bluuebunny/crossref_metadata_2025 huggingface dataset:
Update on Clinical Trials of Tadalafil Demonstrates No Increased Risk of Cardiovascular Adverse Events
Authors: Jackson Graham , Kloner Robert A. , Costigan Timothy M. , Warner Margaret R. , Emmick Jeffrey T.
Published: September 2004

Introduction

Cardiovascular disease and erectile dysfunction (ED) share similar risk factors and often occur concomitantly. Therefore, men with ED may be at increased risk for cardiovascular adverse events.

Aim

The aim of this retrospective analysis was to evaluate the cardiovascular adverse events in clinical trials of tadalafil, an effective medication for the treatment of ED.

Methods

An integrated analysis of cardiovascular adverse events was performed on a database from 35 controlled clinical trials (placebo [N = 2,118] and tadalafil [N = 5,228]) and eight open-label trials of tadalafil (tadalafil [N = 6,939]). Some patients in controlled trials also received tadalafil in the open-label extension phase of four trials. Across all trials, the dose range of tadalafil was 2–25 mg, with the majority of patients receiving tadalafil 20 mg. This analysis represents an update of previous published results.

Results

In 35 controlled tadalafil clinical trials, the incidence of cardiovascular adverse events was low and comparable in tadalafil- and placebo-treated patients. The rate of myocardial infarction (MI) across all controlled and open-label studies was 0.33 per 100 patient-years in tadalafil-treated patients (N = 10,460, patient exposure = 5,088 patient-years). The MI rate in tadalafil-treated patients was comparable to that in placebo-treated patients (0.41 per 100 patient-years; N = 2,118; 489 patient-years), and to that in an age-standardized male population (0.6 per 100 patient-years). The cardiac mortality rate in tadalafil-treated patients across all studies (N = 10,460) was 0.12 per 100 patient-years which was not increased compared with the cardiac mortality rate of 0.26 per 100 patient-years reported in an age-standardized male population.

Conclusions

In tadalafil clinical trials, the incidence of cardiovascular adverse events in patients receiving tadalafil was low and comparable to placebo. Tadalafil did not increase the rate of MI or cardiac mortality compared with reported rates from epidemiological studies. This favorable cardiovascular safety profile for tadalafil is important, because men with ED commonly have cardiovascular disease and may seek medical therapy for ED.
Earliest Time to Onset of Action Leading to Successful Intercourse with Vardenafil Determined in an At-Home Setting: A Randomized, Double-Blind, Placebo-Controlled Trial
Authors: Montorsi Francesco , Padma-Nathan Harin , Buvat Jacques , Schwaibold Hartwig , Beneke Manfred , Ulbrich Ernst , Bandel Tiemo-Joerg , Porst Hartmut
Published: September 2004

Introduction

Vardenafil, a potent and selective oral PDE5 inhibitor, is efficacious and generally well-tolerated in men with erectile dysfunction (ED). Of considerable interest to patients and physicians is an understanding of the time required after dosing to attain penile erection sufficient for successful sexual intercourse.

Aim

To determine the earliest time to onset of action of vardenafil 10 and 20 mg leading to successful intercourse compared to placebo in men with ED.

Methods

A prospective, randomized, double-blind, parallel-group, at-home study of 732 men with ED (mean age 55.5 years) was conducted at 64 sites in North America and Europe. Following a 4-week run-in period, patients were randomized to either vardenafil 10 (N = 237) or 20 mg (N = 248) or placebo (N = 247) to be taken on demand over 4 weeks. Using a stopwatch, patients recorded the elapsed time from dosing to attainment of an erection perceived to be adequate for penetration that led to intercourse completion. Earliest time of onset was defined as the fastest time among the first four doses for each patient. Time points from 25 to 5 minutes were tested for significance (alpha = 0.025) using a backward stepping procedure.

Results

Mean baseline erectile function domain score (13.4) indicated moderate ED. Within 25 minutes after dosing, 50%/53% of men on vardenafil 10/20 mg had at least one erection in the first four doses perceived to be sufficient for penetration with subsequent intercourse completion compared to 26% on placebo (P < 0.0001). A statistically superior response to vardenafil vs. placebo was observed in these responders at all times ≥ 10 and ≥ 11 minutes (P < 0.025) in the 10 and 20 mg groups, respectively. In a retrospective analysis using time intervals of ≤ 15, ≤ 20, ≤ 25 and ≤ 30 minutes between dosing and erection adequate for penetration, 75–77% of these intercourse attempts were successful (SEP3 positive) by patients receiving vardenafil 10/20 mg, compared to 45–47% of attempts by those who received placebo. Vardenafil 10/20 mg was generally well-tolerated with headache (7%/12% vs. 1%) and flushing (6%/9% vs. < 1%) reported more frequently than with placebo. No patient discontinued vardenafil therapy due to adverse events.

Conclusion

In this large, at-home study, the onset of action of vardenafil with subsequent intercourse completion was recognized as early as 10 minutes after dosing.
Vardenafil Improves Patient Satisfaction with Erection Hardness, Orgasmic Function, and Overall Sexual Experience, While Improving Quality of Life in Men with Erectile Dysfunction
Authors: Donatucci Craig , Taylor Terry , Thibonnier Marc , Bangerter Keith , Gittelman Marc , Casey Richard
Published: September 2004

Purpose

The North American Pivotal Trial was designed to investigate the efficacy and safety of vardenafil in males with erectile dysfunction (ED).

