Slope Of Ln Research Articles

The Kinetics and Mechanism of Ligand Substitution Reaction of Aquapentacyanoruthenate(II) with Nitroso-R-salt and α-Nitroso-β-Naphthol in Presence of Anionic Surfactant Micelle

The kinetics and mechanism of ligand substitution reaction of coordinated water in complex, [Ru(CN)5H2O]3− by two incoming naphthalene substituted ligands [Ln], that is, Ln = nitroso-R-salt (NRS) and α-nitroso-β-naphthol (αNβN) have been studied spectrophotometrically by following an increase in absorbance at λmax = 525 nm in aqueous medium in presence of anionic surfactant micelle, sodium dodecyl sulphate (SDS) at 25.0 ± 0.1°C as a function of pH, [nitro-R-salt], [α-nitroso-β-naphthol], [Ru(CN)5H2O3−], [SDS] and ionic strength(I) under pseudo-first-order conditions by taking excess [L]. The values of pseudo-first-order rate constants (kobs) were evaluated from the slope of ln(A∞ − At) versus time plots for each variation. Both systems were found to follow a dissociative mechanism (D), through the formation of an intermediate, [Ru(CN)5]3−. The activation parameters, that is, enthalpy of activation (ΔH≠) and entropy of activation (ΔS≠) were computed from the slope and intercept of ln(kf/T) versus (1/T) plot, which support the proposed mechanistic scheme.

On the temperature dependent profile of interface states and series resistance characteristics in (Ni/Au)/Al 0.22Ga 0.78N/AlN/GaN heterostructures

The bias dependent series resistance ( R s ) and density distribution profile of interface states ( N ss ) of (Ni/Au)/Al 0.22Ga 0.78N/AlN/GaN heterostructure have been investigated by admittance measurements in a wide temperature range of 80–400 K. Experimental results show that both the values of capacitance ( C) and conductance ( G/ ω) were found to be strongly temperature and applied bias voltage dependent. The capacitance–voltage ( C– V) plots give a peak especially at high temperatures in the depletion region and disappear at low temperatures. When the temperature was increased both the values of C and G/ ω reduced. This decrease of capacitance can be understood if the dielectric constant of interfacial layer decreases with increasing temperature. Such temperature dependent behavior of C and G/ ω also can be attributed to the thermal restructuring and reordering of the interface states. The downward curvatures in C– V plots have been attributed to the R s of heterostructure and R s may cause a large deviation in C– V and G/ ω– V data. Therefore, the entire C– V and G/ ω– V measurements were corrected for the effect of R s . Also, the value of R s increases with increasing temperature. The density distribution profile of N ss was obtained from high–low frequency capacitance method. In addition, the temperature dependent ac conductivity ( σ ac ) data obtained between 275 and 400 K show a linear behavior and was fitted to the Arrhenius plot. The E a values were obtained from the slope of ln σ vs 1/ T plots to be −58.5, −59.7, −60.4 and −60.6 meV for the applied biases of −4, −3, −2 and −1 V, respectively.

Sibutramine hydrochloride monohydrate

In the present work, the thermal decomposition of sibutramine hydrochloride monohydrate (SBT) (an appetite suppressant agent) was studied using differential scanning calorimetry (DSC) and thermogravimetry/derivative thermogravimetry (TG/DTG). Solid-state characterization was carried out by diffuse reflectance infrared fourier transform spectroscopy (DRIFT), scanning electron microscopy (SEM) and X-ray powder diffraction (XRPD). Isothermal and non-isothermal methods were employed to determine the kinetic data of decomposition process. From isothermal experiments, activation energy (Ea) can be obtained from slope of ln t versus 1/T, and the value obtained was 96.06 and 101.43 kJ mol−1 in N2 and air atmospheres, respectively. For non-isothermal method Ea can be obtained from plot of logarithms of heating rates, as a function of inverse of temperature, resulting in a value of 96.56 and 98.22 kJ mol−1 in N2 and air atmospheres, respectively. The compatibilities of several commonly used pharmaceutical excipients (microcrystalline cellulose, magnesium stearate, colloidal silicon dioxide, lactose monohydrate) and empty hard-gelatin capsules with SBT were evaluated using DSC. The 1:1 physical mixtures of these excipients with SBT showed physical interaction of the drug with magnesium stearate. On the other hand, DRIFT results did not evidence any chemical modifications.

