Special Pair Research Articles

Geometric Searchable Encryption for Privacy-Preserving Location-Based Services

Location data play an important role in location-based services (LBS) since they can help a service provider analyze users' daily activities and further derive users' behavioral patterns. However, in the meanwhile the use of the location data in LBS can also enable the service provider to track users' journeys which will reveal their personal information, such as house address and places of interest they visited, all of which users are usually unwilling to disclose. Therefore, security and privacy incidents can and do occur often. In this paper, aiming at how to hide location privacy and meanwhile provide an accurate search for LBS, we design a new geometric searchable encryption scheme under a public-key system (a.k.a. asymmetric system) for different types of geometric range queries, which enables the service provider to respond to the range queries from users accurately without learning the information about users' location. Towards this goal, we first exploit a novel encoding, and then develop some sophisticated transformations in combination with a special pairing function, which eventually converts different types of geometric range queries in LBS into different inner product problems. Finally, we present our construction by virtue of the techniques above with the inner product encryption technique. In addition, a comprehensive experimental analysis running on a specific application of privacy-preserving LBS and comparison demonstrate, our proposal is able to guarantee a higher accuracy for users' range queries without any false positive, and meanwhile express richer queries. Furthermore, we show another application of our proposal to privacy-preserving remote medical diagnosis at the end of this paper.

Closure theory for semirings-valued fuzzy sets with applications to new fuzzy structures

Many of the new fuzzy structures, including intuitionistic, neutrosophic, or fuzzy soft sets, use their oven theories and methods for operations with their fuzzy structures, including topological constructions. In the paper we show how basic closure methods could be universally defined in a number of new fuzzy structures, without having to define a new theory for individual fuzzy structures. This approach is based on the transformation of these fuzzy structures into a new type of fuzzy set, called (R,R⁎)-fuzzy sets, whose value sets are special pairs (R,R⁎) of commutative and idempotent semirings. The main advantage of this procedure is that all theoretical results that are proved for (R,R⁎)-fuzzy sets can be relatively easily transformed into an analogous result in all new fuzzy structures that can be transformed into (R,R⁎)-fuzzy sets, without the need to prove this result for individual types of fuzzy structure.

Soliton solution, breather solution and rational wave solution for a generalized nonlinear Schrödinger equation with Darboux transformation

In this paper, the exact solutions of generalized nonlinear Schrödinger (GNLS) equation are obtained by using Darboux transformation(DT). We derive some expressions of the 1-solitons, 2-solitons and n-soliton solutions of the GNLS equation via constructing special Lax pairs. And we choose different seed solutions and solve the GNLS equation to obtain the soliton solutions, breather solutions and rational wave solutions. Based on these obtained solutions, we consider the elastic interactions and dynamics between two solitons.

Role of pheophytin a in the primary charge separation of photosystem I from Acaryochloris marina: Femtosecond optical studies of excitation energy and electron transfer reactions

Photosystem I (PSI) of the cyanobacterium Acaryochloris marina is capable of performing an efficient photoelectrochemical conversion of far-red light due to its unique suite of cofactors. Chlorophyll d (Chl-d) has been long known as the major antenna pigment in the PSI from A. marina, while the exact cofactor composition of the reaction centre (RC) was established only recently by cryo-electron microscopy. The RC consists of four Chl-d molecules, and, surprisingly, two molecules of pheophytin a (Pheo-a), which provide a unique opportunity to resolve, spectrally and kinetically, the primary electron transfer reactions. Femtosecond transient absorption spectroscopy was here employed to observe absorption changes in the 400–860 nm spectral window occurring in the 0.1–500 ps timescale upon unselective antenna excitation and selective excitation of the Chl-d special pair P740 in the RC. A numerical decomposition of the absorption changes, including principal component analysis, allowed the identification of P740(+)Chld2(−) as the primary charge separated state and P740(+)Pheoa3(−) as the successive, secondary, radical pair. A remarkable feature of the electron transfer reaction between Chld2 and Pheoa3 is the fast, kinetically unresolved, equilibrium with an estimated ratio of 1:3. The energy level of the stabilised ion-radical state P740(+)Pheoa3(−) was determined to be ~60 meV below that of the RC excited state. In this regard, the energetics and the structural implications of the presence of Pheo-a in the electron transfer chain of PSI from A. marina are discussed, also in comparison with those of the most diffused Chl-a binding RC.