Materials and Methods

In this randomized, double-blind, placebo-controlled, multicenter, fixed-dose, parallel group, 6-month study, vardenafil at three doses (5 mg, 10 mg, and 20 mg) was compared to placebo with the primary efficacy variables being the International Index of Erectile Function (IIEF) Erectile Function (EF) domain score and per patient diary response success rates for penetration and maintenance of erection through completion of intercourse. Additional efficacy variables included IIEF domain scores measuring intercourse satisfaction, orgasmic function, sexual desire, and overall satisfaction. Diary entries for overall per patient satisfaction rates for hardness and sexual experience were also measured. Improvements in quality of sexual life were assessed using the Fugl-Meyer quality of life (QoL) questionnaire.

Results

Compared to placebo, patients taking 10 mg and 20 mg doses of vardenafil showed statistically significantly greater improvement in IIEF domain scores measuring intercourse satisfaction (10.3 and 10.3 vs. 7.7), orgasmic function (7.1 and 6.9 vs. 5.3), overall satisfaction. (7.1 and 7.1 vs. 5.2) for vardenafil 10 mg and 20 mg vs. placebo, respectively, at last observation carried forward (LOCF). Vardenafil 5 mg was statistically significantly better than placebo for the secondary IIEF domain variables of intercourse satisfaction (8.9 vs. 7.7) and overall satisfaction (6.3 vs. 5.2) for vardenafil vs. placebo, respectively, at LOCF. Per patient satisfaction rates for the secondary diary variables measuring erection hardness (38%, 52%, 58% and 18%) and overall satisfaction (45%, 58%, 62% and 23%) were dose dependent and statistically significantly superior for vardenafil at 5 mg, 10 mg and 20 mg compared with placebo, respectively. Patients’ answers to the Fugl-Meyer QoL questionnaire assessing improvement in sexual life also indicated statistically significant superiority for all doses of vardenafil vs. placebo treatment. The most frequent adverse events (AE) in the 5 mg, 10 mg, and 20 mg of vardenafil and placebo groups, respectively, were: headache (10%, 22%, 21% and 4%), flushing (5%, 10%, 13% and 0%), dyspepsia (1%, 4%, 6% and < 1%), and rhinitis (9%, 14%, 17% and 5%). Most AEs were mild or moderate in severity and transient in nature.

Conclusion

Vardenafil was superior to placebo for IIEF domain scores, per patient success rates for diary questions, and assessment of quality of sexual life, in a broad range of patients with ED irrespective of etiology or severity. Vardenafil was generally well tolerated, with most AEs being mild or moderate in severity and transient in nature.
Determining the Earliest Time Within 30 Minutes to Erectogenic Effect After Tadalafil 10 and 20 mg: A Multicenter, Randomized, Double-Blind, Placebo-Controlled, At-Home Study
Authors: Rosen Raymond C. , Padma-Nathan Harin , Shabsigh Ridwan , Saikali Khalil , Watkins Vish , Pullman William
Published: September 2004

Introduction

Tadalafil is a phosphodiesterase 5 (PDE5) inhibitor used for the treatment of erectile dysfunction (ED). The minimal time to onset of erectogenic effect in the at-home setting has not been evaluated.

Aim

The goal was to determine the earliest time to erectogenic effect leading to successful intercourse within 30 minutes after taking tadalafil 10 and 20 mg.

Methods

The multicenter, randomized, double-blind, placebo-controlled, parallel-group, phase-2 study enrolled men at least 21 years old with a minimum 3-month history of ED. Four single doses each of placebo, tadalafil 10 mg, or 20 mg were taken at home once every 8–10 days. Using a stopwatch, couples recorded in Sexual Encounter Profile diaries the earliest time within 30 minutes after dosing to the first erection adequate for vaginal penetration, and whether the erection led to successful intercourse.

Main Outcome Measures

The primary analysis compared the percentage of erections resulting in successful intercourse between tadalafil groups and placebo at one-minute intervals using a step-down procedure. A secondary analysis compared the overall distribution of time to erectogenic effect between treatment groups using the Cox Regression Method.

Results

Compared to placebo, a significant erectogenic response to tadalafil 20 mg was found from 30 minutes down to 16 minutes after dosing (P = 0.012). Response to tadalafil 10 mg approached significance (P = 0.054) at 30 minutes. As analysed by the Cox Regression Method, a significant erectogenic response was found from 30 minutes down to 15 minutes after dosing for tadalafil 20 mg (P = 0.020), and from 30 minutes down to 26 minutes for tadalafil 10 mg (P = 0.042). Fifty-two percent of men taking tadalafil 20 mg had at least one successful intercourse attempt within 30 minutes compared to 35.1% of men taking placebo (P = 0.038).

