Intensity Of Scattered Laser Light Research Articles

Experimental studies on static laser light scattering of synthetized poly (acrylonitrile-co- methyl methacrylate) copolymer at room temperature

The static light scattering technique (SLS) is one of the absolute techniques that are used for the determination of weight average molecular weight (M¯w) of polymer solutions. In this technique, the scattered laser light intensity is measured at different scattering angles for various polymer concentrations to construct the Zimm plot which can be used for a simultaneous determination of M¯w, radius of gyration (Rg), and the second virial coefficient (A2). In this study, Poly (acrylonitrile–co-methyl methacrylate) copolymer, P(AN-co-MAA), was synthesized from acrylonitrile (AN) and methyl methacrylate (MMA) monomers using the precipitation polymerization method. Polymerization was carried out using potassium persulfate (K2S2O8) as an initiator with monomer ratios 1:1 of AN: MMA. The co-polymerization process was verified by Fourier transform infrared spectroscopy (FTIR). Refractive index (n) and refractive index increment (dn/dc) of the P(AN-co-MAA) copolymer solutions were determined experimentally using a Mach-Zehnder interferometer excited by a low power He-Ne laser in order to calculate the M¯w, Rg, and A2 of the synthetized copolymer using the static laser light scattering technique. M¯w, Rg, and A2 were found to be 9.7 × 105 g/mol, 345 nm, and 5 × 10−7 mol. cm3/g2.

Determination of Chitosan Scattering Parameters by Using Multi Angle Static Laser Light Scattering(MASLLS )

Measurement of polymer characteristics by using the static laser light scattering experiment needs a precisedetermination of its refractive index increment, dn/dc. Through the dependence of Rayleigh scattering coefficient on the squarevalue of the refractive index increment(dn/dc)2. The average molecular weight of the investigated polymer is determined using ahome built of Mach-Zehender Interferometer(MZI) which has been constructed to measure the refractive index, n, of Chitosan atdifferent concentration ranging from 0.002 to 0.008 gm/L. The measurements are carried out through the dependence of fringenumbers on the laser incidence angle of polymer’s solutions. The used laser beam is a He-Ne laser with 543 nm wavelength and2mw in power (from Meridith). The obtained value of dn/dc is 0.198011 L/gm . A static laser light scattering(SLLS) experimentis constructed in our lab to measure the angular distribution of the scattered laser light intensity. From which the Rayleigh ratioRθ, molecular weight MW, second virial coefficient A2 and the square radius of gyration are calculated through what iscalled as Zimm plot method .

Synthesis of ultrafine magnesium oxide and titanium oxide powders

The formation of magnesium and titanium hydroxides (differing in the rate of primary particle formation) and conversion of the hydroxides to ultrafine oxide powders of controlled size have been studied using scanning electron microscopy, X-ray diffraction, differential thermal analysis, and analysis of the particle size distributions of solid materials from scattered laser light intensity. The particle size of the synthesis products has been shown to be influenced by the initial concentration and nature of precursors and precipitants, ultrasonic processing, additions of low-molecular-weight organic compounds, and dehydration temperature and time.

Comparison of Cascade Impaction and Laser Diffraction for Particle Size Distribution Measurements

The Andersen cascade impactor (ACI) and laser diffraction (LD) can be correlated at ambient temperature for aqueous drug formulations atomized by Soft Mist inhalers. A comparison of the two particle size determination methods at different conditions (flow rate, relative humidity) was performed. Under well-defined conditions, the faster LD can substitute the time consuming ACI at least for routine tests. The measurements were performed with three different drug formulations. The aerosol was generated by Soft Mist inhalers, and the droplet distributions were measured simultaneously using a laser diffraction analyzer together with the eight-stage Andersen cascade impactor. The simultaneous measurements ensure that aerosol and air conditions are identical for both LD and ACI. In order to measure the scattered laser light intensity of the aerosol passing the induction port, glass windows were fitted to the induction port. The evaporation effect of the aqueous aerosols on the PSD was investigated at ambient humidity and high humidity (RH > 90%). The simultaneous determination of the droplet size distribution leads to a good correlation between the ACI and LD method only if the measurements were performed at RH of >90%. The humidity of the ambient air had the strongest influence on PSD not only for ACI, but also for LD. In our set-up, the almost saturated air prevents aqueous droplets from drying. The influence of the flow rate on LD was negligible, whereas for ACI, a flow rate dependence is expected. The advantages of LD and the demonstrated compatibility to established EP/USP methods motivate the substitution of the ACI and the use of LD for routine measurements.

