Diffuse Intensity Research Articles

New Concepts of Flow Cytometry Analysis in Oncohematology: Application to Diagnosis and Follow up (Minimal Residual Disease) in AML, ALL and MDS

IntroductionThe development of mass cytometry (CyTOF), using up to 40 concomitant tags for a given sample, has led to the generation of large databases. In order to properly analyze these extensive files, new software solutions have been devised using either mathematical reduction of multidimensional spaces or clustering methods allowing for two-dimensional representations. Such tools as SPADE (SPanning-tree progression Analysis of Density-Normalized events), t-SNE (t-Stochastic Neighborhood Embedding) and FlowSOM (Flow Self Organizing Map) therefore were published with CyTOF data. They have however seldom been used to analyze classical flow cytometry (FCM) data, although current instruments generate 10-12 parameters analyzes that would be good candidates for such analyzes. Here we report on the new paradigm of using such tools to interpret harmonized classical FCM data in particular for minimal residual disease (MRD).Materials and MethodsMultiparametric FCM was performed using panels and recommendations proposed by the Harmonemia group (Lacombe F et al. Leukemia 2016), on a Navios® instrument (Beckman Coulter, Miami, FL) since 2013, yielding a cohort of diagnosis (D) and follow-up (FU) samples of 460 AML (160 D, 300 FU), 695 ALL (129 D, 566 FU), and 150 MDS (100 D, 50 FU). In parallel, 45 normal bone marrow (NBM) samples (respectively 22 for AML and MDS cases and 23 for ALL cases) were processed in the same conditions as pathological samples with the relevant immunophenotyping panels (three combinations for AML/MDS and 3 others for ALL). All files were first processed using specific R-software scripts and Bioconduct or CRAN packages to normalize fluorescence and light diffusion intensity including shift intensity, compensation and biexponential/logical adjustment. Harmonized flow cytometry files (HF) ([1305 pathological + 45 NBM files] x 3 panels corresponding to a total of 4050 HF files) were then generated and used for further analysis.NBM files were adjusted and merged in a single, events-adjusted, representative file of NBM (R-NBM). For each case, merges of this R-NBM, D and FU files were processed using 3 different analysis ways 1) principal component analysis (PCA), 2) t-SNE and 3) FlowSOM. New resulting parameters were generated for each combination of R-NBM, D and FU merged files, i.e. PCA, t-SNE and FlowSOM. These parameters could then be analyzed using the Kaluza® software (Beckman Coulter). Graphical representations of all analyses were then performed in an automated unsupervised manner with Kaluza®, allowing for a direct comparison of NBM and pathological samples for each case. Interestingly, HF files generated by the R software, being integrated in the system, could also be classically analyzed by Kaluza®, in a supervised manner, by drawing gates around PCA/t-SNE clusters or FlowSOM nodes of interest. Such gates allowed to further analyze data by backgating on classical biparametric representations of antibody combinations as well as on the classical CD45/SSC bone marrow cartography.ResultsBoth t-SNE and FlowSOM provide a clear identification of normal and abnormal subsets, while PCA is less discriminative. Comparative simultaneous representations of the three types of samples - (D), (FU) and (NBM)- allow for both a rapid visualization and accurate quantification of normal and abnormal cell subpopulations. The FlowSOM solution further allows to identify and visually characterize specific subsets both within the diagnostic clone and along normal hematopoietic differentiation. FU samples can then be easily analyzed for the persistence of abnormal immunophenotypic characteristics, both in AML and ALL. Even unsupervised results allow for a rapid appreciation and quantification of MRD. Besides, such comparisons, between NBM and D samples provide a new approach of the complexity of MDS. Moreover, both supervised and unsupervised results were comparable.ConclusionThe combination of automated sophisticated multidimensional representation of numerous subsets and their in-depth analysis by classical manual tools of FCM analysis is a truly revolutionary approach. The strength of FCM, which retains and analyses morphological characteristics of the cells, is thus combined to the precision of mathematical analyzes developed for CyTOF. These versatile new tools open the way for a new era of classical FCM analysis in hematological malignancies. [Display omitted] DisclosuresDupont:Beckman Coulter: Employment.

