[Association of urinary cadmium levels with peripheral leukocyte classification counts among middle-aged and older adults aged 40-89 in selected areas of China].

Objective: To investigate the association of urinary cadmium levels with peripheral leukocyte classification counts among middle-aged and older adults aged 40 to 89 years in selected areas of China. Methods: The research was based on the survey of the impact of soil quality of agricultural land on human health in typical areas conducted in 2019-2020. A total of 5 600 middle-aged and older adults aged 40 to 89 years were included by using a multi-stage stratified random sampling method. Baseline characteristics of the subjects were collected and physical examinations were performed. Random midstream urine was collected to measure urinary cadmium and urinary creatinine and fasting venous blood was collected to measure the leukocyte count, neutrophil count, lymphocyte count, monocyte count and eosinophil count. The linear mixed effect model was used to analyse the association of urinary cadmium levels with leukocyte classification counts, and the dose-response relationship between them was analyzed by using the restricted cubic spline (RCS) function. Results: The age of the subjects was (63.17±12.02) years; 2 851 (50.91%) were males; and the M (Q1, Q3) of urinary creatinine-corrected urinary cadmium levels was 2.69 (1.52, 4.69) µg/g·creatinine. After adjusting for confounding factors, the results of linear mixed effects model analysis showed that for each 1-unit increase in urinary creatinine-corrected urinary cadmium level, the percentage change [% (95%CI)] of leukocyte count and lymphocyte count was -1.70% (-2.61%, -0.79%) and -1.57% (-2.86%, -0.26%), respectively. RCS function showed a negative linear relationship between urinary creatinine-corrected urinary cadmium levels and leukocyte counts and lymphocyte counts, respectively (all Pnon-linear>0.05). Conclusion: Urinary cadmium levels are negatively associated with leukocyte count and lymphocyte count among middle-aged and older adults aged 40 to 89 years in selected areas of China.

[Study on formulation and revision of detection methods of "Standards for indoor air quality (GB/T 18883-2022)" in China].

The formulation and revision of the detection methods of indoor air quality standards is an important, rigorous and delicate endeavor. This paper introduced the formulation and revision of the detection methods of the standards for indoor air quality (GB/T 18883-2022), focusing on the revision process, revision principles, main adjustments and technical points of some key indicators to facilitate users to better understand and apply the detection methods in standards for indoor air quality (GB/T 18883-2022).

[Outcome of surgical repair for aortic coarctation with coexisting descending aortic aneurysm in adult patients].

Objective: To evaluate the efficacy of surgical treatment of aortic coarctation combined with descending aortic aneurysm in adult patients. Methods: This is a retrospective cohort study. Adult patients with aortic coarctation who were hospitalized in Beijing Anzhen Hospital from January 2015 to April 2019 were enrolled. The aortic coarctation was diagnosed by aortic CT angiography, and the included patients were divided into the combined descending aortic aneurysm group and the uncomplicated descending aortic aneurysm group based on descending aortic diameter. General clinical data and surgery-related data were collected from the included patients, and death and complications were recorded at 30 days after surgery, and upper limb systolic blood pressure was measured in all patients at discharge. Patients were followed up after discharge by outpatient visit or telephone call for their survival and the occurrence of repeat interventions and adverse events, which included death, cerebrovascular events, transient ischemic attack, myocardial infarction, hypertension, postoperative restenosis, and other cardiovascular-related interventions. Results: A total of 107 patients with aortic coarctation aged (34.1±15.2) years were included, and 68 (63.6%) were males. There were 16 cases in the combined descending aortic aneurysm group and 91 cases in the uncomplicated descending aortic aneurysm group. In the combined descending aortic aneurysm group, 6 cases (6/16) underwent artificial vessel bypass, 4 cases (4/16) underwent thoracic aortic artificial vessel replacement, 4 cases (4/16) underwent aortic arch replacement+elephant trunk procedure, and 2 cases (2/16) underwent thoracic endovascular aneurysm repair. There was no statistically significant difference between the two groups in the choice of surgical approach (all P>0.05). In the combined descending aortic aneurysm group at 30 days after surgery, one case underwent re-thoracotomy surgery, one case developed incomplete paraplegia of the lower extremity, and one case died; and the differences in the incidence of endpoint events at 30 days after surgery were similar between the two groups (P>0.05). Systolic blood pressure in the upper extremity at discharge was significantly lower in both groups compared with the preoperative period (in the combined descending aortic aneurysm group: (127.3±16.3) mmHg vs. (140.9±16.3) mmHg, P=0.030, 1 mmHg=0.133 kPa; in the uncomplicated descending aortic aneurysm group: (120.7±13.2) mmHg vs. (151.8±26.3) mmHg, P=0.001). The follow-up time was 3.5 (3.1, 4.4) years. There were no new deaths in the combined descending aortic aneurysm group, no transient ischemic attack, myocardial infarction or re-thoracotomy surgery, and one patient (1/15) suffered cerebral infarction and 10 patients (10/15) were diagnosed with hypertension. The differences in the occurrence of endpoint events during postoperative follow-up were similar between the two groups (P>0.05). Conclusion: In experienced centers, long-term prognosis of patients with aortic coarctation combined with descending aortic aneurysm is satisfactory post surgical intervention.

