Soil chemical changes in ancient irrigated fields of Udhruḥ, southern Jordan

The goal of this research was the systematic study and comparison of the divided individual effects of UV light irradiation and water leaching during artificial weathering. Spruce (Picea abies Karst.) and Scots pine (Pinus sylvestris L.) samples were irradiated by ultraviolet (UV) light. Another sequence of samples was treated with the combination of UV irradiation and water leaching. The total extent of UV treatment was 20 days for both series of samples. Time relation of UV irradiation and water leaching was 2:1. The chemical changes were observed by FTIR spectroscopy. The difference spectrum was used for determination of the chemical changes. Degradation of lignin was greater for the leached samples than for the pure UV treated samples. Scots pine suffered greater lignin degradation than spruce, and produced higher absorption increase on the absorption region of unconjugated carbonyls. The unconjugated carbonyl groups were the most responsive chemical elements to leaching. Spruce was more susceptible to leaching of unconjugated carbonyl groups than Scots pine. Two absorption bands of unconjugated carbonyl groups at 1706 and 1764 cm−1 wavenumbers were produced by photodegradation. The absorption band at 1764 cm−1 was more sensitive to water leaching than the band at 1706 cm−1.

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Physico-Chemical Investigation of Endodontic Sealers Exposed to Simulated Intracanal Heat Application: Hydraulic Calcium Silicate-Based Sealers

Materials ◽

10.3390/ma14040728 ◽

2021 ◽

Vol 14 (4) ◽

pp. 728

Author(s):

David Donnermeyer ◽

Magdalena Ibing ◽

Sebastian Bürklein ◽

Iris Weber ◽

Maximilian P. Reitze ◽

...

Keyword(s):

Heat Treatment ◽

Thermal Treatment ◽

Film Thickness ◽

Physical Properties ◽

Calcium Silicate ◽

Setting Time ◽

Chemical Properties ◽

Chemical Changes ◽

Time Flow ◽

Heat Application

The aim of this study was to gain information about the effect of thermal treatment of calcium silicate-based sealers. BioRoot RCS (BR), Total Fill BC Sealer (TFBC), and Total Fill BC Sealer HiFlow (TFHF) were exposed to thermal treatment at 37 °C, 47 °C, 57 °C, 67 °C, 77 °C, 87 °C and 97 °C for 30 s. Heat treatment at 97 °C was performed for 60 and 180 s to simulate inappropriate application of warm obturation techniques. Thereafter, specimens were cooled to 37 °C and physical properties (setting time/flow/film thickness according to ISO 6876) were evaluated. Chemical properties (Fourier-transform infrared spectroscopy) were assessed after incubation of the specimens in an incubator at 37 °C and 100% humidity for 8 weeks. Statistical analysis of physical properties was performed using the Kruskal-Wallis-Test (P = 0.05). The setting time, flow, and film thickness of TFBC and TFHF were not relevantly influenced by thermal treatment. Setting time of BR decreased slightly when temperature of heat application increased from 37 °C to 77 °C (P < 0.05). Further heat treatment of BR above 77 °C led to an immediate setting. FT-IR spectroscopy did not reveal any chemical changes for either sealers. Thermal treatment did not lead to any substantial chemical changes at all temperature levels, while physical properties of BR were compromised by heating. TFBC and TFHF can be considered suitable for warm obturation techniques.

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Comparison of the chemical changes in the rhizosphere of the nickel hyperaccumulator Alyssum murale with the non-accumulator Raphanus sativus

Plant and Soil ◽

10.1007/bf00010077 ◽

1994 ◽

Vol 164 (2) ◽

pp. 251-259 ◽

Cited By ~ 66

Author(s):

M. P. Bernal ◽

S. P. McGrath ◽

A. J. Miller ◽

A. J. M. Baker

Keyword(s):

Raphanus Sativus ◽

Chemical Changes ◽

Alyssum Murale ◽

Nickel Hyperaccumulator

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Modeling soil chemical changes induced by grassland afforestation in a sedimentary plain with shallow groundwater

Geoderma ◽

10.1016/j.geoderma.2021.115158 ◽

2021 ◽

Vol 400 ◽

pp. 115158

Author(s):

Claudio R. Mujica ◽

Sergio A. Bea ◽

Esteban G. Jobbágy

Keyword(s):

Shallow Groundwater ◽

Chemical Changes

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SiO2 Promoted CaO Diffusion to C Phase at 1500 and 1700 °C

Energies ◽

10.3390/en14030587 ◽

2021 ◽

Vol 14 (3) ◽

pp. 587

Author(s):

Lijuan Ni ◽

Renxing Wang ◽

Qingya Liu ◽

Junfei Wu ◽

Yue Pan ◽

...

Keyword(s):

Mass Transfer ◽

Close Contact ◽

Chemical Changes ◽

Physical And Chemical ◽

Diffusion Behaviors

To better understand the mass transfer behaviors in CaC2 production from CaO and coke, this paper studies the diffusion behaviors of CaO and graphite, with or without ash, at 1500 and 1700 °C. CaO and graphite are pressed into tablets and heated alone or in close contact. Physical and chemical changes in these tablets are analyzed by XRD and SEM+EDX. In some experiments, thin Mo wires are placed between the closely contacted CaO and graphite tablets to identify the diffusion direction. It is found that the diffusion between CaO and low-ash graphite is very limited. SiO2 in a high-ash graphite diffuses into CaO tablet and reacts with CaO to form Ca2SiO4, which then diffuses into the graphite tablet easily and leads to CaC2 formation at 1700 °C.

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Polar Middle Atmospheric Responses to Medium Energy Electron (MEE) Precipitation Using Numerical Model Simulations

Atmosphere ◽

10.3390/atmos12020133 ◽

2021 ◽

Vol 12 (2) ◽

pp. 133

Author(s):

Ji-Hee Lee ◽

Geonhwa Jee ◽

Young-Sil Kwak ◽

Heejin Hwang ◽

Annika Seppälä ◽

...

Keyword(s):

Climate Model ◽

Middle Atmosphere ◽

Meridional Circulation ◽

Stratospheric Ozone ◽

High Energy ◽

Chemical Changes ◽

Temperature Changes ◽

Mesospheric Temperature ◽

High Energy Electrons ◽

Circulation Changes

Energetic particle precipitation (EPP) is known to be an important source of chemical changes in the polar middle atmosphere in winter. Recent modeling studies further suggest that chemical changes induced by EPP can also cause dynamic changes in the middle atmosphere. In this study, we investigated the atmospheric responses to the precipitation of medium-to-high energy electrons (MEEs) over the period 2005–2013 using the Specific Dynamics Whole Atmosphere Community Climate Model (SD-WACCM). Our results show that the MEE precipitation significantly increases the amounts of NOx and HOx, resulting in mesospheric and stratospheric ozone losses by up to 60% and 25% respectively during polar winter. The MEE-induced ozone loss generally increases the temperature in the lower mesosphere but decreases the temperature in the upper mesosphere with large year-to-year variability, not only by radiative effects but also by adiabatic effects. The adiabatic effects by meridional circulation changes may be dominant for the mesospheric temperature changes. In particular, the meridional circulation changes occasionally act in opposite ways to vary the temperature in terms of height variations, especially at around the solar minimum period with low geomagnetic activity, which cancels out the temperature changes to make the average small in the polar mesosphere for the 9-year period.

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