Coherent and Dissipative Coupling in a Magnetomechanical System.

Hybrid elastic and spin waves hold promises for energy-efficient and versatile generation and detection of magnetic signals, with potentially long coherence times. Here we report on the combined elastic and magnetic dynamics in a one-dimensional magnetomechanical crystal composed of an array of magnetic nanostripes. Phononic and magnonic modes are impulsively excited by an optical ultrafast trigger and their decay is monitored by time-resolved magneto-optical Kerr effect. Complementary Brillouin light scattering measurements and micromagnetic simulations concur in a unified picture, in which the strength and degree of mixing of coherent and dissipative coupling of the quasiparticles are determined quantitatively.

Injury severity score as a predictor of mortality in patients with abdominal trauma at a tertiary Nigerian hospital.

Background: Abdominal trauma is a major cause of morbidity and mortality in low-and middle-income countries. Typical patients present late and very sick with early recognition key to improving outcome. There is a paucity of trauma data in this environment and trauma scoring systems which have been validated in the developed world are yet to find widespread use here. Aim: This study aimed at evaluating role of injury severity score (ISS) in predicting mortality. Patients and Methods: This is a retrospective observational study of patients with abdominal trauma who presented at the University of Ilorin Teaching Hospital from 2013 to 2019. Records were identified and data were extracted and analyzed using Statistical package for social sciences 23. Results: A total of 87 patients were included in the study. There were 73 males and 14 females. The mean overall ISS in this study was 16.06 ± 7.9. Concerning morbidity, the area under the receiver operating characteristic curve in predicting morbidity was 0.843 (95% confidence interval 0.737-0.928). ISS had a strong sensitivity of 90% and specificity 55% at a cut-off of 14.50. Also, the area under the receiver operating characteristic curve in predicting mortality was 0.746 (95% confidence interval 0.588-0.908) and at a cut-off of 16.50; ISS had a specificity of 80% and sensitivity of 60%. The mean ISS of patients with mortality was 22.60 ± 10.5 while the survivors had a mean ISS of 14.7 ± 6.5 (P <.001). The mean ISS for patients who had morbidity was 22.8 ± 8.1 while those without morbidity had a mean ISS of 13.1 ± 5.7 (P <.05). Conclusion: ISS was a good predictor of morbidity and mortality in abdominal trauma in patients in this study. A prospective study with standardized abdominal imaging would be needed to further validate this scoring tool.

Core outcome set for surgical trials in gastric cancer (GASTROS study): international patient and healthcare professional consensus.

BACKGROUND: Surgery is the primary treatment that can offer potential cure for gastric cancer, but is associated with significant risks. Identifying optimal surgical approaches should be based on comparing outcomes from well designed trials. Currently, trials report different outcomes, making synthesis of evidence difficult. To address this, the aim of this study was to develop a core outcome set (COS)-a standardized group of outcomes important to key international stakeholders-that should be reported by future trials in this field. METHODS: Stage 1 of the study involved identifying potentially important outcomes from previous trials and a series of patient interviews. Stage 2 involved patients and healthcare professionals prioritizing outcomes using a multilanguage international Delphi survey that informed an international consensus meeting at which the COS was finalized. RESULTS: Some 498 outcomes were identified from previously reported trials and patient interviews, and rationalized into 56 items presented in the Delphi survey. A total of 952 patients, surgeons, and nurses enrolled in round 1 of the survey, and 662 (70 per cent) completed round 2. Following the consensus meeting, eight outcomes were included in the COS: disease-free survival, disease-specific survival, surgery-related death, recurrence, completeness of tumour removal, overall quality of life, nutritional effects, and 'serious' adverse events. CONCLUSION: A COS for surgical trials in gastric cancer has been developed with international patients and healthcare professionals. This is a minimum set of outcomes that is recommended to be used in all future trials in this field to improve trial design and synthesis of evidence.

The Indications and Findings at Colonoscopy in a Tertiary Hospital in North-Central Nigeria: A Seven-Year Review.

