TDM modelling and evaluation of different domain transforms for LSI

Latent semantic indexing (LSI) is a popular technique used in information retrieval (IR) applications. This paper presents a novel evaluation strategy based on the use of image processing tools. The authors evaluate the use of the discrete cosine transform (DCT) and Cohen Daubechies Feauveau 9/7 (CDF 9/7) wavelet transform as a pre-processing step for the singular value decomposition (SVD) step of the LSI system. In addition, the effect of different threshold types on the search results is examined. The results show that accuracy can be increased by applying both transforms as a pre-processing step, with better performance for the hard-threshold function. The choice of the best threshold value is a key factor in the transform process. This paper also describes the most effective structure for the database to facilitate efficient searching in the LSI system.

AINT/ERIC/TACC: an expanding family of proteins with C-terminal coiled coil domains:an expanding family of proteins with C-terminal coiled coil domains

The AINT/ERIC/TACC genes encode novel proteins with a coiled coil domain at their C-terminus. The founding member of this expanding family of genes, transforming acidic coiled coil 1 (TACC1), was isolated from a BAC contig spanning the breast cancer amplicon-1 on 8p11. Transfection of cells in vitro with TACC1 resulted in anchorage-independent growth consistent with a more "neoplastic" phenotype. Database searches employing the human TACC1 sequence revealed other novel genes, TACC2 and TACC3, with substantial sequence homology particularly in the C-terminal regions encoding the coiled coil domains. TACC2, located at 10q26, is similar to anti-zuai-1 (AZU-1), a candidate breast tumour suppressor gene, and ECTACC, an endothelial cell TACC which is upregulated by erythropoietin (Epo). The murine homologue of TACC3, murine erythropoietin-induced cDNA (mERIC-1) was also found to be upregulated by Epo in the Friend virus anaemia (FVA) model by differential display-PCR. Human ERIC-1, located at 4p16.3, has been cloned and encodes an 838-amino acid protein whose N- and C-terminal regions are highly homologous to the shorter 558-amino acid murine protein, mERIC-1. In contrast, the central portions of these proteins differ markedly. The murine protein contains four 24 amino acid imperfect repeats. ARNT interacting protein (AINT), a protein expressed during embryonic development in the mouse, binds through its coiled coil region to the aryl hydrocarbon nuclear translocator protein (ARNT) and has a central portion that contains seven of the 24 amino acid repeats found in mERIC-1. Thus mERIC-1 and AINT appear to be developmentally regulated alternative transcripts of the gene. Most members of the TACC family discovered so far contain a novel nine amino acid putative phosphorylation site with the pattern [R/K]-X(3)-[E]-X(3)-Y. Genes with sequence homology to the AINT/ERIC/TACC family in other species include maskin in Xenopus, D-TACC in Drosophila and TACC4 in the rabbit. Maskin contains a peptide sequence conserved among eIF-4E binding proteins that is involved in oocyte development. D-TACC cooperates with another conserved microtubule-associated protein Msps to stabilise spindle poles during cell division. The diversity of function already attributed to this protein family, including both transforming and tumour suppressor properties, should ensure that a new and interesting narrative is about to unfold.

Effect of wall thickness on the ferroelastic domain size of BaTiO3

Extremely regular self-organized patterns of 90^o ferroelastic domains have been reported in freestanding single crystal thin films of ferroelectric BaTiO₃. Lukyanchuk et al. [Phys Rev B 79, 144111 (2009)] have recently shown that the domain size as a function of thickness for such free standing films can be well described assuming that the domains are due to stress caused by a surface tension layer that does not undergo the paraelectric–ferroelectric transition. From the starting point of Lukyanchuk’s model, it is shown here that the ‘‘universal’’relationship between domain size and domain wall thickness previously observed in ferroelectrics, ferromagnets and multiferroics is also valid for ferroelastic domains.Further analysis of experimental data also shows that the domain wall thickness can vary considerably (an order of magnitude) from sample to sample even for the same material (BaTiO₃), in spite of which the domain size scaling model is still valid, provided that the correct,sample dependent, domain wall thickness is used.

