Electromagnetic fluctuation-induced interactions in randomly charged slabs

Randomly charged net-neutral dielectric slabs are shown to interact across a featureless dielectric continuum with long-range electrostatic forces that scale with the statistical variance of their quenched random charge distribution and inversely with the distance between their bounding surfaces. By accounting for the whole spectrum of electromagnetic field fluctuations, we show that this long-range disorder-generated interaction extends well into the retarded regime where higher-order Matsubara frequencies contribute significantly. This occurs even for highly clean samples with only a trace amount of charge disorder and shows that disorder effects can be important down to the nano scale. As a result, the previously predicted non-monotonic behavior for the total force between dissimilar slabs as a function of their separation distance is substantially modified by higher-order contributions, and in almost all cases of interest, we find that the equilibrium inter-surface separation is shifted to substantially larger values compared to predictions based solely on the zero-frequency component. This suggests that the ensuing non-monotonic interaction is more easily amenable to experimental detection. The presence of charge disorder in the intervening dielectric medium between the two slabs is shown to lead to an additional force that can be repulsive or attractive depending on the system parameters and can, for instance, wash out the non-monotonic behavior of the total force when the intervening slab contains a sufficiently large amount of disorder charges.Comment: 9 pages, 5 figure

Rapid formation of single crystalline Ge nanowires by anodic metal assisted etching

Germanium nanowires are produced by a novel approach, combining two well known electrochemical and metal assisted chemical etching. The metal assisted etching procedure is enhanced by incorporation of HF in the catalytic solution and application of a constant bias to the substrate. Fast etching, caused by metal nanoparticles, facilitate pore nucleation for further pore growth. The improved current transport de- veloped in the vicinity of the metal nanoparticles maintains a concentrated current density at the pore tip which results in an elongation of the pores in one direction and formation of long nanowires. With this new approach it is possible to fabricate nanowires with diameter below 100 nm and tens of micrometers long

Substrate induced proximity effect in superconducting niobium nanofilms

Structural and superconducting properties of high quality Niobium nanofilms with different thicknesses are investigated on silicon oxide and sapphire substrates. The role played by the different substrates and the superconducting properties of the Nb films are discussed based on the defectivity of the films and on the presence of an interfacial oxide layer between the Nb film and the substrate. The X-ray absorption spectroscopy is employed to uncover the structure of the interfacial layer. We show that this interfacial layer leads to a strong proximity effect, specially in films deposited on a SiO$_2$ substrate, altering the superconducting properties of the Nb films. Our results establish that the critical temperature is determined by an interplay between quantum-size effects, due to the reduction of the Nb film thicknesses, and proximity effects

Dimensional crossover and incipient quantum size effects in superconducting niobium nanofilms

Superconducting and normal state properties of sputtered Niobium nanofilms have been systematically investigated, as a function of film thickness in a d=9-90 nm range, on different substrates. The width of the superconducting-to-normal transition for all films remained in few tens of mK, thus remarkably narrow, confirming their high quality. We found that the superconducting critical current density exhibits a pronounced maximum, three times larger than its bulk value, for film thickness around 25 nm, marking the 3D-to-2D crossover. The extracted magnetic penetration depth shows a sizeable enhancement for the thinnest films, aside the usual demagnetization effects. Additional amplification effects of the superconducting properties have been obtained in the case of sapphire substrates or squeezing the lateral size of the nanofilms. For thickness close to 20 nm we also measured a doubled perpendicular critical magnetic field compared to its saturation value for d>33 nm, indicating shortening of the correlation length and the formation of small Cooper pairs in the condensate. Our data analysis evidences an exciting interplay between quantum-size and proximity effects together with strong-coupling effects and importance of disorder in the thinnest films, locating the ones with optimally enhanced critical properties close to the BCS-BEC crossover regime

Using RAPD markers potential to identify heritability for growth in Fenneropenaeus indicus

Sampling was done using 90 post larvae which were produced by reproduction of some broodstocks of Fenneropenaeus indicus in one day and reared in the same situation for 4 months. Samples were divided into 3 groups: high, medium and low growth (based on weight and length). Genomic DNA was extracted from muscle tissue using the phenol-chloroform method. The polymerase chain reaction (PCR) was carried out using 21 RAPD loci and PCR products were separated on 3% Agarose gel. From 21 loci studied, 12 produced polymorphic bands. The most polymorphic produced bands using OPAQ 9 and the least by OPAQ 7. Search for specific markers in F. indicus one specific band was observed in the low growth group using OPAQ4. The highest genetic distance (0.457) was between the low growth group and the medium and the lowest (0.091) between high growth and medium groups, therefore the highest genetic identity (0.912) was between high growth and medium groups and the lowest (0.633) between low growth group and the medium. Neighbor-joining resulted in two groups, the first including high and medium growth groups and the second low growth group. It appears that low growth group depended on separated population. Considering the mean weight of F1 (mean weight of 90 specimens) (16.25±1.5 g), parental generation mean weight of 15 ±1.2 and mean weight of parent 31.6 g, response to selection (R) and heritability for growth in this species were estimated to be 1.2±0.2 and 0.07±0.01 respectively