[The applications and challenges of liquid chromatography tandem mass spectrometry in maternal and child health].

Due to its ultra-high sensitivity, specificity and throughput, liquid chromatography tandem mass spectrometry (LC-MS/MS) has become an important analytical tool in clinical laboratories in quantifying various small molecules, such as vitamins, bile acids, steroids and other internal metabolites relevant to maternal diseases. As an effective means of screening and diagnosing diseases in preventive medicine, LC-MS/MS has been widely used in maternal and child health, contributing to the reduction of the incidence of maternal and child diseases and premature morbidity and mortality. At present, LC-MS/MS is an emerging and powerful platform in laboratory testing in China, facing both challenges and opportunities. In this article, the representative applications in the field of maternal and child health are summarized and discussed, along with the major hurdles of LC-MS/MS in clinical recognition and implementation.

[Mediation effect of inflammatory biomarkers on the association between blood lead levels and blood pressure changes in Chinese adults].

Objective: To investigate the role of inflammatory biomarkers in the relationship between blood lead levels and blood pressure changes. Methods: A total of 9 910 people aged 18-79 years who participated in the China National Human Biomonitoring in 2017-2018 were included in this study. A self-made questionnaire was used to collect demographic characteristics, lifestyle and other information, and the data including height, weight and blood pressure were determined through physical examination. Blood and urinary samples were collected for the detection of blood lead and cadmium levels, urinary arsenic levels, white blood cells, neutrophils, lymphocytes, and hypersensitive C-reactive protein (hs-CRP). Weighted linear regression models were used to evaluate the associations between blood lead, inflammatory biomarkers and blood pressure. Mediation analysis was performed to investigate the role of inflammation in the relationship between blood lead levels and blood pressure changes. Results: The median (Q1, Q3) age of all participants was 45.4 (33.8, 58.4)years, including 4 984 males accounting for 50.3%. Multivariate logistic regression model analysis showed that after adjusting for age, gender, residence area, BMI, education level, smoking and drinking status, family history of hypertension, consumption frequency of rice, vegetables, and red meat, fasting blood glucose, total cholesterol, triglycerides, blood cadmium and urinary arsenic levels, there was a positive association between blood lead levels, inflammatory biomarkers and blood pressure (P<0.05). Each 2.71 µg/L (log-transformed) increase of the lead was associated with a 2.05 (95%CI: 0.58, 3.53) mmHg elevation in systolic blood pressure (SBP), 2.24 (95%CI: 1.34, 3.14) mmHg elevation in diastolic blood pressure (DBP), 0.25 (95%CI: 0.05, 0.46) mg/L elevation in hs-CRP, 0.16 (95%CI: 0.03, 0.29)×109/L elevation in white blood cells, and 0.11 (95%CI: 0.02, 0.21)×109/L elevation in lymphocytes, respectively. Mediation analysis showed that the levels of hs-CRP significantly mediated the association of blood lead with SBP, with a proportion about 3.88% (95%CI: 0.45%, 7.32%). The analysis also found that the levels of hs-CRP and neutrophils significantly mediated the association of blood lead with SBP, with a proportion about 4.10% (95%CI: 1.11%, 7.10%) and 2.42% (95%CI: 0.07%, 4.76%), respectively. Conclusion: This study suggests that inflammatory biomarkers could significantly mediate the association of blood lead levels and blood pressure changes.

