bluuebunny/crossref_metadata_2025 huggingface dataset:
Impact of diabetes mellitus and metabolic control on bone healing around osseointegrated implants: removal torque and histomorphometric analysis in rats
Authors: de Molon Rafael Scaf , Morais‐Camilo Juliana Aparecida Najarro Dearo , Verzola Mario Henrique Arruda , Faeda Rafael Silveira , Pepato Maria Teresa , Marcantonio Elcio
Published: April 2012

Objectives

To evaluate bone healing around dental implants with established osseointegration in experimental diabetes mellitus (DM) and insulin therapy by histomorphometric and removal torque analysis in a rat model.

Materials and methods

A total of 80 male Wistar rats received a titanium implant in the tibiae proximal methaphysis. After a healing period of 60 days, the rats were divided into four groups of 20 animals each: a 2‐month control group, sacrificed at time (group A), a diabetic group (group D), an insulin group (group I), and a 4‐month control group (group C), subdivided half for removal torque and half for histomorphometric analysis. In the D and I groups the DM was induced by a single injection of 40 mg/kg body weight streptozotocin (STZ). Two days after DM induction, group I received subcutaneous doses of insulin twice a day, during 2 months. Groups C and D received only saline. Two months after induction of DM, the animals of groups D, C and I were sacrificed. The plasmatic levels of glucose (GPL) were monitored throughout the experiment. Evaluation of the percentages of bone‐to‐implant contact and bone area within the limits of the implant threads was done by histomorphometric and mechanical torque analysis. Data were analyzed by anova at significant level of 5%.

Results

The GPL were within normal range for groups A, C and I and higher for group D. The means and standard deviations (SD) for histomorphometric bone area showed significant difference between group D (69.34 ± 5.00%) and groups C (78.20 ± 4.88%) and I (79.63 ± 4.97%). Related to bone‐to‐implant contact there were no significant difference between the groups D (60.81 + 6.83%), C (63.37 + 5.88%) and I (66.97 + 4.13%). The means and SD for removal torque showed that group D (12.91 ± 2.51 Ncm) was statistically lower than group I (17.10 ± 3.06 Ncm) and C (16.95 ± 5.39 Ncm).

Conclusions

Diabetes mellitus impaired the bone healing around dental implants with established osseointegration because the results presented a lower percentage of bone area in group D in relation to groups C and I resulting in a lowest torque values for implant removal. Moreover, insulin therapy prevents the occurrence of bone abnormalities found in diabetic animals and osseointegration was not compromised.
Stem Cells in the Reproductive System
Authors: Kyurkchiev Stanimir , Gandolfi Fulvio , Hayrabedyan Soren , Brevini Tiziana A. L. , Dimitrov Roumen , Fitzgerald Justine S. , Jabeen Asma , Mourdjeva Milena , Photini Stella M. , Spencer Patrick , Fernández Nelson , Markert Udo R.
Published: April 2012

This review article summarizes current knowledge on regulation, functions, and capacities of stem cells in the female and male reproductive tract. Major locations in which pluripotent cells reside and from where they can be isolated are the ovaries, the endometrium, the decidua, and the testis. They include oocytes, embryonic stem cells, trophoblast stem cells, and spermatogonial stem cells, but also several side populations, which can be obtained after certain isolation and culture procedures. The potential of pluripotent cells in the reproductive tract to differentiate is manifold, but heterogenous, depending upon their respective origin. As stem cells have a potential for future application in transplantation and regenerative medicine, this article also reviews the literature on major histocompatibility complex expression on stem cells of the reproductive tract, because of its immunogenic effects, but also because of its potential expression of HLA‐G, a potent immunomodulator mainly associated with trophoblast cells.
Effect of intra‐seasonal variability on vegetation data
Authors: Vymazalová Marie , Axmanová Irena , Tichý Lubomír
Published: April 2012

Questions

It is generally acknowledged that the date of sampling partly determines the floristic composition and layer covers of vegetation plots. However, the effect of vegetation seasonality on the results of vegetation analyses is still insufficiently explored. Here, we investigated two data sets to examine how intra‐seasonal variability of vegetation influences the pattern of: (1) species composition; (2) species richness, number of unrecorded species, plant life‐form spectra; and (3) quantitative changes in cover of individual species and layers.

Location

Deciduous forests and dry grasslands in SE Czech Republic.

Methods

We established 40 forest and 46 dry grassland permanent plots, each sampled in three periods (spring, summer and autumn). We compared species composition and β‐diversity patterns in multi‐dimensional space between different periods of the growing season using permutational multivariate analyses (PERMANOVA, PERMDISP). We used ANOVA for repeated measures and Tukey post‐hoc tests to assess differences in species richness, proportions of unrecorded species, changes in layer cover and plant life‐form spectra.

Results

In the Forest data set, spring plots significantly differed in their species composition from summer and autumn plots, while we found significant differences between different periods of the growing season in the Dry grasslands data set. We confirmed, that the forest species richness was highest in summer plots, while the α‐diversity in spring and summer dry grassland plots were comparable and notably declined in autumn. Although most plant life forms were best recorded in summer, both forest geophytes and dry grassland therophytes were best recorded in spring.