Progressive Audio Scrambling in Compressed Domain

Audio scrambling can be employed to ensure confidentiality in audio distribution. We first describe scrambling for raw audio using the discrete wavelet transform (DWT) first and then focus on MP3 audio scrambling. We perform scrambling based on a set of keys which allows for a set of audio outputs having different qualities. During descrambling, the number of keys provided and the number of rounds of descrambling performed will decide the audio output quality. We also perform scrambling by using multiple keys on the MP3 audio format. With a subset of keys, we can descramble to obtain a low quality audio. However, we can obtain the original quality audio by using all of the keys. Our experiments show that the proposed algorithms are effective, fast, simple to implement while providing flexible control over the progressive quality of the audio output. The security level provided by the scheme is sufficient for protecting MP3 music content.

A time-domain approach to the analysis and modeling of on-body propagation characteristics using synchronized measurements at 2.45 GHz

Modeling of on-body propagation channels is of paramount importance to those wishing to evaluate radio channel performance for wearable devices in body area networks (BANs). Difficulties in modeling arise due to the highly variable channel conditions related to changes in the user's state and local environment. This study characterizes these influences by using time-series analysis to examine and model signal characteristics for on-body radio channels in user stationary and mobile scenarios in four different locations: anechoic chamber, open office area, hallway, and outdoor environment. Autocorrelation and cross-correlation functions are reported and shown to be dependent on body state and surroundings. Autoregressive (AR) transfer functions are used to perform time-series analysis and develop models for fading in various on-body links. Due to the non-Gaussian nature of the logarithmically transformed observed signal envelope in the majority of mobile user states, a simple method for reproducing the failing based on lognormal and Nakagami statistics is proposed. The validity of the AR models is evaluated using hypothesis testing, which is based on the Ljung-Box statistic, and the estimated distributional parameters of the simulator output compared with those from experimental results.

The influence of Notches on Domain Dynamics in Ferroelectric Nanowires

The extent to which notches inhibit axial switching of polarization in ferroelectric nanowires was investigated by monitoring the switching behavior of single crystal BaTiO(3) wires before and after patterning triangular notches along their lengths. Static zero-field domain patterns suggested a strong domain-notch interaction, implying that notches should act as pinning sites for domain wall propagation. Surprisingly though, notches appeared to assist, rather than inhibit, polar switching. The origin of this effect was rationalized using finite element modeling of the electric field distribution along the notched wire; it was found that the air gap associated with the notch acted to enhance the local field, both in the air, and in the adjacent region of the ferroelectric. It seems that this local field enhancement outweighs any pinning interactions.

The Effect of Antinotches on Domain Wall Mobility in Single Crystal Ferroelectric Nanowires

Changes in domain wall mobility, caused by the presence of antinotches in single crystal BaTiO3 nanowires, have been investigated. While antinotches appeared to cause a slight broadening in the distribution of switching events, observed as a function of applied electric field (inferred from capacitance-voltage measurements), the effect was often subtle. Greater clarity of information was obtained from Rayleigh analysis of the capacitance variation with ac field amplitude. Here the magnitude of the domain wall mobility parameter (R) associated with irreversible wall movements was found to be reduced by the presence of antinotches - an effect which became more noticeable on heating toward the Curie temperature. The reduction in this domain wall mobility was contrasted with the noticeable enhancement found previously in ferroelectric wires with notches. Finite element modeling of the electric field, developed in the nanowires during switching, revealed regions of increased and decreased local field at the center of the notch and antinotch structures, respectively; the absolute magnitude of field enhancement in the notch centers was considerably greater than the field reduction in the center of the antinotches and this was commensurate with the manner in, and degree to, which domain wall mobility appeared to be affected. We therefore conclude that the main mechanism by which morphology alters the irreversible component of the domain wall mobility in ferroelectric wire structures is via the manner in which morphological variations alter the spatial distribution of the electric field.

