A fuzzy-based methodological proposal for analysing green areas in urban neighborhoods.

The reduction of the green areas due to the growth of the built-up areas has affected the environmental quality in cities. Nevertheless, some uncertainties remain about the adequate amount of such areas in the urban landscape. This study aims at introducing a methodology to support analysis of green areas in urban neighborhoods. The methodological proposal was based on a fuzzy expert system (FES), a soft computing approach capable of dealing with uncertainties in complex multiple-criteria decision-making. As empirical research, some case studies to introduce and validate the proposed methodology were performed. An agglomerative hierarchical clustering, followed by a Kruskal-Wallis test and multiple pairwise comparisons using the Conover-Iman procedure (significance 0.05), demonstrated that the FES was able to provide outcomes consistent with hypothetical situations, simulated as ideal and critical conditions of green areas. In conclusion, our findings indicate that the methodological proposal based on FES is a promising tool for complex case-by-case analysis in urban neighborhoods.

Intravitreal aflibercept for the treatment of patients with neovascular age-related macular degeneration in routine clinical practice in Latin America: the AQUILA study.

BACKGROUND: AQUILA (NCT03470103) was a prospective, observational, 12-month cohort study evaluating treatment patterns, clinical effectiveness, and safety of intravitreal aflibercept (IVT-AFL) in patients from Latin America with neovascular age-related macular degeneration (nAMD). METHODS: Treatment-naïve and previously treated (switching to IVT-AFL) patients (aged ≥ 55 years) were enrolled from March 2018, with a primary completion date of September 2020, from Argentina, Colombia, Costa Rica, and Mexico. Patients received IVT-AFL in a routine clinical practice setting. RESULTS: Of 274 patients in the full analysis set, 201 were treatment-naïve and 73 had received previous treatment. The mean ± standard deviation number of IVT-AFL injections received by month 12 was 4.2 ± 1.9 (treatment-naïve) and 5.2 ± 2.7 (previously treated). The median duration from diagnosis to IVT-AFL treatment was 1.2 months (treatment-naïve) and 19.5 months (previously treated). Mean best-corrected visual acuity (BCVA) (Early Treatment Diabetic Retinopathy Study [ETDRS] letters) improved from baseline to month 12 by + 5.2 ± 18.3 (treatment-naïve; baseline: 48.2 ± 23.5) and + 3.1 ± 15.3 letters (previously treated; baseline: 47.7 ± 21.4). CONCLUSION: AQUILA is the first study to assess the use of IVT-AFL in routine clinical practice in Latin America. Mean BCVA and other visual acuity outcomes improved in both treatment groups, despite many patients not receiving the IVT-AFL label-recommended regimen of three initial monthly doses, or seven or more injections in 12 months. Patients who did receive the label-recommended number of injections had numerically greater improvements in visual acuity outcomes. Patients with nAMD treated regularly and more frequently with IVT-AFL, therefore, have the potential to achieve outcomes consistent with those observed in interventional studies. TRIAL REGISTRATION: Clinicaltrials.gov, NCT03470103. Registered February 5, 2018, https://clinicaltrials.gov/ct2/show/NCT03470103.

Intravitreal aflibercept for the treatment of patients with diabetic macular edema in routine clinical practice in Latin America: the AQUILA study.

BACKGROUND: AQUILA (NCT03470103) was a prospective, observational, 12-month cohort study to understand treatment patterns and to evaluate the clinical effectiveness and safety of intravitreal aflibercept (IVT-AFL) in patients from Latin America with diabetic macular edema (DME). METHODS: Treatment-naïve and previously treated (switching to IVT-AFL) patients (aged ≥ 18 years) were enrolled from March 2018, with a primary completion date of September 2020, from Argentina, Colombia, Costa Rica and Mexico. Patients received IVT-AFL in a routine clinical practice setting. RESULTS: Of 258 patients in the full analysis set, 181 were treatment-naïve and 77 had received previous treatment. The mean ± standard deviation number of IVT-AFL injections by Month 12 was 3.7 ± 1.8 (treatment-naïve) and 4.0 ± 2.2 (previously treated). The median duration from diagnosis to IVT-AFL treatment was 1.8 months (treatment-naïve) and 16.0 months (previously treated). Mean best-corrected visual acuity (Early Treatment Diabetic Retinopathy Study letters) improved from baseline to Month 12 by + 8.1 ± 17.7 (treatment-naïve; baseline: 54.5 ± 19.4) and + 4.6 ± 15.4 letters (previously treated; baseline: 52.9 ± 18.6). CONCLUSION: AQUILA is the first study to assess the use of IVT-AFL in routine clinical practice in Latin America. Despite few patients being treated with the label-recommended regimen of 5 initial monthly doses or receiving ≥ 8 injections in 12 months, functional and anatomic visual outcomes improved during 12 months of treatment with IVT-AFL. Patients receiving the label-recommended number of injections had numerically greater improvements in visual acuity outcomes. Patients with DME treated regularly and more frequently with IVT-AFL therefore have the potential to achieve outcomes consistent with those observed in interventional studies. Trial registration Clinicaltrials.gov, NCT03470103. Registered February 5, 2018, https://clinicaltrials.gov/ct2/show/NCT03470103.

