A random telegraph signal of Mittag-Leffler type

A general method is presented to explicitly compute autocovariance functions for non-Poisson dichotomous noise based on renewal theory. The method is specialized to a random telegraph signal of Mittag-Leffler type. Analytical predictions are compared to Monte Carlo simulations. Non-Poisson dichotomous noise is non-stationary and standard spectral methods fail to describe it properly as they assume stationarity.     

Incorporation of smooth spherical bodies in the Lattice Boltzmann method

A method to simulate bodies suspended in a Lattice Boltzmann solvent is proposed. It is based on a generalized reaction force that enforces no-slip boundary conditions at the fluid–body interface as the limiting case of an iterative procedure. A smooth version of the Heaviside function allows to treat spherical particles of arbitrary size and produces smooth hydrodynamic forces as particles move in the continuum. Numerical tests demonstrate the accuracy of the method in reproducing the hydrodynamic field around a single particle and the fluid-mediated forces between pairs of particles. The drag force experienced by a particle moving in a straight channel and at various Reynolds numbers is studied as a non-trivial testcase.     

Experimental and theoretical analysis of bias ionization by?α-particles in a nitrogen laser

Nitrogen laser performance with TE configuration and wedge electrodes is analyzed with background ionization in the laser discharge channel by α particles at a low exposition rate. With the bias ionization, the laser power presents two peaks as a function of gas pressure, with one at the normal low pressure, without bias ionization, and the other at high pressure generated by bias ionization. A simple theoretical model has been developed in a trial to understand this behavior. This model was first tested in later results for a TE configuration nitrogen laser, with flat electrodes, without and with bias ionization. It has been observed that due to the competition between electrode shielding by positively charged α particles and bulk ionization by impact, the laser energy is suppressed with pressure below 50 Torr and enhanced above it.     

Novel stereocontrolled addition of allylmetal reagents to alpha-imino esters: efficient synthesis of chiral tetrahydroquinoline derivatives

To prepare in multigram scale new antagonists of the glycine binding site associated to the NMDA receptor, an efficient distereoselective route was set up. The addition of suitable allyltin reagents to chiral N-aryl alpha-imino esters (R-(+)-tert-butyl lactate used as chiral auxiliary), gave the corresponding alpha amino acid-type derivative in high chemical yield and optical purity. This allylation reaction represents a novel example of efficient long-range stereodifferentiation process. In the last part of the synthesis, a regioselective Heck-type cyclization reaction enabled preparation of the target tetrasubstituted exocycle and trisubtituted endocycle double bond derivatives.     

High-performance liquid chromatographic/tandem mass spectrometric identification of the phototransformation products of tebuconazole on titanium dioxide

Tebuconazole is a widely used fungicide. The formation of by-products on irradiated titanium dioxide as a photocatalyst was evaluated. Several species derived from tebuconazole degradation were identified and characterized by HPLC/MS(n). A pattern of reactions accounting for the observed intermediates is proposed. Different parallel pathways are operating (and through these pathways the transformation of the molecule proceeds), leading to a wide range of intermediate compounds. All these molecules are more hydrophylic than tebuconazole. The main steps involved are (1) the hydroxylation of the molecule with the formation of three species having [M + H](+) 324; the hydroxylation occurs on the C-1 carbon and on the aromatic ring in the two ortho-positions; (2) the cleavage of a C--C bond with the release of the tert-butyl moiety and the formation of a species having m/z 250; analogously to step 1, also on this species a further hydroxylation reaction occurs; (3) through the loss of the triazole moiety with the formation of a structure with m/z 257.     

O 1s --> sigma* resonance in O2: inadequacy of only two exchange-split components

The O 1s-->sigma* transition below the O K-edge in O2 has been investigated by absorption, constant ionic state (CIS) experiments, and extensive configuration interaction calculations. CIS scans of the three lowest-lying final states reached in resonant Auger decay provide a wealth of information on energy range, symmetry, and spin multiplicity of the intermediate states with sigma* character. We conclude that the identification of only two exchange-split components is inadequate because a complex manifold of states with sigma* character exists with no unique energy difference between related states.     

Lee-Goldburg solid-state imaging.

A new approach to solid-state imaging (SSI) is presented. The method relies on narrowing the resonance line using the Lee-Goldburg sequence. The technique is easy to implement in practice and may find widespread applications in materials science.     

