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PubMed2004

Hybrid materials containing organometallic cations and 3-D anionic metal dicyanamide networks of type [Cp*2M][M'(dca)3].

A new series of hybrid materials of type [Cp*2M][M'(dca)3] has been prepared by cation templation and structurally characterised (M = Fe(III), Co(III); M'= Mn(II), Fe(II), Co(II), Ni(II), Cd(II); dca-= N(CN)2-). The crystallographic analysis of [Cp*2Fe][Cd(dca)(3)] showed that the [Cd(dca)3]- anionic framework is of a symmetrical 3-D alpha-polonium type, containing octahedral Cd nodes and micro (1,5)-dca bridging ligands. The [Cp*2Fe]+ cations occupy the cube-like cavities within the framework. The cationic and anionic-framework sublattices remain magnetically independent and display susceptibilities, over the range 300 to 2 K, of a Curie-Weiss nature obtained by adding a S= 1/2 (Cp*2Fe+) or a S= 0 (Cp*2Co+) contribution to those of the weakly antiferromagnetically coupled frameworks of M'. These hybrid species do not show any intrinsic long-range magnetic order. The present [Cp*2Fe]M'(dca)3] series display the characteristic, unusually shaped [Cp*2Fe]+ Mossbauer line, in the range 295-5 K, assigned (below 101 K) as the sum of a narrow and a broad line. Relaxation effects were evident. The [Fe(dca)3]- compound showed superimposed low-spin Fe(III) and high-spin Fe(II) lines, the latter giving relaxation broadening effects.

Journal Article↗
PubMed2005

Applying Hybrid-Asbru clinical guidelines using the Spock system.

Clinical Guidelines are a major tool for improving the quality of medical care. Currently, a major research direction is automating the application of guidelines at the point of care. To support that automation, several requirements must be fulfilled, such as specification in a machine-interpretable format, and connection to an electronic patent record. We propose an innovative approach to guideline application, which capitalizes on our Digital electronic Guidelines Library (DeGeL). The DeGeL framework includes a new hybrid model for incremental specification of free-text guidelines, using several intermediate representations. The new approach was implemented, in the case of the Asbru guideline ontology, as the Spock system. Spock's hybrid application engine supports application of guideline represented at an intermediate format. Spock was evaluated in a preliminary fashion by applying several guidelines to sample patient data.

Decision Making, Computer-Assisted↗
PubMed2003

Phylogeography and introgressive hybridization: chipmunks (genus Tamias) in the northern Rocky Mountains.

If phylogeographic studies are to be broadly used for assessing population-level processes relevant to speciation and systematics, the ability to identify and incorporate instances of hybridization into the analytical framework is essential. Here, we examine the evolutionary history of two chipmunk species, Tamias ruficaudus and Tamias amoenus, in the northern Rocky Mountains by integrating multivariate morphometrics of bacular (os penis) variation, phylogenetic estimation, and nested clade analysis with regional biogeography. Our results indicate multiple examples of mitochondrial DNA introgression layered within the evolutionary history of these nonsister species. Three of these events are most consistent with recent and/or ongoing asymmetric introgression of mitochondrial DNA across morphologically defined secondary contact zones. In addition, we find preliminary evidence where a fourth instance of nonconcordant characters may represent complete fixation of introgressed mitochondrial DNA via a more ancient hybridization event, although alternative explanations of convergence or incomplete sorting of ancestral polymorphisms cannot be dismissed with these data. The demonstration of hybridization among chipmunks with strongly differentiated bacular morphology contradicts long-standing assumptions that variation within this character is diagnostic of complete reproductive isolation within Tamias. Our results illustrate the utility of phylogeographic analyses for detecting instances of reticulate evolution and for incorporating this and other information in the inference of the evolutionary history of species.

Animals↗
PubMed1997

A 5.5-Mb high-resolution integrated map of distal 11q13.

The distal part of 11q13, which contains several genes relevant to human diseases, has been poorly mapped as part of genome-wide mapping efforts. In the prospect of drawing a fine-scale integrated map of the area containing KRN1 and OMP, we have established a framework of markers by hybridization to DNA of somatic cell hybrids and by fluorescence in situ hybridization (FISH) on metaphase chromosomes. The probes studied were used to isolate 27 YACs and 16 cosmids that could be organized in three contigs covering approximately 6 Mb. These contigs were separated by two gaps that are likely to contain sequences underrepresented in YAC libraries. They were then integrated based on long-range restriction mapping and DNA-fiber FISH into a high-resolution physical map, which covers a 5.5-Mb region and includes 36 anonymous markers and 10 genes. This map will be used to search for genes within the 2/3 of this region where none have been localized as yet. It will also lay the ground for the characterization of an amplicon surrounding GARP in breast cancer and for the search of disease genes within this region.

