Clinical predictors of Covid-19 mortality in a tertiary hospital in Lagos, Nigeria: A retrospective cohort study.

Background: The predictors of mortality among patients presenting with severe to critical disease in Nigeria are presently unknown. Aim: The aim of this study was to identify the predictors of mortality among patients with COVID-19 presenting for admission in a tertiary referral hospital in Lagos, Nigeria. Patients and Methods: The study was a retrospective study. Patients' sociodemographics, clinical characteristics, comorbidities, complications, treatment outcomes, and hospital duration were documented. Pearson's Chi-square, Fischer's Exact test, or Student's t-test were used to assess the relationship between the variables and mortality. To compare the survival experience across medical comorbidities, Kaplan Meir plots and life tables were used. Univariable and multivariable Cox-proportional hazard analyses were conducted. Results: A total of 734 patients were recruited. Participants' age ranged from five months to 92 years, with a mean ± SD of 47.4 ± 17.2 years, and a male preponderance (58.5% vs. 41.5%). The mortality rate was 9.07 per thousand person-days. About 73.9% (n = 51/69) of the deceased had one or more co-morbidities, compared to 41.6% (252/606) of those discharged. Patients who were older than 50 years, with diabetes mellitus, hypertension, chronic renal illness, and cancer had a statistically significant relationship with mortality. Conclusion: These findings call for a more comprehensive approach to the control of non-communicable diseases, the allocation of sufficient resources for ICU care during outbreaks, an improvement in the quality of health care available to Nigerians, and further research into the relationship between obesity and COVID-19 in Nigerians.

Osteoprotegerin changes in saliva and serum of patients with knee osteoarthritis / Cambios de osteoprotegerina en saliva y suero de pacientes con osteoartritis de rodilla

Objective: The scope of this study was to assess salivary and serum osteoprotegerin (OPG) levels in knee osteoarthritis (OA). Methods: Serum and saliva OPG levels of 30 knee OA and 30 matched healthy controls in this cross-sectional study was assessed by ELISA. Knee pain was assessed by WOMAC. Data were analyzed by Student's t-test, Spearman correlation test and ROC. Results: The mean serum but not saliva OPG level was lower in knee OA than that of the healthy group. WOMAC negatively correlated with serum OPG (r = −0.501; P = 0.000). The serum OPG cutoff value was 237.5 pg/ml for the diagnosis of knee OA. Conclusions: As serum OPG was lower in knee OA and negatively correlated with WOMAC, it seems that detection of OPG in serum but not in saliva may be a probable marker to the diagnosis of knee OA. Key messages: Osteoprotegerin decreases in knee osteoarthritis.(AU)

Objetivo: El alcance de este estudio fue evaluar los niveles de osteoprotegerina (OPG) salival y sérica en la osteoartritis de rodilla (OA). Métodos: Los niveles de OPG en suero y saliva de 30 OA y 30 controles sanos emparejados en este estudio transversal se evaluaron mediante ELISA. El dolor de rodilla fue evaluado por The Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC). Los datos se analizaron mediante la prueba t de Student, la prueba de correlación de Spearman y receiver operating characteristic (ROC). Resultados: El nivel medio de OPG en suero, pero no en saliva fue menor en la artrosis de rodilla que en el grupo sano. WOMAC se correlacionó negativamente con la OPG sérica (r = −0,501; p = 0,000). El valor de corte de OPG sérico fue de 237,5 pg/mL para el diagnóstico de OA de rodilla. Conclusiones: Como la OPG sérica fue más baja en la artrosis de rodilla y se correlacionó negativamente con WOMAC, parece que la detección de OPG en suero, pero no en la saliva puede ser un marcador probable para el diagnóstico de artrosis de rodilla. Mensajes clave: La osteoprotegerina disminuye en la osteoartritis de rodilla.(AU)

Cambios de osteoprotegerina en saliva y suero de pacientes con osteoartritis de rodilla / Osteoprotegerin changes in saliva and serum of patients with knee osteoarthritis

