Computer Studies Made Simple : Data Storage Units

Basic Units of Data Storage are as follows:

Bit:

Computer use binary digits to perform its function.

These binary digits are in the form of 0s and 1s.

A binary Digit is called a bit.

One bit takes one storage location in the memory.

It is the smallest unit for data storage.

Byte:

Byte is a collection of 8 bits.

It is used to store a single character.

The capacity of the memory or the storage is expressed in terms of bytes.

Kilobyte:

A kilobyte consists of 1024 bytes

It is denoted as KB

Megabyte

A megabyte consists of 1024 killobytes.

It is denoted by MB.

Gigabyte:

A gigabyte consists of 1024 megabytes

It is denoted by GB.

Terabyte:

A terbyte consists of 1024 gigabytes

It is denoted by TB

Dermatology Made Simple : Exogenous Eczema :Photodermatitis and Occupational Dermatitis

Photodermatitis

Photodermatitis is caused by interaction of light and chemicals absorbed by the skin.

It can occur due to :

Substances in contact with the skin such as : cosmetics or antibacterials or

Drugs taken orally / intravenously such as Sulphonamides,Tetracyclines etc.

Phytophotodermatitis occurs due to contact with plants.

Occupational Dermatitis:

This occurs due to contact of skin of workers with allergens at their work place.

Risk is increased in case of atopy.

Some of the allergens at work place include:

Detergents and water.

Clues in the history include:

Dermatitis occuring on commencement of a new job.

Symptoms resolve when away from work.

Computer studies made simple : Mark and Character recognition devices:

Mark and Character recognition devices:

These devices are used to read and interpret information written on documents in a specific codes

After scanning / reading this information,these devices convert them into a form that canbe processed by the computer.

Usually these deviced read information that are meant for business documents such as banks cheques,scoring sheets of international tests or departmental and shopping stores.

Optical Mark Recognition / OMR :

This device scans data with a laser and converts it into digital signals.

The digital signals are then sent to computer for further processing.

These are used to process answer sheets of multiple choice or single best answer exams such as GRE,MRCP and PLAB.

Magnetic Ink Character Recognition Reader / MICR:

This device reads text printed with magnetized ink.

It is used by banks for processing of cheques.

The MICR characters are written at left lower edge of the cheque.

These characters represent cheque number,bank sort code,routing number and account number.

Optical Character Recognitions/OCR

This device scans printed characters and converts them into digital codes.

Their applications includes in price tags of shopping stores and utility bills.

Dermatology Made Simple : Exogenous Eczema : Allergic Contact Dematitis:

Allergic Contact Dermatitis

The characteristics of allergic dermatitis are as follows:

Past history of exposure to an allergen

A time period of 48 to 96 hours between exposure to allergen and clinical manifestation of allergy.

Manifestation of allergy in previously exposed areas even if allergen contact occurs at a distant site.

Clinical features of allergy persisiting for number of years.

Pictures of allergic contact dermatitis

Pathophysiology:

Allergic contact Dermatitis is a result of type IV hypersensitivity reaction (which is a type of delayed hypersensitivity)

Antigens enter the epidermis and get combined by a protein mediator which are engulfed by Langerhans cells.

T lymphocytes in regional lymph nodes become sensitized to the antigen.

On future exposure to antigen,an allergic reaction occurs due to accumulation of sensitized T lymphocytes at site of inflammatory response.

Irritant Contact Dermatitis:

This maybe caused by chemicals or physical factors.

Causative Chemicals include:

Detergents

Cosmetic products

Physical factors include:

Clothing materials

Repetitive mechanical trauma

Past exposure is not required for its manifestation.

Computer Studies Made Simple : Source Data Entry Devices

Source Data Entry Devices

These devices are used for direct entry data into the computer system.

They provide a quick and efficient method of inputting data

Examples of Source Data Entry Devices include:

A.      Scanning Devices

B.      Audio Video Devices

A.Scanning Devices:

These include:

1.Barcode Reader

2.Fax machine (Facsimile)

3.Mark and character Recognition Devices such as:

Smart cards

Magnetic strips

Optical Mark Recognition

Magnetic Ink Character Recognition Reader

4.Imaging Systems.

B.Audio / Visual Devices :

1.Audio Input Devices

2.Video Input Devices

3.Didgital Camera

Bar codes:

Barcode represents data printed as vertical lines.

They are specific for a manufacturer or company.

The bar code reader emits a laser beam that can read the bar code and convert it into digital signals that are 

processed by a computer to identify the specific code for a company and canbe also used in superstores or 

markets to generate bills and keep a record of sold items by the proprieter

Dermatology Made Simple : Exogenous Eczema / Contact Dermatitis

Contact Dermatitis:

This occurs due to allergic reaction in the skin due to exposure to allergens both environmental and occupational.

