bluuebunny/crossref_metadata_2025 huggingface dataset:
Aerobic Degradation of a Mixture of Azo Dyes in a Packed Bed Reactor Having Bacteria‐Coated Laterite Pebbles
Authors: Senan Resmi C. , Shaffiqu T. S. , Roy J. Jegan , Abraham T. Emilia
Published: April 2003

A microbial consortium capable of aerobic degradation of a mixture of azo dyes consisting of two isolated strains (RRL, TVM) and one known strain of Pseudomonas putida (MTCC 1194) was immobilized on laterite stones. The amount of bacterial biomass attached to the laterite stones was 8.64 g per 100 g of the stone on a dry weight basis. The packed bed reactor was filled with these stones and had a total capacity of 850 mL and a void volume of 210 mL. The feed consisted of an equal mixture of seven azo dyes both in water as well as in a simulated textile effluent, at a pH of 9.0 and a salinity of 900 mg/L. The dye concentrations of influent were 25, 50, and 100 μg/mL.The residence time was varied between 0.78 and 6.23 h. It was found that at the lowest residence time 23.55, 45.73, and 79.95 μg of dye was degraded per hour at an initial dye concentration of 25, 50, and 100 μg, respectively. The pH was reduced from 9.0 to 7.0. Simulated textile effluent containing 50 μg/mL dye was degraded by 61.7%. Analysis of degradation products by TLC and HPLC showed that the dye mixture was degraded to nontoxic smaller molecules. The bacteria‐coated pebbles were stable, there was no washout even after 2 months, and the reactor was found to be suitable for the aerobic degradation of azo dyes.
Cultivation of Microplantlets Derived from the Marine Red Alga Agardhiellasubulata in a Stirred Tank Photobioreactor
Authors: Huang Yao‐ming , Rorrer Gregory L.
Published: April 2003

Macrophytic marine red algae are a diverse source of bioactive natural compounds. “Microplantlet” suspension cultures established from red algae are potential platforms for biosynthesis of these compounds, provided suitable bioreactor configurations for mass culture can be identified. The stirred tank bioreactor offers high rates of gas‐liquid mass transfer, which may facilitate the delivery of the CO2 in the aeration gas to the phototrophic microplantlet suspension culture. Therefore, the effects of impeller speed and CO2 delivery on the long‐term production of microplantlet biomass of the model red alga Agardhiella subulata was studied within a stirred tank photobioreactor equipped with a paddle blade impeller ( Di/ DT = 0.5). Nutrient medium replacement was required for sustained biomass production, and the biomass yield coefficient based on nitrate consumption was 1.08 ± 0.09 g dry biomass per mmol N consumed. Biomass production went through two exponential phases of growth, followed by a CO2 delivery limited growth phase. The CO2‐limited growth phase was observed only if the specific growth rate in the second exponential phase of growth was at least 0.03 day−1, the CO2 delivery rate was less than 0.258 mmol CO2 L−1 culture h−1, and the plantlet density was at least 10 g fresh mass L−1. Increasing the aeration gas CO2 partial pressure from 0.00035 to 0.0072 atm decreased the cultivation pH from 8.8 to 7.8, prolonged the second exponential phase of growth by increasing the CO2 delivery rate, and also increased the photosynthetic oxygen evolution rate. Impeller speeds ranging from 60 to 250 rpm, which generated average shear rates of 2–10 s−1, did not have a significant effect on biomass production rate. However, microplantlets cultivated in a stirred tank bioreactor ultimately assumed compact spherical shape, presumably to minimize exposure to hydrodynamic stress.
Improvement of Catechin Productivity in Suspension Cultures of Tea Callus Cells
Authors: Shibasaki‐Kitakawa Naomi , Takeishi Junna , Yonemoto Toshikuni
Published: April 2003

In the suspension cultures of tea callus cells, C.sinensiscv. Yabukita, the effects of the culture conditions, such as culture period and light irradiation, on cell growth and catechin production were investigated. The production of flavonoids (catechins + proanthocyanidins) was promoted by inoculating the cells into the fresh medium at the culture period giving the maximum flavonoid content in the cells. The cultivation under light irradiation was repeated several times by inoculating the cells with the maximum flavonoid content. The flavonoid production was significantly increased without inhibiting the cell growth. We obtained the maximum flavonoid production, 1.5 g/dm3 medium, and the maximum content, 150 mg/(g of dry cell weight (DCW)). The latter value was larger than that in the leaves of the tea plant.
Cholesterol Oxidation Using Hollow Fiber Dialyzer Immobilized with Cholesterol Oxidase: Preparation and Properties
Authors: Lin Chi‐Chang , Yang Ming‐Chien
Published: April 2003

The surface of polyacrylonitrile hollow fibers were hydrolyzed and covalently bonded with cholesterol oxidase (COD) via glutaraldehyde. The immobilized amount of the COD increased with the concentration of glutaraldehyde. However, COD immobilized with 10% glutaraldehyde had higher activity than with other concentrations. The stabilities of immobilized COD to pH and temperature were higher than those of native enzyme. The immobilized enzyme retained 80% of initial activity after 15 days when stored at 4 °C, which was longer than native COD. After being reused six times, the COD‐immobilized hollow fiber retained more than 80% of the activity.
Design of New Immobilized‐Stabilized Carboxypeptidase A Derivative for Production of Aromatic Free Hydrolysates of Proteins
Authors: Tardioli P. W. , Fernández‐Lafuente R. , Guisán J. M. , Giordano R. L. C.
Published: April 2003

