Fast fluorescence switching within hydrophilic supramolecular assemblies

We designed a supramolecular strategy to modulate fluorescence in water under optical control. It is based on the entrapment of fluorophore-photochrome dyads within the hydrophobic interior of an amphiphilic polymer. The polymeric envelope around the dyads protects them from the aqueous environment, while imposing hydrophilic character on the overall supramolecular construct. In the resulting assemblies, the photochromic component can be operated reversibly on a microsecond timescale under the influence of ultraviolet stimulations. In turn, the reversible transformations control the emission intensity of the adjacent fluorophore. As a result, the fluorescence of such nanostructured constructs can be photomodulated for hundreds of cycles in water with microsecond switching speeds. Thus, our protocol for fast fluorescence switching in aqueous solutions can eventually lead to the realization of functional probes for the investigation of biological samples.     

Detailed optical characterization of three-dimensional visible-frequency polarization-independent carpet invisibility cloak

The invention of the three-dimensional woodpile photonic crystal by Costas M. Soukoulis and coworkers in 1994 has stimulated much further research—excellent research stimulates further research. Here, we report on using spatially inhomogeneous polymer woodpile structures in the long-wavelength limit as artificial graded-index structures. After briefly reviewing previous work on carpet invisibility cloaks designed by transformation optics, we present new experiments for various focus planes of the inspecting microscope as well as for different inspection angles in three-dimensional space. Numerical ray-tracing modeling is also provided. These data confirm our previous assessment that three-dimensional cloaking is quite robust for these structures.     

Injection-seeded, gain-switched tunable Cr:ZnSe laser

We report a narrow-linewidth, tunable, gain-switched Cr:ZnSe laser operating between 2255 and 2455 nm. The spectral width of the laser was reduced from 125 nm to 0.3 nm by using injection seeding. Seeding was achieved with a second tunable CW Cr:ZnSe laser. The output wavelength was varied by tuning the wavelength of the seed laser. The seeded oscillator produced as high as 157 μJ pulses with 598 μJ incident pump pulse energy at a repetition rate of 1 kHz. The slope efficiency was determined to be 26%.     

Pyridine-2,5-dicarboxylic acid complexes of nickel(II) with 2,2′-bipyridine and 1,10-phenanthroline coligands; syntheses,crystal structures,spectroscopic and thermal studies

Two pyridine-2,5-dicarboxylic acid (pydcH₂) complexes of nickel(II) with 2,2′-bipyridine and 1,10-phenanthroline were synthesized and characterized by elemental, spectroscopic, thermal analysis, magnetic measurements and single crystal X-ray diffraction techniques. Both [Ni(pydc)(bipy)₂]·7H₂O and [Ni(pydc)(phen)₂]·6.5H₂O crystallize in the monoclinic system and P2₁/c space group. The Ni(II) ions are coordinated by two bidentate bipy or phen ligands and one pydc dianion in a distorted octahedral geometry. The pydc ligand is coordinated through the pyridine nitrogen atom and oxygen atom of carboxyl group as a bidentate ligand. Both carboxylate groups of pydc are deprotonated but only the 2-carboxylate is coordinated to the metal. Thermal decompositions of the complexes have been studied over the range 30–600 °C on heating in a static air atmosphere.     

Form-stable electrospun nanofibrous mats as a potential phase change material

A series of Poly vinyl butyral–Poly (acrylic acid) (PVB-PAA) based form-stable phase change materials (PCMs) have been prepared for the use of thermal energy storage applications. Six types of formulations containing five different fatty alcohols were prepared by adding PVB to PAA. Using electrospinning to fabricate nanofibrous mats, our aim was to investigate their properties as form-stable PCMs. Fatty alcohols, 1-Tetradecanol, 1-Hexadecanol, 1-Octadecanol, 1-Eicosanol and 1-Docosanol, were added separately to base formulation. The structural characterization tests were performed by ATR-FTIR spectroscopy. Morphological tests were conducted using Scanning Electron Microscope (SEM). Thermal performances and phase change behaviors were tested by thermogravimetric analysis system (TGA) and differential scanning calorimetry (DSC). The heating cycle phase change enthalpy is measured between 223 and 241?J/g, and the freezing cycle phase change enthalpy is found between 215 and 239?J/g. The main decomposition PVB-PAA based PCMs started at 220?°C. This study suggested that PVB-PAA based PCMs possess well phase change properties and they were found to have an applicable temperature range. With the presented results these materials promise a great potential in thermal energy storage applications.     

