bluuebunny/crossref_metadata_2025 huggingface dataset:
Multidisciplinary approach of complicated crown fractures of both superior central incisors: a case report
Authors: Vâlceanu Anca Silvia , Stratul Stefan‐Ioan
Published: July 2008

Abstract –  Anterior crown fractures are a common form of traumatic dental injuries that mainly affect the maxillary central incisors, in children and teenagers. Since the development of the adhesive dentistry, many case reports of crown fractures restored using adhesive reattachment techniques were published. Complex cases, in which more than one tooth are involved, with fractures differing from each other, require specific treatment of each fracture, taking different advantages of the different remaining tooth structures. This case report describes a patient with dissimilar crown fractures of both superior central incisors. After the endodontic treatment, the patient was treated using the combination of several techniques: periodontal surgery (crown lengthening with apically repositioned flap and osseous resective surgery), adhesive technique and cast restoration plus esthetic crown. The periodontal procedure re‐created the biologic width and proved to be a reliable adjunctive procedure to the adhesive and the prosthetic techniques used.
Basketball players’ experience of dental injury and awareness about mouthguard in China
Authors: Ma Wenli
Published: July 2008

Abstract –  The objective of the present study was to describe the occurrence of orofacial, particularly dental injuries in basketball, and to survey the athletes’ awareness concerning the use of mouthguards during basketball training and competition. A pilot questionnaire was designed and tested with basketball players. Two hundred and thirty‐six male athletes were surveyed. Seventy‐seven players were professional players. Exactly 80.6% professionals and 37.7% semi‐professional athletes had an experience of oral soft tissue laceration and dental injuries in basketball practice. The difference between the two groups is significant. The incidence of dental and oral injuries was related to the length of training time. About 59% of the athletes ranked the risk of orofacial and dental injury in basketball as medium. Although the awareness of mouthguards among the basketball players was very high (80.1%), only one of them had used the custom‐made mouthguard. Most of the athletes gained the knowledge about mouthguards from foreign players (33.5%), media (24.8%) and teammates/classmates (24.3%). The influence of dentists was very weak. Athletes should be informed about the high risk of oral injuries when participating in contact sports. Dentists should play a more significant role in the program of promoting mouthguard use to prevent the occurrence of oral injury in sport participation.
Practicability of a tooth rescue concept – the use of a tooth rescue box
Authors: Filippi Cornelia , Kirschner Horst , Filippi Andreas , Pohl Yango
Published: July 2008

Abstract –  Healing following replantation of avulsed teeth is dependent upon short unphysiologic periods during the extraalveolar phase. A commercially available tooth rescue box was developed and distributed at schools in Hessen, a state in Germany. Aim of the study was to evaluate the availability times of rescue boxes and the storage periods of rescued teeth within the boxes. Two thousand one hundred tooth rescue boxes together with a questionnaire were distributed predominantly at schools. In case of usage of a box, the questionnaire should be filled out by patients and dentists and sent back for evaluation. One hundred seventy‐two (8.2%) questionnaires were sent back. Eighteen questionnaires were incomplete. In the remaining 154 tooth rescue boxes, a total of 201 avulsed teeth and tooth crown fragments were rescued. When accidents occurred near a stored rescue box, the availability time was short (median: 5 min). It was significantly longer (median: 35 min) when the location of the accident was distant to a stored box. Storage of avulsed teeth in the tooth rescue box was longer (median: 2 h) than storage of fractured crown fragments (median: 1 h). Lay people (teachers, pupils) used the rescue boxes correctly without professional help or even advice through telephone. The usage of the tooth rescue box seemed to be self‐explanatory and plausible to lay persons, very short availability times resulted when accidents occurred near stored boxes. Thus, an excellent healing prognosis can be anticipated after replantation. The storage periods of avulsed teeth before the commencement of treatment exceed by far the periods that are acceptable for alternative but unphysiologic media (saline, saliva, milk). It is concluded that tooth rescue boxes should be distributed at locations prone to tooth traumas (schools, kindergartens, sporting facilities, public pools) to enhance the prognosis of avulsed teeth. Emergency units (hospitals, ambulances) should be equipped with tooth rescue boxes as well as every dentist. Tooth rescue boxes are recommended for families with children.
Compliance of children and youngsters in the use of mouthguards
Authors: Matalon Vered , Brin Ilana , Moskovitz Moti , Ram Diana
Published: July 2008

