Chlamydia and Gonorrhea: infertility risks

Most people have probably heard of chlamydia and gonorrhea.  They are both bacterial STDs.  Since neither is life-threatening (as far as I’ve ever heard), they don’t get as much attention as AIDS or syphilis.

A risk with both chlamydia and gonorrhea is that they can be asymptomatic – i.e., the victim doesn’t have any symptoms, so doesn’t know they’ve caught the disease.  However, both chlamydia and gonorrhea, operating undetected, can cause scarring of the reproductive tract.  In males, the vas deferens (aka ductus deferens) can become scarred over; in females, the same can happen to the oviducts.  The individual can thus be rendered infertile.

Both chlamydia and gonorrhea, being bacterial, are treatable with antibiotics.

Jack of Oracle Tutoring by Jack and Diane, Campbell River, BC.

Homeostasis, negative feedback, and thyroxin

Tutoring biology, the concept of negative feedback is important to explain.  Negative feedback is used by all organisms to maintain their living state.  You also use it while driving your car.

More or less, the body needs all its processes to proceed at a constant, continuous rate.  Change is the enemy for biological entities.  However, as you interact with your surroundings – eating, exercising, and so on – change is imposed on your internal environment.  Negative feedback means that when a change happens, your body responds to negate that change – i.e., to bring itself back to normal.  Once back to normal, your body stops its negative response.  It won’t respond again until another change brings it out of normal range.

Consider driving a car – specifically, steering.  Imagine the road is straight, but your car starts drifting to the right.  You correct by steering left, to bring the car back on course.  In so doing, you are applying negative feedback.  The car is going too far right, so you oppose that change of course by steering left.  Once the car is back on course, you stop correcting:  you let the wheel slide back to center.  You won’t steer again until the car begins to drift off course once more.  That process of opposite, corrective response is negative feedback.  You can also call it a feedback loop, since you base your reaction on what is already happening.

Biology has many examples of negative feedback, but we’ll look at the one involving the hormone thyroxin:

The hypothalamus – in the brain – monitors the body’s metabolism.  If the metabolism gets too low, the hypothalamus stimulates the anterior pituitary.  In response, the anterior pituitary releases a hormone that causes the thyroid to release thyroxin.  Thyroxin increases the body’s metabolism.

Once the metabolism reaches an acceptable level, the hypothalamus stops stimulating the anterior pituitary.  In turn, the anterior pituitary ceases to release the thyroid-stimulating-hormone.  Therefore, the thyroid stops releasing thyroxin.  The body’s metabolism remains constant – until another external change depresses it again.

Therefore, the connection among the hypothalamus, anterior pituitary, and thyroid gland constitutes a negative feedback system that maintains the body’s metabolism at a constant rate.  This negative feedback system promotes homeostasis.  Homeostasis means the maintenance of a constant internal environment.

Jack of Oracle Tutoring by Jack and Diane, Campbell River, BC.

Cell efficiency

When you tutor Biology 12, one topic that comes up is cell efficiency.  It’s a bit tricky for some people, because it involves some math.

Putting it simply, imagine a cell is a sphere.  Its volume is what it needs to maintain, whereas its surface area is where it gets its supplies.  You can quickly realize that it’s best to have a big surface area compared to volume (or surface area to volume ratio), so the cell can easily get enough supplies to feed its volume.  Efficiency, in this context, refers to the cell’s surface area to volume ratio:

(1)   \begin{equation*}Eff.=\frac{SA}{V}\end{equation*}

As the radius of a cell grows, its surface area grows, but its volume grows more quickly.  Therefore, its surface area to volume ratio decreases:  its efficiency decreases.

Therefore, cells are better off being small – which is why most cannot be seen with the naked eye.  Ultimately, this same principle (of efficiency) is why a rat can run up the side of a building with ease, but a human cannot.  The human’s muscles, since they have such greater volume than the rat’s, are much less efficient.

Jack of Oracle Tutoring by Jack and Diane, Campbell River, BC

Conservation of momentum

Every year, the physics tutor fields a few questions on conservation of momentum.  It’s an interesting phenomenon because you can use it to explain some familiar, everyday situations.

Momentum is mass times velocity.  Something that is 50 kg, traveling at 12 m/s, has a momentum of 600 kgm/s.  It’s a vector, so two momentums can cancel each other out if they have opposite directions.

One great example of conservation of momentum is how a jet boat works.   The motor takes water, which has an initial momentum of zero, and pushes the water, giving it velocity.  The momentum the water gains needs to be canceled somehow, since total momentum must remain constant.  That’s why the boat goes forward:  to cancel out the backward momentum the water has been given.  The boat gains the same momentum forward that the water gains backward.  From the point of view of physics, that’s why a jet boat moves forward.

Thanks for dropping by, and come again!

Jack of Oracle Tutoring by Jack and Diane, Campbell River, BC.

Does 0.33333….. really equal 1/3?

Hello.  What rain yesterday, here in Campbell River!  Well, we sure needed it.  It’s nice to have more seasonal temperatures after the oven that was last week.

