Therapeutic efficacy and safety of oral tranexamic acid and that of tranexamic acid local infiltration with microinjections in patients with melasma: a comparative study.

BACKGROUND: Tranexamic acid (TXA) has been used orally, intravenously, topically and intradermally (microinjection, microneedling) for treating melasma. However, the comparative efficacy of these different routes of administration remains underevaluated. AIM: To ascertain the comparative efficacy of different routes of administration of TXA. METHODS: In total, 100 consecutive patients with melasma (8 men, 92 women, age range 18-55 years) were randomly assigned to one of two groups comprising 50 patients each. Group A (3 men, 47 women) received oral TXA 250 mg twice daily, while group B (5 men, 45 women) received intradermal microinjections of TXA 4 mg/mL every 4 weeks. The treatment continued for 12 weeks in both groups. Percentage reduction in baseline Melasma Area and Severity Index (MASI) was assessed at 4-week intervals, and response was scored as very good (> 75% reduction), good (50% to < 75% reduction), moderate (25% to < 50% reduction), mild (< 25% reduction) or no response. RESULTS: The study was completed by 39 patients in group A and 41 patients in group B. Very good response was seen in 25 and 32 patients in groups A and B, respectively, while good response was seen in 14 and 9 patients, respectively. Both treatment methods were equally effective, with an average reduction of MASI at 12 weeks of 77.96 ± 9.39 in group A and 79.00 ± 9.64 in group B. The main adverse effects were mild epigastric discomfort, hypomenorrhea, headache and injection site pain, which did not warrant discontinuation of treatment. Two patients in group A had relapses at 24 weeks. CONCLUSION: TXA appears to be an effective and safe treatment for melasma, irrespective of its route of administration.

Profile of Rheumatological Manifestations in Leprosy in a Tertiary Care Hospital from Himachal Pradesh.

The rheumatological manifestations of leprosy occur singly or in varying combinations, particularly during lepra reactions. Despite being third most common, these remain under diagnosed and under reported. This study has been carried out to study the spectrum of rheumatological manifestations in leprosy patients. One hundred consecutive patients of leprosy presenting during January to December 2013 were studied for rheumatological manifestations. Complete hemogram, serum biochemistry, urinalysis, rheumatoid factor, ASO titer, C-reactive protein, ANA, and x-rays for hands, feet, chest and involved joints were performed. These 100 (M:F 66:34) patients aged between 16-80 years had indeterminate (2 patients), TT (4 patients), BT (26 patients), BB (2 patients), and LL leprosy (32 patients). 27 patients had rheumatological manifestations; arthritis involving large or small joints in 23 patients being the commonest. 7 of 24 patients in type-1 lepra reaction had enthesitis in 3 patients and oligoarthritis in 4 patients. Rheumatoid arthritis-like polyarthritis was noted in 19 patients with type-2 reaction. Tenosynovitis, dactylitis, bony changes were also noted. Except for one case, these features were present in patients having lepra reactions. Rheumatoid factor in 14, ANA in 15, C-reactive protein in 45 cases was positive. ASO was positive 34 cases. Symmetrical polyarthritis involving small joints of hands and feet, oligoarthritis, enthesitis and dactylitis are common in leprosy particularly with borderline leprosy, type-2 lepra reaction especially in the presence of positive RAfactor.

Structural and physical properties of Ni1-xVxalloys around and away from quantum critical point.

We investigate the room temperature structure (global and local), temperature dependent magnetic and transport behaviour of Ni1-xVx(0⩽x⩽0.13) alloys. Our Energy Dispersive Analysis of x-rays results show that the prepared compositions are stoichiometric. With increase in V doping, the compounds exhibit a quantum phase transition aroundxc= 0.12, where the ferromagnetic phase is suppressed. Our results show that all the compounds stabilize in face centred cubic structure at RT and the lattice parameter shows unusual behaviour close toxc. The magnetic and heat capacity studies show signature of Griffiths phase on either side ofxc. From 25 K to the lowest collected temperature, we observe a linear T dependence of resistivity atx = 0.1 and aroundxc, which is separated by a Fermi-liquid region aroundx = 0.106. This suggests that the origin of the transport behaviour is different around the quantum critical point and away from it. Our Ni K-edge x-ray Absorption Spectroscopy results show that there is a significant reduction in the first coordination number around Ni central atom on doping. Further, with doping, there is distortion in the first coordination shell around Ni. This suggests, with V doping, the local structure around Ni is different from the global structure as obtained from the x-ray Diffraction results. Interestingly, with doping, we observe a direct connection between the extent of distortion at RT and the magnetic disorder obtained at 2 K. We believe our results will motivate the scientific community to further study the interplay between the structural disorder and quantum fluctuations with temperature at the local level.

