Hydrothermally Synthesized ZnCr- and NiCr-Layered Double Hydroxides as Hydrogen Evolution Photocatalysts.

The layered double hydroxides (LDHs) of transition metals are of great interest as building blocks for the creation of composite photocatalytic materials for hydrogen production, environmental remediation and other applications. However, the synthesis of most LDHs is reported only by the conventional coprecipitation method, which makes it difficult to control the catalyst's crystallinity. In the present study, ZnCr- and NiCr-LDHs have been successfully prepared using a facile hydrothermal approach. Varying the hydrothermal synthesis conditions allowed us to obtain target products with a controllable crystallite size in the range of 2-26 nm and a specific surface area of 45-83 m2∙g-1. The LDHs synthesized were investigated as photocatalysts of hydrogen generation from aqueous methanol. It was revealed that the photocatalytic activity of ZnCr-LDH samples grows monotonically with the increase in their average crystallite size, while that of NiCr-LDH ones reaches a maximum with intermediate-sized crystallites and then decreases due to the specific surface area reduction. The concentration dependence of the hydrogen evolution activity is generally consistent with the standard Langmuir-Hinshelwood model for heterogeneous catalysis. At a methanol content of 50 mol. %, the rate of hydrogen generation over ZnCr- and NiCr-LDHs reaches 88 and 41 µmol∙h-1∙g-1, respectively. The hydrothermally synthesized LDHs with enhanced crystallinity may be of interest for further fabrication of their nanosheets being promising components of new composite photocatalysts.

Excess Enthalpies for Binary Mixtures of the Reactive System Acetic Acid + n-Butanol + n-Butyl Acetate + Water: Brief Data Review and Results at 313.15 K and Atmospheric Pressure.

The data on molar excess enthalpies, HmE, for the binary mixtures acetic acid + n-butanol, acetic acid + n-butyl acetate and n-butanol + n-butyl acetate at 313.15 K and atmospheric pressure were obtained with use of the C80 isothermal mixing calorimeter (Setaram). The correlation of the data was carried out using the NRTL model and Redlich-Kister equation. A comparative analysis with the literature data on all available binary subsystems of the quaternary system was carried out. Other thermodynamic properties (Cp,mE, SmE, ΔmixSm, GmE and ΔmixGm) of the binary systems were estimated using literature data and well-known formulas of classical thermodynamics.

Synthesis and Characterization of Inorganic-Organic Derivatives of Layered Perovskite-like Niobate HSr2Nb3O10 with n-Amines and n-Alcohols.

A protonated and hydrated Dion-Jacobson-phase HSr2Nb3O10∙yH2O was used to prepare two series of inorganic-organic derivatives containing non-covalently intercalated n-alkylamines and covalently grafted n-alkoxy groups of different lengths, as they are promising hybrid materials for photocatalytic applications. Preparation of the derivatives was carried out both under the conditions of standard laboratory synthesis and by solvothermal methods. For all the hybrid compounds synthesized structure, quantitative composition, a type of bonding between inorganic and organic parts as well as light absorption range were discussed using powder XRD, Raman, IR and NMR spectroscopy, TG, elemental CHN analysis, and DRS. It was shown that the inorganic-organic samples obtained contain approximately one interlayer organic molecule or group per proton of the initial niobate, as well as some amount of intercalated water. In addition, the thermal stability of the hybrid compounds strongly depends on the nature of the organic component anchoring to the niobate matrix. Although non-covalent amine derivatives are stable only at low temperatures, covalent alkoxy ones can withstand heat up to 250 °C without perceptible decomposition. The fundamental absorption edge of both the initial niobate and the products of its organic modification lies in the near-ultraviolet region (370-385 nm).

1H NMR Study of the HCa2Nb3O10 Photocatalyst with Different Hydration Levels.

