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1.
Environ Sci Technol ; 2019 Oct 15.
Artigo em Inglês | MEDLINE | ID: mdl-31565932

RESUMO

The ocean is thought to be the terminal sink for poly- and perfluoroalkyl substances (PFAS) that have been produced and released in large quantities for more than 60 years. Regulatory actions have curbed production of legacy compounds such as perfluorooctane sulfonate (PFOS) and perfluorooctanoic acid (PFOA), but impacts of regulations on PFAS releases to the marine environment are poorly understood. Here, we report new data for 21 targeted PFAS in seawater and plankton from the coast, shelf, and slope of the Northwestern Atlantic Ocean. We find strong inverse correlations between salinity and concentrations of most PFAS, indicating that ongoing continental discharges are the major source to the marine environment. For legacy PFAS such as PFOS and PFOA, a comparison of inland and offshore measurements from the same year (2014) suggests that there are ongoing releases to the marine environment from sources such as submarine groundwater discharges. Vertical transport of most PFAS associated with settling particles from the surface (10 m) to deeper waters is small compared to advective transport except for perfluorodecanoic acid (PFDA; 35% of vertical flux) and precursor compounds to PFOS (up to 86%). We find higher than expected bioaccumulation factors (BAFs = Cplankton/Cwater) for perfluorinated carboxylic acids (PFCAs) with five and six carbons (log BAF = 2.9-3.4) and linear PFOS (log BAF = 2.6-4.3) in marine plankton compared to PFCAs with 7-11 carbons. We postulate that this reflects additional contributions from precursor compounds. Known precursor compounds detected here have among the highest BAFs (log BAF > 3.0) for all PFAS in this study, suggesting that additional research on the bioaccumulation potential of unknown organofluorine compounds is urgently needed.

2.
Dalton Trans ; 2019 Oct 28.
Artigo em Inglês | MEDLINE | ID: mdl-31657403

RESUMO

Recently, metal-ion-doped zeolitic imidazolate frameworks have gained considerable attention for their structure tailorability and potential catalytic applications. Herein, Cu ion-doped ZIF-8 nanocrystals were successfully prepared by the mechanical grinding of Cu(NO3)2, ZnO and 2-methylimidazole (HMeIM) using ethanol as an additive. In contrast to the general view that only Cu(ii) is present in Cu-doped ZIF-8, we found the coexistence of Cu(ii) and Cu(i) in this material, which was supported by XPS and X-ray induced Auger electron spectroscopy (XAES) characterizations. Moreover, ethanol might have acted as a reducer to induce the reduction of Cu(ii) during synthesis. Due to the mixed valency of Cu ions, the Cu ion-doped ZIF-8 nanocrystals showed excellent catalytic performance in the dehydrogenative coupling of silanes with alcohols.

3.
Phys Med Biol ; 64(20): 205004, 2019 Oct 10.
Artigo em Inglês | MEDLINE | ID: mdl-31530747

RESUMO

The probability of inter-crystal scattering (ICS) events for 511 keV gamma rays in all current scintillation crystals is high and the ICS events degrade the spatial resolution of PET scanners. In this work, Monte Carlo simulations were performed to study the effects of ICS events on the sensitivity and spatial resolution of PET detectors. LaBr3, LYSO, and PWO that represent scintillation crystals of low, medium and high density, respectively, were used. For a point source placed in the middle of two scintillation detectors of 50 × 50 × 20 mm3 and a lower energy threshold (LET) of 350 keV, the probabilities that at least one gamma ray undergoes ICS are 94%, 84% and 76% for LaBr3, LYSO, and PWO, respectively. The ICS events still provide useful spatial information. The full width at half maximum (FWHM), the full width at tenth maximum (FWTM) and the mean absolute error (MAE) of the curve of the mispositioning of a point source caused by ICS events are 0.45, 3.0 and 0.9 mm if the most popular PET scintillator LYSO is used. The MAE is smaller than the spatial resolution of most current PET scanners. The effect of ICS increases as the detector LET increases, scintillator density decreases, and crystal size decreases. The intrinsic spatial resolutions of a pair of LYSO detectors were calculated using curves of the coincidence counts between one column of the crystals in the two detectors and the sum of the coincidence counts between two opposite crystals of the columns in the two detectors that are in line with the point source changing with the source positions. The latter method removes almost all of ICS events. The FWHM (FWTM) intrinsic spatial resolutions obtained by the two methods are 0.40 (2.0) mm and 0.33 (0.8) mm if the crystal size is 0.5 mm, and are 0.8 (3.0) and 0.68 (1.5) mm if the crystal size is 1.0 mm. ICS events have much bigger contributions to the FWTM rather than the FWHM of the intrinsic spatial resolution of PET detectors. The spatial resolution of a PET scanner can still be improved by decreasing the crystal size to as small as 0.5 mm.