Abstract –  The purpose of the study was to examine the compliance of children wearing their mouthguards, and to evaluate socio‐environmental factors that impact upon the usage of the device. Eighty children attending the student clinic of the Hadassah School of Dental Medicine received mouthguards free of charge. One year later, 69 participants and their parents answered a survey aimed at gaining information regarding compliance and comfort when wearing the mouthguard correlated with gender, ages of parents and child, number of siblings, position of child in the family, socio‐economic status, education of parents and past dental injuries of siblings or parents. Twenty‐nine percent of the children never wore the mouthguard, 32% wore it sometimes, 15.9% wore it when necessary at the beginning but stopped after one month and 23.2% wore the mouthguard whenever needed. About 68% of the participants still possessed the mouthguard one year after receiving it, 44.9% reported that they did not wear the mouthguard because they forgot and 42% reported that the reason for not wearing the appliance was because it was not comfortable. Seventy‐seven percent of the parents were not aware of the existence of this appliance prior to this study. In addition, 47.9% stated that dentists had not offered such treatment to them in the past, 20.8% indicated that their child had never possessed a mouthguard before due to its significant expense and 39.6% stated that they would not invest in this treatment in the future because their child would not wear the appliance. Boys were more comfortable wearing the mouthguard than girls. The younger the child and the later s/he was in the sibling order of the family, the more likely s/he was to lose the mouthguard.
Dental trauma among 5th and 6th grade Arab schoolchildren in Eastern Jerusalem
Authors: Sgan‐Cohen Harold D , Yassin Hillal , Livny Alon
Published: July 2008

Abstract –  Dental trauma is an irreversible pathology which after occurrence is characterized by life long debilitating effects. The objective of the study was to measure the prevalence of trauma in anterior permanent teeth among children and associations with independent variables. A total of 453 5th and 6th grade Arab Eastern Jerusalem schoolchildren participated. Trauma, incisal overjet and lip competence were measured by one examiner in the schools. Reasons and location of trauma were assessed by telephone interviews with the parents. The total prevalence of dental trauma was 33.8%. Severe trauma prevalence (involving dentine) was 12.6%. Severe trauma was more prevalent among boys (OR = 2.03, P = 0.026); children with lip incompetence (OR = 2.71, P = 0.001); and those with an overjet of 4mm or more (OR = 3.73, P < 0.001). The main reported causes for dental trauma were falling (29.1%), sports (16.4%), violence (20%) and playing (20%). According to the parents’ reports, more fall‐related injuries were reported at home, more sport injuries at school, more ‘playing’ injuries ‘outside’ (P < 0.001). Combination of results with a previous study among Jewish schoolchildren demonstrated: severe dental trauma was related to overjet (OR = 1.73, P = 0.002), lip incompetence (OR = 2.19, P < 0.001), gender (OR for males = 1.54, P = 0.005), but not to ethnicity (Arab or Jewish). The reasons for trauma observed in this study were potentially preventable. A community effort should therefore be pursued, with the aim of educating sports teachers, teachers, health personnel and schoolchildren regarding awareness of dental trauma prevention, with emphasis on utilizing mouthguards and early orthodontic intervention, when financially possible.
Incidence and pattern of mandibular fractures in rural population: a review of 324 patients at a tertiary hospital in Loni, Maharashtra, India
Authors: Bither Saurab , Mahindra Uma , Halli Rajshekhar , Kini Yogesh
Published: July 2008

Abstract –  The aim of this study was to document the pattern and incidence of mandibular fractures occurring in rural population, at Rural Dental College and Hospital, Maharashtra, India. A retrospective analysis of patient records and radiographs for the 5‐year period from January 2003 to December 2007 was conducted. Data were identified and analyzed based on age group, gender distribution, anatomic location, and cause of injury. A total of 324 patients with 486 injuries were reviewed, males formed 80.9% and females 19.1% of the studied population, with peak incidence occurring in the 21–30 years age group. The most common fractures site was parasymphysis (39.3%). The etiology of mandibular fractures was road traffic accidents (42.9%), followed by falls (25.9%), assaults and interpersonal violence (20.7%), and animal injuries (10.5%). Our results exhibit that road traffic accidents remain the major cause of mandibular trauma and animal injuries being found exclusively in rural population. There is a variation of incidence and pattern of maxillofacial trauma from region to region.
An investigation into dentists’ management methods of dental trauma to maxillary permanent incisors in Victoria, Australia
Authors: Yeng Thai , Parashos Peter
Published: July 2008

Abstract –  Trauma to anterior teeth in children could become a long‐term problem to dental health. To a large extent, the management actions of the dentists involved will determine the clinical outcome and, in turn, these actions will be related to their levels of knowledge. The aim of this study was to investigate dentists’ knowledge of managing traumatic injuries to maxillary permanent incisors in children. A self‐completion questionnaire containing 19 questions on management methods of treating dental trauma was mailed to 693 dentists in Victoria, Australia. The response rate achieved was 61%. This survey found that some of the respondents had adequate management knowledge for the different types of traumatic injuries, while others did not have the correct information. Approximately half the dentists considered milk as the preferred extraoral storage medium of choice for avulsed teeth and a period of 7–10 days splinting after replantation. A large proportion of dentists showed inadequate knowledge with regard to understanding the biological mechanisms causing replacement root resorption (61%) and external inflammatory root resorption (74%). Overall, the respondents to this survey demonstrated only a moderate level of knowledge in management of traumatic injuries to maxillary permanent incisors in children. Continuing professional development programmes may be a means of improving this deficient knowledge base.
Spatial analysis of dental trauma in 12‐year‐old schoolchildren in Curitiba, Brazil
Authors: Moysés Simone Tetu , Camilotti Augusto Gewehr , Vetorello Marcelo , Moysés Samuel Jorge
Published: July 2008

