246 research outputs found
Anisotropic Zeeman Splitting in YbNi4P2
The electronic structure of heavy-fermion materials is highly renormalised at
low temperatures with localised moments contributing to the electronic
excitation spectrum via the Kondo effect. Thus, heavy-fermion materials are
very susceptible to Lifshitz transitions due to the small effective Fermi
energy arising on parts of the renormalised Fermi surface. Here, we study
Lifshitz transitions that have been discovered in YbNi4P2 in high magnetic
fields. We measure the angular dependence of the critical fields necessary to
induce a number of Lifshitz transitions and find it to follow a simple
Zeeman-shift model with anisotropic g-factor. This highlights the coherent
nature of the heavy quasiparticles forming a renormalised Fermi surface. We
extract information on the orientation of the Fermi surface parts giving rise
to the Lifshitz transitions and we determine the anisotropy of the effective
g-factor to be in good agreement with the crystal field
scheme of YbNi4P2.Comment: 10 pages, 5 figures, prepared for resubmission to SciPos
A Numerical Approach for Solving Optimal Control Problems Using the Boubaker Polynomials Expansion Scheme
In this paper, we present a computational method for solving optimal control problems and the controlled Duffing oscillator. This method is based on state parametrization. In fact, the state variable is approximated by Boubaker polynomials with unknown coefficients. The equation of motion, performance index and boundary conditions are converted into some algebraic equations. Thus, an optimal control problem converts to a optimization problem, which can then be solved easily. By this method, the numerical value of the performance index is obtained. Also, the control and state variables can be approximated as functions of time. Convergence of the algorithms is proved. Numerical results are given for several test examples to demonstrate the applicability and efficiency of the method
Solving an Optimal Control Problem of Cancer Treatment by Artificial Neural Networks
Cancer is an uncontrollable growth of abnormal cells in any tissue of the body. Many researchers have focused on machine learning and artificial intelligence (AI) based on approaches for cancer treatment. Dissimilar to traditional methods, these approaches are efficient and are able to find the optimal solutions of cancer chemotherapy problems. In this paper, a system of ordinary differential equations (ODEs) with the state variables of immune cells, tumor cells, healthy cells and drug concentration is proposed to anticipate the tumor growth and to show their interactions in the body. Then, an artificial neural network (ANN) is applied to solve the ODEs system through minimizing the error function and modifying the parameters consisting of weights and biases. The mean square errors (MSEs) between the analytical and ANN results corresponding to four state variables are 1.54e-06, 6.43e-07, 6.61e-06, and 3.99e-07, respectively. These results show the good performance and efficiency of the proposed method. Moreover, the optimal dose of chemotherapy drug and the amount of drug needed to continue the treatment process are achieved
Microbial biodegradable potato starch based low density polyethylene
Plastic materials remain in the nature for decades. Slow degradation of plastics in the environment caused a public trend to biodegradable polymers. The aim of this research was to produce the microbial biodegradable low density polyethylene with potato starch. Degradation of potato starch based low density polyethylene (LDPE) was investigated in soil rich in microorganisms for 8 months. Weight differences of polymeric samples before and after degradation in soil indicated soil biodegradation. Fourier transform spectroscopy (FTIR) approved the result. Scanning electron microscope (SEM) and weight change after 84 days’ exposure to Pseudomonas aeruginosa confirmed degradation by microorganisms. In addition, potato starch based LDPE was exposed to 8 different kinds of fungi and the degradation was studied visually. Result confirmed the microbialbiodegradability of potato starch based LDPE blend in natural and laboratory condition
Cascade of magnetic field induced Lifshitz transitions in the ferromagnetic Kondo lattice material YbNi4P2
A ferromagnetic quantum critical point is thought not to exist in two and
three-dimensional metallic systems yet is realized in the Kondo lattice
compound YbNi4(P,As)2, possibly due to its one-dimensionality. It is crucial to
investigate the dimensionality of the Fermi surface of YbNi4P2 experimentally
but common probes such as ARPES and quantum oscillation measurements are
lacking. Here, we studied the magnetic field dependence of transport and
thermodynamic properties of YbNi4P2. The Kondo effect is continuously
suppressed and additionally we identify nine Lifshitz transitions between 0.4
and 18 T. We analyze the transport coefficients in detail and identify the type
of Lifshitz transitions as neck or void type to gain information on the Fermi
surface of YbNi4P2. The large number of Lifshitz transitions observed within
this small energy window is unprecedented and results from the particular flat
renormalized band structure with strong 4f-electron character shaped by the
Kondo lattice effect.Comment: 6 pages, 4 figure
Bridging Innate and Adaptive Antitumor Immunity Targeting Glycans
Effective immunotherapy for cancer depends on cellular responses to tumor antigens. The role of major histocompatibility complex (MHC) in T-cell recognition and T-cell receptor repertoire selection has become a central tenet in immunology. Structurally, this does not contradict earlier findings that T-cells can differentiate between small hapten structures like simple glycans. Understanding T-cell recognition of antigens as defined genetically by MHC and combinatorially by T cell receptors led to the “altered self” hypothesis. This notion reflects a more fundamental principle underlying immune surveillance and integrating evolutionarily and mechanistically diverse elements of the immune system. Danger associated molecular patterns, including those generated by glycan remodeling, represent an instance of altered self. A prominent example is the modification of the tumor-associated antigen MUC1. Similar examples emphasize glycan reactivity patterns of antigen receptors as a phenomenon bridging innate and adaptive but also humoral and cellular immunity and providing templates for immunotherapies
- …