Ultrahigh-rate and ultralong-life aqueous batteries enabled by special pair-dancing proton transfer.

The design of Faradaic battery electrodes with high rate capability and long cycle life comparable to those of supercapacitors is a grand challenge. Here, we bridge this performance gap by taking advantage of a unique ultrafast proton conduction mechanism in vanadium oxide electrode, developing an aqueous battery with untrahigh rate capability up to 1000 C (400 A g-1) and extremely long life of 0.2 million cycles. The mechanism is elucidated by comprehensive experimental and theoretical results. Instead of slow individual Zn2+ transfer or Grotthuss chain transfer of confined H+, the ultrafast kinetics and excellent cyclic stability are enabled by rapid 3D proton transfer in vanadium oxide via the special pair dance switching between Eigen and Zundel configurations with little constraint and low energy barriers. This work provides insight into developing high-power and long-life electrochemical energy storage devices with nonmetal ion transfer through special pair dance topochemistry dictated by hydrogen bond.

Inverted region in the reaction of the quinone reduction in the A1-site of photosystem I from cyanobacteria.

Photosystem I from the menB strain of Synechocystis sp. PCC 6803 containing foreign quinones in the A1 sites was used for studying the primary steps of electron transfer by pump-probe femtosecond laser spectroscopy. The free energy gap (- ΔG) of electron transfer between the reduced primary acceptor A0 and the quinones bound in the A1 site varied from 0.12eV for the low-potential 1,2-diamino-anthraquinone to 0.88eV for the high-potential 2,3-dichloro-1,4-naphthoquinone, compared to 0.5eV for the native phylloquinone. It was shown that the kinetics of charge separation between the special pair chlorophyll P700 and the primary acceptor A0 was not affected by quinone substitutions, whereas the rate of A0 → A1 electron transfer was sensitive to the redox-potential of quinones: the decrease of - ΔG by 400meV compared to the native phylloquinone resulted in a ~ fivefold slowing of the reaction The presence of the asymmetric inverted region in the ΔG dependence of the reaction rate indicates that the electron transfer in photosystem I is controlled by nuclear tunneling and should be treated in terms of quantum electron-phonon interactions. A three-mode implementation of the multiphonon model, which includes modes around 240cm-1 (large-scale protein vibrations), 930cm-1 (out-of-plane bending of macrocycles and protein backbone vibrations), and 1600cm-1 (double bonds vibrations) was applied to rationalize the observed dependence. The modes with a frequency of at least 1600cm-1 make the predominant contribution to the reorganization energy, while the contribution of the "classical" low-frequency modes is only 4%.

Chlorophyll a Dimers Bound in the Water-Soluble Protein BoWSCP Photosensitize the Reduction of Cytochrome c.

When bound to water-soluble proteins of the WSCP family, chlorophyll molecules form dimers structurally similar to the "special pair" of chlorophylls (bacteriochlorophylls) in photosynthetic reaction centers. Being exposed to red light (λ ≥ 650 nm) in oxygen-free solutions, chlorophyll a dimers harbored by BoWSCP holoproteins (from Brassica oleracea var. botrytis) have sensitized the reduction of cytochrome c. According to absorption and circular dichroism spectroscopy data, the photochemical process did not significantly impair the structure of chlorophyll a molecules as well as their dimers harbored by BoWSCP protein. Adding tris(hydroxymethyl)aminomethane as an electron donor for chlorophyll recovery stimulated the photoreduction of cytochrome c.

