Analytical approximation for the sphere-sphere Coulomb potential

A simple analytical expression, which closely approximates the Coulomb potential between two uniformly charged spheres, is presented. This expression can be used in the optical potential semiclassical analyses which require that the interaction be analytic on and near the real r-axis.Comment: 4 pages including 3 figures and 1 tabl

Special issue “II-VI semiconductor nanocrystals and hybrid polymer–nanocrystal systems”

: The continuous need to improve the performance of photonic, electronic and optoelectronic devices has stimulated research toward the development of innovative semiconducting materials which display better properties with respect to standard bulk semiconductors [...]

Quantitative comparison between the smartphone based experiments for the gravity acceleration measurement at home

Smartphones are currently proposed as potential portable laboratories to perform a wide variety of physical experiments for teaching purpose. However, the frequent lack of clarity about the ease of replication of the experiments and on their accuracy often limits their effective use. In this work we deeply compare several smartphone-based experiments to determine the gravity acceleration g by only using cheap materials easily available at home. The experiment and the data analysis complexity are progressively increased, starting from fast and easy to replicate methods. The advantages and possible limits of all the methods are deeply discussed in order to allow an evaluation of the most suitable method for any particular teaching scenario

Perbandingan Cross-product Dan Subset Query Pada Multiple Relasi Dengan Metode Cost-based

Ada beberapa model query yang digunakan untuk mengakses data pada 2 tabel atau lebih dalam basis data relasi. Dua model query yang umum antara lain adalah cross product dan subset query, dimana kedua model ini dapat menghasilkan data yang sama. Namun perlu diperhatikan cara mana yang lebih optimal sehingga pada akhirnya didapatkan query dengan waktu akses yang paling minimum. Dengan menggunakan basis data Oracle 10g Express Edition akan dilakukan penelitian untuk mencari model query yang lebih optimal dengan metode cost-based. Parameter yang akan dibandingkan adalah harga/biaya dan waktu yang dihasilkan pada perencanaan eksekusi. Penelitian dilakukan dengan pengelompokkan uji data seperti jumlah data, jumlah relasi, akses tabel penuh atau sebagian dan pengindeksan

Role for the fission yeast RecQ helicase in DNA repair in G2.

Members of the RecQ helicase subfamily are mutated in several human genomic instability syndromes, such as Bloom, Werner, and Rothmund-Thomson syndromes. We show that Rqh1, the single Schizosaccharomyces pombe homologue, is a 3'-to-5' helicase and exists with Top3 in a high-molecular-weight complex. top3 deletion is inviable, and this is suppressed by concomitant loss of rqh1 helicase activity or loss of recombination functions. This is consistent with RecQ helicases in other systems. By using epistasis analysis of the UV radiation sensitivity and by analyzing the kinetics of Rhp51 (Rad51 homologue), Rqh1, and Top3 focus formation in response to UV in synchronized cells, we identify the first evidence of a function for Rqh1 and Top3 in the repair of UV-induced DNA damage in G(2). Our data provide evidence that Rqh1 functions after Rad51 focus formation during DNA repair. We also identify a function for Rqh1 upstream of recombination in an Rhp18-dependent (Rad18 homologue) pathway. The model that these data allow us to propose helps to reconcile different interpretations of RecQ family helicase function that have arisen between work based on the S. pombe system and models based on studies of Saccharomyces cerevisiae SGS1 suggesting that RecQ helicases act before Rad51

Excitation Density Dependence of Optical Oxygen Sensing in Poly(9,9-dioctylfluorene) Waveguides Showing Amplified Spontaneous Emission

Reversible oxygen induced emission quenching of both the Spontaneous Emission (SE) and the Amplified Spontaneous Emission (ASE) of poly(9,9-dioctylfluorene) waveguides is demonstrated. We show that ASE shows a stronger quenching than SE, up to about 6.2 times, but also a stronger decrease when the excitation density increases. We conclude that the fast increase of the ASE decay rate is the main process in determining the ASE detection sensitivity, limiting the potentiality of sensitivity improvement of ASE with respect to SE

Fabrication of free-standing ordered fluorescent polymer nanofibres by electrospinning

The authors are grateful to the Engineering and Physical Sciences Research Council for financial support.We demonstrate a static fabrication approach to make free-standing ordered arrays of fluorescent nanofibres through control of the transverse electrospinning field. The alignment and the density of the nanofibre arrays are optimised by careful design of both the source and collector electrode geometries which can control the transverse electric field over the full path of the jet. In doing so, we fabricate suspended fluorescent nanofibres with an aspect ratio of 10(4), and with a substantially increased density and order parameter (by a factor of similar to 10 compared to random deposition). Electrostatic modelling suggests that the field distribution of the component is the main contribution to the ordering between the plates. This method offers increased efficiency for the creation of ordered fibres collected over a small area and the characterisation of their photoluminescent properties.Publisher PDFPeer reviewe

Refractive effects in the scattering of loosely bound nuclei

A study of the interaction of loosely bound nuclei 6,7Li at 9 and 19 AMeV with light targets has been undertaken. With the determination of unambiguous optical potentials in mind, elastic data for four projectile-target combinations and one neutron transfer reaction 13C(7Li,8Li)12C have been measured on a large angular range. The kinematical regime encompasses a region where the mean field (optical potential) has a marked variation with mass and energy, but turns out to be sufficiently surface transparent to allow strong refractive effects to be manifested in elastic scattering data at intermediate angles. The identified exotic feature, a "plateau" in the angular distributions at intermediate angles, is fully confirmed in four reaction channels and interpreted as a pre-rainbow oscillation resulting from the interference of the barrier and internal barrier farside scattering subamplitudes.Comment: 19 pages, 14 figures, 3 tables to submit to Phys. Rev.

Amplified spontaneous emission and lasing in lead halide perovskites: State of the art and perspectives

Lead halide perovskites are currently receiving increasing attention due to their potential to combine easy active layers fabrication, tunable electronic and optical properties with promising performance of optoelectronic and photonic device prototypes. In this paper, we review the main development steps and the current state of the art of the research on lead halide perovskites amplified spontaneous emission and on optically pumped lasers exploiting them as active materials