Differentiation of Alkyl- and Plasmenyl-phosphatidylcholine by Endogenous Sphingomyelin RT-XLOGP3 Regression for Coronary Artery Disease Plasma Lipidomics Analysis.

Accurate identification between alkyl- and plasmenyl-phosphatidylcholine (PC(O-) and PC(P-)) isomers is a major analytical challenge in lipidomics studies due to a lack of structure-specific ions in conventional tandem mass spectrometry (MS/MS) methods and the absence of universal retention time (RT) references. Given the importance of PC(O-) and PC(P-), an easy-to-apply method for current research is urgently needed. In this study, we present a quadratic RT-XLOGP3SM regression model that uses endogenous sphingomyelin (SM) species in blood samples as retention time (RT) indicators to predict the RTs of PC(O-) and PC(P-) species by coupling their calculated partition coefficients based on XLOGP3. The prediction results were obtained with a root-mean-square error (RMSE) of 0.12 min (1.3%) for the RRHD (rapid resolution high definition) nonlinear LC condition. A lipidomic analysis with RT-XLOGP3SM regression was used to study lipid regulation in coronary artery disease (CAD) outpatient plasma samples, and we found that the types of exhibited regulation were highly dependent on the lipid subclasses in comparison to the healthy control group. In conclusion, given that the quadratic RT-XLOGP3SM regression model predicts the RTs of PC species based on the relative value of XLOGP3 and the RTs of endogenous SM species, it can be expected that most of the C18-based lipidomics analyses could apply this method to increase the identification ability of the PC(O-) and PC(P-) subclasses and to improve the understanding of their physiological functions.

Dimensional Transmutation from Non-Hermiticity.

Dimensionality plays a fundamental role in the classification of novel phases and their responses. In generic lattices of 2D and beyond, however, we found that non-Hermitian couplings do not merely distort the Brillouin zone (BZ), but can in fact alter its effective dimensionality. This is due to the fundamental noncommutativity of multidimensional non-Hermitian pumping, which obstructs the usual formation of a generalized complex BZ. As such, basis states are forced to assume "entangled" profiles that are orthogonal in a lower dimensional effective BZ, completely divorced from any vestige of lattice Bloch states unlike conventional skin states. Characterizing this reduced dimensionality is an emergent winding number intimately related to the homotopy of noncontractible spectral paths. We illustrate this dimensional transmutation through a 2D model whose topological zero modes are protected by a 1D, not 2D, topological invariant. Our findings can be readily demonstrated via the bulk properties of nonreciprocally coupled platforms such as circuit arrays, and provokes us to rethink the fundamental role of geometric obstruction in the dimensional classification of topological states.

Hyperbolic Fringe Signal for Twin Impurity Quasiparticle Interference.

We study the quasiparticle interference (QPI) pattern emanating from a pair of adjacent impurities on the surface of a gapped superconductor (SC). We find that hyperbolic fringes (HFs) in the QPI signal can appear due to the loop contribution of the two-impurity scattering, where the locations of the two impurities are the hyperbolic focus points. For a single pocket Fermiology, a HF pattern signals chiral SC order for nonmagnetic impurities and requires magnetic impurities for a nonchiral SC. For a multipocket scenario, a sign-changing order parameter such as an s_{±} wave likewise yields a HF signature. We discuss twin impurity QPI as a new tool to complement the analysis of superconducting order from local spectroscopy.

Proposal for Observing Yang-Lee Criticality in Rydberg Atomic Arrays.

Yang-Lee edge singularities (YLES) are the edges of the partition function zeros of an interacting spin model in the space of complex control parameters. They play an important role in understanding non-Hermitian phase transitions in many-body physics, as well as characterizing the corresponding nonunitary criticality. Even though such partition function zeroes have been measured in dynamical experiments where time acts as the imaginary control field, experimentally demonstrating such YLES criticality with a physical imaginary field has remained elusive due to the difficulty of physically realizing non-Hermitian many-body models. We provide a protocol for observing the YLES by detecting kinked dynamical magnetization responses due to broken PT symmetry, thus enabling the physical probing of nonunitary phase transitions in nonequilibrium settings. In particular, scaling analyses based on our nonunitary time evolution circuit with matrix product states accurately recover the exponents uniquely associated with the corresponding nonunitary CFT. We provide an explicit proposal for observing YLES criticality in Floquet quenched Rydberg atomic arrays with laser-induced loss, which paves the way towards a universal platform for simulating non-Hermitian many-body dynamical phenomena.