This paper presents stable carboxypeptidase A (CPA)‐glyoxyl derivatives, to be used in the controlled hydrolysis of proteins. They were produced after immobilizing‐stabilizing CPA on cross‐linked 6% agarose beads, activated with low and high concentrations of aldehyde groups, and different immobilization times. The CPA‐glyoxyl derivatives were compared to other agarose derivatives, prepared using glutaraldehyde as activation reactant. The most stabilized CPA‐glyoxyl derivative was produced using 48 h of immobilization time and high activation grade of the support. This derivative was approximately 260‐fold more stable than the soluble enzyme and presented approximately 42% of the activity of the soluble enzyme for the hydrolysis of long‐chain peptides (e.g., cheese whey proteins previously hydrolyzed with immobilized trypsin and chymotrypsin) and of the small substrate N‐benzoylglycyl‐l‐phenylalanine (hippuryl‐l‐Phe). These results were much better than those achieved using the conventional support, glutaraldehyde‐agarose. Amino acid analysis of the products of the acid hydrolysis of CPA (both soluble and immobilized) showed that approximately four lysine residues were linked on the glyoxyl agarose beads, suggesting the existence of an intense multipoint covalent attachment between the enzyme and the support. The maximum temperature of hydrolysis was increased from 50 °C (soluble enzyme) to 70 °C (most stable CPA‐glyoxyl derivative). The most stable CPA‐glyoxyl derivative could be efficiently used in the hydrolysis of long‐chain peptides at high temperature (e.g., 60 °C), being able to release 2‐fold more aromatic amino acids (Tyr, Phe, and Trp) than the soluble enzyme, under the same operational conditions. This new CPA derivative greatly increased the feasibility of using this protease in the production of protein hydrolysates that must be free of aromatic amino acids.
Potential Synergies and Challenges in Refining Cellulosic Biomass to Fuels, Chemicals, and Power
Authors: Wyman Charles E.
Published: April 2003

Lignocellulosic biomass such as agricultural and forestry residues and dedicated crops provides a low‐cost and uniquely sustainable resource for production of many organic fuels and chemicals that can reduce greenhouse gas emissions, enhance energy security, improve the economy, dispose of problematic solid wastes, and improve air quality. A technoeconomic analysis of biologically processing lignocellulosics to ethanol is adapted to project the cost of making sugar intermediates for producing a range of such products, and sugar costs are predicted to drop with plant size as a result of economies of scale that outweigh increased biomass transport costs for facilities processing less than about 10,000 dry tons per day. Criteria are then reviewed for identifying promising chemicals in addition to fuel ethanol to make from these low cost cellulosic sugars. It is found that the large market for ethanol makes it possible to achieve economies of scale that reduce sugar costs, and coproducing chemicals promises greater profit margins or lower production costs for a given return on investment. Additionally, power can be sold at low prices without a significant impact on the selling price of sugars. However, manufacture of multiple products introduces additional technical, marketing, risk, scale‐up, and other challenges that must be considered in refining of lignocellulosics.
High Production System of the Antibacterial Peptide PLG‐1
Authors: Gollop Natan , Toubia Didier , Shushan Galit Ben , Zakin Vered
Published: April 2003

Propionibacterium thoenii P‐127 produces and releases to the growth medium antibacterial agents that can be used as natural preservatives. The concentrations of these antibacterial agents in the growth medium are very low, and their activity can be detected only in concentrated medium, even in a bioreactor. A simple and efficient system to produce propionicin PLG‐1 without the use of a bioreactor was investigated. Fermentation in screw‐cap bottles without shaking produced antibacterial activity similar to that of fermentation in plates, but in a shorter time. Sodium lactate medium (NaLa) was found to be the most supportive for PLG‐1 production compared to lactic acid bacteria media such as M‐17 or beet molasses/corn. The initial concentration of the carbon source, sodium lactate, agar concentration, and the initial pH of the medium affected the synthesis of PLG‐1. Additions of NaCl up to 1% showed no effect on the antibacterial agent production. The optimal conditions for production of the antibacterial agent were fermentation for 9 days in screw‐cap bottles in modified NaLa medium (M‐NaLa) containing 1% yeast extract, 1% tryptic soy broth, 0.9% lactic acid, and 0.6% agar, adjusted to pH of 9.
Mixed Culture Bioconversion of 16‐Dehydropregnenolone Acetate to Androsta‐1,4‐diene‐3,17‐dione: Optimization of Parameters
Authors: Banerjee Tushar , Shukla Aniruddha , Shinde Kirti , Patil Shridhar
Published: April 2003

