We study composition operators between variable exponent Lebesgue spaces and characterize boundedness and compactness of the composition operators on a variable exponent Lebesgue space. We also ...derive a sufficient condition for composition operator to have a closed range and explain some properties which these operators share with the case of Lebesgue spaces.
A rapid high-resolution genome-wide strategy for molecular mapping of major QTL(s)/gene(s) regulating important agronomic traits is vital for in-depth dissection of complex quantitative traits and ...genetic enhancement in chickpea. The present study for the first time employed a NGS-based whole-genome QTL-seq strategy to identify one major genomic region harbouring a robust 100-seed weight QTL using an intra-specific 221 chickpea mapping population (desi cv. ICC 7184 × desi cv. ICC 15061). The QTL-seq-derived major SW QTL (CaqSW1.1) was further validated by single-nucleotide polymorphism (SNP) and simple sequence repeat (SSR) marker-based traditional QTL mapping (47.6% R(2) at higher LOD >19). This reflects the reliability and efficacy of QTL-seq as a strategy for rapid genome-wide scanning and fine mapping of major trait regulatory QTLs in chickpea. The use of QTL-seq and classical QTL mapping in combination narrowed down the 1.37 Mb (comprising 177 genes) major SW QTL (CaqSW1.1) region into a 35 kb genomic interval on desi chickpea chromosome 1 containing six genes. One coding SNP (G/A)-carrying constitutive photomorphogenic9 (COP9) signalosome complex subunit 8 (CSN8) gene of these exhibited seed-specific expression, including pronounced differential up-/down-regulation in low and high seed weight mapping parents and homozygous individuals during seed development. The coding SNP mined in this potential seed weight-governing candidate CSN8 gene was found to be present exclusively in all cultivated species/genotypes, but not in any wild species/genotypes of primary, secondary and tertiary gene pools. This indicates the effect of strong artificial and/or natural selection pressure on target SW locus during chickpea domestication. The proposed QTL-seq-driven integrated genome-wide strategy has potential to delineate major candidate gene(s) harbouring a robust trait regulatory QTL rapidly with optimal use of resources. This will further assist us to extrapolate the molecular mechanism underlying complex quantitative traits at a genome-wide scale leading to fast-paced marker-assisted genetic improvement in diverse crop plants, including chickpea.
Autogenous dissimilar welding of oxygen-free copper to austenitic stainless steel AISI316 was successfully performed by electron beam welding (EBW) using strategic base metal plate tilt of 22 deg and ...beam shift. The effect of focus distance, beam current, and travel speed on the tensile strength, percent elongation, and impact strength of the welded joints was investigated. The maximum tensile strength was achieved to be 282 MPa at a focus distance of 20 mm, a beam current of 40 mA, and a travel speed of 400 mm/min. Elemental integrity was examined through a continuous energy-dispersive spectroscopy (EDS) scan across the joint for all the welded samples. It was observed that the concentration of elements Fe, Cr, and Ni increased, and that of Cu decreased from the copper region to stainless steel (SS) in the weld zone. The microstructures and microhardness profile of the welded joint were studied. A lower microhardness value was present in the weld region due to a higher fraction of Cu in the weld compared with that of SS. Thus, the balance of energy over the dissimilar materials effectively allowed autogenous welding of a pair of materials which is challenging to join.
An evaluation of the crack growth resistance of human coronal dentin was performed on tissue obtained from patients between ages 18 and 83. Stable crack extension was achieved over clinically ...relevant lengths (
0
≤
a
≤
1
mm
) under Mode I quasi-static loading and perpendicular to the nominal tubule direction. Results distinguished that human dentin exhibits an increase in crack growth resistance with extension (i.e. rising
R
-curve) and that there is a significant reduction in both the initiation (K
o) and plateau (K
p
) components of toughness with patient age. In the young dentin (
18
≤
age
≤
35
) there was a 25% increase in the crack growth resistance from the onset of extension (K
o=1.34 MPa m
0.5) to the maximum or “plateau” toughness (K
p=1.65 MPa m
0.5). In comparison, the crack growth resistance of the old dentin (
55
≤
age
) increased with extension by less than 10% from K
o
=1.08 MPa m
0.5 to K
p
=1.17 MPa m
0.5. In young dentin toughening was achieved by a combination of inelastic deformation of the mineralized collagen matrix and microcracking of the peritubular cuffs. These mechanisms facilitated further toughening via the development of unbroken ligaments of tissue and posterior crack-bridging. Microstructural changes with aging decreased the capacity for near-tip inelastic deformation and microcracking of the tubules, which in turn suppressed the formation of unbroken ligaments and the degree of extrinsic toughening.
Bronchial asthma is one of the common chronic respiratory illnesses worldwide, with a global disease burden that affects approximately 300 million individuals. It affects 5-10% of the population in ...developed countries. India constitutes approximately one-tenth of the global disease burden, where an estimated 7 million children are affected by this illness. Airway hyperresponsiveness or bronchial hyperreactivity in asthma is an exaggerated response to numerous exogenous and endogenous stimuli. In India, the most important endogenous stimuli is considered to be fungal antigens from the genus, Aspergillus. Positive skin reactions to Aspergillus fumigatus among individuals with atopic asthma is 10 to 20%; however, a causal relationship is yet to be established. A separate entity, termed "severe asthma with fungal sensitivity," is often used to describe milder allergic reactions to fungal aeroallergens that has fungal sensitization as the starting point of pathogenesis than allergic bronchopulmonary aspergillosis.
A total of 57 patients with bronchial asthma were prospectively enrolled and evaluated for Aspergillus sensitization and its impact on asthma control.