Exceptional Bound States and Negative Entanglement Entropy.

This Letter introduces a new class of robust states known as exceptional bound (EB) states, which are distinct from the well-known topological and non-Hermitian skin boundary states. EB states occur in the presence of exceptional points, which are non-Hermitian critical points where eigenstates coalesce and fail to span the Hilbert space. This eigenspace defectiveness not only limits the accessibility of state information but also interplays with long-range order to give rise to singular propagators only possible in non-Hermitian settings. Their resultant EB eigenstates are characterized by robust anomalously large or negative occupation probabilities, unlike ordinary Fermi sea states whose probabilities lie between 0 and 1. EB states remain robust after a variety of quantum quenches and give rise to enigmatic negative entanglement entropy contributions. Through suitable perturbations, the coefficient of the logarithmic entanglement entropy scaling can be continuously tuned. EB states represent a new avenue for robustness arising from geometric defectiveness, independent of topological protection or nonreciprocal pumping.

Simulation of Interaction-Induced Chiral Topological Dynamics on a Digital Quantum Computer.

Chiral edge states are highly sought after as paradigmatic topological states relevant to both quantum information processing and dissipationless electron transport. Using superconducting transmon-based quantum computers, we demonstrate chiral topological propagation that is induced by suitably designed interactions, instead of flux or spin-orbit coupling. Also different from conventional 2D realizations, our effective Chern lattice is implemented on a much smaller equivalent 1D spin chain, with sequences of entangling gates encapsulating the required time-reversal breaking. By taking advantage of the quantum nature of the platform, we circumvented difficulties from the limited qubit number and gate fidelity in present-day noisy intermediate-scale quantum era quantum computers, paving the way for the quantum simulation of more sophisticated topological states on very rapidly developing quantum hardware.

Plasma ceramides are associated with outcomes in acute ischemic stroke patients.

BACKGROUND/PURPOSE: Sphingolipids are major constituents of eukaryotic cell membranes and play key roles in cellular regulatory processes. Our recent results in an experimental stroke animal model demonstrated changes in sphingolipids in response to acute ischemic brain injury. This study aimed to investigate the plasma levels of sphingosine-1-phosphate (S1P) and ceramides in acute ischemic stroke (AIS) patients and their associations with functional outcomes. METHODS: Plasma samples were collected from patients with AIS at <48 and 48-72 h post stroke and from nonstroke controls. The levels of S1P and ceramides with different fatty acyl chain lengths were measured by the ultra-high-pressure liquid chromatography-electrospray ionization tandem mass spectrometry (UHPLC-ESI-MS/MS). A poor functional outcome was defined as a modified Rankin Scale (mRS) score ≥2 at 3 months after AIS. RESULTS: The results showed that S1P and very-long-chain ceramides were significantly decreased in AIS patients (n = 87; poor outcome, 56.3%) compared to nonstroke controls (n = 30). In contrast, long-chain ceramides were significantly increased in AIS patients. More importantly, higher levels of Cer(d18:1/18:0), Cer(d18:1/20:0), and Cer(d18:1/22:0) at 48-72 h were significantly associated with poor functional outcomes after adjusting for potential clinical confounders, including age, sex, hypertension, and National Institutes of Health Stroke Scale score at admission. CONCLUSION: Our study supported the dynamic metabolism of sphingolipids after the occurrence of AIS. Ceramides could be potential prognostic markers for patients with AIS.

Development of an Efficient and Sensitive Chemical Derivatization-Based LC-MS/MS Method for Quantifying Gut Microbiota-Derived Metabolites in Human Plasma and Its Application in Studying Cardiovascular Disease.

