Questions related to Arctic
I am attempting to express a Plasmodium gene which is extremely AT rich with several repetitions of the same. The peptide I am attempting to express is 506 amino acids long.It has 2 distinct overlapping domains(which i am trying to express together). However I have tried Ecoli BL21(24*C for 12hrs) and Arctic strains(12*C for 24hrs) but I have not been able to generate it. It has a C terminal 6x his tag and not being picked up by western blot. I am using pet24b vector.
I am new at these procedures and any help or suggestion from the community to shed light into this would be of immense help!
Respected all ,
I have been attempting to purify this protein (mol wt - ~17kda). The protein is being expressed in Arctic(DE3) E.coli cell. However I am having an annoying problem of impurities/contaminants, which I am being unable to remove. I am using TritonX100 in the lysis buffer(300mM NaCl, lysozyme, PMSF, 0.25mM arginine) to solubilize the protein. I perform IMAC and I use 100uL of Ni-NTA beads (which I wash with 50mM tris and 500mM NaCl) in the batch method, wherein I am incubating 30ml of the lysate at 4*C for 16hrs.
However the problem is there is a lot of other protein which come up in the elutes along with my protein of interest. Even in the post incubation wash (without imidazole). The sds-profile of flow through , beads and elute are pretty similar as if purification is not happening!
Any suggestion to purify my 6x-His tagged protein would greatly help ! I am using pet24b plasmid
Since 2001, warming increasing repeatedly as global average temperatures in 2015 were 1 degree Celsius or more above the 1880-1899. The rapid declining of Arctic sea ice both the extent and thickness, over the last several decades and retreating of glaciers i.e. the Alps, Himalayas, Andes, Rockies, Alaska and Africa around the world. Does pollutant or increasing GHG is the main reason for changing in temperature globally?
Our university project group is studying the possibility to apply a plan for the (local) restoration of ice based habitats of polar bears (Ursus maritimus). Has the idea already been developed in some way?
Hi, I'd like to try expression of reverse transcriptase with low temperature, 15 °C, due to solubility. Should I use some special plasmids for cold expression? I ordered cells for this purpose - E.coli Arctic express. Is it enough or is it better to combine these cells with plasmids for cold expression? Thank you all!
Before wanting to reduce emissions of greenhouse gas in particular, it is necessary to know the sources and the dynamics. This is what NASA researchers hope to do with a new 3D model that sheds light on the movements of methane in our atmosphere.
Methane (CH4). According to experts, this gas is responsible for 20 to 30% of the temperature increase recorded to date in the context of global warming. And researchers from NASA (United States) are today presenting a new 3D tool intended to visualize the diversity of sources of this powerful greenhouse gas and to track its concentrations and its movements in the atmosphere.
Remember that the global warming potential (GWP) of methane is 25 times greater than that of CO2. And that the sources are numerous. Methane is emitted when fossil fuels such as coal, oil or gas are used. But the oceans also emit methane. Just like wetland soils or agriculture. Rice cultivation, in particular, as well as animal husbandry. Overall, "it is estimated that up to 60% of the current methane flow from the earth to the atmosphere is the result of human activities," said Abhishek Chatterjee, researcher, in a NASA statement. But it remained difficult for scientists - due to a lack of measurement and understanding of feedback phenomena - to predict future trends.
To solve this problem, NASA researchers collected data from emission inventories, field campaigns and even satellite observations. Data they have injected into a model that also estimates emissions from known natural processes. And which also simulates atmospheric chemistry which breaks down methane. Then they added a meteorological model to visualize the path of methane in our atmosphere.
A wide variety of methane sources
The proposed 3D visualization highlights the complexity of the question. It illuminates the movements of methane in the atmosphere according to the landscapes and the seasons. It also shows that high altitude winds can transport methane very far from its sources. It also highlights some specific regions in this area.
Thus 60% of methane emissions come from the tropics. Particularly because the Amazon basin and its wetlands seasonally create, when flooded, an environment low in oxygen and therefore favorable for emissions.
Europe, on the other hand, seems rather preserved. It is the only region that has experienced a decrease in emissions over the past 20 years.
In India, rice and livestock are the main sources of methane emissions. And it is mainly the management of livestock and agricultural waste that currently results in the region, an increase in emissions of 1.5% per year. More generally, in Asia, more than 85% of methane emissions are due to human activities.
