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I am mentoring a trainee who is writing a dissertation on phototherapy for neonatal jaundice. She has been using a spectroradiometer and has noticed that the spectra from LED-based units are all slightly asymmetric. I have also noticed this in publlished papers. In the attached drawing I have exagerated the effect, where the emission of wavelengths longer than the peak emission, but many spectra that I have seen show this effect. Anybody know why this may be?
Thanks in advance
Mike
Michael Lynn
CIE rapporteur
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One possible reason is that there is more lower energy carriers in the conduct band so the spectrum has a tail extending to longer wavelength.
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Carbon markets have become popular, locally and nationally, including in Canada as a way to address carbon pollution. And this raises the question, are carbon price based markets green markets? Why?
I think no, what do you think?
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They are not green markets because they are not cleared by a green market price, they are environmental externality management based markets.
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Can N-methyl-2-pyrollidone be used as a polar, non-protic solvent for absorption & emission studies for various compounds?
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I've used it as a solvent for XRF analysis of elements such as S, Cl etc in organic compounds, for which it is very good (as are quite a few other dipolar aprotic solvents!). I've always used helium flushing for this sort of job, but you can probably get away with air atmosphere for a lot of the possible analytes.
There are toxicity concerns about it; the high boiling point means that volatility isn't much trouble (but work in a fume cupboard anyway); however it will probably pass through the skin barrier quite easily, taking with it whatever is dissolved in it, so I've always used HEAVY DUTY nitrile gloves (NOT the cheap disposable ones) for solvents such as this. Wash the gloves with soap and water after use. Check with your local H&S advisor for the local policy on safe use of solvents such as NMP: I'm not aware of any reason why it should be impossible to work with solvents such as this, but as always, make sure you have the best possible advice and follow it.
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Is there any weather data morphing tool (for hourly weather data) to predict climate change for future using the IPCC AR5 (assessment report 5) emission scenarios I.e. rcp 2.5, rcp 4.5, rcp 6 & rcp 8?
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@Naveen Kishore have you found a way to do this by any chance?
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The new scenario family that IPCC is using in its new reports is a combination of Representative Concentration Pathways (RCPs) and Shared Socio-economic Pathways (SSPs). You can read more about them at these papers:
As there is no probability assigned to different scenarios, scenario users are left with a numerous scenarios projecting the future world regarding the emission (RCPs) and societal and economic conditions (SSPs).
When you are planning to adapt to climate change, the impacts differ with each scenario (SSP-RCP combination. For example, planning for adaptation when you are facing a condition like SSP1-RCP2.6 is much cheaper, easier and achievable compared to a high emission scenario like SSP5-8.5 (combined with a socio-economical condition making adaptation challenging).
The discussion that I'm trying to open here is about the approaches you use / assumption you make in your studies when working with these scenarios. As my main audience is the people who use scenarios, I'll be grateful if you could share this post with people working in these areas.
-----------
Thanks,
Kasra
Research Assistant at University of Waterloo
PhD System Design Engineering
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Hi,
Read my article (meticulously) and send me a direct. I will guide you.
Icen
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I want to understand the mathematics of fluorescence process in terms of excitation and emission wavelengths. I want to develop a general mathematical model with certain specific parameters and without employing a spectrometer, I want to see the emission spectrum mathematically.
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One can construct simple model (Shifted Harmonic Oscillator model) and derive tractable equations to obtain absorption and emission spectra.
1. Absorption and Emission Lite: Assume ground and excited states are shifted classical Harmonic Oscillator. Ground state |g> energy: Eg(R) = 1/2 ω2R2 & Excited state |e> energy: Ee(R) = 1/2 ω2(R - R0)2 + ΔE. Treating R classically one gets absorption (Ia) and emmision (Ie) spectra as:
Ia(e) = exp[(e-ΔE)2/2σ2] Ie(e) = exp[(E-ΔE + ω2R02)2/2σ2] (Arbitrary Units)
absorption and emission is peaked at different energies and the difference is ω2R02 --- stokes shift, see: https://en.wikipedia.org/wiki/Stokes_shift
σ is the linewidth caused by molecules coupling to environment (Homogeneous Broadening) caused because individual molecules see slightly different environment, e.g. ΔE (Inhomogeneous Broadening) is different for different molecule.
2. Absorption and Emission Pro: Same as 1, but treat R quantum mechanically,
this gives |g>|v0> , |g>|v1> ... |g>|vn> states and |g>|v0'> , |g>|v1'> ... |g>|vn'> where |vn> is nth vibrational state centered around 0 and |vn'> nth vibrational state centered around R0.
  • Energy of |g>|vn> --> <vn|<g| H |g>|vn> = (n + 1/2)ℏω and
  • Energy of |g>|vn> --> <vn'|<e| H |e>|vn'> = (n + 1/2)ℏω + ΔE
With this we write the absorption at T = 0K ( or ℏω >> kT)
Ia(e) = ∑n |<vn'|v0>|2 exp[(e-ΔE - nℏω)2/2σ2]
= ∑n (1/n!) * (ωR02/2)n exp[-(ωR02/2)2] exp[(e-ΔE - nℏω)2/2σ2]
Ie(e) = ∑n |<v0'|vn>|2 exp[(e-ΔE + nℏω)2/2σ2]
= ∑n (1/n!) * (ωR02/2)n exp[-(ωR02/2)2] exp[(e-ΔE + nℏω)2/2σ2]
|<v0'|vn>|2 are Franck-Condon factor,
|<v0'|vn>|2 = |<vn'|v0>|2 = (1/n!) * (ωR02/2)n exp[-(ωR02/2)2].
3. Absorption and Emission Pro Max: Same as 2 but at finite temperature T. Assuming instant thermalization --> states are population according to Bolzmann distribution,
Ia(e) = ∑mn |<vn'|vm>|2 exp[(e-ΔE - nℏω)2/2σ2] * Pm
= mn |<vn'|vm>|2 exp[(e-ΔE - nℏω)2/2σ2] * (exp[-βmℏω] /∑kexp[-βkℏω])
= ∑mn (1/n!) * (ωR02/2)n exp[-(ωR02/2)2] exp[(e-ΔE - nℏω)2/2σ2] * (exp[-βmℏω] /∑kexp[-βkℏω])
Ie(e) = ∑mn (1/n!) * (ωR02/2)n exp[-(ωR02/2)2] exp[(e-ΔE + nℏω)2/2σ2] * (exp[-βmℏω] /∑kexp[-βkℏω])
Pm = (exp[-βmℏω] /∑kexp[-βkℏω])
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Q. Why oleic acid show a fluorescence spectra at 437 nm with blue light emission though it has no fluorophore where excitation source used 365 nm ?
