Actually, if you start a time machine from rest on the Earth's surface, you will most likely end up emerging inside the Earth, with likely fatal results. Given general relativity, time machines would most logically travel along geodesic paths, which are analogs in curved manifolds (in this case, the space-time manifold curved by earth's gravity) of straight lines in Euclidean spaces. A simple way to imaging this would be that the time machine would follow the same path as an object that started from its location and with its initial velocity, but was only influenced by gravity (and specifically was not influenced by the electromagnetic and Pauli-exclusion-principle-based normal force that supports you when you stand on something).
That path would look like a highly elliptical orbit that was mostly inside the Earth. Going backward in time would mean going along the geodesic in the opposite direction from the normal forward in time movement. Except for brief intervals where the ends of the orbit emerge from the ground, most of the path will be inside the Earth. I suspect that for trips of any length, there would be serious velocity matching issues on emergence even if you did time arrival to one of those intervals where the path was outside the Earth. The safe way to operate a time machine would be to make the temporal jump after you were in Earth orbit.
What is especially strange about much of academic publishing not changing its traditional subscription model to account for the rise of Internet is that (unlike a lot of other content providers) there is a clear, economically viable alternative.
Instead of charging for subscriptions, journals should get revenue by charging authors to publish (sometimes called "page fees"). Some journals already have page fees that don't cover the cost of publication, in which case they would need to be increased.
Since in biomedical research, at least (which is the area I'm most familiar with and the majority of research published in the US), both the money that currently pays for subscriptions and the money that would pay the author fees come from grants, it should be a global wash in terms of sources and sinks of the money. Subscriptions are payed out of institutional budgets that have as part of their input "indirect costs" (a kind of overhead fee on grants) that are levied by institutions. For example, if a university's indirect cost rate is 40% and a researcher gets a $500,000 grant, $200,000 goes to the university, and the researcher only gets $300,000 to spend herself. With a change to a publication fee model, indirect costs would go down, freeing up money that the researcher could then use to pay the fees.
There would be some redistribution of costs among groups in an institution and between institutions, but in general costs would be shifted to groups that were most successful at publishing, and thus should be in the best position to bear those costs.
One of the biggest advantages of this scheme is that if articles were not behind paywalls, it would be much more feasible to develop automated tools to index, search and analyze them. This hopefully would improve the ability of researchers to keep up with the huge amount that is published even in specialty areas.
This system still requires energy input to launch things into orbit, but the key point is that it requires orders of magnitude less energy than a conventional rocket launch. Without going into the math, the key feature of the launch loop, space elevator, or other "skyhook" technology is that the propulsion system applies force against a structure that is anchored to the ground. This means that most of the energy goes into accelerating the payload.
In a conventional rocket, the propulsion system is pushing against the exhaust. Exhaust comes out of the rocket at very high velocity. This means that most of the energy in a conventional rocket goes into accelerating the exhaust, and only a small amount is available to accelerate the payload.
The other major advantage is that the fuel supply can remain on the ground, and does not need to be accelerated. In a conventional rocket, the first stage, for example, needs to accelerate not only the payload, but all the fuel in the second and higher stages.
The two top sections of the loop would be separated enough that you could connect a capsule to only one of them. Something on the order of a few hundred meters apart. Launching capsules would be connected at the West station to the West to East cable. They would accelerate by applying a magnetic field to that cable, and then release into orbit once fully accelerated. Landing capsules would have to match orbit with a section of the East to West cable near the West end. They would then decelerate by applying a magnetic field to that cable, and would be disconnected (after stopping) at the East station.
On a scale (like that of the diagram) where you could see the entire 2000 km loop, the (for example) 200 m distance between the cables going in opposite directions will not be visible, so it will look like they are not separated.
At least some of them do. There was an incident in September 2008 where automatic trading programs mistakenly responded to an old newspaper article (from 2002) about the bankruptcy of the parent company of United Airlines. The stock dropped from about $12.50 to $3 a share in 15 minutes. You can read reports of the event on Slashdot, Reuters, and many other news sites.
The relevant statistical concepts are the following:
.
True positive (TP)- The person really is a terrorist, and your test detects him (I'm going to use the male pronoun throughout to keep the language less cluttered)
False positive (FP) - The person is not a terrorist, but your test says he is
False negative (FN) - The person is a terrorist, but your test does not detect him
True negative (TN) - The person is not a terrorist, and your test correctly says he is not
.
