Cells Definition and 429 Threads

Yesterday, http://news.yahoo.com/authorities-3-swept-over-waterfall-presumed-dead-180056413.html" when they were washed over Vernal Falls. My first reaction was sadness for the families but, after reading the story of how this happened, I have to wonder how blatently stupid some people can be...

Hi! I came across the concept of endosymbiosis being the way by which eukaryotic cells evolved and that all cell organelles are remnants of prokaryotic cells that lost their ability to survive independently. Is this just speculation or is there a solid scientific basis to this claim? Can anybody...

Hi, I'm currently an undergraduate engineering student and am doing research for the summer writing programs to help analyze and study cell motility and cooperativity when introduced to certain growth factors. For specific growth factors there is a noticeable swarming movement amongst...

what is the Effective emf of 2 cells with zero internal resistance connected in parallel (E1>E2)

Hey folks not sure if this is the right section but I'll give it a go... I'm trying to out find out what percentage of photons a solar cell (preferably gallium arsenide solar cells) will absorb, reflect and diffuse. I have read, from a few links, that the highest absorption rate for silicon...

I've heard that losing weight does not decrease the number of fat cells your body contains. But does this number decrease if you maintain this lower weight over time? I'm thinking that over time, the fat cells die and are replaced at a lower rate.

Hi, I am sorry if this is in the wrong place. I had an idea of using Polymer-fullerene solar cells (http://en.wikipedia.org/wiki/Konarka_Technologies#Polymer-fullerene_solar_cells) in Mobile phones to recharge its battery using Indoor lights. But , unfortunately, these cells are of...

"In chemical signaling, adaptation enables cells to respond to changes in the concentration of a signaling ligand (rather than to the absolute concentration of the ligand) over a very wide range of ligand concentrations. The general principle is one of a negative feedback that operates with a...

Hi, I'm new to this forum so please don't get mad if this post is in the wrong place. I have a laser beam pointed at a solar panel (regular PV cells) and the current comes out as expected on my oscilloscope (small waves varying like pulses between 0.45 and 0.50 V regularly). I tried...

:bugeye: http://www.pnas.org/content/107/40/17194

Ok so I understand how a voltage source works, with electrons flowing from a high potential to a low potential. But I'm a little confused about solar cells. So the way they work is that an incoming photon strikes an electron and gives it enough energy to break free and create a current. But...

hi, I am working on a small solar cell project for which i bought two small solar cells panels of 6volt each producing current of 5.263milli ampere in combination. I want to know that how can i calculate the values of solar cells output in kwh, on the output i have placed two bulbs of 3 volts...

In an electrochemical cell involving copper and magnesium copper gains electrons (is the oxidant) and Magnesium the opposite. I understand that Cu is the least reactive of the two electodes and therefore the Mg gives up electrons to stop the Cu from oxidising, but why does this difference in...

http://www.physorg.com/news/2011-04-solar-power-cells-hidden-magnetic.html

Homework Statement Find the Voltage across A B in the following circuit. Each cells has negligible internal resistance and an EMF of E volts. (First diagram in the attached picture) Homework Equations I'm trying to use Kirchoff's second law. The Attempt at a Solution Now, if I...

someone just asked this as a comment on an article i was reading http://home.howstuffworks.com/fluorescent-lamp6.htm 'Does a phosphor powder give off a photon or electron when struck by light?' I was just thinking maybe a solar cell made of phosphor powder to emit electrons. I...

I am looking into the possibility of getting a PV array fitted on my roof and taking advantage of the (ludicrous) Feed in Tarif scheme that the UK government is offering. A bloke came around and we looked in some charts to find the likely yearly yield and there are some issues of partial...

Is the gibbs free energy of some reaction in an electrochemical cell dependent upon reactant concentration? The Nernst equation clearly states that open circuit potential is dependent upon concentration, and basic thermodynamics states that open circuit potential is directly proportional to...

my understanding is that energy is wasted in a solar cells when light with more frequency than necessary to make an electron cross the band gap comes along and the excess energy is converted to heat. does this mean if you only shined blue light at a solar cell which had a perfect electron gap...

Do our body cells have their moments or are they in the official mood all the time? building proteins, sending signals etc etc. I am not able to clearly say what their moments could be. Maybe spitting some cellular fluid on other cells for no defined purpose but simply to irritate and have fun...

Homework Statement The number of yeast cells in a laboratory culture increases rapidly at first but levels off eventually. The population is modeled by the function below n=f(t)=\frac{a}{1+be^{-t}} where t is measured in hours. at time t=0 the population is 20 cells and is increasing...

Combination of cells... Homework Statement Two cells of emf E1=6V and E2= 5V are joined in parallel with same polarity on same side, without any external load. If their internal resistances are r1=2ohm and r2= 3ohm respectively , then which of the following is true? 1. terminal PD across any...

Hey all. I had a question. What makes the different cone cells in your eye respond to different wavelengths of light? I know that light strikes Retinal and causes it to undergo photoisomerisation, which starts the chain that leads to you seeing something. Do the different cone cells contain...

I'm pretty confused as to how circuit analysis works when using solar cells. They all have ratings for voltage AND for current, but I'm not sure exactly what that means as far as using a cell in a circuit goes. Let's say I have a solar cell rated at 0.5V and 3.5A wired in series with a 1 ohm...

Homework Statement A student constructs a galvanic cell with one half-cell containing 0.11M ferrous nitrate, Fe(NO3)2, and the other half-cell made from 50.0ml of 0.15M oxalic acid and 1.0ml of the 0.11M ferrousnitrate. Ferrous oxalate is only slightly soluble. The half-cells contain iron...

is it possible to interfere in our dna and make the cells reproduce very fast for exp: 10 times in a single second and manipulate the dna in that way so they can't stop renewing or reproducing

Hello my friends, first I want to thank all of those who take their time to helping people like us. I have a question and is what is the most recent guide on making a very powerful Solar Cell, I am very interested in it, and the reason why I want to know this is for making more devices to cut...

