A Combined Macro and Microvascular Model for Whole Limb Heat Transfer

1988 ◽  
Vol 110 (4) ◽  
pp. 259-268 ◽  
Author(s):  
W. J. Song ◽  
S. Weinbaum ◽  
L. M. Jiji ◽  
D. Lemons
Keyword(s):  
Heat Transfer ◽  
Venous Return ◽  
Prototype Model ◽  
Bioheat Equation ◽  
Cross Sectional ◽  
Surface Temperature Distribution ◽  
Wide Range ◽  
Cutaneous Tissue ◽  
Axial Variation ◽  
Arteries And Veins

A new prototype model for whole limb heat transfer is proposed wherein the countercurrent heat exchange from the large central arteries and veins in the core of the limb is coupled to microvascular models for the surrounding muscle and the cutaneous tissue layers. The local microvascular temperature field in the muscle tissue is described by the bioheat equation of Weinbaum and Jiji [1]. The new model allows for an arbitrary axial variation of cross-sectional area and blood distribution between the muscle and cutaneous tissue, accounts for the blood flow to and heat loss from the hand and treats the venous return temperature and surface temperature distribution as unknowns that are determined as part of the solution to the overall boundary value problem. Representative solutions are presented for a wide range of environmental conditions for a limb in both the resting state and during exercise.

A New Fundamental Bioheat Equation for Muscle Tissue: Part I—Blood Perfusion Term

1997 ◽  
Vol 119 (3) ◽  
pp. 278-288 ◽  
Author(s):  
S. Weinbaum ◽  
L. X. Xu ◽  
L. Zhu ◽  
A. Ekpene
Keyword(s):  
Heat Transfer ◽  
Muscle Tissue ◽  
Source Term ◽  
Venous Return ◽  
Blood Perfusion ◽  
Efficiency Coefficient ◽  
Bioheat Equation ◽  
Or Efficiency ◽  
Cross Sectional ◽  
Transfer Unit

A new model for muscle tissue heat transfer has been developed using Myrhage and Eriksson’s [23] description of a muscle tissue cylinder surrounding secondary (s) vessels as the basic heat transfer unit. This model provides a rational theory for the venous return temperature for the perfusion source term in a modified Pennes bioheat equation, and greatly simplifies the anatomical description of the microvascular architecture required in the Weinbaum-Jiji bioheat equation. An easy-to-use closed-form analytic expression has been derived for the difference between the inlet artery and venous return temperatures using a model for the countercurrent heat exchange in the individual muscle tissue cylinders. The perfusion source term calculated from this model is found to be similar in form to the Pennes’s source term except that there is a correction factor or efficiency coefficient multiplying the Pennes term, which rigorously accounts for the thermal equilibration of the returning vein. This coefficient is a function of the vascular cross-sectional geometry of the muscle tissue cylinder, but independent of the Peclet number in contrast to the recent results in Brinck and Werner [8]. The value of this coefficient varies between 0.6 and 0.7 for most muscle tissues. In part II of this study a theory will be presented for determining the local arterial supply temperature at the inlet to the muscle tissue cylinder.

A Three-Dimensional Variable Geometry Countercurrent Model for Whole Limb Heat Transfer

1992 ◽  
Vol 114 (3) ◽  
pp. 366-376 ◽  
Author(s):  
M. Zhu ◽  
S. Weinbaum ◽  
D. E. Lemons
Keyword(s):  
Heat Transfer ◽  
Three Dimensional ◽  
Flow Distribution ◽  
Approximate Theory ◽  
Cross Sectional ◽  
Warm Environment ◽  
Axial Temperature ◽  
Cutaneous Tissue ◽  
New Formulation ◽  
Dimensional Variable

A new formulation of the combined macro and microvascular model for heat transfer in a human arm developed in Song et al. [1] is proposed using a recently developed approximate theory for the heat exchange between countercurrent vessels embedded in a tissue cylinder with surface convection [2]. The latter theory is generalized herein to treat an arm with an arbitrary variation in cross-sectional area and continuous bleed off from the axial vessels to the muscle and cutaneous tissue. The local microvascular temperature field is described by a “hybrid” model which applies the Weinbaum-Jiji [3] and Pennes [4] equations in the peripheral and deeper tissue layers, respectively. To obtain reliable end conditions at the wrist and other model input parameters, a plethysmograph-calorimeter has been used to measure the blood flow distribution between the arm and hand circulations, and hand heat loss. The predictions of the model show good agreement with measurements for the axial surface temperature distribution in the arm and confirm the minimum in the axial temperature variation first observed by Pennes [4] for an arm in a warm environment.