Sensitivity is the ability of the test to detect a true positive and equals TP / (TP + FN), or to put it another way, TP / (number of all terrorists, whether detected or not)
Specificity is the ability of the test to detect a true negative and equals TN / (TN + FP), or to put it another way, TN / (number of people who are not terrorists, whether the tests says they are or not)
.
Generally in statistics, sensitivity and specificity are considered to be properties of the test, independent of the population it is run on, although this probably isn't strictly true in the real world.
.
Positive predictive value (PPV) is the chance that someone who tests positive is really a terrorist and equals TP / (TP + FP), or to put it another way, TP / (all people who test positive, whether they are terrorists or not)
Negative predictive value (NPV) is the chance that someone who tests negative is really not a terrorist and equals TN / (TN + FN), or to put it another way, TN / (all people who test negative, whether they are terrorists or not)
.
In these terms, the statement that the OP makes can be rephrased as: Even a test with good sensitivity and specificity can have poor positive predictive value if the frequency of terrorists is low.
.
Example: Test is 99% sensitive and 99% specific. Terrorists are 0.01% (i.e. one in 10,000)
Consider 1,000,000 people. Terrorists: 100, not terrorists: 999,900
True Positives = 0.99 (sensitivity) * 100 (terrorists) = 99; False Negatives: 100 (terrorists) - 99 (true positives) = 1
True Negatives= 0.99 (specificity) * 999,900 (not terrorists) = 989,901; False Positives: 999,900 (not terrorists) - 989,901 (true negatives) = 9,999
Positive Predictive Value = 99 / (99 + 9,999) ~ 0.0098 = 0.98%
.
Sorry about the lines that consist of a period, but my <br> tags were being ignored there, and I couldn't figure out a better way to insert blank lines to make the post more readable.
Both the store staff and I behaved like civilized adults during this discussion. The sales associate asked for my SSN. I asked if it was required, and when he said it was, I asked to speak to the store manager. The store manager confirmed the statements of the associate. I asked why the SSN was required, we had a conversation about that where I talked about the alternatives discussed in my OP, and the manager said those were not acceptable. I told her I would not buy the phone under those conditions and left.
The entire interaction took about 15 minutes, about half of which was spent actually talking to the manager. No voices were raised. I consider the store manager the appropriate escalation in this situation. If there is a need for further escalation, it's their job to figure out where to escalate to. In addition, it was a Saturday, so I doubt it would have been practical to reach anyone with more authority.
I did not have to give Verizon an SSN when I signed up for their service. I don't have records that show an exact start date handy, but I think they have been my carrier since the late 1990's.
Because I was reporting on my experience at one Sprint store. For me to say "Cellular Providers Require SSN for Contracts" would have required researching policies at a bunch of other companies.
I am a pediatric blood and marrow transplant physician and this is a question I am asked frequently. The decision is one in which a fairly significant amount of money (for most people) is being traded for a very small chance of future benefit. How much money you are willing to spend and how risk-averse you are will probably be the main factors influencing your final decision.
In my opinion, the bottom line is that for a family without any special features in the family medical history, the chances that a clinical scenario will occur in which having a stored cord blood unit from a baby, for the use of either that baby or a relative, is important are very small, but I can think of some. I have been involved in pediatric bone marrow transplant for 12 years (including training) and have not yet actually encountered such a scenario. The procedure involves no additional risk to the baby or mother during delivery, so that if collection and storage were cheap, then it would be easy to say to do it just in case, even though the chance it would ever be useful is very small. However, given the actual costs involved, in my opinion, storage of cord blood for private use is not cost effective compared to other ways that you can spend money to improve safety (for families with no special features in their medical history).
As other people have also pointed out, not every collected cord blood unit is actually usable. We recently had a case at my hospital where the parents had saved the cord blood of a sibling, but the number of cells in the saved cord was so low that we had to collect bone marrow from the sibling anyway.
Family medical history that would lead me to recommend collection would be a sibling who was diagnosed with a disease that can be treated with cord blood transplant (acute leukemia being the most common one). Because of the risk of relapse, this applies whether treatment is complete or not. A weaker indication would be a family history (or a prenatal diagnosis in the baby) of a genetic disorder that either can now or theoretically could be treated in the future with a cord blood transplant. This is much more hypothetical, but it is theoretically possible that the hematopoietic stem cells in the cord blood could be useful in a gene therapy protocol.
