bluuebunny/crossref_metadata_2025 huggingface dataset:
Confronting the buoyant force
Authors: Noll Ellis D.
Published: April 2003

A challenge is posed to the author’s students: Determine the density of a metal cylinder without direct measurement of mass and volume. This paper describes two methods that were developed in response to the challenge.
Visualizing tension and compression
Authors: Taylor Joseph A.
Published: April 2003

The use of everyday materials to support instruction in statics is discussed. Specifically, materials such as cardboard and string are used to demonstrate tension and compression in truss-bridge models.
What's so special about science?
Authors: Holt Rush
Published: April 2003

Science should not be promoted as a mysterious discipline that only a select few can understand. It is the responsibility of science teachers to demystify subjects viewed as “too technical” by the general public.
Interactive spectra demonstration
Authors: Palmquist Bruce C.
Published: April 2003

This report describes an interactive demonstration to help students qualitatively understand emission, continuous, and absorption spectra. Students throw colored balls at a person representing an electron that can move between discrete energy levels.
Quality tools in science education
Authors: Blanton Patricia
Published: April 2003

At a recent Science Teachers’ State Convention, I attended a session called “Quality Tools in Science Education” and was introduced to an approach to classroom management and student involvement modeled after an industry practice called TQM (total quality management).
Inverted images and noninverted shadows
Authors: Layton Bill
Published: April 2003

The shadow of an object placed very near our eye will appear inverted due to the way the eye-brain system corrects the inverted real images formed on our retina. However, very nearsighted individuals may not experience this effect.
The Actio-Reactio Apparatus
Authors: Pfister Hans
Published: April 2003

Although Newton’s third law is one of the easiest to recite, most physics instructors agree that it is one of the more difficult ones to fully comprehend. We present here a very simple kinesthetic apparatus that allows students to “feel” and to “see” the action and reaction force. Use of this apparatus in our Workshop Physics course during the past few years has significantly improved learning gains on the “Force Motion Conceptual Exam” (FMCE).
The Satellite Derotator
Authors: Mungan Carl
Published: April 2003

The physical principles behind an elastic rotational collision demonstration available on a popular video series are analyzed.
Why DC for Long-Range Power Transmission
Authors: Ruby Lawrence
Published: April 2003

The case for dc versus ac power transmission is reviewed. It is concluded that for long transmission distances, i.e. more than 800 km (500 miles), dc transmission is cheaper and probably more reliable. The 1.0-MV Pacific Intertie is cited as an example of a modem efficient dc system.
Dancing Lemon Seed
Authors: Stavrinidis Vassilis
Published: April 2003

Here is a trick using a glass of soda water with some lemon seeds floating in it. Upon stirring the water, you will find the seeds dance up and down because of the bubbles.
Time-Reversal Invariance in a Course for Liberal Arts Students
Authors: Sobel Michael I.
Published: April 2003

To physicists today invariance principles lie at the heart of our understanding of the physical world. To physics educators it is always appealing, yet often inappropriate or counter productive, to bring ideas of contemporary physics into the introductory classroom.
Power, Reaction, and Excitement … in an AC Circuit
Authors: Silverman Mark P.
Published: April 2003

The physics of the fluorescent lamp is discussed, and the ac circuit of such a lamp is analyzed with a focus on basic questions concerning the influence of resistance, reactance, and phase on power consumption, efficiency, and safety.
A Newspaper Trick
Authors: Gardner Martin
Published: April 2003

Here is a physics trick using a sheet of newspaper you hold in your hands and try to poke your index finger through. It is easier than you think thanks to air resistance and inertia.
Real-Time Experimentation Across the Internet
Authors: Tompkins Perry A. , Pingen Georg
Published: April 2003

In order to expose physics students to high-quality laboratory experiments with significance beyond the classroom, we have created a laboratory experiment that can be remotely operated from a computer across the Internet. This exercise was twofold—it allowed students to experience and become familiar with new technologies that are currently used in industry, while providing others with the benefits of actual hardware-based experimentation.
Apparent-Depth Demonstration Using a Plastic Box and Pins
Authors: Cortel Adolf
Published: April 2003

The apparent position of an object and the refractive index of the liquid can be measured using a cheap plastic box filled with water, a few pins, and some more simple items. These materials also allow students to check Snell's law and observe total internal reflection.
Some Exercises on Fractals for High School Students
Authors: Zembrowska K. , Kuźma M.
Published: April 2003

High School students can be fascinated by modern physics problems. A desire to solve ambitious problems is often observed in students between the ages of 14 and 17. At that time, their interest in typical textbook problems seems to decrease. Teenagers turn to physics teachers with requests for interesting measurements or more challenging problems that they might solve. Suggestions given in this note on how to examine fractal structures may prove to be useful as a source of inventive, up-to-date small problems on the physical analysis of the surrounding world.
The Atomic Force Microscope: A Low-Cost Model
Authors: Berger Roland
Published: April 2003

The principal function of the atomic force microscope is quite easy to understand and can simply be demonstrated in the classroom by the proposed model: the topography of a coin is scanned under the mine of a ball-point pen in analogy to the widely used method of raster-scanning a sample with a sharp tip in physics and biology.
Handy Physics for a First-Time Physics Student: The Handy Physics Answer Book, by P. Erik Gundersen
Authors: Rivers Sallie Anne
Published: April 2003

