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Additional Peaks (additional + peak)
Selected AbstractsEnhancement of crystalline perfection by organic dopants in ZTS, ADP and KHP crystals as investigated by high-resolution XRD and SEMJOURNAL OF APPLIED CRYSTALLOGRAPHY, Issue 6 2006S. Parthiban To reveal the influence of complexing agents on crystalline perfection, tristhiourea zinc(II) sulfate (ZTS), ammonium dihydrogen phosphate (ADP) and potassium hydrogen phthalate (KHP) crystals grown by slow-evaporation solution growth technique using low concentrations (5 × 10,3M) of dopants like ethylenediamminetetraacetic acid (EDTA) and 1,10-phenanthroline (phen) were characterized by high-resolution X-ray diffractometry (XRD) and scanning electron microscopy (SEM). High-resolution diffraction curves (DCs) recorded for ZTS and ADP crystals doped with EDTA show that the specimen contains an epilayer, as observed by the additional peak in the DC, whereas undoped specimens do not have such additional peaks. On etching the surface layer, the additional peak due to the epilayer disappears and a very sharp DC is obtained, with full width at half-maximum (FWHM) of less than 10,arcsec, as expected from the plane wave dynamical theory of X-ray diffraction for an ideally perfect crystal. SEM micrographs also confirm the existence of an epilayer in doped specimens. The ZTS specimen has a layer with a rough surface morphology, having randomly oriented needles, whereas the ADP specimen contains a layer with dendric structure. In contrast to ADP and ZTS crystals, the DC of phen-doped KHP shows no additional peak, but it is quite broad (FWHM = 28,arcsec) with a high value of integrated intensity, , (area under the DC). The broadness of the DC and the high value of , indicate the formation of a mosaic layer on the surface of the crystal. However, similar to ADP and ZTS, the DC recorded after etching the surface layer of the KHP specimen shows a very sharp peak with an FWHM of 8 arcsec. An SEM photograph of phen-doped KHP shows deep cracks on the surface, confirming the mosaicity. After removing the surface layer, the SEM pictures reveal a smooth surface. A similar trend is observed with other complexing agents, like oxalic acid, bipy and picolinic acid. However, only typical examples are described in the present article where the effects were observed prominently. The investigations on ZTS, ADP and KHP crystals, employing high-resolution XRD and SEM studies, revealed that some organic dopants added to the solution during the growth lead to the formation of a surface layer, due to complexation of these dopants with the trace metal ion impurities present in the solution, which prevents the entry of impurities, including the solvent, into the crystal, thereby assisting crystal growth with high crystalline perfection. The influence of organic dopants on the second harmonic generation efficiency is also investigated. [source] Coupling between limb tremor and postural sway in Parkinson's diseaseMOVEMENT DISORDERS, Issue 3 2008Graham Kerr BSc, MPhED Abstract Increased tremor and postural instability are motor problems commonly associated with Parkinson's disease (PD). Despite the similarity between these oscillatory forms, little is known about the relation between them, especially for individuals with enhanced tremor. This study was designed to examine the nature of any relation between center of pressure (COP) excursions and postural/resting limb tremor of young, older individuals, and Parkinsonian participants in their different medication states. The resting and postural tremor for the PD participants was characterized by a single, prominent peak frequency between 4 and 7 Hz. The postural tremor for young/older participants contained smaller peaks between 1 to 4 and 7 to 12 Hz although no prominent peak was seen in their resting tremor. The AP and ML COP dynamics of all participants was characterized by a major peak between 0.1 and 0.5 Hz. An additional peak was observed in the COP output of the PD participants between 4 and 7 Hz. While no tremor-COP coupling was observed for the young/old groups, coherence analysis revealed a significant degree of coupling between COP motion and tremor between 4 and 7 Hz for PD participants. These results highlight that the amplified tremor in PD can manifest itself in COP dynamics. This finding may have implications for postural stability for this patient group. © 2007 Movement Disorder Society [source] Resonant Raman scattering in spherical quantum dots: II,VI versus III,V semiconductor nanocrystalsPHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 6 2010Mikhail I. Vasilevskiy Abstract Resonant Raman scattering (RRS) in nearly-spherical nanocrystal (NC) quantum dots (QDs) is discussed with respect to the underlying (Fröhlich-type and optical deformation potential, ODP) mechanisms