Distinct difference configurations: multihop paths and key predistribution in sensor networks

A distinct difference configuration is a set of points in Z2 with the property that the vectors (difference vectors) connecting any two of the points are all distinct. Many specific examples of these configurations have been previously studied: the class of distinct difference configurations includes both Costas arrays and sonar sequences, for example. Motivated by an application of these structures in key predistribution for wireless sensor networks, we define the k-hop coverage of a distinct difference configuration to be the number of distinct vectors that can be expressed as the sum of k or fewer difference vectors. This is an important parameter when distinct difference configurations are used in the wireless sensor application, as this parameter describes the density of nodes that can be reached by a short secure path in the network. We provide upper and lower bounds for the k-hop coverage of a distinct difference configuration with m points, and exploit a connection with Bh sequences to construct configurations with maximal k-hop coverage. We also construct distinct difference configurations that enable all small vectors to be expressed as the sum of two of the difference vectors of the configuration, an important task for local secure connectivity in the application

Two-dimensional patterns with distinct differences; constructions, bounds, and maximal anticodes

A two-dimensional (2-D) grid with dots is called a configuration with distinct differences if any two lines which connect two dots are distinct either in their length or in their slope. These configurations are known to have many applications such as radar, sonar, physical alignment, and time-position synchronization. Rather than restricting dots to lie in a square or rectangle, as previously studied, we restrict the maximum distance between dots of the configuration; the motivation for this is a new application of such configurations to key distribution in wireless sensor networks. We consider configurations in the hexagonal grid as well as in the traditional square grid, with distances measured both in the Euclidean metric, and in the Manhattan or hexagonal metrics. We note that these configurations are confined inside maximal anticodes in the corresponding grid. We classify maximal anticodes for each diameter in each grid. We present upper bounds on the number of dots in a pattern with distinct differences contained in these maximal anticodes. Our bounds settle (in the negative) a question of Golomb and Taylor on the existence of honeycomb arrays of arbitrarily large size. We present constructions and lower bounds on the number of dots in configurations with distinct differences contained in various 2-D shapes (such as anticodes) by considering periodic configurations with distinct differences in the square grid

Progeny of high muscling sires have reduced muscle response to adrenaline in sheep

This study investigated the impact of variation in Australian sheep breeding values (ASBVs) for yearling eye muscle depth (YEMD) within Merino and Poll Dorset sires on intermediary metabolism of progeny. Specifically, the change in the blood concentrations of lactate, non-esterified fatty acids (NEFA) and glucose in response to administration of an exogenous dose of adrenaline was studied. The experiment used 20 Merino and Merino cross Poll Dorset mixed sex sheep. The sires were selected across a range of YEMD ASBVs. The sheep were fitted with indwelling jugular catheters and administered seven levels of adrenaline over a period of 4 days at 4 months of age (0.1, 0.2, 0.4, 0.6, 0.9, 1.2 and 1.6 mu g/kg liveweight (LW)) and 16 months of age (0.1, 0.2, 0.6, 1.2, 1.8, 2.4 and 3.0 mu g/kg LW). A total of 16 blood samples were collected between -30 min and 130 min relative to administration of the adrenaline challenge and were later measured for the plasma concentrations of lactate, NEFA and glucose. These data were then used to calculate the time to maximum substrate concentration, the maximum concentration and the area under curve (AUC) between 0 and 10 min, thus reflecting the substrate's response to exogenous adrenaline. Selection for muscling led to decreased muscle response due to adrenaline, as indicated by lower maximum concentrations and AUC for lactate. The muscles' response to adrenaline was more prominent at 16 months of age than at 4 months of age. Thus, animals selected for increased muscling have lower levels of glycogenolysis in situations where endogenous adrenaline levels are increased like pre-slaughter. This may minimise the risk of poor meat quality in these animals, as they will express higher muscle concentrations of glycogen at slaughter. Adipose tissue was more sensitive to adrenaline in young lambs from high YEMD sires. This shows that high muscled growing lambs utilise their adipose tissue deposits in times of stress to produce energy. This may explain the phenotypic leanness of these animals. Blood glucose levels that are indicative of liver response to adrenaline decreased with selection for muscling. This response may indicate a potential limiting of glucose that is available within animals selected for muscling, leanness and growth for brain function

