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1.
Ray Essen 《Physics in Perspective (PIP)》2010,12(1):51-73
Louis Essen (1908–1997), working at the National Physical Laboratory in Teddington, England, was the first scientist to realize
that the value for the velocity of light used widely during World War II was incorrect. In 1947 he published his first determination
of it, which was 16 kilometers per second higher than the accepted value, causing a great deal of controversy in the scientific
community. His new value was not accepted for several years, until it was shown that it improved the precision of range-finding
by radar. Essen’s result has remained as the internationally accepted value despite a number of attempts to improve on it.
I discuss Essen’s work and also examine other optical and nonoptical determinations that were made in the United States, and
their limits of accuracy. I also identify the reasons why it took so long for Essen’s new value to be accepted, and how it
led to changes in the definition of the units of length and time. 相似文献
2.
Paul Ehrenfest (1880–1933) received his Ph.D. degree at the University of Vienna in 1904 and moved with his wife and young
daughter to St. Petersburg in 1907, where he remained until he succeeded Hendrik Antoon Lorentz (1853–1928) in the chair of
theoretical physics at the University of Leiden in 1912. Drawing upon Ehrenfest’s correspondence of the period, we first examine
Ehrenfest’s difficult and insecure years in St. Petersburg and then discuss his unsuccessful attempts to obtain a position
elsewhere before he was appointed as Lorentz’s successor in Leiden.
Pim Huijnen is writing a doctoral dissertation in history; the present paper is based upon his Master’s Thesis, “‘Die Grenze
des Pathologischen’: Het leven van fysicus Paul Ehrenfest, 1904–1912,” University of Groningen, 2003. A.J.Kox is Pieter Zeeman
Professor of History of Physics at the University of Amsterdam. 相似文献
3.
Su-Juan Qin 《International Journal of Theoretical Physics》2012,51(9):2714-2718
A controlled quantum secure direct communication protocol (Zhang et al. in Int. J. Theor. Phys. 48:2971–2976, 2009) by using four particle cluster states was proposed recently. Yang et al. presented an attack with fake entangled particles (FEP attack) and gave an improvement (Yang et al. in Int. J. Theor. Phys. 50:395–400, 2010). In this paper, we reexamine the protocol’s security and discover that, Bob can also take a different attack, disentanglement attack, to obtain Alice’s secret message without controller’s permission. Moreover, our attack strategy also works for Yang’s improvement. 相似文献
4.
Christian Sichau 《Physics in Perspective (PIP)》2006,8(3):236-254
Based upon a comparison of the viscosity experiments of James Clerk Maxwell (1831–1879) and Oskar Emil Meyer (1834–1909) in
the 1860s, I argue that mathematical theory plays a significant role in both aspects of experimental practice, the design
and construction of an experimental apparatus and the transformation of the observed experimental data into the value of a
physical quantity. I argue further that Maxwell’s and Meyer’s evaluation of each other’s theoretical and experimental work
depended significantly on the mathematical tools they employed in their theories. 相似文献
5.
Controlled plasmon coupling is observed in nanoparticle assemblies composed of 20 nm silver ‘satellite’ nanoparticles tethered
by reconfigurable duplex DNA linkers to a 50 nm gold ‘core’ particle. The assemblies incorporate silver nanoparticle–oligonucleotide
conjugates prepared using a new conjugation method in which the recognition strand is anchored by a 10 base pair, double strand
spacer that presents adjacent 3’- and 5’-thiols to the silver surface. Reconfiguration of the DNA linkers from a compact to
an extended state results in decreased core–satellite coupling and a blue-shift in the gold core plasmon resonance. The structural
basis for the observed resonance modulation is investigated through simulation of the scattering spectra of binary assemblies
with various core–satellite separations. Additional simulations of core–satellite assemblies composed of gold satellite particles
bound to silver cores and of assemblies composed entirely of silver particles are used to clarify the dependence of the coupling
response on the composition of the components and their distribution within the assembly.
Electronic Supplementary Material The online version of this article () contains supplementary material, which is available to authorized users. 相似文献
6.