A math tutor often encounters the topic of converting decimals to fractions.  Terminating decimals are easy:  for instance, 0.9 is 9/10.  Then, 0.31 is just 31/100.  As well, 0.222 is 222/1000, which reduces to 111/500.

What about repeating decimals, such as 0.333333…….?

Well, there’s an algebraic trick for that:

Let x=0.3333…..(Note that x=1x; we just don’t usually write the one.)


(1)   \begin{equation*}10x=3.33333......\end{equation*}

(2)   \begin{equation*}             1x =0.33333......\end{equation*}

Subtracting (2) from (1) gives

(3)   \begin{equation*} 9x=3.00000......\end{equation*}

Of course, 3.00000…. = 3, so

(4)   \begin{equation*}9x=3\end{equation*}

Next, divide both sides by 9 to isolate x:

(5)   \begin{equation*}\frac{9x}{9}=\frac{3}{9}\end{equation*}

Finally, reducing gives

(6)   \begin{equation*}x=\frac{1}{3}\end{equation*}

Recall, we began by defining x as 0.333333…..Now, since we see x is also equal to 1/3, we know that it must be true:

(7)   \begin{equation*}0.33333......=\frac{1}{3}\end{equation*}

Have a great day, and come back for more hints.

Jack of Oracle Tutoring by Jack and Diane, Campbell River, BC.

Distance vs Displacement: Scalar vs Vector

When you tutor physics, a concept that soon comes up is scalar vs vector.  It’s not something most people ever think much about, but the difference is very important – especially in Science 10 and Physics 11.

For example:  distance is a scalar, but displacement is a vector.  If you drive to the store (10 km away), then return home, of course you’ve driven a distance of 20 km.  Distance is a scalar, so you just add the km going to the ones returning.

For the same situation, your displacement when you get back is 0 km.  That’s because, being a vector, displacement considers the direction as well as the value.  From the displacement point of view, every km you travelled to the store got cancelled out as you returned.  For any round trip, your displacement is 0 km.

Displacement can also be defined as how far you are from where you started.  It includes the direction you are from your start point.  Naturally, if you’re back where you started, your displacement is 0.

Jack of Oracle Tutoring by Jack and Diane, Campbell River, BC.

Have a great night.

The double ‘l’ controversy

The other day my wife Diane got on my case about my spelling of “canceled”:

Diane:  You spelled canceled wrong.  It only has one l.  There should be two.

Jack:    You can spell it either way.

Diane:  I’ve been a tutor here in Campbell River since 1986.  It needs two “l”s.

The first dictionary I checked was a Brit one; of course, it backed her up.  Then I got a Webster’s, and it says both “canceled” and “cancelled” are okay.

The general rule I was taught is that if the last syllable is unaccented, you don’t have to double the final consonant.  So travelling can be traveling as well:  both are fine, according to Webster’s (which is Yank, of course).

Diane still wasn’t satisfied; she likes the doubling of the consonant.  For her, only travelling and cancelling will do.

You be the judge.

Jack of Oracle Tutoring by Jack and Diane, Campbell River, BC.

Exponential Growth

Good morning from Jack, your tutor from Campbell River.  It’s brilliantly sunny here, with a high of 27 (or 81 F) expected.  This kind of weather can be so hard for kids just returning to school.

The people entering math 12 will probably encounter exponential growth very soon.  It’s not a term you hear very often, but compound interest is an example of it.  Most natural things grow the same way – while they have the resources.

Exponential growth means that the growth is a percentage of how much is already there.  So if your growth rate is 10%, then you go from 10 to 11 in one year.  If you start with 100, though, you go to 110 in that year.  Interest is the obvious example:  everyone knows that if you have $1000 on deposit, you’ll get more interest than if you’ve only got $100.

Step two is the one that surprises some people.  Let’s imagine you start with 1000 individuals at 10% growth.  At the end of year one, you’ve got 1100 – true enough.  The mistake many people make is that they assume that the following year, the population increases by another hundred, making 1200.  That’s not true.  If you start the second year with 1100, still at 10% growth, the population will increase that year by 110 – which, of course, is 10% of 1100.  So by the end of year two, you’ll have 1210:

1000 + 100=1100  (100 is 10% of 1000).

1100 + 110=1210  (110 is 10% of 1100).

The difference is only 10 at the end of year two, but that difference keeps getting larger because it contributes to the growth of the population.  That’s why, believe it or not, the population will be over 2000 in less than 8 years.  In 32 years it’ll be over 21 000.

The rule of 72 for compound interest says that

(interest rate)x(doubling time)=72

(Of course, that law is an approximation, but actually a very good one.)

Since compound interest is just an example of exponential growth, that law works for anything that grows exponentially.

Enjoy this beautiful day.

Jack of Oracle Tutoring by Jack and Diane, Campbell River, BC.

Algebra: basic

When you tutor math, you see various approaches to algebra.  Here’s my interpretation:

1)  Decide which side you want “x” (or whatever variable you have) to end up on.

