bluuebunny/crossref_metadata_2025 huggingface dataset:
General relativity in two- and three-dimensional space–times
Authors: Collas Peter
Published: March 2005

We consider the general relativity field equations in two- and three-dimensional space–times. We find that in a two-dimensional space–time we can have curvature but not matter. In a three-dimensional space–time we find that empty space must be flat, that a de Sitter solution exists, and that finite mass distributions with constant surface density must have zero ’’surface tension.’’ Finally, an expanding dust-filled universe turns out to be like Milne’s model.
Comparing two forms of instruction in college physics
Authors: Renner John W. , Paske William C.
Published: March 2005

We hypothesize that the amount of learning that takes place in a classroom is related to the teaching methodology employed. To test this hypothesis, several forms of examinations have been administered to the nonscience-major students attending physical sciences classes at the University of Oklahoma in an attempt to determine the relative effectiveness of two instructional methodologies which we label Formal Instruction and Concrete Instruction. The results of these studies indicate a need to seriously reevaluate our present approach to teaching these ’’survey’’ or ’’introductory’’ physics classes designed for the nonscience major.
Stellar spectrum synthesizer
Authors: Landegren G. F.
Published: March 2005

A device is described that employs two diffraction gratings and three or four simple lenses to produce arbitrary absorption or emission spectra that may be Doppler shifted and spectroscopically examined by students some distance away. In this sense it may be regarded as a sort of artificial star whose spectrum may be compared with known spectral standards and qualitatively or quantitatively analyzed as an undergraduate laboratory exercise or simply shown as a demonstration.
The electronic music synthesizer and the physics of music
Authors: Hartmann W. M.
Published: March 2005

We describe the principal modules of analog electronic music synthesizers and discuss some ways that we have used a synthesizer in demonstrations, psychophysical experiments, and an undergraduate laboratory course in the physics of music and acoustics. We consider the synthesis of both steady and transient auditory phenomena.
Life science-related physics laboratory on geometrical optics
Authors: Edwards T. H. , Eicher D. , Nolen J. A.
Published: March 2005

A quantitative laboratory on geometrical optics has been designed for use in a noncalculus introductory physics laboratory for life science majors. The thin lens equation is used by the students to calculate the focal length of the lens necessary to correct a myopic condition in an optical bench simulation of a human eye. Criteria for choice of lenses for the model from standard laboratory apparatus are given.
Best measuring time for a Millikan oil drop experiment
Authors: Kapusta J. I.
Published: March 2005

It is argued that, in a Millikan oil drop experiment, there is a best measuring time for the experimenter to observe the drop because of the Brownian motion of the drop and the reaction time of the experimenter. An equation for the relative error for the excess charge observed on an oil drop is derived, and from it is obtained a formula for the best measuring time.
Equal rights for the reciprocal lattice
Authors: Radford L. E.
Published: March 2005

The reciprocal lattice is frequently generated as a by-product of the direct lattice or as a convenient abstraction which satisfies the Laue equations. The dualistic point of view from projective geometry is invoked to characterize the information contained in the reciprocal lattice more precisely. From this point of view the reciprocal lattice is seen as an alternate and equally complete representation of the geometric structure of crystal systems. The Ewald and Bragg constructions are displayed as symmetric constructions in their respective lattices.
Kinematics and dynamics of elastic rods
Authors: Davidon William C.
Published: March 2005

A simple macroscopic theory of elastic rods is presented in which all assumptions but one are consistent with both Newtonian mechanics and special relativity. The one distinguishing assumption is the inertial equivalence of energy. While invariance of the theory under Lorentz transformations is proved, all physical consequences—including the stress and velocity dependence of the length and inertial mass of a rod as well as the velocities of sound through it—are derived and can be tested in any one inertial frame. Exact wave solutions of the basic equations are obtained for an idealized elastic material in which the velocity of sound is independent of amplitude. These solutions are used to account for the kinematics and dynamics of accelerated rods, including the time-dependent processes which result in their overall Lorentz contraction.
History of molecular beam research: Personal reminiscences of the important evolutionary period 1919–1933
Authors: Estermann Immanuel
Published: March 2005

Dr. Immanuel Estermann was engaged in writing a book on the History of the Molecular Beam Method when he died in Haifa, Israel on 31 March 1973. The original plan of the manuscript was to cover three distinct historical periods: the first, the years 1911–1933, when the center of research in molecular beams was at the University of Hamburg; the second, from 1933 to the outbreak of World War II, when the most active laboratory working in the field was at Columbia University; and the postwar period, when many laboratories on both sides of the Atlantic became actively engaged in this field. The material in this paper deals primarily with the early historical period and would have formed the essence of the first two chapters of the book. In addition to presenting interesting historical facts on a crucial period in the development of quantum physics, it contains some amusing historical sidelights on the research personalities that dominated that period.
Right-angle lever paradox
Authors: Nickerson J. Charles , McAdory Robert T.
Published: March 2005

