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Multiple linear regression and regression with time series error models in forecasting PM10 concentrations in Peninsular Malaysia

Ng KY, Awang N

Environ Monit Assess, 2018 Jan 06;190(2):63.
PMID: 29306973 DOI: 10.1007/s10661-017-6419-z

Frequent haze occurrences in Malaysia have made the management of PM10 (particulate matter with aerodynamic less than 10 μm) pollution a critical task. This requires knowledge on factors associating with PM10 variation and good forecast of PM10 concentrations. Hence, this paper demonstrates the prediction of 1-day-ahead daily average PM10 concentrations based on predictor variables including meteorological parameters and gaseous pollutants. Three different models were built. They were multiple linear regression (MLR) model with lagged predictor variables (MLR1), MLR model with lagged predictor variables and PM10 concentrations (MLR2) and regression with time series error (RTSE) model. The findings revealed that humidity, temperature, wind speed, wind direction, carbon monoxide and ozone were the main factors explaining the PM10 variation in Peninsular Malaysia. Comparison among the three models showed that MLR2 model was on a same level with RTSE model in terms of forecasting accuracy, while MLR1 model was the worst.

Matched MeSH terms: Linear Models*
Fulltext Influence of refractive condition on retinal vasculature complexity in younger subjects

Azemin MZ, Daud NM, Ab Hamid F, Zahari I, Sapuan AH

ScientificWorldJournal, 2014;2014:783525.
PMID: 25371914 DOI: 10.1155/2014/783525

The aim of this study was to compare the retinal vasculature complexity between emmetropia, and myopia in younger subjects.

Matched MeSH terms: Linear Models
Measurement of biochemical oxygen demand of the leachates

Fulazzaky MA

Environ Monit Assess, 2013 Jun;185(6):4721-34.
PMID: 23001555 DOI: 10.1007/s10661-012-2899-z

Biochemical oxygen demand (BOD) of the leachates originally from the different types of landfill sites was studied based on the data measured using the two manometric methods. The measurements of BOD using the dilution method were carried out to assess the typical physicochemical and biological characteristics of the leachates together with some other parameters. The linear regression analysis was used to predict rate constants for biochemical reactions and ultimate BOD values of the different leachates. The rate of a biochemical reaction implicated in microbial biodegradation of pollutants depends on the leachate characteristics, mass of contaminant in the leachate, and nature of the leachate. Character of leachate samples for BOD analysis of using the different methods may differ significantly during the experimental period, resulting in different BOD values. This work intends to verify effect of the different dilutions for the manometric method tests on the BOD concentrations of the leachate samples to contribute to the assessment of reaction rate and microbial consumption of oxygen.

Matched MeSH terms: Linear Models
Relationship between emotional intelligence and job satisfaction in newly qualified Malaysian dentists

Pau A, Sabri BA

Asia Pac J Public Health, 2015 Mar;27(2):NP1733-41.
PMID: 22743863 DOI: 10.1177/1010539512449855

Job satisfaction (JS) is considered to be a key factor in workforce retention. This article reports on the association between emotional intelligence (EI) and JS in newly qualified dentistsemployed in the Malaysian 3-year compulsory service. A postal questionnaire survey collected data on sociodemographic and occupational characteristics, EI, and JS. In a sample of 342 (58.9%) respondents, sociodemographic characteristics were not statistically significantly associated with both EI and JS total scores, whereas overseas graduates scored more highly on the EI scale compared with local graduates. Linear regression analysis indicated that EI was the only statistically significant predictor of JS. EI was statistically significantly associated with JS with patient relationships (r = 0.28; P = .001), peer support (r = 0.30; P = .001), professional development (r = 0.21; P = .001), quality of care (r = 0.57; P = .001), supporting staff (r = 0.24;P = .001), overall JS (r = 0.28; P = .001), and total JS score (r = 0.40; P = .001). However, EI was not statistically significantly associated with JS with income (r = 0.06; P = .302). These findings have implications for the development of interventions to enhance EI and JS in order to promote retention of dentists in the public sector.

