Precise Length Research Articles

Uniform fiber-like polymeric micelles of controlled length containing a photo-cleavable core: Versatile templates toward functional nanotubes

Inorganic nanotubes with unique and well-defined porous structures show promising applications in diverse functional materials. However, it remains a challenge to fabricate inorganic nanotubes with precise length controllability. Herein, we report the synthesis of block copolymers consisting of a crystalline π-conjugated oligo(p-phenylenevinylene) (OPV) block, a hydrophilic poly(2-vinylpyridine) (P2VP) segment and a photo-cleavable o-nitrobenzyl (ONB) junction. By taking advantage of crystallinity of OPV segment, self-seeding approach of living crystallization-driven self-assembly was employed to generate uniform fiber-like micelles composed of an OPV core and a P2VP corona. The P2VP corona was then used to host the formation of silica, titania and Pt(0)-embedded silica shell. After the photo-cleavable OBN junctions were broken under light irradiation, the OPV core can be removed in a good solvent for OPV segments to give silica, titania and Pt(0)-embedded silica nanotubes. Significantly, the Pt(0)-embedded silica nanotubes exhibited much higher catalytic activity toward the reduction of p-nitroaniline than Pt(0)-embedded silica nanofibers with the same Pt content, probably owing to the presence of porous channel for nanotubes. This work opens a new avenue to fabricate inorganic nanotubes of controlled length.

TagBiFC technique allows long-term single-molecule tracking of protein-protein interactions in living cells

Protein-protein interactions (PPIs) are critical for cellular activity regulation. Visualization of PPIs using bimolecular fluorescence complementation (BiFC) techniques helps to understand how PPIs implement their functions. However, current BiFC is based on fluorescent proteins and the brightness and photostability are suboptimal for single molecule tracking experiments, resulting in either low spatiotemporal resolution or incapability of tracking for extended time course. Here, we developed the TagBiFC technique based on split HaloTag, a self-labeling tag that could conjugate an organic dye molecule and thus offered better brightness and photostability than fluorescent proteins for PPI visualization inside living cells. Through screening and optimization, we demonstrated that the reconstituted HaloTag exhibited higher localization precision and longer tracking length than previous methods. Using TagBiFC, we reveal that the dynamic interactions of transcription factor dimers with chromatin DNA are distinct and closely related to their dimeric states, indicating a general regulatory mechanism for these kinds of transcription factors. In addition, we also demonstrated the advantageous applications of TagBiFC in single nucleosome imaging, light-burden imaging of single mRNA, low background imaging of cellular structures. We believe these superior properties of our TagBiFC system will have broad applications in the studies of single molecule imaging inside living cells.

Photo‐controlled alignment and helical organization in main‐chain liquid crystalline alternating polymers

AbstractMaterials with highly ordered nanoscale structures can translate molecular processes to macroscopic function. Here we report on the photo‐controlled organization of achiral alternating copolymers composed of discrete length blocks showing well‐defined sub‐10 nm morphologies. These alternating copolymers consist of main‐chain azobenzene building blocks alternating with discrete oDMS blocks of various precise lengths. Remarkably, we demonstrate the imprinting of a stable helical molecular arrangement in spin‐casted thin films by irradiation with circularly polarized light, without chiral dopant or plasticizer required. By following the out‐of‐equilibrium photo‐switching process over irradiation time, the mechanism of molecular reorganization is unraveled and rationalized with the nature of the morphology. Linear photo‐organization is preferentially reached with flexible and symmetric cylindrical structures while helical photo‐organization is most easily obtained with robust but rotatable lamella structures. These findings suggest that precision in the synthesis and assembly of alternating copolymers can lead to complete control over molecular organization and main‐chain motion.

Functional Role of Class III Myosins in Hair Cells.

