Creep, failure and fracture of ice

A finite element creep bending model has been developed using thick plate theory. The model agrees very well with numerical creep models and with field data collected during a load bearing capacity test of fresh-water ice. A simple numerical formula is derived which can predict the time of the onset of failure using the critical strain energy as a failure criterion. This formula agrees very well with available field data. -- An algorithm has been developed which is able to predict the viscoelastic response of ice under different uniaxial loading conditions. This algorithm has been generalized using the finite element method to predict the viscoelastic response due to multiaxial loading. The general finite element model is capable of solving the ice cover - offshore structure interaction problem. A similar procedure has been used to predict the viscoelastic response of the cracked three-point bend test specimen due to constant cross-head speed loading. -- The linear and non-linear fracture toughness of artificially grown fresh-water ice has been determined during a small-scale experimental program. The effect of rate of loading, test temperature, specimen dimensions, and grain size on fracture toughness has been investigated. -- Finally, the strain rate dependent, critical strain energy per unit volume has been proposed as a failure criterion for ice under different loading rates. The criterion is applicable to ice failure during a laboratory test and failure of ice covers due to interaction with an offshore structure or due to supporting a load for short or long periods of time

Flavonoid Metabolomics in Gerbera hybrida and Elucidation of Complexity in the Flavonoid Biosynthetic Pathway

The flavonoid biosynthetic pathway and flavonoid metabolites have been extensively studied because of their biological roles in plant and animal kingdoms. Flavonoid metabolites are involved in plant resistance, UV-protection, pollinator attraction and have antioxidant effects. Plant species synthesise a large number of secondary metabolites, including flavonoids, carotenoids and others. Flower colour is an important feature for marketing of the ornamental model plant gerbera (Gerbera hybrida). In gerbera, flavonoid metabolites accumulate in the adaxial epidermal layer of flower petals and lead to different flower colours and patterns. These metabolites consist of three subgroups, flavones, flavonols and anthocyanins in gerbera, which have also been used to characterize different cultivars. The cultivars show variation in flower colour according to their anthocyanin type. The acyanic gerbera cultivars have flavonoid profiles comparable to the cyanic cultivars, except for the synthesis and accumulation of specific anthocyanins. Metabolite profiles indicated that all analysed acyanic cultivars have a block in a late stage of the anthocyanin pathway. Ivory, a sport of the pelargonidin-cultivar Estelle, has white flowers. Ivory has flavones and flavonols, but no anthocyanin. Gene expression of all flavonoid pathway genes was similar in Estelle and Ivory. However, both cultivars have two different alleles encoding dihydroflavonol 4-reductase and in Ivory one of them (GDFR1-2) was found to have a point mutation resulting in inactivation of the encoded enzyme. Still, Ivory expresses the second allele (GDFR1-3) and accumulates active DFR enzyme. The cyanidin cultivar President expresses only the GDFR1-3 allele, but cannot synthesize pelargonidin. Therefore, GDFR1-2 contributes specifically to pelargonidin biosynthesis and GDFR1-3 to cyanidin biosynthesis. This could be explained by a coordinated biosynthesis of anthocyanins in multi-enzyme complexes, metabolons. Gerbera chalcone synthases (GCHSs) belong to the superfamily of Type III polyketide synthase enzymes. GCHS1, 3 and 4 have different contributions to the flavonoid pathway, according to the tissue specific and post-transcriptional regulation. RNA interference of CHS encoding genes was used in different gerbera cultivars to show that GCHS1 has the main contribution to anthocyanin accumulation in petal tissues. GCHS4 was strongly expressed in petals but did not lead to anthocyanin accumulation. Still, GCHS4 is expressed and encoded a functional enzyme in the vegetative tissues.Flavonoidit ovat kasvien fenolisia yhdisteitä, jotka voivat olla värittömiä (flavonit ja flavonolit) tai oranssin, punaisen tai sinisen sävyisiä pigmenttejä (antosyaanit). Flavonodit suojaavat kasvia UV-säteilyltä ja taudinaiheuttajilta, ja toisaalta houkuttelevat hyödyllisiä pölyttäjiä. Flavonoidit ovat ravinnossa tärkeitä antioksidantteja ja niiden biosynteesiä on tutkittu paljon. Tässä työssä tutkittiin koristekasvina tunnetun gerberan kukinnon flavonoidien kemiaa, entsymologiaa ja geeniekspressiota. Materiaalina käytettiin lajikkeita, jotka sisälsivät flavoneja (apigeniinia tai luteiinia), flavonoleja (kemferolia tai kversetiiniä) ja/tai antosyaaneja (pelargonidiineja tai syanidiineja). Punaisesta Estelle-lajikkeen sivuhaarana syntyneessä valkoisessa Ivory-lajikkeessa todettiin mutaatio antosyaanibiosynteesille tärkeässä DFR-entsyymiä koodaavassa geenissä. Toinen DFR-alleeli kuitenkin koodasi toimivaa entsyymiä, joka kasvissa ei johtanut pigmentin biosynteesiin vaikka geeni ilmeni. Samalla tavalla flavonoidireitin alkupäässä olevan CHS-entsyymin kohdalla todettiin, että kahdesta kukinnossa ilmenevästä muodosta vain toinen oli tärkeä kukinnon antosyaanien biosynteesille. Toinen vastasi lehtiruotiin muodostuvasta antosyaanista. Yhteenvetona voidaan todeta, että flavonodien biosynteesiä säädellään geberalla geenitoiminnan lisäksi myös proteiinitasolla

