Commercial solar cells have a power conversion efficiency (PCE) in the range of 10–22% with different light absorbers. Graphene, with demonstrated unique structural, physical, and electrical properties, is expected to bring the positive effects on the development of thin film solar cells. Investigations have been carried out to understand whether graphene can be used as a front and back contacts and active interfacial layer in solar cell fabrication. In this review, the current progress of this research is analyzed, starting from the graphene and graphene-based Schottky diode. Also, the discussion was focused on the progress of graphene-incorporated thin film solar cells that were fabricated with different light absorbers, in particular, the synthesis, fabrication, and characterization of devices. The effect of doping and layer thickness of graphene on PCE was also included. Currently, the PCE of graphene-incorporated bulk-heterojunction devices have enhanced in the range of 0.5–3%. However, device durability and cost-effectiveness are also the challenging factors for commercial production of graphene-incorporated solar cells. In addition to the application of graphene, graphene oxides have been also used in perovskite solar cells. The current needs and likely future investigations for graphene-incorporated solar cells are also discussed. A perfeperature , great t3 W/m·K) . Besides3 W/m·K) ,8, medic3 W/m·K) , photo-d3 W/m·K) , energy 3 W/m·K) , and man3 W/m·K) .At present, a number of techniques have been developed for the fabrication of graphene. Besides the initial mechanical exfoliation of highly-organized graphite sheets , chemica2 [Solar energy conversion is another major area where graphene appears frequently. While the current photovoltaic (PV) market is still dominated by Si-based solar cells, thin film PVs that are based on CdTe ,20, copp2  have bee2 . Thin fi2 . On consThe microstructure of graphene consists of a repeatable two-dimensional (2D) hexagonal lattice. Each peak position is occupied by carbon atom, with another equivalent three covalent-bonded nearest neighbors, as shown in When in contact graphene with a semiconductor, a Schottky junction would be formed. However, the Fermi level of graphene could be easily shifted by chemical doping or carrier injection under a bias ,29. TherMoreover, Riazimehr et al.  measured2 flow rate, the number of graphene layers could be well controlled, which also provides a wide selection range of transparency and sheet resistance. Two devices, with and without ZnO blocking layer, were fabricated and characterized. The device with ZnO layer showed a higher efficiency (4.17%) than the one without ZnO (2.81%), indicating the importance of ZnO: a good contact with graphene and current leakage protection. Followed by their initial work, this group reported a great advantage of the graphene-CdTe device with graphene as the back contact. In order to provide a better coverage and contact on CdTe, the graphene was synthesized with a three-dimensional (3D) structure using porous Ni foam as the growth substrate. A similar method was employed to grow graphene and the 3D structure was successfully observed and transferred to CdTe device. The final graphene back contact thickness exceeded 10 µm with an excellent electrical conductivity (550–600 S/cm), which assisted a significant device efficiency improvement up to 9.1%, as shown in 2), this work indicated the possibility of large-scale device fabrication [With high transparency, carrier mobility and flexibility, graphene was first considered to be the alternative contact material. To the best of our knowledge, the first successful graphene-encountered CdTe device was reported by Bi et al.  with conrication .Moreover, graphene-based composite back contact was also tried: Liang et al.  reportedx, which served as a separator between Ag top grid and CdTe. Their device acquired a relatively high efficiency of 2.08%. Moreover, to test the importance of original window layer CdS/CdSe, a separately-prepared CdSe quantum dots was prepared and coated onto the graphene supporting layer, which elevated the efficiency result to 3.1%. Those extra n-type quantum dots also contributed to light-generated electron collecting, which led to a clear increase in both short-circuit current density (Jsc) and external quantum efficiency (EQE), as shown in In addition, impurity doping into graphene was also tried in back contacts. One example is the comparison among boron-doped graphene, intrinsic graphene and reduced graphene oxide (r-GO) . These rsc would be greatly enhanced and the CdTe thickness could also be reduced to around 1 µm to minimize unnecessary carrier generation. This group also claimed that the dangling bonds between graphene networks might generate movable ions, especially with the co-existence of metal dopant. Those free ions would diffuse into the p-n junction interface, and, therefore, cause damage to the device rather than at the back contact interface [In addition to the above experimental results, simulation work also indicated the great potential in the application of graphene in CdTe system. Aldosari et al.  establisnterface . In addinterface . More denterface .Although graphene was already demonstrated with great transparency and conductivity, the actual practice showed that more work is required to optimize the growth conditions, such as growth atmosphere profile and metallic doping, as well as their effects on graphene contact properties. Also, understanding of the thermal stability of graphene and graphene composite is also necessary. Overall, that reported progress showed that graphene could be a suitable replacement for FTO and metal back contact for CdTe system with a lower cost and easy manufacturing.Similar to the CdTe system, graphene was first considered as an alternative front contact. Yin et al.  first resc was about 13 mA/cm2 and the efficiency was around 1%. However, the strong Na diffusion would affect the p-type region, which may affect the built-in potential and the open-circuit voltage (Voc) of the device.Moreover, the Brookhaven National Lab achieved a direct n-doped graphene/CIGS Schottky junction . The strsc and efficiency than the front contact case [According to the literature, very limited investigations have been carried out regarding the successful application of graphene as the back contact for CIGS although the work function requirement was similar to CdTe. But, a simulation work based on refractive index and extinction coefficient indicated that the graphene back contact would lead to a higher Jact case . As predAt present, no experimental record shows the effect of graphene on copper-zinc-tin sulfide (CZTS) system. Only a simulation result predicted the advantage of using graphene front contact, rather than the conventional indium-tin-oxide (ITO) . In theiThe above information, it could be inferred that the application of graphene on CIGS or its relevant materials system is still in its early stage. Similar to CdTe case, more understanding and experience are required for the optimization of transport phenomenon at the GIGS/graphene interface. Based on the current literature, it can be expected that the performance of CIGS solar cells will be further enhanced by the application of graphene.3NH3PbX3 , had been demonstrated with a suitable band gap and high absorption coefficient [2 and Spiro-OMeTAD -9,9′-spirobifluorene) are the most widely-used ETL and HTL, respectively [In the past few years, the organic-inorganic lead-halide perovskite solar cells (PSCs) achieved fast efficiency improvement from 3.8% to 22.1% . The mosfficient . The devectively . DSSC deectively ,58. Thos2 with graphene and lithiated graphene have been successfully employed to enhance both PCE and stability of PSCs [Graphene can be used to improve either or both of charge injection and collection at the electrodes. Thus, the power conversion efficiency and durability can be enhanced. This can alleviate the problematic carrier recombination processes, which are known to increase due to the material instability at the interfaces of soft materials in PSCs. When free charges are fast injected from perovskite to the electron transport layer, the degradation of perovskite and non-radiative recombination are reduced. Subsequently, mixing of mesoporous TiO of PSCs . More in2 composite as the ETL [2 and FTO. Their highest efficiency was 15.6% when compared with typical high-temperature-annealed TiO2 (14.1%). A detailed J-V curve comparison was shown in 2 layer. Those graphene-involved devices had a TiO2 annealing temperature of 150 °C, rather than the typical 500 °C, making the fabrication process less costly. Zhu et al. [2 and perovskite. This insertion minimized the electron extraction time from the perovskite, and, therefore, the efficiency was enhanced from 8.81% to 10.15%.The first reported graphene-enhanced PSC was accomplished through graphene/TiO the ETL . Their gu et al.  reported2 slurry to form the final mixture and spin coated in a TiO2 blocking layer [sc was cut down. According to their results, the 0.4 vol % was the best ratio, with an efficiency of 14.5%, which was clearly higher than their TiO2-only device (11.5%). The corresponding J-V characteristics are shown in 2 also showed an increased efficiency with its reference cell. However, this work showed a lower efficiency of 9.3%, with an r-GO ratio of 0.15 wt % in compact TiO2 and 0.015 wt % in meso-TiO2 [sc and fill factor (FF) was boosted but the Voc