A Point-Set Compression Heuristic for Fiber-Based Certificates of Authenticity

This paper discusses the certificates of authenticity (COAs) that are digitally signed physical objects with a unique random structure. The random structure of a fiber-based COA relies on the fact that if one end-point of a fiber is exposed to light, the other one illuminates. A COA instance is compressed and then combined with the cryptographic hash. Each COA instance is associated with message recovery using issuer's public key. The key optimization goal in this system is to compress as much of the entropy of COA's random structure. The key parameter of the point-compression problem is: computing the COA model, encoding pixel-to-pixel vectors, and heuristically solving the asymmetric traveling salesman problem. The encoding can be done using arithmetic vector. A heuristic is developed that aims at solving point-compression problem and the compression rate is obtained much better.

A certificate of authenticity (COA) is an inexpensive physical object that has a random and unique multidimensional structure S which is hard to near-exactly replicate. An inexpensive device should be able to scan object’s physical “fingerprint,” i.e., obtain a set of features in the form of a multidimensional signal x that pseudo-uniquely represents S. For a given “fingerprint” x and without access to S, it should be computationally difficult to construct an object of fixed dimensions with a “fingerprint” y which is at a bounded proximity from x according to a standardized distance metric. We introduce objects that behave as COAs in the electromagnetic field. The objective is to complement RFIDs so that they are physically, not only digitally, unique and hard to replicate. By enabling this feature, we introduce a tag whose information about the product can be read within a relative far-field, and also whose authenticity can be reliably verified within its near-field. In order to counterfeit a tag, the adversary faces two difficulties – a computational and a manufacturing one. The computational difficulty stems from the hardness of solving linear inverse problems in the electromagnetic field. In order to create an actual tag, the adversary must also manufacture a multidimensional object with a specific three-dimensional topology, dielectric properties, and conductivity.

Summary Reproductive effort (0.14) and the cost of reproduction (-0.09) of 1-year-old bay scallops, Argopecten irradians concentricus, are greater than for longer-lived iteropar- ous mollusc species of the same age but less than for semelparous species. This agrees with theoretical predictions on the relationships between longetivity, reproductive effort, and residual reproductive value for the maximization of reproductive tactics. For a Florida population (representing the southern distributional limit of the species), the production of 2.8 kJ of gametes requires the catabolism of 19.9 kJ of somatic energy reserves, for a 7.1 cost ratio. Reproductive costs such as these are not included in estimates of reproductive effort and are not considered in energetic terms in cost of reproduction indexes. The relatively high reproductive effort enables A. irradians concentricus to maintain a stable population from year to year at this location in spite of a relatively high cost of reproduction (which may in turn accelerate the senescence of individuals within this population).

In the new colony of rhesus macaques at Madingley, no overall difference was found in the length of the inter-birth intervals following the birth of male and female infants. The lack of overall differences in the reproductive costs of raising sons and daughters, was associated with an absence of differences in suckling patterns between male and female infants. It is argued that similar pre-weaning investment in sons and daughters may be related to the presence of similar growth rates for male and female infants during the first year of life. Most high ranking mothers reproduced in consecutive years, while low ranking mothers were more likely to experience two year long inter-birth intervals. Further analyses revealed that this difference was mainly due to the fact that low ranking mothers always failed to reproduce the year after raising a daughter. Thus, no difference was found in the length of inter-birth intervals between high ranking mothers with infants of either sex and low ranking mothers with sons. The daughters of low ranking females suckled more frequently and making more nipple contacts per bout, and such high nipple stimulation was responsible for the reproductive inhibition experienced by their mothers. It is suggested that the high degrees of nipple stimulation may have been a consequence of the high levels of aggression that low ranking females with daughters have been shown to receive, since their mothers could have allowed frequent ventro-ventral contact in order to protect them. Given that low ranking mothers find daughters reproductively costly to raise, it is possible that such high reproductive costs have played a significant role in the evolution of sex ratio biases at birth. As in other primate populations, in this colony low ranking females produced a greater proportion of sons than daughters, and high ranking mothers showed the opposite trend.

