Double Step Research Articles

Biomechanical Study of Walking and Vertical Posture in 4-6-year-old Children with Spastic Forms of Cerebral Palsy

Rehabilitation of children with cerebral palsy (CP) requires a systematic approach and dynamic assessment of the results achieved. The development of methods for assessing the dynamics of motor disorders during medical rehabilitation is of great importance for modern medical rehabilitation. In recent years, there are more and more scientific papers devoted to the study of biomechanical disorders of locomotion in patients with CP. Aim. To assess the features of walking biomechanical characteristics and vertical pose stability in of children 4-6 years old with spastic forms of CP for further formation of rehabilitation groups, taking into account the identified functional disorders. Material and methods. The study included 20 patients (5.4±0.67 years) with spastic forms of CP. A comparative analysis of walking parameters and stabilography of children with spastic diplegia and hepiplegic CP among themselves and with a group of conditionally healthy children (norm group) (n=12) was performed. Results. A statistically significant decrease in the following indicators was found in children with hemi-and paraparesis: walking speed, double step length, and hip flexion/extension angle. Deviations of indicators are more pronounced in spastic diplegia, but are not always equivalent for both limbs; there is a violation step cycle proportions. the decrease in the length of the double step is more pronounced on the affected limb; there is a decrease in the angle of flexion/extension in the knee joint, more pronounced on a healthy limb in patients with hemiplegic CP. A wide range of stabilographic indicators values is observed in both study groups. However, only the average position of the pressure center relative to the frontal plane statistically significantly differs from the norm in the group of children with hemiparesis. In paraparesis, such differences from the norm are much more common: the area of the statokinesiogram, the maximum amplitude of fluctuations in the center of pressure and the energy of the frequency spectrum. The range of values for most indicators in paraparesis is wider. Conclusion. The revealed biomechanical features of walking and stability of the vertical posture of children with spastic forms of CP can serve as a basis for the development of rehabilitation programs. Clinical and rehabilitation groups of children with CP should be formed taking into account the severity of static-dynamic disorders present in patients. This approach will make it possible to plan further rehabilitation treatment of such patients and adequately assess the results obtained.

Effect of increasing speed on whole-body angular momentum during stepping in the elderly

Recent evidence suggests that older adults may have difficulty controlling whole-body angular momentum (H) during volitional stepping, which could impose a major challenge for balance control and result in potential falls. However, it is not known if and how H is influenced by speed when stepping. This study aimed to investigate the effect on H of increasing speed during step initiation in older adults. Twenty-seven healthy individuals over 60 were enrolled in the current study and were instructed to perform a series of step initiations with their dominant leg under two speed conditions: at preferred speed and as fast as possible. Two force plates and a motion-capture system were used to record H and the components of the net external moment (moment arms and ground reaction forces) during the double support and step execution phases of stepping. Results revealed that increasing speed of stepping affected H differently in both stepping phases and in the different planes. H ranges in all three planes increased with speed during the double support phase. During the step execution phase, while H ranges in frontal and transversal planes decreased, sagittal plane H range significantly increased with speed. This increased H range in the sagittal plane, which may result from the task demands, could impose a greater challenge for balance control in the elderly.

Strong trilinear coupling of phonon instabilities drives the avalanche-like hybrid improper ferroelectric transition in SrBi2Nb2O9

