Low-temperature specific heat of antiferromagnetic EuNi5P3 and mixed-valent EuNi2P2 in magnetic fields to 7 T

he specific heats of EUNi(5)P(3), an antiferromagnet, and EuNi2P2, a mixed-valence compound, have been measured between 0.4 and 30 K in magnetic fields of, respectively, 0, 0.5, 1, 1.5, 2.5, 5, and 7 T, and 0 and 7 T. In zero field the specific heat of EuNi5P3 shows a h-like anomaly with a maximum at 8.3 K. With increasing field in the range 0-2.5 T, the maximum shifts to lower temperatures, as expected for an antiferromagnet. In higher fields the antiferromagnetic ordering is destroyed and the magnetic part of the specific heat approaches a Schottky anomaly that is consistent with expectations for the crystal-field/Zeeman levels. In low fields and for temperatures between 1.5 acid 5 K the magnetic contribution to the specific heat is proportional to the temperature, indicating a high density of excited states with an energy dependence that is very unusual for an antiferromagnet. The entropy associated with the magnetic ordering is similar to R In8, confirming that only the Eu2+-with J=7/2, S=7/2, L=0-orders below 30 R. In zero field approximately 20% of the entropy occurs above the Neel temperature, consistent. with the usual amount of short-range order observed in antiferromagnets. The hyperfine magnetic field at the Eu nuclei in EUNi(5)P(3) is 33.3 T, in good agreement with a value calculated from electron-nuclear double resonance measurements. For EuNi2P2 the specific heat is nearly field independent and shows no evidence of magnetic ordering or hyperfine fields. The coefficient of the electron contribution to the specific heat is similar to 100 mJ/mol K-2.

Preparation of the layered double hydroxide (LDH) LiAl2(OH)(7)center dot 2H(2)O, by gel to crystallite conversion and a hydrothermal method, and its conversion to lithium aluminates

A layered double hydroxide (LDH) with chemical composition LiAl2(OH)(7) . 2H(2)O was prepared via a wet chemical route of gel to crystallite (G-C) conversion at 80 degrees C involving the reaction of hydrated alumina gel, Al2O3.yH(2)O (80 < y < 120) with LiOH (Li2O/Al2O3 greater than or equal to 0.5) in presence of hydrophilic solvents such as ethanol under refluxing conditions. The hydrothermal synthesis was carried out using the same reactants by heating to less than or equal to 140 degrees C in a Teflon-lined autoclave under autogenerated pressure (less than or equal to 20 MPa). Transmission electron microscopy showed needle-shaped aggregates of size 0.04-0.1 mu m for the gel to crystallite conversion product, whereas the hydrothermal products consisted of individual lamellar crystallites of size 0.2-0.5 mu m with hexagonal morphology. The LDH prepared through the gel to crystallite conversion could be converted into LiAl(OH)(4) . H2O or LiAl(OH)(3)NO3 . H2O by imbibition of LiOH or LiNO3, respectively, under hydrothermal conditions. Thermal decomposition of LDH above 1400 degrees C gave rise to LiAl5O8 accompanied by the evaporation of Li2O. LiAl(OH)(4) . H2O and LiAl(OH)(3)NO3 . H2O decomposed in the temperature range 400-1000 degrees C to alpha- or beta-LiAlO2. The compositional dependence of the product, the intermediate phases formed during the heat treatment and the possible reactions involved are described in detail.

Triaxial A-value versus swell or collapse for compacted soil - Discussion

A discussion of a technical note with the aforementioned title by Day and Marsh, published in this journal (Volume 121, Number 7, July 1995), is presented. Discussers Robinson and Allam assert that the authors' application of the pore-pressure parameter A to predict and quantify swell or collapse of compacted soils is hard to use because the authors visualize the collapse-swell phenomenon to occur in compacted soils broadly classified as sands and clays. The literature demonstrates that mineralogy has an important role in the volume change behavior of fine-grained soils. Robinson and Allam state that the A-value measurements may not completely predict the type of volume change anticipated in compacted soils on soaking without soil clay mineralogy details. Discussion is followed by closure from the authors.