This is a book review of The Handy Physics Answer Book, by P. Erik Gundersen, Visible Ink Press, Canton, Mich., 1999
Archimedes’ pump
Authors: Gardner Martin
Published: April 2003

Archimedes is said to have invented this simple way to pump water to a higher level. It was actually widely used in ancient times.
Homemade spinner demonstrates formation of solar system
Authors: Heiden David
Published: April 2003

I use a simple device to demonstrate how a sphere can become oblate when it spins. Students get to see how a cloud of gas and dust can form a relatively “flat” solar system.
The rotating face
Authors: Gardner Martin
Published: April 2003

This trick uses a Halloween mask to create an optical illusion.
The unbroken tissue
Authors: Gardner Martin
Published: April 2003

Using a rubber band, attach a square of tissue paper across one end of a cardboard tube. Hold the tube vertically, open end up, and fill the tube with uncooked rice.
Hands-on Experiments with a Voltage Tester
Authors: Jonoska M. , Tuntev A. , Zajkov O.
Published: April 2003

In this paper we propose some very useful and interesting experiments that are quite simple and can be done by teachers or students. The equipment used for these experiments is not expensive; the major device of each experiment is the voltage tester (sometimes called a “neon screwdriver”).1
Pursuing the Ubiquitous Pendulum
Authors: Stinner Art , Metz Don
Published: April 2003

In this paper, we offer three examples, inspired by Galileo's work, for connecting the physics of the pendulum with free fall and the inclined plane. The first example discusses the time it takes for a ball to slide down a frictionless inclined plane along a chord, drawn from the lowest point of a vertical circle to any point on the circle. The second example discusses a timing method that Galileo tested in measuring free fall directly, and the third example outlines an approach we have developed for accurately calculating the period of a pendulum for any angle, using only the kinematics of accelerated motion along an inclined plane, first studied by Galileo.
Collisions Between Rods: A Visual Analysis
Authors: Roura Pere
Published: April 2003

One of the key subjects in introductory physics is the problem of collisions. It provides a nice example where conservation laws of energy and momentum are essential. Two extreme cases are usually solved: elastic and perfectly inelastic collisions. In the very simple one-dimensional case, velocities before and after collision are readily related through the masses of the colliding bodies. Similar solutions can be found for partially inelastic collisions, provided that the degree of energy loss is known. Otherwise, the energy balance equation cannot be written down. Usually, one can reasonably assess whether the collision is perfectly inelastic (for instance, a bullet impinging onto a piece of wood). However, it is a matter of faith to consider a priori a collision as elastic or as being in any intermediate situation. We hope this statement will become clearer to the reader by the end of this paper.
Mysterious siphon
Authors: Gardner Martin
Published: April 2003

Here is a physics trick that involves a glass tube and a container of water. The tube acts as a siphon.
Conceptual Physics in Two-Year Colleges
Authors: Warren William R.
Published: April 2003

Introductory physics courses for nonscience students are available at most four-year colleges and universities, but are less common in two-year colleges. Offering and promoting more such courses in two-year colleges would be a good way to increase the number of students who study physics and raise the overall quality of undergraduate education.
Figuring Physics: A Full Solution and a Challenging Problem
Authors: Pratt John
Published: April 2003

This paper gives a full analysis of a projectile problem in which it is desired to find the required firing angle to hit a target level with the point of projection and to relate this angle to the “line-of-sight” angle of a point directly above the target a distance equal to the distance of the point directly below the target which the projectile would have hit had it been fired horizontally.
University and High School Partnership: Challenging Physics II Students
Authors: Mackin Joan , Sokol Paul E.
Published: April 2003

A partnership between Penn State University and a suburban high school allowed high school students to complete a calculus-based high school physics II course in mechanics and electricity/magnetism. This course was not an AP course or a traditional high school second-level course but was modeled on the dynamic physics course at Penn State. This article describes the strategies and technology tools used, data on student outcomes and achievement, and the development and implementation of the course.
Improved Vacuum Bazooka
Authors: Cockman John
Published: April 2003

This apparatus is a modification to the well-known “vacuum bazooka” (PIRA 2B30.70).1 My vacuum bazooka is easy to construct and demonstrate, requires no precise fittings, foil, or vacuum grease, and propels ping-pong balls at a tremendous velocity!
The weight of time
Authors: Redmount Ian H. , Price Richard H.
Published: April 2003

The apparent weight of an hourglass is an excellent illustration of mechanics concepts. Impluse, momentum, center-of-mass motion, and gravitation all contribute. The average weight is unaltered, but tidal effects decrease the apparent weight while center-of-mass acceleration increases it.
Measuring the coefficient of friction of a low-friction cart
Authors: Larson Roger F.
Published: April 2003

A sonic ranger is used to measure the acceleration of a low-friction cart using data collected from its motion coasting up and down an incline. The uninitiated but experienced physics student may predict the accelerations up and down the incline to be equal. However, when a cart is rolled up an incline, the speed vs time graph produced by sonic ranger clearly shows a point of inflection when the cart reverses direction at its highest point on the ramp. The author then shows how the ratios of the accelerations can be used to determine the coefficient of friction for this event.
Testing Kepler’s laws of planetary motion
Authors: Cohen Harold
Published: April 2003

