bluuebunny/crossref_metadata_2025 huggingface dataset:
Thermal conductivity of irradiated porous silicon down to the oxide limit investigated by Raman thermometry and scanning thermal microscopy
Authors: Massoud A. M. , Chapuis P.-O. , Canut B. , Bluet J.-M.
Published: November 2020

Irradiating porous silicon is expected to reduce thermal conductivity without altering the porous structure and can be studied by optical techniques provided that optical properties can be established reliably. Toward this end, mesoporous silicon (PSi), with a porosity of 56%, was prepared from a p+ Si wafer (0.01–0.02 Ω cm−1 resistivity) and was partially amorphized by irradiation in the electronic regime with 129Xe ions at two different energies (29 MeV and 91 MeV) and five fluences ranging from 1012 cm−2 to 3 × 1013 cm−2. The PSi structure is monitored by scanning electron microscopy. High-resolution transmission electron microscopy shows that the amorphous phase is homogeneous in volume and that there is no formation of amorphous–crystalline core–shell structures. An agreement is found between the thermal conductivity results obtained with micro-Raman thermometry, which is an optical contactless technique heating the sample in the depth, and scanning thermal microscopy, which is an electrical technique heating the sample by contact at the sample surface. A linear relation is established between the effective thermal conductivity and the amorphous fraction, predicting the thermal conductivity of fully amorphous porous Si below 1 W m−1 K−1. The obtained values are comparable to that of SiO2, reduced by a factor of 6 in comparison to non-irradiated porous samples (∼6.5 W m−1 K−1) and smaller than bulk silicon by more than two orders of magnitude.
Accuracy of neural networks for the simulation of chaotic dynamics: Precision of training data vs precision of the algorithm
Authors: Bompas S. , Georgeot B. , Guéry-Odelin D.
Published: November 2020

We explore the influence of precision of the data and the algorithm for the simulation of chaotic dynamics by neural network techniques. For this purpose, we simulate the Lorenz system with different precisions using three different neural network techniques adapted to time series, namely, reservoir computing [using Echo State Network (ESN)], long short-term memory, and temporal convolutional network, for both short- and long-time predictions, and assess their efficiency and accuracy. Our results show that the ESN network is better at predicting accurately the dynamics of the system, and that in all cases, the precision of the algorithm is more important than the precision of the training data for the accuracy of the predictions. This result gives support to the idea that neural networks can perform time-series predictions in many practical applications for which data are necessarily of limited precision, in line with recent results. It also suggests that for a given set of data, the reliability of the predictions can be significantly improved by using a network with higher precision than the one of the data.
Influence of geometry on the giant magnetoimpedance of high-aspect ratio amorphous magnetic ribbons
Authors: Pan Patrick , Moorehead Robert D. , Hayward Thomas J.
Published: November 2020

We study the influence of ribbon geometry on the giant magnetoimpedance (GMI) behavior of both low- and high-aspect ratio [length (l)/width (w) = 2–150] ribbons made from commercially available amorphous magnetic materials. Our results indicate that the variation of the ribbons’ GMI with geometry is due to the combination of edge effects (due to damage created by the ribbon cutting process) and global shape anisotropy. In high-aspect ratio ribbons [length (l)/width (w)≥ 20], we find that the GMI decreases with width, which we suggest is due to the cutting process creating induced stresses that suppress the transverse susceptibility at the edge of the material. In lower aspect ratio ribbons [length (l)/width (w) ≤ 20], shape anisotropy results in a relatively rapid increase in GMI with increasing length. We conclude that, with suitable optimization, high-aspect ratio ribbons prepared from commercially available materials are suitable for use as macro-scale sensors that detect small magnetic fields/strains over a large sensing area.
Strong recoil optical forces on dipoles via high-k plasmons excitation in thin metallic films
Authors: Girón-Sedas J. A. , Rodríguez-Fortuño Francisco J.
Published: November 2020

The recoil optical force that acts on emitters near a surface or waveguide relies on near-field directionality and conservation of momentum. It features desirable properties uncommon in optical forces, such as the ability to produce it via wide-area illumination of vast numbers of particles without the need for focusing or being dynamically switchable via the polarization of light. Unfortunately, these recoil forces are usually very weak and have not been experimentally observed in small dipolar particles. Some works theoretically demonstrate orders-of-magnitude enhancement of these forces via complex nano-structuring involving hyperbolic surfaces or metamaterials, complicating the fabrication and experimental demonstration. In this work, we theoretically and numerically show enhancement of the lateral recoil force by simply using thin metallic films, which support ultra-high-momentum plasmonic modes. The high-momentum carried by these modes imparts a correspondingly large recoil force on the dipole, enhancing the force by several orders of magnitude in a remarkably simple geometry, bringing it closer to practical applications.
Numerical investigation of the Lorentz force effect on two-point statistics in a turbulent channel flow
Authors: Rasam Amin , Pouransari Zeinab
Published: November 2020

