Short Block Research Articles

Improved PEG-Based Construction of Analog Fountain Codes.

This paper proposes an improved progressive edge-growth (PEG) construction of analog fountain codes (AFCs). During edge selection, it simultaneously allocates weight coefficients in descending order. Analysis shows that our proposed construction reduces the probability of large weight coefficients involved in harmful short cycles. Simulation results indicate that it has good block error rate (BLER) in short block length regime.

Development of novel interferometric system for short and long gauge block calibration

Abstract This paper presents the development of a novel multiwavelength Twyman–Green interferometer for gauge block (GB) calibration. In this work, a novel gauge block interferometer (GBI) for both short- and long-gauge block calibration at the SASO-NMCC was designed, built, tested, and described. The interferometer features an optomechanical modulation-based proprietary evaluation system, and the final length value was determined by applying Edlén’s equation to the refractive index of air. The developed interferometric system comprises two setups: one for short GB calibration, and the other for long GB calibration. The first short (GBI) setup utilizes two stabilized lasers, green and red, in vertical-mode operation. Another long GBI utilizes three stabilized lasers in the horizontal mode of operation. The primary characteristics of the interferometric system are explained. An uncertainty analysis with a careful study of the main components, such as wavelength standards, fringe fraction, temperature corrections, refractive index correction, obliquity correction, phase correction, block geometry correction, wavefront correction, and wringing correction, is presented. With interferometry, measurement method (ISO 3650 and ASME B89.1), using our described highly-precision horizontal mode system (GBI), we could achieve uncertainty level of ‘Q[49;0,28 l]nm l (mm)’ (k = 2) in the measurement range ‘125–1000 (mm)’. For the other system(GBI) for short gauge blocks, the associated uncertainty is ‘Q[30;0,27 l]nm l(mm)’ (k = 2) in the range of ‘0.5–100 (mm)’.

A path splitting and pruning strategy on list decoder for PAC codes

AbstractRecently, Arıkan proposed a polarization‐adjusted convolutional (PAC) codes, demonstrating their superior error correction performance over polar codes at short block lengths. It was confirmed that PAC codes approached the optimal performance achievable with limited code length. This paper proposes a novel low‐complexity list decoding algorithm for PAC codes, incorporating path splitting and pruning strategies based on a set of highly reliable information bits. Simulation results reveal that the proposed algorithm significantly reduces sorting complexity and average list size, all while incurring negligible performance loss. Unlike previous pruning algorithms designed for polar codes, the proposed strategy eliminates the need to individually assess the reliability of decoding paths in each decoding process. Instead, the algorithm minimizes redundant decoding paths through a high‐reliability information bit set, constructed using Monte Carlo experiments.

Evidence for biexponential glutamate T2 relaxation in human visual cortex at 3T: A functional MRS study.

Functional magnetic resonance spectroscopy (fMRS) measures dynamic changes in metabolite concentration in response to neural stimulation. The biophysical basis of these changes remains unclear. One hypothesis suggests that an increase or decrease in the glutamate signal detected by fMRS could be due to neurotransmitter movements between cellular compartments with different T2 relaxation times. Previous studies reporting glutamate (Glu) T2 values have generally sampled at echo times (TEs) within the range of 30-450 ms, which is not adequate to observe a component with short T2 (<20 ms). Here, we acquire MRS measurements for Glu, (t) total creatine (tCr) and total N-acetylaspartate (tNAA) from the visual cortex in 14 healthy participants at a range of TE values between 9.3-280 ms during short blocks (64 s) of flickering checkerboards and rest to examine both the short- and long-T2 components of the curve. We fit monoexponential and biexponential Glu, tCr and tNAA T2 relaxation curves for rest and stimulation and use Akaike information criterion to assess best model fit. We also include power calculations for detection of a 2% shift of Glu between compartments for each TE. Using pooled data over all participants at rest, we observed a short Glu T2-component with T2 = 10ms and volume fraction of 0.35, a short tCr T2-component with T2 = 26 ms and volume fraction of 0.25 and a short tNAA T2-component around 15 ms with volume fraction of 0.34. No statistically significant change in Glu, tCr and tNAA signal during stimulation was detected at any TE. The volume fractions of short-T2 component between rest and active conditions were not statistically different. This study provides evidence for a short T2-component for Glu, tCr and tNAA but no evidence to support the hypothesis of task-related changes in glutamate distribution between short and long T2 compartments.