Abstract – The purpose of this study was to build epidemiological indicators on the experience of dental trauma in 12‐year‐old schoolchildren in the city of Curitiba, Brazil, exploring its geographical and population distributions. A geographic information system (GIS) was used, built by means of ArcViewGIS 3.2 software and geographical databases of streets and districts defined within the boundaries of the city of Curitiba, provided by Curitiba’s Institute of Research and Public Planning (IPPUC). The database used in the study was compiled based on an epidemiological survey undertaken in 1998 on a sample of 2126 schoolchildren 12 years old, residing in outlying urban suburbs distributed over 29 micro‐areas in the city of Curitiba. The cases selected for this study were those with a history of dental trauma, thereby comprising a subsample of 327 schoolchildren. The spatial location of the schoolchildren’s homes enabled the events to be visualized on a cartographic basis. The variables of gender, aetiology of the trauma and areas of substandard living conditions were included in the analysis and construction of thematic maps, thus making possible a descriptive analysis of the spatial distribution of dental trauma in the city. Intra‐urban differentials were identified in the prevalence of dental trauma in 12‐year‐old schoolchildren in Curitiba. A greater concentration of occurrences was observed in the eastern region of the city, especially in areas of substandard living conditions. It was possible to conclude that socio‐environmental and geophysical factors are associated with the determination of dental trauma in the city of Curitiba, pointing to the need for the development of public policies especially aimed at areas and populations at greater risk.
Father Doesn’t Know Best? Parents’ Control of Money and Children’s Food Insecurity
Authors: Kenney Catherine T.
Published: July 2008

Although developing‐country research has found that spending on children varies depending on which parent controls income, developed‐country research tends to ignore intrahousehold allocation. This study uses Fragile Families and Child Wellbeing Study data (N= 1,073 couples) to analyze how mothers versus fathers controlling money affects U.S. children’s food insecurity. Results show children are far less likely to experience food insecurity when parents’ pooled income is controlled by their mother than when it is controlled by their father or even when it is jointly controlled. By examining this association between resource control and child well‐being, this study suggests that child outcomes may be improved by altering control over household money, responsibility for feeding work, or both.
Mother and Daughter Reports About Upward Transfers
Authors: Lin I‐Fen
Published: July 2008

Using 619 mother‐daughter dyads interviewed in the 1997 National Longitudinal Surveys of Mature Women and Young Women, this study examines the assistance that adult daughters provide to their mothers and its covariates. Mothers and daughters have low levels of agreement on transfers. Using mothers’ reports identifies different covariates of transfers than using daughters’ reports. After discrepancies between mother and daughter reports are controlled for, only 3 out of 17 covariates examined are related to transfers, including mothers’ widowhood status, the number of mothers’ difficulties with activities of daily living, and the distance between mother and daughter residences. These findings suggest that without controlling for discrepancies between mother and daughter reports, the covariates of upward transfers may be inaccurately identified.
Sequencing of 15 new BoLA‐DRB3 alleles
Authors: Wang K. , Sun D. , Zhang Y.
Published: July 2008

The class II DR of bovine major histocompatibility complex of cattle (BoLA) plays a central role in the regulation of the immune response through their ability to present those peptides to T‐cell receptors. In this work, we sequenced the exon2 of DRB3 to identify new alleles in Chinese yellow cattle, a total of 15 new BoLA‐DRB3 alleles were found.
Impacts of Riparian Forest Removal on Palauan Streams
Authors: MacKenzie Richard A.
Published: July 2008

The 2006 completion of the circum‐island Compact Road on the island of Babeldaob in the Republic of Palau resulted in several deforested stream reaches with modified stream channels. To determine the impacts of deforestation and road construction, various ecosystem parameters were compared between road‐impacted reaches, reforested savanna reaches, and forested reaches. Compared to adjacent forested reaches, road‐impacted reaches received significantly more light (0.4 ± 0.1 vs. 87.8 ± 4.1 % light transmittance, respectively), were significantly warmer (25.7 ± 0.1 vs. 26.1 ± 0.1°C, respectively), and received higher nutrient and sediment loads, all of which were attributed to the removal of riparian vegetation and increased surface runoff from the road. These differences were believed to have shifted the benthic algal community in road‐impacted reaches from diatoms to filamentous algae with significantly greater chl a biomass (10×) and benthic algal ash free dry mass AFDM (3×) compared to adjacent forested reaches. Savanna‐impacted and forested reaches had similar chl a, algal AFDM, and received similar amounts of light. Nutrient and sediment concentrations varied between the two reach types. Results from this study emphasize the need for the maintenance of riparian forests especially with predicted increases in population, development, and deforestation. Future studies are needed to determine effective riparian widths and riparian forest community structure to help resource managers and land owners protect and preserve the many ecosystem services that Palauan streams and watersheds provide.
G Protein Subtype Specificity of Rhodopsin Intermediates Metarhodopsin Ib and Metarhodopsin II
Authors: Morizumi Takefumi , Kimata Naoki , Terakita Akihisa , Imamoto Yasushi , Yamashita Takahiro , Shichida Yoshinori
Published: July 2008

