Scale Disturbances Research Articles

Spatiotemporal variability of the flow in the deep part of the Central Caspian Sea

The paper presents the analysis of hydrophysical observations executed along the Transcaspian section in 2004-2014 during the expeditions by Shirshov Institute of Oceanology of Russian Academy of Sciences. The results used in the paper are the generalization of data obtained in the last decade. Investigations of the current system of the Central Caspian Sea demonstrated that at the northeastern part of the cyclonic circulation there are considerable deviations. The deposits that energy of current disturbances of various spatiotemporal scales makes to the general energy of currents, are calculated. Preliminary results are received of the assessment of water transfer through the Apsheron threshold from the Central to the Southern Caspian Sea and vice versa. It is shown that annual recurrence of concentration of hydrogen sulfide in the benthonic hollows of the Caspian Sea is directly connected with seasonal and synoptic variability of currents at the bottom.

Investigation on stall inception of axial compressor under inlet rotating distortion

This paper applies a numerical approach to improve the understanding of reaction to various inflow conditions for the compressor system and the mechanism of stall inception under rotating inflow distortions. Full annulus, unsteady, three-dimensional computational fluid dynamics has been used to simulate an axial low-speed compressor operating under rotating distorted inflow conditions. The development of the flow through the rotor is then explained in terms of the redistribution of the flow field and the process of stall inception. The results suggest that the increased flow incidence close to the tip region under co-rotating inflow distortion plays an important role on the stall inception process. The presence of a strong modal wave is observed under co-rotating inflow distortions. This leads to a significant impact on the loss of stall margin, as compared with other distorted inflow conditions. There is a significant peak in the flow coefficient at stall for co-rotating inlet distortion. It can be interpreted as a resonant behavior of the compressor under a strong interaction between the flow field and inlet distortion. It indicates that the stall inception is triggered by the perturbation of the rotating distorted inflow through the long length scale disturbances.

Is colourful self-sustaining forb vegetation mere fantasy?

Abstract Biodiversity in urban and suburban environments can be supported through establishment of low maintenance-requiring herbaceous vegetation types. Here, we attempt to provide a perspective on the possibilities and limitations of establishing forb-dominated vegetation to support local biodiversity and contribute to changing public aesthetics concerning green spaces. Plant ecological theories, methods and experiences are the foundation for the design and establishment of such vegetation types. We emphasise the importance of high plant density and recurrent disturbance for the maintenance of forb communities. Well-established ecological theory tells us that totally self-sustaining herbaceous vegetation is not a realistic possibility. Without intervention, herbaceous vegetation will change over time and eventually be colonized by woody species through the process of succession. However, by applying a creative and strategic approach to establishment and subsequent management involving small scale disturbances, rather than solely a uniform maintenance regime, it may be possible to maintain a colourful, aesthetically appealing and species-rich forb dominated community that will support biodiversity and increase public acceptance of alternatives to conventional lawns in urban and suburban environments.

Developing a systematic simulation-based approach for selecting indicators in strategic cumulative effects assessments with multiple environmental valued components

Indicator selection is a critical step in conducting effective strategic cumulative effects assessments. Selecting an appropriate set of indicators to represent multiple and sometimes disparate values is particularly challenging because the interpretation of impacts depends on indicator roles and relationships among indicators. However, systematic approaches for selection of indicators for strategic cumulative effects assessments (CEA) are unclear. For a 909,000ha case study area involving 214 watersheds in coastal British Columbia, we defined a suite of twenty indicators linked to six Valued Components (VCs) that could be forecasted for forest, riparian and species at risk as three key values consistent with present land-use planning policies in British Columbia, Canada. We used spatio-temporal process-based models to project and integrate the stressor–response relationships between forest harvesting and run-of-river power resource management activities and the suite of selected indicators. For a likely development scenario, we assessed the correlative structure among projected indicator responses and, using a PCA-based analysis of outcomes, identified both patterns of potential redundancies and ecological processes linking indicators and dominant processes influencing VCs. Our results suggest that strategic CEAs will benefit if indicator selections are not made independently for each VC. Identifying the type of indicator, i.e., pressure or condition, and scale of its representation was important in determining if assessed impacts for individual indicators could be appropriately integrated to quantify overall impacts in the landscape. Consideration of indicator–indicator relationships both within and among VCs clarifies the influences of spatial scale, potential redundancies among indicators, and the role of underlying ecological processes in interpreting and aggregating indicator responses. Our case study demonstrates that relative scales of ecological processes, disturbances and management actions can limit how cohesive the interpretations of impacts may be across VCs in strategic CEA. Analysis of correlative structures among the twenty indicators suggested criteria-based statistical redundancies occurred between only two indicator pairs, however PCA suggested three ecological processes (road disturbance, Spotted Owl habitat state, retention and recruitment of old forest) were operating to relate behaviors of multiple indicators. Careful consideration of the interacting roles of ecological processes as they relate to values is required when determining appropriate indicators and designing how best to aggregate indicator results into an effective strategic CEA. A three step systematic and generalizable approach to forecasting present and future states of indicators will improve efficiencies and effectiveness of strategic CEA.

