We further demonstrate near-100% position-controlled particle trapping at voltages as low as 0.45 V with nanodiamonds, nanobeads, and DNA from bulk solution within seconds. This trapping scheme can be seamlessly integrated with sensors utilizing graphene as well as other two-dimensional materials.The many unique properties of graphene, such as the tunable optical, electrical, and plasmonic response make it ideally suited for applications such as biosensing. As with other surface-based biosensors, however, the performance is limited by the diffusive transport of target molecules to the surface. Here we show that atomically sharp edges of monolayer graphene can generate singular electrical field gradients for trapping biomolecules via dielectrophoresis. Graphene-edge dielectrophoresis pushes the physical limit of gradient-force-based trapping by creating atomically sharp tweezers. We have fabricated locally backgated devices with an 8-nm-thick HfO The capability of positioning target molecules onto the edges of patterned graphene nanostructures is highly desirable. Here, the authors demonstrate that the atomically sharp edges of graphene can be used as dielectrophoretic tweezers for gradient-force-based trapping applications. Unlike noble metals, such as gold or silver, the carrier concentration in graphene can be tuned, hence enabling the possibility of electrically reconfigurable biosensing11. Nanopatterned graphene such as ribbons11, nanochannels12, or nanopores have all been shown to offer benefits for use in sensing applications. However, biomolecules in viscous media is generally governed by diffusive transport, and the placement of target molecules at the region of highest sensitivity is a key prerequisite to biosensing. Currently, graphene-based biosensors mostly employ DNA or protein immobilization across the entire graphene surface or rely on the random adsorption of biomolecules to the most sensitive regions‒the edges or pores in graphene13. The ability to precisely position and concentrate target molecules onto the edge of patterned graphene nanostructures is highly desirable yet is not extensively studied. Besides biosensing, such capability can also benefit nanophotonic applications for integrating quantum emitters and plasmonic antennas with tunable optoelectronic properties of graphene15.Graphene18, optoelectronic tweezers20, flow-through nanopores22, electrokinetics23, dielectrophoresis (DEP)24, or photothermal methods25 can be used for the aforementioned purposes. However, it is not trivial to integrate such schemes on patterned graphene chips. We show that the atomic-scale thickness of graphene enables ultra-strong DEP forces for trapping nanoscale objects and molecules along patterned edges of graphene. DEP is a widely used method to manipulate biomolecules or polarizable nanoscale objects by using gradient electrical forces obtained from sharp conducting tips, edges, or small gaps between electrodes24. The time-averaged DEP force on a particle of radius R and in a medium of permittivity 2426. However, in this case as our model system is based on nanoscale particles, we assumed a dipole approximation.Various on-chip manipulation techniques, such as optical trappingFT, given byTR is the room temperature and The DEP force depends on the particle volume that goes down with the particle size. However, the thermal Brownian motion becomes very important as we reduce the particle size to sub-micron length scale. To trap a particle, it is required to overcome the thermal force, E|2, it is a scalable particle trapping method, i.e., reducing the radius of curvature of electrode features  or electrode-to-electrode separation28 can significantly boost its magnitude. Patterned metallic nanoelectrodes29 or bottom-up structures such as isolated carbon nanotubes (CNTs)31 have been used to shrink the critical dimension of DEP electrodes into single-digit nanometer scale. Extrapolating this idea further toward the ultimate limit, we conceive a design to turn Angstrom-scale-thickness monolayer graphene into an electrode that provides the sharpest possible edge over millimeter length scales, which cannot be created using lithographically patterned metal nanostructures or even CNTs. Although single-walled CNT electrodes can provide sharp nanometer-scale edges, these devices often suffer from inability to control the gap between CNT electrode and the gate, as well as difficulty to form high-density regular arrays of CNTs. Previously, Xie et al.32 used an atomic force microscopy probe to cut graphene into small-area interdigitated electrodes and showed DEP trapping of CNTs over these structures.Since the DEP force is proportional to the field gradient term ∇|33.In this work, we demonstrate a novel scheme to turn exposed edges of graphene into strong DEP trapping sites. This was done by constructing a robust large-scale graphene-edge DEP platform and trapping nanoparticles and biomolecules at the edge of this monolayer graphene atop an 8-nm-thick insulator with low bias voltages. Such capability can offer graphene-based sensors a unique solution to diffusion-limited mass transport problems2)). A photograph of the chip is shown in Fig. 2 on it. Next, the entire wafer surface, including the Pd electrode, was coated with 8-nm-thick HfO2 deposited by atomic layer deposition (ALD). Then, single-layer graphene grown by chemical vapor deposition (CVD) was transferred onto the wafer and etched into rectangular patterns. In addition to the sharpness of the graphene edge, the nanoscale gap between graphene and the Pd gate electrode (defined by the thickness of the HfO2 layer) further enhances the electric field. Finally, photolithography was employed to pattern Cr/Au contact electrodes, which formed Ohmic contacts to the graphene. The gate and the contact electrodes were arranged in an interdigitated fashion to minimize series resistance and to produce more exposed edges efficiently trap the nanoparticles and molecules. Details of the fabrication process are elaborated in Methods section.Being a gradient-field dependent phenomenon, DEP is greatly enhanced by reducing the radius of curvature of the electrode, with graphene edge providing the sharpest tip Fig. . Reducin2. This density can be further enhanced by reducing the pitch of the gate fingers as well as the graphene segments to 1 µm, which is realistic using i-line optical lithography. In such a case, the trapping site density could be increased to 4 sites per 1 μm2, a nearly 1000× improvement over the current devices. Furthermore, using advanced optical lithography or electron-beam lithography to form the gate fingers and segment the graphene, the trapping density could be further increased by another 1–2 orders of magnitude.The key feature of our processing scheme is the wafer-scale throughput and scalability of trap arrays. In the layout we employed, the gate finger spacing is 15 μm with two graphene segments on either side, and these segments have a pitch of 60 μm. The current design provides a density of four trapping sites per 900 µmE|2), which is responsible for DEP trapping, for a semi-infinite graphene “electrode”, electrically biased by a metal gate electrode, as shown in Fig. 2 layer with a dielectric constant of 13 is assumed between the electrodes. As the experiments were all performed in water, the rest of the simulation domain is assumed to be water with a dielectric constant of 80. The bottom electrode is treated as an ideal metal and graphene is modeled as a layer with zero thickness. An illustration of the simulation domain is shown in Fig. We calculated the gradient of the electric field intensity  factor  for 190 nm polystyrene beads. This is the voltage at which the DEP force is enough to overcome the Brownian motion of the nanoparticles due to their thermal energy. The amplitude of the applied voltage was increased from 400 to 700 mV at a step interval of 50 mV. At each voltage, fluorescence images were collected for 50 s. More beads were trapped at the trapping sites as the voltage amplitude was increased  particles with nitrogen-vacancy (NV) centers  at the trapping sites on graphene  collected after turning on the bias (amplitude 2 V and frequency 100 kHz) show ND particles localized at the trapping sites on a two-dimensional grid defined by orthogonal edges of graphene and buried metal lines.Besides potential applications in biosensing, graphene-based DEP can be utilized for on-chip assembly and array formation of nanoscale quantum emitters such as nanodiamond particles, semiconductor nanocrystals, or plasmonic metal nanoparticles. Rapid on-chip integration of these elements with patterned graphene can be highly desirable for applications in nanosensingene Fig. . The ND Cions) present in the solution should be much greater than the total number of charged sites present across all DNA molecules, as expressed byCDNA is the concentration of DNA and Cions/CDNA (=106) is much higher than 37. The polarizability values were estimated from previously reported empirical findings that correspond to ~3.48 × 10−31 Fm2 and ~1.00 × 10−31 Fm2 for the 10 kbp and 500 bp DNA, respectively37. Next, we calculated the threshold Rg) of 10 kbp DNA with persistence length 50 nm, calculated using a worm-like chain model39, is 238 nm that corresponds to an FT value of 14.4 fN , the threshold 18V2m-3.To demonstrate the utility of the graphene electrodes in capturing biomolecules, we used 10 kbp and 500 bp DNA molecules tagged with YOYO-1 dye  of the system, which is given bySo far, we showed DEP manipulation using high frequency AC fields (1−10 MHz). Reducing the frequency to 100 kHz, results in an interesting localization of the DNA molecules near the graphene edge but the molecules are not tightly trapped at the edge Fig. . This phFor a solution of conductivity 12 μS/cm , the charge relaxation frequency is 270 kHz . As we used low voltages and low-conductivity solutions in our system, the expected temperature rise is minimal. Even for the case where we expect highest Stability of biomolecules is dependent on the temperature of the surrounding environment. We investigated the expected temperature rise in our system based on Joule heating from the relation 41 or tapered nanotips8 wherein field hotspots are located along the edges, enabling tunable mid-IR spectroscopy of ultralow-concentration molecules using graphene plasmons. Our wafer-scale chip platform can also be used for nano-positioning quantum emitters to build nanophotonic circuits or single-photon source arrays42. While we used straight edges of graphene in this work, DEP can also be performed with conductive nanopores44, presenting new opportunities for single DNA translocation and analysis48. Beyond graphene, atomically sharp edges of other 2D materials49 can also be utilized for ultra-strong DEP, providing a practical route to building tunable biosensors.Monolayer graphene can generate ultra-strong dielectrophoresis forces and outperform conventional metal electrodes that are orders of magnitude thicker. We have presented the concept of graphene-edge DEP and constructed a practical device platform to realize it. In our scheme, the critical dimension of graphene electrodes for DEP is controlled by its natural thickness and the insulator deposited by ALD, thus our approach is scalable and highly reproducible at the wafer scale. Using arrays of electrodes, we can selectively trap and position nanoparticles