Two primary methods of proving gas flow meters

Methods for determining mass flow rates of gases for use in calibrating gas flowmeter

The Anisoplanatic Point Spread Function in Adaptive Optics

The effects of anisoplanatism on the adaptive optics point spread function are investigated. A model is derived that combines observations of the guide star with an analytic formulation of anisoplanatism to generate predictions for the adaptive optics point spread function at arbitrary locations within the field of view. The analytic formulation captures the dependencies of anisoplanatism on aperture diameter, observing wavelength, angular offset, zenith angle and turbulence profile. The predictions of this model are compared to narrowband 2.12 um and 1.65 um images of a 21 arcsec binary (mV=7.3, 7.6) acquired with the Palomar Adaptive Optics System on the Hale 5 meter telescope. Contemporaneous measurements of the turbulence profile made with a DIMM/MASS unit are used together with images of the primary to predict the point spread function of the binary companion. Predicted companion Strehl ratios are shown to match measurements to within a few percent, whereas predictions based on the isoplanatic angle approximation are highly discrepant. The predicted companion point spread functions are shown to agree with observations to 10%. These predictions are used to measure the differential photometry between binary members to an accuracy of 1 part in 10^{3}, and the differential astrometry to an accuracy of 1 mas. Errors in the differential astrometry are shown to be dominated by differential atmospheric tilt jitter. These results are compared to other techniques that have been employed for photometry, astrometry, and high contrast imaging.Comment: 26 pages, 7 figure

Addressing the heart failure epidemic: from mechanical circulatory support to stem cell therapy

At an annual cost of over thirty billion dollars annually, the diagnosis and management of heart failure is one of the most significant public health concerns of the twenty first century, as nearly twenty percent of Americans will develop some form of heart failure in their lifetime. The incidence of newly diagnosed heart failure has remained stable over the last several years at approximately 650,000 diagnoses per year; however, due to several contributing factors the prevalence has continued to rise despite substantial advancements in interventional therapies. The three most significant contributing factors to the rising heart failure prevalence have been identified as 1) significant advancements in technology and medical intervention have dramatically improved the survival rate of those experiencing acute coronary events. This has resulted in a greater number of patients who then progress to chronic heart failure. 2) The management of those with chronic heart failure has been dramatically improved which has allowed those with the disease to live longer and 3) heart failure is in large part a disease associated with advancing age. As the population in the United States and other developed countries continue to grow, such a strong association will inevitably result in a rapidly increasing prevalence. Current clinically therapies for managing heart failure can be categorized into three major groups: pharmaceutical therapy, mechanical circulatory support, or cell-based therapy. Pharmaceutical therapies are used in the earlier stages of disease progression or to manage symptoms and comorbidities of later stage heart failure. Mechanical circulatory support is often implemented when the disease progresses to a more severe state, where volume and / or pressure overload of the ventricles is present. Many modalities of mechanical circulatory support serve as a bridge to transplant, as the only long-term treatment of advanced decompensated heart failure is cardiac transplantation. The third category of treatments for HF is cell-based or stem cell therapies. These therapies are still in their infancies but hold significant potential of cardiac regeneration and reversal of the pathologic remodeling associated with heart failure. While the management of the early stages of heart failure have improves, addressing end-stage failure remains a significant obstacle in resolving the U.S. of the heart failure epidemic. The use of ventricular assist devices (VADs) has improved the management of end-stage failure over the last few decades, but VADs serve mostly as a bridge to transplant, so eventually a donor organ and cardiac transplantation is required. As the population continues to grow, the number of patients in need of a donor heart will increase, leading to an even larger discrepancy between the number of donor organs available and those in severe need. While advancements in VAD technology have reduced potential complications and increased the duration and effectiveness of the mechanical circulatory support, a long-term permanent treatment is still very much in need. Cell-based cardiac therapy or cardiac stem cell therapy holds the greatest potential to solving this age-old problem. The ability to not only regenerate dead or damaged tissue in the heart but also reverse pathologic remodeling due to heart failure could cure millions of patients of heart failure, returning them to a healthy, fully functioning state. The last decade has shed much light on the potential of stem cell therapies, but also has illuminated significant barriers to creating a clinically acceptable treatment. While these barriers seem tall, it is crucial that much time and resources be invested into stem cell therapies for cardiac applications as they hold the greatest potential to being able to effectively treat, rather than manage, those with heart failure. In addition to regenerating dead of damaged myocardium, stem cell technology has the potential to grow an entire organ that is patient specific in its origin, and would fully alleviate having to wait for an available donor organ. The ability to grow an entire organ in the lab, which can later be transplanted, would forever change the way medicine is practiced, while saving millions if not billions of lives worldwide

"The Predication Semantics Model: The Role of Predicate: Class in Text Comprehension and Recall"

This paper presents and tests the predication semantics model, a computational model of text comprehension. It goes beyond previous case grammar approaches to text comprehension in employing a propositional rather than a rigid hierarchical tree notion, attempting to maintain a coherent set of propositions in working memory. The authors' assertion is that predicate class contains semantic information that readers use to make generally accurate predictions of a given proposition. Thus, the main purpose of the model-which works as a series of input and reduction cycles-is to explore the extent to which predicate categories play a role in reading comprehension and recall. In the reduction phase of the model, the propositions entered into the memory during the input phase are decreased while coherence is maintained among them. In an examination of the working memory at the end of each cycle, the computational model maintained coherence for 70% of cycles. The model appeared prone to serial dependence in errors: the coherence problem appears to occur because (unlike real readers) the simulation docs not reread when necessary. Overall, the experiment suggested that the predication semantics model is robust. The results suggested that the model emulates a primary process in text comprehension: predicate categories provide semantic information that helps to initiate and control automatic processes in reading, and allows people to grasp the gist of a text even when they have only minimal background knowledge. While needing refinement in several areas presenting minor problems-for example, the lack of a sufficiently complex memory to ensure that when the simulation of the model goes wrong it does not, as at present, stay wrong for successive intervals-the success of the model even at the current restrictive level of detail demonstrates the importance of the semantic information in predicate categories.

Passive Cooling of a Micromechanical Oscillator with a Resonant Electric Circuit

We cool the fundamental mode of a miniature cantilever by capacitively coupling it to a driven rf resonant circuit. Cooling results from the rf capacitive force, which is phase shifted relative to the cantilever motion. We demonstrate the technique by cooling a 7 kHz cantilever from room temperature to 45 K, obtaining reasonable agreement with a model for the cooling, damping, and frequency shift. Extending the method to higher frequencies in a cryogenic system could enable ground state cooling and may prove simpler than related optical experiments in a low temperature apparatus.Comment: 4 pages, 4 figures; minor changes to match published versio