Spacecraft contamination programs within the Air Force Systems Command Laboratories

Spacecraft contamination programs exist in five independent AFSC organizations: Geophysics Laboratory (GL), Arnold Engineering and Development Center (AEDC), Rome Air Development Center (RADC/OSCE), Wright Research and Development Center (MLBT), Armament Laboratory (ATL/SAI), and Space Systems Division (SSD/OL-AW). In addition, a sizable program exists at Aerospace Corp. These programs are complementary, each effort addressing a specific area of expertise: GL's effort is aimed at addressing the effects of on-orbit contamination; AEDC's effort is aimed at ground simulation and measurement of optical contamination; RADC's effort addresses the accumulation, measurement, and removal of contamination on large optics; MLBT's effort is aimed at understanding the effect of contamination on materials; ATL's effort is aimed at understanding the effect of plume contamination on systems; SSD's effort is confined to the integration of some contamination experiments sponsored by SSD/CLT; and Aerospace Corp.'s effort is aimed at supporting the needs of the using System Program Offices (SPO) in specific areas, such as contamination during ground handling, ascent phase, laboratory measurements aimed at understanding on-orbit contamination, and mass loss and mass gain in on-orbit operations. These programs are described in some detail, with emphasis on GL's program

Discovery of an exosite on the SOCS2-SH2 domain that enhances SH2 binding to phosphorylated ligands

Suppressor of cytokine signaling (SOCS)2 protein is a key negative regulator of the growth hormone (GH) and Janus kinase (JAK)-Signal Transducers and Activators of Transcription (STAT) signaling cascade. The central SOCS2-Src homology 2 (SH2) domain is characteristic of the SOCS family proteins and is an important module that facilitates recognition of targets bearing phosphorylated tyrosine (pTyr) residues. Here we identify an exosite on the SOCS2-SH2 domain which, when bound to a non-phosphorylated peptide (F3), enhances SH2 affinity for canonical phosphorylated ligands. Solution of the SOCS2/F3 crystal structure reveals F3 as an α-helix which binds on the opposite side of the SH2 domain to the phosphopeptide binding site. F3:exosite binding appears to stabilise the SOCS2-SH2 domain, resulting in slower dissociation of phosphorylated ligands and consequently, enhances binding affinity. This biophysical enhancement of SH2:pTyr binding affinity translates to increase SOCS2 inhibition of GH signaling

Vaccine-induced neutralizing antibody responses to seasonal influenza virus H1N1 strains are not enhanced during subsequent pandemic H1N1 infection

The first exposure to influenza is presumed to shape the B-cell antibody repertoire, leading to preferential enhancement of the initially formed responses during subsequent exposure to viral variants. Here, we investigated whether this principle remains applicable when there are large genetic and antigenic differences between primary and secondary influenza virus antigens. Because humans usually have a complex history of influenza virus exposure, we conducted this investigation in influenza-naive cynomolgus macaques. Two groups of six macaques were immunized four times with influenza virus-like particles (VLPs) displaying either one (monovalent) or five (pentavalent) different hemagglutinin (HA) antigens derived from seasonal H1N1 (H1N1) strains. Four weeks after the final immunization, animals were challenged with pandemic H1N1 (H1N1pdm09). Although immunization resulted in robust virus-neutralizing responses to all VLP-based vaccine strains, there were no cross-neutralization responses to H1N1pdm09, and all animals became infected. No reductions in viral load in the nose or throat were detected in either vaccine group. After infection, strong virus-neutralizing responses to H1N1pdm09 were induced. However, there were no increases in virus-neutralizing titers against four of the five H1N1 vaccine strains; and only a mild increase was observed in virus-neutralizing titer against the influenza A/Texas/36/91 vaccine strain. After H1N1pdm09 infection, both vaccine groups showed higher virus-neutralizing titers against two H1N1 strains of intermediate antigenic distance between the H1N1 vaccine strains and H1N1pdm09, compared with the naive control group. Furthermore, both vaccine groups had higher HA-stem antibodies early after infection than the control group. In conclusion, immunization with VLPs displaying HA from antigenically distinct H1N1 variants increased the breadth of the immune response during subsequent H1N1pdm09 challenge, although this phenomenon was limited to intermediate antigenic variants

