Click HERE to see this thread with all of the graphics, features, and links.

I broke a nail...dontgetit
Now lavish me with attention and sympathy droolio cause I'm such an attention whore

cry

can i keep your broken nail as a memory for this day

Yeah!

I think I'll go make a thread for you Silver...then i hope everyone else makes one similar to it!

Oh yes please do then I can become more popular and all droolio

interesting not !!!

what, the day you broke my heart cry

Deffinitivly!!

I'll do anything to fit in!

Dont you just love people who dont get sarcasm droolio

yes cry

ill preserve the nail in a jar and ill freeze it so they can clone you in the future if its possible

It is far more interesting than that copy cat thread you made

I might even fake some pics of me too shock that atta do it droolio

make lots of mes and we shall take over the world

In loving memory of Sil's nail http://www.planetsmilies.com/smilies/sign/3/sign30.gif

No no no, not your own, you musnt!

You must find a random picture than fake it, and say its you! That seems really popular also.

cry i love this thread

That bastard ran away with my hair clippings from my last haircut

Omg and then get all ****ed over and start lying to cover my tracks droolio that's the new plan

Ouch

KA POW!!

Deffinitivly!

Thats the fashion these days! droolio

dont you just want to fit in desperately.

Dave Chapelle kicks ass !

'ground breaking news' ?

how can news break the ground ?

And next in my plan is to announce every insignificant detail in my life, like for example what I'm gonna have for breakfast tomorrow droolio

Be on the look out folks, I'm planning for a bagel

hmm... i think irene is copying someone

Not a chance dave, I'm unique, like all the other people here

Im thinking about having some coffee...

Im gonna make a thread about it to clog the forum with more shit than its already clogged with.

im unique at breaking hearts

will some one answer the bloody question

c'mon... i've known you what? 25 years now... you can call me Spence

news is verbally powerful, so it foces people to make machines to break the ground

Evidently, not.

i see is that why r are in the crazy house

not a crazy house my friend

but a unique house

some one already did, so bleh

i said IN a crazy house

IN a unique house in that case

That's it, my fling with you is sooooooo over sneaky2
I'm moving on to the next flavour of the week droolio

And I'll post once and it'll be forgotten droolio

wateva ur still crazy

and il b sur 2 writ lyk dis cuz i fink im kool.

l3t mes noe when us makin tat thred man

wateva cr@p sh!t dung poo droppings l4m3

yous a f00l dude

rolleyes1

How absolutely cool are you.

|il 6i+chi/\/355

You deserve attention and care.





































btw-Thanks again for the siggy!

5i\/3r +34r5

D3|+Y

bannedbannedbannedbannedbannedbannedbannedbannedba
nnedbanned

h0cK3Y H0rR0r

\/\/|/\/D D4/\/C3R

Okay, you got my attention now move on. Please!

\/\/hY

you're using it
I'm flattered

The number of "" smilies in this thread is striking.

It's a social experiment droolio

KILL PEOPLE, NOT TIME

oh, and what are your conclusions so far ?

and u r talking to......who?

you were suppose to say

"and u r talking to...whom?" not who

Well to Irene the social-smilies experimenter, but if you have made an experiment of your own about how to kill people while not killing time I'll be glad to hear from it too

That the "" smilie can be used in many a case

like this

wisdom is kept in the eye of the beholder

some people should just be shot

cry

stupid spork is taking over irene

whats that

The highest of wisdom is continual cheerfulness: such a state, like the region above the moon, is always clear and serene. (rhymes with irene )
-Montaigne

Wow, whats next...

OMG IT DOES!!!!!! jawdrop

thats a sign

k ill be RIGHT BACK in 10 min

Alright, I see what you mean droolio

Droolio too

...

Die please

attention...if i get alot of that i will be scared i kinda dont like peeps staring at me >.<

or was i suposed to say "enough about u guys wut about ME?"

it's never enough about me doll diva

*spills attention all over Irene*

*throws chicken wings everwhere and puts a fish bowl on head with antennas*



kool keith is a genius

Mike I love you like the son i dont want

Agreed.

