Metal Fluorides Passivate II-VI and III-V Quantum Dots.

Quantum dots (QDs) with metal fluoride surface ligands were prepared via reaction with anhydrous oleylammonium fluoride. Carboxylate terminated II-VI QDs underwent carboxylate for fluoride exchange, while InP QDs underwent photochemical acidolysis yielding oleylamine, PH3, and InF3. The final photoluminescence quantum yield (PLQY) reached 83% for InP and near unity for core-shell QDs. Core-only CdS QDs showed dramatic improvements in PLQY, but only after exposure to air. Following etching, the InP QDs were bound by oleylamine ligands that were characterized by the frequency and breadth of the corresponding ν(N-H) bands in the infrared absorption spectrum. The fluoride content (1.6-9.2 nm-2) was measured by titration with chlorotrimethylsilane and compared with the oleylamine content (2.3-5.1 nm-2) supporting the formation of densely covered surfaces. The influence of metal fluoride adsorption on the air stability of QDs is discussed.

Synthesis of graded CdS1-xSex nanoplatelet alloys and heterostructures from pairs of chalcogenoureas with tailored conversion reactivity.

A mixture of N,N,N'-trisubstituted thiourea and cyclic N,N,N',N'-tetrasubstituted selenourea precursors were used to synthesize three monolayer thick CdS1-xSex nanoplatelets in a single synthetic step. The microstructure of the nanoplatelets could be tuned from homogeneous alloys, to graded alloys to core/crown heterostructures depending on the relative conversion reactivity of the sulfur and selenium precursors. UV-visible absorption and photoluminescence spectroscopy and scanning transmission electron microscopy electron energy loss spectroscopy (STEM-EELS) images demonstrate that the elemental distribution is governed by the relative precursor conversion kinetics. Slow conversion kinetics produced nanoplatelets with larger lateral dimensions, behavior that is characteristic of precursor conversion limited growth kinetics. Across a 10-fold range of reactivity, CdS nanoplatelets have 4× smaller lateral dimensions than CdSe nanoplatelets grown under identical conversion kinetics. The difference in size is consistent with a rate of CdSe growth that is 4× greater than the rate of CdS. The influence of the relative sulfide and selenide growth rates, the duration of the nucleation phase, and the solute composition on the nanoplatelet microstructure are discussed.

Mapping Polyclonal Antibody Responses to Infection Using Next-Generation Phage Display.

Peptide phage display has historically been used to epitope map monoclonal antibodies. More recently, by coupling this method with next-generation sequencing (so-called next-generation phage display, NGPD) to mass screen peptide binding events, the methodology has been successfully applied to map polyclonal antibody responses to infection. This leads to the identification of panels of mimotopes that represent the pathogen's epitopes. One potential advantage of using such an approach is that the mimotopes can represent not just linear epitopes but also conformational epitopes or those produced from post-translational modifications of proteins or from other non-protein macromolecules. The mapping of such complex immunological recognition of a pathogen can inform novel serological assay development and vaccine design. Here, we provide detailed methods for the application of NGPD to identify panels of mimotopes that are recognized specifically by antibodies from individuals with a particular infection.

Design Rules for Obtaining Narrow Luminescence from Semiconductors Made in Solution.

Solution-processed semiconductors are in demand for present and next-generation optoelectronic technologies ranging from displays to quantum light sources because of their scalability and ease of integration into devices with diverse form factors. One of the central requirements for semiconductors used in these applications is a narrow photoluminescence (PL) line width. Narrow emission line widths are needed to ensure both color and single-photon purity, raising the question of what design rules are needed to obtain narrow emission from semiconductors made in solution. In this review, we first examine the requirements for colloidal emitters for a variety of applications including light-emitting diodes, photodetectors, lasers, and quantum information science. Next, we will delve into the sources of spectral broadening, including "homogeneous" broadening from dynamical broadening mechanisms in single-particle spectra, heterogeneous broadening from static structural differences in ensemble spectra, and spectral diffusion. Then, we compare the current state of the art in terms of emission line width for a variety of colloidal materials including II-VI quantum dots (QDs) and nanoplatelets, III-V QDs, alloyed QDs, metal-halide perovskites including nanocrystals and 2D structures, doped nanocrystals, and, finally, as a point of comparison, organic molecules. We end with some conclusions and connections, including an outline of promising paths forward.