Conclusions

We suggest that before analysing vegetation plot data, large databases should be carefully stratified according to date of sampling. Based on our results from temperate broad‐leaved forests and dry grasslands, we recommend excluding plots sampled before June, as they might be a potential source of misinterpretation of species composition analyses (with the exception of studies focused on vernal species). The use of autumn plots does not have any strong effect on the results, except in α‐diversity analyses in forest plots, while dry grassland plots are significantly different from the rest of the growing season.
Distribution and richness of aquatic plants across Europe and Mediterranean countries: patterns, environmental driving factors and comparison with total plant richness
Authors: Chappuis Eglantine , Ballesteros Enric , Gacia Esperança
Published: April 2012

Questions

What are the geographic patterns of γ‐diversity of aquatic plants and what are the main driving factors? Are richness trends for aquatic plants similar to total plant richness? Is the Mediterranean area a hot spot for aquatic plants?

Location

Europe and the Mediterranean Basin.

Material

We listed vascular aquatic plant presence or absence for 44 countries. We also compiled total plant species richness and geographic and environmental variables for each country.

Methods

We first analysed country ordination based on their aquatic flora constrained by environmental variables (dbRDA), and selected the environmental variables best explaining species patterns (BEST analysis). Total species richness patterns were studied using maps and latitudinal gradients. We used generalized additive models (GAM) to detect the main environmental factors driving species richness, both for aquatic plants and total plants.

Results

The BEST analysis identified a single variable that best explains aquatic plant species distribution: evapotranspiration. However, richness of aquatic plants vs latitude varies and no clear trend was observed. No relation was found between total plant and aquatic plant richness. Aquatic and total plant richness peak between 40° and 50°N, and values were intermediate at low latitudes. GAM related aquatic plant richness with water resources and rainfall, while total plant richness is mainly driven by evapotranspiration and temperature. Hydrophytes were relatively more abundant at higher latitudes than helophytes and the ratio correlated with evapotranspiration.

Conclusion

Southern and western Europe hold the highest aquatic plant diversity, although no clear latitudinal species richness patterns were found. Aquatic plant richness is mainly driven by water‐related variables. Total plant richness exhibits a latitudinal pattern influenced by the Sahara desert, which depresses richness at low latitudes. Best predictors of total plant richness patterns are water–energy variables.
Oral Contraceptive Containing Chlormadinone Acetate and Ethinylestradiol Reduces Plasma Concentrations of Matrix Metalloproteinase‐2 in Women with Polycystic Ovary Syndrome
Authors: Gomes Valéria A. , Vieira Carolina S. , Jacob‐Ferreira Anna L. , Belo Vanessa A. , Soares Gustavo M. , França Janaína B. , Ferriani Rui A. , Tanus‐Santos Jose E.
Published: April 2012

Biochemical markers of cardiovascular disease, including matrix metalloproteinases (MMPs), are altered in women with polycystic ovary syndrome (PCOS), with many of these alterations thought to be due to excess androgen concentrations. Despite oral contraceptives (OCs) being the first‐line pharmacological treatment in women with PCOS and the importance of MMPs in many physiological conditions and pathological states, including cardiovascular diseases, no study has yet evaluated whether OCs alter plasma concentrations of MMPs. We therefore assessed whether treatment with an OC containing the anti‐androgenic progestogen alters MMP profiles in women with PCOS. We analysed 20 women with PCOS who wanted hormonal contraception (OC‐PCOS group), 20 ovulatory women who required hormonal contraception (OC‐control group) and 20 ovulatory women who wanted non‐hormonal contraception (non‐OC‐control group). OC consisted of cyclic use of 2 mg chlormadinone acetate/30 μg ethinylestradiol for 6 months. Plasma concentrations of MMP‐2, MMP‐9, TIMP‐1 and TIMP‐2 were measured by gelatin zymography or enzyme‐linked immunoassays. OC treatment for 6 months significantly reduced plasma MMP‐2 concentrations in the OC‐control and OC‐PCOS groups and TIMP‐2 and TIMP‐1 concentrations levels in the OC‐control group (all p < 0.05), but had no effects on MMP‐9 concentrations or on MMP‐2/TIMP‐2 and MMP‐9/TIMP‐1 ratios in any group (all p > 0.05). These findings indicated that long‐term treatment with an OC containing chlormadinone acetate plus ethinylestradiol reduced plasma MMP‐2 concentrations in both healthy and PCOS women. As the latter have imbalances in circulating matrix MMPs, treatment of these women with an OC may be beneficial.
Position Paper: Management of Men Complaining of a Small Penis Despite an Actually Normal Size
Authors: Ghanem Hussein , Glina Sidney , Assalian Pierre , Buvat Jacques
Published: April 2012

Introduction

With the worldwide increase in penile augmentation procedures and claims of devices designed to elongate the penis, it becomes crucial to study the scientific basis of such procedures or devices, as well as the management of a complaint of a small penis in men with a normal penile size.

Aim

The aim of this work is to study the scientific basis of opting to penile augmentation procedures and to develop guidelines based on the best available evidence for the management of men complaining of a small penis despite an actually normal size.

