Association of Perinatal Depressive Symptoms with Breastfeeding.

Objective: Perinatal depression (PND) refers to depressive symptoms that occur in women during pregnancy and/or postpartum and is a common perinatal mental health problem. It is unclear whether early breastfeeding behavior is associated with PND symptoms in China. Therefore, this study aimed to investigate the association between PND symptoms and breastfeeding patterns for infants based on a large cohort. Methods: A prospective study was conducted in a community cohort from March 2021 to December 2022. In this study, maternal depressive symptoms were assessed using the Edinburgh postnatal depression scale (EPDS). The assessments were carried out 1 week before and 1 month after delivery. The socio-demographic information of the mothers, their intention to breastfeed, and their feeding status were investigated one-on-one by the hospital's trained medical staff through self-designed questionnaires. The maternity information and physical examination results were obtained through the healthcare records of the patients. Results: A total of 442 pregnant women were included in the study, and the total detection rate of PND was 29.41%, among which the detection rate of mild PND was 24.66%, and the detection rate of severe depression was 4.75%. About 61.99% of the mothers had exclusive breastfeeding within 1 hour after delivery, and 83.71% had exclusive breastfeeding within 24 hours after delivery. The proportion of mothers with PND symptoms and those without PND symptoms who exclusively breastfed for the first time after delivery was 71.54% and 91.67%, respectively. The median duration of exclusive breastfeeding for mothers without depressive symptoms was 3(1,5) months, while the median duration of exclusive breastfeeding for mothers with depressive symptoms was 2(1,3) months, indicating that the duration of exclusive breastfeeding for mothers without depressive symptoms was longer (P < 0.05). Conclusion: There was an association between perinatal depressive symptoms and exclusive breastfeeding. Addressing perinatal depressive symptoms may extend the duration of exclusive breastfeeding.

Magnetic polyphosphazene@Au particles as substrates for multiple-detection of immunoproteins by surface-enhanced Raman spectroscopy.

Au coated magnetic polyphosphazene (MPCTP) composite particles (MPCTP@Au) were fabricated with sensitive SERS activity. The MPCTP particles were generated by coating polyphosphazene on Fe3O4 nanoparticles through precipitation polycondensation of hexachlorocyclotriphosphazene and phloroglucinol. MPCTP@Au composite particles were obtained by deposition of Au nanoparticles on MPCTP by the reduction of HAuCl4. The size and the thickness of the Au shell can be controlled by varying the amount of HAuCl4. The magnetic core endowed the composite particles with good magnetic responsiveness, which allowed the analyte to be enriched and separated from the complex matrix, and significantly simplifying the sample pretreatment procedure. The SERS activity of MPCTP@Au composite particles were evaluated by DTNB as model Raman reporter, and the limits of detection (LOD) of DTNB was 10-8 mol/L. A high efficient SERS immunoassay system based on the MPCTP@Au substrates for the detection of immunoproteins was developed. Human IgG and rabbit IgG were quantitatively determinated simultaneously by this immunoassay system. The quantitative determination of the immunoglobulin G (IgG) was achieved and the LOD of human IgG, rabbit IgG and the mixture of human IgG and rabbit IgG were as low as 10 fg/mL, 100 pg/mL and 1 ng/mL, respectively. The results showed that the MPCTP@Au composite particles have broad application prospects as high performance SERS active substrates for immunoprotein analysis.

Accurate derivation and modelling of criteria of soil extractable and total cadmium for safe wheat production.

