Formation Of Patches Research Articles

Caudal Epidural Blood Patch for Spontaneous Intracranial Hypotension in a Patient Receiving Dual Antiplatelet Therapy

Background: Epidural blood patch (EBP) is routinely used to treat spontaneous intracranial hypotension (SIH). In the case of a patient receiving dual antiplatelet therapy, a caudal EBP was utilized for treatment of his SIH-related chronic headache as the traditional lumbar interlaminar approach was not advisable due to bleeding risk. While there are case reports supporting the efficacy of caudal EPB for treating SIH, none of the cases were performed in patients receiving antiplatelet therapy. In this case, we were uncertain whether antiplatelet agents would interfere with clot formation in the epidural space and preclude successful blood patch formation. Case Report: Herein, we present a 50-year-old man diagnosed with SIH after presenting with a 2-month history of intractable, orthostatic, bifrontal headache. He had undergone coronary stenting 37 days prior and was receiving dual antiplatelet therapy with aspirin and clopidogrel. After the patient failed conservative measures, he elected to proceed with caudal EBP. This provided only 2 hours of symptom relief. One week later, another EBP was performed, this time with complete resolution of the patient’s headache. Conclusion: Our case demonstrates that the caudal approach to EBP may be a safe and effective alternative to interlaminar blood patch for treatment of spontaneous intracranial hypotension in patients at increased bleeding risk related to antiplatelet therapy. Key words: Epidural blood patch, caudal blood patch, CSF leak, postural headache, SIH, spontaneous intracranial hypotension, anticoagulation

Myocardial Patch Formation by Three-Dimensional Culture of Bone Marrow Mesenchymal Stem Cells with 3-Hydroxybutyrate-Co-4-Hydroxybutyrate Under Hypoxia

Herein we researched the effects of a hypoxic microenvironment on bone marrow mesenchymal stem cells (BM-MSCs) on poly 3-hydroxybutyrate-co-4-hydroxybutyrate [P(3HB-co-4HB)] and present a theoretical basis for development of cell transplantation. Mouse bone marrow mesenchymal stem cells were isolated by whole bone marrow culture and surface antigens were analyzed by flow cytometry of passage 5 cells. P(3HB-co-4HB) and bone marrow mesenchymal stem cells were prepared as stem cell patches randomly divided into normoxia (control, 20% oxygen) and hypoxia (3% oxygen) groups. After 24 h, the patch was used for experiments. Cell proliferation was determined by CCK-8 assays. Adhesion, survival, and growth of cells on patches were observed by scanning electron microscopy. Expression of hypoxia-inducible factor-1α (HIF-1α) was tested by real-time quantitative PCR and western blotting. At 2 weeks after addition of cardiomyocyte differentiation inducer 5-azacytidine, cardiac troponin T (cTnT) expression was detected by immunofluorescence. After 24 h, the proliferation of the hypoxic group was considerably greater compared with the normoxic group (n = 12,P < 0 05). SEM demonstrated that the number of viable cells in the hypoxic group was higher than that in the normoxic group. Adhesion between cells and the patch was firm and cell morphology was normal in the hypoxic group. Significant upregulation of HIF-1α mRNA was observed by real-time quantitative PCR after 12 h (P < 0 05). HIF-1αprotein expression in the hypoxia group was considerably higher than that in the normoxia group. cTnT expression in the hypoxic group was more pronounced than that in the normoxic group. Our results show that a hypoxic microenvironment promotes the adhesion, survival, proliferation, and myocardial differentiation of bone marrow mesenchymal stem cells on a P(3HB-co-4HB) patch, which may be mediated by the HIF-1α; pathway.

Direct observation of two-phase flow in deformable fractures of shales: A Utica shale example

