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At least 829 records · Page 46Linked to original sources
PubMed2004

Molecular precursors to gallium oxide thin films.

The donor-functionalised alkoxides [Et(2)Ga(OR)](2)(R = CH(2)CH(2)NMe(2)(1), CH(CH(2)NMe(2))(2)(2), CH(2)CH(2)OMe (3), CH(CH(3))CH(2)NMe(2)(4), C(CH(3))(2)CH(2)OMe (5)) were synthesised by the 1:1 reaction of Et(3)Ga with ROH in hexane or dichloromethane at room temperature. Reaction of Et(3)Ga with excess ROH in refluxing toluene resulted in the isolation of a 1:1 mixture of [Et(2)Ga(OR)](2) and the ethylgallium bisalkoxide [EtGa(OR)(2)](R = CH(2)CH(2)NMe(2)(6) or CH(CH(3))CH(2)NMe(2)(7)). X-ray crystallography showed that compound 6 is monomeric and this complex represents the first structurally characterised monomeric gallium bisalkoxide. Homoleptic gallium trisalkoxides [Ga(OR)(3)](2) were prepared by the 1:6 reaction of [Ga(NMe(2))(3)](2) with ROH (R = CH(2)CH(2)NMe(2)(8), CH(CH(3))CH(2)NMe(2)(9), C(CH(3))(2)CH(2)OMe (10)). The decomposition of compounds 1, 4, 5 and 8 were studied by thermal gravimetric analysis. Low pressure CVD of 1 and 5 resulted in the formation of thin films of crystalline Ga(2)O(3).

Journal Article↗
PubMed2004

Organoaluminium and -gallium compounds with N,N-diisopropylaminomethyl groups.

The N,N-diisopropylaminomethyl aluminium compound [tBu2AlCH2NiPr2 x LiCl]2(1) and the gallium compounds Li[tBu2Ga(CH2NiPr2)2](2) and [tBu2GaCH2N(H)iPr2]Cl x tBu3Ga (3) were prepared by transmetallation of N,N-diisopropylaminomethyllithium LiCH2NiPr2 with di-tert-butylaluminium or -gallium chloride, and characterised by elemental analyses, multinuclear NMR spectroscopy (1H, 13C, 27Al, 7Li) and IR spectroscopy. The crystal structures have been determined by single crystal X-ray diffraction. Compound aggregates as a centrosymmetric dimer, with two Al-C-N units connected by a frame of two LiCl molecules [Al-Cl 2.367(1), Cl-Li 2.339(4) and 2.374(4), Li-N 1.977(4)A]. Compound 2 is a lithium organogallate with two weak LiN bonds [1.965(7) and 1.937(7)A]. Compound 3 contains two different moieties: tBu3Ga and a [tBu2GaCH2N(H)iPr2]+ cation, which are bridged by a Cl- anion [Ga-Cl 2.445(1) and 2.579(1), HCl 2.362(3)A].

Journal Article↗
PubMed2005

Oxidation reactions of an anionic gallium(I) N-heterocyclic carbene analogue with group 16 compounds.

The reactivity of an anionic gallium(I) heterocycle, [K(tmeda)][:Ga([N(Ar)C(H)]2)], Ar = C6H3Pr(i)2-2,6, towards sources of elemental chalcogens and diorgano-dichalcogenides has been investigated and comparisons drawn with the reactivity of the valence isoelectronic N-heterocyclic carbene class of ligand. The reactions of the heterocycle with N2O or (Te)PEt3 yielded the dimeric, dianionic gallium(III) complexes, [K(L)]2[(mu-E)Ga([N(Ar)C(H)]2)]2, E = O, L = tmeda; E = Te, L = THF. Treatment of [K(tmeda)][:Ga([N(Ar)C(H)]2)] with the diphenyl dichalcogenides, PhEEPh, E = Se or Te, gave the one dimensional polymer, [K[(PhSe)2Ga([N(Ar)C(H)]2)]]infinity and the monomeric complex, [K(OEt2)3][(PhTe)2Ga([N(Ar)C(H)]2)], respectively. The X-ray crystal structures of the four complexes are reported.

