가상현실(virtual reality)은 하나의 대체현실(alternate reality)이다. 대체현실 자체는 전혀 새로운 개념이 아니다. 예를 들어, 대니엘 디포우(Daniel Defoe)의 <로빈슨 쿠루소(Robinson Crusoe)>는 대체현실을 다룬 대표적 작품으로 볼 수 있기 때문이다. 우리 나라의 경우는 <홍길동전> 같은 작품을 들 수가 있을 것이다.
Lipopolysaccharides (LPS), also known as lipoglycans,
are large molecules consisting of a lipid and a polysaccharide
joined by a covalent bond; they are found in the outer
membrane of Gram-negative bacteria, act as endotoxins and
elicit strong immune responses in animals.
LPS is the major component of the outer membrane of
Gram-negative bacteria, contributing greatly to the structu
E-Marketing activities summary
iVillage makes most profits by selling banners, text-links and sponsorships from other business. This business is known as the "volume-based" model because volume is a vital factor to attracting advertising clients. However, more and more websites are competing for the advertising business; advertisers are unwilling to post ads on pages that are full of other ads.