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991.
992.
Abhay V. Patil Joshua J. Rychak John S. Allen Alexander L. Klibanov John A. Hossack 《Ultrasound in medicine & biology》2009
A dual frequency excitation method for simultaneous translation and selective real-time imaging of microbubbles is presented. The method can distinguish signals originating from free flowing and static microbubbles. This method is implemented on a programmable scanner with a broadband linear array. The programmable interface allows for dynamic variations in the acoustic parameters and aperture attributes, enabling application of this method to large blood vessels located at varying depths. The performance of the method was evaluated in vitro (vessel diameter 2mm) by quantifying the sensitivity of the method to various acoustic, microbubble, and fluid flow parameters. It was observed that the static microbubble response maximized at the approximate resonance frequency of the microbubble population (estimated from a coulter counter measurement), thus, signifying the need for dual frequency excitation. The static microbubble signal declined from 25 to 12 dB with increasing centerline flow velocities (2.65–15.9cm/s); indicating the applicable range of flow velocities. The maximum intensity of the static microbubbles signal scaled with variations in the microbubble concentration. The rate of increment of static microbubble signal was independent of microbubble concentration. It was deduced that the rate of increment of the static microbubble signal is primarily a function of the pulse frequency, whereas the maximum static microbubble signal intensity is dependent on three parameters: (a) the pulse frequency, (b) the flow velocity and (c) the microbubble concentration. The proposed dual frequency sequence may enable the application of radiation force for optimizing the effect of targeted imaging and modulating drug delivery in large blood vessels with high flow velocities. (E-mail: avp2b@virginia.edu) 相似文献
993.
994.
A.I. Lee M.J. Hoffman N.N. Allen J.T. Sullivan 《International Journal of Obstetric Anesthesia》2010,19(2):223-226
We describe the use of epidural analgesia in a 39-year-old G2P1 parturient presenting at 38+6 weeks estimated gestation with confirmed influenza A H1N1 and superimposed bilateral pneumonia. Although the patient had an uncomplicated intra- and post-partum course, little is known about the safety of performing neuraxial analgesia or anesthesia in patients with influenza. The prevalence of viremia and possible translocation of blood-borne virus to the central nervous system are discussed. 相似文献
995.
The concept of ‘trajectory’ refers to the unfolding of individual service users’ health and illness experiences, the organization of health and social care work surrounding them and the impact this work has on people involved. Using qualitative data from a study completed in two sites in Wales we first reveal the complex character of trajectories encountered in the community mental health field. We show how these can be shaped by features peculiar to mental ill-health per se, and by features with organizational origins. We then use our data to lay bare true divisions of labor. Mental health professionals featured prominently in our study. We also reveal relatively invisible contributions made by professionals on the periphery, support workers, unpaid lay carers and service users. In examining the significance of our findings we identify particular lessons for mental health practitioners, managers and policymakers sharing concerns for the coordination of care. 相似文献
996.
S. A. Fisher D. Allen C. Dorée J. Naylor E. Di Angelantonio D. J. Roberts 《Transfusion medicine (Oxford, England)》2016,26(1):15-33
Vasovagal reactions (VVRs) in blood donors have significant implications for the welfare of donors, donor retention and the management of donor sessions. We present a systematic review of interventions designed to prevent or reduce VVRs in blood donors. Electronic databases were searched for eligible randomised trials to March 2015. Data on study design and outcomes were extracted and pooled using random effects meta‐analyses. Sixteen trials met the inclusion criteria: five trials (12 042 participants) of pre‐donation water, eight trials (3500 participants) of applied muscle tension (AMT) and one trial each of AMT combined with water, caffeine, audio‐visual distraction and/or social support. In donors receiving pre‐donation water, the relative risk (RR) compared with controls for VVRs was 0·79 [95% confidence interval (CI) 0·70–0·89, P < 0·0001] and the mean difference (MD) in severity of VVRs measured with the Blood Donation Reactions Inventory (BDRI) score was ?0·32 (95% CI ?0·51 to ?0·12, P < 0·0001). Excluding trials with a high risk of selection bias, the RR for VVRs was 0·70 (95% CI 0·45–1·11, P = 0·13). In donors who received AMT, there was no difference in the risk of chair recline in response to donor distress from controls (RR 0·76, 95% CI 0·53–1·10, P = 0·15), although the MD in BDRI score was ?0·07 (95% CI ?0·11 to ?0·03, P = 0·0005). There was insufficient data to perform meta‐analysis for other interventions. Current evidence on interventions to prevent or reduce VVRs in blood donors is indeed limited and does not provide strong support for the administration of pre‐donation water or AMT during donation. Further large trials are required to reliably evaluate the effect of these and other interventions in the prevention of VVRs. 相似文献
997.
998.
Dan T. Major Annie Heroux Allen M. Orville Michael P. Valley Paul F. Fitzpatrick Jiali Gao 《Proceedings of the National Academy of Sciences of the United States of America》2009,106(49):20734-20739
The proton transfer reaction between the substrate nitroethane and Asp-402 catalyzed by nitroalkane oxidase and the uncatalyzed process in water have been investigated using a path-integral free-energy perturbation method. Although the dominating effect in rate acceleration by the enzyme is the lowering of the quasiclassical free energy barrier, nuclear quantum effects also contribute to catalysis in nitroalkane oxidase. In particular, the overall nuclear quantum effects have greater contributions to lowering the classical barrier in the enzyme, and there is a larger difference in quantum effects between proton and deuteron transfer for the enzymatic reaction than that in water. Both experiment and computation show that primary KIEs are enhanced in the enzyme, and the computed Swain-Schaad exponent for the enzymatic reaction is exacerbated relative to that in the absence of the enzyme. In addition, the computed tunneling transmission coefficient is approximately three times greater for the enzyme reaction than the uncatalyzed reaction, and the origin of the difference may be attributed to a narrowing effect in the effective potentials for tunneling in the enzyme than that in aqueous solution. 相似文献
999.
1000.
Wynne E. Moss Jonathan N. Pauli Gustavo A. Gutiérrez Allen M. Young Christopher Vaughan Geovanny Herrera M. Zachariah Peery 《Conservation Genetics Resources》2011,3(4):625-627
Hoffmann’s two-toed sloth (Choloepus hoffmanni) is an arboreal mammal found throughout the Neotropics. Due to its limited dispersal power and reliance on forested habitats, C. hoffmanni could serve as a model species for understanding the response of mammals to land cover change. To better understand sloth life history and their response to tropical forest fragmentation and loss, we developed and characterized 16 polymorphic microsatellite markers. We tested each locus with 16–23 C. hoffmanni individuals sampled in northeastern Costa Rica. The number of alleles per locus ranged from three to seven, while mean observed heterozygosity was 0.56 and ranged from 0.33 to 0.75. All loci met Hardy–Weinberg expectations and none of the loci exhibited significant linkage disequilibrium. The microsatellite markers developed herein will be used to investigate dispersal rates and gene flow among habitat patches in Costa Rica, as well as provide insights into the life history of two-toed sloths. 相似文献