Bone strength in small mammals and bipedal birds: do safety factors change with body size?

1982 ◽  
Vol 98 (1) ◽  
pp. 289-301 ◽  
Author(s):  
A. A. Biewener
Keyword(s):  
Body Size ◽  
Small Mammals ◽  
Bending Strength ◽  
Published Data ◽  
Small Animals ◽  
Safety Factors ◽  
Cross Sectional ◽  
Limb Bones ◽  
Significant Difference ◽  
Large Animals

Measurements of the cross-sectional geometry and length of bones from animals of different sizes suggest that peak locomotory stresses might be as much as nine times greater in the limb bones of a 300 kg horse than those of a 0.10 kg chipmunk. To determine if the bones of larger animals are stronger than those of small animals, the bending strength of whole bone specimens from the limbs of small mammals and bipedal birds was measured and compared with published data for large mammalian cortical bone (horses and bovids). No significant difference (P greater than 0.2) was found in the failure stress of bone over a range in size from 0.05-700 kg (233 +/− 53 MN/m2 for small animals compared to 200 +/− 28 MN/m2 for large animals). This finding suggests that either the limb bones of small animals are much stronger than they need to be, or that other aspects of locomotion (e.g. duty factor and limb orientation relative to the direction of the ground force) act to decrease peak locomotory stresses in larger animals.

Theoretical and empirical scaling patterns and topological homology in bone trabeculae.

1998 ◽  
Vol 201 (4) ◽  
pp. 573-590
Author(s):  
S M Swartz ◽  
A Parker ◽  
C Huo
Keyword(s):  
Body Size ◽  
Surface Area ◽  
Cancellous Bone ◽  
Structural Design ◽  
Theoretical Models ◽  
Small Animals ◽  
Bone Trabeculae ◽  
Large Animals ◽  
Vertebrate Skeleton ◽  
Area And Volume

Trabecular or cancellous bone is a major element in the structural design of the vertebrate skeleton, but has received little attention from the perspective of the biology of scale. In this study, we investigated scaling patterns in the discrete bony elements of cancellous bone. First, we constructed two theoretical models, representative of the two extremes of realistic patterns of trabecular size changes associated with body size changes. In one, constant trabecular size (CTS), increases in cancellous bone volume with size arise through the addition of new elements of constant size. In the other model, constant trabecular geometry (CTG), the size of trabeculae increases isometrically. These models produce fundamentally different patterns of surface area and volume scaling. We then compared the models with empirical observations of scaling of trabecular dimensions in mammals ranging in mass from 4 to 40x10(6)g. Trabecular size showed little dependence on body size, approaching one of our theoretical models (CTS). This result suggests that some elements of trabecular architecture may be driven by the requirements of maintaining adequate surface area for calcium homeostasis. Additionally, we found two key consequences of this strongly negative allometry. First, the connectivity among trabecular elements is qualitatively different for small versus large animals; trabeculae connect primarily to cortical bone in very small animals and primarily to other trabeculae in larger animals. Second, small animals have very few trabeculae and, as a consequence, we were able to identify particular elements with a consistent position across individuals and, for some elements, across species. Finally, in order to infer the possible influence of gross differences in mechanical loading on trabecular size, we sampled trabecular dimensions extensively within Chiroptera and compared their trabecular dimensions with those of non-volant mammals. We found no systematic differences in trabecular size or scaling patterns related to locomotor mode.

scholarly journals Nutritional and micronutrient status of adolescent schoolgirls in eastern Sudan: A cross-sectional study

F1000Research ◽  
2017 ◽  
Vol 6 ◽  
pp. 1831
Author(s):  
Hyder M. Mahgoub ◽  
Omar E. Fadlelseed ◽  
Ammar H. Khamis ◽  
Jalal A. Bilal ◽  
Ishag Adam
Keyword(s):  
Cross Sectional Study ◽  
High Rate ◽  
Nutrition Status ◽  
Published Data ◽  
Sectional Study ◽  
Cross Sectional ◽  
Micronutrient Status ◽  
Significant Difference ◽  
More Care ◽  
Eastern Sudan

