Synthesis of Brightly PEGylated Luminescent Magnetic Upconversion Nanophosphors for Deep Tissue and Dual MRI Imaging

A method is developed to fabricate monodispersed biocompatible Yb/Er or Yb/Tm doped β‐NaGdF₄ upconversion phosphors using polyelectrolytes to prevent irreversible particle aggregation during conversion of the precursor, Gd₂O(CO₃)₂?H₂O:Yb/Er or Yb/Tm, to β‐NaGdF₄:Yb/Er or Yb/Tm. The polyelectrolyte on the outer surface of nanophosphors also provided an amine tag for PEGylation. This method is also employed to fabricate PEGylated magnetic upconversion phosphors with Fe₃O₄ as the core and β‐NaGdF₄ as a shell. These magnetic upconversion nanophosphors have relatively high saturation magnetization (7.0 emu g^?1) and magnetic susceptibility (1.7 × 10^?2 emu g^?1 Oe^?1), providing them with large magnetophoretic mobilities. The magnetic properties for separation and controlled release in flow, their optical properties for cell labeling, deep tissue imaging, and their T₁‐ and T₂‐weighted magnetic resonance imaging (MRI) relaxivities are studied. The magnetic upconversion phosphors display both strong magnetophoresis, dual MRI imaging (r₁ = 2.9 mM^?1 s^?1, r₂ = 204 mM^?1 s^?1), and bright luminescence under 1 cm chicken breast tissue.     

Vascular targeted single-walled carbon nanotubes for near-infrared light therapy of cancer

A new approach for targeting carbon nanotubes to the tumor vasculature was tested using human endothelial cells and MCF-7 breast cancer cells in vitro. Single-walled carbon nanotubes were functionalized with the F3 peptide using a polyethylene glycol linker to target nucleolin, a protein found on the surface of endothelial cells in the vasculature of solid tumors. Confocal microscopy and Raman analysis confirmed that the conjugate was internalized by actively dividing endothelial cells. Dividing endothelial cells were used to mimic these cells in the tumor vasculature. Incubation with the conjugate for 8?h or more caused significant cell death in both actively dividing endothelial cells and MCF-7 breast cancer cells, an effect that is hypothesized to be due to the massive uptake of the conjugate. This targeted cell killing was further enhanced when coupled with near-infrared laser treatment. For confluent (non-dividing) endothelial cells, no cytotoxic effect was seen for incubation alone or incubation coupled with laser treatment. These results are promising and warrant further studies using this conjugate for cancer treatment in vivo.     

CdTe quantum dots and polymer nanocomposites for x-ray scintillation and imaging

Investigations are reported on the x-ray scintillation and imaging application of CdTe quantum dots (QDs) and their polymer nanocomposites. Aqueous CdTe QDs with emissions ranging between 510 and 680 nm were prepared and incorporated into polyvinyl alcohol or polymethyl methacrylate polymer matrices. The x-ray luminescent properties were evaluated and a resolution of 5 lines∕mm was obtained from the nanocomposite films. Additionally, the fast decay time, nonafterglow, and superior spectral match to conventional charge coupled devices, show that CdTe QD nanocomposites have high promise for x-ray imaging applications.     

Spatial coherence of backscatter for the nonlinearly produced second harmonic for specific transmit apodizations

To be successful, correlation-based, phase-aberration correction requires a high correlation among backscattered signals. For harmonic imaging, the spatial coherence of backscatter for the second harmonic component is different than the spatial coherence of backscatter for the fundamental component. The purpose of this work was to determine the effect of changing the transmit apodization on the spatial coherence of backscatter for the nonlinearly generated second harmonic. Our approach was to determine the effective apodizations for the fundamental and second harmonic using both experimental measurements and simulations. Two-dimensional measurements of the transverse cross sections of the finite-amplitude ultrasonic fields generated by rectangular and circular apertures were acquired with a hydrophone. Three different one-dimensional transmit apodization functions were investigated: uniform, Riesz, and trapezoidal. An effective apodization was obtained for each transmit apodization by backpropagating the values measured from within the transmit focal zone using a linear angular spectrum approach. Predictions of the spatial coherence of backscatter were obtained using the pulse-echo Van Cittert-Zernike theorem. In all cases the effective apodization at 2f was narrower than the transmit apodization. We demonstrate that certain transmit apodizations result in a greater spatial coherence of backscatter at the second harmonic than at the fundamental.     

Influences of cognitive support on episodic remembering: Tracing the process of loss from normal aging to Alzheimer's disease.

