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This is a copy of the slides presented at the meeting but not formally written up for the volume.
Interactions at magnetic interfaces are central to the operation of virtually all magnetic heterostructures. When the interface is between two magnetic materials, the exchange interaction between spins at the interface is often a dominant force, and can dramatically change the magnetic response of the overall heterostructure. In ferromagnet (FM)/antiferromagnet (AFM) heterostructures, this interaction is often referred to as exchange anisotropy or bias and it has been widely used over the past decade in a wide array of applications such as magnetic recording heads, MRAMs, etc. The powerful implications of interactions between an AFM and a FM have been realized in a wide range of thin film heterostructure with both metallic and oxide constituents. There is, however, much less work on oxide-oxide FM/AFM systems. On the other hand, the development and understanding of functional oxide materials, especially multifunctional materials like BiFeO3 (BFO), have piqued the interest of researchers worldwide with the promise of coupling between order parameters such as ferroelectricity and antiferromagnetism. Recent research suggests that there is exchange coupling and anisotropy between the metallic ferromagnet Co0.9Fe0.1 (CoFe) and the multiferroic, antiferromagnet BFO, showing the possibility to create highly desirable multifunctional systems with new possibilities for device design. Such a result provides the driving force to create multifunctional oxide-oxide systems where exchange interactions could be much stronger then in metal/oxide structures due the added epitaxial nature of the interface. In this study, we use La0.7Sr0.3MnO3(LSMO)/BFO thin film heterostructures as a model system to explore the exchange interaction at an oxide interface. The heterostructures are grown on various vicinal cuts of SrTiO3 single crystal substrates using laser MBE. Structural analysis using x-ray diffraction, transmission electron microscopy and Rutherford backscattering spectrometry reveals high quality films with the pristine interfaces required for exchange coupling. First results from photoemission electron microscope (PEEM) studies reveal that the magnetic LSMO domain structure mimics underneath ferroelectric BFO domain structure, i..e, it is strongly pinned by the underlying AFM structure. The coupling behavior is being characterized by magnetic measurements (SQUID, VSM), which shows a strong enhancement in the coercivity of the LSMO layer, suggesting the existence of exchange bias coupling. We are probing the strength of this coupling using a combination of careful laser MBE growth experiments and physical property measurements. In this paper, we will report results of experiments in which the LSMO layer has been grown by laser MBE in the thickness range of 2-50nm on a  BFO layer.
This is a copy of the slides presented at the meeting but not formally written up for the volume.
At heterojunctions between different oxide perovskite phases both lattice and electronic structure is modified by the junction. One interesting question that several groups have studied is just how far into the neighboring materials these perturbations extend. We have studied this for insulating phases as well as conducting phases. For insulating phases it appears that the lattice distortions are healed in a layer about one unit cell thick. By stacking different materials each of which is only a single unit cell thick we have obtained materials that exhibit new properties determined by the stacking architecture. For example, superlattices that lack inversion symmetry have a built-in polarization that is controlled by the direction of the strain asymmetry. For conducting phases, the electronic structure also seems to be modified mainly in a layer only a few unit cells thick. We have studied this in superlattices of SrTiO3 and LaMnO3 in which we vary the thickness of the layers. We use optical conductivity to probe the electronic structure in the near infrared to near ultraviolet spectral region. The conductivity is close to the average of the two constituents, but differs in certain spectral regions, especially for the films with the thinnest supercells.This work was supported by the Department of Energy Basic Energy Sciences program at the Fredrick Seitz Materials Research Laboratory at the University of Illinois, Urbana, IL.
Employing atomic-scale simulations, the response of a high-angle grain boundary (GB), the soft/hard GB, against external loading was systematically investigated. Under tensile loading close to the hard orientation, strain-induced dynamic recrystallization was observed to initiate through direct soft-to-hard grain reorientation, which was triggered by stress mismatch, inhibited by surface tension from the soft-hard GB, and proceeded by interface ledges. Such grain reorientation corresponds with expansion and contraction of the hard grain along and perpendicular to the loading direction, respectively, accompanied by local atomic shuffling, providing relatively large normal strain of 8.3% with activation energy of 0.04 eV per atom. Tensile strain and residual dislocations on the hard/soft GB facilitate the initiation of dynamic recrystallization by lowering the energy barrier and the critical stress for grain reorientation, respectively.
