Safety Definition and 287 Threads

Until recently, I thought that any theory that contains non-renormalizable interactions in the power-counting sense (i.e. those whose couplings have negative mass dimension) must be an 'effective' theory that necessarily breaks down at some energy. However, I've been looking at Weinberg's QFT...

Dave Mattingly has been a frequent collaborator with Ted Jacobson (his thesis advisor). You know of Jacobson if, for example, you followed the recent discussion of "gravity as entropic force" by Erik Verlinde and others. In 1995 Jacobson derived the Einstein field equation from thermodynamics...

http://pirsa.org/10050002/ Deformations of General Relativity Kirill Krasnov 2010-05-05 "I will describe a very special (infinite-parameter) family of gravity theories that all describe, exactly like General Relativity, just two propagating degrees of freedom. The theories are obtained by...

I've heard talk of this safety threshold for ionizing radiation, whereby if the dose is sufficiently low enough, it would produce no harmful side-effects. Can someone explain to me the reasoning behind this? The way I see it, every single ionizing particle that passes through a cell has a...

Homework Statement An accident safety system uses a spring to absorb the energy of a car before the car collides with a bridge abutment. The vehicle has a mass of 1000kg and the design calls for stopping a car moving at 5m/sec (11.2 mi/hr) in 0.5m. Find the spring constant k Homework...

HI, I have builded a tube buggy out of square 1"1/2 x.085 and was told that it was unsafe so I'm looking into it. Was my design unsafe? My question is round stronger then square if so how much? Question 2 dose welding weaken the steel? Question 3 if round is stronger how much stronger is it...

I'm trying to understand why asymptotic safety is a reasonable approach to quantum gravity. Here is my present understanding: 1. Asymptotic safety is roughly the statement that perturbative gravity (by which i mean a spin 2 field) has a UV fixed point where it becomes like any other conformal...

I heard about a fire safety campaign called "hug a banana" (or similair) The idea was to encourage kids to run toward a large scary shape in yellow overalls and breathing apparatus if they come into your smoke filled bedroom - instead of running and hiding. Since US firefighters wear yellow...

Hi there! (It's not actually a homework question) I just wanted to ask where does the lamp get oxygen to burn on in coal mines. So there must be an inlet for air. Of course it is explained in my book that as the wire mesh distributes the heat therefore the temperature does not rise to the...

I plan to visit Los Angeles around New Year and was picking a hotel when i ran across articles that recommended staying away from downtown LA because of safety concerns(especially at night-time). I read about South Central and know it is one of the most dangerous places in the US(because of gang...

I'm not sure how to work this one... The spring on a safety valve can be compressed 15 mm by a load of 700 kg. In it's working position the compression of the spring is 22 mm. The combined mass of the valve, spring and spindle is 17 kg. Valve diameter is 80 mm. Determine boiler pressure...

Diagram: http://img11.imageshack.us/img11/2442/boltlw.jpg Question: The material for the bolt shown in the angled joint has an ultimate tensile stress of 600MPa and a shear strength of 250MPa. The diameter of the bolt is 10mm. Determine the factor of safety. Assume F=9KN. Stress = Applied...

We already have videos for 5 of the talks. Steven Weinberg http://pirsa.org/09110039/ Martin Reuter http://pirsa.org/09110040/ Jean Zinn-Justin http://pirsa.org/09110041/ Holger Gies http://pirsa.org/09110042/ Benjamin Ward http://pirsa.org/09110043/ Here's the schedule...

Can this be explained in terms of inelastic collisions? This is what I think: The collision is perfectly inelastic because the person and the net move together with the same velocity. This means that the initial kinetic energy of the system (and therefore the kinetic energy of the person) is...

Homework Statement A 1.0g Co(59) target is exposed to a constant fluence rate of thermal neutrons equal to 1E+12 n cm-2 s. Cross section (n,gamma) is 37.18barn and density is 8.9g cm3. What is the initial exposure rate at 1 meter due to neutron capture? Homework Equations...