had a slight decrease due to TiO2 conduction band edge shrinking (negative effect of Li doping). The efficiency of the GO-injected device was 11.8% and the reference cell was 10.3%. Moreover, the GO layer injection significantly reduced the J-V hysteresis. According to the investigators, it is believed that Li-GO layer could reduce the trap-assisted recombination at TiO2/perovskite interface. The addition of Li-GO layer also reduced the device decay rate in the initial stage, but has no clear improvement for the long-term device stability.Also, GO and r-GO were investigated to boost the efficiency of PSCs. The r-GO synthesized by Hummers’ method was mixed with TiOng layer . By alteeso-TiO2 . Besideseso-TiO2 . A modifeso-TiO2  was usedsc could be enhanced. The inverted PSC with GO as the HTL achieved a high PCE of 12.40%, as shown in Research on using graphene-related films as HTL also attracts great attention. Wu et al.  spin-coa2 atmosphere on a pre-heated perovskite layer. In addition, the reference samples had either a spin-coated GO layer from the same GO suspension or a Spiro-OMeTAD layer. After evaporating the top Au grid, the J-V characteristics of PSCs showed that the Spiro-OMeTAD had a greater device efficiency due to both kinds of GO layers, and very little statistical difference could be found between the device efficiency of spin-coated and sprayed GO-based PSCs. However, due to a low stability of Spiro-OMeTAD, the efficiency of PSCs with Spiro-OMeTAD suffered a 41% loss after 1987 h. In the meantime, PSCs with GO showed a significantly good stability, and their efficiency increased from 4.87% to 6.62%, which was a 36% efficiency improvement due to better prevention on photo-generated carrier recombination at GO layer than Spiro-OMeTAD [Different attempts were made to accomplish this new HTL. The performance of r-GO was compared with the most typical Spiro-OMeTAD as the hole-transport layer . The GO o-OMeTAD . Detaile2/CH3NH3PbI3/TSHBC/Au. Moreover, due to a better chemical stability of graphene, the fabrication process was finished in the air with 45% humidity, which was a bad condition for Spiro-OMeTAD fabrication. This group further improved their device efficiency up to 14% with introducing extra graphene sheets into TSHBC layer to improve its hole transportation phenomenon. Also, with a higher water contact angle of TSHBC/graphene than Spiro-OMeTAD, the 14% PSCs could gain a better moisture-resistance, which could also extend the device lifetime as shown in −1, respectively [A similar comparison was also observed by Cao et al. . Moreoveectively . Their b2 solution and reduced by HCl. The r-GO and Spiro-OMeTAD were sequentially spin-coated on perovskite. Since r-GO and Spiro-OMeTAD have different energy levels, holes generated in perovskite could flow into either of them. Reduced GO could also extract holes from lower-level Spiro-OMeTAD and bring them to Au contact. Thus, this combined HTL works more efficient than either of them. Also, the existence of r-GO greatly improved the wettability and stability of PSCs. Another composited HTL, GO/PEDOT:PSS, brought an efficiency of 9.7% while the PSCs with PEDOT:PSS and GO showed only 8.2% and 6.4%, respectively [sh) and lowest sheet resistance (Rs). The addition of graphene improved the device stability compared with bare PEDOT:PSS. In turns, PEDOT:PSS improved the surface coverage of ultrathin graphene.The investigations were conducted not only on the single graphene/GO HTL but also on the graphene/GO-composited HTL. In 2013, Luo et al.  claimed ectively . The com3 layer between graphene and PEDOT:PSS due to better wettability of PEDOT:PSS on graphene/MoO3 shown in 3 layer had an improvement for both graphene and ITO electrodes: The best graphene-based PSCs showed an efficiency change from 12.1% to 17.1%, while the best ITO-based devices showed 17.6% and 18.8%, respectively. 3-composited graphene had a higher work function of 4.71 eV. Also, the graphene sheet resistance dropped down by 5 folds with 2 nm MoO3. These results explained the clear efficiency change. Recently, Yoon et al. [Although application of graphene in ETL and HTL was the primary focus, graphene could also be served as the electrodes of PSCs due to controllable conductivity, great carrier mobility and transparency. PSCs equipped with graphene electrode could be able to accept light from both sides. As reported by You et al. , the CVDn et al.  fabricatIn addition, graphene could also be mixed with perovskite slurry before depositing the adsorption layer. Hadadian et al.  applied Overall, graphene has been demonstrated with sufficient space in PSCs. With the proper enhancement of conductivity and surface compatibility, graphene could bring PSCs to the next stage. The soft nature of graphene also provides possibility to produce flexible PSCs, which could be identical to large-scale and roll-to-roll production.2 but Li-GO/TiO2 double-layer structure was also proved successful. Bu considering the advantage of graphene over FTO, a new ETL/contact structure with graphene and graphene-incorporated ETL might be considered, however; graphene concentration should be maintained at a low level. In HTL fabrication, graphene/GO could be used as HTL by itself or mixed with some typical hole-transport materials. However, the key is to find an efficient structural and electrical binder between graphene/GO and perovskite otherwise the PEC may not be improved. Such binder is also important with graphene front/back contacts in PSCs. In addition, more work could be focused on introducing graphene into perovskite layer due to possibly better perovskite crystal formation, which is vital to improve device efficiency and durability. The above research indicates that the graphene can be used for enhancing the performance of solar cells in various ways. Firstly, graphene can be used in top and back contacts of CdTe solar cells due to its work function matching with CdTe and a better carrier mobility. However, the top contact needs 1–5 layers of graphene in order to minimize the optical absorptions. Due to the zero bandgap of graphene, a schottky junction would be formed between graphene and CdTe, however; no evidence supports that this kind of junction improves carrier separation process. Similarly, graphene is also applied in graphene-composited CIGS or CZTS system  but additional efforts could be made on reducing the contact resistance between graphene and other components  in CIGS and CZTS based cells. In PSCs, graphene could be applied in every component: in ETL, graphene was initially mixed with TiOSince the solar cells are large-area devices, process scalability is very important for a commercial viability of usage of graphene in solar cells. In particular, the top contacts need 1–5 layers of graphene and it is a challenging process to manufacture such materials in large-scale. Also, one of the primary reasons for degradation of PSCs is the heating effect, which produces photo-inactive phase in perovskite layer. Since graphene is one of the highest thermal conductive materials, the heating effect can be significantly controlled by an appropriate level of incorporation of graphene. These research can be very useful steps towards increasing the durability of PSCs. Many investigations indicated that the pristine graphene can be used in solar cells. However, further improvements of conversion efficiency might be possible with functionalized graphene. Therefore, investigations related to the application of functionalized graphene in the solar cells can be very useful in both fundamental and application viewpoints. Also, further investigations are important to understand the application of graphene as front and back contacts of flexible and semitransparent solar cell system.Graphene, with its extremely high carrier mobility and transparency together with suitable work function, had been proved as a suitable replacement of the TCO layer for CdTe and CIGS system. The graphene front contacts could have a mono-layer structure but the back contacts should have adequate thickness to prevent extra current loss. However, the experiment indicated that the graphene layer itself tends to suffer incomplete surface coverage and a higher sheet resistance in a lateral direction, which leads to a current leakage and insufficient carrier transportation. Suitable metallic doping could improve the performance of device. In order to have advantage of band structure, the controllability of number of layers in a graphene manufacturing should be optimized.For the perovskite solar cells (PSCs), a positive effect has also been demonstrated by application of graphene in almost every component. Compared with the conventional design, the usage of graphene enhanced the carrier extraction and device stability (compared with Spiro-OMeTAD). The flexible devices is also achieved by the fabrication of printable graphene-based PSCs on a soft substrate. Also, the preliminary test showed such flexible cells were durable after a large amount of bending cycles. Moreover, the application of graphene in multiple positions already showed a higher efficiency than PSC without graphene. However, the feasibility studies are necessary to integrate graphene usage in the solar cell manufacturing processes. The application of r-GO in PSCs was also briefly discussed. Although the long-term stability test showed the advantage of graphene over the conventional HTL, the loss of device parameters should be addressed before the commercialization stage.


