Biomedical subjects

Qian Niu

Publications and source records attributed to Qian Niu.

At least 19 recordsLinked to original sources

PubMed2026

Lactylome Reprogramming Mediates Therapeutic Response and Adaptation to Neoadjuvant Chemotherapy in Esophageal Squamous Cell Carcinoma.

Esophageal squamous cell carcinoma (ESCC) exhibits high prevalence in China and poor prognosis despite neoadjuvant chemotherapy (NACT), with significant chemoresistance development. Tumor-associated metabolic reprogramming and NACT-induced cellular stress promote lactate accumulation, which serves as a precursor for lysine lactylation (Kla), a post-translational modification potentially regulating cancer progression. We hypothesized that systematic characterization of the lactylome in response to NACT could reveal critical molecular mechanisms underlying treatment and identify new therapeutic vulnerabilities in ESCC. Herein, through comprehensive proteomic and lactylome profiling of tumor and adjacent normal adjacent tissues from 31 ESCC patients (with or without NACT treatment), we identified 8281 proteins and 1836 Kla sites across 62 samples. NACT induced substantial lactylome alterations with 307 differentially expressed Kla sites predominantly in nonhistone proteins involved in DNA damage response and metabolic pathways. Our data revealed that while NACT-induced suppression of energy metabolism, coupled with upregulated 3-hydroxy-3-methylglutaryl reductase degradation 1 complex expression, may exert potential proapoptotic effects, the activation of ribosome biogenesis and increased nucleoprotein lactylation triggered tumor-protective mechanisms. Mechanistically, we demonstrated that DNA damage and elevated lactate levels induced poly(ADP-ribose) polymerase 1 K654 lactylation, enhancing its enzymatic activity and augmenting poly(ADP-ribosyl)ation of downstream targets, potentially playing a pivotal role in chemotherapy resistance-associated pathways. This comprehensive tissue-level landscape of Kla dynamics in ESCC response to chemotherapy establishes Kla as a critical regulatory mechanism in treatment response, potentially offering novel therapeutic targets and predictive biomarkers for personalized treatment strategies.

Humans↗

PubMed2006

Enhanced bioaccumulation of cadmium in carp in the presence of titanium dioxide nanoparticles.

In this study adsorption of Cd onto TiO2 nanoparticles and natural sediment particles (SP) were studied and the facilitated transports of Cd into carp by TiO2 nanoparticles and SP were assessed by bioaccumulation tests exposing carp (Cyprinus carpio) to Cd contaminated water in the presence of TiO2 and SP respectively. The results show that TiO2 nanoparticles had a significantly stronger adsorption capacity for Cd than SP. The presence of SP did not have significant influence on the accumulation of Cd in carp during the 25 d of exposure. However, the presence of TiO2 nanoparticles greatly enhanced the accumulation of Cd in carp. After 25 d of exposure Cd concentration in carp increased by 146%, and the value was 22.3 and 9.07 microg/g, respectively. And there is a positive correlation between Cd and TiO2 concentration. Considerable Cd and TiO2 accumulated in viscera and gills of the fish.

Adsorption↗

PubMed2006

Berry phase effects on the dynamics of quasiparticles in a superfluid with a vortex.

We study quasiparticle dynamics in a Bose-Einstein condensate with a vortex by following the center of mass motion of a Bogoliubov wave packet, and find important Berry-phase effects due to the background flow. We show that the Berry phase invalidates the usual canonical relation between the mechanical momentum and position variables, leading to important modifications of quasiparticle statistics and thermodynamic properties of the condensates. Applying these results to a vortex in an infinite uniform superfluid, we find that the total transverse force acting on the vortex is proportional to the superfluid density. We propose an experimental setup to directly observe Berry phase effects through measuring local thermal atoms' momentum distribution around a vortex.

Journal Article↗

PubMed2006

Berry-phase effect in anomalous thermoelectric transport.