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To the best of my knowledge this phenomenon is never observed using ‘normal’ fluorescence. To measure fluorescence, you need a fluorophore like Laurdan as used in the paper you indicated, see enclosed file. You either used a laser source or a highly sensitive spectrofluorometer (like FP-8500, JASCO).
Using FP-8500 there is one paper (see enclosed file) that describes your findings using photoluminescence:
Sekar, S., Muller, J. G., Karthikeyan, J., Murugan, P., & Lakshminarasimhan, N. (2018). Unveiling the multifunctional roles of hitherto known capping ligand oleic acid as blue emitter and sensitizer in tuning the emission colour to white in red-emitting phosphors. Physical Chemistry Chemical Physics20(28), 19087-19097.
Here you see the excitation and emission spectra of oleic acid that pretty much answers your question.
Best regards.
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the following is a link containing the classification of the commercially available LEDs's semi-conductors and their approximate wavelength spectrum: https://www.researchgate.net/profile/Snehasish-Dutta-Gupta/publication/257761181/figure/tbl1/AS:392793823432709@1470660753744/Commercially-available-LEDs-with-colors-wavelength-range-and-material-used.png
the following is the link for some of the LED's wavelength emission spectrum classified by their semi-conductors: https://toshiba.semicon-storage.com/us/semiconductor/knowledge/e-learning/discrete/chap5/chap5-3.html
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Almost all commercially available LEDs (Especially in the range of the visible spectrum) are phosphor-converted LEDs, The table that you provided is for the spectrum of emitted light of the different semiconductor materials.
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I would like to calculate the emission rates of PM, PM10 and PM2.5 for the final grinding process of cement production using emission rates. Is there a source I can be able to get the emission rates of the above pollutants?
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Hi Jermaine,
Please have a look at the link below, the paper published is an excellent case study, good luck.
Best wishes,
Sofiane
ASSESSMENT OF PARTICULATE MATTER (PM 10 & PM 2.5) AND ASSOCIATED HEALTH PROBLEMS IN DIFFERENT AREAS OF CEMENT INDUSTRY, HATTAR, HARIPUR, January 2013, Journal of Science and Technology 37(2):7-15
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Hello everyone,
I have a system composed of ruthenium and study its absorption and emission (phosphorescence/fluroescence) properties, using Gaussian16 rev.C.01. There's a problem when I try to optimize its 5th excited state, the one that has been found to be associated with the greatest oscillator strength for the absorption.
To begin with, the input keywords are as follow:
# M06/genecp td=(root=5) opt=(maxstep=5) freq=noraman scrf=(iefpcm,solvent=water) pop=dct geom=connectivity guess=read
Unfortunately, at some point there's a shift in excitation energies (bold-typed) from:
Excited State 1: Singlet-A 2.1230 eV 584.00 nm f=0.0012 <S**2>=0.000
Excited State 2: Singlet-A 2.2804 eV 543.71 nm f=0.0030 <S**2>=0.000
Excited State 3: Singlet-A 2.4069 eV 515.12 nm f=0.2133 <S**2>=0.000
Excited State 4: Singlet-A 2.6019 eV 476.51 nm f=0.0036 <S**2>=0.000
Excited State 5: Singlet-A 2.6274 eV 471.89 nm f=0.0038 <S**2>=0.000
to
Excited State 1: Singlet-A 2.2383 eV 553.92 nm f=0.0028 <S**2>=0.000
Excited State 2: Singlet-A 2.4362 eV 508.92 nm f=0.0063 <S**2>=0.000
Excited State 3: Singlet-A 2.4705 eV 501.86 nm f=0.0022 <S**2>=0.000
Excited State 4: Singlet-A 2.5460 eV 486.97 nm f=0.2285 <S**2>=0.000
Excited State 5: Singlet-A 2.5008 eV 495.79 nm f=0.0062 <S**2>=0.000
I am not sure this is correct... However, I've been searching through the web, but didn't find a solution. As for now three different jobs are runing:
1) with calcfc
2) with calcall
3) with maxstep=1
Each has explicitly added Nstates=8
In any case, I got no other idea how to fix it. I'd be glad for an advice!
Thanks.
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Right, SCF + excited state energies - obviously, stupid me... Anyway, I confess I got no theoretical background on the TD-DFT topic. But for my supervisor entirely don't know what I am doing, I ask here, at RG.
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some literature considers soil erosion as the source of GHG emissions, particularly, CO2 and N2O while others mention soil erosion as a sink for GHG, so I want to be clear on that issue.
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Have a look at this useful RG link.
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I understand that Rn is "The fluorescence emission intensity of the reporter dye divided by the fluorescence emission intensity of the passive reference dye" (Thermofisher definition), but I'm a little unsure how that relates to RFU.
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Fluorescence intensity measurements are usually relative, unlike absorbance measurements, because they depend on many factors, such as the instrument settings, the geometry of the sample, the intensity of the exciting light, the sensitivity of the detector, and so forth. So fluorescence intensity measurements are reported as relative fluorescence units (RFU). The size of the numbers has no real meaning. They are arbitrary.
If you wish, you can normalize the fluorescence intensity to some comparator, such as the fluorescence of a reference dye, dividing the first by the second. This could be useful in some circumstances to make it easier to compare measurements made at different times or under different circumstances.
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Hello everyone! I am currently using machine learning procedure for my classifications via QuPath software. These green particles seen on the image sometime can be yellow (meaning there is the same amount of emission of autofluorescence in both the red and green channels, which is logical due to the great spectrum of autofluorescence). So, in this case some of these particles could also be annotated as vessels even if they are not. Do you possibly know if there is solution to that or is it just a software’s limitation? Thank you in advance!