BACKGROUND: Colonoscopy is an invaluable tool used in the diagnosis of colorectal diseases. It is also useful in the prevention and treatment of some of these diseases. The knowledge of the prevailing colorectal diseases is key to planning for prevention. OBJECTIVES: This study aimed at determining the spectra of indications and findings at colonoscopy in a tertiary health facility. METHODS: This was a hospital-based cross-sectional study of all patients who underwent colonoscopy between March 2013 and February 2020. The patients' biodata, indications and findings at colonoscopy were retrieved from the Endoscopy Register. RESULTS: A total of 385 colonoscopy reports were included in the analysis. The age of the patients ranged from 14 to 95 years with a mean age (standard deviation) of 55.9 (15.4) years. There were 219 (57.0%) males and 166 (43.0%) females. The commonest indication for colonoscopy was haematochezia 150 (38.9%) followed by suspected colorectal malignancy 98 (25.5%), abdominal pain 28 (7.3%), altered bowel habit 21 (5.5%), constipation 20 (5.2%), chronic diarrhoea 19 (4.9%), surveillance/ screening 16 (4.2%), occult bleeding and anal pain 7 (1.8%) each, and others 19 (4.9%). The colonoscopy findings were normal findings 116 (30.1%), haemorrhoids 127 (32.9%), colorectal polyps 70 (18.2%), diverticulosis 46 (11.9%), rectal tumour 43 (11.2%), colonic tumour 32 (8.3%), colitis 23 (5.9%), angiodysplasias 6 (1.6), others 12 (3.1%). The findings were not mutually exclusive. Our diagnostic yield was 69.9%. CONCLUSION: The commonest indication and diagnosis for colonoscopy were haematochezia and haemorrhoids respectively. Our diagnostic yield was 69.9%.

CONTEXTE: La coloscopie est un outil précieux utilisé dans le diagnostic des maladies colorectales. Il est également utile dans la prévention et le traitement de certaines de ces maladies. La connaissance des maladies colorectales prédominantes est essentielle à la planification de la prévention. OBJECTIFS: Cette étude visait à déterminer les spectres d'indications et les résultats à la coloscopie dans un établissement de santé tertiaire. MÉTHODES: Il s'agissait d'une étude transversale en milieu hospitalier portant sur tous les patients ayant subi une coloscopie entre mars 2013 et février 2020. Les données biographiques, les indications et les résultats de la coloscopie des patients ont été extraits du registre d'endoscopie. RÉSULTATS: Un total de 385 rapports de coloscopie ont été inclus dans l'analyse. L'âge des patients variait de 14 à 95 ans avec un âge moyen (écart type) de 55,9 (15,4) ans. Il y avait 219 (57,0%) hommes et 166 (43,0 %) femmes. L'indication la plus courante de la coloscopie était l'hématochézie 150 (38,9%) suivie d'une suspicion de malignité colorectale 98 (25,5%), de douleurs abdominales 28 (7,3%), d'altération des habitudes intestinales 21 (5,5%), de constipation 20 (5,2%), de diarrhée chronique 19 (4,9 %), surveillance/dépistage 16 (4,2 %), saignement occulte et douleur anale 7 (1,8 %) chacun, et autres 19 (4,9 %). Les résultats de la coloscopie étaient normaux 116 (30,1%), hémorroïdes 127 (32,9%), polypes colorectaux 70 (18,2%), diverticulose 46 (11,9%), tumeur rectale 43 (11,2%), tumeur colique 32 (8,3%), colite 23 (5,9 %), angiodysplasies 6 (1,6), autres 12 (3,1%). Les résultats n'étaient pas mutuellement exclusifs. Notre rendement diagnostique était de 69,9 %. CONCLUSION: L'indication et le diagnostic les plus courants de la coloscopie étaient respectivement l'hématochézie et les hémorroïdes. Notre rendement diagnostique était de 69,9 %. Mots clés: Maladies colorectales, coloscopie, indications, spectres, rendement diagnostique.

Tunable 2-D magnonic crystals: effect of packing density.

Magnonic crystals, periodic arrays of magnetic structures, have emerged as a promising platform for manipulating and controlling spin waves in magnetic materials. Magnetic antidot nanostructures, representing 2-D magnonic crystals, are versatile platforms for controlling and manipulating magnons. In this work, we systematically investigate the effects of inter-hole spacing and lattice (rhombic and honeycomb) arrangements on the dynamic properties of Ni80Fe20 antidot structures. The dynamic responses of antidot lattices of fixed hole diameter (d = 280 nm) and inter-hole spacing (s) between 90 and 345 nm are investigated using broadband ferromagnetic spectroscopy. Multiple resonance modes sensitive to s are observed due to the inhomogeneous internal field distribution induced by the presence of holes. There is a marked variation in mode frequency, mode intensity and the number of modes for rhombic antidot lattice as the inter-hole spacing and applied field direction are varied. Our experimental results are in good agreement with micromagnetic simulations. Our findings may find application in the design of magnonic-based devices.