Background: Adolescents, especially girls, are susceptible to malnutrition and their diet must be adequate to support their very rapid growth and development. Currently, there is little published data on the nutritional state amongst adolescent girls in Sudan. Methods: A cross sectional study was conducted to assess the nutritional and micronutrient status of adolescent schoolgirls in eastern Sudan during the period of January-February 2015. Weight and height were measured using standard methods. Haemoglobin and ferritin levels were measured using blood samples, and blood films for malaria and stool samples for Schistosoma mansoni were investigated. Nutritional status was assessed according to the WHO 2006 reference values. Copper and zinc concentrations were measured by atomic absorption. Results: Twenty-five (13.7%) out of 183 girls were stunted. Seventy (38.3%) were thin; 17.5, 9.3 and 11.5% had mild, moderate and severe thinness, respectively. Only 10 (5.5%) and six (3.3%) girls were overweight and obese, respectively. The prevalence of anaemia was 77.0%. While there was no significant difference in the haemoglobin, ferritin, copper levels and thinness; thin children had significantly lower zinc (P=0.007). Conclusions: There is a high rate of stunting, thinness and anaemia among adolescent schoolgirls in eastern Sudan. More care has to be taken in order to provide a better nutrition status in the area.

scholarly journals Locomotory stresses in the limb bones of two small mammals: the ground squirrel and chipmunk

1983 ◽  
Vol 103 (1) ◽  
pp. 131-154 ◽  
Author(s):  
A. A. Biewener
Keyword(s):  
Safety Factor ◽  
Ground Squirrel ◽  
High Speed ◽  
Bone Geometry ◽  
Direct Consequence ◽  
Material Strength ◽  
Small Animals ◽  
Limb Bones ◽  
Wide Range ◽  
Large Animals

Peak stresses acting in limb bones should increase with increasing size if the forces acting on the bones increase in direct proportion to the animal's body weight. This is a direct consequence of the scaling of limb bone geometry over a wide range in size in mammals. In addition, recent work has shown that the material strength of bone is similar in large and small animals. If the assumptions in this analysis are correct, large animals would have a lower safety factor to failure than small animals. The purpose of this study was to measure peak stresses acting in the limb bones of small animals during locomotion and compare the results with similar measurements available for larger animals. Locomotory stresses acting in the fore and hindlimb bones of two rodents, the ground squirrel (Spermophilus tridecemlineatus) and chipmunk (Tamais striatus), were calculated using ground force recordings and measurements of limb position taken from high speed x-ray cine films. Peak (compressive) stresses calculated to act in the bones of these animals (−31 to −86 MN/m2) are similar in magnitude to those determined for much larger mammals. The more proximal bones of the fore and hindlimb, the humerus and femur, were found to develop stresses (−31 to −42 MN/m2) significantly lower than those acting in the more distal bones of each limb: the radius, ulna and tibia (−58 to −86 MN/m2). All of the long bones from both species, except their femora, were found to be loaded principally in bending. The caudal cortices of each bone developed a peak compressive stress, whereas the cranial cortices were loaded in tension. Various features of the musculo-skeletal organization and manner of locomotion of these rodents are considered to explain how animals of different size maintain a uniform safety factor to failure.

scholarly journals COMPARATIVE ANALYSIS OF THE TYMOSHENKO METHOD AND THE Γ-METHOD FOR CALCULATION OF CLT PANELS STRENGTH BY BENDING.

2021 ◽  
Vol 2 (7(71)) ◽  
pp. 33-39
Author(s):  
A. Bidakov ◽  
O. Pustovoitova ◽  
I. Raspopov ◽  
B. Strashko
Keyword(s):  
Cross Sections ◽  
Bending Strength ◽  
Engineering Practice ◽  
Correction Factors ◽  
Flexible Joints ◽  
Shear Deformations ◽  
Cross Sectional ◽  
Analogy Method ◽  
Advantages And Disadvantages ◽  
Significant Difference

The γ-method and the Timoshenko method are most often used for calculation the bending strength of CLT panels, the latter of which takes into account the transverse shear deformations of the transverse layers of boards, which are due to the significant difference between the modulus of elasticity and the shear modulus apply the method of Timoshenko's beams. The γ-method treats the CLT panel as a beam on flexible joints, similar to the Derevyagin system beam on plate dowels or Kubler cubes, where the transverse layers of the boards are considered as flexible joints and are not taken into account when calculating the geometric characteristics of cross sections of CLT panels. Taking into account the amount of shear for each type of panels, depending on the configuration of the cross-sectional components, is performed by introducing shear correction factors, which in turn depend on the thickness of the CLT panel layers and their distance from the center of gravity of the panel. The γ-method, like Timoshenko's method, is used in engineering practice more often than the shear analogy method. Each technique has its advantages and disadvantages, as it has a number of specific assumptions to simplify the calculations. This paper highlights the advantages and disadvantages of the γ-method and the Timoshenko method, which are the most common and are contained in many technical opinions of various manufacturers of CLT panels.

