bluuebunny/crossref_metadata_2025 huggingface dataset:
Evidence for ultrafast outflows in radio-quiet AGNs — III. Location and energetics
Authors: Tombesi F. , Cappi M. , Reeves J. N. , Braito V.
Published: February 2012

Using the results of a previous X-ray photoionization modelling of blueshifted Fe K absorption lines on a sample of 42 local radio-quiet AGNs observed with XMM—Newton, in this Letter we estimate the location and energetics of the associated ultrafast outflows (UFOs). Due to significant uncertainties, we are essentially able to place only lower/upper limits. On average, their location is in the interval ∼0.0003–0.03 pc (∼ 102–104rs) from the central black hole, consistent with what is expected for accretion disc winds/outflows. The mass outflow rates are constrained between ∼0.01 and 1 M⊙ yr−1, corresponding to >rsim5–10 per cent of the accretion rates. The average lower/upper limits on the mechanical power are log ĖK ≃ 42.6–44.6 erg s−1. However, the minimum possible value of the ratio between the mechanical power and bolometric luminosity is constrained to be comparable or higher than the minimum required by simulations of feedback induced by winds/outflows. Therefore, this work demonstrates that UFOs are indeed capable to provide a significant contribution to the AGN cosmological feedback, in agreement with theoretical expectations and the recent observation of interactions between AGN outflows and the interstellar medium in several Seyfert galaxies.
Outcomes of the West Australian school healthy food and drink policy
Authors: PETTIGREW Simone , PESCUD Melanie , DONOVAN Robert J.
Published: February 2012

Aim:  The introduction of the Healthy Food and Drink Policy in Western Australian government schools caused controversy. Of particular concern were anticipated financial difficulties associated with replacing high‐margin processed foods with healthier foods that may be more labour intensive and expensive. The present study investigated the outcomes for school canteens to assess whether these concerns were realised.

Methods:  A multi‐method approach was used to obtain data from school principals. Ten principals participated in individual interviews and 310 (44% response rate) responded to an online survey.

Results:  A majority of the study participants reported a favourable attitude to the Policy, both prior to and after its introduction. Most participants perceived improvements in the healthiness and quality of canteen menu items as a result of the Policy. There was a significant increase in the number of school canteens reporting break‐even (19% to 28%), a non‐significant decrease in the number being in profit (57% to 48%), and a non‐significant increase in the number of canteens reporting a loss (10% to 16%). These results appear to be largely the result of higher‐than‐CPI (consumer price index) increases in food prices and a reluctance to pass these increases on to canteen users.

Conclusions:  The results are encouraging in the light of the new National Healthy School Canteen Guidelines. Efforts to improve children's food environments may attract criticism from a vocal minority, but are likely to receive support from key stakeholders.
Increasing dietetic referrals: Perceptions of general practitioners, practice nurses and dietitians
Authors: MITCHELL Lana J. , MACDONALD‐WICKS Lesley , CAPRA Sandra
Published: February 2012

Aim:  To examine Australian private practice dietitians' relationships with general practitioners and practice nurses as a factor that influences dietetic referrals.

Methods:  Semistructured telephone interviews and an online survey were conducted with Australian private practice dietitians (n = 52 and n = 90, respectively) between April and May 2008. Semistructured questionnaires were conducted with general practitioners (n = 11) and practice nurses (n = 12) from the ‘GP Access’ Division of General Practice between March and July 2007.

Results:  General practitioners' relationships with dietitians were believed to be the primary influencing factor on referral, provided by 81% of survey dietitians and 25% of interview dietitians. The most common means of initially forming relationships with general practitioners were face‐to‐face introduction (48%) and introductory letters (37%). Patient feedback via letter, fax or email was the most popular method of maintaining relationships with general practitioners (77%). Meeting with general practitioners in person was believed to be the most effective activity in building relationships with general practitioners and increasing referral rates (42%). Referral was made easier for general practitioners by providing paper (37%) or electronic (19%) referral forms and contact details (19%). The majority of general practitioners and dietitians believed that the ‘Allied Health Services Under Medicare’ made it easier to refer to a dietitian.

Conclusions:  Dietetic referrals can be encouraged through good relationships between general practitioners, practice nurses and dietitians. Private practice dietitians would benefit from cultivating relationships with general practitioners and practice nurses through personal contact and providing good patient feedback.
Syntheses of Chiral N‐(Protected) Tri‐ and Tetrapeptide Conjugates
Authors: Bajaj Kiran , Panda Siva S. , El‐Nachef Claudia , Katritzky Alan R.
Published: February 2012

Cbz‐(protected)‐tri‐ and tetrapeptide conjugates with steroids, sugars, terpenes, and heterocycles were prepared using Cbz‐(protected)‐tri‐ and tetrapeptidoylbenzotriazoles as active intermediates.
Course of pandemic influenza A(H1N1) 2009 virus infection in Dutch patients
Authors: Friesema Ingrid H. M. , Meijer Adam , van Gageldonk‐Lafeber Arianne B. , van der Lubben Mariken , van Beek Janko , Donker Gé A. , Prins Jan M. , de Jong Menno D. , Boskamp Simone , Isken Leslie D. , Koopmans Marion P. G. , van der Sande Marianne A. B. ,   Dutch ZonMw Influenza A(H1N1) 2009 consortium
Published: February 2012

Please cite this paper as: Friesema et al. (2012). Course of pandemic influenza A(H1N1) 2009 virus infection in Dutch patients. Influenza and Other Respiratory Viruses 6(3), e16–e20.

