bluuebunny/crossref_metadata_2025 huggingface dataset:
Image‐Guided Radiosurgery of Head and Neck Cancers
Authors: Ryu Samuel , Khan Mumtaz , Yin Fang‐Fang , Concus Adrianne , Ajlouni Munther , Benninger Michael S. , Kim Jae Ho
Published: June 2004

OBJECTIVES

Radiosurgery precisely delivers a single high dose or a few fractionated doses of radiation to a localized tumor via the stereotactic approach. Some head and neck sites are suitable for radiosurgery since there is minimal or no organ motion. The clinical studies were carried out to determine the accuracy of stereotactic radiosurgery and to demonstrate the effectiveness of radiosurgery in head and neck cancers.

MATERIALS AND METHODS

Thirteen patients were treated with either single‐dose or fractionated radio‐surgery to the tumor. All patients except one with cancer of the lip had received prior treatments including surgery, radiotherapy, and chemotherapy for the primary cancers. The dose ranged 12 to 18 Gy for single‐dose radiosurgery and 30 Gy in 5 or 6 fractions twice a week for fractionated radiosurgery. Tumor localization was achieved via the stereotactic approach.

RESULTS

Accuracy of radiosurgery was within 1.5 mm. Despite the recurrent disease from previous heavy treatments, 9 patients (70%) showed a significant response (complete or >50% tumor reduction) to radiosurgery, and 3 patients had stable disease. Complete tumor response was achieved in 6 patients. All patients had excellent pain relief with functional and cosmetic preservation. There was no acute and subacute radiation toxicity detected clinically during the minimal follow‐up of 6 months.

CONCLUSION

Image‐guided radiosurgery is effective in achieving the local tumor control and pain relief. Radiosurgery provided excellent functional and cosmetic preservation with minimal complication. The results indicate the potential of radiosurgery in the treatment of recurrent and selected primary head and neck cancers. (Otolaryngol Head Neck Surg 2004;130:690‐7.)
Genotype and Phenotype of Glutathione‐S‐Transferase in Patients with Head and Neck Carcinoma
Authors: Konig‐Greger Diemut , Riechelmann Herbert , Wittich Uta , Gronau Silke
Published: June 2004

OBJECTIVE

Association of glutathione‐S‐transferase M1 (GSTM1) polymorphisms and cancer has been demonstrated. Possible underlying mechanisms and genotype‐phenotype correlations are not adequately investigated. The aim of this study was to investigate the influence of the GSTM1‐null‐genotype on the level of GSTM enzyme concentration and on the enzyme activity of GST in patients with head and neck cancer (HNC).

METHODS

We investigated in 83 patients and 91 healthy controls the GSTM1 polymorphisms, GSTM1 protein concentration, GSTM1 protein in tumor tissues, and total GST enzyme activity.

RESULTS

Total GST enzyme activity was significantly lower in patients with HNC (208 ± 9 μmol/min1) than in controls (264 ± 11 μmol/min1, P < 0.0001) but did not depend on GSTM1‐genotype (P = 0.1). GSTM protein concentration in null‐genotype patients (3.6 ± 2.5 μg/mL, mean ± SE) was significantly lower than in GSTM1 allele carriers (26.7 ± 9.6 μg/ml, P < 0.0001); GSTM protein expression did not depend on GSTM1‐genotype (P > 0.5).

CONCLUSION: GST enzyme activity in patients with HNC is suppressed, indicating impaired detoxification capacity of tobacco‐smoke‐related carcinogens. This suppression is not correlated with the GSTM1‐genotype. (Otolaryngol Head Neck Surg 2004;130:718‐25.)
Survival of Veterans With Sleep Apnea: Continuous Positive Airway Pressure Versus Surgery
Authors: Weaver Edward M. , Maynard Charles , Yueh Bevan
Published: June 2004

OBJECTIVES

Continuous positive airway pressure (CPAP) improves sleep apnea survival. We tested whether CPAP is associated with better survival than uvulopalatopharyngoplasty (UPPP).

STUDY DESIGN AND METHODS

This retrospective cohort database study included all sleep apnea patients treated with CPAP or UPPP in Veteran Affairs facilities from October 1997 through September 2001. Treatment groups were compared with Cox regression, adjusting for age, gender, race, year treatment was initiated, and comorbidity. Sleep apnea severity and CPAP use data were not available.

RESULTS

By September 2002, 1339 (7.1%) of 18, 754 CPAP patients and 71 (3.4%) of 2,072 UPPP patients were dead (P < 0.001). After adjustment, CPAP patients had 31% (95% confidence interval, 3% to 67%, P = 0.03) higher probability of being dead at any time, relative to UPPP patients.

CONCLUSIONS

UPPP confers a survival advantage over CPAP, after adjustment for age, gender, race, year of treatment, and comorbidity. However, we were unable to adjust for sleep apnea severity or CPAP use. Surgical treatment should be considered in sleep apnea patients who use CPAP inadequately. (Otolaryngol Head Neck Surg 2004;130: 659‐65.)
Concurrent Laryngeal Abnormalities in Patients with Paradoxical Vocal Fold Dysfunction
Authors: Patel Nalin J. , Jorgensen Carol , Kuhn Joan , Merati Albert L.
Published: June 2004

OBJECTIVE

Our goal was to investigate the presence of laryngeal abnormalities is patients with paradoxical vocal fold dysfunction (PVFD).