Difference in Root Canal Length between Populations

2019 ◽  
Vol 3 (2) ◽  
Keyword(s):  
Root Canal ◽  
Cross Sectional Study ◽  
Published Data ◽  
Cross Sectional ◽  
Black Africans ◽  
Second Molar ◽  
Root Canals ◽  
Length Difference ◽  
Significant Difference ◽  
Conservative Dentistry

Introduction: The objective of the study was to make the comparison of the root canal length of different types of teeth in black-Africans (Bantu) to that of Caucasians and Asians. Materials and Methods: Data from a prospective cross-sectional study of Bantu (Black Africans) subjects aged from 18 to 45 years who were admitted in Service of Conservative Dentistry of Kinshasa University, root canal length were compared with already published data from studies involving Caucasians and Asians. Results: This study includes 720 subjects; 480 (66%) were female and 240 (34%) were male. A total of 818 teeth were examined with 1539 root canals. The upper central incisor and the lower first molar predominated respectively in the maxilla and the mandible regions. There is a significant difference between the canal length of Bantu and Asians in the palatal canal of the upper second molar by 3.1 mm (p= 0.00). Eight different canals of Bantu were longer as compared to a single canal for Asians (p <0.05). This include the Vestibular (V) and palatine (P) canals of Bantu the first premolar (PM1 ), palatal of the second premolar (PM2 ), mesio-vestibular (MV), disto-vestibular (DV) and palatine (P) of the first molar (M1 ) mesio-vestibular and palatal of the second molar (M2 ). The lateral incisors (IL) (p= 0,01) and the canines (p= 0.12) of the Asians were longer than that of the Bantu. The Caucasians presented with longer canines than Bantu with a length difference of 1.7 mm (p= 0.11). Four Caucasians also presented with longer canals of the Mesio-Vestibular (MV) and mesiolingual (ML) of the two molars (M1 and M2 ) as compared to one for Bantu are the longest (p <0.05). Exceptionally, the distal canal (D) of the second molar (M2 ) of the Bantu was longer than that of the Caucasians, with a length difference of 1.5 mm. Conclusion: The root canal length of Bantu is between than those of the most Asian and shortest Caucasian.

Energetics and mechanics of terrestrial locomotion. III. Energy changes of the centre of mass as a function of speed and body size in birds and mammals

1982 ◽  
Vol 97 (1) ◽  
pp. 41-56 ◽  
Author(s):  
N. C. Heglund ◽  
G. A. Cavagna ◽  
C. R. Taylor
Keyword(s):  
Body Size ◽  
Total Power ◽  
Small Animals ◽  
Similar Data ◽  
Centre Of Mass ◽  
Average Speed ◽  
Terrestrial Locomotion ◽  
The Third ◽  
Large Animals ◽  
Level Constant

This is the third in a series of four papers examining the link between the energetics and mechanics of terrestrial locomotion. It reports measurements of the mechanical work required (ECM, tot) to lift and reaccelerate an animal's centre of mass within each step as a function of speed and body size during level, constant average speed locomotion. A force platform was used in this study to measure ECM, tot for small bipeds, quadrupeds and hoppers. We have already published similar data from large animals. The total power required to lift and reaccelerate the centre of mass (ECM, tot) increased nearly linearly with speed for all the animals. Expressed in mass-specific terms, it was independent of body size and could be expressed by a simple equation: ECM, tot/Mb = 0.685 vg + 0.072 where ECM, tot/Mb has the units of W kg-1 and vg is speed in m s-1. Walking involves the same pendulum-like mechanism in small animals as has been described in humans and large animals. Also, running, trotting and hopping produce similar curves of ECM, tot as a function of time during a stride for both the small and large animals. Galloping, however, appears to be different in small and large animals. In small animals the front legs are used mainly for braking, while the back legs are used to reaccelerate the centre of mass within a stride. In large animals the front and hind legs serve to both brake and reaccelerate the animal; this difference in mechanics is significant in that it does not allow the utilization of elastic energy in the legs of small animals, but does in the legs of large animals.

