Hydrogen-Release Mechanisms in Lithium Amidoboranes

Kim, Dong Young,Singh, N. Jiten,Lee, Han Myoung,Kim, Kwang S. WILEY-VCH Verlag 2009 Chemistry Vol.15 No.22

<P>Hydrogen storage: In lithium amidoboranes an initial molecule of H<SUB>2</SUB> is released by the formation of LiH, followed by a redox reaction of the dihydrogen bond formed between LiH<SUP>δ−</SUP> and NH<SUP>δ+</SUP>. In this dehydrogenation process, an intermolecular N&n.bond;B bond forms through the catalytic effect of a Li cation. After releasing the first molecule of H<SUB>2</SUB>, a Li cation binds to a nitrogen atom, lowering the energy barrier for the second H<SUB>2</SUB> loss per lithium amidoborane dimer (see figure). <img src='wiley_img/09476539-2009-15-22-CHEM200900092-content.gif' alt='wiley_img/09476539-2009-15-22-CHEM200900092-content'> </P><P>Alkali-metal amidoboranes have been recently highlighted as materials that satisfy many of the criteria required to make hydrogen-storage media. It is, therefore, crucial for us to understand the dehydrogenation mechanism of these materials for further development towards making successful hydrogen-storage media. In the present study, we attempt to shed light on the mechanisms involved in the loss of one molar equivalent of H<SUB>2</SUB> from solid lithium amidoboranes by using high-level ab initio calculations of monomeric and dimeric compounds in the gas phase. In the lithium amidoborane dimer, H<SUB>2</SUB> is released by the formation of LiH, which is followed by a redox reaction of the dihydrogen bond formed between the strongly basic H<SUP>−</SUP> in LiH and H<SUP>δ+</SUP> bonded to N. In the dehydrogenation process, the Li cation catalyzes the intermolecular N&n.bond;B bond formation; this could lead to new pathways for N&n.bond;B polymerization. After the release of the first molecule of H<SUB>2</SUB>, a Li cation binds to a nitrogen atom, resulting in a lowering of the energy barrier for the second dehydrogenation process per dimer. These results will be useful for the design of future hydrogen-storage media.</P> <B>Graphic Abstract</B> <P>Hydrogen storage: In lithium amidoboranes an initial molecule of H<SUB>2</SUB> is released by the formation of LiH, followed by a redox reaction of the dihydrogen bond formed between LiH<SUP>δ−</SUP> and NH<SUP>δ+</SUP>. In this dehydrogenation process, an intermolecular N&n.bond;B bond forms through the catalytic effect of a Li cation. After releasing the first molecule of H<SUB>2</SUB>, a Li cation binds to a nitrogen atom, lowering the energy barrier for the second H<SUB>2</SUB> loss per lithium amidoborane dimer (see figure). <img src='wiley_img/09476539-2009-15-22-CHEM200900092-content.gif' alt='wiley_img/09476539-2009-15-22-CHEM200900092-content'> </P>

A comparison of native and acid thinned normal and waxy corn starches: Physicochemical, thermal, morphological and pasting properties

Singh Sandhu, K.,Singh, N.,Lim, S.T. Academic Press, etc 2007 FOOD SCIENCE AND TECHNOLOGY -ZURICH- Vol.40 No.9

The starches isolated from normal and waxy corn varieties were hydrolyzed with hydrochloric acid (0.14mol equivalent/L) and evaluated for physicochemical and functional properties. Acid thinning decreased the amylose content and swelling power but increased the solubility. The light transmittance of acid thinned (AT) starch pastes was higher than those of their native starches after similar storage intervals. The scanning electron microscopic observation demonstrated that the acid thinning did not cause any disruption of the granular crystalline structure. Native normal corn starches showed lower onset temperature (T<SUB>o</SUB>) and peak temperature (T<SUB>p</SUB>) as compared to their counterpart AT starches, whereas the reverse was observed for waxy corn starch. Enthalpy of gelatinization (ΔH<SUB>gel</SUB>) was lower in AT normal and waxy starches as compared to their native starches. The percentage of retrogradation (%R) was significantly higher for native corn starches as compared to their AT starches. A significant reduction in peak-(P<SUB>V</SUB>), trough-(T<SUB>V</SUB>), breakdown-(B<SUB>V</SUB>), final-(F<SUB>V</SUB>), and setback viscosity (S<SUB>V</SUB>) was observed by acid thinning, and the reduction was more pronounced in AT waxy starches. Among AT starches, AT waxy starch showed the lowest values of P<SUB>V</SUB>, T<SUB>V</SUB>, B<SUB>V</SUB>, F<SUB>V</SUB> and S<SUB>V</SUB>.

