Narrow Results

In this note, we study NP-selective sets (formally, sets that are selective via NPSV_t functions) as a natural generalization of P-selective sets. We show that, assuming P≠NP∩coNP, the class of NP-selective sets properly contains the class of P-selective sets. We study several properties of NP-selective sets such as self-reducibility, hardness under various reductions, lowness, and nonuniform complexity. We prove many of our results via a “relativization technique,” by using the known properties of P-selective sets. Using this technique, we strengthen a result of Longpré and Selman on hard promise problems and show that the result “NP⊆(NP∩coNP)/poly⇒PH=NP^NP” is implicit in Karp and Lipton’s seminal result on nonuniform classes.

The selectivity limitation has long posed a significant challenge in the conversion of $\mathrm{\text{CO}}$ or ${\mathrm{\text{CO}}}_2$ into liquid hydrocarbon-based sustainable fuels via Fischer–Tropsch synthesis (FTS) and other related processing pathways due to the Anderson–Schulz–Flory (ASF) distribution. The unique pore structure, thermal stability, and acidic sites of ZSM-5 have enabled its widespread applications in various catalytic processes of value-added chemicals and sustainable fuels. In the reaction pathways from $\mathrm{\text{CO}}/{\mathrm{\text{CO}}}_2$ to liquid HCs of interest, incorporating ZSM-5 into metal catalysts provides new opportunities to enhance product selectivity and catalytic activity, and even lower the reaction energetics. This review highlights recent advancements over the past five years in the structural design of ZSM-5-based catalysts aimed at improving the conversion selectivity of advanced liquid biofuels such as renewable diesel and sustainable aviation fuel. It explores innovative strategies for optimizing catalyst composition, the acidity, mesoporosity, and structures of ZSM-5 to design more efficient, selective, and robust catalysts. Additionally, the review addresses the direct hydrogenation of $\mathrm{\text{CO}}$ and ${\mathrm{\text{CO}}}_2$ into C5+ liquid hydrocarbons, focusing on catalyst selection, acidic site optimization, and the structural configuration of ZSM-5. The mechanisms involved in these processes are also surveyed.

In thermophotovoltaic (TPV) systems, it is crucial that the selective emitters can tailor emission spectrum to match the bandgap of photovoltaic (PV) cells and largely enhance the system efficiency. In this work, a metamaterial emitter based on the metal-insulator-metal (MIM) structure is proposed to obtain the high energy conversion efficiencies. The geometric parameters of MIM emitter have been investigated to obtain an excellent radiation spectrum of emitter composed of W and HfO₂. The excellent emission performance of MIM emitter is attributed to the excitation of surface plasmon polariton (SPP) and cavity resonance, and the structure of MIM emitter is insensitive for different polarization modes. The 21 material combinations of MIM emitters have been screened to obtain the optimal emitter matching GaSb and InGaAsSb cells. This work identifies the crucial role of structure and materials into the emitter of a TPV system. In the evaluation of MIM emitter and TPV System, when the operating temperature of emitter increases from 1400K to 2000K, the system efficiency of optimal W/HfO₂/W MIM emitter increases from 20.26% to 30.41%, while the output electric power increases from 3.59kW/m² to 42.48kW/m². The phenomenon indicates that the MIM emitter with the optimal material combinations and geometric parameters can significantly improve the matching degree with GaSb and InGaAsSb cells. Our results will be helpful to expand the optimization scope of metamaterial emitters in TPV systems.

In this paper, an investigation on compact microstrip low-pass filters (MLPFs) with extremely perfect low-pass characteristics and improved out-band suppression has been carried out for the improvement of the selectivity parameter ($\xi$). For this purpose, two different defected ground structures (DGSs) based on Moore fractals and Meander line have been designed and experimentally validated. The proposed third-order low-pass filter (LPF) configurations are designed and simulated using the High-Frequency Structure Simulator (HFSS). To validate the simulation models, the prototypes of the suggested low-pass filters are fabricated using Teflon (TM) substrate having a relative permittivity of 2.65 and a loss tangent of 0.001, and measured using the Vector Network Analyzer. The simulation and measurement results are in good agreement. The proposed filters occupy a compact size of $0.398{\lambda }_g\times 0.398{\lambda }_g$. The selectivity parameter values for the proposed Moore fractals- and Meander line-modeled DGS-based LPFs are 425dB/GHz and 850dB/GHz, respectively. The proposed microstrip low-pass filters offer a significant improvement in the selectivity parameter, offering a maximum value of 850dB/GHz. The proposed filters exhibit a very high figure of merit (FOM), reporting 71,335 for Moore fractals-based LPF and 118,354 for the Meander line-based LPF. These proposed filters are suitable for advanced mobile phone services, $L$-band radar, Global Positioning System, mobile, paging services, Wi-Fi, Bluetooth and wireless LAN.

