Calibration of an electroacoustic transducer without a primary standard.

The Reflections series takes a look back on historical articles from The Journal of the Acoustical Society of America that have had a significant impact on the science and practice of acoustics.

The application of acoustics to heat engines and refrigerators.

The Reflections series takes a look back on historical articles from The Journal of the Acoustical Society of America that have had a significant impact on the science and practice of acoustics.

Using the Design Environment for Low-amplitude Thermoacoustic Energy Conversion in the Classroom.

The Design Environment for Low-amplitude Thermoacoustics Energy Conversion (DeltaEC) is a free software package that is capable of modeling quasi-one-dimensional, multi-domain acoustical networks and includes a 300-page users' guide. The program is a versatile differential equation solver that analyzes a series of "segments" representing ducts, compliances, speakers, etc., that are specified using MKS units. DeltaEC can be a useful pedagogical tool for an introductory course on acoustics in fluids. Examples of its instructional applications include illustration of effective length and quality factor for a Helmholtz resonator and the modes of coupled Helmholtz resonators, as well as standing waves within a resonator of variable cross section and within a catenoidal horn driven by an electrodynamic loudspeaker. Segments representing electrodynamic loudspeakers, radiation loading, and flow resistance in porous media will be used to demonstrate the coupled-oscillatory behavior of a bass-reflex enclosure's complex electrical impedance versus frequency. DeltaEC's plotting features allow immediate visualization of the pressure and velocity fields as well as the power flow or temperature distribution through a network or within a resonator, horn, or waveguide. The "thermo-physical property" feature provides fluid and solid properties at the students' choice of pressure, temperature, and frequency, making it useful as a "handbook" for other assignments.

Periodic self-modulation of an electrodynamically driven heated wire near resonance.

A thin nichrome wire driven near resonance by the Lorentz force and heated by an alternating electrical current is a popular lecture demonstration. Due to the convective cooling of the portions of the wire moving with the greatest amplitude, only glowing regions near a velocity node will be visible in a darkened room. Nonlinear effects and the thermal expansion coefficient of the wire displace the wire's tensioning mass. By adiabatic invariance, the work done on or by the vibrating wire, due to the changes in the mass's elevation, causes the natural frequency of the standing wave resonance to be shifted. Competition between the thermal inertia of the wire and the convective heat transfer coefficient introduces an exponential thermal relaxation time so that the amplitude of vibration is dependent on the ratio of the drive frequency to the changing resonance frequency at an earlier (retarded) time. These thermal and kinetic effects are incorporated into three coupled nonlinear ordinary differential equations that are separated by the method of multiple time scales and are solved numerically, reproducing both the spontaneous appearance of stable periodic amplitude modulation and the hysteretic behavior observed with increasing or decreasing of the drive frequency.

Dynamic stabilization of the Rayleigh-Bénard instability by acceleration modulation.

This paper presents the results of an experimental investigation of the parametric stabilization of Rayleigh-Bénard convection through the imposition of sinusoidal vibration. The ability to dynamically stabilize Rayleigh-Bénard convection using acceleration modulation is of interest to groups who design and study thermoacoustic machines as the introduction of parasitic convection can have deleterious effects on the desired operation and thermodynamic efficiency of the device. These performance issues caused by suspected convective instability have been seen both in traveling wave thermoacoustic refrigerators and cryogenic pulse tube chillers. This paper reports the results of an experiment intended to determine the vibratory, fluidic, and geometric conditions under which a small, rectangular container of statically unstable fluid may be stabilized by vertical vibration with comparison to the computational methods of R. M. Carbo [J. Acoust. Soc. Am. 135, 654-668 (2014)]. Measurements are obtained using a large-displacement kinematic shaker of an original design with the convecting gas characterized using both thermal transport measurements and flow visualization employing tracer particles illuminated by a diode laser light sheet phase-locked to the shaker. These experiments are believed to be the first demonstrating the suppression of convection through vibration in rectangular containers.

Note: A kinematic shaker system for high amplitude, low frequency vibration testing.