This paper describes an experiment to study Kepler’s three laws of planetary motion that is appropriate for lower-division physics and astronomy courses.
The one-dimensional elastic-collision equation: νf=2νc−νi
Authors: Millet L. Edward
Published: April 2003

One-dimensional head-on collisions of two objects, one of mass m1 moving with speed v1, and one of mass m2 moving with speed v2, are often treated in general physics textbooks.
How far should you develop a formula?
Authors: Littauer Raphael
Published: April 2003

A physics problem typically involves several principles, each giving rise to a relationship expressed by an equation.
Studying the motion of an elevator
Authors: Rhyner Charles R.
Published: April 2003

In an interesting and challenging laboratory experiment, students are given the opportunity to study the motion of an elevator with the aid of the data-logging capability of a portable PASCO Science Workshop 500 interface and a mass suspended from a force sensor. From the changes in the apparent weight of the mass over time, the following can be calculated: the acceleration of the elevator, its velocity as it travels between floors, and the distance the elevator travels during its period of motion.
Controlling all variables in an experiment
Authors: Taylor Rebecca , Noll Ellis D.
Published: April 2003

Recently, our students were attempting to experimentally measure a sphere’s moment of inertia by releasing a steel sphere from rest on a straight inclined channel. Why was there such disparity in results?
A behavioral demonstration of Fermat’s principle
Authors: Ganem Joseph
Published: April 2003

Fermat’s principle is demonstrated by observing the behavior of students running and walking between two fixed points. Measurements of path lengths and velocities show that people accurately judge paths of least time for their own motion.
Hollow-tube chimes
Authors: Oliver D. L. R.
Published: April 2003

This note describes a simple and inexpensive method of designing and constructing a musical instrument. Often teachers of the physical sciences are called upon to advise students who are designing musical instrument prototypes. This article discusses the relationship between frequency and tube length for hollow metal tube chimes. A method is explained by which a set of chimes may be designed and constructed so that they cover all standard tones for a range of one or two octaves. The cost of materials will range from $3 to $6.
Communicating with vectors
Authors: Sheets H. David
Published: April 2003

In this introductory physics laboratory exercise, students are introduced to the use of vectors to describe a trajectory. Students produce written descriptions of these trajectories which are then used by other students to reconstruct the trajectory. The original and reproduction trajectory can then be compared and the sources of error discussed and evaluated.
What’s wrong with this question?
Authors: Blickensderfer Roger
Published: April 2003

Physics test questions are often based on models which have limits of applicability. In supplying data for these questions the instructor must be careful not to stray outside the limits of the model. Several examples of poor data selection are given.
The turbulent world of physics explained
Authors: Silverman Chris
Published: April 2003

The minds of physicists are curious things, populated by multitudes of weird and wonderful creatures with wild names bearing meaning only to physicists. In this odd world, we meet Red Giants, Black Holes, Dwarves, and Quarks.
Optical realization of a circular billiard
Authors: Robinett Richard W. , Mulfinger Charles E. , Passaneau John
Published: April 2003

We briefly review the classical mechanics of a point particle in a circular billiard system, classifying the possible trajectories. We then show how this system can be approximately realized experimentally, utilizing an analogy with geometrical ray optics, using a laser and cylindrical reflecting surface.
Archimedes’ principle without the king’s crown
Authors: Daniel Thomas Bruce
Published: April 2003

A concrete demonstration of Archimedes’ principle of buoyancy without direct reference to density is described. Floating and sinking are explained in terms of the weight and shape of objects. This can be effective with students who have not mastered ratios.
Small-scale anisotropies: The final frontier
Authors: Van der Veen Jatila , Lubin Philip , Natoli Paolo , Seiffert Michael
Published: April 2003

In the next few years it will be possible to make maps of the Cosmic Microwave Background (CMB) with sufficient resolution to determine the type of Universe in which we live. The MAP (NASA) and Planck (ESA) Satellites will shed new light on such fundamental questions as whether we live in an open or closed Universe, whether there is a cosmological vacuum energy density (Λ), and the precise amount of dark matter. The key to decoding the information contained within this primordial radiation hinges upon the accurate determination of the power spectrum of its temperature variations at angular scales of a few arc minutes to one degree. Althoug! ! h data from these satellites will not be available for a decade or so, students can now run their own simulations of CMB maps and power spectra on personal computer, using theoretical models.
Mid-winter grouch
Authors: Swartz Clifford E.
Published: April 2003

OK, Coach. Here’s the new team of hopefuls, trying out for the physics varsity. You’ve got to let them know what they’re in for, instill some discipline, and develop a fighting spirit. Of course you will do this by making sure the sport looks easy and attractive. They’ll have a lot of fun here. Tell them how they can team up with their pals to work together.
Hypothetical pre-classical equations of motion
Authors: Disy Ed , Garner James
Published: April 2003