[Analysis of differences and influencing factors of liver injury associated with different strains of 2019-nCoV infection].

Objective: To analyze whether there are differences and related influencing factors in liver injury associated with different strains of 2019-nCoV/SARS-CoV-2 infection. Methods: Data of epidemiology, clinical symptoms, laboratory tests, and treatment outcomes of patients with COVID-19 infection confirmed with Alpha and Delta virus strain in Zhejiang Province were retrospectively collected. Statistical analysis was performed using independent samples t-test or Mann-Whitney U test, χ2 test or Fisher's exact test, and logistic regression analysis. Results: A total of 788 and 381 cases with Alpha and Delta virus strain were included. Vaccination ratio was 0% in Alpha and 85.30% in Delta group (P<0.001), The proportion of patients with fever (80.71% vs. 40.94%, P<0.001) was significantly higher in Alpha than Delta strain group. The proportion of critical ill patients was significantly higher in Delta group (9.90% vs. 1.57%, respectively, P<0.001). The virus negative conversion time was significantly longer in Delta than Alpha group (22 d vs. 11 d, P<0.001), but the incidence of liver injury was significantly higher in Alpha than Delta group (20.05% vs. 13.91%, P=0.011). Univariate analysis showed that Alpha virus strain infection, male sex, body mass index, chronic liver disease, fever, diarrhea, shortness of breath, severe/critical illness, elevated creatine kinase (CK), elevated international normalized ratio (INR) and an elevated neutrophil/lymphocyte ratio was significantly associated with an increased risk of liver injury occurrence, and in patients with pharyngeal pain the risk of liver injury occurrence was significantly reduced. Multivariate analysis showed that shortness of breath [OR, 2.667 (CI: 1.389-5.122); P=0.003], increased CK [OR, 2.544 (CI: 1.414-4.576); P=0.002] and increased INR [OR, 1.721] (CI: 1.074-2.758); P=0.024] was significantly associated with an increased risk of liver injury occurrence, and in patients with pharyngeal pain the risk of liver injury occurrence was significantly reduced [OR, 0.424 (CI: 0.254-0.709); P=0.001]. Conclusion: Although the virulence of the Delta is stronger than Alpha strain, most patients infected with Delta strain vaccinated against COVID-19 in Zhejiang province had milder clinical symptoms and a lower incidence and degree of liver injury. Notably, the infection risk even remains after vaccination; however, symptoms and the incidence of severe and critical illness can be significantly reduced.

[Clinical study of digital six-axis external fixation frame based on CT data for tibiofibular fractures].