It is significant to establish an accurate model to predict cadmium (Cd) criteria for safe wheat production. More importantly, for better evaluation of the risk of Cd pollution in high natural background areas, the soil extractable Cd criteria are needed. In the present study, the soil total Cd criteria were derived using the method of cultivars sensitivity distribution integrated with soil aging and bioavailability as affected by soil properties. Firstly, the dataset that meet the requirements was established. Dataset from thirty-five wheat cultivars planted in different soils published in literature of five bibliographic databases were screened using designated search strings. Then, the empirical soil-plant transfer model was used to normalize the bioaccumulation data. Afterwards, the soil Cd concentration for protecting 95 % (HC5) of the species was calculated from species sensitivity distribution curves, and the derived soil criteria were obtained from HC5 prediction models that based on pH. The process of derivation for soil EDTA-extractable Cd criteria was the same way as the soil total Cd criteria. Soil total Cd criteria ranged from 0.25 to 0.60 mg/kg and soil EDTA-extractable Cd criteria ranged from 0.12 to 0.30 mg/kg. Both the criteria of soil total Cd and soil EDTA-extractable Cd were further validated to be reliable using data from field experiments. The results suggested that the criteria of soil total Cd and soil EDTA-extractable Cd in the study can ensure the safety of Cd in wheat grains and thereby enable local agricultural practitioners to develop appropriate management for croplands.

Establishment and Verification of a Prediction Model for Identifying Pathologic Infections Based on the Clinical Characteristics of Epidermoid Cysts.

Background: To construct a prediction model based on the clinical characteristics of epidermoid cysts to identify pathologic infections, evaluate the diagnostic accuracy of the model, and conduct preliminary verification. Patients and Methods: We conducted a retrospective analysis of 314 patients diagnosed with epidermoid cysts that had been removed surgically. The clinical and pathologic data of all patients were collected. The patients were divided randomly into modeling group and verification group in a 75:25 ratio. In the modeling group, the multifactor logistic regression method was used to construct a prediction model for identifying epidermoid cyst pathologic infection, and the receiver operating characteristic (ROC) curve was used to evaluate the diagnostic accuracy of the model, which was then validated in the verification group. Results: All 314 patients with epidermoid cysts were divided into non-infected group (183 cases) and infected group (131 cases) according to the pathologic results. Logistic regression analysis showed that the disease course, growth trend, redness, and texture of epidermoid cysts were independent factors affecting pathologic infection. The above four indicators were selected to construct the prediction model of epidermoid cyst pathologic infection. In the modeling group, the prediction model showed an area under the curve (AUC) of 0.898, with the sensitivity of 0.830, specificity of 0.890, positive likelihood ratio of 7.523, and negative likelihood ratio of 0.191. The AUC of the prediction model in the verification group was 0.919, which was not significantly different from that of the modeling group (p = 0.886). Conclusions: The prediction model based on the clinical characteristics of epidermoid cysts had good diagnostic accuracy and high specificity; it can be used to identify pathologic infections of epidermoid cysts.

Identification and quantification of the combined phytotoxicity of one element with various valences: Cr(III) and Cr(VI) for barley root elongation as an example.

There is uncertainty in quantifying the toxic effects of total chromium (Cr) in the environment by modeling the toxicity of individual Cr(III) or Cr(VI). In the present study, the effects of Cr(III) and Cr(VI) on barley root elongation were investigated in a hydroponic system where Cr(III) and Cr(VI) combination dose-response experiments under monotoxicity concentration, single-dose addition, and fixed concentration ratios were designed to identify and quantify their combined phytotoxicity of one element with various valences. The results show that the calculated mixed toxicity unit values for 50% inhibition (TUmix50) ranged from 1.06 to 1.45, indicating the weak antagonism effects of Cr(III) and Cr(VI) on barley root toxicity. Also, the single-dose group experiment has proved that the EC50 of Cr(VI) was increased from 71.2 µM to 119.9 µM with Cr(III) addition, which suggested that Cr(III) has antagonism on the toxicity of Cr(VI). While EC50 of Cr(III) was not affected by Cr(VI) addition. After introducing the expansion coefficient of Cr(III) on Cr(VI) toxicity, both the extended concentration addition model (e-CA) based on the log-logistic and Weibull equations and the extended independent action model (e-IA) could more accurately predict the barley root elongation under Cr(III) and Cr(VI) interaction. The e-CA model based on the Weibull equation had almost the best correlation coefficient (R2) and lowest root mean square error (RMSE) between the measured and predicted values. Finally, the combined toxicity and antagonism of the same element with co-existing different valences simultaneously were successfully and firstly identified and quantified in the present study.

