Frequency selective surface using nested split ring slot elements as a lens with mechanically reconfigurable beam steering capability

The design is described of a double layer frequency selective surface which can produce a differential phase shift of 180 ° as the wave propagates through it at normal incidence. The hand of an applied circularly polarized signal is reversed due to the 180° phase shift, and it is demonstrated that the exit circularly polarized output signal can be phase advanced or phase retarded by 180 ° upon rotation of the elements comprising the structure. This feature allows the surface to act as a spatial phase shifter. In this paper the beam steering capabilities of a 10 × 10 array of such elements are demonstrated. Here the individual elements comprising the array are rotated relative to each other in order to generate a progressive phase shift. At normal incidence the 3 dB Axial Ratio Bandwidth for LHCP to RHCP conversion is 5.3% and the insertion loss was found to be -2.3 dB, with minimum axial ratio of 0.05 dB. This array is shown to be able to steer a beam from -40 ° to +40 ° while holding axial ratio at the pointing angle to below 4 dB. The measured radiation patterns match the theoretical calculation and full-wave simulation results. © 2010 IEEE.

IQ-motif selectivity in human IQGAP2 and IQGAP3: binding of calmodulin and myosin essential light chain

The IQGAP [IQ-motif-containing GAP (GTPase-activating protein)] family members are eukaryotic proteins that act at the interface between cellular signalling and the cytoskeleton. As such they collect numerous inputs from a variety of signalling pathways. A key binding partner is the calcium-sensing protein CaM (calmodulin). This protein binds mainly through a series of IQ-motifs which are located towards the middle of the primary sequence of the IQGAPs. In some IQGAPs, these motifs also provide binding sites for CaM-like proteins such as myosin essential light chain and S100B. Using synthetic peptides and native gel electrophoresis, the binding properties of the IQ-motifs from human IQGAP2 and IQGAP3 have been mapped. The second and third IQ-motifs in IQGAP2 and all four of the IQ-motifs of IQGAP3 interacted with CaM in the presence of calcium ions. However, there were differences in the type of interaction: while some IQ-motifs were able to form complexes with CaM which were stable under the conditions of the experiment, others formed more transient interactions. The first IQ-motifs from IQGAP2 and IQGAP3 formed transient interactions with CaM in the absence of calcium and the first motif from IQGAP3 formed a transient interaction with the myosin essential light chain MIc1sa. None of these IQ-motifs interacted with S100B. Molecular modelling suggested that all of the IQ-motifs, except the first one from IQGAP2 formed alpha-helices in solution. These results extend our knowledge of the selectivity of IQ-motifs for CaM and related proteins.

Characterization of the highly conserved VFMGD motif in a bacterial polyisoprenyl-phosphate N-acetylaminosugar-1-phosphate transferase

Polyisoprenyl-phosphate N-acetylaminosugar-1-phosphate transferases (PNPTs) constitute a family of eukaryotic and prokaryotic membrane proteins that catalyze the transfer of a sugar-1-phosphate to a phosphoisoprenyl lipid carrier. All PNPT members share a highly conserved 213-Valine-Phenylalanine-Methionine-Glycine-Aspartic acid-217 (VFMGD) motif. Previous studies using the MraY protein suggested that the aspartic acid residue in this motif, D267, is a nucleophile for a proposed double-displacement mechanism involving the cleavage of the phosphoanhydride bond of the nucleoside. Here, we demonstrate that the corresponding residue in the E. coli WecA, D217, is not directly involved in catalysis, as its replacement by asparagine results in a more active enzyme. Kinetic data indicate that the D217N replacement leads to more than twofold increase in V(max) without significant change in the K(m) for the nucleoside sugar substrate. Furthermore, no differences in the binding of the reaction intermediate analog tunicamycin were found in D217N as well as in other replacement mutants at the same position. We also found that alanine substitutions in various residues of the VFMGD motif affect to various degrees the enzymatic activity of WecA in vivo and in vitro. Together, our data suggest that the highly conserved VFMGD motif defines a common region in PNPT proteins that contributes to the active site and is likely involved in the release of the reaction product.

Free-space optoelectronic switching cores with MPLS for SANs over WDM ring networks

With increasing demands on storage devices in the modern communication environment, the storage area network (SAN) has evolved to provide a direct connection allowing these storage devices to be accessed efficiently. To optimize the performance of a SAN, a three-stage hybrid electronic/optical switching node architecture based on the concept of a MPLS label switching mechanism, aimed at serving as a multi-protocol label switching (MPLS) ingress label edge router (LER) for a SAN-enabled application, has been designed. New shutter-based free-space multi-channel optical switching cores are employed as the core switch fabric to solve the packet contention and switching path conflict problems. The system-level node architecture design constraints are evaluated through self-similar traffic sourced from real gigabit Ethernet network traces and storage systems. The extension performance of a SAN over a proposed WDM ring network, aimed at serving as an MPLS-enabled transport network, is also presented and demonstrated.

