Neural networks as a tool for constructing continuous NDVI time series from AVHRR and MODIS

The long term Advanced Very High Resolution Radiometer (AVHRR)‐Normalized Difference Vegetation Index (NDVI) record provides a critical historical perspective on vegetation dynamics necessary for global change research. Despite the proliferation of new sources of global, moderate resolution vegetation datasets, the remote sensing community is still struggling to create datasets derived from multiple sensors that allow the simultaneous use of spectral vegetation for time series analysis. To overcome the non‐stationary aspect of NDVI, we use an artificial neural network (ANN) to map the NDVI indices from AVHRR to those from MODIS using atmospheric, surface type and sensor‐specific inputs to account for the differences between the sensors. The NDVI dynamics and range of MODIS NDVI data at 1° is matched and extended through the AVHRR record. Four years of overlap between the two sensors is used to train a neural network to remove atmospheric and sensor specific effects on the AVHRR NDVI. In this paper, we present the resulting continuous dataset, its relationship to MODIS data, and a validation of the product.     

Reinforced concrete deep beam shear strength capacity modelling using an integrative bio-inspired algorithm with an artificial intelligence model

The design and sustainability of reinforced concrete deep beam are still the main issues in the sector of structural engineering despite the existence of modern advancements in this area. Proper understanding of shear stress characteristics can assist in providing safer design and prevent failure in deep beams which consequently lead to saving lives and properties. In this investigation, a new intelligent model depending on the hybridization of support vector regression with bio-inspired optimization approach called genetic algorithm (SVR-GA) is employed to predict the shear strength of reinforced concrete (RC) deep beams based on dimensional, mechanical and material parameters properties. The adopted SVR-GA modelling approach is validated against three different well established artificial intelligent (AI) models, including classical SVR, artificial neural network (ANN) and gradient boosted decision trees (GBDTs). The comparison assessments provide a clear impression of the superior capability of the proposed SVR-GA model in the prediction of shear strength capability of simply supported deep beams. The simulated results gained by SVR-GA model are very close to the experimental ones. In quantitative results, the coefficient of determination (R²) during the testing phase (R² = 0.95), whereas the other comparable models generated relatively lower values of R² ranging from 0.884 to 0.941. All in all, the proposed SVR-GA model showed an applicable and robust computer aid technology for modelling RC deep beam shear strength that contributes to the base knowledge of material and structural engineering perspective.

     

High-pressure destruction kinetics of Listeria monocytogenes on pork

OBJECTIVE: To define the incidence of complications of endotracheal intubation and the factors associated with these complications. STUDY DESIGN: During a 22-month period, 227 intubated infants weighing <1,501 g were followed prospectively in a neonatal intensive care unit. Detailed records of events associated with airway management were kept after every intubation, in addition to clinical data. RESULTS: Eleven infants (4.8%) developed respiratory stridor after extubation which was treated with either systemic corticosteroids, racemic epinephrine and/or reintubation for respiratory failure. Four infants were submitted for bronchoscopy, mild subglottic stenosis with tracheal edema was found in 1 patient, granulation tissue and airway edema were noted in 3 infants. Traumatic intubation, prolonged ventilation, multiple intubations and bacterial colonization of the endotracheal tube were the factors associated with postextubation stridor. CONCLUSIONS: Subglottic stenosis is an infrequent complication of endotracheal intubation with current airway management of very-low-birth-weight infants. Less severe complications are still common, but they are usually amenable to clinical treatment. Bronchoscopy should be performed selectively only in infants with clinical evidence of airway obstruction after extubation.     

