Li2B12Si2: the first ternary compound in the system Li/B/Si: synthesis, crystal structure, hardness, spectroscopic investigations, and electronic structure

We present the synthesis, crystal structure, hardness, IR/Raman and UV/Vis spectra, and FP-LAPW calculations of the electronic structure of Li(2)B(12)Si(2), the first ternary compound in the system Li/B/Si. Yellow, transparent single crystals were synthesized from the elements in tin as solvent at 1500 degrees C in h-BN crucibles in arc-welded Ta ampoules. Li(2)B(12)Si(2) crystallizes orthorhombic in the space group Cmce (no. 64) with a=6.1060(6), b=10.9794(14), c=8.4050(8) A, and Z=4. The crystal structure is characterized by a covalent network of B(12) icosahedra connected by Si atoms and Li atoms located in interstitial spaces. The structure is closely related to that of MgB(12)Si(2) and fulfils the electron-counting rules of Wade and Longuet-Higgins. Measurements of Vickers (H(V)=20.3 GPa) and Knoop microhardness (H(K)=20.4 GPa) revealed that Li(2)B(12)Si(2) is a hard material. The band gap was determined experimentally and calculated by theoretical means. UV/Vis spectra revealed a band gap of 2.27 eV, with which the calculated value of 2.1 eV agrees well. The IR and Raman spectra show the expected oscillations of icosahedral networks. Theoretical investigations of bonding in this structure were carried out with the FP-LAPW method. The results confirm the applicability of simple electron-counting rules and enable some structural specialties to be explained in more detail.     

On Particle Phenomenology Without Particle Ontology: How Much Local Is Almost Local?

Recently, Clifton and Halvorson have tried to salvage a particle phenomenology in the absence of particle ontology within algebraic relativistic quantum field theory. Their idea is that the detection of a particle is the measurement of a local observable which simulates the measurement of an almost local observable that annihilates the vacuum. In this note, we argue that the measurements local particle detections are supposed to simulate probe radically holistic aspects of relativistic quantum fields. We prove that in an axiomatic (Haag-Araki) quantum field theory on Minkowski spacetime, formulated in a Hilbert space $\mathcal{H}$ , there is no positive observable C, with norm less than or equal to 1, satisfying the conditions: (1) the expectation value of C in the vacuum state Ω is zero, (2) there is at least one vector state Ψ in $\mathcal{H}$ in which the expectation value of C is different from zero, and (3) there exists at least one spacetime region $\mathcal{O}$ such that the non-selective measurement of C leaves the expectation values of all observables in the local algebra of that region unaltered regardless of the state the system is in. The result reveals a tension between intuitions regarding localization and intuitions regarding causality: to save “particle phenomena” in the absence of particle ontology, one has to feign “particle” detectors with “good” properties as to locality but “bad” behavior as to causality.     

The life and work of Sophie Germain

We discuss the life of Sophie Germain, her struggle to educate herself and to win acceptance within the French mathematical community, and her contributions to number theory and to the theory of elasticity.     

Non-stoichiometric barium ferrite particles for high-density magnetic recording

The organometallic precursor method was employed for the synthesis of β” ferrites, from which non-stoichiometric Ba ferrite particles have been prepared by ionic exchange. The magnetic grains are hexagonal platelets with diameters as low as 50 nm and aspect ratio of 1.5. After annealing, the sample diameter increases to 200 nm while the grains remain single-domain. The Curie temperature is 455°C. Annealed samples show specific magnetization up to 62 emu/g, coercive fields _jH_c close to 2 kOe, and an SFD factor 1−S* of 0.55     

A Synthetic Glycopeptide Vaccine for the Induction of a Monoclonal Antibody that Differentiates between Normal and Tumor Mammary Cells and Enables the Diagnosis of Human Pancreatic Cancer

In studies within the realm of cancer immunotherapy, the synthesis of exactly specified tumor‐associated glycopeptide antigens is shown to be a key strategy for obtaining a highly selective biological reagent, that is, a monoclonal antibody that completely differentiates between tumor and normal epithelial cells and specifically marks the tumor cells in pancreas tumors. Mucin MUC1, which is overexpressed in many prevalent cancers, was identified as a promising target for this strategy. Tumor‐associated MUC1 differs significantly from that expressed by normal cells, in particular by altered glycosylation. Structurally defined tumor‐associated MUC1 cannot be isolated from tumor cells. We synthesized MUC1–glycopeptide vaccines and analyzed their structure–activity relationships in immunizations; a monoclonal antibody that specifically distinguishes between human normal and tumor epithelial cells was thus generated.     

Azimuthal correlations and Bose Einstein effects in the reaction K+p → K+p2π+2π− AT 16 GeV/c

Azimuthal distributions between all possible particle pairs are studied in the reaction K⁺p → K⁺p2(π⁺π^?) at 16 GeV/c. It is shown that the hypothesis of uncorrelated transverse momenta at fixed rapidities of the final-state particles, is sufficient to describe the main features of the data. An interesting exception occurs for identical particle pairs where a genuine short-range correlation, attributed to Bose-Einstein symmetrization, is observed. The correlation length of this effect is shown to be related to the impact parameter distribution of the produced pions.     

Evidence for two back-to-back high-p T jets inK + p interactions at 70 GeV/c

Nucleon structure functions obtained from neutrino and anti-neutrino scattering on iron nuclei at high energies (E _v =30 to 250 GeV) are presented. These results are compared with the results of other lepton-nucleon scattering experiments. The structure functions are used to test the validity of the Gross-Llewellyn-smith sum rule, which measures the number of valence quarks in the nucleons, and to obtain leading and second order QCD fits.     

1,6-asymmetric induction in boron-mediated aldol reactions: application to a practical total synthesis of (+)-discodermolide

By relying solely on substrate-based stereocontrol, a practical total synthesis of the microtubule-stabilizing anticancer agent (+)-discodermolide has been realized. This exploits a novel aldol bond construction with 1,6-stereoinduction from the boron enolate of (Z)-enone 3 in addition to aldehyde 2. The 1,3-diol 7 is employed as a common building block for the C(1)-C(5), C(9)-C(16), and C(17)-C(24) subunits. [reaction--see text]     

Variable Coordination and Conformation of the 3-Cyano-2,4-pentanedionato Anion in a Mixed-Ligand Binuclear Copper(II) Chelate

The addition of dipyridylamine to bis(3-cyano-2,4-pentanedionato)copper(II), Cu(NC-acac)(2), induces changes in the mode of interaction and the conformation of the NC-acac(-) anion. The structure of the resulting binuclear compound was determined from a single microcrystal (monoclinic, space group P2(1), a = 7.894(7) ?, b = 25.550(24) ?, c = 11.661(13) ?, beta = 106.10(8) degrees, Z = 2, R(1) = 0.0564, (w)R(2) = 0.1197). In the addition compound {[Cu(NC-acac)dipyamH](NC-acac)}(2) when the NC-acac(-) acts as a chelating and bridging ligand, it assumes the commonly observed U(Z,Z) conformation, while behavior as weakly N-coordinated unidentate counteranion imposes the rarely encountered S(Z,E) conformation. In the [Cu(NC-acac)dipyamH](NC-acac)] entities one of the copper(II) centers is a 4 + 2 Jahn-Teller complex while the other is a square-based pyramid.