Wow that's pretty complicated - let me get my calculator. nerd

o man thats a sexy quote droll

Check under your mattress next to the dirty mags droolio

this is CNN

thats a quoteable
its going in the history books drool

Ok * kills self *

*Located* nerd

youpi

Bravo

nerd Greetings, female.

Greetings specimen

nerd My blood is being pumped within the area of my cheeks.

good description

Just the cheeks naughty

nerd Currently I am not capable of answering that question. But I must say the decorations of the bedroom look quite enticing, do you wish to follow me to that destination? nerd

the ass cheeks?

You mean that hole in the wall that has a blanket spread on the ground?

nerd I believe that term is quite immature. Please spread it elsewhere.

nerd Incorrect.

Miscalculated

well my calculations prove that writing and speaking are important in engineering. Throughout your career, you will confront many writing situations, including proposals, formal reports, and journal articles. Proposals are important documents in engineering. What does a proposal do? A proposal presents a strategy for solving a problem. A successful proposal needs two elements: a statement of a problem and a proposed solution to that problem. When a proposal works well, these two elements fit as pieces of a jigsaw puzzle. The audiences of proposals include technical readers, who consider the technical merits of the proposal, and management readers, who evaluate the benefits of the proposal.

While proposals often serve as the beginnings of projects in engineering, formal reports and journal articles often serve as the completion points of projects. Formal reports are usually split into three sections: front matter, main text, and back matter. The front matter includes the front cover, title page, contents page, and informative summary. The main text portion of your formal report contains the introduction, discussion, and conclusion sections. The back matter portion of your report contains your appendices, glossary, and references. The front matter and back matter allow you to target multiple audiences. Journal articles are similar to formal reports in content, but because of format differences, generally target only one type of audience.

In all of the situations discussed in these guidelines, you might have to write or present as part of a group. Although collaboration on a document or presentation presents a challenge to the group members, it also has advantages. One advantage is that working in a group broadens the range of ideas that the document or presentation can incorporate. Another advantage is that collaborative work allows the group to draw from the various writing and editing strengths of the members. In a successful group effort, you find a strategy that accents the advantages and mitigates the disadvantages.

No single course can prepare you for every communication situation that you will face as an engineer or scientist. Nonetheless, you should be able to handle most situations if you will first sit down and examine your constraints. One of these constraints is format. Included in these guidelines were some professional examples of format so that you could practice creating documents. You should understand that there are no universal formats for engineering and science. While there may be similarities, the formats that engineers and scientists use at Sandia National Laboratories are not the same formats that engineers and scientists use at IBM or Dow Chemical.

You cannot treat scientific writing in the same way that you treat thermodynamics or anatomy or quantum chemistry. Writing is a craft, not a science. The process of learning to write effectively does not end with these guidelines, or any guidelines for that matter; it continues throughout your career. Hemingway wasn't speaking of scientific writing when he remarked, "We are apprentices of a craft where no one becomes a master." However, Hemingway's remark describes accurately the writing that we as engineers and scientists do.

now those are some calculations

nerd How many seconds are there in a year? If I tell you there are 3.155 x 10^7, you won't even try to remember it. On the other hand, who could forget that, to within half a percent, pi seconds is a nanocentury.

I could care less

not always^ the mind can play tricks on you if you miscalculate 10^7 with 10^8 because both lead to conclusions that we dont know which is the right anser too

* dosnt lavish Irene with attention and sympathy *

I have enough droolio

Nice

My brother writes that kind of stuff.

NERD!

u stole that from somewhere

yes i did...but i know about it

nerd 2.6 Compartmental Models
We have seen that analytical solutions can be given for the voltage along a passive cable with uniform geometrical and electrical properties. If we want to apply the above results in order to describe the membrane potential along the dendritic tree of a neuron we face several problems. Even if we neglect `active' conductances formed by non-linear ion channels a dendritic tree is at most locally equivalent to an uniform cable. Numerous bifurcations and variations in diameter and electrical properties along the dendrite render it difficult to find a solution for the membrane potential analytically (Abbott et al., 1991).