Improper and hybrid-improper ferroelectrics (FEs) host spontaneous polarization ($P$) owing to the anharmonic coupling between polar and nonpolar modes. In general, the unstable zone-boundary nonpolar mode is a primary order parameter that couples to the stable zone-center polar mode to induce $P$. However, in certain FEs, such as the Aurivillius family, the polar mode is also unstable. In such cases, the strength of coupling between polar and nonpolar modes governs whether FE phase transition is a single or double step. Here we investigate a single-step avalanche-like transition in ${\mathrm{SrBi}}_{2}{\mathrm{Nb}}_{2}{\mathrm{O}}_{9}$, an Aurivillius family compound, using inelastic neutron scattering and Raman spectroscopy combined with group theory and first-principles simulations. We find that a strong trilinear coupling constant $\ensuremath{\lambda}$ between the two nonpolar and one polar instabilities enables their single-step condensation at the FE transition temperature ${T}_{FE}$ and overcomes the effect of the positive bi-quadratic coupling that works against it. The ratio of $\ensuremath{\lambda}$ to the leading-order term in the energy invariant polynomial is two to six times larger than in iso-structural ${\mathrm{SrBi}}_{2}{\mathrm{Ta}}_{2}{\mathrm{O}}_{9}$, which undergoes a double-step transition. We identify and track polar and nonpolar instabilities and find their temperature dependence consistent with the theoretical prediction based on the strong trilinear coupling mechanism. From the sign ($\ifmmode\pm\else\textpm\fi{}$) of bi-quadratic coupling constants in the energy invariant polynomial, we further rule out the triggering mechanism to drive the FE transition. Moreover, we observe little change in phonons across ${T}_{FE}$ despite a first-order transition. However, a significant phonon broadening occurs even at 300 K, which we rationalize based on a large anharmonic vibrational amplitude of O atoms in the ${\mathrm{NbO}}_{6}$ octahedra.

Personalized rehabilitation assessment of locomotor functions in Parkinson disease using three-dimensional video analysis of motions

Parkinson disease (PD) is one of the most common neurodegenerative diseases. Its main clinical manifestation is movement disorders. The study of innovative objective methods for the diagnosis and rehabilitation of movement disorders in PD is relevant and in demand taking into account the slowly progressive course of the disease and the complex set of symptoms that subsequently forms a characteristic movement pattern. This article provides an example of a personalized rehabilitation assessment of biomechanical manifestations of the gait function of a patient with exacted diagnosis, stage 3.5 PD according to Hoehn and Yahr, by means of the method of three-dimensional motion video analysis using the Vicon Motion Capture Systems soft-hardware complex. The patient has postural and gait disorders. This method was applied after a rehabilitation course based on the activation of lifting the foot from the support surface (“back push”). Changes in the tempo and rhythm parameters of gait in a patient with PD in comparison to a healthy person were revealed: acceleration of walking pace with shortening of the length of single and double step, a decrease in the time of limb advancement, acceleration of the moment of heel rise and a decrease in walking pace. Analysis of the locomotion also revealed a decrease in the amplitude of flexion-extension in the coxofemoral joint, knee joint and tibio-tarsic on the side with more pronounced Parkinsonism. Insufficient knee flexion and hip extension, excessive dorsal flexion of the foot with insufficient plantar flexion were noted. Revealing the last features of locomotion in a particular case allows one to make a plan for a targeted personalized rehabilitation program for a given patient. Thus, the method of three-dimensional video analysis is a valuable diagnostic tool that makes it possible to objectively assess the existing violations of locomotion and identify the targets of rehabilitation.

Highly Graphitized Fe-N-C Electrocatalysts Prepared from Chitosan Hydrogel Frameworks