Rhodopsin is one of the members of the G protein‐coupled receptor family that can catalyze a GDP–GTP exchange reaction on the retinal G protein transducin (Gt) upon photon absorption. There are at least two intermediate states, meta‐Ib and meta‐II, which exhibit direct interaction with Gt. Meta‐Ib binds to GDP‐bound Gt, while meta‐II forms a complex with Gt having no nucleotide, suggesting that meta‐Ib is a state that initially interacts with Gt. Here we investigated whether or not meta‐Ib exhibits specific interaction with G protein similar to meta‐II, by examining the binding efficiencies of meta‐Ib and meta‐II to Giα and its mutants whose C‐terminal 11 amino acids were replaced with those of Goα, Gqα and Gsα. The affinity of meta‐Ib to the C‐terminal 11 amino acids of Gtα was similar to those of Giα and its mutant with Goα’s C‐terminal 11 amino acids, whereas meta‐II exhibited affinity to the C‐terminal 11 amino acids of Giα mutant with Goα’s C‐terminal 11 amino acids about half of what was seen for Gtα and Giα. Both intermediates exhibited no affinity to the Giα mutants containing the C‐terminal 11 amino acids of Gqα and Gsα. These results suggested that meta‐Ib is the state that exhibits specific interaction with G protein as meta‐II does, although meta‐Ib exhibits a slightly lenient binding selectivity compared to that of meta‐II.
The Ability of Low Level Laser Therapy to Prevent Muscle Tissue Damage Induced by Snake Venom
Authors: Doin‐Silva Rosany , Baranauskas Vitor , Rodrigues‐Simioni Lea , Da Cruz‐Höfling Maria Alice
Published: July 2008

Antivenom therapy has been ineffective in neutralizing the severe local fast developing tissue damage following snakebite envenoming. Herein, some effects of in situ helium neon (HeNe) laser irradiation on rat nerve‐muscle preparation injected with Bothrops jararacussu venom are described. The tibialis anterior muscle was injected with venom diluted in 0.9% saline solution (60 μg/0.02 mL) or saline solution alone. Sixty minutes after venom injection, laser (HeNe) treatment was administered at three incident energy densities: dose 1, a single exposure of 3.5 J cm−2; dose 2, three exposures of 3.5 J cm−2; dose 3, a single exposure of 10.5 J cm−2. Muscle function was assessed through twitch tension recordings whereas muscle damage was evaluated through histopathologic analysis, morphometry of area of tissue affected and creatine kinase (CK) serum levels, and compared to unirradiated muscles. Laser application at the dose of 3.5 J cm−2 reduced the area of injury by 64% (15.9 ± 1.5%vs 44.2 ± 5.7%), decreased the neuromuscular blockade (NMB) by 62% (11.5 ± 2.5%vs 30.4 ± 5.2%) and reduced CK levels by 58% (from 455 ± 4.5% to 190.3 ± 23.4%) when compared with unirradiated controls. Dose 2 showed a poorer benefit than dose 1, and dose 3 was ineffective in preventing the venom effects. Measurements of the absorbance of unirradiated and irradiated venom solution showed no difference in absorption spectra. In addition, no difference in the intensity of partial NMB in nerve‐muscle preparation was shown by unirradiated and irradiated venom. The results indicate that the laser light did not alter venom toxicity. We conclude that HeNe laser irradiation at a dosage of 3.5 J cm−2 effectively reduces myonecrosis and the neuromuscular transmission blocking effect caused by B. jararacussu snake venom. Thus, low level laser therapy may be a promising tool to minimize the severity of some of the local effects of snake envenoming.
Modeling Guided Waves for Damage Identification in Isotropic and Orthotropic Plates Using a Local Interaction Simulation Approach
Authors: Sundararaman Shankar , Adams Douglas E.
Published: July 2008

In this paper, a numerical simulation technique based on the local interaction simulation approach (LISA)/sharp interface model (SIM) is used to study the propagation of Lamb waves in aluminum and orthotropic plates and wave interactions with damage. The LISA/SIM model allows for accurate and fast simulations of sharp changes in material properties across interfaces associated with damage or specimen boundaries. Damage in the form of holes and changes in density and/or stiffnesses are studied for three different plates. These local changes in density and stiffness have dimensions not exceeding the wave length of the interrogating wave form. Wave scatter from these damage sites is shown at different time instants and at specific spatial locations. Multiple site damage cases are studied for all the plate structures. The different scatter patterns associated with intersecting and nonintersecting surface cracks are also studied. Results obtained from a combination of single site damage cases are compared with the composite multiple site damage case to study the usability of commonly applied algorithms for identifying damage. The benefits of observing multiple directions of the displacement field are demonstrated. It is shown that the out-of-plane measurements give a clearer indication of damage sites than the in-plane measurements.
3D Simplified Finite Elements Analysis of Load and Contact Angle in a Slewing Ball Bearing
Authors: Daidié Alain , Chaib Zouhair , Ghosn Antoine
Published: July 2008

