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1. INTRODUCTION We have previously presented a method for optical rectification that has been demonstrated both theoretically and experimentally and can be used for the development of a practical rectification and energy conversion device for the elec tromagnetic spectrum including the visible portion. This technique for optical frequency rectification is based, not on conventional material or temperature asymmetry as used in MIM or Schottky diodes, but on a purely geometric property of the antenna tip or other sharp edges that may be incorporated on patch antennas. This “tip” or e dge in conjunction with a collect or anode providing connection to the external circuit constitutes a tunnel junction. Because such devices act as both the absorber of the incident radiation and the rectifier, they are referred to as “rectennas.” Using current nanofabrication techniques and the selective Atomic Layer Deposition (ALD) process, junctions of 1 nm can be fabricated, which allow for rectif ication of frequencies up to the blue portion of the spectrum (see Section 2). In this paper we treat in detail the role of geometry in nanoscale rectennas for rectification and energy conversion. We also discuss different model analyses and mathematical treatments for electron emission from a sharp tip. which all exhibit the same focusing and tunneling features due to asymmetrical geometry. Due to the incident radiation AC currents are induced along the length of the antenna, which produce oscillating charges at the top or edge of the geometrically asymmetric tunneling junction and corresponding image currents in the anode. The presence of the constricted geometry of the tip or edge gives rise to an e nhanced field at the tip. The oscillating charges in the tunnel junction induce an AC voltage across the gap. If the induced field is sufficient for field emission, a tunneling current is produced. Due to geometric asymmetry (and possible material asymmetry or plasmonic coatings), there is a difference between the potential barriers for forward and reverse bias, which results in a rectified DC current (see section 3). An SEM image of our fabricated geometrically-asymmetric device that we use in our own research is shown in Fig. 1. Note that we have chosen a device structure that has been fabricated on a large scale using standard nanofabri cation techniques.

Researchers disagree about why patients with schizophrenia perform poorly on memory tests. Some argue the presence of a fundamental memory deficit stemming from dysfunction in medial temporal lobe structures, principally the hippocampus. Others, stressing the contributions of impaired attention or executive failings such as a disorganized approach to learning, implicate larger neural networks. We compared data from psychometrically similar procedures, the Wechsler Memory Scale-Revised (WMS-R) and Wechsler Adult Intelligence Scale-Revised (WAIS-R), generated by 17 schizophrenia-spectrum patients and 33 psychiatric controls. We then compared our findings in detail with all published WMS-R/WAIS-R schizophrenia data. Our findings and the literature indicate that the acquisition of new information is disrupted in schizophrenia, but they provide little support for claims that memory deficits are especially pronounced relative to other weaknesses. Since schizophrenia patients exhibit reasonable retention following intervening activity, theories that place primary emphasis upon hippocampal dysfunction are not well supported.

We present a new and viable method for optical rectification. This approach has been demonstrated both theoretically and experimentally and is the basis fot the development of devices to rectify radiation through the visible. This technique for rectification is based not on conventional material or temperature asymmetry as used in MIM (metal/insulator/metal) or Schottky diodes, but on a purely sharp geometric property of the antenna. This sharp “tip” or edge with a collector anode constitutes a tunnel junction. In these devices the rectenna (consisting of the antenna and the tunnel junction) acts as the absorber of the incident radiation and the rectifier. Using current nanofabrication techniques and the selective atomic layer deposition (ALD) process, junctions of 1 nm can be fabricated, which allow for rectification of frequencies up to the blue portion of the spectrum. To assess the viability of our approach, we review the development of nanoantenna structures and tunnel junctions capable of operating in the visible region. In addition, we review the detailed process of rectification and present methodologies for analysis of diode data. Finally, we present operational designs for an optical rectenna and its fabrication and discuss outstanding problems and future work.