Technetium-99m labeling of hippuric and p-amino-hippuric acid in the presence of DTPA: Biological and pharmacokinetic evaluation and comparison with99mTc-DTPA

^99mTc-Hipp as a modified^99mTc-DTPA, and^99mTc-PAH as a new renal agent are developed. Each veal of lyophilised kit contain hippuric (Hipp) or p-aminohippuric acid (PAH), diethyltriaminepentaacetic acid as calciumtrisodium salt (CaNa₃DTPA) and stannouschloride (SnCl₂·xH₂O), in molar ratio Hipp/PAH:DTPA=4∶1. They are high radiochemical purity radiopharmaceuticals, with hydrophilic character and low percentage of protein binding. The ITL chromatography and HPLC analyses of these labeled compounds have shown almost identical results as^99mTc-DTPA, but their biological behavior in rats confirm certain differences.^99mTc-Hipp is a renal agent clearing by the glomerular system, with better pharmacokinetical parameters than^99mTc-DTPA:t _1/2(α)=4.1 min,t _1/2(β)=198.6 min,K _cl=1.2·10⁻²min⁻¹ and a twofold value for blood clearance (Cl=2.07 ml/min).^99mTc-PAH is a quite different renal agent, rapidly secreted by kidney as a tubular secretion agent. Its pharmacokinetical parameters:t _1/2(α)=2.5 min,t _1/2(β)=41.7 min andK _cl=5.1·10⁻⁴ min⁻¹ are almost equal to those of^99mTc-MAG₃, but the blood clearance of Cl=5.22 ml/min is even higher than that of IOH clearance.     

Monitoring of the <Superscript>14</Superscript>C concentration in the stack air of the nuclear power plant VVER Jaslovske Bohunice

¹⁴C releases in the stack air of the NPPs V1 and V2, Jaslovske Bohunice was determined during the year 2004–2010. Radioactivity concentration of ¹⁴C in the stack air was determined in the forms of inorganic ¹⁴CO₂ and ¹⁴C _n H _m . The annual average activity concentration in the stacks air samples varies between 12 and 121 Bq m⁻³. NPP V1, starting with 45 Bq m⁻³ in 2005 is decreasing due to the shutting down of the reactors (the first reactor was shut down in December 2006 and the second reactor in December 2008). The average value of radioactivity concentration for power unit V2 was 32 Bq m⁻³ in 2004 and reached the value of 102 Bq m⁻³ in the first-quarter of the 2010. The average normalized yearly discharge rates were between 0.39 and 0.64 TBq GW_e⁻¹ year⁻¹ (2005–2008), NPP V1 and 0.19–0.61 TBq GW_e⁻¹ year⁻¹ (2004–first-quarter 2010) for NPP V2, Jaslovske Bohunice. Most of the discharged ¹⁴C is in a hydrocarbon form, (95% for Jaslovske Bohunice NPP V2), but the CO₂ fraction may reach 37% in the air stack for Jaslovske Bohunice V1.     

Preliminary studies of 99mTc-PQQ-NMDAR binding and effect of specificity binding by mannitol

Pyrroloquinoline quinone (PQQ) is a powerful neuroprotectant that specifically binds to brain NMDA receptors and inhibits excitotoxicity. Imaging this binding reaction in the brain remains a long sought goal in this field of study, and one of the primary challenges remaining is enabling soluble labeled PQQ to pass the blood–brain barrier (BBB). Previously, our group successfully labeled PQQ with Technetium-99m (^99mTc), a metastable nuclear isomer used in radioactive isotope medical tests. In this work, we determined the specific binding of ^99mTc-PQQ and NMDAR by radioligand receptor assay. Ebselen (EB) and MK-801 both effectively inhibited ^99mTc-PQQ binding. We then investigated methods of opening the BBB using mannitol to enable entry to the brain by ^99mTc-PQQ. Our results showed that 7.5 mL/kg of 20 % mannitol effectively opened the BBB and 20 min was the optimum treatment time. Competition studies showed that mannitol did not affect the specific binding between ^99mTc-PQQ and NMDA receptors. Using this method, the amount of ^99mTc-PQQ uptake and retention was increased most significantly in the hippocampus and cortex, and re-opening the BBB did not affect binding. Together, our results demonstrate that the use of mannitol to open the BBB may contribute significantly to improving image quality by increasing the uptake amount of a water-soluble agent in brain.     