STUDY DESIGN AND SETTING

A retrospective chart review was performed of patients referred for evaluation of paradoxical vocal fold dysfunction between July 2002 and December 2002. The patients completed questionnaires at the time of the office visit. Data collected from the medical record included age, gender, duration of symptoms before evaluation, asthma, gastroesophageal reflux symptoms, and laryngoscopic findings. Exercise stress test was performed when suitable. The diagnosis of PVFD was made based on patient history and laryngoscopy.

RESULTS

Thirty patients were identified. There was a 27:3 (90%) female predominance, and mean age of presentation at was 28 years (range, 12 to 67 years). The median time from the onset of respiratory symptoms to diagnosis was 4.5 years (range, 0.5 to 30 years). Of the 30 patients, 17 (56%) had asthma, 16 had laryngeal findings suggestive of gastroesophageal reflex disease, 4 (12%) had laryngoscopic findings of chronic laryngitis, and 10 (33%) had additional findings, including laryngomalacia, vocal fold motion impairment, sulcus vocalis, nodules, and subglottic stenosis, mostly in the exercise‐induced group.

CONCLUSIONS

Concomitant laryngeal abnormalities are present in a many patients with PVFD, particularly in those with exercise‐induced symptoms. Laryngoscopy is important in the management of these patients. (Otolaryngol Head Neck Surg 2004; 130:686‐9.)
The Versatile Extended Pericranial Flap for Closure of Skull Base Defects
Authors: Smith Jesse E. , Ducic Yadranko
Published: June 2004

OBJECTIVE

We sought to demonstrate the technical aspects of the extended pericranial flap and its versatility in reconstruction of a variety of skull base defects.

STUDY DESIGN

We conducted a retrospective chart review of 32 patients who underwent reconstruction of skull‐base defects with an extended pericranial flap by the senior author (Y.D.) from September 1997 to July 2003.

METHODS

Patients with skull base defects after trauma or extirpative surgery were reconstructed with either a lateral‐ or an anterior‐based vascularized extended pericranial flap. Variables and outcomes measured included: the size and anatomical location of the defect, need for other flaps, preoperative and/or postoperative radiation therapy and/or chemotherapy, bone flap necrosis, hardware exposure, wound dehiscence, postoperative cerebrospinal fluid (CSF) leak, and meningitis.

RESULTS

There was no evidence of flap failure, 2 cases of transient (3 to 4 days) CSF leak without resultant meningitis, 3 patients with hardware exposure, and 2 patients with hydroxyapatite infection. The 2 transient cases of CSF leak both resolved without further surgical intervention or the placement of a lumbar drain.

CONCLUSION: Both the lateral and anteriorly based extended pericranial flaps are reliable and versatile flaps associated with minimal morbidity and a low rate of complications when used to reconstruct defects of the anterolateral skull base. (Otolaryngol Head Neck Surg 2004;130:704‐11.)
Acoustic Neuroma Surgical Cost and Outcome by Hospital Volume in California
Authors: Slattery William H. , Schwartz Marc S. , Fisher Laurel M. , Oppenheimer Mark
Published: June 2004

CONTEXT

Successful outcome of complex surgical techniques depend on the surgical team's level of experience. However, unless benefit is demonstrated in the presence of cost savings, insurance companies are reluctant to approve care from highly experienced hospitals and surgical teams.

OBJECTIVE

To determine the relationship between the number of acoustic neuroma surgeries performed at California hospitals with surgical outcome and hospital stay cost.

DESIGN

Acoustic neuroma surgery information was extracted from the California hospital discharge database and was grouped according to the number of surgeries performed at each hospital.

SETTING. A database review of California hospitals.

PATIENTS

Persons (n= 1,213) undergoing acoustic neuroma surgery at a California hospital between 1996 and 1998.

MAIN OUTCOME MEASURES

Outcome measures included discharge status (routine vs. not routine), medical procedures indicating surgical complications, total cost of hospitalization, and average cost per hospitalization day. Odds ratios were used to compare the hospital volume groups on likelihood of a routine surgical outcome.

RESULTS

The frequency of routine surgical outcome increased as hospital acoustic neuroma surgical volume increased, ranging from 68% among patients in the lowest volume group to 97% in the highest hospital volume group. Patients in the highest hospital volume group were 15 times more likely to have a routine surgical outcome than patients in the lowest hospital volume group. Patients in the second highest volume group were 5 times more likely to have a routine surgical outcome than in the lowest volume group. The two highest volume hospital groups had lower total charges and average charges per day than the two lower volume hospital groups.

CONCLUSIONS

Acoustic neuroma surgeries at higher volume hospitals had higher frequency of routine discharge, lower frequency of apparent complications, and lower average cost of hospitalization. (Otolaryngol Head Neck Surg 2004;130:726‐35.)
Contact Diode Laser Myringotomy and Mitomycin C in Children
Authors: D'Ereditá Riccardo
Published: June 2004

OBJECTIVE

To investigate the use of contact diode laser myringotomy (C‐LAM), combined with topical mitomycin C, as an alternative method for prolonged middle ear ventilation in children with otitis media with effusion.

STUDY DESIGN AND SETTING

Prospective study at a tertiary care pediatric institution.

