An artificial biomineral formed by incorporation of copolymer micelles in calcite crystals

Biominerals exhibit morphologies, hierarchical ordering and properties that invariably surpass those of their synthetic counterparts. A key feature of these materials, which sets them apart from synthetic crystals, is their nanocomposite structure, which derives from intimate association of organic molecules with the mineral host. We here demonstrate the production of artificial biominerals where single crystals of calcite occlude a remarkable 13 wt% of 20 nm anionic diblock copolymer micelles, which act as 'pseudo-proteins'. The synthetic crystals exhibit analogous texture and defect structures to biogenic calcite crystals and are harder than pure calcite. Further, the micelles are specifically adsorbed on {104} faces and undergo a change in shape on incorporation within the crystal lattice. This system provides a unique model for understanding biomineral formation, giving insight into both the mechanism of occlusion of biomacromolecules within single crystals, and the relationship between the macroscopic mechanical properties of a crystal and its microscopic structure.     

Effects of automatic associative activation on explicit and implicit memory tests.

Ss made either a graphemic or a semantic decision concerning word pairs during a study phase. Pair relatedness effects were observed in behavioral measures for the semantic task only, but a physiological measure (event-related potential) showed relatedness effects for both study tasks. Relatedness at study helped subsequent memory for tests involving word generation (fragment completion and cued recall). These effects were independent of those of the level of processing on memory. The results support P. Graf and G. Mandler's (1984) 2-process model of implicit and explicit remembering and demonstrate that automatically activated associations can have significant effects on both types of remembering. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

SOME ASYMPTOTIC PROPERTIES OF THE SAMPLE COVARIANCES OF GAUSSIAN AUTOREGRESSIVE MOVING-AVERAGE PROCESSES

Abstract. The paper deals with the asymptotic variances of the sample covariances of autoregressive moving average processes. Using state-space representations and some matrix Lyapunov equation theory, closed-form expressions are derived for the asymptotic variances of the sample covariances and for the Cramer-Rao bounds on the process covariances. The main results obtained from these expressions are as follows: For ARMA ( p, q ) processes with p ≥ q , the sample covariance of order n is asymptotically efficient if and only if 0 ≤ n ≤ p – q .
For ARMA ( p, q ) processes with p < q , none of the sample covariances is asymptotically efficient.     

Jitter-approximation tradeoff for periodic scheduling

We consider an asymmetric wireless communication setting, where a server periodically broadcasts data items to different mobile clients. The goal is to serve items into a prescribed rate, while minimizing the energy consumption of the mobile users. Abstractly, we are presented with a set of jobs, each with a known execution time and a requested period, and the task is to design a schedule for these jobs over a single shared resource without preemption. Given any solution schedule, its period approximation is the maximal factor by which the average period of a job in the schedule is blown up w.r.t. its requested period, and the jitter is roughly the maximal variability of times between two consecutive occurrences of the same job. Schedules with low jitter allow the mobile devices to save power by having their receivers switched off longer. In this paper we consider a scenario where clients may be willing to settle for non-optimal period approximation so that the jitter is improved. We present a parametric jitter-approximation tradeoff algorithm that allows us to choose various combinations between jitter optimality and period optimality for any given set of jobs. Zvika Brakerski was born in 1981. He received a masters’ degree from Tel-Aviv University in 2002 and is currently employed as an Electric Engineer. Boaz Patt-Shamir received his PhD from MIT in 1995. He was an assistant professor in Northeastern University until 1997, and then he joined the Dept. of Electrical Engineering in Tel Aviv University, where he directs the Computer Communication and Multimedia Laboratory. He held visiting positions at MIT, Boston University, Bellcore, and HP Labs.     

Fast generators for the Diffie-Hellman key agreement protocol and malicious standards

The Diffie-Hellman key agreement protocol is based on taking large powers of a generator of a prime-order cyclic group. Some generators allow faster exponentiation. We show that to a large extent, using the fast generators is as secure as using a randomly chosen generator. On the other hand, we show that if there is some case in which fast generators are less secure, then this could be used by a malicious authority to generate a standard for the Diffie-Hellman key agreement protocol which has a hidden trapdoor.     