Conversely, in the Arctic, more than 70% of emissions are of natural origin. But high latitudes still appear to be responsible for 20% of total emissions. And researchers are concerned about the greenhouse gases that warming soils could release into the atmosphere.
WHAT YOU MUST REMEMBER
Methane is a powerful greenhouse gas.
NASA today offers researchers a new tool for studying the behavior of this gas in our atmosphere.
It already reveals some great patterns.
For example, I know that FWI has been adapted for Mediterranean forests (DOI: 10.1007/s11069-014-1397-8). Do you know similar studies for Arctic regions?
Last Tuesday (8), exactly on World Oceans Day, the US National Geographic Society cartographers decided to present planet Earth with another ocean by adding the Southern Ocean, which surrounds Antarctica, to its four "brothers" older Atlantic, Pacific, Indian and Arctic.
According to Seth Sykora-Bodie, a marine scientist at the US National Oceanic and Atmospheric Administration (NOAA), while it's hard to explain what's different about the region, “everyone will agree that the glaciers are bluer, the air cooler, the mountains more intimidating and the landscapes more captivating than anywhere else you can go,” he told National Geographic.om another ocean by adding the Southern Ocean, which encircles Antarctica, to its four older “brothers” Atlantic, Pacific , Indian and Arctic.
NOAA's official geographer Alex Tait also spoke to the NatGeo website, explaining that official recognition just didn't happen before because “there was never an international agreement”. “It's kind of a geographic geek in some ways,” he summed up. But as of June 8, 2021, the nerd is over: the Southern Ocean is officially the fifth ocean on Earth.
Although the difference between sea and ocean is clear, the size, it is still difficult to say exactly what an ocean is, other than to repeat that they are more extensive liquid masses (the smallest of them is 73 million square kilometers) and deeper. The Spanish navigator Vasco Nuñez de Balboa already recognized, in the beginning of the 16th century, that those waters at the bottom of the world were the "Antarctic Ocean".
Looking for informative maps of ice compression and vessel besetting in the Arctic area – to use in the presentation. Is anyone aware of such maps – for the whole Arctic Area or local areas?
Thanks in advance for possible advices and discussion.
I'm recently doing the research on the impacts of smouldering in the arctic, but due to the travel restriction, I'm doing this remotely. My current issue is to identify the smouldering from satellite data, distinguish it from general wildfires. Does anyone know any method which can allow me doing this?
I know, the question is a bit simplistic. It is also not only about the plants, but more about the photosynthetic organisms ... However, in this time of global biodiversity crisis, we are constantly confronted with prioritizing. Recently I read somewhere that in the Arctic, the photosynthetic algae should be taken care of and not the polar bears. Also in temperate regions, where the habitats are under enormous pressure, shouldn't we pay the greatest attention to the producers/plants? On the local level (local administration, journalists) I am constantly confronted with the question: who do we save first? With this somewhat provocative question, I simply wanted to know/hear what researchers from various fields will say about it (or against it).
I am doing research paper Russian geopolitical interest at Northern sea route. .Soviet and Arctic had long history from 1930, exploring naval base by Arctic circle as today research develop nuclear icebreaker development experiment of raw materials, fisheries, oil etc. EurAsia trade with China and other as one of reason Russian economy is rebuilding,, but in long run Russian could benefit from climate change. I want discuss different opinion, fact and point some problem it could face problem with other global players.
Looking for a good source of information on strong and extreme winds in the Arctic (monthly values, annual extremes etc.). The form of maps (with isolines) will be most interesting (atlases? papers? reports?). Your kind advises will be highly appreciated, thanks in advance.
With the best regards,
This a special question to the naval architects / shipbuilders.
Looking for some tentative estimations of the possible increase of the cost of the vessel built in accordance to be able to operate in the Arctic/Sub-Arctic in comparison to the vessel of the same dimensions/purpose intended for use in the moderate conditions and having no “winterization package”. What could be the cost differences between these two vessels?
I’ve heard about “+30% of cost”, need clarification of this estimation.
Thanks in advance for possible discussion and your opinions.
I am starting a project to compare different meteorological sensors for austere sites (no power, and little solar or wind availability). I know battery performance is a topic I will have to cover, and at this point I have sensors running on NiCd, Li-Ion, and lead-sulphate battery technology. So far most sources focus on only one battery type usually applied to hybrid or normal cars. The internet has some information, but looking for a/some citable articles.
