bluuebunny/crossref_metadata_2025_split huggingface dataset:
DNA supercoiling and its effects on the structure of DNA
Authors: Wang James C. 
Published: April 2013

ABSTRACT
In prokaryotic organisms, there is strong evidence that the DNA is underwound or negatively supercoiled. The degree of supercoiling of intracellular DNA is less certain, and various estimates that can be made from existing data place the specific linking difference (superhelical density) of intracellular DNA in prokaryotes around –0·04. The effects of negative supercoiling on DNA structure are illustrated by the flipping of alternating C-G or T-G sequences from right-handed B- helical form to the left-handed Z-helical form. For a plasmid containing a 42 base-pair alternating C-G insert, the B-to-Z transition occurs at a specific linking difference of –0·031 in a dilute aqueous buffer; the same transition occurs at a specific linking difference of —0·041 for a plasmid containing a 42 base-pair alternating T-G insert. The probing of the structure of a particular sequence of intracellular DNA is discussed.
DNA sequences and chromosome structure
Authors: Southern Edwin M. 
Published: April 2013

ABSTRACT
In this review evidence for the possible relationship between higher order chromosome structure and the distribution of tandem and dispersed repeated sequences in DNA has been examined. Evidence from studies of chromosome diminution in lower eukaryotes suggests that simple sequence DNAs may have a germ-line function and, in mammals, changes in simple sequence methylation, associated with changes in chromosome condensation, support the idea that the centromeric and telomeric heterochromatin may have a function in germ-line cells. For the major families of dispersed repeats, the weight of available evidence suggests that if they do play a role in chromosome organization, it is not an important one. Cytosine methylation is suggested as a candidate for a role in organizing the chromatin. Long-range patterns of methylation in vertebrates, the relationship of this to gene structure, and the association of changes in methylation with gene activity accord with current evidence linking specific nuclear structures to defined points in coding regions.
c-myc gene activation and chromosomal translocation
Authors: Rabbitts T. H. , Baer R. , Davis M. , Forster A. , Rabbitts P. H. , Malcolm S. 
Published: April 2013

ABSTRACT
Burkitt’s lymphoma cells are characterized by the presence of specific chromosomal translocation bringing the immunoglobulin and the c-myc proto-oncogenes into the proximity of each other. Different translocations involve each of the three immunoglobulin loci but the breakpoint with respect to the c-myc gene is shown to be very variable. In t8/14 the breakpoint occurs upstream from the c-myc gene whilst in the variant lymphomas it occurs downstream from the gene. Possible ways in which the translocation affects the c-myc gene are discussed.
Prophylaxis of Thromboembolic Events in Patients with Nephrotic Syndrome
Authors: Pincus Kathleen J , Hynicka Lauren M 
Published: April 2013

OBJECTIVE To review published literature regarding use of strategies to prevent thrombotic events in patients with nephrotic syndrome (NS). DATA SOURCES The MEDLINE/PubMed, EMBASE, and Cochrane databases were queried from 1980 to December 2012 for articles in English using the search terms nephrotic syndrome, thrombosis, thromboembolism, anticoagulation, warfarin, heparin, low-molecular-weight heparin, enoxaparin, dalteparin, tinzaparin, statin, atorvastatin, fluvastatin, lovastatin, pitavastatin, pravastatin, rosuvastatin, simvastatin, aspirin, direct thrombin inhibitor, rivaroxaban, argatroban, lepirudin, bivalirudin, dabigatran, factor Xa inhibitor, fondaparinux, rivaroxaban, clopidogrel, ticlopidine, and prasugrel. STUDY SELECTION AND DATA EXTRACTION All relevant original studies, meta-analyses, systematic reviews, guidelines, and review articles were assessed for inclusion. References from pertinent articles were examined for additional content not found during the initial search. DATA SYNTHESIS NS leads to multiple complications, including hypercoagulability. A small prospective cohort study used enoxaparin for primary prophylaxis and demonstrated successful prevention of thrombotic events with minimal adverse events. Additional information has come in the form of decision analyses, which show potential decreased morbidity and mortality when primary prophylaxis for thrombotic events is used; however, all data have numerous limitations. Other strategies for thrombus prevention, including statins and antiplatelet agents, also have been investigated. CONCLUSIONS When patients with NS are admitted to the hospital, develop an acute medical illness, or acquire an additional thrombotic events risk factor such as surgery, active malignancy, or pregnancy, consideration for primary pharmacologic prophylaxis with appropriately dosed low-molecular-weight heparin or other indicated anticoagulant should include the potential for increased thrombotic events risk in this patient population. Consideration may also be given to the use of primary pharmacologic prophylaxis with low-molecular-weight heparin or oral vitamin K antagonist in patients with membranous nephropathy once the albumin level drops below 2.0–2.5 g/dL. Short-term use of pharmacologic prophylaxis during the first 6 months following diagnosis warrants further investigation.
The Emerging Role of Tiotropium for Patients with Asthma
Authors: Bollmeier Suzanne Gielow , Lee Shin-Yu 
Published: April 2013

