[Clinical significance of monitoring ETV6-RUNX1 fusion gene expression in children with acute lymphoblastic leukemia after allogeneic hematopoietic stem cell transplantation]

Objective: To investigate the clinical significance of monitoring ETV6-RUNX1 fusion gene in children with acute lymphoblastic leukemia (ALL) after allogeneic stem cell transplantation (allo-HSCT) . Methods: Clinical data of 13 children received allo-HSCT in Peking University Institute of Hematology from May 2009 to March 2016 were retrospectively collected. The ETV6-RUNX1 gene was examined by real-time quantitative polymerase chain reaction (RQ-PCR) . The correlation between its expression level and the disease status was analyzed. Results: Of 13 enrolled ALL cases, the ETV6-RUNX1 expression of 7 patients converted to positive after transplant at a median time of 137 days (range, 28-270 days) . The expression level of the first positive sample was 0.034% (range, 0.004%-0.061%) . The duration from ETV6-RUNX1 positive to hematological relapse was 196 days (range, 28-666 days) . Four patients experienced relapse at a median time of 294 days (range, 104-803 days) after allo-HSCT. The ETV6-RUNX1 expression converted to positive prior to MRD. Patients with positive ETV6-RUNX1 gene expression pre-transplantation would be more likely to relapse. Conclusion: Monitoring ETV6-RUNX1 by RQ-PCR could be used to evaluate MRD status after allo-HSCT. Patients with positive ETV6-RUNX1 after transplant had a poor prognosis.

[Significance of PCR detection of HHV6 in gastro biopsy on the course of diarrhea in patients with severe diarrhea after allogeneic hematopoietic stem cell transplantation]

目的

探讨肠黏膜人疱疹病毒6型（HHV6）检测在异基因造血干细胞移植（allo-HSCT）术后重度腹泻患者中的意义。

方法

回顾性分析2015年2月至2016年8月于北京大学血液病研究所行allo-HSCT后出现重度腹泻并行肠镜检查及肠黏膜活检的患者资料；HHV6、CMV、EBV检测采用RT-PCR方法；肠黏膜病理检查也包括免疫组化方法检测CMV早期抗原、CMV晚期抗原，原位杂交检测EBV。

结果

共有45例患者纳入研究，其中21例（46.7%）肠黏膜活检HHV6阳性，包括男13例，女8例，中位年龄29（14~54）岁；肠黏膜HHV6阳性与阴性组患者血CMV阳性检出率差异无统计学意义（76.2%对87.5%，P>0.05），但EBV血症发生率前者（6/21，28.6%）明显高于后者（1/24，4.2%）（P=0.028）；两组患者在腹泻发生的时间、次数及量方面差异无统计学意义（P值均>0.05）。45例患者中44例接受了膦甲酸钠和（或）更昔洛韦抗病毒治疗，抗病毒治疗并没有影响腹泻的进程。

结论

肠黏膜HHV6阳性在allo-HSCT术后重症腹泻患者中发生率高，未发现其对于治疗及预后有临床意义。肠黏膜HHV6阳性并不能证明HHV6在肠道的感染。

Tailored Polyimide-Graphene Nanocomposite as Negative Electrode and Reduced Graphene Oxide as Positive Electrode for Flexible Hybrid Sodium-Ion Capacitors

Redox-active polyimide materials hold a great promise for electrochemical energy storage applications, especially for flexible energy storage devices. However, the low utilization efficiency due to poor electrical conductivity of the materials remains one of the greatest challenges. In this work, we designed and prepared polyimide-graphene composite materials and tested their electrochemical properties in sodium-ion capacitors. By manipulating the interfacial chemistry and interactions between the polyimide and graphene, composite electrode materials with different polyimide particle sizes and morphologies were obtained. Sodium-ion storage capacity was significantly improved, from ∼50 mAh g^-1 for pure polyimide to 225 mAh g^-1 for a polyimide-graphene composite. A hybrid sodium-ion capacitor fabricated with freestanding polyimide-graphene composite as the negative electrode and reduced graphene oxide as the positive electrode delivered energy densities of 55.5 and 21.5 Wh kg^-1 at power densities of 395 and 3400 W kg^-1, respectively. A flexible sodium-ion capacitor with outstanding mechanical properties was also demonstrated.

