Clementine Observations of the Zodiacal Light and the Dust Content of the Inner Solar System

Using the Moon to occult the Sun, the Clementine spacecraft used its navigation cameras to map the inner zodiacal light at optical wavelengths over elongations of 3-30 degrees from the Sun. This surface brightness map is then used to infer the spatial distribution of interplanetary dust over heliocentric distances of about 10 solar radii to the orbit of Venus. We also apply a simple model that attributes the zodiacal light as being due to three dust populations having distinct inclination distributions, namely, dust from asteroids and Jupiter-family comets (JFCs), dust from Halley-type comets, and an isotropic cloud of dust from Oort Cloud comets. The best-fitting scenario indicates that asteroids + JFCs are the source of about 45% of the optical dust cross-section seen in the ecliptic at 1 AU, but that at least 89% of the dust cross-section enclosed by a 1 AU radius sphere is of a cometary origin. When these results are extrapolated out to the asteroid belt, we find an upper limit on the mass of the light-reflecting asteroidal dust that is equivalent to a 12 km asteroid, and a similar extrapolation of the isotropic dust cloud out to Oort Cloud distances yields a mass equivalent to a 30 km comet, although the latter mass is uncertain by orders of magnitude.Comment: To be published in Icaru

Formation of Metal Oxide Nanowire Networks (Nanowebs) of Low-Melting Metals

A method of producing networks of low melting metal oxides such as crystalline gallium oxide comprised of one-dimensional nanostructures. Because of the unique arrangement of wires, these crystalline networks defined as “nanowebs”, “nanowire networks”, and/or “two-dimensional nanowires”. Nanowebs contain wire densities on the order of 109/cm2. A possible mechanism for the fast self-assembly of crystalline metal oxide nanowires involves multiple nucleation and coalescence via oxidation-reduction reactions at the molecular level. The preferential growth of nanowires parallel to the substrate enables them to coalesce into regular polygonal networks. The individual segments of the polygonal network consist of both nanowires and nanotubules of β-gallium oxide. The synthesis of highly crystalline noncatalytic low melting metals such as β-gallium oxide tubes, nanowires, and nanopaintbrushes is accomplished using molten gallium and microwave plasma containing a mixture of monoatomic oxygen and hydrogen. Gallium oxide nanowires were 20-100 nm thick and tens to hundreds of microns long. Transmission electron microscopy (TEM) revealed the nanowires to be highly crystalline and devoid of any structural defects. Results showed that multiple nucleation and growth of gallium oxide nanostructures can occur directly out of molten gallium exposed to appropriate composition of hydrogen and oxygen in the gas phase. The method of producing nanowebs is extendible to other low melting metals and their oxides such as for example: zinc oxide, tin oxide, aluminum oxide, bismuth oxide, and titanium dioxide

Direct Band Gap Gallium Antimony Phosphide (GaSb\u3csub\u3ex\u3c/sub\u3eP\u3csub\u3e1-x\u3c/sub\u3e) Alloys

Here, we report direct band gap transition for Gallium Phosphide (GaP) when alloyed with just 1–2 at% antimony (Sb) utilizing both density functional theory based computations and experiments. First principles density functional theory calculations of GaSbxP1−x alloys in a 216 atom supercell configuration indicate that an indirect to direct band gap transition occurs at x = 0.0092 or higher Sb incorporation into GaSbxP1−x. Furthermore, these calculations indicate band edge straddling of the hydrogen evolution and oxygen evolution reactions for compositions ranging from x = 0.0092 Sb up to at least x = 0.065 Sb making it a candidate for use in a Schottky type photoelectrochemical water splitting device. GaSbxP1−x nanowires were synthesized by reactive transport utilizing a microwave plasma discharge with average compositions ranging from x = 0.06 to x = 0.12 Sb and direct band gaps between 2.21 eV and 1.33 eV. Photoelectrochemical experiments show that the material is photoactive with p-type conductivity. This study brings attention to a relatively uninvestigated, tunable band gap semiconductor system with tremendous potential in many fields

Design of intelligent mesoscale periodic array structures utilizing smart hydrogel

