Ko Value Research Articles

Analytical method for predicting interference in ion mobility spectrometric detection of drug compounds with phthalates

In ion mobility spectrometry (IMS), ions are distinguished by their mobility through a gas, which depends on their size, shape, and charge. Ions with very similar reduced ion mobility (Ko) values are not separated. This technique is widely used for the onsite detection of drug compounds. However, the presence of phthalates can interfere with IMS-based detection of drug compounds because some of them may have Ko values similar to those of drug compounds. In this study, the interference of phthalates in the IMS detection of drug compounds was investigated using drug compounds and phthalates in the molecular weight range of 134–335 g mol−1. The relationships between Ko and the m/z value, collision cross section (CCS), maximum cross section (CSmax), and minimum cross section (CSmin) of the product ions were examined. The CSmax and CSmin values were calculated from the energy-minimized structures of the ions. It was found that the m/z, CCS, and CSmax values were not closely related to the Ko value. However, the CSmin values showed a strong correlation with the Ko values, exhibiting excellent linear relationships with R2 values of 0.997 for the drug compounds and 0.990 for the phthalates. By comparing the CSmin values of drug compounds and phthalates, the probability of their peaks overlapping in the IMS spectra can be determined. For chemicals that are difficult to identify, the overlap of the peaks with the target chemicals can be determined using their CSmin values.

Effects of structure and electronic properties of spinel ferrites on their emissivity in middle and short wavebands

In this study, the samples of a series of spinel ferrites (Fe3O4, NiFe2O4, and CuFe2O4) were prepared to investigate their emissivity performance in the middle and short wavebands. The emissivity of the samples was measured in the temperature range of 27–500 ​°C. The results show that Fe3O4 had the highest average emissivity values of 0.98 in 8–14 ​μm waveband and 0.97 in 3–5 ​μm waveband. In addition, CuFe2O4 had the second-highest values of 0.95 in 8–14 ​μm waveband and 0.92 in 3–5 ​μm waveband. Finally, NiFe2O4 had the lowest values of 0.94 in 8–14 ​μm waveband and 0.59 in 3–5 ​μm waveband. Given that the force constant KO has an effect on the lattice distortion, which, in turn, is an important factor influencing the emissivity performance in 8–14 ​μm waveband, infrared spectrum measurements and an X-ray diffraction refinement of the spinel ferrites were performed for the calculation of KO. The results show that Fe3O4 had a smaller KO value (94.64×103) than NiFe2O4 (95.37×103) and CuFe2O4 (94.72×103), which confirms that KO has an inverse relationship with the emissivity in 8–14 ​μm waveband for the studied series of spinel ferrites. Furthermore, the first principle calculations were used to discuss the effect of electronic transition on the emissivity in 3–5 ​μm waveband. The calculation results show that, for Fe3O4, the O 2p orbitals pass through the Fermi level, resulting in the electronic transition near the Fermi level needs less energy to overcome the band gap than that for NiFe2O4 and CuFe2O4, which indicates that the electronic transition for Fe3O4 is easier. This implies that Fe3O4 would have higher emissivity in 3–5 ​μm waveband than NiFe2O4 and CuFe2O4 do. The band gap values of the series of spinel ferrite samples were measured by UV–Vis diffuse reflectance spectroscopy, and the variation trend of the band gap values is opposite to that of the 3–5 ​μm band emissivity. This study implies that the development of high-infrared-radiation materials with a ferrite spinel structure should aim at reducing the force constant KO and band gap, which is a possible direction for future research.