After a review of ancient Greek mechanics, features of Artistotle’s mechanics are expressed as three hypothetical laws of motion. We apply the equations of motion to standard problems in mechanics with the purpose of modeling misconceptions in mechanics. The mathematics and concepts are simpler than Newtonian dynamics. This new fictitious world exhibits some interesting but strange facts that make it much different from the world in which we live.
Using colliding pendulums to teach Newton’s third law
Authors: Gauld Colin
Published: April 2003

Students do not find it easy to believe Newton’s third law because it implies a concept of force that they do not normally use. Colliding pendulums, used by Newton and his contemporaries, provide a simple means of demonstrating conservation of mementum and illustrating Newton’s third law.
Aetas Mirabilis
Authors: Swartz Clifford E.
Published: April 2003

I recently had occasion to read again Galileo’s Dialogue on Two New Sciences. Although it's hard to read Newton's Principia with its geometrical proofs, it's a delight to follow the banter and brilliant reasoning of the Dialogues. What a marvelous time to have been a scientist! Only three hundred and sixty-five years ago our whole world view was being overthrown by a few men, armed with their brains and some new optical devices.
To a physicist about to teach meteorology
Authors: O’Connell James
Published: April 2003

Physics teachers have the physical science background to teach an introductory course in meteorology. Weather phenomena follow the laws of classical physics: thermodynamics, fluid mechanics, and radiation physics.
Coriolis-effect demonstration on an overhead projector
Authors: Secco Richard Andrew
Published: April 2003

A Plexiglas apparatus with a simple system for launching a ball bearing for use as a Coriolis-effect demonstration on an overhead projector is described. A circular rotating platform is set in motion by hand and an ink-coated steel ball bearing, dropped into a funnel attached to a curved launch ramp, undergoes a Coriolis deflection and leaves an ink-stained track on the rotating platform that is clearly visible on the projected image.
Building a cheap simple generator
Authors: Kagan David T. , Keith Robert
Published: April 2003

A basic and inexpensive AC generator strong enough to light an LED described. It is made out of PVC pipe, string, wire, and magnets. The mechanical energy is supplied by blowing through a straw.
A nostalgic demonstration of the radian
Authors: Buchanan Mel , Graham Mark , Hunter Tom
Published: April 2003

Although it may be safe to put away your spotted yellow power tie and floppy computer disks that are actually floppy, the current generation of students excitedly associate this demonstration of the radian with an icon of the 1980s that is still going strong: Pac-Man™.
Using physlets to teach electrostatics
Authors: Bonham Scott W. , Risley John S. , Christian Wolfgang
Published: April 2003

One of the great difficulties in teaching electrostatics is the abstract nature of the subject. We describe six exercises in electrostatics, how they were used at NCSU, and give suggestions how they might be used in other contexts.
Precessing computer hard drives
Authors: Wagner Judson E.
Published: April 2003

While you are considering how to go about the acquisition of funds to supply your students with the fastest, most versatile, top-of-the-line computers, consider also what might be done with the old, slow, unreliable computers that are gathering dust in your storage room. As computers they may be worthless, but as machines they still have a lot of interesting parts.
A system to change both mass and applied force
Authors: Sullivan Peter , Chaplin Becky
Published: April 2003

Nonuniform acceleration is achieved by using a system whose mass changes and on which the external forces change. The interesting equipment used in the experiment is described. Derivation of a mathematical model describing the velocity of the system as a function of time is included.
Active Physics
Authors: Eisenkraft Arthur ,   Physics Textbook Review Committee
Published: April 2003

This 1998 textbook by Arthur Eisenkraft is one of seven textbooks reviewed in this issue of The Physics Teacher.
Physic-AL
Authors: Martin Brian , Spronk Cornelis ,   Physics Textbook Review Committee
Published: April 2003

This second edition of the textbook by Martin and Spronk is one of seven textbooks reviewed in this issue of The Physics Teacher.
Zeroing in
Authors: Swartz Clifford E.
Published: April 2003

Years ago we had a note in TPT, followed by a numbrer of letters to the editor, on the subject of determining the depth of a well by dropping in a stone. You measure the time it takes until you hear the splash. The solution would be simple, except that you must also account for the travel time of the sound back up the well. The letter writers argued over the most efficient way to solve the rather messy algebra.
Free-body diagrams revisited—II
Authors: Court James E.
Published: April 2003

We reproduce here a continuation of the collection of free-body exercises sent us by Jim Court, the first part of which was published in October.
Homemade interference
Authors: Moloney Michael J.
Published: April 2003

An interference experiment using simple, low-cost materials gives a reasonable value for the wavelength of light. With red and blue filters, this experiment shows without calculations that red light has the longer wavelength.
The Vortex Cannon
Authors: Bouffard Karen
Published: April 2003

This activity is in the “Do-Ahead” category of events. The students will construct a device that will produce a toroidal-shape air wave that will travel the greatest distance with the most accuracy. Directions for constructing samples are given.
Graphical analysis of electric fields of dipoles and bipoles
Authors: Bracikowski Christopher
Published: April 2003