CHLOROPHYLL <i>A</i> DIMERS HARBORED BY WATER-SOLUBLE PROTEIN BoWSCP PHOTOSENSITIZE REDUCTION OF CYTOCHROME <i>C</i>

When bound to water-soluble proteins of the WSCP family, chlorophyll molecules form dimers structurally similar to “special pair” of chlorophylls (bacteriochlorophylls) in photosynthetic reaction centers. Being exposed to red light (λ ≥ 650 nm) in oxygen-free solutions, chlorophyll a dimers harbored by BoWSCP holoproteins (from Brassica oleracea var. botrytis) have sensitized the reduction of cytochrome c. According to absorption and circular dichroism spectroscopy data, the photochemical process did not significantly impair the structure of chlorophyll a molecules as well as their dimers harbored by BoWSCP protein. Adding tris(hydroxymethyl)aminomethane as an electron donor for chlorophyll recovery stimulated the photoreduction of cytochrome c.

Excited State Mixed-Valence Complexes: From the Special Pair to the Creutz-Taube Ion and Beyond.

Compounds and complexes with mixed-valence electronic ground states, such as the Creutz-Taube ion, have proven to be excellent vehicles through which to study intramolecular electron-transfer processes. In a recent contribution by Cadranel and co-workers, time-resolved pump-probe spectroscopy reveals photo-induced metal-to-bridge charge transfer within the homovalent analogue of the Creutz-Taube ion, [{(NH3 )5 Ru}(μ-pz){Ru(NH3 )5 }]4+ , giving rise to two closely lying excited states with mixed-valence character, one with a shorter lifetime (τ=136 ps) and weakly-coupled (Robin-Day Class II) character, the other a longer-lived (τ=2.8 ns) configurational isomer with more delocalized electronic structure. Electron transfer reactions from the longer-lived species demonstrate analogies with the photo-induced reactions of the photosynthetic special pair, suggesting this state as a reference system for excited state mixed-valency, and a framework from which to explore photocatalytic reactions.

Excited State Mixed‐Valence Complexes: From the Special Pair to the Creutz–Taube Ion and Beyond

AbstractCompounds and complexes with mixed‐valence electronic ground states, such as the Creutz–Taube ion, have proven to be excellent vehicles through which to study intramolecular electron‐transfer processes. In a recent contribution by Cadranel and co‐workers, time‐resolved pump‐probe spectroscopy reveals photo‐induced metal‐to‐bridge charge transfer within the homovalent analogue of the Creutz–Taube ion, [{(NH3)5Ru}(μ‐pz){Ru(NH3)5}]4+, giving rise to two closely lying excited states with mixed‐valence character, one with a shorter lifetime (τ=136 ps) and weakly‐coupled (Robin‐Day Class II) character, the other a longer‐lived (τ=2.8 ns) configurational isomer with more delocalized electronic structure. Electron transfer reactions from the longer‐lived species demonstrate analogies with the photo‐induced reactions of the photosynthetic special pair, suggesting this state as a reference system for excited state mixed‐valency, and a framework from which to explore photocatalytic reactions.

Detection method of the neutral temperature in continuous welded rails based on nonlinear ultrasonic guided waves

ABSTRACT The continuous-welded rail (CWR) will generate longitudinal stress when the rail temperature deviates from the neutral temperature (NT). Although CWR has been widely used in modern rail transit systems, real-time monitoring of longitudinal stress in CWR, or equivalently NT, is still a technical challenge. In order to explore the possibility of nonlinear guided waves in NT detection, this paper identifies possible pairs of fundamental and second harmonic waves modes in the rail, and investigates the effects of stress and temperature on the nonlinear parameter of each mode pair that could produce cumulative second harmonics. Both of stress and temperature are found to have significant influence on the nonlinear parameter, thus how to decouple the influences of temperature and stress is the key to NT detection. It is also found that the variation pattern of the nonlinear parameter vs. temperature curve could be completely different for different mode pairs. Furthermore, when the temperature of CWR changes monotonically , the nonlinear parameters of almost all mode pairs increase or decrease monotonically, except one mode pair, the nonlinear parameter of which presents a clear local minimum at NT. Thus, this special mode pair can be used to detect NT without considering the coupling influence of temperature and stress.