Polymer Electrode Materials for Sodium-ion Batteries

Sodium-ion batteries are promising alternative electrochemical energy storage devices due to the abundance of sodium resources. One of the challenges currently hindering the development of the sodium-ion battery technology is the lack of electrode materials suitable for reversibly storing/releasing sodium ions for a sufficiently long lifetime. Redox-active polymers provide opportunities for developing advanced electrode materials for sodium-ion batteries because of their structural diversity and flexibility, surface functionalities and tenability, and low cost. This review provides a short yet concise summary of recent developments in polymer electrode materials for sodium-ion batteries. Challenges facing polymer electrode materials for sodium-ion batteries are identified and analyzed. Strategies for improving polymer electrochemical performance are discussed. Future research perspectives in this important field are projected.

[Risk stratification of type-specific human papillomavirus for cervical precancers: evidence from a cross-sectional study in Shenzhen]

Objective: To analyze the epidemiological genotype features of human papillomavirus (HPV) in cervical infection and their risks for cervical precancers among women in Shenzhen area. Methods: A total of 2 717 individuals ranging in age from 30~59 years were recruited in 18 community health centers of Shenzhen city from March 1 to June 15, 2015 by a cluster sampling method. The results of genotype of HPV, liquid-based cytology (LBC), colposcopy and pathology were analyzed. The clinical sensitivity and specificity as well as positive (PPV) and negative (NPV) predictive values of the combination of different HPV genotype in screening the cervical intraepithelial neoplasia (CIN) 2 and above were estimated. Results: The HPV infection rate in Shenzhen area was 15.9% (432/2 717). The most common HPV genotype was HPV52 (22.9%), followed by HPV16 (12.7%), HPV53 (10.0%), HPV51 (8.6%) and HPV58 (8.1%). Compared with HPV16/18 genotyping, HPV33/16 genotyping had a higher sensitivity (57.1% vs. 42.9%, P<0.05) and an analogous specificity (87.3% vs. 86.9%, P>0.05) in predicting CIN2+ . The sensitivity of combination of HPV33/16 genotyping and low grade squamous intraepithelial lesion (LSIL) positive tested by LBC in predicting CIN2+ was 75.0%, significantly higher than 64.3% of atypical squamous cells of undetermined significance (ASC-US) positive tested by LBC alone (P<0.05). The specificities of these two methods mentioned above in predicting CIN2+ were 83.5% and 89.2%, respectively, without statistical difference (P>0.05). Conclusions: Women infected by HPV have distinct risks for CIN2+ according to different high-risk HPV genotypes. The top five risks were HPV 33, 16, 58, 56, and 68. HPV-positive women triaged by LBC LSIL+ combined with HPV33/16 genotyping may be a potential strategy for cervical cancer screening in developed urban area.

[Analysis of the impact of job characteristics and organizational support for workplace violence]

Objective: To analyze the effect of job characteristics and organizational support for workplace violence, explore the influence path and the theoretical model, and provide a theoretical basis for reducing workplace violence. Methods: Stratified random sampling was used to select 813 medical staff, conductors and bus drivers in Chongqing with a self-made questionnaire to investigate job characteristics, organization attitude toward workplace violence, workplace violence, fear of violence, workplace violence, etc from February to October, 2014. Amos 21.0 was used to analyze the path and to establish a theoretical model of workplace violence. Results: The odds ratio of work characteristics and organizational attitude to workplace violence were 6.033 and 0.669, respectively, and the path coefficients were 0.41 and-0.14, respectively (P<0.05). The Fitting indexes of the model: Chi-square (χ(2)) =67.835, The ratio of the chi-square to the degree of freedom (χ(2)/df) =5.112, Good-of-fit index (GFI) =0.970, Adjusted good-of-fit index (AGFI) =0.945, Normed fit index (NFI) =0.923, Root mean square error of approximation (RMSEA) =0.071, Fit criterion (Fmin) =0.092, so the model fit well with the data. Conclusion: The job characteristic is a risk factor for workplace violence while organizational attitude is a protective factor for workplace violence, so changing the job characteristics and improving the enthusiasm of the organization to deal with workplace violence are conducive to reduce workplace violence and increase loyalty to the unit.