Molecular evaluation of the population of Silver Pomfret (Pampus argenteus) in the Persian Gulf and Oman Sea (Iranian &Kuwaiti waters)

A total of 162 specimens of Silver Pomfret (Pampus argenteus) including 38 samples from Kuwait and 124 samples from Iran (24 from Khouzestan, 24 from Chabahar and 38 from Bushehr) were examined for their DNA structure. DNA from all specimens was extracted using the Phenol-chloroform and amplified using PCR method with a pair of primers with ND sub(2) gene sequence. The PCR products were about 1300 (bp) for all samples. For RFLP analysis 16 restriction enzymes Bcl I, Pst I, Acc II, BseN I, Tru I, Dra I, Alw26 I, Hin6 I, Tas I, Alu I, EcoR I ,Hae III, Hinc II, Hind III, Hinf I and Hpa II were used. DNA bands were visualized by Gel electrophoresis (polyacrylamid) and staining with silver nitrate. Out of 16 enzymes, four showed polymorphism that includedg Hinf I, Alu I, Acc II, and Hpa II. Of the total 162 samples, 13 showed polymorphic patterns. Six haplotypes were rare occurring only once, but others which were only four different kinds occurred more than once. The REAP test gave no significant result for the examined regions (P>0.05). Therefore, our results revealed that the Pampus argenteus stocks in the Persian Gulf and Oman Sea of Iranian and Kuwaiti waters constitute a unique population

Propositions for Examining the Seasonality Construct in Tourism Settings

Propositions for Examining the Seasonality Construct in Tourism Settings Abstract The purpose of this conceptual study is to further develop our understanding of the seasonality construct as a predictor of tourist behavior. This study aims to explain and organize the tourism seasonality literature for a more thorough interpretation; examine how seasonality impacts consumer decision making focusing on the use of inbound and outbound marketing; and establish measurement tools that can help link seasonal destination consumer needs with actual behavior and internet search behavior. The contribution of this study is several thoroughly developed propositions to be used as a guide in further seasonality literature focusing on the measurement of the seasonality construct, specifically the tools to be utilized in seasonality empirical research; the types of seasonality as connected to traveler decision-making; the relationship between traveler search behavior, actual behavior, and seasonal changes; and the organization of seasonal terms in relation to seasonal activity

Discourse connectors: an overview of the history, definition and classification of the term

Many studies have investigated discourse connectors. However, researchers are still grappling with the term in terms of its definition and classification in particular. Many researchers use the term discourse markers (DMs) while others have used terms like linking words, connectives, discourse operators and discourse connectors to refer to the same idea. This paper attempts to better define the term and propose a classification of DCs in written discourse. As is evident from the literature, researchers are unable to agree on the best definition for the term connectors or what is generally known as discourse markers. Researchers in the field have put forward a few different definitions and descriptions of what connectors are and their function in language and some researchers have also developed their own taxonomy and classification for connectors. After reviewing research conducted on connectors, we decided for purposes of this paper to use the term ‘discourse connectors’ mainly because we believe these connectors function to link one portion of information to another one in a text and that while the term discourse marker is a suitable term for spoken discourse, its definition and classification may vary for written discourse. We define DCs as words and expressions that can be accommodated within the text to join one sentence with another sentence or one paragraph to another paragraph or even one idea to another. Finally, we attempt to offer a comprehensive definition and classification of discourse connectors with the aim to provide a better understanding of what DCs are and how they function, with variation from previous reviews of the term

Discourse connectors: an overview of the history, definition and classification of the term

Many studies have investigated discourse connectors. However, researchers are still grappling with the term in terms of its definition and classification in particular. Many researchers use the term discourse markers (DMs) while others have used terms like linking words, connectives, discourse operators and discourse connectors to refer to the same idea. This paper attempts to better define the term and propose a classification of DCs in written discourse. As is evident from the literature, researchers are unable to agree on the best definition for the term connectors or what is generally known as discourse markers. Researchers in the field have put forward a few different definitions and descriptions of what connectors are and their function in language and some researchers have also developed their own taxonomy and classification for connectors. After reviewing research conducted on connectors, we decided for purposes of this paper to use the term ‘discourse connectors’ mainly because we believe these connectors function to link one portion of information to another one in a text and that while the term discourse marker is a suitable term for spoken discourse, its definition and classification may vary for written discourse. We define DCs as words and expressions that can be accommodated within the text to join one sentence with another sentence or one paragraph to another paragraph or even one idea to another. Finally, we attempt to offer a comprehensive definition and classification of discourse connectors with the aim to provide a better understanding of what DCs are and how they function, with variation from previous reviews of the term