Journal Article↗
PubMed2006

Complexes of a gallium heterocycle with transition metal dicyclopentadienyl and cyclopentadienylcarbonyl fragments, and with a dialkylmanganese compound.

The reactivity of several transition metal half sandwich complexes towards an anionic gallium(I) heterocyclic complex, [K(tmeda)][Ga{[N(Ar)C(H)]2}](Ar = C6H3Pri2-2,6), has been investigated. This has led to the anionic half sandwich complexes, [K(tmeda)][(C5H4R)M(CO)n[Ga{[N(Ar)C(H)]2}]](M = V, R = H, n= 3; M = Mn, R = Me, n= 2; M = Co, R = H, n= 1), which crystallographic studies show to form dimers (M = Mn and Co) or a polymer (M = V) through bridging potassium cations. The metal-gallium bond lengths in all complexes are very short which, combined with some spectroscopic evidence, is suggestive of M-Ga pi-bonding. Density functional theory studies of models of all complexes indicate that the level of back-bonding in these complexes is, however, minimal and of a similar order to that seen in analogous complexes incorporating neutral N-heterocyclic carbene ligands. Reactions of the metallocenes, [M(C5H4Me)2](M = V or Cr), with the digallane4, [Ga{[N(Ar)C(H)]2}]2, have afforded the neutral complexes, [M(C5H4Me)2[Ga{[N(Ar)C(H)]2}]], which are thought to be formed via an initial oxidative insertion of the transition metal centre into the Ga-Ga bond of the digallane. X-Ray crystallography shows the complexes to be monomeric. One (M = V) reacts with one equivalent of [K(tmeda)][Ga{[N(Ar)C(H)]2}] to give the crystallographically characterised, anionic bis(gallyl)-complex, [K(tmeda)][V(C5H4Me)2[Ga{[N(Ar)C(H)]2}]2]. For comparison, the reaction of [K(tmeda)][Ga{[N(Ar)C(H)]2}] with [Mn{CH(SiMe3)2}2] was carried out and gave the monomeric, anionic complex, [K(tmeda)][Mn{CH(SiMe3)2}2[Ga{[N(Ar)C(H)]2}]].

Journal Article↗
PubMed2002

Amiodarone pneumonitis diagnosed by gallium-67 scintigraphy.

A 75-year-old man presented with fever, dyspnoea, chest pain and findings suggestive of severe pneumonia including hypoxia and bilateral chest infiltrates. He was given antibiotics without significant effect. He took long-term amiodarone therapy for persistent atrial arrhythmias and also had a history of asbestosis with pre-existing pulmonary interstitial fibrosis. Pulmonary gallium-67 scintigraphy revealed extensive uptake of tracer throughout both lungs consistent with a diagnosis of amiodarone pneumonitis. Treatment of the drug reaction by drug withdrawal and corticosteroids resulted in marked clinical improvement. Pulmonary gallium-67 scintigraphy is a sensitive, but non-specific aid in the diagnosis of this drug effect. It proved valuable in our patient who additionally had asbestosis.

Journal Article↗
PubMed2005

Energy distributions of gallium nanoclusters.

Starting with the heat-capacity data of Breaux et al., [J. Am. Chem. Soc. 126, 8629 (2004)] we use the maximum-entropy method to calculate energy distribution functions for gallium-ion nanoclusters over a wide temperature range (100-1050 K). Specifically, we calculate energy distributions for clusters containing n = 39 and n = 45 gallium atoms. For the case of n = 39 clusters the energy distribution gets systematically broader as a function of temperature with no indication of any marked structural change in the cluster. On the other hand, the energy distribution for the n = 45 cluster first gets broader as a function of temperature but then gets narrower again as the temperature is further increased, indicating that there is some kind of structural transition taking place in this cluster species.