[Distribution and associated factors of high-risk HPV genotypes infection among HPV-positive women who participated cervical screening test in Shenzhen, 2014-2016, China]

Objective: To analyze the distribution and associated factors of high-risk genotypes of HPV in cervical infection among women in Shenzhen. Methods: The information on sociodemographic characteristics and HPV genotypes of HPV-positive women who participated cervical screening test from January 2014 to December 2016 was downloaded from Shenzhen Maternity and Child Healthcare Management Information System. According to the pathogenicity, the high-risk HPV genotypes were divided into 15 types including HPV 16, 18, 31, 33, 35, 39, 45, 51, 52, 53, 56, 58, 59, 66 and 68; and there were 6 low-risk genotypes including HPV 6, 11, 42, 43, 44, and 81. Chi-square tests were applied to compare the proportions of high-risk HPV infection among women who had different sociodemographic characteristics. A non-conditional logistic regression model was used to analyze the associated factors for high-risk HPV infection. Results: In total, all HIV positives received HPV genotyping, with an average age of (38.08±9.38) years old. There were 9 979 (93.9%) high-risk and 645 (6.1%) low-risk HPV infections. The proportions of HPV infections for high-risk type in each year were 91.5%, 93.8%, and 95.6%, increasing with the screening years (χ(2)=54.79, P<0.001). Multivariate logistic regression analysis showed that compared with women younger than 25 years old, women in other age groups (at age 26 to 30 years, 31 to 35 years, 36 to 40 years, 41 to 45 years, and 50 years or older) had increased risks of high-risk HPV infection, with OR (95%CI) of 1.67 (1.20-2.31), 1.49 (1.09-2.03), 1.71 (1.23-2.37), 1.65 (1.19-2.31), and 1.84 (1.26-2.67), respectively; compared with the married, single women had a decreased risk of high-risk HPV infection (OR (95%CI): 0.71 (0.50-1.00)); women received HPV testing in 2015 and 2016 showed higher risk of high-risk HPV infection than those in 2014 (OR (95%CI): 1.43 (1.17-1.74) and 2.03 (1.68-2.46)). The 5 most common HPV genotypes were HPV52 (25.1%, 2 670 cases), followed by HPV16 (19.2%, 2 041 cases), HPV58 (13.3%, 1 413 cases), HPV18 (9.9%, 1 048 cases), and HPV51 (9.3%, 993 cases). Conclusion: Age, marital status, and screening year were associated with high-risk HPV infections. Besides HPV16 and HPV18, the prevention and control on HPV infections for HPV52, HPV58, and HPV51 should be prioritized in Shenzhen area.

[An analysis of the characteristics of perioperative cardiac troponin elevation in orthopaedic surgical patients]

Objective: Perioperative myocardial infarction remains a severe complication in non-cardiac surgery and is one of the major causes of death. Cardiac troponin (cTn) I elevation is associated with short-term and long-term mortality. The aim of the study was to assess the proportion rate of cTnI elevation and its clinical characteristics among patients admitted for orthopaedic surgery with or without cardiovascular events. Methods: This is a retrospective study including 27 744 patients aged 50 years or older who admitted for orthopaedic surgery from 2009-2015 in Beijing Jishuitan Hospital. Results: Two hundred and sixty-five patients [age (71.7±9.9) years] had cTnI level> 0.04 μg/L with 66% (175 patients) of them being female. Among them, 59 patients were isolated troponin rise (ITR) (n=59), 13 were preoperative acute myocardial infarction (AMI), and 193 were postoperative AMI. The proportion of postoperative AMI was 0.69%. Those patients were more likely to have a history of coronary artery disease or hypertension. Non-ST-segment elevation myocardial infarction (NSTEMI) was more common (93.3%) than ST-segment elevation myocardial infarction in these patients. Most of them did not experience ischemic symptoms. Totally 76.7% of the AMI occurred within 3 days of surgery; and the in-hospital mortality rate was 10.4%. Conclusions: Perioperative elevation of troponin is common in patients undergoing orthopaedic surgery. Most postoperative AMI were NSTEMI and with absent or atypical ischemia symptoms. Monitoring troponin levels and electrocardiograph in at-risk patients is needed to find most of the AMI.