Towards an atomistic understanding of polymorphism in molecular solids.

Understanding and controlling polymorphism in molecular solids is a major unsolved problem in crystal engineering. While the ability to calculate accurate lattice energies with atomistic modelling provides valuable insight into the associated energy scales, existing methods cannot connect energy differences to the delicate balances of intra- and intermolecular forces that ultimately determine polymorph stability ordering. We report herein a protocol for applying Quantum Chemical Topology (QCT) to study the key intra- and intermolecular interactions in molecular solids, which we use to compare the three known polymorphs of succinic acid including the recently-discovered γ form. QCT provides a rigorous partitioning of the total energy into contributions associated with topological atoms, and a quantitative and chemically intuitive description of the intra- and intermolecular interactions. The newly-proposed Relative Energy Gradient (REG) method ranks atomistic energy terms (steric, electrostatic and exchange) by their importance in constructing the total energy profile for a chemical process. We find that the conformation of the succinic acid molecule is governed by a balance of large and opposing electrostatic interactions, while the H-bond dimerisation is governed by a combination of electrostatics and sterics. In the solids, an atomistic energy balance emerges that governs the contraction, towards the equilibrium geometry, of a molecular cluster representing the bulk crystal. The protocol we put forward is as general as the capabilities of the underlying quantum-mechanical model and it can provide novel perspectives on polymorphism in a wide range of chemical systems.

An Interacting Quantum Atoms (IQA) and Relative Energy Gradient (REG) Study of the Halogen Bond with Explicit Analysis of Electron Correlation.

Energy profiles of seven halogen-bonded complexes were analysed with the topological energy partitioning called Interacting Quantum Atoms (IQA) at MP4(SDQ)/6-31+G(2d,2p) level of theory. Explicit interatomic electron correlation energies are included in the analysis. Four complexes combine X2 (X = Cl or F) with HCN or NH3, while the remaining three combine ClF with HCN, NH3 or N2. Each complex was systematically deformed by translating the constituent molecules along its central axis linking X and N, and reoptimising its remaining geometry. The Relative Energy Gradient (REG) method (Theor. Chem. Acc. 2017, 136, 86) then computes which IQA energies most correlate with the total energy during the process of complex formation and further compression beyond the respective equilibrium geometries. It turns out that the covalent energy (i.e., exchange) of the halogen bond, X…N, itself drives the complex formation. When the complexes are compressed from their equilibrium to shorter X…N distance then the intra-atomic energy of N is in charge. When the REG analysis is restricted to electron correlation then the interatomic correlation energy between X and N again drives the complex formation, and the complex compression is best described by the destabilisation of the through-space correlation energy between N and the "outer" halogen.

Spatial energy transfer with observation of bimolecular singlet oxygen emission using quantum dots as donors and zinc-phthalocyanine as acceptors.

This study reports the influence of CdSe-ZnS core-shell quantum dots (QDs) for formation of singlet oxygen using zinc-phthalocyanine (ZnPc) dyes in colloidal solutions. Using a microluminescence surface scan technique it was possible to measure accurately the photon diffusion length, or photon mean free path, inside the medium. Analyses were performed for a range of QD concentrations. Photon diffusion length was assigned to the bimolecular singlet oxygen emission at 707 nm. Related singlet oxygen emission was predicted by observing quenching of the photon diffusion length measured at the specific oxygen emission as a function of QD concentration, being a nontrivial phenomenon related to the QD donors. Diffusion length measured at 707 nm increased with QD concentration; in the absence of QDs, as in pure ZnPc samples, the emission peak at 707 nm was not observed.