This note describes a shaker system capable of high peak-velocity, large amplitude, low frequency, near-sinusoidal excitation that has been constructed and employed in experiments on the inhibition of Rayleigh-Bénard convection using acceleration modulation. The production of high peak-velocity vibration is of interest in parametric excitation problems of this type and reaches beyond the capabilities of standard electromagnetic shakers. The shaker system described employs a kinematic linkage to two counter-rotating flywheels, driven by a variable-speed electrical motor, producing peak-to-peak displacements of 15.24 cm to a platform mounted on two guide rails. In operation, this shaker has been demonstrated to produce peak speeds of up to 3.7 m/s without failure.

Steady-state kinetic characterization of sesquiterpene synthases by gas chromatography-mass spectroscopy.

Sesquiterpene synthases produce a wide variety of structurally diverse hydrocarbon products from a single substrate: farnesyl pyrophosphate. Each enzyme will often produce a multitude of products for which the kinetic efficiency is traditionally measured using a radioactivity assay. Here, we introduce a gas chromatography-mass spectroscopy-based assay to measure the formation of a single abundant product from which the kinetic parameters of the enzyme in question can be elucidated. We present an accounting of experimental components and considerations, such as solution conditions and instrument parameters, necessary to perform a standardized vial assay experiment. Further, we outline pilot experiments to establish analyte quantification and the linear range of enzyme concentration versus reaction velocity. Finally, we describe a protocol for a steady-state kinetics experiment, and the processing of experimental data to produce a Michaelis-Menten plot enabling one to derive kinetic parameters.

Transcriptional organization and physiological contributions of the relQ operon of Streptococcus mutans.

The molecular alarmone (p)ppGpp functions as a global regulator of gene expression in bacteria. In Streptococcus mutans, (p)ppGpp synthesis is catalyzed by three gene products: RelA, RelP, and RelQ. RelA is responsible for (p)ppGpp production during a stringent response, and RelP is the primary source of (p)ppGpp during exponential growth, but the role of RelQ has not been thoroughly investigated. In this study, we analyzed the four-gene relQ operon to establish how these gene products may affect homeostasis and stress tolerance in the dental caries pathogen S. mutans. Northern blotting and reverse transcriptase PCR demonstrated that relQ is cotranscribed with the downstream genes ppnK (NAD kinase), rluE (pseudouridine synthase), and pta (phosphotransacetylase). In addition, a promoter located within the rluE gene was shown to drive transcription of pta. Inactivation of relQ, ppnK, or rluE did not significantly affect growth of or stress tolerance by S. mutans, whereas strains lacking pta were more sensitive to acid and oxidative stresses. Interestingly, introduction of an rluE deletion into the pta mutant reversed the deleterious effects of the pta mutation on growth and stress tolerance. Accumulation of (p)ppGpp was also decreased in a pta mutant strain, whereas inactivation of relQ caused enhanced (p)ppGpp synthesis in exponential-phase cells. The results reveal an important role for the relQ operon in the expression of traits that are essential for persistence and pathogenesis by S. mutans and provide evidence for a molecular connection of acetate and (p)ppGpp metabolism with tolerance of acid and oxidative stresses.

Reduction of two red complex bacteria by sustained-release doxycycline and correlation to improvement in mean pocket depth.

OBJECTIVE: The objective was to evaluate the effects of an 8.5% sustained-release doxycycline-containing polymer formulation (SRDF) on deep pockets (pocket depth [PD] ≥ 7 mm) in chronic periodontitis. Total bacterial counts were used to estimate the number of viable bacteria present before treatment and for up to 6 months posttreatment. METHODS: All sites had PD ≥ 5 mm and bled on probing in 23 subjects who received treatment with SRDF. There was an average of 8.7 teeth or 23 sites for each subject. One deep pocket (≥ 7 mm) in each subject was selected for monitoring. This site was sampled prior to treatment and at 7, 21, 91, and 182 days after SRDF placement. The primary endpoints were changes in the viable counts of two red complex species, Porphyromonas gingivalis and Tannerella forsythia. Secondary endpoints were changes in the number of total anaerobic bacteria recovered and changes in PD. RESULTS: Relative to baseline, SRDF reduced the proportions of P. gingivalis and T. forsythia by 88% and 99%, respectively, at day 7. At the conclusion of the monitoring period--182 days--P. gingivalis and T. forsythia were present but at 19% to 20% of the pretreatment values. Total anaerobic counts were reduced by 96% at day 7; by 87% at day 21; and by 75% and 68% at days 91 and 182, respectively. Mean PD for the sample sites (initially ≥ 7 mm) was reduced 2 mm by day 21, and this difference persisted throughout the study. CONCLUSIONS: This study demonstrates SRDF has a significant effect, not only statistically but also microbially and clinically, on deep periodontal sites in patients with chronic periodontitis. SRDF significantly reduced the number of red complex bacteria P. gingivalis and T. forsythia, as well as the number of total anaerobic bacteria. By day 21, PD was reduced by 2 mm, and this reduction was maintained for at least 6 months posttherapy.