Conclusions

This stopwatch-based study demonstrated a pharmacodynamic effect within 30 minutes after dosing for tadalafil 10 and 20 mg.
Efficacy and Safety of On-Demand Oral Tadalafil in the Treatment of Men with Erectile Dysfunction in Taiwan: A Randomized, Double-Blind, Parallel, Placebo-Controlled Clinical Study
Authors: Chen Kuang-Kuo , Jiann Bang-Ping , Lin Johnny Shinn-Nan , Lee Shang-Sen , Huang Shih-Tsung , Wang Chii-Jye , Ju-Ton Hsieh , Su Chung-Kuang , Costigan Timothy M. , Emmick Jeffrey T.
Published: September 2004

Introduction

Tadalafil is a phosphodiesterase type 5 inhibitor for the treatment of erectile dysfunction (ED). Past clinical trials have assessed its efficacy and safety in western populations. Tadalafil has not been investigated in a large clinical trial with a South-east Asian population.

Aim

To assess the efficacy and safety of on-demand tadalafil for the treatment of ED in a 12-week, double-blind, placebo-controlled study in Taiwan.

Methods

Men with mild to severe ED of various etiologies were randomized to receive placebo, tadalafil 10 mg, or tadalafil 20 mg, taken as needed (maximum once daily). Efficacy assessments included the International Index of Erectile Function, the Sexual Encounter Profile (SEP) diary, and a Global Assessment Question (GAQ).

Results

Tadalafil significantly improved erectile function compared with placebo (P < 0.005, all measures). At endpoint, the patients receiving tadalafil reported a greater mean per-patient percentage of successful intercourse attempts (SEP question 3: 70.0%, 10 mg; 78.0%, 20 mg) than placebo-treated patients (42.8%) and a greater proportion of improved erections (GAQ: 92.3% and 84.6% vs. 54.5%). Most treatment-emergent adverse events were mild or moderate. The most common adverse events were back pain, dyspepsia, and myalgia.

Conclusions

Tadalafil was an effective, well-tolerated therapy for men in Taiwan with ED of broad-spectrum severity and etiology.
Antibiotic Soaked Hydrophilic Coated Bioflex: A New Strategy in the Prevention of Penile Prosthesis Infection
Authors: Rajpurkar Atul , Fairfax Marilynn , Li Haikun , Dhabuwala Chirpriya B.
Published: September 2004

Objectives

To find conditions that reduce the susceptibility of penile prostheses to infection, we studied the effect of coating the surface of polyurethane (Bioflex) with a hydrophilic material with and without antibiotics in decreasing bacterial colony counts both in vitro and in experiments in rats.

Materials and Methods

The in vitro experiment was performed using seven strips each of polyvinylpyrrolidone (PVP)-coated and uncoated polyurethane. These strips were dipped in saline for 5 minutes followed by incubation in a suspension of Staphylococcus epidermidis (SE) for a period of 10 minutes. Colony counts were determined after sonication of strips. For the in vitro experiments, 60 rats were used. Thirty animals each had uncoated or coated polyurethane implanted subcutaneously. In each group, strips were implanted after dipping them in either saline (N = 15) or an antibiotic solution (N = 15) consisting of 1 g/L vancomycin and 160 mg/L gentamicin. A bacterial suspension containing SE was then directly introduced into the subcutaneous pockets of all the animals prior to closure. After 7 days, strips were explanted along with 0.5 × 0.5 cm of surrounding tissue, and sonicated. Colony counts were performed on each sonicate. The data were analysed using Student's t-test. A P-value less than or equal to 0.05 was considered to be statistically significant.

Results

The in vitro study demonstrated a statistically significant (41%) reduction in the colony count of SE within the coated polyurethane strips compared to the uncoated Bioflex strips (150 ± 44.7 CFU vs. 253 ± 45.0 CFU, respectively, P-value < 0.05). Animal studies showed that bacterial CFU was highest in the uncoated Bioflex strip (29 ± 24.5 CFU), followed by uncoated Bioflex with antibiotic treatment (24 ± 28.1 CFU), coated Bioflex (17 ± 25.2 CFU) and coated Bioflex with antibiotic treatment (13 ± 16.1 CFU). Antibiotic treatment of coated Bioflex caused a significant reduction in the bacterial CFU compared to uncoated Bioflex (13 ± 16.1 vs. 29 ± 24.5 CFU, respectively, P = 0.04). This represents a 55% reduction in the bacterial count. While the reduction in the bacterial count in the coated Bioflex strip was not statistically different from that in the uncoated strip, a trend towards significance was noted with a 41% reduction (P > 0.05) in bacterial count in the coated Bioflex group compared to uncoated Bioflex.

Conclusions

In conclusion, in vitro studies demonstrate a significant (41%) reduction in the colony count of SE in PVP-coated polyurethane compared to uncoated polyurethane. In vivo study in rats showed that antibiotic treatment of PVP-coated Bioflex resulted in a statistically significant reduction (55%) in colony count of SE compared to uncoated Bioflex.
The Hydrophilic-Coated Inflatable Penile Prosthesis: 1-Year Experience
Authors: Wolter Christopher E. , Hellstrom Wayne J.G.
Published: September 2004

Introduction

Penile prosthesis infections are a devastating complication for both patient and surgeon. Efforts to reduce the risk of infection from these elective procedures are a major focus of research and development by the major prosthesis companies. The Titan inflatable penile prosthesis (Mentor Corporation, Santa Barbara, CA) is coated with polyvinylpyrrolidone (PVP), a hydrophilic substance that reduces bacterial adherence and absorbs and elutes the antibiotics the device is immersed in intraoperatively. The Titan device was introduced to the American market in September 2002. This study reports the 1-year experience in the U.S. with the Titan and compares infection rates with the noncoated Alpha-1 IPP made by Mentor.

