Tunable transmission and harmonic generation in nonlinear metamaterials

We study the properties of a tunable nonlinear metamaterial operating at microwave frequencies. We fabricate the nonlinear metamaterial composed of double split-ring resonators and wires where a varactor diode is introduced into each resonator so that the magnetic resonance can be tuned dynamically by varying the input power. We show that at higher powers the transmission of the metamaterial becomes power dependent, and we demonstrate experimentally power-dependent transmission properties and selective generation of higher harmonics.This work has been supported by the Australian Research Council through the Discovery projects, by the Australian Academy of Science through a travel grant, and by the Air Force Office of Scientific Research AFOSR through the MURI program Grant No. F49620-03-1-0420

Tunable transmission and harmonic generation in nonlinear metamaterials

We study the properties of a tunable nonlinear metamaterial operating at microwave frequencies. We fabricate the nonlinear metamaterial composed of double split-ring resonators and wires where a varactor diode is introduced into each resonator so that the magnetic resonance can be tuned dynamically by varying the input power. We show that at higher powers the transmission of the metamaterial becomes power dependent, and we demonstrate experimentally power-dependent transmission properties and selective generation of higher harmonics.Comment: 3 page

Wave scattering and splitting by magnetic metamaterials

We study experimentally propagation of electromagnetic waves through a slab of uniaxial magnetic metamaterial. We observe a range of novel phenomena including partial focusing and splitting into multiple transmitted beams.We demonstrate that while some of these experimentally observed effects can be described within the approximation of an effective medium, a deeper understanding of the experimental results requires a rigorous study of internal eigenmodes of the lattice of resonators

Using parse tree validation to prevent SQL injection attacks

An SQL injection attack targets interactive web applications that employ database services. Such applications accept user input, such as form fields, and then include this input in database requests, typically SQL statements. In SQL injection, the attacker provides user input that results in a different database request than was intended by the application programmer. That is, the interpretation of the user input as part of a larger SQL statement, results in an SQL statement of a different form than originally intended. We describe a technique to prevent this kind of manipulation and hence eliminate SQL injection vulnerabilities. The technique is based on comparing, at run time, the parse tree of the SQL statement before inclusion of user input with that resulting after inclusion of input. Our solution is efficient, adding about 3 ms overhead to database query costs. In addition, it is easily adopted by application programmers, having the same syntactic structure as current popular record set retrieval methods. For empirical analysis, we provide a case study of our solution in J2EE. We implement our solution in a simple static Java class, and show its effectiveness and scalability. 1

A Methyl Esterase 1 (PvMES1) Promotes the Salicylic Acid Pathway and Enhances Fusarium Wilt Resistance in Common Beans

Common bean (Phaseolus vulgaris L.) is an important food legume. Fusarium wilt caused by Fusarium oxysporum f. sp. phaseoli is one of the most serious soil-born diseases of common bean found throughout the world and affects the yield and quality of the crop. Few sources of Fusarium wilt resistance exist in legumes and most are of quantitative inheritance. In this study, we have identified a methyl salicylate esterase (MES), PvMES1, that contributes to plant defense response by regulating the salicylic acid (SA) mediated signaling pathway in response to Fusarium wilt in common beans. The result showed the role of PvMES1 in regulating SA levels in common bean and thus the SA signaling pathway and defense response mechanism in the plant. Overexpression of the PvMES1 gene enhanced Fusarium wilt resistance; while silencing of the gene caused susceptibility to the diseases. RNA-seq analysis with these transiently modified plants showed that genes related to SA level changes included the following gene ontologies: a) interaction between host and pathogen; b) phenylpropanoid synthesis; and c) sugar metabolism as well as others. These key signal elements activated the defense response pathway in common bean to Fusarium wilt. Collectively, our findings indicate that PvMES1 plays a pivotal role in regulating SA biosynthesis and signaling, and increasing Fusarium wilt resistance in common bean, thus providing novel insight into the practical applications of both SA and MES genes and pathways they contribiute to for developing elite crop varieties with enhanced broad-spectrum resistance to this critical disease

Cultivation of aquatic plants on cow manure digestate : A technical report

Turning animal manure into energy generates a leftover product: digester bio slurry. Generally this bio slurry is separated in a solid and a liquid fraction. The use of the liquid fraction bio slurry (LFBS) in combination with residual heat and flu gas from the CHP unit could proof an interesting way to turning LFBS in to valuable biomass locally and thereby reducing the manure processing costs. The goal of the study described here is to assess the application opportunity of LFBS from a cattle manure co-digester in combination with aquatic biomass. In this study different aquatic plant types (submerged, floating and emerged) are used to observe there growth characteristics on different concentrations (1:50 an 1:100 dilutions) of LFBS. In addition to the aquatic plants soy plants are subjected to the same growth conditions to find out their response to a hydroponic culture using LFBS as sole fertilizer. The used plants (cattail, hornwort, water hyacinth and soy) generally grew well under the selected conditions. Unfortunately hornwort (submerged plant type) was overgrown by duckweed on the surface of the test setup, this might had led to lower biomass productions. Cattail, hornwort and soy were only tested in outside conditions. Water hyacinth was only tested in greenhouse conditions, first in a small scale setup (12 plastic boxes of 60x40 cm) followed by an upscaling step to a race way pond of 175 m2. While water hyacinth is notorious for its growth potential (potentially invasive in tropical and sub-tropical regions) in this study cattail showed higher specific biomass growth. Maximum projected dry matter biomass yields of 32.9 and 38.9 t/ha/year respectively. Soy beans were tested as an alternative to aquatic plants. Beans were directly sown in rockwool, which was used as rooting media floating in the bio slurry dilution. Remarkably the soy plants grew well and even developed beans, the projected yield was comparable to field yield. LFBS proofed to be a suitable nutrient source for the tested plants in an aquatic environment. Especially in countries, such as The Netherlands, where bio slurry and water is abundant, the cultivation of aquatic or terrestrial plants in a LFBS dilution could be an attractive alternative for soil bound agriculture