Pure Parallel Research Articles

Scylla. II. The Spatially Resolved Star Formation History of the Large Magellanic Cloud Reveals an Inverted Radial Age Gradient

The proximity of the Magellanic Clouds provides the opportunity to study interacting dwarf galaxies near a massive host, and spatial trends in their stellar population properties in particular, with a unique level of detail. The Scylla pure parallel program has obtained deep (80% complete to >1 mag below the ancient main-sequence turnoff), homogeneous two-filter Hubble Space Telescope imaging sampling the inner star-forming disk of the Large Magellanic Cloud (LMC), the perfect complement to shallower, contiguous ground-based surveys. We harness this imaging together with extant archival data and fit lifetime star formation histories (SFHs) to resolved color–magnitude diagrams of 111 individual fields, using three different stellar evolutionary libraries. We validate per-field recovered distances and extinctions, as well as the combined global LMC age–metallicity relation and SFH against independent estimates. We find that the present-day radial age gradient reverses from an inside-out gradient in the inner disk to an outside-in gradient beyond ∼2 disk scale lengths, supported by ground-based measurements. The gradients become relatively flatter at earlier look-back times, while the location of the inversion remains constant over an order of magnitude in look-back time, from ∼1 to 10 Gyr. This suggests at least one mechanism that predates the recent intense LMC–Small Magellanic Cloud interaction. We compare observed radial age trends to other late-type galaxies at fixed stellar mass and discuss similarities and differences in the context of potential drivers, implying strong radial migration in the LMC.

The varied clonal trajectory of liver and lung metastases of colorectal cancer

BackgroundThe liver and lungs are the most common sites of colorectal cancer (CRC) metastases. Their involvement can take five different clinical scenarios: lung metastases only, liver metastases only, lung metastases before liver metastases, liver metastases before lung metastases and simultaneous lung and liver metastases. Using clinical and morphological data we studied the clonal trajectory of these scenarios. Materials and methodsA total of 465 (CRC) patients with 7952 liver and 6406 lung metastases were evaluated. Metastases clinical route was deciphered from metastases number, timing, and linear/parallel ratio (LPR)- a computerized parameter used for deducing clonal trajectories. LPR of +1 suggest pure linear dissemination and −1 pure parallel. ResultsLung-only metastases: high percentage of metachronous disease with a long lead time and a low LPR suggest parallel dissemination. Liver-only metastases: Rare metachronous disease with a short lead time, and a high LPR suggest linear spread. Lung-before-liver metastases: rare solitary metastasis, a median gap of 21 months between the organs, high lung and low liver LPRs suggest linear progression to the lungs and parallel dissemination to the liver. Liver-before-lung metastases: low liver and high lung LPRs and a median gap of 16.5 months between the organs suggest parallel dissemination to the liver and linear spread from the liver to the lungs. Simultaneous liver and lung metastases: rare solitary metastasis and similar and high LPRs suggest simultaneous linear progression to both organs. ConclusionsCRC metastases have different dissemination trajectories in different clinical scenarios. This information can potentially impact on clinical management.

Development of a 3D-printed spongy electrode design for microbial fuel cell (MFC) using gyroid lattice

Microbial fuel cell technology addresses both issues in finding new ways to clean water systems while harnessing electricity. Several studies suggest that a single large-scale MFC is proven to be inefficient and expensive. Therefore, producing small-scale MFCs is focused on investigation to provide an efficient system and cost-effective approach. This study used 3D-printed MFCs using a spongy electrode design to produce a modern approach to modifying electrode capacity in energy generation. Furthermore, the study identifies the electrical conductivity of the spongy electrode by determining the voltage generated and power density by stacked MFCs in series, parallel, and hybrid configurations. The MFCs generate a maximum voltage of 633 mV and a current of 14.22 . One way to reduce the effects of voltage reversal in the MFC system is the application of hybrid connection circuits. Parallel-series hybrid connection possesses stable voltage generation of 250−300 𝑚𝑉 with the highest current generation of 115.20 𝜇𝐴. At the same time, the Series-Parallel Connection generates the highest voltage and current of 259 mV and 30 , respectively. The spongy electrode design and hybrid connection produced a maximum power and current density of 29.30 μW⁄m2 and 279.41 μA⁄m2 obtained from a different connection of pure parallel and 28P-2S hybrid connection. Furthermore, water quality parameters were examined (pH, TDS, ORP, and COD), that the MFCs design is efficient in wastewater treatment, with a %COD removal of 95.24% efficiency, reduced ORP from +48.00 mV to -7.00 mV, and the TDS concentration from 270 ppm to 239 ppm.

