849 research outputs found
Improvement of surface flatness in high precision milling
The use of high precision micro components has increased in various industrial fields in recent years. Repeatable techniques are needed to face very tight tolerances and make micro fabrication processes industrially feasible against current micro machining limitation. Improving surface flatness in high precision milling is the main target of the present research. Critical issues such as machining strategy, spindle thermal transient management and tool wear compensation were considered for machining operations on a representative part
Experience-based Auditory Predictions Modulate Brain Activity to Silence as do Real Sounds.
Interactions between stimuli's acoustic features and experience-based internal models of the environment enable listeners to compensate for the disruptions in auditory streams that are regularly encountered in noisy environments. However, whether auditory gaps are filled in predictively or restored a posteriori remains unclear. The current lack of positive statistical evidence that internal models can actually shape brain activity as would real sounds precludes accepting predictive accounts of filling-in phenomenon. We investigated the neurophysiological effects of internal models by testing whether single-trial electrophysiological responses to omitted sounds in a rule-based sequence of tones with varying pitch could be decoded from the responses to real sounds and by analyzing the ERPs to the omissions with data-driven electrical neuroimaging methods. The decoding of the brain responses to different expected, but omitted, tones in both passive and active listening conditions was above chance based on the responses to the real sound in active listening conditions. Topographic ERP analyses and electrical source estimations revealed that, in the absence of any stimulation, experience-based internal models elicit an electrophysiological activity different from noise and that the temporal dynamics of this activity depend on attention. We further found that the expected change in pitch direction of omitted tones modulated the activity of left posterior temporal areas 140-200 msec after the onset of omissions. Collectively, our results indicate that, even in the absence of any stimulation, internal models modulate brain activity as do real sounds, indicating that auditory filling in can be accounted for by predictive activity
Unscrambling Light Automatically on a Photonic Chip
Light beams can get mixed by transmission through a scattering
system like a multimode channel. Separating beams
of the same wavelength and polarization would appear to be
very hard. Although the information carried by the beams is
not fundamentally lost, its recovery requires a coherent interferometric
reconstruction of the original signals, which have
been scrambled among the modes of the system.
In principle, a reconfigurable mesh of 2×2 interferometers
could perform the necessary unitary mathematical operation.1
In practice, however, use of such photonic meshes—the size
of which scales up quadratically with the number of modes—
has been hindered by the need for complex, time-consuming
procedures for calibration, control and configuration. Setting
up and stabilizing a complex network of interferometers can
be challenging, especially for interferometers buried inside
the mesh.
In work this year, we constructed a silicon photonics integrated
mesh that can self-configure automatically to unscramble
arbitrarily mixed optical beams, without any advance knowledge
of the scattering system.2 Our architecture integrates
six thermally controlled Mach-Zehnder interferometers that
are sequentially and automatically adjusted, without calculations,
to simultaneously reconstruct, separate (with a residual
crosstalk of less than –20 dB), and sort out four optical beams
that have been completely mixed in a multimode waveguide.
By keying each signal with a different pilot tone, built-in
transparent detectors3 monitor the evolution of each mode
along the mesh, allowing tuning and adaptive individual feedback
control of each interferometer with a simple, progressive
algorithm.4 The entire mesh, controlled by custom-designed
electronics, resets itself automatically after the mode mixing
is significantly perturbed, can completely reconfigure on a
time scale of a few seconds, and can track modes undergoing
time-varying mixing on a time scale of a few hundred
milliseconds.
Our calibration and control strategy enables scalability to
larger meshes (that is, to higher number of modes) without
substantially increasing control complexity. Further, the principle
of a self-configuring, self-resetting mesh can be extended
to different mesh topologies to implement nonunitary linear
operations4 and emerging programmable photonic processors,5
for applications in fields such as telecommunications, imaging,
sensing, secrecy and quantum information processing. This
work demonstrates that, despite the apparent challenges of
undoing complicated scattering and interferometric mixing
of optical beams, self-configuring and self-stabilizing optics
systems can automatically unscramble light in real time
Effect of a multistrain probiotic (Lactoflorene® Plus) on inflammatory parameters and microbiota composition in subjects with stress-related symptoms
Stress affects the immune system and intestinal microbiota composition and can lead to imbalance between pro- and anti-inflammatory cytokines or to uncontrolled production of cytokines. The effect of emotional stress on secretory IgA levels also indicates that stress decreases mucosal integrity. Our aim was to evaluate whether a probiotic product (Lactoflorene® Plus) can prevent alterations in the immune response associated with self-reported stress and microbiota composition. Healthy adult volunteers who self-reported psychological stress were enrolled and randomised into a placebo and a probiotic group. Salivary stress markers (α-amylase, cortisol, chromogranin A) and immunological parameters (sIgA, NK cell activity, IL-8, IL-10, TNF-α) in feces and the composition of intestinal microbiota were evaluated. Administration of the product did not exert a direct effect on the salivary stress markers or NK cell activity but did reduce abdominal pain and increase faecal IgA and IL-10 levels. The probiotic product induced a moderate increase in Bifidobacterium and Lactobacillus spp., as expected, and in Faecalibacterium spp., and decreased the size of the Dialister spp. and Escherichia and Shigella populations. Administration of the product helped protect the mucosal barrier by supporting the number of short-chain fatty acid producers and decreasing the load of potentially harmful bacteria, thus reducing intestinal inflammation and abdominal discomfort. ClinicalTrials.gov: NCT03234452
Cumulative radiation exposure during thoracic endovascular aneurysm repair and subsequent follow-up
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Progressive decline of decision-making performances during multiple sclerosis
The purpose of this study was to evaluate longitudinally, using the Iowa Gambling Task (IGT), the dynamics of decision-making capacity at a two-year interval (median: 2.1 years) in a group of patients with multiple sclerosis (MS) (n = 70) and minor neurological disability [Expanded Disability Status Scale (EDSS) ≤ 2.5 at baseline]. Cognition (memory, executive functions, attention), behavior, handicap, and perceived health status were also investigated. Standardized change scores [(score at retest-score at baseline)/standard deviation of baseline score] were computed. Results showed that IGT performances decreased from baseline to retest (from 0.3, SD = 0.4 to 0.1, SD = 0.3, p = .005). MS patients who worsened in the IGT were more likely to show a decreased perceived health status and emotional well-being (SEP-59; p = .05 for both). Relapsing rate, disability progression, cognitive, and behavioral changes were not associated with decreased IGT performances. In conclusion, decline in decision making can appear as an isolated deficit in MS. (JINS, 2009, 15, 291-295.
