Optical bistability in PECVD silicon-rich nitride.

We present a study of optical bi-stability in a 3.02 refractive index at 1550nm plasma enhanced chemical vapor deposition (PECVD) silicon-rich nitride (SRN) film, as it pertains to bi-stable switching, memory applications, and thermal sensing applications. In this work we utilize an SRN ring resonator device, which we first characterize at low-power and then compare thermo-optic coefficients, (2.12 ± 0.125) × 10-4/°C, obtained from thermal-heating induced resonance shifts to optically induced resonance shifts as well as estimated propagation loss and absorption. We then measure the time response of this nonlinearity demonstrating the relaxation time to be 18.7 us, indicating the mechanism to be thermal in nature. Finally, we demonstrate bi-stable optical switching.

Demonstration of the DC-Kerr effect in silicon-rich nitride.

We demonstrate the DC-Kerr effect in plasma enhanced chemical vapor deposition (PECVD) silicon-rich nitride (SRN) and use it to demonstrate a third order nonlinear susceptibility, χ(3), as high as (6±0.58)×10-19m2/V2. We employ spectral shift versus applied voltage measurements in a racetrack resonator as a tool to characterize the nonlinear susceptibilities of these films. In doing so, we demonstrate a χ(3) larger than that of silicon and argue that PECVD SRN can provide a versatile platform for employing optical phase shifters while maintaining a low thermal budget using a deposition technique readily available in CMOS process flows.

Management of twenty centimeter segmental bone defect of femoral shaft secondary to infected non-union of fracture using masquelet technique: A case report.

INTRODUCTION: Segmental bone loss is a challenging condition to manage, and some of the techniques employed are difficult for patients to tolerate and involve lengthy treatment and rehabilitation times. The Masquelet technique is a two-stage bone grafting technique used to treat segmental bone defects. The technique has primarily been described for bone defects averaging 5.5 cm in length. This technique's advantages include protection against autograft resorption, relative maintenance of graft position, and prevention of soft-tissue interposition. We present a case report of a male who achieved successful bone defect union utilizing the Masquelet technique for a right femoral shaft infected non-union with a resultant 20 cm bone defect. CASE REPORT: This is a case report of a 28-year old male who presented to our clinic for evaluation and treatment for a segmental bone defect secondary to a right femur fracture with non-union after infection. The patient had been in a motor vehicle collision. Our patient was interested in limb salvage surgery and declined bone transport. Given the significant size of his defect, we opted to treat him utilizing the Masquelet technique. He went on to have a successful union of his defect with associated increased subjective quality of life and functionality. CONCLUSION: The Masquelet technique is a useful limb salvage treatment for patients with segmental bone defects, including large defects of 20 cm in length.

Thermo-optic properties of silicon-rich silicon nitride for on-chip applications.

We demonstrate the thermo-optic properties of silicon-rich silicon nitride (SRN) films deposited using plasma-enhanced chemical vapor deposition (PECVD). Shifts in the spectral response of Mach-Zehnder interferometers (MZIs) as a function of temperature were used to characterize the thermo-optic coefficients of silicon nitride films with varying silicon contents. A clear relation is demonstrated between the silicon content and the exhibited thermo-optic coefficient in silicon nitride films, with the highest achievable coefficient being as high as (1.65±0.08) ×10-4 K-1. Furthermore, we realize an SRN multi-mode interferometer (MMI) based thermo-optic switch with over 20 dB extinction ratio and total power consumption for two-port switching of 50 mW.

User Assessment of a Novel Suspension for a Wheelchair-A Prospective, Randomized, Double Blind Trial.

BACKGROUND: Many Wheelchair users experience adverse effects specific to their situation, some of which might be avoided if suspension systems are integrated into the wheelchair. OBJECTIVES: Our study aimed to compare the user experience using a novel wheelchair suspension system with normal wheels. We tried to quantify the user feelings and impressions while using the different wheels. STUDY DESIGN: Double blinded comparative randomized study. METHODS: The patients were randomized into 2 groups. One used shock absorbing wheels, and the other group had a set of standard wheels with the same exact wheelchairs. The patients were taken to a daily trip by the caregivers and given questionnaires in the second and fourth days. On the morning of the third day the wheels were interchanged, creating a cross over between the groups. We collected general and medical information from the participants. The main outcome measures were the questionnaires filled by the patients and the caregivers aiming to quantify the user experience with the suspension equipped wheels. RESULTS: Statistical significance was reached in 2 questions referred to the patients: "In general-During the ride I didn't feel the bumps" and "I feel very confident when riding the chair" and in one question referred to the caregiver-"It was easy to push the chair in suboptimal ground." CONCLUSIONS: We conclude that the shock absorbing system provided a better user experience in the immediate term than standard wheels. Further study is needed to assess the long-term implications.

Primary Repair of the Medial Collateral Ligament with a Double Row Suture Technique and Suture Tape Augmentation for Acute Tibial-Sided Injuries.