Analysis of temperature dependent electrical characteristics of Au/n-GaAs/GaAs structures in a wide temperature range

The temperature dependence of some electrical parameters of Au/n-GaAs/GaAs structures obtained from the forward bias current–voltage ( I– V) and reverse bias capacitance–voltage ( C– V) characteristics is studied in the temperature range of 79–400 K. The forward bias current I is found to be proportional to I o( T)exp( AV), where A is the slope of Ln( I) –V curves and almost independent of the voltage and temperature, and I o( T) is relatively a weak function of temperature. The semi-logarithmic Ln( I)– V characteristics based on the thermionic emission (TE) mechanism showed a decrease in the ideality factor ( n) and an increase in the zero-bias barrier height ( Φ Bo) with increasing temperature. These behaviors don't obey the pure thermionic emission (TE) theory. However, the barrier height Φ B( C– V) determined from the C −2– V plot at high frequency decreased linearly with the temperature. Analysis of the data indicated that the predominant current conduction mechanism of our sample was a trap-assisted multistep tunneling rather than the other mechanisms.

Phase IIb clinical trial of selenium in prostate cancer patients on active surveillance

5060 Background: The Nutritional Prevention of Cancer Trial demonstrated a 52% lower incidence of prostate cancer in its selenium (Se) arm. Consequently, this trial was designed to assess if Se supplementation would reduce the progression of prostate cancer in subjects on active surveillance for their disease. Methods: A Phase 2b randomized, double-blind placebo-controlled clinical trial was conducted in men with localized prostate cancer who had elected to forego therapy for active surveillance. Subjects <85 years of age with biopsy proven non- metastatic prostate cancer, prostate specific antigen (PSA) levels <50ng/ml, Gleason score <8, no other treatment for prostate cancer, and life expectancy ≥3 years were recruited. A total of 140 men were randomized to placebo (n=46), 200μg/day (n=47) or 800μg/day (n=47) Se p.o. (as selenized yeast) and followed every 3 months for up to 5 years. The primary endpoint was PSA velocity, a surrogate marker of prostate cancer progression. Serum levels of PSA and Se were determined at baseline and at 3-month intervals thereafter. Variance-stabilizing transformation ln(PSA+1) was carried out and PSA velocity (slope of ln(PSA+1)) was estimated using mixed effects regression models. Results: Following adjustment for age, body mass index, serum selenium levels, pack-years of smoking at baseline, duration on study, race, PSA analysis method, and Gleason score; percent changes in PSA velocity (90% CI) for 200 μg/day and 800 μg/day treatment groups vs. placebo were -2.85% (-7.19, 1.70) and -0.70% (-5.16, 3.98), respectively. Estimated mean PSA velocities and PSA doubling times for placebo, 200 μg/day and 800 μg/day treatment groups were 0.09, 0.07, and 0.09 ng/mL/yr; and 4.92, 5.86 and 5.34 years, respectively. Upon secondary analyses, PSA velocity was statistically significantly higher in smokers (vs. non-smokers) (percent change in PSA velocity and 90% CI: 0.09 (0.03, 0.14)). Conclusions: Selenium supplementation did not significantly affect PSA velocity in subjects with non-aggressive disease. Longitudinal analyses also suggest that active surveillance was an appropriate choice for these subjects. Cigarette smoking may influence prostate cancer progression and needs further investigation. This work was supported by PHS CA079080 and CA023074. No significant financial relationships to disclose.

