bluuebunny/crossref_metadata_2025 huggingface dataset:
O18  Lethal photosensitization of oral pathogens via red‐filtered halogen lamp
Authors: Krespi Y , Slatkine M , Marchenko M , Protec J
Published: March 2005

Objectives  The ability of laser irradiation in the presence of photosensitizing agent to induce lethal effect on oral bacteria is well documented. We designed an in vitro experiment to achieve phototoxic results on two common oral pathogens, using a high intensity, red filtered halogen lamp. Our goal was to determine the minimum duration of light exposure and drug dilution to achieve at least 50% reduction in bacterial counts.

Methods  Two common oral pathogens, Porphyromonas gingivalis and Prevotella intermedia were used in this experiment. The source for light energy was continuous working, high intensity, red filtered, halogen lamp (HL). The light was transmitted through a flexible light guide over petri dishes containing live bacteria. Microorganisms were exposed to halogen light for 5, 10 and 20 min. Methylene Blue (MB) in concentrations of 0.1, 0.075, 0.05, 0.025 and 0.01% was used as a photosensitizing agent. Light energy alone and MB alone was used as controls.

Results and discussion  Optimum lethal photosensitization (50% or more bacteria killing) of oral pathogens was achieved under following conditions.

1. Halogen light illumination for 5 min and longer with 0.05% MB.

2. Exposure to light for 20 min in the presence of 0.025 and 0.01% MB.

Light exposure of 20 min in the absence of MB was not effective in killing bacteria. In the absence of light, MB at concentrations of 0.025 and 0.001% was not effective. Reduction of bacteria with the use of 0.05% MB alone was also insignificant. However, 0.075 and 0.1% MB, even in the absence of light was found to be bacteriocidal.

Conclusions  Our in vitro data indicates that we were able to achieve lethal photosensitization of two common oral pathogens with high intensity red filtered HL in the presence of diluted MB. In this era of increased incidence of antibiotic resistance, bacterial killing with laser or light energy in the presence of photosensitizing agents, can prove to be a valuable treatment modality.
P6  Complaints of halitosis related to the oral cavity. A preliminary report of 700 consecutive patients
Authors: Van Den Broek AMWT , Feenstra L , De Baat C
Published: March 2005

Patients with complaints of halitosis do seek treatment from physicians and dental practitioners, because of the fear that their halitosis may interfere with their social activities. Although the prevalence of halitosis has been reported to be as high as 50%, most physicians and dental practitioners are poorly informed about the causes and treatments of halitosis. In order to care for patients with complaints of halitosis a multidisciplinary team was established at the Erasmus Medical Centre, Rotterdam, The Netherlands. The team included a dental hygienist, an otorhinolaryngologist, and a dentist, who developed a special halitosis programme. One short press release regarding the establishment of the team, was provided to the national press‐centre. In the out‐patient clinic more than 700 patients were seen by the team. Using a structured questionnaire fed to a PC, patients answered questions regarding complaints about the oral cavity, the upper respiratory tract, the throat, their general health, their cleansing habits of the oral cavity, and prior experiences with general physicians, dental practitioners, and medical specialists. They underwent examinations of the extent of their halitosis, of the perioral and neck region, the oral cavity, the upper respiratory tract, and the upper digestive tract. Finally, the members of the team came to a joint diagnosis and a joint treatment plan for every individual patient. Of the first 700 consecutive patients around 90% had a natural dentition without removable partial dentures. More than 60% were diagnosed as having periodontal disease with pockets of 4 mm or more in the maxilla. This figure was more than 50% in the mandible. Around 95% had tongue coating.
P8  Halitosis and periodontal disease in subjects with mental disabilities
Authors: Salvador SL , Figueiredo LC
Published: March 2005

Halitosis has been correlated with the concentration of volatile sulfur compounds (VSC) produced in the oral cavity by metabolic activity of bacteria colonizing the periodontal area and the dorsum of the tongue. The aim of this investigation was to study the association among the presence of BANA‐positive species (Treponema denticola, Bacteroides forsythus, Porphyromonas gingivalis), periodontal condition and halitosis in subjects with mental disabilities. This population (17–49 years of age) consisted of 17 Down Syndrome (DS) patients, 17 with Mentally Retarded (MR), and 17 mentally health (control group). The VSC in the human mouth was determined by a portable sulfide monitor (Halimeter®). Clinical parameters (Plaque Index – PlI, Probing Depth – PD and Bleeding on Probing – BOP) were obtained from six reference teeth (# 3, 8, 14, 19, 24, 30). In the same way, subgingival plaque samples were taken from the same selected teeth and from dorsal surface of the tongue and evaluated by BANATM Test (BANAMet). The results were analyzed by Mann–Whitney U Test. PlI and BOP were higher in DS patients (P < 0.01) and PD was similar in DS and health patients (P > 0.05) but higher than MR. No difference was found among three groups for the presence of BANA‐positive species, however the VSC levels were lower (P < 0.01) in DS (log1.9 ± 0.2) than in MR (log 2.2 ± 0.3) and health (log 2.2 ± 0.2) patients. Although the presence of anaerobic periodontal infection was similar in all groups the VSC levels were lower in Down syndrome patients.
P10  Is transmission of bacteria that cause halitosis from pets to humans possible?
Authors: Iwanicka‐Grzegorek E , Lipkowska E , Kepa J , Michalik J , Pierzynowska E
Published: March 2005

Objective  The aim of the study was to determine whether the level of salivary amines in halitosis patients depends on regular contact with pets (dogs and cats) in childhood or at present. It is believed that bacteria metabolizing amine compounds into compounds causing fetor ex ore may be transmitted to humans from animals.