Life-history models are based on the assumption that there is a trade-off between allocation to reproduction and allocation to other functions. We used a field experiment to ask if seed production reduces subsequent survival, vegetative growth or flowering in two forest populations of Geranium maculatum in Illinois, USA, and in one meadow and one forest population of G. sylvaticum in northern Sweden. In each population, one set of plants was prevented from setting seed (stigmas were excised at flower opening) and a second set of plants was allowed to mature seeds naturally. Reproductive effort in control plants (estimated as the seed-mass to leaf-mass ratio) was 0.06 ? 0.01 (Mean ? SE) and 0.08 ? 0.01 in the two G. maculatum populations, and 0.40 ? 0.04 and 0.06 ? 0.01 in the two G. sylvaticum populations. Seed production was associated with a reduced probability of flowering in the subsequent year in the G. sylvaticum populations, but not in the G. maculatum populations. There were no significant differences between treatments in mortality, in the number of leaves produced in the following year, or in the number of flowers produced by floral plants in the second year in any population. Although the seed-mass to leaf-mass ratio of G. sylvaticum control plants was markedly higher in the meadow than in the forest population, this difference in reproductive effort was apparently not associated with a higher cost of reproduction: The proportion of control plants that flowered in the second year was more than twice as high in the meadow population (0.53 vs 0.23), and the response to the experimental prevention of seed production was not stronger in the meadow than in the forest population. The experimental results demonstrate that the seed-mass to leaf-mass ratio need not be a good indicator of the cost of seed production when different species or nonspecific populations in different environments are compared. It is suggested that a greater temporal overlap between reproductive and vegetative growth in G. sylvaticum than in G. maculatum may be important for the difference in reproductive cost between the two species.

Sexes of dioecious species may have dimorphic responses to environmental variation due to differences in resource requirements and reproductive costs. We analyzed the effect of aridity/relative shrub cover, and vicinity to shrub patches on morpho‐chemical traits of sexes of the dioecious perennial grass Poa ligularis in patchy arid ecosystems in northern‐central Patagonia. We hypothesized that sexes of P. ligularis have dimorphic responses in morpho‐chemical traits in relation to the environmental variation induced by aridity/relative shrub cover and vicinity to shrub patches. We selected seven sites across a gradient of increasing aridity and relative shrub cover. We randomly collected 5–10 P. ligularis plants per site registering the sex (female or male) and location with respect to shrub patches (shrub patch or inter‐patch). For each plant, we assessed morpho‐chemical traits (height of the vegetative tillers, length/dry weight/area of blades, specific blade area, nitrogen and soluble phenol concentration in blades). Sexes showed dimorphic responses in height of vegetative tillers, blade length, and blade area with respect to vicinity to shrub patches; and in variation of soluble phenolics in blades in relation to aridity/relative shrub cover. Responses in both sexes were opposite to those expected by aridity, highlighting the role of favorable environments induced by shrub canopies on dimorphic responses of sexes of P. ligularis. Resource‐rich microsites associated with shrub canopies promoted increased plant performance of females with high reproductive costs while resource‐poor open areas, favorable for pollen dispersal, induced improved chemical defenses of males. These results are consistent with the resource availability hypothesis.

Allocation of biomass to sexual and asexual reproduction was studied in a population of a dioicous leafy hepatic species Lophozia silvicola Buch in southern Finland. A higher cost of reproduction in females was indicated in this haploid gametophytic plant. Females of L. silvicola allocated 24% of their biomass to sexual reproduction while males allocated only 2.3%. Sexual reproduction affects vegetative growth by reducing stem length and modifying the branching pattern in gametangial shoots. The average numbers of asexual gemmae present on shoots at the time of study ranged from 800 in females to 1360 in males and 2100 in asexual shoots. Thus, numbers of asexual propagules present on shoots were, on average, almost three times higher in asexual shoots than in females, indicating a possible trade-off between allocation to sexual and asexual reproduction in the three sexual morphs of L. silvicola.

–Yellow perch Perca flavescens were sampled annually in 1973–1988 with bottom trawls in Chequamegon Bay, Lake Superior. Biomass averaged l.6 kg/hectare. Fish l–3 years old made up 64% of the biomass, whereas fish of harvestable size (≥4 years old) made up only 31% of the biomass. Year-class strength was variable among years, but a Ricker recruitment function described the relation between year-class strength and parental stock size, Age-specific mortality increased substantially as fish became sexually mature at age 4, perhaps as a result of energy depletion associated with high reproductive and maintenance costs in a suboptimal thermal environment. Yield-per-recruit analysis indicated that most of the age-specific annual mortality was due to natural causes. Natural mortality, rather than limited recruitment or fishing mortality, was the major factor controlling harvestable stock size, Regardless of the size of a year-class produced, natural mortality greatly reduced its abundance prior to maturity and recruitment to the fishable stock. This high mortality, combined with very slow growth, limits the biomass potential of the harvestable stock, and sustainable yields from this population are therefore low.