Bolted bearing connections are one of the most important connections in some industrial structures, and manufacturers are always looking for a quick calculation model for a safe design. In this context, all the analytical and numerical models reduce the global study to the study of the most critical sector. Therefore, the main inputs for these models are the maximal equivalent contact load and the corresponding contact angle. Thus, a load distribution calculation model that takes all the important parameters, such as the stiffness of the supporting structure and the variation in the contact angle, into consideration is needed. This paper presents a 3D finite element (FE) simplified analysis of load distribution and contact angle variation in a slewing ball bearing. The key element of this methodology, which is based on the Hertz theory, is modeling the rolling elements under compression by nonlinear traction springs between the centers of curvature of the raceways. The contact zones are modeled by rigid shells to avoid numerical singularities. Each raceway curvature center is coupled to the corresponding contact zone by rigid shells. The main contribution of this method is not only the evaluation of the contact loads with a relatively reduced calculation time but also the variation in the contact angle from the deformed coordinates of the curvature centers. Results are presented for several loading cases: axial loading, turnover moment, and a combined loading of axial force and turnover moment. The influence of the most important parameters such as the contact angle, the stiffness of the bearings, and the supporting structure is discussed. Finally, a preliminary experimental validation is conducted on a standard ball bearing. The results presented in this paper seem encouraging. The FE study shows an important influence of several parameters and a good correlation with experimental results. Consequently, this model can be extended to other types of slewing bearings such as roller bearings. Moreover, it can be implemented in complex industrial structures such as cranes and lifting devices to determine the corresponding load distributions and contact angles and, consequently, the most critical sector.
Kinematic Characteristics and Classification of Geared Mechanisms Using the Concept of Kinematic Fractionation
Authors: Chen Dar-Zen , Shieh Win-Bin , Yeh Yu-Ching
Published: July 2008

A methodology based on the concept of kinematic fractionation for the revelation of kinematic characteristics and classification of geared mechanisms is presented. It is shown that structurally nonfractionated geared mechanisms can be considered as the combination of kinematic units (KUs). Each KU is considered as the basic motion transmission module inside a geared mechanism. Admissible connections of KUs are identified according to the structural characteristics of one- and two-degree-of-freedom geared mechanisms of up to four KUs. Graphs in the atlas of the geared mechanisms are classified based on the configurations of KUs. Such configurations are then used to construct possible propagation paths of motion via the assignments of input and output links. Since the propagation paths can be modeled by the control block diagram problems, the kinematic relations between input and output links are formulated to gain matrices. According to the types of entities in a gain matrix, various kinematic behaviors are disclosed. It is believed that such kinematic characteristics can be readily transformed into the functional requirements, and the synthesis of geared mechanisms of up to four KUs can be accomplished much easier.
Design of Nonlinear Springs for Prescribed Load-Displacement Functions
Authors: Jutte Christine Vehar , Kota Sridhar
Published: July 2008

A nonlinear spring has a defined nonlinear load-displacement function, which is also equivalent to its strain energy absorption rate. Various applications benefit from nonlinear springs, including prosthetics and microelectromechanical system devices. Since each nonlinear spring application requires a unique load-displacement function, spring configurations must be custom designed, and no generalized design methodology exists. In this paper, we present a generalized nonlinear spring synthesis methodology that (i) synthesizes a spring for any prescribed nonlinear load-displacement function and (ii) generates designs having distributed compliance. We introduce a design parametrization that is conducive to geometric nonlinearities, enabling individual beam segments to vary their effective stiffness as the spring deforms. Key features of our method include (i) a branching network of compliant beams used for topology synthesis rather than a ground structure or a continuum model based design parametrization, (ii) curved beams without sudden changes in cross section, offering a more even stress distribution, and (iii) boundary conditions that impose both axial and bending loads on the compliant members and enable large rotations while minimizing bending stresses. To generate nonlinear spring designs, the design parametrization is implemented into a genetic algorithm, and the objective function evaluates spring designs based on the prescribed load-displacement function. The designs are analyzed using nonlinear finite element analysis. Three nonlinear spring examples are presented. Each has a unique prescribed load-displacement function, including a (i) “J-shaped,” (ii) “S-shaped,” and (iii) constant-force function. A fourth example reveals the methodology’s versatility by generating a large displacement linear spring. The results demonstrate the effectiveness of this generalized synthesis methodology for designing nonlinear springs for any given load-displacement function.
Computational Identification of Link Adjacency and Joint Incidence in Kinematic Chains and Mechanisms
Authors: Kuo Chin-Hsing , Shih Chien-Jong
Published: July 2008