Personal Audio System: Hearing Symptoms, Habits, and Sound Pressure Levels Measured in Real Ear and a Manikin

2020 ◽  
Vol 63 (6) ◽  
pp. 2016-2026
Author(s):  
Tamara R. Almeida ◽  
Clayton H. Rocha ◽  
Camila M. Rabelo ◽  
Raquel F. Gomes ◽  
Ivone F. Neves-Lobo ◽  
...  
Keyword(s):  
Sound Pressure ◽  
Daily Basis ◽  
Cross Sectional Study ◽  
Normal Hearing ◽  
Chi Square ◽  
Cross Sectional ◽  
The Real ◽  
Significant Difference ◽  
Sound Pressure Levels ◽  
Audio System

Purpose The aims of this study were to characterize hearing symptoms, habits, and sound pressure levels (SPLs) of personal audio system (PAS) used by young adults; estimate the risk of developing hearing loss and assess whether instructions given to users led to behavioral changes; and propose recommendations for PAS users. Method A cross-sectional study was performed in 50 subjects with normal hearing. Procedures included questionnaire and measurement of PAS SPLs (real ear and manikin) through the users' own headphones and devices while they listened to four songs. After 1 year, 30 subjects answered questions about their usage habits. For the statistical analysis, one-way analysis of variance, Tukey's post hoc test, Lin and Spearman coefficients, the chi-square test, and logistic regression were used. Results Most subjects listened to music every day, usually in noisy environments. Sixty percent of the subjects reported hearing symptoms after using a PAS. Substantial variability in the equivalent music listening level (Leq) was noted ( M = 84.7 dBA; min = 65.1 dBA, max = 97.5 dBA). A significant difference was found only in the 4-kHz band when comparing the real-ear and manikin techniques. Based on the Leq, 38% of the individuals exceeded the maximum daily time allowance. Comparison of the subjects according to the maximum allowed daily exposure time revealed a higher number of hearing complaints from people with greater exposure. After 1 year, 43% of the subjects reduced their usage time, and 70% reduced the volume. A volume not exceeding 80% was recommended, and at this volume, the maximum usage time should be 160 min. Conclusions The habit of listening to music at high intensities on a daily basis seems to cause hearing symptoms, even in individuals with normal hearing. The real-ear and manikin techniques produced similar results. Providing instructions on this topic combined with measuring PAS SPLs may be an appropriate strategy for raising the awareness of people who are at risk. Supplemental Material https://doi.org/10.23641/asha.12431435

Parent’s Experiences from the Treatment of their Children at the Physic Children’s Surgery Clinic in Skopje.

2020 ◽  
Vol 4 (1) ◽  
Author(s):  
M. Trajchevska ◽  
A. Lleshi ◽  
S. Gjoshev ◽  
A. Trajchevski
Keyword(s):  
Health Care ◽  
Health Status ◽  
Independent Predictor ◽  
Demographic Data ◽  
Parental Satisfaction ◽  
Pediatric Care ◽  
Simple Random Sample ◽  
Significant Independent Predictor ◽  
Cross Sectional ◽  
Significant Difference

Background: The respect of the needs and wishes of the patients is in the focus of the human health system. The experience of the parents in terms of child’s health care may be used as an indicator of quality of the health care. Material and methods: The research is a quantitative analytical cross-sectional study. In accordance with the inclusion and exclusion criteria, simple random sample of 207 parents / guardians is covered, whose children in the period of three months, had been hospitalized in the hospital department JZUU Pediatric Surgery Clinic in Skopje.It was used a two parted questionnaire. The first part is a standardized questionnaire (Parent Experience of Pediatric Care - PECP), and the second part concerns the general socio-demographic data of the parent/guardian. Statistical evaluation was performed using appropriate statistical programs (Statistics for Windows 7,0 and SPSS 17.0). Results: In accordance with the age of the parents, the survey respondents were divided into two groups: a) age ≤ 33 years - 107 (51.69%) and b) age> 33 years - 100 (48.31%).Significant independent predictor of parental satisfaction from the receipt of their child to the clinic research confirms the age of the parent under / over 33 years due to 4.1% of the change in satisfaction (R2 = 0,041). Parents generally believe that their children's room of the clinic is "good", without significant difference between parental satisfaction from both age groups (Mann-Whitney U Test Z = -0,9613 p = 0,3364). Significant independent predictor of parental satisfaction from the room of their child improves the health status after treatment due to 6% of the change in satisfaction (R2 = 0,060). Parents generally believe that testing and treatment of their children in the clinic was "very good" and an independent significant predictor is to improve the health status after the treatment - 7,8% (R2 = 0,078). Conclusions: Regardless of the generally good parental satisfaction about health care for their children, it is necessary to continuously monitor the status of the clinic in order to consider the possible deficiencies and needs of intervention.