The development of platinum group metal-free (PGM-free) electrocatalysts derived from cheap and environmentally friendly biomasses for oxygen reduction reaction (ORR) is a topic of relevant interest, particularly from the point of view of sustainability. Fe-nitrogen-doped carbon materials (Fe-N-C) have attracted particular interest as alternative to Pt-based materials, due to the high activity and selectivity of Fe-Nx active sites, the high availability and good tolerance to poisoning. Recently, many studies focused on developing synthetic strategies, which could transform N-containing biomasses into N-doped carbons. In this paper, chitosan was employed as a suitable N-containing biomass for preparing Fe-N-C catalyst in virtue of its high N content (7.1%) and unique chemical structure. Moreover, the major application of chitosan is based on its ability to strongly coordinate metal ions, a precondition for the formation of Fe-Nx active sites. The synthesis of Fe-N-C consists in a double step thermochemical conversion of a dried chitosan hydrogel. In acidic aqueous solution, the preparation of physical cross-linked hydrogel allows to obtain sophisticated organization, which assure an optimal mesoporosity before and after the pyrolysis. After the second thermal treatment at 900 °C, a highly graphitized material was obtained, which has been fully characterized in terms of textural, morphological and chemical properties. RRDE technique was used for understanding the activity and the selectivity of the material versus the ORR in 0.5 M H2SO4 electrolyte. Special attention was put in the determination of the active site density according to nitrite electrochemical reduction measurements. It was clearly established that the catalytic activity expressed as half wave potential linearly scales with the number of Fe-Nx sites. It was also established that the addition of the iron precursor after the first pyrolysis step leads to an increased activity due to both an increased number of active sites and of a hierarchical structure, which improves the access to active sites. At the same time, the increased graphitization degree, and a reduced density of pyrrolic nitrogen groups are helpful to increase the selectivity toward the 4e- ORR pathway.

ELECTRODEPOSITION OF SILVER THIN FILMS ON A GOLD SUBSTRATE IN THE PRESENCE OF OCIMUM GRATISSIMUM (Og) AND VERNONIA AMYGDALINA (Va) PLANT LEAF EXTRACTS.

Electrodeposition an advanced thin film deposition method originally used for decorative purposes and now widely used in industrial applications such as electronics, phonics, magnetic recording and protective coatings, has also been used for the production of size and structure-controlled nanoparticles. In this research, the electrodeposition of silver (Ag) films on gold (Au) substrates with two plant (Ocimum gratissimum (Og) and Vernonia amygdalina (Va) leaf extracts as additives was explored . The effect of these leaf extracts immediately after addition and after a prolonged exposure in the electrolyte on the silver deposits was studied using cyclic voltammetry (CV), chronoamperometry (CA) and linear sweep voltammetry (LSV). Silver thin films were electrodeposited on gold film from an electrolyte of 5 mM AgNO3 and later 5 mM AgNO3 +0.1 M KNO3 for 10 minutes, using a double potential step protocol and potentials -0.15 V and -0.3 V with and without the plant leaf extracts. As silver was grown on the gold substrate, silver nanoparticles were also discovered to have been formed in the electrolyte. Though the deposition potential in the presence of the plant leaf extracts affected the kinetics of the silver deposition on the gold substrate, it only slightly affected the silver film thickness on the gold. CV graphs with the plant leaf extracts show lower current densities indicating a slowing down of the deposition/dissolution rates of silver probably due to the adsorption of the leaf extracts on the surface of the growing silver films which may have affected the transport of silver ions (Ag+) towards the electrode and impacted on the silver deposition/dissolution kinetics. The deposited silver film thickness was 7 nm to 8 nm with the Og leaf extract and 1.5 nm to 2 nm with the Va leaf extract. Atomic Force microscope (AFM) was used for viewing the silver films and the mean grain sizes of the Og silver films was calculated to be . This was larger than those of the Va silver films calculated to be While the Va silver films surface roughness was higher at 10.6 , that of the Og silver film was 9.3.

Upcycling of polypropylene with various concentrations of peroxydicarbonate and dilauroyl peroxide and two processing steps

AbstractThe influence of two peroxides (peroxydicarbonate/dilauroyl peroxide) with various concentrations (10–200 mmol/kg PP) and their effective opportunity to introduce long chain branched (LCB) were investigated. The dependence of a single and double extrusion step and the changes of the properties were studied. Experiments were carried out in a single screw extruder at 180°C for the first extrusion step (modification) and at 240°C for the second extrusion step (processing simulation). Melt flow rate and dynamic rheological properties were studied at a measuring temperature of 230°C. For the definitive determination of long chain branched polypropylene (LCB‐PP) served the extensional rheology measurements. The mechanical properties were examined via tensile test and impact tensile test. Summarized, LCB (melt strength) could be observed via extensional rheology for all modified specimens and the mechanical properties were maintained or even improved for the modified samples. Particularly, samples containing dilauroyl peroxide display excellent mechanical properties in this study.

