Snapshots into carbon dots formation through a combined spectroscopic approach

The design of novel carbon dots with ad hoc properties requires a comprehensive understanding of their formation mechanism, which is a complex task considering the number of variables involved, such as reaction time, structure of precursors or synthetic protocol employed. Herein, we systematically investigated the formation of carbon nanodots by tracking structural, chemical and photophysical features during the hydrothermal synthesis. We demonstrate that the formation of carbon nanodots consists of 4 consecutive steps: (i) aggregation of small organic molecules, (ii) formation of a dense core with an extended shell, (iii) collapse of the shell and (iv) aromatization of the core. In addition, we provide examples of routes towards tuning the core-shell design, synthesizing five novel carbon dots that all consist of an electron-dense core covered by an amine rich ligand shell

Iconography of the corpse in the public sphere. Presence and absence of the dead body in times of pandemic

In this article, we examine the visual motif of the corpse and its presence in the public sphere in times of pandemic from an iconographic, political and anthropological perspective. Through the analysis of the representation of the dead body in images presented by modern media, we reflect on how the formal and iconographic schemes of presentation of death were transformed following the irruption of the Covid-19 pandemic in March 2020. The pandemic scheme, which is unusual from a political and anthropological perspective, assumes a particular approach to the problem of the representation of the dead body (anonymous body, carrier of a virus), encrypted in a dialectic between systematic omission and censorship and displacement of the representation of death towards the cumulative symmetry of empty pits or coffins that prefigure the corpse to come. Pandemic iconography, often based on science fiction imagery, outlines the dehumanized restlessness of a dystopian future. Under these exceptional conditions, some corpses, which are a priori anonymous, stand out, showing, even in the suspended space of Covid-19, the permanence of structural schemes of violence that must be denounced and fought in the present. With that in mind, we also examine the corpses claimed by Black Lives Matter and their distinctive representations, which are very different from those of the victims of the epidemic. Finally, through these references and based on the media treatment of Diego Armando Maradona’s body, we consider the significance of the return of the iconic corpse to the center of the public sphere, which imposes a regime of extreme visibility and goes beyond the representative limits of pandemic exceptionality.En este artículo estudiamos, desde una perspectiva iconográfica, política y antropológica, el motivo visual del cadáver y su presencia en la esfera pública en tiempos de pandemia. A partir del análisis de la representación del cuerpo muerto en las imágenes de los medios de comunicación actuales, hemos tratado de pensar cómo se transformaron los esquemas formales e iconográficos de presentación de la muerte con la irrupción, desde marzo de 2020, de la pandemia de Covid-19. El régimen pandémico, excepcional a nivel político y antropológico, supone un acercamiento particular a la problemática de la representación del cuerpo muerto (cuerpo anónimo, portador de un virus), cifrado en una dialéctica entre un régimen de omisión y censura y el desplazamiento de la representación de la muerte hacia la simetría acumulativa de las fosas o ataúdes vacíos que prefiguran el cadáver por venir. La iconografía pandémica, construida con frecuencia sobre el imaginario de la ciencia-ficción, perfila la inquietud deshumanizada de un futuro distópico. En esas condiciones de excepcionalidad, algunos cadáveres, a priori anónimos, se singularizan, mostrando, aún en el espacio en suspenso de la Covid-19, la permanencia de esquemas estructurales de violencia que se deben denunciar y combatir en presente. En ese sentido, proponemos también estudiar los cadáveres reivindicados por el Black Lives Matter y la peculiar forma representativa que toman, muy diferente a los de las víctimas de la epidemia. Finalmente, desde estas coordenadas y a partir del tratamiento mediático del cuerpo de Diego Armando Maradona, consideramos como significativo el retorno al centro de la esfera pública del cadáver icónico, que impone un régimen de extrema visibilidad y desborda los límites representativos de la excepcionalidad pandémica

PROGRESS REPORT ON FRICTION LOSS OF SLURRIES IN STRAIGHT TUBES

This progress report summarizes the results obtained to date on the experimental evaluation of the loss of head entailed in pumping slurries through a straight horizontal tube. The slurries used in the investigation consisted of spherical particles of glass, steel and lead in water. The particle size and concentrations were nominally constant for a given slurry, but the various slurries tested covered the size range from 0.00122 to 0.0722 inches in diameter. Concentrations from zero to approximately 50 per cent by weight were used.</p

Monitoring Cell Death in Regorafenib-Treated Experimental Colon Carcinomas Using Annexin-Based Optical Fluorescence Imaging Validated by Perfusion MRI

Objective To investigate annexin-based optical fluorescence imaging (OI) for monitoring regorafenib-induced early cell death in experimental colon carcinomas in rats, validated by perfusion MRI and multiparametric immunohistochemistry. Materials and Methods Subcutaneous human colon carcinomas (HT-29) in athymic rats (n = 16) were imaged before and after a one-week therapy with regorafenib (n = 8) or placebo (n = 8) using annexin-based OI and perfusion MRI at 3 Tesla. Optical signal-to-noise ratio (SNR) and MRI tumor perfusion parameters (plasma flow PF, mL/100mL/min;plasma volume PV,%) were assessed. On day 7, tumors underwent immunohistochemical analysis for tumor cell apoptosis (TUNEL),proliferation (Ki-67),and microvascular density (CD31). Results Apoptosis-targeted OI demonstrated a tumor-specific probe accumulation with a significant increase of tumor SNR under therapy (mean Delta +7.78 +/- 2.95, control: -0.80 +/- 2.48, p = 0.021). MRI detected a significant reduction of tumor perfusion in the therapy group (mean Delta PF -8.17 +/- 2.32 mL/100 mL/min, control -0.11 +/- 3.36 mL/100 mL/min, p = 0.036). Immunohistochemistry showed significantly more apoptosis (TUNEL;11392 +/- 1486 vs. 2921 +/- 334, p = 0.001),significantly less proliferation (Ki-67;1754 +/- 184 vs. 2883 +/- 323, p = 0.012),and significantly lower microvascular density (CD31;107 +/- 10 vs. 182 +/- 22, p = 0.006) in the therapy group. Conclusions Annexin-based OI allowed for the non-invasive monitoring of regorafenib-induced early cell death in experimental colon carcinomas, validated by perfusion MRI and multiparametric immunohistochemistry

