Frequency Modulation of Spin-Transfer Oscillators

Spin-polarized dc electric current flowing into a magnetic layer can induce precession of the magnetization at a frequency that depends on current. We show that addition of an ac current to this dc bias current results in a frequency modulated (FM) spectral output, generating sidebands spaced at the modulation frequency. The sideband amplitudes and shift of the center frequency with drive amplitude are in good agreement with a nonlinear FM model that takes into account the nonlinear frequency-current relation generally induced by spin transfer. Single-domain simulations show that ac current modulates the cone angle of the magnetization precession, in turn modulating the frequency via the demagnetizing field. These results are promising for communications and signal processing applications of spin-transfer oscillators.Comment: 13 pages, 3 Figure

Apport de la Tomographie en Cohérence Optique (OCT) dans le Glaucome Primitif à Angle Ouvert (GPAO) au Niger

Le But de cet travail est de définir les particularités cliniques et épidémiologiques du GPAO et de rapporter la contribution de la tomographie en cohérence optique (OCT)  dans le diagnostic du glaucome au Niger. Patients et méthodes : Il s’agit d’une étude prospective réalisée au sein du service d’ophtalmologie du CHU Lamordé et la clinique Lumière à Niamey, sur une période de sept (7) mois de Janvier à Juillet 2019, portant sur tous les malades suspects ou présentant un GPAO admis en consultation durant la période ayant bénéficiés d’un OCT et champ visuel. Résultats : Il s’agit de 90 patients, dont l’âge moyen est de 50,44 ±15,81ans avec des extrêmes de 9 et 83 ans avec une prédominance masculine. Les principaux facteurs de risque sont : la myopie (83.33% ), les antécédents familiaux de glaucome (33.33% ) et l’HTA (31.11%.) et La plupart des patients (68,88% ) ont une PIO entre 10-20mmHg ; 75,55% des patients ont une épaisseur cornéenne fine <520µm. Le CV et l’OCT sont pathologiques dans respectivement 88,89% et 91,49% à OD et à OG  dans le GPAO. L’OCT est plus sensible à la détection des lésions rétiniennes dans le glaucome par rapport au CV( p = 0,002-0,04). es couches rétiniennes étaient plus amincies chez les glaucomateux au stade sévère de la maladie. Conclusion : la place de l’OCT est incontestable dans le diagnostic du glaucome  pré-périmétrique, néanmoins un champ visuel est toujours important dans le suivi des glaucomateux.   The aim of this work is to define the clinical and epidemiological features of POAG and to report the contribution of optical coherence tomography (OCT) in the diagnosis of glaucoma in Niger. Patients and methods: This is a prospective study carried out in the ophthalmology department of CHU Lamordé and the Lumière clinic in Niamey, over a period of seven (7) months from January to July 2019, covering all patients suspected of or presenting with POAG admitted for consultation during the period having benefited from an OCT and visual field. Results: These are 90 patients, whose mean age is 50.44 ± 15.81 years with extremes of 9 and 83 years with male predominance. The main risk factors are: myopia (83.33%), family history of glaucoma (33.33%) and hypertension (31.11%). And Most patients (68.88%) have an IOP between 10-20mmHg; 75.55% of patients have a thin corneal thickness <520µm. CV and OCT are respectively 88.89% and 91.49% pathological at OD and OG in POAG. OCT is more sensitive at detecting retinal damage in glaucoma compared to CV; this relationship is statically proven (p = 0.002-0.04). The retinal layers were more thinned in the glaucomatous patients with the severe stage of the disease. Conclusion: the place of OCT is indisputable in the diagnosis of pre-perimetric glaucoma, nevertheless a visual field is always important in the follow-up of glaucomatous patients

Apport de la Tomographie en Cohérence Optique (OCT) dans le Glaucome Primitif à Angle Ouvert (GPAO) au Niger

