Newtonian acceleration scales in spiral galaxies

We revisit the issue of the constancy of the dark matter (DM) and baryonic Newtonian acceleration scales within the DM scale radius by considering a large sample of late-type galaxies. We rely on a Markov Chain Monte Carlo method to estimate the parameters of the halo model and the stellar mass-to-light ratio and then propagate the uncertainties from the rotation curve data to the estimate of the acceleration scales. This procedure allows us to compile a catalogue of 58 objects with estimated values of the B-band absolute magnitude M-B, the virial mass M-vir, and the DM and baryonic Newtonian accelerations (denoted as g(DM)(r(0)) and g(bar)(r(0)), respectively) within the scale radius r(0) which we use to investigate whether it is possible to define a universal acceleration scale. We find a weak but statistically meaningful correlation with M-vir thus making us argue against the universality of the acceleration scales. However, the results somewhat depend on the sample adopted so that a careful analysis of selection effects should be carried out before any definitive conclusion can be drawn.

Enzymatic Solid-Phase Reactor Based on Silica Organofunctionalized with p-Phenylenediamine for Electrochemical Detection of Phenolic Compounds

A new biomaterial, based on silica organofunctionalized with p-phenylenediamine (p-PDA) and the enzyme peroxidase, was used in the development of an enzymatic solid-phase reactor. The analytical techniques used in the characterization showed that the organic ligand was incorporated into the silica matrix. Thus, the silica modified with p-PDA allowed the incorporation of peroxidase by the electrostatic interaction between the carboxylic groups present in the enzyme molecules and the amino groups attached to the silica. The enzymatic solid-phase reactor was used for chemical oxidation of phenols in 1, 4-benzoquinone that was then detected by chronoamperometry. The system allowed the analysis of hydroquinone with a detection limit of 83.6 nmol L-1. Thus, the new material has potential in the determination of phenolic compounds river water samples.

Do Higher Temperatures Increase Growth in the Nocturnal Gecko Homonota darwini (Gekkota: Phyllodactylidae)? A Skeletochronological Assessment Analyzed at Temporal and Geographic Scales

Recent studies predict that several lineages of tropical animals are at particular risk given current estimates of global climate change. Yet, much uncertainty exists on the effects of climate shifts in ectothermic species from cool temperate regions such as Patagonia. In this study, we focus on the impact of environmental temperature on growth, age at sexual maturity, and life-span of the Patagonian gecko Homonota darwini. Skeletochronological methods were used to assess the bone growth rates Of individuals from three populations at different geographic and temporal scales: two populations from Chubut (warm site; 1941 and 2010) and one population from Rio Negro (cold site; 1997-1998). Populations displayed similar bone arrangement and the growth patterns fit a von Bertalanffy curve. Three populations attained reproductive size at a minimum age of 3 yr, but at the cold site two specimens were shown to mature in 4 yr. We found no differences in juvenile growth rates in body size or bone zone width between juveniles of 1 to 3 yr of age from the 1941 warm site and the 2010 warm site. However, these traits appeared to be higher at these two warm sites than at the cold site, which is consistent with the climatic differences among the three localities. Our results suggest that higher temperatures positively affect growth, denoting that global warming might benefit H. darwini, especially the southern populations.

Broad combined orange-red emissions from Eu2+- and Eu3+-doped low-silica calcium aluminosilicate glass

In this paper, a broad combined orange-red emission from Eu2+- and Eu3+-doped low-silica calcium aluminosilicate (LSCAS) glass is reported. Spectroscopic results demonstrate that it is possible to tune the emission wavelength by changing the excitation wavelength in the UV-Vis region. The color coordinates for the emission spectra were calculated, and using the Commission Internationale de l'Eclairage 1931 and 1976 chromatic diagrams, it is possible to note that they are dependent on the excitation wavelength. In addition, the (u', v') color coordinates for the investigated LSCAS samples are close to the Planckian spectrum in the cold region between 2000 and 2600K. Our results show that the Eu:LSCAS system can be used in a white light phosphor when mixed in aggregate with phosphors using green-yellow luminescent ions. (c) 2012 Optical Society of America