and DNA molecules precisely along the atomically sharp edges of graphene. This could facilitate performing of biological assays at low concentrations as well as exploring molecular interactions and conformational changes in confined space. We also demonstrated trapping of DNA molecules from 10 pM solution and on-chip assembly and precise positioning of nanodiamonds. Notably all of these rapid DEP manipulation steps were performed using monolayer graphene around or below 1 V, which makes the low-power graphene-edge DEP attractive for many applications. For example, edge trapping of biomolecules can be readily integrated with graphene nanoresonators2 (300 nm) thermally grown on Si substrate. The gate electrode patterns were exposed and developed using photolithography, followed by a combination of reactive ion etching and wet etching on the SiO2 layer. A metallization layer of Ti/Pd (10/40 nm) was then deposited by electron-beam evaporation and lifted off. Atomic layer deposition of HfO2 at 300 °C was applied to form a dielectric layer (8 nm), which was annealed in nitrogen at 400 °C for 5 minutes. A via layer was patterned using photolithography, and then the HfO2 in localized regions above the Pd metal was reactive-ion etched in SF6 for 30–60 s. The via window through the dielectric layer is intended to provide the ability to subsequently contact the gate electrode with additional contact metallization. Single-layer graphene grown by chemical vapor deposition (CVD) was transferred onto the dielectric layer using a wet transfer process, patterned by photolithography, and then etched using an O2 plasma. Ohmic contacts were patterned next using photolithography, and Cr/Au (10/80 nm) was deposited using electron-beam evaporation and lifted off. Finally, for the convenience of the device measurement, a thick metal layer of Cr/Al (10/300 nm) was patterned and deposited to form low-resistance electrical leads from the gate and Ohmic contacts to the contact pads for electrical probing.Our graphene-edge DEP chip was fabricated starting from a thick layer of SiOA solution volume of ~10 µl was placed on top of graphene electrodes, confined within a reservoir made in adhesive tape. A cover slip was placed to avoid any unwanted evaporation. A probe station was used to apply an AC bias across the contact pads by a function generator (HP 33120 A). The peak amplitude of the voltage used was in the range of 1−3 V. Depending on the particle, the frequency of the AC bias was optimized for polystyrene, DNA molecules, and nanodiamonds. For the polystyrene and ND particles, water was used as a surrounding medium (conductivity ~4 µS/cm), whereas 10 µM KCl solution (conductivity ~12 µS/cm) was used for DNA.Fluorescent nanoparticles used in this work are 190 nm diameter carboxylate-modified polystyrene beads (The data that supports the finding of this study are available from the corresponding author upon request.Peer Review FileAdditional Supplementary FilesSupplementary Movie 1Supplementary Movie 2


Programmed death-1 ligand-1 (PD-L1) an important cancer biomarker that can suppress the immune system and its high expression is often reported to be related with increased tumor aggressiveness in some cancers. Here, we examined and evaluated PD-L1 expression in patients with malignant salivary gland tumor. Moreover, the relationship between PD-L1 immunolocalization and clinical pathological features, as well as the prognosis of malignant salivary gland tumors was investigated.We examined PD-L1expression in 47 patients with malignant salivary gland tumor by immunohistochemical staining. PD-L1 positivity was defined as ≥5% in tumor cell membrane and evaluated according to three categories  in tumor-infiltrating mononuclear cells (TIMCs). Fisher’s exact test was used to compare between PD-L1 expression and clinico-pathological features, and Kaplan–Meier method was used to estimate the distribution of OS by PD-L1 positivity.p = 0.002 and p = 0.016, respectively).PD-L1 expression was detected in 51.1% of malignant salivary gland tumor tissues. No association was observed between PD-L1 immunolocalization in tumor and patient gender, or age. However, PD-L1 immunodetection of tumor cell membranes was significantly associated to stage, recurrence or metastasis after surgery, and patient outcome. On the other hand, PD-L1 immunodetection of tumor-infiltrating mononuclear cells (TIMCs) was significantly associated to recurrence or metastasis after surgery, and patient outcome. PD-L1 positivity in both tumor cell membrane and TIMCs was associated with shorter overall survival (OS) (These findings suggested that patients with PD-L1 positive tumors or TIMCs appear to have poor clinical outcomes in malignant salivary gland tumors. The incidence of malignant salivary gland tumors is relatively low compared to other head and neck cancers. They account for more than 0.5% of all malignancies and approximately 3–6.5% of all head and neck cancers , 2. ThesIt is well known that development and prognosis of malignant tumors are closely associated with host immune functions. Anti-tumor immune responses are induced when the host immune system efficiently identifies the tumor antigen and various T cells are activated. Co-stimulatory molecules and regulative networks play an important role in this progression. There are two groups of co-stimulatory molecules: the tumor necrosis factor TNF receptor (TNFr) superfamily and the immunoglobulin (Ig) superfamily . ProgramThe purpose of our study was to characterize the PD-L1 expression in patients with malignant salivary gland tumor, and to investigate the relationship between PD-L1 expression levels with clinico-pathological features as well as disease outcomes of the patients.Institutional review board (IRB) of the ethical committee of the Yamaguchi University Hospital approved this study (Ref H26–179). Our study was a retrospective one; therefore, informed consent was waived by the IRB.n = 47) with salivary gland cancers  treated surgically at Yamaguchi University Hospital from April 1990 to March 2011 were included in this study. Clinico-pathological characteristics such as gender, age, stage and follow-up data  were retrospectively collected from patients’ medical records.Forty-seven patients  ethyl alcohol . Then, the sections were washed with phosphate-buffered saline (PBS), and heated in a microwave in a Tris-EDTA buffer solution (pH 9.0). The slides were then allowed to cool down, and inserted into a 0.3% hydrogen peroxide/methanol mixture for 20 min at room temperature. After PBS wash, the tissue sections were incubated with Dako REAL™ Peroxidase-Blocking solution  for 30 min at room temperature; then incubated overnight at 4 °C with a rabbit polyclonal anti-PD-L1 antibody . After PBS wash, Dako REAL™ EnVision™ Detection system (Agilent Technologies) was used according to the manufacturer’s protocol to detect the immunostaining. Tissues were then lightly counterstained with hematoxylin , and were subsequently dehydrated in graded (70–100% v/v) ethyl alcohol , inserted in xylene  and mounted with glass coverslips using DPX mounting medium . In case of negative controls, primary antibody was omitted.Tissue samples obtained from biopsy or operation specimens were used to prepare Formalin-Fixed Paraffin-Embedded (FFPE) blocks. Four-micron-thick tumor sections were prepared from these blocks were used for the immunohistochemical analysis. These paraffin-embedded tissue sections were deparaffinized in 100% xylene  for 10 min at room temperature, followed by rehydration using graded , who had no knowledge of the patient’s clinical status. Briefly, five randomly selected areas were examined. The proportion of tumor cells showing high and low immunolabeling in each selected field was determined by counting individual tumor cells at high magnification (× 400). At least 200 tumor cells were counted. PD-L1 tumor positivity was defined as ≥5% tumor cell membrane staining. PD-L1-positive immunolabeling was predominantly located in the cytoplasm and with some nuclear membrane localization  (i.e. lymphocytes and macrophages) was assessed in hematoxylin and eosin-stained slides and evaluated as absent (0), focal (1), mild (2), moderate (3) and marked (4) by three authors , who had no knowledge of the patient’s clinical status. The percentage of PD-L1-positive TIMCs was also evaluated independently. Immunoreactivity for PD-L1 expression was evaluated according to three categories . An adjusted score representing PD-L1 expression was calculated multiplying the percentage of TIMCs that stained positive for PD-L1 and the extent of mononuclear cell infiltration.p value (two-sided) < 0.055 was considered statistically significant.In the present study, we investigated PD-L1 expression and its association with clinical outcome in patients with malignant salivary gland tumor. Overall survival (OS) defined as time from diagnosis to death was analyzed as an end point. In the absence of an event, the end point was censored at last follow-up time. Patient and tumor characteristics were summarized descriptively. PD-L1 positivity was defined as 5% or greater of tumor cell membrane staining. For PD-L1 expression in TIMCs, any score greater than five was considered high. Comparisons between PD-L1 expression and clinico-pathological features were evaluated using Fisher’s exact test for categorical variables. Kaplan–Meier method estimated the distribution of OS by the PD-L1 positivity. All statistical computations were carried out using the StatView software  and a n = 25), mucoepidermoid carcinoma (n = 9), adenocarcinoma (n = 11) and mucinous adenocarcinoma (n = 2). The median follow-up time was 7.4 years [interquartile range (IQR): 1.8–12.8], and the median age was 62 years (range 24–80 years). For malignant salivary gland tumor, clinical stages I, II, III and IV at diagnosis was identified in 9, 18, 5 and 15 patients, respectively.Characteristics of 47 patients with malignant salivary gland tumor included in this study are summarized in Table p = 0.047), recurrence or metastasis after surgery (p = 0.028), and fatal outcome (p = 0.002). On the other hand, PD-L1 positivity was not associated with gender, age at diagnosis.Table p = 0.011), as well as PD-L1 expression levels and outcome of patients (p = 0.049). PD-L1 positivity in TIMCs was not significantly associated with gender (p > 0.999), age (p = 0.769), stage (p = 0.073).Association between PDL-1 expression in TIMC and clinico-pathological factors are presented in Table p = 0.002 and p = 0.016, respectively) , tumor necrosis factor-α (TNF-α) and interleukin-2 (IL-2) which in turn can induce PD-L1 expression on surrounding immune and tumor cells when T-cells recognize antigen and become activated . TIMCs aOur study is a retrospective analysis of PD-L1 expression and we have only analyzed 47 cases of malignant salivary gland tumors. Further prospective studies are needed to understand the role of PD-L1 expression more precisely in immune cells as a predictive and prognostic biomarker in malignant salivary gland tumors.This is the first study that demonstrated the association between PD-L1 positive expression and clinical stage, recurrence or metastasis after surgery and survival time of patients with malignant salivary gland tumors. Our data also showed significant association between PD-L1 expression levels in TIMCs and recurrence or metastasis after surgery or patient outcome.