Methods  The study covered 84 patients suffering from halitosis and 40 healthy controls aged 20–62 (avg. 39.7). Each person completed a questionnaire and was then examined for organoleptic score, VSC by halimeter and evaluation of low molecular mass amines by a ninhydrine colourimetric reaction. Halitosis was diagnosed if the average level of VSC measured by the halimeter was >125 ppb and the organoleptic measurement using a 5‐point scale was >2. Statistical analysis was performed using Wilcoxon's and Chi square tests.

Results  Analysis showed a statistically significant correlation between halitosis and regular contact with pets at present (P < 0.001) or in childhood (P < 0.001).

Conclusions  Pets (dogs, cats) owned in childhood or at present may transmit bacteria that cause halitosis.
P15  Non‐surgical periodontal therapy reduces VSCs according to disease severity
Authors: Da Rocha Nogueira‐Filho G , Peruzzo D , Carvalho MD , Sallum AW
Published: March 2005

The objective of this study was to evaluate the effect of non‐surgical periodontal therapy in VSC formation and its relationship with periodontal disease severity. Twenty‐five periodontal patients without treatment and a control group with 10 subjects were selected. The patients were classified according to their periodontal diagnosis based on clinical attachment level (CAL): marginal gingivitis (MG), slight periodontitis‐CAL = 3 mm (P1), moderate periodontitis‐CAL = 5 mm (P2), severe periodontitis‐CAL = 7 mm (P3) and terminal periodontitis‐CAL > 10 mm (P4). At baseline, all patients received oral hygiene instructions and scaling/root planning. The periodontal parameters: plaque index, gingival index, probing depth and clinical attachment level were evaluated in two experimental periods (T1 = Baseline and T2 = 3 months recall). The Halimeter® was used to detect VSC formation in the same periods. The results after three months showed that VSC formation, probing depth and clinical attachment level decreased similarly in groups MG and P1 (P < 0.05). However, P3 and P4 groups showed the highest VSC formation and persistent bleeding in residual periodontal pockets. Within the limits of this study, it could be concluded that non‐surgical periodontal treatment may interfere in VSC formation according to periodontal disease severity.

Acknowledgement  This work was supported by FAPESP #44052‐01.
P16  Effect of intraoral oxygen release device on breath odor
Authors: Choi YG
Published: March 2005

Objective  To assess the effect of intraoral oxygen release device on the reduction of breath odor.

Methods  Twenty‐two people (age ranged 17–81, mean age = 32, 11 males, 11 females) suffering from breath odor for average 8.3 years across the nation volunteered to participate in this clinical trial. Collection of baseline demographic information and clinical examination was conducted prior to the initial use of the intraoral oxygen release device. After having worn the device at night for 2 weeks, patients were recalled. Concentration of VSC (volatile sulfur compound) using Halimeter® (Interscan Corporation, Chatsworth, CA, USA) was measured and two independent examiners (one male, one female) performed organoleptic measurements, both before and after the use of the device. The two examiners were blinded to the use of device. Data were analyzed with non‐parametric Wilcoxon Signed‐rank test and proportion using statistical package JMP®5.0.1 (SAS Institute, Cary, NC, USA).

Results and discussion  Following use of the device a change in breath odor severity was measured as a decrease of organoleptic breath odor by 58% with one examiner and by 79% with the other examiner. Median VSC level before device use was 111 ppb (parts per billion) and decreased to 75 ppb after device use. The VSC decrease was statistically significant (P‐value = 0.004).

Conclusions  The study indicated that the intraoral oxygen release device is effective in reducing Volatile Sulfur Compound level and organoleptic breath odor.
P17  Clinical comparison of a triclosan/copolymer/NaF dentifrice and a commercially available breath‐freshening dentifrice in reducing breath volatile sulfur compounds overnight: a multiple‐use study
Authors: Niles H , Hunter C , Vazquez J , Williams M , Cummins D
Published: March 2005

Objective  The objective of this randomized, crossover study was to compare the effectiveness of the triclosan/copolymer/NaF dentifrice and a commercially‐available breath freshening dentifrice containing fluoride for their ability to reduce volatile sulfur compounds (VSC) responsible for breath odor overnight.

Methods  Following a one‐week washout period of brushing with a regular fluoride dentifrice, subjects reported to the clinical site without performing oral hygiene, eating or drinking in preparation for baseline breath sampling. Subjects were randomly assigned a test dentifrice and instructed to brush their teeth for 1 min, twice a day for 1 week. On the morning of the 8th day, subjects returned to the test site, having refrained from oral hygiene, eating and drinking, for overnight sampling. Following a second one‐week washout period, subjects repeated the same regimen, but now using the other test product. At each measurement, the level of breath VSC was evaluated using a gas chromatograph equipped with a flame photometric detector. Measurements were taken in duplicate, and then averaged. The levels of VSC were expressed as parts per billion (ppb) in mouth air.

