757 research outputs found
PATENTS, R&D AND LAG EFFECTS: EVIDENCE FROM FLEXIBLE METHODS FOR COUNT PANEL DATA ON MANUFACTURING FIRMS
Hausman, Hall and Griliches (1984) and Hall, Griliches and Hausman (1986) investigated whether there was a lag in the patent-R&D relationship for the U.S. manufacturing sector using 1970¿s data. They found that there was little evidence of anything but contemporaneous movement of patents and R&D. We reexamine this important issue employing new longitudinal patent data at the firm level for the U.S. manufacturing sector from 1982 to 1992. To address unique features of the data, we estimate various distributed lag and dynamic multiplicative panel count data models. The paper also develops a new class of count panel data models based on series expansion of the distribution of individual effects. The empirical analyses show that, although results are somewhat sensitive to different estimation methods, the contemporaneous relationship between patenting and R&D expenditures continues to be rather strong, accounting for over 60% of the total R&D elasticity. Regarding the lag structure of the patents-R&D relationship, we do find a significant lag in all empirical specifications. Moreover, the estimated lag effects are higher than have previously been found, suggesting that the contribution of R&D history to current patenting has increased from the 1970¿s to the 1980¿s.Innovative activity, Patents and R&D, Individual effects, count panel data methods.
Recovery from disturbance requires resynchronization of ecosystem nutrient cycles
Nitrogen (N) and phosphorus (P) are tightly cycled in most terrestrial ecosystems, with plant uptake more than 10 times higher than the rate of supply from deposition and weathering. This near-total dependence on recycled nutrients and the stoichiometric constraints on resource use by plants and microbes mean that the two cycles have to be synchronized such that the ratio of N:P in plant uptake, litterfall, and net mineralization are nearly the same. Disturbance can disrupt this synchronization if there is a disproportionate loss of one nutrient relative to the other. We model the resynchronization of N and P cycles following harvest of a northern hardwood forest. In our simulations, nutrient loss in the harvest is small relative to postharvest losses. The low N:P ratio of harvest residue results in a preferential release of P and retention of N. The P release is in excess of plant requirements and P is lost from the active ecosystem cycle through secondary mineral formation and leaching early in succession. Because external P inputs are small, the resynchronization of the N and P cycles later in succession is achieved by a commensurate loss of N. Through succession, the ecosystem undergoes alternating periods of N limitation, then P limitation, and eventually co-limitation as the two cycles resynchronize. However, our simulations indicate that the overall rate and extent of recovery is limited by P unless a mechanism exists either to prevent the P loss early in succession (e.g., P sequestration not stoichiometrically constrained by N) or to increase the P supply to the ecosystem later in succession (e.g., biologically enhanced weathering). Our model provides a heuristic perspective from which to assess the resynchronization among tightly cycled nutrients and the effect of that resynchronization on recovery of ecosystems from disturbance
Triazolium Salt Organocatalysis: Mechanistic Evaluation of Unusual Ortho-Substituent Effects on Deprotonation
Organocatalysis by N-heterocyclic carbenes is normally initiated by the deprotonation of precursor azolium ions to form active nucleophilic species. Substituent effects on deprotonation have an impact on catalytic efficiency and provide insight into general catalytic mechanisms by commonly used azolium systems. Using an NMR kinetic method for the analysis of C(3)-H/D exchange, we determined log kex–pD profiles for three ortho-substituted N-aryl triazolium salts, which enables a detailed analysis of ortho-substituent effects on deprotonation. This includes N-5-methoxypyrid-2-yl triazolium salt 7 and di-ortho-methoxy and di-ortho-isopropoxyphenyl triazolium salts 8 and 9, and we acquired additional kinetic data to supplement our previously published analysis of N-pyrid-2-yl triazolium salt 6. For 2-pyridyl triazoliums 6 and 7, novel acid catalysis of C(3)-H/D exchange is observed under acidic conditions. These kinetic data were supplemented by DFT analyses of the conformational preferences of 6 upon N-protonation. A C(3) deprotonation mechanism involving intramolecular general base deprotonation by the pyridyl nitrogen of the N(1)-deuterated dicationic triazolium salt is most consistent with the data. We also report kDO values (protofugalities) for deuteroxide-catalyzed exchange for 6–9. The protofugalities for 8 and 9 are the lowest values to date in the N-aryl triazolium series
Refractory topiramate-induced angle-closure glaucoma in a man: a case report
<p>Abstract</p> <p>Introduction</p> <p>Topiramate is a sulphonamide derivative indicated in the treatment of epilepsy and migraine. A known adverse affect is an idiosyncratic reaction that results in angle-closure glaucoma. We describe a patient with bilateral glaucoma related to topiramate that showed some unusual clinical features.</p> <p>Case presentation</p> <p>A 39-year-old Caucasian man presented with acute angle-closure glaucoma; he initially presented with intractable headaches after being treated with an escalating dose of topiramate. Clinical signs included elevated intraocular pressure that was initially refractory to treatment, shallow anterior chambers, and extensive bilateral choroidal effusions. After treatment with intravenous methylprednisolone, in conjunction with conventional glaucoma treatment, there was rapid reduction of intraocular pressure, gradual delayed resolution of the choroidal effusion and induced myopic shift; and eventually a good outcome without optic nerve damage.</p> <p>Conclusion</p> <p>This case illustrates the importance of recognizing this entity in a non-ophthalmic setting and that intravenous methylprednisolone may be useful in the treatment of the condition when it is not responsive to conventional treatment. In addition, it is important to recognize that complete resolution of visual symptoms from the myopic shift may be delayed, despite normalization of intraocular pressure.</p
