Crystal structure of pentakis ethylenediammonium bis undecachlorodiantimonate(III) tetrahydrate, (NH3(CH2)2NH3)5(Sb2Cl11)2·4H2O

The pentakis ethylenediammonium bis undecachlorodiantimonate(III) tetrahydrate salt is monoclinic with the following unit cell dimensions:a=16.271(5) Å,b=13.004(4) Å,c=13.932(4) Å, β=111.72(2)°, space groupP2₁/c withZ=2. The structure was solved by Patterson methods and refined to a finalR value of 0.023 for 4435 reflections withF ₀>4σ(F ₀). The structure shows a layer arrangement perpendicular to thea axis: planes of the [Sb₂Cl₁₁]⁵⁻ bioctahedra alternate with planes of [NH₃(CH₂)₂NH₃]²⁺ dications. The [Sb₂Cl₁₁]⁵⁻ bioctahedra are connected through O−H...Cl hydrogen bonds, such that infinite chains of composition [Sb₂Cl₁₁(H₂O]_n ⁵ⁿ⁻ are formed in the structure, parallel to the twofold axis. These chains are themselves interconnected by means of N−H...Cl and O−H...Cl bonds originating from the [NH₃(CH₂)₂NH₃]²⁺ entities and the water molecules, respectively, and form a threedimensional network.     

Experimental dipole moments for nonisolatable acetic acid structures in a nonpolar medium. A combined spectroscopic, dielectric, and DFT study for self-association in solution

Acetic acid can exist in many possible structural forms depending on its surrounding medium. A recently developed inverse problem methodology (J. Phys. Chem. B 2007, 111, 13064-13074) was utilized in order to elucidate acetic acid structures in a dilute nonpolar medium. In this regard, simultaneous and stopped-flow measurements of the bulk solution densities, refractive indices, relative permittivities, and IR spectra of acetic acid in toluene were performed at several different concentrations in a semibatch closed-loop experimental setup at 298.15 K and 0.1013 MPa. This combined IR spectroscopic and dielectric, density, and refractive index analysis was employed in order to distinguish acetic acid structures and to further determine the dipole moments of the monomer, cyclic dimer, and "lumped-sum" open dimers. The infrared spectra were first analyzed to provide qualitative understanding as well as quantitative estimates for each acetic acid species. Subsequently, the dipole moments of these species were calculated using a direct approach which was primarily based on response surface models. The present method allows the determination of individual dipole moments not only for the monomer but also for the cyclic dimer and the open dimer. The results obtained from this study experimentally show that the cyclic dimer with centrosymmetric structure has a dipole moment approximately 0 D. The results also suggest that the linear dimers are present as mixtures of linear dimers structures. The existence of the linear dimers mixture was also indicated by the experimental infrared analysis of the OH-stretching region (particularly for measurements in n-hexane as solvent) and comparison of these spectra with DFT predictions. Finally, the present methodology which incorporates simultaneous physicochemical and spectroscopic analysis is undoubtedly useful for physicochemical characterization for other nonisolatable solute species and self-associated structures in solution.     

Triboelectric and Piezoelectric Effects in a Combined Tribo‐Piezoelectric Nanogenerator Based on an Interfacial ZnO Nanostructure

In this contribution, combined triboelectric and piezoelectric generators (TPEG) with a sandwich structure of aluminum‐polydimethylsiloxane/polyvinylidene fluoride composite‐carbon (Al‐PPCF‐Carbon) are fabricated for the purpose of mechanical energy harvesting. Improved by the surface modification of PPCF with zinc oxide (ZnO) nanorods through a hydrothermal method, the TPEG generates an open‐circuit voltage (V_oc) of ≈40 V, a short‐circuit current (I_sc) of 0.28 μA with maximum power density of ≈70 mWm^?2_, and maximum conversion efficiency of 34.56%. Subsequently, in order to understand the transduction mechanism of the triboelectric and piezoelectric effects, analyses focusing on the potential composition ratio in the final output and the impact of ZnO interfacial nanostructure are carried out. The observed potential ratio between triboelectric and piezoelectric effects is 12.75:1 and the highest potential improvement by ZnO nanorods of 21.8 V is achieved by the TPEG fabricated with spacer. Finally, the relationships between the voltage, power density, conversion efficiency, and the external load resistances are also discussed. Overall, the fabricated TPEG is proved to be a simple and effective nanogenerator in mechanical energy conversion with enhanced output potential and conversion efficiency.     