Prevalence of, and antigenic variation in, serotype G10 rotaviruses and detection of serotype G3 strains in diarrheic calves: Implications for the origin of G10P11 or P11 type reassortant asymptomatic strains in newborn children in India

Previous studies have shown predominant association of G10P11 type bovine rotavirus-derived reassortant strains with asymptomatic infections in newborn children in India. To understand the epidemiological and genetic basis for the origin of these strains in humans, the relative frequencies of different serotypes among bovine rotaviruses (BRVs) isolated from southern, western and central regions of the country were determined by subgroup and serotype analysis as well as nucleotide (nt) sequence analysis of the genes encoding the outer capsid proteins VP4 and VP7. Since the human G10P11 asymptomatic neonatal strain I321 possessed NSP1 from a human rotavirus, to determine its genetic origin in the bovine strains, comparative analysis of partial gene sequences from representative G10P11 strains was also carried out. The following observations were of great epidemiological significance, (i) G10P11 strains predominated in all the three regions with frequencies ranging between 55.6% and 85.2%. In contrast to the high prevalence of G6 strains in other countries, only one G6 strain was detected in this study and G8 strains represented 5.8% of the isolates, (ii) among the G10 strains, in serotyping ELISA, four patterns of reactivity were observed that appeared to correlate with the differences in electropherotypic patterns and amino acid (aa) sequence of the VP7, (iii) surprisingly, strains belonging to serotype G3 were detected more frequently (10.7%) than those of serotypes G6 and G8 combined, while strains representing the new serotype (G15) were observed in a single farm in Bangalore, and (iv) about 3.9% of the isolates were nontypeable as they exhibited high cross-reactivity to the serotyping MAbs used in the study. Comparative analysis of the VP7 gene sequence from the prototype G3 MAb-reactive bovine strain J63 revealed greatest sequence relatedness (87.6% nt and 96.0% aa) with that of serotype G3 rhesus-monkey strain RRV. It also exhibited high sequence homology with the VP7 from several animal and animal rotavirus-related human G3 strains (Simian SA11; equine ERV316 and FI-14. canine CU-1 and K9; porcine 4F; Feline Cat2 and human HCR3, YO and AU1). Partial nucleotide sequence analysis of the NSP1 gene of J63 showed greatest nt sequence homology (95.9%) to the NSP1 gene allele of the Indian G8 strain, isolated from a diarrheic child, which is likely to have been transmitted directly from cattle and 92.6% homology to that of the bovine G8 strain A5-10 suggesting the likely origin of J63 by gene reassortment between a bovine G8 strain and a G3 animal strain. Prevalence of G10P11 strains in cattle and G10P11 or P11 type reassortant strains in asymptomatic neonates as well as detection of G8P[1] strains in diarrheic children support our hypothesis for bidirectional transmission of rotaviruses between humans and cattle and origin of novel strains catalyzed by the age-old traditions and socio-economic conditions in India.

Photoluminescence of Sr(2-x)Ln(x)CeO(4+x/2) (Ln = Eu, Sm or Yb) prepared by a wet chemical method

A wet chemical route is developed for the preparation of Sr2CeO4 denoted the carbonate-gel composite technique. This involves the coprecipitation of strontium as fine particles of carbonates within hydrated gels of ceria (CeO2.xH(2)O, 40orm Sr2CeO4 with complete phase purity. Doping of other rare-earths is carried out at the co-precipitation stage. The photoluminescence (PL) observed for Sr2CeO4 originates from the Ce4+-O2- charge-transfer (CT) transition resulting from the interaction of Ce4+ ion with the neighboring oxide ions. The effect of next-nearest-neighbor (NNN) environment on the Ce4+-O2- CT emission is studied by doping with Eu3+, Sm3+ or Yb3+ which in turn, have unique charge-transfer associated energy levels in the excited states in oxides. Efficient energy transfer occurs from Ce4+-O2- CT state to trivalent lanthanide ions (Ln(3+)) if the latter has CT excited states, leading to sensitizer-activator relation, through non-resonance process involving exchange interaction. Yb3+-substituted Sr2CeO4 does not show any line emission because the energy of Yb3+-O2- CT level is higher than that of the Ce4+-O2- CT level. Sr2-xEuxCeO4+x/2 shows white emission at xless than or equal to0.02 because of the dominant intensities of D-5(2)-F-7(0-3) transitions in blue-green region whereas the intensities of D-5(0)-F-7(0-3) transitions in orange-red regions dominate at concentrations xgreater than or equal to0.03 and give red emission. The appearance of all the emissions from D-5(2), D-5(1) and D-5(0) excited states to the F-7(0-3) ground multiplets of Eu3+ is explained on the basis of the shift from the hypersensitive electric-dipole to magnetic-dipole related transitions with the variation in site symmetry with increasing concentration of Eu3+. White emission of Sr2-x SmxCeO4+x/2 at xless than or equal to0.02 is due the co-existence of Ce4+-O2- CT emission and (4)G(4)(5/2)-H-6(J) Sm3+ transitions whereas only the Sm3+ red emission prevails for xgreater than or equal to0.03. The above unique changes in PL emission features are explained in terms of the changes in NNN environments of Ce4+. Quenching of Ce4+-O2- CT emission by other Ln(3+) is due to the ground state crossover arising out of the NNN interactions.