Materials and Methods

 Two thousand three hundred and fifty-seven Titan prostheses were implanted in the U.S. from September 2002 to August 2003, compared with the 482 noncoated Alpha-1 IPPs implanted over the same time period. Infection rates were compared, along with bacterial culture data. All data were collected from Mentor's internal database, as generated from the FDA's mandatory reporting of explanted medical devices, and available on the internet.

Results

The infection rate for the coated Titan IPP was 1.06% (25/2357). During the same time period, the infection rate for the Alpha-1 noncoated prosthesis was 2.07% (10/482). Staphylococcus species predominated in both groups (9/25 Titan, 6/10 Alpha-1).

Conclusions

At  1 year  of  follow-up,  the  data  demonstrate  that  the  hydrophilic  coating  on  the Titan IPP confers a significant advantage in reducing the rate of infection over the noncoated device. Long-term follow-up on this first year database is needed before this innovation is accepted as the standard of care for prosthetic surgery. Nevertheless, the theoretical reduction in bacterial adhesion conferred by the hydrophilic PVP surface and the ability to choose which antibiotic the device is immersed in intraoperatively gives the implanting surgeon distinct advantages with this new product.
Self-Reported Premature Ejaculation and Aspects of Sexual Functioning and Satisfaction
Authors: Rowland David , Perelman Michael , Althof Stanley , Barada James , McCullough Andrew , Bull Scott , Jamieson Carol , Ho Kai-Fai
Published: September 2004

Background

Although premature ejaculation (PE) is a common male sexual dysfunction, its relevant parameters have not been adequately studied in large community-based samples.

Objective

To examine the diagnostic utility of two self-report questions based on the DSM-IV-TR definition of PE and to investigate the relationship between self-identified PE, sexual functioning, and sexual satisfaction in men.

Methods

An Internet survey of general health and aspects of sexual functioning and satisfaction was conducted in 2056 males. Subjects were classified as having “probable” or “possible” PE, or as “non-PE” by survey responses.

Results

A total of 1158 men met the selection criteria (sexually active in a stable heterosexual relationship), and 189 (16.3%) were classified as having probable PE by reporting they ejaculated before they wished and indicating it was “very much” or “somewhat” a problem. Another 188 (16.2%) men reported ejaculating before they wished but rated their distress lower and were classified as having possible PE. Compared to non-PE men, those with probable and possible PE reported significantly worse sexual functioning in 6 of 8 study measures. Concern about partner satisfaction was high in all groups. The importance of ejaculatory control and the ability to have intercourse for the desired time was significantly higher in men with PE as compared to non-PE men (P < 0.01).

Conclusions

PE was a common problem, was characterized by a lack of ejaculatory control, and was associated with significant effects on sexual functioning and satisfaction. Additional research on the sensitivity and specificity of these self-report questions should be pursued.
Dimensionality and Validity of a Structured Telephone Reference Check Procedure
Authors: Taylor Paul J. , Pajo Karl , Cheung Gordon W. , Stringfield Paul
Published: September 2004

A structured telephone reference check (STRC) was developed to assess three job‐relevant personality/interpersonal dimensions (Conscientiousness, Agreeableness, customer focus) for a family of entry‐level, customer‐contact jobs within a service organization. The procedure was designed to be brief (a 10–15 minute telephone call with each referee) and easy to administer by untrained recruitment staff. Confirmatory factor analyses on referee ratings for 223 applicants indicated that referees were able to adequately discriminate between dimensions of applicants' past performance. A predictive, criterion‐related validation study on those applicants who were hired demonstrated that the STRC predicted supervisory ratings of job performance (r= .25, p < .01, uncorrected; .36 corrected for range restriction and criterion unreliability). No evidence was found that referees with shorter working relationships with applicants provided less valid ratings.
Muscle afferent contributions to the cardiovascular response to isometric exercise
Authors: Fisher James P. , White Michael J.
Published: September 2004

The cardiovascular response to isometric exercise is governed by both central and peripheral mechanisms. Both metabolic and mechanical stresses on the exercising skeletal muscle produce cardiovascular change, yet it is often overlooked that the afferent signal arising from the muscle can be modified by factors other than exercise intensity. This review discusses research revealing that muscle fibre type, muscle mass and training status are important factors in modifying this peripheral feedback from the active muscles. Studies in both animals and humans have shown that the pressor response resulting from exercise of muscle with a faster contractile character and isomyosin content is greater than that from a muscle of slower contractile character. Athletic groups participating in training programmes that place a high anaerobic load on skeletal muscle groups show attenuated muscle afferent feedback. Similarly, longitudinal studies have shown that specific local muscle training also blunts the pressor response to isometric exercise. Thus it appears that training may decrease the metabolic stimulation of muscle afferents and in some instances chronic exposure to the products of anaerobic metabolism may blunt the sensitivity of the muscle metaboreflex. There may be surprising parallels between the local muscle conditions induced in athletes training for longer sprint events (e.g. 400 m) and by the low‐flow conditions in, for example, the muscles of chronic heart failure patients. Whether their similar attenuations in muscle afferent feedback during exercise are due to decreased metabolite accumulation or to a desensitization of the muscle afferents is not yet known.
Effect of timing of iron supplementation on maternal and neonatal growth and iron status of iron‐deficient pregnant rats
Authors: Gambling L. , Andersen H. S. , Czopek A. , Wojciak R. , Krejpcio Z. , McArdle H. J.
Published: September 2004