Objective: To investigate the clinical effect of applying the digital six-axis external fixation frame based on CT data in the treatment of tibiofibular fractures. Methods: The clinical data of 43 patients with tibiofibular fractures treated by the self-developed digital six-axis external fixation frame based on CT data at Integrated Orthopedic Department of Traditional Chinese Medicine (TCM) and Western Medicine,HongHui Hospital from January 2018 to January 2021 were retrospective analysis.There were 27 males and 16 females,aged (36.0±9.4) years(range:25 to 50 years).AO classification:15 cases of 42A,11 cases of 42B, and 17 cases of 42C.There were 7 open fractures and Gustilo fracture classification:2 cases of type Ⅰ,4 cases of type Ⅱ,and 1 case of type Ⅲ.The two or three plane rings were connected with six connecting rods to form a complete six-axis external fixation frame,and the distal and proximal fracture blocks were connected to the distal and proximal rings by fixation pins,and the lengths of the six connecting rods needed to be adjusted were calculated by using the supporting software according to the CT data after surgery,and then the lengths of the connecting rods were adjusted one by one to complete the reduction of the fracture. The reduction accuracy of this six-axis external fixation brace was evaluated by measuring postoperative radiographs; postoperative recovery and complications were collected,the time of brace removal was recorded,and the function of the affected limb was evaluated according to the Johner-Wruhs score at the final follow-up. Results: Postoperative radiographs showed that all patients achieved satisfactory reduction with lateral displacement(M(IQR)) of 2.3(2.5) mm (range:0.3 to 7.3 mm),anteroposterior displacement of 2.1 (2.4) mm (range:0.3 to 5.7 mm),anteroposterior angulation of 2.5(2.4)°(range:0 to 5°),internal and external angulation of 2.1(1.5)°(range:0 to 4°), and no significant internal or external rotational deformity was detected on the exterior.On the second postoperative day,all patients were able to walk with partial weight-bearing on crutches. All 43 patients were followed up for more than 6 months,with a follow-up period of (33.3±7.3) weeks (range:24 to 42 weeks).The external fixation frame was removed after the fracture healed.The external frame was removed at 20(3)weeks (range:18 to 25 weeks) postoperatively. Up to the final follow up, no secondary fracture occurred in any of them.The Johner-Wruhs score of the affected limb at the last follow-up was excellent in 39 cases and good in 4 cases. Conclusion: The digital six-axis external fixator based on CT data for tibiofibular fractures has the advantages of precise reduction,firm fixation,simple operation,rapid fracture healing,and minimal trauma, which is a minimally invasive method for treating tibiofibular fractures,especially suitable for patients with poor skin and soft tissue conditions such as open injuries.

[Association of cadmium internal exposure with chronic kidney disease in Chinese adults].

Objective: To analyze the association of the cadmium internal exposure with chronic kidney disease (CKD) in Chinese adults aged 18 and older. Methods: A total of 9 821 adults aged 18-79 from the China National Human Biomonitoring (CNHBM) from 2017 to 2018 were included. Blood and urine cadmium exposure levels were measured by inductively coupled plasma mass spectrometry (ICP-MS), and urine cadmium levels were adjusted with urine creatinine; CKD were defined by estimated glomerular filtration (eGFR) using the chronic kidney disease epidemiology collaboration (CKD-EPI). Weights were considered due to complex sampling process for in statistical analysis. Logistic regression is used to analyze the association of blood cadmium, urine cadmium, and urine cadmium adjusted with creatinine exposure levels with CKD, and restricted cube spline (RCS) was used to assess the exposure-response curve of blood cadmium, urine cadmium and urine cadmium adjusted with creatinine with CKD. Results: The weighted age was 44.75 and males accounted for 61.1%. The prevalence rate of CKD was 12.7%. The geometric mean values of blood cadmium, urine cadmium, and urine cadmium adjusted with creatinine were 0.96 µg/L, 0.61 µg/L, and 0.58 µg/g. After adjusting for confounding factors, the weighted logistic regression showed that the lowest quintile (Q1) was compared with the odds ratio (OR) of the highest quintile (Q5) of blood cadmium, urine cadmium, and urine cadmium adjusted with creatinine and the 95% confidence interval (CI) was 1.80 (1.02-3.20), 1.77 (0.94-3.31) and 1.94 (1.11-3.37) respectively. In the restricted cubic spline regression model, non-linear association of blood cadmium, urine cadmium, and urine cadmium adjusted with creatinine with CKD were observed after adjusting for related confounding factors (P<0.001, 0.018, 0.031 respectively). The risk of CKD increased with the increment of cadmium exposure without risk threshold, and the exposure response curve was steeper at low cadmium exposure. Conclusions: Among Chinese adults aged 18 and older, cadmium exposure is positively associated with the risk of chronic kidney disease.

Isotopic determination with molecular emission using laser-induced breakdown spectroscopy and laser-induced radical fluorescence.

