Mass Difference Research Articles

Isotope fractionation of alkaline and alkaline-earth elements (Li, K, Rb, Mg, Ca, Sr, Ba) during diffusion in aqueous solutions

In this study, we used an improved “diffusion cell” method to precisely determine the diffusion-driven kinetic isotope fractionation factors of the Li, K, Rb, Mg, Ca, Sr, and Ba cations in aqueous solutions under room temperature. The obtained isotope fractionation factors (±2σ errors) are, α7/6Li = 0.996139 ± 0.000140, α41/39K = 0.998572 ± 0.000072, α87/85Rb = 0.999333 ± 0.000020, α26/24Mg = 0.999877 ± 0.000010, α44/42Ca = 0.999704 ± 0.000010, α88/86Sr = 0.999781 ± 0.000014, α138/135Ba = 0.999716 ± 0.000018. The results show that the charge of the cation and the ion-water bond length for the aquo ions are the two predominant factors affecting the mass dependence of isotope fractionation (β factor) during cation diffusion in aqueous solutions. Cations with higher charge numbers and shorter ion-water bond lengths exhibit less kinetic isotope fractionation during diffusion. Therefore, the isotope separation effect during diffusion (or β factor) in fluids is fundamentally controlled by the intensity of ion-water interaction. Weaker ion-water interaction (e.g., lower charge number, longer ion-water bond length) leads to less prominent hydrodynamic behavior for diffusing ions at the molecular level, thus more significant isotope fractionation in bulk solutions, and vice versa. Ions of larger radius would show stronger mass dependence of isotope fractionation (β factor), which can cancel the effect of decreasing relative isotope mass difference for heavier elements, thus kinetic isotope fractionation during diffusion in aqueous solutions remains prominent even for heavy elements such as Rb, Sr, and Ba. The diffusion-driven kinetic isotope fractionation factors measured in this study could provide a useful basis for interpreting specific natural isotopic variability of alkaline and alkaline-earth elements in supergene environments where chemical diffusion takes place.

Gluelump masses and mass splittings from SU(3) lattice gauge theory

We compute gluelump masses and mass differences using SU(3) lattice gauge theory. We study states with total angular momentum up to J=3, parity P=+,−, and charge conjugation C=+,−. Computations on four ensembles with rather fine lattice spacings in the range from 0.040 to 0.093 fm allow continuum extrapolations of gluelump mass differences. We complement existing results on hybrid static potentials with the obtained gluelump masses, which represent the limit of vanishing quark-antiquark separation. We also discuss the conversion of lattice gluelump masses to the renormalon subtracted scheme, which is e.g. important for studies of heavy hybrid mesons in the Born-Oppenheimer approximation. Published by the American Physical Society 2024

Hunting for Xb via hidden bottomonium decays Xb→ππχbJ

In this work, we investigate the isospin breaking decay Xb→π0χbJ and the isospin conserved decay Xb→ππχbJ, where Xb is taken to be the heavy quark flavor symmetry counterpart of X(3872) in the bottomonium sector as a B*B¯ molecule candidate. Since the mass of this state may be far below the BB¯* threshold and the mass difference between the neutral and charged bottom meson is small compared to the binding energy of the Xb, the isospin-violating decay channel Xb→π0χbJ would be highly suppressed. The calculated partial width of Xb→ππχb1 is found to be about tens of keVs, 1–2 order(s) of magnitude larger than those of Xb→ππχb2 and Xb→ππχb0. Taking into account the fact that the total width of Xb may be smaller than a few MeV like X(3872), the calculated branching ratios Xb→ππχb1 may reach to orders of 10−2, which makes it a possible channel for the experimental searching of the Xb. Published by the American Physical Society 2024

QED contributions to Ξc+−Ξc′+ mixing

We explore the quantum electrodynamic (QED) corrections to the Ξc+−Ξc′+ mixing within the framework of light-front quark model (LFQM) in the three-quark picture. After explicitly investigating the relation between the Ξc−Ξc′ mixing and the flavor SU(3) and heavy quark symmetry breaking, we derive the QED contributions to the Ξc+−Ξc′+ mixing angle. Numerical results indicate the QED contribution is smaller than the one from the mass difference between the strange and up/down quark provided by a recent lattice quantum chromodynamics analysis. Adding these contributions together we find that at this stage the Ξc+−Ξc′+ mixing is small and still incapable to account for the large SU(3) symmetry breaking in the semileptonic Ξc decays. Published by the American Physical Society 2024

