1

General Science / Is there any quick Probabilities tutorial?

« on: 07/07/2022 11:24:51 »

Hello

Is there a good quick tutorial on probabilities?

If you combine two independent events with an AND condition you multiple their probabilities.
If you combine two independent events with an OR condition you add their probabilities.

However, if you roll a dice, there is a 1/6 chance to get number 6. If you do get a 6, next time when you roll a dice will it again be 1/6 probability? What about 1,000 times?

Are there also any other concepts that are very common/funtamental and should know?

Thanks!

2

Physiology & Medicine / What is protein priming?

« on: 21/06/2022 23:38:37 »

Hello

What is protein priming?

Thanks!

3

Chemistry / Re: KM, Turnover, kcat/KM values: how to translate them into reaction rate?

« on: 11/06/2022 22:45:23 »

Thanks, it is indeed homework-like but I am not in format education anymore.

I am just looking for the equations or one of these nice online calculators if they exist.

The challenge I face are:
1) choose the right property
2) find the right equation as I mostly find definition equations (ok I suppose that is a starting point)
3) navigate the definition restrictions (e.g. kcat/KM seems to work only in specific relative concentrations)
4) as you pointed, find the right units because I need absolute conversion rates e.g. moles per minute or grams per minute and not something relative (at least without knowing how to link it)

The stoichiometry is first order, ie. one substrate converted by one enzyme to give one product (and another one but ok). Now if this happens in one step or multiple is something I don't know but I can bare that approximation.

4

Chemistry / KM, Turnover, kcat/KM values: how to translate them into reaction rate?

« on: 11/06/2022 02:35:13 »

Hello!

I know for an enzyme the below as well as the stoichiometry of the reaction:
1) KM Value
2) Turnover Number
3) kcat/KM Value

I need to know how much substrate will be converted per minute for a given substrate concentration.

Which is the right value/number to use and how?

Thanks!

5

Chemistry / Re: Are there solvents that do not evaporate quickly?

« on: 17/05/2022 21:58:01 »

Thanks, ideally it should not evaporate at all up to e.g. 40C. Is there any solid/semi-solid/gel? I need it not to escape the container, something like jelly beans or emulsion/Voltaren?

6

Chemistry / Are there solvents that do not evaporate quickly?

« on: 17/05/2022 12:55:23 »

Hello

Do you know any solvents that do not evaporate fast? Liquid, solid or gel etc but with small molecule diffusion coefficient similar to water.

Thanks!

7

General Science / Re: How can I colour a solution that contains a specific antigen?

« on: 31/12/2021 00:50:49 »

One type bonds the antibodies to gold nanoparticles, which change colour.

Another type bonds the antibodies to fluorescent jellyfish protein; illumination with UV light makes it glow.

Thanks but I don't really understand how it actually works?

If you want to detect an antigen in a solution and you add to the solution, antibodies that have a dye attached to them, the solution will be coloured anyway?

Unless the colour is created or changes only when the antibodies are attached to an antigen and not if the antibodies are on their own?

8

General Science / How can I colour a solution that contains a specific antigen?

« on: 30/12/2021 01:51:58 »

Hello!

I am not very clear on how immunochemical dyes work.

Is it possible to colour the presence of an antigen in s solution?

How does that work?

What happens after the antibody binds to the antigen and how colour is generated?

Thanks!

9

General Science / Statistical analysis to assess forecast

« on: 13/10/2021 22:55:11 »

Hello!

I am given two different forecasts and at the end of each day, I get the numbers of what actually happened.

What analysis can I use to compare these two forecasts on how well they predict?

I was thinking regression or ANOVA but I don't think they will work because the mean variance will be zero if day by day, the forecast predicts +20% then -20% then +20% etc.

I need to know how many times each forecast is off and by how much on average.

Next, I need to combine the forecasts with a formula to improve the predictions, is that possible?

Thanks!

10

Technology / Is there a gel or tape that will stick to wet cellulose?

« on: 16/06/2021 10:51:29 »

Hello

Is there a gel or tape that will stick to wet cellulose?

Thanks!

11

Geek Speak / Does an average divided by the total make sense?

« on: 13/06/2021 17:14:14 »

Hello

We have a factory with workers who process process potatoes.

When the factory is loaded with 1,000 potatoes, the workers take 1h to process a potato on average.

The next day, the factory is loaded with 1,200 potatoes and the workers take 1.2h to process a potato on average.

As you can see, the performance of potato processing as expressed by the average time to process a potato depends on the loading of the factory with potatoes.

However, the average processing time of a potato divided by the number of loaded potatoes stays the same at 0.001h/potato^2.

Does the above metric make sense and can it be used to assess the productivity of the factory after you exclude the effect of its potato loading? Is dividing an average with the total number of units a valid metric to compare the average between days of various total numbers of units?

