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H K Liu

Publications and source records attributed to H K Liu.

At least 19 recordsLinked to original sources
PubMed2006

Electrochemical hydrogen storage in single-walled carbon nanotube paper.

Single-walled carbon nanotube (SWNT) papers were successfully prepared by dispersing SWNTs in Triton X-100 solution, then filtered by PVDF membrane (0.22 microm pore size). The electrochemical behavior and the reversible hydrogen storage capacity of single-walled carbon nanotube (SWNT) papers have been investigated in alkaline electrolytic solutions (6 N KOH) by cyclic voltammetry, linear micropolarization, and constant current charge/discharge measurements. The effect of thickness and the addition of carbon black on hydrogen adsorption/desorption were also investigated. It was found that the electrochemical charge-discharge mechanism occurring in SWNT paper electrodes is somewhere between that of carbon nanotubes (physical process) and that of metal hydride electrodes (chemical process), and consists of a charge-transfer reaction (Reduction/Oxidation) and a diffusion step (Diffusion).

Absorption↗
PubMed2006

Nickel oxide nanotubes: synthesis and electrochemical performance for use in lithium ion batteries.

Uniform and aligned Nickel Oxide (NiO) nanotube bundles have been synthesized by a template process. Individual nanotubes are 60 microm long with a 200 nm outer diameter and wall thickness of 20-30 nm. The synthesis involved forming Ni(OH)2 nanotubes that were subsequently heated to 350 degrees C in order to fully convert the product to NiO nanotubes. NiO nanotube powder was used in lithium-ion cells for assessment of lithium storage ability and electrochemical performance. Discharge capacity of the NiO nanotube electrode was in excess of 30% higher than that of the standard NiO nanocrystalline powder electrode after 20 cycles. Impedance data suggests the NiO nanotube electrode provides more controlled and sustainable Li diffusion when compared to the NiO reference powder electrode system.

Electric Power Supplies↗
PubMed2005

Changes in egg production rate induced by progesterone injection in broiler breeder hens.

A polycystic ovarian follicle (PCOF) syndrome associated with high baseline concentrations of progesterone (P4) without preovulatory luteinizing hormone (LH) surges has been reported in turkey hens. The PCOF syndrome could be induced in turkey hens by injecting P4 (0.33 mg/kg per d) daily early in the reproductive period for 10 to 12 d and then waiting 3 wk for the syndrome to develop. It was hypothesized that an arrest in laying associated with the PCOF syndrome could be induced by daily injection of P4 in restricted-fed broiler breeder hens. Hens were divided into 5 treatment groups and were injected subcutaneously daily with P4 in canola oil at dosages of 0, 0.17, 0.33, 0.5, and 1.5 mg/kg per d for 13 d, at 14 wk of egg production when they were 41 wk of age. Blood samples were collected on d 7 and 13 immediately before P4 injection. Oviductal and ovarian morphologies were measured at necropsy 1 d after the last P4 injection. Egg production rate was reduced by injection of P4 at dosages < 0.17 mg/kg per d. At dosages of 0.5 and 1.5 mg/kg per d, ovarian hierarchical follicles had regressed. None of the broiler breeder hens had the PCOF syndrome at necropsy, but a high incidence of hens holding hard-shelled uterine eggs for several days was observed. Concentrations of LH decreased with P4 injection at > 0.17 mg/kg per d, and P4 concentrations were increased with P4 injection at > 0.5 mg/kg per d. Estradiol-17beta (E2) concentrations were decreased at all P4 dosages. It was concluded that egg production rate was reduced by daily injection of P4 at dosages > 0.17 mg/kg per d, and egg production ceased and ovarian follicles and the oviduct regressed at dosages > 0.50 mg/kg per d. The PCOF syndrome, however, was not induced in restricted-fed broiler breeder hens by P4 injection.

Animals↗
PubMed2005

Function of a long-term, GLP-1-treated, insulin-secreting cell line is improved by preventing DPP IV-mediated degradation of GLP-1.

