Improved Memory Effect of ZnO Nanorods Embedded in an Insulating Polymethylmethacrylate Layer

Fabrication and characterization of memory devices using ZnO nanorod layer grown by chemical-bath method is reported. The fabricated memory device was found exhibit electrical bistability and nonvolatile memory phenomenon. An additional Polymethylmethacrylate (PMMA) polymer layer coated on ITO substrate prior to nanorod deposition has been found improve the LRS/HRS ratio of the device. The current-voltage characteristics of the memory devices are discussed in terms of formation and rupture of conductive filaments. The devices have shown consistent electrical bistable behavior even for 10(5) resistance-switching cycles. This hybrid ITO/PMMA-ZnO NRs/Al device has potential applications in the field of bistable random access memories.

CO2-selective PEO–PBT (PolyActive™)/graphene oxide composite membranes

CO₂-selective graphene oxide (GO) nano-composite membranes were prepared for the first time by embedding GO into a commercially available poly(ethylene oxide)–poly(butylene terephthalate) (PEO–PBT) copolymer (PolyActive™).

Role of solution pH on the microstructural properties of spin coated cobalt oxide thin films

Cobalt Oxide (Co3o4) thin films have been successfully coated onto glass substrates at various solution pH by sol-gel spin coating technique. The film thickness was estimated using weight gain method and it revealed that the film thickness increased with solution pH values. The prepared film structural, morphological, optical and electrical properties were studied using X-ray diffraction (XRD), scanning electron microscope (SEM), UV-Vis-NIR spectrophotometer and Vander Pau method, respectively. The structure of the films were found to be face centered cubic with preferential orientation along (311) plane. X-ray line profile analysis was used to evaluate the micro structural parameters such as crystallite size, micro strain, dislocation density and stacking fault probability. The crystallite size values are increased with increase of solution pH values and maximum value of crystallite is estimated at 40.8 nm at solution pH 8 +/- 0.1. Morphological results showed that the pH of the solution has a marked effect on morphology of the Co3O4 thin films. The optical studies revealed that the band gap can be tailored between 2.16 to 2.31 eV by altering pH. The thin film formed at a solution pH 7 is found to have a low resistivity and high mobility. The electrical resistivity (p), carrier concentration (n) and mobility (micro) values are 0.1 x 10(3) omega x cm, 8.9 cm2 gammas(-1) and 6.6 x 10(14) cm(-3), respectively for Co3O4 thin film prepared at solution pH 7 +/- 0.1. EDAX studies showed that the cobalt content increased and the oxygen content decreased with increase of pH.

Selective separation of similarly sized proteins with tunable nanoporous block copolymer membranes

An integral asymmetric membrane was fabricated in a fast and one-step process by combining the self-assembly of an amphiphilic block copolymer (PS-b-P4VP) with nonsolvent-induced phase separation. The structure was found to be composed of a thin layer of densely packed highly ordered cylindrical channels with uniform pore sizes perpendicular to the surface on top of a nonordered sponge-like layer. The as-assembled membrane obtained a water flux of more than 3200 L m(-2) h(-1) bar(-1), which was at least an order of magnitude higher than the water fluxes of commercially available membranes with comparable pore sizes, making this membrane particularly well suited to size-selective and charge-based separation of biomolecules. To test the performance of the membrane, we conducted diffusion experiments at the physiological pH of 7.4 using bovine serum albumin (BSA) and globulin-γ, two proteins with different diameters but too close in size (2-fold difference in molecular mass) to be efficiently separated via conventional dialysis membrane processes. The diffusion rate differed by a factor of 87, the highest value reported to date. We also analyzed charge-based diffusive transport and separation of two proteins of similar molecular weight (BSA and bovine hemoglobin (BHb)) through the membrane as a function of external pH. The membrane achieved a selectivity of about 10 at pH 4.7, the isoelectric point (pI) of BSA. We then positively charged the membrane to improve the separation selectivity. With the modified membrane BSA was completely blocked when the pH was 7.0, the pI of BHb, while BHb was completely blocked at pH 4.7. Our results demonstrate the potential of our asymmetric membrane to efficiently separate biological substances/pharmaceuticals in bioscience, biotechnology, and biomedicine applications.

