Microscale Diffractive Lenses Integrated into Microfluidic Devices for Size-Selective Optical Trapping of Particles.

Integration of optical components into microfluidic devices can enhance particle manipulations, separations, and analyses. We present a method to fabricate microscale diffractive lenses composed of aperiodically spaced concentric rings milled into a thin metal film to precisely position optical tweezers within microfluidic channels. Integrated thin-film microlenses perform the laser focusing required to generate sufficient optical forces to trap particles without significant off-device beam manipulation. Moreover, the ability to trap particles with unfocused laser light allows multiple optical traps to be powered simultaneously by a single input laser. We have optically trapped polystyrene particles with diameters of 0.5, 1, 2, and 4 µm over microlenses fabricated in chromium and gold films. Optical forces generated by these microlenses captured particles traveling at fluid velocities up to 64 µm/s. Quantitative trapping experiments with particles in microfluidic flow demonstrate size-based differential trapping of neutrally buoyant particles where larger particles required a stronger trapping force. The optical forces on these particles are identical to traditional optical traps, but the addition of a continuous viscous drag force from the microfluidic flow introduces tunable size selectivity across a range of laser powers and fluid velocities.

Multi-CRAFTI: Relative Collision Cross Sections from Fourier Transform Ion Cyclotron Resonance Mass Spectrometric Line Width Measurements.

Determination of collision cross sections (CCS) using the cross-sectional areas by the Fourier transform ion cyclotron resonance (CRAFTI) technique is limited by the requirement that accurate pressures in the trapping cell of the mass spectrometer must be known. Experiments must also be performed in the energetic hard-sphere regime such that ions decohere after single collisions with neutrals; this limits application to ions that are not much more massive than the neutrals. To mitigate these problems, we have resonantly excited two (or more) ions of different m/z to the same center-of-mass kinetic energy in a single experiment, subjecting them to identical neutral pressures. We term this approach "multi-CRAFTI". This facilitates measurement of relative CCS without requiring knowledge of the pressure and enables determination of absolute CCS using internal standards. Experiments with tetraalkylammonium ions yield CCS in reasonable agreement with the one-ion-at-a-time CRAFTI approach and with ion mobility spectrometry (IMS) when differences in collision energetics are taken into account (multi-CRAFTI generally yields smaller CCS than does IMS due to the higher collision energies employed in multi-CRAFTI). Comparison of multi-CRAFTI and IMS results with CCS calculated from structures computed at the M06-2X/6-31+G* level of theory using projection approximation or trajectory method values, respectively, indicates that the computed structures have CCS increasingly smaller than the experimental CCS as m/z increases, implying the computational model overestimates interactions between the alkyl arms. For ions that undergo similar collisional decoherence processes, relative CCS reach constant values at lower collision energies than do absolute CCS values, suggesting a means of increasing the accessible upper m/z limit by employing multi-CRAFTI.

Barriers for Extrusion of a Guest from the Interior Binding Cavity of a Host: Gas Phase Experimental and Computational Results for Ion-Capped Decamethylcucurbit[5]uril Complexes.

Factors affecting the extrusion of guests from metal ion-capped decamethylcucurbit[5]uril (mc5) molecular container complexes are investigated using both collision-induced dissociation techniques and molecular mechanics simulations. For guests without polar bonds, the extrusion barrier increases with increasing guest volume. This is likely because escape of larger guests requires more displacement of the metal ion caps and, thus, more disruption of the ion-dipole interactions between the ion caps and the electronegative rim oxygens of mc5. However, guests larger than the optimum size for encapsulation displace the ion caps prior to collision-induced dissociation, resulting in less stable complexes and lower dissociation thresholds. The extrusion barriers obtained for guests with polar bonds are smaller than those obtained for similarly sized guests without polar bonds. This is likely because the partial charges on the guest allow electrostatic interactions with the ion cap and rim oxygens of mc5 during extrusion, thus stabilizing the extrusion transition state and reducing the extrusion barrier. Results from this study demonstrate simple principles to consider for designing host-guest complexes with specific guest-loss behaviors. Similar trends are observed between the experimental and computational results, demonstrating that molecular mechanics simulations can be used to approximate the relative stability of mc5 molecular container complexes and likely those of other similar complexes.