Matched MeSH terms: Linear Models
Thermal noise due to surface-charge effects within the Debye layer of endogenous structures in dendrites

Poznanski RR

Phys Rev E Stat Nonlin Soft Matter Phys, 2010 Feb;81(2 Pt 1):021902.
PMID: 20365590

An assumption commonly used in cable theory is revised by taking into account electrical amplification due to intracellular capacitive effects in passive dendritic cables. A generalized cable equation for a cylindrical volume representation of a dendritic segment is derived from Maxwell's equations under assumptions: (i) the electric-field polarization is restricted longitudinally along the cable length; (ii) extracellular isopotentiality; (iii) quasielectrostatic conditions; and (iv) homogeneous medium with constant conductivity and permittivity. The generalized cable equation is identical to Barenblatt's equation arising in the theory of infiltration in fissured strata with a known analytical solution expressed in terms of a definite integral involving a modified Bessel function and the solution to a linear one-dimensional classical cable equation. Its solution is used to determine the impact of thermal noise on voltage attenuation with distance at any particular time. A regular perturbation expansion for the membrane potential about the linear one-dimensional classical cable equation solution is derived in terms of a Green's function in order to describe the dynamics of free charge within the Debye layer of endogenous structures in passive dendritic cables. The asymptotic value of the first perturbative term is explicitly evaluated for small values of time to predict how the slowly fluctuating (in submillisecond range) electric field attributed to intracellular capacitive effects alters the amplitude of the membrane potential. It was found that capacitive effects are almost negligible for cables with electrotonic lengths L>0.5 , contributes up to 10% of the signal for cables with electrotonic lengths in the range between 0.25

Matched MeSH terms: Linear Models
Determination of the binding constants of modafinil enantiomers with sulfated β-cyclodextrin chiral selector by capillary electrophoresis using three different linear plotting methods

Al Azzam KM, Saad B, Aboul-Enein HY

Electrophoresis, 2010 Sep;31(17):2957-63.
PMID: 20690150 DOI: 10.1002/elps.201000266

Binding constants for the enantiomers of modafinil with the negatively charged chiral selector sulfated-β-CD (S-β-CD) using CE technique is presented. The calculations of the binding constants employing three different linearization plots (double reciprocal, X-reciprocal and Y-reciprocal) were performed from the electrophoretic mobility values of modafinil enantiomers at different concentrations of S-β-CD in the BGE. The highest inclusion affinity of the modafinil enantiomers were observed for the S-enantiomer-S-β-CD complex, in agreement with the computational calculations performed previously. Binding constants for each enantiomer-S-β-CD complex at different temperatures, as well as thermodynamic parameters for binding, were calculated. Host-guest binding constants using the double reciprocal fit showed better linearity (r(2)>0.99) at all temperatures studied (15-30°C) and compared with the other two fit methods. The linear van't Hoff (15-30°C) plot obtained indicated that the thermodynamic parameters of complexation were temperature dependent for the enantiomers.

Matched MeSH terms: Linear Models
MIMO model of an interacting series process for Robust MPC via System Identification

Wibowo TC, Saad N

ISA Trans, 2010 Jul;49(3):335-47.
PMID: 20304404 DOI: 10.1016/j.isatra.2010.02.005

This paper discusses the empirical modeling using system identification technique with a focus on an interacting series process. The study is carried out experimentally using a gaseous pilot plant as the process, in which the dynamic of such a plant exhibits the typical dynamic of an interacting series process. Three practical approaches are investigated and their performances are evaluated. The models developed are also examined in real-time implementation of a linear model predictive control. The selected model is able to reproduce the main dynamic characteristics of the plant in open-loop and produces zero steady-state errors in closed-loop control system. Several issues concerning the identification process and the construction of a MIMO state space model for a series interacting process are deliberated.

