bluuebunny/crossref_metadata_2025 huggingface dataset:
The associations between gingival crevice fluid matrix metalloproteinase‐9, tissue inhibitor of metalloproteinase‐1 and periodontitis in human immunodeficiency virus‐positive patients
Authors: Alpagot T. , Suzara V. , Bhattacharyya M.
Published: September 2006

Background and Objective:  The study aimed to determine whether matrix metalloproteinase‐9 (MMP‐9) and tissue inhibitor of metalloproteinase‐1 (TIMP‐1) in gingival crevice fluid could serve as prognostic factors for the progression of periodontitis in human immunodeficiency virus (HIV) ‐positive patients. Activated inflammatory cells produce inflammatory mediators, which stimulate the production of MMPs and their inhibitors. It is likely that the compromised immune system contributes to the pathogenesis of periodontitis in HIV‐positive patients.

Methods:  Clinical measurements including gingival index, plaque index, bleeding index, probing depth, attachment loss, and gingival crevice fluid samples were taken from two healthy sites (including sites with gingival recession, gingival index = 0; probing depth ≤ 3 mm; attachment loss ≤ 2 mm), three gingivitis sites (gingival index > 0; probing depth ≤ 3 mm; attachment loss = 0) and three periodontitis sites (gingival index > 0; probing depth ≥ 5 mm; attachment loss ≥ 3 mm) of each of the 35 patients at baseline visits and 6‐month visits by means of paper strips. Gingival crevice fluid levels of MMP‐9 and TIMP‐1 were determined by sandwich enzyme‐linked immunosorbent assays.

Results:  The mean amounts of MMP‐9 and TIMP‐1 in the gingivitis and periodontitis sites sites were significantly higher than in the healthy sites (P < 0.0001). The progressing site was defined as a site that had 2 mm or more attachment loss during the 6‐month study period. Gingival crevice fluid levels of MMP‐9 were significantly correlated with probing depth, attachment loss, TIMP‐1, age, smoking pack years, and viral load values at baseline and 6‐month visits (0.0001 < P < 0.001). TIMP‐1 levels were only correlated with CD4, viral load, attachment loss, and MMP‐9 (0.001 < P < 0.01). Repeated measures analysis of 11 active sites vs. 269 inactive sites indicated that MMP‐9 and TIMP‐1 levels were significantly higher in active sites than in inactive sites (P < 0.0001). These data indicate that sites with high ginigval crevice fluid levels of MMP‐9 and TIMP‐1 in HIV‐positive patients are at significantly greater risk for progression of periodontitis.
Expression of suppressors of cytokine signaling in diseased periodontal tissues: a stop signal for disease progression?
Authors: Garlet G. P. , Cardoso C. R. , Campanelli A. P. , Martins W. , Silva J. S.
Published: September 2006

Background and Objective:  Inflammatory cytokines are thought to trigger periodontal tissue destruction. In addition to being regulated by anti‐inflammatory mediators, their activity is under the control of suppressors of cytokine signaling (SOCS), which down‐regulate the signal transduction as part of an inhibitory feedback loop. We therefore investigated the expression of SOCS‐1, ‐2 and ‐3, and the cytokines tumor necrosis factor‐α (TNF‐α) and interleukin‐10, in different forms of human periodontal diseases.

Material and Methods:  Quantitative polymerase chain reaction (RealTime‐PCR) was performed with mRNA from gingival biopsies of control subjects and from that of patients with chronic gingivitis and chronic periodontitis.

Results:  Our results show that patients with chronic gingivitis and chronic periodontitis exhibit significantly higher SOCS‐1, ‐2 and ‐3, TNF‐α and interleukin‐10 mRNA expression when compared with healthy controls. The data also demonstrate that SOCS‐1 and ‐3 mRNA expression was higher in tissue from patients with chronic gingivitis than chronic periodontitis, while the levels of SOCS‐2, TNF‐α and interleukin‐10 mRNA were similar in these groups.

Conclusion:  The increased expression of SOCS‐1, ‐2 and ‐3 mRNA in diseased periodontal tissues is believed to be involved in the down‐regulation of inflammatory cytokine and Toll‐like receptor signaling, and therefore in the attenuation of both the inflammatory reaction and disease severity. Furthermore, it is possible that variation in the levels of SOCS mRNA expressed in different forms of periodontal diseases may determine the stable or progressive nature of the lesions.
The compromised tooth: conservative treatment or extraction?
Authors: RICUCCI DOMENICO , GROSSO ANTONIO
Published: September 2006

In everyday practice, the dentist is not seldom faced with the dilemma of assessing teeth troubled by a combination of endodontic, periodontal, and reconstructive problems. As attempts to saving such teeth may carry risks for failure in the mid and long term, a multidisciplinary team approach to a treatment decision is required. Recent advancement of implantology techniques has brought about a useful option to treacherous tooth‐saving efforts in that severly compromised teeth, following extraction, may be replaced by implants. Such an opportunity, however, involves the inherent risk for overuse to the detriment of the basic thrust of dental care to conserve the natural dentition when damaged or diseased. By referring to a variety of clinical treatment scenarios, this article discusses the factors that may assist the clinician to weigh maintenance against extraction of teeth with guarded prognosis.
Developing practice in breastfeeding
Authors: Renfrew Mary J. , Herbert Gill , Wallace Louise M. , Spiby Helen , McFadden Alison
Published: September 2006

