Slow Decay Rate Research Articles

Characterization of radicals in polysorbate 80 using electron paramagnetic resonance (EPR) spectroscopy and spin trapping

Polysorbates are an important class of nonionic surfactants that are widely used to stabilize biopharmaceuticals. The degradation of polysorbate 20 and 80 and the related particle formation in biologics are heavily discussed in the pharmaceutical community. Although a lot of experimental effort was spent in the detailed study of potential degradation pathways, the underlying mechanisms are only sparsely understood. Besides enzymatic hydrolysis, another proposed mechanism is associated with radical-induced (auto)oxidation of polysorbates. To characterize the types and the origin of the involved radicals and their propagation in bulk material as well as in diluted polysorbate 80 solutions, we applied electron paramagnetic resonance (EPR) spectroscopy using a spin trapping approach. The prerequisite for a meaningful experiment using spin traps is an understanding of the trapping rate, which is an interplay of (i) the presence of the spin trap at the scene of action, (ii) the specific reactivity of the selected spin trap with a certain radical as well as (iii) the stability of the formed spin adducts (a slow decay rate). We discuss whether and to which extent these criteria are fulfilled regarding the identification of different radical classes that might be involved in polysorbate oxidative degradation processes. The ratio of different radicals for different scenarios was determined for various polysorbate 80 quality grades in bulk material and in aqueous solution, showing differences in the ratio of present radicals. Possible correlations between the radical content and product parameters such as the quality grade, the manufacturing date, the manufacturer, the initial peroxide content according to the certificate of analysis of polysorbate 80 are discussed.

Variant-specific SARS-CoV-2 within-host kinetics.

Since early 2021, SARS‐CoV‐2 variants of concern (VOCs) have been causing epidemic rebounds in many countries. Their properties are well characterized at the epidemiological level but the potential underlying within‐host determinants remain poorly understood. We analyze a longitudinal cohort of 6944 individuals with 14 304 cycle threshold (Ct) values of reverse‐transcription quantitative polymerase chain reaction (RT‐qPCR) VOC screening tests performed in the general population and hospitals in France between February 6 and August 21, 2021. To convert Ct values into numbers of virus copies, we performed an additional analysis using droplet digital PCR (ddPCR). We find that the number of viral genome copies reaches a higher peak value and has a slower decay rate in infections caused by Alpha variant compared to that caused by historical lineages. Following the evidence that viral genome copies in upper respiratory tract swabs are informative on contagiousness, we show that the kinetics of the Alpha variant translate into significantly higher transmission potentials, especially in older populations. Finally, comparing infections caused by the Alpha and Delta variants, we find no significant difference in the peak viral copy number. These results highlight that some of the differences between variants may be detected in virus load variations.

Quartz OSL and TL dating of pottery, burnt clay, and sediment from Beicun archaeological site, China

This study focuses on characterizing the thermoluminescence (TL) and optically stimulated luminescence (OSL) of quartz in burnt clay, pottery, and the sediments unearthed from a Neolithic site, the Beicun site of the Liangzhu culture. It shows that the initial OSL signals (within 0.8 s) of most burnt clay and pottery sherds are not dominated by the fast component. Results of a heating simulation experiment of sediment quartz show that annealing at temperatures exceeding 600–800 °C decreased the proportion of the fast component in the initial signal slightly. In addition, the proportion of the medium component in the later signal (0.8–5 s) increased significantly, resulting in a decrease in the Fast Ratio value. Therefore, high annealing temperature may be an important reason for the slow decay rate of OSL signals of the burnt clay and pottery samples. The D e (t) plot shows that most of the samples have thermally stable OSL component signals, which have no significant effect on the final OSL ages. The single-aliquot regenerative-dose (SAR) protocol was used to determine the OSL and TL ages for chunk burnt clay and pottery sherds. The high-precision age of the last archaeological heating event, such as sacrifice, burning, or domestic firing, can be obtained by determining the TL and OSL ages of a homogeneous chunk of burnt clay. The OSL results are consistent with the 14 C age of carbon chips extracted from burnt clay. The age of the Beicun site is finally determined to be approximately 5000–5300 BP (BP represents before 2020), belonging to the early period of the Liangzhu culture.