Evaluations of particulate mass loading from visibility observations and atmospheric turbidity measurements

Summary Two extinction models for continental and rural particles were defined by using a very accurate computer programme based on Mie extinction theory for spherical particles. The first extinction model gives several sets of volume extinction coefficients at seven visible and near-infra-red wave-lengths, calculated for twenty-seven Junge-type size distribution curves (with Junge parameter ranging from 1.8 to 4.4) and for eight relative-humidity values of the air. This model also gives the corresponding values of ?ngstr?m's exponent α and mean particle mass. The second extinction model gives similar sets of data, calculated for two lognormal size distribution curves of tropospheric and large rural particles at five relative-humidity values of the air. These monomodal models can be used to determine bimodal extinction models consisting of variable number fractions of tropospheric and rural particles. Evaluations of the particulate mass loading can be obtained from measurements of visual range and atmospheric turbidity, choosing the most appropriate extinction model on the basis of the spectral features characterizing atmospheric attenuation. Measurements of visibility and atmospheric turbidity in two rural localities of the Po Valley were examined by employing both the present extinction models and other extinction models commonly used. The comparison of the results shows that the Junge-type extinction model can be reliably used in cases in which the exponent α is equal to or larger than 1.4. For smaller values of α, the Junge-type extinction model and bimodal model were found to give realistic evaluations of the lower and upper limits of particulate mass loading.

---

Riassunto Usando un programma di calcolo assai accurato, basato sulla teoria di Mie per l'estizione da particelle sferiche, si sono definiti due modelli di estinzione per particelle di origine continentale e rurale. Il primo di questi modelli fornisce diverse serie spettrali dei coefficienti di estinzione da particelle su percorso unitario, relativi a sette lunghezze d'onda nel visibile e vicino infrarosso e calcolati per ventisette distribuzioni dimensionali del tipo di Junge (con parametro di Junge che varia da 1.8 a 4.4) e per otto valori dell'umidità relativa dell'aria. Inoltre, questo modello fornisce i valori corrispondenti dell'esponente di ?ngstr?m α e della massa media delle particelle. Il secondo modello fornisce insiemi simili di dati calcolati per due distribuzioni dimensionali di tipo lognormale, relative a particelle troposferiche e a grandi particelle di origine rurale, e per cinque valori di umidità relativa dell'aria. Questi modelli monomodali possono essere usati per definire modelli bimodali di estinzione, composti da particelle troposferiche e rurali in percentuali numeriche variabili. Scegliendo il modello piú appropriato di estinzione sulla base delle caratteristiche spettrali di attenuazione atmosferica, si possono ricavare valutazioni del contenuto atmosferico di massa delle particelle da misure di visibilità e torbidità atmosferica. Misure di questo tipo, effettuate in due località rurali della pianura padana, sono state esaminate sia mediante i modelli di estinzione qui proposti sia mediante altri modelli di estinzione usati comunemente. Il confronto tra i risultati mostra che il modello di estinzione del tipo di Junge può dare risultati realistici nei casi in cui l'esponente α è maggiore di o egule a 1.4. Per valori minori di α, il modello di Junge e il modello bimodale forniscono rispettivamente una stima di minima e una stima di massima del contenuto atmosferico di massa delle particelle.

---

Резюме Предлагаются две модели экстинции для континентальных и селяских частиц, используя очень точную программу, основанную на теории Ми сферических частиц. Первая модель экстинции дает несколько систем для коэффициентов общемной экстинции при семи длинах волн в видимом и ближнем инфракрасном диапазонах, которые вычислены для 27 распределений по размерам типа Джунджа (с параметром Джунджа в области от 1.8 до 4.4) и для восьми значений относительной влажности воздуха. Эта модель также дает соответствуюшие величины для экспоненты Ангстрема α и среднюю массу частиц. Вторая модель экстинции дает аналогичные системы данных, вычисленных для двух log-нормальных распределений по размерам для тропосферных и больших сельских частиц при пяти значениях относительной влажности воздуха. Эти мономодальные модели могут быть использованы для определения бимодальных моделей экстинции, которые учитывают изменяющиеся численные относительные содержания тропосферных и сельских частиц. Выбирая наиболее соответствуюшую модель экстинции на основе спектральных особенностей, характеризующих атмосфернэе ослабление, можно оденить массовое содержание микрочастиц из измерениц видимости и помутнения атмосферы. Анализируются измерения видимости и помутнения атмосферы в двух сельских райохах долины По, используя предложенные модели экстинции и обычно пременяемые модели экстинции. Сравнение результатов показывает, что модель экстинции типа Джунджа может быть надежно использована в случаях, когда экспонента α равна или больше, чем 1.4. Для меньших значений α получается, что модель экстинции типа Джунджа и бимодальная модель дают реалистические оценки для нижнего и верхнего пределов массового содержания микрочастиц.