The management of medial collateral ligament (MCL) injuries has evolved during the past 30 years. Most heal reliably with conservative management. The treatment of MCL sprains with concomitant other ligamentous injuries continues to be controversial. Surgical management of chronic laxity of the medial structures can be quite difficult, and therefore anatomic repair of the medial support structures in the acute setting is preferred when indicated. Complete avulsion of the superficial and deep MCL from the tibia with disruption of the meniscal coronary ligament have a poor prognosis with non-operative treatment and may be optimally managed with acute surgical repair for improved valgus stability. A recent review demonstrated that there is a role for primary MCL repair for select patients. This technique addresses complete avulsions from the tibia, using multiple anchors for anatomic reattachment of the deep and superficial MCL, SutureBridge construct to enhance footprint compression, and suture tape to augment the MCL repair. Advantages of this technique include utilization of suture tape augmentation to allow for early range of motion, maintenance of the native MCL to preserve proprioception, and repair in the acute setting for faster recovery.

The Society for Obstetric Anesthesia and Perinatology Consensus Statement on the Anesthetic Management of Pregnant and Postpartum Women Receiving Thromboprophylaxis or Higher Dose Anticoagulants.

Venous thromboembolism is recognized as a leading cause of maternal death in the United States. Thromboprophylaxis has been highlighted as a key preventive measure to reduce venous thromboembolism-related maternal deaths. However, the expanded use of thromboprophylaxis in obstetrics will have a major impact on the use and timing of neuraxial analgesia and anesthesia for women undergoing vaginal or cesarean delivery and other obstetric surgeries. Experts from the Society of Obstetric Anesthesia and Perinatology, the American Society of Regional Anesthesia, and hematology have collaborated to develop this comprehensive, pregnancy-specific consensus statement on neuraxial procedures in obstetric patients receiving thromboprophylaxis or higher dose anticoagulants. To date, none of the existing anesthesia societies' recommendations have weighed the potential risks of neuraxial procedures in the presence of thromboprophylaxis, with the competing risks of general anesthesia with a potentially difficult airway, or maternal or fetal harm from avoidance or delayed neuraxial anesthesia. Furthermore, existing guidelines have not integrated the pharmacokinetics and pharmacodynamics of anticoagulants in the obstetric population. The goal of this consensus statement is to provide a practical guide of how to appropriately identify, prepare, and manage pregnant women receiving thromboprophylaxis or higher dose anticoagulants during the ante-, intra-, and postpartum periods. The tactics to facilitate multidisciplinary communication, evidence-based pharmacokinetic and spinal epidural hematoma data, and Decision Aids should help inform risk-benefit discussions with patients and facilitate shared decision making.

Dehydrated Human Amnion/Chorion Grafts May Accelerate the Healing of Ulcers on Free Flaps in Patients With Venous Insufficiency and/or Lymphedema.

OBJECTIVE: Ulceration of free flaps in patients with venous insufficiency and/or lymphedema is an uncommon but challenging problem. We hypothesized that dehydrated human amnion/chorion membrane (Epifix) grafts would accelerate healing of these challenging ulcers. METHODS: Retrospective analysis of prospectively acquired data identified 8 lower extremity free flaps with ulcerations in the context of venous insufficiency and/or lymphedema. The first 4 were flaps that had been treated with conservative wound care to healing. The second group was treated conservatively initially but then converted to treatment with dehydrated human amnion/chorion membrane grafts. The primary endpoint was time to healing. RESULTS: Comparison of Kaplan-Meier survival curves revealed a significant difference between the conservatively and dehydrated human amnion/chorion membrane-treated flap ulcers, favoring graft treatment (P = .0361). In those ulcers that healed, the average time to healing was 87 days for the conservative treatment group and 33 days for the dehydrated human amnion/chorion membrane treatment group (with an average of 1.7 grafts per ulcer). CONCLUSIONS: Dehydrated human amnion/chorion membrane may accelerate healing of ulcers on lower extremity free flaps in patient with lymphedema and/or venous disease in the treated leg.

Patch-clamp recordings of rat neurons from acute brain slices of the somatosensory cortex during magnetic stimulation.

Although transcranial magnetic stimulation (TMS) is a popular tool for both basic research and clinical applications, its actions on nerve cells are only partially understood. We have previously predicted, using compartmental modeling, that magnetic stimulation of central nervous system neurons depolarized the soma followed by initiation of an action potential in the initial segment of the axon. The simulations also predict that neurons with low current threshold are more susceptible to magnetic stimulation. Here we tested these theoretical predictions by combining in vitro patch-clamp recordings from rat brain slices with magnetic stimulation and compartmental modeling. In agreement with the modeling, our recordings demonstrate the dependence of magnetic stimulation-triggered action potentials on the type and state of the neuron and its orientation within the magnetic field. Our results suggest that the observed effects of TMS are deeply rooted in the biophysical properties of single neurons in the central nervous system and provide a framework both for interpreting existing TMS data and developing new simulation-based tools and therapies.

Mechanisms of magnetic stimulation of central nervous system neurons.

