Closure Of Gap Research Articles

Mechanochemical formation of heterogeneous diamond structures during rapid uniaxial compression in graphite

We predict mechanochemical formation of heterogeneous diamond structures from rapid uniaxial compression in graphite using quantum molecular dynamics simulations. Ensembles of simulations reveal the formation of different diamondlike products starting from thermal graphite crystal configurations. We identify distinct classes of final products with characteristic probabilities of formation, stress states, and electrical properties and show through simulations of rapid quenching that these products are nominally stable and can be recovered at room temperature and pressure. Some of the diamond products exhibit significant disorder and partial closure of the energy gap between the highest-occupied and lowest-unoccupied molecular orbitals (i.e., the HOMO-LUMO gap). Seeding atomic vacancies in graphite significantly biases toward forming products with small HOMO-LUMO gap. We show that a strong correlation between the HOMO-LUMO gap and disorder in tetrahedral bonding configurations informs which kinds of structural defects are associated with gap closure. The rapid diffusionless transformation of graphite is found to lock vacancy defects into the final diamond structure, resulting in configurations that prevent $s{p}^{3}$ bonding and lead to localized HOMO and LUMO states with a small gap.

Optical and electronic properties of 2H−MoS2 under pressure: Revealing the spin-polarized nature of bulk electronic bands

Monolayers of transition-metal dichalcogenide semiconductors present spin-valley locked electronic bands, a property with applications in valleytronics and spintronics that is usually believed to be absent in their centrosymmetric (as the bilayer or bulk) counterparts. Here we show that bulk $2\mathrm{H}\text{\ensuremath{-}}\mathrm{Mo}{\mathrm{S}}_{2}$ hides a spin-polarized nature of states determining its direct band gap, with the spin sequence of valence and conduction bands expected for its single layer. This relevant finding is attained by investigating the behavior of the binding energy of $A$ and $B$ excitons under high pressure, by means of absorption measurements and density-functional-theory calculations. These results raise an unusual situation in which bright and dark exciton degeneracy is naturally broken in a centrosymmetric material. Additionally, the phonon-assisted scattering process of excitons has been studied by analyzing the pressure dependence of the linewidth of discrete excitons observed at the absorption coefficient edge of $2\mathrm{H}\text{\ensuremath{-}}\mathrm{Mo}{\mathrm{S}}_{2}$. Also, the pressure dependence of the indirect optical transitions of bulk $2\mathrm{H}\text{\ensuremath{-}}\mathrm{Mo}{\mathrm{S}}_{2}$ has been analyzed by absorption measurements and density-functional-theory calculations. These results reflect a progressive closure of the indirect band gap as pressure increases, indicating that metallization of bulk $\mathrm{Mo}{\mathrm{S}}_{2}$ may occur at pressures higher than 26 GPa.

Acoustic emission technique to monitor crack growth in a mooring chain

Mooring chains are designed for an operational life of 25 years. However, owner/operator data show that a Floating Production Unit (FPU) experiences a mooring line failure every 9 years on average, and periodic inspections are necessary to monitor their integrity. An established condition monitoring technique based on Acoustic Emission (AE) has the potential to be deployed to mooring chains. AE is based on the principle that elastic energy waves are spontaneously released by a material undergoing plastic deformation and crack growth. The purpose of this paper is to present a feasibility study of AE testing to monitor initiation and propagation of stress corrosion cracks in a mooring chain link, in order to establish whether crack initiation and crack extension phases can be detected and discriminated in the course of a static tensile test. The tensile test was carried out in artificial seawater (3% NaCl solution) using a single grade R5 link of diameter 160 mm for 3.7 months where a crack was initiated from a notch. AE features were plotted against time and these plots were extensively discussed with the view of contributing to the closure of a knowledge gap in the experimental literature.