Self-Assembly of Poly(4-vynil-N-alkylpyridinium) Bromide onto Silica: Effect of Side-Chain Length on Structural Aspects at a Molecular Level

Self-assembly of poly(4-vynil-N-alkyl)pyridinium bromide with alkyl side chains of 2, 5, 7, 10, or 16 carbons from ethanolic solutions onto flat silica surfaces was studied by means of ellipsometry, atomic force microscopy (AFM), contact angle measurements, and sum-frequency generation (SFG) vibrational spectroscopy in the CH3 and CH2 stretch region. Ab initio quantum-chemical calculations on the N-alkylpyridinium side-group with restricted Hartree-Fock (RHF) method and 6-311G (d,p) basis set were C one to estimate the charge distribution along the pyridinium ring and the alkyl side-chain. SFG results showed that longer side chains promote the disorientation of the alkyl groups at the surface, corroborating with the contact angle values. AFM images revealed film homogeneity, regardless the alkyl side group. However, after 24 h contact with water, ringlike structures appeared on the film surfaces, when the polycation alkyl side chain had 7 or less carbons, and as the alkyl chain increased to 10 or 16 carbons, the films dewetted because the hydrophobic interactions prevailed over the electrostatic interactions between the pyridinium charged groups and the negatively charged SiO2 surface. Under acid conditions (HCl 0.1 mol.L-1), the film mean thickness values decreased up to 50% of original values when the alkyl side chains were ethyl or pentyl groups due to ion-pair disruption, but for longer groups they remained unchanged. Quantum-chemical optimization and Mulliken electron population showed that (i) from C2 to C15 the positive charge at the headgroup (HG) decreased 0.025, while the charge at combined HG + alpha-CH2 increased 0.037; and (ii) for C6 or longer, the alkyl side group presents a tilt in the geometry, moving away from the plane. Such effects summed up over the whole polymer chain give support to suggest that when the side chains are longer than 7 carbons, the hydrophobic interaction decreases film stability and increases acid resistance.

Spatial-temporal variations in phytoplankton size and colored detrital matter absorption at global and regional scales, as derived from twelve years of SeaWiFS data (1998-2009)

A procedure has been proposed by Ciotti and Bricaud (2006) to retrieve spectral absorption coefficients of phytoplankton and colored detrital matter (CDM) from satellite radiance measurements. This was also the first procedure to estimate a size factor for phytoplankton, based on the shape of the retrieved algal absorption spectrum, and the spectral slope of CDM absorption. Applying this method to the global ocean color data set acquired by SeaWiFS over twelve years (1998-2009), allowed for a comparison of the spatial variations of chlorophyll concentration ([Chl]), algal size factor (S-f), CDM absorption coefficient (a(cdm)) at 443 nm, and spectral slope of CDM absorption (S-cdm). As expected, correlations between the derived parameters were characterized by a large scatter at the global scale. We compared temporal variability of the spatially averaged parameters over the twelve-year period for three oceanic areas of biogeochemical importance: the Eastern Equatorial Pacific, the North Atlantic and the Mediterranean Sea. In all areas, both S-f and a(cdm)(443) showed large seasonal and interannual variations, generally correlated to those of algal biomass. The CDM maxima appeared in some occasions to last longer than those of [Chl]. The spectral slope of CDM absorption showed very large seasonal cycles consistent with photobleaching, challenging the assumption of a constant slope commonly used in bio-optical models. In the Equatorial Pacific, the seasonal cycles of [Chl], S-f, a(cdm)(443) and S-cdm, as well as the relationships between these parameters, were strongly affected by the 1997-98 El Ni o/La Ni a event.

