The impedance of extremeeties such as fingers, arms and legs changes with the blood flow in and out, so this provides another method for plethysmography.
The arterial pulse wave has a very low amplitude and is superimposed on the venous blood volume changes. Pulse wave measurements are possible in many locations including the head (this measurement is called rheoencephalography). Pulse waves can also be measured in the fingers and toes with photoplethysmography.
The fourth heart sound is a low-pitched sound coincident with late diastolic filling of the ventricle due to atrial contraction. It thus occurs shortly before the first heart sound. Although it is also called the atrial sound, and its production requires an effective atrial contraction, the fourth heart sound is the result of vibrations generated within the ventricle. Commonly, its presence indicates increased resistance to filling of the left or right ventricle because of a reduction in ventricular wall compliance, and it is accompanied by a disproportionate rise in ventricular end-diastolic pressure. In patients with a fourth heart sound, its palpable correlate is often present: a concomitant brief presystolic outward movement of the chest wall.
High blood pressure is a very common condition in modern society. It has been estimated that one in five Americans, around 50 million people, suffer from high blood pressure. In general more men than women have high blood pressure, and the number of sufferers of both genders increases rapidly with age.
In around 5% of cases of high blood pressure is caused by kidney problems, but the causes of the other 95% of cases are unknown. There are a number of factors such as race, age, obesity, stress, smoking and lack of exercise that can contribute to the likelihood of a person developing high blood pressure but usually no one cause is directly responsible.
Acoustic wave devices have been in commercial use for more than 60 years. The telecommunications industry is the largest consumer, accounting for ~3 billion acoustic wave filters annually, primarily in mobile cell phones and base stations.
These are typically surface acoustic wave (SAW) devices, and act as bandpass filters in both the radio frequency and intermediate frequency sections of the transceiver electronics. Several of the emerging applications for acoustic wave devices as sensors may eventually equal the demand of the telecommunications market.
Researchers have discovered the precise chemical chain reaction that could be the much-sought-after puberty trigger: The KiSS-1 gene, which produces a protein in the hypothalamus, a part of the brain, which regulates metabolic activity. When the protein connects with a receptor on another gene called GPR54, puberty is believed to begin. This knowledge may guide the development of better drugs for treating hormone disorders related to puberty.
PITTSBURGH–They’re politely called “the awkward years,” but anybody who can remember going through puberty knows “awkward” is an understatement. Now medical researchers believe they’re close to solving the puzzle of puberty.
