Structural Retention Research Articles

Carbon storage implications of active management in mature Pseudotsuga menziesii forests of western Oregon

Mature stands, mid-successional communities in which large live trees are the dominant structural feature, are a major component of forested landscapes across North America. Despite this prominence at regional scales, mature stands have rarely been the focus of research on forest carbon dynamics. We utilized an observational study design to (i) examine the medium-term impact of active management on carbon storage in live and dead vegetation in mature Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco)–dominated stands in western Oregon, and (ii) provide baseline estimates of total non-soil carbon storage during the mature phase of stand development for this forest type. Stands aged 106–193 years at the time of sampling were selected to represent a gradient in harvest intensity, from passive (reserve-based) management, to low-intensity (commercial thinning) and high-intensity (regeneration harvest with structural retention) active management. Active management treatments were implemented following the onset of maturity in stands with no prior management history, and sampling was conducted an average of 38 years and 22 years following treatment (mean for thinned and retention harvest conditions, respectively). Total non-soil carbon storage was significantly greater in stands managed using a reserve-based approach (mean of 575 Mg C ha−1) than those subject to retention harvest (mean 257 Mg C ha−1) 17 to –34 years previously, but was not different from stands managed over extended rotations with commercial thinning (mean 546 Mg C ha−1). A similar trend was evident for carbon storage in live overstory trees, which were also the dominant component of total non-soil carbon in all management conditions. Dead wood pools varied greatly among stands, but estimates did not indicate any systematic differences in carbon storage in dead wood between management conditions. Our results suggest that shifting from passive management to a high-intensity harvest regime in mature Douglas-fir stands will entail substantial reductions in carbon storage. By contrast, managing stands over extended rotations with light thinning may enable the provision of wood products while maintaining relatively high carbon storage in the forest ecosystem. In absolute terms, mean carbon storage across our full sample of unmanaged, low-intensity and high-intensity harvest conditions exceeded previously reported values from inventories of mature plots across a similarly broad range of site conditions, but remains below the potential upper bounds to carbon storage in Douglas-fir-dominated forests. However, total aboveground carbon stocks in excess of 700 Mg ha−1 in individual mature stands in our dataset implies that, under certain conditions, forest biomass approaches its maximum by the close of the mature phase of stand development in Douglas-fir-dominated forests.

Structural and Computational Assessment of the Influence of Wet-Chemical Post-Processing of the Al-Substituted Cubic Li7La3Zr2O12.

Li7La3Zr2O12 (LLZO) and related compounds are considered as promising candidates for future all-solid-state Li-ion battery applications. Still, the processing of those materials into thin membranes with the right stoichiometry and crystal structure is difficult and laborious. The sensitivity of the Li-ion conductive garnets against moisture and the associated Li+/H+ cation exchange makes their processing even more difficult. Formulation of suitable polymer/ceramic hybrid solid state electrolytes could be a prosperous way to reach the future large scale production of solid state Li-ion batteries. In fact, solvent mediated and/or slurry based wet-processing of the LLZO, e.g., tape-casting, could result in irreversible Li-ion loss of the pristine material due to Li+/H+ cation exchange. The concomitant structural changes and loss in functionality in terms of Li-ion conductivity are the results of the above process. Therefore, in the present work a systematic study on the chemical stability and structural retention of Al-substituted LLZO in different solvents is reported. It was found that Li+/H+ exchange in LLZO occurs upon solvent immersion, and its magnitude is dependent on the availability of -OH functional groups of the solvent molecules. As a result, a larger degree of Li+/H+ exchange causes higher increase of the lattice parameter of the LLZO, determined by synchrotron diffraction analyses. The expansion of the cubic unit cell was ascertained, when Li+ was replaced by H+ in the host lattice, by ab initio computational studies. The application of the most common solvent as dispersion medium, i.e., high purity water, causes the most significant Li+/H+ exchange and, therefore, structural change, while acetonitrile was proven to be the best suitable solvent for wet postprocessing of LLZO. Finally, computational calculations suggested that the Li+/H+ exchange could result in diminished ionic, i.e., mixed Li+-H+, conductivity due to the insertion of protons with lower mobility than that of Li-ions.