This paper proposes a novel polarity-control junctionless tunnel field-effect transistor (PC-JL-TFET)-based biosensor for the label-free detection of biomolecule species in efficient ways. Unlike conventional designs, the polarity-control concept induces the generation of drain (n${}^{+}$) and source (p${}^{+}$) regions inside the proposed structure when a bias of $\mp 1.2$ V is applied at the polarity gates-1/2 (PG-1/2), to form a conventional TFET. To capture the biomolecules, a nano-cavity is created within the source region’s dielectric oxide toward the tunneling interface. The presence of biomolecules is electronically detected based on either solely the dielectric constant (neutral biomolecules) or the combination of charge density and dielectric constant (charged biomolecules). The proposed device can perform label-free recognition of biomolecules such as Uricase, Keratin, Biotin, Streptavidin and so on. To investigate the sensing performance of the proposed biosensor, significant biosensing metrics such as the electric field, energy band diagram, tunneling current, subthreshold slope, $I_{\mathrm{\text{ON}}}/I_{\mathrm{\text{OFF}}}$ ratio and threshold voltage have been studied. The proposed PC-JL-TFET biosensor achieves a maximum sensitivity of $5.31\times 10^{10}$ for neutral biomolecules with a dielectric constant of 12 and $1.11\times 10^{10}$ for negatively charged biomolecules $(-1\times 10^{12}{\mathrm{\text{C/cm}}}^2)$ with a dielectric constant of 8. The proposed biosensor’s selectivity, linearity and temperature-based analysis have also been evaluated for different biomolecules. Additionally, real-time practical scenarios, such as partially filled nano-cavities and the random position of biomolecules in the nano-cavity-based analysis, have also been incorporated.

Radon-measure-valued solutions to a size structured population model of the McKendrick–von Foerster-type are analytically studied under general assumptions on individuals’ growth, birth and mortality rates. The model is used to describe changes in size structure of zooplankton when prey size-dependent mortality rate is a consequence of a planktivorous fish foraging in low prey-density environment (commonly found in predator-controlled populations). The model of foraging is based on the optimization of the rate of net energy intake as a function of predator speed. Mortality is defined as an operator on a metric space of nonnegative Radon measures equipped with the bounded Lipschitz distance. The solutions to the size structured model of zooplankton population are studied analytically and numerically. Numerical solutions (derived using the Escalator Boxcar Train (EBT)-like schema), in particular those starting from Dirac deltas corresponding to distinct cohorts, exhibit regularization in time and convergence to the same stationary state.

In biological olfactory systems, interaction of odorant molecules with olfactory receptor proteins is driven by Brownian motion. As a result, at chemical equilibrium, the total number of bound receptors changes randomly in time. Here we investigate the role of this effect, known in physics as adsorption-desorption noise, in the discriminating ability of olfactory receptor neurons. For this purpose we developed a computer program, which generates the adsorption-desorption process in a model neuron. We compared the processes resulting from two different odorants with different affinities for the receptor proteins. We took into account the threshold at which spikes are triggered and we calculated the neuronal selectivity due to the differences in the threshold-crossing statistics for the processes resulting from both odorants. We conclude that selectivity of the spiking response of the whole neuron is much greater than that of its receptor proteins in the near-threshold range of odorant concentrations.