Identification of Determinants of Glucose-Dependent Insulinotropic Polypeptide Receptor That Interact with N-Terminal Biologically Active Region of the Natural Ligand

Glucose-dependent insulinotropic polypeptide receptor (GIPR), a member of family B of the G-protein coupled receptors, is a potential therapeutic target for which discovery of nonpeptide ligands is highly desirable. Structure-activity relationship studies indicated that the N-terminal part of glucose-dependent insulinotropic polypeptide (GIP) is crucial for biological activity. Here, we aimed at identification of residues in the GIPR involved in functional interaction with N-terminal moiety of GIP. A homology model of the transmembrane core of GIPR was constructed, whereas a three-dimensional model of the complex formed between GIP and the N-terminal extracellular domain of GIPR was taken from the crystal structure. The latter complex was docked to the transmembrane domains of GIPR, allowing in silico identification of putative residues of the agonist binding/activation site. All mutants were expressed at the surface of human embryonic kidney 293 cells as indicated by flow cytometry and confocal microscopy analysis of fluorescent GIP binding. Mutation of residues Arg183, Arg190, Arg300, and Phe357 caused shifts of 76-, 71-, 42-, and 16-fold in the potency to induce cAMP formation, respectively. Further characterization of these mutants, including tests with alanine-substituted GIP analogs, were in agreement with interaction of Glu3 in GIP with Arg183 in GIPR. Furthermore, they strongly supported a binding mode of GIP to GIPR in which the N-terminal moiety of GIP was sited within transmembrane helices (TMH) 2, 3, 5, and 6 with biologically crucial Tyr1 interacting with Gln224 (TMH3), Arg300 (TMH5), and Phe357 (TMH6). These data represent an important step toward understanding activation of GIPR by GIP, which should facilitate the rational design of therapeutic agents.

Two Arginine-Glutamate Ionic Locks Near the Extracellular Surface of FFAR1 Gate Receptor Activation

Activation of a number of class A G protein-coupled receptors (GPCRs) is thought to involve two molecular switches, a rotamer toggle switch within the transmembrane domain and an ionic lock at the cytoplasmic surface of the receptor; however, the mechanism by which agonist binding changes these molecular interactions is not understood. Importantly, 80% of GPCRs including free fatty acid receptor 1 (FFAR1) lack the complement of amino acid residues implicated in either or both of these two switches; the mechanism of activation of these GPCRs is therefore less clear. By homology modeling, we identified two Glu residues (Glu-145 and Glu-172) in the second extracellular loop of FFAR1 that form putative interactions individually with two transmembrane Arg residues (Arg-183(5.39) and Arg-258(7.35)) to create two ionic locks. Molecular dynamics simulations showed that binding of agonists to FFAR1 leads to breakage of these Glu-Arg interactions. In mutagenesis experiments, breakage of these two putative interactions by substituting Ala for Glu-145 and Glu-172 caused constitutive receptor activation. Our results therefore reveal a molecular switch for receptor activation present on the extracellular surface of FFAR1 that is broken by agonist binding. Similar ionic locks between the transmembrane domains and the extracellular loops may constitute a mechanism common to other class A GPCRs also.

Domain Bundle Boundaries in Single Crystal BaTiO3 Lamellae: Searching for Naturally Forming Dipole Flux-Closure / Quadrupole Chains

Naturally occurring boundaries between bundles of 90o stripe domains, which form in BaTiO3 lamellae on cooling through the Curie Temperature, have been characterised using both piezoresponse force microscopy (PFM) and scanning transmission electron microscopy (STEM). Detailed interpretation of the dipole configurations present at these boundaries (using data taken from PFM) shows that, in the vast majority of cases, they are composed of simple zigzag 180° domain walls. Topological information from STEM shows that, occasionally, domain bundle boundaries can support chains of dipole flux closure and quadrupole nanostructures, but these kinds of boundaries are comparatively rare; when such chains do exist, it is notable that singularities at the cores of the dipole structures are avoided. The symmetry of the boundary shows that diads and centres of inversion exist at positions where core singularities should have been expected.