bluuebunny/crossref_metadata_2025 huggingface dataset:
A Comparative Study on the Relationship Between Learned Helplessness and Academic Performance in English Classes in Urban and Rural Junior High Schools
Authors: Leng Wei
Published: September 2024

This study selected a total of 441 second-grade students from urban and rural schools in the same city in Guangdong Province as research subjects to explore the relationship between learned helplessness and academic performance in junior middle school English classes and compare the research results of the two schools. The results of the study found that the level of learned helplessness among rural junior high school students was significantly higher than that among urban junior high school students(The average level of learned helplessness among rural students is 3.87/5, while that among urban students is 3.54/5.). The average English score of rural junior high school students was significantly lower than that of urban junior high school students, with an average score difference of 9.35 points. Regardless of whether junior high school students were from urban or rural schools, learned helplessness in English classes had a significant negative impact on English test scores. Additionally, there was a causal relationship between the two, meaning that the level of learned helplessness would affect students' test scores.
A Study on the Relationship Between Parents' Expectations and Junior Middle School Students' Academic Test Scores -- Taking English as an Example
Authors: Li Yalin
Published: September 2024

In the currently prevalent “rat race” phenomenon, which is particularly acute in the field of education. When it comes to discussing the factors underlying the changes in middle school students' English academic achievements, numerous researchers have put forward their viewpoints from different perspectives. This paper summarizes four crucial dimensions that impact middle school students' English achievements and conducts a six-week teaching experiment based on these dimensions. Through the analysis of questionnaire surveys, interviews, and experimental comparisons, it is discovered that the factors influencing students' English achievements, ranked in order of importance from high to low, are: family rearing style, communication and emotional support between parents and children, parents' expectations, and family culture and values. However, while parental expectations have a direct and positive impact on adolescent children, they rank third among the major factors and have a relatively low impact. On the other hand, in the context of family rearing methods that are not suitable for children's development at this stage and incorrect family communication and emotional support, parents' expectations have indirect negative effects.
Pengaruh Affiliate Marketing, Live Streaming Dan Program Flash Sale Terhadap Keputusan Pembelian Produk Somethinc Secara Online Pada Mahasiswa Universitas Malikussaleh
Authors: Kamsiyah  , Jullimursyida  , T. Edyansyah  , Naufal Bachri
Published: September 2024

This study aims to determine the influence of Affiliate Marketing, Live Streaming, and Flash Sale programs on the decision to purchase Somethinc products online among students at Malikussaleh University. A sample of 112 respondents was taken, calculated using the formula of Hair, (2010). Sampling in this study used a nonprobability sampling technique with a purposive sampling method, namely with the criteria of active students and having or currently purchasing Somethinc products. Data collection used primary data in the form of questionnaires distributed offline (directly) and also online (g-form) on social media. The data analysis method used was multiple linear regression analysis using the SPSS program. The distribution of questionnaires that has been conducted by the author obtained research results, namely, partially the Affiliate Marketing variable does not have a significant effect on the decision, possibly due to the low consumer trust in the affiliate partners of Somethinc products, the Live Streaming variable has a significant effect on purchasing decisions because it can reduce the sense of doubt from consumers because it can be seen directly and get clear information from the seller and the Flash Sale variable also has a significant effect partially because this method can increase the sense of urgency for consumers to immediately buy Somethinc products.
Mekânsal Nokta Verilerin Mekânsal İstatistiklerle Analizi: Yenilenebilir Enerji Kaynakları Uygulaması
Authors: Bartan Mehmet Burak , Aytaç Cankurtaran Günseli , Türkşen Özlem
Published: September 2024

Araştırma konusuna yönelik olarak elde edilen verinin konum bilgisi içermesi durumunda veri, mekânsal veri olarak adlandırılır. Nokta ve raster biçiminde tanımlanabilen mekânsal verilerin analizinde mekânsal istatistikler kullanılır. Savunma ve bilişim teknolojileri, sağlık, çevre bilimi, yer bilimi, enerji, şehir ve bölge planlama gibi alanlarda mekânsal verilerle sıklıkla karşılaşılır. Bu çalışmada, Türkiye’de yer alan rüzgâr türbinleri ve güneş panellerine ilişkin nokta verilerin mekânsal istatistiklerle analizi yapılmıştır. Enerji Piyasası Düzenleme Kurumu (EPDK) tarafından lisans verilen işletmelerden rüzgâr türbinleri için Çanakkale ili verileri ve güneş panellerine ilişkin ise ülkemizde lisans verilen tüm nokta verileri dikkate alınmıştır. Nokta verilere ilişkin öznitelik için kurulu güç değerleri ile ilgilenilmiştir. Mekânsal Betimsel İstatistikler, Mekânsal Örüntü Analizi, Mekânsal Otokorelasyon Analizi ve Mekânsal Enterpolasyon başlıklarında RStudio programı kullanılarak mekânsal istatistikler elde edilmiştir. Bu mekânsal istatistiklere göre, Türkiye’de yer alan rüzgâr enerji santrali (RES) ve güneş enerji santrali (GES) kurulu güç değerlerinin mekânsal dağılımının rastgele olmadığı görülmüştür. RES’ler ve GES’ler için 10-kat çapraz doğrulama ile Kriging Analizi uygulanarak nokta verilerin kurulu güç değerleri için öngörüler yapılmıştır.
Investment attractiveness factors in the opinion of companies from Special Economic Zones in Poland
Authors: Misztal Piotr , Kulakou Vasili
Published: September 2024

