Parameter Dt Research Articles

A Comprehensive Evaluation of 4-Parameter Diurnal Temperature Cycle Models with In Situ and MODIS LST over Alpine Meadows in the Tibetan Plateau

Diurnal variation of land surface temperature (LST) is essential for land surface energy and water balance at regional or global scale. Diurnal temperature cycle (DTC) model with least parameters and high accuracy is the key issue in estimating the spatial–temporal variation of DTC. The alpine meadow is the main land cover in the Tibetan Plateau (TP). However, few studies have been reported on the performance of different DTC models over alpine meadows in the TP. Four semi-empirical types of DTC models were used to generate nine 4-parameter (4-para) models by fixing some of free parameters. The performance of the nine 4-para DTC models were evaluated with four in situ and MODIS observations. All models except GOT09-dT-ts (dT means the temperature residual between T0 and T (t→∞); ts means the time when free attenuation begins) had higher correlation with in situ data (R2 > 0.9), while the INA08-ts model performed best with NSE of 0.99 and RMSE of 2.04 K at all sites. The GOT09-ts-τ (τ is the total optical thickness), VAN06-ts-ω1 (ω1 means the half-width of the cosine term in the morning), and GOT01-ts models had better performance, followed by GOT09-dT-τ, GOT01-dT, and VAN06-ts-ω2 (ω2 means the half-width of the cosine term in the afternoon) models. All models had higher accuracy in summer than in other seasons, while poorer performance was produced in winter. The INA08-ts model showed best performance among all seasons. Models with fixing ts could produce higher accuracy results than that with fixing dT. The comparison of INA08-ts model driven by in situ and Moderate Resolution Imaging Spectroradiometer (MODIS) data indicated that the simulation accuracy mainly depended on the accuracy of MODIS LST. The daily maximum temperature generated by the nine models had high accuracy when compared with in situ data. The sensitivity analysis indicated that the INA08-dT and GOT09-dT-ts models were more sensitive to parameter dT, while all models were insensitive to parameter ts, and all models had weak relationship with parameters ω and τ. This study provides a reference for exploring suitable DTC model in the TP.

Toward Achieving the Theoretical Limit of Electron Spin Polarization in Covalently Linked Radical-Chromophore Dyads.

Electron spin systems with non-Boltzmann spin distributions are commonly observed in photophysical and photochemical processes involving free radicals. Understanding the origin of electron spin polarization (ESP) reveals detailed insight into the spin-dependent interactions occurring in these processes. The ability to transfer ESP to the nuclear spins of the solvent to produce large nuclear polarization is itself an active area of research in the field called dynamic nuclear polarization (DNP). Harnessing ESP in such fields demands a large magnitude of ESP and importantly on free radicals that are stable. In this work, we explored various factors that could play a prominent role in generation of ESP on the stable nitroxyl radical. By exploiting the dependence of ESP on the zero-field splitting parameter DT of the chromophore triplets and a careful choice of the chromophores for efficient quenching of their excited states by a free radical, we present here our strategies for designing covalently linked chromophore-free radical dyads, which could generate high magnitudes of ESP. Syntheses and EPR studies on a series of such dyads to demonstrate successful realization of our strategy are reported here. Our work reveals that, along with the DT value and the triplet quenching efficiency, the relative orientational dynamics of the radical and chromophore moiety and an efficient intersystem crossing of the chromophore primarily govern the ESP of the chromophore-radical dyads. One such molecule, an anthraquinone moiety linked to a TEMPO free radical that optimally satisfies the above criteria, produces a very large value of ESP-about 300 times its Boltzmann value-reaching almost half of the theoretical maximum of the radical-triplet pair mechanism of ESP. Coupled with its excellent photostability in benzene and the use of ambient conditions, this molecule should prove to be highly desirable in photoinduced DNP studies and other applications such as highly sensitive magnetometers, which require generation of large nuclear spin polarization in the solvent by transferring the electron spin polarization.