Bright z ∼ 9 Galaxies in Parallel: The Bright End of the Rest-frame UV Luminosity Function from HST Parallel Programs

The abundance of bright galaxies at z > 8 can provide key constraints on models of galaxy formation and evolution, as the predicted abundance varies greatly when different physical prescriptions for gas cooling and star formation are implemented. We present the results of a search for bright z ∼ 9–10 galaxies selected from pure parallel Hubble Space Telescope (HST) imaging programs. We include 132 fields observed as part of the Brightest of Reionizing Galaxies survey, the Hubble Infrared Pure Parallel Imaging Extragalactic Survey, and the WFC3 Infrared Spectroscopic Parallel survey. These observations cover a total of 620 arcmin2, about 70% of which is also covered with Spitzer Space Telescope infrared imaging. We identify 13 candidate galaxies in the range 8.3 < z < 11 with 24.5 < m H < 26.5 (−22.9 < M UV < −21.2), 11 of which constitute new discoveries. This sample capitalizes on the uncorrelated nature of pure parallel observations to overcome cosmic variance and leverages a full multiwavelength selection process to minimize contamination without sacrificing completeness. We perform detailed completeness and contamination analyses, and present measurements of the bright end of the UV luminosity function using a pseudobinning technique. We find a number density consistent with results from Finkelstein et al. and other searches in HST parallel fields. These bright candidates likely reside in overdensities, potentially representing some of the earliest sites of cosmic reionization. These new candidates are excellent targets for follow up with JWST, and four of them will be observed with the NIRSpec prism in Cycle 1.

Carry-based Differential Power Analysis (CDPA) and its Application to Attacking HMAC-SHA-2

In this paper, we introduce Carry-based Differential Power Analysis (CDPA), a novel methodology that allows for attacking schemes that use arithmetical addition. We apply this methodology to attacking HMAC-SHA-2. We provide full mathematical analysis of the method and show that under certain assumptions and with a sufficient amount of traces any key can be revealed. In the experimental part of the paper, we demonstrate successful application of the attack both in software simulation and on an FPGA board using power consumption measurements. With as few as 30K traces measured on the FPGA board, we recover the secrets that allow for forging the HMAC-SHA-2 signature of any message in 3% of the cases — while with 275K traces the success rate reaches 100%. This means that any implementation of HMAC-SHA-2, even in pure parallel hardware, is vulnerable to side-channel attacks, unless it is adequately protected. To the best of our knowledge, this is the first published full-fledged attack on pure hardware implementations of HMAC-SHA-2, which does not require a profiling stage.

Hyper‐heuristic method for processor allocation in parallel tasks scheduling

SummaryScheduling the tasks of parallel scientific applications is very important for efficient utilization of resources and reducing the overall execution time (makespan). Parallel applications typically include both data parallelism and task parallelism. It is known that the scheduling problem on multiprocessor systems problem is NP‐Hard even for applications involving pure task parallelism. The problem becomes more difficult when data parallelism is also taken into consideration. These problems usually considered in two steps, processor allocation and task scheduling, and various algorithms have been proposed. In this study, we introduce a genetic algorithm based hyper‐heuristic approach for the processor allocation problem. Experimental results indicate that the algorithm provides better performance compared to various greedy algorithms.

Design and Testing of 3D-Printed Stackable Plant-Microbial Fuel Cells for Field Applications

The prevalence of non-renewable energy has always been a problem for the environment that needs a long-term solution. Plant-Microbial Fuel Cells (PMFCs) are promising bioelectrochemical systems that can utilize plant rhizodeposition to generate clean electricity on-site, without harming the plants, paving the way for simultaneous agriculture and power generation. However, one of the biggest hurdles in large-scale PMFC application is the diffused nature of power generation without a clear path to consolidate or amplify the small power of individual cells. In this study, stacking configurations of 3D-printed PMFCs are investigated to determine the amplification potential of bioelectricity. The PMFCs designed in this study are made of 3D-printed electrodes, printed from 1.75 mm Proto-pasta (ProtoPlant, USA) conductive PLA filament, and a terracotta membrane acting as the separator. Six cells were constructed with the electrodes designed to tightly fit with the ceramic separator when assembled. An agriculturally important plant (S. Melongena) was utilized as the model plant for testing purposes. Stacking of cells in series had resulted in severe voltage loss while stacking of cells in parallel preserved the voltage and current of the cells. Cumulative stacking verified the increasing voltage losses as more cells are connected in series, while voltage and current were generally supported well as more cells were connected in parallel. Combination stacks were also investigated, but while 2 sets of 3 cells in parallel stacked in series generated proportionately larger power and power density compared to individual cells, the drop in current density suggests that pure parallel stacks are still more attractive for scaling up, at least for the proposed stake design in this study. The results of this study indicated that the scale up of PMFC technology is possible in field applications to continuously generate electricity while growing edible plants.

