Changes In Spectra Research Articles

Comparing the effects of pristine and UV–VIS aged microplastics: Behavioural response of model terrestrial and freshwater crustaceans

Physico-chemical properties of microplastics (MPs) change during weathering in the environment. There is a lack of knowledge about the effects of such environmentally relevant MPs on organisms. We investigated: 1) the physico-chemical changes of MPs due to UV–VIS weathering, and 2) compared the effect of pristine and aged MPs on the behaviour of the water flea Daphnia magna and terrestrial crustacean Porcellio scaber. Dry powders of MPs were produced from widely used polymer types: disposable three-layer polypropylene (PP) medical masks (inner, middle and outer), polyester textile fibres, car tires and low-density polyethylene (LDPE) bags and were subjected to accelerated ultraviolet–visible (UV–VIS) ageing. Our results show that the extent of transformation depends on the type of polymer, with PP showing the most changes, followed by LDPE, textile fibres and tire particles. Obvious fragmentation was observed in PP and textile fibres. In the case of PP, but not polyester textile fibres, changes in FTIR spectra and surface properties were observed. Tire particles and LDPE did not change in size, but clear changes were observed in their FTIR spectra. Most MPs, aged and pristine, did not affect the swimming of daphnids. The only effect observed was a significant increase in path length and swimming speed for the pristine tire particles when the recording was done with particles remaining in the wells. After transfer to a clean medium, this effect was no longer present, suggesting a physical rather than chemical effect. Similarly, woodlice showed no significant avoidance response to the MPs tested, although there was a noticeable trend to avoid soils contaminated with pristine polyester textile fibers and preference towards the soils contaminated with aged MP of the middle mask layer. Overall, the apparent changes in physico-chemical properties of MPs after accelerated ageing were not reflected in their effects on woodlice and daphnids.

Fluorescence of Intrinsic Milk Chromophores as a Novel Verification Method of UV-C Treatment of Milk.

The European Food Safety Authority (EFSA) has approved the use of a 1045 J/L UV-C dose as an adjunct to pasteurization to increase the shelf life and vitamin D3 content of milk. However, there are no verification methods analogous to the alkaline phosphatase test for pasteurized milk to ensure that the desired UV-C dose has been correctly applied. The aim is to develop a real-time in-line detector based on fluorescence spectroscopy. In this study, 22 different UV-C doses (ranging from 0 to 2000 J/L) were applied to milk to assess the impact of photooxidation on intrinsic photosensitive chromophores. Fluorescence spectroscopy (90°-angle) was employed as the method of analysis for monitoring the changes in the fluorescence spectra of chromophores in milk without sample pretreatment. Three important chromophore areas (CAs) were identified: CA 1 (riboflavin), CA 3 (vitamin A and dityrosine) and CA 4 (tryptophan), with statistically significant changes at around 1045 J/L and 1500 J/L. The findings of our preliminary study support our hypothesis that the fluorescence of intrinsic chromophores can be used as verification of the applied UV-C dose.

Isomerization, Protonation, and Hydrolysis Properties of Naphthalimide-Containing Spiropyran in Aqueous Media.

Synthesis of spiropyrans exhibiting ring-opening/closing isomerization driven by external stimuli is a challenging subject for the development of molecular sensors. A napthalimide-containing spiropyran (1) promotes rapid isomerization between the spirocyclic (SP) form and ring-opened merocyanine (MC) form by the change in solvent polarity even under the dark condition at room temperature. In this work, the effect of water on the isomerization behavior of 1 was studied. The addition of water caused an MC-water H-bonding interaction and shifted the resonance MC structure to the zwitterionic form with a lower ground-state energy. The stabilized MC form promoted spontaneous SP → MC isomerization and increased the equilibrium MC concentration. The effect of pH on the behavior of 1 was also studied. In acidic-neutral media, protonation/deprotonation of the naphthalimide moiety led to rapid and reversible changes in the absorption spectra. In contrast, strongly basic media (pH > 12) promoted irreversible base-catalyzed hydrolysis of the alkene moiety.

