Friday, September 24, 2010


Diseases which spread from animals to humans are called zoonotic diseases. Some of these are as follows:

1. Bubonic Plague: 

Caused by the bacteria Yersinia Pestis. Thus plague is normally a problem when humans live in close proximity to rodents. Historically, this has meant rats. Slum populations, with poor hygiene, were thus at greatest risk.

The typical sign of the most common bubonic form of human plague is a swollen and very tender lymph gland, accompanied by pain. The swollen gland is called a bubo. This is usually accompanied by fevers, chills and extreme exhaustion. Natural plague has not evolved significant resistance to antibiotics, and thus remains treatable in most cases.
Since plague is zoonotic, eliminating it from the ecosystem is not possible. The bacteria could always lie latent in its animal reservoir even if somehow eliminated from the human population, thus preserving the possibility of future human infections. This contrasts with other strictly-human diseases, such as smallpox. These non-zoonotic diseases can theoretically be driven extinct by vaccines, since the causative pathogen has no refuge outside of human beings.

2. Avian Influenza:

It is caused by the influenza A viruses most frequently found in birds. Flu viruses are rapidly killed by sunlight and tend to dehydrate to death in the breeze.

Like all contagious intestinal and respiratory infections, avian influenza viruses are density-dependent pathogens with a penchant for darkness, dampness, dirt and weakened immune systems – the perfect conditions in which to mutate and proliferate in birds and humans alike. The poultry and eggs one buys at the store came from birds who lived, day in, day out, in excrement, including the excretory ammonia fumes rising from the decomposing droppings in the chicken and turkey houses.These poisonous gases penetrate egg shells (Carlile, 101). They enter the birds’ airways and immune systems, inviting Salmonella,Campylobacter, and avian influenza viruses to colonize, mutate, and spread. 

The droppings themselves contain disease organisms, antibiotic residues, cysts, larvae, and metals such as copper, zinc, and arsenic (UPC [c;d]).


1. What  is mad cow disease?

2. What are the symptoms of swine flu?

3.  Who on an average suffers more from depression, man/woman?

Wednesday, September 8, 2010

Analog Electronics Ready-Reckoner 1

1. Forbidden energy gap for insulator diamond is 6 eV.

2. Drift velocity is in the direction opposite to that of the electric field and magnitude is proportional to electric field.

3. Semiconductor has forbidden energy gap of about 1 eV.

4. Silicon is largely preferred to germanium because of its large gap energy, which provide improved device properties at high temperatures.

5. In a capacitor, the dielectric strength is the ability of a dielectric to withstand a potential difference without breakdown. Air/vacuum has dielectric constant 1.

6. Only electrolytic capacitors have polarity. High value capacitors are electrolytic.  Electrolytic capacitors need to be connected with the correct polarity.  If not, they can explode. 

7. The voltage of a capacitor falls by an equal fraction in equal time. V = V0 e-t/RC
The physics codes are as follows:
  • V - voltage at any time;
  • V0 - the voltage at the start;
  • t - the time (s);
  • - the resistance of the resistor through which the capacitor discharges (W);
  • C - the capacitance of the capacitance (F);
  • e - the exponential number, 2.718...
The charge follows the same pattern:

Q = Q0 e-t/RC

The current follows the same pattern:

I = I0 e-t/RC

The product between resistance and capacitance (RC) that appears in the formula is called the time constant and is measured in seconds.  It may seem strange that ohms × farads = seconds, but it's true.  If we multiply the base units of ohms and farads, we end up with seconds.

8.  Inductors store energy in the form of magnetic field and delivers it as and when required.

9. A missing electron in the valence band leaves a vacant space there, which is known as the hole.

10.  Under thermal equilibrium for any semiconductor, the product of the number of holes  and the number of electrons  is constant and is independent of the amount of donor and acceptor impurity doping. This relation is known as mass-action law, given by:

n * p = ni

n = number of free electrons per unit volume
p = number of holes per unit volume

ni = intrinsic concentration

Friday, September 3, 2010

8085 Microprocessor - Reader's Bird View

In today's fast-paced environment, every thing requires to be clock-driven, from laser printer to semi-automatic washing machine to car stereo to digital timepiece to apple iPhone. Microprocessors are able to perform substantial (similar or non similar) work per clock cycle. The clock speed determines how many instructions per second the microprocessor/CPU can execute.

If required to define, a microprocessor is a digital electronic component with miniaturized transistor (N-MOSFET ) components on a single semiconductor integrated circuit.

Lets start with a basic microprocessor, the beginners in the INTEL series in the late 1970's: 8085

Salient features collected from trustworthy web links are as follow -

An 8-bit processor

16-bit address bus

Program, data and stack memories occupy the same memory space.

Total addressable memory size is 64 KB = 65536 bytes =  2 pow 32

Stack grows downward

Jump, branch and call instructions use 16 bit addresses

5 interrupts with unequal priority

256 input ports

256 output ports

16 bit program counter

Stack pointer is a 16 bit register, always incremented/decremented by 2

Logical instruction set -AND, OR, XOR, ROTATE

Arithmetic instruction set - Add, Subtract, Increment, Decrement

It has single 5 volt power supply

Processor speed - 3 MHz

Multiplexed address and data bus

Manufactured with N-MOS technology