20 Years nitrogen dynamics study by using APSIM nitrogen model simulation for sustainable management in Jilin China.

The tremendous increase in industrial development and urbanization has become a severe threat to the Chinese climate and food security. The Agricultural Production System Simulator model was used to simulate soil nitrogen in black soil in Yangling Jilin Province for 20 years. The observed values are consistent with the simulated values. The predicted values of total soil NO3--N and NH4+-N nitrogen are 10 kg ha-1 and 5 kg ha-1 higher than the observed values. The total soil NO3--N loss has the same trend as the rainfall, and it increases with the number of rainfall days over the years. The average 20 years losses of NO3--N and NH4+-N observed were 1375.91 kg ha-1, and 9.24 kg ha-1, while in the simulation increase was 1387.01 kg ha-1 and 9.28 kg ha-1, respectively. The difference between the observed and simulated values of NO3--N and NH4+-N of mean loss was 11.15 kg ha-1 and 0.04 kg ha-1 respectively. Moreover, our findings highlight the opportunity further to improve management policies (especially for nitrogen) to maintain crop yield.

A simple method to determine the sampling numbers in decision-making units with unknown variations of soil cadmium.

Sampling number is one critical issue to achieve credible results when surveying soil contamination and making remediation decisions. Traditional methods based on a normal distribution for determining numbers of samples are not always optimal because most distributions of soil heavy metal concentrations followed a log-normal distribution. Moreover, the variation of soil heavy metal concentrations is a prerequisite for previous methods to determine sampling numbers. Unfortunately, the variation is often unknown before soil sampling. Therefore, a simple method under the log-normal distribution without relying on variation to determine quickly the sampling number (QSN) was developed for soil cadmium and compared with other methods based on classical statistics and Chebyshev inequality. Results showed that an equation as a function of sampling areas could be used to determine QSN (QSN = 18.44 × A0.54 + 8.69, A is sampling areas, km2), with acceptable errors ranging from 13 to 33% at the sampling areas of 0.03-10 km2. The developed simple method for QSN was easy to use and cost-effective without prerequisite on the estimation of variation. Moreover, when the sampling cost was enough and the improved accuracy was requested, the increased sampling numbers were recommended as 1.53 times as the number calculated by the simple method. Therefore, the proposed method is believed as a simple and cost-effective method to determine the sampling numbers of soil Cd in decision-making units with unknown variations.

Preparation of Magnetically Recoverable MPCTP-Ag Composite Nanoparticles and Their Application as High-Performance Catalysts.

In the present research, magnetically recyclable polyphosphazene (PCTP)/Ag (MPCTP-Ag) nanoparticles are prepared by a green path, in which PCTP was used to modify Fe3O4 nanoparticles and provide nucleation sites for the reduction of Ag nanoparticles. The prepared MPCTP-Ag nanoparticles were characterized by TEM, SEM, EDS, BET, XRD, vibrating sample magnometry, XPS, and TGA analysis. The catalytic performances of the MPCTP-Ag nanoparticles for the degradation of 4-nitrophenol (4-NP), methylene blue (MB), methyl orange (MO), and their mixtures in the presence of NaBH4 were studied. The main factors affecting the catalytic performance, including temperature, reactant concentration, and catalyst dosage, were investigated. The results showed that the MPCTP-Ag nanoparticles exhibited excellent catalytic activity for the degradation of all three targeted organic contaminants (4-NP, MB, and MO). Moreover, the product retains its catalytic activity after being reused five times by magnetic separation. The results showed that MPCTP-Ag composite nanoparticles were efficient recyclable magnetic nanocatalysts with promising application in environment protection.

Integrating bioavailability and aging in the criteria derivation of cadmium for the safe production of rice in paddy soils.