Le But de cet travail est de définir les particularités cliniques et épidémiologiques du GPAO et de rapporter la contribution de la tomographie en cohérence optique (OCT)  dans le diagnostic du glaucome au Niger. Patients et méthodes : Il s’agit d’une étude prospective réalisée au sein du service d’ophtalmologie du CHU Lamordé et la clinique Lumière à Niamey, sur une période de sept (7) mois de Janvier à Juillet 2019, portant sur tous les malades suspects ou présentant un GPAO admis en consultation durant la période ayant bénéficiés d’un OCT et champ visuel. Résultats : Il s’agit de 90 patients, dont l’âge moyen est de 50,44 ±15,81ans avec des extrêmes de 9 et 83 ans avec une prédominance masculine. Les principaux facteurs de risque sont : la myopie (83.33% ), les antécédents familiaux de glaucome (33.33% ) et l’HTA (31.11%.) et La plupart des patients (68,88% ) ont une PIO entre 10-20mmHg ; 75,55% des patients ont une épaisseur cornéenne fine <520µm. Le CV et l’OCT sont pathologiques dans respectivement 88,89% et 91,49% à OD et à OG  dans le GPAO. L’OCT est plus sensible à la détection des lésions rétiniennes dans le glaucome par rapport au CV( p = 0,002-0,04). es couches rétiniennes étaient plus amincies chez les glaucomateux au stade sévère de la maladie. Conclusion : la place de l’OCT est incontestable dans le diagnostic du glaucome  pré-périmétrique, néanmoins un champ visuel est toujours important dans le suivi des glaucomateux.   The aim of this work is to define the clinical and epidemiological features of POAG and to report the contribution of optical coherence tomography (OCT) in the diagnosis of glaucoma in Niger. Patients and methods: This is a prospective study carried out in the ophthalmology department of CHU Lamordé and the Lumière clinic in Niamey, over a period of seven (7) months from January to July 2019, covering all patients suspected of or presenting with POAG admitted for consultation during the period having benefited from an OCT and visual field. Results: These are 90 patients, whose mean age is 50.44 ± 15.81 years with extremes of 9 and 83 years with male predominance. The main risk factors are: myopia (83.33%), family history of glaucoma (33.33%) and hypertension (31.11%). And Most patients (68.88%) have an IOP between 10-20mmHg; 75.55% of patients have a thin corneal thickness <520µm. CV and OCT are respectively 88.89% and 91.49% pathological at OD and OG in POAG. OCT is more sensitive at detecting retinal damage in glaucoma compared to CV; this relationship is statically proven (p = 0.002-0.04). The retinal layers were more thinned in the glaucomatous patients with the severe stage of the disease. Conclusion: the place of OCT is indisputable in the diagnosis of pre-perimetric glaucoma, nevertheless a visual field is always important in the follow-up of glaucomatous patients

Lavandula angustifolia Extract Improves the Result of Human Umbilical Mesenchymal Wharton's Jelly Stem Cell Transplantation after Contusive Spinal Cord Injury in Wistar Rats

Introduction. The primary trauma of spinal cord injury (SCI) results in severe damage to nervous functions. At the cellular level, SCI causes astrogliosis. Human umbilical mesenchymal stem cells (HUMSCs), isolated from Wharton's jelly of the umbilical cord, can be easily obtained. Previously, we showed that the neuroprotective effects of Lavandula angustifolia can lead to improvement in a contusive SCI model in rats. Objective. The aim of this study was to investigate the effect of L. angustifolia (Lav) on HUMSC transplantation after acute SCI. Materials and Methods. Sixty adult female rats were randomly divided into eight groups. Every week after SCI onset, all animals were evaluated for behavior outcomes. H&E staining was performed to examine the lesions after injury. GFAP expression was assessed for astrogliosis. Somatosensory evoked potential (SEP) testing was performed to detect the recovery of neural conduction. Results. Behavioral tests showed that the HUMSC group improved in comparison with the SCI group, but HUMSC + Lav 400 was very effective, resulting in a significant increase in locomotion activity. Sensory tests and histomorphological and immunohistochemistry analyses verified the potentiation effects of Lav extract on HUMSC treatment. Conclusion. Transplantation of HUMSCs is beneficial for SCI in rats, and Lav extract can potentiate the functional and cellular recovery with HUMSC treatment in rats after SCI. Copyright © 2016 Kayvan Yaghoobi et al

Analysis of Cowpea (Vigna unguiculata) Marketing and Price Trends in Selected Markets of Argungu Local Government Area, Kebbi State, Nigeria

The study analyzed cowpea marketing and price trends in selected rural and urban markets of Argungu Local Government Area, Kebbi State, Nigeria. A single-stage sampling technique was used for sample selection. The samples were collected from purposively selected Kara markets in Argungu (reference market), Felande, Gulma, Lailaba and Sauwa (supplying markets) from the selected Districts. Primary data were obtained from a sample of 100 marketers with the aid of the structured questionnaire. Descriptive statistics and spatial price model were employed in analyzing the data. Results of the analysis shows an average age of marketers to be 34 years, 69% were married and 62% have formal education with an average household size of 8 persons. However, 73% were discovered not join any cooperative association while 79% of them do not have access to credit to finance their business. Analysis of spatial aspects of pricing efficiency showed that the positive price spread is slightly high, even after considering plausible levels of unmeasured transaction costs. The trend in price revealed higher price per bag during the off-season (N27, 000/bag) in July and August and low (N15, 000) during harvest (October,November, December and January). Temporal aspects showed considerable risk was involved in storage operations to achieve high profits. The marketing channels identified in the study area were; Farmers, Village merchants, Wholesalers, Retailers, Processors and finally the Consumers. The constraints identified in the study area were lack of access to credit (25.69%), inadequate market information (24.59%), inadequate market infrastructure (22.65%), provision of quality product (16.02%) and poor storage facilities (11.05%). It is recommended that sellers should form cooperatives that can support them in provision of physical facilities and better dissemination of market intelligence and facts. Accordingly, to alleviate the problem of access to credit in the study area, awareness campaign and provision of such credit facilities at affordable level by the relevant stakeholders (State and Local Government authorities) could be an excellent  performance in enhancing the marketing activities in the study area

