| AskScience AMA Series: I am Dr. Saad Omer and I'm here to talk about vaccines and the diseases they prevent. Ask Me Anything! Posted: 22 Feb 2019 04:00 AM PST With vaccine preventable disease outbreaks making headlines around the world, we would like to welcome Dr. Saad B. Omer for an AMA to answer any questions on vaccines and the diseases they prevent. Dr. Saad B. Omer (www.saadomer.org) is the William H. Foege Chair in Global Health and Professor of Global Health, Epidemiology & Pediatrics at Emory University, Schools of Public Health and Medicine. He has conducted studies in the United States, Guatemala, Kenya, Uganda, Ethiopia, India, Pakistan, Bangladesh, South Africa, and Australia. Dr Omer's research portfolio includes clinical trials to estimate efficacy of maternal and/or infant influenza, pertussis, polio, measles and pneumococcal vaccines and trials to evaluate drug regimens to reduce mother-to-child transmission of HIV. Moreover, he has conducted several studies on interventions to increase immunization coverage and demand. Dr Omer's work has been cited in global and country-specific policy recommendations and has informed clinical practice and health legislation in several countries. He has directly mentored over 100 junior faculty, clinical and research post-doctoral fellows, and PhD and other graduate students. Dr. Omer has published more than 225 papers in peer reviewed journals including the New England Journal of Medicine, JAMA, the Lancet, British Medical Journal, Pediatrics, American Journal of Public Health, and Science. Moreover, he has written op-eds for publications such as the New York Times, Politico, and the Washington Post. Dr. Omer will begin answering questions at 4:30pm EST. submitted by /u/AskScienceModerator [link] [comments] |
| Why does every human has a unqiue voice, and how come voice artists are able to replicate other's voice so authentically? Posted: 21 Feb 2019 09:13 AM PST Some follow up questions: Why do each animal species sound almost similar to us? Why can't we appreciate voice variation in them as can we do in other humans? And what really happens at puberty that cause male voice to become deeper and not of girls? Edit: Thanks for all the awesome replies guys! Didn't expected this question to blew up. I was kind of tripping on acid when I was typing this, I'd read everything properly when I am sobered up. submitted by /u/rishinator [link] [comments] |
| How compressed is water at the deepest reaches of the ocean? Posted: 22 Feb 2019 04:23 AM PST |
| Do your cells stop dividing the second you die? If not, how long do they divide after you are dead? Posted: 22 Feb 2019 07:08 AM PST |
| On the Wikipedia page for "Koch's postulates" it is stated that HIV causing AIDS doesn't follow from them. How so? Posted: 22 Feb 2019 05:34 AM PST |
| Looking at footage of rockets being fired into space, it appears that liftoff relies 100% on burning fuel... why don't they have a mechanical assist, like a vertical version of an aircraft carrier's catapult? Posted: 21 Feb 2019 09:26 PM PST My understanding is that rocket fuel is one of main limiting factors in the kinds of missions we're capable of, making conservation of said fuel a very high priority. Yet, footage suggests that we rely on burning rocket fuel for 100% of the rocket's movement from the ground up. Starting with no momentum, I'd assume those first few seconds after ignition require a disproportionately large amount of fuel relative to the rest of the flight. A push from the ground could source that energy from something other than the rocket itself... seems like such a simple way to get a lot more bang for our buck, so I'd guess there's a good reason for not doing this? Or is there some kind of assist from the platform, but that isn't visually obvious in launch footage? submitted by /u/Haltus_Kain [link] [comments] |
| What is the difference between thinking about moving your arm and actually moving your arm? Posted: 22 Feb 2019 01:58 AM PST |
| How does density affect the speed of seismic waves through the Earth? Posted: 22 Feb 2019 07:43 AM PST So, correct me if I'm wrong, the speed of the seismic waves increase with depth in the mantle but the speed decreases as it enters more dense material (i.e. the core)? I thought waves traveled faster through more dense materials as a rule. Could somebody please clarify this for me. Thanks. submitted by /u/EndOnAnyRoll [link] [comments] |
| Is the (co)sine wave the fundamental building block of signals? How can we prove this? Posted: 22 Feb 2019 07:25 AM PST I couldn't find a better way to phrase this question so please allow me to explain. Before I start, I just want to make clear then when I will be speaking of a 'sine' wave, i'm not just referring to a naked sine(wt) function (w = omega because I don't know how to math in reddit), but also a sine wave with a phase shift (sine, cosine and anything in between) or the complex harmonic function e^(jwt). I don't know how to name these or how to formally refer to these functions more generally. So again, when I say 'sine' wave I mean the sine-function + any phase shift or a complex harmonic function if that is what you call them. It frustrates me when I'm typing this because I don't know how to call that 'shape' regardless of whether it is purely real or complex or regardless its phase. I don't want to be confusing. In Fourier transforms we consider signals to be composites of an (in)finite number of sine functions. To me that seems to imply that the sin function is 'the' purest most naked periodic function. We say, all periodic functions is collection of sine functions. Is it because sine functions are solutions to differential equations that it is 'the' purest periodic function or could there be another periodic function that could serve equally well in Fourier transforms? On intuition I'd say no but I can't come up with a very strong mathematical argument to support this idea. Maybe another slightly different shape that you could also use. Or is the sine wave 'the' periodic function? I've thought about this question a lot but I've never been able to really comprehend how to think about it best. Sorry for the lengthy question. Now that I'm typing it out I really notice that as a non-native English speaker and engineer (and not mathematician) I don't know the right language to talk about this question. submitted by /u/vgnEngineer [link] [comments] |
