Reentrant Adhesion Behavior in Nanocluster Deposition

We simulate the collision of atomic clusters with a weakly attractive surface using molecular dynamics in a regime between soft-landing and fragmentation, where the cluster undergoes large deformation but remains intact. As a function of incident kinetic energy, we find a transition from adhesion to reflection at low kinetic energies. We also identify a second adhesive regime at intermediate kinetic energies, where strong deformation of the cluster leads to an increase in contact area and adhesive energy.Comment: 7 pages, 6 figure

Natural and anthropogenic lead in sediments of the Rotorua lakes, New Zealand

Global atmospheric sources of lead have increased more than 100-fold over the past century as a result of deforestation, coal combustion, ore smelting and leaded petroleum. Lead compounds generally accumulate in depositional areas across the globe where, due to low solubility and relative freedom from microbial degradation, the history of their inputs is preserved. In lakes there is rapid deposition and often little bioturbation of lead, resulting in an excellent depositional history of changes in both natural and anthropogenic sources. The objective of this study was to use sediments from a regionally bounded set of lakes to provide an indication of the rates of environmental inputs of lead whilst taking into account differences of trophic state and lead exposure between lakes. Intact sediment gravity cores were collected from 13 Rotorua lakes in North Island of New Zealand between March 2006 and January 2007. Cores penetrated sediments to a depth of 16–30 cm and contained volcanic tephra from the 1886 AD Tarawera eruption. The upper depth of the Tarawera tephra enabled prescription of a date for the associated depth in the core (120 years). Each core showed a sub-surface peak in lead concentration above the Tarawera tephra which was contemporaneous with the peak use of lead alkyl as a petroleum additive in New Zealand. An 8 m piston core was taken in the largest of the lakes, Lake Rotorua, in March 2007. The lake is antipodal to the pre-industrial sources of atmospheric lead but still shows increasing lead concentrations from <2 up to 3.5 μg g−1 between the Whakatane eruption (5530 ± 60 cal. yr BP) and the Tarawera eruption. Peaks in lead concentration in Lake Rotorua are associated with volcanic tephras, but are small compared with those arising from recent anthropogenic-derived lead deposition. Our results show that diagenetic processes associated with iron, manganese and sulfate oxidation-reduction, and sulfide precipitation, act to smooth distributions of lead from anthropogenic sources in the lake sediments. The extent of this smoothing can be related to changes in sulfate availability and reduction in sulfide driven by differences in trophic status amongst the lakes. Greatest lead mobilisation occurs in mesotrophic lakes during seasonal anoxia as iron and manganese are released to the porewater, allowing upward migration of lead towards the sediment–water interface. This lead mobilisation can only occur if sulfides are not present. The sub-surface peak in lead concentrations in lake sediments ascribed to lead alkyl in petroleum persists despite the diagenetic processes acting to disperse lead within the sediments and into the overlying water

Molecular dynamics simulations of reflection and adhesion behavior in Lennard-Jones cluster deposition

We conduct molecular dynamics simulations of the collision of atomic clusters with a weakly-attractive surface. We focus on an intermediate regime, between soft-landing and fragmentation, where the cluster undergoes deformation on impact but remains largely intact, and will either adhere to the surface (and possibly slide), or be reflected. We find that the outcome of the collision is determined by the Weber number, We i.e. the ratio of the kinetic energy to the adhesion energy, with a transition between adhesion and reflection occurring as We passes through unity. We also identify two distinct collision regimes: in one regime the collision is largely elastic and deformation of the cluster is relatively small but in the second regime the deformation is large and the adhesion energy starts to depend on the kinetic energy. If the transition between these two regimes occurs at a similar kinetic energy to that of the transition between reflection and adhesion, then we find that the probability of adhesion for a cluster can be bimodal. In addition we investigate the effects of the angle of incidence on adhesion and reflection. Finally we compare our findings both with recent experimental results and with macroscopic theories of particle collisions.Comment: 18 pages, 13 figure

Tropical Forest Protection, Uncertainty, and the Environmental Integrity of Carbon Mitigation Policies

Tropical forests are estimated to release approximately 1.7 PgC per year as a result of deforestation. Avoiding tropical deforestation could potentially play a significant role in carbon mitigation over the next 50 years if not longer. Many policymakers and negotiators are skeptical of our ability to reduce deforestation effectively. They fear that if credits for avoided deforestation are allowed to replace fossil fuel emission reductions for compliance with Kyoto, the environment will suffer because the credits will not reflect truly additional carbon storage. This paper considers the nature of the uncertainties involved in estimating carbon stocks and predicting deforestation. We build an empirically based stochastic model that combines data from field ecology, geographical information system (GIS) data from satellite imagery, economic analysis and ecological process modeling to simulate the effects of these uncertainties on the environmental integrity of credits for avoided deforestation. We find that land use change, and hence additionality of carbon, is extremely hard to predict accurately and errors in the numbers of credits given for avoiding deforestation are likely to be very large. We also find that errors in estimation of carbon storage could be large and could have significant impacts. We find that in Costa Rica, nearly 42% of all the loss of environmental integrity that would arise from poor carbon estimates arises in one life zone, tropical wet. This suggests that research effort might be focused in this life zone.climate, economics, carbon sequestration, uncertainty, policy, tropics

Historical and contemporary perspectives on the sediments of Lake Rotorua

Lake Rotorua is probably the oldest continuously inundated lake in New Zealand, occupying a caldera formed by or closely associated with the eruption of the Mamaku ignimbrite and the collapse of the Rotorua caldera (Healy, 1975; Lowe and Green, 1991). The lake has undergone drastic changes in size and depth as a result of tectonics, volcanic activity and erosion. Since the Rotoehu eruption, (~60 kyr), the lake level has fluctuated between 120 m above present (280 m asl) and 10 m below present level. The modern lake covers an area of 79 km2 and has a mean depth of 10 m. Despite its long history of sedimentation, Lake Rotorua has an irregular bathymetry with features including faulted blocks, slumps, hydrothermal explosion craters, springs and large methane discharge pock marks

The application, character, and effectiveness of person-centred care with service-users, and the community within the discipline of podiatry: a scoping review.