Degradation kinetic of dibutyl phthalate (DBP) by sulfate radical- and hydroxyl radical-based advanced oxidation process in UV/persulfate system

Abstract The ultraviolet/persulfate (UV/PS) process was used to degrade dibutyl phthalate (DBP) at different reaction conditions and a steady-state kinetic model was established based on the elementary reactions involved as well. UV/PS process, which can generate both sulfate radical (SO4− ) and hydroxyl radical (HO ) proved by the evidence that methanol had a larger inhibition impact on the degradation than tert-butyl, could effectively degrade DBP. The second-order rate constant of (1.2 ± 0.1) × 108 M−1 s−1 between DBP and SO4− and the second-order rate constant of (6.3 ± 0.1) × 109 M−1 s−1 between DBP and HO were determined by competition kinetics. The degradation efficiency of DBP was affected by PS dosage, initial DBP concentration, solution pH value, natural organic matter (NOM) and inorganic anions. Increasing PS dosage could enhance the degradation of DBP before PS dosage reaching 1.6 mM. However, the pseudo-first-order rate constants (ko) decreased as initial DBP concentration increased probably owing to the radical scavenging effect of DBP. Generally, the ko value decreased slightly at pH values ranged from 4.0 to 6.0 while decreased significantly as pH increased from 6.0 to 8.0, which might be due to the scavenging effect on SO4− and HO by OH− and increasing concentration of HPO 4 2 - (with higher scavenging capacity than H 2 PO 4 - ) from the phosphate buffer with rising pH value. NOM and HCO 3 - showed an inhibition effect on the degradation of DBP through quenching SO4− and HO . However, Cl− had a dual role on the degradation of DBP in the UV/PS system, which enhanced the degradation at lower concentration (0–1 mM) and suppressed as Cl− concentration further increased to 2 mM. Additionally, a simple steady-state kinetic model involving SO4− and HO was developed to simulate the ko values and the radical contributions in this reaction system. Generally, HO had a higher contribution to DBP degradation than SO4− . The total cost including the electrical energy per order and oxidant cost was increased with increasing PS dosage and the oxidant cost was the major one. The results in this study can serve as a guide and indicate that UV/PS process is feasible for the treatment of water contaminated with DBP.

On the design and properties of scaffolds based on vertically aligned carbon nanotubes transferred onto electrospun poly (lactic acid) fibers

Herein, we propose the design of a nanoscaffold based on the hot-press transfer of vertically aligned multi-walled carbon nanotubes (VAMWCNT) onto matrices of electrospun poly (lactic acid) (PLA) fibers. To this end, we created a three-dimensional, bioactive and electrically conductive scaffold that combines the potential of PLA as a biomaterial with the physical-chemical and biological properties of VAMWCNT (PLA/VAMWCNT). Given the well-known hydrophobicity of carbon nanotubes, oxygen-plasma functionalization was applied to the scaffolds in order to attach oxygen-containing groups to their surfaces, with the plasma treatment also responsible for the exfoliation of the VAMWCNT's tips. After plasma-functionalization, electrochemical measurements showed that our scaffold presented an increased electroactive area (1.5-fold) with a ko value of 6.87×10−3cms−1, confirming its applicability as an electrode. Furthermore, we have also demonstrated the feasibility of electrodepositing nanohydroxyapatite (nHAp) crystals onto this nanoarchitectured material, improving its biomimetic and bioactive features. Preliminary biological assays revealed the viability of primary human osteoblast cells cultivated onto the PLA/VAMWCNT-nHAp scaffolds. This investigation has shed light on a practical approach to produce 3D–scaffolds by transferring VAMWCNT onto electrospun polymeric matrices. These novel materials may represent promising alternatives for future tissue engineering applications and thus should be studied further.