Animals↗
PubMed2004

Diastereoselective allylations of allyl-propargyl hybrid cations: synthesis of conjugated 1,5-dien-7-yne frameworks bearing C(4)-stereogenic centers.

[reaction: see text] Chiral C(4)-substituted (E)- or (Z)-1-alkynyl-1-trimethylsilyloxy-2-butene systems provide anti-(Z) or syn-(Z) conjugated dienyne, with a very high level of stereocontrol, on treatment with BF(3).OEt(2) in CH(2)Cl(2) at -50 degrees C in the presence of allyltrimethylsilane. The Cieplak conformation for (E)-substrates and neighboring-group participation for (Z)-substrates are considered to be responsible for the stereochemical consequences.

Journal Article↗
PubMed2026

Recent advances in electrode materials for electrochemical detection of zearalenone.

Zearalenone (ZEN) is an estrogenic mycotoxin commonly found in cereals, animal feed, and processed foods, making it an important concern for food safety and public health. Conventional chromatographic and immunological methods can detect ZEN; however, they often require expensive instruments, lengthy sample preparation, and skilled personnel, which restrict their use for rapid and on-site testing. Electrochemical sensors have attracted enormous interest of the scientific community because of their high sensitivity, rapid response, low cost, miniaturization potential, and compatibility with portable systems. The analytical performance of the electrochemical sensors is strongly influenced by electrode materials, morphology, conductivity, porosity, surface functionality, and the efficiency of bioreceptor immobilization. Despite several reviews on mycotoxin detection, a systematic assessment connecting electrode-material design, modification strategies, sensing mechanisms, and electroanalytical performance specifically for ZEN sensing remain limited. This review critically evaluates recent advances in metal oxides, carbon-based materials, metal-organic- and covalent organic frameworks, MXenes, polymers, and hybrid composites for electrochemical ZEN detection. Particular attention has been given to their roles in electron transfer, analyte enrichment, selectivity, and real-sample analysis. The review also compares the major limitations of current sensing systems, including complex fabrication, matrix interference, insufficient long-term stability, poor inter-electrode reproducibility, and limited scalability. Finally, future directions for developing robust, cost-effective, portable, and commercially viable ZEN sensors are discussed.

Journal Article↗
PubMed1997

Mapping ESTs to the TSC1 candidate interval by use of the 'Science 96' transcript map.

The transcription map of the human genome published by Schuler et al. (1996) is a valuable resource in which approximately one quarter of all human genes have been mapped with respect to genetic framework markers using radiation hybrids. We have taken information from this map to provide potential genes within the TSC1 candidate region on chromosome 9q34. In so doing we have been able to provide an independent assay of the quality of the radiation hybrid mapping by using somatic cell hybrids and a 2 Mb cosmid contig covering the TSC1 region as mapping tools. In addition, we have built sequence contigs of ESTs for 25 clusters. This has shown that about 20% of the relevant EST clusters in the Unigene resource (Boguski & Schuler 1995) contain chimaeric clones.

Animals↗
PubMed1986

Retrieval variability: sources and consequences.

A memory model that differentiates between active traces (ongoing electrochemical neural transmission) and passive traces (chemical/structural modification of neurons) is briefly outlined. Evidence suggests that new information is initially encoded as a passive representation within a fraction of a second, leaving little opportunity for retroactive interference with storage processes. Instead, it appears that retroactive interference results from disruption of post-acquisition processing which is necessary for subsequent retrieval. Using this hybrid cognitive-physiological framework, we examine possible sources of associative performance deficits. A distinction is made between similarity interference (arising from the content similarity of the target and interfering traces) and processing interference (arising from the competition between the two traces for use of a limited capacity processor). Both types of interference can act proactively or retroactively, and the similarity-processing and proactive-retroactive dimensions are viewed as orthogonal to the question of whether information is permanently lost or merely subject to a reversible retrieval failure. When reminder techniques (pretest cuing) are used, numerous instances of memory failure commonly identified as "acquisition failures" are found to be reversible without the occurrence of relevant new learning. This literature review constitutes the greater part of the paper. It is concluded that many memory failures are due at least in part to retrieval failure. Consideration of potential retrieval processes in light of the studies that are reviewed argues for the expansion of the initial active-passive trace distinction to three types of traces. In addition to active traces, these include two distinct types of passive traces, i.e., a small content-addressable reference catalog with innately defined dimensions that is used to locate more detailed passive traces, and a large capacity store of detailed passive traces that is location-addressable. The latter type of passive trace presumably is laid down almost instantaneously as events occur, i.e., in real time, whereas the reference catalog type of passive trace, which is used to address the detailed traces, is established somewhat after the sequence of events is complete. Hence, the reference catalog trace is more vulnerable and results in retrieval failure when it is disrupted.(ABSTRACT TRUNCATED AT 400 WORDS)