Combining Aggregated and Dispersed Tree Retention Harvesting for Conservation of Vascular Plant Communities

Retention harvesting (also called tree retention or structural retention), in which live mature trees are selectively retained within harvested stands at different retention levels and in different patterns (aggregated to dispersed), is increasingly being used to mitigate the negative impacts of forest harvesting on biodiversity. However, the effectiveness of combining different patterns of retention harvesting for conservation and recovery of understory vascular plants in the long term is largely unknown. To address this gap, we compared understory vascular plant diversity, abundance, and composition between aggregated retention and five levels of surrounding dispersed retention (0% [clearcut], 10%, 20%, 50%, 75%) 15 yr postharvest. We also investigated the influence of dispersed retention on the ability of embedded retention patches to support plant communities characteristic of unharvested forests, and whether it varies by patch size of aggregated retention (0.20 ha or 0.46 ha) and position within patches (edge or interior). Species richness, diversity, and cover were higher in the dispersed retention than in the patch retention as the harvested areas favored early-seral plant species. Graminoid cover was greater at the edges than in the interior of large patches. Retention patches as small as 0.2 ha more effectively supported shade-tolerant (forest interior) plant communities when they were surrounded by higher levels of dispersed retention (as compared to patches retained within clearcuts). Overall, the combined use of both aggregated and dispersed retention within a given cutblock benefits both late- and early-seral plant species and thus could effectively conserve understory plant assemblages in harvested landscapes. Sustainable forest management should therefore consider using a range of retention patch sizes combined with varying levels of surrounding dispersed retention in harvest designs to achieve objectives for plant conservation.

Experimental behavior of double-row Y-type perfobond rib shear connectors

Although existing studies have only analyzed Y-type perfobond rib shear connectors arranged in a single row, practical applications can apply numerous such connectors to beams with narrow spaces between them. The present study aimed to evaluate the structural behavior of double-row Y-type perfobond rib shear connectors, and thus describe grouped Y-type perfobond rib shear connectors. Push-out tests were conducted in accordance with Eurocode-4, and the relative slip, shear resistance, and ductility were measured. There were two primary variables (spacing and number of Y-type perfobond rib shear connectors) and three types of test specimens: single row, double rows (120 mm spacing), and double rows (300 mm spacing). The representative single-row specimen was used to validate the push-out test results by providing a comparison with previous tests, and provided a shear resistance reference value. The other two specimen types consisted of multiple Y-type perfobond rib shear connectors attached in parallel to an H-beam. Test results revealed that shear resistance increased as the number of shear connectors increased; however, the structural behavior depended on the shear connector spacing. The specimen with wider spacing demonstrated a better ultimate load and ductility relative to the specimen with narrower spacing. Wider shear connector spacing thus leads to better structural behavior retention.

Combining aggregated and dispersed tree retention harvesting for conservation of vascular plant communities.

Retention harvesting (also called tree retention or structural retention), in which live mature trees are selectively retained within harvested stands at different retention levels and in different patterns (aggregated to dispersed), is increasingly being used to mitigate the negative impacts of forest harvesting on biodiversity. However, the effectiveness of combining different patterns of retention harvesting for conservation and recovery of understory vascular plants in the long term is largely unknown. To address this gap, we compared understory vascular plant diversity, abundance, and composition between aggregated retention and five levels of surrounding dispersed retention (0%[clearcut], 10%, 20%, 50%, 75%) 15yr postharvest. We also investigated the influence of dispersed retention on the ability of embedded retention patches to support plant communities characteristic of unharvested forests, and whether it varies by patch size of aggregated retention (0.20ha or 0.46ha) and position within patches (edge or interior). Species richness, diversity, and cover were higher in the dispersed retention than in the patch retention as the harvested areas favored early-seral plant species. Graminoid cover was greater at the edges than in the interior of large patches. Retention patches as small as 0.2ha more effectively supported shade-tolerant (forest interior) plant communities when they were surrounded by higher levels of dispersed retention (as compared to patches retained within clearcuts). Overall, the combined use of both aggregated and dispersed retention within a given cutblock benefits both late- and early-seral plant species and thus could effectively conserve understory plant assemblages in harvested landscapes. Sustainable forest management should therefore consider using a range of retention patch sizes combined with varying levels of surrounding dispersed retention in harvest designs to achieve objectives for plant conservation.

