By U. Ben. Wesley College.
The linear momentum L of an object at time t was pre- viously defined as L 5 m vc (7 order actonel 35mg line treatment erectile dysfunction. According to Newton’s second law 35 mg actonel with visa medications 4 less, the equation of motion of the center of mass of an object is dL/dt 5SF where SF denotes the resulting force acting on the object. Integrating the equation of motion for the center of mass between time t 5 ti and t 5 tf, we obtain the following relationship: m vc 2 m vc 5Sz (7. The vec- torial sum of the impulse and the linear momentum before the impulse must be equal to the linear momentum after the impulse. According to this equation, the change in the linear mo- mentum of a body during the time interval Dt is equal to the impulse act- ing on the body during the same time interval (Fig. The linear mo- mentum of the body in the direction normal to the impulse remains unaffected. In some situations an external force acting on a body is large compared to other forces exerted on the body but the time interval during which the force acts is small. A force that becomes very large during a very small time interval is called an impulsive force. When an impulsive force acts on a body, there may be an appreciable alteration in velocity during the period of application of the force. If some of the external forces acting on the object during a time interval (tf 2 ti) are impulsive, we may neglect en- tirely the effect of all other external forces on the motion of the object in the same time interval. Although the velocities may be altered as a result of impulse, the change in the spatial position of an object is negligible. Determine the average impact force on a front-seat passenger who is (i) buckled and (ii) not buckled. Experments with dummies indi- cate that if a passenger were not to wear a seat belt, he or she would hit the windshield and that collision would take place in 1 ms. In this particular case, we assume the weight of the front-seat passenger to be 60 kg. Because the im- pulsive force from the collision is much greater than other forces acting on the front passenger (the weight of the passenger and the contact forces between the seat and the passenger), impulse z in both cases is equal to z 5 60 kg [0 2 (120 km/h)] e1 522000 kg? A front-seat passenger wear- ing a seat belt would decelerate as the front of the car was being deformed by the forces of impact. However, a passenger not wearing a seat belt would hit the front of the colliding car with the oncoming velocity. The only significant horizontal force acting on the passenger is the force of impulse by the seat belt. This force di- vided by the mass of the passenger must be equal to its acceleration (de- celeration in this case) and thus: a 5266. Note that the longer it takes for the car to de- form and absorb the shock, the better it is for the safety of the passenger. It is clear that cars loaded in the front with energy-absorbing materials such as steel will have lower values of average acceleration than a light and small car. Even after the front of the car hits the wall and begins decelerating, because the passenger is not tied to the car, he or she will still be mov- ing forward at 120 km/h. The passenger soon will hit the front wind- shield with this velocity, and the duration of the crash is 1 ms in this case. Therefore, the average crash force and the average acceleration during the crash become Fav 522,000,000 e1 (N) a 5233,350 e (m/s2) av 1 This value is about 3,400 times the gravitational acceleration, and surveys of car crashes indicate significant injury to the head at acceleration val- ues above 200 g. When two objects collide, the impulse forces they exert on each other are equal in magnitude but opposite in direction. According to this equation, the sum of linear momentum of two objects during impact must be conserved. The subscripts i and f refer to times immediately before and after the collision, re- spectively. The vector n is the unit vector that is normal to the tangent plane T at the point of contact.