Transcranial magnetic stimulation (TMS) is a stimulation method in which a magnetic coil generates a magnetic field in an area of interest in the brain. This magnetic field induces an electric field that modulates neuronal activity. The spatial distribution of the induced electric field is determined by the geometry and location of the coil relative to the brain. Although TMS has been used for several decades, the biophysical basis underlying the stimulation of neurons in the central nervous system (CNS) is still unknown. To address this problem we developed a numerical scheme enabling us to combine realistic magnetic stimulation (MS) with compartmental modeling of neurons with arbitrary morphology. The induced electric field for each location in space was combined with standard compartmental modeling software to calculate the membrane current generated by the electromagnetic field for each segment of the neuron. In agreement with previous studies, the simulations suggested that peripheral axons were excited by the spatial gradients of the induced electric field. In both peripheral and central neurons, MS amplitude required for action potential generation was inversely proportional to the square of the diameter of the stimulated compartment. Due to the importance of the fiber's diameter, magnetic stimulation of CNS neurons depolarized the soma followed by initiation of an action potential in the initial segment of the axon. Passive dendrites affect this process primarily as current sinks, not sources. The simulations predict that neurons with low current threshold are more susceptible to magnetic stimulation. Moreover, they suggest that MS does not directly trigger dendritic regenerative mechanisms. These insights into the mechanism of MS may be relevant for the design of multi-intensity TMS protocols, may facilitate the construction of magnetic stimulators, and may aid the interpretation of results of TMS of the CNS.

Circadian transcription profile of mouse breast cancer under light-dark and dark-dark conditions.

The circadian clock exists in virtually every cell and regulates key biological processes in cells and tissues. Even in cancer cells, DNA synthesis, cell division and tumor growth are gated by the circadian clock. This study examined the gene expression profiles of transplanted mouse breast tumor cells under normal light-dark (LD) as well as constant dark (DD) conditions. It was found that the overall percentage of rhythmic transcripts in breast tumor tissue was lower than that in normal tissue. Few transcripts had unaltered rhythmic expression patterns under both LD and DD conditions. Most rhythmic transcripts in DD displayed 12h or shorter periods. These results suggest that in addition to the circadian clock control of gene transcription, altering light, feeding, physical activity and other factors characteristically affect the expression of many genes.

Early onset preeclampsia and second trimester serum markers.

OBJECTIVE: To examine serum markers measured in the second trimester to identify women who subsequently develop preeclampsia. METHODS: Clinically defined preeclampsia was confirmed in 45 women who had provided a serum sample as part of Down syndrome screening. Preeclampsia was categorized as mild or severe, as well as early (<32 weeks) or late onset. Each case was matched with five controls based on gestational age and date of serum collection. Stored sera were retrieved and tested for inhibin A, soluble vascular endothelial growth factor receptor 1 (sVEGF R1), placental growth factor (PlGF), and endoglin. Results were converted to multiples of the median (MoM) and compared in case and control pregnancies. Univariate analysis was used to identify the strongest markers, which were then used in a multivariate model. RESULTS: Inhibin A, PlGF, and endoglin were consistently associated with preeclampsia, especially for early onset disease. A multivariate model using the three markers could identify 50% of the pregnancies with early onset preeclampsia with a 2% false positive rate. CONCLUSION: The levels of inhibin A, PlGF, and endoglin in the second trimester can be combined using a predictive model to provide individualized risk estimates for early onset preeclampsia.

Beyond accountability for reasonableness.

This paper is a critique of Norman Daniels' and James Sabin's 'Accountability for Reasonableness' framework for making priority-setting decisions in health care in the face of widespread disagreement about values. Accountability for Reasonableness has been rapidly gaining worldwide acceptance, arguably to the point of becoming the dominant paradigm in the field of health policy. The framework attempts to set ground rules for a procedure that ensures that whatever decisions result will be fair, reasonable, and legitimate to the extent that even those who would be adversely affected will have reason to abide by them. I argue that the framework's four conditions are inadequate to this task. While we certainly require a fair and legitimate procedure for making priority setting decisions in health care despite a lack of consensus on relevant ethical and political issues, we must significantly revise the four conditions, and we cannot avoid facing our substantive disagreements head on if we hope to arrive at decisions that would (and should) be acceptable to everyone. I offer two suggestions. First, there is need for greater public involvement in all stages of deliberation. Second, we should give up on the idea that we can simplify the task of democratic deliberation by disallowing particular kinds or reasons and types of reasoning. Reasons of all kinds should be on the table, but then should be judged on their merits, such as consistency, plausibility and explanatory power, without any regard for their alleged sources of authority.

Absolute measurement of electron-cloud density in a positively charged particle beam.

Clouds of stray electrons are ubiquitous in particle accelerators and frequently limit the performance of storage rings. Earlier measurements of electron energy distribution and flux to the walls provided only a relative electron-cloud density. We have measured electron accumulation using ions expelled by the beam. The ion energy distribution maps the depressed beam potential and gives the dynamic cloud density. Clearing electrode current reveals the static background cloud density, allowing the first absolute measurement of the time-dependent electron-cloud density during the beam pulse.