The likelihood of developing an allergy is directly proportional to increased exposure to a potential allergen.

The incidence of irritant dermatitis is further increased in patients who have skin with disturbed barrier function.

An allergic reaction develops at site of sensitization to an allergen.Even if the allergen affects another skin site later,the patient would still get eczema on the previous site of exposure to allergen.

Clinical features of contact dermatitis:

There would be the following features in Acute Reactions:

Erythema (Redness)

Pruritis (Itching)

Oedema (Swelling)

Vesicle formation

In chronic dermatitis there would be thickening of the skin (Lichenification)

Some examples of contact allergens causing contact Dermatitis:

Cobalt and Nickel (In jewellry)

Perfumes

Formaldehyde

Paraphenylenediamine : found in tattoos

  

Computer Studies Made Simple : Pointing Devices

Pointing Devices

Track Ball:

It is used as an alternative to mouse.

It has a rotating ball at the top which canbe rolled with fingers.

The position of the cursor on the screen changes with rolling the ball with fingers.

It has buttons similar to that of the mouse.

It Is more useful than mouse because it takes less space than moving the mouse.

Touch Pad:

This is a small flat surface on laptop on which user can adjust the position of cursor on the screen by movement of his fingers.

It also has two buttons that have the same function as the right and left buttons of the mouse.

Touch Screen :

This is a video display screen that receives input from touch of finger.

The screen is covered with a plastic layer.There are invisible beams of infrared light behind the screen.

The user enters the data by touching icons or menus on the screen.

Most touch screen computers use sensors to detect the touch of a finger.

  

Dermatology Made Simple : Investigations in Endogenous Eczema:

Investigations of endogenous Eczema:

Skin swabs should be taken in case there is suspicion of secondary bacterial or viral infection.

The swab should be dipped in the transport medium before being applied to the affected skin.        

Note should be made of type of bacteria detected and their culture and sensitivity.

Skin scrapings canbe taken in case a fungal infection is suspected.

Nasal swabs are useful to exclude nasal staphylococcal carriage.

Blood Tests may reveal a raised level of Immunoglobulin E IgE.

RAST test would show specific igE levels against various allergens such as house dust mite,pollens etc.

Skin Biopsy maybe useful in doubious diagnosis.  

Computer Studies Made Simple : Pointing Devices

Pointing Devices

This is an input device that canbe used to control movements of a pointer on the screen.

A pointer is a small symbolic character that canbe seen on the screen.

Examples of Pointer Devices include:

Mouse

Touch pad

Joy stick

Touch Screen

Mouse:

Most commonly used pointer device.

It has got a small ball at the bottom or a laser.

It is moved on a flat screen and the movement of the ball controls the movement of pointer on the screen.

It has got two buttons on the top,the right and left which canbe used to perform different functions.

It is very convenient to use and widely available.

It canbe wireless or connected to the computer with a wire 

Dermatology Made Simple : Eczema Pathophysiology,Types of Eczema and Endogenous Eczema

Eczema Pathophysiology  and Types of Eczema:

There is a recognized association with genetic predisposition in patients with atopic eczema.

In these patient,an abnormality of T helper lymphocyte exists (especially TH 2 cells) that have important role in the disease.

These abnormal TH2 cels interact with Langerhan”s cells causing increased levels of interleukins/IgE and reduction in interferon (INF Gamma) resulting in release of pro-inflammatory cells.

Pathology:

There is oedema in epidermis that cuases separation of keratinocuyes and vesicle formation.

Epidermis becomes thickened and blood vessels become dilated.

There would be inflammatory cell infiltrate in dermis ( of eosinophils).

Types of Eczema:

As discussed before Eczema canbe broadly divided into two types:

Endogenous and Exogenous Eczema

Endogenous Eczema/ Constitutional Eczema :

Atopic Eczema

This usually presents in infancy or early childhood.

It affects face and flexural regions.

There is a strong family history and it is associated with Asthma.

Venous Eczema:

This appears on the lower limbs of patients with venous insufficiency

These patients have backflow of blood from deep to superficial veins leading to venous hypertension.

Patients have peripheral oedema and ulceration may occur as well.

There would be brown haemosiderin pigmentation of skin.

Compression is used for treatment.

Asteatotic Eczema:

This occurs on lower legs of elderly people who have dry skin.

Discoid Eczema:

This occurs on lower limbs and is characterized by annular lesions .

Vesicles may also develop.

It is more common in men that women.

Pompholyx Eczema:

It affects fingers palms and soles.

There are itchy vesicular lesions that develop on these areas.