A solution of the DGLAP equation for gluon at low x

We obtain a solution of the DGLAP equation for the gluon at low x first by expanding the gluon in a Taylor series and then using the method of characteristics. We test its validity by comparing it with that of Glück, Reya and Vogt. The convergence criteria of the approximation used are also discussed. We also calculate εF ₂(x,Q)²/ε In Q ² using its approximate relations with the gluon distribution at low x. The predictions are then compared with the HERA data.     

The first example of a nitrile hydratase model complex that reversibly binds nitriles

Nitrile hydratase (NHase) is an iron-containing metalloenzyme that converts nitriles to amides. The mechanism by which this biochemical reaction occurs is unknown. One mechanism that has been proposed involves nucleophilic attack of an Fe-bound nitrile by water (or hydroxide). Reported herein is a five-coordinate model compound ([Fe(III)(S(2)(Me2)N(3)(Et,Pr))](+)) containing Fe(III) in an environment resembling that of NHase, which reversibly binds a variety of nitriles, alcohols, amines, and thiocyanate. XAS shows that five-coordinate [Fe(III)(S(2)(Me2)N(3)(Et,Pr))](+) reacts with both methanol and acetonitrile to afford a six-coordinate solvent-bound complex. Competitive binding studies demonstrate that MeCN preferentially binds over ROH, suggesting that nitriles would be capable of displacing the H(2)O coordinated to the iron site of NHase. Thermodynamic parameters were determined for acetonitrile (DeltaH = -6.2(+/-0.2) kcal/mol, DeltaS = -29.4(+/-0.8) eu), benzonitrile (-4.2(+/-0.6) kcal/mol, DeltaS = -18(+/-3) eu), and pyridine (DeltaH = -8(+/-1) kcal/mol, DeltaS = -41(+/-6) eu) binding to [Fe(III)(S(2)(Me2)N(3)(Et,Pr))](+) using variable-temperature electronic absorption spectroscopy. Ligand exchange kinetics were examined for acetonitrile, iso-propylnitrile, benzonitrile, and 4-tert-butylpyridine using (13)C NMR line-broadening analysis, at a variety of temperatures. Activation parameters for ligand exchange were determined to be DeltaH(+ +) = 7.1(+/-0.8) kcal/mol, DeltaS(+ +) = -10(+/-1) eu (acetonitrile), DeltaH(+ +) = 5.4(+/-0.6) kcal/mol, DeltaS(+ +) = -17(+/-2) eu (iso-propionitrile), DeltaH(+ +) = 4.9(+/-0.8) kcal/mol, DeltaS(+ +) = -20(+/-3) eu (benzonitrile), and DeltaH(+ +) = 4.7(+/-1.4) kcal/mol DeltaS(+ +) = -18(+/-2) eu (4-tert-butylpyridine). The thermodynamic parameters for pyridine binding to a related complex, [Fe(III)(S(2)(Me2)N(3)(Pr,Pr))](+) (DeltaH = -5.9(+/-0.8) kcal/mol, DeltaS = -24(+/-3) eu), are also reported, as well as kinetic parameters for 4-tert-butylpyridine exchange (DeltaH(+ +) = 3.1(+/-0.8) kcal/mol, DeltaS(+ +) = -25(+/-3) eu). These data show for the first time that, when it is contained in a ligand environment similar to that of NHase, Fe(III) is capable of forming a stable complex with nitriles. Also, the rates of ligand exchange demonstrate that low-spin Fe(III) in this ligand environment is more labile than expected. Furthermore, comparison of [Fe(III)(S(2)(Me2)N(3)(Et,Pr))](+) and [Fe(III)(S(2)(Me2)N(3)(Pr,Pr))](+) demonstrates how minor distortions induced by ligand constraints can dramatically alter the reactivity of a metal complex.     

Irreducible tensors for the groupSU 3

The explicit determination of the matrix elements of theSU ₃ irreducible tensors is carried out by a purely algebraic method. These expressions may be used to compute the Clebsch-Gordan coefficients by orthogonalisation. For the special case of (0,q) tensors simple formulas are derived.In partial fulfillment for the requierements of the doctoral degree at the Institute of Physics of the Academy.     

Overtone spectroscopy of some benzaldehyde derivatives

Overtone spectrum of o, m and p-nitrobenzaldehydes and p-chlorobenzaldehyde has been studied in 2000–12000 cm⁻¹ region. Vibrational frequencies and anharmonicity constants for aryl as well as alkyl CH stretch vibrations have been determined. We have also determined the internuclear distances for the aryl CH bond in the different molecules. The small variation observed in these distances is an indication of the substitution effect. It is observed that in the case of p-disubstituted benzens, the shift in aryl CH bond is proportional to sum of the Hammet σ of the substituents. However in the case of o-disubstituted benzenes it is only 80% of the para-substituted shift.     

