1,413 research outputs found
Voltage and current spectra for matrix power converters
Matrix power converters are used for transforming one alternating-current power supply to another, with different peak voltage and frequency. There are three input lines, with sinusoidally varying voltages which are 120⊠out of phase one from another, and the output is to be delivered as a similar three-phase supply. The matrix converter switches rapidly, to connect each output line in sequence to each of the input lines in an attempt to synthesize the prescribed output voltages. The switching is carried out at high frequency and it is of practical importance to know
the frequency spectra of the output voltages and of the input and output currents. We determine in this paper these spectra using a new method, which has significant advantages over the prior default method (a multiple Fourier series technique), leading to a considerably more direct calculation. In particular, the determination of the input current spectrum is feasible here, whereas it would be a significantly more daunting procedure using the prior method instead
Impact of Oxidation State on Reactivity and Selectivity Differences between Nickel(III) and Nickel(IV) Alkyl Complexes
Described is a systematic comparison of factors impacting the relative rates and selectivities of C(sp3)âC and C(sp3)âO bondâforming reactions at highâvalent Ni as a function of oxidation state. Two Ni complexes are compared: a cationic octahedral NiIV complex ligated by tris(pyrazolyl)borate and a cationic octahedral NiIII complex ligated by tris(pyrazolyl)methane. Key features of reactivity/selectivity are revealed: 1)â
C(sp3)âC(sp2) bondâforming reductive elimination occurs from both centers, but the NiIII complex reacts up to 300âfold faster than the NiIV, depending on the reaction conditions. The relative reactivity is proposed to derive from ligand dissociation kinetics, which vary as a function of oxidation state and the presence/absence of visible light. 2)â
Upon the addition of acetate (AcOâ), the NiIV complex exclusively undergoes C(sp3)âOAc bond formation, while the NiIII analogue forms the C(sp3)âC(sp2) coupled product selectively. This difference is rationalized based on the electrophilicity of the respective MâC(sp3) bonds, and thus their relative reactivity towards outerâsphere SN2âtype bondâforming reactions.The high point: This report describes a systematic comparison of factors impacting the relative rates and selectivities of C(sp3)âC and C(sp3)âO bondâforming reactions at highâvalent Ni centers as a function of oxidation state (NiIII versus NiIV). Two Ni complexes are compared: a cationic octahedral NiIV complex ligated by tris(pyrazolyl)borate and a cationic octahedral NiIII complex ligated by tris(pyrazolyl)methane.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/150547/1/anie201903638.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/150547/2/anie201903638-sup-0001-misc_information.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/150547/3/anie201903638_am.pd
428 REGIONAL KNEE CARTILAGE THICKNESS ANALYSIS IN OSTEOARTHRITIS â A MULTIVENDOR MR SCANNER COMPARISON STUDY AT 3.0T
Establishing the baseline in groundwater chemistry in connection with shale-gas exploration: Vale of Pickering, UK
The baseline chemistry of groundwater from two aquifers in the Vale of Pickering, North Yorkshire, has been investigated ahead of a proposal to explore for shale gas, planning permission for which has recently been granted. Groundwater in a shallow aquifer including Quaternary and/or Jurassic Kimmeridge Clay deposits shows compositions distinct from a Corallian (Jurassic) Limestone aquifer, reflecting different lithologies and hydrogeological conditions. Corallian groundwaters along the margins of the vale are controlled by reaction with carbonate, with redox conditions varying according to degree of aquifer confinement. Superficial aquifer groundwaters are confined and strongly reducing, with some observed high concentrations of dissolved CH4 (up to 37 mg/L; Feb 2016 data). This appears to be of mixed biogenic-thermogenic origin but further work is needed to determine whether the source includes a deeper hydrocarbon reservoir contributing via fractures, or a shallower source in the Quaternary or Kimmeridge sediments. The data show a shallow aquifer with a high-CH4 baseline which pre-dates any shale-gas activity
Community Health Evaluation in Normanton
The Community Health research project was based in the Normanton Neighbourhood Renewal area of Derby. It involved five key parties; the Derby City Partnership, Derby City Primary Care Trust, the Derby City Council Environmental Health and Trading Standards Department, the Centre for
Community Regeneration and the International Centre for Guidance Studies (iCeGS) at the University of Derby. The research activities were led by the iCeGS.