Structural Transformations and Retention of Radiogenic 4He in Platinum Minerals under Mechanical Deformations

The results are presented of the first studies to be carried out on 4He retention under mechanical deformation of isoferroplatinum (Pt3Fe) from a unique placer deposit at the Konder and Uorgalan rivers and from indigenous shows of the alkaline–ultrabasic Konder Massif (Khabarovsk krai, Russia). It was found that the deformation of Pt3Fe of the Pm-3m cell resulted in structural transformations with the appearance of domains and subsequent conversion into native platinum (Pt, Fe) of the Fm-3m cell.

A novel living ink based on Saccharomyces Cerevisae for screen printing process and its applicability in producing braille text dots

We examine the question whether a simple method of printing, the screen printing, can be adapted to print thin layers that grow and acquire the third dimension. Therefore, we report the formulation of a distinctive living microbes based ink suitable for screen printing process. Saccharomyces Cerevisae also known as “Baker’s yeast” is used for the preparation of microbial ink and screen printability has been systematically developed by extensive rheological measurements. For this, the addition of 10%, 20% and 40% w/w triton X-100 surfactant in microbial ink is evaluated in four types of strokes (slumping, flood, mesh and squeegee) associated with screen printing and is further linked with dynamic moduli of the inks. The microbial ink with 20% w/w surfactant shows an optimized rheological properties desired for screen printing process. In order to demonstrate the applicability of the formulated ink, it has been used for screen printing braille text patterns on a normal office paper. The tactile patterns thus obtained (after growth of microbes as well as post processing treatment) are further examined for their structural retention by load bearing characterization. Another impact of this work is that it potentially enables inexpensive braille printing on common office paper, which otherwise is carried out on an expensive specialized paper.

Physical-hydraulic soil attributes in an integrated production system with different “paricá” forest component arrangements

Abstract: The objective of this work was to compare the structural quality and water retention curve of a Haplustox under single, double, and triple “paricá” (Ochroma pyramidale) lines in an integrated production system at 50 months of implantation. Soil was collected from five sampling points considering the distances from the tree lines. Undisturbed samples were collected from the 0.00-0.10 and 0.10-0.20-m layers in order to assess porosity, density, soil penetration resistance, soil water retention curve, and the “S” index. The forest arrangement based on three paricá lines promoted better soil physical conditions than the system using single lines. The main changes were recorded in the 0.10-0.20-m layer, with increased microporosity and decreased cryptoporosity and resistance to penetration. The arrangements using single and double paricá lines result in higher volume of available water and greater soil compaction.

Topsoil removal and cultivation effects on structural and hydraulic properties

Topsoil removal and intensive cultivation of fragile sandy loam soil may reduce water movement into and within the soil and decrease available water capacity. The purpose of this study was to determine if topsoil removal (SSR) and 10-year cultivation have adverse effects on the structural and soil water retention properties. The study was conducted on a fine sandy loam soil in humid tropical coastal plain soils in southern Nigeria. We measured particle size, soil organic matter, pore size through water desorption analysis and infiltration and related water retention properties. Results showed that topsoil removal and cultivation resulted in significant reduction in infiltration, saturated hydraulic conductivity and available water contents and increased the bulk density. Topsoil removal increased fine particle-size fractions and created a shift in pore size distribution to a greater micro porosity. Soil water storage in terms of useful available water (UAW) and easily available water (EAW) were significantly low (p < 0.05) in SSR, reaching 62% reduction. Top soil removal and cultivation resulted in 67% and 32% decreased OM respectively. Loss of OM leading to low water retention at 10 kPa and 1500 kPa indicates a high risk of water stress and quicker soil drying even after heavy rainfall. Loss of organic matter and silt + clay fraction were the major drivers of changes in UAW and EAW in SSR soils. The results of this study confirmed that many structural and water retention characteristics are altered by cultivation and topsoil removal, and are useful in defining the physical quality response indices of fine sandy loam soils.

