Changes In Relative Intensities Research Articles

Plasmonic-Ceria Nanoparticles as Fluorescence Intensity and Lifetime Quenching Optical Sensor.

Ceria nanoparticles have been recently used as an optical fluorescent material with visible emission under ultraviolet excitation, due to the formation of trivalent cerium ions with corresponding oxygen vacancies. This paper introduces the enhancement of both fluorescence emission and lifetime through adding gold nanoparticles. The reason is due to possible coupling between the plasmonic resonance of gold nanoparticles and the fluorescence emission of ceria that has been achieved, along with enhanced formation of trivalent cerium ions. Both factors lead to higher fluorescence intensity peaks and shorter fluorescence lifetimes. As an application, gold-ceria nanoparticles have been used as an optical sensing material for lead particles in aqueous media based on fluorescence quenching. Stern-Volmer constant of in-situ gold-ceria nanoparticles is found to be 2.424 M−1, with a relative intensity change of up to 40% at 0.2 g/L.

Conventional or threshold-hunting TMS? A tale of two SICIs

BackgroundIn human primary motor cortex (M1), the paired-pulse transcranial magnetic stimulation (TMS) paradigm of short-interval intracortical inhibition (SICI) can be expressed conventionally as a percent change in the relative amplitude of a conditioned motor evoked potential to non-conditioned; or adaptive threshold-hunting a target motor evoked potential amplitude in the absence or presence of a conditioning stimulus, and noting the relative change in stimulation intensity. The suitability of each approach may depend on the induced current direction, which probe separate M1 interneuronal populations. ObjectiveTo examine the influence of conditioning stimulus intensity, interstimulus interval (ISI) and current direction for adaptive threshold-hunting and conventional SICI using equivalent TMS intensities. MethodsIn 16 participants (21–32 years), SICI was examined using adaptive threshold-hunting and conventional paired-pulse TMS with posterior-anterior and anterior-posterior stimulation, ISIs of 2 and 3 ms, and a range of conditioning intensities. ResultsInhibition with adaptive threshold-hunting was greater for anterior-posterior stimulation with an ISI of 3 ms (23.6 ± 9.0%) compared with 2 ms (7.5 ± 7.8%, P < 0.001) and posterior-anterior stimulation at both ISIs (2 ms 8.6 ± 8.7%, 3 ms 5.9 ± 4.8%; P < 0.001). There was an association between inhibition obtained with conventional and adaptive threshold-hunting for posterior-anterior but not anterior-posterior stimulation (2 ms only, r = 0.68, P = 0.03). ConclusionsMore inhibition was evident with anterior-posterior than posterior-anterior current for both adaptive threshold-hunting and conventional paired-pulse TMS. Assessment of SICI with anterior-posterior stimulation was not directly comparable between the two approaches. However, the amount of inhibition was dependent on conditioning stimulus intensity and ISI for both SICI techniques.

Abstract 5661: A multi modal mass spectrometry imaging strategy to profile the metabolic hallmarks of colorectal cancer