Synthesis,radiochemical and biological characteristics of <Superscript>99m</Superscript>Tc-8-hydroxy-7-substituted quinoline complex: a novel agent for infection imaging

2,2′-[(8-hydroxyquinolin-7-yl)methylazanediyl]diacetic acid (HQMADA) was synthesized via reaction of 8-hydroxyquinoline with iminodiacetic acid in presence of paraformaldehyde with a yield of 27%. The obtained compound was well characterized via different analytical techniques. Labeling of the synthesized compound with technetium-99m in pertechnetate form (^99mTcO₄ ⁻) in the presence of stannous chloride dihydrate was carried out via chelation reaction. The reaction parameters that affect the labeling yield such as HQMADA concentration, stannous chloride dihydrate concentration, pH of the reaction mixture, and reaction time were studied to optimize the labeling conditions. Maximum radiochemical yield of ^99mTc-HQMADA complex (91.9%) was obtained by using 1.5 mg HQMADA, 50 μg SnCl₂·2H₂O, pH 8 and 30 min reaction time. Biodistribution studies in mice were carried out in experimentally induced infection in the left thigh using E. coli. ^99mTc-HQMADA complex showed higher uptake (T/NT = 5.5 ± 0.3) in the infectious lesion than the commercially available ^99mTc-ciprofloxacin (T/NT = 3.8 ± 0.8). Biodistribution studies for ^99mTc-HQMADA complex in Albino mice bearing septic and aseptic inflammation models showed that ^99mTc-HQMADA complex able to differentiate between septic and aseptic inflammation.     

A novel electrochemical <Superscript>99</Superscript>Mo/<Superscript>99m</Superscript>Tc generator

A novel electrochemical process to avail clinical grade ^99mTc from (n,γ)⁹⁹Mo has been demonstrated. The electrochemical parameters were optimized to maximize the ^99mTc yield with minimal ⁹⁹Mo contamination. ⁹⁹Mo/^99mTc generators containing up to 29.6 GBq (800 mCi) ⁹⁹Mo were developed and their performance were extensively evaluated for 10 days without changing the operating conditions. Very high radioactive concentration of ^99mTcO₄ ⁻ of acceptable quality, commensurate with hospital radiopharmacy requirements could be availed from the system with >90% yield. The compatibility of the product for the formulation of ^99mTc labeled radiopharmaceuticals such as ^99mTc-DMSA and ^99mTc-EC was found to be satisfactory in terms of high labeling yields. The proposed route represents an important step for enhancing the scope of accessing clinical grade ^99mTc from low specific activity (n, γ)⁹⁹Mo.     

Study on mechanism for oxidation of <Emphasis Type="Italic">N,N</Emphasis>-dimethylhydroxylamine by nitrous acid

The oxidation of N,N-dimethylhydroxylamine (DMHAN) by nitrous acid is investigated in perchloric acid and nitric acid medium, respectively. The effects of H⁺, DMHAN, ionic strength and temperature on the reaction are studied. The rate equation in perchloric acid medium has been determined to be −d[HNO₂]/dt = k[DMHAN][HNO₂], where k = 12.8 ± 1.0 (mol/L)⁻¹ min⁻¹ when the temperature is 18.5 °C and the ionic strength is 0.73 mol/L with an activation energy about 41.5 kJ mol⁻¹. The reaction becomes complicated when it is performed in nitric acid medium. When the molarity of HNO₃ is higher than 1.0 mol/L, nitrous acid will be produced via the reaction between nitric acid and DMHAN. The reaction products are analyzed and the reaction mechanism is discussed in this paper.     