Obliquely propagating electron Bernstein wave in arbitrary degenerate plasma

Abstract On employing the linearized Vlasov–Maxwell model, the dispersion relation of obliquely propagating Bernstein wave in thermal electron gas including quantum effect of arbitrary/partial degeneracy in the presence of non-relativistic arbitrary magnetic field limits is derived. In particular, the results are obtained in the propagation range k z &gt; k x with k x ≠ 0 under high frequency (ω ≫ k.v) and weak propagation (Ω ≫ k.v or k → 0) limits. The propagation angle θ ′ $\left({\theta }^{\prime }\right)$ defines the obliqueness of wave such that for θ′ = 0° and 90° we obtain the perpendicular propagating pure Bernstein wave and parallel propagating Langmuir wave, respectively. The graphical analysis of newly reported results is made under the numerically evaluated values and the previously reported results are also retained. The possible applications of present results are found in partially/arbitrary dense astrophysical quantum plasma e.g., in brown dwarfs as well as they have wide ranging potential applications in modern technology e.g., in semi-conductors.

1.5D Time Domain Electromagnetic Inversion Using Global Optimization Methods and Parallel Processing

An innovative comparative study among three different global optimization methods (GOMs) to invert time domain electromagnetic data (TDEM), was applied in the 1.5D subsurface resistivity imaging. These stochastic methods allow the incorporation of different kinds of constraints in the objective function, due to the easiness of implementation in their algorithms and their computational efficiency. Nevertheless, global optimization methods, like any other based on swarm intelligence cost much computational time, including problems with a high number of unknown parameters and when the forward modeling involves time-consuming calculations such as Gaver-Stehfest inverse transforms, Hankel transforms, and others. To overcome this difficulty, we developed a parallel pure MPI version of each GOM, allowing the distribution of the computation among several cores of a cluster. The performances of the classic version of particle swarm optimization (PSO), grey wolf optimizer (GWO), and whale optimization algorithm (WOA) using MPI parallelism for solving 1.5D TDEM inverse problems are compared here in a set of synthetic and real data. The principal outcomes show: (1) These GOMs reproduce quite well the distribution of subsurface resistivity either synthetic models or real data, (2) WOA and PSO exhibit better computational performances, converging first than GWO, (3) WOA provided better performance in the final value achieved of the cost function than PSO and GWO, and (4) pure MPI parallelism provided a 17x and 50x speedup in the computation time for both synthetic and real data, respectively. In a better way to classify this comparison, we analyzed the solutions using total variation (TV) and Global smoothness (GS) constraints, to identify smooth and sharp structures. Additionally, we have diminished the computational time execution with the parallel solution (MPI version of each stochastic traditional method) against the sequential processing.

Mass transfer study on high-pressure membrane dehumidification applied to aircraft environmental control system

Expected to replace conventional condensing dehumidification, pressure-driven membrane dehumidification is an alternative to the high-pressure air dehumidification in aircraft environmental control system (ECS). A high-pressure membrane dehumidification experiment is conducted on a counter-flow hollow fiber membrane module to investigate the dehumidification performance under various operating conditions including feed flow rate, feed pressure and sweep ratio. The experiment achieves the dehumidification rate of 1007 g/h at highest. Taking account of the variation of mass transfer driving force along the flow direction, the theoretical model reaches a good agreement with the experiment data. Based on the validated model, a numerical simulation study is conducted to explore the detailed mass transfer characteristics. The simulation reveals the outstanding distinction between the high-pressure and normal-pressure membrane dehumidification. Driven by water vapor partial pressure difference, the mass transfer in the latter one is determined by humidity ratio only, while that in the former one depends on humidity ratio and pressure altogether. Various combination modes of multiple membrane modules are also investigated for more flexible arrangement in the compact space of aircraft, and it is found that the pure parallel mode performs the best. Finally, exergy analysis is employed to compare with the condensing method. In comparison, the membrane method performs the less exergy destruction especially at low desired outlet humidity ratio.

