Publications

The influence of wrought product form on the fatigue-crack propagation resistance of aluminum-lithium alloys was examined; specifically, results on the growth kinetics of long (greater than 10 mm) fatigue cracks in peak-aged AlLiCuZr 2090-T8X and AlLiCuMgZr 2091-T8 alloys, fabricated as sheet and plate, are presented as a function of microstructure, load ratio and specimen orientation. Contrary to popular belief, it was found that fatigue-crack growth rates at equivalent stress intensity levels are significantly faster and less dependent on specimen orientation in sheet than in plate. Such differences are attributed to the prominent role of crack-tip shielding during fatigue in these alloys, resulting from crack deflection and consequent crack closure from wedging of fracture-surface asperities, which microstructurally is related to variations in the degree of recrystallization, grain morphology and texture between the two product forms.

This work intends to manipulate the internal flow units in Zr55Cu30Ni5Al10 bulk-metallic glasses (BMGs) through plasma-assisted hydrogenation to generate a positive microalloying effect on plasticity. Based on the cooperative shear model theory, serration-flow statistics during nanoindentation loading and creep tests during the holding stage were used to analyze the influence of hydrogen on the behavior of flow units in BMGs. Experimental observations showed that the hydrogen in the Zr55Cu30Ni5Al10 BMGs caused mechanical softening, plasticity improvement, and structural relaxation. Analysis also showed that the average volume, size, and activation energy of internal flow units in the BMGs all increased as a result of the increase in the hydrogen content. The hydrogenation in the BMGs was found to lead to a proliferation of shear bands, which promoted plasticity. The aggregation of these internal flow units reduced the stress required for plastic deformation through shear bands, ultimately causing softening and structural relaxation.

ABSTRACT In this work, BVRI light curves of 55 Type II supernovae (SNe II) from the Lick Observatory Supernova Search programme obtained with the Katzman Automatic Imaging Telescope and the 1 m Nickel telescope from 2006 to 2018 are presented. Additionally, more than 150 spectra gathered with the 3 m Shane telescope are published. We conduct an analyse of the peak absolute magnitudes, decline rates, and time durations of different phases of the light and colour curves. Typically, our light curves are sampled with a median cadence of 5.5 d for a total of 5093 photometric points. In average, V-band plateau declines with a rate of 1.29 mag (100 d)−1, which is consistent with previously published samples. For each band, the plateau slope correlates with the plateau length and the absolute peak magnitude: SNe II with steeper decline have shorter plateau duration and are brighter. A time-evolution analysis of spectral lines in term of velocities and pseudo-equivalent widths is also presented in this paper. Our spectroscopic sample ranges between 1 and 200 d post-explosion and has a median ejecta expansion velocity at 50 d post-explosion of 6500 km s−1 (H α line) and a standard dispersion of 2000 km s−1. Nebular spectra are in good agreement with theoretical models using a progenitor star having a mass <16M⊙. All the data are available to the community and will help to understand SN II diversity better, and therefore to improve their utility as cosmological distance indicators.

The diffusion of ions in solid materials plays an important role in many aspects of materials science, such as the geological evolution of minerals, materials synthesis, and in device performance across several technologies. For example, the realization of multi-valent (MV) batteries, which offer a realistic route to superceding the electrochemical performance of Li-ion batteries, hinges on the discovery of host materials that possess adequate mobility of the multi-valent intercalant to support reasonable charge and discharge times. This has proven especially challenging, motivating the current investigation of ion mobility (Li + , Mg 2+ , Zn 2+ , Ca 2+ , and Al 3+ ) in spinel Mn 2 O 4 , olivine FePO 4 , layered NiO 2 , and orthorhombic δ-V 2 O 5 . In this study, we not only quantitatively assess these structures as candidate cathode materials, but also isolate the chemical and structural descriptors that govern MV diffusion. Our finding that matching the intercalant site preference to the diffusion path topology of the host structure controls mobility more than any other factor, leads to practical and implementable guidelines to find fast-diffusing MV ion conductors.

Medicinal plants have been used as a source of medicine since prehistoric times. They have always held a prominent position at the forefront of all cultures and throughout human history. They are a rich source of phytochemicals, and it is through these phytochemicals that many contemporary medicines have been developed. The Amaranthaceous family includes the herbaceous perennial plant known as Achyranthes aspera, which stands upright. A. aspera is a plant that has a bitter taste and is made up of secondary metabolites such as alkaloids, saponins, tannins, flavonoids, glycosides, steroids, essential oils, and fatty acids. These secondary metabolites are vital in demonstrating improved bioactivity against several ailments. The phytoconstituents can be found in many different sections, including the seeds, the roots, the shoots, and the leaves. This review highlights A. aspera many secondary metabolites and their potential for therapeutic medications.

