SciCombinator

Discover the most talked about and latest scientific content & concepts.

Concept: Rotation

276

Ants can navigate over long distances between their nest and food sites using visual cues [1, 2]. Recent studies show that this capacity is undiminished when walking backward while dragging a heavy food item [3-5]. This challenges the idea that ants use egocentric visual memories of the scene for guidance [1, 2, 6]. Can ants use their visual memories of the terrestrial cues when going backward? Our results suggest that ants do not adjust their direction of travel based on the perceived scene while going backward. Instead, they maintain a straight direction using their celestial compass. This direction can be dictated by their path integrator [5] but can also be set using terrestrial visual cues after a forward peek. If the food item is too heavy to enable body rotations, ants moving backward drop their food on occasion, rotate and walk a few steps forward, return to the food, and drag it backward in a now-corrected direction defined by terrestrial cues. Furthermore, we show that ants can maintain their direction of travel independently of their body orientation. It thus appears that egocentric retinal alignment is required for visual scene recognition, but ants can translate this acquired directional information into a holonomic frame of reference, which enables them to decouple their travel direction from their body orientation and hence navigate backward. This reveals substantial flexibility and communication between different types of navigational information: from terrestrial to celestial cues and from egocentric to holonomic directional memories.

Concepts: Earth, Navigation, Classical mechanics, Rotation, Walking, Rigid body, Frame of reference, Drag-and-drop

161

Phytochrome photoreceptors in plants and microorganisms switch photochromically between two states, controlling numerous important biological processes. Although this phototransformation is generally considered to involve rotation of ring D of the tetrapyrrole chromophore, Ulijasz et al. (2010, Nature 463, 250-254) proposed that the A-ring rotates instead. Here, we apply MAS NMR to the two parent states of following studies of the 23-kDa GAF-domain fragment of phytochrome from Synechococcus OS-B'. Major changes occur at the A-ring covalent linkage to the protein as well as at the protein residue contact of ring D. Conserved contacts associated with the A-ring nitrogen rule out an A-ring photoflip, whereas loss of contact of the D-ring nitrogen to the protein implies movement of ring D. Although none of the methine bridges showed a chemical shift change comparable to those characteristic of the D-ring photoflip in canonical phytochromes, denaturation experiments showed conclusively that the same occurs in Synechococcus OS-B' phytochrome upon photoconversion. The results are consistent with the D-ring being strongly tilted in both states and the C15=C16 double bond undergoing a Z/E isomerization upon light absorption. More subtle changes are associated with the A-ring linkage to the protein. Our findings thus disprove A-ring rotation and are discussed in relation to the position of the D-ring, photoisomerization and photochromicity in the phytochrome family.

Concepts: Protein, Oxygen, Metabolism, Nitrogen, Group, Absorption, Covalent bond, Rotation

158

The response to haloperidol as a first-line neuroleptic and the pattern of neuroleptic rotation after haloperidol failure have not been well defined in palliative care. The purpose of this study was to determine the efficacy of haloperidol as a first-line neuroleptic and the predictors associated with the need to rotate to a second neuroleptic.

Concepts: Cancer, Oncology, Chemotherapy, Palliative care, Frequency, Rotation, Haloperidol, Equator

81

Self-propelled bacteria can be integrated into synthetic micromachines and act as biological propellers. So far, proposed designs suffer from low reproducibility, large noise levels or lack of tunability. Here we demonstrate that fast, reliable and tunable bio-hybrid micromotors can be obtained by the self-assembly of synthetic structures with genetically engineered biological propellers. The synthetic components consist of 3D interconnected structures having a rotating unit that can capture individual bacteria into an array of microchambers so that cells contribute maximally to the applied torque. Bacterial cells are smooth swimmers expressing a light-driven proton pump that allows to optically control their swimming speed. Using a spatial light modulator, we can address individual motors with tunable light intensities allowing the dynamic control of their rotational speeds. Applying a real-time feedback control loop, we can also command a set of micromotors to rotate in unison with a prescribed angular speed.

