Block co-polyMOFs: morphology control of polymer-MOF hybrid materials.

The hybridization of block copolymers and metal-organic frameworks (MOFs) to create novel materials (block co-polyMOFs, BCPMOFs) with controlled morphologies is reported. In this study, block copolymers containing poly(1,4-benzenedicarboxylic acid, H2bdc) and morphology directing poly(ethylene glycol) (PEG) or poly(cyclooctadiene) (poly(COD)) blocks were synthesized for the preparation of BCPMOFs. Block copolymer architecture and weight fractions were found to have a significant impact on the resulting morphology, mediated through the assembly of polymer precursors prior to MOF formation, as determined through dynamic light scattering. Simple modification of block copolymer weight fraction allowed for tuning of particle size and morphology with either faceted and spherical features. Modification of polymer block architecture represents a simple and powerful method to direct morphology in highly crystalline polyMOF materials. Furthermore, the BCPMOFs could be prepared from both Zr4+ and Zn2+ MOFs, yielding hybrid materials with appreciable surface areas and tuneable porosities. The resulting Zn2+ BCPMOF yielded materials with very narrow size distributions and uniform cubic morphologies. The use of topology in BCPMOFs to direct morphology in block copolymer assemblies may open new methodologies to access complex materials far from thermodynamic equilibrium

Breakdown of the static picture of defect energetics in halide perovskites: the case of the Br vacancy in CsPbBr3

We consider the Br vacancy in CsPbBr3 as a prototype for the impact of structural dynamics on defect energetics in halide perovskites (HaPs). Using first-principles molecular dynamics based on density functional theory, we find that the static picture of defect energetics breaks down; the energy of the Br vacancy level is found to be intrinsically dynamic, oscillating by as much as 1 eV on the ps time scale at room temperature. These significant energy fluctuations are correlated with the distance between the neighboring Pb atoms across the vacancy and with the electrostatic potential at these Pb atomic sites. We expect this unusually strong coupling of structural dynamics and defect energetics to bear important implications for both experimental and theoretical analysis of defect characteristics in HaPs. It may also hold significant ramifications for carrier transport and defect tolerance in this class of photovoltaic materials.Comment: 5 figures, 1 tabl

Axial charge segregation and CP violation during the electroweak phase transition with hypermagnetic fields

We study the scattering of fermions off the true vacuum bubbles nucleated during a first order electroweak phase transition in the presence of a background hypermagnetic field. By considering the limit of an infinitely thin bubble wall, we derive and analytically solve the Dirac equation in three spatial dimensions for left and right chirality modes and compute reflection and transmission coefficients for the case when the fermions move from the symmetric toward the broken symmetry phase. Given the chiral nature of the fermion coupling with the background field in the symmetric phase, an axial asymmetry is generated during the scattering processes. This mechanism is thus shown to provide an additional source of CP violation within the standard model. We discuss possible implications for baryon number generation.Comment: 9 pages, 4 EPS figures, uses ReVTeX4. Three references adde

Fermion scattering off electroweak phase transition kink walls with hypermagnetic fields

We study the scattering of fermions off a finite width kink wall during the electroweak phase transition in the presence of a background hypermagnetic field. We derive and solve the Dirac equation for such fermions and compute the reflection and transmission coefficients for the case when the fermions move from the symmetric to the broken symmetry phase. We show that the chiral nature of the fermion coupling with the background field in the symmetric phase generates an axial asymmetry in the scattering processes. We discuss possible implications of such axial charge segregation for baryon number generation.Comment: 9 pages, 3 Postscript figures, uses RevTeX4. Expanded discussion, published versio

Mechanism and Timescales of Reversible p‐Doping of Methylammonium Lead Triiodide by Oxygen