The identification of link adjacency and joint incidence of kinematic chains and mechanisms is important and essential prior to the task of conceptual mechanism design. A careful observation method can be done in general; however, a computational approach is particularly needed for the design automation and algorithmic enumeration. This paper proposes a systematic approach for this goal in which a pseudogenetic concept is employed. The graph identification is then generalized from which the identifications of kinematic chains and mechanisms are automatically mapped. The illustrative examples show that the computation is simple and easily programmable. This development is helpful for the automated structural synthesis of mechanisms.
Bernoulli correction to viscous losses: Radial flow between two parallel discs
Authors: Armengol Jordi , Calbó Josep , Pujol Toni , Roura Pere
Published: July 2008

For a massless fluid (ρ=0), the steady flow along a duct is governed exclusively by viscous losses. In this paper, we show that the velocity profile obtained in this limit can be used to calculate the pressure drop up to the first order in ρ. This method has been applied to the particular case of a duct, defined by two plane-parallel discs. For this case, the first-order approximation results in a simple analytical solution which has been favorably checked against numerical simulations. Finally, an experiment has been carried out with water flowing between the discs. The experimental results show good agreement with the approximate solution.
An introduction to self-assembled quantum dots
Authors: Riel B. J.
Published: July 2008

We give an overview of semiconductor structures that confine charge carriers on a length scale comparable to their de Broglie wavelength, comment on the production and the device applications of such structures, and then describe the properties of self-assembled quantum dots. An idealized model is discussed that reduces the motion of electronic charge carriers confined to a quantum dot to familiar classroom problems. The model allows us to calculate the energy levels in a quantum dot and compare them to the emission spectra of real samples. We calculate the emission spectrum of an InAs self-assembled quantum dot imbedded in GaAs and discuss the limitations of the model.
Equation of state for hard-sphere fluids with and without Kac tails
Authors: Trizac Emmanuel , Pagonabarraga Ignacio
Published: July 2008

We propose a simple derivation of the one-dimensional hard-rod equation of state, with and without a Kac tail (a long-range and weak potential). The case of hard spheres in higher dimension is also addressed, and we recover the virial form of the equation of state in a direct way.
Monitoring thickness deviations in planar multi-layer elastic structures using impedance signatures
Authors: Fisher Karl A.
Published: July 2008

In this letter, a low frequency ultrasonic resonance technique that operates in the 20–80-kHz regime is presented that demonstrates detection of thickness changes on the order of ±10μm. This measurement capability is a result of the direct correlation between the electrical impedance of an electro-acoustic transducer and the mechanical loading it experiences when placed in contact with a layered elastic structure. The relative frequency shifts of the resonances peaks can be estimated through a simple one-dimensional transmission model. Separate experimental measurements confirm this technique to be sensitive to subtle changes in the underlying layered elastic structure.
Active cancellation of occlusion: An electronic vent for hearing aids and hearing protectors
Authors: Mejia Jorge , Dillon Harvey , Fisher Michael
Published: July 2008

The occlusion effect is commonly described as an unnatural and mostly annoying quality of the voice of a person wearing hearing aids or hearing protectors. As a result, it is often reported by hearing aid users as a deterrent to wearing hearing aids. This paper presents an investigation into active occlusion cancellation. Measured transducer responses combined with models of an active feedback scheme are first examined in order to predict the effectiveness of occlusion reduction. The simulations predict 18dB of occlusion reduction in completely blocked ear canals. Simulations incorporating a 1mm vent (providing passive occlusion reduction) predict a combined active and passive occlusion reduction of 20dB. A prototype occlusion canceling system was constructed. Averaged across 12 listeners with normal hearing, it provided 15dB of occlusion reduction. Ten of the subjects reported a more natural own voice quality and an appreciable increase in comfort with the cancellation active, and 11 out of the 12 preferred the active system over the passive system.
Finite element modeling of acousto-mechanical coupling in the cat middle ear
Authors: Tuck-Lee James P. , Pinsky Peter M. , Steele Charles R. , Puria Sunil
Published: July 2008

The function of the middle ear is to transfer acoustic energy from the ear canal to the cochlea. An essential component of this system is the tympanic membrane. In this paper, a new finite element model of the middle ear of the domestic cat is presented, generated in part from cadaver anatomy via microcomputed tomographic imaging. This model includes a layered composite model of the eardrum, fully coupled with the acoustics in the ear canal and middle-ear cavities. Obtaining the frequency response from 100Hzto20kHz is a computationally challenging task, which has been accomplished by using a new adaptive implementation of the reduced-order matrix Padé-via-Lanczos algorithm. The results are compared to established physiological data. The fully coupled model is applied to study the role of the collagen fiber sublayers of the eardrum and to investigate the relationship between the structure of the middle-ear cavities and its function. Three applications of this model are presented, demonstrating the shift in the middle-ear resonance due to the presence of the septum that divides the middle-ear cavity space, the significance of the radial fiber layer on high frequency transmission, and the importance of the transverse shear modulus in the eardrum microstructure.
Testing coherent reflection in chinchilla: Auditory-nerve responses predict stimulus-frequency emissions
Authors: Shera Christopher A. , Tubis Arnold , Talmadge Carrick L.
Published: July 2008

