20 results on '"Fischer, Mark"'
Search Results
2. What Is the Weight of a Single Amoeba and Why Does It Matter?
- Author
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Money, Nicholas P. and Fischer, Mark W. F.
- Abstract
Cell size is an important variable in the study of cellular growth, metabolism, and the cell cycle. The large size of "Amoeba proteus" and the ease with which it can be collected and cultured have made it a star in biology education--and it was a model for research on cell biology before the introduction of molecular genetic methods. Measuring the cytoplasmic density of a single amoeba without modern instrumentation seems like a difficult task, but this was done with supreme accuracy in the 1940s. The solution was based on the familiar Cartesian diver that is used to demonstrate Archimedes's principle. It required the fabrication of a tiny diver that would respond to the additional mass of a cell. Experiments using this method allowed investigators to study changes in size and density associated with feeding, starvation, and cell division. This research is an illustration of the ingenuity of cell biologists in the pre-molecular genetic era of their field, which is often overlooked by contemporary scientists. The consideration of the mass, density, and buoyancy of free-living amoebas encourages a new hypothesis about the evolution of testate amoebas.
- Published
- 2021
- Full Text
- View/download PDF
3. Switchable chiral transport in charge-ordered kagome metal CsV3Sb5
- Author
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Guo, Chunyu, Putzke, Carsten, Konyzheva, Sofia, Huang, Xiangwei, Gutierrez-Amigo, Martin, Errea, Ion, Chen, Dong, Vergniory, Maia G., Felser, Claudia, Fischer, Mark H., Neupert, Titus, and Moll, Philip J. W.
- Published
- 2022
- Full Text
- View/download PDF
4. Trial of ultrasound guided carpal tunnel release versus traditional open release (TUTOR)
- Author
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Eberlin, Kyle R., Dy, Christopher J., Fischer, Mark D., Gluck, James L., Kaplan, F. Thomas D., McDonald, Thomas J., Miller, Larry E., Palmer, Alexander, Walker, Marc E., and Watt, James F.
- Published
- 2022
- Full Text
- View/download PDF
5. Exceptional topological insulators
- Author
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Denner, M. Michael, Skurativska, Anastasiia, Schindler, Frank, Fischer, Mark H., Thomale, Ronny, Bzdušek, Tomáš, and Neupert, Titus
- Published
- 2021
- Full Text
- View/download PDF
6. Magnetotransport of dirty-limit van Hove singularity quasiparticles
- Author
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Xu, Yang, Herman, František, Granata, Veronica, Destraz, Daniel, Das, Lakshmi, Vonka, Jakub, Gerber, Simon, Spring, Jonathan, Gibert, Marta, Schilling, Andreas, Zhang, Xiaofu, Li, Shiyan, Fittipaldi, Rosalba, Fischer, Mark H., Vecchione, Antonio, and Chang, Johan
- Published
- 2021
- Full Text
- View/download PDF
7. Distinct switching of chiral transport in the kagome metals KV3Sb5 and CsV3Sb5.
- Author
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Guo, Chunyu, van Delft, Maarten R., Gutierrez-Amigo, Martin, Chen, Dong, Putzke, Carsten, Wagner, Glenn, Fischer, Mark H., Neupert, Titus, Errea, Ion, Vergniory, Maia G., Wiedmann, Steffen, Felser, Claudia, and Moll, Philip J. W.
- Subjects
ELECTRONIC structure ,METALS ,ELECTRONIC evidence ,ALKALI metals ,SUPERCONDUCTIVITY ,CHIRALITY - Abstract
The kagome metals AV
3 Sb5 (A = K, Rb, Cs) present an ideal sandbox to study the interrelation between multiple coexisting correlated phases such as charge order and superconductivity. So far, no consensus on the microscopic nature of these states has been reached as the proposals struggle to explain all their exotic physical properties. Among these, field-switchable electric magneto-chiral anisotropy (eMChA) in CsV3 Sb5 provides intriguing evidence for a rewindable electronic chirality, yet the other family members have not been likewise investigated. Here, we present a comparative study of magneto-chiral transport between CsV3 Sb5 and KV3 Sb5 . Despite their similar electronic structure, KV3 Sb5 displays negligible eMChA, if any, and with no field switchability. This is in stark contrast to the non-saturating eMChA in CsV3 Sb5 even in high fields up to 35 T. In light of their similar band structures, the stark difference in eMChA suggests its origin in the correlated states. Clearly, the V kagome nets alone are not sufficient to describe the physics and the interactions with their environment are crucial in determining the nature of their low-temperature state. [ABSTRACT FROM AUTHOR]- Published
- 2024
- Full Text
- View/download PDF
8. Distinct switching of chiral transport in the kagome metals KV$_3$Sb$_5$ and CsV$_3$Sb$_5$
- Author
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Guo, Chunyu, van Delft, Maarten R., Gutierrez-Amigo, Martin, Chen, Dong, Putzke, Carsten, Wagner, Glenn, Fischer, Mark H., Neupert, Titus, Errea, Ion, Vergniory, Maia G., Wiedmann, Steffen, Felser, Claudia, and Moll, Philip J. W.
