Solute Concentration Dependence Research Articles

Expanding polymeric feedstocks for powder bed fusion via rational control of liquid–liquid phase separation

AbstractPowder bed fusion (PBF) is a promising technology in polymeric additive manufacturing, whose growth is inhibited by limited material options. In this manuscript, we report the use of thermally induced phase separation (TIPS) to controllably produce polymer powders of polypropylene that are suitable for PBF. Moreover, these studies provide crucial insight into the factors that govern the final size of the produced powder, offering fundamental insight that fosters the rational control of powder fabrication for PBF. More precisely, the impact of polymer concentration, molecular weight, and quench temperature on the size of the powder is demonstrated, where the particle size increases with solution concentration, quench temperature and molecular weight. The molecular weight dependence is consistent with a decrease in polymer solubility with an increase in chain length, while the solution concentration dependence can be explained by the relative fractions of the two phases in the precipitation process of polymer solutions. Careful analysis of the temperature and solution concentration dependence of the powder verifies that droplet coalescence is the governing mechanism in the phase separation‐based particle formation process. Therefore, this fundamental understanding provides pathways to use TIPS to produce powders suitable for PBF from a broad range of polymer solutions.

Structural Spectrum of 2D Materials in Solution: Toward Establishing 2D Assemblies’ Digital Factory

AbstractThe numerous hierarchical architectures of 2D assemblies endow them with a new dimension to realize novel properties. From theoretical perspective, freedoms stem from in‐plane and out‐plane mechanical properties of 2D materials separately, which makes 2D materials embrace more than one “persistence length” giving rise to the diverse morphologies. However, the understanding of 3D architecture formation in 2D assemblies is still in its infancy. In fact, there is even no theoretical classification or reference to help clarify structural difference among numerous experimental obtained 2D assemblies. Based on the theoretical model composed by 2D sheets and Lennard‐Jones liquids, solution concentration dependence of 2D materials conformation is systematically studied, and a ln K behavior is uncovered that can realize the theoretical conformation prediction of 2D materials. More importantly, the digital production line (solution processing procedure) is set up toward establishing the 2D assemblies’ digital factory. The obtained structures may provide a reference to 2D assemblies, which benefits the understanding of the structural difference among different experiments and even help to guide the experimental design of 2D assemblies with targeted architectures and properties.

PERIODIC MESOPOROUS ORGANOSILICAS WITH CHEMICALLY IMMOBILIZED β CYCLODEXTRIN MOIETIES FOR BILE SALTS SORPTION

Mesoporous silicas of MCM‑41 type with surface silanol, 3-aminopropyl, and β‑cyclo­dextrin‑containing groups were prepared by hydrothermal‑assisted base‑catalyzed sol‑gel condensation of structure-forming silanes in the presence of micelles of long‑chain quaternary ammonium salt. Characterization of synthesized silica materials was realized by low‑tempe­rature nitrogen adsorption‑desorption and chemical analysis of surface layer. It was found that addition of ‑cyclodextrin‑containing silane into the sol‑gel reaction mixture causes formation of MCM‑41‑type organosilica with higher surface area and hexagonally arranged uniform mesoporous structure. Sorption ability of synthesized silica materials towards sodium cholate and sodium taurocholate was studied in dependence of solution pH and concentration. It was found that sorption increases due to chemical immobilization of oligosaccharide moieties in the surface layer of silica, and achieves maximal values in the pH regions of molecular forms of bile acids prevailing. Experimental sorption results were analyzed using Freundlich, Redlich - Peterson, and Brunauer - Emmett - Teller models. The formation of island-type structures of bile salts with β‑cyclodextrin-containing surface sorption centers due to cooperative interactions between sorbate moieties was proved.

Ab initio investigation of elastic properties of dilute Cu alloys for high-gradient accelerating structures

The elastic properties and solid solution strengthening of several Cu alloys that may be promising for high gradient applications were studied using ab initio calculations based on density functional theory. Specifically, the temperature and solute concentration dependence of elastic properties including bulk and shear moduli, thermal expansion coefficient, and heat capacity of these alloys were calculated. We found that the bulk and shear moduli are linearly dependent on the solute concentration in the dilute regime and change significantly for different Cu alloys. The thermal expansion coefficient and heat capacity are comparatively less sensitive to solute concentrations. Solid solution strengthening is observed to be linearly correlated with the change of lattice parameter of Cu. This work provides an in-depth understanding of the elastic properties of Cu alloys, which is key for predicting their performance at high gradient in normal conducting accelerating structures.