METHODS

Fifteen children enrolled in the study. Mitomycin C was applied to the intact tympanic membrane in the right ears, whereas saline on the left side was used for controls. C‐LAM was then performed in all ears. Outcome measures included healing rate and scarring, ear infection, and long‐term audiometric follow‐up.

RESULTS

There was no significant difference in median healing rate. In each group, the median was between the third and fourth month. Normal hearing thresholds were obtained in all children at 2‐year follow‐up.

CONCLUSION: C‐LAM proved to be an effective method for medium‐term ventilation, but topical mitomycin C before C‐LAM did not prolong patency rate in our patients. No significant complication was encountered at 2‐year follow‐up. (Otolaryngol Head Neck Surg 2004;130:742‐6.)
Association of Autonomic Dysfunction and Mild Obstructive Sleep Apnea
Authors: Woodson B. Tucker , Brusky Laura T. , Saurajen Adrian , Jaradeh Safwan
Published: June 2004

BACKGROUND

Autonomic dysfunction (AD) has been independently associated with obstructive sleep apnea (OSA). Autonomic abnormalities are generally considered to be secondary to OSA. Autonomic dysfunction may also contribute to OSA. If AD contributes to OSA, we postulated that abnormalities may be present in mild OSA where the confounding causal effects of hypoxemia and sleep disruption are reduced.

OBJECTIVE

We evaluated autonomic function tests and sleep studies in a cohort of subjects with no known diagnosis of OSA.

METHODS

We prospectively enrolled a cohort without diagnosed OSA who were part of an ongoing study of vasomotor rhinitis (VMR) for testing. A battery of autonomic nervous system tests (sudomotor and cardiovagal), nonattended polysomnography, and three‐site esophageal/pharyngeal pH monitoring were performed.

RESULTS

Twenty of 22 patients completed the test battery and 12 (60%) met criteria for OSA (Apnea/Hypopnea Index “AHI” >5 events/hour). AHI correlated to mean tilt table blood pressure decrease (R = 0.58, P = 0.007) and the Valsalva‐mediated phase 2 mean blood pressure decrease (R = 0.52, P = 0.017). OSA severity was related to sympathetic but not parasympathetic abnormalities. No differences in blood pressure responses were related to age, oxygen desaturation nadir, gastroesophageal reflux, VMR, or sleepiness.

CONCLUSION

Autonomic abnormalities suggestive of decreased adrenergic tone are associated with mild OSA. These abnormalities may potentially be secondary but may also precede development of OSA. (Otolaryngol Head Neck Surg 2004;130: 643‐8.)
The Big Match – Lexis v Westlaw
Authors: Norman Paul
Published: June 2004

Lexis and Westlaw are the biggest names in subscription legal database provision, and have been settled here in the UK long enough to be the subject of a little comparative critical examination. I hope to provide this in what follows, with the caveat that my experience is of academic subscriptions, which may vary in content from their commercial counterparts. I do have the advantage of access to the respective American academic versions, so that some comparisons can also be made in that direction.
“Getting it off the ‘Net”: Use of the World Wide Web in a Firm of Solicitors
Authors: Booth Sally
Published: June 2004

This article presents the key findings of the research I carried out in the summer of 2002 for the final year dissertation project of the MSc in Information and Library Management at Bristol University
On Course for a Career in Information and Knowledge Management
Authors: Webb Jela
Published: June 2004

Back in late 1998 I was appointed to head up the Knowledge Management and Development Team in Nat West Bank and given responsibility for devising the strategy and implementing a knowledge management capability in The New Learning Organisation, the bank's centralised learning and development function. No mean feat when supporting 60,000 staff with their training and development needs!
Taxonomy: Classification by Another Name
Authors: Will Leonard
Published: June 2004

The word “taxonomy” is widely used these days in discussions about organising knowledge or information, especially information in electronic form such as that on the Internet. There is no generally accepted definition of what taxonomies are, though the word is usually used to refer to alphabetico-classed schemes of subject headings. These are built on fundamental principles, which have been more fully developed in their application to thesauri and classifications. By recognising that all these kinds of “controlled vocabularies” are just variations on a theme, built from the same components, it is possible to create consistent and complementary tools to provide for the different approaches which users may need.
Information Literacy: Organisational and Law Firm Perspectives
Authors: Macoustra Jane
Published: June 2004

This article is an extended version of my previous article “Information Literacy in a corporate environment” which was published on the FreePint website last year. http//:www.freepint.com/issues/060303.htm. The opinions in this article are solely those of the author. Feedback or discussion is welcomed.
Library and Information Service Provision to the Courts and the Judiciary
Authors: Brookes Eleanor
Published: June 2004

Having agreed to talk about the challenges involved in providing the Court Service with a library and information service, I started to think about this year's conference theme – knowledge without frontiers – and how it applies to that service. The more I reflected on this role, the clearer it became to me that the service's challenges are also its opportunities. By sharing with you some of the challenges that face Library and Information Services (LIS) staff based in Regional libraries and offices throughout England and Wales, I hope to highlight the opportunities that are also afforded.
A World of Knowledge for Legal Hands
Authors: Venturas Anna
Published: June 2004