Evaluation of Ko in Centrifuge Model Using Shear Wave Velocity

Abstract The coefficient of earth pressure at rest (Ko) is an important parameter in the analysis and design of geotechnical structures. Methods based on the shear wave velocity (Vs) can be utilized to estimate Ko using the directionality of a shear wave and its dependence on effective stresses. For centrifuge modeling, it is important to understand the in-flight stress states at various locations during loading-unloading-reloading cycles and to develop a direct method for measuring Ko in flight. In this study, previously proposed methods based on Vs (Vs–Ko relationships) were assessed to determine Ko in a centrifuge model using the results of bender element tests performed in a cross-hole configuration. The suitability of the Vs–Ko relationship for the centrifuge test and variation in Ko with respect to location in the centrifuge model were investigated. Through changes in centrifugal acceleration, the loading and unloading stress conditions were simulated, and the Ko value calculated based on the Vs–Ko relationship was compared to values obtained from an earth pressure transducer and via empirical equations. It was found that the method using a single horizontally propagating Vs and one pressure measurement was adequate to evaluate Ko in a centrifuge model. In addition, Ko in the centrifuge model was higher at the center than near the boundary for the unloading stage because of the arching effect.

Ethanol self‐administration in serotonin transporter knockout mice: unconstrained demand and elasticity

Low serotonin function is associated with alcoholism, leading to speculation that increasing serotonin function could decrease ethanol consumption. Mice with one or two deletions of the serotonin transporter (SERT) gene have increased extracellular serotonin. To examine the relationship between SERT genotype and motivation for alcohol, we compared ethanol self-administration in mice with zero (knockout, KO), one (HET) or two copies (WT) of the SERT gene. All three genotypes learned to self-administer ethanol. The SSRI, fluvoxamine, decreased responding for ethanol in the HET and WT, but not the KO mice. When tested under a progressive ratio schedule, KO mice had lower breakpoints than HET or WT. As work requirements were increased across sessions, behavioral economic analysis of ethanol self-administration indicated that the decreased breakpoint in KO as compared to HET or WT mice was a result of lower levels of unconstrained demand, rather than differences in elasticity, i.e. the proportional decreases in ethanol earned with increasing work requirements were similar across genotypes. The difference in unconstrained demand was unlikely to result from motor or general motivational factors, as both WT and KO mice responded at high levels for a 50% condensed milk solution. As elasticity is hypothesized to measure essential value, these results indicate that KO value ethanol similarly to WT or HET mice despite having lower break points for ethanol.

Kinetics of Carbon Dioxide Reaction with Aqueous Mixture of Piperazine and 2‐Amino‐2‐ethyl‐1,3‐propanediol

AbstractCurrent researchers from environmental and industrial fields are focusing on advanced means of carbon dioxide (CO2) capture to limit its consequences in process industries. They also intend to enhance the mitigation of environmental impart by CO2 especially its greenhouse effect. In this study, the kinetics of CO2 reaction with an aqueous blend of piperazine (PZ) and 2‐amino‐2‐ethyl‐1,3‐propanediol (AEPD) were investigated. It was found that blending of AEPD with a little percentage of PZ generated the observed rate constant, ko, values that were more than twice the direct summation of the ko values of the aqueous pure amines at the corresponding concentration and temperature. The kinetic study of the system was modeled using a termolecular mechanism. Blending 0.05 kmol/m3 of PZ with 0.5 kmol/m3 of AEPD gives an observed rate constant ko value of 2397.9 s−1 at 298 K. This result is comparable to rate constants of other amine mixtures. Thus, the aqueous blend of AEPD with PZ is an attractive solvent for CO2 capture that has good advantages. The PZ that serves as the promoter in the reaction is needed in small fraction, whereas AEPD, which is a sterically hindered amine, increases CO2 absorption capacity of the system. AEPD can be produced from renewable materials. © 2013 Wiley Periodicals, Inc. Int J Chem Kinet 45: 161–167, 2013