We have previously shown that maternal iron (Fe) deficiency not only reduces fetal size, but also increases blood pressure in the offspring when they are adults. In this paper we examine whether there are critical periods when supplementation reverses or fails to reverse the effect both on size and on expression of genes of Fe metabolism. We made dams Fe deficient, mated them and provided supplements of Fe in the diet from the beginning of gestation (0.5 days), from 7.5 days or from 14.5 days. Within 12 h of birth, dams and neonates were killed and tissues taken and examined. Fe deficiency throughout pregnancy reduces neonatal size. Supplementation from the beginning of the first, second or third week all reduced the effect. Maternal haematocrit was restored to normal levels only in animals given supplements for at least 2 weeks. In contrast, the neonates' Fe levels were normal in all supplemented groups. These results were mirrored in liver Fe levels and in transferrin receptor mRNA. Iron‐responsive element (IRE)‐regulated divalent metal transporter 1 (DMT1) increased in maternal and neonatal liver. Non‐IRE‐regulated DMT1 levels did not change in the maternal liver, but decreased in the neonatal liver. H and L ferritin mRNA levels also showed different patterns in the mother and her offspring. Finally, the neonatal size correlated with maternal Fe stores, and not with those of the fetus. The data demonstrate that Fe supplementation during pregnancy is most effective when given early, rather than later, in gestation.
Calcium channels activated by endothelin‐1 in human trophoblast
Authors: Niger C. , Malassiné A. , Cronier L.
Published: September 2004

Ca2+ transfer across the syncytiotrophoblast (ST) of the human placenta is essential for normal fetal development. However, the nature of Ca2+ conductance in the ST and the mechanisms by which it is regulated are poorly understood. With the major signal transduction pathway of endothelin‐1 (ET1) acting via phospholipase C (PLC) and Ca2+, we used ET1 to analyse the nature of Ca2+ channels on cultured trophoblastic cells by means of cytofluorimetric analysis using the ratiometric Ca2+ indicator Indo‐1. Results indicate that ET1 (10−7m) stimulates a biphasic (transient and sustained) increase in [Ca2+]i in trophoblastic cells. This response is mediated by the endothelin receptor B (ETB) coupled to PLC, since treatment with BQ788 (10−6m) or U73122 (2 μm) totally abolished the response. Persistence of the rapid transient rise in [Ca2+]i in Ca2+‐free extracellular medium confirms the release of Ca2+ from intracellular stores in response to ET1 stimulation. Furthermore, abolition of the sustained increase in [Ca2+]i in Ca2+‐free extracellular medium argues in favour of the entry of Ca2+ during the plateau phase. Abolition of this plateau phase by Ni2+ (1 mm) in the presence of extracellular Ca2+ confirmed the existence of an ET1‐induced Ca2+ entry. No evidence for the presence of voltage‐operated channels was demonstrated during ET1 action since nifedipine (10−6m) did not reduce the Ca2+ response and depolarization with a hyper‐potassium solution had no effect. Pharmacological studies using the imidazole derivatives SK&F96365 (30 μm) and LOE 908 (10 μm) partially inhibited the ET1‐evoked Ca2+ response, thus providing evidence for the presence of both store‐operated Ca2+ channels and non‐selective cationic channels in the human ST.
A Two-Temperature Model for the Analysis of Passive Thermal Control
Systems
Authors: Krishnan Shankar , Murthy Jayathi Y. , Garimella Suresh V.
Published: September 2004

Passive control of steady and unsteady thermal loads using effective thermal conductivity enhancers, such as metal foams, internal fins and metal filler particles, is being explored for a variety of electronics applications. The interstices are filled with air, phase change materials, or other fluids. Local thermal equilibrium between the solid filler and the matrix is not ensured in such systems since their thermal diffusivities are frequently very different. The use of a single volume-averaged energy equation for both the phases cannot be justified in such situations. A two-medium approach is used in the present work to account for the local thermal non-equilibrium. Separate energy equations are written for the solid and fluid respectively, and are closed using a steady-state interphase heat transfer coefficient between the two phases. A general momentum equation which includes the Brinkman-Forchheimer extension to Darcy flow is employed. The resulting equations are solved implicitly using a fully transient method on fixed orthogonal co-located finite volumes. Unsteady natural convection in a metal-foam filled cavity is computed. The influence of various parameters such as the ratios of solid-to-fluid thermal conductivities and heat capacities, Rayleigh number, Prandtl number and Darcy number on the thermal and flow fields is investigated. The results illustrate that local thermal equilibrium is not assured, either during the transient or at steady state for the range of parameters considered. Furthermore, even if the steady-state solid-to-fluid temperature differences are small, large temperature differences are seen during the unsteady response.
Melting Heat Transfer Characteristics of Microencapsulated Phase
Change Material Slurries With Plural Microcapsules Having Different Diameters
Authors: Inaba Hideo , Kim Myoung-Jun , Horibe Akihiko
Published: September 2004