Numerical Investigation of Heat Transfer Enhancement Due to Flow Agitators Between Fins

Abstract The paper investigates the heat transfer characteristics of a channel system consisting of mean axial flow and oscillatory cross flow components. A numerical model has been developed to solve the governing equations associated with the flow. The paper identifies advection, diffusion, and oscillation time scales and intensity of squeezing in the channel as critical parameters controlling system behavior. The total Reynolds number parameter is considered in the paper to understand the combined effect of axial and transverse Reynolds numbers on the Nusselt number. Flow visualization techniques are used to understand the boundary layer changes that occur over an oscillation cycle. Nusselt number is found to increase with a reduction in advection and oscillation time scales. A linear relationship is observed between the Nusselt number and total Reynolds number when the axial and transverse Reynolds numbers are comparable. Nondimensional pressure drop is primarily defined by only two parameters: axial Reynolds number and squeezing fraction. The flow visualization results indicate significant heat transfer enhancement in a small fraction of the oscillation cycle characterized by flow conditions similar to Couette flow.

Distance (still) hampers diffusion of innovations

ABSTRACT This paper employs goods and services descriptions from US trademarks to study spatial diffusion of innovations. Identifying novel, fast-spreading tokens (words) in trademark descriptions, we outline patterns of regional innovation and estimate how distance affects diffusion. Novel trademark tokens are frequently new to English, they capture many unpatented innovations, and their appearance in language co-evolves with their use in intellectual property filings. We analyse the introduction of novel tokens to capture the emergence of innovations and show that spatial distance affects their diffusion. Estimating the intensity of diffusion between locations in the United States, we confirm strong, negative effects of distance.

Non-conventional bell-shaped diffuse scattering in low-energy electron diffraction from high-quality epitaxial 2D-materials

A broad, bell-shaped intensity component is observed in low-energy electron diffraction from high-quality epitaxial 2D-systems. Three 2D-systems, graphene on Ir(111), graphene on SiC(0001), and hexagonal boron nitride on Ir(111), have been prepared in situ under ultra-high vacuum conditions. In all three systems—independent of substrate material—similar strong diffuse intensity is observed, exhibiting a width as large as 50% of the Brillouin zone and an integrated intensity more than 10 times the intensity of the Bragg spots. The presented experimental results provide evidence for a common origin of such diffuse diffraction intensity in different atomically thin 2D-materials.

Violence, Social Movements, and Black Freedom Struggles

George Floyd’s murder by police on 26 May 2020 set off a cycle of struggle that was notable for its size, intensity, and rate of diffusion. Starting in Minneapolis, the uprising quickly spread to dozens of other major cities and brought with it a repertoire that included riots, arson, and looting. In many places, these tactics coexisted with more familiar actions like public assemblies and mass marches; however, the inflection these tactics gave to the cycle of contention is not easily reconciled with the protest repertoire most frequently mobilized during movement campaigns in the United States today. This discrepancy has led to extensive commentary by scholars and movement participants, who have often weighed in by considering the moral and strategic efficacy of the chosen tactics. Such considerations should not be discounted. Nevertheless, I argue that both the dynamics of contention witnessed during the uprising and their ambivalent relationship to the established protest repertoire must first be understood in historical terms. By considering the relationship between violence, social movements, and Black freedom struggles in this way, I argue that scholars can develop a better understanding of current events while anticipating how the dynamics of contention are likely to develop going forward. Being attentive to these dynamics should in turn inform our research agendas, and it is with this aim in mind that I offer the following ten theses.

Renewable Energy Generation Gaps in Poland: The Role of Regional Innovation Systems and Knowledge Transfer

Aim of the research is to analyze regional gaps in terms of renewable energy generation across Poland. For this purpose, four types of regions were outlined based on two indicators: the existing renewable energy generation capacity and the current regional energy demand revealed through the number of residents. This classification allowed to reveal regions in Poland that have distinct features of energy gaps and peripherality, while also more successful regions with renewable energy surpluses and distinct sustainable energy potential. For each of the region type key potential systemic problems in terms of renewable energy generation development were given. To understand how peripheral regions and regions with energy gaps could be supported in their development of renewable energy generation the regional innovation systems, social networks, knowledge and technology transfer and diffusion were substantiated. Results of the research can serve as an aid in development of national and regional energy policies, helping to understand peculiarities of local renewable energy generation and the influence of enabling environment peculiar to the specific region, including the regional innovation systems and intensity of knowledge transfer and diffusion.

