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1.
Reddick WE Russell JM Glass JO Xiong X Mulhern RK Langston JW Merchant TE Kun LE Gajjar A 《Magnetic resonance imaging》2000,18(7):787-793
Medulloblastoma is the most common malignant brain tumor in children, and approximately seventy percent of average-risk patients will achieve long-term survival. Craniospinal irradiation (CSI), combined with chemotherapy and surgery, is currently the mainstay of treatment but places children who survive at risk for serious neurocognitive sequelae. These sequelae are intensified with a younger age at treatment, greater elapsed time following treatment, and an increased radiation dose. Many newer treatment approaches have attempted to address this problem by reducing the dose of the CSI component of radiation therapy while maintaining the current survival rates. This study evaluates longitudinal MR imaging during therapy to assess the impact of the two CSI doses (conventional [36 Gy] and reduced [23.4 Gy]) on normal appearing white matter volumes (NAWMV) evaluated in a single index slice. Twenty-six children and young adults at least three years of age enrolled on an institutional protocol for newly diagnosed, previously untreated primary medulloblastoma had at least four MR examinations over a minimum nine month period following CSI. These serial volumes were evaluated as a function of time since CSI in three analyses: 1) all subjects, 2) subjects stratified by age at CSI, and 3) subjects stratified by CSI dose. The first analysis demonstrated that medulloblastoma patients treated with CSI have a significant loss of NAWMV in contradistiction to normally expected maturation. Stratifying the patients by age at CSI found no significant differences in the rate of NAWMV loss. The final analysis stratified the patients by CSI dose and revealed that the rate of NAWMV loss was 23% slower in children receiving reduced-dose. Serial quantitative MR measures of NAWMV may provide a neuroanatomical substrate for assessing functional impact of CSI on normal brain function following treatment for medulloblastoma. 相似文献
2.
Mulhern KR Orchard A Watson DF Detty MR 《Langmuir : the ACS journal of surfaces and colloids》2012,28(17):7071-7082
Chalcogenorhodamine dyes bearing phosphonic acids and carboxylic acids were compared as sensitizers of nanocrystalline TiO(2) in dye-sensitized solar cells (DSSCs). The dyes were constructed around a 3,6-bis(dimethylamino)chalcogenoxanthylium core and varied in the 9 substituent: 5-carboxythien-2-yl in dyes 1-E (E = O, Se), 4-carboxyphenyl in dyes 2-E (E = O, S), 5-phosphonothien-2-yl in dyes 3-E (E = O, Se), and 4-phosphonophenyl in dyes 4-E (E = O, Se). All dyes adsorbed to TiO(2) as mixtures of H aggregates and monomers, which exhibited broadened absorption spectra relative to those of purely amorphous monolayers. Surface coverages of dyes and the extent of H aggregation varied minimally with the surface-attachment functionality, the structure of the 9-aryl group, and the identity of the chalcogen heteroatom. Carboxylic acid-functionalized dyes 1-E and 2-E desorbed rapidly and completely from TiO(2) into acidified CH(3)CN, but phosphonic acid-functionalized dyes 3-E and 4-E persisted on TiO(2) for days. Short-circuit photocurrent action spectra of DSSCs corresponded closely to the absorptance spectra of dye-functionalized films; thus, H aggregation did not decrease the electron-injection yield or charge-collection efficiency. Maximum monochromatic incident photon-to-current efficiencies (IPCEs) of DSSCs ranged from 53 to 95% and were slightly higher for carboxylic acid-functionalized dyes 1-E and 2-E. Power-conversion efficiencies of DSSCs under white-light illumination were low (<1%), suggesting that dye regeneration was inefficient at high light intensities. The photoelectrochemical performance (under monochromatic or white-light illumination) of 1-E and 2-E decayed significantly within 20-80 min of the assembly of DSSCs, primarily because of the desorption of the dyes. In contrast, the performance of phosphonic acid-functionalized dyes remained stable or improved slightly on similar timescales. Thus, replacing carboxylic acids with phosphonic acids increased the inertness of chalcogenorhodamine-TiO(2) interfaces without greatly impacting the aggregation of dyes or the interfacial electron-transfer reactivity. 相似文献
3.
An enantioselective synthesis of (S)-(+)-3-aminomethyl-5-methylhexanoic acid via asymmetric hydrogenation 总被引:2,自引:0,他引:2
Burk MJ De Koning PD Grote TM Hoekstra MS Hoge G Jennings RA Kissel WS Le TV Lennon IC Mulhern TA Ramsden JA Wade RA 《The Journal of organic chemistry》2003,68(14):5731-5734
A concise enantioselective synthesis of (S)-(+)-3-aminomethyl-5-methylhexanoic acid (1, Pregabalin) has been developed. The key step is the asymmetric hydrogenation of a 3-cyano-5-methylhex-3-enoic acid salt 2 with a rhodium Me-DuPHOS catalyst, providing the desired (S)-3-cyano-5-methylhexanoate 3 in very high ee. Subsequent hydrogenation of the nitrile 3 with a heterogeneous nickel catalyst provides Pregabalin 1 in excellent overall yield and purity. 相似文献
4.
