Dominant Period Research Articles

Constraints on the Calibration of Borehole Volumetric Strainmeters Using Rayleigh Wave Vertical Seismic Acceleration

ABSTRACT To ensure the accuracy and reliability of crustal strain measurements requires in situ sensor calibration. In this study, a seismogeodetic approach for the calibration of volumetric strain is introduced. The protocol, which relies on the dilatational character of Rayleigh waves, combines observational and theoretical analyses based on the near-surface properties of the Rayleigh wave vertical seismic acceleration. The calibration coefficient is estimated for a Rayleigh wave dominant period of 15–20 s using strain data and strong-motion records of acceleration from 62 global events (Mw≥7). The approach shows a good agreement with tidal calibration estimates for a Poisson ratio of 0.22–0.27 and Rayleigh wave phase velocity of 3–4 km·s−1. The protocol is straightforward, it requires no sophisticated simulation but only the numerical comparison of a similarly located accelerometer, and offers an alternative or a complement to tidal calibration.

Field and laboratory studies of fluorescence-based technologies for real-time tracking of cyanobacterial cell lysis and potential microcystins release

Elevated levels of dissolved microcystins (MCs) in source water due to rapid cell lysis of harmful cyanobacterial blooms may pose serious challenges for drinking water treatment. Catastrophic cell lysis can result from outbreaks of naturally-occurring cyanophages – as documented in Lake Erie during the Toledo water crisis of 2014 and in 2019, or through the application of algaecides or water treatment chemicals. Real-time detection of cyanobacterial cell lysis in source water would provide a valuable tool for drinking water plant and reservoir managers. In this study we explored two real-time fluorescence-based devices, PhycoSens and PhycoLA, that can detect unbound phycocyanin (uPC) as a potential indication of cell lysis and MCs release. The PhycoSens was deployed at the Low Service pump station of the City of Toledo Lake Erie drinking water treatment plant from July 15 to October 19, 2022 during the annual cyanobacteria bloom season. It measured major algal groups and uPC in incoming lake water at 15-min intervals during cyanobacteria dominant and senescence periods. Intermittent uPC detections from the PhycoSens over a three-month period coincided with periods of increasing proportions of extracellular MCs relative to total (intracellular and extracellular) MCs, indicating potential for uPC use as an indicator of cyanobacterial cell integrity. Following exposures of laboratory-cultured MCs-producing Microcystis aeruginosa NIES-298 (120 μg chlorophyll/L) to cyanophage Ma-LMM01, copper sulfate (0.5 and 1 mg Cu/L), sodium carbonate peroxyhydrate (PAK® 27, 6.7 and 10 mg H2O2/L), and potassium permanganate (2.5 and 4 mg/L), appearance of uPC coincided with elevated fractions of extracellular MCs. The PhycoLA was used to monitor batch samples collected daily from Lake Erie water exposed to algaecides in the laboratory. Concurrence of uPC signal and surge of dissolved MCs was observed following 24-h exposures to copper sulfate and PAK 27. Overall results indicate the appearance of uPC is a useful indicator of the onset of cyanobacterial cell lysis and the release of MCs when MCs are present.

Association between ABO blood type and coronavirus disease 2019 severe outcomes across dominant variant strains.