The purpose of the research is the identification of important determinants shaping the investment attractiveness of the country (region) from the point of view of potential investors and an assessment of the degree of stakeholder satisfaction with existing methods of examining the investment climate and their availability for practical use. In order to assess a set of determinants that exert the most significant influence on a country’s investment climate, a questionnaire was developed consisting of 25 questions of various orientations. These questions were designed to assess the opinions of potential investors regarding the degree of influence of various factors on their decision on capital allocation and the investment climate of a country. The survey was conducted among 506 enterprises and 14 management bodies of Special Economic Zones in Poland from June 10 to July 20, 2023. The final step involved the analysis of the survey results using statistical methods.
Allosteric modulation of the CXCR4:CXCL12 axis by targeting receptor nanoclustering via the TMV-TMVI domain
Authors: García-Cuesta Eva M , Martínez Pablo , Selvaraju Karthik , Ulltjärn Gabriel , Gómez Pozo Adrián Miguel , D'Agostino Gianluca , Gardeta Sofia , Quijada-Freire Adriana , Blanco Gabella Patricia , Roca Carlos , Hoyo Daniel del , Jiménez-Saiz Rodrigo , García-Rubia Alfonso , Soler Palacios Blanca , Lucas Pilar , Ayala-Bueno Rosa , Santander Acerete Noelia , Carrasco Yolanda , Oscar Sorzano Carlos , Martinez Ana , Campillo Nuria E , Jensen Lasse D , Rodriguez Frade Jose Miguel , Santiago César , Mellado Mario
Published: September 2024

CXCR4 is a ubiquitously expressed chemokine receptor that regulates leukocyte trafficking and arrest in both homeostatic and pathological states. It also participates in organogenesis, HIV-1 infection, and tumor development. Despite the potential therapeutic benefit of CXCR4 antagonists, only one, plerixafor (AMD3100), which blocks the ligand-binding site, has reached the clinic. Recent advances in imaging and biophysical techniques have provided a richer understanding of the membrane organization and dynamics of this receptor. Activation of CXCR4 by CXCL12 reduces the number of CXCR4 monomers/dimers at the cell membrane and increases the formation of large nanoclusters, which are largely immobile and are required for correct cell orientation to chemoattractant gradients. Mechanistically, CXCR4 activation involves a structural motif defined by residues in TMV and TMVI. Using this structural motif as a template, we performed in silico molecular modeling followed by in vitro screening of a small compound library to identify negative allosteric modulators of CXCR4 that do not affect CXCL12 binding. We identified AGR1.137, a small molecule that abolishes CXCL12-mediated receptor nanoclustering and dynamics and blocks the ability of cells to sense CXCL12 gradients both in vitro and in vivo while preserving ligand binding and receptor internalization.
Machine learning approaches identify immunologic signatures of total and intact HIV DNA during long-term antiretroviral therapy
Authors: Semenova Lesia , Wang Yingfan , Falcinelli Shane , Archin Nancie , Cooper-Volkheimer Alicia D , Margolis David M , Goonetilleke Nilu , Murdoch David M , Rudin Cynthia D , Browne Edward P
Published: September 2024

Understanding the interplay between the HIV reservoir and the host immune system may yield insights into HIV persistence during antiretroviral therapy (ART) and inform strategies for a cure. Here, we applied machine learning (ML) approaches to cross-sectional high-parameter HIV reservoir and immunology data in order to characterize host–reservoir associations and generate new hypotheses about HIV reservoir biology. High-dimensional immunophenotyping, quantification of HIV-specific T cell responses, and measurement of genetically intact and total HIV proviral DNA frequencies were performed on peripheral blood samples from 115 people with HIV (PWH) on long-term ART. Analysis demonstrated that both intact and total proviral DNA frequencies were positively correlated with T cell activation and exhaustion. Years of ART and select bifunctional HIV-specific CD4 T cell responses were negatively correlated with the percentage of intact proviruses. A leave-one-covariate-out inference approach identified specific HIV reservoir and clinical–demographic parameters, such as age and biological sex, that were particularly important in predicting immunophenotypes. Overall, immune parameters were more strongly associated with total HIV proviral frequencies than intact proviral frequencies. Uniquely, however, expression of the IL-7 receptor alpha chain (CD127) on CD4 T cells was more strongly correlated with the intact reservoir. Unsupervised dimension reduction analysis identified two main clusters of PWH with distinct immune and reservoir characteristics. Using reservoir correlates identified in these initial analyses, decision tree methods were employed to visualize relationships among multiple immune and clinical–demographic parameters and the HIV reservoir. Finally, using random splits of our data as training-test sets, ML algorithms predicted with approximately 70% accuracy whether a given participant had qualitatively high or low levels of total or intact HIV DNA . The techniques described here may be useful for assessing global patterns within the increasingly high-dimensional data used in HIV reservoir and other studies of complex biology.
Proteomic landscape of tunneling nanotubes reveals CD9 and CD81 tetraspanins as key regulators
Authors: Notario Manzano Roberto , Chaze Thibault , Rubinstein Eric , Penard Esthel , Matondo Mariette , Zurzolo Chiara , Brou Christel
Published: September 2024