Abnormal Magnetic Moment and Zero Field Splitting of Some Nickel (II) Complexes

<em>Some complexes of Ni(II) have been prepared with 2-thio-3-acetyl hydantoin (TAHN) and 2-formyl pyridine thiosemicarbazone (FPTS). On the basis of elemental analysis and molar conductivity, the complexes have been formulated as NiL<sub>2</sub>X<sub>2</sub>, where L = TAHN or FPTS and X = Cl<sup>–</sup>, Br<sup>–</sup>, NCS<sup>–</sup>, ClO<sub>4</sub><sup>–</sup>. The infrared spectra of complexes and free ligand reveal that the ligand TAHN is co-ordinated through sulphur and acetyl oxygen, while FPTS ligand co-ordinates through heterocyclic nitrogen and sulphur to Ni(II) metal ion. The magnetic moment of these complexes are found to be 3.20-3.25 B.M. The values are greater than value (2.828 B.M) corresponding to two unpaired electrons of a d<sup>8</sup>-system. The appearance of four absorption bands in their electronic spectra reveal, the tetragonal distortion in the octahedral symmetry of complexes. The zero field splitting parameter(D) and the other crystal field parameters like Dq<sub>(xy)</sub>, Dq<sub>(z)</sub>, Dt have been calculated. The results show that, the tetragonal distortion parameter (Dt) increases in the order of NCS<sup>– </sup>< Cl<sup>–</sup> < Br<sup>–</sup> while the zero field splitting parameter (D) also increases in the same order for both the planer ligands.</em>

Lysozyme stability and amyloid fibrillization dependence on Hofmeister anions in acidic pH.

We have explored an effect of Hofmeister anions, Na2SO4, NaCl, NaBr, NaNO3, NaSCN and NaClO4, on stability and amyloid fibrillization of hen egg white lysozyme at pH 2.7. The stability of the protein was analyzed by differential scanning calorimetry. The Hofmeister effect of the anions was assessed by the parameter dT trs/d[anion] (T trs, transition temperature). We show that dT trs/d[anion] correlates with anion surface tension effects and anion partition coefficients indicating direct interactions between anions and lysozyme. The kinetic of amyloid fibrillization of lysozyme was followed by Thioflavin T (ThT) fluorescence. Negative correlation between dT trs/d[anion] and the nucleation rate of fibrillization in the presence of monovalent anions indicates specific effect of anions on fibrillization rate of lysozyme. The efficiency of monovalent anions to accelerate fibrillization correlates with inverse Hofmeister series. The far-UV circular dichroism spectroscopy and atomic force microscopy findings show that conformational properties of fibrils depend on fibrillization rate. In the presence of sodium chloride, lysozyme forms typical fibrils with elongated structure and with the secondary structure of the β-sheet. On the other hand, in the presence of both chaotropic perchlorate and kosmotropic sulfate anions, the fibrils form clusters with secondary structure of β-turn. Moreover, the acceleration of fibril formation is accompanied by decreased amount of the formed fibrils as indicated by ThT fluorescence. Taken together, our study shows Hofmeister effect of monovalent anions on: (1) lysozyme stability; (2) ability to accelerate nucleation phase of lysozyme fibrillization; (3) amount, and (4) conformational properties of the formed fibrils.

Asymptotics of partial sums of linear processes with changing memory parameter*

We study the limit distribution of partial sums of nonstationary truncated linear process {Xt, t = 1,…, n} with long memory and changing memory parameter dt,n ∈ (0,∞). Two classes of linear processes are investigated, namely, (i) the class of FARIMA-type truncated moving averages with time-varying fractional integration parameter and (ii) the class of time-varying fractionally integrated processes introduced in [A. Philippe, D. Surgailis, and M.-C. Viano, Invariance principle for a class of nonstationary processes with long memory, C. R. Acad. Sci., Paris, Ser. I, 342:269–274, 2006; A. Philippe, D. Surgailis, and M.-C. Viano, Time-varying fractionally integrated processes with nonstationary long memory, Theory Probab. Appl., 52:651–673, 2008]. The cases of fast-changing memory parameter (dt,n = dt does not depend on n) and slowly changing memory parameter (dt,n = d(t/n) for some function d(τ), τ ∈ [0, 1]) are discussed. In the case of fast-changing memory, the limit partial sums process is a type II fractional Brownian motion (fBm) with the Hurst parameter equal to the global maximum of (dt) for class (i) processes and to the mean value of (dt) for class (ii) processes. In the case of slowly changing memory, the limit of partial sums for both classes (i) and (ii) is degenerate and “localized” at the global maximum of the memory function d(∙); however, a nondegenerate limit of the partial sums process is shown to exist when time is suitably rescaled in the vicinity of the maximum point.