Evaluating a voice recognition system: finding the right product for your department.

The Department of Radiology at the University of Utah Health Sciences Center has been in the process of transitioning from the traditional film-based department to a digital imaging department for the past 2 years. The department is now transitioning from the traditional method of dictating reports (dictation by radiologist to transcription to review and signing by radiologist) to a voice recognition system. The transition to digital operations will not be complete until we have the ability to directly interface the dictation process with the image review process. Voice recognition technology has advanced to the level where it can and should be an integral part of the new way of working in radiology and is an integral part of an efficient digital imaging department. The transition to voice recognition requires the task of identifying the product and the company that will best meet a department's needs. This report introduces the methods we used to evaluate the vendors and the products available as we made our purchasing decision. We discuss our evaluation method and provide a checklist that can be used by other departments to assist with their evaluation process. The criteria used in the evaluation process fall into the following major categories: user operations, technical infrastructure, medical dictionary, system interfaces, service support, cost, and company strength. Conclusions drawn from our evaluation process will be detailed, with the intention being to shorten the process for others as they embark on a similar venture. As more and more organizations investigate the many products and services that are now being offered to enhance the operations of a radiology department, it becomes increasingly important that solid methods are used to most effectively evaluate the new products. This report should help others complete the task of evaluating a voice recognition system and may be adaptable to other products as well.

A method for estimating solid organ donor potential by organ procurement region.

OBJECTIVES: This study sought to develop a methodology for estimating potential solid organ donors and measuring donation performance in a geographic region based on readily available data on the hospitals in that region. METHODS: Medical records were reviewed in a stratified random sample of 89 hospitals from 3 regions to attain a baseline of donor potential. Data on a range of hospital characteristics were collected and tested as predictors of donor potential through the use of hierarchical Poisson regression modeling. RESULTS: Five hospital characteristics predicted donor potential: hospital deaths, hospital Medicare case-mix index, total hospital staffed beds, medical school affiliation, and trauma center certification. Regional estimates were attained by aggregating individual hospital estimates. Confidence intervals for these regional estimates indicated that actual donations represented from 28% to 44% of the potential in the regions studied. CONCLUSIONS: This methodology accurately estimates organ donor potential within 3 geographic regions and lays the foundation for evaluating organ donation effectiveness nationwide. Additional research is needed to test the validity of the model in other geographic regions and to further explore organ donor potential in hospitals with fewer than 50 beds.

Analysis of donor versus nondonor demographics.

A retrospective analysis of the demographic features of all potential organ donors over a 3-year period (1994-1996) at one organ procurement organization was conducted. The potential donor pool of 495 people was 42% female and 58% male, with a slight difference in consent by gender. The mean income difference between donors and nondonors was less than $3000 per year (obtained from zip code census data). Educational achievement affected donation at the lowest educational levels. Cause of death influenced donation, with motor vehicle crash victims donating more often. The strongest factor in consent for donation was ethnicity; whites were more likely to donate than were other ethnic groups. The combination of gender, ethnicity, and cause of death improved the probability of determining a positive outcome to 63%. Demographic information on donors and nondonors can increase public and professional understanding as well as influence decision making to improve donation.

Analysis of organ donors in the peripartum period.

This study was a retrospective review of 252 brain-dead potential donors from 1990 to 1996, including 5 organ donors in the peripartum period. The purpose of the study was to determine the effects of pregnancy on organ donor management and recipient outcome. Case analysis of 5 pregnant donors identified problems with hemodynamic stability and electrolyte abnormalities, including hypernatremia, hyperchloremia, and hypocalcemia. In addition, blood glucose was frequently elevated. Two donors were treated for diabetes insipidus. All 5 donors produced organs for 20 transplant recipients. Five heart recipients (including 1 heart-lung), 4 liver recipients, 4 kidney recipients, and 4 pancreas-kidney recipients have reported excellent outcomes. The use of organs from brain-dead organ donors in the peripartum period has minimal impact on donor management and recipient outcome.

Readiness of critical care physicians and nurses to handle requests for organ donation.

