Flavor from Strongly Coupled Supersymmetry

Strongly coupled supersymmetric theories can give rise to composite quarks and leptons at low energy. We show that the internal structure of these particles can explain the origin of three generations and provide a qualitative understanding of mass ratios and mixing angles between the different flavors of fermions, all within a renormalizable theory. The main point of the paper is to show how fermion masses and mixing angles can result from a ``dual'' Frogatt-Nielsen mechanism: fields neutral under $SU(3) \times SU(2) \times U(1)$ which carry flavor quantum numbers are confined within quarks and leptons, and from their perturbative interactions arises the observed flavor structure.Comment: 28 pages, 5 figures, LATEX. A few typos corrected and references adde

Exponentially Small Supersymmetry Breaking from Extra Dimensions

The supersymmetric ``shining'' of free massive chiral superfields in extra dimensions from a distant source brane can trigger exponentially small supersymmetry breaking on our brane of order e^{-2 pi R}, where R is the radius of the extra dimensions. This supersymmetry breaking can be transmitted to the superpartners in a number of ways, for instance by gravity or via the standard model gauge interactions. The radius R can easily be stabilized at a size O(10) larger that the fundamental scale. The models are extremely simple, relying only on free, classical bulk dynamics to solve the hierarchy problem.Comment: RevTex, 1 figure. Comment on mu problem adde

Ion Beam Assisted Deposition of Thin Epitaxial GaN Films

The assistance of thin film deposition with low-energy ion bombardment influences their final properties significantly. Especially, the application of so-called hyperthermal ions (energy <100 eV) is capable to modify the characteristics of the growing film without generating a large number of irradiation induced defects. The nitrogen ion beam assisted molecular beam epitaxy (ion energy <25 eV) is used to deposit GaN thin films on (0001)-oriented 6H-SiC substrates at 700 C. The films are studied in situ by reflection high energy electron diffraction, ex situ by X-ray diffraction, scanning tunnelling microscopy, and high-resolution transmission electron microscopy. It is demonstrated that the film growth mode can be controlled by varying the ion to atom ratio, where 2D films are characterized by a smooth topography, a high crystalline quality, low biaxial stress, and low defect density. Typical structural defects in the GaN thin films were identified as basal plane stacking faults, low-angle grain boundaries forming between w-GaN and z-GaN and twin boundaries. The misfit strain between the GaN thin films and substrates is relieved by the generation of edge dislocations in the first and second monolayers of GaN thin films and of misfit interfacial dislocations. It can be demonstrated that the low-energy nitrogen ion assisted molecular beam epitaxy is a technique to produce thin GaN films of high crystalline quality

General Messenger Gauge Mediation

We discuss theories of gauge mediation in which the hidden sector consists of two subsectors which are weakly coupled to each other. One sector is made up of messengers and the other breaks supersymmetry. Each sector by itself may be strongly coupled. We provide a unifying framework for such theories and discuss their predictions in different settings. We show how this framework incorporates all known models of messengers. In the case of weakly-coupled messengers interacting with spurions through the superpotential, we prove that the sfermion mass-squared is positive, and furthermore, that there is a lower bound on the ratio of the sfermion mass to the gaugino mass.Comment: 37 pages; minor change

Hydrophobic, Carbon Free Gas Diffusion Electrode for Alkaline Applications

In this work we present a carbon free gas diffusion electrode (GDE) design. It is a first step towards improvement of technologies like alkaline fuel cells, some alkaline electrolyzes and metal-air-batteries by circumventing carbon degradation. A nickel-mesh was made hydrophobic and subsequently electrochemically coated with MnOx as electrocatalyst. By this, a carbon free GDE was prepared. The contact angle, specific surface area (BET), pore size distribution, crystal phase (XRD) and electrochemical properties were determined. The deposition scan rate (rscan) during dynamic MnOx deposition altered the macro surface structure, pore size distribution and deposited mass. High catalyst masses with high specific surface area were achieved by lower rscan, but hydrophobicity was decreased. Impedance spectroscopy showed that higher MnOx mass will increase the ohmic resistance, because of the low conductivity of oxides, such as MnOx. The diffusion of dissolved oxygen is the major contributor to the total resistance. However, the polarization resistance was reduced by increased specific surface area of MnOx. It was concluded that the ORR and OER are limited by diffusion in this design but nevertheless showed reasonable activity for ±10 mA cm−2 corresponding to ∼8 Ω cm−2 while references exhibited ∼3.5 Ω cm−2

Thermally stable mesoporous tetragonal zirconia through surfactant-controlled synthesis and Si-stabilization

