Formulation and Characterization of Alginate Microbeads of Clonidine Hydrochloride by Ionotropic Gelation Technique

The objective of this study was to prepare and evaluate sodium alginate microbeads with calcium chloride as cross-linking agent for Clonidine hydrochloride by ionotropic gelation method. Clonidine hydrochloride a centrally acting sympatholytic and imidazoline-derivative hypotensive agent; selective α2-adrenergic agonist. It stimulates alpha2-adrenergic receptors in the brainstem to decrease sympathetic nervous system outflow. It is also administered epidurally to treat pain. Microbeads offer numerous advantages for releasing one of the drugs or part of the same drug immediately while remaining drug or parts of the same can be sustained release. Prepared microbeads were evaluated for particle size, polydispersity index, zeta potential, particle shape, surface morphology, entrapment efficiency and In vitro drug release. The prepared beads were free flowing and white in color. The drug loaded beads showed 72.9±2.4% to 94.6±2.6 % drug entrapment, which was found to increase with increase in alginate concentration. In vitro drug release study of these microbeads indicated controlled release for Clonidine hydrochloride 83.46% release after 48 hours. Hence the observations of all results of the different batches, MBD 11 showed controlled release action and improved drug availability. From this study it could be concluded that the free flowing microbeads of Clonidine hydrochloride could be successfully prepared by ionotropic gelation technique with high entrapment efficiency and prolonged release characteristics. Keywords: Clonidine hydrochloride, Microbeads, Sodium alginate, Calcium chloride, Ionotropic gelation method

Analgesic activity of poly herbal formulation in experimental rats by acetic acid induced writhing test model and Hot plate model

To evaluate analgesic activity of a polyherbal formulation-PHF [hydro-alcoholic extract of Hibiscus rosa-sinensis (50mg), Fennel seeds (50mg), Prosopis cineraria (50mg), & Ficus racemosa (50mg)] compare it with Diclofenac Na by using Eddys hot plate and writhing test in Adult Wistar rats. Rats were divided into four groups of 6 each for both tests. PHF (250, 300 mg/kg, p.o. body weight) and Diclofenac Na (50 mg/kg, p.o.) made as suspensions prepared in 1% carboxy methyl cellulose (control) and were fed to rats orally. The physicochemical evaluations carried out in terms of loss on drying, ash value, extractive values and acid insoluble ash value ect. Qualitative analysis of various phytochemical constituents was determined by the well-known test protocol available in the literature. Phytochemical analysis revealed the presence of phenols, flavonoids, tannins, saponins, alkaloids.  Analgesic activity was assessed by counting the number of writhes induced by 0.7% acetic acid (10 ml/kg) in the 30 min. Number of writhing and percentage protection against writhing was evaluated. In Eddys hot plate method, they were placed individually on hot plate maintained at a temperature of 55 ± 0.5 ºC. The latency to lick the paw (reaction time) was noted at 0, 30, 60, 90 and 120 min. The cut off time was set at 20 sec to avoid damage to the skin. In acetic acid writhing method, PHF (250, 300 mg/kg, p. o.) significantly (p < 0.001) decreased the number of writhing 39±1.55*, 29.0±0.43*resp. Maximum percentage of inhibition of writhing response shown by Diclofenac Na was 73.03 %. In hot plate method, PHF showed a significant increase in the elevated basal reaction time at 30, 60, 90 and 120 min. The results indicated that the poly-herbal formulation possesses good analgesic activity in the experimental animal models. Keyword: Analgesic activity, Physicochemical evaluations, Phytochemical analysis, Hibiscus rosa-sinensis Fennel seeds, Prosopis cineraria, Ficus racemos

Particle density fluctuations

Event-by-event fluctuations in the multiplicities of charged particles and photons at SPS energies are discussed. Fluctuations are studied by controlling the centrality of the reaction and rapidity acceptance of the detectors. Results are also presented on the event-by-event study of correlations between the multiplicity of charged particles and photons to search for DCC-like signals.Comment: Talk presented at Quark Matter 2002, Nantes, Franc

Pion Freeze-Out Time in Pb+Pb Collisions at 158 A GeV/c Studied via pi-/pi+ and K-/K+ Ratios