From micelle supramolecular assemblies in selective solvents to isoporous membranes

The supramolecular assembly of PS-b-P4VP copolymer micelles induced by selective solvent mixtures was used to manufacture isoporous membranes. Micelle order in solution was confirmed by cryo-scanning electron microscopy in casting solutions, leading to ordered pore morphology. When dioxane, a solvent that interacts poorly with the micelle corona, was added to the solution, polymer-polymer segment contact was preferential, increasing the intermicelle contact. Immersion in water gave rise to asymmetric porous membranes with exceptional pore uniformity and high porosity. The introduction of a small number of carbon nanotubes to the casting solution improved the membrane stability and the reversibility of the gate response in the presence of different pH values.

Switchable pH-responsive polymeric membranes prepared via block copolymer micelle assembly

A process is described to manufacture monodisperse asymmetric pH-responsive nanochannels with very high densities (pore density >2 × 10(14) pores per m(2)), reproducible in m(2) scale. Cylindric pores with diameters in the sub-10 nm range and lengths in the 400 nm range were formed by self-assembly of metal-block copolymer complexes and nonsolvent-induced phase separation. The film morphology was tailored by taking into account the stability constants for a series of metal-polymer complexes and confirmed by AFM. The distribution of metal-copolymer micelles was imaged by transmission electron microscopy tomography. The pH response of the polymer nanochannels is the strongest reported with synthetic pores in the nm range (reversible flux increase of more than 2 orders of magnitude when switching the pH from 2 to 8) and could be demonstrated by cryo-field emission scanning electron microscopy, SAXS, and ultra/nanofiltration experiments.

Characterization of Mithun (Bos frontalis) ejaculates and fertility of cryopreserved sperm

Technologies for conservation and propagation of genetic resources in the Mithun (Bos frontalis), a rare semi-wild bovine species of Southeast Asia. Successful cryopreservation of Mithun semen would provide a potential vehicle to address above issue. To date, information on characteristics of Mithun ejaculates is not available and there are no reports of birth of live offspring using cryopreserved Mithun semen collected using AV method. A study was therefore conducted to (i) characterize the Mithun ejaculate, (ii) investigate the effectiveness of Mithun sperm cryopreservation, and (iii) determine whether artificial insemination using frozen-thawed Mithun sperm can result in live offspring. Semen samples collected from eight fertile Mithun bulls were evaluated for colour, consistency, volume, concentration, mass activity and progressive motility. The freshly ejaculated sperm were also evaluated for morphological abnormalities, live sperm counts, acrosome integrity, membrane stability (hypo-osmotic swelling test; HOST) and DNA integrity. Semen samples of good quality were cryopreserved in liquid nitrogen using Tris-egg yolk-glycerol diluent. Post-thaw quality of the cryopreserved sperm in terms of progressive motility, morphological abnormalities, live sperm counts, acrosome integrity, membrane stability and DNA integrity were assessed. In addition, 16 Mithun cows at estrus were inseminated with frozen-thawed Mithun sperm. Following cryopreservation, the percentage of progressive motility (fresh versus frozen-thawed), live sperm counts, morphological abnormalities, acrosome integrity, membrane stability and DNA integrity were found to decrease (P<0.01) with a motility recovery rate of 74+/-9%. Mithun cows inseminated with cryopreserved sperm result 75% conception rate and all the conceived cows maintained full-term pregnancy with delivery of live calves.