Aromatic, microporous polymer networks with high surface area generated in Friedel-Crafts-type polycondensations

A series of novel, microporous polymer networks (MPNs) have been generated in a simple, acid catalysed Friedel-Crafts-type self-condensation of A(2)B(2)- and A(2)B(4)-type fluorenone monomers. Two A2B4-type monomers with 2,7-bis(N, N-diphenylamino) A or 2,7-bis [4-(N, N-diphenylamino) phenyl] D substitution of the fluorenone cores lead to MPNs with high S(BET) surface areas of up to 1400 m(2) g(-1). Two MPNs made of binary monomer mixtures showed the highest Brunauer-Emmett-Teller (BET) surface areas S(BET) of our series (SBET of up to 1800 m(2) g(-1)) after washing the powdery samples with supercritical carbon dioxide. Total pore volumes of up to 1.6 cm(3) g(-1) have been detected. It is observed that the substitution pattern of the monomers is strongly influencing the resulting physicochemical properties of the microporous polymer networks (MPNs).

Crowd Sourcing a New Paradigm for Interactome Driven Drug Target Identification in Mycobacterium tuberculosis

A decade since the availability of Mycobacterium tuberculosis (Mtb) genome sequence, no promising drug has seen the light of the day. This not only indicates the challenges in discovering new drugs but also suggests a gap in our current understanding of Mtb biology. We attempt to bridge this gap by carrying out extensive re-annotation and constructing a systems level protein interaction map of Mtb with an objective of finding novel drug target candidates. Towards this, we synergized crowd sourcing and social networking methods through an initiative `Connect to Decode' (C2D) to generate the first and largest manually curated interactome of Mtb termed `3interactome pathway' (IPW), encompassing a total of 1434 proteins connected through 2575 functional relationships. Interactions leading to gene regulation, signal transduction, metabolism, structural complex formation have been catalogued. In the process, we have functionally annotated 87% of the Mtb genome in context of gene products. We further combine IPW with STRING based network to report central proteins, which may be assessed as potential drug targets for development of drugs with least possible side effects. The fact that five of the 17 predicted drug targets are already experimentally validated either genetically or biochemically lends credence to our unique approach.

Propyl-2-(8-(3,4-Difluorobenzyl)-2 `,5 `-Dioxo-8-AzaspiroBicyclo3.2.1] Octane-3,4 `-Imidazolidine]-1 `-yl) Acetate Induces Apoptosis in Human Leukemia Cells through Mitochondrial Pathway following Cell Cycle Arrest