OBJECTIVE To review clinical data on the use of the long-acting anticholinergic agent tiotropium in patients with asthma. DATA SOURCES A literature search was performed via EMBASE and MEDLINE (1966-November 2012). The search was limited to human data published in the English language. Search terms included asthma, tiotropium, and long-acting anticholinergics. STUDY SELECTION AND DATA EXTRACTION Relevant information related to the use of tiotropium in patients with asthma was reviewed. Randomized controlled trials and open-label trials were included. The references of published articles identified in the search were also examined for additional studies appropriate to include in the review. Data were prioritized if they originated from human studies, especially if derived from randomized, placebo-controlled trials. Trials and case reports involving the use of long-acting anticholinergic tiotropium in asthma patients were included; conversely, trials involving ipratropium were not. DATA SYNTHESIS Two large randomized controlled trials support the safety and efficacy of adding tiotropium to the treatment regimen of select patients with poorly controlled asthma already receiving combination high-dose glucocorticosteroid/long-acting β-agonist (LABA) therapy. Pharmacogenomic studies have shown that patients with polymorphisms of the β2-adrenoreceptor ( ADRB2; 16 Arg/Arg and 16 Arg/Gly) are particularly responsive to treatment with tiotropium. Smaller studies indicate that the advantages may be most pronounced in patients with a predominance of sputum neutrophils and that tiotropium can assist with decreasing the inhaled corticosteroid (ICS) dose. An increased risk of cardiovascular events was not identified. CONCLUSIONS Tiotropium should be considered in patients with asthma who remain symptomatic while receiving high-dose ICS and LABA therapy. Specifically, patients with high sputum neutrophil levels or with 16 Arg/Arg or 16 Arg/Gly polymorphism of the ADRB2 gene appear to respond best.
Intravenous Lipid Emulsion to Reverse Acute Drug Toxicity in Pediatric Patients
Authors: Presley Joseph D , Chyka Peter A 
Published: April 2013

OBJECTIVE To identify and summarize published cases in which intravenous lipid emulsion was used to treat pediatric patients with acute drug toxicities. DATA SOURCES PubMed, SCOPUS, and EMBASE were searched up to December 2012 for relevant publications using the terms fat emulsion, lipid emulsion, Intralipid, Liposyn, Medialipide, Medialipid, lipid rescue, ILE, IVLE, IFE, IVFE, or lipid and intoxication, overdose, poisoning, toxicity, resuscitation, antidote, and rescue that were limited to reports in humans aged 18 years or younger. STUDY SELECTION AND DATA EXTRACTION A publication was included if an intravenous lipid emulsion was used to treat acute-onset drug toxicity as reported in prospective or retrospective observational studies, case reports, and abstracts for patients aged 18 years or younger. DATA SYNTHESIS Fourteen case reports were identified in which intravenous lipid emulsion was used to treat toxicities due to local anesthetics and other medications (amitriptyline, diltiazem, bupropion, dosulepin, lamotrigine, quetiapine, and verapamil). Thirteen cases demonstrated a beneficial response in reversing systemic toxicity; 1 of these patients developed hypertriglyceridemia and pancreatitis. The dosage regimens used in this series were dissimilar. CONCLUSIONS There is an increasing interest in use of intravenous lipid emulsions to treat life-threatening toxicity from several lipophilic drugs in adults and children. Although most of the literature describes adult cases, intravenous lipid emulsion has been used in neonates and adolescents, with generally positive outcomes. Given the life-threatening, sometimes near-death situations in which an intravenous lipid emulsion is typically used after conventional resuscitation is unsuccessful and the dramatic positive response to this therapy in most published cases, its use likely will continue. Continued reporting of pediatric cases will guide the optimal use and safety profile of intravenous lipid emulsion for the emergent reversal of drug toxicity.
Synthesis, Properties, and Applications of Hydrophilic Hollow Carbon Nanoparticles from C60 and its Soot
Authors: Kokubo Ken , Ueno Hiroshi , Nakamura Yuji , Yamakura Shizuka , Oshima Takumi 
Published: April 2013