We develop a theory of the Berry-phase effect in anomalous transport in ferromagnets driven by statistical forces such as the gradient of temperature or chemical potential. Here a charge Hall current arises from the Berry-phase correction to the orbital magnetization rather than from the anomalous velocity, which does not exist in the absence of a mechanical force. A finite-temperature formula for the orbital magnetization is derived, which enables us to provide an explicit expression for the off-diagonal thermoelectric conductivity, to establish the Mott relation between the anomalous Nernst and Hall effects, and to reaffirm the Onsager relations between reciprocal thermoelectric conductivities. A first-principles evaluation of our expression is carried out for the material CuCr(2)Se(4-x)Br(x), obtaining quantitative agreement with a recent experiment.

Journal Article↗

PubMed2006

Bose-Einstein condensation with an entangled order parameter.

We propose a practically accessible non-mean-field ground state of Bose-Einstein condensation, which occurs in an interspecies two-particle entangled state, and is thus described by an entangled order parameter. A suitably defined entanglement entropy is used as the characterization of the non-mean-field nature, and is found to persist in a wide parameter regime. The interspecies entanglement leads to novel interference terms in the dynamical equations governing the single-particle orbital wave function. Experimental feasibility and several methods of probe are discussed. We urge the study of multichannel scattering between different species of atoms.

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PubMed2006

Proper definition of spin current in spin-orbit coupled systems.

The conventional definition of spin current is incomplete and unphysical in describing spin transport in systems with spin-orbit coupling. A proper and measurable spin current is established in this study, which fits well into the standard framework of near-equilibrium transport theory and has the desirable property to vanish in insulators with localized orbitals. Experimental implications of our theory are discussed.

Journal Article↗

PubMed2006

Linear magnetization dependence of the intrinsic anomalous Hall effect.

The anomalous Hall effect is investigated experimentally and theoretically for ferromagnetic thin films of Mn5Ge3. We have separated the intrinsic and extrinsic contributions to the experimental anomalous Hall effect and calculated the intrinsic anomalous Hall conductivity from the Berry curvature of the Bloch states using first-principles methods. The intrinsic anomalous Hall conductivity depends linearly on the magnetization, which can be understood from the long-wavelength fluctuations of the spin orientation at finite temperatures. The quantitative agreement between theory and experiment is remarkably good, not only near 0 K but also at finite temperatures, up to about approximately 240 K (0.8TC).

Journal Article↗

PubMed2005

Berry phase correction to electron density of states in solids.

Liouville's theorem on the conservation of phase-space volume is violated by Berry phase in the semiclassical dynamics of Bloch electrons. This leads to a modification of the phase-space density of states, whose significance is discussed in a number of examples: field modification of the Fermi-sea volume, connection to the anomalous Hall effect, and a general formula for orbital magnetization. The effective quantum mechanics of Bloch electrons is also sketched, where the modified density of states plays an essential role.

Journal Article↗

PubMed2005

Ab initio calculation of the intrinsic spin Hall effect in semiconductors.

Relativistic band theoretical calculations reveal that intrinsic spin Hall conductivity in hole-doped archetypical semiconductors Ge, GaAs, and AlAs is large [approximately 100(planck/e)(Omega cm)(-1)], showing the possibility of a spin Hall effect beyond the four-band Luttinger Hamiltonian. The calculated orbital-angular-momentum (orbital) Hall conductivity is one order of magnitude smaller, indicating no cancellation between the spin and orbital Hall effects in bulk semiconductors. Furthermore, it is found that the spin Hall effect can be strongly manipulated by strains, and that the ac spin Hall conductivity is large in pure as well as doped semiconductors.

Journal Article↗

PubMed2005

Geometric phase for adiabatic evolutions of general quantum states.

The concept of a geometric phase (Berry's phase) is generalized to the case of noneigenstates, which is applicable to both linear and nonlinear quantum systems. This is particularly important to nonlinear quantum systems, where, due to the lack of the superposition principle, the adiabatic evolution of a general state cannot be described in terms of eigenstates. For linear quantum systems, our new geometric phase reduces to a statistical average of Berry's phases. Our results are demonstrated with a nonlinear two-level model.

Journal Article↗

PubMed2005

Compression of atomic phase space using an asymmetric one-way barrier.

We show how to construct asymmetric optical barriers for atoms. These barriers can be used to compress phase-space of a sample by creating a confined region in space where atoms can accumulate with heating at the single photon recoil level. We illustrate our method with a simple two-level model and then show how it can be applied to more realistic multilevel atoms.

