Stepwise synthesis of metal-organic frameworks: replacement of structural organic linkers

We demonstrate how a single-crystal to single-crystal transformation resulting from bridging-linker replacement is possible in extended 2D and 3D metal-organic frameworks (MOFs) by introducing pillared paddlewheel MOF structures into a solution containing dipyridyl linkers. No lateral movement of the layers was observed during this transformation, creating a templating effect from the "parent" structure to the "daughter" structure. A previously unattainable structure was obtained by a two-step synthetic method utilizing the bridging-linker replacement transformation method. Additionally, a bridging-linker insertion was observed when excess linker was used with the 2D MOF structure, inducing an overall 2D to 3D transformation.     

Unveiling 79‐Year‐Old Ixene and Its BN‐Doped Derivative

Polycyclic aromatic hydrocarbons (PAHs) are key components of organic electronics. The electronic properties of these carbon‐rich materials can be controlled through doping with heteroatoms such as B and N, however, few convenient syntheses of BN‐doped PAHs have been reported. Described herein is the rationally designed, two‐step syntheses of previously unknown ixene and BN‐doped ixene (B₂N₂‐ixene), and their characterizations. Compared to ixene, B₂N₂‐ixene absorbs longer‐wavelength light and has a smaller electrochemical energy gap. In addition to its single‐crystal structure, scanning tunneling microscopy revealed that B₂N₂‐ixene adopts a nonplanar geometry on a Au(111) surface. The experimentally obtained electronic structure of B₂N₂‐ixene and the effect of BN‐doping were confirmed by DFT calculations. This synthesis enables the efficient and convenient construction of BN‐doped systems with extended π‐conjugation that can be used in versatile organic electronics applications.     

New Equation for Predicting Pipe Friction Coefficients Using the Statistical Based Entropy Concepts

In general, this new equation is significant for designing and operating a pipeline to predict flow discharge. In order to predict the flow discharge, accurate determination of the flow loss due to pipe friction is very important. However, existing pipe friction coefficient equations have difficulties in obtaining key variables or those only applicable to pipes with specific conditions. Thus, this study develops a new equation for predicting pipe friction coefficients using statistically based entropy concepts, which are currently being used in various fields. The parameters in the proposed equation can be easily obtained and are easy to estimate. Existing formulas for calculating pipe friction coefficient requires the friction head loss and Reynolds number. Unlike existing formulas, the proposed equation only requires pipe specifications, entropy value and average velocity. The developed equation can predict the friction coefficient by using the well-known entropy, the mean velocity and the pipe specifications. The comparison results with the Nikuradse’s experimental data show that the R2 and RMSE values were 0.998 and 0.000366 in smooth pipe, and 0.979 to 0.994 or 0.000399 to 0.000436 in rough pipe, and the discrepancy ratio analysis results show that the accuracy of both results in smooth and rough pipes is very close to zero. The proposed equation will enable the easier estimation of flow rates.     

"Nanoscale zippers" in Gd5(SixGe(1-x))4: symmetry and chemical influences on the nanoscale zipping action

One critical parameter influencing the structural nature of the phase transitions in magnetocaloric materials Gd5(SixGe(1-x))4 is the Si/Ge ratio (x/1-x), because transition temperatures and structures depend crucially on this value. In this study, single-crystal X-ray diffraction indicates that Si and Ge atoms are neither completely ordered nor randomly mixed among the three crystallographic sites for these elements in these structures. Ge atoms enrich the T sites linking the characteristic slabs in these structures, while Si atoms enrich the T sites within them. Decomposition of the total energy into site and bond energy terms provides a rationale for the observed distribution, which can be explained by symmetry and electronegativity arguments. For any composition in Gd5(SixGe(1-x))4, a structure map is presented that will allow for a rapid assessment of the specific structure type.     

Capillary surfaces in a convex cone

We show that a compact embedded hypersurface ${S\subset\mathbb{R}^{n+1}}$ with constant higher-order mean curvature in a convex piecewise smooth cone C which is perpendicular to ?C is part of a hypersphere. Also we prove that an embedded disk type constant mean curvature surface ${S\subset\mathbb{R}^3}$ in a convex polyhedral cone C which makes constant contact angles with ?C is a spherical cap if C has at most five faces. This condition on the number of faces can be dropped if C is a right cone over a regular n-gon and the contact angles are the same on ?S.     

