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Comment Re:faster than light = time travel (Score 1) 226 226

There are a few ways (completely hypothetical) ways to salvage this situation, by imposing another limitation that allow FTL travel, but prevents the set up that allows causality violation. A (probably incomplete) list:

  1. Preferred FTL reference frame - The "default" proposition for an FTL jump-type drive is that you move across space in no time (or a very short time) as measured in the reference frame of the drive when you engage it. The fact that those reference frames can be different for two FTL drives moving at relativistic normal space velocities (or for one drive making successive jumps after a relativistic-scale velocity change) is what allows you to turn FTL travel into causality-violating time travel. If instead, all FTL travel takes place in a single, preferred reference frame (for example, the frame in which the cosmic microwave background radiation has no dipole component) regardless of the velocity of the drive when engaged, it is impossible to create those causality-violating paths.
  2. Virtual particle censorship of wormholes - A similar causality violation can occur with wormhole FTL if you have two wormholes (each with two ends), where the ends are moving at relativistic speeds relative to each other. The limitation that could prevent this is caused by virtual particles in vacuum (which are responsible for things like the Casimir effect). Simplifying greatly, you can "borrow" energy from vacuum to create a virtual particle pair (usually a particle and its antiparticle) as long as the virtual particle lifetime is short enough that the product of the that time and the "borrowed" energy is less than the Plank constant. Since the Plank constant is so small, that means that macroscopically observable virtual particle effects are typically secondary. However, as two wormholes move closer and closer to a condition in which you can loop through both of them and arrive at your start point in zero time, ever greater numbers of virtual particles will make that round trip, which increases the mass moving through the wormholes enough to collapse them before you get to a configuration that allows a zero or negative travel time (and thus leads to a causality violation).

Comment Re:Knowledge is the solution (Score 2) 1051 1051

I am a physician who also performs clinical research. You have a naive faith in the ability of the United States health care system to collected aggregated data like this. There are a few diseases and complications which are reportable to public heath services (these are state-level government agencies) and also some mandatory reporting that occurs to Federal agencies, but it is very limited. There are some voluntary reporting programs, for example the FDA Medwatch site allows reporting of drug complications, but only a tiny fraction of them get reported.

I don't know off the top of my head, but I suspect a few of the vaccine-preventable diseases are rare enough that they are reportable. Most of the other data (specifically any data on complications) is not something that anyone aggregates. See Estimating Seasonal Influenza-Associated Deaths in the United States: CDC Study Confirms Variability of Flu to see the trouble the CDC has getting something as simple as the number of people in the US who die from influenza.

Comment Re:Knowledge is the solution (Score 1) 1051 1051

You say, "government won't take responsibility for the (admittedly unlikely) consequences of a bad result." Please read up on the National Vaccine Injury Compensation Program, through which the United States Federal Government provides no-fault compensation to people injured by vaccines. The program is funded by a tax on vaccines.

Also, we are not talking about "making sure a few children don't get sick". Without vaccines, annual United States deaths from vaccine-preventable illnesses would likely range from tens of thousands to hundreds of thousands (higher in epidemic years). See What Would Happen If We Stopped Vaccinations? on the CDC web site for some data on historical death rates. The cost of treating people who came down with these infections would also lead to a massive spike in the cost of health care, which everyone would wind up paying for in the form of higher premiums, lower salaries (since employers would have to pay higher premiums), and higher taxes.

Comment Fee rather than market (Score 3, Insightful) 97 97

The problem described in the OP is one of several reasons why setting a fee for each ton of carbon dioxide emission is a much better idea that a cap-and-trade scheme. There are numerous other reasons, but I will only highlight the most important.

The entire purpose of either a fee or cap-and-trade scheme is to get carbon consumers to change their behavior (either doing less of things that emit greenhouse gases or by reducing the carbon intensity of the same activities). But almost all the reasonable mitigation measures have long time horizons (years to decades). In cap-and-trade, it is very difficult to predict what the price signal will be at any time in the future. So how can I, as a consumer, decide if it is worth it to buy a more efficient or electric car if there is great uncertainty in how much the carbon control scheme is going to add to my gasoline cost?

Comment Mass versus rest mass (Score 1) 48 48

The summary (and the referenced Wikipedia article) are sloppy about the use of the term "mass", sometimes using it when they should use the term "rest mass". Zero rest mass particles, such as photons, always move at the speed of light in vacuum. Moving at that speed, they do have mass. The relationship between their energy (E), mass (m), and momentum (p) is:

E = pc = mc^2,

where c is the speed of light in vacuum. They fit the definition of uniparticles because those three quantities all scale linearly relative to each other; if you double the momentum, you also double the energy and the mass.

