399 research outputs found
Further developments in the conflation of CFD and building simulation
To provide practitioners with the means to tackle problems related to poor indoor environments, building simulation and computational fluid dynamics can usefully be integrated within a single computational framework. This paper describes the outcomes from a research project sponsored by the European Commission, which furthered the CFD modelling aspects of the ESP-r system. The paper summarises the form of the CFD model and describes the method used to integrate the thermal and flow domains
Vibrational properties of alpha- and sigma-phase Fe-Cr alloy
Experimental investigation as well as theoretical calculations, of the
Fe-partial phonon density-of-states (DOS) for nominally Fe_52.5Cr_47.5 alloy
having (a) alpha- and (b) sigma-phase structure were carried out. The former at
sector 3-ID of the Advanced Photon Source, using the method of nuclear resonant
inelastic X-ray scattering, and the latter with the direct method [K. Parlinski
et al., Phys. Rev. Lett. {78, 4063 (1997)]. The characteristic features of
phonon DOS, which differentiate one phase from the other, were revealed and
successfully reproduced by the theory. Various data pertinent to the dynamics
such as Lamb-Mossbauer factor, f, kinetic energy per atom, E_k, and the mean
force constant, D, were directly derived from the experiment and the
theoretical calculations, while vibrational specific heat at constant volume,
C_V, and vibrational entropy, S were calculated using the Fe-partial DOS. Using
the values of f and C_V, we determined values for Debye temperatures, T_D. An
excellent agreement for some quantities derived from experiment and
first-principles theory, like C_V and quite good one for others like D and S
was obtained.Comment: 4 pages, 3 figure
Experimental and numerical study of local mean age of air
This paper presents the results from the experimental and numerical study of a room with mixing ventilation, focused on the local mean age of air (LMA). The measurements were performed using the tracer gas concentration decay method. The numerical predictions were obtained from the computational fluid dynamics (CFD) module of the latest version of the ESP-r software
Kinetic Determination of Arsenic(III) as Inhibitor of Victoria Blue 4R Oxidation in Strong Acid Solution
A new selective, sensitive and simple kinetic method was developed for the determination of As3+ traces in solution on the basis of their inhibiting effect on Victoria blue 4R (VB) oxidation by KBrO3 in the presence of HCl. The reaction was followed spectrophotometrically at 596.3 nm. The detection limit was 50.00 ng cm–3. The relative error vas 4.2 % to 1.5 % for As3+ in the concentration range from 80.00 to 350.00 ng cm–3. Also, appropriate kinetic equations were formulated and the influence of different ions upon the reaction rate was studied. The developed procedure was successfully applied to the determination of As3+ in various model and real samples
Spectrofluorimetric and HPLC Determination of Morin in Human Serum
Morin is a flavonol antioxidant. In ethanol-water mixtures (70 wt% of ethanol) it reacts with Al3+ to give Al(Morin)(2) in the pH range 3-6. The conditional stability constant of this complex at 298 K was found to be log beta(2) = 16.96 +/- 0.02 at pH 4.40. The complex shows strong fluorescence emission at 500 nm upon excitation at 410 nm. The fluorescence intensity is pH dependent with maximum emission at pH 4.40. Since the complexation reaction enhances the fluorescence of morin, this property was used for the determination of morin in human serum. A linear dependence of the intensity of fluorescence of the complex on the concentration of morin was obtained in morin concentration range from 1.5-30.5 ng mL(-1), relative standard error of measurements was 1.4%. The LOD was 0.02 ng mL(-1) while LOQ was 1.0 ng mL(-1). Serum concentration of morin was also determined using HPLC as a reference method. A C-18 Hypersil Gold AQ column was used with acetonitrile-0.1% v/v phosphoric acid (30:70% v/v) as the mobile phase at 1.0 mL min(-1) flow rate and UV detection at 250 nm. Acceptable relative standard errors (less than 5%) between determinations obtained by the two methods indicate that the fluorescence method is reliable
Ab initio and nuclear inelastic scattering studies of FeSi/GaAs heterostructures
The structure and dynamical properties of the FeSi/GaAs(001) interface
are investigated by density functional theory and nuclear inelastic scattering
measurements. The stability of four different atomic configurations of the
FeSi/GaAs multilayers is analyzed by calculating the formation energies and
phonon dispersion curves. The differences in charge density, magnetization, and
electronic density of states between the configurations are examined. Our
calculations unveil that magnetic moments of the Fe atoms tend to align in a
plane parallel to the interface, along the [110] direction of the FeSi
crystallographic unit cell. In some configurations, the spin polarization of
interface layers is larger than that of bulk FeSi. The effect of the
interface on element-specific and layer-resolved phonon density of states is
discussed. The Fe-partial phonon density of states measured for the FeSi
layer thickness of three monolayers is compared with theoretical results
obtained for each interface atomic configuration. The best agreement is found
for one of the configurations with a mixed Fe-Si interface layer, which
reproduces the anomalous enhancement of the phonon density of states below 10
meVComment: 14 pages, 9 figures, 4 table
Enzimska kinetička metoda za određivanje propranolol-hidrohlorida u farmaceutskim preparatima zasnovana na njegovom inhibitorskom delovanju na holinesterazu
