Few-cycle laser pulse characterization on-target using high-harmonic generation from nano-scale solids.

We demonstrate high-harmonic generation for the time-domain observation of the electric field (HHG-TOE) and use it to measure the waveform of ultrashort mid-infrared (MIR) laser pulses interacting with ZnO thin-films or WS2 monolayers. The working principle relies on perturbing HHG in solids with a weak replica of the pump pulse. We measure the duration of few-cycle pulses at 3200 nm, in reasonable agreement with the results of established pulse characterization techniques. Our method provides a straightforward approach to accurately characterize femtosecond laser pulses used for HHG experiments right at the point of interaction.

Regulating Li-Ion Transport through Ultrathin Molecular Membrane to Enable High-Performance All-Solid-State-Battery.

Solid-state lithium metal batteries with garnet-type electrolyte provide several advantages over conventional lithium-ion batteries, especially for safety and energy density. However, a few grand challenges such as the propagation of Li dendrites, poor interfacial contact between the solid electrolyte and the electrodes, and formation of lithium carbonate during ambient exposure over the solid-state electrolyte prevent the viability of such batteries. Herein, an ultrathin sub-nanometer porous carbon nanomembrane (CNM) is employed on the surface of solid-state electrolyte (SSE) that increases the adhesion of SSE with electrodes, prevents lithium carbonate formation over the surface, regulates the flow of Li-ions, and blocks any electronic leakage. The sub-nanometer scale pores in CNM allow rapid permeation of Li-ions across the electrode-electrolyte interface without the presence of any liquid medium. Additionally, CNM suppresses the propagation of Li dendrites by over sevenfold up to a current density of 0.7 mA cm-2 and enables the cycling of all-solid-state batteries at low stack pressure of 2 MPa using LiFePO4 cathode and Li metal anode. The CNM provides chemical stability to the solid electrolyte for over 4 weeks of ambient exposure with less than a 4% increase in surface impurities.

Charge-State-Enhanced Ion Sputtering of Metallic Gold Nanoislands.

Experimental results on the charge-state-dependent sputtering of metallic gold nanoislands are presented. Irradiations with slow highly charged ions of metallic targets were previously considered to show no charge state dependent effects on ion-induced material modification, since these materials possess enough free electrons to dissipate the deposited potential energy before electron-phonon coupling can set in. By reducing the size of the target material down to the nanometer regime and thus enabling a geometric energy confinement, a possibility is demonstrated to erode metallic surfaces by charge state related effects in contrast to regular kinetic sputtering.

Signatures of Multiband Effects in High-Harmonic Generation in Monolayer MoS_{2}.

High-harmonic generation (HHG) in solids has been touted as a way to probe ultrafast dynamics and crystal symmetries in condensed matter systems. Here, we investigate the polarization properties of high-order harmonics generated in monolayer MoS_{2}, as a function of crystal orientation relative to the mid-infrared laser field polarization. At several different laser wavelengths we experimentally observe a prominent angular shift of the parallel-polarized odd harmonics for energies above approximately 3.5 eV, and our calculations indicate that this shift originates in subtle differences in the recombination dipole strengths involving multiple conduction bands. This observation is material specific and is in addition to the angular dependence imposed by the dynamical symmetry properties of the crystal interacting with the laser field, and may pave the way for probing the vectorial character of multiband recombination dipoles.

Ion-Induced Surface Charge Dynamics in Freestanding Monolayers of Graphene and MoS_{2} Probed by the Emission of Electrons.

We compare the ion-induced electron emission from freestanding monolayers of graphene and MoS_{2} to find a sixfold higher number of emitted electrons for graphene even though both materials have similar work functions. An effective single-band Hubbard model explains this finding by a charge-up in MoS_{2} that prevents low energy electrons from escaping the surface within a period of a few femtoseconds after ion impact. We support these results by measuring the electron energy distribution for correlated pairs of electrons and transmitted ions. The majority of emitted primary electrons have an energy below 10 eV and are therefore subject to the dynamic charge-up effects at surfaces.

Optically Triggered Control of the Charge Carrier Density in Chemically Functionalized Graphene Field Effect Transistors.

Field effect transistors (FETs) based on 2D materials are of great interest for applications in ultrathin electronic and sensing devices. Here we demonstrate the possibility to add optical switchability to graphene FETs (GFET) by functionalizing the graphene channel with optically switchable azobenzene molecules. The azobenzene molecules were incorporated to the GFET channel by building a van der Waals heterostructure with a carbon nanomembrane (CNM), which is used as a molecular interposer to attach the azobenzene molecules. Under exposure with 365 nm and 455 nm light, azobenzene molecules transition between cis and trans molecular conformations, respectively, resulting in a switching of the molecular dipole moment. Thus, the effective electric field acting on the GFET channel is tuned by optical stimulation and the carrier density is modulated.