Scalar-relativistic 5f-in-core pseudopotentials and core-polarization potentials for trivalent actinides: calibration calculations for Ac<Superscript>3+</Superscript>, Cm<Superscript>3+</Superscript> and Lr<Superscript>3+</Superscript> complexes

The performance of recently proposed 5f-in-core pseudopotentials for the trivalent actinides was investigated in calculations for model complexes An³⁺L ⁿ⁻ for three selected actinides (An³⁺ = Ac³⁺, Cm³⁺, Lr³⁺) and eight simple ligands with atoms from the first three periods of the table of elements (L ⁿ⁻ = F⁻, Cl⁻, OH⁻, SH⁻, CO, NH₂⁻, H₂O, H₂S, NH₃). Results of Hartree-Fock and Coupled Cluster with singles, doubles and perturbative triples calculations using basis sets of quadruple-zeta quality are compared to corresponding reference data obtained with scalar-relativistic energy-adjusted 5f-in-valence small-core pseudopotentials. The inclusion of core-polarization potentials in the 5f-in-core pseudopotential calculations and corrections of the basis set superposition error by the counterpoise correction leads to very good agreement between the 5f-in-valence and 5f-in-core pseudopotential results for bond lengths, bond angles and binding energies. Results from 5f-in-core pseudopotential calculations using different density functionals also show reasonable agreement with the more rigorous Coupled Cluster results. It is argued that the An 5f rather than the An f population is a useful criterion for the applicability of a specific An 5f-in-core pseudopotential.     

Hydrolysis behavior of a precursor for bridged polysilsesquioxane 1,4-bis(triethoxysilyl)benzene: a <Superscript>29</Superscript>Si NMR study

The hydrolysis behavior of 1,4-bis(triethoxysilyl)benzene (BTB), a precursor of bridged polysilsesquioxane, was investigated with high-resolution ²⁹Si nuclear magnetic resonance (²⁹Si NMR) spectroscopy at ambient temperature in a system with BTB:ethanol:water:HCl = 1:10:x:0.8 × 10⁻⁴ (x = 3, 6 or 9). Signals due to hydrolyzed triethoxysilyl groups as well as unhydrolyzed triethoxysilyl groups [−Si(OEt)₃, −Si(OEt)₂(OH), −Si(OEt)(OH)₂ and −Si(OH)₃ (OEt = OCH₂CH₃)] formed four sub-regions based on the number of hydroxyl groups bound to a silicon atom. In addition, one silicon environment influenced the other silicon environment by an intra-molecular interaction between two silicon atoms, and each sub-region for monomeric species thus contained four signals. Based on the development of signal intensity, it is revealed that one of the two triethoxysilyl groups in BTB is hydrolyzed preferentially. Thus, when a triethoxysilyl group is hydrolyzed, the −Si(OH) _x (OEt)_3−x (x = 1, 2) groups formed undergo further hydrolysis, which is opposite to the tendency expected from the hydrolysis behavior of organotrialkoxysilanes under acidic conditions.     

The interaction of <Superscript>99m</Superscript>Tc with pyrimidine compounds

The reaction of ^99mTc of different oxidation states (+7, +4) with 2-thiouracil and 5-nitrobarbituric acid have been studied at different temperatures, pH and concentrations. The reaction mixtures have been analyzed at different times using thin layer chromatography (TLC) and a radio detector to show the peaks at the plates. ^99mTc is obtained from the Mo generators with oxidation state (+7). The use of SnCl₂ as a reducing agent gave ^99mTc with oxidation state (+4). It is very difficult to separate the complexes formed from the reactions in very small concentration. The percentage of ^99mTc and its oxidation state involved in the complexes can be determined. The labeling efficiencies (percentage of complex) in the reaction of ^99mTc⁺⁷ with 5-nitro-barbituric-acid increases mostly at pH  10. Both oxidation states of ^99mTc(+7, +4) can be detected at pH’s 4 and 10, but at pH  4, the reduced form ^99mTCO₂, is more pronounced. At pH  7 no complexes were detected and most of ^99mTc remains as ^99mTCO₄ ⁻ . By increasing the ligand concentration, the labeling efficiencies of the complex increases. For the reaction of ^99mTc of oxidation states (+4, +7) with 2-thiouracil at different temperatures and analytical times it is concluded that several complexes with different R_f values were observed in equilibrium and most of these complexes were unstable.     

