Research

We know our physical world at the atomic level is governed by quantum mechanics. Many branches of physics, including atomic and molecular physics, electron micro-device, laser and photonics, all depend on it. Yet, after almost one century of studies, there are still many unanswered questions in quantum physics. First, what is the physical nature of a particle? How can particles be created in the vacuum or disappear into nowhere? Second, how can one explain the “wave behavior” of a free particle? How can a single electron be diffracted from a crystal following the Bragg’s diffraction law?

Apparently, a quantum object can behave both like a particle as well as a wave. This phenomenon is called “wave-particle duality”. So far, there has been no satisfactory explanation to this strange behavior. In most textbooks, the wave-particle duality is usually explained using the “Copenhagen interpretation”, which proposed that the particle itself is a pointed object, but its distribution is like a wave. Such a view, however, is not agreed by many well-known physicists, including Schrödinger, de Broglie and Einstein. Furthermore, the Copenhagen interpretation cannot explain how a single electron can pass through two slits simultaneously. Some physicists, like Richard Feynman, were so pessimistic that they claimed such quantum mysteries could be beyond human comprehension.

In this program, we would like to examine these fundamental questions in quantum physics using a new approach. We proposed a Wave Model by hypothesizing that: (1) Like the photon, a particle is an excitation wave of the quantum vacuum. (2) Different types of particles are different excitation modes of the same vacuum. Based on such thinking, we showed that quantum mechanics can be a natural extension of the classical theory of electrodynamics.

Thus, our work is aimed to address the following specific questions:

(1) How to explain the phenomenon of wave-particle duality in quantum physics?

(2) How to explain why particles can be created in the vacuum?

(3) Can one derive from first principle the well-known quantum wave equations, including the Dirac equation and the Schrödinger equation?

(4) Can one understand the physical meaning of the quantum wave function beyond the Copenhagen interpretation?

Recent publications:

1. Chang, D.C. 2004, What is the physical meaning of mass in view of wave-particle duality? A proposed model. arXiv: physics/0404044. Link: https://arxiv.org/abs/physics/0404044

2. Chang, DC. 2013. A classical approach to the modeling of quantum mass. J. Mod Phys, 4: 21-30.

3. Chang, D.C. 2017, On the Wave Nature of Matter: A transition from classical physics to quantum mechanics. arXiv: physics/0505010v2. Link:https://arxiv.org/abs/physics/0505010v2

4. Chang D. C. 2017. Is there a resting frame in the universe? A proposed experimental test based on a precise measurement of particle mass. Euro. Phys. J. Plus, 132: 140.

5. Chang D. C. 2017. Physical interpretation of the Planck’s constant based on the Maxwell theory. Chin. Phys. B, 26:040301

6. Chang, D. C. 2018. A quantum mechanical interpretation of gravitational redshift of electromagnetic wave. Optik 174, 636-641.

7. Chang, D. C. 2020. A quantum interpretation of the physical basis of mass–energy equivalence. Modern Physics Letters B. 34(18) :203002 (Invited review)

8. Chang, D. C. 2021. Review on the physical basis of wave-particle duality: Conceptual connection between quantum mechanics and the Maxwell theory. Modern Physics Letters B, 35(13) 2130004. https://doi.org/10.1142/S0217984921300040

Book:

张东才，王一，王国彝，陈炯林， 2021. 《我们的物质世界从何而来？》中国青年出版社

Today, many scientific breakthroughs are through interdisciplinary research. As an important foundation of science, physics has tremendous potential to help other branches of science to advance. To illustrate the power of physics in solving important problems in life science, I present here some of my research projects as example: (1) My pioneer work in developing MRI for cancer detection; (2) Development of electroporation for gene transfer technology; (3) Development of bio-photonic techniques to uncover cell signaling mechanisms in a single living cell. This work not only allowed us to gain new insight into the mechanism of cell regulation and cancer development, it also provided a powerful technology for drug discovery.

NMR detection of cancer: Mechanism of contrast generation

One of the most effective ways today to detect cancer is using MRI (Magnetic Resonance Imaging). This technique is based on the nuclear magnetic resonance (NMR) measurement of water hydrogen signal inside the human body. In order to detect cancers using the NMR method, one needs to solve two technical problems: (1) How to produce a contrast between water molecules inside the cell and the extra-cellular water? (2) How to differentiate the water signals in cancer cells from the water signal in normal cells? These difficulties were resolved in the early 1970s through the discovery that the relaxation times of water protons inside the cells were very different from those of the extra-cellular water. Furthermore, we discovered that the relaxation times of water molecules undertake a progressive lengthening during the transformation from normal cells to cancer cells. In this presentation, I will give a concise review of the evidence for these discoveries. Finally, I will discuss the possible physical basis that may account for the relaxation time changes between normal cells and cancer cells.