Our phenomenological model for contact noise because of current crowding in purely two-dimensional conductors confirms that the contacts dominate the measured resistance noise in all graphene field-effect transistors in the two-probe or invasive four-probe configurations, and surprisingly, also in nearly noninvasive four-probe  configuration in the high-mobility devices. The microscopic origin of contact noise is directly linked to the fluctuating electrostatic environment of the metal–channel interface, which could be generic to two-dimensional material-based electronic devices.The impact of the intrinsic time-dependent fluctuations in the electrical resistance at the graphene–metal interface or the contact noise, on the performance of graphene field-effect transistors, can be as adverse as the contact resistance itself, but remains largely unexplored. Here we have investigated the contact noise in graphene field-effect transistors of varying device geometry and contact configuration, with carrier mobility ranging from 5,000 to 80,000 cm The performance of graphene field effect transistors is adversely affected by fluctuations in the electrical resistance at the graphene/metal interface. Here, the authors unveil the microscopic origin of such contact noise, highlighting the role of current crowding. Over the past few years, there has been tremendous progress in creating high-mobility, atomically thin FETs through a combination of low-resistance ohmic contacts13f noise, which is known to degrade the performance of amplifiers, or introduce phase noise/jitter in high-frequency oscillators and converters6The wide spectrum of layered two-dimensional 2D) materials provides the opportunity to create ultimately thin devices with functionalities that cannot be achieved with standard semiconductors. The simplest of such devices is the field-effect transistor (FET). There are several factors that determine the performance of an FET, the key among them being the dielectric environment, quality of the metal–semiconductor contact and the level of low-frequency 1/D materiaf noise. Conflicting claims exist, where some studies attribute the 1/f noise in graphene transistors primarily to noise generated within the channel region78101178910111213141516171819202223242526f noise.Even for the widely studied graphene FET, it is still unclear what the dominant contribution is to the 1/LT22293032LT∼0.1–1 μm  and black phosphorus FETs26In this work we study a series of graphene FETs with different mobilities, substrates and contacting configurations to demonstrate that electrical noise at the metal–graphene junction can be the dominant source of 1/2/p++–Si substrate, etched into a Hall bar shape with surface-contacted Au (99.999%) leads (45VBG). We measure the two-probe  and four-probe  resistance and noise as a function of VBG between the leads 2 and 3  and current  leads). The VBG dependence of R2P and R4P is shown in R4P shows a slightly asymmetric transfer characteristic, known to occur for asymmetric contact dopingVBG≈6 V. R2P, however, shows a second Dirac point at VBG≈31 V because of the combination of hole doping and weak pinning by Au at the contact region3438n−p and R−VBG characteristics confirms the structural integrity and gate tunability of the Fermi level of the graphene channel underneath the contact.We first focus on a single-layer graphene channel on conventional (300 nm) SiO%) leads . Here we%) leads VBG. We mRc, we follow the Landauer approach where the net transmission probability T across the contact is determined by the interplay of the number of propagating modes in the channel and metal regions  and that calculated assuming the Dirac-like dispersion and level broadening ≈80 meV underneath the contact and ≈57 meV in the channel , indicates that the contact resistance is primarily composed of the resistance RT of the graphene layer over the charge transfer length (LT) underneath the contacts. Owing to mismatch between the resistivities of the metal and graphene, LT is significantly smaller than the geometric width Lc (∼1–1.5 μm) of the metal lead, resulting in the current-crowding effect.The shift in the local chemical potential by metal contacts results in a change in resistance that contributes to contact resistance, and determines the extent of current crowding at the gold–graphene interface. To compute the contact resistance  regions 38. FigurρT . Taking RT as the experimentally observed contact resistance Rc  for the second Dirac point at +31 V where the mismatch between the resistivity of the metal and that of the graphene layer underneath is maximum.where μm2 ref.  is the stance Rc , we calcρT=RTW/LT, it is evident that the contact noise is essentially the resistance fluctuations in the graphene layer underneath the contact, that is, nT are the phenomenological Hooge parameter and carrier density in the charge transfer region, respectively. nT and is determined by the kinetics of local disorder induced by trapped charges, chemical modifications and changes in the band dispersion due to hybridization. Assuming a diffusive transport in the charge transfer region with density-independent mobilitySince  refs , 24 and Rc is ≈1 for interface-type contacts or ≈3 for constriction-type contactsnT is the only gate-tunable parameter3438and implies a scaling relation R2P and R4P at all VBG consists of random time-dependent fluctuations with power spectral density f noise due to many independent fluctuators with wide distribution of characteristic switching rates. However, to estimate and compare the total noise magnitude, we have evaluated the ‘variance' SR(f) numerically over the experimental bandwidth.Noise in both density  , where  VBG dependence of R2P and Rc  is ∼10 times larger than that at the main Dirac peak, indicating the significantly larger noise where the current crowding is most severe and contact resistance is the largest. Surprisingly, P and Rc . The oriRc in VBG collapses on a single trace, and varies as n in 12 cm−2), that is, p–p′ regime where Rc reduces to ≲1 kΩ, we observed −3  for both R2P and R4P  and Rg are the metal–graphene interface resistance and graphene channel resistance, respectively. Owing to the inseparability of RT(=Rc) and Rg within this contacting scheme, we plot R4P in R4P≲150–200 Ω, where Rg is small because of heavy electrostatic doping of the channel. However, for R4P≳200 Ω, the deviation from the Rg that causes R4P to overestimate the true Rc. We have observed an R4 scaling of noise for high-mobility suspended graphene devices as well (see The effect of contact noise becomes more severe for invasive surface contacts (leads extending to the current flow path), as demonstrated with a device that has graphene on BN . The tra V−1 s−1  inset. Se of VBG , suggestwell see .I–V characteristics (not shown) and temperature independence of Rc  than the corresponding mobility  of the part on BN, as well as strong substrate-induced doping, both of which can be readily understood by the proximity to charge traps at the SiO2 surface. Although 2 substrate is up to a factor of 10 larger than that on BN, similar to that reported recently192 surface).To verify this, we have fabricated an invasively Cr/Au-contacted device where a single graphene channel was placed partially on BN (thickness ∼10 nm), thus physically separating the channel from the oxide traps2 . The fou2  confirm c points , it is ecently19  over thrRcW, from different classes of devices that were studied in this work. We identify two key factors that have an impact on the contact noise: first, as can be clearly seen in 2, lower on devices with graphene on BN and lowest for suspended graphene devices where all SiO2 has been etched away from under the graphene channel as well as partially from below the contact region  tape. The heterostructures were assembled using a method similar to that described in ref. 3 and O2 plasma, to be 23±2 nm per 60 s .Publisher's note: Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.Supplementary Figures 1-5, Supplementary Notes 1-3 and Supplementary References.