In ecological systems, the fear of predation risk asserts a privilege to the prey species by restricting their exposure to the potential predators. It also imposes costs by constraining the exploration of optimal resources. Additional foods for predators play a pivotal role in the biological conservation programs. The predators have ability to distinguish between the susceptible and infected prey items, and they avoid the latter ones to reduce their fitness cost. A predator-prey model with disease in prey is investigated in this study with an aim to explore the effects of fear factor, additional foods and selective predation on the ecological systems. We also investigate the spatio-temporal model to incorporate the facts that the prey and predator populations perform active movements in the spatial directions for their biological relevance. Both the temporal and spatio-temporal models are analyzed through noteworthy mathematical as well as numerical techniques. Our simulation results show that the level of fear responsible for the reduction in the birth rate of susceptible prey, rate of disease transmission and the selective feeding behavior of predators have potentials to create instability in the ecosystem. In contrast, the level of fear responsible for reduction in the disease prevalence can restore stability in the ecosystem by killing the persistent oscillations. Our eco-epidemic system exhibits chaotic nature if the growth of predators due to additional food sources is very low. We find that the spatio-temporal model demonstrates different spatial patterns of the prey and predator populations in the ecosystem.

A theoretical study on the selectivity of a series of [M(12C4)]${}^{+}$ (M = Li${}^{+}$, Na${}^{+}$, K${}^{+}$, 12C4 = 12-crown-4) complexes for F${}^{-}$, Cl${}^{-}$ and Br${}^{-}$ anions and a number of neutral molecules (CH₃CN, CH₃OH, NH₃, H₂O, py, and 12C4) is reported. At first, it was shown that in the gas phase among all studied halide anions and neutral molecules, halides have much more bonding interaction with all [M(12C4)]${}^{+}$ cations. Calculated interaction energies of above anions and [M(12C4)]${}^{+}$ cations decrease from F${}^{-}$ to Br${}^{-}$. Also the interaction energy of halide anions with [M(12C4)]${}^{+}$ complexes, decreases from [Li(12C4)]${}^{+}$ to [K(12C4)]${}^{+}$. The electron decomposition analysis showed that the bond between [M(12C4)]${}^{+}$ complexes and both the neutral and anion guests is mainly electrostatic in nature. Then the selectivity of [M(12C4)]${}^{+}$ complexes for studied anions and neutral molecules are compared in methanol, acetone, acetonitrile, and nitromethane solutions. It was shown that both the desolvation process of reactants and the strength of host–guest interactions have significant effect on the selectivities. Thus the selectivity of [Li(12C4)]${}^{+}$ cation for NH₃ and H₂O neutral molecules in solution, in contrast to the gas phase, is higher than that for bromide anion. The results of calculations showed that all [M(12C4)]${}^{+}$ complexes, specially [Li(12C4)]${}^{+}$, have high selectivity for F${}^{-}$ over other halide anions and neutral molecules.

Three novel polymers incorporating Schiff bases, derived from condensation reactions of poly(acrylamide) with 5-chloro-2-hydroxybenzaldehyde, 5-bromo-2-hydroxybenzaldehyde and 5-methyl-2-hydroxybenzaldehyde, have been synthesized, and their Cu(II) and Ni(II) complexes have been prepared. The ¹H-NMR signals of the –CH=N– and –NH₂ groups have been utilized to determine the relative abundances of Schiff base and acrylamide groups in the polymers containing Schiff bases. Poly(acrylamide) incorporating Schiff bases and metal complexes thereof have been characterized by molar conductance, magnetic susceptibility and electronic and IR spectral studies. The selectivity of poly(acrylamide) incorporating Schiff bases in forming Ni(II)-aldehyde and Cu(II)-aldehyde complexes has been studied. The Cu(II) and Ni(II) contents in the metal-bearing polymer complexes were determined by the ICP-MS technique.

The derouting of the selective synthesis of crosswise phthalocyanines (Pcs) applied to a statistical precursors mixture leads to the first member of a new family of Pcs bearing three different substituents: the ABAC phthalocyanines. By playing on the precursors' relative ratio, the yields and selectivity of the method have been optimized.

The Ni(II) complex of 5,10,15,20-tetrakis[3${}^{\prime }$,5${}^{\prime }$-di(2${}^{\prime \prime }$-methylbutyloxy)phenyl]porphine was synthesized and characterized by ¹H NMR, UV-vis spectroscopy and MALDI-TOF mass-spectrometry. The stationary phase on the base of synthesized Ni(II) complex was used for chromatographic separation of isomeric methyl- and dimethylpyridines. The high structural selectivity of this sorbent was explained by giving the results of DFT calculation of pyridine derivatives axial complexes with porphyrin Ni(II) complexes.