Objetivo: El alcance de este estudio fue evaluar los niveles de osteoprotegerina (OPG) salival y sérica en la osteoartritis de rodilla (OA). Métodos: Los niveles de OPG en suero y saliva de 30 OA y 30 controles sanos emparejados en este estudio transversal se evaluaron mediante ELISA. El dolor de rodilla fue evaluado por The Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC). Los datos se analizaron mediante la prueba t de Student, la prueba de correlación de Spearman y receiver operating characteristic (ROC). Resultados: El nivel medio de OPG en suero, pero no en saliva fue menor en la artrosis de rodilla que en el grupo sano. WOMAC se correlacionó negativamente con la OPG sérica (r = −0,501; p = 0,000). El valor de corte de OPG sérico fue de 237,5 pg/mL para el diagnóstico de OA de rodilla. Conclusiones: Como la OPG sérica fue más baja en la artrosis de rodilla y se correlacionó negativamente con WOMAC, parece que la detección de OPG en suero, pero no en la saliva puede ser un marcador probable para el diagnóstico de artrosis de rodilla. Mensajes clave: La osteoprotegerina disminuye en la osteoartritis de rodilla.(AU)

Objective: The scope of this study was to assess salivary and serum osteoprotegerin (OPG) levels in knee osteoarthritis (OA). Methods: Serum and saliva OPG levels of 30 knee OA and 30 matched healthy controls in this cross-sectional study was assessed by ELISA. Knee pain was assessed by WOMAC. Data were analyzed by Student's t-test, Spearman correlation test and ROC. Results: The mean serum but not saliva OPG level was lower in knee OA than that of the healthy group. WOMAC negatively correlated with serum OPG (r = −0.501; P = 0.000). The serum OPG cutoff value was 237.5 pg/ml for the diagnosis of knee OA. Conclusions: As serum OPG was lower in knee OA and negatively correlated with WOMAC, it seems that detection of OPG in serum but not in saliva may be a probable marker to the diagnosis of knee OA. Key messages: Osteoprotegerin decreases in knee osteoarthritis.(AU)

Osteoprotegerin changes in saliva and serum of patients with knee osteoarthritis. / Cambios de osteoprotegerina en saliva y suero de pacientes con osteoartritis de rodilla.

OBJECTIVE: The scope of this study was to assess salivary and serum osteoprotegerin (OPG) levels in knee osteoarthritis (OA). METHODS: Serum and saliva OPG levels of 30 knee OA and 30 matched healthy controls in this cross-sectional study was assessed by ELISA. Knee pain was assessed by WOMAC. Data were analyzed by Student's t-test, Spearman correlation test and ROC. RESULTS: The mean serum but not saliva OPG level was lower in knee OA than that of the healthy group. WOMAC negatively correlated with serum OPG (r = -0.501; P = 0.000). The serum OPG cutoff value was 237.5 pg/ml for the diagnosis of knee OA. CONCLUSIONS: As serum OPG was lower in knee OA and negatively correlated with WOMAC, it seems that detection of OPG in serum but not in saliva may be a probable marker to the diagnosis of knee OA. KEY MESSAGES: Osteoprotegerin decreases in knee osteoarthritis.

Covid 19: A Prospective Observational Study on the Cutaneous Manifestations of Patients in Lagos, Nigeria.

BACKGROUND: Cutaneous manifestations of COVID-19 have been documented from Europe, USA, and China but none from Africa to date. Skin findings among Africans differ from Caucasians and it is important to report these in Nigerians with COVID-19. METHODS: A prospective observational review involving patients seen at the Emergency triage, and Isolation wards of the Lagos University Teaching Hospital. Demographic and clinical data were captured; skin and appendages were examined by a dermatologist between 0800hrs and 1600hours to minimise visual errors of artificial light masking cutaneous lesions. RESULTS: Of 235 participants, 17 (7.23%) had recent onset skin rash, with 7 (41.2%) experienced itching and 11 confirmed with COVID-19. There was a male: female ratio of 97:43 (2.3:1) among COVID-19 patients. Cutaneous findings were seen in 12 (5.1%) participants, with the face and trunk mostly affected and acne plus papular eruptions predominating. There was no significant relationship between COVID-19 and recent onset skin rash (χ2, p = 0.87). Only 2 of the 17 participants had a previously existing dermatoses ((χ2, p = 0.84). There was no significant relation between use of medications and onset of rashes (χ2, p = 0.72) or between those with co-morbidities and onset of rashes (χ2, p = 0.51). CONCLUSION: Cutaneous manifestations were found among Nigerian patients with SARS-CoV-2 infection. Most presented with pruritus and papular eruptions and no morphologic pattern was demonstrated. Physicians and dermatologists need to be aware and look out for skin changes in SARS-CoV-2 infection as they may be early pointers to COVID-19. Keywords: Cutaneous findings, manifestations, Skin, COVID-19, Nigeria.