Existing evidence suggests a link between ABO blood type and severe outcomes in coronavirus disease 2019 (COVID-19). We aimed to assess the relationship between blood type and severe outcomes across variant strains throughout the pandemic. This was a multicenter retrospective observational cohort analysis from a large health system in southeastern Michigan using electronic medical records to evaluate emergency encounters, hospitalization, and severe outcomes in COVID-19 based on ABO blood type. Consecutive adult patients presenting to the emergency department with a primary diagnosis of COVID-19 (U07.1) from March 1, 2020 through December 31, 2022 were assessed. Patients who presented during three distinct time intervals that coincided with Alpha, Delta, and Omicron variant predominance were included in the analysis. Exclusions included no record of ABO blood type, positive PCR COVID-19 test within the preceding 28 days, and if transferred from out of the health system. Severe outcomes were inclusive of intensive care unit admission, mechanical ventilation, or death, which, as a composite, represented our primary outcome. Secondary outcomes were hospital admission and length of stay. A logistic regression model was employed to test the association between ABO blood type and severe outcome, adjusting for age, sex, race, vaccination status, Elixhauser comorbidity indices, and the dominant variant time period in which the encounter occurred. Of the 33,796 COVID-19 encounters, 9416 met inclusion criteria; 4071 (43.2%) were type O, 3417 (36.3%) were type A, 459 (4.9%) were type AB, and 1469 (15.6%) were type B blood. Note that 66.4% of the cohort was female (p=0.18). The proportion of composite severe disease among the four blood types was similar and ranged between 8.6% and 8.9% (p=0.98). Note that 53.0% of type A blood patients required hospital admission, compared to 51.9%, 50.4%, and 48.1% of type AB, B, and O blood, respectively (p<0.001). Compared to patients with O blood type (43.2%), non-O blood type (58.8%; composite of A, AB, and B) exhibited no statistically significant difference in the proportion of composite severe disease (8.8%vs. 8.7%; p=0.81) Multivariable regression analyses exhibited no significant difference regarding the presence of severe outcomes among the four blood types or O versus non-O blood types during T1, T2, and T3. ABO blood type was not associated with COVID-19 severe outcomes across the Delta, Alpha, and Omicron dominant COVID waves across a large health system in southeastern Michigan. Further research is needed to better understand if ABO blood type is a risk factor for severe disease among evolving COVID-19 variants and other viral upper respiratory infections.

Synchronous observations of traveling ionospheric disturbances by the multipoint Doppler sounding, ionosonde and the incoherent scatter radar: Case study

In this paper, we present the results of a special experimental study of quiet-time behavior of the mid-latitude ionosphere over Eastern Europe by synchronously operation of different ground-based facilities. For the first time we used data obtained from Kharkiv incoherent scatter (IS) radar, ionosonde and coherent Doppler HF sounding system to detect and investigate traveling ionospheric disturbances (TIDs). The periods close to winter solstice and autumn equinox in 2018 were analyzed. The dominant periods and horizontal phase velocities of registered TIDs were 45–80 min and 230–460 m s−1, respectively. The strongest signatures were observed in the solstice measurement and represented by large amplitudes. Based on results obtained by all three methods, we found the LS TIDs with the same interval of time and altitude of propagation and similar characteristics (the period of about 50 min, estimated vertical 80 m/s and horizontal 460 m/s velocity and horizontal spatial scale size about 1360 km) for winter measurement. Such observational findings confirm the reliability of these TID detection techniques. Possible sources of TIDs generation were considered including solar terminator.

SItomo – A toolbox for splitting intensity tomography and application in the Eastern Alps

The tomographic inversion of shear wave splitting data for upper mantle anisotropy has been a longstanding challenge. This is due to the ray-based approximation of classical approaches and the near-vertical incidence of the core-mantle converted phases such as SKS that are often used. Recent developments include the calculation of finite-frequency sensitivity kernels for SKS splitting intensity observations, which allows us to accurately take into account the sensitivity to anisotropic structure with depth. A requirement of this tomographic technique is a dense station spacing, which results in overlapping sensitivity kernels at depth and allows for the localization of anisotropic structure. This is satisfied by a growing number of temporary seismic deployments, which motivates the desire to image anisotropic complexities with depth. Here, we introduce and make available a toolbox for the MATLAB environment that facilitates the application of finite-frequency splitting intensity tomography to dense seismic arrays. Our implementation includes several key features, including: 1) A forward calculation of splitting intensities and sensitivity kernels for a complex anisotropic model space. 2) Consideration of the dominant period of the wave, allowing for multiple-frequency analysis, as well as the incoming wave’s non-vertical incidence. 3) The inversion can be based on a classical gradient descent, on a form of the conjugate gradient method known as the BFGS algorithm, or on a gradient-informed stochastic reversible jump algorithm, allowing for a data-driven parametrization of the model space. 4) Importing splitting intensity measurements from waveforms processed in SplitRacer allows for fast pre-processing of large data sets due to its fully automatic design. To illustrate our method, we present both synthetic tests and an application to real data. We apply our inversion procedure to data from the Swath-D network, which densely covers the transition of the Central to the Eastern Alps. Previous studies showed evidence for an abrupt lateral change of layered seismic anisotropy that had been attributed to an opening for channeled asthenospheric flow. Using an SKS splitting intensity tomography approach, we can confirm previous inferences while providing additional constraints on the distribution of anisotropy laterally and with depth.