Cytoskeletal motors produce force and motion using the energy from ATP hydrolysis and function in a variety of mechanical roles in cells including muscle contraction, cargo transport, and cell division. Actin-based myosin motors have been shown to play crucial roles in the development and function of the stereocilia of auditory and vestibular inner ear hair cells. Hair cells can contain hundreds of stereocilia, which rely on myosin motors to elongate, organize, and stabilize their structure. Mutations in many stereocilia-associated myosins have been shown to cause hearing loss in both humans and animal models suggesting that each myosin isoform has a specific function in these unique parallel actin bundle-based protrusions. Here we review what is known about the classes of myosins that function in the stereocilia, with a special focus on class III myosins that harbor point mutations associated with delayed onset hearing loss. Much has been learned about the role of the two class III myosin isoforms, MYO3A and MYO3B, in maintaining the precise stereocilia lengths required for normal hearing. We propose a model for how class III myosins play a key role in regulating stereocilia lengths and demonstrate how their motor and regulatory properties are particularly well suited for this function. We conclude that ongoing studies on class III myosins and other stereocilia-associated myosins are extremely important and may lead to novel therapeutic strategies for the treatment of hearing loss due to stereocilia degeneration.

Accuracy of Working Length Measured by Apex Locator and Digital Radiography

OBJECTIVE: The objective of this study was to compare the measurements of electronic and radiographic method of working lengths calculation with actual working length of root canals. Precise working length determination is the most important part for successful root canal procedure. The most commonly used methods to determine the working length in root canal treatment are radiography and electronic apex locator. METHODOLOGY: A cross sectional study was done over a period of 06 months in the Department of Operative Dentistry, Fatima Memorial Hospital, Lahore. Sixty patients who were recommended extraction of their premolar teeth with sixty canals were selected by convenience sampling. The Root ZX* apex locator was used to determine electronic working length exactly identifying the apical constriction. Reference points were identified and radiographic working length were determined 1mm short of radiographic apex. The teeth were extracted along with file cemented before extraction inside root canal. The actual length of the root canal was then calculated using the same files and reference point with 3.5X magnification. Pearson chi square test was applied to compare the apex locator and digital radiographic measurement with actual working length. RESULTS: The Root ZX® apex locator was 95% accurate to identify the apical constriction as compared 70% accuracy given by radiographs within 0.5 mm of the apex. CONCLUSION: Electronic apex locator was more accurate as compared to digital radiography in working length determination. KEYWORDS: Working length (WL), Electronic apex locators (EAL), Radiographic working length(RWL), Apical constriction (AC) HOW TO CITE: Khan GI, Khan MT, Ehsan S, Fayyaz A, Malik HA, Hussain S. Accuracy of working length measured by apex locator and digital radiography. J Pak Dent Assoc 2021;30(1):24-28.

Sharp Turns and Fluorescent Repeats: Modular Construction and Shape-Dependent Electronic Properties of π-Conjugated Chain Molecules.

In search of the design rules for structural ordering of open-chain molecules, we have built a series of zig-zag shaped π-conjugated structures with ring-fused heteroaromatics as sharp turns and tolane-based linear fragments as light-emitting units. Using only a finite number of common building blocks, an efficient "double-elongation" strategy was implemented to construct a series of π-conjugated oligomers with precise length control (55-89 % yields). Our approach takes advantage of the modular nature of the bis(triazolo)benzene synthesis and the masked reactivity of the nitro group. A combination of photophysical and DFT computational studies revealed that the bis(triazolo)benzene-tolane repeat units behave as electronically decoupled light-absorbing/emitting units (λmax,em = 408-422 nm; ΦF = 20-25 % in THF). Such context-independent photophysical properties promise their potential applications in chemical sensing and switching.

All-normal-dispersion dissipative soliton fiber laser using an offset-splicing graded-index-multimode-fiber-based saturable absorber.