Surgical Treatment of 127 Paraclinoid Aneurysms with Multifarious Strategy: Factors Related with Outcome

Few reports have been published discussing surgical outcomes of paraclinoid aneurysms using multifarious treatments such as high-flow bypass. We retrospectively analyzed findings from 127 consecutive patients (19 males, mean age at surgery: 56.8 years, range: 19-81 years) at our hospital. The size of aneurysms ranged from 2.7-43.2 mm (mean: 6.9 mm). Extradural anterior clinoidectomy was used to clip small aneurysms. As large or giant aneurysms required a longer temporal occlusion period and often could not undergo simple clipping, high-flow bypass with anterior clinoidectomy or cervical internal carotid ligation was performed to reduce aneurysm blood flow and induce thrombosis. We reviewed a postoperative modified Rankin Scale (mRS), radiographic outcomes, cerebral infarction, and visual disturbance. In addition, we analyzed factors relating to the outcomes and complications, with focus on the aneurysm size, location, and type of surgical treatment. Good outcomes were achieved in all patients, as follows: mRS 0:100, mRS 1:16, mRS 2:11, and mRS 3-6:0. Among the 127 patients, complete exclusion of aneurysm was achieved in 119 cases (93.7%). Postoperative morbidity included ischemic lesions in 11 (8.6%) and visual disturbance in 24 (18.8%). Significant statistical differences were observed between ischemic complication and aneurysm size and location (P = 0.0001) and surgical treatment (P < 0.0001). Surgical treatment of unruptured paraclinoid aneurysm has high efficacy with good outcomes and a high rate of complete exclusion. However, the rate of visual disturbance is relatively high. Careful surgical techniques and intraoperative monitoring are therefore required.

Aggressive Behavior of Phayre's Leaf Monkeys Towards Domestic Dogs in Cachar District of Assam, India

Phayre’s leaf-monkeys (Trachipithecus phayrei) or Phayre’s langurs are old world monkeys that inhabit South-East Asian tropical forests. The species is under a severe threat due to large scale habitat destruction and disturbances by people living near the habitat of langurs. The present study recorded the aggressive behavior of male langurs towards domestic dogs in the Cachar district of Assam. Response of each member in the troop was observed. The sophisticated behavior of males in safeguarding the weaker members was observed. In conclusion, the harassment by domestic dogs may result in the expulsion of Phayre’s langurs from their native habitat.

Population dynamics of giant barrel sponges on Florida coral reefs

The structure of coral reef benthic communities has changed significantly in recent decades and will likely continue to change with the increasing frequency and scale of disturbances. Reef-building corals and macroalgae have been regularly included in assessments of coral reef communities, however very little is known about the long-term dynamics of sponge populations. The giant barrel sponge Xestospongia muta is a dominant component of Caribbean coral reef communities, and it was previously reported that populations significantly increased in the Florida Keys over 2000–2006. Using surveys of sponges from the same permanent plots on reefs off Key Largo, Florida, USA, this study extended the investigation of the population dynamics of X. muta for 2000–2012 at three depths (15, 20, 30m). Over 12years, the density of X. muta significantly increased by a mean of 122% (range=53–336%) on Conch Reef and by a mean of 44% on Pickles Reef. Both the cover and volume of X. muta concomitantly increased at all sites and increases in both metrics were greater over 2006–2012 relative to 2000–2006 due to decreased mortality of the largest sponges in the population over time. Population growth accelerated at all sites on Conch Reef due to a significant increase in recruitment and sponge survival, and was greater at deeper relative to shallow depths; on Pickles Reef, recruitment decreased, but survival increased and population growth remained constant over time. Despite mortality due to putative pathogenesis, and in contrast to the persistent decline of reef-building corals, these results suggest that conditions on Florida coral reefs have been increasingly favorable for the growth of barrel sponge populations. Given the long lifespan of X. muta, it remains to be seen whether these results represent a persistent change with broad geographic relevance, or stochastic variation in local demographics.