Abstract New methods are required to image the metabolic hallmarks of cancerous tissues and correlate this information with patient tumour pathology, cancer phenotype and treatment outcome. Mass spectrometry imaging (MSI) offers a powerful suite of techniques for imaging metabolites, drugs and proteins in cells and tissues. Here we present a multi-modal MSI strategy and use it to profile PDX, GEMM and biopsy samples. Human and murine colon and small intestine samples were sectioned onto glass slides and stored at -80°C until use. MALDI-MSI (Waters and Bruker) was carried out with pixel sizes between 10 and 50 microns, DESI (Waters) at 20-50 microns and SIMS (IONTOF) at approximately 200 nm per pixel. Data were converted from proprietary format to imzML and analysed in MatLab (2015b, MathWorks) via the SpectralAnalysis software package using non-negative matrix factorisation (NMF) and principal component analysis (PCA). Further reduction and segmentation was achieved using stacked autoencoders and t-distributed stochastic neighbour embedding (t-SNE). To assign the peaks detected to molecular identities, peaks picked from mean spectra were matched to the human metabolome database (HMDB) using custom Matlab scripts. Possible adducts were queried against the database masses, and filtered based on comparison of expected and observed mass, and correlation between the images of the monoisotopic mass and 13C isotope image. Preliminary data show the successful preparation and analysis of multiple GEMM and human tissue samples across several sites by MALDI-MSI, DESI-MSI and SIMS imaging. Converting data to imzML and combining into large, single multi-file images enabled multivariate analysis (MVA) to be performed simultaneously within the same comparison. Of these MVA methods, mass spectrometry imaging (MSI) in combination with t-SNE has been shown to differentiate tumour subpopulations linked with patient outcomes. Current t-SNE methods suffer from three main limitations as compared to other MVA methods; poor computational scaling to large datasets, inability to add new data into the embedding, and inability to return to spectral contributions. By combining t-SNE performed on a subset of data and learning the embedding via deep learning, almost limitless size datasets can be analysed by t-SNE, new data can be incorporated into the embedding, and the spectral contributions towards the three dimensional space can be determined. Database matching on the data from these GEMM samples to the HMDB reveals over 1000 possible molecular assignments, primarily structural lipids, within 10 ppm mass accuracy and with isotope image correlations above 0.6. From these methods, comparisons can be made between the unique molecules detected in different tissues, as well as the relative changes in intensity of those detected between different tissues. Citation Format: Josephine Bunch, Rory T. Steven, Adam J. Taylor, Spencer A. Thomas, Alan M. Race, Alex Dexter, Gregory Hamm, Nicole Strittmatter, Rasmus Havelund, Renata F. Soares, Andrew D. Campbell, Owen J. Sansom, Richard J. Goodwin, Zoltan Takats. A multi modal mass spectrometry imaging strategy to profile the metabolic hallmarks of colorectal cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 5661.

Lanthanide-doped Y3Ga5O12 garnets for nanoheating and nanothermometry in the first biological window

Absorption and luminescence spectra in the first biological window of Nd3+ single-doped and Er3+-Yb3+ co-doped Y3Ga5O12 nano-garnets have been studied to evaluate their potential use as simultaneous optical nanoheaters and nanothermometers in biomedicine. Nd3+-doped nano-garnets uses the 808 nm laser radiation, resonant with the largest absorption peak of the 4I9/2 → 4F5/2 transition, for both heating the nanoparticle and populating the 4F3/2 emitting level. Changes in the relative intensities of different emission peaks between Stark levels of the 4F3/2 (R1,2)→4I9/2 (Z1-5) transition can be directly related to the temperature of the nano-garnet. On the other hand, the Yb3+/Er3+combination takes advantage of the large absorption cross-section of the Yb3+ ions at around 920 nm to heat the sample, while triggering the Yb3+-to-Er3+ upconversion energy transfer processes that populate the thermally coupled 2H11/2,4S3/2 emitting levels of Er3+ ions, whose relative intensity changes with temperature can be calibrated. Accurate spatially- and temperature-controlled optically stimulated heating of these nano-garnets from room temperature up to 75 °C within the first biological windows is proved.

Upconversion Luminescence Enhancement and Relative Intensity Changing Mechanism of β‐NaYF4:20%Yb3+,2%Er3+ Microcrystals in a Two‐Step Ion Exchange Process

AbstractEfficient enhanced upconversion luminescence (UCL) in β‐NaYF4:20%Yb3+,2%Er3+ microcrystals has been synthesized via two‐step ion exchange reaction. The influence of NaF concentration in ion exchange step on the crystal structure and the UCL property are analyzed. High concentration of NaF in the ion exchange process can enhance the UCL efficiently. Time resolved spectra are utilized to investigate the UCL enhancement and relative intensity changing mechanism. Temperature dependent UCL spectra are utilized to understanding the influence of defects on relative intensity changing. It is found that ion exchange with high concentration of NaF will decrease the body defects, which contribute to the UCL enhancement and decrease of red to green emission intensity ratio.

