Intact Units Research Articles

Rocking of single-layer armour units measured by embedded sensors

Single layer randomly placed armour units are used in many rubble mound breakwaters around the world. For these armour layers first extraction of units starts at high loads and can then progress quickly. Before the first extraction of a unit, typically no quantitative description of damage can be given. But additional to extraction, breakage of armour units due to rocking could be a major damage mechanism. This paper treat novel embedded Rocking Sensors. The technique is used to obtain the first measurements of rocking-impact velocities of single-layer units. They are also the first tests where the instrumented units can naturally move with the compacting layer during storm build-up. Physical model tests were performed on an armour layer with XBloc units. With 8 to 10 instrumented units per test run, in total 640 single measurements of the rocking motion of a unit during a 1200 wave test run were obtained, for three water levels and five wave heights. From the Rocking Sensors the number of impacts and rotational impact velocities were obtained. From an image analysis the along-slope settlement of the units during the tests was quantified. The rotational motion expressed by was found to be most convenient to express the motion. It can be seen that the units in the armour layer rock much more often than visually observed. Settlement seems to be a continuous progress, with most units rocking intermittently. Highest impact velocities are seen to occur around the water line, and in the uprush phase of the waves. A maximum impact velocity for all tests of 0.34 m/s (model scale) was measured. A preliminary design expression for rocking impact velocities of single layer units (Xblocs) is given. The paper shows that novel measurement techniques like the Rocking Sensors and vision techniques can and should be used to quantify damage mechanisms to rubble mound single-layer armour, additional to counting the extracted number of intact units.

Super-resolution microscopy reveals focal organization of ER-associated Y-complexes inmitosis.

During mitotic entry of vertebrate cells, nuclear pore complexes (NPCs) are rapidly disintegrated. NPC disassembly is initiated by hyperphosphorylation of linker nucleoporins (Nups), which leads to the dissociation of FG repeat Nups and relaxation of the nuclear permeability barrier. However, less is known about disintegration of the huge nuclear and cytoplasmic rings, which are formed by annular assemblies of Y-complexes that are dissociated from NPCs as intact units. Surprisingly, we observe that Y-complex Nups display slower dissociation kinetics compared with other Nups during in vitro NPC disassembly, indicating a mechanistic difference in the disintegration of Y-based rings. Intriguingly, biochemical experiments reveal that a fraction of Y-complexes remains associated with mitotic ER membranes, supporting recent microscopic observations. Visualization of mitotic Y-complexes by super-resolution microscopy demonstrates that they form two classes of higher order assemblies: large clusters at kinetochores and small, focal ER-associated assemblies. These, however, lack features qualifying them as persisting ring-shaped subassemblies previously proposed to serve as structural templates for NPC reassembly during mitotic exit, which helps to refine current models of nuclear reassembly.

Covalent triazine framework featuring single electron Co2+ centered in intact porphyrin units for efficient CO2 photoreduction

Covalent triazine frameworks (CTFs) are porous materials constructed by the trimerization of aromatic nitriles. They have frequently been utilized in heterogeneous catalysis due to rich nitrogen sites, excellent stability and porosity. In the past decade, many methods have been developed to synthesize CTFs, however, the roles of structural differences of CTFs synthesized by different methods in catalytic performance remain unclear. Herein, we synthesized two Co porphyrin-based CTFs using same porphyrin monomer by different approaches. CTF-TfOH-Co formed by trifluoromethanesulfonic acid vapor catalysis retains original porphyrin units, and Co (active catalytic sites) feature single electrons. In contrast, CTF-ZnCl2-Co synthesized by the ionothermal method no longer preserves the original porphyrin units, and the Co sites have no single electrons. CTF-TfOH-Co exhibits efficient photocatalytic activity for CO2 reduction with a CO yield rate of 2562.8 μmol g-1h−1, which greatly exceeds that of CTF-ZnCl2-Co. Those results highlight that the integrity of the porphyrin units and the electronic state of Co significantly are vital to their photocatalytic performance. Steady-state photoluminescence tests confirm that CTF-TfOH-Co has a better ability to separate photogenerated electron-hole pairs than CTF-ZnCl2-Co, which accounts for its superior photoreduction performance.