ABSTRACTWe have developed a facile synthetic method for highly water-soluble, hollow carbon nanoparticles with a diameter of ∼1 nm, as a so-called fullerenol. The method was extended to fullerene soot to obtain the corresponding hydrophilic carbon materials, and the products were subjected to IR and elemental analysis. Particle size analysis demonstrated the relatively high dispersion of particles with diameters of ∼70 nm, in water. The surface analysis using FE-SEM showed the difference in morphology between fullerene soot and activated carbon as well as between before and after hydrophilic treatment of the soot with hydrogen peroxide. Moreover, this hydrophilic fullerene soot exhibited high antioxidant activity as compared with fullerenol and C60.
Synergism in Binary (MWNT, SLG) Nano-carbons in Polymer Nano-composites: A Raman Study
Authors: Xu Peng , Loomis James , King Ben , Panchapakesan Balaji 
Published: April 2013

ABSTRACTLoad transfer and mechanical strength of reinforced polymers are fundamental to developing advanced composites. This paper demonstrates enhanced load transfer and mechanical strength due to synergistic effects in binary mixtures of nano-carbon/polymer composites. Different compositional mixtures (always 1 wt. % total) of multi-wall carbon nanotubes (MWNTs) and single-layer graphene (SLG) were mixed in polydimethylsiloxane (PDMS), and effects on load transfer and mechanical strength were studied using Raman spectroscopy. Significant shifts in the G-bands were observed both in tension and compression for single as well binary nano-carbon counterparts in polymer composites. Small amounts of MWNT0.1 dispersed in SLG0.9/PDMS samples (subscripts represents weight percentage) reversed the sign of the Raman wavenumbers from positive to negative values demonstrating reversal of lattice stress. A wavenumber change from 10 cm-1 in compression (-10% strain) to 10 cm-1 in tension (50% strain), and an increase in elastic modulus of ∼103% was observed for MWNT0.1SLG0.9/PDMS with applied uniaxial tension. Presence of MWNTs in the matrix reduced the segmental polymeric chain length and provided limited extensibility to the chains. This in turn eliminated compressive deformation of SLG and significantly enhanced load transfer and mechanical strength of composites in tension. The orientation order of MWNT with application of uniaxial tensile strain directly affected the shift in Raman wavenumbers (2D band and G-band) and load transfer. It is observed that the cooperative behavior of binary nano-carbons in polymer composites resulted in enhanced load transfer and mechanical strength. Such binary compositions could be fundamental to developing advanced composites.
The Physical Essence of Mono-dispersed Nanometer Particle Surface Energy by Boundary bond Interaction
Authors: Su Lihong , Yin Xiaowei , Wan Caixia , Qiao Shengru 
Published: April 2013