The (very sad if it ever actually happened) hypothetical scenario that I can think of in which a stored cord blood unit would be the most useful would be if a baby was born, the cord blood was collected and stored. That child subsequently died. At a later time, a sibling was diagnosed with a disease (like a relapsed acute leukemia) in which transplant is indicated. The stored cord blood unit was a match for the sibling and had an adequate number of cells, but no one else in the family was a match. Fortunately, the chances of something like this happening are very, very small.
Pregenerate the tables for each possible angle and code them as 512 byte data blocks at [sin table base address] and [cos table base address]
load register 3 with pseudo-angle shift register 3 left ; i.e. multiply by 2 since sine and cosine results are 2 bytes long load register 1 from [sin table base address], (register 3 value); this is the sine load register 2 from [cos table base address], (register 3 value); this is the cosine
Last two instructions use the addressing mode that adds a register value to an absolute address to determine the final address.
For BMT / PBSCT / UCBT, you have transplanted the bone marrow stem cells, which by definition are those that have the capability to self-renew. So even though the more differentiated (i.e. specialized) cells that are produced from the stem cells have a limited lifespan, the bone marrow stem cells will keep producing blood cells with donor genetic characteristics indefinitely. Note that this doesn't effect the non-blood cells in your body, so those retain the recipient's original genetic characteristics. So although there have been reports of allergies (which are white blood cell mediated) being transferred from donor to recipient, a recipient will not convert to the donor's gender, no matter how much time elapses after the transplant.
In the most common type of hematopoietic stem cell transplant (HSCT; the catchall term that includes bone marrow transplant, peripheral blood stem cell transplant, and umbilical cord blood transplant) all lineages of blood cells (white, red, platelets (which bud off of megakaryocyte cells) ) are replaced by cells of donor origin. Of those 3, only the white cells have DNA, so that's what you are measuring if you do a DNA test for chimerism. But if you look at proteins or carbohydrates (e.g. ABO blood type), you can show that the red blood cells have the phenotype specified by the donor genotype and are thus also donor derived.
It is not. Red blood cells in humans don't have nuclei or DNA. The small number of white blood cells (which do have DNA) that are transferred in a transfusion are rapidly recognized as foreign by the recipient's immune system and destroyed. You might be able to pick up a trace amount of the donor's white blood cell DNA if you did the test very soon after the transfusion, but it would be gone within hours.
I am a pediatric blood and marrow transplant physician. After every successful bone marrow transplant (BMT), peripheral blood stem cell transplant (PBSCT), or umbilical cord blood transplant (UCBT) in which the donor is not the patient or an identical twin, the recipient becomes genetic chimera. The DNA in cells derived from the bone marrow stem cells is different from the DNA in the rest of the recipient's body.
As others have pointed out, this isn't anything new. Significant clinical use of BMT dates back to the 1970's. PBSCT and UCBT came into widespread use in the late 1980's and early 1990's.
My group performed a BMT on a patient with relapsed leukemia a few years ago. The patient unfortunately suffered liver and kidney damage as a result of the BMT. He had a liver transplanted from one donor and later a kidney from another donor. Fortunately, he recovered and has remained leukemia free. He is essentially back to being a normal kid, although he will need to take immunosuppressive mediations to prevent rejection indefinitely. That patient permanently has DNA from 4 different sources (bone marrow, liver, kidney, and his original genotype in all other parts of his body).
To guard against alteration, take your log file (rotated at intervals that are reasonable given resources and your security requirements) and generate a cryptographically secure hash. Send that hash over a secure connection to a trusted certifying authority (CA). The CA appends a timestamp to the hash and digitally signs the message using a public-key cryptosystem. They send the signed, timestamped hash back to you, and also retain their own log of the hashes for added security.
Multiple CAs can be used for added security, since all would have to be subverted in order for you to alter a the log file without detection.
Guarding against deletion is simply a backup problem. You must provide physical security for whatever backup media is chosen to the level needed for your specific requirements.
