Friction is a force that slows down moving objects or prevents stationary objects from moving .
Friction is a contact force .
Friction produces heat .
For example – A matchstick
Friction opposes the motion of an object
When one surface moves over another , these grooves and ridges get caught up with each other and slow down the motion . This causes friction .
Summary
Definition
Friction is a catchall word that refers to any force that resists relative tangential motion (or intended motion).
"Relative tangential motion" is a fancy way to say "slipping" or "sliding".
Its direction is opposite the relative velocity (or intended velocity).
Types
Dry friction
The resistive force between solid surfaces in contact that resists their relative tangential motion.
"Friction" is often synonymous with "dry friction".
Viscous friction-
for more.......... go to this link :)
http://physics.info/friction/summary.shtml
Summary
Definition
Friction is a catchall word that refers to any force that resists relative tangential motion (or intended motion).
"Relative tangential motion" is a fancy way to say "slipping" or "sliding".
Its direction is opposite the relative velocity (or intended velocity).
Types
Dry friction
The resistive force between solid surfaces in contact that resists their relative tangential motion.
"Friction" is often synonymous with "dry friction".
Viscous friction-
for more.......... go to this link :)
http://physics.info/friction/summary.shtml
Force and its effects for class 8. this ppt provides an easy way to understand force and the effects of force by giving various daily life examples. It consists of animations through which students can easily understand.
Force and its effects for class 8. this ppt provides an easy way to understand force and the effects of force by giving various daily life examples. It consists of animations through which students can easily understand.
Kinds of Friction
A moving object is affected by friction. However, the amount of friction may vary depending on the type of surface the object gets in contact with.
Rolling Friction
When an object rolls over a surface , rolling friction is produced. One of the most common examples of rolling friction is the movement of motor vehicle tires on the road , a process that generates heat and sound as by-products. Rolling friction is easier to overcome than sliding friction for similar materials. This type of friction is important to engineers who design certain products. For example, skates, skateboards, and bicycles need wheels that move freely.
Sliding Friction
Sliding friction occurs when two solid surfaces slide over each other. Sliding friction can be useful. For example, you can spread sand on an icy path to improve your footing. Ballet dancers apply a sticky powder to the soles of their ballet slippers so they won’t slip on the dance floor. And when you stop a bicycle with hand brakes, rubber pads slide against the tire surfaces, causing the wheels to slow and eventually stop. On the other hand, sliding friction is a problem if you fall off your bike and skin your knee!
Fluid Friction
Fluids, such as water, oil, or air, are materials that flow easily. Fluid friction occurs when a solid object moves through a fluid. Like rolling friction, fluid friction is easier to overcome than sliding friction.
Static Friction
The friction that acts on objects that are not moving is called static friction. Because of static friction, you must use extra force to start the motion of stationary objects. For example, think about what happens when you try to push a heavy desk across a floor. If you push on the desk with a force less than the force of static friction between the desk and the floor, the desk will not move. To make the desk move, you must exert a force greater than the force of static friction.
Best ppt on friction explaination, types of friction ,advantage & disadvantage of friction.effects of friction, methods of increacing and reducing friction,with example
ORAL MANIFESTATIONS OF SYPHILIS-A reviewishita1994
Syphilis is an infectious disease of most extreme significance these days, which has made a rebound after the presence of AIDS.
It might introduce oral lesions in all stages.
A sharp information on its different oral signs is significant for appropriate determination and satisfactory treatment.
Infective syphilis is brought about by the anaerobic filamentous spirochete, Treponema pallidum.
Previously decade there has been a noteworthy ascent in the prevalence of infective syphilis in the created world.
Striking increments in the recurrence of syphilis have happened in Eastern Europe, and more modest ascents have been accounted for in Western Europe and the US.
Paget’s disease of bone with special reference to dentistry-an insightishita1994
Bone is a dynamic tissue that is constantly renewed. The cell populations that participate in this process; the osteoblasts and osteoclast are derived from different progenitor pools that are under distinct molecular control mechanisms. Together, these cells form temporary anatomical structures, called as basic multicellular units that execute bone remodeling. A number of stimuli affect bone turnover, including hormones, cytokines, and mechanical stimuli. All of these factors affect the amount and quality of the tissue produced. Paget’s disease is a bone disorder characterized by excessive and abnormal remodeling of the bone, resulting in distortion and weakness of affected bones. It is the second‑most common osteo dystrophic condition after osteoporosis.
Epidemiology and Diagnosis of Mucormycosisishita1994
Mucormycosis is an angioinvasive fungal infection due to fungi of the order Mucorales.