Results  At baseline, the mean breath VSC levels for the TCF and breath freshening dentifrice groups were 618 and 581 ppb, respectively. There was no statistically significant difference between the groups. Overnight, the TCF and the breath freshening dentifrice reduced breath mean VSC levels to 267 and 521 ppb, respectively. This gave a 56.7 and 10.2% reduction in VSC levels for these two products, respectively, compared to baseline. The reduction for the TCF dentifrice was significantly different (P < 0.05%) from that of the breath freshening dentifrice.

Conclusion  The results of this randomized, double‐blind, crossover study indicate that the TCF dentifrice was significantly more effective than a commercially‐available breath freshening dentifrice containing fluoride in reducing breath VSC responsible for bad breath overnight.
P19  A study for the effect of tongue cleaning
Authors: Ohmori M , Baba R , Miyazaki A , Sato H , Katano S , Sawaki A , Tanabe S , Masatuki N , Yasukawa T , Hasegawa A , Imade S , Sano A
Published: March 2005

The objective of this study was to evaluate breath odor reduction after giving tongue cleaning instruction to adults. The breath odor of 26 subjects (ages 19–77) was measured before and after tongue cleaning instruction. They were instructed to scrape away tongue coating with a Dental Pro multi‐tufted tongue brush (Jacks co. Ltd.) once or twice a day. They used the tongue brush until they could see no more plaque on their tongue. Oral malodor was evaluated using: two portable sulphide monitors (Halimeter RH‐17, Interscan Co.) and Brethtron, (Yoshida Co.), gas chromatography (GC‐8A, Shimazu) and organoleptic measurements. Organoleptic measurements were estimated on a scale of 0 to 5 as follows : 0 = no odor, 1 = barely noticeable odor, 2 = slight odor, 3 = moderate odor, 4 = strong odor, 5 = severe odor. The subjects were asked to refrain from brushing, eating, drinking, smoking and using mouthwash 2 h before each examination. Tongue coating status was evaluated in five grades by inspection, according to distribution area and thickness of tongue coating. Probing depth, bleeding on probing and dental plaque were assessed. One week of tongue cleaning resulted in reductions in tongue coating status and breath odor. As a result of the before and after measurements, no correlation was observed between tongue cleaning as instructed and bleeding on probing or dental plaque. According to a questionnaire given 1 week after the study, tongue coating status had reverted to pre‐cleaning condition in about 1 day. Therefore, we concluded that tongue cleaning should be done at least once a day to control breath odor.
P28  Analysis of ‘Morning Breath’
Authors: Reinders G , Rabenhorst J
Published: March 2005

The objective of the study was to identify the volatiles responsible for the smell of oral malodour, the so called ‘Morning Breath’ or halitosis. Therefore the breath of volunteers was trapped on different SPME fibers and on Carbotrap 300 and analysed by Thermodesorption‐GC‐MS and Thermodesorption‐GC‐Sniffing Detection. So numerous odour active compounds were identified and their influence on malodour was determined. The identified substances belong to different chemical classes (S‐compounds, N‐compounds, alcohols, acids, phenols). An in vitro aromagram of the malodour was generated. The results indicate that the frequently mentioned ‘Volatile Sulphur Compounds’ (VSC) H2S, methane thiol and dimethyl sulfide only play a minor role in the ‘Morning Breath’. More important are other sulfur compounds, phenolic compounds (phenol, p‐cresol) and N‐compounds (indole, scatole).
P34  Effect of a triclosan/PVM/MA copolymer/fluoride dentifrice on volatile sulfur compounds in vitro
Authors: Pilch S , Williams M , Cummins D
Published: March 2005

Objective  The objective of the investigation was to document the in vitro efficacy of a triclosan/PVM/MA copolymer/fluoride (TCF) dentifrice against the formation of volatile sulfur compounds (VSC) as well as the growth of H2S‐producing bacteria. Clinical studies using organoleptic judges, gas chromatography, or a portable sulfide monitor have generally been employed in the assessment of treatments for the control of oral malodor. However, these studies are not appropriate for screening purposes because of the expense and time required.

Methods  An in vitro method was developed for the purpose of screening new technologies for their ability to control VSC formation and for determining bio‐equivalence of efficacy when implementing changes in existing formulations. The method combines basic microbiological methods, dynamic flow cell techniques and head space analysis. The in vitro VSC method was validated by comparing the efficacy of two dentifrices containing TCF with a control fluoride dentifrice as the TCF products have been clinically proven to control oral malodor.

Results  In the validation studies, the TCF‐containing dentifrices were significantly better (P < 0.05) than the control dentifrice in inhibiting VSC formation and reducing H2S‐producing bacteria. For example, when compared to baseline, the TCF dentifrices reduced VSC formation between 42 and 49% compared to the control dentifrice which reduced VSC formation 3%. There was no significant difference (P > 0.05) between the two TCF dentifrices.