Design of Experiment Rational Optimization of an Inkjet Deposition of Silver on Kapton

In this work we presented a statistical method to optimize the production of conductive layers by inkjet printing. This statistical method, namely Design of Experiment (DOE), was applied to the deposition of silver nanoparticle ink on Kapton. The process optimization was conducted by a double step. In the first phase, we optimized the getting waveform assigned to the piezoelectric head to form the ink drop in order to have the drop with the smaller diameter and standard deviation. In the second step, we optimized the area covered by the deposition of a specific pattern. The deposition strategy was then optimized to best reproduce the theoretical pattern. The entire process was conducted by analyzing the images acquired with a high-resolution camera and successively using DOE to fit the data and determine empirical models linking the process parameters to the measured outcome. These models allowed us to optimize the process by solving a system of equations giving a quantification on the printing quality.

Recovery of tungsten and cobalt from cemented tungsten carbide wastes using carbonate roasting and water leaching

ABSTRACT Tungsten and cobalt can be recovered from cemented tungsten carbide-Co (WC-Co) scraps using a novel process based on roasting of the scraps with Na2CO3 and water leaching of the calcine containing Na2WO4. The process was evaluated at different conditions testing several parameters, including Na2CO3/WC molar ratio 1:1–2:1, roasting temperature in the range 400–900°C, roasting time at 1–3 h, leaching temperature at ambient – 90°C and leaching time 1–3 h. Thermodynamic modeling of the roasting and leaching stages using HSC and Stabcal software allowed an understanding of the speciation of the products at different conditions. Subsequent experiments to determine an optimized conditions of both roasting and water leaching were conducted aiming to yield recoveries of both W and Co in solution over 95%. Roasting of the scraps with Na2CO3 at 800°C in 3 h using Na2CO3/WC molar ratio of 1:1 will produce a Na2WO4 which can be easily water leached. Over 95% W was recovered after water leaching the calcines at 60°C in 3 h. Over 94% Co was recovered as soluble CoSO4 using 1 M H2SO4 with 1.5 M H2SO3 added as a reductant. The double step of CoCO3 precipitation using 1.5 M Na2CO3 and conversion to Co(OH)2 using 8 M NaOH allows a high purity product (>99.5% purity) to be produced with most of the major impurities as Cr and Fe remaining in the residual Na2CO3 and NaOH liquors. The levels of these major impurities are 0.05% Cr and 0.3% Fe in the final Co hydroxide product. Implications: This is a new process to treat W-Co wastes and recover W and Co. To the best of our knowledge, no study was done before in this area.