Reduced threshold for myocardial cell calcium intolerance in the rat heart with aging.

To determine whether advancing age is accompanied by a reduced Ca2+ tolerance, we measured Ca(2+)-dependent diastolic pressure, prolonged relaxation and systolic functional deterioration, spontaneous sarcoplasmic reticulum (SR)-generated Ca2+ oscillations [detected as scattered laser light intensity fluctuations (SLIF)], aftercontractions, and ventricular fibrillation in isolated, isovolumic, atrioventricular-blocked intact hearts from 24- to 26-mo (old) and 6- to 8-mo (young) male Wistar rats. In enzymatically isolated single cardiac myocytes, the likelihood of the occurrence of spontaneous contractile waves driven by spontaneous SR Ca2+ release was also determined. In response to stepwise increase in perfusate Ca2+ concentration (Cao), a reduction in the maximum developed pressure accompanied by an elevation in end-diastolic pressure and a prolonged contraction duration was observed at lower Cao in old vs. young hearts (P < 0.01 for each parameter). Furthermore, Ca(2+)-dependent ventricular fibrillation occurred during pacing in six old but in no young hearts (P < 0.01), aftercontractions were observed in seven old vs. one young heart (P < 0.01), and SLIF increased to a greater extent in old vs. young hearts. In single cardiac myocytes, spontaneous contractile waves occurred more frequently with increasing age (P < 0.01). These results indicate that aging is associated with an increased likelihood for the occurrence of SR-generated Ca2+ oscillations and functional abnormalities that result from these oscillations.

Dusty Plasma Studies in the Gaseous Electronics Conference Reference Cell.

Particle “dust” in processing plasmas is of critical concern to the semiconductor industry because of the threat particles pose to device yield. A number of important investigations into the formation, growth, charging, transport and consequences of particulate dust in plasmas have been made using the Gaseous Electronics Conference Reference Cell as the reactor test-bed. The greatest amount of work to date has been directed toward a better understanding of the role that electrostatic, ion drag, neutral fluid drag and gravitational forces play in governing the dynamic behavior of particle cloud motion. This has been accomplished by using laser light scattering (LLS) techniques to track the motion of suspended particle clouds in rf discharges. Also, statistical correlation’s in the fluctuation of scattered laser light intensity [dynamic laser light scattering (DLLS)] can be used to determine information about particle size, motion, and growth dynamics. These results are reviewed, along with recent work demonstrating that charged dust particles in a plasma can form a strongly coupled Coulomb liquid or solid. New results from DLSS experiments performed in the Reference Cell are presented that show process-induced dust particles confined in an electrostatic trap exhibit low-frequency oscillatory motion consistent with charge density wave (CDW) motion predicted for strongly coupled Coulomb liquids.

Angularly resolved observations of sidescattered laser light from laser-produced plasmas.

Small scale structure is observed in angularly resolved measurements of scattered laser light from 1.06 \ensuremath{\mu}m laser irradiations of CH targets. The structure size varies as the laser spot diameter is changed. The structure is consistent with light produced by the stimulated Brillouin sidescattering instability. The overall angular dependence of the scattered laser light intensity is compared to the distribution predicted by convective growth of stimulated Brillouin sidescattering. Two-dimensional plasma effects are shown to be important in determining the angular distribution of the scattered light.

Coenzyme Q10 enhances cardiac functional and metabolic recovery and reduces Ca2+ overload during postischemic reperfusion.

The effects of coenzyme Q10 (CoQ) were studied in isolated, isovolumic rat hearts during a 30-min period of global ischemia followed by 40 min of reperfusion. After reperfusion 1) the relative recovery of developed pressure (DP) was increased by CoQ (75 vs. 40% of the preischemic value for 20 microM CoQ and control hearts, respectively, P < 0.001); 2) diastolic pressure elevation was decreased by CoQ (20 vs. 50 mmHg in CoQ vs. control hearts, respectively, P < 0.001); and 3) recovery of high-energy phosphates and reduction of inorganic phosphate were approximately twofold greater in CoQ vs. control hearts (P < 0.001 for each parameter). The beneficial effects of CoQ were not observed when CoQ was added at the onset of reperfusion. The total free generation during reperfusion was not affected by CoQ. In unpaced hearts, in the presence of verapamil to prevent spontaneous beating, spontaneous Ca2+ oscillations were measured as scattered laser light intensity fluctuations (SLIF). The transient rise in SLIF in the postischemic reperfused myocardium, which previously has been shown to predict the extent of Ca2+ overload, was suppressed by CoQ (P < 0.001). These results suggest that while early CoQ treatment does not scavenge the primary burst of superoxide or hydroxy radical generation, which occurs on reperfusion, it markedly improves the functional recovery during reperfusion by enhancing the recovery of high-energy phosphates and preventing Ca2+ overload.