Current-Driven Microwave Dynamics in Magnetic Point Contacts as a Function of Applied Field Angle

We have measured microwave frequency, current-driven magnetization dynamics in point contacts made to Co90Fe10/Cu/ Ni80Fe20 spin valves as a function of applied field strength and angle relative to the film plane. As the field direction is varied from parallel to nearly perpendicular, the device power output increases by roughly two orders of magnitude while the frequencies of the excitations decrease. For intermediate angles the excited frequency does not monotonically vary with applied current and also exhibits abrupt, current-dependent jumps. For certain ranges of current, and applied field strength and direction, the excitation linewidths decrease to a few megahertz, leading to quality factors over 18,000

Socio-economic Factors Influencing Extension Workers’ Effective use of Knowledge Management in Agricultural Extension Services

The study assessed the factors influencing extension workers effective use of Knowledge Management (KM) inSokoto State, Nigeria. Purposive sampling procedure was used to sample respondents from the study area andExtension Workers were selected from Sokoto Agricultural Development Project (SADP). Socio-economiccharacteristics were using structured questionnaire and a total of 188 respondents were sampled and data collectedanalysed using descriptive statistics and logit model as tools of analysis. The result of the study showed that 74.4% ofthe extension workers were male and majority (79.8%) were married. More so, 35% of the extension workers arewithin the age range of 31 – 40 years with household average size of 5-10 children. Majority (79%) of the extensionworkers had tertiary education. (35%) had experience ranging from 21-25 years on extension service delivery. About41% of respondents used motor cycle as a mean of transportation. Result of logit model shows that marital status,level of education, service experience, cosmopolitness and means of transportation had positive and significantrelationship with effectiveness of KM whereas household size and rank of extension workers had significant andnegative relationship with KM. It is therefore recommended that KM be encouraged and disseminated through topmanagement approach in SADP. This will avail quality and better extension service delivery by extension agencybecause the vast knowledge and experience garnered on effective extension service delivery by top managementofficer will be shared and passed on to junior officers. This will go in line with strengthening and improving thecapacity building of extension workers

Factors associated with airway colonisation and invasion due to Klebsiella spp.

The clinical significance of a heavy growth of Klebsiella spp. in sputum was studied in 54 patients. All but 3 patients had significant factors potentially associated with respiratory tract colonisation or invasion. Risk factors identified for colonisation of the airway and for invasive disease were similar. Patients with commnunity-acquired Klebsiella infections were more likely to have underlying chronic respiratory diseases. Prior antibiotic use was a risk factor for nosocomial infections which occurred more conunonly with antibiotic-resistant organisms.The most commmon diagnoses were airway colonisation, acute community-acquired chest infections, and nosocomial chest infections. Primary acute conununity-acquired pneumonia was unconunon.The sensitivity and specificity of the sputum Gram stain (in the setting of positive sputum cultures) in suggesting the presence of invasive disease due to Klebsiella spp. were 42% and 69% respectively

Spin-transfer torque induced reversal in magnetic domains

Using the complex stereographic variable representation for the macrospin, from a study of the nonlinear dynamics underlying the generalized Landau-Lifshitz(LL) equation with Gilbert damping, we show that the spin-transfer torque is effectively equivalent to an applied magnetic field. We study the macrospin switching on a Stoner particle due to spin-transfer torque on application of a spin polarized current. We find that the switching due to spin-transfer torque is a more effective alternative to switching by an applied external field in the presence of damping. We demonstrate numerically that a spin-polarized current in the form of a short pulse can be effectively employed to achieve the desired macro-spin switching.Comment: 16 pages, 6 figure

Spatially resolved ultrafast precessional magnetization reversal

Spatially resolved measurements of quasi-ballistic precessional magnetic switching in a microstructure are presented. Crossing current wires allow detailed study of the precessional switching induced by coincident longitudinal and transverse magnetic field pulses. Though the response is initially spatially uniform, dephasing occurs leading to nonuniformity and transient demagnetization. This nonuniformity comes in spite of a novel method for suppression of end domains in remanence. The results have implications for the reliability of ballistic precessional switching in magnetic devices.Comment: 17 pages (including 4 figures), submitted to Phys. Rev. Let