Intramolecular hydrogen bonding steered optical recognition of fluoride ion and consequent opto-chemical logic responses: Spectroscopic and computational studies

This work demonstrates the synthesis and characterization of a thiosemicarbazide core containing Schiff base molecule (MNHC) and its use as a chemosensor for the selective, ratiometric, and colorimetric detection of fluoride ions. The study reveals that in the presence of F− ions, MNHC displays a ratiometric change of absorption maxima at two different wavelengths (432 and 330 nm). MNHC involves an intramolecular hydrogen bonding initiating the possibility of keto-enol tautomerism which is thoroughly investigated by DFT study. Interestingly, the intramolecular hydrogen bonding enhances the acidity of the –NH proton and consequently the –NH center becomes more labile for F− ions binding over the other –NH proton. This fact is confirmed by 1H NMR study. Remarkably, F− ion forms intermolecular hydrogen bonding with the –NH moiety disrupting the intramolecular hydrogen bonding. The changes in absorption spectra in the presence of F− ions occur due to the intermolecular hydrogen bonding-assisted abstraction of the –NH proton. On the other hand, when H2O is added to the MNHC-F− composite, the spectroscopic signature of free MNHC is completely regenerated due to the transfer of proton from H2O to the nitrogen center of MNHC. In addition, 1:1 binding stoichiometry and 53.7 μM detection limit for fluoride ion are also confirmed. Moreover, utilizing these spectroscopic responses, different kinds of important opto-chemical logic gates like YES, NOT, PASS 0, PASS 1, INHIBIT, TRANSFER, and IMPLICATION are developed. Moreover, the F− ion-assisted competitive nature between the intramolecular vs intermolecular hydrogen bonding is thoroughly explored by substantial DFT study.

Mechanochemical Polyoxometalate Super-Reduction with Lithium Metal.

In this first systematic investigation of mechanochemical polyoxometalate (POM) reduction, (TBA)3[PMo12O40] was reacted with n equiv of lithium metal (n = 1-24) to generate PMo12/n products which were shown to be mixtures of electron-rich PMo12Lix species. FTIR analysis revealed the lengthening/weakening of terminal Mo═O bonds with increasing levels of reduction, while EXAFS spectra indicated the onset of Mo-Mo bond formation at n ∼ 8 and a significant structural change at n > 12. Successive MoVI reductions were monitored by XANES and XPS, and at n = 24, results were consistent with the formation of at least one MoIV-MoIV bonded {MoIV3} triad together with MoV. Upon dissolution, the PMo12Lix species present in the solid PMo12/n products undergo electron exchange and single-peak 31P NMR spectra were observed for n = 1-12. For n ≥ 16, changes in solid state and solution 31P NMR spectra coincided with the emergence of features in the UV-vis spectra associated with MoV-MoV and {MoIV3} bonding in an ε-Keggin structure. Bonding between {Li(NCMe)}+ and 2-electron-reduced PMo12 in (TBA)4[PMo12O40{Li(NCMe)}] suggests that super-reduction gives rise to more extensive Li-O bonding that ultimately causes lithium-oxide-promoted TBA cation decomposition and POM degradation, which might explain the appearance of XPS peaks for Mo2C at n ≥ 16. This work has revealed some of the complex, unexplored chemistry of super-reduced POMs and establishes a new, solvent-free approach in the search for a better fundamental understanding of the electronic properties and reactivity of electron-rich nanoscale metal oxides.

Strong and pH dependent fluorescence in unprecedented anthra[2,3-d]imidazole derivatives

We here report the synthesis and characterization of three new molecules based on an unprecedented anthra [2,3-d]imidazole unit. The new heterocycle was unexpectedly formed while attempting to obtain 2,3-diacetamidoanthracene by reducing the corresponding anthraquinone molecules by sodium borohydride. The same reaction was successfully performed using two further different 2,3-diamidoanthraquinone derivatives, thus confirming its generality. The chemical identity of the novel molecules was also proved by realizing single crystals suitable for XRD diffraction and solving the crystalline structure of one of the prepared systems. All the molecules are strong blue emitters in ethanol, with fluorescence quantum yields around 0.40. Because of the acid-base properties of anthraimidazole ring, the optical response was investigated at different pH values. While slight differences were observed in acidic conditions, in the alkaline pH range we observed a dramatic change of the fluorescence spectra in a narrow pH range (from 11 to 13), with the color of the emission turning from blue to green. This feature makes the new class of derivatives here reported very promising as pH sensors working in strongly alkaline conditions.