This paper reports on an approach to practice development in breastfeeding as part of a national programme of work to address inequalities in maternal and child nutrition. The production and dissemination of evidence and guidelines is necessary but not sufficient on its own to effect change in practice, particularly when dealing with complex public health issues. In the case of breastfeeding, review evidence and national guidance have shown that multifaceted changes are essential if policy aspirations are to be realized. The objectives of the programme described here were to (1) inform and enable practice development in breastfeeding in low‐income areas; (2) evaluate the impact of approaches used; and (3) develop robust approaches and appropriate material for use nationally. A conceptual framework was established, and a six‐stage process is outlined. The recruitment of four sentinel sites across whole health economies, involving professionals and the voluntary sector, was an essential component of the programme. The strength of the model is that it provides a structured, cross‐sectoral approach to practice development in public health. A key challenge is to identify whose responsibility it is to resource practice development when a number of disciplines and sectors are involved. This question needs to be addressed if public health guidance is to be of sustained benefit.
‘Informal’ learning to support breastfeeding: local problems and opportunities
Authors: Abbott Stephen , Renfrew Mary J. , McFadden Alison
Published: September 2006

This study explored ‘informal’ learning opportunities in three health economies, both for National Health Service (NHS) staff and lay people wishing to promote and support breastfeeding and for new mothers wishing to breastfeed. The word ‘informal’ indicates local learning opportunities that are not part of recognized academic or professional training courses. Semi‐structured telephone interviews were conducted with 31 key informants, including health visitors, midwives, infant feeding advisers, Sure Start personnel, voluntary organization representatives, Strategic Health Authority representatives, senior nurses and trainers. The results were analysed thematically. In each site, there were regular training events for NHS staff to acquire or update knowledge and skills. Training was provided by a small number of enthusiasts. Midwives and health visitors were the groups who attend most frequently, although many find it difficult to make time. Although many training events were multidisciplinary, few doctors appeared to attend. Individual staff also used additional learning opportunities, e.g. other courses, conferences, web‐based learning, and training by voluntary organizations. Services offered to lay people by the NHS, Sure Start and voluntary organizations included parentcraft, antenatal and post‐natal classes, breastfeeding support groups, ‘baby cafés’ and telephone counselling. Interviewees’ organizations did not have a specific breastfeeding strategy, although action groups were trying to take the agenda forward. Local opportunities were over‐dependent on individual champions working in relative isolation, and support is needed from local health economies for the facilitation of coordination and networking.
A training needs survey of doctors’ breastfeeding support skills in England
Authors: Wallace Louise M. , Kosmala‐Anderson Joanna
Published: September 2006

The study examined the training needs of paediatricians and general practitioners (GPs). Respondents rated their competence on 23 breastfeeding support skills, importance of update in the next 2 years, actual and potential helpfulness of different forms of professional updates, and accessibility in the next 2 years. The perception of organizational barriers to breastfeeding support and practitioners’ knowledge of policies and guidance on breastfeeding were also examined. The sample comprised 120 paediatricians and 57 GPs. Response rates were estimated as between 4% and 29%, depending upon the method of recruitment. Although both groups rated themselves as fairly competent in most of the skill areas, they welcomed training in key areas of practice. Paediatricians identified more areas for update than GPs (t = 3.44; d.f. = 178; P < 0.00001). Those who believed that they were less competent in clinical skills were least likely to seek update (r = 0.35; P < 0.00001). Practical forms of training were most often welcomed. Only 47% of GPs and 62.5% of paediatricians had access to a local breastfeeding policy. There were evident gaps in knowledge on key aspects of public health policy, which could influence local practice; for example, 50.8% of GPs and 47.5% of paediatricians identified a younger age for introducing solids than the minimum according to current government guidance. Organizational barriers to breastfeeding support were experienced by all respondents. Recommendations include purposively targeting training to those least likely to seek training, and developing effective self‐study and observational methods of learning. All training should be evaluated and implemented alongside breastfeeding policies and clinical leadership to improve the practice of all healthcare practitioners.
Pouring Rights Contracts and Childhood Overweight: A Critical Theory Perspective
Authors: Opalinski Andra
Published: September 2006

PURPOSE.  To examine school environments, and in particular, pouring rights contracts and how they relate to childhood overweight from a critical theory perspective.

CONCLUSIONS.  Pouring rights contracts provide a profit to powerful mega‐corporations at the expense of children's health. There is a need to move beyond a solely individual approach to addressing childhood overweight and involve a social ecology approach. This would involve a push for social change, including removal of soda machines from schools, and changing marketing practices targeted at children.