Nonlinear electric response of the diffuse double layer to an abrupt charge displacement inside a biological membrane

In order to elucidate the old, still unsolved problem of how the diffuse electric double layer responds to an abrupt, intramolecular charge displacement inside a biological membrane, we investigated the fastest components of the light-induced electric signals of bacteriorhodopsin and its mutants, in numerous ionic and buffer solutions. The obtained data for temperature and solute concentration dependence were interpreted as a consequence of changes in the capacity of the diffuse double layer surrounding the purple membrane. The possible physiological consequences of this so far not demonstrated phenomenon are discussed.

Alkynyl Linkers as a Design Tool to Gain Control over the Self-Assembly of Meso-Substituted Porphyrins on HOPG.

Self-assembled monolayers (SAMs) fall generally into two broad categories: those that are covalently bound either to the surface or to each other and those that rely on weaker forces such as hydrogen bonding or van der Waals forces. The engineering of the structure of SAMs formed from weaker forces is an exciting and complex field that often utilizes long alkane substituents bound to core moieties. The core provides the unique optical, electronic, or catalytic property desired, while the interdigitation of the alkane chains provides the means for creating well-regulated patterns of cores on the substrate. This design technique sometimes fails because some of the alkane substituents remain extended into solution rather than become interdigitated on the substrate. One contributor to this is steric hindrance between elements of the core and of the alkane chain. It is shown that the use of an alkyne linker between the core and the alkane chain can, in the case of meso-substituted porphyrins, significantly reduce this steric barrier and allow more stable and predictable surface structures to form. In particular, 5,15-bis(1-octynyl)porphyrin and 5,15-bis(1-tetradecynyl)porphyrin are shown to form significantly more stable SAMs than their alkane-linked counterparts. Scanning tunneling microscopy is used to provide detailed surface structures. Temperature and solution concentration dependence of the surface coverage is also reported. Density functional theory (DFT) is used to determine the energetic effects associated with alkane substitution at both the meso and β positions and the beneficial energetic effects of the alkyne linker.

Combinatorial Search for New Solar Water Splitting Photoanode Materials in the Thin-Film System Fe–Ti–W–O

Abstract In order to identify new solar water splitting photoanodes, Fe–Ti–W–O materials libraries were fabricated by combinatorial reactive co-sputtering and investigated by high-throughput characterization methods to elucidate compositional, thickness, and structural properties. In addition, photoelectrochemical measurements such as potentiodynamic photocurrent determination and open circuit potential measurements were performed using an automated scanning droplet cell. In the thin-film library, a quaternary photoactive region Fe30–49Ti29–55W13–22Ox was identified as a hit composition region, comprising binary and ternary phases. The identified region shows a distinct surface morphology with larger grains (∼200 nm) being embedded into a matrix of smaller grains (∼80–100 nm). A maximum photocurrent density of 117 μA/cm2 at a bias potential of 1.45 V vs. RHE in NaClO4 as an electrolyte under standard solar simulating conditions was recorded. Additional samples with compositions from the hit region were fabricated by reactive co-sputtering and spin coating followed by annealing. Synchrotron X-ray diffraction of sputtered Fe32Ti52W16Ox thin-films, annealed in air (600 °C, 700 °C, 800 °C) revealed the presence of the phases FeTiO3 and Ti0.54W0.46O2. The composition Fe48Ti30W22Ox from the hit region was fabricated by spin coating and subsequent annealing for a detailed investigation of its structure and photoactivity. After annealing the spin-coated sample at 650 °C for 6 h, X-ray diffraction results showed a dominant pattern with narrow diffraction lines belonging to a distorted FeWO4 (ferberite) phase along with broad diffraction lines addressed as Fe2TiO5 and in a small fraction also, Fe1.7Ti0.23O3. In hematite, Fe can be substituted by Ti, therefore we suggest that in the newfound ferberite-type phase, Ti partially substitutes for Fe leading to a small lattice distortion and a doubling of the monoclinic unit cell. In addition, Na from the substrate stabilizes the new phase: its tentative chemical formula is NaxFe0.33Ti0.67W2O8. A maximum photocurrent density of around 0.43 mA/cm2 at 1.45 V vs. RHE in 1M NaOH (pH ∼ 13.6) as an electrolyte was measured. Different aspects of the dependence of annealing and precursor solution concentration on phase transformation and photoactivity are discussed.