Programmed death-1 (PD-1) is an immunosuppressive receptor functionally bound with programmed death-ligand 1 (PD-L1), which has been reported in various malignancies. However, only a few studies are available for the clinical significance of PD-1/PD-L1 in nasopharyngeal carcinoma (NPC). In this study, we aim to investigate alterations in PD-1/PD-L1 by using immunohistochemistry analysis in a cohort of consecutively enrolled NPC patients (n = 99). To further analyse the correlation between PD-1/PD-L1 and factors involved in clinico-pathology, haematologic biomarkers, EBV-DNA load and outcomes, we collected clinical data for statistical analysis. We observed that lower haemoglobin (HB) and Body Mass Index (BMI) levels were associated with high levels of PD-L1 staining in NPC patients. Importantly, our results suggested that PD-L1 might be a negative indicator for NPC patients. In contrast, a correlation between the PD-1/PD-L1 level and EBV load was not identified. Moreover, PD-1 positivity was suggested to not be significantly correlated with clinical outcomes. Taken together, our results revealed that PD-L1 might be a potential prognostic biomarker for NPC patients. However, further studies are needed to clarify the underlying mechanism of EBV status in the immunosuppression process induced by the PD-1/PD-L1 axis. Nasopharyngeal carcinoma (NPC) is an Epstein-Barr virus (EBV)-related malignancy, with an annual incidence of 30–80 per 10,000 in endemic regions, such as South China2et al.et al.et al.NPC is characterized by substantial lymphocytic infiltration (mainly of T cells) in the primary tumour46The blockade of the PD-1 and PD-L1 pathway is one of the most promising strategies to activate anti-tumour immunity21In addition, PD-1 and PD-L1 could induce T cell deactivation during chronic viral infections28Taken together, the prognostic value of PD-1/PD-L1 expression in NPC remains largely unknown. Detailed data on potential related biomarkers and EBV infection status with PD-1/PD-L1 are needed to be confirmed by clinical data. Therefore, considering the tremendous therapeutic potential of targeting the PD-1/PD-L1 interaction in NPC, we analysed the prognostic value of PD-1 and PD-L1 in a cohort of NPC patients (n = 99), which were consecutively recruited form a single medical care group over the course of two years. We also evaluated the correlation between PD-1/PD-L1 expression and clinico-pathological parameters as well as potential related haematologic biomarkers, such as the haemoglobin (HB) level. Our study might provide a new strategy for immune checkpoint-blocking therapy.All of the nasopharynx biopsy samples (n = 99) were collected and histologically diagnosed as NPC by experienced pathologists. The samples were fixed with formalin and embedded into paraffin using a tissue processor. Among the 99 patients enrolled, including 68 males and 31 females, the median age was 47.5 years old (range from 20 to 78 years). All patients were treated with intensity-modulated radiation therapy (IMRT) with or without combined chemotherapy. The average follow-up time was 49.4 months (range from 6.7 to 64.9 months). In this cohort, 18 patients encountered disease progression (recurrence and/or metastasis), and 9 patients died during the follow-up period. All tumours were classified as the undifferentiated non-keratinizing phenotype. The characteristics of the enrolled patients are summarized in 3 . In this study, neither PD-1 positivity nor a high level of PD-L1 staining was significantly correlated with the clinico-pathological parameters of age, gender, smoking status, family history of cancer, GTVnx or clinical stage at diagnose. Detailed data are summarized in Table 1PD-1-positive immune cells were present in 44 of the total 99 tumours (44.4%), and PD-L1 staining was detectable in 96 patients (97.0%) and was mainly located at the membrane or in the cytoplasm region (or both) in the tumour cells. PD-L1 was also expressed in tumour-infiltrating lymphocytes (TILs) in a scattered manner. According to the ROC curve analysis for OS, the optimal cut-off value for the H-score was 155 . Thus, when the H-score ≥155, PD-L1 staining was classified as being at a high level (61 cases). PD-1 positivity was defined as cases with PD-1 staining intensity ≥2 in more than 5% of TILs. Representative stainings of PD-1 and PD-L1 in NPC are shown in 2). The BMI of the 99 NPC patients ranged from 16.26 to 33.83 kg/m2. We compared the difference in the BMI level of patients with low or high levels of PD-L1 staining, and our results suggested that patients with a high level of PD-L1 staining had significantly lower BMI levels , calculated by dividing the weight in kilograms by the square of the height in metres  and tumour cells with PD-L1 expression, we used the Kaplan-Meier survival analysis and log-rank tests. In this consecutively enrolled cohort of 99 NPC patients, our results revealed that a high expression of PD-L1 was correlated with shorter OS  in EBV-positive NPC cell lines4748et al.et al.3) was determined by an ROC analysis in this study, which was consistent with previous studies in different NPC samples, where 19 mm3 , pre-therapy laboratory counts of neutrophils, lymphocytes, HB, platelets, albumin, lactate dehydrogenase (LDH), and EBV-DNA copies by quantitative PCR test, as well as follow-up records. All of the patients were followed-up for at least 40 months.For this study, 115 NPC patients were consecutively sampled by one medical care group at Sun Yat-sen University Cancer Center  from December 2010 to December 2012. The cases were selected based on the following criteria: (1) histologically proven NPC with available biopsy specimens; (2) complete clinical data; (3) a new diagnosis; (4) non-distant metastatic NPC; (5) no treatment history or history of other malignant disease; (6) Karnofsky score ≥ 70; (7) received IMRT at Sun Yat-sen University; (8) regular follow-up. Patients with active hepatitis, diabetes, or who failed the follow-up requirements were excluded. Therefore, there were 99 cases that qualified for this study. All medical records were reviewed retrospectively, and all patients were restaged according to the 7All patients received a computed tomography simulation scan at the radiotherapy position. The images included plain and enhanced computed tomography scans. The scope of each scan was from the top of the head to 2 cm below sub-clavicle head (thickness: 3 mm per slice). According to the institutional treatment protocol from Sun Yat-sen University Cancer Center, contouring of targets and organs at risk was performed under the IMRT planning system. The prescribed doses for the NPC patients were applied as follows: (1) planning target volume (PTV) of the primary gross tumour volume (GTVnx): 66–72 Gy at 2.12–2.43 Gy/fraction; (2) PTV of the GTV of the involved lymph nodes (GTVnd): 64–70 Gy; (3) PTV of the high-risk clinical target volume (CTV1): 60–63 Gy; (4) PTV of the low-risk clinical target volume (CTV2): 54–56 Gy. All targets were treated simultaneously using a simultaneous integrated boost technique.2) with 5-fluorouracil (4.0 g/m2), cisplatin (75 mg/m2) with toxoids (75 mg/m2) or triple agent treatment with cisplatin (70 mg/m2), 5-fluorouracil (3.0 g/m2) and toxoids (70 mg/m2) every three weeks for two or three cycles. Concurrent chemotherapy consisted of cisplatin (100 mg/m2) given in week 1, 4, and 7 of radiotherapy.According to the institutional treatment protocol from Sun Yat-sen University Cancer Centre, IMRT was applied for stage I disease as a sole treatment, concurrent chemoradiotherapy for stage II disease, and concurrent chemoradiotherapy (CCRT) +/− neoadjuvant/adjuvant chemotherapy for stage III to IVA-B disease. Among the 99 patients involved in this study, 59 patients (59.6%) received both neoadjuvant chemotherapy (NCT) and concurrent chemotherapy (CCRT); 2 patients (2.0%) received sole NCT; 28 patients (28.3%) received CCRT; and 10 (10.1%) patients received IMRT as a sole treatment. Neoadjuvant chemotherapy consisted of cisplatin (100 mg/m2O2 for 10 min at room temperature and steam-heated for 2.5 min to retrieve the antigen using ethylene diamine tetra acetic acid buffer (PH = 8.0). Subsequent immunostaining was performed with a 50-min incubation period in 37 °C with the monoclonal antibodies for PD-1 and PD-L1  containing 2% sucrose in PBS at 4 °C overnight and embedded into paraffin using a tissue processor . FFPE sections (3 μm thick) were cut with a rotation microtome . Dewaxed paraffin sections were rehydrated by alcohol series, treated with 3% Hnd PD-L1 . The IHCThe percentages of PD-L1-positive tumour cells and PD-1-positive lymphocytes and staining intensity were evaluated by two pathologists who counted 20 sequential high-power fields (0.54 mm field diameter) judged to be representative of the sample, while remaining blinded to clinical information. Staining intensity was scored as follows: 0 for negative or trace; 1 for weak; 2 for moderate; 3 for high. The percentage of stained cells (0–100%) was multiplied by the dominant intensity pattern of staining ranging from 0 to 3. Therefore, the overall semi-quantitative score (H-score) ranged from 0 to 300 .The optimal cut-off point for the expression level of each marker including the PD-L1 H-score and GTVnx were determined by the area under the curve (AUC) of the receiver operating characteristic (ROC) curve at the highest positive likelihood ratio point for overall survival (OS). PD-L1 expression was dichotomized into two groups (High and Low), using a cut-off score of ≥155. PD-1 positivity was defined as cases with PD-1 staining intensity ≥2 in more than 5% of TILs.OS was measured from the date of diagnosis to the date of death or the date of the last follow-up through April 2016. PFS was measured from the date of diagnosis to the date of death or the date of tumour progression (recurrence and/or metastasis) through April 2016. Patients who were still alive at last contact or died from other causes were treated as censored for OS analysis.A chi-square test was used to assess the correlation of the expression of PD-1 and PD-L1 with various clinical parameters such as age, clinical stage and EBV-DNA status. A t-test was used to compare the differences between the BMI, HB level, and neutrophil and lymphocyte counts in patients with different PD-1/PD-L1 immunoreactivity after a normality test (Kolmogorov-Smirnov test). A non-parametric Mann-Whitney U test was applied to compare the differences in albumin, LDH and the neutrophil/lymphocyte ratio in patients with different PD-1/PD-L1 immunoreactivities. A non-parametric Mann-Whitney U test was also applied to compare the differences in the PD-1/PD-L1 H-score in patients with different baseline EBV-DNA status. The number that follows the ± sign is the standard error (s.e.m.) in this article. Survival analysis was depicted by the Kaplan-Meier method defined by cut-off points generated from the ROC. Univariate analyses and multivariate analyses were performed with a log-rank test and Cox regression analysis, respectively. A P value < 0.05 was used to denote statistical significance, and all reported P values are two sided. P values were marked as *P < 0.05, **P < 0.01, ***P < 0.001, indicating different level of significance. These statistical analyses were performed with SPSS 16.0 4849505152535455565758How to cite this article: Zhou, Y. et al. PD-L1 predicts poor prognosis for nasopharyngeal carcinoma irrespective of PD-1 and EBV-DNA load. Sci. Rep.7, 43627; doi: 10.1038/srep43627 (2017).Publisher's note: Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.