- During the daytime, shortwave net radiation is greater than 0 due to albedo is less than 1. If all-wave net radiation shows negtive value for Arctic, Greenland, and Antarctic area, it indicates surface energy is being lost throughout the daytime and night. Is this correct? If so, how to explain it?
- Anyone konw this issue, thanks a lot for your reply.
While working in the Subarctic of Western Siberia, we noticed that in places of active thermokarst the biological productivity of vegetation increases. Plants that are absent in nearby ecosystems with stable permafrost grow in thermokarst-affected ecosystems. Thermokarst is usually associated with human influence. What are the typical responses of productivity and biodiversity to the effects of thermokarst in your research area? Why does thermokarst increase vegetation productivity? Is this a thermal effect? Is this the effect of increasing soil fertility? Is this the effect of reducing competition from indigenous zonal flora? Or is it a complex of the listed reasons?
I am attaching a photograph of the community on the thermokarst slope and a photograph of a typical tundra (latitude N70 °).
A vessel has cracks and pitting in bridge windows. The vessel operatures in extreme climates, hot and cold, from arctic to Equatorial. Looking for failure predictions.
I am currently working on my PhD, and need some background information on the shore-line chronologies related to archaeological cultures and sites in the northern Fennoscandia. I would like to ask the community, if any could give some good references on the subject: a) basic works on the shore-line chronologies and archaeology, and b) new research on the same issues in the coast of Norwegian Arctic Ocean (and Varanger Fiord) and in the coastal Kola Peninsula, Barents Sea and also the White Sea.
We are replacing an old CN analyzer in our communal lab and are reaching out for any recommendations on equipment. Ease of use, purchase and maintenance cost, and reliability are our main criteria. The soils will range from mineral agricultural soils to organic soils from the Arctic. Thanks!
Any data science and/or remote sensing experts have any insight pertaining to multivariate regression and deep neural networking with large feature set inputs and variable temporal data holes necessary for my dissertation work regarding climate change in the Arctic? I would greatly appreciate the feedback!
As an aside, I have utilized feature and stepwise extraction, most NaN mitigation methodologies, and VIF to mitigate multicollinearity prior to training. I’m simply seeking a deep learning solution that integrates all possible data to generate the best model.
Chemical analysis of layers of ice (arctic, antarctic) revealed evidence of climatic changes occurring long before human started polluting our planet-
No. It is not impossible with the REAL & EXACT Pi Value.
The present 2000 year old polygon based so called pi number ; 3.1415926....is NOT PI NUMBER. ( for example all birds can not cross ocean although they appear same . Only one bird Arctic Tern can cross a ocean So, Real Pi is an Arctic Tern ).
Further real Pi is an ALGEBRAIC Number.
Hence, we can get the square root of Pi.
Pi is a geometrical constant. Its official value is 3.14159265358… March 1998 discovery says Pi value is 3.14644660941…. With the official number square root of Pi and squaring of circle are impossible. With 3.14644660941… root Pi is possible and squaring a circle is also possible and done in this paper.
We collected samples from the Arctic and need to get an idea about the best culture media that could be used to purify and culture the green algal components.
For cyanobacteria, we regularly use the BG11 medium but it will be great to have some advice for green algae.
I am looking for data to reproduce a figure similar to Fig. 2 in this paper: https://www.researchgate.net/figure/Circulation-patterns-for-Arctic-and-Northwest-Atlantic-oceans-a-Map-of-Arctic-ocean_fig1_235005148
Does anyone know where such data could be available?
Russian discovery of five Arctic islands and the death of the first Icelandic glacier, Okjökull, are two recent observations for the melting ice in Polar Regions of the earth.
I would like to discuss this matter with RG members.
For my project looking at the biodiversity of phytoplankton in the Arctic, I have calculated Hill numbers and Average Taxonomic Distinctness on my samples, and they both tell very different stories so I would like to include them both. I am just stuck as to how I can justify using both, and if I can't, how do I choose which one to include? Has anyone else ever had a similar decision to make?
I will appreciate if someone can help me to identify larvae of Polychaetes I found them in zooplankton samples quite frequently. This sample is from Amundsen Sea. Aslo I will be very grateful if someone can share an identification key or taxonomic guides how to identify polar polychaetes. I also have more pics from Arctic and Antarctic region and I need key for both Poles.