Quantum chemical intensity determinations of overlapped gas phase infrared bands.

The largest source of experimental error in determining gas phase fundamental infrared intensities arises from the separation of overlapped bands. Quantum chemical calculations at the QCISD/cc-pVTZ and QCISD/aug-cc-pVTZ levels were carried out on four simple hydrocarbons and the fluoro- and chloromethanes with the aim of accurate overlapped band separation. Fundamental vibrational intensity results were compared with individual empirical intensity estimates reported for overlapped band systems. Root mean square differences of 3.7 km mol-1 are found between the experimental and QCISD/cc-pVTZ values for nine overlapped bands of the hydrocarbons and 11.8 km mol-1 for the QCISD/aug-cc-pVTZ values for 12 overlapped bands of the fluoro- and chloromethanes. These values correspond to 14% and 18% of the average hydrocarbon and halomethane intensity values. Previous experimental separation errors were estimated to be quite larger, between 20% and 50%. As quantum calculations are continuously being refined one can expect more accurate band separation results in the future.

An unusual case of nine cilia embedded in the retina after a perforating ocular injury.

PURPOSE: To report an extremely rare case involving a 41-year-old man with nine intraocular cilia embedded in the retina after a perforating ocular injury caused by a metal wire. This case is particularly rare because of the number and location of the cilia. OBSERVATIONS: The patient underwent an uneventful corneal suturing and extracapsular extraction of the damaged lens of his right eye. Intraocular foreign bodies were discovered following surgery and were removed at a later date. Following lens extraction and ocular repair, the patient's best-corrected visual acuity (BCVA) was counting fingers. Fundus examination during follow-up revealed several eyelashes embedded in the retina. Thirty-two days after the injury, the patient showed signs of ocular inflammation. Therefore, the patient underwent vitrectomy and intraocular foreign body removal. Nine cilia were embedded in the retina at the posterior perforation site. At the final follow-up visit, his BCVA was 20/25. CONCLUSION AND IMPORTANCE: This report describes an unusual case where intraocular cilia were embedded in the retina after a perforating ocular injury. The eyelashes caused an intraocular inflammatory reaction that subsided after their removal.

Influence of structure and solubility of chain transfer agents on the RAFT control of dispersion polymerisation in scCO2.

Reversible addition-fragmentation chain transfer (RAFT) dispersion polymerisation of methyl methacrylate (MMA) is performed in supercritical carbon dioxide (scCO2) with 2-(dodecylthiocarbonothioylthio)-2-methylpropionic acid (DDMAT) present as chain transfer agent (CTA) and surprisingly shows good control over PMMA molecular weight. Kinetic studies of the polymerisation in scCO2 also confirm these data. By contrast, only poor control of MMA polymerisation is obtained in toluene solution, as would be expected for this CTA which is better suited for acrylates. In this regard, we select a range of CTAs and use them to determine the parameters that must be considered for good control in dispersion polymerisation in scCO2. A thorough investigation of the nucleation stage during the dispersion polymerisation reveals an unexpected "in situ two-stage" mechanism that strongly determines how the CTA works. Finally, using a novel computational solvation model, we identify a correlation between polymerisation control and degree of solubility of the CTAs. All of this ultimately gives rise to a simple, elegant and counterintuitive guideline to select the best CTA for RAFT dispersion polymerisation in scCO2.

A FFLUX Water Model: Flexible, Polarizable and with a Multipolar Description of Electrostatics.

Key to progress in molecular simulation is the development of advanced models that go beyond the limitations of traditional force fields that employ a fixed, point charge-based description of electrostatics. Taking water as an example system, the FFLUX framework is shown capable of producing models that are flexible, polarizable and have a multipolar description of the electrostatics. The kriging machine-learning methods used in FFLUX are able to reproduce the intramolecular potential energy surface and multipole moments of a single water molecule with chemical accuracy using as few as 50 training configurations. Molecular dynamics simulations of water clusters (25-216 molecules) using the new FFLUX model reveal that incorporating charge-quadrupole, dipole-dipole, and quadrupole-charge interactions into the description of the electrostatics results in significant changes to the intermolecular structuring of the water molecules. © 2019 The Authors. Journal of Computational Chemistry published by Wiley Periodicals, Inc.