Matched MeSH terms: Linear Models
Comparison of signal-to-noise, blank determination, and linear regression methods for the estimation of detection and quantification limits for volatile organic compounds by gas chromatography

Sanagi MM, Ling SL, Nasir Z, Hermawan D, Ibrahim WA, Abu Naim A

J AOAC Int, 2010 2 20;92(6):1833-8.
PMID: 20166602

LOD and LOQ are two important performance characteristics in method validation. This work compares three methods based on the International Conference on Harmonization and EURACHEM guidelines, namely, signal-to-noise, blank determination, and linear regression, to estimate the LOD and LOQ for volatile organic compounds (VOCs) by experimental methodology using GC. Five VOCs, toluene, ethylbenzene, isopropylbenzene, n-propylbenzene, and styrene, were chosen for the experimental study. The results indicated that the estimated LODs and LOQs were not equivalent and could vary by a factor of 5 to 6 for the different methods. It is, therefore, essential to have a clearly described procedure for estimating the LOD and LOQ during method validation to allow interlaboratory comparisons.

Matched MeSH terms: Linear Models
Effect of cellulosic fiber scale on linear and non-linear mechanical performance of starch-based composites

Karimi S, Abdulkhani A, Tahir PM, Dufresne A

Int J Biol Macromol, 2016 Oct;91:1040-4.
PMID: 27339322 DOI: 10.1016/j.ijbiomac.2016.06.061

Cellulosic nanofibers (NFs) from kenaf bast were used to reinforce glycerol plasticized thermoplastic starch (TPS) matrices with varying contents (0-10wt%). The composites were prepared by casting/evaporation method. Raw fibers (RFs) reinforced TPS films were prepared with the same contents and conditions. The aim of study was to investigate the effects of filler dimension and loading on linear and non-linear mechanical performance of fabricated materials. Obtained results clearly demonstrated that the NF-reinforced composites had significantly greater mechanical performance than the RF-reinforced counterparts. This was attributed to the high aspect ratio and nano dimension of the reinforcing agents, as well as their compatibility with the TPS matrix, resulting in strong fiber/matrix interaction. Tensile strength and Young's modulus increased by 313% and 343%, respectively, with increasing NF content from 0 to 10wt%. Dynamic mechanical analysis (DMA) revealed an elevational trend in the glass transition temperature of amylopectin-rich domains in composites. The most eminent record was +18.5°C shift in temperature position of the film reinforced with 8% NF. This finding implied efficient dispersion of nanofibers in the matrix and their ability to form a network and restrict mobility of the system.

Matched MeSH terms: Linear Models
Determination of tamoxifen and its metabolites using micelle to solvent stacking in nonaqueous capillary electrophoresis

Thang LY, See HH, Quirino JP

Electrophoresis, 2016 05;37(9):1166-9.
PMID: 26873060 DOI: 10.1002/elps.201600010

Micelle to solvent stacking was implemented for the recently established NACE-C(4) D method to determine tamoxifen and its metabolites in standard samples and human plasma of breast cancer patients. For stacking, the standard samples and extract after liquid-liquid extraction (LLE) were prepared in methanol and the resulting sample solution was pressure injected after a micellar plug of SDS. Factors that affected the stacking such as SDS concentration, micelle, and sample plug length were examined. The sensitivity enhancement factor (peak height from stacking/peak height from typical injection of sample in BGE) was 15-22. The method detection limits with LLE were in the range of 5-10 ng/mL, which was lower than the established method (where the LLE extract was also prepared in methanol) with reported method detection limits of 25-40 ng/mL. The intraday and interday repeatability were in the range of 1.0-3.4% and 3.8-6.5%, respectively.

Matched MeSH terms: Linear Models
A sequential algorithm for the non-linear dual-sorption model of percutaneous drug absorption

Gumel AB, Kubota K, Twizell EH

Math Biosci, 1998 Aug 15;152(1):87-103.
PMID: 9727298

A sequential algorithm is developed for the non-linear dual-sorption model developed by Chandrasekaran et al. [1,2] which monitors pharmacokinetic profiles in percutaneous drug absorption. In the experimental study of percutaneous absorption, it is often observed that the lag-time decreases with the increase in the donor concentration when two or more donor concentrations of the same compound are used. The dual-sorption model has sometimes been employed to explain such experimental results. In this paper, it is shown that another feature observed after vehicle removal may also characterize the dual-sorption model. Soon after vehicle removal, the plots of the drug flux versus time become straight lines on a semilogarithmic scale as in the linear model, but the half-life is prolonged thereafter when the dual-sorption model prevails. The initial half-life after vehicle removal with a low donor concentration is longer than that with a higher donor concentration. These features, if observed in experiments, may be used as evidence to confirm that the dual-sorption model gives an explanation to the non-linear kinetic behaviour of a permeant.