Background: Due to the functional defects in apoptosis signaling molecules or deficient activation of apoptosis pathways, leukemia has become an aggressive disease with poor prognosis. Although the majority of leukemia patients initially respond to chemotherapy, relapse is still the leading cause of death. Hence targeting apoptosis pathway would be a promising strategy for the improved treatment of leukemia. Hydantoin derivatives possess a wide range of important biological and pharmacological properties including anticancer properties. Here we investigated the antileukemic activity and mechanism of action of one of the potent azaspiro hydantoin derivative, (ASHD). Materials and Methods: To investigate the antileukemic efficacy of ASHD, we have used MTT assay, cell cycle analysis by FACS, tritiated thymidine incorporation assay, Annexin V staining, JC1 staining and western blot analysis. Results: Results showed that ASHD was approximately 3-fold more potent than the parent compounds in inducing cytotoxicity. Tritiated thymidine assay in conjunction with cell cycle analysis suggests that ASHD inhibited the growth of leukemic cells. The limited effect of ASHD on cell viability of normal cells indicated that it may be specifically directed to cancer cells. Translocation of phosphatidyl serine, activation of caspase 3, caspase 9, PARP, alteration in the ratio of BCL2/BAD protein expression as well as the loss of mitochondrial membrane potential suggests activation of the intrinsic pathway of apoptosis. Conclusion: These results could facilitate the future development of novel hydantoin derivatives as chemotherapeutic agents for leukemia.

Scale-dependent relationships between tree species richness and ecosystem function in forests

1. The relationship between species richness and ecosystem function, as measured by productivity or biomass, is of long-standing theoretical and practical interest in ecology. This is especially true for forests, which represent a majority of global biomass, productivity and biodiversity. 2. Here, we conduct an analysis of relationships between tree species richness, biomass and productivity in 25 forest plots of area 8-50ha from across the world. The data were collected using standardized protocols, obviating the need to correct for methodological differences that plague many studies on this topic. 3. We found that at very small spatial grains (0.04ha) species richness was generally positively related to productivity and biomass within plots, with a doubling of species richness corresponding to an average 48% increase in productivity and 53% increase in biomass. At larger spatial grains (0.25ha, 1ha), results were mixed, with negative relationships becoming more common. The results were qualitatively similar but much weaker when we controlled for stem density: at the 0.04ha spatial grain, a doubling of species richness corresponded to a 5% increase in productivity and 7% increase in biomass. Productivity and biomass were themselves almost always positively related at all spatial grains. 4. Synthesis. This is the first cross-site study of the effect of tree species richness on forest biomass and productivity that systematically varies spatial grain within a controlled methodology. The scale-dependent results are consistent with theoretical models in which sampling effects and niche complementarity dominate at small scales, while environmental gradients drive patterns at large scales. Our study shows that the relationship of tree species richness with biomass and productivity changes qualitatively when moving from scales typical of forest surveys (0.04ha) to slightly larger scales (0.25 and 1ha). This needs to be recognized in forest conservation policy and management.

Conformational Diversity in Contryphans from Conus Venom: cis-trans Isomerisation and Aromatic/Proline Interactions in the 23-Membered Ring of a 7-Residue Peptide Disulfide Loop

Conformational diversity or shapeshifting in cyclic peptide natural products can, in principle, confer a single molecular entity with the property of binding to multiple receptors. Conformational equilibria have been probed in the contryphans, which are peptides derived from Conus venom possessing a 23-membered cyclic disulfide moiety. The natural sequences derived from Conus inscriptus, GCV(D)LYPWC* (In936) and Conus loroisii, GCP(D)WDPWC* (Lo959) differ in the number of proline residues within the macrocyclic ring. Structural characterisation of distinct conformational states arising from cis-trans equilibria about Xxx-Pro bonds is reported. Isomerisation about the C2-P3 bond is observed in the case of Lo959 and about the Y5-P6 bond in In936. Evidence is presented for as many as four distinct species in the case of the synthetic analogue V3P In936. The Tyr-Pro-Trp segment in In936 is characterised by distinct sidechain orientations as a consequence of aromatic/proline interactions as evidenced by specific sidechain-sidechain nuclear Overhauser effects and ring current shifted proton chemical shifts. Molecular dynamics simulations suggest that Tyr5 and Trp7 sidechain conformations are correlated and depend on the geometry of the Xxx-Pro bond. Thermodynamic parameters are derived for the cis trans equilibrium for In936. Studies on synthetic analogues provide insights into the role of sequence effects in modulating isomerisation about Xxx-Pro bonds.