Thank you in advance very much,
I'm interested as to why the arctic climate is changing faster than anywhere else? Can anyone mention any mechanisms or theories behind this (apart from the albedo effect) or recommend any papers?
I'm looking for climate change projection data in raster format. Something like is shown in the IPCC 5th report chapter 12.
In particular I'm interested in the Arctic, temperature, precipitation and permafrost. I've had a look at the IPCC data centre and a couple of other online data portals, but without much joy.
Does anyone have any suggestions?
Is burst of polar vortex the culprint behind the abnormal cold weather in US and Canada? Is this linked to the last summer heatwave? Is this alternating severe weather between heatwaves and coldwaves likely to continue under climate change?
I am looking for remote-sensing product that would give the date (day of year) freezup and breakup for pixels (~5 km resolution) in the Arctic. Before calculating it myself, I would like to know if such product is already available.
I wonder whether anyone has used aphid traps in the high Arctic, showing that they make short flights and may transmit non-pers viruses? I have found papers on their presence in Arctic, i.d., etc, but not on their movement. Any info gratefully received. Kind regards. Adrian (Gibbs) I'm an ancient virologist trying to guess how PVY got to North America
the Arctic Council, made up of the eight nations with territory above the arctic circle. issued an 1800 page report on climate changes in circumpolar regions, representing four years of work by more 300 scientist. the report warned that arctic regions are warming.
I am looking for a PDF of the paper 'Estimation of wind loads on ships in wind with a strong gradient', proceedings of 14th international conference on offshore mechanics and arctic engineering, by Werner Blendermann, as input for a discussion on the influence on wind field shape in wind tunnel on wind coefficients and their application.
Many thanks in advance,
So, I am facing a kind of weird problem here.
My SWAT model is situated in a nival, Arctic catchment, and significant percent of it's recharge in summer is snowmelt/icemelt.
When I was building the model, and my only water input was precipitation, the discharge output was completely different than observed values (maybe not completely different... but definetely too small).
To "fix" this problem, I used "point source" option in ArcSWAT to "imitate/mimic" few main subglacial outflows from the glacier, which are main recharge sources in the ablation season.
After doing that operation, FLOW_OUT looked much better, but now, I have the problem with calibration in SWAT-CUP.
Almost every parameter I check with the "one-at-a-time" analysis, seems to be not sensitive.
Charts look like the one attached (this example is for CN2).
Discharge charts looks good, indeed, but still baseflow and peek flows are too low compared to observed, field data.
I tried using parameters from the article suggested by Dr Karim Abbaspour (https://www.sciencedirect.com/science/article/pii/S0022169415001985) and none of them seems to be sensitive.
Any advices are higly appreciated.
i am trying to clone and express M. tuberculosis protein in E. coli arctic express cell line.
i got expression in soluble fraction(40%) during small scale expression test but continuously i'm getting problem in purification.
my protein of interest is fused with n-terminal his-tag followed by MBP.
i tried ni-nta, batch binding for 6 hrs at 4 degree Celsius and but when i ran 12%sds page, 90% protein eluted in sample flow, elution had most of the other bands.
when i did binding with maltose resin it was the same situation.
again, my 80% protein of interest was going in sample flow.
thereafter i dissolved Sample flow in 8M urea,again did ni-nta still the protein was in sample flow.
why my protein is not binding to resin?
should i go for codon optimization to get protein from commercial firms?
size of protein 43kda
fusion tag- MBP 43kda
n terminal his tag
complete size 86kda
These were caught in June 2017 in the Arctic Fram Strait (74°N, just south of Svalbard) within the upper 50m (DCM).
The complete catch (vertical Bongo 500um) consisted of intensively red C. finmarchicus C5 individuals. I am new to researching copepods, but could not find an explanation of this. Does anyone know something more on it? Further North (a few days later), they were typically coloured again.
The results of 2016 expedition of N. Shakhova and I. Semiletov group in East Siberian Sea were published in March 2017. From drilled samples they concluded that the subsea permafrost melts up to 15 to 20 cm pro year. They observed the methane emissions with the largest flows in range of more than 1 kg/m2 daily. They estimate that the entire surface with similar emissions occupies already 10 % of East Siberian Sea, that means from 50.000 to 200.000 km2.