Analysis of the Tribological Conditions in Grinding of Polycrystalline Diamond Based on Single Grain Friction Tests Using the Pin-Disk Principle

Cutting tools made of polycrystalline diamond (PCD) are used for machining of aluminum alloys, fiber-reinforced plastic composites and wood. Compared to cemented carbide tools with geometrically defined cutting edges, PCD tools offer significant advantages with respect to tool life. High demands regarding the cutting edge roughness and the quality of the rake and the flank face usually require a grinding process with diamond grinding wheels. The PCD grinding process, however, is characterized by low material removal rates and high grinding wheel wear. The material removal rate and the grinding wheel wear, in turn, highly depend on the process state variables process force and process temperature. However, the relationship between these process state variables and the process input variables is largely unknown. This work provides a contribution to the closure of this knowledge gap by means of an adapted friction law. A single grain friction test stand using the pin-disk principle was developed, which enables a measurement of the friction force and the contact zone temperature for normal forces and relative speeds that are common in PCD grinding. During the experiments, the specification of the PCD disc, the cross-sectional area of the friction sample made of monocrystalline diamond as well as the process parameters normal force and relative speed were varied. In addition, the tests were carried out without lubrication as well as with a minimum lubrication. A high correlation between the contact force and the coefficient of friction was determined. This relationship was mathematically formulated in a friction law. In addition, a direct influence of the contact force and the relative velocity on the contact zone temperature was identified. The knowledge gained leads to an improved understanding of the PCD grinding process and thus enables a more efficient grinding process design.

Where is the Target Point to Prevent Cortical Hinge Fracture in Medial Closing-Wedge Distal Femoral Varus Osteotomy?

The purpose of this study was to investigate whether the location of the hinge affects the incidence of hinge fracture during medial closing-wedge distal femoral varus osteotomy (DFVO). Twenty knees from 10 fresh-frozen human cadavers (mean age, 75 ± 17 years) were used to perform uniplanar medial closing-wedge DFVO with a 7-mm wedge. Each specimen was randomly assigned to either group A (supracondylar hinge) or group B (lateral condylar hinge). The incidence of hinge fracture and stability was compared between both groups after uniplanar medial closing-wedge DFVO. In group A, 8 of 10 knees had a lateral cortex fracture during closure of the osteotomy gap, and all fractured knees were unstable. Two knees with an intact lateral cortical hinge showed stability under manual valgus and varus forces. After intentional breakage of the lateral cortical hinge, both knees were found to be unstable under the same force. In group B, 2 of 10 knees had a lateral cortex fracture, and 8 knees had no fractures. All specimens were found to be stable under manual valgus and varus forces. After intentional breakage of the lateral cortical hinge in group B, 2 knees were unstable, while 8 knees remained stable. This study showed a significantly higher incidence of lateral cortical hinge fracture and instability in group A than in group B during closure of the osteotomy gap.

Video-Assisted Mini-Open Sublay (VAMOS): A Simple Hybrid Approach for Lateral Incisional Hernias.

PurposeThe purpose is to present a new hybrid approach of lateral incisional hernia repair associated with reduced operative trauma and anatomically optimal mesh placement.MethodsVideo-Assisted Mini-Open Sublay (VAMOS) consists of a laparoscopic atraumatic dissection of the hernia sac, diaphanoscopy, laparoscopically-assisted closure of the fascial gap and mesh placement in sublay position through a minimized skin incision. Feasibility of this concept was assessed in a cohort of 7 consecutive patients.ResultsVAMOS approach was feasible in all 7 patients. Median hernia size was 8 cm, the median skin incision width was 7.7 cm. Median operative time was 86 min. In all patients a sufficient mesh overlap on all sides of the fascial gap was ensured. On short-term follow-up no procedure related complications were recorded, seroma formation occurred in 2 patients. Pain medication was necessary for median 4.9 days. There was no need for pain medication on day 14, whatsoever.ConclusionInitial VAMOS results show that the technique is simple, time-saving and safe. It provides a substantial reduction in postoperative pain compared to an open approach. Through implantation in the intermuscular sublay position and minor access-related trauma, it is possible to achieve a biomechanically optimal mesh position, to lay the foundations for adequate remodelling of the abdominal wall, and to prevent recurrence as well as local complications. All in all, VAMOS appears to have several advantages over current surgical strategies.

