Electronically Variable Pressure Regulator (EVPR)

A new programmable electronically variable pressure regulator (EVPR) concept accurately controls the local outlet or remote system pressure. It uses an integral pulse width modulated rare earth permanent magnet motor operating in response to redundant pressure transducer feedback signals. The EVPR is a simple single stage device that does not use dynamic seals or pilot valving. Conversion of partial revolution motor torque to poppet lifting force is accomplished by pure flexure action to avoid using bearings. The flexure drive (called the ROTAX) has a variable lead to minimize motor weight and power consumption. Breadboard tests were completed successfully on two critical design elements of the EVPR: the ROTAX and the motor. The ROTAX cable system was tested for 250,000 cycles without failure. The breadboard motor met the basic design requirements including the design torque and power consumption. Prototype parts were fabricated, and testing of the prototype EVPR has started. It is PC computer controlled to facilitate programming, data acquisition and analysis. A lightweight dedicated microprocessor is planned for the flightweight EVPR

Navigating the Murk: Ethical and Practical Considerations for the Surgical Treatment of the Sacroiliac Joint Syndrome

The field of spine surgery has many controversies. The surgical treatment of the sacroiliac (SI) joint is, too, fraught with debate. The diagnosis of painful SI joints is currently limited to relief following “diagnostic” injections and pain generated from a suite of clinical maneuvers. Diagnoses of SI joint dysfunction are dependent entirely on patient-reported responses to provocative maneuvers and invasive procedures. There is a glaring lack of objective radiographic and objective physical examination findings for this syndrome. The evidence for treatment, and specifically for the surgical treatment of the SI joint is reviewed and critiqued. Although the surgical techniques are simple, consensus is elusive for both indication and optimal technique. Ethical principles for surgical innovation and practical considerations for the treatment of the SI joint syndrome are discussed at length. Discussed as well are key points to consider when providing informed consent to a patient before proceeding with surgical intervention for this procedure and diagnosis. Spine surgery is a field with considerable regional variation in practice. Even today, the precise indications for arthrodesis, extent, and approach, remain frequently debated; however, as much conversation takes place surrounding lumbar surgery, even more confusion, bias, opinion, and deliberation exists when surgical treatment of the SI joint is considered. This chapter discusses the unique challenges associated with the SI joint and provides practical considerations for the treatment thereof.Open access articleThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]

Arthropod community composition in urban landscapes is shaped by both environmental filtering and dispersal limitation

We assessed the relative importance of environmental filtering and dispersal limitation in structuring foliage- and ground-dwelling arthropod communities in central North Carolina. We hypothesized that differences in both local environment and dispersal distance between sites would predict differences in community composition, but that dispersal distance would be more important for ground arthropods than for foliage arthropods. We used variance partitioning to quantify the relative explanatory power of differences in the local environment and dispersal distance between sampling plots. For foliage arthropods, the full set of predictors explained 37-39% of the variance in community dissimilarity, while the full set of predictors explained 42-56% of the variance for ground arthropods. Environmental predictors alone consistently explained more variance in community dissimilarity than geographic predictors alone for ground arthropods, but the variance explained by each predictor set alone varied for foliage arthropods depending on the metric of community dissimilarity. Examining communities of multiple arthropod groups across the same spatial gradient highlights the scale-dependence of these processes and illustrates how variation in the environment can alter the relative abundance of specialist and generalist taxa

Challenges in the Application of Geometric Constraint Models

Discerning the processes influencing geographic patterns of species richness remains one of the central goals of modern ecology. Traditional approaches to exploring these patterns have focused on environmental and ecological correlates of observed species richness. Recently, some have suggested these approaches suffered from the lack of an appropriate null model that accounts for species’ ranges being constrained to occur within a bounded domain. Proponents of these null geometric constraint models (GCMs), and the mid-domain effect these models produce, argue their utility in identifying meaningful gradients in species richness. This idea has generated substantial debate. Here we discuss what we believe are the three major challenges in the application of GCMs. First, we argue there are actually two equally valid null models for the random placement of species ranges within a domain, one of which actually predicts a uniform distribution of species richness. Second, we highlight the numerous decisions that must be made to implement a GCM that lead to marked differences in the predictions of the null model. Finally, we discuss challenges in evaluating the importance of GCMs once they have been implemented

ANTERIOR CERVICAL SURGICAL RETRACTOR DESIGN

INTRODUCTION During anterior cervical surgeries such as discectomies and corpectomies (removal of the disc separating two vertebrae and removal of the vertebral body itself, respectively1), surgeons implement a retractor device to broaden the view of the spinal area on which they are operating.  The current devices have flaws; including a lack of stability, complicated mechanisms, multiple pieces, or difficulty stacking, and a new retractor is needed.  Stacking, occurs in a multiple level surgery, when more than two or more devices are needed simultaneously to hold the area open.  Our design utilizes the distraction screw to stabilize the retractor in position, without the impediment of the device becoming an obstacle for the surgeons to manoeuvre around. METHODS Based on the expertise of the experienced surgeons, multiple models will be drawn.  The most practical concept will then be developed on autoCAD software.  The lower width of the blades uses a simple rotation-linear motion system.  Meanwhile, the upper part of the blade is rotated about the lower part, allowing the blade to be used at an angle. RESULTS A physical model of the device (as seen in Figure 1 below) has yet to be printed and tested.  Nevertheless, the new model is placed within the patient, allowing the surgeons to work without worrying about the device being an obstruction.  The blades are angled wider at the top and narrower at the bottom), making it easier for the surgeons’ hands to fit in the small void in the patient’s neck. DISCUSSION AND CONCLUSIONS Since a prototype has not been created or clinically tested yet, all results and conclusions are merely speculations.  Our new device is: simple to use, less obstructive, and able to provide a broader view of the operating area.  In addition, in the rare event that these longer blades require stacking, it is very simple to implement.  The surgeon will simply place a second retractor on the second distraction screw. Since every patient is a different size, the blades must be interchangeable.  This way the surgeon can choose what length and height he/she wants the blade to be for each surgery.  Similar to the previous devices, the blades are curved at the bottom with teeth; this helps the device bite into the soft tissue and minimize slipping.  The blades will be made of titanium, which is strong, radiolucent, and easy to sterilize

