Satisfactory Safety Margin Research Articles

Shear performance and strength of reinforced concrete non-prismatic beams with basalt fiber reinforced polymer rebars

Tapered beams, which are horizontal structural elements, possess varying moments of inertia across their length. Among these, the pier cap mode is widely employed in engineering applications. This research explores the influence of incorporating basalt fiber reinforced polymer (BFRP) bars on the shear strength of eight concrete haunched beams. While two of these beams were straight beams, the others have different inclination angles. The study aimed to examine two main factors: the angles of tapered part in the compression chord and the effect of BFRP stirrups. Results from the experiment revealed a direct correlation between increasing tapered angles and the enhancement of shear capacity in haunched beams. Consequently, a comprehensive analysis was conducted using three different codes, leading to the formulation of proposed equations derived from semi-empirical methods. The analysis demonstrated a high level of accuracy in predicting shear strength with a satisfactory safety margin.

IDA-Based Collapse Safety Assessment of Torsional-Irregular Buildings, Considering Ductility and Damage

The complexity in nonlinear behavior of torsional-irregular buildings in combination with uncertainty due to the natural randomness of earthquake records has been always a main challenge for buildings’ seismic design. To find a solution to this challenge, three reinforced concrete (RC) building archetypes were designed and next developed into their nonlinear models. Nonlinear static (pushover) analyses were performed to calculate the capacity of the archetype models in all principal and non-principal directions while incremental dynamic analyses (IDAs) were conducted by applying 30 accelerograms from both near-field and far-field earthquakes. The IDA capacity curves, collapse fragility curves and log-normal cumulative distribution functions (CDFs) were established by including both the aleatory randomness and epistemic uncertainty. Despite previous studies wherein fragility curves were given by evaluating structures’ collapse along structural reference axes or simply on [Formula: see text], [Formula: see text]-axes, in this paper, possible building collapse on a critical non-principal direction (where maximum seismic response was observed) was simulated and its probability was accounted for developing IDA curves and log-normal CDFs. Accordingly, this issue was mirrored in computing available/acceptable collapse margin ratios (CMRs). In addition to the well-known outline used for calculating CMRs in the literature (that is based on estimation of collapse capacity in terms of earthquake intensity measure (IM)), the framework proposed here includes a new method for calculating the CMRs in terms of displacement-based drift, ductility, and damage. The superiority of the proposed method over the former is consistent with the buildings’ design procedure that is governed by storey drift control rather than base-shear strength. Refined statistics of CMRs given by taking into account displacement-based responses illustrate the available CMRs exceed the acceptable CMRs, meaning that a satisfactory safety margin against collapse will be anticipated in the targeted building class if a suitable yielding mechanism with sufficient ductility is provided for seismic force-resisting system by applying seismic design provisions of the current codes.

Development of novel isatin thiazolyl-pyrazoline hybrids as promising antimicrobials in MDR pathogens.

Microbial Multidrug Resistance (MDR) is an emerging global crisis. Derivatization of natural or synthetic scaffolds is among the most reliable strategies to search for and obtain novel antimicrobial agents for the treatment of MDR infections. Here, we successfully manipulated the synthetically flexible isatin moieties to synthesize 22 thiazolyl-pyrazolines hybrids, and assessed their potential antimicrobial activities in vitro against various MDR pathogens, using the broth microdilution calorimetric XTT reduction method. We chose 5 strains to represent the major MDR microorganisms, viz: Methicillin-resistant S. aureus (MRSA), and Vancomycin-resistant E. faecalis (VRE) as Gram-positive bacteria; Carbapenem-resistant K. pneumonia (CRKP), and Extended-spectrum beta-lactamase E. coli (ESBL-E), as Gram-negative bacteria; and Fluconazole-resistant C. albicans (FRCA), as a yeast-like unicellular fungus. The cytotoxicity of compounds 9f and 10h towards mammalian lung fibroblast (MRC-5) cells demonstrated their potential satisfactory safety margin as represented by their relatively high IC50 values. The target compounds showed promising anti-MDR activities, suggesting they are potential leads for further development and in vivo studies.