In contrast, particles with non-zero rest masses (e.g. electrons) follow the equation:

E^2 = (pc)^2 + ((m0)c^2)^2 = (mc^2)^2,

where m0 is the rest mass of the particle. The rest mass of these particles does not change, but their mass does change when they are accelerated. Because of the presence of the rest mass term, the relationship between energy, momentum and mass is no longer linear.

Comment Re:we scrub at 5:30. (Score 1) 141 141

Actually, in the healthcare context, using scrub as a verb most specifically refers to scrubbing your hands in preparation for surgery or another sterile procedure. It can also be used as a synecdoche for the entire process of the provider getting ready for surgery, starting at changing from street clothes to scrubs and ending with donning the sterile gown and gloves (or for a subset of that process if you already put your scrubs on earlier in the day).

Comment Re:Subsidies (Score 1) 827 827

This is an example of price discrimination / price differentiation. It allows the seller (the college in this case) to increase revenue compared to charging the same price for everyone. This is a separate issue from student loans. See the Wikipedia article (or a microeconomics textbook) for a detailed explanation.

Comment Re:How about some other ideas (Score 1) 146 146

I think an issue with the gull wing design would be that it would significantly complicate and perhaps also weaken the design of the fuselage, especially given the need for it to be pressure tight. My idea for a similar concept would be to have a circular seam at the back of the fuselage. The plane would be backed into the gate, the seam opened, and the tail swung out of the way (I've seen cargo planes that have that kind of hatch). Then the entire inside of the fuselage (passengers and baggage) would be pulled out the back onto a receiver structure in the terminal.

You would need a system of rails to allow for this movement and to couple the interior to the fuselage shell. There would also be a safety issue during the movement (since the fuselage moves relative to the passengers next to it in the window seats). A lightweight, non-structural shell that is part of the inside could be used. Alternatively, if the inner surface of the fuselage was completely smooth, with nothing that passengers or gear could catch on, perhaps it would be safe to slowly move the interior out of the fuselage.

Regarding the boarding order, what you are forgetting is that because of the scramble for overhead bin space, airlines allow higher priority passengers (more expensive tickets, frequent fliers, etc) to board first, and those people tend to have the better seats near the front of the plane. I never understood why when the airlines started charging for baggage, they didn't charge for carry on and make checked baggage free (or at least significantly cheaper than carry on). The current system on most US airlines (charge for checked baggage, carry on is free) obviously encourages people to carry more bags on the plane and, IMHO, is a major source of boarding delays.

Comment Clinical Perspective (Score 3, Informative) 83 83

I am a pediatric blood & marrow transplant physician. I have read the article abstract, but I don't subscribe to Science Translational Medicine, so I won't be able to read the article until my hospital library orders & acquires the article. These comments are based only on the abstract.

The Slashdot summary is misleading about what is novel in research. Unrelated donor bone marrow transplants (or hematopoietic stem cell transplants (HSCT), which are a superset) have been done routinely since the 1990's.

Allogeneic (meaning the stem cell source is another person, rather than the patient himself/herself) HSCT patients take immunosupressive medications to try to prevent (or to treat) graft versus host disease (GVHD). If the patient does not develop GVHD, they are usually weaned off the immunosuppressive medications by 6 months after transplant. Patients who do develop GVHD can require years (sometimes 5-10 years) of immunosuppression. In contrast, patients who receive common solid organ transplants (heart, liver, kidney) are usually on immunosuppressive medications for life, although the immunosuppression is typically stronger for the first few months after transplant. The article reports on patients who received simultaneous kidney and HSC transplants from the same donor. Some of these patients could be weaned off of immunosuppression. Although this type of simultaneous transplant is not common, it has been reported before, as well as the finding that patients could come off immunosuppression.

What is novel is the ability to perform unrelated donor transplants using donors who were not good HLA matches (the matching system that is used for HSCT) and not have the recipients develop GVHD. This was accomplished by manipulating the stem cell product after it had been collected from the donor, but before it was infused into the recipient. The majority of HSCT done today are done with unmanipulated stem cell products (I'm not counting processing that often needs to be done when the donor and recipient don't have the same red cell type - which is controlled by a different genetic system than HLA). However, some forms of stem cell product manipulation (T-cell negative selection and CD34+ cell positive selection) have been around for a few decades. They can be successfully used to decrease the risk of GVHD, but at the price of increasing the risk of graft rejection, relapse (for leukemias) and infection. In the end, almost all studies of those methods show that the overall survival or disease-free survival is unchanged.

This article describes a more sophisticated form of stem cell manipulation, in which the graft is enriched in hematopoietic stem cells and tolerogenic graft facilitating cells. There have been past reports of other sophisticated stem cell manipulations giving good results in a study, but these techniques require elaborate facilities to perform, and often when they have been replicated by groups other than the original group, the patient outcomes have not been as good as those in the original report.