Coherent-reflection theory explains the generation of stimulus-frequency and transient-evoked otoacoustic emissions by showing how they emerge from the coherent “backscattering” of forward-traveling waves by mechanical irregularities in the cochlear partition. Recent published measurements of stimulus-frequency otoacoustic emissions (SFOAEs) and estimates of near-threshold basilar-membrane (BM) responses derived from Wiener-kernel analysis of auditory-nerve responses allow for comprehensive tests of the theory in chinchilla. Model predictions are based on (1) an approximate analytic expression for the SFOAE signal in terms of the BM traveling wave and its complex wave number, (2) an inversion procedure that derives the wave number from BM traveling waves, and (3) estimates of BM traveling waves obtained from the Wiener-kernel data and local scaling assumptions. At frequencies above 4kHz, predicted median SFOAE phase-gradient delays and the general shapes of SFOAE magnitude-versus-frequency curves are in excellent agreement with the measurements. At frequencies below 4kHz, both the magnitude and the phase of chinchilla SFOAEs show strong evidence of interference between short- and long-latency components. Approximate unmixing of these components, and association of the long-latency component with the predicted SFOAE, yields close agreement throughout the cochlea. Possible candidates for the short-latency SFOAE component, including wave-fixed distortion, are considered. Both empirical and predicted delay ratios (long-latency SFOAE delay/BM delay) are significantly less than 2 but greater than 1. Although these delay ratios contradict models in which SFOAE generators couple primarily into cochlear compression waves, they are consistent with the notion that forward and reverse energy propagation in the cochlea occurs predominantly by means of traveling pressure-difference waves. The compelling overall agreement between measured and predicted delays suggests that the coherent-reflection model captures the dominant mechanisms responsible for the generation of reflection-source otoacoustic emissions.
Suppressing aliasing noise in the speech feature domain for automatic speech recognition
Authors: Deng Huiqun , O’Shaughnessy Douglas
Published: July 2008

This letter points out that, although in the audio signal domain low-pass filtering has been used to prevent aliasing noise from entering the baseband of speech signals, an antialias process in the speech feature domain is still needed to prevent high modulation frequency components from entering the baseband of speech features. The existence of aliasing noise in speech features is revealed via spectral analysis of speech feature streams. A method for suppressing such aliasing noise is proposed. Experiments on large vocabulary speech recognition show that antialias processing of speech features can improve speech recognition, especially for noisy speech.
A nonlinear finite-element model of the newborn middle ear
Authors: Qi Li , Funnell W. Robert J. , Daniel Sam J.
Published: July 2008

A three-dimensional static nonlinear finite-element model of a 22-day-old newborn middle ear is presented. The model includes the tympanic membrane (TM), malleus, incus, and two ligaments. The effects of the middle-ear cavity are taken into account indirectly. The geometry is based on a computed-tomography scan and on the published literature, supplemented by histology. A nonlinear hyperelastic constitutive law is applied to model large deformations. The middle-ear cavity and the Young’s modulus of the TM have significant effects on TM volume displacements. The TM volume displacement and its nonlinearity and asymmetry increase as the middle-ear cavity volume increases. The effects of the Young’s moduli of the ligaments and ossicles are found to be small. The simulated TM volume changes do not reach a plateau when the pressure is varied to either −3kPa or +3kPa, which is consistent with the nonflat tails often found in tympanograms in newborns. The simulated TM volume displacements, by themselves and also together with previous ear-canal model results, are compared with equivalent-volume differences derived from tympanometric measurements in newborns. The results suggest that the canal-wall volume displacement makes a major contribution to the total canal volume change, and may be larger than the TM volume displacement.
Modeling broadband ocean acoustic transmissions with time-varying sea surfaces
Authors: Siderius Martin , Porter Michael B.
Published: July 2008

Solutions to ocean acoustic scattering problems are often formulated in the frequency domain, which implies that the surface is “frozen” in time. This may be reasonable for short duration signals but breaks down if the surface changes appreciably over the transmission time. Frequency domain solutions are also impractical for source-receiver ranges and frequency bands typical for applications such as acoustic communications (e.g. hundreds to thousands of meters, 1–50kHz band). In addition, a driving factor in the performance of certain acoustic systems is the Doppler spread, which is often introduced from sea-surface movement. The time-varying nature of the sea surface adds complexity and often leads to a statistical description for the variations in received signals. A purely statistical description likely limits the insight that modeling generally provides. In this paper, time-domain modeling approaches to the sea-surface scattering problem are described. As a benchmark for comparison, the Helmholtz integral equation is used for solutions to static, time-harmonic rough surface problems. The integral equation approach is not practical for time-evolving rough surfaces and two alternatives are formulated. The first approach is relatively simple using ray theory. This is followed with a ray-based formulation of the Helmholtz integral equation with a time-domain Kirchhoff approximation.
The extent to which a position-based explanation accounts for binaural release from informational masking
Authors: Gallun Frederick J. , Durlach Nathaniel I. , Colburn H. Steven , Shinn-Cunningham Barbara G. , Best Virginia , Mason Christine R. , Kidd Gerald
Published: July 2008

