538 research outputs found
Kaolin shear thickening fluid reinforced UHMWPE composites for protective clothing
This study reports the designing and reinforcing of impact resistant textile composites using kaolin based shear thickening colloidal dispersions as the filler material. The reinforced fabric is targeted for the chest protection of cricketers. A shear thickening fluid (STF) has been prepared using kaolin and glycerol, at kaolin volume fractions of 34% and 38%. A combination of mixing techniques including mechanical blending and ultra-sonication are used to prepare the colloidal dispersions. Ultra high molecular weight polyethylene (UHMWPE) woven fabric structures are reinforced with the STF. The fabric coated with STF are then measured for their flexibility, and impact resistance using Shirley stiffness tester and a series of modified drop tower tests respectively. Kaolin STF at 38% volume fraction shows best results in impregnated fabric samples. STF reinforced fabrics provide better impact resistance with improved moisture absorption and flexibility in comparison to the conventional chest guard material
Use of Lysolecithin-Permeabilized Infected-Cell Extracts to Investigate thein VitroBiochemical Phenotypes of Poxvirus ts Mutations Altered in Viral Transcription Activity
AbstractLysolecithin permeabilization of vaccinia virus-infected cells was employed to prepare extracts that support faithful transcription initiationin vitroon plasmids possessing early, intermediate, and late viral gene promoters. Conditions which optimize transcription from each promoter were defined. Thein vitrosystem was used to investigate the multifunctional viral mRNA capping enzyme, which also functions as the viral early gene transcription termination factor (VTF) and a viral intermediate gene transcription initiation factor. A low level of signal-dependent termination of early gene transcription was observedin vitrowhich could be elevated by the addition of pure mRNA capping enzyme. VTF-dependent transcription termination was found to be restricted to templates that possessed an early promoter. This restriction mimics that observedin vivoand demonstrates that transcription termination is limited to RNA polymerase molecules that recognize early rather than intermediate or late gene promoters. Extracts prepared from cells infected at the nonpermissive temperature with a virus containing a ts mutation in gene D12L, which encodes the small subunit of VTF, are incapable of supporting both early gene transcription termination and intermediate gene transcription initiation. Both activities are restored upon addition of the purified wild-type mRNA capping enzyme
Gaugino Condensation in M-theory on S^1/Z_2
In the low energy limit of for M-theory on S^1/Z_2, we calculate the gaugino
condensate potential in four dimensions using the background solutions due to
Horava. We show that this potential is free of delta-function singularities and
has the same form as the potential in the weakly coupled heterotic string. A
general flux quantization rule for the three-form field of M-theory on S^1/Z_2
is given and checked in certain limiting cases. This rule is used to fix the
free parameter in the potential originating from a zero mode of the form field.
Finally, we calculate soft supersymmetry breaking terms. We find that
corrections to the Kahler potential and the gauge kinetic function, which can
be large in the strongly coupled region, contribute significantly to certain
soft terms. In particular, for supersymmetry breaking in the T-modulus
direction, the small values of gaugino masses and trilinear couplings that
occur in the weakly coupled, large radius regime are enhanced to order m_3/2 in
M-theory. The scalar soft masses remain small even, in the strong coupling
M-theory limit.Comment: 20 pages, LATE
Martian Atmospheric Methane Plumes from Meteor Shower Infall: A Hypothesis
Methane plumes in the martian atmosphere have been detected using Earth-based spectroscopy, the Planetary Fourier Spectrometer on the ESA Mars Express mission, and the NASA Mars Science Laboratory. The methane's origin remains a mystery, with proposed sources including volcanism, exogenous sources like impacts and interplanetary dust, aqueous alteration of olivine in the presence of carbonaceous material, release from ancient deposits of methane clathrates, and/or biological activity. To date, none of these phenomena have been found to reliably correlate with the detection of methane plumes. An additional source exists, however: meteor showers could generate martian methane via UV pyrolysis of carbon-rich infall material. We find a correlation between the dates of Mars/cometary orbit encounters and detections of methane on Mars. We hypothesize that cometary debris falls onto Mars during these interactions, depositing freshly disaggregated meteor shower material in a regional concentration. The material generates methane via UV photolysis, resulting in a localized "plume" of short-lived methane