Axial Wall Conduction in Pulsating Laminar Flow in a Microtube

2014 ◽  
Author(s):  
Parthasarathi Mishra ◽  
Manoj Kumar Moharana
Keyword(s):  
Heat Transfer ◽  
Laminar Flow ◽  
Constant Heat Flux ◽  
Wall Material ◽  
Working Fluid ◽  
Maximum Effect ◽  
Pulsation Frequency ◽  
Cross Sectional ◽  
Flux Boundary Condition ◽  
Wide Range

A two-dimensional numerical analysis is carried out to understand the effect of pulsation on the axial wall conduction in simultaneously developing single phase laminar flow in a microtube with constant heat flux boundary condition imposed on its outer surface and while the cross-sectional solid faces exposed to the surrounding are kept adiabatic. Water is used as the working fluid and enters the microtube at 300K with a slug velocity that varying with time sinusoidally, thus causing pulsating flows in the microtube. The inlet velocity thus consists of a fixed component and a fluctuating component which varies sinusoidally with time. For this simulation conductivity ratio is considered at a wide range (ksf 2.26–703) while the thickness ratio (δsf), amplitude (A), and flow rate (Re) remain constant. To understand effect of pulsation, frequency of oscillation (f) is changed by taking four different Womersley numbers (1.414, 2, 2.45, and 3.163). Based on the numerical simulation, it is concluded that for a particular pulsation frequency (Wo) there exists an optimum value of ksf at which overall Nusselt number (Nu) is maximum. Effect of pulsation frequency on heat transfer is found to be very small. Heat transfer is found to be increasing at lower thermal conductive microtube wall material (or ksf) while it is decreasing at higher ksf compared to steady flow in microtube. Existing studies do indicate that pulsation (i) increases heat transfer (ii) decreases heat transfer, or (iii) no effect. The researchers actually failed to observe the present overall trend as none of the existing studies considered a widely varying thermal conductive wall material.

The Bleed Off Perfusion Term in the Weinbaum-Jiji Bioheat Equation

1992 ◽  
Vol 114 (4) ◽  
pp. 539-542 ◽  
Author(s):  
S. Weinbaum ◽  
L. M. Jiji ◽  
D. E. Lemons
Keyword(s):  
Energy Equation ◽  
Source Term ◽  
Venous Return ◽  
Effective Conductivity ◽  
Blood Perfusion ◽  
Tissue Temperature ◽  
Bioheat Equation ◽  
Countercurrent System ◽  
Thermal Equilibration ◽  
Arteries And Veins

The microvascular organization and thermal equilibration of the primary and secondary arteries and veins that comprise the bleed off circulation to the muscle fibers from the parent countercurrent supply artery and veins are analyzed. The blood perfusion heat source term in the tissue energy equation is shown to be related to this vascular organization and to undergo a fundamental change in behavior as one proceeds from the more peripheral tissue, where the perfusion term is proportional to the Ta - Tv difference in the parent supply vessels, to the deeper tissue layers where the bleed off vessels themselves form a branching countercurrent system for each muscle tissue cylinder and the venous return temperature can vary between the local tissue temperature and Ta. The consequences of this change in behavior are examined for the Weinbaum-Jiji bioheat equation and a modified expression for the effective conductivity of perfused tissue is derived for countercurrent bleed off exchange.