Butterfly cartilage tympanoplasty outcomes: A single-institution experience and literature review

PurposeIn 1998, Dr. Eavey described the trans-canal inlay butterfly cartilage tympanoplasty technique, also known as cartilage button tympanoplasty. Many retrospective studies have since demonstrated its efficacy and decreased operative time when compared to underlay and overlay tympanoplasty techniques. The butterfly cartilage tympanoplasty approach uses only a cartilage graft to repair tympanic membrane perforations. The aim of this study was to review the literature for studies that examined butterfly cartilage tympanoplasty success rates and outcomes and compare them to outcomes from our cohort. Materials and methodsButterfly cartilage tympanoplasties were performed in 23 pediatric patients and 7 adult patients. We evaluated the tympanic membrane perforation closure rate and hearing results measured by closure of the air-bone gap. ResultsThe reviewed studies evaluating butterfly cartilage tympanoplasties demonstrated perforation closure rates between 71%–100%. The hearing outcomes in the reviewed literature varied, although the majority reported improved hearing. In our cohort, 21 of the 32 repaired tympanic membrane perforations demonstrated complete perforation closure. The mean follow-up length was 13.4 months. The mean air-bone gap decreased from 13.4 dB to 6.9 dB. ConclusionsThe butterfly cartilage/cartilage button technique is effective in closing tympanic membrane perforations and decreasing the air-bone gap in both adults and children.

Laparoscopic repair for parastomal hernia with ongoing barbed suture followed by sandwich-technique: 'Sandwich-plus-technique'.

The incidence of parastomal hernias after a permanent stoma is between 50% and 80% depending on the type of stoma, the definition of the hernia (clinical or radiological), and the length of the follow-up. Surgical therapy is complex and involves several techniques with different recurrence rates. We present three cases where we have closed the hernia gap with continuous, non-resorbable, self-retaining sutures with subsequent use of the sandwich technique (’Sandwich-plus-technique’). There were pronounced parastomal hernias in three female patients (mean age was 72 years and the range was 63–78 years) with permanent colostomata. After laparoscopic adhesiolysis, the closure of the hernia defect was completed with ongoing, barbed non-resorbable 1-0 sutures (polybutester) followed by the sandwich technique. There were no intraoperative complications and currently no clinical or radiological evidence for recurrences of the parastomal hernia. Closure of the hernia gap leads to the additional reconstruction of the lateral abdominal wall, resulting in a larger contact surface for integration of the keyhole mesh and thus prior to implantation of the Sugarbaker mesh. The laparoscopic augmentation of large parastomal hernias using the ‘Sandwich-plus-technique’ is technically complex but achieves very good results in our case series. Further studies and long-term results should prove that the low recurrence rate of the sandwich technique can be further reduced.

Strain-tunable charge carrier mobility of atomically thin phosphorus allotropes

We explore the impact of strain on charge carrier mobility of monolayer $\ensuremath{\alpha}$-, $\ensuremath{\beta}$-, $\ensuremath{\gamma}$-, and $\ensuremath{\delta}$-P, the four well-known atomically thin allotropes of phosphorus, using density functional theory. Owing to the highly anisotropic band dispersion, the charge carrier mobility of the pristine allotropes is significantly higher (more than 5 times in some cases) in one of the principal directions (zigzag or armchair) compared to the other. Uniaxial strain (up to 6% compressive/tensile) leads to band gap alteration in each of the allotropes, especially a direct to indirect band gap semiconductor transition in $\ensuremath{\gamma}$-P and a complete closure of the band gap in $\ensuremath{\gamma}$- and $\ensuremath{\delta}$-P. We find that the charge carrier mobility is enhanced typically by a factor of \ensuremath{\sim}5--10 in all the allotropes due to uniaxial strain; notably, among them an \ensuremath{\sim}250 (30) times increase of the hole (electron) mobility along the armchair (zigzag) direction is observed in $\ensuremath{\beta}$-P ($\ensuremath{\gamma}$-P) under a compressive strain, acting in the armchair direction. Interestingly, the preferred electronic conduction direction can also be changed in the case of $\ensuremath{\alpha}$- and $\ensuremath{\gamma}$-P by applying strain.