Its purpose is to evaluate high-performance computer applications running over pilot ATM networks established by the European PTTs cheap actonel 35mg with amex medications zolpidem. The objectives of HIM are to evaluate the global networks available for imaging order actonel 35mg amex medications or therapy, to establish user needs and requirements for computer applications, and to develop tools for collaborative working. The HIM project comprises 18 partners over 9 countries, including health-care partners, technical partners, and evaluation partners. Currently it is investigating image conferencing using 2-D image sets (CT, MRI, etc), med- ical images in the management of liver disease, cardiology cine sequences, 3-D remote-image processing facility, and image mailbox (e-mailing images in sup- 3. Some of the tools used in the course of the project include: the display utility DisplImage, developed at University College Lon- don, which makes use of the X client-server architecture and the Berkeley Conferencing Tools vic and vat (available in the public domain). The Internet in whatever form could provide the communications infrastructure, the acces- sibility protocol, however, is bound to be based on World Wide Web. In addition, interpreted languages such as Java have been developed to run on the WWW. The Web is a simple yet ingenious system that allows users to interact with documents stored on computers across the Internet as if they were parts of a single hypertext (62). A major reason for the accel- erated growth of the Internet in the last few years is the WWW, which began in 1992 at CERN, the European Laboratory for Particle Physics, as a means of distributing and annotating speci®c research. Technical standards are now de®ned by the World Wide Web consortium, which speci®es four sets of rules creating, publishing and ®nding documents:. Web documents are ordinary text ®les that can be created with any word-processing program. Selecting a link lets the user go to another document (or to another section of the same document). HTML documents (often called pages) can also include color graphics and clips of digitized audio or video. VRML is an open ex- tensible, industry-standard scene description language for 3-D scenes, or worlds, on the Internet. Users of the Web retrieve documents from servers (or Web sites); http allows a networked computer to listen for and respond to incoming request for ®les (hits). Web users can retrieve documents either by manually entering URLs or by selecting links that contain URLs. If the Web is to be adopted as the accessibility medium and the Internet as the communication medium, then there should be a WWW interface to the storage components. It is, therefore, envisaged that HIS, PACS and any other storage mediums will be Web accessible. The integration protocols between PACS/HIS and other information systemsÐsuch as the cardiology information system developed at the University of Belgrade, shown in Figure 3. Alternative databases such as the Neuronal Database in the Human Brain Project (63) and video archiving systems should also be designed with Web interfaces. Furthermore, it is envisaged that the information systems will begin to possess some processing capabilities so, the processing of an image could then be undertaken at the site of storage (64) (Fig. In many countries, legislation requires that all captured health-care information be preserved for a certain period of time (typically 5 to 10 years) before it can be deleted. In such cases, it should be clear who is responsible for the maintenance and integrity of the information. Who is allowed to look at, modify, copy, or delete an item of health-care information? Others may be allowed to look at or copy them, and yet others may not be allowed to access them at all. In clinical applications, the ability to associate patient- related information with the correct patient is vital. In such cases, linkages between diverse types of information need to be protected and must be preserved after information interchange. The situation is complicated in a distributed multimedia environment in which the relation- ship between some items of patient-related information, often in di¨erent formats, must be maintained and other relationships must be severed. Because of the use to which it is put, the preser- vation of information at known and guaranteed levels of integrity is crucial 76 VIRTUAL REALITY AND ITS INTEGRATION INTO A TWENTY-FIRST CENTURY in the health-care domain. Health-care information of all types must be protected from accidental or malicious alteration during interchange and storage.
