Nonlinear mitigation on subcarrier-multiplexed PM-16QAM optical systems.

We report a comprehensive set of experimental, simulation and analytical results on the benefit of nonlinear mitigation strategies for multi-subcarrier (MSC) PM-16QAM transmission systems. First, we demonstrate ~9% maximum reach gain enabled by symbol-rate optimization (SRO) of MSC-PM-16QAM in a 31 channels WDM transmission experiment. Then, we demonstrate that, in the considered experimental scenario, the gain provided by digital backpropagation (DBP) over single-carrier (SC) transmission is similar to that achieved by SRO over MSC transmission. Furthermore, we show that the SRO phenomenon can be weakened after self-channel interference (SCI) removal through DBP. As a result, and due to DBP performance limitations in the experiment, the combined effect of SRO and DBP was found to enable only an additional 4% gain in maximum reach. Finally, we address the impact and symbol-rate dependence of nonlinear phase noise (NLPN) in MSC-PM-16QAM transmission, discussing on the NLPN mitigation capability of standard carrier phase estimation (CPE) and on respective gains that could be achieved through its enhanced mitigation.

Cerebellar compartments for the processing of kinematic and kinetic information related to hindlimb stepping.

We previously showed that proprioceptive sensory input from the hindlimbs to the anterior cerebellar cortex of the cat may not be simply organized with respect to a body map, but it may also be distributed to multiple discrete functional areas extending beyond classical body map boundaries. With passive hindlimb stepping movements, cerebellar activity was shown to relate to whole limb kinematics as does the activity of dorsal spinocerebellar tract (DSCT) neurons. For DSCT activity, whole limb kinematics provides a solid functional framework within which information about limb forces, such as those generated during active stepping, may also be embedded. In this study, we investigated this idea for the spinocerebellar cortex activity by examining the activity of cerebellar cortical neurons during both passive bipedal hindlimb stepping and active stepping on a treadmill. Our results showed a functional compartmentalization of cerebellar responses to hindlimb stepping movements depending on the two types of stepping and strong relationships between neural activities and limb axis kinematics during both. In fact, responses to passive and active stepping were generally different, but in both cases their waveforms were related strongly to the limb axis kinematics. That is, the different stepping conditions modified the kinematics representation without producing different components in the response waveforms. In sum, cerebellar activity was consistent with a global kinematics framework serving as a basis upon which detailed information about limb mechanics and/or about individual limb segments might be imposed.

Compatibility between coherent reflective burst-mode PON and TWDM-PON physical layers.

We discuss the compatibility between reflective PON architectures and the recently defined ITU-T G.989.1 TWDM-PON. Focusing on the upstream, we experimentally demonstrate that, by using burst-mode coherent detection at OLT, reflective PON can achieve the specification target set for TWDM-PON, without requiring precise wavelength accuracy at ONU. Compared to the companion ECOC 2013 paper, we investigate on the differential optical path loss (DOPL) issue, proposing a simple SOA gain control algorithm to achieve reliable transmission for DOPL up to 17 dB.

1306-km 20x124.8-Gb/s PM-64QAM transmission over PSCF with net SEDP 11,300 (b ∙ km)/s/Hz using 1.15 samp/symb DAC.

We demonstrated the transmission of a Nyquist-WDM signal based on PM-64QAM modulation in an EDFA-only submarine configuration composed of 54.4 km-long fiber spans: 20 channels at 124.8-Gb/s were propagated over 1306 km of low-loss pure-silica-core fiber (PSCF). Thanks to an aggressive digital spectral shaping, we achieved a raw spectral efficiency (SE) of 10.4 b/s/Hz, corresponding to 8.67 b/s/Hz net SE when considering a 20% FEC overhead. Transmitter DACs are operated at a record-low 1.15 samples/symbol, enabled by the insertion of advanced anti-alias filters. The achieved SE-times-distance product was 11,327 (b ∙ km)/(s ∙ Hz), the highest reported so far for PM-64QAM. Combining the experimental results with the performance predictions obtained using an analytical model of nonlinear propagation in uncompensated coherent optical systems (the so-called "GN-model"), we show that PM-64QAM is a realistic option for ultra-high capacity systems in the 1,000 km range, carrying up 40 Tb/s in the C-band.

The role of surgical treatment in the rehabilitation protocols of thoraco-lumbar spine injuries.