BACKGROUND: Critical care nurses and physicians usually care for those patients whose condition progresses to brain death and are also often responsible for requesting organ donation from the family of a brain-dead patient. We hypothesized that staff support, knowledge, and training levels would be significantly associated with organ donation rates. OBJECTIVE: To assess the readiness of critical care staff to successfully handle requests for organ donation. METHODS: A total of 1061 critical care staff from 28 hospitals in four separate regions of the United States completed a questionnaire that assessed (1) factual knowledge about organ donation, (2) understanding of brain death, (3) previous training in procedures for requesting donations, and (4) comfort levels with the donation process. RESULTS: Staff training in effective procedures for requesting organ donations was significantly correlated with hospitals' donation rates. Less than a third of respondents, however, had received training in explaining brain death to and requesting organ donation from a grieving family. In hospitals with high rates of organ donation, 52.9% of staff had received training; in hospitals with low rates of organ donation, 23.5% of staff had received training. Levels of factual knowledge about organ donation and brain death were unexpectedly low but were not significantly related to hospitals' rates of organ donation. CONCLUSIONS: Training of critical care nurses and physicians in effective procedures for requesting organ donation is significantly associated with higher rates of organ donation, yet two thirds of critical care staff report no relevant training. Consequently, critical care staff cannot be considered ready to effectively handle requests for organ donation.

Transjugular intrahepatic portosystemic shunt (TIPS).

A transjugular intrahepatic portosystemic shunt (TIPS) is a recently developed radiologic technique that is useful in the treatment of complications of portal hypertension, variceal bleeding, and ascites. A TIPS is an accepted interventional procedure indicated for the select group of patients who either have variceal bleeding that does not respond to sclerotherapy, variceal banding, pharmacologic means, or who have intractable ascites. In this article, the procedure, along with the pre- and post-procedural nursing care, is described.

Improving the request process to increase family consent for organ donation.

The greatest impediment to organ donation is refusal of family consent. This study examined the impact of 3 modifiable elements of the donation request on family consent rates: (1) decoupling (i.e., the family understands and accepts brain death before discussion of organ donation is begun); (2) the procurement coordinator participates in the request for consent; and (3) donation is requested in a quiet, private place. Data on the request process were collected prospectively for 707 medically suitable potential donors who had been referred to 3 organ procurement organizations. The average rate of consent for donation was 62.2%. Higher consent rates were independently associated with the 3 characteristics studied. These components were summarized in the Request Process Scale. Multivariate regression analyses indicated that consent rates can be as high as 74% when all 3 process elements are present. Hospitals and organ procurement organizations should incorporate these elements into their standard of practice when requesting organ donation.

Function of root border cells in plant health: pioneers in the rhizosphere.

Plants dedicate a large amount of energy to the regulated production of living cells programmed to separate from roots into the external environment. This unusual process may be worth the cost because it enables the plant to dictate which species will share its ecological niche. For example, border cells can rapidly attract and stimulate growth in some microorganisms and repel and inhibit the growth of others. Such specificity may provide a way to control the dynamics of adjacent microbial populations in the soil to foster beneficial associations and inhibit pathogenic invasion. Plant genes controlling the delivery of border cells and the expression of their unique properties provide tools to genetically engineer plants with altered border cell quality and quantity. Such variants are being used to test the hypothesis that the function of border cells is to protect plant health by controlling the ecology of the root system.

The impact of a comprehensive, hospital-focused intervention to increase organ donation.

In this article the results of a 2-year intervention designed to increase rates of organ donation while improving services to bereaved families of potential donors are described. The project focused on improving key elements of the organ donation process. The intervention was implemented in 50 hospitals within the service areas of three organ procurement organizations. Results show an increase in identification, referral, and asking rates. The overall donation rate increased significantly, from 33% to 43%. However, consent rates remained unchanged. Future efforts should focus on improving the request process by systematically incorporating practices that are associated with higher consent rates. This should enable hospital and organ procurement organization staff to appropriately and effectively offer families the option of organ donation; further increases in organ donation should follow.

Organ donor potential and performance: size and nature of the organ donor shortfall.