Comparing the Efficacy of Custodiol and Cold Blood Cardioplegia in Myocardial Preservation

Background: Strategies for myocardial protection vary among surgeons, and data on the optimal cardioplegia solution are insufficient. The perfect cardioplegia solution for myocardial protection during cardiac surgery is still controversial. This study aimed to compare the efficacy of custodiol and cold blood cardioplegia in preserving the myocardium. Methods: In this comparative prospective study, the patients were split into two groups of 60 patients each. Group A received Custodiol HTK solution, whereas Group B received cold blood cardioplegia. Preoperative laboratory investigations, operative data, postoperative ICU stays, and complications were compared between groups. Results: The number of cardioplegia doses was significantly greater in Group B (1.05 ± 0.22, vs. 1.90 ± 0.82; p<0.001). There were no significant differences between the cardioplegia groups regarding hospital stay (p= 0.246), intensive care unit stay (p= 0.144), mortality (p= 0.769), low cardiac output (p>0.99), postoperative myocardial infarction (p= 0.432), intra-aortic balloon pump insertion (p= 0.224), reoperation (p>0.99), duration of mechanical ventilation (p= 0.389), pulmonary complications (p= 0.432), stroke (p>0.99), or the need for renal dialysis (p= 0.559). Conclusions: Custodiol cardioplegia could be advantageous in cardiac surgeries when a longer duration is expected. However, this study did not report differences in postoperative outcomes between patients with custodiol or cold blood cardioplegia

Risk factors of falls among elderly living in Urban Suez - Egypt

Introduction: Falling is one of the most common geriatric syndromes threatening the independence of older persons. Falls result from a complex and interactive mix of biological or medical, behavioral and environmental factors, many of which are preventable. Studying these diverse risk factors would aid early detection and management of them at the primary care level. Methods: This is a cross sectional study about risk factors of falls was conducted to 340 elders in Urban Suez. Those are all patients over 60 who attended two family practice centers in Urban Suez. Results: When asked about falling during the past 12 months, 205 elders recalled at least one incident of falling. Of them, 36% had their falls outdoors and 24% mentioned that stairs was the most prevalent site for indoor falls. Falls were also reported more among dependant than independent elderly. Using univariate regression analysis, almost all tested risk factors were significantly associated with falls in the studied population. These risk factors include: living alone, having chronic diseases, using medications, having a physical deficit, being in active, and having a high nutritional risk. However, the multivariate regression analysis proved that the strongest risk factors are low level of physical activity with OR 0.6 and P value 0.03, using a cane or walker (OR 1.69 and P value 0.001) and Impairment of daily living activities (OR 1.7 and P value 0.001). Conclusion: Although falls is a serious problem among elderly with many consequences, it has many preventable risk factors. Health care providers should advice people to remain active and more research is needed in such an important area of Family Practice.Pan African Medical Journal 2013; 14:2