PRACTICE IMPLICATIONS.  Nurses are poised in community situations to actively effect social changes to improve health outcomes of our nation's most vulnerable people, but nurses must get involved.
Distribution of tomato‐infecting begomoviruses and Bemisia tabaci biotypes in Morocco
Authors: Tahiri A. , Sekkat A. , Bennani A. , Granier M. , Delvare G. , Peterschmitt M.
Published: September 2006

Tomato yellow leaf curl virus (TYLCV) and tomato yellow leaf curl Sardinia virus (TYLCSV) (genus Begomovirus, family Geminiviridae) as well as their whitefly vector Bemisia tabaci were reported from the south‐west and central regions of Morocco. To establish a more comprehensive view of tomato begomoviruses and B. tabaci biotypes throughout Morocco, 32 tomato fields were surveyed for tomato yellow leaf curl disease (TYLCD) symptoms in southern and northern regions, and 54 samples of leaves from cultivated plants or weeds and 35 B. tabaci individuals were collected and analysed by PCR, randomly amplified polymorphic DNA and sequencing. Only TYLCV or TYLCSV were detected. TYLCV was detected in 15 plant samples whereas TYLCSV only in 4. Sequence analyses revealed the presence of the ‘Spanish’ strain of TYLCSV and distinguished two genetically distinct strains of TYLCV. The begomovirus infections were unevenly distributed throughout Morocco. In the north‐west and north‐central regions where tomato plants exhibiting TYLCD symptoms were rarely observed, only 1 sample out of 13 tested positive for the presence of a begomovirus. In the north‐east region, the ratio of begomovirus‐positive samples was higher, 6/13, and in the south‐west region, it was the highest, 13/14. Consistently the frequency of plants exhibiting TYLCD‐like symptoms in the northern regions was lower than that in the south‐west region. B. tabaci biotype Q is present throughout the country and in Algeria, whereas biotype B, identified for the first time in Morocco, was detected only in the north‐east region.
On testing biological data for the presence of a boundary
Authors: Milne A.E. , Wheeler H.C. , Lark R.M.
Published: September 2006

Under the boundary line model for a biological data set, where one variable is a biological response (e.g. crop yield) to an independent variable (e.g. available water content of the soil), we interpret the upper (or lower) boundary on a plot of the dependent variable (ordinate) against the independent variable (abscissa) as representing the maximum (or minimum) possible response for a given value of the independent variable. This concept has been widely used in soil science, agronomy and plant physiology; but it has been subject to criticism. In particular, no methods that are used to analyse the boundary line quantify the evidence that the envelope of the plot represents a boundary (in the sense of some limiting response to the independent variable) rather than simply being a fringe of extreme values of no intrinsic biological interest. In this article, we present a novel procedure that tests a data set for evidence of a boundary by considering its statistical properties in the region of the proposed boundary. The method is demonstrated using both simulated and real data sets.
INFLUENCE OF WATER ACTIVITY ON THE ACOUSTIC PROPERTIES OF BREAKFAST CEREALS
Authors: GONDEK EWA , LEWICKI PIOTR P. , RANACHOWSKI ZBIGNIEW
Published: September 2006

Corn and wheat bran flakes were compressed in a plastic cylinder and the generated vibrations were measured by a piezoelectric accelerometer. Amplitude–time records were thoroughly analyzed and the total acoustic energy in arbitrary units, number of acoustic events and energy of a single acoustic event were calculated. Relationships between the time of compression, frequency and sound intensity are presented as acoustograms. All parameters, except the energy of a single acoustic event, were strongly dependent on water activity (Aw). The flakes differed essentially in their ability to propagate vibrations. At low Aw's, both types of flakes were alike, but at higher Aw's, corn flakes damped high‐frequency waves while wheat bran flakes did not show this property.
Structural changes in the myosin filament and cross‐bridges during active force development in single intact frog muscle fibres: stiffness and X‐ray diffraction measurements
Authors: Brunello E. , Bianco P. , Piazzesi G. , Linari M. , Reconditi M. , Panine P. , Narayanan T. , Helsby W.I. , Irving M. , Lombardi V.
Published: September 2006

Structural and mechanical changes occurring in the myosin filament and myosin head domains during the development of the isometric tetanus have been investigated in intact frog muscle fibres at 4°C and 2.15 μm sarcomere length, using sarcomere level mechanics and X‐ray diffraction at beamline ID2 of the European Synchrotron Radiation Facility (Grenoble, France). The time courses of changes in both the M3 and M6 myosin‐based reflections were recorded with 5 ms frames using the gas‐filled RAPID detector (MicroGap Technology). Following the end of the latent period (11 ms after the start of stimulation), force increases to the tetanus plateau value (T0) with a half‐time of 40 ms, and the spacings of the M3 and M6 reflections (SM3 and SM6) increase by 1.5% from their resting values, with time courses that lead that of force by ∼10 and ∼20 ms, respectively. These temporal relations are maintained when the increase of force is delayed by ∼10 ms by imposing, from 5 ms after the first stimulus, 50 nm (half‐sarcomere)−1 shortening at the velocity (V0) that maintains zero force. Shortening at V0 transiently reduces SM3 following the latent period and delays the subsequent increase in SM3, but only delays the SM6 increase without a transient decrease. Shortening at V0 imposed at the tetanus plateau causes an abrupt reduction of the intensity of the M3 reflection (IM3), whereas the intensity of the M6 reflection (IM6) is only slightly reduced. The changes in half‐sarcomere stiffness indicate that the isometric force at each time point is proportional to the number of myosin heads bound to actin. The different sensitivities of the intensity and spacing of the M3 and M6 reflections to the mechanical responses support the view that the M3 reflection in active muscle originates mainly from the myosin heads attached to the actin filament and the M6 reflection originates mainly from a fixed structure in the myosin filament signalling myosin filament length changes during the tetanus rise.
Temperature‐ and exercise‐induced gene expression and metabolic enzyme changes in skeletal muscle of adult zebrafish (Danio rerio)
Authors: McClelland Grant B. , Craig Paul M. , Dhekney Kalindi , Dipardo Shawn
Published: September 2006