Conclusion  Using an in vitro breath VSC model, it has been demonstrated that two variants of a dentifrice containing triclosan, PVM/MA copolymer and fluoride have efficacy that is significantly better than a control fluoridated dentifrice and that there is no significant difference between the triclosan/PVM/MA copolymer/fluoride dentifrice variants.
P42  Subjective symptoms and knowledge of oral malodor on dental students in Thailand
Authors: Sopapornamorn P , Shinada K , Kawaguchi Y
Published: March 2005

The purpose of this study was to investigate subjective symptoms about oral malodor and the knowledge and attitude for bad breath on dental students. The subjects were 213 students from 1st to 6th year undergraduate course of one dental school in Thailand (male: 70, female: 143). Their mean (s.d.) age was 21.0 (1.9). Questionnaire survey was conducted in November 2003. Questionnaire items were subjective symptoms about oral malodor and dry mouth, the knowledge and attitude for bad breath, oral hygiene practice, smoking/drinking habits, and life stress. Five students (2.3%) answered that they concerned their oral malodor often and 87.8% reported sometimes. Of them, 72.9% wanted to receive treatment for their malodor and 70.8% said they suffer from bad breath in daily life. Two‐thirds of students perceived strong oral malodor when waking up. There were no significant differences of the self‐perceived malodor rates between gender or among year of study. More than half of the students did not know that oral diseases and poor oral hygiene are the major causes of bad breath. The students’ attitudes for bad breath were different if the target was family members or friends. The majority of the students (88.7%) answered they perceived dry mouth. Perception of dry mouth was significantly related with self‐reported oral malodor prevalence (P < 0.05). However other oral or behavioral factors did not relate to the self‐reported malodor rates. In this study, dental students perceived bad breath in high prevalence. However the knowledge for bad breath was not enough even the students who already provided dental treatment to the patients. It would be necessary to give them adequate knowledge and methods in education program for managing not only patients’ but also their own oral malodor problem.
Expression pattern of neuronal and skeletal muscle voltage‐gated Na+ channels in the developing mouse heart
Authors: Haufe Volker , Camacho Juan A. , Dumaine Robert , Günther Bernd , Bollensdorff Christian , Von Banchet Gisela Segond , Benndorf Klaus , Zimmer Thomas
Published: March 2005

In the mammalian heart, a variety of voltage‐gated Na+ channel transcripts and proteins have been detected. However, little quantitative information is available on the abundance of each transcript during development, or the contribution of TTX‐sensitive Na+ channels to the cardiac sodium current (INa). Using competitive and real‐time RT‐PCR we investigated the transcription of six Na+ channels (Nav1.1–Nav1.6) and the β1 subunit during mouse heart development. Nav1.5 was predominantly expressed in the adult heart, whereas the splice variant Nav1.5a was the major Na+ channel isoform in embryonic hearts. The TTX‐resistant Na+ channel transcripts (Nav1.5 and Nav1.5a) increased 1.7‐fold during postnatal development. Transcripts encoding TTX‐sensitive Na+ channels (Nav1.1–Nav1.4) and the β1 subunit gradually increased up to fourfold from postnatal day (P)1 to P126, while the Nav1.6 transcript level remained low and constant over the same period. In adults, TTX‐sensitive channel mRNA accounted for 30–40% of the channel pool in whole‐heart preparations (Nav1.3 > Nav1.4 > Nav1.2 ≫ Nav1.1 ∼ Nav1.6), and 16% in mRNA from isolated cardiomyocytes (Nav1.4 > Nav1.3 > Nav1.2 > Nav1.1 > Nav1.6). Confocal immunofluorescence on ventricular myocytes suggested that Nav1.1 and Nav1.2 were localized at the intercalated disks and in the t tubules. Nav1.3 labelling predominantly produced a diffuse but strong intracellular signal. Nav1.6 fluorescence was detected only along the Z lines. Electrophysiological recordings showed that TTX‐sensitive and TTX‐resistant Na+ channels, respectively, accounted for 8% and 92% of the INa in adult ventricular cardiomyocytes. Our data suggest that neuronal and skeletal muscle Na+ channels contribute to the action potential of cardiomyocytes in the adult mammalian heart.
Disruption of excitation–contraction coupling and titin by endogenous Ca2+‐activated proteases in toad muscle fibres
Authors: Verburg Esther , Murphy Robyn M. , Stephenson D. George , Lamb Graham D.
Published: March 2005

This study investigated the effects of elevated, physiological levels of intracellular free [Ca2+] on depolarization‐induced force responses, and on passive and active force production by the contractile apparatus in mechanically skinned fibres of toad iliofibularis muscle. Excitation–contraction (EC) coupling was retained after skinning and force responses could be elicited by depolarization of the transverse‐tubular (T‐) system. Raising the cytoplasmic [Ca2+] to ∼1 μm or above for 3 min caused an irreversible reduction in the depolarization‐induced force response by interrupting the coupling between the voltage sensors in the T‐system and the Ca2+ release channels in the sarcoplasmic reticulum. This uncoupling showed a steep [Ca2+] dependency, with 50% uncoupling at ∼1.9 μm Ca2+. The uncoupling occurring with 2 μm Ca2+ was largely prevented by the calpain inhibitor leupeptin (1 mm). Raising the cytoplasmic [Ca2+] above 1 μm also caused an irreversible decline in passive force production in stretched skinned fibres in a manner graded by [Ca2+], though at a much slower relative rate than loss of coupling. The progressive loss of passive force could be rapidly stopped by lowering [Ca2+] to 10 nm, and was almost completely inhibited by 1 mm leupeptin but not by 10 μm calpastatin. Muscle homogenates preactivated by Ca2+ exposure also evidently contained a diffusible factor that caused damage to passive force production in a Ca2+‐dependent manner. Western blotting showed that: (a) calpain‐3 was present in the skinned fibres and was activated by the Ca2+exposure, and (b) the Ca2+ exposure in stretched skinned fibres resulted in proteolysis of titin. We conclude that the disruption of EC coupling occurring at elevated levels of [Ca2+] is likely to be caused at least in part by Ca2+‐activated proteases, most likely by calpain‐3, though a role of calpain‐1 is not excluded.
The vagus regulates histamine mobilization from rat stomach ECL cells by controlling their sensitivity to gastrin
Authors: Norlén P. , Ericsson P. , Kitano M. , Ekelund M. , Håkanson R.
Published: March 2005