Anisotropic diffusion filtering based on fault confidence measure and stratigraphic coherence coefficients

ABSTRACTWe develop an algorithm for seismic data filtering to preserve the boundary information of faults and other geological bodies while suppressing the noise. Based on the theory of anisotropic diffusion filtering, this method explores the relationship between eigenvalues of the structure tensor and local structural features of three‐dimensional seismic images and innovatively introduces the definition of stratigraphic coherence coefficients. Then we propose a new system to design the eigenvalues of the diffusion tensor by using the fault confidence measure and stratigraphic coherence coefficients, which can control the filtering intensity of seismic data in different orientations. The value of fault confidence measure is close to 0 where there are flat continuous reflectors and the intensity of diffusion is strong. On the contrary, the diffusion is very weak within presumptive fault zones. Results of both synthetic model and real data prove that the proposed method can effectively suppress noise, preserve faults well and enhance the continuity of the reflectors, which can provide basic data with high signal‐to‐noise ratio for subsequent seismic interpretation.

Relationship Between Vertebral Bone Marrow Edema and Early Progression of Intervertebral Disc Wedge or Narrowing After Lumbar Decompression Surgery.

A retrospective study. The aim of this study was to review clinical and imaging features in patients with lumbar spinal canal stenosis (LSS) with and without postoperative early progression of intervertebral disc degeneration (IDD) and to identify predictive factors. Progression of IDD after lumbar decompression surgery can induce low back pain and leg pain, and may require revision surgery. However, risk factors for postoperative radiological changes indicating IDD linked to development of symptoms have not been described. We included 564 patients with LSS without degenerative lumbar scoliosis who underwent lumbar decompression surgery without fusion. Clinical features and imaging findings were compared in cases with (group P) and without (group N) progression of IDD (intervertebral disc wedge or narrowing) at 1 year after surgery. Of the 564 patients, 49 (8.7%) were in group P. On preoperative MRI, all patients in group P had findings of vertebral bone marrow edema (diffuse high intensity on T2-weighted images and low-intensity on T1-weighted images), compared to only 5.4% in group N. The rate of revision surgery was significantly higher in group P in 5 years' follow-up (12.2% vs. 1.4%, P < 0.01). In group P, 44.9% of patients developed postoperative symptoms associated with postoperative radiological changes, and the frequency was higher in narrowing-type than in wedge-type cases. Vertebral bone marrow edema area and IDD grade were not predictors for postoperative early IDD progression. Careful consideration is required to determine whether lumbar decompression surgery should be performed if vertebral bone marrow edema is detected on MRI, since this is a predictor for a negative clinical outcome. If surgery is symptomati-cally urgent, careful clinical and radiological follow-up is required.Level of Evidence: 4.

Iatrogenic Hyperthyroidism With Recurrent Functioning Thyroid Tissue 40 Years After Thyroidectomy for Graves’ Disease