Charge-ordering breakdown dynamics and ferromagnetic resonance studies ofB-site Cu diluted Pr1‒xSrxMnO3.

Here, we report the influence of Jahn-Teller active Cu substitution on the charge-ordering (CO) characteristics of one of the well-known manganite Pr0.45Sr0.55MnO3(S55) with a distorted tetragonal structure. Magnetization studies unveil a complex magnetic phase diagram for S55, showing distinct temperature ranges corresponding to various magnetic phases: a ferromagnetic phase dominated by the Double Exchange interaction withTC∼ 220.5 K, an antiferromagnetic phase belowTN∼ 207.6 K induced by CO with a transition temperature ofTCO∼ 210 K consistent with the specific heatCP(T) data, and a mixed phase in the rangeTNTN(T

Anxiolytic potential of resveratrol and rufinamide combination by modulating GABA-ergic transmission: insights from experiments, molecular docking and dynamics simulations.

Resveratrol is a polyphenolic phytocompound known to possess anxiolytic-like effects but its impact on central gammaaminobutyric acid (GABA) modulation has never been explored. The purpose of this study was to analyze the anxiolytic-like effects of resveratrol alone and in combination with rufinamide, an antiepileptic drug which has never been studied for its anxiolytic potential. The BALB/c mice were tested in a battery of behavior testing after administration of resveratrol (50 mg/kg) and rufinamide (50 mg/kg) alone and in combination. Moreover, molecular docking studies were also carried out to understand the interaction of resveratrol and rufinamide with GABA aminotransferase, GABA receptor and GABA-A transporter type 1. Resveratrol alone exerted notable anxiolytic-like effects and improved outcomes in few experiments but rufinamide alone did not yield any beneficial outcomes. However, the animal co-administered with resveratrol and rufinamide behaved exceptionally well (p<0.05) and preferred open, illuminated and exposed areas of open field, light/dark and elevated plus maze. Further, these animals showed reduced anxiety towards anxiogenic stimuli i.e. holes and marbles in hole board and marble bury tests, respectively. Resveratrol and rufinamide showed moderate to strong binding affinities with GABA proteins, indicating the potential to treat anxiety-like neurological disorders. Moreover, resveratrol and rufinamide were analyzed using molecular docking to determine their interaction with GABA receptors, transporters, and transaminase. The results suggest that their anxiolytic-like effects may be due to inhibiting GABA reuptake transporter 1 protein, leading to increased synaptic levels of GABA neurotransmitter, as seen in stable molecular dynamics results with the 7SK2 GABA transporter protein.

Spin-valve-like magnetoresistance in Mn2NiGa at room temperature.

Spin valves have revolutionized the field of magnetic recording and memory devices. Spin valves are generally realized in thin film heterostructures, where two ferromagnetic (FM) layers are separated by a nonmagnetic conducting layer. Here, we demonstrate spin-valve-like magnetoresistance at room temperature in a bulk ferrimagnetic material that exhibits a magnetic shape memory effect. The origin of this unexpected behavior in Mn(2)NiGa has been investigated by neutron diffraction, magnetization, and ab initio theoretical calculations. The refinement of the neutron diffraction pattern shows the presence of antisite disorder where about 13% of the Ga sites are occupied by Mn atoms. On the basis of the magnetic structure obtained from neutron diffraction and theoretical calculations, we establish that these antisite defects cause the formation of FM nanoclusters with parallel alignment of Mn spin moments in a Mn(2)NiGa bulk lattice that has antiparallel Mn spin moments. The direction of the Mn moments in the soft FM cluster reverses with the external magnetic field. This causes a rotation or tilt in the antiparallel Mn moments at the cluster-lattice interface resulting in the observed asymmetry in magnetoresistance.