Despite the success of hydrocarbon production from unconventional shale reservoirs, the physical processes controlling the production are not yet fully understood. The wettability controlling the two-phase flow in deformable natural fractures of shale is among the processes that still need special attention. With the advances of optical technologies, microfluidics can now be used to observe, measure, and analyse the dynamic changes of flow in fractured systems. However, mimicking the natural wall roughness of the fractures with high precision and having flexibility to allow fracture deformation has remained challenging.We have therefore developed a new microfluidic technique to create tensile fractures in shale with subsurface representative random geometries and roughness, and then observed two-phase flow in these deformable fractures at a high resolution for Utica shale. During the two-phase flow, dynamic contact angles of water-oil in the fractures with varying apertures of 60–100 μm were measured and analysed.Significant contact angle hysteresis was observed when oil displaced water out of the fracture and vice versa. Interestingly, water completely displaced the oil out of the fracture through spontaneous imbibition, although its contact angle in the fracture varied from 20° to 90°. The water velocity in the fracture was found to be correlated to the observed contact angles during the spontaneous imbibition test. The large change in the contact angle was further investigated using fluorescence tracking where patches of oil were observed to remain on the fracture wall despite its water wetness. It was then shown through further investigations that the formation of these oil patches was primarily controlled by mineral heterogeneity than wall roughness.

A Novel Zinc Chelator, 1H10, Ameliorates Experimental Autoimmune Encephalomyelitis by Modulating Zinc Toxicity and AMPK Activation

Previous studies in our lab revealed that chemical zinc chelation or zinc transporter 3 (ZnT3) gene deletion suppresses the clinical features and neuropathological changes associated with experimental autoimmune encephalomyelitis (EAE). In addition, although protective functions are well documented for AMP-activated protein kinase (AMPK), paradoxically, disease-promoting effects have also been demonstrated for this enzyme. Recent studies have demonstrated that AMPK contributes to zinc-induced neurotoxicity and that 1H10, an inhibitor of AMPK, reduces zinc-induced neuronal death and protects against oxidative stress, excitotoxicity, and apoptosis. Here, we sought to evaluate the therapeutic efficacy of 1H10 against myelin oligodendrocyte glycoprotein 35-55-induced EAE. 1H10 (5 μg/kg) was intraperitoneally injected once per day for the entire experimental course. Histological evaluation was performed three weeks after the initial immunization. We found that 1H10 profoundly reduced the severity of the induced EAE and that there was a remarkable suppression of demyelination, microglial activation, and immune cell infiltration. 1H10 also remarkably inhibited EAE-associated blood-brain barrier (BBB) disruption, MMP-9 activation, and aberrant synaptic zinc patch formation. Furthermore, the present study showed that long-term treatment with 1H10 also reduced the clinical course of EAE. Therefore, the present study suggests that zinc chelation and AMPK inhibition with 1H10 may have great therapeutic potential for the treatment of multiple sclerosis.

Soil properties changes earthworm diversity indices in different agro-ecosystem

BackgroundEarthworm communities are generally very sensitive to physico-chemical properties of the soil in different agro-ecosystem i.e. cultivated or non-cultivated which directly or indirectly influence the earthworm survival. The difference in physico-chemical properties of soil at different sites contributed to the formation of population patches for earthworm species. Understanding the physico-chemical properties of soil at a particular site could facilitate the prediction of earthworm species at that site. The objective of the present study was to investigate the diversity, abundance, and distribution of earthworms in cultivated and non-cultivated agroecosystems and their physico-chemical properties affecting the earthworm diversity and abundance.ResultsTotal 10 species of earthworms i.e. Amynthas alexandri, Amynthas morrisi, Eutyphoeus incommodus, Eutyphoeus waltoni, Metaphire birmanica, Metaphire houlleti, Metaphire posthuma, Octochaetona beatrix, Perionyx excavatus, and Polypheretima elongata, were reported. Out of all the reported species, Metaphire posthuma was found to be the most abundant earthworm species in both cultivated and non-cultivated agroecosystems with the occurrence at 56.81% sites. The Shannon-Wiener index (H), Margalef species richness index (DMg) and Pielou species evenness (E) was ranged from 0 to 0.86, 0 to 0.64 and 0.78 to 1 respectively. The principal component analysis resulted in four principal components i.e. PC1, PC2, PC3 and PC4 which contributing variance (%) of 22.96, 19.37, 14.23 and 10.10 respectively. The principal component analysis also showed that physico-chemical parameters of soil such as EC, pH, TDS, texture, OC, moisture, etc. play a critical role in earthworm distribution.ConclusionThe conventional farming system has a negative effect on the earthworm diversity in the soil while the physico-chemical properties of soil also have a determinant effect on the same. Earthworms abundance in the present study have significant direct relation with soil properties at a particular site and vice versa. The diversity indices also change due to the conventional farming system which directly affects the earthworm abundance.