We present the problem of relativistic torques with particular reference to the right-angle lever problem and outline a simple solution. The important elements of our solution are, first, a reexamination of the classical relation between torque and angular momentum and, second, the consequent realization that in relativistic analysis there exists a net internal torque which exactly cancels the net external torque experienced by an extended body in dynamic equilibrium. We find that the lever has constant angular momentum according to all Lorentz inertial reference systems and that this is consistent with the relativistic relationship between torque and angular momentum. Our solution is not restricted to relativity. It is valid for a wider class of theoretical frameworks.
Trace element analysis of blood serum by proton-induced x-ray fluorescence
Authors: Breiter Dennis N. , Roush Marvin L.
Published: March 2005

A study of human blood serum is utilized to demonstrate both the x-ray emission caused by electrons dropping into atomic inner-shell vacancies produced by proton bombardment and the application of such x-ray emissions to trace element analysis. Sample preparation consisted solely of pipetting 25 μl of serum onto low-ash filter paper. Characteristic Kα x rays from copper and zinc were detected by a Si(Li) semiconductor detector to determine trace concentrations of these essential biological metals in the blood. The copper and zinc concentrations in the blood serum sample analyzed were found to be 1.16±0.13 and 0.70±0.07 ng/μl, respectively.
Measurement of refractive index gradients by deflection of a laser beam
Authors: Barnard A. J. , Ahlborn B.
Published: March 2005

In this simple experiment for an undergraduate laboratory a laser beam is passed through the mixing zone of two liquids with different refractive indices. The spatial variation of the refractive index, at different times during the mixing, can be determined from the observed deflection of the beam.
Gravity without geometry
Authors: Rastall Peter
Published: March 2005

A theory of gravitation is developed which is a natural extension of the Newtonian theory. It is compatible with special relativity and with all present-day observations. It requires only elementary mathematics and can be taught in a junior-level mechanics course. It is not a complete theory of gravitation, since it applies only to static or quasistatic gravitational fields, but it enables the unmathematical to gain a good understanding of the physics of gravitation.
Young’s modulus and internal damping in a vibrating rod
Authors: Simpson H. M. , Wolfe P. J.
Published: March 2005

A high-Q mechanical oscillator in the form of a metallic rod with an eddy current driver is described. With this oscillator and a simple crystal transducer the characteristics of a mechanical oscillator can be easily studied and Young’s modulus for the metal can be found. With an inexpensive FM transducer system the internal damping of the metal can also be measured.
Statistical interpretation of quantum theory
Authors: Krips Henry
Published: March 2005

A new approach to axiomatizing quantum theory is suggested that overcomes some of the problems of the more usual methods. The measurement process is not left as a primitive under the new approach, and the density operator is taken as describing the fundamental physical properties of a system. Some differences from the Bohr and Margenau–Park approaches are mentioned.
Lorentz transformations from the first postulate
Authors: Lee A. R. , Kalotas T. M.
Published: March 2005

We present in this paper a derivation of the Lorentz transformation by invoking the principle of relativity alone, without resorting to the a priori assumption of the existence of a universal limiting velocity. Such a velocity is shown to be a necessary consequence of the first postulate, and the fact that it is not infinite is borne out by experiment.
Simplified navigation for self-propelled astronauts
Authors: Freedman Roger A. , Helmy Ibrahim , Zimmerman Peter D.
Published: March 2005

An astronaut in the vicinity of an orbiting spacecraft must navigate himself by means of impulsive velocity changes Δv, imparted by hands or feet or by small rockets. The motion relative to the spacecraft produced by such an impulse is noticeably nonlinear; if ejected from the spacecraft with a typical Δv of magnitude 2 m/sec in the orbital plane of the spacecraft, the astronaut suffers a net transverse deflection of 22.5 cm after 10 sec. Celestial mechanics can give only a numerical solution, which is of little practical help to the astronaut. In this paper we present approximate closed-form solutions valid for low speeds (≲100 m/sec) and short elapsed times (≲0.1 orbital period), for a Skylab-like Earth orbit of semimajor axis 6800 km.
Classical microscopic models of Johnson noise
Authors: Tunaley J. K. E.
Published: March 2005

It is demonstrated that a commom microscopic model of a resistor exhibits a reactive component of the admittance which dominates at sufficiently high frequencies and causes a decrease in the noise spectral density of the current fluctuations. In addition, Nyquist’s theorem is derived for the general classical case including the coulomb interactions between the carriers and the influence of the lattice potential. The significance of the real part of the admittance is made apparent directly.
Robert Resnick: Oersted Medalist for 1974
Authors: Jossem E. Leonard
Published: March 2005

Remarks by the Chairman of the Committee on Awards in presenting Robert Resnick the award of the 1974 Oersted Medal in recognition of his notable contributions to the teaching of physics.
Dual-purpose Millikan experiment with polystyrene spheres
Authors: Wall C. N. , Christensen F. E.
Published: March 2005

