Drivers’ misjudgement of vigilance state during prolonged monotonous daytime driving

To investigate the effects of monotonous daytime driving on vigilance state and particularly the ability to judge this state, a real road driving study was conducted. To objectively assess vigilance state, performance (auditory reaction time) and physiological measures (EEG: alpha spindle rate, P3 amplitude; ECG: heart rate) were recorded continuously. Drivers judged sleepiness, attention to the driving task and monotony retrospectively every 20 min. Results showed that prolonged daytime driving under monotonous conditions leads to a continuous reduction in vigilance. Towards the end of the drive, drivers reported a subjectively improved vigilance state, which was contrary to the continued decrease in vigilance as indicated by all performance and physiological measures. These findings indicate a lack of self-assessment abilities after approximately 3 h of continuous monotonous daytime driving.     

On the Twofold Heck Reaction of 4-vinylcyclohexene and p-dihalobenzenes

The palladium-catalyzed reaction of iodobenzene, p-haloiodobenzenes (p-C₆H₄IX′; X′F, Cl, Br, I) and p-dibromobenzene with 4-vinylcyclohexene (Heck arylation reaction of olefins) was investigated with Pd(OAc)₂/PR₃/Et₃N (R=phenyl, o-tolyl) as a classical catalyst system and with Pd(OAc)₂/KOAc/[BzEt₃N]Cl in DMF as a phase-transfer catalyst system, respectively. Iodobenzene reacts with 4-vinylcyclohexene to give (E)-2-(cyclohex-3-enyl) vinylbenzene ( 1 ) as main product. p-Haloiodobenzenes react with 4-vinylcyclohexene to give (E)-p-halo-2-(cyclohex-3-enyl) vinylbenzene ( 3 ), p-halo-1-(cyclohex-3-enyl) vinylbenzene ( 4 ) or (E,E)-p-bis[2-(cyclohex-3-enyl)vinyl]benzene ( 5 ) depending on the reaction conditions and the catalyst system used. The phase-transfer catalyst system is less reactive but more selective. A reaction temperature of 80°C is necessary for reaction with p-dibromobenzene. The investigations demonstrate the much higher reactivity of the exocyclic double bond of 4-vincylcyclohexene in comparison with the endocyclic one.     

Typology of oases in northern Oman based on Landsat and SRTM imagery and geological survey data

In the desert country of Oman, available water resources are scarce and scattered. In most locations where water can be accessed, this resource is harnessed by oases planted to date palm (Phoenix dactylifera L.) and other crops. So far, little is known about the site-specific conditions determining the existence, size and type of these oases. Remote sensing and image processing techniques were used to locate oases, to characterize the sites according to their topographic, hydrologic and geologic characteristics and to develop a typology of oases in northern Oman.To derive oasis positions, we calculated the Normalized Difference Vegetation Index (NDVI) of Landsat images covering all of northern Oman, subtracted a regional average NDVI, averaged the resulting grid over 3 × 3 pixels and extracted the brightest of five classes determined by a natural breaks algorithm. A buffer of six pixels was added to the oases and the vegetated area as determined by the NDVI was summarized for these polygons. The oasis detection procedure was validated using Google Earth Pro®. Topographic information was derived from data of the Shuttle Radar Topography Mission (SRTM), complemented by digitized Russian military maps, from which mean elevations and elevation range above the oases within a buffer of 2 km were extracted.Water contributing upslope area and distance to streams with catchments of 10 km² and 100 km² were derived from the same elevation model. All geologic formations of northern Oman were assigned to one of 7 groups and tested for influence on vegetation surrounding them. Four such geologic settings were identified and described by categorical variables. All input parameters were used to define oasis types based on cluster analysis.Our algorithm detected 2663 oases in northern Oman, of which 2428 had vegetated areas of more than 0.4 ha, the minimum size for reliable detection. The oases were subdivided into six groups. ‘Plain Oases’ (49% of all oases) lie mostly in the plains east and west of the mountains, and are fed by groundwater flow in Quaternary sediments. ‘Foothill Oases’ (46%) are scattered over the foothills, where they draw their water from groundwater flow that is channeled by rock formations. ‘Mountain Oases’ (3%) and ‘Kawr Oases’ (0.5%) lie in the mountains, close to an unconform boundary between limestones and confining rocks. ‘Drainage Oases’ (0.3%) are the largest oases in northern Oman. They lie close to a drainage channel, which drains the entire area west of the mountains. Finally, ‘Urban Oases’ (1.7%) consist of parks and sporting facilities, which do not lie in conclusive hydrologic settings.     