Journal Article↗
PubMed2006

Investigation of a binuclear gallium complex with bipolar charge transporting capability for organic light-emitting diodes.

Detailed theoretical and experimental investigations have been presented on a novel binuclear gallium complex Ga2(saph)2q2, a potentially active and novel material for organic light-emitting diodes (OLEDs). The density-functional theory has been employed to shed light on the reason why this complex exhibits bipolar character. Theoretical results, such as ionization potential and electron affinity, and optimized geometries are in good agreement with what we have obtained experimentally. Our theoretical analysis provides new insight into the origin of bipolar features. Such character enables the gallium complex to become a prosperous hole and electron transporter used to fabricate single-layer OLEDs, which exhibit better electroluminescence compared with those originated from the previously well-adopted tri(8-hydroxyquinoline)aluminum (Alq3). An OLED device of single Ga2(saph)2q2 layer exhibiting desirable performances has been fabricated, which is in good agreement with the theoretical analysis.

Journal Article↗
PubMed1988

Thyroid uptake of gallium in Graves' disease.

A patient with hyperthyroid Graves' disease presented with ptosis, leading to a workup for myasthenia gravis. An enlarged thymus gland was noted on computed tomography. A scan with gallium-67 citrate showed prominent and diffuse thyroid gland activity as well as prominent lacrimal activity. This finding of thyroid uptake of gallium led to the correct diagnosis of Graves' disease. Such a finding has not been reported previously. The associated thymic, thyroid, and orbital findings in Graves' disease are discussed.

Adult↗
PubMed1988

Gallium-67 localization in herpetic skin lesion.

Previous cases of gallium localization in various cutaneous lesions have been reported, including sporotrichosis, acne vulgaris, sarcoid, lymphoma, and exfoliative erythroderma. This is a report of a case of gallium localization in cutaneous lesions of herpes zoster.

Abdomen↗
PubMed2006

Nitrogen vacancies as major point defects in gallium nitride.

We present results of ab initio calculations for vacancies and divacancies in GaN. Particular attention is paid to nitrogen vacancies and mixed Ga-N divacancies in negatively charged states, which in n-type GaN are found to be energetically comparable with gallium vacancies. We also demonstrate that the activation energy for self-diffusion over the nitrogen sublattice is lower than over the gallium one for all Fermi-level positions, which implies the nitrogen vacancies are major defects in samples annealed at high temperatures. Possibilities for direct observations of nitrogen vacancies through positron annihilation experiments are discussed.

Journal Article↗
PubMed2002

Rb(GaPO4)2(OH)(H2O).H2O: a hydrated rubidium gallium phosphate analogue of GaPO4.2H2O and leucophosphite.

Crystals of the title hydrated rubidium gallium phosphate, rubidium aqua-mu(3)-hydroxo-di-mu-phosphato-digallium hydrate, were synthesized hydrothermally at 453 K under autogenous pressure. The solid crystallizes in the monoclinic system and its structure was determined from single-crystal X-ray diffraction analysis. It is similar to dihydrated gallium phosphate, GaPO(4).2H(2)O, which is isostructural with the mineral leucophosphite. The structure is built up from a three-dimensional anionic framework composed of corner-linked octameric Ga(4)(PO(4))(4)(OH)(2)(H(2)O)(2) units. The Ga atom is in an octahedral coordination. Connection of the Ga(4)P(4) species generates eight-ring channels, in which are encapsulated the Rb(+) cations and water molecules.

Journal Article↗
PubMed2004

A novel gallium arsenate organically templated by propane-1,3-diyldiammonium with a ULM-3-type open framework: [Ga3(AsO4)3(OH)F]-(C3H12N2) x H2O.