A common complaint leveled against the Millikan oil drop experiment, as ususally performed in the undergraduate physics laboratory, is that it often yields values of the electronic charge with inexplicably gross errors. Both students and instructors find such in-the-ballpark values of e highly unsatisfactory. The chief purpose of this article, as far as the value of the electronic charge is concerned, is to show that acceptable values of e are obtainable when polystyrene spheres of specified uniform diameter and density are substituted for oil drops in the experiment. This substitution eliminates the errors associated with the use of oil drops of unknown and variable size and removes much of the guesswork involved in assigning proper index integers to the observed charges, a likely source of error in the oil drop experiment. Because the size of the spheres is given in advance, we can make two independent determinations of the value of e, one with the use of Stokes’s law and a second without its use. Finally, because of the small size of the spheres, we can also make an estimate of the value of the Boltzmann constant, using the effects of Brownian motion on the dispersions of the sets of time measurements taken in the experiment.
Critical point drying: Application of the physics of the P
V
T surface to electron microscopy
Authors: Burstyn Henry Paris , Bartlett Albert A.
Published: March 2005

In electron microscopy of biological materials, the samples must be specially prepared before they can be placed in the high vacuum of an electron microscope. If the samples are prepared in water and if the last stages of the preparation involve evaporation of water from a liquid–vapor interface, surface tension at the interface can generate very high pressures in micrometer-size structures that will distort the structures to the point where much information about their original shapes and configurations is lost. In order to avoid this damaging distortion, the samples are immersed in a fluid such as liquid CO2 in a pressure vessel and the fluid is heated to a temperature higher than its critical temperature where it becomes a gas and can then be removed without the damaging effects of surface tension. The physical details and the advantages and disadvantages of alternative ways of carrying out the process are reviewed. Optimum conditions for carrying out the process are identified, and it is noted that some of the essentials of the process are frequently misunderstood. This ’’practical application’’ of the physics of the critical point can be used to advantage to help students learn about the PVT behavior of real substances and it is of special interest to students in biological sciences.
Easily demonstrable relationship between the microscopic and macroscopic theories of type II superconductivity
Authors: Rochlin Gene I.
Published: March 2005

We present a simplified derivation of approximate solutions for the magnitude of, and the relations between, the three critical fields of a type II superconductor done in the spirit of the Ginzburg−Landau equations. The appearance of an unexpected equation restricting the free choice of macroscopic parameters is shown to be a direct consequence of the ’’correctness’’ of the Ginzburg−Landau theory, i.e., its physical equivalence to the microscopic theory of Bardeen, Cooper, and Schrieffer.
Laboratory learning modules
Authors: Long Robert
Published: March 2005

Laboratory learning modules are self−teaching modules designed to enable a student to learn a measurement technique and familiarize himself with measurement instrumentation independently of a laboratory course. A module developed to help students to learn how to measure electrical resistance is described. The equipment and facility requirements for setting up learning modules are outlined and a list of other laboratory learning modules which have been developed is presented.
Cyclotron resonance of electrons trapped in a microwave cavity
Authors: Elmore W. C.
Published: March 2005

An experiment suitable for an advanced undergraduate laboratory is described in which the free−electron cyclotron resonance of electrons trapped in a microwave cavity by a Penning trap is observed. The systematic errors appear to be less than in the Gardner and Purcell cyclotron resonance experiment, amounting to not more than 20 ppm, probably less. The resonance peak can be located with a precision of 5 ppm with modest equipment. Since the microwave cavity is easy to construct, the experiment constitutes an attractive alternative to one of the Gardner−Purcell variety.
Cryptographic approach to hidden variables
Authors: Herbert Nick
Published: March 2005

An elementary proof of Bell’s theorem on the incompatibility of local hidden−variable theories with quantum mechanics is presented. The proof is based on considerations of error rates in binary message sequences.
Radiation force and the classical mechanics of photons and phonons
Authors: Joyce W. B.
Published: March 2005

From simple physical arguments based on adiabatic invariance, energy conservation, and energy quantization the radiation force f due to a reversible or weakly attenuated beam of light, sound, polarons, relativistic electrons, water waves, Seltzer bubbles, bathyspheres, or any other type of propagating energy in any isotropic medium is shown to be given by f = W/c = Eẋ/c where the beam is characterized by its power W, energy/length E, phase velocity c, and energy velocity = group velocity = particle velocity ẋ. Published data is found to be in agreement, although not to the exclusion of all other theoretical alternatives, and further experiments are suggested. Acceptance of this expression for f is shown to imply, in turn, that classical mechanics can be reformulated to embrace any zero− or finite−rest−energy particle. Geometrical optics and acoustics which become special cases are thus extended to the dynamics of classical photons and phonons.
Energy levels of a charged particle in the field of a spherically symmetric uniform charge distribution
Authors: Zablotney J.
Published: March 2005

The non−relativistic energy spectrum for a negatively charged particle in the field of a spherically symmetric charge distribution is obtained. A complete solution is found which includes a representation of the wavefunction exterior to the charge distribution. The energy eigenvalues are found from the matching condition at the boundary of the nucleus and the energy levels for a mu meson in the field of a lead nucleus are calculated.
Physics useful to a medical student
Authors: Hobbie Russell K.
Published: March 2005

The author recently audited all of the courses taken by first and second year medical students at the University of Minnesota. On the basis of that experience, he recommends physics topics which those students will find useful, such as the Boltzmann factor, diffusion and osmosis, Thevenin’s theorem, nerve conduction, a detailed discussion of the electrocardiogram, relaxation oscillators, feedback, Fourier series, correlation functions, and power spectra. In addition, examples are given of applications of physical principles from each of the major areas of physics.
Elementary applied physics course in principles of biomedical instrumentation
Authors: Griffith O. Frank , Branley Edward A.
Published: March 2005