Effect of cap layer and post growth on-site hydride passivation on the surface and interface quality of InAsP/InP hetero and QW structures

The performance of devices made from III-V compound semiconductors relies heavily on their surface and interface properties. The InAsP/InP material system is recently gaining interest due to its suitability for the next generation of long-haul classical and quantum communication applications. Researchers are studying how surface and interface properties affect the efficiency of the device and concludes that the epitaxial growth conditions responsible for creating surface and interface states require further improvement. To address this, we have studied the effect of the top (cap) layer and post-growth on-site hydride passivation on the properties of InAsP/InP hetero-structures grown using metal-organic vapor phase epitaxy technique. The flow rate and flux ratios of the hydrides significantly affect the surface reaction rates and gas-phase diffusion coefficients, which in turn impact the As↔P exchange mechanisms. Our findings suggest that post-growth on-site arsine passivation encourages the As↔P substitutions at the vicinity of the desorption sites of phosphorus, leading to the arsenic-rich surface of InAsP with the diffused hetero-interfaces. The activation energy for such As↔P exchange reaction mechanism is evaluated as ∼ (1.4 ± 0.3) eV. On the other hand, it has been observed that the thin cap layer of InP protects the surface of the InAsP epilayer and thereby preserving the sharp interface. Further, surface photovoltage and photoluminescence spectroscopy is employed to examine the role of the diffused and sharp interface of InAsP/InP hetero-structures in charge carrier transport, their redistribution and recombination process. Our analysis of the energy transitions occurring in the surface photovoltage and photoluminescence spectrum reveal that the energy band alignment and the subsequent charge carrier redistribution processes is influenced by the surface and interface states. These changes in the surface photovoltage phase spectra of InAsP/InP system also support the role of surface and interface states in the generation and separation of the charge carriers. The study provides insights into the effects of As↔P exchange on surface and interfacial quality, highlighting the implications for optoelectronic device development using InAsP/InP material system.

Characterization of neutron spectrum of polyethylene-moderated AmBe neutron source using a passive single-cylindrical neutron spectrometer

The changes in the neutron spectrum produced by the AmBe neutron source moderated in the polyethylene sphere need to be characterized. A passive single-moderator neutron spectrometer with indium foil activation neutron detector has been developed to characterize the neutron spectrum of an AmBe source inside a polyethylene sphere. The detector response function was calculated using the MCNPX 2.7 program with IRDFF-II nuclear data library. Measurements were conducted by placing the Single-Cylindrical Neutron Spectrometer (SCNS) on the outer surface of the sphere for 5 h. The 116mIn activity due to neutron activation in each indium foil was measured using a gamma spectrometer with an HPGe detector. By identifying the count value at the peak energy of 1294 KeV and considering an HPGe detector efficiency of 3.2% at the foil position 1 mm above the detector surface, the activity of 116mIn was obtained. The activity value of 116mIn from each indium foil was compared with the MCNPX simulation results. The neutron spectrum was unfolded using the UMG 3.3 program with activity data input of 116mIn for each foil and detector response. A neutron spectrum was obtained with a total neutron flux of 634 ± 60 n/cm2·s, consisting of 25% thermal neutrons, 16% epithermal neutrons, and 61% fast neutrons. When compared with the simulation results, the total neutron flux in the spectrum produced by SCNS-In showed only a small difference of 1%. Based on these neutron spectrum measurements, it was determined that placing the AmBe neutron source inside a 15″ diameter PE-sphere will reduce the fast neutron flux by 78%.