Box-Behnken optimization of pin-on-disc wear test process parameters

The Full factorial and Box-Behnken Designs for determination of optimal values of wear rate using pin –on-disc wear test parameters have been successfully carried out. The parameters used are track diameter of the disc, mass difference of specimen before and after the test and speed of the disc. The mathematical model developed for the “smaller-the-better” wear rate response by the Full factorial and Box-Behnken Design methods were adjudged adequate with a pvalue of 0.025 and 0.046 respectively. Also, the adjusted R2 values of the Factorial and Box-Behnken Designs were determined to be 0.89 and 0.69 respectively. The statistical ANOVA analysis carried out on the Box-Behnken Design showed that the track diameter and the mass difference were significant with a p-value of 0.041 and 0.007 respectively. Contour plots and response surface plot developed for the factorial method and the Box-Behnken Design displayed appreciable level of similarity. It was noticed that a reduction of wear was occasioned by an increase in track diameter and speed of the disc.

The Influence of "Super-Shoes" and Foot Strike Pattern on Metabolic Cost and Joint Mechanics in Competitive Female Runners.

The objective of this study is to assess the influence of "super-shoes" on metabolic cost and joint mechanics in competitive female runners and to understand how foot strike pattern may influence the footwear effects. Eighteen competitive female runners ran four 5-min bouts on a force instrumented treadmill at 12.9 km·h -1 in 1) Nike Vaporfly Next% 2™ (SUPER) and 2) Nike Pegasus 38™ (CON) in a randomized and mirrored order. Metabolic power was improved by 4.2% ( P < 0.001; d = 0.43) and metatarsophalangeal (MTP) negative work ( P < 0.001; d = 1.22), ankle negative work ( P = 0.001; d = 0.67), and ankle positive work ( P < 0.001; d = 0.97) were all smaller when running in SUPER compared with CON. There was no correlation between foot strike pattern and the between-shoe (CON to SUPER) percentage change for metabolic power ( r = 0.093, P = 0.715). Metabolic power improved by 4.2% in "super-shoes" (but only by ~3.2% if controlling for shoe mass differences) in this cohort of competitive female runners, which is a smaller improvement than previously observed in men. The reduced mechanical demand at the MTP and ankle in "super-shoes" are consistent with previous literature and may explain or contribute to the metabolic improvements observed in "super-shoes"; however, foot strike pattern was not a moderating factor for the metabolic improvements of "super-shoes." Future studies should directly compare the metabolic response among different types of "super-shoes" between men and women.

Earths Are Not Super-Earths, Saturns Are Not Jupiters: Imprints of Pressure-bump Planet Formation on Planetary Architectures

In protoplanetary disks, sufficiently massive planets excite pressure bumps, which can then be preferred locations for forming new planet cores. We discuss how this loop may affect the architecture of multiplanet systems and compare our predictions with observations. Our main prediction is that low-mass planets and giant planets can each be divided into two subpopulations with different levels of mass uniformity. Low-mass planets that can and cannot reach the pebble isolation mass (the minimum mass required to produce a pressure bump) develop into intra-system similarity “super-Earths” and more diverse “Earths,” respectively. Gas giants that do and do not accrete envelopes quickly develop into similar “Jupiters” and more diverse “Saturns,” respectively. Super-Earths prefer to form long chains via repeated pressure-bump planet formation, while Jupiter formation is usually terminated at pairs or triplets due to dynamical instability. These predictions are broadly consistent with observations. In particular, we discover a previously overlooked mass uniformity dichotomy among the observed populations of both low-mass planets (Earths versus super-Earths) and gas giants (Saturns versus Jupiters). For low-mass planets, planets well below the pebble isolation mass (≲3 M ⊕ or ≲1.5 R ⊕ for Sun-like stars) show significantly higher intra-system pairwise mass differences than planets around the pebble isolation mass. For gas giants, the period ratios of intra-system pairs show a bimodal distribution, which can be interpreted as two subpopulations with different levels of mass uniformity. These findings suggest that pressure-bump planet formation could be an important ingredient in shaping planetary architectures.

