•PAR statistically differed along the disturbance intensity gradient.•Significant differences in diversity were restricted to the sapling layer.•The disturbance released advanced reproduction in ...subcanopy strata.•Our results may guide silvicultural systems patterned after natural processes.
Forest disturbances are discrete events in space and time that disrupt the biophysical environment and impart lasting legacies on forest composition and structure. Disturbances are often classified along a gradient of spatial extent and magnitude that ranges from catastrophic events where most of the overstory is removed to gap-scale events that modify local environmental conditions only. Without question, a paucity of data is available on disturbance events of the intermediate scale (i.e. those events too localized to be classed as catastrophic and too widespread to be considered gap scale). The specific objectives of this study were to quantify and compare canopy structure, understory light regimes, woody species composition, and tree species diversity along a gradient of canopy disturbance caused by an EF1 tornado and to analyze the influence of intermediate-scale disturbance on the successional trajectory of an upland Quercus forest. Statistically significant differences in diversity measures between control (no storm damage), light, or moderate damage class plots were only found in the sapling layer. We documented significant differences (P<0.01) in percent of intercepted PAR between the control and moderate damage classes and between moderate and light classes. Three growing seasons post-disturbance, the understory light regime had largely returned to pre-disturbance conditions. The disturbance event acted primarily as a release mechanism for advanced reproduction in the understory and for stems in the midstory. Our results provide quantitative information on disturbances of this extent and magnitude and can be used to guide silvicultural systems designed to emulate natural disturbance processes, which is an increasingly popular management approach especially on public lands.
•Probability of mortality increased with increasing tree diameter.•The intermediate-scale disturbance altered the developmental pathway.•The wind disturbance accelerated succession toward dominance ...by shade-tolerant taxa.•Our results can be used to develop silvicultural guidelines based on natural events.
Natural disturbances play important roles in shaping the structure and composition of all forest ecosystems and can be used to inform silvicultural practices. Canopy disturbances are often classified along a gradient ranging from highly localized, gap-scale events to stand-replacing events. Wind storms such as downbursts, derechos, and low intensity tornadoes typically result in disturbance that would fall near the center of this gradient and result in intermediate-scale disturbances. Despite their frequency and widespread occurrence, relatively little is known about how intermediate-scale disturbances influence stand development and succession. On 20 April 2011, the Sipsey Wilderness in Alabama was affected by an EF1 tornado with accompanying straight-line winds. In the third growing season after the disturbance, stands were sampled in a stratified subjective sampling design to evaluate the effects of intermediate-scale wind disturbance on structural and successional development of Quercus stands. We established 109 0.04ha plots across a gradient of disturbance grouped into three classes, control (considered to represent pre-disturbance conditions using a space-for-time substitution), light, and moderate categories, to examine the effect of the intermediate-scale wind disturbance. Basal area was reduced from 25.7m2ha−1 to 23.7m2ha−1 and 15.3m2ha−1 for light and moderate disturbance classes, respectively. Logistic regression revealed an increasing probability of mortality during wind disturbance with increasing tree diameter. This intermediate-scale disturbance increased intra-stand heterogeneity and altered the developmental pathway. The stands did not structurally resemble one of the four widely accepted stages of stand development. The disturbance also accelerated succession and released shade-tolerant taxa that were established in midstory and understory strata prior the event.
A recently published study by Harris and colleagues investigated the effects of an antioxidant dietary supplement on retinal and retrobulbar blood flow and found that 1 month of oral supplementation ...produced a statistically significant increase in peak systolic and end diastolic blood flow velocities in all retrobulbar blood vessels examined. In retinal capillary beds surrounding the optic nerve head, significant increases were seen in both mean ocular blood flow velocity and vascular perfusion - indicating a higher proportion of vessels receiving blood. The value of nutritional supplementation is gaining appreciation among health care providers and patients; this is evidenced by the Age-Related Eye Disease Study 2 nutritional formula for macular degeneration and the use of omega fatty acids in dry eye disease.
•A slight majority of gapmaker trees were Pinus stems.•Most gaps were projected to close by subcanopy height growth of a hardwood stem.•Positive relationships were observed between gap size and ...Shannon diversity.•A gap-based approach may work to maintain Pinus stems in hardwood dominated stands.
