2,704 research outputs found
Price Formation under Small Numbers Competition: Evidence from Land Auctions in Singapore
This paper examines the price formation process under small numbers competition using data from Singapore land auctions. The theory predicts that bid prices are less than the zero-profit asset value in these first-price sealed-bid auctions. The model also shows that expected sales price increases with the number of bidders both because each bidder has an incentive to offer a higher price and because of a greater likelihood that a high-value bidder is present. The empirical estimates are consistent with auction theory and show that the standard land attributes are reflected in auction prices as expected. Working Paper No. 04-0
Rotational Cooling of Polar Molecules by Stark-tuned Cavity Resonance
A general scheme for rotational cooling of diatomic heteronuclear molecules
is proposed. It uses a superconducting microwave cavity to enhance the
spontaneous decay via Purcell effect. Rotational cooling can be induced by
sequentially tuning each rotational transition to cavity resonance, starting
from the highest transition level to the lowest using an electric field.
Electrostatic multipoles can be used to provide large confinement volume with
essentially homogeneous background electric field.Comment: 10 pages, 6 figure
Vortex Matter Transition in BiSrCaCuO under Tilted Fields
Vortex phase diagram under tilted fields from the axis in
BiSrCaCuO is studied by local magnetization
hysteresis measurements using Hall probes. When the field is applied at large
angles from the axis, an anomaly () other than the well-known
peak effect () are found at fields below . The angular dependence of
the field is nonmonotonic and clearly different from that of
and depends on the oxygen content of the crystal. The results suggest existence
of a vortex matter transition under tilted fields. Possible mechanisms of the
transition are discussed.Comment: Revtex, 4 pages, some corrections are adde
Antioxidant Activities of Methanol Extract and Solvent Fractions of Marine Macroalga, Avrainvillea erecta (Berkeley) A. Gepp and E.S. Gepp (Dichotomosiphonaceae)
Purpose: To determine the antioxidant activity of methanol extract (ME) and solvent fractions of Avrainvillea erecta as well as their total phenolic and flavonoid contents.Methods: The antioxidant activities of ME as well as its chloroform, butanol, and aqueous fractions (CF, BF and WF, respectively) of A. erecta were evaluated via 2,2-diphenyl-1-picrylhydrazyl (DPPH), nitric oxide (NO) and hydrogen peroxide (H2O2) scavenging assays as well as ferric reducing antioxidant power (FRAP) assay. Total phenolic and flavonoid contents were determined spectrophotometrically.Results: CF and BF possessed equally high DPPH scavenging activity with half-maximal effective concentration (EC50) of 535 and 532 mg/ml, respectively. CF had stronger NO scavenging activity (EC50 743 μg/mL) than ME and BF, although weaker compared with quercetin (EC50 279 μg/ml). CF also produced the highest FRAP value (451 μmol Fe2+/g) among all samples examined. Notably, H2O2 scavenging activity was only found in CF (EC50 387 μg/ml), which was as strong (p > 0.05) as that of gallic acid (EC50 456 μg/mL). BF had the highest total phenolic content while CF had the highest total flavonoid content.Conclusion: CF of A. erecta, which has the highest flavonoid content of all the extracts evaluated, is a potential source of natural antioxidants, especially hydrogen peroxide scavengers.Keywords: Antioxidant, Avrainvillea erecta, Flavonoid, Macroalga, Phenoli
Characteristics of predictor sets found using differential prioritization
<p>Abstract</p> <p>Background</p> <p>Feature selection plays an undeniably important role in classification problems involving high dimensional datasets such as microarray datasets. For filter-based feature selection, two well-known criteria used in forming predictor sets are relevance and redundancy. However, there is a third criterion which is at least as important as the other two in affecting the efficacy of the resulting predictor sets. This criterion is the degree of differential prioritization (DDP), which varies the emphases on relevance and redundancy depending on the value of the DDP. Previous empirical works on publicly available microarray datasets have confirmed the effectiveness of the DDP in molecular classification. We now propose to establish the fundamental strengths and merits of the DDP-based feature selection technique. This is to be done through a simulation study which involves vigorous analyses of the characteristics of predictor sets found using different values of the DDP from toy datasets designed to mimic real-life microarray datasets.