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It is better to mention even if you don't know it, that is much better.Regards
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My probe strongly absorbs photons in the visible region (400 - 800 nm) and displays an intenseband at a characteristic wavelength, λmax 410 nm which was assigned as charge transfer (CT) band. Also, it exhibited yellow fluorescence with strong emission maxima at 570 nm. Generally, the emission appears at a longer wavelength than the absorption edge. How can the emission emit between the absorption spectral range
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Since the energy of fluorescence photons cannot be higher than that of absorbed ones (energy conservation), their wavelenght is longer, since the photon energy is h c/l where h= Planck's constant, c = velocity of light and l is the wavelenght.
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In PL analysis, a material is showing a single emission peak while in Time-resolved and steady-state the Fluorescence at same excitation wavelength we observed many emission peaks for same material. How can it be possible?
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Ashish Gupta - ok - somehow when I read the question first the "and" was obscured and I didn't understand what was meant by "Time resolved steady state" as a single term.
Things to be considered are:
(i) as a trivial suggestion, make sure the lamp is properly monochromated.
(ii) what is the material? the difference may be that of CW illumination vs pulsed, and in the former you may have a build up of long lived states. What is the laser pulse width, repitition rate? You could try chopping the lamp to give the sample some time to recover, although you may not get close to the laser pulse width, repitition rate.
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Hello researchers !
Could you please explain me or help me get the references or books about the basics and fundamentals of time decay/ PL life time/ decay time processes of PL downconversion ?
kindly help me , get some references!
Is there any standard mechanism for time decay?
How are increasing and decreasing time decay measured with a fixed excitation for a particular emission related to concentration of activator ions?
please help me understand this!
Thank you all !
With regards,
Manoj
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Here is a reference for your query...
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In particulate matter source apportionment studies, Na+ and Cl- are usually related to marine aerosol, however, anthropogenic contributions may be underestimated. Which industrial sectors/activities may be related to these elements?
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I have applied N in the soil @ 250 mg kg-1 in 100 gram of soil. After that I have taken the samples in the glass vials having rubber septum and analyzed on GC-ECD. I have got the results which are in 10-6 V/V. I need Nitrous Oxide emission from soil. Total soil used is 100 g and area of head space above soil (in glass Jar) is 0.0094 m2. @Dieter Lohr
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If you want to calculate N2O emissions, you'll need to take two samples and keep track of how much time passes between them.
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When a sample is excited with a radiation of 400nm, a peak at 600nm appears in the emission spectrum. It disappears when a filter is used
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Most spectrometers use a grating and what you may be measuring are the higher diffraction orders.
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How supraharmonics affect the electric vehicle and eletric grid? How to control and mitigate the emission? Is AI is able to control or mitigate the SH emission?
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I want to stain liposomes with Dil (1,1'-Dioctadecyl-3,3,3,3',3'-Tetramethylindocarbocyanine Perchlorate) and evaluate their uptake by macrophages using flow cytometry.
I have read that the fluorescence of Dil is orange-red, and people who have used it in other techniques have told me that the sample gets a reddish/pink color.....
However, I have read that the peak wavelength of the emission spectrum of DiL is about 570 nm, on other sites I have seen that it is 514 nm but that would not be red!!! so I am a bit confused....
Using the blue laser in the flow cytometer.... where would the emission spectrum of the Dil be then? With what other fluorophore would it be comparable...to PE (FL2) for example?
Translated with www.DeepL.com/Translator (free version)
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The emission peak is at 568 nm. PE is a comparable dye. You should use the green laser for maximum excitation. Please find attached an image a spectral viewer.
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Carbon emission data for 35 to 40 years in West Bengal
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A Statistical Analysis of Carbon Dioxide Emission from ...
https://www.ijert.org › a-statistical-analysis-of-carbon-di...
West Bengal is one of the major contributors among identified states. Undesirable emission of CO2 from different sources
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I have read some paper shared the information regarding effect of outdoor organic carbon (OC) on our indoor environment or concentration of OC coming from outdoor environment to indoor environment. But it is possible to measure OC in an ambient environment which is coming from indoor cooking.
Kindly share your views on that and please tell me other alternatives to measure OC generated from street cooking (open cooking).
Thank you
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Depends on the cooking fuel, its duration --GC-MS can detect it
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Our answer is YES. The wave-particle duality is a model proposed to explain the interference of photons, electrons, neutrons, or any matter. One deprecates a model when it is no longer needed. Therefore, we show here that the wave-particle duality is deprecated.
This offers an immediate solution for the thermal radiation of bodies, as Einstein demonstrated experimentally in 1917, in terms of ternary trees in progression, to tri-state+, using the model of GF(3^n), where the same atom can show so-called spontaneous emission, absorption, or stimulated emission, and further collective effects, in a ternary way.
Continuity or classical waves are not needed, do not fit into this philosophy, and are not representable by any edges or updating events, or sink, in an oriented graph [1] model with stimulated emission.
However, taking into account the principle of universality in physics, the same phenomena — even a particle such as a photon or electron — can be seen, although approximately and partially, in terms of continuous waves, macroscopically. Then, the wave theory of electrons can be used in the universality limit, when collective effects can play a role, and explain superconductivity.
This solves the apparent confusion given by the common wave-particle duality model, where the ontological view can become now, however — more indicative of a particle in all cases — and does not depend on amplitude.
This explains both the photoelectric effect, that does not depend on the amplitude, and wave-interference, that depends on the amplitude. The ground rule is quantum, the particle, but one apparently "sees" interference at a distance that is far enough not to distinguish individual contributions.
What is your informed opinion?
REFERENCE
[1] Stephen Wolfram, “A Class of Models with the Potential To Represent Fundamental Physics.” Arxiv; https://arxiv.org/ftp/arxiv/papers/2004/2004.08210.pdf, 2004.
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I am trying to study the interaction of my protein with a small molecule ligand by trp fluorescence spectroscopy. My protein has molecular weight of 16 kDa and has 2 tryptophan residues. I am keeping protein concentration 2uM and gradually increasing the ligand concentration (0-10uM). I am setting up separate binding reactions for each concentration of ligand. Excitation wavelength is 295 nm and emission spectra recorded from 310 to 400 nm. Excitation and emission slits both are 10 nm. Scan speed is 100nm/sec. The buffer used in the study has the following composition: 25mM HEPES-NaOH (pH 7.4), 150 mM NaCl and 10% (v/v) glycerol. The ligand is soluble in DMSO and I am keeping a final 2% (v/v) DMSO in all the reactions. I wish to find the binding affinity and stoichiometry from this study.
