ARSENIC-INDUCED DOWNSHIFT OF RAMAN BAND POSITIONS FOR PYRITE

2020 ◽  
Vol 115 (7) ◽  
pp. 1589-1600
Author(s):  
Qiaoqiao Zhu ◽  
Nigel J. Cook ◽  
Guiqing Xie ◽  
Benjamin P. Wade ◽  
Cristiana L. Ciobanu
Keyword(s):  
Raman Spectroscopy ◽  
Environmental Science ◽  
Raman Band ◽  
Eastern China ◽  
Chemical Properties ◽  
Minor Element ◽  
Minor Elements ◽  
Band Position ◽  
Wide Range ◽  
The Impact

Abstract Pyrite commonly incorporates a wide range of trace and minor elements, which in turn may modify some of the mineral’s physical and chemical properties. Published band position data for the Raman spectra of pyrite show a wide variation, and the relationship between band position and the trace/minor element incorporation in pyrite is poorly constrained until now. This prompted a case study on pyrite with varying As content from the Shizilishan Sr-(Pb-Zn) deposit, eastern China, combining electron probe microanalysis with Raman spectroscopy. Results show a significant correlation, with a major downshift (~10 cm–1) of the positions of all three Raman bands with increase of As content from below 0.05 to 4.89 wt % in pyrite. This phenomenon is attributed to increased bond lengths and local distortions within an expanded pyrite crystal structure. Results highlight the potential that Raman spectroscopy offers to estimate the contents of trace/minor elements—especially As—in pyrite. Given that substitution of As into pyrite often facilitates co-incorporation of both economically useful (Au) and environmentally significant elements (Hg and Tl), Raman methodology could provide valuable, rapid assessment of pyrite chemistry in both gold deposit exploration and environmental science, although the impact of laser heating and mechanical polishing needs to be avoided or effectively reduced. Raman spectroscopy may also find a valuable future role within semiautomated multispectral analytical platforms that can generate close- to-real-time geologic information on freshly drilled core directly at the drill site or in outcrop.

Sediment content and chemical properties of water runoff on biocrusts in drylands

Biologia ◽  
2014 ◽  
Vol 69 (11) ◽  
Author(s):  
Roberto Lázaro ◽  
Juan Mora
Keyword(s):  
Dry Matter ◽  
Chemical Properties ◽  
Soil Surface ◽  
Water Erosion ◽  
Rainfall Simulation ◽  
Water Runoff ◽  
Protective Capacity ◽  
Runoff Water ◽  
Wide Range ◽  
The Impact

AbstractIn drylands, water erosion can be a process with important economic and ecological implications, and is very dependent on the soil surface cover. There is broad agreement that biocrusts protect the soil from erosion in a wide range of circumstances. However, there is little information available on the effect of rain and biocrust types on this protective capacity and there is particularly very little knowledge on the erosive effects of runoff on biocrusts, which are expected to be larger in larger drainage areas, on the resistance of biocrusts to the combined effect of raindrops plus runoff flow and on the solute mobilisation by runoff in biocrusts. To answer these questions, we performed 96 rainfall-simulation in situ factorial experiments, including two biocrust types (cyanobacteria and lichens), three rain types (42, 63 and 77 mm h−1, always 20 min rain), four plot lengths (1, 2, 3 and 4 m long) and four replicates. In each experiment, runoff volume was measured and a runoff sample was taken to determine (i) the amount of dry matter in runoff, (ii) the amount of organic matter among the dry matter, (iii) the electrical conductivity, pH and alkalinity in runoff water. The main findings were: biocrusts strongly protected soil against water erosion, even under the most erosive conditions, and the protection increased with the successional development. Biocrusts were very resistant to the impact of raindrops and also to runoff flow, although an emergent hypothesis arose: under the most erosive conditions, a threshold of erodibility could be reached at the cyanobacterial biocrust. The lichen crust also protected the soil against the removal of soil soluble substances. The development of a biocrust could change the chemical composition of the solutes in runoff.