Anti-PD-1/PD-L1 antibody therapy is a promising clinical treatment for nonsmall-cell lung cancer (NSCLC). However, whether anti-PD-1/PD-L1 antibody therapy can provide added benefits for heavily pretreated patients with advanced NSCLC and whether the efficacy of anti-PD-1/PD-L1 antibody therapy relates to the tumor PD-L1 expression level remain controversial. Thus, this meta-analysis evaluated the efficacy and safety of anti-PD-1/PD-L1 antibody therapy for pretreated patients with advanced NSCLC.Randomized clinical trials were retrieved by searching the PubMed, EMBASE, ASCO meeting abstract, clinicaltrial.gov, and Cochrane library databases. The pooled hazard ratios (HRs) for overall survival (OS) and progression-free survival (PFS), and odds ratios for the overall response rate and adverse events (AEs) were calculated by STATA software.P = 0.015, P for heterogeneity [Ph] = 0.620) and longer OS  than docetaxel, but not PFS . Subgroup analyses according to the tumor PD-L1 expression level showed that anti-PD-1/PD-L1 therapy could significantly improve both OS and PFS in patients with high expressions of PD-L1, but not in those with low expressions. Generally, the rates of grade 3 or 4 AEs of anti-PD-1/PD-L1 therapy were significantly lower than that of docetaxel. However, the risks of pneumonitis and hypothyroidism were significantly higher.Three randomized clinical trials involving 1141 pretreated patients with advanced NSCLC were included. These trials all compared the efficacy and safety of anti-PD-1/PD-L1 antibodies (nivolumab and MPDL3280A) with docetaxel. The results suggested that, for all patients, anti-PD-1/PD-L1 therapy could acquire a greater overall response (odds ratio = 1.50, 95% CI: 1.08–2.07, Anti-PD-1/PD-L1 antibody therapy may significantly improve the outcomes for pretreated advanced NSCLC patients, with a better safety profile than docetaxel. More than 60% of newly diagnosed NSCLC patients present with locally advanced or metastatic disease, which correlates closely with poor prognosis and high mortality.Lung cancer is the leading cause of cancer-related death worldwide, with a 5-year overall survival (OS) rate of only 10% to 15%.,4 little therapeutic progress has been made for squamous cell carcinoma, despite the benefits associated with docetaxel being modest. Although pemetrexed and erlotinib have better side-effect profiles than docetaxel for nonsquamous NSCLC, they have failed to show superiority to docetaxel concerning OS when used as second-line therapy.,6Patients with advanced NSCLC whose disease progresses during or after first-line chemotherapy have limited options. Since the approval of docetaxel as second-line treatment in 1999, after it was shown to provide longer survival than best supportive care,–9 Anti-PD-1/PD-L1 therapy uses PD-1/PD-L1 immune-checkpoint-inhibitor antibodies to disrupt PD-1/PD-L1-mediated signaling and restore antitumor immunity. Furthermore, anti-PD-1/PD-L1 therapy has been reported to be useful for the treatment of cancers with various types of histologic features.–13The programmed death 1 (PD-1) receptor, which is expressed on activated T cells, is activated by the tumor-expressed ligands PD-L1 and PD-L2. The interaction of PD-1 with PD-L1 and PD-L2, which are expressed prevalently in NSCLC, downregulates T cell activation and promotes tumor immune escape.,12,14 However, whether anti-PD-1/PD-L1 antibody therapy could provide added benefits for heavily pretreated patients with advanced NSCLC and whether the efficacy of this treatment relates to the tumor PD-L1 expression level remain unclear. To answer these questions, several randomized trials concerning the efficacy and toxicities of anti-PD-1/PD-L1 antibodies have been conducted.–17 However, the results have been inconsistent and inconclusive, largely owing to the relatively small sample sizes of the individual studies. Thus, to better clarify these issues, we performed a meta-analysis on the efficacy and safety of anti-PD-1/PD-L1 antibody therapy for previously treated patients with advanced NSCLC.As the mechanism by which tumor cells escape recognition and elimination by the immune system is being revealed, many single arm studies concerning the efficacy of anti-PD-1/PD-L1 antibodies have been conducted; these have demonstrated that inhibition of the PD-L1/PD-1 pathway shows encouraging results on survival among all NSCLC subtypes.2The current literature-based meta-analysis was performed to evaluate the efficacy and safety profile of anti-PD-1/PD-L1 antibodies for previously treated advanced NSCLC. All analyses were based on previous published studies, thus no ethical approval and patient consent are required.2.1A literature search of PubMed, EMBASE, ASCO meeting abstracts, clinicaltrial.gov, and Cochrane library  was conducted using the following terms: “Carcinoma, Non Small-Cell Lung” [MeSH] or “NSCLC,” “PD-1” or “PD-L1,” and “Nivolumab” or “MPDL3280A” or “Pembrolizumab,” without restriction on language. The retrieved literatures were then read in their entirety to assess their appropriateness for the inclusion in this meta-analysis by 2 authors (GWZ and YX) independently. The reference lists of reviews and the retrieved articles were searched simultaneously to find additional eligible studies. If studies had partly overlapped subjects, the study with the larger sample size was selected. Any disagreement was resolved by discussion between the 2 authors.2.2The efficacy outcomes analyzed were the OS, progression-free survival (PFS), and overall response rate (ORR). The safety outcomes analyzed were the adverse events (AEs), including fatigue, nausea, decreased appetite, diarrhea, anemia, neutropenia, pneumonitis, and hypothyroidism, among others.2.3The included studies had to fulfill the following selection criteria: published, randomized clinical trials comparing anti-PD-1 or anti-PD-L1 therapy with chemotherapy; including patients with advanced or metastatic NSCLC after failure of previous treatments; and in which the outcomes were estimated by OS or PFS or ORR.2.4The quality of the trials was assessed using the method reported by Jadad et al, which is based on the following 3 questions: whether an appropriate randomization method was reported (0–2 points); whether an appropriate blinding method was reported (0–2 points); and whether withdrawals and dropouts were reported (0–1 point). A trial with fewer than 3 points was considered as low-quality, while other trials (≥3 points) were considered as high-quality trials.2.5The following variables were extracted from each study, if available: first author, year of publication, quality scores, comparison arms, number of patients in each arm, hazard ratios (HRs) for OS and PFS and their 95% confidence intervals (CIs), ORR, PD-L1 expression levels, and any grade and grade 3/4 AEs. All data were independently extracted by 2 investigators (GWZ and YX), who were blinded to the other author's findings, using a standardized data reporting form. Any disagreement between the 2 data extractors were resolved by consultation with 1 independent expert (HU).P-value of the log-rank statistics.The author-reported HRs with 95% CIs were used if possible. When 95% CIs were not directly reported in the original study, they were estimated indirectly using the 2.6P values <0.05 were considered significant. Statistical heterogeneity among the trials was assessed using the standard χ2Q test and was considered statistically significant at P < 0.10. A fixed-effect model (the Mantel–Haenszel method) was used when heterogeneity was absent. Otherwise, a random-effect model (the DerSimonian and Laird method) was used. Subgroup analysis was performed according to the PD-L1 expression level. Potential publication bias was examined by funnel plots and Egger test, with P < 0.05 considered a significant publication bias.The pooled HRs with 95% CIs for OS and PFS, and odds ratios (ORs) with 95% CIs for ORR and AEs were calculated using the STATA SE 10.0 package . HRs >1 favored the chemotherapy arm whereas HRs <1 favored the anti-PD-1/PD-L1 therapy arm. ORs for ORR and AEs >1 reflected a higher overall response and toxicity, respectively, in the immunotherapy arm. 33.1After a thorough electronic search, 1275 reports were identified; of these, 3 randomized trials involving 1141 pretreated patients with advanced NSCLC met the selection criteria and were included in the final analysis  indicated that no significant publication bias existed in this meta-analysis.The funnel plot Fig.  and Egge4,24 Accordingly, several drugs targeting this pathway have been developed, including the anti-PD-1 antibodies nivolumab (BMS-936558), AMP-224, pembrolizumab (MK-3475), and pidilizumab (CT-011), and the anti-PD-L1 antibodies MPDL3280A, MEDI-4736, and BMS-936559 (MDX-1105). Some of these agents have been determined to be effective and safe in advanced NSCLC patients following prior chemotherapy. Moreover, several phase III trials–17 have compared anti-PD-1/PD-L1 drugs with docetaxel in previously treated patients with advanced NSCLC. Although PD-1 and PD-L1 antibodies target different molecules in this pathway, clinical studies have demonstrated similar outcomes with both drugs. The phase III study by Borghaei et al showed that the median OS by treatment with nivolumab, an anti-PD-1 antibody, was 12.2 months, as compared with 9.4 months for treatment with docetaxel in previously treated advanced NSCLC patients. Another study by Spira et al showed that MPDL3280A, a PD-L1 antibody, resulted in a median OS of 11.4 months, as compared with 9.5 months for docetaxel. Their response rates were also similar (19% vs 15%). As a result, the current meta-analysis incorporating all available data from relative studies was deemed necessary to examine the current evidence.The PD-1 receptor is