Bioconversion of 16‐dehydropregnenolone acetate (16‐DPA) to androsta‐1,4‐diene‐3,17‐dione (ADD), an intermediate for the production of female sex hormones, by mixed culture of Pseudomonas diminuta MTCC 3361 and Comamonas acidovorans MTCC 3362 is reported. Various physicochemical parameters for the bioconversion of 16‐DPA to ADD have been optimized in shake flask cultures. Nutrient broth inoculated with actively growing co‐culture proved ideal for bacterial growth and bioconversion. A temperature range of 35–40 °C was most suitable; higher or lower temperatures adversely affected the bioconversion. Dimethylformamide below 2% concentration was the most suitable carrier solvent. Maximum conversion was recorded at 0.5 mg mL−1 16‐DPA. A pH of 5.0 yielded a peak conversion of 62 mol % in 120 h incubation period. Addition of 9α‐hydroxylase inhibitors failed to prevent further breakdown of ADD to nonsteroidal products. 16‐DPA conversion in a 5 L fermenter followed a similar trend.
Screening of Protein‐Ligand Interactions by Affinity Chromatography
Authors: García Carlos D. , Holman Steven C. , Henry Charles S. , Wilson W. William
Published: April 2003

This paper examines affinity chromatography (AC) as an alternative tool for the determination of protein‐ligand interactions for the particular case in which the ligand is the same protein. The methodology is less labor‐intensive and more sample‐efficient than traditional methods used to measure the second virial coefficient ( B22), a parameter commonly used to evaluate protein‐protein interactions. The chromatographic capacity factor ( k′) was studied for lysozyme and equine serum albumin for a wide range of experimental solution conditions such as crystallizing agent concentration, protein concentration and pH. Parallel experiments using AC to determine k′ and static light scattering (SLS) to determine B22 showed that the two parameters were highly correlated. Two different column volumes (∼1 and ∼0.1 mL) were tested and gave essentially the same values for k′, showing the feasibility of miniaturization.
Quantitative Comparison of Lactose and Glucose Utilization in Bifidobacteriumlongum Cultures
Authors: Kim Teak‐Bum , Song Su‐Han , Kang Su‐Cheol , Oh Deok‐Kun
Published: April 2003

In batch cultures, Bifidobacterium longum SH2 has a higher final cell concentration and greater substrate consumption when grown on lactose versus glucose. Continuous cultures were used to compare lactose and glucose utilization by B. longum quantitatively. In the continuous culture, the estimated maintenance coefficients ( m) were similar when on lactose and glucose; the maximum cell yield coefficient ( YX/Smax) was higher on lactose; and the specific consumption rate of lactose ( qS) was lower than that of glucose. Assuming that cell growth followed the Monod model, the maximum specific growth rates ( μmax) and saturation constants ( KS) in lactose and glucose media were determined using the Hanes‐Woolf plots. The respective values were 0.40 h−1 and 78 mg/L for lactose and 0.46 h−1 and 697 mg/L for glucose. The kinetic parameters of the continuous cultures showed that B. longum preferred lactose to glucose, although the specific consumption rate of glucose was higher than that of lactose.
The Impact of Test Outcome Certainty on Interest in Genetic Testing Among College Women
Authors: Paglierani Lisa M. , Kalkwarf Heidi J. , Rosenthal Susan L. , Huether Carl A. , Wenstrup Richard J.
Published: April 2003

Osteoporosis and hemochromatosis are both late‐onset preventable diseases, but future genetic tests for these conditions are likely to differ in their predictive abilities. To determine whether interest in a specific genetic test for hemochromatosis would be higher than interest in a theoretical test for osteoporosis susceptibility, undergraduate women at the University of Cincinnati (N = 181) were surveyed regarding their interest in genetic testing for these conditions. The clinical features of the diseases and the limits of a genetic test for each were described. Sixty‐three percent of the total population was interested in genetic testing with a trend toward higher interest in the osteoporosis group. Disease familiarity, perceived disease severity, and perceived risk for disease appear to be more important predictors of genetic test acceptance than diagnostic specificity. Suggested implications for the development of population genetic screening tests are discussed.
Methionine adenosyltransferase I/III deficiency: two Korean compound heterozygous siblings with a novel mutation
Authors: Kim S. Z. , Santamaria E. , Jeong T. E. , Levy H. L. , Mato J. M. , Corrales F. J. , Mudd S. H.
Published: April 2003

Summary: Two Korean sisters, one detected during neonatal screening, the otherascertained at age 3 years during family screening, have persistent hypermethioninaemia without elevation of plasma tyrosine or severe liver disease.Plasma total homocysteine (tHcy) is mildly elevated, but not so markedly as to establish a diagnosis of homocystinuria due to cystathionine β‐synthase (CBS) deficiency. CBS deficiency was ruled out by the presence of slightly elevatedconcentrations of plasma cystathionine. Although the plasma concentrations of methionine were markedly elevated, plasma S‐adenosylmethionine (AdoMet) was not. This pattern of metabolic abnormalities suggested that the patients have deficient activity of methionine adenosyltransferase (MAT) intheirlivers (MAT I/III deficiency). Molecular genetic studies demonstrate thateach patient is a compound heterozygote for two mutations in MAT1A, the gene that encodes the catalytic subunit that composes MAT I and MAT III: a previously known inactivating G378S point mutation, and a novel W387X truncating mutation. W387X mutant protein, expressed in E. coli and purified, has about 75% of wild‐type activity. Negative subunit interaction between themutant subunits is suggested to explain the hypermethioninaemia of these sisters. They have had normal growth and development and have no mental retardation, neurological abnormalities, or other clinical problems. They are the first individuals of Korean descent proven to have MAT I/III deficiency.
Complex Genetic Disorders: Evaluating When Genetic Research Findings Are Applicable for Genetic Counseling Practice
Authors: Wolpert Chantelle M. , Melvin Elizabeth C. , Speer Marcy C.
Published: April 2003