Toward generalized Milankovitch theory (GMT)

Abstract. In recent decades, numerous paleoclimate records and results of model simulations have provided strong support for the astronomical theory of Quaternary glacial cycles formulated in its modern form by Milutin Milankovitch. At the same time, new findings have revealed that the classical Milankovitch theory is unable to explain a number of important facts, such as the change in the dominant periodicity of glacial cycles from 41 to 100 kyr about 1 million years ago. This transition was also accompanied by an increase in the amplitude and asymmetry of the glacial cycles. Here, based on the results of a hierarchy of models and data analysis, a framework of the extended (generalized) version of the Milankovitch theory is presented. To illustrate the main elements of this theory, a simple conceptual model of glacial cycles was developed using the results of an Earth system model, CLIMBER-2. This conceptual model explicitly assumes the multistability of the climate–cryosphere system and the instability of the “supercritical” ice sheets. Using this model, it is shown that Quaternary glacial cycles can be successfully reproduced as the strongly nonlinear response of the Earth system to the orbital forcing, where 100 kyr cyclicity originates from the phase locking of the precession and obliquity-forced glacial cycles to the corresponding eccentricity cycle. The eccentricity influences glacial cycles solely through its amplitude modulation of the precession component of orbital forcing, while the long timescale of the late Quaternary glacial cycles is determined by the time required for ice sheets to reach their critical size. The postulates used to construct this conceptual model were justified using analysis of relevant physical and biogeochemical processes and feedbacks. In particular, the role of climate–ice sheet–carbon cycle feedback in shaping and globalization of glacial cycles is discussed. The reasons for the instability of the large northern ice sheets and the mechanisms of the Earth system escape from the “glacial trap” via a set of strongly nonlinear processes are presented. It is also shown that the transition from the 41 to the 100 kyr world about 1 million years ago can be explained by a gradual increase in the critical size of ice sheets, which in turn is related to the gradual removal of terrestrial sediments from the northern continents. The implications of this nonlinear paradigm for understanding Quaternary climate dynamics and the remaining knowledge gaps are finally discussed.

Experimental and Numerical Investigation of a Real Four‐Story Building with an Open Ground Floor in a Seismic Region for Proper Strengthening

Many existing buildings fail to meet the requirements of current earthquake resistance codes. Therefore, it is necessary to strengthen and/or upgrade such buildings. Strengthening and/or upgrading include adding new floors, parts, elements, etc. Modern codes usually do not reflect upgrading of existing buildings. These buildings may be damaged and require maintenance and repairs, which may change the original material and structural properties. Design of such buildings is based on dominant vibration periods obtained by empirical dependences according to the building codes or from dynamic numerical analysis using available software. In both cases, the results usually do not consider the present state of the structure, influence of nonstructural elements, and possible differences in material properties in various elements of the building due to construction problems, concrete creep, etc. Such evaluation can be done just based on dynamic analysis, experimental and numeric, whereas the first one is essential. Therefore, the present research is aimed at numerical and experimental investigation of an existing real multistory residential reinforced concrete building before its strengthening and/or upgrading according to the requirements of modern seismic codes. The present study is a first stage of the research. It is focused on obtaining the dynamic parameters of the building before its strengthening and upgrading. Experimental values of natural vibration periods and damping ratios are compared with those obtained numerically. Following these values, the design spectrum of the seismic code is updated and the building is designed using this updated spectrum. The findings of this study form a basis for the second research stage that will be aimed at monitoring and analyzing of this building at each stage of its strengthening and upgrading. This approach iaimed at improving the available techniques for strengthening and upgrading the building. It will also be the basis for further research in this direction.