Amnesia↗
PubMed2001

Adopting hybrid pension plans: financial and communication issues.

This article provides a systematic framework for the evaluation of the movement toward hybrid pension plans by examining the reasons given by firms for converting their existing pension plans to hybrid plans, illustrating the impact of plan changes on expected pension benefits, and identifying winners and losers.

Communication↗
PubMedDate not supplied

A spacer that facilitates construction of implant-supported prostheses frameworks.

This article describes a technique that uses polyvinlysiloxane (PVS) putty impression material to create adequate space between the tissue and inferior margin of a framework in pattern construction for implant supported hybrid dentures. This spacer is easily retrieved from the cast, so the dental technician can evaluate and adjust the spacer to a standardized thickness and shape it to form the framework's underside. Basic framework construction for implant hybrid dentures is also reviewed, including specific dimensions, acrylic retentive features and passive construction. PVS putty impression material is easy to obtain, maintains dimensions well and is easy to shape, making it an excellent choice for use as a spacer and a matrix to preserve the position of denture teeth during fabrication.

Dental Impression Materials↗
PubMed2002

In(2)(OH)(3)(BDC)(1.5) (BDC = 1,4-benzendicarboxylate): an In(III) supramolecular 3D framework with catalytic activity.

The new hybrid inorganic-organic polymer In(2)(OH)(3)[O(4)C(8)H(4)](1.5) has been hydrothermally obtained. Conditions for the synthesis are reported. The crystal structure of this material has been established by single-crystal X-ray diffraction: it is monoclinic, with space group P2(1)/c (Nomicron. 14), a = 6.772(1) A, b = 10.329(2) A, c = 20.152(3) A, beta = 97.573(3) degrees. The In atoms are octahedrally coordinated by three hydroxide groups and three different molecules of carboxylate ligand. The resulting polymeric 3D structure can be envisaged as having been generated from a honeycomb (6,3) 2D that is cross-linked by the BDC organic anions. Data of IR and TGA-DTA studies, as well as the results of reduction of nitroaromatics and selective oxidation of organic sulfide reactions catalyzed by the new material, are reported.

Journal Article↗
PubMed2004

Phylogeny and diversification of the largest avian radiation.

The order Passeriformes ("perching birds") comprises extant species diversity comparable to that of living mammals. For over a decade, a single phylogenetic hypothesis based on DNA-DNA hybridization has provided the primary framework for numerous comparative analyses of passerine ecological and behavioral evolution and for tests of the causal factors accounting for rapid radiations within the group. We report here a strongly supported phylogenetic tree based on two single-copy nuclear gene sequences for the most complete sampling of passerine families to date. This tree is incongruent with that derived from DNA-DNA hybridization, with half of the nodes from the latter in conflict and over a third of the conflicts significant as assessed under maximum likelihood. Our historical framework suggests multiple waves of passerine dispersal from Australasia into Eurasia, Africa, and the New World, commencing as early as the Eocene, essentially reversing the classical scenario of oscine biogeography. The revised history implied by these data will require reassessment of comparative analyses of passerine diversification and adaptation.

Animals↗
PubMed1998

An anchored framework BAC map of mouse chromosome 11 assembled using multiplex oligonucleotide hybridization.