Traditional genetic counseling processes and principles will be extended to a new realm—complex disorders. Although it may seem like a daunting task, understanding the methodologies used to study complex genetic disorders will enable genetic counselors to critically analyze research studies involving complex disorders. In this article, we explain newly evolving methodologies for genetic research, including case‐control studies and transmission disequilibrium testing (TDT). Additionally, a framework is provided for evaluating original research findings and replication studies.
Pathological structure of the kidney from adult mice with mosaic mutation
Authors: Lenartowicz M. , Kowal M. , Buda‐Lewandowska D. , Styrna J.
Published: April 2003

Summary: The mosaic (Atp7amo‐ms) is an X‐linked, lethal mutation in mice. In mosaic mutant males, many clinical features characteristic of defective copper metabolism have been observed and they die at the age of 15 days, exhibiting strongsimilarities to the brindled and macular mutants. About 4% of the mutant males live to sexual maturity and some of them are fertile. In this paper, alterationsin the structure of the kidney from adult mutants are described. Owing to an inherited defect of efflux, copper is accumulated in the kidney of the mutants up to a toxic level and this leads to severe damage of the renal cortex. Pathological changes in the kidney mostly affected the structure of the renal corpuscle and renaltubules.
Blood mononuclear cell coenzyme Q10 concentration and mitochondrial respiratory chain succinate cytochrome‐c reductase activity in phenylketonuric patients
Authors: Hargreaves I. P. , Heales S. J. R. , Briddon A. , Land J. M. , Lee P. J.
Published: April 2003

Summary: Coenzyme Q10 (CoQ10) serves as an electron carrier within the mitochondrial respiratory chain (MRC), where it is integrally involved in oxidative phosphorylation and consequently ATP production. It has recently been suggested that phenylketonuria (PKU) patients may be susceptible to a CoQ10 deficiency as a consequence of their phenylalanine‐restricted diet, which avoids foods rich in CoQ10 and its precursors. Furthermore, the high phenylalanine level in PKU patients not on dietary restriction may also result in impaired endogenous CoQ10 production, as previous studies have suggested an inhibitory effect of phenylalanine on HMG‐CoA reductase, the rate‐controlling enzyme in CoQ10 biosynthesis. We investigated the effect of both dietary restriction and elevated plasma phenylalanine concentration on blood mononuclear cell CoQ10 concentration and the activity of MRC complex II+III (succinate:cytochrome‐c reductase; an enzyme that relies on endogenous CoQ10) in a PKU patient population. The concentrations of CoQ10 and MRC complex II+III activity were not found to be significantly different between the PKU patients on dietary restriction, PKU patients off dietary restriction and the control group, although plasma phenylalanine levels were markedly different. The results from this investigation suggest that dietary restriction and the elevated plasma phenylalanine levels of PKU patients do not effect mononuclear cell CoQ10 concentration and consequently the activity of complex II+III of the MRC.
A Patient's Perspective on Genetic Counseling and Predictive Testing for Alzheimer's Disease
Authors: Neilson Jane
Published: April 2003

The availability of genetic testing for Alzheimer's disease is anticipated to be widespread in the future. As an individual at risk with a family history of Alzheimer's disease, I discuss why I sought predictive tests and how I would use the information from such tests. I relay what I learned in my genetic counseling session, my response to the counseling process, and steps I have since taken. I discuss life planning, psychological and fear of discrimination issues from a patient's perspective.
Short Report: Plasma pipecolic acid is frequently elevated in non‐peroxisomal disease
Authors: Baas J. C. M. , van de Laar R. , Dorland L. , Duran M. , Berger R. , Poll‐The B. T. , de Koning T. J.
Published: April 2003

Summary: We reviewed our data on patients in whom plasma pipecolic acid wasanalysed. Mild to moderate elevations of pipecolic acid were frequently found in non‐peroxisomal disorders and this should be taken into account when interpreting the laboratory data.
Nurse professionalisation and traditional values in Poland and Greece
Authors: Dent Mike
Published: April 2003

This paper examines the similarities and variations in the professional and work organisation of nursing in Greece and Poland. It evaluates the evidence of “convergence” as opposed to “embeddedness” in the professional and gendered organisation of nursing in these two countries. The feminised character of nursing is discussed, in relation to the family within the configuration of health‐care services. This issue also relates to the clientelistic relations and familialism that pervade health‐care delivery in both countries – although for different historical and cultural reasons – and which reflect and reinforce patriarchical relations within these societies.
A Lenz’s law experiment revisited
Authors: Sawicki Charles A.
Published: April 2003

A dipole magnet model predicts a terminal velocity VT proportional to 1/n for n attached identical cylindrical magnets dropped down a copper pipe. Experiments show that VT increases approximately linearly with n. The explanation for this difference is presented.
A desktop universe for the introductory astronomy laboratory
Authors: Marschall Laurence A. , Snyder Glenn A. , Cooper P. Richard
Published: April 2003

Project CLEA (Contemporary Laboratory Experiences In Astronomy) has developed nine computer-based laboratory exercises for introductory astronomy classes. The exercises, which make use of real data from professional observatories, enable students to get a sense of the methods astrophysicists use to learn about the distant objects in the universe.
What topics are taught in introductory astronomy courses?
Authors: Slater Tim , Adams Jeffrey P. , Brissenden Gina , Duncan Doug
Published: April 2003

