Term
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Definition
| Scientific study of deformation and flow properties of matter |
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Term
| Solids are _________ _______ to deformation, liquids are _____ _______ and gases are ________ _________ |
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Definition
| completely resistant,less resistant,completely nonresistant |
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Term
| Rheology describes consistency of products based on ... |
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Definition
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Term
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Definition
| Measure of resistance to flow or thickness of liquids |
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Term
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Definition
| Measure of stickiness or structure of solids |
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Term
| The _______viscosity, greater the resistance of the material to flow |
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Definition
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Term
| Define Viscoelasticity and give an example |
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Definition
| Phenomenon observed in materials exhibiting both elastic behavior and viscous flow. E.g. polymer gel, gelatin |
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Term
| Why is rheology important? |
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Definition
| • It plays an important role in dispensing and formulation of various dosage forms including emulsions, suspensions, creams, lotions and tablet coatings |
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Term
| Rheology helps us understand what? |
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Definition
– Passage through the orifices, including pouring, packaging in bottles,
– Passage through hypodermic needles.
– Removal from jars and extrusion from tubes
– Spreading and adherence to the skin
– Capacity of solids to mix with miscible liquids
– Release of drug from the base |
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Term
| Define shear stress in Newtonian Rheology |
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Definition
| Horizontal force (F) applied over a unit area (A). Unit is dynes/cm2 |
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Term
| Newton proposed that the velocity (δv) of the material over the small distance (δx) that it travels is _______ ________ to shear stress. |
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Definition
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Term
| Define and list unit for rate of shear |
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Definition
| Change in velocity of the material over the small distance is called the rate of shear (δv/δx) . Unit is s-1 |
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Term
| What is poise? Give its' unit |
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Definition
• The unit of viscosity is poise that is defined as the shearing force required to produce a velocity of 1 cm/sec between two parallel planes of liquid each 1 cm2 area and separated by a distance of 1 cm.
• In CGS system, poise is dyne sec/cm2 or g/cm sec |
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Term
| Reciprocal of viscosity is ... |
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Definition
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Term
| There is a Linear relationship between rate of shear and _______ _______ |
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Definition
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Term
| What are Rheograms (also known as consistency curves or flow curves)used for? |
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Definition
| Used to describe the rheologic property of a given dosage form or material. |
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Term
| The simplest form of rheogram is produced by the ______ systems that gives an equation of _______ ________ passing through the origin |
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Definition
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Term
| For Newtonian system the greater the slope of the line, the _______ is the fluidity or _______is the viscosity |
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Definition
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Term
| Viscosity is _______of shear stress equaling _______ _______ |
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Definition
| independent ,Absolute Viscosity |
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Term
| Define Kinematic viscosity |
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Definition
| is the absolute viscosity divided by the density of the liquid at a specific temperature |
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Term
| The units of the Kinematic viscosity |
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Definition
| are the stoke (s) and centistoke. |
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Term
| Viscosity of Newtonian fluids decrease sharply with _______temperature. |
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Definition
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Term
| When do you see Non-Newtonian Rheology? |
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Definition
• Observed in complex heterogenous systems in which the relationship between shear stress and the rate of shear is non linear
• Vast majority of liquids and semisolid dosage forms follow Non -Newtonian rheology |
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Term
| What are 3 common types of Non-Newtonian Rheology? |
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Definition
• 3 common types:
– Plastic rheology
– Pseudoplastic rheology
-Dilatant rheology |
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Term
| During Plastic Flow No flow occurs until a specific shearing stress, called _____ ________, is exceeded. |
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Definition
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Term
| During plastic flow at stresses below yield these substances act as ... |
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Definition
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Term
| Once the yield value is reached the relationship between shear stress and rate of shear become... |
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Definition
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Term
| The rheogram for plastic flow does not pass through the origin, rather it intersects the ______ ________ _______ at a point that gives the yield value. |
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Definition
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Term
| The slope of the rheogram is called the ______ (similar to fluidity in Newtonian system) and its reciprocal is known as the _________ ______υ. |
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Definition
| mobility ,plastic viscosity |
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Term
| Plastic rheology occurs in many ... |
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Definition
| liquid and semisolid preparations |
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Term