Propranolol, a widely used beta-blocker, inhibits the hydrolysis reaction of enzyme cholinesterase. Measurements of the difference in rate of hydrolysis rate between uninhibited and inhibited reactions allow the development of a kinetic method for its determination. Both systems, enzyme-substrate-chromogen and enzyme-substrate-chromogen-inhibitor, were characterized through biochemical kinetic parameters (K-M, 0.326-0.330 mmol/L; V-max, 40.0-43.0 mu mol/Lmin). The inhibition type was recognized as competitive and the inhibition constant, Ki, was determined to be 22.60 mu mol/L. The detection and quantification limits were calculated as 0.004 and 0.0136 mu mol/L, respectively. Accuracy and precision of proposed methods were tested. The proposed method showed good sensitivity, selectivity, simplicity and rapidity, thus it is convenient for clinical applications.Za propranolol, često propisivani neselektivni beta blokator, utvrđeno je da inhibira reakciju enzimske hidrolize butiriltioholin-jodida, koja je katalizovana serumskom holinesterazom. Merenjem razlike u brzini osnovne i inhibitorske reakcije hidrolize u prisustvu propranolola kao inhibitora, moguće je razviti kinetičku metodu za određivanje propranolola. Oba sistema, enzim-supstrat-hromogen kao i enzim-supstrat-hromogen-inhibitor, okarakterisani su biohemijskim kinetičkim parametrima (KM, 0,326-0,330 mmol/L; Vmax, 40-42,99 μmol/L min), inhibicija je definisana kao kompetitivna i određena je konstanta inhibicije 22,60 μmol/L. Da bi se u potpunosti iskoristile sve mogućnosti predložene metode u pogledu osetljivosti, tačnosti, preciznosti i selektivnosti, optimizovani su reakcioni uslovi. Konstruisana je kalibraciona prava, izračunata odgovarajuća jednačina i određeni granica detekcije i kvantifikacije i to 0,004 i 0,0136 μmol/L, redom. Tačnost i preciznost predložene metode su ispitane za tri koncentracije propranolola u oblasti kalibracione prave (0,082-21,120 μmol/L) u pet ponavljanja. Takođe, ispitan je uticaj većeg broja supstanci koje se mogu naći u uzorku na brzinu reakcije. Optimizovana metoda je primenjena za određivanje propranolola u farmaceutskim preparatima. Tačnost predložene metode je ispitana primenom metode standardnog dodatka. Predložena metoda ima dobru osetljivost, selektivnost, jednostavna je i brza, i nadasve lako dostupna, i na taj način primenljiva u velikom broju laboratorija
Chloroplast pigments in post-fire-grown cryptophytes on Vidlič Mountain (Southeastern Serbia)
In this study the content of chloroplast pigments (chlorophyll a, b, a+b, and carotenoids) in the leaves of Geranium macrorrhizum L., Doronicum columnae Ten., Aegopodium podagraria L. and Tussilago farfara L. from a beech forest that had undergone fire on Vidlič Mountain was determined. The same species of plants from a place that had not been exposed to fire were taken as controls. Chloroplast pigments were determined from acetone extracts of these plants spectrophotometrically. In the first year after the fire the content of chlorophyll a, b and a+b in Geranium macrorrhizum L. and Doronicum columnae Ten. was greater than in the plants not exposed to fire. The results were the opposite for Aegopodium podagraria L. and Tussilago farfara L. These differences can be attributed to the different physiology of the plants and consequently their different adaptation patterns. The carotenoid content was higher in the plant species at the fire site than in the area not exposed to fire
Origin of a Simultaneous Suppression of Thermal Conductivity and Increase of Electrical Conductivity and Seebeck Coefficient in Disordered Cubic Cu2ZnSnS4
The parameters governing the thermoelectric efficiency of a material, Seebeck coefficient, electrical, and thermal conductivities, are correlated and their reciprocal interdependence typically prevents a simultaneous optimization. Here, we present the case of disordered cubic kesterite CuZnSnS, a phase stabilized by structural disorder at low temperature. With respect to the ordered form, the introduction of disorder improves the three thermoelectric parameters at the same time. The origin of this peculiar behavior lies in the localization of some Sn lone pair electrons, leading to “rattling” Sn ions. On one hand, these rattlers remarkably suppress thermal conductivity, dissipating lattice energy via optical phonons located below 1.5 THz; on the other, they form electron-deficient Sn—S bonds leading to a p-type dopinglike effect and highly localized acceptor levels, simultaneously enhancing electrical conductivity and the Seebeck coefficient. This phenomenon leads to a 3 times reduced thermal conductivity and doubling of both electrical conductivity and the Seebeck coefficient, resulting in a more than 20 times increase in figure of merit, although still moderate in absolute terms
Attosecond streaking of photoelectron emission from disordered solids
Attosecond streaking of photoelectrons emitted by extreme ultraviolet light
has begun to reveal how electrons behave during their transport within simple
crystalline solids. Many sample types within nanoplasmonics, thin-film physics,
and semiconductor physics, however, do not have a simple single crystal
structure. The electron dynamics which underpin the optical response of
plasmonic nanostructures and wide-bandgap semiconductors happen on an
attosecond timescale. Measuring these dynamics using attosecond streaking will
enable such systems to be specially tailored for applications in areas such as
ultrafast opto-electronics. We show that streaking can be extended to this very
general type of sample by presenting streaking measurements on an amorphous
film of the wide-bandgap semiconductor tungsten trioxide, and on
polycrystalline gold, a material that forms the basis of many nanoplasmonic
devices. Our measurements reveal the near-field temporal structure at the
sample surface, and photoelectron wavepacket temporal broadening consistent
with a spread of electron transport times to the surface
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