| Does wind gave any effect to sound waves? Posted: 21 Feb 2019 04:20 PM PST For example, does their speed and/or direction changes if there's a strong wind blows from the opposite side of the source? submitted by /u/fizarr [link] [comments] |
| How do bird beaks grow in such a particular shape, if they're made out of dead stuff? Posted: 22 Feb 2019 04:52 AM PST Like our hair, beaks are made out of keratin. But to my understanding, each individual hair follicle spews out keratin in a circular shape, creating a very long cylinder. If beaks also grow from the same, dead material, how do they grow out in such a particular shape? submitted by /u/Sammy197 [link] [comments] |
| How does a FM Radio antenna deal with the echoed signals? Posted: 22 Feb 2019 12:26 AM PST Hello, When voice is transmitted over a radio, the transmitter transmits it in all directions, and a few of them reach the receiver antenna (in either straight line or through reflections) with different delays. But why doesn't we hear the echo like we do with Sound? submitted by /u/TheLiyaRs [link] [comments] |
| If honey "lasts forever" and kills bacteria, why does it rot if harvested too early? Posted: 21 Feb 2019 11:57 AM PST |
| So what's up with dogs and TV's? Can get watch it or is it something about the type of TV? Posted: 22 Feb 2019 01:34 AM PST So when I was small I used to hear about how dogs can't watch TV cause it's in 2d. But I keep on seeing these videos of dogs watching TVs. So what's the actual case? submitted by /u/arerator [link] [comments] |
| How does a "sawing" motion improve the cutting ability of a non-serrated knife? Posted: 21 Feb 2019 09:43 PM PST |
| Why does snow melt around pebbles like this? [Example Pic in body] Posted: 21 Feb 2019 06:14 PM PST Was out walking the dog during a light snowfall and noticed many pebbles on the sidewalk where the snow had melted around them, but nowhere else. Pic Hoping to get an explanation as to why this happens. submitted by /u/Erekai [link] [comments] |
| How is Gravitational Potential Energy Stored? Posted: 21 Feb 2019 01:55 PM PST If you move an object upwards, kinetic energy is transferred to GPE and then when you allow it to fall, the GPE is converted back I to KE. How is this potential energy stored in the object or is it more abstract than that. On a separate note, I may be being stupid here but does applying a force not require energy. If so, where does the energy come from when the ground provides a reactive force equal and opposite to weight. Thanks for any help you can give. submitted by /u/HdjsgKd [link] [comments] |
| Why does soap form bubbles? Posted: 21 Feb 2019 12:56 PM PST I know soap is used as a surfactant and as an emulsifier, but I don't really understand why it starts to foam up in water. Could anyone please explain this to me? submitted by /u/Okkuh [link] [comments] |
| If an airplane had a tailwind that was faster than the airplane’s speed, could it still fly? Posted: 21 Feb 2019 09:56 AM PST |
| Why do the effects of some vaccines wear off over time? Posted: 21 Feb 2019 01:06 PM PST Disclaimer: I believe vaccines are effective and necessary but don't understand this aspect. I am not trying to question the practice of vaccination. If vaccines like the MMR vaccine teach your body how to fight off measles why does this effect wear off requiring a booster? submitted by /u/RJG1983 [link] [comments] |
| I just read a research paper about "downregulation of cannabinoid receptors in daily cannabis smokers". Does that mean that cannabis actually does have a mechanism for physical addiction? Posted: 21 Feb 2019 02:03 PM PST Full disclosure, I am a cannabis smoker myself. We've always liked to tell ourselves that weed isn't physically addictive like caffeine or heroin that have direct chemical effects on your brain, it's just psychologically addictive like anything else you enjoy, like TV or shopping. But I recently found this study, and I'm wondering if it means that entire commonly repeated view is maybe not so accurate? Reversible and regionally selective downregulation of brain cannabinoid CB1 receptors in chronic daily cannabis smokers https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3223558/ I don't know what role "cannabinoid" receptors normally play in the human body, but it sure sounds like cannabis is downregulating a neuroreceptor in your brain, sort of like caffeine does to norepinephrine, right? submitted by /u/Reacher-Said-Nothing [link] [comments] |
| How does E. Coli serotype 0157:H7 inhibit protein synthesis? Posted: 21 Feb 2019 01:20 PM PST I know that protein synthesis is inhibited in a way similar to Ricin, but how does the Shiga toxin actually prevent protein synthesis? submitted by /u/REDoROBOT [link] [comments] |
| What pattern would I draw on a map if I followed the suns direction for all the hours of daylight and stay put at night? Posted: 21 Feb 2019 08:00 PM PST Does the pattern change from winter to summer solstice? Does the pattern change from latitude and longitude changes? submitted by /u/klyde_donovan [link] [comments] |
