Spectroscopic studies of neutron-rich in 129 and its β -decay daughter, Sn 129, using the GRIFFIN spectrometer

The β decay of neutron-rich In129 into Sn129 was studied using the GRIFFIN spectrometer at the ISAC facility at TRIUMF. The study observed the half-lives of the ground state and each of the β-decaying isomers. The level scheme of Sn129 has been expanded with thirty-one new γ-ray transitions and nine new excited levels, leading to a reevaluation of the β branching ratios and level spin assignments. The observation of the β decay of the (29/2+) 1911-keV isomeric state in In129 is reported for the first time, with a branching ratio of 2.0(5)%

Molecular dynamics of ribosomal elongation factors G and Tu

Translation on the ribosome is controlled by external factors. During polypeptide lengthening, elongation factors EF-Tu and EF-G consecutively interact with the bacterial ribosome. EF-Tu binds and delivers an aminoacyl-tRNA to the ribosomal A site and EF-G helps translocate the tRNAs between their binding sites after the peptide bond is formed. These processes occur at the expense of GTP. EF-Tu:tRNA and EF-G are of similar shape, share a common binding site, and undergo large conformational changes on interaction with the ribosome. To characterize the internal motion of these two elongation factors, we used 25 ns long all-atom molecular dynamics simulations. We observed enhanced mobility of EF-G domains III, IV, and V and of tRNA in the EF-Tu:tRNA complex. EF-Tu:GDP complex acquired a configuration different from that found in the crystal structure of EF-Tu with a GTP analogue, showing conformational changes in the switch I and II regions. The calculated electrostatic properties of elongation factors showed no global similarity even though matching electrostatic surface patches were found around the domain I that contacts the ribosome, and in the GDP/GTP binding region

A target-protection mechanism of antibiotic resistance at atomic resolution: insights into FusB-type fusidic acid resistance

Antibiotic resistance in clinically important bacteria can be mediated by proteins that physically associate with the drug target and act to protect it from the inhibitory effects of an antibiotic. We present here the first detailed structural characterization of such a target protection mechanism mediated through a protein-protein interaction, revealing the architecture of the complex formed between the FusB fusidic acid resistance protein and the drug target (EF-G) it acts to protect. Binding of FusB to EF G induces conformational and dynamic changes in the latter, shedding light on the molecular mechanism of fusidic acid resistance

Developing academic persistence in the international baccalaureate diploma programme: Educational strategies, associated personality traits and outcomes

The aim of the study was to investigate the relationships between certain educational strategies and students' personality traits, on the one hand, and students' academic performance, on the other, respectively between the latter and two types of outcomes (i.e. students' academic performance and intentions to drop out of high school). These relationships were examined in two educational settings: in the Diploma Programme (DP), a two-year college-preparatory curriculum offered by the International Baccalaureate (IB), an international private educational system, and the traditional Romanian schools. A sample of IB students in 3 Eastern and Central European countries, and a comparison sample of non-IB students in Romania participated in the research. Results reveal several educational strategies and personality traits among those suggested by previous investigations that significantly sustain IB DP students’ academic persistence. Also, IB students’ academic performance and dropout intentions are influenced by these traits and educational strategies, and these effects are fully or partially mediated by academic persistence. A different pattern of associations emerged in the non-IB sample, with independent work style as the most important determinant of academic persistence, suggesting that relative to the traditional Romanian schools, the IB programme promotes a climate that better supports students in completing their education.El objetivo principal de este estudio fue investigar, por una parte, la relación entre ciertas estrategias educativas y los rasgos de personalidad de los estudiantes y, por otra, la práctica educativa de los estudiantes, entre la última y dos tipos de resultados (la práctica educativa de los estudiantes y la intención de abandonar el curso). Ambas relaciones fueron analizadas en diferentes entornos: en el Programa Diploma (DP), un currículo de dos años de preparatorio para la universidad ofrecido por el Bachillerato Internacional (IB), un sistema educacional internacional privado, y las escuelas tradicionales rumanas. Una muestra consta de estudiantes IB procedentes de tres países de Europa del Este y Central y, la otra muestra, para comparar, de estudiantes de Rumanía no pertenecientes al IB. Los resultados muestran que algunas estrategias educativas y los rasgos de personalidad sugeridos por investigaciones previas sostienen significativamente la persistencia académica de los estudiantes del IB DP. Asimismo, el rendimiento académico y las intenciones de abandono de los estudiantes del IB están influenciados por estos rasgos y estrategias educativas, efectos total o parcialmente mediados por la persistencia académica. En cuanto a la muestra de no estudiantes de la IB, emerge un patrón diferente de asociaciones, siendo un estilo de trabajo independiente el factor más determinante en la persistencia académica. Esto sugiere que, en comparación con las escuelas rumanas tradicionales, el programa IB promueve un ambiente que sostiene, de manera más exitosa, la finalización de la educación de los estudiantes