Community Health Workers (CHWs) play an instrumental role in promoting socio-behavioural change at the community level, which results in changed indicators of community health. While outcomes are mostly reviewed for achieving program objectives, it is pertinent to understand the process of program implementation mainly from the perception of participating CHWs.A qualitative study to understand the perception of Sakhi’s (CHWs) regarding the outcomes of their participation in Home-Based Neonatal Care (HBNC) Program implemented by a non-governmental organization (NGO). Data consisted of 3 FGDs and 20 in-depth unstructured interviews with participating Sakhis.Sakhis perceived their ability to take decisions at critical phases of the program as an important factor influencing their performance. The opportunity to participate as a Sakhi in the health programme initiated a process of change at the personal level. The changes perceived by Sakhis were enhancement in knowledge, skills and capabilities of Sakhis. The combination of improved skills, knowledge and attitude had culminated in the process of experiencing self-empowerment for the participating Sakhis. Their ability to positively influence the individuals and community with their initiatives to improve women and child health and save lives in critical situations facilitated development of a new identity and improved societal status in their communities. Changed power-relations at the family and community level promoted the involvement of Sakhis in the broader development agenda. Sakhis’ ability to strategize goals, evaluate their own abilities, their willingness to upgrade knowledge and take others along in bringing social change, was an evident movement towards self-development.An opportunity for local women to participate in development programs creates potential for self-development as a cascading effect in addition to the accomplishment of planned program objective. The use of community health workers (CHWs) has for long been one of the important strategies to address the issue of healthcare outreach. India has a rich history of engaging CHW in health prevention and promotion programmes. A large national CHW scheme was established in the late 1970s that aimed to provide one CHW for every 1000 people in order to provide adequate health care to rural people and to educate them in matters of preventive and promotive health care , and theBeing firmly rooted in communities, the CHW play an instrumental role in promoting socio-behavioural change at the community level, which is expected to result in improvements in individual and community’s health indicators. While several studies –8 have sStarted in 2005, a HBNC program was implemented for over a decade in 160 villages of three blocks in Chandrapur District, Maharashtra by Ambuja Cement Foundation, the corporate social responsibility (CSR) arm of Ambuja Cements Ltd. In this program women from villages who wanted to become CHW were selected and trained to provide services in communities on the lines of the well-known HBNC model proposed by Bang et al.  The SakhThe umbrella term “community health worker” (CHW) embraces a variety of community health aides selected, trained and working in the communities from which they come. The CHW’s roles and activities are tailored to meet the unique needs of their communities. It also depends upon whether they work in the healthcare or social services sector . AlthougSelf-development and empowerment are inherently interrelated. In the context of health and social development, the concept of “empowerment” has received much more attention. Empowerment, both as a process and a goal, has taken considerable prominence within community organisation theories, especially as operationalized by NGOs since 1970s . It has The data presented in this paper are from an exploratory qualitative study that was conducted to understand the challenges faced and mitigation strategies used by Sakhis. The study was conducted adopting a grounded theory approach and data acquired was from 3 focus group discussions and 20 in-depth interviews with Sakhis who met the qualifying criterion of having at least 2 years of experience. A more detailed description of the study’s setting, conceptual framework, process of data analysis, and findings related to challenges and mitigation strategies are reported in another paper .An unexpected recurrent theme emerged while analysing data. While narrating challenges and mitigation strategies many Sakhis had expressed about how they had undergone positive changes at a personal level. This theme was beyond the scope of conceptual framework, and therefore the authors revisited the data to develop a nuanced understanding of the Sakhi’s perception of the effect of her work on herself. Each interview was independently coded by at least two authors and the validity of coding was ensured through joint review of coded sections by three authors . This helped to minimize bias of the authors and ascertained that findings were firmly rooted in experiences shared by the Sakhis. After engaging in several deep reflective discussions on the emerging theme, the authors concurred that the pattern reflected “self-empowerment” that had resulted from the process of working as a CHW.Through the analysis of the data we reviewed the perception of Sakhis regarding the critical phases of their process of engagement and its outcome in terms of empowerment and self-development.There were certain common characteristics observed among the local women willing to participate as Sakhis. Many of them were in the 20–35 year age-group, married, possessed minimal literacy levels, and in most cases their work was restricted to the household chores, though few were involved in farm labour to support the family livelihood.“I got married at the age of 15 and had a baby when I was 18. I was not allowed to talk to anybody. I hated to work in the farm and hence was annoyed with it but did not have any choice. It was then this opportunity for training came up. My in-laws and my husband opposed, but I argued with them to join this work. I left my six-month old baby to be taken care by my sister-in-law for five days during the first training. I suffered a lot because I missed my baby but didn’t quit the training”.In this phase the decision to participate was considered to be the most critical by the local women and the process of empowerment originated at this stage. Their decision was influenced by their family, chiefly by their spouses and in-laws. The Sakhis shared about the nature of support they experienced in joining the program. While some Sakhis experienced enthusiasm and support from their spouse and the immediate family, others did not. Despite lack of support many decided to become a Sakhi. The experiences shared by Sakhis showed a distinctive feature of women who had opted to become a Sakhi – a very strong desire to participate in activities beyond the realm of their household work and familial responsibilities. Though their motivation differed in degree, in most cases women regarded this as an opportunity to perform. High motivation and positive attitude influenced the ability of Sakhis to take a decision about participation. A Sakhi recalled,For many Sakhis it was the first opportunity to independently express and assert their views. Once the Sakhis had asserted and decided to become a CHW, the decision itself helped Sakhis to further build their confidence to initiate work for the community’s health and development. For few Sakhis, an additional factor that helped move toward independent decision making was their selection by the community to become a CHW for their village. In certain cases however local women experienced dissuasion from the community. Their intention and interest in taking on the work as Sakhi were questioned and were mistrusted for their capability and eligibility to become a Sakhi.ACF field supervisors also recommended some potential local women based on the previous interaction with the community. Sakhis perceived recommendation of their name as recognition of their efforts as well as their potential, which encouraged them to participate. A sense of self-esteem emerging out of recognition of their potential by the community enhanced the level of confidence of the women turned Sakhis. Initial fear was replaced with confidence to take upon challenges with the process of engagement. The Sakhis shared that gaining ability to respond to challenges was an elevating experience.During the training we were prepared for this phase. We were told that the patience to take the community with you will count first followed by your ability to provide needed health care services”.“The action phase began with the orientation training followed by field outreach. Each Sakhi developed a customised outreach plan and communication strategy for her village as part of the training. This helped Sakhis to have an improved acceptability for their health messages. Sakhis, being local and always available, got an opportunity to demonstrate their knowledge and skills. Their constant communication and follow-up helped in spreading health awareness especially in case of pregnancy. Sakhis experienced non-acceptance from the community during the initial period, however they continued their efforts to reach individuals and families with health care inputs and support especially during the critical conditions. In this regard, explaining how they were able to deal with difficulties, a Sakhi shared,Sakhis were able to adapt the style of communication through different phases of interaction with the community. They mentioned to have experienced improvement in communication skills, develop a poised attitude and ability to think creatively in a given context. The strong commitment and persistence among the Sakhis helped initiate the process of changing beliefs and practices among the community members. The process of influencing beliefs and attitudes of community also contributed to Sakhi’s improved confidence to act further.“I can’t tell you how happy I feel to see the saved child grow and it is also the same with the family. I built relations with those families. The families have also shared with their child about their gratitude for the efforts we had made to save her”.The experiences shared by Sakhis indicated that the first experience of handling a critical case played a significant role in boosting their confidence. It was evident in the data that technical knowledge and timely decision making ability among the Sakhis got sharper with each critical case handled by them. The experience of handling critical child birth cases was perceived to be a significant differentiator by Sakhis. They placed highest value on handling critical cases that led to saving human life, considering it to be a noble task. Further, Sakhis mentioned it to be a gratifying experience that also elevated their status in the community. The ability to respond to critical cases, ability and courage to take timely decisions and recognition for this ability from their own community and other stakeholders developed an immense sense of self-esteem among the Sakhis. The aspects of saving lives of babies also provided Sakhis with huge satisfaction. As a Sakhi mentioned,“This is our reward. Money doesn’t matter to us but it is the respect that we get in the community which becomes important”.Another Sakhi stated,panchayat initially for health issues and expanded their reach to discussing other development schemes by government, being representative on various committees or to support social action campaign on issues such as alcoholism and tobacco use. Sakhis also helped women to get their ration card or access loan from a bank. These added roles further demanded mobility for a Sakhi. It was evident from the following example that the enhanced mobility and interface of Sakhis with the external world stimulated their aspirations to grow further and influenced choices made by them. A Sakhi-turned-master-trainer mentioned mobility adding to her confidence in being independent.