Matched MeSH terms: Linear Models
Fulltext Factors associated with strain among informal care providers of patients with traumatic brain injury in Malaysia

Bamatraf AA, AlAmodi AA, Ali MA, Chan CM, Mazlan M, Shareef MA

J Family Med Prim Care, 2020 Jun;9(6):2990-2994.
PMID: 32984161 DOI: 10.4103/jfmpc.jfmpc_247_20

Purpose: This study aims to investigate the level of strain and various influencing factors among informal care providers of traumatic brain injury (TBI) patients.
Methods: A cross-sectional study was conducted in a single center in Malaysia via recruiting care providers of patients with TBI. The modified caregiver strain index (MCSI) questionnaires were utilized to ascertain the level of strain. The demographic data of informal care providers were also obtained. Independent sample t-test, analysis of variance (ANOVA), and a linear regression model were processed for data analysis.
Results: A total of 140 informal care providers were included in the study. More than half of informal care providers claimed to have strain (54.3%). Factors associated with increased strain include receiving tertiary education, being of Chinese background, and employed experience higher strain level. Informal care providers with characteristics such as being single, retired and provided care for 5 years experienced a lower level of strain.
Conclusion: Guidance on integrating the TBI knowledge into practice, assessing the care provider's level of strain regularly and providing supportive measures may aid in supporting informal care providers at risk.

Matched MeSH terms: Linear Models
Fulltext Knowledge assessment of snake antivenom among healthcare practitioners involving educational intervention in northern Nigeria: a study protocol

Bala AA, Jatau AI, Yunusa I, Mohammed M, Mohammed AH, Isa AM, et al.

Ther Adv Drug Saf, 2020;11:2042098620935721.
PMID: 32944213 DOI: 10.1177/2042098620935721

Introduction: Snakebite envenoming (SBE) is an important occupational and public health hazard especially in sub-Saharan Africa. For optimum management of SBE, adequate knowledge of Snake antivenom (SAV) is very critical among the healthcare practioners in this region. Information related to the knowledge of SAV use in the management of SBE, as well as SAV logistics is scarce among the Health Care Professionals (HCPs) in Nigeria, particularly in the northern region. We therefore aimed to develop, validate and utilize a tool to assess the SAV knowlegde among HCPs in northern Nigeria. We also sought to implement and evaluate an intervention that could improve the SAV knowledge among the HCPs.
Methods: The proposed study will be conducted in three phases: Phase I will involve the development of the item-pool to be included in the tool, followed by a face, content validity and construct validity. The tool reliability, readability and difficulty index will be determined. Phase II will involve the utilization of the tool to assess baseline SAV knowledge among the HCPs followed by an educational intervention. Multiple Linear Regression analysis will be used to determine the factors associated with SAV knowledge among the HCPs. Lastly, Phase III which will be a repeat of Phase II to assess and evaluate the knowledge after the intervention.
Discussion: The study design and findings may guide future implementation and streamline the intervention of improving SAV knowledge in HCPs training and practice.
Lay Summary: Knowledge assessment and educational intervention of snake antivenom among healthcare practitioners in northern Nigeria: a study protocol Snakebite envenoming (SBE) is an important occupational and public health hazard especially in sub-Saharan Africa. For optimum management of SBE, adequate knowledge of snake antivenom (SAV) is very critical among the healthcare practitioners. The baseline knowledge SAV dosage, mode of administration, availability, and logistics is very relevant among healthcare professionals, particularly those that are directly involved in its logistics. It is paramount that SAV is handled and used appropriately. The efforts and advocacy for the availability for more SAV will be in vain if not handled appropriately before they are used. This study protocol aims to develop a tool, to assess SAV knowledge and effects of educational interventions among healthcare professionals (HCPs) in northern Nigeria. This protocol suggests conducting studies in three phases: (a) Development and validation of SAV knowledge assessment tool, (b) Baseline assessment of SAV knowledge assessment tool among HCPs, and (c) Development, implementation and evaluation of an educational intervention to improve SAV knowledge among HCPs in northern Nigeria.

