3,056 research outputs found
Comparisons of various configurations of the edge delamination test for interlaminar fracture toughness
Various configurations of Edge Delamination Tension (EDT) test specimens, of both brittle (T300/5208) and toughened-matrix (T300/BP907) graphite reinforced composite laminates, were manufactured and tested. The mixed-mode interlaminar fracture toughness, G sub C, was measured using (30/30 sub 2/30/90 sub N)sub s, n=1 or 2, (35/-35/0/90) sub s and (35/0/-35/90) sub s layups designed to delaminate at low tensile strains. Laminates were made without inserts so that delaminations would form naturally between the central 90 deg plies and the adjacent angle plies. Laminates were also made with Teflon inserts implanted between the 90 deg plies and the adjacent angle (theta) plies at the straight edge to obtain a planar fracture surface. In addition, interlaminar tension fracture toughness, GIc, was measured from laminates with the same layup but with inserts in the midplane, between the central 90 deg plies, at the straight edge. All of the EDT configurations were useful for ranking the delamination resistance of composites with different matrix resins. Furthermore, the variety of layups and configurations available yield interlaminar fracture toughness measurements needed to generate delamination failure criteria. The influence of insert thickness and location, and coupon size on G sub c values were evaluated
Anti-microbial and anti-corrosive poly (ester amide urethane) siloxane modified ZnO hybrid coatings from Thevetia peruviana seed oil
The utilization of renewable resources for the
development of organic coatings is a viable means of creating
alternatives to petroleum-based chemicals which are
not eco-friendly. This paper reports the synthesis of polyesteramide–
urethane–silica–zinc oxide hybrid coatings from
Thevetia peruviana seed oil (TPSO). The periphery of ZnO
nano-particles is modified with 3-aminopropyltrimethoxysilane
to prepare silica grafted ZnO composite particles.
The TPSO based polyesteramide was reacted with 4,40-
diisocyanatodicyclohexylmethane in presence of siloxane
modified ZnO to obtain –NCO terminated polyesteramide–
urethane–silica ZnO prepolymer. These hybrid pre-polymers
were casted on tin foil and cured under atmospheric
moisture to obtain eco-friendly, moisture cured polyesteramide–
urethanes–silica–zinc oxide hybrid coating films. The
synthesized polyester and polyurethane formation was confirmed
by using FT-IR and NMR spectroscopic techniques.The resultant hybrid coating films were characterized by
using FT-IR, TGA, DSC, SEM, corrosion resistance and
microbial resistance. Results confirm that with increase of
siloxane modified ZnO content in the polyurethane matrix
thermal stability, glass transition temperature and corrosion
resistance improved. The antibacterial activity shows that
the hybrid films exhibit excellent resistance towards Escherichia
coli and Staphylococcus aureus. The salt spray test
on coated panel samples show good corrosion resistance
properties
Renewable resource based novel antimicrobial polyesteramide-urethenehybrid coatings
The use of renewable resources for the development of coating materials is a viable means to reduce
environmental impact and support sustainability efforts. This paper describes a novel antimicrobial
polyesteramide-urethane-silica- Zinc Oxide (ZnO) hybrid coatings based on milk bush seed oil as
renewable resource. Initially ZnO nanoparticles were modified with aminopropyltrimethoxysilane to get
silica grafted ZnO composite particles. The milk bush oil based polyesteramide were reacted with
excess H12MDI to get NCO terminated polyesteramide-urethanes and the excess NCO was reacted
with silica grafted ZnO composite particles to get the reactive hybrid prepolymers. These prepolymers
were casted on tin foil and cured under atmospheric moisture to get eco-friendly moisture curing
polyesteramide-urethane-silica- Zinc Oxide (ZnO) hybrid coatings films. The coatings films were
evaluated for its antimicrobial and thermo mechanical properties while coated steel specimen were
used for corrosion studies. The techniques such as FTIR, TGA, DSC, DMTA, SEM and XRD have been
used in this study. The hybrid coating films has shown very good antibacterial and antifungal propertie$,
higher thermal stability and better thermo mechanical properties. The improvement in the properties
was dependent" on the concentration of ZnO composite particles in the coating films. The antibacterial
experiments show that the ZnO doped films exhibit excellent antibacterial activity, especially for E.coli.