It is common practice in introductory physics texts to show mathematically — using expansions and approximations — that the electric field far from an electric dipole (two oppositely charged point charges separate by some distance) goes as l/r3, where r is the distance from the center of the dipole. However, most texts do not provide a qualitative explanation of why this is so. A qualitative explanation would be extremely helpful, since students may follow the mathematics of the problem without being able to visualize what the approximations represent physically. Similarly, it can be shown that the electric field far from an electric bipole (two identical point charges separated by some distance) goes as l/r2. The difference in the origin of these two results is explained here pictorially. This qualitative explanation allows students to see how the l/r2 and the l/r3 dependencies arise visually and graphically rather than mathematically.
The cognac kick
Authors: Dindorf Wojciech
Published: April 2003

Here is an amazing little experiment that can be demonstrated at the dinner table or proposed as a special project for your physics students.
Waves in the movies
Authors: Greenslade Thomas B.
Published: April 2003

Recently I saw a video of the movie “Gold-Diggers of 1933.” While this movie (MGM/UA Home Video M301673) is perhaps best known for the Busby Berkeley number in which the dancers play violins outlined in neon tubes, the opening number has two knockout examples of transverse waves. In discussing the progression of the disturbance, remember that the various objects in the medium through which the wave passes perform the same motions, but with a constant phase difference between adjacent objects.
Guide to adopting technology in the physics classroom
Authors: Rios José M. , Madhavan Santosh
Published: April 2003

As the use of technology in physics courses becomes increasingly popular, there seems to be a dearth of material to guide the novice to make an informed decision about introducing technology; this note fills that need.
g-whizz
Authors: McClelland John A.
Published: April 2003

In the review of current textbooks it is pointed out that g should be described as the strength of the gravitational field rather than as acceleration. This distinction may benefit from a little elaboration.
Mousetrap racing car
Authors: Bouffard Karen
Published: April 2003

The objective of this physics contest is to build a mousetrap car that will travel in a circular path on the floor. The car must be able to start from rest, travel in excess of 2 pi radians, and stop as close to 3 pi radians (1.5 revolutions) as possible.
Good odd days
Authors: Korsunsky Boris
Published: April 2003

The article presents a collection of curious quotations from a mid-century physics textbook. These quotations provide an insight into the realities of the times and help the teachers put physics content in historical context.
A potential Gauss’s law lab
Authors: Lietz Martha
Published: April 2003

This paper describes the procedure and the results of a simple lab wherein the students measure the potential versus radius for a circular electrode configuration. The students must determine, using Gauss’s law, if this configuration simulates a cylindrical capacitor or a spherical one.
Aquarium, Computer, and Alaska range mirages
Authors: Tape Carl H.
Published: April 2003

Superior mirages, such as those of the Alaska Range mountains, can be understood both from a simple laboratory experiment and a computer simulation. An aquarium filled with several solutions is used to produce mirages with up to seven images, and a computer program is used to simulate three- and five-image mirages.
Carotenoid Modulation of Immune Function and Sexual Attractiveness in Zebra Finches
Authors: Blount Jonathan D. , Metcalfe Neil B. , Birkhead Tim R. , Surai Peter F.
Published: April 2003

One hypothesis for why females in many animal species frequently prefer to mate with the most elaborately ornamented males predicts that availability of carotenoid pigments is a potentially limiting factor for both ornament expression and immune function. An implicit assumption of this hypothesis is that males that can afford to produce more elaborate carotenoid-dependent displays must be healthier individuals with superior immunocompetence. However, whether variation in circulating carotenoid levels causes variation in both immune function and sexual attractiveness has not been determined in any species. In this study, we show that manipulation of dietary carotenoid supply invokes parallel changes in cell-mediated immune function and sexual attractiveness in male zebra finches (
Taeniopygia guttata
).
Expression of Heteropolymeric Ferritin Improves Iron Storage inSaccharomyces cerevisiae
Authors: Kim Hye-Jin , Kim Hyang-Mi , Kim Ji-Hye , Ryu Kyeong-Seon , Park Seung-Moon , Jahng Kwang-Yeup , Yang Moon-Sik , Kim Dae-Hyuk
Published: April 2003

Saccharomyces cerevisiaewas engineered to express different amount of heavy (H)- and light (L)-chain subunits of human ferritin by using a low-copy integrative vector (YIp) and a high-copy episomal vector (YEp). In addition topep4::HIS3allele, the expression host strain was bred to have the selection markersleu2−andura3−for YIplac128 and YEp352, respectively. The heterologous expression of phytase was used to determine the expression capability of the host strain. Expression in the new host strain (2805-a7) was as high as that in the parental strain (2805), which expresses high levels of several foreign genes. Following transformation, Northern and Western blot analyses demonstrated the expression of H- and L-chain genes. The recombinant yeast was more iron tolerant, in that transformed cells formed colonies on plates containing more than 25 mM ferric citrate, whereas none of the recipient strain cells did. Prussian blue staining indicated that the expressed isoferritins were assembled in vivo into a complex that bound iron. The expressed subunits showed a clear preference for the formation of heteropolymers over homopolymers. The molar ratio of H to L chains was estimated to be 1:6.8. The gel-purified heteropolymer took up iron faster than the L homopolymer, and it took up more iron than the H homopolymer did. The iron concentrations in transformants expressing the heteropolymer, L homopolymer, and H homopolymer were 1,004, 760, and 500 μg per g (dry weight) of recombinant yeast cells, respectively. The results indicate that heterologously expressed H and L subunits coassemble into a heteropolymer in vivo and that the iron-carrying capacity of yeast is further enhanced by the expression of heteropolymeric isoferritin.
Identification of a Third Sulfate Activation System inSinorhizobiumsp. Strain BR816: the CysDN Sulfate Activation Complex
Authors: Snoeck Carla , Verreth Christel , Hernández-Lucas Ismael , Martínez-Romero Esperanza , Vanderleyden Jos
Published: April 2003