When I run apt-get using a sources.list file
with the line I cited above in it, the output is:
# apt-get update Get:1 http://security.debian.org stable/updates/main Packages [189kB] Hit http://non-us.debian.org stable/non-US/main Packages Hit http://non-us.debian.org stable/non-US/main Release Hit http://non-us.debian.org stable/non-US/contrib Packages Hit http://non-us.debian.org stable/non-US/contrib Release Hit http://non-us.debian.org stable/non-US/non-free Packages Hit http://non-us.debian.org stable/non-US/non-free Release Hit http://non-us.debian.org stable/non-US/main Sources Hit http://non-us.debian.org stable/non-US/main Release Hit http://non-us.debian.org stable/non-US/contrib Sources Hit http://non-us.debian.org stable/non-US/contrib Release Hit http://ftp.us.debian.org stable/main Packages Hit http://ftp.us.debian.org stable/main Release Hit http://ftp.us.debian.org stable/non-free Packages Hit http://ftp.us.debian.org stable/non-free Release Hit http://ftp.us.debian.org stable/contrib Packages Hit http://ftp.us.debian.org stable/contrib Release Hit http://ftp.us.debian.org stable/main Sources Hit http://ftp.us.debian.org stable/main Release Hit http://ftp.us.debian.org stable/non-free Sources Hit http://ftp.us.debian.org stable/non-free Release Hit http://ftp.us.debian.org stable/contrib Sources Hit http://ftp.us.debian.org stable/contrib Release Get:2 http://ftp.us.debian.org testing/main Packages [2983kB] Hit http://non-us.debian.org stable/non-US/non-free Sources Hit http://non-us.debian.org stable/non-US/non-free Release Hit http://non-us.debian.org testing/non-US/main Packages Hit http://non-us.debian.org testing/non-US/main Release Hit http://non-us.debian.org testing/non-US/contrib Packages Hit http://non-us.debian.org testing/non-US/contrib Release Hit http://non-us.debian.org testing/non-US/non-free Packages Hit http://non-us.debian.org testing/non-US/non-free Release Hit http://non-us.debian.org testing/non-US/main Sources Hit http://non-us.debian.org testing/non-US/main Release Hit http://non-us.debian.org testing/non-US/contrib Sources Hit http://non-us.debian.org testing/non-US/contrib Release Hit http://non-us.debian.org testing/non-US/non-free Sources Hit http://non-us.debian.org testing/non-US/non-free Release Get:3 http://security.debian.org stable/updates/main Release [110B] Hit http://security.debian.org stable/updates/contrib Packages Get:4 http://security.debian.org stable/updates/contrib Release [113B] Hit http://security.debian.org stable/updates/non-free Packages Get:5 http://security.debian.org stable/updates/non-free Release [114B] Get:6 http://security.debian.org testing/updates/main Packages [2535B] Get:7 http://security.debian.org testing/updates/main Release [111B] Hit http://security.debian.org testing/updates/contrib Packages Get:8 http://security.debian.org testing/updates/contrib Release [114B] Hit http://security.debian.org testing/updates/non-free Packages Get:9 http://security.debian.org testing/updates/non-free Release [115B] Get:10 http://ftp.us.debian.org testing/main Release [81B] Get:11 http://ftp.us.debian.org testing/non-free Packages [59.8kB] Get:12 http://ftp.us.debian.org testing/non-free Release [85B] Get:13 http://ftp.us.debian.org testing/contrib Packages [60.3kB] Get:14 http://ftp.us.debian.org testing/contrib Release [84B] Get:15 http://ftp.us.debian.org testing/main Sources [1173kB] Get:16 http://ftp.us.debian.org testing/main Release [83B] Get:17 http://ftp.us.debian.org testing/non-free Sources [24.5kB] Get:18 http://ftp.us.debian.org testing/non-free Release [87B] Get:19 http://ftp.us.debian.org testing/contrib Sources [27.2kB] Get:20 http://ftp.us.debian.org testing/contrib Release [86B] Fetched 4520kB in 29s (156kB/s) Reading Package Lists... Done Building Dependency Tree... Done
How do you explain the fact that apt-get is retreving
information from security.debian.org for testing distribution
packages? The page you cite says it has "no official support"
but clearly at least some of the packages are getting
security updates, perhaps unofficially.
The line for security updates for the testing distribution (taken directly from my/etc/apt/sources.list file) is:
deb http://security.debian.org/ testing/updates main contrib non-free
I agree that it was reasonable to present the hard problem the first time around. But after seeing that the outcome of the contest was so far from the initial goal, DARPA should scale back for next year.