Effect of HIx solution concentration on ion-exchange membrane performance in electro-electrodialysis

Electro-electrodialysis (EED) has been applied to the thermochemical water-splitting iodine-sulfur process for hydrogen production to enhance the hydrogen iodide (HI) component in the HI–I2–H2O mixture (HIx solution). In this work, the HIx solution concentration dependence of conductivity and transport number as the membrane-performance indexes of Nafion 212 and a styrene-grafted poly(ethylene-co-tetrafluoroethylene) (ETFE) membrane was investigated experimentally. From a theoretical analysis of measurements based on the new EED model, the effects of the H+ and I− contents and the diffusion coefficients of H+ and I− in the evaluated membranes on conductivity and transport number were as follows: HIx solution concentration dependence of the H+ and I− contents exhibited a significantly small or different variation in comparison with that of conductivity and transport number, indicating that the dominant factors for conductivity and transport number would not be the H+ and I− contents; thereby, the effect of the diffusion coefficients of H+ and I− should not be ruled out. In terms of the conductivity of Nafion 212, the diffusion coefficient of H+ is the dominant factor because the existence of I− was negligible, whereas in the case of the ETFE-St membrane, the effect of the diffusion coefficient of I− should be considered. The diffusion coefficient of I− could more strongly affect transport number for the evaluated membranes rather than the diffusion coefficient of H+, indicating that the H+ selectivity of the membranes could be determined relatively based on variations of I− behavior in the membranes.

Solvation thermodynamics of anti-tuberculosis Isoniazid in aqueous and in aqueous electrolytic media

Abstract Isoniazid forms one of the most potent antitubercular drugs effective against M. tuberculosis which functions in combination with pyrazinamide, rifampicin and ethambutol drugs. A drug is subjected to many complex processes from the time it is administered to the time the biologic response is affected. The physical properties give an idea of various types of interactions taking place between drug and water molecule. Keeping this in mind we have measured densities (ρ) and speeds of sound (u) of Isoniazid (INH) in aqueous, aqueous sodium chloride and potassium chloride (0.06 mol·kg−1 and 0.1 mol·kg−1 in water) at three different temperatures i.e. T = (288.15, 298.15 and 308.15) K in the concentration range of (0.01 to 0.1) mol·kg−1. From these experimental data, apparent molar volume ( V ϕ ) of solute, isentropic compressibility ( κ s ) of solution, apparent molar isentropic compressibility ( κ ϕ ) of Isoniazid (INH) in water and in aqueous solutions of 0.06 and 0.1 mol·kg−1 sodium chloride and potassium chloride have been calculated. The limiting apparent molar expansivity ( E ϕ 0 ) of solute and coefficient of thermal expansion ( α ∗ ) of Isoniazid (INH) have also been calculated. Transfer parameters have been interpreted from the point of view of concentration dependence of solute–solvent interactions. Infinite dilution values of V ϕ and κ ϕ have also obtained from extrapolation to zero molality and have been utilized in obtaining transfer volumes ( Δ tr V ϕ 0 ) and transfer compressibility ( Δ tr κ ϕ 0 ) of Isoniazid (INH) from aqueous solutions of 0.06 mol·kg−1 and 0.1 mol·kg−1 sodium chloride and potassium chloride at different temperatures. Results are used to analyze the nature of solute-solvent, solute-solute interaction and structure making/breaking ability of solute in the aqueous solution.

Concentration polarization and permeate flux variation in a vibration enhanced reverse osmosis membrane module

The performance of a vibration enhanced reverse osmosis membrane module for desalination of artificial seawater was investigated with computational fluid dynamics (CFD) simulations and experiments. The computational model couples fluid dynamics with solutes transport inside the full length domain containing ‘zigzag’ spacers using a two dimensional, transient Large Eddy Simulation turbulence model. Both the local concentration dependent solute properties and variation of permeate flux over the membrane surface were predicted with the model. Membrane local permeate flux, concentration polarization, shear rate, and mass transfer were also calculated. The results suggest concentration polarization in the seawater desalination process could be reduced by imposing vibration on the reverse osmosis membrane. It was determined that the higher the vibration frequency the higher the membrane permeate flux while keeping the vibration amplitude constant. The CFD simulation predictions are validated against experimental data of permeate fluxes with good agreement.