Dielectric Function of Undoped and Doped Poly2-methoxy-5-(3 `,7 `-dimethyloctyloxy)-1,4-phenylene-vinylene] by Ellipsometry in a Wide Spectral Range

Ellipsometric measurements in a wide spectral range (from 0.05 to 6.5 eV) have been carried out on the organic semiconducting polymer, poly2-methoxy-5-(3',7'-dimethyloctyloxy)-1,4-phenylene-vinylene] (MDMO-PPV), in both undoped and doped states. The real and imaginary parts of the dielectric function and the refractive index are determined accurately, provided that the layer thickness is measured independently. After doping, the optical properties show the presence of new peaks, which could be well-resolved by spectroscopic ellipsometry. Also for the doped material, the complex refractive index, with respect to the dielectric function, has been determined. The broadening of the optical transitions is due to the delocalization of polarons at higher doping level. The detailed information about the dielectric function as well as refractive index function obtained by spectroscopic ellipsometry allows not only qualitative but also quantitative description of the optical properties of the undoped/doped polymer. For the direct characterization of the optical properties of MDMO-PPV, ellipsometry turns out to be advantageous compared to conventional reflection and transmission measurements.

A rain forest dusk chorus: cacophony or sounds of silence?

A rain forest dusk chorus consists of a large number of individuals of acoustically communicating species signaling at the same time. How different species achieve effective intra-specific communication in this complex and noisy acoustic environment is not well understood. In this study we examined acoustic masking interference in an assemblage of rain forest crickets and katydids. We used signal structures and spacing of signalers to estimate temporal, spectral and active space overlap between species. We then examined these overlaps for evidence of strategies of masking avoidance in the assemblage: we asked whether species whose signals have high temporal or spectral overlap avoid calling together. Whereas we found evidence that species with high temporal overlap may avoid calling together, there was no relation between spectral overlap and calling activity. There was also no correlation between the spectral and temporal overlaps of the signals of different species. In addition, we found little evidence that species calling in the understorey actively use spacing to minimize acoustic overlap. Increasing call intensity and tuning receivers however emerged as powerful strategies to minimize acoustic overlap. Effective acoustic overlaps were on average close to zero for most individuals in natural, multispecies choruses, even in the absence of behavioral avoidance mechanisms such as inhibition of calling or active spacing. Thus, call temporal structure, intensity and frequency together provide sufficient parameter space for several species to call together yet communicate effectively with little interference in the apparent cacophony of a rain forest dusk chorus.

Insertion Reactions of Six-Membered Cyclopalladated N,N `,N `'-Triarylguanidine, Pd{kappa(2)(C,N)-C6H3Me-3(NHC(NHAr)(=NAr))-2)(mu-Br)](2) (Ar=2-MeC6H4) with PhCC C-C(O)OR (R = Me and Et): A Gateway to Second Orthopalladation through Novel Rearrangements