X+(X=Ar,Kr,N2)+H2OX^{+} (X=Ar, Kr, N_{2}) + H_{2}O charge-transfer luminescence: Vibrationally-selected H2O+A~−X~H_{2}O^{+} \tilde{A} - \tilde{X} emissions

Author Institution: Philips Laboratory, PL/WSSIExothermic low-energy (1-20 $eV^{+}$ c.m.) charge-transfer reactions are primarily governed by the energy resonance criterion. They thus offer a convenient means of producing ions in a narrow energy range of rovibronic states. A further constraint on the probability of populating near-resonant charge-transfer states is the necessity of a favourable Frank-Condon overlap between the vibrational wavefunctions of the reactants and the products. Rotational energy transfer is insignificant due to the long-range nature of charge-transfer process. Consequently, if electronically excited states are accessed in near-resonant charge-transfer collisions, omission spectra can be observed involving only few excited state vibrational levels with near-thermal rotational distributions. We have studied charge-transfer luminescence from following systems: \begin{eqnarray} \begin{array}{ll} Ar^{+}(^{2}P_{3/2}) + H_{2}O &\rightarrow Ar + H_{2}O^{+} (\widetilde{X}\ ^{2}B_{1}) + 3.14eV \\ Kr^{+}(^{2}P_{1/2}) + H_{2}O &\rightarrow Kr + H_{2}O^{-} (\widetilde{X}\ ^{2}B_{1}) + 2.04 eV \\ N_{2} + H_{2}O &\rightarrow N_{2} + H_{2}O^{+} (\widetilde{X}\ ^{2}B_{1}) + 2.096 eV \end{array} \end{eqnarray} The luminescence is produced by propagating a mass and energy-selected ion beam through a collision cell that is fiber-optically coupled to an optical multichannel analyzer. The 0.5 nm (fwhm) resolution spectra show that the reaction exothermicity is almost exclusively partitioned to internal modes of $H_{2}O^{+}$, yielding $H_{2}O^{+} \widetilde{A}^{2}A_{1}$ sate products in few bending vibrational levels at energies given by the respective exothermicities. In some cases emissions from previously not observed high K levels (up to $K = 6$) are identified that are related to dynamical effects. The most recent $Kr^{1} + H_{2}O$ luminescence measurements are carried out with a very sensitive liquid-nitrogen cooled CCD detector providing greater than 40% quantum efficiency in the 600-800 nm range. We plan measurements at considerably higher resolution and hope to determine hitherto unknown spectroscopic constants in order to support the numerous computational studies of the $H_{2}O^{+} \bar{A}^{2}A_{1} = \widetilde{X}^{2}B_{1}$ Renner-Teller system

Successful renal transplant in patient with controlled pulmonary non-tuberculous mycobacterium infection

No Abstract

The solar cycle effect on the atmosphere as a scintillator for meteor observations

We discuss using high solar cycle atmospheric conditions as sensors for observing meteors and their properties. High altitude meteor trails (HAMTs) have sometimes been observed with HPLA (High Power Large Aperture) radars. At other times they are not seen. In the absence of systematic studies on this topic, we surmise that the reason might be differing atmospheric conditions during the observations. At EISCAT HAMTs were observed in 1990 and 1991. Very high meteor trails were observed with Israeli L-band radars in 1998, 1999 and 2001. Through the Leonid activity, around the latest perihelion passage of comet Tempel-Tuttle, optical meteors as high as 200 km were reported. This was partly due to new and better observing methods. However, all the reported periods of high altitude meteors seem to correlate with solar cycle maximum. The enhanced atmospheric and ionospheric densities extend the meteoroid interaction range with the atmosphere along its path, offering a better possibility to distinguish differential ablation of the various meteoric constituents. This should be studied during the next solar maximum, due within a few years.54001011