Indefinite and bidirectional near-infrared nanocrystal photoswitching.

Materials whose luminescence can be switched by optical stimulation drive technologies ranging from superresolution imaging1-4, nanophotonics5, and optical data storage6,7, to targeted pharmacology, optogenetics, and chemical reactivity8. These photoswitchable probes, including organic fluorophores and proteins, can be prone to photodegradation and often operate in the ultraviolet or visible spectral regions. Colloidal inorganic nanoparticles6,9 can offer improved stability, but the ability to switch emission bidirectionally, particularly with near-infrared (NIR) light, has not, to our knowledge, been reported in such systems. Here, we present two-way, NIR photoswitching of avalanching nanoparticles (ANPs), showing full optical control of upconverted emission using phototriggers in the NIR-I and NIR-II spectral regions useful for subsurface imaging. Employing single-step photodarkening10-13 and photobrightening12,14-16, we demonstrate indefinite photoswitching of individual nanoparticles (more than 1,000 cycles over 7 h) in ambient or aqueous conditions without measurable photodegradation. Critical steps of the photoswitching mechanism are elucidated by modelling and by measuring the photon avalanche properties of single ANPs in both bright and dark states. Unlimited, reversible photoswitching of ANPs enables indefinitely rewritable two-dimensional and three-dimensional multilevel optical patterning of ANPs, as well as optical nanoscopy with sub-Å localization superresolution that allows us to distinguish individual ANPs within tightly packed clusters.

The Use of Thiazide Diuretics for the Treatment of Hypertension in Patients With Advanced Chronic Kidney Disease.

The use of thiazide diuretics for the treatment of hypertension in patients with advance chronic kidney disease. Thiazides have been recommended as the first-line for the treatment of hypertension, yet their use has been discouraged in advanced chronic kidney disease (CKD), as they are suggested to be ineffective in advanced CKD. Recent data suggest that thiazide diuretics may be beneficial blood pressure control in addition to natriuresis in existing CKD. This review discusses the commercially available thiazides with a focus on thiazide pharmacology, most common adverse effects, clinical uses of thiazide diuretic, and the evidence for efficacy of thiazide use in advanced CKD.

Next-Generation Phage Display to Identify Peptide Ligands of Deubiquitinases.

Phage display (PD) is a powerful method and has been extensively used to generate monoclonal antibodies and identify epitopes, mimotopes, and protein interactions. More recently, the combination of next-generation sequencing (NGS) with PD (NGPD) has revolutionized the capabilities of the method by creating large data sets of sequences from affinity selection-based approaches (biopanning) otherwise challenging to obtain. NGPD can monitor motif enrichment, allow tracking of the selection process over consecutive rounds, and highlight unspecific binders. To tackle the wealth of data obtained, bioinformatics tools have been developed that allow for identifying specific binding sequences (binders) that can then be validated. Here, we provide a detailed account of the use of NGPD experiments to identify ubiquitin-specific protease peptide ligands.

Persistent nucleation and size dependent attachment kinetics produce monodisperse PbS nanocrystals.

Modern syntheses of colloidal nanocrystals yield extraordinarily narrow size distributions that are believed to result from a rapid "burst of nucleation" (La Mer, JACS, 1950, 72(11), 4847-4854) followed by diffusion limited growth and size distribution focusing (Reiss, J. Chem. Phys., 1951, 19, 482). Using a combination of in situ X-ray scattering, optical absorption, and 13C nuclear magnetic resonance (NMR) spectroscopy, we monitor the kinetics of PbS solute generation, nucleation, and crystal growth from three thiourea precursors whose conversion reactivity spans a 2-fold range. In all three cases, nucleation is found to be slow and continues during >50% of the precipitation. A population balance model based on a size dependent growth law (1/r) fits the data with a single growth rate constant (k G) across all three precursors. However, the magnitude of the k G and the lack of solvent viscosity dependence indicates that the rate limiting step is not diffusion from solution to the nanoparticle surface. Several surface reaction limited mechanisms and a ligand penetration model that fits data our experiments using a single fit parameter are proposed to explain the results.