4.
Artigo em Inglês | MEDLINE | ID: mdl-31538687

RESUMO

Excellent nonlinear optical materials simultaneously meet the requirements of large SHG response, phase-matching capability, wide transparency windows, considerable energy band-gap, good thermal stability and structure stability. Herein, two new promising nonlinear optical (NLO) crystals LiMII (IO3 )3 (MII =Zn and Cd) are rationally designed by the aliovalent substitution strategy from the commercialized α-LiIO3 with the perfect parallel alignment of IO3 groups. Compared with parent α-LiIO3 and related AI 2 MIV (IO3 )6 , the title compounds exhibit more stable covalent 3D structure, and overcome the racemic twinning problem of AI 2 MIV (IO3 )6 . More importantly, both compounds inherit NLO-favorable structure merits of α-LiIO3 and show larger SHG response (≈14× and ≈12×KDP), shorter absorption edge (294 and 297 nm) with wider energy band-gap (4.21 and 4.18 eV), good thermal stability (460 and 430 °C), phase-matching behaviors, wider optical transparency window and good structure stability, achieving an excellent balance of NLO properties.

5.
Br J Clin Pharmacol ; 2019 Aug 08.
Artigo em Inglês | MEDLINE | ID: mdl-31396983

RESUMO

AIMS: Type 2 diabetes mellitus (T2DM) is commonly complicated by renal impairment. Polyethylene glycol loxenatide (PEX168) is a novel long-acting glucagon-like peptide-1 receptor agonist for T2DM. PEX168 pharmacokinetics (PK) was studied to identify requirements for dose-modification in T2DM complicated by renal impairment. METHODS: This was a single-center, open-labeled, parallel-group, single-dose, phase I clinical trial of patients with mild and moderate renal impairment, and with or without T2DM. Age-, sex-, and body mass index (BMI)-matched subjects with normal renal function, and with or without T2DM were recruited as controls. Subjects received a single abdominal subcutaneous injection of PEX168 200 µg. Pharmacokinetic samples were taken at 0, 24, 48, 72, 96, 120, 144, 216, 312, 480, 648, and 720 h. RESULTS: Twenty-three patients were included in the pharmacokinetics analysis. Vz/F and CL/F were lower in the moderate impairment group than in the other groups. The mean t1/2 (163 h) in the moderate impairment group was prolonged compared to the mild impairment (117 h) and normal (121 h) groups. AUC0-inf increased by 13% and 100.7% in patients with mild and moderate renal impairment. Most adverse events were mild gastrointestinal disorders, with only one serious adverse event observed. CONCLUSION: A single dose of 200 µg of PEX168 was in general well tolerated in patients with renal impairment. The in vivo clearance rate of PEX168 in patients with moderate renal impairment is slower than in patients with mild renal impairment and normal renal function and dose adjustment might be required (ClinicalTrials.org #NCT02467790).

6.
Dalton Trans ; 48(35): 13423-13429, 2019 Sep 21.
Artigo em Inglês | MEDLINE | ID: mdl-31433416

RESUMO

Silver doped TiO2 (Ag-TiO2) materials show high activity and good stability in photocatalysis, but the mechanism could not be illustrated clearly due to their imprecise and inhomogeneous characteristics. Ag-doped titanium-oxo clusters (Ag-TOCs) with an exact crystal structure, which are rarely reported, are beneficial for further understanding structure-property relationships. Herein, six new Ag-TOCs with a butterfly-like Ti8Ag2 core have been synthesized through facile solvothermal reactions, in which two Ag ions are successfully linked to the surface of the Ti8 core. Of interest, the Ti6 unit of the Ti8Ag2 core is similar to that found in the anatase structure and may be a promising model for Ag-TiO2 materials. The band gaps of these Ag-TOCs show different values mainly affected by different ligands. DFT calculations revealed that the lowest energy bands of Ag-TOCs are attributed to the Ag-to-TiO core charge transfer bands. Additionally, all Ag-TOCs exhibit good photoelectric response and high photodegradation activity towards organic dyes.