Thermal Stability of Thin Virtual Substrates for High Performance Devices

2006 ◽  
Vol 913 ◽  
Author(s):  
Sarah H Olsen ◽  
Steve J Bull ◽  
Peter Dobrosz ◽  
Enrique Escobedo-Cousin ◽  
Rimoon Agaiby ◽  
...  
Keyword(s):  
Thermal Stability ◽  
Raman Spectroscopy ◽  
Layer Thickness ◽  
Critical Thickness ◽  
Great Promise ◽  
Initial Growth ◽  
Strained Si ◽  
Strained Layers ◽  
Wide Range ◽  
The Impact

AbstractDetailed investigations of strain generation and relaxation in Si films grown on thin Si0.78Ge0.22 virtual substrates using Raman spectroscopy are presented. Good virtual substrate relaxation (>90%) is achieved by incorporating C during the initial growth stage. The robustness of the strained layers to relaxation is studied following high temperature rapid thermal annealing typical of CMOS processing (800-1050 °C). The impact of strained layer thickness on thermal stability is also investigated. Strain in layers below the critical thickness did not relax following any thermal treatments. However for layers above the critical thickness the annealing temperature at which the onset of strain relaxation occurred appeared to decrease with increasing layer thickness. Strain in Si layers grown on thin and thick virtual substrates having identical Ge composition and epilayer thickness has been compared. Relaxation through the introduction of defects has been assessed through preferential defect etching in order to verify the trends observed. Raman signals have been analysed by calibrated deconvolution and curve-fitting of the spectra peaks. Raman spectroscopy has also been used to study epitaxial layer thickness and the impact of Ge out-diffusion during processing. Improved device performance and reduced self-heating effects are demonstrated in thin virtual substrate devices when fabricated using strained layers below the critical thickness. The results suggest that thin virtual substrates offer great promise for enhancing the performance of a wide range of strained Si devices.

scholarly journals Nanocellulose: Resources, Physio-Chemical Properties, Current Uses and Future Applications

2021 ◽  
Vol 3 ◽  
Author(s):  
Prabhpreet Kaur ◽  
Neha Sharma ◽  
Meghana Munagala ◽  
Rangam Rajkhowa ◽  
Ben Aallardyce ◽  
...  
Keyword(s):  
Energy Use ◽  
High Surface ◽  
High Surface Area ◽  
Chemical Properties ◽  
Value Added ◽  
Processing Technique ◽  
Future Research ◽  
Wide Range ◽  
Systems View ◽  
The Impact

The growing environmental concerns due to the excessive use of non-renewable petroleum based products have raised interest for the sustainable synthesis of bio-based value added products and chemicals. Recently, nanocellulose has attracted wide attention because of its unique properties such as high surface area, tunable surface chemistry, excellent mechanical strength, biodegradability and renewable nature. It serves wide range of applications in paper making, biosensor, hydrogel and aerogel synthesis, water purification, biomedical industry and food industry. Variations in selection of source, processing technique and subsequent chemical modifications influence the size, morphology, and other characteristics of nanocellulose and ultimately their area of application. The current review is focused on extraction/synthesis of nanocellulose from different sources such as bacteria and lignocellulosic biomass, by using various production techniques ranging from traditional harsh chemicals to green methods. Further, the challenges in nanocellulose production, physio-chemical properties and applications are discussed with future opportunities. Finally, the sustainability of nanocellulose product as well as processes is reviewed by taking a systems view. The impact of chemicals, energy use, and waste generated can often negate the benefit of a bio-based product. These issues are evaluated and future research needs are identified.