expressed on activated T cells; when it binds to one of its key ligands, PD-L1 or PD-L2, T-cell activation is inhibited and the antitumor immune response is dampened. Many tumor cells, including NSCLC, overexpress PD-L1 to evade the immunological surveillance.This literature-based meta-analysis involving 1141 previously treated patients with advanced NSCLC who showed disease progression during or after first-line chemotherapy showed encouraging results; the findings indicated that anti-PD-1/PD-L1 antibody therapy could significantly improve the ORR and OS compared with single-agent docetaxel chemotherapy alone, without evidence of statistical heterogeneity.P = 0.134). However, there was statistical heterogeneity between the 3 included trials, with the study by Brahmer et al showing that anti-PD-1/PD-L1 therapy could improve PFS compared to docetaxel, while the other 2 did not. Differences in the patient characteristics might contribute to the increased clinical heterogeneity. However, in order to prevent clinical heterogeneity induced by varying expression levels of PD-L1, subgroup analyses were performed according to the expression of PD-L1. In Brahmer et al's study, the percentages of patients whose tumors expressed PD-L1 at ≥1%, ≥5%, and ≥10% during immunotherapy were 54%, 36%, and 31%, respectively. In the POPLAR study and Borghaei et al's study,,17 the corresponding proportions were 66%, 35%, and 17% and 53%, 41%, and 37%, respectively. The rates were similar between the immunotherapy and docetaxel groups. The results of the subgroup analyses showed that anti-PD-1/PD-L1 therapy significantly improved the PFS in patients with higher expression of PD-L1, but not in those with low expression, irrespective of the cut-off used. These results suggest that patients with overexpression of PD-L1, as a predictor of sensitivity to anti-PD-1/PD-L1 drugs, could achieve prolonged PFS from anti-PD-1/PD-L1 therapy. This also implies that a subset of patients would especially benefit from PD-1/PD-L1 blockers, and further exploration of this finding is needed. In terms of the OS, a meaningful separation of the OS curves was observed across all prespecified expression levels, consistent with the results of PFS, and there was a trend toward a longer OS as the PD-L1 expression level increased (PD-L1 expression ≥1%: HR = 0.62; ≥5%: HR = 0.48; ≥10%: HR = 0.44; Fig. Concerning the PFS, the results showed no significant effect of anti-PD-1/PD-L1 antibody therapy in the overall study population P = 0.13. HoweverThe safety and toxicities of anti-PD-1/PD-L1 therapy were also explored in this meta-analysis. Anti-PD-1/PD-L1 therapy showed lower risks of grade 3 or 4 AEs than docetaxel. For any grade AEs, hematological AEs, such as anemia and neutropenia, and gastrointestinal reactions, such as nausea, decreased appetite, and diarrhea, were all significantly less common with anti-PD-1/PD-L1 therapy. We speculate that the reason for this finding is that docetaxel has many general properties of chemotherapy and can hence injure epithelium-derived cells and renewing cell populations, while anti-PD-1/PD-L1 drugs do not. However, anti-PD-1/PD-L1 drugs are associated with higher risks of immune-related AEs, including pneumonitis and hypothyroidism, than docetaxel. Nevertheless, in the included studies, these immune-related AEs were efficiently managed with the use of protocol guidelines. In other words, the safety profile of anti-PD-1/PD-L1 therapy was acceptable, suggesting that these drugs might become more popular and widely used in clinical practice.Some relevant limitations existed in our study. First, to date, only three randomized clinical trials investigating the efficacy and safety of anti-PD-1/PD-L1 antibodies for previously treated NSCLC as second-line treatment have been conducted, so the number of reports incorporated in this meta-analysis was hence limited. However, there were 1141 previously treated patients included in this meta-analysis, and there was little evidence of statistical heterogeneity. As a result, our results can be considered generally reliable. Second, our meta-analysis, like all studies based on aggregated data, did not reach the level of evidence obtainable with a meta-analysis based on individual patient data.In conclusion, anti-PD-1/PD-L1 therapy may significantly improve the outcomes for patients with pretreated advanced NSCLC, with a favorable safety profile. Therefore, the use of anti-PD-1/PD-L1 therapy in clinical practice is worth further exploring in patients with pretreated advanced NSCLC. More randomized controlled trials with large sample sizes are needed to establish the patient population that would benefit most from this therapy.


Bi2Te3 grows during the solvothermal process with the simultaneous reduction of graphite oxide into graphene. The in situ formation process of the hybrid has been investigated by X-ray diffraction and X-ray photoelectron spectra. The Li-storage mechanism and performance of Bi2Te3/G and bare Bi2Te3 have been studied by galvanostatic cycling and cyclic voltammetry. The Bi2Te3/G sandwich exhibits an obviously improved cycling stability compared to bare Bi2Te3. The enhancement in electrochemical performance can be attributed to the combined conducting, confining and dispersing effects of graphene for Bi2Te3 nanoplates and to the self-assembled sandwich structure.A sandwich structured Bi Li/Li+) and relatively large Li-storage capacity (660 mAh g−1) with the formation of Li3Sb composition [3Sb [Although carbon based materials are presently the dominant anodes in commercial Li-ion batteries, there is still a great challenge to develop alternative anode materials in order to meet the requirement of high-performance Li-ion batteries ,2. Alloyposition . Howeverx, where M is an electrochemically inert element and acts as the buffering matrix. The improvement in electrochemical performance could also be realized by using nanostructured materials [Many measures have been taken to alleviate the volume changes for Sb during alloying/de-alloying processes. Previous work ,8,9,10 saterials ,12,13,14aterials ,16,17,182-bonded carbon atoms [3Bi composition [2Te3-nanoplate/graphene-nanosheet (Bi2Te3/G), where Te can also reversibly store Li by forming Li2Te [2Te3 could be realized by constructing a Bi2Te3/G hybrid with a sandwich structure.Graphene, a flat monolayer of spon atoms , was alson atoms , high spon atoms  and highon atoms . Our preon atoms ,24. Simiposition ,25,26,272Te3/G and bare Bi2Te3. For comparison, the standard diffraction peaks of Bi2Te3 are also given. All the diffraction peaks can be indexed to hexagonal Bi2Te3 (JCPDS No. 89-2009) for both Bi2Te3/G and bare Bi2Te3. The diffraction peaks of graphene that should appear at around 2θ = 25 °C cannot be detected, suggesting that the restacking of graphene sheets after reduction was inhibited by uniformly loading Bi2Te3 plates between the graphene sheets. The graphene content is roughly estimated to be 11.5 wt% by the carbon content analysis.2Te3/G are analyzed as shown in 2Te3/G hybrid has formed with the simultaneous formation Bi2Te3 and reduction of GO during the one-step solvothermal process. To check the reduction status of GO during the solvothermal reactions, C1s XPS spectra of GO and Bi2Te3 prepared by the solvothermal route without adding GO in the precursors. Generally, the sample exhibits a hexagonal plate shape with a size of around 0.5–3 μm. However, smaller sized broken plates with an irregular shape can also be observed. The thickness of the plates is roughly estimated to be 50–100 nm from some vertically  aligned plates denoted by the arrows. 2Te3/G hybrid. It is obvious from the transparent graphene that Bi2Te3 plates are located between the graphene sheets. The size of the Bi2Te3 plates is below 2 μm. A three-dimensional (3D) sandwich structure is thus constructed by alternatively arranged graphene layer and Bi2Te3 layer as clearly indicated by the arrows. The transparent nature of the graphene layer suggests that it is rather thin, composed probably of single or few layers of graphene sheets.2Te3/G was further characterized by TEM as shown in 2c. Note that nearly all of the Bi 2Te3 plates are anchoring on graphene without forming free Bi2Te3 plates even after vigorous ultrasonication. The wrinkles and folded edges of graphene indicate that the graphene layer is rather thin, which agrees with the SEM observation. The enlarged view of the circled part in 2Te3 plates can be observed from 2Te3 plate is evident. From a vertically aligned plate, the thickness of the plate is estimated to be 15 nm, which is much smaller compared with that of bare Bi2Te3. The thickness of the Bi2Te3 plates is in the range of 10−20 nm after observing some plates at the edges or defect sites of graphene. It is worth noting that the number of the Bi2Te3 plates with a regular hexagon is much smaller compared with that of bare Bi2Te3 plates. It is believed that the irregular shape and small thickness of the Bi2Te3 plates in Bi2Te3/G are caused by the inhibited diffusion and re-crystallization of small sized Bi2Te3 particles due to the pinning effect of the defects and the oxygen-containing groups in graphene [The microstructure of Bigraphene . The pre2Te3/G and Bi2Te3 were measured to clarify the electrochemical reaction mechanism of Bi2Te3 with Li. As seen in 2Te3 with Li exhibits a multi-step mechanism, evidenced by the multi-peak feature of the CV plots. During the first cathodic scan, three reduction peaks, located at 2.0, 1.25, and 0.6 V, respectively, appear as indicated by the black line in 3a. The small peak at 2.0 V is related possibly to the insertion reaction of Li ion into layered Bi 2Te3 without significantly destroying its crystal structure [2Te (2Li + Te → Li2Te) [3Bi (3Li + Bi → Li3Bi) [3 