Glucagon-like peptide-1 (GLP-1) is an important insulinotropic hormone with potential in the treatment of type 2 diabetes. However, the short biological half-life of the peptide after cleavage by dipeptidylpeptidase IV (DPP IV) is a major limitation. Inhibition of DPP IV activity and the development of resistant GLP-1 analogues is the subject of ongoing research. In this study, we determined cell growth, insulin content, insulin accumulation and insulin secretory function of a insulin-secreting cell line cultured for 3 days with either GLP-1, GLP-1 plus the DPP IV inhibitor diprotin A (DPA) or stable N-acetyl-GLP-1. Native GLP-1 was rapidly degraded by DPP IV during culture with accumulation of the inactive metabolite GLP-1(9-36)amide. Inclusion of DPA or use of the DPP IV-resistant analogue, N-acetyl-GLP-1, improved cellular function compared to exposure to GLP-1 alone. Most notably, basal and accumulated insulin secretion was enhanced, and glucose responsiveness was improved. However, prolonged GLP-1 treatment resulted in GLP-1 receptor desensitization regardless of DPP IV status. The results indicate that prevention of DPP IV action is necessary for beneficial effects of GLP-1 on pancreatic beta cells and that prolonged exposure to GLP-1(9-36)amide may be detrimental to insulin secretory function. These observations also support the ongoing development of DPP-IV-resistant forms of GLP-1, such as N-acetyl-GLP-1.

Animals↗
PubMed2005

Enhancement of ionic conductivity of PEO based polymer electrolyte by the addition of nanosize ceramic powders.

The ionic conductivity of polyethylene oxide (PEO) based solid polymer electrolytes (SPEs) has been improved by the addition of nanosize ceramic powders (TiO2 and AL2O3). The PEO based solid polymer electrolytes were prepared by the solution-casting method. Electrochemical measurement shows that the 10 wt% TiO2 PEO-LiClO4 polymer electrolyte has the best ionic conductivity (about 10(-4) S cm(-1) at 40-60 degrees C). The lithium transference number of the 10 wt% TiO2 PEO-LiClO4 polymer electrolyte was measured to be 0.47, which is much higher than that of bare PEO polymer electrolyte. Ac impedance testing shows that the interface resistance of ceramic-added PEO polymer electrolyte is stable. Linear sweep voltammetry measurement shows that the PEO polymer electrolytes are electrochemically stable in the voltage range of 2.0-5.0 V versus a Li/Li+ reference electrode.

Aluminum Oxide↗
PubMed2004

Effect of chronic progesterone injection on egg production in Japanese quail.

Young laying turkey hens ceased laying and developed a polycystic ovarian follicle (PCOF) syndrome 3 wk after injections of progesterone (P4) ceased. It was hypothesized that laying Japanese quail chronically injected with progesterone (P4) would respond with reduced or arrested egg production and altered ovarian morphology similar to that seen in turkeys expressing the PCOF syndrome, and could thus serve as a model to study the PCOF syndrome. To test these hypotheses, 6 trials were conducted with young photosensitive Japanese quail photostimulated to induce sexual maturity with either 24L:0D or 14L:10D at 6 or 8 wk of age, and used after 3 to 5 wk of egg production. The quail were injected once daily at dosages of 0, 0.17, 0.33, 0.5, 1.5, 3.0, or 4.5 mg of P4/kg per d, or twice daily at dosages of 0 and 1.5 mg of P4/kg for 8 to 14 d and were then necropsied 1 d after the last injection or after waiting an additional 8 to 14 d. During the injection period, egg production was not different among P4 dosages <1.5 mg of P4/kg per d, but decreased at dosages of 1.5 mg of P4/kg per d or greater. A decrease in egg production was found with twice daily injections of 1.5 mg of P4/kg. The decrease in egg production rate ceased and egg production resumed 5 to 7 d after the last injections of 3.0 and 4.5 mg of P4/kg per d or twice-daily injections of 1.5 mg of P4/kg. Compared with control hens, a high percentage of hens (from 12 to 75%) held a hard-shelled egg in the uterus during single daily injections at dosages of 3.0 and 4.5 mg of P4/kg per d and twice daily injections of 1.5 mg of P4/kg. Ovary and oviductal weights, and number of hierarchical follicles were not changed after chronic P4 injection, but more atretic follicles were found in hens at the end of 8 to 12 d of P4 injection. In conclusion, a decreasing egg production rate was induced by chronic P4 injection, but the decrease ceased and egg production resumed 5 to 7 d after the last injections in laying Japanese quail. Young quail hens, unlike young turkey hens, did not develop a PCOF-like syndrome after P4 injection.

Animals↗
PubMed2004

Development of a cannulation procedure for broiler breeder hens.

