Structure Functions are not Parton Probabilities

The common view that structure functions measured in deep inelastic lepton scattering are determined by the probability of finding quarks and gluons in the target is not correct in gauge theory. We show that gluon exchange between the fast, outgoing partons and target spectators, which is usually assumed to be an irrelevant gauge artifact, affects the leading twist structure functions in a profound way. This observation removes the apparent contradiction between the projectile (eikonal) and target (parton model) views of diffractive and small x_{Bjorken} phenomena. The diffractive scattering of the fast outgoing quarks on spectators in the target causes shadowing in the DIS cross section. Thus the depletion of the nuclear structure functions is not intrinsic to the wave function of the nucleus, but is a coherent effect arising from the destructive interference of diffractive channels induced by final state interactions. This is consistent with the Glauber-Gribov interpretation of shadowing as a rescattering effect.Comment: 35 pages, 8 figures. Discussion of physical consequences of final state interactions amplified. Material on light-cone gauge choices adde

Spatio-temporal dynamics of quantum-well excitons

We investigate the lateral transport of excitons in ZnSe quantum wells by using time-resolved micro-photoluminescence enhanced by the introduction of a solid immersion lens. The spatial and temporal resolutions are 200 nm and 5 ps, respectively. Strong deviation from classical diffusion is observed up to 400 ps. This feature is attributed to the hot-exciton effects, consistent with previous experiments under cw excitation. The coupled transport-relaxation process of hot excitons is modelled by Monte Carlo simulation. We prove that two basic assumptions typically accepted in photoluminescence investigations on excitonic transport, namely (i) the classical diffusion model as well as (ii) the equivalence between the temporal and spatial evolution of the exciton population and of the measured photoluminescence, are not valid for low-temperature experiments.Comment: 8 pages, 6 figure

Light-Front Holography, Light-Front Wavefunctions, and Novel QCD Phenomena

Light-Front Holography, a remarkable feature of the AdS/CFT correspondence, maps amplitudes in anti-de Sitter (AdS) space to frame-independent light-front wavefunctions of hadrons in physical space-time. The model leads to an effective confining light-front QCD Hamiltonian and a single-variable light-front Schrodinger equation which determines the eigenspectrum and the light-front wavefunctions of hadrons for general spin and orbital angular momentum. The coordinate z in AdS space is identified with a Lorentz-invariant coordinate zeta which measures the separation of the constituents within a hadron at equal light-front time and determines the off-shell dynamics of the bound-state wavefunctions and the fall-off in the invariant mass of the constituents. The soft-wall holographic model, modified by a positive-sign dilaton metric, leads to a remarkable one-parameter description of nonperturbative hadron dynamics -- a semi-classical frame-independent first approximation to the spectra and light-front wavefunctions of meson and baryons. The model predicts a Regge spectrum of linear trajectories with the same slope in the leading orbital angular momentum L of hadrons and the radial quantum number n. The hadron eigensolutions projected on the free Fock basis provides the complete set of valence and non-valence light-front Fock state wavefunctions which describe the hadron's momentum and spin distributions needed to compute measures of hadron structure at the quark and gluon level. The effective confining potential also creates quark- antiquark pairs. The AdS/QCD model can be systematically improved by using its complete orthonormal solutions to diagonalize the full QCD light-front Hamiltonian or by applying the Lippmann-Schwinger method to systematically include the QCD interaction terms. A new perspective on quark and gluon condensates is also presented.Comment: Presented at LIGHTCONE 2011, 23 - 27 May, 2011, Dallas, T

Integrated analysis of environmental and genetic influences on cord blood DNA methylation in new-borns

Epigenetic processes, including DNA methylation (DNAm), are among the mechanisms allowing integration of genetic and environmental factors to shape cellular function. While many studies have investigated either environmental or genetic contributions to DNAm, few have assessed their integrated effects. Here we examine the relative contributions of prenatal environmental factors and genotype on DNA methylation in neonatal blood at variably methylated regions (VMRs) in 4 independent cohorts (overall n = 2365). We use Akaike’s information criterion to test which factors best explain variability of methylation in the cohort-specific VMRs: several prenatal environmental factors (E), genotypes in cis (G), or their additive (G + E) or interaction (GxE) effects. Genetic and environmental factors in combination best explain DNAm at the majority of VMRs. The CpGs best explained by either G, G + E or GxE are functionally distinct. The enrichment of genetic variants from GxE models in GWAS for complex disorders supports their importance for disease risk

Priority lists for weed research in the wet- and dry- tropics of north Queensland