Eigenvalue repulsions in the quasinormal spectra of the Kerr-Newman black hole

We study the gravito-electromagnetic perturbations of the Kerr-Newman (KN) black hole metric and identify the two $-$ photon sphere and near-horizon $-$ families of quasinormal modes (QNMs) of the KN black hole, computing the frequency spectra (for all the KN parameter space) of the modes with the slowest decay rate. We uncover a novel phenomenon for QNMs that is unique to the KN system, namely eigenvalue repulsion between QNM families. Such a feature is common in solid state physics where \eg it is responsible for energy bands/gaps in the spectra of electrons moving in certain Schr\"odinger potentials. Exploiting the enhanced symmetries of the near-horizon limit of the near-extremal KN geometry we also develop a matching asymptotic expansion that allows us to solve the perturbation problem using separation of variables and provides an excellent approximation to the KN QNM spectra near extremality. The KN QNM spectra here derived are required not only to account for the gravitational emission in astrophysical environments, such as the ones probed by LIGO, Virgo and LISA, but also allow to extract observational implications on several new physics scenarios, such as mini-charged dark-matter or certain modified theories of gravity, degenerate with the KN solution at the scales of binary mergers.

Biochemical components ofSphagnumand persistence in peat soil

The amounts and arrangements of polysaccharides (cellulose and hemicellulose), proteins, phenolic lignin, and pectin that make up plant tissue, in part, determine its decay rate. Lignin-rich and/or nitrogen-poor tissue has been described as biochemically recalcitrant causing a slow decay rate. Although a controversial mechanism for organic matter storage in soils with mineral particles, biochemical recalcitrance is still poorly understood in organic peat soil (Histosols). To investigate the role of Sphagnum in formation of peat soil, we characterize biochemical components for 10 species and examine persistence of the components in soil to 150 cm depth in three peatland ecosystems. We hypothesize that species from hummock microforms have more biochemical structural components and cohesion than species from hollows. Relative proportions of biochemical components changed markedly between plant material and the top 10 cm of peat soil, suggesting that decomposition occurred at the peat soil surface, but thereafter relative proportions of biochemical components did not vary significantly to 150 cm deep. A few differences in biochemical components that distinguished hummock species from hollow species persisted to the deepest depth sampled. Although persistence of the lignin-like component was expected, persistence of soluble and ionically bound pectin compounds was surprising as these biopolymers are thought to be readily decomposable. Our findings indicate that structural components of Sphagnum, specifically polysaccharides and pectin in addition to oft-cited phenolic lignin-like components, persist in peat soil and should not be overlooked in trying to understand carbon dynamics in Sphagnum-dominated ecosystems.

Fluorine-18 Fluorodeoxyglucose Isolation Using Graphene Oxide for Alternative Radiopharmaceutical Spillage Decontamination in PET Scan

Radiopharmaceuticals (RPC) used for diagnostic and therapeutic purposes in nuclear medicine may contaminate surface areas due to spillage during its preparation or accident during RPC transfer from laboratory to the treatment room. Fluorine-18 Fluorodeoxyglucose (18F-FDG) is the most common RPC for positron emission tomography (PET) scan in nuclear medicine due to its ideal annihilation converted energy at 511 keV and short half-life at 109.8 min. Ineffective medical waste management of 18F-FDG may pose a risk to the environment or cause unnecessary radiation doses to the personnel and public. Depending on the incident rate of these events, simple decontamination methods such as the use of chemicals and swabs might not be cost-effective and sustainable in the environment. This study aims to propose an alternative method to decontaminate 18F-FDG by using graphene oxide (GO). GO was synthesised using the Hummers method while the physical morphology was analysed using a field emission scanning electron microscope (FESEM). 18F-FDG adsorption efficiency rate using GO nanolayers was analysed based on the kinetic study of the GO:18F-FDG mixtures. The chemical adsorbability of the material was analysed via UV–vis spectrophotometer to interlink the microstructures of GO with the sorption affinity interaction. Resultantly, the adsorption rate was effective at a slow decay rate and the optical adsorption of GO with 18F-FDG was dominated by the π → π* plasmon peak, which was near 230 nm. By elucidating the underlining GO special features, an alternative technique to isolate 18F-FDG for the decontamination process was successfully proven.