All-normal-dispersion (ANDi) dissipative soliton mode-locking is realized based on nonlinear multimode interference (NMI), which is implemented by offset-splicing three pieces of graded-index multimode fibers (GIMFs) and acts as a saturable absorber. The higher-order modes can be excited by offset-splicing GIMFs (OS-GIMFs), which eliminates adding the step multimode fiber (SIMF) into the resonant cavity and the precise length requirement of the SIMF. In the experiment, the stable dissipative soliton mode-locking at 1030 nm can be obtained with the pulse width of 7.3 ps and the repetition rate of 20.52 MHz, and the bandwidth is 6.98 nm. The maximum output is 3.2 mW with the pump power of 257 mW. The OS-GIMFs can significantly improve the saturated absorption and can easily realize dissipative soliton mode-locking in ANDi regions, which makes it attractive in ultrafast photonics.

Heparin length in the coating of extremely small iron oxide nanoparticles regulates in vivo theranostic applications.

The positive contrast of extremely small iron oxide nanoparticles (ESIONP) in magnetic resonance imaging (MRI) rejuvenates this class of metal nanoparticles (NP).Yet, the current synthesis often lacks the possibility of adjusting the core size (while it is a key element for ESIONP-based MRI contrast behaviour), and also involved multiple complex steps before obtaining a ready-to-use probe for medical applications. In this study, we faced these challenges by applying heparin oligosaccharides (HO) of different lengths as coatings for the preparation of HEP-ESIONP with a one-pot microwave method. We demonstrated that the HO length could control the core size during the synthesis to achieve optimal positive MRI contrast, and that HEP-ESIONP were endowed directly with anticoagulant properties and/or a specific antitumor activity, according to the HO used. Relevantly, positron emission tomography (PET)-based in vivo biodistribution study conducted with 68Ga core-doped HEP-ESIONP analogues revealed significant changes in the probe behaviours, the shortening of HO promoting a shift from hepatic to renal clearance. The different conformations of HO coatings and a thorough in vitro characterisation of the probes' protein coronas provided insight into this crucial impact of HO length on opsonization-mediated immune response and elimination. Overall, we were able to identify a precise HO length to get an ESIONP probe showing prolonged vascular lifetime and moderate accumulation in a tumor xenograft, balanced with a low uptake by non-specific organs and favourable urinary clearance. This probe met all prerequisites for advanced theranostic medical applications with a dual MRI/PET hot spot capability and potential antitumor activity.

Effect of precise linker length, bond density, and broad temperature window on the rheological properties of ethylene vitrimers.

Dynamic networks which undergo topology conserving exchange reactions, sometimes called vitrimers, show properties intermediate to thermosets and thermoplastics. The dynamic nature of the networks results in complex rheological properties and has attracted much attention in the past decade for self-healing, malleable and recyclable polymers. Here, we investigate a series of precise, high crosslink density telechelic ethylene vitrimers as a function of temperature and crosslink density. The networks show a rubbery plateau at high frequencies and a terminal flow regime at lower frequencies. With increasing crosslink density, the rubbery plateau modulus shows a monotonic increase and the terminal flow shifts to lower frequencies. The plateau modulus at high frequency increases as a function of temperature, as expected for a conserved network topology. When plotted against inverse temperature, the zero shear viscosities show a characteristic Arrhenius behavior, and the activation energy monotonically increases with crosslink density. Crossover frequency and shift factors (from time temperature superposition) also show Arrhenius behavior with activation energies in good agreement with those determined from zero shear viscosity. A positive deviation from this Arrhenius trend is observed beginning as high as 100 K above the glass transition temperature for C6 and C8 networks. Further investigations of such networks are critical for the development of sustainable and recyclable replacements for commercial plastics.