Quantum dots: synthesis, bioapplications, and toxicity

Ferrite nanoparticles of basic composition Ni_0.7-x Zn _x Cu_0.3Fe₂O₄ (0.0 ?? x ?? 0.2, x = 0.05) were synthesized through auto-combustion method and were characterized for structural properties using X-ray diffraction [XRD], scanning electron microscopy, transmission electron microscopy, and Fourier transform infrared spectroscopy [FT-IR]. XRD analysis of the powder samples sintered at 600°C for 4 h showed the cubic spinel structure for ferrites with a narrow size distribution from 28 to 32 nm. FT-IR showed two absorption bands (v ₁ and v ₂) that are attributed to the stretching vibration of tetrahedral and octahedral sites. The effect of Zn doping on the electrical properties was studied using dielectric and impedance spectroscopy at room temperature. The dielectric parameters (??', ????, tan??, and ?? _ac) show their maximum value for 10% Zn doping. The dielectric constant and loss tangent decrease with increasing frequency of the applied field. The results are explained in the light of dielectric polarization which is similar to the conduction phenomenon. The complex impedance shows that the conduction process in grown nanoparticles takes place predominantly through grain boundary volume. PACS: 75.50.Gg; 78.20; 77.22.Gm.     

High static gain single-phase PFC based on a hybrid boost converter

In this paper, a single-phase unity power factor rectifier, based on a hybrid boost converter, resulting from the integration of a conventional dc–dc boost converter and a switched-capacitor voltage doubler is proposed, analysed, designed and tested. The high-power rectifier is controlled by two feedback loops with the same control strategy employed in the conventional boost-based rectifier. The main feature of the proposed rectifier is its ability to output a dc voltage larger than the double of the peak value of the input line voltage, while subjecting the power switches to half of the dc-link voltage, which contributes to reducing the cost and increasing the efficiency. Experimental data were obtained from a laboratory prototype with an input voltage of 220 Vrms, line frequency of 60 Hz, output voltage of 800 Vdc, load power of 1000 W and switching frequency of 50 kHz. The efficiency of the prototype, measured in the laboratory, was 96.5% for full load and 97% for half load.     

Differentiated PDGFRα-Positive Cells: A Novel In-Vitro Model for Functional Studies of Neuronal Nitric Oxide Synthase

It is evident that depletion of interstitial cells and dysfunction of nitric oxide (NO) pathways are key players in development of several gastrointestinal (GI) motility disorders such as diabetic gastroparesis (DGP). One of the main limitations of DGP research is the lack of isolation methods that are specific to interstitial cells, and therefore conducting functional studies is not feasible. The present study aims (i) to differentiate telomerase transformed mesenchymal stromal cells (iMSCs) into platelet-derived growth factor receptor-α-positive cells (PDGFRα-positive cells) using connective tissue growth factor (CTGF) and L-ascorbic acids; (ii) to investigate the effects of NO donor and inhibitor on the survival rate of differentiated PDGFRα-positive cells; and (iii) to evaluate the impact of increased glucose concentrations, mimicking diabetic hyperglycemia, on the gene expression of neuronal nitric oxide synthase (nNOS). A fibroblastic differentiation-induction medium supplemented with connective tissue growth factor was used to differentiate iMSCs into PDGFRα-positive cells. The medium was changed every day for 21 days to maintain the biological activity of the growth factors. Gene and protein expression, scanning electron and confocal microscopy, and flow cytometry analysis of several markers were conducted to confirm the differentiation process. Methyl tetrazolium cell viability, nitrite measurement assays, and immunostaining were used to investigate the effects of NO on PDGFRα-positive cells. The present study, for the first time, demonstrated the differentiation of iMSCs into PDGFRα-positive cells. The outcomes of the functional studies showed that SNAP (NO donor) increased the survival rate of differentiated PDGFRα-positive cells whereas LNNA (NO inhibitor) attenuated these effects. Further experimentations revealed that hyperglycemia produced a significant increase in expression of nNOS in PDGFRα-positive cells. Differentiation of iMSCs into PDGFRα-positive cells is a novel model to conduct functional studies and to investigate the involvement of NO pathways. This will help in identifying new therapeutic targets for treatment of DGP.     