So, just what is it that people teach in ASTRO 101? Very likely the astronomy-naı̈ve physicist will have to figure that out “on the run” and perhaps alone. There are lifelines, however.
A toy airplane for projectile-motion experiments
Authors: Wetherhold Jeffrey
Published: April 2003

While toy hunting at a local department store, I came upon a reasonably priced, interesting toy airplane that flies in a circle and drops a toy bomb. With some modifications this toy can be used in an exciting and highly motivating projectile-motion experiment with good results.
The shaken-soda syndrome
Authors: Kagan David
Published: April 2003

Two identical soda cans released at the same time on an incline will roll down at the same rate. However, if one of the cans is shaken, it will lose the race. Experimental evidence is presented that points to the presence of bubbles as the cause of the greater energy transfer to the fluid in the case of the shaken can.
Online homework: Does it make a difference?
Authors: Bonham Scott , Beichner Robert , Deardorff Duane
Published: April 2003

We carried out an experiment to evaluate the relative value of web-based computer homework with thoroughly hand-graded paper homework. In this note we present a general summary of our findings, appropriate for a general practitioner.
What should students learn?
Authors: Pasachoff Jay M.
Published: April 2003

It is important for students to learn about the exciting things that are now going on in astronomy. But the application of physics research to astronomy seems bogged down in the phases of the Moon and the cause of the seasons.
What should students remember?
Authors: Caton Daniel
Published: April 2003

The San Diego AAS/AAPT meeting in January 2001 stirred debate on the subject matter to be addressed in introductory astronomy courses. Teachers must choose what material to cover: classical basics or the “new and exciting”?
Teaching the Doppler shift using a machine gun analogy
Authors: Rothenstein Bernhard
Published: April 2003

In a recent note in this journal, Dibble compared the available derivations of the Doppler-shift formula using as a criterion the time invested and the amount of understanding achieved. I believe that we can breathe more life into the problem by considering a machine gun that fires successive bullets at a constant period Ts, which hit a taget at a constant period, To.
More on one-dimensional collisions
Authors: Hu Hui
Published: April 2003

For the general one-dimensional head-on collision of two particles, very simple forms of formulas for the final velocities are obtained, and an alternative definition of the coefficient of restitution is presented.
Magnetic domains of floppy disks and phone cards using toner fluid
Authors: Bichsel Ena S. , Wilson Brenda , Geerts Wilhelmus J.
Published: April 2003

We developed a novel technique to visualize recorded bit patterns in magnetic materials by using an emulsion of toner particles in rubbing alcohol or a water-soap solution. Results on various media including telephone cards, floppy disks, and flexible refrigerator magnets are discussed.
Inward “Centrifugal” Force on a Helium-Filled Balloon: An Illustrative Experiment
Authors: Aguilella Vicente M. , Alcaraz Antonio , Ramírez Patricio
Published: April 2003

A demonstration of a paradoxical “inward centrifugal force” in a circular motion is presented. It can be visualized by placing a helium balloon inside a car that is taking a bend. The analysis of the problem in an inertial frame allows for the right explanation of the phenomenon observed, and avoids the use of a centrifugal force directed—in this case—to the center of curvature of the trajectory.
Installing studio physics
Authors: Furtak T. E. , Ohno T. R.
Published: April 2003

We describe how we implemented studio teaching at the Colorado School of Mines. This includes our solution to the problem of how to develop computer-assisted learning units and how to manage independent learning groups.
Falling Sticks and Falling Balls
Authors: Bacon M. E. , Harpst Michael R. , Nakazawa Ryohei
Published: April 2003

The behavior of a falling stick, pivoted at one end, and a ball released from the same height as the end of the stick, is investigated theoretically and experimentally. The study is made possible through the use of the computer to perform the numerical computations and analysis of the experimental data. The study provides undergraduates with an opportunity to carry out a relatively simple project with interesting results.
A Friction Experiment
Authors: Takahashi Leo
Published: April 2003

Force-sensor friction experiments such as the one in Vernier Software’s Physics with Computers depend on an object moving with constant velocity in order to measure the force of kinetic friction; when a block is pulled by a horizontal force sensor and the block moves along a horizontal surface with constant velocity, Newton’s first law ensures that the force-sensor reading is a measure of the frictional force. The difficulty in performing the experiment is that it associates kinetic friction only with constant speeds. This experiment offers a way of avoiding this difficulty.
How I Misunderstood Newton’s Third Law
Authors: Hughes Mark J.
Published: April 2003

Every teacher is faced with the task of helping students develop accurate understanding of the physics concepts that govern the world around us. Whether you are a beginning teacher or a seasoned veteran, this year will present you with many situations in which you will be required to rethink the way you understand many concepts you thought you knew very well. Here is such an experience.
Compact Disk Optics
Authors: Gluck Paul
Published: April 2003

Periodic structures ranging from crystal lattices through steel rulers to radio-antenna arrays may act as diffraction gratings. Because compact disks are so familiar to our students, their use as reflection gratings has become popular.
The Equivalence Principle and the Dynamics of an Accelerated Helium-Filled Balloon
Authors: Gauthier N.
Published: April 2003