Wave and scattering operators for the nonlinear Klein-Gordon equation on a quarter-plane

We consider the initial-boundary value problem for the nonlinear Klein-Gordon equation posed on a quarter-plane with Dirichlet non zero boundary conditions. We construct the wave and scattering operators for this model in the scattering-supercritical regime. We study the influence of the boundary data on the asymptotic behavior of solutions. We show that if the boundary data has sufficiently slow decay rate, it affects the order of the nonlinearity for which we are able to construct the scattering operator. This suggests a modification for the critical value of the nonlinear term due to the presence of non zero boundary condition. In order to prove our results, we construct an explicit formula for the solutions to corresponding linear Klein-Gordon equation on a quarter-plane. Using this explicit formula, we obtain weighted Sobolev estimates for the solution to the complete nonlinear problem. In order to control the long-time behavior of the solution we find an operator J suitable for our settings, analogous to operator x+it∂x in the case of NLS equation.

Longer characteristic wavelength in a novel engineered photoprotein Mnemiopsin 2.

We designed two mutants of photoprotein Mnemiopsin 2 (Mn2) including M52I and V144I, where the mutations were applied in the EF-hand loops I and III. Far-UV CD measurements demonstrated that the stability of the helices in the wild-type (WT) protein is greater compared with the mutants. Heat-induced denaturation experiments in the apo-form of photoproteins showed that WT Mn2 has higher value of the enthalpy change for the unfolding process, indicating that it has more stabilizing interaction compared with mutants. According to the activity measurement data, both mutants, particularly V144I have lower initial intensity as well as slower decay rate as compared with the WT photoprotein. Importantly, it was found that V144I variant shows 25nm of red shift in the characteristic wavelengths as compared with the WT photoprotein. This finding can be considered as an advantage for in vivo application of photoprotein for imaging purposes. It concluded that this position on loop III of Mn2 is a hotspot point for characteristic wavelength determination. However, further research on this mutant is needed for making stable variants of Mn2 with novel optical features.

Persistence of Fecal Indicators and Microbial Source Tracking Markers in Water Flushed from Riverbank Soils

Sewer overflows and exfiltration can potentially contaminate water bodies with pathogens from wastewater. Microbial source tracking (MST) methods such as the detection of the HF183 gene target of Bacteroides have been proposed to monitor human fecal pollution inputs to surface waters; however, the persistence of HF183 and other MST markers in water flushed from soils after contamination events is not well understood. In this study, the persistence and decay of two culture-based fecal indicators, Escherichia coli and enterococci, and two molecular MST markers, HF183 and pepper mild mottle virus (PMMoV), were evaluated in riverbank soils spiked with untreated sewage, which were left idle for 1, 14, 28, 60, and 121 days under dark conditions and then flushed with synthetic rainwater. All four microbial indicators were still detected in flush water 4 months after the soil was contaminated. PMMoV persisted much longer and had a slower decay rate than the other microbial indicators, and E. coli degraded most rapidly. In consecutive flushing experiments with fresh (1 day) sewage-spiked soils, HF183, E. coli, and enterococci were all detected after 20 consecutive flushes with rainwater, but PMMoV was not detected after the fifth flush. Our findings indicate that water (e.g., stormwater interflow) flushing through riverbank soils that have previously been contaminated by sewer overflows or sewer exfiltration can potentially be a source of microbial pollution to surface waters, even for several months after the contamination occurs. Results from this study also demonstrate the benefits of using multiple human-associated fecal indicators to distinguish pollution from different microbial groups in water bodies.Graphical abstract

Unusual dynamical properties of disordered polaritons in microcavities

The strong light-matter interaction in microcavities gives rise to intriguing phenomena, such as cavity-mediated transport that can potentially overcome the Anderson localization. Yet, an accurate theoretical treatment is challenging as the matter (e.g.,molecules) are subject to large energetic disorder. In this article, we develop the Green's function solution to the Fano-Anderson model and use the exact analytical solution to quantify the effects of energetic disorder on the spectral and transport properties in microcavities. Starting from microscopic equation of motions, we derive an effective non-Hermitian Hamiltonian and predict a set of scaling laws: (i) The complex eigen-energies of the effective Hamiltonian exhibit an exceptional point, which leads to underdamped coherent dynamics in the weak disorder regime, where the decay rate increases with disorder, and overdamped incoherent dynamics in the strong disorder regime, where the slow decay rate decreases with disorder. (ii) The total density of states of disordered ensembles can be exactly partitioned into the cavity, bright-state and dark-state local density of states, which are determined by the complex eigen solutions and can be measured via spectroscopy. (iii) The cavity-mediated relaxation and transport dynamics are intimately related such that the energy-resolved relaxation and transport rates are proportional to the cavity local density of states. The ratio of the disorder averaged relaxation and transport rates equals the molecule number, which can be interpreted as a result of a quantum random walk. (iv) A turnover in the rates as a function of disorder or molecule density can be explained in terms of the overlap of the disorder distribution function and the cavity local density of states. These findings reveal the significant impact of the dark states on the transport properties of disordered ensembles in cavities.

