Diluted manganese on the bond-centered site in germanium

The functional properties of Mn-doped Ge depend to large extent on the lattice location of the Mn impurities. Here, we present a lattice location study of implanted diluted Mn by means of electron emission channeling. Surprisingly, in addition to the expected substitutional lattice position, a large fraction of the Mn impurities occupies the bond-centered site. Corroborated by ab initio calculations, the bond-centered Mn is related to Mn-vacancy complexes. These unexpected results call for a reassessment of the theoretical studies on the electrical and magnetic behavior of Mn-doped Ge, hereby including the possible role of Mn-vacancy complexes

Direct observation of substitutional Ga after ion implantation in Ge by means of extended x-ray absorption fine structure

We present an experimental lattice location study of Ga atoms in Ge after ion implantation at elevated temperature (250°C). Using extended x-rayabsorption fine structure (EXAFS) experiments and a dedicated sample preparation method, we have studied the lattice location of Ga atoms in Ge with a concentration ranging from 0.5 at. % down to 0.005 at. %. At Ga concentrations ≤0.05 at.%, all Ga dopants are substitutional directly after ion implantation, without the need for post-implantation thermal annealing. At higher Ga concentrations, a reduction in the EXAFS amplitude is observed, indicating that a fraction of the Ga atoms is located in a defective environment. The local strain induced by the Ga atoms in the Ge matrix is independent of the Ga concentration and extends only to the first nearest neighbor Ge shell, where a 1% contraction in bond length has been measured, in agreement with density functional theory calculations.We acknowledge the support from the Research Foundation Flanders, the epi-team from imec, the KU Leuven GOA 09/06 project, the IUAP program P6/42 and the Australian Research Council. S.C. acknowledges support from OCAS NV by an OCAS-endowed chair at Ghent University

Sex-specific fundamental and formant frequency patterns in a cross-sectional study

An extensive developmental acoustic study of the speech patterns of children and adults was reported by Lee and colleagues [Lee et al., J. Acoust. Soc. Am. 105, 1455-1468 (1999)]. This paper presents a reexamination of selected fundamental frequency and formant frequency data presented in their report for 10 monophthongs by investigating sex-specific and developmental patterns using two different approaches. The first of these includes the investigation of age- and sex-specific formant frequency patterns in the monophthongs. The second, the investigation of fundamental frequency and formant frequency data using the critical band rate (bark) scale and a number of acoustic-phonetic dimensions of the monophthongs from an age- and sex-specific perspective. These acoustic-phonetic dimensions include: vowel spaces and distances from speaker centroids; frequency differences between the formant frequencies of males and females; vowel openness/closeness and frontness/backness; the degree of vocal effort; and formant frequency ranges. Both approaches reveal both age- and sex-specific development patterns which also appear to be dependent on whether vowels are peripheral or non-peripheral. The developmental emergence of these sex-specific differences are discussed with reference to anatomical, physiological, sociophonetic and culturally determined factors. Some directions for further investigation into the age-linked sex differences in speech across the lifespan are also proposed

Knee valgus in self-initiated vertical jump landings: developmental and gender comparisons

The study examined gender and developmental differences in knee valgus angle and external knee valgus moment at the time of maximal vertical ground reaction force (MGRFz) in self-initiated vertical jump (VJ) landings. Fifty-six subjects grouped by age (pre-pubescent (8-11 yrs); post-pubescent (19-29 yrs)) and gender jumped for a ball set at 50% of their maximum VJ height then landed on two feet with only their dominant foot on the force plate. Statistical analyses of motion analysis (3-D) and GRF data showed that children had greater valgus angles (p = .003) and moments (p = .026) at MGRFz compared to adults. Females had greater (p = .016) valgus moments than males, but similar valgus angles at MGRFz. It will be important to ensure that as both boys and girls progress through puberty they develop an ability to offset high valgus moments and land with good lower extremity alignment

Knee valgus in self-initiated vertical jump landings: developmental and gender comparisons