Structural patterns of beech and silver fir suggest stability and resilience of the virgin forest Sinca in the Southern Carpathians, Romania

The structural patterns and dynamics of a primeval silver fir (Abies alba) – European beech (Fagus sylvatica) forest in the Southern Carpathians (Romania) were assessed to gain deeper insight into species interactions and mechanisms of coexistence, and to study the influence of species composition on forest structure. At 21 sample plots, each covering 0.123ha within an area of 240ha, all living and dead trees ⩾6cm dbh (diameter at breast height) were mapped and measured. Regeneration was assessed on four sub-plots per plot. Additionally, a 1-ha permanent plot established in 2003 was re-measured in 2013 to obtain information on stand dynamics. Point pattern analyses were conducted to study the spatial patterns and tree-to-tree interactions. The overall dbh distributions of beech and fir tended to indicate sustainable population structures. The share of beech varying from 24.8% to 95% (average 58%) in stand basal area did not influence stand parameters such as basal area or volume, nor the distribution of growing stock to different canopy layers. We found fir to dominate the lowest dbh classes in plots that were strongly dominated by beech in the top layer and vice versa, locally indicating species alternation. The regeneration density of fir was lower than of beech, although browsing by ungulates was negligible. In contrast to its share among living trees, fir contributed two-thirds to the deadwood volume. The 10-year changes in forest structure and mortality rate on the 1-ha plot were very small, suggesting the absence of recent intermediate or severe disturbances. The spatial patterns of the dead trees and of the living beech and fir in different canopy layers agreed with a disturbance regime dominated by stochastic small-scale events. Although the spatial patterns of beech and fir were similar, the tree-to-tree interactions indicated a higher intraspecific competition of beech than of fir and a higher shade tolerance of fir particularly in later stages of development. Both could be important factors for the coexistence of the two species. We conclude that the primeval fir–beech forest Sinca shows under the present small scale disturbance regime a high stability and structural resilience. Temporal changes in species composition only lead to small fluctuations in stand parameters and do not threaten the long-term coexistence of beech and fir. Forest managers may vary the species composition of fir–beech forests without substantially influencing the overall forest structure or productivity.

Does Nasal Surgery Improve OSA in Patients with Nasal Obstruction and OSA? A Meta-analysis.

To perform a systematic review and meta-analysis to determine if isolated nasal surgery in patients with obstructive sleep apnea and nasal airway obstruction improves obstructive sleep apnea. Computerized searches were performed in PubMed, EMBASE, and the Cochrane Library through October 2014. Manual searches and subject matter expert input was also solicited. A search protocol was defined a priori, and 2 independent investigators performed the data extraction, focusing on relevant data, including quality data polysomnography data, and taking note of methodological quality and risk for bias. The 10 studies meeting criteria included a total of 320 patients. There were 2 randomized controlled trials, 7 prospective studies, and 1 retrospective study. There was a significant improvement in the pooled results of both Epworth Sleepiness Scale (ESS; difference 3.53, 95% confidence interval [CI] [0.64, 6.23]) and Respiratory Disturbance Index (RDI; 11.06, 95% CI [5.92, 16.19]) scores with isolated nasal surgery. There was no significant improvement in the Apnea Hypopnea Index (AHI) in the random effects model (4.83, 95% CI [-1.6, 11.62]). The pooled results showed that isolated nasal surgery for patients with nasal obstruction and obstructive sleep apnea improved some sleep parameters, as shown by significant improvements in ESS and RDI, but had no significant improvements on AHI. Future controlled studies with larger groups are needed to confirm the benefits of isolated nasal surgery in this patient population.

Decreasing seagrass density negatively influences associated fauna.