Tunneling nanotubes (TNTs) are open actin- and membrane-based channels, connecting remote cells and allowing direct transfer of cellular material (e.g. vesicles, mRNAs, protein aggregates) from the cytoplasm to the cytoplasm. Although they are important especially, in pathological conditions (e.g. cancers, neurodegenerative diseases), their precise composition and their regulation were still poorly described. Here, using a biochemical approach allowing to separate TNTs from cell bodies and from extracellular vesicles and particles (EVPs), we obtained the full composition of TNTs compared to EVPs. We then focused on two major components of our proteomic data, the CD9 and CD81 tetraspanins, and further investigated their specific roles in TNT formation and function. We show that these two tetraspanins have distinct non-redundant functions: CD9 participates in stabilizing TNTs, whereas CD81 expression is required to allow the functional transfer of vesicles in the newly formed TNTs, possibly by regulating docking to or fusion with the opposing cell.
Burnout experience among healthcare workers post third COVID-19 wave in India; findings of a cross-sectional study
Authors: Sidiq Mohammad , Ch Sai Jaya Prakash , Janakiraman Balamurugan , Chahal Aksh , Khan Imran , Kaura Surbhi , Kashoo Faizan , Khan Farha , Khan Shabnam , Sehgal Chhavi Arora , Baranwal Shashank , Popli Sheenam , Alghadier Mshari
Published: September 2024

Background

The pandemic exacerbated burnout experienced by healthcare personnel, whose mental health had long been a public health concern before COVID-19. This study used the Copenhagen burnout inventory (CBI) tool to assess burnout and identify predictors among Indian healthcare workers managing COVID-19.

Methods

A cross-sectional study was conducted from June to December 2022, after the third pandemic wave. A web-based, fillable Google form was used to recruit COVID-19 management professionals from multiple Jaipur district hospitals. Healthcare professionals provided socio-demographic, work-related, and CBI scores. Multiple linear regression was used to control for model covariant independent variables.

Results

We evaluated the responses of a total of 578 participants with a mean age of 36.59 ± 9.1 years. Based on the CBI cut-off score of 50, 68.1% reported burnout. A total of 67.5%, 56.4%, and 48.6% of healthcare workers reported work-related, personal, and patient-related burnout, respectively. High burnout scores were significantly associated with the nursing profession (β = 7.89, 95% CI; 3.66, 12.11, p < 0.0001). The p-value indicates the probability of observing the data if the null hypothesis is true, and the confidence interval shows the range within which we can be 95% confident that the true effect lies. An independent relationship exists between male gender and higher personal-related burnout scores (β = 4.45, 95% CI 1.9–6.9).

Conclusion

This study identified key indicators that need further emphasis and the need for organizational and individual-level burnout monitoring in healthcare delivery sectors. Health workers continue to experience burnout due to a combination of personal, professional, and patient-related factors. This underscores the need for targeted organizational and individual interventions. The findings also suggest that the CBI tool could identify healthcare worker burnout risk groups.
Silkworm Gut Microflora as a Source: Biotechnological Applications
Authors: Sharma Kritika
Published: September 2024

The term "microflora" has gained popularity as researchers explore the symbiotic relationships between microorganisms and their hosts, from our skin to our gut. Insects, including the silkworm, have mutualistic ties with their gut microflora, making them a valuable resource for studying essential molecules. The silkworm, with its rapid generation time, abundant genetic resources, well-defined genetic background, and numerous homologous genes, is an ideal model organism for various life science studies. Silkworm rearing is simple, inexpensive, and does not require ethical clearance, allowing the gut microflora of Bombyx mori to be harnessed for biotechnological applications. Silkworm gut microbes can synthesize and produce extracellular enzymes, such as cellulases, proteases, and lipases, which are crucial for industries ranging from biofuel production to waste management and textile processing. Additionally, these microbes can produce vitamins, such as vitamin B12, and metabolites like short-chain fatty acids (SCFAs), which have potential applications in the food and pharmaceutical industries. Antimicrobial substances produced by the gut microflora, including bacteriocins and lactic acid, are of particular therapeutic importance, offering natural alternatives to traditional antibiotics and contributing to the development of novel antimicrobial therapies. Moreover, the antioxidants generated by these symbionts, such as glutathione and superoxide dismutase (SOD), have significant implications for health supplements and cosmetics, owing to their ability to combat oxidative stress and support immune function. Beyond their metabolic capacities, silkworm symbionts can be used to enhance health, target and manage agricultural pests, and control vectors of human diseases in an environmentally friendly manner. Recent research has also highlighted the potential of mutualistic symbiotic bacteria for plastic disposal, with enzymes like PETases showing promise in degrading synthetic polymers. Despite extensive knowledge on the biology and physiology of the silkworm Bombyx mori, few studies have focused on its gut microflora. Modern genetic techniques, such as the genetic transformation of silkworms with genes of interest, may help overcome these research gaps. Increasing research efforts on silkworm gut microflora will not only reveal new symbiotic relationships but also identify new sources of biotechnologically important molecules and enzymes for therapeutic and industrial applications.
Unmasking Essential Thrombocythemia: Myocardial Infarction as a Rare Complication in a Young Patient
Authors: Bourzeg Khaoula , Garni Houda El , Elmassrioui Joumana , Aityahya Abdelkarim , Jamili Mohammed El , Karimi Saloua El , Hattaoui Mustapha El
Published: September 2024