Sinorhizobiumsp. strain BR816 possesses twonodPQcopies, providing activated sulfate (3′-phosphoadenosine-5′-phosphosulfate [PAPS]) needed for the biosynthesis of sulfated Nod factors. It was previously shown that the Nod factors synthesized by anodPQdouble mutant are not structurally different from those of the wild-type strain. In this study, we describe the characterization of a third sulfate activation locus. Two open reading frames were fully characterized and displayed the highest similarity with theSinorhizobiummelilotihousekeeping ATP sulfurylase subunits, encoded by thecysDNgenes. The growth characteristics as well as the levels of Nod factor sulfation of acysDmutant (FAJ1600) and anodP1 nodQ2 cysDtriple mutant (FAJ1604) were determined. FAJ1600 shows a prolonged lag phase only with inorganic sulfate as the sole sulfur source, compared to the wild-type parent. On the other hand, FAJ1604 requires cysteine for growth and produces sulfate-free Nod factors. Apigenin-inducednodgene expression for Nod factor synthesis does not influence the growth characteristics of any of the strains studied in the presence of different sulfur sources. In this way, it could be demonstrated that the “household” CysDN sulfate activation complex ofSinorhizobiumsp. strain BR816 can additionally ensure Nod factor sulfation, whereas the symbiotic PAPS pool, generated by thenodPQsulfate activation loci, can be engaged for sulfation of amino acids. Finally, our results show that rhizobial growth defects are likely the reason for a decreased nitrogen fixation capacity of bean plants inoculated withcysDmutant strains, which can be restored by adding methionine to the plant nutrient solution.
Insecticidal Activity Associated with the Outer Membrane Vesicles of
Xenorhabdus nematophilus
Authors: Khandelwal Puneet , Banerjee-Bhatnagar Nirupama
Published: April 2003

Xenorhabdus nematophilus
secretes a large number of proteins into the culture supernatant as soluble proteins and also as large molecular complexes associated with the outer membrane. Transmission electron micrographs of
X. nematophilus
cells showed that there was blebbing of the outer membrane from the surface of the bacterium. The naturally secreted outer membrane vesicles (OMVs) were purified from the culture supernatant of
X. nematophilus
and analyzed. Electron microscopy revealed a vesicular organization of the large molecular complexes, whose diameters varied from 20 to 100 nm. A sodium dodecyl sulfate-polyacrylamide gel electrophoresis profile of the vesicles showed that in addition to outer membrane proteins, several other polypeptides were also present. The membrane vesicles contained lipopolysaccharide, which appeared to be of the smooth type. Live cells of
X. nematophilus
and the OMV proteins derived from them exhibited oral insecticidal activity against neonatal larvae of
Helicoverpa armigera
. The proteins present in the OMVs are apparently responsible for the biological activity of the OMVs. The soluble proteins left after removal of the OMVs and the outer membrane proteins also showed low levels of oral toxicity to
H. armigera
neonatal larvae. The OMV protein preparations were cytotoxic to Sf-21 cells in an in vitro assay. The OMV proteins showed chitinase activity. This is the first report showing toxicity of outer membrane blebs secreted by the insect pathogen
X. nematophilus
into the extracellular medium.
Spatial and Temporal Analysis of the Microbial Community in Slow Sand Filters Used for Treating Horticultural Irrigation Water
Authors: Calvo-Bado Leo A. , Pettitt Tim R. , Parsons Nick , Petch Geoff M. , Morgan J. Alun W. , Whipps John M.
Published: April 2003

An experimental slow sand filter (SSF) was constructed to study the spatial and temporal structure of a bacterial community suppressive to an oomycete plant pathogen,Phytophthora cryptogea. Passage of water through the mature sand column resulted in complete removal of zoospores of the plant pathogen. To monitor global changes in the microbial community, bacterial and fungal numbers were estimated on selective media, direct viable counts of fungal spores were made, and the ATP content was measured. PCR amplification of 16S rRNA genes and denaturing gradient gel electrophoresis (DGGE) were used to study the dynamics of the bacterial community in detail. The top layer (1 cm) of the SSF column was dominated by a variable and active microbial population, whereas the middle (50 cm) and bottom (80 cm) layers were dominated by less active and diverse bacterial populations. The major changes in the microbial populations occurred during the first week of filter operation, and these populations then remained to the end of the study. Spatial and temporal nonlinear mapping of the DGGE bands provided a useful visual representation of the similarities between SSF samples. According to the DGGE profile, less than 2% of the dominating bands present in the SSF column were represented in the culturable population. Sequence analysis of DGGE bands from all depths of the SSF column indicated that a range of bacteria were present, with 16S rRNA gene sequences similar to groups such asBacillus megaterium, Cytophaga,Desulfovibrio,Legionella,Rhodococcus rhodochrous,Sphingomonas, and an uncharacterized environmental clone. This study describes the characterization of the performance, and microbial composition, of SSFs used for the treatment of water for use in the horticultural industry. Utilization of naturally suppressive population of microorganisms either directly or by manipulation of the environment in an SSF may provide a more reproducible control method for the future.
A New Rate Law Describing Microbial Respiration
Authors: Jin Qusheng , Bethke Craig M.
Published: April 2003

