RAFT Polymerization of a Biorenewable/Sustainable Monomer via a Green Process

A biorenewable polymer is synthesized via a green process using the RAFT principle for the first time in supercritical CO2 at 300 bar and 80 °C. α-Methylene-γ-butyrolactone polymers of various chain lengths and molecular weights are obtained. The molecular weights vary from 10 000 up to 20 000 with low polydispersity indexes (PDI <1.5). Furthermore, the monomer conversion in supercritical CO2 is substantially higher, respectively 85% for ScCO2 compared to ≈65% for polymerizations conducted in dimethyl formamide (DMF) solvent. Chain extensions are carried out to confirm the livingness of the formed polymers in ScCO2. This opens up future possibilities of the formation of different polymer architectures in ScCO2. The polymers synthesized in ScCO2 have glass transition temperature (Tg) values ranging from 155 up to 190 °C. However, the presence of residual monomer encapsulated inside the formed polymer matrix affects the glass transition of the polymer that is lowered by increasing monomer concentrations. Hence, additional research is required to eliminate the remaining monomer concentration in the polymer matrix in order to arrive at the optimal Tg

Expression of complementary RNA from chloroplast transgenes affects editing efficiency of transgene and endogenous chloroplast transcripts

The expression of angiosperm chloroplast genes is modified by C-to-U RNA editing. The mechanism for recognition of the ∼30 C targets of editing is not understood. There is no single consensus sequence surrounding editing sites, though sites can be grouped into small ‘clusters’ of two to five sites exhibiting some sequence similarity. While complementary RNA that guides nucleotides for alteration has been detected in other RNA modification systems, it is not known whether complementary RNA is involved in chloroplast editing site recognition. We investigated the effect of expressing RNA antisense to the sequences −20 to +6 surrounding the RpoB-2 C target of editing, which is a member of a cluster that includes the PsbL-1 and Rps14-1 sites. Previous experiments had shown that chloroplast rpoB transgene transcripts carrying only these 27 nt were edited in vivo at the proper C. Though transcripts carrying sequences −31 to +60 surrounding the RpoB-2 sites were edited in chloroplast transgenic plants, transcripts carrying the −31 to +62 region followed by the 27 nt complementary region were not edited at all. In contrast, a similar construct, in which the C target as well as the preceding and subsequent nucleotides were mismatched within the 27 nt region, was efficiently edited. The presence of any of the four transgenes carrying RpoB-2 sequences in sense and/or antisense orientation resulted in reduced editing at the PsbL-1 site. Chloroplast transgenic plants expressing the three different antisense RNA constructs exhibited abnormal growth and development, though plants expressing the 92 nt sense transcripts were phenotypically normal

Integrated Analysis of Production Potential and Profitability of a Horizontal Well in the Lower Glen Rose Formation, Maverick County, Texas

The U.S. Department of Energy/Morgantown Energy Technology Center (DOE/METC) awarded a contract in 1991 to Prime Energy Corporation (PEC) to demonstrate the benefit of using horizontal wells to recover gas from low permeability formations. The project area was located in the Chittim field of Maverick County, Texas. The Lower Glen Rose Formation in the Chittim field was a promising horizontal well candidate based on the heterogenous nature of the reservoir (suggested by large well-to-well variances in reserves) and the low percentage of economical vertical wells. Since there was substantial evidence of reservoir heterogeneity, it was unknown whether the selected, wellsite would penetrate a reservoir with the desired properties for a horizontal well. Thus, an integrated team was formed to combine geologic analysis, seismic interpretation, reservoir engineering, reservoir simulation, and economic assessment to analyze the production potential and profitability of completing a horizontal well in the Lower Glen Rose formation

Off-resonance saturation as an MRI method to quantify mineral- iron in the post-mortem brain