Dark- or Light-Colored Melanins: Generating Pigments Using Fe2+ and H2O2

2017 ◽  
Author(s):  
Koen Vercruysse ◽  
Shelby Russell ◽  
Juan Knight ◽  
Najwa Stewart ◽  
Nicole Wilson ◽  
...  
Keyword(s):  
Chemical Change ◽  
Chemical Properties ◽  
Size Exclusion ◽  
Air Oxidation ◽  
Wide Range ◽  
Exclusion Chromatography ◽  
Yellow Orange ◽  
Ft Ir ◽  
Dark Color ◽  
The Impact

We have studied the formation of melanin-like pigments from catechol or pyrogallol and a wide range of other phenolic compounds using Fe<sup>2+</sup> and H<sub>2</sub>O<sub>2</sub>. Combining UV_Vis spectroscopic measurements and size-exclusion chromatography analyses we evaluated the impact of the intensity of the oxidation reaction by varying the concentration of H<sub>2</sub>O<sub>2</sub> present in the reaction mixtures. All compounds tested, except tyrosine, reacted readily leading to mixtures that were black, brown or yellow-orange in color. For many compounds tested, the use of increasing concentrations of H<sub>2</sub>O<sub>2 </sub>resulted in either precipitation of the pigment or the formation of a soluble, lighter-colored pigment. With catechol or pyrogallol as model compounds, and using different concentrations of H<sub>2</sub>O<sub>2</sub>, several materials were synthesized, purified and dried. The physic-chemical properties of these materials were compared to the properties of melanin-like pigments synthesized from the same precursors using air-oxidation in an alkaline environment. For both precursors, a distinct chemical change, as judged from FT-IR spectroscopy, was introduced in the melanin structures when using H<sub>2</sub>O<sub>2</sub> as the oxidizing agent and the relative intensity of this distinct signal strengthened with increasing concentration of H<sub>2</sub>O<sub>2</sub> used in the reaction. In general, our results suggest that depending on the precursor molecule and the intensity of the oxidizing reaction conditions involved, light- or dark-colored melanin-like pigments can be generated. This may be an important factor when evaluating the visible outlook of histological or archeological specimens: the presence of a lighter color or the absence of a dark color may not necessarily mean the absence of melanin-like biomolecules.

Dark- or Light-Colored Melanins: Generating Pigments Using Fe2+ and H2O2

2017 ◽  
Author(s):  
Koen Vercruysse ◽  
Shelby Russell ◽  
Juan Knight ◽  
Najwa Stewart ◽  
Nicole Wilson ◽  
...  
Keyword(s):  
Chemical Change ◽  
Chemical Properties ◽  
Size Exclusion ◽  
Air Oxidation ◽  
Wide Range ◽  
Exclusion Chromatography ◽  
Yellow Orange ◽  
Ft Ir ◽  
Dark Color ◽  
The Impact

We have studied the formation of melanin-like pigments from catechol or pyrogallol and a wide range of other phenolic compounds using Fe<sup>2+</sup> and H<sub>2</sub>O<sub>2</sub>. Combining UV_Vis spectroscopic measurements and size-exclusion chromatography analyses we evaluated the impact of the intensity of the oxidation reaction by varying the concentration of H<sub>2</sub>O<sub>2</sub> present in the reaction mixtures. All compounds tested, except tyrosine, reacted readily leading to mixtures that were black, brown or yellow-orange in color. For many compounds tested, the use of increasing concentrations of H<sub>2</sub>O<sub>2 </sub>resulted in either precipitation of the pigment or the formation of a soluble, lighter-colored pigment. With catechol or pyrogallol as model compounds, and using different concentrations of H<sub>2</sub>O<sub>2</sub>, several materials were synthesized, purified and dried. The physic-chemical properties of these materials were compared to the properties of melanin-like pigments synthesized from the same precursors using air-oxidation in an alkaline environment. For both precursors, a distinct chemical change, as judged from FT-IR spectroscopy, was introduced in the melanin structures when using H<sub>2</sub>O<sub>2</sub> as the oxidizing agent and the relative intensity of this distinct signal strengthened with increasing concentration of H<sub>2</sub>O<sub>2</sub> used in the reaction. In general, our results suggest that depending on the precursor molecule and the intensity of the oxidizing reaction conditions involved, light- or dark-colored melanin-like pigments can be generated. This may be an important factor when evaluating the visible outlook of histological or archeological specimens: the presence of a lighter color or the absence of a dark color may not necessarily mean the absence of melanin-like biomolecules.