Recently, the gut microbiota has been found to be associated with many diseases, such as inflammatory bowel disease, depression, Parkinson's disease, cancer, metabolic syndrome, and cardiovascular disease (CVD). Among various gut microbiota-derived metabolites (GMs), short-chain fatty acids (SCFAs), bile acids (BAs), and tryptophan (TRP) metabolites are the most frequently discussed metabolites. LC-MS/MS shows advantages in quantifying the levels of metabolites with good sensitivity and selectivity; however, the poor ionization efficiency and polar characteristics of SCFAs make their analysis challenging, especially when analyzing plasma samples with low SCFA concentrations. Moreover, without characteristic fragment ions for unconjugated BAs and different detection ion modes for TRP metabolites and BAs, GM analysis is complex and time-consuming. To overcome these problems, we developed a derivatization method combined with LC-MS/MS to enhance the sensitivity and LC retention of GMs. Through derivatization with 3-nitrophenylhydrazine (3-NPH), 7 SCFAs, 9 bile acids, and 6 tryptophan metabolites can be simultaneously analyzed via separation within 14 min on a reversed-phase C18 column. For accurate quantification, 13C6-3NPH-labeled standards were used as one-to-one internal standards. This derivatization approach was optimized and then validated. We further applied this method to investigate the targeted GM profile in patients with CVD. The results showed a significant reduction in plasma butyrate levels in CVD patients compared with healthy controls, suggesting its potentially protective role in CVD. In summary, this work provides a sensitive and effective LC-MS/MS method for simultaneously quantifying gut microbiota-related metabolites in human plasma, which could benefit various future gut microbiota-related studies.

Topological Defect Engineering and PT Symmetry in Non-Hermitian Electrical Circuits.

We employ electric circuit networks to study topological states of matter in non-Hermitian systems enriched by parity-time symmetry PT and chiral symmetry anti-PT (APT). The topological structure manifests itself in the complex admittance bands which yields excellent measurability and signal to noise ratio. We analyze the impact of PT-symmetric gain and loss on localized edge and defect states in a non-Hermitian Su-Schrieffer-Heeger (SSH) circuit. We realize all three symmetry phases of the system, including the APT-symmetric regime that occurs at large gain and loss. We measure the admittance spectrum and eigenstates for arbitrary boundary conditions, which allows us to resolve not only topological edge states, but also a novel PT-symmetric Z_{2} invariant of the bulk. We discover the distinct properties of topological edge states and defect states in the phase diagram. In the regime that is not PT symmetric, the topological defect state disappears and only reemerges when APT symmetry is reached, while the topological edge states always prevail and only experience a shift in eigenvalue. Our findings unveil a future route for topological defect engineering and tuning in non-Hermitian systems of arbitrary dimension.

Topological Switch for Non-Hermitian Skin Effect in Cold-Atom Systems with Loss.

We propose a realistic cold-atom quantum setting where topological localization induces nonreciprocal pumping. This is an intriguing non-Hermitian phenomenon that illustrates how topology, when assisted with atom loss, can act as a "switch" for the non-Hermitian skin effect (NHSE), rather than as a passive property that is modified by the NHSE. In particular, we present a lattice-shaking scenario to realize a two-dimensional cold-atom platform, where nonreciprocity is switched on only in the presence of both atom loss and topological localization due to time-reversal symmetry breaking. The resultant nonreciprocal pumping is manifested by asymmetric dynamical evolution, detectable by atomic populations along the system edges. Our setup may trigger possible applications in nonreciprocal atomtronics, where loss and topological mechanisms conspire to control atomic transport. Its quantum nature will also facilitate future studies on the interplay between non-Hermiticity and many-body physics.

A Sparse Conjugate Gradient Adaptive Filter.

In this letter, we propose a novel conjugate gradient (CG) adaptive filtering algorithm for online estimation of system responses that admit sparsity. Specifically, the Sparsity-promoting Conjugate Gradient (SCG) algorithm is developed based on iterative reweighting methods popular in the sparse signal recovery area. We propose an affine scaling transformation strategy within the reweighting framework, leading to an algorithm that allows the usage of a zero sparsity regularization coefficient. This enables SCG to leverage the sparsity of the system response if it already exists, while not compromising the optimization process. Simulation results show that SCG demonstrates improved convergence and steady-state properties over existing methods.

