Antioxidant and spermatozoa: a complex story- A review

The artificial insemination is a common practice in domestic animals, but the use of frozen semen compromises the fertility of goat spermatozoa based on pregnancy rates from AI. This could be due to a poor resistance of goat spermatozoa to cryopreservation stresses compared to sperm from other domesticated mammals. Lipid peroxidation caused by reactive oxygen species limits the success in this species. Reports revealed that inclusion of antioxidants in cryopreservation media improved quality of semen against LPO. Moreover, inclusion of enzymatic and nonenzymatic antioxidants (vitamin C, glutathione reduced etc) in diluents at appropriate concentration can help in holding the semen at refrigeration temperature for many days

Soil biological properties as influenced by long-term manuring and fertilization under sorghum (Sorghum bicolor) -wheat (Triticum aestivum) sequence in Vertisols

The effect of long-term manuring and fertilization on soil biological properties was studied under the long term fertilizer experiment on sorghum [Sorghum bicolor (L.) Moench] -wheat (Triticum aestivum L.) sequence conducted on Vertisols. The treatments comprised 50% RDF, 100% RDF, 150% RDF,100% RDF (-S), 100% RDF + 2.5 kg Zn/ ha to wheat crop only, 100% RD of NP, 100% RD of N, 100% RDF + FYM @ 10 tonnes/ha, 100% RDF + S @ 37.5 kg/ ha, FYM @ 10 tonnes/ha, 75% RDF and control. The assessment of soil biological properties at 40 and 70 days after sowing revealed that, significantly highest CO2 evolution was recorded at 70 DAS of sorghum under 100% RDF + FYM @ 10 tonnes/ ha ( 66.82 mg/ 100 kg). Soil microbial biomass carbon was also influenced significantly with the combined application of NPK+FYM (278.9 mg/ kg). The soil enzyme activity, viz. dehydrogenase (55.01 µg TPF/g/24 hr), urease (47.9 mg NH4/kg/ 24 hr) and cellulase (52.23 µg glucose/g/24 hr) were significantly influenced with the application of 100% RDF + FYM @ 10 tonnes/ha. Similarly, the application of 100% RDF + FYM @ 10 tonnes/ha recorded significantly higher grain yield of sorghum

Quasiparticle bandgap engineering of graphene and graphone on hexagonal boron nitride substrate

Graphene holds great promise for post-silicon electronics, however, it faces two main challenges: opening up a bandgap and finding a suitable substrate material. In principle, graphene on hexagonal boron nitride (hBN) substrate provides potential system to overcome these challenges. Recent theoretical and experimental studies have provided conflicting results: while theoretical studies suggested a possibility of a finite bandgap of graphene on hBN, recent experimental studies find no bandgap. Using the first-principles density functional method and the many-body perturbation theory, we have studied graphene on hBN substrate. A Bernal stacked graphene on hBN has a bandgap on the order of 0.1 eV, which disappears when graphene is misaligned with respect to hBN. The latter is the likely scenario in realistic devices. In contrast, if graphene supported on hBN is hydrogenated, the resulting system (graphone) exhibits bandgaps larger than 2.5 eV. While the bandgap opening in graphene/hBN is due to symmetry breaking and is vulnerable to slight perturbation such as misalignment, the graphone bandgap is due to chemical functionalization and is robust in the presence of misalignment. The bandgap of graphone reduces by about 1 eV when it is supported on hBN due to the polarization effects at the graphone/hBN interface. The band offsets at graphone/hBN interface indicate that hBN can be used not only as a substrate but also as a dielectric in the field effect devices employing graphone as a channel material. Our study could open up new way of bandgap engineering in graphene based nanostructures.Comment: 8 pages, 4 figures; Nano Letters, Publication Date (Web): Oct. 25 2011, http://pubs.acs.org/doi/abs/10.1021/nl202725

Towards understanding the myometrial physiome: approaches for the construction of a virtual physiological uterus