The UK's national library today serves a wider range of users than ever before. The British Library is the world's largest supplier of vital information to science, technology, business, engineering and academia, either at the walk-in reading rooms at St Pancras, London or remotely from the Document Supply Service in Yorkshire. It has also become an advocate for the implementation of a national collection of foreign, comparative and international legal research materials. Additionally, the Library is a well-used resource for professionals such as social workers and clinicians requiring information about the legal framework within which they operate.
Classification of closely spaced subsurface objects using electromagnetic induction data and blind source separation algorithms
Authors: Hu Wei , Collins Leslie M.
Published: June 2004

Most research in the subsurface object identification area assumes that objects are well isolated from each other and thus that a single signature is measured by the sensing system. In the scenario where multiple closely spaced subsurface objects are present within the field of view of the sensor, the signals measured using electromagnetic induction sensors are mixed, and the mixed measurements cannot be used to determine the identity of each of the individual objects using conventional techniques. Since only the mixed observations are available, and these are usually available at multiple target/sensor orientations, separating individual signals from the set of mixtures can be posed as a blind source separation (BSS) problem. In this paper we consider two approaches to source separation, one based on the second‐order statistics and the other based on the fourth‐order statistics. Following the source separation, object classification performance is obtained using the separated sources and a Bayesian classifier. We analyze the strengths and weaknesses of each BSS approach and compare their performance.
Alpha‐cellulose δ13C variation in mangrove tree rings correlates well with annual sea level trend between 1982 and 1999
Authors: Yu Ke‐Fu , Zhao Jian‐Xin , Liu Tung‐Sheng , Wang Pin‐Xian , Qian Jun‐Long , Chen Te‐Gu
Published: June 2004

A pilot study of tree rings in a modern mangrove tree (Rhizophora apiculata) from Leizhou Peninsula, northern South China Sea shows that (1) the tree‐rings are annual; (2) the ring widths decrease; and (3) their alpha‐cellulose δ13C values increase from 1982 to 1999 AD, consistent with the trends of annual sea level, salinity and sea surface temperatures in the same period. We propose that such changes were caused by increasingly longer duration of waterlogging in response to sea‐level rise. If this is the case, alpha‐cellulose δ13C in mangrove tree rings can be used as a potential indicator of past sea level fluctuations.
Histone variant H2ABbd confers lower stability to the nucleosome
Authors: Gautier Thierry , Abbott D Wade , Molla Annie , Verdel Andre , Ausio Juan , Dimitrov Stefan
Published: June 2004

The histone H2ABbd is a novel histone variant of H2A with a totally unknown function. We have investigated the behaviour of the H2ABbd nucleosomes. Nucleosomes were reconstituted with recombinant histone H2ABbd and changes in their conformations at different salt concentrations were studied by analytical centrifugation. The data are in agreement with H2ABbd being less tightly bound compared with conventional H2A in the nucleosome. In addition, stable cell lines expressing either green fluorescent protein (GFP)–H2A or GFP–H2ABbd were established and the mobility of both fusions was measured by fluorescence recovery after photobleaching. We show that GFP–H2ABbd exchanges much more rapidly than GFP–H2A within the nucleosome. The reported data are compatible with a lower stability of the variant H2ABbd nucleosome compared with the conventional H2A particle.
Numerical estimate of the stability curve for the flow past a rotating cylinder
Authors: Xiong Jun , Ling Guocan , Zhu Keqin
Published: June 2004

It is demonstrated that the primary instability of the wake of a two-dimensional circular cylinder rotating with constant angular velocity can be qualitatively well described by the Landau equation. The coefficients of the Landau equation are determined by means of numerical simulations for the Navier–Stokes equations. The critical Reynolds numbers, which depend on the angular velocity of the cylinder, are evaluated correctly by linear regression.
Faxén-like relations for a nonuniform suspension
Authors: Ichiki Kengo , Prosperetti Andrea
Published: June 2004

The first part of the paper shows how ensemble averages that correspond to a prescribed statistically nonuniform spatial distribution of particles can be evaluated starting from a statistically uniform ensemble. The method consists of attributing to each realization of the uniform ensemble a suitable weight which is explicitly constructed. As an application of this general procedure, in the second part of the paper, the behavior of particles subjected to force or torque in a statistically nonuniform suspension and the behavior of a suspension subjected to a uniform shear are studied. In particular, it is shown how the average translational and angular velocities of the particles with respect to the mixture satisfy Faxén-like relations. Furthermore, it is pointed out that several quantities which vanish in an identical way in the case of a uniform suspension are nonzero in the presence of spatial nonuniformities.
Stochastic coherent adaptive large eddy simulation method
Authors: Goldstein Daniel E. , Vasilyev Oleg V.
Published: June 2004

In this paper we propose a novel approach called the stochastic coherent adaptive large eddy simulation (SCALES) method which takes advantage of both the coherent vortex simulation (CVS) and large eddy simulation (LES) methods. With the SCALES method a wavelet filter is applied to a turbulent field such that the maximum number of modes are resolved in the simulation, given the balance between computing resources and user defined acceptable simulation error. As with CVS, the wavelet thresholding filter will allow a SCALES simulation to resolve and “track” the coherent energetic structures in a turbulent flow field. The wavelet filter compression in SCALES will be substantially greater than the “ideal” wavelet compression used in CVS, making it cost effective for simulating high Re number flows. The SCALES methodology will simulate the most important modes given the resources available. Because of the higher wavelet compression the subgrid scales (SGS) in a SCALES simulation will contain both coherent and incoherent modes like with LES. In this work the SCALES method is presented for both velocity and vorticity space wavelet filtering. A novel coherency diagram of a turbulent field is introduced to present the physical relationships between direct numerical simulation and different large eddy capturing methods. In this work we show that with both LES filtering and SCALES filtering the residual SGS field contains both coherent and incoherent parts and that with both methodologies the total SGS dissipation is dominated by the coherent part of the SGS field. A possible implementation of the SCALES methodology for incompressible turbulent flows is also discussed.
Numerical study of vortical structures around a wall-mounted cubic obstacle in channel flow
Authors: Hwang Jong-Yeon , Yang Kyung-Soo
Published: June 2004