Crystallisation process of Al80Fe10Ti10 amorphous phase

In the present study, crystallisation behaviours of the Al80Fe10Ti10 amorphous phase (prepared by mechanical alloying) has been investigated using X-ray diffraction and differential thermal analysis techniques. It was found that Al80Fe10Ti10 amorphous phase exhibits one-stage crystallisation on heating [amorphous to Al13Fe4, Al(Fe,Ti) and Al5Fe2 intermetallic phases]. The activation energies for crystallisation of Al80Fe10Ti10 amorphous phase were determined as 326, 322, 351 and 301 kJ mol−1 by means of the Kissinger–Akahira–Sunose, Flynn–Wall–Ozawa, Friedman and Afify equations respectively. Kinetic parameters such as Avarmi exponent or reaction order n and frequency factor Ko were also discussed. The reaction orders obtained for the crystallisation was ∼2·03, suggesting that a diffusion controlled crystallisation process with a decreasing nucleation rate was the crystallisation mechanism. The deduced Ko value for crystallisation peak was calculated to be 6·75×1010 s−1.

Estimativa da umidade na capacidade de campo em solos sob Cerrado

Objetivou-se, com este trabalho, estimar a umidade na capacidade de campo (θcc) a partir de equação baseada na curva de retenção de água do solo (CRA) e de correlações com atributos físico-hídricos e dados de textura e matéria orgânica, para solos muito-argilosos, argilosos, médios e arenosos. O estudo foi realizado com 2242 amostras de solo do Cerrado, das quais constavam informações sobre classificação textural, atributos físicos e retenção da água do solo. Para 745 amostras havia ainda informação sobre a condutividade hidráulica saturada (Ko) e, para 472, sobre teores de argila, silte, areia e matéria orgânica. Para as amostras com Ko medida, θcc foi determinada com base em parâmetros da equação de Genuchten (1980), assumindo-se que a taxa de drenagem (<img src="/img/revistas/rbeaa/v15n2/t.jpg">) é uma porcentagem p de Ko. Consideraram-se valores de p iguais a 0,0025; 0,0050; 0,0100; 0,0150 e 0,0200. Verificou-se, então, ser possível estimar θcc a partir de equação baseada na CRA, considerando-se <img src="/img/revistas/rbeaa/v15n2/t.jpg">como sendo 1% do valor de Ko. θcc também pode ser estimada em função da umidade no ponto de inflexão da CRA e da porosidade total para cada horizonte do solo. Para <img src="/img/revistas/rbeaa/v15n2/t.jpg">equivalente a 1% do valor de Ko, a tensão de água no solo correspondente à θcc se situou entre 6,5 e 7,5 kPa.

Electrochemical and Spectroscopic Dynamics of Nanostructured Polynuclear Sulphonic Acid-Doped Poly(2, 5-dimethoxyaniline)

Conducting and electroactive nanostructured poly(2, 5-dimethoxyaniline), PDMA, doped with anthracene sulphonic acid, ASA, and phenanthrene sulphonic acid, PSA, respectively, were prepared by oxidative polymerisation of 2, 5-dimethoxyaniline, DMA, with ammonium persulphate as oxidant. Scanning electron microscope, SEM, images of the polymers showed well defined nanotubes and fibrils with diameters of between 50 to 100 nm and 200 to 300 nm for PDMA-ASA and PDMA-PSA, respectively. Evidence of the incorporation of ASA and PSA into the PDMA backbone was provided by UV-Vis and FTIR analyses. Electrochemical interrogation of the sulphonic acid-doped polymers by cyclic voltammetry showed that both PDMA-ASA and PDMA-PSA exhibit quazi-reversible electrochemistry. The standard rate constant, ko, for the charge transfer reactions of PDMA-ASA and PDMA-PSA were 3.81 x 10-4 cm s-1 and 3.27 x 10-5 cm s-1, respectively. There was a relationship between the ko value and the formal potential, E0ʹ, of the polymeric nanomaterial. PDMA-ASA that had larger ko value gave an E0ʹ value of 134 mV which was lower than that of PDMA-PSA by 19 mV, indicating that PDMA-ASA has lower activation energy than PDMA-PSA for the electron transfer process Electrochemical impedance spectroscopy over a range of potentials showed that the polymeric nanotubues exhibited high conductivities, though the SA-doped polymer was more conducting.