The evaluation of reaction energies between solids using density functional theory (DFT) is of practical importance in many technological fields and paramount in the study of the phase stability of known and predicted compounds. In this work, we present a comparison between reaction energies provided by experiments and computed by DFT in the generalized gradient approximation (GGA), using a Hubbard U parameter for some transitionmetal elements (GGA+U).We use a data set of 135 reactions involving the formation of ternary oxides from binary oxides in a broad range of chemistries and crystal structures. We find that the computational errors can be modeled by a normal distribution with a mean close to zero and a standard deviation of 24 meV/atom. The significantly smaller error compared to the more commonly reported errors in the formation energies from the elements is related to the larger cancellation of errors in energies when reactions involve chemically similar compounds. This result is of importance for phase diagram computations for which the relevant reaction energies are often not from the elements but from chemically close phases (e.g., ternary oxides versus binary oxides). In addition, we discuss the distribution of computational errors among chemistries and show that the use of a Hubbard U parameter is critical to the accuracy of reaction energies involving transition metals even when no major change in formal oxidation state is occurring.

Improvement in endurance exercise performance in adult humans following sprint interval training (SIT) has been attributed to mitochondrial (mito) biogenesis. However, this conclusion has been inferred from mito biogenic signaling, and not synthesis of new mito protein. Muscle protein synthesis (MPS) and mito biogenic responses to SIT have not been measured, nor have sex‐specific responses. We hypothesized that males and females would have similar rates of MPS, mito biogenesis, and overall individual protein synthetic rates after 9 sessions of SIT. 21 healthy adults (11 male, 10 female, 23±1 years, body mass index: 22.8±0.6 kg/m 2 ; mean±SE) were orally administered deuterium oxide (D 2 O) for measurements of protein synthetic rates for 4 weeks while completing SIT. Maximal oxygen uptake increased (males from 43.4±2.1 to 44.0±2.3; females from 39.5±0.9 to 42.5±1.3 ml/kg/min; P =0.002) following SIT. MPS was greater in males compared with females in the mixed (150%; P <0.001), cytosolic (135%; P =0.038), and mito (135%; P =0.056) fractions. Kinetic proteomics identified 60 proteins that responded differently to SIT between the sexes ( P <0.05); all were greater in males. For the first time, we document greater MPS and mito biogenesis in response to SIT in males compared with females, and present the first data describing the synthetic response of individual proteins in humans during exercise training. Grant Funding Source : Supported by the Office of Naval Research (N00014‐10‐1‐0247)

An understanding of how fatigue cracks grow in bone is of importance as fatigue is thought to be the main cause of clinical stress fractures. This study presents new results on the fatigue-crack growth behavior of small surface cracks (∼75–1000μm in size) in human cortical bone, and compares their growth rates with data from other published studies on the behavior of both surface cracks and many millimeter, through-thickness large cracks. Results are obtained with a cyclically loaded cantilever-beam geometry using optical microscopy to examine for crack growth after every 100–500 cycles. Based on the current and previous results, small fatigue cracks appear to become more resistant to fatigue-crack growth with crack extension, analogous to the way the fracture resistance of cortical bone increases with crack growth. Mechanistically, a theory attributing such behavior to the development of bridges in the wake of the crack with crack growth is presented. The existence of such bridges is directly confirmed using optical microscopy.

Although multiple studies find that offspring of depressed mothers are at risk for depressive disorders, there is uncertainty about the specific mechanisms that are at work--particularly with respect to modifiable factors that might be targeted for early intervention. The present work examines that parenting behaviors may operate as mediators, moderators, or independent influences on the development of youth depressive symptoms. One hundred one mothers and their early adolescent children participated in positive and negative interaction tasks. Maternal and youth self-reports of youth depressive symptoms were collected at baseline, 9-month, and 18-month assessments. Maternal history of depression was significantly associated with maternal-reported, but not youth self-reported, depressive symptomatology. Maternal positive and negative interaction behaviors in positive contexts were associated with higher youth self-reported depressive symptoms. Maternal positive interaction behaviors in positive contexts and maternal negative interactive behaviors in conflict contexts were associated with higher youth self-reported depressive symptoms. We found no evidence for maternal interaction behaviors serving as a mediator and little evidence of maternal interaction behaviors serving as a moderator of the relationship between maternal and offspring depression. Low maternal positive engagement tended to be more consistently associated with maternal- and self-reported youth depressive symptoms. The present findings suggest that characteristics of mother-child interactions that are associated with youth depressive symptomatology are pertinent to youth with and without a mother with a history of depression.

We present photometry, spectroscopy, and host-galaxy integral-field spectroscopy of the Type II supernova (SN) 2016esw in CGCG~229-009 from the first day after the explosion up to 120 days. Its light-curve shape is similar to that of a typical SN II; however, SN 2016esw is near the high-luminosity end of the SN II distribution, with a peak of $M^{\rm max}_{V}=-18.36$ mag. The $V$-band light curve exhibits a long recombination phase for a SN II (similar to the long-lived plateau of SN 2004et). Considering the well-known relation between the luminosity and the plateau decline rate, SN 2016esw should have a $V$-band slope of $\sim 2.10$ mag (100 days)$^{-1}$; however, SN 2016esw has a substantially flatter plateau with a slope of $1.01\pm 0.26$ mag (100 days)$^{-1}$, perhaps indicating that interacting Type II supernovae are not useful for cosmology. At 19.5 days post-explosion, the spectrum presents a boxy H$\alpha$ emission line with flat absorption profiles, suggesting interaction between the ejecta and circumstellar matter. Finally, based on the spectral properties, SN 2016esw shows similarities with the luminous and interacting SN 2007pk at early epochs, particularly in terms of observable line features and their evolution.