Influence of the dominant period and duration of seismic motion on seismic damage of river levees

Influence of the dominant period and duration of seismic motion on seismic damage of river levees

Potential Volcanic Origin of the 2023 Short-period Tsunami in the Izu Islands, Japan

On October 8, 2023, at 21:40 UTC (6:40 on October 9 local time), a tsunami warning was issued for the Izu Islands and southwest Japan. This tsunami was initially considered to be associated with the Mw 4.7 earthquake at 20:25 UTC (5:25 JST). However, we know events of this magnitude are far too small to generate observed tsunamis from coseismic deformation alone. In this study, we analyzed the ocean-bottom pressure records of DONET and S-net, real-time cabled observation networks on the Pacific coast of Japan. We find that the dominant period of this tsunami was relatively short, 250 sec, and that the largest tsunami occurred at 21:13 (6:13 JST) near Sofu-gan volcano. In addition, T waves, or the ocean-acoustic waves, were clearly observed by DONET – we posit these correspond to a vigorous swarm-like seismic event at the same region of the tsunami source. We formally invert for the tsunami source and find that several tsunami sources with an interval of about 4 min are necessary to reproduce the observed records. These most likely correspond to volcanic eruptions.

COVID-19 vaccine effectiveness against severe COVID-19 requiring oxygen therapy, invasive mechanical ventilation, and death in Japan: A multicenter case-control study (MOTIVATE study)

IntroductionSince the SARS-CoV-2 Omicron variant became dominant, assessing COVID-19 vaccine effectiveness (VE) against severe disease using hospitalization as an outcome became more challenging due to incidental infections via admission screening and variable admission criteria, resulting in a wide range of estimates. To address this, the World Health Organization (WHO) guidance recommends the use of outcomes that are more specific to severe pneumonia such as oxygen use and mechanical ventilation. MethodsA case-control study was conducted in 24 hospitals in Japan for the Delta-dominant period (August-November 2021; “Delta”) and early Omicron (BA.1/BA.2)-dominant period (January-June 2022; “Omicron”). Detailed chart review/interviews were conducted in January-May 2023. VE was measured using various outcomes including disease requiring oxygen therapy, disease requiring invasive mechanical ventilation (IMV), death, outcome restricting to “true” severe COVID-19 (where oxygen requirement is due to COVID-19 rather than another condition(s)), and progression from oxygen use to IMV or death among COVID-19 patients. ResultsThe analysis included 2125 individuals with respiratory failure (1608 cases [75.7%]; 99.2% of vaccinees received mRNA vaccines). During Delta, 2 doses provided high protection for up to 6 months (oxygen requirement: 95.2% [95% CI:88.7–98.0%] [restricted to “true” severe COVID-19: 95.5% {89.3–98.1%}]; IMV: 99.6% [97.3–99.9%]; fatal: 98.6% [92.3–99.7%]). During Omicron, 3 doses provided high protection for up to 6 months (oxygen requirement: 85.5% [68.8–93.3%] [“true” severe COVID-19: 88.1% {73.6–94.7%}]; IMV: 97.9% [85.9–99.7%]; fatal: 99.6% [95.2–99.97]). There was a trend towards higher VE for more severe and specific outcomes. ConclusionMultiple outcomes pointed towards high protection of 2 doses during Delta and 3 doses during Omicron. These results demonstrate the importance of using severe and specific outcomes to accurately measure VE against severe COVID-19, as recommended in WHO guidance in settings of intense transmission as seen during Omicron.

