Wikipedia:Reference desk/Archives/Science/2014 April 24

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April 24

Material

Do you know any other material that lighter and strong as plywood ?195.94.247.195 (talk) 06:43, 24 April 2014 (UTC)

Oriented strand board? --Canley (talk) 07:02, 24 April 2014 (UTC)

Aluminum? Shadowjams (talk) 07:21, 24 April 2014 (UTC)

Spider web, among many others. Stainless steel has a better strength to weight ratio than aluminum. You will find a list of materials in the specific strength article.--Shantavira|^{feed me} 07:46, 24 April 2014 (UTC)

Titanium? Oda Mari (talk) 09:25, 24 April 2014 (UTC)

It should be pointed out that oriented strand board, while comparable to plywood in certain applications, is an insufficient substitute in others. While good for uses with distributed forces (like subflooring), OSB doesn't hold up well when the forces are concentrated. I remember an episode of This Old House where they went to a hurricane test center. They demonstrated the difference betweeen OSB and plywood for protection of windows by simulating a wind-borne 2x4 board hitting it. While the 2x4 bounced off the plywood, it punched right through the OSB - the laminated sheets do a better job of spreading the concentrated force, whereas the strands in the OSB just ripped apart. -- 162.238.240.55 (talk) 12:59, 24 April 2014 (UTC)

It would help it we knew what you wanted to use it for. A simple google for "plywood substitute light" has plenty of options but it really depends on what you want to use it for. 196.214.78.114 (talk) 09:18, 24 April 2014 (UTC)

Agreed. Based on the baseline material being plywood, I'm guessing they want something inexpensive and it doesn't matter if it's flammable, and perhaps it needs to be a thermal and electrical insulator. In that case, some form of plastic might qualify, and would also be more water resistant than plywood. StuRat (talk) 03:06, 25 April 2014 (UTC)

For reference, "strong" isn't really a well-defined term, unless you specify what type of strength you mean. E.g. spider silk is mentioned above, but it relatively low shear strength and compressive strength, especially compared to plywood. What it is good at is tensile strength. Our article Ultimate_tensile_strength has a table sortable by density and other factors. You might also be interested in toughness, or our general article Strength_of_materials. As others have pointed out, we might be able to recommend a specific material if you have a specific use in mind. SemanticMantis (talk) 16:40, 24 April 2014 (UTC)

Celebrex in UK

Can anyone give me a link to a credible article that tells me why Celebrex was banned in the UK please? I googled on "celebrex banned in uk" and got lots of online pharmacies - oh and the WP page! Thank you.--TammyMoet (talk) 10:11, 24 April 2014 (UTC)

Who says it was banned? This (undated) article from the Medicines and Healthcare Products Regulatory Agency says 600,000 people in the UK take it. The NHS website has information about it here. Cancer Research has a page on the drug here. All of that suggests its currently prescribed in the UK. -- Finlay McWalterᚠTalk 10:22, 24 April 2014 (UTC)

The document name for the MHRA thing suggests its from December 2004. -- Finlay McWalterᚠTalk 10:23, 24 April 2014 (UTC)

The only relatively recent thing I can find at the MHRA's website is this 2011 document which notes the withdrawal of use for the drug in Europe, for the treatment of "intestinal polyps in familial adenomatous polyposis" - for reasons of inefficacy. I can't find any notice about its other uses, and no evidence of a general ban. -- Finlay McWalterᚠTalk 10:29, 24 April 2014 (UTC)

That reiterates European Medicines Agencys instruction. I can't find anything on their site that describes any general ban or voluntary withdrawal. -- Finlay McWalterᚠTalk 12:03, 24 April 2014 (UTC)

I also looked at the National Institute for Health and Care Excellence website. They don't explicitly mention Celecoxib or Celebrex, but if you put either term in, they link to their clinical best practice notes for conditions where they say COX-2 NSAIDs are indicated. Again there's no evidence there that there's any kind of UK ban. -- Finlay McWalterᚠTalk 10:48, 24 April 2014 (UTC)

From what I can gather the "MHRA should strive to uphold the current European legislative ban on DTCA" See: http://www.mhra.gov.uk/SearchHelp/GoogleSearch/index.htm?q=celebrex%20ban. So it would seem it is not the product but the method of marketing/distributing it. 196.214.78.114 (talk) 10:50, 24 April 2014 (UTC)

Well that's all odd. I used to be on Celebrex but was taken off it and was told it was because it was being withdrawn in the UK. --TammyMoet (talk) 11:47, 24 April 2014 (UTC)

There were concerns at one point (this is mostly according to our article on it) that it would suffer from side effects similar to Vioxx. Those concerns appear to have subsided. Discovery and development of cyclooxygenase 2 inhibitors is an interesting review of all the COX-2 inhibitors, of which both Vioxx and Celebrex are. Shadowjams (talk) 03:59, 25 April 2014 (UTC)

First moment of area

How do you know which dimensions to include when calculating the first moment of area? For example if you're calculating the shear stress at a particular point on a rectangular beam, you would calculate the 2nd moment of area for the whole beam but for the first moment of area, which dimensions do you use for the area? I'm trying to calculate the first moment of area in question 1 of this example, http://www.docstoc.com/docs/78966553/ENGI3110PP2. I also don't know which value to use for the thickness. Clover345 (talk) 20:34, 24 April 2014 (UTC)

The purpose of investigating the first moment of area is to find the axis about which this moment is zero; that axis is then called the neutral axis. The beam appears to be rectangular in cross section, with dimensions 6 in by 3 in. By inspection, we can assume that the neutral axis passes through the centroid of this rectangle. If you check that by analysis you will find that the contribution (to the first moment of area) of the area above the centroidal axis is the same in magnitude, but opposite in sign, as the area below the centroidal axis, confirming that this is the neutral axis. Dolphin (t) 13:08, 28 April 2014 (UTC)