Weak Complexes Research Articles

Robust silicon dioxide @ epoxy resin micronanosheet superhydrophobic omnipotent protective coating for applications

Superhydrophobic coating have presented enormous application value in mechanical, architectural and other engineering in decade. However, there are some problems that we have to envisage, such as weak mechanical strength, complex technologies and toxic modifiers, which greatly limits its applications in real-life. Here, an omnipotent robust silicon dioxide @ epoxy resin coating was successfully prepared by a facile and environment friendly process, and the whole process can be accomplished in a beaker without any usage of toxic reagents. The as-prepared coating presents excellent waterproof ability, mechanical stability, long-time stability and can be coated almost on any solid substrates. What is more, the superhydrophobic coating also exhibits better survivability to face various intricate environments in nature such as windy, dusty, icing and torridity. Hence, this omnipotent silicon dioxide @ epoxy resin coating possesses enormous application potential in many fields and the facile and environment friendly productive process gives it possibility to be quantity produced in industry.

Oxidative Formation and Removal of Complexed Mn(III) by Pseudomonas Species.

The observation of significant concentrations of soluble Mn(III) complexes in oxic, suboxic, and some anoxic waters has triggered a re-evaluation of the previous Mn paradigm which focused on the cycling between soluble Mn(II) and insoluble Mn(III,IV) species as operationally defined by filtration. Though Mn(II) oxidation in aquatic environments is primarily bacterially-mediated, little is known about the effect of Mn(III)-binding ligands on Mn(II) oxidation nor on the formation and removal of Mn(III). Pseudomonas putida GB-1 is one of the most extensively investigated of all Mn(II) oxidizing bacteria, encoding genes for three Mn oxidases (McoA, MnxG, and MopA). P. putida GB-1 and associated Mn oxidase mutants were tested alongside environmental isolates Pseudomonas hunanensis GSL-007 and Pseudomonas sp. GSL-010 for their ability to both directly oxidize weakly and strongly bound Mn(III), and to form these complexes through the oxidation of Mn(II). Using Mn(III)-citrate (weak complex) and Mn(III)-DFOB (strong complex), it was observed that P. putida GB-1, P. hunanensis GSL-007 and Pseudomonas sp. GSL-010 and mutants expressing only MnxG and McoA were able to directly oxidize both species at varying levels; however, no oxidation was detected in cultures of a P. putida mutant expressing only MopA. During cultivation in the presence of Mn(II) and citrate or DFOB, P. putida GB-1, P. hunanensis GSL-007 and Pseudomonas sp. GSL-010 formed Mn(III) complexes transiently as an intermediate before forming Mn(III/IV) oxides with the overall rates and extents of Mn(III,IV) oxide formation being greater for Mn(III)-citrate than for Mn(III)-DFOB. These data highlight the role of bacteria in the oxidative portion of the Mn cycle and suggest that the oxidation of strong Mn(III) complexes can occur through enzymatic mechanisms involving multicopper oxidases. The results support the observations from field studies and further emphasize the complexity of the geochemical cycling of manganese.

Matrix Isolation and Ab Initio Study on the CHF3···CO Complex.

Intermolecular complexes between CHF3 and CO have been studied by ab initio calculations and IR matrix isolation spectroscopy. The computations at the MP2 and CCSD(T) levels of theory indicated five minima on the potential energy surface (PES). The most energetically favorable structure is the C(CO)-H(CHF3) coordinated complex ( Cs symmetry) with the stabilization energy of 0.84 kcal/mol as computed at the CCSD(T) level (with ZPVE and BSSE corrections). This is the only structure experimentally found in argon and krypton matrixes, whereas the weaker non-hydrogen-bonded complexes predicted by theory were not detected. The vibrational spectrum of this complex is characterized by a red-shift of the CF3 asymmetric stretching, splitting of the C-H bending mode, and blue-shifts of the C-H and C-O stretching vibrations as compared to the monomer molecules. The observed complexation-induced shifts of CHF3 and CO fundamentals are in good agreement with the computational predictions. It was shown that both MP2 and CCSD(T) calculations generally provided a reasonable description of the vibrational properties for the weak intermolecular complexes of fluoroform.