A Cross Sectional Survey of Chicken Astroviruses Antibody in Broiler and Sonali (Cross-Bred) Chickens in Selected Areas in Bangladesh

2020 ◽  
Vol 43 (1) ◽  
pp. 75-80
Author(s):  
Md Zulfekar Ali ◽  
Mohammad Moktader Moula ◽  
Zafar Ahmed Bhuiyan ◽  
Muhammad Tariq Javed
Keyword(s):  
Age Groups ◽  
Winter Season ◽  
Cross Sectional Survey ◽  
Cross Sectional ◽  
Blood Samples ◽  
Elisa Kit ◽  
Published Report ◽  
Poultry Birds ◽  
Wide Range ◽  
Group B

AbstractChicken astroviruses (CAstV) are enteric viruses of poultry causing gastroenteritis, malabsorption, gout and white chick disease commonly known as runting-stunting syndrome (RSS). It can affect the wide range of poultry birds, especially chicken, turkey and duck worldwide. To our best knowledge there is no published report on presence of antibodies against CAstV in Bangladesh. Therefore, the study aimed to detect the presence of CAstV antibodies in broilers and sonali chickens (a cross-bread) in Bangladesh through a cross-sectional survey. A total of 454 blood samples from 66 flocks of broiler (n=343) and sonali chickens (n=111) of different ages were obtained during 2017 from four districts. The birds were healthy but were not vaccinated against CAstV. The samples were tested for specific antibodies against CAstV Group B by using commercially available ELISA kit. Overall, 16.74% (76/454) samples and 34.84% (23/66) flocks were positive for CAstV antibodies. The seroprevalence of CAstV was significantly (p=0.001) higher in sonali chickens (36.96%) than broiler (10.20%), while it was significantly higher (p=0.001) in birds of Bogura district (36.94%) than the other three districts. Regarding the age groups, seroprevalence was insignificantly (p=0.192) higher in sonali chicken before laying age (45%) than during laying age (27.45%). Regarding the seasons, CAstV infection was prevalent significantly (p=0.001) higher in winter season. Thus, the present study indicated the presence of CAstV in poultry in Bangladesh, so further studies are required to find out the magnitude of the problem in the country.

Celiac Disease in Kosovar Albanian Children: Evaluation of Clinical Features and Diagnosis

2020 ◽  
Vol 16 (3) ◽  
pp. 241-247
Author(s):  
Atifete Ramosaj-Morina ◽  
Alije Keka-Sylaj ◽  
Arbana Baloku Zejnullahu ◽  
Lidvana Spahiu ◽  
Virgjina Hasbahta ◽  
...  
Keyword(s):  
Celiac Disease ◽  
Disease Onset ◽  
Clinical Manifestations ◽  
Gastrointestinal Symptoms ◽  
Dominant Mode ◽  
Primary School Children ◽  
Cross Sectional ◽  
Classical Form ◽  
Wide Range ◽  
The Mean

Background: Celiac disease is an immune-mediated disorder characterized by variable clinical manifestations, specific antibodies, HLA-DQ2/DQ8 haplotypes, and enteropathy. Objectives: The aim of this study was to present the clinical spectrum and patterns of celiac disease in Kosovar Albanian children. Methods: A cross-sectional retrospective study was performed with Albanian children aged 0-18 years, treated for celiac disease in the Pediatric Clinic, University Clinical Center of Kosovo from 2005 to 2016. Results: During the study period, 63 children were treated for celiac disease. The mean age at diagnosis was 5.5 years (SD ± 3.31). The mean age at celiac disease onset was 3.3 years (SD ± 2.02), while the mean delay from the first symptoms indicative of celiac disease to diagnosis was 2.2 years (SD ± 2.09). More than 70% of the patients were diagnosed in the first 7 years of life, mainly presented with gastrointestinal symptoms, while primary school children and adolescents mostly showed atypical symptoms (p<0.001). The classical form of celiac disease occurred in 78% of the cases. Sixty (95%) patients carried HLA-DQ2.5, DQ2.2 and/or HLA-DQ8 heterodimers, and only three of them tested negative. Conclusions: Kosovo, as the majority of developing countries, is still facing the classical form of celiac disease as the dominant mode of presentation; as a result, most children with other forms of the celiac disease remain undiagnosed. : Physicians should be aware of the wide range of clinical presentations and utilize low testing thresholds in order to prevent potential long-term problems associated with untreated celiac disease.