The problem is that I am not getting any definite pattern in the emission spectra of the protein upon increasing the ligand concentration; I am getting fluorescence enhancement for some ligand concentrations, for others I am getting fluorescence quenching. Please suggest a solution to this problem. (The protein and ligand interacts, that has been checked by other methods).
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Hello.
You need to take the absorption and fluorescence spectra of each concentration of only ligand and subtract them from the corresponding concentration of ligand-protein. If your protein and ligand both absorb at the same wavelengths, UV and fluorescence are not very good methods for the study. You need to correct the absorbance for the inner filter effect as well as the fluorescence intensity by easily available mathematical equations.
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In dumping operation of hot wet materials, for example, there is emission of particulate matter together with water vapor, which difficult the measurement of opacity. Is there any way to solve this problem, or other techniques to quantify the PM?
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Hello René. Thank you for the points raised. I am talking about an open system in an external environment (materials yards). The temperature of the materials dumped is around 100-200°C. The volume of materials is small, 1 or 2 m3. They are wetted before the dumping operation to avoid dust emission, mainly total suspended particles (TSP) and PM10. I would like to measure the particles concentration or any parameter related to the particles emission. The opacity was the easiest way that we found to determine if there is or not PM emission, however, the vapor generated in the process interferes in the measurements.
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Several studies on combustion of bio diesel/petroleum fuel blends in IC engines and other power generation / combustion devices discussed extensively about the influence of fuel unsaturation on NOx emissions. A fundamental question arises on how we quantify fuel unsaturation?
I would like to start a discussion on the topic - How to quantify fuel unsaturation ? what would be an appropriate index to quantify unsaturation irrespective of the family of origin of fuels - like methyl esters, ether, alcohol , alkanes, alkenes, alkynes or aromatics or a weighted combination of aforementioned categories.
Our research group's take on this -
We have established a parameter - Degree of unsaturation that serves as a common platform across different fuel families (esters/alkanes/aromatics) to quantify the effects of fuel unsaturation, particularly with petroleum/bio-diesel blends. DOU can be evaluated based on the average molecular formula of the fuel alone without involving complex and expensive experimental procedures such as those involved in the measurement of iodine number and bromine number.
If interested, please follow the link to access the research work we have conducted at our laboratory to investigate the effect of fuel unsaturation on nitric oxide emissions.
Message me to get a copy of this article.
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While cultivation, Water hyacinth reduces carbon dioxide by photosynthesis. But it produces methane by its roots which increases greenhouse gases in the atmosphere.
1. Is it negative/positive greenhouse gas emission by water hyacinth while cultivating it???
2. Is it viable to reduce greenhouse gases mainly carbon dioxide gas from the atmosphere integrated with biofuel production by water hyacinth???
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Dear Sadman, In broad sense, water hyacinth endangers aquatic ecosystems and stifles organic growth.
The exponential increase of water hyacinth responses in increased carbon dioxide (CO2) uptake at rates of 3.4 - 5.4 g C-CO2 m-2 per day, as noted for tropical lakes.
Rapid growth rates demonstrate its ability to mobilise and retain nutrients in the tissues, as well as metabolize large amounts of CO2 (CO2).
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I am using this method to calculate an emission spectrum, but I get: ERROR: The total intensity calculated using the analytic sum rules is null. How can I solve that?
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I am facing the same problem.Did you find the solution? Diana Uriza
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I need to use Rhodamine B dye in water for my project. The light source I am using is a blue LED. I wanted to know that if the excitation and emission wavelength of the Rhodamine B dye is same for all kinds of light like green laser light or blue LED light. If not, then what would be the excitation and emission wavelength of Rhodamine B dye in blue light?
Thanks in advance
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@Abbishek Gururaj, I am facing the same problem. Can you please tell me what happened afterwards.
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What is the impact of large fire emissions on satellite and in-situ (ARGO floats) Chl a measurements?
How accurate are satellite observations of surface ocean Chl a during large fire events (close and at increasing distance to the fire emission source)?
Is there a consensus on correction to be applied in that regard?
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Thank you, Nagalakshmi, for your answer.
I apologise for not formulating my question clearly enough. I was thinking about biogeoArgo floats. I was wondering how increased aeolian deposition to surface water (from fires for example) could bias say backscattering measurements and chlorophyl measurements made by those floats for example. Same question regarding increased fire emissions in the atmosphere; how do they disturb satellite measurements of Chlorophyll. Is there any acknowledged correction to be applied to such measurements ?
Thanks again
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This is the flue gas composition from the Ammonia fired furnace which I have modeled in Aspen Plus. Does anyone have any idea about NOx emissions? Is this emission amount of emission accepted by the EPA?
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Generally for the cement industry it is a stack emission at 10% O2 dry for 500 mg/NM3 of NOx as NO2. The Power Industry at least in Europe is 200
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like fire wood co2 emission has been calculated by the given formula by IPCC with default values of net calorific values and emission factor.
is the same value use for the cow dung cakes and agricultural waste or not?
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To calculate CO2 you need a proximate and ultimate analysis plus the gross CV of whatever fuel you are using. To get the Bio %age your need to look at the c14 %age via a mass spec.
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I have been running a förster resonans emission transfer (FRET) assay, using a dnp/mca conjugated peptide probe for my protease of interest. However I have problems with the assay; sometimes the assay works fine and I get really nice and clear signals, but sometimes the signal from both the FRET-peptide control (w/o protease) and buffer only control (i.e. only the buffer) declines dramatically during the timecourse of the experiment, and the signal from the protease is much weaker than normal (after correction for the declining background...).
Experimental setup:
Peptide: dnp-NH-GTQVKLIGHR-CO-mca. Detected fluorometrically at 392 nm using an excitation wavelength of 325 nm according to litterature. 20ug/ml final concentration
Buffer: 50mM Hepes (pH 7.4), 200 mM NaCl, and 2 mM DTT
Enzyme: Ctss, 0.1 ug
Plate and buffer pre-heated to 37 degrees.
Read in Spectramax M2e using fluorescence kinetik read with 325 exitation, 392 emission and 325 auto-cut off filter.
Any idea of what might be going wrong?
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I can think of two potential problems, both with simple solutions.
1. The peptide is sticking to the plastic of the microplate. The enzyme can also do this. The solution is to include in the buffer 0.01% Triton X-100 or some other non-ionic detergent at a concentration below its critical micellar concentration.