5.
D. Hennig C. Mulhern 《The European Physical Journal B - Condensed Matter and Complex Systems》2012,85(1):1
We consider the dynamics for a system consisting of three coupled, driven and damped
particles evolving in a symmetric and spatially-periodic potential landscape. The three
coupled particles, known as a trimer, form a one-dimensional chain. Our main focus is
concentrated on running solutions for this system. In particular, we explore the nature of
these solutions. Therefore, proofs are derived showing that for the three coupled
particles in a running state 1) each particle travels the same distance in a single period
and, 2) there is only one possible transport scenario – namely when the particles travel
in rod-like motion. It is also shown that in such a state, the particles, evolving on a
periodic attractor, no longer exchange energy with one another. Thus in a running state
the three-particle system, evolving in general in a high-dimensional phase space,
effectively reduces to a single-particle system and motion takes place on a lower
dimensional attractor, viz. a limit cycle. Furthermore analysis is carried out exploring
how the frequency of the driving affects coherent particle transport. Numerical evidence
demonstrates that there is a small window of frequencies for which (low-dimensional) limit
cycles exist allowing for directed particle transport to occur. 相似文献
6.
We construct a prototypical example of a spatially-open autonomous Hamiltonian system in which localised, but otherwise unbiased, ensembles of initial conditions break spatio-temporal symmetries in the subsequent ensemble dynamics, despite time reversal symmetry of the equations of motion. Together with transient chaos, this provides the mechanism for the occurrence of a current. Transporting trajectories pass through transient chaos and subsequently cross surfaces of no-return, after which they perform solely regular motion so that the current is of continual ballistic nature. 相似文献
7.
A highly crystalline form of lithium intercalated MoS2 was investigated by performing TDPAC measurements on the 740 — (44) 141 keV γ?γ cascade in99Tc. Analysis of the data reveals the presence of two static efg interactions with the following parameters: $$\begin{array}{*{20}c} {\begin{array}{*{20}c} {v_q = 114(3) MHz,} & {\eta _1 = 0.57(5),} & {\delta _1 = 0.48(5);} \\\end{array}} \\ {\begin{array}{*{20}c} {v_{q2} = 645(19) MHz,} & {\eta = 0.45(5),} & {\delta _2 = 0.11(2).} \\\end{array}} \\\end{array}$$ 相似文献
8.
Uemura YJ Luke GM Sternlieb BJ Brewer JH Carolan JF Hardy WN Kadono R Kempton JR Kiefl RF Kreitzman SR Mulhern P Riseman TM Williams DL Yang BX Uchida S Takagi H Gopalakrishnan J Sleight AW Subramanian MA Chien CL Cieplak MZ Xiao G Lee VY Statt BW Stronach CE Kossler WJ Yu XH 《Physical review letters》1989,62(19):2317-2320
9.
Mulhern D Brooker S Görls H Rau S Vos JG 《Dalton transactions (Cambridge, England : 2003)》2006,(1):51-57
A novel, and quite general, approach for the preparation of tris(heteroleptic) ruthenium(II) complexes is reported. Using this method, which is based on photosubstitution of carbonyl ligands in precursors such as [Ru(bpy)(CO)(2)Cl(2)] and [Ru(bpy)(Me(2)bpy)(CO)(2)](PF(6))(2), mononuclear and dinuclear Ru(II) tris(heteroleptic) polypyridyl complexes containing the bridging ligands 3,5-bis(pyridin-2-yl)-1,2,4-triazole (Hbpt) and 3,5-bis(pyrazin-2-yl)-1,2,4-triazole (Hbpzt) have been prepared. The complexes obtained were purified by column chromatography and characterized by HPLC, mass spectrometry, 1H NMR, absorption and emission spectroscopy and by electrochemical methods. The X-ray structures of the compounds [Ru(bpy)(Me(2)bpy)(bpt)](PF(6))x0.5C(4)H(10)O [1x0.5C(4)H(10)O], [Ru(bpy)(Me(2)bpy)(bpzt)](PF(6))xH(2)O (2xH(2)O) and [Ru(bpy)(Me(2)bpy)(CH(3)CN)(2)](PF(6))(2)xC(4)H(10)O (6xC(4)H(10)O) are reported. The synthesis and characterisation of the dinuclear analogues of 1 and 2, [{Ru(bpy)(Me(2)bpy)}(2)bpt](PF(6))(3)x2H(2)O (3) and [{Ru(bpy)(Me(2)bpy)}(2)bpzt](PF(6))(3) (4), are also described. 相似文献
10.
We present evidence for a nonsingular origin of the Universe with intial conditions determined by quantum physics and relativistic
gravity. In particular, we establish that the present temperature of the microwave background and the present density of the
Universe agree well with our predictions from these intial conditions, after evolution to the present age using the Einstein-Friedmann
equation. Remarkably, the quantum origin for the Universe naturally allows its evolution at exactly the critical density.
We also discuss the consequences of these results to some fundamental aspects of quantum physics in the early Universe. 相似文献