Growth kinetics determine the polydispersity and size of PbS and PbSe nanocrystals.

A library of thio- and selenourea derivatives is used to adjust the kinetics of PbE (E = S, Se) nanocrystal formation across a 1000-fold range (k r = 10-1 to 10-4 s-1), at several temperatures (80-120 °C), under a standard set of conditions (Pb : E = 1.2 : 1, [Pb(oleate)2] = 10.8 mM, [chalcogenourea] = 9.0 mM). An induction delay (t ind) is observed prior to the onset of nanocrystal absorption during which PbE solute is observed using in situ X-ray total scattering. Density functional theory models fit to the X-ray pair distribution function (PDF) support a Pb2(µ2-S)2(Pb(O2CR)2)2 structure. Absorption spectra of aliquots reveal a continuous increase in the number of nanocrystals over more than half of the total reaction time at low temperatures. A strong correlation between the width of the nucleation phase and reaction temperature is observed that does not correlate with the polydispersity. These findings are antithetical to the critical concentration dependence of nucleation that underpins the La Mer hypothesis and demonstrates that the duration of the nucleation period has a minor influence on the size distribution. The results can be explained by growth kinetics that are size dependent, more rapid at high temperature, and self limiting at low temperatures.

Superinfection Exclusion of Alphaherpesviruses Interferes with Virion Trafficking.

Superinfection exclusion (SIE) is a phenomenon in which a primary viral infection interferes with secondary viral infections within that same cell. Although SIE has been observed across many viruses, it has remained relatively understudied. A recently characterized glycoprotein D (gD)-independent SIE of alphaherpesviruses presents a novel mechanism of coinfection restriction for herpes simplex virus 1 (HSV-1) and pseudorabies virus (PRV). In this study, we evaluated the role of multiplicity of infection (MOI), receptor expression, and trafficking of virions to gain greater insight into potential mechanisms of alphaherpesvirus SIE. We observed that high-MOI secondary viral infections were able to overcome SIE in a manner that was independent of receptor availability. We next assessed virion localization during SIE through live microscopy of fluorescently labeled virions and capsid assemblies. Analysis of these fluorescent assemblies identified changes in the distribution of capsids during SIE. These results indicate that SIE during PRV infection inhibits viral entry or fusion while HSV-1 SIE inhibits infection through a postentry mechanism. Although the timing and phenotype of SIE are similar between alphaherpesviruses, the related viruses implement different mechanisms to restrict coinfection. IMPORTANCE Most viruses utilize a form of superinfection exclusion to conserve resources and control population dynamics. gD-dependent superinfection exclusion in alphaherpesviruses is well documented. However, the undercharacterized gD-independent SIE provides new insight into how alphaherpesviruses limit sequential infection. The observations described here demonstrate that gD-independent SIE differs between PRV and HSV-1. Comparing these differences provides new insights into the underlying mechanisms of SIE implemented by two related viruses.

Obstructive Sleep Apnea and Hypertension: Updates to a Critical Relationship.

PURPOSE OF REVIEW: Obstructive sleep apnea (OSA) is an underdiagnosed illness linked to essential hypertension (HTN), resistant hypertension (r-HTN), and cardiovascular disease (CVD). This review provides updates on the epidemiology, pathophysiology, and treatments of OSA-associated HTN. RECENT FINDINGS: Mild sleep apnea increases the risk for HTN. Eighty-nine percent of young patients aged 18-35 with HTN not attributed to secondary causes have underlying OSA. Home sleep studies are noninferior to formal polysomnography for OSA diagnosis. Nocturnal oxygen desaturation rate is positively correlated with HTN severity. Gut microbiome neo-colonization in response to high-fat diet cravings in patients with OSA alters immune function and worsens HTN. Carbonic anhydrase inhibitors and probiotics show newfound potential for OSA-associated HTN treatment. OSA recognition improves hospital outcomes after a STEMI. Hypoxia-inducible factor (HIF) transcription increases in a dose-dependent manner to hypoxia, and HIFs are strongly linked to cancer growth. OSA and HTN are comorbid conditions with adversely connected pathophysiology including sympathetic hyperactivity, gut dysbiosis, proinflammation, endothelial damage, rostral fluid shifts, pharyngeal collapse, intravascular fluid retention, nocturnal energy expenditure, and metabolic derangements. The dose-response effect of OSA on HTN severity challenges blood pressure (BP) control, so those with refractory HTN should be screened for OSA.