Concepts: DNA, Gene, Genetics, Bacteria, Organism, Control theory, Feedback, Rotation

45

A 3D numerical model of the earth’s core with a viscosity two orders of magnitude lower than the state of the art suggests a link between the observed westward drift of the magnetic field and superrotation of the inner core. In our model, the axial electromagnetic torque has a dominant influence only at the surface and in the deepest reaches of the core, where it respectively drives a broad westward flow rising to an axisymmetric equatorial jet and imparts an eastward-directed torque on the solid inner core. Subtle changes in the structure of the internal magnetic field may alter not just the magnitude but the direction of these torques. This not only suggests that the quasi-oscillatory nature of inner-core superrotation [Tkalčić H, Young M, Bodin T, Ngo S, Sambridge M (2013) The shuffling rotation of the earth’s inner core revealed by earthquake doublets. Nat Geosci 6:497-502.] may be driven by decadal changes in the magnetic field, but further that historical periods in which the field exhibited eastward drift were contemporaneous with a westward inner-core rotation. The model further indicates a strong internal shear layer on the tangent cylinder that may be a source of torsional waves inside the core.

Concepts: Magnetic field, Fundamental physics concepts, Earth's magnetic field, Earth, Torque, Rotation, Outer core, Inner core

39

When placing one hand on each side of a mirror and making synchronous bimanual movements, the mirror-reflected hand feels like one’s own hand that is hidden behind the mirror. We developed a novel mirror box illusion to investigate whether motoric, but not spatial, visuomotor congruence is sufficient for inducing multisensory integration, and importantly, if biomechanical constraints encoded in the body schema influence multisensory integration. Participants placed their hands in a mirror box in opposite postures (palm up, palm down), creating a conflict between visual and proprioceptive feedback for the hand behind the mirror. After synchronous bimanual hand movements in which the viewed and felt movements were motorically congruent but spatially in the opposite direction, participants felt that the hand behind the mirror rotated or completely flipped towards matching the hand reflection (illusory displacement), indicating facilitation of multisensory integration by motoric visuomotor congruence alone. Some wrist rotations are more difficult due to biomechanical constraints. We predicted that these biomechanical constraints would influence illusion effectiveness, even though the illusion does not involve actual limb movement. As predicted, illusory displacement increased as biomechanical constraints and angular disparity decreased, providing evidence that biomechanical constraints are processed in multisensory integration.

Concepts: Rotation, Proprioception, Hand, Place, Phantom limb, Vilayanur S. Ramachandran

28

Objective: Solventless dry powder coating methods have many advantages compared to solvent-based methods: they are more economical, simpler, safer, more environmentally friendly and easier to scale up. The purpose of this study was to investigate a highly effective dry powder coating method using the mechanofusion system, a mechanochemical treatment equipped with high compressive and shearing force.Materials and methods: Acetaminophen (AAP) and carnauba wax (CW) were selected as core particles of the model drug and coating material, respectively. Mixtures of AAP and CW with and without talc were processed using the mechanofusion system.Results: Sustained AAP release was observed by selecting appropriate processing conditions for the rotation speed and the slit size. The dissolution rate of AAP processed with CW substantially decreased with an increase in talc content up to 40% of the amount of CW loaded. Increasing the coating amount by two-step addition of CW led to more effective coating and extended drug release. Scanning electron micrographs indicated that CW adhered and showed satisfactory coverage of the surface of AAP particles.Conclusion: Effective CW coating onto the AAP surface was successfully achieved by strictly controlling the processing conditions and the composition of core particles, coating material and glidant. Our mechanochemical dry powder coating method using the mechanofusion system is a simple and promising means of solventless pharmaceutical coating.

