Analytical and numerical computation of error propagation of model parameters

Linear and nonlinear regression analyses based on the least-squares method play a fundamental role in the evaluation of scientific data. A large number of valuable papers have dealt with various applications of the least-squares method in the chemical literature. They, however, usually contain tremendous formulas for computing the error estimates of the estimated parameters. This paper presents a simple numerical solution based on the well-known simplex method to this problem. Elaborate enzyme kinetic data published earlier have been chosen to test the simplex method extended with error estimation. The capability of the numerical method is demonstrated by the revision of the originally calculated error propagation. Our program might prove useful in handling either chemical or biological data.     

pH-oscillations in a closed chemical system of CaSO3-H2O2-HCO3(-)

Long-lasting large amplitude periodic change of the pH is measured in an aqueous suspension of CaSO(3)-H(2)O(2)-HCO(3)(-) at 2.0-10.0 °C in a closed reactor. The amplitude can be as large as 2 pH units between pH 5 and 7. The observed phenomenon is explained and simulated by taking into account a slow dissolution of CaSO(3), which serves as a continuous supply of HSO(3)(-) for a H(+)-producing autocatalytic composite reaction between H(2)O(2) and HSO(3)(-). Protonation of HCO(3)(-) to form CO(2) in a reversible reaction provides for the necessary negative feedback in [H(+)].     

A functional equation involving comparable weighted quasi-arithmetic means

We discuss the functional equation $$f(M(x,y))=f(N(x,y)) \qquad (x,y\in I) $$ where I is a nonvoid open subinterval of the set of real numbers ?, f:?I??? is an unknown function, and M, N are weighted quasi-arithmetic means on?I. Our typical assumption will be that M and N are comparable. Complete solution will be presented under the additional supposition that f is the product of the generating functions of?M and?N, respectively.     

Characterization of thermal transport in micro/nanoscale wires by steady-state electro-Raman-thermal technique

In this work, a novel steady-state electro-Raman-thermal (SERT) technique is developed to characterize the thermal transport in one-dimensional micro/nanoscale materials. The SERT technique involves steady-state joule heating of a suspended sample and measuring its middle point temperature based on the temperature dependence of the Raman shift peak intensity. The thermal conductivity is determined from a linear fitting of the temperature against heating power. Multi-wall carbon nanotube bundles are characterized using the SERT technique to verify its measurement capacity. As it does not need to track the transient process of heat transfer, the SERT technique has the great potential for measuring short materials down to nm long.     

Nonequilibrium interlayer transport in pulsed laser deposition

We use time-resolved surface x-ray diffraction measurements with microsecond range resolution to study the growth kinetics of pulsed laser deposited . Time-dependent surface coverages corresponding to single laser shots were determined directly from crystal truncation rod intensity transients. Analysis of surface coverage evolution shows that extremely fast nonequilibrium interlayer transport, which occurs concurrently with the arrival of the laser plume, dominates the deposition process. A much smaller fraction of material, which is governed by the dwell time between successive laser shots, is transferred by slow, thermally driven interlayer transport processes.     

The effect of carboxylic acids on the oxidation of coated iron oxide nanoparticles

⁵⁷Fe Mössbauer spectroscopy, XRD, and TEM were used to investigate the effect of mandelic- and salicylic acid coatings on the iron oxide nanoparticles. These two carboxylic acids have similar molecules size and stoichiometry, but different structure and acidity. Significant differences were observed between the Mössbauer spectra of samples coated with mandelic acid and salicylic acid. These results indicate that the occurrence of iron microenvironments in the mandelic- and salicylic acid-coated iron oxide nanoparticles is different. The results can be interpreted in terms of the influence of the acidity of carboxylic acids on the formation, core/shell structure, and oxidation of coated iron oxide nanocomposites.     