Methods

We reviewed the literature and evaluated the evidence about what the normal penile size is, what patients complaining of a small penis usually suffer from, benefits vs. complications of surgery, penile stretching or traction devices, and outcome with patient education and counseling. Repeated presentation and detailed discussions within the Standard Committee of the International Society for Sexual Medicine were performed.

Main Outcome Measure

Recommendations are based on the evaluation of evidence-based medical literature, widespread standards committee discussion, public presentation, and debate.

Results

We propose a practical approach for evaluating and counseling patients complaining of a small-sized penis.

Conclusions

Based on the current status of science, penile lengthening procedure surgery is still considered experimental and should only be limited to special circumstances within research or university institutions with supervising ethics committees.
Deposition Rate, Texture, and Mechanical Properties of SiC Coatings Produced by Chemical Vapor Deposition at Different Temperatures
Authors: Long Ying , Javed Athar , Chen Zhao‐ke , Xiong Xiang , Xiao Ping
Published: April 2012

Silicon carbide (SiC) coatings were produced on carbon/carbon (C/C) composites substrates using chemical vapor deposition (CVD) at different temperatures (1100°C, 1200°C, and 1300°C). The deposition rate was found to increase with deposition temperature from 1100°C to 1200°C. From 1200°C to 1300°C, the deposition rate decreased. SiC coating produced at 1200°C exhibited a strong (111) texture compared with the coatings produced at other temperatures. Both hardness and Young's modulus were also found to be higher in the coating produced at 1200°C. The variation in mechanical properties with the increase in temperature from 1100°C to 1300°C showed a direct correlation with the change in deposition rate and (111) texture. Microstructure analysis shows that the change in CVD temperature leads to the change in grain size, crystallinity, and density of stacking faults of SiC coatings, which appears to have no significant effect on mechanical properties of SiC compared with the texture observed in SiC coating. For the coating deposited at 1200°C, both the hardness and Young's modulus increased gradually from the substrate/coating interface to the top surface. The nonuniformity of mechanical properties along the cross‐section of the coating is attributed to the nonuniform microstructure.
Creating a Sustainable Market for Biofuels: Some Governance Issues  La création d’un marché durable des biocarburants : quelques questions de gouvernance  Einen nachhaltigen Markt für Biokraftstoffe schaffen: Einige Fragen zur Governance
Authors: Zezza Annalisa
Published: April 2012

summary

Creating a Sustainable Market for Biofuels: Some Governance Issues

Ambitious targets set in the European Union and in the United States are shaping the evolution of the biofuels sector with regard to production, use and trade and creating concerns over sustainability issues. Setting standards and establishing certification schemes represent an attempt to ensure that biofuel production is perceived in a sustainable manner with regard to its environmental and socio‐economic impacts. Initiatives on biofuel sustainability have been put in place by national governments, international organisations, companies and non‐governmental organisations. The EU Directive on sustainable biofuels represents one of the first cases of application of a public standard for biofuel production. The emergence of different approaches to biofuel certification might create trade tensions that could be avoided through international harmonisation or bilateral mutual recognition agreements. Certification schemes might also be claimed to impose additional costs that would be difficult for developing countries and small producers to bear. Increasing biofuel trade requires a large effort in terms of negotiations on criteria and agreed methodologies on sustainability. A large interdisciplinary analytical effort is still needed in order to understand and measure the relationship between energy markets, agricultural markets and the environment as well as the interactions between policies.
Stroke Complicating Transcatheter Aortic Valve Implantation: Incidence, Risk Factors and Outcome
Authors: Leker Ronen R. , Eichel Roni , Verber Ami , Cohen Jose. E. , Lotan Chaim , Danenberg Haim D.
Published: April 2012

Background

Transcatheter aortic valve implantation is a novel therapeutic option for patients at high risk for surgical heart valve replacement that carries a risk for periprocedural stroke.

Patients and methods

Consecutive patients undergoing transcatheter aortic valve implantation with the self-expandable Medtronic-Corevalve Revalving system were included in a single-centre prospective database. Strokes complicating transcatheter aortic valve implantation in the first five-days following the procedure were documented, and the differences between patients with and without stroke were studied.

Results

Seventy-two patients (32 men, mean age 80·5 ± 6·2) underwent transcatheter aortic valve implantation from September 2008 to April 2011. Of these, eight (11%) had focal neurological deficits in the periprocedural period (three transient ischaemic attacks, five strokes of which three were minor, one moderate, and one major). Patients with stroke/ transient ischaemic attacks did not differ from those without cerebral ischaemia in baseline criteria or procedural variables. Six of the events were believed to be embolic resulting from dislodgement of calcific material from the aortic valve, and one transient ischaemic attack was secondary to hypoperfusion during severe bradycardia. One patient with basilar occlusion died, but the remaining six patients survived and all had a modified Rankin score ≤2 at 90 days. None of the patients had a recurrent stroke during follow-up.

