A quantum-mechanical treatment of Szilard's engine: Implications for the entropy of information

We present a quantum-mechanical analysis of Szilard's famous single-molecule engine, showing that it is analogous to the double-slit experiment. We further show that the energy derived from the engine's operation is provided by the act of observing the molecule's location. The engine can be operated with no increase in physical entropy, and the second law of thermodynamics does not compel us to relate physical entropy to informational entropy. We conclude that information per seis a subjective, idealized, concept separated from the physical realm. Physical entropy depends on physical objects and physical interactions, and any entropy change owing to observations is entirely a result of the entropy created in the physical apparatus by the process of observation.     

Computation and physics: Wheeler's meaning circuit?

Computation is a physical process, inevitably utilizing physical degrees of freedom. Computation, therefore, is restricted by the laws of physics and also by the construction materials and operating environments available in our actual universe. These restrictions have been investigated for a quarter century. A discussion of this field is provided, too concise to be a review, but only intended as a guide to the literature. Physical law, in turn, consists of algorithms for information processing. Therefore, the ultimate form of physical laws must be consistent with the restrictions on the physical executability of algorithms, which is in turn dependent on physical law.     

Sex Differences in Physical Activity in People After Stroke: A Cross-sectional Study

OBJECTIVE: Adequate physical activity after stroke is critical for cardiovascular health. Although sex is a potential factor associated with post-stroke physical activity, its mechanism remains unclear. This study aimed to examine sex differences in human physical activity following stroke. METHOD: A cross-sectional study with 62 participants (men: 42, women: 20) was conducted. Physical activity was measured for three consecutive days using a step activity monitor. The walking durations per day in light physical activity, moderate-to-vigorous physical activity, and total physical activity were calculated. Sex differences in walking duration were compared using Welch''s t-tests or Mann-Whitney U tests. RESULTS: Women had a significantly greater walking duration in light physical activity and in total than did the men. In contrast, no significant differences were found in moderate-to-vigorous physical activity. CONCLUSION: This study reported sex differences in the walking duration after stroke. Moreover, it found that women spent more time in low intensity physical activity than men. Our results will be useful for planning interventions to increase physical activity and decrease sedentary behavior after stroke.     

Inference in quantum physics

In quantum physics all experimental information is discrete and stochastic. But the values of physical quantities are considered to depict definite properties of the physical world. Thus physical quantities should be identified with mathematical variables which are derived from the experimental data, but which exhibit as little randomness as possible. We look for such variables in two examples by investigating how it is possible to arrive at a value of a physical quantity from intrinsically stochastic data. With the aid of standard probability calculus and elementary information theory, we are necessarily led to the quantum theoretical phases and state vectors as the first candidates for physical quantities.     

Physical content of preparation-question structures and Brouwer-Zadeh lattices

We give a criterion to compare the physical content of different mathematical structures derived from a preparation-question structure. Then this criterion is used in order to compare the physical content of the (Jauch-Piron's) property lattice with the physical content of the poset of testable properties. We prove that for complete preparation-question structures these two structures carry the same physical content; moreover the set of testable properties has the algebraic structure of the Brouwer-Zadeh lattice. For more general preparation-question structures the physical content of the poset of testable property can be larger than that of the property lattice. Physically relevant examples of the possible cases are given.     

Single-molecular methodologies for the physical biology of protein machines

Physical biology is an interdisciplinary field that bridges biology with physical sciences and engineering. Single-molecule physical biology focuses on dynamics of individual biomolecules and complexes, aiming to answering basic questions about their functions and mechanisms. It takes advantages of physical methodologies to gain quantitative understanding of biological processes, often engaging precise physical measurements of reconstructed objects to avoid interference from unnecessary complications. In this review, we (i) briefly introduce concepts of single-molecule physical biology, (ii) describe extensively used single-molecule methodologies that have been developed to address key questions in two important objects of single-molecule physical biology, namely, nucleic acid-interacting proteins and membrane-interacting proteins, and (iii) show by a few successful examples how one may use single-molecule methods to deepen our understanding of protein machines.     

自制金割效应物理摆的研究性实验

金割效应物理摆是将数学中的优选法与物理实验中的复摆结合起来并用计算机处理数据的自制教学仪器.把金割效应物理摆作为研究性实验进行开设,更有利于培养学生的开拓精神和创新能力.     

The parallel transport of a vector: Its physical meaning in three geometrical unified field theories

The physical interpretation of the parallel transport of a vector is analyzed in three classical geometric unified field theories: the theory of physical space and the theories of Weyl and Infeld. In physical space it is found to be a Fermi-Walker transport in the presence of electromagnetic interactions.     

模糊综合评判在学生物理实验技能测评中的应用研究

本文运用模糊综合评判理论,构建了一套综合测评学生物理实验技能的模型与方法,避免了传统的物理实验考试、考核的弊端,提升了物理实验考核的公平、公正和科学性,提高了学生学习大学物理实验课程的兴趣和积极性。     

Learning physical states of bulk crystalline materials from atomic trajectories in molecular dynamics simulation

Melting of crystalline material is a common physical phenomenon, yet it remains elusive owing to the diversity in physical pictures. In this work, we proposed a deep learning architecture to learn the physical states (solid- or liquid-phase) from the atomic trajectories of the bulk crystalline materials with four typical lattice types. The method has ultra-high accuracy (higher than 95%) for the classification of solid-liquid atoms during the phase transition process and is almost insensitive to temperature. The atomic physical states are identified from atomic behaviors without considering any characteristic threshold parameter, which yet is necessary for the classical methods. The phase transition of bulk crystalline materials can be correctly predicted by learning from the atomic behaviors of different materials, which confirms the close correlation between atomic behaviors and atomic physical states. These evidences forecast that there should be a more general undiscovered physical quantity implicated in the atomic behaviors and elucidate the nature of bulk crystalline melting.     