Electrospun γ-Fe2O3 nanofibers as bioelectrochemical sensors for simultaneous determination of small biomolecules

Nanofibers of α-Fe₂O₃ and γ-Fe₂O₃ have been obtained after the controlled calcination of precursor nanofibers synthesized by electrospinning. α-Fe₂O₃ nanofibers showed an irregular toruloid structure due to the decomposition of poly (4-vinyl) pyridine in air while γ-Fe₂O₃ nanoparticles decorated nanofibers were observed after the calcination under N₂ atmosphere. Electrochemical measurements showed that different electrochemical behaviors were observed on the glassy carbon electrodes modified by α-Fe₂O₃ and γ-Fe₂O₃ nanofibers. The electrode modified by γ-Fe₂O₃ nanofibers exhibited high electrocatalytic activities toward oxidation of dopamine, uric acid and ascorbic acid while α-Fe₂O₃ nanofibers cannot. Furthermore, the γ-Fe₂O₃ modified electrode can realize the selective detection of biomolecules in ternary electrolyte solutions. The synthesis of nanofibers of α-Fe₂O₃ and γ-Fe₂O₃ and their electrochemical sensing properties relationship have been discussed and analyzed based on the experimental results.

[Clinical features and early treatment effects in intermediate risk and poor risk acute myeloid leukemia with EVI1 positive]

OBJECTIVE

To investigate the clinical biological characteristics of EVI1 positive acute myeloid leukemia (AML) and its effect on early chemotherapy.

METHODS

The clinical and biological cha-racteristics of 33 AML patients with EVI1 positive were retrospectively analyzed in 361 AML patients who were diagnosed and treated in our institute from March 2015 to July 2016, and the clinical and biological features, and rates of the induced remission were compared between the intermediate risk and poor risk with EVI1 positive AML, moreover, the influential factors on complete remission (CR) were analyzed. The expression of EVI1/ABL was tested in 32 healthy donors to confirm the abnormal threshold of EVI1 expression.

RESULTS

The definition of EVI1 positive was that the quantitative expression of EVI1/ABL was more than 8.0%. The 33 AML patients with EVI1 positive were found in 361 newly diagnosed AML patients, in which the female and male patients were 17 and 16 respectively, the median age was 45 (18-67) years, with a median follow-up of 6.6 (0.7-13.2) months. Intermediate karyotype was found in 17 patients(including 9 patients with normal karyotypes,1 patient with +8);unfavorable karyotype was found in 14 patients [including 7 patients with -7/7q^-,4 patients with t (v;11q23),3 patients with inv(3)/t(3;3), and 2 patients without mitotic figures]. The rate of CR in the first induction chemotherapy was 42.4%, and the rate of total CR was 60.6%. According to the NCCN, 16 intermediate risk patients and poor risk patients were divided, without favorable risk patients. The rate of CR in the first induction chemotherapy were 68.8% and 17.6% (P=0.005) in the intermediate risk and poor risk respectively, that of total CR were 81.3% and 41.2%(P=0.032), and the rates of relapse were 7.7% and 14.3%.Univariable analysis revealed that unfavorable karyotype could affect the rate of CR in the first reduction chemotherapy and that of total CR (P=0.004, 0.029). The poor risk patients had higher mortality (41.2% vs. 6.3%, P=0.039) and lower overall survival (OS)(P=0.012).

CONCLUSION

EVI1 may be not an independent prognostic factor for the AML patients considering the appea-rance in the intermediate and poor risk patients. It predicts poor outcome in the EVI1 positive AML patients who have unfavorable karyocytes, such as -7/7q^-, t(v;11q23), and inv(3)/t(3;3), and also a low rate of both CR in the first induction chemotherapy and total CR. It also has a low rate of long-term survival and high mortality in the AML patients with EVI1 positive, who may benefit from allogeneic bone marrow transplantation as soon as possible.

Jujube leaf green tea extracts inhibits hepatocellular carcinoma cells by activating AMPK

Here we evaluated the anti-hepatocellular carcinoma activity by the Jujube leaf green tea extracts (JLGTE). We showed that JLGTE exerted anti-proliferative, cytotoxic and pro-apoptotic activities against HepG2 and primary human hepatocellular carcinoma cells. It was however non-cytotoxic to the normal hepatocytes. JLGTE activated AMP-activated protein kinase (AMPK) signaling, which was required for its cytotoxicity against hepatocellular carcinoma cells. Silence of AMPKα1, via targeted short hairpin RNAs or CRISPR-Cas9 genome editing, inhibited JLGTE-induced AMPK activation and HepG2 cell apoptosis. Further, in-activation of AMPK by a dominant negative AMPKα1 (T172A) also alleviated JLGTE's cytotoxicity against HepG2 cells. On the other hand, forced-activation of AMPK by introduction of a constitutively-active AMPKα1 (T172D) mimicked JLGTE's actions and led to HepG2 cell apoptosis. These results suggest that JLGTE inhibits human hepatocellular carcinoma cells possibly via activating AMPK.