Detection and tracking of short duration variations of power system disturbances using modified potential function

This study introduces a modified potential function based modeling approach for real-time disturbance tracking. Real-time tracking requires the least complex techniques for processing and classification and still provide accurate results. Time required to detection of the power quality disturbance should be small enough so that the further mitigation action may be taken. The proposed FRTD algorithm is able to detect the disturbances in 3–5 samples. The proposed FRTD algorithm is principally based upon potential function, which has been modified so as to give the one-dimensional position vector corresponding to the voltage sag and swell, with complexity O(1) with no pre-process complexity. The method detects the transient in 3–5 samples at sampling frequency of 12.8kHz. Potential function uses the current nonlinear drift velocity vector along with a prior knowledge of the power system disturbance to compute the unknown parameter in the form of diffusion matrix, Dt. The parameter Dt has been used to detect the events in the signal. Magnitude of Dt play vital role to detect the events. FRTD algorithm has been tested to track and detect the power system disturbances such as voltage sag, swell, and transient. The algorithm has been tested on hardware interfaced with MATLAB. 1000 samples of different types of power system disturbances such as voltage swell, voltage sag, oscillatory-transient and impulsive-transient have been tested. FRTD algorithm is having the efficiency of 99.83%.

Synthesis, characterization, and ascorbic acid oxidase biomimetic catalytic activity of cobalt(III) oxime complexes

A new tetradentate tetraaza ligand was prepared via Schiff-base condensation of 3,4-diaminotoluene with 2,3-butandione monoxime in aqueous solution. This ligand coordinates cobalt(III) through nitrogen donors in equatorial positions with loss of one oxime proton with concomitant formation of an intramolecular hydrogen bond. A series of cobalt(III) complexes, [CoLX2] (X = Cl−, Br−, or I−), [SCNCoLBr], [CNCoLBr], [BF2CoLBr], and [YCoLBr]ClO4 (Y = pyridine, thiophene, triphenylphosphine, or n-pentylamine), was synthesized. The compounds were characterized based on the elemental analysis (C, H, N), electrical conductance, magnetic moment measurements, and spectral studies (IR, 1H NMR, and UV-Vis). Thermal stabilities of representative complexes were examined by using thermal analysis (TGA and DTG). The reported complexes are d6 low-spin diamagnetic and a distorted octahedral environment was proposed. All complexes undergo tetragonal distortion as evidenced by splitting of 1T1g and 1T2g levels of the pseudo-octahedral symmetry. The ligand field parameters such as DqE , DqA , and the tetragonal splitting Dt have been computed and correlated with the nature of the coordinated axial ligands. The reported cobalt(III) complexes exhibit promising catalytic activity toward aerobic oxidation of ascorbic acid to the corresponding dehydroascorbic acid. The oxidase catalytic activity is linked to both the tetragonal splitting parameter Dt and the Lewis-acidity of cobalt(III) created by the nature of the coordinated axial ligands. The probable mechanistic implications of the catalytic oxidation reactions are discussed.

Spectral changes of brain activity in rat offspring exposed to aluminium during gestation and lactation

Exposure to aluminium during gestation causes changes in mammalian brain development and behavior. Our aim was to perform spectral analysis on electrocortical activity of Sprague Dawley male pups (30?3 days of age) whose mothers were treated with aluminium during gestation and lactation. There was a higher presence of power spectra in the delta range of parietal electrocortical activity, a lower presence in the theta range and increased values of the parameter DT as the ratio of delta to theta range in pups indirectly exposed to aluminium (whose mothers were drinking a 0.5% water solution of aluminium chloride during the gestation and lactation periods), compared to controls.