A Weight Index for the Standardized Uptake Value in 2-Deoxy-2-[F-18]fluoro-d-glucose-Positron Emission Tomography

Known errors in the standardized uptake value (SUV) caused by variations in subject weights W encountered can be corrected by lean body mass or body surface area (bsa) algorithms replacing W in calculations. However this is infrequently done. The aims of the work here are: quantify sensitivity to W, encourage SUV correction with an approach minimally differing from tradition, and show what improvements in the SUV coefficient of variation (cv) for a population can be expected. Selected for analyses were 2-deoxy-2-[F-18]fluoro-D-glucose (FDG) SUV data from positron emission tomography (PET) and PET/computed tomography (CT) scans at the University of Tennessee as well as from the literature. A weight sensitivity index was defined as -n=slope of ln(SUV/W) vs. lnW. The portion of the SUV variability due to this trend is removed by using the defined [formula: see text], or a virtually equal SUVm using [formula: see text], with Q and ID being tissue specific-activity and injected dose. [formula: see text] measures performance. Adapting to animal studies' tradition, [formula: see text] is preferred over the conventional [formula: see text]. For FDG in adults [formula: see text] from averaging over most tissues. In children, however, [formula: see text]. Tissues have the same index if their influx constants are independent of W. Suggested, therefore, is a very simplified [formula: see text], which is dimensionless and keeps the same population averages as traditional SUVs. It achieves [formula: see text]. Hence, for cv's of SUVs below approximately 1/3 improvements over tradition are possible, leading to F's<0.95. Accounting additionally for height, as in SUVbsa, gives very little improvement over the simplified approach here and gives essentially the same F's as SUVm. Introduced here is a weight index useful in reducing variability and further understanding the SUV. Addressing weight sensitivity is appropriate where the cv of the SUVs is below about 1/3. Proposed is the very simple approach of using an average of an adult patient's weight and approximately 70 kg for FDG SUV calculations. Unlike other approaches the dimensionless population average of SUVms is unchanged from tradition.

Coarsening Kinetics and Coarsened Si Size Distribution of Spray-Formed High Loading Hypereutectic Al-Si Alloys in the Semisolid State

The coarsening behavior of spray-formed A-35wt%Si and A-45wt%Si alloys in the semisolid state were studied. The coarsening kinetic and Si size distributions after coarsening at various temperatures and times in the semi-solid state were investigated. The coarsening exponents, n, the rate constants, K, in the LSW theory, and the modified rate constants were determined from previous works. The coarsening activation energies of the two spray-formed alloys were calculated from the slopes of ln(KT) vs. 1/T plots. The Si size distribution functions after holding at various temperatures and times in the semisolid state were determined for the two spray-formed alloys. The effects of the stokes-motion in addition to pure diffusion mechanism on the variations of coarsened Si size distribution were also investigated.

High negative temperature coefficient of resistance of heteroepitaxial (Ba, Sr) TiO 3 single crystal films prepared by pulsed laser deposition

Heteroepitaxial (Ba, Sr)TiO 3 (BST) films were grown on cleaved single crystal <100> MgO substrates by pulsed laser deposition. Highly <100> oriented BST films with atomic flat surfaces were obtained. By measuring Current–Voltage characteristics, a significant negative temperature coefficient of resistance (about − 4.95% at 300 K) was observed which is different from the positive temperature effect as reported for poly-crystal BST films. As has been suggested the positive temperature coefficient of resistance is attributed to the temperature-dependent barrier height and width at grain boundaries. In this paper, the negative temperature effect of resistance observed in our experiment is discussed and explained by the activation of electrons trapped by oxygen vacancies and absence of grain boundaries. Deep level spectroscopy measurement indicated that the activation energy is approximately 0.31 eV, which is consistent with the value deduced from the slope of ln ⁡ R ∼ 1 T curve.

The thermopower of transition-metal double-perovskites: A sensitive probe of their electronic structures around the Fermi level

Abstract We report on a comparative study of S ( T ) for a series of transition-metal double-perovskites A 2 BB′O 6 (A – Ca, Sr, Ba, and B, B′ = transition metal ions), some of them known to have half-metallic ground states. For Sr 2 BB′O 6 with BB′ = CrMo, CrW, CrRe, FeMo, and FeRe (ferrimagnetic with high Curie temperatures), S ( T ) is metallic, for B′ = Mo and W it is n-type and for B′ = Re, p-type. For A 2 FeMoO 6 (A = Ca, Sr, Ba), the crystallographic differences (monoclinic, tetragonal and cubic space-groups, respectively) are accompanied by prominent differences in their (metallic) S ( T ). For the insulating Sr 2 MnReO 6 and Ba 2 MnReO 6 , the onset of ferromagnetic order below T c ∼ 120 K is marked by a steep drop of S ( T ) accompanied by only a slight change in the slope of ln ρ versus 1/ T 1/2 . Significant conclusions were drawn from the experimental results without the need for elaborate models.