The present study has been performed for obtaining the heat transfer enhancement characteristics of the plural microencapsulated solid-liquid phase change materials (PCM) slurry having different sizes, which flows in a straight tube heated under a constant wall heat flux condition. In the turbulent flow region, the friction factor of the plural PCM slurry was found to be lower than that of pure water flow due to the drag reducing effect of the PCM slurry. The heat transfer coefficient of the plural PCMs slurry flow in the tube was increased by both effects of latent heat evolved in phase change process and micro-convection around plural microcapsules with different diameters. The experimental results revealed that the average heat transfer coefficient of the plural PCMs slurry flow was about 2∼2.8 times greater than that of a single phase of water.
Experimental Investigation of the Potential of Metallic Porous
Inserts in Enhancing Forced Convective Heat Transfer
Authors: Pavel Bogdan I. , Mohamad Abdulmajeed A.
Published: September 2004

The present experimental work investigates the effect of a metallic porous matrix, inserted in a pipe, on the rate of heat transfer. The pipe is subjected to a constant and uniform heat flux. The effects of porosity and thickness of the porous matrix on the heat transfer rate and pressure drop are investigated. That is, the surface temperature distribution along a heated section of the pipe, the pressure drop over this section, as well as the inlet temperature of the air were continuously monitored with a data acquisition system and recorded when steady-sate conditions were attained. The results obtained for a range of Reynolds numbers 1000–4500, comprise both laminar and turbulent regime. Also, the results are compared with the clear flow case where no porous insert was used. It is shown that higher heat transfer rates are achieved when using porous inserts at the expense of a reasonable pressure drop, which depends on the permeability of the porous matrix.
Effect of Squealer Geometry on Tip Flow and Heat Transfer for a
Turbine Blade in a Low Speed Cascade
Authors: Saxena Vikrant , Ekkad Srinath V.
Published: September 2004

A detailed investigation on the effect of squealer geometries on the blade tip leakage flow and associated heat transfer is presented for a scaled up high pressure turbine blade in a low-speed wind tunnel facility. The linear cascade is made of four blades with the two corner blades acting as guides. The tip profile of a first stage rotor blade is used to fabricate the two-dimensional blade. The wind tunnel accommodates an 116° turn for the blade cascade. The mainstream Reynolds number based on the axial chord length based on cascade exit velocity is 4.83×105. An upstream wake effect is simulated with a spoked wheel wake generator placed upstream of the cascade. A turbulence grid placed even farther upstream generates a free-stream turbulence of 4.8%. The center blade has a tip clearance gap of 1.56% with respect to the blade span. Static pressure measurements are obtained on the blade surface and the shroud. Results show that the presence of the squealer alters the tip gap flow field significantly and produces lower overall heat transfer coefficients. The effects of different squealer arrangements are basically to study the effect of squealer rim placement on tip leakage flow and associated heat transfer. Detailed heat transfer measurements are obtained using a steady state liquid crystal technique. The effect of periodic unsteady wake effect is also investigated by varying the wake Strouhal number from 0–0.4. Results show that suction side squealers may be favorable in terms of overall reduction in heat transfer coefficients over the tip surface. However, the presence of a full squealer is most beneficial in terms of reducing overall heat load on the tip surface. There is reasonable effect of wake induced periodicity on tip heat transfer.
An Experimental Investigation of Flow Boiling Characteristics of Water in Parallel Microchannels
Authors: Steinke Mark E. , Kandlikar Satish G.
Published: September 2004

Microchannels are being considered in many advanced heat transfer applications including automotive and stationary fuel cells as well as electronics cooling. However, there are a number of fundamental issues from the heat transfer and fluid mechanics perspectives that still remain unresolved. The present work focuses on obtaining the fundamental heat transfer data and two-phase flow patterns present during flow boiling in microchannels. An experimental investigation is performed for flow boiling using water in six parallel, horizontal microchannels with a hydraulic diameter of 207 μm. The ranges of parameters are: mass flux from 157 to 1782 kg/m2s, heat flux from 5 to 930 kW/m2, inlet temperature of 22°C, quality from sub-cooled to 1.0, and atmospheric pressure at the exit. The corresponding single-phase, all-liquid flow Reynolds number range at the saturation conditions is from 116 to 1318. The measured single-phase, adiabatic pressure drop agreed with the conventional theory within the experimental error. The experimental single-phase Nusselt number was found to be between the constant heat flux and the constant wall temperature boundary conditions, corresponding to NuH and NuT respectively. The flow visualization demonstrates that the flow reversal condition in parallel flow channels is due to bubble nucleation followed by its rapid growth. In addition, the dry-out condition is observed, showing a change in the contact angles of the liquid-vapor interface. The local flow boiling heat transfer coefficient exhibits a decreasing trend with increasing quality. A comparison with the nucleate boiling dominant regime of a flow boiling correlation shows good agreement, except for the large peak in two-phase heat transfer coefficient observed at the onset of nucleate boiling.
A new approach to Monte Carlo simulations in statistical physics: Wang-Landau sampling
Authors: Landau D. P. , Tsai Shan-Ho , Exler M.
Published: September 2004