Quercus-Pinus forests of the eastern USA cover millions of hectares and span a variety of ecoregions. Understanding the influence of natural disturbance on developmental and successional pathways is important for managers that wish to sustain Pinus spp. in these mixtures. Quantifying developmental and successional patterns in this forest type can help assess the need to actively manage natural processes and inform silvicultural prescriptions to achieve management goals. Little research has been conducted on natural, gap-scale disturbance processes in Quercus stands with strong components of Pinus taeda, Pinus virginiana, and Pinus echinata. We examined 60 canopy gaps in a Quercus-Pinus forest on the southern Cumberland Plateau in Alabama to document gap formation, closure, and other characteristics and to analyze the influence of localized disturbance on development and succession. The majority of gapmaker trees (56%) were Pinus individuals and 44% were hardwoods. Most gaps (58%) closed by height growth of subcanopy trees. The majority of these gap filler taxa were hardwoods: Quercus (39%), Carya (14%), Nyssa sylvatica (12%), and other hardwoods (15%), with Pinus representing 14%. The number of Pinus gapmakers and the number of gaps projected to fill by subcanopy recruitment of hardwoods indicated the forest was in the latter stages of a composition shift from Pinus to a much stronger Quercus component. Significant positive relationships existed between gap size and sapling diversity (r2=0.15, P=0.002), tree diversity (r2=0.21, P=0.0002), and total stem diversity (r2=0.29, P<0.0001) indicating a positive relationship may exist between gap size and diversity on xeric ridge tops where shade-tolerant species are less competitive. We speculated the ridge top positions contributed to the relatively high gap formation rates noted in this study. Pinus composition was found to be patchy, indicating a gap-based approach may be used to manage for Pinus recruitment in hardwood dominated systems.
Geometric or electronic confinement of guests within nanoporous hosts holds promise for imparting catalytic functionality, including single-metal-atom catalytic functionality, to existing materials. ...When the nanoporous host is a metal–organic framework (MOF), single-metal-ion catalysts have typically been installed by grafting to an open site on an inorganic node, with the node effectively becoming the support for the catalyst. This approach, however, imposes compositional constraints, as the node not only needs to be receptive to grafting, but also must be capable of stabilizing the framework against solvent evacuation, chemical exposure, and heating. Here, we show that disk-like, Anderson polyoxometalate clusters (RhMo 6 O 24 n − and Mo 7 O 24 m − ; POMs) can be confined in pore-specific and orientation-specific fashion within the hierarchically porous, Zr( iv )-based MOF, NU1K. Self-limiting loading of one cluster per pore, and associated nano-confinement, serve to isolate each POM and prevent consolidation caused by sintering. Additionally, the oriented confinement serves to expose individual rhodium atoms to candidate gas-phase reactants, while enabling the rhodium atom to employ a well-defined oxy-molybdenum cluster, rather than a MOF node, as a support. Synchrotron-based difference-electron-density maps and differential pair-distribution-function analyses of scattered X-rays establish cluster siting and orientation and confirm isolation. Nanoconfined ( i.e. , MOF- and POM-confined) single-rhodium( iii )-atoms are catalytically competent for an illustrative gas-phase reaction, CO oxidation by O 2 , with the MOF-isolated POM enormously outperforming nonporous, MOF-free, solid (NH 4 ) 3 H 6 RhMo 6 O 24 ·6H 2 O. This work highlights the value of MOF-based nano-confinement and oriented isolation of planar POMs as a means of uniformly presenting and stabilizing potent single-metal-atom catalysts, in reactant-accessible form, on well-defined supports.
The present review illustrates the state of the art of regenerative medicine (RM) as applied to surgical diseases and demonstrates that this field has the potential to address some of the unmet needs ...in surgery. RM is a multidisciplinary field whose purpose is to regenerate in vivo or ex vivo human cells, tissues, or organs to restore or establish normal function through exploitation of the potential to regenerate, which is intrinsic to human cells, tissues, and organs. RM uses cells and/or specially designed biomaterials to reach its goals and RM-based therapies are already in use in several clinical trials in most fields of surgery. The main challenges for investigators are threefold: Creation of an appropriate microenvironment ex vivo that is able to sustain cell physiology and function in order to generate the desired cells or body parts; identification and appropriate manipulation of cells that have the potential to generate parenchymal, stromal and vascular components on demand, both in vivo and ex vivo; and production of smart materials that are able to drive cell fate.
Abstract
Objectives
The WHO Access, Watch and Reserve (AWaRe) classification has been developed to support countries and hospitals in promoting rational use of antibiotics while improving access to ...these essential medicines. We aimed to describe patterns of worldwide antibiotic use according to the AWaRe classification in the adult inpatient population.
Methods
The Global Point Prevalence Survey on Antimicrobial Consumption and Resistance (Global-PPS) collects hospital antibiotic use data using a standardized PPS methodology. Global-PPS 2015, 2017 and 2018 data, collected by 664 hospitals in 69 countries, were categorized into AWaRe groups to calculate proportional AWaRe use, Access-to-Watch ratios and the most common indications for treatment with selected Watch antibiotics. Only prescriptions for systemic antibiotics on adult inpatient wards were analysed.
Results
Regional Access use ranged from 28.4% in West and Central Asia to 57.7% in Oceania, whereas Watch use was lowest in Oceania (41.3%) and highest in West and Central Asia (66.1%). Reserve use ranged from 0.03% in sub-Saharan Africa to 4.7% in Latin America. There were large differences in AWaRe prescribing at country level. Watch antibiotics were prescribed for a range of very different indications worldwide, both for therapeutic and prophylactic use.
