674 research outputs found
Flux Expulsion - Field Evolution in Neutron Stars
Models for the evolution of magnetic fields of neutron stars are constructed,
assuming the field is embedded in the proton superconducting core of the star.
The rate of expulsion of the magnetic flux out of the core, or equivalently the
velocity of outward motion of flux-carrying proton-vortices is determined from
a solution of the Magnus equation of motion for these vortices. A force due to
the pinning interaction between the proton-vortices and the neutron-superfluid
vortices is also taken into account in addition to the other more conventional
forces acting on the proton-vortices. Alternative models for the field
evolution are considered based on the different possibilities discussed for the
effective values of the various forces. The coupled spin and magnetic evolution
of single pulsars as well as those processed in low-mass binary systems are
computed, for each of the models. The predicted lifetimes of active pulsars,
field strengths of the very old neutron stars, and distribution of the magnetic
fields versus orbital periods in low-mass binary pulsars are used to test the
adopted field decay models. Contrary to the earlier claims, the buoyancy is
argued to be the dominant driving cause of the flux expulsion, for the single
as well as the binary neutron stars. However, the pinning is also found to play
a crucial role which is necessary to account for the observed low field binary
and millisecond pulsars.Comment: 23 pages, + 7 figures, accepted for publication in Ap
Wieldy Finger and Hand Motion Detection for Human Computer Interaction
We have developed a gesture based interface for human computer interaction under the research field of computer vision.Earlier system have used the costlier system devices to make an effective interaction with systems, instead we have worked on the web cam based gesture input system.Our goal was to propound lesser cost, wieldy, object detection technique using blobs for detection of fingers.And to give number of count of the same.In addition, we have also implemented the hand gesture recognition
Novel 5-oxo-hexahydroquinoline derivatives: design, synthesis, in vitro P-glycoprotein-mediated multidrug resistance reversal profile and molecular dynamics simulation study
Overexpression of the efflux pump P-glycoprotein (P-gp) is one of the important mechanisms of multidrug resistance (MDR) in many tumor cells. In this study, 26 novel 5-oxo-hexahydroquinoline derivatives containing different nitrophenyl moieties at C-4 and various carboxamide substituents at C-3 were designed, synthesized and evaluated for their ability to inhibit P-gp by measuring the amount of rhodamine 123 (Rh123) accumulation in uterine sarcoma cells that overexpress P-gp (MES-SA/Dx5) using flow cytometry. The effect of compounds with highest MDR reversal activities was further evaluated by measuring the alterations of MES-SA/Dx5 cells' sensitivity to doxorubicin (DXR) using MTT assay. The results of both biological assays indicated that compounds bearing 2-nitrophenyl at C-4 position and compounds with 4-chlorophenyl carboxamide at C-3 demonstrated the highest activities in resistant cells, while they were devoid of any effect in parental nonresistant MES-SA cells. One of the active derivatives, 5c, significantly increased intracellular Rh123 at 100 mu M, and it also significantly reduced the IC50 of DXR by 70.1% and 88.7% at 10 and 25 mu M, respectively, in MES-SA/Dx5 cells. The toxicity of synthesized compounds against HEK293 as a noncancer cell line was also investigated. All tested derivatives except for 2c compound showed no cytotoxicity. A molecular dynamics simulation study was also performed to investigate the possible binding site of 5c in complex with human P-gp, which showed that this compound formed 11 average H-bonds with Ser909, Thr911, Arg547, Arg543 and Ser474 residues of P-gp. A good agreement was found between the results of the computational and experimental studies. The findings of this study show that some 5-oxo-hexahydroquinoline derivatives could serve as promising candidates for the discovery of new agents for P-gp-mediated MDR reversal
Fast determination of bisphenol A in spiked juice and drinking water samples by pipette tip solid phase extraction using cobalt metal organic framework as sorbent
A cobalt metal organic framework was prepared with rapid ultrasound assisted method by treatment of cobalt nitrate with pyridine 2,6-dicarboxilic acid dissolved in ethanolic media and used as a sorbent for pipette tip solid phase extraction of Bisphenol A (BPA) and its determination in spiked juice and drinking water samples by HPLC. Parameters which influence extraction efficiency such as pH, sample volume, amount of sorbent, type and volume of eluent, and number of draw/eject cycles for extraction and elusion were tested and optimized. Results showed that best extraction efficiency could be obtained at pH 3, 150 â”L of sample volume, 3 mg of adsorbent and 10 â”L of methanol as elution solvent. Numbers of draw/eject cycles for both sample extraction and elution were 7 cycles. Limit of detection and limit of quantification of this method were 0.07 and 0.3 ”g L-1, respectively, with linear dynamic range of 0.3 to 300 ”g L-1 for BPA. This method was applied successfully for determination of BPA in five spiked juices and drinking water samples.               KEY WORDS: Cobalt metal organic framework, Bisphenol A, Pipette-tip solid phase extraction, Juice analysis Bull. Chem. Soc. Ethiop. 2018, 32(3), 595-602.DOI: https://dx.doi.org/10.4314/bcse.v32i3.1
The elusiveness of old neutron stars
Old neutron stars (ONSs) which have radiated away their internal and
rotational energy may still shine if accreting the interstellar medium. Despite
their large number, only two promising candidates have been detected so far and
rather stringent limits on their observability follow from the analysis of
ROSAT surveys. This contrasts with optimistic theoretical estimates that
predicted a large number of sources in ROSAT fields. We have reconsidered the
issue of ONSs observability, accounting for the spin and magnetic field
evolution over the neutron star lifetime. In the framework of a spin-induced
field decay model, we show that the total number of ONSs which are, at present,
in the accretion stage is reduced by a factor ~5 over previous figures if the
characteristic timescale for crustal current dissipation is ~ 10^8 - 10^9 yr.
This brings theoretical predictions much closer to observational limits. Most
ONSs should be at present in the propeller phase and, if subject to episodic
flaring, they could be observable.Comment: 10 pages Latex, 5 ps figures. To be formatted with the AASTeX
package. Accepted for publication in Ap
Successful use of axonal transport for drug delivery by synthetic molecular vehicles
We report the use of axonal transport to achieve intraneural drug delivery. We constructed a novel tripartite complex of an axonal transport facilitator conjugated to a linker molecule bearing up to a hundred reversibly attached drug molecules. The complex efficiently enters nerve terminals after intramuscular or intradermal administration and travels within axonal processes to neuron cell bodies. The tripartite agent provided 100-fold amplification of saturable neural uptake events, delivering multiple drug molecules per complex. _In vivo_, analgesic drug delivery to systemic and to non-targeted neural tissues was greatly reduced compared to existing routes of administration, thus exemplifying the possibility of specific nerve root targeting and effectively increasing the potency of the candidate drug gabapentin 300-fold relative to oral administration
Persistent random walk on a one-dimensional lattice with random asymmetric transmittances
We study the persistent random walk of photons on a one-dimensional lattice
of random asymmetric transmittances. Each site is characterized by its
intensity transmittance t (t') for photons moving to the right (left)
direction. Transmittances at different sites are assumed independent,
distributed according to a given probability density Distribution. We use the
effective medium approximation and identify two classes of probability density
distribution of transmittances which lead to the normal diffusion of photons.
Monte Carlo simulations confirm our predictions.Comment: 7 pages, submitted to Phys. Rev.
- âŠ