Applied physics courses at the intermediate undergraduate level can meet the increased technological need in a number of professional areas. The course in physical principles of instrumentation described in this article was designed to broaden medical technologists’ understanding of their equipment, and serves as an example for developing similar courses applicable in other areas.
Physics and the view of nature in traditional China
Authors: Uritam R. A.
Published: March 2005

We give an account of topics suitable for a model course in traditional Chinese science. A preliminary discussion examines problems in the study of non−Western science generally. An understanding of the indigenous Chinese view of nature requires an exposition of the development of natural philosophy from its Taoist and Naturalist origins to its culmination in the Neo−Confucian synthesis during the Sung dynasty. The central idea that emerges is the concept of a unified, interrelated organism as a model of nature. This affected the specialized fields of science: we survey briefly mathematics and astronomy, but concentrate on physics, especially its strongest subfields, acoustics and magnetism. We try to present Chinese science as a coherent view of nature in its own right, but also compare it with Western science, and explore the influences of Chinese science on the evolution of Western science and on present−day world science. Extensive references for further study are presented throughout this report.
Measurement of the thermal properties of a metal using a relaxation method
Authors: Fox John N. , McMaster Richard H.
Published: March 2005

An undergraduate experiment is described which employs a relaxation method for the measurement of the thermal conductivity and specific heat of a metallic sample in the temperature range 0–100°C.
Pure states, mixtures, and polarization
Authors: Geldart D. J. W. , Kiang D.
Published: March 2005

Some specific difficulties and pitfalls frequently encountered by beginning students in quantum mechanics relating to pure states, mixtures, and polarization are emphasized and clarified.
Sound velocity and diffraction intensity measurements based on Raman–Nath theory of the interaction of light and ultrasound
Authors: Neeson John F. , Austin Stephen
Published: March 2005

A method is described for the measurement of the velocity of sound in various liquids, based on the Raman–Nath theory of light–sound interaction. An analog computer program which calculates the intensity of the light scattered into the various diffraction orders has been adapted for use on a digital computer. The equipment used in this experiment is available in most undergraduate physics laboratories.
Precision timing applied to a driven mechanical oscillator
Authors: Blair J. Morris
Published: March 2005

A circuit is described that enables one to use simple equipment to improve the precision with which the frequency of a driven mechanical vibrator can be measured. The resonance frequency of the system consisting of a mass suspended from a spring is calculated by a procedure that simplifies the application of the general equation which is valid for all masses.
Publications in the history of physics during 1973
Authors: Brush Stephen G.
Published: March 2005

More than 50 books and 14 periodicals published in 1973 have been analyzed for contributions to the history of physics. The subjects most frequently discussed were optics, ether, relativity, mechanics, and atomic or nuclear physics. A survey of this literature is presented in the form of a chronological review of relevant aspects of the history of physics, from Chinese optics in the 5th century B.C. to the discovery of parity nonconservation in the 20th century A.D. Brief comments are made on current controversies among historians of science, such as the significance of ’’anticipation’’ of modern ideas in the writings of earlier scientists, and the role of experiment in the work of Galileo and Einstein. The most important new publication by a single author is James Bell’s The Experimental Foundations of Solid Mechanics, a treatise which seems to have been ignored by most historians of physics.
A synthesizer for use in physics of music courses
Authors: Nicklin R. C.
Published: March 2005

The PAiA 2720 Synthesizer, available in modular kit form, provides an easy and inexpensive way to do some demonstrations for physics of music courses that would be very difficult with conventional apparatus. The synthesis of sounds is discussed together with details of the PAiA. An inexpensive way to use a good oscilloscope to project waveforms is discussed, and ten demonstrations are suggested.
Experience with a course in physics for visual arts majors
Authors: Bearse R. C. , McKay D. W.
Published: March 2005

We have taught a one-semester course for visual arts students for five semesters. The course is visually oriented with many demonstrations. The art faculty is very pleased with the course, but student satisfaction is more tempered.
Integrated circuit counter for cosmic ray experiments
Authors: Gould C. R. , Ives R. L.
Published: March 2005

An inexpensive cosmic ray detection system is described that consists of two Geiger counters and an integrated circuit scaler. A measurement of the azimuthal variation in the intensity of cosmic rays is discussed as an example of the type of experiment that can be performed with this arrangement.
The life and work of Joseph Fraunhofer (1787−1826)
Authors: Leitner Alfred
Published: March 2005

Fraunhofer perfected methods for making optical glass and for testing its quality. He studied the dark lines in the spectrum of sunlight and used them to chart the dispersion of optical material with a precision spectrometer. He used scientific methods to produce truly excellent achromatic and aplanatic lenses, and optical instruments including astronomical refracting telescopes of large aperture. He analyzed diffraction patterns with precision; discovered the spectroscopic uses of gratings; made gratings ruled with up to 7670 lines/in., and determined wavelengths of Fraunhofer lines to four significant figures. He also noted the phenomenon of grating blaze, the polarizing effect of gratings, and effects of periodic errors in the rulings.
Postsynaptic Receptor Trafficking Underlying a Form of Associative Learning
Authors: Rumpel Simon , LeDoux Joseph , Zador Anthony , Malinow Roberto
Published: March 2005