The effect of the final state Coulomb interaction on particles produced in Pb+Pb collisions at 158 A GeV/c has been investigated in the WA98 experiment through the study of the pi-/pi+ and K-/K+ ratios measured as a function of transverse mass. While the ratio for kaons shows no significant transverse mass dependence, the pi-/pi+ ratio is enhanced at small transverse mass values with an enhancement that increases with centrality. A silicon pad detector located near the target is used to estimate the contribution of hyperon decays to the pi-/pi+ ratio. The comparison of results with predictions of the RQMD model in which the Coulomb interaction has been incorporated allows to place constraints on the time of the pion freeze-out.Comment: 9 pages, 12 figure

Azimuthal anisotropy and correlations in p+p, d+Au and Au+Au collisions at 200 GeV

We present the first measurement of directed flow ($v_1$) at RHIC. $v_1$ is found to be consistent with zero at pseudorapidities $\eta$ from -1.2 to 1.2, then rises to the level of a couple of percent over the range $2.4 < |\eta| < 4$. The latter observation is similar to data from NA49 if the SPS rapidities are shifted by the difference in beam rapidity between RHIC and SPS. Back-to-back jets emitted out-of-plane are found to be suppressed more if compared to those emitted in-plane, which is consistent with {\it jet quenching}. Using the scalar product method, we systematically compared azimuthal correlations from p+p, d+Au and Au+Au collisions. Flow and non-flow from these three different collision systems are discussed.Comment: Quark Matter 2004 proceeding, 4 pages, 3 figure

Azimuthal anisotropy: the higher harmonics

We report the first observations of the fourth harmonic (v_4) in the azimuthal distribution of particles at RHIC. The measurement was done taking advantage of the large elliptic flow generated at RHIC. The integrated v_4 is about a factor of 10 smaller than v_2. For the sixth (v_6) and eighth (v_8) harmonics upper limits on the magnitudes are reported.Comment: 4 pages, 6 figures, contribution to the Quark Matter 2004 proceeding

All-optical switching and strong coupling using tunable whispering-gallery-mode microresonators

We review our recent work on tunable, ultrahigh quality factor whispering-gallery-mode bottle microresonators and highlight their applications in nonlinear optics and in quantum optics experiments. Our resonators combine ultra-high quality factors of up to Q = 3.6 \times 10^8, a small mode volume, and near-lossless fiber coupling, with a simple and customizable mode structure enabling full tunability. We study, theoretically and experimentally, nonlinear all-optical switching via the Kerr effect when the resonator is operated in an add-drop configuration. This allows us to optically route a single-wavelength cw optical signal between two fiber ports with high efficiency. Finally, we report on progress towards strong coupling of single rubidium atoms to an ultra-high Q mode of an actively stabilized bottle microresonator.Comment: 20 pages, 24 figures. Accepted for publication in Applied Physics B. Changes according to referee suggestions: minor corrections to some figures and captions, clarification of some points in the text, added references, added new paragraph with results on atom-resonator interactio

Strange Resonance Production in p+p and Au+Au Collisions at RHIC Energies

Resonance yields and spectra from elementary p+p and Au+Au collisions at $\sqrt{s_{\rm NN}} =$ 200 GeV from the STAR experiment at RHIC are presented and discussed in terms of chemical and thermal freeze-out conditions. Thermal models do not adequately describe the yields of the resonance production in central Au+Au collisions. The approach to include elastic hadronic interactions between chemical freeze-out and thermal freeze-out suggests a time of $\Delta \tau>$5 fm/c.Comment: 4 pages, 7 figures, proceedings of the Quark Matter 2004, in Oakland, California, to be published in Journal of Physics G: Nuclear and Particle Physic

Identified particles at large transverse momenta in STAR in Au+Au collisions @ sqrt(s_NN) = 200 GeV

We report measurements of the ratios of identified hadrons (pi,K,p,Lambda) in Au+Au collisions at sqrt(s_NN) = 200 GeV as a function of both collision centrality and transverse momentum (p_T). Ratios of anti-baryon to baryon yields are independent of p_T within 2<p_T <6 GeV/c indicating that, for such a range, our measurements are inconsistent with theoretical pQCD calculations predicting a decrease due to a stronger contribution from valence quark scattering. For both strange and non-strange species, a strong baryon enhancement relative to meson yields is observed as a function of collision centrality in this intermediate p_T region, leading to p/pi and Lambda/K ratios greater than unity. The nuclear modification factor, R_cp (central relative to peripheral collisions), is used to illustrate the interplay between jet quenching and hadron production. The physics implications of these measurements are discussed with reference to different theoretical models.Comment: 5 pages, 4 figures. Proceedings of Quark Matter 2004 Conference, Jan 2004, Oakland, USA. Submitted to Journal of Physics