Because of the potential implementation of indoor wireless local area networks (LANs) and personal communication networks (PCNs) it is important to understand propagation of signals in the UHF band ...inside buildings. The authors explore features of office buildings of modern construction that influence propagation between transmitter and receiver located on the same floor. One feature is the clear space between ceiling and furnishings or floor that results in excess attenuation of the signal. A second feature is reflection and transmission at interior and exterior walls. Diffraction at corners and propagation along the exterior wall are also shown to be a significant means for radiation to reach the receivers. The influences of the first two features are combined into a computer program that evaluates the sector average signal, which is then compared with measurements.< >
In defining path loss for narrowband systems, it is common to introduce the concept of the sector or local average in order to remove the rapid (Rayleigh or Rician) fading. As originally developed ...for cellular mobile radio (CMR) systems, the sector average is obtained from the spatial average of the received signal as the mobile traverses a path of 20 or so wavelengths. This approach has also been applied indoors with the assumption that a unique average could be obtained by moving either end of the radio link. Unlike the CMR path for indoor propagation, however, both ends of the radio link are in a rich multipath environment. It is shown both theoretically and experimentally that moving both ends of the link is required to achieve a unique average. When averaging is accomplished by moving only one end, the result can experience variations of as much as /spl plusmn/2 dB when the other end is moved by a fraction of a wavelength.< >
The potential implementation of wireless radio local area networks (LANs) and personal communication services inside buildings requires a thorough understanding of signal propagation within ...buildings. In this work the authors develop a theory which explains propagation between a transmitter and a receiver located on different floors of a building. Depending on the structure of the building and the location of the antennas, either direct ray propagation through floors or diffraction outside the building will determine the propagation characteristics and range dependence of the signal sector average as the number of floors between the transmitter and the receiver is increased.< >
Neutrinos are elementary particles that carry no electric charge and have little mass. As they interact only weakly with other particles, they can penetrate enormous amounts of matter, and therefore ...have the potential to directly convey astrophysical information from the edge of the Universe and from deep inside the most cataclysmic high-energy regions. The neutrino's great penetrating power, however, also makes this particle difficult to detect. Underground detectors have observed low-energy neutrinos from the Sun and a nearby supernova, as well as neutrinos generated in the Earth's atmosphere. But the very low fluxes of high-energy neutrinos from cosmic sources can be observed only by much larger, expandable detectors in, for example, deep water or ice. Here we report the detection of upwardly propagating atmospheric neutrinos by the ice-based Antarctic muon and neutrino detector array (AMANDA). These results establish a technology with which to build a kilometre-scale neutrino observatory necessary for astrophysical observations.
Clinicult, a selective medium for culturing Neisseria gonorrhoeae, was field-tested in a gonorrhea screening program in Seattle, Wash., in 1973. The results with this medium and with the Transgrow ...and Thayer-Martin culture systems were compared as to sensitivity and specificity. A total of 5,141 women from three patient groups were included in the study. Group 1 consisted of 720 female patients of the venereal disease clinic of the Seattle-King County Health Department, who served as the control group. When this group was screened with the Clinicult and Thayer-Martin culture media, the Thayer-Martin medium proved superior in identifying positive carriers. Group 2 was composed of approximately 2,000 patients from five different facilities, including family planning clinics and hospital out-patient services. No statistical difference in accuracy was found between the two culture systems used for this group--Clinicult and Transgrow. Group 3 was comprised of approximately 2,500 female patients who were screened with the Clinicult and Transgrow cultures by their own private physician or his staff. The Clinicult system proved significantly less effective than the Transgrow culture in identifying infected females in group 3. The physicians varied greatly in their ability to use the Clinicult system successfully. Possible reasons for their errors may have been (a) lack of motivation and of care by their office personnel in conducting the necessary additional procedures required with Clinicult, (b) the inhibitory nature of the medium, and (c) the failure of the medium to produce colonies of adequate size. The staffs of communitywide screening programs for gonorrhea need to be highly selective in choosing the medical facilities in which to use the Clinicult culture system. When laboratory facilities are available for the full utilization of the Thayer-Martin medium, this system is preferable. When, however, standard culture procedures are not readily available, Clinicult, properly used, can reduce the central laboratory load by eliminating the need for processing negative cultures.
