A new representation of power spectral density and correlation function by means of fractional spectral moments

In this paper, a new perspective for the representation of both the power spectral density and the correlation function by a unique class of function is introduced. We define the moments of order γ$\gamma$ (γ∈C$\gamma \in \mathbb{C}$) of the one sided power spectral density and we call them Fractional Spectral Moments (FSM). These complex quantities remain finite also in the case in which the ordinary spectral moments diverge, and are able to represent the whole Power Spectral Density and the corresponding correlation function.     

Solar‐Energy Production and Energy‐Efficient Lighting: Photovoltaic Devices and White‐Light‐Emitting Diodes Using Poly(2,7‐fluorene), Poly(2,7‐carbazole), and Poly(2,7‐dibenzosilole) Derivatives

World energy needs grow each year. To address global warming and climate changes the search for renewable energy sources with limited greenhouse gas emissions and the development of energy‐efficient lighting devices are underway. This Review reports recent progress made in the synthesis and characterization of conjugated polymers based on bridged phenylenes, namely, poly(2,7‐fluorene)s, poly(2,7‐carbazole)s, and poly(2,7‐dibenzosilole)s, for applications in solar cells and white‐light‐emitting diodes. The main strategies and remaining challenges in the development of reliable and low‐cost renewable sources of energy and energy‐saving lighting devices are discussed.     

Attitudes toward Corporate Responsibilities in Western Europe and in Central and East Europe

• This study investigated the attitudes toward social, economic, and environmental corporate responsibilities of 3064 current managers and business students in 8 European countries.
• Participants in Western European countries had significantly different perspectives on the importance of these corporate responsibilities (CR) than those in Central and East European countries. Within each country, environmental CR is perceived as most important in both CEE and Western European countries. Across countries, Western European respondents accord more importance to social CR and less importance to economic CR. CEE countries are not homogenous, e.g., CR attitudes in the Czech Republic are closer to that of Western Europeans, possibly triggered by the accession to EU.
• Work experience (managers vs. business students) influences social and environmental orientations more than the economic orientation for only some countries. Generational differences were found as well: Business students attribute more importance to environmental CR and less importance to social CR than managers.

     

Contradictory relationship between Hurst parameter and queueing performance (extended version)

Long Range Dependent (LRD) network traffic does not behave like the traffic generated by the Poisson model or other Markovian models. From the network performance point of view, the main difference is that LRD traffic increases queueing delays due to its burstiness over many time scales. LRD behavior has been observed in different types and sizes of networks, for different applications (e.g., WWW) and different traffic aggregations. Since LRD behaviour is not rare nor isolated, accurate characterization of LRD traffic is very important in order to predict performance and to allocate network resources. The Hurst parameter is commonly used to quantify the degree of LRD and the burstiness of the traffic. In this paper we investigate the validity and effectiveness of the Hurst parameter. To this end, we analyze the UCLA Computer Science Department network traffic traces and compute their Hurst parameters. Queueing simulation is used to study the impact of LRD and to determine if the Hurst parameter accurately describes such LRD. Our results show that the Hurst parameter is not by itself an accurate predictor of the queueing performance for a given LRD traffic trace.     

Regression and correlation analyses of a linear relation between random intervals

In this paper we develop regression and corrclation analyses of a certain general linear relation between two random elements whose values are non-empty compact intervals. To this purpose, we firstly extend the least-squares method to deal with the involved random elements on the basis of a generalized metric defined on the space of the considered intervals. As a complementary study, a coefficient quantifying the strength of the linear relation between the two random elements is also presented, and a discussion of the extreme values for this measure is presented. A real-life example illustrates these studies. Research partially supported by DGESIC/MEC Grants No. DGE-99-PB98-1534 and No. DGE-98-PB97-1282.     

Influence of Fe3+/Fe2+ Ratio on the Crystallization of Iron-Rich Glasses Made with Industrial Wastes

The influence of the Fe³⁺/Fe²⁺ ratio on the crystallization of iron-rich glasses was investigated in this study. The glass batches were made from two hazardous industrial wastes: mud (goethite and jarosite) originating from the zinc hydrometallurgical process and electric arc furnace dust (EAFD). Glass compositions were prepared by adding different percentages of carbon powder. The crystallization process was investigated by a combined thermogravimetry/differential thermal analysis technique, in air or nitrogen atmospheres, using powder and bulk glass samples. The crystalline phases formed, i.e., pyroxene and spinels, and their relative ratio were determined by X-ray diffractometry. The experimental results indicated that melting temperature and crystallization behavior were influenced by the initial Fe³⁺/Fe²⁺ ratio and by the amount of carbon added to the glass batch. For goethite and jarosite glass compositions, decreasing the Fe³⁺/Fe²⁺ ratio increased the crystallization rate by favoring magnetite formation. For EAFD glass compositions, the addition of carbon to the batch inhibited chromite–magnetite spinel formation and favored the attainment of an amorphous glassy phase.     

Intentional inhibition in memory and hallucinations: Directed forgetting and updating.

Hallucinations have been recently associated with inhibitory deficits in memory. In this study, the authors investigated whether hallucinations were related to difficulties to inhibit irrelevant information from episodic memory (Experiment 1) and working memory (Experiment 2). In Experiment 1, a directed forgetting task was used. This task measures participants' ability to intentionally forget some recently learned material, when instructions indicate that it is no longer relevant. In Experiment 2, an updating task was used. This task requires participants to intentionally suppress irrelevant information from working memory. Results showed that patients with schizophrenia with hallucinations presented inhibitory deficits in the directed forgetting task and an increase in the number of intrusions in the updating task, compared to patients without hallucinations and healthy controls. No correlations were found between indices of inhibition and other general, negative or positive symptoms. These findings support the existence of an association between intentional inhibition in memory and hallucinations, and they suggest that problems to suppress memory representations can underlie hallucinations in schizophrenia. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Direct Coupling Reactions of Alkynylsilanes Catalyzed by Palladium(II) Chloride and a Di(2‐pyridyl)methylamine‐Derived Palladium(II) Chloride Complex in Water and in NMP

Symmetrical internal alkynes can be prepared either by diarylation of mono‐ and bis(trimethylsilyl)acetylene (TMSA and BTMSA) catalyzed by ligand‐less palladium(II) chloride or by a di(2‐pyridyl)methylamine‐derived palladium(II ) chloride complex 1 (typical 0.1–1 mol % of Pd loading) in water using pyrrolidine as base and tetra‐n‐butylammonium bromide as additive. Alternatively, this same process is performed in NMP in the presence of tetra‐n‐butylammonium acetate (TBAA) as base with even lower Pd loadings (0.001–1 mol % Pd). The same reaction conditions are applied to the synthesis of unsymmetrical internal alkynes by monoarylation of silylated terminal alkynes. Aryl iodides can be coupled with TMSA, BTMSA and silylated terminal alkynes under heating or at room temperature, whereas for aryl bromides couplings are performed under water reflux or at 110 °C in the case of NMP. Complex 1 can be reused during several cycles either in water or in NMP without loss of catalytic activity. These simple reaction conditions allow the preparation of internal alkynes without secondary products, most probably by succesive protiodesilylation‐Sonogashira coupling.