The ECL cells in the oxyntic mucosa secrete histamine in response to gastrin, stimulating parietal cells to produce acid. Do they also operate under nervous control? The present study examines histamine mobilization from rat stomach ECL cells in situ in response to acute vagal excitation and to food or gastrin following vagal or sympathetic denervation. Applying the technique of microdialysis, we monitored the release of histamine by radioimmunoassay. Microdialysis probes were placed in the submucosa on either side of the stomach, 3 days before experiments. The rats were awake during microdialysis except when subjected to electrical vagal stimulation. One‐sided electrical vagal stimulation raised serum gastrin and mobilized gastric histamine. However, gastrin receptor blockade prevented the histamine mobilization, indicating that circulating gastrin accounts for the response. Vagal excitation by hypoglycaemia (insulin) or pylorus ligation did not mobilize either gastrin or histamine. The histamine response to food was almost abolished by gastrin receptor blockade, and it was halved on the denervated side after unilateral subdiaphragmatic vagotomy. While the histamine response to a near‐maximally effective dose of gastrin was unaffected by vagotomy, the response to low gastrin doses was reduced significantly. Abdominal ganglionic sympathectomy failed to affect the histamine response to either food or gastrin. In conclusion, gastrin is responsible for most of the food‐evoked mobilization of ECL‐cell histamine. The histamine response to electrical vagal stimulation reflects the effect of circulating gastrin rather than a direct action of the vagus on the ECL cells. Vagal denervation was accompanied by an impaired histamine response to food intake, probably reflecting the right‐ward shift of the serum gastrin concentration–histamine response curve. The results suggest that the vagus controls the sensitivity of the ECL cells to gastrin.
Physiological properties of rod photoreceptor electrical coupling in the tiger salamander retina
Authors: Zhang Jian , Wu Samuel M.
Published: March 2005

Using dual whole‐cell voltage and current clamp recording techniques, we investigated the gap junctional conductance and the coupling coefficient between neighbouring rods in live salamander retinal slices. The application of sinusoidal stimuli over a wide range of temporal frequencies allowed us to characterize the band‐pass filtering properties of the rod network. We found that the electrical coupling of all neighbouring rods exhibited reciprocal and symmetrical conductivities. On average, the junctional conductance between paired rods was 500 pS and the coupling coefficient (the ratio of voltage responses of the follower cell to those of the driver cell), or K‐value, was 0.07. Our experimental results also demonstrated that the rod network behaved like a band‐pass filter with a peak frequency of about 2–5 Hz. However, the gap junctions between adjacent rods exhibited linearity and voltage independency within the physiological range of rods. These gap junctions did not contribute to the filtering mechanisms of the rod network. Combined with the computational modelling, our data suggest that the filtering of higher frequency rod signals by the network is largely mediated by the passive resistive and capacitive (RC) properties of rod plasma membranes. Furthermore, we found several attributes of rod electrical coupling resembling the physiological properties of gene‐encoded Cx35/36 gap junctions examined in other in vitro studies. This indicates that the previously found Cx35/36 expression in the salamander rod network may be functionally involved in rod–rod electrical coupling.
Science and fiction: An interdisciplinary approach
Authors: Zander Arlen R.
Published: March 2005

An interdisciplinary (ID) course based on science fiction is described. The course was developed by a four−man team consisting of a physicist, a poet, a psychologist, and a literary scholar. A unique feature of the course is that all of the teaching team meet every class. Objectives, structure and development of the course are discussed with particular emphasis on the ID approach, and a typical syllabus for one book is described in detail. Both qualitative and quantitative evaluations of the course are presented.
The electromagnetic radiation from a finite antenna
Authors: Uman Martin A. , McLain D. Kenneth , Krider E. Philip
Published: March 2005

Textbooks rarely give time−domain solutions to antenna problems. For the case of a finite linear antenna along which a fixed current waveform propagates, we present analytical time−domain solutions for the electric and magnetic radiation (far) fields. We also give computer solutions for the total (near and far) fields. The current waveform used as an example in the computer calculations approximates that of a lightning return−stroke, a common geophysical example of the type of radiation source under consideration.
Use of the PSI technique in prerequisite courses
Authors: Park John T. , Snow William R.
Published: March 2005