A Simple Whole-Plasmid PCR Method to Construct High-Diversity Synthetic Phage Display Libraries.

Phage display technology utilises peptide and antibody libraries with very high diversities to select ligands with specific binding properties. The production of such libraries can be labour intensive and technically challenging and whilst there are commercial sources of libraries, the exploitation of the resulting binders is constrained by ownership of the libraries. Here, a peptide library of ~ 1 × 109 variants for display on gene VIII was produced alongside three VHH antibody libraries with similar diversity, where 12mer, 16mer or 21mer CDR3s were introduced into the highly stable cAbBCII10 scaffold displayed on gene III. The cloning strategy used a simple whole-plasmid PCR method and type IIS restriction enzyme assembly that facilitate the seamless insertion of diversity into any suitable phage coat protein or antibody scaffold. This method reproducibly produced 1 × 109 variants from just 10 transformations and the four libraries had relatively low bias with 82 to 86% of all sequences present as single copies. The functionality of both peptide and antibody libraries were demonstrated by selection of ligands with specific binding properties by biopanning. The peptide library was used to epitope map a monoclonal antibody. The VHH libraries were pooled and used to select an antibody to recombinant human collagen type 1.

Recurrent thrombosis of an arteriovenous fistula as a complication of COVID-19 in a chronic hemodialysis patient: A case report.

Patients with end-stage kidney disease are at increased risk of death from coronavirus disease 2019 (COVID-19). In addition, severe COVID-19 has been associated with an increased risk of arterial and venous thromboses. In this report, we describe the case of a hemodialysis patient who developed an otherwise-unexplained thrombosis of an arteriovenous fistula during a symptomatic COVID-19 infection. Despite prompt treatment with three technically successful thrombectomies along with systemic intravenous heparin and two rounds of catheter-directed thrombolysis with tissue plasminogen activator, the fistula rapidly re-thrombosed each time and he required tunneled dialysis catheter placement. He subsequently required admission for hypoxemia from COVID-19 pneumonia and ultimately developed a catheter-related blood stream infection that likely contributed to his death. As the fistula had been previously well functioning and no angiographic explanation for the thrombosis was found, we speculate in this case the recurrent thromboses were related to the hypercoagulable state characteristic of severe COVID-19. Interventionalists performing hemodialysis access procedures should be aware of the prothrombotic state associated with COVID-19 and should consider it when deliberating how to best plan and approach access interventions in patients with symptomatic COVID-19.

Free Trions with Near-Unity Quantum Yield in Monolayer MoSe2.

Trions, quasiparticles composed of an electron-hole pair bound to a second electron and/or hole, are many-body states with potential applications in optoelectronics. Trions in monolayer transition metal dichalcogenide (TMD) semiconductors have attracted recent interest due to their valley/spin polarization, strong binding energy, and tunability through external gate control. However, low materials quality (i.e., high defect density) has hindered efforts to understand the intrinsic properties of trions. The low photoluminescence (PL) quantum yield (QY) and short lifetime of trions have prevented harnessing them in device applications. Here, we study the behavior of trions in a series of MoSe2 monolayers, with atomic defect density varying by over 2 orders of magnitude. The QY increases with decreasing defect density and approaches unity in the cleanest material. Simultaneous measurement of the PL lifetime yields both the intrinsic radiative lifetime and the defect-dependent nonradiative lifetime. The long lifetime of ∼230 ps of trions allows direct observation of their diffusion.

