Towards engineering in memristors for emerging memory and neuromorphic computing: A review

Resistive random-access memory(RRAM),also known as memristors,having a very simple device structure with two terminals,fulfill almost all of the fundamental requirements of volatile memory,nonvolatile memory,and neuromorphic characteristics.Its memory and neuromorphic behaviors are currently being explored in relation to a range of materials,such as biological materials,perovskites,2D materials,and transition metal oxides.In this review,we discuss the different electrical behaviors exhibited by RRAM devices based on these materials by briefly explaining their corresponding switching mechanisms.We then discuss emergent memory technologies using memristors,together with its potential neuromorphic applications,by elucidating the different material engineering techniques used during device fabrication to improve the memory and neuromorphic performance of devices,in areas such as ION/IOFF ratio,endurance,spike time-dependent plasticity(STDP),and paired-pulse facilitation(PPF),among others.The emulation of essential biological synaptic functions realized in various switching materials,including inorganic metal oxides and new organic materials,as well as diverse device structures such as single-layer and multilayer hetero-structured devices,and crossbar arrays,is analyzed in detail.Finally,we discuss current challenges and future prospects for the development of inorganic and new materials-based memristors.

Comparison of Laryngoscopic View and Hemodynamic Changes with Flexitip McCoy and Macintosh Laryngoscope Blade in Predicted Easy and Difficult Airway

Objective: To compare the laryngoscopic view and the hemodynamic changes by using flexitip McCoy laryngoscope with Macintosh laryngoscope. Method: Study design-Prospective randomized controlled study. A total of 220 patients were included in the study. Patients were allocated on the basis of their airway anatomy in to two groups, one is predicted easy group and the other one was predicted difficult airway group. Among each group, half of the patient intubation was performed with Macintosh blade and the other half was intubated with the help of McCoy blade. The airway prediction was done on the basis of Mallampati grade, thyromental distance, inter incisor gap, jaw protrusion and weight of the patient. Larygoscopic view and hemodynamic changes were recorded. Results: The change in pulse rate was significantly (p = 0.01) higher among the patients of Group B (85.02 ± 10.13) as compared to Group A (79.20 ± 13.11) after induction in predicted easy patients. Similar observation was found for pulse rate after laryngoscopy among both predicted easy and difficult patients. The diastolic blood pressure was significantly (p = 0.0001) higher in Group B (86.34 ± 9.78) than Group A (77.12 ± 11.66) after induction among predicted easy patients. However, diastolic blood pressure was significantly (p = 0.0004) higher in Group A (82.00 ± 10.98) compared with Group B (75.00 ± 9.06) after induction among predicted difficult patients. The average time taken during laryngoscopy was in-significantly (p > 0.05) higher in Group B (13.90 ± 5.95) compared with Group A (12.42 ± 3.58) among predicted easy patients. However, the time taken was significantly (p = 0.0001) higher in Group A (20.83 ± 2.47) than Group B (12.66 ± 3.0) in predicted difficult patients. A majority of the patients of both the groups were in Grade I (Group A = 61.8%, Group B = 81.8%) followed by Grade II (Group A = 38.2%, Group B = 18.2%) among predicted easy patients. Conclusion: It was concluded that the McCoy blade may be an answer to Macintosh blade in difficult airway cases, but not the substitute of Macintosh blade in every case. The McCoy blade improved laryngeal view in patients with limited neck extension.

Management of Airway in a Patient with Traumatic Sub-glottic Stenosis

Tracheal stenosis or tracheal injury is a distressing condition. The silicone tracheal T-tube presents a substitute for stent of this complicated disease. We have come across a case of tracheal perforation in which tracheoplasty was planned. After traceoplasty silicone tracheal T-tube was placed as a stent. We were not able to connect silicone tracheal T-tube with Bain circuit with ET TUBE No. 8.5, 8, 7.5, 7 connector and it was difficult to ventilate the patient now. We have tried other ET TUBE connector and finally we succeeded to connect ET TUBE No. 5.5 connector with Bain circuit and we were able to ventilate the patient.

Epidemiology and Control of Congo Fever in Sacrificial Animals of Pakistan

The cases and deaths due to Crimean-Congo haemorrhagic fever(CCHF)virus commonly known as Congo virus(fatality rate 15%)have been reported throughout Pakistan from the last few years especially during religious occasion,Eid-ul-Azha.The annual increase in death rates due to CCHF demonstrate the importance of awareness of Congo fever at academia as well as public level.The symptoms of Congo fever which appear one to nine days after tick bite,include sudden high fever,muscle aches,abdominal pain,headache,dizziness,sore eyes,jaundice,mood swings,confusion,aggression,and sensitivity to light.The other signs include sore throat,joint pain,vomiting,diarrhea,hemorrhages,and bleeding from skin and large intestine.The Infection has been reported in many species of wild as well as domestic animals including hares,cattle,sheep,goats,dogs,mice and hedgehogs.At least 31 species of Hyalomma,Boophilus,Rhipicephalus,Dermacentor(Ixodidae:hard ticks)act as vector of CCHF in which transovarial,transstadial and venereal transmission occurs.The virus attacks the immune system of the host and influences the immune cells.The Congo fever virus can be isolated from blood,plasma and many body tissues(kidneys,liver,spleen,lungs,brain and bone marrow).Mice inoculation,enzyme-linked immunosorbent assay(ELISA),reverse transcription polymerase chain reaction(RT-PCR)can be used for detection of the infection.Furthermore,IgM and IgG antibodies against CCHFV can also be detected and quantified.Education of general public,tick control with acaricides,use of anti-CCHFV immunoglobulin,usage of approved repellents to prevent tick bites,wearing neutral-coloured garments,application of a permethrin spray to the clothing,avoiding tall grasses and shrubs,applying sunscreen,avoiding direct contact with the blood or tissues of animals are the factors for successful prevention of the infection.