[Clinical value of PCR for viral detection of bronchoalveolar lavage fluid in the diagnosis and treatment of pneumonia after allogeneic hematopoietic stem cell transplantation]

Objective: To analyze the clinical value of real-time PCR for virus detection in the diagnosis and treatment of patients after allo-HSCT who had no infection evidence of pneumonia using routine pathogen detection panel. Methods: The clinical data of 71 episodes with acute lung injury from May 2015 to March 2017 after allo-HSCT in hematology department of Peking University People's Hospital (PKUPH) were retrospectively analyzed. PCR for virus detection and other routine pathogen detection tests were performed on bronchoalveolar lavage fluid (BALF) samples. Results: Among 71 episodes with acute lung injury, a total of 15 patients were diagnosed as lower respiratory tract disease merely associated with virus (detection rate of 21.13%) , 19 episodes were absent of lower respiratory tract infection. The median time from allo-HSCT to the occurrence of lung injury were 176 (49-1 376) d and 196 (57-457) d respectively (z=-0.191, P=0.864) . There were no statistical differences for baseline characteristics and clinical features between two groups. The 100-day attributable mortalities were 13.3% (2/15) and 26.3% (5/19) (χ(2)=0.864, P=0.426) . Patients with low-dose steroids treatment had favorable outcome than those with high-dose steroids treatment (the dose of methylprednisolone ≥250 mg/d as standard) [4.2% (1/24) vs 60.0% (6/10) ]. In patients with detectable virus in BALF, 2 patients died with early high-dose steroids treatment, while 11 patients survived with no steroids treatment or late application. Conclusions: Virus infection should be considered in post-HSCT pneumonia patient with negative result using routine pathogen detection panel. Expanding virus detection panel by PCR in BALF could increase diagnostic precision and might be instructive to treatment.

An Improved Binary Differential Evolution Algorithm for Feature Selection in Molecular Signatures

The discovery of biomarkers from high-dimensional data is a very challenging task in cancer diagnoses. On the one hand, biomarker discovery is the so-called high-dimensional small-sample problem. On the other hand, these data are redundant and noisy. In recent years, biomarker discovery from high-throughput biological data has become an increasingly important emerging topic in the field of bioinformatics. In this study, we propose a binary differential evolution algorithm for feature selection. Firstly, we suggest using a two-stage approach, where three filter methods including the Fisher score, T-statistics, and Information gain are used to generate the feature pool for input to differential evolution (DE). Secondly, in order to improve the performance of differential evolution algorithm for feature selection, a new variant of binary DE called BDE is proposed. Three optimization strategies are incorporated into the BDE. The first strategy is the heuristic method in initial stage, the second one is the self-adaptive parameter control, and the third one is the minimum change value to improve the exploration behaviour thus enhance the diversity. Finally, Support vector machine (SVM) is used as the classifier in 10 fold cross-validation method. The experimental results of our proposed algorithm on some benchmark datasets demonstrate the effectiveness of our algorithm. In addition, the BDE forged in this study will be of great potential in feature selection problems.

Structural Regulation of PdCu2 Nanoparticles and Their Electrocatalytic Performance for Ethanol Oxidation

Two types of PdCu₂ nanoparticles were prepared through one-pot synthesis and a two-step reducing process, named as PdCu₂-1 and PdCu₂-2, respectively. The morphology and structure of as-prepared samples were investigated by transmission electron microscopy, high-resolution transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and inductively coupled plasma-optical emission spectrometry. Results showed that more Pd atoms were buried in the inside of PdCu₂-1, whereas more available Pd sites were distributed on the surface of PdCu₂-2. The electrochemical measurements indicated that both PdCu₂-1 and PdCu₂-2 nanoparticles showed a higher electrocatalytic activity than that for pure Pd nanoparticles. In particular, PdCu₂-2 predictably exhibited a better stability and durability as well as a lower onset potential and a higher catalytic current density than that of PdCu₂-1 toward ethanol oxidation in alkaline media. On the basis of these studies, the formation mechanisms of both the PdCu₂ catalysts and the relationship between their structure and properties were discussed in this paper.

