Rapid and cheap prototyping of a microfluidic cell sorter.

Development of a microfluidic device is generally based on fabrication-design-fabrication loop, as, unlike the microelectronics design, there is no rigorous simulation-based verification of the chip before fabrication. This usually results in extremely long, and hence expensive, product development cycle if micro/nano fabrication facilities are used from the beginning of the cycle. Here, we illustrate a novel approach of device prototyping that is fast, cheap, reliable, and most importantly, this technique can be adopted even if no state-of-the-art microfabrication facility is available. A water-jet machine is used to cut the desired microfluidic channels into a thin steel plate which is then used as a template to cut the channels into a thin sheet of a transparent and cheap polymer material named Surlyn® by using a Hot Knife™. The feature-inscribed Surlyn sheet is bonded in between two microscope glass slides by utilizing the techniques which has been being used in curing polymer film between dual layer automotive glasses for years. Optical fibers are inserted from the sides of chip and are bonded by UV epoxy. To study the applicability of this prototyping approach, we made a basic microfluidic sorter and tested its functionalities. Sample containing microparticles is injected into the chip. Light from a 532-nm diode laser is coupled into the optical fiber that delivers light to the interrogation region in the channel. The emitted light from the particle is collected by a photodiode (PD) placed over the detection window. The device sorts the particles into the sorted or waste outlets depending on the level of the PD signal. We used fluorescent latex beads to test the detection and sorting functionalities of the device. We found that the system could detect all the beads that passed through its geometric observation region and could sort almost all the beads it detected.

Hollow Bragg waveguides fabricated by controlled buckling of Si/SiO2 multilayers.

We describe integrated air-core waveguides with Bragg reflector claddings, fabricated by controlled delamination and buckling of sputtered Si/SiO2 multilayers. Thin film deposition parameters were tailored to produce a desired amount of compressive stress, and a patterned, embedded fluorocarbon layer was used to define regions of reduced adhesion. Self-assembled air channels formed either spontaneously or upon heating-induced decomposition of the patterned film. Preliminary optical experiments confirmed that light is confined to the air channels by a photonic band-gap guidance mechanism, with loss ~5 dB/cm in the 1550 nm wavelength region. The waveguides employ standard silicon processes and have potential applications in MEMS and lab-on-chip systems.

Thermal tuning of hollow waveguides fabricated by controlled thin-film buckling.

We describe the thermal tuning of air-core Bragg waveguides, fabricated by controlled formation of delamination buckles within a multilayer stack of chalcogenide glass and polymer. The upper cladding mirror is a flexible membrane comprising high thermal expansion materials, enabling large tuning of the air-core dimensions for small changes in temperature. Measurements on the temperature dependence of feature heights showed good agreement with theoretical predictions. We applied this mechanism to the thermal tuning of modal cutoff conditions in waveguides with a tapered core profile. Due to the omnidirectional nature of the cladding mirrors, these tapers can be viewed as waveguide-coupled, tunable Fabry-Perot filters.

Chip-scale spectrometry based on tapered hollow Bragg waveguides.

We describe a micro-spectrometer that exploits out-of-plane radiation at mode cutoff in a tapered leaky waveguide clad by omnidirectional Bragg reflectors. The device can be viewed as a side-coupled, tapered Fabry-Perot cavity. An effective-index transfer-matrix model reveals that optimal resolution is dependent on the reduction or mitigation of back-reflection and standing waves leading up to the cutoff point. We address this by insertion of low numerical aperture optics between the taper and the detector, and demonstrate an experimental resolution as small as approximately 1 nm and operating bandwidth >100 nm in the 1550 nm range, from a tapered waveguide with footprint approximately 50 microm x 500 microm. The device combines the small size of a Fabry-Perot instrument with the detector array compatibility and fixed optics of a grating-based instrument.

Inexpensive, universal serial bus-powered and fully portable lab-on-a-chip-based capillary electrophoresis instrument.

