November 25th, 2005
Q: Where can I donate cord blood?
A: If you are interested, or someone you know is interested, in donating cord blood, look for a “Cord Blood Bank” or collecting hospital within or close to your community. There are only a small number of cord blood banks in the United States, so donation to a local bank is not possible in many areas.
If there is not an NMDP Cord Blood Bank in your community, refer to the Non-NMDP Cord Blood Bank list on this Web site or contact any major university hospital or medical center in your state to see if they accept cord blood donations.
Q: Why isn’t there a cord blood bank or collecting hospital in my area?
A: Cord blood donation is currently not possible in many communities. Many communities do not have the technical and financial resources needed to establish and operate a public cord blood bank. Although cord blood banks are developing throughout the United States, the annual number of births far exceeds the expected need for cord blood storage.
Q: Does it cost me anything to donate cord blood?
A: There is no cost for donating. Unrelated donor cord blood banks will take care of the procedure and cover the cost of processing and storing your baby’s cord blood unit. However, parents also have the option of storing cord blood exclusively for use within their own family for a fee. Several banks in the United States will collect and store cord blood reserved for private use. A list of these banks is available at www.parentsguidecordblood.com
Q: Are there any risks to donating cord blood?
A: Donating cord blood is medically safe. Donating poses no health risks to you or your baby. Donating does not affect your baby or your birth experience because the cord blood is collected after your baby is born. If you or your baby experience any complications during delivery, your doctor will not collect the cord blood.
Q: I have been approached, or contacted, by a self-storage program about storing my child’s cord blood. Should I store the cord or donate it?
A: Donating your child’s cord blood or storing it for private use is a personal decision that only you can make. If you have a child with leukemia or other disease that may be treatable by transplant and you are pregnant, talk with your oncologist or pediatrician about saving your baby’s cord blood. For more information see the Non-NMDP Cord Blood Bank list.
Families may feel a great deal of pressure from the promotions and advertisements they receive from the for-profit private storage cord blood banks. The NMDP agrees with the policy statement of The American Academy of Pediatrics (AAP) issued in 1999:
AAP’s second recommendation follows:
“Given the difficulty of making an accurate estimate of the need for autologous [donation from self] transplantation and the ready availability of allogeneic [donation from sibling or unrelated person] transplantation, private storage of cord blood as “biological insurance” is unwise. However, banking should be considered if there is a family member with a current or potential need to undergo a stem cell transplantation.”
(Words in italics added by the NMDP.)
Q: What will happen to my child’s cord blood if I donate it?
A: After the baby’s birth, the umbilical cord is clamped, breaking the link between the baby and the placenta. The small amount of blood remaining in the placenta and umbilical cord, typically three to five fluid ounces, is drained and taken to a cord blood bank where the unit is processed and samples are sent for tests. To be stored, the cord blood unit must meet these standards:
The unit must be large enough.
The maternal and family health history must meet eligibility guidelines.
Tests of the cord blood unit and the mother’s blood sample must show no signs of infection or other possible problems.
If the unit meets these standards, it is frozen and stored in a liquid nitrogen freezer. The cord blood unit is then listed on the NMDP’s Registry, where it will be searched for a matching recipient and then transplanted.
Q: Who has access to the donated cord blood?
A: Once the donated cord blood is processed and stored at the Cord Blood Bank, it is listed on the NMDP Registry and available to patients all over the world who are searching for a match. The cord blood can be transplanted into any patient whose doctor selects the cord as a match for that patient.
Remember that donating cord blood to a public bank is different than storing the cord blood for your family’s private use. The donated cord blood is not reserved for your family. Also, some donated cord blood units cannot be stored. Some units are too small or have other factors that make them unsuitable for storage in a public bank.
Q: How long can cord blood be stored before it expires?
A: Studies have shown good cord blood cell recovery after up to ten years of storage (Clin Exp Immunol 1997; 107, Suppl 1). Studies are ongoing to determine the storage life of cord blood units.
