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Lexington, MA, United States

Noncontact detection of the homemade explosive constituents urea nitrate, nitromethane and ammonium nitrate is achieved using photodissociation followed by laser-induced fluorescence (PD-LIF). Our technique utilizes a single ultraviolet laser pulse (approximately 7 ns) to vaporize and photodissociate the condensed-phase materials, and then to detect the resulting vibrationally-excited NO fragments via laser-induced fluorescence. PD-LIF excitation and emission spectra indicate the creation of NO in vibrationally-excited states with significant rotational energy, useful for low-background detection of the parent compound. The results for homemade explosives are compared to one another and 2,6-dinitrotoluene, a component present in many military explosives. Source

Turitsyn S.K.,Aston University | Bale B.G.,Aston University | Bale B.G.,Lincoln Laboratory | Fedoruk M.P.,Russian Academy of Sciences
Physics Reports

Nonlinear systems with periodic variations of nonlinearity and/or dispersion occur in a variety of physical problems and engineering applications. The mathematical concept of dispersion managed solitons already has made an impact on the development of fibre communications, optical signal processing and laser science. We overview here the field of the dispersion managed solitons starting from mathematical theories of Hamiltonian and dissipative systems and then discuss recent advances in practical implementation of this concept in fibre-optics and lasers. © 2012 Elsevier B.V. Source

Protein coronas have been the focus of a great deal of study recently due to their inevitable formation and their impact on the biological consequences of nanomaterials. Although the field is still far from completely and definitively understanding protein coronas, we now have a good understanding of their behavior and their key characteristics. Protein corona composition changes with the environment and time, and also the physical properties of the underlying nanoparticle. More importantly, the protein corona has significant biological impact. Because we have a basic understanding of coronas, we can now move forward to exploiting their unique properties. Here, we discuss some emerging ways in which the protein corona is explicitly utilized for different applications in biology and medicine. © 2015 Future Medicine Ltd. Source

Tsiligkaridis T.,Lincoln Laboratory
IEEE Transactions on Signal Processing

We consider the problem of secure communications in a MIMO setting in the presence of an adversarial jammer equipped with nj transmit antennas and an eavesdropper equipped with ne receive antennas. A multiantenna transmitter, equipped with nt antennas, desires to secretly communicate a message to a multiantenna receiver equipped with nr antennas. We propose a transmission method based on artificial noise and linear precoding and a two-stage receiver method employing beamforming. Under this strategy, we first characterize the achievable secrecy rates of communication and prove that the achievable secure degrees-of-freedom (SDoF) is given by d-{s}=n-{r}-nj in the perfect channel state information (CSI) case. Second, we consider quantized CSI feedback using Grassmannian quantization of a function of the direct channel matrix and derive sufficient conditions for the quantization bit rate scaling as a function of transmit power for maintaining the achievable SDoF ds with perfect CSI and for having asymptotically zero secrecy rate loss due to quantization. Numerical simulations are also provided to support the theory. © 1991-2012 IEEE. Source

Aguilar C.A.,Lincoln Laboratory | Craighead H.G.,Cornell University
Nature Nanotechnology

Deoxyribonucleic acid (DNA) is the blueprint on which life is based and transmitted, but the way in which chromatin-a dynamic complex of nucleic acids and proteins-is packaged and behaves in the cellular nucleus has only begun to be investigated. Epigenetic modifications sit 'on top of' the genome and affect how DNA is compacted into chromatin and transcribed into ribonucleic acid (RNA). The packaging and modifications around the genome have been shown to exert significant influence on cellular behaviour and, in turn, human development and disease. However, conventional techniques for studying epigenetic or conformational modifications of chromosomes have inherent limitations and, therefore, new methods based on micro- and nanoscale devices have been sought. Here, we review the development of these devices and explore their use in the study of DNA modifications, chromatin modifications and higher-order chromatin structures. © 2013 Macmillan Publishers Limited. All rights reserved. Source

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