Matched MeSH terms: Linear Models
Fulltext Quality of life among cancer patients undergoing chemotherapy in government hospitals in Peninsular Malaysia

Subramaniam, Suhasinee, Sherina Mohd Sidik, Rampal, Lekhraj, Siti Irma Fadhilah, Periasamy, Ummavathy

Malaysian Journal of Medicine and Health Sciences, 2019;15(1):5-15.
MyJurnal

To determine the quality of life (physical health, psychological, social relationships and environment domains) among cancer patients undergoing chemotherapy in government hospitals in Peninsular Malaysia. Methods: The data were collected using self-administered questionnaires. Descriptive statistics were conducted to obtain frequency and percentage of variables. Independent sample T-test and One way ANOVA were used to determine the association between variables. Multiple linear regression model was used to determine the significant predictors. The predictors of each domain was analysed separately. Results: Quality of life among cancer patients undergoing chemotherapy in this study was determined by four domains which were physical health, psychological, social relationships and environment. The overall mean score for physical health was 52.60, psychological was 52.55, social relationships was 50.79 and environment was 51.16. The significant predictors of physical effect domain were monthly income, cancer stage, social support, nausea and vomiting. The significant predictors of psychological domain were race, marital status, cancer stage, nausea and vomiting. The significant predictors of social relationships domain were race, educational level, social support, nausea and vomiting. The significant predictors of environment domain were race, marital status, hopelessness level, nausea and vomiting. Conclusion: The quality of life among chemotherapy cancer patients is important to be observed. Based on the predictors found in this study, appropriate interventions can be taken to improve the quality of life outcomes and the response towards the treatment.

Matched MeSH terms: Linear Models
Profiling of cured residue of solvent-based adhesives by attenuated total reflectance-Fourier transform infrared spectroscopy with chemometrics for forensic investigation

Saman SA, Chang KH, Abdullah AFL

J Forensic Sci, 2021 Mar;66(2):608-618.
PMID: 33202056 DOI: 10.1111/1556-4029.14625

Abuse of solvent-based adhesives jeopardizes world population, especially the young generation. Adhesive-related exhibits encountered in forensic cases might need to be determined if they could have come from a particular source or to establish link between cases or persons. This study was aimed to discriminate solvent-based adhesives, especially to aid forensic investigation of glue sniffing activities. In this study, thirteen brands with three samples each, totaling at 39 adhesive samples, were analyzed using attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy followed by chemometric methods. Experimental output showed that adhesive samples utilized in this study were less likely to change in their ATR-FTIR profiles over time, at least up to 2 months. No interference from plastic materials was noticed based on ATR-FTIR profile comparison. Physical examination could differentiate the samples into two groups, namely contact adhesives and cement adhesives. A principal component analysis-score linear discriminative analysis (PC-score LDA) model resulted in 100% and 98.6% correct classification in discriminating the two groups of adhesive samples, forming seven discriminative clusters. Test set with adhesive samples applied glass slide and plastic substrates also demonstrated a 100% correct classification into their respective groups. As a conclusion, the method allowed for discrimination of adhesive samples based on the spectral features, displaying relationship among samples. It is hoped that this comparative information is beneficial to trace the possible source of solvent-based adhesives, whenever they are recovered from a crime scene, for forensic investigation.

Matched MeSH terms: Linear Models
Fulltext Evaluation of extra virgin olive oil adulteration with edible oils using ATR-FTIR spectroscopy