The photocatalytic activity of layered perovskite-like oxides in water splitting reaction is dependent on the hydration level and species located in the interlayer slab: simple or complex cations as well as hydrogen-bonded or non-hydrogen-bonded H2O. To study proton localization and dynamics in the HCa2Nb3O10·yH2O photocatalyst with different hydration levels (hydrated-α-form, dehydrated-γ-form, and intermediate-ß-form), complementary Nuclear Magnetic Resonance (NMR) techniques were applied. 1H Magic Angle Spinning NMR evidences the presence of different proton containing species in the interlayer slab depending on the hydration level. For α-form, HCa2Nb3O10·1.6H2O, 1H MAS NMR spectra reveal H3O+. Its molecular motion parameters were determined from 1H spin-lattice relaxation time in the rotating frame (T1ρ) using the Kohlrausch-Williams-Watts (KWW) correlation function with stretching exponent ß = 0.28: Ea=0.2102 eV, τ0=9.01 × 10-12 s. For the ß-form, HCa2Nb3O10·0.8H2O, the only 1H NMR line is the result of an exchange between lattice and non-hydrogen-bonded water protons. T1ρ(1/T) indicates the presence of two characteristic points (224 and 176 K), at which proton dynamics change. The γ-form, HCa2Nb3O10·0.1H2O, contains bulk water and interlayer H+ in regular sites. 1H NMR spectra suggest two inequivalent cation positions. The parameters of the proton motion, found within the KWW model, are as follows: Ea=0.2178 eV, τ0=8.29 × 10-10 s.

NMR Study of Intercalates and Grafted Organic Derivatives of H2La2Ti3O10.

The protonated perovskite-like titanate H2La2Ti3O10 has been used to produce organic-inorganic hybrids with simple organic molecules: methylamine, methanol, monoethanolamine, and n-butylamine. The optimal pathways for the preparation of such hybrids are summarized. Solid-state NMR, combined with thermal analysis, Raman, and IR spectroscopy, has been applied to determine the bonding type in the obtained organic-inorganic hybrids. It has been found that, in the methanolic hybrid, the organic residues are covalently bound to the inorganic matrix. In contrast, in the methylamine and n-butylamine hybrids, the organic molecules are intercalated into the inorganic matrix in cationic forms. The structure of the monoethanolamine hybrid is composite and includes both the covalently bound and intercalated organic species.

Comprehensive Analysis of the Copper Exchange Implemented in Ammonia and Protonated Forms of Mordenite Using Microwave and Conventional Methods.

This article presents the results of a comprehensive study of copper-exchanged mordenite samples prepared from its ammonia and protonated forms (Si/Al = 10) using two different ion exchange methods: conventional and microwave (MW)-assisted. The protonated H-MOR-10 sample was obtained by calcination of commercial NH4MOR-10; in this case, a slight degradation of the mordenite framework was observed, but the resulting defects were partially restored after the first ion-exchange procedure of protons for copper ions. The level of copper exchange in the studied materials was found to be limited to 70%. Regardless of the exchange procedure, the replacement of ammonium or proton ions with copper led to a linear increase in the a/b ratio of cell parameters in accordance with an increase in the level of copper exchange, which means that all Cu2+ cations are ion-exchangeable and enter the main mordenite channel. Thermal analysis indicated a correlation between the replacement of various ammonium and hydroxyl groups by copper ions during the exchange treatment and their dehydroxylation energy during thermal decomposition. As a conclusion: MW-assisted treatment proved itself as an efficacious method for the synthesis of copper-exchanged mordenites, which not only significantly reduces preparation time but leads to a systematically higher copper exchange level.

Comparative In Vitro Evaluation of Antibacterial and Osteogenic Activity of Polysaccharide and Flavonoid Fractions Isolated from the leaves of Saussurea controversa.

The osteogenic, cytotoxic, and antibacterial activities of polysaccharide (PS-SC) and flavonoid (F-SC) fractions isolated from the leaves extract of Saussurea controversa were studied in vitro. F-SC consists of the five quercetin glycosides in the ratio 2:8:10:1:4, which were isolated from the leaves extract of S. controversa and have been characterized previously. PS-SC was first isolated from the leaves extract of S. controversa and has been described. PS-SC consists in 30 compounds is characterized by a high degree of heterogeneity with a heterogeneity index of 19.74. The Mw and Mn of PS-SC were 108.6 and 5.5 kDa, respectively. Structural fragments are represented by galactose, arabinose, xylose, glucose, uronic acids, mannose, and rhamnose in a 10.1:3.3:2.2:2.1:1.7:0.9:0.5 molar ratio. F-SC as compared with PS-SC showed in vitro microbicidal (50 g/L) and better bacteriostatic (6.25 g/L versus 25 g/L of PS-SC) effects against the 24-h growth of Staphylococcus aureus strain 209 P and a 21-day absence of cytotoxicity on human adipose-derived multipotent mesenchymal stromal cells (hAMMSCs). Both fractions (PS-SC>F-SC) at doses of 10-50 mg/L stimulated differentiation of hAMMSCs into secreting osteoblasts accompanied by local mineralization of extracellular matrix. These fractions of S. controversa and especially F-SC, might be promising peroral drugs in the complex treatment of bone fractures and for prophylaxis of their infectious complications.