GRBAS and Cape-V Scales: High Reliability and Consensus When Applied at Different Times

Objectives. To evaluate whether the overall dysphonia grade, roughness, breathiness, asthenia, and strain (GRBAS) scale, and the Consensus Auditory Perceptual Evaluation-Voice (CAPE-V) scale show the same reliability and consensus when applied to the same vocal sample at different times. Study Design. Observational cross-sectional study. Methods. Sixty subjects had their voices recorded according to the tasks proposed in the CAPE-V scale. Vowels /a/ and /i/ were sustained between 3 and 5 seconds. Reproduction of six sentences and spontaneous speech from the request "Tell me about your voice" were analyzed. For the analysis of the GRBAS scale, the sustained vowel and reading tasks of the sentences was used. Auditory-perceptual voice analyses were conducted by three expert speech therapists with more than 5 years of experience and familiar with both the scales. Results. A strong correlation was observed in the intrajudge consensus analysis, both for the GRBAS scale as well as for CAPE-V, with intraclass coefficient values ranging from 0.923 to 0.985. A high degree of correlation between the general GRBAS and CAPE-V grades (coefficient = 0.842) was observed, with similarities in the grades of dysphonia distribution in both scales. The evaluators indicated a mild difficulty in applying the GRBAS scale and low to mild difficulty in applying the CAPE-V scale. The three evaluators agreed when indicating the GRBAS scale as the fastest and the CAPE-V scale as the most sensitive, especially for detecting small changes in voice. Conclusions. The two scales are reliable and are indicated for use in analyzing voice quality.

Design of a Dinuclear Nickel(II) Bioinspired Hydrolase to Bind Covalently to Silica Surfaces: Synthesis, Magnetism, and Reactivity Studies

Presented herein is the design of a dinuclear Ni-II synthetic hydrolase [Ni-2(HBPPAMFF)(mu-OAc)(2)(H2O)]-BPh4 (1) (H(2)BPPAMFF = 2-[(N-benzyl-N-2-pyridylmethylamine)]-4-methyl-6-[N-(2-pyridylmethyl)aminomethyl)])-4- methyl-6-formylphenol) to be covalently attached to silica surfaces, while maintaining its catalytic activity. An aldehyde-containing ligand (H(2)BPPAMFF) provides a reactive functional group that can serve as a cross-linking group to bind the complex to an organoalkoxysilane and later to the silica surfaces or directly to amino-modified surfaces. The dinuclear Ni-II complex covalently attached to the silica surfaces was fully characterized by different techniques. The catalytic turnover number (k(cat)) of the immobilized (NiNiII)-Ni-II catalyst in the hydrolysis of 2,4-bis(dinitrophenyl)phosphate is comparable to the homogeneous reaction; however, the catalyst interaction with the support enhanced the substrate to complex association constant, and consequently, the catalytic efficiency (E - k(cat)/K-M) and the supported catalyst can be reused for subsequent diester hydrolysis reactions.

The importance of vertical and horizontal dimensions of the sediment matrix in structuring nematodes across spatial scales

Intensive surveys have been conducted to unravel spatial patterns of benthic infauna communities. Although it has been recognized that benthic organisms are spatially structured along the horizontal and vertical dimensions of the sediment, little is known on how these two dimensions interact with each other. In this study we investigated the interdependence between the vertical and horizontal dimensions in structuring marine nematodes assemblages. We tested whether the similarity in nematode species composition along the horizontal dimension was dependent on the vertical layer of the sediment. To test this hypothesis, three-cm interval sediment samples (15 cm depth) were taken independently from two bedforms in three estuaries. Results indicated that assemblages living in the top layers are more abundant, species rich and less variable, in terms of species presence/absence and relative abundances, than assemblages living in the deeper layers. Results showed that redox potential explained the greatest amount (12%) of variability in species composition, more than depth or particle size. The fauna inhabiting the more oxygenated layers were more homogeneous across the horizontal scales than those from the reduced layers. In contrast to previous studies, which suggested that reduced layers are characterized by a specific set of tolerant species, the present study showed that species assemblages in the deeper layers are more causal (characterized mainly by vagrant species). The proposed mechanism is that at the superficial oxygenated layers, species have higher chances of being resuspended and displaced over longer distances by passive transport, while at the deeper anoxic layers they are restricted to active dispersal from the above and nearby sediments. Such restriction in the dispersal potential together with the unfavorable environmental conditions leads to randomness in the presence of species resulting in the high variability between assemblages along the horizontal dimension.