OBJECTIVES: To estimate the potential for solid organ donation; to identify modifiable reasons for nondonation. DESIGN: Retrospective medical records review. SETTING: Sixty-nine acute care hospitals in four geographic areas of the United States in 1990, and a stratified random sample of 89 hospitals in three of the same areas and 33 of the same hospitals in 1993. PATIENTS: PATIENTS < or = 70 yrs of age who were brain dead and medically suitable for donation. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: Standard forms were used to record patient demographic and hospital information. Reasons for nondonation were coded as "not identified," "family not asked," "consent denied," or "other." The main outcome measures were rate of donation and rates of nonidentification, not asking, and nonconsent. Organ donation occurred among 33% (299/916) of medically suitable cases identified in 1990 (95% confidence interval 30% to 36%). Ninety-four potential donors were not identified, 156 were not asked, 326 families denied consent, and 41 potential donors were categorized as "other," including patients who had suffered a cardiac arrest, and medical examiner prohibition of donation. In the 1993 study, organ donation occurred in an estimated 33% of suitable cases. In 1990, rates of donation were highest among patients <50 yrs of age, patients who died of traumatic causes, and non-Hispanic white patients. Logistic regression showed lower odds of donation for African American patients (odds ratio 0.38, 95% confidence interval 0.23 to 0.63) independent of potentially confounding hospital and patient variables (p=.0001). Donation rates did not vary by hospital size or type. CONCLUSIONS: Despite legal and policy initiatives, only one third of potential donors became donors in 1990, with similar results in 1993. Extrapolating the 1990 findings to the United States suggests a pool of 13,700 medically suitable donors per year. Prospective identification and requesting donation in all suitable potential donor cases could lead to 1,800 additional donors per year.

Differential Expression of Proteins and mRNAs from Border Cells and Root Tips of Pea.

Many plants release large numbers of metabolically active root border cells into the rhizosphere. We have proposed that border cells, cells produced by the root cap meristem that separate from the rest of the root upon reaching the periphery of the cap, are a singularly differentiated part of the root system that modulates the environment of the plant root by producing specific substances to be released into the rhizosphere. Proteins synthesized in border cells exhibit profiles that are very distinct from those of the root tip (root cap, root meristem, and adjacent cells). In vivo-labeling experiments demonstrate that 13% of the proteins that are abundant in preparations from border cells are undetectable in root tip preparations. Twenty-five percent of the proteins synthesized by border cells in a 1-h period are rapidly excreted into the incubation medium. Quantitative variation in levels of specific marker proteins, including glutamine synthetase, heat-shock protein 70, and isoflavone reductase, also occurs between border cells and cells in the root tip. mRNA differential-display assays demonstrate that these large qualitative and quantitative differences in protein expression are correlated with similarly distinct patterns of gene expression. These observations are consistent with the hypothesis that a major switch in gene expression accompanies differentiation into root border cells, as expected for cells with specialized functions in plant development.

Molecular cloning and expression of mRNAs encoding H1 histone and an H1 histone-like sequences in root tips of pea (Psium sativum L.).

Two cDNA clones representing mRNAs, highly expressed in pea root tips, were isolated by mRNA differential display. Ribonuclease protection analyses showed different patterns of expression of these two messages in several pea tissues. Sequence analysis showed that the first clone, PsH1b-40, has 100% homology with a previously isolated H1 histone cDNA, PsH1b. However, it has an additional 30 nt at the 3' end which is absent in PsH1b, suggesting possible multiple polyadenylation sites in the same mRNA. The second clone, PsH1b-41, encodes a deduced 19.5 kDa protein of 185 amino acids with an isoelectric point of 11.5. The putative globular domain of the encoded protein showed 67-71% residue identity with globular domains of 28 kDa pea PsH1b H1 histone and Arabidopsis thaliana H1-1 H1 histone. It has 9 repeating motifs of (T/S)XXK. In the C-terminal domain, there are four lysine-rich repeating motifs of SXK(T/S)PXKKXK which may be involved in chromatin condensation and decondensation. Southern blot analysis of nuclear DNA shows that PsH1-41 belongs to a multigene family.