Capillary electrophoresis is a cornerstone of lab-on-a-chip (LOC) implementations for medical diagnostics. However, the infrastructure needed to operate electrophoretic LOC implementations tends to be large and expensive, hindering the development of portable or low-cost systems. A custom-designed and highly integrated microelectronic chip for high-voltage generation switching and interfacing is recently developed. Here, the authors integrate the microelectronic chip with a microfluidic chip, a solid-state laser, filter, lens and several dollars worth of electronic components to form an inexpensive and portable platform, which is the size of a mobile telephone. This compact system has such reduced power requirements that the complete platform can be operated using a universal serial bus link to a computer. It is believed that this system represents a significant advancement in practical LOC implementations for point-of-care medical diagnostics.

Minimizing errors of omission: behavioural reenforcement of heparin to avert venous emboli: the BEHAVE study.

OBJECTIVE: To improve patient safety by increasing heparin thromboprophylaxis for medical-surgical intensive care unit patients using a multiple-method approach to evidence-based guideline development and implementation. DESIGN: Prospective longitudinal observational study. SETTING: Medical-surgical intensive care unit. PARTICIPANTS: Multidisciplinary clinicians caring for critically ill patients in a 15-bed medical-surgical closed intensive care unit. INTERVENTIONS: Phase 1 was a 3-month baseline period during which we documented anticoagulation and mechanical thromboprophylaxis. Phase 2 was a 1-yr period in which we implemented a thromboprophylaxis guideline using a) interactive multidisciplinary educational in-services; b) verbal reminders to the intensive care unit team; c) computerized daily nurse recording of thromboprophylaxis; d) weekly graphic feedback to individual intensivists on guideline adherence; and e) publicly displayed graphic feedback on group performance. Phase 3 was a 3-month follow-up period 10 months later, during which we documented thromboprophylaxis. Computerized daily nurse recording of thromboprophylaxis continued in this period. MEASUREMENTS AND MAIN RESULTS: Intensive care unit and hospital mortality rates were similar across phases, although patients in phase 2 had higher Acute Physiology and Chronic Health Evaluation II scores than patients in phases 1 and 3. The proportion (median % [interquartile range]) of intensive care unit patient-days of heparin thromboprophylaxis in phases 1, 2, and 3 was 60.0 (0, 100), 90.9 (50, 100), and 100.0 (60, 100), respectively (p=.01). The proportion (median % [interquartile range]) of days during which heparin thromboprophylaxis was omitted in error in phases 1, 2, and 3 was 20 (0, 53.8), 0 (0, 6.3), and 0 (0, 0), respectively (p<.001). CONCLUSIONS: After development and implementation of an evidence-based thromboprophylaxis guideline, we found significantly more patients receiving heparin thromboprophylaxis. Guideline adherence was maintained 1 yr later. Further research is needed on which are the most effective strategies to implement patient safety initiatives in the intensive care unit.

Improving patients' safety locally: changing clinician behaviour.

Safety initiatives in hospitals should focus on common health care interventions that when used appropriately can improve important health outcomes, and when used inappropriately or not at all, result in substantial harm. We suggest that errors of omission should be a safety priority. We focus on preventive health care interventions, and describe five steps that can improve patients' safety by changing clinician behaviour. The steps are to: do an environmental scan; understand current behaviour, target behaviour for change (why, what, when, where, and who); adopt effective strategies to change behaviour; and synergise.

Small core rib waveguides with embedded gratings in As2Se3 glass.

Low-loss shallow-rib waveguides were fabricated using As2Se3 chalcogenide glass and polyamide-imide polymer. Waveguides were patterned directly in the As2Se3 layer by photodarkening followed by selective wet etching. Theory predicted a modal effective area of 3.5-4 microm2, and this was supported by near-field modal measurements. The Fabry-Perot technique was used to estimate propagation losses as low as ~0.25 dB/cm. First-order Bragg gratings near 1550 nm were holographically patterned in some waveguides. The Bragg gratings exhibited an index modulation on the order of 0.004. They were used as a means to assess the modal effective indices of the waveguides. Small core As2Se3 waveguides with embedded Bragg gratings have potential for realization of all-optical Kerr effect devices.