To elucidate molecular, cellular, and circuit changes that occur in the brain during learning, we investigated the role of a glutamate receptor subtype in fear conditioning. In this form of learning, animals associate two stimuli, such as a tone and a shock. Here we report that fear conditioning drives AMPA-type glutamate receptors into the synapse of a large fraction of postsynaptic neurons in the lateral amygdala, a brain structure essential for this learning process. Furthermore, memory was reduced if AMPA receptor synaptic incorporation was blocked in as few as 10 to 20% of lateral amygdala neurons. Thus, the encoding of memories in the lateral amygdala is mediated by AMPA receptor trafficking, is widely distributed, and displays little redundancy.
Detection of
Cryptosporidium
and Identification to the Species Level by Nested PCR and Restriction Fragment Length Polymorphism
Authors: Coupe Stephane , Sarfati Claudine , Hamane Samia , Derouin Francis
Published: March 2005

Cryptosporidiosis is an emerging protozoan disease associated with large waterborne outbreaks. Diagnosis relies on microscopic examination of stools, but this method cannot identify the infecting species of
Cryptosporidium
. We have developed a test based on nested PCR and restriction fragment length polymorphism (RFLP) that offers simple identification of
Cryptosporidium hominis
,
Cryptosporidium parvum
, and most other human infective species in stool samples. Purified
C. parvum
oocysts were used for PCR development. Extracted DNA was amplified by nested PCR targeting a 214-bp fragment of the 18S RNA gene. Enzymatic restriction sites were identified by bioinformatic analysis of all published
Cryptosporidium
18S rRNA sequences. Experiments with spiked stool samples gave an estimated PCR detection limit of one oocyst. Specificity was assessed by testing 68 stool samples from patients with microscopically proven cryptosporidiosis and 31
Cryptosporidium
-negative stools. Sixty-seven (98.5%) of the 68 stool samples from patients with microscopically proven cryptosporidiosis and 2 of the other stool samples were positive by PCR and could be genotyped. RFLP analysis identified 36
C. hominis
, 19
C. parvum
, 8
Cryptosporidium meleagridis
, and 6
Cryptosporidium felis
or
Cryptosporidium canis
samples. Species determination in 26 PCR-positive cases was in full agreement with DNA sequencing of the 18S rRNA hypervariable region. The excellent sensitivity of PCR, coupled with the accuracy of RFLP for species identification, make this method a suitable tool for routine diagnosis and genotyping of
Cryptosporidium
in stools.
Characterization of Rotavirus Strains in a Danish Population: High Frequency of Mixed Infections and Diversity within the VP4 Gene of P[8] Strains
Authors: Fischer T. K. , Eugen-Olsen J. , Pedersen A. G. , Mølbak K. , Böttiger B. , Rostgaard K. , Nielsen N. M.
Published: March 2005

We characterized the G and P types from 162 rotavirus-positive stool specimens collected from 162 persons in Denmark (134 children and 28 adults) with acute diarrhea in 1998, 2000, and 2002. Samples were obtained during outpatient consultations (73%) and from hospitalized patients (27%). Although more than 20 different G-P combinations were identified, only 52% represented the globally most common types G1P[8], G2P[4], and G4P[8]. The G9 genotype, which is emerging worldwide, was identified in 12% of all samples. Twenty-one percent of the samples were of mixed genotypic origin, which is the highest frequency reported in any European population. The standard reverse transcription-PCR methods initially failed to identify a considerable fraction of the rotavirus P strains due to mutations at the VP4 primer-binding sites of P[8] strains. The application of a degenerate P[8] primer resulted in typing of most VP4 strains. There was considerable year-to-year variation among the circulating G-P types, and whereas G1P[8] was predominant in 1998 (42% of samples) and 2002 (26%), G2P[4] was the strain that was most frequently detected in 2000 (26% of samples). Our findings might implicate challenges for rotavirus vaccine implementation in a European population and underscore the importance of extensive strain surveillance prior to, during, and after introduction of any vaccine candidate.
Role of Real-Time Molecular Typing in the Surveillance of
Campylobacter
Enteritis and Comparison of Pulsed-Field Gel Electrophoresis Profiles from Chicken and Human Isolates
Authors: Michaud Sophie , Ménard Suzanne , Arbeit Robert D.
Published: March 2005