The charge and mass symmetry breaking in the KK K¯ system

In the framework of the Faddeev equations in configuration space, we investigate the K(1460) meson as a resonant state of the KKK¯ kaonic system. We perform calculations for the particle configurations K 0 K + K − and K0K+K0¯ within two models: the ABC model, in which all three particles are distinguishable, and the AAC model when two particles are identical. The models differ in their treatment of the kaon mass difference and the attractive Coulomb force between the K + K − pair. We found that the Coulomb shift adds over 1 MeV to the three-body binding energy. The expected correction to the binding energy due to mass redistribution from AA to AB is found to be negligible, up to a maximum of 6% of the relative mass correction. At the same time, the symmetry of the wave function is distorted depending on the mass ratio value. We found that the repulsive KK interaction plays an essential role in the binding energy of the KKK¯ system and reports the mass of 1461.8 or 1464.1 MeV for the neutral K 0(1460) and 1466.5 or 1468.8 MeV for the charged K +(1460) resonances, respectively, depending on the parameter sets for KK and KK¯ interactions.

Coalescence sum rule and the electric charge- and strangeness-dependences of directed flow in heavy ion collisions

The rapidity-odd directed flows (v1) of identified hadrons are expected to follow the coalescence sum rule when the created matter is initially in parton degrees of freedom and then hadronizes through quark coalescence. A recent study has considered the v1 of produced hadrons that do not contain u or d constituent quarks. It has constructed multiple hadron sets with a small mass difference but given difference in electric charge Δq and strangeness ΔS between the two sides, where a nonzero and increasing Δv1 with Δq has been proposed to be a consequence of electromagnetic fields. In this study, we examine the consequence of coalescence sum rule on the Δv1 of the hadron sets in the absence of electromagnetic fields. We find that in general Δv1≠0 for a hadron set with nonzero Δq and/or ΔS due to potential v1 differences between u¯ and d¯ and between s and s¯ quarks. We further propose methods to extract the coefficients for the Δq- and ΔS-dependences of the direct flow difference, where a nonzero constant term would indicate the breaking of the coalescence sum rule. The extraction methods are then demonstrated with transport model results.

High-Throughput Glycan Profiling of Human Serum IgG Subclasses Using Parallel Reaction Monitoring Peptide Bond Fragmentation of Glycopeptides and Microflow LC-MS.

LC-MS-based N-glycosylation profiling in four human serum IgG subclasses (IgG1, IgG2, IgG3, and IgG4) often requires additional affinity-based enrichment of specific IgG subclasses, owing to the high amino acid sequence similarity of Fc glycopeptides among subclasses. Notably, for IgG4 and the major allotype of IgG3, the glycopeptide precursors share identical retention time and mass and therefore cannot be distinguished based on precursor or glycan fragmentation. Here, we developed a parallel reaction monitoring (PRM)-based method for quantifying Fc glycopeptides through combined transitions generated from both glycosidic and peptide bond fragmentation. The latter enables the subpopulation of IgG3 and IgG4 to be directly distinguished according to mass differences without requiring further enrichment of specific IgG subclasses. In addition, a multinozzle electrospray emitter coupled to a capillary flow liquid chromatograph was used to increase the robustness and detection sensitivity of the method for low-yield peptide backbone fragment ions. The gradient was optimized to decrease the overall run time and make the method compatible with high-throughput analysis. We demonstrated that this method can be used to effectively monitor the relative levels of 13 representative glycoforms, with a good limit of detection for individual IgG subclasses.

The Curious Early History of the Cabibbo–Kobayashi–Maskawa Matrix: Miracles Happen!