The clinical dynamics of influenza A(H1N1) 2009 infections in 61 laboratory‐confirmed Dutch cases were examined. An episode lasted a median of 7·5 days of which 2 days included fever. Respiratory symptoms resolved slowly, while systemic symptoms peaked early in the episode and disappeared quickly. Severity of each symptom was rated highest in the first few days. Furthermore, diarrhoea was negatively associated with viral load, but not with faecal excretion of influenza virus. Cases with comorbidities appeared to have higher viral loads than the cases without, suggesting a less effective immune response. These results complement information obtained through traditional surveillance.
Generation of Ensemble Streamflow Forecasts Using an Enhanced Version of the Snowmelt Runoff Model1
Authors: Harshburger Brian J. , Walden Von P. , Humes Karen S. , Moore Brandon C. , Blandford Troy R. , Rango Albert
Published: February 2012

Harshburger, Brian J., Von P. Walden, Karen S. Humes, Brandon C. Moore, Troy R. Blandford, and Albert Rango, 2012. Generation of Ensemble Streamflow Forecasts Using an Enhanced Version of the Snowmelt Runoff Model. Journal of the American Water Resources Association (JAWRA) 48(4): 643‐655. DOI: 10.1111/j.1752‐1688.2012.00642.x

Abstract:  As water demand increases in the western United States, so does the need for accurate streamflow forecasts. We describe a method for generating ensemble streamflow forecasts (1‐15 days) using an enhanced version of the snowmelt runoff model (SRM). Forecasts are produced for three snowmelt‐dominated basins in Idaho. Model inputs are derived from meteorological forecasts, snow cover imagery, and surface observations from Snowpack Telemetry stations. The model performed well at lead times up to 7 days, but has significant predictability out to 15 days. The timing of peak flow and the streamflow volume are captured well by the model, but the peak‐flow value is typically low. The model performance was assessed by computing the coefficient of determination (R2), percentage of volume difference (Dv%), and a skill score that quantifies the usefulness of the forecasts relative to climatology. The average R2 value for the mean ensemble is >0.8 for all three basins for lead times up to seven days. The Dv% is fairly unbiased (within ±10%) out to seven days in two of the basins, but the model underpredicts Dv% in the third. The average skill scores for all basins are >0.6 for lead times up to seven days, indicating that the ensemble model outperforms climatology. These results validate the usefulness of the ensemble forecasting approach for basins of this type, suggesting that the ensemble version of SRM might be applied successfully to other basins in the Intermountain West.
Influence of children's oral health‐related quality of life on school performance and school absenteeism
Authors: Piovesan Chaiana , Antunes José Leopoldo Ferreira , Mendes Fausto Medeiros , Guedes Renata Saraiva , Ardenghi Thiago Machado
Published: February 2012

Objective: This study assessed the relation of child oral health‐related quality of life with school performance and school absenteeism.

Methods: We followed a cross‐sectional design with a multistage random sample of 312 12‐year‐old schoolchildren living in Brazil. The participants completed the child perceptions questionnaire (CPQ11–14) that provides information about psychological factors, while their parents or guardians answered questions on their socioeconomic status measured by parents' education level and household income. A dental examination of each child provided information on the prevalence of caries and dental trauma. Data on school performance, which included the results of baseline Brazilian language (Portuguese) tests, and school absenteeism (school days missed) were obtained from the school register. Multilevel linear regression was used to investigate the association among psychological and socioeconomic status and children's school performance.

Results: In the multiple model, after adjusting for individual covariates, being a girl was associated with higher school performance (P < 0.05), whereas low household income (P < 0.05), higher mean of CPQ11–14 (P < 0.05), and higher school days missed (P < 0.001) were identified as individual determinants of lower school performance. When the school‐level covariates were included in the model, the association between subjects' level characteristics and school performance still persisted.

Conclusion: Children's school performance and absence were influenced by psychological and socioeconomic conditions.
Outcomes of patients with first‐episode schizophrenia at one‐year follow‐up: Findings from theNationalMentalHealthRegistry inMalaysia
Authors: Chee Kok‐Yoon , Muhammad Dain Norsiatul Azma , Abdul Aziz Salina , Syed Mokhtar Sharifah Suziah , Mat Junus Mazni , Zam Zam Ruzanna , Yahya Badiah , Cheah Yee‐Chuan
Published: February 2012

Introduction

This first outcome study for people with first‐episode schizophrenia (FES) inMalaysia was based on data collected from theNationalMentalHealthRegistry (NMHR). The aim of the study was to assess the outcome of patients diagnosed with schizophrenia, one year after contact with mental health services; and to evaluate treatments as well as the utilization of medical and other services in the country.

Methods

All patients withFESregistered inNMHRbetween 1March 2004 and 28February 2005 were included and 79 centers carried out outcome assessments. Socio‐demographic and clinical data were collected and compared with the data inNMHRthat was gathered one year ago. Descriptive statistic was used to analyze the data.

