Behavioral ontogeny in larvae and early juveniles of the giant trevally (Caranx ignobilis) (Pisces: Carangidae)

Behavior of young (8−18 mm SL) giant trevally (Caranx ignobilis), a large coral-reef−associated predator, was observed in the laboratory and the ocean. Size was a better predictor of swimming speed and endurance than was age. Critical speed increased with size from 12 to 40 cm/s at 2.7 cm/s for each mm increase in size. Mean scaled critical speed was 19 body lengths/s and was not size related. Swimming speed in the ocean was 4 to 20 cm/s (about half of critical speed) and varied among areas, but within each area, it increased at 2 cm/s for each mm increase in size. Swimming endurance in the laboratory increased from 5 to 40 km at 5 km for each mm increase in size. Vertical distribution changed ontogenetically: larvae swam shallower, but more variably, and then deeper with growth. Two-thirds of individuals swam directionally with no ontogenetic increase in orientation precision. Larvae swam offshore off open coasts, but not in a bay. In situ observations of C. ignobilis feeding, interacting with pelagic animals, and reacting to reefs are reported. Manus

Probing the limits of strength in diamonds: From single- and nano-crystalline to diamond-like-carbon (DLC)

As the hardest known material, diamond represents the benchmark for the ultimate strength of materials. It is thus a very attractive material for a number of mechanical applications. Recent advances in synthesis techniques have enabled the fabrication of diamond in thin film form with various microstructures: single- and nano-crystalline and tetrahedral-amorphous or diamond-like carbon (DLC) [1, 2]. Microcompression has been demonstrated to enable the interrogation of even the strongest form of diamond - a -oriented single crystal - achieving the strength limit predicted by simulations (Figure 1) [3, 4]. Nowadays, these allotropes of carbon with high strength and low friction are used in microelectronics and micro-electromechanical systems (MEMS) as structure components [5]. However, the effects of these new nanostructures on the mechanical properties of these allotropes is mostly unknown especially at different service temperatures. In this study, the mechanical properties of single crystalline, nanocrystalline, and amorphous forms of diamond are systematically studied by conducting in situ microcompression at various temperatures in scanning electron microscope (SEM). This allows the investigation of thermally-activated defect behavior and activation energy for several different nanostructures of diamond. This is then correlated with the deformed structures using high resolution transmission electron microscope (HRTEM) and Raman spectroscopy to interpret the deformation mechanisms. Please click Additional Files below to see the full abstract

Plasticity and size effects in germanium: From cryogenic to elevated temperatures

Germanium is extensively used as a substrate in functional components of devices and microelectromechanical systems (MEMS) because of its tunable band structure and carrier mobility via. strain engineering [1]. The mechanical properties of Ge with a diamond-cubic structure at such small scales, i.e. in range of micro/nano-meter, are expected to be extraordinary since the improved strength and ductility of brittle crystals with minimized geometries [2]. Recent advances in nano-mechanical testing systems enable the investigation of the size- and temperature-dependent deformation behaviors and relevant parameters [3]. In the present study, micro-compression of FIB-machined micropillars is conducted to obtain a thorough understanding of the plasticity and size effects of Ge from cryogenic to elevated temperatures, i.e. in the range of -100°C to 600°C, shown in Figure 1(a). Dislocation motion in Ge is quantitatively evaluated as a function of sample size and crystalline orientation at the low temperature regime. Furthermore, the brittle-to-ductile transition is investigated to study the transition of deformation mechanisms, i.e. full to partial dislocation motion on the glide set, at the elevated temperatures regime [4]. Deformed regions in micropillars are subsequently characterized using HRTEM to track dislocations and microtwins. An unambiguous interpretation of dislocation processes in the diamond-cubic structure will be presented. Please click Additional Files below to see the full abstract

Effects of remote limb ischemic conditioning on muscle strength in healthy young adults: A randomized controlled trial