An efficient enzymatic-free electrochemical sensor is firstly developed based on the self-assemblied film of a sandwich mixed (phthalocyaninato) (porphyrinato) europium(III) double-decker complex, Eu(Pc)[T(OH)PP], [Pc = phthalocyaninate, T(OH)PP = 5,10,15,tris (4-tert-butylphenyl)-20-(4-hydroxyphenyl)porphyrinate] prepared by using a solution-processing QLS method. The Eu(Pc)[T(OH)PP]semiconducting active layer on an ITO working electrode leads to a good sensing property for the detection of dopamine with an excellent selectivity, due to the high Eu(Pc)[T(OH)PP] molecular ordering/packing in the QLS film and more favorable interaction between the Eu(Pc)[T(OH)PP] and DA molecules. The amperometric responses are linearly proportional to the concentration of dopamine in the range of 8–100 $\mu$M, with a low detection limit of 4.8 $\mu$M and good sensitivity, indicating the great potential of electroactive tetrapyrrole rare earth sandwich type complexes in the field of nonenzymatic electrochemical sensors.

$N$-methyl mesoporphyrin IX (NMM) is a water-soluble, non-symmetric porphyrin with excellent optical properties and unparalleled selectivity for G-quadruplex (GQ) DNA. G-quadruplexes are non-canonical DNA structures formed by guanine-rich sequences. They are implicated in genomic stability, longevity, and cancer. The ability of NMM to selectively recognize GQ structures makes it a valuable scaffold for designing novel GQ binders. In this review, we survey the literature describing the GQ-binding properties of NMM as well as its wide utility in chemistry and biology. We start with the discovery of the GQ-binding properties of NMM and the development of NMM-binding aptamers. We then discuss the optical properties of NMM, focusing on the light-switch effect — high fluorescence of NMM induced upon its binding to GQ DNA. Additionally, we examine the affinity and selectivity of NMM for GQs, as well as its ability to stabilize GQ structures and favor parallel GQ conformations. Furthermore, a portion of the review is dedicated to the applications of NMM-GQ complexes as biosensors for heavy metals, small molecules ($e.g.$ ATP and pesticides), DNA, and proteins. Finally and importantly, we discuss the utility of NMM as a probe to investigate the roles of GQs in biological processes.

In this manuscript, we have studied the selectivity in the complexation of fullerene species by a Fe${}_{\mathrm{\text{2}}}$Pc${}_{\mathrm{\text{3}}}$ metallo-organic helicate (1) assembled using a bidentate phthalocyanine (Pc) as ligand. The large aromatic internal surface of this helicate shows a strong selectivity towards the encapsulation of C${}_{\mathrm{\text{70}}}$ from a mixture of C${}_{\mathrm{\text{60}}}$ and C${}_{\mathrm{\text{70}}}$. On the other hand, a bisimidazole-containing naphthalenediimide was used to perform guest exchange experiments over [fullerene $\subset$1] complexes, taking advantage of the strong coordination bond of the imidazole ring to the Zn centers in the Pc cavity.

In this work, the interaction of metal-free octaethylporphyrin (P) and a Mn(III) octaethylporphyrin chloride (MnP) films with various RNA nucleoside molecules (adenosine [A], cytidine [C], guanosine [G] and uridine [U]) was investigated to elucidate a possible molecular recognition. The porphyrin film-nucleoside interaction took place in solution, which was analyzed to quantify the nucleoside adsorption. The films were investigated by using microscopy and spectroscopic techniques (SEM, AFM, UV-Vis and IR), in addition to the in-plane film conductivity. Experimental results were correlated with DFT calculations to investigate binding energies, separation distances, and adsorption sites, among others. From these results, it was observed that purine bases were preferably adsorbed by the metal-free porphyrin film, while pyrimidine bases were adsorbed on the manganese porphyrin surface. Conductivity results exhibited the highest resistance for the bare metal-free film, but its conductivity increases after nucleoside adsorption, being the purine molecules the most resistive and the pyrimidine molecules the most conductive. In contrast, the Mn porphyrin film showed the highest conductivity, but after nucleoside adsorption, the resistivity increased for purine and pyrimidine bases, being pyrimidines the less conductive. DFT calculations showed binding energies PG>PA>PC>PU and MnPC>MnPG>MnPA>MnPU, which were consistent with experimental findings. In general, the main interactions took place between the porphyrin core and the pentose of the nucleoside, while MnP formed Mn porphyrin-nucleoside arrangements with octahedral geometry. The calculated UV-Vis spectra were in agreement with the experimental plots. From these results, changes in nucleoside adsorption can lead to a selective recognition of nucleoside molecules.