We describe a Monte Carlo algorithm for doing simulations in classical statistical physics in a different way. Instead of sampling the probability distribution at a fixed temperature, a random walk is performed in energy space to extract an estimate for the density of states. The probability can be computed at any temperature by weighting the density of states by the appropriate Boltzmann factor. Thermodynamic properties can be determined from suitable derivatives of the partition function and, unlike “standard” methods, the free energy and entropy can also be computed directly. To demonstrate the simplicity and power of the algorithm, we apply it to models exhibiting first-order or second-order phase transitions.
All-reflective automated beam alignment device for ultrafast lasers
Authors: Anderson Matt , Ward Catherine
Published: September 2004

We present a novel device for automatically aligning laser beams using two quadrature photodiodes set immediately behind slightly transparent mirrors. The system utilizes feedback electronics and a LABVIEW program to automatically align an ultrafast laser quickly and accurately, even in the presence of gross thermal warping of the optical table. The design and implementation of this device is straightforward, making it an ideal research project for undergraduate students.
What do students really learn from interactive multimedia? A physics case study
Authors: Yeo Shelley , Loss Robert , Zadnik Marjan , Harrison Allan , Treagust David
Published: September 2004

Interactive multimedia is promoted as an effective and stimulating medium for learning science, but students do not always interact with multimedia as intended by the designers. We discuss students’ interactions with an interactive multimedia program segment about projectile motion in the context of long jumping. Qualitative data were collected using a video camera and split-screen recorder to record each student’s image, voice, and student–program interactions. Left to themselves, students’ interactions were superficial, but when asked to explain their observations of projectile motion illustrations, they were observed to retain common intuitive conceptions. Only following researcher intervention did students develop an awareness of abstract aspects of the program. These results suggest that, despite interactivity and animated graphics, interactive multimedia may not produce the desired outcome for students learning introductory physics concepts.
Nibbling at A/D in introductory electronics
Authors: Donnelly Denis
Published: September 2004

Circuits for four-bit digital/analog (D/A) and analog/digital (A/D) converters, suitable for the laboratory of an introductory electronics course, are provided. By placing variable resistors in the D/A circuit, students have some control over the step sizes in the conversion process. A component level A/D provides students an opportunity to directly observe the steps in the conversion process.
An elementary treatment of the reverse sprinkler
Authors: Jenkins Alejandro
Published: September 2004

We discuss the reverse sprinkler problem: How does a sprinkler turn when submerged and made to suck in water? We propose a solution that requires only a knowledge of mechanics and fluid dynamics at the introductory university level. We argue that as the flow of water starts, the sprinkler briefly experiences a torque that would make it turn toward the incoming water, while as the flow of water ceases it briefly experiences a torque in the opposite direction. No torque is expected when water is flowing steadily into it unless dissipative effects, such as viscosity, are considered. Dissipative effects result in a small torque that would cause the sprinkler arm to accelerate toward the steadily incoming water. Our conclusions are discussed in light of an analysis of forces, conservation of angular momentum, and the experimental results reported by others. We review the conflicting published treatments of this problem, some of which have been incorrect and many of which have introduced complications that obscure the basic physics involved.
Quantum mysteries revisited again
Authors: Aravind P. K.
Published: September 2004

This paper describes a device, consisting of a central source and two widely separated detectors with six switch settings each, that provides a simple gedanken demonstration of the nonclassical correlations that are the subject of Bell’s theorem without relying on either statistical effects or the occurrence of rare events. The mechanism underlying the operation of the device is revealed for readers with a knowledge of quantum mechanics.
Discovery-based Gauss’s law
Authors: Schneider Mark B.
Published: September 2004

The mathematical parallels between electrostatics and laminar fluid flow are exploited to develop a set of problems that lead introductory physics students to discover Gauss’s law. The primary fluid experiment involves examining the flow between two closely spaced plates and the continuity equation in two dimensions. The extrapolation of the two-dimensional velocity field to three dimensions yields a radial dependence that is analogous to Coulomb’s law. This analogy allows the student to predict an electrical version of the continuity equation equivalent to Gauss’s law.
On negative streamers: A deterministic approach
Authors: Arrayás Manuel
Published: September 2004

The formation of streamers and spontaneous branching is commonly observed in dielectric breakdown phenomena. We discuss a deterministic streamer model that explains branching phenomena in terms of a Laplacian instability similar to that found in viscous fingering. Particular attention is paid to the physical interpretation of the model.
Swimming in Newtonian space–time: Orbital changes by cyclic changes in body shape
Authors: Longo Michael J.
Published: September 2004

I investigate whether, in the context of Newtonian physics, a satellite can change its orbit by cyclic shape changes without any external forces other than gravity. This question has been discussed in the context of general relativity, and Wisdom has estimated that a swimmer near the surface of the Earth using meter-sized deformations can achieve a displacement of ∼10−23 m. I show that much larger displacements, ∼10−7 m, can occur for a Newtonian swimmer. Such a swimmer can change its orbit by rotating about its center of mass and trading chemical, solar, or other energy for orbital energy, without the need for any propellant.
Time-reversal breaking of acoustic waves in a cavity
Authors: Bertaix Vincent , Garson Julien , Quieffin Nicolas , Catheline Stefan , Derosny Julien , Fink Mathias
Published: September 2004