2. The fluorophore is suffering photodamage as a result of an excessive number of flashes from the light source. There are two simple solutions. One is to reduce the number of flashes per measurement. The other is to make measurements at less frequent intervals.
Make sure you always use the same settings for the measurement for every experiment in order to get consistent results. You can save the setup to prevent accidentally using the wrong settings.
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Hi,
I plan to write my thesis on sustainable solutions to reduce carbon emissions in inbound logistics. As a result, I'm looking for articles and was wondering if you have any recommendations.
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I'm a PhD student in polymer physics particularly on photophysics of conjugated polymers. While reviewing literature I come across an article by Shu Hu and coworkers on 'Effect of Thermal Annealing on Conformation of MEH-PPV Chains in Polymer Matrix: Coexistence of H- and J-Aggregates' in which they assign the emission peak (I00) of H-type aggregates at lower energy than J-type aggregate when they coexist, which, I think, contradicts Kasha theory.
Some body help me explain this.
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Thanks a lot!
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Dear all,
I am trying to optimize my panels for our confocal laser microscopy experiments and with our available laser/filter setup, it would be great to have antibodies/Streptavidin that would be coupled to a fluorochrome with a more or less narrow excitation around 488nm and a emission wavelength around 605nm or longer. It might be wishful thinking, but does anyone know any fitting (new?) colors that would be useful?
Thanks for your efforts & best wishes,
Urs
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Hi: It's an "old" fluorophore, but you could try DCM - https://omlc.org/spectra/PhotochemCAD/html/038.html - excitation max ~490 and peak emission ~620 nm (in methanol). Because it's a laser dye it is very stable.
This book - https://www.chem.ucla.edu/~craigim/pdfmanuals/catalogs/Lamdachrome-laser-dyes.pdf seems to be out of print now but contains a lot of good information on laser dyes (fluorophores used in tunable dye lasers). You might be able to find another suitable molecule there?
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I am using fluorescence spectroscopy to determine stability parameters for human acidic fibroblast growth factor 1. (FGF1). The fraction unfolded for FGF1 is determined from the ratio of emission at 350 nm to 308 nm corresponding to tryptophan and tyrosine emissions respectively. So, what I need is the fraction unfolded, do I still need to subtract blank from the 350 nm and 308 nm fluorescence reading separately at each denaturant concentration?
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That's something. Thank you.
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I am a new researcher in the X-fluorescence Computed Tomography field. I am doing the attenuation correction of the XFCT imaging system and I am confused with something.
As we know that while doing the attenuation correction for emission tomography, we need to convert the attenuation coefficient value for the energy of 511 KeV by using some Bi/Trilinear method! That means :
""Transmission CT energy ( attenuation coefficient value) ==> Emission CT energy ( attenuation coefficient value) "".
As it is known XFCT has two parts: Fluorescent Excitation ( Transmission) and Fluorescent Emission. I have Attenuation co-efficient values for 30KeV energy.
What will be the process for converting the attenuation co-efficient values for XFCT? Would I need to convert the attenuation co-efficient value two times ( for transmission and emission) ?
I am a bit confused about this problem!
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you are right.
There are two attenuation coefficients involved:
a) that of the excitation radiation, which has a photon energy a bit higher than the absorption edge energy of the excited atom, and
b) that of the fluorescence radiation, the photon energy of which is smaller than
and the edge energy.
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Spectral overlap in my case, between UV of analyte and emission of probe, not that much overlap and I found spectral overlap integral, R0 and FRET efficiency values. But I can't conclude it, because there seen only slight life time change. So can I say, both IFE and FRET be the mechanism means combined effect of IFE and FRET may be the reason?
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I did not understood what did you obtain, so I may only guess. Generally, suppose you add analyte with absorption at the probe's excitation wavelength, than probe's fluorescence intensity will decrease due to IFE, but lifetime will not change. If there is analyte's abscorption at the probe's emission wavelength, probe's emission intensity could decrease either due to just reabsorption (in this case lifetime will not change) or FRET (if analyte and probe are close; in this case lifetime will decrease). But if probe binds to analyte, both intensity and lifetime could change just due to binding, this should br also accounted for...
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I have synthesized fluorescent probe which is a Schiff base zinc metal complex used for the detection of food color. I got good overlap with UV of analyte and emission of probe. Now I am confused, IFE or FRET of Dynamic PET is my mechanism? O have also get a blue shift in the emission spectrum upon addition of analyte.
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What is Food color ?
To identify the mechanism of a detection process, you have to theorize the behavior of our probe depending of the different models. This includes the prediction of behavior of your probe in conditions that you have still not tested. A successful prediction will offer you plenty of confidence.
Spectroscopic evidences are part of the job. And, as you mentioned, a change in the fluorescence spectrum is not predicted by FRET or PET.
Quantitative measurements offer also pieces of evidence. The quenching efficiency can be calculated in the case of FRET and partially calculated for PET.
An example of quatitative analysis of fluorescence quenching experiment was discussed in “Can anyone help me to do stern volmer plot in flourescence quenching?” at
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1) How to understand the charger transfer happen through the intermolecular or intramolecular band by UV and fluorescence spectroscopy?
2) How to understand the charge transfer in donor-acceptor molecules happening in an excited state or ground state?
3) Donor-Acceptor directly linked to each other without any spacer, absorption spectra of it have two bands,
In polar solvent, when excited at longer wavelength band emission is quenched while excited at shorter wavelength band has emission in the green region.
While in a non-polar solvent, when excited at longer wavelength band red emission is observed while excited shorter wavelength band has emission in the red region and green region(emission spectra shows two bands).
Can anyone please suggest what could be the reason behind it?
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Dear Harsha Agrawal
Indeed, in a polar solvent, upon excitation in the longer wavelength band, the emission is quenched, and upon excitation in the shorter wavelength band, emission is observed in the green region.
Being in a non-polar solvent, when excited in a longer wavelength band, red emission is observed, while when excited in a shorter wavelength band, emission is observed in the red and green regions.
It is sometimes possible that the emission spectra show two bands.