PURPOSE: To employ an off‐resonance saturation method to measure the mineral‐iron pool in the postmortem brain, which is an endogenous contrast agent that can give information on cellular iron status. METHODS: An off‐resonance saturation acquisition protocol was implemented on a 7 Tesla preclinical scanner, and the contrast maps were fitted to an established analytical model. The method was validated by correlation and Bland‐Altman analysis on a ferritin‐containing phantom. Mineral‐iron maps were obtained from postmortem tissue of patients with neurological diseases characterized by brain iron accumulation, that is, Alzheimer disease, Huntington disease, and aceruloplasminemia, and validated with histology. Transverse relaxation rate and magnetic susceptibility values were used for comparison. RESULTS: In postmortem tissue, the mineral‐iron contrast colocalizes with histological iron staining in all the cases. Iron concentrations obtained via the off‐resonance saturation method are in agreement with literature. CONCLUSIONS: Off‐resonance saturation is an effective way to detect iron in gray matter structures and partially mitigate for the presence of myelin. If a reference region with little iron is available in the tissue, the method can produce quantitative iron maps. This method is applicable in the study of diseases characterized by brain iron accumulation and can complement existing iron‐sensitive parametric methods

Design, Implementation and First Measurements with the Medipix Neutron Camera in CMS

The Medipix detector is the first device dedicated to measuring mixed-field radiation in the CMS cavern and able to distinguish between different particle types. Medipix2-MXR chips bump bonded to silicon sensors with various neutron conversion layers developed by the IEAP CTU in Prague were successfully installed for the 2008 LHC start-up in the CMS experimental and services caverns to measure the flux of various particle types, in particular neutrons. They have operated almost continuously during the 2010 run period, and the results shown here are from the proton run between the beginning of July and the end of October 2010. Clear signals are seen and different particle types have been observed during regular LHC luminosity running, and an agreement in the measured flux rate is found with the simulations. These initial results are promising, and indicate that these devices have the potential for further and future LHC and high energy physics applications as radiation monitoring devices for mixed field environments, including neutron flux monitoring. Further extensions are foreseen in the near future to increase the performance of the detector and its coverage for monitoring in CMS.Comment: 15 pages, 16 figures, submitted to JINS

Double parton interactions in photon+3 jet events in ppbar collisions sqrt{s}=1.96 TeV

We have used a sample of photon+3 jets events collected by the D0 experiment with an integrated luminosity of about 1 fb^-1 to determine the fraction of events with double parton scattering (f_DP) in a single ppbar collision at sqrt{s}=1.96 TeV. The DP fraction and effective cross section (sigma_eff), a process-independent scale parameter related to the parton density inside the nucleon, are measured in three intervals of the second (ordered in pT) jet transverse momentum pT_jet2 within the range 15 < pT_jet2 < 30 GeV. In this range, f_DP varies between 0.23 < f_DP < 0.47, while sigma_eff has the average value sigma_eff_ave = 16.4 +- 0.3(stat) +- 2.3(syst) mb.Comment: 15 pages, 13 figure

Dependence of the ttˉt\bar{t} production cross section on the transverse momentum of the top quark

We present a measurement of the differential cross section for $t\bar{t}$ events produced in $p\bar{p}$ collisions at $\sqrt{s}=1.96$ TeV as a function of the transverse momentum ($p_T$) of the top quark. The selected events contain a high-$p_T$ lepton ($\ell$), four or more jets, and a large imbalance in $p_T$, and correspond to 1 fb${}^{-1}$ of integrated luminosity recorded with the D0 detector. Each event must have at least one candidate for a $b$ jet. Objects in the event are associated through a constrained kinematic fit to the $t\bar{t}\to WbW\bar{b} \to \ell\nu b q\bar{q}'\bar{b}$ process. Results from next-to-leading-order perturbative QCD calculations agree with the measured differential cross section. Comparisons are also provided to predictions from Monte Carlo event generators using QCD calculations at different levels of precision.Comment: 8 pages, 6 figures, 4 tables, updated to reflect the published versio

Observation of ZZ production in ppbar collisions at sqrt(s) = 1.96 TeV

We present an observation for ZZ -> l+l-l'+l'- (l, l' = e or mu) production in ppbar collisions at a center-of-mass energy of sqrt(s) = 1.96 TeV. Using 1.7 fb-1 of data collected by the D0 experiment at the Fermilab Tevatron Collider, we observe three candidate events with an expected background of 0.14 +0.03 -0.02 events. The significance of this observation is 5.3 standard deviations. The combination of D0 results in this channel, as well as in ZZ -> l+l-nunubar, yields a significance of 5.7 standard deviations and a combined cross section of sigma(ZZ) = 1.60 +/- 0.63 (stat.) +0.16 -0.17 (syst.) pb.Comment: 7 pages, 1 figure, 2 tables Modified slightly following review proces