Audiological Outcomes of Stapedotomy: Our Experience

Objective: This study was aimed to sequentially document the patient’s audiological improvement after stapedotomy as measured by pure tone audiometry.Material and Methods: This prospective clinical study was performed in a total of 100 patients (age range: 20 – 63 years), diagnosed with Otosclerosis who underwent Stapedotomy at the Department of Otology, Madras ENT Research Foundation, Chennai between September 2010 to March 2012. Pre-operative and Post-operative audiometric evaluation was done using the same conventional pure tone audiometer with standard calibrations. Post-operative audiometry was sequentially performed at 6 months, 1 year and 2 years. Bone-conduction and air conduction thresholds and the Air-bone gap (ABG), were assessed at each schedule at 0.5 KHz, 1 KHz, 2 KHz and 4 KHz frequencies respectively.Result: All patients had significant audiological improvement as measured by their sequential pure tone audiometries. Overall, the frequency specific pre-operative mean average Air-Bone gap was 52.3dB at 500Hz, 36.5dB at 1KHz, 39.3dB at 2KHz, 38.7dB at 4KHz and the frequency specific postoperative mean average Air-Bone Gap closure was achieved by 27.8dB at 500Hz, 29.6dB at 1KHz, 13.6dB at 2KHz, 11.4dB at 4KHz, by the time of 2 years of follow up. A successful closure of AB gap >10dB was achieved in these speech frequencies in 80% of cases. The frequency specific bone-conduction thresholds were unchanged postoperatively. Two patients developed post-operative vertigo, out of which 1 developed SNHL after 3 weeks of surgery.Conclusion: The study confirms that stapedotomy is a safe and successful procedure in the hands of a well trained otologist, providing long-term hearing improvement to patients with otosclerosis.

Early life exposure to air pollution particulate matter (PM) as risk factor for attention deficit/hyperactivity disorder (ADHD): Need for novel strategies for mechanisms and causalities

Epidemiological studies have demonstrated that air pollution particulate matter (PM) and adsorbed toxicants (organic compounds and trace metals) may affect child development already in utero. Recent studies have also indicated that PM may be a risk factor for neurodevelopmental disorders (NDDs). A pattern of increasing prevalence of attention deficit/hyperactivity disorder (ADHD) has been suggested to partly be linked to environmental pollutants exposure, including PM. Epidemiological studies suggest associations between pre- or postnatal exposure to air pollution components and ADHD symptoms. However, many studies are cross-sectional without possibility to reveal causality. Cohort studies are often small with poor exposure characterization, and confounded by traffic noise and socioeconomic factors, possibly overestimating the study associations. Furthermore, the mechanistic knowledge how exposure to PM during early brain development may contribute to increased risk of ADHD symptoms or cognitive deficits is limited. The closure of this knowledge gap requires the combined use of well-designed longitudinal cohort studies, supported by mechanistic in vitro studies. As ADHD has profound consequences for the children affected and their families, the identification of preventable risk factors such as air pollution exposure should be of high priority.

Frustrated quantum magnetism in the Kondo lattice on the zigzag ladder

The interplay between Kondo effect, indirect magnetic interaction and geometrical frustration is studied in the Kondo lattice on the one-dimensional zigzag ladder. Using the density-matrix renormalization group (DMRG), the ground state and various short- and long-range spin- and density-correlation functions are calculated for the model at half-filling as a function of the antiferromagnetic Kondo interaction down to $J=0.3t$ where $t$ is the nearest-neighbor hopping on the zigzag ladder. Geometrical frustration is shown to lead to at least two critical points: Starting from the strong-$J$ limit, where almost local Kondo screening dominates and where the system is a nonmagnetic Kondo insulator, antiferromagnetic correlations between nearest-neighbor and next-nearest-neighbor local spins become stronger and stronger, until at $J^{\rm dim}_{\rm c} \approx 0.89t$ frustration is alleviated by a spontaneous breaking of translational symmetry and a corresponding transition to a dimerized state. This is characterized by antiferromagnetic correlations along the legs and by alternating antiferro- and ferromagnetic correlations on the rungs of the ladder. A mechanism of partial Kondo screening that has been suggested for the Kondo lattice on the two-dimensional triangular lattice is not realized in the one-dimensional case. Furthermore, within the symmetry-broken dimerized state, there is a magnetic transition to a $90^{\circ}$ quantum spin spiral with quasi-long-range order at $J^{\rm mag}_{\rm c} \approx 0.84t$. The quantum-critical point is characterized by a closure of the spin gap (with decreasing $J$) and a divergence of the spin-correlation length and of the spin-structure factor $S(q)$ at wave vector $q=\pi/2$. This is opposed to the model on the one-dimensional bipartite chain, which is known to have a finite spin gap for all $J>0$ at half-filling.