CONTEXTE: Des manifestations cutanées du COVID-19 ont été documentées en Europe, aux Etats-Unis et en Chine, mais aucune en Afrique à ce jour. Les manifestations cutanées chez les Africains diffèrent de celles des Caucasiens et il est important de les signaler chez les Nigérians atteints de COVID-19. MÉTHODES: Une étude observationnelle prospective impliquant des patients vus au triage des urgences et dans les services d'isolement de l'hôpital universitaire de Lagos. Les données démographiques et cliniques ont été saisies ; la peau et les appendices ont été examinés par un dermatologue entre 8h00 et 16h00 pour minimiser les erreurs visuelles de la lumière artificielle masquant les lésions cutanées. RÉSULTATS: Sur 235 participants, 17 (7,23 %) ont présenté une éruption cutanée d'apparition récente, dont 7 (41,2 %) ont eu des démangeaisons et 11 ont été confirmées par le COVID-19. Il y avait un rapport hommes/femmes de 97:43 (2,3:1) parmi les patients atteints de COVID-19. Des signes cutanés ont été observés chez 12 (5,1 %) participants, le visage et le tronc étant les plus touchés, avec une prédominance de l'acné et des éruptions papuleuses. Il n'y avait pas de relation significative entre le COVID-19 et les éruptions cutanées d'apparition récente (χ2, p = 0,87). Seulement 2 des 17 participants avaient une dermatose déjà existante ((χ2, p = 0,84). Il n'y avait pas de relation significative entre la prise de médicaments et l'apparition d'éruptions cutanées (χ2, p = 0,72) ou entre les personnes présentant des comorbidités et l'apparition d'éruptions cutanées (χ2, p = 0,51). CONCLUSION: Des manifestations cutanées ont été constatées chez les patients nigérians atteints d'une infection par le SRAS-CoV-2. La plupart d'entre eux présentaient un prurit et des éruptions papuleuses et aucun modèle morphologique n'a été mis en évidence. Les médecins et les dermatologues doivent être attentifs et rechercher les modifications cutanées dans l'infection par le SRAS-CoV-2, car elles peuvent être des signes précurseurs du COVID-19. MOTS CLÉS: Résultats cutanés, manifestations, Peau, COVID-19, Nigéria.

Immersion vaccines against Yersinia ruckeri infection in rainbow trout: Comparative effects of strain differences.

The protective effects of autogenous and commercial ERM immersion vaccines (bacterins based on Yersinia ruckeri, serotype O1, biotypes 1 and 2) for rainbow trout (Oncorhynchus mykiss) were compared in order to evaluate whether the use of local pathogen strains for immunization can improve protection. In addition, the effect of the bacterin concentration was established for the commercial product. Following sublethal challenge of vaccinated and non-vaccinated control fish with live bacteria, we followed the bacterial count in the fish (gills, liver and spleen). The expression of genes encoding immune factors (IL-1ß, IL-6, IL-8, IL-10, IFN-γ, MHCI, MHCII, CD4, CD8, TCRß, IgM, IgT, IgD, cathelicidins 1 and 2, SAA and C3) and densities of immune cells in organs were recorded. Both vaccines conferred protection as judged from the reduced bacterial load in exposed fish. Innate immune genes were upregulated in all groups following bacterial challenge but significantly more in non-vaccinated naive fish in which densities of SAA-positive immune cells increased. Immunoglobulin genes were upregulated on day 5 post-challenge, and fish vaccinated with the high commercial bacterin dosage showed increased IgM levels by ELISA on day 14 post-challenge, reflecting that the vaccine dosage was correlated to protection. In conclusion, both vaccine types offered protection to rainbow trout when exposed to live Y. ruckeri and no significant difference between commercial and autogenous vaccines was established.

