Large Magnetoresistance and Jahn Teller effect in Sr2_2FeCoO6_6

Neutron diffraction measurement on the spin glass double perovskite Sr$_2$FeCoO$_6$ reveals site disorder as well as Co$^{3+}$ intermediate spin state. In addition, multiple valence states of Fe and Co are confirmed through M\"{o}ssbauer and X-ray photoelectron spectroscopy. The structural disorder and multiple valence lead to competing ferromagnetic and antiferromagnetic interactions and subsequently to a spin glass state, which is reflected in the form of an additional $T$-linear contribution at low temperatures in specific heat. A clear evidence of Jahn-Teller distortion at the Co$^{3+}$-O$_6$ complex is observed and incorporating the physics of Jahn-Teller effect, the presence of localized magnetic moment is shown. A large, negative and anomalous magnetoresistance of $\approx$ 63% at 14K in 12T applied field is observed for Sr$_2$FeCoO$_6$. The observed magnetoresistance could be explained by applying a semi-empirical fit consisting of a negative and a positive contribution and show that the negative magnetoresistance is due to spin scattering of carriers by localized magnetic moments in the spin glass phase

A PERSPECTIVE REVIEW ON APPLICATIONS OF NANOPARTICLE MEDIATED DRUG DELIVERY TO THE CNS

Delivery of drugs into the brain is one of the most interesting and challenging areas of research. The blood-brain barrier (BBB) is a highly selective semipermeable membrane that separates blood from the brain in the central nervous system. It acts as a barrier to protect the brain from microbes, neurotoxins and other chemical substances and also blocks the entry of many drugs into the brain. An estimated 6.8 billion people die every year from CNS diseases like Parkinson’s disease, Alzheimer’s disease, sclerosis, brain stroke, dementia and others. According to WHO, one billion people are affected worldwide, about 50 million suffer from epilepsy and 24 million suffer from Alzheimer and other dementias. This indicates the importance of the delivery of drugs into the brain for treating various neurological diseases and psychological disorders. In drug targeting, a concept was introduced by Dr. Paul Ehrlich as a ‘magic bullet’ that gave tremendous hope for the researches to deliver drugs into the brain. This review discuses about various drug targeting strategies and applications of nanotechnology in designing drug delivery systems with the ability to cross through the BBB for treating neurological diseases

EVALUATION OF A NOVEL, NATURAL LOCUST BEAN GUM AS A SUSTAINED RELEASE AND MUCOADHESIVE COMPONENT OF TIZANIDINE HYDROCHLORIDE BUCCAL TABLETS

Mucoadhesive polymers that bind to the gastric mucins or epithelial cell surface are useful in drug delivery for the purpose of increasing the intimacy andduration of contact of the drug with the absorbing membrane. Mainly synthetic polymers are in use for this purpose. Probably the biodegradability of thesynthetic polymers is questionable. In the present work mucoadhesive buccal tablets of tizanidine hydrochloride were prepared using locust bean gumthat has better mucoadhesive property than synthetic polymer. The in vitro adhesive and mucoadhesive strength and swelling property of mucoadhesivmaterial locust bean gum were evaluated by Share Stress and Park and Robinson methods. Buccal formulations of tizanidine hydrochloride tablets werprepared using locust bean gum, and thickness, hardness, friability, weight variation, and assay of tablets were tested. The in vitro drug release studof tizanidine hydrochloride exhibited extended drug release profile for tablets prepared. Higuchi and Peppas data reveal that the drug released by nonFickiandiffusion mechanism. The presentstudyshowsthat formulationcontaining 50% locust bean gum havegreatermucoadhesivepropertythan allotherformulation.Increasein concentrationof locust bean gum increasesin the bioadhesivestrengthand swellingratioin the 50mgof locust bean gum.Keywords: Mucoadhesive, Tizanidine hydrochloride, Tablets, Locust bean gum

Incidence of Chirodiscoides caviae in Laboratory Rats-Screening, Identification and Treatment