Q: How soon should I notify the cord blood bank in my area or my doctor about donating my child’s umbilical cord blood?
A: It is recommended that someone who is interested in donating contact the cord blood bank by the 34th week of pregnancy.
Q:Why is there a need for women from all racial and ethnic groups to donate their baby’s cord blood?
A: Because the tissue traits that are used to match a cord blood unit with a patient are inherited, a patient’s most likely match will be cord blood donated by someone of the same heritage. American Indian and Alaska Native, Asian, Black and African American, Hispanic and Latino, Native Hawaiian and Other Pacific Islander, and multiple-race patients face a greater challenge in finding a match than White patients.
NMDP cord blood banks are working in local communities to increase the racial and ethnic diversity of NMDP cord blood listings. From 2001 to 2003, the likelihood of finding a matched cord blood unit has grown at least twofold for patients from all racial and ethnic groups. Still, some patients are unable to find a match because of the rarity of their tissue traits. Some tissue traits are more likely to be found among people of a particular racial or ethnic heritage. That is why a pressing need remains for more cord blood donations from American Indian and Alaska Native, Asian, Black and African American, Hispanic and Latino, Native Hawaiian and Other Pacific Islander, and multiple-race donors.
Q: Is cord blood donation confidential?
A: Identifying information is never exchanged between a cord blood donor and cord blood transplant recipient. The identity of the cord blood donor is kept confidential at the cord blood bank.
Q: How does the National Marrow Donor Program support cord blood donation?
A: The NMDP has developed a central Registry of cord blood units that physicians may search. In addition, several mechanisms exist for physicians to search cord blood banks not currently participating with The NMDP. Physicians can obtain additional information from the NMDP Office of Patient Advocacy at 1 (888) 999-6743. Outside the United States, call 1 (612) 627-8140.
November 20th, 2005
The helicopter is type of aircraft in which lift is obtained by means of one or more power-driven horizontal propellers called rotors. When the rotor of a helicopter turns it produces reaction torque which tends to make the craft spin also. On most helicopters a small rotor near the tail compensates for this torque. On twin-rotor craft the rotors spin in opposite directions, so their reactions cancel each other. The helicopter is propelled in a given direction by inclining the axis of the main rotor in that direction. The helicopter’s speed is limited by the fact that if the blades rotate too fast they will produce compressibility effects on the blade moving forward and stall effects on the rearward moving blade, at the same time.
Although the helicopter was only recently fully developed, its concept can date back to the late 1400’s. Since then, helicopters have been put into use by society in many ways. One can find helicopters in both civil and military areas. The early helicopters were mainly developed for military use, but later became certified for civilian use. Since then helicopters have evolved greatly, specifically with the design. Because a helicopter can perform more actions than a fixed-wing aircraft can, it is more complicated to fly. The helicopter must compensate for a variety of forces, like the spinning force induced by the main rotors. The engineering behind designing a helicopter is complex with a variety of issues to be understood .
The Main Rotor : The lifting force is produced by the rotors. As they spin they cut into the air and produce lift. Each blade produces an equal share of the lifting force. Spinning the rotor against the air causes lift, allowing the helicopter to rise vertically or hover. Tilting the spinning rotor will cause flight in the direction of the tilt.
The Tail Rotor : The tail rotor is very important. If you spin a rotor using an engine, the rotor will rotate, but the engine and the helicopter will try to rotate in the opposite direction. This is called TORQUE REACTION. By applying more or less pitch (angle) to the tail rotor blades it can be used to make the helicopter turn left or right, becoming a rudder.
The tail rotor is connected to the main rotor through a gearbox.
When using the tail rotor trying to compensate the torque, the result is an excess of force in the direction for which the tail rotor is meant to compensate, which will tend to make the helicopter drift sideways. Pilots tend to compensate by applying a little cyclic pitch, but designers also help the situation by setting up the control rigging to compensate. The result is that many helicopters tend to lean to one side in the hover and often touch down consistently on one wheel first.