Both exercise training and cold acclimatization induce muscle remodelling in vertebrates, producing a more aerobic phenotype. In ectothermic species exercise training and cold‐acclimatization represent distinct stimuli. It is currently unclear if these stimuli act through a common mechanism or if different mechanisms lead to a common phenotype. The goal of this study was to survey responses that represent potential mechanisms responsible for contraction‐ and temperature‐induced muscle remodelling, using an ectothermic vertebrate. Separate groups of adult zebrafish (Danio rerio) were either swim trained or cold acclimatized for 4 weeks. We found that the mitochondrial marker enzyme citrate synthase (CS) was increased by 1.5× in cold and by 1.3× with exercise (P < 0.05). Cytochrome c oxidase (COx) was increased by 1.2× following exercise training (P < 0.05) and 1.2× (P= 0.07) with cold acclimatization. However, only cold acclimatization increased β‐hydroxyacyl‐CoA dehydrogenase (HOAD) compared to exercise‐trained (by 1.3×) and pyruvate kinase (PK) relative to control zebrafish. We assessed the whole‐animal performance outcomes of these treatments. Maximum absolute sustained swimming speed (Ucrit) was increased in the exercise trained group but not in the cold acclimatized group. Real‐time PCR analysis indicated that increases in CS are primarily transcriptionally regulated with exercise but not with cold treatments. Both treatments showed increases in nuclear respiratory factor (NRF)‐1 mRNA which was increased by 2.3× in cold‐acclimatized and 4× in exercise‐trained zebrafish above controls. In contrast, peroxisome proliferator‐activated receptor (PPAR)‐α mRNA levels were decreased in both experimental groups while PPAR‐β1 declined in exercise training only. Moreover, PPAR‐γ coactivator (PGC)‐1α mRNA was not changed by either treatment. In zebrafish, both temperature and exercise produce a more aerobic phenotype, but there are stimulus‐dependent responses (i.e. HOAD and PK activities). While similar changes in NRF‐1 mRNA suggest that common responses might underlie aerobic muscle remodelling there are distinct changes (i.e. CS and PPAR‐β1 mRNA) that contribute to specific temperature‐ and exercise‐induced phenotypes.
Structural and Acoustic Behavior of Chiral Truss-Core Beams
Authors: Spadoni A. , Ruzzene M.
Published: September 2006

This paper analyzes the structural and acoustic behavior of sandwich beams with a chiral truss-core. This particular core configuration is considered to exploit some of the unique properties of the chiral geometry and to explore their potential benefits in terms of sound-transmission reduction and vibration isolation. The chiral core is composed of circular elements or nodes, joined by ligaments or ribs. The arrangement of nodes and ribs is such that chiral assemblies exhibit in-plane negative Poisson’s ratio behavior as well as unique deformation patterns. The vibroacoustic performance of the considered beams is evaluated through a numerical model, formulated by employing dynamic shape functions derived directly from the distributed parameter model of beam elements. This formulation allows an accurate evaluation of the dynamic response of the considered structures at high frequencies with a limited number of elements. Furthermore, such a numerical model can be coupled with a Fourier-transform-based analysis of the sound radiated by the structure in a surrounding fluid medium. The structural-acoustic behavior of the proposed beams is investigated in terms of kinetic energy of the constraining layers and sound pressure levels corresponding to an incident pressure wave. A sensitivity study investigates the influence of core configuration and geometry on the beam performance. Moreover, the performance of the chiral core is compared to that of cores with “square” and hexagonal topologies. The results demonstrate the design flexibility offered by the proposed core design, whose configuration is defined by a number of independent parameters that can be modified and optimized to enhance the structural-acoustic performance of the beam.
Effects of Rotary Inertia and Shear Deformation on Nonlinear Free Vibration of Microbeams
Authors: Ramezani Asghar , Alasty Aria , Akbari Javad
Published: September 2006

In this paper, the large amplitude free vibration of a doubly clamped microbeam is considered. The effects of shear deformation and rotary inertia on the large amplitude vibration of the microbeam are investigated. To this end, first Hamilton’s principle is used in deriving the partial differential equation of the microbeam response under the mentioned conditions. Then, implementing the Galerkin’s method the partial differential equation is converted to an ordinary nonlinear differential equation. Finally, the method of multiple scales is used to determine a second-order perturbation solution for the obtained ODE. The results show that nonlinearity acts in the direction of increasing the natural frequency of the doubly clamped microbeam. Shear deformation and rotary inertia have significant effects on the large amplitude vibration of thick and short microbeams.
A Semi-Active, High-Torque, Magnetorheological Fluid Limited Slip Differential Clutch
Authors: Kavlicoglu Barkan , Gordaninejad Faramarz , Evrensel Cahit , Fuchs Alan , Korol George
Published: September 2006