Integrated effects of the heat recovery ventilation and heat source on decay rate of indoor airborne particles: A comparative study

Given the high concentration of indoor airborne particles during the winter and their harmful effects on human health, it is of great importance to examine combined effects of the ventilation and heat source on indoor particle dispersion. The present study aims to investigate transient dispersion and deposition of indoor particles under the heat recovery ventilation (HRV). Five groups of particles with different diameters ranging from 0.1 to 10 μm were taken into account, representing the inhalable indoor airborne particles. By considering three different heating systems, including the radiator, floor heating system and fan coil, the integrated ventilation-heating effects on particle dispersion were evaluated and compared. An Eulerian-Lagrangian CFD model was developed to predict turbulent characteristics of the airflow field and unsteady particle trajectories. The role of particle size, air change rate and outdoor temperature was addressed. In addition, influence of the heat source position on the particle decay rate and removal efficiency was investigated. The results indicated that the impact of heating system on the particle decay rate is weakened by increasing the ventilation rate. Among all heating systems, the radiator renders the highest dispersion rate and the slowest decay rate, even lower than a single HRV unit. It was revealed that, for an intermediate ventilation rate, the particle deposition rate in fan coil system is 3.6 and 2.4 times faster than the radiator and floor heating systems, respectively. It was also found that displacing the radiator to the opposite side of the ventilation unit quadruplicates the removal efficiency and leads to 146% enhancement of the decay rate coefficient.

Revisting Lennard Jones, Morse, and N-M potentials for metals

A significant source of error was found in the paper by Zhen and Davies which is highly cited for use in calculating Lennard Jones N-M potential parameters. This error was corrected for and a new more easily implemented method for determining N-M parameters was developed. N-M parameters for 38 metallic elements were calculated using this new method in addition to Morse and Lennard Jones 6-12 parameters. Molecular dynamics simulations were carried out to illustrate the increased accuracy of the new parameters. The predicted bulk modulus of silver using Zhen and Davies parameters was off by approximately 40%, while the bulk modulus calculated using the parameters generated in this study was within 2% of the experimental value. Finally, a discussion on the limitations of each potential type for describing different metallic systems is presented. In particular, the overly slow decay rate of the N-M potential with distance is addressed for small values of parameter “m”.

Quiet zone generation in an acoustic free field using multiple parametric array loudspeakers.

This paper investigates the feasibility of remotely generating a quiet zone in an acoustic free field using multiple parametric array loudspeakers (PALs). A primary sound field is simulated using point monopoles located randomly in a two-dimensional plane, or three-dimensional (3D) space, whereas the secondary sound field is generated by multiple PALs uniformly distributed around the circumference of a circle sitting on the same plane as the primary sources, or on the surface of a sphere for 3D space. A quiet zone size is defined as the diameter of the maximal circular zone within which the noise reduction is greater than 10 dB. The size of this quiet zone is found to be proportional to 0.19λN for N secondary sources with a wavelength λ when the primary and secondary sources are in the same plane, whereas it is found to be 0.55λN1/2 for the 3D case. The size of the quiet zones generated by PALs is similar to that observed with traditional omnidirectional loudspeakers; however, the effects of using PALs on the sound field outside the target zone is much smaller due to their sharp radiation directivity and slow decay rate along the propagation distance. Experimental results are also presented to validate these numerical simulations.

The mechanism of intramolecular halogen bonding enhanced the quantum efficiency of ultralong organic phosphorescence in the aggregated state.