Relations between absorption, emission, and excited state chemical potentials from nanocrystal 2D spectra.

For quantum-confined nanomaterials, size dispersion causes a static broadening of spectra that has been difficult to measure and invalidates all-optical methods for determining the maximum photovoltage that an excited state can generate. Using femtosecond two-dimensional (2D) spectroscopy to separate size dispersion broadening of absorption and emission spectra allows a test of single-molecule generalized Einstein relations between such spectra for colloidal PbS quantum dots. We show that 2D spectra and these relations determine the thermodynamic standard chemical potential difference between the lowest excited and ground electronic states, which gives the maximum photovoltage. Further, we find that the static line broadening from many slightly different quantum dot structures allows single-molecule generalized Einstein relations to determine the average single-molecule linewidth from Stokes' frequency shift between ensemble absorption and emission spectra.

Au/TiO2-Catalyzed Benzyl Alcohol Oxidation on Morphologically Precise Anatase Nanoparticles.

Au nanoparticles (NP) on TiO2 have been shown to be effective catalysts for selective oxidation reactions by using molecular oxygen. In this work, we have studied the influence of support morphology on the catalytic activity of Au/TiO2 catalysts. Two TiO2 anatase supports, a nanoplatelet-shaped material with predominantly the {001} facet exposed and a truncated bipyramidal-shaped nanoparticle with predominantly the {101} facet exposed, were prepared by using a nonaqueous solvothermal method and characterized by using DRIFTS, XPS, and TEM. Au nanoparticles were deposited on the supports by using the deposition-precipitation method, and particle sizes were determined by using STEM. Au nanoparticles were smaller on the support with the majority of the {101} facet exposed. The resulting materials were used to catalyze the aerobic oxidation of benzyl alcohol and trifluoromethylbenzyl alcohol. Support morphology impacts the catalytic activity of Au/TiO2; reaction rates for reactions catalyzed by the predominantly {101} material were higher. Much of the increased reactivity can be explained by the presence of smaller Au particles on the predominantly {101} material, providing more Au/TiO2 interface area, which is where catalysis occurs. The remaining modest differences between the two catalysts are likely due to geometric effects as Hammett slopes show no evidence for electronic differences between the Au particles on the different materials.

Performance of Spherical Quantum Well Down Converters in Solid State Lighting.

We report the color conversion performance of amber and red emitting quantum dots (QDs) on InGaN solid-state lighting (SSL) light emitting diode (LED) packages. Spherical quantum well (SQW) architectures (CdS/CdSe1-xSx/CdS) were prepared using a library of thio- and selenourea synthesis reagents and high throughput synthesis robotics. CdS/CdSe1-xSx QDs with narrow luminescence bands were coated with thick CdS shells (thickness = 1.6-7.5 nm) to achieve photoluminescence quantum yields (PLQY) up to 88% at amber and red emission wavelengths (λmax = 600-642 nm, FWHM < 45 nm). The photoluminescence from SQWs encapsulated in silicone and deposited on LED packages was monitored under accelerated aging conditions (oven temperature = 85 °C, relative humidity = 5-85%, blue optical power density = 3-45 W/cm2) by monitoring the red photon output over several hundred hours of continuous operation. The growth of a ZnS shell on the SQW surface increases the stability under long-term operation but also reduces the PLQY, especially of SQWs with thick CdS shells. The results illustrate that the outer ZnS shell layer is key to optimizing the PLQY and the long-term stability of QDs during operation on SSL packages.

Initial Outcomes Following Introduction of Percutaneous Arteriovenous Fistula Program with Comparison to Historical Surgically Created Fistulas.