Thin Split Thickness Skin Grafting on Human Acellular Dermal Matrix Scaffold for the Treatment of Deep Burn Wounds.

BACKGROUND: Use of AlloDerm™ is highly suggested for the treatment of deep burns and burn sequela reconstruction. Scar formation and contracture are recognized as long-term consequences of split-thickness skin autografting, which is applied for full-thickness burn injuries. Mature fibroblasts, in the absence of dermis, seem to secrete collagen in the reformed scar pattern. OBJECTIVE: To process AlloDerm™ from fresh allograft and use it as a dermal substitute for covering deep wounds in burn patients and evaluate its effectiveness. METHODS: In this case-series, 7 patients with deep burn wounds involving different locations on the body surface were exposed to combined AlloDerm™ (processed from fresh human allograft) with thin split thickness skin autograft on it. On the 5th post-operative day, wound dressings were changed to evaluate the graft survival with the human acellular dermal matrix scaffold. To determine the skin profiles, follow-ups continued for at least 6 months. RESULTS: The results showed excellent graft take, good elasticity, acceptable thickness, and little contracture and scarring according to fix surgeon assessment in 6 patients. Graft rejection happened only in one patient with chronic electrical injury. CONCLUSION: AlloDerm™ derived from cadaver skin and combination of it with thin split thickness skin auto grafting constitute a cost-effective and favorable option for the treatment of deep burn wounds in our center, considering the increased tendency of the population towards organ donation in the event of brain death.

Epidemiologic profile of nosocomial infections among paediatric patients in a referral hospital in Hamadan, west of Iran.

Healthcare-associated infections (HC-AI) are major health problem with high financial impact. HC-AIs are one of the main causes of morbidity and mortality in paediatric hospitals. This study was performed to determine the epidemiology of HC-AIs in children admitted to medical wards of Besat Hospital in Hamadan, west of Iran. Data on cases of HC-AIs in paediatrics were collected from March 2017 to February 2018 in Besat Hospital. The medical records of eligible cases were extracted from Iranian Nosocomial Infections Surveillance Software. During the study period, a total of 355 HC-AIs in children were detected, 213 (60%) in boys and 214 (60.3%) in the 0-4-year age group. Of these, bloodstream infection was the most frequent infection in both age groups (37.38% in 0-4 years and 34.75% in 5-14 years). Escherichia coli was the common detected microorganism in girls (25.84% in those aged 0-4 years and 24.53% in 5-14 years), whereas Staphylococcus was more prevalent in boys (33.6% in those aged 0-4 years and 29.55% in 5-14 years). HC-AIs were more prevalent in burn, haematology and intensive care unit wards. In Besat Hospital, bloodstream infection and urinary tract infection were the most frequent infections among paediatric patients, and E. coli and Staphylococcus were the commonest detected microorganism in girls and boys respectively. Preventive activities should be targeted to reduce the rate of HC-AIs in wards associated with more contamination.

Decoding of facial strains via conformable piezoelectric interfaces.

Devices that facilitate nonverbal communication typically require high computational loads or have rigid and bulky form factors that are unsuitable for use on the face or on other curvilinear body surfaces. Here, we report the design and pilot testing of an integrated system for decoding facial strains and for predicting facial kinematics. The system consists of mass-manufacturable, conformable piezoelectric thin films for strain mapping; multiphysics modelling for analysing the nonlinear mechanical interactions between the conformable device and the epidermis; and three-dimensional digital image correlation for reconstructing soft-tissue surfaces under dynamic deformations as well as for informing device design and placement. In healthy individuals and in patients with amyotrophic lateral sclerosis, we show that the piezoelectric thin films, coupled with algorithms for the real-time detection and classification of distinct skin-deformation signatures, enable the reliable decoding of facial movements. The integrated system could be adapted for use in clinical settings as a nonverbal communication technology or for use in the monitoring of neuromuscular conditions.