Structural and optical properties of MoO 3 and V 2O 5 thin films prepared by Spray Pyrolysis

MoO 3 and V 2O 5 thin films were prepared on glass substrates by Spray Pyrolysis technique at a substrate temperature of 423 K. The precursor solutions were obtained by varying the concentrations of MoCl 5 and VCl 3 in bi-distilled water. The structural investigation conducted by X-ray diffraction showed that MoO 3 and V 2O 5 thin films were polycrystalline with orthorhombic structure. The optical properties studied in the 300–2500 nm range suggest that the thin film behaviours are related to bound electronic states. The optical band gaps have been estimated from slopes of ln( αhν) versus hν plots of MoO 3 and V 2O 5 films were 3.35 and 2.44 eV, respectively. The electrical conductivity was measured using four probes method.

Synthesis, characterization, conduction and gas sensing properties of novel multinuclear metallo phthalocyanines (Zn, Co) with alkylthio substituents

Compound 1 has been prepared by the reaction of 4-nitrophthalonitrile and 2-nitro-2-methyl-1,3-propanediol by the common method of nucleophilic substitution of an activated nitro group in an aromatic ring. Interesting binuclear metallophthalocyanines (M = Zn and Co), compounds 2 and 3, respectively, of a new type have been synthesized from compound 1, 4,5-bis(hexylthio)phthalonitrile, and the corresponding metal salts [Zn(OAc) 2 and CoCl 2] by the method of statistically mixed condensation. Compound 2 was converted to the tetranuclear zinc (II) phthalocyanine 4 by the reaction with NaOH solution and activated zinc powder in a mixture of MeOH and THF as the solvent. Impedance spectroscopy (IS) and d.c conductivity ( σ d.c) measurements were performed on spin coated films of these compounds as a function of temperature (290–400 K) and frequency (40–10 5 Hz.) The sensing properties for volatile organic compounds (VOCs) were also investigated. Although the d.c conductivity shows typical Arrehenius behaviour for compound 2, a discontinous point was observed in the slope of ln σ d.c versus 1/ T plot for compound 4. Unlike the films of 2 and 4, the d.c behaviour of compound 3 obeys the variable range hopping (VRH) model. At room temperature, a curved line was observed from the complex plane plots of impedance for all compounds. These curved lines transformed into a full semicircle with increasing temperature. The a.c conductivity of the films is represented by the form ω s . The dependency of the frequency exponent s on temperature suggests a correlated barrier hopping. A sensor using compound 4 as the sensing layer had the highest sensitivity for all volatile organic compounds investigated and showed complete reversibility even at room temperature. The results indicated that the film of compound 4 has potential as a sensitive coating for the monitoring of VOC vapours.

NMR and Viscosity Investigation of Clathrate Hydrate Formation and Dissociation

To better understand clathrate hydrate mechanisms, nuclear magnetic resonance (NMR) and viscosity measurements were employed to investigate tetrahydrofuran (THF) hydrate formation and dissociation processes. In NMR experiments, the proton spin lattice relaxation time (T1) of THF in deuterium oxide (D2O) was measured as the sample was cooled from room temperature down to the hydrate formation region. The D2O structural change around THF during this process was examined by monitoring the rotational activation energy of THF, which can be obtained from the slope of ln(1/T1) vs 1/T. No evidence of hydrate precursor formation in the hydrate region was found. T1 measurements of THF under constant subcooling temperature indicate that THF hydration shells do not undergo much structural rearrangement during induction. The T1 of THF was also measured as the sample was warmed back to room temperature after hydrate dissociation. T1 values of THF after hydrate dissociation were consistently smaller than those before hydrate formation and never returned to original values. It was proposed that this difference in T1 after hydrate dissociation indicates that the THF−D2O solution is more microscopically homogeneous than before hydrate formation. In viscosity experiments, a Champion Technologies hydrate rocking cell (CTHRC) was used to probe the residual viscosity phenomenon after Green Canyon (GC) gas hydrate as well as THF hydrate dissociation. The residual viscosity reported in the literature was observed after GC hydrate dissociation but not after THF hydrate dissociation. Because GC hydrate behavior involves significant amounts of gas mass transfer while THF hydrate does not, one might conclude that the residual viscosity observed after GC hydrate dissociation was likely caused by the supersaturated gas concentration and its general effect on solvent viscosity, not necessarily by a clathrate water structure lingering from the solid.

