Reversible Thermal Tuning of All‐Dielectric Metasurfaces

All‐dielectric metasurfaces provide a powerful platform for a new generation of flat optical devices, in particular, for applications in telecommunication systems, due to their low losses and high transparency in the infrared. However, active and reversible tuning of such metasurfaces remains a challenge. This study experimentally demonstrates and theoretically justifies a novel scenario of the dynamical reversible tuning of all‐dielectric metasurfaces based on the temperature‐dependent change of the refractive index of silicon. How to design an all‐dielectric metasurface with sharp resonances by achieving interference between magnetic dipole and electric quadrupole modes of constituted nanoparticles arranged in a 2D lattice is shown. Thermal tuning of these resonances can cause drastic but reciprocal changes in the directional scattering of the metasurface in a spectral window of 75 nm. This change can result in a 50‐fold enhancement of the radiation directionality. This type of reversible tuning can play a significant role in novel flat optical devices including the metalenses and metaholograms.     

The use of acetylene glow discharge for improving adhesive bonding of polymeric films

Coating of polyethylene (PE), poly(vinyl fluoride) (PVF), poly(tetrafluoroethylene) (PTFE), and poly(vinyl chloride) (PVC) films with flow discharge-polymerized acetylene was investigated. The influence of glow discharge experimental conditions on the nature of the coated layer, the films' wettability, surface roughness, and adhesive joint strength was determined. It was found that coating of these films with plasma-polymerized acetylene led to the formation of a rough, crosslinked, irremovable layer with an improved wettability. The presence of the plasma-polymerized acetylene on the film surface lead to a large improvement in the adhesive joint strength of these films with epoxy adhesive. Best results were obtained with films coated at a low acetylene flow rate. Increase in glow discharge power and treatment time lead to a further improvement.     

Synthesis and field bioassay of some analogs of sex pheromone of citrus mealybug,Planococcus citri (Risso)

A series of structural analogs of (s+)-cis-(1R)-3-isopropenyl-2,2-dimethylcyclobutanemethanol acetate, sex pheromone of the citrus mealybug,Planococcus citri (Risso), was synthesized. The analogs were tested in a field bioassay in order to determine the structure-activity relationships of the pheromone. All changes in structure reduced the activity of the test compounds, to various degrees. The most active analog tested was the homolog (+)-cis-(1R)-3-isopropenyl-2,2-dimethylcyclobutaneethanol acetate (IV), whose activity, at a higher dosage, was comparable to that of the pheromone. The alcohol (+)-cis-(1R)-3-isopropenyl-2,2-dimethylcyclobutanemethanol was tested in mixtures with the pheromone and found to be neither an inhibitor nor a Synergist. The results show that all functional groups of the pheromone molecule are essential for optimal biological activity.Homoptera: Coccoidea: Pseudococcidae.Contribution from the Agricultural Research Organization (ARO), The Volcani Center, Bet Dagan, Israel, No. 1667-E, 1986 series.Levi Eshkol Postdoctoral Fellow, 1984–1986.     

The initiation of in situ polymerization of vinyl monomers in polyester by glow discharge

Glow discharge initiation of in situ polymerization of acrylic acid and other vinyl monomers incorporated in PET films was investigatigated. The influence of glow discharge conditions such as the gas used, plasma power, discharge current, and plasma treatment time on polymerization yield was determined. Though glow discharge effects are limited to the film surface, in situ polymerization of the vinyl monomers took place and the vinyl polymer could be found all through the film cross section. At short plasma treatment time only surface modification took place, while at longer treatment time bulk modification occurred, too. Good polymerization yields were obtained. Gel effect behavior was observed. Mechanical properties of the modified PET film were not changed, while the contact angle with water improved when polar vinyl monomers were used.     

Heating experiments with a radiative cooling system

A hybrid space-cooling system for hot arid zones previously investigated by the authors was based on the nocturnal radiative cooling of water circulated through flat plate radiators. Preliminary investigations also indicated that the same system, with no modifications to the physical set-up, could provide a significant proportion of the winter heating requirements of buildings exposed to these climatic conditions, where summers are hot yet winters are frequently cold enough to justify the installation of heating systems.

The heat output of the system averaged 370 W/m² of collector under the sunny but cool conditions typical of Sde-Boker winters. However, on windy and overcast days the thermostat control prevented water circulation and the system was inoperative. The primary factors determining the heat output were the intensity of global solar radiation incident on the collectors, wind speed and the temperature difference between the water in the roof pond and the ambient air. An expression was derived linking these parameters, which may be used to predict the heat output of the specific system with a high degree of accuracy, and thus define the climatic conditions where such a system may be of value.     