Influence of Shear Reinforcement on Thin Web Pretensioned Concrete Beams

The objective of this paper is to present the results of the experimental study which was carried out on influence of shear reinforcement of pretensioned concrete thin web beams made with M50 grade concrete. Four pretensioned beams B000, B400, B200 and B100 of the same length, cross section and prestress force were fabricated with no stirrups, 400 mm c/c, 200 mm c/c and 100 mm c/c spacing of stirrups, respectively. The effect of varying percentage of shear reinforcement on cracking load, crack propagation, deflection, ultimate capacity, failure mode and beam ductility was examined. Deflection of the each test beam was measured up to ultimate load at an incremental loading of 2.5 tonne (25 kN). The test results were analyzed for cracking loads and ultimate loads and compared with theoretically estimated values. It has been observed that the loads are found to be increased while increasing percentage of web reinforcement. All the shear reinforced beams exhibited delay in appearance of first crack when compared with beam B000. The reason for the delay in the magnitude of first crack load is recognized as the contribution of shear reinforcement arresting the diagonal shear cracks in the shear zone. The energy abortion capacity of the beams increased while decreasing in the stirrup spacing in the shear span. The beam B100 which was reinforced by double the amount of the web reinforcement than the beam B200 showed a satisfactory margin of safety above 1.50 and ductility response of 3.81.

Single-Coil Defibrillator Leads Yield Satisfactory Defibrillation Safety Margin in Hypertrophic Cardiomyopathy.

Single-coil defibrillator leads have gained favor because of their potential ease of extraction. However, a high defibrillation threshold remains a concern in patients with hypertrophic cardiomyopathy (HCM), and in many cases, dual-coil leads have been used for this patient group. There is little data on using single-coil leads for HCM patients. We evaluated 20 patients with HCM who received an implantable cardioverter-defibrillator (ICD) on the left side in combination with a dual-coil lead. Two sets of defibrillation tests were performed in each patient, one with the superior vena cava (SVC) coil "on" and one with the SVC coil "off". ICDs were programmed to deliver 25 joules (J) for the first attempt followed by maximum energy (35 J or 40 J). Shock impedance and shock pulse width at 25 J in each setting as well as the results of the shock were analyzed. All 25-J shocks in both settings successfully terminated ventricular fibrillation. However, shock impedance and pulse width increased substantially with the SVC coil programmed "off" compared with "on" (66.4±6.1 ohm and 14.0±1.3 ms "off" vs. 41.9±5.0 ohm and 9.3±0.8 ms "on", P<0.0001 respectively). Biphasic 25-J shocks with the SVC coil 'off' successfully terminated ventricular fibrillation in HCM patients, indicating a satisfactory safety margin for 35-J devices. Single-coil leads appear appropriate for left-sided implantation in this patient group. (Circ J 2016; 80: 2199-2203).

Satisfactory margin of safety against shear failure of lightweight reinforced concrete beams: 3D finite element modeling

In concrete structures a satisfactory margin of safety should be ensured against shear failure that might occur under the forces that act upon the structure during its lifetime. Therefore, knowledge of the design and construction guidelines for shear of normal and high strength Lightweight Concrete (LWC) beams is desirable to better understand the structural design and performance of LWC beams. Thus, research is required to address and investigate the contribution of concrete compressive strength, shear span to depth ratio, tensile reinforcement ratio, and shear stirrups spacing as well as the failure mechanisms in situation of using LWC beams. As a result, this paper presents Nonlinear Finite Element Analysis (NLFEA) results of reinforced LWC beams because of the main benefits of NLFEA by providing substantial savings in the cost, time, and effort compared with the fabrication and experimental testing of structure elements as well as the ability to change any parameter of interest and the capability of demonstrating any interesting behavior at any load value and at any location in the system. After reasonable validation of NLFEA with the experimental test results, the NLFEA was expanded to provide a parametric study of fourteen hundred LWC beams that correlates the ultimate shear stress to studied parameters. Results indicated that the lower bound was for the beams with shear span to depth ratio, concrete compressive strength, and tensile reinforcement ratio of 5, 27.5 MPa, and 0.71%, respectively, and the upper bound was for the beams with shear span to depth ratio, concrete compressive strength, and tensile reinforcement ratio of 1, 68.8 MPa, and 2.21%, respectively. In addition, the performance of simulated models was investigated in terms of ultimate load capacity, ductility and energy absorption. Finally, a new parametric model is introduced in this paper to compute the shear strength of reinforced LWC beams without stirrups. The proposed equation was compared with numerous previous analytical models and founded that some models to be in a good agreement.