The design, development, and performance characterization of a magnetorheological (MR) fluid clutch for automotive limited slip differential (LSD) applications is presented in this study. The controllability of MR fluids provides an adjustable torque transmission and slippage for the LSD application. Three-dimensional electromagnetic finite element analysis (FEA) is performed to optimize the magnetic circuit and clutch design. Based on the results obtained from the FEA, the theoretical torque transfer capacity of the clutch is predicted utilizing Bingham-Plastic constitutive model. The clutch is characterized at different velocities and electromagnet electric input currents. Both the torque transfer capacity and the response time of the clutch were examined. It was demonstrated that the proposed MR fluid LSD clutch is capable of transferring controllable high torques with a fast response time.
Semi-Active Static Output Feedback Variable Structure Control for Two-Stage Vibration Isolation System
Authors: Zhao Cheng , Chen Lesheng , Chen Dayue
Published: September 2006

A semi-active static output feedback variable structure control (VSC) strategy is presented to control a two-stage vibration isolation system in this paper. A continuous output feedback VSC controller which utilizes the measurements from a limited number of sensors installed at strategic locations is designed and a bypass electrorheological (ER) damper is applied to achieve the best control effect more rapidly and accurately. The determination of sliding surface in terms of the Routh-Hurwitz stability criterion is combined with continuous controller design such that the control law is completely decoupled from external excitations, which are hard to measure or estimate. The self-adaptability of the vibration isolation system with respect to external disturbances, the robustness of the control method with respect to parameter variations and the effectiveness of vibration isolation are demonstrated by numerical simulation results. It showed that the designed semi-active static output feedback VSC strategy realized by the ER damper can achieve better performance than those of optimally passive damping and maximum damping variety even if system parameter uncertainties exist.
Adaptive Control of Rotor Vibration Using Compact Wavelets
Authors: Cole M. O. T. , Keogh P. S. , Burrows C. R. , Sahinkaya M. N.
Published: September 2006

This paper investigates the use of dyadic wavelets for the control of multifrequency rotor vibration. A scheme for real-time control of rotor vibration using an adaptive wavelet decomposition and reconstruction of time-varying signals is proposed. Quasi-periodic control forces are constructed adaptively in real-time to optimally cancel vibration produced by nonsmooth disturbance forces. Controller adaptive gains can be derived using a model-based synthesis or from system identification routines. The controller is implemented on a flexible rotor system incorporating two radial magnetic bearings, with standard proportional-integral-derivative control employed in a parallel feedback loop for rotor levitation. An experimental investigation of controller performance is used to deduce the best choice of wavelet basis for various operating conditions. These include steady synchronous forcing, step changes in synchronous forcing and multifrequency forcing produced by a rotor impact mechanism.
Fabrication and Characterization of Flexible Substrates for Use in the Development of Miniaturized Wireless Sensor Network Modules
Authors: Majeed Bivragh , Delaney Kieran , Barton John , McCarthy Niall , O’Mathuna Sean C. , Alderman John
Published: September 2006

In this paper we describe the materials-related challenges in applying folded flex packaging technology to wireless sensor networks and propose solutions for implementing miniaturized 5mm cube platforms. The focus is to apply thin silicon stacking methods using thin flexible substrate interconnect and in particular to investigate the behavior of the selected materials. Both commercial and in-house polyimide substrates, in the thickness range 25μm down to 3μm (each with 4μm of sputtered copper) were analyzed for appropriate electrical, chemical, and mechanical properties. The characterization highlighted that in flex of thickness below 10μm, a dramatic decrease in stiffness occurs and the polyimide wrinkles due to stresses generated by the copper sputtering process. An evaluation determined that specific steps, such as polymer support ring formation, could be employed to eliminate impact of wrinkling on the process of developing the 5mm cube prototypes.
Heightened Thermal Convection as a Result of Splitting a Square Cavity Diagonally in Half
Authors: Ridouane El Hassan , Campo Antonio
Published: September 2006

This investigation addresses the thermogeometric performance of a two-square cavity system contrasted against a two-isosceles triangular cavity system, with an exactly equal heating segment and comparable cooling segment. When one square cavity is cut diagonally in half, it results in a pair of isosceles triangular cavities. The isosceles triangular cavity on the left is heated from the left vertical wall, the top wall is insulated, and the inclined wall is cold; the so-called HIC triangular cavity. The isosceles triangular cavity on the right is heated from the right vertical wall, the bottom wall is insulated, and the inclined wall is cold; the so-called HCI triangular cavity. It may be speculated that the two-isosceles triangular cavity system may find application in the miniaturization of electronic packaging severely constrained by space and/or weight. The finite volume method, accounting for temperature-dependent thermophysical properties of air, is employed to perform the computational analysis. Representative height-based Rayleigh numbers assume values up to 106 to avoid oscillations that occur at a Rayleigh number between RaH=2×106 and 2.2×106. Numerical results are reported for the velocity field, the temperature field, and the local and the mean convective coefficient along the heated vertical wall. Under a dominant conduction condition for RaH=103, the heat flux across the derived two-isosceles triangular system is 334% higher than its counterpart across the original two-square system. In contrast, for a dominant convection condition for RaH=106, this margin diminishes to 20%, but still constitutes a significant improvement. For the design of two-triangular cavity systems, a NuH correlation equation has been constructed yielding a maximum error of 2% at RaH=104.
Numerical Thermal Simulation of Cryogenic Power Modules Under Liquid Nitrogen Cooling
Authors: Ye Hua , Efstathiadis Harry , Haldar Pradeep
Published: September 2006