Discussion

Periprocedural cerebral ischaemia following transcatheter aortic valve implantation is not uncommon, but most patients have good outcomes. There was no particular pre-transcatheter aortic valve implantation or procedural risk factor profile that increased the risk for periprocedural stroke. Further studies are warranted to examine whether patients that are at higher risk for developing stroke after transcatheter aortic valve implantation can be identified.
Diagnostic performance of P wave duration in the identification of left atrial enlargement in dogs
Authors: Savarino P. , Borgarelli M. , Tarducci A. , Crosara S. , Bello N. M. , Margiocco M. L.
Published: April 2012

Objectives: To determine sensitivity and specificity of P wave duration in the identification of left atrial enlargement in dogs.

Methods: Electrocardiograms from normal dogs and dogs with various cardiovascular diseases were evaluated. Inclusion criteria were the availability of an electrocardiogram showing a stable isoelectric line, easily recognizable P waves and good quality two‐dimensional echocardiographic estimate of left atrial dimensions using the left atrial to aortic root ratio.

Using a metal caliper system, P wave duration was measured to the nearest 10 milliseconds for six consecutive heart beats; data were then averaged for each dog. The accuracy of P wave duration in predicting left atrial enlargement was determined using a receiver operating characteristic analysis.

Results: One hundred and fifty‐six dogs were included in the study. Average P wave durations of 20, 30, 40 and 50 milliseconds yielded sensitivities of 100, 85, 68 and 40% and specificities of 0, 16, 64 and 93%, respectively, for the diagnosis of Left Atrial Enlargement by echocardiography. The estimated area under curve of the receiver operating characteristic curve was 0·70 (95% confidence interval: 0·60 to 0·80).

Clinical Significance: The diagnostic performance of P wave duration for identification of left atrial enlargement in dogs presents considerable limitations.
Markers of vulnerability to obsessive–compulsive disorder in an ultra‐high risk sample of patients who developed psychosis
Authors: Fontenelle Leonardo F. , Lin Ashleigh , Pantelis Christos , Wood Stephen J. , Nelson Barnaby , Yung Alison R.
Published: April 2012

Aims: The study aims to identify markers of vulnerability to obsessive–compulsive disorder (OCD) in an ultra‐high risk sample of patients who developed psychosis.

Methods: Three hundred and eleven patients at ultra‐high risk for psychosis were examined at baseline and after a mean of 7.4 years follow‐up. Patients who developed psychosis with OCD (PSY + OCD; n = 13) and psychosis without OCD (PSY − OCD; n = 45) were compared in terms of socio‐demographic and clinical features.

Results: PSY + OCD patients displayed greater severity of depression before and after conversion to PSY + OCD, and increased rates of depressive disorders before exhibiting PSY + OCD. However, they only displayed greater severity of anxiety and increased rates of non‐OCD anxiety disorders after psychosis. Further, PSY + OCD patients were more likely to report a positive family history for anxiety disorders than PSY − OCD.

Conclusion: Although depression and a family history of anxiety disorder may act as vulnerability markers for OCD in psychosis, the resulting anxiety may be a correlate or a consequence of PSY + OCD.
Establishing and operating an early intervention service for psychosis in a defined catchment area of northwestern Greece within the context of the local mental health network
Authors: Mantas Christos , Mavreas Venetsanos
Published: April 2012

Aim: The study aims to present briefly the development of an early intervention service (EIS) for psychosis in a rural catchment area of north‐western Greece within the context of the local mental health network, its structure and procedures, and the results of its operation 2 years after its establishment.

Method: Established in December 2007, our EIS is the first service in Greece for patients with a first‐episode psychosis. The context and the local mental health network are described, and the EIS operation, including clinical, educational, community and research activities, is outlined. Assessment measures are presented to evaluate the EIS progress 2 years after its establishment.

Results: Between December 2007 and December 2009, EIS received 45 referrals, retaining 38 patients in its caseload. The mean duration of untreated psychosis was 26.6 ± 41.0 months (median = 12 months). Thirty‐seven patients (82.2%) were hospitalized after their first referral, 14 under a compulsory order (31.1%). The duration of hospitalization ranged from 2 to 69 days, with a median of 13 days. Mean (±SD) duration of the follow‐up was 14.8 ± 8.5 months, indicating adequate adherence to EIS, with particularly low relapse rates (20%).

Conclusions: Our EIS seems to be successfully established within the local mental health network. Our collaboration with the local mobile mental health unit enabled our communication with rural primary healthcare centers. The collaboration of patients' family and the participation of the mobile mental health unit to the continuity of care contributed greatly to the brief duration of hospitalization and the high adherence to follow‐up rates.
A PSYCHOANALYTIC PERSPECTIVE ON ETHICS, SELF‐DECEPTION AND THE CORRUPT PHYSICIAN
Authors: Gabbard Glen O. , Hobday Gabrielle S.
Published: April 2012

abstract

In this paper the authors use a psychoanalytic perspective to understand observations about the modes of self‐deception that operate in physicians who have been dishonest or have engaged in other transgressions of ethics guidelines. They emphasize that it is inaccurate to categorize physicians as simply honest or dishonest, ethical or unethical. Physicians who have been ethical practitioners may rationalize sexual relations with patients, stealing from professional treasuries, lying, or other transgressions while convincing themselves that they have acted in an honourable manner. The authors share their experience of evaluating these phenomena in over 300 physicians who were referred to a specialized treatment centre by licensing boards, hospitals, physician health organizations or ethics committees. They note the high prevalence of defensive compartmentalization, temporal splitting and projective disavowal as means of tolerating behaviours they would generally regard as unethical. They also examine the implications of these modes of self‐deception for psychotherapy.
A Side‐by‐Side Comparison of Pervious Concrete and Porous Asphalt1
Authors: Welker Andrea L. , Barbis James D. , Jeffers Patrick A.
Published: April 2012