Solubility, acid-base properties and thermodynamics of interaction between three NTA-phosphonate derivatives and the main cationic components (H+, Na+, Mg2+ and Ca2+) of natural fluids

Abstract Solution thermodynamics of three aminophosphonic acids are studied in this work. In particular, the protonation constants [ log ( K i H /mol kg−1)] of N-phosphonomethyliminodiacetic acid (NTAP), N,N-Bis(phosphonomethyl)glycine (NTAP2) and Nitrilotris(methylenephosphonic acid) (NTAP3) and the solubility of NTAP were determined by potentiometric measurements (ISE-[H+] glass electrode) in three different ionic media, namely NaCl(aq), (CH3)4NCl(aq) and (C2H5)4NI(aq) at different ionic strengths (in the range 0 log K i H on ionic strength and temperature was studied by Debye-Huckel type equation and by Specific ion Interaction Theory (SIT). At infinite dilution, the refined values of the first protonation constants are: log ( K i H /mol kg−1) = 11.4 ± 0.1, 12.4 ± 0.1 and 13.3 ± 0.1 for NTAP, NTAP2 and NTAP3, respectively and the enthalpy changes relative to the first protonation step are: −15.7 ± 0.3, −20.5 ± 0.4 and –33.5 ± 0.2 kJ mol−1 (same order). The basicity trend: NTAP3 > NTAP2 > NTAP is observed in all the ionic media. The differences in the values of the protonation constants obtained in the three ionic media were also interpreted in terms of formation of weak complex and eleven Na+/L species are obtained using the so called ΔpK method. Solubility investigations performed on NTAP allowed us to determine the Setschenow and the activity coefficients of the neutral species. The values of the total and specific solubility in pure water are: log ( S 0 T /mol kg−1) = −1.431 ± 0.003 and log ( S 0 0 /mol kg−1) = −2.293 ± 0.006, respectively. The formation constants of the three ligands with Ca2+ and Mg2+ cations were determined at T = 298.15 K in NaCl(aq) at I = 0.151 mol kg−1, finding the presence of the ML and MHL species. The stability of the Ca2+/L is slightly higher than that of the Mg2+/L ones.

Weak polyelectrolyte complexation driven by associative charging.

Weak polyelectrolytes are relevant for a wide range of fields; in particular, they have been investigated as "smart" materials for chemical separations and drug delivery. The charges on weak polyelectrolytes are dynamic, causing polymer chains to adopt different equilibrium conformations even with relatively small changes to the surrounding environment. Currently, there exists no comprehensive picture of this behavior, particularly where polymer-polymer interactions have the potential to affect charging properties significantly. In this study, we elucidate the novel interplay between weak polyelectrolyte charging and complexation behavior through coupled molecular dynamics and Monte Carlo simulations. Specifically, we investigate a model of two equal-length and oppositely charging polymer chains in an implicit salt solution represented through Debye-Hückel interactions. The charging tendency of each chain, along with the salt concentration, is varied to determine the existence and extent of cooperativity in charging and complexation. Strong cooperation in the charging of these chains is observed at large Debye lengths, corresponding to low salt concentrations, while at lower Debye lengths (higher salt concentrations), the chains behave in apparent isolation. When the electrostatic coupling is long-ranged, we find that a highly charged chain strongly promotes the charging of its partner chain, even if the environment is unfavorable for an isolated version of that partner chain. Evidence of this phenomenon is supported by a drop in the potential energy of the system, which does not occur at the lower Debye lengths where both potential energies and charge fractions converge for all partner chain charging tendencies. The discovery of this cooperation will be helpful in developing "smart" drug delivery mechanisms by allowing for better predictions for the dissociation point of delivery complexes.

Long-range-corrected Rung 3.5 density functional approximations.