Microfabrication of net shape zirconia/alumina nanocomposite micro parts

Recently, there are growing demands in manufacturing of net shape micro parts for wide range of applications due to the increasing interest in miniaturization. In this paper, the fabrication of tetragonal phase zirconia/alumina (YSZ/Al2O3) nanocomposite micro-parts with high quality is presented. The fabrication process is based on soft lithography and colloidal powder dispersion. Experimental results showed that by optimizing the soft lithography and the dispersion process, it was possible to produce high-resolution micro-parts with well dispersed alumina. The X-ray diffraction results had confirmed the important role of the alumina particles in eliminating the emergence of monoclinic phase while the microstructures reveal a pure tetragonal phase. In addition, the sintered YSZ/Al2O3 micro parts achieved micro hardness with 20% superior to the pure YSZ sintered micro-parts with the addition of 5% alumina

Bifilm defects and porosity in Al cast alloys

Liquid Al and Mg-base alloys are so reactive that it is reasonable to assume that the surface layer is always oxidised. If liquid aluminium entered a mould cavity with a velocity greater than a critical value, the surface skin of the liquid metal would fold over onto itself and be submerged into the bulk liquid with a volume of air entrapped within it, creating what is called a bifilm defect. This defect not only acts as a crack but also it is recognized to initiate hydrogen porosity in the solidified casting, which has been found to have detrimental effects on the tensile and fatigue properties of the castings produced. Previous research suggested that during solidification the hydrogen, in excess of the solubility limit, comes out of solution and diffuses into the bifilm gap, expanding it into a pore. Also, placing liquid metal in a vacuum may cause its entrained bifilms to expand, enhancing their buoyancy and therefore their floatation to the surface of the melt. In this work, a casting from an A356 Al alloy was allowed to solidify under vacuum. The solidified casting was sectioned into two halves, and the internal surfaces of the pores were investigated using an SEM to determine their relationship with double oxide film defects

The improved giant magnetostrictive actuator oscillations via positive position feedback damper

This article contemplates the demeanor of the giant magnetostrictive actuator (GMA) when a positive position feedback (PPF) damper is used to enable tight control over its vibration. The methodology followed here mathematically searches for the approximate solution for the motion equations of the GMA with the PPF damper, which has been accomplished by using one of the most famous perturbation methods. The multiple scale perturbation technique (MSPT) of the second-order approximation is our strategy to obtain the analytical results. The stability of the system has also been investigated and observed by implementing frequency response equations to close the concurrent primary and internal resonance cases. By utilizing Matlab and Maple programs, all numerical discussions have been accomplished and explained. The resulting influence on the amplitude due to changes in the parameters' values has been studied by the frequency response curves. Finally, a comparison between both the analytical and numerical solutions using time history and response curves is made. In addition to the comparison between our PPF damper's effect on the GMA, previous works are presented. To get our target in this article, we have mentioned some important applications utilized in the GMA system just to imagine the importance of controlling the GMA vibration

Effect of Nickel Content on the Corrosion Resistance of Iron-Nickel Alloys in Concentrated Hydrochloric Acid Pickling Solutions

The effect of Ni content on the resistance against corrosion of Fe-36% Ni and Fe-45% Ni alloys in 1 M hydrochloric acid pickling solution was reported. Various electrochemical and spectroscopic techniques such as potentiodynamic cyclic polarization (CPP), open-circuit potential (OCP), electrochemical impedance spectroscopy (EIS), potentiostatic current-time (PCT), and scanning electron microscopy (SEM), and energy dispersive spectroscopy (EDS) have been employed. CPP measurements indicated that the corrosion current and corrosion rate recorded lower values for the alloy that had higher nickel content. OCP curves proved that the presence of high Ni content shifts the absolute potential to the positive potential direction. EIS results revealed that the surface and polarization resistances were much higher for the alloy with higher Ni content. PCT curves also showed that the absolute currents were lower for Fe-45% Ni alloy. All results were in good agreement with others and confirmed clearly that the corrosion resistance in HCl solutions for Fe-45% Ni alloy was higher than that obtained for Fe-45% Ni alloy