EPR and optical investigation of ultraviolet-emitting Gd3Ga5O12 garnet

Singh, Vijay,Sivaramaiah, G.,Singh, N.,Mohapatra, M.,Hakeem, D. A.,Pathak, M. S.,Rao, J. L. Springer-Verlag 2018 Journal of materials science Materials in electron Vol.29 No.2

<P>Gd3Ga5O12 garnet was prepared by a solution combustion method and characterized using powder X-ray diffraction, electron paramagnetic resonance (EPR) and optical spectroscopic techniques. EPR spectrum of the samples at ambient and low temperatures exhibited resonance signal at g approximate to 2 attributed to Gd3+ ions disposed in an octahedral symmetry. The optical absorption spectrum showed a band centered at 274 nm attributed to S-8(7/2)-> I-6(J) transition of the Gd3+ ions. The excitation spectrum showed a maximum at 273 nm along with two relatively weaker peaks at 276 and 279 nm. These three excitation bands were assigned to the transitions S-8(7/2)-> I-6(J). The emission spectrum showed two peaks centered at 311 and 306 nm that were assigned to the transitions P-6(7/2)-> S-8(7/2) and P-6(5/2)-> S-8(7/2) of Gd3+, respectively. To evaluate the phosphor performance, several magnetic and thermodynamic parameters for the system were calculated adopting standard procedure.</P>

Accuracy of Ultrasonography in Early Pregnancy Diagnosis in Doe

Singh, N.S.,Gawande, P.G.,Mishra, O.P.,Nema, R.K.,Mishra, U.K.,Singh, Mohan Asian Australasian Association of Animal Productio 2004 Animal Bioscience Vol.17 No.6

The present study was undertaken to evaluate the accuracy of ultrasonography in early pregnancy diagnosis in goats. Ultrasonographic scanning with real time B-mode ultrasound machine having 5 MHz linear array transducer was performed on gravid uterus (n=24) obtained from slaughterhouse (Group I). Crown rump length (CRL) measured by ultrasound was found significantly different (p<0.05) with actual CRL measured after dissection in early pregnancy. However, age predicted by ultrasound through the measurement of CRL was found highly correlated (r=0.92) with age measured after dissection through CRL and the weight of fetus. Ages predicted by ultrasound through the measurement of trunk diameter (TD) and uterine diameter (UD) and ages measured after dissection were found highly and equally correlated (r=0.98) and did not differ significantly. Data from six does synchronized (Group II) with PGF2$\alpha$ (Estrumate) at 11 days apart were collected through ultrasound from 17 to 42 days post breding. The correlation between CRL and gestational age was high (r=0.97) in day 30 to 42 post breeding. A high coefficient of correlation (r=0.98) was also observed between predicated age by ultrasound and actual age calculated after kidding. The correlation between CRL and gestational age by the formula Y=(a+bX) i.e. Y=24.42+0.39 X where Y=gestational age and X=CRL, was recorded very high (r=0.99). Accuracy of ultrasonography was lowest on day 17 to 19 (66%) and reached 100% on day 34. Data from 30 does (group III) randomly subjected to only one time ultrasounds scanning to assess the accuracy of pregnancy diagnosis were also obtained. Ages predicted by TD and UD measurements were observed to be non-significantly different with actual age obtained after kidding and correlation between ages predicted by TD and UD measurement with actual age after kidding was found equally and highly correlated (r=0.98). The operator's accuracy in the whole experiment including all three groups was found to be 92%. The sensitivity was 93% and specificity was 86%. From the present study, it was observed that CRL was the most reliable parameter to find out gestational age in early pregnancy and the new formula derived was found very accurate to find out gestational age. TD and UD were also found to be equally reliable parameter to find out gestational age in mid and late stage of pregnancy through ultrasonography. It was concluded that ultrasonography by real time B mode with 5 MHz transrectal transducer was found to be reliable, safe and accurate and practicable means in diagnosing early pregnancy diagnosis as early as 25 days post breeding.