The Agile Alert System For Gamma-Ray Transients
In recent years, a new generation of space missions offered great
opportunities of discovery in high-energy astrophysics. In this article we
focus on the scientific operations of the Gamma-Ray Imaging Detector (GRID)
onboard the AGILE space mission. The AGILE-GRID, sensitive in the energy range
of 30 MeV-30 GeV, has detected many gamma-ray transients of galactic and
extragalactic origins. This work presents the AGILE innovative approach to fast
gamma-ray transient detection, which is a challenging task and a crucial part
of the AGILE scientific program. The goals are to describe: (1) the AGILE
Gamma-Ray Alert System, (2) a new algorithm for blind search identification of
transients within a short processing time, (3) the AGILE procedure for
gamma-ray transient alert management, and (4) the likelihood of ratio tests
that are necessary to evaluate the post-trial statistical significance of the
results. Special algorithms and an optimized sequence of tasks are necessary to
reach our goal. Data are automatically analyzed at every orbital downlink by an
alert pipeline operating on different timescales. As proper flux thresholds are
exceeded, alerts are automatically generated and sent as SMS messages to
cellular telephones, e-mails, and push notifications of an application for
smartphones and tablets. These alerts are crosschecked with the results of two
pipelines, and a manual analysis is performed. Being a small scientific-class
mission, AGILE is characterized by optimization of both scientific analysis and
ground-segment resources. The system is capable of generating alerts within two
to three hours of a data downlink, an unprecedented reaction time in gamma-ray
astrophysics.Comment: 34 pages, 9 figures, 5 table
Successful neuropsychological rehabilitation in a patient with Cerebellar Cognitive Affective Syndrome
The objective of this case study was to describe the neuropsychological rehabilitation of a 16-year-old patient who presented a Cerebellar Cognitive Affective Syndrome (CCAS) following a bilateral cerebellar hemorrhage. The patient presented severe and diffuse cognitive deficits, massive behavioral disorders, and emotion regulation difficulties. The cognitive rehabilitation was performed in the chronic phase (one year after the onset of the hemorrhage) using a transdisciplinary neurobehavioral approach based on the patient's favorite interest (soccer). A significant behavioral and cognitive improvement was observed. The patient became progressively independent in all activities of daily living and was discharged home. The Functional Independence Measure at discharge was 124/126 (vs. 37/126 at entry). The patient was able to complete his schooling despite the mild cognitive and behavioral sequelae. This first description of the use of neurobehavioral therapy in a case of chronic CCAS suggests that (a) major clinical improvement can occur more than one year after the onset of the CCAS, showing the importance of long-term and intensive neurorehabilitation; and (b) when the cerebellum cannot properly play its regulator role in cognition, neuropsychological intervention through a behavioral and cognitive approach can be of great help by acting as an external modulator to help the patient regain control over himself
All-optical mode unscrambling on a silicon photonic chip
Propagation of light beams through scattering or multimode systems may lead
to randomization of the spatial coherence of the light. Although information is
not lost, its recovery requires a coherent interferometric reconstruction of
the original signals, which have been scrambled into the modes of the
scattering system. Here, we show that we can automatically unscramble four
optical beams that have been arbitrarily mixed in a multimode waveguide,
undoing the scattering and mixing between the spatial modes through a mesh of
silicon photonics Mach-Zehnder interferometers. Using embedded transparent
detectors and a progressive tuning algorithm, the mesh self-configures
automatically and reset itself after significantly perturbing the mixing,
without turning off the beams. We demonstrate the recovery of four separate 10
Gbits/s information channels, with residual cross-talk between beams of -20dB.
This principle of self-configuring and self-resetting in optical systems should
be applicable in a wide range of optical applications.Comment: 23 pages, 10 figure
Balanced bilinguals favor lexical processing in their opaque language and conversion system in their shallow language
Referred to as orthographic depth, the degree of consistency of grapheme/phoneme correspondences varies across languages from high in shallow orthographies to low in deep orthographies. The present study investigates the impact of orthographic depth on reading route by analyzing evoked potentials to words in a deep (French) and shallow (German) language presented to highly proficient bilinguals. ERP analyses to German and French words revealed significant topographic modulations 240–280 ms post-stimulus onset, indicative of distinct brain networks engaged in reading over this time window. Source estimations revealed that these effects stemmed from modulations of left insular, inferior frontal and dorsolateral regions (German > French) previously associated to phonological processing. Our results show that reading in a shallow language was associated to a stronger engagement of phonological pathways than reading in a deep language. Thus, the lexical pathways favored in word reading are reinforced by phonological networks more strongly in the shallow than deep orthography
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