http://chineseinput.net/에서 pinyin(병음)방식으로 중국어를 변환할 수 있습니다.
변환된 중국어를 복사하여 사용하시면 됩니다.
Ptak, Maciej,Stefań,ska, Dagmara,Gą,gor, Anna,Svane, Katrine L.,Walsh, Aron,Paraguassu, Waldeci The Royal Society of Chemistry 2018 Physical chemistry chemical physics Vol.20 No.34
<P>We report the synthesis, crystal structure, vibrational and luminescence properties of two heterometallic perovskite-type metal-organic frameworks (MOFs) containing the ammonium cation (NH4<SUP>+</SUP>, Am<SUP>+</SUP>): [NH4][Na0.5Cr0.5(HCOO)3] (AmNaCr) and [NH4][Na0.5Al0.475Cr0.025(HCOO)3] (AmNaAlCr) in comparison to the previously reported [NH4][Na0.5Al0.5(HCOO)3] (AmNaAl). The room-temperature crystal structure of AmNaCr and AmNaAlCr was determined to be <I>R</I>3̄. The hydrogen bonding (HB) energy calculated using density functional theory (DFT) agrees well with experimental data, and confirms the existence of almost identical H-bonding in AmNaCr and AmNaAl, with three short hydrogen bonds and a longer trifurcated H-bond. Temperature-dependent Raman measurements supported by differential scanning calorimetry show that AmNaCr does not undergo any structural phase transitions in the 80-400 K temperature range. The high-pressure Raman spectra of AmNaCr show the onset of two structural instabilities near 0.5 and 1.5 GPa. The first instability involves weak distortion of the framework, while the second leads to irreversible amorphization of the sample. High-pressure DFT simulations show that the unit cell of the AmNaCr compound contracts along the <I>c</I> axis, which leads to a shortening of the trifurcated H-bond. The optical properties show that both studied crystals exhibit Cr<SUP>3+</SUP>-based emission characteristic of intermediate ligand field strength.</P>
Ptak, Maciej,Svane, Katrine Louise,Walsh, Aron,Paraguassu, Waldeci Royal Society of Chemistry 2019 Physical chemistry chemical physics Vol.21 No.8
<P>We report the high-pressure properties of two heterometallic perovskite-type metal-organic frameworks (MOFs) templated by dimethylammonium (NH2(CH3)2, DMA<SUP>+</SUP>) with the general formula [DMA]MI0.5CrIII0.5(HCOO)3, where M<SUP>I</SUP> = Na<SUP>+</SUP> (DMANaCr) and K<SUP>+</SUP> (DMAKCr). The high-pressure Raman scattering studies show crystal instabilities in the 4.0-4.4 GPa and 2.0-2.5 GPa ranges for DMANaCr and DMAKCr, respectively. The mechanism is similar in the two compounds and involves strong deformation of the metal-formate framework, especially pronounced for the subnetwork of CrO6 octahedra, accompanied by substantial compressibility of the DMA<SUP>+</SUP> cations. Comparison with previous high-pressure Raman studies of sodium-chromium heterometallic MOFs show that the stability depends on the templated cation and increases as follows: ammonium < imidazolium < DMA<SUP>+</SUP>. Density functional theory (DFT) calculations are performed to get a better understanding of the structural properties leading to the existence of phase transitions. We calculate the energy of the hydrogen bonds (HBs) between the DMA<SUP>+</SUP> cation and the metal formate cage, revealing a stronger interaction in the DMAKCr compound due to a HB arrangement that primarily involves the energetically preferred bonding to KO6 octahedra. This material however also has a smaller structural tolerance factor (TF) and a higher vibrational entropy than DMANaCr. This indicates a more flexible crystal structure, explaining the lower phase transition pressure, as well as the previously observed phase transition at 190 K, which is absent in the DMANaCr compound. The DFT high-pressure simulations show the largest contraction to be along the trigonal axis, leading to a minimal distortion of the HBs formed between the DMA<SUP>+</SUP> cations and the metal-formate sublattice.</P>
Ingestion and surgical retrieval of an endodontic file: a case report
Ptak Devon Marta,Alon Elinor,Amato Robert Bruce,Tassinari Julia,Velasquez Adrian 대한치과보존학회 2023 Restorative Dentistry & Endodontics Vol.48 No.4
Ingestions and aspirations of foreign bodies are rare, but do occasionally occur during dental treatment. Although reports exist, few include photos demonstrating the extensive surgical intervention that may be necessary to manage such events. Perhaps this lack of visualization, and associated lack of awareness, is one of the reasons some clinicians still provide nonsurgical root canal therapy (NSRCT) without a rubber dam. This case report outlines the medical treatment of a 30-year-old male who initially presented to a general dentist’s office (not associated with the authors) for NSRCT of their mandibular right first molar. A rubber dam was not used for this procedure, during which the accidental ingestion of an endodontic K-file occurred. The patient was subsequently hospitalized for evaluation and treatment, consisting of numerous imaging studies, endoscopic evaluation, and surgical removal of the file from his small intestine. The ingestion of foreign bodies, and the associated complications, can be reduced through the routine use of a rubber dam, which is considered the standard of care for NSRCT. This case graphically illustrates the potential consequences associated with deviating from the standard of care and should remind clinicians that a rubber dam is necessary for all cases of NSRCT.
A NOTE ON k-HYPERREFLEXIVITY OF TOEPLITZ-HARMONIC SUBSPACES
Budzynski, Piotr,Piwowarczyk, Kamila,Ptak, Marek Korean Mathematical Society 2014 대한수학회보 Vol.51 No.6
The 2-hyperreflexivity of Toeplitz-harmonic type subspace generated by an isometry or a quasinormal operator is shown. The k-hyperreflexivity of the tensor product $\mathcal{S}{\otimes}\mathcal{V}$ of a k-hyperreflexive decom-posable subspace $\mathcal{S}$ and an abelian von Neumann algebra $\mathcal{V}$ is established.
Adam Sieradzki,Justyna Trzmiel,Maciej Ptak,Mirosław Mączka 대한금속·재료학회 2015 ELECTRONIC MATERIALS LETTERS Vol.11 No.6
In this study, the dielectric properties of a polycrystalline metal organic framework [(CH3)2NH2][Na0.5Fe0.5(HCOO)3] (DMNaFe) sample were investigated. The DMNaFe sample exhibited a typical relaxor-like relaxation response in addition to a ferroelastic order-disorder phase transition. Analysis of the frequency dependence of the complex permittivity revealed the characteristic two-power-law dipolar glass relaxor behavior of the DMNaFe, indicating complex cluster formation in the material. Moreover, an unusual transformation associated with the ferroelastic phase transition from the generalized Mittag-Leffler relaxation pattern (low-temperature ordered phase) to the Havriliak- Negami one (high-temperature disordered phase) was detected. The relaxation data obtained for the investigated sample were interpreted based on the stochastic approach to relaxation processes.
A NOTE ON k-HYPERREFLEXIVITY OF TOEPLITZ-HARMONIC SUBSPACES
Piotr Budzynski,Kamila Piwowarczyk,Marek Ptak 대한수학회 2014 대한수학회보 Vol.51 No.6
The 2-hyperreflexivity of Toeplitz-harmonic type subspace generated by an isometry or a quasinormal operator is shown. The k- hyperreflexivity of the tensor product S ⓧ V of a k-hyperreflexive decom- posable subspace S and an abelian von Neumann algebra V is established.