Changes in Blood pH and Ammonia Following Repeat Sprint Performance

The relationship between relative intensity and changes in blood pH and ammonia are not well characterized. PURPOSE: The primary aim of the study was to determine how changes in relative exercise intensity following repeat sprint performance affect changes in blood pH and blood ammonia concentrations. METHODS: Healthy college- age males (n = 12) completed completed one 30 second Wingate cycle sprint test as a familiarization trial. A minimum of 48 hours after the familiarization trial, participants returned to the lab. Resting venous and capillary blood samples were obtained to determine blood ammonia, pH, and lactate levels. Participants then completed 3 Wingate sprint tests, separated by 5 minutes each. Finger capillary blood was immediately obtained after each test to determine lactate and pH values. After the final test, an additional venous blood sample was obtained to determine blood ammonia values. RESULTS: Data are shown as 1st vs. 2nd vs. 3rd tests, respectively. There was a significant effect for time for peak power (750.08 ± 39.55 vs. 675.42 ± 30.01 vs. 615.60 ± 37.72 Watts); F = 4.66, p = 0.05, mean power (632.67 ± 30.71 vs. 561.25 ± 22.16 vs. 524.40 ± 26.46 Watts); F = 5.04, p = 0.04, pH (7.72 ± 0.01 vs. 7.63 ± 0.02 vs. 7.62 ± 0.02); F = 70.18, p < 0.01, and lactate (12.36 ± 1.14 vs. 14.10 ± 1.13 vs. 16.95 ± 1.22 mg/dL); F= 42.02, p < 0.01. Blood ammonia values did increase from pre- to post-exercise (0.33 ± 0.09 vs. 1.07 ± 0.22 mg/dl); t = 3.62, p < 0.01, but there was no correlation between post-exercise ammonia values and change in peak or mean power. There was a weak, but significant correlation between change in peak power and change in pH (R2 = 0.34, p = 0.05) and change in mean power and change in pH (R2 = 0.44, p = 0.02). CONCLUSIONS: Greater reductions in peak power and mean power correlated with change in blood pH, but not post-exercise ammonia values.

Increased Delay Between Gadolinium Chelate Administration and T1-Weighted Magnetic Resonance Imaging Acquisition Increases Contrast-Enhancing Tumor Volumes and T1 Intensities in Brain Tumor Patients

The aim of this study was to evaluate the impact of delayed T1-weighted (T1-w) MRI acquisition after gadolinium chelate administration on brain tumor volumes and T1-w intensities. Fifty-five patients with histologically confirmed, contrast-enhancing intra-axial brain tumors were analyzed in this prospective test-retest study. Patients underwent 2 consecutive 3 T MRI scans (separated by a 1-minute break) during routine follow-up with contrast-enhanced T1 (ceT1-w), T2, and FLAIR acquisition. Macrocyclic gadolinium chelate-based contrast agent was only administered before the first ceT1-w acquisition; median latency to ceT1-w acquisition was 6.72 minutes (IQR, 6.53-6.92) in the first and 16.27 minutes (IQR, 15.49-17.26) in the second scan. Changes in tumor volumes and relative ceT1-w intensities between the 2 acquisitions were quantitatively assessed following semiautomated tumor segmentation (separately for contrast-enhancement [CE], necrosis [NEC], and nonenhancing [NE] tumor). Semiautomatically segmented CE tumor volumes were significantly larger in the second acquisition (median +32% [1.2 cm]; IQR, 16%-62%; P < 0.01), which corresponded to a 10% increase in CE tumor diameter (+0.3 cm). Contrarily, NEC and NE tumor volumes were significantly smaller (median -24% [IQR, -36% to -54%], P < 0.01 for NEC and -2% [IQR, -1% to -3%], P = 0.02 for NE tumor). Bland-Altman plots confirmed a proportional bias toward higher CE and lower NEC volumes for the second ceT1-w acquisition. Relative ceT1-w intensities for both early- (regions already enhancing in the first scan) and late-enhancing (newly enhancing regions in the second scan) tumor were significantly increased in the second acquisition (by 5.8% and 27.3% [P < 0.01, respectively]). Linear-mixed effects modeling confirmed that the increase in CE volumes and CE intensities is a function of the interval between contrast agent injection and ceT1-w acquisition (P < 0.01 each). Our study indicates that the maximum extent of CE tumor volumes and intensities may increase beyond the time frame of 4 to 8 minutes after contrast agent injection and potentially affects the diagnosis of progressive or recurrent disease because late-enhancing recurrent disease might not be unequivocally detected on standard follow-up MRI.

Invivo MRI detection of atherosclerosis in ApoE-deficient mice by using tenascin-C-targeted USPIO.