Characterization of a Thermostable Family 1 Glycosyl Hydrolase Enzyme from <Emphasis Type="Italic">Putranjiva roxburghii</Emphasis> Seeds

A 66-kDa thermostable family 1 Glycosyl Hydrolase (GH1) enzyme with β-glucosidase and β-galactosidase activities was purified to homogeneity from the seeds of Putranjiva roxburghii belonging to Euphorbiaceae family. N-terminal and partial internal amino acid sequences showed significant resemblance to plant GH1 enzymes. Kinetic studies showed that enzyme hydrolyzed p-nitrophenyl β-d-glucopyranoside (pNP-Glc) with higher efficiency (K _cat/K _m = 2.27 × 10⁴ M⁻¹ s⁻¹) as compared to p-nitrophenyl β-d-galactopyranoside (pNP-Gal; K _cat/K _m = 1.15 × 10⁴ M⁻¹ s⁻¹). The optimum pH for β-galactosidase activity was 4.8 and 4.4 in citrate phosphate and acetate buffers respectively, while for β-glucosidase it was 4.6 in both buffers. The activation energy was found to be 10.6 kcal/mol in the temperature range 30–65 °C. The enzyme showed maximum activity at 65 °C with half life of ~40 min and first-order rate constant of 0.0172 min⁻¹. Far-UV CD spectra of enzyme exhibited α, β pattern at room temperature at pH 8.0. This thermostable enzyme with dual specificity and higher catalytic efficiency can be utilized for different commercial applications.     

Some remarks on equilibrium state in dynamic condition

For dehydration of CaC₂O₄·H₂O and thermal dissociation of CaCO₃ carried out in Mettler Toledo TGA/SDTA-851^e/STAR^e thermobalance similar experimental conditions was applied: 9–10 heating rates, q = 0.2, 0.5, 1, 2, 3, 6, 12, 24, 30, and 36 K min⁻¹, for sample mass 10 mg, in nitrogen atmosphere (100 ml min⁻¹) and in Al₂O₃ crucibles (70 μl). There were analyzed changes of typical TGA quantities, i.e., T, TG and DTG in the form of the relative rate of reaction/process intended to be analyzed on-line by formula (10). For comparative purposes, the relationship between experimental and equilibrium conversion degrees was used (for P = P^\ominus P = P^{{\ominus}} ). It was found that the solid phase decomposition proceeds in quasi-equilibrium state and enthalpy of reaction is easily “obscured” by activation energy. For small stoichiometric coefficients on gas phase side (here: ν = 1) discussed decomposition processes have typical features of phenomena analyzable by known thermokinetic methods.     

Study of magnetic ferrite nanoparticles labeled with <Superscript>99m</Superscript>Tc-pertechnetate

This study examined the applications of novel non-polymer magnetic ferrite nanoparticles (Fe₃O₄ NPs) labeled with ^99mTc-pertechnetate (^99mTcO₄ ⁻). The radiochemistry, chemistry, and biodistribution of Fe₃O₄ NPs labeled with ^9mTcO₄ ⁻ were analyzed. This paper employed instant thin layer chromatography and magnetic adsorption to evaluate the labeling efficiency and stability of ^99mTc-Fe₃O₄ at various reaction conditions. A scanning electron microscope, X-ray diffractometer, Fourier transform infrared spectrometer, laser particle size analyzer, and superconducting quantum interference device magnetometer were used to analyze the physical and chemical properties of the Fe₃O₄ and ⁹⁹Tc-Fe₃O₄ nanoparticles. The biodistribution and excretion of ^99mTc-Fe₃O₄ were also investigated. Radiochemical analyses showed that the labeling efficiency was over 92% after 1 min in the presence of a reducing agent. Hydroxyl and amine groups covered the surface of the Fe₃O₄ particles. Therefore, ⁹⁹Tc (VII) reduced to lower oxidation states and might bind to Fe₃O₄ NPs. The sizes of the ⁹⁹Tc-Fe₃O₄ NPs were about 600 nm without ultrasound vibrations, and the particle sizes were reduced to 250 nm under ultrasound vibration conditions. Nonetheless, Fe₃O₄ NPs and ⁹⁹Tc-Fe₃O₄ NPs exhibited superparamagnetic properties, and the saturation magnetization values were about 55 and 47 emu/g, respectively. The biodistribution showed that a portion of the ^99mTc-Fe₃O₄ nanoparticles might embolize in a pulmonary capillary initially; the embolism radioactivity was cleared from the lungs and was then taken up by the liver. ^99mTc-Fe₃O₄ metabolized very slowly only 1–2% of the injected dose (ID) was excreted in urine and about 2.37% ID/g was retained in the liver 4 h after injection. Radiopharmaceutically, ^99mTc-Fe₃O₄ NPs displayed long-term retention, and only ^99mTc-Fe₃O₄ NPs that dissociated to free pertechnetate could be excreted in urine. This research evaluated the feasibility of non-polymer magnetic ferrite NPs labeled with technetium as potential radiopharmaceuticals in nuclear medicine.     