Seagrass meadows globally are disappearing at a rapid rate with physical disturbances being one of the major drivers of this habitat loss. Disturbance of seagrass can lead to fragmentation, a reduction in shoot density, canopy height and coverage, and potentially permanent loss of habitat. Despite being such a widespread issue, knowledge of how such small scale change affects the spatial distribution and abundances of motile fauna remains limited. The present study investigated fish and macro faunal community response patterns to a range of habitat variables (shoot length, cover and density), including individual species habitat preferences within a disturbed and patchy intertidal seagrass meadow. Multivariate analysis showed a measurable effect of variable seagrass cover on the abundance and distribution of the fauna, with species specific preferences to both high and low seagrass cover seagrass. The faunal community composition varied significantly with increasing/decreasing cover. The faunal species composition of low cover seagrass was more similar to sandy control plots than to higher cover seagrass. Shannon Wiener Diversity (H′) and species richness was significantly higher in high cover seagrass than in low cover seagrass, indicating increasing habitat value as density increases. The results of this study underline how the impacts of small scale disturbances from factors such as anchor damage, boat moorings and intertidal vehicle use on seagrass meadows that reduce shoot density and cover can impact upon associated fauna. These impacts have negative consequences for the delivery of ecosystem services such as the provision of nursery habitat.

Mass Footprints of the North Pacific Atmospheric Blocking Highs

Abstract The mass footprints associated with atmospheric blocks over the North Pacific are evaluated by constructing daily tendencies of total mass over the blocking domain from three-dimensional mass fluxes throughout the life cycle of a composite blocking event. The results highlight the major role of mass convergence driven by low-frequency (with periods &amp;gt;1 week) atmospheric disturbances during both the development and decay stage of a block. Specifically, low-frequency eddies are responsible for the accelerated mass buildup 4 days prior to the peak intensity of a block, and they also account for the rapid mass loss afterward. High-frequency, subweekly scale disturbances have statistically significant positive contributions to the mass loss during the decay stage, and also show weak negative contributions to the development of the blocking high prior to the peak of the high. The majority of the mass convergence (divergence) responsible for the intensification (decay) of the blocking high occurs in the middle-to-lower troposphere and is largely attributed to mass flux driven by low-frequency meridional (zonal) winds. Also discussed are the implications of this new mass perspective of atmospheric blocks for understanding dynamics of blocking highs and for model bias detection and attribution.

Wave pattern induced by a moving atmospheric pressure disturbance

A moving low atmospheric pressure is a main feature of tropical cyclones, which can induce a system of forced water waves and is an important factor that cause water level rise during a storm. A numerical model based on the nonlinear shallow water equations is applied to study the forced waves caused by an atmospheric pressure disturbance moving with a constant velocity over water surface. The effects of the moving speed, the spatial scale and the central pressure drop of the pressure disturbance are discussed. The results show that the wave pattern caused by a moving low-pressure is highly related with its moving speed. The wave pattern undergoes a great change as the moving speed approaches the wave velocity in shallow water. When the moving speed is less than the wave velocity, the distribution of water surface elevation is nearly the same as that of the pressure disturbance, and the maximum of the water surface elevation is located at the center of pressure. When the moving speed is larger than the wave velocity, a triangle shaped wave pattern is formed with a depression occurs in front of the pressure center, and the maximum of the water surface elevation lags behind the center of pressure. As the moving speed increases, the maximum of the water surface elevation firstly increases and then decreases, which reaches a peak when the moving speed is close to the wave velocity. The maximum of water surface elevation is approximately in proportion to the central pressure drop, and slightly affected by the spatial scale of pressure disturbance. Both the central pressure drop and the spatial scale of the pressure disturbance do not significantly affect the forced wave pattern. However, a clear difference can be noticed on the ratio of the maximum water surface elevation in moving pressure situation to that in static situation, when the moving speed is close to the wave velocity. A pressure disturbance with smaller spatial scale and smaller central pressure drop will give a larger ratio when the moving speed is close to the wave velocity.