A participatory decision making approach was used to prioritize weed research for the wet- and dry-tropics of north Queensland using stakeholders, an expert panel, external reviewers, and the computerized priority-setting system (QDNRM MODSS). From 246 weeds identified, 53 weeds were found to be of major concern. A score was developed for each weed, which accounted for its priority in individual shires and the number of times it was prioritized across the 47 shires. The 22 dry- and 31 wet-tropics weeds were scored by an expert panel against 12 criteria based on economic, environmental and social impacts and current research knowledge with higher scores for greater impact and greater amount of needed research. Several ‘what if’ scenarios were run through QDNRM MODSS by altering the relative importance of criteria. The best criterion for prioritizing weed research was when impact was given higher importance than research needs. Mikania micrantha, Chromolaena odorata, Mimosa invisa, and Eupatorium catarium were the top four weeds of the wet-tropics, and Prosopis spp., Parthenium hysterophorus, Jatropha gossypiifolia, and Cryptostegia grandiflora for the dry-tropics. Priority lists will be used to decide the order in which weeds should be researched and what type of research needed to be done

Frequency and Severity of Neutropenia Associated with Food and Drug Administration Approved and Compounded Formulations of Lomustine in Dogs with Cancer

BACKGROUND: Compounded lomustine is used commonly in veterinary patients. However, the potential variability in these formulations is unknown and concern exists that compounded formulations of drugs may differ in potency from Food and Drug Administration (FDA)‐approved products. HYPOTHESIS/OBJECTIVES: The initial objective of this study was to evaluate the frequency and severity of neutropenia in dogs treated with compounded or FDA‐approved formulations of lomustine. Subsequent analyses aimed to determine the potency of lomustine obtained from several compounding pharmacies. ANIMALS: Thirty‐seven dogs treated with FDA‐approved or compounded lomustine. METHODS: Dogs that received compounded or FDA‐approved lomustine and had pretreatment and nadir CBCs performed were eligible for inclusion. Variables assessed included lomustine dose, neutrophil counts, and severity of neutropenia. Lomustine 5 mg capsules from 5 compounding sources were tested for potency using high‐pressure liquid chromatography (HPLC) with ultraviolet (UV) detection. RESULTS: Twenty‐one dogs received FDA‐approved lomustine and 16 dogs were treated with lomustine prescribed from a single compounding pharmacy. All dogs treated with FDA‐approved lomustine were neutropenic after treatment; 15 dogs (71%) developed grade 3 or higher neutropenia. Four dogs (25%) given compounded lomustine became neutropenic, with 2 dogs (12.5%) developing grade 3 neutropenia. The potency of lomustine from 5 compounding pharmacies ranged from 50 to 115% of the labeled concentration, with 1 sample within ±10% of the labeled concentration. CONCLUSIONS AND CLINICAL IMPORTANCE: These data support broader investigation into the potency and consistency of compounded chemotherapy drugs and highlight the potential need for greater oversight of these products

Expression of arylamine N-acetyltransferase in human intestine

Background—Arylamine N-acetyltransferases in humans (NAT1 and NAT2) catalyse the acetylation of arylamines including food derived heterocyclic arylamine carcinogens. Other substrates include the sulphonamide 5-aminosalicylic acid (5-ASA), which is an NAT1 specific substrate; N-acetylation of 5-ASA is a major route of metabolism. NAT1 and NAT2 are both polymorphic. 
Aims—To investigate NAT expression in apparently healthy human intestines in order to understand the possible role of NAT in colorectal cancer and in the therapeutic response to 5-ASA. 
Methods—The intestines of four organ donors were divided into eight sections. DNA was prepared for genotyping NAT1 and NAT2 and enzymic activities of NAT1 and NAT2 were determined in cytosols prepared from each section. Tissue was fixed for immunohistochemistry with specific NAT antibodies. Western blotting was carried out on all samples of cytosol and on homogenates of separated muscle and villi after microdissection. 
Results—NAT1 activity of all cytosols was greater than NAT2 activity. NAT1 and NAT2 activities correlated with the genotypes of NAT1 and NAT2 and with the levels of NAT1 staining determined by western blotting. The ratio of NAT1:NAT2 activities showed interindividual variations from 2 to 70. NAT1 antigenic activity was greater in villi than in muscle. NAT1 was detected along the length of the villi in the small intestine. In colon samples there was less NAT1 at the base of the crypts with intense staining at the tips. 
Conclusions—The interindividual variation in NAT1 and NAT2 in the colon could affect how individuals respond to exposure to specific NAT substrates including carcinogens and 5-ASA. 

 Keywords: arylamine N-acetyltransferase; 5-aminosalicylate; colorectal cancer; drug metabolism; inflammatory bowel disease; die