Reliability of Elastic‐Plastic Frame Structures

An effective algorithm for estimating the reliability of frame structures made of an elastic perfectly plastic material is presented. It is assumed that the structure is working in uniaxial state of stress, the material parameters and the limit values of the loads are described by random variables, all loads are acting in a static manner, the probability density functions of all random variables, which describe the structure and loads are known. As the structure reliability measure the probability of failure and corresponding reliability index are regarded. The dead (constant) load and the climatic loads are taken into account. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Heterogeneous Catalysis to Drive the Waste-to-Pharma Concept: From Furanics to Active Pharmaceutical Ingredients

A perspective on the use of heterogeneous catalysis to drive the waste-to-pharma concept is provided in this contribution based on the conversion of furanics to active pharmaceutical ingredients (APIs). The provided overview of the concept in this perspective article has been exemplified for two key molecule examples: Ancarolol and Furosemide.     

Crystal,electronic structure and hydrogenation properties of the Mg5.57Ni16Ge7.43 cluster phase with a new type of polyhedron

The ternary germanide Mg_5.57Ni₁₆Ge_7.43 (cubic, space group Fmm, cF116) belongs to the structural family based on the Th₆Mn₂₃-type. The Ge1 and Ge2 atoms fully occupy the 4a (mm symmetry) and 24d (m.mm) sites, respectively. The Ni1 and Ni2 atoms both fully occupy two 32f sites (.3m symmetry). The Mg/Ge statistical mixture occupies the 24e site with 4m.m symmetry. The structure of the title compound contains a three-core-shell cluster. At (0,0,0), there is a Ge1 atom which is surrounded by eight Ni atoms at the vertices of a cube and consequently six Mg atoms at the vertices of an octahedron. These surrounded eight Ni and six Mg atoms form a [Ge1Ni₈(Mg/Ge)₆] rhombic dodecahedron with a coordination number of 14. The [GeNi₈(Mg/Ge)₆] rhombic dodecahedron is encapsulated within the [Ni₂₄] rhombicuboctahedron, which is again encapsulated within an [Ni₃₂(Mg/Ge)₂₄] pentacontatetrahedron; thus, the three-core-shell cluster [GeNi₈(Mg/Ge)₆@Ni₂₄@Ni₃₂(Mg/Ge)₂₄] results. The pentacontatetrahedron is a new representative of Pavlyuk's polyhedra group based on pentagonal, tetragonal and trigonal faces. The dominance of the metallic type of bonding between atoms in the Mg_5.57Ni₁₆Ge_7.43 structure is confirmed by the results of the electronic structure calculations. The hydrogen sorption capacity of this intermetallic at 570 K reaches 0.70 wt% H₂.     

Key role of molecular kinetic energy in early stages of pentacene island growth

Organic molecular beam deposition is studied systematically at thermal and hyperthermal regimes aiming at investigating the role of molecular kinetic energy on the growth mechanism of pentacene submonolayers on SiO _x /Si. We show that the kinetic energy of the impinging molecule (E _k ) plays a crucial role in determining island structure and shape, distribution of island sizes, the crystalline quality of the first monolayer, and even the growth mode of subsequent layers. With increasing E _k , the island structure changes from fractal to nonfractal, the shape becomes more anisotropic and the island size more uniform, pointing to correlated island growth. Moreover, while 3D island growth is observed for thermal organic molecular beam deposition, supersonic molecular beam deposition gives rise to layer-by-layer growth, at least for the first two layers. When E _k ≥5.0 eV, the first monolayer is composed of large single crystalline domains which can extend over up to 10 μm, inferred from comparing atomic force micrographs of height and net transverse shear force. In these growth conditions both the high surface diffusivity and energy redistribution play a major role. We propose a mechanism where the energy dissipation occurring during the molecule–surface collision leads to the reorientation of whole islands during island coalescence, resulting in the elimination of grain boundaries.     

A DFT/TD‐DFT study for the ground and excited states of peramine and some pyrrolopyrazinone compounds

Peramine, a heterocyclic natural molecule, reveals two main, different in nature, electronic absorption bands. Theoretical calculations at the TD‐B3LYP/6–311++G(d,p) level of theory show that the electronic excitations are connected predominantly with π → π^* and charge‐transfer (CT) transitions. Excitation of electrons from the pyrrolopyrazinone ring to the side chain plays a role in creating the CT transition. The character and energy of the first 30 singlet–singlet electronic transitions have also been investigated for the most stable conformation of peramine. Copyright © 2009 John Wiley & Sons, Ltd.     

The Vitamin D Status Among Tibetans

UVB from the sun and intake from food are the only human sources of vitamin D. Tibet is a unique region for comparisons of these sources: (1) it lies at a low latitude and at a high altitude and has very large annual fluences of UVB; (2) the traditional Tibetan food is poor in vitamin D. Blood samples were taken from 63 persons of different age, with different occupations and staying at different places. UVB doses at these places were measured. The samples were analyzed by a standard radioimmune assay for determination of the serum concentration of 25 hydroxyvitamin D (25(OH)D). The main finding was that among nomads, there seems to be severe vitamin D deficiency (serum levels of 25(OH)D < 30 n m ). We tentatively propose that the low level of 25(OH)D of nomads is related to their clothing and sun exposure habits. For persons of other occupations (students, teachers and farmers) the levels are higher, although a significant fraction of these persons also have lower levels than 75 n m , by many regarded as a limit for insufficiency related to a number of negative health conditions. The annual dose of vitamin D-generating UVB is about five times larger in Lhasa than in Oslo. Despite this, the average vitamin D status seems to be similar, except in the case of nomads. This phenomenon is certainly related to food habits. In conclusion, the 25(OH)D status among nomads in Tibet appears to be alarmingly low. However, for people of other occupations the status is more normal.     