Numerical analyses of key parameters of nonlinear asynchronous optical sampling using dual-comb system

Absolute distance measurement based on the asynchronous optical sampling with using a dual-comb system has the characteristics of large range, fast measurement speed, and high accuracy, which has wide application prospects in the field of precision measurement of geometric quantities, such as the space technology, equipment manufacturing, etc. Recently, the invention of the femtosecond frequency comb is a milestone in the field of precision length measurement. Many approaches to the absolute distance measurement have been proposed. Among them, the dual-comb system with asynchronous optical sampling can realize a length measurement with fast speed, high accuracy, and long range. Especially, the temporal method combining the asynchronous optical sampling with nonlinear intensity cross-correlation can effectively avoid influencing of the carrier-envelope offset frequency on the ranging accuracy in the measurement process. The time-of-flight information can be obtained by the time interval between the reference pattern and the measurement pattern. Even so, the selection of the repetition rate and the difference of repetition rates will strongly influence the temporal sampling interval of the measurements. Therefore, the theoretical model and key parameters for the ranging are numerically studied for the non-linear asynchronous optical sampling by using a dual-comb system of absolute distance measurement. After analysis, the effects of source parameters (repetition frequency and repetition frequency difference), fine fitting of second harmonic signal, and timing jitter on ranging accuracy are studied respectively. The numerical analysis results show that the method of choosing a reasonable repetition frequency and repetition frequency difference is beneficial to the improvement of the ranging accuracy. When the sampling interval of the dual-comb system is a constant, the time value between the reference and measurement patterns can be obtained by the interpolation method of fine curve fitting, and it will further improve the ranging accuracy. In addition, the time jitter of the femtosecond pulses is also an important factor that can affect the ranging accuracy. By changing the difference in the repetition rate, the measurement speed can also be improved. After that, the cumulative ranging error caused by time jitter can be reduced. Therefore, the appropriate increasing of measurement speed can effectively reduce the influence of timing jitter on ranging.

An Analysis of the Optical System of a Length Measurement Comparator

In the paper, the optical system of a precise bar length measuring comparator is analysed. The requirements for such a system are determined and systematized. The impact of the resolution, signal discretization frequency, image blurring, bar edge measurement indeterminacy and camera noise on measuring the bar width and establishing the bar position is discussed upon. Various algorithms have been analysed and finally a bar edge identification algorithm oriented to the scale calibration accuracy and the high processing speed was proposed. In the end of the paper, conclusions are provided.

Control of filament length by a depolymerizing gradient

Cells assemble microns-long filamentous structures from protein monomers that are nanometers in size. These structures are often highly dynamic, yet in order for them to function properly, cells maintain them at a precise length. Here we investigate length-dependent depolymerization as a mechanism of length control. This mechanism has been recently proposed for flagellar length control in the single cell organisms Chlamydomonas and Giardia. Length dependent depolymerization can arise from a concentration gradient of a depolymerizing protein, such as kinesin-13 in Giardia, along the length of the flagellum. Two possible scenarios are considered: a linear and an exponential gradient of depolymerizing proteins. We compute analytically the probability distributions of filament lengths for both scenarios and show how these distributions are controlled by key biochemical parameters through a dimensionless number that we identify. In Chlamydomonas cells, the assembly dynamics of its two flagella are coupled via a shared pool of molecular components that are in limited supply, and so we investigate the effect of a limiting monomer pool on the length distributions. Finally, we compare our calculations to experiments. While the computed mean lengths are consistent with observations, the noise is two orders of magnitude smaller than the observed length fluctuations.

Determining the freeze-thaw performance of mortar samples using length change measurements during freezing

The Freeze-thaw (FT) performance of cementitious materials is dependent on the degree of saturation (DOS). It has been proposed that FT damage can occur during freezing when the DOS is greater than a critical DOS (DOSCR). In a previous study, a systematic methodology has been developed to determine the DOSCR of cement paste samples using high precision length change measurements during freezing and thawing in a thermomechanical analyzer (TMA). This paper explores the extension of the established methodology to mortar samples to determine their DOSCR. The influence of the drying temperature and the characteristics of FT cycle (temperature range, heating and cooling rate) were investigated to determine their impact on the FT performance of the mortar samples. The mortar samples tested in this study were obtained by making concrete and then wet sieving the concrete to obtain mortar. Mixtures with different air void content and air void quality were prepared in this study in order to determine the impact of air void content and air void quality on the FT performance of the samples using TMA testing. The results confirm that length change measurements can be used to determine DOSCR of mortar. A correlation considering the probability of failure was found to exist between the air void quality and the FT performance of mortar samples. The approach presented in this paper provides an alternative method that can complement other existing tests to determine the DOSCR for use in the sorption-based model.