I think the key would be to pick lesser challenges that are both useful goals in their own right, and also build components needed for the final goal of fully automonous operation. Some examples (in rough order of increasing difficulty) might be:
Convoy follower - Teams are allowed to have a human-piloted lead vehicle that drives the course, and all the robot has to do is successfully tag along. The lead vehicle can provide positioning cues to the follower, but remote control is not allowed. This would be useful in the real world because if two drivers in the lead vehicle could direct a 20-truck convoy, it would save manpower and decrease the number of troops at risk.
Convoy leader / remote control - One drawback with the convoy follower approach above is that it puts the humans in the lead vehicle, which is the one most vulnerable to mines and ambushes. Another approach would be to allow contestants to remote control the robot from a chase vehicle, with the restriction that the chase vehicle needs to stay some distance (say 200-300 meters) behind the robot. You could also do remote control from a high altitude aircraft. Given that in a war against a regional-level adversary like Iraq, the US would be expected to control the air, this would get the human operators off the ground, where they would be vulnerable to guerrilla operations.
Route known in advance - Robots are fully automonous, but teams can map the route out to whatever level of detail they want before the race. The robots still need to deal with whatever the conditions are on the acutal race day. This would be useful for supply convoys making runs over known routes.
Could you clarify exactly what a 'consumer market approval' is? Is it done in house by the company making the product or by a third party institution? Are there generally accepted standards for the process or does each reviewing group have their own procedure?
Here is a (non-exhaustive) list of possibilities: 1. Cuckoo's egg attacks where file is not what its name (or other metadata) claims it to be. 2. Denial of service (DOS) attacks where a node tries to overwhelm the P2P system by sending a ridiculous number of queries. This is especially a problem with Gnutella since the initial search protocol is so inefficient. 3. Corrupting or not passing data - Many P2P architectures call for nodes to relay or aggregate information from other nodes. If a node drops or corrupts data, the prototcol won't work or will be much less efficient.
An alternative solution would have been to let players choose to have the offensive names remapped to non-offensive names for their e-mails only. The offending player could name his planet A**h***, but any other player who wanted to could ask that it be remapped to a non-offensive term (e.g. Norfolk).
Of course, you would have to rewrite the code for the program so that it would do the appropriate (player specific) translation on incoming and outgoing messages. More work, but no arbitrarily imposed censorship: each player gets to choose whether they see the original (offensive but funny) names in all their glory or the tame substitutes.
Don't see how to extend this to the filtering issue posed in this thread, though.
Slashdot Mirror
Actually, if you start a time machine from rest on the Earth's surface, you will most likely end up emerging inside the Earth, with likely fatal results. Given general relativity, time machines would most logically travel along geodesic paths, which are analogs in curved manifolds (in this case, the space-time manifold curved by earth's gravity) of straight lines in Euclidean spaces. A simple way to imaging this would be that the time machine would follow the same path as an object that started from its location and with its initial velocity, but was only influenced by gravity (and specifically was not influenced by the electromagnetic and Pauli-exclusion-principle-based normal force that supports you when you stand on something).
That path would look like a highly elliptical orbit that was mostly inside the Earth. Going backward in time would mean going along the geodesic in the opposite direction from the normal forward in time movement. Except for brief intervals where the ends of the orbit emerge from the ground, most of the path will be inside the Earth. I suspect that for trips of any length, there would be serious velocity matching issues on emergence even if you did time arrival to one of those intervals where the path was outside the Earth. The safe way to operate a time machine would be to make the temporal jump after you were in Earth orbit.
What is especially strange about much of academic publishing not changing its traditional subscription model to account for the rise of Internet is that (unlike a lot of other content providers) there is a clear, economically viable alternative.
Instead of charging for subscriptions, journals should get revenue by charging authors to publish (sometimes called "page fees"). Some journals already have page fees that don't cover the cost of publication, in which case they would need to be increased.
Since in biomedical research, at least (which is the area I'm most familiar with and the majority of research published in the US), both the money that currently pays for subscriptions and the money that would pay the author fees come from grants, it should be a global wash in terms of sources and sinks of the money. Subscriptions are payed out of institutional budgets that have as part of their input "indirect costs" (a kind of overhead fee on grants) that are levied by institutions. For example, if a university's indirect cost rate is 40% and a researcher gets a $500,000 grant, $200,000 goes to the university, and the researcher only gets $300,000 to spend herself. With a change to a publication fee model, indirect costs would go down, freeing up money that the researcher could then use to pay the fees.