Magnonic crystal as a medium with tunable disorder on a periodical lattice.

We show that periodic magnetic nanostructures represent a perfect system for studying excitations on disordered periodical lattices because of the possibility of controlled variation of the degree of disorder by varying the applied magnetic field. Magnetic force microscopy images and ferromagnetic resonance (FMR) data collected inside minor hysteresis loops for a periodic array of Permalloy nanowires were used to demonstrate correlation between the type of FMR response and the degree of disorder of the magnetic ground state.

Band diagram of spin waves in a two-dimensional magnonic crystal.

The dispersion curves of collective spin-wave excitations in a magnonic crystal consisting of a square array of interacting saturated nanodisks have been measured by Brillouin light scattering along the four principal directions of the first Brillouin zone. The experimental data are successfully compared to calculations of the band diagram and of the Brillouin light scattering cross section, performed through the dynamical matrix method extended to include the dipolar interaction between the disks. We found that the fourfold symmetry of the geometrical lattice is reduced by the application of the external field and therefore equivalent directions of the first Brillouin zone are characterized by different dispersion relations of collective spin waves. The dispersion relations are explained through the introduction of a bidimensional effective wave vector that characterizes each mode in this magnonic metamaterial.

Magnetic field dependence of the lowest-frequency edge-localized spin wave mode in a magnetic nanotriangle.

An understanding of the spin dynamics of nanoscale magnetic elements is important for their applications in magnetic sensing and storage. Inhomogeneity of the demagnetizing field in a non-ellipsoidal magnetic element results in localization of spin waves near the edge of the element. However, relative little work has been carried out to investigate the effect of the applied magnetic fields on the nature of such localized modes. In this study, micromagnetic simulations are performed on an equilateral triangular nanomagnet to investigate the magnetic field dependence of the mode profiles of the lowest-frequency spin wave. Our findings reveal that the lowest-frequency mode is localized at the base edge of the equilateral triangle. The characteristics of its mode profile change with the ground state magnetization configuration of the nanotriangle, which, in turn, depends on the magnitude of the in-plane applied magnetic field.

Nanostructured magnonic crystal with magnetic-field tunable bandgap.

Most experimental investigations into magnonic bandgaps are based on structures composed of single-constituent magnetic materials. Here we report Brillouin and numerical studies of the spin dynamics of a bi-component magnonic crystal, viz. a one-dimensional periodic array of alternating permalloy and cobalt 150 nm-wide nanostripes. Our measurements, together with those for a similar crystal composed of 250 nm-wide nanostripes, suggest that for a stripe width ratio of 1:1, the bandgap width of such magnonic arrays increases with crystal lattice constant. The bandgap parameters are strongly dependent on external magnetic field. This magnetic-field tunability of the bandgap is expected to be a crucial property of devices based on magnonic crystals. The agreement between numerical calculations, based on finite element analysis, and the experimental data is generally good.

Assessment of some renal indices in people occupationally exposed to lead.

Exposure to lead has been reported to have adverse health implications. An assessment of renal function in people occupationally exposed to lead was carried out using the following biochemical markers urea, creatinine, sodium, potassium, chloride and bicarbonate. A total of 53 test subjects (mean age 30.9 ± 7.7) were randomly selected among some workers occupationally exposed to lead in Osogbo city and 42 apparently healthy subjects (mean age 30.1 ± 1.2) were used as controls. The plasma urea, creatinine, chloride and bicarbonate concentration were determined using modified Berthelot method, Jaffe's reaction, Schales and Schales method and back titration methods, respectively. The plasma sodium and potassium concentrations were determined using flame emission spectrophotometry while blood lead level was also determined using atomic absorption spectrophotometry. The result showed significant increases in mean plasma concentration of creatinine (84.9 ± 13.6-97.4 ± 28.7 µmol/L), sodium (131.9 ± 3.9-134.8 ± 3.7 mmol/L) and chloride (98.2 ± 4.0-100.4 ± 3.9 mmol/L) in test subjects when compared with controls (p < 0.05). Furthermore, significant increases (p < 0.01) were observed in mean plasma concentration of urea (4.7 ± 1.2-5.7 ± 1.3 mmol/L) and blood lead levels (18.5 ± 3.5-69.7 ± 13.2 mg/L) in test subjects in comparison with controls. In contrast, there were no significant differences observed when mean plasma potassium and bicarbonate levels in test subjects were compared with controls (p > 0.05). These results indicate that occupational exposure to lead may compromise renal function.