Crystals of the title oxyfluorinated gallium arsenate, viz. tris(arsenato)fluorohydroxotrigallium propane-1,3-diyldiammonium monohydrate, were synthesized hydrothermally at 453 K under autogenous pressure, using 1,3-diaminopropane as the structure-directing agent. The solid crystallizes in the orthorhombic system and its structure was determined from single-crystal X-ray diffraction analysis. The structure is similar to that of gallium or aluminium phosphates with the ULM-3 structural type and is built up from a three-dimensional anionic framework composed of corner-linked hexameric Ga3(AsO4)3(OH)F units. The Ga atoms have an octahedral [GaO4(OH)F] or trigonal-bipyramidal [GaO4(OH) and GaO4F] coordination. These units are connected to one another and to the tetrahedral AsO4 groups via OH or F bridges. The three-dimensional framework contains ten-ring channels along [010], crosslinked by eight-ring channels along [110] and [110]. The diprotonated organic species and water molecules reside within the ten-ring channels. The cation is linked to the framework via an N-H...F hydrogen bond. A strong N-H...O hydrogen bond links the cation and the water molecule.

Journal Article↗
PubMed1999

Strongly photonic macroporous gallium phosphide networks

A photo-assisted electrochemical etching technique to fabricate macropores in single-crystalline gallium phosphide (GaP) with variable porosity has been developed. Scanning electron microscopy and x-ray diffraction experiments confirm that the material consists of three-dimensional, interconnected random networks with pore sizes of about 150 nanometers. Optical transmission measurements demonstrate that the nonabsorbing disordered structures strongly scatter light. The photonic strength is controlled by filling the pores with liquids of different refractive indices. Macroporous gallium phosphide filled with air has the highest scattering efficiency for visible light.

Journal Article↗
PubMed1999

Room temperature lasing at blue wavelengths in gallium nitride microcavities

Lasing action has been demonstrated at blue wavelengths in vertical cavity surface-emitting lasers at room temperature. The microcavity was formed by sandwiching indium gallium nitride multiple quantum wells between nitride-based and oxide-based quarter-wave reflectors. Lasing action was observed at a wavelength of 399 nanometers under optical excitation and confirmed by a narrowing of the linewidth in the emission spectra from 0.8 nanometer below threshold to less than 0.1 nanometer (resolution limit) above threshold. The result suggests that practical blue vertical cavity surface-emitting lasers can be realized in gallium-nitride-based material systems.

Journal Article↗
PubMed1989

Detection of human malignant melanoma with gallium-67 citrate and N-isopropyl-(I-123) p-iodo-amphetamine.

Using N-isopropyl-(I-123)p-iodo-amphetamine (I-123 IMP) and gallium-67 citrate, it was possible to detect human malignant melanomas. I-123 IMP imaging was helpful in detecting melanomas occurring in the legs and arms, and the 4 hour image was better than the 1 hour image. Moreover, while gallium scintigraphy more clearly detects human malignant melanoma, I-123 IMP allows for the detection of human malignant melanoma within 1 hour after administration.

Aged↗
PubMedDate not supplied

Doxorubicin-gallium-transferrin conjugate overcomes multidrug resistance: evidence for drug accumulation in the nucleus of drug resistant MCF-7/ADR cells.

