New alicyclic diterpenes and ent-labdanes from gutierrezia solbrigii

The investigation of the aerial parts of $\text{Gutierrezia solbrigii}$ afforded in addition to known compounds nine new ent-labdane derivatives, an aromatic ester and five alicyclic diterpenes. The structures were elucidated by highfield ¹H NMR spectroscopy.     

Solution of Evolution Equation for Longitudinal Structure Function F L upto Next-to-Next-to-Leading Order and Its t-Evolution at Small-x

The aim of the present paper is to calculate longitudinal structure function F _L from QCD (Quantum Chromodynamics) evolution equation in next-to-next-to-leading order (NNLO) at small-x. The calculation of F _L is important for the phenomenological study of gluon distribution function inside the nucleon. Here we use Taylor Series Expansion method to solve the evolution equation for small-x and thus obtain t-evolution of F _L structure function. The calculated results are compared with H1 and ZEUS data and results of Block and Donnachie-Landshoff (DL) models.     

Identities and congruences for the general partition and Ramanujan’s tau functions

We present some identities and congruences for the general partition function p _r (n). In particular, we deduce some known identities for Ramanujan’s tau function and find simple proofs of Ramanujan’s famous partition congruences for modulo 5 and 7. Our emphasis throughout this paper is to exhibit the use of Ramanujan’s theta functions to generate identities and congruences for general partition function.     

New congruences for $$\ell $$-regular partitions for $$\ell \in \{5,6,7,49\}$$∈{5,6,7,49}

We find several new congruences for \(\ell \)-regular partitions for \(\ell \in \{5,6,7,49\}\) and also find alternative proofs of the congruences for 10- and 20-regular partitions which were proved earlier by Carlson and Webb (Ramanujan J 33:329–337, 2014) by using the theory of modular forms. We use certain p-dissections of \((q;q)_{\infty }\), \(\psi (q)\), \((q;q)_{\infty }^3\) and \(\psi (q^2)(q;q)_{\infty }^2\).     

Tertiary amine effect: synthesis of some novel spirosubstituted pyrido[2,3-d]pyrimidines

5-Formyl-6-tertiaryamino uracils 3 prepared from 6-chloro-5-formyl uracil derivative 1 react with barbituric acids 4 in the presence of base catalyst to afford a novel class of spirosubstituted pyrido[2,3-d]pyrimidines 5 via 1,6-electro-cyclisation in excellent yields.     

Effect of seeded substrates on hydrothermally grown ZnO nanorods

We report a study on the effect of seeding on glass substrates with zinc oxide nanocrystallites towards the hydrothermal growth of ZnO nanorods from a zinc nitrate hexahydrate and hexamethylenetetramine solution at 95 °C. The seeding was done with pre-synthesized ZnO nanoparticles in isopropanol with diameters of about 6–7 nm as well as the direct growth of ZnO nanocrystallites on the substrates by the hydrolysis of pre-deposited zinc acetate film. The nanorods grown on ZnO nanoparticle seeds show uniform dimensions throughout the substrate but were not homogenously aligned vertically from the substrate and appeared like nanoflowers with nanorod petals. Nanorods grown from the crystallites formed in situ on the substrates displayed wide variations in dimension depending upon the preheating and annealing conditions. Annealing the seed crystals below 350 °C led to scattered growth directions whereupon preferential orientation of the nanorods perpendicular to the substrates was observed. High surface to volume ratio which is vital for gas sensing applications can be achieved by this simple hydrothermal growth of nanorods and the rod height and rod morphology can be controlled through the growth parameters.     

Application of negative ion MS/MS to the identification of N-glycans released from carcinoembryonic antigen cell adhesion molecule 1 (CEACAM1)

Structures of N-glycans released from rat CEACAM1 expressed in human embryonic kidney cells were determined by MALDI and negative ion nanospray MS/MS techniques. The major carbohydrates were bi-, tri- and tetra-antennary complex glycans with and without sialic acid, fucose and bisecting GlcNAc residues. High-mannose glycans, predominantly Man(5)GlcNAc(2), were also found. The negative ion fragmentation technique easily identified the branching pattern of the triantennary glycans (mainly branched on the 6-antenna) and the presence of 'bisecting' GlcNAc residues (attached to the 4-position of the core mannose), features that are difficult to determine by traditional techniques. Sialic acids were in both alpha2-3 and alpha2-6 linkage as determined by MALDI-TOF MS following linkage-specific derivatization.     

Toward the control of the magnetic anisotropy of Fe(II) cubes: a DFT study

We present the results of our all-electron density-functional calculations on the magnetic anisotropy of the [Fe4(sap)4(MeOH)4] and [Fe4(sae)4(MeOH)4] polynuclear complexes. Our calculations, which predict that only the second complex is a single-molecule magnet (with a magnetic anisotropy energy barrier of 5.6 K), are in qualitative agreement with the experimental data. The analysis of the projected anisotropies of each Fe(II) ion, together with a study of the variation of the D value as a function of several geometrical parameters, allows us to qualitatively understand the different magnetic behaviors of both complexes. In addition to this, we also present a simple rule based on the analysis of the molecular orbitals of the system that allows us to predict how to enhance (by a factor of 6, approximately) the magnetic anisotropy barrier of these systems. Specifically, we will show that, for high-spin Fe(II) ions, the local easy axis of magnetization is perpendicular to the plane defined by the Fe(II)-d orbital which is doubly occupied. If similar rules were found for other metal ions, rational synthetic strategies to control magnetic anisotropy could be established.