Nuraznee Mashodi, Nurul Yani Rahim, Norhayati Muhammad, Saliza Asman

Malaysian Journal of Applied Sciences, 2020;5(1):35-44.
MyJurnal

Extra virgin olive oil (EVOO) is categorized as expensive oil due to high-quality nutritional value. Unfortunately, EVOO is easily adulterated with other low-quality edible oils. Therefore, this study was done to differentiate and analyze the adulteration of EVOO with other edible oils using Attenuated Total Reflectance-Fourier Transform Infrared (ATR-FTIR) spectroscopy. The study was used several edible oils included canola oil, corn oil, sunflower oil, and soybean oil as an adulterant for EVOO. The adulterant EVOO samples were prepared by mixing with dissimilar concentrations of the solely edible oils (20 %, 40 %, 60 % and 80 % (v/v)). The main functional groups of EVOO and other edible oils are O-H, C-H, C=C and C=O groups were assigned around 3500 cm-1, 2925 cm-1, 3006 cm-1 and 1745 cm-1 wavenumbers, respectively. From the comparison of EVOO and other adulterant edibles oil spectra, it showed that the EVOO has the lowest absorbance intensity at around 3006 cm-1 represented double bond which is closely related to the composition of oil sample. The adulteration of EVOO was evaluated by analysing the changes in the absorbance based on the linear regression analysis graph of the bands at 3006 and 2925 cm-1 and the limit of detection (LOD) was measured. The graph of A3008/A2925 with good relative coefficients (R2) and lower LOD is more favourable than the linear regression graph of A3006 versus percentage of edible oils added in EVOO. This study showed that ATR-FTIR spectroscopy is a convenient tool for analysing the adulteration of EVOO.

Matched MeSH terms: Linear Models
Hyperkalemia measurement between Blood Gas Analyser and Main Laboratory Biochemistry Analyser

Ismail MH, Baharuddin KA, Suliman MA, Mohd Shukri MF, Che Has SN, Lo ZZ

Med J Malaysia, 2021 03;76(2):157-163.
PMID: 33742622

INTRODUCTION: Potassium level is measured for patients with high risk of hyperkalemia in the emergency department (ED) using both blood gas analyser (BGA) and biochemistry analyser (BCA). The study was conducted to evaluate the correlation and agreement of potassium measurement between BGA and BCA.
MATERIALS AND METHODS: This is a prospective cross-sectional study on the data obtained from Hospital Universiti Sains Malaysia (Hospital USM) from Jun 2018 until May 2019. Blood samples were taken via a single prick from venous blood and sent separately using 1ml heparinised syringe and were analysed immediately in ED using BGA (Radiometer, ABL800 FLEX, Denmark) and another sample was sent to the central laboratory of Hospital USM and analysed by BCA (Architect, C8000, USA). Only patients who had potassium levels ≥5.0mmol/L on blood gas results were included. A total of 173 sample pairs were included. The correlation and agreement were evaluated using Passing and Bablok regression, Linear Regression and Bland-Altman test.
RESULT: Of the 173 sample pairs, the median of potassium level based on BGA and BCA were 5.50mmol/L (IQR: 1.00) and 5.90mmol/L (IQR: 0.95) respectively. There was significant correlation between two measurements (p<0.001, r: 0.36). The agreement between the two measurements showed within acceptable mean difference which was 0.27 mmol/L with 95% limit of agreement were 1.21mmol/L to 1.73mmol/L.
CONCLUSION: The result of blood gas can be used as a guide for initial treatment of hyperkalaemia in critical cases where time is of the essence. However, BCA result is still the definitive value.

Matched MeSH terms: Linear Models
Distinguishing normal and aggregated alpha-synuclein interaction on gold nanorod incorporated zinc oxide nanocomposite by electrochemical technique

Adam H, Gopinath SCB, Arshad MKM, Parmin NA, Hashim U

Int J Biol Macromol, 2021 Feb 28;171:217-224.
PMID: 33418041 DOI: 10.1016/j.ijbiomac.2021.01.014

Misfolding and accumulation of the protein alpha synuclein in the brain cells characterize Parkinson's disease (PD). Electrochemical based aluminum interdigitated electrodes (ALIDEs) was fabricated by using conventional photolithography method and modified the surfaces with zinc oxide and gold nanorod by using spin coating method for the analysis of PD protein biomarker. The device surface modified with gold nanorod of 25 nm diameter was used. The bare devices and the surface modified devices were characterized by Scanning Electron Microscope, 3D-Profilometer, Atomic Force Microscope and high-power microscope. The above measurement was also performed to measure the interaction of antibody with aggregated alpha-synuclein for normal, aggregated and aggregated alpha synuclein in human serum and distinguished against 3 control proteins (PARK1, DJ-1 and Factor IX). The detection limit for normal alpha synuclein was 1 f. with the sensitivity of 1 f. on a linear regression (R2 = 0.9759). The detection limit for aggregated alpha synuclein was 10 aM with the sensitivity of 1 aM on a linear regression (R2 = 0.9797). Also, the detection limit of aggregated alpha synuclein in serum was 10 aM with the sensitivity of 1 aM on a linear regression (R2 = 0.9739). These results however indicate that, serum has only minimal amount of alpha synuclein.