- Subjects
Condensed Matter - Strongly Correlated Electrons ,Condensed Matter - Materials Science ,Strongly Correlated Electrons (cond-mat.str-el) ,Materials Science (cond-mat.mtrl-sci) ,FOS: Physical sciences - Abstract
The kagome metals AV$_3$Sb$_5$ (A=K,Rb,Cs) present an ideal sandbox to study the interrelation between multiple coexisting correlated phases such as charge order and superconductivity. So far, no consensus on the microscopic nature of these states has been reached as the proposals struggle to explain all their exotic physical properties. Among these, field-switchable electric magneto-chiral anisotropy (eMChA) in CsV$_3$Sb$_5$ provides intriguing evidence for a rewindable electronic chirality, yet the other family members have not been likewise investigated. Here, we present a comparative study of magneto-chiral transport between CsV$_3$Sb$_5$ and KV$_3$Sb$_5$. Despite their similar electronic structure, KV$_3$Sb$_5$ displays negligible eMChA, if any, and with no field switchability. This is in stark contrast to the non-saturating eMChA in CsV$_3$Sb$_5$ even in high fields up to 35 T. In light of their similar band structures, the stark difference in eMChA suggests its origin in the correlated states. Clearly, the V kagome nets alone are not sufficient to describe the physics and the interactions with their environment are crucial in determining the nature of their low-temperature state.
- Published
- 2023
9. A mechanism for $\pi$ phase shifts in Little-Parks experiments: application to 2H-TaS$_2$ intercalated with chiral molecules and to 4Hb-TaS$_2$
- Author
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Fischer, Mark H., Lee, Patrick A., and Ruhman, Jonathan
- Subjects
Condensed Matter - Superconductivity - Abstract
Recently, unusual $\pi$ phase shifts in Little-Parks experiments performed on two systems derived from the layered superconductor 2H-TaS$_2$ were reported. These systems share the common feature that additional layers have been inserted between the 1H-TaS$_2$ layers. In both cases, the $\pi$ phase shift has been interpreted as evidence for the emergence of exotic superconductivity in the 1H layers. Here, we propose an alternative explanation assuming that superconductivity in the individual 1H layers is of conventional $s$-wave nature derived from the parent 2H-TaS$_2$. We show that a negative Josephson coupling between neighboring 1H layers can explain the observations. Furthermore, we find that the negative coupling arises naturally due to the well understood spin-momentum locking of Ising type in a single 1H layer together with the inversion symmetry of the double layer. By paying attention to the overall inversion symmetry in the material, we can also explain the absence of a $\pi$ phase shift in the control sample when achiral molecules are intercalated. In the exotic superconductivity scenario, it is challenging to explain why the critical temperature is almost the same as in the parent material and, in the 4Hb case, the superconductivity's robustness to disorder. Both are non-issues in our picture, which further pinpoints the common origin of the effect and exposes the common features that are special in these two systems., Comment: Update on the mechanism for negative Josephson coupling. In particular, we emphasize the importance of time-reversal-symmetry breaking in the tunneling Hamiltonian
- Published
- 2023
10. Multicenter randomized trial of carpal tunnel release with ultrasound guidance versus mini-open technique.
- Author
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Eberlin, Kyle R., Amis, Benjamin P., Berkbigler, Thomas P., Dy, Christopher J., Fischer, Mark D., Gluck, James L., Kaplan, F. Thomas D., McDonald, Thomas J., Miller, Larry E., Palmer, Alexander, Perry, Paul E., Walker, Marc E., and Watt, James F.
