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 [...]

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

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

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

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.

PELATIHAN PENYUSUNAN PROGRAM PEMBELAJARAN MODEL PEMBELAJARAN ABAD 21 DI TK DHARMA WANITA PROVINSI BENGKULU

Tujuan kegiatan pengabdian pada masyarakat ini adalah Meningkatkan kemampuan guru dalam penyusunan Rencana Pelaksanaan Pembelajaran (RPP) dalam Pembelajaran Abad 21 yang digunakan mengajar di TK. Pemecahan masalah dalam kegiatan pengabdian pada masyarakat ini dilakukan dengan melaksanakan kegiatan kegiatan pengabdian masyarakat melalui  pelatihan Model Pembelajaran Abad 21 yang diikuti para guru TK Dharma Wanita Propinsi Bengkulu. Khalayak sasaran dalam kegiatan pengabdian pada masyarakat ini adalah seluruh guru TK Dharma Wanita Provinsi Bengkulu berjumlah 13 orang guru. Metode kegiatan yang akan dilakukan dalam kegiatan pengabdian pada masyarakat ini adalah: Metode Ceramah; Metode Tanya-jawab, Penugasan (latihan) tentang penyusunan rencana pelaksanaan pembelajaran (RPP) dalam Pembelajaran Abad 21. Hasil kegiatan penyusunan rencana pembelajaran Abad 21 di TK Dharma Wanita Provinsi Bengkulu,  dan setelah dilakukan evaluasi dan penilaian serta balikan dari peserta disimpulkan kegiatan berjalan dengan baik  sesuai tujuan. Hasil penyusunan rencana pelaksanaan pembelajaran yang dibuat oleh guru berada pada kriteria baik  artinya seluruh komponen rencana pelaksanaan pembelajaran (RPP) dalam Pembelajaran Abad 21 sudah dilakukan dengan lengkap dan baik. Saran setelah kegiatan hendaknya perlu pelatihan untuk memberikan tentang komponen dan indikator atau kriteria-kriteria penyusunan rencana pelaksanaan pembelajaran Abad 2

Determination of the best empiric method to quantify the amplified spontaneous emission threshold in polymeric active waveguides

Amplified Spontaneous Emission (ASE) threshold represents a crucial parameter often used to establish if a material is a good candidate for applications to lasers. Even if the ASE properties of conjugated polymers have been widely investigated, the specific literature is characterized by several methods to determine the ASE threshold, making comparison among the obtained values impossible. We quantitatively compare 9 different methods employed in literature to determine the ASE threshold, in order to find out the best candidate to determine the most accurate estimate of it. The experiment has been performed on thin films of an homopolymer, a copolymer and a host:guest polymer blend, namely poly(9,9-dioctylfluorene) (PFO), poly(9,9-dioctylfluorene-cobenzothiadiazole) (F8BT) and F8BT:poly(3- hexylthiophene) (F8BT:rrP3HT), applying the Variable Pump Intensity (VPI) and the Variable Stripe Length (VSL) methods. We demonstrate that, among all the spectral features affected by the presence of ASE, the most sensitive is the spectral linewidth and that the best way to estimate the ASE threshold is to determine the excitation density at the beginning of the line narrowing. We also show that the methods most frequently used in literature always overestimate the threshold up to more than one order of magnitude