The rate of microbial respiration can be described by a rate law that gives the respiration rate as the product of a rate constant, biomass concentration, and three terms: one describing the kinetics of the electron-donating reaction, one for the kinetics of the electron-accepting reaction, and a thermodynamic term accounting for the energy available in the microbe's environment. The rate law, derived on the basis of chemiosmotic theory and nonlinear thermodynamics, is unique in that it accounts for both forward and reverse fluxes through the electron transport chain. Our analysis demonstrates how a microbe's respiration rate depends on the thermodynamic driving force, i.e., the net difference between the energy available from the environment and energy conserved as ATP. The rate laws commonly applied in microbiology, such as the Monod equation, are specific simplifications of the general law presented. The new rate law is significant because it affords the possibility of extrapolating in a rigorous manner from laboratory experiment to a broad range of natural conditions, including microbial growth where only limited energy is available. The rate law also provides a new explanation of threshold phenomena, which may reflect a thermodynamic equilibrium where the energy released by electron transfer balances that conserved by ADP phosphorylation.
Inactivation of Bacteria in Seawater by Low-Amperage Electric Current
Authors: Park Jong-Chul , Lee Min Sub , Lee Dong Hee , Park Bong Joo , Han Dong-Wook , Uzawa Masakazu , Takatori Kosuke
Published: April 2003

Seawater used in mariculture has been suspected of being a potential source of infection. In this study, the lethal effects of low-amperage electric treatment on microorganisms were examined in natural seawater and in seawater inoculated with
Vibrio
parahaemolyticus
. In both cases, bacteria including
V
.
parahaemolyticus
in seawater were completely eliminated in 100 ms by a 0.5-A, 12-V direct current. Electron microscopic investigation of the electrically treated bacteria revealed substantial structural damage at the cellular level. In conclusion, our results indicate that low-amperage electric treatment is effective for rapid inactivation of microorganisms in seawater.
Emergence of Modularity in Genotype-Phenotype Mappings
Authors: Kvasnička Vladimír , Pospí Jiří
Published: March 2003

A novel evolutionary method that allows us to study the emergence of modularity for genotype-phenotype mapping in the course of Darwinian evolution is described. The method is based on composite epigenotypes with two parts: a binary genotype; and a mapping of genes onto phenotype characters. For such generalized epigenotypes the modularity is determined in the following intuitive way: The genes are divided into two subgroups; simultaneously with this decomposition there is defined an accompanying decomposition of the set of phenotype characters. We expect that for epigenotypes with modular structures the genes from one group will be mapped onto characters from the same group, that is, that the appearance of crosslink mappings will be maximally suppressed. A fundamental question for all of evolutionary biology (and also for evolutionary algorithms and connectionist cognitive science) is the mechanism of evolutionary emergence of modular structures. The presented explanatory model is an implementation of the assumption that variation in genotype is produced on a faster time scale than variation in the genotype-phenotype mapped part. Moreover, the evaluation of the epigenotype in the evolutionary algorithm is based on directly selectable properties (corresponding to the decomposition of the set of phenotype characters). The modularity of genotypephenotype mapping emerges in the simulations.
Learning and the Evolution of Language: The Role of Cultural Variation and Learning Costs in the Baldwin Effect
Authors: Munroe Steve , Cangelosi Angelo
Published: March 2003

The Baldwin effect has been explicitly used by Pinker and Bloom as an explanation of the origins of language and the evolution of a language acquisition device. This article presents new simulations of an artificial life model for the evolution of compositional languages. It specifically addresses the role of cultural variation and of learning costs in the Baldwin effect for the evolution of language. Results show that when a high cost is associated with language learning, agents gradually assimilate in their genome some explicit features (e.g., lexical properties) of the specific language they are exposed to. When the structure of the language is allowed to vary through cultural transmission, Baldwinian processes cause, instead, the assimilation of a predisposition to learn, rather than any structural properties associated with a specific language. The analysis of the mechanisms underlying such a predisposition in terms of categorical perception supports Deacon's hypothesis regarding the Baldwinian inheritance of general underlying cognitive capabilities that serve language acquisition. This is in opposition to the thesis that argues for assimilation of structural properties needed for the specification of a full-blown language acquisition device.
Evolvable Self-Replicating Molecules in an Artificial Chemistry
Authors: Hutton Tim J.
Published: March 2003

This paper gives details of Squirm3, a new artificial environment based on a simple physics and chemistry that supports self-replicating molecules somewhat similar to DNA. The self-replicators emerge spontaneously from a random soup given the right conditions. Interactions between the replicators can result in mutated versions that can outperform their parents. We show how artificial chemistries such as this one can be implemented as a cellular automaton. We concur with Dittrich, Ziegler, and Banzhaf that artificial chemistries are a good medium in which to study early evolution.
Artificial Life and the Chinese Room Argument
Authors: Anderson David , Copeland B. Jack
Published: March 2003

