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1.
Tahmasbian Iman Xu Zhihong Nguyen Thi Thu Nhan Che Rongxiao Omidvar Negar Lambert Geoffrey Bai Shahla Hosseini 《Journal of Soils and Sediments》2019,19(12):3969-3981
Purpose
This study aimed to understand the mechanisms of the variations in carbon (C) and nitrogen (N) pools and examine the possibility of differentiating the burning effects from seasonal and pre-existed N limitations in a native suburban forest ecosystem influenced by prescribed burning in subtropical Australia.
Materials and methodsSoil and litterfall samples were collected from two study sites from 1 to 23 months since last burnt. Soil labile C and N pools, soil C and N isotopic compositions (δ13C and δ15N), litterfall mass production (LM), and litterfall total C, total N, δ13C and δ15N were analysed. In-situ gas exchange measurements were also conducted during dry and wet seasons for Eucalyptus baileyana and E. planchoniana.
Results and discussionThe results indicated that labile C and N pools increased within the first few months after burning, with no correlations with climatic factors. Therefore, it was possible that the increase was due to the burning-induced factors such as the incorporation of ashes into the soil. The highest values of soil and litterfall δ15N, observed when the study was commenced at the experimental sites, and their high correlations with climatic factors were indicative of long-term N and water limitation. The 13C signals showed that soil N concentrations and climatic factors were also two of the main factors controlling litterfall and foliage properties mainly through the changes in photosynthetic capacity and stomatal conductance.
ConclusionsLong-term soil N availabilities and climatic factors were the two of the main driving factors of C and N cycling in the studied forest sites. Further studies are needed to compare soil and litterfall properties before and after burning to profoundly understand the effects of prescribed burning on soil labile C and N variations.
相似文献2.
Iman Tahmasbian Zhihong Xu Kadum Abdullah Jun Zhou Roya Esmaeilani Thi Thu Nhan Nguyen Shahla Hosseini Bai 《Journal of Soils and Sediments》2017,17(8):2091-2103
Purpose
The main objective of this study was to examine the potential of using hyperspectral image analysis for prediction of total carbon (TC), total nitrogen (TN) and their isotope composition (δ13C and δ15N) in forest leaf litterfall samples.Materials and methods
Hyperspectral images were captured from ground litterfall samples of a natural forest in the spectral range of 400–1700 nm. A partial least-square regression model (PLSR) was used to correlate the relative reflectance spectra with TC, TN, δ13C and δ15N in the litterfall samples. The most important wavelengths were selected using β coefficient, and the final models were developed using the most important wavelengths. The models were, then, tested using an external validation set.Results and discussion
The results showed that the data of TC and δ13C could not be fitted to the PLSR model, possibly due to small variations observed in the TC and δ13C data. The model, however, was fitted well to TN and δ15N. The cross-validation R2 cv of the models for TN and δ15N were 0.74 and 0.67 with the RMSEcv of 0.53% and 1.07‰, respectively. The external validation R2 ex of the prediction was 0.64 and 0.67, and the RMSEex was 0.53% and 1.19 ‰, for TN and δ15N, respectively. The ratio of performance to deviation (RPD) of the predictions was 1.48 and 1.53, respectively, for TN and δ15N, showing that the models were reliable for the prediction of TN and δ15N in new forest leaf litterfall samples.Conclusions
The PLSR model was not successful in predicting TC and δ13C in forest leaf litterfall samples using hyperspectral data. The predictions of TN and δ15N values in the external litterfall samples were reliable, and PLSR can be used for future prediction.3.
Kandeel M Abdelaziz I Elhabashy N Hegazy H Tolba Y 《Pakistan journal of biological sciences: PJBS》2011,14(11):627-633
Gentamicin (GS) is a potent antimicrobial exhibiting concentration dependent bacterial killing. A high dose ofgentamicin (10 mg kg(-1)) is required to reach sufficient concentrations in specific fluids as cerebrospinal fluid and to be effective on antibiotics resistant bacteria as well as treatment of acute and dangerous illness. Using a rat model, the renal toxicity and oxidative stress of administering gentamicin (10 mg kg(-1) daily for 7 days) either in a single dose or divided into 2 doses was investigated. The safety of dose regimens was assessed through oxidant-antioxidant parameters as well as renal function tests. Typical renal damage and high oxidative stress were evident in the control group receiving 100 mg kg(-1) gentamicin daily for 7 days. This was verified by high serum urea, uric acid, creatinine as well as increase in the levels of oxidative stress biomarkers as malondialdehyde, NO, total antioxidant capacity and decrease in reduced glutathione level. At any of the used regimen, 10 mg kg(-1) gentamicin did not provide high compromise for renal functions nor significantly increased the oxidative stress and tissue damage. Based on microscopic lesions scores and biochemical analysis, there were no significant differences between single or two divided dosages of gentamicin at dose rate of 10 mg kg(-1) day(-1). Further studies are required for applications in other animals of human subjects. 相似文献
4.