7.
J Am Chem Soc ; 141(32): 12663-12672, 2019 Aug 14.
Artigo em Inglês | MEDLINE | ID: mdl-31328516

RESUMO

Smart materials are highly desirable over the recent decade due to the growing demand of complicated nature. Stable stimuli-responsive smart materials exhibit widespread potential for applications in smart windows, sensors, separators, chemical valves, and release platforms but are rare. Despite being good candidates, viologen-based multifunctional smart materials are still a challenging task for chemists. To obtain such materials, the judicious strategy is to introduce polynuclear metal-carboxylate clusters as electron donors into a stable framework to increase chromic sensitivity. Toward this endeavor, we have synthesized a novel viologen-based polymer with a unique Anderson-like metal-carboxylate cluster, [Zn7(bpybc)3(o-BDC)6]·2NO3·6H2O (bpybc = 1,1'-bis(4-carboxyphenyl)-4,4'-bipyridinium, o-BDC = o-benzenedicarboylic acid) (1), which is a particular 7-fold interpenetrated framework with a 3D pcu network in which bpybc ligand as the linker and Zn7O30C12 as the second building unit (Zn7 SBU) were used as 6-connected nodes. More importantly, it shows excellent chromic behavior in response to multiple external stimuli especially soft X-ray and UV dual light, temperature, electricity, and organic amines, which stand out in the viologen-based polymers. Interestingly, the coloration process of 1 from "core" to "edge" is observed upon heating at the appropriate temperature, which has not yet been found in other reported thermochromic materials. Of particular interest for 1 is the couple of quaternary stimuli-sensitive abilities because it simultaneously meets the following conditions: (i) the capability of withstanding high light, higher temperature, extreme pH, and other harsh conditions; and (ii) the high sensitivity to external stimuli keeping away from photodegradation, thermal relaxation, side reactions, and so on. To be noted, 1 has high thermal stability and chemical stability, which are excellent advantages as smart materials. To further develop possible practical utilization, 1 has been doped into the polymer matrixes to construct a hybrid film, which not only keeps the response to external stimuli but also significantly improves the repeatability of the photochromic process, indicating that a new smart device with multi-stimuli-responsive functions will emerge successively in the future.

8.
IEEE Trans Cybern ; 2019 Jul 02.
Artigo em Inglês | MEDLINE | ID: mdl-31283517

RESUMO

This paper is concerned with position-based synchronization of networked harmonic oscillators. Note that synchronization cannot be achieved via current-position-based protocols. The objective of this paper is to investigate the positive effects of network-induced delays on the synchronization of networked harmonic oscillators. That is, if taking network-induced delays into account, the motion of harmonic oscillators can be really synchronized via a proper position-based control protocol. In doing so, the harmonic oscillators are connected via a shared digital communication network. Different from some existing results, system measurements from oscillator nodes are sampled in an asynchronous way; and network-induced delays are assumed to be time varying and bounded, and they do not need to be synchronous with those from the other communication channels. At each oscillator node, a buffer is embedded into the controller to store the newest sampled-data packets transmitted from its neighboring nodes through communication channels. Then, based on the store of the buffer, the controller computes its control signal with its own period. As a result, the overall synchronization error system is modeled as a linear system with multiple interval time-varying delays. By employing the discretized Lyapunov-Krasovskii functional method, a sufficient condition on synchronization of networked harmonic oscillators is derived, which can ensure that the synchronization error system is asymptotically stable for network-induced delays falling into a certain closed interval whose lower bound is a positive real number. This condition is thus used to design suitable control protocols in terms of linear matrix inequalities with several tuning parameters. Finally, a multirobot platform is given to demonstrate the effectiveness of the proposed method.