Peptides and biologics provide unique opportunities to modulate intracellular targets not druggable by conventional small molecules. Most peptides and biologics are fused with cationic uptake ...moieties or formulated into nanoparticles to facilitate delivery, but these systems typically lack potency due to low uptake and/or entrapment and degradation in endolysosomal compartments. Because most delivery reagents comprise cationic lipids or polymers, there is a lack of reagents specifically optimized to deliver cationic cargo. Herein, we demonstrate the utility of the cytocompatible polymer poly(propylacrylic acid) (PPAA) to potentiate intracellular delivery of cationic biomacromolecules and nano-formulations. This approach demonstrates superior efficacy over all marketed peptide delivery reagents and enhances delivery of nucleic acids and gene editing ribonucleoproteins (RNPs) formulated with both commercially-available and our own custom-synthesized cationic polymer delivery reagents. These results demonstrate the broad potential of PPAA to serve as a platform reagent for the intracellular delivery of cationic cargo.
Topochemical polymerization reactions hold the promise of producing ultra-high molecular weight crystalline polymers. However, the totality of topochemical polymerization reactions has failed to ...produce ultra-high molecular weight polymers that are both soluble and display variable functionality, which are restrained by the crystal-packing and reactivity requirements on their respective monomers in the solid state. Herein, we demonstrate the topochemical polymerization reaction of a family of para-azaquinodimethane compounds that undergo facile visible light and thermally initiated polymerization in the solid state, allowing for the first determination of a topochemical polymer crystal structure resolved via the cryoelectron microscopy technique of microcrystal electron diffraction. The topochemical polymerization reaction also displays excellent functional group tolerance, accommodating both solubilizing side chains and reactive groups that allow for post-polymerization functionalization. The thus-produced soluble ultra-high molecular weight polymers display superior capacitive energy storage properties. This study overcomes several synthetic and characterization challenges amongst topochemical polymerization reactions, representing a critical step toward their broader application.
Control of equilibrium and non‐equilibrium thermomechanical behavior of poly(diketoenamine) vitrimers is shown by incorporating linear polymer segments varying in molecular weight (MW) and ...conformational degrees of freedom into the dynamic covalent network. While increasing MW of linear segments yields a lower storage modulus at the rubbery plateau after softening above the glass transition (Tg), both Tg and the characteristic time of stress relaxation are independently governed by the conformational entropy of the embodied linear segments. Activation energies for bond exchange in the solid state are lower for networks incorporating flexible chains; the network topology freezing temperature decreases with increasing MW of flexible linear segments but increases with increasing MW of stiff segments. Vitrimer reconfigurability is therefore influenced not only by the energetics of bond exchange for a given network density, but also the entropy of polymer chains within the network.
Go with the flow: Microstructural and architectural attributes of vitrimers are powerful design elements for controlling their mechanical and rheological properties. Conformational entropy of their embodied monomer segments appears to dominate such properties for architecturally similar vitrimer networks.
Stable redox-active conjugated molecules with exceptional electron-donating abilities are key components for the design and synthesis of ultralow band gap conjugated polymers. While hallmark ...electron-rich examples such as pentacene derivatives have been thoroughly explored, their poor air stability has hampered their broad incorporation into conjugated polymers for practical applications. Herein, we describe the synthesis of the electron-rich, fused pentacyclic pyrazino2,3-b:5,6-b’diindolizine (PDIz) motif and detail its optical and redox behavior. The PDIz ring system exhibits a lower oxidation potential and a reduced optical band gap than the isoelectronic pentacene while retaining greater air stability in both solution and the solid state. The enhanced stability and electron density, together with readily installed solubilizing groups and polymerization handles, allow for the use of the PDIz motif in the synthesis of a series of conjugated polymers with band gaps as small as 0.71 eV. The tunable absorbance throughout the biologically relevant near-infrared I and II regions enables the use of these PDIz-based polymers as efficient photothermal therapeutic reagents for laser ablation of cancer cells.
Enhancing the response to interferon could offer an immunological advantage to the host. In support of this concept, we used a modified form of the transcription factor STAT1 to achieve ...hyper-responsiveness to interferon without toxicity and markedly improve antiviral function in transgenic mice and transduced human cells. We found that the improvement depended on expression of a PARP9-DTX3L complex with distinct domains for interaction with STAT1 and for activity as an E3 ubiquitin ligase that acted on host histone H2BJ to promote interferon-stimulated gene expression and on viral 3C proteases to degrade these proteases via the immunoproteasome. Thus, PARP9-DTX3L acted on host and pathogen to achieve a double layer of immunity within a safe reserve in the interferon signaling pathway.
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