An engineering physics course, in which the Personalized System of Instruction (PSI) technique has been used, has been designed to meet the requirements that all of a prescribed list of subjects be covered and that the course be completed within a single semester. The course was modified so that it has two levels of mastery for each unit: a passing level and a complete mastery level. All students were required to reach a passing level of mastery on all of the required material. Grades were assigned according to the number of complete mastery level examinations passed. It was found that unit deadlines are necessary to insure completion of the material, but they do not hinder progress because only passing mastery is required by each deadline. Ninety−two percent of the students who have completed the course indicate a preference for this PSI technique over the regular lecture.
An inexpensive, easily constructed, double plasma machine
Authors: Schneider S.E. , Burde C.M. , Lonngren K.E.
Published: March 2005

An inexpensive double plasma machine suitable for demonstration use is described.
On the ’’derivation’’ of Einstein’s field equations
Authors: Yilmaz Hüseyin
Published: March 2005

It is shown that the conventional correspondence procedure used in the transition from Newtonian to the Einsteinian theory of gravitation is not unique. A new procedure of correspondence whereby the theory is required to reduce to a special relativistic limit before it reduces to the Newtonian limit is described. It is shown that the special relativistic correspondence leads to first and second order requirements, whereas the Newtonian correspondence leads only to first order requirements. The resulting theory is logically plausible and experimentally viable.
Constellation course: Interaction between the sciences and the arts
Authors: Hallett Linda Rahm , Kalman Calvin S.
Published: March 2005

A two-semester course is discussed that focuses on the idea that developments in the sciences and the arts together reveal a constant process of mutual influence and cross-fertilization. The course develops this thesis using examples from physics, art, literature, and philosophy from Greek times to the present day.
Bound-state wave packets
Authors: Segre Carlo U. , Sullivan J. D.
Published: March 2005

We point out that a convenient way to construct wave packets is to superimpose bound-state eigenfunctions. The resulting packets can be used to study spreading, scattering, and reflection as well as features unique to bound-state phenomena. The infinite square well and the infinite square well with a δ-function barrier are illustrated.
Phase-space of a driven, damped pendulum (Josephson weak link)
Authors: Falco Charles M.
Published: March 2005

We have generated a number of phase-space diagrams for several physically significant differential equations, including those describing the motion of a driven, damped pendulum and a Josephson weak link. These phase-space diagrams can lead to considerable insight into the complex behavior exhibited by these systems. A number of these phase-space diagrams were generated with parameters that can be duplicated with suitable mechanical models, allowing them to be used in conjunction with such models for a detailed study of the behavior of the driven, damped pendulum and Josephson weak link.
Some geometrical features of fields
Authors: Karioris Frank G. , Mendelson Kenneth S.
Published: March 2005

There are many ways of demonstrating electric and magnetic fields for introductory physics students, but in most instances only qualitative features of fields are treated. Sometimes, a student may be misled into believing that the electric field produced in a shallow electrolytic tank by two small electrodes is the same as the field produced by two equal and opposite charges (or by a bar magnet) in free space. In this paper we show how some quantitative, but purely geometrical, features of field lines can be used to distinguish between these two cases. Equations are derived for field lines and radii of curvature of field lines for several idealized cases. We show that the radius of curvature of a field line is a unique and distinguishing feature of each of the four charge configurations treated. These purely geometrical criteria are applied to two typical experimental field plots to characterize them and to show that experimental constraints introduce departures from theoretical models.
Inertia of energy and the liberated photon
Authors: Antippa Adel F.
Published: March 2005

We follow through the different variants of Einstein’s intuitive photon-in-a-box derivation of the inertia of energy, and end with the very simple ’’radiating atom’’ derivation.
The hanging string as a model of metric distortion
Authors: Meckler Alvin
Published: March 2005

The identification of a string as a curve allows the statement of a physical postulate which has as an immediate consequence the differential equation of the curve. The applied force appears as the gradient of the tension. It is possible to rewrite the differential equation as an equation for a geodesic in a transformed space, with the tension now incorporated into the metric. The field equation can be chosen to be the equation relating the transformed scalar curvature to the tension. The geometrization of physics is traceable. By the same procedure, the differential equation of a light ray may be derived, and the index of refraction may be related to the distorted geometry.
Extraction of relativistic concepts
Authors: Steib Michael Lee
Published: March 2005

Two elementary algebra word problems are presented which have answers helpful enough in the derivation of the effects of special relativity that little else need be added in this derivation. The two problems are entirely in the classical setting before any reference is made to relativistic assumptions. The chance for confusion related to relativistic assumption is thus extracted and concentrated into a very short and direct part of the derivations for the contraction of lengths, retardation of time, and nonsynchronization of clocks. Thus these effects of the constancy of the speed of light follow immediately and directly from the assumption of the constancy of this speed in a way which elucidates the logical connection between the assumption and the effects.
Formalism for the rotation matrix of rotations about an arbitrary axis
Authors: Palazzolo Alan
Published: March 2005

In this paper a formalism is developed that enables one to write down by inspection the matrix which represents the transformation between two coordinate systems, one of which is rotated by an angle ϑ about an arbitrary axis. Only the direction cosines of the rotation axis and ϑ need be known. It is pointed out that this transformation is not discussed in the usual treatments of classical mechanics.
Science and society test for scientists: Transportation
Authors: Hafemeister David
Published: March 2005