It is significant to derive an appropriate cadmium (Cd) threshold for the rice to ensure that the Cd concentration of rice grains meets the food safety standards. In the present study, soil thresholds for Cd were derived using the method of species sensitivity distribution based on aging time, cultivars, and soil properties. Dataset from thirty-nine rice cultivars planted in different soils published in literature of five bibliographic databases were screened using designated search strings to explore their differences in Cd accumulation capacity in paddy soil. The empirical soil-plant transfer model was used to normalize the bioaccumulation data. Later, the soil Cd concentration for protecting 95% (HC5) of the cultivars was calculated using species sensitivity distribution curves fitted by the Burr III function. The soil Cd criteria derived from the added approach for risk assessment were proposed as continuous criteria based on the combination of soil pH and organic carbon in soil. Soil Cd criteria ranged from 0.34 to 1.18 mg/kg. The prediction model for HC5 was applied to field experimental data to validate its validity and applicability. The predicted Cd thresholds were less than the field experiment Cd thresholds. In conclusion, this study provided valuable and scientific bases for setting soil Cd criteria for paddy soils.

Epidemiological and spatiotemporal analyses of HIV/AIDS prevalence among older adults in Sichuan, China between 2008 and 2019: A population-based study.

OBJECTIVES: To describe epidemiological trends and spatial distributions of HIV/AIDS among older adults (aged ≥50) in Sichuan Province, China during 2008-19, and provide scientific reference for HIV/AIDS prevention, intervention and treatment. METHODS: Data on HIV/AIDS cases reported in 2008-19 was extracted from the Case Report System. The Cochran-Armitage trend test was used to determine epidemic trends. Spatial autocorrelation and space-time analysis were conducted with ArcGIS10.6 and ArcGIS Pro2.4, respectively. RESULTS: A total of 77854 HIV/AIDS cases among older adults were included in the study. Newly reported cases increased from 320 in 2008 to 22189 in 2019, and the reported incidence rate (number of new reported cases/older adult population) rose from 0.001% to 0.077%. Infections through heterosexual transmission increased from 65.3% to 98.2% of total cases in older adults in this period. Spatial analysis at the county-level showed significant clustering throughout Sichuan, with the main hot spots concentrated in the southeast. Spatiotemporal analysis indicated that most of the southeastern counties/districts were Consecutive Hot Spots. CONCLUSIONS: Older adults have become a key population in the HIV/AIDS epidemic in Sichuan; comprehensive prevention and intervention measures targeted to older adults are urgently needed to control the spread of HIV/AIDS.

Cadmium stress in paddy fields: Effects of soil conditions and remediation strategies.

Cadmium (Cd) toxicity in paddy soil and accumulation in rice plants and grains have got global concern due to its health effects. This review highlights the effects of soil factors including soil organic matter, soil pH, redox potential, and soil microbes which influencing Cd uptake by rice plant. Therefore, a comprehensive review of innovative and environmentally friendly management practices for managing Cd stress in rice is lacking. Thus, this review discusses the effect of Cd toxicity in rice and describes management strategies to offset its effects. Moreover, future research thrusts to reduce its uptake by rice has also been highlighted. Through phytoremediation, Cd may be extracted and stabilized in the soil while through microbes Cd can be sequestrated inside the microbial bodies. Increased Cd uptake in hyperaccumulator plants to remediate and convert the toxic form of Cd into non-toxic forms. While in chemical remediation, Cd can be washed out, immobilized and stabilized in the soil through chemical amendments. The organic amendments may help through an increase in soil pH, adsorption in its functional groups, the formation of complexations, and the conversion of exchangeable to residual forms. Developing rice genotypes with restricted Cd uptake and reduced accumulation in grain through conventional and marker-assisted breeding are fundamental keys for safe rice production. In this regard, the use of molecular techniques including identification of QTLs, CRISPR/Cas9, and functional genomics may be quite helpful.

Effects of Fe and Mn cations on Cd uptake by rice plant in hydroponic culture experiment.