Numerical simulation of a hybrid system using Peltier thermal switches in magnetic refrigeration

• A 2D transient model of a hybrid magnetic refrigeration system using Peltier modules as the heat switches was established. • The actual transient thermal response of the Peltier modules was considered in the model. • The comparison of the hybrid system with the AMR mode and the Peltier mode was done. • At 4.00 Hz and 0.20 A, the COP and cooling power density of the hybrid system exceeded that of the pure AMR mode. • The influence of operating parameters on the hybrid system performance was evaluated. To overcome the shortcoming of the low cooling power density in the ordinary magnetic refrigerator, a hybrid system using Peltier thermal switches in magnetic refrigeration has been proposed by researchers. In the system, the magnetic material is sandwiched between Peltier modules which are used as the thermal switches to transport the heat to and from the material undergoing the magnetic refrigeration cycle. To analyze the system, a two-dimensional transient model is established by considering the thermal characteristics of the Peltier module, which has not been done before. With the model, the performance of the hybrid system was firstly compared with that using the pure parallel plate active magnetic regenerator (AMR) mode and that using the pure Peltier mode. Compared with pure parallel plate AMR mode, the hybrid system using Peltier thermal switches in magnetic refrigeration can significantly increase the cooling power density at low frequencies (1.60 Hz – 4.00 Hz). In this frequency range, the coefficient of performance (COP) of pure parallel plate AMR mode decreased rapidly with the increase of frequency, while the COP of the hybrid system decreased slowly, and at 4.00 Hz and 0.20 A, the COP of the hybrid exceeded that of the pure parallel plate AMR mode. Compared with pure Peltier mode, the hybrid system can achieve the same cooling power with less power consumption and obtain a higher COP. Furthermore, the influence of operating parameters on the performance of the hybrid system, which included utilization factor, input current, the outlet temperature of the cold-end heat exchanger, frequency, and the number of refrigeration units, was investigated. The results show that, when using Peltier thermal switches, the actual transient thermal response of the Peltier module plays an important role in the hybrid system, which is ignored in previous literature. To achieve efficient operation at high frequency, when using Peltier thermal switches, the thermal response time of the Peltier modules as well as the Joule heating effect, etc, needs to be carefully evaluated.

Patterns of metastases progression- The linear parallel ratio.

Linear and parallel are the two leading models of metastatic progression. In this study we propose a simple way to differentiate between them. While the linear model predicts accumulation of genetic and epigenetic alterations within the primary tumor by founder cells before spreading as waves of metastases, the parallel model suggests preclinical distribution of less advanced disseminated tumor cells with independent selection and expansion at the ectopic sites. Due to identical clonal origin and time of dispatching, linear metastases are expected to have comparable diameters in any specific organ while parallel metastases are expected to appear in variable sizes. Retrospective revision of chest CT of oncological patients with lung metastases was performed. Metastasis number and largest diameters were recorded. The sum number of metastases with a similar diameter (c) and those without (i) was counted and the linear/parallel ratio (LPR) was calculated for each patient using the formula (∑c-∑i)/(∑c+∑i). A LPR ratio of 1 implies pure linear progression pattern and -1 pure parallel. 12,887 metastases were measured in 503 patients with nine malignancy types. The median LPR of the entire group was 0.71 (IQR 0.14-0.93). In carcinomas of the pancreas, prostate, and thyroid the median LPR was 1. Median LPRs were 0.91, 0.65, 0.60, 0.58, 0.50 and 0.43 in renal cell carcinomas, melanomas, colorectal, breast, bladder, and sarcomas, respectively. Metastatic spread of thyroid, pancreas, and prostate tumors is almost exclusively by a linear route. The spread of kidney, melanoma, colorectal, breast, bladder and sarcoma is both linear and parallel with increasing dominance of the parallel route in this order. These findings can explain and predict the clinical and genomic features of these tumors and can potentially be used for evaluation of metastatic origin in the individual patient.