BACKGROUND: Rehabilitation is a crucial issue in the management of spinal cord injuries (SCI) but, in these patients, the primary treatment can bias the outcome of recovery protocols. AIM: Purpose of this paper is to review our case load in the treatment of surgical failures and to define the role of surgery in thoraco-lumbar injuries rehabilitation. PATIENTS AND METHODS: Between 2000 and 2009 seventy patients with post-traumatic paraplegia were referred to Surgical Department as rehabilitation was unfeasible due to inadequate spine injury treatment. Forty-six had had surgery, 24 were treated conservatively Twenty-five patients had a thoracic lesion, 9 a lumbar lesion and 36 a lesion of the thoraco-lumbar junction. A total of 44 surgical procedures were performed (by anterior, posterior or anterior-posterior). RESULTS: On postoperative imaging sagittal alignment was found good in 93% of cases and acceptable in 7%. All patients regained the sitting position within 5 days after surgery. Wound healing problems requiring revision were observed in 4 cases. Major complications were a cerebro spinal fluid (CSF) leakage and a massive pulmonary embolism case in the early post-op. CONCLUSIONS: Wrong primary treatment frequently leads to demanding revision procedures with increased risks for the patient and more than double costs for the health care system. Whatever the technique a stable spine is the target in surgery of SCI allowing a quick and effective rehabilitation without external orthosis.

The organization of cortical activity in the anterior lobe of the cat cerebellum during hindlimb stepping.

We recorded from over 280 single cortical neurons throughout the medial anterior lobe of the cat cerebellum during passive movements of the hindlimbs resembling stepping on a moving treadmill. We used three stepping patterns, unilateral stepping of either the ipsilateral or contralateral leg and bipedal stepping in an alternating gait pattern. We found that over 60% of the neurons, mostly Purkinje cells, responded to stepping of one or both legs, and over 40% to more than one type of stepping pattern. Responsive cells were distributed throughout the five anterior lobules, and the highest concentration was found in traditional hindlimb areas in lobules 2 and 3. A comparison of response waveforms showed that they are similar for neighboring cells in many parts of the cerebellar cortex, and they tend to form local blob-like groupings. Response patterns, i.e., relationship among responses to each stepping type, tended to be similar within a local group. The groupings extend further in the parasagittal dimension (up to about a third of a lobule) than in the transverse dimension (about 1 mm), and they may form functional modules. A principal component analysis also showed that the responses were composed of a four basis waveforms (principal components) that explained about 80% of the response waveform variance that were nearly identical to those derived from dorsal spinocerebellar tract (DSCT) responses to similar stepping movements. We reconstructed the locations of the recorded neurons on a 2D map of the cerebellar cortex showing the spatial distribution of responsive cells according to their response characteristics. We propose, on the basis of these results, that the sensory input to the cerebellum from the hindlimbs is distributed to multiple zones that may each contribute to a different component of cerebellar function.

Posterior lumbar fusion by peek rods in degenerative spine: preliminary report on 30 cases.

PURPOSE: Pre-curved peek rods to support posterior lumbar fusion have been available in the market since 4 years. Potential advantages using this new technology are increased load sharing on the anterior column promoting interbody fusion, reduced stress on bone-screw interface decreasing the rate of screw mobilization and, in the long term, reduced incidence of adjacent level disc degeneration. METHODS: The authors retrospectively reviewed 30 cases in which posterior fusion was supported by peek rods, analyzing early complications, rate of fusion and clinical outcome. RESULTS: At an average follow-up of 18 months, both clinical and radiographic results were satisfactory with only one case requiring surgical revision for a mechanical complication. CONCLUSIONS: The semi-rigid systems can now be considered a viable option in the lumbar degenerative disease, although clinical evaluations are necessary in the longer term.

Analytical results on channel capacity in uncompensated optical links with coherent detection.

Based on a recently introduced model of non-linear propagation, we propose analytical formulas for the capacity limit of polarization-multiplexed ultra-dense WDM uncompensated coherent optical systems at the Nyquist limit, assuming both lumped and ideally distributed amplification. According to these formulas, capacity fundamentally depends on the transmitted power spectral density and on the total optical WDM bandwidth, whereas it does not depend on symbol-rate. Also, capacity approximately decreases by 2 [bit/s/Hz] for every doubling of link length. We show examples of capacity calculations for specific ultra-long-haul links with different polarization-multiplexed (PM) constellations, i.e. ideal PM-Gaussian, PM-QPSK (quadrature-phase shift keying) and PM-QAM (quadrature amplitude modulation). We show that the launch power maximizing capacity is independent of link length and modulation format. We also discuss the usable range of PM-QAM systems and validate analysis with simulations.