БІОМЕХАНІЧНІ АСПЕКТИ ХОДЬБИ ДІТЕЙ МОЛОДШОГО ШКІЛЬНОГО ВІКУ

Мета. Визначити особливості часової структури ходьби практично здорових дітей 6-8 років. Методи. Для виконання поставлених завдань використано такі методи дослідження, як аналіз науково-методичної літератури та документальних матеріалів, відеометрія, пакет прикладної програми“БіоВідео”. Результати. Ходьба є циклічним локомоторним рухом, здійснюваним за способом відштовхування. Характерною особливістю ходьби є наявність постійного контакту опорної ноги (період одиночної опори) або обох ніг (період подвійної опори). Саме ходьба може служити в якості критерію оцінки стану моторики людини. У той же час, накопичені більш ніж за столітній період дані, що стосуються питань фазового складу ходьби, ролі і цільової спрямованості кожної з фаз в циклі подвійного кроку, механізму реалізації основних рухових дій, принципово один від одного не відрізняються. При цьому інформація про формування біомеханіки ходьби у молодших школярів обмежена. Проведені дослідження свідчать про те, що тривалість фази подвійної опори при лівій опорній нозі у практично здорових хлопців 6 років дорівнює в середньому 0,12 с (S = 0,01 с), у дівчат – 0,14 с (S = 0,01 с), водночас у практично здорових хлопців і дівчат 7 років показники тривалості цієї фази однакові і складають 0,14 с (S = 0,01 с), так само однакова тривалість цієї фази у хлопців і дівчат 8 років і становить 0,16 с (S = 0,02 с у хлопців і S = 0,01 с у дівчат). Необхідно відмітити, що статистично значущої різниці у показнику тривалості фази подвійної опори при лівій опорній нозі між хлопцями та дівчатами у кожній з віковихкатегорій 7–8 років не спостерігалоя (p > 0,05) на відміну від хлопців і дівчат 6 років, у яких показники тривалості цієї фази статистично значуще відрізнялися (р < 0,05), що підтверджено за допомогою критерію Стьюдента для незалежних вибірок. Варто відмітити, що у заключній фазі подвійного кроку ходьби, зафіксовано статистично значуще збільшення її тривалості у дівчат 7 років, порівняно з хлопцями цього віку на 0,04 с (p < 0,05), її тривалість становить у дівчат 7 років, а також у хлопців і дівчат 8 років в середньому 0,24 с (S = 0,03 с у дівчат 7 років і хлопців 8 років і S = 0,02 с у дівчат 8 років). Висновок. В результаті проведеного дослідження була вивчена структура циклу ходьби практично здорових дітей 6–8 років, значимість яких підтверджена об’єктивними часовими показниками. Підтверджено думку ряду фахівців, які вказують, що біомеханічна структура локомоторного акту практично повністю складається у віці 7-8 років.Ключові слова: діти молодшого шкільного віку, статодинамічна постава, часова структура ходьби, біомеханічні аспекти.

Effect of residual nanocrystals on thermal stability and mechanical properties of metalloid-containing amorphous alloys

Herein we present the amorphization, thermal stability, crystallization behavior, and mechanical properties of (Ni60Nb40)100-x-ySixBy (x = 0, 5 and 10 at.%, y = 0, 5 at.%) alloys with six distinct compositions. We investigated the influence of the nanocrystals formed by the addition of Si and B on the thermal stability and mechanical properties of the (Ni60Nb40)100-x-ySixBy (x = 0, 5 and 10 at.%, y = 0, 5 at.%) alloys. The phase and thermal stabilities of the alloys were studied using X-ray diffraction, high-resolution transmission electron microscopy, and differential scanning calorimetry and the mechanical properties were characterized by nanoindentation testing. It was found that single-step crystallization occurred in B-free alloys, whereas double step crystallization occurred in B-containing alloys. B-free (Ni60Nb40)90Si10 alloy exhibited the highest onset temperature of 714 °C, and B-containing (Ni60Nb40)95B5 alloy shows the lowest onset temperature at 642 °C. The microstructure of B-containing amorphous alloys consists of nano-sized metallic crystals with a size of less than 5 nm embedded in an amorphous phase. The existence of residual nanocrystals facilitates heterogeneous nucleation during crystallization of the amorphous phase, weakening the thermal stability of amorphous alloys. Crystallization of the amorphous phase remarkably enhances the mechanical properties of (Ni60Nb40)100-x-ySixBy (x = 0, 5 and 10 at.%, y = 0, 5 at.%) alloys, with a 40–60% increase in hardness and 19–88% increase in elastic modulus. An increase in mechanical properties after crystallization is lower in B-containing alloys because of the lower nano-intermetallic phases formation after crystallization, due to the presence of the residual nanocrystals.

