W
        =
        
          
            1
            2
          
        
        c
        
          (
          
            
              e
              
                
                  b
                  
                    i
                    j
                    k
                    l
                  
                
                
                  E
                  
                    i
                    j
                  
                
                
                  E
                  
                    k
                    l
                  
                
              
            
            −
            1
          
          )
        
      
    
    {\displaystyle W={\frac {1}{2}}c\left(e^{b_{ijkl}E_{ij}E_{kl}}-1\right)}

Gent-elastic material
W
        =
        −
        
          
            
              μ
              
                J
                
                  m
                
              
            
            2
          
        
        ln
        ⁡
        
          (
          
            1
            −
            
              (
              
                
                  
                    
                      λ
                      
                        1
                      
                      
                        2
                      
                    
                    +
                    
                      λ
                      
                        2
                      
                      
                        2
                      
                    
                    +
                    
                      λ
                      
                        3
                      
                      
                        2
                      
                    
                    −
                    3
                  
                  
                    J
                    
                      m
                    
                  
                
              
              )
            
          
          )
        
      
    
    {\displaystyle W=-{\frac {\mu J_{m}}{2}}\ln \left(1-\left({\frac {\lambda _{1}^{2}+\lambda _{2}^{2}+\lambda _{3}^{2}-3}{J_{m}}}\right)\right)}
  where 
  
    
      
        μ
        >
        0
      
    
    {\displaystyle \mu >0}
   is the shear modulus for infinitesimal strains and 
  
    
      
        
          J
          
            m
          
        
        >
        0
      
    
    {\displaystyle J_{m}>0}
   is a stiffening parameter, associated with limiting chain extensibility.
A nitrovasodilator is a pharmaceutical agent that causes vasodilation (widening of blood vessels) by donation of nitric oxide (NO), and is mostly used for the treatment and prevention of angina pectoris. This group of drugs includes nitrates (esters of nitric acid), which are reduced to NO in the body, as well as some other substances. Examples
Here is a list of examples of the nitrate type (in alphabetical order):

Nitrovasodilators which arent nitrates include molsidomine and its active metabolite linsidomine, as well as sodium nitroprusside. These substances do not need to be reduced to donate NO. Medical uses
The nitrates are used for the treatment and prevention of angina and acute myocardial infarction, while molsidomine acts too slowly to be useful for the treatment of acute angina. For quick action in the treatment of angina, glyceryl trinitrate is used in form of a sublingual spray (nitro spray) or as soft capsules to be crunched.Nitroprusside is used intravenously for the treatment of hypertensive crises, heart failure, and lowering of blood pressure during surgery. Contraindications
Nitrovasodilators are contraindicated under circumstances where lowering of blood pressure can be dangerous. This includes, with some variation between the individual substances, severe hypotension (low blood pressure), shock including cardiogenic shock, and anaemia. Whether a specific drug is useful or harmful under heart failure and myocardial infarction depends on its speed of action: Fast acting substances such as glyceryl trinitrate and nitroprusside can be helpful for controlling blood pressure and consequently the amount of blood the heart has to pump, if the application is monitored continuously.