Iron (Fe) and manganese (Mn) are nutritional components of rice, plays an important role in its physiological processes and can minimize absorption of cadmium (Cd) in rice. Fe, Mn, and Cd transporters such as CAL1, OsNRAMP5, OsNRAMP1, OsIRT1, OsHMA3, and OsNAAT1 regulate uptake of Cd in rice. However, the effect of exogenous application of Fe, and Mn on the accumulation of Cd and relative expression (RE) of these transporters in rice has not been investigated. Therefore, a hydroponic culture experiment was conducted to investigate the impact of Fe and Mn on Cd uptake and RE of these transporters in rice. The results showed that the Fe and Mn application significantly decreased Cd in the roots and shoots of rice. Whereas, Cd concentration in the rice significantly increased with increasing Cd concentration in the solution. The addition of manganese in the culture medium can reduce the cadmium content of rice roots by 11.9-82.3% and shoots by 11.6-85.0%, while the addition of iron in the culture medium can reduce the cadmium content of rice roots and shoots by 26-65% and 9-683% respectively. Meanwhile, application of sufficient doses of Fe and Cd in solution culture increased RE of CAL1, OsNRAMP5, OsNRAMP1, OsIRT1, and OsNAAT1 in roots, whereas expression level of OsHMA3 was decreased. Similarly, expression level of CAL1, OsNRAMP5, and OsNRAMP1 significantly increased in roots in high Cd and Mn deficient treatments. This may be concluded that the Cd increases expression of CAL1, OsNRAMP5, OsNRAMP1, OsIRT1, and OsNAAT1 but decreases OsHMA3 expression in rice roots, which resulted in increased Cd uptake in hydroponically grown rice.

Modified Cornell electrocardiographic criteria in the assessment of left ventricular hypertrophy geometry of patients with essential hypertension.

To evaluate the value of modified Cornell electrocardiographic criteria in the assessment of left ventricular hypertrophy (LVH) for patients with essential hypertension. A total of 381 patients with essential hypertension diagnosed in our hospital were selected. Using the left ventricle (LV) geometric patterns classified by the American Society of Echocardiography (ASE), we examined the distribution of the modified Cornell criteria of Ravl + SD (the deepest S wave in 12-lead ECG) in different geometric patterns and analyzed the correlation of modified Cornell criteria with changes in the LV geometric patterns using multiple linear regression analysis. The distribution of modified Cornell criteria, Sokolow-Lyon criteria (RV5/V6 + SV1), and Cornell criteria (Ravl + SV3) in gender-specific hypertensive geometric patterns were significantly different (P ≤ .01 for all). The voltage of Ravl + SD in male patients showed an increase trend in the normal geometry (NG), concentric remodeling (CR), concentric hypertrophy (CH), and eccentric hypertrophy (EH) groups, and this increase trend was significantly in the unadjusted model and the adjusted model. The voltages of Ravl + SV3 and RV5/V6 + SV1 of male patients in CR, CH and RH groups showed a gradual increase trend, but the increase trend in CR group has no statistical significance compared to that in NG group (P ≥ .05). The voltages of Ravl + SD , RV5/V6 + SV1, and Ravl + SV3 in female patients in CR, CH and EH groups showed a trend of increase after decrease in the adjusted model. In conclusion, the modified Cornell criteria could dynamically reflect left ventricular hypertensive geometry of male patients.

Determining optimum sampling numbers for survey of soil heavy metals in decision-making units: taking cadmium as an example.