| In case of ________ _______, yield value determines how much the bottle needs to be shaken before product flows |
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Definition
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Term
| Define Pseudoplastic Flow (Shear Thinning System) |
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Definition
| Pseudoplastic materials begin to flow instantaneously when stress is applied, they exhibit no yield value |
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Term
| The rheogram of a pseudoplastic material begins at ... |
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Definition
| the origin and hence no yield value is observed. |
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Term
| Viscosity of a pseuodplastic material decreases with ______ shearing rate. |
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Definition
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Term
| Give examples of Pseudoplastic Flow (Shear Thinning System) |
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Definition
• Ketchup does not easily flow when in bottle, but flows once the bottle is shaken
• Aqueous solution of polymers show this type of rehology
• Pharmaceutical products containing water soluble polymers such as suspending agents, viscosity modifiers etc. are examples |
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Term
| What type of principle can be used to increase the stability of systems |
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Definition
| Pseudoplastic Flow (Shear Thinning System) |
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Term
| Dilatant Flow (Shear Thickening System) is ... |
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Definition
| • Exact opposite of pseudoplastic systems |
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Term
| Materials that increase in volume under an applied force is called ... |
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Definition
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Term
| Dilatants exhibit an ______in resistance to flow, i.e. increase in viscosity, with increasing rates of shear. |
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Definition
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Term
| The more effort you put into stirring a dilatant material, the more _______ it becomes to stirring. This is usually an indication that the applied force is causing the material to adopt a more ordered structure. |
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Definition
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Term
| Give an example of a Dilatant |
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Definition
• Whipping cream : thickens when stirred
• Observed in suspension with very high solid content (40 – 50%) |
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Term
| In what systems solid particles in suspension are loosely aggregated at rest resulting in lower viscosity. When stress is applied the particles break apart and distribute in the medium |
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Definition
| Dilatant Flow (Shear Thickening System) |
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Term
| A thixotropic material becomes _______ fluid with increasing time of applied force. The applied force could be _________, ________ or _______ |
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Definition
| more, stirring, pumping or shaking |
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Term
| Can thixotropic or work softening be reversed? |
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Definition
| It is often reversible, so that if left undisturbed for some time a thixotropic slurry regains its viscosity |
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Term
| Thixotropic systems usually contain _______ particles that provide a loose three dimensional structure via numerous points of contact throughout the sample. |
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Definition
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Term
| At rest thixotropic system structure provides a degree of ______ on the system that resembles a ________ |
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Definition
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Term
| What measures fluid viscosity at a given shear rate |
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Definition
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Term
| To determine viscosity in Newtonian systems, instruments that operate .... |
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Definition
| a single shear rate can be used |
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Term
| To determine viscosity in Non Newtonian systems, instruments that operate .... |
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Definition
| with variable shear rate is used |
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Term
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Definition
| Study of deformation and flow in biological systems |
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Term
| Biological fluids are _______ materials that are _________ complex |
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Definition
| viscoelastic, rheologically |
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Term
| Changes in the rheological properties of a biological fluid can provide important information as to the _________ ________ of a given physiological system. |
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Definition
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Term
| Is blood is a non-Newtonian fluid or Newtonian fluid? |
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Definition
| Blood is a non-Newtonian fluid |
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Term
| The flow properties of blood is determined by |
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Definition
| hematocrit (Hct) and plasma viscosity |
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Term
| Elevated Hct is associated with |
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Definition
| arteriosclerosis, angina, myocardial infarction. |
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Term
| Viscosity of lung epithelial mucus ________ in cystic fibrosis patients |
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Definition
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Term
| The viscosity of cervical mucus _______at mid menstrual cycle in order to facilitate the penetration of spermatozoa |
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Definition
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Term
| _______of different systems could affect quality and stability of newtonian and non-newtonin systems |
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Definition
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Term
| How does Rheology effect dosage forms? |
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Definition
• Rheology of suspensions and emulsions : Final product should be pourable or injectable
• Removal and spreading of ointments: Addition of pharmaceutical additives could change the properties of the ointment base. Removal from container esp. important in case of elderly patients
Polymeric gels used in drug delivery: Polymers used in drug delivery. Development of systems that gel in situ upon administration |
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