Computer Studies Made Simple : Modems

Modems

Modem is a device that converts digital signals into analogue signals and analog signals into digital signals.

They send and receive data from one computer to another using telephone lines.

In order for the data to be received and sent, both computers should have modems

The term modem stands for Modulation and Demodulation.

Modulation:

The process of converting digital signal into analogue signal is called modulation.

The computer stores data in digital form.

It is converted into analog form by the modem in order to be transmitted via telephone lines to another computer.

Demodulation:

The process of converting analogue signal into digital signal is called as demodulation.

The modem of the receiving computer receives data in analogue form and then converts it into digital form to be received by the computer.

Characteristics of modem:

Speed

This is the rate at which modem can send data in bypes per second.

The speed of modems varies from 300 bps to 56 kbps.

Testing

The modems can test the digital connection with a computer and they can also test analog connection with

remote modem.

Voice over Data

Modems can provide the facility of voice conversation while the data is being transmitted.

Error control:

Modems use different methos of controlling errors for transmitted data.

Computer Studies Made Simple : Types of communication Media used in computer Networks:

Types of communication Media used in  computer Networks

The path along which data is transmitted from one place to another  is called as communication medium or communication channel.

Following are the types of communication media:

Guided Media:

In this method,the communication devices are directly connected to one another by some form of physical media such as wires.

It is also called as bounded media.

Some examples of this type of medium include:

Twisted pair

Co-axial cable

Fiber optics

Unguided Media:

In this type of medium,communication devices communicate with each other using air or space via broadcast signals.

Some examples of these broad cast signals include:

Radio signals

Microwave signals

Infrared signals.

This type of medium is used in places where it is not possible to install cables.

Some examples of unbounded media are as follows:

Microwave

Communication satellite

Mobile communications. 

Endocrinology Made Simple : Amiodarone Induced Thyroid Dysfunction

Amiodarone Induced Thyroid Dysfunction

Amiodarone causes thyroid dysfunction through its high iodine content.

Hypothyroidism is more common and is seen in 85 % cases.

Thyrotoxicosis occurs in 10 – 15 % cases.

Amiodarone induced thyrotoxicosis occurs by one of the following two ways:

1.Activation of Grave”s disease : Type 1 thyrotoxicosos

2.Destructive Thyroiditis : Type 2 Thyrotoxicosis

Grave”s disease induced by Amiodarone is generally treated with high dose thionamides: Methimazole and 

Propylthiouracil.

Perchlorate can be used to reduce further uptake by Thyroid gland.

Steroids are given for treatment of Type 2 Thyrotoxicosis.

Thyroid functions are monitored every 6 months in euthyroid patients on Amiodarone.

In patients with significant coronary artery disease or those who are elderly,a lower dose should be started.

Amiodarone induced Hypothroidism can cause fatigue as  a side effect.

Patients with Amiodarone induced Hypothyroidism should  be treated with levothyroxine to bring their TSH with in a normal range.

Other side effects of Amiodarone include:

Corneal deposits

Skin discoloration

Hepatotoxicity and

Pulmonary Fibrosis

Computer Studies Made Simple : Types of Communication Media Used in computer Networks

Types of Communication Media Used in computer Networks

The path through which data is transmitted from one place to another is called communication media or communication channel.

There are different types of communication media:

Guided Media:

In this type of medium,communication devices are directly connected with each other by using some physical media like wires.

It is also called as bounded media.

Some examples of bounded media are as follows:

Co-axial cable

Twisted pair

Fibre optics

Unguided Media:

In this medium,communication devices communicate with each other through air or space using broadcast 

radio signals,microwave signals and infrared signals.

Unbounded media is used where it is impossible to install cables.

Data can be transferred all over the world using this medium.

It is also called unbounded medium.

Some examples of this type of medium includes:

Communication satellite

Microwave

Mobile communication

Endocrinology Made Simple : Alcoholic ketoacidosis

Alcoholic ketoacidosis:

This is seen in overuse of alcohol.

It is characterized by anion gap acidosis,increased osmolal gap,ketonemia,or ketonuria and variable blood glucose levels.

Blood glucose levels are mostly higher than 250 mg/dl in patients with diabetic ketoacidosis.

Clinical features:

Impaired mental function with ketonuria.

Mildly elevated plasma glucose levels.

Plasma glucose levels can be low,high or normal.

High plasma glucose levels can be due to impaired insulin secretion combined with increased insulin resistance.

Biochemically the patients with alcoholic ketoacidosis will have increased anion and osmolal gap.

Complications

Potential complications in Alcoholic ketoacidosis includes the following:

Alcohol withdrawal

Electrolyte imbalance

Aspiration pneumonia

Wernicke”s encephalopathy :

This can occur due to administration of glucose that can increase utilization of thiamine and thus aggravating thiamine deficiency and causing Wrnicke”s encephalopathy.

Management:

Most patients will respond to an administration of intravenous dextrose containing normal saline and thiamine.

All patients should be hospitalized for treatment.

Insulin is generally not required.

Dextrose leads to an increase in insulin secretion that leads to metabolism of ketone bodies to bicarbonate.

Thiamine is likely to be deficient in all will alcohol consumption unless proven otherwise.

Computer Studies Made Simple : Bandwidth

 Bandwidth

This refers to amount of data that canbe transferred through a communication medium in one second.

The bandwidth of a digital signal is measured in bits/second or bytes per second.

Bandwidth of analog signal is measured in cycles/second or Hertz.

Baseband:

This is a communication technique in which digital signalas are placed on transmission line without a change in modulation.

It means that digital signals are transmitted directly over a transmission line.

It transmits only one signal at a time

Digital signals are commonly called baseband signals.

Spectrum of a baseband signal, energy E per unit frequency as a function of frequency f. The total energy is the area under the line.

Broadband

This is a technique to transmit large amounts of data such as voice and video over long distance.

It can send data by modulating each signal onto a different frequency.

It transmits several streams of data simultaneously using FDM Frequency Division Multiplexing technique.

FDM divides the bandwidth of a communication line into smaller frequency bandwidths.

Each part of the communication line canbe used for transmitting data separately.

Broadband is faster than Base band.

It is used for direct communication between very high speed computers such as mainframe computers,

It includes microwave,satellite,co-axial cable and fibre-optic media.