Effect of Ce substitution on the local magnetic ordering and phonon instabilities in antiferromagnetic DyCrO3perovskites.

A detailed crystal structure analysis, temperature and field dependence of magnetic characteristics and phonon instabilities for different compositions (0.1 ⩽x⩽ 0.5) of Dy1-xCexCrO3solid-solutions have been reported. All the investigated compounds exhibit distorted orthorhombic crystal structure with a distortion factor ofdOct/dCell∼ 6 × 10-3/3.5 ppm (forx∼ 0.2) forPbnmspace group that follows Vegard's law. The bonds between apical oxygen atoms (OA1) and Cr atoms stand more rigidly in comparison with the basal oxygen atoms (OB1/OB2) resulting the octahedral distortion and thereby causing the changes in phonon modes. The CrO6octahedral tilt angleθrotates with respect to the Miller pseudocubic axis [101] which varies from 10.36° (x= 0.1) to 12.25° (x= 0.5) and significantly influences the Ag(5) phonon stability by 3% for a change in A-site mean radius from 1.095 Å to 1.141 Å forx= 0.1 and 0.5, respectively. From the magnetization measurements we find that these series of compositions exhibit canted antiferromagnetic (AFM) ordering with Néel temperature,TN1that increases from 151.8 K (x= 0.1) to 162 K (x= 0.5) which also manifests as a significant reduction in the magneto-crystalline anisotropy (HK∼ 2.58 kOe → 2.07 kOe,K1∼ 36.47 J m-3→ 18.97 J m-3) while maintaining the stable Γ4(Gx,Ay,Fz) AFM configuration. Both Dzyaloshinskii-Moriya interaction method and modified Curie-Weiss law are employed to analyse the inverse paramagnetic susceptibility,χ-1(T>TN1). Further, we have evaluated the symmetric (JS) and antisymmetric exchange (DAS) constants, which show progressively increasing trend (JS→ 10.08 K to 11.18 K andDAS→ 1.24 K to 1.73 K) with the incorporation of Ce inside the perovskite lattice. Furthermore, the role of Ce substitution on the low-temperature spin reorientation transition (TSR∼ 3.5 K → 16.8 K pertaining to the Γ25phase configuration) and emergence ofΓ2(Fx,Cy,Gz;FxR,CyR)weak-FM phase between 31 K and 45.5 K are discussed in consonance with the phonon spectra.

Magnetization reversal, field-induced transitions andH-Tphase diagram of Y1-xCexCrO3.

We report a systematic study of the magnetic phase diagram in theH-Tplane, negative magnetization (NM), exchange interactions and field-induced spin-flop transitions in the distorted perovskite Y1-xCexCrO3. Locked AFM and weak-FM configurations in Γ4(Gz,Fy,Ax) phase of YCrO3(S= 3/2 ground state) unlocks into the Γ2(Fz,Gy,Cx;FzR,CxR) phase of the canted AFM and FM structures with the dilute substitution of Ce (x⩾ 0.05). The asymmetric and symmetric exchange interaction (JAS∼ 0.11 meV andJS∼ 0.85 meV) between the trivalent Ce and Cr enable the positive quartic-anisotropy field (HK4∼ 2.85 × 102Oe) along with the second order anisotropy field (HK2∼ 5.93 × 102Oe). Unlike the pristine YCrO3compound, the Ce incorporated system exhibits a giant fourth-order anisotropy constant (K4= 1.35 × 105erg/c.c.) due to the asymmetric exchange interaction between the trivalent Ce-Cr which further lifts the free energy of the system and causes lag in the onset of AFM ordering showing the significant thermal hysteresis (ΔT∼ 10 K) in the field-cooled (FC)-warming measurement protocol as compared to the FC-cooling mode. The H-T phase diagram, mapped from the isothermal magnetization data and differential magnetic susceptibility data with different measurement protocols clearly distinguishes three prominent regions below theTN(∼150 K), viz (i) long-range canted AFM + weak FM phase (Γ4(Gz,Fy,Ax)), (ii) Γ24mixed phase and (iii) robust Γ2(Fz,Gy,Cx;FzR,CxR) AFM + FM phases. Tunable spin-flopped transition (∼ 30 kOe), significant negative exchange-bias field (HEB∼ 2.5 kOe), huge coercive field (HC∼ 22 kOe) and large NM (ΔM∼ 280 emu/mole) are the unique characteristic features of the current investigated system.