Early puberty in local Naga boar of India: assessment through epididymal spermiogram and in vivo pregnancy

Male Naga pig of India, a miniature breed is known for its meat quality and early puberty. No scientific efforts were made to verify the farmers' view that this breed reaches puberty at around 2 months of age. A preliminary study was, therefore, conducted with the objectives: (a) to find out the age at puberty based on mature spermiogram and in vivo pregnancy and (b) to record the sperm morphology in different parts of the epididymis. Animals were selected from two different age groups: group I aged 53 days and 2.4 kg and group II of 85 days and 3.0 kg. Semen samples collected from different sections of epididymis were analyzed for sperm motility, live spermatozoa, and morphological abnormalities. Motility increased (P<0.01) and live spermatozoa and total morphological abnormalities decreased (P<0.001) from caput through cauda epididymis in both the groups. Sperm motility, live spermatozoa and morphologically normal spermatozoa in each section of the epididymis were higher (P<0.01) in group II than I. Boars with >60% progressive motility, >70% live spermatozoa, <15% total morphological abnormalities and <10% abnormal acrosomes in cauda epididymal spermatozoa were considered mature spermiogram. As per this definition, pigs of group II had only mature spermiogram. In vivo pregnancy confirmation indicated that Naga boar could impregnate female as early as 90 days of age. In conclusion, Naga boar attained puberty by not later than 3 months with 3.0 kg, which is the lowest body weight at puberty in this species reported so far, as reflected by mature epididymal spermiogram and in vivo pregnancy confirmation.

Preservation of mithun (Bos frontalis) semen at refrigeration temperature

The objective of the present study was to investigate the possibility of preserving mithun (Bos frontalis) spermatozoa at refrigeration temperature using tris-egg yolk diluent. Semen samples were collected from four adult mithun bulls through rectal massage method. Good quality semen samples (n=30) were preserved at 4 degrees C using tris-egg yolk diluent for 72 h. Progressive motility, live spermatozoa count and morphological abnormalities were evaluated every 12 h until 72 h of preservation. The colour, consistency and mass activity of fresh semen samples were found to be creamy white, medium and 3+ to 4+ (5+ scale), respectively. The average (mean+/-S.E.) volume (ml), pH and spermatozoa concentration (10(6) ml(-1)) of fresh semen samples were found to be 0.6+/-0.01, 6.8+/-0.03 and 425+/-48, respectively. Progressive motility and live spermatozoa count were found to be less than 30% (P<0.01) after 48 h of storage. Head (P<0.05), midpiece (P<0.05), tail (P<0.01) and total (P<0.01) abnormalities were found to be increased significantly over the time of storage. It was observed that progressive motility and live spermatozoa count remained above 30% and 40%, respectively, until 36 h of storage. Simultaneously the percentage of morphologically abnormal spermatozoa was found to be significantly low until 36 h of storage. The results indicate that it is possible to preserve mithun spermatozoa at refrigeration temperature in tris-egg yolk diluent, which can be further used for artificial insemination within 36 h of storage.

Development and validation of a sensitive radioimmunoassay procedure for estimating FSH in mithun (Bos frontalis) plasma

The present study was designed to develop and validate a simple and sensitive radioimmunoassay (RIA) procedure to estimate FSH in mithun (Bosfrontalis) plasma. The assay was carried out in 100 [L of mithun plasma. The bovine FSH standards (10 to 5000 pg/100 microL/tube) in hormone-free plasma were used in the assay. The sensitivity of the assay was 20 pg/100 microL/tube, which corresponded to 0.20 ng/mL plasma. The 50% relative binding sensitivity of the assay was 80 pg/100 microL/tube, which corresponded to 0.80 ng/mL plasma. The intra- and inter-assay coefficients of variation were 4.6% and 12.4%, respectively. The biological validation of the assay was carried out in plasma samples that were collected during different stages of the estrous cycle. In the entire estrous cycle, plasma FSH concentration (p < 0.01) attained two peaks (on day 3 to 4 before estrus 5.1 +/- 0.3 ng/mL and on the day of estrus 6.9 +/- 0.2 ng/mL). FSH concentration remained at basal level (1.3 +/- 0.1 to 1.6 +/- 0.2 ng/mL) during day 4 to 16 of the estrous cycle. The concentration of plasma FSH was found to be significantly (p < 0.05) higher (4.9 +/- 0.3 to 6.8 +/- 0.5 ng/mL) until 48 h following the estrus onset. In conclusion, the RIA procedure that was developed in the current study is sufficiently reliable and sensitive to estimate different physiological levels of FSH in mithun plasma.