Oligomerization of an ansa-ferrocene with pyrazabole bridge

ansa-Ferrocenes with pyrazabole bridges are chemically robust entities and therefore suitable building blocks for the synthesis of rigid-rod polymers that combine redox-active Fe(II) centers and beltene-like π faces. The specific monomers we developed bear OEt groups at both tetracoordinated boron atoms (for solubility reasons) and ethynyl substituents at the 4-positions of the two pyrazole rings. Polymerization was accomplished by a condensation reaction with 1,4-diiodobenzene using a Sonogashira–Hagihara-type protocol. As a result, oligomers with a number-average molecular weight of Mn = 7.6 kDa and dispersity of Ð = 1.55 were obtained, suggesting an average chain length of about 14 repeating units based on gel permeation chromatography analysis in THF relative to narrow polystyrene standards. The molecular weight determination was complemented by MALDI-TOF mass spectrometry and (heteronuclear) NMR spectroscopy to verify the intact pyrazabole monomer repeat units and the nature of the end groups. The oligomers were further characterized by UV–vis spectroscopy and cyclic voltammetry, which demonstrated the successful synthesis of a new class of redox-active materials.

Sustainable Selective Propanol Production via Continuous Flow Conversion of Glycerol over Synergistic Bifunctional Catalysts: An Exploration into Factors Affecting Activity

AbstractSelective hydrogenolysis of glycerol to propanol is a sustainable reaction, which can play a critical role in the future of the propylene market, as one step dehydration of this sustainable propanol provides access to sustainable propylene. In this work, Copper (Cu) – Tungstosilicic acid (HSiW) catalysts were studied for the hydrogenolysis of glycerol. For the first time over a Cu catalyst, this study reports a yield of ∼76 % for direct conversion of glycerol to propanols in continuous flow mode. Several advanced characterization techniques were employed to study the fresh and used catalysts. The presence of intact Keggin units of HSiW solid acid (with medium acidity) in the vicinity of small clusters of copper sites improved the performance and lifetime of these bifunctional catalysts. This study offers insights into the nature of the active sites required for the hydrogenolysis reaction, which was achieved without using expensive PGMs.

Application of a novel constitutive model to evaluate the shear deformation of discontinuity

Landslides are one of the most common geological disasters with the complicated spatiotemporal processes, which can be partially reproduced in slip shear failure along the discontinuity in laboratory tests. However, the assessment and evaluation of shear behavior along the discontinuity is time-consuming and high-cost. To solve this problem, a new constitutive model is proposed to predict the shear deformation behavior of the discontinuity. In this model, the discontinuity is assumed to be composed of intact units and failed units. In the shearing process, intact units and failed units jointly bear the external loads, and intact units are gradually transformed into failed units. A damage control variable is introduced to link the mechanical response of units with the macroscopic discontinuous deformation, thereby obtaining the final expression of the new model. The model parameters can be determined directly from several standard laboratory shear tests. Subsequently, the comparison analysis among the predictive results of the new model, previous models and engineering projects is conducted. Finally, the sensitivity of model parameters is systematically discussed. A hardening index HI is proposed to characterize the shear deformation characteristics in the hardening stage, and its relationship with model parameters C and r is in a power form. The results are expected to provide theoretical guidance for landslide prediction and thus reduce the occurrence frequency of geohazards.

Latinx adolescent migrant challenges in reuniting with family members

Family reunification occurs when migrants relocate without intact family units, and later reunite in new countries. Family serial migration and reunification is a global issue, relating to both voluntary and involuntary migrants who seek physical safety, psychological well-being, and economic self-sufficiency in new countries. Early studies alluded to a joyful family reconsolidation, while recent studies have found stressful reunions. This study provides an overview of the family reunification process of Latinx adolescents who have migrated to join their families in the United States (U.S.). The study conducted detailed interviews of 20 Latinx adolescents, aged 12–18 years old, in order to provide an in-depth examination of their pre and postmigration experiences. The results reveal three phases of family reunification: Latinx adolescents’ experiences after their parent(s) left to migrate to the U.S.; their own migration journey to the U.S.; and their family reunification, adaptation, and adjustment to the U.S. The findings suggest that it is essential for mental health professionals to understand and acknowledge the multiple psychosocial challenges of Latinx adolescents’ reuniting with their families in a new country. This includes feelings of abandonment and grief after their parent(s) departure to the U.S., their own migration journey to the U.S. which may have been experienced as traumatic, and psychosocial challenges in adjustment and adaptation in the U.S. after family reunification.