An ion mobility spectrometer sensor system for subsurface use

An ion mobility spectrometer (IMS) probe system for real-time, subsurface soil-gas sampling applications is presented. The system includes an IMS and supporting electronics encased in a 51 mm diameter stainless steel probe housing. The IMS was challenged in the laboratory with 2,6-di-tert-butylpyridine (DtBP) and tetrachloroethylene (PCE) in zero air yielding reduced ion mobility constants (Ko) values of 1.42 cm2/Vs (n = 3) and 1.79 ± 0.01 cm2/Vs (n = 3), respectively. A resolving power of 38 and 31 was obtained for DtBP and PCE, respectively. The system was deployed at a PCE-contaminated site to demonstrate its performance under field conditions. PCE was detected in the vapor samples as evidenced by peaks with a Ko value of 1.80 ± 0.01 cm2/Vs for two measurements that were taken 6 min apart. The presence of PCE at the contaminated site was confirmed by GC-MS analysis of a gas sample at an EPA-certified laboratory, suggesting that this IMS system can be used to detect PCE under field conditions.

Scanning Electrochemical Microscopy. 59. Effect of Defects and Structure on Electron Transfer through Self-Assembled Monolayers

Electron transfer (ET) rate kinetics through n-alkanethiol self-assembled monolayers (SAMs) of alkanethiols of different chain lengths [Me(CH2)nSH; n=8, 10, 11, 15] on Au and Hg surfaces and ferrocene (Fc)-terminated SAMs (poly-norbornylogous and HS(CH2)12CONHCH2Fc) on Au were studied using cyclic voltammetry and scanning electrochemical microscopy (SECM). The SECM results allow determination of the ET kinetics of solution-phase Ru(NH3)63+/2+ through the alkanethiol SAMs on Au and Hg. A model using the potential dependence of the measured rate constants is proposed to compensate for the pinhole contribution. Extrapolated values of koML for Ru(NH3)63+/2+ using the model follow the expected exponential decay (beta is 0.9) for different chain lengths. For a Fc-terminated poly-norbornyl SAM, the standard rate constant of direct tunneling (ko is 189+/-31 s(-1)) is in the same order as the ko value of HS(CH2)12CONHCH2Fc. In blocking and Fc SAMs, the rates of ET are demonstrated to follow Butler-Volmer kinetics with transfer coefficients alpha of 0.5. Lower values of alpha are treated as a result of the pinhole contribution. The normalized rates of ET are 3 orders of magnitude higher for Fc-terminated than for blocking monolayers. Scanning electron microscopy imaging of Pd nanoparticles electrochemically deposited in pinholes of blocking SAMs was used to confirm the presence of pinholes.

Discussion of “Forms and sand transport in shallow hydraulic fractures in residual soil”Appears in Canadian Geotechnical Journal, 43: 1061–1073.