Performance Analysis of NR Polar Codes at Short Information Blocks for Control Channels

Performance Analysis of NR Polar Codes at Short Information Blocks for Control Channels

An activity-specificity trade-off encoded in human transcription factors

Transcription factors (TFs) control specificity and activity of gene transcription, but whether a relationship between these two features exists is unclear. Here we provide evidence for an evolutionary trade-off between the activity and specificity in human TFs encoded as submaximal dispersion of aromatic residues in their intrinsically disordered protein regions. We identified approximately 500 human TFs that encode short periodic blocks of aromatic residues in their intrinsically disordered regions, resembling imperfect prion-like sequences. Mutation of periodic aromatic residues reduced transcriptional activity, whereas increasing the aromatic dispersion of multiple human TFs enhanced transcriptional activity and reprogramming efficiency, promoted liquid–liquid phase separation in vitro and more promiscuous DNA binding in cells. Together with recent work on enhancer elements, these results suggest an important evolutionary role of suboptimal features in transcriptional control. We propose that rational engineering of amino acid features that alter phase separation may be a strategy to optimize TF-dependent processes, including cellular reprogramming.

Oligoelectrolyte-mediated, pH-triggered release of hydrophobic drugs from non-responsive micelles: Influence of oligo(2-vinyl pyridine)-loading on drug-loading, release and cytotoxicity

pH-responsive polymeric micelles have been extensively studied for nanomedicine and take advantage of pH differentials in tissues for the delivery of large doses of cytotoxic drugs at specific target sites. Despite significant advances in this area, there is a lack of versatile and adaptable strategies to render micelles pH-responsive that could be widely applied to different payloads and applications. To address this deficiency, we introduce the concept of oligoelectrolyte-mediated, pH-triggered release of hydrophobic drugs from non-responsive polymeric micelles as a highly effective approach with broad scope. Herein, we investigate the influence of the oligoelectrolyte, oligo(2-vinyl pyridine) (OVP), loading and polymer molecular weight on the pH-sensitivity, drug loading/release and cytotoxicity of poly(ethylene glycol-b-ε-caprolactone) (PEG-b-PCL) micelles using copolymers with either short or long hydrophobic blocks (PEG4PCL4 and PEG10PCL10, respectively). The micelles were characterized as a function of pH (7.4 to 3.5). Dynamic light scattering (DLS) revealed narrow particle size distributions (PSDs) for both the blank and OVP-loaded micelles at pH 7.4. While OVP encapsulation resulted in an increase in the hydrodynamic diameter (Dh) (cf. blank micelles), a decrease in the pH below 6.5 led to a decrease in the Dh consistent with the ionization and release of OVP and core collapse, which were further supported by proton nuclear magnetic resonance (1H NMR) spectroscopy and UV–visible (UV–vis) spectrophotometry. The change in zeta potential (ζ) with pH for the OVP-loaded PEG4PCL4 and PEG10PCL10 micelles was different, suggesting that the location/distribution of OVP in the micelles is influenced by the polymer molecular weight. In general, co-encapsulation of drugs (doxorubicin (DOX), gossypol (GP), paclitaxel (PX) or 7-ethyl-10-hydroxycamptothecin (SN38)) and OVP in the micelles proceeded efficiently with high encapsulation efficiency percentages (EE%). In vitro release studies revealed the rapid, pH-triggered release of drugs from OVP-loaded PEG10PCL10 micelles within hours, with higher OVP loadings providing faster and more complete release. In comparison, no triggered release was observed for the OVP-loaded PEG4PCL4 micelles, implying a strong molecular weight dependency. In metabolic assays the drug- and OVP-loaded PEG10PCL10 micelles were found to result in significant enhancement of the cytotoxicity compared to drug-loaded micelles (no OVP) or other controls. Importantly, micelles with low OVP loadings were found to be nearly as effective as those with high OVP loadings. These results provide key insights into the tunability of the oligoelectrolyte-mediated approach for the effective formulation of pH-responsive micelles and pH-triggered drug release.

Block-length aware enumerative sphere shaping for probabilistic shaping optical transmission system.