Depending on the clinical presentation it is classified as rhinocerebral, pulmonary, cutaneous, gastrointestinal, disseminated or other, which includes uncommon rare forms, such as endocarditis, osteomyelitis, peritonitis, renal, etc.
The disease was first described in 1876 when Fürbinger described in Germany a patient who died of cancer and in whom the right lung showed a hemorrhagic infarct with fungal hyphae and a few sporangia.
In 1885, Arnold Paltauf published the first case of disseminated mucormycosis, which he named “Mycosis mucorina”.
His drawings of the etiologic agent showed the presence of sporangiophores and rhizoid-like structures, and this led to the conclusion that the infection was most probably caused by Lichtheimia corymbifera.
Over time, more cases were diagnosed, and the incidence of the disease has increased.
Currently, Mucorales fungi are the next most common mold pathogens after Aspergillus, leading to invasive fungal disease in patients with malignancies or transplantation.
The incidence of mucormycosis has also increased significantly inpatients with diabetes, which is the commonest underlying risk factor globally.
Τhe epidemiology of mucormycosis is evolving as new immunomodulating agents are used in the treatment of cancer and autoimmune diseases, and as the modern diagnostic tools lead to the identification of previously uncommon genera/species such as the Apophysomyces or Saksenaea complex.
Oral cancer is the world’s 6th most common malignancy and has one of the lowest survival rates, often due to late diagnosis. The most important determinant factor in cancer survival is diagnostic delay and it directly affects the survival rate.
Most oral cancers are preceded by precancerous lesions and early cancers that can be identified by visual inspection of the oral cavity. Conventional oral examination is useful in the discovery of some oral lesions, but it does not identify all potentially premalignant lesions, as some are not readily apparent to visual inspection alone.
Adjunctive techniques have emerged that may facilitate early detection of oral premalignant and malignant lesions. Thorough clinical examinations being one of the best modalities in suspecting the pathology, the biggest disadvantage in the diagnosis lies in detecting the site of biopsy and also whether biopsy is required or not in early lesions.
Nowadays various diagnostic aids have been established in detecting such lesions but easy chair-side techniques can be used if possible. And one such technique is by using vital staining with dyes which is used for early recognition of lesion and also can improve the patient survival rate.
CLINICOPATHOLOGICAL FEATURES OF PERIPHERAL OSSIFYING FIBROMA IN A SERIES OF 4...ishita1994
Peripheral ossifying fibromas are benign mesenchymal lesions that usually arise in the anterior maxilla of young female patients. Histologically they consist of spindle cell proliferation with focal mineralization. We reviewed 48 specimens from 41 patients and recorded the clinical data, sex, and age of the patients, site, and size of the lesions, treatment, and postoperative outcome. Histologically the presence of mature, woven bone, cementum, and calcifications was evaluated and evaluated immunohistochemically. Lesions were more frequent in female patients in the third and fourth decade and were usually in the lower maxilla and smaller than 2 cm. All lesions were conservatively excised, and they relapsed in eight patients. Histopathologically, the lesions were poorly circumscribed, with moderately cellular proliferation, and with no discernible architectural pattern. All tumors showed some degree of mineralization, the presence of immature bone being the most common. Immunohistochemical examination showed staining of tumoral cells for smooth muscle actin and CD68. Lesions tended to occur more commonly in female patients, but one decade later than usually reported. We found a higher recurrence rate in lesions that contained cementum-like material but without bone formation, suggesting a lack of maturation in this group. Immunohistochemical results were consistent with myofibroblastic differentiation but they added no information about the behavior of the lesions.
Pathophysiology of myoepithelial cells in salivary glandsishita1994
In salivary glands and other exocrine glands, there are
star‑shaped cells lying between the basal lamina and the acinar
and ductal cells. These cells structurally resemble epithelial cells
and smooth muscles and, thus, are referred to as myoepithelial
cells (MECs). Because of their shape and interwoven processes,
they were commonly referred to as “star‑shaped cells” or
“basket cells.” Tamarin described these cells as being “like an
octopus sitting on a rock”.
Current concepts of pemphigus with a deep insight into its molecular aspectishita1994
Pemphigus vulgaris is an autoimmune bullous disease involving both the skin and mucosal areas, which
is characterized by intraepithelial flaccid blisters and erosions. The pathogenesis of this disease is not
yet completely established, but novel intuitions into its pathogenesis have recently been published. An
unanswered question in its pathophysiology is the mechanism of acantholysis or loss of keratinocyte
cell adhesion. Acantholysis seems to result from a communal action of autoantibodies against numerous
keratinocyte self‑antigens, of which desmogleins 1 and 3, desmocollins and nondesmosome components,
such as the mitochondrion, might take part in the disease initiation. Lately, apoptosis was described as
a possible underlying mechanism of acantholysis. Likewise, apoptolysis is assumed to be the association
between suprabasal acantholytic and cell death pathways. Hence, the present review focuses on the current
concepts in the pathogenesis of the pemphigus in a nutshell.