Direct Observations of a Polar Cap Patch Formation Associated With Dayside Reconnection Driven Fast Flow

AbstractDayside solar‐produced concentrated F region plasma can be transported from the midlatitude region into the polar cap during geomagnetically disturbed period, creating plasma density irregularities like polar cap patches, which can cause scintillation and degrade performance of satellite communication and navigation at polar latitudes. In this paper, we observed and investigated a dynamic formation process of a polar cap patch during the 13 October 2016 intense geomagnetic storm. During the storm main phase, storm‐enhanced density (SED) was formed within an extended period of strong southward interplanetary magnetic field (IMF) Bz condition. Total electron content (TEC) map shows that a polar cap patch was segmented from the SED plume. The Sondrestrom Incoherent Scatter Radar (ISR) was right underneath the segmentation region and captured the dynamic process. It shows that the patch segmentation was related with a sudden northeastward flow enhancement reaching ~2 km/s near the dayside cusp inflow region. The flow surge was observed along with abrupt E region electron temperature increase, F region ion temperature increase, and density decrease. The upstream solar wind and IMF observations suggest that the flow enhancement was associated with dayside magnetic reconnection triggered by a sudden and short period of IMF By negative excursion. Quantitative estimation suggests that plasma density loss due to enhanced frictional heating was insufficient for the patch segmentation because the elevated F region density peaking at ~500 km made dissociative recombination inefficient. Instead, the patch was segmented from the SED by low‐density plasma transported by the fast flow channel from earlier local time.

Diel vertical migration and individual behavior of nekton beyond the ocean's twilight zone

Diel vertical migration (DVM) is normally limited to the upper 1000 m. However, the use of ship-borne and stationary submerged echosounders in the Red Sea unveiled consistent formation of daytime patches extending to 1200-1300 m, the patches dissolving at night when individuals migrated shallower. The diel vertical migration was not synchronized, and in the evening 4–5 h passed from the first to the last individual leaving their continuously dark daytime habitat. The mean ascent and descent speeds were ~15 cm s−1. Individuals were active upon return to deep water in the morning, some swimming rapidly up and down at speeds of up to ~25 cm s−1, with abrupt changes in swimming direction. Patch formation was swift, in spite of dilute overall population density, suggesting remote signaling to team up with conspecifics. Vertical swimming subsided as patches became established and persisted at 2–3 cm s−1 within patches. The acoustic target strength of the individuals peaked at ~ -55 dB (38 kHz) and was constant regardless of vertical swimming directions. Based on the behavioral and acoustic evidence squids (Sthenoteuthis sp) are likely acoustic targets.

Machine-Learning-Accelerated Perovskite Crystallization

Summary Perovskites have seen significant research interest in the last decade. As ternary and quaternary compounds, their chemical space is exceptionally large, yet perovskite development has been limited to a restricted set of chemical constituents often discovered through trial and error. Here, we report a high-throughput experimental framework for the discovery of new perovskite single crystals. We use machine learning (ML) to guide the sequence of ever-improved robotic synthetic trials. We perform high-throughput syntheses of perovskite single crystals with a protein crystallization robot and characterize the outcomes with the aid of convolutional neural network-based image recognition. We then use an ML model to predict the optimal conditions for the synthesis of a new perovskite single crystal, enabling us to report the first synthesis of (3-PLA)2PbCl4.This material exhibits strong blue emission, illustrating the applicability of the method in identifying new optoelectronic materials.

Phosphorous removal improvements and cost reductions leveraging cationic polymers and anionic polyacrylamides in Chemically Enhanced Treatment Wetland (CETW) systems