Development of multidrug resistance (MDR) in cancer cells decreases net doxorubicin (ADR) uptake as a result of increased efflux, increased intracellular sequestration, and decreased membrane permeability. In this study, we investigated whether conjugation of ADR to transferrin (Tf) could overcome MDR in breast cancer cells. The multidrug resistant MCF-7/ADR breast cancer cell line was over 1000-fold more resistant to ADR, than its parental MCF-7 cell line, as determined by 3[H]-thymidine assay. The MCF-7/ADR cell line also expressed both MDR1 and MRP genes, as detected by RT-PCR. The ADR was coupled using a glutaraldehyde technique to human transferrin saturated with either ferric chloride (Fe-Tf) or gallium nitrate (Ga-Tf). These conjugates were tested for cytotoxicity on both MCF-7 and MCF-7/ADR cells after 6 days of incubation. The doxorubicin-gallium-transferrin conjugate (ADR-Ga-Tf) exhibited approximately the same inhibitory effect as ADR on MCF-7 cells with IC50s of 2.34 x 10(-3) microM and 1.42 x 10(-3) microM, respectively. However in MCF-7/ADR cells ADR-Ga-Tf reversed resistance to free ADR and decreased 100-fold the IC50 from 8.98 microM with free ADR to 9.52 x 10(-2) microM. ADR-Fe-Tf was 10-fold more inhibitory to MCF-7/ADR cells than free ADR. Compared to Ga-Tf, ADR-Ga-Tf was 500- and 3000-fold more inhibitory to MCF-7 and MCF-7/ADR cells, respectively. These results demonstrated that ADR-Ga-Tf reverses resistance to free ADR and Ga-Tf in MCF-7/ADR cells. The distribution of ADR in both cell lines was examined by fluorescence microscopy. It was noted that ADR mainly accumulated in the cytoplasm around the nucleus in MCF-7/ADR cells, but in both the cytoplasm and nucleus of MCF-7 cells. However the conjugate of ADR-Ga-Tf allowed ADR to accumulate in the cytoplasm and nucleus of both the MCF-7/ADR and MCF-7 cells. Further investigation of MDR1 and MRP genes expression by RT-PCR demonstrated that Ga-Tf decreased expression of the MRP more than the MDR1 gene. Therefore the reversal of resistance to ADR by the ADR-Ga-Tf conjugate is mediated by the transferrin receptor transmembrane transport mechanism, redistribution of ADR into the nucleus of ADR resistant MCF-7/ADR cells and inhibition of MRP gene expression.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMedDate not supplied

Role of gallium arsenide laser irradiation at 890 nm as an adjunctive to anti-tuberculosis drugs in the treatment of pulmonary tuberculosis.

BACKGROUND: Tuberculosis is a global emergency with about nine million people developing disease every year. The long duration of treatment has emerged as a major obstacle in the control of tuberculosis. There is a need for development of new drugs and or shortened therapy. METHODS: The present study was carried out to explore whether any benefit could be achieved by the addition of low level energy laser therapy (LLLT) to the conventional anti-tubercular chemotherapy. One-hundred-thirty new sputum smear positive patients of pulmonary tuberculosis were enrolled to evaluate the bio-stimulatory effects of Gallium Arsenide laser irradiation at 890 nm, as an adjuvant therapy. These patients were randomly divided into two groups to receive either LLLT or sham irradiation (control) concomitantly with anti-tuberculosis chemotherpy. RESULTS: The patients treated with semiconductor laser as an adjuvant therapy along with anti-tuberculosis drugs had a faster clearance of tubercle bacilli from the sputum as compared to the control group (P value at :45 days=0.1392, 60 days=0.0117, 75 days=0.00805, 90 days=0.00739). CONCLUSIONS: These findings provide preliminary evidence that low level laser therapy with Gallium Arsenide laser may be a promising adjunctive therapy for patients with tuberculosis. Faster conversion of sputum should prevent the development of resistant mutants.

Antitubercular Agents↗
PubMed1990

Investigation of physicochemical and in-vivo behavior of diastereomeric iron-59, gallium-68, and indium-111-EHPG trivalent metal complexes.

EHPG (N, N'-ethylenebis-[2-(o-hydroxyphenyl)glycine]) trivalent metal complexes show diagnostic potential both in radiopharmaceutical applications (gallium-68, indium-111) and as MRI contrast agents (iron). Although several publications report similar behavior of iron, gallium and indium complexes, we observe significant differences between EHPG complexes of these metals both in physicochemical and in vivo analyses. In addition, stereospecific behavior has been observed for the two diastereomers of EHPG when complexed with each metal. Complexes of Fe[59Fe], 68Ga, and 111In with meso, racemic, and unseparated EHPG have been evaluated. Relative lipophilicity has been measured with HPLC. Blood clearance and liver uptake have been correlated with pM values, stability constants and metal ion reduction potentials.

Animals↗