Hybrid Al2O3-Cu/water nanofluid flow and heat transfer over vertical double forward-facing step

Turbulent heat transfer and hybrid Al2O3-Cu-nanofluid over vertical double forward facing-step is numerically conducted. The k-? standard model based on finite volume method in 2-D are applied to investigate the influences of Reynolds number, step height, volume fractions hybrid Al2O3-Cu-nanofluid on thermal performance. In this paper, different step heights for three cases of vertical double forward-facing step are adopted by five different of volume fractions of hybrid (Al2O3-Cu-water) nanofluid varied for 0.1, 0.33, 0.75, 1, and 2, while the Reynolds number different between 10000 to 40000 with temperature is constant. The main findings revealed that rise in local heat transfer coefficients with raised Reynolds number and maximum heat transfer coefficient was noticed at Re = 40000. Also rises in heat transfer coefficient detected with increased volume concentrations of hybrid (Al2O3-Cu-water) nanofluid and the maximum heat transfer coefficient found at hybrid Al2O3-Cu-water nanofluid of 2% in compared with others. It is also found that rise in surface heat transfer coefficient at 1st step-Case 2 was greater than at 1st step-Case 1 and 3 while was higher at 2nd step-Case 3. Average heat transfer coefficient with Reynolds number for all cases are presented in this paper and found that the maximum average heat transfer coefficient was at Case 2 compared with Case 1 and 3. Gradually increases in skin friction coefficient remarked at 1st and 2nd steps of the channel and drop in skin friction coefficient was obtained with increased of Reynolds number. Counter of velocity was presented to show the re-circulation regions at 1st and 2nd steps as clarified the enrichment in heat transfer rate. Furthermore, the counter of turbulence kinetic energy contour was displayed to provide demonstration for achieving thermal performance at second step for all cases.

Biocompatible pectin-based hybrid hydrogels for tissue engineering applications

Hybrid hydrogels made of chemically modified pectin, gelatin and xanthan gum have been formulated and processed through a double crosslinking step, aimed at wound healing applications.

Protocol for microplastic pollution monitoring in freshwater ecosystems: Towards a high-throughput sample processing - MICROPLASTREAM

Robust and reproducible quantification of microplastic pollution in freshwater ecosystems requires the processing of a large amount of samples collected in varying environmental conditions. Such samples are characterized by a high amount of organic matter compared to microplastics and are highly variable in terms of the quantity and the composition of matrices, requiring a standardized analytical protocol for sample treatment and analysis. However, two important and time-consuming steps for microplastic recovery are the elimination of organic matter and microscopic inspection of samples. Here, we developed and validated a protocol, targeting particles with length ranging from 700 µm to 5 mm, that includes a double-step digestion of organic matter, consisting of incubation with potassium hydroxide followed by hydrogen peroxide solutions, and two stereomicroscopic analyses. In addition, we developed several technical improvements allowing reducing the time needed to process samples, such as the design of an adapted filter-cap to improve the content transfer. The absence of physical and chemical alterations in the investigated microplastic pellets and the average reduction of 65.8% (± 9.59 SD) of organic matter in real samples demonstrated that our protocol is fit for purpose. We recommend a second stereomicroscopic analysis to avoid underestimating microplastic concentration and particle size distribution biased towards larger particles. When used for a large-scale monitoring of microplastic pollution, this protocol resulted in an estimated time of 38 h for one person for the treatment of a batch of 24 samples, allowing a higher throughput sample processing and reproducible quantification.• Protocol customization towards high-throughput sample processing• Double step digestion to improve organic matter elimination• Importance of stereomicroscopic analysis for microplastic recovery