Pigeon herpes encephalomyelitis virus (PHEV) was compared with seven avian herpesviruses for antigenic relatedness using monospecific antisera and the indirect fluorescent-antibody (IFA), agar-gel-immunodiffusion, and serum-neutralization tests. No antigenic relationship was detected between PHEV and Marek's disease virus, turkey herpesvirus, infectious laryngotracheitis virus, and duck enteritis virus. A common precipitating antigen was detected between the PHEV and pigeon herpesvirus (PHV), owl herpesvirus (OHV), and falcon herpesvirus (FHV). These four viruses also cross-reacted in the IFA test. Weak neutralizing activity was detected only between PHV antiserum and PHEV. These results suggest that the PHEV should be classified as a herpesvirus related to, but distinct from, the PHV-OHV-FHV group of viruses with which it shares common antigens. 相似文献
5.
Syah YM Achmad SA Ghisalberti EL Hakim EH Iman MZ Makmur L Mujahiddin D 《Fitoterapia》2000,71(6):630-635
A new stilbene dimer, andalasin A (1), together with the known stilbene oxyresveratrol and the 2-arylbenzofuran glycoside mulberroside C, have been isolated from the wood of Morus macroura. The structure of the new compound was elucidated on the basis of spectroscopic data. Compound 1 shows weak antinematodal and moderate antifungal properties. 相似文献
6.
Yana M. Syah Sjamsul A. Achmad Emilio L. Ghisalberti Euis H. Hakim Muhammad Z. N. Iman Lukman Makmur Didin Mujahiddin 《Fitoterapia》2000,71(6)
A new stilbene dimer, andalasin A (1), together with the known stilbene oxyresveratrol and the 2-arylbenzofuran glycoside mulberroside C, have been isolated from the wood of Morus macroura. The structure of the new compound was elucidated on the basis of spectroscopic data. Compound 1 shows weak antinematodal and moderate antifungal properties. 相似文献
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8.
Kadry Abdel Khalik Iman Al-Gohary Yassin Al-Sodany 《Arid Land Research and Management》2017,31(3):316-334
The present study aimed to determine floristic composition, the structure of the vegetation, and species distribution at 16 sample plots in Wadi Fatimah, Mecca, Saudi Arabia, highlighting the ecological factors that affect species distribution. The study revealed 100 plant species belonging to 34 families. Fabaceae and Poaceae were the dominant families, and chamaephytes and therophytes were predominant life forms, which demonstrate a typical desert life-form spectrum. Altitude showed a highly significant association with species frequency distribution. The highest species richness value of 23 species per plot was recorded in the coastal plain (Vegetation groups II & III). The lowest species richness value of 9 species per plot was recorded in the littoral salt marsh (Vegetation group I). Chorological analysis exhibited the Saharao-Arabian–Sudano-Zambezian chorotypes, 47% of the studied species were bi-regional. Using TWINSPAN, DCA, and CCA multivariate analysis, four major vegetation groups were classified into three main ecosystems (I) Halopeplis perfoliata, Suaeda fruticosa, Acacia tortilis, and Suaeda fruticosa, representing the littoral salt marsh; (II) Rhazya stricta and Haloxylon salicornicum, characterized by the coastal plain; and (III) Senna italica, Glinus lotoides, and Tribulus macropterus were the leading groups in the inland mountainous country. The CCA ordination showed that the separation of Vegetation group III along the axis was affected by Mg, K, and P concentration, and VG IV was significantly associated with silt, clay, and fine sand content. Furthermore, the Vegetation group I was significantly correlated with Na and Ca concentration, and VG II group was significantly correlated with heavy metal concentrations of elements as Fe, Pb, Zn, Ni, and Cu. 相似文献
9.
Electrospun composite fibers of poly-lactic acid (PLA), chitosan (Ch) and paclitaxel (PTX) were fabricated for surface covering of a polymeric prototype PLA stent by means of single nozzle electrospinning approach to prepare a low cytotoxicity drug-eluting stent. Different concentrations of the drug (40 %, 60 %, 80 %, 100 % and 120 %) and chitosan (3 %, 5 %, 7 % and 9 %) were incorporated to reach the optimum composite fibers. The electrospun composite fibers were subjected to detailed analyses including scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), tensile test, MTT assay, cell culture and in vitro drug release. Results have confirmed a proper physical encapsulation of PTX in the polymeric matrix in which no chemical bonding was detected between the polymers and the drug. Among the fabricated composite fibers, specimens including 40 % and 60 % drug also exhibited an excellent cytotoxicity and controlled drug release. SEM images have proved the effect of paclitaxel in resisting cell adhesion and propagation on the fibers. Findings from this study suggest a novel polymer/drug coating that could be potentially applicable in surface covering of polymeric stents e.g. PLA stents. 相似文献
10.
Kazemi Esmaeil Nazari Sajad Sourinejad Iman Pourkazemi Mohammad Paknejad Hamed Eslamloo Khalil 《Aquaculture International》2021,29(6):2731-2750
Aquaculture International - The objective of the present work was to survey the effects of different sources of zinc supplements on serum enzymatic activities, the expression of genes related to... 相似文献