Reference:

1. Chang, D.C., Hazlewood, C.F., Nichols, B.L., and Rorschach, H.E. 1972. Spin-echo studies on cellular water. Nature 235:170-171.

2. Hazlewood, C.F., Chang, D.C., Medina, D., Cleveland, G., and Nichols, B.L. 1972. Distinction between the preneoplastic and neoplastic state of murine mammary glands. Proc. Natl. Acad. Sci. USA 69:1478-1480.

3. Hazlewood, C.F., Chang, D.C., Nichols, B.L., and Woessner, D.E. 1974. NMR Transverse relaxation times of water protons in skeletal muscle. Biophys. J. 14:583-606.

4. Chang, D.C. and Woessner, D.E. 1977. "Bound water" in barnacle muscle as indicated in NMR studies. Science 198:1180-1181.

5. Chang, D.C. and Woessner, D.E. 1978. Spin echo study of Na23 relaxation in skeletal muscle: Evidence of sodium ion binding inside a biological cell. J. Mag. Res. 30:185‑191.

6. Beall, P.T., Asch, B.B., Chang, D.C., Medina, D., and Hazlewood, C.F. 1980. Distinction of normal, preneoplastic and neoplastic mouse mammary primary cell cultures by water NMR relaxation times. J. Nat. Cancer Inst. 64(2):335-338.

7. Michael, L., Seitz, P., Wood, J.M., Chang, D.C., Hazlewood, C.F., and Entman, M. 1980. Mitochondrial water in myocardial ischemia: Investigation with nuclear magnetic resonance. Science 208:1267-1269.

8. Donald Chang, NMR detection of cancer: Mechanism of contrast generation. Bulletin of the American Physical Society, APS March Meeting (2021) link: http://hdl.handle.net/1783.1/108878

Development of electroporation for gene transfer technology

Electroporation is a phenomenon in which the cell membrane is temporarily permeabilized by exposure to an intense electric field. This phenomenon can be used to introduce a variety of exogenous molecules, particularly DNA, into living cells. Electrofusion is a related phenomenon by which neighboring cells can be induced to fuse by applying a pulse of electric field. Both electroporation and electrofusion are related to an electrical breakdown of the cell membrane. Electroporation is now a principal method of gene transfer, for both prokaryotic and eukaryotic cells. Electrofusion is found to be the most efficient method of cell fusion and has important uses in agriculture and in the production of hybridomas.

Reference:

1. Chang, D.C. 1989. Cell poration and cell fusion using an oscillating electric field. Biophys. J. 56:641-652.

2. Chang, D.C. and Reese, T.S. 1990. Changes of membrane structure induced by electroporation as revealed by rapid-freezing electron microscopy. Biophys. J. 58:1-12.

3. Chang, D.C., Gao, P.Q. and Maxwell, B.L. 1991. High efficiency gene transfection by electroporation using a radio-frequency electric field. Biophys. Biochim. Acta 1992:153-160.

4. Chang, D.C. 1996. Electroporation and electrofusion. In: The Encyclopedia of Molecular Biology and Molecular Medicine, ed. by R.A. Meyers, VCH Publishers, Weinheim, Germany. Vol. 2, pp 198-206.

5. Chang, D.C. Sowers, A.E., Chassy, B. and Saunders, J.A., 1992. Guide to Electroporation and Electrofusion, Academic Press, San Diego. (Book, 581 pages).

6. Chang, D.C. 2004. Electroporation and electrofusion. In: Encyclopedia of Molecular Cell Biology and Molecular Medicine. Ed. by R.A. Meyers, Wiley-VCH Publishers, Weinheim, Germany. Vol. 4, pp.135-157.

7. Deng P, Chang DC, Lee YK, Zhou J, Li G. 2011. DNA transfection of bone marrow mesenchymal stem cells using micro electroporation chips. 2011 IEEE international conference on Nano/Micro engineered and molecular systems (NEMS), p. 96-9.