“Now I can travel very far for work, I don’t feel afraid even if I am alone. Feel like my home wherever I go”.The Sakhis’ experiences revealed that their performance of roles was also shaped by their ability to influence social customs and practices. Acknowledgment by community members and health providers encouraged Sakhis to take initiative and also go beyond their predetermined role in the project and contribute in other aspects of community health and village development issues. Beginning with women and child care, they moved on to working on addressing issue of child marriage, sanitation, nutrition, decisions regarding contraception and quality of health care provided by public health system. Sakhis believed their effort helped in improving awareness among the community about relationship of health issues with social customs such as early age of marriage. Sakhis engaged with “I feel my village should always remain good and healthy, and zero mortality is my aim”.Another Sakhi discussed the value she found in interacting with experts and external contacts. Interestingly, these aspirations are not limited to herself or her family. A Sakhi mentioned,Based on the experiences shared by Sakhis about the process of their participation and self –growth through this process, an empowerment framework seems to be emerging. The process appeared to have begun with personal changes at an intrinsic level, which over the period of time expanded to the Sakhis’s standing in the society as an empowered woman involved in managing affairs of the community. The components of this process are described below sequentially, however, they are likely to have occurred parallel to each other with substantial overlaps.“I might have remained just like that, uneducated and unhappy about not utilising my potential, if I had not been part of this program”. Sakhis appeared to have learned to overcome their fears by confronting the fear and continuing with their work. As expressed by a Sakhi, “I feel when we do something, initially we are scared but later the fear just withers”. Over time, Sakhis were able to replace their initial fears with larger dreams for their own community’s development.Sakhis experienced an emergence of a new identity for themselves which is clearly highlighted from an example. As a Sakhis mentioned, “I have two children and both are studying. One is pursuing BSc and other one is in 11th. When it came to paying their fees I used my earned money and took a decision to pay it off. My dream today is to ensure that my children are well educated”.Sakhis earned honorarium for their work. The earning, though not very substantial, provided Sakhis with respect and confidence which was highlighted in the example shared by a Sakhi.It was evident in most cases that Sakhi’s earning became an additional support for the family and in most cases it was utilised for domestic needs and education of their children. Sakhis shared that, with access to finance, their involvement in household financial decisions improved. The finding corroborates with another study conducted by ACF which suggested the access to finance through self-earning regardless of the magnitude develops a sense of confidence among the women working as veterinary health workers .“The decision benefited me a lot and my husband too turned supportive seeing the work I did”. Another Sakhi shared, “Now our family also doesn’t disallow us. In fact they say they are very proud of our work and earning money is inconsequential”. In other words, as Sakhis started acquiring financial independence, they started getting a say in their family affairs and their role as Sakhi was accepted.The journey of Sakhis began with influencing family members for their consent to participate in the program. Non-cooperation and lack of support at family level in certain cases were replaced with acceptance and trust. A Sakhi who faced resistance initially mentioned, “Yes, I am respected today. If a meeting is held, they invite me in it. Whenever anew committee is formed, they always offer a post to me”.Sakhis started being included in consultations related to other development agenda at the village level. The communities started seeking Sakhis to represent their interests by being on village level development committees such as education or sanitation committees. This elevated their status in the society. As a Sakhi expressed, “After being a Sakhi, I got habituated to being occupied. I am eager to work more in whatever way it may be”.The major learning as perceived by Sakhis in this case has specifically been in terms of improved knowledge, skills and attitudes. These aspects appeared to be interdependent and having a mutually fostering effect. The earned knowledge and learnt skills promoted positive attitude in the Sakhis, which in turn helped them take calculated risks and informed decisions while addressing difficult situations. The experience of successfully addressing difficult situations further accentuated the Sakhis’ self-image, increased their self-esteem, through vicarious learning and also strengthened their knowledge and skills. This ongoing process appeared to have triggered the process of empowerment in which the Sakhis’ growth was not limited to the personal level, but also at the societal level. Some Sakhis grew to become ASHAs or their supervisors and master trainers, others pursued education at secondary level and some also started working as CHW on other development projects. In other words, the Sakhis developed aspirations to perform effectively in future and not be without any constructive work. A Sakhi put this very simply and clearly – Sakhis, the key actors in the program, experienced a significant transformation in terms of improved ability in decision making which helped them to evolve their own identity. Sakhis place significant importance to creation of their identity. The elevated status for Sakhis in their community and an emergence of leadership reflected in their involvement in domain areas apart from health signifies empowerment.Women, an imperative segment of the society, have often been denied a fair role in the process of development, especially in underprivileged areas. The program played an instrumental role in encouraging local women to participate and contribute in working for their communities’ health and development. Further, it paved a path for gender integration in development at a local level by providing opportunities for women to enhance and use their knowledge and skills for the development of their own community.


EGFR基因突变状况的不一致性。表皮生长因子受体（epidermal growth factor receptor, EGFR）突变是晚期非小细胞肺癌（non-small cell lung cancer, NSCLC）患者获益于酪氨酸激酶抑制剂（tyrosine kinase inhibitor, TKI）治疗的预测因子，本研究旨在探讨NSCLC原发灶与相应转移灶之间EGFR基因突变状况。应用TaqMan RT-PCR的方法检测35例病理确诊为NSCLC患者原发灶和相应转移灶的EGFR基因突变型，余下6例为EGFR野生型。35例转移灶中18例为EGFR基因突变型，17例为EGFR野生型。35对配对标本中，11对（31.43%）标本出现原发灶EGFR基因突变，而转移灶为EGFR基因野生型，18对原发灶及转移灶均为EGFR基因突变型，且突变具体位点相同，6对原发灶及转移灶均为EGFR基因野生型。NSCLC原发灶与转移灶的EGFR基因表达不一致率为31.43%（11/35, P=0.008）。原发肺癌病灶中有29例为EGFR基因表达存在不一致性。NSCLC原发灶与转移灶的 Louis, MO, USA）上进行扩增；⑦应用SDS 2.0软件对扩增曲线进行分析并判断EGFR基因突变阴、阳性。实验大致过程如下：①两位病理科医生分别在显微镜下核对石蜡组织的H E染色玻片，选取肿瘤组织>80%的石蜡块；②切取每片10 μm厚的蜡片4张；③使用TIANamp基因组DNA提取试剂盒（TIANGEN BIOTECH, 北京)从切片中提取出原发肺癌组织和转移灶的基因组DNA；④进行DNA提取物的验证：甘油醛-3-磷酸脱氢酶（glyceraldehyde-3-phosphate dehydrogenase, GAPDH）管家基因（300 bp）PCR扩增，1.3Fisher’s检验。P < 0.05为有统计学差异。统计分析采用SPSS 16.0统计学软件。计数资料分析采用22.135对NSCLC病例的配对标本中，原发灶均是已经完整切除的肺部病灶，35例配对的转移灶中，29例是纵隔淋巴结转移灶（9枚隆突下淋巴结，8枚主动脉下淋巴结，8枚下气管旁淋巴结，4枚上气管旁淋巴结），4例是脑转移病灶，2例是锁骨上淋巴结转移灶。所有病例在获得肿瘤标本前未曾接受过EGFR靶向治疗。病例的一般情况数据如下：中位年龄为57岁（38岁-72岁）；女性14例（40%），男性21例（60%）；病理学类型为：鳞癌1例（2.9%），腺鳞癌3例（8.6%），腺癌31例（88. 5%）；肿瘤分期：Ⅲa期24例（68.6%），Ⅲb期3例（8.6%），Ⅳ期8例（22.8%）；吸烟史：不吸烟者16例（45.8%），既往吸烟者13例（37.1%），现时吸烟者6例（17.1%）。2.2EGFR基因突变RT-PCR扩增曲线见EGFR基因突变型，余下6例为EGFR野生型。29例原发肺癌病灶EGFR突变类型分别为第19号外显子突变15例、第21号外显子突变14例。其中第19号外显子突变中均为E746-A750缺失；第21号外显子突变中13例为第858位密码子碱基替换突变，1例为第861位密码子碱基替换突变。EGFR基因突变型，17例为EGFR野生型。18例EGFR基因突变型转移灶的具体突变类型为：第19号外显子突变11例、第21号外显子突变7例。其中第19号外显子突变中均为E746-A750缺失；第21号外显子突变中均为第858位密码子碱基替换突变（35例转移灶中18例（18/35, 51.43%）为2.3EGFR基因野生型的病例，其相应的转移灶分别为：3例脑转移病灶、2例锁骨上淋巴结转移灶和1例上气管旁淋巴结转移灶，这6例转移灶的EGFR基因均为野生型，与原发病灶一致。6例NSCLC原发灶为EGFR基因突变型的病例中，只有18例EGFR基因突变，而其余11例转移灶为EGFR基因野生型。18例EGFR突变型的转移灶中，11例为第19号外显子突变，病灶分别为：3例下气管旁淋巴结转移灶、3例隆突下淋巴结转移灶、3例主动脉下淋巴结转移灶及2例上气管旁淋巴结转移灶，第19号外显子突变均为E746-A750缺失；另外7例为第21号外显子突变，其相应转移灶分别为：2例下气管旁淋巴结转移灶、2例隆突下淋巴结转移灶、2例主动脉下淋巴结转移灶及1例脑转移灶，第21号外显子突变均为第858位密码子碱基替换突变。转移灶的EGFR基因突变位点与原发病灶的突变位点一致。29例原发灶P=0.008）原发灶EGFR基因突变阳性而转移灶为EGFR基因野生型的患者其转移灶分别为：4例隆突下淋巴结转移灶、3例下气管旁淋巴结转移灶、3例主动脉下淋巴结转移灶。其原发灶EGFR基因突变类型为：第19号外显子突变4例（均为E746-A750缺失）、第21号外显子突变7例（6例为第858位密码子碱基替换突变，1例为第861位密码子碱基替换突变），其相应转移灶均为EGFR基因野生型，与原发灶EGFR基因表达不一致。11例（11/35, 31.43%, P=0.008）标本出现原发灶EGFR基因突变，而转移灶为EGFR基因野生型，18对原发灶及转移灶均为EGFR基因突变型，且突变具体位点相同，6对原发灶及转移灶均为EGFR基因野生型。研究结果显示转移灶与原发灶的EGFR基因表达存在不一致性，其不一致率为31.43%（11/35, P=0.008）。35例原发NSCLC病灶与相应转移灶配对标本中，11例（31.43%, 3EGFR突变者对TKI治疗的反应率及PFS均较EGFR野生型者明显升高。检测EGFR基因突变来筛选获益于TKI治疗的患者已经推广使用。目前转移病灶的EGFR基因状况是否与原发病灶保持一致尚不明确。当晚期NSCLC患者在决定是否使用EGFR TKI治疗时，进行EGFR基因突变状况检测，是否原发病灶与转移病灶同时检测更合适，也无法定论。在晚期NSCLC患者中EGFR基因突变状况的一致性，共检测了35对配对的原发肺癌病灶与相应转移灶的EGFR基因。研究结果显示转移灶与原发灶的EGFR基因表达存在不一致性。入组病例中有11例（31.43%）出现原发灶EGFR基因突变，而其对应的转移灶为EGFR基因野生型。这一发现与最近几项同类研究的结果相似，Park和Gow等研究结果显示在NSCLC原发灶与相应转移灶之间EGFR基因表达的不一致率分别为11.9%（12/101，直接测序法），16.8%（17/101，异源双链分析法）、27%（18/67，TaqMan RT-PCR法) 、33%（16/45，免疫组化）、28%（7/25，直接测序法）。各个实验检测EGFR基因突变的方法不同及病例入组标准的差异可能是造成不一致率存在差异的原因。本研究比较了NSCLC原发病灶与相应转移病灶之间EGFR基因突变型，表达一致。另一个研究对比8例肺癌患者原发灶与转移灶的基因表达，EGFR基因、KRAS、P53在原发灶与转移灶之间都保持了一致性。然而这些研究的入组病例数都很少。然而，某些研究却发现相反的结果。Matsumoto在研究中有8例肺腺癌脑转移灶患者可找到相应的肺部原发病灶，其中6例脑转移灶和肺部原发病灶均为EGFR基因突变型晚期NSCLC患者中有明显疗效，能有效延长PFS、提高生活质量-16。TKI治疗是否是晚期肺癌患者合适的治疗，根据EGFR突变类型来选择是关键，然而EGFR基因在原发灶与转移灶之间存在着不一致性，所以如果对肺癌原发灶及转移灶同时进行EGFR基因检测，可能对患者的治疗有更好的指导意义。EGFR TKI治疗在总之，本实验发现在NSCLC原发病灶与转移灶之间的EGFR基因状况的不一致率为31.43%。这种原发灶与转移灶EGFR基因状况的不一致性可能对晚期NSCLC患者选择EGFR TKI治疗有一定程度的影响，同时也是将来相关临床试验设计时需考虑到的因素之一，尚有待大样本量的研究来进一步验证其临床意义。