The goal of the present study was to assess the contribution of real-time molecular typing, used alone or with clinical surveillance, to the prompt identification of clusters of
Campylobacter
enteritis. Potential poultry sources were sought by comparing the pulsed-field gel electrophoresis genotypes of human and fresh whole retail chicken isolates collected during the same study period. Among 183 human isolates, 82 (45%) had unique genotypes, 72 (39%) represented 26 clusters of 2 to 7 isolates each, and 29 (16%) represented three clusters of 8 to 11 isolates each. Molecular typing was useful for the confirmation of outbreaks suspected on the basis of epidemiological surveillance, but for most small clusters, no epidemiological link could be established. Thus, the added value of real-time molecular typing is questionable, since the numerous small clusters identified were of unclear public health significance. Among 177 chickens, 41 (23%) yielded campylobacter isolates; of these, 19 (46%) had genotypes similar to those of 41 (22%) human isolates. However, a temporal association was demonstrated in only a minority of cases, and most genotypes were present only in a single species, suggesting that sources other than chickens are important in human campylobacteriosis. Further investigation with samples from water and other possible environmental sources is needed to define the most efficient strategy for the application of molecular typing and identification of the source(s) of sporadic cases of campylobacteriosis.
Prevalence of Norovirus among Visitors from the United States to Mexico and Guatemala Who Experience Traveler's Diarrhea
Authors: Chapin Amy R. , Carpenter Colleen M. , Dudley William C. , Gibson Lucy C. , Pratdesaba Rafael , Torres Olga , Sanchez Domingo , Belkind-Gerson Jaime , Nyquist Irene , Kärnell Anders , Gustafsson Bjorn , Halpern Jane L. , Bourgeois A. Louis , Schwab Kellogg J.
Published: March 2005

Traveler's diarrhea (TD) is the most common infectious illness acquired by visitors to developing nations. The purpose of this study was to utilize molecular diagnostic techniques to determine the prevalence of norovirus (NoV) in TD occurring among visitors from the United States to Guatemala and Mexico. Stool samples (
n
= 54) were collected from 34 TD cases and analyzed for NoV by reverse transcription-PCR and oligoprobe confirmation. The overall prevalence of NoV was 65%. Interestingly, all NoV-positive stool samples were identified as genogroup I NoVs, and time spent at travel destinations was found to be an important factor in determining the frequency of infection (
P
= 0.003). Eleven NoV-positive stool samples also tested positive for enterotoxigenic
Escherichia coli
, indicating that dual infections with this leading bacterial cause of TD were very common. Results of this study suggest that NoV infection is a frequent occurrence among travelers to Mexico and Guatemala who experience episodes of TD. In addition, the simple molecular detection method utilized here will serve to facilitate more in-depth epidemiological studies of this emergent viral pathogen in travelers and other at-risk populations.
Molecular Subtyping and Characterization of Bovine and HumanStreptococcus agalactiaeIsolates
Authors: Sukhnanand Sharinne , Dogan Belgin , Ayodele Maranatha O. , Zadoks Ruth N. , Craver Mary Patricia J. , Dumas Nellie B. , Schukken Ynte H. , Boor Kathryn J. , Wiedmann Martin
Published: March 2005

Streptococcus agalactiaecauses severe invasive disease in humans and mastitis in cattle. Temporally matched bovine milk isolates and clinical human invasive isolates (52 each) collected in New York State over 18 months were characterized by molecular subtyping and phenotypic methods to probe the interspecies transmission potential of this species. EcoRI ribotyping differentiated 17 ribotypes, and DNA sequencing of the housekeeping genesodAand the putative virulence genehylBdifferentiated 7 and 17 allelic types, respectively. Human and bovine isolates were not randomly distributed between ribotypes orhylBandsodAclusters. The combined analysis of all subtyping data allowed the differentiation of 39 clonal groups; 26 groups contained only bovine isolates, and 2 groups contained both human and bovine isolates. The EcoRI ribotype diversity among bovine isolates (Simpson's numerical index of discrimination [mean ± standard deviation], 0.90 ± 0.05) being significantly higher than that among human isolates (0.42 ± 0.15) further supports that these isolates represent distinct populations. Eight human isolates, but no bovine isolates, showed an IS1548 transposon insertion inhylB, which encodes a hyaluronidase. Based on data for 43 representative isolates, human isolates, on average, showed lower hyaluronidase activities than bovine isolates. Isolates with the IS1548 insertion inhylBshowed no hyaluronidase activity. Human and bovine isolates did not differ in their abilities to invade HeLa human epithelial cells. Our data show that (i) EcoRI ribotyping, combined withhylBandsodAsequencing, provides a discriminatory subtype analysis ofS. agalactiae; (ii) most human invasive and bovineS. agalactiaeisolates represent distinct subtypes, suggesting limited interspecies transmission; and (iii) hyaluronidase activity is not required for all human infections.
Molecular Characterization of an Epidemic Clone of Panantibiotic-ResistantPseudomonas aeruginosa
Authors: Deplano A. , Denis O. , Poirel L. , Hocquet D. , Nonhoff C. , Byl B. , Nordmann P. , Vincent J. L. , Struelens M. J.
Published: March 2005