9.
IEEE Trans Cybern ; 2019 Jul 11.
Artigo em Inglês | MEDLINE | ID: mdl-31295143

RESUMO

This paper focuses on the network-based modeling and proportional-integral (PI) control for a continuous-time direct-drive-wheel system in a wireless network environment. The developed system can simplify configuration, reduce bus cables, and realize vehicle height adjustment. A novel network-based model is first established by constructing a PI control system and taking network-induced delays and stochastic packet dropouts into account. By using two different artificial delays to characterize the update of proportional and integral control signals, the network-based PI control system is modeled as a stochastic impulsive system with two input delays and reset equations at updating instants. Then, through involving the reset states and the relationship among two delayed states and the current state in the discontinuous Lyapunov-Krasovskii functional and actively introducing the upper bounds of nonzero network-induced delays, some exponential mean-square stability and H∞ performance conditions with less conservatism are derived in terms of tractable linear matrix inequalities. An algorithm is presented to determine the minimum H∞ performance and the corresponding PI control parameters by combining a particle swarm optimization technique with the performance condition. These results can be extended to a network-based PI control of general continuous-time linear systems. A ZigBee-based network simulation platform is finally built and some simulation results are provided to validate the proposed methods.

10.
Environ Int ; 132: 104808, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31182229

RESUMO

Since 2001, twenty-eight halogenated groups of persistent organic pollutants (POPs) have been banned or restricted by the Stockholm Convention. Identifying new POPs among the hundreds of thousands of anthropogenic chemicals is a major challenge that is increasingly being met by state-of-the-art mass spectrometry (MS). The first step to identification of a contaminant molecule (M) is the determination of the type and number of its constituent elements, viz. its elemental composition, from mass-to-charge (m/z) measurements and ratios of isotopic peaks (M + 1, M + 2 etc.). Not every combination of elements is possible. Boundaries exist in compositional space that divides feasible and improbable compositions as well as different chemical classes. This study explores the compositional space boundaries of persistent and bioaccumulative organics. A set of ~305,134 compounds (PubChem) was used to visualize the compositional space occupied by F, Cl, and Br compounds, as defined by m/z and isotope ratios. Persistent bioaccumulative organics, identified by in silico screening of 22,049 commercial chemicals, reside in more constrained regions characterized by a higher degree of halogenation. In contrast, boundaries surrounding non-halogenated chemicals could not be defined. Finally, a script tool (R code) was developed to select potential POPs from high resolution MS data. When applied to household dust (SRM 2585), this approach resulted in the discovery of previously unknown chlorofluoro flame retardants.

11.
Environ Health Perspect ; 127(6): 67006, 2019 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-31170009

RESUMO

BACKGROUND: Between 2013 and 2015, concentrations of poly- and perfluoroalkyl substances (PFAS) in public drinking water supplies serving at least six million individuals exceeded the level set forth in the health advisory established by the U.S. Environmental Protection Agency. Other than data reported for contaminated sites, no systematic or prospective data exist on the relative source contribution (RSC) of drinking water to human PFAS exposures. OBJECTIVES: This study estimates the RSC of tap water to overall PFAS exposure among members of the general U.S. METHODS: We measured concentrations of 15 PFAS in home tap water samples collected in 1989-1990 from 225 participants in a nationwide prospective cohort of U.S. women: the Nurses' Health Study (NHS). We used a one-compartment toxicokinetic model to estimate plasma concentrations corresponding to tap water intake of PFAS. We compared modeled results with measured plasma PFAS concentrations among a subset of 110 NHS participants. RESULTS: Tap water perfluorooctanoic acid (PFOA) and perfluorononanoic acid (PFNA) were statistically significant predictors of plasma concentrations among individuals who consumed [Formula: see text] cups of tap water per day. Modeled median contributions of tap water to measured plasma concentrations were: PFOA 12% (95% probability interval 11%-14%), PFNA 13% (8.7%-21%), linear perfluorooctanesulfonic acid (nPFOS) 2.2% (2.0%-2.5%), branched perfluorooctanesulfonic acid (brPFOS) 3.0% (2.5%-3.2%), and perfluorohexanesulfonic acid (PFHxS) 34% (29%-39%). In five locations, comparisons of PFASs in community tap water collected in the period 2013-2016 with samples from 1989-1990 indicated increases in quantifiable PFAS and extractable organic fluorine (a proxy for unquantified PFAS). CONCLUSIONS: Our results for 1989-1990 compare well with the default RSC of 20% used in risk assessments for legacy PFAS by many agencies. Future evaluation of drinking water exposures should incorporate emerging PFAS. https://doi.org/10.1289/EHP4093.