Structural, Morphological and Antimicrobial Study of ZnO/Ag Nanoparticles

Metal oxide nanoparticles gain attention in the field of biomedical applications because of their unique physico-chemical properties and emerging out as an alternative to antibiotics. The major cause of most of the human diseases is the bacterial infection. However, antibiotics used in the cure show other complications to human health. Therefore, the purpose of the present work is to investigate the antibacterial properties of ZnO/Ag nanoparticles on the test bacterial strains, Escherichia coli (E. coli). ZnO/Ag nanoparticles are synthesized using surfactant mediated route in a single step and double step procedure. Here, CTAB and hydrazine hydrate used as a surfactant and reducing agents respectively. The synthesized nanoparticles are characterized by x-ray diffraction, scanning electron microscopy and energy dispersive x-ray spectroscopy for structure, morphology and compositional properties. The antibacterial activities of these nanoparticles are also studied using the agar-well diffusion technique. The result analysis shows that synthesized nanopaticles are spherical in shape, having particles of the size 6 nm and 13 nm in the desired elemental composition. ZnO/Ag nanoparticles possessed a strong antibacterial effect against E. coli. This study signifies that ZnO/Ag metal oxide nanoparticles exhibit stronger antimicrobial activity against pathogen bacteria E. coli which may works effectively on the antibacterial and antifungal infections.

Comparison of single step versus double step screening for GDM

Introduction: There is a lot of debate over what type of screening is needed to be done for GDM, especially with India being touted as the diabetes capital of the world. Materials and Methods: A total of 240 consecutive patients were screened using the two methods in accordance with the laid down procedures and guidelines for the tests with 120 patients in each arm of the study. The positive cases were then followed up till delivery to describe risk of Caesarean section and perinatal morbidities if any were encountered. Results: In the primary outcome it was found that though more cases of GDM were detected with Single Step, maternal and neonatal morbidities were the same and no significant statistical difference was found in either of them. Conclusions: This study shows that both Single step and double step are efficacious though double step seems to be more convenient for maximum number of patients. Keywords: Gestational Diabetes Mellitus, Screening GDM, Diagnosis of GDM.

Detecting the abuse of 19-norsteroids in doping controls: A new gas chromatography coupled to isotope ratio mass spectrometry method for the analysis of 19-norandrosterone and 19-noretiocholanolone.

The detection of 19-norsteroids abuse in doping controls currently relies on the determination of 19-norandrosterone (19-NA) by gas chromatography-tandem mass spectrometry (GC-MS/MS). An additional confirmatory analysis by gas chromatography coupled to isotope ratio mass spectrometry (GC-C-IRMS) is performed on samples showing 19-NA concentrations between 2.5 and 15 ng/ml and not originated from pregnant female athletes or female treated with 19-norethisterone. 19-Noretiocholanolone (19-NE) is typically produced to a lesser extent as a secondary metabolite. The aim of this work was to improve the GC-C-IRMS confirmation procedure for the detection of 19-norsteroids misuse. Both 19-NA and 19-NE were analyzed as target compounds (TCs), whereas androsterone (A), pregnanediol (PD), and pregnanetriol (PT) were selected as endogenous reference compounds (ERCs). The method was validated and applied to urine samples collected by three male volunteers after the administration of nandrolone-based formulations. Before the instrumental analysis, urine samples (<25 ml) were hydrolyzed with β-glucuronidase from Escherichia coli and extracted with n-pentane. Compounds of interest were purified through a single (for PT) or double (for 19-NE, 19-NA, A, and PD) liquid chromatographic step, to reduce the background noise and eliminate interferences that could have affect the accuracy of δ13 C values. The limit of quantification (LOQ) of 2 ng/ml was ensured for both 19-NA and 19-NE. The 19-NE determination could be helpful in case of "unstable" urine samples, in late excretion phases or when coadministration with 5α-reductase inhibitors occur.

Effect of a Multimodal Movement Intervention in Patients With Neurogenic Claudication Based on Lumbar Spinal Stenosis and/or Degenerative Spondylolisthesis-A Pilot Study.

