A density-gradient model for the H II galaxy I ZW 18

1990 ◽  
Vol 362 ◽  
pp. 100 ◽  
Author(s):  
Alison Campbell
Keyword(s):  
Density Gradient ◽  
Gradient Model

Five Layered Optiprep based Density Gradient Model is a Promising Model for Enrichment of Viable X Chromosome Bearing Spermatozoa in Bubalus bubalis

2020 ◽  
Author(s):  
Rajni Kumari ◽  
Kanisht Batra ◽  
Vinay Kumar ◽  
Aman Kumar ◽  
Trilok Nanda
Keyword(s):  
Sex Ratio ◽  
Density Gradient ◽  
X Chromosome ◽  
Density Gradient Centrifugation ◽  
Gradient Centrifugation ◽  
Dairy Farming ◽  
Farm Animals ◽  
Murrah Buffalo ◽  
Bull Semen ◽  
Gradient Model

Background: A reliable method for controlling the sex of farm animals has the potential to revolutionize dairy farming. This can only be achieved by use of a method capable of separating X and Y chromosome bearing spermatozoa at lower cost and causing no significant damages to sperm viability. Realizing significance of buffaloes in Indian dairy farming, present study was aimed to develop appropriate density gradient model for enrichment of X chromosome bearing spermatozoa population in semen of Murrah buffalo bull. Methods: Density gradient centrifugation (DGC) technique was employed for enriching X chromosome spermatozoa in buffalo bull semen using four gradient media viz., Percoll, Optiprep, Ficoll and Sucrose. Percentage enrichment of X chromosome bearing spermatozoa in all the DGC models was determined by SYBR green based Real Time PCR. Result: Our investigations revealed that number of layers and centrifugation speed (g) factors in a density gradient centrifugation model, have significant effect on the percentage enrichment of X chromosome content in semen samples.Three layers, four layers and five layers density gradient centrifugation models showed significant differences (P less than 0.05) in the sex ratio towards X spermatozoa population in semen (61.72%±0.81, 64.55%±0.26 and 67.31±0.33%) respectively. Density gradient centrifugation models with centrifugation speed (g) 200x g and 300x g also showed significant differences (P less than 0.05) in the sex ratio towards X spermatozoa population in semen (66.36%±0.25 and 62.69±0.22%) respectively. Out of all DGC models, Optiprep density gradient model with 5 layers and centrifugation at 200xg (O3) yielded maximum enrichment (72.4%±1.38). In conclusion, O3 poses to be a promising model for enrichment of X spermatozoa in buffalo bull semen.

scholarly journals Integration of the Density Gradient Model into a General Purpose Device Simulator

VLSI Design ◽  
2002 ◽  
Vol 15 (4) ◽  
pp. 751-759 ◽  
Author(s):  
Andreas Wettstein ◽  
Oleg Penzin ◽  
Eugeny Lyumkis
Keyword(s):  
Density Gradient ◽  
Systems Engineering ◽  
General Purpose ◽  
Integrated Systems ◽  
Discretization Scheme ◽  
Dinger Equation ◽  
Gradient Model ◽  
Reference Manual ◽  
Good Agreement ◽  
Standard Density

A generalized Density Gradient model has been implemented into the device simulator Dessis [DESSIS 7.0 reference manual (2001). ISE Integrated Systems Engineering AG, Balgriststrasse 102, CH-8008 Zürich].We describe the multidimensional discretization scheme used and discuss our modifications to the standard Density Gradient model. The evaluation of the model shows good agreement to results obtained by the Schro¨dinger equation.

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