Experimental validation of an analytical model for nonlinear propagation in uncompensated optical links.

Link design for optical communication systems requires accurate modeling of nonlinear propagation in fibers. This topic has been widely analyzed in last decades with partial successes in special conditions, but without a comprehensive solution. Since the introduction of coherent detection with electronic signal processing the scenario completely changed because this category of systems shows better performances in links without in-line dispersion management. This change to uncompensated transmission allowed to modify the approach in the study of nonlinear fiber propagation and in recent years a series of promising analytical models have been proposed. In this paper, we present an experimental validation over different fiber types of an analytical model for nonlinear propagation over uncompensated optical transmission links. Considering an ultra-dense WDM system, we transmitted ten 120-Gb/s PM-QPSK signals over a multi-span system probing different fiber types: SSMF, PSCF and NZDSF. A good matching was found in all cases showing the potential of the analytical model for accurate performance estimation that could lead to powerful tools for link design.

DNA replication control through interaction of E2F-RB and the origin recognition complex.

The E2F transcription factor and retinoblastoma protein control cell-cycle progression and DNA replication during S phase. Mutations in the Drosophila dE2F1 and dDP genes affect the origin recognition complex (DmORC) and initiation of replication at the chorion gene replication origin. Here we show that mutants of Rbf (an retinoblastoma protein homologue) fail to limit DNA replication. We also show that the dDP, dE2F1 and Rbf proteins are located in a complex with DmORC, and that dE2F1 and DmORC are bound to the chorion origin of replication in vivo. Our results indicate that dE2F1 and Rbf function together at replication origins to limit DNA replication through interactions with DmORC.

Performance evaluation of coherent WDM PS-QPSK (HEXA) accounting for non-linear fiber propagation effects.

Coherent-detection (CoD) permits to fully exploit the four-dimensional (4D) signal space consisting of the in-phase and quadrature components of the two fiber polarizations. A well-known and successful format exploiting such 4D space is Polarization-multiplexed QPSK (PM-QPSK). Recently, new signal constellations specifically designed and optimized in 4D space have been proposed, among which polarization-switched QPSK (PS-QPSK), consisting of a 8-point constellation at the vertices of a 4D polychoron called hexadecachoron. We call it HEXA because of its geometrical features and to avoid acronym mix-up with PM-QPSK, as well as with other similar acronyms. In this paper we investigate the performance of HEXA in direct comparison with PM-QPSK, addressing non-linear propagation over realistic links made up of 20 spans of either standard single mode fiber (SSMF) or non-zero dispersion-shifted fiber (NZDSF). We show that HEXA not only confirms its theoretical sensitivity advantage over PM-QPSK in back-to-back, but also shows a greater resilience to non-linear effects, allowing for substantially increased span loss margins. As a consequence, HEXA appears as an interesting option for dual-format transceivers capable to switch on-the-fly between PM-QPSK and HEXA when channel propagation degrades. It also appears as a possible direct competitor of PM-QPSK, especially over NZDSF fiber and uncompensated links.

Serum BLyS/BAFF predicts the outcome of acute hepatitis C virus infection.

B-lymphocyte stimulator/B activating factor (BLyS/BAFF) is a tumour necrosis factor-family cytokine that plays a key role in generating and maintaining the mature B-cell pool. BLyS/BAFF expression by macrophages is stimulated by interferon-gamma and interleukin-10, and its serum levels are increased in chronic hepatitis C (CHC). The aim of this study was to assess serum levels of BLyS/BAFF in patients with acute hepatitis C (AHC) and correlate them with disease outcome. We studied 28 patients with AHC (14 males, mean age 59.3 +/- 15 years), followed for at least 7 months since onset, comparing them with 86 CHC patients and 25 healthy blood donors (HBD). BLyS/BAFF levels were assessed at baseline (within 4 weeks of onset) and during follow-up. BLyS/BAFF median levels were significantly higher in AHC (1485 pg/mL) than in CHC (1058 pg/mL) and in HBD (980 pg/mL) (P < 0.001). BLyS/BAFF levels were higher in AHC patients evolving to chronicity (1980 pg/mL) than in those with a self-limited course (1200 pg/mL), (P = 0.02). By logistic regression analysis, higher BLyS/BAFF levels were independently associated with persistence of HCV infection (OR 29.7; 95% CI: 1.73-508.20). High serum levels of BLyS/BAFF at onset of AHC can predict its evolution to chronic infection.