SURGERY FOR JUVENILE OTOSCLEROSIS: A LITERATURE REVIEW

Otosclerosis is a disease characterized by abnormal bony growth and remodeling around the otic capsule. Although adults make up the majority of patients, otosclerosis is also encountered in children. However, the literature on juvenile otosclerosis is still limited. The main therapeutic options for children with otosclerosis are hearing aids or stapes surgery. Despite many years of treating pediatric patients with stapes surgery, the issue of whether to perform the operation is still a subject of debate. To identify suitable literature on juvenile otosclerosis, a search was performed using the following databases: PubMed, Web of Science, and Medline, and based on the search criteria 19 articles were found suitable for the review. The current evidence indicates that stapes surgery for juvenile otosclerosis is a safe and effective procedure which leads to closure of the air-bone gap over both short and long terms. Complications of stapes surgery are extremely rare and in the majority of cases comprise transient vertigo. Age itself should not be a contraindication to stapes surgery for juvenile otosclerosis.

NIEKTÓRE PRZYCZYNY NIEPOWODZEŃ CHIRURGICZNEGO LECZENIA OTOSKLEROZY NA PODSTAWIE OPISU PRZYPADKU

IntroductionSurgical treatment of otosclerosis requires considerable experience of the otosurgeon, especially in advanced cases or in an ear with an unusually narrow external auditory canal, a narrow niche of the round window, a significantly thickened stapes footplate, or an exposed or hanging facial nerve. Case involving subsequent reoperations by different surgeons can be particularly difficult. Collective knowledge of treatment failures during otosclerosis reoperation, as set out in the literature, does not list the difficulties encountered, fails to assess most causes of failure, and does not describe remedies and corrective techniques.Material and MethodsThe course of treatment followed by a 55-year-old complaining of progressive, bilateral, mixed hearing loss due to otosclerosis is described. The patient’s treatment consisted of stapes mobilization, followed by stapedotomy and restapedotomy of the right ear, and stapetodomy of the left ear.ResultsThere was short-term improvement of hearing after mobilization of the stapes, but its subsequent deterioration, with elevation of both the air- and bone-conduction thresholds in the right ear, were indications for reoperation and stapedotomy. Short-term improvement in hearing was achieved after the operation, followed by rapid hearing loss. Due to this and growing balance disorders after nearly a year, a restapedotomy was performed with complete closure of the air-bone gap. Then, due to hearing deterioration in the left ear, a successful stapedotomy was performed in this ear.ConclusionsRevision operations in otosclerosis require a lot of experience of the otosurgeon due to the many reasons for failure, particularly when the first surgery was performed elsewhere. An air-bone gap, severe tinnitus, and balance disorders are indications for reoperation by an experienced otosurgeon, as common causes of failure are postoperative adhesions and subsequent stapes immobilization.

Assessing the Crown Closure of Nypa on UAV Images using Mean-Shift Segmentation Algorithm

<p>Utilization of very high-resolution images becomes a new trend in forest management, particularly in the detection and identification of forest stand variables. This paper describes the use of mean-shift segmentation algorithm on unmanned aerial vehicles (UAV) images to measure crown closure of nypa (Nypa fructicans) and gap. The 27 combinations of the parameter values such as spatial radius (hs), range radius (hr), and minimum region size (M). Gap detection and nypa crown closure measurements were performed using a hybrid between pixel-based (maximum likelihood classifier) and object-based approaches (segmentation). For evaluation of the approach performance, the accuracy assessment was done by comparing object-based classification results (segmentation) and visual interpretation (ground check). The study found that the best combination of segmentation parameter was the combination of hs 10, hr 10 and M 50, with the overall accuracy of 76,6% and kappa accuracy of 55.7%.</p>

