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December 15[edit]

Blood Pressure differential[edit]

A person registered a blood pressure with a wide differential between systolic and diastolic pressure (say 150/60), what physiological conditions (if any) would that indicate?

Full disclosure: past test question.

Thanks in advance. — Preceding unsigned comment added by 174.113.7.240 (talk) 01:32, 15 December 2011 (UTC)[reply]

See Pulse pressure#High .28Wide.29 Pulse Pressure. --Tango (talk) 01:41, 15 December 2011 (UTC)[reply]

And if you have concerns about your health, see a doctor. No one here is qualified to diagnose medical conditions over the internet. ←Baseball Bugs ^{What's up, Doc?} carrots→ 12:26, 15 December 2011 (UTC)[reply]

Aren't you making quit a leap here Bugs, assuming that the OP is suffering from hypochondriasis of medical students? Reliving past tests may well affect one's pulse, but there is no indication that is happening here. -- 19:51, 15 December 2011 (UTC) — Preceding unsigned comment added by 203.82.91.133 (talk)

Medical students' disease is the applicable link (search on Google for 'isolated systolic hypertension')--Aspro (talk) 20:03, 15 December 2011 (UTC)[reply]

Exploding electrode[edit]

What would cause a pure graphite electrode to explode during use? Explode may be the wrong term - it suddenly cracked open lengthwise and briefly thereafter disintegrated, sending shrapnel flying everywhere. The electrode was cylindrical, about 3 mm in diametre, and was used in a modified Castner reaction. Plasmic Physics (talk) 11:13, 15 December 2011 (UTC)[reply]

Was it a (very) porous electrode. Could metal ions have had enough time to diffuse into it. Is their a chance that the polarity got reversed. Had it been immersed in an acid solution previously. Did this cell involve any carbonates. The lengthwise split suggest the outer surface expanded (like putting wedges in a wooden log). What exactly where the chemicals involved. In other words - Need more info. Who said chemistry wasn’t exiting.--Aspro (talk) 19:39, 15 December 2011 (UTC)[reply]

It is the chemists who "exit" suddenly when things start exploding.Edison (talk) 01:24, 16 December 2011 (UTC)[reply]

Please blame my spell checker for losing the 'gh' there in the last word. And agree also, that they do from time to time they disappear in a puff of smoke with a loud report (or should that be a loud retort) :-)--Aspro (talk) 14:59, 16 December 2011 (UTC)[reply]

Exighting? That would be a cool word, if it actually, er, existed. What you need is "exciting". :) -- Jack of Oz ^{[your turn]} 06:29, 17 December 2011 (UTC) [reply]

Were you trying to make that sodium metal electrolytically? Graeme Bartlett (talk) 22:36, 17 December 2011 (UTC)[reply]

Yes, I did try to make sodium metal electrolytically. No, the electrode was not exceptionally porous. Prior to being used in this way, the electrodes were cleaned and dried. The chemicals used was 98% sodium hydroxide monohydrate, and an initial quantity of water to initiate the process. The reaction ran according to plan for some time, before this happened. Plasmic Physics (talk) 07:09, 18 December 2011 (UTC)[reply]

After repeated reactions, it only occured once yet. Plasmic Physics (talk) 11:12, 19 December 2011 (UTC)[reply]

how can i get :- a)ammonia gas ---- b)potassium hydride[edit]

how can i get :- a)ammonia gas ---- b)potassium hydride from :- water - oxygen - carbon dioxide - potasium - nitrogen ("Note : you can use some or all the previous substances")

My try to solve this : a) 6K + N₂ -----> 2K₃N then K₃N + 3H₂O -----> 3KOH + NH₃ but i am not sure from the reaction between potassium and nitrogen , is it true reaction???

b)i don't know how to get this :( — Preceding unsigned comment added by Mido22 (talk • contribs) 12:47, 15 December 2011 (UTC)[reply]

I have no idea how "practical" (vs "write a balance reaction") an answer this is, but our article on potassium notes that nitrogen is used to extinguish potassium fires--therefore they do not likely react with each other. Looking up what K₃N would be, we have an interesting article about nitride chemicals, which addresses whether this one is likely (with a side-note about Li₃N being easy to make by the type of reaction you propose. Looking in the lithium#Chemistry and compounds section, you can find the answer to whether direct reaction between potassium and nitrogen is expected to occur. DMacks (talk) 15:19, 15 December 2011 (UTC)[reply]

I doubt K and N would react. How about adding K to water which IIRC will produce KOH and H2. You could then react the H2 with N to make ammonia (assuming you have the apparatus for the haber process. SmartSE (talk) 16:48, 15 December 2011 (UTC)[reply]

If we can get a source of carbon monoxide, we can generate hydrogen gas from the Water gas shift reaction. That's often a precursor for Ammonia production. --Jayron32 23:52, 15 December 2011 (UTC)[reply]