Rung 3.5 functionals are a new class of approximations for density functional theory. They provide a flexible intermediate between exact (Hartree-Fock, HF) exchange and semilocal approximations for exchange. Existing Rung 3.5 functionals inherit semilocal functionals' limitations in atomic cores and density tails. Here we address those limitations using range-separated admixture of HF exchange. We present three new functionals. LRC-ωΠLDA combines long-range HF exchange with short-range Rung 3.5 ΠLDA exchange. SLC-ΠLDA combines short- and long-range HF exchange with middle-range ΠLDA exchange. LRC-ωΠLDA-AC incorporates a combination of HF, semilocal, and Rung 3.5 exchange in the short range, based on an adiabatic connection. We test these in a new Rung 3.5 implementation including up to analytic fourth derivatives. LRC-ωΠLDA and SLC-ΠLDA improve atomization energies and reaction barriers by a factor of 8 compared to the full-range ΠLDA. LRC-ωΠLDA-AC brings further improvement approaching the accuracy of standard long-range corrected schemes LC-ωPBE and SLC-PBE. The new functionals yield highest occupied orbital energies closer to experimental ionization potentials and describe correctly the weak charge-transfer complex of ethylene and dichlorine and the hole-spin distribution created by an Al defect in quartz. This study provides a framework for more flexible range-separated Rung 3.5 approximations.

Abnormal Tetrel Bonds between Formamidine and TH3F: Substituent Effects

AbstractAb initio calculations have been performed for the complexes of formamidine (FA) with TH3F (T=C, Si, Ge, and Sn) as well as the complexes of FA derivatives including CH3, NH2, OH, OCH3, CH2CH3, CH2CH2CH3, CH(CH3)2, CF3, and F with SiH3F. In general, each complex is stabilized by both a main tetrel bond and a secondary interaction. The stability of the complex increases in the order T=C < Ge < Si < Sn, inconsistent with the magnitude of the σ‐hole on the tetrel atom. The (Z)‐FA complex is more stable than the (E)‐FA analogue. The imino nitrogen atom of FA is a better tetrel acceptor than most nitrogenated bases; it shows a particularly strong affinity for SiH3F with an interaction energy of ∼60 kJ/mol. Four electron‐donating groups give rise to the opposite effect on the strength of the tetrel bond: a weakening effect for OH and OCH3 but an enhancement for CH3 and NH2; the largest interaction energy occurs in CH3‐(Z)‐FA‐SiH3F, amounting to a magnitude of 80 kJ/mol. Two electron‐withdrawing groups have a larger weakening effect than OH and OCH3. The effect of the larger alkyl group is dependent on the type of complex. The weak complexes of CH3F are driven by electrostatic and dispersion interactions, while the strong complexes of TH3F (T=Si, Ge, and Sn) are dominated by electrostatic and polarization interactions, as well as orbital interactions.

Thermodynamic Study on the Protonation and Na+, Ca2+, Mg2+-Complexation of a Biodegradable Chelant (HEIDA) at Different Ionic Strengths and Temperatures

A potentiometric method has been used for the determination of the protonation constants of N-(2-hydroxyethyl)iminodiacetic acid (HEIDA or L) at various temperatures 283.15 ≤ T/K ≤ 383.15 and different ionic strengths of NaCl(aq), 0.12 ≤ I/mol·kg−1 ≤ 4.84. Ionic strength dependence parameters were calculated using a Debye–Huckel type equation, Specific Ion Interaction Theory and Pitzer equations. Protonation constants at infinite dilution calculated by the SIT model are $$ \log_{10} \left( {{}^{T}K_{1}^{\text{H}} } \right) = 8.998 \pm 0.008 $$ (amino group), $$ \log_{10} \left( {{}^{T}K_{2}^{\text{H}} } \right) = 2.515 \pm 0.009 $$ and $$ \log_{10} \left( {{}^{T}K_{3}^{\text{H}} } \right) = 1.06 \pm 0.002 $$ (carboxylic groups). The formation constants of HEIDA complexes with sodium, calcium and magnesium were determined. In the first case, the formation of a weak complex species, NaL, was found and the stability constant value at infinite dilution is log10KNaL = 0.78 ± 0.23. For Ca2+ and Mg2+, the CaL, CaHL, CaL2 and MgL species were found, respectively. The calculated stability constants for the calcium complexes at T = 298.15 K and I = 0.150 mol·dm−3 are: log10βCaL = 4.92 ± 0.01, log10βCaHL = 11.11 ± 0.02 and $$ \log_{10} \beta_{\text{Ca{L}}_{2}} $$ = 7.84 ± 0.03, while for the magnesium complex (at I = 0.176 mol·dm−3): log10βMgL = 2.928 ± 0.006. Protonation thermodynamic functions have also been calculated and interpreted.