Crop yield gap and stability in organic and conventional farming systems

A key challenge for sustainable intensification of agriculture is to produce increasing amounts of food and feed with minimal biodiversity loss, nutrient leaching, and greenhouse gas emissions. Organic farming is considered more sustainable, however, less productive than conventional farming. We analysed results from an experiment started under identical soil conditions comparing one organic and two conventional farming systems. Initially, yields in the organic farming system were lower, but approached those of both conventional systems after 10–13 years, while requiring lower nitrogen inputs. Unexpectedly, organic farming resulted in lower coefficient of variation, indicating enhanced spatial stability, of pH, nutrient mineralization, nutrient availability, and abundance of soil biota. Organic farming also resulted in improved soil structure with higher organic matter concentrations and higher soil aggregation, a profound reduction in groundwater nitrate concentrations, and fewer plant-parasitic nematodes. Temporal stability between the three farming systems was similar, but when excluding years of Phytophthora outbreaks in potato, temporal stability was higher in the organic farming system. There are two non-mutually exclusive mechanistic explanations for these results. First, the enhanced spatial stability in the organic farming system could result from changes in resource-based (i.e. bottom-up) processes, which coincides with the observed higher nutrient provisioning throughout the season in soils with more organic matter. Second, enhanced resource inputs may also affect stability via increased predator-based (i.e. top-down) control. According to this explanation, predators stabilize population dynamics of soil organisms, which is supported by the observed higher soil food web biomass in the organic farming system.We conclude that closure of the yield gap between organic and conventional farming can be a matter of time and that organic farming may result in greater spatial stability of soil biotic and abiotic properties and soil processes. This is likely due to the time required to fundamentally alter soil properties.

Towards a robust and consistent middle Eocene astronomical timescale

Until now, the middle Eocene has remained a poorly constrained interval of efforts to produce an astrochronological timescale for the entire Cenozoic. This has given rise to a so-called “Eocene astronomical timescale gap” (Vandenberghe et al., 2012). A high-resolution astrochronological calibration for this interval has proven to be difficult to realize, mainly because carbonate-rich deep-marine sequences of this age are scarce. In this paper, we present records from middle Eocene carbonate-rich sequences from the North Atlantic Southeast Newfoundland Ridge (IODP Exp. 342, Sites U1408 and U1410), of which the cyclical sedimentary patterns allow for an orbital calibration of the geologic timescale between ∼38 and ∼48 Ma. These carbonate-rich cyclic sediments at Sites U1408 and U1410 were deposited as drift deposits and exhibit prominent lithological alternations (couplets) between greenish nannofossil-rich clay and white nannofossil ooze. The principal lithological couplet is driven by the obliquity of Earth's axial tilt, and the intensity of their expression is modulated by a cyclicity of about 173 kyr. This cyclicity corresponds to the interference of secular frequencies s3 and s6 (related to the precession of nodes of the Earth and Saturn, respectively). This 173-kyr obliquity amplitude modulation cycle is exceptionally well recorded in the XRF (X-ray fluorescence)-derived Ca/Fe ratio. In this work, we first demonstrate the stability of the (s3–s6) cycles using the latest astronomical solutions. Results show that this orbital component is stable back to at least 50 Ma, and can thus serve as a powerful geochronometer in the mid-Eocene portion of the Cenozoic timescale. We then exploit this potential by calibrating the geochronology of the recovered middle Eocene timescale between magnetic polarity Chrons C18n.1n and C21n.Comparison with previous timescales shows similarities, but also notable differences in durations of certain magnetic polarity chrons. We present a revision of previous astronomical timescales from the Equatorial and South Atlantic, to overcome the differences between different mid-Eocene astrochronologies. Using our new records from the North Atlantic, combined with existing records from the South Atlantic (ODP Site 1263 and Hole 702B) and Equatorial Atlantic (ODP Site 1260), we revise the durations of magnetic polarity Chrons C18n.1n to C21n, thereby arriving at a robust and self-consistent closure of the middle Eocene astronomical timescale gap.