Background: Graves’ disease is an immune-mediated cause of thyrotoxicosis treated with anti-thyroid drugs (ADTs), radioactive iodine (RAI) or thyroidectomy. Thyroidectomy has been documented to have the lowest rate of recurrence amongst treatment options1. Data regarding long-term recurrence rates is limited beyond 54 months.Clinical Case: An asymptomatic 59 year old female was found to have recurrent thyrotoxicosis on routine laboratory testing. The patient underwent thyroidectomy at age 19 years for Graves’ disease. Prior records unavailable to clarify initial surgical intervention. The patient had post-surgical hypothyroidism which was managed with levothyroxine 100mcg once daily for over 20 years. A biochemically euthyroid state was clearly documented on prior laboratory testing. Initial laboratory testing with TSH <0.01mIU/L (0.45-4.50), FT3 2.8ng/dL (0.8-1.7). Levothyroxine was discontinued with persistent thyrotoxicosis after 8 weeks: TSH <0.01, FT3 5.7, FT4 1.74. Radioactive Iodine Uptake and scan was obtained after administration of 6uCi of iodine-131 which demonstrated 50.8% uptake of radioactive iodine at 24 hours (Normal 10-30%). The left thyroid gland was noted to be in normal position and enlarged with diffuse increase intensity of radiotracer uptake. The right thyroid gland was surgically absent. The patient subsequently underwent completion thyroidectomy with endocrine surgery with resolution of hyperthyroid state. Surgical pathology was benign and consistent with Graves’ disease and multinodular goiter. The patient did become hypothyroid post-operatively and required levothyroxine replacement. She is clinically and biochemically euthyroid on levothyroxine 100mcg once daily 14 months post-operatively.Conclusion: This is a case of recurrent hyperthyroidism approximately 40 years after definitive treatment with thyroidectomy. Although it is unclear whether patient underwent total thyroidectomy or subtotal thyroidectomy for initial intervention, the recurrence of thyrotoxicosis after such a long period of time has not previously been reported in the literature to the knowledge of this writer. This has important implications regarding the underlying pathophysiology of Graves’ disease and the ability of remnant thyroid tissue to regenerate over time. This also has important implications for long-term monitoring in patients with history of thyroidectomy for Graves’ disease.Reference: 1. Sundaresh, V., Brito, J. P., Wang, Z., Prokop, L. J., Stan, M. N., Murad, M. H., & Bahn, R. S. (2013). Comparative effectiveness of therapies for Graves’ hyperthyroidism: a systematic review and network meta-analysis. The Journal of clinical endocrinology and metabolism, 98(9), 3671–3677.

Empirical method for rapid quantification of intrinsic fluorescence signals of key metabolic probes from optical spectra measured on tissue-mimicking turbid medium.

.Significance: Optical fluorescence spectroscopy technique has been explored extensively to quantify both glucose uptake and mitochondrial metabolism with proper fluorescent probes in small tumor models in vivo. However, it remains a great challenge to rapidly quantify the intrinsic metabolic fluorophores from the optically measured fluorescence spectra that contain significant distortions due to tissue absorption and scattering.Aim: To enable rapid spectral data processing and quantify the in vivo metabolic parameters in real-time, we present an empirical ratio-metric method for rapid fluorescence spectra attenuation correction with high accuracy.Approach: A first-order approximation of intrinsic fluorescence spectra can be obtained by dividing the fluorescence spectra by diffuse reflectance spectra with some variable powers. We further developed this approximation for rapid extraction of intrinsic key metabolic probes (2-NBDG for glucose uptake and TMRE for mitochondrial function) by dividing the distorted fluorescence spectra by diffuse reflectance intensities recorded at excitation and emission peak with a pair of system-dependent powers. Tissue-mimicking phantom studies were conducted to evaluate the method.Results: The tissue-mimicking phantom studies demonstrated that our empirical method could quantify the key intrinsic metabolic probes in near real-time with an average percent error of .Conclusions: An empirical method was demonstrated for rapid quantification of key metabolic probes from fluorescence spectra measured on a tissue-mimicking turbid medium. The proposed method will potentially facilitate real-time monitoring of key metabolic parameters of tumor models in vivo using optical spectroscopy, which will significantly advance translational cancer research.

Prediction and observation of intermodulation sidebands from anharmonic phonons in NaBr

A quantum Langevin model, similar to models used recently for optomechanics, was used to predict intermodulation phonon sidebands (IPS). Ab initio calculations of anharmonic phonons in rocksalt NaBr showed these spectral features as "many-body effects". Modern inelastic neutron scattering measurements on a crystal of NaBr at 300K revealed diffuse intensity at high phonon energy from a predicted upper IPS. The transverse optical (TO) part of the new features originates from phonon intermodulation between the transverse acoustic (TA) and TO phonons. The longitudinal optical (LO) spectral features originate from three-phonon coupling between the TA modes and the TO lattice modes. The partner lower IPS proves to be an "intrinsic localized mode". Interactions with the thermal bath broaden and redistribute the spectral weight of the IPS pair. These sidebands are a probe of anharmonicity and quantum noise, which originate from interactions between the phonons in NaBr.

