scholarly journals Tuning the Thermal Stability and Photoisomerization of Azoheteroarenes through Macrocycle Strain

2020 ◽  
Author(s):  
Sergi Vela ◽  
Alan Scheidegger ◽  
Raimon Fabregat ◽  
Clemence Corminboeuf
Keyword(s):  
Thermal Stability ◽  
Optical Switching ◽  
Extreme Values ◽  
Quantum Yields ◽  
Molecular Scaffolds ◽  
Potential Applications ◽  
Fundamental Research ◽  
Switching Characteristics ◽  
The Impact ◽  
Bridge Length

<p>Azobenzene and its derivatives are one of the most-widespread molecular scaffolds in a range of modern applications, as well as in fundamental research. After photoexcitation, azo-based photoswitches revert back to the most stable isomer in a timescale (t<sub>1/2</sub>) that determines the range of potential applications. Attempts to bring t<sub>1/2</sub> to extreme values prompted to the development of azobenzene and azoheteroarene derivatives that either rebalance the E- and Z- isomer stabilities, or exploit unconventional thermal isomerization mechanisms. In the former case, one successful strategy has been the creation of macrocycle strain, which tends to impact the E/Z stability asymmetrically, and thus significantly modifies t<sub>1/2</sub>. On the bright side, bridged derivatives have shown an improved optical switching owing to the higher quantum yields and absence of degradation. However, in most (if not all) cases, bridged derivatives display a <i>reversed</i> thermal stability (more stable Z-isomer), and smaller t<sub>1/2</sub> than the acyclic counterparts, which restricts their potential interest to applications requiring a fast forward and backwards switch. In this paper, we investigate the impact of alkyl bridges to the thermal stability of phenyl-azoheteroarenes using computational methods, and we reveal that is indeed possible to combine such improved photo-switching characteristics while preserving the <i>regular</i> thermal stability (more stable E-isomer), and increased t<sub>1/2</sub> values under the appropriate connectivity and bridge length.</p>

scholarly journals Tuning the Thermal Stability and Photoisomerization of Azoheteroarenes through Macrocycle Strain

2020 ◽  
Author(s):  
Sergi Vela ◽  
Alan Scheidegger ◽  
Raimon Fabregat ◽  
Clemence Corminboeuf
Keyword(s):  
Thermal Stability ◽  
Optical Switching ◽  
Extreme Values ◽  
Quantum Yields ◽  
Molecular Scaffolds ◽  
Potential Applications ◽  
Fundamental Research ◽  
Switching Characteristics ◽  
The Impact ◽  
Bridge Length

<p>Azobenzene and its derivatives are one of the most-widespread molecular scaffolds in a range of modern applications, as well as in fundamental research. After photoexcitation, azo-based photoswitches revert back to the most stable isomer in a timescale (t<sub>1/2</sub>) that determines the range of potential applications. Attempts to bring t<sub>1/2</sub> to extreme values prompted to the development of azobenzene and azoheteroarene derivatives that either rebalance the E- and Z- isomer stabilities, or exploit unconventional thermal isomerization mechanisms. In the former case, one successful strategy has been the creation of macrocycle strain, which tends to impact the E/Z stability asymmetrically, and thus significantly modifies t<sub>1/2</sub>. On the bright side, bridged derivatives have shown an improved optical switching owing to the higher quantum yields and absence of degradation. However, in most (if not all) cases, bridged derivatives display a <i>reversed</i> thermal stability (more stable Z-isomer), and smaller t<sub>1/2</sub> than the acyclic counterparts, which restricts their potential interest to applications requiring a fast forward and backwards switch. In this paper, we investigate the impact of alkyl bridges to the thermal stability of phenyl-azoheteroarenes using computational methods, and we reveal that is indeed possible to combine such improved photo-switching characteristics while preserving the <i>regular</i> thermal stability (more stable E-isomer), and increased t<sub>1/2</sub> values under the appropriate connectivity and bridge length.</p>

scholarly journals Tuning the Thermal Stability and Photoisomerization of Azoheteroarenes through Macrocycle Strain