Effects of a uniform and static magnetic field in the streamwise direction with different Hartmann numbers on the average structure of velocity and pressure fluctuations in a magneto-hydrodynamic turbulent channel flow are investigated. Direct numerical simulations (DNSs) are performed at low magnetic Reynolds numbers and under subcritical conditions with the bulk Reynolds number Reb = 5600, based on the channel height, using a very long domain to analyze two-point velocity and pressure fluctuations. Comparisons are made with DNS data of channel flow with a spanwise magnetic field and also without a magnetic field. Results indicate a substantial increase in the large-scale flow anisotropy, more alignment of flow structures with the mean flow and substantial elongation of flow structures in the streamwise direction in case of the streamwise magnetic field. On the contrary, the spanwise magnetic field did not have a comparable influence on the large scale flow anisotropy. Streak spacing increased linearly with increasing Hartmann number with the magnetic field in the streamwise direction. The magnetic field in the spanwise direction was more effective in increasing the streak spacing at a lower Hartmann number. The mean size of the quasi-streamwise vortex rolls was not affected with the introduction of a magnetic field. The effect of the Hartmann number on turbulent scales shows that scales grow largely with increasing magnetic field strength. The influence of the magnetic fields on pressure fluctuations was similar in the two cases and confined to large-scale weak correlations, where their length was substantially increased, especially in the spanwise direction.
Generation of intense spatially coherent superradiant pulses in strongly oversized 2D periodical surface-wave structure
Authors: Ginzburg N. S. , Zaslavsky V. Yu. , Malkin A. M. , Sergeev A. S. , Zotova I. V. , Sharypov K. A. , Shunailov S. A. , Shpak V. G. , Ul'masculov M. R. , Yalandin M. I.
Published: November 2020

We present the results of experiments on generation of high-power superradiant (SR) pulses by an extended electron bunch moving in a cylindrical surface-wave structure with two-dimensional periodical corrugation. In such a structure, azimuthally propagating wave fluxes are excited, which synchronize radiation from different azimuthal segments of a tubular electron bunch with a diameter greatly exceeding the wavelength. This facilitates a drastic increase in total electron current and, correspondingly, in SR pulses peak power while maintaining the azimuthal coherence of the radiation. In experiments carried out, subnanosecond 90 GHz SR pulses with a record-level peak power of up to 150 MW and an axially symmetric directional pattern were generated. The results of experiments are in line with the theoretical predictions based on the quasi-optical approach and direct particle-in-cell simulations.
Effective Navier-slip in non-Newtonian fluid flows over corrugated surfaces
Authors: Chen Jia , Han Sang Mok , Hwang Wook Ryol
Published: November 2020

In this study, we show that complex local flow fields, particularly those near corrugated surfaces, can be accurately reproduced with effective Navier-slip boundary conditions over an imaginary smooth surface, in which the normalized slip length can be considered as a surface property even for non-Newtonian fluid flows. The expression for the normalized slip length was derived analytically using the effective viscosity and effective shear rate in a pressure-driven channel flow with a corrugated surface, based on the two-parameter model by separating geometrical and rheological factors with the effective viscosity concept. Our framework was established on the combination of the force balance approach for slip length characterization and the flow quantification method based on the energy dissipation rate. Effects of corrugated patterns with various aspect ratios were investigated. For verification, an example stick–slip–stick flow problem was tested and the results were compared with those of direct simulations. We report that the dimensionless normalized slip length appears to be almost constant and independent of the flow rate (or pressure drop). This implies that the normalized slip length is nearly independent of rheological properties. In addition, the dimensionless slip length of non-Newtonian fluids was found to be close to that of a Newtonian fluid, and it depends on the flow geometry itself.
A lower-dimensional approximation model of turbulent flame stretch and its related quantities with machine learning approaches
Authors: Ren Jiahao , Wang Haiou , Xing Jiangkuan , Luo Kun , Fan Jianren
Published: November 2020

Flame stretch and its related quantities are three-dimensional (3D), while most planar imaging techniques, widely used in turbulent combustion, can only provide lower-dimensional information of these quantities. In the present work, based on a direct numerical simulation (DNS) database, artificial neural network (ANN) and random forest (RF) models were developed to predict the 3D flame stretch and its related quantities such as the tangential strain rate, displacement velocity, and curvature from lower-dimensional information that can be accessed experimentally. It was found that the performance of the RF model is better than that of the ANN model. In the RF model, the correlation coefficients between the modeled and actual values are more than 0.97, and the determination coefficients are over 0.95. The model performance deteriorates with increasing turbulent intensity. The probability density functions of various quantities predicted by the RF model are in good agreement with those of the DNS. Compromising the model performance and the computational cost, a simplified RF model was proposed by using a few optimal input features. It was found that the discrepancies between the modeled and actual values mainly occur in highly curved regions, which explains the observation that the prediction errors increase with increasing turbulent intensity. Overall, the predictions of the simplified RF model agree well with the actual values.
Multiple magnetic order parameters coexisting in multiferroic hexaferrites resolved by soft x rays
Authors: Ueda Hiroki , Tanaka Yoshikazu , Wakabayashi Yusuke , Tsurumi Junto , Takeya Jun , Kimura Tsuyoshi
Published: November 2020