Characterization of skin penetration efficacy by Au-coated Si microneedle array electrode

Investigation of skin penetration efficacy by a silicon microneedle array is presented. Experiments were performed on porcine and chicken skin samples in vitro and on human skin in vivo. Solid microneedle arrays (13×13mm2), each consisting of 100 microneedles, were designed and fabricated by deep reactive ion etching process. To evaluate the penetration efficacy through the mechanically and electrically resistant upper skin layer of stratum corneum, the electrical skin impedance change with applied force was measured by using Au-coated Si microneedle array as working electrode in 2 and 3 electrode configurations. Skin impedance changes between 2 and 8% were measured when applying incremental force, increased from 1 to 10N on a Au metalized microneedle array electrode. When impact assisted penetration of microneedle array was applied instead of incremental increase of applied force, a significant impedance reduction of up to 50% on animal skin and 95% on human skin was obtained, which is a strong evidence of successful skin penetration. Furthermore, the microneedle array electrode showed consistently lower interface impedance compared to the flat electrode for the samples involved. Analyses of Si microneedle mechanical properties revealed that by proper use a satisfactory safety margin (>60) can be achieved.

Formulation and characterisation of lyophilised rapid disintegrating tablets using amino acids as matrix forming agents

Despite recent advances in the formulation of lyophilised rapid disintegrating tablets (RDTs), the inclusion of matrix supporting/disintegration enhancing agents has been limited to the use of saccharides and polyols. In this study, the feasibility of using amino acids as matrix forming agents in lyophilised RDTs was investigated. Twelve amino acids were chosen (alanine, arginine, threonine, glycine, cysteine, serine, histidine, lysine, valine, asparagine, glutamine and proline), and the suitability for freeze drying, mechanical properties and disintegration time after inclusion of the amino acids at varied concentration were studied. In addition, the porosity of the RDTs and wettability profile of the amino acids were investigated to understand the mechanisms of disintegration. The results suggest the suitability of these amino acids for the lyophilisation regime, as they displayed satisfactory safety margin between the glass transition and shelf temperature (−40 °C), except proline-based formulations. Moreover, the crystallisation behavior of alanine, glycine, cysteine and serine at high concentration increased the stability of the formulation. The characterisation of the RDTs suggests that high concentration of the amino acids is required to enhance the mechanical properties, whereas only optimum concentrations promote the disintegration. Moreover, wetting time of the amino acid and porosity of the tablet are the two factors that control the disintegration of RDTs.

The Azygos Defibrillator Lead for Elevated Defibrillation Thresholds: Implant Technique, Lead Stability, and Patient Series

Conventional insertion of implantable cardioverter-defibrillator (ICD) includes an evaluation of the defibrillation threshold (DFT). Implanting an ancillary defibrillation lead in the azygos vein has been introduced as a therapeutic option in patients with "high" DFT. This study reports the efficacy and stability of azygos defibrillation coils implanted for elevated DFTs. This is a retrospective review of seven consecutive patients with right and left pectoral, single- and dual-chamber, and biventricular ICDs and elevated DFTs, in whom an azygos defibrillation coil was introduced. Addition of an azygos defibrillator lead achieved a satisfactory safety margin during single energy defibrillation efficacy testing in four out of seven patients, with success at maximum device output in two patients. No satisfactory safety margin was achieved in the remaining patient, despite the further addition of a subcutaneous defibrillation coil. No change in lead position was observed over a mean radiographic follow-up of 8 months. No complications were noted during a mean follow-up of 14 months, including no deaths, and no ICD shocks. Implanting a defibrillation coil into the azygos vein is feasible and safe. In a majority of patients with failed defibrillation efficacy testing, adding an azygos coil achieves success on repeat testing. Therefore, this technique is one option for lowering the defibrillation threshold in patients who fail DFT testing of their ICD.