and Li2Te successively, both of which are stable phases at room temperature [2Te3 upon Li uptake [2Te3 cannot be recovered after the anodic scan [In tructure . The pea→ Li2Te) , and the→ Li3Bi) ,27. Duriperature . The lowi uptake . This al3Bi (peak A) and Li2Te (peak B and peak C). The CV plots of bare Bi2Te3 are also given for comparison as seen in 2Te3 display a similar feature as those of Bi2Te3/G except that the peak intensity decreases more rapidly with scans, indicative of its lower reversibility. The relatively high reversibility of Bi2Te3/G can be attributed to the incorporation of graphene that improves the electrode kinetics and keeps the electrode integrity.Note that three oxidation peaks , at 1.0, 1.8 and 1.9 V, respectively, appear during the anodic scans, corresponding to the successive de-lithiation reactions of Li2Te3 and Bi2Te3/G at 50 mA g−1 at various cycles. Bi2Te3/G hybrid gives a first discharge (Li-uptake) capacity of 731 mAh g−1 and a first charge (Li-extraction) capacity of 481 mAh g−1. The first irreversible capacity can be attributed to the reduction decomposition of the electrolyte and the formation of the solid state interface (SEI) layer. Successive potential plateaus can be seen during the charge-discharge cycling, which correspond to the current peaks in the CV plots. The appearance of the potential plateaus is due to the two-phase coexistence of original phase (Te or Bi) and the Li-alloys . As shown in the figure, bare Bi2Te3 exhibits lower charge-discharge capacities compared with Bi2Te3/G. The theoretical maximum capacity of Bi2Te3 is 401 mAh g−1, related to the formation of Li2Te and Li3Bi. Considering the fact that graphene itself shows a relatively low capacity of around 300 mAh g−1, as reported in our previous work [2Te3/G should be lower than that of bare Bi2Te3. The high yieldable of Bi2Te3/G is possibly due to the synergistic effect between Bi2Te3 and graphene. On one hand, as discussed above, the presence of graphene can restrain the crystal growth of Bi2Te3, which is favorable for rapid Li ion diffusion within the active material. On the other hand, the separator effect of Bi2Te3 plates for graphene sheets maximizes the exposure of the graphene surface to the electrolyte, especially for the edges and vacancies on graphene. The edges and vacancies can supply additional sites for Li storage [2Te3/G shows a progressive polarization upon cycling, but the extent is smaller than bare Bi2Te3 owing to the presence of the conductive graphene.ous work , the the storage . Note th2Te3 and Bi2Te3/G charged at 50 and 200 mA g−1 and discharged at 50 mA g−1. Note that Bi2Te3/G demonstrates an obviously slower capacity fade compared to bare Bi2Te3. After 50 cycles at 200 mA g−1 (about 0.5 C), a charge capacity of 158 mAh g−1 can be retained for Bi2Te3/G. In contrast, the charge capacity of bare Bi2Te3 drops rapidly to 33 mAh g−1. The Bi2Te3/G hybrid also shows improved cycling stability compared with Bi2Te3-graphite composite [2Te3 plates, in addition to offering effective conducting networks. The 3D sandwich structure also facilitates the Li-ion diffusion within the free space and across the electrode/electrolyte interface. In addition, the free space within the sandwich also affords additional room to buffer the volume changes. It should be stressed that the long-term cycling stability of the Bi2Te3/G hybrid is not satisfactory yet owing to the intrinsic large volume changes of the Bi2Te3 during alloying/de-alloying processes. However, it is clear that graphene plays an important role in enhancing the electrochemical properties of Bi2Te3. It also should be noted that the large-scaled of Bi2Te3/G is not favored due to the toxicity, price, and resource scarcity of Bi and Te. Nevertheless, it shows promising application in micro-batteries due to the possibility of micro processing of graphene and Bi2Te3.omposite  and otheomposite ,26. The 3, 1.5 mmol of Na2TeO3 and 0.4 g of NaOH was added to the above suspension with sonication. After stirring for 12 h, the mixed solution was then transferred to a Teflon-lined stainless steel autoclave (100 mL) and heated in an electric oven at 180 °C for 24 h. The as-obtained product was collected by centrifugation, washed with deionized water and absolute ethanol for several times and dried at 40 °C under vacuum for 10 h. Bare Bi2Te3 was also synthesized using a similar method without adding GO.Graphite oxide , prepared by a modified Hummer’s method , was addα radiation (λ = 0.1541 nm). X-ray photoelectron spectra (XPS) were collected on a KRATOS AXIS ULTRA-DLD spectrometer with a monochromatic Al Kα radiation (hv = 1486.6 eV). The morphologies of the products were observed by field emission scanning electron microscopy (FE-SEM) on a FEI-sirion microscope and transmission electron microscopy (TEM) on a JEM 2100F microscope. The carbon content analysis was conducted on a Flash EA 1112 tester.The X-ray diffraction (XRD) patterns were obtained on a Rigaku D/Max-2550pc powder diffractometer using Cu K2Te3/G and Bi2Te3 were performed with a half-cell configuration using CR2025-type coin cells. The working electrodes were prepared by spreading a slurry composed of 75 wt% active material (Bi2Te3/G or Bi2Te3/G), 15 wt% poly(vinylidene fluoride) (PVDF) and 10 wt% acetylene black onto Ni foam followed by drying at 100 °C for 12 h under vacuum. The loading mass of the active material is around 2 mg. The cells were assembled in an Ar-filled glove box using Li foil as the counter electrode and Celgard 2300 membrane as the separator. The electrolyte used was 1 M LiPF6 in ethylene carbonate (EC)/dimethyl carbonate (DMC) (volume ratio 1:1). The cells were galvanostatically charged-discharged at 50 mA g−1 between 0.005 and 2.5 V vs. Li/Li+ on a Neware battery tester . The specific capacity of Bi2Te3/G was calculated based on the total weight of Bi2Te3 and graphene. Cyclic voltammetry (CV) tests were carried out on an Arbin BT2000 system at a scan rate of 0.1 mV s−1 between 0.005 and 2.5 V vs. Li/Li+. All of the electrochemical measurements were carried out at room temperature.The electrochemical measurements of Bi2Te3/G sandwich has been prepared by an in situ route with alternatively arranged Bi2Te3 nanoplates and graphene nanosheets. The diffusion and re-crystallization of Bi2Te3 in Bi2Te3/G are inhibited due to presence of oxygen-containing groups and defects on graphene, leading to more irregular shape and smaller thickness of Bi2Te3 in Bi2Te3/G compared with those in bare Bi2Te3. Both Bi2Te3/G and Bi2Te3 exhibit a multi-step lithiation mechanism. The Bi2Te3/G hybrid can yield a higher-than-the-theoretical charge capacity of mAh h−1 at 50 mA g−1 due to the synergistic effect between Bi2Te3 and graphene. The Bi2Te3/G hybrid shows an obviously improved cycling stability compared with bare Bi2Te3. The improved cycling stability is attributed to the 3D sandwich structure, where graphene not only buffers the volume changes but also immobilizes Bi2Te3 nanoplates, in addition to offering effective conducting networks. The unique sandwich structure also facilitates Li-ion diffusion at the electrode/electrolyte interface and within the free space of the sandwich.The Bi


As troves of microbiome sequencing data provide improved resolution of patterns of microbial diversity, new approaches are needed to understand what controls these patterns. Many microbial ecologists are using cultivated model microbial communities to address this challenge. in vitro communities in terms of taxonomic diversity, trophic levels, intraspecific diversity, and the abiotic environment? What are the best ways to manipulate and measure inputs and outputs in model community experiments? In this perspective, I briefly address some of these challenges on the basis of our experience developing fermented food model communities. Future work integrating genetic and molecular approaches with cultivated model microbial communities will allow microbial ecology to develop a more mechanistic understanding of microbiome diversity.As troves of microbiome sequencing data provide improved resolution of patterns of microbial diversity, new approaches are needed to understand what controls these patterns. Many microbial ecologists are using cultivated model microbial communities to address this challenge. These systems provide opportunities to identify drivers of microbiome assembly, but key challenges and limitations need to be carefully considered in their development, implementation, and interpretation. How well do model microbial communities mimic  In the mid-1900s, the field of plant ecology was at a turning point. After decades of developing methods and metrics to describe patterns of plant diversity, an understanding of the processes that shaped this diversity was still largely unknown. Most studies of plant communities were observational surveys across environmental gradients or across time and used statistical approaches to infer what processes might structure plant community composition . StartinOver the past several years, I have argued that microbial ecology faces a turning point similar to that which plant ecology faced in the mid-1900s 911. With 12–Cultivation of microbes from microbial communities is most certainly not a new endeavor, and many cultured microbial species have been used for decades to answer fundamental questions in microbiology and microbial ecology , 19. ThiMy lab has been developing fermented food , cabbage leaf, and planarian worm cultivated model microbial communities in an effort to dissect patterns of microbiome diversity. Here, I present some of the most important lessons we have learned about the challenges and opportunities of these systems. Just as experiments using old fields could not fully represent all plant communities, cultivated model