Engineering topics

Tan, L

Publications and source records attributed to Tan, L.

4 records

DOE OSTI2011

Time-dependent Protein-directed Growth of Gold Nanoparticles within a Single Crystal of Lysozyme

Gold nanoparticles are useful in biomedical applications due to their distinct optical properties and high chemical stability. Reports of the biogenic formation of gold colloids from gold complexes has also led to an increased level of interest in the biomineralization of gold. However, the mechanism responsible for biomolecule-directed gold nanoparticle formation remains unclear due to the lack of structural information about biological systems and the fast kinetics of biomimetic chemical systems in solution. Here we show that intact single crystals of lysozyme can be used to study the time-dependent, protein-directed growth of gold nanoparticles. The protein crystals slow down the growth of the gold nanoparticles, allowing detailed kinetic studies to be carried out, and permit a three-dimensional structural characterization that would be difficult to achieve in solution. Furthermore, we show that additional chemical species can be used to fine-tune the growth rate of the gold nanoparticles.

59 BASIC BIOLOGICAL SCIENCES↗

DOE OSTI2010

Magnetic structure of Gd[subscript 5]Ge[subscript 4]

Gd{sub 5}Ge{sub 4} crystallizes in the orthorhombic space group Pnma, and orders antiferromagnetically below the Neel temperature T{sub N} {approx} 127 K. We have employed x-ray resonant magnetic scattering to elucidate the details of the magnetic structure. The magnetic unit cell is the same as the chemical unit cell. From azimuth scans and the Q dependence of the magnetic scattering, all three Gd sites in the structure were determined to be in the same magnetic space group Pnma. The magnetic moments are primarily aligned along the c axis and the c components of the magnetic moments at the three different sites are equal. The ferromagnetic Gd-rich slabs are stacked antiferromagnetically along the b direction.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗

DOE OSTI2010

Systematics of x-ray resonant scattering amplitudes in RNi[subscript 2]Ge[subscript 2] (R=Gd,Tb,Dy,Ho,Er,Tm): The origin of the branching ratio at the L edges of the heavy rare earths

Abstract not provided

Kim, J W↗

NASA NTRS2005

Status of the MODIS Level 1B Algorithms and Calibration Tables

The Moderate Resolution Imaging Spectroradiometer (MODIS) makes observations using 36 spectral bands with wavelengths from 0.41 to 14.4 m and nadir spatial resolutions of 0.25km, 0.5km, and 1km. It is currently operating onboard the NASA Earth Observing System (EOS) Terra and Aqua satellites, launched in December 1999 and May 2002, respectively. The MODIS Level 1B (L1B) program converts the sensor's on-orbit responses in digital numbers to radiometrically calibrated and geo-located data products for the duration of each mission. Its primary data products are top of the atmosphere (TOA) reflectance factors for the sensor's reflective solar bands (RSB) and TOA spectral radiances for the thermal emissive bands (TEB). The L1B algorithms perform the TEB calibration on a scan-by-scan basis using the sensor's response to the on-board blackbody (BB) and other parameters which are stored in Lookup Tables (LUTs). The RSB calibration coefficients are processed offline and regularly updated through LUTs. In this paper we provide a brief description of the MODIS L1B calibration algorithms and associated LUTs with emphasis on their recent improvements and updates developed for the MODIS collection 5 processing. We will also discuss sensor on-orbit calibration and performance issues that are critical to maintaining L1B data product quality, such as changes in the sensor's response versus scan-angle.

MODIS LEVEL 1B ALGORITHMS↗