“Strong artificial life” refers to the thesis that a sufficiently sophisticated computer simulation of a life form is a life form in its own right. Can John Searle's Chinese room argument [12]—originally intended by him to show that the thesis he dubs “strong AI” is false—be deployed against strong ALife? We have often encountered the suggestion that it can be (even in print; see Harnad [8]). We do our best to transfer the argument from the domain of AI to that of ALife. We do so in order to show once and for all that the Chinese room argument proves nothing about ALife. There may indeed be powerful philosophical objections to the thesis of strong ALife, but the Chinese room argument is not among them.
Efectos cotidianos de las normas perversas en la tolerancia a la corrupción
Authors: Dols José Miguel Fernández , Fernández Luis Venancio Oceja
Published: March 2003

El presente informe analiza empíricamente uno de los efectos más importantes de las normas perversas (Fernández-Dols, 1992): su capacidad para crear una mayor tolerancia a la corrupción entre las personas que la sufren. Para ello se ha llevado a cabo un cuestionario en el que un grupo de 123 sujetos (66 conductores y 57 no conductores) evaluaban el comportamiento de una persona capaz de perdonar, de forma arbitraria, multas de tráfico. En un caso las multas eran con respecto a la transgresión de una norma perversa en España (el límite de velocidad en las carreteras generales) mientras que en el otro caso se trataba de una norma cuya transgresión no es obvia y generalizada (el conducir tras haber ingerido alcohol). Los resultados muestran claramente una mayor tolerancia a la condonación de la multa en el caso del exceso de velocidad, lo) que apoya la relación entre corrupción y norma perversa apuntada en nuestra hipótesis.
Presentación, discurso y persuasión en testigos
Authors: Fdez Jorge Sobral , Ederra Angel Prieto
Published: March 2003

En el presente experimento se ocupa del impacto persuasivo de las declaraciones de testigos presenciales ante jurados simulados. Presentamos a nuestros sujetos un juicio hipotético en el que la evidencia principal en contra del acusado es la declaración de un testigo presencial. Se mantiene siempre constante el contenido del testimonio, manipulando el atractivo físico del testigo, la percepción de su status/poder y su estilo de habla mediante un entrenamiento especial. Los resultados se discuten a la luz del modelo de probabilidades de elaboración de Petty y Cacioppo (1986).
Análisis de la deliberación de jurados que varían en tamaño y regla de decisión
Authors: de Paul Velasco Pilar
Published: March 2003

Se estudian los efectos del tamaño del jurado (doce o seis miembros) y de la regla de decisión (unanimidad o mayoría de dos tercios) en el proceso de interacción, analizando las deliberaciones mediante el Método de Observación de Bales. Asimismo, se analiza si las variaciones en tamaño y regla afectan al nivel de participación de los miembros durante la deliberación.

Los resultados apoyan la existencia de un diferente estilo de deliberación en los jurados de mayor tamaño.

Además, los miembros de jurados de menor tamaño participan en mayor medida, pero no existen diferencias significativas respecto a las variaciones en la regla de decisión.
Social representations of AIDS among Italian health care workers
Authors: Mannetti Lucia , Pierro Antonio
Published: March 2003

The study investigates health care workers' representations of AIDS and its sufferers as a part of a larger research program aimed at providing a better understanding of the factors that affect health care workers' helping behaviour. 345 Italian health care workers from public hospitals were requested to write «the first things that came to their minds when thinking of AIDS and of AIDS sufferers». From Multiple Correspondence Analysis three principal axes emerged: the first one expresses a distinction between a view focused on ways of transmission and a view focused on the affective impact; the second one expresses a distinction between a view of AIDS as a serious danger and a view that stresses the media construction of the problem; the third one expresses a distinction between a purely medical view and an emphatic-emotional view.

Contrary to previous results from research on the general public, in this case higher levels of scientific knowledge are not associated with less negative reactions toward AIDS sufferers.
Imagen y norma social sobre la estereotipia
Authors: Cano Ignacio , Ros María
Published: March 2003

Históricamente los estereotipos han sido conceptualizados de acuerdo con tres dimensiones: emotiva, cognitiva y social. Las diferencias en dicha conceptualización, desde enfoques que conciben los estereotipos de forma patológica hasta corrientes que los consideran como esquemas propios del proceso normal de percepción, han desembocado en varias controversias que afectan al mismo concepto de estereotipo. Este trabajo trata de estudiar la imagen social de los estereotipos, en especial en relación con tres aspectos polémicos en la explicación del proceso de la estereotipia: los estereotipos como imágenes de grupos sociales predominantemente negativas o neutras; la extensión o no de los estereotipos a todos los perceptores y a todos los grupos, y su grado de fiabilidad; y la posible existencia de una norma social contraria a la estereotipia. Nuestros resultados principales confirman la existencia de dicha norma social inhibidora que incide fundamentalmente sobre los rasgos negativos de los estereotipos, limitándolos.