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61.
Anterior cingulate and cerebellar GABA and Glu correlations measured by ¹H J-difference spectroscopy
Waddell KW Zanjanipour P Pradhan S Xu L Welch EB Joers JM Martin PR Avison MJ Gore JC 《Magnetic resonance imaging》2011,29(1):19-24
Gamma-aminobutyric acid (GABA) and glutamate (Glu) levels, normalized to total creatine (tCr), were measured in the anterior cingulate and cerebellar vermis in healthy adults (n=19, age=24.6±6.4 years) using 1H MRS at 3 T, and metabolite correlations across regions and subjects were determined. Mean anterior cingulate and cerebellar GABA/tCr ratios were 0.31 (0.08) and 0.23 (0.06), respectively, while corresponding Glu levels were 1.16 (0.10) and 0.70 (0.07), respectively. Anterior cingulate and cerebellar glutamate levels were correlated (r=0.6103, P=.0140), although it is noted that when adjusted for multiple comparisons, all correlations reported here cluster to a P value of .0583. It is unlikely that this correlation is driven by correlations in tCr, since interregional correlations were not observed for other metabolites referenced to tCr. Correlations were also observed among metabolites in both the anterior cingulate and cerebellar vermis. In the former, N-acetylasparate was linearly dependent on glutamate (r=0.6577, P=.0063) and, at or below this significance threshold, four metabolites were correlated in the cerebellar vermis (Ins/tCh: r=0.6261, P=.0109. NAA/tCh: r=0.6426, P=.0082. NAA/Glu: r=0.6412, P=.0085. tCh/Glu: r=0.6193, P=0.0122). 相似文献
62.
Combating Multidrug‐Resistant Bacteria: Current Strategies for the Discovery of Novel Antibacterials
Dr. Kieron M. G. O'Connell Dr. James T. Hodgkinson Dr. Hannah F. Sore Dr. Martin Welch Prof. George P. C. Salmond Dr. David R. Spring 《Angewandte Chemie (International ed. in English)》2013,52(41):10706-10733
The introduction of effective antibacterial therapies for infectious diseases in the mid‐20th century completely revolutionized clinical practices and helped to facilitate the development of modern medicine. Many potentially life‐threatening conditions became easily curable, greatly reducing the incidence of death or disability resulting from bacterial infections. This overwhelming historical success makes it very difficult to imagine life without effective antibacterials; however, the inexorable rise of antibiotic resistance has made this a very real and disturbing possibility for some infections. The ruthless selection for resistant bacteria, coupled with insufficient investment in antibacterial research, has led to a steady decline in the efficacy of existing therapies and a paucity of novel structural classes with which to replace them, or complement their use. This situation has resulted in a very pressing need for the discovery of novel antibiotics and treatment strategies, the development of which is likely to be a key challenge to 21st century medicinal chemistry. 相似文献
63.
Yang Y. Markow M.S. Welch A.J. Rylander H.G. III 《Quantum Electronics, IEEE Journal of》1990,26(12):2232-2239
A multiple-layer phantom consisting of a thin absorbing layer sandwiched between two nonabsorbing layers was created to simulate laser-induced thermal lesions in the eye. The nonabsorbing layers consisted of clear egg white, and the thin (20-40-μm) absorbing layer was created with black spray paint. Heat generated in the absorbing layer during 0.5-10-s argon irradiation was conducted to the adjacent egg white. Sufficient heat produced a region of coagulation that was graphically evidenced by the characteristic whiteness of cooked egg white. Light reflected from the lesion was monitored with a video camera and used as a feedback signal to control irradiation time. The laser irradiation was automatically ended when the diameter of the reflectance parameter related to coagulation thickness reached a preselected value 相似文献
64.
65.
Xu J Sun G Rossin R Hagooly A Li Z Fukukawa KI Messmore BW Moore DA Welch MJ Hawker CJ Wooley KL 《Macromolecules》2007,40(9):2971-2973
Radiolabeling studies were employed to investigate the influence of structure on the efficiency of surface functionalization for poly(acrylic acid)-coated shell crosslinked nanoparticles (SCKs) with two types of amine-terminated DOTA chelators. An intricate interplay between the chemical and physical properties of both the DOTA derivative and the SCK nanostructures was revealed, demonstrating the importance of structural control. 相似文献
66.
