Aspects of asphaltene aggregation obtained from coarse-grained molecular modeling

We have performed a molecular-simulation-based study to explore some of the underlying mechanisms of asphaltene aggregation. The daunting complexity of the crude oil + asphaltene system precludes any type of meaningful molecular simulation unless some assumptions are made with respect to the key physical and chemical properties that must be explicitly described. In the present work, we focus on molecular simulations of a coarse-grained model of asphaltene molecules in pure solvents, which are based on the assumption that the general size asymmetry and asphaltene morphology play a key role in the aggregation process. We use simple single isotropic Lennard-Jones sites to represent paraffinic and aromatic C₆ segments, which are used as building blocks for the description of continental asphaltene models and solvent moieties. The energy and size parameters for the intermolecular models (ε and σ) for solute and solvent molecules are chosen to reproduce the experimental density of the liquid phase for different mixtures. An explicit pure solvent is considered, and the relationship between the aggregation mechanism and the solvent nature is investigated through direct simulation of the aggregation process. The results reproduce accurately expected trends observed for more-complex models as well as experiments, for example, strong aggregation of asphaltene molecules in <i>n-</i>heptane and high solubility in toluene. Different asphaltene models based on different geometries reveal that even at this level of simplification the topology of the molecules (number and position of aliphatic branches) does affect the way molecules aggregate

Evidence for a Prepore Stage in the Action of Clostridium perfringens Epsilon Toxin

Clostridium perfringens epsilon toxin (ETX) rapidly kills MDCK II cells at 37°C, but not 4°C. The current study shows that, in MDCK II cells, ETX binds and forms an oligomeric complex equally well at 37°C and 4°C but only forms a pore at 37°C. However, the complex formed in MDCK cells treated with ETX at 4°C has the potential to form an active pore, since shifting those cells to 37°C results in rapid cytotoxicity. Those results suggested that the block in pore formation at 4°C involves temperature-related trapping of ETX in a prepore intermediate on the MDCK II cell plasma membrane surface. Evidence supporting this hypothesis was obtained when the ETX complex in MDCK II cells was shown to be more susceptible to pronase degradation when formed at 4°C vs. 37°C; this result is consistent with ETX complex formed at 4°C remaining present in an exposed prepore on the membrane surface, while the ETX prepore complex formed at 37°C is unaccessible to pronase because it has inserted into the plasma membrane to form an active pore. In addition, the ETX complex rapidly dissociated from MDCK II cells at 4°C, but not 37°C; this result is consistent with the ETX complex being resistant to dissociation at 37°C because it has inserted into membranes, while the ETX prepore readily dissociates from cells at 4°C because it remains on the membrane surface. These results support the identification of a prepore stage in ETX action and suggest a revised model for ETX cytotoxicity, i) ETX binds to an unidentified receptor, ii) ETX oligomerizes into a prepore on the membrane surface, and iii) the prepore inserts into membranes, in a temperature-sensitive manner, to form an active pore

New insights into the neolithisation process in southwest Europe according to spatial density analysis from calibrated radiocarbon dates

The agricultural way of life spreads throughout Europe via two main routes: the Danube corridor and the Mediterranean basin. Current archaeological literature describes the arrival to the Western Mediterranean as a rapid process which involves both demic and cultural models, and in this regard, the dispersal movement has been investigated using mathematical models, where the key factors are time and space. In this work, we have created a compilation of all available radiocarbon dates for the whole of Iberia, in order to draw a chronological series of maps to illustrate temporal and spatial patterns in the neolithisation process. The maps were prepared by calculating the calibrated 14C date probability density curves, as a proxy to show the spatial dynamics of the last hunter-gatherers and first farmers. Several scholars have pointed out problems linked with the variability of samples, such as the overrepresentation of some sites, the degree of regional research, the nature of the dated samples and above all the archaeological context, but we are confident that the selected dates, after applying some filters and statistical protocols, constitute a good way to approach settlement spatial patterns in Iberia at the time of the neolithisation process