Cryo-EM structure of the whole photosynthetic reaction center apparatus from the green sulfur bacterium Chlorobaculum tepidum

Light energy absorption and transfer are very important processes in photosynthesis. In green sulfur bacteria light is absorbed primarily by the chlorosomes and its energy is transferred via the Fenna-Matthews-Olson (FMO) proteins to a homodimeric reaction center (RC). Here, we report the cryogenic electron microscopic structure of the intact FMO-RC apparatus from Chlorobaculum tepidum at 2.5 Å resolution. The FMO-RC apparatus presents an asymmetric architecture and contains two FMO trimers that show different interaction patterns with the RC core. Furthermore, the two permanently bound transmembrane subunits PscC, which donate electrons to the special pair, interact only with the two large PscA subunits. This structure fills an important gap in our understanding of the transfer of energy from antenna to the electron transport chain of this RC and the transfer of electrons from reduced sulfur compounds to the special pair.

Quantum mechanical analysis of excitation energy transfer couplings in photosystem II

We evaluated excitation energy transfer (EET) coupling (J) between all pairs of chlorophylls (Chls) and pheophytins (Pheos) in the protein environment of photosystem II based on the time-dependent density functional theory with a quantum mechanical/molecular mechanics approach. In the reaction center, the EET coupling between Chls PD1 and PD2 is weaker (|J(PD1/PD2)| = 79 cm−1), irrespective of a short edge-to-edge distance of 3.6 Å (Mg-to-Mg distance of 8.1 Å), than the couplings between PD1 and the accessory ChlD1 (|J(PD1/ChlD2)| = 104 cm−1) and between PD2 and ChlD2 (|J(PD2/ChlD1)| = 101 cm−1), suggesting that PD1 and PD2 are two monomeric Chls rather than a “special pair”. There exist strongly coupled Chl pairs (|J| > ∼100 cm−1) in the CP47 and CP43 core antennas, which may be candidates for the red-shifted Chls observed in spectroscopic studies. In CP47 and CP43, Chls ligated to CP47-His26 and CP43-His56, which are located in the middle layer of the thylakoid membrane, play a role in the “hub” that mediates the EET from the lumenal to stromal layers. In the stromal layer, Chls ligated to CP47-His466, CP43-His441, and CP43-His444 mediate the EET from CP47 to ChlD2/PheoD2 and from CP43 to ChlD1/PheoD1 in the reaction center. Thus, the excitation energy from both CP47 and CP43 can always be utilized for the charge-separation reaction in the reaction center.

Advances in the Spectroscopic and Structural Characterization of Core Light-Harvesting Complexes from Purple Phototrophic Bacteria.

Purple phototrophic bacteria are ancient anoxygenic phototrophs and attractive research tools because they capture light energy in the near-infrared (NIR) region of the spectrum and transform it into chemical energy by way of uphill energy transfers. The heart of this reaction occurs in light-harvesting 1-reaction center (LH1-RC) complexes, which are the simplest model systems for understanding basic photosynthetic reactions within type-II (quinone-utilizing) reaction centers. In this Perspective, we highlight structure-function relationships concerning unresolved fundamental processes in purple bacterial photosynthesis, including the diversified light-harvesting capacity of LH1-associated BChl molecules, energies necessary for photoelectric conversion in the RC special pairs, and quinone transport mechanisms. Based on recent progress in the spectroscopic and structural analysis of LH1-RC complexes from a variety of purple phototrophs, we discuss several key factors for understanding how purple bacteria resource light energy in the inherently energy-poor NIR region of the electromagnetic spectrum.

Electronic structure and energetics of a heterodimeric BChl g'/Chl a' special pair generated by exposure of Heliomicrobium modesticaldum to dioxygen.