We investigated, by using soft x rays, one of the most fundamental properties in multiferroics, that is, coupled or decoupled feature among coexisting multiple (anti)ferroic order parameters for two types of multiferroic hexaferrites. Circular dichroic signals observed at x-ray resonance for diffraction and absorption enable us to resolve several kinds of magnetic domains, which are spatial distributions of the respective order parameters. We examined magnetic field effects on the domains and unveiled the features of the order parameters. It is found that the coupled or decoupled features of the order parameters are explained by the symmetry analysis based on the Landau theory. These findings contribute to an understanding of magnetoelectric couplings in multiferroics and to exploiting a wide variety of their functionalities. In addition, we suggest a circular dichroic specular off-peak scattering at resonance as a powerful technique for studying a surface state of a magnetic order in an expansive range of quantum materials.
Specialization of tuna: A numerical study on the function of caudal keels
Authors: Zhang Jun-Duo , Sung Hyung Jin , Huang Wei-Xi
Published: November 2020

Tunas are known for their extraordinary swimming performance, which is accomplished through various specializations. The caudal keels, a pair of lateral keel-like structures along the caudal peduncle, are a remarkable specialization in tunas and have convergently arisen in other fast-swimming marine animals. In the present study, the hydrodynamic function of caudal keels in tuna was numerically investigated. A three-dimensional model of yellowfin tuna with caudal keels was constructed based on previous morphological and anatomical studies. Vortical structures and pressure distributions are analyzed to determine the mechanisms of thunniform propulsion. A leading-edge vortex and a trailing-edge vortex are attached to the caudal fin and enhance the thrust. By comparing models of tuna with and without caudal keels, it is demonstrated that caudal keels generate streamwise vortices that result in negative pressure and reduce the transverse force amplitude. Moreover, the orientations of the streamwise vortices induced by caudal keels are opposite to those on the pressure side of the caudal fin. Therefore, caudal keels reduce the negative effects of the streamwise vortices adjacent to the caudal fin and thereby enhance the thrust on the caudal fin. A systematic study of the effects of variations in the Strouhal number (St), the Reynolds number (Re), and the cross-sectional shape of the body on the swimming of tuna is also presented. The effects of caudal keels are magnified as Re and St increase, whereas the cross-sectional shape has no major influence on the caudal keel mechanism.
Electron and hole mobility of rutile GeO2 from first principles: An ultrawide-bandgap semiconductor for power electronics
Authors: Bushick K. , Mengle K. A. , Chae S. , Kioupakis E.
Published: November 2020

Rutile germanium dioxide (r-GeO2) is a recently predicted ultrawide-bandgap semiconductor with potential applications in high-power electronic devices, for which the carrier mobility is an important material parameter that controls the device efficiency. We apply first-principles calculations based on density functional and density functional perturbation theory to investigate carrier-phonon coupling in r-GeO2 and predict its phonon-limited electron and hole mobilities as a function of temperature and crystallographic orientation. The calculated carrier mobilities at 300 K are μelec,⊥c→=244 cm2 V−1 s−1, μelec,∥c→=377 cm2 V−1 s−1, μhole,⊥c→=27 cm2 V−1 s−1, and μhole,∥c→=29 cm2 V−1 s−1. At room temperature, carrier scattering is dominated by the low-frequency polar-optical phonon modes. The predicted Baliga figure of merit of n-type r-GeO2 surpasses several incumbent semiconductors such as Si, SiC, GaN, and β-Ga2O3, demonstrating its superior performance in high-power electronic devices.
How Things Work
Authors: Crane H. Richard
Published: November 2020

For many years, Crane’s column "How Things Work" appeared in The Physics Teacher. This book represents 70 columns appearing between 1983 and 1991. Unpuzzling the mysteries of everyday life, Crane explains clearly the inner workings of things, all of which are familiar household objects. All the devices and phenomena covered involve physics principles and require explanations that are not immediately obvious.

Key highlights:Topics range from toys to spider webs, from ring interferometers to gasoline pumpsExplanations are simple and understandable at all levelsEntertaining and educational

How Things Work is highly readable and will appeal to anyone interested in physics generally. The collection is invaluable for physics teachers as a useful source of inspiration in the course of their teaching. Students will gain considerable understanding from the author’s flair for experimental devices.
1990
Authors: Crane H. Richard
Published: November 2020

Sending up balloons to get the profiles of temperature, pressure, relative humidity, and wind velocity in the atmosphere is a big, worldwide operation. In the United States there are on average two release stations per state, and worldwide the total is about 800. To make the data compatible, the times of release of balloons are the same for all participating countries: daily at 600 and 1800 hours GMT. For combination with its own data, the U.S. National Weather Service receives, within two hours after the standard launch times, the data from the USSR, Japan, China, India, and other nations. These data go first to a central computer in Maryland. From there, pertinent regional data are sent to the Weather Service stations throughout the United States for release via the local newspapers, TV, and radio.
DEMONSTRATIONS
Authors: Feltyberger Earl R. , Mallmann James , Schmidt Judy M. , Senior Thomas
Published: November 2020

Concept: Higher power light bulbs must have a lower resistance than lower power light bulbs, since they have to pass more current. Thus, when they are placed in series, they experience the lower voltage drop, and the lower power light will light brightly, but the higher power bulb will light very little.
Speed & Velocity
Authors: Nelson Jane Bray , Nelson Jim
Published: November 2020