scholarly journals Raman Spectroscopy of Amorphous Carbon

1997 ◽  
Vol 498 ◽  
Author(s):  
D. R. Tallant ◽  
T. A. Friedmann ◽  
N. A. Missert ◽  
M. P. Siegal ◽  
J. P. Sullivan
Keyword(s):  
Raman Spectroscopy ◽  
Amorphous Carbon ◽  
Hydrogen Content ◽  
Level Structure ◽  
Chemical Properties ◽  
High Energy ◽  
Film Deposition ◽  
Forms Of Carbon ◽  
The Impact ◽  
Deposition Conditions

ABSTRACTAmorphous carbon is an elemental form of carbon with low hydrogen content, which may be deposited in thin films by the impact of high energy carbon atoms or ions. It is structurally distinct from the more well-known elemental forms of carbon, diamond and graphite. It is distinct in physical and chemical properties from the material known as diamond-like carbon, a form which is also amorphous but which has a higher hydrogen content, typically near 40 atomic percent. Amorphous carbon also has distinctive Raman spectra, whose patterns depend, through resonance enhancement effects, not only on deposition conditions but also on the wavelength selected for Raman excitation. This paper provides an overview of the Raman spectroscopy of amorphous carbon and describes how Raman spectral patterns correlate to film deposition conditions, physical properties and molecular level structure.

THE IMPACT OF LEADERSHIP PRACTICES TO TEAM MEMBERS’ SATISFACTION

2009 ◽  
Vol 8 (1) ◽  
Author(s):  
Chalimah .
Keyword(s):  
Conflict Resolution ◽  
Leadership Practices ◽  
Hotel Industry ◽  
Leader Behavior ◽  
Team Leader ◽  
Shop Floor ◽  
Team Members ◽  
Top Executives ◽  
Wide Range ◽  
The Impact

eamwork is becoming increasingly important to wide range of operations. It applies to all levels of the company. It is just as important for top executives as it is to middle management, supervisors and shop floor workers. Poor teamwork at any level or between levels can seriously damage organizational effectiveness. The focus of this paper was therefore to examine whether leadership practices consist of team leader behavior, conflict resolution style and openness in communication significantly influenced the team member’s satisfaction in hotel industry. Result indicates that team leader behavior and the conflict resolution style significantly influenced team member satisfaction. It was surprising that openness in communication did not affect significantly to the team members’ satisfaction.

Stress, anxiety, depression and burnout in frontline health care workers during COVID-19 pandemic: a brief systematic review and new data from Russia

2021 ◽  
Author(s):  
Ekaterina Mosolova ◽  
Dmitry Sosin ◽  
Sergey Mosolov
Keyword(s):  
Risk Factors ◽  
Systematic Review ◽  
Female Gender ◽  
Assessment Tools ◽  
Care Workers ◽  
Younger Age ◽  
Wide Range ◽  
Associated Risk Factors ◽  
Anxiety Depression ◽  
The Impact

During the COVID-19 pandemic, healthcare workers (HCWs) have been subject to increased workload while also exposed to many psychosocial stressors. In a systematic review we analyze the impact that the pandemic has had on HCWs mental state and associated risk factors. Most studies reported high levels of depression and anxiety among HCWs worldwide, however, due to a wide range of assessment tools, cut-off scores, and number of frontline participants in the studies, results were difficult to compare. Our study is based on two online surveys of 2195 HCWs from different regions of Russia during spring and autumn epidemic outbreaks revealed the rates of anxiety, stress, depression, emotional exhaustion and depersonalization and perceived stress as 32.3%, 31.1%, 45.5%, 74.2%, 37.7% ,67.8%, respectively. Moreover, 2.4% of HCWs reported suicidal thoughts. The most common risk factors include: female gender, nurse as an occupation, younger age, working for over 6 months, chronic diseases, smoking, high working demands, lack of personal protective equipment, low salary, lack of social support, isolation from families, the fear of relatives getting infected. These results demonstrate the need for urgent supportive programs for HCWs fighting COVID-19 that fall into higher risk factors groups.