Many wetland systems worldwide struggle with high nutrient influx from urban and agricultural inputs that often disturbs ecosystem balance. In the Florida Everglades, concentrations above 15 μg P L−1 have been shown to affect ecosystem balance and have long term effects on downstream periphyton, detritus, soil and macrophyte. Current Stormwater Treatment Areas (STAs) have been shown to effectively lower P levels on average to 41 μg P L−1 (SD of 31 μg P L−1). These levels, released into downstream Water Conservation Areas, exceed a long-term goal of 10 μg L−1 total P targeted for STA outflow concentrations. Here, we look at enhancing P removal through chemical addition to treatment wetland systems through a series of in-situ mesocosm studies informed through laboratory jar tests. In-situ mesocosm results showed Fe and Al metal-based coagulants lowered filtered total phosphorus (FTP) levels but they did not create settleable flocs, thus resulting in no change or even higher unfiltered total phosphorus (UTP) levels when compared to non-dosed control mesocosms. Proprietary cationic polymer blends and anionic polyacrylamide (PAM) added post coagulant dosing were tested to enhance P-removal performance. Cationic polymer addition significantly lowered FTP when combined with Al-based coagulants, suggesting enhanced charge neutralization, and improved UTP removal when combined with Fe-based coagulants, signifying improved bridging or electrostatic patch formation to create larger/denser floc. The addition of PAM after coagulant dosing generally did not improve FTP removal but did improve UTP removal when dosed at levels >0.5 mg L−1. For Fe-based systems, doubling PAM dosage (from 0.5 to 1.0 mg L−1) was slightly more beneficial for UTP removal than doubling coagulant blend dosage. For Al-based systems, doubling coagulant blend dosage was slightly more effective for UTP removal than doubling PAM dosage, but the difference was not significant. The chemical cost savings from utilizing PAMS were large: doubling coagulant blend dose increased chemical costs by $28,000–$100,000 per 1B L of water treated depending upon blend, while doubling PAM dose marginally increased chemical costs by $1700. Wetlands enhanced with chemical addition achieved levels as low as 20–25 μg L−1 UTP and <10 μg L−1 FTP under field conditions. These were lower than average achievable levels by non-dosed mesocosms (84 μg L−1 UTP and 43 μg L−1 FTP). While the goal of 10 μg L−1 total P was not met by these chemically enhanced treatment wetland (CETW) systems, strategic placement to treat water prior to entrance into STAs can potentially help STAs meet this criterion by extending the STAs' effectiveness and lifespan. More importantly, these systems can help mitigate downstream ecosystem imbalance and combat the formation and migration of a moving P front.

Understanding the Efficiency of Aluminum Coagulants Used in Dissolved Air Flotation (DAF)

This paper reports on the efficiency of five aluminum coagulants for the treatment of a paper mill wastewater by dissolved air flotation (DAF). The coagulants studied were: alum, a polyaluminum chloride coagulant of high aluminum content and intermediate basicity (PAC-MB), another with intermediate aluminum content and high basicity (PAC-HB), a polyaluminum nitrate sulfate of intermediate aluminum content and basicity (PANS) and one hybrid coagulant formed by the combination of PANS and a mixture of polyamines (PANS-PA). The influence of Al speciation on contaminants removal and the main flocculation mechanisms involved have been analyzed. High removal of suspended solids together with significant removal of dissolved and colloidal material (COD and silica) were obtained, which is required for extended reuse of this process water. PAC-HB was the best product for removing suspended solids (85%) and soluble silica (50%) with a rather limited COD removal (5%), while PANS-PA obtained high turbidity (90%) and silica removal (45%) together with a significant soluble COD removal (15%). Monomeric Al (Ala, Alm) was more efficient in removing suspended solids and soluble COD than polymeric or colloidal Al (Alc, Alu), but the latter was more efficient in removing soluble silica. Results demonstrated that the main flocculation mechanism varies with the aluminum dosage, being predominantly charge neutralization at low dosages and sweep flocculation at high dosages. The floc strength factor however, was very high and similar for all the coagulants and dosages tested (85–90%), as it was mainly determined by the behavior of the pre-flocculated suspended solids present in wastewater. The reflocculation factor varied from 45 to 75% at the lowest dosages to almost zero at the highest dosages, confirming the transition from charge neutralization to sweep flocculation. The flocs formed by PANS-PA had lower strength than the others and it decreased with the dosage while its reflocculation factor was almost zero, even at low dosages. Due to the polyamines present in this coagulant, its flocculation mechanism is through both charge neutralization and patch formation, especially at low dosages, and sweep flocculation and interparticle bridge formation at high dosages.