Premature labour (PTL) is the single most significant factor contributing to neonatal morbidity in Europe with enormous attendant healthcare and social costs. Consequently, it remains a major challenge to alleviate the cause and impact of this condition. Our ability to improve the diagnosis and treatment of women most at risk of PTL is, however, actually hampered by an incomplete understanding of the ways in which the functions of the uterine myocyte are integrated to effect an appropriate biological response at the multicellular whole organ system. The level of organization required to co-ordinate labouring uterine contractile effort in time and space can be considered immense. There is a multitude of what might be considered mini-systems involved, each with their own regulatory feedback cycles, yet they each, in turn, will influence the behaviour of a related system. These include, but are not exclusive to, gestational-dependent regulation of transcription, translation, post-translational modifications, intracellular signaling dynamics, cell morphology, intercellular communication and tissue level morphology. We propose that in order to comprehend how these mini-systems integrate to facilitate uterine contraction during labour (preterm or term) we must, in concert with biological experimentation, construct detailed mathematical descriptions of our findings. This serves three purposes: firstly, providing a quantitative description of series of complex observations; secondly, proferring a database platform that informs further testable experimentation; thirdly, advancing towards the establishment of a virtual physiological uterus and in silico clinical diagnosis and treatment of PTL

Use of chelating agent for optimum post thaw quality of buck semen

Ejaculates (35) from adult Sirohi bucks (2–4 years old) were utilized for the present study to find out the freezability of buck semen at different levels of chelating agent used (ethylene diamine tetra acetic acid - EDTA: 0, 0.01, 0.05 and 0.1%) by conventional method of freezing. The ejaculates were collected twice at weekly intervals using artificial vagina and were extended to maintain sperms concentration approximately 100 million / dose (0.25 ml) with tris- citric acid- fructose (TCF) diluent having 10% (v/v) egg yolk and 6% (v/v) glycerol as cryo protecting agent. Filling and sealing of straws were done at 5ºC in cold handing cabinet after 4 h of equilibration period then straws were vapor frozen for 10 min above 2 cm of liquid nitrogen and finally put in to liquid nitrogen. Post thaw motility, live sperm count, abnormalities, acrosomal integrity and hypo osmotic swelling test had been conducted to know freezability. Analysis of data using SPSS 16 revealed that post thaw motility, live sperm count, abnormalities, acrosomal integrity and hypo osmotic swelling positive spermatozoa differed significantly at different levels of EDTA. The post thaw motility, live sperm count, acrosomal integrity and hypo osmotic swelling positive spermatozoa were significantly highest in 0.1% of EDTA used in the present study. So, 0.01% EDTA can be used as an additive in semen dilutor in routine freezing process for better post thaw recovery of buck semen

Atomically thin boron nitride: a tunnelling barrier for graphene devices

We investigate the electronic properties of heterostructures based on ultrathin hexagonal boron nitride (h-BN) crystalline layers sandwiched between two layers of graphene as well as other conducting materials (graphite, gold). The tunnel conductance depends exponentially on the number of h-BN atomic layers, down to a monolayer thickness. Exponential behaviour of I-V characteristics for graphene/BN/graphene and graphite/BN/graphite devices is determined mainly by the changes in the density of states with bias voltage in the electrodes. Conductive atomic force microscopy scans across h-BN terraces of different thickness reveal a high level of uniformity in the tunnel current. Our results demonstrate that atomically thin h-BN acts as a defect-free dielectric with a high breakdown field; it offers great potential for applications in tunnel devices and in field-effect transistors with a high carrier density in the conducting channel.Comment: 7 pages, 5 figure

Influence of cysteamine supplementation during in vitro culture of early stage caprine embryos on blastocyst production

The objective of this study was to evaluate the effect of cysteamine supplementation on embryo development in mCR2 media. The COCs (1251) were matured in TCM–199 medium containing FSH (5µg/ml), LH (10µg/ml), follicular fluid (10%), FBS (10%) with 3 mg/ml BSA for 27h at 38.5°C and 5% CO2 in an incubator. Matured oocytes were co-cultured with 1×106 spermatozoa/ml collected from a Sirohi buck in fertTALP (10% FBS+ 4mg/ml BSA and 10 µg/ml heparin) for 18 h in incubation. After 18 h of sperm-oocytes, co-incubation of oocytes with sperms were washed in embryo development medium to remove sperm cells adhered to zonapellucida. Presumptive zygotes (1,171) were selected and randomly divided into 2 groups. Group 1, the presumptive zygotes (610) were cultured in mCR2aa as a control for 12 days. Group 2, the presumptive zygotes (561) were culture in mCR2aa medium supplemented with 100 µM cysteamine for 10 days. The percentage of cleavage, morula, and blastocyst production in groups 1 and 2 were 36.39% and 31.71% (cleavage); 21.62% and 30.89% (morula); 4.95% and 8.98% (blastocyst) respectively. In conclusion, results indicated that the addition of cysteamine to the IVC medium stimulates caprine embryo development and blastocyst production

