Developing Flexible Discrete Event Simulation Models in an Uncertain Policy Environment

On February 1st, 2010 U.S. President Barack Obama submitted to Congress his proposed budget request for Fiscal Year 2011. This budget included significant changes to the National Aeronautics and Space Administration (NASA), including the proposed cancellation of the Constellation Program. This change proved to be controversial and Congressional approval of the program's official cancellation would take many months to complete. During this same period an end-to-end discrete event simulation (DES) model of Constellation operations was being built through the joint efforts of Productivity Apex Inc. (PAl) and Science Applications International Corporation (SAIC) teams under the guidance of NASA. The uncertainty in regards to the Constellation program presented a major challenge to the DES team, as to: continue the development of this program-of-record simulation, while at the same time remain prepared for possible changes to the program. This required the team to rethink how it would develop it's model and make it flexible enough to support possible future vehicles while at the same time be specific enough to support the program-of-record. This challenge was compounded by the fact that this model was being developed through the traditional DES process-orientation which lacked the flexibility of object-oriented approaches. The team met this challenge through significant pre-planning that led to the "modularization" of the model's structure by identifying what was generic, finding natural logic break points, and the standardization of interlogic numbering system. The outcome of this work resulted in a model that not only was ready to be easily modified to support any future rocket programs, but also a model that was extremely structured and organized in a way that facilitated rapid verification. This paper discusses in detail the process the team followed to build this model and the many advantages this method provides builders of traditional process-oriented discrete event simulations

Exploration of an on-site pharmacist intervention within Australian residential aged care facilities using normalisation process theory: A mixed-methods study

Residents living in residential aged care facilities (RACFs) continue to experience medication-related harm. There is ongoing interest in expanding the role of pharmacists, including on-site pharmacists (OSPs), to help improve medication management in RACFs. The objectives of this mixed-methods study were to explore the extent and ways in which on-site pharmacists (OSPs) were normalised within RACFs as part of a complex intervention seeking to improve medication management. This study consisted of semistructured interviews informed by normalisation process theory (NPT) and a quantitative survey adapted from the normalisation measure development questionnaire (NoMAD) instrument which is underpinned by NPT. Semistructured interviews with prescribers, RACF managers, RACF nursing staff, OSPs, residents, and family members (n = 47) indicated that most participants supported OSPs within RACFs that having OSPs in RACFs made sense and was perceived as beneficial and that participants were invested in working with OSPs who often became part of routine practice, i.e., “normalised.” Prescribers, RACF managers, and nursing staff (health care team members) completed the adapted survey, and their responses (n = 16) strongly complemented the positive qualitative findings. Overall, OSPs were positively appraised by health care team members as well as residents and family members and were generally considered to be normalised within their respective RACFs. This study explored the normalisation of OSPs within RACFs. From the perspective of residents, family members, health care team members, and OSPs, OSPs could become part of routine practice within Australian RACFs. The findings of this study also highlighted the value of using theory to guide the evaluation of a pharmacist intervention in RACFs and the utility of applying NPT in a new setting, Australian RACFs. Importantly, the findings of this study could help inform the future role of OSPs working and the rollout of OSPs within Australian RACFs

Pseudorandom Error-Correcting Codes

We construct pseudorandom error-correcting codes (or simply pseudorandom codes), which are error-correcting codes with the property that any polynomial number of codewords are pseudorandom to any computationally-bounded adversary. Efficient decoding of corrupted codewords is possible with the help of a decoding key. We build pseudorandom codes that are robust to substitution and deletion errors, where pseudorandomness rests on standard cryptographic assumptions. Specifically, pseudorandomness is based on either $2^{O(\sqrt{n})}$-hardness of LPN, or polynomial hardness of LPN and the planted XOR problem at low density. As our primary application of pseudorandom codes, we present an undetectable watermarking scheme for outputs of language models that is robust to cropping and a constant rate of random substitutions and deletions. The watermark is undetectable in the sense that any number of samples of watermarked text are computationally indistinguishable from text output by the original model. This is the first undetectable watermarking scheme that can tolerate a constant rate of errors. Our second application is to steganography, where a secret message is hidden in innocent-looking content. We present a constant-rate stateless steganography scheme with robustness to a constant rate of substitutions. Ours is the first stateless steganography scheme with provable steganographic security and any robustness to errors

