Size‐Dependence of the Melting Temperature of Individual Au Nanoparticles

Nanoparticles have an immense importance in various fields, such as medicine, catalysis, and various technological applications. Nanoparticles exhibit a significant depression in melting point as their size goes below ≈10 nm. However, nanoparticles are frequently used in high temperature applications such as catalysis where temperatures often exceed several 100 degrees which makes it interesting to study not only the melting temperature depression, but also how the melting progresses through the particle. Using high‐resolution transmission electron microscopy, the melting process of gold nanoparticles in the size range of 2–20 nm Au nanoparticles combined with molecular dynamics studies is investigated. A linear dependence of the melting temperature on the inverse particle size is confirmed; electron microscopy imaging reveals that the particles start melting at the surface and the liquid shell formed then rapidly expands to the particle core.     

Examining the possibilities of applying high pressure to preserve yoghurt supplemented with probiotic bacteria

Natural yoghurt was subject to pressures of 200 and 250 MPa/4 and 18°C/15 min, after which milk-activated inocula of Lactobacillus acidophilus and Bifidobacterium sp. were added. The yoghurts were stored for 4 weeks at refrigeration temperature. After preparation and each week of storage, the count of bacteria, acidity, antibacterial property and an organoleptic assessment was determined. The highest survival rate was demonstrated by the bacteria of Lactobacillus delbrueckii ssp. bulgaricus, Streptococcus thermophilus and Bifidobacterium sp. in the yoghurt pressurised 200 MPa/15min at 4°C. Acidity increases in the control yoghurts were higher than in the pressurised ones. Pressurised yoghurts demonstrated weaker antibacterial effect in comparison to control yoghurts. Slight changes in the smell and taste were observed after pressurisation. Yoghurts pressurised at 18°C were characterised by more favourable organoleptic properties. Better conciseness of the curd and lower whey seep out were observed in pressurised yoghurt.     

Chiral mirror and optical resonator designs for circularly polarized light: suppression of cross-polarized reflectances and transmittances

A left-handed chiral sculptured thin film (STF) that reflects strongly at the wavelength of the circular Bragg resonance tends to partially convert the handedness of incident LCP (left-circularly-polarized) light to RCP (right-circularly-polarized). We show that the cross-polarized component of the reflected RCP beam can be eliminated by interference with an additional RCP beam that is reflected at the interface of an isotropic cover and an AR (antireflecting) layer. For best results the refractive index and thickness of the AR layer need to accommodate a phase change on reflection that occurs at the chiral film. Effective suppression of the reflectances R_RR, R_RL, R_LR and the transmittances T_RL, T_LR can be achieved by sandwiching the chiral reflector between such amplitude and phase-matched AR coatings. Co-polarized chiral reflectors of this type may form efficient handed optical resonators. For LCP light the optical properties of such a handed resonator are formally the same as the properties of the isotropic passive or active Fabry–Perot resonators, but the handed resonator is transparent to RCP light.     

Inner hair cell loss and steady-state potentials from the inferior colliculus and auditory cortex of the chinchilla

Steady-state evoked potentials were measured from unanesthetized chinchillas both before and after carboplatin-induced selective inner hair cell loss. Recordings were made from both the inferior colliculus (IC) and the auditory cortex (AC). The steady-state potential was measured in the form of the envelope following response (EFR), obtained by presenting a two-tone stimulus (f1 = 2000 Hz; f2 = 2020, 2040, 2080, 2160, or 2320 Hz), and measuring the magnitude of the Fourier coefficient at the f2-f1 difference frequency. From the IC, precarboplatin, EFR amplitude vs difference tone frequency showed a bandpass pattern, with maximum amplitude at either 160 or 80 Hz, depending upon stimulus level. Postcarboplatin, the preferred difference frequency was 80 Hz for all stimulus levels. From the AC, EFR amplitude versus difference tone frequency also showed a bandpass pattern, with the maximum amplitude at 80 Hz both pre- and postcarboplatin. EFR amplitude from the IC was decreased for some conditions postcarboplatin, while the amplitude from the AC showed no significant change.     

LP formulations of the shortest path tree problem

Based on a pair of primal-dual LP formulations of the shortest path tree problem, the first algorithmic approach to reoptimizing the shortest paths subject to changes in the edge weights was proposed by S. Pallottino and M.G. Scutellá in 2003. We shall here focus solely on their introductory sections, propose some simplifications of the models considered, and finally relate the resulting models to the presentation of single-source shortest path problems in textbooks treating this subject with but limited or no reference to LP.Received: April 2004, Revised: August 2004, MSC classification: 90C05, 90C35, 90B10 Dedicated to the memory of Stefano Pallottino     

The role of excited species in ultraviolet-laser materials ablation III. Non-stationary ablation of organic polymers

The role of non-stationary effects in nano-second ultraviolet (UV) excimer-laser ablation of organic polymers is discussed. The model includes reversible changes in absorption related to darkening and bleaching effects. Comparison of calculations and experimental data for polyimide demonstrates that the photophysical model describes the ablation kinetics quite well.     

Successions in Words and Compositions

We consider words over the alphabet [k] = {1, 2, . . . , k}, k ?? 2. For a fixed nonnegative integer p, a p-succession in a word w ₁ w ₂ . . . w _n consists of two consecutive letters of the form (w _i , w _i ?+ p), i = 1, 2, . . . , n ? 1. We analyze words with respect to a given number of contained p-successions. First we find the mean and variance of the number of p-successions. We then determine the distribution of the number of p-successions in words of length n as n (and possibly k) tends to infinity; a simple instance of a phase transition (Gaussian-Poisson-degenerate) is encountered. Finally, we also investigate successions in compositions of integers.     

Global estimates of fundamental solutions for higher-order Schr?dinger equations

In this paper we first establish global pointwise time-space estimates of the fundamental solution for Schr?dinger equations, where the symbol of the spatial operator is a real non-degenerate elliptic polynomial. Then we use such estimates to establish related L ^p ?CL ^q estimates on the Schr?dinger solution. These estimates extend known results from the literature and are sharp. This result was lately already generalized to a degenerate case (cf. [4]).     

A Hydrocarbon-sensitized Argon Ionization Detector for the Detection of Inorganic Compunds

Noble gas ionization detectors make it possible to determine inorganie trace components in gases. Among the several modes of operation of these detectors the hydrocarbon-sensitized argon detector is a farourable compromise with regard to the relation of the expense to the attainable detection limit. The suitability of this detector for the determination of H₂, O₂, N₂, CH₄ and CO₂, in pure gases is shown.     

Bessel and annular beams for materials processing

Non‐Gaussian beam profiles such as Bessel or annular beams enable novel approaches to modifying materials through laser‐based processing. In this review paper, properties, generation methods and emerging applications for non‐conventional beam shapes are discussed, including Bessel, annular, and vortex beams. These intensity profiles have important implications in a number of technologically relevant areas including deep‐hole drilling, photopolymerization and nanopatterning, and introduce a new dimension for materials optimization and fundamental studies of laser‐matter interactions.