A cannulation and serial bleeding procedure has been developed to monitor the peripheral patterns of hormones associated with reproduction for up to 10 d in broiler breeder hens. Hens were cannulated via the jugular vein and returned to individual cages. The unrestrained cannulated hens were connected to a tether and swivel system that permitted constant infusion for maintenance of the cannula prior to serial bleeding and unrestrained long-term serial bleeding for up to 10 d. In a short-term experiment hens were bled every 12 min for 36 h, and in a long-term experiment hens were bled hourly for 10 d. In these experiments, 1.5-mL blood samples were collected at each time point with sodium citrate as the anticoagulant. To avoid hemodilution, after removal of plasma the red blood cells were reconstituted with saline to the original volume and returned to the hen of origin. Collection of serial blood samples was successful from 94% of hens in the short-term experiment and 79% of hens in the long-term experiment. Egg production was not affected (P > 0.05) during the 6 wk following serial bleeding in the short-term experiment. For hens that continued laying, egg production for 10 d prior to cannulation was not different (P > 0.05) from egg production for the 10 d during serial bleeding in the long-term experiment. However, late in the reproductive cycle many hens (25%) stopped laying when serially bled. It is concluded that this cannulation procedure can be used to study short-term or long-term peripheral patterns of hormones associated with oviposition and ovulation in laying broiler breeder hens.

Animals↗
PubMed2004

Preovulatory surge patterns of luteinizing hormone, progesterone, and estradiol-17beta in broiler breeder hens fed ad libitum or restricted fed.

Spontaneous ovulations are induced by preovulatory surges of luteinizing hormone (LH) and progesterone (P4) during ovulatory cycles in birds, but estradiol-17beta (E2) levels are relatively constant. Egg production is enhanced in restricted fed (RF) in comparison with ad libitum fed (FF) broiler breeder hens, but changes in concentrations and peripheral patterns of LH, P4, and E2 during ovulatory cycles in broiler breeder hens are poorly documented. The hypothesis of this study was that high resolution patterns of peripheral LH, P4, and E2 during preovulatory surges would not be different between FF and RF broiler breeder hens. Seven FF and 6 RF broiler breeder hens were photostimulated with 16 L:8 D at 22 wk of age. At 28 wk of age, the hens were cannulated for serial blood sampling and switched to a 24L:0D photoperiod to allow preovulatory surges of LH and P4 to run freely. Three days after cannulation, hens were serially bled every 12 min for 36 h. The FF hens were heavier than the RF hens (5.60 +/- 0.35 vs. 3.60 +/- 0.28 kg, respectively; P < 0.01). During the 10 d before cannulation, total egg production of the FF and RF hens (8.3 +/- 1.4 and 6.8 +/- 1.3 eggs, respectively; P = 0.08) and normal egg production (5.6 +/- 1.8 and 6.5 +/- 1.8 eggs, respectively; P = 0.37) were not different. The FF hens, however, had more abnormal eggs than the RF hens (2.7 +/- 1.7 and 0.3 +/- 0.8 eggs, respectively; P < 0.01). None of the hormonal measurements was different between the FF and RF hens (P > 0.05). The concentrations of hormones for the FF and RF hens, respectively, were as follows: baseline LH (2.79 +/- 0.45 vs. 2.94 +/- 0.60 ng/mL) and P4 (1.68 +/- 0.56 vs. 1.41 +/- 0.43 ng/mL), overall mean LH (3.18 +/- 0.45 vs. 3.10 +/- 0.46 ng/mL) and P4 (2.32 +/- 0.55 vs. 2.09 +/- 0.91 ng/ mL), preovulatory surge amplitude of LH (5.43 +/- 1.27 vs. 3.88 +/- 1.24 ng/mL) and P4 (6.08 +/- 2.09 vs. 6.71 +/- 3.91 ng/ mL), preovulatory surge duration of LH (7.52 +/- 1.80 vs. 5.74 +/- 3.18 h) and P4 (7.52 +/- 1.42 vs. 8.20 +/- 1.24 h), and overall mean E2 (0.25 +/- 0.05 vs. 0.23 +/- 0.05 ng/mL). In conclusion, there were no differences in total egg production or normal egg production between FF and RF broiler breeder hens, but the FF hens laid more abnormal eggs. Also, there were no differences in the concentrations or peripheral patterns of LH, P4, and E2 during preovulatory surges between the FF and RF broiler breeder hens.

Animals↗
PubMed2004

In-situ fabrication of nanostructured cobalt oxide powders by spray pyrolysis technique.

Nano-crystalline Co3O4 and CoO powders have been prepared by a spray pyrolysis approach. The effects of the reaction temperature and initial salts on the crystallinity and phase composition have been studied. Based on the TEM and XRD results, the crystal sizes were in the range of 1-10 nm. SEM and TEM observations also reveal that the nano-powders easily create micron-scale spherical agglomerates. The Co3O4 powders obtained by spraying nitrate solution at 500 degrees C show high specific surface area, which according to the BET method is 82.37 m2/g. The time/temperature phase diagram of cobalt oxides developed from XRD and DTA/TGA analyses shows the existence of a CoO phase at low and high temperature ranges when some specific preparation conditions are applied.

