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Manu Prakash - One of the best experts on this subject based on the ideXlab platform.
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RESEARCH ARTICLE Punch Card Programmable Microfluidics
2016Co-Authors: George Korir, Manu PrakashAbstract:Small volume fluid handling in single and multiphase microfluidics provides a promising strategy for efficient bio-chemical assays, low-cost point-of-care diagnostics and new ap-proaches to scientific discoveries. However multiple barriers exist towards low-cost field deployment of programmable microfluidics. Incorporating multiple pumps, mixers and dis-crete valve based control of nanoliter fluids and droplets in an integrated, programmable manner without additional required external components has remained elusive. Combining the idea of Punch Card programming with arbitrary fluid control, here we describe a self-contained, hand-crank powered, multiplex and robust programmable microfluidic platform. A paper tape encodes information as a series of Punched holes. A mechanical reader/actua-tor reads these paper tapes and correspondingly executes operations onto a microfluidic chip coupled to the platform in a plug-and-play fashion. Enabled by the complexity of codes that can be represented by a series of holes in Punched paper tapes, we demonstrate inde-pendent control of 15 on-chip pumps with enhanced mixing, normally-closed valves and a novel on-demand impact-based droplet generator. We demonstrate robustness of operatio
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Punch Card programmable microfluidics.
PLOS ONE, 2015Co-Authors: George Korir, Manu PrakashAbstract:Small volume fluid handling in single and multiphase microfluidics provides a promising strategy for efficient bio-chemical assays, low-cost point-of-care diagnostics and new approaches to scientific discoveries. However multiple barriers exist towards low-cost field deployment of programmable microfluidics. Incorporating multiple pumps, mixers and discrete valve based control of nanoliter fluids and droplets in an integrated, programmable manner without additional required external components has remained elusive. Combining the idea of Punch Card programming with arbitrary fluid control, here we describe a self-contained, hand-crank powered, multiplex and robust programmable microfluidic platform. A paper tape encodes information as a series of Punched holes. A mechanical reader/actuator reads these paper tapes and correspondingly executes operations onto a microfluidic chip coupled to the platform in a plug-and-play fashion. Enabled by the complexity of codes that can be represented by a series of holes in Punched paper tapes, we demonstrate independent control of 15 on-chip pumps with enhanced mixing, normally-closed valves and a novel on-demand impact-based droplet generator. We demonstrate robustness of operation by encoding a string of characters representing the word “PunchCard MICROFLUIDICS” using the droplet generator. Multiplexing is demonstrated by implementing an example colorimetric water quality assays for pH, ammonia, nitrite and nitrate content in different water samples. With its portable and robust design, low cost and ease-of-use, we envision Punch Card programmable microfluidics will bring complex control of microfluidic chips into field-based applications in low-resource settings and in the hands of children around the world.
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Integrated Punch Card controlled normally-closed valves.
2015Co-Authors: George Korir, Manu PrakashAbstract:(A) Schematic of normally-closed valves depicting mechanism of operation. (B) 3D printed cantilever beam array with spaced pins (2 mm apart), utilized for implementing 15 independent normally-closed valves. (C, D) Micrograph from video of ten normally-closed valves under operation (side view), all of which are independently actuated based on the Punch Card tape. (E) Normally-closed valve in action, at a single instance of opening and closing depicting the time duration for a single cycle (0.54 seconds). The image depicts the entire region of PDMS deformation with a completely collapsed channel.
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Punch Card controlled integrated multiplexed microfluidic pumps.
2015Co-Authors: George Korir, Manu PrakashAbstract:(A) A series of images of a single channel coupled to the rotating gear disc during one pumping cycle. (B) To characterize the flow pattern with each actuation, fluorescent polystyrene beads (2 μm) were used in de-ionized water. (C) Pumping in each cycle revealed a characteristic asymmetric pulsatile oscillatory flow depicted above as a kymograph. The amplitude of directed unidirectional flow depends on actuation height (h) and the angular velocity (ω) from the hand-crank. (D) Top-down view of the microfluidic chip with simultaneous operation of six Punch Card controlled integrated micro-pumps. Net flow rate in a fluidic line is a function of exact pattern of Punched hole (number of holes Punched and spacing between the same, an example pattern depicted above). (E) Effective flow rate characterized as a function of h and ω, easily achieving typical values demonstrated by integrated micro-pumps.