Adsorption of SO2 and NH3 onto copper/graphene nanosheets composites: Statistical physics interpretations, thermodynamic investigations, and site energy distribution analyses

Copper/graphene nanosheets composites (CGCs) were adopted as multi-gas adsorbents to remove two harmful gases (i.e., ammonia and sulfur dioxide) in the atmospheric environment, respectively. Methods such as N2 adsorption/desorption, scanning electron microscopy, and X-ray diffraction were selected to fully characterize CGCs. Under laboratory conditions, the adsorption isotherms of NH3 and SO2 onto CGCs at three different temperatures (298.15 K, 308.15 K, and 318.15 K) and different pressures (0 ∼ 1.8 bar) were quantitatively tested. A multilayer model with saturation (M5) was adopted as the best suitable model to explore the adsorption mechanism for SO2-CGCs and NH3-CGCs adsorption systems from a molecular level. The numerical simulation results demonstrated that the adsorption of NH3 by CGCs is a multi-anchorage process and a pure parallel adsorption position (298.15 K), a multi-linking process and a mixed adsorption orientation (308.15 K and 318.15 K). In contrast, SO2-CGCs adsorption system at 298.15 K, 308.15 K, and 318.15 K, there will be a multi-molecule process and a pure non-parallel adsorption position. Overall, from statistical physical, thermodynamic and SED analyses, the adsorption mechanism of SO2 and NH3 on CGCs, which was mainly governed by the density of receptor sites (Dm), was a spontaneous exothermic reversible adsorption process driven by physical interaction forces for which van der Waals interactions were responsible, while the high temperature is detrimental to the occurrence of high adsorption capacity.

Research on Cross-scale Micro-gripper Based on Multi-stable Flexible Mechanism

&lt;p&gt;In order to solve the problems of low precision, small stroke, and inabilityto grip objects across scales (um-mm) in traditional micro-gripper, a multi-stable flexible mechanism-based cross-scale micro-gripper structure was proposed. The multi-stable structure is combined with the traditional amplifying mechanism. The leftside of the micro -gripper adopts a lever mechanism and a parallelogram mechanism, and the right side adopts three different bistables in series to achieve eight-stable state. Finally, the parallelogram mechanism ensures the end of the micro-gripper. The output is pure parallel movement. Firstly, the overall structure design of the micro-gripper is introduced; secondly, the displacement amplification ratio and multi -stable characteristics of the amplification mechanism are deduced through theoretical calculation; finally, the performance and reliability of the micro-gripper are verified by the simulation analysis of the model by finite element. The micro-gripper has high magnification, large grippering range, compact structure, and can realize parallel grippering across μm-mm.&lt;/p&gt;

Flexible Matrix of Controllers for Real Time Parallel Control

This work aims to develop a novel system, including software and hardware, to perform independent control tasks in a genuine parallel manner. Currently, to control processes with various sampling periods, distributed control systems are most commonly utilized. The main goal of this system is to propose an alternative solution, which allows simultaneous control of both fast and slow processes. The presented approach utilizes FPGA (Field Programmable Gate Array) with Nios II processor (Intel Soft Processor Series) to implement and maintain instances of independent controllers. Instances can implement FDMC (Fast Dynamic Matrix Control) and PID (Proportional-Integral-Derivative) control algorithms with various sampling times. The FPGA-based design allows for true independence of controllers’ execution both from one another and the managing processor. Also, pure parallel execution allows for implementing slow and fast controllers in the same device. The complete flexible system with a matrix of controllers working in parallel in real-time was tested with both simulated and actual control processes (servomotor), yielding the same results as fully simulated experiments.

Development of a high-resolution SSR-SPECT system for preclinical imaging and neuroimaging

Techniques like single photon emission computed tomography (SPECT) show high potential in small animals in vivo imaging framework. In this context, the spatial resolution represents an important parameter influencing scanner design, given the small size of the anatomical structures to be investigated. The purpose of the present work was to assess the performance of a scintigraphic system with an improved spatial resolution by applying the previously described Super Spatial Resolution (SSR) method. Our dual-head SPECT system is composed of gamma cameras based on the Hamamatsu H13700 position-sensitive photomultiplier tube (PSPMT). In each detector head, the PSPMT is coupled to a 28 × 28 array of CRY018 scintillation crystals. The pure Tungsten parallel square hole collimator ensures the position sensitivity, and a dedicated resistive chain readout so as an ADC board have been proprietary designed.To finalize the mechanical development of the SSR-SPECT system several tests were carried out. Based on the results obtained in the test phase, a partial review of the mechanical design was performed. Then a dedicated mechanical motion software was developed, and in particular, a kinematic software debugging and testing was assessed. Several experiments were carried out by using Derenzo phantoms and capillaries filled with radioactive sources. Finally, the performance of our system was evaluated by performing small animal imaging studies.The SPECT spatial resolution was experimentally determined to be about 1.6 mm. We reach a resolution of 1.18 mm by applying the SSR based on two images.The results of this study demonstrated the good capability of the system as a suitable tool for preclinical imaging especially in fields like neuroscience for the study of small brain structures.