An Insight into Different Strategies for Control and Prophylaxis of Fasciolosis:A Review

Fasciolosis is one of the important diseases of livestock and has zoonotic importance.Fasciolosis can cause huge economic losses due to decrease in milk and meat production,decreased feed conversion ratio,and cost of treatment.Treatment and prophylaxis strategies for Fasciola infection are formed based on epidemiological data.The control of Fasciola infection can be attained by treating the animals with active anthelmintics.The use of different combinations of anthelmintics with a possible rotation is more effective against immature as well as adult flukes.Control of the intermediate host(snail)is vital for the reduction of fasciolosis.Due to the rapid growth of snails,the eradication is quite difficult in waterlogged and marshy areas.The use of different grazing methods and treatment of grazing areas can also help to control fasciolosis.A variety of antigens generated by Fasciola spp.have been shown to protect against liver fluke infection.The crude antigens,excretory/secretory,and refined antigens and their combination can be used as prophylactic treatment for the control of fasciolosis.The use of any of the single or combination of these methods can be very effective for the control of fasciolosis.

Thickness-dependent monochalcogenide GeSe-based CBRAM for memory and artificial electronic synapses

Investigating the promising chalcogenide materials for the development of memory and advanced neuromorphic computing applications is a critical step in realizing electronic memory and synaptic devices that can efficiently emulate biological synaptic functions.However,the assessment of monochalcogenide materials for the fabrication of highly scalable memory and electronic synaptic devices that can accurately mimic synaptic functions remain limited.In the present study,we investigated the thickness-dependent resistive switching(RS)behavior of conductive bridge random access memory(CBRAM)based on a monochalcogenide GeSe switching medium for its possible application in high-performance memory and electronic synapses.GeSe thin films of different thicknesses(6,13,24,35,47,and 56 nm)were deposited via sputtering to fabricate CBRAM devices with a stacking sequence of Ag/GeSe/Pt/Ti/SiO_(2).The devices exhibited compliance current(CC)-free and electroforming-free RS with highly stable endurance and retention characteristics with no major degradation.All devices with a thickness of 6 nm had a low-resistance state(LRS),which required an initial reset to ensure reliable switching cycles.The devices with a thickness of 47 nm and above exhibited the co-existence of unipolar resistive switching(U-RS)and bipolar resistive switching(B-RS)with the CC-controlled transition between the two switching behaviors.Multilevel resistance states in the 24-nm device between a high-resistance state(HRS)and an LRS were achieved by controlling the set-CC(from 5 mA to CC-free)and the reset stop voltage(from–0.5 to–1.0 V)during the set and reset processes,respectively.The analog RS behavior of the device was further investigated with appropriate pulse measurements to emulate vital synaptic functions,including long-term potentiation(LTP),long-term depression(LTD),spike-rate-dependent plasticity(SRDP),spike-timing-dependent plasticity(STDP),paired-pulse facilitation(PPF),paired-pulse depression(PPD)and post-tetanic potentiation(PTP).Overall,the detailed investigation of thickness-dependent GeSe monochalcogenide material indicates that it is a highly suitable candidate for use in highly scalable memory devices and electronic synapses for neuromorphic computing applications.

Optimizing the thickness of Ta_(2)O_(5) interfacial barrier layer to limit the oxidization of Ta ohmic interface and ZrO_(2) switching layer for multilevel data storage

The multilevel storage capability of nonvolatile resistive random access memory(ReRAM)is greatly de-sired to accomplish high functioning memory density.In this study,Ta_(2)O_(5) thin film with different thick-nesses(2,4,and 6 nm)was exploited as an appropriate interfacial barrier layer for limiting the formation of the interfacial layer between the 10 nm thick sputtering deposited resistive switching(RS)layer and Ta ohmic electrode to improve the switching cycle endurance and uniformity.Results show that lower form-ing voltage,narrow distribution of SET-voltages,good dc switching cycles(10^(3)),high pulse endurance(10^(6) cycles),long retention time(10^(4) s at room temperature and 100℃),and reliable multilevel resis-tance states were obtained at an appropriate thickness of∼2 nm Ta_(2)O_(5) interfacial barrier layer instead of without Ta_(2)O_(5) and with∼4 nm,and∼6 nm Ta_(2)O_(5) barrier layer,ZrO_(2)-based memristive devices.Besides,multilevel resistance states have been scientifically investigated via modulating the compliance current(CC)and RESET-stop voltages,which displays that all of the resistance states were distinct and stayed stable without any considerable deprivation over 10^(4) s retention time and 104 pulse endurance cycles.The I-V characteristics of RESET-stop voltage(from−1.7 to−2.3 V)of HRS are found to be a good linear fit with the Schottky equation.It can be seen that Schottky barrier height rises by increasing the stop-voltage during RESET-operation,resulting in enhancing the data storage memory window(on/offratio).Moreover,RESET-voltage and CC control of HRS and LRS revealed the physical origin of the RS mecha-nism,which entails the formation and rupture of conducting nanofilaments.It is thoroughly investigated that proper optimization of the barrier layer at the ohmic interface and the switching layer is essential in memristive devices.These results demonstrate that the ZrO_(2)-based memristive device with an optimized∼2 nm Ta_(2)O_(5) barrier layer is a promising candidate for multilevel data storage memory applications.