Understanding the thermal performance of power modules under liquid nitrogen cooling is important for the design of cryogenic power electronic systems. When the power device is conducting electrical current, heat is generated due to Joule heating. The heat needs to be efficiently dissipated to the ambient in order to keep the temperature of the device within the allowable range; on the other hand, it would be advantageous to boost the current levels in the power devices to the highest possible level. Projecting the junction temperature of the power module during cryogenic operation is a crucial step in designing the system. In this paper, we present the thermal simulations of two different types of power metal-oxide semiconductor field effect transistor modules used to build a cryogenic inverter under liquid nitrogen pool cooling and discussed their implications on the design of the system.
Asymptotically Consistent Numerical Approximation of Hemolysis
Authors: Farinas Marie-Isabelle , Garon André , Lacasse David , N’dri Donatien
Published: September 2006

In a previous communication, we have proposed a numerical framework for the prediction of in vitro hemolysis indices in the preselection and optimization of medical devices. This numerical methodology is based on a novel interpretation of Giersiepen-Wurzinger blood damage correlation as a volume integration of a damage function over the computational domain. We now propose an improvement of this approach based on a hyperbolic equation of blood damage that is asymptotically consistent. Consequently, while the proposed correction has yet to be proven experimentally, it has the potential to numerically predict more realistic red blood cell destruction in the case of in vitro experiments. We also investigate the appropriate computation of the shear stress scalar of the damage fraction model. Finally, we assess the validity of this consistent approach with an analytical example and with some 3D examples.
A Model of Stress and Strain in the Interosseous Ligament of the Forearm Based on Fiber Network Theory
Authors: Pfaeffle H. James , Fischer Kenneth J. , Srinivasa Arun , Manson Theodore , Woo Savio L-Y. , Tomaino Matthew
Published: September 2006

Fiber network theory was developed to describe cloth, a thin material with strength in the fiber directions. The interosseous ligament (IOL) of the forearm is a broad, thin ligament with highly aligned fibers. The objectives of this study were to develop a model of the stress and strain distributions in the IOL, based on fiber network theory, to compare the strains from the model with the experimentally measured strains, and to evaluate the force distribution across the ligament fibers from the model. The geometries of the radius, ulna, and IOL were reconstructed from CT scans. Position and orientation of IOL insertion sites and force in the IOL were measured during a forearm compression experiment in pronation, neutral rotation, and supination. An optical image-based technique was used to directly measure strain in two regions of the IOL in neutral rotation. For the network model, the IOL was represented as a parametric ruled three-dimensional surface, with rulings along local fiber directions. Fiber strains were calculated from the deformation field, and fiber stresses were calculated from the strains using average IOL tensile properties from a previous study. The in situ strain in the IOL was assumed uniform and was calculated so that the net force predicted by the network model in neutral rotation matched the experimental result. The net force in the IOL was comparable to experimental results in supination and pronation. The model predicted higher stress and strain in fibers near the elbow in neutral rotation, and higher stresses in fibers near the wrist in supination. Strains in neutral forearm rotation followed the same trends as those measured experimentally. In this study, a model of stress and strain in the IOL utilizing fiber network theory was successfully implemented. The model illustrates variations in the stress and strain distribution in the IOL. This model can be used to show surgeons how different fibers are taut in different forearm rotation positions—this information is important for understanding the biomechanical role of the IOL and for planning an IOL reconstruction.
Compressive Properties of Mouse Articular Cartilage Determined in a Novel Micro-Indentation Test Method and Biphasic Finite Element Model
Authors: Cao Li , Youn Inchan , Guilak Farshid , Setton Lori A
Published: September 2006