Thermal decomposition of some biologically active complexes of ruthenium (III) with quinolone derivatives

A series of new complexes with mixed ligands of the type RuL₂(DMSO) _m Cl₃·nH₂O ((1) L: norfloxacin (nf), m = 1, n = 1; (2) L: ciprofloxacin (cp), m = 2, n = 2; (3) L: ofloxacin (of), m = 1, n = 1; (4) L: enrofloxacin (enro), m = 0.5, n = 4; DMSO: dimethylsulfoxide) were synthesised and characterised by chemical analysis and IR data. In all complexes both fluoroquinolone derivative and DMSO act as unidentate. The thermal behaviour steps were investigated in synthetic air flow. The thermal transformations are complex processes according to TG and DTG curves including dehydration, quinolone derivative and DMSO degradation respectively. The final product of decomposition is ruthenium (IV) oxide.     

Determination of sulfation pattern in brain glycosaminoglycans by chip-based electrospray ionization ion trap mass spectrometry

Chondroitin sulfate (CS) and dermatan sulfate (DS) glycosaminoglycans display variability of sulfation in their constituent disaccharide repeats during chain elongation. Since a large proportion of the extracellular matrix of the central nervous system (CNS) is composed of proteoglycans, CS/DS disaccharide degree and profile of sulfation play important roles in the functional diversity of neurons, brain development, and some of its pathological states. To investigate the sulfation pattern of CS/DS structures expressed in CNS, we introduced here a novel method based on an advanced system encompassing fully automated chip nanoelectrospray ionization (nanoESI) in the negative ion mode and high capacity ion trap multistage mass spectrometry (MS²–MS³) by collision-induced dissociation (CID). This method, introduced here for the first time in glycomics of brain glycosaminoglycans, was particularly applied to structural investigation of disaccharides obtained by β-elimination and digestion with chondroitin B and AC I lyase of hybrid CS/DS chains from wild-type mouse brain. Screening in the chip-MS mode of DS disaccharide fraction resulting after depolymerization with chondroitin B lyase revealed molecular ions assigned to monosulfated disaccharide species having a composition of 4,5-Δ-[IdoA-GalNAc]. By optimized CID MS²–MS³, fragment ions supporting the localization of sulfate ester group at C4 within GalNAc were produced. Chip ESI MS profiling of CS disaccharide fraction obtained by depolymerization of the same CS/DS chain using chondroitin AC I lyase indicated the occurrence of mono- and bisulfated 4,5-Δ-[GlcA-GalNAc]. The site of oversulfation was determined by MS²–MS³, which provided sequence patterns consistent with a rare GlcA-3-sulfate–GalNAc-6-sulfate structural motif.      

Synthesis and structural characterization of amino-functionalized polysaccharides

A variety of carbohydrates, in particular polysaccharides can be subjected to chemical modification to obtain derivatives with amphiphilic properties, which enable biochemical or biological reactions at the polymer surface. In the present work, a polydisperse maltodextrin mixture of average molecular weight 3000 was coupled with 1,6-hexamethylenediamine (HMD) via reductive amination reaction. Resulting products were characterized by thermal analysis and positive nanoelectrospray quadrupole time-of-flight (Q-TOF) mass spectrometry (MS) and tandem mass spectrometry (MS/MS). Both thermal analysis and MS screening confirmed the formation of the HMD-polysaccharide coupling products. Moreover, HMD-linked polysaccharide chains containing 2 to 26 glucose building blocks were identified by nanoESI Q-TOF MS. MS/MS fragmentation using collision-induced dissociation (CID) at low ion acceleration energies provided strong evidence for HMD-maltodextrin linkage formation and the set of sequence ions diagnostic for the composition and structure of a HMD-linked chain containing 18 glucose residues.      

Electrospray ionization quadrupole time-of-flight tandem mass spectrometric analysis of hexamethylenediamine-modified maltodextrin and dextran

A combined methodology for obtaining at the preparative scale and characterization by nanoelectrospray ionization (nanoESI) quadrupole time-of-flight (QTOF) mass spectrometry (MS) and tandem MS (MS/MS) of linear polysaccharides modified at the reducing end is presented. Two polydisperse maltodextrins (1000 and 3000 Da) and a high molecular weight polydisperse dextran (6000 Da) were coupled with hexamethylenediamine (HMD). The coupling products were analyzed by nanoESI-QTOF-MS in the positive ion mode and MS/MS using collision-induced dissociation (CID) at low energies. In the HMD-M1000 mixture, the polysaccharide chains containing from 2 to 8 Glc residues were detected, while in HMD-M3000 we identified a complete series of chains containing from 8 to 21 Glc moieties. The employed ESI conditions enhanced the detection of chains with up to 46 Glc residues in the HMD-D6000 sample. By optimized MS/MS, HMD-modified polysaccharides of 3, 4, 5, 12 and 46 degrees of polymerization yielded product ion spectra exhibiting the whole set of Y- and B-fragment ions. The MS structural data were obtained within a few minutes of signal acquisition, with a sample consumption situating the analysis sensitivity in the picomolar range.