Ultralong organic phosphorescence (UOP) has broad application prospects in many fields, but realizing its high quantum efficiency is still full of challenges. One of the main reasons is that the internal luminescence mechanism is unclear and theoretical investigations to reveal the inner structure-property relationship are highly desired. Herein, the internal mechanism of halogen bonding enhancing the quantum efficiency of UOP is studied through the combination of quantum mechanics and molecular mechanics methods coupled with the thermal vibration correlation function (TVCF) method. Geometric and electronic data are obtained by density functional theory (DFT) and time-dependent density functional theory (TD-DFT) calculations. Transition properties, energy gaps, intermolecular interactions, excited state dynamics as well as Huang-Rhys factors and reorganization energies are analyzed in detail. The results show that the high phosphorescence quantum efficiency benefits from the fast intersystem crossing (ISC) process and the slow non-radiative decay process. The halogen bonding, which cooperates with the effects of aromatic carbonyl and heavy atoms, not only accelerates the ISC rate by increasing the spin-orbit coupling effect, but also restricts the molecular motion and reduces the non-radiative energy consumption. Furthermore, through wise molecular design, an efficient UOP molecule with fast ISC and slow non-radiative decay rates is proposed. This work provides an insight into realizing efficient UOP emission via intramolecular halogen bonding.

Dynamics of latent HIV under clonal expansion.

The HIV latent reservoir exhibits slow decay on antiretroviral therapy (ART), impacted by homeostatic proliferation and activation. How these processes contribute to the total dynamic while also producing the observed profile of sampled latent clone sizes is unclear. An agent-based model was developed that tracks individual latent clones, incorporating homeostatic proliferation of cells and activation of clones. The model was calibrated to produce observed latent reservoir dynamics as well as observed clonal size profiles. Simulations were compared to previously published latent HIV integration data from 5 adults and 3 children. The model simulations reproduced reservoir dynamics as well as generating residual plasma viremia levels (pVL) consistent with observations on ART. Over 382 Latin Hypercube Sample simulations, the median latent reservoir grew by only 0.3 log10 over the 10 years prior to ART initiation, after which time it decreased with a half-life of 15 years, despite number of clones decreasing at a faster rate. Activation produced a maximum size of genetically intact clones of around one million cells. The individual simulation that best reproduced the sampled clone profile, produced a reservoir that decayed with a 13.9 year half-life and where pVL, produced mainly from proliferation, decayed with a half-life of 10.8 years. These slow decay rates were achieved with mean cell life-spans of only 14.2 months, due to expansion of the reservoir through proliferation and activation. Although the reservoir decayed on ART, a number of clones increased in size more than 4,000-fold. While small sampled clones may have expanded through proliferation, the large sizes exclusively arose from activation. Simulations where homeostatic proliferation contributed more to pVL than activation, produced pVL that was less variable over time and exhibited fewer viral blips. While homeostatic proliferation adds to the latent reservoir, activation can both add and remove latent cells. Latent activation can produce large clones, where these may have been seeded much earlier than when first sampled. Elimination of the reservoir is complicated by expanding clones whose dynamic differ considerably to that of the entire reservoir.

Sharp Decay Rates for Localized Perturbations to the Critical Front in the Ginzburg–Landau Equation

We revisit the nonlinear stability of the critical invasion front in the Ginzburg–Landau equation. Our main result shows that the amplitude of localized perturbations decays with rate \(t^{-3/2}\), while the phase decays diffusively. We thereby refine earlier work of Bricmont and Kupiainen as well as Eckmann and Wayne, who separately established nonlinear stability but with slower decay rates. On a technical level, we rely on sharp linear estimates obtained through analysis of the resolvent near the essential spectrum via a far-field/core decomposition which is well suited to accurately describing the dynamics of separate neutrally stable modes arising from far-field behavior on the left and right.

Overcoming the Rate-Directionality Trade-off: A Room-Temperature Ultrabright Quantum Light Source.

Deterministic GHz-rate single photon sources at room temperature would be essential components for various quantum applications. However, both the slow intrinsic decay rate and the omnidirectional emission of typical quantum emitters are two obstacles toward achieving such a goal which are hard to overcome simultaneously. Here, we solve this challenge by a hybrid approach using a complex monolithic photonic resonator constructed of a gold nanocone responsible for the rate enhancement, enclosed by a circular Bragg antenna for emission directionality. A repeatable process accurately binds quantum dots to the tip of the antenna-embedded nanocone. As a result, we achieve simultaneous 20-fold emission rate enhancement and record-high directionality leading to an increase in the observed brightness by a factor as large as 800 (130) into an NA = 0.22(0.5). We project that these miniaturized on-chip devices can reach photon rates approaching 1.4 × 108 photons/s and pure single photon rates of >107 photons/second after temporal purification processes, thus enabling ultrafast light-matter interfaces for quantum technologies at ambient conditions.