Vortical structures around a wall-mounted cubic obstacle in channel flow are studied using numerical simulation. Flows of low-to-moderate Reynolds numbers up to Re=3500 are considered. The objective of this work is to elucidate characteristics of coherent vortical structures produced by the presence of the wall-mounted cubic obstacle, including horseshoe vortex systems upstream of the obstacle, lateral vortices in the vicinity of the two lateral faces of the cube, and hairpin vortices in the near-wake region. As the flow approaches the cube, the adverse pressure gradient produces three-dimensional boundary-layer separation, resulting in the formation of laminar horseshoe vortices. As the Reynolds number increases, the structure of the horseshoe vortex system becomes complex and the number of vortices increases in pairs. The distribution of skin friction on the cube-mounted wall reflects the effect of the horseshoe vortices. Unsteady horseshoe vortex systems are hardly found as long as the upstream flow is fully viscous; they are obtained when the cube is placed in the entrance region of a developing channel flow. The unsteady horseshoe vortex systems are characterized by a repeated process of generation, translation, and mutual merging of the vortices. The laminar wake is characterized by a pair of spiral vortices behind the obstacle; distinct singular points are identified leading to consistent flow topology. In the case of a turbulent wake, however, it is observed that the flow becomes less coherent in the near-wall region downstream of the obstacle. Instead, coherent structures such as lateral vortices and hairpin vortices are found in the vicinity of the two lateral faces of the cube and in the turbulent near-wake region, respectively. Quasiperiodic behaviors of those vortices are noticed and their frequencies are computed. The translating speed of the head portion of a hairpin vortex is lower than the streamwise mean velocity at that location. In the vicinity of the lower wall downstream of the cube, vortical structures of various length scales are identified; they become gradually elongated downstream of the flow reattachment.
A new device for the generation of microbubbles
Authors: Gordillo José M. , Cheng Zhengdong , Ganan-Calvo Alfonso M. , Márquez M. , Weitz D. A.
Published: June 2004

In this paper we present a new method for the production of bubble-liquid suspensions (from now on BLS) composed of micron-sized bubbles and with gas to liquid volume ratios larger than unity. We show that the BLS gas fraction λ=Qg/Ql, being Qg and Ql the flow rates of gas and liquid, respectively, is controlled by a dimensionless parameter which accounts for the ratio of the gas pressure inside the device to the liquid viscous pressure drop from the orifices where the liquid is injected to the exit, where the BLS is obtained. This parameter permits the correct scaling of the BLS gas volume fraction of all the experiments presented.
Influence of magnetic field on the electrical breakdown characteristics in cylindrical diode
Authors: Li Shou-Zhe , Uhm Han S.
Published: June 2004

The influence of magnetic field on the electrical breakdown properties is investigated by applying a magnetic field along the longitudinal direction in a cylindrical diode for two electrical polarities. Breakdown characteristics in a crossed magnetic field are analyzed with the equivalentreduced-electric-field concept and Townsend criterion. The discharge experiment at reduced pressure is carried out in the moderate magnetic field. Experimental investigation is concentrated on the magnetic dependent behavior of the electrical breakdown in the lower pressure side of Paschen’s minimum. It is found that the electrical breakdown characteristics with respect to the magnetic field depend on electrical polarity of the cylindrical diode, which is interpreted by taking the gyromotion of the individual electrons in the diode into accounts under the moderate magnetic field in the lower pressure side of Paschen’s minimum.
Taylor vortices in annular spherical flow at large aspect ratios
Authors: Loukopoulos Vassilios C. , Karahalios George T.
Published: June 2004

Motivated by recent theoretical and experimental work, we numerically investigate spherical Couette flow with a view to obtaining for the first time Taylor vortices at large aspect ratios σ such as 0.38, 0.42, and 0.48. It is found that Taylor vortices can exist, stable or time-dependent, in a range of Reynolds numbers [Re1, Re2] and their formation depends on the aspect ratio, on the imposition of various rotationary conditions on the boundaries, on the history of the flow and on the rate at which energy is transferred into the fluid to its final value. With increasing σ the range [Re1, Re2] manifests a clear tendency to shorten.
Chemical reaction-driven tip-streaming phenomena in a pendant drop
Authors: Fernandez J. M. , Homsy G. M.
Published: June 2004