Hyperbaric oxygen therapy in Plastic Surgery practice: case series and literature overview.

Hyperbaric oxygen therapy (HBOT) is the use of 100% oxygen at pressures more than atmospheric. Several approved applications and indications exist for HBOT in the literature. Non-healing wounds, such as diabetic and vascular insufficiency ulcers, have 1 Clinic of Plastic and Reconstructive Surgery, Department of Neurosciences, University Hospital of Padova, Padova, Italy 2 Department of Physiology, University of Padova, Padova, Italy Corresponding author: Ilaria Tocco-Tussardi, e-mail: ilaria.toccotussardi@gmail.com © Copyright 2019, CIC Edizioni Internazionali, Romabeen a major area of application, and the use of HBOT as an adjunct has been approved by several studies and trials. HBOT is also indicated for acute soft tissue infections like clostridial myonecrosis, necrotising soft tissue infections, as also for traumatic wounds, crush injury, compartment syndrome, and compromised skin grafts and flaps. Another major area of application of HBOT is radiation-induced wounds. With increasing availability of chambers and studies proving the benefits of use, HBOT should be considered as an essential part of the overall management strategy for plastic surgeons.

Heat-Resistant Aphanizomenon flos-aquae (AFA) Extract (Klamin®) as a Functional Ingredient in Food Strategy for Prevention of Oxidative Stress.

Microalgae are generally considered an excellent source of vitamins, minerals, and bioactive molecules that make them suitable to be introduced in cosmetics, pharmaceuticals, and food industries. Aphanizomenon flos-aquae (AFA), an edible microalga, contains numerous biomolecules potentially able to prevent some pathologies including age-related disorders. With the aim to include an AFA extract (Klamin®) as a functional ingredient in baked products, we investigated if its bioactive molecules are destroyed or inactivated after standard cooking temperature. The AFA extract was exposed to heat stress (AFA-HS), and no significant decrease in pigment, polyphenol, and carotenoid content was detected by spectroscopic analysis. Thermal stability of AFA-HS extract was demonstrated by thermogravimetric analysis (TGA), and no change in the morphology of the granules of the powder was noticed by SEM microscopic observation. By Folin-Ciocalteu, ORAC, and ABTS assays, no change in the antioxidant activity and polyphenol contents was found after high-temperature exposition. When added in cell culture, solubilized AFA-HS lost neither its scavenging ability against ROS generation nor its protective role against Abeta, the main peptide involved in Alzheimer's disease. Prebiotic and antioxidant activities of AFA extract that are not lost after thermal stress were verified on E. coli bacteria. Finally, AFA-HS cookies, containing the extract as one of their ingredients, showed increased polyphenols. Here, we evaluate the possibility to use the AFA extract to produce functional food and prevent metabolic and age-related diseases.

Comparison of neuronal activities of external cuneate nucleus, spinocerebellar cortex and interpositus nucleus during passive movements of the rat's forelimb.

In this paper we examined the neuronal activities of external cuneate nucleus, spinocerebellar Purkinje cells and interpositus nucleus during passive forelimb movements in anesthetized rats with the aim of identifying common or different patterns of activation across structures. By means of principal components analysis, we identified two main patterns of discharge which explained most of the dataset variance. One component characterized the movement-related activity of external cuneate and spinocerebellar cortical neurons, while the other reflected neuronal activity of the interpositus nucleus. We also found that both principal components were related to global forelimb kinematics but, while most of the variance of the activity of external cuneate cells and spinocerebellar Purkinje cells was explained by the limb axis orientation and orientation velocity, interpositus neurons' firing was best related to length and length velocity. This difference in the forelimb kinematics representation observed in external cuneate nucleus and spinocerebellar cortex compared with the interpositus nucleus is discussed with respect to the specific role that these structures may play also during active control of limb movements.

Performance evaluation and assessment of receiver impairments of a novel PolSK transceiver based on differential demodulation.