If using 314mW red laser and cylindrical optics to project a line 500mm x 2mm, will it have brightness as 1mW laser that projects a dot with r=1mm since the area difference? 1000mm / (1mm^2*3.14) Would the projected line of that brightness be dangerous if bounced off the reflective surface...

Homework Statement An 8” long, 2.5” diameter, solid bar of Class 40 cast iron is subjected to both a torque of 75,000 lbf-in and an axial compressive load of 165,000 lbf. If these two loads can increase at a constant ratio, calculate the safety factor.Homework Equations \sigmax=F/A \tauxy=Tr/J...

The link to the video is here: http://motls.blogspot.com/2009/07/cern-weinberg-about-asymptotic-safety.html

For a certain sexah project I'm going to do, I have a bunch of lasers that have an intensity of "<5mW". I have 780nm IR lasers and 650nm red lasers. When i made a lazy hookup to a 3V power source, the red laser was briiiiight which leads me to believe I've only ever used <1mW lasers in our labs...

We bought some rechargeable batteries a few years ago. However, we managed to lose the charger that went with it. :rolleyes: Now we bought some new rechargeable batteries with a new charger. This one is of a different brand. We still have the old batteries. My dad wants to use the new...

These braces were installed on the concrete support pillers at ground level of a very large 6 level mall. Would the engineers comment on the safety of this construction, in particular drilling through the concrete support structure

hey guys i need some help...why is it safer to be near a wall during an explosion?

As it is stated in 10 CFR 50.46 maximum clad temperature should not exceed 2200 F(1204 C) but I have read in "Nuclear Safety" by G. Petrangelli that fissuring of the cladding starts at about 800-900 C. I want to know the safety limit or margin for cladding in NPPs. I could't find any...

Hi everyone, As part of the IB program, we are all required to design an experiment and write about how we would go about testing it . My instructor's decided that the best way to test this would be to "Determine using physics whether a Smart Car is safe in a crash" Since this is a...

Is neutral wire at 0 potential?? Does that mean we can easily touch it??

"We thank J. Distler and R. Percacci for animated discussions which triggered this investigation. Furthermore, we are grateful to J.P. Blaizot, A. Codello, R. Loll, E. Manrique, and M. Reuter for useful conversations..." It's interesting to contemplate the different ways that progress in...

http://arxiv.org/abs/0901.2984 Asymptotic safety in higher-derivative gravity Dario Benedetti, Pedro F. Machado, Frank Saueressig 4 pages (Submitted on 20 Jan 2009) "We study the non-perturbative renormalization group flow of higher-derivative gravity employing functional renormalization...

I recently disassembled my Big Screen CRT projection tv. I have been well aware of the danger of the capacitors in CRT TV's and I managed to take the TV apart and remove the capacitors all without killing myself. However, I was doing some more reading online and it seems there is another danger...

Hi, I am new to building large candy rockets, and I have a target of building a candy rocket that can reach an altitude of over 40,000ft. I am mostly concerned with the safety when casting such propellants. I am looking at casting over 200 pounds of propellant. Any one got any advice. I have...

I have a question about safety wire. Safety wire is used to secure fastners to prevent them from loosening. What are the benefits of the twist in the wire between points? Here is a explanation of safety wire."[URL http://en.wikipedia.org/wiki/safety_wire I read but don't see a clear...

Loll's CDT and Assymptotic Safety proven to be directly related. The interesting part is this one: 7. Lattice Lattice implementations for gravity in four dimensions have been put forward based on Regge calculus techniques [27, 28] and causal dynamical triangulations [29]. [...] Within...

Hi, An isolation transformer is used in order to "safely" separate one part of an electric circuit from the mains. (description in http://en.wikipedia.org/wiki/Isolation_transformer" ) Still I have problems grasping the important concept of such a transformer. I have spent some time...

are the safety protocols in place in setablishments dealing with fissionable material adequate for public safety? is there any good places to get more information on why the safety isn't good enough? =)

I was on a 'Working at Height' course and at the end of the course they deemed it necessary to suspend us from a harness so we would know what it would feel like to be suspended from a harness. This caused me to get a sore back which I reported to my supervisor the next day. I carried on working...