Further Stabilization of Leu<Superscript>155</Superscript> Mutant Thermolysins by Mutation of an Autodegradation Site

The autodegradation-resistant mutant thermolysins (TLNs), L155A (Leu¹⁵⁵ to Ala) and L155S (Leu¹⁵⁵ to Ser), were previously constructed by site-directed mutagenesis to enhance thermostability. These mutations suppressed autodegradation at position 154–155, resulting in increased thermostability. However, a new autodegradation site became apparent in these mutant TLNs, at position 155–156. In this study, further stabilization of the mutant TLNs to suppress this new autodegradation was attempted by the substitution of Ile¹⁵⁶ to Asp and Val (L155A-I156N, L155A-I156V, L155S-I156N, and L155S-I156V). SDS–PAGE analysis showed that the autodegradation at 155–156 of all double-mutant TLNs was suppressed. Thermostability at 80 °C was enhanced in all double-mutant TLNs (half-life at 80 °C: WT, 18.3 min; L155A, 25.0 min; L155S, 24.0 min; L155A-I156N, 60.8 min; L155A-I156V, 62.4 min; L155S-I156N, 93.3 min; and L155S-I156V, 40.0 min), and k _cat/K _m values were: WT, 220; L155A, 240; L155S, 123; L155A-I156N, 62; L155A-I156V, 760; L155S-I156N, 240; and L155S-I156V, 520 min⁻¹ mM⁻¹.     

Synthesis,radiolabelling and biodistribution of HYNIC-Tyr<Superscript>3</Superscript> octreotide: a somatostatin receptor positive tumour imaging agent

In vivo imaging of tumours using radiolabelled somatostatin (SST) analogues has become an accepted clinical tool in oncology. HYNIC-Tyr³ octreotide and Tyr³ octreotide were synthesized by FMOC solid-phase peptide synthesis using a semi-automated synthesizer. These were analyzed and purified by RP-HPLC, mass spectroscopy, IR spectroscopy, ¹H NMR and ¹³C NMR. The prochelator 6-BOC-HYNIC was also synthesised and characterised indigenously. HYNIC-Tyr³ octreotide was labelled with ^99mTc using Tricine and EDDA as coligand by SnCl₂ method. Labelling with ^99mTc was performed at 100 °C for 15 min and radiochemical analysis by ITLC and HPLC methods. The radiochemical purity of the complex was over 98% and log p value was found to be −1.27 ± 0.12. The stability of radiolabelled peptide complex was checked at 37 °C up to 24 h. Blood clearance and protein-binding study was also performed. In vivo biodistribution studies in rat showed uptake of ^99mTc-HYNIC-TOC in kidney than any other organs. The blood clearance was faster with rapid excretion through kidneys and relatively low uptake in liver.     