Diminished tolerance of prehypertrophic, cardiomyopathic Syrian hamster hearts to Ca2+ stresses.

Although abnormal myocardial calcium homeostasis in the cardiomyopathic hamster (CMH) has been documented in the hypertrophic stage of the disease, the Ca2+ tolerance before the hypertrophic stage has not been investigated. We studied isovolumic contractile function in response to a variety of Ca2+ stresses including increases in perfusate [Ca2+] (Cao), the Ca2+ channel agonist Bay K 8644, and alpha- or beta-adrenergic agonists of isolated perfused hamster hearts from 24-45-day-old male CMH, BIO 14.6 strain, and age- and sex-matched F1B strain controls. The coronary flow at a constant perfusion pressure did not differ between two groups at baseline or after any Ca2+ stress. At a Cao of 1.0 mM, neither end-diastolic pressure (EDP) nor developed pressure (DP) nor half relaxation time (RT1/2) during stimulation at 1-3 Hz differed between the two groups; as Cao was increased up to 10 mM, CMH hearts showed a lower threshold for the occurrence of a Ca2+ overload profile: EDP and RT1/2 increased to a greater, and DP to a lesser, extent in CMH than in control hearts. To determine whether calcium influx via Ca2+ channels mediates the lower threshold for Ca2+ overload in CMH hearts, we measured resting pressure and scattered laser light intensity fluctuation (SLIF) in unstimulated hearts. Prior studies have shown that SLIF is generated by microscopic tissue motion caused by diastolic spontaneous sarcoplasmic reticulum Ca2+ release and that SLIF amplitude reflects the extent of cell and sarcoplasmic reticulum Ca2+ loading. The Ca(2+)-dependent increase in resting pressure in unstimulated hearts was highly correlated with an increase in SLIF, and this relation was steeper in CMH than in control hearts. CMH hearts also showed a reduced threshold for the occurrence of a Ca2+ overload profile in response to the adrenergic receptor agonists and the Ca2+ channel agonist during electrical stimulation in a Cao of 2.0 mM: maximum DP achieved with each agonist was significantly less and the dose-response curves to each agonist were shifted leftward in CMH versus control hearts. In CMH hearts EDP began to increase at a significantly lower concentration of each agonist, and the maximum extent of increase in EDP in response to all agonists was significantly enhanced compared with control hearts. In response to beta-adrenergic or Ca2+ channel agonists, neither resting pressure nor SLIF in unstimulated hearts increased in control or in CMH hearts. In contrast, in response to alpha-adrenergic stimulation, both SLIF and resting pressure increased to a greater extent in CMH than in control hearts.(ABSTRACT TRUNCATED AT 400 WORDS)

Frequency, amplitude, and propagation velocity of spontaneous Ca++-dependent contractile waves in intact adult rat cardiac muscle and isolated myocytes.

Spontaneous contractile waves due to spontaneous calcium cycling by the sarcoplasmic reticulum occur in unstimulated bulk rat papillary muscle and single rat cardiac myocytes with intact sarcolemmal function. We used video analytic techniques to quantify the wave characteristics in both bulk muscle and myocytes; laser-light scattering techniques were also employed in muscle. In muscle bathed in physiological concentrations of calcium, the true periodicity of these waves was a fraction of 1 Hz and increased up to several hertz with increases in cell calcium. This was paralleled by an increase in the frequency of scattered laser light intensity fluctuations. In myocytes, a range of spontaneous contractile wave frequencies similar to that which occurred in the muscle was observed; it could be demonstrated that an increase in superfusate calcium concentrations (2-15 mM at 23 degrees C) increases the oscillation frequency but not amplitude. In both myocytes and muscle, low concentrations of caffeine (0.5 mM) and higher temperature increased the oscillation frequency but diminished their amplitude. However, the scattered light fluctuations did not change with temperature and decreased with caffeine. These results demonstrate that (1) the true frequency of spontaneous sarcoplasmic reticulum oscillations in the unstimulated rat muscle and single myocytes with intact sarcolemmal function is low, i.e., a fraction of a hertz; (2) with cell calcium loading, the oscillation frequency accelerates to those frequencies measured previously in the "calcium overload" state; (3) while scattered light fluctuations which sample myofilament motion are a sensitive, noninvasive method of detecting the oscillations in bulk muscle, they can be insensitive to the divergent changes in oscillation amplitude and frequency.