Growth Kinetics of ZnO Nanocrystals in the Presence of a Base: Effect of the Size of the Alkali Cation

Following an earlier study (J. Am. Chem Soc. 2007, 129, 4470) describing a very unusual growth kinetics of ZnO nanoparticles, we critically evaluate here the proposed mechanism involving a crucial role of the alkali base ion in controlling the growth of ZnO nanoparticles using other alkali bases, namely, LiOH and KOH. While confirming the earlier conclusion of the growth of ZnO nanoparticles being hindered by an effective passivating layer of cations present in the reaction mixture and thereby generalizing this phenomenon, present experimental data reveal an intriguing nonmonotonic dependence of the passivation efficacy on the ionic size of the alkali base ion. This unexpected behavior is rationalized on the basis of two opposing factors: (a) solvated cationic radii and (b) dissociation constant of the base.

Dynamics of freely suspended films with surface tension

We have studied the hydrodynamics of freely suspended membranes, liquid as well as crystalline, with surface tension. We find that nonlinear coupling to thermally excited undulations gives a singular contribution to the kinetic coefficients of these systems at low frequency and wavenumber. Our results differ in some important respects from those of Katz and Lebedev on this problem, and can be tested in mechanical impedance as well as time-correlation studies.

Pressure-induced phase transitions in LiRbSO4: a Raman spectroscopic study

Room-temperature Raman spectra of LiRbSO4 were studied as a function of pressure up to 170 kbar for two different orientations of the crystal. Four pressure-induced phase transitions at about 2, 17, 32 and 57 kbar were observed. The transitions at 17 and 57 kbar have slow kinetics, taking about 4 h for their completion. These phase transitions are associated with the orientations of the SO4 ions in the unit cell.

Heraproteiinivalmisteen vaikutus laihdutukseen ja laihdutustuloksen pysyvyyteen ylipainoisilla aikuisilla

