Critical properties of the one-dimensional spin-1/2 antiferromagnetic Heisenberg model in the presence of a uniform field

In the presence of a uniform field the one-dimensional spin-$\frac{1}{2}$ antiferromagnetic Heisenberg model develops zero frequency excitations at field-dependent 'soft mode' momenta. We determine three types of critical quantities, which we extract from the finite-size dependence of the lowest excitation energies, the singularities in the static structure factors and the infrared singularities in the dynamical structure factors at the soft mode momenta. We also compare our results with the predictions of conformal field theory.Comment: 12 pages, REVTEX, 7 figures, submitted to Physical Review

The K-theory of the C*-algebras of 2-rank graphs associated to complete bipartite graphs

Using a result of Vdovina, we may associate to each complete connected bipartite graph $\kappa$ a $2$-dimensional square complex, which we call a tile complex, whose link at each vertex is $\kappa$. We regard the tile complex in two different ways, each having a different structure as a $2$-rank graph. To each $2$-rank graph is associated a universal C*-algebra, for which we compute the K-theory, thus providing a new infinite collection of $2$-rank graph algebras with explicit K-groups. We determine the homology of the tile complexes, and give generalisations of the procedures to complexes and systems consisting of polygons with a higher number of sides.Comment: 24 pages, 9 figures. Revised 2020/10/05. Section 4 and Figure 8 added Revised 2021/02/17. New figure (7) added. Changes made for clarit

Mutation of BRAF V600E in Iraqi Female Patients Diagnosed With Breast Cancer

هدفت هذه الدراسة الى التحري عن وجود طفرة BRAF V600E من عدمها في الاناث التي تم تشخيصهن بالاصابة بسرطان الثدي وفي اعمار مختلفة، حيث تم جمع عينات الدم والانسجة من 46 مريضة وباعمار(46± 3.54)، حيث تم تقسيمها اللى مجموعتين، المجموعة التي  تحت العلاج الكيمياوي وعددها 31 مصابة والمجموعة الاخرى بدون علاج كيمياوي وعددها 15 مصابة كما تم مقارنة النتائج مع مجموعة الاصحاء كمجموعة سيطرة وعددهم 23 شخصا وباعمار(47.93±3.05) سنة.تم اجراء  تفاعل البلمرة المتسلسل ( (PCR وباستخدام بوادئ تم تصميمها ضمن الدراسة الحالية على جميع العينات. اظهرت النتائج عدم وجود علاقة مابين الاصابة بسرطان الثدي وطفرة BRAF V600E في المرضى العراقين المشمولين بالدراسة الحالية.This study aimed to investigate the possible presence of BRAF V600E mutation in the Iraqi female patients who diagnosed with breast cancer in different ages, in which Blood and tissue samples were collected from 46 female patients with  age (46.73±3.54);Those were divided into two groups; who took chemotherapy (31 persons) as treated group and without chemotherapy as an untreated group (15 persons) and from (23) healthy person with age(47.93±3.05).  Polymerase chain reaction (PCR) were done with newly designed primers. The results revealed no correlation between breast cancer occurrence and BRAF V600E mutation in the Iraqi patients enrolled  in the current study. &nbsp

Stereochemical studies on protonated bridgehead amines. ^1H NMR determination of cis and trans B-C ring-fused structures for salts of hexahydropyrrolo [2,1-a] isoquinolines and related C ring homologs. Capture of unstable ring-fused structures in the solid state

Acid-addition salts of tricyclic isoquinolines 2a/b, 3a/b, 4a-4c, 5, 6a/b, 7, 8a/b, 9a/b, and 17a/b were studied by high-field ^1H NMR in CDCl_3 solution. Cis (e.g., 14 and 15 in Figure 1) and trans (e.g., 13)B-C ring-fused structures were identified by using the vicinal ^3J(CH-NH) coupling constants, which demonstrate a Karplus-like behavior. In some cases, we initially observed a trans form, which converted to a cis A form by N H proton exchange. For 4c.HBr, the exchange process was slowed by addition of trifluoroacetic acid. In many cases, cis A and cis B structures were preferred in solution. The pendant phenyl group exerted a strong influence on the preferred solution structure. Observation of the initial, unstable trans-fused structures was related to their capture in the solid state and release intact on dissolution. X-ray diffraction was performed on the HBr salts of 2a (B-C cis), 2b (B-C cis), and 4c (B-C trans). The result for 4c.HBr confirmed the connection between the initial trans form in solution and the solid state. For 17b.HCI two conformers, associated with hindered rotation about the bond connecting the 2,6-disubstituted phenyl group to the tricyclic array, were detected at ambient probe temperature; however, rotamers were not observed for either of the two forms (trans and cis A) of 17a.HBr. Two conformers were also found for 16b.HBr. Temperature-dependent behavior was recorded in the ^1H NMR spectra of 17b.HBr and 16b.HBr; the activation free energy for interconversion of conformers was estimated to be in the vicinity of 17 kcal/mol for the former and 14-15 kcal/mol for the latter. The ^1H NMR spectrum of butaclamol hydrochloride (20.HC1), a potent neuroleptic agent, in Me_2SO-d_6 revealed two species in a ratio of 81:19, which were assigned as trans and cis A forms, respectively. ^1H NMR data for various free bases are also presented and discussed. Empirical force field calculations on three model hydrocarbons are discussed from a perspective of finding an explanation for the configurational/conformational behavior of the bridgehead ammonium salts. Diverse literature examples of structures for protonated bridgehead amines are also discussed. A tentative rationale is suggested for the preference of cis A forms in some protonated tetrahydroisoquinoline derivatives