ABSTRACTLightweight porous foams have been of particular interest in recent years, since they have a very unique set of properties which can be significantly different from their solid parent materials. These properties arise from their random porous structure which is generated through specialized processing techniques. Their unique structure gives these materials interesting properties which allow them to be used in diverse applications. In particular, highly porous Al foams have been used in aircraft components and sound insulation; however due to the difficulty in processing and the random nature of the foams, they are not well understood and thus have not yet been utilized to their full potential. The objective of this study was to integrate experiments and simulations to determine whether a relationship exists between the relative density (porous density/bulk density) and the mechanical properties of open-cell Al foams. Compression experiments were performed using an Instron Universal Testing Machine (IUTM) on ERG Duocel open-cell Al foams with 5.8% relative density, with compressive loads ranging from 0-6 MPa. Foam models were generated using a combination of an open source code, Voro++, and MATLAB. A Finite Element Method (FEM)-based software, COMSOL Multiphysics 4.3, was used to simulate the mechanical behavior of Al foam structures under compressive loads ranging from 0-2 MPa. From these simulated structures, the maximum von Mises stress, volumetric strain, and other properties were calculated. These simulation results were compared against data from compression experiments. CES EduPack software, a materials design program, was also used to estimate the mechanical properties of open-cell foams for values not available experimentally, and for comparison purposes. This program allowed for accurate prediction of the mechanical properties for a given percent density foam, and also provided a baseline for the Al foam samples tested via the IUTM method. Predicted results from CES EduPack indicate that a 5.8% relative density foam will have a Young’s Modulus of 0.02-0.92 GPa while its compressive strength will be 0.34-3.37 MPa. Overall results revealed a relationship between pores per inch and selected mechanical properties of Al foams. The methods developed in this study can be used to efficiently generate open-cell foam models, and to combine experiments and simulations to calculate structure-property relationships and predict yielding and failure, which may help in the pursuit of simulation-based design of metallic foams. This study can help to improve the current methods of characterizing foams and porous materials, and enhance knowledge about theirproperties for novel applications.

Patterns of male reproductive allocation provide insight into life-history characteristics. The trade-offs associated with resource and female group defence are well-defined. However, less is understood about trade-offs in species that practise scramble-competition polygyny, where successful strategies may favour competitive mate-searching rather than contest competition and fighting. White-tailed deer (Odocoileus virginianus) practise scramble-competition polygyny where solitary males search for and assess receptivity of females scattered across the landscape. Physically mature males are expected to do most of the breeding because of the high energetic costs of reproduction and high social status. However, young males may collectively sire one-third of offspring. To gain a better understanding of trade-offs associated with scramble-competition polygyny, we quantified metrics associated with reproductive effort and success. We quantified changes in body mass of harvested males, energetic costs of locomotion based on movements of GPS radiocollared males and timing of reproduction via temporal genetic parentage assignments. Young males (1.5 and 2.5years old) sired offspring, but their mating success was mainly limited to peak rut, when most females were in oestrus. Furthermore, multiple paternity was common, indicating opportunistic reproduction. Reproductive effort, indexed by body mass loss, was highest in prime-age males (5.5-6.5years old). Surprisingly, young and postprime males also exhibited significant body mass loss, indicative of investment in reproductive effort. Movement rates increased twofold to fourfold during rut as a function of mate search activities, but cost of locomotion would cause only about one-third of observed body mass loss. Because males are capital breeders, we infer most of body mass loss is due to reduced foraging. In scramble-competition polygyny, the repeated location of potential mates and assessment of their oestrous status appear to be important constituents of male mating strategies. Therefore, mating success may be influenced by time management and spatial memory, and not based solely on social dominance. Thus, reproductive effort should be greater for individuals capable of reducing time foraging. For those that cannot, opportunistic mating opportunities may arise when operative adult sex ratios are low. Our analyses reveal valuable insight into the trade-offs associated with scramble-competition polygyny.