Molecular emission can be used for isotopic analysis in laser-induced breakdown spectroscopy (LIBS) due to its large isotopic shift. However, spectral weakness and interference have become the main flaws in molecular isotopic analysis, causing deterioration of quantitative accuracy and sensitivity. Here, to overcome these problems, laser-induced radical fluorescence (LIRF) was applied to enhance the molecular spectra and eliminate the spectral interference. The root mean square errors of cross validation (RMSECVs) of boron and carbon isotopes (11BO, 10BO, 12CN, and 13CN) improved to 2.632, 5.721, 5.990, and 1.543 at.%, as compared with 16.96, 35.79, 57.10, and 13.89 at.%, respectively, obtained in the case without LIRF. The limits of detection (LoDs) of 11BO, 10BO, 12CN, and 13CN were 0.9858, 0.8470, 1.606, and 1.193 at.%, respectively. This work demonstrates the feasibility of LIBS-LIRF to achieve isotopic determination with high accuracy and sensitivity.

One-point and multi-line calibration method in laser-induced breakdown spectroscopy.

The calibration-free laser-induced breakdown spectroscopy (CF-LIBS) and its variations are low cost, short time consumption, and high adaptability. However, seeking a more flexible and simple quantitative analysis method remains a challenge. A one-point and multi-line calibration (OP-MLC) was presented as a simple quantitative analysis method of LIBS. The results showed that OP-MLC-LIBS method can achieve quantitative analysis using only one standard sample, and the average relative errors (AREs) are 9, 22, 21 and 36% for Mn, Cr, Ni and Ti elements in six tested low-alloy steel samples, respectively. The method requires neither a large number of standard samples nor complicated calculations, which provides a flexible and low-cost quantitative analysis approach for development and application of LIBS.

Determination of boron with molecular emission using laser-induced breakdown spectroscopy combined with laser-induced radical fluorescence.

Boron is an essential element for industry, but it is hard to accurately and rapidly determine high boron content with conventional laser-induced breakdown spectroscopy (LIBS), due to the matrix and self-absorption effect. Using molecular emission is an alternative method for boron content analysis, but its weak spectra are major challenges. Here, boron monoxide (BO) radicals were used to establish calibration assisted by LIBS and laser-induced radical fluorescence (LIBS-LIRF). Two types of BO radical excitations, vibrational ground state excitation (LIRFG) and vibrational excited state excitation (LIRFE), were compared. The results showed that LIRFG achieved better sensitivity with a limit of detection of 0.0993 wt.%, while the LIRFE was more accurate with a root mean square error of cross validation of 0.2514 wt.%. In conclusion, this work provided a potential approach for molecular emission analysis with LIBS-LIRF.

[A new method of measuring leg length discrepancy on radiograph in patients undergoing total hip arthroplasty].

Objective: To investigate the reliability of the distance between the tip of the greater trochanter and inter-teardrop line (GT-IT) in evaluating the leg length discrepancy (LLD) in patients underwent total hip arthroplasty (THA). Methods: Patients who underwent THA in Xi'an Honghui Hospital from August 2015 to February 2016 were enrolled in this study.The patients were measured for bilateral hips anterior-posterior (AP) radiograph preoperatively and postoperatively.Four distances measured, included: GT-IT, the tip of lesser trochanter and bi-ischial line (LT-BI); LT-IT and the anterior superior iliac spine and the medial malleolus (ASIS-MM). Magnification factor was considered when calculating absolute values.Intraclass correlation coefficient (ICC) was used to detect the reliability of the measurement data.Single factor analysis and paired t test were performed to compare data among the methods. Results: The ICC values of the four groups were greater than 0.80, which showed excellent agreement in the measurements.Single factor analysis of variance showed there were no statistically significant differences in the LLDs of the four groups preoperatively and postoperatively (F=0.914, 0.886, both P>0.05). There was no significant differences in preoperative and postoperative LLD between group GT-IT and group ASIS-MM, LT-BI or LT-IT(t=-1.544-1.114, all P>0.05). The LLDs were comparable between group LT-BI, ASIS-MM and LT-IT both preoperatively and postoperatively (t=1.577, 0.976, 1.344, -0.087, all P>0.05). And the LLD in group LT-IT and ASIS-MM were equivalent preoperatively and postoperatively (t=0.130, 1.063, both P>0.05). Bland-Altman plot illustrated high level of agreements between the four methods. Conclusion: Great reliability can be obtained with the GT-IT in evaluating the LLD in patients undergoing THA.