Determination of singlet oxygen quantum yield based on the behavior of solvent dimethyl sulfoxide oxidation by singlet oxygen

BackgroundPhotodynamic therapy (PDT) is emerging as a promising cancer treatment. The PDT efficacy is primarily attributed to the generation of singlet oxygen (1O2), stemming from the integrated effects of the photosensitizer, oxygen, and light. The singlet oxygen quantum yield (ΦΔ) serves as a bridge that links these parameters to the overall efficacy of PDT. The near-infrared luminescence of 1O2 provides a direct way for determining ΦΔ, but suffers from a poor signal-to-noise ratio. While the chemical trap probe method is detection-friendly, but it has a strict requirement for the excitation wavelength. Therefore, the existing methods for ΦΔ measurement are insufficient. ResultsIn this work, we developed an approach to determine ΦΔ of a broader range of photosensitizers using only the commonly used solvent dimethyl sulfoxide (DMSO), which can be oxidized by 1O2 to dimethyl sulfone. This method establishes the relationship between 1O2 production and changes in DMSO absorption spectra, eliminating the need for additional chemical probes. This method was validated by measuring the ΦΔ of rose bengal (RB) through systematic changes in absorption spectrum of DMSO under various RB concentrations and different excitation light power densities. Moreover, the ΦΔ of hematoporphyrin monomethyl ether (HMME), as determined by this method, is consistent with measurements obtained using the 1,3-diphenylisobenzofuran (DPBF) trapping probe. This consistency further validates the reliability of this method. Significance and noveltyThis work presents a direct, probe-free method to determine ΦΔ, reducing potential interference and expanding the range of useable excitation wavelengths. Its ability to measure ΦΔ using only DMSO enhances the accuracy of photosensitizer measurement, and broadens the applicability of the method to a wide range of samples, thereby advancing research on the properties of photosensitizers and further promoting the development of PDT.

A new dual-functional strategy to desensitize and sense the explosive and toxic 1,3,5-trinitro-1,3,5-triazinane by cyclo[n]carbons (n = 10,14,18).

In this work, in order to find new strategy to solve the safe problem of one famous high energy compound 1,3,5-trinitro-1,3,5-triazinane (RDX) under the impact and static electricity environment, cyclo[n]carbons (n = 10, C10; n = 14, C14; n = 18, C18) were employed to construct novel energetic composites (RDX@C10, RDX@C14, RDX@C18) with RDX for the first time. The investigated results showed that C10, C14 and C18 all can form stable composites with RDX through a exothermal process. Three cyclo[n]carbons could not only decrease the impact sensitivity of RDX by decreasing the positive ESP values and transferring the HPV region. But also could reduce the electrostatic sensitivity greatly by decreasing the energy gap, increasing the EHOMO and controlling the active electron-induced process and reaction. Among them, the desensitization effect by C18 and C14 was found to be much better than C10. In addition, three cyclo[n]carbons may be used as new sensors for the detection of RDX, due to the fast recovery time under different lights, and great change in the UV-Vis spectrum. These improvements may provide valuable insights for enhancing the safe performance of high energy compounds with similar structures to RDX, and broaden the application sphere of cyclo[n]carbons. All of the calculations on the structures were carried out by using the Gaussian 09 software at the M06-2X/6-311G(d,p) level. In addition, further calculations on the properties and interactions were performed by using the Multiwfn software.

Multiband electromagnetically induced transparency-like on metamaterials

In recent years, the electromagnetically induced transparency-like (EIT-like) of metamaterials has been widely concerned due to obtain high Q, which has potential applications in the field of sensing and slow light. In this paper, an EIT-like metamaterial structure in the microwave band was investigated, which can realize to multi-band EIT-like phenomena. The equivalent circuit method and the electric field distribution are used to study the EIT -like effect’ mechanism, and the multi-band EIT-like phenomenon is discussed by analyzing its structural parameters. The results show that the multi-band EIT in the proposed structure is obtained by coupling multiple bright modes to multiple dark modes. The change of transmission spectrum is discussed by changing the environmental permittivity. The results have potential applications in areas such as refractive index sensing, filters.