Reinhard Siegmund-Schultze 《Physics in Perspective (PIP)》2007,9(1):26-57
The theoretical physicist Philipp Frank (1884–1966) and the applied mathematician Richard von Mises (1883–1953) both received
their university education in Vienna shortly after 1900 and became friends at the latest during the Great War.They were attached
to the Vienna Circle of Logical Positivists and wrote an influential two-part work on the differential and integral equations
of mechanics and physics, the Frank-Mises, of 1925 and 1927, with its second edition following in 1930 and 1935.This work
originated in the lectures that the mathematician Bernhard Riemann (1826–1866) delivered on partial differential equations
and their applications to physical questions at the University of G?ttingen between 1854 and 1862, which were edited and published
posthumously in1869 by the physicist Karl Hattendorff (1834–1882).The immediate precursor of the Frank-Mises, however, was
the extensive revision of Hattendorff’s edition of Riemann’s lectures that the mathematician Heinrich Weber (1842–1913) published
in two volumes, the Riemann-Weber, of 1900 and 1901, with its second edition following in 1910 and 1912. I trace this historical
lineage, explore the nature and contents of the Frank-Mises, and discuss its complementary relationship to the first volume
of the text that the mathematicians Richard Courant (1888–1972) and David Hilbert (1862–1943) published on the methods of
mathematical physics in 1924, the Courant-Hilbert,which, when it and its second volume of 1937 were translated into English
and extensively revised in 1953 and 1961, eclipsed the classic Frank-Mises. 相似文献
7.
A. Santagata D. Spera G. Albano R. Teghil G. P. Parisi A. De Bonis P. Villani 《Applied Physics A: Materials Science & Processing》2008,93(4):929-934
The analytical response of a fs/ns double-pulse laser induced breakdown spectroscopy technique based on the orthogonal reheating
induced by a ns-laser pulse on a fs-laser ablation plume is presented. All investigations have been performed in air at atmospheric
pressure and employing certified copper-based-alloy targets. The emission intensities of the considered electronic transitions
of Pb(I), Sn(I) and Zn(I) have been normalised with a Cu(I) emission line intensity belonging to the same considered spectral
range. Emission data, acquired with inter-pulse steps of 2 μs within the delay range of 1–200 μs, have shown that fractionation
takes place. Nevertheless, excellent linear regression coefficients (0.998–0.999), despite the target’s large compositional
variation and fractionation effects, have been obtained by integrating all emission intensity data along the whole inter-pulse
delays used. Deviations from the theoretical ratio of the Zn(I)/Cu(I) emission intensities are shown and some hypotheses about
the processes involved are formulated. 相似文献
8.
Quirino Majorana (1871–1957) was an outstanding Italian experimental physicist who investigated a wide range of phenomena
during his long career in Rome,Turin, and Bologna. We focus on his experiments in Turin during 1916–1921 and in Bologna during
1921–1934 to test the validity of Albert Einstein’s postulate on the constancy of the speed of light and to detect gravitational
absorption. These experiments required extraordinary skill, patience, and dedication, and all of them confirmed Einstein’s
postulate and Isaac Newton’s law of universal gravitation to high precision. Had they not done so, Majorana’s fame among historians
and physicists no doubt would be much greater than it is today.
Giorgio Dragoni is Professor of History of Physics at the University of Bologna. Giulio Maltese is a Roman member of the Italian
Society for the History of Physics and Astronomy. Luisa Atti is a Bolognese member of the Association for the Teaching of
Physics. 相似文献
9.
Peter Heering 《Physics in Perspective (PIP)》2006,8(1):52-63
I discuss our replication of the wire-torsion experiments that Charles Augustin Coulomb (1736–1806) reported in a session
of the Paris Académie des Sciences in 1784. I first explain the nature and purpose of the replication method and then apply it to an analysis of Coulomb’s experiments.
I conclude by placing Coulomb’s presentation of his memoir into its specific historical contest. 相似文献
10.
B. I. Turko V. B. Kapustyanyk V. P. Rudyk M. V. Partika M. V. Kvasnytsya A. P. Vas’kiv 《Journal of Applied Spectroscopy》2007,74(2):310-312
We have studied the behavior of the intrinsic absorption edge in zinc oxide thin films in the temperature range 80–300 K.
We have observed that the intrinsic absorption edge in films with crystal sizes of ≈45 nm or larger is described by the empirical
Urbach’s rule, while in films with crystallite sizes of ≈15 nm, it is described by a modified Urbach’s rule. We have calculated
the effective frequency of phonons taking part in formation of the absorption edge.
__________
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 74, No. 2, pp. 275–277, March–April, 2007. 相似文献
11.