Evaluation of CMIP6 model performance in simulating the PDO and its future change

This study comprehensively assesses the model performance in simulating the variation of the Pacific Decadal Oscillation (PDO) in the winter time (November to March) during the historical period of 1870–2014 using 40 models from phase 6 of the Coupled Model Intercomparison Project (CMIP6). Its future change is also investigated under four Shared Socioeconomic Pathway scenarios on the basis of 17 CMIP6 models. Results show that CMIP6 models can reasonably reproduce the observed sea surface temperature anomaly mode associated with the PDO, with high spatial correlation coefficients of above 0.7. However, CMIP6 models generally perform poorly in simulating the variability of the PDO, with low correlation coefficients for most models, except FGOALS-g3 (0.57), GISS-E2-1-H (0.42), and NESM3 (0.37), which present a relatively greater correlation. The multi-model ensemble (MME) outperforms the individual models and can capture the dominant periodicity of the PDO (∼50 years), but it fails to capture the periodicity of ∼20 years. Additionally, the MME result underestimates the variability of the PDO. In response to future warming, the PDO is expected to transfer from a negative to positive phase around the 2050s. The 50-year periodicity of the PDO is projected to decrease compared to the historical period.摘要本文基于40个CMIP6模式输出结果, 系统评估了模式对历史时期太平洋年代际振荡(PDO)的模拟性能, 并利用其中17个模式的4种共享社会经济路径情景数据预估了PDO未来可能变化趋势. 结果表明, CMIP6模式能够合理再现PDO相关海表温度异常的空间模态, 但模式模拟PDO位相演变的能力普遍较弱. 多模式集合能够合理再现PDO的50年左右周期, 但无法模拟出其20年左右周期, 并且低估了PDO的变化幅度. 在未来变暖情景下, PDO可能在2050左右出现由负位相向正位相的转变, 同时其50年左右周期也将明显缩短.

Synchronization phenomena observed in glacial–interglacial cycles simulated in an Earth system model of intermediate complexity

Abstract. The glacial–interglacial cycles of the Quaternary exhibit 41 kyr periodicity before the Mid-Pleistocene Transition (MPT) around 1.2–0.8 Myr ago and ∼ 100 kyr periodicity after that. From the viewpoint of dynamical systems, proposed mechanisms generating these periodicities are broadly divided into two types: (i) nonlinear forced responses of a mono- or multi-stable climate system to the astronomical forcing or (ii) synchronization of internal self-sustained oscillations to the astronomical forcing. In this study, we investigate the dynamics of glacial cycles simulated by the Earth system model of intermediate complexity CLIMBER-2 with a fully interactive carbon cycle, which reproduces the MPT under gradual changes in volcanic-CO2 degassing and regolith cover. We report that, in this model, the dominant frequency of glacial cycles is set in line with the principle of synchronization. It is found that the model exhibits self-sustained oscillations in the absence of astronomical forcing. Before the MPT, glacial cycles synchronize to the 41 kyr obliquity cycles because the self-sustained oscillations have periodicity relatively close to 41 kyr. After the MPT the timescale of internal oscillations becomes too long to follow every 41 kyr obliquity cycle, and the oscillations synchronize to the 100 kyr eccentricity cycles that modulate the amplitude of climatic precession. The latter synchronization occurs with the help of the 41 kyr obliquity forcing, which enables some terminations and glaciations to occur robustly at their right timing. We term this phenomenon vibration-enhanced synchronization because of its similarity to the noise-enhanced synchronization known in nonlinear science. While we interpret the dominant periodicities of glacial cycles as the result of synchronization of internal self-sustained oscillations to the astronomical forcing, the Quaternary glacial cycles show facets of both synchronization and forced response.