In an interesting recent article, V. M. Aguilella et al. (Phys. Teach. 40, 214–216 (April 2002) analyzed the dynamics of a helium-filled balloon tied by a string to the seat of a car that is moving at constant speed in a horizontal curve. To achieve their goal, the authors carefully apply Newton's laws of motion to a situation involving a noninertial frame of reference. This note, whose purpose is twofold, is meant to complement the article by Aguilella and his colleagues.
Period of an Interrupted Pendulum
Authors: Miller Bradley E.
Published: April 2003

While demonstrating a classic conservation-of-energy problem to my AP Physics students, I became curious about the periodic motion that ensued for certain initial conditions. The original problem consists of releasing a mass at the end of a string from an initial position horizontal to the plane of a table. The string comes in contact with a peg some distance below the point where the string is attached at the top. One is asked to find what minimum fraction of the string's length should the peg be placed to have the mass complete a circle about the peg. However, when the mass is released from much lower heights, the system undergoes periodic motion that can be thought of as an interrupted pendulum.
Reforming Physics Instruction Via RTOP
Authors: MacIsaac Dan , Falconer Kathleen
Published: April 2003

We report how physics teachers can use recent science education research developments to refine their own teaching and improve their students' conceptual achievement gains. The development of the Reformed Teaching Observation Protocol (RTOP) has produced a valuable tool for reflecting upon and improving physics teaching. Instructor RTOP scores have been found to strongly correlate with student conceptual gains in introductory science and physics courses. We discuss the underpinnings of reformed teaching and RTOP, how to use it to constructively evaluate and critique physics teaching and to guide personal teaching improvement.
Two Large-Scale Devices for Demonstrating a Bernoulli Effect
Authors: Cohen Harold , Horvath David
Published: April 2003

An object placed in a moving fluid experiences a net force when the speed of the fluid is greater on one side of the object than on the other. This is due to a difference in pressure on the two sides of the object and is known as the Bernoulli effect. A number of demonstrations of this Bernoulli effect have appeared in the physics teaching literature.1–4 In this article, we describe two such demonstrations that are quite dramatic and suitable for showing to large classes.5
Speed of Electromagnetic Signal Along a Coaxial Cable
Authors: Mak Se-yuen
Published: April 2003

One common paradox students find perplexing in learning about electric current is the apparent contradiction between the tiny drift speed of free electrons in a conductor, say about 1 m/h, and the response of a current “in no time” when the circuit is switched on or off. These phenomena can be understood in terms of the speed of the electrical signal, which travels at or near the speed of light. As soon as the circuit is closed, apart from inductive delay, an electric field is set up almost simultaneously throughout the circuit. It is the electric field that causes electrons to start drifting at all points in the circuit. This paper describes an experiment for measuring the speed of an electromagnetic signal in a coaxial cable.
My cup runneth over
Authors: McCarthy Thomas K.
Published: April 2003

This is a nice demonstration of superheating in a clean container and the impact of small nucleation “seeds” in producing a boil.
The Doppler Effect of a Sound Source Moving in a Circle
Authors: Saba Marcelo M. F. , Rosa Rafael Antônio da S.
Published: April 2003

When I first heard about an experiment that illustrates the Doppler effect by twirling a buzzer around one's head,1 I was intrigued and wondered if this experiment would work or not. In fact, it works because you usually do not place both ears exactly in the center of the circle; this would be very difficult indeed. When the source moves in a circle, the distance from the center is always constant, and there is no approaching or receding velocity at all. Holding a microphone in the same hand that holds the string that is attached to the buzzer easily shows this simple fact. No Doppler effect is observed. Although several qualitative demonstrations and experiments of the Doppler effect have been published,1,2 only a very few quantitative experiments are found in the literature.3 Having devised a new method to quantify the Doppler effect, described in a previous article,4 we thought it would be a good physics and geometry exercise to calculate and measure the frequency variations when the microphone is placed on the circular path of the buzzer.
An Implementation of Physics by Inquiry in a Large-Enrollment Class
Authors: Scherr Rachel E.
Published: April 2003

As physics instructors, we enjoy access to a variety of powerful instructional materials. Among them are classroom-tested inquiry-based laboratory curricula such as Physics by Inquiry1 and Workshop Physics.2 Unfortunately, such materials are often tested in conditions unattainable in introductory physics courses. In particular, the recommended instructor-student ratio tends to be larger than we can afford. This article describes an implementation of Physics by Inquiry in a liberal-arts physics class with 70 students and one instructor. I discuss the choices I made with the materials under these circumstances, describe the challenges that arose, and offer evidence that the course was fairly successful. Examples such as this one show that proven instructional materials can be put to good use even in circumstances that fall outside the tested conditions.
Inexpensive rotating-arm device for angular-motion labs
Authors: Altshuler Ken , Pollock Peter
Published: April 2003

This article describes in detail how to build low-cost laboratory devices to study angular motion. Three different laboratory investigations are described to study Newton’s second law for rotational motion and the property of angular momentum conservation.
Flight without Bernoulli
Authors: Waltham Chris
Published: April 2003

Presented here is a very simple physical model of flight that relies only on Newton’s second law and yet is able to reproduce all the salient features of a more rigorous fluid dynamical treatment. From a pedagogical point of view the model helps understand the origins of lift and drag in terms of forces rather than pressures, and enables all the important points to be made without recourse to complicated mathematics.
Making waves: A classroom torsional wave machine (Part II)
Authors: Skeldon Kenneth D. , Milne Janet E. , Grant Alastair I. , Palmer David A.
Published: April 2003