Acoustic emission spectrum characteristics of structural coal destruction in negative pressure environment

Abstract The uniaxial compression experiments under a low-pressure environment were performed by using structural coal samples. The frequency domain response characteristics of coal mass failure under loading in a low-pressure environment were acquired by FFT transformation and wavelet packet decomposition. The results show: As the loading stress of coal increases, the AE spectrum becomes more abundant, and the whole AE spectrum shows a left-shift trend. When the gas pressure increases, the acoustic emission signals change from low-frequency high-energy to high-frequency low-energy, the frequency band gradually narrates, and the spectrum changes from complex multi-peak shape to single-peak shape. As stress increases, the proportion of energy in the band 0-4.38 kHz gradually increases, while that in other bands gradually decreases. The energy response to stress changes in the two frequency bands of 2.92-4.38 kHz and 4.38-5.84 kHz is the most obvious. When the pressure changes, the energy in three frequency bands of 2.92-4.38 kHz, 4.38-5.84 kHz, and 7.3-8.76 kHz present an evident response trend with the pressure change, and the response trend (increase) of the latter two is exactly opposite (decrease) to that of the former. This phenomenon indicates that 2.92-4.38 kHz and 4.38-5.84 kHz are the characteristic frequency bands of the coal fracture process. The findings of this research offer crucial foundational data to support the monitoring and early warning of coal and gas outburst hazards.

Nitrogen mustard induces dynamic nuclear protein spectrum change and DNA-protein crosslinking, with p97 mediating repair

Nitrogen mustard (NM) is a chemotherapeutic agent capable of alkylating nucleophilic proteins and DNA, causing severe cell damage. However, no reports have been on the dynamic changes in proteomics induced by NM. In this study, we established a model of acute exposure to NM for 1 h and a continuous cultured model for 24 h after NM removal (repair stage) using 16HBE cells. The nuclear protein spectrum and nuclear proteins crosslinked with DNA were analyzed, and the function of p97 during NM damage was examined. An hour of NM exposure resulted in severe changes in the nuclear protein spectrum and protein into the cell nucleus, which is mainly involved in nuclear acid-related issues. After 24 h, the return to normal process of the types and amounts of differentially expressed proteins was inhibited by si-p97. The main processes involved in si-p97 intervention were nucleocytoplasmic transport, processing in the endoplasmic reticulum, metabolic abnormalities, and DNA-response; however. An hour of exposure to NM increased DNA-protein crosslinking (DPC), total-H2AX, and p-H2AX. In contrast, si-p97 only further increased or maintained their levels at 24 h yet not at 1 h. The effect of the proteasome inhibitor, MG132, was similar to that of si-p97. The siRNA of DVC1, a partner of p97, also increased the DPC content. Both si-p97 and si-DVC1 increased the cytoplasmic levels of the proteasome (PSMD2). These results suggest acute NM exposure induces severe nuclear protein spectral changes, rapid protein influx into the nucleus, DPC formation, and DNA double-strand breaks. Furthermore, our data indicated that p97 is involved in normal protein spectrum maintenance and DPC removal after NM withdrawal, requiring the participation of DVC1 and the proteasome.

Influence of N2 admixture on mode transition of discharge in N2–Ar helicon plasma

Effects of N2 admixture on multiple wave modes and transitions were investigated in N2–Ar helicon plasma under fixed input power and magnetic field. The structures of helicon waves were measured by a B-dot probe to verify the different eigenmodes. The experimental results show that the plasma morphology, emission spectrum, and spatial profile change significantly during mode transitions with the N2–Ar ratio. The calculated results from the pressure balance model indicate that the densities of species N2, N+, Ar, and Ar+ will change largely during mode transition around some specific N2 percentages, which will help to improve the application of N2–Ar helicon plasma in material processing greatly.

Noise and flow characteristics of variable backwards- and forward-facing steps and gaps in laminar boundary layer

