Azomesogens containing an ethoxyethyl terminal chain: synthesis and characterization

Two homologous mesogenic series, the ethoxyethyl 4-(4'-n-alkoxyphenylazo)benzoates (I) and the ethoxyethyl [4-(4'-n-alkoxybenzoyloxy)phenylazo]-4'-benzoates (II), both containing a terminal ethoxyethyl chain, have been synthesized. In series I, all nine members synthesized exhibit only an enantiotropic smectic A mesophase. In series II, all 12 homologues exhibit an enantiotropic nematic mesophase; a smectic A phase appears in the n-butyloxy derivative as a enantiotropic phase and persists through to the n-hexadecyloxy member. The mesomorphic properties of both series are compared with each other and also with the properties of other structurally related series to evaluate the effects of the ethoxyethyl chain on mesomorphism.     

An efficient one-pot synthesis of functionally diverse 2-aminothiazoles from isothiocyanates,amidines/guanidines and halomethylenes

An efficient one-pot method for the synthesis of 2-aminothiazoles using simple starting materials like isothiocyanates, amidines/guanidines and various halomethylenes is reported. The synthesis of 2-aminothiazoles involves reactions such as nucleophilic addition, S-alkylation and intramolecular nucleophilic substitution in which amines departs as the leaving group.     

Dielectric and Viscoelastic Behavior of Poly-(n-Butyl Methacrylate) Containing Cholesteric Compounds

Dielectric and dynamic mechanical behavior of poly(n-butyl methacrylate) (PBMA) containing small concentrations of cholesteryl chloride (ChCl), cholesteryl caprylate (ChCp), and cholesteryl laurate (ChL) have been studied in the temperature range -20 to 80°C. Tan αmax (dielectric and mechanical) in all systems containing an additive shifts to lower temperature compared to that in pure PBMA. In the glassy region, the dynamic storage modulus E′ for all the PBMA plus additive systems is higher than that for pure PBMA. This behavior is similar to the β-peak suppression and the increase in tensile strength of poly(vinyl chloride) on addition of a small concentration of plasticizer. Using the WLF equation with C₁ and C₂ obtained from the data on pure PBMA, the reference temperature T_o for PBMA plus additive systems are determined for the best fit of the experimental points to the WLF curve and are in agreement with measured glass-transition temperatures. With respect to T_o of pure PBMA, the T_o of PBMA plus additive systems are lowered, and the lowering due to these additives is in the order ChL < ChCp < ChCl. From spectrophotometric studies in solutions of polymer plus additives, equilibrium constants for the 1:1 and 1:2 complexes between the polymer and the additive are evaluated. The magnitude of the equilibrium constant K₁ increases in the order ChL > ChCp > ChCl, and hence it is concluded that the extent of β-peak suppression depends on the strength of polymer-additive interaction.     

Chiral discrimination asserted by enantiomers of Ni (II), Cu (II) and Zn (II) Schiff base complexes in DNA binding, antioxidant and antibacterial activities

Chiral Schiff base ligands (S)-H(2)L and (R)-H(2)L and their complexes (S-Ni-L, R-Ni-L, S-Cu-L, R-Cu-L, S-Zn-L and R-Zn-L) were synthesized, characterized and examined for their DNA binding, antioxidant and antibacterial activities. The complexes showed higher binding affinity to calf thymus DNA with binding constant ranging from 2.0×10(5) to 4.5×10(6) M(-1). All the complexes also exhibited remarkable superoxide (56-99%) and hydroxyl scavenging (45-89%) activities as well as antibacterial activities against gram (+) and gram (-) bacteria. However, none of the complexes showed antifungal activity. Conclusively, S enantiomers of the complexes were found to be relatively more efficient for DNA interaction, antioxidant and antibacterial activities than their R enantiomers. This study reveals the possible utilization of chiral Schiff base complexes for pharmaceutical applications.     