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Enhanced mixing is achieved using a zig-zag pattern of Punched holes.
2015Co-Authors: George Korir, Manu PrakashAbstract:(A) Photomicrograph of six Punch Card controlled pumps driven by a zig-zag pattern (right inset). Left inset depicts the same device run through a traditional syringe pump (at the same flow rate) to highlight the striking difference in fluid mixing at the end of the channel (200 μm wide). (B) Mixing is quantified by mean-shift clustering approach (see methods for details) comparing four regions in the micro-channel marked a, b, c, d along the outflow. Six identified clusters merge into two. (C) Photomicrographs from video data reveal the mechanism for mixing. Pulsatile nature of flow induces increased folding of neighboring flow lines (and hence net interface length) thus enhancing diffusion and mixing.
John E. Mcnulty - One of the best experts on this subject based on the ideXlab platform.
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Punch Card Technology and the Racial Gap in Residual Votes
2015Co-Authors: Justin Buchler, Matthew Jarvis, John E. McnultyAbstract:Votomatic-style Punch Card voting systems produce higher rates of residual voting than other technologies, but the effect of Punch Card voting systems is not uniform. Minority voters are less likely to have their votes properly recorded with Punch Card systems than are nonminorities. This racial gap occurs, for the most part, because Punch Card systems lead to higher rates of “undervoting ” by minorities. When election administrators switch to other systems, such as optical scan systems, the racial gap is significantly reduced. Punch Card voting systems, then, constitute a disproportionate obstacle to minority voting. This effectively gives less weight to votes cast by minorities than to votes cast by nonminorities, and arguably violates constitutional requirements for equal voting rights.The mechanism is similar to the literacy tests that were abandoned after the 1970 amendments to the Voting Rights Act. P unch Card voting has been with us for over forty years.It originated at the University of California, Berkeley,where Professor Joseph Harris and his collaborators came up with a method of using simple, inexpensive, easily portable equipment to record votes that could be tabulated mechanically using the computer technology of the day. Because Punch Card systems were cheap and their results could be tal-lied quickly, the technology was widely adopted. In the 2000 presidential election, almost one third of all voters (32.1 per-cent) used Punch Cards—more than any other type of votin
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Punch Card Technology and the Racial Gap in Residual Votes
Perspectives on Politics, 2004Co-Authors: Justin Buchler, Matthew G. Jarvis, John E. McnultyAbstract:Votomatic-style Punch Card voting systems produce higher rates of residual voting than other technologies, but the effect of Punch Card voting systems is not uniform. Minority voters are less likely to have their votes properly recorded with Punch Card systems than are nonminorities. This racial gap occurs, for the most part, because Punch Card systems lead to higher rates of “undervoting” by minorities. When election administrators switch to other systems, such as optical scan systems, the racial gap is significantly reduced. Punch Card voting systems, then, constitute a disproportionate obstacle to minority voting. This effectively gives less weight to votes cast by minorities than to votes cast by nonminorities, and arguably violates constitutional requirements for equal voting rights. The mechanism is similar to the literacy tests that were abandoned after the 1970 amendments to the Voting Rights Act. The authors are grateful to UC Berkeley's Survey Research Center for research support and are deeply indebted to Henry E. Brady. Our thanks also to the anonymous reviewers and to the editorial staff at Perspectives on Politics for their helpful suggestions and hard work on our behalf.
Arnet Isabelle - One of the best experts on this subject based on the ideXlab platform.
