3,660 research outputs found
Emerging roles in plant biotechnology for the second messenger cGMP - guanosine 3’, 5’-cyclic monophosphate
Second messengers are small transient molecules that transmit and/or modulate environmental or hormonal signals linking them to complex and often systemic physiological responses. Recent reports have renewed interest in the second messenger guanosine 3’, 5’-cyclic monophosphate (cGMP) since it has been shown to directly mediate an ever increasing number of plant responses ranging from themodification of cyclic nucleotide gated ion channels to the regulation of tran scription of many cGMPresponsive genes. Here some of these cGMP dependent responses will be reviewed emphasising their role in plant stress responses. Finally, potential applications of cGMP in plant biotechnology will be discussed
Pressure Induced Quantum Phase Transitions
A quantum critical point is approached by applying pressure in a number of
magnetic metals. The observed dependence of Tc on pressure necessarily means
that the magnetic energy is coupled to the lattice. A first order phase
transition occurs if this coupling exceeds a critical value: this is inevitable
if diverges as Tc approaches zero. It is argued that this is the cause of the
first order transition that is observed in many systems. Using Landau theory we
obtain expressions for the boundaries of the region where phase separation
occurs that agree well with experiments done on MnSi and other materials. The
theory can be used to obtain very approximate values for the temperature and
pressure at the tricritical point in terms of quantities measured at ambient
pressure and the measured values of along the second order line. The values of
the tricritical temperature for various materials obtained from Landau theory
are too low but it is shown that the predicted values will rise if the effects
of fluctuations are included.Comment: 12 pages including figure
Monte Carlo simulations for Ising spins with spin greater than 1/2 applied to the square and triangular lattices with antiferromagnetic interactions and comparing results using Kawasaki and Glauber dynamics
This paper has a pedagogical introduction. We describe the correct method for performing Monte Carlo simulations of Ising model systems with spin greater than one half. Correct and incorrect procedures are clearly outlined and the consequences of using the incorrect procedure are shown. The difference between Kawasaki and Glauber dynamics is then outlined and both methods are applied to the antiferromagnetic square and triangular lattices for S =1
- …