Bioactive mushroom polysaccharides as antitumor: an overview

Immuno-therapies are gaining more importance to treat certain forms of cancer. The goal of therapies is to enhance person’s own IgG, IgA, IgM, IgD, IgE and macrophages to combat with neoplastic cells hence the effectiveness of the immune system. Since, early civilization mushrooms are considered as potent food as well as medicine. Mushrooms are well known for their bioactive compounds such as chizophyllan, lentinan, grifolan, PSP (polysaccharide-peptide complex) and PSK (polysaccharide-protein complex) which are considered as medicines against melignancy. They prevent oncogenesis by the direct effect on tumor metastasis and exhibits antitumor effects by the induction of immune response in host. Mushroom polysaccharides have promising future for treatment of cancers due to their mode of action and efficacy. Also there are some hurdles during this treatment, but it will start a new era of safer and effective medicine based on mushroom polysaccharides.     

A study of room-temperature ferromagnetism in transition metal and fluorine-doped spray-pyrolyzed SnO2 thin films

Room-temperature ferromagnetism has been observed in Co- or Mn-doped SnO₂ and Co- and F-co-doped SnO₂ thin films. A maximum magnetic moment of 0.80μ_B/Co ion has been observed for Sn_0.90Co_0.10O_1.925−δF_0.075 thin films, whereas in the case of Sn_1−xMn_xO_2−δ it was 0.18μ_B/Mn ion for x=0.10. The magnetization of both Sn_1−xCo_xO_2−δ and Sn_1−xCo_xO_2−y−δF_y thin films depends on the free carrier concentration. An anomalous Hall effect has been observed in the case of Co-doped SnO₂ films. However, the same was not observed in the case of Mn-doped SnO₂ thin films. Carrier-mediated interaction is convincingly proved to be the cause of ferromagnetism in the case of Co:SnO₂. It is, however, proposed that no carrier-mediated interaction exists in the case of Mn:SnO₂. Present studies indicate that dopants and hence electronic cloud-lattice interaction plays an important role in inducing ferromagnetism.     

A band-mixing Hartree-Fock model for62Zn

Energy levels and electromagnetic transitions in⁶²Zn have been calculated using band-mixing formalism in the framework of deformed Hartree-Fock theory. Matrix elements of Adjusted-Surface Delta Interaction (ASDI) and of Tabakin interaction have been used. Detailed structure of various nuclear states in terms of bands has been discussed. Although the calculated spectra for both the interactions are somewhat compressed as compared to the observed spectra, the ASDI results are in substantially better agreement with experiments. Several additional states of high spin (J>4) have been predicted.B(E2) transitions between inter-band as well as some of the intraband states are calculated to stimulate further experiments.     

Structure of nuclei in the regionA = 70

The structure of the selenium nuclei in the regionA = 70 is studied using our deformed configuration mixing (DCM) shell model based on Hartree-Fock states. An effective interaction given by Kuo and modified by Bhatt is used. An attempt is made to understand the coexistence of shapes in selenium nuclei.     

The structure of collective bands in 68Ge: A microscopic view

The collective bands of states of ⁶⁸Ge are studied using a deformed-configuration-mixing shell model based on Hartree-Fock intrinsic states. An effective interaction given by Kuo has been used. The configuration space includes the single-particle orbits $\text{1}\text{p}{}_{\mathrm{<mtext>3</mtext><mtext>2</mtext>}}\text{, 0}\text{f}{}_{\mathrm{<mtext>5</mtext><mtext>2</mtext>}}\text{, 1}\text{p}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{and}\text{0}\text{g}{}_{\mathrm{<mtext>9</mtext><mtext>2</mtext>}}$. The collective positive- and negative-parity states are classified into different bands on the basis of the E2 transition probabilities amongst them. The agreement with the experiment is quite satisfactory. An attempt has been made to understand the structure of the nearly degenerate triplet of the 8⁺ states and their decay schemes.