Functional role of the core gap in the middle part of tropomyosin.

Tropomyosin (Tpm) is an α-helical coiled-coil actin-binding protein playing an essential role in the regulation of muscle contraction. The middle part of the Tpm molecule has some specific features, such as the presence of noncanonical residues as well as a substantial gap at the interhelical interface, which are believed to destabilize a coiled-coil and impart structural flexibility to this part of the molecule. To study how the gap affects structural and functional properties of α-striated Tpm (the Tpm1.1 isoform that is expressed in cardiac and skeletal muscles) we replaced large conserved apolar core residues located at both sides of the gap with smaller ones by mutations M127A/I130A and M141A/Q144A. We found that in contrast with the stabilizing substitutions D137L and G126R studied earlier, these substitutions have no appreciable influence on thermal unfolding and domain structure of the Tpm molecule. They also do not affect actin-binding properties of Tpm. However, they strongly increase sliding velocity of regulated actin filaments in an invitro motility assay and cause an oversensitivity of the velocity to Ca2+ similar to the stabilizing substitutions D137L and G126R. Molecular dynamics shows that the substitutions studied here increase bending stiffness of the coiled-coil structure of Tpm, like that of G126R/D137L, probably due to closure of the interhelical gap in the area of the substitutions. Our results clearly indicate that the conserved middle part of Tpm is important for the fine tuning of the Ca2+ regulation of actin-myosin interaction in muscle.

Trends in MD/PhD Graduates Entering Psychiatry: Assessing the Physician-Scientist Pipeline.

The goal of this study was to identify trends in MD/PhD graduates entering psychiatry, to compare these trends with other specialties, and to review strategies for enhancing the physician-scientist pipeline. Data on 226,588 medical students graduating from Liaison Committee on Medical Education accredited programs between 1999 and 2012 (6626 MD/PhDs) were used to evaluate the number, percentage, and proportion of MD/PhDs entering psychiatry in comparison with other specialties (neurology, neurosurgery, internal medicine, family medicine, and radiation oncology). Linear regression and multiple linear regression determined whether these values increased over time and varied by sex. Over 14years, an average of 18 MD/PhDs (range 13-29) enrolled in psychiatry each year. The number of MD/PhDs going into psychiatry significantly increased, although these gains were modest (less than one additional MD/PhD per year). The proportion of students entering psychiatry who were MD/PhDs varied between 2.9 and 5.9 per 100 residents, with no significant change over time. There was also no change in the percentage of MD/PhDs entering psychiatry from among all MD/PhD graduates. The rate of increase in the number of MD/PhDs going into psychiatry did not differ significantly from other specialties except for family medicine, which is decreasing. The rate of MD/PhDs going into psychiatry was higher for women, suggesting closure of the sex gap in 17years. Despite the increase in the number of MD/PhDs entering psychiatry, these numbers remain low. Expanding the cohort of physician-scientists dedicated to translational research in psychiatry will require a multipronged approach.

Pension Fund Restoration Policy in General Equilibrium

This paper quantifies the business cycle effects and distributional implications of pension fund restoration policy after the economy has been hit by a financial shock. We extend a canonical New-Keynesian dynamic general equilibrium model with a tractable demographic structure and a pension fund. Numerical simulations show that economies with pension funds that primarily write off accumulated pension wealth to restore financial adequacy behave similarly to an economy without a pension fund. Significant deviations from laissez-faire arise when the pension fund increases the pension fund contribution rate to close the funding gap or postpones the closure of the funding gap. At a cost of significantly distorting aggregate labour supply and output, the pension fund can shelter the group of retirees from unanticipated shocks by guaranteeing the value of their accumulated pension wealth. A defined benefit pension fund can be welfare improving to the group of agents that is already born in the period the financial shock hits. However, since pension funding gaps are typically closed over an extended period of time, a part of the welfare gains to currently alive agents comes at the expense of future, currently unborn, generations.