The First Molecule‐Based Blue‐Light Optical‐Dielectric Switching Material in Both Hybrid Bulk Crystal and Flexible Thin Film Forms

AbstractThree Japanese scientists are awarded the 2014 Nobel Prize in Physics for the invention of a new energy‐efficient light source, the blue light‐emitting diode, which has great potential in photoelectric applications. However, exploring excellent blue‐light materials is still a bigger challenge than red/green ones, especially those with optical‐dielectric dual channels of dielectricity and photoluminescence, which are rarely reported and gradually become the main research objects and nodi in the information industry. Herein, the first molecular blue‐light switching material, (4‐methoxybenzylaminum)2ZnCl4 (1) with many advantages, such as light weight, easy, and environment‐friendly processing, controllability, flexibility, and so on, performs optical and dielectric dual switching simultaneously in a single‐molecule integrated module. And the multifunctional switching ON/OFF channels can be manipulated in the bulk crystal or unidirectional film by applying an external thermal signal, which shows a high signal‐to‐noise ratio of 2:1 and a strong fatigue resistance. Besides, the dense film maintains the structural retention characteristic after more than 10 000 times of folding over 90°, which is the mark of its real genius as an ultraflexible blue‐light device. This finding will promote the application of blue‐light materials in optoelectronic devices and open up a new era of molecule‐based blue‐light switchable multifunctional materials.

Binary phase solid-state photopolymerization of acrylates: design, characterization and biomineralization of 3D scaffolds for tissue engineering

Porous polymer scaffolds designed by the cryogel method are attractive materials for a range of tissue engineering applications. However, the use of toxic crosslinker for retaining the pore structure limits their clinical applications. In this research, acrylates (HEA/PEGDA, HEMA/PEGDA and PEGDA) were used in the low-temperature solid-state photopolymerization to produce porous scaffolds with good structural retention. The morphology, pore diameter, mineral deposition and water absorption of the scaffold were characterized by SEM and water absorption test respectively. Elemental analysis and cytotoxicity of the biomineralized scaffold were revealed by using XRD and MTT assay test. The PEGDA-derived scaffold showed good water absorption ability and a higher degree of porosity with larger pore size compared to others. XRD patterns and IR results confirmed the formation of hydroxyapatite crystals from an alternative socking process. The overall cell proliferation was excellent, where PEGDA-derived scaffold had the highest and the most uniform cell growth, while HEMA/PEGDA scaffold showed the least. These results suggest that the cell proliferation and adhesion are directly proportional to the pore size, the shape and the porosity of scaffolds.

Strategies for the seismic upgrading of pairs of buildings in a historic precinct

This paper reports on a theoretical student design project to seismically upgrade buildings in a historic precinct of Wellington. The unique feature of the structural upgrading, heritage retention and adaptation, and new building interventions in the precinct was that all retrofitting designs were applied to pairs or clusters of buildings in order to develop new strategies for their seismic retrofit.&#x0D; The tying of buildings together as part of retrofitting is rarely encountered in earthquake engineering practice but this can be an important retrofitting approach as shown by the following design outcomes and case-study example. The main finding from the architectural design and seismic retrofit of 70 clusters of two to three buildings was the diversity of the retrofitting strategies that were applied. Two primary categories of retrofitting were identified; tying existing buildings together, and tying existing buildings to new buildings, with each category incorporating several variants. This paper highlights the advantages of retrofitting clusters of buildings to prevent seismic pounding, and for other economic and architectural reasons.

Effect of Graphene Oxidation Rate on Adsorption of Poly‐Thymine Single Stranded DNA

In order to understand how oxidation rate of graphene surfaces affects single‐stranded poly‐thymine, poly(T)20, structure during physisorption, all‐atom molecular dynamics simulations are performed. In aqueous solutions, poly(T)20 is a complex structure with stacked and coiled regions. However, on the graphene surfaces, there are three different regimes for the adsorption process, which heavily depends on the surface oxidation: (1) on pristine graphene or graphene oxide (GO) with low oxygen coverage (GO 5%) the stacked poly(T)20 structure becomes unfolded due to formation of strong π–π interactions with the surface, (2) on graphene oxide with moderate oxygen coverage (GO 10%–25%) the structure of poly(T)20 is well preserved because of the balance between van der Waals and electrostatic interactions, and (3) on graphene oxide with high oxygen content (GO 30%–60%) stacked poly(T)20 structure is locally disrupted due to formation of strong hydrogen bonds with the surface. Moreover, surface roughness due to the presence of oxygen groups plays a pivotal role in structural retention of poly(T)20 by preventing its nucleobases from forming π–π stacking interactions with the surface.