Matthew Trainer 《Physics in Perspective (PIP)》2008,10(2):212-223
In 1905 Lord Kelvin (1824–1907) was awarded the second John Fritz Medal for a lifetime of outstanding achievements in science
and technology. I sketch Kelvin’s life, education, and work in thermodynamics, electrical technology, and instrumentation,
and his role in the laying of the Atlantic cable. I then turn to Kelvin’s four visits to America, in 1876 on the centenary
of the Declaration of Independence of the United States of America; in 1884 when he gave his famous Baltimore Lectures at
The Johns Hopkins University; in 1897 when he visited Niagara Falls for the third time and advised George Westinghouse (1846–1914)
on how to develop its enormous water power for the generation of electricity; and in 1902 when he advised George Eastman (1854–1932)
on the development of the photographic industry.
Written in connection with the Kelvin Centenary Year 2007; see “Celebrating the Life of Lord Kelvin,” University of Glasgow
News Review No. 11 (2007), 4.
Matthew Trainer: Matthew Trainer received his M.Phil. degree in physical sciences at the University of Edinburgh in 1980 and
currently is a laboratory instructor at the University of Glasgow where his research focuses in part on the life and work
of Lord Kelvin. 相似文献
12.
13.
Anatoliy K. Prykarpatsky Nikolai N. Bogolubov 《International Journal of Theoretical Physics》2012,51(1):237-245
R. Feynman’s “heretical” approach (Dyson in Am. J. Phys. 58:209–211, 1990; Dyson in Phys. Today 42(2):32–38, 1989) to deriving the Lorentz force based Maxwell electromagnetic equations is revisited, the its complete legacy is argued both
by means of the geometric considerations and its deep relation with the vacuum field theory approach devised (Prykarpatsky
et al. in Int. J. Theor. Phys. 49:798–820, 2010; Prykarpatsky et al. in Preprint ICTP, 2008, ). Being completely classical, we reanalyze the Feynman’s derivation from the classical Lagrangian and Hamiltonian points
of view and construct its nontrivial relativistic generalization compatible with the vacuum field theory approach. 相似文献
14.
On the face of some recent experiments claiming the simultaneous presence of both ‘sharp interference’ and ‘highly reliable
which way information’ and some others casting light on the origin of complementarity in quantum interferometric experiments, the whole
issue is reviewed on the basis of our earlier precise formulation of Bohr’s complementarity principle. It is pointed out that
contradicting the principle (in this specific formulation) is impossible without contradicting quantum mechanics and a lack
of general consensus regarding the origin of the mutual exclusiveness is at the root of the controversy and confusions.
相似文献
15.
In the centennial of Ettore Majorana’s birth (1906–1938?), we re-examine some aspects of his fundamental scientific production in atomic and molecular physics, including a not well known short communication. There, Majorana critically discusses Fermi’s solution of the celebrated Thomas–Fermi equation for electron screening in atoms and positive ions. We argue that some of Majorana’s seminal contributions in molecular physics already prelude to the idea of exchange interactions (or Heisenberg–Majorana forces) in his later works on theoretical nuclear physics. In all his papers, he tended to emphasize the symmetries at the basis of a physical problem, as well as the limitations, rather than the advantages, of the approximations of the method employed. 相似文献
16.
Charles H. Holbrow 《Physics in Perspective (PIP)》2011,13(1):36-57
Horace Richard Crane (1907–2007) was born and educated in California. His childhood was full of activities that helped him
become an outstanding experimental physicist. As a graduate student at the California Institute of Technology (1930–1934),
he had the good fortune to work with Charles C. Lauritsen (1892–1968) just as he introduced accelerator-based nuclear physics
to Caltech. They shared the euphoric excitement of opening up a new field with simple, ingenious apparatus and experiments.
This work prepared Crane for his career at the University of Michigan (1935–1973) where in the 1950s, after making the first
measurement of the electron’s magnetic moment, he devised the g−2 technique and made the first measurement of the anomaly in the electron’s magnetic moment. A man of direct, almost laconic
style, he made lasting contributions to the exposition of physics to the general public and to its teaching in high schools,
community colleges, four-year colleges, and universities. I tell how he became a physicist and describe some of his early
achievements. 相似文献
17.