2)  Get all the x terms to that side, and all the numbers to the other side.

To do this, you do a series of operations:  always the same to both sides.

3)  Divide out the coefficient of x.

Here’s an example:

7x – 1 = 5x + 9

Let’s get the x’s on the left.  To get rid of the 5x on the right, we subtract 5x from both sides:

7x – 1 = 5x + 9

-5x         -5x

On the left, 7x – 5x = 2x.  On the right, 5x – 5x = 0.  We are left with:

2x – 1 =         9

Now, let’s get the numbers to the other side.  To get rid of a -1, we add 1 (as always, to both sides):

2x  – 1 =        9

      +1          +1

2x       =        10

Now we divide both sides by the coefficient of x, which is 2:

    \[ \frac{2x}{2}\ = \frac{10}{2}\]

Finally, we have the result:

x         =         5.

I’ll be talking more about algebra, of course, but for the first day back, this is probably good.

Jack of Oracle Tutoring By Jack and Diane, Campbell River, BC.

Have a great day.  All the luck this school year, and come visit me often for more tips!

School Supplies: A tutor’s point of view

Last year, listening to French radio, I heard a surprising report:  school supply shopping is the second most stressful occasion for a great many parents, second only to Christmas shopping.

If that’s true, it doesn’t need to be.  What’s more, I can explain why:

1) With Christmas shopping, you’re not told what to get – whereas with school supply shopping, you usually are.

2) While, with Christmas shopping, there is a deadline, there really isn’t one in the same way when it comes to school supply shopping.

I’ve heard that a lot of people fear the expense of back-to-school shopping.  I can’t comment on the other dimensions of it (clothes, for instance), but I can tell you this:  school supplies don’t have to be (that) expensive.

In front of me I’ve got two big-box store flyers from Friday’s paper.  I’ll admit that if you have to shop today, you might pay around $15 for a zipper binder (of course, you can pay a lot more if you want), then another $15 or more for a school bag.  (This is all before tax.)

Coloured pencils, if you need those, might run around $2.50 to $6.00.  Buy a good name – not cheap ones.  When you’re a tutor, you see a lot of school supplies.  I’ve noticed that many kinds of coloured pencils – especially cheap ones – don’t hold a sharp point.  You don’t want your kid to be stuck with coloured pencils whose leads keep breaking.  Ask what the good names are.  I use Staedtler, but there are other good ones around.  I’d guess a name like Hilroy would be pretty trustworthy – although I’ve never tried their coloured pencils.

For just normal pencils (rather than colour), I prefer mechanical rather than wood.  Get 0.7 leads – they last longer and break way less often (as opposed to 0.5).  A twelve pack of Bic 0.7 plastic pencils will cost maybe $4.  If they don’t get lost, your kid probably wouldn’t use more than half of them the whole year.  Pens are even cheaper than pencils – unless you want to pay more for something special.

One note, though, about mechanical pencils:  you can’t get them for most kids until they’re in grade 5 or later.  The reason is that the kids just play with them.  If your kid is earlier than grade 5, you probably want wooden pencils.

Erasers:  get white ones.  Staedtler is one kind I use, but most white erasers are pretty good.  At one place, they’re on for less than a dollar apiece right now.  If it’s not lost, one could last you for years.

Paper – both loose leaf and graph – might be the most variably priced item.  You might have to pay a lot on a given day at a given place.  However, my wife says she’s seen 150 sheets of loose leaf for less than a dollar recently. If you’re paying more than that today, you should probably look elsewhere.  Graph paper is usually more – you might have to pay 3 or 4 dollars for around 100 sheets – but you can sometimes get it for a lot less.  Kids don’t usually use much of it, anyway.

Markers, if you need them, might be around what coloured pencils cost.  A ruler you can get for less than a dollar.  A scientific calculator shouldn’t cost more than $15.  I know I could get a good one for less.  The less fancy, the better.  As long as it has sin, cos, and tan on it, as well as square root, you’re probably pretty safe.  Of course, you shouldn’t need to buy a new calculator every year.

There are other odds and ends, but let’s make a rough total of the items I’ve mentioned.  You might be looking at around $60 to $75 before tax.  You could do better, depending on where you live and how much hunting you’re willing to do.

Where I live, some stores have school supply lists right at the front entrance.  You can find your kid’s school and grade, then pick up a list of supplies.

If your kid goes to the first day of school with just a few pencils and pens, some paper, a binder, a calculator, and the coloured pencils, they’ll probably be all right.  When they get home, they can tell you what they’re missing, and you can get the rest that night.

One final point:  Look for school supplies again in a month.  Watch the prices go up and down.  Eventually you’ll probably be able to get almost everything cheaper than you can today.  Stock up when it’s cheap.  Ask your kid what works and what doesn’t – and why.  If you familiarize yourself with school supplies, you’ll be on top.  Like most things, they’re best to buy before you need them.

Good luck!

Jack of Oracle Tutoring by Jack and Diane, Campbell River, BC.