1,323 research outputs found
Internal noise driven generalized Langevin equation from a nonlocal continuum model
Starting with a micropolar formulation, known to account for nonlocal
microstructural effects at the continuum level, a generalized Langevin equation
(GLE) for a particle, describing the predominant motion of a localized region
through a single displacement degree-of-freedom (DOF), is derived. The GLE
features a memory dependent multiplicative or internal noise, which appears
upon recognising that the micro-rotation variables possess randomness owing to
an uncertainty principle. Unlike its classical version, the new GLE
qualitatively reproduces the experimentally measured fluctuations in the
steady-state mean square displacement of scattering centers in a polyvinyl
alcohol slab. The origin of the fluctuations is traced to nonlocal spatial
interactions within the continuum. A constraint equation, similar to a
fluctuation dissipation theorem (FDT), is shown to statistically relate the
internal noise to the other parameters in the GLE
Ultra-narrow and widely tunable Mn^(2+) Emission from Single Nanocrystals of ZnS-CdS alloy
Extensively studied Mn-doped semiconductor nanocrystals have invariably
exhibited photoluminescence (PL) over a narrow energy window of width <= 149
meV in the orange-red region and a surprisingly large spectral width (>= 180
meV), contrary to its presumed atomic-like origin. Carrying out emission
measurements on individual single nanocrystals and supported by ab initio
calculations, we show that Mn PL emission, in fact, can (i) vary over a much
wider range (~ 370 meV) covering the deep green-deep red region and (ii)
exhibit widths substantially lower (~ 60-75 meV) than reported so far, opening
newer application possibilities and requiring a fundamental shift in our
perception of the emission from Mn-doped semiconductor nanocrystals.Comment: 5 pages, 5 figure
Transcriptional profiling and consensus molecular subtype (CMS) assignment to understand response and resistance to anti-EGFR therapy in colorectal cancer
View full abstracthttps://openworks.mdanderson.org/leading-edge/1057/thumbnail.jp
Asymmetric rotations and dimerization driven by normal to modulated phase transition in 4-biphenylcarboxy coupled L-phenylalaninate
Amongst the derivatives of 4-biphenylcarboxylic acid and amino acid esters,
the crystal structure of 4-biphenylcarboxy-(L)-phenylalaninate is unusual owing
to its monoclinic symmetry within a pseudo-orthorhombic lattice. The distortion
is described by disparate rotational property around the chiral centers
( -129 degrees and 58 degrees) of the two
molecules in the asymmetric unit. Each of these molecules comprise of planar
biphenyl moieties ( = 0 degrees). Using
temperature dependent single crystal X-ray diffraction experiments we show that
the compound undergoes a phase transition below 124 K that is
characterized by a commensurate modulation wave vector, =
, = . The (3+1) dimensional modulated
structure at = 100 K suggests that the phase transition drives the biphenyl
moieties towards non coplanar conformations with significant variation of
internal torsion (
degrees). These intramolecular rotations lead to dimerization of the molecular
stacks that are described predominantly by intermolecular tilts and small
variations in intermolecular distances. Atypical of modulated structures and
superstructures of biphenyl and other polyphenyls, the rotations of individual
molecules are asymmetric ( 5
degrees) while of one independent molecule is two
to four times larger than the other. Crystal-chemical analysis and phase
relations in superspace suggest multiple competing factors involving
intramolecular steric factors, intermolecular H--CC--H
contacts and weak C--HO hydrogen bonds that govern the
distinctively unequal torsional property of the molecules
Appendiceal Adenocarcinoma PDX Models Have Improved Tumor Growth in an Orthotopic Tumor Environment
https://openworks.mdanderson.org/sumexp23/1085/thumbnail.jp
Goblet Cell Tumors of the Appendix: Clinical & Molecular Features
View full abstracthttps://openworks.mdanderson.org/leading-edge/1047/thumbnail.jp
Utility of plasma tumor marker levels in management of patients with appendiceal adenocarcinoma
View full abstracthttps://openworks.mdanderson.org/leading-edge/1049/thumbnail.jp
Biochar and its importance on nutrient dynamics in soil and plant
Biochar, an environmentally friendly soil conditioner, is produced using several thermochemical processes. It has unique characteristics like high surface area, porosity, and surface charges. This paper reviews the fertilizer value of biochar, and its effects on soil properties, and nutrient use efficiency of crops. Biochar serves as an important source of plant nutrients, especially nitrogen in biochar produced from manures and wastes at low temperature (≤ 400 °C). The phosphorus, potassium, and other nutrient contents are higher in manure/waste biochars than those in crop residues and woody biochars. The nutrient contents and pH of biochar are positively correlated with pyrolysis temperature, except for nitrogen content. Biochar improves the nutrient retention capacity of soil, which depends on porosity and surface charge of biochar. Biochar increases nitrogen retention in soil by reducing leaching and gaseous loss, and also increases phosphorus availability by decreasing the leaching process in soil. However, for potassium and other nutrients, biochar shows inconsistent (positive and negative) impacts on soil. After addition of biochar, porosity, aggregate stability, and amount of water held in soil increase and bulk density decreases. Mostly, biochar increases soil pH and, thus, influences nutrient availability for plants. Biochar also alters soil biological properties by increasing microbial populations, enzyme activity, soil respiration, and microbial biomass. Finally, nutrient use efficiency and nutrient uptake improve with the application of biochar to soil. Thus, biochar can be a potential nutrient reservoir for plants and a good amendment to improve soil properties
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