Due to its large transmission capacity and low complexity, probabilistic shaping (PS) technology has been attracting increasing attention. The commonly used constant composition distribution matching (CCDM) in PS technology, which generates amplitude sequences with a fixed empirical distribution, exhibits higher rate loss for short block lengths. In this paper, we present a block-length aware enumerative sphere shaping (BA-ESS) designed to implement probability shaping within high-order modulation formats, which can transition between static (BA-ESS-S) and dynamic (BA-ESS-D) modes based on the block length. When dealing with short block lengths, it will be switched to the static mode. On the contrary, for longer block lengths, the algorithm will be transitioned to dynamic mode, which is a real-time coding method that effectively reduces storage complexity. We validate the transmission performance of this scheme through a 28 GBaud PS-64QAM simulation system and an 8 GBaud PS-64QAM transmission experiment. Through the analysis of simulation results, it can be observed that BA-ESS achieves handsome gains over ESS and optimum ESS (OESS). When all three schemes reach the NGMI threshold, for a block length of 40, BA-ESS provides OSNR gains of 0.88 dB and 0.34 dB compared to ESS and OESS, respectively. Additionally, experimental results indicate that for a block length of 20, the BA-ESS scheme offers an OSNR gain of 0.97 dB relative to ESS.

Sequence-agnostic motion-correction leveraging efficiently calibrated Pilot Tone signals.

This study leverages externally generated Pilot Tone (PT) signals to perform motion-corrected brain MRI for sequences with arbitrary k-space sampling and image contrast. PT signals are promising external motion sensors due to their cost-effectiveness, easy workflow, and consistent performance across contrasts and sampling patterns. However, they lack robust calibration pipelines. This work calibrates PT signal to rigid motion parameters acquired during short blocks (˜4 s) of motion calibration (MC) acquisitions, which are short enough to unobstructively fit between acquisitions. MC acquisitions leverage self-navigated trajectories that enable state-of-the-art motion estimation methods for efficient calibration. To capture the range of patient motion occurring throughout the examination, distributed motion calibration (DMC) uses data acquired from MC scans distributed across the entire examination. After calibration, PT is used to retrospectively motion-correct sequences with arbitrary k-space sampling and image contrast. Additionally, a data-driven calibration refinement is proposed to tailor calibration models to individual acquisitions. In vivo experiments involving 12 healthy volunteers tested the DMC protocol's ability to robustly correct subject motion. The proposed calibration pipeline produces pose parameters consistent with reference values, even when distributing only six of these approximately 4-s MC blocks, resulting in a total acquisition time of 22 s. In vivo motion experiments reveal significant ( ) improved motion correction with increased signal to residual ratio for both MPRAGE and SPACE sequences with standard k-space acquisition, especially when motion is large. Additionally, results highlight the benefits of using a distributed calibration approach. This study presents a framework for performing motion-corrected brain MRI in sequences with arbitrary k-space encoding and contrast, using externally generated PT signals. The DMC protocol is introduced, promoting observation of patient motion occurring throughout the examination and providing a calibration pipeline suitable for clinical deployment. The method's application is demonstrated in standard volumetric MPRAGE and SPACE sequences.