Epidemiology and Aging 49 suggests that factors associated with frailty and increased 45 ture actonel 35 mg mastercard medicine quinidine. Other more speciﬁc estrogen agonists order 35 mg actonel free shipping symptoms 0f pregnancy, such as risk of falling contribute to fracture risk as well. The raloxifene, have also been identiﬁed as useful to prevent beneﬁt has been a comprehensive and integrated 46 osteoporotic bone loss. Although a staple of By the mid-1980s, the role of estrogen decline in therapy for osteoporosis for years, estrogen had not been women contributing to bone loss was well established. Potential biases Patterns of change in bone mineral relating to periods of related to the characteristics of women given estrogen hormonal change over the lifetime had been identiﬁed therapy in clinical practice, including the fact that these and a threshold for risk of osteoporotic fracture estab- women were often thinner and healthier than other lished. The Women’s Health Initiative, a reducing bone loss at critical periods, such as during the multioutcome trial of estrogen use as protective for hip perimenopausal period. This if not more important, were risk factors that contributed ﬁnding, plus options now available with other medica- to the fall leading to fracture. Early studies identiﬁed tions, have opened the questin of whether estrogen is the those at risk of falling and demonstrated some overlap ﬁrst-line treatment for osteoporosis. In addition, following the better prospectively establish the role of falling in rela- observation that older men are experiencing a major tion to risk of fracture. The largest of these, the Study of Osteoporotic Fractures, established that bone mineral density and falls Summing Up were both risk factors for fracture. Furthermore, risk factors contributing to both lower bone mineral density, Thus, epidemiologic methods have contributed to a such as smoking, and risk factors contributing to risk of complex and dynamic understanding of risk of disease in falling, such as reduced vision and strength, also con- old age, identifying factors that are related to "classical" tributed to risk of fracture. Tinetti and col- they relate not to one organ system speciﬁcally, but iden- leagues identiﬁed that risk of falling was modiﬁable by tify how even small deﬁcits in multiple organ systems can testing an algorithmic approach to diagnosis and inter- contribute to risk of poor health outcomes in old age. Many of these to prevent fracture needed to account for the hetero- contributions have been incorporated in a variety of geneity in the at-risk population, as the goal was to evidence-based practice guidelines, and the possibilities prevent fractures without increasing fear of falling, which for the future are bright. Epidemiology can be an impor- could itself lead to decline in functional independence. The Fracture Interven- and psychologic problems of the elderly, to identify new tion Trial established the efﬁcacy of alendronate ﬁrst in avenues for intervention and to test these interventions, prevention of vertebral fractures and later for hip frac- and to adapt the interventions to the practical realities of 50 T. In this way, epidemiologic method can func- ing maximum height and distinguishing birth cohort effects tion as an important adjunct in the mission of promoting from actural loss of stature with aged. The dynamics of dimen- of being overweight and change in weight on risk of coro- sions of age-related disability 1982 to 1994 in the U. The therapeutic challenge of systolic hyper- adults: Expanding familiar approaches in the Health ABC tension. Hypertension versus catastrophic disability: a longitudinal view of the dis- and risk of stroke in an elderly population. Five-year ﬁndings of the hypertension deterc- Hypotheses about the bottom of the iceberg. Mortality and protective effect of emotional vitality on adverse health morbiditiy results from the European working party on outcomes in disabled older women. Prevention of stroke sectional relationships between religion, physical health, by antihypertensive drug treatment in older persons with social support, and depressive symptoms. Longitudinal tiated and administered by the National Heart Foundation changes in serum cholesterol in man: An epidemio- of Australia. Type of fall and risk of hip and infarction on magnetic resonance imaging and neuro- wrist fractures: the Study of Osteoporotic Fractures. SHEP Cooperative intervention to reduce the risk of falling among elderly Research Group. Effect of derived from relative risks: an analysis applied to the alendronate on risk of fracture in women with low bone population of Sweden. Rela- parison of the effects of raloxifene and estrogen on bone in tive contributions of aging and estrogen deﬁciency to postmenopausal women. A hypothesis: the causes of hip Women’s Health Initiative clinical trial and observational fractures. This page intentionally left blank 6 Psychosocial Inﬂuences on Health in Later Life Elizabeth C. Steinhauser Geriatricians face an enormous intellectual and personal resources, factors likely to inﬂuence the future func- challenge in understanding the interactive complexi- tioning and disability management of the patient in the ties—physical, psychosocial, functional, and spiritual—of community. Successful geriatric assess- Now considered the optimal standard of care, a sys- ment and treatment depend not only on recognition tematic approach to comprehensive geriatric assessment of pathology but, perhaps more importantly, on under- attends to multiple personal domains, including but not standing how such pathology relates to the "whole limited to physical health, mental health, function, person. This scope of inquiry is signiﬁcantly The interactive complexities of geriatric medicine broader than other medical specialities and makes have led geriatricians to consider relatively unique care performing comprehensive assessment a formidable approaches, most notably the multidisciplinary approach, task within the shorter encounter time frames of most which utilizes expertise from a number of disciplines in managed care environments.
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