There would be some redistribution of costs among groups in an institution and between institutions, but in general costs would be shifted to groups that were most successful at publishing, and thus should be in the best position to bear those costs.
One of the biggest advantages of this scheme is that if articles were not behind paywalls, it would be much more feasible to develop automated tools to index, search and analyze them. This hopefully would improve the ability of researchers to keep up with the huge amount that is published even in specialty areas.
Darth, please check your sarcasm detector. It seems to be off or broken.
This system still requires energy input to launch things into orbit, but the key point is that it requires orders of magnitude less energy than a conventional rocket launch. Without going into the math, the key feature of the launch loop, space elevator, or other "skyhook" technology is that the propulsion system applies force against a structure that is anchored to the ground. This means that most of the energy goes into accelerating the payload.
In a conventional rocket, the propulsion system is pushing against the exhaust. Exhaust comes out of the rocket at very high velocity. This means that most of the energy in a conventional rocket goes into accelerating the exhaust, and only a small amount is available to accelerate the payload.
The other major advantage is that the fuel supply can remain on the ground, and does not need to be accelerated. In a conventional rocket, the first stage, for example, needs to accelerate not only the payload, but all the fuel in the second and higher stages.
If people are interested, I can supply some math.
The two top sections of the loop would be separated enough that you could connect a capsule to only one of them. Something on the order of a few hundred meters apart. Launching capsules would be connected at the West station to the West to East cable. They would accelerate by applying a magnetic field to that cable, and then release into orbit once fully accelerated. Landing capsules would have to match orbit with a section of the East to West cable near the West end. They would then decelerate by applying a magnetic field to that cable, and would be disconnected (after stopping) at the East station.
On a scale (like that of the diagram) where you could see the entire 2000 km loop, the (for example) 200 m distance between the cables going in opposite directions will not be visible, so it will look like they are not separated.
At least some of them do. There was an incident in September 2008 where automatic trading programs mistakenly responded to an old newspaper article (from 2002) about the bankruptcy of the parent company of United Airlines. The stock dropped from about $12.50 to $3 a share in 15 minutes. You can read reports of the event on Slashdot, Reuters, and many other news sites.
The relevant statistical concepts are the following:
True positive (TP)- The person really is a terrorist, and your test detects him (I'm going to use the male pronoun throughout to keep the language less cluttered)
False positive (FP) - The person is not a terrorist, but your test says he is
False negative (FN) - The person is a terrorist, but your test does not detect him
True negative (TN) - The person is not a terrorist, and your test correctly says he is not
Sensitivity is the ability of the test to detect a true positive and equals TP / (TP + FN), or to put it another way, TP / (number of all terrorists, whether detected or not)
Specificity is the ability of the test to detect a true negative and equals TN / (TN + FP), or to put it another way, TN / (number of people who are not terrorists, whether the tests says they are or not)
Generally in statistics, sensitivity and specificity are considered to be properties of the test, independent of the population it is run on, although this probably isn't strictly true in the real world.
Positive predictive value (PPV) is the chance that someone who tests positive is really a terrorist and equals TP / (TP + FP), or to put it another way, TP / (all people who test positive, whether they are terrorists or not)
Negative predictive value (NPV) is the chance that someone who tests negative is really not a terrorist and equals TN / (TN + FN), or to put it another way, TN / (all people who test negative, whether they are terrorists or not)
In these terms, the statement that the OP makes can be rephrased as: Even a test with good sensitivity and specificity can have poor positive predictive value if the frequency of terrorists is low.
Example: Test is 99% sensitive and 99% specific. Terrorists are 0.01% (i.e. one in 10,000)
Consider 1,000,000 people. Terrorists: 100, not terrorists: 999,900
True Positives = 0.99 (sensitivity) * 100 (terrorists) = 99; False Negatives: 100 (terrorists) - 99 (true positives) = 1
True Negatives= 0.99 (specificity) * 999,900 (not terrorists) = 989,901; False Positives: 999,900 (not terrorists) - 989,901 (true negatives) = 9,999
Positive Predictive Value = 99 / (99 + 9,999) ~ 0.0098 = 0.98%
Sorry about the lines that consist of a period, but my <br> tags were being ignored there, and I couldn't figure out a better way to insert blank lines to make the post more readable.
I am the OP. Read the post again. I offered the two alternative means of payment, and the Sprint Store Manager turned both of them down.