A MODELING SYSTEM FOR CLIMATE CHANGE RISK ASSESSMENT, MANAGEMENT AND HEDGING IN COASTAL AREAS

2017 ◽  
Author(s):  
Sergei Soldatenko ◽  
Sergei Soldatenko ◽  
Genrikh Alekseev ◽  
Genrikh Alekseev ◽  
Alexander Danilov ◽  
...  
Keyword(s):  
Climate Change ◽  
Risk Assessment ◽  
Coastal Areas ◽  
Mitigation Strategies ◽  
System Structure ◽  
The Arctic ◽  
Risk Modeling ◽  
Wide Range ◽  
Adverse Weather ◽  
The Impact

Every aspect of human operations faces a wide range of risks, some of which can cause serious consequences. By the start of 21st century, mankind has recognized a new class of risks posed by climate change. It is obvious, that the global climate is changing, and will continue to change, in ways that affect the planning and day to day operations of businesses, government agencies and other organizations and institutions. The manifestations of climate change include but not limited to rising sea levels, increasing temperature, flooding, melting polar sea ice, adverse weather events (e.g. heatwaves, drought, and storms) and a rise in related problems (e.g. health and environmental). Assessing and managing climate risks represent one of the most challenging issues of today and for the future. The purpose of the risk modeling system discussed in this paper is to provide a framework and methodology to quantify risks caused by climate change, to facilitate estimates of the impact of climate change on various spheres of human activities and to compare eventual adaptation and risk mitigation strategies. The system integrates both physical climate system and economic models together with knowledge-based subsystem, which can help support proactive risk management. System structure and its main components are considered. Special attention is paid to climate risk assessment, management and hedging in the Arctic coastal areas.

The Management of Post-Tonsillectomy Morbidity in Patients With Sleep Apnoea

2019 ◽  
Vol 70 (10) ◽  
pp. 3738-3740
Keyword(s):  
Day Surgery ◽  
Sleep Apnoea ◽  
Integrative Approach ◽  
Multicenter Studies ◽  
Therapeutic Modalities ◽  
Advantages And Disadvantages ◽  
Obstructive Sleep ◽  
Wide Range ◽  
The Impact ◽  
Surgery Center

The Tonsillectomy in children or adults is an intervention commonly encountered in the ENT (Ear Nose and Throat) and Head and Neck surgeon practice. The current tendency is to perform this type of surgery in major ambulatory surgery centers. Two objectives are thus pursued: first of all, the increase of the patient quality of life through the reintegration into the family as quickly as possible and secondly, the expenses associated with continuous hospitalization are reduced. Any tertiary (multidisciplinary) sleep center must ensure the complete diagnosis and treatment (including surgery) of sleep respiratory disorders. Under these conditions the selection of patients and especially the implementation of the specific protocols in order to control the postoperative complications it becomes essential. The present paper describes our experience of tonsillectomy as treatment for selected patients with chronic rhonchopathy (snoring) and mild to moderate obstructive sleep apnoea. It was presented the impact of antibiotics protocols in reducing the main morbid outcomes following tonsillectomy, in our day surgery center. The obtained results can also be a prerequisite for the integrative approach of the patients with sleep apnoea who were recommended surgical treatment. Considering the wide range of therapeutic modalities used in sleep apnoea, each with its specific advantages and disadvantages, more extensive and multicenter studies are needed. Keywords: post-tonsillectomy morbidity, day surgery center, sleep disorders

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