ATRIAL VOLTAGE ANALYSIS FOLLOWING VEIN OF MARSHALL ETHANOL INFUSION PREDICTS MITRAL LINE BLOCK

Abstract Background The vein of Marshall (VoM) is a promising target for atrial fibrillation (AF) treatment, matching with the ‘Coumel triangle‘ by housing triggers, autonomic connections, and serving as a substrate for perimitral flutters. Lateral mitral line (ML) represents a fundamental part for AF treatment, but achieving bidirectional block through endocardial ablations is challenging. VoM ethanol infusion (VOM–EI) facilitates ML block, with the newly–formed bipolar lesion serving as an effectiveness index. Voltage analysis assessment after VOM–EI in predicting ML block is poorly investigated. Purpose To compare unipolar and bipolar low–voltage areas (LVAs) along VOM trajectory after VOM–EI, and their role in predicting ML block. Methods We enrolled 59 patients undergoing catheter ablation of persistent AF or ML–dependent atrial flutter. High–density voltage mapping of left atrium was followed by VOM–EI and LA remapping. The area width difference was obtained and defined as ΔLVA. Normal bipolar voltage cutoffs were 0.50 mV in sinus rhythm or 0.29 mV in AF. Unipolar cutoffs were 2.7 mV and 1.1 mV, respectively. After VOM–EI, anatomical lesions included PVI, linear lesion for dome and ML isthmus. Systematic lines block validation was performed, defining ML block after coronary sinus (CS) electrograms sequence inversion (septal–to–lateral) during left atrial appendage pacing. Radiofrequency (RF) applications into the CS–great cardiac vein targeted epicardial gaps if present. Ablation time for ML block (AblTime) was obtained. Results In our cohort, 94.5% achieved ML block. Bipolar and unipolar low voltage areas after VOM–EI were 9,9 ± 6,9 cm2 and 12,2 ± 5,9 cm2 respectively. Bipolar ΔLVAs were significantly lower than unipolar ΔLVA (8.2 ± 6.5 cm2 vs. 9.4 ± 6.0 cm2; p=0.03) (Fig 1). A strong linear correlation between AblTime and bipolar ΔLVA (R: 0.76), and a significant correlation between AblTime and unipolar ΔLVA (R: 0.6) were found (Fig 2). Patients requiring RF applications into the CS for ML block (13/59, 22%) showed lower ΔLVAs in logistic regression for both bipolar (p&amp;lt;0.01) and unipolar (p=0.03) analyses. Conclusions VOM–EI induces unipolar LVAs wider than bipolar along the mitral isthmus trajectory. Unipolar and bipolar voltage analysis predicts a short time ML block achievement. Moreover, wider unipolar and bipolar LVAs following VOM–EI correlates with higher likelihood to avoid the targeting of epicardial gaps via the CS musculature.

Triblock Glycopolymers with Two 10-mer Blocks of Activating Sugars Enhance the Activation of Acrosomal Exocytosis in Mouse Sperm.

Carbohydrate recognition is imperative for the induction of sperm acrosomal exocytosis (AE), an essential phenomenon in mammalian fertilization. In mouse sperm, polynorbornene 100-mers displaying fucose or mannose moieties were effective at inducing AE. In contrast, glycopolymers exhibiting glucose sugars resulted in no AE activation. To further elucidate the role of ligand density on the activation of AE in mouse sperm, a triple-stain flow cytometry assay was employed to determine the efficacy of polynorbornene block copolymers with barbell-like sequences as initiators of AE. Triblock (ABA or ABC) copolymers were synthesized by ring-opening metathesis polymerization (ROMP) with one or two activating sugars, mannose or fucose, and one nonactivating sugar, glucose. The active ligand fractions in the polymers varied from 10, 20, or 40%. Simultaneously, random copolymers comprising 20% activating ligands were prepared to confirm the importance of ligand positionality in AE activation in mouse sperm. Polynorbornene 100-mers possessing two 10-mer blocks of activating sugars were the most effective copolymers at inducing AE with levels of AE comparable to their homopolymer counterparts and more effective than their random analogues. Small-angle X-ray scattering (SAXS) was then performed to verify that there were no differences in the conformations of the glycopolymers contributing to their varying AE activity. SAXS data analysis confirmed that all of the glycopolymers assumed semiflexible cylindrical structures with similar radii and Kuhn lengths. These findings suggest that the overall ligand density of the sugar moieties in the polymer is less important than the positionality of short blocks of high-density ligands for AE activation in mouse sperm.

Performance errors during rodent learning reflect a dynamic choice strategy

Humans, even as infants, use cognitive strategies, such as exploration and hypothesis testing, to learn about causal interactions in the environment. In animal learning studies, however, it is challenging to disentangle higher-order behavioral strategies from errors arising from imperfect task knowledge or inherent biases. Here, we trained head-fixed mice on a wheel-based auditory two-choice task and exploited the intra- and inter-animal variability to understand the drivers of errors during learning. During learning, performance errors are dominated by a choice bias, which, despite appearing maladaptive, reflects a dynamic strategy. Early in learning, mice develop an internal model of the task contingencies such that violating their expectation of reward on correct trials (by using short blocks of non-rewarded "probe" trials) leads to an abrupt shift in strategy. During the probe block, mice behave more accurately with less bias, thereby using their learned stimulus-action knowledge to test whether the outcome contingencies have changed. Despite having this knowledge, mice continued to exhibit a strong choice bias during reinforced trials. This choice bias operates on a timescale of tens to hundreds of trials with a dynamic structure, shifting between left, right, and unbiased epochs. Biased epochs also coincided with faster motor kinematics. Although bias decreased across learning, expert mice continued to exhibit short bouts of biased choices interspersed with longer bouts of unbiased choices and higher performance. These findings collectively suggest that during learning, rodents actively probe their environment in a structured manner to refine their decision-making and maintain long-term flexibility.