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Early biomarker response and patient preferences to oral and intramuscular vitamin B12 substitution in primary care: a randomised parallel-group trial
EMH Swiss Medical Publishers, 2017Co-Authors: Metaxas Corina, Arnet Isabelle, Mathis Déborah, Jeger Cyrill, Hersberger, Kurt Eduard, Walter PhilippAbstract:BACKGROUND: Vitamin B12 (VB12) deficiency can be treated with oral high-dose substitution or intramuscular (i.m.) injection of VB12. Whenever alternative routes of administration exist, patient prefer-ences should be considered when choosing the treatment. We aimed to assess outpatient preferences towards oral or IM VB12 substitution and confirm noninferiority of early biomarker response with oral treat-ment, in a typical primary care population. METHODS: Prospective randomised nonblinded parallel-group trial. Patients were recruited by their general practitioner and randomly as-signed to oral or IM treatment. Group O-oral was given 28 tablets of 1000 μg cyanocobalamin in a monthly Punch Card fitted with an elec-tronic monitoring system. Group I-IM received four, weekly injections of 1000 μg hydroxocobalamin. Blood samples were drawn before the first administration and after 1, 2 and 4 weeks of treatment, and ana-lysed for VB12, holotranscobalamin (HoloTc), homocysteine (Hcy) and methylmalonic acid (MMA). For group O-oral, treatment adherence and percentage of days with 2 dosing events were calculated. Before and after 28 days of treatment, patients were asked to fill in a ques-tionnaire about their preference for the therapy options and associ-ated factors. RESULTS: Between November 2013 and December 2015, 37 patients (age: 49.5 ± 18.5 years; women: 60.5%) were recruited for oral (19) or IM (18) treatment. Baseline values with 95% confidence intervals for serum VB12, HoloTc, Hcy and MMA were 158 pmol/l [145-172], 49.0 pmol/l [40.4-57.5], 14.8 µmol/l [12.0-17.7] and 304 nmol/l [219-390], respective-ly, in group O-oral and 164 pmol/l [154-174], 50.1 pmol/l [38.7-61.6], 13.0 µmol/l [11.0-15.1] and 321 nmol/l [215-427], respectively, in group I-IM (not significant). After 1 month of treatment, levels of VB12 and HoloTc showed a significant increase compared with baseline (group O-oral: VB12 354 pmol/l [298-410] and HoloTc 156 pmol/l [116-196]; group I-IM: VB12 2796 pmol/l [1277-4314] and HoloTc 1269 pmol/l [103-2435]). Hcy and MMA levels showed a significant decrease compared with baseline (group O-oral: Hcy 13.8 µmol/l [10.7-16.8] and MMA 168 nmol/l [134-202]; group I-IM: Hcy 8.5 µmol/l [7.1-9.8] and MMA 156 nmol/l [121-190]). HoloTc and MMA levels were normalised in all patients after 4 weeks of treatment, whereas normalisation of VB12 and Hcy was reached by all patients in group I-IM only. Response of VB12, HoloTc and Hcy was more pronounced in group I-IM (p
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Early biomarker response and patient preferences to oral and intramuscular vitamin B12 substitution in primary care: a randomised parallel-group trial
EMH Schweizerischer Arzteverlag, 2017Co-Authors: Metaxas Corina, Arnet Isabelle, Mathis Déborah, Jeger Cyrill, Hersberger, Kurt Eduard, Walter PhilippAbstract:Vitamin B12 (VB12) deficiency can be treated with oral high-dose substitution or intramuscular (i.m.) injection of VB12. Whenever alternative routes of administration exist, patient preferences should be considered when choosing the treatment. We aimed to assess outpatient preferences towards oral or IM VB12 substitution and confirm noninferiority of early biomarker response with oral treatment, in a typical primary care population.; Prospective randomised nonblinded parallel-group trial. Patients were recruited by their general practitioner and randomly assigned to oral or IM treatment. Group O-oral was given 28 tablets of 1000 µg cyanocobalamin in a monthly Punch Card fitted with an electronic monitoring system. Group I-IM received four, weekly injections of 1000 µg hydroxocobalamin. Blood samples were drawn before the first administration and after 1, 2 and 4 weeks of treatment, and analysed for VB12, holotranscobalamin (HoloTc), homocysteine (Hcy) and methylmalonic acid (MMA). For group O-oral, treatment adher-ence and percentage of days with 2 dosing events were calcu-lated. Before and after 28 days of treatment, patients were asked to fill in a questionnaire about their preference for the therapy options and associated factors.; Between November 2013 and December 2015, 37 patients (age: 49.5 ± 18.5 years; women: 60.5%) were recruited for oral (19) or IM (18) treatment. Baseline values with 95% confidence intervals for serum VB12, HoloTc, Hcy and MMA were 158 pmol/l [145-172], 49.0 pmol/l [40.4-57.5], 14.8 µmol/l [12.0-17.7] and 304 nmol/l [219-390], respective-ly, in group O-oral and 164 pmol/l [154-174], 50.1 pmol/l [38.7-61.6], 13.0 µmol/l [11.0-15.1] and 321 nmol/l [215-427], respectively, in group I-IM (not significant). After 1 month of treatment, levels of VB12 and HoloTc showed a significant increase compared with baseline (group O-oral: VB12 354 pmol/l [298-410] and HoloTc 156 pmol/l [116-196]; group I-IM: VB12 2796 pmol/l [1277-4314] and HoloTc 1269 pmol/l [103-2435]). Hcy and MMA levels showed a significant decrease compared with baseline (group O-oral: Hcy 13.8 µmol/l [10.7-16.8] and MMA 168 nmol/l [134-202]; group I-IM: Hcy 8.5 µmol/l [7.1-9.8] and MMA 156 nmol/l [121-190]). HoloTc and MMA levels were normalised in all patients after 4 weeks of treatment, whereas normalisation of VB12 and Hcy was reached by all patients in group I-IM only. Response of VB12, HoloTc and Hcy was more pronounced in group I-IM (p <0.01) and the