The following activities are presented: Activity 9. Measurement of Speed on a Smooth and Level Surface.Activity 10. Comparison of Average Speed and Final Speed.Activity 11. Comparing Linear Speed and Circular Speed.Activity 12. Making Graphs of Constant Speed Using Vibrating Timer Tape.Activity 13. Constant Speed Problem (Whiteboard Problem).Activity 14. Pace Yourself.Activity 15. Worksheet — Constant Speed.Activity 16. Measurement of Speed on an Inclined Plane (Average vs. Final Speed).Activity 17. Velocity vs. Time Graphs Using a Motion Probe.Activity 18. Relative Motion and Related Rate ActivitiesActivity 19. Finding Speed and Velocity of a Car Traveling with Uniform Circular Motion.Activity 20. Flying in Circles — Speed.Activity 21. Kinematics of a Student — Speed.Activity 22. Worksheet — Motion with Constant Speed.
Laser Alignment — the X-Y Position Indicator
Authors: Kallard T.
Published: November 2020

A laser is the best and simplest device for drawing a straight line through space. He-Ne lasers produce narrow, straight beams that can be projected for hundreds of meters. These lasers operate continuously and their red beams can be used as guidelines for alignment jobs. The laser tubes are carefully centered within the stainless steel housings so that the beams are pre-aligned and parallel with the housings. Thus, by aligning the steel cylinders mechanically, the laser beams are aligned optically. These encapsulated alignment lasers are low in cost, light in weight, can withstand rough handling and are operated on either battery power or standard 110/220 volt electrical power. Just a few of their uses: tunnel alignment, bridge construction, masonry work, trench alignment and pipe laying. Even small construction companies and subcontractors such as plumbers, electricians and surveyors employ alignment lasers as time, cost and labor-saving devices.
Approximating the Radius of Curvature of Small Concave Mirrors
Authors: Kallard T.
Published: November 2020

For the investigation of reflections from curved surfaces, the He-He laser is an excellent light source. It can be employed to approximate the radius of curveture and focal length of concave mirrors whose radius and focal length are unknown.
Spirograms
Authors: Kallard T.
Published: November 2020

This experiment involves a device for the sinusoidal deflection of light beams. It consists of two small plane mirrors which rotate at equal speeds in opposite directions. The mirrors are slightly inclined with relation to their axes of rotation but the axes themselves are parallel to each other.
The Mascelyne Type Beamshifter
Authors: Kallard T.
Published: November 2020

The collimated laser beam is focused with the help of a long focal length lens (L) on the screen at F (see Fig. 90). A glass wedge is introduced between the lens L and the viewing screen. In Position #1 the laser beam will suffer a deflection δ and will be focused at B. For small wedge angles the displacement will be Δ = BF = δd1.
Methods for Spreading Laser Beams
Authors: Kallard T.
Published: November 2020

Often it is necessary to spread a narrow, collimated laser beam to fill some aperture with light of uniform intensity. For example, this beam spreading is necessary to fill a diffraction grating to obtain the maximum resolving power; or, to provide a full field view in a Fizeau interferometer…
Polarization by Double Refraction
Authors: Kallard T.
Published: November 2020

All crystals except those belonging to the cubic system are birefringent. One incident ray gives rise to two refracted rays. These two rays are separated clearly in only a small number of crystals. Crystals of calcite (calcium carbonate) are used to demonstrate the phenomenon of double refraction. Calcite cleaves easily in the form of a parallelepiped (rhombohedron). Such crystals are available commercially. The demonstration setup illustrated below is not drawn to scale.
Young’s Double Slit Method for Producing Interference
Authors: Kallard T.
Published: November 2020

The narrow laser beam illuminates a double slit (S1 and S2). The distance d between the slits S1 and S2 is called the slit separation. A beam expander is necessary for the demonstration when the separation between the slits is wider than the diameter of the laser beam.
Interferometric Temperature Monitoring
Authors: Kallard T.
Published: November 2020

A small He-Ne laser can be used to continuously measure the temperature of a transparent substrate during vacuum deposition.

In a vacuum deposition process, a metallic material is vaporized under intense heat inside a vacuum chamber and the metallic vapors are deposited onto a substrate. The laser beam is directed to the surface of the transparent substrate through the glass wall of the vacuum chamber. Some of the light is reflected from the surface of the substrate through the opposite wall of the vacuum chamber to a converging lens outside the chamber. The beam is received by a photo-detector whose amplified output drives a strip chart recorder. The schematic for the temperature monitoring apparatus using interference effect is shown below.
Using a Michelson Interferometer to Measure the Index of Refraction of a Gas
Authors: Kallard T.
Published: November 2020

A Michelson-type interferometer is set up using a beam splitter and two front surface mirrors, M1 and M2. A small vacuum chamber is placed in the “fixed leg” of the interferometer..
Michelson Interferometer Used for Vibration Analysis
Authors: Kallard T.
Published: November 2020