Essential thrombocythemia (ET) is a rare myeloproliferative disorder characterized by elevated platelet counts and seldom presents with myocardial infarction (MI), particularly in younger individuals without traditional cardiovascular risk factors. We report the case of a 41-year-old woman with no significant medical history who presented with acute chest pain and elevated troponin levels. Her laboratory results indicated a markedly high platelet count, and coronary angiography revealed thrombotic stenosis in the proximal left anterior descending artery. Diagnosis of ET was confirmed by JAK2-V617F mutation and bone marrow biopsy. The patient was initially treated with hydroxyurea to reduce platelet levels, allowing for successful angioplasty three weeks later. This case highlights the importance of considering ET in the differential diagnosis of MI, especially in younger patients without other risk factors, and underscores the need for tailored management and close monitoring in such rare presentations.
Population Dynamics and Environmental Correlates of Insect Pests in Watermelon, Citrullus lanatus (T.)
Authors: B R Archana , Pujar Kishor , Priyanka  , T Chethan, , M Harish Varma,
Published: September 2024

The study was conducted in Kandavara village, Chikkaballapur district, during 2021, investigated the insect pest complex affecting watermelon, Citrullus lanatus (T) following standard crop management practices but without any insecticidal interventions to assess the natural occurrence of insect pests. Weekly observations were made from February to April (2021) employing various sampling methods to monitor key pests, including leaf miners, thrips, whiteflies, fruit flies, leaf-eating caterpillars, and pumpkin beetles. The study revealed that leaf miners, Liriomyza trifolii (Frick) were the first to appear, peaking in the 11th Standard Meteorological Week (SMW) with 6.45 leaf mines per five leaves. Thrips, Thrips palmi Karny and whiteflies, Bemisia tabaci (Gennadius) emerged during the vegetative stage, showing a significant positive correlation with maximum temperature. Fruit flies, Zeugodacus cucurbitae (Coquillett) caused the most significant damage during the fruiting stage, with a peak incidence of 14.92 per cent in the 15th SMW. The study highlighted that higher temperature had a positive correlation with pest populations, while rainfall had a negative correlation reducing the pest activity. These findings emphasize the importance of precise timing in pest management interventions to minimize crop losses and enhance the sustainability and productivity of watermelon cultivation in India.
Martian high‐altitude photoelectrons independent of solar zenith angle
Authors: Xu Shaosui , Liemohn Michael , Bougher Stephen , Mitchell David
Published: April 2016

Many aspects of the Martian upper atmosphere are known to vary with solar zenith angle (SZA). One would assume that dayside photoelectron fluxes are also SZA dependent, especially when transport along a semivertical magnetic field line is significant. However, our investigation presented here of the observed Martian high‐altitude (∼400 km) photoelectron fluxes by the magnetometer/electron reflectometer (MAG/ER) instruments on board Mars Global Surveyor (MGS) shows that the photoelectron fluxes are better correlated with just the solar irradiance, without SZA factored in, and also that the median photoelectron fluxes are independent of SZA, especially for high energies (above 100 eV). For lower energies (below 70 eV), the observed fluxes tend to vary to some degree with SZA. Such counterintuitive results are due to the existence of a photoelectron exobase, only above which the photoelectrons are able to transport and escape to high altitudes. Two methods are used here to determine the altitude range of this exobase, which varies between 145 km and 165 km depending on the atmosphere and SZA. Through our SuperThermal Electron Transport (STET) model, we found that the integral of the production rate above the photoelectron exobase, and therefore the high‐altitude photoelectron fluxes, is rather independent of SZA. Such an independent relationship concerns energy redistribution in the Martian upper atmosphere, using photoelectrons to map magnetic topology and connectivity, as well as ion escape. This finding can also be carefully adapted to other solar bodies with semivertical magnetic fields at ionospheric altitudes, such as Earth, Jupiter, and Saturn.
Time‐dependent magnetohydrodynamic simulations of the inner heliosphere
Authors: Merkin V. G. , Lyon J. G. , Lario D. , Arge C. N. , Henney C. J.
Published: April 2016

This paper presents results from a simulation study exploring heliospheric consequences of time‐dependent changes at the Sun. We selected a 2 month period in the beginning of year 2008 that was characterized by very low solar activity. The heliosphere in the equatorial region was dominated by two coronal holes whose changing structure created temporal variations distorting the classical steady state picture of the heliosphere. We used the Air Force Data Assimilate Photospheric Flux Transport (ADAPT) model to obtain daily updated photospheric magnetograms and drive the Wang‐Sheeley‐Arge (WSA) model of the corona. This leads to a formulation of a time‐dependent boundary condition for our three‐dimensional (3‐D) magnetohydrodynamic (MHD) model, LFM‐helio, which is the heliospheric adaptation of the Lyon‐Fedder‐Mobarry MHD simulation code. The time‐dependent coronal conditions were propagated throughout the inner heliosphere, and the simulation results were compared with the spacecraft located near 1 astronomical unit (AU) heliocentric distance: Advanced Composition Explorer (ACE), Solar Terrestrial Relations Observatory (STEREO‐A and STEREO‐B), and the MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft that was in cruise phase measuring the heliospheric magnetic field between 0.35 and 0.6 AU. In addition, during the selected interval MESSENGER and ACE aligned radially allowing minimization of the effects of temporal variation at the Sun versus radial evolution of structures. Our simulations show that time‐dependent simulationsreproduce the gross‐scale structure of the heliosphere with higher fidelity, while on smaller spatial and faster time scales (e.g., 1 day) they provide important insights for interpretation of the data. The simulations suggest that moving boundaries of slow‐fast wind transitions at 0.1 AU may result in the formation of inverted magnetic fields near pseudostreamers which is an intrinsically time‐dependent process. Finally, we show that heliospheric current sheet corrugation, which may result in multiple sector boundary crossings when observed by spacecraft, is caused by solar wind velocity shears. Overall, our simulations demonstrate that time‐dependent heliosphere modeling is a promising direction of research both for space weather applications and fundamental physics of the heliosphere.
M ≥ 7 earthquake rupture forecast and time‐dependent probability for the sea of Marmara region, Turkey
Authors: Murru M. , Akinci A. , Falcone G. , Pucci S. , Console R. , Parsons T.
Published: April 2016

