W. Zhang

We experimentally demonstrate a polarizing beam splitter (PBS) for the THz frequency region, based on artificial dielectrics. The PBS exhibits power efficiencies as high as 95% and extinction ratios as high as 104:1.

We implemented pressure-dependent terahertz time-domain spectroscopy. Compared with traditional far-IR spectroscopy with a diamond anvil cell, we can measure at much lower frequencies, down to 0.1 THz, giving us access to many interesting dynamics. The pressure tuning range is from room pressure to 5 kpsi, while the temperature tuning range is from 77 to 473 K. With this large range of tuning parameters, we are able to map out phase diagrams of materials based on their THz spectrum. Pressure-dependent THz-TDS results for R-camphor are shown as an example.

We theoretically and experimentally study the scattering of p-polarized EM waves from 1D arrays of thin metal plates at THz frequencies. In the simulation results, the reflectance is normally small but extraordinarily high under certain conditions. The resonant conditions correspond to coupled excitations between the surface modes along the array and the cavity modes inside the parallel-plate waveguides formed by the plates. Experimentally, we measure the transmittance of the 1D array, and show good agreement between theory and experiment.

We experimentally demonstrate an isolator suitable for the THz spectral regime. The isolator is designed by combining a polarizing beamsplitter with a quarter-wave plate, both based on the same artificial-dielectric technology. The artificial-dielectric medium comprises of a stack of 30 μm thick metal plates that form an array of parallel-plate waveguides. The isolator exhibits an isolation of 52 dB with an insertion loss less than one dB, at a frequency of 0.46 THz, which rivals the performance of commercially available Faraday isolators for optical wavelengths.

Metal-organic frameworks are an important class of porous materials exhibiting a variety of promising properties that are related to the unique atomic-level structural features found in the solids. Using terahertz time-domain spectroscopy, the relationship between the large-amplitude low-frequency vibrations and the mechanochemical features found in these materials can be elucidated, providing deep insight into the origins of the favourable phenomena.

The nature of the low-frequency vibrational motions occurring within disordered solids has been a topic of great debate of the last several decades. Using a combination of experimental terahertz time-domain spectroscopy and state-of-the-art quantum mechanical simulations, the dynamics of disordered solids are obtained with atomic-level detail. Such understanding has wide-reaching implications, as these motions are responsible for many physical phenomena including spontaneous crystallisation, charge transfer, and pharmaceutical stability.

Research Objective Assisted living (AL) communities are licensed and regulated by states, which vary dramatically in their requirements. Little is understood about how states’ approaches to regulating AL are associated with residents’ health outcomes. The objective of this study was to examine if states that implemented changes to their regulations related to staff training and direct care staffing levels in AL witnessed reductions in rates of hospital admissions among AL residents. Study Design Retrospective cohort study using 100% Medicare claims, MedPAR, and assessment data. Data on AL regulations, over time, were identified using techniques from legal epidemiology, qualitative content analysis, and text mining. Two separate linear probability models and a difference in difference framework were used to examine the association between acute care hospitalization and changes in regulations pertaining to staff training (model 1) and direct care staffing levels (model 2), adjusting for time trends, resident characteristics (i.e., age, sex, race, dual‐eligibility, chronic conditions), and state‐license fixed effects. Population Studied With the Medicare Master Beneficiary Summary File and a methodology to identify Medicare beneficiaries residing in large AL communities (25+ beds), we identified a cohort of 889 154 Medicare beneficiaries enrolled in traditional Medicare and residing in 10 825 continuously operating, large AL communities between 2007 and 2017. Principal Findings During this 11‐year period, six states changed their staff training requirements and two states changed their regulations pertaining to direct care staffing levels. On average, AL residents had 0.0168 (SD = 0.128) hospitalizations per month. A change in state regulations to increase or establish minimum staffing levels was associated with a reduction in the probability of hospitalization during the month of −0.0025 percentage points (95%CI = −0.004–0.000). A change in state regulations that introduced or increased requirements for staff training was associated with a reduction in the probability of hospitalization during the month of −0.0020 percentage points (95%CI = −0.004–0.000). Conclusions The policy effects represent clinically important differences of approximately 12% in the mean monthly hospitalization rate. These results suggest that changes in state regulations requiring staff training and minimum direct care staffing levels are associated with reductions in hospitalization among AL residents. Implications for Policy or Practice States are responsible for regulating AL. These findings set the stage for additional exploration into the optimal regulatory environment to ensure optimal outcomes for AL residents. As AL continues to care for an increasingly vulnerable population of residents, over 40% with a diagnosis of dementia, it is essential to understand the impact of regulations pertaining to direct care staffing on the care provided in these settings. Primary Funding Source National Institutes of Health.

Research Objective States regulate licensed care settings, such as assisted living (AL) residences, to protect residents, including many with cognitive impairments such as ADRD. States take varying approaches to critical issues in AL, including defining admission criteria, safety, and egress features, and discharge and eviction processes. Yet, researchers have not fully explored how state regulations affect resident care outcomes, which is the purpose of this study. To accomplish this goal, we developed a novel approach. Study Design Previous work by team members linked administrative lists of licensed AL facilities to Medicare claims. The current project created a dataset of states’ regulations with the use of methods from health services research, legal epidemiology, qualitative content analysis, and text mining. Our team sourced state AL license and certification regulations from Nexis Uni legal database for current requirements and changes over time. This method produced documents that describe states’ regulations for each of the 192 licensed or certified settings. We then coded these documents into dichotomous categories that can be linked to our existing dataset of Medicare claims. Population Studied This study examined all states’ AL regulations between 2007 and 2018, and lists maintained by state licensing agencies. Principal Findings We identified 192 unique types of state‐licensed or certified AL settings distinguished in the regulations, of which 171 were matched to state administrative records. Many states have subcategories or additional certifications with a range of between 2 and 22 license types, and 38 states license or certify at least one dementia‐specific setting. The ability to link our existing dataset of Medicare claims and our categorization of state regulatory requirements allowed for analysis of the relationships between regulatory changes and resident care outcomes. Conclusions This method advances previous observations that AL regulation varies by state. However, we extend prior knowledge by establishing a novel and reliable method for sourcing regulations and conducting text analysis that identifies the most salient aspects of facility licensure and certification and determining how these change over time. Our dataset allows us to quantify differences within and across states and to estimate how these regulatory variations impact AL residents’ health service use and outcomes. Implications for Policy or Practice State agencies lack evidence about what works when implementing administrative requirements for AL settings. This study presents a reliable method for sourcing and analyzing the content of regulatory codes and identifying substantive changes made from one year to the next. This method allows researchers to conduct analyses that provide evidence regarding the impact of regulatory requirements on AL residents’ access to and use of health services. An added benefit to our approach is that researchers can use these methods to conduct more sophisticated analyses of state and intrastate variation on health outcomes. State licensing officials may benefit from and use this information when making regulatory changes. Primary Funding Source National Institutes of Health.