why are holes heavier than electrons?The question comes from semiconductors in electronics engineering

The concept of electron and hole effective mass in
semiconductors has been developed starting from the mobility of carriers (be them
electrons or holes). When an external electricc field `E` (or equivalent a potential
difference) is applied to the semiconductor it will start to conduct electric current,
by the motion of electrons and holes. The carries will accelerate into the electric
field, and will be decelerated by different collisions (scientific term is different
scattering mechanisms) that happen in their motion through the semiconductor. The
average drift velocity of the carriers is of course proportional to the field
applied.

`v_d = mu*E`

Here
above `mu` is the mobility of the carriers (different for electrons or holes). This
mobility in turn is conceivable to be inverse proportional to the mass (and charge) of
the carriers (as Newton second law states `F = m*a` , the accelerating force here is the
electric force) and inverse proportional to the time `tau` between two collisions (that
decelerate the carriers).

`mu = q/m*tau`

Here above `m` is the effective mass of the carriers.
Again. this concept of effective mass relates to the fact that carriers are accelerated
by the electric force and they need to obey the Newton second
law.

In solid state physics there have been derived methods
to experimentally measure the value of carrier mobility `mu`, by measuring the Hall
coefficient and the resistivity of the material. Thus, from these experimental
determinations, usually for semiconductors the mass of holes has been determined to be
greater than the mass of electrons. This means that in electric field the holes
accelerate less than electrons.

Now for the theoretical
explanations.

Everybody learns that in semiconductors there
are bands of energy. Thus the last two bands are called valence band and conduction
band. Usually when we draw on paper these bands we represent them as two horizontal
lines separated by a gap (forbidden band). What is little known is that in fact from
quantum calculus the shape of these bands is not linear. The bands are like two rotation
ellipsoids having a minimum distance at one point between them (the forbidden band). It
has been mathematically shown, that the radius of curvature of the ellipsoids
representing the bands are proportional to the effective mass of carriers. (The
conduction band curvature accounts for the electron mass and the valence band curvature
for the holes mass). Hence the mass of holes is greater than the mass of electrons by
quantum computations of allowed bands energy (which in turn comes from the structure of
the crystal and the structure of the composing atoms
themselves).

Who is that "ashen fantastic figure gliding toward Gatsby through the amorphous trees?"

The entire quote:

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He must have felt that he had lost the old warm
world, paid a high price for living too long with a single dream. He must have looked up
at an unfamiliar sky through frightening leaves and shivered as he found what a
grotesque thing a rose is and how raw the sunlight was upon the scarcely created grass.
A new world, material without being real, where poor ghosts, breathing dreams like air,
drifted fortuitously about...like that ashen, fantastic figure gliding toward him
through the amorphous
trees."

This comes from
chapter 8. Myrtle Wilson, Tom Buchanan's mistress, has been run over by a car. It was
Gatsby's car, but Daisy was driving it. Daisy and Gatsby and Nick, Jordan and Tom had
been driving back to Long Island after being in NYC where Gatsby forced Daisy to tell
Tom she never loved him, and she really could not say that she never
loved him. When they passed by Myrtle and George Wilson's garage, Myrtle, who
had been locked upstairs by George, her husband, because George had learned Myrtle was
having an affair, saw Gatsby's car from the window. She thought it was Tom and ran down
to talk to him, ran in front of the car, and Daisy ran her over. George does not know
WHO killed his wife, but Tom, who figures out what happened, comes upon the accident
because he is driving behind Gatsby and Daisy. He has been trying to sell George a car
and knows George, so he whispers something to him. Later, we find out that he no doubt
told George that the car that hit Myrtle was Gatsby's car. George assumes that Gatsby is
Myrtle's lover, not Tom.

So, the "ashen figure" is George.
He has gone to Long Island to find the car. He figures out that it belongs to Gatsby.
Gatsby, who has never used his pool all summer, decides to have one last swim before he
lets his servants drain it, and Geroge is hiding in the trees, waiting for him. He rises
up from the trees and kills Gatsby.

Evaluate the indefinite integral of y= 1/(x^2 - 11)

We notice that the denominator of the function is a
difference of squares.

We'll re-write the function as a sum
of 2 irreducible ratios:

1/(x^2-11) =
1/(x-sqrt11)(x+sqrt11)

1/(x-sqrt11)(x+sqrt11) =
A/(x-sqrt11) + B/(x+sqrt11)

We'll multiply the first ratio
from the right side, by (x+sqrt11), and the second ratio, by
(x-sqrt11).