Hi everybody :D (try no.3 to post this, huh, so I'll be short)! It was great reading your discussions, now I have one question for you, I hope you can help me. I started working in a lab that uses radioligand binding assays routinely. We use tritium labeled steroid hormones. I know that...

I haven't heard much about this in detail, but does anyone know what changes they made in the structural design of the Freedom Tower to prevent the collapse of the tower in the case of it being attacked via jetliners? I know it can't be 100% certain, but I would think they would have done...

Hi, In the safety case for the new Large Hadron Collider (LHC), the possibility of creating artificial black holes is considered. The main argument for the case that there is nothing to worry about, is that cosmic rays collide regularly with atoms in the upper atmosphere with much higher...

With (hand shake) agreements. http://www.newsdaily.com/stories/n02498013-americanairlines-faa/

Homework Statement a) You have been asked to design a convector heater (electric radiator) which has a metal body. Detail an appropriate method of preventing electric shock for users of this product, and show how such a protection strategy could be implemented in your design. (15) b)...

I heard and read several times that a pebble bed reactor is "safer" than a PWR or a BWR. However, I fail to figure out how. After all, light-water reactors also have negative temperature coefficients, which seem to be the "invention" that makes the pebble bed reactor "inherently safe". But I...

Hi there, I have a safety question. I want to produce high temperature, high pressure steam. On a 1/2 inch tube, length is about 1 meter. Initially I put cold water in tube. Then pump it to 4000 psi. Now I will heat it to achieve about 380C. (in this process, I will open a purge valve many...

Apparently, I heard CA glues were toxic while being warmed through hot glue guns. How long would an average human being survive if he were stuck in a closed room with his glue gun left one? I'm just wondering based on safety measures...since I heard CA held cyanide, I was wondering what the...

Vehicle Safety Features Your task is to identify social issues, such as cost benefit analysis, requiring or arising from the development of safety features for vehicles, to research information about the issues you have identified, and to create a communication product to synthesize your...

Homework Statement I am looking for safety features in the design of a football helmet that can be explained using physics terms. for instance, kinetic motion, etc... 2. The attempt at a solution The different designs of cages on football helmets. Also, how the padding on the inside...

Hi there. I am new so I have no idea where to put this. I'd be glad if the moderator can help me put this in the right spot. So here is my question: What makes a parachute safe in a physics sense? I need a proper source. I've been looking for this for hours and I couldn't find anything...

Homework Statement TWO ALUMINIUM STRIPS EACH 75mmx5mm ARE RIVETED TOGETHER TO FORM A CONTINUOUS LENGTH THE JOINT IS MADE USING 6 RIVETS EACH 5mm IN DIA THE ULTIMATE SHEAR STRENGTH OF THE RIVET MATERIAL IS 70MN/m2 AND THE UTS OF THE ALUMINIUM IS 30MN/m2 IF THE MAXIMUM TENSILE FORCE APPLIED TO...

Hi all I'm writing a paper on the relation of safety to acceleration and velocity. The actual topic of the essay is that only acceleration is related to safety, however I disagree, as unless in a vacuum, the forces of friction of external gases and fluids would affect the human body at high...

are contact lenses dangerous for eyes? i hate glasses. another question is that is there any contact lenses which are colored and also do glasses job too?

After a brief venture over into the medical/RHP side of things, I find myself drawn back into nuclear engineering. Glad it happened before I got too deep into something else! I've just started working on my MS, and I am trying to find some sort of direction for myself. Anyways, one subset of...

more travel plans, what's new right! Well I have an opportunity to visit mexico city for 5 days. However half the people I talk to say I shouldn't go, it's not safe, I'll be mugged and kidnapped. The other half say it's all overblown and safe enough. What are your thoughts and experiences...