Conventional Measurements of Sulfur Dioxide (SO2) in Red Wine Overestimate SO2 Antimicrobial Activity

Conventional approaches to measuring sulfur dioxide (SO2) in wine, such as aeration-oxidation, iodometric titration, and flow-injection analysis, are known to overestimate molecular SO2, particularly in red wine because of the dissolution of weak anthocyanin-bisulfite complexes during analysis. Methods for determining molecular SO2 without perturbing anthocyanin-bisulfite complexes and other weak adducts exist, e.g., headspace gas-detection tube measurements. However, it is unclear whether SO2 values achieved through conventional methods (“Molecular SO2”) or nonperturbing methods (molecular SO2) provide a better measure of antimicrobial activity. In our work, white and pseudo-red wines were prepared with varying additions of SO2; the red wine was produced by spiking the white wine with an anthocyanin extract. “Molecular SO2” and molecular SO2 concentration in white wines were well correlated, but “Molecular SO2” was significantly higher in red wines. Wines were inoculated with Saccharomyces cerevisiae strain EC1118 (Lallemand), and viability and culturability were evaluated at regular intervals. Both culturable and viable cell counts decreased significantly for treatments with 0.5 to 2.0 mg/L molecular SO2 in the white and red wines, and for 0.5 to 2.0 mg/L “Molecular SO2” in the white wine, but concentrations >2.0 mg/L “Molecular SO2” were necessary to decrease cell counts in the red wine. These results indicate that anthocyanin-bisulfite complexes have negligible antimicrobial activity, and that conventional approaches to measuring “Molecular SO2” are poorly suited to predicting the microbial stability of red wines.

Cryosolution infrared study of hydrogen bonded halothane acetylene complex

The interactions between halothane (2-bromo-2-chloro-1,1,1-trifluoroethane) and acetylene (C2H2) are studied by FTIR spectroscopy. Results obtained in liquid cryosolutions in Kr suggest weak complex formation stabilized by H – bond. The complexation enthalpy (∼11 kJ/mol) is evaluated in a series of temperature measurements (T ∼ 120–160 K) of integrated intensity of selected bands performed in liquefied Kr. The quantum chemical MP2/6-311++G(2d,2p) calculations predict four different structures of the complex. The most stable and populated (94% at T∼120 K) structure corresponds to the H – bond between H atom of halothane and pi-electron of triple bond between C atoms of acetylene. Wave numbers of vibrational bands of the most stable structure are calculated in anharmonic approximation implemented in Gaussian program.

Spectroscopic evidence of weak complex formation between N,N-dimethylformamide and fluoroform in the gas phase

The interactions between N,N-dimethylformamide (DMF) and fluoroform (CHF3) in the gas phase are studied with the help of FTIR spectroscopy. Temperature changes observed in the region of the CO stretching mode of DMF suggest a weak complex formation that results in a red wavenumber shift of the ν(CO) band. Series of van Hoff plots obtained by means of temperature and concentration spectroscopic measurements give the energy of the complex formation ΔE ∼ −19.6 kJ/mol. Ab initio calculations performed at the MP2/6–311++G(df,pd) level are in good agreement with the experimental results.