primary hypothesis that oral VB12 treatment would be noninfe-rior to IM treatment was rejected. Average adherence to thera-py was 99.6 ± 1.1% and days with 2 dosing events reached 5.6%. Before randomisation, preference was in favour of oral treatment (45.9%, n = 17) over IM administration (21.6%, n = 8). Twelve patients (32.4%) had no preference. Nine (24.3%) patients changed their preference after treatment. Patients who obtained their preferred route of administration main-tained their preference in the case of oral treatment and changed their preference after IM treatment.; Differences in VB12 levels between groups were higher than expected. Therefore, noninferiority of oral treat-ment had to be rejected. However, normalisation of HoloTc and MMA was reached by all patients after a 1-month treatment period. The clinical benefit of the exaggerated biomarker re-sponse after IM treatment within a typical primary care popula-tion is questionable. Midterm biomarker effects and patient preferences should be considered when a therapeutic scheme is chosen. Initial rating in favour of either IM or oral therapy can change over time and justifies repeated re-evaluation of patient preferences. (ClinicalTrials.gov ID NCT01832129)
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Success of a sustained pharmaceutical care service with electronic adherence monitoring in patient with diabetes over 12 months
'BMJ', 2015Co-Authors: Boeni Fabienne, Hersberger, Kurt E., Arnet IsabelleAbstract:We report on the first polypharmacy adherence monitoring over 371 days, integrated into a pharmaceutical care service (counselling, electronic multidrug Punch Cards, feedback on recent electronic records) for a 65-year-old man with diabetes after hospital discharge. The initial daily regimen of four times per day with 15 pills daily changed after 79 days into a daily regimen of two times per day with 9 pills daily for the next 292 days. The patient removed all medication from the multidrug Punch Cards (taking adherence 100%) and had 96.9% correct dosing intervals (timing adherence). The 57 evening doses showed the least variation in intake times at 17 h 45 min±8 min. Over the observation year, the patient was clinically stable. He was very satisfied with the multidrug Punch Card and the feedback on electronic records. In conclusion, long-term monitoring of polypharmacy was associated with the benefit of successful disease management
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Success of a sustained pharmaceutical care service with electronic adherence monitoring in patient with diabetes over 12 months
'BMJ', 2015Co-Authors: Boeni Fabienne, Hersberger, Kurt E., Arnet IsabelleAbstract:We report on the first polypharmacy adherence monitoring over 371 days, integrated into a pharmaceutical care service (counselling, electronic multidrug Punch Cards, feedback on recent electronic records) for a 65-year-old man with diabetes after hospital discharge. The initial daily regimen of four times per day with 15 pills daily changed after 79 days into a daily regimen of two times per day with 9 pills daily for the next 292 days. The patient removed all medication from the multidrug Punch Cards (taking adherence 100%) and had 96.9% correct dosing intervals (timing adherence). The 57 evening doses showed the least variation in intake times at 17 h 45 min±8 min. Over the observation year, the patient was clinically stable. He was very satisfied with the multidrug Punch Card and the feedback on electronic records. In conclusion, long-term monitoring of polypharmacy was associated with the benefit of successful disease management
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Multidrug Punch Cards in primary care : a mixed methods study on patients' preferences and impact on adherence
'Frontiers Media SA', 2014Co-Authors: Boeni Fabienne, Hersberger, Kurt E., Arnet IsabelleAbstract:Multidrug Punch Cards are frame Cards with 28 plastic cavities filled with a patient's oral solid medication. They are used in primary care to facilitate medication management and to enhance adherence. Main criticism concerned handling difficulties and fading knowledge about medication of patients using them. This study aimed at exploring daily use, preferences, and adherence of primary care patients using multidrug Punch Cards.; Community pharmacies in Switzerland recruited primary care patients using multidrug Punch Cards. A mixed methods approach was applied with quantitative interviews performed by telephone and qualitative interviews face-to-face.; Of 149 eligible patients from 21 community pharmacies, 22 participated 2011 in the quantitative and 11 participated 2013/14 in the qualitative interview. Patients were very satisfied with the multidrug Punch Cards and stated increased medication safety. All considered adherence as very important. Self-reported adherence was 10 (median) on a visual analog scale (0 = no intake, 10 = perfect adherence). The absence of package inserts and predefined handling difficulties e.g., tablets spiking at removal were not perceived as problems.; Patients are satisfied with the multidrug Punch Cards, feel safe, mostly have no handling problems and adhere to their treatment. Trust in health-care professionals and patients' experiences emerged as key variables for initiating multidrug Punch Card use and for medication adherence. This mixed methods study invalidates previous concerns about disadvantages of multidrug Punch Cards. Health-care professionals should actively recommend them for primary care patients with polypharmacy and poor adherence
George Korir - One of the best experts on this subject based on the ideXlab platform.
