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On the Proof of Fixed-Point Convergence for Plug-and-Play ADMM
No full textIn most state-of-the-art image restoration methods, the sum of a data-fidelity and a regularization term is optimized using an iterative algorithm such as ADMM (alternating direction method of multipliers). In recent years, the possibility of using denoisers for regularization has been explored in several works. A popular approach is to formally replace the proximal operator within the ADMM framework with some powerful denoiser. However, since most state-of-the-art denoisers cannot be posed as a proximal operator, one cannot guarantee the convergence of these so-called plug-and-play (PnP) algorithms. In fact, the theoretical convergence of PnP algorithms is an active research topic. In this letter, we consider the result of Chan et al. (IEEE TCI, 2017), where fixed-point convergence of an ADMM-based PnP algorithm was established for a class of denoisers. We argue that the original proof is incomplete, since convergence is not analyzed for one of the three possible cases outlined in the letter. Moreover, we explain why the argument for the other cases does not apply in this case. We give a different analysis to fill this gap, which firmly establishes the original convergence theorem
Strand-specific affinity of host factor hnRNP C1/C2 guides positive to negative-strand ratio in Coxsackievirus B3 infection
No full textCoxsackievirus B3 is an enterovirus, with positive-sense single-stranded RNA genome containing `Internal Ribosome Entry Site' (IRES) in the 5MODIFIER LETTER PRIMEUTR. Once sufficient viral proteins are synthesized in the cell from the input RNA, viral template switches from translation to replication to synthesize negative-strand RNA. Inhibition of translation is a key step in regulating this switch as the positive-strand RNA template should be free of ribosomes to enable polymerase movement. In this study, we show how a host protein hnRNP C1/C2 inhibits viral RNA translation. hnRNP C1/C2 interacts with stem-loop V in the IRES and displaces poly-pyrimidine tract binding protein, a positive regulator of translation. We further demonstrate that hnRNP C1/C2 induces translation to replication switch, independently from the already known role of the ternary complex (PCBP2-3CD-cloverleaf RNA). These results suggest a novel function of hnRNP C1/C2 in template switching of positive-strand from translation to replication by a new mechanism. Using mathematical modelling, we show that the differential affinity of hnRNP C1/C2 for positive and negative-strand RNAs guides the final +/- RNA ratio, providing first insight in the regulation of the positive to negative-strand RNA ratio in enteroviruses
Role of interface quality in iron oxide core/shell nanoparticles on heating efficiency and transverse relaxivity
No full textCore/shell Fe3O4/gamma-Fe2O3 nanoparticles have been designed as a promising agent for magnetic hyperthermia and contrast agents for MRI imaging applications, because of their high magnetic moment and biocompatibility. Three sets of core/shell nanoparticles with the same core diameter of 8 nm and shell thicknesses of 1, 3 and 5 nm were synthesized by chemical coprecipitation. The nanoparticles were coated with PEG and the specific absorption rate for the nanoparticles was determined by applying 3.6 kA/m alternating magnetic field with 236 kHz frequency. The biocompatibility of the nanoparticles was confirmed by MTT assay. Three sets of nanoparticles presented in the study have shown the ability to kill 80-85% HeLa cells upon exposure to alternating magnetic field for 10 minutes in the presence of the nanoparticles. The transverse relaxivity of water protons for the three sets of the nanoparticles were obtained using 400 MHz Bruker NMR. The core/shell interface structure is found to be of poor quality because of interface defects which results in interface spin glass structures. The existence of the spin glass clusters suppresses the interface exchange coupling which leads to weak interface magnetic anisotropy. The insignificant role of core/shell structure on the heating efficiency is attributed to the insignificant contribution of the interface structure towards the effective anisotropy
Rh(III)-Catalyzed Oxidative Annulation of Sulfoximines with Arylalkynyl Silanes via Desilylation
No full textRh(III) catalyzed oxidative synthesis of 1,2-benzothiazine derivatives using sulfoximine as a directing group under C-H activation strategy is reported. In this study, we utilized arylalkynyl silanes as an alternate for terminal alkynes to obtain the 1,2-benzothiazine derivatives via desilylation pathway. The developed methodology shows a good range of functional group tolerance and furnished the products in moderate yields
Ultra-Sensitive Fiber Optic Gas Sensor Using Graphene Oxide Coated Long Period Gratings
No full textIn this letter, we develop two types of refractive index based sensors using single-mode fiber (SMF-28) to sense hazardous toxic gases in underground mines. The first sensor design is simply a graphene-oxide (GO) deposited long period grating (LPG) and second sensor consist of two LPGs with an interspacing distance of 1 cm (Delta l) acting as Mach-Zehnder interferometer (MZI). In addition, we also confirm GO deposition on the SMF using ultraviolet-visible spectroscopy, atomic force microscopy (AFM), and field emission scanning electron micrograph (FESEM). Our experiment results show that the sensitivity of two-LPGs based fiber optic sensor (SLPG-2 = 76.32 dB/RIU) is higher as compared to the single LPG sensor (SLPG-1 = 54.65 dB/RIU). Hence, reported graphene oxide deposited long period grating sensor possess better sensitivity and can detect maximum 1.52 x 10(-5) index variation in the optical telecommunication band
Experimental investigation of flat plate closed loop pulsating heat pipe