Biocompatible Materials↗
PubMed2003

Influence of photoperiod and age of photostimulation on the incidence of polycystic ovarian follicle syndrome in turkey breeder hens.

An arrest in egg laying associated with a polycystic ovarian follicle syndrome (PCOF) has been recently reported early in the egg production period in turkey hens photostimulated at 30 wk of age (WOA) with continuous light. When autopsied 2 to 3 wk after laying ceased, the ovaries of PCOF hens contained an increased number of mature size (F1) yolky follicles in comparison with normally laying hens plus several larger cystic follicles, while their oviducts were equal in weight to oviducts of hens laying normally. Four experiments were conducted to examine effects of age at photostimulation and photoperiod [14L:10D (14L) or continuous lighting 24L:0D (24L)] on the incidence of the PCOF syndrome. Turkey hens of the egg line were given short-day photostimulation of 6L:18D at 16 WOA and then photostimulated with either 14L or 24L at various ages between 26 to 70 WOA. Egg production was followed for 6 to 8 wk, and hens that stopped laying eggs during this period were autopsied 2 to 3 wk later to determine presence and incidence of the PCOF syndrome. At 26 WOA, the PCOF incidence was 80% with 24L lighting and 31% with 14L lighting (P = 0.006). At 28 WOA, the PCOF incidence was 56% with 24L lighting and 25% with 14L lighting (P = 0.072). At 31, 34, and 41 WOA, there were no differences (P > or = 0.10) in incidence of the PCOF syndrome between the 24L and 14L treatments. Within the 24L treatment, the PCOF incidence at 26 and 28 WOA (80 and 56%) were greater than at 31 WOA and older ages (< or = 20%; P < or = 0.025). Within the 14L lighting treatment, the PCOF incidence was not different among ages (26 WOA, 31% to 48 WOA, 0%; P > or = 0.05). It was concluded that the incidence of the PCOF syndrome is greater when photosensitive Egg line turkey hens are photostimulated at relatively young ages (less than 31WOA) and with 24L in comparison to 14L lighting.

Aging↗
PubMed2002

Fabrication and properties of spray-dried nanofeatured spherical Ni(OH)2 materials.

Spherical agglomerates of nanostructured beta-phase Ni(OH)2 with the general formula Ni1-xCox(OH)2 (x = 0, 0.1, 0.3) for use as cathode materials were produced by a modified method including coprecipitation of Ni or Ni composite hydroxide and further spray drying of the precipitated and washed slurry. This process leads to the formation of spherical agglomerate particles with a narrow Gaussian-type distribution range. The method permits faster and cheaper production of cathode materials with a higher specific surface area and similar or better capacity and cycle life compared with the materials prepared via conventional technology.

Aerosols↗
PubMed2002

Nanocrystalline alpha-Ni(OH)2 prepared by ultrasonic precipitation.

Nanocrystalline alpha-Ni(OH)2 was prepared by an ultrasonic precipitation/stirring method. Results of X-ray diffraction, transmission electron microscopy, infrared, and thermogravimetric measurements confirm that the sample obtained is alpha phase. Compared with the sample prepared without ultrasonic stirring, the crystal structure of the alpha phase sample has been changed from beta phase. The crystalline size of the sample is about 20 nm, which is smaller than the sample produced without ultrasonic stirring (70 nm).

Chemical Precipitation↗
PubMed2001

Concentration change patterns of luteinizing hormone and progesterone and distribution of hierarchical follicles in normal and arrested laying turkey hens.