Results

Of 2604 registered patients withFES, only 37.7% had their outcomes successfully assessed. Among those assessed, 25.5% were lost to follow‐up and 45.8% were followed‐up in different centers. Only two patients committed suicide. Increases in weight gain and body mass index were major concerns. On a positive note, employability improved. Forty percent of the patients had their antipsychotics changed over the one‐year period but about 20% of patients were on polytherapy at baseline and after one year. The use of anticholinergic medication dropped remarkably after the one‐year treatment period.

Discussion

This study has shown that one of the great barriers in conducting a nationwide outcome assessment ofFESpatients was the high attrition rate. Nevertheless, these findings provided an important glimpse into the socio‐demographic and clinical outcomes of the patients.
Association between long‐term aspirin use and periodontal attachment level in humans: a cross‐sectional investigation
Authors: Faizuddin M , Tarannum F , Korla N , Swamy S
Published: February 2012

Background:  Pharmaceutical inhibition of host response pathways may be an adjunctive or alternative strategy for treating periodontal diseases. In addition to inhibition of prostaglandin synthesis, aspirin is known to modify the action of cyclo‐oxygenase, changing its activity to a lipoxygenase and leading to formation of lipoxins which have a proresolving effect. This study evaluated the periodontal attachment level of subjects on long‐term low dose aspirin therapy.

Methods:  Oral hygiene index simplified, clinical attachment loss and bleeding index were recorded for 162 subjects who were on long‐term (>6 months) low dose (75 mg and 150 mg) aspirin therapy (study group) and 146 subjects not taking the drug (control group).

Results:  Mean clinical attachment loss was 2.38 ± 0.49 mm in the control group and 2.01 ± 0.69 mm in the study group. The difference was statistically significant at p < 0.001. Correlation analysis suggested that there was a negative correlation between clinical attachment loss and duration of aspirin intake but the clinical attachment loss was not significantly different in the two dosage groups.

Conclusions:  The results of this study suggest that low dose aspirin may reduce the risk of periodontal attachment loss. This hypothesis needs to be tested by larger sample sized prospective cohort studies.
Splenic artery ligation: A protection against hepatic ischemia/reperfusion injury in partially hepatectomized rats
Authors: Irie Takumi , Ito Koji , Ozasa Hisashi , Noda Yumi , Ikeda Satoru , Tanaka Shinji , Arii Shigeki , Horikawa Saburo
Published: February 2012

Aim:  In liver resection, the temporary occlusion of the hepatoduodenal ligament (Pringle maneuver) is often used. However, the maneuver causes ischemia/reperfusion (I/R) injury in the remnant liver. Heme oxygenase (HO)‐1 has a cytoprotective role against this injury. Our aim is to investigate whether splenic artery ligation induces HO‐1 expression in the liver and ameliorates the hepatic I/R injury in partially hepatectomized rats.

Methods:  Rats underwent splenic artery ligation by occluding the main splenic artery. Two days later, the total hepatic ischemia (Pringle maneuver) was conducted, and then a two‐thirds partial hepatectomy (PH) was performed just before the start of reperfusion. HO inhibitor was twice injected s.c. at 3 and 16 h before the Pringle maneuver. HO‐1 levels were determined by western blotting. Liver injury was biochemically assessed.

Results:  In normal rats, HO‐1 was highly expressed in the spleen, but not in the liver. Splenic artery ligation induced HO‐1 in the livers. When rats underwent 20 and 30 min of Pringle maneuver/PH, survival rates were 28% and 8%, respectively. Splenic artery ligation significantly improved both the survival rates: 73% and 56%, respectively. Under these conditions, administration of HO‐1 inhibitor at least partly negated the efficacy of splenic artery ligation. Splenic artery ligation also increased the recovery rate of the remnant liver mass and platelet counts in Pringle maneuver/PH‐treated rats.

Conclusion:  Splenic artery ligation was significantly effective on the hepatic I/R injury in partially hepatectomized rats. Induction of HO‐1 may be at least partly involved in the improvement of this injury.
The Combined Prognostic Potential of Serum High‐Sensitivity Cardiac Troponin I and N‐Terminal pro‐B‐Type Natriuretic Peptide Concentrations in Dogs with Degenerative Mitral Valve Disease
Authors: Hezzell M.J. , Boswood A. , Chang Y.‐M. , Moonarmart W. , Souttar K. , Elliott J.
Published: February 2012

Background

Identification of factors associated with decreased survival in dogs with degenerative mitral valve disease (DMVD) will allow more accurate prognosis. N‐terminal pro‐B‐type natriuretic peptide (NT‐proBNP) is negatively associated with survival in dogs with DMVD. In human patients, multimarker strategies provide superior risk stratification compared with single markers.

Hypothesis

High‐sensitivity cardiac troponin I (hscTnI) and other clinical variables will be associated with survival time in dogs with DMVD. Measuring hscTnI and NT‐proBNP in combination will be prognostically superior to measurement of either marker alone. The rate of change of these markers will vary according to cause of death.

Animals

Client‐owned dogs (n = 202) with DMVD of varying severity and age‐matched healthy control dogs (n = 30) recruited from first opinion private practice.