Pankaj Kumar S. C. Jain Vikram Kumar Suresh Chand R. P. Tandon 《Applied Physics A: Materials Science & Processing》2009,94(2):281-286
Current–voltage (J–V) characteristics of organic bulk heterojunction diodes based on an interpenetrating network of poly(3-hexylthiophene) (P3HT)
and [6,6]-phenyl C61-butyric acid methyl esters (PCBM) have been studied in the dark and under halogen lamp illumination. The diodes contained
1:1 and 1:0.6 weight ratios of P3HT and PCBM. For both diodes the currents measured in dark (J
d
, commonly known as the dark current) in forward bias are found to agree with the space charge limited current (SCLC). The
illuminated current consists of a current due to applied voltage (J
da
) and the light generated current (J
L
). J
da
extracted from the illuminated current agrees well with Shockley’s diffusion and recombination current. This observation
shows that illumination changes the SCLC into Shockley’s diffusion and recombination current. The forward current under illumination
has been observed to be greater than the dark current, which is contrary to the photo–voltaic (PV) theory. This result is
well explained by the change of SCLC into Shockley’s diffusion and recombination current.
Former address of S.C. Jain: IMEC, Kapeldreef 75, 3001 Leuven, Belgium. 相似文献
18.
This research aims for an objective identification, tracking, and a statistical analysis of the Moving Magnetic Features (MMFs)
around sunspots using SOHO/MDI high-resolution magnetograms. To this end, we develop a computerized tracking program and study
the motion and magnetism of the outflows of MMFs around 26 sunspots. Our method locates 4–27 MMFs per hour, with higher counts
for large sunspots. We differentiate MMFs into type α that have a polarity opposite to the parent sunspots, and type β that share the sunspot’s polarity. These sunspots’ MMF subsets exhibit a wide range of central tendencies which have distinctive
correlations with the sunspots. In general, α-MMFs emerge farther from the sunspot, carry less flux, and move faster than β-MMFs. The typical α/β-MMFs emerge at 2.2–8.1/0.1–3.2 Mm outside the penumbra limb, with lifetimes of 1.1–3.1/1.3–2.0 h. They are 1.1–6.6/1.4–3.6
Mm2 in area and carry 1.4–12.5/4.8–11.4 ×1018 Mx of flux. They travel a distance of 2.7–5.9/2.8–3.6 Mm with the speed of 0.5–0.9/0.4–0.7 km/s. Compared to the α-MMFs produced by large sunspots, those of small spots are smaller. They emerge closer to sunspot, move farther, live longer,
and carry less flux. β-MMFs show much less correlation with the sunspots. The flux outflow carried by the MMFs ranges from 0.2 to 8.3 × 1019Mx· h−1 and does not show obvious correlation with the sunspots’ evolution. The frequency distributions of the MMFs’ distance traveled,
area, and flux are exponential. This suggests the existence of numerous small, weak, and short-timescale magnetic objects
which might contribute to the sunspot flux outflow. 相似文献
19.
N. D. Lu Y. Q. Zhou T. G. Shen P. L. Ji J. Sun B. G. Yuan F. C. Yu 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2009,54(3):707-710
The paper investigated a composite photonic crystal patch antenna by using the method of finite difference time domain (FDTD).
The results show that there exists a wave resonance state at 2.635 GHz, where the real part of the permittivity and permeability
are all negative; its refraction index is –1. The effect has largely enhanced the electromagnetic wave’s resonance intensity,
and has improved the localized extent of electromagnetic energy obviously in such photonic crystal structure (PBG), resulting
in a higher antenna gain, a lower return loss, and a better improvement of the antenna’s characteristics. Due to such the
advantages, the use of patch antennas can be extended to such fields as mobile communication, satellite communication, aviation,
etc. 相似文献
20.
We analyze the forgotten communication of Ettore Majorana (1906–1938?) on the Thomas-Fermi statistical model of the atom,
which he presented on December 29, 1928, during the XXII General Meeting of the Italian Physical Society in Rome, and which
was published in Il Nuovo Cimento, the Society’s journal, in 1929. His communication was not mentioned subsequently in any of the numerous publications of
Enrico Fermi (1901–1954) and his group in Rome, nor in any of the later accounts of Majorana’s life and work. We place Majorana’s
contribution within the context of contemporary research on the subject, point out its influence on the final formulation
of the Thomas-Fermi statistical model by Fermi and Edoardo Amaldi (1908–1989) in 1934, and discuss Majorana’s other scientific
contributions before his mysterious disappearance in 1938.
Francesco Guerra is Professor of Theoretical Physics in the Department of Physics at the University of Rome “La Sapienza.”
His main fields of research are quantum-field theory, statistical mechanics of complex systems, and the history of nuclear
physics. Nadia Robotti is Professor of History of Physics in the Department of Physics at the University of Genoa. Her main
fields of research are the history of atomic physics, quantum mechanics, and nuclear physics. 相似文献