Atomic Partitioning of the MPn (n = 2, 3, 4) Dynamic Electron Correlation Energy by the Interacting Quantum Atoms Method: A Fast and Accurate Electrostatic Potential Integral Approach.

Recently, the quantum topological energy partitioning method called interacting quantum atoms (IQA) has been extended to MPn (n = 2, 3, 4) wave functions. This enables the extraction of chemical insight related to dynamic electron correlation. The large computational expense of the IQA-MPn approach is compensated by the advantages that IQA offers compared to older nontopological energy decomposition schemes. This expense is problematic in the construction of a machine learning training set to create kriging models for topological atoms. However, the algorithm presented here markedly accelerates the calculation of atomically partitioned electron correlation energies. Then again, the algorithm cannot calculate pairwise interatomic energies because it applies analytical integrals over whole space (rather than over atomic volumes). However, these pairwise energies are not needed in the quantum topological force field FFLUX, which only uses the energy of an atom interacting with all remaining atoms of the system that it is part of. Thus, it is now feasible to generate accurate and sizeable training sets at MPn level of theory. © 2019 The Authors. Journal of Computational Chemistry published by Wiley Periodicals, Inc.

Infrared Intensification and Hydrogen Bond Stabilization: Beyond Point Charges.

Infrared band intensification of the A-H bond stretching mode of A-H···B acid-base systems has long been known to be the most spectacular spectral change occurring on hydrogen bonding. A QTAIM/CCTDP model is reported here to quantitatively explain the electronic structure origins of intensification and investigate the correlation between experimental enthalpies of formation and infrared hydrogen bond stretching intensifications amply reported in the literature. Augmented correlation-consistent polarized triple-zeta quantum calculations at the MP2 level were performed on complexes with HF and HCl electron acceptors and HF, HCl, NH3, H2O, HCN, acetonitrile, formic acid, acetaldehyde, and formaldehyde electron donor molecules. The A-H stretching band intensities are calculated to be 3 to 40 times larger than their monomer values. Although the acidic hydrogen atomic charge is important for determining the intensities of HF complexes relative to HCl complexes with the same electron donor, they are not important for infrared intensifications occurring on hydrogen bond formation for a series of bases with a common acid. Charge transfers are found to be the most important factor resulting in the intensifications, but dipolar polarization effects are also significant for each series of complexes. A mechanism involving intra-acid and intermolecular electron transfers as well as atomic polarizations is proposed for understanding the intensifications. The calculated sums of the intermolecular electron transfer and acid dipolar polarization contributions to the dipole moment derivatives for each series of complexes are highly correlated with their enthalpies of formation and H-bond intensifications. This could be related to increasing electron transfer from base to acid that correlates with the calculated hydrogen bonding energies and may be a consequence of the A-H bond elongation on complex formation having amplitudes similar to those expected for the A-H vibration.

Clinical Assessment of Rosemary-based Toothpaste (Rosmarinus officinalis Linn.): A Randomized Controlled Double-blind Study.

The present study was to investigate the action of a toothpaste made from the extract of Rosmarinus officinalis Linn. (rosemary) in a clinical randomized, controlled, open and double-blind trial. One hundred and ten volunteers fulfilled the inclusion criteria and were randomly separated into two groups according to the toothpastes used: Group A (experimental) and Group B (control). They were assessed at baseline and 30 days after the study using the gingival bleeding index (GBI) and the plaque index (PI). Data analysis was conducted to calculate the effects of the two toothpastes on gingival bleeding and plaque, using measurements such as the excess relative risk (ERR), the Relative Risk Reduction (RRR), the Absolute Risk Reduction (ARR) and the Number Needed for Treatment (NNT). The two toothpastes provided similar results in terms of the reduction in the risk of gingival bleeding (relative and absolute): a reduction of 38% in Group A, ERR=0.38; a reduction of 29.3% in Group B, ERR=0.293; A and B reduced by 18% ARR=0.18). The reductions in bacterial plaque were also similar (22.7% reduction in Group A, RRR=0.227; 28% reduction in Group B, RRR= 0.28). The number needed for treatment values for bleeding and plaque were A and B NNT=5 and A and B NNT=7, respectively. The rosemary-based toothpaste effectively treated gingival bleeding and reduced bacterial plaque, when compared with conventional toothpaste.