Kinetics and equilibrium adsorption study of selenium oxyanions onto Al/Si and Fe/Si coprecipitates

Inappropriate treatments for the effluents from semiconductor plants might cause the releases and wide distributions of selenium (Se) into the ecosystems. In this study, Al/Si and Fe/Si coprecipitates were selected as model adsorbents as they often formed during the wastewater coagulation process, and the removal efficiency of selenite (SeO3) and selenate (SeO4) onto the coprecipitates were systematically examined. The removal efficiency of SeO3 and SeO4 was highly related to surface properties of Al/Si and Fe/Si coprecipitates. The surface-attached Al shell of Al/Si coprecipitates shielded a portion of negative charges from the core SiO2, resulting in a higher point of zero charge than that of Fe/Si coprecipitates. Thus, adsorption of SeO3/SeO4 was favorable on the Al/Si coprecipitates. Adsorptions of both SeO3 and SeO4 on Al/Si coprecipitates were exothermic reactions. On Fe/Si coprecipitates, while SeO3 adsorption also showed the exothermic behavior, SeO4 adsorption occurred as an endothermic reaction. The kinetic adsorption data of SeO3/SeO4 on Al/Si and Fe/Si coprecipitates were described well by the pseudo-second-order kinetic model. SeO4 and SeO3 adsorption on Fe/Si or Al/Si were greatly inhibited by the strong PO4 ligand, whereas the weak ligand such as SO4 only significantly affected SeO4 adsorption. The weakest complex between SeO4 and Al was implied by the essentially SeO4 desorption as SeO4/PO4 molar ratios decreased from 0.5 to 0.2. These results were further confirmed by the less SeO4 desorption (41%) from Fe/Si coprecipitates than that from Al/Si coprecipitates (78%) while PO4 was added sequentially.

Current NMR Techniques for Structure-Based Drug Discovery.

A variety of nuclear magnetic resonance (NMR) applications have been developed for structure-based drug discovery (SBDD). NMR provides many advantages over other methods, such as the ability to directly observe chemical compounds and target biomolecules, and to be used for ligand-based and protein-based approaches. NMR can also provide important information about the interactions in a protein-ligand complex, such as structure, dynamics, and affinity, even when the interaction is too weak to be detected by ELISA or fluorescence resonance energy transfer (FRET)-based high-throughput screening (HTS) or to be crystalized. In this study, we reviewed current NMR techniques. We focused on recent progress in NMR measurement and sample preparation techniques that have expanded the potential of NMR-based SBDD, such as fluorine NMR (19F-NMR) screening, structure modeling of weak complexes, and site-specific isotope labeling of challenging targets.

Into the theory of the partial-filling affinity capillary electrophoresis and the determination of apparent stability constants of analyte-ligand complexes.

The partial-filling affinity capillary electrophoresis (pf-ACE) works with a ligand present in a background electrolyte that forms a weak complex with an analyte. In contrast to a more popular mobility-shift affinity capillary electrophoresis, only a short plug of the ligand is introduced into a capillary in the pf-ACE. Both methods can serve for determining apparent stability constants of the formed complexes but this task is hindered in the pf-ACE by the fact that the analyte spends only a part of its migration time in a contact with the ligand. In 1998, Amini and Westerlund published a linearization strategy that allows for extracting an effective mobility of an analyte in the presence of a neutral ligand out of the pf-ACE data. The main purpose of this paper is to show that the original formula is only approximate. We derive a new formula and demonstrate its applicability by means of computer simulations. We further inspect several strategies of data processing in the pf-ACE regarding a risk of an error propagation. This establishes a good practice of determining apparent stability constants of analyte-ligand complexes by means of the pf-ACE.