Characterization and performance evaluation of polymeric nanofiltration membranes for the separation of strategic elements from aqueous solutions

Nanofiltration (NF) can be used for the separation of mono- and divalent ions as well as for uncharged solutes, such as strategic elements from aqueous solutions. In dependence of pH and feed solution concentration, the element species and membrane charge may vary, which can strongly affect the separation performance. The aqueous solution of interest is acidic, sulfate-rich, and originated from a microbial leaching process of an accrued flue dust from German copper ore smelting with various strategic elements included. The separation of Ge, Mo, Re, Co, Cu, and Zn was evaluated in a cross-flow set-up (flow velocity: 0.5ms−1, transmembrane pressure: 10 – 20bar). For fundamental understanding, the flux, permeability, and separation performance of the utilized polyamide NF membranes (NF99HF, UTC-60) were investigated with NaCl and MgSO4 and compared to those of the strategic elements. Moreover, the surface characteristics of the membranes were analyzed by AFM, SEM, FTIR, contact angle analysis, and streaming potential measurements. The utilized membranes show differences regarding e.g. morphology, smoothness, and location of the isoelectric point. Nevertheless, the experimental results indicated that Re and Ge can be separated from the multicomponent solution with both tested membranes.

Is dynamic heterogeneity of water in presence of a protein denaturing agent different from that in presence of a protein stabilizer? A molecular dynamics simulation study

Rotational and translational dynamic heterogeneities (DHs) of ambient aqueous solutions of trimethylamine-N-oxide (TMAO) and tetramethylurea (TMU) at several solute concentrations have been investigated and compared. Motional characteristics of water molecules at solute interfaces and in bulk solutions have been thoroughly examined for the search of slow dynamics. Note, TMAO possesses zwitterionic structure and is a protein stabilizer whereas TMU is a neutral dipolar molecule and a strong denaturant. Results suggest that water-TMAO solutions possess stronger DH than water-TMU solutions with the solute concentration dependence being stronger for TMAO than for TMU. Diffusive dynamics slows down near the solute surface for both the solutes. Solvation structure shows TMAO-water interaction is stronger than TMU-water interaction, producing longer H-bond fluctuation timescale in TMAO solutions. In short, this paper presents, for the first time, a systematic and comparative study of motional features and inter-species interactions between aqueous solutions containing solutes that differ in their individual impacts on protein stability. Time-dependent rotational non-Gaussian parameter, \(\alpha_{2}^{r} (t)\), for bulk (solid lines) and interfacial (dash-dot-dot lines) water –OH bonds at two different concentration regimes of TMAO and TMU (upper panel) and at various concentrations of TMAO (lower panel). Vertical dashed lines indicate peak positions of \(\alpha_{2}^{r} (t)\) on time axis for bulk solutions. Representations are color-coded.

Adsorption kinetics of phosphonic acids and proteins on functionalized Indium tin oxide surfaces using electrochemical impedance spectroscopy

Phosphonic acids (PAs) are known to have a spontaneous affinity for chemisorption onto several metal oxide surfaces. The self – assembled monolayer (SAM) of phosphonates provides a platform for further surface modifications using biomolecules that can be adopted for the development of sensors and biosensors. With this in view, we studied adsorption kinetics of different phosphonic acids of short chain lengths such as phosphonopropionic acid (PPA), aminobenzylphosphonic acid (ABPA), benzylphosphonic acid (BPA), butylphosphonic acid (BuPA), and a long chain decylphosphonic acid (DecPA) on ITO surface using electrochemical impedance spectroscopy (EIS) at short and long time scales. The dependence of solution concentration on formation kinetics is studied and the existences of two discrete kinetics were revealed. We show from our studies that the rate of adsorption is controlled by diffusion at small time scales. Further, the phosphonic acid modified surface is also used as a substrate for the adsorption of cytochromeC (CytC) (a heme protein) and urease (an enzyme) and the kinetics of their adsorption has been studied.

