Countdown to Hiroshima

On August 6th, 1945 at approximately 8: 15 a.m. the United States dropped a uranium-based atomic bomb code named Little Boy, on the Japanese city of Hiroshima. The initial explosion, which was the equivalent of 13,000 tons of TNT, killed 45,000 of the largely civilian population instantly. Hundreds of thousands more would die of radiation-related illnesses in the decades to follow and a conservative estimate puts the death toll from the Hiroshima bombing at 200,000. Three days later, the United States would drop another atomic bomb composed of plutonium and code named Fat Boy, on the Japanese city of Nagasaki killing an estimated 70,000 instantly. The bombings led to the unconditional surrender by the Japanese and signified the end of World War II. Although there is significant historical literature detailing the bombing of Hiroshima, there are few multimedia presentations that utilize current computer technology to detail the events of the bombing. Using this technology will provide the user the opportunity to customize their learning experience by enabling them to navigate through the information and learn about the bombing through objective interactive content that uses modern technology to explain the events that led to the atomic bombing of Hiroshima

Water Law in the United States and Brazil--Climate Change & Two Approaches to Emerging Water Poverty

This article examines two of the major water legal regimes in the Americas-that of Brazil and the United States. Both countries have extensive wet and dry regions and both hydro-regimes face a significant threat from global warming. Brazil, for instance, is home to between eight and fifteen percent of the world\u27s fresh water, and its fast-growing economy and population present major challenges in management and allocation. The U.S. also faces major water allocation problems resulting from past settlement policies; unsustainable reclamation projects; and also fast-growing domestic, industrial and agricultural demand. In the United States, water has traditionally been perceived as a renewable and limitless resource, a cultural legacy that has exerted a powerful influence on the nation\u27s common law. Similarly, in Brazil, the notion of water as infinitely abundant drove water policies until the enactment of the Constitution in 1988. In both countries, however, hydrological realities have become impossible to ignore. Their respective laws and jurisprudence have begun shifting toward management and allocation systems that acknowledge the limited nature of the resource. This article surveys the two countries\u27 water regimes, offering a brief history of their evolution and then focusing on the challenges of the present. It examines how the notion of a strong private property right in water is slowly (in the North-American case) and more abruptly (in the Brazilian case) evolving in the face of increased governmental intervention. The article then turns to the challenges of climate change. In Brazil, policies that fail to take desertification into account may threaten the country\u27s energy supply as well as the availability of potable water. In the United States, ignoring climate change in water management and allocation policies could significantly increase the existing water scarcity in the West and exacerbate the growing and already serious water shortage in the traditionally humid East

The Importance of Information and Participation Principles in Environmental Law in Brazil

This article explores the two different kinds of uncertainty, ‘hard’ uncertainty (unknown unknowns) and ‘soft’ uncertainty (known unknowns), in the context of environmental law decision making. First, the authors argue that these different categories should not be treated the same when facing decisions under uncertainty. To deal with these different uncertainties, a tiered risk analysis process is called for, using participatory techniques to turn hard uncertainty into (more manageable) soft uncertainty as well as to increase the legitimacy of environmental decision making, even in cases of hard uncertainty. This methodology can and should apply to all instances of domestic, transnational and international environmental law making. This article applies this conceptual platform to analyze how participatory techniques can be factored in to manage uncertainty by reference to two domestic systems – American and Brazilian environmental law – as well as to international (environmental) law. The authors conclude that managing uncertainty in the environmental decision-making process is a procedural justice tool to promote more balanced and equitable outcomes

Rolling Tachyon Boundary State, Conserved Charges and Two Dimensional String Theory

The boundary state associated with the rolling tachyon solution on an unstable D-brane contains a part that decays exponentially in the asymptotic past and the asymptotic future, but it also contains other parts which either remain constant or grow exponentially in the past or future. We argue that the time dependence of the latter parts is completely determined by the requirement of BRST invariance of the boundary state, and hence they contain information about certain conserved charges in the system. We also examine this in the context of the unstable D0-brane in two dimensional string theory where these conserved charges produce closed string background associated with the discrete states, and show that these charges are in one to one correspondence with the symmetry generators in the matrix model description of this theory.Comment: LaTeX file, 37 pages; v3: references added; v4: minor change