Imprinted genes uniquely drive and support fetoplacental growth by controlling the allocation of maternal resources to the fetus and affecting the newborn’s growth. We previously showed that alterations of the placental imprinted gene expression are associated with suboptimal perinatal growth and respond to environmental stimuli including socio-economic determinants. At the same time, maternal psychosocial stress during pregnancy (MPSP) has been shown to affect fetal growth. Here, we set out to test the hypothesis that placental imprinted gene expression mediates the effects of MPSP on fetal growth in a well-characterized birth cohort, the Stress in Pregnancy (SIP) Study. We observed that mothers experiencing high MPSP deliver infants with lower birthweight (P=0.047). Among the 109 imprinted genes tested, we detected panels of placental imprinted gene expression of 23 imprinted genes associated with MPSP and 26 with birthweight. Among these genes, five imprinted genes (CPXM2, glucosidase alpha acid (GAA), GPR1, SH3 and multiple ankyrin repeat domains 2 (SHANK2) and THSD7A) were common to the two panels. In multivariate analyses, controlling for maternal age and education and gestational age at birth and infant gender, two genes, GAA and SHANK2, each showed a 22% mediation of MPSP on fetal growth. These data provide new insights into the role that imprinted genes play in translating the maternal stress message into a fetoplacental growth pattern.
Normal odd-chain SFA (OCSFA), particularly tridecanoic acid (n-13 : 0), pentadecanoic acid (n-15 : 0) and heptadecanoic acid (n-17 : 0), are normal components of dairy products, beef and seafood. The ratio of n-15 : 0:n-17 : 0 in ruminant foods (dairy products and beef) is 2:1, while in seafood and human tissues it is 1:2, and their appearance in plasma is often used as a marker for ruminant fat intake. Human elongases encoded by elongation of very long-chain fatty acid (ELOVL)1, ELOVL3, ELOVL6 and ELOVL7 catalyse biosynthesis of the dominant even-chain SFA; however, there are no reports of elongase function on OCSFA. ELOVL transfected MCF7 cells were treated with n-13 : 0, n-15 : 0 or n-17 : 0 (80 µm) and products analysed. ELOVL6 catalysed elongation of n-13 : 0→n-15 : 0 and n-15 : 0→n-17 : 0; and ELOVL7 had modest activity toward n-15 : 0 (n-15 : 0→n-17 : 0). No elongation activity was detected for n-17 : 0→n-19 : 0. Our data expand ELOVL specificity to OCSFA, providing the first molecular evidence demonstrating ELOVL6 as the major elongase acting on OCSFA n-13 : 0 and n-15 : 0 fatty acids. Studies of food intake relying on OCSFA as a biomarker should consider endogenous human metabolism when relying on OCSFA ratios to indicate specific food intake.
While maternal folate deficiency has been linked to poor pregnancy outcomes such as neural tube defects, anaemia and low birth weight, the relationship between folate and preterm birth (PTB) in the context of the US post-folic acid fortification era is inconclusive. We sought to explore the relationship between maternal folate status and PTB and its subtypes, i.e. spontaneous and medically indicated PTB.
Boston Birth Cohort, a predominantly urban, low-income, race/ethnic minority population at a high risk for PTB.
Mother–infant dyads (n 7675) enrolled in the Boston Birth Cohort. A sub-sample (n 2313) of these dyads had maternal plasma folate samples collected 24–72 h after delivery.
Unadjusted and adjusted logistic regressions revealed an inverse relationship between the frequency of multivitamin supplement intake and PTB. Compared with less frequent use, multivitamin supplement intake 3–5 times/week (adjusted OR (aOR) = 0·78; 95 % CI 0·64, 0·96) or >5 times/week (aOR = 0·77; 95 % CI 0·64, 0·93) throughout pregnancy was associated with reduced risk of PTB. Consistently, higher plasma folate levels (highest v. lowest quartile) were associated with lower risk of PTB (aOR = 0·74; 95 % CI 0·56, 0·97). The above associations were similar among spontaneous and medically indicated PTB.
If confirmed by future studies, our findings raise the possibility that optimizing maternal folate levels across pregnancy may help to reduce the risk of PTB among the most vulnerable US population in the post-folic acid fortification era.
In September 2016, the annual meeting of the International Union for Quaternary Research’s Loess and Pedostratigraphy Focus Group, traditionally referred to as a LoessFest, met in Eau Claire, Wisconsin, USA. The 2016 LoessFest focused on “thin” loess deposits and loess transportation surfaces. This LoessFest included 75 registered participants from 10 countries. Almost half of the participants were from outside the United States, and 18 of the participants were students. This review is the introduction to the special issue for Quaternary Research that originated from presentations and discussions at the 2016 LoessFest. This introduction highlights current understanding and ongoing work on loess in various regions of the world and provides brief summaries of some of the current approaches/strategies used to study loess deposits.
With the rapid development of telescopes, both temporal cadence and the spatial resolution of observations are increasing. This in turn generates vast amount of data, which can be efficiently searched only with automated detections in order to derive the features of interest in the observations. A number of automated detection methods and algorithms have been developed for solar activities, based on the image processing and machine learning techniques. In this paper, after briefly reviewing some automated detection methods, we describe our efficient and versatile automated detection method for solar filaments. It is able not only to recognize filaments, determine the features such as the position, area, spine, and other relevant parameters, but also to trace the daily evolution of the filaments. It is applied to process the full disk Hα data observed in nearly three solar cycles, and some statistic results are presented.