The Abrupt Resumptions of Pulsations in α Cygni (Deneb)

Paddock’s 1927–1935 radial velocities of α Cygni (Deneb) show semi-regular pulsations with a dominant period of about 12 days. Lucy found many periods of lesser amplitude. In Paddock’s data and subsequent 1956 data from Abt, after the large-amplitude pulsations seemed to damp down, abruptly new sets of pulsations started within a fraction of a day. Five of those resumptions occurred with intervals averaging 72.4 ± 0.3 days. These resumptions seem to start at any phase during the pulsations. We are unaware of this behavior in any other star. We also find evidence of this behavior in the 1977–1982 radial velocity data of Parthasarathy & Lambert and the 1997–2001 photometry/radial velocity data of Richardson et al., as well as in photometric data from the NASA Transiting Exoplanet Survey Satellite (TESS) spacecraft and ground-based visual observations in the AAVSO International Database. The ground-based data have too infrequent sampling intervals to confirm the ∼70-day resumption intervals or to pinpoint the day and phase of abrupt amplitude increase. The TESS data, with 2-minute cadence, shows one instance of pulsation resumption, but does not have a long enough time series to confirm a ​​​​​70-day interval. Without any evidence for duplicity, we cannot explain this behavior as being due to a companion in a highly eccentric orbit. α Cygni is one of the Luminous Blue Variables (supergiants) and these resumptions may be related to the microvariations produced in convective layers below their atmospheres, pulsation-driven shocks and rarefactions, or pulsation-convection interactions. We encourage further observations by ground-based observers and using the TESS spacecraft to confirm the ∼70-day resumption interval and lack of correlation with pulsation phase in both radial velocity and light curve data.

Incidence and severity of pulmonary embolism in COVID-19 infection: Ancestral, Alpha, Delta, and Omicron variants.

Little information is available regarding incidence and severity of pulmonary embolism (PE) across the periods of ancestral strain, Alpha, Delta, and Omicron variants. The aim of this study is to investigate the incidence and severity of PE over the dominant periods of ancestral strain and Alpha, Delta, and Omicron variants. We hypothesized that the incidence and the severity by proximity of PE in patients with the newer variants and vaccination would be decreased compared with those in ancestral and earlier variants. Patients with COVID-19 diagnosis between March 2020 and February 2022 and computed tomography pulmonary angiogram performed within a 6-week window around the diagnosis (-2 to +4 weeks) were studied retrospectively. The primary endpoints were the associations of the incidence and location of PE with the ancestral strain and each variant. Of the 720 coronavirus disease 2019 patients with computed tomography pulmonary angiogram (58.6 ± 17.2 years; 374 females), PE was diagnosed among 42/358 (12%) during the ancestral strain period, 5/60 (8%) during the Alpha variant period, 16/152 (11%) during the Delta variant period, and 13/150 (9%) during the Omicron variant period. The most proximal PE (ancestral strain vs variants) was located in the main/lobar arteries (31% vs 6%-40%), in the segmental arteries (52% vs 60%-75%), and in the subsegmental arteries (17% vs 0%-19%). There was no significant difference in both the incidence and location of PE across the periods, confirmed by multivariable logistic regression models. In summary, the incidence and severity of PE did not significantly differ across the periods of ancestral strain and Alpha, Delta, and Omicron variants.

Helioseismic Investigation of Quasi-biennial Oscillation Source Regions

We studied the temporal evolution of quasi-biennial oscillations (QBOs) using acoustic mode oscillation frequencies from the Global Oscillation Network Group. The data used here span more than 25 yr, covering solar cycles 23 and 24 and the ascending phase of cycle 25. The analysis reveals that QBO-like signals are present in both the cycles, but with different periods. The dominant QBO period in cycle 23 is found to be about 2 yr, while it is about 3 yr in cycle 24. Furthermore, the quasi-biennial oscillatory signals are present only during the ascending and high-activity phases of cycle 23 and quickly weaken around 2005, during the declining phase. In comparison, the QBO signals are present throughout cycle 24, starting from 2009 to 2017. We also explored the depth dependence in QBO signals and obtained a close agreement at all depths, except in the near-surface shear layer. A detailed analysis of the near-surface shear layer suggests that the source region of QBOs is probably within a few thousand kilometers just below the surface.