12.
IEEE Trans Cybern ; 2019 Jun 12.
Artigo em Inglês | MEDLINE | ID: mdl-31199279

RESUMO

An event-triggered mechanism is of great efficiency in reducing unnecessary sensor samplings/transmissions and, thus, resource consumption such as sensor power and network bandwidth, which makes distributed event-triggered estimation a promising resource-aware solution for sensor network-based monitoring systems. This paper provides a survey of recent advances in distributed event-triggered estimation for dynamical systems operating over resource-constrained sensor networks. Local estimates of an unavailable state signal are calculated in a distributed and collaborative fashion based on only invoked sensor data. First, several fundamental issues associated with the design of distributed estimators are discussed in detail, such as estimator structures, communication constraints, and design methods. Second, an emphasis is laid on recent developments of distributed event-triggered estimation that has received considerable attention in the past few years. Then, the principle of an event-triggered mechanism is outlined and recent results in this subject are sorted out in accordance with different event-triggering conditions. Third, applications of distributed event-triggered estimation in practical sensor network-based monitoring systems including distributed grid-connected generation systems and target tracking systems are provided. Finally, several challenging issues worthy of further research are envisioned.

13.
Dalton Trans ; 48(27): 10320-10326, 2019 Jul 21.
Artigo em Inglês | MEDLINE | ID: mdl-31210232

RESUMO

Two new alkali-metal bismuth iodates KBi(IO3)3(OH) (1) and NaBi(IO3)4 (2) have been synthesized by a hydrothermal method via tuning of alkali-metal ions. Compound 1 crystallizes in the space group P1[combining macron] and features a [Bi(IO3)3(OH)]n chain with eight-membered Bi-O-I-O-Bi-O-I-O rings. The [Bi(IO3)3(OH)]n chain consists of paddlewheel-like dimeric Bi2(OH)2(IO3)4 units linked by IO3 pairs. Compound 2 in the polar space group Cc features a [Bi(IO3)4]- double layer with Bi4I4 eight-membered rings (8-MRs). NaBi(IO3)4 exhibits a strong second harmonic generation (SHG) response of ∼5.0 × KDP (KH2PO4) and a wide transmittance window (0.4-12 µm), and structure analyses and theoretical calculations reveal that polarization results mainly from the proper alignment of the IO3 groups. The calculated electronic structure based on the DFT method indicates that the BiOn and IO3 groups dominate their optical properties.

14.
Am J Pathol ; 189(8): 1664-1679, 2019 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-31121134

RESUMO

Endothelial barrier dysfunction is a central factor in the pathogenesis of persistent lung inflammation and protein-rich edema formation, the hallmarks of acute respiratory distress syndrome. However, little is known about the molecular mechanisms that are responsible for vascular repair and resolution of inflammatory injury after sepsis challenge. Herein, we show that hypoxia-inducible factor-1α (HIF-1α), expressed in endothelial cells (ECs), is the critical transcriptional factor mediating vascular repair and resolution of inflammatory lung injury. After sepsis challenge, HIF-1α but not HIF-2α expression was rapidly induced in lung vascular ECs, and mice with EC-restricted disruption of Hif1α (Hif1af/f/Tie2Cre+) exhibited defective vascular repair, persistent inflammation, and increased mortality in contrast with the wild-type littermates after polymicrobial sepsis or endotoxemia challenge. Hif1af/f/Tie2Cre+ lungs exhibited marked decrease of EC proliferation during recovery after sepsis challenge, which was associated with inhibited expression of forkhead box protein M1 (Foxm1), a reparative transcription factor. Therapeutic restoration of endothelial Foxm1 expression, via liposomal delivery of Foxm1 plasmid DNA to Hif1af/f/Tie2Cre+ mice, resulted in reactivation of the vascular repair program and improved survival. Together, our studies, for the first time, delineate the essential role of endothelial HIF-1α in driving the vascular repair program. Thus, therapeutic activation of HIF-1α-dependent vascular repair may represent a novel and effective therapy to treat inflammatory vascular diseases, such as sepsis and acute respiratory distress syndrome.