Nucleotide analogs and molecular modeling studies reveal key interactions involved in substrate recognition by the yeast RNA triphosphatase
RNA triphosphatases (RTPases) are involved in the addition of the distinctive cap structure found at the 5âČ ends of eukaryotic mRNAs. Fungi, protozoa and some DNA viruses possess an RTPase that belongs to the triphosphate tunnel metalloenzyme family of enzymes that can also hydrolyze nucleoside triphosphates. Previous crystallization studies revealed that the phosphohydrolase catalytic core is located in a hydrophilic tunnel composed of antiparallel ÎČ-strands. However, all past efforts to obtain structural information on the interaction between RTPases and their substrates were unsuccessful. In the present study, we used computational molecular docking to model the binding of a nucleotide substrate into the yeast RTPase active site. In order to confirm the docking model and to gain additional insights into the molecular determinants involved in substrate recognition, we also evaluated both the phosphohydrolysis and the inhibitory potential of an important number of nucleotide analogs. Our study highlights the importance of specific amino acids for the binding of the sugar, base and triphosphate moieties of the nucleotide substrate, and reveals both the structural flexibility and complexity of the active site. These data illustrate the functional features required for the interaction of an RTPase with a ligand and pave the way to the use of nucleotide analogs as potential inhibitors of RTPases of pathogenic importance
Martian Methane From a Cometary Source: A Hypothesis
In recent years, methane in the martian atmosphere has been detected by Earth-based spectroscopy, the Planetary Fourier Spectrometer on the ESA Mars Express mission, and the NASA Mars Science Laboratory. The methane's origin remains a mystery, with proposed sources including volcanism, exogenous sources like impacts and interplanetary dust, aqueous alteration of olivine in the presence of carbonaceous material, release from ancient deposits of methane clathrates, and/or biological activity. An additional potential source exists: meteor showers from the emission of large comet dust particles could generate martian methane via UV pyrolysis of carbon-rich infall material. We find a correlation between the dates of Mars/cometary orbit encounters and detections of methane on Mars. We hypothesize that cometary debris falls onto Mars during these interactions, generating methane via UV photolysis
-Parity Violation in Flavor Changing Neutral Current Processes and Top Quark Decays
We show that supersymmetric -parity breaking () interactions
always result in Flavor Changing Neutral Current (FCNC) processes. Within a
single coupling scheme, these processes can be avoided in either the charge
or the charge quark sector, but not both. These processes are
used to place constraints on \Rp couplings. The constraints on the first and
the second generations are better than those existing in the literature. The
\Rp interactions may result in new top quark decays. Some of these violate
electron-muon universality or produce a surplus of quark events in
decays. Results from the CDF experiment are used to bound these \Rp
couplings.Comment: LaTeX, 20 pages, spelling corrected from origina
Noninvasive In Vivo Imaging to Evaluate Immune Responses and Antimicrobial Therapy against Staphylococcus aureus and USA300 MRSA Skin Infections
Staphylococcus aureus skin infections represent a significant public health threat because of the emergence of antibiotic-resistant strains such as methicillin-resistant S. aureus (MRSA). As greater understanding of protective immune responses and more effective antimicrobial therapies are needed, a S. aureus skin wound infection model was developed in which full-thickness scalpel cuts on the backs of mice were infected with a bioluminescent S. aureus (methicillin sensitive) or USA300 community-acquired MRSA strain and in vivo imaging was used to noninvasively monitor the bacterial burden. In addition, the infection-induced inflammatory response was quantified using in vivo fluorescence imaging of LysEGFP mice. Using this model, we found that both IL-1α and IL-1ÎČ contributed to host defense during a wound infection, whereas IL-1ÎČ was more critical during an intradermal S. aureus infection. Furthermore, treatment of a USA300 MRSA skin infection with retapamulin ointment resulted in up to 85-fold reduction in bacterial burden and a 53% decrease in infection-induced inflammation. In contrast, mupirocin ointment had minimal clinical activity against this USA300 strain, resulting in only a 2-fold reduction in bacterial burden. Taken together, this S. aureus wound infection model provides a valuable preclinical screening method to investigate cutaneous immune responses and the efficacy of topical antimicrobial therapies
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