Effect of Geometric Parameters (β and τ) on Behaviour of Cold Formed Stainless Steel Tubular X-Joints

CIDECT guideline of carbon steel is frequently applied to design the cold-formed stainless steel tubular X-joints. The allowable range of the brace to chord width ratio (β) had been recorded in this guideline without mention to specific limits for the brace to chord thickness ratio (τ). Therefore, this study was carried out to investigate the effect of β and τ ratios on the behaviour of tubular X-joints by using LUSAS software. Three numerical models were created based on the stainless steel sheet type which symbolled as XD (duplex EN1.4462), XH (high strength austenitic), and XN (normal AISI 304). A good consistency was achieved with the experimental test in terms of load–deflection behaviour, ultimate joint strength, and failure modes within a maximum error of 8.63%. Parametric studies results indicated that the increased of (β) ratio at constant (τ?=?1) capable to increase the joint strength which was quite conservative with the CIDECT design strengths of specimens failed with the chord side wall failure, while it was unconservative to chord face failure. Hence, equations were proposed to calculate the joint strength for specimens failed by chord face failure. A range of (0.4–2) had proposed for (τ) ratio. The ultimate joint strength obviously increased at high values of (τ) ratio within a constant value of (β?=?1). Moreover, the chord side wall and brace local buckling failure modes observed when (τ?>?0.5) and (τ?≤?0.5), respectively, which indicated that the brace local buckling failure can be only occurred when (β?>?0.85) and (τ?≤?0.5).     

Novel porous matrix and bioreactors for high density cultures of insulinoma cell lines: Insulin secretion and response to glucose

This paper describes the use of a novel porous matrix, Porocell, for high density, tissue-like culture of two insulinoma cell lines, CRI-D2 and CRI-D11. Both these cell lines have previously been shown not to secrete insulin in response to glucose. Porocell is a macro-porous, polymeric material manufactured in the shape of discs that are 6·2 mm in diameter and 2 mm in thickness. Insulinoma cells were cultured in two different mini-bioreactors, each containing six Porocell discs inoculated with 2·5 × 10⁶ cells per disc. In surface aerated, stirred bioreactors, the insulinoma cells grew as closely packed dense cell sheets penetrating deep into the pores of Porocell. In a second type of system, a packed-bed perfused mini-bioreactor, flat, extended monolayers of cells were observed growing throughout the Porocell matrix. In both bioreactor configurations, viable cell populations were maintained for 30 days because of the excellent oxygen and nutrient transfer properties of Porocell. CRI-D2 insulinoma cells cultured in static flasks and on Porocell did not show any insulin secretion in response to 30 min exposures in media supplemented with 5·5–16·7 mmol dm⁻³ glucose. However, in long term (14–19 day) cultures, CRI-D2 cells growing in Porocell secreted low, but measurable amounts (25–35 pmol dm⁻³) of insulin in medium supplemented with elevated (14·5 mmol dm⁻³) glucose concentrations. The glucose uptake rates of cells cultured in 4·0 mmol dm⁻³ glucose increased linearly from 1·0 to 2·3 mmol dm⁻³ day⁻¹ over a period of 19 days. At 14·5 mmol dm⁻³ glucose concentration, the uptake rate increased from 1·0 to 7·05 mmol dm⁻³ day⁻¹ over the same period of culture. Contrary to previous studies, we have demonstrated that the CRI-D2 cell line cultured at high cell density in Porocell is capable of secreting insulin when exposed to prolonged and elevated concentrations of glucose. The Porocell mini-bioreactors are easy to use, robust systems that can be used for long-term studies of primary and tumorgenic islet cell function and response to secretagogues. © 1998 SCI.     

Quantum dots: synthesis, bioapplications, and toxicity

ABSTRACT: This review introduces quantum dots (QDs) and explores their properties, synthesis, applications, delivery systems in biology, and their toxicity. QDs are one of the first nanotechnologies to be integrated with the biological sciences and are widely anticipated to eventually find application in a number of commercial consumer and clinical products. They exhibit unique luminescence characteristics and electronic properties such as wide and continuous absorption spectra, narrow emission spectra, and high light stability. The application of QDs, as a new technology for biosystems, has been typically studied on mammalian cells. Due to the small structures of QDs, some physical properties such as optical and electron transport characteristics are quite different from those of the bulk materials.