Network connectance and autonomy analyses of the photosynthetic apparatus in tropical tree species from different successional groups under contrasting irradiance conditions

Biological systems are complex dynamical systems whose relationships with environment have strong implications on their regulation and survival. From the interactions between plant and environment can emerge a quite complex network of plant responses rarely observed through classical analytical approaches. The objective of this current study was to test the hypothesis that photosynthetic responses of different tree species to increasing irradiance are related to changes in network connectances of gas exchange and photochemical apparatus, and alterations in plant autonomy in relation to the environment. The heat dissipative capacity through daily changes in leaf temperature was also evaluated. It indicated that the early successional species (Citharexylum myrianthum Cham. and Rhamnidium elaeocarpum Reiss.) were more efficient as dissipative structures than the late successional one (Cariniana legalis (Mart.) Kuntze), suggesting that the parameter DT (T oCair - T oCleaf) could be a simple tool in order to help the classification of successional classes of tropical trees. Our results indicated a pattern of network responses and autonomy changes under high irradiance. Considering the maintenance of daily CO2 assimilation, the tolerant species (C. myrianthum and R. elaeocarpum) to high irradiance trended to maintain stable the level of gas exchange network connectance and to increase the autonomy in relation to the environment. On the other hand, the late successional species (C. legalis) trended to lose autonomy, decreasing the network connectance of gas exchange. All species showed lower autonomy and higher network connectance of the photochemical apparatus under high irradiance.

Reply to comment by R. Bousquet et al. on “Subduction factory: 1. Theoretical mineralogy, densities, seismic wave speeds and H2O contents”

[1] Steady increases in the mineral physical property database, new methods of calculating the physical properties of rocks, and the growing understanding of ultrahighpressure rocks [e.g., Liou et al., 2000] has stimulated considerable effort in recent years to calculate rock physical properties at high to ultrahigh pressure. One approach [e.g., Hacker et al., 2003] is to use the mineral abundances and mineral compositions of natural rocks determined in the field and in experiments. Another approach [e.g., Kerrick and Connolly, 2001] uses the thermodynamic properties of minerals to calculate mineral abundances and mineral compositions. Both approaches have strengths and weaknesses [Hacker et al., 2003]: the former is grounded in the reality that the mineral abundances and mineral compositions actually exist in natural rocks, the latter has the internal consistency and elegance that comes from a purely theoretical approach. Between these two end-member methodologies lie a range of approaches, including that presented by Bousquet et al. [1997]. Hacker et al. [2003] and Bousquet et al. [1997] both used metamorphic facies determined from a combination of natural and experimental studies; the boundaries of the facies fields are relatively similar but differ in key areas where temperatures are low (and thus equilibrium is often not attained) or pressures are unusually high (an area of active research). Hacker et al. [2003] used natural mineral abundances and compositions to calculate rock physical properties from a mineral equation of state that uses a third-order finite strain approximation with full consideration of the effects of changes in pressure and temperature. Bousquet et al. [1997] calculated mineral abundances from assumed mineral compositions and calculated rock densities at 1 bar and 25 C [Goffe et al., 2003] using an unspecified procedure. Because the thermal expansivities and compressibilities of key minerals such as feldspar translate into density changes of 15% over the 800 C to 3 GPa pressure range of interest [Hacker and Abers, 2004], the differences in these approaches will necessarily lead to different calculated densities. [2] Our calculated densities do not violate thermodynamics as implied by Bousquet et al. [2005]. With increasing temperature, thermodynamics requires the entropy of a system to increase whereas the density of the system may increase or decrease. With increasing pressure, thermodynamics requires the density of a system to increase, but we and Bousquet et al. [1997, 2005] present calculated densities for the solid minerals, not the whole system which includes H2O in addition to the solid minerals. The specific example cited, of a temperature-dependent increase in density at 800 C and 1.0–1.5 GPa, is caused by the dehydration of amphibole. Our new results ‘‘contradict’’ our previous results [Hacker, 1996] because our new calculations explicitly consider the effect of Fe. [3] We are perplexed by Bousquet et al.’s [2005] suggestion that our density calculations contradict densities of natural rocks measured by Austrheim [1987]. Austrheim [1987] measured granulite facies anorthositic rocks with densities of 2.79–3.21 g/cm and mafic eclogites of 3.5– 3.6 g/cm but did not specify mineral abundances or compositions, precluding a direct comparison. If, however, we use mineral compositions from Austrheim and Griffin [1985] and assume mineral abundances typical for granulites (50% plagioclase, 25% garnet, and 25% pyroxene) and eclogites (50% garnet and 50% pyroxene), we calculate STP densities of 3.20 and 3.61 g/cm, in agreement with those measured by Austrheim, who noted that the presence of microcracks and alteration in his rocks would lower the density measurements. It is even more difficult to make comparisons between our calculated densities and the other papers cited by Bousquet et al. [2005]. Green and Ringwood [1967] did not measure the densities of their experimental rocks. Ito and Kennedy [1971] did not measure garnet compositions and reported only a single pyroxene composition. Bousquet et al. [2005] are correct to note that within individual facies fields our calculated densities depend only on the formula weight, molar volume, expansivity a, @a/@T, isothermal bulk modulus KT, @KT/@P, shear modulus m, @m/@P, G = (@lnm/@lnr)P, Gruneisen parameter gth, and the second Gruneisen parameter dT = (@lnKT/@lnr)P; we do not model the changes in mineral composition and abundance within those individual fields. JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 110, B02207, doi:10.1029/2004JB003490, 2005