Polar Nature of (CH3NH3)3Bi2I9 Perovskite-Like Hybrids.

High-quality single crystals of perovskite-like (CH3NH3)3Bi2I9 hybrids have been synthesized, using a layered-solution crystal-growth technique. The large dielectric constant is strongly affected by the polar ordering of its constituents. Progressive dipolar ordering of the methylammonium cation upon cooling below 300 K gradually converts the hexagonal structure (space group P63/mmc) into a monoclinic phase (C2/c) at 160 K. A well-pronounced, ferrielectric phase transition at 143 K is governed by in-plane ordering of the bismuth lone pair that breaks inversion symmetry and results in a polar phase (space group P21). The dielectric constant is markedly higher in the C2/c phase above this transition. Here, the bismuth lone pair is disordered in-plane, allowing the polarizability to be substantially enhanced. Density functional theory calculations estimate a large ferroelectric polarization of 7.94 µC/cm2 along the polar axis in the P21 phase. The calculated polarization has almost equal contributions of the methylammonium and Bi3+ lone pair, which are fairly decoupled.

Osmolyte-Like Stabilizing Effects of Low GdnHCl Concentrations on d-Glucose/d-Galactose-Binding Protein.

The ability of d-glucose/d-galactose-binding protein (GGBP) to reversibly interact with its ligands, glucose and galactose, makes this protein an attractive candidate for sensing elements of glucose biosensors. This potential is largely responsible for attracting researchers to study the conformational properties of this protein. Previously, we showed that an increase in the fluorescence intensity of the fluorescent dye 6-bromoacetyl-2-dimetylaminonaphtalene (BADAN) is linked to the holo-form of the GGBP/H152C mutant in solutions containing sub-denaturing concentrations of guanidine hydrochloride (GdnHCl). It was hypothesized that low GdnHCl concentrations might lead to compaction of the protein, thereby facilitating ligand binding. In this work, we utilize BADAN fluorescence spectroscopy, intrinsic protein UV fluorescence spectroscopy, and isothermal titration calorimetry (ITC) to show that the sub-denaturing GdnHCl concentrations possess osmolyte-like stabilizing effects on the structural dynamics, conformational stability, and functional activity of GGBP/H152C and the wild type of this protein (wtGGBP). Our data are consistent with the model where low GdnHCl concentrations promote a shift in the dynamic distribution of the protein molecules toward a conformational ensemble enriched in molecules with a tighter structure and a more closed conformation. This promotes the increase in the configurational complementarity between the protein and glucose molecules that leads to the increase in glucose affinity in both GGBP/H152C and wtGGBP.

Highly Efficient Liquid-Phase Exfoliation of Layered Perovskite-like Titanates HLnTiO4 and H2Ln2Ti3O10 (Ln = La, Nd) into Nanosheets.

Nanosheets of layered perovskite-like oxides attract researchers as building blocks for the creation of a wide range of demanded nanomaterials. However, Ruddlesden-Popper phases are difficult to separate into nanosheets quantitatively via the conventional liquid-phase exfoliation procedure in aqueous solutions of bulky organic bases. The present study has considered systematically a relatively novel and efficient approach to a high-yield preparation of concentrated suspensions of perovskite nanosheets. For this, the Ruddlesden-Popper titanates HLnTiO4 and H2Ln2Ti3O10 (Ln = La, Nd) have been intercalated by n-alkylamines with various chain lengths, exposed to sonication in aqueous tetrabutylammonium hydroxide (TBAOH) and centrifuged to separate the nanosheet-containing supernatant. The experiments included variations of a wide range of conditions, which allowed for the achievement of impressive nanosheet concentrations in suspensions up to 2.1 g/L and yields up to 95%. The latter were found to strongly depend on the length of intercalated n-alkylamines. Despite the less expanded interlayer space, the titanates modified with short-chain amines demonstrated a much higher completeness of liquid-phase exfoliation as compared to those with long-chain ones. It was also shown that the exfoliation efficiency depends more on the sample stirring time in the TBAOH solution than on the sonication duration. Analysis of the titanate nanosheets obtained by means of dynamic light scattering, electron and atomic force microscopy revealed their lateral sizes of 30-250 nm and thickness of 2-4 nm. The investigated exfoliation strategy appears to be convenient for the high-yield production of perovskite nanosheet-based materials for photocatalytic hydrogen production, environmental remediation and other applications.

