Without variable valve timing or variable valve lift, the valve timing must be the same for all engine speeds and conditions, therefore compromises are necessary. An engine equipped with a variable valve timing actuation system is freed from this constraint, allowing performance to be improved over the engine operating range.
A variety of medical specialists treat people with osteoporosis, including internists, gynecologists, family doctors, endocrinologists, rheumatologists, physiatrists, orthopaedists, and geriatricians. There are a number of ways to find a doctor who treats osteoporosis patients. If you have a primary care or family doctor, discuss your concerns with him or her. Your doctor may treat the disease or be able to refer you to an osteoporosis specialist.
For more complicated cases of lupus, a rheumatologist is usually the primary doctor. Other specialists are consulted as needed. For mental health problems such as depression, anxiety, psychosis, or other behavioral changes, see your family medical doctor or internist, or a psychiatrist. For the treatment of organ problems, a doctor who specializes in diseases of that particular organ system may work together with a rheumatologist or immunologist.