ABSTRACTThe surface energy quantifies the disruption of intermolecular bond that occurs when a surface is created. The paper discusses critical size dc of mono-dispersed nanometer particle by analyzing the change of interfacial surface energy. The traditional theory neglects that the mono-dispersed nanometer particle has quantum standing wave in its internal structure with a size below critical dc. During the preparation of mono-dispersed nanometer powder, the large surface energy is formed ont only by cutting surface bond but also by forming quantum standing wave that opposites to interfacial edge unsaturated bond on the nanometer partcile surface atom. The preparation process of nanometer material needs more energy than the size surpass dc material. The new theory can explain why the melting point of nanometer powder decreases and other phenomina of nanometer material.
Effect of Growth Pressure and Gas-Phase Chemistry on the Optical Quality of InGaN/GaN Multi-Quantum Wells
Authors: Armour E.A. , Byrnes D. , Arif R.A. , Lee S.M. , Berkman E.A. , Papasouliotis G.D. , Li C. , Stokes E.B. , Hefti R. , Moyer P. 
Published: April 2013

ABSTRACTBlue light-emitting diodes (LED's), utilizing InGaN-based multi-quantum well (MQW) active regions deposited by organometallic chemical vapor epitaxy (OMVPE), are one of the fundamental building-blocks for current solid-state lighting applications. Studies [1,2] have previously been conducted to explore the optical and physical properties of the active MQW's over a variety of different OMVPE growth conditions. However, the conclusions of these papers have often been contradictory, possibly due to a limited data set or lack of understanding of the fundamental fluid dynamics and gas-phase chemistry that occurs during the deposition process.Multi-quantum well structures grown over a range of pressures from typical low-pressure production processes at 200 Torr, up to near-atmospheric growth conditions at 700 Torr, have been investigated in this study. At all growth pressures, clear trends of gas-phase chemical reactions are observed for increased gas residence times (lower gas speeds from the injector flange and lower rotation rates) and increased V/III ratios (higher NH3 flows).Confocal microscopy, excitation-dependent PL (PLE), and time-resolved photo-luminescence (TRPL) have been employed on these MQW structures to investigate the carrier lifetime characteristics. Confocal emission images show spatially-separated bright and dark regions. The bright regions are red-shifted in wavelength relative to the dark regions, suggesting microscopic spatial localization of high indium content regions. As the growth pressure and gas residence times are reduced, a larger difference in band-gap between bright and dark regions, longer lifetimes, and higher average PL intensities can be obtained, indicating that higher optical quality material can be realized. Optimized MQW's grown at high pressure exhibit higher PLE slope intensities and IQE characteristics than lower pressure samples. Results on simple LED structures indicate that the improvement in MQW optical quality at high pressures translates to higher output power at a 110 A/cm2 injection current density.
Negative Contrast Curves for Two-photon Free Radical Polymerization Systems and Their Potential Applications in Sub-diffraction Limited Two-photon Photolithography
Authors: DeVoe Robert J. , Lee Tzu-Chen , Gates Brian J. 
Published: April 2013

ABSTRACT:Two-photon fabrication is a powerful method of fabricating complex microstructures. Superresolution by methods analogous to stimulated emission depletion (STED) has been described previously, enabling sub-100 nm imaging with 800 nm light. STED-related methods of enhancing imaging resolution require photoresists with exposure conditions for which the photoresist exhibits negative contrast, i.e., image density decreases with increasing exposure from the depletion beam. We have observed decreasing voxel size with increasing exposure during two-photon initiated polymerization of acrylate- and methacrylate-based photoresists, that is, negative imaging contrast, γ < 0, independent of the type of photoinitiator. Negative contrast is not observed in epoxy-type photoresists containing photoacid generators. An investigation of the exposure conditions has led us to conclude that radical-radical recombination at high exposure is responsible for negative contrast. Results of the investigation, discussion of the proposed mechanism for negative contrast and implications for two-photon superresolution will be presented.
Atomistic Ordering in Body Centered Cubic Uranium-Zirconium Alloy
Authors: Moore Alex P. , Beeler Ben , Baskes Michael , Okuniewski Maria , Deo Chaitanya S. 
Published: April 2013