We describe a chemical oscillatory phenomenon which occurs as follows: a pendant drop of water is immersed in a viscous oil, both phases containing reagents which react to produce a surfactant at the interface. As the drop falls away from the tip of a small needle, the remaining interface spontaneously elongates into a sharp cone and ejects small droplets from the pointed tip. The tip then either contracts and re-elongates periodically, or remains steadily elongated. Small droplets continue to be ejected in either case, and the phenomenon persists over a period of tens of minutes. Quantitative measurements connect these chemically driven phenomena with studies in four-roll mills. A mechanism is proposed by which these phenomena are sustained by Marangoni stresses.
An iterative study of time independent induction effects in magnetohydrodynamics
Authors: Bourgoin M. , Odier P. , Pinton J.-F. , Ricard Y.
Published: June 2004

We introduce a new numerical approach to study magnetic induction in flows of an electrically conducting fluid submitted to an external applied field B0. In our procedure the induction equation is solved iteratively in successive orders of the magnetic Reynolds number Rm. All electrical quantities such as potential, currents, and fields are computed explicitly with real boundary conditions. We validate our approach on the well known case of the expulsion of magnetic field lines from large scale eddies. We then apply our technique to the study of the induction mechanisms in the von Kármán flows generated in the gap between coaxial rotating disks. We demonstrate how the omega and alpha effects develop in this flow, and how they could cooperate to generate a dynamo in this homogeneous geometry. We also discuss induction effects that specifically result from boundary conditions.
Multi-component droplet growth. I. Experiments with supersaturated n-nonane vapor and water vapor in methane
Authors: Peeters P. , Pieterse G. , Hrubý J. , van Dongen M. E. H.
Published: June 2004

Droplet growth rates of droplets suspended in methane gas and supersaturated water and/or n-nonane vapor are experimentally determined. The experiments are performed by applying the nucleation pulse principle using a modified shock tube. The droplets are optically detected using a combination of constant angle Mie scattering and light extinction measurements. From the analysis of the droplet growth rates in the binary systems the diffusion coefficients of water in methane and n-nonane in methane have been determined at two different conditions, being 11 bar and 242 K, and 44 bar and 247 K. The droplet growth rates in the ternary system have been determined at the same two conditions. From the analysis of these experiments it is evident that supersaturated water vapor does not condense onto n-nonane droplets while supersaturated n-nonane vapor does condense onto water droplets. This can be related to the wetting properties of liquid water on liquid n-nonane and vice versa.
Multi-component droplet growth. II. A theoretical model
Authors: Peeters P. , Pieterse G. , van Dongen M. E. H.
Published: June 2004

A droplet growth model is formulated that describes the growth of homogeneous multi-component droplets suspended in a dilute gas–vapor mixture. The droplet is suspended in a real carrier gas, in which the vapors are diluted. The model is applicable for all Knudsen numbers. It is shown that the model can easily be extended to describe the growth of layered droplets. The model calculations are compared to the results of droplet growth experiments of supersaturated water and/or supersaturated n-nonane in methane. The model performs well for all the cases, except for the case when supersaturated n-nonane vapor is added to supersaturated water vapor in methane gas. In the latter case it is proposed that the discrepancies originate from the incomplete wetting of n-nonane on liquid water at the given conditions.
On the use of chemical reaction rates with discrete internal energies in the direct simulation Monte Carlo method
Authors: Gimelshein S. F. , Gimelshein N. E. , Levin D. A. , Ivanov M. S. , Wysong I. J.
Published: June 2004

The conventional chemical reaction models of the direct simulation Monte Carlo method developed with the assumption of continuous rotational or vibrational modes that are shown to exhibit systematic errors when used with discrete energy modes. A reaction model is proposed that is consistent with the use of discrete energy distributions of rotational and vibrational modes, and is equally applicable to diatomic and polyatomic systems. The sensitivity of the model to variations of different reaction rate parameters is examined. The revised chemical reaction model is then applied to the modeling of hypersonic flows over spacecraft in the Martian and Earth atmospheres.
Nonlinear dynamics of inclined films under low-frequency forcing
Authors: Argyriadi K. , Serifi K. , Bontozoglou V.
Published: June 2004

The evolution of an inclined liquid film, subjected to regular inlet disturbances of small frequency, f, is studied experimentally and computationally. The fluorescence imaging method is used to quantitatively document film thickness at a downstream window of the flow channel, and a Galerkin finite-element solution of the Navier–Stokes equation of motion is invoked to predict the entire spatio-temporal dynamics of the free surface. Experiments confirm that, below a certain frequency, fp, the regular wave train is destroyed by the appearance of one or more parasitic crests behind each major wave. Experiments and simulations indicate that parasitic crests are not the result of spatially unlocalized instabilities in the substrate, but originate in a regular way from a depression developing at the tails of growing solitary waves. Their downstream fate is dictated by the proximity of the next major wave, and thus different scenarios are predicted and observed for f≈fp and f≪fp. A theoretical explanation of the phenomenon is suggested in terms of the radiation properties of growing solitary crests, as described by Chang, Demekhin, and Kalaidin [SIAM (Soc. Ind. Appl. Math.) J. Appl. Math. 58, 1246 (1998)].
Existence of the Bogoliubov S(g) operator for the (:φ4:)2 quantum field theory
Authors: Wreszinski Walter F. , Manzoni Luiz A. , Bolina Oscar
Published: June 2004

We prove the existence of the Bogoliubov S(g) operator for the (:φ4:)2 quantum field theory for coupling functions g of compact support in space and time. The construction is nonperturbative and relies on a theorem of Kisyński. It implies almost automatically the properties of unitarity and causality for disjoint supports in the time variable.
Ultra hard x rays from krypton clusters heated by intense laser fields
Authors: Issac R. C. , Vieux G. , Ersfeld B. , Brunetti E. , Jamison S. P. , Gallacher J. , Clark D. , Jaroszynski D. A.
Published: June 2004