Remote limb ischemic conditioning (RLIC) is a clinically feasible method in which brief, sub-lethal bouts of ischemia protects remote organs or tissues from subsequent ischemic injury. A single session of RLIC can improve exercise performance and increase muscle activation. The purpose of this study, therefore, was to assess the effects of a brief, two-week protocol of repeated RLIC combined with strength training on strength gain and neural adaptation in healthy young adults. Participants age 18-40 years were randomized to receive either RLIC plus strength training (n = 15) or sham conditioning plus strength training (n = 15). Participants received RLIC or sham conditioning over 8 visits using a blood pressure cuff on the dominant arm with 5 cycles of 5 minutes each alternating inflation and deflation. Visits 3-8 paired conditioning with wrist extensors strength training on the non-dominant (non-conditioned) arm using standard guidelines. Changes in one repetition maximum (1 RM) and electromyography (EMG) amplitude were compared between groups. Both groups were trained at a similar workload. While both groups gained strength over time (P = 0.001), the RLIC group had greater strength gains (9.38 ± 1.01 lbs) than the sham group (6.3 ± 1.08 lbs, P = 0.035). There was not a significant group x time interaction in EMG amplitude (P = 0.231). The RLIC group had larger percent changes in 1 RM (43.8% vs. 26.1%, P = 0.003) and EMG amplitudes (31.0% vs. 8.6%, P = 0.023) compared to sham conditioning. RLIC holds promise for enhancing muscle strength in healthy young and older adults, as well as clinical populations that could benefit from strength training

Another Look at the Linear Probability Model and Nonlinear Index Models

We reassess the use of linear models to approximate response probabilities of binary outcomes, focusing on average partial effects (APE). We confirm that linear projection parameters coincide with APEs in certain scenarios. Through simulations, we identify other cases where OLS does or does not approximate APEs and find that having large fraction of fitted values in [0, 1] is neither necessary nor sufficient. We also show nonlinear least squares estimation of the ramp model is consistent and asymptotically normal and is equivalent to using OLS on an iteratively trimmed sample to reduce bias. Our findings offer practical guidance for empirical research

Late-Time Spectral Observations of the Strongly Interacting Type Ia Supernova PTF11kx

PTF11kx was a Type Ia supernova (SN Ia) that showed time-variable absorption features, including saturated Ca II H&K lines that weakened and eventually went into emission. The strength of the emission component of H{\alpha} increased, implying that the SN was undergoing significant interaction with its circumstellar medium (CSM). These features were blueshifted slightly and showed a P-Cygni profile, likely indicating that the CSM was directly related to, and probably previously ejected by, the progenitor system itself. These and other observations led Dilday et al. (2012) to conclude that PTF11kx came from a symbiotic nova progenitor like RS Oph. In this work we extend the spectral coverage of PTF11kx to 124-680 rest-frame days past maximum brightness. These spectra of PTF11kx are dominated by H{\alpha} emission (with widths of ~2000 km/s), strong Ca II emission features (~10,000 km/s wide), and a blue "quasi-continuum" due to many overlapping narrow lines of Fe II. Emission from oxygen, He I, and Balmer lines higher than H{\alpha} is weak or completely absent at all epochs, leading to large observed H{\alpha}/H{\beta} intensity ratios. The broader (~2000 km/s) H{\alpha} emission appears to increase in strength with time for ~1 yr, but it subsequently decreases significantly along with the Ca II emission. Our latest spectrum also indicates the possibility of newly formed dust in the system as evidenced by a slight decrease in the red wing of H{\alpha}. During the same epochs, multiple narrow emission features from the CSM temporally vary in strength. The weakening of the H{\alpha} and Ca II emission at late times is possible evidence that the SN ejecta have overtaken the majority of the CSM and agrees with models of other strongly interacting SNe Ia. The varying narrow emission features, on the other hand, may indicate that the CSM is clumpy or consists of multiple thin shells.Comment: 12 pages, 7 figures, 1 table, re-submitted to Ap