Normal older adults, incident Alzheimer's disease (AD) patients, and prevalent AD patients were examined across a 3-year interval in episodic memory tasks that varied in terms of study time, organizability, and retrieval cues. There were marked overall preclinical deficits among the incident AD patients, although these patients were as effective as the normal older adults in utilizing more study time, organizability, and retrieval cues to improve memory at baseline. When these patients were diagnosed with AD at follow-up, they showed negligible gains from increased study time and organizability when memory was assessed with free recall, although they profited from the provision of retrieval cues. This pattern of results was also seen in the prevalent AD patients at both times of measurement. These results indicate that a general impairment of episodic memory may precede reductions in cognitive reserve capacity in the early development of AD. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Limb reduction defects in the A/J mouse strain associated with maternal blood loss

We previously described a high incidence of digit/limb anomalies in the offspring of A/J mice subjected to surgery on day 12.5 postconception (p.c.), but not in the offspring of untreated control mice. To investigate the cause of these defects, we compared the offspring of mice in experimental groups involving adrenalectomy, sham adrenalectomy, blood sampling, and anesthesia with the offspring of control mice. All treatments significantly reduced fetal weight and increased resorptions as compared with the controls. The highest incidence of digit anomalies occurred in the offspring of dams from which blood samples had been drawn on days 12.5, 14.5, and 15.5 p.c. The incidence of isolated cleft palate was also increased in the offspring of mice that had been subjected to blood sampling. We conclude that digit anomalies in the offspring of A/J mice result from fetal vascular disruptive phenomena subsequent to maternal blood loss induced hypovolemia and hypoperfusion to the uterus and placenta as has been suggested for uterine vascular clamping, misoprostol, chorionic villus sampling, and cocaine teratogenesis. The etiology for cleft lip in these mice may involve mechanisms unrelated to uterine/placental hypoperfusion.     

Fundamental studies of copper anode passivation during electrorefining: Part III. The effect of thiourea

Thiourea has been extensively used as a grain refiner in industrial copper electrorefining processes. The influence of thiourea on deposit structure and morphology has received considerable study; however, the effect of thiourea and its degradation chemistry on the passivation behavior of commercial copper anodes is still not fully understood. This study was conducted to provide useful information regarding the electrochemical response of a commercial copper anode in the absence and presence of thiourea. Chronopotentiometry measurements were performed in synthetic electrolytes containing different thiourea concentrations and in industrial electrolytes obtained directly from a commercial tank house. Passivation time (t _p ) and periodic passivation phenomena were found to be closely associated with thiourea concentration and degradation.     

GigaOp DSP on FPGA

DSP algorithms such as automated target recognition and SONAR beamforming are a good match for FPGA technology due to their regular structure, available parallelism, pipeline-ability, and modest data word sizes. FPGA implementations of these applications outperformed their DSP and microprocessor counterparts by factors ranging from 10× on up with an equivalent sustained computational rate of more than 2 GOps/second per FPGA. This paper introduces a set of criteria which have a great impact on how well an application maps to FPGA technology. It then describes two applications in detail and the process of mapping each to FPGA technology. Comparisons with software implementations are made and followed by conclusions and future challenges.     

Changes in culture, changes in personality: The influence of individualism in a longitudinal study of women.

The influence of increasing individualism in U.S. culture on personality development was investigated with an index recently developed by H. Gough (1991) that traces changes in individualism from 1950 to 1985. Seventy-seven women followed from 1958 to 1989 (assessed at ages 21, 27, 43, and 52) showed increases on the index of individualism that paralleled changes in large cross-sectional samples over the same period. Increases on the individualism index were associated with increases in self-focus (narcissism) and decreases in norm adherence. Increases over the long middle period (1963–1964 to 1981), when the largest change occurred, were predicted by college-age measures of ego strength and adjustment and showed a positive relation to psychosocial and physical health at age 43. Increases in individualism may have helped women respond to radical changes in women's roles during the late 1960s and 1970s. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Trust, trustworthiness, and trust propensity: A meta-analytic test of their unique relationships with risk taking and job performance.

The trust literature distinguishes trustworthiness (the ability, benevolence, and integrity of a trustee) and trust propensity (a dispositional willingness to rely on others) from trust (the intention to accept vulnerability to a trustee based on positive expectations of his or her actions). Although this distinction has clarified some confusion in the literature, it remains unclear (a) which trust antecedents have the strongest relationships with trust and (b) whether trust fully mediates the effects of trustworthiness and trust propensity on behavioral outcomes. Our meta-analysis of 132 independent samples summarized the relationships between the trust variables and both risk taking and job performance (task performance, citizenship behavior, counterproductive behavior). Meta-analytic structural equation modeling supported a partial mediation model wherein trustworthiness and trust propensity explained incremental variance in the behavioral outcomes when trust was controlled. Further analyses revealed that the trustworthiness dimensions also predicted affective commitment, which had unique relationships with the outcomes when controlling for trust. These results generalized across different types of trust measures (i.e., positive expectations measures, willingness-to-be-vulnerable measures, and direct measures) and different trust referents (i.e., leaders, coworkers). (PsycINFO Database Record (c) 2011 APA, all rights reserved)