Development of bio-photonic techniques to study cell signaling mechanisms

In recent years, our laboratory has been focusing on developing innovative optical techniques for the study of these molecular signaling systems in a single living cell. These techniques include labeling specific proteins with GFP (green fluorescence protein) using gene-fusion, and measurements of protein-protein interaction using the FRET (fluorescence resonance energy transfer) method. Our approach has certain advantages. First, since these optical methods are non-invasive, we can preserve the organization and structure of the cell during the biological study. Thus, the information obtained is highly reliable. Second, by conducting the study in a single cell, we can avoid the problem of cell synchrony, which would be difficult to achieve in a cell population study. Third, in the single cell study, we can correlate the temporal- and spatial-dependent changes of a specific signaling molecule with a particular cellular event. Finally, using the FRET technique, we can measure the dynamics of a specific protein-protein interaction or the activation of a given enzyme within a single cell. Such measurements are not possible using conventional biochemical methods. Furthermore, we had developed this FRET techniques into a high-throughput drug screening thechnology.

Reference:

1. Chang, D.C. and Meng, C. 1995. A localized elevation of cytosolic free calcium is associated with cytokinesis in zebrafish embryo. J. Cell Biol. 131:1539-1545.

2. Li, C.J., Heim, R., Lu, P., Pu, Y.M., Tsien, R.Y. and Chang, D.C. 1999. Dynamic redistribution of calmodulin in HeLa cells during cell division as revealed by a GFP-calmodulin fusion protein technique. J Cell Sci. 112 (10):1567-1577.

3. Chang, D.C. and Lu, P. 2000. Multiple types of calcium signals are associated with cell division in zebrafish embryo. Microscopy Res. Tech., 49 (2): 111-122.

4. Gao, W.H., Pu Y.M., Luo, K.Q. and Chang D.C. 2001.Temporal relationship between cytochrome c release and mitochondrial swelling during UV-induced apoptosis in living HeLa cells. J. Cell Sci. 114:2855-2862.

5. Chang, D.C., Xu, N.H. and Luo, K.Q. 2003. Degradation of cyclin B is required for the onset of anaphase in mammalian cells. J. Biol. Chem. 278:37865-37873.

6. Chang, D.C., Zhou, L.Y. and Luo, K.Q. 2005. Using GFP and FRET technologies for studying signaling mechanisms of apoptosis in a single living cell. In: Biophotoncs-Optical Science and Engineering for the 21st Century. Springer, New York, pp25-38.

7. Chang, D.C. 2007. Using biophotonics to study signaling mechanisms in a single living cell. Intl J Mod Phys B, 21 (23/24):4091-4103.

8. Xu, N.H. and Chang, D.C. 2007. Different thresholds of MPF inactivation are responsible for controlling different mitotic events in mammalian cell division. Cell Cycle, 6(13):1639-1645.

9. Tian, H., Ip, L., Luo, H., Chang, D.C. and Luo, K.Q. 2007. A high throughput drug screen based on fluorescence resonance energy transfer (FRET) for anti-cancer activity of compounds from herbal medicine. British J. Pharm. 150:321-334.

To protect the environment, many countries are actively promoting the use of green energy and green transport (mostly Electric Vehicles, EVs). We have invented a new charging systems to combine green energy with green transport. More specifically, they are to facilitate the use of solar power for charging electric cars.

To overcome the problem of the current charging method and to make the solar energy charging EV quick and convenient, we have proposed to develop a new charging system using a highly portable intermediate energy carrier. The portable intermediate energy carrier can be charged outside of the EV. Thus, there is no idling time required for the EV while the car is being charged using solar power.

We have applied a dozen of patents for such charging systems, including Chinese, US, Hong Kong and PCT patents.

Reference:

D. C. Chang, K. Tang, and L. Fu, Charging System for Using Solar Energy to Power EV, US 63/165,160.

How to control nuclear weapons and make our world safer?

Today, the entire mankind is living under the shadow of nuclear war. The stocks of nuclear weapons in US and Russia at present are more than enough to destroy all major cities in our world. How can we protect human from this nuclear threat? As a first step of nuclear armament control, we propose to revise the Treaty on the Non-Proliferation of Nuclear Weapons to add a new article, which specifies that all existing and future nuclear weapons will have two sets of launching codes. The first set of launching code will be controlled by the government owning those nuclear weapons, just like what is practiced today. The second set of launching code will be controlled by a new international body established by the United Nation. The launch of the nuclear weapon will require both sets of codes. That means, no government can launch any nuclear weapon unilaterally without the approval of the international body. This will be greatly helpful to prevent accidental nuclear war or nuclear blackmail.

Technically, this system is not difficult to setup. But of course, politically, it will face tremendous challenges. However, the difficulty of implementing this proposal could be less than the proposal of banning all nuclear weapons.

Refence:

Donald Chang, How to control nuclear weapons and make our world safer? Bulletin of the American Physical Society, APS March Meeting (2021) link: http://hdl.handle.net/1783.1/108622