Hybrid Higher-Order Skin-Topological Modes in Nonreciprocal Systems.

Higher-order phases are characterized by corner or hinge modes that arise due to the interesting interplay of localization mechanisms along two or more dimensions. In this work, we introduce and construct a novel class of "hybrid" higher-order skin-topological boundary modes in nonreciprocal systems with two or more open boundaries. Their existence crucially relies on nonreciprocal pumping in addition to topological localization. Unlike usual non-Hermitian "skin" modes, they can exist in lattices with vanishing net reciprocity due to the selective nature of nonreciprocal pumping: While the bulk modes remain extended due to the cancellation of nonreciprocity within each unit cell, boundary modes experience a curious spontaneous breaking of reciprocity in the presence of topological localization, thereby experiencing the non-Hermitian skin effect. The number of possible hybridization channels increases rapidly with dimensionality, leading to a proliferation of distinct phases. In addition, skin modes or hybrid skin-topological modes can restore unitarity and are hence stable, allowing for experimental observations and manipulations in non-Hermitian photonic and electrical metamaterials.

Chiral Voltage Propagation and Calibration in a Topolectrical Chern Circuit.

We propose an electric circuit array with topologically protected unidirectional voltage modes at its boundary. Instead of external bias fields or Floquet engineering, we employ negative impedance converters with current inversion (INICs) to accomplish a nonreciprocal, time-reversal symmetry-broken electronic network we call a topolectrical Chern circuit (TCC). The TCC features an admittance bulk gap fully tunable via the resistors used in the INICs, along with a chiral voltage boundary mode reminiscent of the Berry flux monopole present in the admittance band structure. The active circuit elements in the TCC can be calibrated to compensate for dissipative loss.

Characterization of RyDEN (C19orf66) as an Interferon-Stimulated Cellular Inhibitor against Dengue Virus Replication.

Dengue virus (DENV) is one of the most important arthropod-borne pathogens that cause life-threatening diseases in humans. However, no vaccine or specific antiviral is available for dengue. As seen in other RNA viruses, the innate immune system plays a key role in controlling DENV infection and disease outcome. Although the interferon (IFN) response, which is central to host protective immunity, has been reported to limit DENV replication, the molecular details of how DENV infection is modulated by IFN treatment are elusive. In this study, by employing a gain-of-function screen using a type I IFN-treated cell-derived cDNA library, we identified a previously uncharacterized gene, C19orf66, as an IFN-stimulated gene (ISG) that inhibits DENV replication, which we named Repressor of yield of DENV (RyDEN). Overexpression and gene knockdown experiments revealed that expression of RyDEN confers resistance to all serotypes of DENV in human cells. RyDEN expression also limited the replication of hepatitis C virus, Kunjin virus, Chikungunya virus, herpes simplex virus type 1, and human adenovirus. Importantly, RyDEN was considered to be a crucial effector molecule in the IFN-mediated anti-DENV response. When affinity purification-mass spectrometry analysis was performed, RyDEN was revealed to form a complex with cellular mRNA-binding proteins, poly(A)-binding protein cytoplasmic 1 (PABPC1), and La motif-related protein 1 (LARP1). Interestingly, PABPC1 and LARP1 were found to be positive modulators of DENV replication. Since RyDEN influenced intracellular events on DENV replication and, suppression of protein synthesis from DENV-based reporter construct RNA was also observed in RyDEN-expressing cells, our data suggest that RyDEN is likely to interfere with the translation of DENV via interaction with viral RNA and cellular mRNA-binding proteins, resulting in the inhibition of virus replication in infected cells.

Realistic Floquet Semimetal with Exotic Topological Linkages between Arbitrarily Many Nodal Loops.