Numerical treatment of partial differential equations such as the cable equation requires a discretization of the spatial variable. Hence, all derivatives with respect to spatial variables are approximated by the corresponding quotient of differences. Essentially we are led back to the discretized model of Fig. 2.16, that has been used as the starting point for the derivation of the cable equation. After the discretization we have a large system of ordinary differential equations for the membrane potential at the chosen discretization points as a function of time. This system of ordinary differential equations can be treated by standard numerical methods.

In order to solve for the membrane potential of a complex dendritic tree numerically, compartmental models are used that are the result of the above mentioned discretization (Bower and Beeman, 1995; Yamada et al., 1989; Ekeberg et al., 1991). The dendritic tree is divided into small cylindric compartments with an approximatively uniform membrane potential. Each compartment is characterized by its capacity and transversal conductivity. Adjacent compartments are coupled by the longitudinal resistance that are determined by their geometrical properties (cf. Fig. 2.19).


Figure 2.19: Multi-compartment neuron model. Dendritic compartments with membrane capacitance C and transversal resistance RT are coupled by a longitudinal resistance r = (RL + RL)/2. External input to compartment is denoted by I. Some or all compartments may also contain nonlinear ion channels (variable resistor in leftmost compartment).

Once numerical methods are used to solve for the membrane potential along the dendritic tree, some or all compartments can be equipped with nonlinear ion channels as well. In this way, effects of nonlinear integration of synaptic input can be studied (Mel, 1994). Apart from practical problems that arise from a growing complexity of the underlying differential equations, conceptual problems are related to a drastically increasing number of free parameters. The more so, since almost no experimental data regarding the distribution of any specific type of ion channel along the dendritic tree is available. To avoid these problems, all nonlinear ion channels responsible for generating spikes are usually lumped together at the soma and the dendritic tree is treated as a passive cable. For a review of the compartmental approach we refer the reader to the book of Bower and Beeman (Bower and Beeman, 1995). In the following we illustrate the compartmental approach by a model of a cerebellar granule cell.



2.6.0.1 A multi-compartment model of cerebellar granule cells
As an example for a realistic neuron model we discuss a model for cerebellar granule cells in turtle developed by Gabbiani and coworkers (Gabbiani et al., 1994). Granule cells are extremely numerous tiny neurons located in the lowest layer of the cerebellar cortex. These neurons are particularly interesting because they form the sole type of excitatory neuron of the whole cerebellar cortex (Ito, 1984).

Figure 2.20 shows a schematic representation of the granule cell model. It consists of a spherical soma and four cylindrical dendrites that are made up of two compartments each. There is a third compartment at the end of each dendrite, the dendritic bulb, that contains synapses with mossy fibers and Golgi cells.


Figure 2.20: Schematic representation of the granule cell model (not to scale). The model consists of a spherical soma (radius 5.0 m) and four cylindrical dendrites (diameter 1.2 m, length 88.1 m) made up of two compartments each. There is a third compartment at the end of each dendrite, the dendritic bulb, that contains synapses with mossy fibers (mf) and Golgi cells (GoC). The active ion channels are located at the soma. The dendrites are passive. The axon of the granule cell, which rises vertically towards the surface of the cerebellar cortex before it undergoes a T-shaped bifurcation, is not included in the model.

One of the major problems with multi-compartment models is the fact that the spatial distribution of ion channels along the surface of the neuron is almost completely unknown. In the present model it is therefore assumed for the sake of simplicity that all active ion channels are concentrated at the soma. The dendrites, on the other hand, are described as a passive cable.

The granule cell model contains a fast sodium current INa and a calcium-activated potassium current IK(Ca) that provide a major contribution for generating action potentials. There is also a high-voltage activated calcium current ICa(HVA) similar to the IL-current discussed in Section 2.3.4. Finally, there is a so-called delayed rectifying potassium current IKDR that also contributes to the rapid repolarization of the membrane after an action potential (Hille, 1992).