Effect of selected metal ions on the photocatalytic degradation of bog lake water natural organic matter

Herein we report the photocatalytic degradation of natural organic matter from a bog lake (Lake Hohloh, Black Forest, Germany) in the presence of 0, 5, and 10 μmol L⁻¹ of added Cu²⁺, Mn²⁺, Zn²⁺ and Fe³⁺. The reactions were followed by size exclusion chromatography with organic carbon detection (SEC-DOC) and by measurements of low molecular weight organic acids. Addition of Cu²⁺ had the largest effect of all four studied metals, leading to a retardation in the molecular size changes in NOM: degradation of the larger molecular weight fraction was inhibited leading to reduced production of smaller molecular weight metabolites. Similarly, addition of Cu²⁺ reduced the production of formic and oxalic acids, and reduced the bioavailability of the partially degraded NOM.     

Combination of biological mechanisms for a concept study of a fracture-tolerant bio-inspired ceramic composite material

The biological materials nacre and wood are renowned for their impressive combination of toughness and strength. The key mechanisms of these highly complex structures are crack deflection at weak interfaces, crack bridging, functional gradients and reinforcing elements. These principles were applied to a more fracture-tolerant model material which combined porous stiff ceramic layers, manufactured by freeze casting, infiltrated and bonded by a polymer phase reinforced with fabric layers. In the hybrid composites, crack deflection occurred at the ceramic–fabric interface and the intact fabric layers served as crack-bridging elements. Fabric-reinforced epoxy layers stabilized the fracture behaviour and delayed catastrophic failure of the material. The influence of the different components was analysed by varying the ceramic, fabric and interface properties. More ductile fabrics lead to larger strain to failure and more crack bridging but reduced the composite strength and stiffness after initial cracking. Higher elastic mismatch between the components improved crack deflection and bridging but resulted in deterred load transfer and a lower strength. The stiffness and strength of the ceramic layers influenced the elastic properties of the laminar composite and the initial crack resistance. Flaw tolerance was increased with polymer infiltration. We show with our hybrid ceramic–fabric composite as a bio-inspired concept study how fracture toughness, work of fracture and tolerance for cracking can be tailored when the contributing factors, i.e. the ceramic, the fabric and their interface, are modified.     

The Twin Diffie–Hellman Problem and Applications

We propose a new computational problem called the twin Diffie–Hellman problem. This problem is closely related to the usual (computational) Diffie–Hellman problem and can be used in many of the same cryptographic constructions that are based on the Diffie–Hellman problem. Moreover, the twin Diffie–Hellman problem is at least as hard as the ordinary Diffie–Hellman problem. However, we are able to show that the twin Diffie–Hellman problem remains hard, even in the presence of a decision oracle that recognizes solutions to the problem—this is a feature not enjoyed by the Diffie–Hellman problem, in general. Specifically, we show how to build a certain “trapdoor test” that allows us to effectively answer decision oracle queries for the twin Diffie–Hellman problem without knowing any of the corresponding discrete logarithms. Our new techniques have many applications. As one such application, we present a new variant of ElGamal encryption with very short ciphertexts, and with a very simple and tight security proof, in the random oracle model, under the assumption that the ordinary Diffie–Hellman problem is hard. We present several other applications as well, including a new variant of Diffie and Hellman’s non-interactive key exchange protocol; a new variant of Cramer–Shoup encryption, with a very simple proof in the standard model; a new variant of Boneh–Franklin identity-based encryption, with very short ciphertexts; a more robust version of a password-authenticated key exchange protocol of Abdalla and Pointcheval. This paper was solicted by the Editors-in-Chief as one of the best papers from EUROCRYPT 2008, based on the recommendation of the program committee. Part of this work completed while at CWI. Supported by the research program Sentinels. Supported by NSF award number CNS-0716690.     

Practical Chosen Ciphertext Secure Encryption from Factoring

We propose a practical public-key encryption scheme whose security against chosen-ciphertext attacks can be reduced in the standard model to the assumption that factoring is intractable.