Dapsone gel 5% in combination with adapalene gel 0.1%, benzoyl peroxide gel 4% or moisturizer for the treatment of acne vulgaris: a 12-week, randomized, double-blind study.

PURPOSE: To evaluate the safety and efficacy of dapsone gel 5% in the treatment of acne when used in combination with adapalene gel 0.1%, benzoyl peroxide gel 4% or moisturizer. METHODS: This was a twelve-week, randomized, double-blind study. Patients aged 12 years and older (n=301) applied dapsone gel twice daily and were randomly assigned (1:1:1) to one of three additional treatments, applied once daily. RESULTS: By week 12, dapsone gel combined with any of the three additional treatments reduced the mean number of inflammatory lesions. However, the authors did not detect a significant difference in the reduction of inflammatory lesions when dapsone was used in combination with adapalene gel or with benzoyl peroxide gel compared to the dapsone plus moisturizer combination group (P=0.052 for both versus moisturizer combination). Patients treated with dapsone gel combined with adapalene showed a significantly better response in reduction in non-inflammatory and total acne lesion count than those who received the moisturizer combination. Local adverse reactions in all three treatment groups were minimal and generally mild in severity. CONCLUSION: Dapsone gel in combination with adapalene gel or benzoyl peroxide gel is safe and well tolerated for the treatment of acne vulgaris.

Efficacy and safety of dapsone gel 5% for the treatment of acne vulgaris in adolescents.

Two 12-week, randomized, vehicle-controlled. double-blinded pivotal studies and a 12-month. long-term, open-label, noncomparative safety study were conducted to evaluate the efficacy and safety of dapsone gel 5% in patients with acne vulgaris. Of 3516 participants enrolled in the 3 trials, 1306 participants (37%) were adolescents aged 12 to 15 years and comprised the subgroup reported here. Participants randomly were assigned to twice-daily treatment with dapsone gel (n=578) or vehicle gel (n=547) in the pivotal studies and received open-label treatment with dapsone gel in the long-term safety study (n=181). In the pivotal studies, success based on achieving a Global Acne Assessment Score (GAAS) of 0 (none) or 1 (minimal) at week 12 was significantly greater for the dapsone gel-treated adolescent participants (40.1%; 232/578) compared with the vehicle gel-treated adolescent participants (28.2%; 154/547) (P<.001). Treatment with dapsone gel in adolescents also resulted in clinically meaningful improvements in acne lesion counts by week 12 in the pivotal studies and for up to 12 months in the long-term safety study. The incidence of adverse events, including application-site events, was low and similar between treatment groups in the pivotal studies and was similarly low in the long-term safety study. Results from the large number of adolescent participants in these 3 studies show that dapsone gel is an effective and safe topical therapy for the treatment of acne vulgaris in adolescents aged 12 to 15 years for up to 12 months.

Dapsone gel 5% for the treatment of acne vulgaris: safety and efficacy of long-term (1 year) treatment.

Dapsone gel 5%, a topical formulation of dapsone, was shown to deliver clinically effective doses of dapsone with minimal systemic absorption in 2 randomized, vehicle-controlled, 12-week studies of patients with acne vulgaris. A 12-month, open-label, long-term safety study further evaluated the safety and efficacy of dapsone gel. Patients at least 12 years of age with acne vulgaris (N = 486) applied dapsone gel twice daily for up to 12 months. Application site reactions related to treatment were reported in 8.2% of the patients and were mostly mild to moderate in severity. Common nonapplication site adverse events included headache (20%) and nasopharyngitis (15%). No significant changes in hematology or blood chemistry parameters were observed. At one month, mean reduction from baseline in inflammatory lesion counts was 30.6%. At 12 months, mean reduction from baseline was 58.2%, 19.5%, and 49.0% for inflammatory, noninflammatory, and total lesion counts, respectively, (all P=.002 compared to baseline). These results show that dapsone gel 5% is safe and effective for long-term treatment of acne vulgaris and has a rapid onset of action.