We forecast time‐independent and time‐dependent earthquake ruptures in the Marmara region of Turkey for the next 30 years using a new fault segmentation model. We also augment time‐dependent Brownian passage time (BPT) probability with static Coulomb stress changes (ΔCFF) from interacting faults. We calculateMw > 6.5 probability from 26 individual fault sources in the Marmara region. We also consider a multisegment rupture model that allows higher‐magnitude ruptures over some segments of the northern branch of the North Anatolian Fault Zone beneath the Marmara Sea. A total of 10 differentMw = 7.0 toMw = 8.0 multisegment ruptures are combined with the other regional faults at rates that balance the overall moment accumulation. We use Gaussian random distributions to treat parameter uncertainties (e.g., aperiodicity, maximum expected magnitude, slip rate, and consequently mean recurrence time) of the statistical distributions associated with each fault source. We then estimate uncertainties of the 30 year probability values for the next characteristic event obtained from three different models (Poisson, BPT, and BPT + ΔCFF) using a Monte Carlo procedure. The Gerede fault segment located at the eastern end of the Marmara region shows the highest 30 year probability, with a Poisson value of 29% and a time‐dependent interaction probability of 48%. We find an aggregated 30 year Poisson probability ofM > 7.3 earthquakes at Istanbul of 35%, which increases to 47% if time dependence and stress transfer are considered. We calculate a twofold probability gain (ratio time dependent to time independent) on the southern strands of the North Anatolian Fault Zone.
Delaying precipitation and lightning by air pollution over the Pearl River Delta. Part I: Observational analyses
Authors: Guo Jianping , Deng Minjun , Lee Seoung Soo , Wang Fu , Li Zhanqing , Zhai Panmao , Liu Huan , Lv Weitao , Yao Wen , Li Xiaowen
Published: April 2016

The radiative and microphysical effects of aerosols can affect the development of convective clouds. The objective of this study is to reveal if the overall aerosol effects have any discernible impact on the diurnal variations in precipitation and lightning by means of both observational analysis and modeling. As the first part of two companion studies, this paper is concerned with analyzing hourly PM10, precipitation, and lightning data collected during the summers of 2008–2012 in the Pearl River Delta region. Daily PM10 data were categorized as clean, medium, or polluted so that any differences in the diurnal variations in precipitation and lightning could be examined. Heavy precipitation and lightning were found to occur more frequently later in the day under polluted conditions than under clean conditions. Analyses of the diurnal variations in several meteorological factors such as air temperature, vertical velocity, and wind speed were also performed. They suggest that the influence of aerosol radiative and microphysical effects serve to suppress and enhance convective activities, respectively. Under heavy pollution conditions, the reduction in solar radiation reaching the surface delays the occurrence of strong convection and postpones heavy precipitation to late in the day when the aerosol invigoration effect more likely comes into play. Although the effect of aerosol particles can be discernible on the heavy precipitation through the daytime, the influence of concurrent atmospheric dynamics and thermodynamics cannot be ruled out.
Isolating the roles of different forcing agents in global stratospheric temperature changes using model integrations with incrementally added single forcings
Authors: Aquila V. , Swartz W. H. , Waugh D. W. , Colarco P. R. , Pawson S. , Polvani L. M. , Stolarski R. S.
Published: April 2016