Methods

Prospective cohort study relating clinical variables at enrollment in dogs with DMVD to survival time (all‐cause, cardiac, and noncardiac mortality). Multivariable Cox regression analysis was used to identify factors associated with survival. Measurements were obtained approximately every 6 months. Repeated measures models were constructed to assess changes over time.

Results

hscTnI, LVEDDN, heart rate, and age were independently associated with decreased survival time (all‐cause mortality). Survival times were shortest in dogs in which both serum hscTnI and NT‐proBNP were increased. hscTnI and NT‐proBNP increased more rapidly in dogs that died of cardiac disease.

Conclusions and Clinical Importance

Serum hscTnI has prognostic value in dogs with DMVD. Measurement of NT‐proBNP and hscTnI is prognostically superior to measuring either alone. Serial measurement strategies provide additional prognostic information.
Effects of the source of social comparison information on former cancer patients’ quality of life
Authors: Brakel Thecla M. , Dijkstra Arie , Buunk Abraham P.
Published: February 2012

Objective. Life, following curative treatment, can be a struggle for former cancer patients. In this phase of their illness, social comparison information may help to improve a patient's quality of life (QOL). The objective of this study was to determine whether the effects of this information depend on the following two variables: (1) the individual's physical health and (2) the individual's sensitivity to social comparison.

Design. In the current study, the effects on a patient's QOL were tested that occur when they are listening to a psychological oncological expert talking about cancer patients’ experiences. Three different recorded interviews with experts were compared (on negative emotions, effective coping, or both), and individual differences were tested as moderators. In addition, the expert source conditions were compared with a condition in which the source was not an expert but a former patient.

Methods. In a randomized field experiment, 154 Dutch former cancer patients (Mage= 55 years; 68% women) were assigned to one of the four conditions (three expert source and one former patient source condition). QOL was assessed after 2 months.

Results. The effects of the expert source conditions on QOL depended on the participants’ physical health (good vs. poor) and on the participants’ sensitivity to social comparison (whether the recipient reacts with contrast or identification), as indicated by significant three‐way interactions (p < .001). Depending on these two variables, one of the three expert source conditions was at least as effective as the former patient source condition.

Conclusions. The results show that desired and undesired effects are found when individual differences relevant to the processing of intervention information are examined.

Statement of contribution

What is already known on this subject? 

It is known that social comparison processes are important determinants of emotions and QoL. In addition, research has shown that QoL in (former) cancer patients is lowered and interventions are needed.

What does this study add? 

This study showed that the application of social comparison as a method to increase QoL in cancer patients can be beneficial: It showed that applying the auditory channel, in which the expert source becomes more prominent, is effective. In addition, the study illustrates that psycho‐social interventions can have side‐effects; a phenomenon that has hardly been addressed in the literature and in practice.
P2Y1 purinoreceptors are fundamental to inhibitory motor control of murine colonic excitability and transit
Authors: Hwang Sung Jin , Blair Peter J. , Durnin Leonie , Mutafova‐Yambolieva Violeta , Sanders Kenton M. , Ward Sean M.
Published: February 2012

Key points 

Normal colonic motility is regulated by excitatory and inhibitory motor neurons, and previous studies have shown that both components of neural regulation are important for normal propulsion of colonic contents.

Inhibitory neural control consists of two main components, and the major neurotransmitters have been identified as nitric oxide and purines; we investigated the nature of the receptors responsible for purine inhibitory motor control of the colon using mice with P2Y1 receptors deactivated.

Inhibitory control of the colon by purine neurotransmitters was dramatically decreased in these animals and transit of fecal pellets was delayed.

Inhibitory responses to purine neurotransmission and exogenous β‐NAD, a neurotransmitter candidate, were completely abolished in P2Y1 receptor knockouts.

These studies demonstrate the importance of purinergic neural regulation of colonic motility and suggest this form of neural regulation depends upon P2Y1 receptors to receive and transduce inhibitory neural signals.
Embryonic assembly of auditory circuits: spiral ganglion and brainstem
Authors: Marrs Glen S. , Spirou George A.
Published: February 2012

Key points 

Neural activity in sensory systems is important for proper assembly of neural circuits during early development.

In the auditory system, the timing for functional synapse formation and reliance of central circuit formation on peripherally generated activity are unknown.

We used a novel whole‐head slice preparation and genetically labelled auditory neurons to provide the first assay of cells at embryonic ages and reveal a peripheral‐to‐central maturation sequence.

Auditory nerve fibres generate spontaneous action potentials by embryonic day 14 and drive third order central neurons by embryonic day 17, nearly 2 weeks before hearing onset.