This is a report on the incidence and treatment of the guinea pig fur mite Chirodiscoides caviae, which  was so far considered as host specific, in a conventional colony of laboratory rats. Chirodiscoides caviae  infestation in laboratory rats was accidentally observed during the screening of Syphacia obvelata by the  peri-anal cellophane tape test (CTT). The organism was identified by comparing the morphology described  by various researchers and was differentially diagnosed from other common mites of rat, Radfordia ensifera  and Notoedres muris. The adult male mites (n=15) were of 330.2±13.3 μm long and the females (n=15)  495.5±25.2 μm. Later on, the entire rat colony consisting of Wistar, Sprague Dawley and Spontaneously  Hypertensive Rats (SHR) and the mice colony of Balb/c and Swiss Albino were randomly sampled and  screened for the presence of the mite by the cellophane tape technique. All the rat strains were found positive  for C. caviae infestation, which was more concentrated towards the posterior region of the body and,  collectively, the screening results of C. caviae revealed that the posterio-dorsal and peri-anal regions are  most suitable for sampling-suggesting that, the infestation pattern of C. caviae in rats has similarities to that  of guinea pigs. Interestingly the mice colony was found free from the infestation. The Cellophane tape test was found to be an easier method than fur examination by hair plucking and equally  accurate for screening of fur mite in a colony of laboratory rats. No clinical symptoms were observed in  any of the animals in the colony, which possessed infestation. The facility strictly practised physical separation  of animals by species, which pointed to the only possibility of cross infestation being through indirect  contact between guinea pigs and laboratory rats and thereby questioning previous reports on the mode of  transmission of C. caviae. The entire colony was effectively treated with 0.2% Ivermectin spray followed by  1% spray in an interval of 2 weeks. This report is the first one, which demonstrates the guinea pig fur mite  in laboratory rats. It also questions the so far documented “host specificity” and “direct contact” mode of  transmission and demonstrates indirect contact as a possible mode of transmission.

A Numerical Study of Penetration in Concrete Targets by Eroding Projectiles of Different Materials

Numerical simulations have been performed to examine the effect of three different eroding rod materials on the penetration in concrete targets. Same kinetic energy is delivered to concrete target using cylindrical rods of Aluminium, Iron, and Copper of identical size. Impact velocities have been varied to keep the kinetic energy the same. Penetration characteristics like centerline interface velocity, penetrator deceleration, plastic strain in the target, and energy partitioning during penetration have been studied for the three different penetrator materials. In all three cases, penetration proceeds nearly hydrodynamically. It is seen that even though the steady-state penetration ceases before reaching the hydrodynamic limit, the secondary penetration takes the total penetration beyond the hydrodynamic value. Plastic strain in the target material is a measure of damage beyond the crater produced by penetration. The lateral extent of plastic strain in target is more for Aluminium penetrator compared to the other two. Energy partitioning during penetration provides details of the rate at which energy is entering into the target. Kinetic energy delivered to the target during impact is partitioned into internal energy and kinetic energy of the target. Finally, the influence of target thickness on the extent of plastic strain has been studied. The result shows that Aluminium penetrators inflict maximum damage to targets of finite thickness

Griffiths phase-like behaviour and spin-phonon coupling in double perovskite Tb2_{2}NiMnO6_{6}

The Griffiths phase-like features and the spin-phonon coupling effects observed in Tb$_2$NiMnO$_6$ are reported. The double perovskite compound crystallizes in monoclinic $P2_1/n$ space group and exhibits a magnetic phase transition at $T_c \sim$ 111 K as an abrupt change in magnetization. A negative deviation from ideal Curie-Weiss law exhibited by 1/$\chi(T)$ curves and less-than-unity susceptibility exponents from the power-law analysis of inverse susceptibility are reminiscent of Griffiths phase-like features. Arrott plots derived from magnetization isotherms support the inhomogeneous nature of magnetism in this material. The observed effects originate from antiferromagnetic interactions which arise from inherent disorder in the system. Raman scattering experiments display no magnetic-order-induced phonon renormalization below $T_c$ in Tb$_2$NiMnO$_6$ which is different from the results observed in other double perovskites and is correlated to the smaller size of the rare earth. The temperature evolution of full-width-at-half-maximum for the {\it stretching} mode at 645 cm$^{-1}$ presents an anomaly which coincides with the magnetic transition temperature and signals a close connection between magnetism and lattice in this material.Comment: 17 pages, 8 figures; accepted in J. Appl. Phy

Shock Wave Behaviour of Polymeric Materials for Detonation Waveshapers

This paper discusses the experimental determination of explosive shock attenuation parameters of four different polymers viz., Teflon, Phenol formaldehyde, Polyethylene foam and Polypropylene foam. These polymers are candidate materials for waveshapers in shaped charge warheads. Cylindrical specimens of the polymer materials were subjected to explosive shock loading by the detonation of RDX:Wax (95:5). Shock arrival time was measured using piezo-wafers positioned at known spatial intervals in the specimens. Initial shock velocity, stabilised shock velocity and attenuation constant were determined. These parameters are essential for the design of waveshapers. Foams have better shock attenuating properties compared to solids due to their cellular structure. Polypropylene foam has the highest shock attenuating characteristic among the four materials studied