2020 ◽  
Author(s):  
Sergi Vela ◽  
Alan Scheidegger ◽  
Raimon Fabregat ◽  
Clemence Corminboeuf
Keyword(s):  
Thermal Stability ◽  
Optical Switching ◽  
Extreme Values ◽  
Quantum Yields ◽  
Molecular Scaffolds ◽  
Potential Applications ◽  
Fundamental Research ◽  
Switching Characteristics ◽  
The Impact ◽  
Bridge Length

<p>Azobenzene and its derivatives are one of the most-widespread molecular scaffolds in a range of modern applications, as well as in fundamental research. After photoexcitation, azo-based photoswitches revert back to the most stable isomer in a timescale (t<sub>1/2</sub>) that determines the range of potential applications. Attempts to bring t<sub>1/2</sub> to extreme values prompted to the development of azobenzene and azoheteroarene derivatives that either rebalance the E- and Z- isomer stabilities, or exploit unconventional thermal isomerization mechanisms. In the former case, one successful strategy has been the creation of macrocycle strain, which tends to impact the E/Z stability asymmetrically, and thus significantly modifies t<sub>1/2</sub>. On the bright side, bridged derivatives have shown an improved optical switching owing to the higher quantum yields and absence of degradation. However, in most (if not all) cases, bridged derivatives display a <i>reversed</i> thermal stability (more stable Z-isomer), and smaller t<sub>1/2</sub> than the acyclic counterparts, which restricts their potential interest to applications requiring a fast forward and backwards switch. In this paper, we investigate the impact of alkyl bridges to the thermal stability of phenyl-azoheteroarenes using computational methods, and we reveal that is indeed possible to combine such improved photo-switching characteristics while preserving the <i>regular</i> thermal stability (more stable E-isomer), and increased t<sub>1/2</sub> values under the appropriate connectivity and bridge length.</p>

Evaluation of the Impact of Fatty Acid Methyl Ester (FAME) Contamination on the Thermal Stability of Jet A

2013 ◽  
Author(s):  
Jr Morris ◽  
Shardo Robert W. ◽  
Higgins James ◽  
Cook Kim ◽  
Tanner Rhonda ◽  
...  
Keyword(s):  
Thermal Stability ◽  
Fatty Acid ◽  
Methyl Ester ◽  
Fatty Acid Methyl Ester ◽  
Acid Methyl Ester ◽  
Acid Methyl ◽  
The Impact ◽  
Thermal Stability Of

Short Review and opinion: New matter properties and applications based on Hybrids Graphene based Metamaterials

2020 ◽  
Vol 04 ◽  
Author(s):  
A. Guillermo Bracamonte
Keyword(s):  
Short Review ◽  
New Materials ◽  
Design And Synthesis ◽  
Chemical Structures ◽  
Current State ◽  
Potential Applications ◽  
Fundamental Research ◽  
Miniaturized Instrumentation ◽  
And Control ◽  
Conductive Properties

: Graphene as Organic material showed special attention due to their electronic and conductive properties. Moreover, its highly conjugated chemical structures and relative easy modification permitted varied design and control of targeted properties and applications. In addition, this Nanomaterial accompanied with pseudo Electromagnetic fields permitted photonics, electronics and Quantum interactions with their surrounding that generated new materials properties. In this context, this short Review, intends to discuss many of these studies related with new materials based on graphene for light and electronic interactions, conductions, and new modes of non-classical light generation. It should be highlighted that these new materials and metamaterials are currently in progress. For this reason it was showed and discussed some representative examples from Fundamental Research with Potential Applications as well as for their incorporations to real Advanced devices and miniaturized instrumentation. In this way, it was proposed this Special issue entitled “Design and synthesis of Hybrids Graphene based Metamaterials”, in order to open and share the knowledge of the Current State of the Art in this Multidisciplinary field.

scholarly journals Extraordinary thermal behavior of graphene oxide in air for electrode applications

