Exact quantum,quasiclassical forward and reverse reaction probabilities for a colldmear asymmetric model reaction

Detailed quasiclassical and time-independent quantum reaction probabilities are given for a surface on which large discrepancies between quasiclassical and wavepacket results have previously been found. The quasiclassical results are shown to agree relatively reasonably with the oscillation-averaged time-independent quantum ones if the quasiclassical reverse probabilities are chosen in the threshold region.     

Electronic absorption spectroscopy of cooled supersonic expansions: dynamics of the 1B1u state of trans-butadiene

An ultraviolet absorption technique is developed for studying molecules cooled in a supersonic expansion. In this experiment, the temperature-dependent contribution to the diffuseness of electronically excited states is reduced for CS₂ and butadiene. The broadness of the spectral features of the butadiene ¹B_1u state is independent of temperature     

Nanocarriers as Active Ingredients Enhancers in the Cosmetic Industry—The European and North America Regulation Challenges

“Flawless skin is the most universally desired human feature” is an iconic statement by Desmond Morris. Skin indicates one´s health and is so important that it affects a person’s emotional and psychological behavior, these facts having propelled the development of the cosmetics industry. It is estimated that in 2023, this industry will achieve more than 800 billion dollars. This boost is due to the development of new cosmetic formulations based on nanotechnology. Nanocarriers have been able to solve problems related to active ingredients regarding their solubility, poor stability, and release. Even though nanocarriers have evident benefits, they also present some problems related to the high cost, low shelf life, and toxicity. Regulation and legislation are two controversial topics regarding the use of nanotechnology in the field of cosmetics. In this area, the U.S. FDA has taken the lead and recommended several biosafety studies and post-market safety evaluations. The lack of a global definition that identifies nanomaterials as a cosmetic ingredient is a hindrance to the development of global legislation. In the EU, the legislation regarding the biosafety of nanomaterials in cosmetics is stricter. “The cost is not the only important issue, safety and the application of alternative testing methods for toxicity are of crucial importance as well”.     

The advantage of indices of dispersion in queueing approximations

A recent robust queueing approximation for open queueing networks exploits partial characterizations of each arrival process by its rate and index of dispersion for counts (IDC), which is a scaled version of the variance–time curve. Even though only means and variances (as functions of time) are involved, we show that the IDC provides a basis for more accurate approximations than traditional two-moment partial characterizations. For the $GI∕GI∕1$ queue, this approach applied to the arrival and service processes fully characterizes the model.     

Stable isotopic and geochemical variability within shallow groundwater beneath a hardwood hammock and surface water in an adjoining slough (Everglades National Park,Florida, USA)

Data from a 10-month monitoring study during 2007 in the Everglades ecosystem provide insight into the variation of δ¹⁸O, δD, and ion chemistry in surface water and shallow groundwater. Surface waters are sensitive to dilution from rainfall and input from external sources. Shallow groundwater, on the other hand, remains geochemically stable during the year. Surface water input from canals derived from draining agricultural areas to the north and east of the Everglades is evident in the ion data. δ¹⁸O and δD values in shallow groundwater remain near the mean of?2.4 and?12 ‰, respectively. ¹⁸O and D values are enriched in surface water compared with shallow groundwater and fluctuate in sync with those measured in rainfall. The local meteoric water line (LMWL) for precipitation is in close agreement with the global meteoric water line; however, the local evaporation line (LEL) for surface water and shallow groundwater is δ D=5.6 δ¹⁸O+1.5, a sign that these waters have experienced evaporation. The intercept of the LMWL and LEL indicates that the primary recharge to the Everglades is tropical cyclones or fronts. δ deuterium to δ¹⁸O excess (D_ex values) generally reveal two moisture sources for precipitation, a maritime source during the fall and winter (D _ex>10 ‰) and a continental-influenced source (D _ex<10 ‰) in the spring and summer.     

Complete integrability in statistical mechanics and the Yang-Baxter equations

In this paper we give a differential formulation of the Yang-Baxter equations. The concept of “exactly solvable” for lattice models is related to the Frobenius concept of complete integrability. These ideas are illustrated in the context of the Baxter model.     

Dimer fluorescence of some β-dicarbonyl compounds

Luminescence and absorption spectra of β-dicarbonyl compounds have been studied over the concentration range 10^?7–10^?2 M. The temperature dependence of the emission maxima was followed from 10 to 70°C. The emission and long-wave absorption at high concentrations is related to dimers of the enol tautomer. The association constant and change in free energy are evaluated.     

Interactions between two spheres falling along their line of centers in a viscoelastic fluid

An experimental investigation is presented in which the distance between two identical spheres falling along their line of centers in a viscoelastic fluid is determined as a function of time. It is found, for all five experimental fluids, that for small initial separations of the spheres, the two spheres eventually converge. However, for large initial separations, the two spheres eventually diverge. This leads to the definition of a critical initial separation distance. From this quantity a characteristic time can be derived for the two sphere fluid system which depends solely upon fluid properties. The implications of this study for suspension rheology are discussed.     

Classifying patterns by automorphism group: An operator theoretic approach

This paper considers the problem of enumerating the elements of a set under a group action with a given automorphism group. The problem is approached from a linear algebraic point of view, with a class of identities obtained by applications of appropriate linear operators and functionals. A variety of new counting and enumerating results are obtained in this manner, and the connections to the recent work of de Bruijn, Foulkes, Sheehan, Stockmeyer and White are defined. Included among the new results are general formulas for enumerating patterns with a given automorphism group when a group acts on the range and domain of a finite function space. In this case, the multilinear computing techniques developed by Williamson are exploited.