Kinetic study of the Ce(III)‐, Mn(II)‐ or Fe(phen)32+‐catalyzed Belousov‐Zhabotinsky reaction with 2‐ketoglutaric acid

The Belousov‐Zhabotinsky (BZ) reaction of bromate ion with 2‐ketoglutaric acid (KGA) in aqueous sulfuric acid catalyzed by Ce(III), Mn(II), or Fe(phen)₃²⁺ ion exhibits sustained barely damped oscillations under aerobic conditions. In general, the reaction oscillates without an induction period. Fe(phen)₃²⁺ ion behaves differently from Ce(III) and Mn(II) ions in catalyzing this oscillating system. The gem‐diol form of KGA exhibits different behavior from that of the keto form of KGA in the BZ reaction. The kinetics and mechanism of the reaction of KGA with Ce(IV), Mn(III), or Fe(phen)₃³⁺ ion was investigated. The order of relative reactivities of metal ions toward reaction with KGA is Mn(III) > Ce(IV) ≫ Fe(phen)₃³⁺. Experimental results are rationalized. © 2001 John Wiley & Sons, Inc. Int J Chem Kinet 33: 101–107, 2001     

Kinetic study of the Ce(III)‐, Mn(II)‐, or ferroin‐catalyzed Belousov‐Zhabotinsky reaction with pyruvic acid

The Ce(III)‐, Mn(II)‐, or ferroin (Fe(phen)₃²⁺)‐catalyzed reaction of bromate ion and pyruvic acid (PA) or its dimer exhibits oscillatory behavior. Both the open‐chain dimer (parapyruvic acid, γ‐methyl‐γ‐hydroxyl‐α‐keto‐glutaric acid, DPA1) and the cyclic‐form dimer (α‐keto‐γ‐valerolactone‐γ‐carboxylic acid, DPA2) show more sustained oscillations than PA monomer. Ferroin behaves differently from Ce(III) or Mn(II) ion in catalyzing these oscillating systems. The kinetics of reactions of PA, 3‐brompyruvic acid (BrPA), DPA1, or DPA2 with Ce(IV), Mn(III), Fe(phen)₃³⁺ ion were investigated. The order of relative reactivity of pyruvic acids toward reaction with Ce(IV), Mn(III), or Fe(phen)₃³⁺ ion is DPA2 > DPA1 > BrPA > PA and that of metal ions toward reaction with pyruvic acids is Mn(III) > Ce(IV) > Fe(phen)₃³⁺. The rates of bromination reactions of pyruvic acids are independent of the concentration of bromine and the order of reactivity toward bromination is (DPA1, DPA2) > BrPA > PA. Experimental results are rationalized. © 2000 John Wiley & Sons, Inc. Int J Chem Kinet 32: 408–418, 2000     

Photoacoustic Imaging of Nanoparticle Transport in the Kidneys at High Temporal Resolution

Noninvasive monitoring of kidney elimination of engineered nanoparticles at high temporal and spatial resolution will not only significantly advance our fundamental understandings of nephrology on the nanoscale, but also aid in the early detection of kidney disease, which affects more than 10 % of the worldwide population. Taking advantage of strong NIR absorption of the well‐defined Au₂₅(SG)₁₈ nanocluster, photoacoustic (PA) imaging was used to visualize its transport in situ through the aorta to the renal parenchyma and its subsequent filtration into the renal pelvis at a temporal resolution down to 1 s. High temporal and spatial resolution imaging of Au₂₅(SG)₁₈ kidney elimination allowed the accurate quantification of the glomerular filtration rate (GFR) of individual kidneys in normal and pathological conditions, broadening the biomedical applications of engineered nanoparticles in preclinical kidney research.     

Frequency‐sensitive switching control effect induced by two‐photon resonance in an EIT‐based layered medium

The optical response of an atomic vapor can be coherently manipulated by tunable quantum interference occurring in atomic transition processes. A periodic layered medium whose unit cells consist of a dielectric and an EIT (electromagnetically induced transparency) atomic vapor is designed for light propagation manipulation. Such an EIT‐based periodic layered medium exhibits a flexible frequency‐sensitive optical response, where a very small change in probe frequency can lead to a drastic variation of reflectance and transmittance. As the destructive quantum interference relevant to two‐photon resonance arises in EIT atoms interacting with both control and probe fields, the controllable optical processes that depend sensitively on the external control field will take place in this EIT‐based periodic layered medium. Such a frequency‐sensitive and field‐controlled optical behavior of reflection and transmission in the EIT photonic crystal can be applicable to designs of new devices such as photonic switches, photonic logic gates and photonic transistors, where one laser field can be controlled by the other one, and would have potential applications in the areas of integrated optical circuits and other related techniques (e.g., all‐optical instrumentations).     