The vibrating surface under study is placed in an optical field consisting of two mutually coherent plane waves which propagate in somewhat different directions. If the surface is diffuse, a fringe pattern will be formed on it due to the interference of the two plane waves. If a time-averaged image of the surface vibrating within this interference field is formed (with a camera or by utilizing visual persistence of the eye), it is found that the visibility of the fringes formed on the surface is modulated by a function of the local amplitude of vibration. Thus loci of constant vibrational amplitude can be directly observed as regions of high or low fringe visibility in the image of the surface. Fringe visibility contrast can be enhanced by optical processing of the image.
The Fabry-Perot Interferometer
Authors: Kallard T.
Published: November 2020

A Fabry-Perot interferometer consists of a pair of flat glass plates with semi-reflecting surfaces accurately parallel to each other and separated by distance d. An extended source of light, such as a frosted glass plate illuminated from the rear, is required to produce Fabry-Perot fringes. The concentric circular fringes are produced by the multiple reflection of light in the air film between the silver or aluminum coated surfaces.
Image Plane and Focal Length Determination Using Laser Speckle
Authors: Kallard T.
Published: November 2020

The phenomenon known as a speckle pattern results when laser light is reflected from or transmitted through an object having an optically rough surface.
Interference in Scattered Light
Authors: Kallard T.
Published: November 2020

Most interference experiments demand careful adjustment of the apparatus. There is a very simple way to obtain beautiful interference fringes with the help of a He-Ne laser. The following experiment utilizes two luminous point sources derived from the same beam by means of scattering and diffraction. The setup is shown in Fig. 201.
Demonstrating the Paths of Diffracted Rays
Authors: Kallard T.
Published: November 2020

This setup shows ray paths in a plane, not just spots on a screen, representing the different orders of diffraction from a grating. The diffraction angles of the various orders can be measured directly.
The Poisson-Arago Spot
Authors: Kallard T.
Published: November 2020

From Fresnel’s wave theory of light Poisson deduced in 1818 that a spot of light should appear at the center of the shadow of a circular obstruction. Poisson’s predicted spot had been observed by Maraldi one hundred years earlier. Arago performed Poissson’s thought experiment and rediscovered Maraldi’s long forgotten spot. This phenomenon is one historically imprtant confirmation of Fresnel’s wave theory of light and it is known as the Poisson-Arago bright spot.
Measuring the Diameter of a Hair by Diffraction
Authors: Kallard T.
Published: November 2020

It is often necessary to measure the diameter of fine wire, hair, yarn or filament. The diffraction of laser light has been used in industry to measure the thickness of fine yarn or wire during the fabrication process.
Diffraction of Light by Ultrasonic Waves
Authors: Kallard T.
Published: November 2020

Among the techniques for controlling the output radiation of laser light sources, the interaction of ultrasonic and optical beams is proving to be one of the most versatile and useful.
Thin-film Optical Waveguide
Authors: Kallard T.
Published: November 2020

Light waves can be guided in thin dielectric films that are the two-dimensional analog of optical fibers. Thin-film optical devices can be made very small and they can be placed next to each other on a single substrate, forming an optical system. In recent years there have been important advances in thin-film light guides. Integrated optical circuits, two-dimensional optical elements, electro-optic, acousto-optic and nonlinear optical devices have been extensively studied.
Heat
Authors: Edge R. D.
Published: November 2020

Experiment 4.01 The hygrometer

Materials: straws, card, rubber band, tape, hair.
Wave Motion
Authors: Edge R. D.
Published: November 2020

Experiment 5.01 Longitudinal Waves

Materials: - rubber bands, marbles, paper clips tape
Computer Applications
Authors: McCullough Jodi , McCullough Roy
Published: November 2020

Vernier Software, 8565 SW Beaverton-Hillsdale Hwy., Portland, OR 97225; 503-297-5317; www.vernier.com
Master Equipment List
Authors: Roeder John L.
Published: November 2020

1. Designing a Roller Coasterinclined plane (e.g., 1” x 6” (or 8”) x 4’ boards from building supply company table, with one side propped up with books or bricks)metersticklow-friction cart (e.g., PASCO, Hall’s)supports for inclined plane (e.g., books or bricks)spring scale, to measure force in newtons
The Role of the Sciences in General Education
Authors: Roller Duane
Published: November 2020

Although the sciences have long had a place in the college curriculum, the role which they should be called upon to play today is immensely more prominent and significant than ever before. The public is, today, thoroughly aware that our culture in its material aspects has been profoundly affected by technologic advances and that we are continually facing problems of how best to utilize the results. Less generally or consciously understood, however, is the radically new character of many of the ideas and concepts that have long been emerging from the sciences, and the extent to which they are in serious conflict with traditional beliefs held precious by many persons. Yet we must face the expectation that it is by these new views that our culture eventually will be dominated. Still less generally appreciated is the extent to which the tested methods and technics of the sciences provide the general public with the means for attacking a large variety of problems with confidence and efficiency, and how highly probable it is that these scientific procedures will eventually be utilized to solve many of the crucial problems of living. To the scientist, on the other hand, all this seems obvious, although he is just beginning to take it into full account in planning his science courses for the general student. When college and school administrative bodies understand it more thoroughly, we may expect a whole-hearted and vigorous effort on their part to help place the sciences in the important place they must occupy in any program of liberal education that is truly modern.
A Physicist’s Peace
Authors: Condon E. U.
Published: November 2020