Potassium hydride or Potassium Hydroxide? Dropping water on potassium gives potassium hydroxide and hydrogen gas. If you want potassium hydride, you need to collect the hydrogen, then heat the potassium up and blow the hydrogen over it (as per Humphry Davy). Ammonia's harder - the nitrogen needs to be fixed. SmartSE is right about direct combination of nitrogen and hydrogen in the Haber Process, but you need high pressure, temperature, and typically a metal catalyst. Buddy431 (talk) 04:05, 16 December 2011 (UTC)[reply]

If you put your nitrogen through an electric discharge you can react this active nitrogen with potassium to make K3N. This reacts with water to make ammonia. A very expensive way to make it. Graeme Bartlett (talk) 04:44, 20 December 2011 (UTC)[reply]

Gasoline fuel cell[edit]

Do these exist? How do they compare with ICE? I know they are more expensive, but performance wise. ScienceApe (talk) 12:58, 15 December 2011 (UTC)[reply]

I'd like to better answer the question but that means that I'd have to better understand it as well. And I don't.

I've often heard the term "fuel cell" used to refer to a small (a couple gallons) fuel tank in a street legal car that is used for racing on weekends. But looking at ICE, I have no idea what you're comparing a gasoline fuel cell to (or my definition of it).

And finally, in the first question, you asked if they exist but in the final sentence you say that they are more expensive. So which is it? Do you wonder if they exist or know they do and therefore wonder if they are worth the cost? Dismas|^(talk) 19:49, 15 December 2011 (UTC)[reply]

ICE is almost certainly, from the context, an internal combustion engine, driving an alternator. A fuel cell converts a fluid fuel directly into electricity. They have three chambers, separated by two metallised semi-permeable membranes. The fuel is pumped into one of outer chambers, air/oxygen into the other. The 'burn' at membranes, and the exhaust is removed from the middle chamber. Methanol/ethanol fuel cells were going to be the next laptop power supply, a few years ago, but seem to have dropped of the radar. I'm also not sure how well they scale to the 1 hp (750 W) plus of gasoline engines. CS Miller (talk) 20:37, 15 December 2011 (UTC)[reply]

While proton exchange membrane fuel cells are what most people think of when someone says "fuel cell", they aren't the only type of fuel cell. Due to their low operating temperature (which makes them attractive for automotive applications), PEM fuel cells primarily use hydrogen fuel. There are some PEM variants which directly use methanol or ethanol as fuel (Direct methanol fuel cells and direct-ethanol fuel cells), but those are less developed than the hydrogen fueled ones. In contrast to PEM fuel cells, there are also solid oxide fuel cells and molten carbonate fuel cells. These operate at much higher temperatures, and as a consequence can easily use gasoline directly as a fuel source (there are some prototype PEM systems which use gasoline fuel, but they almost all use a separate step to first reform the gasoline into hydrogen). The drawbacks to using SOFC & MCFC for automotive applications are that their high operating temperatures mean that they take a long time to start up, so aren't good for the intermittent usage inherent in cars. Additionally, their construction tends to be more fragile than PEM fuel cells, so are better suited to stationary applications, rather than being bumped around in a car. Researchers are working on both the robustness and the operating temperature of SOFCs & MCFCs, so it's possible that at some time in the future there will be a direct gasoline fuel cell that is suited toward automotive applications. -- 140.142.20.101 (talk) 00:33, 16 December 2011 (UTC)[reply]

Indeed. I figured anyone who didn't know what ICE stood for, probably wasn't qualified to answer my question anyway :P ScienceApe (talk) 19:46, 17 December 2011 (UTC)[reply]

In what way is the Higgs mechanism not a fundamental force?[edit]

Seems that all the bosons of the standard model are mediators of forces, so why not the Higgs boson? What makes it different from the others? Goodbye Galaxy (talk) 15:36, 15 December 2011 (UTC)[reply]

The Higgs boson is a spin-0 boson (AKA scalar boson). All other Standard Model bosons are Spin-1 Gauge bosons (AKA gauge vector boson). The key word here is gauge, not boson. The Higgs boson is not a gauge vector boson so it is not associated with a gauge interaction (AKA fundamental force). Dauto (talk) 15:52, 15 December 2011 (UTC)[reply]

Odd math[edit]

Let's take an event which lasted 4 years, say from 1941 to 1945. Now if I want to briefly describe this event year by year, I arrive to the odd number of 5 years (including 1941). Is there some reference in math to such an odd division?--46.204.24.211 (talk) 18:41, 15 December 2011 (UTC)[reply]

It depends on if/how you count the end points, also known as inclusive vs. exclusive counting. If the event started on Jan. 1 1941, and ended on Dec. 31, 1945, then it will have lasted five years. On the other hand, 1945-1941=4, but this is "not counting" the year 1941. So we get a duration of four years if the event starts on Dec 31 1941 and ends on Dec. 31 1945. There's some relevant info at Counting#Inclusive_counting, and also at Closed_interval#Excluding_the_endpoints. SemanticMantis (talk) 19:02, 15 December 2011 (UTC)[reply]

See also: fencepost error. --Carnildo (talk) 02:10, 16 December 2011 (UTC)[reply]