BACKGROUND: The concept of person-centred care is embedded within healthcare policy, focusing on long-term conditions and multimorbidity. The evidence that person-centred care is being operationalised effectively across all areas of healthcare is limited. The aim of this scoping review was to explore the application, features, and effectiveness of person-centred care with service-users, carers, and the community within podiatry. METHODS: The scoping review was based upon Arksey and Malley's five stage framework. The following databases were searched between January 2010 and March 2021: AMED, CINAHL, Embase, Cochrane library, SocINDEX, British Education Index, Business Source Complete, MEDLINE (EBSCO), and the EThOS 'Global electronic thesis and dissertation' repository, Prospero, and reference lists of included papers. Primary research articles were included if they reported on a person-centred care focused intervention with podiatry. Research terms were developed, appropriate databases identified, and an initial search resulted in 622 papers which, following removal of duplicates and critical appraisal, resulted in 18 eligible papers. Data extracted involved the types of person-centred care utilised, intervention details, motivations for engaging in person-centred care interventions, and intervention barriers and challenges. RESULTS: Eighteen articles were included in the review. The main type of person-centred care utilised was patient/carer activities around self-management. None of the studies considered the role of the podiatrist as a person-centred care agent. The data on interventions generated the following themes 'service facilitated person-centred care' where a change has been made to service delivery, 'direct clinician delivery' where the intervention is delivered by the clinician with the patient present and 'patient instigated participation' where patient motivation is required to engage with an activity beyond the consultation. Outcome measures associated with quality of care and effectiveness were absent. CONCLUSION: There is a lack of congruency between the concept of person-centred care and how it is operationalised. A whole system approach that considers commissioning, organisational leadership, the role of the practitioners and patients has not been considered. There is immense scope for the podiatrist to play an important part in the personalised-care agenda, but currently research that can evidence the effectiveness of person-centred care in podiatry is absent. REVIEW REGISTRATION: Open Science Framework ( osf.io/egjsd )

Penentuan Jumlah Bus Yang Optimal Dengan Menggunakan Metode Goal Programming (Studi Kasus Di Trayek B 35 Jurusan Terboyo - Cangkiran Semarang)

Transportasi adalah sarana pendukung utama bagi kegiatan di suatu kota. Dengan sarana transportasi yang baik maka kegiatan akan dapat berjalan dengan lancar. Masalah yang sering dihadapi dalam transportasi adalah terjadinya ketidakseimbangan antara permintaan dan ketersediaan alat transportasi. Dinas perhubungan kota Semarang adalah instansi pemerintah yang bertugas mengatur masalah transportasi di kota Semarang. Meskipun jumlah trayek di kota Semarang saat ini telah dibatasi namun terlihat bahwa jumlah bus yang ada saat ini terlalu banyak atau tidak seimbang dengan kebutuhan. Dalam penulisan ini akan dibahas masalah penentuan jumlah bus yang optimal agar terjadi keseimbangan antara permintaan dan jumlah bus yang disediakan sehingga penumpang dapat terlayani dengan baik dan biaya operasional bus dapat lebih efisien. Trayek yang diteliti adalah trayek Terboyo Cangkiran di kota Semarang. Penelitian ini mencoba menggunakan model Goal Programming yang sebelumnya sangat jarang digunakan dalam penentuan jumlah bus. Kelebihan dari model Goal Programming adalah dapat menghitung dengan berbagai tujuan sekaligus. Di dalam masalah transportasi banyak pihak yang terlibat seperti pengusaha bus yang menginginkan keuntungan yang maksimal dan juga penumpang yang menginginkan tranportasi yang nyaman dan murah. Kepentingan yang bertentangan itu perlu dicari titik keseimbangannya karena jumlah bus yang terlalu banyak akan merugikan pengusaha dan bila terlalu sedikit akan merugikan konsumen. Dari hasil penelitian dan perhitungan diperolah bahwa untuk trayek Terboyo Cangkiran jumlah bus yang optimal adalah 16 bus atau lebih sedikit dari yang ada saat ini yaitu 25 bus. Oleh karena itu diharapkan dinas perhubungan dapat mengkaji ulang masalah ini dengan mengurangi jumlah bus yang ada dan memindahkannya ke trayek yang masih membutuhkan. Sehingga transportasi di kota Semarang khususnya trayek Terboyo Cangkiran dapat berjalan dengan lancar

Rigidly Rotating Strings in Stationary Spacetimes

In this paper we study the motion of a rigidly rotating Nambu-Goto test string in a stationary axisymmetric background spacetime. As special examples we consider the rigid rotation of strings in flat spacetime, where explicit analytic solutions can be obtained, and in the Kerr spacetime where we find an interesting new family of test string solutions. We present a detailed classification of these solutions in the Kerr background.Comment: 19 pages, Latex, 9 figures, revised for publication in Classical and Quantum Gravit