Global Health and Disability: A Review and Call to Action for All Rehabilitation Professions
The World Health Organization estimates 15% of the world’s population is living with disability and anticipates an increase as the population ages. Disability is a growing healthcare concern and presents a tremendous burden to all nations. The world will soon need to provide health and rehabilitative care for an enormous number of persons with disability. The purpose of this article is to provide a brief narrative review pertaining to global health and rehabilitation, and to motivate the rehabilitation professions in taking immediate action through further investment in global health initiatives to manage both the current and projected burden of disability. A deficient level of research exists in global health by the rehabilitation professions and there is significant lag in their efforts when compared to other healthcare professions. The World Health Organization’s World Report on Disability (2011), Global Disability Action Plan 2014-2021, and the Global Burden of Disease study are pivotal bodies of work in this field. They serve as both a model and a challenge to affect large-scale global change among the rehabilitation professions. Collectively, an immediate effort is needed to bolster disability and rehabilitation research in developing nations, global rehabilitative outreach programs, and improve access to rehabilitative healthcare to persons with disability in order to fully address the magnitude of this matter
Selenium hyperaccumulation offers protection from cell disruptor herbivores
<p>Abstract</p> <p>Background</p> <p>Hyperaccumulation, the rare capacity of certain plant species to accumulate toxic trace elements to levels several orders of magnitude higher than other species growing on the same site, is thought to be an elemental defense mechanism against herbivores and pathogens. Previous research has shown that selenium (Se) hyperaccumulation protects plants from a variety of herbivores and pathogens. Selenium hyperaccumulating plants sequester Se in discrete locations in the leaf periphery, making them potentially more susceptible to some herbivore feeding modes than others. In this study we investigate the protective function of Se in the Se hyperaccumulators <it>Stanleya pinnata </it>and <it>Astragalus bisulcatus </it>against two cell disrupting herbivores, the western flower thrips (<it>Frankliniella occidentalis</it>) and the two-spotted spider mite (<it>Tetranychus urticae</it>).</p> <p>Results</p> <p><it>Astragalus bisulcatus </it>and <it>S. pinnata </it>with high Se concentrations (greater than 650 mg Se kg<sup>-1</sup>) were less subject to thrips herbivory than plants with low Se levels (less than 150 mg Se kg<sup>-1</sup>). Furthermore, in plants containing elevated Se levels, leaves with higher concentrations of Se suffered less herbivory than leaves with less Se. Spider mites also preferred to feed on low-Se <it>A. bisulcatus </it>and <it>S. pinnata </it>plants rather than high-Se plants. Spider mite populations on <it>A. bisulcatus </it>decreased after plants were given a higher concentration of Se. Interestingly, spider mites could colonize <it>A. bisulcatus </it>plants containing up to 200 mg Se kg<sup>-1 </sup>dry weight, concentrations which are toxic to many other herbivores. Selenium distribution and speciation studies using micro-focused X-ray fluorescence (μXRF) mapping and Se K-edge X-ray absorption spectroscopy revealed that the spider mites accumulated primarily methylselenocysteine, the relatively non-toxic form of Se that is also the predominant form of Se in hyperaccumulators.</p> <p>Conclusions</p> <p>This is the first reported study investigating the protective effect of hyperaccumulated Se against cell-disrupting herbivores. The finding that Se protected the two hyperaccumulator species from both cell disruptors lends further support to the elemental defense hypothesis and increases the number of herbivores and feeding modes against which Se has shown a protective effect. Because western flower thrips and two-spotted spider mites are widespread and economically important herbivores, the results from this study also have potential applications in agriculture or horticulture, and implications for the management of Se-rich crops.</p
Fabrication of high-entropy nitrides and carbonitrides
In high-entropy alloys, the use of multiple principle alloying elements is known to entropically stabilize the material. Refractory nitrides and carbides of transition metals are widely known for their ultra high-temperature stability and their high hardness, properties that make them valuable materials for extreme environments, such as coating the exterior of hypersonic flight vehicles and the interior of nuclear reactors. By creating entropy-stabilized complex solid solutions of nitrides and carbides, one can take advantage of the inherent favorable properties of these materials, as well as increased thermal stability and solid solution strengthening. Five-metal systems are chosen using first-principles calculations to describe the energetic distribution of possible atomic configurations, in order to identify systems that are likely to form an entropy-stabilized solid solution. Bulk samples of equiatomic, hexanery (5-metal), high-entropy refractory nitrides and carbonitrides were then fabricated to demonstrate this concept, by using a combination of high-energy ball milling, spark plasma sintering, and hot pressing. The uniformity of the microstructures is characterized, and single-phase solid solutions are achieved, thus demonstrating the ability to entropically stabilize multi-component random mixtures of refractory carbides and nitrides.