The soil characterization of the region between the Maltepe-Beykoz Fault and the Marmara Sea in İstanbul (Türkiye) with the integrated HVSR (Nakamura technique) and MASW method

Completing the earthquake recurrence period of the Marmara segment, one of the two seismic gaps of the northern Anatolian fault zone, necessitates earthquake hazard studies for Istanbul, considering the population density. This study focuses on determining the soil properties of the study area in the Maltepe district of Istanbul. The Maltepe, with its large population density, stands very close to this fault zone and is vulnerable to earthquake damage. The soil properties such as Vs30, dominant period (T0), and amplification ratio (A0) were determined with the MASW from surface wave analysis methods at 48 points and the HVSR approach of microtremor analysis methods at 26 points. These point-based properties were mapped in the GIS environment, and spatial distribution maps were prepared. In addition, seismic vulnerability (Kg) and effective shear strain (γe) calculations for different acceleration values were carried out to detect deformation-failure on the surface. It was understood from the maps and the 2D cross-sections produced to examine the lateral and vertical changes that the soil conditions in the study area developed under the control of the Maltepe Beykoz fault (MBF). Accordingly, the two sides of the MBF lineament were determined with different geophysical outputs by their different geological origins. Namely, the alluvial part in the coastal part was defined by low Vs30, high period, and Kg values; on the contrary, the more rigid parts located at high elevations were described by relatively high Vs30, low period, and Kg values. In addition, it was understood that the deltaic sediments spread loosely and undulated in the alluvium at the SE part of the MBF lineament. These results obtained in the study are significant for predicting disaster damages and taking precautions before disasters. In addition, the scientific data potential of the outcomes of this study will make future studies, which are carried out to determine other parameters to be used during the taking of the precautions, more accessible.

The Mid-Pleistocene Transition from Budyko’s Energy Balance Model

Here we revisit the long-standing question of which dynamical processes were responsible for a change in the dominant periodicity of glacial cycles from ∼41 to ∼100 thousand years that occurred roughly 1 million years ago. We investigate this phenomenon, the so-called Mid-Pleistocene Transition (MPT), using an Energy Balance Model (EBM) framework. EBMs are the simplest form of global climate models, allowing for a deeper mathematical analysis to complement the physical understanding gained from more complex higher-dimensional models. We argue that a low-order flip-flop model based on a latitudinally averaged EBM provides new insights into the fundamental dynamics. A recent extension of this EBM adds equations of latitudinally averaged quantities, one for the snow/albedo line, and one for the maximum ice extent. This system of three ordinary differential equations admits glacial cycles with similar spectral characteristics as the proxy records. The period and amplitude of the cycles are controlled by a critical bifurcation parameter. When we include orbital forcing to the model and tune the evolution of the bifurcation parameter to a stack of benthic δ18O records, we observe a transition with similar features to the MPT. The transition follows a mechanism that was recently suggested in the literature: the slow ramping of the internal period via regimes of frequency locking. We demonstrate this clearly by means of a bifurcation analysis using continuation software, which reveals a bifurcation structure primarily organized by Arnold tongues and grazing bifurcations. This work strengthens the case for ramping with frequency locking as a mechanism for the MPT by providing a clear demonstration of the mechanism in a physically-derived model and providing a candidate bifurcation parameter that guides the dynamics through different frequency locking regimes.

Long COVID Among Wisconsin Workers in the Workers' Compensation System: Associations With Sociodemographics, Vaccination, and Predominant Variant Period From March 1, 2020 to July 31, 2022.

This analysis aimed to determine the likelihood of developing long COVID among Wisconsin workers while adjusting for sociodemographics, COVID-19 vaccination, industry, and occupation. This retrospective analysis determined the odds ratios of developing long COVID among Wisconsin workers who were compensated for COVID-19 lost time during March 1, 2020 to July 31, 2022. A total of 234 workers (11.7%) were determined to have long COVID. Factors associated with long COVID were age ≥40 years, non-White race, infection occurrence during the initial and Omicron variant dominant periods, and the absence of COVID-19 vaccination. Workers in manufacturing and public administration were more likely to develop long COVID compared with those in health care and social assistance. Long COVID disproportionately affects some worker groups. This calls for more worker protection and preventative care to mitigate its impact.