Cerebellar granule cells receive excitatory input from mossy fibers and inhibitory input from Golgi cells. Inhibitory input is conveyed by fast GABA-controlled ion channels with a conductance that is characterized by a bi-exponential decay; cf. Section . Excitatory synapses contain both fast AMPA and voltage-dependent NMDA-receptors. How these different types of synapse can be handled in the context of conductance-based neuron models has been explained in Section 2.4.

Figure 2.21 shows a simulation of the response of a granule cell to a series of excitatory and inhibitory spikes. The plots show the membrane potential measured at the soma as a function of time. The arrows indicate the arrival time of excitatory and inhibitory spikes, respectively. Figure 2.21A shows nicely how subsequent EPSPs add up almost linearly until the firing threshold is finally reached and an action potential is triggered. The response of the granule cell to inhibitory spikes is somewhat different. In Fig. 2.21B a similar scenario as in subfigure A is shown, but the excitatory input has been replaced by inhibitory spikes. It can be seen that the activation of inhibitory synapses does not have a huge impact on the membrane potential. The reason is that the reversal potential of the inhibitory postsynaptic current of about -75 mV is close to the resting potential of -68 mV. The major effect of inhibitory input therefore is a modification of the membrane conductivity and not so much of the membrane potential. This form of inhibition is also called `silent inhibition'.


Figure 2.21: Simulation of the response of a cerebellar granule cell to three subsequent excitatory (A) and inhibitory (B) spikes. The arrival time of each spike is indicated by an arrow. A. Excitatory postsynaptic potentials nicely sum up almost linearly until the firing threshold is reached and an action potential is fired. B. In granule cells the reversal potential of the inhibitory postsynaptic current is close to the resting potential. The effect of inhibitory spikes on the membrane potential is therefore almost negligible, though there is a significant modification of the membrane conductivity (`silent inhibition').

A final example shows explicitly how the spatial structure of the neuron can influence the integration of synaptic input. Figure 2.22 shows the simulated response of the granule cell to an inhibitory action potential that is followed by a short burst of excitatory spikes. In Fig. 2.22A both excitation and inhibition arrive on the same dendrite. The delay between the arrival time of inhibitory and excitatory input is chosen so that inhibition is just strong enough to prevent the firing of an action potential. If, on the other hand, excitation and inhibition arrive on two different dendrites, then there will be an action potential although the timing of the input is precisely the same; cf. Fig. 2.22B. Hence, excitatory input can be suppressed more efficiently by inhibitory input if excitatory and inhibitory synapses are closely packed together.

This effect can be easily understood if we recall that the major effect of inhibitory input is an increase in the conductivity of the postsynaptic membrane. If the activated excitatory and inhibitory synapses are located close to each other on the same dendrite (cf. Fig. 2.22A), then the excitatory postsynaptic current is `shunted' by nearby ion channels that have been opened by the inhibitory input. If excitatory and inhibitory synapses, however, are located on opposite dendrites (cf. Fig. 2.22B), then the whole neuron acts as a `voltage divider'. The activation of an inhibitory synapse `clamps' the corresponding dendrite to the potassium reversal potential which is approximately equal to the resting potential. The excitatory input to the other dendrite results in a local depolarization of the membrane. The soma is located at the center of this voltage divider and its membrane potential is accordingly increased through the excitatory input.

The difference in the somatic membrane potential between the activation of excitatory and inhibitory synapses located on the same or on two different dendrites may decide whether a spike is triggered or not. In cerebellar granule cells this effect is not very prominent because these cells are small and electrotonically compact.

I hate you all droolio

cought u red handed now go to the kmc jail

Thanks

welcome

Yep

You can't afford me luv

with the spork? a bit violent dont u think...

Your cheaper than tex

bad move but funny still

And better too naughty

where do you live?

No I mean as a slave You think I would let tex in my house?

In Canadialand

Irene gets her money by stripping at McDonalds

jockey

^ Yea! Haha I love that comerical where the vacuum cleaner eats his pants

Umm? Wrong forum? Lmao..

Least they pay well droolio

Fries arnt worth anything babe