Satellite instruments show a cooling of global stratospheric temperatures over the whole data record (1979–2014). This cooling is not linear and includes two descending steps in the early 1980s and mid‐1990s. The 1979–1995 period is characterized by increasing concentrations of ozone‐depleting substances (ODSs) and by the two major volcanic eruptions of El Chichón (1982) and Mount Pinatubo (1991). The 1995–present period is characterized by decreasing ODS concentrations and by the absence of major volcanic eruptions. Greenhouse gas (GHG) concentrations increase over the whole time period. In order to isolate the roles of different forcing agents in the global stratospheric temperature changes, we performed a set of simulations using the NASA Goddard Earth Observing System Chemistry‐Climate Model with prescribed sea surface temperatures. We find that in our model simulations the cooling of the stratosphere from 1979 to present is mostly driven by changes in GHG concentrations in the middle and upper stratosphere and by GHG and ODS changes in the lower stratosphere. While the cooling trend caused by increasing GHGs is roughly constant over the satellite era, changing ODS concentrations cause a significant stratospheric cooling only up to the mid‐1990s, when they start to decrease because of the implementation of the Montreal Protocol. Sporadic volcanic events and the solar cycle have a distinct signature in the time series of stratospheric temperature anomalies but do not play a statistically significant role in the long‐term trends from 1979 to 2014. Several factors combine to produce the step‐like behavior in the stratospheric temperatures: in the lower stratosphere, the flattening starting in the mid‐1990s is due to the decrease in ozone‐depleting substances; Mount Pinatubo and the solar cycle cause the abrupt steps through the aerosol‐associated warming and the volcanically induced ozone depletion. In the middle and upper stratosphere, changes in solar irradiance are largely responsible for the step‐like behavior of global temperature anomalies, together with volcanically induced ozone depletion and water vapor increases in the post‐Pinatubo years.
Impact of urbanization patterns on the local climate of a tropical city, Singapore: An ensemble study
Authors: Li Xian‐Xiang , Koh Tieh‐Yong , Panda Jagabandhu , Norford Leslie K
Published: April 2016

The effect of urbanization and urbanization pattern on the thermal environment and local rainfall is investigated in the tropical coastal city, Singapore. The Weather Research and Forecasting (WRF) model is employed with 5 one‐way nested domains and the highest horizontal resolution is 300 m. The urban effect is taken into account by a single‐layer urban canopy model. Several scenarios with idealized urbanization patterns are designed and simulated for an ensemble of 28 members. In the asymmetric urbanization scenarios, in which either the southern or northern part of Singapore is urbanized while the other part is forest, the magnitude of urban heat island (UHI) intensity is higher than that in the symmetric urbanization scenario, in which the urban and forest land use is homogeneously distributed in Singapore. The anthropogenic heat (AH) associated with the urban areas will exacerbate the UHI intensity. Most of the rainfall in the examined cases occurs from late morning to afternoon when the sea breeze blows northeastward. The results suggest that sea breezes have stronger influence on the rainfall than the urbanization pattern since the downwind part always gets more rainfall than the upwind part. The urbanization and associated AH can have two opposite effects on the rainfall amount: increasing rainfall through increasing buoyancy by AH and decreasing rainfall through reducing evaporation by converting greenery to impervious surfaces. The ultimate effect is dependent on the relative strength of these two influences.
Spatiotemporal fusion of multiple‐satellite aerosol optical depth (AOD) products using Bayesian maximum entropy method
Authors: Tang Qingxin , Bo Yanchen , Zhu Yuxin
Published: April 2016

Merging multisensor aerosol optical depth (AOD) products is an effective way to produce more spatiotemporally complete and accurate AOD products. A spatiotemporal statistical data fusion framework based on a Bayesian maximum entropy (BME) method was developed for merging satellite AOD products in East Asia. The advantages of the presented merging framework are that it not only utilizes the spatiotemporal autocorrelations but also explicitly incorporates the uncertainties of the AOD products being merged. The satellite AOD products used for merging are the Moderate Resolution Imaging Spectroradiometer (MODIS) Collection 5.1 Level‐2 AOD products (MOD04_L2) and the Sea‐viewing Wide Field‐of‐view Sensor (SeaWiFS) Deep Blue Level 2 AOD products (SWDB_L2). The results show that the average completeness of the merged AOD data is 95.2%,which is significantly superior to the completeness of MOD04_L2 (22.9%) and SWDB_L2 (20.2%). By comparing the merged AOD to the Aerosol Robotic Network AOD records, the results show that the correlation coefficient (0.75), root‐mean‐square error (0.29), and mean bias (0.068) of the merged AOD are close to those (the correlation coefficient (0.82), root‐mean‐square error (0.19), and mean bias (0.059)) of the MODIS AOD. In the regions where both MODIS and SeaWiFS have valid observations, the accuracy of the merged AOD is higher than those of MODIS and SeaWiFS AODs. Even in regions where both MODIS and SeaWiFS AODs are missing, the accuracy of the merged AOD is also close to the accuracy of the regions where both MODIS and SeaWiFS have valid observations.
Wet scavenging of soluble gases in DC3 deep convective storms using WRF‐Chem simulations and aircraft observations
Authors: Bela Megan M. , Barth Mary C. , Toon Owen B. , Fried Alan , Homeyer Cameron R. , Morrison Hugh , Cummings Kristin A. , Li Yunyao , Pickering Kenneth E. , Allen Dale J. , Yang Qing , Wennberg Paul O. , Crounse John D. , St. Clair Jason M. , Teng Alex P. , O'Sullivan Daniel , Huey L. Gregory , Chen Dexian , Liu Xiaoxi , Blake Donald R. , Blake Nicola J. , Apel Eric C. , Hornbrook Rebecca S. , Flocke Frank , Campos Teresa , Diskin Glenn
Published: April 2016