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RESEARCH ARTICLE Punch Card Programmable Microfluidics
2016Co-Authors: George Korir, Manu PrakashAbstract:Small volume fluid handling in single and multiphase microfluidics provides a promising strategy for efficient bio-chemical assays, low-cost point-of-care diagnostics and new ap-proaches to scientific discoveries. However multiple barriers exist towards low-cost field deployment of programmable microfluidics. Incorporating multiple pumps, mixers and dis-crete valve based control of nanoliter fluids and droplets in an integrated, programmable manner without additional required external components has remained elusive. Combining the idea of Punch Card programming with arbitrary fluid control, here we describe a self-contained, hand-crank powered, multiplex and robust programmable microfluidic platform. A paper tape encodes information as a series of Punched holes. A mechanical reader/actua-tor reads these paper tapes and correspondingly executes operations onto a microfluidic chip coupled to the platform in a plug-and-play fashion. Enabled by the complexity of codes that can be represented by a series of holes in Punched paper tapes, we demonstrate inde-pendent control of 15 on-chip pumps with enhanced mixing, normally-closed valves and a novel on-demand impact-based droplet generator. We demonstrate robustness of operatio
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Punch Card programmable microfluidics.
PLOS ONE, 2015Co-Authors: George Korir, Manu PrakashAbstract:Small volume fluid handling in single and multiphase microfluidics provides a promising strategy for efficient bio-chemical assays, low-cost point-of-care diagnostics and new approaches to scientific discoveries. However multiple barriers exist towards low-cost field deployment of programmable microfluidics. Incorporating multiple pumps, mixers and discrete valve based control of nanoliter fluids and droplets in an integrated, programmable manner without additional required external components has remained elusive. Combining the idea of Punch Card programming with arbitrary fluid control, here we describe a self-contained, hand-crank powered, multiplex and robust programmable microfluidic platform. A paper tape encodes information as a series of Punched holes. A mechanical reader/actuator reads these paper tapes and correspondingly executes operations onto a microfluidic chip coupled to the platform in a plug-and-play fashion. Enabled by the complexity of codes that can be represented by a series of holes in Punched paper tapes, we demonstrate independent control of 15 on-chip pumps with enhanced mixing, normally-closed valves and a novel on-demand impact-based droplet generator. We demonstrate robustness of operation by encoding a string of characters representing the word “PunchCard MICROFLUIDICS” using the droplet generator. Multiplexing is demonstrated by implementing an example colorimetric water quality assays for pH, ammonia, nitrite and nitrate content in different water samples. With its portable and robust design, low cost and ease-of-use, we envision Punch Card programmable microfluidics will bring complex control of microfluidic chips into field-based applications in low-resource settings and in the hands of children around the world.
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Integrated Punch Card controlled normally-closed valves.
2015Co-Authors: George Korir, Manu PrakashAbstract:(A) Schematic of normally-closed valves depicting mechanism of operation. (B) 3D printed cantilever beam array with spaced pins (2 mm apart), utilized for implementing 15 independent normally-closed valves. (C, D) Micrograph from video of ten normally-closed valves under operation (side view), all of which are independently actuated based on the Punch Card tape. (E) Normally-closed valve in action, at a single instance of opening and closing depicting the time duration for a single cycle (0.54 seconds). The image depicts the entire region of PDMS deformation with a completely collapsed channel.