15.
Environ Sci Technol ; 53(7): 3419-3428, 2019 04 02.
Artigo em Inglês | MEDLINE | ID: mdl-30852890

RESUMO

During the investigation of dechlorane-related chemicals in North American wildlife, two unknown polychlorinated compounds (referred to as U1 and U2) were discovered. After extensive sample cleanup, structural information on U1 and U2 was characterized by gas chromatography (GC) coupled with single quadrupole mass spectrometer (MS) or GC-quadrupole time-of-flight (QToF) MS. Mass spectral evidence suggests that both U1 and U2 are structurally related to Dechlorane 603 (Dec603; C17H8Cl12), an analogue of the chlorinated flame retardant Dechlorane Plus. From the results we suspect U1 (C17H9Cl11) to be a monohydro analogue of Dec603 (i.e., one chlorine atom in Dec603 is replaced by a hydrogen atom). U1 may be formed via the degradation of Dec603's stereoisomers or present as an impurity in commercial Dec603 products. Mass spectral characterization of U2 (C17H7OCl11) suggests it is a carbonylic derivative of Dec603, likely formed via metabolic transformation of Dec603 or its photoisomer. Semiquantitative measurement revealed that U1 and U2 were present at estimated median concentrations of 49 ng/g lipid weight (lw) and 59 ng/g lw in peregrine falcon ( Falco peregrinus) eggs, from the mid-Atlantic region of the United States, and 4.6 and 3.0 ng/g lw in shortfin mako shark ( Isurus oxyrinchus) livers from the western North Atlantic Ocean, respectively. Our results demonstrate the occurrence of these two novel Dec603-related chemicals in both terrestrial and aquatic ecosystems.


Assuntos
Retardadores de Chama , Tubarões , Animais , Oceano Atlântico , Ecossistema , Monitoramento Ambiental , Fígado , Mid-Atlantic Region
16.
MBio ; 10(1)2019 02 19.
Artigo em Inglês | MEDLINE | ID: mdl-30782663

RESUMO

Kaposi's sarcoma-associated herpesvirus (KSHV) is a human gammaherpesvirus associated with the development of Kaposi's sarcoma (KS). KSHV target cells include endothelial cells, B cells, monocytes, epithelial cells, dendritic cells, macrophages, and fibroblasts. KSHV entry into target cells is a complex multistep process and is initiated by the binding and interaction of viral envelope glycoproteins with the cellular receptors. In the current studies, we have found that EphA4 promotes KSHV glycoprotein H/glycoprotein L (gH/gL)-mediated fusion and infection better than does ephrin A2 (EphA2) in HEK293T cells, indicating that EphA4 is a new KSHV entry receptor. To confirm that epithelial cells express EphA2 and EphA4, we analyzed the expression of EphA2 and EphA4 in epithelial cells, endothelial cells, B cells, monocytes, fibroblasts using RNA sequencing (RNA-seq) data analysis of existing data sets. We found that these cell types broadly express both EphA2 and EphA4, with the exception of monocytes and B cells. To confirm EphA4 is important for KSHV fusion and infection, we generated EphA2 and EphA4 single- and double-knockout cells. We found that both EphA2 and EphA4 play a role in KSHV fusion and infection, since EphA2-EphA4 double-knockout cells had the greatest decrease in fusion activity and infection compared to single-knockout cells. Fusion and infection of KSHV were rescued in the EphA2-EphA4 double-knockout cells upon overexpression of EphA2 and/or EphA4. EphA2 binds to both Epstein-Barr virus (EBV) and KSHV gH/gL; however, EphA4 binds only to KSHV gH/gL. Taken together, our results identify EphA4 as a new entry receptor for KSHV.IMPORTANCE The overall entry mechanism for herpesviruses is not completely known, including those for the human gammaherpesviruses Kaposi's sarcoma-associated herpesvirus (KSHV) and Epstein-Barr virus (EBV). To fully understand the herpesvirus entry process, functional receptors need to be identified. In the current study, we found that EphA4 can also function for a KSHV entry receptor along with EphA2. Interestingly, we found that EphA4 does not function as an entry receptor for EBV, whereas EphA2 does. The discovery of EphA4 as a KSHV entry receptor has important implications for KSHV pathogenesis in humans, may prove useful in understanding the unique pathogenesis of KSHV infection in humans, and may uncover new potential targets that can be used for the development of novel interventional strategies.


