Mechanism for nonequilibrium symmetry breaking and pattern formation in magnetic films

Magnetic thin films exhibit a strong variation in properties depending on their degree of disorder. Recent coherent x-ray speckle experiments on magnetic films have measured the loss of correlation between configurations at opposite fields and at the same field, upon repeated field cycling. We perform finite temperature numerical simulations on these systems that provide a comprehensive explanation for the experimental results. The simulations demonstrate, in accordance with experiments, that the memory of configurations increases with film disorder. We find that non-trivial microscopic differences exist between the zero field spin configuration obtained by starting from a large positive field and the zero field configuration starting at a large negative field. This seemingly paradoxical beahvior is due to the nature of the vector spin dynamics and is also seen in the experiments. For low disorder, there is an instability which causes the spontaneous growth of line-like domains at a critical field, also in accord with experiments. It is this unstable growth, which is highly sensitive to thermal noise, that is responsible for the small correlation between patterns under repeated cycling. The domain patterns, hysteresis loops, and memory properties of our simulated systems match remarkably well with the real experimental systems.Comment: 12 pages, 10 figures Added comparison of results with cond-mat/0412461 and some more discussio

Protein mechanical unfolding: importance of non-native interactions

Mechanical unfolding of the fourth domain of Distyostelium discoideum filamin (DDFLN4) was studied by all-atom molecular dynamics simulations, using the GROMOS96 force field 43a1 and the simple point charge explicit water solvent. Our study reveals an important role of non-native interactions in the unfolding process. Namely, the existence of a peak centered at the end-to-end extension 22 nm in the force-extension curve, is associated with breaking of non-native hydrogen bonds. Such a peak has been observed in experiments but not in Go models, where non-native interactions are neglected. We predict that an additional peak occurs at 2 nm using not only GROMOS96 force field 43a1 but also Amber 94 and OPLS force fields. This result would stimulate further experimental studies on elastic properties of DDFLN4.Comment: 27 pages, 15 figure

Mixing of ultracold atomic clouds by merging of two magnetic traps

We demonstrate a method to make mixtures of ultracold atoms that does not make use of a two-species magneto-optical trap. We prepare two clouds of 87Rb atoms in distinct magnetic quadrupole traps and mix the two clouds by merging the traps. For correctly chosen parameters the mixing can be done essentially without loss of atoms and with only minor heating. The basic features of the process can be accounted for by a classical simulation of particle trajectories. Such calculations indicate that mixing of different mass species is also feasible, opening the way for using the method as a starting point for making quantum gas mixtures.Comment: 12 pages, 13 figures. Fig. 10 corrected. Fig. 13 updated with more points and better statistics. A couple of paragraphs rephrased and typos corrected. References update

Hysteresis multicycles in nanomagnet arrays

We predict two new physical effects in arrays of single-domain nanomagnets by performing simulations using a realistic model Hamiltonian and physical parameters. First, we find hysteretic multicycles for such nanomagnets. The simulation uses continuous spin dynamics through the Landau-Lifshitz-Gilbert (LLG) equation. In some regions of parameter space, the probability of finding a multicycle is as high as ~0.6. We find that systems with larger and more anisotropic nanomagnets tend to display more multicycles. This result demonstrates the importance of disorder and frustration for multicycle behavior. We also show that there is a fundamental difference between the more realistic vector LLG equation and scalar models of hysteresis, such as Ising models. In the latter case, spin and external field inversion symmetry is obeyed but in the former it is destroyed by the dynamics, with important experimental implications.Comment: 7 pages, 2 figure

Finite size effects on thermal denaturation of globular proteins

Finite size effects on the cooperative thermal denaturation of proteins are considered. A dimensionless measure of cooperativity, Omega, scales as N^zeta, where N is the number of amino acids. Surprisingly, we find that zeta is universal with zeta = 1 + gamma, where the exponent gamma characterizes the divergence of the susceptibility for a self-avoiding walk. Our lattice model simulations and experimental data are consistent with the theory. Our finding rationalizes the marginal stability of proteins and substantiates the earlier predictions that the efficient folding of two-state proteins requires the folding transition temperature to be close to the collapse temperature.Comment: 3 figures. Physical Review Letters (in press

Commissioning and co‐production in health and care services in the United Kingdom and Ireland: An exploratory literature review

© 2024 The Authors. Health Expectations published by John Wiley & Sons Ltd. This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY), https://creativecommons.org/licenses/by/4.0/Introduction: This exploratory literature review seeks to examine the literature around commissioning processes in the co‐production of health and care services, focusing on two questions: How do health and care commissioning processes facilitate and/or pose barriers to co‐production in service design and delivery? What are the contextual factors that influence these processes? Method: A systematic search of three databases (Medline, Public Health and Social Policy and Practice) and a search platform (Web of Science) was conducted for the period 2008–2023. A total of 2675 records were retrieved. After deduplication, 1925 were screened at title and abstract level. Forty‐seven reports from 42 United Kingdom and Ireland studies were included in the review. A thematic synthesis of included studies was conducted in relation to the research questions. Results: The review identified one overarching theme across the synthesised literature: the complexity of the commissioning landscape. Three interconnected subthemes illuminate the contextual factors that influence this landscape: commissioners as leaders of co‐production; navigating relationships and the collective voice. Conclusion: Commissioning processes were commonly a barrier to the co‐production of health and care services. Though co‐production was an aspiration for many commissioners, the political and economic environment and service pressures meant that it was often not fully realised. More flexible funding models, longer‐term pilot projects, an increased emphasis in social value across the health and care system and building capacity for strong leadership in commissioning is needed. Patient and Public Contribution: Patients and the public did not contribute to this review as it was a small piece of work following on from a completed project, with no budget for public involvement.Peer reviewe