Evaluation of motor toxicity and anticonvulsant efficacy of barbiturates and benzodiazepines in a bicyclophosphate seizure model in mice

1. 4-Alkyl derivatives of 2,6,7-trioxa-l-phosphabicyclo [2.2.2] octane-I-oxide [Bicyclophosphates (BP)] are highly toxic convulsants and potent GABAA receptor antagonists. 2. The effects of various clinical used anticonvulsant drugs, barbiturates and benzodiazepines, on motor performance and 4-isopropylbicyclophosphate (IPBP), a homologue of BP, induced myoclonic and generalized tonic-clonic seizures were investigated in mice. 3. The anticonvulsant drugs were IP administered 30 min. prior to the inverted screen test, a measure of minimal neurological deficit, and were then challenged with a 97% convulsant dose of IPBP (0.15 mg/kg, SC). 4. The results show that: 1) benzodiazepines are more likely to have favorable motor toxicity and anticonvulsant profiles than barbiturates. 2) Various doses of these drugs that did not significantly cause motor impairment increase the mean latencies to myoclonic and generalized tonic-clonic seizures. 3) The increase in anticonvulsant activity is associated with a comparable increase in motor impairment. 4) Only 45-0088-S, an open-ring derivative of 1,4-benzodiazepines, and clonazepam have protective indices of more than 5, a satisfactory margin of safety. 5. The potential use of 45-0088-S and clonazepam in the treatment of BP-induced seizures should be explored further.

Effects of initial polarity on defibrillation threshold with biphasic pulses.

Previous studies have shown that the polarity of epicardial patches significantly affects the defibrillation efficacy of monophasic shocks. However, whether this improvement can be extended to different pulsing methods and lead systems, such as biphasic shocks using endocardial defibrillating electrodes, is unknown. Twenty consecutive patients undergoing testing and permanent implant using an Endotak lead system with a biphasic device were included in the study. In each patient the defibrillation threshold was determined delivering biphasic pulses with the distal coil as the cathode and the proximal coil as the anode during the positive phase and with the polarity reversed. The initial electrode polarity tested was chosen randomly. The defibrillation threshold was defined as the lowest pulse amplitude that effectively terminated ventricular fibrillation induced with 60-Hz alternating current. For each biphasic pulse peak voltage, pulse duration, resistance, and stored energy were recorded. Of the 20 patients, 12 (60%) had lower defibrillation threshold when the proximal coil was negative, whereas only 2 patients had a lower defibrillation threshold when the distal coil was negative. In four patients a subcutaneous patch would have been required if only the biphasic pulse with the distal coil as negative had been tested. The mean stored defibrillation threshold energy was lower with the configuration using the proximal coil as cathode (16.3 +/- 8.8 J vs 21.5 +/- 11 J; P < 0.01). Change in the initial polarity of biphasic shocks may influence defibrillation efficacy and should, therefore, be assessed in each patient to achieve a more satisfactory safety margin and minimize the use of more invasive lead configurations.

Potential Renal Solute Load of Infant Formulas

The potential renal solute load (PRSL) of infant feedings is the sum of dietary nitrogen (expressed as mmol of urea, i.e., mg nitrogen divided by 28), sodium, potassium, chloride and phosphorus. The PRSL determines the renal solute load, and, therefore, the osmolar concentration of the urine. When water intake is reduced and/or water losses are increased, the renal concentrating ability may be exceeded, and negative water balance (dehydration) may ensue. Under these circumstances, feedings providing high PRSL lead more rapidly to dehydration than do feedings providing lower PRSL. On the basis of simulated clinical situations and epidemiologic data, it is concluded that conventional infant formulas (PRSL 135–177 mosmol/l, or 20–26 mosmol/100 kcal) provide a satisfactory margin of safety. A feeding providing the upper limits for concentrations of protein and electrolytes specified by the Food and Drug Administration rule does not afford a satisfactory margin of safety. It is recommended that the upper limit for protein content of infant formulas be decreased from 4.5 g/100 kcal to 3.2 g/100 kcal and that an upper limit for phosphorus concentration of infant formulas be set at 93 mg/100 kcal. Maximum PRSL will then be 221 mosmol/l (33 mosmol/100 kcal).