Controlling second-harmonic diffraction by nano-patterning MoS2 monolayers.

Monolayers of transition metal dichalcogenides have a strong second-order nonlinear response enabling second-harmonic generation. Here, we control the spatial radiation properties of the generated second harmonic by patterning MoS2 monolayers using focused ion beam milling. We observe diffraction of the second harmonic into the zero and first diffraction orders via an inscribed one-dimensional grating. Additionally, we included a fork-like singularity into the grating to create a vortex beam in the first diffraction order.

Effect of Perioperative Pregabalin on Postoperative Quality of Recovery in Patients Undergoing Off-Pump Coronary Artery Bypass Grafting (OPCABG): A Prospective, Randomized, Double-Blind Trial.

OBJECTIVES: Use of pregabalin is increasing in cardiac surgical patients. However, studies using comprehensive scoring systems are lacking on the drug's impact on postoperative recovery. The authors tested the hypothesis that perioperative oral pregabalin improves the postoperative quality of recovery as assessed using the Quality of Recovery (QoR-40) questionnaire in patients undergoing off-pump coronary artery bypass grafting (OPCABG). DESIGN: This was a randomized, double-blind, placebo-controlled study. SETTINGS: Tertiary-care hospital. PARTICIPANTS: Patients undergoing OPCABG. INTERVENTIONS: Patients were assigned randomly to the following 2 groups: the pregabalin group (those who received pregabalin, 150 mg capsule orally, 1 hour before surgery and 2 days postoperatively [75 mg twice a day] starting after extubation; n = 37); and the control group (those who received 2 similar-looking multivitamin capsules at similar times; n = 34). The QoR-40 scores were noted preoperatively and 24 hours after extubation. MEASUREMENTS AND MAIN RESULTS: Both groups were comparable in terms of preoperative patient characteristics and baseline QoR-40 scores. Global scores were significantly improved in the pregabalin group compared with the control group in the postoperative period (177±9 v 170±9; p = 0.002). QoR-40 values in the dimensions of emotional state (p = 0.005), physical comfort (p = 0.04), and pain (p = 0.02) were improved in the pregabalin group. CONCLUSIONS: Perioperative pregabalin improved postoperative quality of recovery as assessed using the QoR-40 questionnaire in patients undergoing OPCABG. Perioperative pregabalin offered advantages beyond better pain control, such as improved physical comfort and better emotional state; therefore, the drug's use in the perioperative period is recommended.

Sympatho-vagal balance, as quantified by ANSindex, predicts post spinal hypotension and vasopressor requirement in parturients undergoing lower segmental cesarean section: a single blinded prospective observational study.

Hypotension subsequent to spinal anesthesia occurs in a significant number of parturients undergoing lower segment caesarian section. Currently available methods to predict the incidence of hypotension, its severity and the outcome are sub-optimal. Many workers have used basal heart rate as one of the predictors. But using this method it is not possible to objectively analyze and predict the extent and severity of hypotension. We used an equipment measuring the level of sympatho-vagal balance, ANSiscope™, which derives these values from computed value of RR interval variability. We made a single measure of the value which was blinded to the patient and the anesthesiologist. We studied one hundred eight patients who underwent lower segment caesarian section under spinal anesthesia and found the variability of preoperative ANSindex (% activity displayed by the equipment) from 9 to 65 %. Higher ANSindex value was significantly associated with post spinal hypotension (p 0.017). A value of 24 % indicated the critical level above which hypotension appeared commonly. The ANSindex value might help anesthesiologist to anticipate and prepare for hypotension that is likely to ensue.

Optoelectronic memory using two-dimensional materials.

An atomically thin optoelectronic memory array for image sensing is demonstrated with layered CuIn7Se11 and extended to InSe and MoS2 atomic layers. Photogenerated charge carriers are trapped and subsequently retrieved from the potential well formed by gating a 2D material with Schottky barriers. The atomically thin layered optoelectronic memory can accumulate photon-generated charges during light exposure, and the charges can be read out later for data processing and permanent storage. An array of atomically thin image memory pixels was built to illustrate the potential of fabricating large-scale 2D material-based image sensors for image capture and storage.

An Atomically Layered InSe Avalanche Photodetector.

Atomically thin photodetectors based on 2D materials have attracted great interest due to their potential as highly energy-efficient integrated devices. However, photoinduced carrier generation in these media is relatively poor due to low optical absorption, limiting device performance. Current methods for overcoming this problem, such as reducing contact resistances or back gating, tend to increase dark current and suffer slow response times. Here, we realize the avalanche effect in a 2D material-based photodetector and show that avalanche multiplication can greatly enhance the device response of an ultrathin InSe-based photodetector. This is achieved by exploiting the large Schottky barrier formed between InSe and Al electrodes, enabling the application of a large bias voltage. Plasmonic enhancement of the photosensitivity, achieved by patterning arrays of Al nanodisks onto the InSe layer, further improves device efficiency. With an external quantum efficiency approaching 866%, a dark current in the picoamp range, and a fast response time of 87 µs, this atomic layer device exhibits multiple significant advances in overall performance for this class of devices.