Johdanto: Lihavuus on maailmalaajuisesti merkittävä kansanterveydellinen ja –taloudellinen ongelma. Lihavuuden ehkäisemiseksi ja epidemian leviämisen hillitsemiseksi on tärkeää tuntea lihavuuteen vaikuttavat tekijät. Yksittäisistä ruoka-aineista maidon käytön on havaittu monissa epidemiologisissa ja kokeellisissa tutkimuksissa olevan yhteydessä alhaisempaan painoon, ehkäisevän lihomista ja edistävän laihtumista. Maidon sisältämistä yhdisteistä kalsiumin vaikutuksia on tutkittu eniten. Myös heraproteiinin on esitetty olevan yksi mahdollinen painoon vaikuttava komponentti, ja näyttöä tästä on saatu eläinkokeista. Tavoitteet: Tutkimuksessa tavoitteena oli selvittää, vaikuttaako päivittäin nautittu heraproteiinia sisältävä välipalajuoma laihtumiseen tai saavutetun laihdutustuloksen pysyvyyteen ylipainoisilla aikuisilla. Aineisto ja menetelmät: Tutkimus toteutettiin osana Valio Oy:n OMPPU2-tutkimusta, joka oli satunnaistettu, lumekontrolloitu ja kaksoissokkoutettu kahden rinnakkaisen ryhmän tutkimus. Tutkimus alkoi rekrytoinneilla alkuvuodesta 2010, joissa tutkimukseen valittiin 105 ylipainoista (BMI 27–35), tervettä, 20–50-vuotiasta naista ja miestä. Tutkimushenkilöt satunnaistettiin tutkimus- ja verrokkiryhmiin, ja molemmat ryhmät nauttivat tutkimusvalmisteensa päivittäin hedelmätäysmehuun sekoitettuna (tutkimusryhmä heraproteiinijauheen ja verrokkiryhmä maltodekstriinijauheen). Tutkimus koostui kahdesta jaksosta: viiden kuukauden laihdutusjaksosta ja tätä seuranneesta kolmen kuukauden painonhallintajaksosta. Tutkimuskäynneillä tutkimuksen alussa, laihdutusjakson lopussa ja painonhallintajakson lopussa mitattiin tutkimushenkilöiden paino ja vyötärönympärys sekä määritettiin kehonkoostumus bioimpedanssilaitteella. Tutkimushenkilöiden ruoankäyttö ja ravinnonsaanti laskettiin samoissa aikapisteissä kerättyjen kolmen päivän ruokapäiväkirjojen perusteella. Tutkimushenkilöitä, joilla tutkimusvalmisteen käyttö oli alle 50 %, ei otettu huomioon tilastoanalyyseissä. Tilastollinen analyysi tehtiin käyttäen kahden riippumattoman otoksen t-testiä ja kaksisuuntaista parittaista t-testiä normaalijakautuneilla muuttujilla, ja Mann-Whitneyn U-testiä ja Wilcoxonin ttestiä ei-normaalijakautuneilla muuttujilla. Tutkimusvalmisteen ja painonmuutosten välinen korrelaatio laskettiin käyttäen Pearsonin korrelaatiokertoimia. Tulokset on ilmaistu keskiarvoina (keskihajonta). Tulokset: Molemmat ryhmät laihtuivat laihdutusjakson aikana. Heraproteiiniryhmässä painonpudotus oli 2,4 (3,8) kg (p=0,002) ja verrokkiryhmässä 3,4 (4,1) kg (p<0,001). Ryhmien välinen ero ei ollut merkitsevä. Rasvamassa väheni verrokkiryhmässä 2,4 (3,8) kg (p<0,001), mikä oli viiteellisesti enemmän (p=0,054) kuin heraproteiiniryhmässä 1,1 (3,1) kg (p=0,129). Rasvaprosentti ja viskeraalirasvan määrä pienenivät verrokkiryhmässä heraproteiiniryhmää enemmän (p<0,025). Vyötärönympärys pieneni heraproteiiniryhmässä 1,9 (3,0) cm (p=0,001) ja verrokkiryhmässä 3,8 (3,8) cm (p<0,001) ryhmien välisen eron ollessa merkitsevä (p=0,017). Maltodekstriinin käyttö korreloi käänteisesti painonmuutosten kanssa laihdutusjaksolla (r=-0,389, p=0,013). Painonhallintajaksolla painossa ei tapahtunut merkitseviä muutoksia kummassakaan ryhmässä. Heraproteiinin käytön ja painonmuutosten välisestä negatiivisesta korrelaatiosta oli viitteitä tällä jaksolla (r=-0,344, p=0,063). Kun tarkasteltiin koko tutkimuksen aikana tapahtuneita muutoksia (laihdutusjakson alusta painonhallintajakson loppuun), ei ryhmien välillä ollut merkitseviä eroja painon tai kehonkoostumuksen muutoksissa. Energiansaanti väheni molemmissa ryhmissä merkitsevästi laihdutusjakson aikana (p<0,01), mutta muutos ei eronnut ryhmien välillä. Ravintoaineista rasvan saanti väheni (p<0,001) ja C-vitamiinin saanti lisääntyi (p<0,001) molemmissa ryhmissä laihdutusjaksolla. Alkoholin saanti väheni verrokkiryhmässä (p=0,017). Proteiinin saanti lisääntyi heraproteiiniryhmässä merkitsevästi enemmän kuin verrokkiryhmässä (p=0,002). Painonhallintajaksolla energiansaanti ei muuttunut kummassakaan ryhmässä laihdutusjakson loppuun verrattuna. Fyysisessä aktiivisuudessa tutkimuksen aikana ei ollut eroa ryhmien välillä. Johtopäätökset: Heraproteiinin ei havaittu tehostavan laihdutusta maltodekstriiniin verrattuna tässä tutkimuksessa. Sen sijaan maltodekstriiniä nauttineessa ryhmässä rasvaprosentti ja erityisesti vatsan alueen rasva pienenivät heraproteiiniryhmää enemmän laihdutusjaksolla. Tulos oli lähes täysin vastakkainen tutkimushypoteesin kanssa, eikä vaikuttaisi selittyvän eroilla energiansaannissa tai fyysisessä aktiivisuudessa. Tämä tutkimus ei siis tue olettamusta, että heraproteiini osana laihdutusruokavaliota auttaisi laihdutuksessa. Painonhallintajaksolla heraproteiinin ja painonmuutosten välinen lähes merkitsevä käänteinen korrelaatio saattaa viitata heraproteiinin merkitykseen painonhallinnassa. Vapaasti elävien ihmisten kohdalla sekoittavia tekijöitä on kuitenkin vaikea vakioida, mikä vaikeuttaa johtopäätösten tekemistä.