Length scales of dynamic heterogeneities of low and high molecular weight glass formers from multidimensional NMR

Das Ziel der vorliegenden Arbeit ist die Untersuchung der räumlichen und zeitlichen Aspekte der heterogenen Dynamik in Modellglasbildnern. Dabei wird vor allem die langsame alpha-Relaxationsdynamik oberhalb des Glasüberganges Tg untersucht. Die nukleare Magnetresonanz zeigt ihre einmalige Vielseitigkeit bei der Untersuchung molekularer Dynamik, wenn die angewandten Techniken und Experimente durch Simulationen unterstützt werden. Die räumliche Aspekt dynamischer Heterogenitäten wird untersucht durch ein reduziertes vierdimensionales Spindiffusionsexperiment (4D3CP), ein Experiment, das Reorientierungsraten örtlich korreliert. Eine Simulation dieses Experimentes an einem System harter Kugeln liefert wertvolle Informationen über die Auswertemethode des 4D3CP Experiments. Glycerol und o-terphenyl werden durch das 4D3CP Experiment untersucht. Die erhaltenen Resultate werden mit bereits publizierten Daten des polymeren Glasbildners PVAc verglichen. Während PVAc und o-terphenyl eine Längenskale von 3.7 nm bzw. 2.9 nm aufweisen, ist die Längenskale von Glycerol signifikant kleiner bei 1.1 nm. Ein neues Experiment, welches sensitiv auf Translationsbewegung reagiert, wird vorgestellt. Durch Verwendung eines pi-Impulszuges kann eine separate Evolution unter dem Hamiltonian der dipolaren Kopplung und der chemischen Verschiebungsanisotropie erreicht werden.

Comparison of model potentials for molecular dynamics simulation of crystalline silica

Simulationen von SiO2 mit dem von van Beest, Kramer und vanSanten (BKS) entwickelten Paarpotenzial erzeugen vielezufriedenstellende Ergebnisse, aber auch charakteristischeSchwachstellen. In dieser Arbeit wird das BKS-Potenzial mitzwei kürzlich vorgeschlagenen Potenzialen verglichen, dieeffektiv Mehrteilchen-Wechselwirkungen beinhalten. Der ersteAnsatz erlaubt dazu fluktuierende Ladungen, der zweiteinduzierbare Polarisierungen auf den Sauerstoffatomen. Die untersuchten Schwachstellen des BKS Potenzialsbeinhalten das Verhältnis der zwei Gitterkonstanten a und cim Quarzübergang, das von BKS falsch beschrieben wird.Cristobalit und Tridymit erscheinen instabil mit BKS.Weiterhin zeigt die BKS-Zustandsdichte charakteristischeAbweichungen von der wahren Zustandsdichte. DerÜbergangsdruck für den Stishovit I-II Übergang wird deutlichüberschätzt. Das Fluktuierende-Ladungs-Modell verbesserteinige der genannten Punkte, reproduziert aber viele andereEigenschaften schlechter als BKS. DasFluktierende-Dipol-Modell dagegen behebt alle genanntenArtefakte. Zusätzlich wird der druckinduzierte Phasenübergang imalpha-Quarz untersucht. Alle Potentiale finden die selbeStruktur für Quarz II. Bei anschliessender Dekompressionerzeugt BKS eine weitere Phase, während die beiden anderenPotentiale wieder zum alpha-Quarz zurückkehren. Weiterhinwerden zwei Methoden entwickelt, um die piezoelektrischenKonstanten bei konstantem Druck zu bestimmen. Die Ergebnissegeben Hinweise auf eine möglicherweisenicht-elektrostatische Natur der Polarisierungen imFluktuierende-Dipole-Modell. Mit dieser Interpretation scheint das Fluktuierende-DipolPotential alle verfügbaren experimentellen Daten am bestenvon allen drei untersuchten Ansätzen zu reproduzieren.