Photocatalytic Hydrogen Production from Aqueous Solutions of Glucose and Xylose over Layered Perovskite-like Oxides HCa2Nb3O10, H2La2Ti3O10 and Their Inorganic-Organic Derivatives.

Nowadays, the efficient conversion of plant biomass components (alcohols, carbohydrates, etc.) into more energy-intensive fuels, such as hydrogen, is one of the urgent scientific and technological problems. The present study is the first one focused on the photoinduced hydrogen evolution from aqueous D-glucose and D-xylose using layered perovskite-like oxides HCa2Nb3O10, H2La2Ti3O10, and their organically modified derivatives that have previously proven themselves as highly active photocatalysts. The photocatalytic performance was investigated for the bare compounds and products of their surface modification with a 1 mass. % Pt cocatalyst. The photocatalytic experiments followed an innovative scheme including dark stages as well as the control of the reaction suspension's pH and composition. The study has revealed that the inorganic-organic derivatives of the layered perovskite-like oxides can provide efficient conversion of carbohydrates into hydrogen fuel, being up to 8.3 times more active than the unmodified materials and reaching apparent quantum efficiency of 8.8%. Based on new and previously obtained data, it was shown that the oxides' interlayer space functions as an additional reaction zone in the photocatalytic hydrogen production and the contribution of this zone to the overall activity is dependent on the steric characteristics of the sacrificial agent used.

Crystal-Chemical and Thermal Properties of Decorative Cement Composites.

The advanced tendencies in building materials development are related to the design of cement composites with a reduced amount of Portland cement, contributing to reduced CO2 emissions, sustainable development of used non-renewal raw materials, and decreased energy consumption. This work deals with water cured for 28 and 120 days cement composites: Sample A-reference (white Portland cement + sand + water); Sample B-white Portland cement + marble powder + water; and Sample C white Portland cement + marble powder + polycarboxylate-based water reducer + water. By powder X-ray diffraction and FTIR spectroscopy, the redistribution of CO32-, SO42-, SiO44-, AlO45-, and OH- (as O-H bond in structural OH- anions and O-H bond belonging to crystal bonded water molecules) from raw minerals to newly formed minerals have been studied, and the scheme of samples hydration has been defined. By thermal analysis, the ranges of the sample's decomposition mechanisms were distinct: dehydration, dehydroxylation, decarbonation, and desulphuration. Using mass spectroscopic analysis of evolving gases during thermal analysis, the reaction mechanism of samples thermal decomposition has been determined. These results have both practical (architecture and construction) and fundamental (study of archaeological artifacts as ancient mortars) applications.

Physical-Chemical Exfoliation of n-Alkylamine Derivatives of Layered Perovskite-like Oxide H2K0.5Bi2.5Ti4O13 into Nanosheets.

In the present work, we report the results on exfoliation and coating formation of inorganic-organic hybrids based on the layered perovskite-like bismuth titanate H2K0.5Bi2.5Ti4O13·H2O that could be prepared by a simple ion exchange reaction from a Ruddlesden-Popper phase K2.5Bi2.5Ti4O13. The inorganic-organic hybrids were synthesized by intercalation reactions. Exfoliation into nanosheets was performed for the starting hydrated protonated titanate and for the derivatives intercalated by n-alkylamines to study the influence of preliminary intercalation on exfoliation efficiency. The selected precursors were exfoliated in aqueous solutions of tetrabutylammonium hydroxide using facile stirring and ultrasonication. The suspensions of nanosheets obtained were characterized using UV-vis spectrophotometry, dynamic light scattering, inductively coupled plasma spectroscopy, and gravimetry. Nanosheets were coated on preliminarily polyethyleneimine-covered Si substrates using a self-assembly procedure and studied using atomic force and scanning electron microscopy.