Gain calibration of CCD systems at VBO

The system gain of two CCD systems in regular use at the Vainu Bappu Observatory, Kavalur, is determined at a few gain settings. The procedure used for the determination of system gain and base-level noise is described in detail. The Photometrics CCD system at the 1-m reflector uses a Thomson-CSF TH 7882 CDA chip coated for increased ultraviolet sensitivity. The gain is programme-selected through the parameter 'cgain' varying between 0 and 4095 in steps of 1. The inverse system gain for this system varies almost linearly from 27.7 electrons DN-1 at cgain = 0 to 1.5 electrons DN-1 at cgain = 500. The readout noise is less than or similar 11 electrons at cgain = 66. The Astromed CCD system at 2.3-m Vainu Bappu Telescope uses a GEC P8603 chip which is also coated for enhanced ultraviolet sensitivity. The amplifier gain is selected in discrete steps using switches in the controller. The inverse system gain is 4.15 electrons DN-1 at the gain setting of 9.2, and the readout noise approximately 8 electrons.

A simplified kinetic model for oxidative dehydrogenation of ethylbenzene over Pd-NaBr/Al2O3 catalyst

The oxidative dehydrogenation of ethylbenzene is gaining considerable importance in recent years as a promising alternative for styrene production. This vapour phase reaction has been studied over Pd-NaBr/Al2O3 catalyst in the temperature range 623-793 K in a fixed bed reactor. Kinetic analysis of this reaction has been done using a recursion procedure developed in this work from first principles. The advantage of this method is the absence of any restriction on the conversion level as it uses an integrated rate equation. The rate of styrene formation was found to follow a linear relationship with concentration of ethylbenzene and shows a Langmuir type dependence on the concentration of oxygen.

Composite material and piezoelectric coefficient uncertainty effects on structural health monitoring using feedback control gains as damage indicators

This article addresses uncertainty effect on the health monitoring of a smart structure using control gain shifts as damage indicators. A finite element model of the smart composite plate with surface-bonded piezoelectric sensors and actuators is formulated using first-order shear deformation theory and a matrix crack model is integrated into the finite element model. A constant gain velocity/position feedback control algorithm is used to provide active damping to the structure. Numerical results show that the response of the structure is changed due to matrix cracks and this change can be compensated by actively tuning the feedback controller. This change in control gain can be used as a damage indicator for structural health monitoring. Monte Carlo simulation is conducted to study the effect of material uncertainty on the damage indicator by considering composite material properties and piezoelectric coefficients as independent random variables. It is found that the change in position feedback control gain is a robust damage indicator.

Propagating intensity disturbances in polar corona as seen from AIA/SDO

Context. Polar corona is often explored to find the energy source for the acceleration of the fast solar wind. Earlier observations show omni-presence of quasi-periodic disturbances, traveling outward, which is believed to be caused by the ubiquitous presence of outward propagating waves. These waves, mostly of compressional type, might provide the additional momentum and heat required for the fast solar wind acceleration. It has been conjectured that these disturbances are not due to waves but high speed plasma outflows, which are difficult to distinguish using the current available techniques. Aims. With the unprecedented high spatial and temporal resolution of AIA/SDO, we search for these quasi-periodic disturbances in both plume and interplume regions of the polar corona. We investigate their nature of propagation and search for a plausible interpretation. We also aim to study their multi-thermal nature by using three different coronal passbands of AIA. Methods. We chose several clean plume and interplume structures and studied the time evolution of specific channels by making artificial slits along them. Taking the average across the slits, space-time maps are constructed and then filtration techniques are applied to amplify the low-amplitude oscillations. To suppress the effect of fainter jets, we chose wider slits than usual. Results. In almost all the locations chosen, in both plume and interplume regions we find the presence of propagating quasi-periodic disturbances, of periodicities ranging from 10-30 min. These are clearly seen in two channels and in a few cases out to very large distances (approximate to 250 `') off-limb, almost to the edge of the AIA field of view. The propagation speeds are in the range of 100-170 km s(-1). The average speeds are different for different passbands and higher in interplume regions. Conclusions. Propagating disturbances are observed, even after removing the effects of jets and are insensitive to changes in slit width. This indicates that a coherent mechanism is involved. In addition, the observed propagation speed varies between the different passpands, implying that these quasi-periodic intensity disturbances are possibly due to magneto-acoustic waves. The propagation speeds in interplume region are higher than in the plume region.

How fast is ultrafast chemistry

The field of ultrafast chemistry has seen a string of remarkable discoveries in the recent years. In this article we briefly discuss some of the problems solved recently. The understanding that has emerged from these studies has important consequences non only in chemistry but also in diverse biological processes.

Effect of chronic administration of Tamoxifen on fertility in male bonnet monkeys (Macaca radiata)

Administration of Tamoxifen via the Alzet pump at a rate of 50 mu g hr(-1) for 90 days in the adult male bonnet monkeys Macaca radiata had no effect on the serum testosterone concentration determined at 10 AM and 10 PM as well as total sperm count determined at 15-day intervals over a period of 260 days. However, a significant reduction in sperm motility was observed beyond 90 days up until the 225th day. Breeding studies conducted from day 90 to 260 revealed that these males were infertile.