1 = A(x+sqrt11) +
B(x-sqrt11)

We'll remove the brackets from the right
side:

1 = Ax + Asqrt11+ Bx -
Bsqrt11

We'll combine the like
terms:

1 = x(A+B) +
sqrt11(A-B)

For the equality to hold, the like terms from
both sides have to be equal:

A+B =
0

A = -B

sqrt11(A-B) =
1

We'll divide by sqrt11:

A-B
= 1/sqrt11

A+A = 1/sqrt11

2A =
1/sqrt11

We'll divide by 2:

A
= 1/2sqrt11

B = -1/2sqrt11

The
function 1/(x^2-11) = 1/2sqrt11(x+sqrt11) -
1/2sqrt11(x-sqrt11)

Int dx/(x^2-11) = (1/2sqrt11)*[Int
dx/(x-sqrt11) - Intdx/(x+sqrt11)]

We'll solve Int
dx/(x-sqrt11) using substitution technique:

We'll note
(x-sqrt11) = t

We'll differentiate both
sides:

dx = dt

 Int
dx/(x-sqrt11) = Int dt/t

Int dt/t = ln t + C = ln
(x+sqrt11) + C

Intdx/(x+sqrt11) = ln (x+sqrt11) +
C

Int dx/(x^2 - 11) = (1/2sqrt11)*[ln (x-sqrt11)-ln
(x+sqrt11)] + C

 We'll use the quotient property of the
logarithms:

Int dx/(x^2 - 11) =
(1/2sqrt11)*[ln (x-sqrt11)/(x+sqrt11)] + C

Assess the successes and failures of Reconstruction.

I would say that one undeniable success of Reconstruction
would be the passage of the Civil War Amendments.  The embedding  of the abolition of
slavery, the assurance of voting rights, and the extension of equal protection into the
Constitution helped to move people of color as part of the American political
landscape.  At the same time, I would say that the idea of the nation moving as one unit
towards an end where people of color, specifically African-Americans, would be seen as
part of its composition could also be considered a success.  One of the overwhelming
failures would be the lack of transitional help consistently and thoroughly offered to
African-Americans to see themselves as a part of the American vision.  It is nearly
impossible to envision what slavery was like for African-Americans and to live in its
shadow requires a greater level of empathy than what was present at the time. 
Additionally, the lack of a national focus on the elements of Reconstruction continued
to add to the fragmented nature of the country, something with which Lincoln's death did
not help.

In what sense is Petrarch insincere in Sonnet 18 (sonnet inside)?a. Through professing his desire to be alone, he really craves the attention of...

If those four are your options, I would have to go with
C.  It is the only one that makes sense.

To me, what the
poem is saying is basically "you are so wonderful and beautful that I can't even manage
to write a poem about or talk about you -- you're just too good for
words."

If that's what he's talking about in this poem,
then only C really makes sense.  He's not really trying to get attention for himself so
it's not A.  He never claims his love is a secret so it's not B.  He doesn't praise
himself in the last lines so it's not D.

C kind of makes
sense because he does flatter her even though he can't actually describe
her.

When Scout takes Boo home, she understands many things as she sees the street from a new point of view. Explain some of the things she "sees" now.

After taking Boo home, Scout stood in front of the window
"to the left of the brown door."  From her new vantage point, Scout was able to see that
Boo was probably able to watch the whole street whenever he wanted.  As she thought back
over the events of her daily life, Scout understood that Boo had formed a protective
attachment to her and her brother, Jem, from simply observing them.  Boo had no
interaction with others, except for a very few close relatives, etc., so he chose to
come to know Jem and Scout in the way he was able, as well as to show him affection for
them by leaving them gifts and, eventually, by saving their lives.  Despite his
differences from other people, Boo was kind and lonely and reached out to Jem and Scout
in the only way he knew how.  His world consisted of that house and his view of the
street; Jem, Scout, and Atticus became his family.  He loved them because they loved
each other.

From Frankenstein, list three truths about human nature and find three events that relate to these truths.I'm not quite sure what is meant here by...

Another profound truth about humanity demonstrated in Mary
Shelley's Frankenstein is the selfishness of man that dominates his
nature. The subtitle, A Modern Prometheus, even suggests this
selfishness as Prometheus selfishly pursued his desire of bringing man fire even though
he knew Zeus would not approve.  This universal selfishness, inherent in both gods
and human nature alike, threads through the entire narrative as with all three major
characters in this novel, their selfish motives take precedence over their rationality,
their practicality, and their concern for even those they
love.

Walton, for insistance, justifies in his letters to
his sister his "love for the marvellous" in pursuing his goal of reaching the North
Pole.  Likewise, Victor, selfishly justifies his not reporting the cause of the murder
of his brother William and places blame solely upon the
creature:

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When I reflected on his [the creature's] crimes
and malice, my hatred and revenge burst all bounds of moderation.  I would have made a
pilgrimage to the highest peak of the Andes, could I, when there, have precipitated him
to their base.  I wished to see him again, that i might wreak the utmost extent of
abhorrence on his head, and avenge the deaths of William and Justine. (Chapter
9)

And, similarly, the
creature places blame upon Victor in his murderous revenge against
Victor:

have I not suffered enough that you seek
to increase my misery?....Remember, that I am thy creature; I ought to be thy Adam; but
I am rather the fallen angel, whom thou drivest from joy for no misdeed....Listen to me,
Frankenstein.  You accuse me or murder; and yet you would, with a satisfied conscience,
destroy your own creature. (Chapter 10)