Effect of pressure on the Curie temperature of R xCo 70− xB 30 (R = Y, Tm) amorphous alloys

The initial ac-susceptibility and the Curie temperature T C of amorphous R x Co 70− x B 30 alloys (R = Y, Tm; x = 2, 4, 6, 8) have been investigated under high hydrostatic pressure up to 9 kbar over a wide temperature range from 80 to 500 K. A small decrease in T C was observed under pressure for all the R x Co 70− x B 30 alloys studied. The value of the pressure parameter dT C/dp decreases monotonically from −0.1 to −0.6 K/kbar with increasing content of the R element and decreasing T C. Using the theoretical band models of magnetism, the studied R x Co 70− x B 30 alloys can be characterised as homogeneous strong itinerant ferromagnets.

Polarized electronic absorption spectra of Co2+ ions in the kieserite-type compounds CoSO4 � H2O and CoSeO4 � H2O

Polarized electronic absorption spectra of the kieserite-type compounds CoSO4 · H2O and CoSeO4 · H2O have been obtained at room temperature (spectral range 35 000-5000 cm-1) and at liquid nitrogen temperature (visible spectral region), using microscope-spectrometric techniques. The spectra are interpreted and evaluated in terms of a tetragonal crystal field formalism for the d7 configuration, in regard to the pseudotetragonal elongation of the CoO4(H2O)2 octahedra, known from previous X-ray structure investigations, employing the tetragonal parameters Dq, Dt, and Ds, and the Racah parameters B and C. The observed and calculated energy levels are in good agreement for the following parameter sets: CoSO4 · H2O: Dq=826, Dt=40, Ds=350, B=856, C=3580 cm-1; CoSeO4· H2O: Dq=817, Dt=44, Ds=406, B=841, C=3490 cm-1; corresponding ‘cubic’ crystal field strengths Dqcub are 803 and 792 cm-1, respectively. The values of Dq(cub), Racah B and C are in the common range for Co2+ ions in (pseudo) octahedral fields of oxygen ligands, and their differences in CoSO4· H2O compared to CoSeO4 · H2O are consistent with somewhat different mean Co-O bond lengths and with a slightly higher covalent contribution to Co-O bonding in the selenate compound. The values found for the parameter Dt, which is directly correlated to the extent of tetragonal distortion, are much lower than expected from purely geometrical considerations, thus confirming a significantly higher position of H2O ligands in the spectrochemical series compared to oxygen ligands belonging to SO4 or SeO4 groups.