We describe the molecular characterization of a multiresistantPseudomonas aeruginosaclone causing an outbreak in the intensive care unit (ICU) of a tertiary-care university hospital. Analysis included antimicrobial susceptibility profile, O-serotyping, pulsed-field gel electrophoresis, and amplified fragment length polymorphism. Resistance mechanisms were characterized, including production of naturally occurring and acquired β-lactamases, porin expression, and efflux pump systems. Eighteen patients were colonized or infected with multiresistantP. aeruginosa. MultiresistantP. aeruginosawas panresistant to penicillins, cephalosporins, carbapenems, aminoglycosides, and fluoroquinolones and remained susceptible only to colistin. Sixteen isolates (89%) belonged to serotype O:11, pulsed-field gel electrophoresis type A1, and amplified fragment length polymorphism type A. Resistance characterization of this epidemic clone showed an overexpression of the chromosomal cephalosporinase AmpC combined with decreased expression of porin OprD and the absence of metallo-β-lactamase or extended-spectrum beta-lactamase. An upregulation of the MexXY efflux system due to anagrZmutation in themexZrepressor was detected. This epidemic clone was restricted to the ICU and was not found elsewhere in hospital. Contamination of the ICU environment and the hands of an ICU nurse with this clone suggests possible hand-borne transmission. Implementation of contact precautions effectively controlled transmission of the epidemic clone. This study illustrates the ability of multiresistantP. aeruginosato cause an outbreak with significant morbidity and mortality and underscores the need to identify clonal outbreaks, which require targeted infection control measures.
Analysis of
Salmonella enterica
Serotype Typhi Pulsed-Field Gel Electrophoresis Patterns Associated with International Travel
Authors: Kubota K. , Barrett T. J. , Ackers M. L. , Brachman P. S. , Mintz E. D.
Published: March 2005

Typhoid fever is a significant cause of morbidity and mortality worldwide, causing an estimated 16 million cases and 600,000 deaths annually. Although overall rates of the disease have dramatically decreased in the United States, the number of travel-related infections has increased in recent decades. Drug resistance among
Salmonella enterica
serotype Typhi strains has emerged worldwide, making antimicrobial susceptibility testing an important function in public health laboratories. Pulsed-field gel electrophoresis (PFGE) subtyping of food-borne and waterborne pathogens has proven to be a valuable tool for the detection of outbreaks and laboratory-based surveillance. This retrospective study examined the distribution of PFGE patterns of
S. enterica
serotype Typhi isolates from patients with a history of international travel. Isolates were collected as part of a passive laboratory-based antimicrobial susceptibility surveillance study. Isolates were PFGE subtyped by using the restriction enzyme XbaI to restrict the total genomic DNA. Isolates indistinguishable with XbaI were further characterized using the restriction enzyme BlnI. A total of 139 isolates were typed, representing travel to 31 countries. Restriction fragment patterns consisted of 14 to 18 fragments ranging in size from 580 to 40 kbp. Seventy-nine unique PFGE patterns were generated using XbaI. Isolates from the same geographic region did not necessarily have similar PFGE patterns. Of the 139 isolates, 46 (33%) were resistant to more than one antimicrobial agent (multidrug resistant [MDR]). Twenty-seven (59%) of 46 MDR isolates had indistinguishable PFGE patterns with both XbaI and BlnI. It appears that MDR
S. enterica
serotype Typhi has emerged as a predominant clone in Southeast Asia and the Indian subcontinent.
CHROMagar Candida as the Sole Primary Medium for Isolation of Yeasts and as a Source Medium for the Rapid-Assimilation-of-Trehalose Test
Authors: Murray Melissa P. , Zinchuk Riva , Larone Davise H.
Published: March 2005

The chromogenic medium BBL CHROMagar Candida (CAC) was evaluated as a sole primary medium for the isolation of yeasts from clinical specimens in which yeasts are the primary concern. Additionally, the reliability of the rapid-assimilation-of-trehalose (RAT) test in yielding correct results with isolates taken from CAC was assessed. A total of 270 throat, urine, and genital (TUG) specimens were streaked onto CAC, Sabouraud dextrose agar (SDA), inhibitory mold agar (IMA), and Mycosel (MYC). A total of 69 blood culture broths that were smear positive for yeast were streaked onto CAC and SDA. A 1-h RAT test (NCCLS M35-A) was performed simultaneously on isolates from CAC and SDA. A total of 112 TUG specimens yielded yeast colonies (CAC, 111 colonies; IMA, 105; SDA, 103; MYC, 91). The 69 blood culture yeasts grew on both CAC and SDA. Mixed cultures of yeasts were detected on 11 CAC plates but were unrecognized on other media. Colonies suspected of being
C. glabrata
on 32 CAC plates were all RAT test positive and confirmed to be
C. glabrata
; of 59 colonies with various characteristics of color and morphology on CAC, none were RAT positive, and all were conventionally identified as yeasts other than
C. glabrata
(sensitivity and specificity, 100%). The same isolates from SDA tested for RAT produced six false negatives and no false positives (sensitivity, 81%; specificity, 100%). The results show that CAC can be used as the sole primary medium for recovery of yeasts from clinical specimens. Additionally, isolates grown on CAC yield excellent results with the RAT test utilized in this study.
Detection of Human Picornaviruses by Multiplex Reverse Transcription-PCR and Liquid Hybridization
Authors: Jokela Pia , Joki-Korpela Päivi , Maaronen Marita , Glumoff Virpi , Hyypiä Timo
Published: March 2005