The noise and flow characteristics of combined backwards-facing and forward-facing steps (BFS and FFS) are experimentally investigated in an acoustic wind tunnel using a far-field microphone array and Particle Image Velocimetry (PIV), respectively. The step models considered have a step height H of 10∼40 mm and a step gap L of 10∼100 mm, and the Reynolds number is ( Re H=) 2.1 × 105∼1.1 × 106. The incoming flow boundary layer is laminar, and the step height is approximately 3∼28 of the boundary layer thickness. The results show that the noise is closely related to the step type, step height H and the gap L. In the step-only configuration, the BFS noise does not vary with the step height H 1 and is much lower than the FFS noise, of which the sound pressure level depends on U 0 5.8∼ U 0 6.2 within the height range H 2. As for the combined step model (BFS&FFS), the noise spectrum changes significantly with the step heights and gaps. When H 1> H 2, the noise spectrum resembles the BFS-only due to the flow shield of the FFS from the upstream BFS. When H 1< H 2, the noise spectrum is dominated by the FFS, especially at higher H 2 or longer gap L due to more face area of the FFS exposed to the incoming flow. As H 1= H 2, the noise resembles the BFS in the low-frequency range and the FFS at high frequencies, respectively. Generally, the step-only and BFS&FFS have broadband noise characteristics, except when the ratio L/H is small, the noise spectrum has the characteristics of a typical cavity dominated by tonal peaks.

Correlation between disease severity indices and quality of life measurement tools in atopic dermatitis patients

Reports regarding the correlation and effect size of change of the full spectrum of quality of life and disease severity measures applied in-person to patients with atopic dermatitis are scarce. To assess quality-of-life with 3 different instruments and to evaluate disease severity indices and to determine their correlation and effect size of change between two measurements. Patient-level data were obtained through two in-person visits. Sociodemographic information and data related to disease distribution, severity (through the BSA, EASI, SCORAD, POEM, and itching scales), and the impact of atopic dermatitis on quality of life using the DLQI and Skindex-29, and EQ-5D, were assessed. The correlation between change in quality-of-life scores and disease severity scores in addition to the standardized effect size were also evaluated. Only 139 out of 212 patients completed the follow-up visit. BSA highly correlated with SCORAD and EASI, and the lowest correlation was found with POEM. The best correlation of pruritus VAS was found with sleep disturbance. The SCORAD score highly correlated with EASI, and the lowest correlation was found with POEM. The magnitude of the effect at initiation of the study vs follow-up was in average moderate to important. Patients with atopic dermatitis experience a substantial burden on quality of life. Disease activity correlates better with quality-of-life measurements when the disease is less severe after starting therapy. POEM and Skindex-29 seem to be optimal to determine disease severity and quality of life in adults with atopic dermatitis.

Diameter Optimization of No-Core Fiber for High Refractive Index Sensing

This study presents a simulation-based modal analysis to optimize the no-core fiber (NCF) sensor design for high refractive index (HRI) applications. The goal is to improve the sensitivity of the sensor towards HRI by solving problems in conventional optical fiber sensors (OFS), such as sophisticated fabrication methods, high fragility, and potential effects on long-term reliability. Furthermore, in previous work, most OFS applications focused on detecting mediums with a low refractive index (LRI). Hence, the goal of this study is to overcome these constraints. For this research, the Wave Optics module in COMSOL Multiphysics® software was used to optimize the NCF diameter, which ranged from 100 μm to 150 μm. Simulations include changes in the refractive index (RI) of the analyte in the surrounding medium of the sensor to analyse the efficiency of the NCF in HRI sensing completely, ranging from 1.46 RIU to 1.56 RIU. The performance is then assessed by monitoring the intensity change in the power spectrum, which reflects the reaction of leaky modes to various HRI conditions. The findings indicate that decreasing the size of the NCF sensor enhances sensitivity in detecting HRI mediums by amplifying the leakage loss of each order leaky mode, as opposed to a larger NCF diameter. This effect is due to the reduced confinement of modes in a smaller diameter NCF. The 100 μm diameter NCF has exceptional refractive index (RI) sensitivity and linearity, measuring 88.996 dB/RIU and 0.7783, respectively. Accordingly, NCF proves to be a promising candidate for utilization in HRI sensing applications, given its high sensitivity and straightforward fabrication, making it easily implementable and practical for real-world use.

Conformational Changes in DNA and Protein Biomolecules in Pathogenesis of Ischemic Stroke.