The interaction of ultrashort laser pulses with krypton clusters at intensity up to 1.3×1018 Wcm−2 has been investigated. Intense Kα and Kβ emission from krypton at 12.66 and 14.1 keV, respectively, has been observed using conventional solid state x-ray detectors. The measured x-ray spectra have broad bremsstrahlung continuum reaching to photon energies up to 45 keV, with evidence that approximately 10% of electrons that are heated to very high electron temperatures, which is consistent with a two-temperature electron distribution. This is ascribed to the presence of a hot electron population, similar to that found in laser–solid interactions. The highest laser energy to x-ray conversion efficiency observed is 9.2×10−7, which is equivalent to 45 nJ x-ray pulse energy from the 12.66 keV krypton Kα transition.
Modeling of stationary waves on a thin viscous film down an inclined plane at high Reynolds numbers and moderate Weber numbers using energy integral method
Authors: Usha R. , Uma B.
Published: June 2004

The theory describing the nonlinear stationary waves of finite amplitude and long wavelength on a thin viscous Newtonian film at high Reynolds numbers and moderate Weber numbers has been developed using the energy integral method (EIM). The linear instability of the uniform flow by EIM has been analyzed and the linear instability threshold has been obtained as cot θ/Re=6/5, which agrees with the classical results of the Orr–Sommerfeld analysis by Benjamin [J. Fluid Mech. 2, 554 (1957)] and Yih [Phys. Fluids 6, 321 (1963)] and verified experimentally by Liu and Gollub [Phys. Rev. Lett. 70, 2289 (1993)]. Further, in the frame of reference moving with the steady wave speed, the second order approximate equations reduce to a third order dynamical system. While wave transitions in real life involve complex spatio-temporal dynamics and many of these transitions lead to chaotic waves that are not stationary traveling waves, bifurcation of stationary traveling waves has been examined as a preliminary study of the more complex transitions. Stability of the fixed points of the dynamical system, parametric regimes of heteroclinic orbits and Hopf bifurcations are delineated. Numerical integration has been carried out in order to study the different bifurcation scenarios as the phase speed deviates from the Hopf-bifurcation thresholds. Four different bifurcation scenarios have been observed and the dependence of bifurcation scenarios on the inclination angle, Reynolds numbers and Weber numbers have been discussed. Although the results obtained by the momentum integral method and EIM exhibit similar bifurcation scenarios, there are quantitative differences which shows that the modeling differences exist in the literature.
Effects of hydrophobic surface on skin-friction drag
Authors: Min Taegee , Kim John
Published: June 2004

Effects of hydrophobic surface on skin-friction drag are investigated through direct numerical simulations of a turbulent channel flow. Hydrophobic surface is represented by a slip-boundary condition on the surface. When a slip-boundary condition is used in the streamwise direction, the skin-friction drag decreases and turbulence intensities and turbulence structures, near-wall streamwise vortices in particular, are significantly weakened. When a slip-boundary condition is used in the spanwise direction, on the other hand, the drag is increased. It is found that near-wall turbulence structures are modified differently, resulting in drag increase. It is also found that the slip length must be greater than a certain value in order to have a noticeable effect on turbulence. An important implication of the present finding is that drag reduction in turbulent boundary layers is unlikely with hydrophobic surface with its slip length on the order of a submicron scale.
Killing initial data revisited
Authors: Maerten Daniel
Published: June 2004

Considering the Killing vector fields on a Lorentzian manifold in terms of their lapse and shift along a space-like hypersurface, we give a new definition of the Killing Initial Data (KID) of Beig and Chruściel [Class. Quantum Grav. 14-1A, A83 (1996)]. We define, on these new KID’s, the bracket operation induced by the usual Lie bracket of Killing vector fields on the Lorentzian manifold, and study the conditions for our new KID’s to form a Lie algebra. The interesting fact is that these conditions only depend on data along the hypersurface.
A note on the decay of vorticity in shallow flow calculations
Authors: Brocchini M. , Colombini M.
Published: June 2004

Vorticity dynamics is studied within the viscous formulation of the nonlinear shallow water equations framework with a major emphasis on the description of decay of vortical structures. Suitable transport equations for vorticity and enstrophy are derived and the nature of one specific contribution which leads to localized vorticity/enstrophy dissipation is clarified showing that steep gradients of the flow depth act as sinks of vorticity/enstrophy and not only as sources. One simple example of importance for natural water flows is, finally, discussed.
Forced magnetic reconnection in the inviscid Taylor problem
Authors: Cole Andrew , Fitzpatrick Richard
Published: June 2004

The equations of incompressible inviscid two-dimensional MHD (magnetohydrodynamics) are numerically evolved in order to study a well-known model of forced magnetic reconnection. This problem, known as the Taylor problem, considers the response of a tearing-stable slab plasma equilibrium to a sudden, small amplitude boundary perturbation. The applied perturbation is such as to force magnetic reconnection and subsequent magnetic island formation within the plasma. The early dynamical phases of the reconnection process are investigated and found to be in good agreement with the analytic predictions of Hahm and Kulsrud [Phys. Fluids 28, 2412 (1985)]. Recent criticisms of this analysis by Ishizawa and Tokuda [Phys. Plasmas 8, 376 (2001)] are shown to be unwarranted.
Deformed Harry Dym and Hunter–Zheng equations
Authors: Brunelli J. C. , Das Ashok , Popowicz Ziemowit
Published: June 2004