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Punch Card controlled integrated multiplexed microfluidic pumps.
2015Co-Authors: George Korir, Manu PrakashAbstract:(A) A series of images of a single channel coupled to the rotating gear disc during one pumping cycle. (B) To characterize the flow pattern with each actuation, fluorescent polystyrene beads (2 μm) were used in de-ionized water. (C) Pumping in each cycle revealed a characteristic asymmetric pulsatile oscillatory flow depicted above as a kymograph. The amplitude of directed unidirectional flow depends on actuation height (h) and the angular velocity (ω) from the hand-crank. (D) Top-down view of the microfluidic chip with simultaneous operation of six Punch Card controlled integrated micro-pumps. Net flow rate in a fluidic line is a function of exact pattern of Punched hole (number of holes Punched and spacing between the same, an example pattern depicted above). (E) Effective flow rate characterized as a function of h and ω, easily achieving typical values demonstrated by integrated micro-pumps.
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Enhanced mixing is achieved using a zig-zag pattern of Punched holes.
2015Co-Authors: George Korir, Manu PrakashAbstract:(A) Photomicrograph of six Punch Card controlled pumps driven by a zig-zag pattern (right inset). Left inset depicts the same device run through a traditional syringe pump (at the same flow rate) to highlight the striking difference in fluid mixing at the end of the channel (200 μm wide). (B) Mixing is quantified by mean-shift clustering approach (see methods for details) comparing four regions in the micro-channel marked a, b, c, d along the outflow. Six identified clusters merge into two. (C) Photomicrographs from video data reveal the mechanism for mixing. Pulsatile nature of flow induces increased folding of neighboring flow lines (and hence net interface length) thus enhancing diffusion and mixing.
Justin Buchler - One of the best experts on this subject based on the ideXlab platform.
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Punch Card Technology and the Racial Gap in Residual Votes
2015Co-Authors: Justin Buchler, Matthew Jarvis, John E. McnultyAbstract:Votomatic-style Punch Card voting systems produce higher rates of residual voting than other technologies, but the effect of Punch Card voting systems is not uniform. Minority voters are less likely to have their votes properly recorded with Punch Card systems than are nonminorities. This racial gap occurs, for the most part, because Punch Card systems lead to higher rates of “undervoting ” by minorities. When election administrators switch to other systems, such as optical scan systems, the racial gap is significantly reduced. Punch Card voting systems, then, constitute a disproportionate obstacle to minority voting. This effectively gives less weight to votes cast by minorities than to votes cast by nonminorities, and arguably violates constitutional requirements for equal voting rights.The mechanism is similar to the literacy tests that were abandoned after the 1970 amendments to the Voting Rights Act. P unch Card voting has been with us for over forty years.It originated at the University of California, Berkeley,where Professor Joseph Harris and his collaborators came up with a method of using simple, inexpensive, easily portable equipment to record votes that could be tabulated mechanically using the computer technology of the day. Because Punch Card systems were cheap and their results could be tal-lied quickly, the technology was widely adopted. In the 2000 presidential election, almost one third of all voters (32.1 per-cent) used Punch Cards—more than any other type of votin
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Punch Card Technology and the Racial Gap in Residual Votes
Perspectives on Politics, 2004Co-Authors: Justin Buchler, Matthew G. Jarvis, John E. McnultyAbstract:Votomatic-style Punch Card voting systems produce higher rates of residual voting than other technologies, but the effect of Punch Card voting systems is not uniform. Minority voters are less likely to have their votes properly recorded with Punch Card systems than are nonminorities. This racial gap occurs, for the most part, because Punch Card systems lead to higher rates of “undervoting” by minorities. When election administrators switch to other systems, such as optical scan systems, the racial gap is significantly reduced. Punch Card voting systems, then, constitute a disproportionate obstacle to minority voting. This effectively gives less weight to votes cast by minorities than to votes cast by nonminorities, and arguably violates constitutional requirements for equal voting rights. The mechanism is similar to the literacy tests that were abandoned after the 1970 amendments to the Voting Rights Act. The authors are grateful to UC Berkeley's Survey Research Center for research support and are deeply indebted to Henry E. Brady. Our thanks also to the anonymous reviewers and to the editorial staff at Perspectives on Politics for their helpful suggestions and hard work on our behalf.