The mechanical properties of articular cartilage serve as important measures of tissue function or degeneration, and are known to change significantly with osteoarthritis. Interest in small animal and mouse models of osteoarthritis has increased as studies reveal the importance of genetic background in determining predisposition to osteoarthritis. While indentation testing provides a method of determining cartilage mechanical properties in situ, it has been of limited value in studying mouse joints due to the relatively small size of the joint and thickness of the cartilage layer. In this study, we developed a micro-indentation testing system to determine the compressive and biphasic mechanical properties of cartilage in the small joints of the mouse. A nonlinear optimization program employing a genetic algorithm for parameter estimation, combined with a biphasic finite element model of the micro-indentation test, was developed to obtain the biphasic, compressive material properties of articular cartilage. The creep response and material properties of lateral tibial plateau cartilage were obtained for wild-type mouse knee joints, by the micro-indentation testing and optimization algorithm. The newly developed genetic algorithm was found to be efficient and accurate when used with the finite element simulations for nonlinear optimization to the experimental creep data. The biphasic mechanical properties of mouse cartilage in compression (average values: Young’s modulus, 2.0MPa; Poisson’s ratio, 0.20; and hydraulic permeability, 1.1×10−16m4∕N‐s) were found to be of similar orders of magnitude as previous findings for other animal cartilages, including human, bovine, rat, and rabbit and demonstrate the utility of the new test methods. This study provides the first available data for biphasic compressive properties in mouse cartilage and suggests a promising method for detecting altered cartilage mechanics in small animal models of osteoarthritis.
Controlled Self-Assembly of Collagen Fibrils by an Automated Dialysis System
Authors: Strasser Stefan , Zink Albert , Heckl Wolfgang M. , Thalhammer Stefan
Published: September 2006

In vitro self-assembled collagen fibrils form a variety of different structures during dialysis. The self-assembly is dependent on several parameters, such as concentrations of collagen and α1-acid glycoprotein, temperature, dialysis time, and the acid concentration. For a detailed understanding of the assembly pathway and structural features like banding pattern or mechanical properties it is necessary to study single collagen fibrils. In this work we present a fully automated system to control the permeation of molecules through a membrane like a dialysis tubing. This allows us to ramp arbitrary diffusion rate profiles during the self-assembly process of macromolecules, such as collagen. The system combines a molecular sieving method with a computer assisted control system for measuring process variables. With the regulation of the diffusion rate it is possible to control and manipulate the collagen self-assembly process during the whole process time. Its performance is demonstrated by the preparation of various collagen type I fibrils and native collagen type II fibrils. The combination with the atomic force microscope (AFM) allows a high resolution characterization of the self-assembled fibrils. In principle, the represented system can be also applied for the production of other biomolecules, where a dialysis enhanced self-assembly process is used.
Effect of Assumed Stiffness and Mass Density on the Impact Response of the Human Chest Using a Three-Dimensional FE Model of the Human Body
Authors: Kimpara Hideyuki , Iwamoto Masami , Watanabe Isao , Miki Kazuo , Lee Jong B. , Yang King H. , King Albert I.
Published: September 2006

The mass density, Young’s modulus (E), tangent modulus (Et), and yield stress (σy) of the human ribs, sternum, internal organs, and muscles play important roles when determining impact responses of the chest associated with pendulum impact. A series of parametric studies was conducted using a commercially available three-dimensional finite element (FE) model, Total HUman Model for Safety (THUMS) of the whole human body, to determine the effect of changing these material properties on the predicted impact force, chest deflection, and the number of rib fractures and fractured ribs. Results from this parametric study indicate that the initial chest apparent stiffness was mainly influenced by the stiffness and mass density of the superficial muscles covering the torso. The number of rib fractures and fractured ribs was primarily determined by the stiffness of the ribcage. Similarly, the stiffness of the ribcage and internal organs contributed to the maximum chest deflection in frontal impact, while the maximum chest deflection for lateral impact was mainly affected by the stiffness of the ribcage. Additionally, the total mass of the whole chest had a moderately effect on the number of rib fractures.
Stress Relaxation of Porcine Gluteus Muscle Subjected to Sudden Transverse Deformation as Related to Pressure Sore Modeling
Authors: Palevski Avital , Glaich Ittai , Portnoy Sigal , Linder-Ganz Eran , Gefen Amit
Published: September 2006

Computational studies of deep pressure sores (DPS) in skeletal muscles require information on viscoelastic constitutive behavior of muscles, particularly when muscles are loaded transversally as during bone-muscle interaction in sitting and lying immobilized patients. In this study, we measured transient shear moduli G(t) of fresh porcine muscles in vitro using the indentation method. We employed a custom-made pneumatic device that allowed rapid (2000mm∕s)4mm indentations. We tested 8 gluteus muscles, harvested from 5 adult pigs. Each muscle was indented transversally (perpendicularly to the direction of fibers) at 3 different sites, 7 times per site, to obtain nonpreconditioned (NPC) and preconditioned (PC) G(t) data. Short-term (GS) and long-term (GL) shear moduli were obtained directly from experiments. We further fitted measured G(t) data to a biexponential equation G(t)=G1∙exp(−t∕τ1)+G2∙exp(−t∕τ2)+G∞, which provided good fit, visually and in terms of the correlation coefficients. Typically, plateau of the stress relaxation curves (defined as 10% difference from final GL) was evident ∼20s after indentation. Short-term shear moduli GS (mean NPC: 8509Pa, PC: 5711Pa) were greater than long-term moduli GL (NPC: 609Pa, PC: 807Pa) by about an order of magnitude. Statistical analysis of parameters showed that only G2 was affected by preconditioning, while GL, GS, G∞, τ1, τ2, and G1 properties were unaffected. Since DPS develop over time scales of minutes to hours, but most stress relaxation occurs within ∼20s, the most relevant property for computational modeling is GL (mean ∼700Pa), which is, conveniently, unaffected by preconditioning.
Determination of External Forces—Application to the Calibration of an Electromagnetic Actuator
Authors: Bucher Izhak , Rosenstein Moshe
Published: September 2006

