9 research outputs found
Ultra-Low Power Neuromorphic Obstacle Detection Using a Two-Dimensional Materials-Based Subthreshold Transistor
Accurate, timely and selective detection of moving obstacles is crucial for
reliable collision avoidance in autonomous robots. The area- and
energy-inefficiency of CMOS-based spiking neurons for obstacle detection can be
addressed through the reconfigurable, tunable and low-power operation
capabilities of emerging two-dimensional (2D) materials-based devices. We
present an ultra-low power spiking neuron built using an electrostatically
tuned dual-gate transistor with an ultra-thin and generic 2D material channel.
The 2D subthreshold transistor (2D-ST) is carefully designed to operate under
low-current subthreshold regime. Carrier transport has been modelled via
over-the-barrier thermionic and Fowler-Nordheim contact barrier tunnelling
currents over a wide range of gate and drain biases. Simulation of a neuron
circuit designed using the 2D-ST with 45 nm CMOS technology components shows
high energy efficiency of ~3.5 pJ/spike and biomimetic class-I as well as
oscillatory spiking. It also demonstrates complex neuronal behaviors such as
spike-frequency adaptation and post-inhibitory rebound that are crucial for
dynamic visual systems. Lobula giant movement detector (LGMD) is a
collision-detecting biological neuron found in locusts. Our neuron circuit can
generate LGMD-like spiking behavior and detect obstacles at an energy cost of
<100 pJ. Further, it can be reconfigured to distinguish between looming and
receding objects with high selectivity.Comment: Main text along with supporting information. 4 figure
Near-direct bandgap / type-II pn heterojunction for enhanced ultrafast photodetection and high-performance photovoltaics
PN heterojunctions comprising layered van der Waals (vdW) semiconductors have
been used to demonstrate current rectifiers, photodetectors, and photovoltaic
devices. However, a direct or near-direct bandgap at the heterointerface that
can significantly enhance optical generation, for high light absorbing
few/multi-layer vdW materials, has not yet been shown. In this work, for the
first time, few-layer group-6 transition metal dichalcogenide (TMD) is
shown to form a sizeable (0.7 eV) near-direct bandgap with type-II band
alignment at its interface with the group-7 TMD through density
functional theory calculations. Further, the type-II alignment and
photogeneration across the interlayer bandgap have been experimentally
confirmed through micro-photoluminescence and IR photodetection measurements,
respectively. High optical absorption in few-layer flakes, large conduction and
valence band offsets for efficient electron-hole separation and stacking of
light facing, direct bandgap on top of gate tunable are shown
to result in excellent and tunable photodetection as well as photovoltaic
performance through flake thickness dependent optoelectronic measurements.
Few-layer flakes demonstrate ultrafast response time (5 s) at high
responsivity (3 A/W) and large photocurrent generation and responsivity
enhancement at the heterostructure overlap region (10-100X) for 532 nm laser
illumination. Large open-circuit voltage of 0.64 V and short-circuit current of
2.6 A enables high output electrical power. Finally, long term
air-stability and a facile single contact metal fabrication process makes the
multi-functional few-layer / heterostructure diode
technologically promising for next-generation optoelectronic applications.Comment: Manuscript- 27 pages, 8 figures. Supporting Information- 17 pages, 17
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Reversible hysteresis inversion in MoS<sub>2</sub> field effect transistors
MoS2 devices: variable temperature measurements unveil reversible hysteresis mechanisms Defects and traps in MoS2 van der Pauw devices give rise to a hysteresis inversion mechanism which is reversible with temperature. A team led by Saurabh Lodha at the Indian Institute of Technology Bombay performed variable temperature hysteresis measurements on four- and two-terminal MoS2 devices, both suspended and supported on a SiO2 substrate. The onset of a clockwise hysteresis at room temperature was attributed to intrinsic MoS2 defects, whereas an additional mechanism resulting in an anticlockwise hysteresis was observed at higher temperature, and attributed to extrinsic charge trapping and de-trapping between the oxide and the silicon gate. By leveraging the temperature dependence of the hysteresis in MoS2, the authors developed a non-volatile memory and a temperature sensor
Electrocardiographic changes in takotsubo cardiomyopathy
?Takotsubo cardiomyopathy (TC) is a unique transient nonischemic cardiomyopathy that mimics acute myocardial infarction (MI). The aim of our study was to evaluate electrocardiographic changes in patients with TC, including the frequency of ST elevation and other abnormalities
Enhanced responsivity and detectivity of fast WSe2 phototransistor using electrostatically tunable in-plane lateral p-n homojunction
In photodetectors based on 2D materials, a trade-off often exists between responsivity and speed. Here, the authors attenuate this issue via integration of a lateral, in-plane, electrostatically tunable p-n homojunction with a conventional WSe2 phototransistor
Cardiovascular adverse events associated with smoking-cessation pharmacotherapies
Smoking continues to be the leading cause of preventable deaths in the USA, accounting for one in every five deaths every year, and cardiovascular (CV) disease remains the leading cause of those deaths. Hence, there is increasing awareness to quit smoking among the public and counseling plays an important role in smoking cessation. There are different pharmacological methods to help quit smoking that includes nicotine replacement products available over the counter, including patch, gum, and lozenges, to prescription medications, such as bupropion and varenicline. There have been reports of both nonserious and serious adverse CV events associated with the use of these different pharmacological methods, especially varenicline, which has been gaining media attention recently. Therefore, we systematically reviewed the various pharmacotherapies used in smoking cessation and analyzed the evidence behind these CV events reported with these therapeutic agents
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Adapting the HCT-CI Definitions for Children, Adolescents, and Young Adults with Hematologic Malignancies Undergoing Allogeneic Hematopoietic Cell Transplantation
Allogeneic hematopoietic cell transplantation is a curative procedure for hematologic malignancies but is associated with a significant risk of non-relapse mortality (NRM). The Hematopoietic Cell Transplantation–Comorbidity Index (HCT-CI) is a prognostic tool that discriminates this risk in all age groups. A recent survey of transplant physicians demonstrated that 79% of pediatric providers used the HCT-CI infrequently, and most reported concerns about its applicability in the younger population. We conducted a retrospective study using the Center for International Blood and Marrow Transplant Research database to examine the impact of expanded HCT-CI definitions on NRM in pediatric and young adult patients with hematologic malignancies. We included 5790 patients <40 years old receiving allogeneic transplants between 2008 and 2017 to examine broader definitions of comorbidities in the HCT-CI, including history of mechanical ventilation and fungal infection, estimated glomerular filtration rate, and body mass index (BMI) percentiles. Multivariable Fine-Gray models were created to determine the effect of each HCT-CI defining comorbidity and its modification on NRM and were used to develop 2 novel risk scores. We next developed the expanded HCT-CI for children and young adults (youth with malignancies; expanded ymHCT-CI), where 23% patients had an increased comorbidity score, compared to the HCT-CI. Comorbidities with hazard ratio < 1.2 were then removed to create the simplified HCT-CI for children and young adults (youth with malignancies; simplified ymHCT-CI), which demonstrated higher scores corresponded to a greater risk of NRM (P < .001). These novel comorbidity indexes with broader definitions are more relevant to pediatric and young adult patients, and prospective studies are needed to validate these in the younger patient population. It remains to be seen whether the development of these pediatric-specific and practical risk indexes increases their use by the pediatric transplant community