Goldstein J.,The Graduate Center, CUNY
Antipode | Year: 2013
This essay provides an analysis of the "dirty" history and geography of enclosure, as both an instance of primitive accumulation and a production of nature. Specifically, I reconsider the English enclosures as a struggle over the land-use designation of "waste". Whereas both open fields and common waste lands were an essential and valuable part of the common right economy, advocates of enclosure came to see these same lands as wasted commons; lands that were potentially, but not yet, improved. This dialectic of waste and potential permeates the fabric of the nature produced through enclosure, which I name terra economica. Typically, this terrain has been understood as a passive repository of free resources, extending across absolute space. While such accounts consider the making of nature into a universal means of production, it is equally important to consider the ways in which nature is produced as a universal condition of production. © 2012 The Author. Antipode. © 2012 Antipode Foundation Ltd.
Ranaldi R.,The Graduate Center, CUNY
Reviews in the Neurosciences | Year: 2014
Reward seeking is controlled by conditioned stimuli (CSs). There is a positive relation between mesocorticolimbic dopamine (DA) and the performance of learned reward-directed behavior. The mechanisms by which reward-, including drug-, associated stimuli come to acquire the capacity to activate the DA systems are not fully understood. In this review, we discuss the possible neurochemical mechanisms within the ventral tegmental area that may be involved in how CSs acquire the capacity to activate ventral tegmental area (VTA) DA neurons based on principles of long-term potentiation in the VTA and the role of mesocorticolimbic DA in reward-related learning. We propose that CSs function as such because they acquire the capacity to activate VTA DA neurons. Furthermore, CSs come to acquire this control of VTA DA cells when there is coincident N-methyl-d-aspartate receptor stimulation on VTA DA cells and strong depolarization of VTA DA cells, possibly by muscarinic acetylcholine receptor stimulation on these cells. This coincident activity leads to the strengthening of CS-associated glutamatergic synapses and the control by CSs of mesocorticolimbic DA systems and reward-directed behavior. © 2014 by De Gruyter.
Chatterjee S.,The Graduate Center, CUNY
Nanoscale | Year: 2012
Self-assembly based on nucleic acid systems has become highly attractive for bottom-up fabrication of programmable matter due to the highly selective molecular recognition property of biomolecules. In this context, Y-shaped DNA (Y-DNA) provides an effective building block for forming unique self-assembled large-scale architectures. The dimension and growth of the nano- and microstructures depend significantly on the configurational stability of Y-DNA as a building block. Here we present structural studies of Y-DNA systems using a time-resolved FRET (Förster resonance energy transfer) technique. A fluorophore (Alexa 488) and an acceptor (DABCYL) were placed at two different ends of Y-DNA, and the lifetime of the fluorophore was measured to probe the relative distance between the donor and acceptor. Our results confirmed different distances between the arms of the Y-DNA and highlighted the overall structural integrity of the Y-DNA system as a leading building block for molecular self-assembly. Temperature dependent lifetime measurements indicated configurational changes in the overall Y-DNA nanoarchitecture above 40 °C.
Hexner D.,Technion - Israel Institute of Technology |
Levine D.,Technion - Israel Institute of Technology |
Levine D.,The Graduate Center, CUNY
Physical Review Letters | Year: 2015
The properties of the absorbing states of nonequilibrium models belonging to the conserved directed percolation universality class are studied. We find that, at the critical point, the absorbing states are hyperuniform, exhibiting anomalously small density fluctuations. The exponent characterizing the fluctuations is measured numerically, a scaling relation to other known exponents is suggested, and a new correlation length relating to this ordering is proposed. These results may have relevance to photonic band-gap materials. © 2015 American Physical Society.
Ge L.,CUNY - College of Staten Island |
Ge L.,The Graduate Center, CUNY |
Stone A.D.,Yale University
Physical Review X | Year: 2014
We consider the role of degeneracy in parity-time (PT ) symmetry breaking for non-Hermitian wave equations beyond one dimension.We show that if the spectrum is degenerate in the absence of T breaking, and T is broken in a generic manner (without preserving other discrete symmetries), then the standard PT symmetry-breaking transition does not occur, meaning that the spectrum is complex even for infinitesimal strength of gain and loss. However, the realness of the entire spectrum can be preserved over a finite interval if additional discrete symmetries x are imposed when T is broken, if x decouples all degenerate modes. When the decoupling holds only for a subset of the degenerate spectrum, there can be a partial PT transition in which this subset remains real over a finite interval of T breaking. If the spectrum has odd degeneracy, a fraction of the degenerate spectrum can remain in the symmetric phase even without imposing additional discrete symmetries, and they are analogous to dark states in atomic physics. These results are illustrated by the example of different T -breaking perturbations of a uniform dielectric disk and sphere, and a group-theoretical analysis is given in the disk case. Finally, we show that multimode coupling is capable of restoring the PT -symmetric phase at finite T breaking.We also analyze these questions when the parity operator is replaced by another spatial symmetry operator and find that the behavior can be qualitatively different.