High pressure study of magnetocaloric effect in Ho3Co and Tb3Co.

The magnetocaloric effect of intermetallic compounds of Tb3Co and Ho3Co is studied under high pressures up to ∼1 GPa using pressure dependent dc magnetisation and specific heat measurements at ambient conditions. The magnetic entropy change (-ΔS M) obtained from magnetisation data and adiabatic change in temperature (ΔT ad) determined from zero-field specific heat and magnetisation data are found to be nearly identical within error limits with those deduced from purely field dependent specific heat experiments. With increasing hydrostatic pressure to ∼1 GPa, the -ΔS M and ΔT ad, both show a significant enhancement of about 37% and 13%, respectively for 9 T field change in case of Tb3Co. On the other hand, Ho3Co exhibits a decrease of about 8% in both -ΔS M and ΔT ad with increasing pressure. The refrigerant capacity (RC) also increases from 650 J kg-1 to 847 J kg-1 in the case of Tb3Co and it goes down from 665 J kg-1 to 615 J kg-1 for Ho3Co for an increase of pressure to 1 GPa. With increasing pressure, the peak widths of both -ΔS M and ΔT ad increase in case of Tb3Co, although the increase is more in -ΔS M. However, such noticeable changes in peak widths with pressure were not observed in Ho3Co. At ambient pressure, peak of -ΔS M ([Formula: see text]) scales with [Formula: see text] for both the compounds, consistent with the prediction of mean field theory (MFT) for second order magnetic transition. However, deviation from MFT was noticed at high pressures as [Formula: see text] was found to scale with [Formula: see text] instead of [Formula: see text] for both the alloys. Further, normalised -ΔS M curves for different ΔH and pressures collapse on a single universal curve in both the compounds thereby indicating that the second order magnetic transition persists even up to ∼1 GPa pressure.

Electronic properties in itinerant ferromagnet SrRu1-x Ti x O3.

Here, we study the electrical transport and specific heat in 4d based ferromagnetic material SrRuO3 and its Ti substituted SrRu1-x Ti x O3 series (x ⩽ 0.7). The SrRuO3 is a metal and shows itinerant ferromagnetism with transition temperature T c ∼ 160 K. The nonmagnetic Ti4+ (3d 0) substitution would not only weaken the active Ru-O-Ru channel but is also expected to tune the electronic density and electron correlation effect. A metal to insulator transition has been observed around x ∼ 0.4. The nature of charge transport in paramagnetic-metallic state (x ⩽ 0.4) and in insulating state (x > 0.4) follows modified Mott's variable range hopping model. In ferromagnetic-metallic state, resistivity shows a T 2 dependence below T c which though modifies to T 3/2 dependence at low temperature. In Ti substituted samples, temperature range for T 3/2 dependence extends to higher temperature. Interestingly, this T 3/2 dependence dominates in whole ferromagnetic regime in presence of magnetic field. This evolution of electronic transport behavior can be explained within the framework of Fermi liquid theory and electron-magnon scattering mechanism. The negative magnetoresistance exhibits a hysteresis and a crossover between negative and positive value with magnetic field which is connected with magnetic behavior in series. The decreasing electronic coefficient of specific heat with x supports the increasing insulating behavior in present series. We calculate a high Kadowaki-Woods ratio (x ⩽ 0.3) for SrRuO3 which increases with substitution concentration. This signifies an increasing electronic correlation effect with substitution concentration.

Critical behavior and magnetocaloric effect across the magnetic transition in Mn1+xFe4-xSi3.