Crystal Structure and Polarized Electronic Absorption Spectra of NaCo 2(SeO 3) 2(OH)

The crystal structure of hydrothermally synthesized NaCo 2 (SeO 3) 2(OH) has been determined by direct and Fourier methods using single crystal X-ray diffraction data up to sin θ/λ = 0.8 Å -1 [orthorhombic, space group Pbnm, a = 8.338(1) Å, b = 13.268(3) Å c = 6.042(1) Å Z = 4; R w = 0.023 for 1407 unique reflections with F o > 2σ(F o)|. The structure of NaCo 2(SeO 3) 2(OH) consists of [4 + 2]-coordinated Na atoms, distorted CoO 6 octahedra, pyramidal SeO 3 groups, and hydroxyl groups. The CoO 6 polyhedra form 1 ∞ [Co 4O 14] 20- zigzag chains, analogous to the respective Me 2+ chains in the olivine structure type. These chains are connected via the selenite groups and sodium atoms. The O atom of the hydroxyl group belongs to three CoO 6 polyhedra and forms a bifurcated hydrogen bond (3.312 Å, 2×). Furthermore, polarized electronic absorption spectra of NaCo 2(SeO 3) 2(OH) have been measured in the range from 4000 to 40,000 cm -1 using microscope spectrometric techniques. The spectra are characterized by electric dipole transitions at the acentric Co 2+ site [Co(2)]. An interpretation of the band splitting and polarization behavior is attempted in terms of a pseudotetragonal field component and the imposed actual monoclinic site pertubation, yielding 4 A 2 (F) and 4 A″( F) as respective ground states. Tetragonal crystal field calculations give Dq = 630, Dt = -135, Ds = -111, B = 843, and C = 3520 cm -1, which corresponds to a "cubic" Dq of 709 cm -1. The sign and magnitude of the tetragonal parameter Dt is in good agreement with the pseudotetragonal compression of the Co(2)O 6 polyhedron.

Initial stages of ion-induced interfacial mixing in the Ag-Pd system

AgPd superlattices were prepared by sequential thermal evaporation in a high-vacuum system. The structure of the films has been investigated on the basis of large-angle X-ray diffraction spectra measured in Θ–2Θ reflection geometry. Comparison between experimental and calculated spectra shows that the interplanar distance in palladium layers is dependent on the percentage concentration of palladium atoms in the superlattice unit cells. Ion implantation with 300 keV Ar 2+ ions has been performed in order to study the ion-beam-mixing process in the AgPd superlattice targets. The mixing parameter Dt ΦF D = 22.5 A ̊ 5/eV is determined for the initial stage of the process (i.e. for ion doses ranging from 4 × 10 13 to 5 × 10 14 ions/cm 2).

Laser probe 40Ar [sbnd]39Ar measurements of loss profiles within individual hornblende grains from the Giants Range Granite, northern Minnesota, USA

A Nd-glass laser has been used as a “probe”, mapping natural argon diffusion in partially outgassed hornblende grains at a resolution of around 50 μm. The hornblendes are from the Giants Range Granite (2700 Ma), Minnesota, taken approximately 2 km from the contact with the Duluth Gabbro Complex (1100 Ma). The full range of ages can be discerned within individual hornblende grains using the laser extraction technique, but more importantly, diffusion profiles up to 500 μm in length have been detected. The profiles reflect large variations in “domain” size within single grains. Diffusive argon loss was controlled not only by lattice-dominated volume diffusion, but a network of fast diffusion paths (now defined by biotite inclusions) and also indirectly by mineral reactions associated with the contact metamorphism. Three natural argon loss profiles from subgrains of different sizes yield good fits to theoretical volume diffusion loss curves, and a mean time-integrated diffusion parameter ( D(t)dt) of (7.1 ± 0.9) × 10 −5 cm 2. This parameter constrains the possible heat loss models for the Duluth Gabbro.