Tang R. Ford J. Pryor B. Anandakugan S. Welch P. Burt C. 《Electron Device Letters, IEEE》1997,18(9):426-428
A comprehensive study on the effect of extrinsic base optimization on the RF performance of an advanced SiGe HBT is presented. An optimized extrinsic poly base with its interface to the epi-base passivated by boron ions is demonstrated to enhance the fmax and the current gain almost two times and to reduce the low-frequency 1/f noise ten times and noise figure (NF) 0.5 dB, achieving fmax of 45 GHz, 1/f noise corner frequency of 700 Hz at IB=1.0 μA, NF⩽1.0 dB at 900 MHz. Early voltage VA of ⩾200 V is achieved, while maintaining a BVCEO of ⩾8.0 V 相似文献
67.
Dzurko K.M. Scifres D.R. Hardy A. Welch D.F. Waarts R.G. O'Brien S. 《Electronics letters》1992,28(16):1477-1478
A large aperture ring laser having a diffraction limited output measuring 0.2 degrees *0.2 degrees is described. The design uses angled incidence onto monolithic gratings for feedback and mode selectivity. Devices of this design have exhibited threshold current density less than 300 A/cm/sup 2/ and over 500 mW of single frequency output power.<> 相似文献
68.
Dent ML McClaine EM Welch TE 《The Journal of the Acoustical Society of America》2007,122(6):3609-3614
The properties of the Franssen effect (FE) were measured in budgerigars and zebra finches. To elicit the FE, listeners are presented with a signal which has been split into a transient component, carrying an abrupt onset and ramped offset and separated in space from the sustained component which has a slowly rising onset and longer duration. When these two signals are played under certain conditions, the perception is that of a long-duration steady state tone being played at the location of the transient. The birds were trained using operant conditioning methods on a categorization task to peck a left key when presented with a stimulus from a left speaker and to peck a right key when presented with a stimulus from a right speaker. Once training was completed, FE stimuli were presented during a small proportion of trials. The FE was measured at speaker separations of 60 degrees and 180 degrees in both echoic and echoic-reduced conditions. Both species of birds exhibited the FE, although to varying degrees, across conditions. These results show that nonmammals also experience the FE illusion in confusing listening situations in a manner similar to mammals, suggestive of similar auditory processing mechanisms. 相似文献
69.
Chromatographic enantioseparations on the order of a few seconds can be achieved by supercritical fluid chromatography using short columns packed with chiral stationary phases. The evolution of ‘world record’ speeds for the chromatographic separation of enantiomers has steadily dropped from an industry standard of 20–40 min just two decades ago, to a current ability to perform many enantioseparations in well under a minute. Improvements in instrument and column technologies enabled this revolution, but the ability to predict optimal separation time from an initial method development screening assay using the tmin cc predictor greatly simplifies the development and optimization of high‐speed chiral chromatographic separations. In this study, we illustrate how the use of this simple tool in combination with the workhorse technique of supercritical fluid chromatography on customized short chiral columns (1–2 cm length) allows us to achieve ultrafast enantioseparations of pharmaceutically relevant compounds on the 5–20 s scale, bringing the technique of high‐throughput enantiopurity analysis out of the specialist realm and into the laboratories of most researchers. 相似文献
70.
Kenwright JL Galloway WR Blackwell DT Isidro-Llobet A Hodgkinson J Wortmann L Bowden SD Welch M Spring DR 《Chemistry (Weinheim an der Bergstrasse, Germany)》2011,17(10):2981-2986
Herein, a new copper-catalysed strategy for the synthesis of rare nitrogen-linked seven-, eight- and nine-membered biaryl ring systems is described. It is proposed that the reaction proceeds through a highly activated intramolecularly co-ordinated copper catalyst. The process is technically simple, proceeds under relatively mild conditions, displays a broad substrate scope and forms biologically valuable products that are difficult to synthesise by other methods. We envisage that this methodology will prove useful in a wide synthetic context, with possible applications in both target-oriented and diversity-oriented synthesis. 相似文献