The reaction of Pd{kappa(2)(C,N)-C6H3Me-3-(NHC(NHAr)(=NAr))-2}(mu-Br)](2) (Ar = 2-MeC6H4; 1) with 4 equiv of PhC C-C(O)OMe in CH2Cl2 afforded Pd{kappa(2)(C,N)-C(Ph)=C(C(O)OMe)C(Ph)=C(C(O)-OMe)C6H3Me-3(N=C(NH Ar)(2))-2}Br] (Ar = 2-MeC6H4; 2) in 70% yield, and the aforementioned reaction carried out with 10 equiv of PhC C-C(O)OR (R = Me, and Et) afforded an admixture of two regioisomers of Pd{kappa(3)(N,C,O)-O=C(OR)-C5Ph3(C(O)OR)C(C(O)OR)C6H3Me-3(N=C(NHAr)( 2))- 2}Br] (Ar = 2-MeC6H4; R = Me (3a/3b), Et (4a/4b)) in 80 and 87% yields, respectively. In one attempt, the minor regioisomer, 4b, was isolated from the mixture in 6% yield by fractional crystallization. Palladacycles 3a/3b and 4a/4b, upon stirring in CH2Cl2/MeCN (1/1, v/v) mixture at ambient condition for S days, afforded Pd{eta(3)-allyl,(KN)-N-1)-C-5(C(O)OR)(2)Ph3C-(C(O)OR)C6H3Me-3(N=C(NH Ar)(2))(-2)}Br] (Ar = 2-MeC6H4; R = Me (5a/5b), Et (6a/6b)) in 94 and 93% yields, respectively. Palladacycles 3a/3b and 4a/4b, upon reaction with AgOTf in CH2CH2/Me2C(O) (1/1, v/v) mixture at ambient temperature for 15 min, afforded Pd{kappa(3)(N,C,O)-O=C(OR)C5Ph3(C(O)OR)C(C(O)OR)C6H3Me-3(N=C(NHAr)(2 ))-2}(OTf)] (Ar = 2-MeC6H4; R = Me (7a/7b), Et (8a/8b)) in 79 and 77% yields, respectively. Palladacycles 7a/7b and 8a/ 8b, upon reflux in PhC1 separately for 6 h, or palladacycles 5a/5b and 6a/6b, upon treatment with AgOTf in CH2Cl2/Me2C(O) (7/3, v/v) mixture for 15 min, afforded Pd{(eta(2)-Ph)C5Ph2(C(O)OR)kappa(2)(C,N)-C(C(O)OR)C6H3Me-3(N=C(NHAr) (2))-2}(OTf)] (Ar = 2-MeC6H4; R = Me (9a/9h), Et (10a/10b)) in >= 87% yields. Palladacycles 9a/9b, upon stirring in MeCN in the presence of excess NaOAc followed by crystallization of the reaction mixture in the same solvent, afforded Pd{kappa(3)(N,C,C)-(C6H4)C5Ph2(C(O)OMe)(2)C(C(O)OMe)(2)C6H3Me-3(N=C( NHAr)(2))-2}(NCMe)] (Ar = 2-MeC6H4; 11a/11b) in 82% yield. The new palladacycles were characterized by analytical, IR, and NMR (H-1 and C-13) spectroscopic techniques, and the molecular structures of 2, 3a, 4a, 4b, 5a, 6a, 7a, 9a, 10a, and 11a-d(3) were determined by single crystal X-ray diffraction. The frameworks in the aforementioned palladacycles, except that present in 2, are unprecedented. Plausible pathways for the formation of new palladacycles and the influence of the guanidine unit in 1, substituents in alkynes, reaction conditions, and electrophilicity of the bromide and the triflate upon the frameworks of the insertion products have been discussed.

Bioengineering of AAV2 Capsid at Specific Serine, Threonine, or Lysine Residues Improves Its Transduction Efficiency in Vitro and in Vivo

We hypothesized that the AAV2 vector is targeted for destruction in the cytoplasm by the host cellular kinase/ubiquitination/proteasomal machinery and that modification of their targets on AAV2 capsid may improve its transduction efficiency. In vitro analysis with pharmacological inhibitors of cellular serine/threonine kinases (protein kinase A, protein kinase C, casein kinase II) showed an increase (20-90%) on AAV2-mediated gene expression. The three-dimensional structure of AAV2 capsid was then analyzed to predict the sites of ubiquitination and phosphorylation. Three phosphodegrons, which are the phosphorylation sites recognized as degradation signals by ubiquitin ligases, were identified. Mutation targets comprising eight serine (S) or seven threonine (T) or nine lysine (K) residues were selected in and around phosphodegrons on the basis of their solvent accessibility, overlap with the receptor binding regions, overlap with interaction interfaces of capsid proteins, and their evolutionary conservation across AAV serotypes. AAV2-EGFP vectors with the wild-type (WT) capsid or mutant capsids (15 S/T -> alanine A] or 9 K -> arginine R] single mutant or 2 double K -> R mutants) were then evaluated in vitro. The transduction efficiencies of 11 S/T -> A and 7 K -> R vectors were significantly higher (similar to 63-90%) than the AAV2-WT vectors (similar to 30-40%). Further, hepatic gene transfer of these mutant vectors in vivo resulted in higher vector copy numbers (up to 4.9-fold) and transgene expression (up to 14-fold) than observed from the AAV2-WT vector. One of the mutant vectors, S489A, generated similar to 8-fold fewer antibodies that could be cross-neutralized by AAV2-WT. This study thus demonstrates the feasibility of the use of these novel AAV2 capsid mutant vectors in hepatic gene therapy.