Abstract The 1973 Kobayashi–Maskawa paper proposed a compelling link between Cabibbo’s flavor mixing scheme and ${\mathcal {C}}$${\mathcal {P}}$ violation but, since it required the existence of six quarks at a time when the physics community was happy with only three, it received zero attention. However, two years after the paper appeared—at which time it had received a grand total of two citations—the charmed quark was discovered and it finally got some notice and acceptance. After this stumbling start, it subsequently emerged as the focal point of an enormous amount of experimental and theoretical research activity. In an invited talk at a KEK symposium to celebrate the 50th anniversary of the KM paper, I reviewed some of the less well known circumstances that occurred in the years preceding and following the paper’s appearance. Some spoilers: (i) Kobayashi and Maskawa (and a number of other Japanese physicists) were convinced about the existence of the charmed quark nearly three years before its “discovery” at Brookhaven and SLAC. (ii) The matrix provided in their seminal 1973 paper was mathematically incorrect. Another version that was in common use for the following 12 years was technically correct, but not really a rotation matrix. (iii) The CKM matrix ${\mathcal {C}}$${\mathcal {P}}$ phase was only measurable because of the very specific hierarchy of the flavor mixing angles and meson masses. (iv) Similarly, the neutrino mixing discovery, and the PMNS matrix measurability were only possible because of favorable values of the neutrino mass differences and mixing angles. In addition I include some speculations about what may be in store for the future.

Mapping m6A Sites on HIV-1 RNA Using Oligonucleotide LC-MS/MS.

The biological significance of chemical modifications to the ribonucleic acid (RNA) of human immunodeficiency virus type-1 (HIV-1) has been recognized. However, our understanding of the site-specific and context-dependent roles of these chemical modifications remains limited, primarily due to the absence of nucleotide-resolution mapping of modification sites. In this study, we present a method for achieving nucleotide-resolution mapping of chemical modification sites on HIV-1 RNA using liquid chromatography and tandem mass spectrometry (LC-MS/MS). LC-MS/MS, a powerful tool capable of directly analyzing native RNAs, has proven effective for mapping RNA modifications in small RNA molecules, including ribosomal RNA and transfer RNA. However, longer RNAs have posed challenges, such as the 9 Kb HIV-1 virion RNA, due to the complexity of and ambiguity in mass differences among RNase T1-cleaved RNA fragments in LC-MS/MS data. Here, we introduce a new target RNA enrichment method to isolate small local RNA fragments of HIV-1 RNA that potentially harbor site-specific N6-methyladenosine (m6A) modifications. In our initial trial, we used target-specific DNA probes only and encountered insufficient RNA fragmentation due to inefficient S1 digestion near the target site. Recognizing that inefficient S1 digestion by HIV-1 RNA is likely due to the formation of secondary structures in proximity to the target site, we designed multiple DNA probes annealing to various sites of HIV-1 RNA to better control the structures of RNA substrates for S1 digestion. The use of these non-target DNA probes significantly improved the isolation of more homogeneous target RNA fragments of approximately 50 bases in length. Oligonucleotide LC-MS/MS analysis of these isolated target RNA fragments successfully separated and detected both m6A-methylated and non-methylated oligomers at the two m6A-predicted sites. The principle of this new target enrichment strategy holds promise and should be broadly applicable to the analysis of any lengthy RNA that was previously deemed infeasible for investigation using oligonucleotide LC-MS/MS.

Prevalence of overweight and obesity among nurses in Bahrain: A cross-sectional study.

This study aims to estimate the prevalence of overweight and obesity among nurses in Bahrain. A cross-sectional design. A secondary data from a convenience sample of 550 nurses working in three hospitals in the Kingdom of Bahrain. The prevalence of overweight and obesity was determined by calculating the percentages of BMI using the World Health Organization classification. Most participants were females (n = 488, 89.1%), ages 31 to 40 (n = 239, 43.8%). The mean BMI was 26.9 (±4.4). The prevalence of overweight and obesity was 43.2% and 21.4%, respectively. The prevalence of overweight and obesity is associated with nationality and shift work. We used BMI to estimate the prevalence of overweight and obesity. However, BMI does not consider muscle mass, bone density, body composition, and racial and sex differences. Therefore, in future studies, body fat proportion and muscle mass need to be measured to estimate the prevalence and predict risks.