Understanding and controlling the energy level alignment at interfaces with metal halide perovskites (MHPs) is essential for realizing the full potential of these materials for use in optoelectronic devices. To date, however, the basic electronic properties of MHPs are still under debate. Particularly, reported Fermi level positions in the energy gap vary from indicating strong n- to strong p-type character for nominally identical materials, raising serious questions about intrinsic and extrinsic defects as dopants. ​In this work, photoemission experiments demonstrate that thin films of the prototypical methylammonium lead triiodide (MAPbI3) behave like an intrinsic semiconductor in the absence of oxygen. Oxygen is then shown to be able to reversibly diffuse into and out of the MAPbI3 bulk, requiring rather long saturation timescales of ≈1 h (in: ambient air) and over 10 h (out: ultrahigh vacuum), for few 100 nm thick films. Oxygen in the bulk leads to pronounced p-doping, positioning the Fermi level universally ≈0.55 eV above the valence band maximum. The key doping mechanism is suggested to be molecular oxygen substitution of iodine vacancies, supported by density functional theory calculations. This insight rationalizes previous and future electronic property studies of MHPs and calls for meticulous oxygen exposure protocols.Deutsche Forschungsgemeinschaft http://dx.doi.org/10.13039/501100001659DFG http://dx.doi.org/10.13039/501100001659German Research Foundation http://dx.doi.org/10.13039/501100001659Peer Reviewe

Fermion Scattering off CP-Violating Electroweak Bubble Wall

A general prescription to solve the Dirac equation in the presence of CP-violating electroweak bubble wall is presented. The profile of the bubble wall is not specified except that the wall height is $m_0$ and zero deep in the broken- and the symmetric-phase regions, respectively, where $m_0$ is a fermion mass given by the Higgs-vacuum-expectation value and the Yukawa coupling. The CP-violating effects are evaluated by regarding CP-violating part of the bubble wall as a perturbation to CP-conserving solutions. The basic quantity, $R_{R\rightarrow L}-\bar R_{R\rightarrow L}$, which would contribute to the cosmological baryon asymmetry, is estimated for some typical profiles of the wall, where $R_{R\rightarrow L}$($\bar R_{R\rightarrow L}$) is the reflection coefficient of right-handed chiral fermion (anti-fermion).Comment: 30 pages, 2 figures ( uuencoded tar.Z file of PS files is appended ), plain TeX with phyzzx, tables and epsf,SAGA-HE-55--KYUSHU-HET-1

Equivalence of Narcissistic Personality Inventory constructs and correlates across scoring approaches and response formats

The prevalent scoring practice for the Narcissistic Personality Inventory (NPI) ignores the forced-choice nature of the items. The aim of this study was to investigate whether findings based on NPI scores reported in previous research can be confirmed when the forced-choice nature of the NPI’s original response format is appropriately modeled, and when NPI items are presented in different response formats (true/false or rating scale). The relationships between NPI facets and various criteria were robust across scoring approaches (mean score vs. model-based), but were only partly robust across response formats. In addition, the scoring approaches and response formats achieved equivalent measurements of the vanity facet and in part of the leadership facet, but differed with respect to the entitlement facet

Scattering in the Presence of Electroweak Phase Transition Bubble Walls

We investigate the motion of fermions in the presence of an electro\-weak phase transition bubble wall. We derive and solve the Dirac equation for such fer\-mions, and compute the transmission and reflection coefficients for fermions traveling from the symmetric to the asymmetric phases separated by the domain wall.Comment: TPI--MINN--54, NUC--MINN--93/30--T, UMN--TH--1226/93, LaTex, 29 page

Automated analysis of morphometric parameters for accurate definition of erythrocyte cell shape

none6openM.C.Albertini; L.Teodori; E.Piatti; M.P.Piacentini; A.Accorsi; M.B.L.RocchiAlbertini, MARIA CRISTINA; L., Teodori; Piatti, Elena; Piacentini, MARIA PIERA; Accorsi, Augusto; Rocchi, MARCO BRUNO LUIG

Axially asymmetric fermion scattering off electroweak phase transition bubble walls with hypermagnetic fields

We show that in the presence of large scale primordial hypermagnetic fields, it is possible to generate an axial asymmetry for a first order electroweak phase transition. This happens during the reflection and transmission of fermions off the true vacuum bubbles, due to the chiral nature of the fermion coupling with the background field in the symmetric phase. We derive and solve the Dirac equation for such fermions and compute the reflection and transmission coefficients for the case when these fermions move from the symmetric to the symmetry broken phase. We also comment on the possible implications of such axial charge segregation processes for baryon number generation.Comment: 8 pages, 2 Encapsulated Postscript figures, uses ReVTeX and epsfig.sty, expanded discussion, version to appear in Phys. Rev.