This information provides a timeline for initial auditory circuit assembly and the basis to explore mechanisms for initial sensory circuit assembly.
An Aspect of Heat Transfer in Accelerating Turbulent Boundary Layers
Authors: Launder B. E. , Lockwood F. C.
Published: February 2012

Theoretical consideration indicates that, in an accelerated turbulent flow, the thermal boundary layer may penetrate significantly beyond the edge of the velocity boundary layer. This effect may contribute in part to the marked decrease in Stanton number which has been reported in accelerated turbulent boundary layers. This paper presents theoretical solutions to turbulent velocity and thermal boundary layers in flow between converging planes where the wall temperature varies as the free-stream velocity raised to a positive exponent. The solutions clearly illustrate that, as the wall-temperature variation is made less rapid, the thermal boundary layer penetrates progressively further beyond the velocity boundary layer, causing the Stanton number to decrease.
Forced Laminar Flow Convection in a Horizontal Tube With Variable Viscosity and Free-Convection Effects
Authors: Shannon R. L. , Depew C. A.
Published: February 2012

The influence of free convection and variable viscosity on forced laminar flow of ethylene glycol initially at 32 deg F was investigated. The flow was horizontal in a circular tube with uniform wall heat flux and a fully developed velocity profile at the onset of heating. Local measurements were made for the calculation of Nusselt number, Reynolds number, Prandtl number, and Grashof number. Reynolds numbers ranged from 6 to 300, Grashof numbers ranged up to 2800, Prandtl numbers ranged from 26 to 500, and Graetz numbers ranged from 3 to 4800. The theoretical analysis established that the conditions for fully developed flow in the absence of free convection require an exponential variation of viscosity with temperature and that Nu and (dp/dx) are functions of Gz and viscosity ratio, μw/μb, only for both the developing and the fully developed region for this viscosity variation. Numerical results for flow and heat transfer which are in agreement with experiment were also obtained. Further substantiation of the free-convection parameter Ra1/4/Nu(Gz) was obtained.
Mass-Transfer Model in Subcooled Nucleate Boiling
Authors: Snyder N. W. , Robin T. T.
Published: February 2012

The mass-transfer model of subcooled boiling, conceived in 1952 by N. W. Snyder, is reviewed. Described is an experiment in which a water-vapor bubble was studied from its growth on a heated surface, through a thermal layer, and into a turbulent stream of subcooled water flowing parallel to the heated surface. The effectiveness of the turbulent subcooled stream in removing heat deposited by condensation on the surface of the bubble was determined. The results show that the thermal-energy transport associated with the mass-transfer mechanism in boiling heat transfer can be absorbed effectively at the top of the bubble. Also given are the results of a theoretical investigation in which two models of bubble dynamics were derived. The first model describes the artificial bubble produced in the experiment just noted. The second model describes the dynamics of a bubble growing on a heated surface, into a subcooled liquid, and with an evaporating thin liquid film below the bubble on the heated surface. The results show that the importance of the mass-transfer mechanism has been underestimated in the past and that this mechanism is responsible for a substantial portion, or almost all, of the heat transfer in subcooled nucleate boiling in forced convection.
Effect of Vortices Induced by Corona Discharge on Free-Convection Heat Transfer From a Vertical Plate
Authors: Franke M. E.
Published: February 2012

Experimental results are presented to show that columnar, counterrotating, vertical vortices can be produced on a heated, vertical, flat plate under free-convection conditions in air using a high-voltage d-c electric field. The vortices result from the corona discharge on 0.002-in.-dia parallel wires of alternate high voltage and ground potential placed vertically on the surface of a phenolic laminate plate. Heat-transfer rates are measured using an energy-balance method, and the thermal boundary layer is made visible using a Mach-Zehnder interferometer. Experimental curves are presented to illustrate the increase in the heat-transfer rate with increase in the electric-field power. Interference photographs and frames from a motion picture show the effects of the vortices on the thermal boundary layer. The convective part of the heat transfer from the 10 × 10 in. plate is more than doubled before the electric-field power becomes as large as 5 percent of the increase in the heat-transfer rate. Local heat-transfer rates are highest at the high-voltage wires and lowest at the grounded wires.
Temperature Distributions in Solid and Hollow Cylinders Due to a Moving Circumferential Ring Heat Source
Authors: Watts R. G.
Published: February 2012

Analytical solutions are presented for temperature distributions in solid and hollow cylinders which are due to a moving circumferential ring heat source. These heat transfer problems arise in practice in metal cutting. Solutions are obtained by the use of finite Hankel transforms.
Void Fractions in Subcooled Flow Boiling
Authors: Larsen P. S. , Tong L. S.
Published: February 2012

A semianalytic model is presented for the prediction of void fractions in subcooled flow boiling at elevated pressures. The model is based on the formation and growth of a bubble boundary layer adjacent to the heated surface at a rate determined by the difference between the imposed surface heat transfer and the heat removal capability of the subcooled liquid core of the flow. The latter heat transfer rate is determined by the analogy between heat and momentum transfer in the liquid employing empirical friction-factor data for low-quality two-phase flow. The analysis is compared to experimental results.
Some Correlations for Resistances to Heat and Momentum Transfer in the Viscous Sublayer at Rough Walls
Authors: Sood N. S. , Jonsson V. K.
Published: February 2012

Functions for the resistance to heat and momentum transfer in the region near the wall have been defined for flows with various geometries, and correlations from available literature on rough wall friction and heat transfer have been made for these functions. The functions may then be used in the expressions for velocity and temperature profiles to solve the turbulent boundary-layer equations for flows over rough surfaces. Roughnesses such as those formed by machined grooves, piston-rings, wires, and three-dimensional elements have been included in the correlations.
On the Stability of Slip Flows in Parallel Heated Passages
Authors: Rhodes C. A.
Published: February 2012