Utilization of solid residue from hydrothermal liquefaction of breadfruit pulp for the production of bio-briquette using cassava starch as binder

The generation of agro-waste as a result of increase in agro and food processing activities is on the increase due to rapid increase in human population. Hence the need to eliminate these waste by converting them into a useful product or energy source. This work presents the use of bio-char from hydrothermal liquefaction of breadfruit pulp to produce bio-briquettes with cassava starch as a binder. The response surface method using design expert was used to design the experiment with particle size, press pressure and binder dosage as factors, to determine the parameter combination that will produce briquettes of high energy density. The briquette with the highest calorific value 26.75 MJ/kg was produced at the parameter combination of 450 mm−6 particle size, 5 MPa press pressure, and 20 % binder dosage. The ultimate analysis carried on the produced briquette gave carbon, hydrogen, nitrogen and sulphur content of 47.22 %, 3.88 %, 0.69 %, and 0.42 % respectively, with oxygen content of 4.79 % by percentage mass difference. While the proximate analysis gave moisture, ash, volatile matter, and fixed carbon content of 7.8 %, 3.9 %, 43.7 %, and 44.6 % respectively. Other characterization test carried out gave combustion rate of 4.5 g/min, ignition time of 3.5 min, density of 0.86 g/cm3, compressive strength of 8.31 N/mm2, shatter index of 0.89, and hydrophobicity of 61.3 %. These findings shows that briquettes produced with bio-char from HTL of breadfruit pulp can be used as solid fuel for domestic and mini-industrial heating purposes, as well as eliminate waste from processing of breadfruit.

Quantitative Peptidomics Using Reductive Methylation of Amines.

A number of different approaches have been used for quantitative peptidomics. In this protocol, we describe the method in which peptides are reacted with formaldehyde and sodium cyanoborohydride, which converts primary and secondary amines into tertiary amines. By using different combinations of regular reagents, deuterated reagents (2H), and reagents containing deuterium and 13C, it is possible to produce five isotopically distinct forms of the methylated peptides, which can be quantified by mass spectrometry. Peptides with free N-termini that are primary amines incorporate two methyl groups using this procedure, which differ by 2Da for each of the five isotopic combinations. Peptides that contain unmodified lysine residues incorporate additional pairs of methyl groups, leading to larger mass differences between isotopic forms. The reagents are commercially available, relatively inexpensive, and chemically stable.

Dynamical origin of universal two-pole structures and their light quark mass evolution

Two-pole structures refer to the fact that two dynamically generated states are located close to each other between two coupled channels and have a mass difference smaller than the sum of their widths. Thus, the two poles overlap in the invariant mass distribution of their decay products, creating the impression that only one state exists. This phenomenon was first noticed for the Λ(1405) and the K1(1270), and then for several other states. This report explicitly shows how the two-pole structures emerge from the underlying universal chiral dynamics describing the coupled-channel interactions between a heavy matter particle and a pseudo-Nambu-Goldstone boson. Furthermore, we predict similar two-pole structures in other systems dictated by chiral symmetry, such as the isospin 1/2 K¯∑c − πΞ′c coupled channel, awaiting experimental discoveries.

Efficacy of digital guide-assisted implant restoration in anterior teeth aesthetics and its impact on labial bone mass.

To analyze the efficacy of digital guide-assisted implant restoration technique in enhancing the anterior teeth aesthetics and its impact on labial bone mass. We retrospectively analyzed clinical data from 90 patients who underwent maxillary anterior teeth implant restoration at The First People's Hospital of Fuyang, Hangzhou, from January 2021 to September 2023. The patients were divided into two groups: a conventional group (n=45, 45 implants, standard implant restoration) and a digital group (n=45, 45 implants, digital guide-assisted implant). We compared implant positional deviations, changes in dental plaque index (PLI), aesthetic effect scores, labial bone mass differences, and the occurrence of adverse reactions post-treatment between the two groups. The digital group exhibited significantly less deviation in root position in the buccolingual and vertical directions, less neck deviation in the buccolingual and vertical directions, and less apical deviation than the conventional group (P=0.021, P=0.005, P=0.016, P=0.008, P=0.026, respectively). Three months postoperatively, the digital group demonstrated a significantly lower mean PLI (P<0.001), higher white and pink aesthetic scores (P=0.021, P=0.005), and increased alveolar ridge height and coronal and middle labial bone mass (P=0.006, P=0.015, P=0.008). Additionally, this group experienced lower incidence of adverse reactions (4.44% vs. 17.78%) compared with the conventional group (P=0.044). The digital guide-assisted implant restoration significantly enhances implant accuracy, reduces bone resorption, improves aesthetic outcomes, and ensures higher safety.