A qualitative multiplex reverse transcription (RT)-PCR and liquid hybridization assay for the detection of human enteroviruses, rhinoviruses, parechoviruses, and Aichi virus was developed. Furthermore, a separate assay for the recognition of hepatitis A virus was established to complement the test pattern so that all human picornaviruses were covered. The amplicons, which represented the 5′ untranslated regions of the viral RNA genomes, were identified in liquid hybridization reactions with genus-specific digoxigenin-labeled oligonucleotide probes. The sensitivity of the multiplex RT-PCR and liquid hybridization assay was 10 to 100 picornavirus genome equivalents for representatives of each picornavirus genus. The hepatitis A virus assay exhibited a sensitivity of 10 genome copies. Both the uniplex and the multiplex tests were highly specific for the target viruses. Twenty-three clinical samples, including cerebrospinal fluid, serum, and nasopharyngeal swab specimens, were used for clinical evaluation of the multiplex RT-PCR assay. The results obtained were consistent with the results of routine virus diagnostic assays. Furthermore, the assay was used to screen 68 stool specimens for the presence of parechoviruses and Aichi virus. One sample was found to contain parechovirus RNA, whereas no Aichi virus was detected. The assay described here can be applied for the efficient identification of human enteroviruses and rhinoviruses in clinical specimens and simultaneously enables the collection of information on the epidemiology and clinical outcomes of infections caused by the currently poorly known human parechoviruses and Aichi virus.
Characterization of Virulence Plasmids and Serotyping of
Rhodococcus equi
Isolates from Submaxillary Lymph Nodes of Pigs in Hungary
Authors: Makrai László , Takayama Saki , Dénes Béla , Hajtós István , Sasaki Yukako , Kakuda Tsutomu , Tsubaki Shiro , Major Andrea , Fodor László , Varga János , Takai Shinji
Published: March 2005

The plasmid types and serotypes of 164
Rhodococcus equi
strains obtained from submaxillary lymph nodes of swine from different piggeries in 28 villages and towns located throughout the country were examined. The strains were tested by PCR for the presence of 15- to 17-kDa virulence-associated protein antigen (VapA) and 20-kDa virulence-associated protein antigen (VapB) genes. Plasmid DNAs were isolated and analyzed by digestion with restriction endonucleases to estimate size and compare their polymorphism characteristics. None of the 164 isolates contained the
vapA
gene, and 44 (26.8%) isolates were positive for the
vapB
gene, showing a product of the expected 827-bp size in the PCR amplification. The 44 isolates of intermediate virulence contained virulence plasmids that were identified as types 1 (3 isolates), 4 (1 isolate), 5 (36 isolates), 6 (1 isolate), and 7 (2 isolates) and as a new variant (1 isolate). On the basis of restriction digestion patterns of plasmid DNAs, we tentatively designated the variant as type 17. Use of the serotyping method of Prescott showed that 110 (67.1%) out of the 164 isolates were typeable and that serotype 2 predominated (83 isolates [50.6%]), followed by serotype 1 (26 strains [15.9%]). Only one isolate belonged to serotype 3. A total of 54 (32.9%) isolates were untypeable in Prescott's system. The prevalence of
R. equi
strains of intermediate virulence among the isolates that came from the submaxillary lymph nodes of swine in Hungary was lower than that seen with isolates obtained elsewhere.
Trends in Drug Resistance, Serotypes, and Molecular Types of
Streptococcus pneumoniae
Colonizing Preschool-Age Children Attending Day Care Centers in Lisbon, Portugal: a Summary of 4 Years of Annual Surveillance
Authors: Nunes S. , Sá-Leão R. , Carriço J. , Alves C. R. , Mato R. , Avô A. Brito , Saldanha J. , Almeida J. S. , Sanches I. Santos , de Lencastre H.
Published: March 2005

Of the nasopharyngeal cultures recovered from 942 day care center (DCC) attendees in Lisbon, Portugal, 591 (62%) yielded
Streptococcus pneumoniae
during a surveillance performed in February and March of 1999. Forty percent of the isolates were resistant to one or more antimicrobial agents. In particular, 2% were penicillin resistant and 20% had intermediate penicillin resistance. Multidrug resistance to macrolides, lincosamides, and tetracycline was the most frequent antibiotype (17% of all isolates). Serotyping and molecular typing by pulsed-field gel electrophoresis were performed for 202 out of 237 drug-resistant pneumococci (DRPn). The most frequent serotypes were 6B (26%), 14 (22%), 19F (16%), 23F (10%), and nontypeable (12%). The majority (67%) of the DRPn strains were representatives of nine international clones included in the Pneumococcal Molecular Epidemiology Network; eight of them had been detected in previous studies. Fourteen novel clones were identified, corresponding to 26% of the DRPn strains. The remaining 7% of the strains were local clones detected in our previous studies. Comparison with studies conducted since 1996 in Portuguese DCCs identified several trends: (i) the rate of DRPn frequency has fluctuated between 40 and 50%; (ii) the serotypes most frequently recovered have remained the same; (iii) nontypeable strains appear to be increasing in frequency; and (iv) a clone of serotype 33F emerged in 1999. Together, our observations highlight that the nasopharynxes of children in DCCs are a melting pot of successful DRPn clones that are important to study and monitor if we aim to gain a better understanding on the epidemiology of this pathogen.