Despite abundant library resources for many organisms, physical mapping of these organisms has been seriously limited due to lack of efficient library screening techniques. We have developed a highly efficient strategy for large-scale screening of genomic libraries based on multiplex oligonucleotide hybridization on high-density genomic filters. We have applied this strategy to generate a bacterial artificial chromosome (BAC) anchored map of mouse chromosome 11. Using the MIT mouse SSLP data, 320 pairs of oligonucleotide probes were designed with an "overgo" computer program that selects new primer sequences that avoid the microsatellite repeat. BACs identified by these probes are automatically anchored to the chromosome. Ninety-two percent of the probes identified positive clones from a 5.9-fold coverage mouse BAC library with an average of 7 positive clones per marker. An average of 4.2 clones was confirmed for 204 markers by PCR. Our data show that a large number of clones can be efficiently isolated from a large genomic library using this strategy with minimal effort. This strategy will have wide application for large-scale mapping and sequencing of human and other large genomes.

Animals↗
PubMed1997

Building human genome maps with radiation hybrids.

Genome maps are crucial tools in human genetic research, providing known landmarks for locating disease genes and frameworks for large-scale sequencing. Radiation hybrid mapping is one technique for building genome maps. In this paper, we describe the methods used to build radiation hybrid maps of the entire human genome. We present the hidden Markov model that we employ to estimate the likelihood of a map despite uncertainty about the data, and we discuss the problem of searching for maximum-likelihood maps. We describe the graph algorithms used to find sparse but reliable initial maps and our methods of extending them. Finally, we show results validating our software on simulated data, and we describe our genome-wide human radiation hybrid maps and the evidence supporting them.

Chromosome Mapping↗
PubMed2001

Immunosuppressive properties of CD95L-transduced "killer" hybrids created by fusing donor- and recipient-derived dendritic cells.

Allogeneic immune responses, which are initiated by dendritic cells (DCs) of both donor and host origins, remain a major obstacle in organ transplantation. Presentation of intact major histocompatibility complex (MHC) molecules by allogeneic DCs and allogeneic peptides by syngeneic DCs leads to complex allogeneic immune responses. This study reports a novel strategy designed to suppress both pathways. A stable DC line XS106 (A/J mouse origin) was transfected with CD95L cDNA and fused with splenic DCs purified from allogeneic BALB/c mice. The resulting "killer" DC-DC hybrids: (1) expressed CD95L and MHC class I and class II molecules of both A/J and BALB/c origins, while maintaining otherwise characteristic surface phenotypes of mature DCs; (2) inhibited MHC class I- and class II-restricted mixed leukocyte reactions between the parental strains by triggering apoptosis of alloreactive T cells; and (3) abolished delayed-type hypersensitivity responses of A/J (and BALB/c) mice to BALB/c-associated (and A/J-associated) alloantigens when injected intravenously into A/J (and BALB/c) mice. The onset of graft-versus-host disease in (BALB/c x A/J) F1 hosts receiving A/J-derived hematopoietic cell transplantation was suppressed significantly (P <.001) by killer DC-DC hybrid treatment. These results form both technical and conceptual frameworks for clinical applications of CD95L-transduced killer hybrids created between donor DCs and recipient DCs in the prevention of allogeneic immune responses following organ transplantation.

Animals↗
PubMedDate not supplied

Immediate occlusal loading of Osseotite implants in the completely edentulous mandible.

PURPOSE: This article reports the preliminary data from a clinical study of immediately loaded, full-arch, screw-retained prosthesis with distal extensions (hybrid prosthesis) supported by Osseotite implants placed in the edentulous mandible. MATERIALS AND METHODS: Fifteen patients who received 103 implants were enrolled in this study. The first 2 patients received both immediately loaded and submerged implants, while the remaining patients had all implants immediately loaded. The first 9 patients received a temporary prosthesis within 4 hours of surgery, and the hybrid prosthesis, made of a titanium framework and acrylic resin teeth, was placed after 6 months. The last 6 patients received the same type of hybrid prosthesis within 36 hours of surgery. Marginal bone loss was monitored via periapical radiographs by a computerized technique. RESULTS: One failure (out of the 92 immediately loaded implants) occurred after 3 weeks of function because of infection. A cumulative success rate of 98.9% was achieved for up to 48 months of follow-up, while the prosthetic cumulative success rate for the same period was 100%. Marginal bone loss at the immediately loaded implants was within the generally accepted conventional limits for standard delayed loading protocols. DISCUSSION: This technique can reduce treatment time but should be applied with caution. CONCLUSION: The preliminary results of this study suggest that rehabilitation of the edentulous mandible by an immediately loaded hybrid prosthesis supported by 5 to 6 implants may represent a viable alternative treatment to the classical delayed loading protocols.