T2K neutrino flux prediction

cited By 15 art_number: 012001 affiliation: Centre for Particle Physics, Department of Physics, University of Alberta, Edmonton, AB, Canada; Albert Einstein Center for Fundamental Physics, Laboratory for High Energy Physics (LHEP), University of Bern, Bern, Switzerland; Department of Physics, Boston University, Boston, MA, United States; Department of Physics and Astronomy, University of British Columbia, Vancouver, BC, Canada; Department of Physics and Astronomy, University of California Irvine, Irvine, CA, United States; IRFU, CEA Saclay, Gif-sur-Yvette, France; Institute for Universe and Elementary Particles, Chonnam National University, Gwangju, South Korea; Department of Physics, University of Colorado at Boulder, Boulder, CO, United States; Department of Physics, Colorado State University, Fort Collins, CO, United States; Department of Physics, Dongshin University, Naju, South Korea; Department of Physics, Duke University, Durham, NC, United States; IN2P3-CNRS, Laboratoire Leprince-Ringuet, Ecole Polytechnique, Palaiseau, France; Institute for Particle Physics, ETH Zurich, Zurich, Switzerland; Section de Physique, DPNC, University of Geneva, Geneva, Switzerland; H. Niewodniczanski Institute of Nuclear Physics PAN, Cracow, Poland; High Energy Accelerator Research Organization (KEK), Tsukuba, Ibaraki, Japan; Institut de Fisica d’Altes Energies (IFAE), Bellaterra (Barcelona), Spain; IFIC (CSIC and University of Valencia), Valencia, Spain; Department of Physics, Imperial College London, London, United Kingdom; INFN Sezione di Bari, Dipartimento Interuniversitario di Fisica, Università e Politecnico di Bari, Bari, Italy; INFN Sezione di Napoli and Dipartimento di Fisica, Università di Napoli, Napoli, Italy; INFN Sezione di Padova, Dipartimento di Fisica, Università di Padova, Padova, Italy; INFN Sezione di Roma, Università di Roma la Sapienza, Roma, Italy; Institute for Nuclear Research, Russian Academy of Sciences, Moscow, Russian Federation; Kobe University, Kobe, Japan; Department of Physics, Kyoto University, Kyoto, Japan; Physics Department, Lancaster University, Lancaster, United Kingdom; Department of Physics, University of Liverpool, Liverpool, United Kingdom; Department of Physics and Astronomy, Louisiana State University, Baton Rouge, LA, United States; Université de Lyon, Université Claude Bernard Lyon 1, IPN Lyon (IN2P3), Villeurbanne, France; Department of Physics, Miyagi University of Education, Sendai, Japan; National Centre for Nuclear Research, Warsaw, Poland; State University of New York at Stony Brook, Stony Brook, NY, United States; Department of Physics and Astronomy, Osaka City University, Department of Physics, Osaka, Japan; Department of Physics, Oxford University, Oxford, United Kingdom; UPMC, Université Paris Diderot, Laboratoire de Physique Nucléaire et de Hautes Energies (LPNHE), Paris, France; Department of Physics and Astronomy, University of Pittsburgh, Pittsburgh, PA, United States; School of Physics, Queen Mary University of London, London, United Kingdom; Department of Physics, University of Regina, Regina, SK, Canada; Department of Physics and Astronomy, University of Rochester, Rochester, NY, United States; III. Physikalisches Institut, RWTH Aachen University, Aachen, Germany; Department of Physics and Astronomy, Seoul National University, Seoul, South Korea; Department of Physics and Astronomy, University of Sheffield, Sheffield, United Kingdom; University of Silesia, Institute of Physics, Katowice, Poland; STFC, Rutherford Appleton