Journal Article↗

PubMed2004

Superconductivity modulated by quantum size effects.

We have fabricated ultrathin lead films on silicon substrates with atomic-scale control of the thickness over a macroscopic area. We observed oscillatory behavior of the superconducting transition temperature when the film thickness was increased by one atomic layer at a time. This oscillating behavior was shown to be a manifestation of the Fabry-Perot interference modes of electron de Broglie waves (quantum well states) in the films, which modulate the electron density of states near the Fermi level and the electron-phonon coupling, which are the two factors that control superconductivity transitions. This result suggests the possibility of modifying superconductivity and other physical properties of a thin film by exploiting well-controlled and thickness-dependent quantum size effects.

Journal Article↗

PubMed2004

Quantum chaos of bogoliubov waves for a bose-einstein condensate in stadium billiards.

We investigate the possibility of quantum (or wave) chaos for the Bogoliubov excitations of a Bose-Einstein condensate in billiards. Because of the mean field interaction in the condensate, the Bogoliubov excitations are very different from the single particle excitations in a noninteracting system. Nevertheless, we predict that the statistical distribution of level spacings is unchanged by mapping the non-Hermitian Bogoliubov operator to a real symmetric matrix. We numerically test our prediction by using a phase shift method for calculating the excitation energies.

Journal Article↗

PubMed2004

Spin-orbit coupling and Berry phase with ultracold atoms in 2D optical lattices.

We show how spin-orbit coupling and Berry phase can appear in two-dimensional optical lattices by coupling atoms' internal degrees of freedom to radiation. The Rashba Hamiltonian, a standard description of spin-orbit coupling for two-dimensional electrons, is obtained for the atoms under certain circumstances. We discuss the possibility of observing associated phenomena, such as the anomalous Hall and spin Hall effects, with cold atoms in optical lattices.

Journal Article↗

PubMed2004

Transition to instability in a kicked bose-einstein condensate.

A periodically kicked ring of a Bose-Einstein condensate is considered as a nonlinear generalization of the quantum kicked rotor. For weak interactions between atoms, periodic motion (antiresonance) becomes quasiperiodic (quantum beating) but remains stable. There exists a critical strength of interactions beyond which quasiperiodic motion becomes chaotic, resulting in an instability of the condensate manifested by exponential growth in the number of noncondensed atoms. Similar behavior is observed for dynamically localized states (essentially quasiperiodic motions), where stability remains for weak interactions but is destroyed by strong interactions.

Journal Article↗

PubMed2004

First principles calculation of anomalous Hall conductivity in ferromagnetic bcc Fe.

We perform a first principles calculation of the anomalous Hall effect in ferromagnetic bcc Fe. Our theory identifies an intrinsic contribution to the anomalous Hall conductivity and relates it to the k-space Berry phase of occupied Bloch states. This dc conductivity has the same origin as the well-known magneto-optical effect, and our result accounts for experimental measurement on Fe crystals with no adjustable parameters.

Journal Article↗

PubMed2003

Entanglement generation and multiparticle interferometry with neutral atoms.

We study the preparation and manipulation of states involving a small number of interacting particles. By controlling the splitting and fusing of potential wells, we show how to interconvert Mott-insulator-like and trapped BEC-like states. We also discuss the generation of "Schrödinger cat" states by splitting a microtrap and taking into practical consideration the asymmetry between the resulting wells. These schemes can be used to perform multiparticle interferometry with neutral atoms, where interference effects can be observed only when all the participating particles are measured.

Journal Article↗

PubMed2003

Nonlinear evolution of quantum states in the adiabatic regime.

We investigate adiabatic evolution of quantum states as governed by the nonlinear Schrödinger equation and provide examples of applications with a nonlinear tunneling model for Bose-Einstein condensates. Our analysis not only spells out conditions for adiabatic evolution of eigenstates but also characterizes the motion of noneigenstates which cannot be obtained from the former in the absence of the superposition principle. We find that Aharonov-Anandan phases play the role of classical canonical actions and are conserved in the adiabatic evolution of noneigenstates.

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