Synthesis and characterisation of photoreactive silanes for the self-assembly on functionalised silica surfaces

The aim of this thesis was to investigate novel techniques to create complex hierarchical chemical patterns on silica surfaces with micro to nanometer sized features. These surfaces were used for a site-selective assembly of colloidal particles and oligonucleotides. To do so, functionalised alkoxysilanes (commercial and synthesised ones) were deposited onto planar silica surfaces. The functional groups can form reversible attractive interactions with the complementary surface layers of the opposing objects that need to be assembled. These interactions determine the final location and density of the objects onto the surface. Photolithographically patterned silica surfaces were modified with commercial silanes, in order to create hydrophilic and hydrophobic regions on the surface. Assembly of hydrophobic silica particles onto these surfaces was investigated and finally, pH and charge effects on the colloidal assembly were analysed. In the second part of this thesis the concept of novel, "smart" alkoxysilanes is introduced that allows parallel surface activation and patterning in a one-step irradiation process. These novel species bear a photoreactive head-group in a protected form. Surface layers made from these molecules can be irradiated through a mask to remove the protecting group from selected regions and thus generate lateral chemical patterns of active and inert regions on the substrate. The synthesis of an azide-reactive alkoxysilane was successfully accomplished. Silanisation conditions were carefully optimised as to guarantee a smooth surface layer, without formation of micellar clusters. NMR and DLS experiments corroborated the absence of clusters when using neither water nor NaOH as catalysts during hydrolysis, but only the organic solvent itself. Upon irradiation of the azide layer, the resulting nitrene may undergo a variety of reactions depending on the irradiation conditions. Contact angle measurements demonstrated that the irradiated surfaces were more hydrophilic than the non-irradiated azide layer and therefore the formation of an amine upon irradiation was postulated. Successful photoactivation could be demonstrated using condensation patterns, which showed a change in wettability on the wafer surface upon irradiation. Colloidal deposition with COOH functionalised particles further underlined the formation of more hydrophilic species. Orthogonal photoreactive silanes are described in the third part of this thesis. The advantage of orthogonal photosensitive silanes is the possibility of having a coexistence of chemical functionalities homogeneously distributed in the same layer, by using appropriate protecting groups. For this purpose, a 3',5'-dimethoxybenzoin protected carboxylic acid silane was successfully synthesised and the kinetics of its hydrolysis and condensation in solution were analysed in order to optimise the silanisation conditions. This compound was used together with a nitroveratryl protected amino silane to obtain bicomponent surface layers. The optimum conditions for an orthogonal deprotection of surfaces modified with this two groups were determined. A 2-step deprotection process through a mask generated a complex pattern on the substrate by activating two different chemistries at different sites. This was demonstrated by colloidal adsorption and fluorescence labelling of the resulting substrates. Moreover, two different single stranded oligodeoxynucleotides were immobilised onto the two different activated areas and then hybrid captured with their respective complementary, fluorescent labelled strand. Selective hybridisation could be shown, although non-selective adsorption issues need to be resolved, making this technique attractive for possible DNA microarrays.

Molekulardynamiksimulationen zur Untersuchung des Mischalkali-Effektes in silikatischen Gläsern