Site‐Resolved Observation of Vibrational Energy Transfer Using a Genetically Encoded Ultrafast Heater

Allosteric information transfer in proteins has been linked to distinct vibrational energy transfer (VET) pathways in a number of theoretical studies. Experimental evidence for such pathways, however, is sparse because site‐selective injection of vibrational energy into a protein, that is, localized heating, is required for their investigation. Here, we solved this problem by the site‐specific incorporation of the non‐canonical amino acid β‐(1‐azulenyl)‐l ‐alanine (AzAla) through genetic code expansion. As an exception to Kasha's rule, AzAla undergoes ultrafast internal conversion and heating after S₁ excitation while upon S₂ excitation, it serves as a fluorescent label. We equipped PDZ3, a protein interaction domain of postsynaptic density protein 95, with this ultrafast heater at two distinct positions. We indeed observed VET from the incorporation sites in the protein to a bound peptide ligand on the picosecond timescale by ultrafast IR spectroscopy. This approach based on genetically encoded AzAla paves the way for detailed studies of VET and its role in a wide range of proteins.     

Scattering of plane-waves by an impedance half-plane at the interface between isorefractive media

The scattering of plane waves by an impedance half-plane located at the interface of two isorefractive media is investigated. The scattered field, in addition to the diffracted and geometrical optics fields, is analyzed numerically and compared to the scattered field of perfectly conducting half-plane. The effect of the isorefractive media on the scattered field is also examined.     

Modeling of Tarsus-Adana-Gaziantep highway-induced noise pollution within the scope of Adana city and estimated the affected population

The purpose of this study is, via employing SoundPLAN 7.3 software, to model the noise pollution that Tarsus-Adana-Gaziantep (TAG) Highway passing through Adana city induces in Adana city center and to designate the ratio of population exposed to the noise. The study was executed in an area extending from a 17 km-route of TAG Highway passing through Adana city center and 1900.62 ha area that surrounding 500 m north and 500 m south directions of this particular route.     

Beware the Black-Box: On the Robustness of Recent Defenses to Adversarial Examples

Many defenses have recently been proposed at venues like NIPS, ICML, ICLR and CVPR. These defenses are mainly focused on mitigating white-box attacks. They do not properly examine black-box attacks. In this paper, we expand upon the analyses of these defenses to include adaptive black-box adversaries. Our evaluation is done on nine defenses including Barrage of Random Transforms, ComDefend, Ensemble Diversity, Feature Distillation, The Odds are Odd, Error Correcting Codes, Distribution Classifier Defense, K-Winner Take All and Buffer Zones. Our investigation is done using two black-box adversarial models and six widely studied adversarial attacks for CIFAR-10 and Fashion-MNIST datasets. Our analyses show most recent defenses (7 out of 9) provide only marginal improvements in security (<25%), as compared to undefended networks. For every defense, we also show the relationship between the amount of data the adversary has at their disposal, and the effectiveness of adaptive black-box attacks. Overall, our results paint a clear picture: defenses need both thorough white-box and black-box analyses to be considered secure. We provide this large scale study and analyses to motivate the field to move towards the development of more robust black-box defenses.     

Implementation and Evaluation of Age-Aware Downlink Scheduling Policies in Push-Based and Pull-Based Communication

As communication systems evolve to better cater to the needs of machine-type applications such as remote monitoring and networked control, advanced perspectives are required for the design of link layer protocols. The age of information (AoI) metric has firmly taken its place in the literature as a metric and tool to measure and control the data freshness demands of various applications. AoI measures the timeliness of transferred information from the point of view of the destination. In this study, we experimentally investigate AoI of multiple packet flows on a wireless multi-user link consisting of a transmitter (base station) and several receivers, implemented using software-defined radios (SDRs). We examine the performance of various scheduling policies under push-based and pull-based communication scenarios. For the push-based communication scenario, we implement age-aware scheduling policies from the literature and compare their performance with those of conventional scheduling methods. Then, we investigate the query age of information (QAoI) metric, an adaptation of the AoI concept for pull-based scenarios. We modify the former age-aware policies to propose variants that have a QAoI minimization objective. We share experimental results obtained in a simulation environment as well as on the SDR testbed.