Undetectable Watermarks for Language Models

Recent advances in the capabilities of large language models such as GPT-4 have spurred increasing concern about our ability to detect AI-generated text. Prior works have suggested methods of embedding watermarks in model outputs, by $\textit{noticeably}$ altering the output distribution. We ask: Is it possible to introduce a watermark without incurring $\textit{any detectable}$ change to the output distribution? To this end we introduce a cryptographically-inspired notion of undetectable watermarks for language models. That is, watermarks can be detected only with the knowledge of a secret key; without the secret key, it is computationally intractable to distinguish watermarked outputs from those of the original model. In particular, it is impossible for a user to observe any degradation in the quality of the text. Crucially, watermarks should remain undetectable even when the user is allowed to adaptively query the model with arbitrarily chosen prompts. We construct undetectable watermarks based on the existence of one-way functions, a standard assumption in cryptography

Ybp1 and Gpx3 signaling in Candida albicans govern hydrogen peroxide-induced oxidation of the Cap1 transcription factor and macrophage escape

Peer reviewedPublisher PD

Magnetic Shape Memory Micro-Pump for Intra-Cranial Drug Delivery

Magnetic shape-memory alloys exhibit strong magneto-structural coupling enabling large magnetic-field-induced deformation. Local control of twinning via variable inhomogeneous magnetic fields initiates local reversible deformation. Previous work produced a valve-less micropump consisting of a Ni-Mn-Ga single crystal, a casing, and a rod magnet. The micropump successfully pumped fluid in opposite directions when the magnet was turned clockwise and counter clockwise. Our current work modifies this micropump for application in rat a head stage, which would simultaneously monitor electroencephalograph data and deliver 0.5-5.0 μl of a drug solution at 100-500 nl/min directly to the rat’s brain. These improvements and the application of the magnetic-shape-memory-alloy technology will foster further improvements in the technology, as well as stimulate further development of MSMA based actuation and sensor devices

The Toxicity of Silver Nanoparticles (AgNPs) to Three Freshwater Invertebrates With Different Life Strategies: Hydra vulgaris, Daphnia carinata, and Paratya australiensis

The toxicity of manufactured nanoparticles varies greatly depending on the test species in consideration and estimates of toxicity may also be confounded by test media in which the organisms are cultured. For a more comprehensive toxicity evaluation, species at different trophic levels or with life strategies, tested in different media should be included. In this study, we examined the toxicity of tyrosine-coated silver nanonparticles (tyr-AgNP) to three Australian freshwater invertebrates: Hydra vulgaris, Daphnia carinata, and Paratya australiensis. Tyr-AgNPs were synthesized, characterized and their behavior was examined in different media used for acute toxicity tests. Additionally, the sensitivity of tested organisms to tyr-AgNPs was compared to ionic silver (Ag+). Based on the LC50 values of both tyr-AgNPs and Ag+ ions at different time points, D. carinata was found to be the most sensitive species followed by P. australiensis and H. vulgaris. NP stability studies revealed that tyr-AgNPs were least stable in hydra medium followed by daphnid and shrimp media. This study demonstrates that significant differences in NP toxicity to aquatic organisms exist and the test media and the life strategy of the species play a key role in these differences. Therefore, it is recommended that a multispecies approach is used in predictive risk assessment of NPs and to ensure protection of native species from possible toxic effects from NPs released into aquatic systems. Also recommended is to carefully investigate the fate and behavior of NPs in different media in assessing NP toxicity and emphasize the need to use native species in developing relevant regulatory frameworks

The toxicity of silver nanoparticles (AgNPs) to three freshwater invertebrates with different life strategies: Hydra vulgaris, Daphnia carinata, and Paratya australiensis

The toxicity of manufactured nanoparticles varies greatly depending on the test species in consideration and estimates of toxicity may also be confounded by test media in which the organisms are cultured. For a more comprehensive toxicity evaluation, species at different trophic levels or with life strategies, tested in different media should be included. In this study, we examined the toxicity of tyrosine-coated silver nanonparticles (tyr-AgNP) to three Australian freshwater invertebrates: Hydra vulgaris, Daphnia carinata, and Paratya australiensis. Tyr-AgNPs were synthesized, characterized and their behavior was examined in different media used for acute toxicity tests. Additionally, the sensitivity of tested organisms to tyr-AgNPs was compared to ionic silver (Ag+). Based on the LC50 values of both tyr-AgNPs and Ag+ions at different time points, D. carinata was found to be the most sensitive species followed by P. australiensis and H. vulgaris. NP stability studies revealed that tyr-AgNPs were least stable in hydra medium followed by daphnid and shrimp media. This study demonstrates that significant differences in NP toxicity to aquatic organisms exist and the test media and the life strategy of the species play a key role in these differences. Therefore, it is recommended that a multispecies approach is used in predictive risk assessment of NPs and to ensure protection of native species from possible toxic effects from NPs released into aquatic systems. Also recommended is to carefully investigate the fate and behavior of NPs in different media in assessing NP toxicity and emphasize the need to use native species in developing relevant regulatory frameworks