Model Reduction for Quantum Systems: Discrete-time Quantum Walks and Open Markov Dynamics

A general approach to obtain reduced models for a wide class of discrete-time quantum systems is proposed. The obtained models not only reproduce exactly the output of a given quantum model, but are also guaranteed to satisfy physical constraints, namely complete positivity and preservation of total probability. A fundamental framework for exact model reduction of quantum systems is constructed leveraging on algebraic methods, as well as novel results on quantum conditional expectations in finite-dimensions. The proposed reduction algorithm is illustrated and tested on prototypical examples, including the quantum walk realizing Grover's algorithm.Comment: 16 page

Algebraic Reduction of Hidden Markov Models

The problem of reducing a Hidden Markov Model (HMM) to one of smaller dimension that exactly reproduces the same marginals is tackled by using a system-theoretic approach. Realization theory tools are extended to HMMs by leveraging suitable algebraic representations of probability spaces. We propose two algorithms that return coarse-grained equivalent HMMs obtained by stochastic projection operators: the first returns models that exactly reproduce the single-time distribution of a given output process, while in the second the full (multi-time) distribution is preserved. The reduction method exploits not only the structure of the observed output, but also its initial condition, whenever the latter is known or belongs to a given subclass. Optimal algorithms are derived for a class of HMM, namely observable ones

Improving the Therapeutic Potential of G-CSF through Compact Circular PEGylation Based on Orthogonal Conjugations

: In this study, a circular conjugate of granulocyte colony-stimulating factor (G-CSF) was prepared by conjugating the two end-chains of poly(ethylene glycol) (PEG) to two different sites of the protein. For the orthogonal conjugation, a heterobifunctional PEG chain was designed and synthesized, bearing the dipeptide ZGln-Gly (ZQG) at one end-chain, for transglutaminase (TGase) enzymatic selective conjugation at Lys41 of G-CSF, and an aldehyde group at the opposite end-chain, for N-terminal selective reductive alkylation of the protein. The cPEG-Nter/K41-G-CSF circular conjugate was characterized by physicochemical methods and compared with native G-CSF and the corresponding linear monoconjugates of G-CSF, PEG-Nter-G-CSF, and PEG-K41-G-CSF. The results demonstrated that the circular conjugate had improved physicochemical and thermal stability, prolonged pharmacokinetic interaction, and retained the biological activity of G-CSF. The PEGylation strategy employed in this study has potential applications in the design of novel protein-based therapeutics

Anti-HER2 Super Stealth Immunoliposomes for Targeted-Chemotherapy

: Liposomes play an important role in the field of drug delivery by virtue of their biocompatibility and versatility as carriers. Stealth liposomes, obtained by surface decoration with hydrophilic polyethylene glycol (PEG) molecules, represented an important turning point in liposome technology, leading to significant improvements in the pharmacokinetic profile compared to naked liposomes. Nevertheless, the generation of effective targeted liposomes - a central issue for cancer therapy - has faced several difficulties and clinical phase failures. Active targeting remains a challenge for liposomes. In this direction, we designed a new Super Stealth Immunoliposomes (SSIL2) composed of a PEG-bi-phospholipids derivative that stabilizes the polymer shielding over the liposomes. Furthermore, its counterpart, conjugated to the fragment antigen-binding of trastuzumab (Fab'TRZ -PEG-bi-phospholipids), is firmly anchored on the liposomes surface and correctly orients outward the targeting moiety. Throughout this study, the performances of SSIL2 are evaluated and compared to classic stealth liposomes and stealth immunoliposomes in vitro in a panel of cell lines and in vivo studies in zebrafish larvae and rodent models. Overall, SSIL2 shows superior in vitro and in vivo outcomes, both in terms of safety and anticancer efficacy, thus representing a step forward in targeted cancer therapy, and valuable for future development. This article is protected by copyright. All rights reserved

Minimal resources for exact simulation of quantum walks

Quantum walks are stochastic processes generated by a quantum evolution mechanism, allowing for speed-up in spreading and hitting-time performance with respect to their classical counterparts. Investigating the role of the memory effects for these models, we address the problem of finding the minimal linear system that exactly reproduces the evolution of the output distribution of a quantum walk. After adapting the classical approach to our setting, we investigate analytically and numerically the structural complexity of quantum walks, both in general and in particular examples. Lastly, we focus on Grover’s algorithm, a quantum computing search algorithm that can be re-framed as a quantum walk, showing that it allows for a dramatic reduction in its representation

Winning tennis matches with fewer points or games than the opponent

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Efficacy of PEGylated ciliary neurotrophic factor superagonist variant in diet-induced obesity mice

: Ciliary neurotrophic factor (CNTF) is a neurotrophic cytokine able to induce appetite reduction, weight loss and antidiabetic effects. However, its susceptibility to neutralizing anti-CNTF antibodies in patients hampered its use for treatment of human obesity and diabetes. In addition, CNTF has a very short plasma half-life, which limits its use as a therapeutic agent. Solutions, directed to prolong its in vivo effects, vary from the implantation of encapsulated secreting cells to identification of more active variants or chemical modification of the protein itself. PEGylation is a widely used modification for shielding proteins from circulating antibodies and for increasing their plasma half-life. Here, we have selected DH-CNTF, a CNTF variant which has a 40-fold higher affinity for the CNTF receptor α accompanied by an increased activity in cellular assays. The PEGylated DH-CNTF retained the biological activity of native protein in vitro and showed a significant improvement of pharmacokinetic parameters. In an acute model of glucose tolerance, the PEG-DH-CNTF was able to reduce the glycemia in diet-induced obese animals, with a performance equaled by a 10-fold higher dose of DH-CNTF. In addition, the PEGylated DH-CNTF analog demonstrated a more potent weight loss effect than the unmodified protein, opening to the use of CNTF as weight reducing agent with treatment regimens that can better meet patient compliance thanks to reduced dosing schedules

Exercise-induced arousal affects free-choices to inhibit

Objectives Previous research has demonstrated that exercise\u2013induced arousal has the ability to improve the stopping of an already initiated response. So far the effects of arousal on response inhibition have been investigated with paradigms concerned with inhibition driven by external stimuli. Since in everyday life situations the origin of decisions to inhibit might be entirely internally driven, the present study aims to explore whether intentional action and inhibition responses depend on the physical exertion in a cycle ergometer test. Design and method While cycling in conditions of low and high exercise-induced arousal, participants were asked to respond to cued and free-choice targets following the presentation of three varieties of masked primes that could elicit congruent or incongruent prime-response conflicts. Results In condition of high exercise-induced arousal an improvement on reaction times was observed in both cued and free-choice action conditions and less omission errors in cued action trials. Concerning free-choice behavior, overall participants made more \u2018action\u2019 choices when compared to the low arousal condition. Conclusions Our results widen previous evidence by showing that as for externally driven cognitive processes, also intentional action and inhibition choices are modulated by exercise. Under specific conditions arousal helps individuals to perform the tasks rapidly and efficiently even when task\u2019 requirements are entirely internally driven. However higher-order processes, such as making a free-choice, resulted impaired