Infrared emission spectroscopy and ab initio calculations on VCl

The emission spectrum of VCl has been investigated at high resolution in the 3000-19 400 cm⁻¹ region using a Fourier transform spectrometer. The bands were excited in a high temperature carbon tube furnace by the reaction of vanadium metal vapor and a trace of BCl₃ as well as in a microwave discharge lamp by the reaction of VOCl₃ vapor with active nitrogen. The spectra were recorded using the Fourier transform spectrometer associated with the McMath-Pierce telescope of the National Solar Observatory at Kitt Peak. The analysis of the system of VCl (previously labeled as ) has been extended by analyzing the rotational structure of some additional bands. A rotational analysis of the , , and subbands of the 0-2, 0-1, 0-0, and 1-0 bands, and the subband of the 0-1 and 0-0 bands has been obtained and molecular constants have been extracted. The subband was not identified in any of the assigned bands. The spectroscopic properties of the low-lying electronic states of VCl have been predicted by CASSCF/CMRCI ab initio calculations and the experimental assignments are supported by the ab initio results.     

Ferromagnetism in fcc twinned 2.4 nm size Pd nanoparticles

The onset of ferromagnetism has been experimentally observed in small Pd particles of average diameter 2.4 nm. High-resolution studies reveal that a high percentage of the fcc particle exhibits single and multiple twinning boundaries. The spontaneous magnetization close to 0.02 emu/g seems to indicate that only a small fraction of atoms holds a permanent magnetic moment and contributes to ferromagnetism. The possible origin of ferromagnetism is briefly discussed according to different models recently reported.     

Correction algorithm for finite sample statistics

Assume in a sample of size M one finds M_i representatives of species i with . The normalized frequency , based on the finite sample, may deviate considerably from the true probabilities p_i. We propose a method to infer rank-ordered true probabilities r_i from measured frequencies M_i. We show that the rank-ordered probabilities provide important informations on the system, e.g., the true number of species, the Shannon- and the Renyi-entropies.Received: 14 July 2003, Published online: 5 February 2004PACS: 02.50.-r Probability theory, stochastic processes, and statistics - 02.60.-x Numerical approximation and analysis - 07.05.Kf Data analysis: algorithms and implementation; data management     

Complementary detection of prostate-specific antigen using In2O3 nanowires and carbon nanotubes

We report complementary detection of prostate-specific antigen (PSA) using n-type In2O3 nanowires and p-type carbon nanotubes. Our innovation involves developing an approach to covalently attach antibodies to In2O3 NW surfaces via the onsite surface synthesis of phosphonic acid-succinylimide ester. Electronic measurements under dry conditions revealed complementary response for In2O3 NW and SWNT devices after the binding of PSA. Real-time detection in solution has also been demonstrated for PSA down to 5 ng/mL, a benchmark concentration significant for clinical diagnosis of prostate cancer, which is the most frequently diagnosed cancer.     

Surface rheology of two-dimensional percolating networks: Langmuir films of polymer pancakes

We report surface rheological measurements on Langmuir films of submicron-sized polymer coils (pancakes). The dynamics of the sol phase is found to be governed by free volume as in the simplest percolation problem. The observed rheology of the percolated phase (gel-like) is compatible with predictions for compressed arrangements of highly deformed soft particles interacting through their contact interfaces.     

Colorimetric signaling of large aromatic hydrocarbons via the enhancement of aggregation processes

[graph: see text] In this paper, the use of aggregation processes in squaraine derivatives as signaling protocols in the development of colorimetric probes for certain neutral guest (aromatic hydrocarbons) has been studied.     

Phase transition in Bi<Subscript>8</Subscript>Fe<Subscript>6</Subscript>Ti<Subscript>3</Subscript>O<Subscript>27</Subscript> multiferroic ceramics

The polycrystalline Bi₈Fe₆Ti₃O₂₇ compound was prepared by a high-temperature solid-state reaction technique. Preliminary structural analysis by X-ray diffraction (XRD) confirms the formation of a single-phase compound in an orthorhombic crystal system at room temperature. The elemental content of the compound was analyzed by EDAX microanalysis. Microstructural analysis by scanning electron microscopy (SEM) shows that the compound has well defined grains, which are distributed uniformly throughout the surface of the pellet sample. Detailed studies of temperature-dependent dielectric response at various frequencies show dielectric anomalies at 380, 389 and 403°C for 10 kHz, 100 kHz, and 1 MHz respectively. The hysteresis loop observed by applying an electric field of 12 kV/cm on the poled sample with smaller remanent polarization supports the existence of ferroelectricity in this material. The value of d₃₃ of the compound was found to be 19 pC/N.      

On the supersingular reduction of elliptic curves

Let a∈Q and denote byE _a the curvey ² = (x ² + l)(x + a). We prove thatE _a(F_p) is cyclic for infinitely many primesp. This fact was known previously only under the assumption of the generalized Riemann hypothesis. Research partially supported by NSERC grant A9418.