The Influence of Water Currents on Movement Patterns on Sand in the Crown-of-Thorns Seastar (Acanthaster cf. solaris)

Outbreaks of the coral-eating crown-of-thorns seastar (Acanthaster cf. solaris) threaten coral reefs of the Indo-Pacific. Movement patterns may play an important role in the spread of outbreak populations, but studies investigating adult movement behavior are scarce. It remains unknown if Acanthaster cf. solaris orientates in inter-reef areas using chemical, visual, or mechanical cues (e.g., water currents) or which trigger is used for the onset of movement. We investigated the movement patterns of adult starved, fed, and blinded A. cf. solaris on sand at two sites with different unidirectional water current strengths. We found that the movement direction of the seastars in strong currents was downstream, whereas movement in weaker currents was random and independent from the current direction. However, the directionality of movement was consistently high, independent of the nutritional state, its visual abilities, or current strength. Starved A. cf. solaris started to move significantly faster compared to fed individuals. Therefore, starvation might trigger the onset of movement. Our findings indicate that navigation of A. cf. solaris in inter-reef areas is inefficient. Movements between reefs may be random or current-dependent and finding a new reef from a distance subject to chance, unless it is only few meters away

The role of vision for navigation in the crown-of-thorns seastar, Acanthaster planci

Coral reefs all over the Indo-Pacific suffer from substantial damage caused by the crown-of-thorns seastar Acanthaster planci, a voracious predator that moves on and between reefs to seek out its coral prey. Chemoreception is thought to guide A. planci. As vision was recently introduced as another sense involved in seastar navigation, we investigated the potential role of vision for navigation in A. planci. We estimated the spatial resolution and visual field of the compound eye using histological sections and morphometric measurements. Field experiments in a semi-controlled environment revealed that vision in A. planci aids in finding reef structures at a distance of at least 5 m, whereas chemoreception seems to be effective only at very short distances. Hence, vision outweighs chemoreception at intermediate distances. A. planci might use vision to navigate between reef structures and to locate coral prey, therefore improving foraging efficiency, especially when multidirectional currents and omnipresent chemical cues on the reef hamper chemoreception

CPU to FPGA Power Covert Channel in FPGA-SoCs

FPGA-SoCs are a popular platform for accelerating a wide range of applications due to their performance and flexibility. From a security point of view, these systems have been shown to be vulnerable to various attacks, especially side-channel attacks where an attacker can obtain the secret key of a cryptographic algorithm via laboratory mea- surement equipment or even remotely with sensors implemented inside the FPGA logic itself. Fortunately, a variety of countermeasures on the algorithmic level have been proposed to mitigate this threat. Beyond side- channel attacks, covert channels constitute another threat which enables communication through a hidden channel. In this work, we demonstrate the possibility of implementing a covert channel between the CPU and an FPGA by modulating the usage of the Power Distribution Network. We show that this resource is especially vulnerable since it can be easily controlled and observed, resulting in a stealthy communication and a high transmission data rate. The power usage is modulated using simple and inconspicuous instructions executed on the CPU. Additionally, we use Time-to-Digital Converter sensors to observe these power variations. The sensor circuits are programmed into the FPGA fabric using only standard logic components. Our covert channel achieves a transmission rate of up to 16.7 kbit/s combined with an error rate of 2.3%. Besides a good transmission quality, our covert channel is also stealthy and can be used as an activation function for a hardware trojan

High-Resolution EM Attacks Against Leakage-Resilient PRFs Explained - And An Improved Construction

Achieving side-channel resistance through Leakage Resilience (LR) is highly relevant for embedded devices where requirements of other countermeasures such as e.g. high quality random numbers are hard to guarantee. The main challenge of LR lays in the initialization of a secret pseudorandom state from a long-term key and public input. Leakage-Resilient Pseudo-Random Functions (LR-PRFs) aim at solving this by bounding side-channel leakage to non-exploitable levels through frequent re-keying. Medwed et al. recently presented an improved construction at ASIACRYPT 2016 which uses \u27unknown-inputs\u27 in addition to limited data complexity and correlated algorithmic noise from parallel S-boxes. However, a subsequent investigation uncovered a vulnerability to high-precision EM analysis on FPGA. In this paper, we follow up on the reasons why such attacks succeed on FPGAs. We find that in addition to the high spatial resolution, it is mainly the high temporal resolution which leads to the reduction of algorithmic noise from parallel S-boxes. While spatial resolution is less threatening for smaller technologies than the used FPGA, temporal resolution will likely remain an issue since balancing the timing behavior of signals in the nanosecond range seems infeasible today. Nonetheless, we present an improvement of the ASIACRYPT 2016 construction to effectively protect against EM attacks with such high spatial and high temporal resolution. We carefully introduce additional key entropy into the LR-PRF construction to achieve a high remaining security level even when implemented on FPGAs. With this improvement, we finally achieve side-channel secure LR-PRFs in a practical and simple way under verifiable empirical assumptions