Monodisperse Long-Chain Sulfobetaine-Capped CsPbBr₃ Nanocrystals and Their Superfluorescent Assemblies

Ligand-capped nanocrystals (NCs) of lead halide perovskites, foremost fully inorganic CsPbX₃ NCs, are the latest generation of colloidal semiconductor quantum dots. They offer a set of compelling characteristics—large absorption cross section, as well as narrow, fast, and efficient photoluminescence with long exciton coherence times—rendering them attractive for applications in light-emitting devices and quantum optics. Monodisperse and shape-uniform, broadly size-tunable, scalable, and robust NC samples are paramount for unveiling their basic photophysics, as well as for putting them into use. Thus far, no synthesis method fulfilling all these requirements has been reported. For instance, long-chain zwitterionic ligands impart the most durable surface coating, but at the expense of reduced size uniformity of the as-synthesized colloid. In this work, we demonstrate that size-selective precipitation of CsPbBr₃ NCs coated with a long-chain sulfobetaine ligand, namely, 3-(N,N-dimethyloctadecylammonio)-propanesulfonate, yields monodisperse and sizable fractions (>100 mg inorganic mass) with the mean NC size adjustable in the range between 3.5 and 16 nm and emission peak wavelength between 479 and 518 nm. We find that all NCs exhibit an oblate cuboidal shape with the aspect ratio of 1.2 × 1.2 × 1. We present a theoretical model (effective mass/k·p) that accounts for the anisotropic NC shape and describes the size dependence of the first and second excitonic transition in absorption spectra and explains room-temperature exciton lifetimes. We also show that uniform zwitterion-capped NCs readily form long-range ordered superlattices upon solvent evaporation. In comparison to more conventional ligand systems (oleic acid and oleylamine), supercrystals of zwitterion-capped NCs exhibit larger domain sizes and lower mosaicity. Both kinds of supercrystals exhibit superfluorescence at cryogenic temperatures—accelerated collective emission arising from the coherent coupling of the emitting dipoles

Comparison of CT, MRI, and F-18 FDG PET/CT for initial N-staging of oral squamous cell carcinoma: a cost-effectiveness analysis.

BACKGROUND AND PURPOSE Treatment of oral squamous cell carcinoma (OSCC) is based on clinical exam, biopsy, and a precise imaging-based TNM-evaluation. A high sensitivity and specificity for magnetic resonance imaging (MRI) and F-18 FDG PET/CT are reported for N-staging. Nevertheless, staging of oral squamous cell carcinoma is most often based on computed tomography (CT) scans. This study aims to evaluate cost-effectiveness of MRI and PET/CT compared to standard of care imaging in initial staging of OSCC within the US Healthcare System. METHODS A decision model was constructed using quality-adjusted life years (QALYs) and overall costs of different imaging strategies including a CT of the head, neck, and the thorax, MRI of the neck with CT of the thorax, and whole body F-18 FDG PET/CT using Markov transition simulations for different disease states. Input parameters were derived from literature and willingness to pay (WTP) was set to US $100,000/QALY. Deterministic sensitivity analysis of diagnostic parameters and costs was performed. Monte Carlo modeling was used for probabilistic sensitivity analysis. RESULTS In the base-case scenario, total costs were at US$239,628 for CT, US $240,001 for MRI, and US$239,131 for F-18 FDG PET/CT whereas the model yielded an effectiveness of 5.29 QALYs for CT, 5.30 QALYs for MRI, and 5.32 QALYs for F-18 FDG PET/CT respectively. F-18 FDG PET/CT was the most cost-effective strategy over MRI as well as CT, and MRI was the cost-effective strategy over CT. Deterministic and probabilistic sensitivity analysis showed high robustness of the model with incremental cost effectiveness ratio remaining below US $100,000/QALY for a wide range of variability of input parameters. CONCLUSION F-18 FDG PET/CT is the most cost-effective strategy in the initial N-staging of OSCC when compared to MRI and CT. Despite less routine use, both whole body PET/CT and MRI are cost-effective modalities in the N-staging of OSCC. Based on these findings, the implementation of PET/CT for initial staging could be suggested to help reduce costs while increasing effectiveness in OSCC

Melting of magnetic order in NaOsO₃ by femtosecond laser pulses

NaOsO3 has recently attracted significant attention for the strong coupling between its electronic band structure and magnetic ordering. Here, we used time-resolved magnetic x-ray diffraction to determine the timescale of the photoinduced antiferromagnetic dynamics in NaOsO3. Our measurements are consistent with a sub-100 fs melting of the antiferromagnetic long-range order that occurs significantly faster than the lattice dynamics as monitored by the transient change in intensity of selected Bragg structural reflections, which instead show a decrease of intensity on a timescale of several ps