Both the store staff and I behaved like civilized adults during this discussion. The sales associate asked for my SSN. I asked if it was required, and when he said it was, I asked to speak to the store manager. The store manager confirmed the statements of the associate. I asked why the SSN was required, we had a conversation about that where I talked about the alternatives discussed in my OP, and the manager said those were not acceptable. I told her I would not buy the phone under those conditions and left.
The entire interaction took about 15 minutes, about half of which was spent actually talking to the manager. No voices were raised. I consider the store manager the appropriate escalation in this situation. If there is a need for further escalation, it's their job to figure out where to escalate to. In addition, it was a Saturday, so I doubt it would have been practical to reach anyone with more authority.
I did not have to give Verizon an SSN when I signed up for their service. I don't have records that show an exact start date handy, but I think they have been my carrier since the late 1990's.
Because I was reporting on my experience at one Sprint store. For me to say "Cellular Providers Require SSN for Contracts" would have required researching policies at a bunch of other companies.
I am a pediatric blood and marrow transplant physician and this is a question I am asked frequently. The decision is one in which a fairly significant amount of money (for most people) is being traded for a very small chance of future benefit. How much money you are willing to spend and how risk-averse you are will probably be the main factors influencing your final decision.
In my opinion, the bottom line is that for a family without any special features in the family medical history, the chances that a clinical scenario will occur in which having a stored cord blood unit from a baby, for the use of either that baby or a relative, is important are very small, but I can think of some. I have been involved in pediatric bone marrow transplant for 12 years (including training) and have not yet actually encountered such a scenario. The procedure involves no additional risk to the baby or mother during delivery, so that if collection and storage were cheap, then it would be easy to say to do it just in case, even though the chance it would ever be useful is very small. However, given the actual costs involved, in my opinion, storage of cord blood for private use is not cost effective compared to other ways that you can spend money to improve safety (for families with no special features in their medical history).
As other people have also pointed out, not every collected cord blood unit is actually usable. We recently had a case at my hospital where the parents had saved the cord blood of a sibling, but the number of cells in the saved cord was so low that we had to collect bone marrow from the sibling anyway.
Family medical history that would lead me to recommend collection would be a sibling who was diagnosed with a disease that can be treated with cord blood transplant (acute leukemia being the most common one). Because of the risk of relapse, this applies whether treatment is complete or not. A weaker indication would be a family history (or a prenatal diagnosis in the baby) of a genetic disorder that either can now or theoretically could be treated in the future with a cord blood transplant. This is much more hypothetical, but it is theoretically possible that the hematopoietic stem cells in the cord blood could be useful in a gene therapy protocol.
The (very sad if it ever actually happened) hypothetical scenario that I can think of in which a stored cord blood unit would be the most useful would be if a baby was born, the cord blood was collected and stored. That child subsequently died. At a later time, a sibling was diagnosed with a disease (like a relapsed acute leukemia) in which transplant is indicated. The stored cord blood unit was a match for the sibling and had an adequate number of cells, but no one else in the family was a match. Fortunately, the chances of something like this happening are very, very small.
Table lookup FTW!
Pregenerate the tables for each possible angle and code them as 512 byte data blocks at [sin table base address] and [cos table base address]
load register 3 with pseudo-angle
shift register 3 left ; i.e. multiply by 2 since sine and cosine results are 2 bytes long
load register 1 from [sin table base address], (register 3 value); this is the sine
load register 2 from [cos table base address], (register 3 value); this is the cosine
Last two instructions use the addressing mode that adds a register value to an absolute address to determine the final address.
No, my FooBar Beta 2008 Promethium Sapphire Bandicoot TX 0.000045 has the clearly superior name.
For BMT / PBSCT / UCBT, you have transplanted the bone marrow stem cells, which by definition are those that have the capability to self-renew. So even though the more differentiated (i.e. specialized) cells that are produced from the stem cells have a limited lifespan, the bone marrow stem cells will keep producing blood cells with donor genetic characteristics indefinitely. Note that this doesn't effect the non-blood cells in your body, so those retain the recipient's original genetic characteristics. So although there have been reports of allergies (which are white blood cell mediated) being transferred from donor to recipient, a recipient will not convert to the donor's gender, no matter how much time elapses after the transplant.
