Dynamically generated decoherence-free subspaces and subsystems on superconducting qubits.

Decoherence-free subspaces and subsystems (DFS) preserve quantum information by encoding it into symmetry-protected states unaffected by decoherence. An inherent DFS of a given experimental system may not exist; however, through the use of dynamical decoupling (DD), one can induce symmetries that support DFSs. Here, we provide the first experimental demonstration of DD-generated decoherence-free subsystem logical qubits. Utilizing IBM Quantum superconducting processors, we investigate two and three-qubit DFS codes comprising up to six and seven noninteracting logical qubits, respectively. Through a combination of DD and error detection, we show that DFS logical qubits can achieve up to a 23% improvement in state preservation fidelity over physical qubits subject to DD alone. This constitutes a beyond-breakeven fidelity improvement for DFS-encoded qubits. Our results showcase the potential utility of DFS codes as a pathway toward enhanced computational accuracy via logical encoding on quantum processors.

Quantum Crosstalk Robust Quantum Control.

The prevalence of quantum crosstalk in current quantum devices poses challenges for achieving high-fidelity quantum logic operations and reliable quantum processing. Through quantum control theory, we develop an analytical condition for achieving crosstalk-robust single-qubit control of multiqubit systems. We examine the effects of quantum crosstalk via a cumulant expansion and develop a condition to suppress the leading order contributions to the dynamics. The efficacy of the condition is illustrated in the domains of quantum state preservation and noise characterization through the development of crosstalk-robust dynamical decoupling and quantum noise spectroscopy (QNS) protocols. Using the IBM Quantum Experience, crosstalk-robust state preservation is demonstrated on 27 qubits, where up to a 3.5× improvement in coherence decay is observed for single-qubit product and multipartite entangled states. Through the use of noise injection, we demonstrate crosstalk-robust dephasing QNS on a seven qubit processor, where a 10^{4} improvement in reconstruction accuracy over alternative protocols is found. Together, these experiments highlight the significant impact the crosstalk suppression condition can have on improving multiqubit characterization and control on current quantum devices.

Neural control of rapid binocular eye movements: Saccade-vergence burst neurons.

During normal viewing, we direct our eyes between objects in three-dimensional (3D) space many times a minute. To accurately fixate these objects, which are usually located in different directions and at different distances, we must generate eye movements with appropriate versional and vergence components. These combined saccade-vergence eye movements result in disjunctive saccades with a vergence component that is much faster than that generated during smooth, symmetric vergence eye movements. The neural control of disjunctive saccades is still poorly understood. Recent anatomical studies suggested that the central mesencephalic reticular formation (cMRF), located lateral to the oculomotor nucleus, contains premotor neurons potentially involved in the neural control of these eye movements. We have therefore investigated the role of the cMRF in the control of disjunctive saccades in trained rhesus monkeys. Here, we describe a unique population of cMRF neurons that, during disjunctive saccades, display a burst of spikes that are highly correlated with vergence velocity. Importantly, these neurons show no increase in activity for either conjugate saccades or symmetric vergence. These neurons are termed saccade-vergence burst neurons (SVBNs) to maintain consistency with modeling studies that proposed that such a class of neuron exists to generate the enhanced vergence velocities observed during disjunctive saccades. Our results demonstrate the existence and characteristics of SVBNs whose activity is correlated solely with the vergence component of disjunctive saccades and, based on modeling studies, are critically involved in the generation of the disjunctive saccades required to view objects in our 3D world.

Cognitive swarming in complex environments with attractor dynamics and oscillatory computing.

Neurobiological theories of spatial cognition developed with respect to recording data from relatively small and/or simplistic environments compared to animals' natural habitats. It has been unclear how to extend theoretical models to large or complex spaces. Complementarily, in autonomous systems technology, applications have been growing for distributed control methods that scale to large numbers of low-footprint mobile platforms. Animals and many-robot groups must solve common problems of navigating complex and uncertain environments. Here, we introduce the NeuroSwarms control framework to investigate whether adaptive, autonomous swarm control of minimal artificial agents can be achieved by direct analogy to neural circuits of rodent spatial cognition. NeuroSwarms analogizes agents to neurons and swarming groups to recurrent networks. We implemented neuron-like agent interactions in which mutually visible agents operate as if they were reciprocally connected place cells in an attractor network. We attributed a phase state to agents to enable patterns of oscillatory synchronization similar to hippocampal models of theta-rhythmic (5-12 Hz) sequence generation. We demonstrate that multi-agent swarming and reward-approach dynamics can be expressed as a mobile form of Hebbian learning and that NeuroSwarms supports a single-entity paradigm that directly informs theoretical models of animal cognition. We present emergent behaviors including phase-organized rings and trajectory sequences that interact with environmental cues and geometry in large, fragmented mazes. Thus, NeuroSwarms is a model artificial spatial system that integrates autonomous control and theoretical neuroscience to potentially uncover common principles to advance both domains.