Detection was measured for a 500Hz tone masked by noise (an “energetic” masker) or sets of ten randomly drawn tones (an “informational” masker). Presenting the maskers diotically and the target tone with a variety of interaural differences (interaural amplitude ratios and/or interaural time delays) resulted in reduced detection thresholds relative to when the target was presented diotically (“binaural release from masking”). Thresholds observed when time and amplitude differences applied to the target were “reinforcing” (favored the same ear, resulting in a lateralized position for the target) were not significantly different from thresholds obtained when differences were “opposing” (favored opposite ears, resulting in a centered position for the target). This irrelevance of differences in the perceived location of the target is a classic result for energetic maskers but had not previously been shown for informational maskers. However, this parallellism between the patterns of binaural release for energetic and informational maskers was not accompanied by high correlations between the patterns for individual listeners, supporting the idea that the mechanisms for binaural release from energetic and informational masking are fundamentally different.
A new sound coding strategy for suppressing noise in cochlear implants
Authors: Hu Yi , Loizou Philipos C.
Published: July 2008

In the n-of-m strategy, the signal is processed through m bandpass filters from which only the n maximum envelope amplitudes are selected for stimulation. While this maximum selection criterion, adopted in the advanced combination encoder strategy, works well in quiet, it can be problematic in noise as it is sensitive to the spectral composition of the input signal and does not account for situations in which the masker completely dominates the target. A new selection criterion is proposed based on the signal-to-noise ratio (SNR) of individual channels. The new criterion selects target-dominated (SNR⩾0dB) channels and discards masker-dominated (SNR<0dB) channels. Experiment 1 assessed cochlear implant users’ performance with the proposed strategy assuming that the channel SNRs are known. Results indicated that the proposed strategy can restore speech intelligibility to the level attained in quiet independent of the type of masker (babble or continuous noise) and SNR level (0–10dB) used. Results from experiment 2 showed that a 25% error rate can be tolerated in channel selection without compromising speech intelligibility. Overall, the findings from the present study suggest that the SNR criterion is an effective selection criterion for n-of-m strategies with the potential of restoring speech intelligibility.
Fast volumetric integral-equation solver for acoustic wave propagation through inhomogeneous media
Authors: Bleszynski E. , Bleszynski M. , Jaroszewicz T.
Published: July 2008

Elements are described of a volumetric integral-equation-based algorithm applicable to accurate large-scale simulations of scattering and propagation of sound waves through inhomogeneous media. The considered algorithm makes possible simulations involving realistic geometries characterized by highly subwavelength details, large density contrasts, and described in terms of several million unknowns. The algorithm achieves its competitive performance, characterized by O(NlogN) solution complexity and O(N) memory requirements, where N is the number of unknowns, through a fast and nonlossy fast Fourier transform based matrix compression technique, the adaptive integral method, previously developed for solving large-scale electromagnetic problems. Because of its ability of handling large problems with complex geometries, the developed solver may constitute an efficient and high fidelity numerical simulation tool for calculating acoustic field distributions in anatomically realistic models, e.g., in investigating acoustic energy transfer to the inner ear via nonairborne pathways in the human head. Examples of calculations of acoustic field distribution in a human head, which require solving linear systems of equations involving several million unknowns, are presented.
Beamforming correction for dipole measurement using two-dimensional microphone arrays
Authors: Liu Yu , Quayle Alexander R. , Dowling Ann P. , Sijtsma Pieter
Published: July 2008

In this paper, a beamforming correction for identifying dipole sources by means of phased microphone array measurements is presented and implemented numerically and experimentally. Conventional beamforming techniques, which are developed for monopole sources, can lead to significant errors when applied to reconstruct dipole sources. A previous correction technique to microphone signals is extended to account for both source location and source power for two-dimensional microphone arrays. The new dipole-beamforming algorithm is developed by modifying the basic source definition used for beamforming. This technique improves the previous signal correction method and yields a beamformer applicable to sources which are suspected to be dipole in nature. Numerical simulations are performed, which validate the capability of this beamformer to recover ideal dipole sources. The beamforming correction is applied to the identification of realistic aeolian-tone dipoles and shows an improvement of array performance on estimating dipole source powers.
Analysis of noncircular fluid-filled boreholes in elastic formations using a perturbation model
Authors: Şimşek Ergün , Sinha Bikash K.
Published: July 2008

This paper presents a perturbation model to obtain flexural mode dispersions of noncircular fluid-filled boreholes in homogeneous elastic formations. The perturbation model is based on Hamilton’s principle with a modified procedure for the reference state selection in order to handle the directional sensitivity of the flexural modes. The accuracy of the perturbation model has been confirmed by comparison to boundary integral solutions. Numerical results confirm that for a fast formation, even modes, and for a slow formation, odd modes are more sensitive to changes in the borehole elongation and azimuth. Even though the focus of this work is on elliptical boreholes and breakouts, the formulation is valid for any kind of noncircular borehole.