Responses to global financial standards in emerging markets: Regulatory neoliberalism and the Basel II Capital Accord

AbstractThis paper examines the diffusion of the Basel II Capital Accord into emerging markets (EMs). The literature on the diffusion of financial standards reinforces determinism: carefully derived standards such as those around financial liberalization are assumed to be applicable to all markets in an effort to promote stability and international harmonization. Attempts to use financial liberalization and macroprudential toolkits such as Basel II, however well intentioned, can increase rather than mitigate financial instability, due in part to unevenness in the adoption of financial standards. We analyse rich, action research data on the response of banks in 19 EMs in Asia, the Middle East, and Eastern Europe to the advent of Basel II. We find heterogeneous rather than universalistic responses, captured as four types of behavioural variations leading to differences in the intensity of diffusion: Reformist, Instigative, Disobliging and Cosmetic. The variations reflect regulatory neoliberalism. The typology contributes to our understanding of the interaction between bank behaviour, regulator stance and institutional context as determinants of the diffusion of global financial standards.

Feline Spongy Encephalopathy With a Mutation in the ASPA Gene.

Canavan disease is an autosomal recessive leukodystrophy caused by mutations in the gene encoding aspartoacylase (ASPA), which hydrolyses N-acetylaspartate (NAA) to acetate and aspartate. A similar feline neurodegenerative disease associated with a mutation in the ASPA gene is reported herein. Comprehensive clinical, genetic, and pathological analyses were performed on 4 affected cats. Gait disturbance and head tremors initially appeared at 1 to 19 months of age. These cats eventually exhibited dysstasia and seizures and died at 7 to 53 months of age. Magnetic resonance imaging of the brain revealed diffuse symmetrical intensity change of the cerebral cortex, brainstem, and cerebellum. Gas chromatography-mass spectrometry analysis of urine showed significant excretion of NAA. Genetic analysis of the 4 affected cats identified a missense mutation (c.859G>C) in exon 6 of the ASPA gene, which was not detected in 4 neurologically intact cats examined as controls. Postmortem analysis revealed vacuolar changes predominantly distributed in the gray matter of the cerebrum and brain stem as well as in the cerebellar Purkinje cell layer. Immunohistochemically, these vacuoles were surrounded by neurofilaments and sometimes contained MBP- and Olig2-positive cells. Ultrastructurally, a large number of intracytoplasmic vacuoles containing mitochondria and electron-dense granules were detected in the cerebral cortex. All 4 cats were diagnosed as spongy encephalopathy with a mutation in the ASPA gene, a syndrome analogous to human Canavan disease. The histopathological findings suggest that feline ASPA deficiency induces intracytoplasmic edema in neurons and oligodendrocytes, resulting in spongy degeneration of the central nervous system.

Вплив хімічного складу на теплостійкість литої конструкційної сталі

The paper presents the results of the study of the influence of chemical composition, temperature, stress and operating time on the creep and durability of structural steels. It is shown that the efficiency of structural steels in conditions of elevated temperatures and loads depends on the chemical composition, stress level, operating time and temperature. The influence of alloying elements is associated with the inhibition of the process of weakening of heat-resistant steels due to the reduction of their diffusion mobility and intensity of redistribution between the ferrite and secondary phases, their coagulation and reduction of structural defects. Mathematical models of relative elongation and fracture time in the process of creep from operating conditions and degree of alloying of steel are constructed. It is established that the efficiency of heat-resistant structural steels depends on 61 - 64% of the degree of alloying, 18 - 21% - the value of external stress, 7 - 18% - temperature and 11% of operating time. It is shown that the coagulation of carbides and nitrides in steels doped with nitrogen and vanadium is slower than carbides in steels doped with molybdenum, which more effectively shifts the softening process of heat-resistant steel in the region of higher temperatures and time. Keywords: steel, heat resistance, chemical composition, temperature, stress, creep, durability.