Probing Many-Body Systems near Spectral Degeneracies

The diagonal elements of the time correlation matrix are used to probe closed quantum systems that are measured at random times. This enables us to extract two distinct parts of the quantum evolution, a recurrent part and an exponentially decaying part. This separation is strongly affected when spectral degeneracies occur, for instance, in the presence of spontaneous symmetry breaking. Moreover, the slowest decay rate is determined by the smallest energy level spacing, and this decay rate diverges at the spectral degeneracies. Probing the quantum evolution with the diagonal elements of the time correlation matrix is discussed as a general concept and tested in the case of a bosonic Josephson junction. It reveals for the latter characteristic properties at the transition to Hilbert-space localization.

Nano-confined synthesis of multi yolk-shell Co-NC@N-HCSs hybrid as sulfur host for high performance lithium-sulfur batteries

Lithium-sulfur (Li-S) battery has been considered as one promising rechargeable battery with ultrahigh theoretical energy density. However, its practical application is mainly hindered by volume expansion during cycling and irreversible shuttle effect of soluble lithium polysulfides (LiPSs). Herein, we reported a rational design and fabrication of multi yolk-shell Co-NC@ nitrogen doped hollow carbon spheres (Co-NC@N-HCSs) as sulfur host for high performance Li-S batteries via a nano-confined synthesis strategy. The growth mechanism of multi yolk-shell ZIF-67s@N-HCSs nanostructure was studied and the ZIF-67 yolks were tunable by changing the reactant concentration. Regarding to multi yolk-shell Co-NC@N-HCSs hybrid, the nitrogen doped carbon shell provides effective physical confinement, abundant sulfur loading space and volume expansion alleviation, while the multi polar Co-NC yolks can enhance the internal electron conductivity inside the cavity and offer stronger chemisorption capability for LiPSs as well as catalytic effects on the redox reaction of LiPSs. Benefiting from the unique multi yolk-shell design, the S/Co-NC@N-HCSs electrode with sulfur content of 80.82 wt%, exhibits high discharge capacity of 1173 mAh g−1 at 0.1C and 995.8 mAh g−1 at 1C. It also shows long cycle life up to 450 cycles with a slow capacity decay rate of 0.13% per cycle. The electrochemical performance of S/Co-NC@N-HCSs is obviously promoted compared with S/N-HCSs, suggesting its potential to develop high performance lithium sulfur batteries.

Graphene oxide-wrapped cobalt-doped oxygen-deficient titanium dioxide hollow spheres clusters as efficient sulfur immobilizers for lithium-sulfur batteries

The design of efficient sulfur host material is of great importance to address the undesirable polysulfide shuttling effect in the lithium-sulfur battery. Herein, we designed and constructed a sulfur immobilizer with multi-level sulfur storage space, which consists of the cluster of Co@TiO2 hollow spheres tightly wrapped by graphene oxide (labeled as Co@TiO2/GO). This structure provided a multi-level sulfur storage space, that is, the sulfur was encapsulated in the cavity of the Co@TiO2 hollow spheres, between Co@TiO2 spheres and GO sheets and in the interlaminar pores of GO. This enabled the inner and outer surfaces of the Co@TiO2 hollow spheres to better participate in the conversion reaction of lithium polysulfides (LPS). Moreover, the incorporated Co nanoparticles and abundance of oxygen vacancies effectively captured LPS and boosted their redox reaction kinetics. Therefore, this multi-level sulfur storage space is very beneficial to the storage and blockade of polysulfides and the improvement of the energy storage performance of the lithium-sulfur battery. Due to these beneficial structural features, the initial discharge capacity of Co@TiO2/GO/S cathode reached 807 mAh g−1 at 1C with a slow decay rate of 0.053% per cycle for 500 cycles, and high rate performance with a capacity of 552 mAh g−1 at 5C.