Effect of Tetrahydropalmatine , an Alkaloid on Spore Germination of Some Fungi

(S . Maurya),(J . S . Srivastava),(R . N . Jha),(V . B . Panday),(U . P . Singh) 한국균학회 2001 Mycobiology Vol.29 No.3

N/A N/A

Serum and CSF Mineral Profile of Himalayan Yak (Bas grunniens) in their Natural Habitat

Singh, S.P.,Kumar, N.,Sharma, K.B.,Kumar, R. Asian Australasian Association of Animal Productio 1999 Animal Bioscience Vol.12 No.2

Mineral profile of serum and cerebrospinal fluid (CSF) of 15 Himalayan Yak (adult female, n=8; adult male n=4 and young male,n=3) was studied in their natural habitat at an altitude of 3300 meters above mean sea level at Sangla in north western Himalayas. The macro and micro minerals estimated in serum and CSF were; Sodium, Potassium, Calcium and Magnesium and Zinc, Copper and Iron respectively. The values recorded among different Yak groups did not significantly differ from each other except serum iron and haemoglobin which were significantly higher (p<0.05 ) in young male Yaks compared to the adult male and female Yaks. An observation of great significance was considerably higher potassium and lower sodium level in Yaks compared to other bovine species of plains. The serum potassium values in some adult female Yaks were recorded as high as 10.4 mEq/l and the values varied between 6.6 to 9.8 mEq/l in young male Yaks. The serum Sodium values and Na:K ratios in Yak serum ranged between 117.5 to 122.6 mEq/l and 13.7 to 15.3 respectively. The possible relationship of high serum Potassium value with hypoxic conditions and hostile mountain environment has been discussed.

Leucaena Seeds as Protein Supplement in the Rations of Growing Sheep

Singh, Sultan,Kundu, S.S.,Negi, A.S.,Gupta, S.K.,Singh, N.P.,Pachouri, V.C. Asian Australasian Association of Animal Productio 2002 Animal Bioscience Vol.15 No.10

The study was carried out to evaluate leucaena seeds as a protein replacement of mustard seed cake (MSC) in the concentrate mixture of growing lambs. Fifteen owing male lambs (Local${\times}$Corridale) with an average body weight of 16.3 kg were allocated into three dietary treatments (T1, T2, and T3) with five animals in each group. Animals were offered dry mixed grass, berseem hay and concentrate mixture to meet their nutrient requirements. In concentrate mixture of T1, (Control) MSC was used as protein source, while in T2 and T3 groups, 25 and 50% of MSC was replaced by leucaena leucocephala seeds. On completion of three months (90 days) of feeding, a digestion cum-metabolism trial was conducted to determine DMI, nutrient utilization, and nitrogen balance. Changes in body weight were recorded at 15 day internals and eating patterns were recorded for 3 consecutive days at the end of the feeding trial. MSC had higher CP contents than leucaena seeds (27.0%). Mimosine contents in leucaena seeds were 1.1 compared to 0.2 and 0.4% in concentrate mixture of T2 and T3 group, respectively. Dry matter intake varied non-significantly ($79.3{\pm}1.2$ to $83.4{\pm}1.3g/kg$ $w^{0.75}$) across the dietary treatments. Digestibility of DM and cell wall polysaccharides (NDF, ADF. Cellulose and hemicellulose) were comparable, however CP digestibility was relatively lower in leucaena luecocephala seeds based groups (T2 $45.5{\pm}1.7$ and T3 $46.7{\pm}3.5$) compared to MSC supplemented group (T1 $47.7{\pm}0.9%$). The growth rate of lambs was non-significantly higher in T1 ($79.2{\pm}5.4$) compared to T2 ($73.8{\pm}8.8$) and T3 ($73.9{\pm}7.0$), respectively. The animals were in positive nitrogen balance and N-balance varied from 1.8 to 2.9 g/d across treatment groups. The eating rate (% of total offered) of concentrate up-to 15 min was relatively higher in T1 (82.4) than T2 (74.2) and T3 (77.8%). However no effect of leucaena seeds was recorded on total DMI of animals. The results of the study revealed that the inclusion of up to 50% leucaena seeds, as protein source in concentrate mixture of lambs had no adverse effect on DMI, nutrient utilization, eating patterns, nitrogen balance and growth performance of lambs.