Valence and conduction bands in nodal loop semimetals (NLSMs) touch along closed loops in momentum space. If such loops can proliferate and link intricately, NLSMs become exotic topological phases, which require nonlocal hopping and are therefore unrealistic in conventional quantum materials or cold atom systems alike. In this Letter, we show how this hurdle can be surmounted through an experimentally feasible periodic driving scheme. In particular, by tuning the period of a two-step periodic driving or certain experimentally accessible parameters, we can generate arbitrarily many nodal loops that are linked with various levels of complexity. Furthermore, we propose to use both a Berry-phase related winding number and the Alexander polynomial topological invariant to characterize the fascinating linkages among the nodal loops. This Letter thus presents a class of exotic Floquet topological phases that has hitherto not been proposed in any realistic setup. Possible experimental confirmation of such exotic topological phases is also discussed.

Floquet Mechanism for Non-Abelian Fractional Quantum Hall States.

Three-body correlations, which arise between spin-polarized electrons in the first excited Landau level, are believed to play a key role in the emergence of enigmatic non-Abelian fractional quantum Hall (FQH) effects. Inspired by recent advances in Floquet engineering, we investigate periodic driving of anisotropic two-body interactions as a route for controllably creating and tuning effective three-body interactions in the FQH regime. We develop an analytic formalism to describe this Floquet-FQH protocol, which is distinct from previous approaches that instead focus on band structure engineering via modulation of single-particle hopping terms. By systematically analyzing the resulting interactions using generalized pseudopotentials, we show that our Floquet-FQH approach leads to repulsive as well as attractive three-body interactions that are highly tunable and support a variety of non-Abelian multicomponent FQH states. Finally, we propose an implementation of the protocol in optically dressed ultracold polar molecules with modulated Rabi frequencies.

Generalized Pseudopotentials for the Anisotropic Fractional Quantum Hall Effect.

We generalize the notion of Haldane pseudopotentials to anisotropic fractional quantum Hall (FQH) systems that are physically realized, e.g., in tilted magnetic field experiments or anisotropic band structures. This formalism allows us to expand any translation-invariant interaction over a complete basis, and directly reveals the intrinsic metric of incompressible FQH fluids. We show that purely anisotropic pseudopotentials give rise to new types of bound states for small particle clusters in the infinite plane, and can be used as a diagnostic of FQH nematic order. We also demonstrate that generalized pseudopotentials quantify the anisotropic contribution to the effective interaction potential, which can be particularly large in models of fractional Chern insulators.

Publisher's Note: Generalized Pseudopotentials for the Anisotropic Fractional Quantum Hall Effect [Phys. Rev. Lett. 118, 146403 (2017)].

This corrects the article DOI: 10.1103/PhysRevLett.118.146403.

Speech quality and stable gain trade-offs in adaptive feedback cancellation for hearing aids.

This paper addresses trade-offs in adaptive feedback cancellation (AFC) for hearing aids. Aggressive AFC for improved added stable gain (ASG) reduces speech quality. In this paper, the hearing-aid speech quality index (HASQI) is used to investigate AFC performance before the system becomes unstable. It is demonstrated that for a desired speech quality, multiple AFC algorithms can be evaluated for their ASG and computational efficiency. An example is presented with HASQI = 0.8, baseline AFC, and two advanced approaches. For the advanced AFCs, ASG gains of 4 and 7 dB were obtained at additional computational complexity of 8% and 11%, respectively.

Position-Momentum Duality and Fractional Quantum Hall Effect in Chern Insulators.

We develop a first quantization description of fractional Chern insulators that is the dual of the conventional fractional quantum Hall (FQH) problem, with the roles of position and momentum interchanged. In this picture, FQH states are described by anisotropic FQH liquids forming in momentum-space Landau levels in a fluctuating magnetic field. The fundamental quantum geometry of the problem emerges from the interplay of single-body and interaction metrics, both of which act as momentum-space duals of the geometrical picture of the anisotropic FQH effect. We then present a novel broad class of ideal Chern insulator lattice models that act as duals of the isotropic FQH effect. The interacting problem is well-captured by Haldane pseudopotentials and affords a detailed microscopic understanding of the interplay of interactions and nontrivial quantum geometry.