Stream primary producers relate positively to watershed natural gas measures in north-central Arkansas streams

Construction of unconventional natural gas (UNG) infrastructure (e.g., well pads, pipelines) is an increasingly common anthropogenic stressor that increases potential sediment erosion. Increased sediment inputs into nearby streams may decrease autotrophic processes through burial and scour, or sediment bound nutrients could have a positive effect through alleviating potential nutrient limitations. Ten streams with varying catchment UNG well densities (0–3.6wells/km2) were sampled during winter and spring of 2010 and 2011 to examine relationships between landscape scale disturbances associated with UNG activity and stream periphyton [chlorophyll a (Chl a)] and gross primary production (GPP). Local scale variables including light availability and water column physicochemical variables were measured for each study site. Correlation analyses examined the relationships of autotrophic processes and local scale variables with the landscape scale variables percent pasture land use and UNG metrics (well density and well pad inverse flow path length). Both GPP and Chl a were primarily positively associated with the UNG activity metrics during most sample periods; however, neither landscape variables nor response variables correlated well with local scale factors. These positive correlations do not confirm causation, but they do suggest that it is possible that UNG development can alleviate one or more limiting factors on autotrophic production within these streams. A secondary manipulative study was used to examine the link between nutrient limitation and algal growth across a gradient of streams impacted by natural gas activity. Nitrogen limitation was common among minimally impacted stream reaches and was alleviated in streams with high UNG activity. These data provide evidence that UNG may stimulate the primary production of Fayetteville shale streams via alleviation of N-limitation. Restricting UNG activities from the riparian zone along with better enforcement of best management practices should help reduce these possible impacts of UNG activities on stream autotrophic processes.

Impacts of Windfarm Development Activities on Rocky Plateaus - Discussions on Chalkewadi plateau, Dist. Satara, Maharashtra

Rocky plateaus are ecologically very important as they harbor special diversity and are part of catchments of major rivers of Maharashtra. Detailed studies on the components and fragility of rocky plateau ecosystems are sparse. Recently, the instances of these plateaus being subjected to various land use changes without detailed assessments, have affected the balance of the complex ecosystem and the services offered by them. Windfarm development is one major activity on the rocky plateaus for which little data is available on ecosystem level impacts. Results of the present study describe the Chalkewadi plateau complex, Satara district and impacts on the plateau surface brought about by the development of a high-density windfarm. Broad observations were made on the changing land use, microhabitats and associated vegetation. Manual analysis of Google Earth images of the plateau was done to understand the nature and scale of the ground-level disturbance. Results show that even though the actual area under windmill establishment is relatively smaller compared to the total plateau area, its environmental footprint is relatively large. The network of temporary and permanent roads, created to erect and operate the windfarm, has dissected the habitat and corridors of wildlife movement. An increase in road kill incidences was observed. Roads have also initiated erosional features all along the plateau surface. Disturbance due to windfarms is widespread on the plateau with the only exception being in the Reserve Forest area and disconnected smaller plateaus. Our results complement conclusions from other studies regarding negative impacts of windfarms on birds and reptiles. Thus overall impact of windfarms, in terms of habitat destruction is significant and should be studied in depth before establishment of wind farms. Establishment of windfarms on ecologically sensitive areas should be avoided as far as possible. However, we recommend good ecological management practices that could reduce the impacts, if wind farm establishment is inevitable. The recommendations can be applied to other plateaus in Sahyadri where windfarms are already in place

Emergency department companions of stroke patients: implications on quality of care.

Acute care of stroke victims largely relies on the rapid identification and timely clinical and radiological assessment. We evaluated the effect of the number of patient companions on the efficiency of the diagnostic process in the emergency department (ED).Consecutive stroke patients admitted to the ED between August 2011 and October 2012 were evaluated. Clinical, epidemiological, and timeline data (symptoms onset, ED arrival, computed tomography [CT] scanning, and recombinant tissue plasminogen activator infusion), as well as the number of accompanying persons in the ED were prospectively recorded. We used multivariate Poisson log linear models to analyze the association of number of companions adjusted and door-to-CT times and logistic regression for the analysis of the successful identification of stroke patient by ED triage nurse.Out of a total of 724 stroke patients admitted, data regarding number of ED companions were available for 610 (84.3%) patients. Number of companions was associated with higher National Institute of Health Stroke Scale and speech disturbances. It was found to be independently associated with shorter time to CT scanning adjusted for the stroke severity, sex, and speech disturbances (no companions as a reference group, relative risks 0.82, 0.73, and 0.70 for 1, 2, and ≥3 companions, respectively, all P < 0.001). Similarly, number of companions was associated with higher rates of stroke recognition by the triage nurse adjusted for covariates (odds ratios 2.11, 2.62, and 4.11, respectively, all P < 0.05).Our findings suggest that the family members and other companions could serve as facilitators of faster and more effective ED management of stroke patients, possibly improving their outcome.

