Extended physical systems that have been made to vibrate, like a string on a guitar, cannot return to their state of equilibrium without exerting forces on the area around them. These forces then lead to the phenomenon of waves, disturbances that propagate through a medium. The vibrating guitar string causes a sound wave to propagate through the medium of the air.
This course has two complementary goals. The first is to provide you with the concepts and mathematical tools necessary to understand and explain a broad range of vibrations and waves. This will allow you to gain a deeper appreciation for the true nature and beauty of phenomena like music and rainbows, which all of us observe or experience every day.
Waves complete 2016
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The Chikungunya virus infection in Brazil has raised several concerns due to the rapid dissemination of the virus and its association with several clinical complications. Nevertheless, there is limited information about the genomic epidemiology of CHIKV circulating in Brazil from surveillance studies. Thus, to better understand its dispersion dynamics in Rio de Janeiro (RJ), one of the most affected states during the 2016-2019 epidemic waves, we generated 23 near-complete genomes of CHIKV isolates from two main cities located in the metropolitan mesoregion, obtained directly from clinical samples. Our phylogenetic reconstructions suggest the 2019-CHIKV-ECSA epidemic in RJ state was characterized by the co-circulation of multiple clade (clade A and B), highlighting that two independent introduction events of CHIKV-ECSA into RJ state have occurred between 2016-2019, both mediated from the northeastern region. Interestingly, we identified that the two-clade displaying eighteen characteristic amino acids changes among structural and non-structural proteins. Our findings reinforce that genomic data can provide information about virus genetic diversity and transmission dynamics, which might assist in the arbovirus epidemics establishing of an effective surveillance framework.
Earlier this year, the EU and Turkey reached an agreement that has largely halted the flow of migrants from points east through Turkey, on to Greece and eventually to other parts of the EU. According to the United Nations High Commissioner for Refugees (UNHCR), about 8,000 migrants arrived in Greece between April and July 2016 after the agreement with Turkey was put into full effect. Before the agreement, about 150,000 migrants had arrived in Greece between January and March 2016.
At the same time, some of the movement toward Europe is shifting to a southern Mediterranean route to Italy, with flows of largely sub-Saharan African migrants (not Syrians, Afghans or Iraqis) on the rise. Italy has received about 90,000 migrants on its shores since the start of 2016, roughly similar to the first half of 2015. The UNHCR also estimates that over 2,500 people have lost their lives in the Mediterranean between January and May of 2016.
European publics have been far from satisfied with how the EU has handled the historic number of refugees arriving there. A spring 2016 Pew Research Center survey conducted across 10 EU member states following the EU-Turkey agreement found that majorities in each country disapproved of how the EU was dealing with the refugee issue.
With thousands of new asylum requests through the first part of 2016, along with over 1 million in 2015, first-instance decisions can now take several months or up to a year to process. These delays do not include appeals asylum seekers may make after a negative first-time decision. Appeals can take up to an additional year to be adjudicated.
The number of European Union member states has grown since 1985, with significant increases in 1995, 2004 and 2007. Although data for some countries in some years are missing (see Appendix A), historical estimates of asylum seekers in this report include all 30 countries (EU-28 plus Norway and Switzerland), even though many of these countries were not considered part of the EU until recent years. At the time of the publication of this report, the UK was still part of the European Union, even though the country voted on June 23, 2016, to leave the EU.
You can see visible light because the visible-light photons travel in small waves, and your eye is small. But because radio waves are big, your eye would need to be big to detect them. So while regular telescopes are a few inches or feet across, radio telescopes are much larger. The Green Bank Telescope in West Virginia is more than 300 ft wide and can be seen in Figure 3. The Arecibo Telescope in the jungle in Puerto Rico is almost 1,000 ft across. They look like gigantic versions of satellite TV dishes, but they work like regular telescopes.
When astronomers look for radio waves, they see different objects and events than they see when they look for visible light. Places that seem dark to our eyes, or to regular telescopes, burn bright in radio waves. Places where stars form, for example, are full of dust. That dust blocks the light from getting to us, so the whole area looks like a black blob. But when astronomer turns radio telescopes to that spot, they can see straight through the dust: they can see a star being born.