Design, simulation, and characterization of a radial opposed migration ion and aerosol classifier (ROMIAC)

We present the design, simulation, and characterization of the radial opposed migration ion and aerosol classifier (ROMIAC), a compact differential electrical mobility classifier. We evaluate the performance of the ROMIAC using a combination of finite element modeling and experimental validation of two nearly identical instruments using tetra-alkyl ammonium halide mass standards and sodium chloride particles. Mobility and efficiency calibrations were performed over a wide range of particle diameters and flow rates to characterize ROMIAC performance under the range of anticipated operating conditions. The ROMIAC performs as designed, though performance deviates from that predicted using simplistic models of the instrument. The underlying causes of this non-ideal behavior are found through finite element simulations that predict the performance of the ROMIAC with greater accuracy than the simplistic models. It is concluded that analytical performance models based on idealized geometries, flows, and fields should not be relied on to make accurate a priori predictions about instrumental behavior if the actual geometry or fields deviate from the ideal assumptions. However, if such deviations are accurately captured, finite element simulations have the potential to predict instrumental performance. The present prototype of the ROMIAC maintains its resolution over nearly three orders of magnitude in particle mobility, obtaining sub-20 nm particle size distributions in a compact package with relatively low flow rate operation requirements

Validasi Metode Analisis Multiresidu Pestisida Organoklor dalam Salak Menggunakan Kromatografi Gas-Detektor Penangkap Elektron

Validation of methods is a key step in the accreditation process of the method. Validation of organoklor pesticide residues method in snakefruit based on the method recommended by FAO-WHO, conducted in LPPT-UGM reported in this study. Snake fruit was homogenized, extracted using toluene/2-propanol (2:1), cleaned up using activated carbon and Celite 545, followed by analysis using gas chromatography-electron capture detector. Validation covered specificity and selectivity, limits of detection and quantification, linear range, precision and accuracy. Validation results showed good specificity and selectivity shown by the inter-peak chromatogram resolution greater than 1.5. Limits of detection and quantification for heptaklor, endosulfan, dieldrin and p, p-DDT were 0.002 and 0.006, 0.5 and 1.7; 0.0006 and 0.002, as well as 0.014 and 0.047 ppm respectively. The linear range for heptaklor, endosulfan, dieldrin, and p,p-DDT were 0.0017 to 2 ppm, 0.165 to 2 ppm, 0.023 to 2 ppm and 0.229 to 2 ppm, respectively. Precision methods meet the acceptance of Horwitz RSD value less than 12.78% at a concentration of 0.3 ppm. Accuracy is indicated by recovery, for each pesticide in the range of 80-110% acceptance at a concentration of 0.1 ppm. Analysis of organochlorine pesticides in three commercial snakefruit samples showed no pesticide residues at concentrations higher than the detection limit.ASBTRAKValidasi metode merupakan tahap kunci dalam proses akreditasi suatu metode. Validasi metode uji residu pestisida organoklor dalam salak berdasarkan metode yang direkomendasikan FAO-WHO, di LPPT-UGM dilaporkan pada penelitian ini. Buah salak dihomogenisasi, diekstraksi menggunakan toluen/2-propanol (2:1), clean up menggunakan karbon aktif dan Celite 545, dilanjutkan analisis menggunakan kromatografi gas-detektor penangkap elektron. Validasi mencakup spesifisitas dan selektivitas, batas deteksi dan kuantifikasi, range linier, presisi serta akurasi. Hasil validasi menunjukkan spesifisitas dan selektivitas yang baik ditunjukkan dengan resolusi antar puncak kromatogram lebih besar dari 1,5. Batas deteksi dan batas kuantifikasi untuk heptaklor, endosulfan, dieldrin dan p,p-DDT secara berturut-turut adalah 0,002 dan 0,006; 0,5 dan 1,7; 0,0006 dan 0,002; serta 0,014 dan 0,047 ppm. Range linier untuk heptaklor adalah 0,0017-2 ppm, endosulfan 0,165-2 ppm, dieldrin 0,023-2 ppm dan p,p-DDT 0,229-2 ppm. Presisi metode memenuhi batas keberterimaan Horwitz dengan nilai RSD lebih kecil dari 12,78% pada konsentrasi 0,3 ppm. Akurasi ditunjukkan dengan recovery, untuk tiap pestisida masuk dalam rentang keberterimaan 80-110% pada konsentrasi 0,1 ppm. Analisis pestisida organoklorin pada 3 sampel salak komersial menunjukkan tidak adanya residu pestisida dengan konsentrasi lebih tinggi dari batas deteksi