Clinical estimation of trunk position among mechanically ventilated patients.

OBJECTIVES: Trunk position at 45 degrees from the horizontal is associated with a decreased risk of gastroesophageal aspiration. The objectives of this study were to determine the accuracy of trunk flexion estimates compared to a reference standard measurement, and to determine agreement about trunk flexion among ICU clinicians. DESIGN: Prospective observational study. SETTING: Two university-affiliated medical-surgical ICUs. PATIENTS AND PARTICIPANTS: Thirty-three mechanically ventilated ICU patients, seven residents, two fellows, three intensivists, and twenty-eight bedside nurses. INTERVENTIONS: Prospectively, concurrently, and independently during rounds, one bedside nurse, one resident, one fellow, and one intensivist clinically estimated the trunk flexion of mechanically ventilated patients. To record the reference standard, a trained investigator measured trunk position in the vertical plane using a goniometer. MEASUREMENTS AND RESULTS: We made 438 clinical assessments on 33 patients aged 57.2+/-19.4 (SD) years with an APACHE II score of 27.3+/-9.4. Mean trunk flexion estimates were: nurses 24.3+/-12.3 degrees from the horizontal, residents 20.2+/-13.7, fellows 20.3+/-10.8, and intensivists 21.1+/-13.1 compared to the reference standard measurement 16.2+/-9.0 degrees. The accuracy of trunk flexion estimates was fair to moderate [intraclass correlation for reference standard versus nurses (ICC 0.42), residents (ICC 0.52), fellows (ICC 0.36), and intensivists (ICC 0.55)]. The agreement among different groups of clinicians was moderate. CONCLUSIONS: In mechanically ventilated patients, we found that clinical estimates of trunk position were moderately good, agreement amongst caregivers was moderately good, but that all clinicians tended to overestimate the angle of semirecumbency.

Photoinduced refractive index change in As2Se3 by 633nm illumination.

Photodarkening of amorphous As2Se3 thin films was generated by a 633-nm HeNe laser. The refractive index and absorption coefficient of the chalcogenide glass was determined, both before and after exposure, by analyzing the material's transmission spectrum. In order to accurately determine the optical constants, the thin film's non-uniform thickness was accounted for. The increase in the refractive index and the coefficient of absorption was investigated and was found to demonstrate saturation with increased exposure time. Index changes as high as 0.05, or 2%, were obtained in As2Se3, a promising glass for all-optical switching.

Prevention and diagnosis of venous thromboembolism in critically ill patients: a Canadian survey.

BACKGROUND: Venous thromboembolism (VTE) confers considerable morbidity and mortality in hospitalized patients, although few studies have focused on the critically ill population. The objective of this study was to understand current approaches to the prevention and diagnosis of deep venous thrombosis (DVT) and pulmonary embolism (PE) among patients in the intensive care unit (ICU). DESIGN: Mailed self-administered survey of ICU Directors in Canadian university affiliated hospitals. RESULTS: Of 29 ICU Directors approached, 29 (100%) participated, representing 44 ICUs and 681 ICU beds across Canada. VTE prophylaxis is primarily determined by individual ICU clinicians (20/29, 69.0%) or with a hematology consultation for challenging patients (9/29, 31.0%). Decisions are usually made on a case-by-case basis (18/29, 62.1%) rather than by preprinted orders (5/29, 17.2%), institutional policies (6/29, 20.7%) or formal practice guidelines (2/29, 6.9%). Unfractionated heparin is the predominant VTE prophylactic strategy (29/29, 100.0%) whereas low molecular weight heparin is used less often, primarily for trauma and orthopedic patients. Use of pneumatic compression devices and thromboembolic stockings is variable. Systematic screening for DVT with lower limb ultrasound once or twice weekly was reported by some ICU Directors (7/29, 24.1%) for specific populations. Ultrasound is the most common diagnostic test for DVT; the reference standard of venography is rarely used. Spiral computed tomography chest scans and ventilation-perfusion scans are used more often than pulmonary angiograms for the diagnosis of PE. ICU Directors recommend further studies in the critically ill population to determine the test properties and risk:benefit ratio of VTE investigations, and the most cost-effective methods of prophylaxis in medical-surgical ICU patients. INTERPRETATION: Unfractionated subcutaneous heparin is the predominant VTE prophylaxis strategy for critically ill patients, although low molecular weight heparin is prescribed for trauma and orthopedic patients. DVT is most often diagnosed by lower limb ultrasound; however, several different tests are used to diagnose PE. Fundamental research in critically ill patients is needed to help make practice evidence-based.

