Prognostic model to predict postoperative acute kidney injury in patients undergoing major gastrointestinal surgery based on a national prospective observational cohort study.

Background: Acute illness, existing co-morbidities and surgical stress response can all contribute to postoperative acute kidney injury (AKI) in patients undergoing major gastrointestinal surgery. The aim of this study was prospectively to develop a pragmatic prognostic model to stratify patients according to risk of developing AKI after major gastrointestinal surgery. Methods: This prospective multicentre cohort study included consecutive adults undergoing elective or emergency gastrointestinal resection, liver resection or stoma reversal in 2-week blocks over a continuous 3-month period. The primary outcome was the rate of AKI within 7 days of surgery. Bootstrap stability was used to select clinically plausible risk factors into the model. Internal model validation was carried out by bootstrap validation. Results: A total of 4544 patients were included across 173 centres in the UK and Ireland. The overall rate of AKI was 14·2 per cent (646 of 4544) and the 30-day mortality rate was 1·8 per cent (84 of 4544). Stage 1 AKI was significantly associated with 30-day mortality (unadjusted odds ratio 7·61, 95 per cent c.i. 4·49 to 12·90; P < 0·001), with increasing odds of death with each AKI stage. Six variables were selected for inclusion in the prognostic model: age, sex, ASA grade, preoperative estimated glomerular filtration rate, planned open surgery and preoperative use of either an angiotensin-converting enzyme inhibitor or an angiotensin receptor blocker. Internal validation demonstrated good model discrimination (c-statistic 0·65). Discussion: Following major gastrointestinal surgery, AKI occurred in one in seven patients. This preoperative prognostic model identified patients at high risk of postoperative AKI. Validation in an independent data set is required to ensure generalizability

Theoretical design of core modified (oxa and thia) porphyrin based organic dyes with bridging thiophene linkers

Density functional theory calculations at the B3LYP/6-31G* level of theory are employed to assess the suitability of core modified porphyrin analogs as organic dyes for solar cell application. The composite photosensitizer consists of a core modified (mono/di oxa and thia substituted) porphyrin as donor bridged at the β-position to the acceptor (cyanoacrylic acid group) by a thiophene unit. The vertical excitation energy of the modeled dyes is calculated using the time-dependent density functional theory (TD-DFT) approach. The designed sensitizers are screened based on their electronic properties, such as HOMO–LUMO gap, position of HOMO–LUMO energy levels with respect to the conduction band of TiO2 and redox potential of the electrolyte, UV-vis absorption spectra etc. The free energy of injection was also evaluated based on the redox properties of the dyes in their ground and excited states. Apart from investigating the electronic structure of the dyes, we have also carried out theoretical calculations to model the interaction of the dye with the surface of the semiconductor by considering a (TiO2)16 nanocluster

Quantum chemical design of carbazole- and pyridoindole-based ambipolar host materials for blue phosphorescent OLEDs

Density functional theory has been employed to design thirty two host molecules for blue electrophosphorescence by incorporating dibenzofuran (DBF), dibenzothiophene (DBT), phenylcarbazole (Ph-Cbz), benzofuropyridine (DBF), benzothiopyridine (BTP) and phenyl pyridoindole (Ph-Cb1) subunits into N-phenyl carbazole (Ph-Cbz) and phenyl α-carboline (Ph-Cb1) core units. We have systematically investigated the role of linking positions of subunits into the core moiety and nature of core units on the electronic properties of the newly developed host materials. Results illustrate that substituting the subunits at the Ph-Cbz core may yield hosts with improved electronic properties when compared to the same subunit at the Ph-Cb1 core. The electronic properties are modulated efficiently through the nature and substituted positions (para and meta) of the subunits at the core units. Substitution of the subunits at the para-position of the Ph-Cbz core yields hosts with better charge injections. The same substitution at the meta-position results in better charge transport, higher triplet energy and lower singlet–triplet energy difference (ΔE<SUB>ST</SUB>). Among the newly designed host molecules, 25, 26, 27, 28, 29, 30, 31 and 32 are found to be promising hosts molecules with a lower barrier for hole and electron injection, a clear charge-separated state, balanced charge transport for both hole and electron, and lower ΔE<SUB>ST</SUB> values compared with an experimentally reported high potential host molecule (host 3)

Rational design of carbazole- and carboline-based ambipolar host materials for blue electrophosphorescence: a density functional theory study