Science and society questions on transportation are posed on such topics as energy intensiveness and efficiency, San Diego freeway noise, air pollution in the Los Angeles air basin, the 55-mph speed limit, the ’’umbrella principle,’’ the Bay Area Rapid Transit (BART) system of San Francisco, and the hydrogen-fueled airplane. Back-of-the-envelope sophomore physics is utilized in attempting to answer the questions.
Variation in differential and total cross sections due to different radial wave functions
Authors: Williamson W. , Greene T.
Published: March 2005

Three different sets of analytic wave functions are used to calculate the Na(3s→3p) differential and total electron excitation cross sections by using the Born approximation. As would be expected, significant differences in the results are found, and the calculation can be used as an example in elementary quantum mechanics to demonstrate just how much variation in the cross section and line strengths there is for Na(3s→3p).
Unitary transformations of the Dirac equation
Authors: Weaver D. L.
Published: March 2005

The motivation, derivation, and properties of some unitary transformations of the Dirac equation are discussed, including the Foldy–Wouthuysen, Cini–Touschek, and Melosh transformations as members of a general class of such transformations. In addition, some spin-1 considerations are outlined, as well as a way of dealing with free massless electrons and Maxwell’s equations in a format parallel to rest-system considerations.
Observing teaching: An introduction to empirical techniques
Authors: Aubrecht Judith D. , Aubrecht Gordon J.
Published: March 2005

This paper will sketch some answers (incomplete but hopefully suggestive) to these questions: (1) Why observe teaching at all? (2) Why is it so hard to study teaching? (3) What sort of observation of teaching has already been done? (4) What are current directions in research and practice in observation? (5) What might be especially useful for, or appealing to, physicists?
Experiment in elementary statistics
Authors: Fernando P. C. B.
Published: March 2005

Articles on simple laboratory exercises in statistics have appeared in recent issues of the American Journal of Physics. This paper describes a similar experiment (but with a somewhat different pedagogic approach) which was introduced three years ago at the very beginning of an undergraduate laboratory course in physics offered at the Vidyodaya Campus of the University of Sri Lanka. An important feature of the exercise to be discussed is that students verify empirically the various aspects of the Gaussian distribution. They obtain a working knowledge of, and a confidence in, some of the commonly used simple statistical procedures, and in particular they are introduced to the sampling technique.
The Lenz vector and orbital analog computers
Authors: Harter W. G.
Published: March 2005

A single geometrical diagram based on the Lenz vector shows the qualitative and quantitative features of all three types of Coulomb orbits. A simple analog computer can be made for an overhead projector by using this theory, and a number of interesting effects can be efficiently demonstrated.
Maxwell form of the linear theory of gravitation
Authors: Campbell William B. , Morgan Thomas A.
Published: March 2005

A treatment of the linear theory is given that closely parallels the usual E and B formulation of electromagnetic theory. In Part I, an introductory exposition of gravitational radiation is presented. The tidal gravitational field strength E is defined, and it is shown that E is the measurable quantity which characterizes a gravitational wave. The important point is made that the problem of detecting gravitational waves is really the same problem as detecting tidal accelerations due to a time-varying Newtonian gravitational field. In Part II, the magnetic-type gravitational field strength B is defined and Maxwell-like field equations are used to determine the polarization states of a gravitational wave. The detection of gravitational waves by Weber-type cylinders is discussed.
On Einstein, light quanta, radiation, and relativity in 1905
Authors: Miller Arthur I.
Published: March 2005

Section 8 of Einstein’s relativity paper of 1905, ’’On the Electrodynamics of Moving Bodies,’’ is analyzed in its historical context. The relationship of this section to the rest of the relativity paper, to the genesis of relativity theory, and to contemporaneous work on radiation theory—in particular, to that of Max Abraham—is discussed.
How children swing
Authors: Curry Stephen M.
Published: March 2005

Everyone knows how to do it, but not everyone knows how it works. In this analysis of the motion of a playground swing, it is shown that, under conditions of constant pumping, the stored energy increases approximately exponentially with time. A comparison is made between this system and other parameteric amplifiers in various fields of physics, and the problem of starting a swing from rest is discussed.
Accelerator physics: An undergraduate course in experimental nuclear physics
Authors: Fielder Douglas S.
Published: March 2005

A 2-semester-hour experimental course utilizing the SUNY Oneonta 0.5-MeV Van de Graaff accelerator has been offered for three consecutive years. The most important course requirement is completion of six or seven laboratory projects including complete written reports. Theory is emphasized only to the extent that it is needed to complete and understand the projects. Student responses on course evaluation forms together with the instructor’s evaluation of the course indicate that it has been useful and valuable for nearly all students who have completed it.
Elementary derivation of the perturbation equations of celestial mechanics
Authors: Burns Joseph A.
Published: March 2005

The equations of celestial mechanics that govern the time rates of change of the orbital elements are completely derived using elementary dynamics, starting from only Newton’s equation and its solution. Two orbital equations and the four most meaningful orbital elements—semimajor axis a, eccentricity e, inclination i, and longitude of pericenter Ω—are written in terms of the orbital energy E and angular momentum H per unit mass. The six resulting equations are differentiated with respect to time to see the effect on the orbital elements of small changes in E and H. The usual perturbation equations in terms of disturbing force components are then derived by computing the manner in which perturbing forces change E and H. The results are applied in a qualitative discussion of the orbital evolution of particles in nonspherical gravitational fields, through atmospheres, and under the action of tides.
The thermostat—turn it down
Authors: Dowling John , Swartz Philip
Published: March 2005