Conformational changes in DNA and protein biomolecules were studied in ischemic stroke (IS) cases varying severity by Raman spectroscopy. The conformational structure of hematoporphyrin was found to change in IS patients, leading to a higher (I1355/I1550)/(I1375/I1580) ratio (hemoglobin affinity of for ligands) and an increase in I1375/I1172 (a change in pyrrole conformation). Changes in genomic DNA spectra were observed at frequencies caused by stretching vibrations of primary amines (3400 cm-1), secondary amines and hydroxyls involved in hydrogen bonding (3100 cm-1), and CH2 groups of sugar phosphates (2900 cm-1) and vibrations of vibrational bonds between nitrogenous bases and sugars (1400 cm-1). The significant changes observed in genomic DNA and hemoglobin spectra were assumed to indicate conformational rearrangements of the molecules in IS. Severe IS was associated with maximum changes in DNA and hemoglobin spectra.

Probing collectivity in heavy-ion collisions with fluctuations of the pT spectrum

Event-by-event fluctuations in the initial stages of ultrarelativistic nucleus-nucleus collisions depend little on rapidity. The hydrodynamic expansion which occurs in later stages then gives rise to correlations among outgoing particles which depend weakly on their relative rapidity. Azimuthal correlations, through which anisotropic flow (vn(pT)) is defined, have been the most studied. Here we study a new observable introduced in 2020 by Schenke, Shen and Teaney and dubbed v0(pT), which quantifies the relative change in the pT spectrum induced by a fluctuation. We describe how it can be measured. Using hydrodynamic simulations, we make quantitative predictions for v0(pT) of charged and identified hadrons. We then discuss how v0(pT) relates to two phenomena which have been measured: The increase of the mean transverse momentum in ultracentral collisions, and the event-by-event fluctuations of the transverse momentum per particle [pT]. We show that v0(pT) determines the dependence of these quantities on the pT cuts implemented in the analysis. We quantitatively explain the rise of σpT observed by ATLAS as the upper pT-cut is increased from 2 to 5 GeV/c.

Polarized and Evanescent Guided Wave Surface-Enhanced Raman Spectroscopy of Ligand Interactions on a Plasmonic Nanoparticle Optical Chemical Bench.

This study examined applications of polarized evanescent guided wave surface-enhanced Raman spectroscopy to determine the binding and orientation of small molecules and ligand-modified nanoparticles, and the relevance of this technique to lab-on-a-chip, surface plasmon polariton and other types of field enhancement techniques relevant to Raman biosensing. A simplified tutorial on guided-wave Raman spectroscopy is provided that introduces the notion of plasmonic nanoparticle field enhancements to magnify the otherwise weak TE- and TM-polarized evanescent fields for Raman scattering on a simple plasmonic nanoparticle slab waveguide substrate. The waveguide construct is called an optical chemical bench (OCB) to emphasize its adaptability to different kinds of surface chemistries that can be envisaged to prepare optical biosensors. The OCB forms a complete spectroscopy platform when integrated into a custom-built Raman spectrograph. Plasmonic enhancement of the evanescent field is achieved by attaching porous carpets of Au@Ag core shell nanoparticles to the surface of a multi-mode glass waveguide substrate. We calibrated the OCB by establishing the dependence of SER spectra of adsorbed 4-mercaptopyridine and 4-aminobenzoic acid on the TE/TM polarization state of the evanescent field. We contrasted the OCB construct with more elaborate photonic chip devices that also benefit from enhanced evanescent fields, but without the use of plasmonics. We assemble hierarchies of matter to show that the OCB can resolve the binding of Fe2+ ions from water at the nanoscale interface of the OCB by following the changes in the SER spectra of 4MPy as it coordinates the cation. A brief introduction to magnetoplasmonics sets the stage for a study that resolves the 4ABA ligand interface between guest magnetite nanoparticles adsorbed onto host plasmonic Au@Ag nanoparticles bound to the OCB. In some cases, the evanescent wave TM polarization was strongly attenuated, most likely due to damping by inertial charge carriers that favor optical loss for this polarization state in the presence of dense assemblies of plasmonic nanoparticles. The OCB offers an approach that provides vibrational and orientational information for (bio)sensing at interfaces that may supplement the information content of evanescent wave methods that rely on perturbations in the refractive index in the region of the evanescent wave.