Online health community (OHC) moderators help facilitate conversations and provide information to members. However, the necessity of the moderator in helping members achieve goals by providing the support they need remains unclear, with some prior research suggesting that moderation is unnecessary or even harmful for close-knit OHCs. Similarly, members’ perceptions of moderator roles are underexplored. Starting January of 2013, WebMD moderators stopped working for WebMD communities. This event provided an opportunity for us to study the perceived role of moderators in OHCs.We examine the OHC members’ perception on OHC moderators by studying their reactions toward the departure of moderators in their communities. We also analyzed the relative posting activity on OHCs before and after the departure of moderators from the communities among all members and those who discussed moderators’ departures.We applied a mixed-methods approach to study the posts of all 55 moderated WebMD communities by querying the terms relating to discussions surrounding moderators’ disappearance from the WebMD community. We performed open and axial coding and affinity diagramming to thematically analyze patients’ reactions to the disappeared moderators. The number of posts and poster groups (members and moderators) were analyzed over time to understand posting patterns around moderators’ departure.Of 821 posts retrieved under 95 threads, a total of 166 open codes were generated. The codes were then grouped into 2 main themes with 6 total subthemes. First, patients attempted to understand why moderators had left and what could be done to fill the void left by the missing moderators. During these discussions, the posts revealed that patients believed that moderators played critical roles in the communities by making the communities vibrant and healthy, finding solutions, and giving medical information. Some patients felt personally attached with moderators, expressing they would cease their community participation. On the other hand, patients also indicated that moderators were not useful or sometimes even harmful for peer interactions. The overall communities’ posting activity, which was already in decline, showed no significant difference before and after the moderators’ departure. In fact, the overall posting activities of the communities were declining well before the moderators’ departure. These declining posting activities might be the reason why WebMD removed the moderators.Compassionate moderators who provide medical expertise, control destructive member posts, and help answer questions can provide important support for patient engagement in OHCs. Moderators are in general received positively by community members and do not appear to interfere with peer interactions. Members are well aware of the possibility of misinformation spreading in OHCs. Further investigation into the attitudes of less vocal community members should be conducted. In-person patient support groups, often organized by hospitals and clinical moderators, are a well-established mechanism to encourage peer-patient interaction, help patients improve self-efficacy, and educate patients about self-care management -4. As WeTo successfully administer OHCs, we need to understand the critical role that moderators have in OHCs. A study revealed effective moderation styles for various negative online behaviors  . AlthougUnlike in face-to-face support groups, where moderators are often clinicians known to participants, moderators in OHCs do not have an immediate connection and the trust of members. Moderators are also unable to provide medical consultation. Furthermore, one prior study found that moderators urging patients to talk to their health care providers instead of consulting the community was highly associated with decreased peer-patient interaction . Health WebMD , an onliHealth professional moderators at WebMD were those with clinical backgrounds, providing clinical expertise to patient members by answering members’ questions and participating in conversations. Nevertheless, the HPMs would follow the same guidelines given to STMs, where HPMs would not be allowed to give personalized medical consultation. Health professional moderators could clarify clinical concepts and knowledge that would be useful for self-management, or direct ways to discuss with the members’ own health care providers.WebMD, however, made a decision to let go of the STMs starting January of 2013. Members were not notified of this change in staffing prior to its occurrence, but quickly picked up on the absence of moderators. The departure of STMs triggered patient members to talk about their experiences with moderators, including HPMs, as part of the communities. The sudden departure of moderators from WebMD provided critical information about how patients perceived the benefits and disadvantages of having moderators in their communities when faced with loss of moderation.While prior research has clearly demonstrated the benefit of moderators in OHCs, there is a limited understanding of the community member’s perceptions of moderators in their participation with OHCs. In this paper, we will investigate: (1) member’s perceptions of moderators in OHCs, and (2) the summary statistics analysis on OHC retention and moderators’ removal to understand both qualitative and quantitative aspects of moderators’ roles and influences in OHCs.We first walk through the data collection process, including community selection, followed by the descriptions on our mixed-methods analysis.Our institutional review board (IRB) determined this study to be unregulated because our data were publicly available and did not involve human subjects. WebMD has a total of 55 moderated communities. In January of 2015, we wrote an automated crawling program, which downloaded all 55 communities and saved the data to a local database software, MySQL (Oracle) . The craa) moderators leaving or (b) members’ perceived moderators’ roles, 2 coders manually went through each post to determine the relevance  and (7) The communities to investigate using our qualitative and quantitative analysis procedures were finalized. The result of this process is delineated in To best select active communities that can lend us more data regarding members’ discussions on moderators’ roles at WebMD, the following process was adopted: (1) From the total of 55 WebMD moderated communities, the top 20 communities which had the most posts in total after excluding nonhuman health-related community  were selected. (2) Posts made before November 2012 and those made by moderators were excluded. (3) A regular expression query with the keywords related to moderators was conducted: “moderator[s],” “mod[s],” “[moderator names of that community].” The query was conducted on both the title and the message body of each post; (4) All posts under the threads that contained the query result posts were then collected. (5) The communities that came with zero query results when (3) was performed were excluded. (6) To further filter whether the thread was about  of the data collection, 2 coders worked together with the first 5 communities on determining the criteria for relevance, asking about the posts that were related to discussion about moderators. If the post contained any dialogue about WebMD moderators—either STMs or HPMs, the post was flagged as relevant. The resulting criteria for relevance were as follows: First, the post should be about moderators, not other synonym that did not mean community moderators . Second, even though the post does not explicitly mention moderators’ removal from WebMD, if it contains any opinion about the moderators, it is included. The 2 coders divided the rest of the communities to code for relevance.We analyzed the whole thread in which related posts were its part. One main reason for excluding the thread was that when the whole thread of a post ended without someone intervening to inform the poster that the moderator had left, in case a moderator left without the poster’s knowledge.For the posts determined as relevant, a mixed-methods approach was adopted to understand the phenomenon using thematic analysis in addition to the quantitative methods employed. The thematic analysis  was usedWith the resulting codes, an affinity diagram exercise was performed  See Mul to conduIn this section, we first report the community selection and the summary statistics of posting activities. We then further examine qualitative aspects of how members perceived having moderators, providing us with insights for how moderators should be implemented in OHCs. The follow-up posting activity analysis of the members who participated in the discussions was then reported.A total of 14 communities were found to have included moderator-related keywords after having filtered out nonhuman health-related communities and relatively less active communities.In this section, the results of the overall posting activities, identification of related posts for further qualitative analysis, and the posting activity analysis of the members who participated in the discussions about moderators leaving WebMD communities have been reported.For the 14 resulting WebMD communities for us to analyze, 6-15 STMs and 1-7 HPMs have been moderating each community. It was found that these communities had, on average, 650 members per STM (ranging from 260 members per moderator on the Breast Cancer community to 1526 members per moderator on the Sex and Relationships community). On average, STMs started 255 threads and posted 1115 replies . On average, HPMs started 36 threads and posted 690 replies (from 0 to 119 thread starting posts and from 0 to 3348 replies). Further detailed breakdown of the activities are delineated in the Multimeda As shown in The last date of the STMs’ posts ranged between November 17 and December 20, 2012. Members’ posts related to moderators’ departure started as early as November 17, 2012 (the last posting date of the Sex and Relationships community) and persisted till December 20, 2012. There was a one-time post, an identical one, made by one STM in March to a few of the communities, asking members to share their experiences around insurance to a WebMD email address. Other than this particular post, no other posts have been made by STMs after December 20, 2012. One STM came back to the Fibromyalgia community with a regular member profile, updating about her current situation of finding a new job and health issues she is dealing with.In December 2012 (when STMs last posted) and January 2013, the discussion about moderator leaving WebMD peaked. Since then, members continued to talk about how moderators left, sharing opinions and solutions around STMs’ departure.The thematic analysis of 821 posts resulted in generating 166 codes. From these codes, 6 subthemes grouped into 2 main themes from conversations about moderators during the period from December 2012 to February 2014 see  were ideThe process by which the members figured out the news that the STMs have left WebMD was consistent across the 11 communities and is as follows: members first noticed moderators were gone; next, the groups shared the news individuals received from WebMD that the moderators had been removed from the forums; and finally, members pondered why the moderators had been removed, shared members’ initial reaction to the decision, and discussed how the community would continue to function in their absence .In figuring out moderators’ absence, members (1) noticed that moderators no longer participated, and (2) together they attempted to understand reasons for why moderators left. These discussions led to (3) discussions about solutions for not having moderators in their communities.WebMD community members’ posts revealed that they had not received any public notification about STMs’ departure from the communities. Instead, members slowly started realizing in mid-January 2013 that their moderators were not posting on their communities any more. This finding demonstrates that moderators’ roles were salient enough that their absence was quickly detected by members. Members started noticing that moderators were no longer posting, and they were seeking reasons for the absence of moderators’ posts:It seems that there are no more moderators on the community boards, and nobody is posting. Is anyone still here?LupusMembers who participated in multiple communities were able to publicize the idea that something suspicious was happening at the WebMD level, not just in one community:I am active in four WebMD communities. No mods posting in any of them. Maybe they