2021 ◽  
Author(s):  
Joong Tark Han ◽  
Joon Young Cho ◽  
Jeong Hoon Kim
Keyword(s):  
Thermal Stability ◽  
Graphene Oxide ◽  
Physical Properties ◽  
Thermal Behavior ◽  
Stability Of Solution ◽  
Exfoliated Graphene ◽  
Potential Applications ◽  
Thermal Stability Of

The thermal stability of solution-exfoliated graphene oxide (GO) in air is one of the most important physical properties influencing its potential applications. To date, majority of the GO prepared by...

scholarly journals 1142 Comprehensive Phenotyping Of Ambulatory Sleep Patterns In Multiple Sclerosis

SLEEP ◽  
2020 ◽  
Vol 43 (Supplement_1) ◽  
pp. A435-A435
Author(s):  
T J Braley ◽  
A L Kratz ◽  
D Whibley ◽  
C Goldstein
Keyword(s):  
Multiple Sclerosis ◽  
Sleep Quality ◽  
Extreme Values ◽  
Sleep Onset ◽  
External Support ◽  
Poor Sleep ◽  
Sleep Patterns ◽  
Poor Sleep Quality ◽  
Historical Cohort ◽  
The Impact

Abstract Introduction The majority of sleep research in persons with multiple sclerosis (PwMS) has been siloed, restricted to evaluation of one or a few sleep measures in isolation. To fully characterize the impact of sleep disturbances in MS, multifaceted phenotyping of sleep is required. The objective of this study was to more comprehensively quantify sleep in PwMS, using a recently developed multi-domain framework of duration, continuity, regularity, sleepiness/alertness, and quality. Methods Data were derived from a parent study that examined associations between actigraphy and polysomnography-based measures of sleep and cognitive function in MS. Actigraphy was recorded in n=55 PwMS for 7-12 days (Actiwatch2®, Philips Respironics). Sleep metrics included: duration=mean total sleep time (TST, minutes); continuity=mean wake time after sleep onset (minutes), and regularity=stddev wake-up time (hours). ‘Extreme’ values for continuity/regularity were defined as the most extreme third of the distributions. ‘Extreme’ TST values were defined as the lowest or highest sixth of the distributions. Sleepiness (Epworth Sleepiness Scale score) and sleep quality [Pittsburgh Sleep Quality Index (PSQI) sleep quality item] were dichotomized by accepted cutoffs (&gt;10 and &gt;1, respectively). Results Sleep was recorded for a mean of 8.2 days (stddev=0.95). Median (1st, 3rd quartile) values were as follows: duration 459.79 (430.75, 490.60), continuity 37.00 (23.44, 52.57), regularity 1.02 (0.75, 1.32), sleepiness/alertness 8 (4, 12), and sleep quality 1.00 (1.00, 2.00). Extreme values based on data distributions were: short sleep &lt;=426.25 minutes (18%), long sleep &gt;515.5 minutes (16%), poor sleep continuity ≥45 minutes (33%), and poor sleep regularity ≥1.17 hours (33%). Sleepiness and poor sleep quality were present in 36% and 40% respectively. For comparison, in a historical cohort of non-MS patients, the extreme third of sleep regularity was a stddev of 0.75 hours, 13% had ESS of &gt;10, and 16% had poor sleep quality. Conclusion In this study of ambulatory sleep patterns in PwMS, we found greater irregularity of sleep-wake timing, and higher prevalence of sleepiness and poor sleep quality than published normative data. Efforts should be made to include these measures in the assessment of sleep-related contributions to MS outcomes. Support The authors received no external support for this work.