Molecular Simulation Study of the Kinetics and Mechanism of Micellization of Charged and Uncharged Block Copolymer in Aqueous Solution: Polystyrene-Block-Poly(acrylic acid) PS-b-PAA

The micellization kinetics, dynamics, and diffusional properties of poly(styrene)-block-poly(acrylic acid) copolymer chains in salt-free aqueous solution have been investigated as a function of the copolymer composition (XPS ) for the cases of un-ionized (charge density f = 0) and ionized PAA blocks (charge density f = 1), for the first time to our knowledge via atomistic molecular dynamic simulations. The micelle formation mechanism was inspected by tracking the population of unimers and clusters across the simulation trajectory; it confirmed that the asymmetric copolymer micelle formation followed a combined approach of unimer insertion and cluster fusion mechanisms, while symmetric micelle formation followed the unimer insertion method exclusively. Micelle formation took a longer time for copolymers having charged (ionized) PAA blocks (f > 0) and relatively short PS blocks (number fraction of PS repeat units in copolymer XPS < 0.5) due to the presence of a greater number of hydrophobic groups, in agreement with the micellization kinetics observed for model copolymer micelles via DPD (Dissipative Particle Dynamics) simulation studies in literature. The conformational dynamics were studied using the relaxation of backbone dihedral angles and radius of gyration, for the core and corona blocks, respectively, showed that the PS blocks relaxed slower as compared to the soluble PAA blocks in solution due to their hydrophobic nature. The conformational relaxation time increased linearly for the PS blocks and was invariant for the PAA blocks with respect to XPS. The interaction dynamics of the PS-b-PAA copolymer micelles studied via the relaxation times of the PAA-PAA inter-chain (τHB,PP) and PAA-water inter-molecular hydrogen bonds (τHB,PW) showed the increase of τHB,PP, and the decrease of τHB,PW in solution with the increase in XPS. The PAA-water H-bond relaxes slower at f = 1 than that at f = 0 due to the stronger affinity of ionized PAA units with water molecules. The diffusivity of the copolymer chains decreased exponentially with an increase in XPS value, which is in agreement with the theoretical and experimental observations described in the literature.

Evaluating the Douglas-Cohen IRT Goodness of Fit Measure With BIB Sampling of Items.

Methods to detect item response theory (IRT) item-level misfit are typically derived assuming fixed test forms. However, IRT is also employed with more complicated test designs, such as the balanced incomplete block (BIB) design used in large-scale educational assessments. This study investigates two modifications of Douglas and Cohen's 2001 nonparametric method of assessing item misfit, based on A) using block total score and B) pooling booklet level scores for analyzing BIB data. Block-level scores showed extreme inflation of Type I error for short blocks containing 5 or 10 items. The pooled booklet method yielded Type I error rates close to nominal in most conditions and had power to detect misfitting items. The study also found that the Douglas and Cohen procedure is only slightly affected by the presence of other misfitting items in the block. The pooled booklet method is recommended for practical applications of Douglas and Cohen's method with BIB data.

Balancing ensemble averaging and signal stationarity when processing acoustic data recorded during a rocket launch

There are many important details to consider when collecting acoustical data during a rocket launch including system noise floor, dynamic range and transducer sensitivity. In this talk, the choice of signal processing parameters will also be shown to be important. Since the pressures are created by turbulence, ensemble averaging is key to reducing random variation. As such, the use of a Hanning window with 50% overlap would be customary for performing this type of processing. However, as the rocket lifts off, the source location moves, and the data can only be considered stationary for short blocks of time. Therefore, the ability to average is limited by non-stationarity. To balance these competing phenomena, an adjustable windowing function such as the Tukey window may be more appropriate than Hanning. Noise data collected at two different launches will be used to compare of the Hanning window with 50% overlap to that using of the Tukey window with a taper of α = 0.25, which filters 12.5% of the signal at each extremity, with 87.5% overlap. The use of both window types will be compared when estimating auto spectral densities and integrated overall levels. The effect of blocksize will also be determined.

Low-Viscosity Route to High-Molecular-Weight Water-Soluble Polymers: Exploiting the Salt Sensitivity of Poly(N-acryloylmorpholine).