This work is supported by the U.S. Office of Naval Research MURI program (Grant No. N00014-15- 1-2863
Real-world outcomes of sipuleucel-T treatment in PROCEED, a prospective registry of men with metastatic castration-resistant prostate cancer.
BackgroundThe large registry, PROVENGE Registry for the Observation, Collection, and Evaluation of Experience Data (PROCEED)(NCT01306890), evaluated sipuleucel-T immunotherapy for asymptomatic/minimally symptomatic metastatic castration-resistant prostate cancer (mCRPC).MethodsPROCEED enrolled patients with mCRPC receiving 3 biweekly sipuleucel-T infusions. Assessments included overall survival (OS), serious adverse events (SAEs), cerebrovascular events (CVEs), and anticancer interventions (ACIs). Follow-up was for ≥3 years or until death or study withdrawal.ResultsIn 2011-2017, 1976 patients were followed for 46.6 months (median). The median age was 72 years, and the baseline median prostate-specific antigen level was 15.0 ng/mL; 86.7% were white, and 11.6% were African American. Among the patients, 1902 had 1 or more sipuleucel-T infusions. The median OS was 30.7 months (95% confidence interval [CI], 28.6-32.2 months). Known prognostic factors were independently associated with OS in a multivariable analysis. Among the 1255 patients who died, 964 (76.8%) died of prostate cancer (PC) progression. The median time from the first infusion to PC death was 42.7 months (95% CI, 39.4-46.2 months). The incidence of sipuleucel-T-related SAEs was 3.9%. The incidence of CVEs was 2.8%, and the rate per 100 person-years was 1.2 (95% CI, 0.9-1.6). The CVE incidence among 11,972 patients with mCRPC from the Surveillance, Epidemiology, and End Results-Medicare database was 2.8%; the rate per 100 person-years was 1.5 (95% CI, 1.4-1.7). One or more ACIs (abiraterone, enzalutamide, docetaxel, cabazitaxel, or radium 223) were received by 77.1% of the patients after sipuleucel-T; 32.5% and 17.4% of the patients experienced 1- and 2-year treatment-free intervals, respectively.ConclusionsPROCEED provides contemporary survival data for sipuleucel-T-treated men in a real-world setting of new life-prolonging agents, which will be useful in discussing treatment options with patients and in powering future trials with sipuleucel-T. The safety and tolerability of sipuleucel-T in PROCEED were consistent with previous findings
Referral pathways for TIA patients avoiding hospital admission : a scoping review
Objective: To identify the features and effects of a pathway for emergency assessment and referral of patients with suspected transient ischaemic attack (TIA) in order to avoid admission to hospital.Design: Scoping review.Data sources: PubMed, CINAHL Web of Science, Scopus.Study selection: Reports of primary research on referral of patients with suspected TIA directly to specialist outpatient services.Data extraction: We screened studies for eligibility and extracted data from relevant studies. Data were analysed to describe setting, assessment and referral processes, treatment, implementation and outcomes.Results: 8 international studies were identified, mostly cohort designs. 4 pathways were used by family doctors and 3 pathways by emergency department physicians. No pathways used by paramedics were found. Referrals were made to specialist clinic either directly or via a 24-hour helpline. Practitioners identified TIA symptoms and risk of further events using a checklist including the ABCD2 tool or clinical assessment. Antiplatelet medication was often given, usually aspirin unless contraindicated. Some patients underwent tests before referral and discharge. 5 studies reported reduced incident of stroke at 90 days, from 6–10% predicted rate to 1.3–2.1% actual rate. Between 44% and 83% of suspected TIA cases in these studies were referred through the pathways.Conclusions: Research literature has focused on assessment and referral by family doctors and ED physicians to reduce hospitalisation of patients with TIA. No pathways for paramedical use were reported. We will use results of this scoping review to inform development of a paramedical referral pathway to be tested in a feasibility trial
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