Role of LH and prostaglandin F2alpha on the development and regression of corpus luteum in mithun (Bos frontalis) estrous cycle

The present investigation was designed to study the role of LH and prostaglandin F2alpha (PGF2alpha) on the development and regression of corpus luteum (CL) in the mithun estrous cycle. Blood samples were collected from jugular vein and PGF2alpha secretion was evaluated on the basis of peripheral 15-keto-13,14-dihydro-PGF2alpha (PGFM) concentration. The daily variations in plasma LH, PGFM, and progesterone (P4) concentrations throughout the estrous cycle were monitored in morning and evening blood samples. The variations in plasma LH, PGFM, and P4 concentrations during the early luteal phase were monitored in blood samples that were collected every 2 h until 120 h following the onset of estrus (Day 0). The pulsatile secretion patterns of plasma LH, PGFM and P4 during estrus (Day 1), mid-diestrus (Day 10), and luteolysis (Day 14) were assessed in blood samples that were collected every 15 min for 6h. In the estrous cycle, P4 concentration increased above basal level on day 6-7, peaked on day 10-12 and declined thereafter. Following estrus, a significant (P<0.01) gradual increase in P4 concentration was observed. LH concentration was found to be significantly (P<0.01) greater around estrus and it declined gradually (P<0.01) following estrus. In the estrous cycle, PGFM concentration increased above basal level on day 9-11, peaked on day 16-17, and declined thereafter. The frequency of LH pulses and basal LH concentration were found to be significantly (P<0.01) greater on day 1, but significantly (P<0.01) greater amplitude of LH pulses was found on day 10 and 14. The frequency of P4 and PGFM pulses was found to be significantly (P<0.01) greater on day 1. In contrast, the amplitude of P4 and PGFM pulses and basal P4 and PGFM concentrations were found to be significantly (P<0.01) greater on day 10 and 14. The results indicate that probably the early stages of CL development continued until day 5-6 of the estrous cycle and a fully functional CL existed approximately at the mid estrous cycle. Luteolysis probably started since day 11-13 of the cycle and completed before the onset of the next estrus. The elevated basal LH concentration along with frequent low amplitude LH pulses were probably required for the early stages of CL development. In contrast, the high amplitude LH pulses of lower frequency during the mid estrous cycle were either sufficient or not required for maintaining the luteal function. Whereas, PGF2alpha pulses of greater amplitude and elevated basal PGF2alpha concentration during the mid and late estrous cycle were probably responsible for luteolysis.

Secretion patterns of luteinising hormone, follicle-stimulating hormone and 17beta-oestradiol during oestrus and the mid-luteal phase of the oestrous cycle in mithun (Bos frontalis)

The present study reports the pulsatile secretion of gonadotrophins and 17beta-oestradiol (OE2) on the day of oestrus and at the mid-luteal phase of the oestrous cycle in mithun (Bos frontalis). The frequency of luteinising hormone (LH) and follicle-stimulating hormone (FSH) pulses was found to be greater (P < 0.05) on the day of oestrus than at the mid-luteal phase. In contrast, the amplitude of the LH and FSH pulses was greater (P < 0.01) at the mid-luteal phase than on the day of oestrus. A synchronised (P < 0.01) LH and FSH secretion pattern was found only at the mid-luteal phase. A pulsatile secretion pattern for OE2 in the peripheral circulation was evident for both phases of the oestrous cycle. The frequency of the OE2 pulses did not differ significantly in different phases of the oestrous cycle. In contrast, the amplitude of the OE2 pulses and the basal OE2 concentration were found to be greater (P < 0.01) at the mid-luteal phase than on the day of oestrus. A synchronised (P < 0.01) LH and OE2 secretion pattern was observed in both phases of the oestrous cycle. In contrast, a synchronised (P < 0.05) FSH and OE2 secretion pattern was found only on the day of oestrus. In conclusion, a different pattern of LH and FSH secretion was observed in both phases of the oestrous cycle, mainly on the day of oestrus, which indicates a differential regulatory mechanism of LH and FSH release. In addition, as in cattle, OE2 exerts a positive feedback on LH and FSH release on the day of oestrus and on LH release at the mid-luteal phase of the oestrous cycle in mithun. Also, as in cattle, the greater basal plasma OE2 concentration and increased amplitude of OE2 pulses exert a negative feedback on FSH release at the mid-luteal phase of the oestrous cycle.