Welker, Andrea L., James D. Barbis, and Patrick A. Jeffers, 2012. A Side‐by‐Side Comparison of Pervious Concrete and Porous Asphalt. Journal of the American Water Resources Association (JAWRA) 48(4): 809‐819. DOI: 10.1111/j.1752‐1688.2012.00654.x

Abstract:  This article compares the performance of two permeable pavements, pervious concrete and porous asphalt, that were installed side‐by‐side in fall 2007. Because the pavements are located directly adjacent to one another, they experience the same vehicle loads, precipitation, and pollution loads. These permeable pavements are part of an infiltration stormwater control measure (SCM). This article focuses on the comparison of water quality parameters, maintenance and durability, and user perception. Eleven different water quality parameters were analyzed at this site for 19 different storm events over a one year period: pH, conductivity, total suspended solids, chlorides, total nitrogen, total phosphorus, total dissolved copper, total dissolved lead, total dissolved cadmium, total dissolved chromium, and total dissolved zinc. Results from the two pavement types were compared using the Mann–Whitney U‐test. The only parameter that was found to be statistically different between the two pavements was pH. Periodic inspection of the two pavement types indicated that after two years of use both pavements were wearing well. However, there was some evidence of clogging of both pavements and some evidence of surface wear. A survey of users of the lot indicated that the perception of these permeable pavements was favorable.
Infective endocarditis of presumed dental origin and the new NICE guidelines: a case report
Authors: de Gea Rico A. , Williams J.V. , Ranjadayalan K. , Revington P.J.
Published: April 2012

Introduction:  Antimicrobial prophylaxis against infective endocarditis (IE) in patients undergoing interventional procedures is no longer recommended. We present a case of IE following dental treatment for which NICE guidelines were followed.

Case report:  A 59‐year‐old gentleman presented with a 1 week history of general malaise, nausea, loss of appetite and lethargy after minimal exertion. Known mitral valve prolapse was reported, and an initial differential diagnosis included subacute bacterial endocarditis. An echocardiogram and Streptococcus mitis growth in the blood cultures supported the likely diagnosis. He was referred to the Oral and Maxillofacial Surgery Department where his previous dental history revealed dental treatment 1 month before admission. In line with the current National Institute for Health and Clinical Excellence (NICE) guidelines, the patient did not receive antibiotics preoperatively.

Discussion:  Dental professionals should be able to recognise the signs and symptoms of IE. It is important to remain informed about such a pathological entity and be aware of its diagnosis and management. Patients with certain cardiac conditions who are at increased risk of developing IE still remain at risk, despite the recent change in the NICE guidelines. The promotion of preventive dentistry and medicine is crucial to reduce the overall risk of IE.
Survival after diagnosis of hepatocellular carcinoma and potential impact of treatment in a hepatitis B or C infected cohort
Authors: Thein Hla‐Hla , Walter Scott R. , Gidding Heather F. , Amin Janaki , Law Matthew G. , George Jacob , Dore Gregory J.
Published: April 2012

Aim:  Little is known about the patterns of care and the impact of hepatocellular carcinoma (HCC) treatment on health outcomes at a population level. We conducted a population‐based cohort study to examine HCC survival trends among people diagnosed with hepatitis B (HBV) or hepatitis C virus (HCV) infection, to determine predictors of receiving potentially curative therapy for HCC, and to examine the impact of HCC treatment on survival in New South Wales, Australia.

Methods:  The Kaplan–Meier method was used to estimate survival, logistic regression to determine predictors of potentially curative therapy and Cox proportional hazards models to determine the impact of HCC treatment on survival. Years of potential life lost (YPLL) were calculated.

Results:  During the period 1993–2007, 1081 cases of HCC were diagnosed. Median survival increased from 10.4 months during 1993–1997 to 18.4 months during 1998–2002, with no further improvement thereafter. Younger age at diagnosis (<65 years), being Asian‐born and having multiple comorbid conditions increased the odds of receiving curative therapy. The effect of HCC treatment on the risk of mortality was similar between the HBV‐ and HCV‐related HCC groups. Tumor‐specific therapies had adjusted hazard ratios ranging 0.06–0.25 and palliative/supportive therapy alone had adjusted hazard ratios ranging 0.76–1.08. The average YPLL per person was 23.3.