Optimum sampling number (OSN) is one critical issue to achieve credible results when surveying heavy metals in soil and undertaking risk assessment for sustainable land use or remediation decisions. Although traditional methods, such as classical statistics, geostatistics, and simulated annealing algorithm, have been used to determine OSN for surveying soil heavy metals, their usefulness is limited because the distribution of soil heavy metal concentration approximately follows a log-normal distribution. Furthermore, existing correction equations for the log-normal distribution may overestimate or underestimate the OSN, and they have not been applied to estimate the OSN of soil heavy metals. The objective of the present study was to find a simple model under the log-normal distribution that determined the OSN for surveying of soil heavy metals in decision-making units. To test the effectiveness and accuracy of this model, soil heavy metals in 17 contaminated areas generating 200 multiscale units were analyzed. Determining equations for OSN, including classical statistics and approximate correction equations, were compared. Results showed that the equation for determining OSN by ordinary least squares (OSN_OLS) was computationally simple and straightforward because of an adjustment of the classic log-normal equation without relying on consulting the adjusted Student t-tables for a noncentralized data distribution. Compared with other OSN determining equations, sampling numbers by OSN_OLS were closer to optimum numbers and effectively avoided the risk of overestimation or underestimation. Descriptive statistics indicated that the estimated pollution results by OSN_OLS in representative units were very similar to original sampling with more sampling information. Furthermore, compared with other OSN-determining equations, the mapping based on OSN_OLS not only described the trends of spatial variation but also improved mapping accuracy. We conclude that OSN_OLS is an effective, straightforward, and exact model to estimate the OSN for surveying of soil heavy metals in decision-making units.

Identification of cadmium bioaccumulation in rice (Oryza sativa L.) by the soil-plant transfer model and species sensitivity distribution.

Contamination of agricultural soil with cadmium (Cd) poses a severe threat to food safety and human health, especially for Cd in rice. It is very important to identify Cd bioaccumulation in rice in order to screen Cd-safe cultivars. In the present study, 183 pairs of rice and soil data collected from Cd-contaminated soil were used to investigate the differences of Cd bioaccumulation in grains among rice cultivars. The results showed that the adverse effect on grain Cd accumulation of japonica was less than that of indica under Cd exposure. The percentage of japonica with grain Cd concentration exceeding 0.2 mg/kg reduced 50.3% compared with indica. Partial correlation analyses suggested that lower pH contributed to Cd accumulation in grains, and a significant increase in grain Cd concentration was observed with increasing soil Cd concentration. The bioaccumulation factors (BCF) of Cd in rice grains could be divided into 5 grades by combining an empirical soil-plant transfer model with species sensitivity distribution (SSD). Grades with lower Cd bioaccumulation (grades 1 and 2) were dominated by japonica, and the intrinsic sensitivity index of Cd-enrichment (k value) and straw to grain transfer factors (TF) increased with ascending grades. Average k value and TF of cultivars in grade 5 were 1.4-7.9 and 1.5-5.7 times higher than those of cultivars in grades 1 to 4, which eventually caused the increase of Cd accumulation in grains. The lower level of Cd absorption and translocation contributed to reducing the bioaccumulation of Cd in rice grains had been proved by the classification of rice on Cd accumulation. Considering the influence of soil properties and intrinsic sensitivity of rice, cultivars with grain Cd bioaccumulation controlled at low levels to safe for human consumption could be identified on Cd-contaminated soils.

Overexpression of miR-361-5p in triple-negative breast cancer (TNBC) inhibits migration and invasion by targeting RQCD1 and inhibiting the EGFR/PI3K/Akt pathway.