Strong Effects of Molecular Structure on Electron Transport in Carbon/Molecule/Copper Electronic Junctions

Carbon/molecule/copper molecular electronic junctions were fabricated by metal deposition of copper onto films of various thicknesses of fluorene (FL), biphenyl (BP), and nitrobiphenyl (NBP) covalently bonded to flat, graphitic carbon. A "crossed-wire" junction configuration provided high device yield and good junction reproducibility. Current/voltage characteristics were investigated for 69 junctions with various molecular structures and thicknesses and at several temperatures. The current/voltage curves for all cases studied were nearly symmetric, scan rate independent, repeatable at least thousands of cycles and exhibited negligible hysteresis. Junction conductance was strongly dependent on the dihedral angle between phenyl rings and on the nature of the molecule/copper "contact". Junctions made with NBP showed a decrease in conductivity of a factor of 1300 when the molecular layer thickness increased from 1.6 to 4.5 nm. The slope of ln(i) vs layer thickness for both BP and NBP was weakly dependent on applied voltage and ranged from 0.16 to 0.24 A(-1). These attenuation factors are similar to those observed for similar molecular layers on modified electrodes used to study electrochemical kinetics. All junctions studied showed weak temperature dependence in the range of approximately 325 to 214 K, implying activation barriers in the range of 0.06 to 0.15 eV. The carbon/molecule/copper junction structure provides a robust, reproducible platform for investigations of the dependence of electron transport in molecular junctions on both molecular structure and temperature. Furthermore, the results indicate that junction conductance is a strong function of molecular structure, rather than some artifact resulting from junction fabrication.

Two-dimensional second-order factorial moment for shower particles produced in 28Si-emulsion collisions at 14.6 A GeV

The anomalous scaling behaviour of two-dimensional second-order factorial moment F2 for shower particles produced in 28Si-emulsion collisions at 14.6 A GeV has been investigated. The slopes of ln ⟨F2⟩ versus ln M plots for different values of Hurst exponent H have been determined. The parameter ‘a’ that characterizes the upward bending of ln ⟨F2⟩ versus ln M plots has been determined. A comparison of our results with the corresponding results for events generated using UrQMD model indicates that the upward bending of the two-dimensional moment cannot be explained by the model.

Electrical characterization of strontium tartrate single crystals

The a.c. and d.c. conductivity of SrC 4H 4O 6·3H 2O are measured and are found to lie between usual conductivities of semiconductor and insulator. Temperature dependence of d.c. conductivity shows intrinsic conduction, which is confirmed by the slope of ln σ versus ln f data. Due to application of thermal energy, noticeable conductivity peaks imply liberation of water molecules during dehydration and the formation of strontium oxalate. The conductivity plot has a nature similar to the intrinsic-to-extrinsic transition found in normal semiconductors. There occurs Efros hopping conduction in our samples.

1,2-propanediol-cellulose-acrylamide graft copolymers

1,2-Propanediol–cellulose–acrylamide graft copolymers (PCACs) were developed for enhanced oil recovery. They were prepared with acrylamide and 1,2-propanediol (PDO)–cellulose, which was formed through the addition of glycols to cellulose by the Shotten–Baumann reaction between 3-chloro-1,2-propanediol and cellulose. The graft copolymerization was initiated with a redox system between Ce4+ and glycols in cellulose. The infrared spectrum of PDO–cellulose had some characteristic absorption bands around 2960 (νCH) and 1050 cm−1 (νCO) that also appeared for the PDO group and pyranose ring of cellulose, respectively. The rate of Ce4+ consumption by PDO–cellulose was investigated through the calculation of the overall kinetic constant from the slopes of ln(D − DR) versus time (where D is the absorbance and DR is the absorbance of the original polysaccharide solution) The results showed that PDO–cellulose had high reactivity and that there were two mechanisms of oxidation by Ce4+ with PDO–cellulose. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 3022–3029, 2004