Line transversals to blown up closed balls

The number ?? _d (k) is defined as the minimum ???>?0 such that the following holds: For any finite family ${\mathcal {F}=\{B_1,B_2, \ldots , B_n\}}$ of closed balls in ${{\mathbb{R}}^d}$ such that every k elements of ${\mathcal {F}}$ have a common line transversal, the elements of the blown up family ${\lambda\mathcal {F}=\{\lambda B_1,\lambda B_2, \ldots , \lambda B_n\}}$ have a common line transversal. In this paper we show that ${\lambda_d(d+1)\leq4, \lambda_2(4)\leq 2\sqrt 2}$ and ??₂(3)?<?2.88.     

Line Transversals to Translates of a Convex Body

Let K be a convex body in the plane. Define λ(K,t) as the smallest number satisfying the following: if F\mathcal{F} is any family of translates of K such that every t members of F\mathcal{F} have a common transversal, then all the members of l(K,t)F\lambda(K,t)\mathcal{F} have a common transversal. We give bounds for λ(K,3) and λ(K,4) for a general convex figure K. In particular, we obtain that λ(K,3)≤1.79 when K is the Euclidean disc.     

Protein–ligand interaction of T. cruzi trans-sialidase inhibitors: a docking and QM/MM MD study

The trans-Sialidase from Trypanosoma cruzi (TcTS) might be a key enzyme in search of new and more effective anti-Trypanosoma cruzi agents. In this report, molecular docking and quantum mechanical/molecular mechanical (QM/MM) molecular dynamics (MD) simulations were employed to determine the binding mode of the three TcTS inhibitors, two quinolinones derivatives (DHQ and THQ) and DANA. The results show that the sulfone group from THQ plays an important role in the protein-inhibitor interactions. In addition, a detailed analysis of the interactions of these inhibitors with key residues inside the binding pocket of TcTS has been carried out using AM1/MM. The residues Asp59, Asp247, Arg35, Arg245, and Arg314 are appointed as key residues to affinity energy of the complexes studied. Finally, the B3LYP/MM and AM1/MM methods were used to calculate global interaction energy, in order to understand the potential of these inhibitors. Among the inhibitors studied, THQ is confirmed as the most efficient one for inhibiting TcTS.     

Preparation,spectroscopic, and electrochemical characterization of metal(II) complexes with Schiff base ligands derived from chitosan: correlations of redox potentials with Hammett parameters

The chitosan–(Fe(II), Co(II), and Cu(II)) complexes were prepared by mixing chitosan (Chi) powder with a salicylaldehyde (Sal, 5-hydrogen (–H)) and their 5-bromo (–Br), 5-chloro (–Cl), 5-methoxy (–OCH₃), 5-fluoro (–F), 5-methyl (–CH₃), and 5-nitro (–NO₂) derivatives (groups R) and mixing these with FeCl₂ and CuCl₂ in ethanol and with Co(CH₃COO)₂ solutions in butanol at 80 °C over 8 h in heterogeneous phase, followed by extraction with ethanol and butanol, respectively. The complexes were characterized by FTIR and UV–vis spectroscopy, elemental analysis, and cyclic voltammetry. A linear correlation between the metal formal potential versus the Hammett parameters of the substituents was observed. The electron-withdrawing groups shift the redox potential to positive values, as a result of lowering the energy of the highest occupied molecular orbital. The formal potential was used as a measurement for the driving force of chitosan complexes for redox reactions.     

Slicing Convex Sets and Measures by a Hyperplane

Given convex bodies K ₁,…,K _d in ℝ ^d and numbers α ₁,…,α _d ∈[0,1], we give a sufficient condition for existence and uniqueness of an (oriented) halfspace H with Vol (H∩K _i )=α _i ⋅Vol K _i for every i. The result is extended from convex bodies to measures.     

A variational approach to norm attainment of some operators and polynomials

If X is an Asplund space, then every uniformly continuous function on Bx＊ which is holomorphic on the open unit ball, can be perturbed by a w＊ continuous and homogeneous polynomial on X＊ to obtain a norm attaining function on the dual unit ball. This is a consequence of a version of Bourgain-Stegall＇s variational principle. We also show that the set of N-homogeneous polynomials between two Banach spaces X and Y whose transposes attain their norms is dense in the corresponding space of N-homogeneous polynomials. In the case when Y is the space of Radon measures on a compact K, this result can be strengthened.