Thermodynamic study of N-acetyl glycine in aqueous tetraethylammonium iodide solutions in the temperature interval (288.15 to 308.15) K: Volumetric and acoustic study

Knowledge of thermodynamic properties of substituted amino acids in aqueous medium can provide valuable information regarding the stabilisation mechanism of proteins. In this study, we report the density and ultrasonic speeds of N-acetyl glycine in (0.03, 0.05, 0.1, 0.15 and 0.2)mol⋅kg−1 aqueous solutions of tetraethylammonium iodide (TEAI) at temperatures (288.15, 293.15, 298.15, 303.15 and 308.15)K and at pressures 101kPa. From these results, the apparent molar volume and acoustical parameters, coefficient of isentropic compression, molal hydration number and apparent molar isentropic compression have been evaluated. The partial molar volume, partial molar isentropic compression, and their corresponding transfer functions were calculated. These results were used to interpret the type of interactions occurring in the ternary mixtures using the co-sphere overlap model. The pair and triplet interaction coefficients have been calculated from both the properties. The concentration and temperature dependence of (solute+solute) and (solute+solvent) interactions in the present study was also discussed. The partial molar volumes were used to obtain the partial molar isobaric expansibilities for N-acetyl glycine to examine the temperature dependence of such interactions. The structure-making/breaking ability of N-acetyl glycine has also been discussed in terms of the sign of ∂CP,∅0∂PT.

Aggregation behavior of polystyrene-b-poly(acrylic acid) at the air–water interface

The aggregation behavior of amphiphilic block copolymer polystyrene-b-poly(acrylic acid) (PS-b-PAA) at the air–water interface was investigated through surface pressure measurements (isotherms, compression–expansion hysteresis and compression relaxation experiments), Brewster Angle Microscopy (BAM) imaging and Atomic Force Microscopy (AFM) imaging. It is found that PS-b-PAA (Mn = 11490 g mol−1, PAA wt%∼62%) forms a stable Langmuir monolayer on the water surface (pH = 7) by using N,N-dimethylformamide (DMF) as the spreading solvent. The aggregation of block copolymer is induced by an initial diffusion of DMF into water from the interface. Upon compression of the film, the pseudoplateau observed in the Langmuir isotherm corresponds to a “pancake-to-brush” transition with the PAA chains gradually dissolving in the water subphase and stretching underneath the PS cores. Based on the isotherms and the BAM images, it is suggested that the polymer chain dynamics in spreading solutions with different concentrations at the time of solvent diffusion influence the interfacial behavior of block copolymers significantly. The Langmuir–Blodgett (LB) films prepared at different surface pressures from different spreading solution concentrations were scanned by AFM. A variety of morphologies such as wormlike, porous and reticulate structures, and dots were observed. The isotherms and AFM images show the spreading solution concentration and surface pressure dependence of the aggregation behavior of PS-b-PAA copolymer at the air–water interface.

Measuring the Grafting Density of Nanoparticles in Solution by Analytical Ultracentrifugation and Total Organic Carbon Analysis

Many of the solution phase properties of nanoparticles, such as their colloidal stability and hydrodynamic diameter, are governed by the number of stabilizing groups bound to the particle surface (i.e., grafting density). Here, we show how two techniques, analytical ultracentrifugation (AUC) and total organic carbon analysis (TOC), can be applied separately to the measurement of this parameter. AUC directly measures the density of nanoparticle-polymer conjugates while TOC provides the total carbon content of its aqueous dispersions. When these techniques are applied to model gold nanoparticles capped with thiolated poly(ethylene glycol), the measured grafting densities across a range of polymer chain lengths, polymer concentrations, and nanoparticle diameters agree to within 20%. Moreover, the measured grafting densities correlate well with the polymer content determined by thermogravimetric analysis of solid conjugate samples. Using these tools, we examine the particle core diameter, polymer chain length, and polymer solution concentration dependence of nanoparticle grafting densities in a gold nanoparticle-poly(ethylene glycol) conjugate system.