Symptoms were well controlled in a majority of patients (57.89%) and partly controlled in 14.04%. Uncontrolled symptoms were observed in only 28.07% of patients. The proportion of patients with uncontrolled symptoms was higher among patients who were sensitized (45.00%) compared with patients who were not sensitized (18.92%). The proportion of patients with well-controlled symptoms was higher in individuals who were not sensitized compared with individuals who were sensitized (62.16% versus 50.00%).
The severity of asthma was associated with fungal sensitization, with sensitization to Aspergillus as a part of the pathogenesis. Aspergillus sensitization is significantly associated with bronchiectasis, even in the absence of clinical features.
Fatigue of biomaterials: Hard tissues Arola, D.; Bajaj, D.; Ivancik, J. ...
International journal of fatigue,
09/2010, Letnik:
32, Številka:
9
Journal Article
Recenzirano
Odprti dostop
The fatigue and fracture behavior of hard tissues are topics of considerable interest today. This special group of organic materials comprises the mineralized (roughly 50% mineral by volume or ...greater) and load-bearing tissues of the human body; it includes bone, cementum, dentin and enamel. An understanding of their fatigue behavior and the influence of loading conditions and physiological factors (e.g. aging and disease) on the mechanisms of degradation are essential for achieving lifelong health. But there is much more to this topic than the immediate medical issues. There are many challenges to characterizing the fatigue behavior of hard tissues, much of which is attributed to size constraints and the complexity of their microstructure. The relative importance of the constituents on the type and distribution of defects, rate of coalescence, and their contributions to the initiation and growth of cracks, are formidable topics that have not reached maturity. Hard tissues also provide a medium for learning and a source of inspiration in the design of new microstructures for engineering materials. This article briefly reviews fatigue of hard tissues with shared emphasis on current understanding, the challenges and the unanswered questions.
An understanding of the fatigue and fracture behavior of hard tissues (e.g., bone and tissues of the human tooth) is critical to the maintenance of physical and oral health. Recent studies suggest ...that there are a number of mechanisms contributing to crack extension and crack arrest in these materials, and that they appear to be a function of moisture and age of the tissue. An understanding of these processes can provide new ideas that are relevant to the design of multi-functional engineering materials. As a result, we have adopted the use of microscopic Digital Image Correlation (DIC) to examine the mechanisms of crack growth resistance and near-tip displacement distribution for cracks in human dentin that are subjected to opening mode loads. We have also developed a special compact tension (CT) specimen that permits evaluation of crack extension within small portions of tissue under both quasi-static and fatigue loads. The specimen embodies a selected portion of hard tissue within a resin composite restorative and enables an examination of diseased tissue, or portion with specific physiology, that would otherwise be impossible to evaluate. In this paper we describe application of these experimental methods and present some recent results concerning fatigue crack growth and stable crack extension in dentin and across the dentin-enamel-junction (DEJ) of human teeth.
Although striations are often used in evaluating fatigue crack growth in engineering materials, they have not been used in studying the mechanics of fracture in hard tissues. The primary objective of ...this study was to evaluate the striations resulting from fatigue crack growth in the dentin of human teeth. Compact tension (CT) specimens obtained from the coronal dentin of molars from young (17 < or = age < or = 37 years) and senior (age > or = 50 years) patients were subjected to cyclic Mode I loads. Striations evident on the fracture surfaces were examined using a scanning electron microscope (SEM) and contact profilometer. Fatigue crack growth striations that developed in vivo were also examined on fracture surfaces of restored molars. A power spectrum analysis of surface profiles from the CT specimens showed that the striation spacing ranged from 50 to 170 microm. The average spacing in the dentin of seniors (130 +/- 23 microm) was significantly larger (p < 0.001) than that in young dentin (88 +/- 13 microm). Fatigue striations in the restored teeth exhibited features that were consistent with those that developed in vitro and a spacing ranging from 59 to 95 microm. Unlike metals, the striations in dentin developed after a period of cyclic loading that ranged from 1 x 10(3) to 1 x 10(5) cycles. A quantitative evaluation of the striation spacing using the Bates-Clark equation suggested that cyclic crack growth within the restored teeth occurred at a stress intensity range near 0.7 MPa x m(0.5), and a stress range of approximately 12 MPa.
Abstract In this study the crack growth resistance behavior and fracture toughness of human tooth enamel were quantified using incremental crack growth measures and conventional fracture mechanics. ...Results showed that enamel undergoes an increase in crack growth resistance (i.e. rising R -curve) with crack extension from the outer to the inner enamel, and that the rise in toughness is a function of distance from the dentin enamel junction (DEJ). The outer enamel exhibited the lowest apparent toughness (0.67 ± 0.12 MPa m0.5 ), and the inner enamel exhibited a rise in the growth toughness from 1.13 MPa m0.5 /mm to 3.93 MPa m0.5 /mm. The maximum crack growth resistance at fracture (i.e. fracture toughness ( Kc )) ranged from 1.79 to 2.37 MPa m0.5 . Crack growth in the inner enamel was accompanied by a host of mechanisms operating from the micro- to the nano-scale. Decussation in the inner enamel promoted crack deflection and twist, resulting in a reduction of the local stress intensity at the crack tip. In addition, extrinsic mechanisms such as bridging by unbroken ligaments of the tissue and the organic matrix promoted crack closure. Microcracking due to loosening of prisms was also identified as an active source of energy dissipation. In summary, the unique microstructure of enamel in the decussated region promotes crack growth toughness that is approximately three times that of dentin and over ten times that of bone.
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