Ageism, age relations, and garment industry work in Montreal.

This study examined the complexities of age relations at work. Garment workers believed that their fate was linked to ageism and that their work experience was discounted by management. Managers wanted to be rid of older workers because they commanded higher wages than younger workers. The issue was cost reduction, and age was implicated unintendedly. Still, managers seemed to use stereotypical images to discourage older workers and they did not organize work routines to facilitate the adaptation of them. Instead, they subcontracted the easy jobs, relying on the experience of the older employees for difficult work while not adapting the workplace. Theoretically, the authors argue that ageism and age discrimination can best be understood through a recognition of the importance of structured age relations and human agency.

MMI multiplexer for dual-channel erbium-doped waveguide amplifiers.

A multimode interference coupler is proposed for pumping two erbium-doped waveguide amplifiers from a single 980 nm pump channel. Simulations predict that a device less than 2500 microm long can be made with signal and pump power losses of 0.28 dB and 0.63 dB respectively. The calculated 1 dB excess loss bandwidth of the device is 57 nm.

Diversity and the state of sociological aging theory.

In the literature on aging there have been almost simultaneous calls for researchers to make more explicit links between theory and research and for researchers to incorporate diversity in their work. Although gerontologists have begun to document diversity, theory is often absent from this research. In this article, the author examines sociological aging theories of inequality and argues that this absence of theory may not be due to an oversight on the part of researchers. Rather, aging theories need to be rethought to be better suited for diversity research.

Peritoneal membrane transport and hypoalbuminemia: cause or effect?

OBJECTIVE: Peritoneal membrane transport has been associated with serum albumin and clinical outcome. We examined the relationship between serum albumin and peritoneal membrane transport status before and after the initiation of peritoneal dialysis. SETTING: Patients were followed at a tertiary-care regional nephrology program at St. Joseph's Hospital, McMaster University, Hamilton, Ontario, Canada. METHODS: Incident peritoneal dialysis patients between 1 January 1995 and 31 May 1998 were eligible if there was a peritoneal equilibration test within 180 days of starting dialysis, and a serum albumin value measured within 90 days prior to, and 20 to 70 days after initiating dialysis. MAIN OUTCOME MEASURES: Serum albumin, before and after the initiation of dialysis, and the presence of proteinuric renal disease were compared with the peritoneal equilibration test results. RESULTS: Among 67 identified patients, there were 7 high, 27 high-average, 26 low-average, and 7 low transporters and the mean serum albumin values before dialysis were 35.1, 37.4, 37.8, and 40.4 g/L, respectively (p < 0.001). Serum albumin values prior to the initiation of dialysis correlated significantly with the 4-hour D/P creatinine ratio (r = -0.251, p = 0.040). After initiation of dialysis, the correlation was stronger (r= -0.447, p< 0.001). Serum albumin prior to initiation of dialysis was lower for those with proteinuric than nonproteinuric renal disease (36.4 g/L vs 38.8 g/L, p = 0.04). The trend to lower serum albumin in high transporters was seen in patients with both proteinuric and nonproteinuric renal disease. CONCLUSION: The association between higher peritoneal membrane transport and lower serum albumin is present before initiation of dialysis in both proteinuric and nonproteinuric renal disease. The poor outcomes associated with low serum albumin and higher peritoneal membrane transport might be explained by other underlying factors. The contribution of inflammation, malnutrition, and fluid overload requires further study.

