A Simple Multi-band Metamaterial Absorber with Combined Polarization Sensitive and Polarization Insensitive Characteristics for Terahertz Applications

This paper presents a simple multi-band metamaterial absorber for terahertz applications. The unit cell of the proposed structure consists of a single square ring having gaps at the centers on three of its sides. The proposed absorber produces three absorption bands for all polarizations and hence the design can be considered as insensitive to polarization variation. It provides an average absorption of 96.92% for the TE polarization with a peak absorption of 99.44% at 3.87 THz and for the TM polarization, it provides an average absorption of 98.4% with a peak absorption of 99.86% at 3.87 THz. An additional absorption peak is observed for the TE polarization at 1.055 THz that gradually diminishes with the increase in polarization angle and completely vanishes for the TM polarization. Thus, the structure displays a hybrid polarization response with polarization insensitivity in three bands and polarization sensitivity in one band. Parametric analysis has been carried out validating the optimal selection of the design parameters. The simplicity of the design and its combined polarization sensitive and polarization insensitive absorption characteristics can find tremendous applications in the field of terahertz imaging and sensing.

     

A Hybrid Terahertz Metamaterial Sensor Using a Hexagonal Ring Resonator with Bio-medical Applications

Plasmonics - In recent years, novel terahertz (THz) metamaterial sensors are being actively explored by the research community. These structures absorb the incident THz waves, and their absorption...     

Role for mTOR signaling and neuronal activity in morphine-induced adaptations in ventral tegmental area dopamine neurons

While the abuse of opiate drugs continues to rise, the neuroadaptations that occur with long-term drug exposure remain poorly understood. We describe here a series of chronic morphine-induced adaptations in ventral tegmental area (VTA) dopamine neurons, which are mediated via downregulation of AKT-mTORC2 (mammalian target of rapamycin complex-2). Chronic opiates decrease the size of VTA dopamine neurons in rodents, an effect seen in humans as well, and concomitantly increase the excitability of the cells but decrease dopamine output to target regions. Chronic morphine decreases mTORC2 activity, and overexpression of Rictor,?a component of mTORC2, prevents morphine-induced changes in cell morphology and activity. Further, local knockout of Rictor in VTA decreases DA soma size and reduces rewarding responses to morphine, consistent with the hypothesis that these adaptations represent a mechanism of reward tolerance. Together, these findings demonstrate a novel role for AKT-mTORC2 signaling in mediating neuroadaptations to opiate drugs of abuse.     

An Octaband Polarization Insensitive Terahertz Metamaterial Absorber Using Orthogonal Elliptical Ring Resonators

Plasmonics - Terahertz metamaterial absorbers are the latest developments that have tremendous applications in terahertz spectroscopy and terahertz imaging. Especially, the research progressed in...     

Bacteriophage T4 gp2 Interferes with Cell Viability and with Bacteriophage Lambda Red Recombination

The T4 head protein, gp2, promotes head-tail joining during phage morphogenesis and is also incorporated into the phage head. It protects the injected DNA from degradation by exonuclease V during the subsequent infection. In this study, we show that recombinant gp2, a very basic protein, rapidly kills the cells in which it is expressed. To further illustrate the protectiveness of gp2 for DNA termini, we compare the effect of gp2 expression on Red-mediated and Int-mediated recombination. Red-mediated recombination is nonspecific and requires the transient formation of double-stranded DNA termini. Int-mediated recombination, on the other hand, is site specific and does not require chromosomal termini. Red-mediated recombination is inhibited to a much greater extent than is Int-mediated recombination. We conclude from the results of these physiological and genetic experiments that T4 gp2 expression, like Mu Gam expression, kills bacteria by binding to double-stranded DNA termini, the most likely mode for its protection of entering phage DNA from exonuclease V.     

Chips to hits

A report on the IBC USA International Microtechnology Conference 'Chips to hits', San Diego, USA, 27 October to 1 November 2001.     

Self-Administration of Ethanol,Cocaine, or Nicotine Does Not Decrease the Soma Size of Ventral Tegmental Area Dopamine Neurons

Our previous observations show that chronic opiate administration, including self-administration, decrease the soma size of dopamine (DA) neurons in the ventral tegmental area (VTA) of rodents and humans, a morphological change correlated with increased firing rate and reward tolerance. Given that a general hallmark of drugs of abuse is to increase activity of the mesolimbic DA circuit, we sought to determine whether additional drug classes produced a similar morphological change. Sections containing VTA were obtained from rats that self-administered cocaine or ethanol and from mice that consumed nicotine. In contrast to opiates, we found no change in VTA DA soma size induced by any of these other drugs. These data suggest that VTA morphological changes are induced in a drug-specific manner and reinforce recent findings that some changes in mesolimbic signaling and neuroplasticity are drug-class dependent.