Enhanced osteogenic differentiation of mesenchymal stem cells on metal-organic framework based on copper, zinc, and imidazole coated poly-l-lactic acid nanofiber scaffolds.

The presence of inorganic bioactive minerals with polymers can accelerate and promote several processes including: bone cell joining, proliferation, differentiation, and expression of osteogenic proteins. In this study, zinc (Zn), copper (Cu), and imidazole metal-organic framework (MOF) nanoparticles were synthesized and coated over poly-l-lactic acid (PLLA) nanofibrous scaffolds for bone tissue engineering application. The surface and bioactive features of the scaffolds were characterized. The osteogenic potential of the scaffolds on human adipose tissue-derived mesenchymal stem cells (MSCs) was evaluated. Zn-Cu imidazole MOF coated PLLA scaffolds (PLLA@MOF) showed a comparable rate of MSC proliferation with the pure PLLA scaffolds and tissue culture plate (TCP). However, the PLLA@MOF potential of osteogenic differentiation was significantly greater than either pristine PLLA scaffolds or TCP. Hence, coating Zn-Cu imidazole MOF has a significant effect on the osteogenesis of MSC. Therefore, PLLA@MOF is novel scaffolds with bioactive components which are crucial for osteoconductivity and also able to provoke the osteogenesis and angiogenesis.

Piezoelectric Tooth Aligner for Accelerated Orthodontic Tooth Movement.

In this paper, we propose a device that can induce vibration to potentially accelerate the rate of orthodontic tooth movement and thus reduce the duration of the orthodontic treatment. This is accomplished by harmonically exciting a polyvinylidene fluoride (PVDF) piezoelectric actuators to generate vibration and hence generate cyclic loading at 30 Hz. PVDF is a popular piezoelectric polymer because of its high flexibility, biocompatibility, and low cost. Generally, application of cyclic loading (vibration) reverses bone loss, stimulates bone mass, induces cranial growth, and accelerates tooth movement. This reduce the pain experience and discomfort associated with the orthodontic treatment and also enhances the patient compliance with the treatment. Vibration has the advantage of minimal side effects in comparison to medicinal treatments. The device is attached to either a positioner or teeth aligner. The main advantage of this work is that the device can be adjusted and repositioned in a different location of the teeth aligner. We propose one device that incorporates vibration, harmonic function generation, and the housing unit for the battery and processor. Current approaches require an external device, which is relatively cumbersome to the patient. Theoretical analysis based on the distributed parameter model is utilized to justify our claim. Piezoelectric actuation behavior is simulated using Finite Element Analysis.

One-way sound propagation via spatio-temporal modulation of magnetorheological fluid.

This manuscript details the possibility of achieving one-way sound propagation using a smart fluid such as magnetorheological fluid (MRF) by subjecting it to a spatio-temporally varying magnetic field. The local speed of sound in MRF is dependent on applied magnetic field as demonstrated in several experimental works and this property of MRF has been leveraged, in this work, to induce one-way bandgaps. Initially, a general wave equation pertaining to fluid with space-and-time-varying material properties was derived. Assuming plane wave propagation in one dimension, an approximate Floquet solution was imposed and the dispersion relationship was obtained. A comprehensive finite element analysis was conducted and good agreement was noted between the numerical and theoretical dispersion relations. It was concluded that space-time periodic modulation of fluid density and local sound speed is necessary to induce asymmetry in the band diagram around the ω axis. The feasibility of real-world implementation using MRF has been discussed. A parametric study detailing the effect of viscosity on the one-way bandgaps has been undertaken. It was found that one-way bandgaps formed at relatively lower frequencies are more robust to viscous corruption. A real-world implementation may be feasible if the viscosity of MRF is less than 3000 Pa-s.

A sub-cc nonlinear piezoelectric energy harvester for powering leadless pacemakers.