ABSTRACTThe metallic binary-alloy fuel Uranium-Zirconium is important for the use of the new generation of advanced fast reactors. Uranium-Zirconium goes through a phase transition at higher temperatures to a (gamma) Body Centered Cubic (BCC) phase. The BCC high temperature phase is particularly important, since the BCC phase corresponds to the temperature range in which the fast reactors will operate. A semi-empirical MEAM (Modified Embedded Atom Method) potential is presented for Uranium-Zirconium. The physical properties of the Uranium-Zirconium binary alloy were reproduced using Molecular Dynamics (MD) simulations and Monte Carlo (MC) simulations with the MEAM potential. This is a large step in making a computationally acceptable fuel performance code.
Traps and Defects in Pre- and Post-Aged AlGaN-GaN High Electron Mobility Transistors
Authors: Sin Yongkun , Foran Brendan , Presser Nathan , LaLumondiere Stephen , Lotshaw William , Moss Steven C. 
Published: April 2013

ABSTRACTHigh electron mobility transistors (HEMTs) based on AlGaN/GaN hetero-structures are promising for both commercial and military applications that require high power, high voltage, and high temperature operation. Reliability and radiation effects of AlGaN-GaN HEMTs need to be thoroughly studied before they are successfully deployed in potential satellite systems. A few AlGaN HEMT manufacturers have recently reported encouraging reliability, but long-term reliability of these devices under high electric field operation and extreme space environments still remains a major concern. A large number of traps and defects are present in the bulk as well as at the surface, leading to undesirable characteristics including current collapse. The present study is part of our investigation to study traps and defects in the AlGaN HEMT devices using micro-analytical techniques before and after they are life-tested.
Wettability Alteration in High-Temperature and High-Salinity Carbonate Reservoirs
Authors: Sharma Gaurav , Mohanty Kishore K. 
Published: April 2013

Summary
The goal of this work was to change the wettability of a carbonate rock from mixed-wet toward water-wet at high temperature and high salinity. Three types of surfactants in dilute concentrations (&lt;0.2 wt%) were used. Initial surfactant screening was performed on the basis of aqueous stability at these harsh conditions. Contact-angle experiments on aged calcite plates were conducted to narrow the list of surfactants, and spontaneous-imbibition experiments were conducted on field cores for promising surfactants. Secondary waterflooding was carried out in cores with and without the wettability-altering surfactants. It was observed that most but not all surfactants were aqueous-unstable by themselves at these harsh conditions. Dual-surfactant systems, mixtures of a nonionic and a cationic surfactant, increased the aqueous stability. Some of the dual-surfactant systems proved effective for wettability alteration and could recover could recover 70 to 80% OOIP (original oil in place) during spontaneous imbibition. Secondary waterflooding with the wettability-altering surfactant increased the oil recovery over the waterflooding without the surfactants (from 29 to 40% of OOIP).
Frac Packing: Best Practices and Lessons Learned From More Than 600 Operations
Authors: Weirich John , Li Jeff , Abdelfattah Tarik , Pedroso Carlos 
Published: April 2013

Summary
Frac packing is a completion technique that merges two distinct processes—hydraulic fracturing and gravel packing. The main challenge of a frac-pack completion is the successful creation of high-conductivity fractures with the tip-screenout (TSO) technique and the placement of proppant within those fractures and in the annulus between the screen and wellbore wall. This is further compounded by having to do so in an ultra high-permeability environment, in which high fluid-leakoff rates are evident.
From 1997 to 2006, job data from more than 600 frac-packing operations, representing an estimated 5% of the worldwide total, have been compiled into a database. This paper reviews well information and key frac-packing parameters. Also summarized are engineering implementations and challenges, best practices, and lessons learned. Essential frac-pack design parameters that were attained from the step-rate test (SRT) and minifrac test are evaluated. These include bottomhole pressure, rock-closure time, and fracturing-fluid efficiency. Downhole pressure and temperature are also discussed because of their importance to the post-completion efficiency evaluation and fracturing-fluid-optimization phase.
Worldwide case histories are provided that demonstrate how to both deploy different frac-packing systems and pack the wellbore during extreme conditions with improved packing efficiency and a higher chance of success.