Clinical assessment of rosemary-based toothpaste (rosmarinus officinalis linn. ): a randomized controlled double-blind study

Abstract The present study was to investigate the action of a toothpaste made from the extract of Rosmarinus officinalis Linn. (rosemary) in a clinical randomized, controlled, open and double-blind trial. One hundred and ten volunteers fulfilled the inclusion criteria and were randomly separated into two groups according to the toothpastes used: Group A (experimental) and Group B (control). They were assessed at baseline and 30 days after the study using the gingival bleeding index (GBI) and the plaque index (PI). Data analysis was conducted to calculate the effects of the two toothpastes on gingival bleeding and plaque, using measurements such as the excess relative risk (ERR), the Relative Risk Reduction (RRR), the Absolute Risk Reduction (ARR) and the Number Needed for Treatment (NNT). The two toothpastes provided similar results in terms of the reduction in the risk of gingival bleeding (relative and absolute): a reduction of 38% in Group A, ERR=0.38; a reduction of 29.3% in Group B, ERR=0.293; A and B reduced by 18% ARR=0.18). The reductions in bacterial plaque were also similar (22.7% reduction in Group A, RRR=0.227; 28% reduction in Group B, RRR= 0.28). The number needed for treatment values for bleeding and plaque were A and B NNT=5 and A and B NNT=7, respectively. The rosemary-based toothpaste effectively treated gingival bleeding and reduced bacterial plaque, when compared with conventional toothpaste.

Resumo O presente estudo investigou a ação de uma pasta de dente feita a partir do extrato de Rosmarinus officinalis Linn. (Alecrim) em um ensaio clínico randomizado, controlado, aberto e duplo-cego. Cento e dez voluntários preencheram os critérios de inclusão e foram separados aleatoriamente em dois grupos de acordo com as pastas usadas: Grupo A (experimental) e Grupo B (controle). Eles foram avaliados no início e 30 dias após o estudo usando o índice de sangramento gengival (GBI) e o índice de placa (PI). A análise dos dados foi realizada para calcular os efeitos das duas pastas dentárias sobre sangramento gengival e placa, usando medidas como o excesso de risco relativo (ERR), a Redução do Risco Relativo (RRR), a Redução do Risco Absoluto (ARR) e o Número Necessário para Tratamento (NNT). As duas pastas de dentes proporcionaram resultados semelhantes em termos de redução do risco de sangramento gengival (relativo e absoluto): redução de 38% no Grupo A, ERR=0,38; Uma redução de 29,3% no Grupo B, ERR=0,293; A e B reduziram-se em 18% ARR=0,18). As reduções na placa bacteriana também foram semelhantes (redução de 22,7% no Grupo A, RRR=0,227, redução de 28% no Grupo B, RRR=0,28). O número necessário para tratamento de sangramento e placa foi A e B NNT=5 e A e B NNT=7, respectivamente. A pasta de dente à base de alecrim tratou efetivamente o sangramento gengival e reduziu a placa bacteriana, quando comparada à pasta dentífrica convencional.

Decomposition of Møller-Plesset Energies within the Quantum Theory of Atoms-in-Molecules.

We discuss two main approaches to decompose the Møller-Plesset perturbation theory molecular energies into atomic contributions within the interacting quantum atoms (IQA) formalism, as implemented in the programs Morphy and AIMAll. For this purpose, the so-called intraatomic energies (also known as self-energies) of a representative set of 55 small molecules are compared with each other. The origin of the possible discrepancies between both approaches is analyzed, and linear models linking the two approaches are proposed for each atom type.

FTIR and dispersive gas phase fundamental infrared intensities of the fluorochloromethanes: Comparison with QCISD/cc-pVTZ results.

New experimental values of the fundamental infrared gas phase intensities of the fluorochloromethanes have been determined by integrating the areas of vibrational bands contained in the PNNL spectral library using homemade software. The root mean square differences of these values and averages of experimental values determined at lower resolution during the latter part of the 20th century is 26.6 km mol-1. All but one of the low resolution intensities are smaller than the PNNL values. The exception is the ν1,ν4 overlapped band intensity of CF3Cl that has a standard deviation of the low resolution values of ±112.5 km mol-1, larger than the observed difference of 102.5 km mol-1. The use of an augmented triple zeta basis set at the QCISD level results in an rms difference of only 8.4 km mol-1 for the fluoro- and chloromethane PNNL intensities, whereas a comparison of these with results at the QCISD/cc-pVTZ level produces an error twice as large, 16.2 km mol-1. As such these results suggest that future comparisons of theoretical intensities with experimental values should take into account integrated intensities that can be obtained from hundreds of spectra in the PNNL library. Furthermore, the intensity values obtained from the PNNL spectra confirm electronegativity model results previously reported based on the low resolution intensities.