Development of a method for studying 241Pu/241Am activity ratio in the soil of the main Semipalatinsk test site areas.

The methodology for determination of 241Pu in soils of the main test sites of the Semipalatinsk Test Site (STS) has been developed. The results of 241Am and 241Pu activity determination in soil samples sampled at the main testing sites of the STS are presented. 241Pu/241Am activity ratio is calculated. In most cases, on local sites, 241Pu/241Am activity ratio is in a rather narrow range, which makes it possible to estimate 241Pu activity based on the results of 241Am gamma-spectrometric analysis. The accuracy of 241Pu activity estimation using this method will be about 50%, which is quite enough in most cases.

Study of n-alkylamine Intercalated Layered Perovskite-Like Niobates HCa2Nb3O10 as Photocatalysts for Hydrogen Production From an Aqueous Solution of Methanol.

A series of hybrid niobates HCa2Nb3O10×RNH2, containing n-alkylamines (R = Me, Et, Pr, Bu, Hx, Oc) intercalated into the interlayer space, has been thoroughly studied concerning the photocatalytic hydrogen production from a model aqueous solution of methanol for the first time. All the hybrid photocatalysts were synthesized by the conventional ceramic technique followed by protonation and intercalation of n-alkylamines. The products were characterized using XRD, Raman, IR and diffuse reflectance spectroscopy, TGA, CHN-analysis and SEM. Photocatalytic measurements were conducted according to an advanced scheme taking into account possible changes in the photocatalyst concentration because of sedimentation, pH shifts and exfoliation of the samples into nanoplatelets. Special attention was also paid to the feasible improvement of the photocatalytic activity of the samples via their modification with Pt nanoparticles as a cocatalyst. In the series of amine derivatives, the highest rate of hydrogen generation was demonstrated by the Pt-loaded HCa2Nb3O10×BuNH2 reaching apparent quantum efficiency of 13% in the 220-340 nm range. The initial HCa2Nb3O10 showed comparable efficiency of 8.3% that is greater than for other amine derivatives. It was demonstrated that for the investigated samples the photocatalytic activity correlates with their ability of water intercalation.

Synthesis of Organic-Inorganic Hybrids Based on Perovskite-like Bismuth Titanate H2K0.5Bi2.5Ti4O13·H2O and n-Alkylamines.

New organic-inorganic hybrids have been synthesized by the intercalation of n-alkylamines (methylamine, ethylamine, n-propylamine, n-butylamine, n-hexylamine, and n-octylamine) into the structure of the protonated and hydrated form of the perovskite-like layered titanate H2K0.5Bi2.5Ti4O13·H2O (HKBT4·H2O). The possibility of the synthesis of the hybrid materials was studied in a wide range of conditions. It was found that interlayer water plays a crucial role in the formation of intercalated hybrids. The obtained compounds were characterized with powder X-ray diffraction analysis; Raman, IR, and NMR spectroscopies; thermogravimetry (TG), TG coupled with mass spectrometry, and CHN analyses; and scanning electron microscopy. It was suggested that the intercalated n-alkylamines exist in the form of alkylammonium ions forming a paraffin-like bilayer with an average tilting angle of ∼77.5°. The obtained HKBT4×RNH2 compounds contain 0.4-0.7 n-alkylamine molecules per formula unit as well as the varied amount of intercalated water. By gentle heating, they can be obtained as dehydrated forms, which are thermally stable up to 250 °C.

Layered Titanate H2Nd2Ti3O10 Intercalated With n-Butylamine: A New Highly Efficient Hybrid Photocatalyst for Hydrogen Production From Aqueous Solutions of Alcohols.

A layered perovskite-type oxide intercalated with n-butylamine is reported as an efficient photocatalyst for hydrogen production from aqueous solutions of alcohols for the first time. The hybrid photocatalyst H2Nd2Ti3O10×BuNH2 was synthesized by solid-state ceramic method followed by protonation, intercalation of methylamine and subsequent substitution by n-butylamine. The product was characterized by powder XRD, TGA, STA-MS, DRS, IR, and Raman spectroscopy, CHN analysis, SEM. Intercalation of n-butylamine caused a dramatic increase in photocatalytic activity of H2Nd2Ti3O10 in the reaction of hydrogen evolution from aqueous solutions of methanol, ethanol, and n-butanol under UV radiation. While the non-intercalated Pt-loaded H2Nd2Ti3O10 showed a maximum quantum efficiency of only 2% in the 220-340 nm range, the efficiency for hybrid samples reached 23% under the same conditions and after variation of experimental parameters even 52% efficiency was achieved. This effect may be associated with the significant expansion of the interlayer space, which is considered as a separate reaction zone.