This is being called a physicist’s war. The physicists are being called upon to devote themselves, and they are devoting themselves, to the design and development of devices to help our army and navy win the fight for freedom.
Reminiscences of the Early Years of the Association
Authors: Webster David L.
Published: November 2020

It is about 15 years, now, since research men at M.I.T. began to talk lightly about their budgets in terms of a new unit, the “megabuck.” About 15 years before that time, even a thousand dollars looked so big and awesome to most of us that we did not think of calling it a kilobuck, though in a less lawful, but more lucrative, industry it was called a “grand.” Going back still another 15 years or so, we may recall the time before World War I, when the whole shop equipment of the Stanford Physics Department was just one pair of pliers. Even this had been bought by my good friend P. A. Ross with his own money. Research was not quite impossible in those days, “the days of string and sealing wax”—it was in one of those days that C. T. R. Wilson set fire to a piece of string to start the operation of the world’s first cloud chamber—but research physicists were still few and far between. More so in America than in England, France, or Germany; and a trip to a meeting of the American Physical Society was a great event.
Presentation of the Oersted Award to Professor Clifford N. Wall
Authors: Zemansky Mark W.
Published: November 2020

The rewards of the research physicist are often numerous. The eminent research physicist is promoted rapidly, at times to a specially endowed professorship, and is eligible for medals, prizes, remunerative lecture engagements, and other awards. He is interviewed on television, quoted in the daily papers, and consulted by Government leaders. The eminent teacher, on the other hand, is often treated as though he were partly a work horse and partly a loafer. To make matters worse, at least six times a year he is forced to listen to that nauseating libel which is meant to be so humorous, namely, that “He who can does, but he who can’t teaches.” The American Association of Physics Teachers, devoted, at least in part, to the task of raising the morale of teachers and of educating the public to understand and to value the work of teachers, is one of the very few organizations that has established a tangible award in recognition of superior contributions to the art of teaching. This award is the Oersted medal, and at this joint meeting of the American Physical Society and the American Association of Physics Teachers we are happy to present our eighteenth medal to another really great teacher, Professor Clifford N. Wall.
Reminiscences of Professor Paul Ehrenfest
Authors: Uhlenbeck G. E.
Published: November 2020

I Feel greatly honored by the award of the Oersted Medal for my contributions to the teaching of Physics. It is very pleasant, and it came to me as quite a surprise, to receive recognition for one’s daily work. This is especially the case with teaching, which is such an “abstract” occupation and where all one does is just talk and where one has so rarely the feeling that one has accomplished something.
Fashions in Thermodynamics
Authors: Zemansky Mark W.
Published: November 2020

Of all the branches of physics that I have taught the subject of thermodynamics has interested me most. It all started in 1925 when I was an instructor at the City College of New York and a graduate student at Columbia University. I shared an office with Henry Semat and we were close friends then as we are now. The chairman of our Physics Department, a wise, kind, and cultured man named William Fox, offered Semat and me the opportunity to teach our first elective courses. Up to that time, we had taught only prescribed first-year physics. I remember that Semat chose to teach mechanics and I chose the subject of heat. Professor Fox gave us complete freedom to conduct our courses as we pleased.
New Era in Science?
Authors: Buchta J. W.
Published: November 2020

Many weeks ago, before October 4, the birthday of Sputnik, Secretary Verbrugge required that I register a title for these remarks. Events since that day have made the title more appropriate. But, they also make it more difficult to feel satisfied with what one says. The remarks should, for comfort, have been written several months ago, rather than several days ago!
Presentation of Paul Kirkpatrick as the Oersted Medalist for 1958
Authors: Eaton Vernet E.
Published: November 2020

The Oersted Medal is awarded annually by the American Association of Physics Teachers “for notable contributions to the teaching of physics.” As we honor our medalist, we also in a sense honor Hans Christian Oersted, and it is quite appropriate that we look to see if these two men, a century apart, possessed certain interests and qualities in common.
Robert Wichard Pohl : Oersted Medalist for 1959
Authors: Overbeck C. J.
Published: November 2020

Today we honor Robert Wichard Pohl, Professor Emeritus of Physics and former Director of the Institute of Experimental Physics, Goettingen, Germany, as the twenty-fourth Oersted Medalist. He joins that distinguished group of men who have made exceptionally “notable contributions to the teaching of physics.” Dr. Pohl is the second European selected to receive this honor, the other person being Professor Arnold Sommerfeld. The accomplishments of Dr. Pohl have been recognized before by the American Association of Physics Teachers. In 1953, the Awards Committee selected him for Honorary Membership in the Association. Only three other men hold such Honorary Memberships.
Discovery of Interference by Thomas Young
Authors: Pohl Robert W.
Published: November 2020

I was very pleased when Professor Overbeck sent me the message that the American Association of Physics Teachers planned to present me with the Oersted Medal. I extend my sincere gratitude to the Association for this honorable award.
The Most Important Thing
Authors: Sears Francis W.
Published: November 2020