Equi-Gaussian curvature folding

In this paper we introduce a new type of folding called equi-Gaussian curvature folding of connected Riemannian 2-manifolds. We prove that the composition and the cartesian product of such foldings is again an equi-Gaussian curvature folding. In case of equi-Gaussian curvature foldings, f: M → P _n , of an orientable surface M onto a polygon P _n we prove that

Synthesis and characterizations of Ho2O3 modified SrBi2Nb2O9 ceramics

SrBi_2-xHo_xNb₂O₉ (0?≤?x?≤?0.5) ceramics were prepared through the conventional solid state route. The materials have been characterized by XRD, FTIR and SEM. All compounds were pure and well crystallized. In FTIR spectroscopy, the spectral patterns of the crystal structures of these polyphases are unique and smoothly different from each other. The grains were prone to become spherical with increasing x. Dielectric and electrical properties of these materials as a function of temperature at different frequencies have been carried out. The dielectric constant and dielectric loss were found to decrease with an increase of the holmium concentration at room temperature. Reaching up to x?=?0.4 and x?=?0.5, the diffusivity increases, leading to the occurrence of relaxor behavior. 20–30 at.% Ho doping on the Bi-site can fill up the oxygen vacancies and decrease the AC conductivity. However, at higher doping levels greater than 40% holmium oxide, the AC conductivity is found to increase.     

Synthesis,structural and dielectric properties of SrBi<Subscript>2 – <Emphasis Type="Italic">x</Emphasis></Subscript>Sm<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>Nb<Subscript>2</Subscript>O<Subscript>9</Subscript>

The SrBi_{2 – x} Sm _x Nb₂O₉ (x = 0, 0.4, 0.5) structure were synthesized by a conventional solid-state method. The X-ray diffraction shows an orthorhombic at room temperature. Dielectric constant, loss tangent and Ac conductivity of Sm-doped SrBi₂Nb₂O₉ were carried out, as well. A higher concentration of samarium (x = 0.4 and 0.5) doping leads to a significant reduction in dielectric constant and in Curie temperature. Rather relaxor type of behaviour took place.     

S-parameter performance degradation in power RF N-LDMOS devices due to hot carrier effects

This paper reports comparative study of technology reliability after accelerated ageing tests under various conditions (electrical and/or thermal stress) and RF life-tests reliability with pulsed bench for radar applications in S-band. It is important to understand the effects of the reliability degradation mechanisms on the S-parameters and in turn on static and dynamic parameters.The analysis of the experimental results is presented and the physical processes responsible for the observed degradation at different stress conditions are studied by means of 2D ATLAS–SILVACO simulations.S-parameters degradation of hot-carrier stressed n-MOS transistors can be explained by the transconductance and miller capacitance shifts, which are resulted from the interface state generation (traps), which results in a build up of negative charge at Si/SiO₂ interface. More interface states are created due to a located maximum impact ionization rate at the gate edge. From our experimental results, hot electron induced RF performance degradation should be taken into consideration in the design of the power RF MOS devices.     

The Field-Dependent Magnetization of d5–d7 Metal β−Diketonate Complexes and Their Macromolecular Polymers

A vibrating sample magnetometer (VSM) has been used to study the field-dependent magnetization, M(H), of the d⁵?d⁷ metal acetates [M(OAc)₂.nH₂O], metal β?diketonate complexes [M(tba)₂(H₂O)₂] and the macromolecular polymers [M(tba)₂(4,4-bipy)]_n (where, M = Mn(II), Fe(II), and Co(II), OAc = O₂CCH₃, tba = deprotonated 3-benzoyl-1.1.1-trifluoroacetone, and 4,4-bipy = 4,4′-bipyridine). The magnetic field strength (H) was applied in the range of 0?10⁴ O_e at ambient temperature (ca. 23°C). The experimental results showed that the d⁵?d⁷ metal acetate, complexes and polymers exhibit low paramagnetic properties excepting [Fe(tba)₂(4,4-bipy)]_n polymer, which had negative magnetization M(emu/g) showing diamagnetic properties in the range 0?10⁴ O_e. The magnetization was almost equal to zero without an applied magnetic field (H(O_e)) for each d⁵?d⁷ metal acetate, complex, and polymer. The linear M(H) curve had a magnetic saturation for iron and manganese acetate species at the magnetic field strengths of 3.1 × 10³ and 4.7 × 10³ Oe, respectively. The external magnetic field reached 9.0 × 10³ O_e without any saturation magnetization for the cobalt compounds. The coordination effect of 3-benzoyl-1.1.1-trifluoroacetone (H-tba) and 4,4′-bipyridine (4,4′-bipy) ligands on the field-dependent magnetization M(H) and paramagnetic behavior of d⁵?d⁷ metal atoms is discussed. The field-dependent magnetization M(H) curves of metal β?diketonate complexes and the polymers including d⁵?d⁷ metal acetates showed a weak field octahedral geometry.     

Remote‐Controlled Hydrogel Depots for Time‐Scheduled Vaccination

Remote‐controlled drug depots represent a highly valuable tool for the timely controlled administration of pharmaceuticals in a patient compliant manner. Here, the first pharmacologically controlled material that allows for the scheduled induction of a medical response in mice is described. To this aim, a novel, humanized biohybrid material that releases its cargo in response to a small‐molecule stimulus licensed for human use is developed. The functionality of the material in mice is demonstrated by the remote‐controlled delivery of a vaccine against the oncogenic human papillomavirus type 16. It is shown that the biohybrid depot‐mediated immunoprotection is equivalent to the classical multi‐injection‐based vaccination. These results indicate that this material can be used as a universal remote‐controlled vehicle for the patient‐compliant delivery of vaccines and pharmaceuticals.