Optical absorption studies on (V 2O 5) 1− x–(MoO 3) x thin films

Thin films of ( V 2 O 5) 1−x–( MoO 3) x (0≤x≤1) were prepared by the electron beam evaporation technique in an oxygen partial pressure of 2×10 −4 mbar and at a substrate temperature of 423 K. The optical absorption studies in the wavelength range 300–1500 nm suggested the increase of the optical bandgap with increasing x and showed a curvilinear behaviour. The width of the localized states E e estimated from the slopes of ln α vs hν plots of (V 2O 5) 1− x –(MoO 3) x films were in the range 0.42–0.35 eV. The electrical conductivity decreased with the increase of composition x.

Living Radical Polymerization: Use of an Excess of Nitroxide as a Rate Moderator

The kinetics of the living radical polymerization of n-butyl acrylate (BuA) in the presence of an excess of N-tert-butyl-N-(1-diethylphosphono-2,2-dimethylpropyl)-N-oxyl (DEPN) as a rate moderator has been studied in the temperature range 115−125 °C. The equilibrium rate constant K = kd/kc between dormant and active chains was determined experimentally from the slope of ln([BuA]0/[BuA]) vs time. It obeys the following Arrhenius relation: K = 4.93 × 105 exp(−119.3 kJ mol-1/RT), i.e., K = 1.09 × 10-10 mol L-1 at 125 °C. Some straightforward analytical kinetic equations that only depend on the excess of DEPN as the experimental parameter were established. These equations were successfully applied to simulate the DEPN-mediated polymerization of n-butyl acrylate initiated by either a styryl-DEPN alkoxyamine or an AIBN/DEPN bicomponent system. Last, the slow degradation of DEPN was considered in order to account for the upward deviation of the kinetics when a great excess of DEPN was used.

N-tert-Butyl-1-diethylphosphono-2,2-dimethylpropyl nitroxide as counter radical in the controlled free radical polymerization of styrene: kinetic aspects

The controlled free radical polymerization of styrene with N-tert-butyl-1-diethylphosphono-2,2-dimethylpropyl nitroxide (DEPN) as counter radical was studied. Polymerizations were performed in bulk, with a DEPN-capped polystyryl as alkoxyamine initiator, in the presence of an excess of DEPN nitroxyl free radicals. Kinetics of the polymerization were followed at 115°C, 125°C and 130°C. The equilibrium rate constant K = kd/kc of exchange between dormant and active species was determined experimentally from the slope of Ln([styrene]0/[styrene]) versus time. The obtained Arrhenius relation was the following: K (mol·L–1) = 1.45×107exp (–113.5 kJ·mol–1/RT), i.e., K = 1.9×10–8 mol·L–1 at 125°C. This result is consistent with a much faster polymerization of styrene with DEPN than with Tempo as nitroxyl counter radical (K = 2.1×10–11 mol·L–1 at 125°C determined previously by Fukuda).

N-tert-Butyl-1-diethylphosphono-2,2-dimethylpropyl nitroxide as counter radical in the controlled free radical polymerization of styrene: kinetic aspects

The controlled free radical polymerization of styrene with N-tert-butyl-1-diethylphosphono-2,2-dimethylpropyl nitroxide (DEPN) as counter radical was studied. Polymerizations were performed in bulk, with a DEPN-capped polystyryl as alkoxyamine initiator, in the presence of an excess of DEPN nitroxyl free radicals. Kinetics of the polymerization were followed at 115°C, 125°C and 130°C. The equilibrium rate constant K = kd/kc of exchange between dormant and active species was determined experimentally from the slope of Ln([styrene]0/[styrene]) versus time. The obtained Arrhenius relation was the following: K (mol·L–1) = 1.45×107exp (–113.5 kJ·mol–1/RT), i.e., K = 1.9×10–8 mol·L–1 at 125°C. This result is consistent with a much faster polymerization of styrene with DEPN than with Tempo as nitroxyl counter radical (K = 2.1×10–11 mol·L–1 at 125°C determined previously by Fukuda).