The salt spray test on coated specimen show good corrosion resistance properties for hybrid coating
Expression of nestin - a stem cell associated intermediate filament in human CNS tumours
Background & objectives: Nestin is an intermediate filament protein expressed in undifferentiated cells during the development of brain and is considered as a marker for neuroepithelial stem cells. Expression of this protein in various CNS tumour cells suggests the possibility of existence of tumour stem cell modulating the evolution. We carried out an immunohistochemical study to demonstrate the expression of nestin and its co-expression with neuronal and glial intermediate filament and correlate with the grade of malignancy. Methods: Formalin fixed, paraffin processed sections from two human foetuses, 16 brain tumours of both neuronal and glial lineage and two metastatic tumours were immunostained with polyclonal antibody to nestin. Serial sections from primary brain tumours were also stained with monoclonal antibody to neurofilament (NF) and glial fibrillary acidic protein (GFAP). Fluorescent double labeling was carried out on four cases using laser confocal microscopy, to document co-localization of nestin with other intermediate filaments in the tumour cells. Results: Nestin expression was observed along the paraventricular zone of human foetuses and in brain tumours of both glial and neuronal lineage, of both high and low grades of malignancy. In addition, mature dysplastic spinal motor neurons adjacent to tumour and cerebellar Purkinje cells also expressed nestin along with neurofilament. Interpretation & conclusion: Nestin expression was noted in both low and high grade brain tumours and dysplastic neurons and did not parallel the malignant grade of the tumour. The expression of nestin in tumour cells and dysplastic neurons suggests aberrant expression of antigenically primitive proteins in cells to facilitate remodelling of the cell and migration. More studies are needed to elucidate the concept
Magneto-transport characteristics of La1.4Ca1.6Mn2O7 thin film deposited by spray pyrolysis
Polycrystalline thin films of double layer manganite La_1.4Ca_1.6Mn_2O_7
(DLCMO) have been deposited by nebulized spray pyrolysis on single crystal
LaAlO_3 substrates. These single phase films having grain size in the range
70-100 nm exhibit ferromagnetic transition at T_C ~ 107K. The short range
ferromagnetic ordering due to in plane spin coherence is evidenced to occur at
a higher temperature around 225 K. Insulator/semiconductor to metal transition
occurs at a lower temperature T_P ~ 55K. The transport mechanism above T_C is
of Mott`s variable range hopping type. Below T_C the current-voltage
characteristics show non-linear behaviour that becomes stronger with decreasing
temperature. At low temperatures below T_CA ~ 30K a magnetically frustrated
spin canted state is observed. The DLCMO films exhibit resonable low field
magnetoresistance and at 77K the magnetoresistance ratio is ~ 5% at 0.6 kOe and
\~ 13% at 3 kOe.Comment: 14 pages, 7 figure
Cooling rate dependence of the antiferromagnetic domain structure of a single crystalline charge ordered manganite
The low temperature phase of single crystals of NdCaMnO
and GdCaMnO manganites is investigated by squid
magnetometry. NdCaMnO undergoes a charge-ordering
transition at =245K, and a long range CE-type antiferromagnetic state
is established at =145K. The dc-magnetization shows a cooling rate
dependence below , associated with a weak spontaneous moment. The
associated excess magnetization is related to uncompensated spins in the
CE-type antiferromagnetic structure, and to the presence in this state of
fully orbital ordered regions separated by orbital domain walls. The observed
cooling rate dependence is interpreted to be a consequence of the rearrangement
of the orbital domain state induced by the large structural changes occurring
upon cooling.Comment: REVTeX4; 7 pages, 4 figures. Revised 2001/12/0
SYNTHESIS, CHARACTERIZATION AND ANTIBACTERIAL EVALUATIONS OF NOVEL HYBRID POLYESTERAMIDEURETHANES PREPARED FROM YELLOW OLEANDA SEED OIL
Air drying polyesteramide-urethanes resins were synthesized from Thevetia peruviana
seed oil commonly known as Yellow oleanda (a tropical ornamental shrub) having
about 68.8% unsaturated and 30.9% saturated fatty acids. The physico- chemical
characterization of the optimized unsaturated FAME such as hydroxyl value, iodine
value, saponification value, refractive index, inherent viscosity were carried out using
standard methods. Through condensation reaction the N,N'- bis(2-hydroxyethyl)
Thevetia peruviana (HETA) prepared from the FAME reacted with isophthalic acid to
form polyesteramide. The latter undergo urethanation with H1
'
2MDI. The structural
elucidation of the moisture cured polyesteramide-urethane coating was based on
FTIR, 1H-NMR and 13C-NMR spectroscopic methods. The coatings films were
evaluated for its antihacterial activity and thermal stability properties on TGA and
DSC. The SEM of the --uating films was also examined
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