We examine wet scavenging of soluble trace gases in storms observed during the Deep Convective Clouds and Chemistry (DC3) field campaign. We conduct high‐resolution simulations with the Weather Research and Forecasting model with Chemistry (WRF‐Chem) of a severe storm in Oklahoma. The model represents well the storm location, size, and structure as compared with Next Generation Weather Radar reflectivity, and simulated CO transport is consistent with aircraft observations. Scavenging efficiencies (SEs) between inflow and outflow of soluble species are calculated from aircraft measurements and model simulations. Using a simple wet scavenging scheme, we simulate the SE of each soluble species within the error bars of the observations. The simulated SEs of all species except nitric acid (HNO3) are highly sensitive to the values specified for the fractions retained in ice when cloud water freezes. To reproduce the observations, we must assume zero ice retention for formaldehyde (CH2O) and hydrogen peroxide (H2O2) and complete retention for methyl hydrogen peroxide (CH3OOH) and sulfur dioxide (SO2), likely to compensate for the lack of aqueous chemistry in the model. We then compare scavenging efficiencies among storms that formed in Alabama and northeast Colorado and the Oklahoma storm. Significant differences in SEs are seen among storms and species. More scavenging of HNO3 and less removal of CH3OOH are seen in storms with higher maximum flash rates, an indication of more graupel mass. Graupel is associated with mixed‐phase scavenging and lightning production of nitrogen oxides (NOx), processes that may explain the observed differences in HNO3 and CH3OOH scavenging.
Connectivity of earthquake‐triggered landslides with the fluvial network: Implications for landslide sediment transport after the 2008 Wenchuan earthquake
Authors: Li Gen , West A. Joshua , Densmore Alexander L. , Hammond Douglas E. , Jin Zhangdong , Zhang Fei , Wang Jin , Hilton Robert G.
Published: April 2016

Evaluating the influence of earthquakes on erosion, landscape evolution, and sediment‐related hazards requires understanding fluvial transport of material liberated in earthquake‐triggered landslides. The location of landslides relative to river channels is expected to play an important role in postearthquake sediment dynamics. In this study, we assess the position of landslides triggered by the Mw 7.9 Wenchuan earthquake, aiming to understand the relationship between landslides and the fluvial network of the steep Longmen Shan mountain range. Combining a landslide inventory map and geomorphic analysis, we quantify landslide‐channel connectivity in terms of the number of landslides, landslide area, and landslide volume estimated from scaling relationships. We observe a strong spatial variability in landslide‐channel connectivity, with volumetric connectivity (ξ) ranging from ~20% to ~90% for different catchments. This variability is linked to topographic effects that set local channel densities, seismic effects (including seismogenic faulting) that regulate landslide size, and substrate effects that may influence both channelization and landslide size. Altogether, we estimate that the volume of landslides connected to channels comprises 43 + 9/−7% of the total coseismic landslide volume. Following the Wenchuan earthquake, fine‐grained (<~0.25 mm) suspended sediment yield across the Longmen Shan catchments is positively correlated to catchment‐wide landslide density, but this correlation is statistically indistinguishable whether or not connectivity is considered. The weaker‐than‐expected influence of connectivity on suspended sediment yield may be related to mobilization of fine‐grained landslide material that resides in hillslope domains, i.e., not directly connected to river channels. In contrast, transport of the coarser fraction (which makes up >90% of the total landslide volume) may be more significantly affected by landslide locations.
The importance of biotic entrainment for base flow fluvial sediment transport
Authors: Rice Stephen P. , Johnson Matthew F. , Mathers Kate , Reeds Jake , Extence Chris
Published: April 2016

Sediment transport is regarded as an abiotic process driven by geophysical energy, but zoogeomorphological activity indicates that biological energy can also fuel sediment movements. It is therefore prudent to measure the contribution that biota make to sediment transport, but comparisons of abiotic and biotic sediment fluxes are rare. For a stream in the UK, the contribution of crayfish bioturbation to suspended sediment flux was compared with the amount of sediment moved by hydraulic forcing. During base flow periods, biotic fluxes can be isolated because nocturnal crayfish activity drives diel turbidity cycles, such that nighttime increases above daytime lows are attributable to sediment suspension by crayfish. On average, crayfish bioturbation contributed at least 32% (474 kg) to monthly base flow suspended sediment loads; this biotic surcharge added between 5.1 and 16.1 t (0.21 to 0.66 t km−2 yr−1) to the annual sediment yield. As anticipated, most sediment was moved by hydraulic forcing during floods and the biotic contribution from baseflow periods represented between 0.46 and 1.46% of the annual load. Crayfish activity is nonetheless an important impact during baseflow periods and the measured annual contribution may be a conservative estimate because of unusually prolonged flooding during the measurement period. In addition to direct sediment entrainment by bioturbation, crayfish burrowing supplies sediment to the channel for mobilization during floods so that the total biotic effect of crayfish is potentially greater than documented in this study. These results suggest that in rivers, during base flow periods, bioturbation can entrain significant quantities of fine sediment into suspension with implications for the aquatic ecosystem and base flow sediment fluxes. Energy from life rather than from elevation can make significant contributions to sediment fluxes.
Bed load sediment transport inferred from seismic signals near a river
Authors: Roth Danica L. , Brodsky Emily E. , Finnegan Noah J. , Rickenmann Dieter. , Turowski Jens M. , Badoux Alexandre
Published: April 2016