A miniature nonlinear piezoelectric energy harvester is developed to power state of the art leadless cardiac pacemakers from cardiac motions. The energy harvester is integrated in the leadless pacemaker and is connected to the myocardium. The energy harvester converts myocardial motions to electricity to power leadless pacemakers. The energy is stored in a battery or supercapacitor and is used for pacing. The device is composed of a bimorph piezoelectric beam confined in a gray iron frame. The system is assembled at high temperature and operated at the body temperature. The mismatch in the coefficients of thermal expansion of the beam and the frame causes the beam to buckle in body temperature. This intentional buckling makes the beam unstable and improves the power production and robustness of the device. Having high natural frequency is a major problem in microelectromechanical systems energy harvesters. Considering the small size of the energy harvester, 0.5 cm3, the natural frequency is expected to be high. In our design, the natural frequency is lowered significantly using a buckled beam and a proof mass. Since the beam is buckled, the design is bistable and nonlinear, which could increase the output power. In this article, the device is analytically modeled, and the natural frequencies and mode shapes of the energy harvester are analytically derived. The terms corresponding to geometric nonlinearities are included in the electromechanical coupled governing equations. The simulations show that the device generates sufficient electricity to power leadless pacemakers.

Conjugate unscented transformation-based uncertainty analysis of energy harvesters.

This article presents a probabilistic approach to investigate the effect of parametric uncertainties on the mean power, tip deflection, and tip velocity of linear and nonlinear energy harvesting systems. Recently developed conjugate unscented transformation algorithm is used to compute the statistical moments of the output variables with multidimensional Gaussian uncertainty in parameters. The principle of maximum entropy is used to construct the probability density function of output variables from the knowledge of obtained statistical moments. The probability density functions for mean power were significantly complicated in shape with two and three distinct peaks for the nonlinear monostable and nonlinear bistable harvesters, respectively. Monte-Carlo simulations with N = 8 × 104 samples for monostable harvester and N = 6.5 × 104 samples for bistable harvester were used for validating the probability density functions. It is concluded that conjugate unscented transformation methodology affords a significant computational advantage without compromising accuracy. In addition, using conjugate unscented transformation method, we show that the dependence of mean power on parameters (excitation frequency, excitation amplitude, etc.), when multidimensional uncertainties are present, is decidedly different relative to a purely deterministic trend. The discrepancy in predicted power between the deterministic and uncertain trends for the monostable harvester, for instance, reach a maximum of 100%, 234%, and 110% for base frequency, base acceleration, and magnet gap, respectively. The deterministic trend consistently overestimates the harvested power relative to the uncertain trends. This work, therefore, may have applications in evaluating "worst case scenario" for harvested power. The major advantage of the presented methodology relative to extant techniques in energy harvesting literature is the accurate and computationally effective applicability to multidimensional uncertainty in parameters.

Nanoscale plasmonically enhanced photodetector based on a gold nanoring.

A nanoscale germanium-gold Schottky photodetector (PD) is proposed based on a nanoring supporting localized surface plasmon excitation. A design methodology is presented based on maximizing resonant transmission power throughput of light from the active region of the PD. Numerical calculations show significant field enhancement of about 200 times in the near-field zone inside of the nanoring, which is utilized to compensate the responsivity decrease due to PD active region volume shrinkage, providing the responsivity of 338 mA/W at a 1310 nm detection wavelength. In addition, the incident wavelength is detected in about one-seventh of the absorption length of bulk germanium, yielding about 33% of the external quantum efficiency. The ratio of responsivity to the active region volume of the PD is calculated to be approximately 100 times that of similar studies.

Experimental investigation of fan-folded piezoelectric energy harvesters for powering pacemakers.

This paper studies the fabrication and testing of a magnet free piezoelectric energy harvester (EH) for powering biomedical devices and sensors inside the body. The design for the EH is a fan-folded structure consisting of bimorph piezoelectric beams folding on top of each other. An actual size experimental prototype is fabricated to verify the developed analytical models. The model is verified by matching the analytical results of the tip acceleration frequency response functions (FRF) and voltage FRF with the experimental results. The generated electricity is measured when the EH is excited by the heartbeat. A closed loop shaker system is utilized to reproduce the heartbeat vibrations. Achieving low fundamental natural frequency is a key factor to generate sufficient energy for pacemakers using heartbeat vibrations. It is shown that the natural frequency of the small-scale device is less than 20 Hz due to its unique fan-folded design. The experimental results show that the small-scale EH generates sufficient power for state of the art pacemakers. The 1 cm3 EH with18.4 gr tip mass generates more than16 µW of power from a normal heartbeat waveform. The robustness of the device to the heart rate is also studied by measuring the relation between the power output and the heart rate.