Cytoskeleton of a cell is made up of microfilaments, microtubules and intermediate filaments. Keratins are diverse proteins. These intermediate filaments maintain the structural integrity of the keratinocytes. The word keratin covers these intermediate filament-forming proteins within the keratinocytes. They are expressed in a specific pattern and according to the stage of cellular differentiation. They always occur in pairs. Mutations in the genes which regulate the expression of keratin proteins are associated with a number of disorders which show defects in both skin and mucosa. In addition, there are a number of disorders which are seen because of abnormal keratinization. These keratins and keratin-associated proteins have become important markers in diagnostic pathology. This review article discusses the classification, structure, functions, the stains used for the demonstration of keratin and associated pathology. The review describes the physiology of keratinization, pathology behind abnormal keratin formation and various keratin disorders.
Romanowsky staining or Romanowsky–Giemsa staining, is a prototypical staining technique, widely used in hematology and cytopathology.
They are used to differentiate cells for microscopic examination in air dried cytological smears or pathological specimens, especially blood and bone marrow films, and to detect parasites such as malaria within the blood.
Romanowsky stains is a neutral dye containing both acid and basic dyes in combination. It contains both azure B (electron acceptor) and eosin Y (electron donor).
The value of Romanowsky staining lies in its ability to produce a wide range of hues, allowing cellular components to be easily differentiated. This phenomenon is referred to as the Romanowsky effect, or more generally as metachromasia.
These stains allow better estimation of cell size, nuclear size, cell cytoplasm and identify ground substances by metachromasia.
The tissue section is colourless because the fixed protein has the same refractive index as that of glass. We use dyes that have specific affinity with the different tissue proteins and colour them differently.
Colour is seen by the eye as a result of the effect of certain electromagnetic waves on the rods and cones of the retina. These waves, which have a varying length, will determine the colour that is seen.
White light being composed of all the colours of the visible spectrum varies in wavelength from 4,000 Â to 8,000 Â.
If light of a specific wavelength is absorbed from white light the resultant light will then be coloured, the colour being dependent upon the particular wavelength that has been removed.
Ghost cells are translucent balloon shaped , elliptical epithelial cells are recognized as swollen, pale, eosinophilic cells.
They are seen either singly or in sheets with a clear conservation of basic cellular outline, generally with apparent clear areas or with some remnants indicative of the site previously occupied by the nucleus.
The transformation of epithelial cells into more resistant terminally differentiated apoptotic cells i.e., ghost cells are responsible for the banal behavior of neoplasms and they also help in relieving the stress of the forming neoplasm.
The most accepted nature of ghost cells is aberrant keratinization that is altered form of keratin as it doesn’t stain with normal cytokeratin antibodies.
Tonofilaments have been observed universally in the ghost cells of all the odontogenic or non-odontogenic tumors but these solely don’t satisfy their nature which is also found to be positive for enamel proteins in odontogenic tumors.
Although, studies prove an intricate functional relationship exists between Wnt and Notch signalling during development of neoplasms and in assigning cells to particular fates.
Their relationship along with other signalling pathways complex interaction during tumorigenesis also needs intensive evaluation and this would help revealing the missing link between odontogenic and non-odontogenic tumors exhibiting these similar looking mysterious ghost cells.
Mineralization (calcification) is the process of deposition of insoluble calcium salts in a tissue. It is one of the important steps in the formation of hard tissues of the body that is enamel, dentin, bone, and cementum. The synthetic cells, along with the help of the enzyme alkaline phosphatase, aid the mineralization process. The mineral content (inorganic portion) of all the hard tissues of the body is mainly in the form of Calcium hydroxyapatite crystals, Ca10(PO4)6(OH)2.
When calcium phosphate deposition is initiated, the crux is then to control spontaneous precipitation from tissue fluids supersaturated in calcium and phosphate ions and to limit it to well-defined sites. Formative cells achieve this by creating microenvironments that facilitate mineral ion handling and by secreting proteins that stabilize calcium and phosphate ions in body fluids and/or control their deposition onto a receptive extracellular matrix.