Development of Klebsiella pneumoniae Capsule Polysaccharide-Conjugated Vaccine Candidates Using Phage Depolymerases.

Klebsiella pneumoniae is an important pathogen associated with nosocomial infection and has developed increasing resistance to antibiotics such as extended-spectrum β-lactams and carbapenem. In recent years, K. pneumoniae isolates have emerged as a major cause of global community-acquired infections such as pneumonia and pyogenic liver abscess. Although serotypes K1 and K2 have been identified as the predominant capsular types associated with invasive infections, no K. pneumoniae vaccine is commercially available, probably due to immunogenicity loss in the traditional depolymerization method to obtain capsule polysaccharide (CPS) for the preparation of conjugated vaccine. In this study, we successfully retained immunogenicity by using K1 (K1-ORF34) and K2 (K2-ORF16) CPS depolymerases that were identified from phages to cleave K1 and K2 CPSs into intact structural units of oligosaccharides with intact modifications. The obtained K1 and K2 oligosaccharides were separately conjugated with CRM197 carrier protein to generate CPS-conjugated vaccines. Immunization experiments of mice showed both K1 and K2 CPS-conjugated vaccines induced anti-CPS antibodies with 128-fold and 64-fold increases of bactericidal activities, respectively, compare to mice without vaccinations. Challenge tests indicated that K1 or K2 CPS-conjugated vaccine and divalent vaccine (a mixture of K1 and K2 CPS-conjugated vaccines) protected mice from subsequent infection of K. pneumoniae by the respective capsular type. Thus, we demonstrated K1 and K2 CPS-conjugated vaccines prepared by CPS depolymerases is a promising candidate for developing vaccines against human K. pneumoniae infections.

Simulated grazing and nitrogen addition facilitate spatial expansion of Leymus chinensis clones into saline‐alkali soil patches: Implications for Songnen grassland restoration in northeast China

AbstractThe spatial expansion characteristic of most clonal plant species makes them produce large networks by elongating rhizomes/stolons, and occupy more physical space; thus it could contribute to restoring patchy degraded grasslands. Grazing and fertilization may affect the expansion of clonal plants, and thus can affect the vegetation recovery of degraded grassland. However, these have never been tested under field conditions. A field study was conducted from 2014 to 2019 to evaluate the effects of simulated moderate grazing (SG) and nitrogen (N) addition on spatial expansion of Leymus chinensis, a widespread clonal plant species in the eastern part of the Eurasian steppe. Results showed that SG and N addition increased the number of L. chinensis ramets (small but intact modules units of this plants and with its own roots) growing in saline‐alkali soil patches; moreover, SG increased the total rhizome length and bud density of these ramets across the years by 59% and 52%, and N addition increased them by 88% and 98%, respectively. SG and N addition also increased the community biomass of the saline‐alkali soil patches by 27% and 74%, respectively. Under SG conditions, more biomass of L. chinensis was allocated to belowground organs, and to ramets growing in saline‐alkali soil patches. The findings demonstrated that both SG and N addition improved the spatial expansion of L. chinensis from favourable patches into saline‐alkali soil patches, thereby potential ramet recruitment and vegetation reconstruction. Moderate grazing management or fertilization could improve the restoration of patchy degraded grasslands by affecting the spatial expansion of clonal plants.