Atherosclerosis is the main cause of cardiovascular and cerebrovascular diseases. Non-invasive molecular imaging to detect and characterize the plaques is essential for reducing life-threatening cardiovascular events. To investigate the possibility of the anti-tenascin-C-USPIO specific probe as a molecular marker of atherosclerotic plaques detected by 7.0-T magnetic resonance imaging (MRI). Twenty ApoE-/- mice fed with a high fat diet were used for detecting the aorta arch atherosclerotic plaques by 7.0-T MRI at 16 and 24 weeks. Ten mice in the targeted group were injected with anti-tenascin-C-USPIO and another ten in the control group were injected with pure USPIO (n = 5 each time point in each group). Histopathologic examination was used to evaluate the plaques and immunohistochemistry analysis was used to compare tenascin-C expression. The relative signal intensity (rSI) changes of the targeted group decreased more than those of the control group (16 weeks: -15.65 ± 0.78% vs. -3.43 ± 2.57%; 24 weeks: -26.38 ± 1.54% vs. -11.12 ± 1.60%, respectively; P < 0.05). Histopathological analyses demonstrated visible atherosclerotic plaques formation and development over time from 16 weeks to 24 weeks. Tenascin-C expression of the plaques at 24 weeks was higher than that at 16 weeks (0.22 ± 0.04 vs. 0.13 ± 0.02, P < 0.05). The MR images correlated well with the progression of atherosclerotic plaques. Tenascin-C expression increased with the progression of atherosclerosis. Anti-tenascin-C-USPIO could provide a useful molecular imaging tool for detecting and monitoring atherosclerotic plaques by MRI.

Hydrophobicity of silica thin films: The deconvolution and interpretation by Fourier-transform infrared spectroscopy

This work investigated the synthesis of dimethoxydimethylsilane:tetraethoxysilane (DMDMS:TEOS) silica thin films as well as the effect of DMDMS:TEOS molar ratios and calcination temperature on hydrophobic properties of silica thin films and its correlation with the FTIR spectra behaviour. The silica thin films were synthesized by sol-gel method using combination of DMDMS and TEOS as silica precursors, ethanol as solvent and ammonia as catalyst, with DMDMS and TEOS molar ratio of 10:90, 25:75, 50:50, 75:25 and 90:10. The results showed that DMDMS:TEOS molar ratio had significant impact on the hydrophobic properties of silica thin films coated on a glass surface. Furthermore, the correlation between water contact angle (WCA) and DMDMS:TEOS molar ratio was found to be in a parabolic shape. Concurrently, the maximum apex of the parabola obtained was observed on the DMDMS:TEOS molar ratio of 50:50 for all calcination temperature. It was clearly observed that the silica xerogel exhibiting notable change in relative peak intensities showed FTIR peak splitting of υasymmetric Si-O-Si. To uncover what happened at the FTIR peak, the deconvolution was conducted in Gaussian approach. It was established that the changes in the Gaussian peak component were related to DMDMS:TEOS molar ratios and the calcination temperature that allowed us to tailor the DMDMS:TEOS silica polymer structure model based on the peak intensity ratios. With the increase of DMDMS:TEOS molar ratio, the ratio of (cyclic Si-O-Si)/(linear Si-O-Si) decreased, whilst the ratio of (C-H)/(linear Si-O-Si) increased. Both ratios intersected at DMDMS:TEOS molar ratio of 50:50 with contribution factor ratio of 1:16 and 1:50 for silica xerogel calcined at 300°C and 500°C respectively. The importance of this research is the DMDMS:TEOS molar ratio plays an important role in determining the hydrophobic properties of thin films.

Stabilization of α-BiFeO3 structure by Sr2+ and its effect on multiferroic properties

We report a study on the effect of the substitution of Bi3+ by Sr2+ on the stabilization of R3c structure of Bi1−xSrxFeO3 (0 ≤ x ≤ 0.3, Δx = 0.05), and its effect in the magnetic and dielectric behavior. Stoichiometric mixtures of Bi2O3, Fe2O3 and SrO were mixed and milled for 5 h using a ball to powder weight ratio of 10:1 by high-energy ball milling. The obtained powder were pressed at 900 MPa to obtain cylindrical pellets and sintered at 800 °C for 2 h. X-ray diffraction and Rietveld refinement were used to evaluate the effect of Sr2+ on the crystal structure. In addition, vibrating sample magnetometry (VSM) and dielectric tests were used for describing the multiferroic behavior. The results show that Sr-doped BiFeO3 particles present rhombohedral structure (R3c) characteristic of α-BiFeO3 when the doping is below 0.10 mol of Sr. Additionally, a gradual decrease in the amount of secondary phases with the increase of the amount of strontium is observed. For doping concentration higher than 0.15 mol of Sr, a phase transition to an orthorhombic symmetry (β-BiFeO3, Pbnm) is detected. Besides, changes in relative intensities of reflection peaks planes (110) and (104) are associated with the phase transformations and with the magnetic and dielectric behavior. The α-BiFeO3 phase show antiferromagnetic behavior and high values of dielectric permittivity, whereas the β-BiFeO3 phase show a ferromagnetic behavior and low dielectric permittivity.