A novel functional inorganic imprinted ZnFe₂O₄@Ag₃PO₄/SiO₂ photocatalyst was synthesized by a facile sol–gel method combined with the surface imprinting technique, which possessed excellent stability. By optimizing the amount of materials, we determine the preferable addition amounts of tetraethoxysilane (TEOS) and tetracycline to be 0.06mL and 0.06g, respectively. This as-prepared functional inorganic imprinted ZnFe₂O₄@Ag₃PO₄/SiO₂ photocatalyst was proved to not only exhibit high photocatalytic activity (the photodegradation rate was 61.52% under the simulated sunlight irradiation of 60min), but also possess a strong oriented ability to selectively recognize and photocatalyze tetracycline (the coefficient of selectivity ($k_{\mathrm{\text{selectivity}}})$ was 5.14 for ciprofloxacin and 3.63 for gatifloxacin). Moreover, the functional inorganic imprinted ZnFe₂O₄@Ag₃PO₄/SiO₂ photocatalyst prepared with SiO₂ as the inorganic imprinted layer has good stability and can be recycled many times. This work not only puts forward a novel design idea of functional semiconductor materials but also is expected to be widely applied to the oriented catalysis for a target substance according to the practical requirement.

Many current sorbents are limited for U(VI) concentration from aqueous solutions due to their inappropriate structures and surface chemistry. Herein, we report the rapid sorption of U(VI) with high capacities and selectivity by amidoxime modified ordered mesoporous SBA-15 with two typical morphologies (i.e., rods and plates) via a post-grafting method. Variables of the geochemical conditions (contact time, pH value, initial concentration, temperature and coexisting metal ions) are investigated. The results show that the mesostructures including morphologies and pore length of SBA-15 perform the dominant function for the fast sorption kinetics (10min for plates, 20min for rods), while the modified amidoxime groups make the excellent U(VI) sorption capacities (646.2mg$\cdot$g${}^{-1}$ for plates, 499.8mg$\cdot$g${}^{-1}$ for rods at pH 5.0 and $T$ 298.15K) and high selectivity possible. U(VI) adsorbed amidoxime-functionalized SBA can also be effectively regenerated by HCl solutions and reused well after six cycles.

Hydrogen peroxide (H₂O${}_2)$ is an important chemical with wide fields of applications in the chemical industry, medicine and environmental protection. The preparation of H₂O₂ by the oxygen reduction reaction (ORR) via the two-electron pathway has the advantages of simple operation and environmental friendliness. Nevertheless, the kinetics of ORR is relatively slow, and the energy efficiency of electrochemical synthesis of H₂O₂ is seriously limited by the competitive four-electron pathway. Therefore, the electrosynthesis of H₂O₂ requires an electrocatalyst with both high catalytic activity and selectivity. In this study, Cu nanoparticles supported on carbon composites (Cu/C) were proposed and had been applied as the catalysts for the electrochemical synthesis of H₂O₂. Taking advantage of the cross-linking reaction between sodium alginate (SA) and metal ions, Cu nanoparticles were directly supported on carbon materials. The porous structure of carbon materials and the introduction of Cu improved the H₂O₂ selectivity of the catalysts. In O₂-saturated 0.1M KOH, the optimized catalyst exhibited good activity with a selectivity of 88–90% in the potential range of 0.2–0.6V for the electrosynthesis of H₂O₂, and the selectivity remained 70% after 6h of operation.

Highly ordered TiO₂ nanotube arrays were fabricated by anodization in an ethylene glycol solution containing NH₄F. A pair of platinum electrodes was deposited on the surface of the nanotube layer to fabricate a Pt/TiO₂ nanotube arrays hydrogen sensor. The subject sensors exhibited a seven order of magnitude change in resistance with a response time of 13 s at room temperature upon exposure to 2000 ppm (parts per million) hydrogen. We investigated the hydrogen response of the Pt/TiO₂ sensors as a function of the length of the nanotubes and compared their activity with that of a reference film.