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segmentationmore about segmentation

segmentation

 

  3  definitions  found 
 
  From  Webster's  Revised  Unabridged  Dictionary  (1913)  [web1913]: 
 
  Segmentation  \Seg`men*ta"tion\,  n. 
  The  act  or  process  of  dividing  into  segments;  specifically 
  (Biol.),  a  self-division  into  segments  as  a  result  of  growth; 
  cell  cleavage;  cell  multiplication;  endogenous  cell 
  formation. 
 
  {Segmentation  cavity}  (Biol.),  the  cavity  formed  by  the 
  arrangement  of  the  cells  in  segmentation  or  cleavage  of 
  the  ovum;  the  cavity  of  the  blastosphere.  In  the  gastrula 
  stage,  the  segmentation  cavity  in  which  the  mesoblast  is 
  formed  lies  between  the  entoblast  and  ectoblast.  See 
  Illust.  of  {Invagination}. 
 
  {Segmentation  nucleus}  (Biol.),  the  body  formed  by  fusion  of 
  the  male  and  female  pronucleus  in  an  impregnated  ovum.  See 
  the  Note  under  {Pronucleus}. 
 
  {Segmentation  of  the  ovum},  or  {Egg  cleavage}  (Biol.),  the 
  process  by  which  the  embryos  of  all  the  higher  plants  and 
  animals  are  derived  from  the  germ  cell.  In  the  simplest 
  case,  that  of  small  ova  destitute  of  food  yolk,  the  ovum 
  or  egg  divides  into  two  similar  halves  or  segments 
  (blastomeres),  each  of  these  again  divides  into  two  and 
  so  on  thus  giving  rise  to  a  mass  of  cells  (mulberry  mass, 
  or  morula),  all  equal  and  similar,  from  the  growth  and 
  development  of  which  the  future  animal  is  to  be  formed. 
  This  constitutes  regular  segmentation.  Quite  frequently, 
  however,  the  equality  and  regularity  of  cleavage  is 
  interfered  with  by  the  presence  of  food  yolk,  from  which 
  results  unequal  segmentation.  See  {Holoblastic}, 
  {Meroblastic},  {Alecithal},  {Centrolecithal}, 
  {Ectolecithal},  and  {Ovum}. 
 
  {Segmentation  sphere}  (Biol.),  the  blastosphere,  or  morula. 
  See  {Morula}. 
 
  From  WordNet  r  1.6  [wn]: 
 
  segmentation 
  n  1:  (embryology)  the  repeated  division  of  a  fertilised  ovum 
  [syn:  {cleavage}] 
  2:  separation  by  the  creation  of  a  boundary  that  divides  or 
  keeps  apart  [syn:  {division},  {partition},  {partitioning}, 
  {subdivision},  {sectionalization}] 
 
  From  The  Free  On-line  Dictionary  of  Computing  (13  Mar  01)  [foldoc]: 
 
  segmentation 
 
    (Or  "segmentation  and  reassembly",  SAR)  Breaking 
  an  arbitrary  size  {packet}  into  smaller  pieces  at  the 
  transmitter.  This  may  be  necessary  because  of  restrictions  in 
  the  communications  channel  or  to  reduce  {latency}.  The  pieces 
  are  joined  back  together  in  the  right  order  at  the  reciever 
  ("reassembly").  Segmentation  may  be  performed  by  a  {router} 
  when  routing  a  packet  to  a  network  with  a  smaller  maximum 
  packet  size. 
 
  The  term  segmentation"  is  used  in  {ATM},  in  {TCP/IP},  it  is 
  called  fragmentation"  an  is  performed  at  the  {IP}  layer 
  before  the  fragments"  are  passed  to  the  {transport  layer}. 
 
  See  for  example  {ATM  forum}  {UNI}  4.0  specification. 
 
  [Better  reasons?] 
 
  (1999-06-14)




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