Assuntos
Herpesvirus Humano 8/fisiologia , Receptor EphA4/metabolismo , Receptores Virais/metabolismo , Internalização do Vírus , Células Endoteliais/metabolismo , Efrina-A2/genética , Efrina-A2/metabolismo , Células Epiteliais/metabolismo , Fibroblastos/metabolismo , Perfilação da Expressão Gênica , Técnicas de Inativação de Genes , Teste de Complementação Genética , Células HEK293 , Humanos , Receptor EphA4/genética
17.
Med Phys ; 46(4): 1608-1619, 2019 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-30723932

RESUMO

PURPOSE: High-sensitivity and high-resolution depth-encoding positron emission tomography (PET) detectors are required to simultaneously improve the sensitivity and spatial resolution of a PET scanner so that the quantitative accuracy of PET studies can be improved. The semi-monolithic scintillator PET detector has the advantage of measuring the depth of interaction with single-ended readout as compared to the traditional pixelated scintillator detector, and significantly reducing the edge effect that deteriorates the spatial resolution at edges of the detector as compared to the monolithic scintillator detector if a long rectangular semi-monolithic detector is used. In this work, depth-encoding PET detector modules were built by using long rectangular semi-monolithic scintillators and single-ended readout by silicon photomultiplier (SiPM) arrays. The performance of the detector modules was measured. METHODS: The rectangular semi-monolithic scintillator detector has an outside dimension of 11.6 × 37.6 × 10 mm3 and consists of 11 polished lutetium-yttrium oxyorthosilicate (LYSO) slices measuring 1 × 37.6 × 10 mm3 . The enhanced specular reflector (ESR) was glued on both cross-sectional surfaces of each crystal slice. For the face opposite to the SiPM array and the two end faces of the detectors, surface treatments with and without black paint were implemented for performance comparison. The bottom face of the semi-monolithic detector was coupled to a 4 × 12 SiPM array that was grouped along rows and columns separately into 16 signals. The four row signals were used to identify the slices, and the 12 column signals were used to estimate the y (monolithic direction) and z (depth direction) interaction positions. The detector was irradiated at multiple positions with a collimated 511 keV gamma beam. The collimated beam was obtained with electronic collimation by using a 22 Na point source and a reference detector. The estimated width of the gamma beam is around 0.5 mm. The flood histogram for crystal slices was measured by using the center of gravity (COG) method. The COG method and the squared COG method were used for y position estimation. The standard deviation of the column signals, the ratio of maximum to the sum of the column signals, and the sum of squared column signals were used for z position estimation. RESULTS: All slices were clearly resolved from the measured flood histograms for both detectors with different crystal surface treatments. The estimated y positions roughly linearly change with the true positions at the middle of the detector until ~5 mm from both ends of the detector. The y and z spatial resolutions of the detectors were estimated for all middle positions located more than 5 mm from both ends of the detector. The squared COG method provides better y position resolution than the COG method. The three z estimation methods provide similar depth of interaction (DOI) resolution. Surface treatment with black paint significantly improves both y and z position resolution but degrades the energy and timing resolution of the detectors. The average full width half maxima (FWHM) spatial resolution is improved from 1.77 to 1.07 mm in the y direction by using the squared COG method and from 2.71 to 1.55 mm in the z direction by using the standard deviation method. The slice-based average energy resolution degrades from 15.8% to 24.9%. The timing resolution of the entire detector module degrades from 596 to 788 ps. CONCLUSION: The performance of rectangular semi-monolithic scintillator PET detectors with two different crystal surface treatments was measured. The detectors provide superior spatial resolution and depth-encoding capability and can be used to develop small animal and dedicated breast and brain PET scanners that can simultaneously achieve high spatial resolution, high sensitivity, and low cost.