On the other hand if you observe a hovering helicopter head-on you will often note that the rotor is slightly tilted. All this is a manifestation of the drift phenomenon. The helicopter is steered in any direction by inclining the axis of the main rotor in that direction. Flying a helicopter requires great concentration. You must use one hand on the control lever that is at your side (the collective control stick) to raise or lower the helicopter, while at the same time controlling the throttle (not an easy task). This is a control which is only found in helicopters and is linked to the engine power. Moving this up and down changes the pitch of the main rotors. As the pitch is increased more power is required from the engines so that the rotor speed is kept at the same level.
You must use your other hand on the control lever that is just in front of you (the cyclic control stick) to move the helicopter forward, backward and to either side, as if you were in a conventional aircraft.
Moving it forward or back will point the nose of the helicopter up or down. It does this by varying the angle of the rotor blades as they go round, tilting the rotor back and forth. When moved left or right the rotor tilts in that direction and the helicopter banks and rolls.
And finally you must use the tail rotor pedals, on the floor, to control the pitch of the tail-rotor. For straight flight, the pitch of the tail rotor is set to prevent the helicopter from turning to the right as the main rotor turns to the left. The pilot pushes the left pedal to increase the pitch of the tail rotor and turn to the left. Pushing the right pedal decreases the pitch of the tail rotor and turns the helicopter to the right.
Flying a helicopter requires entirely different skills than flying conventional aircraft. This is why it is difficult to fly a vertical take-off or landing. On tandem rotors helicopters, like Boeing ’s Chinook, that had not tail rotor, the pedals are connected to the swashplates and cyclicly change pitch on both rotors in equal, but opposite directions. For example, if the left pedal is pressed at a hover, the front rotor disk tips left and the rear rotor tips right so that the helicopter yaws to the left.
How the Helicopter Flies
Flight of a helicopter is governed by the pitch or angle of its rotor blades as they sweep through the air. For climbing and descending, the pitch of all the blades is changed at the same time and in the same degree.
To Climb, the angle ot pitch of the blades is increased. To descend, the pitch of the blades is decreased. Because all blades are acting simultaneously, or collectively, this is known as collective pitch .
For forward, backward and sideways flight an additional change of pitch is provided. By this means the pitch of each blade increases at the same selected point in its circular pathway. This is the cyclic pitch.
With these two controls in mind let us make an imaginary flight. With the engine warmed up and the rotor blades whirling above us in flat pitch, that is, with no angle or bite in the air, we are ready to start. We increase the collective pitch. The rotor blades bite into the air, each to the same degree, and lift the helicopter vertically. Now we decide to fly forward. We still have collective pitch to hold us in the air and we adjust the cyclic pitch so that as each blade passes over the tail of the helicopter, it has more bite on the air than when it passes over the nose. Naturally the helicopter travels forward.
Now we decide to stop and hover motionless so we put the cyclic pitch in neutral, the rotor blades now have the same pitch throughout their cycle, and the collective pitch holds the helicopter suspended in space without moving in any direction. In short, it is the cyclic and collective pitch which gives the helicopter its unique ability to fly forward, backwards, sideways, rise and descend vertically and hover motionless in the air , making it one of the most versatile vehicles known by man.
November 10th, 2005
Mesothelioma is an uncommon form of cancer, usually associated with previous exposure to asbestos. In this disease, malignant (cancerous) cells develop in the mesothelium, a protective lining that covers most of the body’s internal organs. Its most common site is the pleura (outer lining of the lungs and chest cavity), but it may also occur in the peritoneum (the lining of the abdominal cavity) or the pericardium (a sac that surrounds the heart).
Most people who develop mesothelioma have worked on jobs where they inhaled asbestos particles, or have been exposed to asbestos dust and fibre in other ways, such as by washing the clothes of a family member who worked with asbestos, or by home renovation using asbestos cement products.