The synthetic cells achieve this property by secreting proteins that stabilize Calcium and Phosphate in the body fluids and control their deposition onto the extracellular matrix. These proteins are:
1. Salivary proteins
2. Enamel matrix protein
3. Dentin, cementum, and bone matrix proteins.
Histologically, the lesion shows a highly vascular proliferation that resembles granulation tissue.
Numerous small and larger endothelium-lined channels are formed that are engorged with red blood cells. These vessels sometimes are organized in lobular aggregates, and may be called as lobular capillary haemangioma.
The surface is usually ulcerated and replaced by a thick fibrinopurulent membrane.
A mixed inflammatory cell infiltrate of neutrophils, plasma cells, and lymphocytes is evident.
Neutrophils are most prevalent near the ulcerated surface; chronic inflammatory cells are found deeper in the specimen.
It is also called Oral Fibroma or Irritational Fibroma or Focal Fibrous Hyperplasia.
Fibroma is a benign neoplasm of fibrous connective tissue origin.
It is characterized by excessive proliferation of fibroblast cells with synthesis of large amount of collagen.
Although a large number of fibrous over-growths are found inside the oral cavity, most of these are reactive lesions occurring as a result of trauma or local irritation and therefore true fibromas are extremely rare.
Jain G et al (2017) stated that traumatic irritants include calculi, foreign bodies, overhanging margins, restorations, margins of caries, chronic biting, sharp spicules of bones, and overextended borders of appliances. Fibroma, a benign neoplasm of fibroblastic origin, is reactive in nature and represents a reactive hyperplasia of fibrous connective tissue in response to local irritation or trauma rather than being a true neoplasm.
8 th edition TNM classification and significance of depth of invasionishita1994
Diagnosis of oral cancer is completed for:
Initial diagnosis
Staging
Treatment planning
A complete history, and clinical examination is first completed, then a wedge of tissue is cut from the suspicious lesion for tissue diagnosis. In this procedure, the surgeon cuts all, or a piece of the tissue, to have it examined under a microscope by a pathologist.
Leukoplakia can be defined as a “white patch” or “plaque” in the oral cavity, which cannot be scrapped off and which cannot be characterized clinically or pathologically as any other disease.
This excludes lesions such as lichen planus, candidiasis, leukoedema, white spongy nevus, and obvious frictional keratosis.
The term leukoplakia should be used to recognise white plaques of questionable risk having excluded (other) known diseases or disorders that carry no risk for cancer-WHO 2005.
Mandibular central incisors are two in number
Mandibular central incisor and lateral are similar in anatomy and complement each other in function
They are smaller than the maxillary central incisors
Mandibular central incisor erupts between the age of 7 and 8 years
First tooth from the midline in each lower quadrant
Depth of invasion in oral squamous cell carcinomaishita1994
It is the most common malignant epithelial tissue neoplasm of the oral cavity.
It is derived from the stratified squamous epithelium.
Since oral squamous cell carcinomas constitute bulk of the oral malignancies (above 90 %) it is thus commonly referred to as Oral Cancer.
Tuberculosis is a disease characterized by granulomatous lesions caused by Mycobacterium Tuberculosis. A German scientist Robert Koch discovered the causative organism of TB in 1882.
Since time immemorial, it has been a global health problem. TB has shown a decline in its prevalence globally; however, it is still highly prevalent in Asian countries.
TB is usually overlooked in the differential diagnosis of oral lesions as it is supposed to be a rare entity.
Oral manifestations of TB occur either due to infected sputum or due to hematogenous spread.
TB is an age old disease and has been known to mankind for thousands of years.
Role of human papillomavirus and tumor suppressor genesishita1994
Oral cancer is synonymous to Squamous Cell Carcinoma (SCC) of oral mucosal origin that accounts for more than 90% of all malignant presentations at the aforementioned anatomical sites.
More than 300,000 new cases worldwide are being diagnosed with oral SCC (OSCC) annually.
Approximately, 30,000 (US) & 40,000(EUROPE).
Oral cancer is estimated by the WHO to be the 8th most common cancer worldwide.
In India & other Asian countries, oral & oropharyngeal carcinomas (OCs) comprise up to half of all malignancies, with this particularly high prevalence being attributed to the influence of carcinogens & region-specific epidemiological factors, especially tobacco & betel quid chewing.
Model Attribute Check Company Auto PropertyCeline George
In Odoo, the multi-company feature allows you to manage multiple companies within a single Odoo database instance. Each company can have its own configurations while still sharing common resources such as products, customers, and suppliers.