[Effect of workplace bullying on posttraumatic stress disorder in nursing staff].

Objective: To investigate the relationship between workplace bullying and posttraumatic stress disorder (PTSD) in nursing staff, and to analyze the role of psychological capital between workplace bullying and PTSD. Methods: From December 2014 to June 2015, convenience sampling was used to collect 496 nurses from 5 grade A tertiary hospitals in a province of China. Their workplace bullying, psychological capital, and PTSD status were assessed using the Negative Acts Questionnaire, Psychological Capital Questionnaire, and Posttraumatic Stress Disorder Self-Rating Scale, respectively. The correlation between variables was analyzed using a structural equation model. Results: Among these nurses, the scores of negative acts, psychological capital, and PTSD were 37.15±12.83, 78.81±16.54, and 34.56±12.52, respectively. The score on each dimension of negative acts was positively correlated with that on each dimension of PTSD (P<0.01) ; the score on each dimension of psychological capital was negatively correlated with that on each dimension of PTSD and negative acts (P<0.01). Negative acts had a positive predictive effect on PTSD (ß=0.539, P<0.01) , which was reduced after inclusion of psychological capital (ß=0.513, P<0.01). The path coefficient was 0.62 for the effect of negative acts on PTSD, -0.18 for the effect of negative acts on psychological capital, and -0.11 for the effect of psychological capital on PTSD (P<0.05) . Conclusion: Workplace bullying is a predictive factor for PTSD, and psychological capital plays a mediating role between workplace bullying and PTSD. The manager should reduce workplace bullying to improve the psychological capital in nursing staff and to prevent and reduce PTSD.

Adaptive laser shock micro-forming for MEMS device applications.

Laser shock micro-forming is a non-thermal laser forming method that uses laser-induced shockwave to modify surface properties and to adjust shapes and geometry of work pieces. The magnitude and spatial distribution of the laser-induced shockwaves depend on the energy profiles of the laser beam focused on sample surfaces. In this paper, we present an adaptive optical technique to engineer spatial profiles of laser beams to control the shapes, sizes, and locations of the laser-induced shockwaves and the resulting forming features. Using a spatial light modulator, this adaptive laser beam forming tool was used to process free-standing MEMS structures in aluminum, which has led to highly uniform forming features. Shockwave simultaneously excited by multiple laser beams generated by the spatial light modulator and its effects on the micro-forming process were also studied. The results presented in this paper show that the adaptive optics laser beam forming is an effective and flexible method to generate shockwave with various shapes and sizes of wavefront and at multiple locations for laser processing at microscales.

ACTN3 R577X genotype and performance of elite middle-long distance swimmers in China.

The ACTN3 gene is one of the genes that have a potential influence on physical performance. Studies have shown that the 577R genotype of ACTN3 is more prevalent in sprint athletes, while the 577X genotype is more prevalent in endurance athletes. In swimming, both power and endurance related phenotypes are equally needed for swimmers to excel at the elite level. Therefore, the ACTN3 R577X polymorphism may become a genetic marker for swimmers. The study aimed to examine the association of the ACTN3 R577X genotype with the performance of elite middle-long distance (MLD) swimmers. The distributions of the ACTN3 R577X (rs1815739) genotype and allele were examined in a general population (206) and a group of elite MLD swimmers (160) in China by using PCR-RFLP and TOF. Compared with the general population, the elite MLD swimmers, especially the females, had a higher frequency of the RR genotype. The swimmers had a higher frequency of the R allele than the general population. However, the difference was not statistically significant. After being stratified by performance, the difference of the R allele frequency between the international master athletes and the general population was statistically significant. The elite MLD swimmers had a higher frequency of the RR genotype than the RX+XX genotype compared with the general population. The ACTN3 R577X polymorphism was associated with the performance of elite MLD swimmers in China. The SNP R577X could be used as a biomarker for selecting elite MLD swimmers in China.