The nature of the magnetic transition, critical scaling of magnetization, and magnetocaloric effect in Mn1+xFe4-xSi3 (x = 0 to 1) are studied in detail. Our measurements show no thermal hysteresis across the magnetic transition for the parent compound which is in contrast with the previous report and corroborate the second order nature of the transition. The magnetic transition could be tuned continuously from 328 K to 212 K with Mn substitution at the Fe site. The Mn substitution leads to a linear increase in the unit cell volume and a slight reduction in the effective moment. A detailed critical analysis of the magnetization data for x = 0.0 and 0.2 is performed in the critical regime using the modified Arrott plots, Kouvel-Fisher plot, universal curve scaling, and scaling analysis of magnetocaloric effect. The magnetization isotherms follow modified Arrott plots with critical exponent (ß [Formula: see text] 0.308, γ [Formula: see text] 1.448, and δ [Formula: see text] 5.64) for the parent compound (x = 0.0) and (ß [Formula: see text] 0.304, γ [Formula: see text] 1.445, and δ [Formula: see text] 5.64) for x = 0.2. The Kouvel-Fisher and universal scaling plots of the magnetization isotherms further confirm the reliability of our critical analysis and values of the exponents. These values of the critical exponents are found to be same for both the parent and doped samples which do not fall under any of the standard universality classes. The exchange interaction decays as J(r) ~ r-3.41 following the renormalization group theory and the observed critical exponents correspond to lattice dimensionality d = 2, spin dimensionality n = 1, and the range of interaction σ = 1.41. This value of σ(<2) indicates long-range interaction between magnetic spins. A reasonable magnetocaloric effect ΔSm [Formula: see text] -6.67 J/Kg-K and -5.84 J/Kg-K for x = 0.0 and 0.2 compounds, respectively, with a huge relative cooling power (RCP ~ 700 J/Kg) for 9 T magnetic field change is observed. The universal scaling of magnetocaloric effect further mimics the second order character of the magnetic transition. The obtained critical exponents from the critical analysis of magnetocaloric effect agree with the values deduced from the magnetic isotherm analysis.

Effect of Tb substitution in naturally layered LaMn2Si2: magnetic, magnetocaloric, magnetoresistance and neutron diffraction study.

Evolution of physical and magnetic properties of La rich La1-x Tb x Mn2Si2 (x = 0, 0.1 and 0.225) compounds is studied using temperature and field dependent dc magnetization, electrical transport, and heat capacity measurements. LaMn2Si2 undergoes a paramagnetic to antiferromagnetic ordering at T N ~ 400 K and a long range ferromagnetic ordering below T C ~ 308 K. However, the substitution of Tb at La site results in the contraction of unit cell as well as decrease in the Mn-Mn spacing, which leads to an additional antiferromagnetic phase below T N ~ 87 K and 257 K for La0.9Tb0.1Mn2Si2 and La0.775Tb0.225Mn2Si2, respectively. Using magnetization isotherm results, we have constructed an H-T phase diagram for x = 0.225 and have found the coexistence of this additional antiferromagnetic phase with ferromagnetic phase. The phase coexistence at x ~ 0.225 is further analysed using magnetoresistance (MR) and magnetocaloric effect (MCE) studies and a reasonable correlation is established between MCE and MR. In order to analyse the nature of the magnetic transition at T C, a universal master curve is constructed by rescaling the magnetic entropy curves. Low temperature neutron diffraction measurements performed on the polycrystalline samples revealed a canted ferromagnetic structure for x ~ 0.1 and a canted antiferromagnetic structure for x ~ 0.225.

Large positive magnetoresistance and Dzyaloshinskii-Moriya interaction in CrSi driven by Cr 3d localization.

Spin chiral systems with Dzyaloshinskii-Moriya (DM) interaction due to broken inversion symmetry are extensively studied for their technological applications in spintronics and thermoelectrics. Here, we report an experimental study on the magnetization, magnetoresistance (MR) and electronic structure of a non-centrosymmetric compound CrSi with B20 crystal structure. Both magnetization and MR shows competing ferromagnetic (FM) and antiferromagnetic (AFM) correlations with the FM correlations being comparatively weaker indicating the presence of DM interaction in CrSi. A large positive MR [Formula: see text] obtained at 5 K and 5 T magnetic field arises due to the stronger AFM correlations. Resonant photoemission shows both localized and itinerant nature of Cr 3d electrons to be present in CrSi and this is supported by the temperature dependence of magnetic susceptibility. Drastic variation in the density of states along with valence band broadening at low temperature indicates the increase in hybridization between Cr 3d and Si 3s-3p states which enhances the localization effects. Spin polarized itinerant Cr 3d electrons give rise to AFM spin density wave in CrSi. Magnetic interaction between the localized and itinerant Cr 3d electrons are found to be crucial for realizing DM interaction in this system. Spectral density of states derived from high resolution valence band measurements provides evidence of electronic topological transition in CrSi. Large density of polarized itinerant electrons which varies with temperature and the large positive MR with AFM correlations suggests CrSi as a potential candidate for both the thermoelectric and spintronics applications.