MP2-IQA: upscaling the analysis of topologically partitioned electron correlation.

When electronic correlation energy is partitioned topologically, a detailed picture of its distribution emerges, both within atoms and between any two atoms. This methodology allows one to study dispersion beyond its more narrow definition in long-range Rayleigh-Schrödinger perturbation theory. The interacting quantum atoms (IQA) method was applied to MP2/6-31G(d,p) (uncontracted) wave functions of a wide variety of systems: glycine…water (hydration), the ethene dimer (π-π interactions), benzene (aromaticity), cyclobutadiene (antiaromaticity), and NH3BH3 (dative bond). Through the study of molecular complexes it turns out that dispersion energy is either important to a system's stabilization (for the C2H4 dimer) or not important (for Gly…H2O). We have also discovered that the delocalization in benzene lowers the strength of Coulomb repulsion in the bonds, which has been quantified for the first time through IQA. Finally, we showed that the nature of the dative bond is much different from that of a regular covalent bond as it is not destabilized by electronic correlation. Finally, the conclusions obtained for these archetypical systems have implications for the future of the quantum topological force field FFLUX in the simulation of larger systems. Graphical abstract Atomic and bond dynamic correlation energies are now available thanks to IQA. Larger molecules can now be accessed to include resonance and solvation of FFLUX force field.

Probing the robustness of the charge-charge transfer-dipolar polarization model and infrared intensities.

The robustness of the QTAIM charge-charge transfer-dipolar polarization parameters for the CH, CF, and CCl stretching and bending distortions of the fluoro- and chloromethanes was determined comparing results calculated at three quantum levels, MP2/6-311G++(3d,3p), QCISD/cc-pVTZ, and QCISD/aug-cc-pVTZ. The correlation coefficients between the MP2/6-311G++G(d,p) and QCISD/cc-pVTZ results with those of QCISD/aug-cc-pVTZ intensities are excellent, 0.934 and 0.988, respectively, showing that the parameters converge with increasing quality of the quantum levels. In spite of numerical differences, the interpretation of the electronic structure changes occurring for these vibrations is the same for all three quantum levels. Accurate determination of charge transfer-counterpolarization effects is important for properly describing electron density changes for small molecular distortions.

Machine Learning of Dynamic Electron Correlation Energies from Topological Atoms.

We present an innovative method for predicting the dynamic electron correlation energy of an atom or a bond in a molecule utilizing topological atoms. Our approach uses the machine learning method Kriging (Gaussian Process Regression with a non-zero mean function) to predict these dynamic electron correlation energy contributions. The true energy values are calculated by partitioning the MP2 two-particle density-matrix via the Interacting Quantum Atoms (IQA) procedure. To our knowledge, this is the first time such energies have been predicted by a machine learning technique. We present here three important proof-of-concept cases: the water monomer, the water dimer, and the van der Waals complex H2···He. These cases represent the final step toward the design of a full IQA potential for molecular simulation. This final piece will enable us to consider situations in which dispersion is the dominant intermolecular interaction. The results from these examples suggest a new method by which dispersion potentials for molecular simulation can be generated.

The Transferability of Topologically Partitioned Electron Correlation Energies in Water Clusters.

The electronic effects that govern the cohesion of water clusters are complex, demanding the inclusion of N-body, Coulomb, exchange and correlation effects. Here we present a much needed quantitative study of the effect of correlation (and hence dispersion) energy on the stabilization of water clusters. For this purpose we used a topological energy partitioning method called Interacting Quantum Atoms (IQA) to partition water clusters into topological atoms, based on a MP2/6-31G(d,p) wave function, and modified versions of GAUSSIAN09 and the Quantum Chemical Topology (QCT) program MORFI. Most of the cohesion in the water clusters provided by electron correlation comes from intramolecular energy stabilization. Hydrogen bond-related interactions tend to largely cancel each other. Electron correlation energies are transferable in almost all instances within 1 kcal mol-1 . This observed transferability is very important to the further development of the QCT force field FFLUX, especially to the future modelling of liquid water.