Troublesome trade-offs: balancing urban activities and values when securing a city-centre governmental quarter

Background Homeland security measures increasingly affect urban life and activities. Standoff distance, which prevents unscreened vehicles from approaching within a certain distance of a building, is a widely applied measure when protecting buildings against attacks with vehicle-borne improvised explosive devices. This measure both is rather inexpensive and has few negative externalities when implemented in rural areas. Unfortunately, sites with protection needs often are situated in city centres. Methods We apply the so-called Security Function Framework to illuminate the externalities or the ‘troublesome trade-offs’ between protecting a high-value site against vehicle-borne improvised explosive devices and protecting other urban values. Results This paper demonstrates that standoff creates challenges for other important values, such as functional office spaces for all employees, deliveries and emergency vehicle access. Simultaneously, standoff creates opportunities for reinforcing social-responsibility requirements, such as accessibility for pedestrians and environmental considerations. Conclusions Security measures can have both negative and positive externalities and planning might alleviate some of the negative ones

A novel underdetermined source recovery algorithm based on k-sparse component analysis

Sparse component analysis (SCA) is a popular method for addressing underdetermined blind source separation in array signal processing applications. We are motivated by problems that arise in the applications where the sources are densely sparse (i.e. the number of active sources is high and very close to the number of sensors). The separation performance of current underdetermined source recovery (USR) solutions, including the relaxation and greedy families, reduces with decreasing the mixing system dimension and increasing the sparsity level (k). In this paper, we present a k-SCA-based algorithm that is suitable for USR in low-dimensional mixing systems. Assuming the sources is at most (m−1) sparse where m is the number of mixtures; the proposed method is capable of recovering the sources from the mixtures given the mixing matrix using a subspace detection framework. Simulation results show that the proposed algorithm achieves better separation performance in k-SCA conditions compared to state-of-the-art USR algorithms such as basis pursuit, minimizing norm-L1, smoothed L0, focal underdetermined system solver and orthogonal matching pursuit

Laser-Induced Reversible and Irreversible Changes in Silicon Nanostructures: One- and Multi-Phonon Raman Scattering Study

Reversible/irreversible changes in the Raman spectra of mesoporous silicon (<i>meso</i>-PSi) induced by laser heating were investigated. It is shown that whereas identical Raman spectra of single crystalline silicon can be obtained at different laser irradiances, these spectra change significantly in both reversible and irreversible ways in silicon nanostructures such as porous silicon (PSi). Whereas band shift and broadening in first- and second-order scattering were found to be reversible, surface phonon scattering events changed irreversibly. Given the importance of Raman spectroscopy in characterizing the pivotal role played by surface chemical bonds such as Si–H in the performance of PSi-based photovoltaics and microelectronics, our study highlights that great care must be taken to avoid Raman laser-induced effects on these bonds

Deubiquitinase function of arterivirus papain-like protease 2 suppresses the innate immune response in infected host cells

Protein ubiquitination regulates important innate immune responses. The discovery of viruses encoding deubiquitinating enzymes (DUBs) suggests they remove ubiquitin to evade ubiquitin-dependent antiviral responses; however, this has never been conclusively demonstrated in virus-infected cells. Arteriviruses are economically important positive-stranded RNA viruses that encode an ovarian tumor (OTU) domain DUB known as papain-like protease 2 (PLP2). This enzyme is essential for arterivirus replication by cleaving a site within the viral replicase polyproteins and also removes ubiquitin from cellular proteins. To dissect this dual specificity, which relies on a single catalytic site, we determined the crystal structure of equine arteritis virus PLP2 in complex with ubiquitin (1.45 Å). PLP2 binds ubiquitin using a zinc finger that is uniquely integrated into an exceptionally compact OTU-domain fold that represents a new subclass of zinc-dependent OTU DUBs. Notably, the ubiquitin-binding surface is distant from the catalytic site, which allowed us to mutate this surface to significantly reduce DUB activity without affecting polyprotein cleavage. Viruses harboring such mutations exhibited WT replication kinetics, confirming that PLP2-mediated polyprotein cleavage was intact, but the loss of DUB activity strikingly enhanced innate immune signaling. Compared with WT virus infection, IFN-β mRNA levels in equine cells infected with PLP2 mutants were increased by nearly an order of magnitude. Our findings not only establish PLP2 DUB activity as a critical factor in arteriviral innate immune evasion, but the selective inactivation of DUB activity also opens unique possibilities for developing improved live attenuated vaccines against arteriviruses and other viruses encoding similar dual-specificity proteases