Heliobacteria are anoxygenic phototrophs that have a Type I homodimeric reaction center containing bacteriochlorophyll g (BChl g). Previous experimental studies have shown that in the presence of light and dioxygen, BChl g is converted into 81-OH-chlorophyll aF (hereafter Chl aF), with an accompanying loss of light-driven charge separation. These studies suggest that the reaction center only loses the ability to transfer electrons once both BChl g' molecules of the P800 special pair have been converted to Chl aF'. The present work confirms that the partially converted BChl g'/Chl aF' special pair remains functional in samples exposed to dioxygen by demonstrating its presence using hyperfine couplings obtained from Q-band 1H ENDOR, 2D 14N HYSCORE and DFT methods. The DFT calculations of the BChl g'/BChl g' homodimeric primary donor, which are based on the recently published X-ray crystal structure, predict that the unpaired electron spin is equally delocalized over both BChl g' molecules and provide an excellent match to the experimental hyperfine couplings of the anaerobic samples. Exposure to dioxygen leads to substantial changes in the hyperfine interactions, indicative of greater localization of the unpaired electron spin. The measured hyperfine couplings are reproduced in the DFT calculations by replacing one of the BChl g' molecules of the primary donor with a Chl aF' molecule. The calculations reveal that the spin density becomes localized on BChl g' in the heterodimeric primary donor. Time-dependent DFT calculations demonstrate that conversion of either or both of the accessory BChl g molecules and/or one of the BChl g' molecules of P800 to Chl aF' results in minor effects on the energy of the charge-separated states. In contrast, if both of the BChl g' molecules of P800 are converted a large increase in the energy of the charge-separated state occurs. This suggests that the reaction center remains functional when only one half of the dimer is converted, however, conversion of both halves of the P800 dimer leads to loss of function.

Distinct contribution of two cyclic electron transport pathways to P700 oxidation.

Cyclic electron transport (CET) around Photosystem I (PSI) acidifies the thylakoid lumen and downregulates electron transport at the cytochrome b6f complex. This photosynthetic control is essential for oxidizing special pair chlorophylls (P700) of PSI for PSI photoprotection. In addition, CET depending on the PROTON GRADIENT REGULATION 5 (PGR5) protein oxidizes P700 by moving a pool of electrons from the acceptor side of PSI to the plastoquinone pool. This model of the acceptor-side regulation was proposed on the basis of the phenotype of the Arabidopsis (Arabidopsis thaliana) pgr5-1 mutant expressing Chlamydomonas (Chlamydomonas reinhardtii) plastid terminal oxidase (CrPTOX2). In this study, we extended the research including the Arabidopsis chlororespiratory reduction 2-2 (crr2-2) mutant defective in another CET pathway depending on the chloroplast NADH dehydrogenase-like (NDH) complex. Although the introduction of CrPTOX2 did not complement the defect in the acceptor-side regulation by PGR5, the function of the NDH complex was complemented except for its reverse reaction during the induction of photosynthesis. We evaluated the impact of CrPTOX2 under fluctuating light intensity in the wild-type, pgr5-1 and crr2-2 backgrounds. In the high-light period, both PGR5- and NDH-dependent CET were involved in the induction of photosynthetic control, whereas PGR5-dependent CET preferentially contributed to the acceptor-side regulation. On the contrary, the NDH complex probably contributed to the acceptor-side regulation in the low-light period but not in the high-light period. We evaluated the sensitivity of PSI to fluctuating light and clarified that acceptor-side regulation was necessary for PSI photoprotection by oxidizing P700 under high light.

Quantum coherent energy transport in the Fenna–Matthews–Olson complex at low temperature

In the primary step of natural light harvesting, the solar photon energy is captured in a photoexcited electron-hole pair, or an exciton, in chlorophyll. Its conversion to chemical potential occurs in the special pair reaction center, which is reached by downhill ultrafast excited-state energy transport through a network of chromophores. Being inherently quantum, transport could in principle occur via a matter wave, with vast implications for efficiency. How long a matter wave remains coherent is determined by the intensity by which the exciton is disturbed by the noisy biological environment. The stronger this is, the stronger the electronic coupling between chromophores must be to overcome the fluctuations and phase shifts. The current consensus is that under physiological conditions, quantum coherence vanishes on the 10-fs time scale, rendering it irrelevant for the observed picosecond transfer. Yet, at low-enough temperature, quantum coherence should in principle be present. Here, we reveal the onset of longer-lived electronic coherence at extremely low temperatures of ∼20 K. Using two-dimensional electronic spectroscopy, we determine the exciton coherence times in the Fenna-Matthew-Olson complex over an extensive temperature range. At 20 K, coherence persists out to 200 fs (close to the antenna) and marginally up to 500 fs at the reaction center. It decays markedly faster with modest increases in temperature to become irrelevant above 150 K. At low temperature, the fragile electronic coherence can be separated from the robust vibrational coherence, using a rigorous theoretical analysis. We believe that by this generic principle, light harvesting becomes robust against otherwise fragile quantum effects.