Radio telescopes show the secrets of the nearest star, too. The light we see from the Sun comes from near the surface, which is about 9,000oF. But above the surface, the temperature reaches 100,000oF. Radio telescopes help us learn more about these hot parts, which send out radio waves.
Massive objects like these black holes warp the fabric of space, called space-time. Imagine setting a bowling ball, which weighs a lot, on a trampoline. The trampoline sags down. Weighty stuff in space makes space-time sag just like the trampoline. When radio waves coming from distant galaxies travel over that sag to get to Earth, the shape acts just like the shape of a magnifying glass on Earth: telescopes then see a bigger, brighter picture of the distant galaxy.
Energy density distribution of shaped waves inside scattering media mapped onto a complete set of diffusion modes. / Ojambati, Oluwafemi Stephen; Mosk, Allard; Vellekoop, Ivo Micha et al.
N2 - We show that the spatial distribution of the energy density of optimally shaped waves inside a scattering medium can be described by considering only a few of the lowest eigenfunctions of the diffusion equation. Taking into account only the fundamental eigenfunction, the total internal energy inside the sample is underestimated by only 2%. The spatial distribution of the shaped energy density is very similar to the fundamental eigenfunction, up to a cosine distance of about 0.01. We obtained the energy density inside a quasi-1D disordered waveguide by numerical calculation of the joined scattering matrix. Computing the transmission-averaged energy density over all transmission channels yields the ensemble averaged energy density of shaped waves. From the averaged energy density obtained, we reconstruct its spatial distribution using the eigenfunctions of the diffusion equation. The results from our study have exciting applications in controlled biomedical imaging, efficient light harvesting in solar cells, enhanced energy conversion in solid-state lighting, and low threshold random lasers.
AB - We show that the spatial distribution of the energy density of optimally shaped waves inside a scattering medium can be described by considering only a few of the lowest eigenfunctions of the diffusion equation. Taking into account only the fundamental eigenfunction, the total internal energy inside the sample is underestimated by only 2%. The spatial distribution of the shaped energy density is very similar to the fundamental eigenfunction, up to a cosine distance of about 0.01. We obtained the energy density inside a quasi-1D disordered waveguide by numerical calculation of the joined scattering matrix. Computing the transmission-averaged energy density over all transmission channels yields the ensemble averaged energy density of shaped waves. From the averaged energy density obtained, we reconstruct its spatial distribution using the eigenfunctions of the diffusion equation. The results from our study have exciting applications in controlled biomedical imaging, efficient light harvesting in solar cells, enhanced energy conversion in solid-state lighting, and low threshold random lasers.
For more information on the forcing mechanisms which led to the development of the present 2015/2016 El Niño, please refer to our previous story, "El Niño Watch: A Comparison of Current Conditions with Past Events." Visit the Jet Propulsion Laboratory's Center for Climate Sciences for current El Niño observations from various NASA Earth observing satellites.
There are some atypical storm patterns related to the present El Niño, as noted in the above Surfline article, involving weather systems that are more tropical in nature when it is well into the winter storm season. One example is Hurricane Pali, which reached Category 2 status as it was drifting near the Intertropical Convergence Zone (ITCZ) in the Central Pacific between the Hawaiian islands and the Marshall Islands from the 7th through the 13th of January 2016. This marks the first time in historical records that a hurricane formed this early in the calendar year in the Central Pacific region (see Figure 4). Official reports on Hurricane Pali, as well as other Central Pacific tropical storms, may be obtained from the Central Pacific Hurricane Center. The strength and fetch of wind generated by Pali was enough to send substantial s
This anomaly translates to increased size and quality of surf in Hawaii and on the entire U.S. West Coast. So far in January 2016, the North Pacific has seen a back to back stream of large, swell-producing storms traveling from West to East. February looks to be no different based on long range forecast models. In conclusion, based on historical comparisons between averages and El Niño months during the 1997/1998 and 1982/1983 events (e.g., Figure 5) and the conditions at present (Figure 6), surfers across the Pacific are in for a good to epic year in 2016. 2ff7e9595c
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