My mini-review will help you answer these questions:
Solvatochromism and Nonradiative Decay of Intramolecular Charge-Transfer Excited States: Bands-of-Energy Model, Thermodynamics, and Self-Organization
Article
Full-text available
  • December 2012
  • ChemPhysChem Vladimir S. Pavlovich
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I need assistance on Environmental Attributes ( that means any and all claims, credits, benefits, emissions reductions, offsets, and allowances, howsoever entitled, resulting from the avoidance of the emission of any gas, chemical, or other substance to the air, soil or water)
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I agree
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Please share MATLAB code of Dynamic Economic dispatch? I want to use dynamic economic dispatch with electric vehicle. please share if you have. (sonijatin1995@gmail.com)
Thank you in advance
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Bhai jate program lako ..copy past na karo
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I am using a FITC caspase 8 kit and The fluorescence intensity was measured at 485 nm excitation and 535 nm emission using a fluorescence plate reader. Please as soon as you can. Your input will be highly appreciated.
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You can normalize your apoptotic activity against the total amount of DNA by applying a DAPI or Hoechst stain.
If you are working with cells a lot you should check-out Cellseeker https://www.cellseeker.org/). This is an easy and free to use app to organize and inventory your cell collection online.
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What are the major pathways to achieve India's target of Net Zero (CO2) Emission by 2070 ?
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Its depends upon individual level (life style) to industrial, political level and many other factors.
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Needed detailed explanation
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u can check this paper maybe itis help
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Thank you everyone for the helpful answers on the best basis set that gives the most accurate value in the DFT calculation of the excitation energy of molecules.
Last questions please:
My target is using DFT to predict the emission wavelength of bioluminescent molecules. As suggested, the ground-state (GS) and excited state (ES) geometrics of all the species studied were optimized with the B3LYP/6-311+G(2d,p) model. I am trying to predict emission spectra with the TDDFT method. I know that the difference between the energy of the optimized excited state and the molecular energy would give the emission energy from which the wavelength of the emitted light can be calculated. But it appears that I have four energies for the calculated excitation energy (Root = 1) (see screenshot 1; three are in Hartree, one is in eV).
Which of these should be used with the molecular energy (Screenshot 2) for this emission energy (i.e. the difference)?
PS: Just a newbie in computation chemistry trying hard to learn.
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If you look closely at the numbers, you will find that the "Excited State Energy" is the difference between the TD-X and the RB3LYP energy and that the excitation energy is the same as the Excited State energy, just with a different unit.
The order of magnitude of that is also at least plausible for a molecule with this stoichiometry.
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Dear Researcher,
I hope you are healthy and doing very well, I open this debate in order to find information about how to measure the cost of the CO2 equiv emissions in buildings, neighborhoods, small villages if any? since I am not sure how can we measure, please bear in mind the neighbors can't be studied as the energy producer (companies), which pay energy emission rights.
I really appreciate your insights on this subject.
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Sorry please perhaps there is error . Refers to this Article Sir "Study on Appraisal of Per Capita Consumption of Charcoal and Firewood as an Alternative Energy Sources for Domestic Usage in Keffi Nasarawa State Nigeria". You might have some idea related to your area. Thank you
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What is the relationship between the excitation intensity and the emission intensity of carbon quantum dots ?
Exactly what area of the wavelength is the fluorescence emission of carbon quantum dots? is it possible at close to 700 nm?
What is the particle size range of carbon quantum dots and what is the relationship between it and the wavelength of fluorescence emission?
Thanks to everyone who can help in the above questions.
Best Regards
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Dear Saptarshi Mandal,
Thank you very much for your helpful tips. Thank you for your valuable reference.
Best Regards
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Is it possible to use the Synthetic Control Method in the firm-level study?
Currently, I am trying to measure the impact of environmental regulation (state-level emission trading scheme) on a firm's green innovation. I have used DID and PSM-DID but want to use SCM with firm-level data, is it applicable? I found most of the paper used state-level data. Expecting your kind opinion in this regard.
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In principle, you could use it. The reason for the application you mentions has to do with the number of treated units. The SCM can reach situations where the rest of the methods are not adequate (e.g., a single treated unit). This is often the case of state-level policies vs firm-level events (we usually have many observations and treated units in the latter case).
You can have a look at Cunningham's Causal inferente: the mitxtape (https://mixtape.scunning.com/), which can be of some help here.
All the best,
José-Ignacio
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I select florescence intensity method, well scan.
Excitation filter and emission filter, some times I select lens instead of emission filter.
I got values not a curve?!
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well,you must read some books related to lighting systems,simply it depend upon lamp type, watt,age,dimension of surface,some factors,watts to lumens factor and angle of inclination (get curve).There is famous equation in this field
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At present, the measurement of greenhouse gases in aquatic ecosystem is often used in situ measurement and model simulation. I am interested in whether remote sensing can reverse the emission of greenhouse gases in aquatic ecosystem. Is there anyone who does this work? Are there any recommended articles?
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Dear Yadi,
could you be more precise on what exactly you mean by "reverse"? I am not quite sure whether you are looking for new techniques (such as remote sensing) to MEASURE greenhouse gases in aquatic ecosystems or whether you are looking for new ways to REDUCE/MITIGATE emissions from aquatic ecosystems (or potentially even ways to enhance their storage capacity as carbon sinks).
Thanks & best wishes to Beijing,
Julius
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We are observing emission from both the Edge and the Bandpass filters on excitation with a Pulsed Laser. The emission is significantly high with multiple/uncontrolled peaks superimposed on the actual photoluminescence data in the whole spectral range of interest. This is becoming particularly difficult in TRPL measurements. Is this issue very common? Please let me know if any specific filters can be used to overcome this issue.
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You may use EBG coomon-mode filter to mitigate the quoted phenomenon
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We have observed 5 different peak of pyrene molecule in its emission spectra. what could be the possible reason for this?
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I think the cause is the functionalization of pyrene with functional groups having double bonds with 2 carbon atoms both by sp hybridization and triple bonds (1 sigma and 2 pi bonds). This condition can extend the π-conjugation system leading to a bathochromic shift from the emission band to the visible region. Furthermore, the shift results in the vibrational structure of the emission spectrum and at the same time prove that the ground state interactions occurring of the pyrene with the potential host molecule are provided by the emission spectrum.
Hopefully, this answer can provide some insight.
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To anyone with more experience in the area of CMC determination,
I am working with a small molecule that can exist in 2 states which can both self-assemble, and my goal is to show a difference in their ability to aggregate. The easiest way of showing this would clearly be to just calculate the two CMC values, but I have run into significant issues in doing so.