To optimise patients’ outcomes and gain insight into transmitted drug resistance (TDR) among human immunodeficiency virus (HIV)-1 treatment-naive patients in Beijing, the prevalence of TDR was assessed. Demographic and clinical data of 1241 treatment-naive patients diagnosed between April 2014 and February 2015 were collected. TDR was defined using the Stanford University HIV drug resistance mutations database. The risk factors were evaluated by multi-logistic regression analysis. Among 932 successfully amplified cases, most were male (96.78%) and infected through men having sex with men (91.74%). Genotype were CRF01_AE (56.44%), B (20.60%), CRF07_BC (19.96%), C (1.61%) and other genotypes (1.39%). The overall prevalence of TDR was 6.12%. Most frequent mutations occurred in non-nucleoside reverse transcriptase inhibitors (NNRTIs) (3.11%), followed by protease inhibitors (PIs) (2.25%) and nucleoside reverse transcriptase inhibitors (NRTIs) (1.32%). Furthermore, HIV-1 genotype was associated with high risk of resistance, in which genotype C and other genotype may have higher risk for resistance. The prevalence among treatment-naive patients in Beijing was low. Resistance to NNRTIs was higher than with PIs or NRTIs. Continuous monitoring of regional levels of HIV-1 TDRs would contribute to improve treatment outcomes and prevent failures.
DNA nanostructures are a set of materials with well-defined physical, chemical, and biological properties that can be used on their own or incorporated with other materials for many applications. Herein, the practical aspects of utilizing DNA nanostructures (structural or dynamic) as materials are comprehensively covered. This article first summarizes properties of DNA molecules and practical considerations and then discusses the fundamental design principles of structural DNA nanostructures. Finally, various aspects of dynamic DNA nanostructure-based actuation and computation are included.
We quantify what drives the rise in medical expenditures over the life-cycle using a stochastic dynamic overlapping generations model of health investment. Three motives for health investment are considered. First, health delivers a flow of utility each period (the consumption motive). Second, better health enables people to allocate more time to productive or pleasurable activities (the investment motive). Third, better health improves survival prospects (the survival motive). We find that, overall, the consumption motive plays a dominant role, whereas the investment motive is more important than the consumption and survival motives until the forties. The survival motive is quantitatively less important when compared to the other two motives. We also conduct a series of counter-factual policy experiments to investigate how government policies impacting health insurance coverage, Social Security, and health care technological progress affect the behavior of medical expenditures, and social welfare.
The analytical expression between the line profile and its corresponding pulsation velocity field is derived by the assumption of Doppler Imaging (DI). Based on this approach, numerical experiments of the recovery of the one dimensional nonradial pulsation velocity distribution from the residual line profiles are presented.
Radiocarbon accelerator mass spectrometry (AMS) techniques were used to date total organic carbon and plant seeds in the lFs core sequence (36°48′N, 100°08′E) from Qinghai Lake, China. This core was drilled ∼18 m into Qinghai Lake sediments as part of an international cooperative research project, “Scientific Drilling at Qinghai Lake in the Northeastern Tibetan Plateau: High-Resolution Paleoenvironmental Records of Eastern Asia Linked to Global Change,” which began in 2004. Based on the differences in lithology and total organic content (TOC) in core lFs, the core was divided into 3 sections for age-modeling purposes: the upper ∼499 cm lacustrine silty clay to clay; the middle unit of silty clay with silt layers from 499–901 cm; and the lower 901–1861 cm silty clay, loess-like silt, and fine sand layers. Three different approaches are applied to the reservoir age problem. First, a simple linear regression gives an offset of 1342 yr. If the core is divided into three sections, linear regressions can be applied separately for the three segments, which results in an age estimate for the average hardwater effect of ∼135 yr BP for the surface section up to 499 cm. If extrapolated for deeper sections, these results imply a higher reservoir offset for those two sections, which may be as much as 1143 and 2523 yr, but this assumes that there are no discontinuities in the core. A third approach using a wiggle-matching approach gave an offset of 196 yr. This study concludes that the reservoir age of Qinghai Lake is complex, but these new data add to our understanding of the 14C chronology of Qinghai Lake for the last 32 ka.
The B type star 53 Persei was discovered in 1977 by Smith (1977) as the prototype of a separate group of B-type variables showing light and line profile variability. The physical cause of the variability was thought to be nonradial pulsation (NRP) (see, e.g. Smith et al. 1984). However, the NRP model for this star has been questioned by Balona (1986) who suggested the rotational modulation (RM) model to explain the variability. In order to resolve the long lasting debate about 53 Persei, a campaign was initiated to organize coordinated optical photometry and spectroscopy from the ground, and Far-UV photometry from Voyager in 1991 January. This paper presents the results of period analysis on the groundbased UBV data. In another paper, Smith & Huang (1994) report the new identification of pulsation modes using Voyager Far-UV photometry combined with the results from optical observations. Some preliminary results from APT uvby observations taken at a single site are also cited for comparison.