Pharmacokinetics of dapsone gel, 5% for the treatment of acne vulgaris.

BACKGROUND: Oral dapsone has been available for over 60 years and has been used to treat severe acne vulgaris; however, the oral formulation is known to cause dose-dependent haematological reactions and is currently indicated only for diseases such as dermatitis herpetiformis and Hansen's disease. A gel formulation of dapsone was recently developed to treat acne vulgaris. As dapsone is administered topically, it was expected that systemic absorption would be considerably lower than that observed with oral dapsone therapy, thereby avoiding any adverse haematological effects. OBJECTIVE: To report the pharmacokinetic profile of topically applied dapsone gel, 5% in the treatment of acne vulgaris. STUDY PARTICIPANTS AND METHODS: Three prospective, open-label studies enrolled a total of 548 subjects with acne vulgaris: two phase I pharmacokinetic studies (crossover and drug interaction) and one phase III long-term safety study. In the crossover study (n = 18), topical dapsone gel applied twice daily for a total of 14 days to 22.5% of the body surface area was compared with a single dose of oral dapsone 100mg (the typical clinical dose). In the drug-interaction study (n = 24), oral trimethoprim/sulfamethoxazole monotherapy, topical dapsone gel monotherapy and the two in combination were used twice daily for 7, 21 and 7 days, respectively. In the long-term safety study (n = 506), topical dapsone gel was applied twice daily to acne-affected areas for up to 12 months. Blood samples were drawn at various timepoints in each study to assess drug and metabolite concentrations. Systemic concentrations of dapsone, N-acetyl dapsone, dapsone hydroxylamine, trimethoprim and sulfamethoxazole were determined, according to the study design. RESULTS: In the crossover study, the mean area under the plasma concentration-time curve (AUC) from 0 to 24 hours for dapsone was 417.5 ng x h/mL after 2 weeks of dapsone gel therapy (n = 10), compared with an AUC from time zero to infinity of 52,641 ng x h/mL after a single dose of oral dapsone; this represents a 126-fold lower systemic exposure for dapsone gel at typical therapeutic doses. In the drug-interaction study, the AUC from 0 to 12 hours for dapsone was 221.52 ng x h/mL after 3 weeks of dapsone gel monotherapy compared with 320.3 ng x h/mL after 1 week of coadministration with trimethoprim/sulfamethoxazole. In the long-term safety study, the mean plasma dapsone concentrations ranged from 7.5 to 11 ng/mL over 12 months. Overall, total systemic exposures to dapsone and its metabolites were approximately 100-fold less for dapsone gel than for oral dapsone, even in the presence of trimethoprim/sulfamethoxazole. There were no reports of any haematological adverse events. CONCLUSIONS: Topical application of dapsone gel in various settings ranging from 2 weeks to 12 months resulted in systemic exposures to dapsone and its metabolites that were approximately 100-fold less than those after oral dapsone at a therapeutic dose level. The concentrations of dapsone and its metabolites reached steady state and did not increase during prolonged treatment.

Two randomized studies demonstrate the efficacy and safety of dapsone gel, 5% for the treatment of acne vulgaris.

BACKGROUND: A new aqueous gel formulation of dapsone has been developed that allows clinically-effective doses of dapsone to be administered topically with minimal systemic absorption. OBJECTIVES: The goal of these studies was to evaluate the efficacy and safety of dapsone gel, 5% in the treatment of acne. METHODS: Patients 12 years of age and older with acne vulgaris (N = 3010) participated in two identically-designed 12-week, randomized, double-blind studies of twice-daily monotherapy with dapsone gel, 5%, versus a vehicle gel. RESULTS: Dapsone gel-treated patients achieved superior results in terms of the investigator's global acne assessment (P < .001) and the mean percentage reduction in inflammatory, noninflammatory, and total lesion counts (all, P < .001) at week 12. Reductions in inflammatory lesion counts favoring dapsone gel over vehicle were apparent as early as 2 weeks and reached statistical significance by 4 weeks. No clinically significant changes in laboratory parameters, including hemoglobin, even among glucose-6-phosphate dehydrogenase-deficient patients, were observed. Adverse events were comparable between the treatment groups and rarely led to discontinuation. LIMITATIONS: Adjunctive topical treatments and their impact on acne were not studied in this trial. CONCLUSIONS: Dapsone gel, 5% appears to be an effective, safe, and well-tolerated treatment for acne vulgaris, with a rapid onset of action.