The authors should be commended for their long-term extensive research effort in hydraulic fracturing (Murdoch 1993a, 1993b, 1993c). In the investigation under discussion, four sand-filled hydraulic fracture tests were carried out to better understand the forms of hydraulic fractures created in shallow saprolite and to compare them with those in other geologic materials under similar conditions. It was observed by the authors in their field experiments that the fractures were shaped like slightly asymmetric saucers that were roughly flat-lying in their centers and slightly curve upwards. In fact, similar fracture pattern was observed in laboratory experiments on hydraulic fracturing conducted by injecting cement bentonite and epoxy into clay specimens with overconsolidation ratio of 5 under similar free surface boundary condition (Chin 1996; Au 2001; Au et al. 2003, 2005; Soga et al. 2003). It has also been demonstrated experimentally in the laboratory that hydraulic fracture may be initiated by injecting a small volume of fluid into highly overconsolidated clay. The fracturing fluid then propagates along the initiated cracks, perpendicular to the direction of major principal stress, and develops them into large fractures afterwards. A theoretical model of hydraulic fracture propagation has been developed by the authors by adapting the software Fran2d under the framework of linear elastic fracture mechanics to explain the observed fracture forms. The discussers agree with the authors wholeheartedly that understanding of the controls on fracture form has useful applications. However, there are some points presented in the paper that are worth discussing and clarifying. It is unclear to the discussers why the hydraulic fractures were created in the B horizon above the saprolite while ‘‘the primary objective of the investigation is to describe the forms of hydraulic fractures in saprolite and compare them with the forms created in other geologic materials.’’ It is evident from the authors’ description that the material properties of B horizon are quite different from those of saprolite. As the degree of saturation of the specimens is well below unity, the accuracy of the results of unconsolidated– undrained (UU) triaxial tests in describing the stress–strain characteristics and quantifying the shear strength parameters is doubtful. Increase in effective stress within the specimens can still occur with the increase in confining stress even in the UU test. The argument is substantiated by the fact that the friction angle of the soil measured by the authors decreases when the confining stress increases. The modulus of elasticity of soil, determined by the UU test, may not be appropriate for the numerical simulation of the tensile failure fracture. The modulus of elasticity of soil is very dependent on its strain. It is well known that the modulus of elasticity of soil determined by the triaxial test is considerably lower than its actual value in the field, as the strain is considerably higher. The Ko value determined by Malin (2005) in his hydraulic fracture experiment is quite different from that obtained by the authors using flat-blade dilatometer measurements in the same project. The authors may have to elaborate on their choice of the Ko value used in their numerical simulations. The fracture toughness (KIC) was introduced as a parameter used to estimate the fracturing pressure by Murdoch (1993b). The measured fracturing pressure of approximately 300 kPa is approximately 9 times the undrained shear strength, i.e., 34 kPa. The result is consistent with the theoretical ultimate cavity expansion pressure in soil (Au et al. 2006). However, the magnitude of fracturing pressure is dependent on injection rate and overconsolidation ratio of the soil (Mori and Tamura 1987; Au 2001; Soga et al. 2003), as shown in Fig. D1, where Pf is the fracturing pressure and 0 v is the effective overburden pressure. However, both the injection rate for the experiments and the overconsolidation ratio of the soil were not given in the paper. On the basis of the given Ko value, the discussers envisage that the soil is highly overconsolidated. As a result, the soil may behave elastically. Therefore, the use of linear elastic fracture mechanics to simulate the fracture propagation process may be appropriate. Otherwise, the applicability of elastic analysis in hydraulic fracturing should be carefully considered. However, the adjusted intrinsic soil parameters obtained by the authors assuming the validity of the approach is worth discussing. It was concluded by Murdoch (1993b) that ‘‘When soil is completely saturated, KIC is essentially zero. Nevertheless, well-developed hydraulic fractures were created in soil of negligible toughness.’’ The exReceived 9 March 2007. Accepted 15 October 2007. Published on the NRC Research Press Web site at cgj.nrc.ca on 1 February 2008.

Solubility and solubility product at 22°C of UO2(c) precipitated from aqueous U(IV) solutions

Solubility studies on UO2(c), precipitated at 90°C from low-pH U(IV) solutions, were conducted under rigidly controlled redox conditions maintained by EuCl2 as a function of pH and from the oversaturation direction. Samples were equilibrated for 24 days at 90°C and then for 1 day at 22°C. X-ray diffraction (XRD) analyses of the solid phases, along with the observed solubility behavior, identified UO2(c) as the dominant phase at pH≳1.2 and UO2(am) as the dominant phase at pH≳1.2. The UV-Vis-NIR spectra of the aqueous phases showed that aqueous uranium was present in the tetravalent state. Our ability to effectively maintain uranium in the tetravalent state during experiments and the recent availability of reliable values of Pitzer ion-interactionparameters for this system have helped to set reliable upper limits for the log Ko value of ≤ −60.2 + 0.24 for the UO2(c) solubility [UO2(c) + 2H2O ⇌ U4+ + 4OH−] and of >−11.6 for the formation of U(OH)4(aq) [U4++ 4H2O ⇌ U(OH)4(aq) + 4H+]