Laboratory, Harwell Oxford, Warrington, United Kingdom; Department of Physics, University of Tokyo, Tokyo, Japan; Institute for Cosmic Ray Research, Kamioka Observatory, University of Tokyo, Kamioka, Japan; Institute for Cosmic Ray Research, Research Center for Cosmic Neutrinos, University of Tokyo, Kashiwa, Japan; Department of Physics, University of Toronto, Toronto, ON, Canada; TRIUMF, Vancouver, BC, Canada; Department of Physics and Astronomy, University of Victoria, Victoria, BC, Canada; Faculty of Physics, University of Warsaw, Warsaw, Poland; Institute of Radioelectronics, Warsaw University of Technology, Warsaw, Poland; Department of Physics, University of Warwick, Coventry, United Kingdom; Department of Physics, University of Washington, Seattle, WA, United States; Department of Physics, University of Winnipeg, Winnipeg, MB, Canada; Faculty of Physics and Astronomy, Wroclaw University, Wroclaw, Poland; Department of Physics and Astronomy, York University, Toronto, ON, Canada references: Astier, P., (2003) Nucl. Instrum. Methods Phys. Res., Sect. A, 515, p. 800. , (NOMAD Collaboration), NIMAER 0168-9002 10.1016/j.nima.2003.07.054; Ahn, M., (2006) Phys. Rev. D, 74, p. 072003. , (K2K Collaboration), PRVDAQ 1550-7998 10.1103/PhysRevD.74.072003; Adamson, P., (2008) Phys. Rev. D, 77, p. 072002. , (MINOS Collaboration), PRVDAQ 1550-7998 10.1103/PhysRevD.77.072002; Aguilar-Arevalo, A., (2009) Phys. Rev. D, 79, p. 072002. , (MiniBooNE Collaboration), PRVDAQ 1550-7998 10.1103/PhysRevD.79.072002; (2003) Letter of Intent: Neutrino Oscillation Experiment at JHF, , http://neutrino.kek.jp/jhfnu/loi/loi_JHFcor.pdf, T2K Collaboration; Abe, K., (2011) Nucl. Instrum. Methods Phys. Res., Sect. A, 659, p. 106. , (T2K Collaboration), NIMAER 0168-9002 10.1016/j.nima.2011.06.067; Abe, K., (2011) Phys. Rev. Lett., 107, p. 041801. , (T2K Collaboration), PRLTAO 0031-9007 10.1103/PhysRevLett.107.041801; Abe, K., (2012) Phys. Rev. D, 85, p. 031103. , (T2K Collaboration), PRVDAQ 1550-7998 10.1103/PhysRevD.85.031103; Fukuda, Y., (2003) Nucl. Instrum. Methods Phys. Res., Sect. A, 501, p. 418. , NIMAER 0168-9002 10.1016/S0168-9002(03)00425-X; Beavis, D., Carroll, A., Chiang, I., (1995), Physics Design Report, BNL 52459Abgrall, N., (2011) Phys. Rev. C, 84, p. 034604. , (NA61/SHINE Collaboration), PRVCAN 0556-2813 10.1103/PhysRevC.84.034604; Abgrall, N., (2012) Phys. Rev. C, 85, p. 035210. , (NA61/SHINE Collaboration), PRVCAN 0556-2813 10.1103/PhysRevC.85.035210; Bhadra, S., (2013) Nucl. Instrum. Methods Phys. Res., Sect. A, 703, p. 45. , NIMAER 0168-9002 10.1016/j.nima.2012.11.044; Van Der Meer, S., Report No. CERN-61-07Palmer, R., Report No. CERN-65-32, 141Ichikawa, A., (2012) Nucl. Instrum. Methods Phys. Res., Sect. A, 690, p. 27. , NIMAER 0168-9002 10.1016/j.nima.2012.06.045; Matsuoka, K., (2010) Nucl. Instrum. Methods Phys. Res., Sect. A, 624, p. 591. , NIMAER 0168-9002 10.1016/j.nima.2010.09.074; Abe, K., (2012) Nucl. Instrum. Methods Phys. Res., Sect. A, 694, p. 211. , (T2K Collaboration), NIMAER 0168-9002 10.1016/j.nima.2012.03.023; Abgrall, N., (2011) Nucl. Instrum. Methods Phys. Res., Sect. A, 637, p. 25. , (T2K ND280 TPC Collaboration), NIMAER 0168-9002 10.1016/j.nima.2011.02. 036; Amaudruz, P.-A., (2012) Nucl. Instrum. Methods Phys. Res., Sect. A, 696, p. 1. , (T2K ND280 FGD Collaboration), NIMAER 0168-9002 10.1016/j.nima.2012.08. 