We present a novel transceiver setup for Polarization Shift Keying (PolSK) modulation using a simple transmitter and a receiver based on differential demodulation. The transmitter is made up of a LiNbO(3) phase modulator with the input fiber pigtailed at 45 degrees with respect to the principal axes of the modulator. The receiver is composed of an asymmetric Mach-Zehnder Interferometer (AMZI) and a couple of balanced photodetectors (BPD), as usually employed for receiving DPSK. To our knowledge, it is the first time such receiver structure is applied to PolSK. In order to fully assess the system performance of the proposed setup, we have carried out numerical simulations using a semi-analytical technique for bit-error-rate evaluation and performed experimental measurements at 10 Gbit/s. After having optimized transceiver performances, we evaluated the resilience to receiver impairments to verify the viability of a realistic implementation. Surprisingly, PolSK shows a better sensitivity using a single-end receiver (with the AMZI tuned at the minimum transmittance point) than using a balanced one. Another improvement has been obtained optimizing the driving voltage at the transmitter: this leads to a "non-ideal" PolSK modulation with non-orthogonal symbols, which shows an enhanced performance thanks to a synchronous phase modulation.

Fundamental performance limits of optical duobinary.

We present a rigorous analysis defining the fundamental performance limits of duobinary line-coding for optical communications. First, we compare the back-to-back performance of duobinary and intensity modulation systems in an AWGN channel satisfying the Nyquist criterion, with both linear and quadratic receiver. We show that, also for duobinary and quadratic receiver, matched filtering is the best achievable condition. Then, we derive a detailed performance analysis of duobinary in an ASE-noise-limited direct-detection optical system considering noise on the entire space of polarizations. We show that for duobinary line-coding the expression of the bit error rate depends both on the shape of the transmitted pulse and on the receiver optical filter. Comparing duobinary coded and uncoded intensity modulation systems, we show the intrinsic advantages of using the duobinary line-coding in a system based on quadratic detection. Finally, some results for realistic setups are obtained through simulation and compared to the fundamental limits in order to show how close to those limits state-of-the-art systems can operate.

Long-haul 10 Gbit/s linear and non-linear IMDD transmission over uncompensated standard fiber using a SQRT-metric MLSE receiver.

We experimentally demonstrated Intensity-Modulated Direct-Detection (IMDD) single-channel 1,040 km linear transmission and 800 km non-linear transmission at 10 Gb/s over standard single-mode (G.652) fiber, without any optical dispersion compensation or mitigation, using a Maximum-Likelihood Sequence-Estimation (MLSE) receiver employing the square-root (SQRT) branch metric with off-line processing. These experiments were designed as to probe the limits of the MLSE approach. They successfully showed that long-haul uncompensated transmission is in principle possible with MLSE, even in the presence of large uncompensated dispersion and strong intra-channel fiber non-linearities, provided that enough complexity can be built into the receiver. In the linear 1,040 km experiment, a Bit Error Rate (BER) of 10(-3) was achieved with an Optical Signal-to-Noise Ratio (OSNR) penalty with respect to back-to-back of 2.9 dB, using two samples per bit and 16,384 trellis states. Several other set-ups were tested as well, including the use of only one sample per bit and fewer trellis states. In the non-linear 800 km experiment, power was ramped up to 12 dBm, exciting substantial Kerr non-linearity, whose induced spectral-broadening exacerbated the effects of the large uncompensated dispersion of the link. Using an MLSE receiver with 1,024 states, we demonstrated a non-linear threshold of 9 dBm. We benchmarked this experiment towards simulations addressing various electrical and optical dispersion compensation strategies. We also carried out an analysis of error run-lengths, on both experiments, which showed that error burstiness may change considerably depending on the number of processor states, OSNR and the amount of non-linearity in the link.

Cerebellar cortical activity in the cat anterior lobe during hindlimb stepping.

We recorded from over 250 single cortical neurons throughout the medial anterior lobe of the cat cerebellum during passive movements of the ipsilateral hindlimb resembling stepping on a moving treadmill. We applied three different quantitative analysis techniques to determine the extent of neuronal modulation that could be accounted for by the stepping movements. The analyses all indicated that up to half the recorded neurons in all five lobules responded to these passive hindlimb movements. We reconstructed the locations of the recorded neurons on a 2-D map of the cerebellar cortex in order to determine the spatial distribution of responsive cells. Cells that were located in the classical hindlimb projection areas of the anterior lobe (in lobules 2 and 3) were generally most responsive to the limb movement with activity patterns that generally had a linear relationship to hindlimb kinematics. Cells in lobules 4 and 5, considered as classical forelimb areas of the cerebellum, were also responsive. Although these cells tended to have noisier firing patterns, many were found to be modulated nevertheless by the hindlimb movements. We also found a clear demarcation between zones b and c, with a higher fraction of responsive cells in all lobules located in zone b.