We study the deformed Harry Dym and Hunter–Zheng equations with two arbitrary deformation parameters. These reduce to various other known models in appropriate limits. We show that both these systems are bi-Hamiltonian with the same Hamiltonian structures. They are integrable and belong to the same hierarchy corresponding to positive and negative flows. We present the Lax pair description for both the systems and construct the conserved charges of negative order from the Lax operator. For the deformed Harry Dym equation, we construct the nonstandard Lax representation for two special classes of values of the deformation parameters. In general, we argue that a nonstandard description will involve a pseudodifferential operator of infinite order.
On wall-pressure sources associated with the unsteady separation in a vortex-ring/wall interaction
Authors: Naguib Ahmed M. , Koochesfahani Manoochehr M.
Published: June 2004

Molecular tagging velocimetery measurements from an earlier investigation are used to study the wall-pressure and the flow structures responsible for its generation in the flow field resulting from the impingement of an axisymmetric vortex ring on a flat wall. The velocity-field data are used to obtain the spatial distribution of the pressure sources, and the result is employed in conjunction with the solution to Poisson’s equation to yield the wall-pressure information. The outcome reveals a characteristic wall-pressure signature that is produced repeatedly whenever the primary vortex ring interacts with the wall to form vortex rings with opposite sense of vorticity. The details of the signature are analyzed and related to specific flow features and their mutual interaction at different phases of the generation/evolution cycle of the new rings. Finally, the flow mechanisms leading to the generation of substantial positive and negative wall pressure in the characteristic signature are clarified.
Algebraic and Dirac–Hestenes spinors and spinor fields
Authors: Rodrigues Waldyr A.
Published: June 2004

Almost all presentations of Dirac theory in first or second quantization in physics (and mathematics) textbooks make use of covariant Dirac spinor fields. An exception is the presentation of that theory (first quantization) offered originally by Hestenes and now used by many authors. There, a new concept of spinor field (as a sum of nonhomogeneous even multivectors fields) is used. However, a careful analysis (detailed below) shows that the original Hestenes definition cannot be correct since it conflicts with the meaning of the Fierz identities. In this paper we start a program dedicated to the examination of the mathematical and physical basis for a comprehensive definition of the objects used by Hestenes. In order to do that we give a preliminary definition of algebraic spinor fields (ASF) and Dirac–Hestenes spinor fields (DHSF) on Minkowski space–time as some equivalence classes of pairs (Ⅺu,ψⅪu), where Ⅺu is a spinorial frame field and ψⅪu is an appropriate sum of multivectors fields (to be specified below). The necessity of our definitions are shown by a careful analysis of possible formulations of Dirac theory and the meaning of the set of Fierz identities associated with the bilinear covariants (on Minkowski space–time) made with ASF or DHSF. We believe that the present paper clarifies some misunderstandings (past and recent) appearing on the literature of the subject. It will be followed by a sequel paper where definitive definitions of ASF and DHSF are given as appropriate sections of a vector bundle called the left spin-Clifford bundle. The bundle formulation is essential in order to be possible to produce a coherent theory for the covariant derivatives of these fields on arbitrary Riemann–Cartan space–times. The present paper contains also Appendixes A–E which exhibits a truly useful collection of results concerning the theory of Clifford algebras (including many tricks of the trade) necessary for the intelligibility of the text.
Bounds on convection driven by internal heating
Authors: Lu Lu , Doering Charles R. , Busse Friedrich H.
Published: June 2004

Bounds are derived for the space–time averaged temperature 〈T〉 of a fluid layer in the Boussinesq approximation between fixed-temperature horizontal boundaries subject to uniform heating H throughout the volume. The analysis is carried out for both finite and infinite Prandtl number fluids. While the average temperature 〈T〉∼H in the purely conductive state, convection enhances the heat transport beyond static conduction reducing the temperature. Lower bounds to the average temperature of the layer scale with the magnitude of the imposed heat flux, with one scaling exponent for the arbitrary Prandtl number case and another for the infinite Prandtl number model. Specifically, it is proven here that at large heating rates where convection is important, 〈T〉⩾c1H2/3 for finite Prandtl number fluids and 〈T〉⩾c2H5/7 for infinite Prandtl number fluids. Explicit prefactors c1 and c2 for the scaling bounds are computed as well.
Dynamical and Chemical Evolution of IZw18
Authors: Recchi Simone
Published: June 2004

We study the effect of different star formation regimes on the dynamical and chemical evolution of IZw18, the most metal-poor dwarf galaxy locally known. To do that we adopt a two-dimensional hydrocode coupled with detailed chemical yields originating from Type II and Type Ia supernovae and from intermediate-mass stars. Particular emphasis is devoted to the problem of mixing of metals. We conclude that, under particular conditions, cooling of metals occurs with a timescale of the order of 10 Myr, thus confirming the hypothesis of instantaneous mixing adopted in chemical evolution models. We try to draw conclusions about the star formation history and the age of the last burst in IZw18.