020; Battistoni, G., Cerutti, F., Fasso, A., Ferrari, A., Muraro, S., Ranft, J., Roesler, S., Sala, P.R., (2007) AIP Conf. Proc., 896, p. 31. , APCPCS 0094-243X 10.1063/1.2720455; A. Ferrari, P. R. Sala, A. Fasso, and J. Ranft, Report No. CERN-2005-010A. Ferrari P. R. Sala A. Fasso J. Ranft Report No. SLAC-R-773A. Ferrari P. R. Sala A. Fasso J. Ranft Report No. INFN-TC-05-11R. Brun, F. Carminati, and S. Giani, Report No. CERN-W5013Zeitnitz, C., Gabriel, T.A., (1993) Proceedings of International Conference on Calorimetry in High Energy Physics, , in Elsevier Science B.V., Tallahassee, FL; Fasso, A., Ferrari, A., Ranft, J., Sala, P.R., Proceedings of the International Conference on Calorimetry in High Energy Physics, 1994, , in; Beringer, J., (2012) Phys. Rev. D, 86, p. 010001. , (Particle Data Group), PRVDAQ 1550-7998 10.1103/PhysRevD.86.010001; Eichten, T., (1972) Nucl. Phys. B, 44, p. 333. , NUPBBO 0550-3213 10.1016/0550-3213(72)90120-4; Allaby, J.V., Tech. Rep. 70-12 (CERN, 1970)Chemakin, I., (2008) Phys. Rev. C, 77, p. 015209. , PRVCAN 0556-2813 10.1103/PhysRevC.77.015209; Abrams, R.J., Cool, R., Giacomelli, G., Kycia, T., Leontic, B., Li, K., Michael, D., (1970) Phys. Rev. D, 1, p. 1917. , PRVDAQ 0556-2821 10.1103/PhysRevD.1.1917; Allaby, J.V., (1970) Yad. Fiz., 12, p. 538. , IDFZA7 0044-0027; Allaby, J.V., (1969) Phys. Lett. B, 30, p. 500. , PYLBAJ 0370-2693 10.1016/0370-2693(69)90184-1; Allardyce, B.W., (1973) Nucl. Phys. A, 209, p. 1. , NUPABL 0375-9474 10.1016/0375-9474(73)90049-3; Bellettini, G., Cocconi, G., Diddens, A.N., Lillethun, E., Matthiae, G., Scanlon, J.P., Wetherell, A.M., (1966) Nucl. Phys., 79, p. 609. , NUPHA7 0029-5582 10.1016/0029-5582(66)90267-7; Bobchenko, B.M., (1979) Sov. J. Nucl. Phys., 30, p. 805. , SJNCAS 0038-5506; Carroll, A.S., (1979) Phys. Lett. B, 80, p. 319. , PYLBAJ 0370-2693 10.1016/0370-2693(79)90226-0; Cronin, J.W., Cool, R., Abashian, A., (1957) Phys. Rev., 107, p. 1121. , PHRVAO 0031-899X 10.1103/PhysRev.107.1121; Chen, F.F., Leavitt, C., Shapiro, A., (1955) Phys. Rev., 99, p. 857. , PHRVAO 0031-899X 10.1103/PhysRev.99.857; Denisov, S.P., Donskov, S.V., Gorin, Yu.P., Krasnokutsky, R.N., Petrukhin, A.I., Prokoshkin, Yu.D., Stoyanova, D.A., (1973) Nucl. Phys. B, 61, p. 62. , NUPBBO 0550-3213 10.1016/0550-3213(73)90351-9; Longo, M.J., Moyer, B.J., (1962) Phys. Rev., 125, p. 701. , PHRVAO 0031-899X 10.1103/PhysRev.125.701; Vlasov, A.V., (1978) Sov. J. Nucl. Phys., 27, p. 222. , SJNCAS 0038-5506; Feynman, R., (1969) Phys. Rev. Lett., 23, p. 1415. , PRLTAO 0031-9007 10.1103/PhysRevLett.23.1415; Bonesini, M., Marchionni, A., Pietropaolo, F., Tabarelli De Fatis, T., (2001) Eur. Phys. J. C, 20, p. 13. , EPCFFB 1434-6044 10.1007/s100520100656; Barton, D.S., (1983) Phys. Rev. D, 27, p. 2580. , PRVDAQ 0556-2821 10.1103/PhysRevD.27.2580; Skubic, P., (1978) Phys. Rev. D, 18, p. 3115. , PRVDAQ 0556-2821 10.1103/PhysRevD.18.3115; Feynman, R.P., (1972) Photon-Hadron Interactions, , Benjamin, New York; Bjorken, J.D., Paschos, E.A., (1969) Phys. Rev., 185, p. 1975. , PHRVAO 0031-899X 10.1103/PhysRev.185.1975; Taylor, F.E., Carey, D., Johnson, J., Kammerud, R., Ritchie, D., Roberts, A., Sauer, J., Walker, J., (1976) Phys. Rev. D, 14, p. 1217. , PRVDAQ 0556-2821 10.1103/PhysRevD.14.1217; Abgrall, N., (2013) Nucl. Instrum. Methods Phys. Res., Sect. A, 701, p. 99. , NIMAER 0168-9002 10.1016/j.nima.2012.10.079; Hayato, Y., (2002) Nucl. Phys. B, Proc. Suppl., 112, p. 171. , NPBSE7 0920-5632 10.1016/S0920-5632(02)01759-0 correspondence_address1: Abe, K.; Institute for Cosmic Ray Research, Kamioka Observatory, University of Tokyo, Kamioka, Japan coden: PRVDA abbrev_source_title: Phys Rev D Part Fields Gravit Cosmol document_type: Article source: Scopu