Structural correlations in the enhancement of ferroelectric property of Sr doped BaTiO3.

The effect of Sr doping in BaTiO3 (BTO) with nominal compositions Ba0.80Sr0.20TiO3 (BSTO) have been explored on its structural, lattice vibration, dielectric, ferroelectric and electrocaloric properties. The temperature dependent dielectric results elucidate the enhancement in dielectric constant and exhibit three frequency independent transitions around 335, 250 and 185 K, which are related to different structural transitions. All these transitions occur at lower temperature as compared with pristine BTO, however; remnant electric polarization (P r) of BSTO is much higher than in BTO. The value of P r is ∼5 µC cm-2 at room temperature and the maximum P r ∼ 8 µC cm-2 is observed at tetragonal to orthorhombic and orthorhombic to rhombohedral transitions. The electro-caloric effect shows the maximum adiabatic change in temperature ΔT ∼ 0.24 K at cubic to tetragonal transition. The temperature dependent synchrotron x-ray diffraction and Raman results show correlations between P r, crystal structure and lattice vibrations. Our results demonstrate the enhancement in ferroelectric properties of BTO with Sr doping. The origin of the enhancement in ferroelectric property is also discussed in correlations with the appearance of superlattice peak around room temperature due to TiO6 octahedral distortion. These enhanced properties would be useful to design lead free high quality ferroelectric and piezoelectric materials.

Elevated iron stores are associated with HIV disease severity and mortality among postpartum women in Zimbabwe.

OBJECTIVES: The relationship between Fe status and HIV infection is complex and poorly understood. While anaemia is a major complication of HIV infection, higher Fe stores may be associated with disease progression. There is limited and conflicting data available from Africa. DESIGN: Cross-sectional and prospective cohort study. SETTING, SUBJECTS AND METHODS: We examined the association between postpartum Fe status (Hb, serum ferritin (SF) and transferrin receptor (TfR)) and viral load (VL) and HIV-related mortality in 643 HIV-positive Zimbabwean women over a period of 12 months. RESULTS: In non-anaemic women a log10 increase in SF was associated with a 2.3-fold increase in VL (P = 0.019); this association was absent in anaemic women. In prospective analyses, a log10 increase in SF was associated with a 4-fold increase in mortality by 12 months (P = 0.002). Hb was negatively associated with VL (P = 0.001) and mortality (P = 0.047). The adverse associations between SF and both VL and mortality were found at SF concentrations > 45 microg/l (P < 0.05). Controlling for alpha1 acid glycoprotein, a marker of inflammation, attenuated the association between both SF and VL and mortality, but these remained significant. CONCLUSIONS: These results are consistent with the hypothesis that high Fe stores have adverse consequences in HIV infection. If adverse consequences are real, our data suggest that they occur at SF concentrations exceeding those consistent with adequate Fe nutriture.

Magnetoresistance studies on RPd(2)Si (R = Tb, Dy, Lu) compounds.

Magnetoresistance studies on RPd(2)Si (R = Tb, Dy and Lu) compounds show large negative magnetoresistance (MR) in TbPd(2)Si and DyPd(2)Si near the magnetic ordering temperature. Positive MR at low temperature in the ferromagnetic Dy compound is shown to arise from the orbital contribution (the Lorentz force effect). As a consequence, a deviation from the linear relation between MR and isothermal entropy change (i.e. the magnetocaloric effect) is observed. In the case of the Tb compound, anomalous magnetoresistance behavior is observed at 3 K, where the resistivity is found to be different before and after magnetic field cycling. These results suggest complex magnetic behavior in TbPd(2)Si.

Photo-induced insulator-metal transition probed by Raman spectroscopy.

