Evanescent field optical readout of graphene mechanical motion at room temperature

Graphene mechanical resonators have recently attracted considerable attention for use in precision force and mass sensing applications. To date, readout of their oscillatory motion has typically required cryogenic conditions to achieve high sensitivity, restricting their range of applications. Here we report the first demonstration of evanescent optical readout of graphene motion, using a scheme which does not require cryogenic conditions and exhibits enhanced sensitivity and bandwidth at room temperature. We utilise a high $Q$ microsphere to enable evanescent readout of a 70 $\mu$m diameter graphene drum resonator with a signal-to-noise ratio of greater than 25 dB, corresponding to a transduction sensitivity of $S_{N}^{1/2} =$ 2.6 $\times 10^{-13}$ m $\mathrm{Hz}^{-1/2}$. The sensitivity of force measurements using this resonator is limited by the thermal noise driving the resonator, corresponding to a force sensitivity of $F_{min} = 1.5 \times 10^{-16}$ N ${\mathrm{Hz}}^{-1/2}$ with a bandwidth of 35 kHz at room temperature (T = 300 K). Measurements on a 30 $\mu$m graphene drum had sufficient sensitivity to resolve the lowest three thermally driven mechanical resonances.Comment: Fixed formatting errors in bibliograph

On the Transmission of Colour Image Over Double Generalized Gamma FSO Channel

In this paper performance analysis of colour image Free Space Optics (FSO) transmission over Double Generalized Gamma (DGG) turbulence communication channel is carried out. At the reception side, we have used an average bit error rate (ABER) for reconstructed image performance measure, as the function of FSO link transmission parameters, such as propagation distance, Rytov variance and turbulence shaping and severity parameters (γ1, γ2, m1, m2). Obtained results cover a large number of colour image FSO transmission scenarios, for Gamma-Gamma, Double-Weibull and K turbulence models channels considered as special cases

Synchronous imaging for rapid visualization of complex vibration profiles in electromechanical microresonators

Synchronous imaging is used in dynamic space-domain vibration profile studies of capacitively driven, thin n+ doped poly-silicon microbridges oscillating at rf frequencies. Fast and high-resolution actuation profile measurements of micromachined resonators are useful when significant device nonlinearities are present. For example, bridges under compressive stress near the critical Euler value often reveal complex dynamics stemming from a state close to the onset of buckling. This leads to enhanced sensitivity of the vibration modes to external conditions, such as pressure, temperatures, and chemical composition, the global behavior of which is conveniently evaluated using synchronous imaging combined with spectral measurements. We performed an experimental study of the effects of high drive amplitude and ambient pressure on the resonant vibration profiles in electrically-driven microbridges near critical buckling. Numerical analysis of electrostatically driven post-buckled microbridges supports the richness of complex vibration dynamics that are possible in such micro-electromechanical devices.Comment: 7 pages, 8 figure, submitted to Physical Review

Analysis of Single Event Transient Effects in Standard Delay Cells Based on Decoupling Capacitors

Single Event Transients (SETs), i.e., voltage glitches induced in combinational logic as a result of the passage of energetic particles, represent an increasingly critical reliability threat for modern complementary metal oxide semiconductor (CMOS) integrated circuits (ICs) employed in space missions. In rad-hard ICs implemented with standard digital cells, special design techniques should be applied to reduce the Soft Error Rate (SER) due to SETs. To this end, it is essential to consider the SET robustness of individual standard cells. Among the wide range of logic cells available in standard cell libraries, the standard delay cells (SDCs) implemented with the skew-sized inverters are exceptionally vulnerable to SETs. Namely, the SET pulses induced in these cells may be hundreds of picoseconds longer than those in other standard cells. In this work, an alternative design of a SDC based on two inverters and two decoupling capacitors is introduced. Electrical simulations have shown that the propagation delay and SET robustness of the proposed delay cell are strongly influenced by the transistor sizes and supply voltage, while the impact of temperature is moderate. The proposed design is more tolerant to SETs than the SDCs with skew-sized inverters, and occupies less area compared to the hardening configurations based on partial and complete duplication. Due to the low transistor count (only six transistors), the proposed delay cell could also be used as a SET filter

Supplementary material for the article: Ilić, B.; Dimkić, I.; Unković, N.; Grbić, M. L.; Vukojević, J.; Vujisić, L.; Tešević, V.; Stanković, S.; Makarov, S.; Lučić, L. Millipedes vs. Pathogens: Defensive Secretions of Some Julids (Diplopoda: Julida) as Potential Antimicrobial Agents. Journal of Applied Entomology 2018, 142 (8), 775–791. https://doi.org/10.1111/jen.12526

Supplementary material for: [https://doi.org/10.1111/jen.12526]Related to published version: [http://cherry.chem.bg.ac.rs/handle/123456789/2198

Vortex dynamics in confined stratified conditions

We report on linear spin dynamics in the vortex state of the Permalloy dots subjected to stratified (magnetic) field. We demonstrate experimentally and by simulations the existence of two distinct dynamic regimes corresponding to the vortex stable and metastable states. Breaking cylindrical symmetry leads to unexpected eigenmodes frequency splitting in the stable state and appearance of new eigenmodes in the metastable state above the vortex nucleation field. Dynamic response in the metastable state strongly depends on relative orientation of the external rf pumping and the bias magnetic fields. These findings may be relevant for different vortex states in confined and stratified conditions

Supplementary material for the article: Ilić, B.; Dimkić, I.; Unković, N.; Grbić, M. L.; Vukojević, J.; Vujisić, L.; Tešević, V.; Stanković, S.; Makarov, S.; Lučić, L. Millipedes vs. Pathogens: Defensive Secretions of Some Julids (Diplopoda: Julida) as Potential Antimicrobial Agents. Journal of Applied Entomology 2018, 142 (8), 775–791. https://doi.org/10.1111/jen.12526

Supplementary material for: [https://doi.org/10.1111/jen.12526]Related to published version: [http://cherry.chem.bg.ac.rs/handle/123456789/2198

Search for dark matter produced in association with bottom or top quarks in √s = 13 TeV pp collisions with the ATLAS detector

A search for weakly interacting massive particle dark matter produced in association with bottom or top quarks is presented. Final states containing third-generation quarks and miss- ing transverse momentum are considered. The analysis uses 36.1 fb−1 of proton–proton collision data recorded by the ATLAS experiment at √s = 13 TeV in 2015 and 2016. No significant excess of events above the estimated backgrounds is observed. The results are in- terpreted in the framework of simplified models of spin-0 dark-matter mediators. For colour- neutral spin-0 mediators produced in association with top quarks and decaying into a pair of dark-matter particles, mediator masses below 50 GeV are excluded assuming a dark-matter candidate mass of 1 GeV and unitary couplings. For scalar and pseudoscalar mediators produced in association with bottom quarks, the search sets limits on the production cross- section of 300 times the predicted rate for mediators with masses between 10 and 50 GeV and assuming a dark-matter mass of 1 GeV and unitary coupling. Constraints on colour- charged scalar simplified models are also presented. Assuming a dark-matter particle mass of 35 GeV, mediator particles with mass below 1.1 TeV are excluded for couplings yielding a dark-matter relic density consistent with measurements