Assuntos
Algoritmos , Tomografia por Emissão de Pósitrons/instrumentação , Contagem de Cintilação/instrumentação , Silício/química , Animais , Estudos Transversais , Desenho de Equipamento , Raios gama
18.
J Hazard Mater ; 367: 658-667, 2019 Apr 05.
Artigo em Inglês | MEDLINE | ID: mdl-30654283

RESUMO

We exploit a novel role of MgAl-layered double oxide (LDO) as a powerful sweeper to remove trace emulsified water and organic acids from contaminated oil. Notably, 0.4 g of LDO enable to purify 20 mL of contaminated oil with 0.2 g of water and 0.1 mL of octanoic acid, and the separation efficiency reaches 94.6 and 28.2%, respectively. The separation process is initiated with the immobilization of water droplets at the crystalline matrix of LDO (driven by the unique water memory effect), accompanied by the LDO converted to MgAl-layered double hydroxide (LDH). LDH possesses a high point of zero charge and abundant OH- and Mg2+/Al3+ on its layered surface, which enables it to remove the acids via neutralization and complexing reactions. The immobilized water and adsorbed acids are eventually swept by collecting the solids. The collected solids, mainly composed of LDH, can be regenerated to LDO for recycle through a calcination process. Economy evaluation reveals it takes $6.7 for LDO to purify every cubic meters of emulsion, much more cost-effective than the reported CaSO4•0.5H2O and Fe3O4-based adsorbents. The robust performance with the competitive economy points to the high potential of LDO for oil regeneration.

19.
Inorg Chem ; 58(3): 2201-2207, 2019 Feb 04.
Artigo em Inglês | MEDLINE | ID: mdl-30666876

RESUMO

Beryllium (Be) has high ionization energy (9.32 eV) with the greatest degree of covalency in the group IIA elements, and BeO4 tetrahedra (and BeO3 triangles) with covalent character are generally presented in beryllates. An unprecedented BeO6 trigonal prism with ultralong Be-O bonds as well as a BeO4 common tetrahedron is discovered in a new deep ultraviolet crystal Li13BeBe6B9O27 (LBeBBO) with a ∞2[Be6B9O33] double-layer framework. The BeO6 unit and its bond character are verified by an isostructural crystal Li13(Mg0.45Be0.55)Be6B9O27, while the orbital theory and charge density difference further clarify the ionic character of the BeO6 unit. Phonon dispersion confirms the structural stability of LBeBBO.

20.
Environ Sci Technol ; 2018 Nov 27.
Artigo em Inglês | MEDLINE | ID: mdl-30407800

RESUMO

Exposure- and risk-based assessments for chemicals used indoors or applied to humans (i.e., in near-field environments) necessitate an aggregate exposure pathway framework that aligns chemical exposure information from use sources to internal dose and eventually to their potential for health effects. Such a source-to-effect continuum is advocated to balance the complexity of human exposure and the insufficiency of relevant data for thousands of existing and emerging chemicals. Here, we introduce the Risk Assessment, IDentification And Ranking-Indoor and Consumer Exposure (RAIDAR-ICE) model, which establishes an integrated framework to evaluate human exposure due to indoor use and direct application of chemicals to humans. As a model evaluation, RAIDAR-ICE faithfully reproduces exposure estimates inferred from biomonitoring data for 37 chemicals with direct and indirect near-field sources. RAIDAR-ICE generates different rankings for 131 chemicals based on different exposure- and risk-based assessment metrics, demonstrating its versatility for diverse chemical screening goals. When coupled with a far-field RAIDAR model, the near-field RAIDAR-ICE model enables assessment of aggregate human exposure. Overall, RAIDAR-ICE is a powerful tool for high-throughput screening and prioritization of human exposure to neutral organic chemicals used indoors.

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