Amplified optomechanics in a unidirectional ring cavity

We investigate optomechanical forces on a nearly lossless scatterer, such as an atom pumped far off-resonance or amicromirror, inside an optical ring cavity. Our model introduces two additional features to the cavity: an isolator is used to prevent circulation and resonant enhancement of the pump laser field and thus to avoid saturation of or damage to the scatterer, and an optical amplifier is used to enhance the effective Q-factor of the counterpropagating mode and thus to increase the velocity-dependent forces by amplifying the back-scattered light. We calculate friction forces, momentum diffusion, and steady-state temperatures to demonstrate the advantages of the proposed setup.

A silicone elastomer vaginal ring for HIV prevention containing two microbicides with different mechanisms of action

Vaginal rings are currently being developed for the long-term (at least 30 days) continuous delivery of microbicides against human immunodeficiency virus (HIV). Research to date has mostly focused on devices containing a single antiretroviral compound, exemplified by the 25 mg dapivirine ring currently being evaluated in a Phase III clinical study. However, there is a strong clinical rationale for combining antiretrovirals with different mechanisms of action in a bid to increase breadth of protection and limit the emergence of resistant strains. Here we report the development of a combination antiretroviral silicone elastomer matrix-type vaginal ring for simultaneous controlled release of dapivirine, a non-nucleoside reverse transcriptase inhibitor, and maraviroc, a CCR5-targeted HIV-1 entry inhibitor. Vaginal rings loaded with 25 mg dapivirine and various quantities of maraviroc (50– 400 mg) were manufactured and in vitro release assessed. The 25 mg dapivirine and 100 mg maraviroc formulation was selected for further study. A 24-month pharmaceutical stability evaluation was conducted, indicating good product stability in terms of in vitro release, content assay, mechanical properties and related substances. This combination ring product has now progressed to Phase I clinical testing.

Design of a silicone intravaginal ring for the delivery of oxybutynin

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Interlaboratory ring test of time-resolved fluoroimmunoassays for zeranol and alpha-zearalenol and comparison with zeranol test kits

Many zeranol immunoassay test kits cross-react with toxins formed by naturally occurring Fusarium spp. fungi, leading to false-positive screening results. This paper describes the evaluation and application of recently published, dry reagent time-resolved fluoroimmunoassays (TR-FIA) for zeranol and the toxin alpha-zearalenol. A ring test of bovine urine fortified with zeranol and/or alpha-zearalenol in four European Union National Reference Laboratories demonstrated that the TR-FIA tests were accurate and robust. The alpha-zearalenol TR-FIA satisfactorily quantified alpha-zearalenol in urine fortified at 10-30 ng ml(-1) . The specificity-enhanced zeranol TR-FIA accurately quantified zeranol in the range 2-5 ng ml(-1) and gave no false-positive results in blank urine, even in the presence of 30 ng ml(-1) alpha-zearalenol. Zeranol TR-FIA specificity was demonstrated further by analysing incurred zeranol-free urine samples containing natural Fusarium spp. toxins. The TR-FIA yielded no false-positive results in the presence of up to 22 ng ml(-1) toxins. The performance of four commercially available zeranol immunoassay test kits was more variable. Three kits produced many false-positive results. One kit produced only one potential false-positive using a protocol that was longer than that of the TR-FIA. These TR-FIAs will be valuable tools to develop inspection criteria to distinguish illegal zeranol abuse from contamination arising from in vivo metabolism of Fusarium spp. toxins.

Double split ring slot FSS reflectarray for difference pattern generation

A report is presented on a split ring slot frequency selective surface (FSS) reflector whose element design and distribution allows generation of far-field difference patterns. The reflector operates by converting linearly polarised plane wave fronts into two orthogonal polarisations each with a deep null in the centre of the radiation pattern. The far-field measurement presented is in good agreement with the simulation and demonstrates a null depth of ?20dB in the centre of the radiation pattern.