The project had two main objectives. The first was to map health-related service provision in the Normanton area, and then secondly, to ascertain the reach and impact of that provision. An important sub-component of the evaluation element was to enhance community capacity by recruiting and
training a group of community evaluators in research and evaluation techniques to become competent community evaluators
Effective action in DSR1 quantum field theory
We present the one-loop effective action of a quantum scalar field with DSR1
space-time symmetry as a sum over field modes. The effective action has real
and imaginary parts and manifest charge conjugation asymmetry, which provides
an alternative theoretical setting to the study of the particle-antiparticle
asymmetry in nature.Comment: 8 page
Can we use medical examiners' records for suicide surveillance and prevention research in Nova Scotia?
Introduction: Medical examiners' records can contribute to our understanding of the extent of suicide in a population, as well as associated sociodemographic and other factors
The efficacy of a lateral wedge insole for painful medial knee osteoarthritis after prescreening : a randomized clinical trial
OBJECTIVE:
Lateral wedge shoe insoles decrease medial knee loading, but trials have shown no effect on pain in medial knee osteoarthritis (OA). However, insoles' loading effects are inconsistent, and they can increase patellofemoral loading. We hypothesized that insoles would reduce pain in preselected patients.
METHODS:
In persons with painful medial knee OA, we excluded those with patellofemoral OA and those with pain <4/10. We further excluded participants who, in a gait laboratory using lateral wedges, did not show at least a 2% reduction in knee adduction moment (KAM) compared with their shoes and a neutral insole. We then randomized subjects to lateral wedge vs. neutral insole for 8 week periods separated by an 8 week washout. Primary outcome was knee pain over the past week (0-10) and secondary outcomes nominated activity pain and KOOS pain. We carried out mixed model analyses adjusted for baseline pain.
RESULTS:
Of 83 participants, 21 (25%) were excluded because of insufficient reduction in KAM. Of 62 included, mean age was 64.2 years (SD 9.1); 37.1% were women. Lateral wedge insoles produced a greater reduction in knee pain than neutral insoles (difference 0.7 on 0-10 scale; 95%CI 0.1, 1.2; p = 0.02). Secondary outcomes showed mixed findings.
CONCLUSIONS:
In persons prescreened to eliminate those with patellofemoral OA and biomechanical non-responders, lateral wedge insoles reduced knee pain, but the effect of treatment was small and is likely of clinical significance in only a minority of patients. Targeting patients may identify those who respond to this treatment
The impact of COVID-19 on the cancer care of adolescents and young adults and their well-being:Results from an online survey conducted in the early stages of the pandemic
Background
Because of the global spread of coronavirus disease 2019 (COVIDâ19), oncology departments across the world have rapidly adapted their cancer care protocols to balance the risk of delaying cancer treatments and the risk of COVIDâ19 exposure. COVIDâ19 and associated changes may have an impact on the psychosocial functioning of patients with cancer and survivors. This study was designed to determine the impact of the COVIDâ19 pandemic on young people living with and beyond cancer.
Methods
In this crossâsectional study, 177 individuals, aged 18 to 39 years, were surveyed about the impact of COVIDâ19 on their cancer care and psychological wellâbeing. Participants also reported their information needs with respect to COVIDâ19. Responses were summarized with a content analysis approach.
Results
This was the first study to examine the psychological functioning of young patients and survivors during the first weeks of the COVIDâ19 pandemic. A third of the respondents reported increased levels of psychological distress, and as many as 60% reported feeling more anxious than they did before COVIDâ19. More than half also wanted more information tailored to them as young patients with cancer.
Conclusions
The COVIDâ19 pandemic is rapidly evolving and changing the landscape of cancer care. Young people living with cancer are a unique population and might be more vulnerable during this time in comparison with their healthy peers. There is a need to screen for psychological distress and attend to young people whose cancer care has been delayed. As the lockdown begins to ease, the guidelines about cancer care should be updated according to this population's needs.</p
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