Homework Statement I'm a little confused as to how the nucleolus in a eukaryotic cell manages to synthesize proteins. For example, in the nucleolus, does it contain DNA that it uses to synthesize ribosomal RNA, which then synthesizes ribosomal subunits? Then the ribosomal subunits go out into...

So, this is my first post in the medical science section of the forum. So I was just in the shower and a question occurred to me. When I hear about how the brain controlling the body it's always "the brain tells this group of muscles to do something"...or 'the brains tells this organ system what...

Hello all, this is my first post here. I know these things have been discussed before in this forum, but that was several years ago, and I have some questions that weren't asked. Basically, I need to know how information is stored in the brain, presumably as memories. What I already know is...

hi ,world 1-What is the importance of salt bridge? According to my textbook : 1-connects between the two solutions without allowing a direct contact between them So what is the problem of direct contact? 2-Neutralizes the charges which are formed in the solution of two half cells...

Homework Statement The standard reduction potentials for Ni2+ and Sn2+ are as follows: Ni2+ + 2e− → Ni E° = −0.23 V Sn2+ + 2e− → Sn E° = −0.14 V Calculate the equilibrium constant at 25°C for the reaction Sn2+(aq) + Ni(s)→ Sn(s) + Ni2+(aq) Homework Equations Nernst...

I believe in the future stem cells will cure everything and stop the aging process, and I also think that any mammal traveling at high speed would be affected by failing organs and a weaker immune system (just my opinion). So, two people of the same age are on Earth. They are identical twins...

Hi everybody. I keep on reading Rohatgi's book "An introduction to Probability and Statistics". Just now I am working in the following problem: We have n cells numbered 1 to n and n balls numbered 1 to n. We place at random the n balls in the n cells, with no cell receiving more than one ball...

Hi, when a tumor is removed from a mouse that has been killed just minutes earlier, and then this tumor is cut using a scalpel, how long do cells sticking to this scalpel survive? I am asking because I just cut a tumor, then left the scalpel on the table for 10-15 minutes, and then when...

1. If two cells, one of 4.5V and one of 3V are connected in parallel what is the potential Difference across the junctions between them. 2. I = \frac{V}{R} 3. As 4.5v is greater it is the potential difference as they don't add up?

I would like to know why is a solution of ZnSO4 necessary in a Zinc half cell when connected to a Cu half cell. The ions Zn2+ are produced by the zinc electrode so a priori no solution of ZnSO4 is needed and plain water would be enough. More generally, why a half cell always needs both the...

Hello everyone, I have a quick question. Ok the endoneurium is a layer of delicate connective tissue that encloses the myelin sheath of a nerve fiber within a fasciculus. Now my question is supporting cells of the nervous system like glial cells usually connect two nerve fibres together, so...

Homework Statement Two cells that divide on Earth each 10s start a travel to the Sun at v = 0.85c (Distance earth-sun: 1.5·10^11 m). How many cells should exist when the rocket they travel in carshes with the Sun? Homework Equations Time dilation: t=t0/sqrt[1-v2] being t0 the time from a...

I understand that space might be made up of individual units, such that you can't have a location which is between two units. When moving, a particle would just "pop" into the next unit repeatedly instead of smoothly moving - like how a computer screen works with pixels. Do I understand that at...

[SIZE="3"]I'm not a biology students, so please use the simple language. The group of cells working in coordination for the same end is called a tissue. The combination of different tissues working in harmony together is called an organ. Different organs functioning according to some defined...

I have the following questions regarding solar panels. 1)Why solar panels which use sunlight concentrators gain in efficiency despite they produce larger currents?Usually it`s believed that with increase in current flow efficiency should fall. Example here is a fuel cells. 2)Currently...

Could somebody expain me the following questions: 1)Why hydrogen fuel cell needs catalyst (such as platinum) to operate, while elcectrochemical elements (such as zinc-air) do not? 2)Why power density increase in fuel cells leads to efficiency decrease while in electrochemical batteries it...

Homework Statement The maximum size to which a cell may grow is limited by the cell's ? Homework Equations NIL The Attempt at a Solution It's a multiple-choice question... so i picked nucleus. My argument is that the nucleus controls the internal functions of the cell. However...

Considering this is for a condensed matter course, I'm assuming it'll belong here :) I cannot, for the life of me, figure out why solar cells are operated in forward bias as that would counteract the electron-hole separation in the depletion zone. Wouldn't it make more sense to operate them...

I keep thinking of doing something with Solar Power. (Southern UK) The easiest, conceptually would be very basic homemade thermal panels but then there's the problem of how to use the hot (warm) water. That involves plumbing and a special hot tank. Once you've gone for that, you may as well...

Hi I just finished reading the chapter on electrochemistry from my chemistry textbook (I just took the first half of general college chemistry this past semester) and I feel like I’m missing something- I don’t understand how electric fields play into the operation of the battery. I understand...

I just read this article and began wondering if the woman hadn't died from cancer, would she have lived forever? http://en.wikipedia.org/wiki/HeLa

When I was reading back over my book to re-write my notes, I saw the words, "The Cl2 is the electrode (cathode). It must be in a solution with its ions i.e Cl- has KCL." My question is, why does the Chlorine gas have to be in a solution with its ions? If anyone could answer this, it would be...

Hi all, I recently made my own hydrogen fuel cell and really enjoyed the process and everything I learned. I didn't know much about electronics or cells, so it was a great learning experience. In my research I found that chemical engineers made a nanometal to work as a catalyst instead of the...