The 2021 Magnonics Roadmap.

Magnonics is a budding research field in nanomagnetism and nanoscience that addresses the use of spin waves (magnons) to transmit, store, and process information. The rapid advancements of this field during last one decade in terms of upsurge in research papers, review articles, citations, proposals of devices as well as introduction of new sub-topics prompted us to present the first roadmap on magnonics. This is a collection of 22 sections written by leading experts in this field who review and discuss the current status besides presenting their vision of future perspectives. Today, the principal challenges in applied magnonics are the excitation of sub-100 nm wavelength magnons, their manipulation on the nanoscale and the creation of sub-micrometre devices using low-Gilbert damping magnetic materials and its interconnections to standard electronics. To this end, magnonics offers lower energy consumption, easier integrability and compatibility with CMOS structure, reprogrammability, shorter wavelength, smaller device features, anisotropic properties, negative group velocity, non-reciprocity and efficient tunability by various external stimuli to name a few. Hence, despite being a young research field, magnonics has come a long way since its early inception. This roadmap asserts a milestone for future emerging research directions in magnonics, and hopefully, it will inspire a series of exciting new articles on the same topic in the coming years.

Spin re-orientation in magnetostatically coupled Ni(80)Fe(20) ellipsoidal nanomagnets.

We investigate the influence of magnetostatic coupling on the spin configurations and magnetization reversal mechanism in a one-dimensional linear chain of densely packed Ni(80)Fe(20) ellipsoidal nanomagnets arranged in two basic configurations (elements coupled along the major or minor axes). Using magnetic force microscopy (MFM) we observed that for geometrically identical ellipsoidal nanomagnets the magnetic states at remanence are strongly dependent on the arrangement of the ellipsoid due to competition between the inherent shape and configuration anisotropies. When the elements are coupled along the major axis, the individual elements adopt a single domain magnetic state at remanence for field applied along the linear chain. This is in contrast with a wide range of magnetic states (single vortex states, double vortex states and modified single domain states) observed for elements coupled along the minor axis and also isolated elements. We have conducted a detailed investigation on the magnetization reversal mechanisms for both configurations and have correlated our experimental results with micromagnetic simulations.

Linear chains of nanomagnets: engineering the effective magnetic anisotropy.

This paper investigates the control of effective magnetic anisotropy in Permalloy linear chain arrays, achieved by tuning the symmetry arrangement of the ellipsoidal nanomagnets and the film thickness. When the ellipsoidal nanomagnets are coupled along their easy axis, stronger effective magnetic anisotropy is achieved compared to when the nanomagnets are coupled along their hard axis. A clear transition from a single domain state to a combination of complex flux closure states such as a vortex or double vortices is observed at different applied field angles when the film thickness is varied in the range from 20 nm to 100 nm. Tunable microwave absorption spectra, obtained by ferromagnetic resonance spectroscopy, established the complex interplay between the shape anisotropy and magnetostatic interactions, which becomes more intriguing at different film thicknesses and applied field angles. The micromagnetic simulations are in good agreement with the experimental results. Our results demonstrate possible ways of manipulating the effective magnetic anisotropy in arrays of nanomagnets for magnonic and microwave applications.

Safety and tolerability of injectable Rilpivirine LA in HPTN 076: A phase 2 HIV pre-exposure prophylaxis study in women.

