Atomic spectroscopy on a chip

Abstract: We demonstrate the ability to generate extremely large rubidium densities in uncoated hollow-core photonic band-gap fibers using lightinduced atomic desorption. Once the fiber is exposed to Rb vapor for 1-2 weeks, and this atomic source is removed, the fiber yields large desorbable densities for an extended period of time. We show that optical depths greater than e -1200 can be created within seconds. Our observed Rb densities are several orders of magnitude larger than any previously reported to be generated optically, and allow for the demonstration of a relatively easy-touse fiber-based vapor cell capable of producing large optical depths without the need for thermal tuning. H. Schmidt and A. Imamoğlu, "Giant Kerr nonlinearities obtained by electromagnetically-induced transparency," Opt. Lett. 21, 1936Lett. 21, -1938Lett. 21, (199

Charge ordering and antiferromagnetic transitions in Nd<SUB>x</SUB>Ca<SUB>1-x</SUB>MnO<SUB>3</SUB> (x= 0.2, 0.3) manganites

In this paper we present transport, magnetic and electron paramagnetic resonance (EPR) studies of electron doped manganites Nd<SUB>x</SUB>Ca<SUB>1-x</SUB>MnO<SUB>3</SUB>(x=0.2,0.3) with a view to compare and contrast their properties with those of the hole doped Nd<SUB>0.5</SUB>Ca<SUB>0.5</SUB>MnO<SUB>3</SUB> and other manganites. The samples were prepared by the solid-state reaction method and the composition was verified using X-ray and EDAX measurements. Magnetization measurements on the x=0.2 sample (NCMO 0.2) show a peak at 155 K accompanied by a sharp increase in the resistivity. In the case of x=0.3 sample (NCMO 0.3) a peak in the magnetization along with an increase in the resistivity is observed at 220 K. From a comparison of the EPR results in the two compounds, we conclude that the transition in NCMO 0.2 is an antiferromagnetic transition which is likely to be a charge ordering transition as well and that in NCMO 0.3 is only a charge ordering transition at which long-range magnetic order is not established. We infer that in this compound the long-range antiferromagnetic order sets in at a much lower temperature below which the EPR signal disappears due to the opening of an antiferromagnetic gap

Charge ordering and antiferromagnetic transitions in NdxCa1−xMnO3(x=0.2,0.3)Nd_xCa_{1-x}MnO_3(x = 0.2, 0.3) manganites

In this paper we present transport, magnetic and electron paramagnetic resonance (EPR) studies of electron doped manganites $Nd_xCa_{1-x}MnO_3(x = 0.2, 0.3)$ with a view to compare and contrast their properties with those of the hole doped $Nd_{0.5}Ca_{0.5}MnO_3$ and other manganites. The samples were prepared by the solid-state reaction method and the composition was verified using X-ray and EDAX measurements. Magnetization measurements on the x = 0.2 sample (NCMO 0.2) show a peak at 155 K accompanied by a sharp increase in the resistivity. In the case of x = 0.3 sample (NCMO 0.3) a peak in the magnetization along with an increase in the resistivity is observed at 220 K. From a comparison of the EPR results in the two compounds, we conclude that the transition in NCMO 0.2 is an antiferromagnetic transition which is likely to be a charge ordering transition as well and that in NCMO 0.3 is only a charge ordering transition at which long-range magnetic order is not established. We infer that in this compound the long-range antiferromagnetic order sets in at a much lower temperature below which the EPR signal disappears due to the opening of an antiferromagnetic gap

Non-Uniform and Non-Random Binding of Nucleoprotein to Influenza A and B Viral RNA

The genomes of influenza A and B viruses have eight, single-stranded RNA segments that exist in the form of a viral ribonucleoprotein complex in association with nucleoprotein (NP) and an RNA-dependent RNA polymerase complex. We previously used high-throughput RNA sequencing coupled with crosslinking immunoprecipitation (HITS-CLIP) to examine where NP binds to the viral RNA (vRNA) and demonstrated for two H1N1 strains that NP binds vRNA in a non-uniform, non-random manner. In this study, we expand on those initial observations and describe the NP-vRNA binding profile for a seasonal H3N2 and influenza B virus. We show that, similar to H1N1 strains, NP binds vRNA in a non-uniform and non-random manner. Each viral gene segment has a unique NP binding profile with areas that are enriched for NP association as well as free of NP-binding. Interestingly, NP-vRNA binding profiles have some conservation between influenza A viruses, H1N1 and H3N2, but no correlation was observed between influenza A and B viruses. Our study demonstrates the conserved nature of non-uniform NP binding within influenza viruses. Mapping of the NP-bound vRNA segments provides information on the flexible NP regions that may be involved in facilitating assembly

Pre-existing heterosubtypic immunity provides a barrier to airborne transmission of influenza viruses.

Human-to-human transmission of influenza viruses is a serious public health threat, yet the precise role of immunity from previous infections on the susceptibility to airborne infection is still unknown. Using the ferret model, we examined the roles of exposure duration and heterosubtypic immunity on influenza transmission. We demonstrate that a 48 hour exposure is sufficient for efficient transmission of H1N1 and H3N2 viruses. To test pre-existing immunity, a gap of 8-12 weeks between primary and secondary infections was imposed to reduce innate responses and ensure robust infection of donor animals with heterosubtypic viruses. We found that pre-existing H3N2 immunity did not significantly block transmission of the 2009 H1N1pandemic (H1N1pdm09) virus to immune animals. Surprisingly, airborne transmission of seasonal H3N2 influenza strains was abrogated in recipient animals with H1N1pdm09 pre-existing immunity. This protection from natural infection with H3N2 virus was independent of neutralizing antibodies. Pre-existing immunity with influenza B virus did not block H3N2 virus transmission, indicating that the protection was likely driven by the adaptive immune response. We demonstrate that pre-existing immunity can impact susceptibility to heterologous influenza virus strains, and implicate a novel correlate of protection that can limit the spread of respiratory pathogens through the air

Quantum enhancement of a coherent ladar receiver using phase-sensitive amplification

We demonstrate a balanced-homodyne LADAR receiver employing a phase-sensitive amplifier (PSA) to raise the effective photon detection efficiency (PDE) to nearly 100%. Since typical LADAR receivers suffer from losses in the receive optical train that routinely limit overall PDE to less than 50% thus degrading SNR, PSA can provide significant improvement through amplification with noise figure near 0 dB. Receiver inefficiencies arise from sub-unity quantum efficiency, array fill factors, signal-local oscillator mixing efficiency (in coherent receivers), etc. The quantum-enhanced LADAR receiver described herein is employed in target discrimination scenarios as well as in imaging applications. We present results showing the improvement in detection performance achieved with a PSA, and discuss the performance advantage when compared to the use of a phase-insensitive amplifier, which cannot amplify noiselessly.United States. Defense Advanced Research Projects Agency. Quantum Sensors ProgramUnited States. Air Force Research Laboratory (Contract FA8750- 09-C-0194