Role of Temperature on the Phase Modification of TiO2 Nanoparticles Synthesized by the Precipitation Method

Nanostructured TiO2 samples have been synthesized successfully by a simple precipitation method. The prepared samples are characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared (FTIR), photoluminescence (PL) spectroscopy, ultra violet (UV) spectroscopy and Raman spectroscopy respectively. The as-prepared TiO2 nanoparticls appear to be a single anatase phase with average crystalline size 37.68 nm at 150 ∘C and found to be transformed from anatase to rutile phase during the annealing of samples in the temperature range from 150 ∘C to 600 ∘C. The TEM images indicate the particle sizes are in the range between 12 and 25 nm for anatase phase TiO2 at 400 ∘C and 30–45 nm for rutile phase TiO2 at 600 ∘C. The luminescence property of the TiO2 nanoparticles studied by the emission properties confirms the presence of defect levels caused by the oxygen vacancies. Raman spectroscopy was used to identify and quantity the amorphous and crystalline TiO2 phases. FTIR studies reveal weak complex vibrations between the titanium and oxygen species and also additional unsaturated sites (Ti3+) through incorporation of (OH) groups, not otherwise seen in bulk TiO2.

Exceptional Experiences Following Exposure to a Sham “God Helmet”: Evidence for Placebo, Individual Difference, and Time of Day Influences

It has been claimed that applying weak complex electromagnetic patterns to the temporal lobes in a “God Helmet” stimulates the intrusion of right-hemispheric processes to awareness, resulting in exceptional experiences (ExEs). We explored the roles of wearing a sham helmet, time of day, and individual differences (paranormal belief, synesthesia, locus of control, hyperesthesia, and prior anomalous experiences) in alterations in consciousness and ExEs in the absence of neural stimulation. Thirty-two skeptics and 35 paranormal believers completed baseline, sham (morning), and sham (afternoon) conditions. Participants relaxed in a Faraday chamber for 30 minutes. Exit interviews explored subjective experiences and participants completed the Phenomenology of Consciousness Inventory (PCI). A mixed-model analysis of covariance found that believers scored higher than skeptics on some PCI dimensions, there was no influence of study conditions on PCI scores, and there was no interaction between belief and study conditions. An inductive thematic analysis identified a coding scheme for ExE. Believers reported more ExEs than skeptics. Regression models supported roles for hyperesthesia in alterations in consciousness and synesthesia in ExEs.

Modeling solubility and acid-base properties of some polar side chain amino acids in NaCl and (CH3)4NCl aqueous solutions at different ionic strengths and temperatures

The aim of the paper is to perform a critical analysis of the thermodynamic properties of five L-α-amino acids, namely arginine, aspartic acid, glutamic acid, glutamine and histidine. New potentiometric measurements to determine protonation constants and solubility (not for arginine) in NaCl and (CH3)4NCl aqueous solutions are reported, in order to investigate the medium effect. A preliminary analysis of the state of art evidenced the considerable amount of data in the ionic strength range 0 < I/mol kg−1 ≤ 0.1 and a lack of data (especially for arginine and glutamine) above 0.1 mol kg−1. For this reason, this paper deals with an analysis of both the literature and the new experimental data, assigning a weight to each datum as a function of its reliability. The ionic strength dependence of the protonation constants was interpreted using the EDH (Extended Debye-Hückel), the SIT (Specific ion Interaction Theory) and the Pitzer approaches. Simultaneous analysis of solubility data and protonation constants allowed us to obtain the Setschenow and the activity coefficients of all the species involved in the equilibria. The differences between the two media were also interpreted considering the formation of weak complexes between the ions of the supporting electrolytes and the ligands according to the complex formation model.Finally, recommended, tentative or provisional data for protonation constants and protonation enthalpy changes of the five amino acids at different temperatures and ionic strengths are provided.

Structure and Bonding in Uranyl(VI) Peroxide and Crown Ether Complexes; Comparison of Quantum Chemical and Experimental Data.