Lopsidedness in WHISP galaxies I. Rotation curves and kinematic lopsidedness

The frequently observed lopsidedness of the distribution of stars and gas in disc galaxies is still considered as a major problem in galaxy dynamics. It is even discussed as an imprint of the formation history of discs and the evolution of baryons in dark matter haloes. Here, we analyse a selected sample of 70 galaxies from the Westerbork Hi Survey of Spiral and Irregular Galaxies. The Hi data allow us to follow the morphology and the kinematics out to very large radii. In the present paper, we present the rotation curves and study the kinematic asymmetry. We extract the rotation curves of the receding and approaching sides separately and show that the kinematic behaviour of disc galaxies can be classified into five different types: symmetric velocity fields where the rotation curves of the receding and approaching sides are almost identical; global distortions where the rotation velocities of the receding and approaching sides have an offset that is constant with radius; local distortions leading to large deviations in the inner and negligible deviations in the outer parts (and vice versa); and distortions that divide the galaxies into two kinematic systems that are visible in terms of the different behaviour of the rotation curves of the receding and approaching sides, which leads to a crossing and a change in side. The kinematic lopsidedness is measured from the maximum rotation velocities, averaged over the plateau of the rotation curves. This gives a good estimate of the global lopsidedness in the outer parts of the sample galaxies. We find that the mean value of the perturbation parameter denoting the lopsided potential as obtained from the kinematic data is 0.056. Altogether, 36% of the sample galaxies are globally lopsided, which can be interpreted as the disc responding to a halo that was distorted by a tidal encounter. In Paper II, we study the morphological lopsidedness of the same sample of galaxies.

Lopsidedness in WHISP galaxies II. Morphological lopsidedness

The distribution of stars and gas in many galaxies is asymmetric. This so-called lopsidedness is expected to significantly affect the dynamics and evolution of the disc, including the star formation activity. Here, we measure the degree of lopsidedness for the gas distribution in a selected sample of 70 galaxies from the Westerbork Hi Survey of Spiral and Irregular Galaxies. This complements our earlier work (Paper I) where the kinematic lopsidedness was derived for the same galaxies. The morphological lopsidedness is measured by performing a harmonic decomposition of the surface density maps. The amplitude of lopsidedness A(1), the fractional value of the first Fourier component, is typically quite high (about 0.1) within the optical disc and has a constant phase. Thus, lopsidedness is a common feature in galaxies and indicates a global mode. We measure A(1) out to typically one to four optical radii, sometimes even further. This is, on average, four times larger than the distance to which lopsidedness was measured in the past using near-IR as a tracer of the old stellar component, and therefore provides a new, more stringent constraint on the mechanism for the origin of lopsidedness. Interestingly, the value of A(1) saturates beyond the optical radius. Furthermore, the plot of A(1) versus radius shows fluctuations that we argue are due to local spiral features. We also try to explain the physical origin of this observed disc lopsidedness. No clear trend is found when the degree of lopsidedness is compared to a measure of the isolation or interaction probability of the sample galaxies. However, this does not rule out a tidal origin if the lopsidedness is long-lived. In addition, we find that the early-type galaxies tend to be more morphologically lopsided than the late-type galaxies. Both results together indicate that lopsidedness has a tidal origin.

Effect of fluctuations on the freezing of a colloidal suspension in an external periodic potential

We incorporate the effects of fluctuations in a density functional analysis of the freezing of a colloidal liquid in the presence of an external potential generated by interfering laser beams. A mean-field treatment, using a density functional theory, predicts that with the increase in the strength of the modulating potential, the freezing transition changes from a first order to a continuous one via a tricritical point for a suitable choice of the modulating wavevectors. We demonstrate here that the continuous nature of the freezing transition at large values of the external potential V-e survives the presence of fluctuations. We also show that fluctuations tend to stabilize the liquid phase in the large V-e regime.

Symplectic integration of nonlinear Hamiltonian systems

There exist several standard numerical methods for integrating ordinary differential equations. However, if one is interested in integration of Hamiltonian systems, these methods can lead to wrong results. This is due to the fact that these methods do not explicitly preserve the so-called 'symplectic condition' (that needs to be satisfied for Hamiltonian systems) at every integration step. In this paper, we look at various methods for integration that preserve the symplectic condition.