Thermally stable, highly mesoporous Si-stabilized ZrO₂ was prepared by sol–gel-synthesis. By utilizing the surfactant dodecylamine (DDA), large mesopores with a pore width of ∼9.4 nm are formed. Combined with an NH₃-treatment on the hydrogel, a high specific surface area of up to 225 m² g⁻¹ and pore volume up to 0.46 cm³ g⁻¹ are obtained after calcination at 973 K. The individual contributions of Si-addition, DDA surfactant and the NH₃-treatment on the resulting pore system were studied by inductively coupled plasma with optical emission spectrometry (ICP-OES), X-ray diffraction (XRD), N₂ sorption, and transmission electron microscopy (TEM). Electron tomography was applied to visualize and investigate the mesopore network in 3D space. While Si prevents the growth of ZrO₂ crystallites and stabilizes the t-ZrO₂ phase, DDA generates a homogeneous mesopore network within the zirconia. The NH₃-treatment unblocks inaccessible pores, thereby increasing specific surface area and pore volume while retaining the pore width distribution

Nanosized Cu-SSZ-13 and its application in NH3−SCRNH_3-SCR

Nanosized SSZ-13 was synthesized hydrothermally by applying N, N, N-trimethyl-1-adamantammonium hydroxide (TMAdaOH) as a structure-directing agent. In the next step, the quantity of TMAdaOH in the initial synthesis mixture of SSZ-13 was reduced by half. Furthermore, we varied the sodium hydroxide concentration. After ion-exchange with copper ions (Cu2+ and Cu+), the Cu-SSZ-13 catalysts were characterized to explore their framework composition (XRD, solid-state NMR, ICP-OES), texture (N2-sorption, SEM) and acid/redox properties (FT-IR, TPR-H2, DR UV-Vis, EPR). Finally, the materials were tested in the selective catalytic reduction of NOx with ammonia (NH3-SCR). The main difference between the Cu-SSZ-13 catalysts was the number of Cu2+ in the double six-membered ring (6MRs). Such copper species contribute to a high NH3-SCR activity. Nevertheless, all materials show comparable activity in NH3-SCR up to 350 °C. Above 350 °C, NO conversion decreased for Cu-SSZ-13(2–4) due to side reaction of NH3 oxidation

Nanosized Cu-SSZ-13 and Its Application in NH3-SCR

Nanosized SSZ-13 was synthesized hydrothermally by applying N,N,N-trimethyl-1-adamantammonium hydroxide (TMAdaOH) as a structure-directing agent. In the next step, the quantity of TMAdaOH in the initial synthesis mixture of SSZ-13 was reduced by half. Furthermore, we varied the sodium hydroxide concentration. After ion-exchange with copper ions (Cu2+ and Cu+), the Cu-SSZ-13 catalysts were characterized to explore their framework composition (XRD, solid-state NMR, ICP-OES), texture (N2-sorption, SEM) and acid/redox properties (FT-IR, TPR-H2, DR UV-Vis, EPR). Finally, the materials were tested in the selective catalytic reduction of NOx with ammonia (NH3-SCR). The main difference between the Cu-SSZ-13 catalysts was the number of Cu2+ in the double six-membered ring (6MRs). Such copper species contribute to a high NH3-SCR activity. Nevertheless, all materials show comparable activity in NH3-SCR up to 350 °C. Above 350 °C, NO conversion decreased for Cu-SSZ-13(2–4) due to side reaction of NH3 oxidation

Influence of framework n(Si)/n(Al) ratio on the nature of Cu species in Cu-ZSM-5 for NH3−SCR−DeNOxNH_3-SCR-DeNO_x

Nanosized Cu-containing ZSM-5 catalysts with different n(Si)/n(Al) ratio of 18.9–50.5 were prepared by ion-exchange. The physico-chemical characterization clearly shows that the molar ratio of framework T atoms influences the nature and distribution of copper species. According to DR UV-Vis, TPR-H2, EPR, or FT-IR spectroscopy analyses, the amount of aggregated copper species increases with increasing the framework n(Si)/n(Al) ratio. Thus, the activity of the Cu-containing ZSM-5 with n(Si)/n(Al) ratio of 47.0—50.5 in the selective catalytic NO reduction with NH3 (NH3-SCR-DeNOx) significantly decreases compared to the other materials (n(Si)/n(Al) ratio of 18.9—19.6). The reaction mechanism has been discussed in light of the results of 2D COS (two-dimensional correlation spectroscopy) analysis of IR spectra and catalytic properties of the zeolites. The results make evident that enhanced activity of Cu-containing ZSM-5 in NH3-SCR-DeNOx is correlated with the formation of different NOx− under the experimental conditions. © 2022 The Authors. ChemCatChem published by Wiley-VCH GmbH

Selective catalytic reduction of NOxNO_x over micro-/meso-/macroporous Cu-SAPO-34

Micro-/meso-/macroporous Cu-containing SAPO-34 prepared by the post-synthetic modification of a commercial support with diethylamine (DEA), shows enhanced activity in NH3-SCR-DeNOx.</jats:p