BACKGROUND: Daily oral TDF/FTC is protective against HIV infection when used for pre-exposure prophylaxis (PrEP). However, daily adherence to oral PrEP is difficult for many; therefore, finding alternative PrEP strategies remains a priority. HPTN 076 evaluated the long-acting injectable form of rilpivirine (RPV), known as RPV LA for safety, pharmacokinetics and acceptability. METHODS: HPTN 076 (NTC 02165202) was a phase 2, double-blind, 2:1 randomized trial comparing the safety of 1200mg RPV LA (LA) to placebo (P). The study included a 28-day oral run-in phase of daily, self- administered oral RPV (25 mg), with directly observed oral dosing about six times. Of 136 enrolled sexually active, HIV-uninfected, low HIV-risk African (100) and US (36) adult women, injectable product was administered in two gluteal, intramuscular (IM) injections once every eight weeks to 122 participants following the oral run-in phase. A maximum of six injection time points occurred over a 48-week period. Acceptability, safety, tolerability and pharmacokinetic (PK) data were collected throughout the study. This paper includes primary endpoint data collected up to the week 52 post enrollment. FINDINGS: The median age of the enrolled population was 31 years (IQR: 25,38), median weight 75 kg (IQR: 64, 89), median body mass index (BMI) 30 (IQR: 27, 35), 46% married, 94% Black and 60% unemployed. A total of 122 (80 LA, 42 P) women received at least one injection and 98 (64 LA, 34 P) received all six injections. During the injection phase, three women withdrew from the study (2 LA, 1 P) and 16 women discontinued study product (10 LA, 6 P). Fourteen women (11 LA and 3 P) discontinued oral study product and did not enter the injection phase. Study product discontinuations were not significantly different between the two arms throughout. Of the product discontinuations in the injection phase, 8% in LA and 5% in P arm were due to adverse events (AEs), including one randomized to the P arm with prolonged QTc interval on EKG. The proportion of women who experienced Grade 2 or higher AEs during the injection phase as the primary outcome was not significantly different between the two arms [73.8%, 95% CI: (63.2%, 82.1%) for LA and 73.8%, 95% CI: (58.9%, 84.7%), p>0.99]. Transient Grade ≥2 liver abnormalities occurred in 14% of women in the LA arm compared with 12% in P arm. Three LA women (4%) developed Grade 3 injection site reactions compared with none in P arm. In participants who received at least 1 injection, the geometric mean of overall RPV trough concentrations (Ctrough) was 62.2 ng/mL. In participants who received all six injections, the geometric mean of CTrough through the injection phase and after the last injection were 72.8 ng/mL and 100.9 ng/mL, respectively. At week 52 (eight weeks after last injection), the geometric mean of RPV Ctrough was 75.0 ng/mL. At the last injection visit (Week 44), 80 % of women who answered acceptability questions strongly agreed that they would think about using- and 68% that they would definitely use a PrEP injectable in the future. INTERPRETATION: RPV LA IM injections every eight weeks in African and US women were safe and acceptable. Overall, despite more injection site reactions and pain in the participants receiving RPV LA the injections were well tolerated. Data from this study support the further development of injectable PrEP agents.

Controlling the magnetization reversal in exchange-biased Co/CoO elongated nanorings.

We report on the control of magnetization reversal in exchange-biased Co/CoO nanorings resulting from the competition between field-cooling-induced unidirectional anisotropy at the Co/CoO interface and shape anisotropy of the elongated Co nanorings. We observed that the magnetization reversal mechanisms and magnitudes of exchange bias fields are strongly dependent on the strength and orientation of the cooling field relative to the major axis of the nanorings. Our results demonstrate a convenient technique to control the magnetization reversal modes in ferromagnetic nanorings.

Interplay between intra- and inter-nanowires dynamic dipolar interactions in the spin wave band structure of Py/Cu/Py nanowires.

We have studied both experimentally and theoretically the reprogrammable spin wave band structure in Permalloy(10 nm)/Cu(5 nm)/Permalloy(30 nm) nanowire arrays of width w = 280 nm and inter-wire separation in the range from 80 to 280 nm. We found that, depending on the inter-wire separation, the anti-parallel configuration, where the magnetizations of the two Permalloy layers point in opposite directions, is stabilized over specific magnetic field ranges thus enabling us to directly compare the band structure with that of the parallel alignment. We show that collective spin waves of the Bloch type propagate through the arrays with different magnonic bandwidths as a consequence of the interplay between the intra- and inter-nanowire dynamic dipolar interactions. A detailed understanding, e.g. whether they have a stationary or propagating character, is achieved by considering the phase relation (in-phase or out-of-phase) between the dynamic magnetizations in the two ferromagnetic layers and their average value. This work opens the path to magnetic field-controlled reconfigurable layered magnonic crystals that can be used for future nanoscale magnon spintronic devices.

Assessment of normal forearm compartment pressures in a Nigerian population.