were given time off for the holidays? DiabetesTo answer these questions, a number of members emailed the website directly and shared the replies from WebMD that WebMD had removed STMs from communities in December 2012 see . MembersThese communities no longer have moderators. The members are expected to inform others of the rules and policies. I am simply informing you of the facts.Pain managementMembers voiced their frustration about not being told about the change in the communities in advance:NO GOODBYE? Just over. The top of the site still says moderator mediated. No one has said anything to us? FibromyalgiaAs members realized moderators no longer participated in their communities, they attempted to figure out why moderators left.Members reacted strongly against moderators being removed from the communities and attempted to understand the rationale behind the decision. Members from the community suspected that budget cuts were the primary reasons for removal of the moderators. Members shared concerns about the moderators’ employment status, demonstrating the close relationships many had forged with the moderators. One member from a community shared evidence that WebMD had a budget cut, of which laying off moderators was a part. The following quote exemplifies the strong reaction to WebMD’s decision:Why??? Why would they deliberately sabotage a great site like Web.M.D.??? For what purpose??? Where are the BIG CHIEFS ??? What have they to say for themselves???Sex and Relationshipsthis is part of the changes which take place every day....businesses finding ways to cut or reduce costs....I am sure the moderators were paid for being here as are the other professional people who were here as well.FibromyalgiaIn one community, a member posted a press release on WebMD’s budget cut, which they believed provided a reason for the layoffs:For all those who have made inquiries about our missing leaders, apparently this is the answer: Forbes news release of December, 11, 2012 at 9:29AM(Breast Cancer)WebMD Cutting Staff 14%--250 Jobs. In Cost Cutting Program WebMD this morning disclosed plans to cut 250 jobs about 14% of the company’s staff as part of a plan to reduce annual operating expenses by about $45 million. The company said the plan is designed to “streamline its operations, reduce costs, and better focus its resources on increasing user engagement, improving customer satisfaction, and driving innovation.” As members accepted that moderators were no longer with them and attempted to understand why such a decision was made, the discussion moved on to how they, as WebMD community members, should proceed in maintaining their communities.Members discussed ways to independently manage their communities—to “stand united”  and make sure members regulate and facilitate conversations themselves. Some members predicted lack of moderators would produce problems, and advocated for strong mechanisms for self-regulation; others believed that communities could thrive without moderators, so long as they could provide a strong support system for each other.A few members stated that they no longer wanted to participate in the communities, as they were upset by WebMD’s decision to remove the moderators and bothered by increased spammers and trolls. One participant in the Pain Management community urged members to “ignore the trolls” and not “give [the trolls] any power to mess up” the community.To sustain the communities, members needed to stay and support each other. For instance, members discussed “staying strong for each other and the new ones that come [to WebMD] for help” and urged that they “do [their] best to help [new comers] in any way [they] know how” (Breast Cancer). In response to some members stating they would leave, other members asked them to stay:I’m sorry to see you go [David]. There are too few of us who have remained here over all the changes during the years (I’ve been around about 15 or more). Please reconsider. You help so many people. Anyway, hope you stay well and will contribute as you can to other groups.DiabetesI understand your needing a break, but you will be missed. Your insight and experience are a valuable asset to the other members of this community.Pain managementMembers also discussed that peer knowledge would not be enough and moderators were essential in communities requiring immediate answers to medical problems. Members discussed concrete actions they could take to fill the void left by the departure of the moderators, such as facilitating conversations by posting questions to elicit responses from “the wonderful people here” (Breast Cancer). After focused conversations about solutions to moderators being gone, members continued to encourage community members to monitor spam and advertisements. A member also shared one tactic of controlling malicious posts: “to not reply.” (Diabetes) we can report it and see what happens and then FLAG IT AS SPAM by the FMILY here so no one bothers to read it! Members began to practice self-moderation on their communities. They would tell other members not to share medical advice and provided alternative ways to get help at low cost (Pain Management), thus mirroring the prior activities of paid moderators. Members also put self-moderation into practice by reporting people; this task was not favorably received and caused one member to note that she or he “really miss(es) the moderators” (Pain Management). Furthermore, members shared websites that members should be careful of visiting. Members encouraged those who stated they would leave the community to stay, in an effort to sustain the community.While making sense of moderators being gone, patients shared their past experiences of having moderators as part of their communities. Throughout this process, even though HPMs still stayed on WebMD, members discussed their perceptions about health professionals as moderators. Contrasting opinions emerged about HPMs. Patients had conflicting views of whether moderators gave pragmatic help. Patients expressed that moderators were critical in ensuring the community did not include hostile messages, spams, and misleading information. Patients reported they felt personally attached with moderators. On the other hand, some expressed moderators were not useful and that peer support was more critical.Of the members who commented on the utility of moderators, most mentioned moderators to be helpful. Although STMs were the ones who left the communities, members discussed experiences around HPMs as well, allowing us to understand members’ experiences around not just STMs but also HPMs:I notice very few of the boards have doctors posting to them anymore. They were one of the reasons why I joined WebMD.Sex and Relationships. ” Similarly, a member stated, “While the support from people who are “suffering” from the same health problems is the most important thing on these blogs, expert advice [was] invaluable to [them] all. Members from the Diabetes community also felt that “the presence of mods experts in their fields to answer questions” was helpful. Members from Breast Cancer also noted the importance of moderators who are “ experts” on the topic: and that they “had always awaited a promised ‘expert’ for this board” (Breast Cancer).Many members did not draw a clear distinction between HPMs and STMs until some members clarified that there is a difference between STMs and HPMs. This perception was best illustrated by the sentiment that medical expertise was a unique resource that moderators could provide the communities. For instance, members in Sex and Relationships discussed how they missed doctors on the forum and expressed “personal experience doesn’t always match having a medical opinion” and that although members “have tons of personal experience, [they] sure as heck don’t have the required learning Although the STMs did not have the medical expertise, members appreciated the unique help provided by these STMs. These moderators helped keep the communities interested by posting articles, news, and information about WebMD. Members felt confident that moderators would find solutions to problems that arose on the forum. Members believed moderators ensured communities kept their “focus and no bickering.” Members did not “feel as safe posting here”  as they did when the presence of moderators was obvious. Being monitored by moderators made some members feel safe to participate in the community. Members declared their intent to leave, saying that they “joined because it was not like all the other social networking sites" (Diabetes). They “did not feel comfortable here now” because “mods used to tend to these issues [monitoring spams] in a timely fashion and keep an eye out” (Breast Cancer). Apart from a policing role, moderators helped maintain communities by picking up conversation when it slowed down. Members felt people were not posting anymore because the moderators were gone.Members from all communities saw an effect of not having moderators—spams lasting too long on the boards before being deleted, and that “New members are posting with rather radical ideas and trying to convince others that they are right” (Diabetes). The community being a “public, world-wide site with the communities open to anyone” (Diabetes), not having moderation made many members no longer feel safe posting.Members not only considered moderators to be helpful, but developed personal ties with them. They demonstrated these ties by voicing concerns about them losing their jobs. Several posters commented that moderators were like family members; for example, one wrote, “It is like losing a family member [...] To you all we will miss you” (Breast Cancer) and another similarly posted “we really loved having you on this board. We felt we were part of a large family” (Breast Cancer). In the Fibromyalgia community, members coordinated sending a card for one of the moderators. In the Depression community, a member started a thread to thank one of the moderators and wish her well. Some posters tried to petition WebMD to bring back the moderators, on the Sex and Relationships community, a thread called “BRING BACK OUR MODERATORS!!!” was posted with 17 replies in which the members vented on why moderators had to leave: “Complete madness to fire them.”Several members even threatened to leave the communities after learning about STMs leaving WebMD. One member wrote how she had been on WebMD for over 10 years and said:It was and has been my life-‐line and support for info from very good ladies. But Excuse ME-‐-‐-‐You are NOT the only Medical Information site on the Internet. I do believe you have just Stepped in IT [Breast Cancer].Some members wondered where they could find their former community members on other websites. One member suggested to start a discussion titled ”Refugees from that other site“ for the members to meet up and continue to support one another (Breast Cancer). Another suggested Facebook site where members can find the other members. Several Breast Cancer community members discovered that former members had posted about a discussion thread called “Friends from WebMDs Support Board” at another breast cancer forum.While most patients who commented about moderators believed they were helpful and important members of their communities, some patients discussed how they did not find moderators’ help to be useful. These members considered peer-support as the main benefit to participation in OHCs, and felt that moderators could deter the dynamic exchange of ideas among