Investigation on self-absorption at reduced air pressure in quantitative analysis using laser-induced breakdown spectroscopy.

The self-absorption at reduced air pressure for quantitative analysis of Mn and Cu elements in steel using laser-induced breakdown spectroscopy was investigated. The calibration curves of Mn and Cu elements at the air pressures of 100, 80, 50, 20, and 1 kPa were studied. The results show that, the nonlinearity of calibration curves which caused by self-absorption effects at atmosphere could be significantly improved by reducing the air pressure to 1 kPa, and the coefficients of determination (R2) of linear calibration curves of Mn and Cu lines are all higher than 0.99. The further study explored that the reason for the improvement was that the induced plasma became low density and the self-absorption coefficient was close to 1 when the air pressure reduced to 1 kPa.

Background removal in soil analysis using laser- induced breakdown spectroscopy combined with standard addition method.

The matrix effect of powder samples, especially for soil samples, is significant in laser-induced breakdown spectroscopy (LIBS), which affects the prediction accuracy of the element concentration. In order to reduce this effect of the soil samples in LIBS, the standard addition method (SAM) based on background removal by wavelet transform algorithm was investigated in this work. Five different kinds of certified reference soil samples (lead (Pb) concentrations were 110, 283, 552, 675, and 1141 ppm, respectively) were used to examine the accuracy of this method. The root mean square error of prediction (RMSEP) was more than 303 ppm by using the conventional calibration method. After adoption of SAM with background removal by wavelet transform algorithm, the RMSEP was reduced to 25.7 ppm. Therefore, the accuracy of the Pb element was improved significantly. The mechanism of background removal by wavelet transform algorithm based on SAM is discussed. Further study demonstrated that this method can also improve the predicted accuracy of the Cd element.

Sensitive determinations of Cu, Pb, Cd, and Cr elements in aqueous solutions using chemical replacement combined with surface-enhanced laser-induced breakdown spectroscopy.

In this study, chemical replacement combined with surface-enhanced laser-induced breakdown spectroscopy (CR-SENLIBS) was for the first time applied to improve the detection sensitivities of trace heavy metal elements in aqueous solutions. Utilizing chemical replacement effect, heavy metal ions in aqueous solution were enriched on the magnesium alloy surface as a solid replacement layer through reacting with the high chemical activity metallic magnesium (Mg) within 1 minute. Unitary and mixed solutions with Cu, Pb, Cd, and Cr elements were prepared to construct calibration curves, respectively. The CR-SENLIBS showed a much better detection sensitivity and accuracy for both unitary and mixed solutions. The coefficients of determination R2 of the calibration curves were above 0.96, and the LoDs were of the same order of magnitude, i.e., in the range of 0.016-0.386 µg/mL for the unitary solution, and in the range of 0.025-0.420 µg/mL for the mixed solution. These results show that CR-SENLIBS is a feasible method for improving the detection sensitivity of trace element in liquid sample, which definitely provides a way for wider application of LIBS in water quality monitoring.

De novo transcriptome analysis of tobacco seedlings and identification of the early response gene network under low-potassium stress.

Tobacco is an economically important crop, and its potassium content can greatly affect the quality of tobacco leaves. However, the molecular mechanism involved in potassium starvation in tobacco has not been elucidated to date. In this study, Illumina (Solexa) sequencing technology was used to analyze the transcriptome of tobacco seedlings under low-potassium stress for 6, 12, and 24 h. After analysis, 107,824 assembled unigenes were categorized into 57 GO functional groups, and 31,379 unigenes (29.08%) were clustered into 25 COG categories. A total of 9945 genes were classified into 233 KEGG pathways, and 15,209 SSRs were found among the 107,824 unigenes. Between the two samples, 1034 genes were differentially expressed. Twelve randomly selected gene expression levels were analyzed by quantitative RT-PCR, and the results were highly consistent with those obtained by Solexa sequencing. Our results provide a comprehensive analysis of the gene-regulatory network of tobacco seedlings under low-potassium stress.