2024.06.01 Introducing a competency framework for languag learning materials ...Sandy Millin
http://sandymillin.wordpress.com/iateflwebinar2024
Published classroom materials form the basis of syllabuses, drive teacher professional development, and have a potentially huge influence on learners, teachers and education systems. All teachers also create their own materials, whether a few sentences on a blackboard, a highly-structured fully-realised online course, or anything in between. Despite this, the knowledge and skills needed to create effective language learning materials are rarely part of teacher training, and are mostly learnt by trial and error.
Knowledge and skills frameworks, generally called competency frameworks, for ELT teachers, trainers and managers have existed for a few years now. However, until I created one for my MA dissertation, there wasn’t one drawing together what we need to know and do to be able to effectively produce language learning materials.
This webinar will introduce you to my framework, highlighting the key competencies I identified from my research. It will also show how anybody involved in language teaching (any language, not just English!), teacher training, managing schools or developing language learning materials can benefit from using the framework.
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Read| The latest issue of The Challenger is here! We are thrilled to announce that our school paper has qualified for the NATIONAL SCHOOLS PRESS CONFERENCE (NSPC) 2024. Thank you for your unwavering support and trust. Dive into the stories that made us stand out!
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This is a presentation by Dada Robert in a Your Skill Boost masterclass organised by the Excellence Foundation for South Sudan (EFSS) on Saturday, the 25th and Sunday, the 26th of May 2024.
He discussed the concept of quality improvement, emphasizing its applicability to various aspects of life, including personal, project, and program improvements. He defined quality as doing the right thing at the right time in the right way to achieve the best possible results and discussed the concept of the "gap" between what we know and what we do, and how this gap represents the areas we need to improve. He explained the scientific approach to quality improvement, which involves systematic performance analysis, testing and learning, and implementing change ideas. He also highlighted the importance of client focus and a team approach to quality improvement.
Welcome to TechSoup New Member Orientation and Q&A (May 2024).pdfTechSoup
In this webinar you will learn how your organization can access TechSoup's wide variety of product discount and donation programs. From hardware to software, we'll give you a tour of the tools available to help your nonprofit with productivity, collaboration, financial management, donor tracking, security, and more.
The French Revolution, which began in 1789, was a period of radical social and political upheaval in France. It marked the decline of absolute monarchies, the rise of secular and democratic republics, and the eventual rise of Napoleon Bonaparte. This revolutionary period is crucial in understanding the transition from feudalism to modernity in Europe.
For more information, visit-www.vavaclasses.com
The French Revolution Class 9 Study Material pdf free download
Friction
1.
2. What is friction ?
• Friction is a force that slows down
moving objects or prevents
stationary objects from moving .
• Friction opposes the motion of an
object
3. •Friction is a contact force .
•Friction produces heat .
•For example – A matchstick
4.
5. Causes of friction
• When one surface moves over
another , these grooves and
ridges get caught up with each
other and slow down the motion .
This causes friction .
6.
7. Types of friction
• There are four types of friction :-
1. Static friction
2. Sliding friction
3. Rolling friction
4. Fluid friction
Three
main
types of
friction
14. Fluid friction
• Friction on moving objects
through fluids such as air and
water is called Fluid friction .
• This frictional force that fluids
exert on objects is called drag .
15. • It depends on the following reasons
:-
1.Shape of the object .
2.Speed of the object with respect
to fluid .
16. Advantages of friction
• It would be easy to walk .
• Without friction we could not
write.
• Brakes in vehicles help to stop
because of friction .
18. Disadvantages of friction
• It causes wastage of energy
because any object that moves
has to overcome the force of
friction .
• The soles of our shoes wear out
in a few months due to friction .
19. • Friction generates heat .
Sometimes this can be harmful .
The heat produced in a fast
moving machine is very high .
Proper arrangements should be
made to cool the machine ,
otherwise it can get damage .
20. The soles of shoes
being damaged due to
friction
21. Decreasing friction
• Polishing – It smoothens the
surface and thus reduces
friction .
• Lubrication – It can be done with
graphite , oil or grease.
22. • For example - Graphite is used in
machines as lubricant to reduce
friction .
• Streamlining – Streamlined shape
which is rounded in front and
narrow at the back .
• For example – Birds , aeroplanes
(aerodynamic)
23. • Ball bearing – Rolling friction is
less than sliding friction so ball
bearings are used to reduce
friction
26. Increasing friction
• Tyres have design and grooves to
increase friction so that they
don’t slide on the wet road .
• To walk easily on ground in rainy
season sand and gravel is placed .
27. • To get a firm grip on the ground
spikes are provided on the shoes
sole used by players .
• Gymnasts apply a coarse
substance on their hands to
improve their grip