A new method to estimate time-varying external forces acting upon a vibrating structure is presented in this paper. The method is developed for a force-calibrating device which is designed to be rigid in the operating frequency band and, therefore, it was believed that simple force-gauges should recover the applied forces. It has been observed that the inertia of the vibrating calibration device distorts the estimated force, even when the excitation is only one-third of the first natural frequency. Unlike traditional methods, the frequency response need not be inverted, alternatively a smoothed, Lagrange multiplier based estimation method is formed. With the proposed method, an electromagnetic excitation device can be calibrated such that the electromagnetic forces can be compared with theoretical estimates. The unique features of the proposed method are: (a) Compensation for inertia forces; (b) incorporation of measured reaction forces in a mixed analytical and experimentally obtained model; (c) possible independence on elastic stiffness forces; and (d) closed form, integral equations. New equations relating the externally applied forces and various measurable physical parameters are established, for example: The dependency upon the air-gap, current, and magnetic flux can be found.
An Improved Component-Mode Synthesis Method to Predict Vibration of Rotating Spindles and Its Application to Position Errors of Hard Disk Drives
Authors: Eguchi Takehiko , Nakamiya Teruhiro
Published: September 2006

This paper describes an accurate mathematical model that can predict forced vibration of a rotating spindle system with a flexible stationary part. In particular, we demonstrate this new formulation on a hard disk drive (HDD) spindle to predict its position error signal (PES). This improved method is a nontrivial extension of the mathematical model by Shen and his fellow researchers, as the improved method allows the flexible stationary part to comprise multiple substructures. When applied to HDD vibration, the improved model consists not only a rotating hub, multiple rotating disks, a stationary base, and bearings (as in Shen’s model) but also an independent flexible carriage part. Moreover, the carriage part is connected to the stationary base with pivot bearings and to the disks with air bearings at the head sliders mounted on the far end of the carriage. To build the improved mathematical model, we use finite element analysis (FEA) to model the complicated geometry of the rotating hub, the stationary base and the flexible carriage. With the mode shapes, natural frequencies, and modal damping ratios obtained from FEA, we use the principle of virtual work and component-mode synthesis to derive an equation of motion. Naturally, the stiffness and damping matrices of the equation of motion depend on properties of the pivot and air bearings as well as the natural frequencies and mode shapes of the flexible base, the flexible carriage, the hub, and the disks. Under this formulation, we define PES resulting from spindle vibration as the product of the relative displacement between the head element and the disk surface and the error rejection transfer function. To verify the improved model, we measured the frequency response functions using impact hammer tests for a real HDD that had a fluid-dynamic bearing spindle, two disks, and three heads. The experimental results agreed very well with the simulation results not only in natural frequencies but also in gain and phase.
SUMO1
Haploinsufficiency Leads to Cleft Lip and Palate
Authors: Alkuraya Fowzan S. , Saadi Irfan , Lund Jennifer J. , Turbe-Doan Annick , Morton Cynthia C. , Maas Richard L.
Published: September 2006

The posttranslational modification sumoylation can have multiple effects on its substrate proteins. We studied a patient with isolated cleft lip and palate and a balanced chromosomal translocation that disrupts the SUMO1 (small ubiquitin-related modifier) gene, resulting in haploinsufficiency. In mouse, we found that Sumo1 is expressed in the developing lip and palate and that a Sumo1 hypomorphic allele manifests an incompletely penetrant orofacial clefting phenotype. Products of several genes implicated in clefting are sumoylated, and the Sumo1 hypomorphic allele interacts genetically with a loss-of-function allele for one of these loci. Thus, sumoylation defines a network of genes important for palatogenesis.
Comment on "A Keystone Mutualism Drives Pattern in a Power Function"
Authors: Alonso David , Pascual Mercedes
Published: September 2006

Vandermeer and Perfecto (Reports, 17 February 2006, p. 1000) reported a general power law pattern in the distribution of a common agricultural pest. However, there is an exact analytical solution for the expected cluster distribution under the proposed null model of density-independent growth in a patchy landscape. Reanalysis of the data shows that the system is not in a critical state but confirms the importance of a mutualism.
Structural Basis of
glmS
Ribozyme Activation by Glucosamine-6-Phosphate
Authors: Klein Daniel J. , Ferré-D'Amaré Adrian R.
Published: September 2006

The
glmS
ribozyme is the only natural catalytic RNA known to require a small-molecule activator for catalysis. This catalytic RNA functions as a riboswitch, with activator-dependent RNA cleavage regulating
glmS
messenger RNA expression. We report crystal structures of the
glmS
ribozyme in precleavage states that are unliganded or bound to the competitive inhibitor glucose-6-phosphate and in the postcleavage state. All structures superimpose closely, revealing a remarkably rigid RNA that contains a preformed active and coenzyme-binding site. Unlike other riboswitches, the
glmS
ribozyme binds its activator in an open, solvent-accessible pocket. Our structures suggest that the amine group of the
glmS
ribozyme-bound coenzyme performs general acid-base and electrostatic catalysis.