of the exciton,phonon interaction. Their relative contribution for different QD materials, both II,VI and III,V is compared. It is shown that the (usually overlooked) ODP interaction is entirely responsible for an additional peak in the RRS spectra, situated near the transverse-optical (TO) phonon frequency, which has been observed for InP, InAs and, recently, CdTe QDs. RRS spectra calculated using continuum models for confined phonons and excitons and taking into account both interaction mechanisms are in excellent agreement with these experimental data. [source] Female sex pheromone suppression and the fate of sex-peptide-like peptides in mated moths of Helicoverpa armigeraARCHIVES OF INSECT BIOCHEMISTRY AND PHYSIOLOGY (ELECTRONIC), Issue 3 2007V.K. Nagalakshmi Abstract Insect males produce accessory gland (MAG) factors that are transferred in the seminal fluid to females during copulation, and elicit changes in the mated female's behavior and physiology. Our previous studies showed that the injection of synthetic Drosophila melanogaster sex-peptide (DrmSP) into virgin females of the moth Helicoverpa armigera causes a significant inhibition of pheromone production. In this and other moth species, pheromone production, correlated with female receptivity, is under neuroendocrine control due to the circadian release of the neuropeptide PBAN. In this study, we show that PBAN, present in the hemolymph during the scotophase in females, is drastically reduced after mating. We also identify 4 DrmSP-like HPLC peaks (Peaks A, S1, S2, and B) in MAGs, with increasing levels of DrmSP immunoreactivity during the scotophase, when compared to their levels observed during the photophase. In H. armigera MAGs, a significant reduction in the pheromonostatic peak (Peak B) was already evident after 15 min of copulation, and depletion of an additional peak (Peak S2) was evident after complete mating. Peak A is also detected in female brains, increasing significantly 1 h after mating, at which time inhibition of pheromone biosynthesis also occurs. However, changes corresponding to the other MAG peaks were not detected in mated female tissues. Arch. Insect Biochem. Physiol. 64:142,155, 2007. © 2007 Wiley-Liss, Inc. [source] Thermal behaviour of cubic phases rich in 1-monooleoyl- rac -glycerol in the ternary systemFEBS JOURNAL, Issue 1 2003- d -glucoside/water, 1-monooleoyl- rac -glycerol/n -octyl- Using synchrotron X-ray diffraction the thermal behaviour was studied of the cubic phases in the 1-monooleoyl- rac -glycerol (MO)/n -octyl-,- d -glucopyranoside (OG)/2H2O system with 58 or 45 wt % MO concentration and varying OG/2H2O contents. These MO contents correspond to a Pn3m cubic single-phase or a Pn3m cubic phase in excess water on the binary MO/water axis of the ternary phase diagram. The cubic liquid crystalline phases are stable with small fractions of OG, while higher OG concentrations trigger a cubic-to-lamellar phase transition. Moreover, with increasing OG concentration the initial Pn3m structure is completely converted to an Ia3d structure prior to the L, phase being formed. Upon heating this effect is reversed, resulting in an Ia3d -to- Pn3m phase transition. For some samples additional peaks were observed in the diffractograms upon heating, resulting from the metastability notoriously shown by bicontinuous cubic phases. This judgement is supported by the fact that upon cooling these peaks were absent. Remarkably, both the Ia3d and the Pn3m cubic structures could be in equilibrium with excess water in this ternary system. A comparison is made with previous results on n -dodecyl-,- d -maltoside (DM), showing that cubic phases with OG have higher thermal and compositional stability than with DM. [source] Enhancement of crystalline perfection by organic dopants in ZTS, ADP and KHP crystals as investigated by high-resolution XRD and SEMJOURNAL OF APPLIED CRYSTALLOGRAPHY, Issue 6 2006S. Parthiban To reveal the influence of complexing agents on crystalline perfection, tristhiourea zinc(II) sulfate (ZTS), ammonium dihydrogen phosphate (ADP) and potassium hydrogen phthalate (KHP) crystals grown by slow-evaporation solution growth technique using low concentrations (5 × 10,3M) of dopants like ethylenediamminetetraacetic acid (EDTA) and 1,10-phenanthroline (phen) were characterized by high-resolution X-ray diffractometry (XRD) and scanning electron microscopy (SEM). High-resolution diffraction curves (DCs) recorded for ZTS and ADP crystals doped with EDTA show that the specimen contains an epilayer, as observed by the additional peak in the DC, whereas undoped specimens do not have such additional peaks. On etching the surface layer, the additional peak due to the epilayer disappears and a very sharp DC is obtained, with full width at half-maximum (FWHM) of less than 10,arcsec, as expected from the plane wave dynamical