End-of-life evaluation and biodegradation of Poly(lactic acid) (PLA)/Polycaprolactone (PCL)/Microcrystalline cellulose (MCC) polyblends under composting conditions

The present study evaluates biodegradation of the polyblends of poly(lactic acid) (PLA), polycaprolactone (PCL) and microcrystalline cellulose (MCC) in different compositions and comparison of the properties of those blends with that of neat PLA and neat PCL. The samples were melt extruded and blended to evaluate the environmental fate of the polyblends under simulated composting conditions following the standard ASTM International D5338-15 protocol. It was seen that blends with a higher concentration of PCL and MCC in the PLA matrix showed higher carbon mineralization percentage in comparison to the blends having low PCL and MCC components. Molecular weight analysis of the samples showed a decrease in their weight due to chain scission mechanism leading to the formation of intermediates. Analytical techniques revealed the formation of microbial biofilms on the blended biopolymeric surfaces. Field emission scanning electron microscopy showed the formation of fibril-like structures by PLA, and the formation of rough patches on the PCL surface re-confirmed biodegradation of the samples. This work fuels interest in the material characterization of PLA/PCL/MCC based polyblends and helps in tuning the biodegradability of the studied samples according to the demands.

Rendgenološki aspekti upale pluća COVID-19

Coronavirus disease 2019 (COVID-19) is a severe infectious disease of the respiratory system with clinical signs of severe acute respiratory syndrome. The causative agent is coronavirus 2 (SARS-CoV-2). Common symptoms of COVID-19 pneumonia are fever, cough, shortness of breath, myalgia, expectoration of sputum and sore throat. The X-ray image of COVID-19 pneumonia has its own characteristics and changes with the evolution of the disease. At the beginning of the disease, the radiological finding in the lungs may be normal or changes may be visualized in the lungs in the form of multiple hazy vaguely delineated shadows, which occur gradually, discreetly and modestly, and in the later stage confluence into larger first irregular patch formations, then they grow into a massive irregular shadow of the intensity of the frosted glass, only to diffusely cover the whole lung. Inflammatory changes are usually bilateral, less often unilateral localization, predominantly in the middle or lower lung field, on the periphery along the chest wall and / or supraphrenic. The aim of this paper is to present an X-ray image of COVID-19 pneumonia and our experiences in the X-ray diagnosis of this disease. The material of the paper consists of selected digital radiographs of the lungs and heart and CT of the lungs with pneumonia COVID-19 in 220 patients, which are during the COVID-19 pandemic from April to July 2020. were examined in covid rendgen CC Niš. The results are presented illustratively. Conclusion: The X-ray examination methods in the diagnosis of COVID-19 pneumonia are sovereign, dominant and unrivaled, and the knowledge of the authors and collaborators and the experience gained through many years of work in the profession and co-X-ray are of crucial importance.

Multi-Scale Assessment of Urban Gardens as Constructed Habitats for Biodiversity Conservation in Jeddah, Saudi Arabia

Biodiversity in arid urban environments depends upon habitat formation that balances both bioclimatic and biophysical environment needs. There is the potential for urban gardens to establish symbiotic ecosystem services from microhabitat formation that collectively form an assemblage of ecological patches to connect a diverse range of flora and fauna, and establish community driven nursery and seed collection initiatives. This study of urban garden habitats situated within a new urban district of Jeddah Saudi. The analysis concentrates on the ability of garden spatial formations to construct a heterogeneous spatial morphology of sub-patch within the larger urban landscape patch. Patch and subpatch formations are examined based on the criteria of (I) assemblage of the spatial habitat (characterized by shape and spatial organization); (II) integration of spatial, functional and vegetation plantation patterns; (III) connectivity. Findings reveal that garden layout is structured by the integration and layering of plant types to generate cool understory habitat with seedling establishment, and water conservation. Designed layout of the garden as a spatial pattern is augmented with a range of microclimate mediators to dim solar exposure within the plantation habitat. A strong heterogeneity in plant formations and combinations is seen to dominant the garden formations.

A Computational Systems Approach to Rational Design of Nose-to-Brain Delivery of Biopharmaceutics

In this work, a computational systems approach, comprising models at different time and length scales, is developed to elucidate the fundamental chemical, physical, transport, and biological processes in relation to the design of a novel nose-to-brain drug delivery system for the treatment of neurodegenerative diseases. In particular, a kinetic model is established to describe the formation of a hydrogel patch, via the enzymatic cross-linking of tyramine-modified hyaluronic acid, on the olfactory cleft. A fluid transport model is employed to describe the flow of a cross-linkable viscoelastic polymer solution through an applicator in terms of tube and reactive fluid characteristics (e.g., tube geometry, volumetric flow rate, and viscosity). The spreading of the deposited HA droplet on a mucus substrate is modeled via the development of a dynamic droplet deformation model. Subsequently, a dynamic drug release model is formulated to quantify the release rate of an active pharmaceutical ingredient (e.g., long-acting insulin analogues) from a distributed population of drug-loaded polymeric carriers embedded into a hydrogel matrix in terms of molecular and morphological properties of the hydrogel–drug carriers system. Finally, the drug flux from the hydrogel–mucosa interface to the olfactory bulb via the epithelium and lamina propria olfactory sublayers is modeled with a series of dynamic mass transport models. The various mathematical models are integrated together following a multiscale modeling approach to aid the identification of key design system parameters and material properties that can lead to the optimization of the complex drug carriers–hydrogel, droplet deposition, film formation, and drug delivery system to achieve a desired therapeutic effect over a two-week delivery time.