Capacitance of Nanoporous Carbon-Based Supercapacitors Is a Trade-Off between the Concentration and the Separability of the Ions

Nanoporous carbon-based supercapacitors store electricity through adsorption of ions from the electrolyte at the surface of the electrodes. Room temperature ionic liquids, which show the largest ion concentrations among organic liquid electrolytes, should in principle yield larger capacitances. Here, we show by using electrochemical measurements that the capacitance is not significantly affected when switching from a pure ionic liquid to a conventional organic electrolyte using the same ionic species. By performing additional molecular dynamics simulations, we interpret this result as an increasing difficulty of separating ions of opposite charges when they are more concentrated, that is, in the absence of a solvent that screens the Coulombic interactions. The charging mechanism consistently changes with ion concentration, switching from counterion adsorption in the diluted organic electrolyte to ion exchange in the pure ionic liquid. Contrarily to the capacitance, in-pore diffusion coefficients largely depend on the composition, with a noticeable slowing of the dynamics in the pure ionic liquid.

Mesoporous Ni/Ce1−xNixO2−y heterostructure as an efficient catalyst for converting greenhouse gas to H2 and syngas

A heterostructure of highly dispersed Ni nanoparticles in pore channels of Ni–CeO₂ solid solution, having excellent thermo-stability, redox properties, and metal/support synergy, is identified as an efficient nanocatalyst for converting greenhouse gas into H₂ energy and syngas.

Structural evolution of palladium nanoparticles and their electrocatalytic activity toward ethanol oxidation in alkaline solution

Palladium nanoparticles with smaller particle size exhibit better electrocatalytic activity toward ethanol oxidation.

Control over the morphology and phase of MnOx formed in the modified Hummers' method and impact on the electrocapacitive properties of MnOx–graphite oxide composite electrodes

The controllable morphology and crystalline phase of manganese oxides formed in the Hummer's method have an impact on the electrocapacitive performance of the resulting composite materials.

Desired crystal oriented LiFePO4 nanoplatelets in situ anchored on a graphene cross-linked conductive network for fast lithium storage

Electron transfer and lithium ion diffusion rates are the key factors limiting the lithium ion storage in anisotropic LiFePO4 electrodes. In this work, we employed a facile solvothermal method to synthesize a "platelet-on-sheet" LiFePO4/graphene composite (LFP@GNs), which is LiFePO4 nanoplatelets in situ grown on graphene sheets with highly oriented (010) facets of LiFePO4 crystals. Such a two-phase contact mode with graphene sheets cross-linked to form a three-dimensional porous network is favourable for both fast lithium ion and electron transports. As a result, the designed LFP@GNs displayed a high rate capability (∼56 mA h g(-1) at 60 C) and long life cycling stability (∼87% capacity retention over 1000 cycles at 10 C). For comparison purposes, samples ex situ modified with graphene (LFP/GNs) as well as pure LiFePO4 platelets (LFP) were also prepared and investigated. More importantly, the obtained LFP@GNs can be used as a basic unit for constructing more complex structures to further improve electrochemical performance, such as coating the exposed LFP surface with a thin layer of carbon to build a C@LFP@GN composite to further enhance its cycling stability (∼98% capacity retention over 1000 cycles at 10 C).

Stabilization of silicon nanoparticles in graphene aerogel framework for lithium ion storage

Schematic illustration of the preparation of Si/RGO-AG.

Rigid three-dimensional Ni3S4 nanosheet frames: controlled synthesis and their enhanced electrochemical performance

Rigid three-dimensional (3D) Ni₃S₄ nanosheet frames assembled from ultrathin nanosheets are synthesized via a facile solvothermal method.

Solvothermal synthesis of MnFe2O4 colloidal nanocrystal assemblies and their magnetic and electrocatalytic properties

Submicrometer MnFe₂O₄ colloidal nanocrystal assemblies (CNAs) have been synthesized controllably by using a solvothermal method through simply adjusting synthetic reagents.