PURPOSE: The forearm is prone to raised compartment pressure and it is the second most common site for compartment syndrome. The normal compartment pressure of the forearm should be known and serve as a benchmark for the diagnosis of acute and chronic compartment syndrome. This study was aimed to determine the normal compartment pressures of the forearm using a digital compartment pressure monitor. METHODS: This was a prospective hospital-based study of the uninjured forearm in 30 patients, who presented with closed unilateral forearm fracture at the accident and emergency department of a tertiary health care facility, between June 2012 and December 2013. Approval was sought and obtained from institutions ethical committee. An 18 gauge bevelled-tip needle, attached to a Compass TM digital compartment pressure monitor made by Mirador USA, was used to measure the pressures in the compartments of the forearm. Data obtained were analysed using the Stata 12. Significance was determined at p < 0.05. RESULTS: The mean age was 38.3 ± 18.3 years with male-to-female ratio of 2.3:1. The pressures in the volar compartment of the forearm ranged from 1 to 8 mmHg with a mean ± SD compartment pressure of 4.7 ± 1.5 mmHg. In the dorsal compartment the pressure ranged from 2 to 8 mmHg with a mean ± SD of 4.9 ± 1.7 mmHg SD, while the lateral compartment measurement ranged between 1 and 5 mmHg with a mean ± SD of 3.6 ± 1.1 mmHg. There was significant positive correlation (p < 0.01) between the compartment pressures in the volar, dorsal, and lateral compartments. CONCLUSION: The normal compartment pressure for forearm is 4.4 ± 1.6 mmHg and ranged from 1 to 8 mmHg from this study in our environment. This will serve as reference value when forearm compartment pressure is being measured.

Origin of relationship between ferromagnetic response and damage in stretched systems.

This article presents a study whose purpose is to elucidate the damage effects in thin films on their magnetic response. Co40Fe40B20 and Ni80Fe20 films of different nanometric thicknesses were stretched by more than 10% and in situ probed by atomic force microscopy measurements to determine their irreversible mechanical behavior (multi-cracking, buckling). Once these phenomena have been well identified, magnetic behavior of these stretched systems has been studied by ferromagnetic resonance to measure resulting magnetic anisotropy and damping evolutions. All of these experimental studies show that the magnetic properties are mainly affected by the stresses generated during the damage but not by the local discontinuities induced by the numerous cracks and buckles. This is in particular confirmed by the almost zero sensitivity to the damage of the magnetic properties of Ni80Fe20 alloy which is known for its vanishing magnetostriction.

Field evolution of the magnetic normal modes in elongated permalloy nanometric rings.

The eigenmode spectrum of elongated permalloy rings with relatively wide arms is investigated by combined Brillouin light scattering and ferromagnetic resonance measurements as a function of the applied field intensity, encompassing both vortex and onion ground states. To reproduce the frequencies and the spatial profiles of the measured modes we performed micromagnetic simulations which solve the discretized Landau-Lifshitz-Gilbert equation in the time domain and calculate locally the Fourier transform. This allowed us to correlate the field dependence of different modes to their localization inside different portions of the rings. With the rings in the vortex ground state, in addition to radial, fundamental, and azimuthal modes, a localized mode, existing in the element portions where the internal field assumes its minima, has been measured and identified. This latter mode, whose frequency decreases for increasing field intensity, becomes soft near the transition from vortex to onion state and determines the change in symmetry of the magnetic ground state. After the transition, it is replaced by two edge modes, localized on the internal and external boundary of the rings, respectively.

Robust electric-field tunable opto-electrical behavior in Pt-NiO-Pt planar structures.

Capacitor-like metal-NiO-metal structures have attracted large interest in non-volatile memory applications based on electric field control of resistance, known as resistive switching (RS). Formation of conducting nanofilaments by the application of an electric field (electroformation) is considered an important pre-requisite for RS. Besides RS, due to the wide band gap and p-type semiconducting nature, NiO has been used to fabricate heterojunctions for photodetector applications. However, very little is known about the electrical and opto-electrical properties of NiO films in planar structure. Here, we demonstrate intriguing photoresponse and electrical behavior in electroformed Pt-NiO-Pt planar structures. While the pristine devices show ohmic electrical behavior and negligible photoresponse, the electroformed devices exhibit a nonlinear rectification behavior and a remarkable photoresponse at low voltage biases. More interestingly, the devices show a dramatic change of sign of rectification under light illumination at higher voltage biases. A polarity dependent and robust gain phenomenon is demonstrated in these devices. The large sensitivity, fast response, simple design and ease of preparation of these planar structures make them attractive for integration with current circuit technologies and various novel opto-electrical applications.