β\beta and β\beta-delayed neutron decay of the N=82N=82 nucleus 49131^{131}_{~49}In82_{82}

International audienceThe half-lives of three β-decaying states of In8249131 have been measured with the GRIFFIN γ-ray spectrometer at the TRIUMF-ISAC facility to be T1/2(1/2−)=328(15)ms, T1/2(9/2+)=265(8)ms, and T1/2(21/2+)=323(55)ms, respectively. The first observation of γ rays following the βn decay of In131 into Sn130 is reported. The β-delayed neutron emission probability is determined to be P1n=12(7)% for the 21/2+ state and 2.3(3)% from the combined 1/2− and 9/2+ states of In8249131 observed in this experiment. A significant expansion of the decay scheme of In131, including 17 new excited states and 35 new γ-ray transitions in Sn8150131 is also reported. This leads to large changes in the deduced β-branching ratios to some of the low-lying states of Sn131 compared to previous work with implications for the strength of the first-forbidden β transitions in the vicinity of doubly magic Sn8250132

Collective 2p-2h intruder states in 118Sn^{118}\mathrm{Sn} studied via β\beta decay of 118In^{118}\mathrm{In} using the GRIFFIN spectrometer at TRIUMF

International audienceThe low-lying structure of semimagic Sn118 has been investigated through the β decay of In118 (T1/2=4.45 min) to study shape coexistence via the reduced transition probabilities of states in the 2p-2h proton intruder band. This high-statistics study was carried out at TRIUMF-ISAC with the GRIFFIN spectrometer. In total, 99 transitions have been placed in the level scheme with 43 being newly observed. Three low-lying γ-ray transitions with energies near 285 keV have been resolved from which the 2intr.+→0intr.+ 284.52-keV transition was determined to have half of the previous branching fraction leading to a B(E2;22+→02+) of 21(4) W.u. compared to 39(7) W.u. from the previous measurement. Calculations using sd IBM-2 with mixing have also been made to compare the experimental B(E2) values to the theoretical values and to make comparisons to the Sn114,116 isotopes previously studied using the same theoretical model

β\beta Decay of 132^{132}In and Spectroscopy of 132^{132}Sn and 131^{131}Sb with the GRIFFIN Spectrometer

International audienceSpectroscopy of doubly magic 50132Sn82 has been performed with the GRIFFIN spectrometer at TRIUMF-ISAC following the β decay of 49132In83. The analysis has allowed for the placement of a total of 70 transitions and 29 excited states in Sn132. Detailed spectroscopy has also been performed on Sb131, resulting from the β decay of Sn131, produced from the β-delayed neutron decay of In132. Measurement of γ rays in both Sn131 and Sb131 has led to the determination of the β-delayed neutron emission probability Pn from In132. This is the first time that Pn has been measured for this nucleus by using γ spectroscopy, and the new value of 12.3(4)% is consistent with the most recent β-n counting experiment. Additionally, γ-γ angular correlations have been performed in Sn132, supporting the spin assignments of several excited states. Novel ab initio calculations are presented which describe several of the excited states, and these are compared with the experimental spectrum