Vibrational relaxation of NO(υ=1) by oxygen atoms

The rate constant kO(υ=1) for NO(υ=1) vibrational relaxation by O has been measured at room temperature using a laser photolysis-laser probe technique. Vibrationally excited NO and relaxer O atoms were formed using 355 nm laser photolysis of a dilute mixture of NO2 in argon bath gas. The time evolution of both the NO(υ=1) and the O atoms was monitored using laser-induced fluorescence (LIF). The required absolute O-atom densities were obtained through a comparison of O-atom LIF signals from the photolysis source and from a titrated cw microwave source. At early times the O atoms constitute the most important loss mechanism for the nascently produced NO(υ=1). Possible effects from NO(υ=1) vibrational ladder-climbing and from thermal expansion have been shown to be minimal. The rate constant kO(υ=1)=(2.4±0.5)×10−11 cm3 s−1 determined herein is a factor of 2 to 3 lower than the generally accepted value of kO(υ=1) used in thermospheric modeling. The present value for kO(υ=1) is the same, within the error bars, as the kO(υ=2,3) previously measured in this laboratory using an entirely different technique, resonant infrared laser excitation of NO(υ=0). This result suggests that the collisional relaxation rates are independent of υ. A recent quasiclassical trajectory calculation, in which both allowed NO–O surfaces have been explicitly considered, predicts a collisional relaxation rate which is in good agreement with the present result. The kO(υ=1) value, along with previously measured rate constants for NO–O high-pressure recombination (krec∞) and isotope exchange (kiso), can serve as a proxy for the rate coefficient kC describing the formation of a long-lived NO2* intermediate from O+NO collisions. The present value for kO(υ=1) is significantly lower, however, than a recent determination of krec∞ and also the value of kC derived from kiso. In the latter case the comparison is not as straightforward.

A Simple Method for the Determination of Ko-Value in Sandy Soils

A laboratory test method for the determination of the coefficient of earth pressure at rest, Ko, in sandy soils is presented. In this method, initially, a series of undrained cyclic triaxial tests were made on high-quality undisturbed sand samples recovered by the in-situ freezing sampling method (FS sample), in order to obtain the relationship between the shear modulus at very small strain, Go, and the effective confining stress, σ'c. Next, the Go was also calculated based on elastic wave theory by using the shear wave velocity measured at a depth from which the undisturbed samples were recovered. By equalizing the Go values obtained from these two independent methods, the coefficient of earth pressure at rest, Ko, in the sandy soils, can be determined using the proposed simple method. The Ko-value of a diluvial sand obtained using this method is 0.84. Based on the test results on the sand samples obtained by the rotary type triple tube sampling method (TS sample), recovered from the same soil layer and the same depth, however, the Ko value obtained with this method was 1.44, which is considerably larger than that obtained from the FS sample. The larger Ko value of the TS sample compared with that of the FS sample is because the initial shear modulus of the TS sample is much lower than that of the FS sample for the same level of confining stress due to sample disturbance.

Electrical method of predicting in situ stress state of normally consolidated clays: Meegoda, N J; Arulanandan, K In: Use of In Situ Tests in Geotechnical Engineering (papers to the Conference, Blacksburg, 23–25 June 1986)P794–808. Publ New York: ASCE, 1986 (ASCE Geotechnical Special Publication No 6)

The electrical method was used to characterize the electrical anisotropy, shape and cementation of fine grained soils. It was found that for normally consolidated soils there is a strong dependence of fabric anisotropy on the in situ coefficient of lateral earth pressure at rest (Ko). The in situ coefficient of lateral earth pressure at rest also depends on fabric friction. A correlation is established between Ko and electrical index which reflects the strong dependence of fabric anisotropy and fabric friction. It was found that there is a reasonable agreement between the predicted Ko value from the electrical index and the measured Ko value for several soils with consolidation pressures above 68 KPa.

