Download ##BEST## Beam Ka
Wendy Akerson
I have two 5D Mark 3 camera bodies which I use to shoot weddings. At night's end, the lights are OUT and my camera cannot auto focus in such darkness or very low light, so I need the assist beam to help me out and turn on. My cameras are shooting in 'one shot' mode, and under the menu section AF, the AF assist-beam is enabled and 'on' yet still the red beam of light will not go on. What is happening here? The problem is doubled when I am trying to fire a flash either on or off camera, and because the auto-focus can't find anything to focus on (with no red assist beam to help) in such low light, the shutter will not work. I can override this but I'm still shooting in such low light, and my beam isn't going on to help. I haven't been able to find this exact issue on the message board--or folks say it resolved for them when they got out of AI servo and put their camera on One Shot mode, which I've already done. Thanks for help!!
Hi Mike, I am using a Yongnuo Digital speedlite YN600EX-RT flash. Is it a problem with my flash? I guess I am confused about where the red assist beam is emitted and controlled from--is it actually coming from my flash but controlled by my camera? Or emitted from the flash and controlled both by settings on my camera AND the flash?
I am using a Yongnuo Speedlite YN600-EX-RT that is at least 5 years old, maybe more (not sure) and I'm not sure how to enable the AF assist beam on the flash itself. Do you enable that through the flash directly, somehow, or via the camera it's attached to? Do you know what AF point I can't use to make sure the speedlite assist beam goes off?
Narrator: Mayo Clinic's Cancer Center offers a full range of services and treatment options to meet your individual needs, including the latest innovations in proton beam therapy. Our new proton beam therapy program has the most up-to-date technology called intensity modulated pencil beam scanning. This is a highly targeted and precise way of administering radiation therapy. It allows delivery of higher doses of radiation to tumors while minimizing the damage to nearby healthy tissue and organs. Significant benefits can be achieved by integrating proton beam therapy with other treatment approaches. Children, young adults and healthy older adults with potentially curable cancers located near or within critical organs will receive the greatest benefit. So let's see how it works.
Common sources of protons used in proton beam facilities are hydrogen gas and water. In the case of water, the protons come from removing a hydrogen atom from a water molecule. These tiny particles are then modified so that they carry an electrical charge. The charged protons are accelerated at 2/3 the speed of light in a series of magnets called the synchrotron. This proton beam is then directed by even more magnets down the beam line into the treatment rooms and aimed precisely at the patient's tumor.
During the treatment, the beam is delivered into the tumor where it stops in a burst of energy. The biggest impact is released precisely within the tumor, where the energy from the proton beam breaks the tumor cell's DNA, damaging them beyond repair and rendering the cancer cells unable to reproduce. Unlike conventional x-ray photon therapy, which delivers a steady stream of damaging radiation to normal tissue surrounding the tumor, protons deliver minimal dose outside the tumor. Therefore, proton therapy can avoid damaging and debilitating side effects to the normal surrounding tissues.
Intensity modulated pencil beam scanning will be used at the Mayo Clinic Proton Beam Centers. It is the most advanced form of proton beam therapy and uniquely conforms the radiation dose to the shape of the tumor. The precise proton beam is used like a brush to paint every part of the tumor while sparing surrounding tissue. Its precision allows the targeting of tumors near critical organs, like the esophageal cancer shown here, with much less dose and less risk of potential damage to the nearby spinal cord, heart and lungs. During one treatment session, the proton may be delivered to the tumor from more than one angle. The patient, meanwhile, can't see or feel the proton beam at all. This therapy is also a particular benefit to pediatric patients in that it can provide the same or higher dose to a tumor while delivering less overall radiation exposure to their vulnerable growing organs. This results in less risk of toxicity, growth delays or radiation-induced malignancies. Greater control of radiation doses, more accurate targeting of tumors and reduced side effects. These are just a few of the potential benefits of cancer treatment at the Mayo Clinic Proton Beam Therapy Program.
External beam radiation therapy comes from a machine that aims radiation at your cancer. It is a local treatment, which means it treats a specific part of your body. For example, if you have cancer in your lung, you will have radiation only to your chest, not to your whole body.