Thermochemical study on ternary complex of dysprosium <Emphasis Type="Italic">m</Emphasis>-nitrobenzoic acid with <Emphasis Type="Italic">o</Emphasis>-phenanthroline

A ternary binuclear complex of dysprosium chloride hexahydrate with m-nitrobenzoic acid and 1,10-phenanthroline, [Dy(m-NBA)₃phen]₂·4H₂O (m-NBA: m-nitrobenzoate; phen: 1,10-phenanthroline) was synthesized. The dissolution enthalpies of [2phen·H₂O(s)], [6m-HNBA(s)], [2DyCl₃·6H₂O(s)], and [Dy(m-NBA)₃phen]₂·4H₂O(s) in the calorimetric solvent (V_DMSO:V_MeOH = 3:2) were determined by the solution–reaction isoperibol calorimeter at 298.15 K to be \Updelta_\texts H_\textm^q \Updelta_{\text{s}} H_{\text{m}}^{\theta } [2phen·H₂O(s), 298.15 K] = 21.7367 ± 0.3150 kJ·mol⁻¹, \Updelta_\texts H_\textm^q \Updelta_{\text{s}} H_{\text{m}}^{\theta } [6m-HNBA(s), 298.15 K] = 15.3635 ± 0.2235 kJ·mol⁻¹, \Updelta_\texts H_\textm^q \Updelta_{\text{s}} H_{\text{m}}^{\theta } [2DyCl₃·6H₂O(s), 298.15 K] = −203.5331 ± 0.2200 kJ·mol⁻¹, and \Updelta_\texts H_\textm^q \Updelta_{\text{s}} H_{\text{m}}^{\theta } [[Dy(m-NBA)₃phen]₂·4H₂O(s), 298.15 K] = 53.5965 ± 0.2367 kJ·mol⁻¹, respectively. The enthalpy change of the reaction was determined to be \Updelta_\textr H_\textm^q = 3 6 9. 4 9 ±0. 5 6   \textkJ·\textmol ^{- 1} . \Updelta_{\text{r}} H_{\text{m}}^{\theta } = 3 6 9. 4 9 \pm 0. 5 6 \;{\text{kJ}}\cdot {\text{mol}}^{ - 1} . According to the above results and the relevant data in the literature, through Hess’ law, the standard molar enthalpy of formation of [Dy(m-NBA)₃phen]₂·4H₂O(s) was estimated to be \Updelta_\textf H_\textm^q \Updelta_{\text{f}} H_{\text{m}}^{\theta } [[Dy(m-NBA)₃phen]₂·4H₂O(s), 298.15 K] = −5525 ± 6 kJ·mol⁻¹.     

Synthesis and biological evaluation of <Superscript>99m</Superscript>Tc-HEDTA/HYNIC-MPP4 complex for 5-HT<Subscript>1A</Subscript> receptor imaging

5-HT_1A receptor is associated with a variety of pathophysiology of neuropsychiatric disorders. Accordingly, we have synthesized a new 5-HT_1A receptor ligand (HYNIC-MPP4) and labeled it with ^99mTc using N-(2-hydroxyethyl)ethylenediaminetriacetic acid (HEDTA) as coligand. ^99mTc-HEDTA/HYNIC-MPP4 was prepared under pH 6 at room temperature. Biodistribution of 99mTc-HEDTA/HYNIC-MPP4 in normal mice showed that this complex had moderate brain uptake (0.60% ID·g⁻¹ at 2 min p.i.) and good retention. The hippocampus had the highest radioactivity uptake at 2 min p.i. (1.84% ID⋆g⁻¹). The ratio of Hipp/CB was 3.1 at 2 min p.i. and increased to 4.4 at 60 min p.i. After blocking with 8-hydroxy-2-(dipropylamino) tetralin, the uptake of hippocampus was decreased significantly from 1.84% ID·g⁻¹ to 0.53% ID·g⁻¹ at 2 min p.i., while the cerebellum had no significant decrease. This ^99mTc complex could be a potent agent for 5-HT_1A receptor imaging. Supported by the National Natural Science Foundation of China (Grant No. 20401004) and the Analysis and Test fund of Beijing Normal University     

Catalytic and Thermodynamic Characterization of Endoglucanase (CMCase) from <Emphasis Type="Italic">Aspergillus oryzae</Emphasis> cmc-1