Dynamical SUSY Breaking in Meta-Stable Vacua

Dynamical supersymmetry breaking in a long-lived meta-stable vacuum is a phenomenologically viable possibility. This relatively unexplored avenue leads to many new models of dynamical supersymmetry breaking. Here, we present a surprisingly simple class of models with meta-stable dynamical supersymmetry breaking: N=1 supersymmetric QCD, with massive flavors. Though these theories are strongly coupled, we definitively demonstrate the existence of meta-stable vacua by using the free-magnetic dual. Model building challenges, such as large flavor symmetries and the absence of an R-symmetry, are easily accommodated in these theories. Their simplicity also suggests that broken supersymmetry is generic in supersymmetric field theory and in the landscape of string vacua.Comment: 48 pages, 1 figure, added discussion about the spectrum and some cosmological implication

Dynamical model of the dielectric screening of conjugated polymers

A dynamical model of the dielectric screening of conjugated polymers is introduced and solved using the density matrix renormalization group method. The model consists of a line of quantized dipoles interacting with a polymer chain. The polymer is modelled by the Pariser-Parr-Pople (P-P-P) model. It is found that: (1) Compared to isolated, unscreened single chains, the screened 1Bu- exciton binding energy is typically reduced by ca. 1 eV to just over 1 eV; (2) Covalent (magnon and bi-magnon) states are very weakly screened compared to ionic (exciton) states; (3) Screening of the 1Bu- exciton is closer to the dispersion than solvation limit.Comment: 12 pages, 2 figure

Spacetime Energy Decreases under World-sheet RG Flow

We study renormalization group flows in unitary two dimensional sigma models with asymptotically flat target spaces. Applying an infrared cutoff to the target space, we use the Zamolodchikov c-theorem to demonstrate that the target space ADM energy of the UV fixed point is greater than that of the IR fixed point: spacetime energy decreases under world-sheet RG flow. This result mirrors the well understood decrease of spacetime Bondi energy in the time evolution process of tachyon condensation.Comment: 25 pages, 4 figures, harvma

Catastrophic drought in the Afro-Asian monsoon region during Heinrich Event 1

Between 18,000 and 15,000 years ago, large amounts of ice and meltwater entered the North Atlantic during Heinrich Stadial 1. This caused substantial regional cooling, but major climatic impacts also occurred in the tropics. Here we demonstrate that the height of this stadial, ca. 17-16,000 years ago ("Heinrich Event 1"), coincided with one of the most extreme and widespread megadroughts of the last 50,000 years or more in the Afro-Asian monsoon region, with potentially serious consequences for Paleolithic cultures. Late Quaternary tropical drying commonly is attributed to southward drift of the Intertropical Convergence Zone, but the broad geographic range of the H1 Megadrought suggests that severe, systemic weakening of Afro-Asian rainfall systems also occurred, probably in response to sea surface cooling

Sb-based low-noise avalanche photodiodes

Accurate detection of weak optical signals is a key function for a wide range of applications. A key performance parameter is the receiver signal-to-noise ratio, which depends on the noise of the photodetector and the following electrical circuitry. The circuit noise is typically larger than the noise of photodetectors that do not have internal gain. As a result, a detector that provides signal gain can achieve higher sensitivity. This is accomplished by increasing the photodetector gain until the noise associated with the gain mechanism is comparable to that of the output electrical circuit. For avalanche photodiodes (APDs), the noise that arises from the gain mechanism, impact ionization, increases with gain and depends on the material from which the APD is fabricated. Si APDs have established the state-of-the-art for low-noise gain for the past five decades. Recently, APDs fabricated from two Sb-based III-V compound quaternary materials, AlxIn1-xAsySb1-y and AlxGa1-xAsySb1-y, have achieved noise characteristics comparable to those of Si APDs with the added benefit that they can operate in the short-wave infrared (SWIR) and extended SWIR spectral regions. This paper describes the materials and device characteristics of these APDs and their performance in different spectral regions