Scalable Transfer of Suspended Two-Dimensional Single Crystals.

Large-scale suspended architectures of various two-dimensional (2D) materials (MoS2, MoSe2, WS2, and graphene) are demonstrated on nanoscale patterned substrates with different physical and chemical surface properties, such as flexible polymer substrates (polydimethylsiloxane), rigid Si substrates, and rigid metal substrates (Au/Ag). This transfer method represents a generic, fast, clean, and scalable technique to suspend 2D atomic layers. The underlying principle behind this approach, which employs a capillary-force-free wet-contact printing method, was studied by characterizing the nanoscale solid-liquid-vapor interface of 2D layers with respect to different substrates. As a proof-of-concept, a photodetector of suspended MoS2 has been demonstrated with significantly improved photosensitivity. This strategy could be extended to several other 2D material systems and open the pathway toward better optoelectronic and nanoelectromechnical systems.

Tailoring the physical properties of molybdenum disulfide monolayers by control of interfacial chemistry.

We demonstrate how substrate interfacial chemistry can be utilized to tailor the physical properties of single-crystalline molybdenum disulfide (MoS2) atomic-layers. Semiconducting, two-dimensional MoS2 possesses unique properties that are promising for future optical and electrical applications for which the ability to tune its physical properties is essential. We use self-assembled monolayers with a variety of end termination chemistries to functionalize substrates and systematically study their influence on the physical properties of MoS2. Using electrical transport measurements, temperature-dependent photoluminescence spectroscopy, and empirical and first-principles calculations, we explore the possible mechanisms involved. Our data shows that combined interface-related effects of charge transfer, built-in molecular polarities, varied densities of defects, and remote interfacial phonons strongly modify the electrical and optical properties of MoS2. These findings can be used to effectively enhance or modulate the conductivity, field-effect mobility, and photoluminescence in MoS2 monolayers, illustrating an approach for local and universal property modulations in two-dimensional atomic-layers.

Cytomorphometric analysis of oral buccal mucosal smears in tobacco and arecanut chewers who abused with and without betel leaf.

BACKGROUND: Tobacco in any form (smoking or chewing), arecanut chewing, and alcohol are considered to be the major extrinsic etiological factors for potentially malignant disorders of the oral cavity and for squamous cell carcinoma, the most common oral malignancy in India. An increase in nuclear diameter (ND) and nucleus-cell ratio (NCR) with a reduction in cell diameter (CD) are early cytological indicators of dysplastic change. The authors sought to identify cytomorphometric changes in ND, CD, and NCR of oral buccal cells in tobacco and arecanut chewers who chewed with or without betel leaf. METHODS: Participants represented 3 groups. Group I consisted of 30 individuals who chewed tobacco and arecanut with betel leaf (BQT chewers). Group II consisted of 30 individuals who chewed tobacco and arecanut without betel leaf (Gutka chewers). Group III comprised 30 apparently healthy nonabusers. Cytological smears were prepared and stained with modified-Papanicolaou stain. RESULTS: Comparisons between Groups I and II and Groups II and III showed that ND was increased, with P values of .054 and .008, respectively, whereas a comparison of Groups I and III showed no statistical significance. Comparisons between Groups I and II and Groups II and III showed that CD was statistically reduced, with P values of .037 and <.000, respectively, whereas comparison of Groups I and III showed no statistical significance. Comparisons between Groups I and II and groups II and III showed that NCR was statistically increased, with P values of <.000, whereas a comparison of Groups I and III showed no statistical significance. CONCLUSIONS: CD, ND, and NCR showed statistically significant changes in Group II in comparison with Group I, which could indicate larger and earlier risk of carcinoma for Gutka chewers than in BQT chewers.

Bowel Obstruction From Biliary Stent Migration: An Unusual Case of Abdominal Pain.

Endoscopic biliary stent placement is an important procedure that is commonly done in patients with malignant obstruction of the biliary tree. However, it can also be done to relieve non-maligant obstructions short term until more curative surgical interventions can be performed. There are two main types of stents used for these procedures: self-expanding metal stents (SEMSs) and plastic stents. Each of these stent types has different indications, and determining the correct stent for each individual patient is important. Here, we present a case of a 73-year-old female who presented with abdominal pain due to small bowel obstruction caused by a dislodged biliary duct stent. We hope to promote more focus on selecting the right stent type for each patient and encouraging follow-up visits after placement, especially for those with a history of medical noncompliance.