The Potential Applications of Raman Spectroscopy in Unravelling Complex Palaeowildfire Ecosystems

2021 ◽  
Author(s):  
Thomas Theurer ◽  
David Muirhead ◽  
David Jolley ◽  
Dmitri Mauquoy
Keyword(s):  
Raman Spectroscopy ◽  
Carbonaceous Material ◽  
Complex Interactions ◽  
Intensity Changes ◽  
Potential Applications ◽  
Ecosystem Studies ◽  
History Of ◽  
The Impact ◽  
Unique Relationship

&lt;p&gt;Raman spectroscopy represents a novel methodology of characterising plant-fire interactions through geological history, with enormous potential. Applications of Raman spectroscopy to charcoal have shown that this is an effective method of understanding intensity changes across palaeofire regimes. Such analyses have relied on the determination of appropriate Raman parameters, given their relationship with temperature of formation and microstructural changes in reference charcoals. Quantitative assessments of charcoal microstructure have also been successfully applied to the assessment of carbonaceous maturation under alternate thermal regimes, such as pyroclastic volcanism. Palaeowildfire systems in association with volcanism may present a complex history of thermal maturation, given interactions between detrital charcoals and volcanogenic deposition. However, whilst palaeofire and volcanic maturation of carbonaceous material are well understood individually, their interaction has yet to be characterised. Here we present the first analysis of palaeofire charcoals derived from volcanic ignition utilising Raman spectroscopy. Our results indicate that complex interactions between volcanism and palaeofire systems may be better understood by the characterisation of charcoal microstructure, alongside palaeobotanical and ecosystem studies. Understanding the unique relationship between wildfires and volcanism, and the impact that this has on the fossil record, may better assist our understanding of wildfire systems in deep history. Further still, this highlights the potential for better understanding the socioecological impacts of modern and future wildfire systems closely associated with volcanic centres.&amp;#160;&lt;/p&gt;

Bias correction of extreme values of high resolution climate simulations for risk analysis.

2021 ◽  
Author(s):  
luis Augusto sanabria ◽  
Xuerong Qin ◽  
Jin Li ◽  
Robert Peter Cechet
Keyword(s):  
Climate Change ◽  
Bias Correction ◽  
Extreme Values ◽  
The Body ◽  
Future Climate ◽  
Return Periods ◽  
Climate Conditions ◽  
Mitigation And Adaptation ◽  
Climate Simulations ◽  
The Impact

Abstract Most climatic models show that climate change affects natural perils' frequency and severity. Quantifying the impact of future climate conditions on natural hazard is essential for mitigation and adaptation planning. One crucial factor to consider when using climate simulations projections is the inherent systematic differences (bias) of the modelled data compared with observations. This bias can originate from the modelling process, the techniques used for downscaling of results, and the ensembles' intrinsic variability. Analysis of climate simulations has shown that the biases associated with these data types can be significant. Hence, it is often necessary to correct the bias before the data can be reliably used for further analysis. Natural perils are often associated with extreme climatic conditions. Analysing trends in the tail end of distributions are already complicated because noise is much more prominent than that in the mean climate. The bias of the simulations can introduce significant errors in practical applications. In this paper, we present a methodology for bias correction of climate simulated data. The technique corrects the bias in both the body and the tail of the distribution (extreme values). As an illustration, maps of the 50 and 100-year Return Period of climate simulated Forest Fire Danger Index (FFDI) in Australia are presented and compared against the corresponding observation-based maps. The results show that the algorithm can substantially improve the calculation of simulation-based Return Periods. Forthcoming work will focus on the impact of climate change on these Return Periods considering future climate conditions.

A Novel Gemini Cationic Viscoelastic Surfactant-Based Fluid for High Temperature Well Stimulation Applications

2021 ◽  
Author(s):  
Dawn Friesen ◽  
Brian Seymour ◽  
Aaron Sanders
Keyword(s):  
Thermal Stability ◽  
High Temperature ◽  
Chain Length ◽  
Surfactant Concentration ◽  
Gemini Surfactant ◽  
Alkyl Chain ◽  
Friction Reduction ◽  
Fluid Viscosity ◽  
Viscoelastic Surfactant ◽  
The Impact