Analysis of explosives by nuclear magnetic resonance spectrometry

In order to evaluate the applicability of NMR to the analysis of explosives, the method was used to analyse explosives from actual cases. The results were then compared with results from other analytical methods, mainly TLC and GC/MS. For unexploded samples NMR was found to be a simple, fast and reliable method, often allowing the identification of mixtures without pre-separation. Some post-explosion samples were also successfully analysed by NMR. Although sensitivity problems still exist, NMR showed a surprisingly promising prospects for the difficult field of post-explosion analysis.     

The law of limited excellence: publication productivity of Israel Prize laureates in the life and exact sciences

The present paper extends Lotka’s theorem—which we rename as “the law of limited excellence”—while empirically modelling the scientific productivity of 46 Israel Prize laureates in the life and exact sciences—a group best described as ‘Star Scientists’. By focusing on this highly selective group we expose unequal scientific productivity even amongst Israel’s most prolific scientists. Specifically, we test the invariance of Lotka’s law by focusing attention on the extreme tail of publication distributions while empirically exploring the non-linearity of its seemingly “flat” tail. By exposing the rarity of excellence even in this extreme end of publication productivity we extend the generality of Lotka’s theorem and expose that—like a fractal—the tail of excellence behaves as the entire distribution. We end this empirical contribution by suggesting a few implications for research and policy.     

The effects of fructose and phosphate infusions on dry matter intake of lactating cows

The objective of this study was to examine the effects of fructose and phosphate (Pi) infusions on dry matter intake by dairy cows to further understand the mechanisms controlling feed intake related to hepatic energy status. We performed 3 experiments in which we infused fructose and Pi intravenously or abomasally to Holstein cows. The first experiment used 8 cows (4–8 d postpartum) in a duplicated 4 × 4 Latin square experiment with 1 square of multiparous and 1 square of primiparous cows. A 2 × 2 factorial arrangement of treatments was used including jugular infusions of solutions (1 L/h) containing fructose or glucose (0.6 mol/h) and Pi (NaH₂PO₄) or NaCl (0.3 mol/h). Periods were 24 h, including 2 h for infusions and 22 h for recovery. The second experiment used 4 multiparous cows (74–81 d postpartum) in a 4 × 4 Latin square design and infused fructose or glucose and either Pi or no Pi at the same rates as experiment 1. Periods were 24 h, including 1 h for infusions and 23 h for recovery. The third experiment used 4 ruminally cannulated multiparous cows (15–26 d postpartum) in a 4 × 4 Latin square design and infused fructose or glucose and either Pi or NaCl at the same rates as experiment 1 but to the abomasum. Periods were 24 h, including 1 h for infusions and 23 h for recovery. In each experiment, feed intake was recorded by a computerized data acquisition system; blood was analyzed for the concentrations of glucose, nonesterified fatty acids, and Pi; and the liver was analyzed for the concentration of Pi (experiments 2 and 3 only). Overall, fructose infusion increased DMI by fresh cows when infused intravenously and abomasally, but it did not affect DMI by mid-lactation cows. Fructose infusion also reduced hepatic Pi, and Pi infusion increased hepatic Pi when infused abomasally but not intravenously. These results suggest that fructose increases feed intake, likely by sequestering Pi and preventing ATP production. When infused intravenously to multiparous cows, Pi increased DMI and did not affect hepatic Pi content. However, when infused abomasally, Pi reduced DMI and increased hepatic Pi content. These results suggest that although Pi infusion prevents the effect of fructose loading and reduces DMI, it also increases intake through a competing mechanism. Examining long-term effect of Pi infusion on DMI could determine if competing mechanisms complicate the determination of P requirement for dairy cows. These results are consistent with the control of feed intake by hepatic energy status in dairy cows.     

Ruthenium electrodeposition on silicon from a room-temperature ionic liquid

Electrochemical deposition of ruthenium on n-type silicon from an ionic liquid is reported for the first time. The study was performed by dissolving ruthenium(III) chloride in a 1-butyl-3-methyl imidazolium hexafluorophosphate (BMIPF₆) room-temperature ionic liquid (RTIL). Cyclic voltammetry (CV) studies demonstrate reduction and stripping peaks at −2.1 and 0.2 V vs. Pt quasi-reference, corresponding to the deposition and dissolution of ruthenium, respectively. Metallic Ru films of ∼100 nm thickness have been deposited and were analyzed using scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS).     

Incorporating non-motion cues into 3D motion segmentation

We address the problem of segmenting an image sequence into rigidly moving 3D objects. An elegant solution to this problem in the case of orthographic projection is the multibody factorization approach in which the measurement matrix is factored into lower rank matrices. Despite progress in factorization algorithms, their performance is still far from satisfactory and in scenes with missing data and noise, most existing algorithms fail.In this paper we propose a method for incorporating 2D non-motion cues (such as spatial coherence) into multibody factorization. We show the similarity of the problem to constrained factor analysis and use the EM algorithm to find the segmentation. We show that adding these cues improves performance in real and synthetic sequences.