Soames' & Southam's Oral Pathology

2018 ◽  
Author(s):  
Max Robinson ◽  
Keith Hunter ◽  
Michael Pemberton ◽  
Philip Sloan
Keyword(s):  
Skin Diseases ◽  
Oral Pathology ◽  
Pathological Features ◽  
Oral Diseases ◽  
Oral Medicine ◽  
Cross Sectional ◽  
Facial Region ◽  
Wide Range ◽  
Cross Sectional Imaging ◽  
Key Aspects

A sound understanding of clinical oral pathology is essential if a dental clinician is to navigate successfully through clinical guidelines, make timely referrals to specialists, and provide good care for patients. This new edition of Soames' & Southam's Oral Pathology provides a clear and friendly guide for students, practitioners, and the whole dental team. Thoroughly updated for today's clinical practice, this textbook covers 'must-know' oral pathology and integrates key aspects of oral medicine. It begins by explaining the principles of clinical assessment, the synthesis of a differential diagnosis, and the selection of further investigations including laboratory tests. Ten chapters bring this theory to life by looking at the clinical and pathological features of a wide range of common oral diseases including oral cancer, salivary gland disorders, and diseases of the jaws. Two new chapters address skin diseases affecting the oro-facial region and neck lumps. A final chapter highlights the importance of clinical oral pathology in the context of systemic human disease. New radiology content includes examples of cross-sectional imaging. Photomicrographs have been replaced with carefully selected images to illustrate key pathological features. Each chapter includes key points boxes and tables to aid learning. Written by experts in both oral pathology and oral medicine, this new edition is a must-have for dentistry students, and those working in the field, providing current and trustworthy information.

scholarly journals Oxidative status in plasma, urine and saliva of girls with anorexia nervosa and healthy controls: a cross-sectional study

2021 ◽  
Vol 9 (1) ◽  
Author(s):  
Alexandra Gaál Kovalčíková ◽  
Ľubica Tichá ◽  
Katarína Šebeková ◽  
Peter Celec ◽  
Alžbeta Čagalová ◽  
...  
Keyword(s):  
Oxidative Stress ◽  
Anorexia Nervosa ◽  
Redox Homeostasis ◽  
Oxidative Status ◽  
Carbonyl Stress ◽  
Healthy Controls ◽  
Psychosomatic Disorder ◽  
Cross Sectional ◽  
Wide Range ◽  
Markers Of Oxidative Stress

Abstract Background Anorexia nervosa (AN) is a serious psychosomatic disorder with unclear pathomechanisms. Metabolic dysregulation is associated with disruption of redox homeostasis that might play a pivotal role in the development of AN. The aim of our study was to assess oxidative status and carbonyl stress in plasma, urine and saliva of patients with AN and healthy controls. Methods Plasma, spot urine, and saliva were collected from 111 girls with AN (aged from 10 to 18 years) and from 29 age-matched controls. Markers of oxidative stress and antioxidant status were measured using spectrophotometric and fluorometric methods. Results Plasma advanced oxidation protein products (AOPP) and advanced glycation end products (AGEs) were significantly higher in patients with AN than in healthy controls (by 96, and 82%, respectively). Accordingly, urinary concentrations of AOPP and fructosamines and salivary concentrations of AGEs were higher in girls with AN compared with controls (by 250, and 41% in urine; by 92% in saliva, respectively). Concentrations of thiobarbituric acid reactive substances (TBARS) in saliva were 3-times higher in the patients with AN than in the controls. Overall antioxidants were lower in plasma of girls with AN compared to the controls, as shown by total antioxidant capacity and ratio of reduced and oxidized glutathione (by 43, and 31%, respectively). Conclusions This is the first study assessing wide range of markers of oxidative status in plasma, urine and saliva of the patients with AN. We showed that both, higher levels of markers of oxidative stress and lower antioxidants play a role in redox disruption. Restoration of redox homeostasis might be of the clinical relevance

scholarly journals Kinematic Analysis of Lower Limb Joint Asymmetry during Gait in People with Multiple Sclerosis

Symmetry ◽  
2021 ◽  
Vol 13 (4) ◽  
pp. 598
Author(s):  
Massimiliano Pau ◽  
Bruno Leban ◽  
Michela Deidda ◽  
Federica Putzolu ◽  
Micaela Porta ◽  
...  
Keyword(s):  
Multiple Sclerosis ◽  
Lower Limb ◽  
Sagittal Plane ◽  
Cross Sectional Study ◽  
Camera Motion ◽  
Cross Sectional ◽  
Temporal Parameters ◽  
Wide Range ◽  
Edss Score ◽  
Spatio Temporal