Methylammonium Polyiodides: Remarkable Phase Diversity of the Simplest and Low-Melting Alkylammonium Polyiodide System.

Newly discovered methylammonium polyiodides (MAIx) are unique precursors for innovative solvent-free technologies in perovskite photovoltaics because MAIx are liquids at room temperature and demonstrate high chemical reactivity. We investigated the features of an MAI-I2 system and built up a first phase diagram in wide temperature and composition ranges using data from differential scanning calorimetry, single-crystal X-ray diffraction, and visual thermal analysis. The phase diagram has been found to differ drastically from that of any related systems owing to the unique propensity of methylammonium toward forming a diversity of polyiodides with complicated crystal structures, namely, MAI2, MAI2.67, MAI4, and MAI5.5, found in this system for the first time. The performed density functional theory calculations revealed the crucial role of entropy contributing to the formation of higher methylammonium polyiodides, in good agreement with experimental data.

Determination of GnRH and its synthetic analogues' abuse in doping control: Small bioactive peptide UPLC-MS/MS method extension by addition of in vitro and in vivo metabolism data; evaluation of LH and steroid profile parameter fluctuations as suitable biomarkers.

Gonadotropin-releasing hormone (GnRH) and its small peptide synthetic analogues are included in Section S2 of the World Anti-Doping Agency (WADA) Prohibited List as they stimulate pituitary luteinizing hormone (LH) and testicular testosterone (T) secretion. Both the following approaches can be applied for determination of abuse of these peptides: direct identification of intact compounds and their metabolites in athletes' biofluids and evaluation of LH and T concentrations as mediate markers of drug intake. To develop an effective concept for GnRH and its analogues determination in anti-doping control, in vitro and in vivo studies were conducted. A new method was applied to the evaluation of the slow-release profile of buserelin, goserelin, and leuprolide biodegradable microspheres after the intramuscular injection in male volunteers. Eight metabolites of 10 GnRH analogues were identified after incubation with human kidney microsomes, most of them were leuprolide degradation products. Obtained data were added into ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) method for GnRH analogues determination. The detection time windows for administered peptides and their metabolites in urine samples were evaluated with 2 sample preparation techniques: dilute-and-shoot and solid-phase extraction. To support the second hypothesis, the measurement of LH and the main parameters of the steroid profile were performed in urine samples. Just 1 compound among those investigated resulted in the LH concentration dropping to non-physiological levels. Thus, for doping-control purposes, monitoring of hormone levels fluctuations could be applied only together with longitudinal passport steroid profile data.

Solid-phase extraction of small biologically active peptides on cartridges and microelution 96-well plates from human urine.

Currently liquid chromatography - mass spectrometry (LC-MS) analysis after solid-phase extraction (SPE) on weak cation-exchange cartridges is a method of choice for anti-doping analysis of small bioactive peptides such as growth hormone releasing peptides (GHRPs), desmoporessin, LHRH, and TB-500 short fragment. Dilution of urine samples with phosphate buffer for pH adjustment and SPE on weak cation exchange microelution plates was tested as a means to increase throughput of this analysis. Dilution using 200 mM phosphate buffer provides good buffering capacity without affecting the peptides recoveries. SPE on microelution plates was performed on Waters Positive Pressure-96 Processor with subsequent evaporation of eluates in nitrogen flow. Though the use of smaller sample volume decreases the pre-concentration factor and increases the limits of detection of 5 out of 17 detected peptides, the recovery, linearity, and reproducibility of the microelution extraction were comparable with cartridge SPE. The effectiveness of protocols was confirmed by analysis of urine samples containing ipamorelin, and GHRP-6 and its metabolites. SPE after urine sample dilution with buffer can be used for faster sample preparation. The use of microelution plates decreases consumption of solvents and allows processing of up to 96 samples simultaneously. Cartridge SPE with manual рН adjustment remains the best option for confirmation. Copyright © 2015 John Wiley & Sons, Ltd.