microbial communities have important limitations that need to be considered during the development, utilization, and interpretation of these systems.One of the most important questions to ask during the development of cultivated model microbial communities is how well they represent microbial communities that reproducibly form outside the lab. In some cases, representing reality may not be the goal. Many highly synthetic model communities have been used to ask general questions about ecology and evolution that develop and test theory or techniques and make no attempt to mimic nature . Our worin situ would be cultured and included in model microbial communities. Complete communities can be recreated for some low-diversity and easy-to-culture systems, but it is difficult to isolate all of the species in highly diverse microbial communities. In these more complex systems, representation in model communities can come at higher taxonomic levels, such at the genus or family level. For example, in complex host-associated microbial communities or high-diversity free-living communities, not all of the taxa detected by sequencing can be cultured, but often numerous representatives from across genera or families can be  recreate highly controlled lab experiments in more complex natural microbiomes to demonstrate ecological relevance and (ii) link observations from the lab  with microbiome sequencing data from the field . A great model of the first approach is the nectar microbial community of the flowering plant rocesses , 39–41. ing data , 43, butOld-field plant communities did not solve all of the grand challenges of plant ecology and had many limitations. As I have just briefly described, cultivated model microbial communities also have caveats and limitations (too many to cover in this limited space) that will prevent them from solving all of the unresolved questions about microbial community assembly. Despite this, I believe the use of cultivated model microbial communities has a bright future. One productive path forward is a cross-biome approach, where multiple microbial systems are used to address the same questions or characterize the same phenomenon. Most labs have focused on one model system for their questions of choice. But the relative importance of an ecological or evolutionary process may be unique to a particular microbial community because of the specific taxonomic composition or environmental constraints of that community. The most powerful advances will come from identifying truly generalizable microbiome assembly phenomena that occur in many different types of microbiomes. This could come from using the same cultivated model microbial communities across different hosts/environments or from the use of different microbial communities that naturally vary in taxonomic composition or complexity. To allow for labs to easily test their findings in already established model systems, we should prioritize efforts to create easy-to-access and standardized libraries of cultivated model microbial communities.I also strongly believe that the integration of cultivated model microbial communities with emerging genetic and molecular methods will provide a much needed mechanistic understanding of microbiome assembly. Many cultivated model microbial communities have been used primarily to quantify the relative impacts of ecological and evolutionary processes on community assembly, and the genes and molecules that regulate these processes are often not identified. By applying tools such as Barseq  and imag


Community structure is an important feature of a complex network, where detection of the community structure can shed some light on the properties of such a complex network. Amongst the proposed community detection methods, the label propagation algorithm (LPA) emerges as an effective detection method due to its time efficiency. Despite this advantage in computational time, the performance of LPA is affected by randomness in the algorithm. A modified LPA, called CLPA-GNR, was proposed recently and it succeeded in handling the randomness issues in the LPA. However, it did not remove the tendency for trivial detection in networks with a weak community structure. In this paper, an improved CLPA-GNR is therefore proposed. In the new algorithm, the unassigned and assigned nodes are updated synchronously while the assigned nodes are updated asynchronously. A similarity score, based on the Sørensen-Dice index, is implemented to detect the initial communities and for breaking ties during the propagation process. Constraints are utilised during the label propagation and community merging processes. The performance of the proposed algorithm is evaluated on various benchmark and real-world networks. We find that it is able to avoid trivial detection while showing substantial improvement in the quality of detection. Over the decade, network analysis has been widely applied in various research fields such as biology, transportation, sociology and bibliometric studies123The label propagation algorithm (LPA)et al.et al.et al.The relative simplicity of LPA, coupled with these issues, led scientists to seek improvements and enhancements in this algorithm. Leung The implementation of constraints and fixed update sequences in the CLPA-GNR allow it to produce accurate and deterministic detection. However, the drawback of the CLPA-GNR is its tendency of obtaining trivial detection in networks with weak community structureMNS) that is used in the CLPA-GNR, the Sørensen-Dice index (SDI) is implemented as the similarity score in SSCLPA. Similar to the function of the MNS in the CLPA-GNR, SDI is used in the early stage of the algorithm to detect initial communities. Aside from that, it can substitute the capacity score in the CLPA-GNR to break ties between multiple communities during the propagation processes.Similar to its predecessor, the proposed algorithm consists of constraints that are applied at various stages of the algorithm. The restrictions are gradually relaxed towards the end of the algorithm. A new constraint is implemented in the SSCLPA, where communities that reach certain threshold of strength values are exempted from the propagation or merging processes. This new form of constraint is crucial in delaying the formation of monster size communities, hence allowing the growth of other communities. By limiting the growth of specific communities, the chances of getting trivial detection can be eliminated. Instead of the mutual neighbour score NMI ranges from 0 to 1, where NMI = 1 when two partitions are identical. If a partition is totally independent of another partition, then NMI = 0. On the other hand, the modularity (Q)Qds)Q and Qds.The SSCLPA is tested on various benchmark networks before it is implemented on any real-world network. Three types of benchmark networks are employ in this study, namely the Lancichinetti-Fortunato-Radicchi (LFR)1921Q value is chosen for the purpose of comparison.The performance of the proposed algorithm is also compared to the other community detection methods: LPA1126μ, which represents the average percentage of edges that connect a pair of nodes from different communities. Note that the strength of the community structure decreases as the value of μ increases.The LFR benchmark networks are the most popular benchmark networks for community detection algorithms, as they contain features that are common in the real-world networks. Furthermore, the degree of nodes and the sizes of the communities in the generated LFR synthetic networks are always heterogeneous. One of the most important parameters in the LFR networks is the mixing parameter, kavg = 20 and kmax = 50. On the other hand, the exponent for the degree sequence and the exponent for the community size distribution are fixed at γ = 2 and β = 1. The rest of the parameters are depicted in We generated 4 groups of LFR networks in this investigation. The average and maximum degrees are fixed at NMI = 0 indicate that those algorithms can only detect a single community in the networks. Thus, the detection is trivial and the algorithms cannot uncover any community structure in those networks. The present algorithm manages to detect community structure in all the groups of the LFR networks, even in networks with high μ values. The other LPA based algorithms, including the original LPA, get trivial detection when μ ≥ 0.6. Infomap also faces a similar problem at high μ values. We highlight that not only does the SSCLPA detect communities at high μ values (μ ≥ 0.7), the quality of the detection is also good. For instance, in the SNSC case D increases, the number of intra-community edges that are converted to inter-community edges is increased. The value of D is varied from 10% to 80% in this work. As shown in NMI than all the LPA based algorithms. Moreover, instead of getting trivial detection like the other LPA based algorithms at the higher D values, the results of the proposed algorithm are comparable to those from Blondel which has the best performance in the RC networks. We note that the RN shows a sudden spike in the NMI value at D = 70%. Apparently, this phenomenon is caused by the tendency of RN to detect large number of communities in networks with weak community structure. This tendency of RN renders its detection unreliable in finding meaningful communities in those kind of networks.The RC benchmark networks have 512 nodes with 16 communities of highly heterogeneous size. Initially, a RC network consists of 16 isolated k-cliques. Similar to the role of NMI value in the Football network and it is also the second best algorithm in the Zachary network. Its performance in the Pol-books network is less than desirable, but this is compensated for by having the second highest Qds value  be a network where Vs and VGR are