Single-step fabrication of refractive microlens arrays.

Arrays of submillimeter microlenses are made from droplets of UV-curable optical adhesive dispensed from a pressurized syringe under computer control. Measurements of the focal length uniformity, the minimum focused spot size, and the spherical aberration are presented. An excellent lens diameter and focal length uniformity are achieved over 100 element arrays.

Knowledge, power and experience: variation in physicians' perceptions of breast cancer risk factors.

Recent theory in anthropology has increasingly been concerned with issues of power. Anthropology also has a long history of interest in variation in cultural knowledge, which, we argue, benefits from attention to power relations. To show this, we examine perceptions of breast cancer risk factors among physicians. Although physicians share a general cultural model of breast cancer risk factors, variation exists, especially between university-based physicians and community-based physicians. The nature of the work performed in these two settings influences the acquisition of various sources of information and frames what is considered valid information. Similar to Foucault's argument, we find that physicians working in a university setting are more disciplined in discussing their perceptions of breast cancer risk factors, compared to community-based physicians, who move away from the centers of knowledge and power (universities).

V-groove gratings for infrared beam splitting: reply.

It is acknowledged that scalar diffraction theory may not be used to design accurately gratings with submicrometer features. This does not negate the concept of the v-groove beam-splitting grating.

Structure and meaning in models of breast and cervical cancer risk factors: a comparison of perceptions among Latinas, Anglo women, and physicians.

This article reports on a study of perceptions of breast and cervical cancer risk factors among 27 U.S.-born Chicanas, 39 Mexican and 28 Salvadoran immigrants, 27 Anglo women, and 30 physicians in northern Orange County, California. In open-ended responses explaining why women might be at risk for both cancers, Latinas expressed two general themes: physical stress and trauma to the body, and behavior and lifestyle choices. Interviewees ranked the specific risk factors that they themselves mentioned. Cultural consensus of ranked data revealed that Mexican and Salvadoran immigrants had a model of cancer risks that was different from those of Anglo women and physicians. U.S.-born Chicanas were bicultural in their views, which overlapped with both Mexican women's and Anglo women's views, but less so with physicians' views. Comparing views about the two cancers revealed that general themes apply across both cancers, that Latina immigrants agreed less on the risk factors for cervical cancer than for breast cancer, and that there is a consistent pattern in the different ways Latinas, Anglos, and physicians perceive risk factors for both cancers.

Understanding knowledge and attitudes about breast cancer. A cultural analysis.

OBJECTIVE: To evaluate knowledge and attitudes about breast cancer risk factors among Latinas, Anglo-American women, and physicians. DESIGN: Ethnographic interviews employing systematic data collection methods. PARTICIPANTS: Twenty-eight Salvadoran immigrants, 39 Mexican immigrants, 27 Chicanas, and 27 Anglo-American women selected through an organization-based network sampling and a convenience sample of 30 primary care physicians in Orange County, Calif. MAIN OUTCOME MEASURES AND RESULTS: Data analysis using qualitative content analysis and quantitative cultural consensus analysis, a mathematical technique that determines the degree of shared knowledge within groups and estimates "culturally correct" answers (cultural models), was employed. The content analysis revealed different beliefs about breast cancer risk factors, particularly between the Latinas and the physicians. The cultural consensus analysis found two broad cultural models (defined as groups with ratios between the first and second eigenvalues of > or = 3 and no negative competency scores). A Latina model (ratio = 3.4), formed by the Salvadorans, Mexicans, and Chicanas, emphasized breast trauma and "bad" behaviors, including drinking alcohol and using illegal drugs as risk factors. A biomedical model (ratio = 3.0), embraced by physicians and Anglo-American women, emphasized risk factors described in the medical literature, such as family history and age. Within these broad models, each group of respondents also differed enough in their beliefs to form their own, often stronger, cultural models. CONCLUSIONS: Ethnography can provide important insights about culturally based knowledge and attitudes about disease. An understanding of the distinctive cultural models regarding breast cancer risk factors will aid future cancer control interventions.