Mapping the macaque superior temporal sulcus: functional delineation of vergence and version eye-movement-related activity.

It is currently thought that the primate oculomotor system has evolved distinct but interrelated subsystems to generate different types of visually guided eye movements (e.g., saccades/smooth pursuit/vergence). Although progress has been made in elucidating the neural basis of these movement types, no study to date has investigated all three movement types on a large scale and within the same animals. Here, we used fMRI in rhesus macaque monkeys to map the superior temporal sulcus (STS) for BOLD modulation associated with visually guided eye movements. Further, we ascertained whether modulation in a given area was movement type specific and, if not, the modulation each movement type elicited relative to the others (i.e., dominance). Our results show that multiple areas within STS modulate during all movement types studied, including the middle temporal, medial superior temporal, fundus of the superior temporal, lower superior temporal, and dorsal posterior inferotemporal areas. Our results also reveal an area in dorsomedial STS that is modulated almost exclusively by vergence movements. In contrast, we found that ventrolateral STS is driven preferentially during versional movements. These results illuminate an STS network involved in processes associated with multiple eye movement types, illustrate unique patterns of modulation within said network as a function of movement type, and provide evidence for a vergence-specific area within dorsomedial STS. We conclude that producing categorically different eye movement types requires access to a common STS network and that individual network nodes are recruited differentially based upon the type of movement generated.

UVA-photoactivated riboflavin treatment of vaginal cells derived from pelvic organ prolapse cases.

BACKGROUND: The pathophysiology of pelvic organ prolapse (POP) involves vaginal collagen degradation. Strengthening collagen by UVA-photoactivated cross-linking has been demonstrated and suggested target applications include the vaginal wall. AIM: To identify UVA irradiation and riboflavin effects on vaginal cells. MATERIALS AND METHODS: Vaginal cells were incubated for 24 h (DMEM/F-12 Ham's media) and were exposed to riboflavin (0, 0.1 and 10%) for 30 min before UVA photoactivation. Percentages of live, apoptotic and necrotic cells were determined by propidium iodide/Hoechst 33342 stains. RESULTS: UVA decreased vaginal cell viability [mean ± standard error of the mean: 26.2 ± 0.5% vs. control (43.9 ± 3.8%)], but riboflavin blocked UVA-induced damage (57.9 ± 2.7 and 56.7 ± 2.1% at 0.1 and 10% riboflavin, respectively). Cells treated with low- and high-dose riboflavin had lower apoptosis (32.9 ± 1.0 and 35.5 ± 0.9%, respectively). Furthermore, riboflavin-treated cells had reduced necrosis (9.3 ± 1.7, 7.8 ± 3.0%) versus UVA-only (32.4 ± 5.5%) or control (17.1 ± 2.8%). Viability was similar for cells from the cervical and hymenal segments. CONCLUSION: The results demonstrated that riboflavin attenuated UVA damage in vaginal cells by inhibiting necrosis. Cervical and hymenal end vaginal cells were equally affected by UVA. UVA phototoxicity was reduced by the presence of riboflavin.

Mindfulness Practice Is Associated With Improved Well-Being and Reduced Injury Risk in Female NCAA Division I Athletes.