- Subjects
ULTRASONIC imaging ,SURGEONS ,CARPAL tunnel syndrome - Abstract
Comparative studies of carpal tunnel release with ultrasound guidance (CTR-US) vs. mini-open CTR (mOCTR) are limited, prompting development of this randomized trial to compare efficacy and safety of these techniques. Patients were randomized (2:1) to CTR-US or mOCTR, treated by experienced hand surgeons (median previous cases: 12 CTR-US; 1000 mOCTR), and followed for 3 months. Among 149 randomized patients, 122 received CTR-US (n = 94) or mOCTR (n = 28). Mean incision length was 6 ± 2 mm in the wrist (CTR-US) vs. 22 ± 7 mm in the palm (mOCTR) (p < 0.001). Median time to return to daily activities (2 vs. 2 days; p = 0.81) and work (3 vs. 4 days; p = 0.61) were similar. Both groups reported statistically significant and clinically important improvements in Boston Carpal Tunnel Questionnaire Symptom Severity and Functional Status Scales, Numeric Pain Scale, and EuroQoL-5 Dimension 5-Level, with no statistical differences between groups. Freedom from wound sensitivity and pain favored CTR-US (61.1% vs. 17.9%; p < 0.001). Adverse event rates were low in each group (2.1% vs. 3.6%; p = 0.55). The efficacy and safety of CTR-US were comparable to mOCTR despite less previous surgical experience with CTR-US. The choice of CTR technique should be determined by shared decision-making between patient and physician. identifier is NCT05405218. [ABSTRACT FROM AUTHOR]
- Published
- 2023
- Full Text
- View/download PDF
11. Interacting topological quantum chemistry of Mott atomic limits
- Author
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Soldini, Martina O., Astrakhantsev, Nikita, Iraola, Mikel, Tiwari, Apoorv, Fischer, Mark H., Valentí, Roser, Vergniory, Maia G., Wagner, Glenn, and Neupert, Titus
- Subjects
Condensed Matter - Strongly Correlated Electrons ,Strongly Correlated Electrons (cond-mat.str-el) ,FOS: Physical sciences - Abstract
Topological quantum chemistry (TQC) is a successful framework for identifying (noninteracting) topological materials. Based on the symmetry eigenvalues of Bloch eigenstates at maximal momenta, which are attainable from first principles calculations, a band structure can either be classified as an atomic limit, in other words adiabatically connected to independent electronic orbitals on the respective crystal lattice, or it is topological. For interacting systems, there is no single-particle band structure and hence, the TQC machinery grinds to a halt. We develop a framework analogous to TQC, but employing $n$-particle Green's function to classify interacting systems. Fundamentally, we define a class of interacting reference states that generalize the notion of atomic limits, which we call Mott atomic limits, and are symmetry protected topological states. Our formalism allows to fully classify these reference states (with $n=2$), which can themselves represent symmetry protected topological states. We present a comprehensive classification of such states in one-dimension and provide numerical results on model systems. With this, we establish Mott atomic limit states as a generalization of the atomic limits to interacting systems.
- Published
- 2022
12. Simulating a ring-like Hubbard system with a quantum computer
- Author
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Suchsland, Philippe, Barkoutsos, Panagiotis Kl., Tavernelli, Ivano, Fischer, Mark H., Neupert, Titus, and University of Zurich
- Subjects
Quantum Physics ,Condensed Matter - Strongly Correlated Electrons ,Strongly Correlated Electrons (cond-mat.str-el) ,530 Physics ,11476 Digital Society Initiative ,General Earth and Planetary Sciences ,FOS: Physical sciences ,10192 Physics Institute ,Computational Physics (physics.comp-ph) ,Quantum Physics (quant-ph) ,Physics - Computational Physics ,3100 General Physics and Astronomy ,General Environmental Science - Abstract
We develop a workflow to use current quantum computing hardware for solving quantum many-body problems, using the example of the fermionic Hubbard model. Concretely, we study a four-site Hubbard ring that exhibits a transition from a product state to an intrinsically interacting ground state as hopping amplitudes are changed. We locate this transition and solve for the ground-state energy with high quantitative accuracy using a variational quantum algorithm executed on an IBM quantum computer. Our results are enabled by a variational ansatz that takes full advantage of the maximal set of commuting Z(2) symmetries of the problem and a Lanczos-inspired error mitigation algorithm. They are a benchmark on the way to exploiting near term quantum simulators for quantum many-body problems., Physical Review Research, 4 (1), ISSN:2643-1564
- Published
- 2022
- Full Text
- View/download PDF
13. Role of topology and symmetry for the edge currents of a two-dimensional superconductor
- Author
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Holst, Maximilian F, Sigrist, Manfred, Fischer, Mark H, and University of Zurich
- Subjects
530 Physics ,General Earth and Planetary Sciences ,10192 Physics Institute ,3100 General Physics and Astronomy ,General Environmental Science - Abstract
The bulk-boundary correspondence guarantees topologically protected edge states in a two-dimensional topological superconductor. Unlike in topological insulators, these edge states are, however, not connected to a quantized (spin) current as the electron number is not conserved in a Bogolyubov-de Gennes Hamiltonian. Still, edge currents are in general present. Here we use the two-dimensional Rashba system as an example to systematically analyze the effect symmetry reductions have on the order-parameter mixing and the edge properties in a superconductor of Altland-Zirnbauer class DIII (time-reversal-symmetry preserving) and D (time-reversal-symmetry breaking). In particular, we employ both Ginzburg-Landau and microscopic modeling to analyze the bulk superconducting properties and edge currents appearing in a strip geometry. We find edge (spin) currents independent of bulk topology and associated topological edge states which evolve continuously even when going through a phase transition into a topological state. Our findings emphasize the importance of symmetry over topology for the understanding of the nonquantized edge currents., Physical Review Research, 4 (1), ISSN:2643-1564
- Published
- 2022
14. Role of Topology and Symmetry for the Edge Currents of a 2D Superconductor
- Author
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Holst, Maximilian F., Sigrist, Manfred, and Fischer, Mark H.