If the hotspots include 10 % of the entire ESAS surface, 200.000 km2 and on this surface, at the estimated quantities 1 kg/m2, we calculate annually emissions, we get 70 Gton. This is today 14 times more in one year, as it is (it should be) the entire methane quantity in the atmosphere (5 Gton). At lower surface margin we get approx. 20 Gton.
And if we stay at before 5 years measured real 200 g/m2, this gives on the estimated hotspot surface 5 times smaller annual quantity of emission, 14 Gton. Already this is almost 3 times of the entire "current official" methane quantity in atmosphere (IPCC).
Take into account that methane is in short time, because its atmosphere concentrations are only rising, 150 times stronger as CO2, and that these today's emissions are already doubling the entire Earth's greenhouse effect. The only solution to save the life on this planet, is to prevent these emissions, to capture them, to use THIS METHANE instead all other fossil energy. How much time do we have ??
I am trying to express and purify a 60kDa, His10-tagged, recombinant protein containing 10 methionine residues, which I think may be causing the productions of multiple N-terminal truncated species during expression. My initial expression was at 37C, which may have resulted in a rapid expression resulting in the multiple truncated species. With that in mind, my plan moving forward was to try to decrease temperature using the same cell line as before, and if that does not help, transforming my plasmid into Arctic cells which contain the Cpn60 chaperone protein.
Any additional suggestions for methods for minimizing truncation during expression would be greatly appreciated.
I'm looking for examples of Community-based economic developement project in the Arctic. I know well the Canadian context but I'm looking for examples in Alaska, Greenland, Russia and in the Nordic Countries.
We are recruiting two M.S. or Ph.D. students to work on Arctic and agricultural ecohydrology, ecosystem ecology, and expert assessment. We would like to reach the largest possible audience and wanted to know what listservs or venues you subscribe to. Thanks!
Yes. Observations show a global-scale decline of snow and ice over many years, especially since 1980 and increasing during the past decade, despite growth in some places and little change in others. Most mountain glaciers are getting smaller. Snow cover is retreating earlier in the spring. Sea ice in the Arctic is shrinking in all seasons, most dramatically in summer. Reductions are reported in permafrost, seasonally frozen ground and river and lake ice. Important coastal regions of the ice sheets on Greenland and West Antarctica, and the glaciers of the Antarctic Peninsula, are thinning and contributing to sea level rise. The total contribution of glacier, ice cap and ice sheet melt to sea level rise is estimated as 1.2 ± 0.4 mm/yr for the period 1993 to 2003.
I have some references for carbon pools/stocks in these soils (eg. Tarnocai, Koven, Hugelius etc), that I guess are based on the area, but for some reason I cant seem to find the actual area itself..
I was wondering if there were any publications or data available on the different sea ice zones in the eastern Bering sea and the timing of their formation throughout the year. I'm particularly interested in the types of sea ice found within approximately 200 to 300 km from mainland Alaska. Anything on sea ice in the Kuskokwim Bay would be a bonus. Many thanks. Edouard
We would like to put collar on foxes in the Arctic. T°c can reach -35°c. We need a GPS logger that can resist to those extreme T°c, a drop-off system, and a VHF unit to be able to find the collar again. Foxes are not easily trappable many times. The best, I think would be to have a WiFi tool on the GPS unit that could send the data on an external logger that we could set up on the dens for example, so that most data are safe. Has anyone does that before? If yes what material have you been using?
Thanks for your help
With the large amount of current research in to the reduction of sea ice in the Artic, has anyone written any paper or conducted further research into the impact of increased shipping traffic preventing the formation of new ice?
This is not my speciality, but is of great interest.
I'm a marine researcher with Fisheries and Oceans Canada but I holiday/temp-work aboard private exploration mega yachts. We have a lot of phenomenal amateur footage (still and video) coming out of the Arctic (recently from two successful passes through the Northwest passage). For example, photography of 42 different polar bears.
Could this be of use to anyone's project?
For example, see the short doc: https://youtu.be/A1Qx8U6mu6A
Dr. Du Preez
In our ongoing research of Siberian ice-wedge polygon mires (http://www.pimdeklerk-palynology.eu/html/polygon_mires_-e_siberia-.html) I am currently working on a rather clastic profile from the Lena Delta that shows clear signs of cryoturbation in various profile trajectories.
