Restoring longleaf pine (Pinus palustris) in loblolly pine (P. taeda) stands on the coastal plain of North Carolina

To support the development of silvicultural protocols for restoring longleaf pine (LLP; Pinus palustris Mill.) and its characteristic herbaceous understory in loblolly pine (LBP; P. taeda L.) stands, a three-year study was conducted on moderately well- and well-drained soils in Onslow County, North Carolina. A replicated field experiment was conducted to test the effects of selected silvicultural treatments on planted LLP seedlings, understory vegetation, and plant resources. Seven canopy treatments included four uniform canopy density treatments defined by target residual basal area [Control, MedBA (9 m2/ha), LowBA (4.5 m2/ha), and Clearcut] and three circular gap treatments defined by area [LG (5027 m2), MG (2827 m2), and SG (1257 m2)]. Within each canopy treatment, three cultural treatments including control (C), herbicide (H), and herbicide plus fertilization (H + F) were applied. Among the canopy treatments, LLP seedlings planted in the Clearcut had higher survival rate after the first three growing seasons compared to Controls. Canopy treatment significantly improved seedling root collar diameter (RCD) growth, but interacted with applied cultural treatment. C within Control had the smallest RCD, and H + F within Clearcut had the largest RCD. Canopy treatment significantly affected the percentage of seedlings in height growth such that Control plots had significantly lower percentage of seedlings in height growth than other canopy treatments. H and H + F also significantly increased the percentage of seedling in height growth compared to C. Among the uniform canopy treatments, ground layer vegetation cover significantly changed over three years, but showed different trends for different functional groups. By the 2010 growing season, H increased forb cover and proportions of total herbaceous and forb covers, but decreased covers of woody, graminoids and proportion of graminoid cover. Clearcut resulted in greater midstory LBP density by the 2009 and 2010 growing seasons. Herbicide application (H and H + F) significantly decreased target woody density, but increased LBP density by the 2010 growing season. Clearcut resulted in greater aboveground biomass of woody, herbaceous and graminoid species, but it did not affect the proportions of herbaceous, graminoids and forbs. H significantly decreased woody aboveground biomass and graminoid proportion. H + F significantly decreased woody aboveground biomass, but increased herbaceous proportion. Canopy treatment did not affect species richness, but herbicide application (H and H + F) reduced woody species richness at the scale from 0.1 to 100 m2. Non-metric multidimensional scaling (NMS) and multi-response permutation preocudure (MRPP) analyses concluded that the variation of understory vegetation among sampled plots was attributed to soil characteristics, especially soil texture, rather than experimental treatments. Gap size affected neither survival and growth of planted LLP seedlings after the first three growing seasons nor the abundance of ground layer vegetation and density of midstory woody plants by the third growing season after harvest. Within-gap position significantly affected the growth of planted LLP seedlings, but it did not affect their survival or the abundance of ground layer vegetation. Both gap size and within-gap position significantly affected gap light index (GLI), but they did not affect surface soil moisture and affected soil temperature only in 2009. Although within-gap position did affect foliar P and K concentrations, these effects showed neither consistency over the two years nor followed expected pattern of changes (i.e., high close to center and low at edge or inside forest). Our results supported the hypothesis of light limitation on seedling growth in gaps. GLI significantly differed among four uniform canopy treatments, nonlinearly increasing with decreasing basal area. H resulted in higher soil temperature in both 2009 and 2010. Foliar Ca, Mg, Zn and Fe concentrations significantly increased after the prescribed fire in 2010, while foliar N, Cu and Na concentrations significantly decreased. The effects of canopy and/or cultural treatments on foliar nutrients were not consistent over the two years. The RCD of planted LLP seedlings was positively correlated with GLI and foliar P, Ca and Zn concentrations, but negatively correlated with soil temperature

The finite element analysis of the in plane and out of plane harmonic responses of piezoresponse force microscopy cantilever

The harmonic response under the in plane and out of plane driving force separately and model analysis of the widely used SCM-PIT probe were carried out in the consideration of the typical piezoresponse force microscopy working condition by finite element method. It is shown that there are symmetric modes of the resonance at 68, 408, 1139, 2244 kHz, and antisymmetric modes at 646, 1020, and 3077 kHz in the first seven eigenmodes. The symmetric modes of the harmonic response are verified by the frequency sweep method from the piezoresponse phase signals experimentally. It is also revealed that different driving frequencies should be used in the resonance-enhanced PFM imaging in the consideration of the domain structures. The driving frequency of 68, 408, 1139, 2244 kHz should be preferred in the resonance-enhanced PFM imaging of the out of plane domains, while the driving frequency of 646, 1020 and 3077 kHz should be used for the imaging of in plane domains in order of achieved the best resonance-enhanced effect

