Detailed peak fitting analysis of the Zn 2p photoemission spectrum for metallic films and its initial oxidation stages

The metallic Zn 2p photoemission spectra hold a complex background that requires individual assignment of Shirley background for each peak comprising the spectra. For this reason, a close fit requires the use of the Shirley‐Vegh‐Salvi‐Castle background‐type under the active background approach. We found that the intensity of the plasmon peaks and their associated background cannot be described through existing energy loss (intrinsic and extrinsic) formalisms. We also analyzed the Zn 2p and O 1s spectra for the initial stages of oxide formation at various oxygen exposures. We found that the composition of the oxide layer is ZnO_1.00±0.10 for all exposures, suggesting that our assessment of the primary function of metallic Zn is accurate and can be employed for quantitative studies. We also present a set of parameters to accurately fit and resolve the metallic and oxide Zn 2p peaks.     

Dependence of emulsion stability on particle size: Relative importance of drop concentration and destabilization rate on the half lifetimes of O/W nanoemulsions

This study reports the behavior of ionic dodecane-in-water nanoemulsions in distinct salt concentrations. Systems of smaller particle size (74–285 nm) were synthesized by a sudden dilution of an equilibrated mixture. Larger size systems (384–670 nm) were obtained from a set of formerly smaller nanoemulsions that evolved unperturbed for 2 weeks. Characteristic destabilization times for flocculation, coalescence, and Ostwald ripening were evaluated. In general, it was observed that stability increases with drop size. However, this size dependence is largely the consequence of the lower particle concentration of the coarser emulsions.     

Multifunctional Benzothiadiazole-Based Small Molecules Displaying Solvatochromism and Sensing Properties toward Nitroarenes,Anions, and Cations

Aryl or heteroaryl 5-substituted imidazo-benzothiadiazole derivatives were synthesized and shown to display remarkable solvatofluorochromism and selectively sense mercury(II) cations, acetate anions, and nitroaromatic derivatives, with discrimination between p-nitrophenol and picric acid. These novel sensors are of importance these days, as the detection of explosives is a high priority in issues of national security and environmental protection. To determine the ion binding properties of the sensors, their absorption and fluorescence emission spectra upon binding different cations and anions were compared. Significant shifts in the spectra were only observed for mercury(II) and acetate. The binding of these two ions was further studied using ¹H NMR. The binding properties of different nitroaromatic compounds were also determined, and the results showed the importance of the presence of a phenol group in the guest molecule. Specifically, the two sensors were shown to discriminate between p-nitrophenol and picric acid. Finally, the mechanism of fluorescence quenching upon addition of nitrophenols was determined by computational methods.     

Evaluation of a multi‐fiber exchange solid‐phase microextraction system and its application to on‐site sampling

Until recently, multiple solid‐phase microextraction fibers could not be automatically desorbed in a single gas chromatographic sequence without manual intervention from an operator. This drawback had been a critical issue, particularly during the analysis of numerous on‐site samples taken with various fiber assemblies. Recently, a Multi‐Fiber Exchange system, designed to overcome this flaw found in other commercially available autosamplers, was released. In the current research, a critical evaluation of the Multi‐Fiber Exchange system performance in terms of storage stability and long‐term operation is presented. It was established in the course of our research that the Multi‐Fiber Exchange system can operate continuously and precisely for multiple extraction/injection cycles. However, when the effect of residence time of commercial fibers on the Multi‐Fiber Exchange tray was evaluated, results showed that among the evaluated fiber coatings, Carboxen/polydimethylsiloxane was the only coating capable of efficient storage on the tray for up to 24 h after field sampling without suffering significant loss of analytes (≤10% for benzene, toluene, ethylbenzene, o‐xylene, decane, and limonene). Additionally, the system capability for high‐throughput analysis was demonstrated by the unattended desorption of multiple fibers after on‐site sampling of toluene, indoor air levels, in a polymer synthesis lab.     

Configuration‐Dependent Photoinduced Electron Transfer in Diastereomeric Naphthalene‐Amino‐Naphthalene Triads

Novel diastereomeric triads containing two naphthalene chromophores have been designed in which an electron‐donating amine moiety is covalently integrated into the connecting bridge. Photophysical studies (steady‐state and time‐resolved fluorescence) in solvents of different polarity have been performed. A remarkable stereodifferentiation in the intramolecular fluorescence quenching was found in acetonitrile. Laser flash photolysis gave rise to naphthalene‐derived radical cations, which were also quenched by the amine with an even higher degree of stereodifferentiation. The results are in agreement with thermodynamic estimations and indicate that photoinduced electron transfer (PET) is the main quenching pathway. Furthermore, theoretical calculations have allowed us to explain the experimentally observed stereodifferentiation in PET quenching.     

An approximate global solution of Einstein’s equation for a rotating compact source with linear equation of state

We use analytic perturbation theory to present a new approximate metric for a rigidly rotating perfect fluid source with equation of state (EOS) $\epsilon +(1-n)p=\epsilon _0$ . This EOS includes the interesting cases of strange matter, constant density and the fluid of the Wahlquist metric. It is fully matched to its approximate asymptotically flat exterior using Lichnerowicz junction conditions and it is shown to be a totally general matching using Darmois–Israel conditions and properties of the harmonic coordinates. Then we analyse the Petrov type of the interior metric and show first that, in accordance with previous results, in the case corresponding to Wahlquist’s metric it can not be matched to the asymptotically flat exterior. Next, that this kind of interior can only be of Petrov types I, D or (in the static case) O and also that the non-static constant density case can only be of type I. Finally, we check that it can not be a source of Kerr’s metric.     

Rigid motions and generalized Newtonian gravitation

In an effort to contribute to a better understanding of General Relativity, here we lay the foundations of generalized Newtonian gravity, which unifies inertial forces and gravitational fields. We also formulate a kind of equivalence principle for this generalized Newtonian theory. Finally, we prove that the theory we propose here can be obtained as the non-relativistic limit of General Relativity.     

Wahlquist’s metric versus an approximate solution with the same equation of state

We compare an approximation of the singularity-free Wahlquist exact solution with a stationary and axisymmetric metric for a rigidly rotating perfect fluid with the equation of state $\mu +3p=\mu _0$ , a sub-case of a global approximate metric obtained recently by some of us. We see that to have a fluid with vanishing twist vector everywhere in Wahlquist’s metric the only option is to let its parameter $r_0\rightarrow 0$ and using this in the comparison allows us in particular to determine the approximate relation between the angular velocity of the fluid in a set of harmonic coordinates and $r_0$ . Through some coordinate changes we manage to make every component of both approximate metrics equal. In this situation, the free constants of our metric take values that happen to be those needed for it to be of Petrov type D, the last condition that this fluid must verify to give rise to the Wahlquist solution.     

Flavor changing neutral currents and a Z′

We consider a non-universal Z′ that affects primarily the third generation fermions as an example of new physics associated with the top-quark. We first discuss constraints on the mass and coupling strength of such a Z′. We then turn our attention to the flavor changing neutral currents (FCNC) present in the model. We discuss the experimental constraints and their implications. We propose an ansatz to understand the smallness of the FCNC in terms of the CKM matrix.     

Saturation in Linear Optimization

In a solvable linear optimization problem, a constraint is saturated if it is binding at a certain optimal solution and it is weakly saturated if it is binding at a proper subset of the optimal set. Nonsaturation and weak saturation can be seen as redundancy phenomena in the sense that the elimination of a finite number of these constraints preserves the value of the given problem. We consider also the effect of sufficiently small perturbations of the cost coefficients in the classification of a given constraint as either saturated or nonsaturated.