The first total synthesis of neohelmanticins A–D,amino derivatives of the 1,2-dihydroxypropane core and biological evaluation

A concise total synthesis of neohelmanticins A–D has been accomplished in 15 steps starting from commercially available gallic acid. Swern oxidation conditions, a Grignard reaction, Sharpless kinetic resolution, and regioselective ring opening of an epoxide with lithium aluminum hydride (LAH) are the key features to install the basic core, dihydroxy phenyl propane 2. One hydroxyl group of this core was esterified with tiglic acid followed by the oxidation and esterification with corresponding acids to yield neohelmanticins A–D.     

Comment on: “Universal relation between spectroscopic constants”

Kaur and Mahajan [1] have claimed to derive a universal relation InG = 1.91578(±0.09727) + 0.97111(±0.03809) In Δ between the Sutherland parameter Δ(=ω _er _e ² /2D_e) and the dimensionless parameterG(= 8ω _ex_e/B_e) for the ground as well as excited electronic states of diatomic molecules. Validity of this relation is checked and we find that the relation is not correct. Next, we checked the validity of the relation Δ = 2.2r_e for the alkali group diatomic molecules. This relation is also found not to be correct.     

Collision strengths for transitions in Ni XIX

In this paper we present calculations of electron impact excitation collision strengths for transitions among the 89 fine-structure levels of the 2s²2p⁶, 2s²2p⁵3ℓ, 2s2p⁶3ℓ, 2s²2p⁵4ℓ, and 2s2p⁶4ℓ configurations of Ni XIX, for which flexible atomic code (FAC) has been adopted. Comparisons are made with the earlier available results in the literature, and the anomalies observed have been discussed.      

Nitric oxide (NO) production inhibitory constituents of Tabebuia avellanedae from Brazil

From the water extract of Brazilian Tabebuia avellanedae, two new iridoids (1, 2) and a new phenylethanoid glycoside (3) have been isolated together with twelve known compounds (4-15). Their structures were determined based on the spectroscopic data. The isolated compounds inhibited nitric oxide (NO) production in lipopolysaccharide (LPS)-activated macrophage-like J774.1 cells. Compounds 1, 3, 10, 11, and 12 showed inhibitory activities more potent (IC50, 13.8-26.1 microg/ml) than a positive control N(G)-monomethyl-L-arginine (L-NMMA; IC50, 27.4 microg/ml).     

Performance Models for Multi-rate Circuits in Switched Multi-Channel Optical Networks

We consider optical networks with nodes interconnected by links comprising multiple channels. The blocking performance of such networks depends on the channel-switching capabilities of the nodes. In this paper, we focus on developing analytical models for evaluating the blocking performance in circuit-switched optical networks. Several architectures for channel-switching are presented. Multi-rate circuits may be established if different circuits are allocated different number of channels. Depending on how the network can assign the channels to circuits that request more than one channel, it is classified as a Data Splitting Network (DSN) or a non-DSN. We consider multi-rate circuits which require either a single channel or a given number of channels k (>1). Analytical models for computing blocking probabilities are developed for various channel-switching architectures at the nodes. The validity of the models is shown by comparing the analytical results with simulations. Numerical results in a single-fiber TDM wavelength-routing network suggest that limited channel-switching may be sufficient even for circuits that require more than one channel or slot. A comparison of DSN and non-DSN shows that data splitting can accommodate more multi-slot circuits at the expense of blocking more single-slot circuits.This work was supported in part by NSF Grants ANI-9973098 and ANI-9973111     

Multistrange Baryon elliptic flow in Au+Au collisions at square root of sNN=200 GeV

We report on the first measurement of elliptic flow v2(pT) of multistrange baryons Xi- +Xi+ and Omega- + Omega+ in heavy-ion collisions. In minimum-bias Au+Au collisions at square root of s(NN)=200 GeV, a significant amount of elliptic flow, comparable to other nonstrange baryons, is observed for multistrange baryons which are expected to be particularly sensitive to the dynamics of the partonic stage of heavy-ion collisions. The pT dependence of v2 of the multistrange baryons confirms the number of constituent quark scaling previously observed for lighter hadrons. These results support the idea that a substantial fraction of the observed collective motion is developed at the early partonic stage in ultrarelativistic nuclear collisions at the Relativistic Heavy Ion Collider.     

Direct observation of the ... 4+-to-2+ ... [corrected] gamma transition in 8Be

Electromagnetic transition rates provide an important test for nuclear structure models. The nucleus 8Be exhibits a pronounced alpha-cluster structure and is a building block for more complex cluster nuclei. Here we report on the first observation of the gamma transition between the 4(+) and 2(+) states of 8Be in the 4He+4He reaction. The measured on-resonance cross section of 165+/-54 nb leads to a B(E2) of25+/-8e(2) fm(4), in good agreement with alpha-cluster models and sophisticated ab initio structure calculations.     

Fluorescent aggregates of 1-(p-butyloxyphenyl)-4-(p-cyanophenyl)buta-1E,3E-diene: temperature sensing and photoimaging applications

The use of fluorescent solid films of a 1-(p-butyloxyphenyl)-4-(p-cyanophenyl)buta-1E, 3E-diene as an efficient temperature sensor is described. The fluorescence changes in these films are proposed to occur due to a reversible temperature-dependent variation in its monomer-aggregate ratio. Photoisomerization of the butadiene chromophore in solid films was observed to occur only at elevated temperatures (> 120^∘C), making the material also useful for reversible photochemical generation of fluorescence patterns with nondestructive readout properties.     

One-electron oxidation of [CCOCC]-* in the gas phase forms stable and decomposing forms of CCCCO

The radical anion [CCOCC]-* may be made in the source of a VG ZAB 2HF mass spectrometer by the reaction between F-(from SF6) and (CH3)3SiC[triple bond]COC[triple bond]CSi(CH3)3. Vertical (Franck-Condon) one-electron oxidation of [CCOCC]-* in the first collision cell produces both singlet and triplet CCOCC. A combination of experiment and molecular modelling (at the CCSD(T)/aug-cc-pVDZ//B3LYP/6-31G* level of theory) gives data which are consistent with the CCOCC neutrals rearranging over small barriers to form singlet and triplet CCCCO in exothermic reactions. Both singlet and triplet CCCCO formed in this way have excess energy. Singlet CCCCO has sufficient excess energy to effect decomposition exclusively to CCC and CO. In contrast, some of the triplet CCCCO neutrals are stable, while others decompose to CCC and CO.