Changes in Plasma Concentrations of LH, FSH, Estradiol 17-beta and Progesterone During Oestrus in Mithun (Bos frontalis)

The objective of the present study was to establish the changes in plasma concentrations of LH, FSH, estradiol 17-beta (E2) and progesterone (P4), as well as to understand their temporal relationships during oestrus in mithun (Bos frontalis). The experiment was conducted on 11 mithuns during third or fourth postpartum oestrous cycle. Since oestrus onset the jugular vein blood samples were collected every 2 h for 72 and 96 h, respectively from the animals without and with standing heat. The LH, FSH, E2 and P4 concentrations were estimated in plasma. The P4 concentration was fluctuated throughout the oestrus period and the average P4 concentration was found significantly (p<0.05) lower on the day of oestrus onset. The multiple rises in LH and FSH concentrations above the basal level in spike like fashion were observed throughout the oestrus period irrespective of the occurrence of standing heat. A significant (p<0.01) gradual increase in the average daily E2 concentration was observed till day 2 following oestrus onset irrespective of the occurrence of standing heat. A significant (p<0.05) simultaneous increase in LH, FSH and E2 concentrations and a transient increase in P4 concentration at approximately the time of standing heat onset were observed. During investigation a definite temporal coupling between LH and FSH rises was absent throughout the oestrus period. The results suggest that (1) the multiple short-duration low-amplitude LH and FSH surges during oestrus may be crucial for the final maturation of ovulatory follicle and subsequent ovulation in mithun; (2) a differential mechanism for controlling LH and FSH secretions probably exists in mithun.

Endocrine control of estrous cycle in mithun (Bos frontalis)

The objective of the present study was to establish the profiles of luteinising hormone (LH), follicle stimulating hormone (FSH), estradiol 17beta (E2) and progesterone (P4) secretion and their interrelationships during the natural estrous cycle of mithun (Bos frontalis). Daily blood samples were collected from second or third postpartum estrous cycles for determination of plasma concentrations of LH, FSH, E2 and P4. Concentration of P4 was found to be lowest on the day of estrus. It increased following estrus, attained the highest concentration on day 11 and decreased thereafter. Concentrations of LH and FSH varied significantly (p<0.01) during the first and last 6 days of the cycle and their variations were found to be synchronised. Both LH and FSH attained a biphasic peak during the estrous cycle. This biphasic peak lasted on from day -5 to day 3 of the cycle. The variations in maximum LH and FSH concentrations of both the phases did not differ significantly. During the entire estrous cycle, the E2 concentrations attained either one peak or two peaks. The first peak, approximately on day 4 before estrus was common in all animals. One additional peak was found on the day of estrus in 45% animals. A significant (p<0.01) negative relationship was found between P4 and, LH and FSH during the first and last 6 days of cycle. But a significant (p<or=0.01) negative relationship between E2 and, LH and FSH was found only during the last 6 days of cycle. The results suggest a negative feedback mechanism on LH and FSH release by E2 and P4 during the respective phases of cycle. A sustained increase in LH and FSH levels during the period before estrus was probably necessary for the final maturation of ovulatory follicle and subsequent ovulation.