L-Band Temporal Coherence Assessment and Modeling Using Amplitude and Snow Depth over Interior Alaska

Interferometric synthetic aperture radar (InSAR) provides the capability to detect surface deformation. Numerous processing approaches have been developed to improve InSAR results and overcome its limitations. Regardless of the processing methodology, however, temporal decorrelation is a major obstacle for all InSAR applications, especially over vegetated areas and dynamic environments, such as Interior Alaska. Temporal coherence is usually modeled as a univariate exponential function of temporal baseline. It has been, however, documented that temporal variations in surface backscattering due to the change in surface parameters, i.e., dielectric constant, roughness, and the geometry of scatterers, can result in gradual, seasonal, or sudden decorrelations and loss of InSAR coherence. The coherence models introduced so far have largely neglected the effect of the temporal change in backscattering on InSAR coherence. Here, we introduce a new temporal decorrelation model that considers changes in surface backscattering by utilizing the relative change in SAR intensity between two images as a proxy for the change in surface scattering parameters. The model also takes into account the decorrelation due to the change in snow depth between two images. Using the L-band Advanced Land Observation Satellite (ALOS-2) Phased Array type L-band Synthetic Aperture Radar (PALSAR-2) data, the model has been assessed over forested and shrub landscapes in Delta Junction, Interior Alaska. The model decreases the RMS error of temporal coherence estimation from 0.18 to 0.09 on average. The improvements made by the model have been statistically proved to be significant at the 99% confidence level. Additionally, the model shows that the coherence of forested areas are more prone to changes in backscattering than shrub landscape. The model is based on L-band data and may not be expanded to C-band or X-band InSAR observations.

Exploiting Lightweight Statistical Learning for Event-Based Vision Processing.

This paper presents a lightweight statistical learning framework potentially suitable for low-cost event-based vision systems, where visual information is captured by a dynamic vision sensor (DVS) and represented as an asynchronous stream of pixel addresses (events) indicating a relative intensity change on those locations. A simple random ferns classifier based on randomly selected patch-based binary features is employed to categorize pixel event flows. Our experimental results demonstrate that compared to existing event-based processing algorithms, such as spiking convolutional neural networks (SCNNs) and the state-of-the-art bag-of-events (BoE)-based statistical algorithms, our framework excels in high processing speed (2× faster than the BoE statistical methods and >100× faster than previous SCNNs in training speed) with extremely simple online learning process, and achieves state-of-the-art classification accuracy on four popular address-event representation data sets: MNIST-DVS, Poker-DVS, Posture-DVS, and CIFAR10-DVS. Hardware estimation shows that our algorithm will be preferable for low-cost embedded system implementations.

Octupolar Metastructures for a Highly Sensitive, Rapid, and Reproducible Phage-Based Detection of Bacterial Pathogens by Surface-Enhanced Raman Scattering.

The development of fast and ultrasensitive methods to detect bacterial pathogens at low concentrations is of high relevance for human and animal health care and diagnostics. In this context, surface-enhanced Raman scattering (SERS) offers the promise of a simplified, rapid, and high-sensitive detection of biomolecular interactions with several advantages over previous assay methodologies. In this work, we have conceived reproducible SERS nanosensors based on tailored multilayer octupolar nanostructures which can combine high enhancement factor and remarkable molecular selectivity. We show that coating novel multilayer octupolar metastructures with proper self-assembled monolayer (SAM) and immobilized phages can provide label-free analysis of pathogenic bacteria via SERS leading to a giant increase in SERS enhancement. The strong relative intensity changes of about 2100% at the maximum scattered SERS wavelength, induced by the Brucella bacterium captured, demonstrate the performance advantages of the bacteriophage sensing scheme. We performed measurements at the single-cell level thus allowing fast identification in less than an hour without any demanding sample preparation process. Our results based on designing well-controlled octupolar coupling platforms open up new opportunities toward the use of bacteriophages as recognition elements for the creation of SERS-based multifunctional biochips for rapid culture and label-free detection of bacteria.