Conclusion:  The burden of viral hepatitis‐related HCC is substantial. Despite treatment advances in recent years, there has been no significant improvement in HCC survival. Efforts to improve HCC screening and early diagnosis are required to deliver curative treatment which clearly has a survival advantage.
Peristaltic Pumping of Blood Through Small Vessels of Varying Cross-Section
Authors: Misra J. C. , Maiti S.
Published: April 2012

The paper is devoted to a study of the peristaltic motion of blood in the micro-circulatory system. The vessel is considered to be of varying cross-section. The progressive peristaltic waves are taken to be of sinusoidal nature. Blood is considered to be a Herschel-Bulkley fluid. Of particular concern here is to investigate the effects of amplitude ratio, mean pressure gradient, yield stress, and the power law index on the velocity distribution, streamline pattern, and wall shear stress. On the basis of the derived analytical expressions, extensive numerical calculations have been made. The study reveals that velocity of blood and wall shear stress are appreciably affected due to the nonuniform geometry of blood vessels. They are also highly sensitive to the magnitude of the amplitude ratio and the value of the fluid index.
Electric-field-induced band gap of bilayer graphene in ionic liquid
Authors: Yamashiro Yusuke , Ohno Yasuhide , Maehashi Kenzo , Inoue Koichi , Matsumoto Kazuhiko
Published: April 2012

Ionic liquid-gated graphene field-effect-transistors (G-FETs) were fabricated to generate a band gap in bilayer graphene. The transfer characteristics of the G-FETs revealed that the transconductance when using the ionic-liquid gate was significantly higher than that when using the back gate, because an electrical double layer formed in the ionic liquid with 200-fold the capacitance of a 300-nm-thick SiO2 layer. The results indicate that the ionic-liquid-gate structure enables application of an effective electric field. Moreover, an increase in the resistance of the bilayer graphene was clearly observed as the magnitude of the electric-field intensity was increased, owing to the creation of the band gap. From measurements of electrical characteristics as a function of temperature, a band gap of 235 meV was created in bilayer graphene at an ionic-liquid-gate voltage of −3.0 V.
Interfacing spherical harmonics and room simulation algorithms
Authors: Vorlaender Michael , Pollow Martin , Pelzer Soenke
Published: April 2012

Room acoustic simulation by using geometrical acoustics is usually implemented with binaural receivers. Wave models such as FEM are easily applicable with binaural interfaces as well. This way, however, the signals are restricted to a specific set of HRTF, and a tedious task is to adapt the results to a proper reproduction system with very limited possibilities of listener individualization. With a more general interface such as spherical harmonics, room acoustic spatial data could be created in intermediate solutions. In post-processing this can lead to various binaural representations or to reproduction with Ambisonics (Dalenbäck, ICA 1995). In this paper it is discussed how standard routines in geometrical acoustics must be changed in order to implement multi-channel spherical microphone arrays. Furthermore, the corresponding output data can be multi-channel time signals or temporal SH coefficients or any other suitable spectral format. The amount of data and signal processing affects CPU time and memory. The discussion therefore is focused on feasibility and on consequences on the real-time performance on the one hand, and on the spatial quality of the room response, on the other.
Representation of the spatial impulse response of a room
Authors: Fazi Filippo M. , Noisternig Markus , Warusfel Olivier
Published: April 2012

Microphone arrays allow for the measurement of the so-called spatial impulse response (SIR) of a room or of a concert hall. The SIR provides a local description of the reverberant field of that environment as a function of both time and space. It is shown that, under given assumptions, the SIR can be described by means of an integral operator, the so-called Herglotz wave function, which represents an infinite superposition of plane waves arriving from all possible directions. The kernel of this operator (the Herglotz kernel) contains all the information on the SIR. In practical cases only a limited amount of information is available to compute the Herglotz kernel, typically because a finite number of sensors is used for the measurement. In that respect, several alternatives are discussed to represent the Herglotz density as a sum of a finite number of basis functions. Some results for numerical simulations are then presented, which show the Herglotz kernel for simple examples. Finally, some limitations of this representation are discussed, especially those imposed by the use of real microphone arrays.
The effects of acoustic power and exposure time on the hyperecho in ultrasound images at 55 °C using MRI and US guided HIFU in a bovine liver specimen
Authors: Li Faqi , Yi Huarong , Zhong Mingsong , Ai Huijian , Chen Jie , Wang Zhibiao
Published: April 2012

Ex vivo bovine liver specimens were exposed to the MRI-guided HIFU with the focusing depth of 15 mm in the specimens and various acoustic power (50 W, 100 W, 150 W, 200 W, 250 W and 300 W). Our interest was focused on a case of 55° C in situ temperature. The temperature in situ was monitored via the T-map of MRI. The exposure time needed to reach 55° C in the focus for a acoustic power was recorded. The same procedure was repeated to new but similar bovine liver exposed to the US-guided HIFU with the same sonication parameters. The procedure was also monitored by a passive cavitation detection system. The results showed to reach 55° C in situ the exposure time decreased with the increase of acoustic power. The coagulative necrosis occurred when the acoustic power was 50 W, but no hyperecho in US images and half harmonic emission were found. The coagulative necrosis, hyperechoic US images and half harmonic emissions were observed when the acoustic power was 100 W or greater. At 55° C, since no boiling bubbles occurred, therefore we concluded that the hyperecho in US images were caused by acoustic cavitation whose occurrence is determined by the applied acoustic power. Keywords: MRI-guided HIFU, US-guided HIFU, Coagulative necrosis, hyperecho, Acoustic cavitation This work was supported by National Nature and Science Foundation of China (No. 30830040, 30970827)
Efficient generation of cavitation bubbles by dual-frequency exposure
Authors: Yasuda Jun , Takagi Ryo , Yoshizawa Shin , Umemura Shin-ichiro
Published: April 2012