Multi-disciplinary characterizations of the BedrettoLab – a new underground geoscience research facility

Abstract. The increased interest in subsurface development (e.g., unconventional hydrocarbon, engineered geothermal systems (EGSs), waste disposal) and the associated (triggered or induced) seismicity calls for a better understanding of the hydro-seismo-mechanical coupling in fractured rock masses. Being able to bridge the knowledge gap between laboratory and reservoir scales, controllable meso-scale in situ experiments are deemed indispensable. In an effort to access and instrument rock masses of hectometer size, the Bedretto Underground Laboratory for Geosciences and Geoenergies (“BedrettoLab”) was established in 2018 in the existing Bedretto Tunnel (Ticino, Switzerland), with an average overburden of 1000 m. In this paper, we introduce the BedrettoLab, its general setting and current status. Combined geological, geomechanical and geophysical methods were employed in a hectometer-scale rock mass explored by several boreholes to characterize the in situ conditions and internal structures of the rock volume. The rock volume features three distinct units, with the middle fault zone sandwiched by two relatively intact units. The middle fault zone unit appears to be a representative feature of the site, as similar structures repeat every several hundreds of meters along the tunnel. The lithological variations across the characterization boreholes manifest the complexity and heterogeneity of the rock volume and are accompanied by compartmentalized hydrostructures and significant stress rotations. With this complexity, the characterized rock volume is considered characteristic of the heterogeneity that is typically encountered in subsurface exploration and development. The BedrettoLab can adequately serve as a test-bed that allows for in-depth study of the hydro-seismo-mechanical response of fractured crystalline rock masses.

Impaired function of rDNA transcription initiation machinery leads to derepression of ribosomal genes with insertions of R2 retrotransposon.

Eukaryotic genomes harbor hundreds of rRNA genes, many of which are transcriptionally silent. However, little is known about selective regulation of individual rDNA units. In Drosophila melanogaster, some rDNA repeats contain insertions of the R2 retrotransposon, which is capable to be transcribed only as part of pre-rRNA molecules. rDNA units with R2 insertions are usually inactivated, although R2 expression may be beneficial in cells with decreased rDNA copy number. Here we found that R2-inserted rDNA units are enriched with HP1a and H3K9me3 repressive mark, whereas disruption of the heterochromatin components slightly affects their silencing in ovarian germ cells. Surprisingly, we observed a dramatic upregulation of R2-inserted rRNA genes in ovaries lacking Udd (Under-developed) or other subunits (TAF1b and TAF1c-like) of the SL1-like complex, which is homologues to mammalian Selective factor 1 (SL1) involved in rDNA transcription initiation. Derepression of rRNA genes with R2 insertions was accompanied by a reduction of H3K9me3 and HP1a enrichment. We suggest that the impairment of the SL1-like complex affects a mechanism of selective activation of intact rDNA units which competes with heterochromatin formation. We also propose that R2 derepression may serve as an adaptive response to compromised rRNA synthesis.

Enhancing the resilience of Zostera noltei seagrass meadows against Arenicola spp. bio-invasion: A decision-making approach

Seagrass meadows provide important and valuable ecosystem services. They are affected by several natural and human-induced stressors, but a combination of natural recovery and management actions have recently inverted the worldwide reduction. The main objectives of this study were to provide science-based knowledge on ecology and restoration, framed on environmental-related policies. By coupling the general guidelines with practical experience, obtained from sequential in situ experiments carried out for several months in a show-case study area, this study provides guidelines useful for restoration practitioners. A decision-making approach is proposed to answer the following questions: 1) What is the best Zostera noltei transplanting method? 2) What is the best technique to reduce the bioturbation activity of Arenicola spp.?, 3) Do bioturbation reduction techniques affect the survival rate of Z. noltei transplants?, and finally, 4) What are the key steps to maximize the success of a Z. noltei transplant and increase the species’ resilience? Having a Portuguese coastal lagoon as show-case (Mira Channel, Ria de Aveiro), different transplant and restoration methodologies were tested (i.e. metal frames, nails, bamboo sticks, shoots inserted unanchored into the sediment, and intact units of sediment with seagrasses, named as SODs) to assure low environmental impact on donor meadows, high survival rate of transplanted shoots and the recovery of fragmented or lost meadows. Moreover, to potentially reverse a degraded Arenicola spp. colonized seagrass habitat, different types of natural membranes were tested. Results showed that the best transplanting method is the use of SODs as the self-facilitation process of Z. noltei is enhanced, while being the least invasive for the donor population. The use of a natural membrane can significantly decrease the bioturbation stress caused by Arenicola spp., with jute membrane being the best option, given its cost-handling-benefit trade-offs. Enhancing the success of seagrass restoration requires the implementation of effective measures by environmental restoration practitioners. We defined a three-step process to improve the resilience of Z. noltei. This stepwise approach consists on 1) Characterization of the donor population, 2) Identification of the constraints and implementation of measures to prevent them, and 3) Scale-up the restoration plan. The application of this stepwise approach in intertidal coastal and estuarine systems management will, therefore, facilitate the success of Z. noltei restoration plans.