Acoustic time-reversal is a well-established technique that focuses an ultrasonic wave on the location of its source. It is based on the time-reversal invariance of the wave equation and is usually implemented using time-reversal mirrors made up of a hundred of piezoelectric transducers. However, a time-reversal experiment can be performed in a closed cavity (a water-filled beaker) with only one transducer as a pulse-echo system. This easy-to-build and low cost experiment involves students in the general concept of the time-reversal invariance of the wave equation. We show that it also can be adapted to become an ultrasonic time-reversal thermometer. A careful study of the focal point shows a dependence of its position as a function of temperature variations.
The physical limits of communication or Why any sufficiently advanced technology is indistinguishable from noise
Authors: Lachmann Michael , Newman M. E. J. , Moore Cristopher
Published: September 2004

It has been well known since the pioneering work of Claude Shannon in the 1940s that a message transmitted with optimal efficiency over a channel of limited bandwidth is indistinguishable from random noise to a receiver who is unfamiliar with the language in which the message is written. We derive some similar results about electromagnetic transmissions. In particular, we show that if electromagnetic radiation is used as a transmission medium, the most information-efficient format for a given message is indistinguishable from blackbody radiation. The characteristic temperature of the radiation is set by the amount of energy used to make the transmission. If information is not encoded in the direction of the radiation, but only in its timing, energy, and polarization, then the most efficient format has the form of a one-dimensional blackbody spectrum.
Exploring factors affecting measurements of the static coefficient of friction: An application of fractional factorial experiment design
Authors: Folkerts Timothy J.
Published: September 2004

The common undergraduate experiment for determining the static coefficient of friction between a wooden block and a horizontal tabletop often produces inconsistent results. We show how several factors influence the measured magnitude and consistency of the coefficient of friction. We utilize a fractional factorial experimental design, which is a method that has been specifically developed to effectively and efficiently uncover key factors that most strongly influence experimental results.
Photolithographic fabrication of diffraction and interference slit patterns for the undergraduate laboratory
Authors: Slogoff Harriet , Mackowiak Jeff , Shishkov Milen , Johnson Alan T.
Published: September 2004

Measuring the interference and diffraction patterns produced by light passing through single and double narrow slits is a classic undergraduate physics experiment that dramatically confirms the wave nature of light. Despite this critical educational role, the experiment often is problematic because of the failings of commercially available slit patterns which produce faint unconvincing projected patterns. We discuss a low cost photolithographic process that produces diffraction slits in a chromium film deposited on a glass substrate. Slit dimensions as small as 4 μm are attainable with this method with complete control over the spacing of double slits. The method also can be used to expand the variety of slit patterns to two-dimensional arrays and circular patterns.
Reflection of light from a uniformly moving mirror
Authors: Gjurchinovski Aleksandar
Published: September 2004

We derive a formula for the law of reflection of a plane-polarized light beam from an inclined flat mirror in uniform rectilinear motion by applying the Huygens–Fresnel principle. We then use this formula and the postulates of special relativity to show that the moving mirror is contracted along the direction of its motion by the usual Lorentz factor. The result emphasizes the reality of Lorentz contraction by showing that the contraction is a direct consequence of the first and second postulates of special relativity, and is not a consequence of the relativistic measurement of the length.
Einstein’s mirror and Fermat’s principle of least time
Authors: Gjurchinovski Aleksandar
Published: September 2004

We derive a formula for the reflection of light from a uniformly moving mirror based on Fermat’s principle of least time.
Inflammatory Exposure and Historical Changes in Human Life-Spans
Authors: Finch Caleb E. , Crimmins Eileen M.
Published: September 2004

Most explanations of the increase in life expectancy at older ages over history emphasize the importance of medical and public health factors of a particular historical period. We propose that the reduction in lifetime exposure to infectious diseases and other sources of inflammation—a cohort mechanism—has also made an important contribution to the historical decline in old-age mortality. Analysis of birth cohorts across the life-span since 1751 in Sweden reveals strong associations between early-age mortality and subsequent mortality in the same cohorts. We propose that a “cohort morbidity phenotype” represents inflammatory processes that persist from early age into adult life.
Living with the Past: Evolution, Development, and Patterns of Disease
Authors: Gluckman Peter D. , Hanson Mark A.
Published: September 2004

Epidemiological observations have led to the hypothesis that the risk of developing some chronic noncommunicable diseases in adulthood is influenced not only by genetic and adult life-style factors but also by environmental factors acting in early life. Research in evolutionary biology, developmental biology, and animal and human physiology provides support for this idea and suggests that environmental processes influencing the propensity to disease in adulthood operate during the periconceptual, fetal, and infant phases of life. This “developmental origins of health and disease” concept may have important biological, medical, and socioeconomic implications.
Direct Sub-Angstrom Imaging of a Crystal Lattice
Authors: Nellist P. D. , Chisholm M. F. , Dellby N. , Krivanek O. L. , Murfitt M. F. , Szilagyi Z. S. , Lupini A. R. , Borisevich A. , Sides W. H. , Pennycook S. J.
Published: September 2004

Despite the use of electrons with wavelengths of just a few picometers, spatial resolution in a transmission electron microscope (TEM) has been limited by spherical aberration to typically around 0.15 nanometer. Individual atomic columns in a crystalline lattice can therefore only be imaged for a few low-order orientations, limiting the range of defects that can be imaged at atomic resolution. The recent development of spherical aberration correctors for transmission electron microscopy allows this limit to be overcome. We present direct images from an aberration-corrected scanning TEM that resolve a lattice in which the atomic columns are sepa-rated by less than 0.1 nanometer.