In the most common type of hematopoietic stem cell transplant (HSCT; the catchall term that includes bone marrow transplant, peripheral blood stem cell transplant, and umbilical cord blood transplant) all lineages of blood cells (white, red, platelets (which bud off of megakaryocyte cells) ) are replaced by cells of donor origin. Of those 3, only the white cells have DNA, so that's what you are measuring if you do a DNA test for chimerism. But if you look at proteins or carbohydrates (e.g. ABO blood type), you can show that the red blood cells have the phenotype specified by the donor genotype and are thus also donor derived.
It is not. Red blood cells in humans don't have nuclei or DNA. The small number of white blood cells (which do have DNA) that are transferred in a transfusion are rapidly recognized as foreign by the recipient's immune system and destroyed. You might be able to pick up a trace amount of the donor's white blood cell DNA if you did the test very soon after the transfusion, but it would be gone within hours.
I am a pediatric blood and marrow transplant physician. After every successful bone marrow transplant (BMT), peripheral blood stem cell transplant (PBSCT), or umbilical cord blood transplant (UCBT) in which the donor is not the patient or an identical twin, the recipient becomes genetic chimera. The DNA in cells derived from the bone marrow stem cells is different from the DNA in the rest of the recipient's body.
As others have pointed out, this isn't anything new. Significant clinical use of BMT dates back to the 1970's. PBSCT and UCBT came into widespread use in the late 1980's and early 1990's.
My group performed a BMT on a patient with relapsed leukemia a few years ago. The patient unfortunately suffered liver and kidney damage as a result of the BMT. He had a liver transplanted from one donor and later a kidney from another donor. Fortunately, he recovered and has remained leukemia free. He is essentially back to being a normal kid, although he will need to take immunosuppressive mediations to prevent rejection indefinitely. That patient permanently has DNA from 4 different sources (bone marrow, liver, kidney, and his original genotype in all other parts of his body).
To guard against alteration, take your log file (rotated at intervals that are reasonable given resources and your security requirements) and generate a cryptographically secure hash. Send that hash over a secure connection to a trusted certifying authority (CA). The CA appends a timestamp to the hash and digitally signs the message using a public-key cryptosystem. They send the signed, timestamped hash back to you, and also retain their own log of the hashes for added security.
Multiple CAs can be used for added security, since all would have to be subverted in order for you to alter a the log file without detection.
Guarding against deletion is simply a backup problem. You must provide physical security for whatever backup media is chosen to the level needed for your specific requirements.
When I run apt-get using a sources.list file with the line I cited above in it, the output is:
How do you explain the fact that apt-get is retreving information from security.debian.org for testing distribution packages? The page you cite says it has "no official support" but clearly at least some of the packages are getting security updates, perhaps unofficially.
The line for security updates for the testing distribution (taken directly from my /etc/apt/sources.list file) is:
deb http://security.debian.org/ testing/updates main contrib non-free
I agree that it was reasonable to present the hard problem the first time around. But after seeing that the outcome of the contest was so far from the initial goal, DARPA should scale back for next year.
I think the key would be to pick lesser challenges that are both useful goals in their own right, and also build components needed for the final goal of fully automonous operation. Some examples (in rough order of increasing difficulty) might be:
Could you clarify exactly what a 'consumer market approval' is? Is it done in house by the company making the product or by a third party institution? Are there generally accepted standards for the process or does each reviewing group have their own procedure?
Here is a (non-exhaustive) list of possibilities:
1. Cuckoo's egg attacks where file is not what its name (or other metadata) claims it to be.
2. Denial of service (DOS) attacks where a node tries to overwhelm the P2P system by sending a ridiculous number of queries. This is especially a problem with Gnutella since the initial search protocol is so inefficient.
3. Corrupting or not passing data - Many P2P architectures call for nodes to relay or aggregate information from other nodes. If a node drops or corrupts data, the prototcol won't work or will be much less efficient.
An alternative solution would have been to let players choose to have the offensive names remapped to non-offensive names for their e-mails only. The offending player could name his planet A**h***, but any other player who wanted to could ask that it be remapped to a non-offensive term (e.g. Norfolk).
Of course, you would have to rewrite the code for the program so that it would do the appropriate (player specific) translation on incoming and outgoing messages. More work, but no arbitrarily imposed censorship: each player gets to choose whether they see the original (offensive but funny) names in all their glory or the tame substitutes.
Don't see how to extend this to the filtering issue posed in this thread, though.