updated separately in two propagation processes in the SSCLPA. On the one hand, the size of the detected communities is increased by allocating Vs into the communities. On the other hand, the detected communities are strengthened in term of the density of the communities by reallocating VGR amongst the detected communities. In the original LPA, all the labels of the nodes are updated in one propagation process. As the labels of the nodes are affected by the labels of the neighbouring nodes during the propagation process, the labels of the nodes are susceptible to the changes of the labels of all the nodes in a network if they are updated in a single propagation process. By separating the updates of the labels of VS and VGR in two propagation process, VS and VGR are only susceptible to the changes in the labels of VS and VGR during their corresponding label propagation processes, respectively. To be precise, the labels of VS are only affected by the changes in the labels of VS as the labels of VGR remain the same throughout the label propagation involving VS. The same concept is applied during the label propagation involving VGR. Hence, this update strategy is a more organised way of updating the labels of nodes than that in the original LPA.Let VS are updated synchronously. Thus, an update sequence is not required. However, VGR is updated asynchronously. The rules for the update sequence in this case are as follows:Nodes are arranged in ascending order based on the number of solo neighbouring nodes. Solo neighbouring nodes are neighbouring nodes that are solo nodes. Nodes with lesser solo neighbouring nodes are updated first.Nodes are then arranged in ascending order based on their degree. Nodes with a lower degree value are updated first.In the proposed algorithm, the labels of The update sequence of nodes are decided by update rule 1 first. If multiple number of nodes have the same number of solo neighbouring nodes, then update rule 2 is applied on those nodes. The possible candidate labels of the target nodes are lesser if the number of solo neighbouring nodes is lesser. Furthermore, nodes with a low degree usually serve as the peripheral member nodes in large communities. Hence these update rules prioritise nodes that have a lesser influence on the labels of the other nodes. The rules are implemented in all processes unless otherwise stated.There are 4 main processes that are being utilised extensively in the 5 main stages in the proposed algorithm see . These aIt is common to find that after a few iterations of the LPA, some of the detected communities are far stronger than most of the others. These communities will grow exponentially in the later stages of the LPA. Eventually, this phenomenon may lead to trivial detection, where the LPA only detects a single community that consists of all the nodes in a network. In order to prevent this kind of detection, communities that exceed a strength threshold are exempted from the propagation and merging processes. By doing so, the other communities have the chance to grow without competing with those communities.Given that where where α, is the strength value that determines the number of communities to be exempted and α value brings about more exempted communities and we note that this process is executed prior to other processes as CEC plays a crucial part in those processes.Finally, VS into detected communities. Nodes are updated synchronously in CLP unless stated otherwise. Let node ci is eligible to claim Let ci ∉ CEC.Q0 is the minimum Q1 is the first quartile of Q0 or Q1. This condition is defined differently at various stages of the algorithm.If The CLP is a label propagation process that assigns CLP Condition (1) is simply the label propagation condition of the original LPA. However, this condition does not always increase or retain the strength of the communities after the solo nodes enter the communities. Therefore, CLP Condition (3) is implemented for this purpose. Finally, CLP Condition (2) ensures that the target solo nodes do not enter the exempted communities.SDI (c1 and c2. The targeted node vS1 is connected to c1 and c2 via vS1 with vS1 with c1 provided that the CLP Condition (3) is satisfied. The labels of the nodes remain the same if there is a tie in the If there is a tie between multiple communities, the mean of the VGR and reallocate them if necessary. The GNR is identical to the CLP process, but it is implemented on the group nodes VGR instead of the solo nodes VS. So, similar to the CLP, the GNR needs to fulfil the conditions that are applied on the CLP before VGR can be reallocated from one community to another. If there is a tie between multiple communities, the mean of the SDI  is a relaxed version of the merging condition in the CLPA-GNRThe flowchart of the SSCLPA is depicted in SDI is calculated.Initial labeling: Every single node in a network is given a unique label.SDI calculation: The SDI of all the pairs of nodes, x and y, in an undirected and unweighted network is calculated:In this stage, the nodes are assigned unique initial labels and the x and y respectively. It must be noted that y and vice verse. The term x and y.where SDI Grouping. The sizes of the detected communities are increased by using CLP 1 and the communities are strengthen by GNR 1.k1 grouping: Nodes with one degree are assigned the label of its sole neighbouring node.SDI Grouping: Solo nodes VS, in ascending order of degree, are assigned into communities where the member nodes of the communities have the highest SDI score with each other. Let x, and the highest SDI score of node x is defined as x will be assigned into a community with a set of nodes, VM ⊂ V if the following conditions are satisfied:HTH VS is updated according to the predefined update sequence. In this CLP, a community ci must have at least one member node which has the highest SDI score with the target solo node CLP 1: This is an asynchronous CLP so GNR 1: CLP Condition (2) is not required in this GNR. CLP Condition (3) is defined as This stage aims to detect as many communities as possible in a network. Nodes with one degree are grouped with their sole neighbouring nodes to form communities. Then, more communities are found by using the highest to highest (HTH) CLP 2 & GNR 2: Here we execute the CLP and GNR processes with CLP Condition (3) of GM 1: Execute the GM process on communities with more than 3 member nodes, GM 2: Unlike GM 1, all the detected communities, regardless of their sizes, can be merged. However, a new condition where the modularity score does not decrease after the merging is added in GM 2. This additional condition controls the merging of the communities with lesser than 4 member nodes. The labels of the nodes again remain the same if there is a tie between multiple communities.In this stage, both the CLP 2 and GNR 2 processes are executed iteratively in order to further increase the sizes of the communities. Every time the CLP 2 is executed, it is followed by the GNR 2 for enhancement purpose. In order to reduce the large number of communities that are detected in Stage 2, GM1 and GM2 are introduced in this stage. Similarly, GNR 2 is executed after the CLP and GM processes in order to strengthen the detected communities.In Stage 4, GM 1 and GM 2 are executed iteratively to further reduce the number of communities, until the networks reach a stability where the number of communities cannot be further reduced.VS, if not all, will be assigned into communities by using CLPA 3/4/5/6. In order to do so, the constraints on the CLP 3/4/5/6 are gradually relaxed from CLP 3 to 6. Furthermore, the remaining communities will be merged for the last time by using GM 3. As usual, GNR 3/4/5 are used to strengthen the communities after the CLP and GM processes. Similar to the CLP 3/4/5/6, the constraints in the GNR 3/4/5 are gradually relaxed. In networks with a weak community structure, some of the processes are omitted in order to avoid trivial detection. This procedure is explained in the legend of ci will absorb a solo node vSj into the community as long as vSj is connected with Smallest to largest CLP (STL-CLP): Start from the smallest and proceed to the largest communities, a community vSj has the chance to enter an exempted community provided that the number of edges from the solo node to the exempted communities, ci is an exempted community or not. Thus, CLP Condition (3) in the CLP 3/4/5/6 and GNR 3/4/5 is defined as follow:CLP 3/4/5/6 and GNR 3/4/5: In these label propagation processes, a solo node In the last stage, STL-CLP is used to boost the size of the communities that do not grow in size during the previous stages. Then, most of the the For CLP 3 and GNR 3:For CLP 4 and GNR 4:Q0, Q1 and Q2 are the minimum, first quartile and median of the For CLP 5 and GNR 5:Finally, the CLP Condition (3) is omitted in CLP 6.GM 3: Generally, this process is very similar to GM 2, except that it can handle ties between multiple communities. In case of a tie, the values of RatioB−RatioA for each pair of communities are compared. The pair of communities with the SDI, allocation of one degree nodes, and the HTH SDI grouping run on t represents the number of iterations before convergence, the time complexity of the EC-CLP and EC-GNR processes are The time complexity of the initial labelling is represented by tS4 be the number of iterations before Stage 4 reaches a convergence in the labels. The time complexity of Stage 4 is Stage 4 of the proposed algorithm is iterative. Let hart see , the timHow to cite this article: Chin, J. H. and Ratnavelu, K. A semi-synchronous label propagation algorithm with constraints for community detection in complex networks. Sci. Rep.7, 45836; doi: 10.1038/srep45836 (2017).Publisher's note: Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.