Review of particle properties

This review of the properties of leptons, mesons, and baryons is an updating of Review of Particle Properties, Particle Data Group [Rev. Mod. Phys. 45, No. 2, Part II, Supplement (1973)]. Data are evaluated, listed, averaged, and summarized in tables.     

Soft-pion limits of the inclusive pion distributions in NN → π± + anything at rest

The PCAC hypothesis of extrapolating off mass shell is used to show that the invariant pion distributions in the reactions $\text{N}\text{N}\text{→ π}{}^{\mathrm{\pm }}\text{+}$ anything at rest must vanish as the pion momentum tends to zero, a behavior which is supported by recent data on $\text{p}\text{n}\text{→ π}{}^{\mathrm{\pm }}\text{+}$ anything.     

Decomposition of extended superfields into irreducible representations of supersymmetry

We give the decomposition of superfields with arbitrary Lorebtz and U(N) indices, in terms of irreducible representations of N extended [including U(N)] supersymmetry. The spectra of the superspin and super-U(N) Casimir operators as well as one missing label operator are given in closed form.     

Multiple ionization of argon in coincidence with projectile ions in 60–120 MeV Si q+-Ar collisions

A projectile ion-recoil ion coincidence technique has been employed to study the multiple ionization and the charge transfer processes in collisions of 60–120 MeV Si ^q+ (q = 4−14) ions with neutral argon atoms. The relative contribution of different ionization channels, namely; direct ionization, electron capture and electron loss leading to the production of slow moving multiply charged argon recoil ions have been investigated. The data reported on the present collision system result from a direct measurement in the considered impact energy for the first time. The total ionization cross-sections for the recoil ions are shown to scale as q ^1.7/E _p ^0.5 , where E _p is the energy in MeV of the projectile and q its charge state. The recoil fractions for the cases of total- and direct ionizations are found to decrease with increasing recoil charge state j. The total ionization fractions of the recoils are seen to depend on q and to show the presence of a ‘shell-effect’ of the target. Further, the fractions are found to vary as 1/j ² upto j = 8+. The average recoil charge state 〈j〉 increases slowly with q and with the number of lost or captured electrons from or into the projectile respectively. The projectile charge changing cross-sections σ _qq′ are found to decrease with increasing q for loss ionization and to increase with q for direct-and capture ionization processes respectively. The physics behind various scaling rules that are found to follow our data for different ionization processes is reviewed and discussed.     

Probing the influence of local coordination environment on the properties of Fe-type nitrile hydratase model complexes

A series of four structurally related cis-dithiolate-ligated Fe(III) complexes, [Fe(III)(DITpy)2]Cl (1), [Fe(III)(DITIm)2]Cl (2), [Fe(III)(ADIT)2]Cl (3), and [Fe(III)(AMIT)2]Cl (4), are described. The structural characterization of 3 as well as the spectroscopic properties of 3 and 4 has been previously reported. Crystal data for 1, 2, and 4 are as follows: 1.3H2O crystallizes in the orthorhombic space group Pca2(1) with a = 19.800(4) A, b = 18.450(4) A, c = 14.800(3) A, and Z = 8. 2.(1/2)EtOH.1/2H2O crystallizes in the monoclinic space group Cc with a = 24.792(4) A, b = 14.364(3) A, c = 17.527(3) A, beta = 124.91(2) degrees, and Z = 8. 4 crystallizes in the triclinic space group P1 with a = 8.0152(6) A, b = 10.0221(8) A, c = 11.8384(10) A, alpha = 73.460(3) degrees, beta = 71.451(5) degrees, gamma = 72.856(4) degrees, and Z = 2. Complexes 1-4 share a common S2N4 coordination environment that consists of two cis-thiolates, two trans-imines, and two cis-terminal nitrogen donors: Nterm = pyridine (1), imidazole (2), and primary amine (3 and 4). The crystallographically determined mean Fe-S bond distances in 1-4 range from 2.196 to 2.232 A and are characteristic of low-spin Fe(III)-thiolate complexes. The low-spin S = 1/2 ground state was confirmed by both EPR and magnetic susceptibility measurements. The electronic spectra of these complexes are characterized by broad absorption bands centered near approximately 700 nm that are consistent with ligand-to-metal charge-transfer (CT) bands. The complexes were further characterized by cyclic voltammetry measurements, and all possess highly negative Fe(III)/Fe(II) redox couples ( approximately -1 V vs SCE, saturated calomel electrode) indicating that alkyl thiolate donors are effective at stabilizing Fe(III) centers. Both the redox couple and the 700 nm band in the visible spectra show solvent-dependent shifts that are dependent upon the H-bonding ability of the solvent. The implications of these results with respect to the active site of the iron-containing nitrile hydratases are also discussed.