Huge breeding aggregations of red-sided garter snakes (Thamnophis sirtalis parietalis) at overwintering dens in Manitoba provide a unique opportunity to identify sources of mortality and to clarify factors that influence a snake's vulnerability to these factors. Comparisons of sexes, body sizes, and body condition of more than 1000 dead snakes versus live animals sampled at the same time reveal significant biases. Three primary sources of mortality were identified. Predation by crows, Corvus brachyrhynchos (590 snakes killed), was focussed mostly on small snakes of both sexes. Crows generally removed the snake's liver and left the carcass, but very small snakes were sometimes brought back to the nest. Suffocation beneath massive piles of other snakes within the den (301 dead animals) involved mostly small males and (to a lesser extent) large females; snakes in poor body condition were particularly vulnerable. Many emaciated snakes (in= 142, mostly females) also died without overt injuries, probably due to depleted energy reserves. These biases in vulnerability are readily interpretable from information on behavioral ecology of the snakes. For example, sex biases in mortality reflect differences in postemergence behavior and locomotor capacity, the greater attractiveness of larger females to males, and the high energy costs of reproduction for females.

Sex-specific differences in animal behavior commonly reflect unique reproductive interests. In the nematode Caenorhabditis elegans, hermaphrodites can reproduce without a mate and thus prioritize feeding to satisfy the high energetic costs of reproduction. However, males, which must mate to reproduce, sacrifice feeding to prioritize mate-searching behavior. Here, we demonstrate that these behavioral differences influence sexual dimorphism at the organelle level; young males raised on a rich food source show constitutive induction of gut tubular lysosomes, a non-canonical lysosome morphology that forms in the gut of hermaphrodites when food is limited or as animals age. We found that constitutive induction of gut tubular lysosomes in males results from self-imposed dietary restriction through DAF-7/TGFβ, which promotes exploratory behavior. In contrast, age-dependent induction of gut tubular lysosomes in hermaphrodites is stimulated by self-fertilization activity. Thus, separate reproductive tradeoffs influence tubular lysosome induction in each sex, potentially supporting different requirements for reproductive success.

As part of our continuing research work, studies toward the self-aggregation behaviour of amphiphilic triblock copolymers containing β-CD-Pluronic F127 polyrotaxane as a central block and hydrophilic brush-like PPEGMA as flanking blocks in aqueous solution were conducted by using dynamic and static light scattering (DLS and SLS) analyses and transmission electron microscopy (TEM). These self-aggregates are characterized by a unique random coil structure. Their hydrodynamic radius (Rh) and radius of gyration (Rg) decrease as the number of the entrapped β-CD molecules increases, while the core of the random coils becomes looser due to the increase of the rigidity and steric hindrance of the brush-like polymer chains. Interestingly, it was observed that the morphology of the aggregates changes greatly after loading amphotericin B (AmB). According to the DLS/SLS and TEM results, it was speculated that a solid sphere is formed, and that the density of spheres increases as the number of entrapped β-CDs increases. For these self-aggregates, as the number of entrapped β-CDs increases, their drug-loading content (DLC) and drug-loading efficiency (DLE) for AmB increases, while their hemolytic activity against rabbit erythrocytes decreases. It appears that the multiple hydrogen-bonding interactions between AmB and the entrapped β-CDs make a significant contribution to the morphology change of the self-aggregates and their high loading capability for AmB.

Computational imaging and light field technology promise to deliver the required six-degrees-of-freedom for natural scenes in virtual reality. Already existing extensions of standardized video coding formats, such as multi-view coding and multi-view plus depth, are the most conventional light field video coding solutions at the moment. The latest multi-view coding format, which is a direct extension of the high efficiency video coding (HEVC) standard, is called multi-view HEVC (or MV-HEVC). MV-HEVC treats each light field view as a separate video sequence, and uses syntax elements similar to standard HEVC for exploiting redundancies between neighboring views. To achieve this, inter-view and temporal prediction schemes are deployed with the aim to find the most optimal trade-off between coding performance and reconstruction quality. The number of possible prediction structures is unlimited and many of them are proposed in the literature. Although some of them are efficient in terms of compression ratio, they complicate random access due to the dependencies on previously decoded pixels or frames. Random access is an important feature in video delivery, and a crucial requirement in multi-view video coding. In this work, we propose and compare different prediction structures for coding light field video using MV-HEVC with a focus on both compression efficiency and random accessibility. Experiments on three different short-baseline light field video sequences show the trade-off between bit-rate and distortion, as well as the average number of decoded views/frames, necessary for displaying any random frame at any time instance. The findings of this work indicate the most appropriate prediction structure depending on the available bandwidth and the required degree of random access.

Current trends, challenges, and perspectives of anti-fogging technology: Surface and material design, fabrication strategies, and beyond