Potential Renal Solute Load of Infant Formulas

The potential renal solute load (PRSL) of infant feedings is the sum of dietary nitrogen (expressed as mmol of urea, i.e., mg nitrogen divided by 28), sodium, potassium, chloride and phosphorus. The PRSL determines the renal solute load, and, therefore, the osmolar concentration of the urine. When water intake is reduced and/or water losses are increased, the renal concentrating ability may be exceeded, and negative water balance (dehydration) may ensue. Under these circumstances, feedings providing high PRSL lead more rapidly to dehydration than do feedings providing lower PRSL. On the basis of simulated clinical situations and epidemiologic data, it is concluded that conventional infant formulas (PRSL 135-177 mosmol/l, or 20-26 mosmol/100 kcal) provide a satisfactory margin of safety. A feeding providing the upper limits for concentrations of protein and electrolytes specified by the Food and Drug Administration rule does not afford a satisfactory margin of safety. It is recommended that the upper limit for protein content of infant formulas be decreased from 4.5 g/100 kcal to 3.2 g/100 kcal and that an upper limit for phosphorus concentration of infant formulas be set at 93 mg/100 kcal. Maximum PRSL will then be 221 mosmol/l (33 mosmol/100 kcal).

Selenium in the environment

Selenium is one of the most widely distributed elements of the earth's crust. Much of the selenium in the earth's crust occurs associated with sulfide minerals. The presence or absence of selenium in any soil is dependent upon the composition of the parent material, and is also dependent upon leaching or processes subsequent to soil formation, that may have added selenium. Selenium can be easily oxidized from Se 0 to Se +4 or Se +6. Selenium is usually recovered as a by-product of the refining of the sulfide ores of other metals such as copper. The greatest amounts of selenium are used for the manufacture of the photoelectric cell. Selenium is taken up by plants as selenate, selenite or organic selenium. Se 75 selenite in 30 minutes was translocated primarily to selenomethionine. In sheep or pigs the duodenum is the main site of Se 75 absorption. Selenium is excreted in the feces, the urine, and the expired air, the amounts and proportions depending upon the level and form of the intake, the nature of the rest of the diet, and the species. A dietary intake of 0.1 μg/g Se provides a satisfactory margin of safety for grazing sheep and cattle. In humans, the recommended daily allowance for selenium is between 100 to 200 μg/day. The toxicity of selenium to animals varies with the amounts of chemical forms of selenium ingested, with the duration and continuity of intake, and with the type and nature of the diet, especially its protein and sulfate content. Deficiency of selenium results in selenium responsive diseases in various animal species, such as muscular dystrophy, exudative diathesis and hepatosis dietetica. Selenium also prevents several type of chemically induced cancer in animals, and, where more selenium occurs in the environment, human cancer death rates are lower. Selenium deficient rats and lambs develop abnormal electrocardiograms accompanied by blood pressure changes. Human heart disease mortality is also lower in the high selenium areas. In China, a large clinical trial is underway showing that selenium prevents a congestive heart failure in children from severely selenium deficient areas.

Collagenase

This study reports the use of a purified form of the enzyme collagenase (Nucleolysin) to effect dissolution of the normal nucleus pulposus in a series of dogs and monkeys. A consistent dissolution effect has been observed. The toxicity of the enzyme to surrounding local tissues has been studied in the same species with an indication of safety in all areas other than intrathecal administration. A margin of safety in intrathecal administration between the effective dose and toxic dose has been suggested in the monkey. Mice LD50 studies and systemic toxicity studies in dogs show a satisfactory margin of safety for this enzyme. Guinea pig studies show no significant antigenicity.