Via the method of fluorescence using a hydrophobic dye, the commonly used probes I have seen being used are Nile Red and pyrene. Pyrene's emission peaks are seemingly quenched upon increasing the concentration of my molecule via FRET. I have considered using this quenching to determine CMC, but the 2 states have different FRET efficiencies so that has not given sensible data.
Moving outside the range of FRET, Nile Red's emission peak unfortunately almost perfectly overlaps with the emission of State A, and it is completely overshadowed. Additionally, Nile Red and it's sibling Nile Blue (which I have also tried) don't work well at my operating range of pH ~2.5 due to the amines becoming charged, more hydrophilic, and then not being sequestered as efficiently.
So, would anyone be able to suggest a strategy for determining the molecule's CMC? Or possibly suggest a hydrophobic dye that could operate at the pH range of 2-4? Attached are he absorbance spectra of the 2 states for reference.
Thanks for any help that you can offer.
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Since the molecule is fluorescent, have you considered monitoring the fluorescence excitation and emission spectra, intensities or the lifetimes? Self-association would probably have an effect on one or more of these properties.
The challenge is the high concentration of the compound that is likely going to be needed, causing a severe inner filter effect. To deal with this problem, you can use a triangular cross-section cuvette in the spectrofluorometer to allow you to measure the surface fluorescence by reflection, or rectangular cuvette with a short pathlength.
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I have observed emission and excitation spectrum intensity reduce by increasing temperature from 08 k to room temperature. What is the major reason ?
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The radiative emission process competes with other non-radiative excited state deactivation mechanisms, like rotational relaxation, vibrational deactivation and the like. Increasing the rigidity of a molecule's surrounding makes those pathways more unlikely. Therefore, cooling a almost always increases fluorescence emission intensity. Or, telling it the other way round: increasing temperatures increases non-radiative deactivation, therefore emission intensity goes down on warming up
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I have synthesized a compound which is pure as well as no other possible diastereomers are present in it, as evident from ¹H NMR. On inspection of its photophysical properties an anomaly was noted as described below:
- when the compound was excited in the region (~400 - 450 nm) of its highest absorbance a low intensity emission peak was observed at about 500-550 nm with indication of excimer like entity formation (600 - 650 nm) on varying the concentrations.
- On the other hand , excitation of the molecule at a peak of lower absorbance, near to the λmax around 350 nm a very high intensity and sharp single emission peak was observed around 380 nm with no excimer like entity at higher concentrations.
What could be the plausible reasons behind these observations?
I would be grateful for valued suggestions, if any.
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If your fluorescence spectrometer allows, I would suggest doing a full EEM (excitation emission matrix) measurement. Or at least measure excitation spectra for your different emission bands. If excitation spectra are the same for two bands, there must be an excited state process leading to those two emissions. If they are differing, there must be two ground state compounds present with different absorbance spectra. A highly fluorescent impurity might get unnoticed from measuring absorbance spectrum or NMR, but still exist in small amounts.
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what are the emission from Sohar port and Free Zone? what and health impact of industrial activities like emission heavy metal
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There does not appear to be any public information on this matter. You need to talk to officials at Sohar Port Authority to request information.
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I am trying to calculate carbon footprint of a 1km Cable, but cant find emission factor for lubricant i kinda need its GWP emission factor as raw material and GWP emission factor as its average waste treatment !
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Dear Hamza Karmoum,
The study sounds interesting. You might try to go to the enterprise and do field research to get the emission factors. Some LCA emission factors can only be obtained through field research.
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I am having trouble recognizing whether the emission picks that I am seeing are from the light source of the instrument or from my sample?? is there a way to better discriminate them?
(I am not talking about the excitation wavelength)
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Arezoo Setayesh, you should measure your spectrum without a sample (Io(lambda), where lambda is lights wavelength) and spectrum with sample (I(lambda)). Then you can calculate the spectrum of your sample as
S(lambda) = I(lambda) / Io(lambda)
This is a correct operation if you avoid saturation of your receiver for any spectral range, otherwise, you should adjust incident light intensity or receiver's sensitivity.
In fact, this is an extended version of Gerhard Martens answer.
I hope it helps.
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I am looking for a vendor that sells a dichroic mirror (M1 in the attached schematic) with high reflection >80% at 975nm and high transmission >80% at 2800nm. Ideally, it would be a high pass filter with 1000nm cutoff on a substrate with low absorption in mid-ir like CaF2 etc. Thorlabs and Iradian are have offered to make such a filter on request but that will cost thousands of dollars.
If you have worked with mid-ir lasers and purchased such a filter from a vendor, please let me know. My budget is around $500.
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Someone suggested "Layertec (Germany), they do offer Dichroic Mirror / pump mirror HR 980nm, HT 2-3-3.5um. Costs around $500." You can check it out.
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Dozens of experiments have been performed with light rays, beginning from Fizeau, in order to establish the local constancy of the speed of light and verify how speeds sum up.
It was verified that the speed of light is independent on the speed of its source, otherwise it would be not hard to determine an absolute speed of the platform of emission.
From the verified independence of the speed of light on its source, one might expect also the independence of its direction on the normal component of the source.
That further independence, if found true, although still preventing the detection of an absolute speed, would show that exists a system locally at rest where light is emitted and travels, infringing the equivalence of IRFs, a preferred frame.
Lorentz Transformations predict such light drifting. Michelson and Morley, Michaleson Gale and similar experiments, did not verify such feature.
I am not aware though that experiments were performed with the intent to verify the "transverse" motion of a light beam. The "drifting" light beam, as seen departing from a moving source, is not so hard to be verified nowadays.
That is the basic principle on which Einstein's clock is based.
Synchrotron light would suffice to discriminate.
The syncrotron light passing through an orifice, normal to the plane of the circle of the synchrotron would show the effect.
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Synchrotron_radiation_energ y_flux.png
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In Stern-Volmer equation, are F and F0 the intensities taken at the same wavelength from emission spectra or the maximal intensities of the each curve? For example, how to calculate quenching rate or binding constants if fluorescence quenching is accompanied with red or blue shift?
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Well, that is an intriguing question because red or blue shifts in the emission spectra is usually interpreted as changes in the environment of the fluorescent probe. Such changes affect the electronic distribution and consequently modify the energy gaps, which reflects in the change of the wavelength emitted.