The structure, chemical bonding, and thermodynamics of alkali ions in M[12-crown-4]+, M[15-crown-5]+, and M[18-crown-6]+, M[UO2(O2)(OH2)2]+4,5, and M[UO2(O2)(OH)(OH2)]n1-n (n = 4, 5) complexes have been explored by using quantum chemical (QC) calculations at the ab initio level. The chemical bonding has been studied in the gas phase in order to eliminate solvent effects. QTAIM analysis demonstrates features that are very similar in all complexes and typical for electrostatic M-O bonds, but with the M-O bonds in the uranyl peroxide systems about 20 kJ mol-1 stronger than in the corresponding crown ether complexes. The regular decrease in bond strength with increasing M-O bond distance is consistent with predominantly electrostatic contributions. Energy decomposition of the reaction energies in the gas phase and solvent demonstrates that the predominant component of the total attractive (ΔEelec + ΔEorb) energy contribution is the electrostatic component. There are no steric constraints for coordination of large cations to small rings, because the M+ ions are located outside the ring plane, [On], formed by the oxygen donors in the ligands; coordination of ions smaller than the ligand cavity results in longer than normal M-O distances or in a change in the number of bonds, both resulting in weaker complexes. The Gibbs energies, enthalpies, and entropies of reaction calculated using the conductor-like screening model, COSMO, to account for solvent effects deviate significantly from experimental values in water, while those in acetonitrile are in much better agreement. Factors that might affect the selectivity are discussed, but our conclusion is that present QC methods are not accurate enough to describe the rather small differences in selectivity, which only amount to 5-10 kJ mol-1. We can, however, conclude on the basis of QC and experimental data that M[crown ether]+ complexes in the strongly coordinating water solvent are of outer-sphere type, [M(OH2)n+][crown ether], while those in weakly coordinating acetonitrile are of inner-sphere type, [M-crown ether]+. The observation that the M[UO2(O2)(OH)(OH2)]n1-n complexes are more stable in solution than those of M[crown ether]+ is an effect of the different charges of the rings.

An adaptive level set method for improving image segmentation

Segmentation is one of the most significant techniques in image processing studies. But the major limitations of low contrast, ambiguous boundary and complex morphology of images usually lead to unsatisfactory segmentation, especially in heavily noisy medical images. To address this problem, an attempt by improving Distance Regularized Level Set Evolution (DRLSE) model has been made to build up an effective and accurate active contour model to improve the segmentation ability. In this study, a balance concept between the pushing force and image’s contour strength of DRLSE model was adapted for contour segmentations, so the contour convergent/divergent force will be re-defined to make it more feasible for complicated boundaries. The proposed concept integrates the bilateral filtering and Canny contour, and the improved edge indicator function into the DRLSE model. The most important step is to adapt the improved edge indicator function appropriately with the Canny contour. To verify our proposed DRLSE scheme, different testing images are used. The experimental results show that the proposed approach has been examined and tested successfully in most cases. Consequently, the developed algorithm including the DRLSE model combing the Canny contour with an improved g edge indicator, demonstrate the effectiveness and reliability, especially in the testing samples with weak edges and complex topologies.

Balancing Biocompatibility, Internalization and Pharmacokinetics of Polycations/siRNA by Structuring the Weak Negative Charged Ternary Complexes with Hyaluronic Acid.

Polycations are generally used to work as delivery vector to develop siRNA-based therapy for gene-related diseases. The contradiction between inevitable toxicity, internalization, and pharmacokinetics of polycations/siRNA is a critical challenge for polycations and impedes their further application. Herein, we synthesized the ECMD polycations and constructed ECMD/siRNA/HA complexes with slight negative charge to address the above mentioned issue. We found that equipping with HA could effectively shield the positive charge and dramatically improve cell viability. Moreover, the ternary complexes with slight negative charge exhibited similar cellular uptake efficiency and knockdown efficiency compared with ECMD/siRNA binary complexes because of CD44 protein-mediated endocytosis. Pharmacokinetics experiment and in vivo distribution elucidated that the ternary complexes with negative charge could help to prolong the circulation time of siRNA in blood and affect the organs distribution after i.v. injection. In addition, with time going by, the accumulation amount of siRNA loaded by the ternary complexes was much more in tumor compared with the binary complexes. Therefore, we believed that building the complexes was a feasible method to further develop polycationic vectors for siRNA delivery.