Acrylic Resins↗
PubMed2002

Intercalated organic-inorganic perovskites stabilized by fluoroaryl-aryl interactions.

Crystals of several new hybrid tin(II) iodide-based perovskites, involving 2,3,4,5,6- pentafluorophenethylammonium or phenethylammonium cation bilayers and intercalated aryl or perfluoroaryl molecules, were grown by slow evaporation of a methanol solution containing the hybrid perovskite and the intercalating species. The (C(6)F(5)C(2)H(4)NH(3))(2)SnI(4).(C(6)H(6)) structure was solved at -75 degrees C in a monoclinic C2/c subcell [a = 41.089(12) A, b = 6.134(2) A, c = 12.245(3) A, beta = 94.021(5) degrees, Z = 4] and consists of sheets of corner-sharing distorted SnI(6) octahedra separated by bilayers of pentafluorophenethylammonium cations. The intercalated benzene molecules form a single well-ordered layer interposed between adjacent fluoroaryl cation layers. The corresponding hybrid with an unfluorinated organic cation and fluorinated intercalating molecule, (C(6)H(5)C(2)H(4)NH(3))(2)SnI(4).(C(6)F(6)), is isostructural [a = 40.685(4) A, b = 6.0804(6) A, c = 12.163(1) A, beta = 93.136(2) degrees, Z = 4]. For each intercalated system, close C...C contacts (3.44-3.50 A) between the aromatic cation and the intercalated molecule are indicative of a significant face-to-face interaction, similar to that found in the complex C(6)H(6).C(6)F(6). Crystal growth runs with the organic cation and prospective intercalating molecule either both fluorinated or both unfluorinated did not yield stable intercalated compounds, demonstrating the significance of fluoroaryl-aryl interactions in the current intercalated structures. Thermal analysis of (C(6)F(5)C(2)H(4)NH(3))(2)SnI(4).(C(6)H(6)) and (C(6)H(5)C(2)H(4)NH(3))(2)SnI(4).(C(6)F(6)) crystals yields, in addition to the characteristic transitions of the parent perovskite, endothermic transitions [12.6(5) and 32.1(8) kJ/mol, respectively] with an onset at 145 degrees C and a weight loss corresponding to the complete loss of the intercalated molecule. The relatively high deintercalation temperature (well above the boiling point of benzene and hexafluorobenzene) demonstrates the usefulness of the hybrid perovskites in providing a stable framework for the examination of the fluoroaryl-aryl interaction, as well as the potential importance of this interaction in tailoring new hybrid perovskites. UV-vis absorption measurements on (C(6)H(5)C(2)H(4)NH(3))(2)SnI(4).(C(6)F(6)) thin films indicate a small reversible wavelength shift to higher energy for the tin(II) iodide framework exciton peak (with respect to that of the parent perovskite spectrum), from 608(2) nm [2.04 eV] to 595(2) nm [2.08 eV], and a corresponding shift in the band edge position. This spectral shift can most reasonably be attributed to subtle structural changes induced in the tin(II) iodide sheets by the intercalated hexafluorobenzene molecules.

Journal Article↗
PubMed1998

Involvement of actin microfilaments in the replication of human parainfluenza virus type 3.

Several studies indicate that paramyxoviruses require a specific cellular factor(s) for transcription of their genomic RNAs. We previously reported that the cellular cytoskeletal protein actin, in its polymeric form, participates in the transcription of human parainfluenza virus type 3 (HPIV3) in vitro. In the present study, we investigated the role of the polymeric form of actin, i.e., the actin microfilaments of the cytoskeletal framework, in the reproduction of HPIV3 in vivo. Pulse-chase labeling analyses indicate that the viral nucleocapsid-associated proteins, NP and P, are present predominantly in the cytoskeletal framework during infection. By in situ hybridization, we found that viral mRNAs and genomic RNA were synthesized from the nucleocapsids that were bound to the cytoskeletal framework. Double immunofluorescent labeling and confocal microscopy of the cytoarchitecture revealed that the viral nucleocapsids are specifically localized on the actin microfilaments. Treatment of cells with the actin-depolymerizing agent, cytochalasin D, resulted in the inhibition of viral RNA synthesis and ribonucleoprotein accumulation. These results strongly suggest that actin microfilaments play an important role in the replication of HPIV3.

Actin Cytoskeleton↗