</p> <p>Results</p> <p>A simulation study employing analytical measures such as the distance between classes before and after transformation using principal component analysis is implemented on toy datasets. From these analyses, the necessity of adjusting the differential prioritization based on the dataset of interest is established. This conclusion is supported by comparisons against both simplistic rank-based selection and state-of-the-art equal-priorities scoring methods, which demonstrates the superiority of the DDP-based feature selection technique. Reapplying similar analyses to real-life multiclass microarray datasets provides further confirmation of our findings and of the significance of the DDP for practical applications.</p> <p>Conclusion</p> <p>The findings have been achieved based on analytical evaluations, not empirical evaluation involving classifiers, thus providing further basis for the usefulness of the DDP and validating the need for unequal priorities on relevance and redundancy during feature selection for microarray datasets, especially highly multiclass datasets.</p
Pressure Dependence of the Irreversibility Line in BiSrCaCuO:Role of Anisotropy in Flux-Line Formation
One of the important problems of high-temperature superconductivity is to
understand and ultimately to control fluxoid motion. We present the results of
a new technique for measuring the pressure dependence of the transition to
superconductivity in a diamond anvil cell. By measuring the third harmonic of
the {\it ac} susceptibility, we determine the onset of irreversible flux
motion. This enables us to study the effects of pressure on flux motion. The
application of pressure changes interplanar spacing, and hence the interplanar
coupling, without significantly disturbing the intraplanar superconductivity.
Thus we are able to separate the effects of coupling from other properties that
might affect the flux motion. Our results directly show the relationship
between lattice spacing, effective- mass anisotropy, and the irreversibility
line in BiSrCaCuO. Our results also demonstrate
that an application of 2.5 GPa pressure causes a dramatic increase in
interplanar coupling.Comment: 4 pages, 4 figure
Investigating The Vortex Melting Phenomenon In BSCCO Crystals Using Magneto-Optical Imaging Technique
Using a novel differential magneto-optical imaging technique we investigate
the phenomenon of vortex lattice melting in crystals of Bi_2Sr_2CaCu_2O_8
(BSCCO). The images of melting reveal complex patterns in the formation and
evolution of the vortex solid-liquid interface with varying field (H) or
temperature (T). We believe that the complex melting patterns are due to a
random distribution of material disorder or inhomogeneities across the sample,
which create fluctuations in the local melting temperature or field value. To
study the fluctuations in the local melting temperature / field, we have
constructed maps of the melting landscape T_m(H,r), viz., the melting
temperature (T_m) at a given location (r) in the sample at a given field (H). A
study of these melting landscapes reveals an unexpected feature: the melting
landscape is not fixed, but changes rather dramatically with varying field and
temperature along the melting line. It is concluded that the changes in both
the scale and shape of the landscape result from the competing contributions of
different types of quenched disorder which have opposite effects on the local
melting transition.Comment: Paper presented at the International Symposium on Advances in
Superconductivity & Magnetism: Materials, Mechanisms & Devices September
25-28, 2001, Mangalore, India. Symposium proceedings will be published in a
special issue of Pramana - Journal of Physic
Glycerol residue - a rich source of glycerol and medium chain fatty acids
Glycerol residue, a by-product of glycerol refining from a palm kernel oil methyl ester plant, was found to be a good source of glycerol and medium chain fatty acids. From analyses of twelve samples, it was found to contain, on average, 20.2 % glycerol and 6.6 % fatty acids. The fatty acids comprised mainly C8:0 (30.3 %), C10:0 (9.4 %) and C12:0 (40.8 %)
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