In that case, I agree with Nilimesh Das , I would take the maximal intensities of each curve, because they are referent to the specific electronic transition that you are tracking, the shift is a secondary effect... Another point is that if you take F0 and F at the same wavelength you will be overestimating the quenching. I think this work can help you: Vivian, James T., and Patrik R. Callis. "Mechanisms of tryptophan fluorescence shifts in proteins." Biophysical journal 80.5 (2001): 2093-2109.
And last but not the least, are you working with a low concentration of quenchers? Did you correct the inner filter effect? I have published results of fluorescence experiments in which a saw shift in the emission spectra, but when I corrected the inner filter, the shift disappeared (Povinelli, Ana Paula Ribeiro, et al. "Details of the cooperative binding of piperlongumine with rat serum albumin obtained by spectroscopic and computational analyses." Scientific reports 9.1 (2019): 1-11.). In that case, the quencher absorbed the light according to its own absorbance spectra causing an “optical ilusion”. In this work we showed the possibility of building Stern-Volmer plot based on the area under the spectra.
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The preparation of copper nanoclusters made of copper nanoclusters by polyT, the first excitation can be detected in the enzyme marker, but the second excitation can not be detected, we do not know if the copper nanoclusters can not be activated after the first excitation, or the synthetic copper nanoclusters.
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Hello Yuhui, sorry to see that your very interesting technical question has not yet received any expert answers. Although we frequently worked with new copper compounds in the past, I'm not really an expert when it comes to fluorescence studies of copper clusters. However, I can recommend to you a few potentially useful literature references. For example, please have a look at the following articles:
In Situ Generation of Fluorescent Copper Nanoclusters Embedded in Monolithic Eggshell Membrane: Properties and Applications
Size-controlled atomically precise copper nanoclusters: Synthetic protocols, spectroscopic properties and applications
Highly fluorescent copper nanoclusters for sensing and bioimaging
(please see attached pdf file)
Of course this is only a small selection potentially helpful articles. You can easily find and access other relevant references when you search the "Publications" section of RG for the term "fluorescence of copper nanoclusters":
I hope this helps. Good luck with your work and best wishes, Frank Edelmann
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I think CuS is p-type direct band-gap semiconductor while LED is based on PN junction. So I hardly ever read papers in which CuS is used for light emission. If you have read correlative papers, please tell me.
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Unlike Enclosed fixtures that do not allow for proper ventilation can have a significant impact on the temperature of the LED bulb, causing it to overheat and shortening its lifespan. That's why some bulbs warn against using them in enclosed ceiling fans or fully enclosed porch light fixtures.
Best Regards
Dr. Fatemeh Khozaei
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on which parameter value of excitation wavelength depends for PL emission spectra of CdO nanoparticles
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In PL measurement  typically the excitation wavelength ranges from 300nm -450 nm. The emission is at longer wavelengths, ex. the blue emission (430 nm) green emission (510 nm)  or orange luminescence (620 nm). The excitation wavelength must match the absorption band of your material, otherwise there energy transfer will not be possible.
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For calculation I am looking into the wavelength and intensity for nitrogen II lines obtained from optical emission spectroscopy. The Data is attached here. I got positive slope from the fit. For fitting I am using scipy.linregress method in python . Where I am doing mistake ? Any help would be really appreciated. Thank you in advance.
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I think that there may be some operational mistakes. Did you correct the line intensities by the efficiency curve of optical system? May the lines you selected be self-absorbed? Maybe you just used the wrong units for variables and constants, just like Boltzmann constant (K or eV?) in your calculation. If there were atomic lines in your spectra and LTE is satisfied, you can use the Saha-Boltzmann plot ( ) to determine the electron temperature.
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We are looking for phosphorescent (not fluorescent) micro-particles as a model system for light emission measurements in the case of diffuse light sources. Ideally the lifetime should be of several seconds up to minutes, and emission should be in the visible. Commercial solutions are much less than for the case of fluorescent particles.
Thank you.
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Ciao Giovanni,
In our paper here you will see that its possible to tune the lifetime of the emission without necessarily sacrificing the brightness of the long-lived luminescence - we were targeting the seconds range:
Regards
Bryce
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Hello all....
I need an organic dye which will exhibit blue and red emission. Could you suggest any? DCM will show red emission whereas Coumarin C6 will show green emission individually.
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Please Suggest me how energy band gap influence the Photoluminescence emission peak ?
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Monalisha Mohanta When a semiconductor or a dielectric material is excited above the bandgap energy and as a result of relaxation, luminescence is observed is called photoluminescence. As a result of relaxation, if only photons are emitted, the bandgap will be a "direct" bandgap, while, if in addition to photons, phonons are also emitted, the bandgap will be an "indirect" bandgap. Since, the phonons emission is due to the defects, impurities, and dopants between CB and VB. When only photons are emitted, the relaxation is called radiative, while, when only phonons are emitted, the relaxation is called nonradiative. We can only find the bandgap energy from PL data in the case of radiative relaxation (direct bandgap). In nonradiative relaxation, when an electron passes its energy to the phonons, is called Shockley–Read–Hall recombination and when a relaxing electron passes its energy to another electron or hole is called Auger recombination. From PL data, intensity, line edge, and FWHM are the characteristics parameters i.e. higher intensity means low defect density and greater FWHM gives poor structure and vice versa. In addition to all the above, the energy bandgap calculation from PL data is subject to many limitations. For example, PL emissions do not give an exact bandgap like UV-Vis absorbance (Tauc plot). The bandgap calculated by the PL study will always be less than the original bandgap. Emission spectra are usually solvent dependent and are shifted with the change in solvent polarity due to solvent relaxation, the excitation spectra are usually preferred for bandgap calculations.
In the following video, I have explained all the above discussions in detail. Links to the files used in the Origin tutorial video have been provided in the video description. Thanks
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The paper shows "the corresponding emission spectra of blue and green FCP(fluorescent copolymer) at various excitation wavelengths showed that the peaks of emission spectra had nearly not shifted as excitation wavelengths change (Fig. 1C and D), which indicated good monodispersion of FCP in size and fluorescence."
But I don't understand why they are related.
As far as I know, isn’t the emission wavelength independent of the excitation wavelength?
So why it can mean good monodispersion of FCP in size and fluorescence.
Could someone can explain to me? Thanks!
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