Optimal smoothing schedules for real-time streams

We consider the problem of smoothing real-time streams (such as video streams), where the goal is to reproduce a variable-bandwidth stream remotely, while minimizing bandwidth cost, space requirement, and playback delay. We focus on lossy schedules, where data may be dropped due to limited bandwidth or space. We present the following results. First, we determine the optimal tradeoff between buffer space, smoothing delay, and link bandwidth for lossy smoothing schedules. Specifically, this means that if two of these parameters are given, we can precisely calculate the value for the third which minimizes data loss while avoiding resource wastage. The tradeoff is accomplished by a simple generic algorithm, that allows one some freedom in choosing which data to discard. This algorithm is very easy to implement both at the server and at the client, and it enjoys the nice property that only the server decides which data to discard, and the client needs only to reconstruct the stream.In a second set of results we study the case where different parts of the data have different importance, modeled by assigning a real weight to each packet in the stream. For this setting we use competitive analysis, i.e., we compare the weight delivered by on-line algorithms to the weight of an optimal off-line schedule using the same resources. We prove that a natural greedy algorithm is 4-competitive. We also prove a lower bound of 1.23 on the competitive ratio of any deterministic on-line algorithm. Finally, we give a few experimental results which seem to indicate that smoothing is very effective in practice, and that the greedy algorithm performs very well in the weighted case.Received: 21 November 2001, Accepted: 6 November 2003, Published online: 6 February 2004Research supported in part by Israel Ministry of Science. An extended abstract of this paper appeared in Proc. 19th ACM Symp. on Principles of Distributed Computing, July 2000.     

Development of a sweet pepper harvesting robot

This paper presents the development, testing and validation of SWEEPER, a robot for harvesting sweet pepper fruit in greenhouses. The robotic system includes a six degrees of freedom industrial arm equipped with a specially designed end effector, RGB‐D camera, high‐end computer with graphics processing unit, programmable logic controllers, other electronic equipment, and a small container to store harvested fruit. All is mounted on a cart that autonomously drives on pipe rails and concrete floor in the end‐user environment. The overall operation of the harvesting robot is described along with details of the algorithms for fruit detection and localization, grasp pose estimation, and motion control. The main contributions of this paper are the integrated system design and its validation and extensive field testing in a commercial greenhouse for different varieties and growing conditions. A total of 262 fruits were involved in a 4‐week long testing period. The average cycle time to harvest a fruit was 24 s. Logistics took approximately 50% of this time (7.8 s for discharge of fruit and 4.7 s for platform movements). Laboratory experiments have proven that the cycle time can be reduced to 15 s by running the robot manipulator at a higher speed. The harvest success rates were 61% for the best fit crop conditions and 18% in current crop conditions. This reveals the importance of finding the best fit crop conditions and crop varieties for successful robotic harvesting. The SWEEPER robot is the first sweet pepper harvesting robot to demonstrate this kind of performance in a commercial greenhouse.     

Alleviation of Severe Skin Insults Following High-Dose Irradiation with Isolated Human Fetal Placental Stromal Cells

Skin exposure to high-dose irradiation, as commonly practiced in radiotherapy, affects the different skin layers, causing dry and wet desquamation, hyperkeratosis fibrosis, hard to heal wounds and alopecia and damaged hair follicles. Fetal tissue mesenchymal stromal cells (f-hPSC) were isolated from excised human fetal placental tissue, based on their direct migration from the tissue samples to the tissue dish. The current study follows earlier reports on for the mitigation of acute radiation syndrome following whole body high-dose exposure with remotely injected f-hPSC. Both the head only and a back skin flap of mice were irradiated with 16 &18 Gy, respectively, by 6MeV clinical linear accelerator electron beam. In both locations, the irradiated skin areas developed early and late radiation induced skin damages, including cutaneous fibrosis, lesions, scaring and severe hair follicle loss and reduced hair pigmentation. Injection of 2 × 10⁶ f-hPSC, 3 and 8 weeks following 16 Gy head irradiation, and 1 and 4 weeks following the 18 Gy back skin only irradiation, resulted in significantly faster healing of radiation induced damages, with reduction of wet desquamation as measured by surface moisture level and minor recovery of the skin viscoelasticity. Detailed histological morphometry showed a clear alleviation of radiation induced hyperkeratosis in f-hPSC treated mice, with significant regain of hair follicles density. Following 16 Gy head irradiation, the hair follicles density in the scalp skin was reduced significantly by almost a half relative to the controls. A nearly full recovery of hair density was found in the f-hPSC treated mice. In the 18 Gy irradiated back skin, the hair follicles density dropped in a late stage by ~70% relative to naïve controls. In irradiated f-hPSC treated mice, it was reduced by only ~30% and was significantly higher than the non-treated group. Our results suggest that local injections of xenogeneic f-hPSC could serve as a simple, safe and highly effective non-autologous pro-regenerative treatment for high-dose radiation induced skin insults. We expect that such treatment could also be applied for other irradiated organs.     

Utilizing digital traces of mobile phones for understanding social dynamics in urban areas

Understanding land use in urban areas, from the perspective of social function, is beneficial for a variety of fields, including urban and highway planning