Diversity patterns and community structure of the ground-associated macrofauna along the beach-inland transition zone of small tropical islands

Biodiversity follows distinct and observable patterns. Where two systems meet, biodiversity is often increased, due to overlapping occurrence ranges and the presence of specialized species that can tolerate the dynamic conditions of the transition zone. One of the most pronounced transition zones occurs at shores, where oceans and terrestrial habitat collide, forming the shore–inland transition zone. The relevance of this transition zone in shaping a system’s community structure is particularly pronounced on small islands due to their high shore-to-inland-area ratio. However, the community structure of insular faunas along this transition zone is unknown. Here, we investigated the diversity patterns along the beach–inland transition zone of small islands and tested the hypothesis that species diversity increases toward the transition zone where beach and interior habitat meet. By measuring environmental parameters, resource availability, and ground-associated macrofauna diversity along transects running across the beach–inland transition zone, we show that a gradual change in species composition from beach to the inland exists, but neither taxa richness, diversity, nor overall abundance changed significantly. These findings offer important insights into insular community structure at the transition zone from sea to land that are relevant to better understand the dynamic and unique characteristics of insular ecosystems

A method for continuous239Pu determinations in Arctic and Antarctic ice cores

Atmospheric nuclear weapons testing (NWT) resulted in the injection of plutonium (Pu) into the atmosphere and subsequent global deposition. We present a new method for continuous semi-quantitative measurement of 239Pu in ice cores, which was used to develop annual records of fallout from NWT in ten ice cores from Greenland and Antarctica. The 239Pu was measured directly using an Inductively Coupled Plasma – Sector Field Mass Spectrometer, thereby reducing analysis time and increasing depth-resolution with respect to previous methods. To validate this method, we compared our one year averaged results to published 239Pu records and other records of NWT. The 239Pu profiles from four Arctic ice cores reflected global trends in NWT and were in agreement with discrete Pu profiles from lower latitude ice cores. The 239Pu measurements in the Antarctic ice cores tracked low latitude NWT, consistent with previously published discrete records from Antarctica. Advantages of the continuous 239Pu measurement method are (1) reduced sample preparation and analysis time; (2) no requirement for additional ice samples for NWT fallout determinations; (3) measurements are exactly co-registered with all other chemical, elemental, isotopic, and gas measurements from the continuous analytical system; and (4) the long half-life means the 239Pu record is stable through time

Specific protein antigen delivery to human Langerhans cells in intact skin

Immune modulating therapies and vaccines are in high demand, not least to the recent global spread of SARS-CoV2. To achieve efficient activation of the immune system, professional antigen presenting cells have proven to be key coordinators of such responses. Especially targeted approaches, actively directing antigens to specialized dendritic cells, promise to be more effective and accompanied by reduced payload due to less off-target effects. Although antibody and glycan-based targeting of receptors on dendritic cells have been employed, these are often expensive and time-consuming to manufacture or lack sufficient specificity. Thus, we applied a small-molecule ligand that specifically binds Langerin, a hallmark receptor on Langerhans cells, conjugated to a model protein antigen. Via microneedle injection, this construct was intradermally administered into intact human skin explants, selectively loading Langerhans cells in the epidermis. The ligand-mediated cellular uptake outpaces protein degradation resulting in intact antigen delivery. Due to the pivotal role of Langerhans cells in induction of immune responses, this approach of antigen-targeting of tissue-resident immune cells offers a novel way to deliver highly effective vaccines with minimally invasive administration

Allochthonous resources are less important for faunal communities on highly productive, small tropical islands

Abstract Ecosystems are interconnected by energy fluxes that provide resources for the inhabiting organisms along the transition zone. Especially where in situ resources are scarce, ecosystems can become highly dependent on external resources. The dependency on external input becomes less pronounced in systems with elevated in situ production, where only consumer species close to the site of external input remain subsidized, whereas species distant to the input site rely on the in situ production of the ecosystem. It is largely unclear though if this pattern is consistent over different consumer species and trophic levels in one ecosystem, and whether consumer species that occur both proximate to and at a distance from the input site differ in their dependency on external resource inputs between sites. Using stable isotope analysis, we investigated the dependency on external marine input for common ground‐associated consumer taxa on small tropical islands with high in situ production. We show that marine input is only relevant for strict beach‐dwelling taxa, while the terrestrial vegetation is the main carbon source for inland‐dwelling taxa. Consumer species that occurred both close (beach) and distant (inland) to the site of marine input showed similar proportions of marine input in their diets. This supports earlier findings that the relevance of external resources becomes limited to species close to the input site in systems with sufficient in situ production. However, it also indicates that the relevance of external input is also species‐dependent, as consumers occurring close and distant to the input site depended equally strong or weak on marine input