The majority of people with Multiple Sclerosis (pwMS), report lower limb motor dysfunctions, which may relevantly affect postural control, gait and a wide range of activities of daily living. While it is quite common to observe a different impact of the disease on the two limbs (i.e., one of them is more affected), less clear are the effects of such asymmetry on gait performance. The present retrospective cross-sectional study aimed to characterize the magnitude of interlimb asymmetry in pwMS, particularly as regards the joint kinematics, using parameters derived from angle-angle diagrams. To this end, we analyzed gait patterns of 101 pwMS (55 women, 46 men, mean age 46.3, average Expanded Disability Status Scale (EDSS) score 3.5, range 1–6.5) and 81 unaffected individuals age- and sex-matched who underwent 3D computerized gait analysis carried out using an eight-camera motion capture system. Spatio-temporal parameters and kinematics in the sagittal plane at hip, knee and ankle joints were considered for the analysis. The angular trends of left and right sides were processed to build synchronized angle–angle diagrams (cyclograms) for each joint, and symmetry was assessed by computing several geometrical features such as area, orientation and Trend Symmetry. Based on cyclogram orientation and Trend Symmetry, the results show that pwMS exhibit significantly greater asymmetry in all three joints with respect to unaffected individuals. In particular, orientation values were as follows: 5.1 of pwMS vs. 1.6 of unaffected individuals at hip joint, 7.0 vs. 1.5 at knee and 6.4 vs. 3.0 at ankle (p < 0.001 in all cases), while for Trend Symmetry we obtained at hip 1.7 of pwMS vs. 0.3 of unaffected individuals, 4.2 vs. 0.5 at knee and 8.5 vs. 1.5 at ankle (p < 0.001 in all cases). Moreover, the same parameters were sensitive enough to discriminate individuals of different disability levels. With few exceptions, all the calculated symmetry parameters were found significantly correlated with the main spatio-temporal parameters of gait and the EDSS score. In particular, large correlations were detected between Trend Symmetry and gait speed (with rho values in the range of –0.58 to –0.63 depending on the considered joint, p < 0.001) and between Trend Symmetry and EDSS score (rho = 0.62 to 0.69, p < 0.001). Such results suggest not only that MS is associated with significantly marked interlimb asymmetry during gait but also that such asymmetry worsens as the disease progresses and that it has a relevant impact on gait performances.

scholarly journals Minimum acceptable diet among children aged 6–23 months in South Kivu, Democratic Republic of Congo: a community-based cross-sectional study

2021 ◽  
Vol 21 (1) ◽  
Author(s):  
Richard Mbusa Kambale ◽  
Gaylord Amani Ngaboyeka ◽  
Joe Bwija Kasengi ◽  
Sarah Niyitegeka ◽  
Boss Rutakaza Cinkenye ◽  
...  
Keyword(s):  
Democratic Republic ◽  
Democratic Republic Of Congo ◽  
Feeding Practices ◽  
Cross Sectional Study ◽  
Sectional Study ◽  
Community Based ◽  
Cross Sectional ◽  
Republic Of Congo ◽  
Wide Range ◽  
South Kivu

Abstract Background Suboptimal child nutrition remains the main factor underlying child undernutrition in Democratic Republic of Congo (DRC). This study aimed to assess the prevalence of minimum acceptable diet and associated factors among children aged 6–23 months old. Methods Community-based cross-sectional study including 742 mothers with children aged 6–23 months old was conducted in 2 Health Zones of South Kivu, Eastern DRC. WHO indicators of Infant and Young Child Feeding (IYCF) regarding complementary feeding practices were used. Logistic regression analysis was used to quantify the association between sociodemographic indicators and adequate minimum acceptable diet for both univariate and multivariate analysis. Results Overall, 33% of infants had minimum acceptable diet. After controlling for a wide range of covariates, residence urban area (AOR 2.39; 95% CI 1.43, 3.85), attendance postnatal care (AOR 1.68; 95% CI 1.12, 2.97), education status of mother (AOR 1.83; 95% CI 1.20, 2.77) and household socioeconomic status (AOR 1.72; 95% CI 1.14, 2.59) were factors positively associated with minimum acceptable diet. Conclusion Actions targeting these factors are expected to improve infant feeding practices in South Kivu.

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