On the solvability of the indefinite Hamburger moment problem

In this paper, we present a new approach for the solvability of the indefinite Hamburger moment problem in the class of generalized Nevanlinna functions with a given negative index, which is more algebraic and completely different from the existing method [8] based on the step-by-step Schur algorithm. As a by-product of this approach, we simultaneously obtain a concrete rational solution of such an indefinite Hamburger moment problem when the solvability conditions are met. The basic strategy focuses on the structural characteristics of the Hankel matrix and the relation among the Hankel, Loewner, Bezout and some other structured matrices

Magnetic properties of dashing rocks loess at Timaru, South Island, New Zealand

The relationships between magnetic susceptibility and pedogenic development are different in various regions of the world. For example, loess magnetic susceptibility shows a positive correlation with pedogenic development in Chinese Loess Plateau (CLP),

The finite element analysis of the in plane and out of plane harmonic responses of piezoresponse force microscopy cantilever

The harmonic response under the in plane and out of plane driving force separately and model analysis of the widely used SCM-PIT probe were carried out in the consideration of the typical piezoresponse force microscopy working condition by finite element method. It is shown that there are symmetric modes of the resonance at 68, 408, 1139, 2244 kHz, and antisymmetric modes at 646, 1020, and 3077 kHz in the first seven eigenmodes. The symmetric modes of the harmonic response are verified by the frequency sweep method from the piezoresponse phase signals experimentally. It is also revealed that different driving frequencies should be used in the resonance-enhanced PFM imaging in the consideration of the domain structures. The driving frequency of 68, 408, 1139, 2244 kHz should be preferred in the resonance-enhanced PFM imaging of the out of plane domains, while the driving frequency of 646, 1020 and 3077 kHz should be used for the imaging of in plane domains in order of achieved the best resonance-enhanced effect

Fault-Tolerant Converter with a Modular Structure for HVDC Power Transmitting Applications

For the high-voltage direct-current (HVDC) power transmission system of offshore wind power, dc/dc converters are the potential solution to collect the power generated by off-shore wind farms to HVDC terminals. The converters operate with high-voltage gain, high efficiency, and fault tolerance over a wide range of operating conditions. In this paper, an isolated ultrahigh step-up dc/dc converter with a scalable modular structure is proposed for HVDC offshore wind power collection. A flyback-forward converter is employed as the power cell to form the expandable electrically isolated modular dc/dc converter. The duty ratio and phase-shift angle control are also developed for the proposed converter. Fault-tolerant characteristics of the converter are illustrated through the redundancy operation and fault-ride-through tests. Redundancy operation is designed to maintain high operation efficiency of the converters and fault-ride-through operation improves the converter reliability under harsh operating conditions. Analytical studies are carried out, and a 750-W prototype with three modular cells is built and experimentally tested to verify the performance of the proposed modular dc/dc converter

Mesenchymal Stem Cell-Derived Exosomes for Myocardial Infarction Treatment

Myocardial infarction (MI) is a major cause of morbidity and mortality in modern society. Over the past decades, mesenchymal stem cell (MSCs)-based therapy has shown promising results in the treatment of MI due to their unique properties of multi-differentiation ability, immune-privileged phenotype and paracrine activity. Recently, MSC-derived exosomes (MSC-EXO) have been proposed as a promising therapeutic strategy for MI with their ability to inhibit cardiomyocyte apoptosis and stimulate vascular angiogenesis. They also aid immunoregulation and rejuvenation of cardiomyocyte senescence by transporting their unique content such as proteins, lipids, and miRNAs. Compared with MSC transplantation, MSC-EXO administration has shown several advantages, including lower toxicity and immunogenicity and no risk of tumor formation. Nonetheless the potential mechanisms underlying MSC-EXO-based therapy for MI are not fully understood. In addition, lack of modification of MSC-EXOs can impact therapeutic efficacy. It is vital to optimize MSC-EXO and enhance their therapeutic efficacy for MI. We summarize the recent advances regarding biological characteristics, therapeutic potential and mechanisms, and optimal approaches to the use of MSC-EXOs in the treatment of MI