Strongly correlated electron systems give an opportunity to manipulate charge, orbital, magnetic and structural phases of matter. Here we show that the insulating phase where charges are localized can be delocalized through photo-excitation which, in turn changes the structure locally, inducing an orthorhombic to rhombohedral phase transition. The I-M transition was witnessed for La(1-x)Sr(x)MnO(3) compounds in Raman spectra and photo-induced conduction simultaneously. A simple continuous argon ion laser source was used for optical excitation. The photon energy was 2.53 eV and the power can be chosen anywhere between 5 and 45 mW. Our studies clearly bring out the role of local disorder in the form of Jahn-Teller distortion in the localization of electrons.

High pressure study of magnetic properties of Tb3Co.

The magnetic properties of rare earth rich intermetallic compound, Tb3Co, were studied under external pressures up to ∼1.21 GPa. The application of external pressure results in a decrease of the transition temperatures, [Formula: see text] (paramagnetic to modulated antiferromagnetic) by about 6 K, and the order to order transition that coincides with a glass transition at 72 K by about 15 K, respectively. The low temperature drop in the zero-field cooled magnetisation signifying the strengthening of spin-orbit coupling remains more or less unaffected (shifts only by 3 K) by the external pressures but significant changes in the magnetic behaviour were observed above 40 K. The overall long range non-collinear magnetic order coexisting with glassy behaviour (below 72 K) is sustained even at ∼1.07 GPa pressure. The rate of decay of [Formula: see text] (d[Formula: see text]) is found to be linear with -7.2 K GPa-1 up to ∼0.9 GPa and then it deviates from linearity. The magnetic relaxations and memory effects studied under different measurement protocols confirm the presence of glassiness right up to the highest pressure, although the glassy behaviour is weakened to some extent with increasing pressure as reflected by faster relaxations.

Magnetic glassy behaviour coupled with long range non-collinear magnetic order in Tb3Co.

Detailed and systematic study of rare earth rich intermetallic compound Tb3Co, using dc magnetisation, neutron powder diffraction, and linear and non-linear ac-susceptibilities, shows the presence of an unexpected magnetic glassy state along with complex non-collinear or modulated antiferromagnetic (AFM) order. Our neutron diffraction study shows that the magnetic structure remains more or less the same except for a decrease in moment values in the temperature range of 2 K-70 K and rules out any phase transition around 30 K. However, it reveals sharp changes in structural parameters around 30 K, which indicates strong spin-lattice coupling and change in strength. It appears to be mainly responsible for the observed increase in ZFC magnetisation on warming around 30 K. Another important unexpected result of this study is the strong frequency dispersion in linear and non-linear (higher order harmonics) ac-susceptibilities below [Formula: see text] K. The analysis in terms of various spin glass theoretical formulisms and even stronger frequency dispersion in non-linear susceptibilities provides evidence for the presence of a spin glass like state in Tb3Co. The final picture that emerges out of this study is that a spin glass like state coexists with the long range modulated AFM order below 72 K.

Membrane raft-dependent regulation of phospholipase Cgamma-1 activation in T lymphocytes.

Numerous signaling molecules associate with lipid rafts, either constitutively or after engagement of surface receptors. One such molecule, phospholipase Cgamma-1 (PLCgamma1), translocates from the cytosol to lipid rafts during T-cell receptor (TCR) signaling. To investigate the role played by lipid rafts in the activation of this molecule in T cells, an influenza virus hemagglutinin A (HA)-tagged PLCgamma1 was ectopically expressed in Jurkat T cells and targeted to these microdomains by the addition of a dual-acylation signal. Raft-targeted PLCgamma1 was constitutively tyrosine phosphorylated and induced constitutive NF-AT-dependent transcription and interleukin-2 secretion in Jurkat cells. Tyrosine phosphorylation of raft-targeted PLCgamma1 did not require Zap-70 or the interaction with the adapters Lat and Slp-76, molecules that are necessary for TCR signaling. In contrast, the Src family kinase Lck was required. Coexpression in HEK 293T cells of PLCgamma1-HA with Lck or the Tec family kinase Rlk resulted in preferential phosphorylation of raft-targeted PLCgamma1 over wild-type PLCgamma1. These data show that localization of PLCgamma1 in lipid rafts is sufficient for its activation and demonstrate a role for lipid rafts as microdomains that dynamically segregate and integrate PLCgamma1 with other signaling components.