Triple-negative breast cancer (TNBC) is the leading cause of cancer-related death in women. Previous studies indicated that miR-361-5p was downregulated in breast cancer, however, the exact effect of miR-361-5p on TNBC requires further investigation. In the present study, we investigated whether miR-361-5p can act as a tumor suppressor by targeting required for cell differentiation 1 homolog (RQCD1) and inhibiting epidermal growth factor receptor (EGFR)/phosphoinositide 3-kinase (PI3K)/protein kinase B (Akt) pathway in TNBC. The expression of miR-361-5p and RQCD1 was determined by quantitative reverse transcription PCR (qRT-PCR) and/or western blot in TNBC and the adjacent tissues. miR-361-5p mimics were constructed and transfected to TNBC cell line MDA-MB-231. Cells were divided into three groups: blank control group, miRNA mimic negative control (NC) group, and miR-361-5p mimics group. Expression of miR-361-5p, mRNA and protein expression of PI3K, Akt, EGFR, phosphorylated (p)-EGFR/PI3K/Akt, and protein expression of RQCD1 and matrix metallopeptidase 9 (MMP-9) in MDA-MB-231 were measured by qRT-PCR/western blot after transfection. Cell viability was determined by CCK-8 assay. Cell migration and invasion ability were evaluated by scratch and transwell assay, respectively. miR-361-5p target gene was determined by bioinformatics analysis and luciferase reporter assay. RQCD1 was identified as a target of miR-361-5p by TargetScan and confirmed by luciferase reporter assay. Downregulated miR-361-5p and upregulated RQCD1 were observed in TNBC tissues. Expression of EGFR, PI3K, Akt and MMP-9 was inhibited in cells treated with miR-361-5p mimics. Transfection of miR-361-5p mimics also inhibited the phosphorylation of EGFR, PI3K, and Akt. Suppressed cell viability, migration, and invasion was found in miR-361-5p mimics groups. Our results indicated that overexpression of miR-361-5p might act as a suppressor in TNBC by targeting RQCD1 to inhibit the EGFR/PI3K/Akt signaling pathway.

Toxicity Thresholds Based on EDTA Extractable Nickel and Barley Root Elongation in Chinese Soils.

The uncertainty in the risk assessment of trace metal elements in soils when total metal contents are used can be decreased by assessing their availability and/or extractability when the soils have a high background value or different sources of trace metal elements. In this study, the added water-soluble nickel (Ni) toxicity to barley root elongation was studied in 17 representative Chinese soil samples with and without artificial rainwater leaching. The extractability of added Ni in soils was estimated by three sequential extractions with ethylenediaminetetraacetic acid (EDTA). The results showed that the effective concentration of EDTA extractable Ni (EC50), which caused 50% inhibition of barley root elongation, ranged from 46 to 1019 mg/kg in unleached soils and 24 to 1563 mg/kg in leached soils. Regression models for EDTA extractable Ni and total Ni added to soils against soil properties indicated that EDTA extractable Ni was significantly correlated with the total Ni added to soils and that pH was the most important control factor. Regression models for toxicity thresholds based on EDTA extractable Ni against soil properties showed that soil citrate dithionate extractable Fe was more important than soil pH in predicting Ni toxicity. These results can be used to accurately assess the risk of contaminated soils with high background values and/or different Ni sources.

Molecular speciation and transformation of soil legacy phosphorus with and without long-term phosphorus fertilization: Insights from bulk and microprobe spectroscopy.

Soil legacy phosphorus (P) represents a substantial secondary P resource to postpone the global P crisis. To fully utilize this P reserve, the transformation of legacy P speciation in a black soil with and without P fertilization for 27 years was investigated by chemical fractionation, molecular-level bulk (P K-edge X-ray absorption near-edge, XANES; solution 31P nuclear magnetic resonance) and microprobe (µ-X-ray fluorescence and µ-XANES) spectroscopy. Results from both fractionation and P bulk-XANES concordantly indicated that Ca2-P [Ca(H2PO4)2] acts as a reserve of labile P in response to soils with or without P fertilization. Cropping for 27 years depleted hydroxyapatite while enriched iron-bound P in soils irrespective of P application. Similar accumulation of soil organic P (Po), probably due to root residue inputs, occurred in both soils with and without P fertilization; the accumulated Po was present as orthophosphate diesters in soils with P fertilization more than in soils without P fertilization, suggesting that the release of labile Po was triggered by soil P deficits. These results provide vital information for agronomically and environmentally sustainable P management by demonstrating the potential crop availability of legacy soil P, which could reduce future P fertilization.

A new model integrating short- and long-term aging of copper added to soils.