If you do not use this metric, you will say that the second day, the processing time of the factory was 1.2h/potato which is 0.2h/potato less than yesterday so you will be worried that the performance has dropped and there is an issue while in fact it can be a 'natural' drop of performance due to higher load and no other issue would exist.

Any ideas?

If the metric makes sense, what are the implications if the relationship between loading and the average processing time is not linear?

Thanks!

12

Geek Speak / Re: Why the median does not change?

« on: 13/06/2021 14:44:23 »

Another thing that might help us answer is if you tell us what you plan to do with the "answer" you get.

I want a KPI to measure the significance of delays in the total journey time of the fleet.

E.g. delays (taking into account the magnitude of the delays and the number of planes that were delayed) accounted for 5% of the journey time.

If this KPI goes to 10%, I will know that delays were more significant part of the journeys in total.

My question is mathematically, what is the most accurate way to measure that?

Average delay across the fleet divided by average whole journey time?

Median delay across the fleet divided by median whole journey time?

Total minutes of delays divided by total total minutes of whole journey time?

Would the first and third give the same result?

13

Geek Speak / Re: Why the median does not change?

« on: 12/06/2021 21:43:26 »

Thanks for your replies.

To make more clear what I am looking for, imagine any type of distribution of a graph between number of planes vs journey time for one day and another graph like this for another day two.

We want to compare the two distributions to see how much more delay we had in %. Obviously, this % will be based not only on the magnitude of the additional journey time for each delayed plane but also the number of planes with additional journey time. E.g. we can have 1,000 planes delayed by 1h but we can also have 100 planes delayed by 30h or anything else. This dual effect is what I am trying to capture and I am looking for the most accurate analysis to do that which will be as presentative as possible without the risk of skewed results.

1) One way to analyse this, is to take the average of day one and day two and find the difference. Would that be accurate given than the average may not be a good overall approximation for every distribution and given that the distributions of day one and two may be very different?

2) Another way to analyse this, is to take the median of day one and day two and find the difference. Would that be accurate given than the median may not be a good overall approximation for every distribution and also it may be too insensitive to outliers or distributions with two peaks etc?

3) A third way to analyse this, is to calculate the area under the graph by multiplying the number of planes times their journey time for day one and day two and find the difference.

Do all the above three ways give the same result? If not, which is the most accurate especially if we want a result for almost any type of possible distribution?

Or is there any fourth better way?

Thanks!

14

Geek Speak / Why the median does not change?

« on: 12/06/2021 18:41:59 »

Hello

Let's say we have 10 airplanes going from city A to city B on the 1/1/21.
Let's say all the 10 planes take 5h each for the journey.
The median journey time will be 5h.

Let's say the same journeys happen on the 2/1/21.
Now the 8 planes take 5h each and the rest 2 planes take 8h each.
What is the median journey time?

What metric would calculate the total transit time impact of the 2 planes which were delayed for 3h each?
Especially when we have a distribution of thousands of airplanes with many outliers where the average can be skewed?

Thanks!

15

Geek Speak / What is the power of regression?

« on: 04/06/2021 19:36:08 »

Hello

Regression is used to elucidate the relationship between two factors.

If we simply graph those two factors we can see the line and identify their relationship.

What is so special about regression that is so widely used then?

16

Cells, Microbes & Viruses / How does norovirus causes loss of taste?

« on: 16/05/2021 21:35:13 »

Hello

I read on Wikipedia that norovirus can cause loss of taste but I was not able to find more information.

Any idea?

Thanks!

17

Physics, Astronomy & Cosmology / What is the maximum solubility of a substance?

« on: 16/05/2021 21:34:05 »

Hello

What is the maximum solubility of glucose oxidase in water?

I read various numbers like 0.2 or 5 mg per mL water but I wander if that is only it?

Also, are there any ways to increase solubility?

Thanks!

18

Technology / Is there a device to freeze my drink asap?

« on: 27/02/2021 18:04:44 »

Hello

Is there a device to freeze my drink asap?

I drink cold beverages that are produced hot so it takes almost an hour to cool it properly!

For small budgets ideally.

Thanks

19

Physics, Astronomy & Cosmology / Can you simply explain ion exchange?

« on: 07/02/2021 13:07:26 »

Hello

Can you explain in simple words what is ion exchange?

I cannot figure out from wikipedia, is it resins that are conductive to specific ions under voltage or that contain specific ions which can adsorb other ions under specific (what?) conditions?

After use, do ion exchange materials get saturated and need regeneration?

Thanks!

20

Physics, Astronomy & Cosmology / What is electro-osmotic flow hysteresis?

« on: 07/02/2021 12:30:23 »

Hello

Can you explain please what is electro-osmotic flow hysteresis?

Thanks