On/off-switchable LSPR nano-immunoassay for troponin-T

Regeneration of immunosensors is a longstanding challenge. We have developed a re-usable troponin-T (TnT) immunoassay based on localised surface plasmon resonance (LSPR) at gold nanorods (GNR). Thermosensitive poly(N-isopropylacrylamide) (PNIPAAM) was functionalised with anti-TnT to control the affinity interaction with TnT. The LSPR was extremely sensitive to the dielectric constant of the surrounding medium as modulated by antigen binding after 20 min incubation at 37 °C. Computational modelling incorporating molecular docking, molecular dynamics and free energy calculations was used to elucidate the interactions between the various subsystems namely, IgG-antibody (c.f., anti-TnT), PNIPAAM and/or TnT. This study demonstrates a remarkable temperature dependent immuno-interaction due to changes in the PNIPAAM secondary structures, i.e., globular and coil, at above or below the lower critical solution temperature (LCST). A series of concentrations of TnT were measured by correlating the λLSPR shift with relative changes in extinction intensity at the distinct plasmonic maximum (i.e., 832 nm). The magnitude of the red shift in λLSPR was nearly linear with increasing concentration of TnT, over the range 7.6 × 10−15 to 9.1 × 10−4 g/mL. The LSPR based nano-immunoassay could be simply regenerated by switching the polymer conformation and creating a gradient of microenvironments between the two states with a modest change in temperature.

A Facile Strategy for All-Optical Controlling Platform by Using Plasmonic Perfect Absorbers

Dual-band light absorption with the maximal absorptivity up to 99.7% and the minimal spectral bandwidth down to 3 nm is obtained in the plasmonic absorbers consisting of triple-layer plasmonic crystal-nonlinear medium cavity-metal substrate structure, where the intercalated dielectric material is chosen to be a Kerr medium cavity. Efficient all-optical controlling with high spectral intensity change ratios and detecting signal-to-noise is achieved for the system after a slight increase of pumping intensity. These impressive results mainly result from the strong plasmonic resonant field confinement in the middle nonlinear Kerr medium cavity and the near-perfect relative intensity change response by the ultra-sharp anti-reflection spectrum. This work can lay a foundation for advanced all-optical devices by exploiting light perfect absorption behavior and resonant optical field enhancement.

Structural and optical properties of CdZnTe quantum dots capped with a bifunctional Molecule

CdTe and ternary CdZnTe quantum dots capped with 3-mercaptopropionic acid in aqueous medium with different percentages of Zn have been prepared using K2TeO3 as a source of tellurium. The structure and morphology of these quantum dots were characterized by XRD, TEM, EDX, FTIR and Raman spectroscopy. The results revealed that the ternary CdZnTe quantum dots (QDs) have nearly spherical shape with hexagonal structure. Doping with Zn leads to a pronounced change in relative intensity of the X-ray diffraction peaks. The optical properties were investigated by using UV–Vis absorption and photoluminescence measurements. The UV–Vis showed a gradual increase in the optical band gap of ternary alloy compound of CdZnTe QDs plus a continuous shift of photoluminescence emission with increasing of Zn content. The color distribution analysis showed a gradual change in color with Zn percentage for red, green and blue components. The nanoparticle sizes were determined from optical absorption, XRD, Raman and HRTEM measurements indicating that the prepared binary CdTe and ternary CdZnTe capped with MPA are in a strong confinement regime as an indicative of quantum dots structure.

Effects of hydrogen bonding with H2O on the resonance Raman spectra of uracil and thymine

The effects of explicit hydrogen bonding with H2O on the resonance Raman spectra of uracil and thymine are examined computationally. The three bonding sites in uracil and thymine that form the lowest energy uracil-H2O and thymine-H2O complexes, as well as a more limited number of low-lying ones containing two waters, are considered. The ground state structures are optimized at the PBE0/aug-cc-pVTZ level of theory in H2O (C-PCM), and the gradients of the bright excited state (S1) are computed at the TD-CAM-B3LYP/aug-cc-pVTZ level of theory in H2O (C-PCM). As the resonance Raman spectrum is governed by the ground state normal modes and the excited state Cartesian gradient (within the Herzberg-Teller formalism), the differences between spectra of uracil- and thymine-(H2O)n, n=1 or 2, are compared in terms of these two factors. Explicit hydrogen bonding to water is found to cause changes in both relative peak positions and intensities for the resonance Raman spectra of uracil and thymine when compared to the isolated molecules. The effect of hydrogen bonding is primarily on the ground state normal mode character, especially for the high frequency modes (>1600cm−1), rather than on the excited state Cartesian gradients. Different hydrogen bonding sites are found to have different contributions to the resulting resonance Raman spectra, and inclusion of explicit hydrogen bonding on the carbonyl bond opposite to the ring nitrogen is necessary to obtain good agreement between the simulated and experimental resonance Raman spectra for uracil and thymine.

