Timelike and null geodesics in the Nordström field

The timelike and null geodesics are investigated in the Nordström geometry and it is found that incoming geodesics always encounter a turning point at a finite radial distance. The limits for escape, bound and stable orbits are obtained and they are closer to the source as compared to their counterparts in the Schwarzschild’s field.     

Formal total synthesis of camptothecin via ring-closing metathesis strategy

A formal total synthesis of camptothecin 1 is presented. The key steps include construction of the D-ring of camptothecin featuring an efficient ring-closing metathesis (RCM) reaction and the subsequent Michael addition of nitropropane across the double bond of the dihydropyridone 3.     

Novel PI Indices of Hexagonal Chains

Problems don't hung on trees. Formulation of a good problem is often the most important part of a (theoretical) research. New problems usually arise when you try to solve old problems. Ivan Gutman, June 27, 1995.The Padmakar–Ivan (PI) index of hexagonal chains (i.e., the molecular graphs of unbranched catacondensed benzenoid hydrocarbons) is examined. The index PI is a graph invariant defined as the summation of the sums of edges of n _eu and n _ev over all the edges of connected graph G, where n _eu is the number of edges of G lying closer to u than to v and n _ev is the number of edges of G lying closer to v than to u. An efficient calculation of formula for PI for hexagonal chains are put forward.     

Biodegradability of polylactide bottles in real and simulated composting conditions

As new biodegradable polymers and their packaging applications are emerging, there is a need to address their environmental performance. In particular, there is a need to understand the time required for their complete disintegration, before these materials are deployed in commercial composting processes. Standards developed by ASTM and ISO evaluate the biodegradation of biodegradable plastic materials in simulated controlled composting conditions. However, a more detailed understanding of the biodegradation of complete packages is needed in order to have a successful composting operation. This paper investigates the biodegradation performance of polylactide (PLA) bottles under simulated composting conditions according to ASTM and ISO standards, and these results are compared with a novel method of evaluating package biodegradation in real composting conditions. Two simulated composting methods were used in this study to assess biodegradability of PLA bottles: (a) a cumulative measurement respirometric (CMR) system and (b) a gravimetric measurement respirometric (GMR) system. Both CMR and GMR systems showed similar trends of biodegradation for PLA bottles and at the end of the 58th day the mineralization was 84.2±0.9% and 77.8±10.4%, respectively. PLA bottle biodegradation in real composting conditions was correlated to their breakdown and variation in molecular weight. Molecular weight of 4100 Da was obtained for PLA bottles in real composting conditions on the 30th day. The biodegradation observed for PLA bottles in both conditions explored in this study matches well with theoretical degradation and biodegradation mechanisms; however, biodegradation variability exists in both conditions and is discussed in this paper.     

Anionic polymerization of methyl methacrylate with Cr(C5H7O2)3–Al(C2H5)3 catalyst system

A homogeneous catalyst system, Cr(C₅H₇O₂)₃–Al(C₂H₅)₃, was used for the polymerization of methyl methacrylate. The yield of polymer increased up to an Al/Cr ratio of 12 and thereafter remained almost constant with increasing Al/Cr. The rate of polymerization increased linearly with increasing catalyst and monomer concentrations at Al/Cr = 12. The molecular weight, however, decreased with increasing catalyst concentration and increased with increasing monomer concentration, indicating anionic polymerization reaction. NMR studies of the polymers indicated the presence of a stereoblock structure, which changed to heteroblock structure in presence of triethylamine and hydroquinone as additives in the catalyst. In the light of these observations, the mechanism of the polymerization is discussed.     

Simultaneous determination of itraconazole and hydroxyitraconazole in human plasma by high-performance liquid chromatography

The development and validation of a high-performance liquid chromatography (HPLC) method for the simultaneous determination of itraconazole and its metabolite, hydroxyitraconazole, in human plasma is described. The method involved liquid-phase extraction of itraconazole and hydroxyitraconazole using a hexane-dichloromethane (70:30) mixture, after addition of loratidine as an internal standard (IS). Separation was achieved with a reversed-phase C18 column (250 mm x 4.6 mm) employing fluorescence detection (excitation: 264 nm, emission: 380 nm). The mobile phase consisted of [0.01% triethylamine solution adjusted to pH 2.8 with orthophosphoric acid-acetonitrile (46:54)]-isopropanol (90:10, v/v) at a flow rate of 1.0 ml/min. For both the drug and metabolite, the standard curve was linear from 5.0 to 500 ng/ml with goodness of fit (r2) greater than 0.98 observed with four precision and accuracy batches during validation. An observed recovery was more than 70% for drug, metabolite and internal standard. The applicability of this method to pharmacokinetic studies was established after successful application during 35 subjects bioavailibity study. The method was found to be precise, accurate and specific during the study.     

On Isospectral Deformations of an Inhomogeneous String

For an anyon model in two spatial dimensions described by a modular tensor category, the topological S-matrix encodes the mutual braiding statistics, the quantum dimensions, and the fusion rules of anyons. It is nontrivial whether one can compute the S-matrix from a single ground state wave function. Here, we define a class of Hamiltonians consisting of local commuting projectors and an associated matrix that is invariant under local unitary transformations. We argue that the invariant is equivalent to the topological S-matrix. The definition does not require degeneracy of the ground state. We prove that the invariant depends on the state only, in the sense that it can be computed by any Hamiltonian in the class of which the state is a ground state. As a corollary, we prove that any local quantum circuit that connects two ground states of quantum double models (discrete gauge theories) with non-isomorphic abelian groups must have depth that is at least linear in the system’s diameter. As a tool for the proof, a manifestly Hamiltonian-independent notion of locally invisible operators is introduced. This gives a sufficient condition for a many-body state not to be generated from a product state by any small depth quantum circuit; this is a many-body entanglement witness.     

Total Synthesis of Resorcylic Acid Lactone (−)-Neocosmosin A Using Palladium-Catalyzed α-Arylation of Enones as the Key Step

The total synthesis of the 14-membered resorcylic acid lactone neocosmosin A is described. The key step in the synthesis is the palladium-catalyzed α-arylation of TES-enol ethers of enones. The employment of the α-arylation approach to this class of resorcylic acid lactones is a new approach, which has the scope of being generalized into a unified approach for the synthesis of this class of natural products.     

A photoactivatable prenylated cysteine designed to study isoprenoid recognition.

Protein prenylation, involving the alkylation of a specific C-terminal cysteine with a C(15) or C(20) isoprenoid unit, is an essential posttranslational modification required by most GTP-binding proteins for normal biological activity. Despite the ubiquitous nature of this modification and numerous efforts aimed at inhibiting prenylating enzymes for therapeutic purposes, the function of prenylation remains unclear. To explore the role the isoprenoid plays in mediating protein-protein recognition, we have synthesized a photoactivatable, isoprenoid-containing cysteine analogue (2) designed to act as a mimic of the C-terminus of prenylated proteins. Photolysis experiments with 2 and RhoGDI (GDI), a protein which interacts with prenylated Rho proteins, suggest that the GDI is in direct contact with the isoprenoid moiety. These results, obtained using purified GDI as well as Escherichia coli (E. coli) crude extract containing GDI, suggest that this analogue will be an effective and versatile tool for the investigation of putative isoprenoid binding sites in a variety of systems. Incorporation of this analogue into peptides or proteins should allow for even more specific interactions between the photoactivatable isoprenoid and any number of isoprenoid binding proteins.