Simulated Small Scale Disturbances Increase Decomposition Rates and Facilitates Invasive Species Encroachment in a High Elevation Tropical Andean Peatland

AbstractTropical alpine peatlands are important carbon reservoirs and are a critical component of local hydrological cycles. In high elevation peatlands slow decomposition rates result from a nutrient‐poor substrate resistant to decay. The responses of páramo peatland ecosystems to increased nutrient additions and physical disturbance due to agricultural activities are unknown. Here, we conducted a two‐year fertilization and physical disturbance experiment in a Sphagnum—dominated peatland in the Central Andes of Colombia. We hypothesized that fertilization and physical disturbance will diminish the ability of the peat to store organic matter by increasing decomposition and that vascular plants will displace Sphagnum as the dominant plant group. We simulated cattle activity by adding manure as a fertilizer and physical disturbance as a proxy for cattle trampling. Species composition varied in proportion to the intensity of disturbance. Sphagnum cover was reduced under any disturbance treatment. Non‐native grasses usually found in cattle pastures invaded treatments with fertilizer additions or physical disturbance. Overall aboveground plant biomass doubled in fertilized treatments, suggesting that plant biomass production was nutrient limited. Decomposition rates tripled in disturbed treatments as compared to controls. This reduces the ability of the peatland to store organic matter. Andean peatlands are prized ecological assets; however, our results show that the El Morro páramo peatland experienced increased decomposition rates over short time periods after small‐scale disturbances. This created profound consequences for the ecological services offered by these peatlands.

Changes in stand structure and tree vigor with repeated prescribed fire in an Appalachian hardwood forest

Without large scale disturbances to alter forest structure and open the canopy, historically oak-dominated forests of the central and Appalachian hardwood regions of eastern North America are shifting to dominance by shade-tolerant, ‘mesophytic’ species. In response, prescribed fire is applied with increasing frequency and spatial extent to decrease non-oak species and promote dominance of oak species. However, relatively few studies have examined impacts of repeated fire to forest structure and tree vigor across multiple years and varied terrain. In this study, we examined tree vigor, tree mortality, and stand structure in response to different burn treatments: Frequent (burned 4 times in eight years), Less Frequent (burned 2 times in eight years), and Fire-Excluded. We hypothesized that fire-driven decreases in stem density and basal area would be greatest for small size classes, especially of shade-tolerant species on drier landscape positions, and would increase with burn frequency and fire temperature. We expected trees surviving fire to exhibit increased crown vigor over time since fire. Prescribed fire effects depended on tree size-class and landscape position. About 60% of surviving midstory trees (10–20cm diameter at breast height (DBH)) and 25% of overstory trees (⩾20cm DBH) on sub-xeric and intermediate landscape positions experienced crown dieback. Fire-Excluded sites had fewer trees with crown dieback (11–28% across size classes) compared to burned sites (21–87%). Throughout the duration of the study, midstory and overstory maples had significantly greater likelihood of increased crown dieback compared to oaks. Paradoxically, midstory maples had a higher survival probability than similarly-sized oaks, while overstory maples had lower survival than overstory oaks. The greatest reductions in density and basal area occurred in saplings (trees 2–10cm DBH) and midstory trees on sub-xeric and intermediate (but not sub-mesic) landscape positions. Both Less Frequent and Frequent burning reduced density and basal area of sapling and mid-story shade-tolerant species, but also of mid-story chestnut oaks. Individual tree mortality was positively correlated with char height after the first burn regardless of burn frequency. A large and significant initial sprouting response to fire dissipated over time and with repeated burning. Future assessments of mortality and vigor of residual trees following fire are essential for evaluating the long-term effectiveness of prescribed fire management in shifting species composition away from ‘mesophytic’ species and toward oaks, and could help guide management choices regarding repeated prescribed burning.

Long-term Subjective and Objective Outcomes of Adenotonsillectomy in Korean Children With Obstructive Sleep Apnea Syndrome.