Probing the Thermodynamic and Magnetic Properties of UV-B-Emitting GdAlO3 Phosphors by ESR and Optical Techniques

Singh, V.,Sivaramaiah, G.,Mohapatra, M.,Rao, J. L.,Singh, N.,Pathak, M. S.,Singh, P. K.,Dhoble, S. J. Springer Science + Business Media 2017 Journal of Electronic Materials Vol.46 No.2

<P>GdAlO3 phosphor samples have been prepared by a solution combustion method. X-ray diffraction analysis revealed that the GdAlO3 phosphor stabilized in orthorhombic phase. The optical absorption spectrum showed bands due to Gd3+ ions as well as defect level in the host. The excitation spectrum exhibited a dominant band with maximum at 273 nm. Upon excitation at 273 nm, ultraviolet-B (UV-B) emission with maximum at 312 nm was observed from the undoped sample, being attributed to P-6(7/2) -> S-8(7/2) transition of Gd3+ ion. The UV-B emission was enhanced at liquid-nitrogen temperature (77 K), most probably due to increased ground-state population according to the Boltzmann distribution law. Electron spin resonance spectra of samples at both room and liquid-nitrogen temperature exhibited resonance signals at g ae 2, attributed to Gd3+ ions arranged with octahedral symmetry linked via oxygen bridges. Various magnetic and thermodynamic parameters for the phosphor system were evaluated by standard procedures. Correlation of these values with the optical properties suggested that the GdAlO3 phosphor can be effectively used as an UV-B light source for industrial applications at room temperature.</P>

PL and ESR of Gd3+ in LaMgAl11O19 phosphors

Singh, Vijay,Singh, N.,Pathak, M. S.,Watanabe, S.,Gundu Rao, T. K.,Singh, Pramod K.,Kwon, Young-Wan Springer-Verlag 2018 Journal of materials science Materials in electron Vol.29 No.6

<P>LaMgAl11O19 doped with different concentrations of gadolinium phosphors were synthesized by combustion and characterized using X-Ray diffraction to identify the crystalline phase. Photoluminescence studies on the sample showed emission peaks at 313 and 306 nm with lambda(exi) = 273 nm corresponding to the P-6 (J) -> S-8(7/2) transitions of Gd3+ ions. In phosphors with low dopant concentrations, dominant electron spin resonance lines are observed with g (eff) similar to 1.96, 1.98, 4.2, and 6.0. With increasing concentrations, the spectrum appears to be U-shaped, and main lines are seen at g (eff) similar to 1.98, 2.04, 2.8, 4.1 and 6.2. Distortions in the immediate environment of Gd3+ ions lead to relatively strong crystal fields and the appearance of lines in the low field region of the spectrum.</P>

Charge and mass transport properties of La₂Ni_0.95Al_0.05O_4.025+δ

Jeon, S.Y.,Singh, B.,Im, H.N.,Seong, K.P.,Song, S.J. Elsevier Sequoia 2014 Journal of alloys and compounds Vol.589 No.-

<P>In this work, mass and charge transport properties of acceptor doped lanthanum nickelate, La2Ni0.95Al0.05O4.025+delta d (LNAO), were analyzed. The thermal expansion, electrical conductivity and thermoelectric power of LNAO were measured as a function of temperature in 25-1000 degrees C range and oxygen partial pressure ( pO(2)) in -14 <= log (pO(2)/atm)6 <= -1 range. The average thermal expansion coefficient was 13.77 x 10 (6) K (1). The electrical conductivity was analyzed in relation to the thermoelectric power to elucidate the positive deviation of the activity coefficient of hole on the basis of the delocalized electron model. The thermoelectric power measurement shows a p-type to n- type transition. The chemical diffusion coefficient (D-chem) and surface exchange coefficient (ksurf.) were calculated by 4-probe DC conductivity measurement and ksurf. was slightly higher than ((D) over tilde Dchem). The best- estimated hole-mobility values showed very weak temperature dependence. The results were compared with the literature results on La2NiO4+ d. (C) 2013 Elsevier B.V. All rights reserved.</P>