Pooled analysis of WHO Surgical Safety Checklist use and mortality after emergency laparotomy

Background The World Health Organization (WHO) Surgical Safety Checklist has fostered safe practice for 10 years, yet its place in emergency surgery has not been assessed on a global scale. The aim of this study was to evaluate reported checklist use in emergency settings and examine the relationship with perioperative mortality in patients who had emergency laparotomy. Methods In two multinational cohort studies, adults undergoing emergency laparotomy were compared with those having elective gastrointestinal surgery. Relationships between reported checklist use and mortality were determined using multivariable logistic regression and bootstrapped simulation. Results Of 12 296 patients included from 76 countries, 4843 underwent emergency laparotomy. After adjusting for patient and disease factors, checklist use before emergency laparotomy was more common in countries with a high Human Development Index (HDI) (2455 of 2741, 89.6 per cent) compared with that in countries with a middle (753 of 1242, 60.6 per cent; odds ratio (OR) 0.17, 95 per cent c.i. 0.14 to 0.21, P <0001) or low (363 of 860, 422 per cent; OR 008, 007 to 010, P <0.001) HDI. Checklist use was less common in elective surgery than for emergency laparotomy in high-HDI countries (risk difference -94 (95 per cent c.i. -11.9 to -6.9) per cent; P <0001), but the relationship was reversed in low-HDI countries (+121 (+7.0 to +173) per cent; P <0001). In multivariable models, checklist use was associated with a lower 30-day perioperative mortality (OR 0.60, 0.50 to 073; P <0.001). The greatest absolute benefit was seen for emergency surgery in low- and middle-HDI countries. Conclusion Checklist use in emergency laparotomy was associated with a significantly lower perioperative mortality rate. Checklist use in low-HDI countries was half that in high-HDI countries.Peer reviewe

Estas son algunas de las habilidades blandas demandadas en Colombia

Este producto forma parte de una serie de infografías de divulgación científica que buscan reseñar algunas de las investigaciones más importantes en las que ha tenido participación la Universidad EAFIT, publicadas en las revistas especializadas más prestigiosas del mund

Global variation in anastomosis and end colostomy formation following left-sided colorectal resection

Background End colostomy rates following colorectal resection vary across institutions in high-income settings, being influenced by patient, disease, surgeon and system factors. This study aimed to assess global variation in end colostomy rates after left-sided colorectal resection. Methods This study comprised an analysis of GlobalSurg-1 and -2 international, prospective, observational cohort studies (2014, 2016), including consecutive adult patients undergoing elective or emergency left-sided colorectal resection within discrete 2-week windows. Countries were grouped into high-, middle- and low-income tertiles according to the United Nations Human Development Index (HDI). Factors associated with colostomy formation versus primary anastomosis were explored using a multilevel, multivariable logistic regression model. Results In total, 1635 patients from 242 hospitals in 57 countries undergoing left-sided colorectal resection were included: 113 (6·9 per cent) from low-HDI, 254 (15·5 per cent) from middle-HDI and 1268 (77·6 per cent) from high-HDI countries. There was a higher proportion of patients with perforated disease (57·5, 40·9 and 35·4 per cent; P < 0·001) and subsequent use of end colostomy (52·2, 24·8 and 18·9 per cent; P < 0·001) in low- compared with middle- and high-HDI settings. The association with colostomy use in low-HDI settings persisted (odds ratio (OR) 3·20, 95 per cent c.i. 1·35 to 7·57; P = 0·008) after risk adjustment for malignant disease (OR 2·34, 1·65 to 3·32; P < 0·001), emergency surgery (OR 4·08, 2·73 to 6·10; P < 0·001), time to operation at least 48 h (OR 1·99, 1·28 to 3·09; P = 0·002) and disease perforation (OR 4·00, 2·81 to 5·69; P < 0·001). Conclusion Global differences existed in the proportion of patients receiving end stomas after left-sided colorectal resection based on income, which went beyond case mix alone