Methylprednisolone for acute spinal cord injury: An inappropriate standard of care

N 1987, high forceps were used to deliver a newborn girl in a hospital in Southern California. Acute SCI remains a devastating condition, and little progress has been made toward improving or curing neurological outcome. However, since the results of NASCIS II were published in 1990, the use of MP in the treatment of this disorder has become an accepted standard. 3,7 The 1-year follow-up results from NASCIS II have been reported 4 but were less publicized. Since early and 1-year results from NASCIS III have become available, acute care medical institutions are presently faced with the decision of whether to incorporate the recommended 48-hour protocol proposed in this latest study into their existing 24-hour protocols. Methods. Published results from NASCIS II and III were reviewed in the context of the original study design, including primary outcomes compared with post-hoc comparisons. Data were retroconverted from tabular form back to raw form to allow direct inspection of changes in treatment groups. These findings were further analyzed with respect to justification of practice standards. Although well-designed and well-executed, both NASCIS II and III failed to demonstrate improvement in primary outcome measures as a result of the administration of methylprednisolone. Post-hoc comparisons, although interesting, did not provide compelling data to establish a new standard of care in the treatment of patients with acute SCI. Conclusions. The use of methylprednisolone administration in the treatment of acute SCI is not proven as a standard of care, nor can it be considered a recommended treatment. Evidence of the drug's efficacy and impact is weak and may only represent random events. In the strictest sense, 24-hour administration of methylprednisolone must still be considered experimental for use in clinical SCI. Forty-eight-hour therapy is not recommended. These conclusions are important to consider in the design of future trials and in the medicolegal arena. KEY WORD

Cold Helium Pressurization for Liquid Oxygen / Liquid Methane Propulsion Systems: Fully-Integrated Initial Hot-Fire Test Results

A prototype cold helium active pressurization system was incorporated into an existing liquid oxygen (LOX) / liquid methane (LCH4) prototype planetary lander and hot-fire tested to collect vehicle-level performance data. Results from this hot-fire test series were used to validate integrated models of the vehicle helium and propulsion systems and demonstrate system effectiveness for a throttling lander. Pressurization systems vary greatly in complexity and efficiency between vehicles, so a pressurization performance metric was also developed as a means to compare different active pressurization schemes. This implementation of an active repress system is an initial sizing draft. Refined implementations will be tested in the future, improving the general knowledge base for a cryogenic lander-based cold helium system

The many colours of ‘the dress’

YesThere has been an intense discussion among the public about the colour of a dress, shown in a picture posted originally on Tumblr (http://swiked. tumblr.com/post/112073818575/ guys-please-help-me-is-this-dress white-and; accessed on 10:56 am GMT on Tue 24 Mar 2015). Some people argue that they see a white dress with golden lace, while others describe the dress as blue with black lace. Here we show that the question “what colour is the dress?” has more than two answers.The full text was made available at the end of the publisher's embargo, 14th May 201

Don't let spurious accusations of pseudoreplication limit our ability to learn from natural experiments (and other messy kinds of ecological monitoring)

Pseudoreplication is defined as the use of inferential statistics to test for treatment effects where treatments are not replicated and/or replicates are not statistically independent. It is a genuine but controversial issue in ecology particularly in the case of costly landscape-scale manipulations, behavioral studies where ethics or other concerns may limit sample sizes, ad hoc monitoring data, and the analysis of natural experiments where chance events occur at a single site. Here key publications on the topic are reviewed to illustrate the debate that exists about the conceptual validity of pseudoreplication. A survey of ecologists and case studies of experimental design and publication issues are used to explore the extent of the problem, ecologists’ solutions, reviewers’ attitudes, and the fate of submitted manuscripts. Scientists working across a range of ecological disciplines regularly come across the problem of pseudoreplication and build solutions into their designs and analyses. These include carefully defining hypotheses and the population of interest, acknowledging the limits of statistical inference and using statistical approaches including nesting and random effects. Many ecologists face considerable challenges getting their work published if accusations of pseudoreplication are made – even if the problem has been dealt with. Many reviewers reject papers for pseudoreplication, and this occurs more often if they haven't experienced the issue themselves. The concept of pseudoreplication is being applied too dogmatically and often leads to rejection during review. There is insufficient consideration of the associated philosophical issues and potential statistical solutions. By stopping the publication of ecological studies, reviewers are slowing the pace of ecological research and limiting the scope of management case studies, natural events studies, and valuable data available to form evidence-based solutions. Recommendations for fair and consistent treatment of pseudoreplication during writing and review are given for authors, reviewers, and editors