Large area resist-free soft lithographic patterning of graphene.

Large area low-cost patterning is a challenging problem in graphene research. A resist-free, single-step, large area and cost effective soft lithographic patterning strategy is presented for graphene. The technique is applicable on any arbitrary substrate that needs to be covered with a graphene film and provides a viable route to large-area patterning of graphene for device applications.

CRAB score for prediction of colectomy within 2 years following admission for acute severe ulcerative colitis.

Background: The Oxford and Swedish indexes were developed to predict in-hospital colectomy in acute severe ulcerative colitis (ASUC), but not long-term prediction, and all these indexes were based on Western data. Our study aimed to analyze the predictors of colectomy within 3 years of ASUC in an Indian cohort and derive a simple predictive score. Methods: A prospective observational study was conducted in a tertiary health care center in South India over a period of 5 years. All patients admitted with ASUC were followed up for a period of 24 months after the index admission, to look for progression to colectomy. Results: A total of 81 (47 male) patients were included in the derivation cohort. Fifteen (18.5%) patients required colectomy during a follow-up period of 24 months. On regression analysis, C-reactive protein (CRP) and serum albumin were independent predictors of 24-month colectomy. The CRAB (CRP + AlBumin) score was obtained by multiplying coefficient of beta to albumin and CRP (CRAB score = CRP x 0.2 - Albumin x 0.26). The CRAB score demonstrated an AUROC of 0.923 and a score of >0.4 with a sensitivity of 82% and specificity of 92% for the prediction of 2-year colectomy following ASUC. The score was validated in a validation cohort of 31 patients, and at >0.4, the score had a sensitivity of 83% and a specificity of 96% in predicting colectomy. Conclusion: CRAB score is a simple prognostic score that can predict 2-year colectomy in ASUC patients with high sensitivity and specificity.

Tumour Microenvironment as a Potential Immune Therapeutic Target for Tongue Cancer Management.

Immunotherapy is a promising approach in the management of human cancers and has been proven to provide a durable response in many cancers. It is helpful as an adjuvant therapy for cancers and at present is considered as a fourth pillar supporting surgery, chemotherapy and radiotherapy. In the treatment of oral cancer, immunotherapy is approved in late-stage diseases where surgical resection cannot be carried out or fails, leading to recurrences and metastasis. Evidences suggest that when given as a first-line treatment, it can elicit an immune response that shrinks tumours, which could provide long-term benefit for patients. But unlike the traditional approach which follows the uniform protocol for all oral cancer patients, effective immunotherapy requires a more site-specific personalized approach. The aim of this paper is to review the various immune evasive mechanisms adopted by tumour cells and their relevance as potential targets for immunotherapy in oral tongue squamous cell carcinoma.

Nanoscale friction on MoS2/graphene heterostructures.

Stacked hetero-structures of two-dimensional materials allow for a design of interactions with corresponding electronic and mechanical properties. We report structure, work function, and frictional properties of 1 to 4 layers of MoS2 grown by chemical vapor deposition on epitaxial graphene on SiC(0001). Experiments were performed by atomic force microscopy in ultra-high vacuum. Friction is dominated by adhesion which is mediated by a deformation of the layers to adapt the shape of the tip apex. Friction decreases with increasing number of MoS2 layers as the bending rigidity leads to less deformation. The dependence of friction on applied load and bias voltage can be attributed to variations in the atomic potential corrugation of the interface, which is enhanced by both load and applied bias. Minimal friction is obtained when work function differences are compensated.

Interface engineering of charge-transfer excitons in 2D lateral heterostructures.

The existence of bound charge transfer (CT) excitons at the interface of monolayer lateral heterojunctions has been debated in literature, but contrary to the case of interlayer excitons in vertical heterostructure their observation still has to be confirmed. Here, we present a microscopic study investigating signatures of bound CT excitons in photoluminescence spectra at the interface of hBN-encapsulated lateral MoSe2-WSe2 heterostructures. Based on a fully microscopic and material-specific theory, we reveal the many-particle processes behind the formation of CT excitons and how they can be tuned via interface- and dielectric engineering. For junction widths smaller than the Coulomb-induced Bohr radius we predict the appearance of a low-energy CT exciton. The theoretical prediction is compared with experimental low-temperature photoluminescence measurements showing emission in the bound CT excitons energy range. We show that for hBN-encapsulated heterostructures, CT excitons exhibit small binding energies of just a few tens meV and at the same time large dipole moments, making them promising materials for optoelectronic applications (benefiting from an efficient exciton dissociation and fast dipole-driven exciton propagation). Our joint theory-experiment study presents a significant step towards a microscopic understanding of optical properties of technologically promising 2D lateral heterostructures.