BACKGROUND: Recently, there has been an abundance of encouraging data regarding the creation of percutaneous arteriovenous fistulas. Despite promising data regarding their clinical maturation, a paucity of data exists which provides direct comparison between percutaneously created AVFs (pAVF) and open surgically created AVFs (sAVF). This study has 2 primary objectives: First, to compare clinical outcomes of pAVFs to sAVFs, with emphasis on clinical maturation and frequency of postoperative interventions to facilitate maturation. Second, to contribute toward the evidence-based incorporation of the pAVF procedure into the hemodialysis access algorithm. METHODS: A single-center retrospective review was performed on all consecutive patients undergoing surgically created brachiocephalic arteriovenous fistula (BC-AVF, sAVF group) from January 1, 2018 to December 31, 2018 and Ellipsys-created percutaneous arteriovenous fistula (pAVF group) from January 1, 2019 to December 31, 2019. Comparative analysis between groups was performed. RESULTS: A total of 24 patients underwent Ellipsys-created pAVF with mean age of 56.7 ± 22.6 years (12 males [50%], 12 females [50%]) and 62 patients underwent surgically created BC-AVF with mean age of 62.5 ± 13.2 years (32 males [52%], 30 females [48%]). Both the pAVF and sAVF groups had comparable mean operating times (60 ± 40 vs. 56 ± 25 min, P = 0.67) and frequency of procedural technical success (23 [96%] vs. 62 [100%], P = 0.28), respectively. The pAVF group had a lower clinical maturation rate (12 [52%] vs. 54 [87%], P = 0.003) and a higher primary failure rate (9 [39%] vs. 6 [10%], P = 0.003) when compared to the sAVF group. The pAVF group had an increased overall rate of undergoing a postoperative intervention (18 [78%] vs. 13 [21%], P< 0.001), as well as an increased number of total postoperative interventions (1.1 ± 0.9 vs. 0.3 ± 0.6 interventions, P< 0.001) compared to the sAVF group. Percutaneous transluminal angioplasty of the juxta anastomotic segment was the most prevalent postoperative intervention performed in the pAVF group and occurred at a significantly increased frequency when compared to the sAVF group rate (13 [57%] vs. 5 [8%], P< 0.001). CONCLUSIONS: In our single-center retrospective review, patients undergoing Ellipsys-created pAVF in the first year following introduction of percutaneous endovascular had inferior rates of clinical maturation and underwent more postoperative interventions when compared to historical patients undergoing surgically created BC-AVF. Outcome discrepancies compared to previously reported Ellipsys data demonstrate a need for further studies examining the practical translatability of the pAVF.

Initial 6-month quality review of a percutaneous endovascular arteriovenous fistula program.

BACKGROUND: Percutaneous arteriovenous fistulas have recently proven successful alternatives to surgical arteriovenous fistulas with encouraging initial results. The Ellipsys Endovascular Arteriovenous Fistula System utilizing ultrasound and thermal energy has recently received approval for use in the United States. At the University of New Mexico, we developed an integrated service between Vascular Surgery, Interventional Radiology, and Interventional Nephrology for percutaneous arteriovenous fistulas utilizing Ellipsys. METHODS: We performed a retrospective chart review of the initial 6 months (January 1st 2019 to July 1st 2019) of 18 percutaneous arteriovenous fistula placements to evaluate our initial technical success rate, the number of arteriovenous fistulas meeting maturation characteristics or use in dialysis, and to identify areas for quality improvement. RESULTS: Initial technical success was achieved in 17 out of 18 arteriovenous fistulas (94.4%). Three patients did not report for any follow-up at the end of the initial 6 months. Of the remaining patients, 7 out of 15 were using their arteriovenous fistulas or meeting maturation characteristics at the end of the study (46.7%). Patient loss to follow-up/no-show (16.7%), patient not yet requiring hemodialysis (27.8%), and poor post-surgical maturation and/or need for additional maturation procedures (55.6%) were the predominate reasons for non-use. We identified improved coordination of care, early intervention, and outpatient dialysis center education as the primary areas of focus for quality improvement. CONCLUSION: Initial technical success rate of percutaneous arteriovenous fistulas placement was comparable to published studies. Early and aggressive secondary angiographic interventions of arteriovenous fistulas failing to meet cannulation requirements, improved coordination of post-operative care, and outpatient dialysis center education appear to be the primary targets for quality improvement.