Microbubbles are known to enhance high intensity focused ultrasound (HIFU) treatment, which is a new cancer treatment method. Highly negative acoustic pressure can efficiently generate cavitation microbubbles, but it is difficult to obtain at the focus of HIFU because of nonlinear propagation. In our previous study, a “Dual-Frequency Excitation” method was suggested to synthesize waveforms emphasizing either the positive-peak-pressure or the negative-peak-pressure by superimposing the second harmonic onto the fundamental. In this study, four different type of dual-frequency exposure sequence at the fundamental frequency of 0.8 MHz were used, and the behavior of cavitation bubbles captured by a high-speed camera was compared. In the first and second sequences, the positive-peak-pressure emphasized (P) and negative-peak-pressure emphasized (N) waves were employed for 125 μs, respectively. In the third sequence, the N and P waves were employed in the earlier and later 62.5 μs, respectively, and they were exchanged in the forth sequence. In the results, the amount of cavitation bubbles generated by the third sequence was significantly more than the other three sequences. The cavitatin bubbles, generated by the N waves, are thought to have provided a pressure-release surface converting the P to N waves, which further generated cavitation bubbles.
Detection of high intensity focused ultrasound induced cavitation activity in liver tissue
Authors: Fan Tingbo , Liu Zhenbo , Guo Xiasheng , Zhang Dong
Published: April 2012

Microbubbles are known to be able to enhance the thermal effect of ultrasound. In HIFU procedure, microbubbles can be generated when the peak negative pressure is large enough or the temperature exceeds the boiling point. In this work, cavitation activities in various exposure protocols with equal total acoustic energy but variable focus pressure and variable duty cycle were monitored in vitro. A 10 MHz focused passive cavitation detector transducer was used to capture acoustic emissions emanated from liver tissue exposed to 1.12 MHz HIFU pulses, while the focus temperature was recorded. The inertial cavitation dose (ICD) was calculated to analyze the cavitation activity qualitatively. The correlations of cavitation activity, temperature and focus pressure were discussed. [This work is supported by the National Basic Research Program 973 (Grant No. 2011CB707900) from Ministry of Science and Technology, China, National Natural Science Foundation of China (11174141), and the Fundamental Research Funds for the Central Universities (Grant Nos. 1103020402, 1116020410 and 1112020401)]
Effect of geometric uncertainties and variations on the one-dimensional sound transmission in a duct with periodic resonator array
Authors: Ih Jeong-Guon , Yim Eun-Ok
Published: April 2012

Sound transmission in a one-dimensional duct with periodic resonator array is characterized by Bragg stopband due to periodicity and resonance stopband due to resonator. Involved geometric parameters affecting the acoustic characteristics are resonator spacing, resonator length, widths or areas of main duct and resonator. Distortions of such geometric parameters are due to uncertainties in manufacturing and due to intentional design variations for focusing on a target frequency range. A side-branch array was taken as the test example. Stopband information was obtained by four-pole matrix and Bloch wave theory. Area and length ratios between side-branch and main duct periodicity properties were varied from zero to unity. Randomized distortions were generated from either Gaussian or uniform random distribution. As a deterministic distortion, sine function was employed. Simulation results showed that bandwidths and frequencies of stopbands were highly affected by the length ratio. Along with the increase of random distortion rate or function period of deterministic distortions, sound transmission at stopbands decreases, while passband transmission increases. It was also shown that one can change the bandwidth and/or frequency of stopbands as desired for sound reduction. (Work partially supported by BK21 project and NCRC (NRF 2011-0018242))
Design of compartmental silencer for HVAC system
Authors: Chan Y. H. , Choy Y. S. , Leung R. C. K.
Published: April 2012

Air conditioning and ventilation system is the major noise sources in the commercial building. Noise will be propagated from fan and through the associated ductwork into working area. In order to reduce the noise transmitted, varies type of silencers can be placed in the ductwork to absorb noise or reflect them back to the source. Usually the dominant noise is low-to-middle frequencies, which active noise control has the potential to control the low-frequency noise, issue related to reliability and cost remains. Concerning the real practical situation, passive control is the most preferable choice. The traditional in-duct silencers are in splitter type, with a bulk of fibrous material as duct lining. The existing passive silencers are usually bulky and long and can give a desirable performance at mid-to-high frequencies. Most ideally the silencer in concerned should be able to handle a broad frequency band and compact in size. In this paper, the performance of a new silencer design was examined and optimized using computation approach with experimental verification.
Determination of sound reflection coefficient of circular duct using time-domain computational fluid dynamics method
Authors: Liu Chen , Ji Zhenlin
Published: April 2012