Preparations, Properties, and Crystal Structures of trans-[Rh(CN)2(NH3)4]Cl·H2O and trans-[Rh(CN)2(en)2]Cl

Abstract Syntheses of the title new complex compounds of Rh(III) were successful. Single, sharp IR peaks of ν (C≡N) were observed at 2130 cm−1 (trans-[Rh(CH)2(NH3)4]Cl·H2O) and 2170 cm−1 (trans-[RH(CN)2(en)2]Cl), respectively. The values of the ligand field tetragonal parameter Dt were estimated to be −366 and −377 cm−1, respectively, based on the 1Ega (D4h)←1A1g Aig transition (37100 cm−1: trans-[Rh(CN)2(NH3)4]+; 37000 cm−1: trans-[Rh(CN)2(en)2]+). The X-ray crystal data are: for trans-[Rh(CN)2(NH3)4]Cl·H2O, orthorhombic, Cmcm, a=7.961(3), b=17.295(2), c=7.436(3) Å, Dc=1.79, Dm=1.79 g cm−3, Z=4; for trans-[Rh(CN)2(en)2]Cl, monoclinic, P21⁄n, a=9.665(4), b=9.107(3), c=6.779(3) Å, β=109.68(2)°, Dc=1.85, Dm=1.83 g cm−3, Z=2. The N≡C–Rh–C≡N sequence of trans[Rh(CN)2(NH3)4]+ lies in a line of m2m Symmetry in the crystal. The central Rh atom of trans-[Rh(CN)2(en)2]+ occupies the special position of inversion symmetry. The important geometrical data of the complexes are Rh–N=2.07(1), Rh–C=2.02(3) Å, N–Rh–N=88.0(5)° (trans-[Rh(CN)2(NH3)4]+) and Rh–N=2.080(3), 2.072(3), Rh–C=2.047(4) Å, N–Rh–N (within chelate ring)=82.7(1)° (trans-[Rh(CN)2(en)2]+).

Ion beam mixing in Au-Cu compositionally modulated alloys

Ion beam mixing in Au-Cu compositionally modulated alloys (CMA) has been studied by means of the Θ-2Θ large-angle X-ray diffraction technique. The ion mixing was performed using 300 keV Ar 2+ ions. A statistical model of the superlattice structure was applied for estimating spreads of the mixed regions. A mixing parameter Dt ΦF D was estimated for each sample with the average value of 90 A ̊ 5 eV .

Complete Theory of Paramagnetism in Transition Metal Ions IV. The d2 and d8 Electron Configurations in Cubic (Oh and Td), Tetragonal (D4h), and Trigonal (D3d) Symmetry

AbstractOn the basis of the diagonalization of the complete Coulomb repulsion, ligand field, spin‐orbit interaction, and Zeeman effect matrices, the magnetic properties were calculated for the octahedral and tetrahedral d2 and d8 electron systems. In addition, the corresponding tetragonally and trigonally distorted systems were likewise studied. Irreducible tensor operator (Racah) methods were used in both weakfield and intermediate‐field coupling, and complete agreement of the results was achieved. The magnetization was evaluated by direct numerical differentiation of the energies, followed by Boltzmann averaging, and no assumptions limiting the applicability to high temperatures and small magnetic fields were introduced.Plots are presented giving the effective magnetic moment μeff as function of the ligand field parameter 10 Dq in Oh and Td symmetry for a fixed set of values of B, C, ζ, and k. In D4h and D3d symmetry, similar plots are furnished which present μeff as function of the parameter Dt or D. Here 10Dq as well as K = Ds/Dt = Dσ/Dτ assume fixed values. The H‐dependence of μeff is found to be minor. The effect of a variation in the parameter values B, C, ζ, and k is likewise studied. The results may be employed in an accurate comparison of experimental magnetic and spectroscopic data with theory.

Aromatic diamine complexes. I. Nickel(II) complexes with o-phenylenediamine, 1,8-diaminonaphthalene and 2-2-diaminobiphenyl

Nickel(II) complexes containing two and three molecules of the aromatic diamines, o-phenylenediamine, 1,8-diaminonaphthalene and 2-2′-diaminobiphenyl are described. The complexes have been characterised by magnetic and infrared and visible spectral, measurements. Those complexes containing two molecules of diamine have been shown to have D 4h symmetry. The significance of the tetragonal splitting parameter Dt and axial ligand field strengths Dq 2 of the acid groups is discussed.