1

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!

2

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!

3

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!

4

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!

5

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!

6

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!

7

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?

8

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!

9

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!

10

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

11

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!

12

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

13

Chemistry / What is the relationship between enzyme activity and substrate concentration?

« on: 24/01/2021 12:26:53 »

Hello

If an enzyme converts 1umol of substrate per minute when the substrate concentration is 1mM, what will be the conversion rate when the concentration is 0.1mM?

Is there a quick calculator for that?

Thanks

14

Physics, Astronomy & Cosmology / How do indoors diesel heaters handle exhaust gases?

« on: 23/01/2021 12:37:26 »

Hello

How do indoors diesel heaters handle exhaust gases?

I am puzzled.

Thanks!

15

Physics, Astronomy & Cosmology / How can I calculate the force needed to rotate an object?

« on: 18/01/2021 18:36:34 »

Hello

If an object is hanging, how can I calculate the force to just start rotating it with minimal velocity?

Assuming no friction or any other obstacle from where it hangs.

Thanks!

16

Technology / What are the methods to reverse a rotation?

« on: 13/01/2021 19:41:31 »

Hello

if something rotates clockwise, how can we use that rotational movement to make something else to rotate anticlockwise?

What are the available methods for this?

Thanks!

17

Chemistry / Can enzyme act as ligands?

« on: 11/01/2021 09:14:47 »

Hello

Can enzymes be used to bind specific molecules without converting them?

Thanks!

18

Physiology & Medicine / Is something injected in the subcutaneous tissue passing through the liver?

« on: 09/01/2021 14:58:46 »

Hello

If something is injected in the subcutaneous tissue, will this pass through liver?

As I imagine it, it will be injected into the interstitial fluid of the subcutaneous tissue. It will then flow into the lymph or vein blood and then into kidneys to be excreted.

Would it pass through the liver first and then the kidneys or the opposite?

Thanks!

19

Physics, Astronomy & Cosmology / Is ΔG° released in full?

« on: 29/12/2020 09:56:51 »

Hello

Methane oxidation has a ΔG° of 121 kJ/mol.

Does that mean that if I burn 1 mole of methane at room temperature, 121 kJ of heat will be released in the room?

Or it will be less or more because some energy will be used for the reaction or the kinetics of the molecules?

Thanks!

20

Physics, Astronomy & Cosmology / How does oxygen limits water based reactions?

« on: 24/12/2020 18:50:42 »

Hello!

For reactions that occur inside water solutions and have oxygen as one of the substrates, how much does oxygen limit these reactions?

Oxygen inside water is normally very low and also the oxygen from the atmosphere does not easily diffuse inside the water to replenish any consumed oxygen.

Can you help me please estimate what is the bottleneck that oxygen poses for oxygen consuming reactions inside water solutions?

Thanks!