We examine broadband (5–480 Hz) seismic data from the Erlenbach stream in the Swiss Prealps, where discharge, precipitation, and bed load transport are independently constrained. A linear inversion of seismic spectra, exploiting isolated discharge or rain events, identifies the signals generated by water turbulence and rainfall. This allows us to remove the contributions of turbulence and rainfall from the seismic spectra, isolating the signal of bed load transport. We calibrate the regression for bed load transport during one storm and then use this regression with precipitation and discharge data to calculate bed load transport rates from 2 months of seismic spectra. Our predicted bed load transport rates correlate reasonably well with transport rates from calibrated geophones embedded in the channel (r2 ~ 0.6, p < 10−10). We find that the seismic response to rainfall is broadband (~16–480 Hz), while water turbulence and sediment transport exhibit seismic power primarily in lower frequencies (<100 Hz), likely due to longer attenuation path lengths. We use the varying attenuation at each seismometer to infer that a downstream waterfall is the primary source of the water turbulence signal. Our results indicate that deconstruction of seismic spectra from rivers can provide insight into the component signals generated by water turbulence, rainfall, and sediment transport. Further, the regression of seismic spectra with precipitation, discharge, and bed load transport data for a single calibration period enables the estimation of transport for subsequent periods with only precipitation, discharge, and seismic data. Hence, in combination with precipitation and discharge data, seismic data can be used to monitor bed load sediment transport.
Seasonal climate signals from multiple tree ring metrics: A case study of Pinus ponderosa in the upper Columbia River Basin
Authors: Dannenberg Matthew P. , Wise Erika K.
Published: April 2016

Projected changes in the seasonality of hydroclimatic regimes are likely to have important implications for water resources and terrestrial ecosystems in the U.S. Pacific Northwest. The tree ring record, which has frequently been used to position recent changes in a longer‐term context, typically relies on signals embedded in the total ring width of tree rings. Additional climatic inferences at a subannual temporal scale can be made using alternative tree ring metrics such as earlywood and latewood widths and the density of tree ring latewood. Here we examine seasonal precipitation and temperature signals embedded in total ring width, earlywood width, adjusted latewood width, and blue intensity chronologies from a network of six Pinus ponderosa sites in and surrounding the upper Columbia River Basin of the U.S. Pacific Northwest. We also evaluate the potential for combining multiple tree ring metrics together in reconstructions of past cool‐ and warm‐season precipitation. The common signal among all metrics and sites is related to warm‐season precipitation. Earlywood and latewood widths differ primarily in their sensitivity to conditions in the year prior to growth. Total and earlywood widths from the lowest elevation sites also reflect cool‐season moisture. Effective correlation analyses and composite‐plus‐scale tests suggest that combining multiple tree ring metrics together may improve reconstructions of warm‐season precipitation. For cool‐season precipitation, total ring width alone explains more variance than any other individual metric or combination of metrics. The composite‐plus‐scale tests show that variance‐scaled precipitation reconstructions in the upper Columbia River Basin may be asymmetric in their ability to capture extreme events.
Deposition and fate of organic carbon in floodplains along a tropical semiarid lowland river (Tana River, Kenya)
Authors: Omengo Fred O. , Geeraert Naomi , Bouillon Steven , Govers Gerard
Published: April 2016

Inland waters organic carbon (OC) burial by sedimentation has recently been shown to be an important component in river catchment carbon (C) budgets. However, data on OC burial by sedimentation are hitherto largely limited to temperate zones. We investigated the deposition and fate of sediment‐associated OC in the floodplains of the tropical lowland Tana River (Kenya), between two main gaging stations (Garissa and Garsen). Freshly deposited surface sediments and sediment cores were sampled and analyzed for OC, total nitrogen content, stable isotope signatures (δ13C) of OC, and grain size distribution. In addition, we incubated sediment cores to quantify CO2 production as a proxy for OC mineralization. While the floodplain receives sediment with a relatively low OC content (1.56 ± 0.42%), sediments are enriched with OC inputs from floodplain vegetation to levels above 3%. Sediment cores show a sharp decrease of OC with depth, from 3 to 12% OC in the (sub) surface to less than 1% OC below approximately 60 cm depth. Relatively elevated OC mineralization rates (0.14 ± 0.07 mol. CO2 kgC−1 d−1) were recorded. We used these data to make a first assessment of the C burial efficiency of the Tana River floodplain. In contrast to what is observed in temperate environments, over 50% of C present in the top layers is lost in less than a century. While significant amounts of OC are buried in the Tana River floodplain, the high rates of postdepositional loss limit the development of a long‐term C sink within this tropical floodplain.
A decadal precession of atmospheric pressures over the North Pacific
Authors: Anderson Bruce T. , Gianotti Daniel J. S. , Furtado Jason C. , Di Lorenzo Emanuele
Published: April 2016

Sustained droughts over the Northwestern U.S. can alter water availability to the region's agricultural, hydroelectric, and ecosystem service sectors. Here we analyze decadal variations in precipitation across this region and reveal their relation to the slow (~10 year) progression of an atmospheric pressure pattern around the North Pacific, which we term the Pacific Decadal Precession (PDP). Observations corroborate that leading patterns of atmospheric pressure variability over the North Pacific evolve in a manner consistent with the PDP and manifest as different phases in its evolution. Further analysis of the data indicates that low‐frequency fluctuations of the tropical Pacific Ocean state energize one phase of the PDP and possibly the other through coupling with the polar stratosphere. Evidence that many recent climate variations influencing the North Pacific/North American sector over the last few years are consistent with the current phase of the PDP confirms the need to enhance our predictive understanding of its behavior.