Density functional theory has been employed to design 41 host molecules for blue electrophosphorescence by incorporating electron donor (carbazole (cbz)) and electron acceptor (α-carboline (Cb1)) units into N-phenylcarbazole (PhCbz). We have systematically investigated the influence of the number (mono-, di-, and trisubstituted) and positions of Cb1 and Cbz substitution on an array of electronic properties of the designed hosts. The results underline that the substitution of the N-phenyl ring with a carboline unit yields host molecules with low charge injection barriers, balanced charge transport, efficient charge separation, high triplet energy (E<SUB>T</SUB>), and low singlet–triplet energy difference (ΔE<SUB>ST</SUB>). For disubstituted hosts, the second subunit can either be Cb1 or Cbz substituted at the 2/7 position of PhCbz, while substituting the 2 and 3 positions of PhCbz with Cbz subunits generates trisubstituted hosts with efficient electronic properties. Thus, our results indicate that both number and position of subunit substitution in PhCbz play a decisive role in designing hosts with appropriate electronic properties. Among the 41 systems considered in the study, we have identified the two most efficient hosts, and their electronic properties are found to be very promising compared to some of the experimentally reported analogous hosts

Design of medium band gap random terpolymers containing fluorene linked diketopyrrolopyrrole and thiophene co-monomers: an experimental and theoretical study

In this study, new polymers PTFDPP, PBTFDPP, PTTFDPP, PTCNEFDPP, PTDCNFDPP and PTPTFDPP were designed and synthesized by employing a D–A random copolymer strategy involving 9,9-dihexylfluorene (electron donor) linked to diketopyrrolopyrrole (electron acceptor) and thiophene comonomer (as donor as well as acceptor). Their optical band gap and HOMO and LUMO energy levels were estimated from ultraviolet-visible spectroscopy and cyclic voltammetry. By changing the nature of thiophene from donor to acceptor state, the HOMO and LUMO energy levels and optical band gaps were modified, which varied from 1.75 to 1.65 eV. A series of systematic density functional theory (DFT) calculations have been performed on model co-polymers to gain insights into the structural, electronic, optical and charge transport properties. The experimental values are in close agreement with calculated electronic properties. Salient findings from both experimental and calculated values indicate that these new polymers can be efficiently exploited for the development of new donor materials for OPV applications

Identifying the influential spreaders in multilayer interactions of online social networks

Online social networks (OSNs) portray a multi-layer of interactions through which users become a friend, information is propagated, ideas are shared, and interaction is constructed within an OSN. Identifying the most influential spreaders in a network is a significant step towards improving the use of existing resources to speed up the spread of information for application such as viral marketing or hindering the spread of information for application like virus blocking and rumor restraint. Users communications facilitated by OSNs could confront the temporal and spatial limitations of traditional communications in an exceptional way, thereby presenting new layers of social interactions, which coincides and collaborates with current interaction layers to redefine the multiplex OSN. In this paper, the effects of different topological network structure on influential spreaders identification are investigated. The results analysis concluded that improving the accuracy of influential spreaders identification in OSNs is not only by improving identification algorithms but also by developing a network topology that represents the information diffusion well. Moreover, in this paper a topological representation for an OSN is proposed which takes into accounts both multilayers interactions as well as overlaying links as weight. The measurement results are found to be more reliable when the identification algorithms are applied to proposed topological representation compared when these algorithms are applied to single layer representations

Computational design of high triplet energy host materials for phosphorescent blue emitters

A series of host molecules for blue electrophosphorescence have been designed using density functional theory by incorporating electron donors (carbazole (cbz) and diphenylamine (tph)) and electron acceptors (benzimidazole (bzi) and diphenylphosphine oxide (pho)) into the p-bis(triphenylsilyl)benzene (UGH2) moiety. Results obtained from the electronic structure calculations show that the triplet energy (ET), HOMO and LUMO energy levels and HOMO–LUMO gap (Eg) of the designed hosts can be modulated through different linking topologies. Among the designed host molecules benzimidazole with an N-linkage exhibits a higher triplet energy, when compared to the same host with a C-linkage. Asymmetric substitution on an inert host (UGH2) more effectively tunes the charge injection barrier from neighboring layers, HOMO and LUMO energies and Eg than symmetric substitution. The electron injection barrier is substantially diminished when electron transporting units are substituted in the para-position of the core unit compared to the same in the meta-position. Among the newly designed host molecules mcbz–pN–bzi, pcbz–pN–bzi, and ptph–pN–bzi are found to be good host materials for blue emitting phOLEDs