Impact of vaccination and variants of concern on long COVID clinical phenotypes

BackgroundDefining patterns of symptoms in long COVID is necessary to advance therapies for this heterogeneous condition. Here we aimed to describe clusters of symptoms in individuals with long COVID and explore the impact of the emergence of variants of concern (VOCs) and vaccination on these clusters.MethodsIn a prospective, multi centre cohort study, individuals with symptoms persisting > 4 weeks from acute COVID-19 were divided into two groups based on timing of acute infection; pre-Alpha VOC, denoted wild type (WT) group and post-Alpha VOC (incorporating alpha and delta dominant periods) denoted VOC group. We used multiple correspondence analysis (MCA) and hierarchical clustering in the WT and VOC groups to identify symptom clusters. We then used logistic regression to explore factors associated with individual symptoms.ResultsA total of 417 individuals were included in the analysis, 268 in WT and 149 in VOC groups respectively. In both groups MCA identified three similar clusters; a musculoskeletal (MSK) cluster characterised by joint pain and myalgia, a cardiorespiratory cluster and a less symptomatic cluster. Differences in characteristic symptoms were only seen in the cardiorespiratory cluster where a decrease in the frequency of palpitations (10% vs 34% p = 0.008) and an increase in cough (63% vs 17% p < 0.001) in the VOC compared to WT groups was observed. Analysis of the frequency of individual symptoms showed significantly lower frequency of both chest pain (25% vs 39% p = 0.004) and palpitations (12% vs 32% p < 0.001) in the VOC group compared to the WT group. In adjusted analysis being in the VOC group was significantly associated with a lower odds of both chest pain and palpitations, but vaccination was not associated with these symptoms.ConclusionThis study suggests changes in long COVID phenotype in individuals infected later in the pandemic, with less palpitations and chest pain reported. Adjusted analyses suggest that these effects are mediated through introduction of variants rather than an effect from vaccination.

Analysis of Changes in Rainfall Concentration over East Africa

Understanding the spatial and temporal distribution of precipitation is important in agriculture, water management resources, and flood disaster management. The present study analyzed the changes in rainfall concentration over East Africa (EA). Three matrices—the precipitation concentration index (PCI), the precipitation concentration degree (PCD), and the precipitation concentration period (PCP)—were used to examine the changes in rainfall during 1981–2021. The changes in spatial variance annually and during two seasons, namely, “long rains” (March to May [MAM]) and “short rain” (October to December [OND]), were estimated using an empirical orthogonal function (EOF). The study employed the robust statistical metrics of the Theil–Sen estimator to detect the magnitude of change and modified Mann–Kendall (MMK) to examine possible changes in rainfall concentration. The localized variation of the power series within the series for PCI, PCD, and PCP variability was performed using the continuous wavelet transform. The findings showed that the concentration of rainfall patterns of EA occurred in four months of the total months in a year over most parts, with the western sides experiencing uniform rainfall events throughout the year. The EOF analysis revealed a homogeneous negative pattern during the MAM season over the whole region for PCD, PCI, and PCP for the first mode, which signified reduced rainfall events. Moreover, the MMK analysis showed evidence of declining trends in the PCD annually and during the MAM season, while the opposite tendency was noted for the OND season where an upward trend in the PCD was observed. Interestingly, areas adjacent to Lake Victoria in Uganda and Lake Tanganyika in Tanzania showed increasing trends in the PCD for annual and seasonal time scales. The analysis to characterize the rainfall cycle and possible return period, considering the indices of PCD, PCI, and PCP, showed higher variability during the year 2000, while much variability was presented in the PCP for the annual period. During the MAM and OND seasons, a 1-year band as a dominant period of variability was observed in all the indices. Overall, the findings of the present study are crucial in detecting the observed changes in rainfall concentration for avoiding the loss of life and property, as well as for coping with potential changes in water resources.