No full textPulsating heat pipes (PHPs) have promised to be effective heat spreaders. From the fabrication perspective, the PHPs are less intensive than their conventional counterparts. Despite the advantages, there still exists shortage of data in both experimental and analytical domains towards reliable design and prediction of PHP performance. In this study, a flat plate closed loop PHP has been experimentally investigated for its thermal performance. The PHP with 12 channels, each 2.2 mm deep x 2.0 mm wide, was tested with deionized water for a fill ratio of 70% by volume for various orientations starting from vertical evaporator below condenser (90 degrees) to near horizontal (7.5 degrees) orientation for a single heat load of 50 W to calibrate the test setup against published literature. The PHP was also tested for methanol with various fill ratios (30, 40, 50, 60 and 70%) for 50 W. The best performing fill ratio of methanol was tested for various heat loads (10 to 100 W) for the vertical and the near horizontal orientation. An attempt has been made to resolve the critical angle after which the PHP ceases to perform when tilted towards horizontal orientation. The PHP performance as expected was best at the 90 degrees (vertical) orientation with very little deterioration up to 45 degrees. The thermal resistances were estimated for two fluids, for various orientations, heat loads and fill ratios. The results indicate that at near horizontal orientation methanol performed better than water for 70% fill ratio. The 40% fill ratio of methanol yielded the least thermal resistance for all orientations. Also the thermal resistance of the PHP decreased with increasing heat load for different orientations. The PHP operated successfully up to 7.5-10 degrees below which the PHP was observed to have dry out
A luminescent inorganic-organic hybrid, Cd(C16H10N2O8S)(H2O)], for the selective and recyclable detection of chromates and dichromates in aqueous solution
No full textA new inorganic-organic hybrid compound Cd(H2L)(H2O)], 1, {where, H2L2- = 4,4 `-sulfonylbis(phenylene)bis(oxamate)} has been prepared under solvothermal conditions. The compound has a three-dimensional structure. The compound exhibits strong luminescence behavior, and was used for the detection of chromate and dichromate anions in aqueous media at low concentrations. The compound exhibited high selectivity and recyclability for the detection of low concentrations (ppm levels) of chromate and dichromate ions. Compound 1 was also found to be an effective catalyst for the Knoevenagel condensation involving aromatic aldehyde and malononitrile under green solvent-free conditions with high yield and recyclability
Group size and decision making: experimental evidence for minority games in fish behaviour
No full textAnimals tend to learn and make decisions inductively, and simple, individual-level behavioural decisions can scale up to yield interesting emergent properties at the population level. The minority game is a theoretical formulation based on the principle of inductive learning, wherein a group of individuals, each facing two equivalent choices, self-organize to achieve maximum coordination. Coordination increases with memory length up to a certain threshold, and thereafter, at very high memory lengths, decisions resemble a random choice game. We invoked and observed minority games in guppies, Poecilia reticulata, by forcing them to choose between two symmetric chambers in a series of repeated trials. At an intermediate timescale, guppies self-organized into a globally efficient state featuring maximum coordination. After a large number of trials, the guppies approached a steady state in which they behaved as if they were randomly choosing between the two chambers. Intriguingly, both the time taken to reach this globally efficient state (i.e. learning time) and the grouping behaviour for decision making depended on the sexual composition of the fish populations. We identified a positive correlation between group size and learning time in the experiments, which we further explored using simulations to uncover the form of decision-making framework at play, testing between a leader-based framework and a consensus-based one. Our simulations supported the presence of a consensus-based decision-making process in the system. This work also provides an unexplored general framework to further investigate and understand simple decision-making dynamics and structure in animal groups
Approximate Birkhoff-James orthogonality and smoothness in the space of bounded linear operators
No full textWe study approximate Birkhoff-James orthogonality of bounded linear operators defined between normed linear spaces X and Y. As an application of the results obtained, we characterize smoothness of a bounded linear operator T under the condition that K(X, Y), the space of compact linear operators is an M-ideal in L(X, Y), the space of bounded linear operators
Interaction of convective organization with monsoon precipitation, atmosphere, surface and sea: The 2016 INCOMPASS field campaign in India
No full textThe INCOMPASS field campaign combines airborne and ground measurements of the 2016 Indian monsoon, towards the ultimate goal of better predicting monsoon rainfall. The monsoon supplies the majority of water in South Asia, but forecasting from days to the season ahead is limited by large, rapidly developing errors in model parametrizations. The lack of detailed observations prevents thorough understanding of the monsoon circulation and its interaction with the land surface: a process governed by boundary-layer and convective-cloud dynamics. INCOMPASS used the UK Facility for Airborne Atmospheric Measurements (FAAM) BAe-146 aircraft for the first project of this scale in India, to accrue almost 100 h of observations in June and July 2016. Flights from Lucknow in the northern plains sampled the dramatic contrast in surface and boundary-layer structures between dry desert air in the west and the humid environment over the northern Bay of Bengal. These flights were repeated in pre-monsoon and monsoon conditions. Flights from a second base at Bengaluru in southern India measured atmospheric contrasts from the Arabian Sea, over the Western Ghats mountains, to the rain shadow of southeast India and the south Bay of Bengal. Flight planning was aided by forecasts from bespoke 4 km convection-permitting limited-area models at the Met Office and India's NCMRWF. On the ground, INCOMPASS installed eddy-covariance flux towers on a range of surface types, to provide detailed measurements of surface fluxes and their modulation by diurnal and seasonal cycles. These data will be used to better quantify the impacts of the atmosphere on the land surface, and vice versa. INCOMPASS also installed ground instrumentation supersites at Kanpur and Bhubaneswar. Here we motivate and describe the INCOMPASS field campaign. We use examples from two flights to illustrate contrasts in atmospheric structure, in particular the retreating mid-level dry intrusion during the monsoon onset