The study examined gender and developmental differences in knee valgus angle and external knee valgus moment at the time of maximal vertical ground reaction force (MGRFz) in self-initiated vertical jump (VJ) landings. Fifty-six subjects grouped by age (pre-pubescent (8-11 yrs); post-pubescent (19-29 yrs)) and gender jumped for a ball set at 50% of their maximum VJ height then landed on two feet with only their dominant foot on the force plate. Statistical analyses of motion analysis (3-D) and GRF data showed that children had greater valgus angles (p = .003) and moments (p = .026) at MGRFz compared to adults. Females had greater (p = .016) valgus moments than males, but similar valgus angles at MGRFz. It will be important to ensure that as both boys and girls progress through puberty they develop an ability to offset high valgus moments and land with good lower extremity alignment

Loading rate in self-initiated vertical jump landings: developmental and gender comparisons

The study compared gender and developmental differences in vertical loading rate upon a two-footed landing from a self-initiated VJ. Fifty-seven subjects grouped by age (pre-pubescent (8-11 yrs); post-pubescent (19-29 yrs)) and gender consented to participate. Subjects jumped for a ball set at 50% of their maximum VJ height, and landed on two feet, facing forward, with only their dominant foot on the force plate. Motion analysis (3-D) and ground reaction force (GRF) data were collected. Statistical analyses indicated significant developmental differences in vertical loading rate normalized to kinetic energy, but no gender differences. Children may have higher loading rates because they lack the experience, strength, and associated neuromuscular patterns that prepare them to modulate force as adults do

KNEE VALGUS IN SELF-INITIATED VERTICAL JUMP LANDINGS: DEVELOPMENTAL AND GENDER COMPARISIONS

The study examined gender and developmental differences in knee valgus angle and external knee valgus moment at the time of maximal vertical ground reaction force (MGRFz) in self-initiated vertical jump (VJ) landings. Fifty-six subjects grouped by age (pre-pubescent (8-11 yrs); post-pubescent (19-29 yrs)) and gender jumped for a ball set at 50% of their maximum VJ height then landed on two feet with only their dominant foot on the force plate. Statistical analyses of motion analysis (3-D) and GRF data showed that children had greater valgus angles (p = .003) and moments (p = .026) at MGRFz compared to adults. Females had greater (p = .016) valgus moments than males, but similar valgus angles at MGRFz. It will be important to ensure that as both boys and girls progress through puberty they develop an ability to offset high valgus moments and land with good lower extremity alignment

LOADING RATE IN SELF-INITIATED VERTICAL JUMP LANDINGS: DEVELOPMENTAL AND GENDER COMPARISONS

The study compared gender and developmental differences in vertical loading rate upon a two-footed landing from a self-initiated VJ. Fifty-seven subjects grouped by age (pre-pubescent (8-11 yrs); post-pubescent (19-29 yrs)) and gender consented to participate. Subjects jumped for a ball set at 50% of their maximum VJ height, and landed on two feet, facing forward, with only their dominant foot on the force plate. Motion analysis (3-D) and ground reaction force (GRF) data were collected. Statistical analyses indicated significant developmental differences in vertical loading rate normalized to kinetic energy, but no gender differences. Children may have higher loading rates because they lack the experience, strength, and associated neuromuscular patterns that prepare them to modulate force as adults do

Observed Quality and Consistency of Fifth Graders’ Teacher–Student Interactions: Associations With Feelings, Engagement, and Performance in School

This study examined how overall quality and within-day consistency in fifth graders’ teacher-student interactions related to feelings about, engagement, and academic performance in school. Participants were 956 children in a national study. Students who experienced higher quality interactions reported more positive feelings about school, were more engaged, performed better in math and reading, and had more closeness and less conflict with teachers. Independent of overall interaction quality, students who experienced less consistency in their interactions with teachers, whether it was with the same teacher or across teachers, were less engaged and had more teacher-reported conflict. Findings emphasize the separate contributions of both high quality and consistency of teacher–student interactions to students’ success