Mesoscale Periodic Array Structures (MPAS, also known as crystalline colloidal arrays), composed of aqueous or nonaqueous dispersions of self-assembled submicron colloidal spheres are emerging toward the development of advanced optical devices for technological applications. This is because of their unique optical diffraction properties and the ease with which these intriguing properties can be modulated experimentally. Moreover our recent advancements in this area which include 'locking' the liquid MPAS into solid or semisolid polymer matrices for greater stability with longer life span, and incorporation of CdS quantum dots and laser dyes into colloidal spheres to obtain nonlinear optical (NLO) responses further corroborate the use of MPAS in optical technology. Our long term goal is fabrication of all-optical and electro-optical devices such as spatial light modulators for optical signal processing and flat panel display devices by utilizing intelligent nonlinear periodic array structural materials. Here we show further progress in the design of novel linear MPAS which have the ability to sense and respond to an external source such as temperature. This is achieved by combining the self-assembly properties of polymer colloidal spheres and thermoshrinking properties of smart polymer gels. At selected temperatures the periodic array efficiently Bragg diffracts light and transmits most of the light at other temperatures. Hence these intelligent systems are of potential use as fixed notch filters optical switches or limiters to protect delicate optical sensors from high intensity laser radiation

Phase I Study of the Safety and Pharmacokinetics of Plerixafor in Children Undergoing a Second Allogeneic Hematopoietic Stem Cell Transplantation for Relapsed or Refractory Leukemia

AbstractThe safety, pharmacokinetics, and biological effect of plerixafor in children as part of a conditioning regimen for chemo-sensitization in allogeneic hematopoietic stem cell transplantation (HSCT) have not been studied. This is a phase I study of plerixafor designed to evaluate its tolerability at dose of .24 mg/kg given intravenously on day −4 (level 1); day −4 and day −3 (level 2); or day −4, day −3, and day −2 (level 3) in combination with fludarabine, thiotepa, melphalan, and rabbit antithymocytic globulin for a second allogeneic HSCT in children with refractory or relapsed leukemia. Immunophenotype analysis was performed on blood and bone marrow before and after plerixafor administration. Twelve patients were enrolled. Plerixafor at all 3 levels was well tolerated without dose-limiting toxicity. Transient gastrointestinal side effects of National Cancer Institute–grade 1 or 2 in severity were the most common adverse events. The area under the concentration-time curve increased proportionally to the dose level. Plerixafor clearance was higher in males and increased linearly with body weight and glomerular filtration rate. The clearance decreased and the elimination half-life increased significantly from dose level 1 to 3 (P < .001). Biologically, the proportion of CXCR4+ blasts and lymphocytes both in the bone marrow and peripheral blood increased after plerixafor administration

Steroid Binding to Autotaxin Links Bile Salts and Lysophosphatidic Acid Signalling

Autotaxin (ATX) generates the lipid mediator lysophosphatidic acid (LPA). ATX-LPA signalling is involved in multiple biological and pathophysiological processes, including vasculogenesis, fibrosis, cholestatic pruritus and tumour progression. ATX has a tripartite active site, combining a hydrophilic groove, a hydrophobic lipid-binding pocket and a tunnel of unclear function. We present crystal structures of rat ATX bound to 7α-hydroxycholesterol and the bile salt tauroursodeoxycholate (TUDCA), showing how the tunnel selectively binds steroids. A structure of ATX simultaneously harbouring TUDCA in the tunnel and LPA in the pocket, together with kinetic analysis, reveals that bile salts act as partial non-competitive inhibitors of ATX, thereby attenuating LPA receptor activation. This unexpected interplay between ATX-LPA signalling and select steroids, notably natural bile salts, provides a molecular basis for the emerging association of ATX with disorders associated with increased circulating levels of bile salts. Furthermore, our findings suggest potential clinical implications in the use of steroid drugs

Structure and properties of ilmenite from first principles

Published versio

Evidence-based guideline : unexplained infertility

The GDG would like to acknowledge the help of many clinicians and professional organizations who refereed the content of the guideline and submitted helpful comments to the draft version. Special thanks to the steering committee of the ESHRE SIG Andrology for the feedback on the formulations of the key questions and the final draft of the guideline.Peer reviewe