So my bottom line is that this result is exciting, but needs at minimum validation in a multicenter study before it starts to look like a game changer.

To address some of the other comments:

1) The concern about graft-versus-leukemia effects is a valid one and it will need to be studied. However, that is not an issue when doing a transplant for a non-malignant disease, so it would be a definite win for those patients. For leukemias, the GVL effect is strongest in CML, then AML, and weakest in ALL (kids don't get CLL, so I don't know much about that disease). Ultimately it would take clinical trials to determine if the benefit from less GVHD outweighs increased relapse risk (if any) from decreased GVL.

2) The article uses reduced-intensity radiation / chemotherapy, which isn't exactly a picnic, but it is less toxic than standard-dose (10-14 Gy) total body irradiation and 120 mg/kg cyclophosphamide (or 4 day busulfan and 120-200 mg/kg cyclophosphamide).

Comment Re:One question (Score 1) 332 332

IANAL, but the short answer is basically judges can order whatever they want in theory, although in practice there are significant limitations (more on that below). Another big point to mention is that the United States uses a common law system, meaning that large parts of the law have never been defined by a statute (i.e. a law passed by a legislature). The major limitations:

1. The judicial selection process almost always picks people who are not going to go off the deep end and start issuing crazy orders, but generally stick close to what is authorized by statutory, regulatory, or case law.

2. Orders from lower courts can be appealed and overturned by appellate courts.

3. There are mechanisms in place to impeach judges.

Within the law, there are various factors that limit orders judge are supposed to issue, and I suspect a relevant one here is jurisdiction. Divorce is a matter for state courts, and if the divorce is occurring in a state where Facebook doesn't have enough of a presence to bring it under the judge's jurisdiction, ordering the parties to swap passwords may be a lot simpler (from a legal perspective) compared to whatever they would have to do to bring another action in Federal court or in a state court with jurisdiction over Facebook to compel Facebook to turn over the data. I'm not sure why the court didn't just ask Facebook to turn over the relevant data. Of course it's also possible they did and Facebook refused, or the court knows that Facebook has refused similar requests (as distinguished from orders) in the past.

Comment Re:Inflation (Score 3, Informative) 696 696

This is a very good point. The Federal Reserve currently holds about $1.6 trillion in U.S. Treasury securities. So it would be possible to sell those securities (which pulls the money that others use to buy them out of the economy) so that the the coin hack had no net effect on the money supply until the Federal government spent more than $1.6 trillion.

I would argue that we need the additional fiscal stimulus given the weakness in the economy, and that stimulus would not be inflationary. For the people worried about inflation, though, having the Federal Reserve sell Treasury securities would delay any theoretically possible inflationary impact of the coin hack for about a year.

Comment Re:Inflation (Score 5, Informative) 696 696

I am the OP. As several people have posted, this approach is exactly equivalent to printing money. The reason it needs to be platinum coins rather than paper bills is that there is a law that limits the total value of paper bills that can be printed, but there appears to be no limit on the value of platinum coins that can be minted.

Of course, if you were to print a large enough amount of money, it would lead to inflation (or asset price bubbles, which actually seem to occur first in the current economy). The mechanism by which excess money supply causes inflation is by increasing demand to the point where bottlenecks appear in the economy. For example, people want cars, have money to buy them, but there aren't enough factories right now to supply demand - so the price of the limited pool of available cars is bid up. If labor markets are tight, employers looking for people to work to fill the demand created by the extra money will need to bid up wages to attract workers.

The key point is that all those mechanisms only work if an economy, or significant parts of it, are operating near peak capacity. This is the complete opposite of the situation we are in right now. Industrial capacity utilization was at 76.7% in June, several percentage points below the 1972-2010 average (80.4%) an well below the 85.1% peak in the 1990's. Unemployment is also high compared to historical averages.

In the current environment, it is vastly more likely that increasing the money supply will improve economic conditions without triggering inflation. Even at its pre-financial crisis recent peak (when unemployment was much lower than it is now), annual inflation (CPI-U, Dec 2006 to Dec 2007) was only 4.1%. Also keep in mind that the entire amount created ($5 trillion in my example in the OP) will not hit the economy at once. Initially it will be in an account at the Federal Reserve, and only as the government spends the money would it reach the economy.

Comment Re:Postpone only (Score 4, Interesting) 696 696

I am the OP. The reason this approach counts as an 'escape hatch' is that it appears that the executive branch already has the authority to carry it out (in 31 USC 5112(k) ). To stop it, Congress would need to pass a law. To do that in the face of a presidential veto would require 2/3 supermajorities in both the House and Senate. As long as Obama can get 34 of the 51 Democrats in the Senate (or 53 Democrats plus independents who caucus with the Democrats) to back this approach, there is nothing that the House can do to stop it.

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