Graphitic carbon nitride nanosheets via acid pretreatments for promoted photocatalysis toward degradation of organic pollutants

Acid treatment serves as an effective engineering strategy to modify the structure of graphitic carbon nitride (g-C3N4) for enhanced metal-free photocatalysis, while their lacks a comprehensive understanding about the impacts of different acid species and acid treatment approaches on the intrinsic structure and properties of g-C3N4 and structure–activity relationships are ambiguous. Employing inorganic/organic acids including hydrochloric acid (HCl), nitric acid (HNO3), acetic acid (HAc), sulphuric acid (H2SO4), or oxalic acid (H2C2O4) as treatment acids, herein, we compare the impacts of different acid pretreatment approaches on the structure and properties of g-C3N4. Due to different acid-melamine interaction modes and the activation roles of various acids, the obtained g-C3N4 samples exhibit varied structures, physiochemical properties and photocatalytic activities. Compared with bulk graphitic carbon nitride (BCN), g-C3N4 prepared by acid pretreatment show enhanced photocatalytic performance on bisphenol A (BPA) degradation. The photocatalytic degradation rates of BPA by g-C3N4 prepared by HNO3, HAc, H2SO4, H2C2O4, or HCl pretreatment are about 2.2, 2.7, 2.8, 3.2 and 3.8 folds faster than that by BCN. HCl pretreatment proves to be the optimal approach, with the derived g-C3N4 (HTCN) showing more intact heptazine structural units, and increased specific surface area, which promote the exposure of more active sites, accelerate charge transfer, and give rise to a notable improvement in photocatalysis, eventually. Mechanistic investigations through quenching experiments and electron paramagnetic resonance (EPR) characterization unveil that superoxide ion radical (O2−) and photo-induced holes (h+) worked principally in the photodegradation reaction. This work provides new insights for the rational selection of acid types and treatment methods to synthesize metal-free carbon nitrides with improved activity for photocatalytic applications.

Forty Steps to Harvest a Graft

Over the past two decades, the stages or steps of follicular unit excision (FUE) harvesting have been described in the medical literature. This article details and identifies the sequence of steps necessary to distinguish the ideal donor harvesting parameters for each patient. The physician’s knowledge and skills should allow for a personalized (and often modified) approach to the different areas of the patient’s scalp. Understanding and performing the sequential steps to harvest intact follicular units (FUs) without damage or injury is an important part of the successful completion of the process. Not all doctors follow the same process or steps for harvesting follicles. In fact, the first few FUs harvested should be used to help identify and establish the necessary parameters to obtain the ideal harvested graft later. Naturally, extra effort may be required to determine the correct sequence and technique for each patient. It also is important to understand that there may be anatomical differences between areas of a patient’s scalp, and it may be necessary to adapt and adjust accordingly. This article describes the 40 steps that we believe are essential for the effective harvesting of uninjured grafts. A single error in any single step may be the difference between success and failure.