Molecular beam epitaxy of highly mismatched N-rich GaNSb and InNAs alloys

GaN materials alloyed with group V anions form the so-called highly mismatched alloys (HMAs). Recently, the authors succeeded in growing N-rich GaNAs and GaNBi alloys over a large composition range by plasma-assisted molecular beam epitaxy (PA-MBE). Here, they present first results on PA-MBE growth and properties of N-rich GaNSb and InNAs alloys and compare these with GaNAs and GaNBi alloys. The enhanced incorporation of As and Sb was achieved by growing the layers at extremely low growth temperatures. Although layers become amorphous for high As, Sb, and Bi content, optical absorption measurements show a progressive shift of the optical absorption edge to lower energy. The large band gap range and controllable conduction and valence band positions of these HMAs make them promising materials for efficient solar energy conversion devices

Neighborhood disadvantage across the transition from adolescence to adulthood and risk of metabolic syndrome

This study investigates the association between neighborhood disadvantage from adolescence to young adulthood and metabolic syndrome using a life course epidemiology framework. Data from the United States-based National Longitudinal Study of Adolescent to Adult Health (n = 9500)and a structural equation modeling approach were used to test neighborhood disadvantage across adolescence, emerging adulthood, and young adulthood in relation to metabolic syndrome. Adolescent neighborhood disadvantage was directly associated with metabolic syndrome in young adulthood. Evidence supporting an indirect association between adolescent neighborhood disadvantage and adult metabolic syndrome was not supported. Efforts to improve cardiometabolic health may benefit from strategies earlier in life

Invisible Higgs Boson Decay into Massive Neutrinos of 4th Generation

Results from several recent experiments provide inderect evidences in the favor of existence of a 4th generation neutrino. Such a neutrino of mass about 50 GeV is compatible with current physical and astrophysical constraints and well motivated in the framework of superstring phenomenology. If sufficiently stable the existence of such a neutrino leads to the drastic change of Higgs boson physics: for a wide range of Higgs boson masses the dominant mode of Higgs boson decay is invisible and the branching ratios for the most promising modes of Higgs boson search are significantly reduced. The proper strategy of Higgs boson searches in such a framework is discussed. It is shown that in the same framework the absence of a signal in the search for invisible Higgs boson decay at LEP means either that the mass of Higgs is greater than 113.5 GeV or that the mass difference between the Higgs mass and doubled neutrino mass is small.Comment: 8 pages, 2 figure

Demonstration of an application-aware resilience mechanism for dynamic heterogeneous networks

Business uptake of IP-centric services has been strong and necessitates reliable, highly-available, high-quality Internet access. Real time services such as mission-critical broadcast video, video conferencing and voice over IP (VoIP) have low tolerance for short-term network outages. However, applications like bulk data transfer maybe much more resistant to such events. Many different network resilience mechanisms can be offered to customers by service providers allowing for slower (or faster) recovery of network access. Yet in current networks, offering different resilience mechanisms for different services is complicated, involving multiple interfaces. In this work, we propose that services be offered differentiated resilience levels within a single physical interface. In order to do so, an application aware resilience mechanism is proposed based on using the supplementary IP header type of service (ToS) field to define arbitrary values in addition to the 6-bit differentiated services code points (DSCP). This mechanism allows different levels of resilience to be assigned to applications such as VoIP for emergency and mission critical services

Power spectrum of many impurities in a d-wave superconductor

Recently the structure of the measured local density of states power spectrum of a small area of the \BSCCO (BSCCO) surface has been interpreted in terms of peaks at an "octet" of scattering wave vectors determined assuming weak, noninterfering scattering centers. Using analytical arguments and numerical solutions of the Bogoliubov-de Gennes equations, we discuss how the interference between many impurities in a d-wave superconductor alters this scenario. We propose that the peaks observed in the power spectrum are not the features identified in the simpler analyses, but rather "background" structures which disperse along with the octet vectors. We further consider how our results constrain the form of the actual disorder potential found in this material.Comment: 5 pages.2 figure