Conclusions
We observed considerable variations in AWaRe prescribing and high use of Watch antibiotics, particularly in lower- and upper-middle-income countries, followed by high-income countries. The WHO AWaRe classification has an instrumental role to play in local and national stewardship activities to assess prescribing patterns and to inform and evaluate stewardship activities.
•Composition and structure were analyzed after an intermediate disturbance event.•The disturbance accelerated succession toward hardwood dominance.•The resultant structure represented the mixed stage ...of development.•Canopy disturbance alone was insufficient to regenerate Pinus species.
Increasingly, forest managers intend to create or maintain mixed Pinus-hardwood stands. This stand assemblage may be driven by a variety of objectives but is often motivated by the desire to enhance native forest diversity and promote resilience to perturbations. Documenting the effects of natural disturbances on species composition and stand structure, and thus successional and developmental pathways, in stands with these mixtures is essential to achieve these goals. The specific objectives of this study were to quantify and compare the impacts of an intermediate-severity canopy disturbance on woody species composition, canopy structure, understory light regimes, and species diversity in mixed Pinus (Pinus taeda and Pinus virginiana)-hardwood stands on the Cumberland Plateau in Alabama. The natural intermediate-severity disturbance disproportionately removed large Pinus stems, promoted hardwood dominance, and effectively accelerated succession. The resultant stand structure did not resemble one of the widely recognized stages of stand development and was best characterized by the mixed-stage of development. The canopy disturbance did not significantly alter canopy-layer species diversity, but seedling- and sapling-layer diversity was significantly greater in disturbed neighborhoods. Results from this study may be used as guidelines by managers of mixed Pinus-hardwood systems. To maintain a Pinus component in stands that are succeeding to hardwood dominance, canopy disturbance alone is insufficient and must be planned in conjunction with competition reduction measures in the regeneration layer, such as fire or herbicide application. Conversely, if managers wish to promote a hardwood component in pure or near pure Pinus stands, creation of variably sized canopy openings throughout the stand may recruit hardwood reproduction to larger size classes, as the intermediate-severity disturbance documented here accelerated succession toward hardwood dominance.
Social networking Web sites such as Facebook have grown rapidly in popularity. It is unknown how such sites affect the ways in which medical trainees investigate and interact with graduate medical ...education (GME) programs.
To evaluate the use of social networking Web sites as a means for osteopathic medical students, interns, residents, and fellows to interact with GME programs and report the degree to which that interaction impacts a medical trainee's choice of GME program.
An anonymous, 10-item electronic survey on social networking Web sites was e-mailed to osteopathic medical student, intern, resident, and fellow members of the American College of Osteopathic Family Physicians. The weighted least squares test and the Fisher exact test were used for data analysis.
A total of 9606 surveys were distributed, and 992 (10%) were completed. Nine hundred twenty-eight (93%) of the respondents used social networking Web sites, with the most popular services being Facebook (891 90%; P=.03), the Student Doctor Network (278 28%), and LinkedIn (89 9%; P=.03). Three hundred fifty-three respondents (36%; P=.52) were connected with a professional organization and 673 (68%; P=.73) used social networking Web sites for job searching related to GME programs or postresidency employment. Within the population of 497 third-, fourth-, and fifth-year osteopathic medical students, 136 (27%) reported gleaning information about programs through social networking Web sites (P=.01). Within the total population, 100 of 992 (10%) reported that this information influenced their decisions (P=.07). Of note, 144 (14%) of the total 992 respondents reported that the programs they applied to did not have any presence on social networking Web sites (P=.05).
Our results indicate that social networking Web sites have a present and growing influence on how osteopathic medical students, interns, residents, and fellows learn about and select a GME program.
The ground flora stratum affects stand structure, resource acquisition, nutrient cycling, and taxonomic richness in forest ecosystems. Disturbances such as thinning and prescribed fire alter forest ...understory growing conditions that generally increase ground flora cover and richness. We studied annual changes in ground flora assemblages over three growing seasons after fire in thinned and frequently burned (3-year rotation) Pinus–Quercus stands. Our results corroborated trends from other studies that indicated greater ground flora richness and cover after thinning and burning compared with thin-only treatments. We also found that the stratum experienced relatively rapid succession between growing seasons that complimented the tolerance succession model. Forbs had reduced cover and richness from increasingly difficult growing conditions over time and were replaced by woody plants, shrubs, and seedlings. This likely occurred from changing competition dynamics that favored quick growth in the first growing season and long-term investment in vertical growth in the third growing season. The successful regeneration pathways also fit ground flora regeneration models and added a unique pathway to strengthen the predictive power of these models. As many stand management goals are focused towards improving biodiversity, prescribed fire and thinning may be used to increase understory richness in Pinus–Quercus stands.
Celotno besedilo
Dostopno za:
BF, DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
PDF