Monomeric extracellular endoglucanase (25 kDa) of transgenic koji (Aspergillus oryzae cmc-1) produced under submerged growth condition (7.5 U mg⁻¹ protein) was purified to homogeneity level by ammonium sulfate precipitation and various column chromatography on fast protein liquid chromatography system. Activation energy for carboxymethylcellulose (CMC) hydrolysis was 3.32 kJ mol⁻¹ at optimum temperature (55 °C), and its temperature quotient (Q ₁₀) was 1.0. The enzyme was stable over a pH range of 4.1–5.3 and gave maximum activity at pH 4.4. V _max for CMC hydrolysis was 854 U mg⁻¹ protein and K _m was 20 mg CMC ml⁻¹. The turnover (k _cat) was 356 s⁻¹. The pK _a1 and pK _a2 of ionisable groups of active site controlling V _max were 3.9 and 6.25, respectively. Thermodynamic parameters for CMC hydrolysis were as follows: ΔH* = 0.59 kJ mol⁻¹, ΔG* = 64.57 kJ mol⁻¹ and ΔS* = −195.05 J mol⁻¹ K⁻¹, respectively. Activation energy for irreversible inactivation ‘E _a(d)’ of the endoglucanase was 378 kJ mol⁻¹, whereas enthalpy (ΔH*), Gibbs free energy (ΔG*) and entropy (ΔS*) of activation at 44 °C were 375.36 kJ mol⁻¹, 111.36 kJ mol⁻¹ and 833.06 J mol⁻¹ K⁻¹, respectively.     

Influence of dry density on HTO diffusion in GMZ bentonite

With the low permeability and high swelling property, Gaomiaozi (GMZ) bentonite is regarded as the favorable candidate backfilling material for a potential repository. The diffusion behaviors of HTO in GMZ bentonite were studied to obtain effective diffusion coefficient (D _e) and accessible porosity (ε) by through- and out-diffusion experiments. A computer code named Fitting for diffusion coefficient (FDP) was used for the experimental data processing and theoretical modeling. The D _e and ε values were (5.2–11.2) × 10⁻¹¹ m²/s and 0.35–0.50 at dry density from 1,800 to 2,000 kg/m³, respectively. The D _e values at 1,800 kg/m³ was a little higher than that of at 2,000 kg/m³, whereas the D _e value at 1,600 kg/m³ was significantly higher (approximately twice) than that of at 1,800 and 2,000 kg/m³. It may be explained that the diffusion of HTO mainly occurred in the interlayer space for the highly compacted clay (dry density exceeding 1,300 kg/m³). 1,800 and 2,000 kg/m³ probably had similar interlayer space, whereas 1,600 kg/m³ had more. Both D _e and ε values decreased with increasing dry density. For compacted bentonite, the relationship of D _e and ε could be described by Archie’s law with exponent n = 4.5 ± 1.0.     

Thermodynamic investigation of room temperature ionic liquid

The molar heat capacities of the room temperature ionic liquid 1-butyl-3-methylimidazolium hexafluoroborate (BMIPF₆) were measured by an adiabatic calorimeter in temperature range from 80 to 390 K. The dependence of the molar heat capacity on temperature is given as a function of the reduced temperature (X) by polynomial equations, C _P,m (J K⁻¹ mol⁻¹) = 204.75 + 81.421X − 23.828 X ² + 12.044X ³ + 2.5442X ⁴ [X = (T − 132.5)/52.5] for the solid phase (80–185 K), C _P,m (J K⁻¹ mol⁻¹) = 368.99 + 2.4199X + 1.0027X ² + 0.43395X ³ [X = (T − 230)/35] for the glass state (195 − 265 K), and C _P,m (J K⁻¹ mol⁻¹) = 415.01 + 21.992X − 0.24656X ² + 0.57770X ³ [X = (T − 337.5)/52.5] for the liquid phase (285–390 K), respectively. According to the polynomial equations and thermodynamic relationship, the values of thermodynamic function of the BMIPF₆ relative to 298.15 K were calculated in temperature range from 80 to 390 K with an interval of 5 K. The glass transition of BMIPF₆ was measured to be 190.41 K, the enthalpy and entropy of the glass transition were determined to be ΔH _g = 2.853 kJ mol⁻¹ and ΔS _g = 14.98 J K⁻¹ mol⁻¹, respectively. The results showed that the milting point of the BMIPF₆ is 281.83 K, the enthalpy and entropy of phase transition were calculated to be ΔH _m = 20.67 kJ mol⁻¹ and ΔS _m = 73.34 J K⁻¹ mol⁻¹.