Modeling of retention time for polychlorinated biphenyl congeners in human adipose tissue using quantitative structure–retention relationship methodology

In this study, quantitative structure–retention relationship methodology was employed for prediction retention time of the 209 polychlorinated biphenyl (PCBs) in human adipose tissue on the DB-1701 column. The molecular descriptor was calculated, and most important ones were selected by stepwise multiple linear regression (SW-MLR) approaches. These descriptors are symbolically represented as BEHp2, JGI1, MATS3e, RDF050m which are an independent variable used for generation of linear and nonlinear model by multiple linear regression (MLR) and support vector machine (SVM) methods, respectively. Comparison of statistical parameters of these models indicated that the SVM model performed better than MLR which represents the nonlinear relationship between the structural feature and retention time of PCBs on this chromatographic condition. The relative standard error (SE) of the training and test set for the SVM model was 0.67 and 0.76, and the square correlation coefficients (R 2) were 0.977 and 0.970, respectively. The mean effect analysis indicated that the polarity and structural features of studied PCBs are important factors responsible for chromatographic retention of these chemicals at the same chromatographic condition.

Effects of surface‐applied and soil‐incorporated lime on some physical attributes of a Dystrudept soil

AbstractIt is generally accepted that liming ameliorates soil acidity. However, the method of lime application is thought by many to influence its effectiveness in acid soils. In this study, we wanted to assess the degree of effectiveness of surface‐applied lime and lime incorporated into the soil on soil structural attributes and water retention of a Dystrudept soil in the SE region of the State of Paraná, Brazil. Lime was added at the rate of 15 t/ha to soil through: (i) surface broadcasting, (ii) incorporation via ploughing and harrowing, (iii) incorporation via subsoiling and harrowing. A control treatment with zero lime application was included in the experiment. The addition of lime by surface broadcasting resulted in significant reductions in soil bulk density (BD) and macroporosity (Ma) and increases in total porosity (TP) and microporosity (Mi) of the top soil layer (0–0.10 m). The reverse was the case in the 0.10‐ to 0.20‐m soil layer; where lime was incorporated via ploughing and harrowing, increases in BD and reductions in TP and Ma were observed. Addition of lime also significantly increased soil water retention, with maximum retention recorded from soil amended with surface broadcast lime. Changes in soil chemical attributes (increases in pH, Ca2+ and Mg2+ contents; reductions in potential acidity and Al3+ content) were responsible for the changes observed in structural and physical attributes, and water retention. Bearing in mind the lower application costs, improvement in the soil chemical attributes for plant development and soil physical quality, surface broadcast lime can be considered a promising alternative for no‐till farmers.

Effects of gasification temperature and atmosphere on char structural evolution and AAEM retention during the gasification of Loy Yang brown coal

This study aims to investigate the influence of gasification temperature on the evolution of char structure and the retention of alkali and alkaline earth metallic (AAEM) species for a Victorian brown coal. The experiments were carried out at 800, 850 and 900°C in pure CO2, 15% H2O balanced with Ar and 15% H2O balanced with CO2 in a one-stage fluidised-bed/fixed-bed reactor. FT-Raman spectroscopy was used to characterise the structural features of the chars obtained at varying conversion levels during gasification. The concentrations of AAEM species in the chars left after gasification were quantified with inductively coupled plasma – optical emission spectroscopy. The specific char-O2 reactivity of the gasified char was measured in a thermogravimetric analyser. The results show that the CO2 and H2O partly compete for the active sites on the char. The increasing total Raman area caused by the formation of O-containing structures in char does not appear to be the only factor determining the char gasification rate in H2O-containing atmospheres. With increasing temperature, CO2 plays an increasingly more important role in the char evolution and subsequently influences the AAEM retention in char from the gas mixture. The gasification temperature does not change the individual reaction pathway for char-CO2 or char-H2O reaction within temperature range investigated.