Effect of Layer-Stacking on the Electronic Structure of Graphene Nanoribbons

The evolution of electronic structure of graphene nanoribbons (GNRs) as a function of the number of layers stacked together is investigated using \textit{ab initio} density functional theory (DFT) including interlayer van der Waals interactions. Multilayer armchair GNRs (AGNRs), similar to single-layer AGNRs, exhibit three classes of band gaps depending on their width. In zigzag GNRs (ZGNRs), the geometry relaxation resulting from interlayer interactions plays a crucial role in determining the magnetic polarization and the band structure. The antiferromagnetic (AF) interlayer coupling is more stable compared to the ferromagnetic (FM) interlayer coupling. ZGNRs with the AF in-layer and AF interlayer coupling have a finite band gap while ZGNRs with the FM in-layer and AF interlayer coupling do not have a band gap. The ground state of the bi-layer ZGNR is non-magnetic with a small but finite band gap. The magnetic ordering is less stable in multilayer ZGNRs compared to single-layer ZGNRs. The quasipartcle GW corrections are smaller for bilayer GNRs compared to single-layer GNRs because of the reduced Coulomb effects in bilayer GNRs compared to single-layer GNRs.Comment: 10 pages, 5 figure

Quantitative Excited State Spectroscopy of a Single InGaAs Quantum Dot Molecule through Multi-million Atom Electronic Structure Calculations

Atomistic electronic structure calculations are performed to study the coherent inter-dot couplings of the electronic states in a single InGaAs quantum dot molecule. The experimentally observed excitonic spectrum [12] is quantitatively reproduced, and the correct energy states are identified based on a previously validated atomistic tight binding model. The extended devices are represented explicitly in space with 15 million atom structures. An excited state spectroscopy technique is presented in which the externally applied electric field is swept to probe the ladder of the electronic energy levels (electron or hole) of one quantum dot through anti-crossings with the energy levels of the other quantum dot in a two quantum dot molecule. This technique can be applied to estimate the spatial electron-hole spacing inside the quantum dot molecule as well as to reverse engineer quantum dot geometry parameters such as the quantum dot separation. Crystal deformation induced piezoelectric effects have been discussed in the literature as minor perturbations lifting degeneracies of the electron excited (P and D) states, thus affecting polarization alignment of wave function lobes for III-V Heterostructures such as single InAs/GaAs quantum dots. In contrast this work demonstrates the crucial importance of piezoelectricity to resolve the symmetries and energies of the excited states through matching the experimentally measured spectrum in an InGaAs quantum dot molecule under the influence of an electric field. Both linear and quadratic piezoelectric effects are studied for the first time for a quantum dot molecule and demonstrated to be indeed important. The net piezoelectric contribution is found to be critical in determining the correct energy spectrum, which is in contrast to recent studies reporting vanishing net piezoelectric contributions.Comment: Accepted for publication in IOP Nanotechnology Journa

Tuning ultrafast electron thermalization pathways in a van der Waals heterostructure

Ultrafast electron thermalization - the process leading to Auger recombination, carrier multiplication via impact ionization and hot carrier luminescence - occurs when optically excited electrons in a material undergo rapid electron-electron scattering to redistribute excess energy and reach electronic thermal equilibrium. Due to extremely short time and length scales, the measurement and manipulation of electron thermalization in nanoscale devices remains challenging even with the most advanced ultrafast laser techniques. Here, we overcome this challenge by leveraging the atomic thinness of two-dimensional van der Waals (vdW) materials in order to introduce a highly tunable electron transfer pathway that directly competes with electron thermalization. We realize this scheme in a graphene-boron nitride-graphene (G-BN-G) vdW heterostructure, through which optically excited carriers are transported from one graphene layer to the other. By applying an interlayer bias voltage or varying the excitation photon energy, interlayer carrier transport can be controlled to occur faster or slower than the intralayer scattering events, thus effectively tuning the electron thermalization pathways in graphene. Our findings, which demonstrate a novel means to probe and directly modulate electron energy transport in nanoscale materials, represent an important step toward designing and implementing novel optoelectronic and energy-harvesting devices with tailored microscopic properties.Comment: Accepted to Nature Physic