Phototransformation of Brominated Disinfection Byproducts and Toxicity Elimination in Sunlit-Ozonated Reclaimed Water.

Ozonation is universally used during water treatment but can form hazardous brominated disinfection byproducts (Br-DBPs). While sunlight exposure is advised to reduce the risk of Br-DBPs, their phototransformation pathways remain insufficiently understood. Here, sunlight irradiation was found to reduce adsorbable organic bromine by 63%. Applying high-resolution mass spectrometry, the study investigated transformations of dissolved organic matter in sunlit-ozonated reclaimed water, revealing the number and abundance of assigned formulas decreased after irradiation. The Br-DBPs with O/C < 0.6 and MW > 400 Da were decreased or removed after irradiation, with the majority being CHOBr compounds. The peak intensity reduction ratio of CHOBr compounds correlated positively with double bound equivalent minus oxygen ratios but negatively with O/C, suggesting that photo-susceptible CHOBr compounds were highly unsaturated. Mass difference analysis revealed that the photodegradation pathways were mainly oxidation aligned with debromination. Three typical CHOBr molecular structures were resolved, and their photoproducts were proposed. Toxicity estimates indicated decreased toxicity in these photoproducts compared to their parent compounds, in line with experimentally determined values. Our proposed phototransformation pathways for Br-DBPs enhance our comprehension of their degradation and irradiation-induced toxicity reduction in reclaimed water, further illuminating their transformation under sunlight in widespread environmental scenarios.

Alpha-1-Antitrypsin (A1AT) Proteotyping by LC-MS/MS.

The diagnosis of alpha-1-antitrypsin (A1AT) deficiency is established by quantitation of protein concentration in serum (immunoassay) followed by determination of specific allelic variants by phenotyping (isoelectric focusing (IEF) gel electrophoresis) and/or allele-specific genotyping. Various phenotyping and genotyping methodologies are available, and each has their own advantages and disadvantages. As an alternative, mass spectrometry is emerging as a powerful tool in the identification and quantitation of proteins and peptides. The method described here, referred to as proteotyping, is a proteomic method using trypsin digestion and tandem mass spectrometry that detects the most common deficiency alleles, S and Z, associated with A1AT deficiency.This qualitative mass spectrometry method is based on the principle that the S and Z mutations lead to amino acid changes which result in a change in the mass of the A1AT protein. When the A1AT protein is proteolytically digested, multiple peptides are generated, two of which include the sites of the S and Z mutations, respectively. Peptides generated from wild-type A1AT (M alleles) differ in sequence and mass from peptides generated from the S and Z alleles at these two specific locations. The mass difference allows for differentiation of S and Z peptides, representing the deficiency alleles, from non-S and non-Z peptides, representing the wild-type alleles (M). Interpretation of the peptide patterns in conjunction with A1AT quantitation by immunoassay allows for an accurate assessment for the presence of deficiency alleles in the majority of patients.

A fast and time-efficient machine learning approach to dark matter searches in compressed mass scenario

Various analyses for searching for the signature of SUSY or exotic particles have been carried out by the experiments at CERN. These analyses made use of traditional cut and count methods. While this method has yielded promising results, it has been challenging in the region where the mass difference between SUSY particles is small. Deep learning is currently widely employed in most data analysis tasks, including high energy physics, and has made significant advances in almost all fields for collecting and interpreting huge data samples. In this paper, a fast and time-efficient classification technique is proposed, utilizing machine learning algorithms to distinguish dark matter signal from SM background in compressed mass spectra scenarios at a center-of-mass energy of 14 TeV. A classification model was built in a short amount of time using 2D histograms produced with less amount of data, effectively reducing computational costs through the transfer learning of pre-trained deep models while maintaining a high level of classification accuracy.