ObjectivesAdenotonsillar hypertrophy is the most common etiology in pediatric obstructive sleep apnea syndrome (OSAS), and adenotonsillectomy is the mainstay of treatment modalities. This study evaluates the long-term effectiveness of adenotonsillectomy in children with OSAS.MethodsSubjective symptoms evaluated with a 7-point Likert scale and objective respiratory disturbances evaluated by polysomnography were compared before and after adenotonsillectomy.ResultsA total of 17 children with OSAS aged 4-15 years (mean age, 6.65±3.02 years; male:female, 13:4) completed the study. The mean follow-up period was 57 months (range, 30 to 98 months). Significant changes were found in apnea-hypopnea index (from 12.49±12.96 to 1.96±2.01, P<0.001), apnea index (from 5.64±7.57 to 0.53±0.78, P=0.006), minimum SaO2 (from 81.88±14.36 to 92.76±4.31, P=0.003), snoring (from 43.28±70.63 to 10.70±13.72, P=0.042), and arousal index (from 19.58±7.57 to 11.36±3.99, P=0.006) after adenotonsillectomy. Significant changes were also found after surgery in most of symptoms including snoring, witnessed apnea, morning headache, mouth breathing, gasping during sleep, restless sleep, nasal obstruction, and difficulty with morning arousal. Long-term surgical cure rate and response rate were 47.1% (8/17) and 70.6% (12/17), respectively.ConclusionMost of subjective OSAS symptoms and objective respiratory disturbances improved continuously about 5 years after adenotonsillectomy in children with OSAS. However, close follow-up and a sufficient observation period are necessary because of the risk for long-term incomplete resolution.

川西亚高山森林林窗不同时期土壤转化酶和脲酶活性的特征

As an important small scale disturbance,forest gaps are often considered to be major drivers in the natural forest regeneration. Moreover,forest gaps can play essential roles in soil processes including the dynamics of soil enzyme activity,since the snow,precipitation and sunshine duration could be redistributed in different gap location due to the effects of forest canopy. Subalpine forest in western Sichuan is a typical cold biome,which often displays sensitive responses to environment disturbance because of its fragile characters. As yet,more and more recent studies have concentrated on gap characteristics and seedling regeneration processes in this area,but little attention has been given to the effects of forest gap on soil enzyme activity. As we know,soil invertase and urease are the key enzymes involved in the soil organic carbon and nitrogen transformation,respectively,and the changes of their activities are closely associated with the carbon and nitrogen cycling. Therefore,to understand the effects of forest gap on soil invertase and urease activities at different seasons in alpine forest,a field experiment was conducted in a Picea asperata plantation forest in western Sichuan. The dynamics of soil invertase and urease activity under gap center,gap edge and under-canopy were investigated from June 2012 to May 2013.Soil samples in soil organic layer and mineral soil layer were collected in growing season( completely soil thawing stage,early stage and later stage of growing season) and freeze-thaw season( onset stage of freezing,deeply soil freezing stage and soil thawing stage). The results showed that soil invertase activity in soil organic layer was higher than that in mineral soil layer regardless of forest gap location. Soil invertase activity during the growing season in both soil organic layer and mineral soil layer showed the order: gap center under-canopy gap edge,but soil urease activity showed the order: gap center gap edge under-canopy. In comparison with gap edge and under-canopy,gap center exhibited higher soil invertase activity at onset stage of freezing and deeply soil freezing stage,while soil invertase activity in under-canopy was higher than that of gap center and gap edge at soil thawing stage. In addition,soil urease activity at onset stage of freezing and soil thawing stage was significantly higher in under-canopy than that in gap center and gap edge,although which at deeply soil freezing stage showed few differences in different gap locations. The results here imply that gap location has a profound impact on soil invertase and urease activities at different seasons in subalpine forest.

Experimental Investigation of Stall Inception Mechanisms of Low Speed Contra Rotating Axial Flow Fan Stage

The present paper is an attempt in understanding the stall inception mechanism in a low speed, contra rotating axial flow fan stage, using wavelet transforms. The rotors used in this study have relatively large tip gap (about 3% of the blade span) and aspect ratio of 3. The study was carried out near stall and at stall mass flow conditions for different speed ratios of rotor-2 to rotor-1. Unsteady pressure data from the casing wall mounted sensors are used to understand the stall inception mechanism. The wavelet transform clearly indicates that stall inception occurs mainly through long length scale disturbances for both rotors. It also reveals that short length disturbances occur simultaneously or intermittently in the case of rotor-1. The analysis shows the presence of a strong modal disturbance with 25–80% of the rotor frequency in the case of rotor-1 at the stall mass flow for all the speed combinations studied. The most interesting thing observed in the present study is that the frequency amplitude of the disturbance level is very small for both rotors.