In der vorliegenden Arbeit wird mittels Molekulardynamik(MD)-Computersimulationen die Dynamik von verschiedenen Alkalisilikaten in der Schmelze und im Glas untersucht. Es ist bekannt, daß diese Systeme ionenleitend sind, was auf eine hohe Mobilität der Alkaliionen im Vergleich zu den glasbildenden Komponenten Si und O zurückzuführen ist. Im Mittelpunkt des Interesses steht der sog. Mischalkalieffekt (MAE), der in ternären Mischungen aus Siliziumdioxid mit zwei Alkalioxiden auftritt. Gegenüber Mischungen mit nur einer Alkaliionensorte weisen letztere Systeme eine signifikante Verlangsamung der Alkaliionendiffusion auf. Zunächst werden zwei binäre Alkalisilikate simuliert, nämlich Lithiumdisilikat (LS2) und Kaliumdisilikat (KS2). Die Simulationen zeigen, daß der Ursprung der hohen Mobilität der Alkaliionen in der Struktur begründet ist. KS2 und LS2 weisen auf intermediären Längenskalen Ordnung auf, die in partiellen statischen Strukturfaktoren durch Prepeaks reflektiert ist. Die den Prepeaks zugrundeliegende Struktur erklärt sich durch perkolierende Netzwerke aus alkalioxidreichen Kanälen, die als Diffusionskanäle für die mobilen Alkaliionen fungieren. In diesen Kanälen bewegen sich die Ionen mittels Sprüngen (Hopping) zwischen ausgezeichneten Plätzen. In der Simulation beobachtet man für die hohen Temperaturen (4000K>=1500K) eine ähnliche Aktivierungsenergie wie im Experiment. Im Experiment findet allerdings unterhalb von ca.1200K ein Crossover in ein Arrheniusverhalten mit höherer Aktivierungsenergie statt, welches von der Simulation nicht nachvollzogen wird. Das kann mit der in der Simulation nicht im Gleichgewicht befindlichen Si-O-Matrix erklärt werden, bei der Alterungseffekte beobachtet werden. Am stärksten ist der MAE für eine Alkalikomponente, wenn deren Konzentrationsanteil in einem ternären Mischalkalisystem gegen 0 geht. Daher wird ein LS2-System untersucht, in dem ein Li-Ion gegen ein K-Ion getauscht wird. Der Einfluß des K-Ions ist sowohl lokal in den charakteristischen Abständen zu den ersten nächsten Nachbarn (NN) zu sehen, als auch in der ortsaufgelösten Koordinationszahlverteilung bis zu Längenskalen von ca. 8,5 Angstrom. Die Untersuchung der Dynamik des eingesetzten K-Ions zeigt, daß die Sprungwahrscheinlichkeit nicht mit der Lokalisierung, einem Maß für die Bewegung eines Teilchens um seine Ruheposition, korreliert ist, aber daß eine chemische Umgebung mit wenig Li- und vielen O-NN oder vielen Li- und wenig O-NN ein Sprungereignis begünstigt. Zuletzt wird ein ternäres Alkalisilikat (LKS2) untersucht, dessen Struktur alle charakteristischen Längenskalen von LS2 und KS2 aufweist. Es stellt sich also eine komplexe Struktur mit zwei perkolierenden Subnetzwerken für Alkaliionen ein. Die Untersuchung der Dynamik zeigt eine geringe Wahrscheinlichkeit dafür auf, daß Ionen in ein Subnetzwerk andersnamiger Ionen springen. Auch kann gezeigt werden, daß das Modellpotential den MAE reproduzieren kann, daß also die Diffusionskonstanten in LKS2 bei bis zu einer Größenordnung langsamer sind als in KS2 bzw. LS2. Der beobachtete Effekt stellt sich zudem vom funktionalen Verlauf her so dar, wie er beim MAE erwartet wird. Es wurde auch festgestellt, daß trotz der zeitlichen Verzögerung in den dynamischen Größen die Anzahl der Sprünge pro Zeit nicht geringer ist und daß für niedrige Temperaturen (d.h.im Glas) Sprünge auf den Nachbarplatz mit anschließendem Rücksprung auf die vorherige Position deutlich wahrscheinlicher sind als bei hohen Temperaturen (also in der Schmelze). Die vorliegenden Resultate geben Aufschluß über die Details der Mechanismen mikroskopischer Ionenleitung in binären und ternären Alkalisilikaten sowie dem MAE.