comment: Supercedes prior version, cond-mat/990312

Resonance Patterns in a Stadium-shaped Microcavity

We investigate resonance patterns in a stadium-shaped microcavity around $n_ck R \simeq 10$, where $n_c$ is the refractive index, $k$ the vacuum wavenumber, and $R$ the radius of the circular part of the cavity. We find that the patterns of high $Q$ resonances can be classified, even though the classical dynamics of the stadium system is chaotic. The patterns of the high $Q$ resonances are consistent with the ray dynamical consideration, and appears as the stationary lasing modes with low pumping rate in the nonlinear dynamical model. All resonance patterns are presented in a finite range of $kR$.Comment: 8 pages, 9 figure

Effect of sintering temperature under high pressure in the uperconductivity for MgB2

We report the effect of the sintering temperature on the superconductivity of MgB2 pellets prepared under a high pressure of 3 GPa. The superconducting properties of the non-heated MgB2 in this high pressure were poor. However, as the sintering temperature increased, the superconducting properties were vastly enhanced, which was shown by the narrow transition width for the resistivity and the low-field magnetizations. This shows that heat treatment under high pressure is essential to improve superconducting properties. These changes were found to be closely related to changes in the surface morphology observed using scanning electron microscopy.Comment: 3 Pages including 3 figure