Thank you very much, Professor Olsen. When I was informed at the regular meeting of the Awards Committee last spring that a rump session of the other committee members had already been held in my absence, and that a decision had been reached which I might protest but could not outvote, I replied by quoting the following limerick.
Freedom, Responsibility, and Barriers
Authors: Michels Walter C.
Published: November 2020

Professor Verbrugge, President Parker ladies and gentlemen. I am deeply touched by the honor that the Awards Committee of the American Association of Physics Teachers has done me today. It is only natural that the recipient of the Oersted Medal, knowing how little he has been able to accomplish and how badly he has done some of his teaching, should wonder how he has bluffed the Committee into believing that he deserves it. Rather than to pursue that line, I should like to say that I consider myself the representative of a considerable number of persons with whom I have had the extremely good fortune to be associated—far better fortune than I deserve. Any contributions that I may have made to the teaching of physics are at least as much theirs as mine.
H. Richard Crane: Oersted Medalist for 1976
Authors: Guernsey Janet B.
Published: November 2020

It is hard to imagine a physicist and teacher with a broader range of interest and expertise than H. Richard Crane, George P. Williams University Professor at the University of Michigan, Department Chairman for seven years. A consistent developer of new techniques of measurement, new methods of teaching, his concern is not only with students who will become physicists but also with those who will become tomorrow’s citizens engaged in pursuits not involving the sciences. A prolific contributor of journal articles and papers presented at scientific meetings, he is internationally recognized for his work in physics education, nuclear physics, biophysics, high-energy accelerators and fundamental constants. His present research is in geomagnetism.
The Robert A. Millikan Lecture Award 1972
Authors: Donnally Bailey L.
Published: November 2020

The AAPT Awards Committee selected Arnold A. Strassenburg to receive the Robert A. Millikan Lecture Award for 1972. This award, which is given for “notable and creative contributions to the teaching of physics,” was presented at the annual summer meeting in Albany, held at the State University of New York in June 1972.
Standards and Best Practices
Authors:   NASA and AAPT
Published: November 2020

Many of the activities in this guide provide an opportunity to teach about standard physics Core Disciplinary Ideas (CDI) in mechanics and beyond. The specific referenced standards are listed below. Further, most Cross-Cutting Concepts (CCC) and many Science and Engineering Practices (SEP) can be explicitly addressed through these activities.
Constant Velocity
Authors:   NASA and AAPT
Published: November 2020

Estimate the average speed of an airplane as it travels between two points.
Additional Resources
Authors:   NASA and AAPT
Published: November 2020

ACTIVITY The 747 and its competitors
Year 2012 F=ma Contest
Authors: Kisačanin Branislav , Zhang Eric K.
Published: November 2020

This chapter contains year 2012 F = ma exam problems and solutions.
Structural and functional characterization of the pore-forming domain of pinholin S
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68
Authors: Steger Lena M. E. , Kohlmeyer Annika , Wadhwani Parvesh , Bürck Jochen , Strandberg Erik , Reichert Johannes , Grage Stephan L. , Afonin Sergii , Kempfer Marin , Görner Anne C. , Koch Julia , Walther Torsten H. , Ulrich Anne S.
Published: November 2020

Significance

With growing antibiotic resistance in bacteria, understanding the lytic cycle of bacteriophages can help developing phage therapy. In the double-stranded DNA bacteriophage φ21, the integral membrane protein pinholin S
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68 triggers lysis by forming small “pinholes.” It has been proposed that the second transmembrane helix (TMD2) is sufficient to form these pores, which we could confirm in a reconstituted model system, showing a pore diameter of about 2 nm. Using NMR, we determined the structure of TMD2 as it is embedded and aligned in the membrane, revealing a right-handed glycine zipper motif in a prime position for homo- and heteromeric helix–helix interactions. Molecular models are derived from these data to illustrate the assembly of the pinholes via inactive and active dimers.
A modeling framework for adaptive lifelong learning with transfer and savings through gating in the prefrontal cortex
Authors: Tsuda Ben , Tye Kay M. , Siegelmann Hava T. , Sejnowski Terrence J.
Published: November 2020

Significance

The prefrontal cortex (PFC) enables humans’ ability to flexibly adapt to new environments and circumstances. Disruption of this ability is often a hallmark of prefrontal disease. Neural network models have provided tools to study how the PFC stores and uses information, yet the mechanisms underlying how the PFC is able to adapt and learn about new situations without disrupting preexisting knowledge remain unknown. We use a neural network architecture to show how hierarchical gating can naturally support adaptive learning while preserving memories from prior experience. Furthermore, we show how damage to our network model recapitulates disorders of the human PFC.
Selectivity filter ion binding affinity determines inactivation in a potassium channel
Authors: Boiteux Céline , Posson David J. , Allen Toby W. , Nimigean Crina M.
Published: November 2020