theory of X-ray diffraction for an ideally perfect crystal. SEM micrographs also confirm the existence of an epilayer in doped specimens. The ZTS specimen has a layer with a rough surface morphology, having randomly oriented needles, whereas the ADP specimen contains a layer with dendric structure. In contrast to ADP and ZTS crystals, the DC of phen-doped KHP shows no additional peak, but it is quite broad (FWHM = 28,arcsec) with a high value of integrated intensity, , (area under the DC). The broadness of the DC and the high value of , indicate the formation of a mosaic layer on the surface of the crystal. However, similar to ADP and ZTS, the DC recorded after etching the surface layer of the KHP specimen shows a very sharp peak with an FWHM of 8 arcsec. An SEM photograph of phen-doped KHP shows deep cracks on the surface, confirming the mosaicity. After removing the surface layer, the SEM pictures reveal a smooth surface. A similar trend is observed with other complexing agents, like oxalic acid, bipy and picolinic acid. However, only typical examples are described in the present article where the effects were observed prominently. The investigations on ZTS, ADP and KHP crystals, employing high-resolution XRD and SEM studies, revealed that some organic dopants added to the solution during the growth lead to the formation of a surface layer, due to complexation of these dopants with the trace metal ion impurities present in the solution, which prevents the entry of impurities, including the solvent, into the crystal, thereby assisting crystal growth with high crystalline perfection. The influence of organic dopants on the second harmonic generation efficiency is also investigated. [source] Discriminant analysis of autofluorescence spectra for classification of oral lesions in vivoLASERS IN SURGERY AND MEDICINE, Issue 5 2009J.L. Jayanthi MSc, MPhil Abstract Background and Objectives Low survival rate of individuals with oral cancer emphasize the significance of early detection and treatment. Optical spectroscopic techniques are under various stages of development for diagnosis of epithelial neoplasm. This study evaluates the potential of a multivariate statistical algorithm to classify oral mucosa from autofluorescence spectral features recorded in vivo. Study Design/Methods Autofluorescence spectra were recorded in a clinical trial from 15 healthy volunteers and 34 patients with diode laser excitation (404,nm) and pre-processed by normalization, mean-scaling and its combination. Linear discriminant analysis (LDA) based on leave-one-out (LOO) method of cross validation was performed on spectral data for tissue characterization. The sensitivity and specificity were determined for different lesion pairs from the scatter plot of discriminant function scores. Results Autofluorescence spectra of healthy volunteers consists of a broad emission at 500,nm that is characteristic of endogenous fluorophores, whereas in malignant lesions three additional peaks are observed at 635, 685, and 705,nm due to the accumulation of porphyrins in oral lesions. It was observed that classification design based on discriminant function scores obtained by LDA-LOO method was able to differentiate pre-malignant dysplasia from squamous cell carcinoma (SCC), benign hyperplasia from dysplasia and hyperplasia from normal with overall sensitivities of 86%, 78%, and 92%, and specificities of 90%, 100%, and 100%, respectively. Conclusions The application of LDA-LOO method on the autofluorescence spectra recorded during a clinical trial in patients was found suitable to discriminate oral mucosal alterations during tissue transformation towards malignancy with improved diagnostic accuracies. Lasers Surg. Med. 41:345,352, 2009. © 2009 Wiley-Liss, Inc. [source] Effects of MgCl2 Crystallographic Structure on Active Centre Formation in Immobilized Single-Centre and Ziegler,Natta Catalysts for Ethylene PolymerizationMACROMOLECULAR RAPID COMMUNICATIONS, Issue 21 2008Rubin Huang Abstract The ability of a MgCl2 support to activate a transition metal catalyst has been found to depend both on the crystallographic structure of the support and on the nature of the catalyst. A high degree of crystallographic disorder can be very effective for the immobilization and activation of titanium and vanadium complexes, but is not necessarily effective for zirconocene activation. A highly disordered support prepared by the reaction of MgBu2 with HCl gave high activity with TiCl4 but low activity with (n -PrCp)2ZrCl2. High polymerization activities with the zirconocene were only obtained with supports of type MgCl2/AlRn(OEt)3,n prepared from the reaction of AlR3 with MgCl2,·,1.1EtOH. These supports are characterized by additional peaks in the X-ray diffraction pattern, indicating the presence of a crystalline structure which is absent in the other supports