We report a new one-pot low-viscosity synthetic route to high molecular weight non-ionic water-soluble polymers based on polymerization-induced self-assembly (PISA). The RAFT aqueous dispersion polymerization of N-acryloylmorpholine (NAM) is conducted at 30 °C using a suitable redox initiator and a poly(2-hydroxyethyl acrylamide) (PHEAC) precursor in the presence of 0.60 M ammonium sulfate. This relatively low level of added electrolyte is sufficient to salt out the PNAM block, while steric stabilization is conferred by the relatively short salt-tolerant PHEAC block. A mean degree of polymerization (DP) of up to 6000 was targeted for the PNAM block, and high NAM conversions (>96%) were obtained in all cases. On dilution with deionized water, the as-synthesized sterically stabilized particles undergo dissociation to afford molecularly dissolved chains, as judged by dynamic light scattering and 1H NMR spectroscopy studies. DMF GPC analysis confirmed a high chain extension efficiency for the PHEAC precursor, but relatively broad molecular weight distributions were observed for the PHEAC-PNAM diblock copolymer chains (Mw/Mn > 1.9). This has been observed for many other PISA formulations when targeting high core-forming block DPs and is tentatively attributed to chain transfer to polymer, which is well known for polyacrylamide-based polymers. In fact, relatively high dispersities are actually desirable if such copolymers are to be used as viscosity modifiers because solution viscosity correlates closely with Mw. Static light scattering studies were also conducted, with a Zimm plot indicating an absolute Mw of approximately 2.5 × 106 g mol-1 when targeting a PNAM DP of 6000. Finally, it is emphasized that targeting such high DPs leads to a sulfur content for this latter formulation of just 23 ppm, which minimizes the cost, color, and malodor associated with the organosulfur RAFT agent.

Integrity of Melamine Formaldehyde Bonds in Ponderosa Pine Cross-Laminated Timber: Isolating Adhesive Compatibility Effect

Abstract The integrity of melamine formaldehyde bonds in prototype cross-laminated timber (CLT) specimens was tested as part of a project on utilization of ponderosa pine (Pinus ponderosa) from forest restoration programs in the western United States. Bond integrity tests, block shear, and cyclic delamination are prescribed by ANSI/APA PRG-320 (ANSI/APA 2019) and ANSI 405 (ANSI 2018) to qualify new products. Of these, the cyclic delamination criterion is particularly challenging for layups developed in research labs and pilot plants. Delamination is often blamed on poor compatibility between adhesive and wood species, clamping pressure, or distribution of adhesive, neglecting other potential factors. One of the study objectives was to separate the effect of adhesive compatibility from other potential factors affecting bond integrity in CLT. Bonding integrity tests were conducted on prototype specimens bonded with melamine formaldehyde adhesive. Three types of specimens were studied: (1) specimens harvested from panels fabricated in an industrial CLT plant, (2) specimens harvested from panels fabricated in a pilot-line, and (3) short blocks cross-laminated from 102 by 102-mm sections. The short blocks included sections with juvenile wood and blue stain on bonded surfaces. All samples passed the PRG-320 block shear criteria. All short blocks passed the delamination criterion, demonstrating sufficient adhesive compatibility with the surfaces regardless of heavy presence of blue stain and juvenile wood. Specimens harvested from panels did not meet the delamination criterion. Delaminations developed near preexisting interlaminar gaps observed in prototype panels, which may be related to thickness variation or to inconsistent clamping pressure.

A Study on Determining the Optimal Feedback Rate in Distributed Block Diagonalization with Limited Feedback for Dense Cellular Networks

In this study, we explore a downlink cellular network where each base station (BS) engages in simultaneous communication with multiple users through spatial division multiple access (SDMA). The positions of both BSs and users are established through independent random point processes, effectively representing the cellular network. SDMA utilizes block diagonalization (BD) at each BS, employing multiple receive antennas for each user. To implement BD, users quantize and provide feedback on their downlink channels to their respective BSs. The net spectral efficiency, measuring the effective rate accounting for both downlink and uplink resource usage, serves as a performance metric. In prior research, the optimal feedback rate in terms of maximizing net spectral efficiency has been approximated in this scenario. The corresponding approximations effectively illustrate the asymptotic behavior of the optimal number as a function of the length of the coherent channel block. However, the accuracy of the approximation diminishes when the length of the coherent channel block is relatively small. Given that the length of the coherent channel block can assume relatively small values depending on wireless environments, achieving a precise estimate across the entire range of the coherent block length holds significant importance. Consequently, this paper focuses primarily on enhancing the accuracy of the approximation for the optimal feedback rate. In order to achieve a more precise estimation, we analyze the derivative of the net spectral efficiency, which encompasses two functions that demonstrate distinct growth rates. In contrast to prior studies, both functions are rigorously approximated through mathematical analysis. As a result, the proposed approximation significantly improves the accuracy compared to previous studies, particularly when dealing with short coherent channel block lengths. Moreover, this approximation generally achieves near-optimal performance, regardless of system parameters.