Volumetric approach to the interaction of diglycine in aqueous solutions of sulpha drugs at T = 288.15–308.15 K

Densities, ρ, were measured for ternary mixture of diglycine in aqueous of (0.01, 0.02, 0.03, and 0.04)molkg−1 sulphanilamide (SAM), sulphanilic acid (SAN), and sulphosalicylic (SSAD) acid dihydrate at T=288.15–308.15K, using vibrating tube digital densimeter. Apparent molar volume, Vϕ, has been determined from the experimental densities and the least-square fitting was carried out for the calculation of limiting apparent molar volumes values Vϕ0, and the increase in the Vϕ0 values has the following order in the investigated system: SAN<SAM<SSAD. The calculated Vϕ0 values indicate that diglycine–SSAD interactions are stronger than the other two drugs. These data were used to calculate the transfer ΔtrVϕ0 values of partial molar volumes. Transfer parameters have been interpreted from the point of view of concentration dependence of solute–solute and solute–solvent interactions. The limiting apparent molar expansibility Eϕ0 values for diglycine in aqueous solution of drugs have positive value and decrease with rise of temperature. The calculated values of thermal expansion coefficient, α2, have small and positive values whereas the values of Hepler's constant, ∂2Vϕ0/∂T2, have positive value except with SSAD. Hydration numbers have also been determined. The variation of these parameters with concentration and temperature clearly suggests the roles of diglycine and sulpha drugs in solute–solvent interactions.

Thermodynamic (volume and compressibility) and spectral investigations of the glycine, diglycine and triglycine in aqueous α- and β-cyclodextrin solutions at T=298.15K

Abstract Apparent molar volumes and apparent molar adiabatic compressibilities have been determined for glycine, diglycine, and triglycine in aqueous α- and β-cyclodextrin (0.002–0.008 mol kg− 1) solutions by measurements of densities and speeds of sound at 298.15 K. The limiting apparent molar volume, limiting apparent molar adiabatic compressibilities, and their corresponding slopes were computed using the density and speed of sound data. These data were used to calculate the transfer values of partial molar volumes and partial molar adiabatic compressibilities at infinite dilution. Transfer parameters have been interpreted from the point of view of concentration dependence of solute–solute and solute–solvent interactions. These transfer parameters have further been used to calculate the group contribution of a peptide backbone (− CH2CONH−)n unit. The experimental results have also been discussed on the basis of 1H NMR measurements.

Thermodynamic Study of Some Amino Acids, 2-Aminopropanoic Acid, 2-Amino-3-methylbutanoic Acid, 2-Amino-4-methylpentanoic Acid, and 2-Amino-3-phenylpropanoic Acid in Aqueous Saccharide Solutions at Different Temperatures: Volumetric and Ultrasonic Study

Knowledge of thermodynamic properties of amino acids in aqueous medium can provide valuable information about the stabilization mechanism of proteins. In this study, we report the density and speed of sound of some amino acids (2-aminopropanoic acid, 2-amino-3-methylbutanoic acid, 2-amino-4-methylpentanoic acid, and 2-amino-3-phenylpropanoic acid) in aqueous fructose, d-(+)-cellobiose, and d-melezitose solutions (0.1 mol·kg−1) at (293.15, 298.15, 303.15, and 308.15) K. From these data, the apparent molar volume and apparent molar adiabatic compressibility have been evaluated. The partial molar volume, partial molar adiabatic compressibility, and their corresponding transfer functions were calculated. These results were used to interpret the type of interactions occurring in the ternary mixtures using the cosphere overlap model. The concentration and temperature dependence of solute−solute and solute−solvent interactions in the present study was also discussed.

Iron oxyhydroxide nanoparticles formed by forced hydrolysis: dependence of phase composition on solution concentration

Nanoparticles of single-phase lepidocrocite (γ-FeOOH) and goethite (α-FeOOH) have been synthesized by forced hydrolysis of ferric nitrate with no other additives, and the particles have been characterized by XRD, FT-IR and TEM. At low Fe(NO(3))(3) concentrations the hydrolysis product is predominantly γ-FeOOH, while at high concentrations it is α-FeOOH. These particles are nanometers in size and fall within narrow particle size distributions. The dependence of the oxyhydoxide phase on ferric nitrate concentration is attributed to two thermodynamic factors, the enthalpy of formation and the surface enthalpy of hydration at the oxide-water interface (which is a function of surface area). Two potential mechanisms for the phase-specific growth are proposed that explain the solution concentration dependence of the phase formed. Three other common nanoscale particles (α-Fe(2)O(3), Fe(3)O(4) and γ-Fe(2)O(3)) have also been prepared by relatively simple thermal/chemical treatment of the γ-FeOOH nanoparticles.