The energy saved in turning the thermostat down overnight is examined. The model for the house is a 1500-ml water-filled beaker. The beaker is in an ice–water bath. The energy required to maintain the beaker at TH (20 °C), TL (15 °C), and to raise the temperature from TL to TH is determined. Times to cool and heat are noted. The data are extrapolated to fit typical house situations, and resultant energy savings are shown.
An approximate method for classical scattering problems
Authors: Fulcher L. P. , Davis B. F. , Rowe D. A.
Published: March 2005

An approximate method of calculating scattering cross sections is presented. Newton’s second law and the conservation of energy are used to relate the scattering angle to the impulse delivered to the projectile by the scatterer. In order to calculate the impulse, it is necessary to know the time dependence of the trajectory. We assume that the projectile travels the two asymptotes to the actual trajectory with constant velocity.
Neutron chemistry with a 252Cf fission source
Authors: Johnston Francis J.
Published: March 2005

Californium-252 in microgram quantities serves as a convenient and efficient laboratory neutron source for activation experiments. The properties of such sources are described. Experimental procedures and results are presented to illustrate the saturation of activity, half-life determination, simple γ spectra, and hot-atom chemistry.
Fluid dynamic phenomena can be demonstrated with stereo shadowgraphs of stratified fluid
Authors: McCutchen C. W.
Published: March 2005

Thermally stratified water has a refractive index that varies with height. If an object passes through the water, the waters part at its front and rejoin at the rear. The rejoining waters are seldom in perfect register vertically, so the surface of confluence between them is marked by a jump in temperature and therefore in refractive index, and is visible in shadowgraphic projection. Two shadowgraphs in stereo display the surface in three dimensions. If the shape and motion of any surfaces of confluence are known, the motion of the fluid everywhere else can be computed. The observer seems automatically to do this calculation approximately in his head. As a cheap, convenient, mathematically elegant, and psychologically natural way of displaying flow phenomena, the method should have a place in the teaching of hydrodynamics.
Teaching physical science from original sources by a discussion method
Authors: Nicola Michel
Published: March 2005

A general physical science course employing mainly original readings and taught primarily by the discussion method is described. A free type of discussion class seeking to stimulate learning is advocated in favor of direct teaching. While most of the effort is spent on basic scientific questions, these are studied for the insights they can provide the general student into the meaning of explanation, understanding, and reality.
On the generally covariant Dirac equation
Authors: Chapman Tim C. , Leiter Darryl J.
Published: March 2005

Using explicit tetrads for any given metric and Fock–Ivanenko coefficients of the generally covariant Dirac equation, we develop a formal method to relate the wave function in a noninertial frame to that in the inertial frame. The resulting equivalence transformations are exact. The familiar cases of the rotating frame and generalized hyperbolic motion are given as examples.
Student investigation of models for the drag force
Authors: Hart F. X. , Little C. A.
Published: March 2005

An experiment is described that allows students to compare the predictions of several models for the drag force with observations made in the laboratory. The students can determine the ranges of validity of the Stokes’s law and Newton’s law expressions for the drag force as well as discover the good agreement with experiment obtained by the numerical solution of the exact equation of motion. The computer program devised for this purpose can be used to simulate the motion of falling objects in situations not directly covered in the laboratory.
A physicist examines the Kennedy assassination film
Authors: Alvarez Luis W.
Published: March 2005

The motion picture film of the Kennedy assassination taken by Abraham Zapruder was one of the most important exhibits examined by the Warren Commission. The author uses the tools of the physicist to draw some conclusions that escaped the notice of the Commission and its expert FBI photointerpreters. Among the subjects treated are (1) the timing of the gun shots, (2) a theoretical and experimental investigation of the ’’backward snap’’ of the President’s head immediately after he was killed—yielding the surprising result that it was consistent with a shot fired from the rear, (3) the speed at which the camera was running, and (4) a previously undetected deceleration of the President’s automobile just before the final shot. The emphasis throughout is not on the assassination but rather on the application of elementary physics principles to the solution of practical problems.
Computer holograms with a desk-top calculator
Authors: Marsh James S. , Smith Richard C.
Published: March 2005

Computer-generated holograms have been produced on the plotter of an HP 9100B desk-top calculator. The use of simple stick objects allows us to calculate analytically the Fourier transform, the amplitude and relative phase of which are represented on the plot. Techniques for efficiency enhancement and saturation reduction are discussed.
Demonstration of physical optics with 1.0-cm wavelength
Authors: Andrews C. L.
Published: March 2005

We describe the construction of simple microwave sources of centimeter wavelength with bulk-effect diodes and accessory equipment for experiments and demonstrations in physical optics. A peculiar advantage of 1-cm wavelengths over the longer wavelengths is the high directivity of hand-sized parabolic reflectors. Thus we emphasize Fraunhofer diffraction. The collimator and telescope of a student spectrometer for light are replaced by a collimator and telescope for centimeter waves. We describe the construction of equipment for demonstrations with centimeter wavelengths on an overhead projector.