物理美学对物理教学的意义

在实施新课程改革的大背景下,运用理论与实践相结合的方法就物理美学对物理教学的意义做了论述,以引起同行们对物理美学研究及其应用的关注．     

Generalized Heisenberg algebra and algebraic method: The example of an infinite square-well potential

We discuss the role of generalized Heisenberg algebras (GHA) in obtaining an algebraic method to describe physical systems. The method consists in finding the GHA associated to a physical system and the relations between its generators and the physical observables. We choose as an example the infinite square-well potential for which we discuss the representations of the corresponding GHA. We suggest a way of constructing a physical realization of the generators of some GHA and apply it to the square-well potential. An expression for the position operator x in terms of the generators of the algebra is given and we compute its matrix elements.     

优化模式物理参数的扩展四维变分同化方法

数值模拟的一个重要误差来源是模式物理参数,为提高模拟准确率,如何改进模式物理参数是亟需解决的问题.本文对经典四维变分同化技术进行了改进,提出了一种新的利用观测资料来同时优化模式初始场和物理参数的扩展四维变分同化方法,并以Ekman边界层模式和Lorenz模式为例进行了数值试验.结果表明,利用本文提出的新方法,通过对观测资料的变分同化,可以在实现对模式初始场进行优化的同时,纠正了模式物理参数中的误差,从而有效提高了模式的模拟准确率.该方法对于改进数值模式物理参数有着重要的促进意义.     

物理农业技术在现代农业基础科学与工程研究中的应用

在强调物理农业对现代农业发展重大意义的基础上,本文从物理因素对农作物繁育生长的促进作用和运用物理技术手段及采集农业环境信息两个方面叙述了物理农业技术在基础农业科学与农业工程研究领域中的应用与发展现状,并结合我国农业环境,提出了以先进的物理农业技术为切入点,重点发展物理农业的现代农业发展模式.     

远程物理实验控制平台的设计与开发

将网络远程控制技术运用于物理实验教学中,设计并开发出远程物理实验控制平台.该平台的建设能够有效地实现物理实验设备硬件资源共享,为各高校开展物理实验课程提供了全新的方法和途径.     

Real-time synthesis of clarinet-like instruments using digital impedance models

A real-time synthesis model of wind instruments sounds, based upon a classical physical model, is presented. The physical model describes the nonlinear coupling between the resonator and the excitor through the Bernoulli equation. While most synthesis methods use wave variables and their sampled equivalent in order to describe the resonator of the instrument, the synthesis model presented here uses sampled versions of the physical variables all along the synthesis process, and hence constitutes a straightforward digital transposition of each part of the physical model. Moreover, the resolution scheme of the problem (i.e., the synthesis algorithm) is explicit and all the parameters of the algorithm are expressed analytically as functions of the physical and the control parameters.     

A BOSON-FERMION DESCIPTION OF THE NUCLEAR MANY-BODY PROBLEM

A new formalism of the nuclear many-body problem is established in which one ean work with various physical state vector spaces consisting of both Fermions and Bosons, all being equivalent to the original one consisting only of Fermions.With the help of the usual commutation relations and anticommutation relations between the annihilation and creation operators of Boson and Fermion, a generalized state vector space is established, which contains all the physical spaces each being equivalent to the original physical space in terms of pure Fermion operators. Transformation between the state vectors in various equivalent physical spaces are constructed. Basic operators in the original state space are transformed into effective operators in the new physical spaces.     

Renormalization and asymptotic behavior in a finite quantum field theory with shadow states

In this paper we present a study of the renormalization problem in a finite quantum field theory with shadow states for a system of a physical scalar field interacting with a physical fermion field. In order to make the theory finite, two fermion shadow fields are introduced. We observe that the stability criterion of renormalization can not be satisfied simultaneously by both physical fields and shadow fields, if the finiteness of the theory is to be maintained. A physical interpretation of this result is given. Furthermore, we find that the effective complete propagators for large space-like momenta behave like free field propagators without the logarithmic factors observed in the non-abelian gauge theory.     

Effects of physical activity on quality of life and physical function in postoperative patients with gastrointestinal cancer

Objectives: This study was to clarify changes in physical function and quality of life (QOL) for postoperative, and to examine the influence of the amount of physical activity on these variables. Methods: This study included 29 patients who underwent gastrointestinal cancer surgery. The QOL measurement was used to the European Organization for Research and Treatment of Cancer Quality of Life Questionnaire for preoperative and 2nd and 4th postoperative weeks. Physical function measured knee extension strength, 4 m walk time, 5 times sit-to-stand test, and 6-minute walk for preoperative and 1st and 2nd postoperative weeks. The amount of physical activity score was based on METs-hours, which is estimated from cumulative physical activity. As basic characteristics were investigated cancer stage, comorbidities and complications, and operative. Statistical analysis was repeated measures analysis of variance was performed to observe postoperative changes in physical function and QOL. Furthermore, stepwise multiple regression analysis was used to the parameters of physical function and QOL affected by the physical activity score were investigated. Results: Physical function decreased postoperatively and generally improved 2nd postoperative week. Though scores on the QOL functional scales improved, some items did not improve sufficiently. Multiple regression analysis showed that physical activity score had an effect on constipation and emotion functioning. Conclusions: Improvement in symptom scales is not sufficient in a short period of time, and they need to be followed up by increasing the amount of physical activity and promoting instantaneous exercise.