Structural and Gas Retention Changes Induced by Ozonization of Cobalt(II) and Manganese(II) Hexacyanocobaltates(III)

Transition metal hexacyanocobaltates are porous materials with open metal sites and a wide variety of pores. In this work, manganese(II) and cobalt(II) hexacyanocobaltates(III) have been selected to explore the interactions between the open metal sites located in their pores and the guest molecules: hydrogen, carbon dioxide, water and methanol. An experimental setup was designed and implemented to conduct post-synthesis modification of the solids with ozone. Samples were dehydrated, ozonized and saturated with methanol in situ. Ozone molecules acted on the open metal sites changing their oxidation state, causing a contraction of the unit cell and inducing a stronger interaction of the molecules of water and methanol with the lattice. This strengthening prevented the lattice from being evacuated without compromising its framework stability. The decomposition temperature decreased in all ozonized samples as a consequence of the elongation and weakening of the cobalt-carbon bond. Active infrared and Raman bands were used to monitor the interaction between the open metal sites at the framework surface and the guest molecules. The cell contraction and the presence of residual methanol molecules in the porosity reduced the hydrogen and carbon dioxide retention capacity of the samples.

Mechano-chemical stabilization of three-dimensional carbon nanotube aggregates

Here we report a combined study of experiments and simulations to understand how chemical functional groups can mechanically stabilize aggregates of carbon nanotubes (CNTs). Ultralow density aggregates of chemically functionalized CNTs, in the form of macro-scale spheres made by freeze-drying method, show mechanical stabilization and near complete elastic recovery during deformation. Simulations of interacting functionalized carbon nanotube aggregates show better structural retention compared to non-functionalized CNTs under compression, suggesting that the atomic-level interactions between functional groups on adjoining CNTs help maintain structural rigidity and elastic response during loading. Aggregates of non-functionalized CNTs collapses under similar loading conditions. The dynamic mechanical responses of CNT macrostructures and mechano-chemical stabilization are directly observed using in-situ deformation inside a scanning electron microscope.

Needle-free jet injection of intact phospholipid vesicles across the skin: a feasibility study.

Needle-free liquid jet injectors are devices developed for the delivery of pharmaceutical solutions through the skin. In this paper, we investigated for the first time the ability of these devices to deliver intact lipid vesicles. Diclofenac sodium loaded phospholipid vesicles of two types, namely liposomes and transfersomes, were prepared and fully characterized. The lipid vesicles were delivered through a skin specimen using a jet injector and the collected samples were analyzed to assess vesicle structural integrity, drug retention and release kinetics after the injection. In this regard, data concerning size, size distribution, surface charge of vesicles and bilayer integrity and thickness, before and after the injections, were measured by dynamic light scattering experiments, cryo-electron microscopy, and X-ray scattering techniques. Finally, the effect of vesicle fast jet injection through the skin on drug release kinetics was checked by in vitro experiments. The retention of the morphological, physico-chemical, and technological features after injection, proved the integrity of vesicles after skin crossing as a high-speed liquid jet. The delivery of undamaged vesicular carriers beneath the skin is of utmost importance to create a controlled release drug depot in the hypoderm, which may be beneficial for several localized therapies. Overall results reported in this paper may broaden the range of application of liquid jet injectors to lipid vesicle based formulations thus combining beneficial performance of painless devices with those of liposomal drug delivery systems.

The neural language systems that support healthy aging: Integrating function, structure, and behavior.

Although healthy aging is generally characterized by declines in both brain structure and function, there is variability in the extent to which these changes result in observable cognitive decline. Specific to language, age-related differences in language production are observed more frequently than in language comprehension, although both are associated with increased right prefrontal cortex activation in older adults. The current paper explores these differences in the language system, integrating them with theories of behavioral and neural cognitive aging. Overall, data indicate that frontal reorganization of the dorsal language stream in older adults benefits task performance during comprehension, but not always during production. We interpret these results in the CRUNCH framework (compensation-related utilization of neural circuits hypothesis), which suggests that differences in task and process difficulty may underlie older adults' ability to successfully adapt. That is, older adults may be able to neurally adapt to less difficult tasks (i.e., comprehension), but fail to do so successfully as difficulty increases (i.e., production). We hypothesize greater age-related differences in aspects of language that rely more heavily on the dorsal language stream (e.g., syntax and production) and that recruit general cognitive resources that rely on frontal regions (e.g., executive function, working memory, inhibition). Moreover, there should be a relative sparing of tasks that rely predominantly on ventral stream regions. These results are both consistent with patterns of age-related structural decline and retention and with varying levels of difficulty across comprehension and production. This neurocognitive framework for understanding age-related differences in the language system centers on the interaction between prefrontal cortex activation, structural integrity, and task difficulty.