Of course the pollen data does not provide much information on the local vegetation development because of considerable homogenisation of the material, but I hope that it reveals some insights in the effect of cryoturbation on the sediment and pollen record, since it is also an important process of ice-wedge polygon development.
So now I am searching for other pollen data of such disturbed soils, but I have not yet found much.
Does anybody of you perhaps know of studies that I could use for comparison?
Thanks and best wishes from Karlsruhe,
I am trying to investigate on iceberg water. Why it is acidic (pH 5) and also what all tests I can carry out for better understanding of iceberg water. Any suggestions?
By chance I recently found out about the project "The Changing Arctic Ocean: implication for marine biology and biogeohemistry." After reading the description of the project, I realized that it was very content coincides with my scientific activities. I have for many years engaged in the problems of changes in the biochemical regime of the Barents Sea, the relationship of these changes to the climate and biological processes in the Arctic. My Institute has the most complete in the World hydrochemical data base in the western Arctic. Potentially, we have the information in order to model the details of climate change, biochemical and biological processes in the Barents Sea over the last 50 years. Unfortunately, my institution and I personally do not have scientific contacts with scientists from the UK. Consequently, I could not find an opportunity to participate in the project.
If any of the participants in the project will be of interest to cooperate with me and my institution, I am ready to discuss the possibility.
I tried to draw the Arctic arrows(set mproj nps) of u & v winds using the grads.
Data is NCEP/NCAR R1 regular grid 144x73, but it looks complicated.
Because, higher latitude of grid is continuously smaller and arrow spacing will be smaller from low to high latitude I think. Skip function was not helpful in grads.
If someone who know how can we draw Arctic arrows to be regular, please help me for this problem.
I am looking for a threshold levels of Hg in muscle or liver of the seabirds.
I found the publication of Dietz et al (2013) that provides information for eggs, but not for muscle of liver. Also the chapter in Demore et al (2005), but they do not present too much information for Hg in liver and muscle.
Dietz et al. (2013) What are the toxicological effects of mercury in Arctic biota?
Science of the Total Environment.
Demore et al (2005) Biological effects. AMAP Assessment 2002 : Heavy Metals in the Arctic 2005.
My question is specifically about the Arctic Ocean, not permafrost, not tropics, not global data. Also I need not just data (they are available), but analysis of satellite data, validity, etc for specifically Arctic Ocean.
I am using Modis visible subsets and swath images with 250 m and 500 m resolution to visually characterize the occurrence of sea ice leads for specific regions in the Arctic.
Unfortunately the Images prior to 8 May 2012 are not available at the NASA websites anymore due to a hard disc failure and no solution of the problem is expected for the near future. Therefore I am looking for satellite imagery that is highly enough resolved to distinguish single sea ice leads.
My study period is March to April 2012. The regions are in the western Arctic north of Svalbard, Greenland, Ellesmere Island and in the Beaufort Sea.
Any suggestions about where to start to get the most recent breakthroughs? I am giving a presentation to the Tundra Conservation Network. When at AGU last month I already found some good leads but I wanted to test this scientific social network to see if I could really benefit from it!
Provided that polar regions are dense in carbon, and ice and snow have relatively low bromine content, where does this large content of bromine, which is significantly responsible for the depletion of ozone in the lower atmosphere, originate and how? Also, given that there are different types of reactivity for halides as compared to OH and ozone, is there a correlation between the type and amount of reactive halogen species to the ODE (ozone depletion event) rate?
Just recently (April 26, 2013), scientists have been studying the excessive release of the element bromine in polar regions, indicating that this element comes from snow and ice. However, the bromine content of snow and ice is relatively low and although the whole polar ice cap releases bromine in the lower atmosphere, it is still not enough to cause severe depletion of the ozone. My question is, where do these large amounts of bromine in the lower atmosphere come from considering that polar regions are dense in carbon and not in bromine. It is interesting for me since bromine compounds are considered significant contributors to the depletion of ozone in the lower atmosphere, which is one of the most contentious topics in ecology.
Also, how are salts transported from the ocean and oxidized to become reactive halogen species in the air? And let's say, bromine explosion is a natural occurrence, and there are different reactivity of halogens as compared to OH and ozone, would the effect on the ozone be better or worse if other halogens, such as chlorine and iodine, are activated through mechanisms which are coupled to bromine chemistry?