Using an elastic magnifier to increase power output and performance of heart-beat harvesters.

Embedded piezoelectric energy harvesting (PEH) systems in medical pacemakers have been a growing and innovative research area. The goal of these systems, at present, is to remove the pacemaker battery, which makes up 60%-80% of the unit, and replace it with a sustainable power source. This requires that energy harvesting systems provide sufficient power, 1-3 µW, for operating a pacemaker. The goal of this work is to develop, test, and simulate cantilevered energy harvesters with a linear elastic magnifier (LEM). This research hopes to provide insight into the interaction between pacemaker energy harvesters and the heart. By introducing the elastic magnifier into linear and nonlinear systems oscillations of the tip are encouraged into high energy orbits and large tip deflections. A continuous nonlinear model is presented for the bistable piezoelectric energy harvesting (BPEH) system and a one-degree-of-freedom linear mass-spring-damper model is presented for the elastic magnifier. The elastic magnifier will not consider the damping negligible, unlike most models. A physical model was created for the bistable structure and formed to an elastic magnifier. A hydrogel was designed for the experimental model for the LEM. Experimental results show that the BPEH coupled with a LEM (BPEH + LEM) produces more power at certain input frequencies and operates a larger bandwidth than a PEH, BPEH, and a standard piezoelectric energy harvester with the elastic magnifier (PEH + LEM). Numerical simulations are consistent with these results. It was observed that the system enters high-energy and high orbit oscillations and that, ultimately, BPEH systems implemented in medical pacemakers can, if designed properly, have enhanced performance if positioned over the heart.

Modeling and analysis of optical properties of a gold nanoring based on electric and magnetic dipoles.

The optical behavior of a plane-wave excited gold nanoring (NR), originated from localized surface plasmon resonance is modeled by two coupled electric- and magnetic-point dipoles. Considering the extinction cross-section spectrum, it is found that the electric-dipole effect is dominant in comparison with the magnetic-dipole effect although the magnetic-dipole signature is observable in the near-field response of the NR. In addition, the far-field electromagnetic radiation pattern of the NR verifies the corresponding radiation pattern of the point dipoles. The numerical simulation near-field results are in agreement with the proposed electric- and magnetic-dipole theory.

Antihypoxic activities of Eryngium caucasicum and Urtica dioica.

OBJECTIVE: Urtica dioica and Eryngium spp. have been used in traditional medicine for many years. In spite of many works, nothing is known about their protective effect against hypoxia-induced lethality. MATERIALS AND METHODS: Protective effects of U. dioica (UD) aerial parts and E. caucasicum (EC) inflorescence against hypoxia-induced lethality in mice were evaluated by three experimental models of hypoxia, asphyctic, haemic and circulatory. RESULTS: Statistically significant protective activities were established in some doses of extracts in three models. Antihypoxic activity was especially pronounced in polyphenol fractions in asphyctic model. EC polyphenol fraction at 400 mg/kg prolonged survival time (48.80 ± 4.86, p < 0.001) which was comparable with that of phenytoin (p > 0.05). It was the most effective extract in circulatory model, too. It prolonged survival time significantly respect to control group (p < 0.001). UD extracts protected the mice but the response was not dose-dependent. In haemic model, extracts of EP significantly and dose dependently prolonged survival time as compared to control group (p < 0.001). At 600 mg/kg, EP was the most effective one, being capable of keeping the mice alive for 12.71 ± 0.75 min. Only the concentration of 300 mg/kg of UD was effective (p < 0.001). CONCLUSIONS: Extracts showed remarkable antihypoxic effects. Pharmacological effects may be attributed to the presence of polyphenols in the extracts.