Young photosensitive turkey hens of a line selected for increased egg production (Egg line) were photostimulated with constant light [24 h light:0 h darkness] at 30 wk of age. Egg laying became arrested in 6 of 12 the hens after only 2 to 3 wk of laying. Ovarian morphology and changes in concentrations of plasma hormones [luteinizing hormone (LH), progesterone (P4), and estradiol-17beta (E2)] over 10 d of serial bleeding were compared between the arrested laying and normal laying hens. The number of ovarian follicles heavier than 1.0 g was much greater in arrested laying hens, and some of the arrested laying hens presented a polycystic ovarian follicle condition. The oviducts of the arrested laying hens were fully developed and were similar in weight to those of normal laying hens. In arrested laying hens the plasma concentration of LH was relatively low (1.72 +/- 0.30 ng mL(-1)) and without preovulatory surges. In normal laying hens the baseline concentration of LH was 2.60 +/- 0.71 ng mL(-1), and the interval between LH surges was 26.8 h. In the arrested laying hens, the plasma concentration of P4 was relatively high (4.66 +/- 1.28 ng mL(-1)) and without preovulatory surges. In normal laying hens the baseline concentration of P4 between surges was 1.76 +/- 0.24 ng mL(-1). Plasma E2 concentrations were not different between normal laying and arrested laying hens. In conclusion, ovulations and ovipositions ceased in the arrested laying hens, but the entrance of follicles into the follicular hierarchy and hierarchical growth continued, leading to an accumulation of numerous mature follicles in the ovary. In addition, some of the accumulated mature follicles might have resumed growing, leading to the formation of cystic ovarian follicles.

Animals↗
PubMed2001

Preovulatory luteinizing hormone surge interval in old and young laying turkey hens early in the egg production period.

Egg production rate normally declines with duration of the reproductive period, but hen age and duration of the reproductive period are usually confounded. Initiation of egg production can be delayed in turkey hens with short-day lighting, allowing hen age to be separated from duration of the reproductive period. The objective of the present report is to determine if the interval between luteinizing hormone (LH) surges is different between old and young laying turkey hens during the peak of egg production. Turkey hens were given short-day lighting [6 h light (L):18 h darkness (D)] at 16 wk of age, and were photostimulated with 24L:OD (constant light) at 30 (young hens) or at 70 (old hens) wk of age. Egg production in the young hens started about 2 wk after they were photostimulated, but some of the old hens had started laying at 64 wk of age while under short-day lighting, and all old hens were laying after 1 wk of photostimulation. To monitor the interval between plasma LH surges at peak of production, hens were serially bled hourly for 240 h, starting about 6 wk after photostimulation. The interval of LH surges was not different between young (n = 5) and old (n = 10) laying hens. Not all LH surges were coincident with oviposition of eggs 1 to 2 d later (blind LH surges), and the percentage of young hens with at least one blind LH surge was higher than for old hens (60% of young hens and 10% of old hens). The baseline concentration of LH was not different between the young and old laying hens. In conclusion, the interval between LH surges, baseline concentration of LH, and amplitude of LH surges were not related to age of the hens during the peak rate of lay.

Age Factors↗
PubMed2001

Frequency of luteinizing hormone surges and egg production rate in turkey hens.

Whether the interval between preovulatory surges of LH was different between lines of turkey hens with either poor (RBC3 line, peak at 55%) or excellent rate of egg production (Egg line, peak at 85%) was examined. Laying hens were cannulated and bled hourly for 10 days at peak of production. A constant light photoschedule was used to avoid diurnal masking of innate circadian rhythms. The mean interval between LH surges in the RBC3 line was longer than in the Egg line and had a higher coefficient of variation. A few longer LH surge intervals (72 h) were found in some RBC3 line hens (2 of 7 hens), but none were found in Egg line hens (0 of 11 hens). All progesterone (P4) surges were coupled with LH surges, but not all LH-P4 surges were coupled with ovipositions (blind LH-P(4) surges). The percentage of blind LH-P4 surges was not different between lines. The baseline concentration of LH was higher in Egg line than RBC3 line hens, but LH surge amplitude, and surge duration were not different. The baseline and surge amplitude concentrations of P4 were not different between lines, nor was the concentration of estradiol-17beta. The longer interval between LH surges was the major factor tested that was associated with the poorer egg production rate in RBC3 line hens in comparison to Egg line hens. A higher incidence of blind LH surges further contributed to lower egg production in RBC3 line turkey hens.

Animals↗
PubMed2000

Tris(2-cyanoethyl)amine.

In the title compound, N(CH(2)CH(2)CN)(3), (I), the three cyanoethyl groups adopt a conformation with the CN groups oriented in the same direction, suggesting the compound may behave as a potential tripodal ligand.

Journal Article↗
PubMed2000

Hexakis(antipyrine-O)terbium(III) triperchlorate.

In the title compound, hexakis(1,2-dihydro-1,5-dimethyl-2-phenyl-3H-pyrazol-3-one-O)terbium(III) triperchlorate, [Tb(C(11)H(12)N(2)O)(6)](ClO(4))(3), the Tb atom lies on a site of $\overline 3$ crystallographic symmetry and the unique Tb-O distance is 2.278 (2) A. One of the perchlorate anions has threefold crystallographic symmetry, while the other is disordered about a $\overline 3$ site.

Journal Article↗