Self-preservation and structural transition of gas hydrates during dissociation below the ice point: an in situ study using Raman spectroscopy.

The hydrate structure type and dissociation behavior for pure methane and methane-ethane hydrates at temperatures below the ice point and atmospheric pressure were investigated using in situ Raman spectroscopic analysis. The self-preservation effect of sI methane hydrate is significant at lower temperatures (268.15 to 270.15 K), as determined by the stable C-H region Raman peaks and AL/AS value (Ratio of total peak area corresponding to occupancies of guest molecules in large cavities to small cavities) being around 3.0. However, it was reduced at higher temperatures (271.15 K and 272.15 K), as shown from the dramatic change in Raman spectra and fluctuations in AL/AS values. The self-preservation effect for methane-ethane double hydrate is observed at temperatures lower than 271.15 K. The structure transition from sI to sII occurred during the methane-ethane hydrate decomposition process, which was clearly identified by the shift in peak positions and the change in relative peak intensities at temperatures from 269.15 K to 271.15 K. Further investigation shows that the selectivity for self-preservation of methane over ethane leads to the structure transition; this kind of selectivity increases with decreasing temperature. This work provides new insight into the kinetic behavior of hydrate dissociation below the ice point.

Assessment of Carotid Plaque Inflammation in Diabetic and Nondiabetic Patients—An Exploratory Ultrasmall Superparamagnetic Iron Oxide-Enhanced Magnetic Resonance Imaging Study

Ultrasmall superparamagnetic iron oxide (USPIO)-enhanced magnetic resonance (MR) imaging enables the identification of inflammation within the atheroma, predominantly by USPIO uptake by macrophages present in atherosclerotic tissue. Diabetic patients, however, may have dysfunctional macrophage activity, which may affect utilization of USPIO in identifying plaque inflammation in this patient cohort. Fifteen diabetic and fifteen nondiabetic patients underwent USPIO-enhanced carotid MR imaging using 1.5T MR system. Pre- and post-USPIO carotid MR images were manually coregistered. The percentage decrease in the signal intensity after USPIO administration was calculated as a relative measure of the USPIO uptake. Diabetic and nondiabetic patients had comparable demographics and comorbidities. The mean global, maximum quadrant, and maximum slice changes showing change in relative signal intensity as a result of USPIO administration were comparable for the two patient cohorts (P > .05). USPIO can identify inflammatory burden with carotid atheroma in both diabetic and nondiabetic patients.

Nitroaromatic detection and infrared communication from wild-type plants using plantnanobionics.

Plant nanobionics aims to embed non-native functions to plants by interfacing them with specifically designed nanoparticles. Here, we demonstrate that living spinach plants (Spinacia oleracea) can be engineered to serve as self-powered pre-concentrators and autosamplers of analytes in ambient groundwater and as infrared communication platforms that can send information to a smartphone. The plants employ a pair of near-infrared fluorescent nanosensors-single-walled carbon nanotubes (SWCNTs) conjugated to the peptide Bombolitin II to recognize nitroaromatics via infrared fluorescent emission, and polyvinyl-alcohol functionalized SWCNTs that act as an invariant reference signal-embedded within the plant leaf mesophyll. As contaminant nitroaromatics are transported up the roots and stem into leaf tissues, they accumulate in the mesophyll, resulting in relative changes in emission intensity. The real-time monitoring of embedded SWCNT sensors also allows residence times in the roots, stems and leaves to be estimated, calculated to be 8.3 min (combined residence times of root and stem) and 1.9 min mm-1 leaf, respectively. These results demonstrate the ability of living, wild-type plants to function as chemical monitors of groundwater and communication devices to external electronics at standoff distances.