Complexes of Bifunctional DO3A-N-(α-amino)propinate Ligands with Mg(II), Ca(II), Cu(II), Zn(II), and Lanthanide(III) Ions: Thermodynamic Stability,Formation and Dissociation Kinetics,and Solution Dynamic NMR Studies

The thermodynamic, kinetic, and structural properties of Ln³⁺ complexes with the bifunctional DO3A-ACE⁴⁻ ligand and its amide derivative DO3A-BACE⁴⁻ (modelling the case where DO3A-ACE⁴⁻ ligand binds to vector molecules) have been studied in order to confirm the usefulness of the corresponding Gd³⁺ complexes as relaxation labels of targeted MRI contrast agents. The stability constants of the Mg²⁺ and Ca²⁺ complexes of DO3A-ACE⁴⁻ and DO3A-BACE⁴⁻ complexes are lower than for DOTA⁴⁻ and DO3A³⁻, while the Zn²⁺ and Cu²⁺ complexes have similar and higher stability than for DOTA⁴⁻ and DO3A³⁻ complexes. The stability constants of the Ln(DO3A-BACE)⁻ complexes increase from Ce³⁺ to Gd³⁺ but remain practically constant for the late Ln³⁺ ions (represented by Yb³⁺). The stability constants of the Ln(DO3A-ACE)⁴⁻ and Ln(DO3A-BACE)⁴⁻ complexes are several orders of magnitude lower than those of the corresponding DOTA⁴⁻ and DO3A³⁻ complexes. The formation rate of Eu(DO3A-ACE)⁻ is one order of magnitude slower than for Eu(DOTA)⁻, due to the presence of the protonated amine group, which destabilizes the protonated intermediate complex. This protonated group causes the Ln(DO3A-ACE)⁻ complexes to dissociate several orders of magnitude faster than Ln(DOTA)⁻ and its absence in the Ln(DO3A-BACE)⁻ complexes results in inertness similar to Ln(DOTA)⁻ (as judged by the rate constants of acid assisted dissociation). The ¹H NMR spectra of the diamagnetic Y(DO3A-ACE)⁻ and Y(DO3A-BACE)⁻ reflect the slow dynamics at low temperatures of the intramolecular isomerization process between the SA pair of enantiomers, R-Λ(λλλλ) and S-Δ(δδδδ). The conformation of the C_α-substituted pendant arm is different in the two complexes, where the bulky substituent is further away from the macrocyclic ring in Y(DO3A-BACE)⁻ than the amino group in Y(DO3A-ACE)⁻ to minimize steric hindrance. The temperature dependence of the spectra reflects slower ring motions than pendant arms rearrangements in both complexes. Although losing some thermodynamic stability relative to Gd(DOTA)⁻, Gd(DO3A-BACE)⁻ is still quite inert, indicating the usefulness of the bifunctional DO3A-ACE⁴⁻ in the design of GBCAs and Ln³⁺-based tags for protein structural NMR analysis.     

Experimental Study of Halloysite Nanofluids in Pool Boiling Heat Transfer

Halloysite nanotube (HNT) which is cheap, natural, and easily accessible 1D clay, can be used in many applications, particularly heat transfer enhancement. The aim of this research is to study experimentally the pool boiling heat transfer (PBHT) performance of novel halloysite nanofluids at atmospheric pressure condition from typical horizontal heater. The nanofluids are prepared from halloysite nanotubes (HNTs) nanomaterials-based deionized water (DI water) with the presence of sodium hydroxide (NaOH) solution to control pH = 12 to obtain stable nanofluid. The nanofluids were prepared with dilute volume concentrations of 0.01–0.5 vol%. The performance of PBHT is studied via pool boiling curve and pool boiling heat transfer coefficient (PBHTC) from the typical heater which is the copper horizontal tube with a thickness of 1 mm and a diameter of 22 mm. The temperatures of the heated tube surface are measured to obtain the PBHTC. The results show an improvement of PBHTC for halloysite nanofluids compared to the base fluid. At 0.05 vol% concentration, HNT nanofluid has the best enhancement of 5.8% at moderate heat flux (HF). This indicates that HNT is a potential material in heat transfer applications.