Comparison of frequency-selective screen-based linear to circular split-ring polarisation convertors

This study presents the use of periodic arrays of freestanding slot frequency-selective screens (FSS) as a means for generating circularly polarised signals from an incident linearly polarised signal at normal incidence to the structure. Measured and simulated results for crossed, linear and various ring slot element shapes in single and double-layer polarisation convertor structures are presented for 10 GHz operation. It is shown that 3 dB axial ratio (AR) bandwidths of 21% can be achieved with the one-layer perforated screen design and that the rate of change is lower than the double-layer structures. An insertion loss of 0.34 dB can be achieved for the split circular ring double-layer periodic array, and of the three topologies presented the hexagonal split-ring polarisation convertor gives the lowest variation of AR with angle of incidence 1.8 dB/45° and 3.6 dB/45° for the single and double-screen FSS, respectively. In addition, their tolerance to angle of incidence variation is presented. The capability of the surfaces reported here as twist polariser or spatial isolator components has been demonstrated with up to -30 dB isolation between incident and re-reflected signals for the double-layer designs being measured. © 2010 The Institution of Engineering and Technology.

Split-Ring FSS Spiral Phase Plate

This letter gives the first report of a planar phase plate structure based on frequency selective surface (FSS) technology for the generation of helical far-field radiation patterns with circular polarization properties.The unit cell of the structure comprises two orthogonal split-ring resonators designed to ensure 180$^{\circ}$ phase shift between orthogonal transmission coefficients. This property is exploited to obtain progressive rotational phase shift within the structure and thus synthesize 360$^{\circ}$ spiral phase profile. Measured far-field radiation patterns demonstrate spiral phase front generation for 10-GHz circularly polarized waves transmitted through the structure.

IQ-motif peptides as novel anti-microbial agents

The IQ-motif is an amphipathic, often positively charged, a-helical, calmodulin binding sequence found in a number of eukaryote signalling, transport and cytoskeletal proteins. They share common biophysical characteristics with established, cationic a-helical antimicrobial peptides, such as the human cathelicidin LL-37. Therefore, we tested eight peptides encoding the sequences of IQ-motifs derived from the human cytoskeletal scaffolding proteins IQGAP2 and IQGAP3. Some of these peptides were able to inhibit the growth of Escherichia coli and Staphylococcus aureus with minimal inhibitory concentrations (MIC) comparable to LL-37. In addition some IQ-motifs had activity against the fungus Candida albicans. This antimicrobial activity is combined with low haemolytic activity (comparable to, or lower than, that of LL-37). Those IQ-motifs with anti-microbial activity tended to be able to bind to lipopolysaccharide. Some of these were also able to permeabilise the cell membranes of both Gram positive and Gram negative bacteria. These results demonstrate that IQ-motifs are viable lead sequences for the identification and optimisation of novel anti-microbial peptides. Thus, further investigation of the anti-microbial properties of this diverse group of sequences is merited.

Molecular similarity between myelodysplastic form of chronic myelomonocytic leukemia and refractory anemia with ring sideroblasts

Chronic myelomonocytic leukemia is similar to but a separate entity from both myeloproliferative neoplasms and myelodysplastic syndromes, and shows either myeloproliferative or myelodysplastic features. We ask whether this distinction may have a molecular basis. We established the gene expression profiles of 39 samples of chronic myelomonocytic leukemia (including 12 CD34-positive) and 32 CD34-positive samples of myelodysplastic syndromes by using Affymetrix microarrays, and studied the status of 18 genes by Sanger sequencing and array-comparative genomic hybridization in 53 samples. Analysis of 12 mRNAS from chronic myelomonocytic leukemia established a gene expression signature of 122 probe sets differentially expressed between proliferative and dysplastic cases of chronic myelomonocytic leukemia. As compared to proliferative cases, dysplastic cases over-expressed genes involved in red blood cell biology. When applied to 32 myelodysplastic syndromes, this gene expression signature was able to discriminate refractory anemias with ring sideroblasts from refractory anemias with excess of blasts. By comparing mRNAS from these two forms of myelodysplastic syndromes we derived a second gene expression signature. This signature separated the myelodysplastic and myeloproliferative forms of chronic myelomonocytic leukemias. These results were validated using two independent gene expression data sets. We found that myelodysplastic chronic myelomonocytic leukemias are characterized by mutations in transcription/epigenetic regulators (ASXL1, RUNX1, TET2) and splicing genes (SRSF2) and the absence of mutations in signaling genes. Myelodysplastic chronic myelomonocytic leukemias and refractory anemias with ring sideroblasts share a common expression program suggesting they are part of a continuum, which is not totally explained by their similar but not, however, identical mutation spectrum. © 2013 Ferrata Storti Foundation.