Crusotomy: a safe, simple surgical technique to facilitate resection and reconstruction of poorly accessible auricular tumors.

BACKGROUND: Carcinomas of the ear are commonly referred to Mohs surgeons because of their tendency for subclinical spread and location in poorly accessible anatomic areas. A simple technique, the crusotomy, is described that improves access to superior conchal lesions, facilitating resection of these tumors and repair of their resultant defects. OBJECTIVE: To describe a surgical technique, the crusotomy, which facilitates the resection and repair of poorly accessible auricular tumors. METHODS: Five patients with superior conchal tumors are presented who underwent crusotomy before resection of their tumors. All patients had immediate reconstruction of the resultant defect with either local flaps or grafts and were seen in follow-up at 1-week and 1-month intervals. RESULTS: Excellent cosmetic results were obtained in all five patients with no postoperative complications. CONCLUSION: Crusotomy is a safe, rapid, and simple technique that facilitates the resection and repair of poorly accessible auricular tumors.

Local antimicrobial therapy after initial periodontal treatment.

AIM: The aim of this single-blind, randomized, parallel-designed clinical trial (RCT) was to evaluate the clinical and microbiological effects of three sustained-release biodegradable polymers delivered into periodontal pockets following initial periodontal therapy. METHODS: Forty-seven patients (28 females and 19 males) with a mean age of 51 years (range 29-71) underwent a periodontal examination at baseline (i.e. Week 0) and after 18 weeks. This included the assessment of the Plaque Index (PlI), Bleeding on Probing (BOP), Pocket Probing Depths (PPD) and Probing Attachment Levels (PAL) at six sites per tooth. Two to 4 months prior to baseline, all subjects had received initial periodontal therapy including motivation, instruction in oral hygiene practices and full-mouth scaling and root planing. At the treatment appointment (i.e. Week 2), the patients were randomly assigned to receive either Atridox trade mark, Elyzol Dental Gel or PerioChip at all residual periodontal pockets with a probing depth >/= 5 mm and concomitant BOP. In accordance with the manufacturer's recommendations, Elyzol Dental Gel was applied for a second time 7 days later. In addition to the clinical evaluation, subgingival microbiological samples were collected prior to treatment (i.e. Week 2) and at Weeks 4 and 18. Analysis of variance/covariance was used to evaluate changes from baseline to Week 18 for the clinical parameters. RESULTS: Between the baseline and 18-week examinations, subjects treated with Atridox showed a significantly greater gain in mean PAL of 0.33 mm +/- 0.09 (SD) than subjects treated with Elyzol Dental Gel [0.03 mm +/- 0.09 (SD)](p = 0.03). However, the gain in PAL of 0.16 mm +/- 0.10 (SD) found after PerioChip application did not differ significantly from that obtained following the application of Atridox(p = 0.27). Of the sites treated with Atridox, 42% gained >/= 1 mm PAL and 9% >/= 2 mm PAL as opposed to the sites treated with Elyzol Dental Gel, in which 34% gained >/= 1 mm PAL and 8% gained >/= 2 mm PAL. Of the sites treated with PerioChip, 36% gained >/= 1 mm and 6% gained >/= 2 mm PAL following a completed initial periodontal therapy. CONCLUSIONS: The application of the three biodegradable sustained release devices tested following initial periodontal therapy resulted in a statistically significant gain in mean PAL for AtridoxTM and a significant reduction in PPD for all three devices during the study period. Furthermore, when sites treated with Atridox were compared with sites treated with Elyzol, a significant difference in mean PAL gain (0.3 mm) was observed.