Transient Response of the Gulf Stream to Multiple Hurricanes in 2017

Autonomous underwater glider observations collected during and after 2017 Hurricanes Irma, Jose, and Maria show two types of transient response within the Gulf Stream. First, anomalously fresh water observed near the surface and within the core of the Gulf Stream offshore of the Carolinas likely resulted from Irma's rainfall being entrained into the Loop Current-Gulf Stream system. Second, Gulf Stream volume transport was reduced by as much as 40% for about 2 weeks following Jose and Maria. The transport reduction had both barotropic and depth-dependent characteristics. Correlations between transport through the Florida Straits and reanalysis winds suggest that both local winds in the Florida Straits and winds over the Gulf Stream farther downstream may have contributed to the transport reduction. To clarify the underlying dynamics, additional analyses using numerical models that capture the Gulf Stream's transient response to multiple tropical cyclones passing nearby in a short period are needed

Instabilities of waves in nonlinear disordered media

We develop a self-consistent theory of temporal fluctuations of a speckle pattern resulting from the multiple scattering of a coherent wave in a weakly nonlinear disordered medium. The speckle pattern is shown to become unstable if the nonlinearity exceeds a threshold value. The instability is due to a feedback provided by the multiple scattering and manifests itself in spontaneous fluctuations of the scattered intensity. The development of instability is independent of the sign of nonlinearity.Comment: 6 pages, 2 PostScript figures, accepted to Phys. Rev. Let

Autonomous and Lagrangian ocean observations for Atlantic tropical cyclone studies and forecasts

Author Posting. © The Oceanography Society, 2017. This article is posted here by permission of The Oceanography Society for personal use, not for redistribution. The definitive version was published in Oceanography 30, no. 2 (2017): 92–103, doi:10.5670/oceanog.2017.227.The tropical Atlantic basin is one of seven global regions where tropical cyclones (TCs) commonly originate, intensify, and affect highly populated coastal areas. Under appropriate atmospheric conditions, TC intensification can be linked to upper-ocean properties. Errors in Atlantic TC intensification forecasts have not been significantly reduced during the last 25 years. The combined use of in situ and satellite observations, particularly of temperature and salinity ahead of TCs, has the potential to improve the representation of the ocean, more accurately initialize hurricane intensity forecast models, and identify areas where TCs may intensify. However, a sustained in situ ocean observing system in the tropical North Atlantic Ocean and Caribbean Sea dedicated to measuring subsurface temperature, salinity, and density fields in support of TC intensity studies and forecasts has yet to be designed and implemented. Autonomous and Lagrangian platforms and sensors offer cost-effective opportunities to accomplish this objective. Here, we highlight recent efforts to use autonomous platforms and sensors, including surface drifters, profiling floats, underwater gliders, and dropsondes, to better understand air-sea processes during high-wind events, particularly those geared toward improving hurricane intensity forecasts. Real-time data availability is key for assimilation into numerical weather forecast models.The NOAA/AOML component of this work was originally funded by the Disaster Relief Appropriations Act of 2013, also known as the Sandy Supplemental, and is currently funded through NOAA research grant NA14OAR4830103 by AOML and CARICOOS, as well as NOAA’s Integrated Ocean Observing System (IOOS). The TEMPESTS component of this work is supported by NOAA through the Cooperative Institute for the North Atlantic Region (NA13OAR4830233) with additional analysis support from the WHOI Summer Student Fellowship Program, Nortek Student Equipment Grant, and the Rutgers University Teledyne Webb Graduate Student Fellowship Program. The drifter component of this work is funded through NOAA grant NA15OAR4320071(11.432) in support of the Global Drifter Program

Wax crystallization from solution in hierarchical morphology templated by random poly(ethylene-co-butene) self-assemblies

Semicrystalline poly(ethylene-butene) (PEB-n) random copolymers can modify the sizes of wax crystals and thus improve the viscoelastic properties of crude oil and middle distillate fuels at low temperatures. The wax-copolymer interactions in solution are rather complex and not fully understood. When the copolymer self-assembles at temperatures higher than the wax cloud point a hierarchy of morphologies templated by the primordial polymer structure evolves with decreasing temperature. Multilevel structures showing characteristic sizes from 10 mu m to 1 nm are formed upon cooling in solutions of semicrystalline PEB-7.5 copolymers and in wax containing mixed solutions. The coplymer structures with the different wax molecules were evaluated by three SANS techniques (conventional SANS, focusing-SANS and ultra-SANS) and contrast matching. Complementary microscopy techniques allowed a direct visualization of these structures in real space

mXSS attacks: Attacking well-secured web-applications by using innerHTML mutations

Back in 2007, Hasegawa discovered a novel Cross-Site Scripting (XSS) vector based on the mistreatment of the backtick character in a single browser implementation. This initially looked like an implementation error that could easily be fixed. Instead, as this paper shows, it was the first example of a new class of XSS vectors, the class of mutation-based XSS (mXSS) vectors, which may occur in innerHTML and related properties. mXSS affects all three major browser families: IE, Firefox, and Chrome. We were able to place stored mXSS vectors in high-profile applications like Yahoo! Mail, Rediff Mail, OpenExchange, Zimbra, Roundcube, and several commercial products. mXSS vectors bypassed widely deployed server-side XSS protection techniques (like HTML Purifier, kses, htmlLawed, Blueprint and Google Caja), client-side filters (XSS Auditor, IE XSS Filter), Web Application Firewall (WAF) systems, as well as Intrusion Detection and Intrusion Prevention Systems (IDS/IPS). We describe a scenario in which seemingly immune entities are being rendered prone to an attack based on the behavior of an involved party, in our case the browser. Moreover, it proves very difficult to mitigate these attacks: In browser implementations, mXSS is closely related to performance enhancements applied to the HTML code before rendering; in server side filters, strict filter rules would break many web applications since the mXSS vectors presented in this paper are harmless when sent to the browser. This paper introduces and discusses a set of seven different subclasses of mXSS attacks, among which only one was previously known. The work evaluates the attack surface, showcases examples of vulnerable high-profile applications, and provides a set of practicable and low-overhead solutions to defend against these kinds of attacks

A new two-dimensional scintillation detector system for small angle neutron scattering experiments

A new two-dimensional position-sensitive detector system for small-angle neutron scattering experiments is under development. It is based on a 60 x 60 cm(2) large Li-6-glass scintillator for the neutron capture and dispersion of the emitted light on an array of photomultiplier tubes for the derivation of the event position. For subthermal neutrons of 8 Angstrom, an efficiency of 96% and a spatial resolution of 8 mm are to be achieved. Major improvements have been made in the signal- and data-processing branch, which aims at an electronical dead time of 1 mus. A fast digitalization method using free-running analog-to-digital converters for each photomultiplier combined with field-programmable gate arrays for a parallel event detection in all channels has been applied. A subsequent farm of up to 16 floating-point digital signal processors is used to provide enough computing power for an improved reconstruction of the event position according to a maximum likelihood method