Significance

The role of the selectivity filter in controlling potassium channel activity is different for different channels, despite identical sequences and structures. While KcsA and voltage-gated channels experience C-type inactivation by collapsing their selectivity filters under reduced potassium concentration, the mechanism by which the MthK channel regulates gating at the filter is unclear. Unlike the KcsA selectivity filter that experiences a uniform titration of its ion binding sites, leading to collapse, high-resolution X-ray structures of the pore-only MthK channel reveal that only the central S2 site loses its ion at low concentrations, insufficient for a conformational change. The selectivity filters of MthK and KcsA differ in their ion affinities due to interactions behind the filter, determining their inactivation phenotypes.
Evolution of insulin at the edge of foldability and its medical implications
Authors: Rege Nischay K. , Liu Ming , Yang Yanwu , Dhayalan Balamurugan , Wickramasinghe Nalinda P. , Chen Yen-Shan , Rahimi Leili , Guo Huan , Haataja Leena , Sun Jinhong , Ismail-Beigi Faramarz , Phillips Nelson B. , Arvan Peter , Weiss Michael A.
Published: November 2020

Significance

Protein sequences evolve under multiple constraints, including structure, stability, and bioactivity. Yet hidden constraints (inapparent in the native structure) may underlie informational content of protein sequences. An invariant aromatic residue in vertebrate insulins—a phenylalanine at its receptor-binding surface—is required for cellular folding efficiency. Any amino acid substitution impairs cellular biosynthesis, even tyrosine, whose related aromatic side chain preserves native structure and allows function within the range of natural variation. Our results suggest that sequences required for insulin’s bioactivity (similar in all vertebrates) are frozen at the edge of nonfoldability. Whereas evolved regulatory networks are ordinarily robust, proinsulin’s precarious foldability both underlies a rare monogenic form of diabetes and provides an evolutionary backdrop to the present obesity-related diabetes pandemic.
Structure of human endo-α-1,2-mannosidase (MANEA), an antiviral host-glycosylation target
Authors: Sobala Łukasz F. , Fernandes Pearl Z. , Hakki Zalihe , Thompson Andrew J. , Howe Jonathon D. , Hill Michelle , Zitzmann Nicole , Davies Scott , Stamataki Zania , Butters Terry D. , Alonzi Dominic S. , Williams Spencer J. , Davies Gideon J.
Published: November 2020

Significance

The glycosylation of proteins is a major protein modification that occurs extensively in eukaryotes. Glycosidases in the secretory pathway that trim N-linked glycans play key roles in protein quality control and in the specific modifications leading to mature glycoproteins. Inhibition of glucosidases in the secretory pathway is a proven therapeutic strategy, that holds great promise in the treatment of viral disease. The enzyme endo-α-1,2-mannosidase (MANEA) provides an alternative processing pathway to evade glucosidase inhibitors. We report the three-dimensional structure of human MANEA and complexes with enzyme inhibitors that we show act as antivirals for bovine viral diarrhea and human dengue viruses. The structure of MANEA will support inhibitor optimization and the development of more potent antivirals.
Samir Amin in Beijing: delving into China’s delinking policy
Authors: Macheda Francesco , Nadalini Roberto
Published: November 2020

According to the neoliberal narratives, opening up to the world system has deformed the structure of the Chinese economy, thereby passively serving the needs of the centre. In his works, Samir Amin offers the theoretical basis to demystify such narratives. However, he only cursorily analysed the specific policies through which China has achieved the goal of subordinating the domestic market to the logic of internal development. This article attempts to fill this gap by investigating the strategy adopted by the Chinese authorities, which allowed the country to integrate itself into global relations without abandoning its strategy of delinking from imperialism.
The mRNA m6A reader YTHDF2 suppresses proinflammatory pathways and sustains hematopoietic stem cell function
Authors: Mapperley Christopher , van de Lagemaat Louie N. , Lawson Hannah , Tavosanis Andrea , Paris Jasmin , Campos Joana , Wotherspoon David , Durko Jozef , Sarapuu Annika , Choe Junho , Ivanova Ivayla , Krause Daniela S. , von Kriegsheim Alex , Much Christian , Morgan Marcos , Gregory Richard I. , Mead Adam J. , O’Carroll Dónal , Kranc Kamil R.
Published: November 2020

The mRNA N6-methyladenosine (m6A) modification has emerged as an essential regulator of normal and malignant hematopoiesis. Inactivation of the m6A mRNA reader YTHDF2, which recognizes m6A-modified transcripts to promote m6A-mRNA degradation, results in hematopoietic stem cell (HSC) expansion and compromises acute myeloid leukemia. Here we investigate the long-term impact of YTHDF2 deletion on HSC maintenance and multilineage hematopoiesis. We demonstrate that Ythdf2-deficient HSCs from young mice fail upon serial transplantation, display increased abundance of multiple m6A-modified inflammation-related transcripts, and chronically activate proinflammatory pathways. Consistent with the detrimental consequences of chronic activation of inflammatory pathways in HSCs, hematopoiesis-specific Ythdf2 deficiency results in a progressive myeloid bias, loss of lymphoid potential, HSC expansion, and failure of aged Ythdf2-deficient HSCs to reconstitute multilineage hematopoiesis. Experimentally induced inflammation increases YTHDF2 expression, and YTHDF2 is required to protect HSCs from this insult. Thus, our study positions YTHDF2 as a repressor of inflammatory pathways in HSCs and highlights the significance of m6A in long-term HSC maintenance.