Rarified flows in heated passages are shown to have instabilities under certain conditions similar to those occurring with laminar continuum flows. As in the case of continuum flows these instabilities occur where the rate of change of pressure drop with mass flow rate at constant heat input is negative. As gases become more highly rarified, the slope of the pressure drop with flow rate no longer becomes negative and flows are stable. Stability regions are defined by the ratio of outlet to inlet temperature, Knudsen number at the inlet to the passage, and the product of Reynolds number at the inlet and diameter-to-length ratio.
Interacting Effects of Geometry and Gravity Upon the Extreme Boiling Heat Fluxes
Authors: Lienhard John H.
Published: February 2012

Previous studies of the dynamic and thermodynamic similarity of the peak and minimum pool boiling heat fluxes provide a basis for correlating variable-gravity data. This method is explained and applied to existing data. The dependence of the extreme heat fluxes upon g1/4, developed by Zuber for the flat plate geometry, is shown to be inapplicable in other geometries.
The Unidimensional Solidification of a Binary Eutectic System With a Time-Dependent Surface Temperature
Authors: Tien R. H. , Geiger G. E.
Published: February 2012

The realistic boundary condition of the surface temperature varying with time is used in the heat transfer analysis of the solidification of a binary eutectic alloy system. The system occupies a semi-infinite region and consists of a solid zone, a freezing zone, and a liquid zone. The heat released in the freezing zone is treated as a discontinuous heat generation. The solid-fraction distribution in the freezing zone, given as a function of temperature, is solved simultaneously with the temperature distribution, which is given as a function of distance within the freezing zone. Using the “heat balance integral” technique, the method for the solution of the temperature distribution and the thickness of each region is given. As an example, the results are shown in graphical form for an Al-5 percent Cu alloy.
Transient Temperature Response of a Thin-Walled, Transpiration-Cooled Porous Surface
Authors: Scott C. J.
Published: February 2012

A transient energy balance is applied to a porous surface which is subjected to a high temperature, forced convection environment. A discussion of the experimental measurement of the heat transfer coefficient with porous wall cooling is presented along with an examination of the simplifying assumptions made in the data reduction process. Experimental measurements are presented for the special case of a porous disk aligned normal to the oncoming flow. The experimental investigation was conducted in a 6 × 9-in. blowdown supersonic wind tunnel at a Mach number of 3.0 and a running time of 30 sec.
Friction and Heat Transfer Characteristics in Turbulent Swirl Flow Subjected to Large Transverse Temperature Gradients
Authors: Thorsen R. , Landis F.
Published: February 2012

Friction and heat transfer characteristics of turbulent air flowing through tubes with twisted strip swirl promoters were studied experimentally and analytically. Data were obtained for pitch-to-diameter ratios as low as 3.15 and for Reynolds numbers up to 100,000. Both heating and cooling tests were run for tube wall to fluid bulk temperature ratios from 0.6 to 1.9 (degR/degR) to evaluate compressibility and buoyancy effects. Both temperature-varying properties and the centrifugal force field imposed on the compressible fluid by the twisted strips cause considerable deviations from the incompressible heat transfer predictions. Experimental results are presented as deviations to the incompressible predictions and can be correlated by f=fo(Tˆw/Tˆb)−0.1(HeatingandCooling)Nu=Nuo(Tˆw/Tˆb)−0.32(1+0.25Gr/Re)(Heating)Nu=1.07Nuo(Tˆw/Tˆb)−0.1(1−0.25Gr/Re)(Cooling) where the subscript “o” refers to the incompressible analytical solution. The analysis presented is more direct and complete than the previous development by Smithberg and Landis [3]2 by also accounting for curvature effects and the significant tape distortions encountered with tightly twisted strips.
Pool Boiling on Polished and Chemically Etched Stainless-Steel Surfaces
Authors: Vachon R. I. , Tanger G. E. , Davis D. L. , Nix G. H.
Published: February 2012

This paper presents pool boiling data at atmospheric pressure for mechanically polished and chemically etched 304 stainless-steel surfaces in contact with distilled water. The surfaces were prepared by these techniques to produce variation in nucleation sites. Surface roughness was varied from 2–61 rms. The results show the changes in heat transfer with varying rms surface roughness and preparation technique. The Rohsenow pool boiling correlation was used to discuss the data.
A General Heat Transfer Correlation for Annular Flow Condensation
Authors: Soliman M. , Schuster J. R. , Berenson P. J.
Published: February 2012

The interaction between friction, momentum, and gravity, as they affect the heat transfer process during annular flow condensation inside tubes, is studied. Analytical forms for each of these forces are derived and incorporated in a correlation that predicts the local heat transfer coefficient. The predictions agree well with the available experimental data over a wide range of vapor velocities and over a range of Prandtl numbers from 1 to 10. The analysis also yields a means for predicting the onset of liquid run-back in the presence of an adverse gravitational field.
Influence of Axial Heat Diffusion in Liquid Metal-Cooled Ducts With Specified Heat Flux
Authors: Burchill W. E. , Jones B. G. , Stein R. P.
Published: February 2012