AWARENESS ABOUT INDOOR AIR POLLUTION IN GENERAL POPULATION OF RAWALPINDI AND ISLAMABAD

2018 ◽  
Vol 8 (2) ◽  
pp. 80-83
Author(s):  
Nadia Tariq ◽  
Tamkeen Jaffry ◽  
Rahma Fiaz ◽  
Abdul Majid Rajput ◽  
Sadaf Khalid
Keyword(s):  
Air Pollution ◽  
General Population ◽  
Indoor Air ◽  
Indoor Air Pollution ◽  
Economic Status ◽  
Educational Status ◽  
Epidemiological Studies ◽  
Cross Sectional Survey ◽  
Cross Sectional ◽  
Significant Difference

Background: Indoor air pollutants are increasingly being associated with respiratory illnesses leading to high degree of morbidity and mortality. There are not sufficient epidemiological studies from Pakistan which assess level of awareness of indoor air pollution resulting in respiratory diseases in population. Methods: This cross sectional survey was carried out on general population of Rawalpindi/Islamabad. Sample size was 223 study subjects selected by non-probability convenient sampling. Knowledge of the study subjects was determined with regard to indoor air pollution, its effects on health and different sources of indoor air pollution with the help of a questionnaire. The influence of age, gender, educational status and socio economic status on the level of awareness was also analyzed. Results: Out of total 223 participants, 115 were males and108 females. Participants aware of indoor air pollution were 91.5% and adequate awareness about its sources was 80.7%. Those who knew indoor air pollution is detrimental to health were 95.1%. Awareness about building construction dust as source of indoor air pollution was maximum (84.8%). There was significant difference in awareness among participants with different monthly incomes and educational status and also between males and females. Conclusion: This study concludes that general population of Rawalpindi/Islamabad has fairly good awareness about sources of indoor air pollution. Use of harmful material causing indoor air pollution should be limited or substituted with better ones where possible.

Assessment of Knowledge and Practice of Various Eye Diseases in Sulaimani: A Descriptive Study

2018 ◽  
pp. 1-6
Author(s):  
Abdulrahman M. Ibrahem ◽  
Salah Q. Mahmood ◽  
Muhammed Babakir-Mina ◽  
Salar Ibrahim Ali ◽  
Bakhtyar Kamal Talabany
Keyword(s):  
Vision Loss ◽  
Good Practice ◽  
Study Data ◽  
Eye Diseases ◽  
Vision Impairment ◽  
P Value ◽  
Published Data ◽  
Knowledge Level ◽  
Cross Sectional ◽  
Knowledge And Practice

Knowledge and practice of public, especially patients about eye diseases are important to reduce magnitude of human blindness. Vision and sight are very essential because they allow us to connect to each other’s. In accordance to the recently published data; the estimation of 253 million people lives with vision impairment, 36 million are blind and 217 million suffer from moderate to severe vision impairment. A descriptive cross-sectional study was conducted at Shahid Dr. Aso Hospital in Sulaimani city-Iraq, from April to August 2017 by face-to-face interview through close ended questionnaire for data collecting. All data were analyzed by Statistical Package for Social Sciences version 22.0 software. P-value of < 0.05 was considered as a statistically significant. A total of 430 patients were randomly chosen to participate in the study. They were 254 (59.1%) males and 176 (40.9%) females. 76.7% of respondents was worrying about vision loss, 0.7% was worrying about hair loss. Of the participants, 32.8% was with a good knowledge level and 40.5% was with a poor knowledge level, as well as 3.1% was in a good practice and 58.8% was in a poor practice level. Female knowledge mean score was 9.53±4.96 and male knowledge mean score was 8.42±5.45, the practice mean score of males was 4.33±1.96 and mean practice score of females was 4.13±1.93. The study data indicate the worrying of participates about vision loss is in the highest proportion and the awareness and practice of patients about eye diseases is unsatisfactory. Health education campaigns are needed to improve personal awareness about vision related problems and for better eye health.

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