Single Molecule Localization Microscopy Analyses of DNA-Repair Foci and Clusters Detected Along Particle Damage Tracks

High-LET particle irradiation as being provided from heavy ion accelerator facilities has an increasing impact on bio-medical research and cancer treatment. Nevertheless, there are a lot of open questions concerning the understanding of damaging mechanisms and repair processes within the light of radio-sensitivity and thus, individualized medical applications. The three-dimensional architecture of genomes on the meso- and nano-scale acts in combination with epigenetic gene activation as an important player of gene regulation and fundamental biological processes such as DNA damage response and repair. So far only little is known about the impact of high-LET particles on the chromatin architecture along the passing track when they are “lumbering” through the cell nucleus. How does a cell nucleus manage such complex damages and re-organize the chromatin towards functionally intact units? Is there a radio-sensitivity related difference in this reaction? Here, we present some approaches to investigate spatial and topological parameters of chromatin to glimpse some aspects related to these questions. Two cell lines, a radio-resistant glioblastoma and a radio-sensitive fibroblast cell line, were used and irradiated by N-ions in 90° and 10° radiation beam geometry. Nano-probing of particle induced damage sites along particle tracks, and the recruited DNA repair proteins (as presented here for 53BP1and Rad51) in combination with super-resolution Single Molecule Localization Microscopy (SMLM) are powerful methods for geometric and topological analyses to study particle related mechanisms of chromatin conformation and repair complexes in single cells. We used variable tools for such investigations based on image free high precision SMLM, nano-scaled molecule distribution analyses, appropriate metrics following Ripley´s distance frequencies and cluster formation analyses, as well as topological quantifications employing persistence homology. The data reveal a cell type specific nano-architecture of DNA damage foci along particle tracks and their dynamic molecular re-arrangements during repair. Comparing the topology of repair foci by persistence homology suggests similarities of repair cluster formation along given particle tracks. Our studies contribute to the molecular understanding of cellular radiation response at sub-light microscopic chromatin levels; thereby showing how chromatin architecture around complex damage sites and repair foci nano-architecture may contribute to ongoing repair processing.

THE CONNECTING QUANTITIES PROCESS TO SOLVE FRACTION MATHEMATICAL PROBLEMS OF MIDDLE SCHOOL STUDENTS

Purpose of the study: The concept of student fraction, in general, is to understand a small part of an intact part so that students' understanding of fractions as quantities needs to be considered in the context of quantitative reasoning. This study aimed to explore and describe the reasoning of junior high school students in Bima, Indonesia, in understanding the relationship of quantities as a fraction.
 Methodology: Research was conducted with qualitative research, which was descriptive exploratory with the stages of giving the Fraction Problem Task (FPT) and task-based interviews. The subjects in this study were 4 students selected from grades 8 and grade 9, who had studied fraction material and were chosen based on the categorization shown by students on the answer sheet.
 Main Findings: The results of this study described that there were two forms of student reasoning approaches, namely the variable and the non-variable approach. In the variable approach, students used multilevel variables, namely level one and level two, whereas, in a non-variable approach, students connected quantities directly, without involving variables.
 Applications of this study: The process of connecting quantities involved quantitative reasoning with different quantitative operations, such as the quantity combination in the form of multiplication, addition, and concurrent combination of multiplication and addition.
 Novelty/Originality of this study: In the process of linking quantities, students were connecting composite units with intact units directly, and students were connecting composite units, continuous units, and then connecting to intact units.

Surgical treatment of military with multilevel lumbar vertebral spondylolysis

Purpose. To demonstrate the effectiveness of an isolated fixation technique of multilevel spondylosis disorders in young patients.Materials and methods. Two military men were operated for multilevel spondylosis of lumbar vertebra (LII, LIV and LIV, LV).Results and discussion. Patients underwent bone autoplasty and osteosynthesis of vertebral arches using hybrid lamina transpedicular system in a screw-rod-hook form. Good anatomic and functional results were got.Conclusion. Avoidance of fixation of intact functional spinal units allows to achieve good treatment results and classify this operation as organ sparing surgery.