Kinetic Studies of the Decomposition of Tris(oxalato)cobaltate(III) Ion in Binary Solvents of Water with Organic Solvents

The kinetic studies of the decomposition of tris(oxalato)cobaltate(M) ion [Co(C204)8]3- were made in the binary solvents of water with methanol (MeOH), ethanol (Et0H), t-butyl alc o hol (t-BuOH), dimethyl sulfoxide (DMSO), and acetonitrile (AN) at an ionic strength of O.2 mol dm-3 and at 25--40°C. In all solvents the rate of decomposition of the cobalt(III) complex ion was described as d[[Co(C204)3]3-]= k obs[[Co (C2O4)3]3-], where (1/2)kobs=k0+kh[H+]+k2h [H+]2 in the solutions of the neutral to acidic region. The values of ko, kh, and kth were determined under various conditions. The ko value was independent of the sorts of solven t of the binary-aqueous media, and also of the mole fraction of solvents. On the other hand, th e values of kh and km increased in the following order: t-BuOH<Et0H<Me0H<DMSO<AN at a mole fraction of 0.2, where the activation parameter s were determined for the each reaction path of ko, kh, and k2h. They were also dependent on the mole fraction of solvents u s e d and increased with an increase in the amount of the organic constitute. The activationent ropy aelΔh for the ko path was negative or very small if positive in all solvents, while ΔSh and Δ2h were, in general, very large in all solvents. The results obtained were discu s s ed in terms of (1) the permittivity of solvents, ( 2 ) the stability of the solvated proton (HSalv+), and ( 3 ) the stability of the proposed intermediate species with solvation.

Isothermal compression of grossular garnets to 250 Kbar and the effect of calcium on the bulk modulus

The effect of pressure on the lattice parameter, and hence on the volume, of two samples of grossularite garnet (Ca3Al2Si3O12) has been measured at room temperature up to 250 kbar with the use of a diamond anvil highpressure X ray diffraction camera. The pressure to which the sample was subjected was measured by means of the NaCl internal pressure standard. A least squares fit of the pressure-volume to the Birch-Murnaghan equation yields a bulk modulus value of KO = 1.74 ± 0.04 Mbar when a (∂K/∂P)∣P=0 value of 4.25 (Halleck, 1973) is used. This KO value is in agreement with the value of 1.704 Mbar obtained by Halleck [1973], using ultrasonic techniques. A comparison of the bulk moduli of grossularite, pyrope, and almandite shows that KO∝ Vo−1 for Ca and Mg garnets as expected from static lattice models. On the other hand, KO∝ Vo−5 for the Mg-Fe garnet solid solutions. This behavior has not been explained by available theories.

Kinetic studies on the hydrolyses of alpha-, beta-, and gamma-cyclodextrins by Taka-amylase A.

1) Hydrolyses of α-, β-, and γ-cyclodextrins catalyzed by Taka-amylase A*3 [EC 3.2.1.1] were studied at pH 5.3 and 25°C. 2) The rate parameters, Michealis constant Km and molecular activity ko for the cleavage of the cyclodextrin ring, were determined for the three cyclodextrins by using glucoamylase*4 [EC 3.2.1.3] in the analytical procedure to discriminate ring cleavage from the subsequent hydrolysis of chain product. It was found that the ko value increased markedly in the order α-, β-, and γ-cyclodextrins, but the Km values did not differ to any great extent among the three cyclodextrins. 3) By using glucoamylase, it was shown that the multiple attack mechanism was operative in the hydrolysis of cyclodextrins by this enzyme, and the degree of multiple attack was estimated to be 1.5±0.1, irrespective of the kind of cyclodextrin.