In this paper, the software FLUENT is used as simulation tool, and the two-dimensional time-domain Computational Fluid Dynamics (CFD) approach is employed to compute the sound reflection coefficient of circular duct without and with gas flow. In the absence of mean flow, the pressure far-field boundary condition could be used as non-reflecting boundary condition in Fluent, and good agreement between the CFD prediction and experiment measurement available in the literature is observed. For the case with gas flow, the general non-reflecting boundary condition is available only with the density-based solver (high-speed compressible flow or Strong coupling flow) in FLUENT, and it is difficult to acquire the convergent solution for the calculation that the density-based solver is used to compute the reflection coefficient of circular pipe. Therefore, the non-reflecting boundary condition is not applied in the model. The computational results from time-domain CFD approach basically agree with experimental results available in the literature with gas flow, but there are some discrepancies at low frequencies. Finally, the effect of oblique termination on the the sound reflection coefficient of circular duct is studied numerically and discussed.
Incorporating real-world measurement and analysis experiences in the teaching of advanced acoustics
Authors: Sommerfeldt Scott D. , Gee Kent L. , Neilsen Tracianne B.
Published: April 2012

In the teaching of advanced undergraduate and graduate-level acoustics, rigorous mathematical presentation and extensive homework sets are the norm. However, students often fail to see the connection between theoretical models and appropriate application to “real-world” situations. Consequently, efforts have been made in courses at Brigham Young University to find collaborative measurement and analysis opportunities that help bridge this gap. Although this effort is still in its infancy, three examples are discussed in this paper. The first was measurements of skateboarding park noise levels in a nearby neighborhood. The second involved analysis of the sound system and crowd noise levels inside and outside the Brigham Young University football stadium. The third example discussed was a graduate course project to assess feasibility of creating active zones of silence in a data center. Lessons learned by students (and faculty!) are described.
The course of Theoretical Acoustics in Graduate University of Chinese Academy of Sciences
Authors: Zhang Hailan
Published: April 2012

Theoretical Acoustics has been a course in Graduate University of Chinese Academy of Sciences since it was founded in 1978. The course covers basic theories of vibration and acoustics. The 120 hour course is given in 2 terms of the first year. Every year 50-60 students from different institutes attend the course with different mathematical and physical background. One feature of the course is the application of the functional analysis theory. The common ground of the vibration of the coupled multi freedom system, string, membrane and room is extracted and a uniform theory of vibration is presented in the form of the operator theory. Besides, many numerical results of acoustic fields, especially the transient fields, given in the course provide more intuitive understanding and help students learn the physics better.
Reproduction of immersive sound using directional and conventional loudspeakers
Authors: Tan Ee Leng , Gan Woon Seng
Published: April 2012

Visual and audio cues play very important roles in 3D media. In such media, 3D sound effects allow game developer or a movie director to position sound effects potentially anywhere in a virtual space surrounding the viewer. Hence, accuracy of 3D sound is critical to prevent any degradation of the overall 3D experience. While there are many breakthroughs in the display technology, 3D visual content is still delivered with the current audio systems, which does not accurately deliver 3D sound. This limitation is directly linked to the dispersive nature of the conventional loudspeaker, and the reproduced 3D sound may be perceived to lack sharpness in the spatial imaging due to reverberant nature of the room acoustics. For a directional loudspeaker, the reproduced 3D sound may seem to lack spaciousness due to little influence by the room acoustics. Since most of the loudspeakers in existing sound system are dispersive in nature, 3D audio image tends to be degraded. To solve this problem, we propose a unique setup which comprises of conventional and directional loudspeakers. This setup exploits high directivity of directional loudspeakers to recreate a high quality 3D sound and to recreate the spaciousness of the audio using the conventional loudspeaker.
New 3D audio for ultra high definition digital TV; loudspeaker configuration and method for virtual elevation effect rendering
Authors: Kim Sunmin , Lee Young Woo , Jo Hyun , Park Youngjin , Pulkki Ville
Published: April 2012

This paper suggests the next-generation audio system for ultra high definition digital TV in terms of loudspeaker layout and corresponding rendering method. First part introduces the listening test results of perceived audio quality with several loudspeaker arrangements in order to find the optimal configuration of loudspeakers for a next-generation multichannel sound system. The subjective evaluations focused on the loudspeaker configurations at the top layer were carried out with test materials by mixing in studio and from B-format recordings. The results show that the perceptual difference in the overall quality achieved with the new 10.2-channel vertical surround system with 3 top loudspeakers and the reference system was imperceptible. Second part presents the virtual elevation effect rendering algorithm which can give a listener an impression of virtual 10.2 channel speakers using the conventional 7.1 channel speaker system (ITU-R BS.775-2) placed in horizontal plane. The proposed virtual height speaker rendering method consists of a generic head-related transfer function (HRTF) and a mixing algorithm based on four loudspeakers. For subjective evaluation three kinds of playbacks were compared; Original 10.2 channel signals, proposed 7.1 channel signals, and down-mixed 7.1 channel signals.