Biocompatible polyurethanes with thermally-induced shape memory properties derived from three-arm branched poly(ε-caprolactone-co-γ-butyrolactone)-b-poly(lactide) block copolymers

A series of poly(lactide)-based polyurethanes with cross-linked network structure was synthesized through the chain extension of three-arm branched poly(ε-caprolactone-co-γ-butyrolactone)-b-poly(lactide) (3PBCL-b-PLA) block copolymers with various molecular weights and optical activities of PLA blocks. The structure of the synthesized poly(lactide)-based polyurethanes was analyzed, and it was confirmed that they contained the cross-linked network structure. Effects of the molecular weight and optical activity of PLA block on the various properties such as crystallization, mechanical property, shape memory performance, thermal stability and hydration ability were discussed. By simultaneously adjusting the molecular weight and optical activity of PLA blocks, the crystallization of flexible PCBL blocks and rigid PLA blocks in the synthesized cross-linked polyurethanes was effectively controlled, which was the basis for constructing poly(lactide)-based polyurethanes with a broad ranged mechanical property, excellent shape memory properties and controllable hydration ability. The synthesized polyurethanes exhibited adjusted tensile strength and elongation at break in the range of 11.2–32.4 MPa and 41–753 %, with the water content varying from 1.1 % to 20.1 %, respectively. The shape fixity ratio and shape recovery ratio of L-PU2.9 could reach 90.9 % and 96.0 %, respectively. The effect of stereocomplex-crystallization on the properties of poly(lactide)-based polyurethane was also analyzed. Stereocomplexed polyurethane based on 3PCL-b-PLA block copolymer enantiomers with short PLA block was constructed, which achieves fully stereocomplexation in a wide mixing ratio (20–50 %). It was found that the formation of a small number of stereocomplex-crystals can change the properties of poly(lactide)-based polyurethane in a wide range. Eventually, it was demonstrated by in vitro hemolysis test, cytotoxicity test and live/death staining that the synthetic poly(lactide)-based polyurethanes exhibited excellent biocompatibility. These results suggested that these biocompatible shape memory poly(lactide)-based polyurethanes with tunable mechanical properties and hydration ability demonstrated the promising potential as an excellent implantation for biomedical application.

Disentangling the dynamic interplay between muscle damage and energetics in male boxers during a short training block.

Boxing is a combat sport linked to muscle damage (e.g., soreness, rising creatine kinase [CK]) and energetic biomarkers (e.g., urea, glucose). These factors have not, however, been examined dynamically in terms of day-to-day, lagged and reciprocal effects during normal training. This study investigated the dynamic interplay between muscle damage and energetics in male boxers during a short training block. Thirteen amateur boxers were monitored over 16 consecutive days during early-season training. The participants were assessed each morning for plasma CK, urea, glucose, and creatinine (days 1 and 16 only) concentrations, before self-reporting muscle soreness (1-10 scale). Within-person contemporaneous (lag-0) and temporal (lag-1) networks were estimated using multilevel vector autoregression. Muscle soreness, CK, urea, and glucose presented different trajectories with training, but with some heterogeneity reflecting within-person variances (47% to 78%). The contemporaneous network yielded a significant positive edge (or correlation) between CK and soreness (r = 0.44), along with negative CK-glucose and glucose-urea edges. More significant edges emerged in the temporal network, with soreness linked to CK (r = 0.19), glucose (r = -0.28) and urea (r = 0.22), whilst the CK-glucose edge sign switched. In summary, daily fluctuations in muscle damage and energetic activity, which presented in a normal physiological range, were highly variable among boxers during early-season training. Within-person networks indicated some interrelatedness between CK, soreness, urea, and glucose, although the nature and presence of these relationships were contingent on temporal ordering. These inconsistences reflect the pleiotropy of energetic biomarkers in training and recovery.