A Note on Henstock-Itô's Non-Stochastic Integral

It is well-known that the generalized Riemann approach using non-uniform mesh has given rise to integrals which are more general than the Riemann integral. In this note, motivated by earlier studies on stochastic integrals, we consider special interval-point pair in defining the Riemann sum, where the point (or the tag) is the left-hand point of the interval. We show that this approach in fact is equivalent to the Lebesgue integral. Hence this simplifies McShane's construction of interval-point pair. Moreover, by restricting to the tag as the left hand point of the interval, the integration-by-substitution and by-parts formulae become easy consequences of the definition.

Influence of dimple textures on the tribological performances of tapered roller bearings under starved lubrication

PurposeThe purpose of this paper is to study the influence of dimple textures on the friction and wear properties of tapered roller bearings (TRBs) with many pattern parameters, e.g. diameter, depth and area density under starved lubrication.Design/methodology/approachThe pattern parameters include the dimple diameter (D; 60, 100 and 200 µm), dimple depth (H; 5, 10 and 20 µm) and area density (S; 6%, 12% and 24%). Dimples were fabricated on the outer ring (OR) of TRBs using a laser marking machine. The tribological properties of dimple-textured TRBs under starved lubrication were studied on a vertical universal friction wear tester with special friction pairs. The effect mechanisms of dimple textures on the tribological properties of TRBs are presented and summarized through experiments and discussions.FindingsWhen dimple-textured TRBs revolve under starved lubrication, the average coefficients of friction (ACOF) and wear losses are markedly lower than those of non-textured bearings. S has the greatest influence on the COF curve. When D is 100 µm and S is 24%, the ACOF and wear losses are both lowest, i.e. 0.00426 and 0.51 mg, respectively. Under the same test conditions, compared with the non-textured group, its COF and wear loss decreased by 35.6% and 62.5%, respectively.Originality/valueThis work provides a useful reference for the research on the raceways of textured TRBs.

Ultrafast Symmetry-Breaking Charge Separation in a Perylene Bisimide Dimer Enabled by Vibronic Coupling and Breakdown of Adiabaticity.

Perylene bisimides (PBIs) have received great attention in their applicability to optoelectronics. Especially, symmetry-breaking charge separation (SB-CS) in PBIs has been investigated to mimic the efficient light capturing and charge generation in natural light-harvesting systems. However, unlike ultrafast CS dynamics in donor-acceptor heterojunction materials, ultrafast SB-CS in a stacked homodimer has still been challenging due to excimer formation in the absence of rigidifying surroundings such as a special pair in the natural systems. Herein, we present the detailed mechanism of ultrafast photoinduced SB-CS occurring in a 1,7-bis(N-pyrrolidinyl) PBI dimer within a cyclophane. Through narrow-band and broad-band transient absorption spectroscopy, we demonstrate that ultrafast SB-CS in the dimer is enabled by the combination of (1) vibrationally coherent charge-transfer resonance-enhanced excimer formation and (2) breakdown of adiabaticity (formation of SB-CS diabats) in the excimer state via structural and solvent fluctuation. Quantum chemical calculations also underpin that the participation of strong electron-donating substituents in overall vibrational modes plays a crucial role in triggering the ultrafast SB-CS. Therefore, our work provides an alternative route to facilitate ultrafast SB-CS in PBIs and thereby establishes a novel strategy for the design of optoelectronic materials.