Working Length of Maxillary Primary First Molars in Children Aged 2-6 Years

An accurate and reproducible working length determination is a crucial aspect in pulpectomy. The cleaning, shaping and obturation cannot be adept precisely unless the working length is determined accurately. The determination of precise working length is one of the keys to accomplishment in endodontic therapy. Thus the aim of the study was to compare the working length of each root canal obtained for primary maxillary first molars in children aged 2-6 years. A retrospective study was carried out using digital records of 1,372 children who reported to the Department of Paediatric and Preventive Dentistry from June 2019 to March 2020. A total of 380 records were finally included for the study evaluation, which included maxillary primary first molars (54,64) Patients between the age group of 2-6 years were included in the study. The following data were retrieved from the dental records: age, gender, working length of each canal and pulpal pathology. The records were examined and noted in a spreadsheet. The collected data were analysed by computer software SPSS version 21 using one-way Anova test with the level of significance set at 5%. The mean age was observed to be 4.14 years in the present study. The mean working length was found to be 9.82mm (MB canal), 9.79mm (DB canal), 13.28mm (Palatal canal) with respect to pulpal pathology such as pain, swelling, abscess and resorption (P = 0.00). The reported data may help clinicians to obtain a thorough understanding of the working length of the primary maxillary first molars.

Investigations of dynamic phenomena of precision length measurement system

The development of the automotive industry is conditioned by the application of production technologies, which directly depend on production volumes. Today's development of car production is possible only in conjunction with the volume of production, ensuring both the parameters of assembly and production quality. Their constant monitoring is related to the application of the verification tools and technologies used. Such is the length measurement process that needs to be precise in the automotive industry.The paper analyzes the precision length measurement system and its dynamic characteristics. The research is applied to solve the problems of dynamic processes of a precision length measuring system, and the obtained results can be used in the development of precision systems for other purposes. The obtained results describe the vibrations of the length measuring system housing and the measuring head, which show the weak points of the system at the respective frequencies. The paper analyzes the precision length measurement system and its dynamic characteristics. The obtained results describe the vibrations of the length measuring system housing and the measuring head, which show the weak points of the system at the respective frequencies.

Intraflagellar transport during assembly of flagella of different length in Trypanosoma brucei isolated from tsetse flies.

Multicellular organisms assemble cilia and flagella of precise lengths differing from one cell to another, yet little is known about the mechanisms governing these differences. Similarly, protists assemble flagella of different lengths according to the stage of their life cycle. Trypanosoma brucei assembles flagella of 3 to 30 µm during its development in the tsetse fly. This provides an opportunity to examine how cells naturally modulate organelle length. Flagella are constructed by addition of new blocks at their distal end via intraflagellar transport (IFT). Immunofluorescence assays, 3D electron microscopy and live-cell imaging revealed that IFT was present in all T. brucei life cycle stages. IFT proteins are concentrated at the base, and IFT trains are located along doublets 3-4 and 7-8 and travel bidirectionally in the flagellum. Quantitative analysis demonstrated that the total amount of flagellar IFT proteins correlates with the length of the flagellum. Surprisingly, the shortest flagellum exhibited a supplementary large amount of dynamic IFT material at its distal end. The contribution of IFT and other factors to the regulation of flagellum length is discussed.