An analysis has been made of the temperature distribution and heat transfer in a generalized, symmetrical annular space including the effects of axial diffusion of heat in the fluid with the assumption of slug flow and with arbitrary heat-flux distributions at the walls of a section between two infinitely long adiabatic inlet and outlet sections. An examination has been made of the effects produced by including axial diffusion and varying the Peclet number, the length of heated section, and the heat-flux distributions. The results may be applied to estimate the extent of the influence of axial diffusion and to correct predictions which have neglected it.
Experimental and Analytical Study of the Combined Geometric Analog Computer
Authors: Razelos P. , Elrod H. G. , Paschkis V.
Published: February 2012

A method for obtaining approximate solutions of transient three-dimensional heat-conduction problems has been investigated here analytically and experimentally. The method is based on the well-known principle of analogy between flow of heat and electricity and comprises a continuous resistance medium of resistivity ρe but discrete capacitances, which are introduced into the resistance medium through spherical electrodes. It has been shown that the internal behavior of the system is influenced only by the pitch diameter ratio λ of the spheres. Fundamental solutions for the infinite medium have been obtained and the analysis has shown that the system behaves like one having a resistivity ρe* which can be calculated from the actual resistivity of the liquid and the steady-state Green’s function of the fluid-sphere system. Experiments for the determination of the steady-state and transient Green’s functions are described. The accuracy of the method has also been investigated, and an illustrative example is given.
A Study of the Temperature Profiles Measured in the Thermal Sublayer of Water, Freon-113, and Methyl Alcohol During Pool Boiling
Authors: Lippert T. E. , Dougall R. S.
Published: February 2012

Experiments were made of the time-average temperature and thermal-fluctuation profiles occurring during pool boiling from a horizontal copper surface with water, Freon-113, and methanol as fluids. These profiles show a similar nature when scaled by a length called the sublayer thickness, δ. These results show that the correlations for sublayer thickness with other system parameters can be divided into two distinct regimes. For low heat fluxes, one relation correlates the data of all three fluids. At higher heat fluxes, the correlating requires different constants for the different fluids in a manner similar to boiling heat-transfer correlations.
Combined Free and Forced Laminar Convection in a Horizontal Tube With Uniform Heat Flux
Authors: Shannon R. L. , Depew C. A.
Published: February 2012

The influence of free convection on forced laminar flow of water initially at the ice point was investigated. The flow was horizontal in a circular tube with uniform wall heat flux and a fully developed velocity profile at the onset of heating. Local measurements were made for the calculation of Nusselt number, Reynolds number, Prandtl number, and Grashof number. Reynolds numbers ranged from 120 to 2300, Grashof numbers ranged up to 2.5 × 105, and Graetz numbers ranged from 1.5 to 1000. The Nusselt number was not significantly affected in the thermal entry region, but values which are 2 1/2 times those expected for uniform properties were discovered far down the tube at x/D ≈ 700. The data were correlated with fair agreement by the parameter (GrPr)1/4/NuGz, where NuGz is the Nusselt number based on locally uniform physical properties.
The Effect of a Spherical Protuberance on the Local Heat Transfer to a Turbulent Boundary Layer
Authors: Seban R. A. , Caldwell G. L.
Published: February 2012

Local heat transfer coefficients are presented for a single spherical protuberance on a plate, along which the boundary layer was turbulent, for air speeds from 50 to 150 fps. Two spheres were used to produce ratios of sphere diameter to boundary-layer thickness of the order of 2 and 0.7. The heat transfer coefficient behind the sphere depends approximately on the eight-tenths power of the velocity, its maximum is located about 2 dia downstream of the sphere, and the downstream effect is limited spanwise to a region about 4 dia in width.
The Evaporation of Water Droplets in Superheated Steam
Authors: Lee Kwan , Ryley D. J.
Published: February 2012

The evaporation of a water droplet, diameter 230-1130μ, suspended on a 50μ diameter glass fiber was measured optically for the following range of variables: droplet Reynolds number 64-250, superheated steam pressure 14.7–29 psia, degrees of superheat 5–61 deg F; velocity 9–39 fps. The correlating equation was found to be Nu¯=2+0.74Re0.5Pr0.33 The apparatus and technique were proven using air as the evaporating medium. Calculations were made of the heating-up period at the beginning, and the drop asphericity at the end of a given test.
Approximate Analysis of Transient Laminar Boundary-Layer Development
Authors: Schetz J. A. , Oh Sin K.
Published: February 2012

Transient development of the boundary layer on a flat plate following the impulsive start of motion of the surrounding fluid is analyzed approximately. The Howarth-Dorodnitzin transformation and a Crocco Integral are used to relate the temperature field to the approximate velocity field which is obtained in a “constant density” plane. The solution for the velocity field is determined using the unsteady Momentum Integral equation with a new type of profile. Expressions for the boundary-layer development time and model surface temperature at the end of the development time are presented. Good agreement with a roughly determined experimental flow development time is achieved.
An Experimental Investigation of Heat Transfer From a Spray Cooled Isothermal Cylinder
Authors: Hodgson J. W. , Saterbak R. T. , Sunderland J. E.
Published: February 2012