Spectral properties of the layer potentials associated with elasticity equations and transmission problems on Lipschitz domains

We study the invertibility of βI+K and βI+K^′ in L²(∂Ω) for where K,K^′ are double layer potentials related to elasticity equations and Ω is bounded Lipschitz domain in Rn. Consequently, the spectrum on real line lies in . Applications to transmission problems are also presented.     

Signal Intensity for Contrast Enhancement as a Function of the Molarity of Gadolinium-Based MRI Contrast Media

Gadolinium is the central metal that is used as magnetic resonance imaging (MRI) contrast media. Because the metal has toxicity on its own, it causes fibrosis or sclerosis of skin or internal organs, which may lead to disability in joint movement, or even death in the worst case. In the current study, the T ₁ contrast media, Dotarem, was diluted to various molarities to measure the signal intensity of T ₁-weighted images as a function of the molarity. The molarity that showed the maximum measurement value of the signal intensity was examined to determine the proper amount of contrast media injected for the MRI scan. The change in the intensity of the signal from the tumor tissue was determined based on the passage of time after injection. The distribution of the maximum signal intensities depending on the time to repeat showed that the signal distribution had >95% of the maximum values when the dilution concentration was in the range of 0.00095–0.00135 mmol/ml. Thus, it is most desirable when 0.084 mmol/kg (patient weight) of contrast media is injected. In experiments involving tumors 0.084, 0.1, and 0.15 mmol/kg were injected to measure the average signal intensity for each molarity. Compared to the signal intensity at a molarity of 0.084 mmol/kg, the three patient’s signal intensities were measured to increase by 6.2, 7.6, and 5.7% at a molarity of 0.1 mmol/kg, and by 21.4, 18.8, and 17.7% at a molarity of 0.15 mmol/kg. However, according to the correlation between the contract media injection amount and the signal intensity increase, the contrast effect was not improved much despite the increase in the injection amount by 19.04 and 78.5%. This study revealed that the optimal level of contrast media of 0.084 mmol/kg body weight should be administered by considering the body weight of patients and the effects of media to reduce side effects of a high dose of contrast media and to prevent environmental pollution.     

Charge exchange ionization in collision cells as a method to detect the presence of long-lived excited electronic states of polyatomic ions

Charge exchange ionization in collision cells installed in a double focusing mass spectrometer with reversed geometry has been used to detect the presence of a long-lived excited electronic state of benzene ion. In particular, the first collision cell located between the ion source and the magnetic sector was modified to serve as an ion source for the reagent ion generated by charge exchange with the primary ion. Strong reagent ion signals were observed when the ionization energies of the reagents (1,3-C4H6, CS2, CH3Cl) were lower than the recombination energy (approximately 11.5 eV) of the excited state benzene ion, while the signals were negligible for reagents (CH3F,CH4) with higher ionization energy. The fact that a strong signal is observable only for electronically exoergic charge exchange is useful for detecting the presence of a long-lived electronically excited state.     

Fine Tuning of Vesicle Assembly and Properties Using Dual Hydrophilic Triblock Copolypeptides

The design, synthesis, and self‐assembly of the first dual hydrophilic triblock copolypeptide vesicles, ${\rm R}_{m}^{{\rm H}} {\rm E}_{n} {\rm L}_{o} $ and ${\rm K}_{m}^{{\rm P}} {\rm R}_{n}^{{\rm H}} {\rm L}_{o} $ , is reported. Variation of the two distinct hydrophilic domains is used to tune cellular interactions without disrupting the self‐assembled structure. The aqueous self‐assemblies of these triblock copolypeptides in water are characterized using microscopy and DLS. Cell culture studies are used to evaluate cytotoxicity as well as intracellular uptake of the vesicles. The ability of polypeptides to incorporate ordered chain conformations that direct self‐assembly, combined with the facile preparation of functional, multiblock copolypeptide sequences of defined lengths, allow the design of vesicles attractive for development as drug carriers.