BACKGROUND: Injury in sport is an inherent risk to participation, and it can have devastating consequences for the athlete, both mentally and physically. Previous research has found that impairments in well-being can increase the risk of injury, and that various forms of mindfulness training and practice can improve well-being and mental health in various populations. HYPOTHESIS: Mindfulness would be associated with greater well-being and lower risk of injury. STUDY DESIGN: Cohort study. LEVEL OF EVIDENCE: Level 3. METHODS: A total of 21 female Division I athletes underwent a formal 6-week mindfulness training program and were encouraged to continue mindfulness exercises. The athletes completed daily surveys on their smartphones in relation to mood, muscle readiness (soreness), readiness to train, energy level, daily training load, and whether they had participated in mindfulness training that day. Linear mixed effects models were used to evaluate well-being variables and mindfulness state, and separate mixed effects logistics regression models were used to evaluate injury incidence and wellness variables. RESULTS: On days with mindfulness practice, athletes reported higher mood (19.6 [18.8-20.3] vs 19.4 [18.6-20.1, P = 0.03), muscle readiness (18.9 [17.8-20.0] vs 18.6 [17.5-19.6], P = 0.03), readiness to train (78.7 [75.9-81.5] vs 77.4 [74.7-80.2], P < 0.01), and energy level (19.3 [18.6-20.1] vs 18.8 [18.1-19.5, P < 0.01) than on the days when they did not participate in mindfulness training. Mindfulness practice was associated with significantly reduced likelihood of suffering an acute injury the following day (odds ratio, 0.42; 95% CI, 0.42-0.43; P < 0.01). CONCLUSION: On an individual level, participation in mindfulness by female collegiate athletes was associated with a dramatic reduction in injury risk the following day. In addition, mindfulness was associated with significantly improved mood, muscle readiness, readiness to train, and energy level. CLINICAL RELEVANCE: These findings suggest that mindfulness training in athletes may improve well-being and reduce the risk of injury among high-level athletes.

Bayesian optimization of distributed neurodynamical controller models for spatial navigation.

Dynamical systems models for controlling multi-agent swarms have demonstrated advances toward resilient, decentralized navigation algorithms. We previously introduced the NeuroSwarms controller, in which agent-based interactions were modeled by analogy to neuronal network interactions, including attractor dynamics and phase synchrony, that have been theorized to operate within hippocampal place-cell circuits in navigating rodents. This complexity precludes linear analyses of stability, controllability, and performance typically used to study conventional swarm models. Further, tuning dynamical controllers by manual or grid-based search is often inadequate due to the complexity of objectives, dimensionality of model parameters, and computational costs of simulation-based sampling. Here, we present a framework for tuning dynamical controller models of autonomous multi-agent systems with Bayesian optimization. Our approach utilizes a task-dependent objective function to train Gaussian process surrogate models to achieve adaptive and efficient exploration of a dynamical controller model's parameter space. We demonstrate this approach by studying an objective function selecting for NeuroSwarms behaviors that cooperatively localize and capture spatially distributed rewards under time pressure. We generalized task performance across environments by combining scores for simulations in multiple mazes with distinct geometries. To validate search performance, we compared high-dimensional clustering for high- vs. low-likelihood parameter points by visualizing sample trajectories in 2-dimensional embeddings. Our findings show that adaptive, sample-efficient evaluation of the self-organizing behavioral capacities of complex systems, including dynamical swarm controllers, can accelerate the translation of neuroscientific theory to applied domains.

Electron transfer within charge-localized arylhydrazine-centered mixed valence radical cations having larger bridges.

Kinetics for intramolecular charge transfer between two diarylhydrazine units, measured by ESR, are reported for six charge-localized mixed valence compounds having 9, 11, 13, and 16 bonds between the nitrogen atoms. A 17-bond bridged compound had too slow electron transfer to measure the rate constant by ESR. The optical spectra of these radical cations are compared with tert-butyl,aryl-substituted hydrazines, and rate constants calculated using parameters derived from the optical spectra are compared with the experimental values where possible. The charge-transfer band overlapped too badly with bridge-centered absorption for the 16-bond bridged compound to allow the comparison to be made. The 13-bond bridged compound gave worse agreement than the other compounds. Its optical rate constant was about 5.4 times the ESR rate constant at a temperature between the ranges in which the data were collected.

Charge distribution in arylhydrazine-centered mixed valence compounds with smaller bridges (five to nine bonds between closest nitrogens).

Charge distribution in six aromatic-bridged, aryldialkylhydrazine-centered mixed valence radical cations is discussed through consideration of their optical spectra. The compounds considered have two 2-phenyl-2,3-diazabicyclo-[2.2.2]octane-3-yl (HyPh) charge-bearing units linked by a 1,4-phenylene bridge and its p-methoxyphenyl (HyAn) analogue, as well as the (HyPh)(2)-substituted 1,4-naphthalene, 2,6-naphthalene, 9,10-anthracene, and 4,4'-biphenyl compounds in methylene chloride and acetonitrile. Consideration of band shape and position leads us to assign the 1,4-phenylene- and 2,6-naphthalene-bridged compounds as charge-delocalized (class III) in both solvents, but the 1,4-naphthalene-bridged one lies closer to the borderline, and appears to be charge-localized (class II) in acetonitrile. The 4,4'-biphenyl-bridged compound is clearly class II in acetonitrile, and possibly also in methylene chloride. The lowest energy absorption band for the 9,10-anthracene-bridged compound is assigned as a bridge-to-HyPh band, and its charge distribution is not clear. Problems with the often-used relationship that the electronic coupling is half the transition energy for the lowest energy band of class III mixed valence compounds are discussed, as is interpretation of the vertical reorganization energy near the class II, class III borderline.