Most radiation therapy machines use photon beams. Photons are also used in x-rays, but x-rays use lower doses. Photon beams can reach tumors deep in the body. As they travel through the body, photon beams scatter little bits of radiation along their path. These beams do not stop once they reach the tumor but go into normal tissue past it.
Protons are particles with a positive charge. Like photon beams, proton beams can also reach tumors deep in the body. However, proton beams do not scatter radiation on their path through the body and they stop once they reach the tumor. Doctors think that proton beams might reduce the amount of normal tissue that is exposed to radiation. Clinical trials are underway to compare radiation therapy using proton beams with that using photons beams. Some cancer centers are using proton beams in radiation therapy, but the high cost and size of the machines are limiting their use.
There are many types of external beam radiation therapy, all of which share the goal of delivering the highest prescribed dose of radiation to the tumor while sparing the normal tissue around it. Each type relies on a computer to analyze images of the tumor in order to calculate the most precise dose and treatment path possible.
Most people have external beam radiation therapy once a day, five days a week, Monday through Friday. Radiation is given in a series of treatments to allow healthy cells to recover and to make radiation more effective. How many weeks you have treatment depends on the type of cancer you have, the goal of your treatment, the radiation dose, and the radiation schedule.
Most of the time, you will get external beam radiation therapy as an outpatient. This means that you will have treatment at a clinic or radiation therapy center and will not stay the night in the hospital.
You will have a 1- to 2-hour meeting with your doctor or nurse before you begin radiation therapy. At this time, you will have a physical exam, talk about your medical history, and maybe have imaging tests. Your doctor or nurse will discuss external beam radiation therapy, its benefits and side effects, and ways you can care for yourself during and after treatment. You can then choose whether to have external beam radiation therapy.
People often wonder if they will be radioactive when they are having treatment with radiation. External beam radiation therapy will not make you radioactive. You may safely be around other people, even pregnant women, babies, and young children.
Cara:
Dr. Ross, my sister and I have been learning more about external beam radiation therapy. We made a list of questions that I brought with me today. Can we go over them together?
Narrator Summary:
External beam radiation therapy uses high doses of radiation to destroy cancer cells and shrink tumors. A large machine aims radiation at the cancer. The machine moves around you, without touching you.
Users can access the publicly available BEAM source code using this Github link: -UCB-STI/beam.
Please contact Lawrence Berkeley National Laboratory staff with any questions or inquiries about applying BEAM to your region of interest.
With these motivations and the fact that there is difference between lifetime values obtain with cold neutron beams and confined ultracold neutrons, we are running another neutron lifetime measurement on the NG-C beamline focused on understanding systematic effects. A competitive beam-style experiment provides distinctly different systematics from all ultracold neutron bottle experiments. This new measurement should help to resolve the difference while improving the precision of tests of the SM.
In the beam technique, the lifetime is measured by counting the absolute number of protons within a fiducial volume while continuously monitoring the absolute neutron flux. We completed the first experiment in 2003, and the uncertainty in the result was dominated by systematic effects associated with the neutron counting. Since that time, the group has successfully refined the ability to measure absolute neutron fluence at the level of 0.06%, and with this improvement, neutron counting is no longer the limiting systematic effect. In 2013 we published an updated value of (887.7 +/- 2.2) s using the new neutron counting results. We are now working on a new iteration of the experiment to measure the lifetime with a focus on testing and accounting for possible systematic effects.
The general approach to determining the neutron lifetime from a beam of cold neutrons is the same as that employed in the previous measurement. Figure 1 illustrates the method. A beam of cold neutrons enters a segmented proton trap (shown in Figure 2). If a neutron decays, the proton is confined by a 4.6 T magnetic field and electrostatic potentials on both ends of the trap. Periodically, the upstream electrodes (referred to as the door) are lowered, and a ramp voltage is applied to the central electrodes to eject any proton from the trap. The proton follows the magnetic field line out of the direct beam and onto a silicon detector held at a high potential to accelerate and detect the proton. While that process repeats itself, the downstream neutron flux monitor continuously monitors the neutron beam.
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