Structural insights into the mechanism of c-di-GMP-bound YcgR regulating flagellar motility in Escherichia coli.

The motile-sessile transition is critical for bacterial survival and growth. Cyclic-di-GMP (c-di-GMP) plays a central role in controlling this transition and regulating biofilm formation via various effectors. As an effector of c-di-GMP in Escherichia coli and related species, the PilZ domain-containing protein YcgR responds to elevated c-di-GMP concentrations and acts on the flagellar motor to suppress bacterial motility in a brakelike fashion, which promotes bacterial surface attachment. To date, several target proteins within the motor, MotA, FliG, and FliM, along with different regulatory mechanisms have been reported. However, how YcgR acts on these components remains unclear. Here, we report that activated YcgR stably binds to MotA at the MotA-FliG interface and thereby regulates bacterial swimming. Biochemical and structural analyses revealed that c-di-GMP rearranges the PilZ domain configuration, resulting in the formation of a MotA-binding patch consisting of an RXXXR motif and the C-tail helix α3. Moreover, we noted that a conserved region in the YcgR-N domain, which is independent of MotA interaction, is necessary for motility regulation. On the basis of these findings, we infer that the YcgR-N domain is required for activity on other motor proteins. We propose that activated YcgR appends to MotA via its PilZ domain and thereby interrupts the MotA-FliG interaction and simultaneously interacts with other motor proteins via its YcgR-N domain to inhibit flagellar motility. Our findings suggest that the mode of interaction between YcgR and motor proteins may be shared by other PilZ family proteins.

Spider silk-inspired universal strategy: Directional patching of one-dimensional nanomaterial-based flexible transparent electrodes for smart flexible electronics

With high figure of merits (FOMs) and intelligent responsiveness, flexible transparent electrodes (FTEs) based on one-dimensional nanomaterials (1DNMs), covering silver nanowires (AgNWs), copper nanowires (CuNWs) and carbon nanotubes (CNTs), are of great promise for smart flexible electronics. Inspired by directional collection of water droplets on wetted spider silks, we propose a universal strategy applicable to AgNW-based FTEs, CuNW-based FTEs and CNT-based FTEs. That is, the 1DNM-based FTEs are wetted by patch precursor mist and then, due to a synergism of surface energy gradient (making the 1DNMs preferentially capture patch precursor microdroplets) and anisotropic fast volatilization (producing a driving force for power-free microdroplet transport), are directionally patched in a mild way (ultraviolet-triggering). The directional formation of flexible conductive patches at the junctions of 1DNMs can significantly lower and stabilize the contact resistance of 1DNM-1DNM, and thus both high electri-optical and electri-mechanical FOMs of 1DNM-based FTEs are achieved. Moreover, because of the switchability of conducting polypyrrole (PPy) in the patches, the patched FTEs have a switching behavior of electrical conductivity in response to periodic electrical stimuli. Upon the electrical switch, the smart flexible electronic devices integrated with patched 1DNM-based FTEs are proved to be of practicability and reliability. The bioinspired universal strategy opens up a new avenue to achieve high FOMs of 1DNM-based FTEs of potential use in smart flexible electronics. This study also offers an attractive approach for directional repair or reconstruction of 1DNMs, as well as for precise intelligentization on solid surfaces or interfaces.