We investigate the role of a classroom torsional wave machine as a science prop and teaching aid, having already considered the physics behinds its design and operation in a companion article last month. We now present a selection of experiments designed to compare theory with experiment, demonstrate basic wave phenomena, and introduce fascinating concepts such as cut-off frequency and dispersion.
Filters for color mixing
Authors: Williamson Robert M.
Published: April 2003

Sources and prices of good quality plastic color filters are given, as is information about using them for additive and subtractive color mixing.
The double-elliptic harmonograph
Authors: Greenslade Thomas B.
Published: April 2003

Harmonographs are mechanical devices that compound perpendicular simple-harmonic motions of various frequencies, amplitudes, and phasings. Building such an apparatus would be an excellent independent project for students who savor the experimental side of physics.
Flying high, thinking low? What every aeronaut needs to know
Authors: Silverman Mark P.
Published: April 2003

The news report of a balloonist floating far above his intended altitude (in a lawnchair!) provides motivation for exploring the behavior of ideal gases and their implications for the thermodynamic properties of the Earth’s atmosphere.
Making sense of how students make sense of mechanical waves
Authors: Wittmann Michael C. , Steinberg Richard N. , Redish Edward F.
Published: April 2003

We have investigated student difficulties with mechanical waves and used the idea of mental models to organize our findings. Mental models describe the analogies and guidelines used to come to understand a topic. We find that individual students use both correct and incorrect mental models to make sense of a single physical situation.
Diffraction patterns with light and motion sensors
Authors: Rylander Jeffrey W. , Miller John J.
Published: April 2003

In the past, our students have studied diffraction patterns by passing laser light through a diffraction grating and onto a piece of paper that could be used to record the position of the bright spots with a pencil. Interfacing a motion and light sensor has enhanced the quality of observation as well as speeded up the process.
Measuring friction on falling muffin cups
Authors: Angell Carl , Ekern Trond
Published: April 2003

An experiment easy to carry out using modern information technology (data-logging) equipment is presented. At the same time we show an example of how to implement some knowledge about models and hypotheses in physics education.
Weight—A pictorial view
Authors: Sokolowski Andrzej
Published: April 2003

Here is a demonstration method that I have used to teach the difference between force of gravity and weight.
News clippings for introductory astronomy
Authors: Bobrowsky Matthew
Published: April 2003

Most students entering our introductory astronomy course for nonscience majors arrive not merely lacking scientific facts—they also have misconceptions about the nature of science, and many have a handicapping “science anxiety” (in addition to math anxiety). So I have added a “current science” requirement to our introductory course. Each student must compile a file of five astronomy news articles taken from readily available sources.
Curves of constant width
Authors: Flaten James A.
Published: April 2003

Curves of constant width have the same breadth regardless of how they are rotated. Highly noncircular curves with this property may be constructed geometrically. Such curves make good rollers, manhole covers, and allow one to drill nearly square holes.
Optics experiments using a laser pointer
Authors: O’Connell James
Published: April 2003

Laser pointers are an inexpensive source of near-parallel, bright, polarized light beams. Nine basic optics experiments are discussed that demonstrate the wave nature of light and the optical properties of water.
How big is our Sun?
Authors: Moldwin Mark
Published: April 2003

Putting large numbers into human perspective by using ratios of a known quantity to an unknown quantity is an important scientific skill. An astronomy activity that encourages the use of estimation and helps students get a handle on large numbers is the making of a scale model of Earth and Sun that is relative in both size and distance.
Rapid Actin Transport During Cell Protrusion
Authors: Zicha Daniel , Dobbie Ian M. , Holt Mark R. , Monypenny James , Soong Daniel Y. H. , Gray Colin , Dunn Graham A.
Published: April 2003

Transformed rat fibroblasts expressing two variants of green fluorescent protein, each fused to β-actin, were used to study actin dynamics during cell protrusion. The recently developed FLAP (fluorescence localization after photobleaching) method permits the tracking of one fluorophore after localized photobleaching by using the other as a colocalized reference. Here, by visualizing the ratio of bleached to total molecules, we found that actin was delivered to protruding zones of the leading edge of the cell at speeds that exceeded 5 micrometers per second. Monte Carlo modeling confirmed that this flow cannot be explained by diffusion and may involve active transport.
Overproduction of
Thermus
sp. Strain T2 β-Galactosidase in
Escherichia coli
and Preparation by Using Tailor-Made Metal Chelate Supports
Authors: Pessela Benevides C. C. , Vian Alejandro , Mateo César , Fernández-Lafuente Roberto , García José L. , Guisán José M. , Carrascosa Alfonso V.
Published: April 2003

A novel thermostable chimeric β-galactosidase was constructed by fusing a poly-His tag to the N-terminal region of the β-galactosidase from
Thermus
sp. strain T2 to facilitate its overexpression in
Escherichia coli
and its purification by immobilized metal-ion affinity chromatography (IMAC). The poly-His tag fusion did not affect the activation, kinetic parameters, and stability of the β-galactosidase. Copper-iminodiacetic acid (Cu-IDA) supports enabled the most rapid adsorption of the His-tagged enzyme, favoring multisubunit interactions, but caused deleterious effects on the enzyme stability. To improve the enzyme purification a selective one-point adsorption was achieved by designing tailor-made low-activated Co-IDA or Ni-IDA supports. The new enzyme was not only useful for industrial purposes but also has become an excellent model to study the purification of large multimeric proteins via selective adsorption on tailor-made IMAC supports.
Effect of Signal Compounds and Incubation Conditions on the Culturability of Freshwater Bacterioplankton
Authors: Bruns Alke , Nübel Ulrich , Cypionka Heribert , Overmann Jörg
Published: April 2003