Presentation of a rare, highly aggressive peritoneal disease: desmoplastic small round cell tumor and its therapeutic options

SummaryBackgroundDesmoplastic small round cell tumor is a rare highly aggressive peritoneal disease (sarcoma) with mortality rates up to 70% in the first 3 years after diagnosis. It mainly affects young men. Patients clinically complain about diffuse abdominal pain.MethodsThis case report describes the clinical course of a 69-year-old man who presented with recurrent abdominal pain. Physical examination, laboratory testing, imaging, and gastroscopy were performed. Intra-abdominal peritoneal biopsies were taken during diagnostic laparoscopy.ResultsPhysical examination was unremarkable. Laboratory results showed elevated white blood cells, C‑reactive protein, and negative tumor markers. Computed tomography and positron emission tomography scan revealed extensive peritoneal metastases with diffuse intra-abdominal signal intensities and ascites. Gastroscopy was unremarkable, whereas diagnostic laparoscopy confirmed imaging results with a peritoneal cancer index of 39. Extensive immunohistochemical and consecutive molecular investigations led to the diagnosis of an intraperitoneal desmoplastic small round cell tumor.ConclusionOur case report demonstrates a very rare cause of recurrent abdominal pain. Desmoplastic small round cell tumor is a rare and highly aggressive undifferentiated sarcoma, which mainly affects young men. Treatment options include chemotherapy, radiotherapy, cytoreductive surgery, and/or hyperthermic intraperitoneal chemotherapy. Standardized treatment protocols are still lacking because only a few cases have been described so far. Differential diagnoses include all malignancies with peritoneal masses.

Effect of Wind on Soil-Atmosphere Gas Exchange

Global climate change in recent decades is accompanied by rising temperatures and increasing cyclonic activity with strong air flows. How do they affect soil respiration? Is it possible to expect an increase in CO2 emissions and, consequently, a positive feedback of climate change through the greenhouse effect? These questions cannot be answered without the insight into the effect of wind speed on the gas exchange between soil and atmosphere in different landscapes. The paper summarizes the long-term measurements of CO2 efflux from forest-steppe chernozems (Kursk oblast, Russia) in natural and anthropogenic landscapes with forest or herbaceous vegetation depending on wind speed; it presents a physically grounded approach to its quantitative first-approximation (linear) description. The approach assumes an impact of wind through increased forced convection and turbulent diffusivity along with a potential reduction in diffusion mass transfer due to a decrease in the gradient of CO2 concentration between the atmosphere and soil. The constructed inverse parabolic dependence adequately describes the empirical data and assumes a twofold increase in the emission with the wind speed increase to the critical value of 3 m/s and its decreases to the initial level with the further wind speed increase to 6–7 m/s. The intensity of forced convection of soil air turns out to be by five–six orders of magnitude lower than the wind speed in the atmosphere but not inferior to the intensity of conventional isothermal CO2 diffusion, which suggests that this mechanism is to be taken into account in the models of soil–atmosphere gas exchange.

The Influence of Boundary Layer Mixing Strength on the Evolution of a Baroclinic Cyclone

AbstractSubgrid-scale turbulence in numerical weather prediction models is typically handled by a PBL parameterization. These schemes attempt to represent turbulent mixing processes occurring below the resolvable scale of the model grid in the vertical direction, and they act upon temperature, moisture, and momentum within the boundary layer. This study varies the PBL mixing strength within 4-km WRF simulations of a 26–29 January 2015 snowstorm to assess the sensitivity of baroclinic cyclones to eddy diffusivity intensity. The bulk critical Richardson number for unstable regimes is varied between 0.0 and 0.25 within the YSU PBL scheme as a way of directly altering the depth and magnitude of subgrid-scale turbulent mixing. Results suggest that varying the bulk critical Richardson number is similar to selecting a different PBL parameterization. Differences in boundary layer moisture availability, arising from reduced entrainment of dry, free tropospheric air, lead to variations in the magnitude of latent heat release above the warm frontal region, producing stronger upper-tropospheric downstream ridging in simulations with less PBL mixing. The more amplified flow pattern impedes the northeastward propagation of the surface cyclone and results in a westward shift of precipitation. In addition, trajectory analysis indicates that ascending parcels in the less-mixing simulations condense more water vapor and terminate at a higher potential temperature level than do ascending parcels in the more-mixing simulations, suggesting stronger latent heat release when PBL mixing is reduced. These results suggest that spread within ensemble forecast systems may be improved by perturbing PBL mixing parameters that are not well constrained.