and contains highly Lewis acidic sites able to generate the active metallocenium species. [source] Optical gravitational lensing experiment: OGLE-1999-BUL-19 , the first multipeak parallax eventMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 2 2002Martin C. Smith Abstract We describe a highly unusual microlensing event, OGLE-1999-BUL-19. Unlike most standard microlensing events, this event exhibits multiple peaks in its light curve. The Einstein radius crossing time for this event is approximately 1 yr, which is unusually long. We show that the additional peaks in the light curve can be caused by the very small value for the relative transverse velocity of the lens projected on to the observer plane (). Since this value is significantly less than the speed of the orbit of the Earth around the Sun (v,, 30km s,1), the motion of the Earth induces these multiple peaks in the light curve. This value for is the lowest velocity so far published and we believe that this is the first multiple-peak parallax event ever observed. We also found that the event can be somewhat better fitted by a rotating binary-source model, although this is to be expected since every parallax microlensing event can be exactly reproduced by a suitable binary-source model. A face-on rotating binary-lens model was also identified, but this provides a significantly worse fit. We conclude that the most likely cause for this multipeak behaviour is parallax microlensing rather than microlensing by a binary source. However, this event may be exhibiting a slight binary-source signature in addition to these parallax-induced multiple peaks. With spectroscopic observations it is possible to test this ,parallax plus binary-source' hypothesis and (in the instance that the hypothesis turns out to be correct) to simultaneously fit both models and obtain a measurement of the lens mass. Furthermore, spectroscopic observations could also supply information regarding the lens properties, possibly providing another avenue for determining the lens mass. We also investigated the nature of the blending for this event, and found that the majority of the I -band blending is contributed by a source roughly aligned with the lensed source. This implies that most of the I -band blending is caused by light from the lens or a binary companion to the source. However, in the V band, there appears to be a second blended source 0.35 arcsec away from the lensed source. Hubble Space Telescope observations will be very useful for understanding the nature of the blends. We also suggest that a radial velocity survey of all parallax events will be very useful for further constraining the lensing kinematics and understanding the origins of these events and the excess of long events toward the bulge. [source] Annealing crystallization of a-Ge/Al/Si and a-Ge/Si thin filmsPHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 9 2005F. Fajardo Abstract This work describes the temperature-induced crystallization of amorphous Ge (a-Ge) as a function of the thickness of the a-Ge films (in the 12,2600 nm range), which were deposited both onto c-Si substrates and c-Si substrates covered with aluminium. After deposition, the samples were submitted to cumulative thermal annealing treatments. It is shown that the temperature of crystallization depends on the thickness of the a-Ge films and to the presence (or not) of the Al layer. For an annealing temperature (Ta) of ,700 °C, for example, the Raman spectra of films thinner than ,1000 nm and deposited onto c-Si substrates are completely dominated by the sharp phonon mode of crystalline Si. Films with thicknesses equal to 300, 1000 and 2600 nm, deposited onto Al/c-Si, and treated at Ta = 600 °C, on the other hand, clearly display two additional peaks at 405 and 490 cm,1. They correspond to the Raman modes of Si,Ge and Si,Si modes, suggesting the formation of a SiGe alloy during the thermal anneal of the films. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Aharonov,Bohm effect of a quantum ring in the Kondo regimePHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 2 2003U. F. Keyser Abstract We investigate a small tuneable quantum ring fabricated by direct local oxidation using an atomic force microscope. The device contains very few electrons and is tuned into the Kondo regime. We study this Kondo effect by temperature dependent measurements. At finite bias voltages we observe additional peaks. These vanish with increasing temperature indicating Kondo correlations for these excited states. Additionally, the geometry of our device allows to study Aharonov,Bohm oscillations in the Kondo regime for a device containing less than ten electrons. We observe a modulation of the Kondo effect with a reduced Aharonov,Bohm period explained by electron,electron interaction in our small quantum ring. [source] | ||||||||||||||||