The effects of speech processing units on auditory stream segregation and selective attention in a multi-talker (cocktail party) situation

Speech unfolds at different time scales. Therefore, neuronal mechanisms involved in speech processing should likewise operate at different (corresponding) time scales. The present study aimed to identify speech units relevant for selecting speech streams in a multi-talker situation. Functional connectivity was extracted from the continuous EEG while young adults detected targets within one stream in the presence of a different, task-irrelevant stream. In two separate groups, either the attended or the ignored stream was manipulated so that it contained intact, word-wise scrambled, syllable-wise scrambled, or spectrally scrambled speech. We found functional brain networks that were sensitive to the difference between the situations when speech was meaningful at sentence vs. at word level, but not between when speech was meaningful at word vs. only valid at syllable level, irrespective of whether the speech units were manipulated in the attended or the ignored stream. These functional brain networks operated in the delta and theta bands corresponding to integrating information from longer time windows. Further, the networks, which could be linked with suppressing information from the to-be-ignored stream included brain areas associated with high-level processing of speech. These results are compatible with late filtering models of auditory attention, as they suggest that the length of intact speech units in the to-be-ignored stream affects processes of attentional selection. However, we found no evidence for speech-to-brain coupling differences as a function of the intact unit of speech in either stream. Thus, although the current results do not rule out that early processes of speech processing affect stream selection in a cocktail party situation, neither do they provide supporting for it.

Sarcomere Lengths Become More Uniform Over Time in Intact Muscle-Tendon Unit During Isometric Contractions

The seemingly uniform striation pattern of skeletal muscles, quantified in terms of sarcomere lengths (SLs), is inherently non-uniform across all hierarchical levels. The SL non-uniformity theory has been used to explain the force creep in isometric contractions, force depression following shortening of activated muscle, and residual force enhancement following lengthening of activated muscle. Our understanding of sarcomere contraction dynamics has been derived primarily from in vitro experiments using regular bright-field light microscopy or laser diffraction techniques to measure striation/diffraction patterns in isolated muscle fibers or myofibrils. However, the collagenous extracellular matrices present around the muscle fibers, as well as the complex architecture in the whole muscles may lead to different contraction dynamics of sarcomeres than seen in the in vitro studies. Here, we used multi-photon excitation microscopy to visualize in situ individual sarcomeres in intact muscle tendon units (MTUs) of mouse tibialis anterior (TA), and quantified the temporal changes of SL distribution as a function of SLs in relaxed and maximally activated muscles for quasi-steady state, fixed-end isometric conditions. The corresponding muscle forces were simultaneously measured using a force transducer. We found that SL non-uniformity, quantified by the coefficient of variation (CV) of SLs, decreased at a rate of 1.9–3.1%/s in the activated muscles, but remained constant in the relaxed muscles. The force loss during the quasi-steady state likely did not play a role in the decrease of SL non-uniformity, as similar force losses were found in the activated and relaxed muscles, but the CV of SLs in the relaxed muscles underwent negligible change over time. We conclude that sarcomeres in the mid-belly of maximally contracting whole muscles constantly re-organize their lengths into a more uniform pattern over time. The molecular mechanisms accounting for SL non-uniformity appear to differ in active and passive muscles, and need further elucidation, as do the functional implications of the SL non-uniformity.

Exploring the regional disc bulge response of the cervical porcine intervertebral disc under varying loads and posture

Nerve compression due to intervertebral disc (IVD) bulging is a known mechanism for low back pain and typically occurs in the posterior region of the disc. Most in vitro studies are limited in the ability to quantify the magnitude of bulging on the posterior aspect of the disc due to the boney structures that occlude a direct line-of-sight in the intact functional spinal units (FSUs). This study examined anterior and posterior annulus fibrosus (AF) bulges in reduced (posterior elements removed) cervical porcine specimens across four loading conditions and two postures. Surface scans from the anterior and posterior aspect of the IVD were recorded in both neutral and flexed postures using a 3D laser scanner to characterize changes in AF bulge. A significant negative correlation was observed for peak AF bulge on the anterior and posterior side of the disc in a flexed posture (Pearson’s r = −0.448; p = 0.002; r2 = 0.2003). The results from this investigation support that there may be a connection between the magnitude of AF bulge on the posterior side and estimations computed using the anterior side.