Alkylated trimethylene-bridged bis(p-phenylenediamines).

One and two electron oxidation of N,N',N'',N'''-tetramethyl-1,5,12,16-tetraaza[5,5]paracyclophane (Me3C), a bis-trimethylene bridged bis-p-phenylene diamine (PD), and its ethyl and isopropyl analogues are discussed. The monocation and dication are both stable, as demonstrated by optical studies that show they are in equilibrium in solution, with an especially small difference in first and second oxidation potentials for Me3C in MeCN (+23 to -20 mV, measured by simulation of the optical spectrum and of the cyclic voltammogram, respectively). The monocations have charge localized in one PD unit and show a Hush-type mixed valence transition between their PD0 and PD.+ groups. The dications Me3C2+ and Et3C2+ have optical spectra that appear to show large splittings between their PD.+ groups and have a weak ESR spectrum, and 1H NMR data show that the former is a ground-state singlet. iPr3C2+ has a very different optical spectrum and exhibits a triplet ESR spectrum at 120 K. X-ray crystal structures show that for Me3C0 the N(CH2)3N units on each side are in doubly anti (aa) conformations that put the aryl rings as far apart as possible, but Me3C2+ has doubly gg N(CH2)3N trimethylene bridges and both N,N and C,C distances between the PD.+ groups that are significantly below van der Walls contact. In contrast, iPr3C0 is in a doubly ag conformation, and its diradical dication is suggested to be a triplet because it does not attain the doubly gg conformation.

Interpretation of mixed-valence compound optical spectra near the class II/III border: dinitrobiphenyl and dinitrophenanthrene radical anions.

The optical spectra of 4,4'-dinitrobiphenyl and other similar 9-bond bridged radical anions show that these mixed-valence compounds are predominantly charge-localized in the high lambda(S) solvent MeCN, charge-delocalized in the low lambda(S) solvent HMPA, and show intermediate behavior in DMF. Hush analysis of the localized charge-transfer band in MeCN allowed the calculation of the electronic coupling between nitro groups (Hab). Hab changes with bridge structure, depending mainly on the twist angle between the two aromatic rings: Hab is higher for the planar 9,9-dimethyl-2,7-dinitrofluorene radical anion (1100 cm(-1)) and about one-half of this value for the more twisted 2,2'-dimethyl-4,4'-dinitrobiphenyl radical anion (540 cm(-1)). The reorganization energy lambda decreases as Hab increases. We suggest that this is due to a decrease of the internal reorganization energy lambda(v) as the Class II/Class III borderline is approached, and that lambda(v) should be zero at the borderline. Subtracting from the experimental spectra the fraction corresponding to the delocalized part (taken as the spectrum in HMPA or THF), we get localized charge-transfer bands that show a significant cutoff effect at the low energy side, as predicted by classical Marcus-Hush theory.

Evaluation of a temperature-restricted, mucosal tuberculosis vaccine in guinea pigs.

Tuberculosis (TB) is currently the leading cause of death in humans by a single infectious agent, Mycobacterium tuberculosis. The Bacillus Calmette-Guérin (BCG) vaccine prevents pulmonary TB with variable efficacy, but can cause life-threatening systemic infection in HIV-infected infants. In this study, TBvac85, a derivative of Mycobacterium shottsii expressing M. tuberculosis Antigen 85B, was examined as a safer alternative to BCG. Intranasal vaccination of guinea pigs with TBvac85, a naturally temperature-restricted species, resulted in serum Ag85B-specific IgG antibodies. Delivery of the vaccine by this route also induced protection equivalent to intradermal BCG based on organ bacterial burdens and lung pathology six weeks after aerosol challenge with M. tuberculosis strain Erdman. These results support the potential of TBvac85 as the basis of an effective TB vaccine. Next-generation derivatives expressing multiple M. tuberculosis immunogens are in development.

Mixed valence compounds as probes to determine the polarity of 1-butyl-3-methylimadazolium ionic liquids.