The bond-valence deficiency model:a new application to describe mineral surface reactions

Die Bindungsvalenz-Theorie ist eine unter Mineralogen bekannte Methodik, mittels derer es möglich ist, Kristallstrukturen auf ihre Vollständigkeit zu überprüfen. Durch die Arbeiten z.B. von BROWN (1981, 2002) wurde der Anwendungsbereich dieser Theorie erweitert. Neuere Ansätze (z.B. Schindler et al. 2004 a,b) ermöglichen es nun Strukturen und Eigenschaften von Mineraloberflächen unter Berücksichtigung der Bindungsvalenz-Theorie neu zu interpretieren. Während ältere Theorien zum Kristallwachstum in der Mehrzahl interne Faktoren berücksichtigen (Bravais, Donnay & Harker, Hartman & Perdok), hat sich in jüngerer Zeit das Gewicht der Interpretation von Kristallformen auf die Untersuchung des Einflusses von externen Faktoren verlagert. Die in dieser Arbeit vorgestellte Herangehensweise (Bindungsvalenz-Defizit Model), erlaubt es nun beide Sichtweisen zu vereinheitlichen, so dass sowohl interne als auch externe Einflüsse auf das Kristallwachstum gleichermaßen berücksichtigt werden können

First-principles analysis of the interplay between electronic structure and volume change in colquiriite compounds during Li intercalation

A main source of capacity fading in lithium-ion batteries is the degradation of the active cathode materials caused by the series of volume changes during charge and discharge cycles. The quaternary colquiriite-type fluorides Li$_x$CaFeF$\mathrm{_6}$ and Li$_x$CaCoF$\mathrm{_6}$ were reported to have negligible volume changes in specific Li concentration ranges, making the underlying colquiriite structure a promising candidate for so-called zero-strain behavior. Using first-principles electronic structure calculations based on density functional theory with a Hubbard-$U$ correlation correction on the transition-metal ions, we systematically investigate the equilibrium volumes of the colquiriite-type fluorides Li$_x$CaMF$\mathrm{_6}$ with M =Ti, V, Cr, Mn, Fe, Co, and Ni at the Li concentrations $x$=0, 1, and 2. We elucidate the connection between the total volume of the structures and the local volumes of fluorine coordinated octahedra around the cations, and we find trends along the series of the 3d transition-metal elements. In the lithiation step from $x$=1 to $x$=2 we find volume changes of about 10 %, and we discuss the discrepancy to the experimentally reported smaller value for Li$_x$CaFeF$\mathrm{_6}$. From $x$=0 to $x$=1 we describe the compensating structural mechanisms that lead to an exceptionally small volume change of Li$_x$CaMnF$\mathrm{_6}$. This compound is therefore a particularly promising zero-strain cathode material.Comment: 13 pages, 9 Figure

Molecular dynamics study of CO2 absorption and desorption in zinc imidazolate frameworks

This research utilised two high-performance computing facilities. Development of the force field was carried out using Queen Mary's MidPlus computational facilities, supported by QMUL Research-IT and funded by EPSRC grant EP/K000128/1. The molecular dynamics simulations were carried out using the ARCHER UK National Supercomputing Service (http://www.archer.ac.uk), with access made available through our membership of the UK's HEC Materials Chemistry Consortium, which is funded by EPSRC (EP/L000202). MG and CY were supported by both the China Scholarship Council and Queen Mary University of London. AM was supported by a European Union Marie Sklodowska-Curie fellowship