Abstract Viscoelastic surfactant (VES)-based fracturing fluids can reduce the risk of formation damage when compared with conventional polymer-based fracturing systems. However, many VES systems lose viscoelasticity rapidly under high-temperature conditions, leading to high fluid leakoff and problems in proppant placement. A gemini cationic VES-based system offering thermal stability above 250°F and its efficiency in friction reduction is presented in this paper. Rheology measurements were conducted on viscoelastic cationic gemini surfactant fluids as a function of temperature (70 – 300°F) and surfactant concentration. The length of surfactant alkyl chain was varied to investigate the impact of surfactant chain length on VES fluid viscosity at elevated temperatures. The effect of flow rate on friction reduction capability of the surfactant fluid was measured on a friction flow loop. Foam rheology measurements were conducted to evaluate the VES fluid's ability to maintain high temperature viscosity with reduced surfactant concentration. A gemini cationic surfactant was used to prepare a viscoelastic surfactant system that could maintain viscosity over 50 cP at a shear rate of 100 s−1up to at least 250°F. With this system, viscoelastic gel viscosity was maintained without degradation for over 18 hours at 250°F, and the fluid showed rapid shear recovery throughout. Decreasing the average alkyl chain length on the surfactant reduced the maximum working temperature of the resulting viscoelastic gel and showed the critical influence of surfactant structure on the resulting fluid performance. The presence of elongated, worm-like micelles in the fluid provided polymer-like friction reduction even at low surfactant concentrations, with friction reduction of over 70% observed during pumping (relative to fresh water) up to a critical Reynolds number. Energized fluids could also be formulated with the gemini surfactant to give foam fluids suitable for hydraulic fracturing or wellbore cleanouts. The resulting viscoelastic surfactant foams had viscosities over 50 cP up to at least 300°F with both nitrogen and carbon dioxide as the gas phase. The information presented in this paper is important for various field applications where thermal stability of the treatment fluid is essential. This will hopefully expand the use of VES-based systems as an alternative to conventional polymer systems in oilfield applications where a less damaging viscosified fluid system is required.

IIOT and Real Time Data Analytics - Maximizing the Impact on Safety and Productivity

2021 ◽  
Author(s):  
Ryan Daher ◽  
Nesma Aldash
Keyword(s):  
Real Time ◽  
Case Studies ◽  
Data Analytics ◽  
Contact Tracing ◽  
Time Data ◽  
Seamless Integration ◽  
Location Services ◽  
Industrial Internet ◽  
Potential Applications ◽  
The Impact

Abstract With the global push towards Industry 4.0, a number of leading companies and organizations have invested heavily in Industrial Internet of Things (IIOT's) and acquired a massive amount of data. But data without proper analysis that converts it into actionable insights is just more information. With the advancement of Data analytics, machine learning, artificial intelligence, numerous methods can be used to better extract value out of the amassed data from various IIOTs and leverage the analysis to better make decisions impacting efficiency, productivity, optimization and safety. This paper focuses on two case studies- one from upstream and one from downstream using RTLS (Real Time Location Services). Two types of challenges were present: the first one being the identification of the location of all personnel on site in case of emergency and ensuring that all have mustered in a timely fashion hence reducing the time to muster and lessening the risks of Leaving someone behind. The second challenge being the identification of personnel and various contractors, the time they entered in productive or nonproductive areas and time it took to complete various tasks within their crafts while on the job hence accounting for efficiency, productivity and cost reduction. In both case studies, advanced analytics were used, and data collection issues were encountered highlighting the need for further and seamless integration between data, analytics and intelligence is needed. Achievements from both cases were visible increase in productivity and efficiency along with the heightened safety awareness hence lowering the overall risk and liability of the operation. Novel/Additive Information: The results presented from both studies have highlighted other potential applications of the IIOT and its related analytics. Pertinent to COVID-19, new application of such approach was tested in contact tracing identifying workers who could have tested positive and tracing back to personnel that have been in close proximity and contact therefore reducing the spread of COVID. Other application of the IIOT and its related analytics has also been tested in crane, forklift and heavy machinery proximity alert reducing the risk of accidents.

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