Radical cations and dications of three bishydrazines belonging to the Class II mixed valence compounds have been generated, either spontaneously or by oxidation with AgSbF6, in two 1-butyl-3-methylimidazolium (4+) ionic liquids having BF4(-) and PF6(-) as counterions. The optical spectra of these intermediates have allowed evaluation of Marcus' reorganization energy lambda(s), a parameter that is directly proportional to the solvent polarity. Remarkable differences in lambda(s), as large as 600 cm(-1), have been observed as a function of the counterion, with these data providing support for the observed differences between both ionic liquids (4(+)BF4(-) and 4(+)PF6(-)) in catalysis. However, in terms of polarity, the lambda(s) values rank the hydrophilic 4(+)BF4(-) as being similar to dimethyl sulfoxide and dimethylformamide, while the polarity of hydrophobic 4(+)PF6(-) is analogous to acetonitrile. Overall, our results indicate that ionic liquids are not exceptional liquids in terms of polarity.

The ups and downs of peer review.

This article traces the history of peer review of scientific publications, plotting the development of the process from its inception to its present-day application. We discuss the merits of peer review and its weaknesses, both perceived and real, as well as the practicalities of several major proposed changes to the system. It is our hope that readers will gain a better appreciation of the complexities of the process and, when serving as reviewers themselves, will do so in a manner that will enhance the utility of the exercise. We also propose the development of an international on-line training program for accreditation of potential referees.

Aging and immunity in nonhuman primates: I. Effects of age and gender on cellular immune function in rhesus monkeys (Macaca mulatta).

Immunity declines with advancing age. Lymphocyte proliferation, natural killer cell activity, and antibody response to tetanus toxoid vaccination were evaluated in cohorts of rhesus monkeys (Macaca mulatta) aged 2-36 years in order to characterize senescent changes in immune function. The results were analyzed in accordance with host age. Lymphocyte proliferation was generally low in older monkeys, especially males. Lymphocytes from old male monkeys responded significantly less to test mitogens than did those of old female (P<.05) or young males and females (P<.01). Natural killer cell function was similarly decreased in old monkeys; however, for this function there was no apparent gender difference. Antibody response to tetanus vaccine was less in older monkeys but was also low in several of the younger moskeys. These data confirm our expectation that, like other mammalian species, the rhesus monkey shows a decline in immune function with age and demonstrate further that the changes are more marked in males. Rhesus monkeys, therefore, are suitable for the investigation of mechanisms of immune senescence.

Assessment of sprint and change-of-direction performance in college football players.

The aim of the current study was to investigate the relationship between straight-sprint and change-of-direction performance. Total sprinting time and split time at 5 m were collected from 44 college football players during a 15-m straight sprint (SS15m) and a 15-m zigzag sprint with two 60° changes of direction (COD15m). Differences in sprinting time between COD15m and SS15m and between COD5m and SS5m were expressed as percentage of decrement at 5 m and 15 m (Δ%5m and Δ%15m). Significant and high correlations emerged between SS15m and COD15m (r = .86, P < .0001), SS5m and SS15m (r = .92, P < .0001), SS5m and COD5m (r = .92, P < .0001), and COD5m and COD15m (r = .71, P < .0001). Δ%5m and Δ%15m showed a range of 1.2-30.0% and 34.9-59.4%, respectively. These results suggested how straight-sprint and change-of-direction performance are similar abilities in college football players, in particular when a smaller angle of the change of direction is considered. Moreover, it seems necessary to have athletes undergo tests that mimic the demands of football game, which is characterized by sprint on short distances and with changes of direction.

The mechanism of flight guidance in honeybee swarms: subtle guides or streaker bees?

When a honeybee swarm takes off to fly to its new home site, less than 5% of the bees in the swarm have visited the site and thereby know in what direction the swarm must fly. How does the small minority of informed bees indicate the swarm's flight direction to the large majority of uninformed bees? Previous simulation studies have suggested two possible mechanisms of visual flight guidance: the informed bees guide by flying in the preferred direction but without an elevated speed (subtle guide hypothesis) or they guide by flying in the preferred direction and with an elevated speed (streaker bee hypothesis). We tested these hypotheses by performing a video analysis that enabled us to measure the flight directions and flight speeds of individual bees in a flying swarm. The distributions of flight speed as a function of flight direction have conspicuous peaks for bees flying toward the swarm's new home, especially for bees in the top of the swarm. This is strong support for the streaker bee hypothesis.