Degenerate nonlinear parabolic equations with discontinuous diffusion coefficients

This paper is devoted to the study of some nonlinear parabolic equations with discontinuous diffusion intensities. Such problems appear naturally in physical and biological models. Our analysis is based on variational techniques and in particular on gradient flows in the space of probability measures equipped with the distance arising in the Monge–Kantorovich optimal transport problem. The associated internal energy functionals in general fail to be differentiable, therefore classical results do not apply directly in our setting. We study the combination of both linear and porous medium type diffusions and we show the existence and uniqueness of the solutions in the sense of distributions in suitable Sobolev spaces. Our notion of solution allows us to give a fine characterization of the emerging critical regions, observed previously in numerical experiments. A link to a three phase free boundary problem is also pointed out.

Interactions of diffusion and nonlocal delay give rise to vegetation patterns in semi-arid environments

Vegetation pattern is caused by local instability in phase space, which can reflect the distribution characteristics of vegetation in the studied space. In semi-arid environment, the vegetation roots will not only absorb the water resources near themselves, but also absorb the water resources in the whole study area, that is to say, the absorption of water resources by vegetation roots is a nonlocal process. Meanwhile, the feedback mechanism of soil-water diffusion plays an important role in the process of water absorption by vegetation roots. However, it is not clear that how the feedback mechanism of nonlocal water absorption by vegetation roots and soil-water diffusion affects vegetation pattern. In this paper, we construct a positive feedback vegetation-water model with nonlocal delay. The instability of Turing pattern is analyzed by analytical method, and the conditions of stable pattern occurrence are obtained. At the same time, we use multi-scale analysis method to obtain the amplitude equation of vegetation-water system. We found that the non-local water absorption intensity of vegetation roots and the feedback of soil-water diffusion can cause the phase change of vegetation pattern. The change of nonlocal water absorption intensity will produce mixed vegetation pattern structure. The enhancement of soil-water diffusion feedback intensity will change the vegetation pattern structure: low density cold spot patterns → mixed patterns → high density hot spot patterns. The isolation between vegetation patches will be increased as that nonlocal water absorption intensity is enhanced or the feedback intensity of soil-water diffusion is increased. We also revealed that increasing the feedback intensity of soil water diffusion or nonlocal strength within a certain range is helpful to increase the vegetation density, while excessive feedback intensity or nonlocal strength will induce land desertification.

Bioactivity of microporous borate glass-ceramics prepared from solution and derived glasses

Microporous borate compositions based on the formula xB2O3•(100–x)(0.5CaO•0.45Na2O•0.05P2O5) (x = 56.1 and 51.1 mol%) have been prepared from solution. The dried products were subjected to heat-treatment at 600 and 700 °C for 3 h to obtain borate glass-ceramics with scaffold-like structure. Bioactivity and degradation were tested in simulated body fluid (SBF) at 37 °C for different time intervals. Scanning (SEM) and transmission (TEM) electron microscopy, infrared spectroscopy (FTIR) and X-ray diffraction (XRD) were used to examine the correlation between bioactivity and microstructure. Results indicated that the type and concentration of crystalline CaNaB5O9 and CaNa3B5O10 phases, in addition to concentration of bridging and non-bridging oxygen atoms, are the factors affecting the apatite forming ability and composition degradation. XRD and SEM results showed that the as-prepared compositions and those heat-treated at 600 and 700 °C are crystalline matrices, while TEM-EDP of selected region exhibited halo diffuse intensity with clear bright spots. These features indicate that the crystalline phases are dispersed in amorphous phase. After immersion in SBF, TEM-EDP proved that the crystalline hydroxyapatite (HA) phase was formed on amorphous phase. The type of product after reaction in SBF is influenced by the nature of borate network. For melt-derived borate glasses, hydrous species of B(OH)3 and amorphous calcium phosphate are formed. Microporous borate glass-ceramics exhibited a good in vitro bioactive response through the formation of hydroxyapatite, except when the matrix is rich in CaNa3B5O10 phase. The results of this study suggest that the solution-method can be used to prepare microporous bioactive borate glass-ceramics, such as three-dimensional porous scaffolds, which are of particular interest for the clinical application in bone regeneration.