patients and peers.For example, a member stated that HPMs did not weigh in with medical expertise when needed. Certain moderators’ questions were thought to be unhelpful for the community, such as “What turns you on?” in the case of Sex and Relationships community, which seemed to minimize the seriousness of the medical focus of the community. Other examples of ineffective moderation included inappropriate language spreading out even in the presence of moderators.Members who saw moderators’ roles as providing medical expertise did not find HPMs to be helpful, as they cannot “treat, diagnose, or exam the people” (Sex and Relationships). In addition, members discussed how the “one size fit all” advice coming from the HPMs was not helpful; rather, peers’ “one-on-one, spiritually rewarding” support would be more beneficial for the community (Diabetes).A few members considered others’ shared personal experience as more critical than moderators’ help. In an exchange between 2 members on the Sex and Relationships community, they shared their belief that their community did not seem to need HPMs’ involvement:Member 1: It’s got to a point where we do not need a doctor, we’re too good Member 2: I think you are right? We really are better than any doctor, any day, Right???A similar sentiment was found in the Fibromyalgia community:It’s the people that make the community and the support we gain from each other that keep us coming back.Some members believed that the absence of moderators might facilitate increased sharing among peers. Members believed that self-efficacy was essential and that moderators could not help with disease management. This thought was especially apparent on the Diabetes community. Patients felt that the communities did a good job of self-regulating and making sure that no one was claiming to share medical advice; rather, they were sharing anecdotal experiences. As one poster commented:I think there are a lot of very smart people who post on the various boards and I have never seen anyone claim to be an expert. We post what we know through personal experiences or something that has worked for us [Sex and Relationships].Although members believed that moderators may not improve the chemistry of communities, they did acknowledge that the website was losing long-term membership with the absence of moderators. Several members of the Diabetes community mentioned that it is up to the patients themselves to manage their disease, and that moderators cannot help. Similar sentiments were echoed on the Sex and Relationships community, noting that peer’s expertise was important.. Many believe that patients gravitate to these communities because they are free from professional governance [OHCs were primarily developed to connect patients to others with similar disease processes in an attempt to provide emotional and informational support -28. Whilvernance ,31. By iThis analysis of the departure of STMs from WebMD communities offers several insights into the role that moderators play on OHCs. Longstanding community members quickly detected moderators’ absence. The departure spurred conversation and debate on the communities about the utility of moderators. This rapid detection of the departure of moderators appeared to be indicative of the important role moderators played on many of the communities, such that the void was noted quickly. This void was validated by our quantitative analysis demonstrating that many of the moderators were active on communities. The close personal ties that many community members felt with moderators was demonstrated by the fact that many members worried about the employment status of the moderators, and some further petitioned WebMD to bring the moderators back.Although many participants appeared to be especially appreciative of the pragmatic help that moderators had provided to their communities, such as monitoring for trolls and stimulating conversation when it had slowed, many of these roles were quickly assumed by community members. However, members did not enjoy these tasks, which often made them comment on how they missed the moderators. Community members also worked to create a sense of camaraderie and encourage their peers to continue to post, thus filling in the void left by the moderators. These tasks appeared to be less bothersome to posters. Such altruistic behavior is often observed in closely knit online communities, which is one of the strongest sources of maintaining online participation ,33.Several posters commented they did not feel as safe participating after moderators had left their communities, even as members tried to step in and report inappropriate posting activity. This finding suggests that even on vibrant communities, the role of the professional moderators may be unique and irreplaceable. This role of professional moderators, however, should be distinguished from general moderators or informal leaders in online community literature ,35. The Although the general sentiment of community members toward moderators was positive, this sentiment was not universal. The departure of the moderators spurred debate on some communities, which felt that the utility of the moderators might vary according to the disease process the community dealt with. Members were insightful in their discussions about the tension between having moderators versus not having moderators. Having moderators can potentially impede conversation but limit the exchange of erroneous information. The lack of moderators or self-moderated communities can have strong community dynamics but requires strong commitment by the members to self-moderate bothersome, unmoderated exchanges by visitors and new comers with either ill intent or lack of knowledge around the community norms and common ground. Furthermore, not having moderators and committed members would lead to reduced access to health professional knowledge or validated information.A few members threatened to, and eventually left their communities, after removal of the moderators. Some spoke about attempting to find people who had left for other websites. The remaining members believed that their communities were less active. However, this analysis has revealed that the overall posting activity of the WebMD health communities was declining throughout the study period, so it is difficult to infer that the decline in posting activity was a result of the moderators’ departure. Rather, the decline of member participation was followed by STMs’ and HPMs’ increased posting activity. Moderators’ increased activities showed WebMD’s effort to increase participation, which was evidenced by a study that reported qualitative analysis on the post content of WebMD’s moderators . The resThe participation decline observed in WebMD is a canonical retention problem in social media. Thus, user migration has been widely studied to understand how to retain and attract users in social media platforms -42. MainAnother reason for decline in member participation might be due to the members not seeing health benefits as Su et al have discussed in their literature review of eHealth Systems . HoweverWe also found the lack of distinction community members drew between HPMs and STMs. Although WebMD only dismissed STMs, members did not initially pick up on the fact that HPMs were still active members of their communities. Similarly, even on communities where there were HPMs participating , some members were frustrated because they did not realize that there were HPMs (and such moderators were desired). Online health information consumers are keen on finding indicators for the source of information -46. ThusOur study has implications for future OHC development. By exploring the impact of the removal of STMs from several well-established communities and the discussions ensued among participants, an insight was gained into what aspects of moderators’ presence and posting activity are most appreciated by members and helpful:OHCs need explicit, systematic policing activities put into place to help members feel safe and agree on continued participation. This was a universal sentiment expressed on the communities; members appreciated this role that moderators had previously played and did not enjoy assuming this responsibility. Given the disproportionate number of verbal members who volunteer to take on the moderating role, strong dependence on these members will threaten the sustainability of the communities.The importance of HPMs may vary according to health topics of the communities. It is difficult to characterize which communities benefited most from moderators from our study, given the more or less similar participation pattern across all communities. However, members’ conversations revealed the needs are different among different communities, where communities such as diabetes or heart disease might need immediate help from health professionals. Further work should clarify and identify what characteristics of illness experiences drive members to seek health professionals’ knowledge online rather than peers’ social support.The background of moderators  should be explicit. Some WebMD community members demonstrated a poor understanding of the distinction between HPMs and STMs, where some thought HPMs have left the communities. Even in communities with an HPM, posters noted that they had been promised such an expert on the community and yet had still not encountered him. Explicit signatures should be available for every post and profile, clarifying if the moderator has undergone any professional health training, or is an STM. If an STM, whether the STM has any professional knowledge on health should be presented explicitly.Major community changes, such as removing moderators, should be communicated to members with advanced notice. Much of the discussion about moderators centered around communities attempting to understand what had happened to them after they noticed their absence. Members’ frustration about the decision to remove moderators, and the lack of notification, was apparent in their posts. Members felt betrayed, and as many of them had developed close bonds with moderators, were upset about not being able to say their goodbyes to these members of their communities.Our data source was limited to observed, publicly available posts. Thus, our analysis is limited to those who are verbal and have expressed opinions. Other rich metadata sources can be used to further analyze deeper insights about OHC activities, such as user logs, page views, and click streams . The resThe analysis of STMs’ departure from WebMD communities provided a critical insight into the utility of moderators in OHCs. By analyzing the reactions of community members in 11 different illness communities to moderators’ departure, it was found that members perceive that moderators play an important role in OHCs, stimulating discussion and making them feel safe. However, this quantitative analysis of the posting activities shows that moderators’ efforts were not enough to increase the already decreasing member participation. Our work disputes a widely held belief about patients’ blindly accepting other patients’ shared information in OHCs and preferring nongovernance. Although moderators’ efforts did not play a large-scale influence on member participation, their presence was effective and favored by the core members. The discussion on member attrition and attraction in OHCs contributes to the call for analyzing attrition as a core research in eHealth systems . This st