Chronic low-back pain is a major individual, social, and economic burden. The impairment ranges from deterioration of gait, limited mobility, to psychosocial distress. Due to this complexity, the demand for multimodal treatments is huge. Our purpose is to compare the effects of a multimodal movement intervention (MI) (coordinative–cognitive exercises and dancing program) with standard physical therapy (PT) on gait, physical function, and quality of life in patients with lumbar spinal stenosis (LSS). The study design is based on a 6-week intervention with a two (group: MI/PT) by two (measurement time points: pre-/post-test) parallel group design with random assignment. Twenty-four subjects (18 female/6 male, 70.8 ± 10.6 years old) diagnosed with LSS were included and randomly allocated to the MI or PT group. The primary outcomes are minimum toe clearance (MTC) and double step length (DSL) variability and the Timed “Up & Go” test (TUG). Secondary outcomes are the Brief Pain Inventory, the short Fall Efficacy Scale–International (sFES-I), and the Oswestry Disability Index. Nine subjects for each group could be analyzed. The MTC variability revealed a significant between-group difference in the posttest (p = 0.008) showing a lower MTC variability for the MI compared to the PT group. The MI group displayed an improved TUG (p = 0.031) and a reduced sFES-I (p = 0.044). The decreased MTC variability and fear of falling as well as the improved functional mobility may contribute to a reduced risk of falling. For the subsequent study, further kinematic and cognitive parameters should be analyzed, and the number of participants has to be increased.Clinical Trial Registration: German Clinical Trial Register (ID: DRKS00021026/URL: https://www.drks.de/drks_web/navigate.do?navigationId=trial.HTML&TRIAL_ID=DRKS00021026).

Photovoltaic array maximum power point tracking via modified perturbation and observation algorithm

One drawback of PVs is their low efficiency. As the PVs have a unique maximum Power Point for a specified irradiation level, there must be an effective method for extracting maximum power from the PV module to raise the efficiency. Conventional Perturbation and Observation (P&amp;amp;O) is a simple algorithm for maximum power point tracking (MPPT) but it suffers from oscillation during steady state conditions and is deviated from the maximum power point during slow and rapid irradiation level change. This paper presents a modified P&amp;amp;O by adding variation in PV current as a third in addition to the voltage and power variation parameters. This new algorithm is capable of eliminating the MPPT deviation. To increase the perturbation speed, a double step is taken as the tracking is deviated from the MPP. The modified P&amp;amp;O algorithm is used to control the duty cycle of DC-DC buck converter. The simulation shows that the modified P&amp;amp;O is faster than the conventional. The power loss due to oscillation before attaining the steady state is less for modified P&amp;amp;O. For slow irradiation level change (ramp up 600 to 1000 and ramp down 1000-800) W/m2, the modified P&amp;amp;O shows less tracking diverge. As the irradiation level changes rapidly from 800 to 200 W/m2, it's shown that the modified algorithm attains the steady state faster than the conventional P&amp;amp;O and the average efficiency increased by 4.34%.

Facile one-pot synthesis of CuO nanosheet for application as electrocatalyst for methanol oxidation

Herein, a simple single step procedure for synthesis of CuO nanosheets (CuO-NS) at room temperature is reported. The structural and morphological evaluation proves that material is highly crystalline in nature. The electrocatalytic activity of CuO-NS for CH3OH oxidation was evaluated using cyclic voltammetry, electrochemical impedance spectroscopy, and chronoamperometry methods in 0.5 M NaOH. The prepared catalyst showed comparable performance in terms of electrocatalytic current in comparison with reported electrodes modified with various transition metal-oxides. The electrochemical studies on CuO-NS reveal intriguing methanol electrooxidation properties with current density of 4.24 mA/cm2 and 75% current retention even after 2000 s, demonstrating its stability in methanol oxidation reaction (MOR). The improved activity of the electrocatalyst is due to mesoporosity and high surface area. Reaction kinetics and mechanism for CH3OH oxidation were studied. Double step chronoamperometric technique shows that CH3OH oxidation was irreversible. The results elucidate superior performance of the prepared catalyst for CH3OH oxidation and are notably promising in direct methanol fuel cell applications.