Emerging trends in solution self-assembly of block copolymers

Since the foundation of macromolecular science by Staudinger, advances in polymer chemistry have unveiled enormous avenues for controlling chemical structures at the molecular scale. As a typical self-assembling polymer covalently linked by chemically distinct polymer blocks, amphiphilic block copolymers (BCPs) spontaneously form a variety of nanostructures with diverse functional applications, especially in the fields of nanomedicine and biomaterials. Self-assembling processes could occur at single chain level (i.e., intrachain folding) or involve multiple chains with similar and dissimilar chemical structures (i.e., interchain association). This review article discusses recent trends concerning solution self-assembly of BCPs, including the formation of inverted mesophases, self-folding into single-chain nanoparticles (SCNPs), compartmentalized nanoparticles with sophisticated functions, and nanostructures of amphiphilic copolymers with precise chain lengths and predetermined sequences, by highlighting selected examples.

Developing protocols for in‐water morphometric measurements of cetaceans using stereo‐videogrammetry

AbstractMorphometry underpins the basic knowledge of any organism's population demographics and dynamics. Such understanding enables the investigation of trends with important conservation implications including monitoring the health of individuals and changes in population dynamics over time. By detecting declines in health prior to the onset of significant mortality, monitoring of body condition can potentially allow time for a management response to avert population decline. We trialed the use of a diver‐operated stereo‐video (SDOV) system for making morphometric measurements of dwarf minke whales (Balaenoptera acutorostrata subsp.), a small oceanic rorqual, in the Great Barrier Reef, Australia. The SDOV system produced 68% more precise replicate total body length measurements than a single‐camera system, while both systems achieved a mean error below 0.5%. The increased precision offered by a SDOV system is desirable for longitudinal monitoring of growth rates and body condition. Optimal application of this method relied on adherence to protocols for both data collection and analysis beyond those dictated by the equipment user manuals. We provide recommendations for these field and analytical protocols, which may be suitable for use with other cetaceans when in‐water access is available.

Analysis of thermal contribution to the measurement uncertainty in step gauge calibration

Thermal expansion errors represent an important source of measurement uncertainty in precision length measurements. The authors present research performed on thermal error minimisation in calibration of step gauges, with the goal to develop a new high precision procedure for step gauge calibration in the Slovenian National Dimensional Metrology Laboratory. Thermal conditions during step gauge calibration were analyzed by using a combination of experimental measurements and Finite Element Method (FEM) simulations. Good final agreement between the experimental measurements and the simulation proves that the FEM simulation is a useful tool for studying and compensating thermal errors. The final outcome of the research is a non-linear model for compensating thermal expansion of a step gauge during calibration in a microclimatic chamber, where the temperature is controlled within the limits of (20 ± 0.1) °C. Different types of step gauges were examined and modelled which are used commonly for testing the performance of Coordinate Measuring Machines (CMMs). The results show that the developed error compensation method is effective enough for our metrology purposes as regards measurement uncertainty.

A Variance Model in NRTK-Based Geodetic Positioning as a Function of Baseline Length

This study examines the effect of baseline length on accuracy and precision in Network Real-Time Kinematic (NRTK) positioning and develops an experimental mathematical model to express this effect. The study also measures the performances of the Flaechen Korrektur Parameter (FKP) and Virtual Reference Stations (VRS) methods at different baseline lengths. The study makes use of the stations that form two Continuously Operating Reference Station (CORS) networks, one of which is local and the other national. Calculations were made to perform various geodetic operations, such as datum transformations between the two networks, identifications of positional velocities, and epoch shifting. BERNESE (v5.2) software was used to identify coordinate values assumed to be true based on International GNSS Service (IGS) products. No significant changes were observed in the RMSE values in baseline lengths of up to 40 km. In contrast, an average linear correlation of 69.2% was determined between precision and baseline length. Measurements were evaluated and tested using the variance model created as a function of the baseline length, in line with the aims of the study, and the results were found to be consistent. Moreover, in an examination of the Root Mean Square Error (RMSE) and precision values of the FKP and VRS measurements, no significant differences were observed. The mean differences were at the millimetre level.