Stage-dependent effects of a non-native invasive saltmarsh plant on the seedling establishment of a native seagrass

Concerns on the environmental disruption and ecosystem degradation due to the biological invasions are growing, with far-reaching consequences for the resilience of recipient ecosystems. While numerous studies mostly emphasized the negative impacts of invasive species on native species at a single time point, there is a lack of knowledge whether and how the invasion impacts vary with time. Here, we provide an empirical study on stage-dependent invasive impacts in an intertidal seagrass habitat (Zostera japonica), which is undergoing invasion of an invasive cordgrass (Spartina. alterniflora). Combining results from field surveys and experiments suggested that, impacts of cordgrass on seedling establishment of native seagrass species shift from facilitation at the initial stage of invasion to inhibition at the later stage when the invasive cordgrass become densely vegetated, causing density-dependent effects. In addition, at the later stage, patch expansion of cordgrass triggered degradation of seagrass-dominant habitats, showing the remnant patches of seagrass-dominant habitat have a strong patch-size dependent effect, with an optimal patch size of ~8 m2 and ~1.5 cm detritus to the establishment of seagrass seedlings. These stage-dependent effects strongly linked to water movement and sedimentation rate. Both of them are modified by the abundance of the invasive cordgrass and patch formation through transforming native seagrass habitat with invasion. Our findings highlight the importance of unraveling stage-dependent impacts for assessing the consequences of biological invasion on native ecosystems degradation.

A Three-Dimensional Assessment of Soil δ13C in a Subtropical Savanna: Implications for Vegetation Change and Soil Carbon Dynamics

Tree/shrub encroachment into drylands is a geographically widespread vegetation change that often modifies soil organic carbon (SOC) storage and dynamics, and represents an important yet uncertain aspect of the global carbon (C) cycle. We quantified spatial patterns of soil δ13C to 1.2 m depth in a subtropical savanna to evaluate the magnitude and timing of woody encroachment, and its impacts on SOC dynamics. Woody encroachment dramatically altered soil δ13C spatial patterns throughout the profile; values were lowest in the interiors of woody patches, increased towards the peripheries of those patches, and reached highest values in the surrounding grasslands. Soil δ13C and 14C revealed this landscape was once dominated by C4 grasses. However, a rapid vegetation change occurred during the past 100–200 years, characterized by (1) the formation and expansion of woody patches across this landscape, and (2) increased C3 forb abundance within remnant grasslands. Tree/shrub encroachment has substantially increased SOC and the proportion of new SOC derived from C3 plants in the SOC pool. These findings support the emerging perspective that vegetation in many dryland ecosystems is undergoing dramatic and rapid increases in SOC storage, with implications for the C cycle at regional and global scales.

Polar Cap Patch Prediction in the Expanding Contracting Polar Cap Paradigm

AbstractSpace weather can cause serious disturbances of global navigation satellite systems (GNSS) used for positioning and navigation purposes. This paper describes a new method to forecast space weather disturbances on GNSS at high latitudes, in which we describe the formation and propagation of polar cap patches and predict their arrival at the nightside auroral oval. The space weather prediction model builds on the expanding/contracting polar cap (ECPC) paradigm and total electron content (TEC) observations from the Global Positioning System (GPS) network. The input parameter is satellite observations of the interplanetary magnetic field at the first Lagrange point. To validate our prediction model, we perform a case study in which we compare the results from our prediction model to observations from the GPS TEC data from the MIT's Madrigal database, convection data from Super Dual Auroral radar network, and scintillation data from Svalbard. Our results show that the ECPC paradigm describes the polar cap patch motion well and can be used to predict scintillations of GPS signals at high latitudes.

Ice sheet flow with thermally activated sliding. Part 2: the stability of subtemperate regions.

The onset of sliding in ice sheets may not take the form of a sharp boundary between regions at the melting point, in which sliding is permitted, and regions below that temperature, in which there is no slip. Such a hard switch leads to the paradox of the bed naturally wanting to refreeze as soon as sliding has commenced. A potential alternative structure is a region of subtemperate sliding. Here temperatures are marginally below the melting point and sliding velocities slower than they would if the bed was fully temperate. Rather than being controlled by a standard sliding law, sliding velocities are then constrained by the need to maintain energy balance. This thermal structure arises in temperature-dependent sliding laws in the limit of strong sensitivity to temperature. Here, we analyse the stability of such subtemperate regions, showing that they are subject to a set of instabilities that occur at all length scales between ice thickness and ice sheet length. The fate of these instabilities is to cause the formation of patches of frozen bed, raising the possibility of highly complicated cold-to-temperate transitions with spatial structures at short length scales that cannot be resolved in large-scale ice sheet simulation codes.