Asymptotic distributions of M-estimators in a spatial regression model under some fixed and stochastic spatial sampling designs

In this paper, we consider M-estimators of the regression parameter in a spatial multiple linear regression model. We establish consistency and asymptotic normality of the M-estimators when the data-sites are generated by a class of deterministic as well as a class of stochastic spatial sampling schemes. Under the deterministic sampling schemes, the data-sites are located on a regular grid but may have aninfill component. On the other hand, under the stochastic sampling schemes, locations of the data-sites are given by the realizations of a collection of independent random vectors and thus, are irregularly spaced. It is shown that scaling constants of different orders are needed for asymptotic normality under different spatial sampling schemes considered here. Further, in the stochastic case, the asymptotic covariance matrix is shown to depend on the spatial sampling density associated with the stochastic design. Results are established for M-estimators corresponding to certain non-smooth score functions including Huber’s ψ-function and the sign functions (corresponding to the sample quantiles). Research of Lahiri is partially supported by NSF grant no. DMS-0072571. Research of Mukherjee is partially supported by the Academic Research Grant R-155-000-003-112 from the National University of Singapore.     

Sequential separation by HDEHP of carrier-free101,105,106Rh,103,104,105,106,110,112Ag and104,105,107,109,111Cd produced in alpha-particle activated palladium

Carrier free^101,105,106Rh,^{103,104,105,106,110,112}Ag and^{104,105,107,109,111}Cd radioisotopes were produced simultaneously by -particle irradiation of palladium target material in a variable energy cyclotron. The radioisotopes produced were extracted and separated from the activated target by LLX using HDEHP as liquid cation exchanger. With the help of -ray spectrometry the presence of several radioisotopes in the activated target matrix and their purity at each step of the separation was confirmed.     

Liquid-liquid extraction of α-activation products of iron with HDEHP

The carrier-free radiotracers,^52,56Mn,^55,56,58Co and^56,57Ni were produced simultaneously by accelerated -particle activation of iron. They were subsequently studied through LLX using the liquid cation exchanger, HDEHP, as an extractant. A considerable enrichment of individual carrier free radionuclides of manganese, cobalt and nickel was achieved. Production and verification of purity of the carrier-free radiotracers at different stages of their extraction were carried out by -ray spectroscopic studies.     

Membrane protein microarrays

This paper describes the fabrication of microarrays consisting of G protein-coupled receptors (GPCRs) on surfaces coated with gamma-aminopropylsilane (GAPS). Microspots of model membranes on GAPS-coated surfaces were observed to have several desired properties-high mechanical stability, long range lateral fluidity, and a thickness corresponding to a lipid bilayer in the bulk of the microspot. GPCR arrays were obtained by printing membrane preparations containing GPCRs using a quill-pin printer. To demonstrate specific binding of ligands, arrays presenting neurotensin (NTR1), adrenergic (beta1), and dopamine (D1) receptors were treated with fluorescently labeled neurotensin (BT-NT). Fluorescence images revealed binding only to microspots corresponding to the neurotensin receptor; this specificity was further demonstrated by the inhibition of binding in the presence of excess unlabeled neurotensin. The ability of GPCR arrays to enable selectivity studies between the different subtypes of a receptor was examined by printing arrays consisting of three subtypes of the adrenergic receptor: beta1, beta2, and alpha2A. When treated with fluorescently labeled CGP 12177, a cognate antagonist analogue specific to beta-adrenergic receptors, binding was only observed to microspots of the beta1 and beta2 receptors. Furthermore, binding of labeled CGP 12177 was inhibited when the arrays were incubated with solutions also containing ICI 118551, and in a manner consistent with the higher affinity of ICI 118551 for the beta2 receptor relative to that for the beta1 receptor. The ability to estimate binding affinities of compounds using GPCR arrays was examined using a competitive binding assay with BT-NT and unlabeled neurotensin on NTR1 arrays. The estimated IC(50) value (2 nM) for neurotensin is in agreement with the literature; this agreement suggests that the receptor -G protein complex is preserved in the microspot. This first ever demonstration of direct pin-printing of membrane proteins and ligand-binding assays thereof fills a significant void in protein microchip technology--the lack of practical microarray-based methods for membrane proteins.     

Multiple one-electron oxidation and reduction of trinuclear bis(2,4-pentanedionato)ruthenium complexes with substituted diquinoxalino[2,3-a:2′,3′-c]phenazine ligands

The complexes (μ₃-L¹/L²)[Ru(acac)₂]₃, acac⁻ = 2,4-pentanedionato, L¹ = 2,3,8,9,14,15-hexachlorodiquinoxalino[2,3-a:2′,3′-c]phenazine and L² = 2,3,8,9,14,15- hexamethyldiquinoxalino[2,3-a:2′,3′-c]phenazine, undergo stepwise one-electron oxidation involving a total of three electrons and stepwise one-electron reduction with three (L²) or four electrons (L¹). All reversibly accessible states were characterized by UV–Vis–NIR spectroelectrochemistry. Oxidation leads to mixed-valent intermediates {(μ₃-L)[Ru(acac)₂]₃}⁺ and {(μ₃-L)[Ru(acac)₂]₃}²⁺ of which the Ru^IIIRu^IIRu^II combinations exhibit higher comproportionation constants K_c than the Ru^IIIRu^IIIRu^II states – in contrast to a previous report for the unsubstituted parent systems {(μ₃-L³)[Ru(acac)₂]₃}^+/2+, L³ = diquinoxalino[2,3-a:2′,3′-c]phenazine. No conspicuous inter-valence charge transfer absorptions were observed for the mixed-valent intermediates in the visible to near-infrared regions. The monocations and monoanions were characterized by EPR spectroscopy, revealing rhombic ruthenium(III) type signals for the former. Electron addition produces ruthenium(II) complexes of the reduced forms of the ligands L, a high resolution EPR spectrum with ¹⁴N and ^35,37Cl hyperfine coupling and negligible g anisotropy was found for {(μ₃-L¹)[Ru(acac)₂]₃}⁻. DFT calculations of (μ₃-L¹)[Ru(acac)₂]₃ confirm several ligand-centered low-lying unoccupied MOs for reduction and several metal-based high-lying occupied MOs for electron withdrawal, resulting in low-energy metal-to-ligand charge transfer (MLCT) transitions.     

Anomalies in quantitative measurement of 40K in natural samples

Journal of Radioanalytical and Nuclear Chemistry - Efficiency calibration by standard materials of known activity is usual protocol for γ-ray spectrometry. In general, 40K activity is measured...     

Production and separation of 111In: an important radionuclide in life sciences: a mini review

¹¹¹In is amongst the frequently used radionuclides in diagnostic nuclear medicine. Therefore its production and subsequent separation chemistry have been widely investigated since late 40s. ¹¹¹In is commonly produced in proton or α-particle induced reactions on cadmium or silver targets. However, in recent past, various heavy ion (⁷Li, ¹¹B, ¹²C etc.) activation routes have been proposed for its production. In this mini review, we have tried to portray the production routes of ¹¹¹In and chemical separation methodologies reported so far in the literature in a concise form. A critical analysis presented in this review will be helpful to select suitable nuclear reaction and radiochemical method to produce high purity ¹¹¹In for applications.     

Cross-spectral density matrix of the far field generated by a blackbody source

An expression is derived for the cross-spectral density matrix, valid in the paraxial region of the far field, generated by a planar blackbody source. With the help of it we determine the spectral degrees of polarization and of cross-polarization of the far field.