Aging refers to the processes by which the bioavailability/toxicity, isotopic exchangeability, and extractability of metals added to soils decline overtime. We studied the characteristics of the aging process in copper (Cu) added to soils and the factors that affect this process. Then we developed a semi-mechanistic model to predict the lability of Cu during the aging process with descriptions of the diffusion process using complementary error function. In the previous studies, two semi-mechanistic models to separately predict short-term and long-term aging of Cu added to soils were developed with individual descriptions of the diffusion process. In the short-term model, the diffusion process was linearly related to the square root of incubation time (t1/2), and in the long-term model, the diffusion process was linearly related to the natural logarithm of incubation time (lnt). Both models could predict short-term or long-term aging processes separately, but could not predict the short- and long-term aging processes by one model. By analyzing and combining the two models, we found that the short- and long-term behaviors of the diffusion process could be described adequately using the complementary error function. The effect of temperature on the diffusion process was obtained in this model as well. The model can predict the aging process continuously based on four factors-soil pH, incubation time, soil organic matter content and temperature.

Enriching Silver Nanocrystals with a Second Noble Metal.

Noble-metal nanocrystals have received considerable interests owing to their fascinating properties and promising applications in areas including plasmonics, catalysis, sensing, imaging, and medicine. As demonstrated by ample examples, the performance of nanocrystals in these and related applications can be augmented by switching from monometallic to bimetallic systems. The inclusion of a second metal can enhance the properties and greatly expand the application landscape by bringing in new capabilities. Seeded growth offers a powerful route to bimetallic nanocrystals. This approach is built upon the concept that preformed nanocrystals with uniform, well-controlled size, shape, and structure can serve as seeds to template and direct the deposition of metal atoms. Seeded growth is, however, limited by galvanic replacement when the deposited metal is less reactive than the seed. The involvement of galvanic replacement not only makes it difficult to control the outcome of seeded growth but also causes degradation to some properties. We have successfully addressed this issue by reducing the salt precursor(s) into atoms with essentially no galvanic replacement. In the absence of self-nucleation, the atoms are preferentially deposited onto the seeds to generate bimetallic nanocrystals with controlled structures. In this Account, we use Ag nanocubes as an example to demonstrate the fabrication of Ag@M and Ag@Ag-M (M = Au, Pd, or Pt) nanocubes with a core-frame or core-shell structure by controlling the deposition of M atoms. A typical synthesis involves the titration of Mn+ (a precursor to M) ions into an aqueous suspension containing Ag nanocubes, ascorbic acid, and poly(vinylpyrrolidone) under ambient conditions. In one approach, aqueous sodium hydroxide is introduced to increase the initial pH of the reaction system. At pH = 11.9, ascorbic acid is dominated by ascorbate monoanion, a much stronger reductant, to suppress the galvanic replacement between Mn+ and Ag. In this case, the M atoms derived from the reduction by ascorbate monoanion are sequentially deposited on the edges, corners, and side faces to generate Ag@M core-frame and then core-shell nanocubes. The other approach involves the use of ascorbic acid as a relatively weak reductant while Mn+ is cotitrated with Ag+ ions in the absence of sodium hydroxide. At pH = 3.2, when the molar ratio of Ag+ to Mn+ is sufficiently high, the added Ag+ ions can effectively push the galvanic reaction backward and thus inhibit it. As a result, coreduction of the two precursors by ascorbic acid produces Ag and M atoms for the generation of Ag@Ag-M core-frame nanocubes with increasingly thicker ridges. The Ag@Ag-Pd core-frame nanocubes can serve as a dual catalyst to promote the stepwise reduction of nitroaromatics to aminoaromatics and then oxidation to azo compounds. The consecutive reactions can be monitored using surface-enhanced Raman scattering (SERS). The Ag@Au core-shell nanocubes with Au shells of three or six atomic layers exhibit plasmonic peaks almost identical to those of the Ag nanocubes while the chemical stability and SERS activity are substantially augmented. For both types of bimetallic nanocubes, the Ag cores can be selectively removed to generate nanoframes and nanoboxes.