Matched MeSH terms: Linear Models
Fulltext Root structure-function relationships in 74 species: evidence of a root economics spectrum related to carbon economy

Roumet C, Birouste M, Picon-Cochard C, Ghestem M, Osman N, Vrignon-Brenas S, et al.

New Phytol, 2016 May;210(3):815-26.
PMID: 26765311 DOI: 10.1111/nph.13828

Although fine roots are important components of the global carbon cycle, there is limited understanding of root structure-function relationships among species. We determined whether root respiration rate and decomposability, two key processes driving carbon cycling but always studied separately, varied with root morphological and chemical traits, in a coordinated way that would demonstrate the existence of a root economics spectrum (RES). Twelve traits were measured on fine roots (diameter ≤ 2 mm) of 74 species (31 graminoids and 43 herbaceous and dwarf shrub eudicots) collected in three biomes. The findings of this study support the existence of a RES representing an axis of trait variation in which root respiration was positively correlated to nitrogen concentration and specific root length and negatively correlated to the root dry matter content, lignin : nitrogen ratio and the remaining mass after decomposition. This pattern of traits was highly consistent within graminoids but less consistent within eudicots, as a result of an uncoupling between decomposability and morphology, and of heterogeneity of individual roots of eudicots within the fine-root pool. The positive relationship found between root respiration and decomposability is essential for a better understanding of vegetation-soil feedbacks and for improving terrestrial biosphere models predicting the consequences of plant community changes for carbon cycling.

Matched MeSH terms: Linear Models
Fulltext A Multi-Sensor Comparative Analysis on the Suitability of Generated DEM from Sentinel-1 SAR Interferometry Using Statistical and Hydrological Models

Mohammadi A, Karimzadeh S, Jalal SJ, Kamran KV, Shahabi H, Homayouni S, et al.

Sensors (Basel), 2020 Dec 16;20(24).
PMID: 33339435 DOI: 10.3390/s20247214

Digital elevation model (DEM) plays a vital role in hydrological modelling and environmental studies. Many essential layers can be extracted from this land surface information, including slope, aspect, rivers, and curvature. Therefore, DEM quality and accuracy will affect the extracted features and the whole process of modeling. Despite freely available DEMs from various sources, many researchers generate this information for their areas from various observations. Sentinal-1 synthetic aperture radar (SAR) images are among the best Earth observations for DEM generation thanks to their availabilities, high-resolution, and C-band sensitivity to surface structure. This paper presents a comparative study, from a hydrological point of view, on the quality and reliability of the DEMs generated from Sentinel-1 data and DEMs from other sources such as AIRSAR, ALOS-PALSAR, TanDEM-X, and SRTM. To this end, pair of Sentinel-1 data were acquired and processed using the SAR interferometry technique to produce a DEM for two different study areas of a part of the Cameron Highlands, Pahang, Malaysia, a part of Sanandaj, Iran. Based on the estimated linear regression and standard errors, generating DEM from Sentinel-1 did not yield promising results. The river streams for all DEMs were extracted using geospatial analysis tool in a geographic information system (GIS) environment. The results indicated that because of the higher spatial resolution (compared to SRTM and TanDEM-X), more stream orders were delineated from AIRSAR and Sentinel-1 DEMs. Due to the shorter perpendicular baseline, the phase decorrelation in the created DEM resulted in a lot of noise. At the same time, results from ground control points (GCPs) showed that the created DEM from Sentinel-1 is not promising. Therefore, other DEMs' performance, such as 90-meters' TanDEM-X and 30-meters' SRTM, are better than Sentinel-1 DEM (with a better spatial resolution).

Matched MeSH terms: Linear Models

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