The local and overall heat transfer around a horizontal, isothermal, circular cylinder exposed to a crossflow of a water-in-air spray has been determined experimentally. The investigation involved a closed loop wind tunnel in which a spray nozzle and an electrically heated test cylinder were located. The rate of heat transfer was measured for free stream air Reynolds numbers of 30,000, 75,000, and 118,000; the water-to-air mass flow ratios varied from 0 to 0.13. Results indicate that two-component heat transfer coefficients may be thirty times those of single-component (air) flow.
Transient Film Boiling of Water on a Horizontal Wire
Authors: Pitts D. R. , Yen H. H. , Jackson T. W.
Published: February 2012

This paper reports an experimental and analytical investigation of transient film boiling of water from a horizontal submerged platinum wire following a large step change in wire temperature. Experimental vapor growth rate data were obtained from high-speed motion pictures with pool temperatures very close to saturation and wire temperatures ranging from 1245 to 1739 deg F. An analytical solution for vapor growth rate which assumes the primary mode of heat transfer within the vapor to be conduction is presented. Heat transfer rates based on the characteristic vapor growth time were calculated from measured vapor formation data.
Heat Transfer and Pressure Distribution in Open Cavity Flow
Authors: Emery A. F. , Sadunas J. A. , Loll M.
Published: February 2012

The heat transfer and pressure distribution in a rectangular cavity in a Mach 3 flow were investigated for a rectangular and an inverted-wedge recompression step. Noticeable differences between the results for the two steps were found in the recovery factors, but no real differences were detected in the heat-transfer coefficients or the velocity profiles. Heat-transfer coefficients in the cavity were determined by transient techniques and were found to range from 50 to 110 percent of the flat-plate value just prior to the expansion step.
Collapse of Vapor Bubbles With Translatory Motion
Authors: Wittke D. D. , Chao B. T.
Published: February 2012

The collapse of vapor bubbles in a subcooled liquid is studied under conditions that heat transfer is the controlling mechanism. Emphasis is placed on the effect of translatory motion and the presence of noncondensable gas on the collapse rate. The governing conservation equations are cast into appropriate dimensionless forms, and numerical solutions are presented for the bubble history with Jakob number, Pe´clet number, and dimensionless persistent bubble radius as parameters. The predicted collapse behavior agrees satisfactorily with experimental data which cover ranges of Jakob number from 7 to 45, Pe´clet number from 100 to 7700, and persistent bubble radius from 7.5 to 40 percent of the initial radius. The analysis also yields detailed information on the temperature field surrounding a collapsing bubble, with or without translatory motion. Results for the latter vindicated the anticipated inadequacy of the thin thermal boundary-layer assumption used in published analyses.
Heat Exchange in Fluid-Dense Particle Moving Beds
Authors: Sissom L. E. , Jackson T. W.
Published: February 2012

The characteristics of nonisothermal two-phase steady flow in a vertical pipe of constant area were investigated experimentally. Temperature and pressure distributions were determined, and the void fraction was measured under flowing conditions. Aluminum granules of 0.027 in. mean diameter flowed with gravity while heated air was forced countercurrently to the solids flow. Reynolds numbers, based on the superficial air velocity, from 10 to 50 were investigated. The solids flow rate was varied from 472 to 18,900 lbm/hr-sq ft. Utilizing the regeneration principle, the effective length of a fluid-to-particle heat exchanger was determined. Its small value and the large surface area to volume ratio (2980 sq ft/cu ft) indicate that such a heat exchanger would be very compact.
Natural Convection Heat Transfer From Horizontal Rectangular Fin Arrays
Authors: Harahap F. , McManus H. N.
Published: February 2012

Average heat-transfer coefficients are presented for fin arrays positioned with the base oriented horizontally. The flow field associated with the natural convection from the fin arrays was investigated and used as a model to find parameters to generalize the data. The proposed correlation overcomes the inadequacy of parameters available previously for horizontal rectangular fins.
Natural Convection From Vertical Surfaces, The Convection Transient Regime
Authors: Gebhart B. , Dring R. P. , Polymeropoulos C. E.
Published: February 2012

Transient natural convection response for external flow is determined experimentally and compared with the double integral theory predictions for processes wherein all transient effects are important. The theory is shown to give very accurate predictions of response for such processes. Similar agreement for the quasi-static and conduction dominated processes is discussed. The forms of the generalized thermal capacity and time variables arising in the theory are substantiated by the absence of a residual Prandtl number or Grashof number effect in comparing experimental response with predicted response. All measured responses are in agreement with the theory prediction that temperature overshoot does not occur for a vertical surface.
The Transient Response of Crossflow Heat Exchangers, Evaporators, and Condensers
Authors: Myers G. E. , Mitchell J. W. , Norman R. F.
Published: February 2012

The transient behavior of crossflow heat exchangers with one fluid mixed is discussed in this paper. The response to a step change in the inlet temperature of the mixed fluid is evaluated for cases in which the wall capacitance may be considered large. An approximate integral technique was used to obtain this solution to the governing differential equations. These results are summarized by a design chart for calculating the time required to attain 90 percent response. Design curves for calculating the entire transient as a function of time for the special case of an evaporator or condenser are additionally determined to extend the work of previous investigators. A new set of parameters for use in transient analysis is suggested which allows greater insight into the transient problem than does the more conventional set that includes the steady-state parameters. The range of validity of the large wall capacitance approximation is evaluated.