An appliance comprised of thermally insulated compartment and a heat pump used for the purpose of cooling and preserving things is usually referred as fridge freezers. It means that to transfer the heat from the freezer to the external environment and cooling the contents stored in the freezer to the required temperature. The fridge freezer is a popular appliance which is used to store the food items, medicines, chemicals etc. and also it decreases the reproduction rate of bacteria. To say in a simple way a fridge freezer is used to reduce the rate of spoilage of stuffs that are stored in the freezers or in simple way we can say that to protect the things from getting spoiled by maintaining them at a low temperature.

A fridge freezer can maintain temperature below and equal to the freezing point of water. A fridge freezer is relatively modern invention for among the kitchen appliances in many of the hotels, bakeries and restaurants. The fridge freezers have been replaced the iceboxes which had been a common appliance for almost a century in the past. The common use of freezer units finds in households and in industries and commerce. The operating point of most freezers is 0oF which can be said as ‘-18oC’. In domestic or households the freezers are generally used as the upright units in refrigerators. Many of the modern freezers come with an ice dispenser built in their door.

Commercial fridge freezer units were in use for almost 40 years earlier to the common household refrigerators. Toxic gas systems were used in the earlier freezer systems which were find unsafe to use in households, since the gas systems were occasionally leaked. Practical household freezers were launched in around 1915 and were safe and accepted by many of the households regarding the safety and quality of cooling. In the year 1930s the non-flammable synthetic freezers were introduced into market which uses Freon or R-12. During that time only sixty percent of households in United States were owned the freezers.

A fridge freezer works on the vapor compression cycle. In the vapor compression cycle a refrigerant such as Freon enters into compressor and circulates as low pressure vapor below the room temperature. The circulating vapor is then compressed and exits the compressor as superheated vapor with high pressure. This high pressured super heated vapor travels through coils or tubes comprising the condenser, which are cooled by exposing to air. The condenser generally cools the vapor and brings the vapor into liquid state which is still under pressure. A fan is present in the freezer which blows air from the freezer compartment across these coils and the refrigerant completely vaporizes, drawing heat from the box and making the box still cold. The cooled air in the freezer is still warmer than the refrigerant in the evaporator. The refrigerant leaves the evaporator, when it is fully vaporized and heated slightly, and returns to the inlet of compressor to continue the cycle.
The theory of Nursing is the term referred to the body that supports nursing knowledge practice. In their professional academic education, the nurses will be able to study a range of subjects which can be applied for the practice. This knowledge of nursing can be derived from dedicated and experiential learning from sources such as either from research on nursing or non-nursing sources. Universally accepted definition of nursing is a science that deals with people involving in many sectors of health care. They study and implement the learnt concepts for the betterment.

The degree of Nursing can also be referred as the Bachelor of Science in Nursing (BSN). It is a four year academic-degree in the fundamentals and principles of nursing and field of science. The degree is granted by accredited university or similar academies. The eligibility criteria for a person is to sit for the licensing examination (NCLEX-RN) to become a registered nurse after graduating either a two year program with an Associate's Degree of Nursing(ADN) or from a four-year nursing program with a Bachelor of Science in Nursing (BSN). The following are the prospects that nurses undergo in a BSN degree for a professional role along with coursework in nursing science, nursing informatics, research and development and finally leadership qualities.

NCLEX (National Council Licensure EXamination) is an examination conducted for the licensing of nurses in the US. NCLEX examinations are thoroughly designed and conducted to test the abilities, skills and knowledge essential to the safe and effective practice of nursing at the entry-level. The NCLEXs are two types, the NCLEX-RN and NCLEX-PN which are developed and owned by the National Council of State Boards of Nursing, Inc. (NCSBN).Each board of nursing requires a candidate to pass the appropriate NCLEX examination, for the ensurement of the public protection. NCLEX-RN exams are for registered nurses and the NCLEX-PN are for practical nurses as the abbreviation stands for. The NCLEX examinations are conducted in the form of computerized adaptive testing (CAT) format

An advanced level of education and research can be obtained by pursuing the masters. The Master of Science in Nursing (MSN) is such a degree for Registered and graduated Nurses. It is so required to become a master such as a Nurse Practitioner, Nurse anesthetist, Nurse Midwife Clinical Nurse Specialist, , Nurse Administrator, Health Policy expert, or a Clinical nurse leader. The master degree is considered an entry-level professionalism for nurse educators, managers and other staff. This degree is preliminary for doctorate-level nurse education. The following may be an advanced specialties that a graduate-level degree may focus as acute care, adult, family, palliative care, pediatric, geriatrics, neonatal, psychiatric, women's health, etc.

The level that is even more advanced to the masters is the doctorate-level degrees in nursing: Doctor of Nursing Practice (DNP or DrNP), Doctor of Nursing Science (DNSc, DNS or DSN) and Doctor of Philosophy (PhD) in Nursing. The PhD and DNS degree programs are generally considered research-oriented, whereas the phased-out DNP program is a practice-oriented or clinical doctorate.