Research on the centre distance separability of parallel shaft line gear pair

For gear pairs with centre-distance separability, transmission ratios are not affected by centre distance error. Based on space curve meshing theory, the centre distance separability of a line gear pair was studied. A novel line gear pair called the separable and pure rolling parallel shaft line gear pair (SPRPSLG) was proposed, which has centre-distance separability characteristics and pure rolling transmission. The basic design theory of the SPRPSLG pair was established. A design method of the SPRPSLG pair with an eccentric arc tooth profile was given. An SPRPSLG pair example was designed and manufactured using the form milling method. Kinematic experiments and meshing efficiency experiments were conducted. Gear contact spot testing and gear contact simulation analysis were carried out. The SPRPSLG pair was shown to have centre distance separability, which provides a further theoretical basis for the popularization and application of line gears.

Algorithm 1016

In this article, we introduce the Python framework PyMGRIT, which implements the multigrid-reduction-in-time (MGRIT) algorithm for solving (non-)linear systems arising from the discretization of time-dependent problems. The MGRIT algorithm is a reduction-based iterative method that allows parallel-in-time simulations, i.e., calculating multiple time steps simultaneously in a simulation, using a time-grid hierarchy. The PyMGRIT framework includes many different variants of the MGRIT algorithm, ranging from different multigrid cycle types and relaxation schemes, various coarsening strategies, including time-only and space-time coarsening, and the ability to utilize different time integrators on different levels in the multigrid hierachy. The comprehensive documentation with tutorials and many examples and the fully documented code allow an easy start into the work with the package. The functionality of the code is ensured by automated serial and parallel tests using continuous integration. PyMGRIT supports serial runs suitable for prototyping and testing of new approaches, as well as parallel runs using the Message Passing Interface (MPI). In this manuscript, we describe the implementation of the MGRIT algorithm in PyMGRIT and present the usage from both a user and a developer point of view. Three examples illustrate different aspects of the package itself, especially running tests with pure time parallelism, as well as space-time parallelism through the coupling of PyMGRIT with PETSc or Firedrake.

Fuzzy Logic Controller for an EV’s Dual-Source Hybridization

This paper presents an energy management system (EMS) based on fuzzy logic control (FLC) strategy combined with power filtering. This strategy is developed for an Electric Vehicle (EV) hybrid energy storage systems (HESS). The proposed control and energy management strategy (EMS) aims to ensure an efficient power split guaranteeing that battery and supercapacitors (SC) provide the continuous and transient-power, respectively, adopting a pure electric vehicle fully-active parallel topology. In order to develop the studied system model, the Energetic Macroscopic Representation (EMR) approach is adopted. Considering SC’s control criterion, and battery root mean square RMS current reducing, an evaluation of the proposed EMS and developed model was conducted using MATLAB/SIMULINK simulation under New European Driving Cycle (NEDC) and compared to the classical only battery storage configuration.

The effect of postcard reminders on vaccinations among the elderly: a block-randomized experiment

AbstractPrior research in the behavioral sciences has demonstrated that reminders can be an effective tool for encouraging health-related behavior changes. This article extends that literature by reporting the outcome of a randomized controlled trial of mailed vaccination reminders. In addition to making a substantive contribution regarding the efficacy of mailed reminders, this article also makes a methodological contribution: it illustrates how researchers can study the causal impact of an intervention even when a pure parallel trial is not possible. In this study, the Louisiana Department of Health sent postcard reminders regarding four recommended vaccinations (influenza, tetanus, shingles and pneumonia) to 208,867 senior residents of Louisiana. We used block randomization and a stepped wedge design to assess the efficacy of the intervention. Individuals were blocked by their prior vaccine record and randomized to receive the postcard in one of four consecutive months (October–January). The reminder postcard had an overall positive effect on vaccination rates. The statistically significant and substantively small increase in overall vaccination rates was driven by participants who received the postcard reminder early in the intervention period.