- Subjects
Superconductivity (cond-mat.supr-con) ,Condensed Matter - Superconductivity ,FOS: Physical sciences - Abstract
The bulk-boundary correspondence guarantees topologically protected edge states in a two-dimensional topological superconductor. Unlike in topological insulators, these edge states are, however, not connected to a quantized (spin) current as the electron number is not conserved in a Bogolyubov-de Gennes Hamiltonian. Still, edge currents are in general present. Here, we use the two-dimensional Rashba system as an example to systematically analyze the effect symmetry reductions have on the order-parameter mixing and the edge properties in a superconductor of Altland-Zirnbauer class DIII (time-reversal-symmetry preserving) and D (time-reversal-symmetry breaking). In particular, we employ both Ginzburg-Landau and microscopic modeling to analyze the bulk superconducting properties and edge currents appearing in a strip geometry. We find edge (spin) currents independent of bulk topology and associated topological edge states which evolve continuously even when going through a phase transition into a topological state. Our findings emphasize the importance of symmetry over topology for the understanding of the non-quantized edge currents., 13 pages, 8 figures
- Published
- 2021
15. Switchable chiral transport in charge-ordered kagome metal CsV3Sb5.
- Author
-
Guo, Chunyu, Putzke, Carsten, Konyzheva, Sofia, Huang, Xiangwei, Gutierrez-Amigo, Martin, Errea, Ion, Chen, Dong, Vergniory, Maia G., Felser, Claudia, Fischer, Mark H., Neupert, Titus, and Moll, Philip J. W.
- Abstract
When electric conductors differ from their mirror image, unusual chiral transport coefficients appear that are forbidden in achiral metals, such as a non-linear electric response known as electronic magnetochiral anisotropy (eMChA)1–6. Although chiral transport signatures are allowed by symmetry in many conductors without a centre of inversion, they reach appreciable levels only in rare cases in which an exceptionally strong chiral coupling to the itinerant electrons is present. So far, observations of chiral transport have been limited to materials in which the atomic positions strongly break mirror symmetries. Here, we report chiral transport in the centrosymmetric layered kagome metal CsV
3 Sb5 observed via second-harmonic generation under an in-plane magnetic field. The eMChA signal becomes significant only at temperatures below T ′ ≈ 35 K, deep within the charge-ordered state of CsV3 Sb5 (TCDW ≈ 94 K). This temperature dependence reveals a direct correspondence between electronic chirality, unidirectional charge order7 and spontaneous time-reversal symmetry breaking due to putative orbital loop currents8–10. We show that the chirality is set by the out-of-plane field component and that a transition from left- to right-handed transport can be induced by changing the field sign. CsV3 Sb5 is the first material in which strong chiral transport can be controlled and switched by small magnetic field changes, in stark contrast to structurally chiral materials, which is a prerequisite for applications in chiral electronics.Change of chirality from left- to right-handed transport in the layered kagome metal CsV3 Sb5 can be controlled by small magnetic field changes, a required feature for chiral electronic applications. [ABSTRACT FROM AUTHOR]- Published
- 2022
- Full Text
- View/download PDF
16. What Is the Weight of a Single Amoeba and Why Does It Matter?
- Author
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Money, Nicholas P. and Fischer, Mark W. F.