The effect of signal compounds and of different incubation conditions on the culturability (i.e., the fraction of all cells capable of growth) of natural bacterioplankton from the eutrophic lake Zwischenahner Meer was investigated over a period of 20 months. Numbers of growing cells were determined by the most-probable-number technique in liquid media containing low concentrations (10 μM) of the signal compounds
N
-(oxohexanoyl)-
dl
-homoserine lactone,
N
-(butyryl)-
dl
-homoserine lactone, cyclic AMP (cAMP), or ATP. cAMP was the most effective signal compound, leading to significantly increased cultivation efficiencies of up to 10% of the total bacterial counts. Microautoradiography with [2,8-
3
H]cAMP, combined with fluorescence in situ hybridization, demonstrated that cAMP was taken up by 18% of all cells. The bacterial cAMP uptake systems had a very low

K
m

value of ≤1 nM. Analysis of the cultured bacteria by 16S rRNA gene fingerprinting showed that different bacterial phylotypes were recovered in the presence and in the absence of cAMP. Consequently, the addition of cAMP caused a stimulation of otherwise nonculturable bacteria. Phylogenetically different bacteria were also recovered at different temperatures and oxygen partial pressures. Throughout the study period, mainly members of the β-subclass of the
Proteobacteria
were cultivated. In addition, some members of the
Actinomycetales
were enriched. Quantification by culture-independent fluorescence in situ hybridization demonstrated that β-
Proteobacteria
and
Actinomycetales
also dominated the natural bacterioplankton assemblage. Sequence comparison revealed that two members of the
Actinomycetales
which reached high numbers in the natural bacterioplankton assemblage could actually be enriched by our cultivation approach.
Coupling of Bacterial Endosymbiont and Host Mitochondrial Genomes in the Hydrothermal Vent Clam
Calyptogena magnifica
Authors: Hurtado Luis A. , Mateos Mariana , Lutz Richard A. , Vrijenhoek Robert C.
Published: April 2003

The hydrothermal vent clam
Calyptogena magnifica
(Bivalvia: Vesicomyidae) depends for its nutrition on sulfur-oxidizing symbiotic bacteria housed in its gill tissues. This symbiont is transmitted vertically between generations via the clam's eggs; however, it remains uncertain whether occasionally symbionts are horizontally transmitted or acquired from the environment. If symbionts are transmitted strictly vertically through the egg cytoplasm, inheritance of symbiont lineages should behave as if coupled to the host's maternally inherited mitochondrial DNA. This coupling would be obscured, however, with low rates of horizontal or environmental transfers, the equivalent of recombination between host lineages. Population genetic analyses of
C. magnifica
clams and associated symbionts from eastern Pacific hydrothermal vents clearly supported the hypothesis of strictly maternal cotransmission. Host mitochondrial and symbiont DNA sequences were coupled in a clam population that was polymorphic for both genetic markers. These markers were not similarly coupled with sequence variation at a nuclear gene locus, as expected for a randomly mating sexual population. Phylogenetic analysis of the two cytoplasmic genes also revealed no evidence for recombination. The tight association between vesicomyid clams and their vertically transmitted bacterial endosymbionts is phylogenetically very young (<50 million years) and may serve as a model for the origin and evolution of eukaryotic organelles.
P1 Trisaccharide (Galα1,4Galβ1,4GlcNAc) Synthesis by Enzyme Glycosylation Reactions Using Recombinant
Escherichia coli
Authors: Liu Ziye , Lu Yuquan , Zhang Jianbo , Pardee Keith , Wang Peng George
Published: April 2003

The frequency of
Escherichia coli
infection has lead to concerns over pathogenic bacteria in our food supply and a demand for therapeutics. Glycolipids on gut cells serve as receptors for the Shiga-like toxin produced by
E. coli
. Oligosaccharide moiety analogues of these glycolipids can compete with receptors for the toxin, thus acting as antibacterials. An enzymatic synthesis of the P1 trisaccharide (Galα1,4Galβ1,4GlcNAc), one of the oligosaccharide analogues, was assessed in this study. In the proposed synthetic pathway, UDP-glucose was generated from sucrose with an
Anabaena
sp. sucrose synthase and then converted with an
E. coli
UDP-glucose 4-epimerase to UDP-galactose. Two molecules of galactose were linked to
N
-acetylglucosamine subsequently with a
Helicobacter pylori
β-l,4-galactosyltransferase and a
Neisseria meningitidis
α-1,4-galactosyltransferase to produce one molecule of P1 trisaccharide. The four enzymes were coexpressed in a single genetically engineered
E. coli
strain that was then permeabilized and used to catalyze the enzymatic reaction. P1 trisaccharide was accumulated up to 50 mM (5.4 g in a 200-ml reaction volume), with a 67% yield based on the consumption of
N
-acetylglucosamine. This study provides an efficient approach for the preparative-scale synthesis of P1 trisaccharide with recombinant bacteria.