Concepts: Wax, Scanning electron microscope, Rotation, Micrograph, Beeswax, Shoe polish, Waxes, Carnauba wax

28

Use of a stability ball alone and stability ball chair were evaluated in the Veterans Health Administration as possible alternatives to incorporate with regular office chair use. The evaluation of stability ball use was conducted under the auspices of a work site health promotion program as a cross-over trial with participants rotating through use of the stability ball, stability ball chair, and regular office chair on a monthly basis for a total duration of 3 months. Rotations on regular office chairs served as the control. Three medical facilities participated. A total of 193 employees completed a baseline questionnaire; 159 completed at least one post-rotation questionnaire. Self-reported measures included perceived posture when sitting, perceptions of overall balance, energy levels, job performance, safety, and pain. Use was associated with improvements in perceived posture (p < 0.0001) and energy levels (p = 0.007) for stability ball users compared with the office chair control, and improvements in perceived posture (p < 0.0001) and overall balance (p = 0.05) for stability ball chair users compared with the control. Use of stability balls at work decreases the likelihood of reporting pain from regular office chair use from approximately 45% to 21%. Alternatively, a high number of participants reported pain with use of the stability ball alone and stability ball chair, 42% and 45%, respectively. The perceived risks and benefits of stability ball use should be weighed when incorporating use. [Supplementary materials are available for this article. Go to the publisher's online edition of Journal of Occupational and Environmental Hygiene for the following free supplementary resource: Post-Active Sitting Device Questionnaire].

Concepts: Perception, Sense, Rotation, Sitting, Chair, Office chair, Chairs, Balls

28

The helical flow pump (HFP) is a novel rotary blood pump invented for developing a total artificial heart (TAH). The HFP with a hydrodynamic levitation impeller, which consists of a multi-vane impeller involving rotor magnets, stator coils at the core position, and double helical-volute pump housing, was developed. Between the stator and impeller, a hydrodynamic bearing is formed. Since the helical volutes are formed at both sides of the impeller, blood flows with a helical flow pattern inside the pump. The developed HFP showed maximum output of 19 l/min against 100 mmHg of pressure head and 11 % maximum efficiency. The profile of the H-Q (pressure head vs. flow) curve was similar to that of the undulation pump. Hydrodynamic levitation of the impeller was possible with higher than 1,000 rpm rotation speed. The normalized index of the hemolysis ratio of the HFP to centrifugal pump (BPX-80) was from 2.61 to 8.07 depending on the design of the bearing. The HFP was implanted in two goats with a left ventricular bypass method. After surgery, hemolysis occurred in both goats. The hemolysis ceased on postoperative days 14 and 9, respectively. In the first experiment, no thrombus was found in the pump after 203 days of pumping. In the second experiment, a white thrombus was found in the pump after 23 days of pumping. While further research and development are necessary, we are expecting to develop an excellent TAH with the HFP.

Concepts: Heart, Fluid dynamics, Pump, Rotation, Artificial heart, Stator, Centrifugal pump, Pumps

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PURPOSE: There is a lot of inter-individual variation in the rotational anatomy of the distal femur. This study was set up to define the rotational anatomy of the distal femur in the osteo-arthritic knee and to investigate its relationship with the overall coronal alignment and gender. METHODS: CT-scans of 231 patients with end-stage knee osteo-arthritis prior to TKA surgery were obtained. This represents the biggest series published on rational geometry of the distal femur in literature so far. RESULTS: The posterior condylar line (PCL) was on average 1.6° (SD 1.9) internally rotated relative to the surgical transepicondylar axis (sTEA). The perpendicular to trochlear anteroposterior axis (⊥TRAx) was on average 4.8° (SD 3.3°) externally rotated relative to the sTEA. The relationship between the PCL and the sTEA was statistically different in the different coronal alignment groups (p < 0.001): 1.0° (SD 1.8°) in varus knees, 2.1° (SD 1.8°) in neutral knees and 2.6° (SD 1.8°) in valgus knees. The same was true for the ⊥TRAx in these 3 groups (p < 0.02).There was a clear linear relationship between the overall coronal alignment and the rotational geometry of the distal femur. For every 1° in coronal alignment increment from varus to valgus, there is a 0.1° increment in posterior condylar angle (PCL vs sTEA). CONCLUSION: The PCL was on average 1.6° internally rotated relative to the sTEA in the osteo-arthritic knee. The relationship between the PCL and the sTEA was statistically different in the different coronal alignment groups. LEVEL OF EVIDENCE: III.

Concepts: Mathematics, Femur, Knee, Euclidean geometry, Rotation, Valgus deformity, Tibia, Patella