- Subjects
- *
ARCHIMEDES' principle , *AMOEBA , *CELL size , *CELL growth , *STARVATION , *CYTOLOGY - Abstract
Cell size is an important variable in the study of cellular growth, metabolism, and the cell cycle. The large size of Amoeba proteus and the ease with which it can be collected and cultured have made it a star in biology education—and it was a model for research on cell biology before the introduction of molecular genetic methods. Measuring the cytoplasmic density of a single amoeba without modern instrumentation seems like a difficult task, but this was done with supreme accuracy in the 1940s. The solution was based on the familiar Cartesian diver that is used to demonstrate Archimedes's principle. It required the fabrication of a tiny diver that would respond to the additional mass of a cell. Experiments using this method allowed investigators to study changes in size and density associated with feeding, starvation, and cell division. This research is an illustration of the ingenuity of cell biologists in the pre-molecular genetic era of their field, which is often overlooked by contemporary scientists. The consideration of the mass, density, and buoyancy of free-living amoebas encourages a new hypothesis about the evolution of testate amoebas. [ABSTRACT FROM AUTHOR]
- Published
- 2021
- Full Text
- View/download PDF
17. USE YOUR POWER: Harnessing individual engagement and community commitment to shape care plans.
- Author
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FISCHER, MARK
- Published
- 2023
18. New approaches: Creating more effective strategies to reduce new HIV rates among Black and Latino MSM.
- Author
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FISCHER, MARK
- Published
- 2022
19. Effect of Myopic Defocus on Baseball Batting Performance.
- Author
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Reuscher, Nelly, Bulson, Ryan, Kempgens, Christian, Fischer, Mark, and Hayes, John
- Subjects
- *
BASEBALL , *MYOPIA , *ATHLETES , *SEX distribution , *VISUAL acuity , *VISUAL perception , *DESCRIPTIVE statistics , *ATHLETIC ability , *REFRACTIVE errors - Abstract
Background: Numerous studies have investigated the importance of visual clarity in simulated athletic performance and, surprisingly, have observed that several sports-related tasks are resilient to low-tomoderate levels of retinal defocus. The purpose of this study was to determine the effect of myopic defocus on baseball batting performance, as well as the influence of gender, preferred hand, refractive error, and previous baseball experience. Methods: Thirty visually normal (visual acuity at least 20/20, stereoacuity better than 50 arc seconds of stereoacuity) young-adult participants were pitched 20 baseballs from a pitching machine under four conditions in a randomized order: plano (control), +1.00 D, +2.00 D, and +3.00 D. All participants were tested under binocular viewing conditions, with their habitual distance correction in place. Two independent observers graded the batting performance via a quality-of-contact score. Results: Batting performance was significantly reduced under +2.00 D and +3.00 D conditions, but not under the +1.00 D condition. The overall effect of retinal defocus was significant (F = 9.137, p < 0.001). Previous baseball experience yielded a statistically significant difference in performance, but neither refractive error, hand, order, nor gender significantly influenced performance. A high linear correlation between both observers was found (R2 = 0.99). Conclusion: This study demonstrated that baseball batting performance was resilient to low levels of retinal defocus for amateur baseball players. The threshold level of myopic defocus where performance declined appears to be lower for baseball than for other simulated sportsrelated activities in the literature, including golf putting, cricket batting, and basketball free throws, suggesting that the influence of myopic defocus on athletic performance is likely task-dependent. [ABSTRACT FROM AUTHOR]
- Published
- 2021
20. The observation of π-shifts in the Little-Parks effect in 4Hb-TaS 2 .
- Author
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Almoalem A, Feldman I, Mangel I, Shlafman M, Yaish YE, Fischer MH, Moshe M, Ruhman J, and Kanigel A
- Abstract
Finding evidence of non-trivial pairing states is one of the greatest experimental challenges in the field of unconventional superconductivity. Such evidence requires phase-sensitive probes susceptible to the internal structure of the order parameter. We report the measurement of the Little-Parks effect in the unconventional superconductor candidate 4Hb-TaS
2 . In half of our rings, which are fabricated from single-crystals, we find a π-shift in the transition-temperature oscillations. According to theory, such a π-shift is only possible if the order parameter is non-s-wave. In the absence of crystallographic defects, the shift provides evidence of a multi-component order parameter. Thus, this observation increases the likelihood of the two-component order parameter scenario in 4Hb-TaS2 . Furthermore, we show that Tc is enhanced as a function of the out-of-plane field when a constant in-plane field is applied, which we explain using a two-component order-parameter., (© 2024. The Author(s).)- Published
- 2024
- Full Text
- View/download PDF
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